DE10300555B4 - A deterioration determination device for an engine exhaust gas control device and deterioration determination method - Google Patents

Abstract

Deterioration determining device for an exhaust gas control device,
marked by:
an exhaust gas control device (42) provided in an exhaust gas passage (40) of an internal combustion engine (1) and activatable by adding a reducing agent;
a reducing agent adding means (71) for adding the reducing agent to the exhaust gas control device (42) under a condition that the internal combustion engine (1) stops from an operating state;
an exhaust gas control device temperature measuring device (79) provided on the exhaust gas control device (43) for measuring an exhaust gas control device temperature;
a temperature obtaining time measuring means (80) for measuring a time which decreases from a time when the reducing agent is added by the reducing agent adding means (71) to a time when the exhaust gas controlling apparatus temperature decreases to a predetermined temperature after rising due to the addition of the reducing agent; expires; and
a deterioration determining means (80) for determining that the exhaust gas control device (42) has not deteriorated when the time measured by the temperature obtaining time measuring means (80) is longer than a predetermined time, and for determining that the exhaust gas control device (42) has deteriorated, if...

Description

The The invention relates to deterioration determination devices and a deterioration determination method for an engine exhaust gas control device.

Of the catalysts for removing nitrogen oxides (NOx) from an exhaust gas, there is a storage-reduction type NO x catalyst which absorbs NO x during a state of excessive oxygen concentration (fuel lean state) and which outputs stored NO x when a state of low oxygen concentration (fuel-rich state) Adding fuel as a reducing agent is brought into the exhaust gas, so that the discharged NOx reacts with the fuel (HC) on an activated catalyst (platinum (Pt) or the like) and reduced to N ₂ , which is discharged to the ambient air.

Of the NOx catalyst has a NOx absorbent, the NOx from the exhaust while a lean state of the exhaust gas and absorbs NOx during a gives off rich state of the exhaust gas, and a noble metal catalyst, which is activated by fuel as a reducing agent Oxidation-reduction reactions between NOx and fuel simplify. The NOx catalyst controls the exhaust gas through a combination of the NOx storage release function and the activation function.

Therefore include factors for a deterioration of the NOx catalyst a deterioration in the absorption-release function of the NOx absorbent and a deterioration in terms of Activation function of the noble metal catalyst. Examples of causes The deterioration of the NOx catalyst is a reduction in terms of NOx storage ability due to sulfur poisoning (S poisoning), a reduction the activation of the noble metal catalyst due to sintering and the same.

Examples of the method of determining the degree of deterioration of the above-mentioned catalyst include a method as disclosed in U.S. Pat JP 08-232644 A in which the degree of deterioration of a catalyst is determined from the time required between changing the catalyst environment to a rich state to cause NOx to be discharged from the catalyst and ending the discharge of the NOx ( when the duty level of an air-fuel ratio sensor reaches a duty level corresponding to a rich air-fuel ratio), a method as described in U.S. Pat JP 2000-104 536 A in which a catalyst deterioration is detected on the basis of a signal from a NOx sensor provided downstream of a catalyst (a time chart of the NOx sensor signal, the gradient of a NOx concentration in the time chart, and the time of a catalyst regeneration process). , a procedure as it is in JP 11-229 859 A wherein, using a temperature sensor provided on a NOx catalyst and a NOx sensor provided downstream of the catalyst, deterioration of the catalyst based on the states of NOx removal at the time of high is disclosed Temperature of the NOx catalyst and at the time of a low temperature thereof according to a time-dependent information is determined by the temperature sensor as a temperature indication means and the NOx sensor, a method as shown in FIG JP 07-208151 A is described in which, using a NOx sensor provided downstream of a NOx catalyst, it is determined that the catalyst has deteriorated when the time elapsing from the completion of the NOx emission from the catalyst until the value output in accordance with the NOx concentration detected by the NOx sensor increases to a predetermined value, is less than or equal to a predetermined value, and so on.

In all of the above methods, the concentration of NOx or oxygen (O ₂ ) or the like in the exhaust gas is measured, and deterioration of the catalyst is determined from the value of the concentration. For measuring the concentration of the above-mentioned gas, it is necessary for gas to flow around the sensor for the measurement. When the gas is not flowing, the value obtained by the measurement of the sensor merely indicates the concentration of the exhaust gas around the sensor, but does not necessarily show the concentration of an atmosphere of the catalyst provided upstream of the sensor. on the concentration of the exhaust gas, which is discharged from the internal combustion engine. Therefore, for performing a catalyst deterioration method, as mentioned above, it is necessary that the engine is in operation and discharges exhaust gas, and therefore exhaust gas has to flow. While the internal combustion engine is operating, various conditions with respect to the exhaust gas such as temperature, concentration, flow rate, flow rate thereof, etc., change depending on the load of the internal combustion engine, its rotational speed and so on. Since each of the above catalyst deterioration methods makes a determination as to the deterioration of the catalyst during the operation of the internal combustion engine, it is necessary to consider changes in various conditions depending on the conditions from the operating state of the internal combustion engine occur.

in the Regarding the process, the deterioration of a catalyst determined by using a NOx sensor, which is the NOx concentration was detected, a NOx sensor with highly accurate measurement for the detection the deterioration for a practical use is not provided. Therefore, if such NOx sensor actually to Determining the catalyst deterioration is used Very high cost or very low accuracy in determining the deterioration.

The DE 41 00 397 C2 describes a generic deterioration determining apparatus for an exhaust gas control apparatus having a catalyst provided in an exhaust passage of an internal combustion engine for controlling exhaust gas discharged from the internal combustion engine, catalyst exhaust gas inflow temperature measuring means for measuring a temperature of an exhaust gas inflow into the catalyst, a catalyst temperature measuring means for measuring a catalyst temperature the catalyst, a reducing agent adding means for adding a reducing agent to the catalyst and a temperature difference detecting means for detecting a difference in the catalyst temperature from the temperature of the exhaust gas inflow occurring when the reducing agent is added to the catalyst by the reducing agent adding means. Furthermore, the describes DE 41 00 397 C2 a monitoring of the degree of conversion of a catalyst at the light-off temperature of the catalyst is reached. It is in accordance with the DE 41 00 397 C2 determines how the catalyst has deteriorated due to a difference of Abgaseinströmtemperatur and Abgasausströmtemperatur.

The DE 40 27 207 A1 describes a method for determining the activity of the catalyst. In this case, a temperature limit is determined and compared a temperature measurement with just this limit. If this temperature measured value is smaller than the temperature limit value, a message is issued. The DE 40 27 207 A1 thus monitors the activity of the catalyst by comparing a temperature difference with a limit.

In the DE 42 27 207 C2 Another method for checking a catalyst is described.

It is an object of the invention, a highly accurate determination in In view of the deterioration of NOx control ability of a catalyst independently allow the accuracy of the detection of an exhaust gas concentration.

These Task is solved with the features of the independent claims. advantageous Further developments of the invention are specified in the subclaims.

One The first aspect of the invention is a deterioration determination method for one An exhaust control device for determining a deterioration the exhaust control device, comprising: adding a reducing agent to the exhaust gas control device to the exhaust gas control device to warm, when it is detected that an internal combustion engine is about to stop, while the internal combustion engine is in operation and the exhaust gas control device, which is provided in the exhaust passage of the internal combustion engine through Add a reducing agent is activated; Measuring a time, the from the addition of the reducing agent until a temperature of the Reduced exhaust control device to a predetermined temperature; and determining that the exhaust gas control device does not deteriorate if the time being measured is longer than a predetermined one Time is, and determining that the exhaust control device itself has deteriorated if the time measured is shorter than is a predetermined time.

For performing this deterioration determination method, a deterioration determining device for an exhaust gas control device is used, comprising: an exhaust gas control device provided in an exhaust passage of an internal combustion engine and activatable by adding a reducing agent; a reducing agent adding means for adding the reducing agent to the exhaust gas control device under a condition that the engine stops from an operating state; an exhaust gas control device temperature measuring device provided in the exhaust gas control device for measuring an exhaust gas control device temperature; a temperature obtaining time measuring means for measuring a time which elapses from a time when the reducing agent is added by the reducing agent adding means at a time when the exhaust gas control device temperature decreases to a predetermined temperature after being increased due to the addition of the reducing agent; and deterioration determining means for determining that the exhaust gas control device has not deteriorated when the time measured by the temperature obtaining time measuring means is longer than a predetermined time, and for determining that the exhaust gas control device has deteriorated when the time taken by the exhaust gas control device has deteriorated Temperature measurement time measuring device is shorter than a predetermined time.

The is called, that in the method and in the device to the following It is determined whether the catalyst has deteriorated. Simultaneously with the detection that the internal combustion engine is about is to stop, fuel to the exhaust gas control device added, which is provided with the catalyst. Due to the added fuel, the catalyst temperature, that is, the exhaust gas control device temperature is raised, to activate the catalyst. A time that runs until the catalyst temperature to a predetermined temperature decreases, which stops the activation of the catalyst is measured. The time from the addition of the fuel until the predetermined Temperature is reached, is compared with a time of adding the fuel to an undiluted catalyst runs in the same way until the catalyst temperature is at a predetermined temperature decreased after the increase due to the addition of the fuel. On the basis of the comparison result is determined whether the catalyst has deteriorated. The aforementioned predetermined Temperature is a temperature at which the activation of a fresh or new catalyst of the same type as the catalyst, which is provided in the exhaust gas control device, due to a Waste of temperature stops, after the temperature has risen to a temperature that allows the activation of the new catalyst.

There the catalyst deterioration determination control is performed After the engine has stopped, it becomes possible to determine the deterioration perform under constant conditions without being affected by different conditions Conditions is influenced, which generates in the internal combustion engine become. Further, there is no need for concentration the exhaust gas for to measure the determination of the deterioration of the catalyst, it is not necessary to have an exhaust gas concentration sensor with high accuracy to use.

Even though the criterion in the first aspect, which is used to determine the Deterioration is used, the length of time of increase in the catalyst temperature due to an oxidation-reduction reaction of the fuel, added to the catalyst, it is possible to control the catalyst temperature directly using, for example, a thermocouple or the like as means for determining the time of the catalyst temperature increase measure up. Therefore, it becomes possible To measure the catalyst temperature in a state in which the Internal combustion engine is stopped and there is no gas flow. When measuring the catalyst temperature, there is a case where the catalyst temperature can not be measured directly. For this Case it is possible the Temperature of the exhaust gas, which flows out of the catalyst through Use the temperature measuring device to measure on a downstream Side of the catalyst is provided, and the measured temperature to use indirectly as a catalyst temperature.

A Condition for implementing the first point of view is possible. If the exhaust gas control device temperature is lower than or equal to a reducing agent activation temperature at which the activation caused by adding the reducing agent, the Adding the reducing agent to the exhaust gas control device despite the stopping of the engine avoided.

A further condition is also possible. The An exhaust gas control device further has an exhaust gas temperature measuring device, the upstream from the exhaust gas control device for measuring a temperature of inflowing Exhaust gas is provided, which flows into the exhaust gas control device, and when the exhaust gas control device temperature is higher than the temperature of the inflowing exhaust gas is, the addition of the reducing agent to the exhaust gas control device despite the stopping of the engine avoided.

In the first embodiment For example, fuel is added as a reducing agent to the catalyst and a temperature rise of the catalyst is measured. But when the catalyst temperature is lower than or equal to the reductant activation temperature is at which a temperature rise reaction by adding Fuel is caused to remain added fuel deposited catalyst, so that the catalyst deterioration not done can be. When the exhaust control device temperature is higher than the temperature of the exhaust gas is that in the exhaust gas control device flows in, means that a temperature increase reaction by fuel on the Catalyst in the exhaust gas control device progresses. If therefore during this state the time of catalyst temperature rise, the is measured after the addition of the fuel, is a accurate measurement of time impossible, because fuel is present before the addition of the fuel. Therefore is it possible that Control of the first aspect among the above To avoid conditions.

The exhaust gas control device may further include a storage reduction function for storing nitrogen oxide present in the exhaust gas in a main body of the exhaust gas control apparatus when the exhaust gas inflow is in a state of excessive oxygen concentration, and for discharging and reducing the nitrogen oxide stored in the main body when the exhaust gas inflow is in a low oxygen concentration state, and a memory estimating means for estimating a Storage amount of nitrogen oxide. With this structure, when the storage estimating means estimates that the storage amount of the nitrogen oxide is less than or equal to a predetermined amount, the addition of the reducing agent to the exhaust gas control device is avoided despite the engine stop.

Of the Catalyst has a NOx absorbent, the NOx depending from the ambient atmosphere stores and discharges. Therefore, a means for a temperature increase due to the heat provided by the Oxidation-reduction reactions of the added fuel with the NOx absorbent emitted NOx is generated. But when at the time of deterioration determination after the internal combustion engine continues, the storage of NOx in the NOx absorbent is less than or the same for sufficient Reactions required with the amount of added fuel Amount is low, a temperature rise ability of the catalyst lowers. When Consequence it will be impossible to determine if a temperature drop due to deterioration of the catalyst or by inadequate oxidation-reduction reactions is caused. Therefore, it is appropriate to the amount of storage of the NOx via the NOx storage estimator appreciate and the addition of the reducing agent to the exhaust gas control device to avoid if the estimated amount of storage is less than or equal to a predetermined amount.

Therefore will it be possible the catalyst deterioration determination independent of Variations in the flow rate of the exhaust gas, the exhaust gas concentration and so on, depending on the operating condition of the internal combustion engine are caused, too achieve.

In The second aspect of the invention becomes deterioration by a deterioration determination method for an exhaust gas control device determining, comprising: adding a fuel to a Catalyst provided within an exhaust gas control device is provided on an exhaust system of an internal combustion engine when a temperature of the catalyst becomes greater than or equal to a temperature, in an oxidation-reduction reaction on an undiluted Catalyst starts; Measuring a catalyst temperature and a upstream Exhaust gas temperature at an upstream side of the catalyst; and determining a condition of deterioration of the exhaust gas control device based on a temperature difference of the upstream exhaust gas temperature of the catalyst temperature.

To the Carry out of the deterioration determination method described above a deterioration determining device for an exhaust gas control device the following: a catalyst in an exhaust passage of a Internal combustion engine is provided for controlling exhaust gas generated by ejected from the internal combustion engine becomes; a catalyst inflow exhaust gas temperature measuring device for measuring a temperature of an exhaust gas flow entering the catalyst flows. A catalyst temperature measuring device for measuring a catalyst temperature the catalyst; a reducing agent adding means for adding Adding a reducing agent to the catalyst; a differential temperature detection device or a temperature difference detection device for Detecting a difference of the catalyst temperature from the temperature the exhaust gas inflow, which occurs when the reducing agent to the catalyst the reducing agent adding means is added; and a deterioration determining means to determine that the catalyst has deteriorated, if either a condition that a detected temperature of the exhaust gas inflow when the occurrence of a temperature difference by the temperature difference detection means is detected, greater than is a predetermined temperature, or a condition that the Temperature difference caused by the temperature difference detection means is detected, lower than a predetermined temperature difference is satisfied is.

Of Further, the reducing agent adding means may add the addition of Reduction realize when the catalyst temperature is a reference temperature reached, which is set to a temperature at which an oxidation-reduction reaction at a undegraded catalyst begins.

Exhaust gas components such as HC, CO and NOx undergo oxidation-reduction reactions on the catalyst and therefore change to H ₂ O, CO ₂ , N ₂ and so on, which are released into the ambient air. The temperature (ignition temperature) at which the catalyst is activated so that the oxidation-reduction reactions of HC, CO and NOx start at the catalyst increases as the catalyst deteriorates. A deteriorated catalyst has a reduced ability to store and discharge NOx. Therefore, it decreases Likewise, the amount of NOx that reacts with the reductant on the catalyst per unit time as the catalyst degrades. That is, the amount of oxidation-reduction reactions decreases. Also, with reductions in the amount of the oxidation-reduction reactions, the amount of increase in the catalyst temperature caused by reaction heat generated by the oxidation-reduction reactions, that is, the difference between the catalyst temperature and the catalyst exhaust gas inflow temperature, decreases.

The Deterioration detection method uses this characteristic. This means, that the inflammation temperature an undiluted catalyst as a predetermined detection temperature is set and a reducing agent to a subject in question Catalyst is added in the deterioration determination, when the detection temperature is reached. Based on the degree of a temperature rise reaction caused by the addition of the reducing agent, the state of deterioration becomes of the catalyst determined.

If at a time of adding the fuel into the exhaust passage of the internal combustion engine, the catalyst temperature is lower or is equal to an activation temperature at which an oxidation-reduction reaction begins at the catalyst, and therefore a temperature rise reaction is not caused, the exhaust gas control device with the Catalyst only a portion of the exhaust passage. During this state For example, the catalyst temperature and the temperature of the exhaust gas are upstream of the same as the catalyst. Therefore, if the fuel is at or below the activation temperature is added, the added stored Fuel on the catalyst or is discharged into the ambient air. Therefore, if the addition of the fuel is performed at a time, when the temperature of the catalyst, that of the deterioration determination is exposed to or over the temperature rises, during which an oxidation-reduction reaction begins on a catalyst without deterioration, the detection with regard to the deterioration of the catalyst.

in the With regard to the catalyst exhaust gas inflow temperature measuring device and the catalyst temperature measuring device include examples of Method of measuring a method in which the exhaust gas temperature and the catalyst temperature directly via a thermocouple or the like be measured. Especially with regard to the catalyst temperature is a measuring method in which the temperature of the exhaust gas downstream of the Catalyst is measured and the measured temperature as a Catalyst temperature is considered, as an example. With regard to the temperature difference detection device it is possible to use a procedure in which signals are based on the temperatures detected by the Katalysatorabgaseinströmungstemperaturmesseinrichtung and the catalyst temperature measuring device are measured by a ECU (electronic control unit) are processed, and a Exhaust gas at which a temperature difference (At) occurs is detected.

The The exhaust control device further has a memory reduction function for storing a nitrogen oxide contained in the exhaust gas is, in a main body the exhaust gas control device when the exhaust gas inflow in a condition of excessive oxygen concentration and for draining and reducing the stored in the main body Nitrous oxide, when the exhaust gas inlet in a state lower Oxygen concentration is located, and a memory estimator to appreciate a storage amount of the nitrogen oxide. If with this structure by the memory estimator estimated is that the storage amount of nitrogen oxide is lower than or equal to a predetermined amount, the addition of the reducing agent avoided by the reducing agent addition device.

In the NOx catalyst, a supporter is loaded with a NOx absorbent that stores and discharges NOx depending on the ambient atmosphere, and with a noble metal that facilitates reactions between discharged NOx and the reducing agent. Therefore, the catalyst is heated by a heat of reaction generated by the oxidation-reduction reactions between the added fuel and the NOx discharged from the NOx absorbent on the noble metal. Using this temperature increase reaction, the determination of the deterioration of the NOx catalyst is performed. For performing the deterioration determination of the NOx catalyst by the above-mentioned method, it is necessary that an amount of NOx necessary for the deterioration determination is stored in the NOx catalyst, and that the stored NOx can be discharged when a reaction between NOx and the reducing agent for the deterioration determination. Therefore, when the amount of NOx stored in the NOx catalyst is estimated to be less than or equal to the amount needed for the deterioration determination, it is possible to avoid the addition of the reducing agent to the NOx catalyst within the exhaust control system direction, that is, to avoid the execution of the deterioration determination.

Out the aforementioned deterioration detection method needed based on the catalyst deterioration determination method a difference between the maximum values of Δt largely the amount of NOx storage, this means, the temperature rise reaction based on an oxidation-reduction reaction between NOx and the reducing agent. Therefore, the NOx storage amount, the for this Determination method needed is used as the aforementioned estimated amount of NOx storage, and others Determination procedure can also be carried out. With regard to the Memory estimator Is it possible, For example, use a method in which the NOx storage amount, the for the case of a new catalyst is required until a maximum value generated by Δt will, while a load state of the internal combustion engine, the amount of fuel added into the combustion chamber, the exhaust gas temperature required for the storage of NOx Time, and so on, is calculated in advance, and will in the ECU as a NOx memory map stored, and with reference to this figure a minimum amount of NOx storage required for a given catalyst is necessary in assessing deterioration, it is estimated that and will the esteemed Value used as the NOx storage amount.

In summary is the concept that meets the considerations described above underlying, as follows: the degree of deterioration of one Exhaust gas control device is determined using the fact that the exhaust gas control device is activated, in particular the temperature increases when a reducing agent is added becomes. The characteristic of the temperature response of the exhaust gas control device is examined using a single detected parameter, which describes the temperature response. The parameter can be the Time until the exhaust gas control device a certain temperature achieved, or be the temperature when the exhaust gas control device the ignition temperature (Light-off temperature) reached.

embodiments The invention are illustrated in the drawing. Show it:

1 FIG. 10 is a schematic diagram illustrating a diesel engine system according to a first embodiment of the invention; FIG.

2 FIG. 11 is a conceptual diagram illustrating a structure in the vicinity of an ECU according to the first embodiment; FIG.

3 Fig. 11 is a conceptual sectional diagram of a catalyst enclosure in the first embodiment;

4 Fig. 15 is a graph indicating catalyst temperature rise time and the detection references thereof in the first embodiment;

5 Fig. 11 is a map A indicating the amount of fuel added in the first embodiment;

6 Fig. 10 shows a map B showing the expected activation time in the first embodiment;

7 Fig. 10 is a flowchart showing a catalyst deterioration determination control in the first embodiment;

8th Fig. 10 is a schematic diagram showing a diesel engine system according to a second embodiment of the invention;

9 FIG. 10 is a conceptual diagram showing a structure in the vicinity of an ECU according to the second embodiment; FIG.

10 Fig. 12 is a graph showing relations between the ignition temperature and the catalyst temperature of the second embodiment;

11 Fig. 15 is a graph showing relationships between the temperature difference Δt and the catalyst deterioration in the second embodiment; and

12 Fig. 10 is a flowchart showing a catalyst deterioration determination control in the second embodiment.

One first embodiment, wherein the deterioration determining device and the deterioration determining method for an engine exhaust control device to be applied to a diesel engine system will be described below described.

With reference to 1 is an internal combustion engine (hereinafter simply referred to as "internal combustion engine") 1 is a four-cylinder diesel internal combustion engine system that is a fuel delivery system 10 , Combustion chambers 20 , an inlet system 30 , an exhaust system or an exhaust system 40 and so on as main sections has. A structure of the diesel engine system will be described below.

The fuel delivery system 10 has one too drove pump 11 , a pressure collection chamber (common rail) 12 , Fuel Injectors 13 , a shut-off valve 14 , a fuel supply nozzle 17 , an engine fuel passage P1, a fuel addition passage P2, and the like. The feed pump 11 increases the pressure of the fuel pumped up from a fuel tank (not shown) and supplies the pressurized fuel to a common pipe 12 over the engine fuel passage P1. The common management 12 performs the function of maintaining a predetermined pressure of the high-pressure fuel supplied from the supply pump 11 is supplied (pressure accumulation function), and distributes the pressurized fuel to the fuel injection valves 13 , Every fuel injection valve 13 is an electromagnetic valve having an electromagnetic solenoid (not shown). Every fuel injection valve 13 is suitably opened to fuel in a corresponding one of the combustion chambers 20 inject.

The feed pump 11 guides a portion of the fuel pumped up from the fuel tank to the fuel adding nozzle 17 via the fuel addition passage P2. The shut-off valve 14 is at the fuel addition passage P2 from the supply pump 11 to the fuel supply nozzle 17 intended. In an emergency, the shut-off valve switches 14 the fuel addition passage P2, so that the supply of the fuel stops. The fuel supply nozzle 17 is a solenoid valve similar to the fuel injectors 13 , The fuel supply nozzle 17 adds fuel as a reducing agent to the exhaust system 40 through an injection too.

The inlet system 30 makes a passage into the combustion chambers 20 supplied intake air (intake passage). On the other hand, the exhaust system forms 40 a passage of exhaust gas coming from the combustion chambers 20 is discharged (exhaust passage).

The internal combustion engine 1 is further with a known charging device (turbocharger) 50 Mistake. The turbocharger 50 has a turbine wheel 52 and a compressor 53 through a wave 51 are connected. The compressor 53 is the intake air in the intake system 30 exposed. The turbine wheel 52 is the exhaust gas in the exhaust system 40 exposed. The turbocharger so constructed 50 achieves an effect of raising the inlet pressure (charging effect) by rotating the compressor 53 by the use of the exhaust gas flow (exhaust pressure) passing through the turbine wheel 52 is recorded.

In the inlet system 30 is an intercooler 31 downstream of the turbocharger 50 and forcibly cools the intake air heated due to the charging. A throttle valve 32 farther downstream from the intercooler 31 is provided, is an electronically controlled opening-closing valve, the opening can be adjusted continuously or continuously. The throttle valve 32 performs the function of reducing the passage area (passage area contents) of the intake passage for adjusting (decreasing) the intake air supply under a predetermined condition.

The internal combustion engine 1 is also with an exhaust gas recirculation passage (EGR passage) 60 provided a passage upstream of the combustion chambers 20 (a passage in the inlet system 30 ) and a passage downstream of the combustion chambers 20 (a passage in the exhaust system 40 ) redirects. In particular, the EGR passage connects 60 a connection between an exhaust manifold 40a upstream of the turbocharger 50 in the exhaust system 40 and a passage downstream of the throttle valve 32 in the intake system 30 , The EGR passage 60 performs the function of properly recycling a portion of the exhaust gas into the intake system 30 by. The EGR passage 60 is with an EGR valve 61 , which is infinitely opened and closed by an electronic control to close the flow rate of the exhaust gas through the ERG passage 60 free to set, and an ERG cooler 62 provided to cool exhaust gas passing through the EGR passage 60 flows (returns).

In the exhaust system 40 is the exhaust manifold 40a , which communicates with the combustion chambers, coupled with a cylinder head. Along an exhaust path on a downstream side at a location of the turbine wheel 52 are an exhaust passage 40b , a NOx catalyst enclosure 42 and an exhaust passage 40c provided, which are sequentially connected in this order toward a downstream side. The NOx catalyst enclosure 42 contains a NOx catalyst 42b The accumulator-reduction type, which removes hazardous components such as NOx and the like from the exhaust gas, as described below.

Various sensors are mounted at different locations on the internal combustion engine and provide signals regarding the environmental conditions of the locations, the operating state of the internal combustion engine 1 and so on.

That is, a line pressure sensor 70 a detection signal corresponding to that in the common line 12 collected fuel pressure. A fuel pressure sensor 71 gives a detection signal corresponding to the pressure of the fuel (fuel pressure) entering the fuel adding nozzle 17 is introduced by the fuel in the fuel addition passage 22 flows, off. An air flow meter 72 gives a detection signal corresponding to the amount of flow of the intake air (intake air amount) in the intake system 30 upstream of the throttle valve 32 from. An air / fuel ratio sensor (A / F sensor) 73 outputs a detection signal continuous with the concentration of oxygen in the exhaust gas upstream of the NOx catalyst enclosure 42 in the exhaust system 40 changes. An exhaust gas temperature sensor 74 outputs a detection signal corresponding to the temperature of the exhaust gas downstream of the NOx catalyst enclosure 42 in the exhaust system 40 from. A NOx sensor 75 outputs a detection signal continuous with the concentration of NOx in the exhaust gas downstream of the NOx catalyst enclosure 42 in the exhaust system 40 changes. A catalyst exhaust gas inflow temperature sensor 78 outputs a detection signal corresponding to the temperature of the exhaust gas inflow at an inlet of the NOx catalyst enclosure 42 from. A catalyst temperature sensor 79 gives a detection signal corresponding to the temperature of the catalyst in the NOx catalyst enclosure 42 from.

Further, an accelerator operation amount sensor is 76 attached to an accelerator pedal (not shown) and outputs a detection signal in accordance with the amount of depression of the pedal. The detection signal from the accelerator operation amount sensor 76 serves as a basis for an amount of work that comes from the internal combustion engine 1 is required. A crank angle sensor 77 outputs a detection signal (pulse) every predetermined rotation angle of an output shaft (crankshaft) of the internal combustion engine 1 from. An ignition switch 90 Outputs signals including a start control and a stop control of the internal combustion engine 1 initiate, and also serves as a main circuit breaker. These sensors 70 to 79 and 90 are electric with an electronic control unit (ECU) 80 connected.

As in 2 has indicated, the ECU has 80 a logical operation circuit having a central processing unit (CPU) 81 , a read-only memory (ROM) 82 , an access memory (RAM) 83 , an auxiliary RAM 84 that retains stored information even when vehicle operation stops, a time counter 85 , and so on, which are connected and as well with an input port 86 and an output port 87 via a bidirectional bus 88 are connected. The input port 86 has an A / D converter.

The ECU 80 Gives detection signals from the various sensors via the input port 86 one. Based on these signals, the CPU performs 81 from the ECU 80 Basic controls with regard to the fuel injection of the internal combustion engine 1 and the like, and also performs various controls on the operating state of the internal combustion engine 1 by, for example, a fuel adding control in terms of the determination of an amount of fuel injected for the addition of a reducing agent (fuel serving as a reducing agent), the addition timing, and so on, and also performs controls related to the stopping of the engine 1 and so forth from programs that are in the ROM 82 are stored.

The fuel delivery system 10 for supplying the fuel to the combustion chambers via the fuel injection valves 13 , the NOx catalyst contained in the exhaust system 40 provided is the ECU 80 for controlling the functions of the fuel supply system 10 and the NOx catalyst, and so on constitute an exhaust gas control device for the internal combustion engine 1 according to the embodiment. The aforementioned controls including the fuel adding control and the like are performed by operations of various elements of the exhaust gas control device including the ECU 80 realized that outputs instruction signals with respect to the aforementioned controls.

Of the above-mentioned components of the internal combustion engine 1 becomes the NOx catalyst enclosure 42 that in the exhaust system 40 is described below, described in detail with respect to their structure and function.

3 FIG. 10 is an enlarged sectional view of the NOx catalyst enclosure. FIG 42 , in the 1 is shown, along with a portion of the internal structure of the NOx catalyst enclosure 42 , The NOx catalyst enclosure 42 contains a NOx catalyst 42b the memory reduction type.

The NOx catalyst 42b is, for example, using a support consisting mainly of alumina (Al ₂ O ₃ ) and by loading the surfaces of the support with a substance serving as a NOx absorbent, such as alkali metals including potassium (K), sodium (Na), lithium (Li), cesium (Ce) and so on, and alkaline earth metals including barium (Ba), calcium (Ca) and so forth, as well as rare earths including ythrium (Y) and so forth formed in combination with a noble metal which serves as an oxidation catalyst (noble metal catalyst) such as platinum (Pt) or the like. In this embodiment, the absorbent is supported on a filter that traps particles contained in the exhaust gas.

The NOx absorbent has a characteristic of storing NOx during a high oxygen concentration state in the exhaust gas and discharging NOx during a low oxygen concentration state in the exhaust gas. When HC, CO, or the like is present in the exhaust gas when NOx is discharged into the exhaust gas, oxidation-reduction reactions occur between the NOx as oxidation components and the HC and CO as reduction components due to the noble metal catalyst undergoing the oxidation reactions of HC or CO simplified. That is, HC and CO are oxidized to CO ₂ and H ₂ O and NOx is reduced to N ₂ .

The noble metal catalyst of the NOx catalyst 42b simplifies the oxidation of HC so that heat from the oxidation reactions of HC raises the catalyst temperature.

When a predetermined limit amount of NOx is stored in the NOx absorbent, the NOx absorbent becomes unable to store even more NOx despite a state of high oxygen concentrations in the exhaust gas. With reference to the internal combustion engine 1 becomes a control for restoring the NOx storage capability of the NOx catalyst 42b as described below is repeated at predetermined intervals. That is, before the storage of the NOx in the NOx catalyst 42b that in the NOx catalyst enclosure 42 reaches a limit amount, a reducing agent in an exhaust passage upstream of the NOx catalyst enclosure 42 is added to the NOx catalyst 42b for the reduction of NOx stored therein.

The NOx control will be described in detail below.

Usually has a fuel-air mixture in a diesel internal combustion engine, that for the combustion is provided in a combustion chamber, a high oxygen concentration in most operating areas. The oxygen concentration in a mixture for A combustion is provided directly in the oxygen concentration of the exhaust gas with a subtraction of the amount of oxygen, that for the combustion is used.

If the oxygen concentration (air-fuel ratio) of the Mixture is high, then means that the oxygen concentration (air-fuel ratio) of the Exhaust gas in principle becomes correspondingly high.

Since the NOx catalyst 42b the characteristic for storing NO _x has, when the oxygen concentration of the exhaust gas is high, and for reducing the NO _x to NO ₂ or NO, when the oxygen concentration of the exhaust gas is low, as mentioned above, the NOx catalyst stops 42b The NOx continues as long as the concentration of oxygen in the exhaust gas is high. However, the storage of NOx in the NOx catalyst 42b a border. When the NOx catalyst 42b stores a limit amount of NOx, the NOx in the exhaust gas easily passes through the NOx catalyst enclosure 42 without any further storage of NOx in the NOx catalyst 42b therethrough.

For resuming the NOx storage capability of the NOx catalyst, it is necessary to add a reducing agent into the NOx absorbent contained in the NOx catalyst 42b is available. However, due to the engine concentration, it is unlikely that the exhaust gas having a low oxygen concentration, that is, the exhaust gas containing a large amount of fuel serving as a reducing agent, is unleashed when normal fuel injection into the engine is performed. Therefore, it is a normal procedure to adopt a method in which additional fuel injection is performed by injecting fuel as an unburned fuel separately from the main injection performed to drive the power conversion in the combustion chambers of an internal combustion engine, a method in which fuel in the exhaust gas is injected from a fuel addition nozzle provided in the exhaust passage and so on. By such a method, fuel is injected into the exhaust gas to increase the amount of a reducing agent component in the exhaust gas, so that the NOx storage capability is restored by the reducing agent component and therefore the catalyst is regenerated (NOx catalyst regeneration control).

The ECU 80 of the internal combustion engine 1 continuously monitors the concentration of NOx in the exhaust gas downstream of the NOx catalyst 42b on the basis of the output signal from the NOx sensor 75 , The NO _x storage capability (storage efficiency) of the NO _x catalyst 42b decreases when an amount of NOx contained in the NOx catalyst 42b is increased, that is, when the amount of NOx contained in the NOx catalyst 42b is stored, the maximum amount (saturation amount) of NOx reached by the NOx catalyst 42b can be stored. That is, if the amount of NOx contained in the NOx catalyst 42b is increased, the concentration of NOx passing through the NOx catalyst enclosure 42 passes and is discharged downstream increases. Thus, there is a correlation between the transition of the storage of NOx in the NOx catalyst 42b and the Transition from the concentration of NOx in the exhaust gas from the NOx catalyst enclosure 42 is omitted. Therefore, the amount of NOx contained in the NOx catalyst 42b is stored on the basis of the nature of the transition from the NOx concentration.

Therefore, if the _NOx concentration in the exhaust gas downstream of the NOx catalyst Mount 42 greater than a predetermined concentration, the ECU determines 80 in that the storage of the NOx in the NOx catalyst 42b reaches a predetermined amount and performs fuel adding control by adding unburned fuel into the exhaust gas through the use of a fuel adding device as follows. That is, fuel enters the exhaust upstream of the NOx catalyst enclosure 42 in the exhaust system 40 for temporarily increasing the amount of a reductant component in the exhaust gas entering the NOx catalyst enclosure 42 flows, is added and thereby reduces the air-fuel ratio of the exhaust gas. As a result, the NOx in the catalyst reacts with the fuel provided as a reducing agent and is therefore removed.

In an example control method, an engine operation history or the like that is detected in the sub-RAM determines 84 more specifically, from the stored output signals of the accelerator operation amount sensor 76 , the crank angle sensor 77 , the time counter 85 , and so on, the CPU 81 determines whether the fuel addition is to be performed as a NOx removal process, as compared with in advance in the ROM 82 stored programs.

By the above-described recovery method of the NO _x catalyst 42b represents the NOx catalyst 42b restores its NOx storage capacity. However, if the recovery process of the NOx catalyst 42b is repeated, the exhaust gas control performance of the catalyst gradually lowers due to a time-dependent deterioration or the like.

Examples of problems caused by deteriorated exhaust gas control performance of the catalyst are an increase in the reducing agent activation temperature at which the catalyst is activated by the addition of a reducing agent, a lowering of the reaction efficiency of the catalyst, and the like. When the NO x removal control is performed by the use of a deteriorated NO x catalyst with reference to a predetermined temperature preset at the reductant activation temperature of a NO x catalyst in a new state (fresh catalyst), sufficient NO x removal due to the difference the reducing agent activation temperature can not be performed. Therefore, it is necessary to determine the degree of deterioration of the NOx catalyst 42b to determine and perform the NOx removal control according to the deterioration degree.

One NOx catalyst deterioration determination method in the first embodiment The invention will be described below.

As described above, a deteriorated catalyst has a higher activation temperature and a lower reaction performance than an undegraded catalyst. If therefore, as in 4 For example, when the fuel is added to a deteriorated catalyst and to a fresh catalyst under the same conditions, the catalysts experience a difference in time elapsed from the temperature rise caused by the addition of the fuel to the time when Catalyst temperature reaches a predetermined temperature at which the catalyst activity disappears. Using this characteristic, deterioration of the catalyst is detected. That is, after fuel as a reductant to the NOx catalyst 42b is added, the catalyst activation time is measured. A reduction in the catalyst activation time is used as a factor for deterioration of the catalyst.

The catalyst activation time can be more accurately measured when the measurement is performed in a state free from influences of the internal combustion engine 1 is, that is free from influences, such as the flow rate of the exhaust gas, the exhaust gas concentration and so on. Therefore, the measurement of the catalyst activation time is performed in a state where the atmosphere of the NOx catalyst 42b is largely stable, that is, in a state in which the internal combustion engine 1 is stopped, and in which the catalyst temperature of the NOx catalyst 42b is still in a temperature range that allows the NOx catalyst 42b is activated by the addition of fuel.

For measuring the catalyst activation time after stopping the engine 1 Fuel is simultaneously with the stopping of the engine 1 added. That means that simultaneously with the operation of the ignition switch 90 to a stop side, a stop signal is output to the ECU. In response, the ECU performs 80 an engine stop control by. Simultaneously with the engine stop control, the ECU performs 80 a catalyst bad by determination. The catalyst deterioration determination control and the engine stop control will be described below.

At the time of stopping the internal combustion engine 1 becomes a stop signal in response to the turning of the ignition switch 90 to the stop side by the ECU 80 detected. Based on the detection signal, the CPU performs 81 an engine stop control carried out in the ROM 82 is stored. Main controls associated with the engine stop control include stopping the fuel delivery system 10 stopping the supply of oxygen to the combustion chambers by closing the throttle valve 32 , the supply of electrical power to devices that also operate after stopping the engine, such as devices associated with the cooling of the engine 1 or the like, setting the turn-off time of the electric power and the like.

Simultaneously with the switching of the ignition key 90 to the stop side, the ECU detects 80 a signal from the catalyst temperature sensor 79 and determines if the catalyst temperature is higher than or equal to a temperature that permits activation of added fuel. Subsequently, the ECU detects 80 a signal from the catalyst exhaust gas inflow temperature sensor 78 and determines a difference between the temperature based on the catalyst exhaust gas inflow temperature sensor 78 and the temperature based on the catalyst temperature sensor 79 , When the of the catalyst temperature sensor 79 detected temperature is higher than the temperature of the catalyst exhaust gas inflow temperature sensor 78 is detected, there is a possibility of a temperature increase reaction occurring in the NOx catalyst 42b occurs, and therefore, the fuel addition after the stop of the internal combustion engine 1 not performed but the normal engine stop control is performed.

When the of the catalyst temperature sensor 79 detected temperature is substantially equal to or lower than the temperature of the catalyst exhaust gas inflow temperature sensor 78 is detected, the period from the previous fuel addition to the current stop of the internal combustion engine 1 and the period of starting the engine 1 until the current stop of the internal combustion engine 1 with reference to in the RAM 83 stored data and the time counter 85 calculated. If one of the periods is equal to or less than a predetermined time, it can be assumed that the present storage of the NOx in the NOx catalyst 42b is less than a predetermined amount of NOx due to the reactions with the added fuel, and therefore, the fuel addition becomes after stopping the engine 1 avoided and normal combustion engine continued control is performed.

When the above-mentioned measured time is equal to or longer than the predetermined time, fuel enters the exhaust passage via the fuel adding nozzle 17 added. At this point, the CPU determines 81 an amount of added fuel S based on the catalyst temperature at the time of fuel addition with reference to a map A (FIG. 5 ), which are in the ROM 82 is stored. Panel A indicates an amount of fuel that must be added to an undiluted fresh catalyst at a predetermined catalyst temperature such that reactions of fuel continue until the catalyst temperature falls to or below a temperature that facilitates activation of the fresh catalyst. Therefore, with reference to Figure A, a predetermined amount of fuel is introduced into the exhaust gas by controlling the electromagnetic solenoid of the fuel supply nozzle 17 added.

In connection with the determination of the ECU 80 For performing the addition of fuel, a stop control of the electric power stored in the ROM 82 the ECU 80 is stored, carried out so that the electrical power of the ECU 80 is not stopped until the catalyst deterioration determination control ends.

The time (Tact) that elapses from the addition of the fuel until the result of the detection based on the signal from the catalyst temperature sensor 79 reaches a predetermined temperature at which the activation of a fresh catalyst stops, is determined by the time counter 85 measured. Furthermore, the CPU reads 81 from a figure B ( 6 ), which are in the ROM 82 is an expected activation time (Ttrg), that is, a time during which a temperature increase reaction of the fuel, which continues to an undiluted catalyst at a predetermined catalyst temperature and a predetermined exhaust gas inflow temperature, before the catalyst temperature reaches a predetermined temperature.

The CPU 81 compares the measured time (Tact) of the time counter 85 from the addition of the fuel until the predetermined temperature is reached, with the expected activation time (Ttrg). If Tact is shorter than Ttrg, the CPU determines 81 that the NOx catalyst 42b has deteriorated. If Tact is longer than Ttrg detects the CPU 81 that the NOx catalyst 42b has not reached a deteriorated state. The CPU saves this 81 these results in the auxiliary RAM 84 and terminates the catalyst deterioration determination control. Then the electrical power of the ECU 80 stopped by the stop control of the electric power.

A specific process of "catalyst deterioration detection control" performed by the ECU 80 of the internal combustion engine 1 is executed according to the embodiment will be described below with reference to the flowchart of 7 described.

First, in S701, the ignition switch 90 switched to the stop page. In response, the ECU performs 80 the engine stop control by. Along with this control, the catalyst deterioration determination control is also performed.

following In S702, it is determined whether the catalyst temperature of the NOx catalyst (Catalyst temperature) equal to the catalyst temperature or greater than this is the one that allows the catalyst to pass through a reducing agent is activated (catalyst activation temperature). When the catalyst temperature greater than is the catalyst activation temperature or equal to this the process continues to the subsequent step. When the catalyst temperature is lower than the catalyst activation temperature the process proceeds to S715 where the fuel addition, that is, the catalyst deterioration determination control, is stopped. Subsequently, in S716, the engine stop control executed. Then the routine ends.

In S703 determines if the catalyst temperature is lower than or equal to the temperature of the exhaust gas that is in the catalyst flows. When the catalyst temperature is lower than or equal to the exhaust gas inflow temperature is, the process proceeds to the subsequent step. When the catalyst temperature is higher as the exhaust gas inflow temperature is the process proceeds to S715, in which the fuel addition is stopped. Subsequently, in S716, the engine stop control executed. Then the routine ends.

In S704, it is determined whether the period between the previous fuel addition, that is, the previous reduction of NOx and the present determination, as well as the period between the start of the internal combustion engine 1 and the present detection are not longer than or equal to the time periods (predetermined periods) necessary for the storage of NOx in the NOx catalyst 42b needed. If the periods are equal to or longer than the predetermined periods, the process proceeds to the subsequent step. If the periods are shorter than the predetermined periods, the process proceeds to S715 where the fuel addition is stopped. Subsequently, the engine stop control is executed in S716. Then the routine ends.

In the aforementioned steps S702 to S704 is determined whether the catalyst deterioration determination control is executable. The steps described below are used to determine whether the catalyst has deteriorated.

In S705 becomes an expected activation time Ttrg from the catalyst temperature and the exhaust gas inflow temperature estimated with reference to Figure B. The following is in S706 the measurement of the activation time started. In S707 is the amount of the added fuel S, according to the catalyst temperature with reference to Figure A, added. Of the Operation then proceeds to the subsequent step.

In S708 to S710, the time elapsing from the execution of step S707 becomes the catalyst temperature is equal to or lower than a predetermined one Value is. In S708 it is determined if the catalyst temperature is equal to or lower than the predetermined value. If the Catalyst temperature equal to or lower than the predetermined Is value, the process proceeds to the subsequent step. In S710, the value "1" is added to the value Tact in S708 it is determined that the catalyst temperature is higher than is the predetermined value, the process proceeds to S709, where "1" is added to Tact. Thereafter, the process returns to S708. This is repeated until the catalyst temperature is equal to or less than the predetermined one Value is.

In S711, the value Tact and the value Ttrg are compared. If the value Tact is lower than the value Ttrg, the process proceeds to S712, where it is determined that the NOx catalyst 42b has worsened. If Tact is greater than or equal to Ttrg, the process proceeds to S713, where it is determined that the NOx catalyst 42b did not worsen. This is the result of S712 or S713 in the auxiliary RAM 84 the routine is saved and ended.

Although in this routine, the process steps associated with the expected activation time, the activation time, and the fuel addition are performed sequentially in S705 to S707 the sequence of these process steps is not limited; For example, these steps may be performed concurrently.

In this embodiment, the periods from the previous fuel addition and the starting of the internal combustion engine 1 measured at the time of the present determination to determine the amount of NOx present in the NOx catalyst 42b is estimated to estimate for the determination. However, other methods of estimating the storage of NOx in the catalyst may be employed. For example, it is suitable to have another NOx sensor and a flow meter upstream of the NOx catalyst enclosure 42 and to store the NOx in the NOx catalyst 42b from the flow rate of the exhaust gas and the difference between the NOx concentrations detected upstream and downstream of the exhaust gas control device. Although the catalyst temperature and the exhaust gas temperature are used as factors for determining the expected activation time in the above-mentioned embodiment, it is also possible to add other factors such as a catalyst atmosphere temperature that changes depending on the water temperature, the air temperature and so on , For the factors determining the amount of added fuel, it is also possible to adopt the exhaust gas temperature, the catalyst atmosphere temperature and so on as factors besides the catalyst temperature. Although in the above-mentioned embodiment, the determination is made on the basis of a single measurement process, it is more preferable to perform the catalyst deterioration determination control multiple times and to make the determination based on collective results to further improve the accuracy of the detection.

Although, in the above embodiment, the catalyst temperature sensor 79 is used as an exhaust gas control device temperature measuring device for directly measuring the catalyst temperature, that is, the temperature of the exhaust gas control device, the exhaust gas device temperature measuring device is not limited thereto. For example, it is also possible, the temperature of the exhaust gas, which from the NOx catalyst 42b is omitted by the use of a temperature sensor downstream of the NOx catalyst 42b is provided, and to use the detected exhaust gas temperature as an indirect catalyst temperature.

In the above embodiment the time is up, until the catalyst temperature rises to a predetermined temperature, used as a criterion to determine if the catalyst has worsened. If different detection criteria provided become possible, it becomes possible the degree of deterioration of a fresh catalyst to the Time of execution the catalyst deterioration determination control as well determine.

The Acceptance of the deterioration determining device and method according to the first embodiment make it possible, independently of different conditions of the internal combustion engine, whether the catalyst has deteriorated.

below becomes a second embodiment in which the deterioration determining device and the method of an engine exhaust control device of the invention are applied to a diesel engine combustion system. In the second embodiment Be constructions with those of the first embodiment are comparable, by comparable reference numerals in the drawings and are not described below.

8th FIG. 10 shows a diesel engine system to which a deterioration determining apparatus and a deterioration determining method according to the second embodiment are applied. This in 8th system shown is not with the NOx sensor 75 , the catalyst temperature sensor 79 and the ignition switch 90 provided in the first embodiment are provided. These components are not essential elements in the second embodiment. This in 8th shown system can with the NOx sensor 75 , the catalyst temperature sensor 79 and the ignition switch 90 be provided as in the first embodiment.

9 shows an electrical construction about an ECU in this embodiment. In comparison with the in 2 The construction shown assumes an ECU 80 in the in 9 shown construction no signals from a NOx sensor, a catalyst temperature sensor and an ignition switch on. The catalyst deterioration determination in this embodiment does not need these signals. However, these signals can be sent to the ECU 80 for a purpose other than the catalyst deterioration determination, in this embodiment.

Further, in this embodiment, the control with respect to the stop of the internal combustion engine 1 "by the ECU 80 is executed as described above in connection with the first embodiment is described, not essential.

When a catalyst regeneration control as described above in connection with the first embodiment is performed, the amount of added fuel as a reducing agent, the addition timing thereof and the like depending on the catalyst temperature (exhaust gas temperature) of the NOx catalyst 42b which is to be regenerated, vary from the amount of NOx stored in the catalyst, and so on. In determining the amount of fuel added and the addition timing, values are calculated based on the exhaust gas control capability of the NOx catalyst 42b fixed to the vehicle at the time of installation. However, the exhaust gas control capability of the NOx catalyst changes 42b due to a time-dependent deterioration or the like when the NOx catalyst 42b used over a long time. Therefore, it is necessary to know the degree of deterioration of the NOx catalyst 42b and to change the control values for use in the NOx catalyst regeneration control according to the degree of deterioration.

The catalyst deterioration determination with respect to the NOx catalyst 42b in this embodiment will be described below. Examples of problems caused in terms of lowered exhaust gas performance of the catalyst include a rise in temperature (ignition temperature) at which oxidation-reduction reactions between the reducing agent added to the exhaust gas and the NOx start from the exhaust gas NOx catalyst 42b is ejected, which is caused by lowering of the oxidation-reduction ability, as in 10 as well as other problems such as a reduction in NOx storage reaction performance including a reduction in the storage of NOx in the NOx catalyst 42b , a reduction in the output of NOx, and so on. When the NO x removal control is performed by using a deteriorated catalyst with respect to a predetermined temperature, which is, for example, occupied by the ignition temperature and the light-off temperature of a catalyst in a new state (fresh catalyst), sufficient NO x removal can be achieved can not be achieved due to the difference in the ignition temperature. That is, when fuel is added to a deteriorated catalyst at approximately the ignition temperature of a fresh catalyst, the fuel is deposited on the deteriorated catalyst or discharged into the atmosphere as an unburned gas because oxidation-reduction reactions on the catalyst do not proceed ,

Also if oxidation-reduction reactions worsened on one Catalyst take place, the point of the highest temperature is through the deteriorated catalyst is achieved due to the temperature raising effect the oxidation-reduction reactions become lower and the reaction rate of it also slower. When the catalyst regeneration control based on a fresh catalyst among the above conditions specified is the temperature of the deteriorated catalyst can highest Reach for the temperature the deteriorated catalyst is possible due to the oxidation-reduction reactions. However, because the catalyst regeneration control is based on a fresh catalyst is carried out, it is determined that the temperature rise due to an insufficient amount of fuel is not which is exposed to the reactions on the catalyst is. This determination gives the possibility of a lot of fuel to add to the catalyst, which is greater than the amount of fuel is necessary to remove NOx. In this case, stores fuel on the catalyst or is from the catalyst as an unburned Gas in the atmosphere emitted.

As a means for measuring the ignition temperature, the catalyst exhaust gas inflow temperature sensor 78 and the catalyst exhaust outflow temperature sensor 74 used. If the exhaust gas contains no reducing agent or if the temperature of the NOx catalyst 42b is lower than the activation temperature, although the exhaust gas contains a reducing agent, the oxidation-reduction reaction between fuel and NOx occurs on the NOx catalyst 42b not up. Therefore, in this state, the exhaust gas temperature Tin at the inlet side of the NOx catalyst 42b and the exhaust gas temperature Tex on the exhaust side of the NOx catalyst 42b essentially the same.

However, when the NOx from the NOx catalyst 42b is removed by the fuel added to the exhaust gas, the oxidation-reduction reactions concerning the removal of NOx cancel the exhaust-side temperature Tex so that Tin results in smaller Tex, and therefore a temperature difference Δt occurs between Tin and Tex. The inlet side temperature Tin at the time of occurrence of a temperature difference Δt is an ignition temperature.

After the ignition temperature is reached, the temperature difference Δt between Tin and Tex is taken into account. Due to a lowering of the NOx storage releasability required for the oxidation-reduction reactions, and more particularly, a lowering of the NOx discharge capability, a deteriorated catalyst allows a smaller amount of catalyst of NOx into the exhaust gas per unit time as a fresh catalyst even in a state where the catalyst atmosphere is rich. Since the exhaust gas contains a sufficient amount of fuel subjected to the oxidation-reduction reactions with the discharged NOx, and therefore raises the catalyst temperature, the amount of the oxidation-reduction reactions per unit time is determined by the amount of discharged NOx.

Therefore occurs due to the difference in the amount of oxidation-reduction reactions per unit time a difference in the increase of the catalyst temperature which causes at the time of the oxidation-reduction reactions becomes.

That is, in the case of a deteriorated catalyst having a reduced amount of oxidation-reduction reactions, the temperature difference Δt between Tin and Tex (Tex-Tin) is not very large as in 11 is indicated. However, in the case of a fresh catalyst having a relatively large amount of the oxidation-reduction reactions, the temperature difference Δt is large.

There Further, a deteriorated catalyst has a reduced oxidation-reduction ability the deteriorated catalyst achieves a lower maximum value a catalyst temperature by oxidation-reduction reactions as the fresh catalyst due to a synergistic effect a reduced discharge amount of NOx, the oxidation-reduction reactions and the reduced oxidation-reduction ability subject to the catalyst.

Under consideration the circumstances mentioned above The catalyst deterioration determination is based on carried out by variations of the temperature difference at the time of ignition temperature occurs between a deteriorated catalyst and a undegraded catalyst. As a method of investigation becomes an ignition detection temperature, as a reference in determining catalyst degradation serves, pre-set and fuel is added when the catalyst in question the ignition determination temperature reached. Based on the presence / absence of a Temperature raising reaction and the degree of reaction will be the Determination carried out with respect to the deterioration of the catalyst.

More specifically, an ignition detection temperature is preset as a reference for the determination of the deterioration. Further, using a catalyst whose ignition temperature is equal to the ignition-purifying temperature, the increase of the temperature of the catalyst caused by addition of the fuel thereto is measured, and is determined as a temperature rise value. Then, the ignition detection temperature and the temperature rise value in the ROM 82 the ECU 80 saved in advance. In the process of deterioration determination, exhaust gas is caused to be in the NOx catalyst 42b flows, and temperatures Tin, Tex become upstream and downstream of the NOx catalyst 42b over the catalyst exhaust gas inflow temperature sensor 78 and the catalyst exhaust outflow temperature sensor 74 measured. At the time when the CPU 81 Detects that the temperatures Tin, Text have reached the ignition initiation temperature sends the CPU 81 a signal to the fuel supply nozzle 17 to add a predetermined amount of fuel into the exhaust gas.

For the fuel addition, a predetermined amount of the NOx in the NOx catalyst 42b verified in advance. The predetermined amount may be set as an amount of NOx required to continue the oxidation-reduction reactions with the added fuel until the catalyst temperature of the NOx catalyst 42b is raised to a maximum value by the oxidation-reduction reactions. Therefore, the aforesaid preset amount of the fuel added is also set as an amount needed to achieve the oxidation-reduction reactions with the above-mentioned stored amount of NOx.

As a means for checking the stored amount of NOx, an image for calculating one of the internal combustion engine is provided 1 ejected amount of NOx from the amount of fuel in the internal combustion engine 1 is injected, and information obtained from the accelerator operation amount sensor 76 , the air / fuel ratio sensor 73 and so on, in the ROM 82 saved in advance. On the basis of the map and the time period between the previous fuel addition and the current fuel addition, the amount of NOx entering the NOx catalyst becomes 42b has flowed, calculated. When the calculated value reaches the predetermined amount of storage of the NOx, it is assumed that the NOx catalyst 42b has stored the predetermined amount of NOx.

When the temperature difference Δt after fuel is added, between the temperatures Tin and Tex flowing through the catalyst exhaust gas inflow temperature sensor 78 and the catalyst exhaust outflow temperature sensor 74 measured, does not exist, the CPU determines 81 that the NOx catalyst 42b worsens Has. When the temperature difference Δt is equal to or greater than the predetermined value, the CPU determines 81 that the NOx catalyst 42b has not deteriorated.

Under Use of the method described above becomes the reducing agent added when the ignition initiation temperature is reached, and it is determined whether the catalyst deteriorates Has. In the detection process, a temperature elevation reaction occurs on when the fuel is at the ignition initiation temperature is added. However, when the temperature difference .DELTA.t smaller is a predetermined value, there is a possibility of insufficient Progress of the temperature raising reaction due to insufficient Amount of NOx stored, an insufficient amount of the reducing agent, that's added, and so on. For this case, therefore, the Determination avoided or will the deterioration determination by to redo of the investigation.

With regard to the "catalyst deterioration determination control" provided by the ECU 80 of the internal combustion engine 1 In this embodiment, a specific process will be described below with reference to the flowchart of FIG 12 described.

First At S601 to S603, the catalyst temperature becomes the ignition-detection temperature brought. When it is determined in S601 that the catalyst temperature higher than the ignition-detection temperature is, this step is repeated until the catalyst temperature lower than the ignition initiation temperature becomes. When the catalyst temperature is less than or equal to the ignition initiation temperature , the process proceeds to the subsequent step. In S602, it is determined whether or not the catalyst temperature is lower equal to the ignition initiation temperature is. If the determination at S610 is "NO", the answer at S602 becomes "YES" because the determination of "NO" at S601 means the catalyst temperature is less than or equal to the ignition initiation temperature is. Then, the process proceeds to S603.

In S603, it is determined whether the catalyst temperature is equal to the ignition initiation temperature is. When the catalyst temperature is the ignition average temperature is the same, the process proceeds to S604 in which a predetermined amount of fuel is added. If it is not determined in S603 that the catalyst temperature the ignition initiation temperature is the same, the process returns to S602. The determination steps from S602 and S603 are repeated until the catalyst temperature the ignition initiation temperature becomes equal. While This repeated process increases the catalyst temperature. When the catalyst temperature over the ignition-detection temperature rises while the detection steps of S602 and S603 are repeated, the Answer at S602 "NO" and the process returns back to S601.

After this the catalyst temperature of the ignition average temperature As a result of the process from S601 to S603 becomes the same, the fuel addition becomes executed in S604.

After fuel is added in S604, it is determined in S605 whether the temperature difference between the exhaust gas inflow temperature detected by the catalyst exhaust gas inflow temperature sensor 78 is measured, and the Abgasausströmungstemperatur, by the Katalysatorabgasausströmungstemperatursensor 74 is measured (Abgasausströmungstemperatur - Abgaseinströmungstemperatur) is less than a predetermined value.

If it is determined that the temperature difference is greater than or equal to a predetermined Is value, the process proceeds to S609 in which it is determined is that the catalyst has not deteriorated. Then ends the routine. If it is determined in S605 that the temperature difference is less than the predetermined value, the process proceeds to the next step.

In S606 becomes a determination of the temperature difference carried out. If the temperature difference is less than 1 ° C, the process proceeds S608, where it is determined that the catalyst is deteriorating Has. Then the routine ends. When the temperature difference is greater than 1 ° C, the process proceeds to S607, in which a clear determination due to the insufficient oxidation-reduction reactions is avoided. Then, the routine ends or the process returns to S601 to start the routine perform the same determination process again.

In the catalyst deterioration determination of this embodiment, fuel is added when the ignition-purifying temperature is reached, and the presence / absence of a temperature-raising reaction caused by the addition of fuel and the amount of the temperature-raising reaction are detected at the same time. However, these factors can be handled separately. For example, it is possible to adopt a process in which the temperature at which the catalyst starts a temperature-raising reaction is detected, and a temperature difference .DELTA.t is detected from the detected temperature, and this value with the Entzün is compared to determine if the catalyst has deteriorated. With respect to a method for detecting the temperature at which the catalyst starts a temperature-raising reaction, fuel is added to a catalyst whose ignition temperature is to be detected when the temperature of the catalyst is low, for example, at the ignition temperature of a fresh catalyst Fuel deposits on the catalyst. Then, the catalyst temperature is raised, and the ignition temperature of the catalyst is detected at which a difference between Tin and Tex due to the deposited fuel occurs. After the ignition temperature is detected, a value Δtmax is detected in a similar manner. This determination method makes it possible to detect the degree of deterioration of a subject catalyst based on the degree of increase in the ignition temperature as well as the presence / absence of deterioration of the catalyst.

The Use of the catalyst deterioration determining device and the method according to this embodiment makes it possible the Deterioration of NOx removal capability of a catalyst without using a NOx sensor.

Although the first and second embodiments as the reducing agent adding means are the fuel adding nozzle 17 which is a fuel injection device provided in the exhaust passage for adding fuel to the exhaust gas, the adding means is not limited thereto. For example, it is possible to add fuel to a combustion chamber at a timing other than the combustion stroke so that the added fuel is discharged from the combustion chamber as unburned fuel that can be used as a reducing agent. That is, the device is not particularly limited as long as a reducing agent can be added to an exhaust gas control device.

Even though in the foregoing description, the apparatus and method the invention mainly in conjunction with a storage-reduction type NOx catalyst is described, the invention is not limited to a NOx catalyst of the memory reduction type, but also to others Catalysts that have a characteristic of warming up in the Have response to an addition of a reducing agent, such as Three-way catalysts for the exhaust gas control of gasoline engines and the like are used Filters, and so on.

at In such applications, the invention realizes deterioration detection as in the above embodiments.

While the Invention is described with reference to what is currently as their preferred embodiments considered, it is understandable that the invention is not limited to the disclosed embodiments or constructions limited is. In contrast, the invention is intended to be various Modifications and equivalents Covers arrangements. While additionally the various elements of the disclosed invention in different Combinations and configurations are shown by way of example are other combinations and configurations including more, less or just a single embodiment within as well the basic idea and the scope of the invention.

With Referring to characteristics of a NOx catalyst having a reduction tendency a catalyst activation ability and a raise inclination the reducing agent activation temperature according to the deterioration of the catalyst As a result, fuel as a reducing agent becomes the NOx catalyst by adding from fuel into the exhaust over a fuel injector added under the condition under which the internal combustion engine stopped is. Then the time that elapses until the temperature of the NOx catalyst is a predetermined temperature reached after rising, measured. If the measured time is shorter than is an expected catalyst activation time, it is determined that the catalyst has deteriorated.

Claims (11)

A deterioration determining device for an exhaust gas control device, characterized by an exhaust gas control device ( 42 ) in an exhaust passage ( 40 ) of an internal combustion engine ( 1 ) is provided and which can be activated by adding a reducing agent; a reducing agent addition device ( 71 ) for adding the reducing agent to the exhaust gas control device (FIG. 42 ) under a condition that the internal combustion engine ( 1 ) stops from an operating condition; an exhaust gas control device temperature measuring device ( 79 ) connected to the exhaust gas control device ( 43 ) is provided for measuring an exhaust gas control device temperature; a temperature acquisition time measuring device ( 80 ) for measuring a time from a time when the reducing agent through the reducing agent addition means ( 71 ) is added, up to ei at the time when the exhaust gas control device temperature decreases to a predetermined temperature after the increase due to the addition of the reducing agent expires; and a deterioration determining means ( 80 ) for determining that the exhaust gas control device ( 42 ) has not deteriorated, when the temperature rise time measuring device ( 80 ) measured time is longer than a predetermined time, and for determining that the exhaust gas control device ( 42 ) has deteriorated when the time measured by the temperature obtaining time measuring means is shorter than a predetermined time. A deterioration determining device according to claim 1, characterized in that when the exhaust gas control device temperature is lower than or equal to a reducing agent activation temperature at which activation is caused by adding the reducing agent, addition of the reducing agent to the exhaust gas control device ( 42 ) despite the stopping of the internal combustion engine ( 1 ) is avoided. Deterioration detection device according to claim 1 or 2, characterized in that the exhaust gas control device ( 42 ) further comprises an exhaust gas temperature measuring device ( 78 ) upstream of the exhaust control device (FIG. 42 ) for measuring a temperature of an exhaust gas inflow into the exhaust gas control device ( 42 ), and when the exhaust gas control device temperature is higher than the temperature of the exhaust gas inflow, the addition of the reducing agent to the exhaust gas control device (FIG. 42 ) despite the stopping of the internal combustion engine ( 1 ) is avoided. Deterioration determining device according to one of claims 1 to 3, characterized in that the exhaust gas control device ( 42 Further, a memory reduction function for storing a nitrogen oxide present in the exhaust gas in a main body of the exhaust gas control device (FIG. 42 When the exhaust gas inflow is in a state of excessive oxygen concentration, and for discharging and reducing the nitrogen oxide stored in the main body when the exhaust gas inflow is in a state of low oxygen concentration. Deterioration detection device according to claim 4, characterized in that the exhaust gas control device ( 42 ) comprises a storage estimating means for estimating a storage amount of the nitrogen oxide, and when it is estimated by the storage estimating means that the storage amount of the nitrogen oxide is less than or equal to a predetermined amount, the addition of the reducing agent to the exhaust gas control apparatus ( 42 ) despite the stopping of the internal combustion engine ( 1 ) is avoided. A deterioration determination method for an exhaust gas control device for determining a deterioration of the exhaust gas control device (FIG. 42 ) in an exhaust passage ( 40 ) of the internal combustion engine ( 1 ) is provided, characterized by adding a reducing agent to the exhaust gas control device ( 42 ) to the exhaust control device ( 42 ) when it is detected that an internal combustion engine ( 1 ) is about to stop while the internal combustion engine ( 1 ) is in operation, and wherein the exhaust gas control device is activatable by adding a reducing agent; Measuring a time that elapses from the addition of the reducing agent until a temperature of the exhaust gas control device ( 42 ) is reduced to a predetermined temperature; and determining that the exhaust gas control device ( 42 ) has not degraded, when the measured time is longer than a predetermined time, and determining that the exhaust gas control device ( 42 ) has deteriorated if the time is shorter than a predetermined time. Deterioration determination device for an exhaust gas control device, characterized by a catalyst ( 42b ) in an exhaust passage ( 40 ) of an internal combustion engine ( 1 ) for controlling one of the internal combustion engine ( 1 ) exhaust gas is provided; a catalyst exhaust gas inflow temperature measuring device ( 78 ) for measuring a temperature of an exhaust gas flow entering the catalyst ( 42b flows in; a catalyst temperature measuring device ( 74 ) for measuring a catalyst temperature of the catalyst ( 42b ); a reducing agent addition device ( 17 ) for adding a reducing agent to the catalyst ( 42b ); a temperature difference detection device ( 80 ) for detecting a difference in the catalyst temperature from the temperature of the exhaust gas inflow, which occurs when the reducing agent to the catalyst ( 42b ) by the reducing agent addition device ( 17 ) will admit; and a deterioration determining means ( 80 ) to determine that the catalyst ( 42b ) has deteriorated when a condition that the detected temperature of the exhaust gas inflow when the occurrence of a temperature difference by the temperature difference detecting means (FIG. 80 ) is detected, greater than a predetermined temperature is, is fulfilled. Deterioration determining device according to claim 7, characterized in that the reducing agent adding device ( 17 ) realizes the addition of the reducing agent when the catalyst temperature reaches a reference temperature which is set as a temperature at which an oxidation-reduction reaction starts at an undiluted catalyst. Deterioration detection device according to claim 7 or 8, characterized in that the exhaust gas control device Further, a memory reduction function for storing a nitrogen oxide present in the exhaust gas in a main body the exhaust gas control device when the exhaust gas inflow in a condition of excessive oxygen concentration and for draining and reducing the nitrogen oxide that in the main body is stored when the exhaust gas inflow in a state lower Oxygen concentration is located. Deterioration detection device according to claim 9 characterized in that the exhaust gas control device a memory estimator to appreciate a storage amount of the nitrogen oxide, and if by the memory estimator is appreciated that the storage amount of the nitrogen oxide is less than or equal to a predetermined amount, the addition of the reducing agent is avoided by the reducing agent addition device. A deterioration determination method for an exhaust gas control device, characterized by adding a fuel to a catalyst ( 42b ) provided within an exhaust gas control device used in an exhaust system ( 40 ) of an internal combustion engine ( 1 ) is provided when a temperature of the catalyst ( 42b ) becomes equal to or greater than a temperature at which an oxidation-reduction reaction starts from an undiluted catalyst; Measuring a catalyst temperature and an upstream exhaust gas temperature on an upstream side of the catalyst ( 42b ); and determining that the catalyst has deteriorated when a condition that the detected temperature of the exhaust gas inflow when the occurrence of a temperature difference by the temperature difference detecting means ( 80 ) is detected, is greater than a predetermined temperature, is met.