JPH07180615A - Exhaust recycle control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To surely remove an object adhering to an EGR valve or a recycle passage by forcedly opening the EGR valve to variably control the opening according to the running condition of an internal combustion engine for keeping then EGR quantity to fixed quantity during speed reducing fuel cutting in an internal combustion engine. CONSTITUTION:The opening of an EGR valve 6 detected by a lift quantity sensor 18 is inputted together with the outputs of an intake-air negative-pressure sensor 19 and an engine-speed sensor 20 into a control device 30 to be used in target-value operation when the opening of the EGR valve 6 is controlled. In speed reducing fuel-cutting running in an internal combustion engine, the EGR valve 6 is forcedly opened, and the opening of it is variably controlled according to an engine speed so that EGR quantity during the speed reducing fuel cutting can be kept at a fixed quantity wherein an attachment to the EGR valve 6 or an exhaust gas recycle passage 5 can be removed to the minimum. In variably controlling such an EGR valve opening, an exclusive target-value map, wherein the target opening of the EGR valve 6 is preset according to the engine speed, is used to decide a valve opening.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device for an internal combustion engine mounted on a vehicle and recirculating a part of the exhaust gas to the intake system of the engine, and more particularly to an exhaust gas recirculation control valve. The present invention relates to the improvement of the exhaust gas recirculation control device configuration suitable for always properly maintaining the state of the recirculation system such as automatically removing the deposits.

[0002]

2. Description of the Related Art As is well known as an exhaust gas recirculation control device, a part of gas discharged from an internal combustion engine mounted on a vehicle is taken out from an exhaust system, and an appropriate temperature, timing, flow rate, etc. are controlled for this gas. It is a device that recirculates to the intake system of the engine. Also,
By recirculating exhaust gas to the intake system,
The combustion temperature of the gas can be lowered, and NOx which is a harmful component in the combustion exhaust gas (N
It is also well known that the generation of O and NO2) becomes suppressed.

By the way, such an exhaust gas recirculation control device usually has at least a recirculation passage for recirculating a part of the exhaust gas of the internal combustion engine to the intake system of the engine and an exhaust gas recirculation control valve for opening and closing the recirculation passage. It is configured to have. In the exhaust gas recirculation control device, due to the nature of recirculating the combustion exhaust gas through the recirculation passage and the exhaust gas recirculation control valve, foreign matter may adhere to the recirculation passage and the exhaust gas recirculation control valve, which are the paths. . If foreign matter adheres to the recirculation passage or the exhaust recirculation control valve and the recirculation control valve sticks, the above-mentioned exhaust recirculation control itself becomes impossible, and the above-mentioned NOx suppression is also insignificant.

Therefore, conventionally, for example, Japanese Patent Laid-Open No. 4-2596
As in the device described in Japanese Patent No. 53, the exhaust gas recirculation control valve is forcibly opened by the intake negative pressure remaining in the surge tank when the engine is stopped, and is attached to the recirculation control valve. I was trying to suck the kimono into the intake passage.

[0005]

As described above, if it is possible to remove the adhering matter adhering to the exhaust gas recirculation control valve by sucking it into the intake passage, the recirculation control valve seems to be stuck. Things will certainly be avoided.

However, normally, with the intake negative pressure remaining in the surge tank when the engine is stopped, even when the exhaust gas recirculation control valve is forcibly opened, the differential pressure upstream and downstream of the valve is small, It is not always possible to obtain a sufficient air flow for sucking the deposits into the intake passage.

Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-9937, the exhaust gas recirculation control valve is forcibly opened at the time of deceleration fuel cut, and the intake pressure before and after the recirculation control valve is opened. Techniques for performing failure diagnosis of those recirculation systems based on fluctuations are known.

Further, for example, in Japanese Unexamined Patent Publication No. 4-58026, the exhaust gas recirculation control valve and the ISC are also used at the time of fuel cut (however, when the engine speed is equal to or higher than a predetermined speed).
(Idle speed control) A technique is disclosed in which both the valve and the valve are forcibly opened to increase the amount of intake air, which in turn reduces the consumption of lubricating oil.

As described above, even though it is not intended to remove the foreign matter adhering to the exhaust gas recirculation control valve, the engine is forcedly opened during fuel cut while the engine is operating. Techniques for making valves are known. It is certainly expected that if the exhaust gas recirculation control valve is forcibly opened during operation in this manner, a sufficient air flow for sucking the deposits into the intake passage will be obtained.

However, if the exhaust gas recirculation control valve is forcibly opened while the engine is rotating at high speed even during fuel cut, the differential pressure upstream and downstream of the recirculation control valve is large, and the intake air amount is also large. Since it is increased, it may cause a drivability failure such that the so-called engine brake does not work properly.

On the contrary, even if the exhaust gas recirculation control valve is forcibly opened while the engine is rotating at a low speed, the amount of intake air does not increase much, and the air flow for sucking the deposits into the intake passage is still small. There is a concern that it may not be enough.

The present invention has been made in view of the above circumstances, and it is possible to reliably remove the deposits adhering to the exhaust gas recirculation control valve and the recirculation passage, and also to improve drivability. An object of the present invention is to provide an exhaust gas recirculation control device for an internal combustion engine that can be maintained.

[0013]

In order to achieve such an object, according to the present invention, a recirculation passage for recirculating a part of exhaust gas of an internal combustion engine to an intake system of the engine and opening / closing the recirculation passage. The exhaust gas recirculation control valve and the operating conditions of the internal combustion engine for forcibly opening the exhaust gas recirculation control valve during deceleration fuel cut of the internal combustion engine and maintaining the exhaust gas recirculation amount during the deceleration fuel cut at a constant amount. And a control means for variably controlling the opening of the exhaust gas recirculation control device for the internal combustion engine.

[0014]

[Function] By forcibly opening the exhaust gas recirculation control valve during deceleration fuel cut of the internal combustion engine, it is possible to obtain a sufficient air flow for sucking the deposits on the recirculation control valve into the intake passage. What is expected is as described above.

Further, even though the fuel is being cut, forcibly opening the exhaust gas recirculation control valve when the engine is rotating at high speed causes a drivability defect,
On the contrary, it is difficult to obtain a sufficient air flow for removing the deposit even if the control valve is forcibly opened while rotating at a low speed.

Therefore, here, through the above control means,
During the deceleration fuel cut of the internal combustion engine, in addition to forcibly opening the exhaust gas recirculation control valve, in order to maintain the exhaust gas recirculation amount during the deceleration fuel cut to a constant amount, the The opening is variably controlled.

That is, this means that when the engine is rotating at a high speed during the deceleration fuel cut, the drivability failure such as the engine braking not being effective is not brought about based on the understanding of the operating conditions, and moreover, the above-mentioned. This means that the opening degree of the exhaust gas recirculation control valve that is forcibly opened is controlled to the side that suppresses the opening degree so that the minimum air flow for removing the adhering matter is obtained. On the other hand, during the same deceleration fuel cut, when the engine is rotating at low speed,
Also in this case, it means that the opening degree of the exhaust gas recirculation control valve that is forcibly opened is controlled so as to be increased so that the minimum air flow for removing the adhering matter is obtained.

As described above, the operating conditions of the internal combustion engine are set to maintain the exhaust gas recirculation amount during deceleration fuel cut to a constant amount, that is, a constant amount that can remove the deposits on the exhaust gas recirculation control valve to a minimum. Accordingly, by controlling the opening degree variably, it becomes possible to remove deposits on the control valve and the return passage while maintaining the drivability appropriately. By properly removing the adhering matter in this way, the exhaust gas recirculation control valve is prevented from sticking and changes in the flow rate characteristics of the exhaust gas recirculation control are prevented.

The operating conditions of the internal combustion engine that can be referred to for controlling the opening degree of the exhaust gas recirculation control valve include not only the engine speed but also the intake air amount into the engine intake system and the intake pipe internal pressure. is there. Of these, the engine speed is particularly effective as an element that allows the operating conditions to be more directly ascertained, and when the operating condition is the engine speed, the control means described above is also used. Thus, according to the engine speed, the opening degree of the exhaust gas recirculation control valve is controlled to be smaller as the engine speed is higher, and the opening degree of the exhaust gas recirculation control valve is controlled to be larger as the engine speed is lower.

Further, as such an exhaust gas recirculation control device,
(A) The exhaust gas recirculation control valve is forcibly opened during deceleration fuel cut of the internal combustion engine, and the presence or absence of failure of the recirculation control valve is diagnosed based on the difference in intake pressure before and after the recirculation control valve is opened. And (b) diagnostic condition control means for variably controlling the opening degree of the exhaust gas recirculation control valve according to the operating condition of the internal combustion engine so as to maintain the intake pressure difference constant during the diagnosis. Can be further provided.

The fault diagnosing means (a) itself is well known. However, the difference in intake pressure before and after opening the exhaust gas recirculation control valve is also usually changed according to the operating conditions of the engine, and the exhaust gas recirculation control valve is simply forced to open. However, the only problem is how to set the reference for determining the presence or absence of a failure for this difference in intake pressure.

Therefore, by providing the above-mentioned diagnostic condition control means (b), it is possible to improve the variation in the intake pressure difference before and after the exhaust gas recirculation control valve is opened in accordance with the operating condition of the engine. Be able to absorb. This also makes it possible to obtain more reliable information about the diagnosis result by the failure diagnosis means.

The operating conditions of the internal combustion engine, which can be referred to in controlling the opening degree of the exhaust gas recirculation control valve in this case, include the rotational speed of the engine, the intake air amount to the engine intake system, and the intake pipe internal pressure. and so on. Also here, the engine speed is particularly effective as an element that allows the operating conditions to be more directly grasped. When the operating condition to be referred to is the engine speed, the diagnosis condition control means, in accordance with the engine speed, decreases the opening degree of the exhaust gas recirculation control valve as the engine speed increases, and exhausts as the engine speed decreases. The degree of opening of the recirculation control valve will be greatly controlled.

Further, as the above-described exhaust gas recirculation control device, (c) at the start of deceleration fuel cut of the internal combustion engine, the opening degree of the exhaust gas recirculation control valve is gradually opened from 0 to the opening degree controlled by the control means. Further, it further comprises a gradual change control means for gradual change control. It can also be configured.

According to the structure further including such a gradual change control means, it becomes possible to obtain a better drivability, for example, a feeling of rapid deceleration due to engine braking is alleviated.

Further, the gradual change control means, the failure diagnosis means and the diagnosis condition control means may be combined with the exhaust gas recirculation control device. With such a configuration, the exhaust gas recirculation control device can be realized as a device that also has the above-described operational effects of the respective means.

[0027]

FIG. 1 shows the configuration of an embodiment of an exhaust gas recirculation control device for an internal combustion engine according to the present invention.

Now, in the exhaust gas recirculation control system of this embodiment shown in FIG. 1, a gasoline engine is assumed as the engine (internal combustion engine) 1. The engine 1 has an intake passage (intake pipe) 2 for taking air into a cylinder (not shown) in the engine 1 and an exhaust passage (exhaust pipe) for exhausting combustion gas from the engine 1.
3 and 3 are connected.

Then, the exhaust passage 3 and the intake passage 2
An exhaust gas recirculation passage (recirculation passage) 5 is provided in the exhaust gas passage 3, and the exhaust passage 3 and the intake passage 2 are connected by the recirculation passage 5.

That is, as shown in FIG. 1, one end of the exhaust gas recirculation passage 5 is opened to the exhaust passage 3, and the other end is located downstream of the throttle valve 4 in the intake passage 2. The exhaust gas is opened so that a part of the exhaust gas is returned to the intake passage 2 through the return passage 5.

A negative pressure responsive exhaust gas recirculation control valve 6 is provided in the middle of the recirculation passage 5. The exhaust gas recirculation control valve 6 is for adjusting the amount of exhaust gas recirculated to the intake passage 2.

That is, the exhaust gas recirculation control valve 6 has a valve body 7
The recirculation passage 5 is controlled to be opened and closed by the vertical movement of the valve body 7. The valve body 7 is supported by the diaphragm 8 via a rod 9.

On the other hand, the exhaust gas recirculation control valve 6 has a negative pressure chamber (diaphragm chamber) partitioned by the diaphragm 8.
It has two air chambers, that is, an air chamber 10 and an atmosphere chamber 11, and together with these air chambers, through the devices and mechanisms described below,
The vertical movement of the valve body 7 is controlled.

First, the negative pressure chamber 10 includes the negative pressure solenoid valve 1
Through the negative pressure introduction passage 13 in which 2 is arranged, it is communicated with the negative pressure outlet 14 of the intake passage 2. The negative pressure outlet 14 is provided in the intake passage 2 immediately downstream of the throttle valve 4.

The negative pressure chamber 10 is also in communication with the atmosphere through an atmosphere introducing passage 16 in which an atmosphere solenoid valve 15 is arranged. A compression coil spring 17 is disposed inside the negative pressure chamber 10, and a combined negative pressure formed by the intake negative pressure (intake pipe negative pressure) at the communication destination and the atmospheric pressure is applied to the coil. When the diaphragm 8 is displaced against the spring force of the spring 17, the valve body 7 supported by the diaphragm 8 moves upward. That is, the valve body 7
Is configured to increase the effective passage area of the return passage 5 as the negative pressure in the negative pressure chamber 10 increases. The combined negative pressure inside the negative pressure chamber 10 is the negative pressure solenoid valve 12 described above.
And the amount of drive of the atmosphere solenoid valve 15 are determined.

In this way, by driving and controlling the negative pressure solenoid valve 12 and the atmospheric solenoid valve 15, the communication mode between the negative pressure chamber 10 and the intake negative pressure and the atmosphere can be controlled, and by extension, the same. An operating negative pressure corresponding to the target exhaust flow rate can be applied to the negative pressure chamber 10.

A lift amount sensor 18 is provided in the exhaust gas recirculation control valve 6, and the movement amount (lift amount) of the valve body 7, that is, the opening degree of the exhaust gas recirculation control valve 6 is provided through the lift amount sensor 18. It is supposed to be detected.

On the other hand, the control device 30 controls each driving amount of the negative pressure solenoid valve 12 and the atmospheric solenoid valve 15 so as to apply the working negative pressure corresponding to the target exhaust flow rate to the negative pressure chamber 10. It is a device. It is assumed that the negative pressure solenoid valve 12 and the atmospheric solenoid valve 15 are driven, that is, opened and closed, by so-called duty control which is well known as one of pulse width modulation methods.

The controller 30 includes the lift amount sensor 18, an intake negative pressure sensor 19 provided in, for example, a surge tank (not shown) of the engine 1, and a crankshaft (not shown) of the engine 1. The engine speed sensor 20 provided is connected.

Of these, the opening degree of the exhaust gas recirculation control valve 6 detected by the lift amount sensor 18 is input to the control device 30 as a signal Ps and is controlled by the control device 30. It is used as a monitor signal for the opening.

Further, the intake negative pressure of the engine 1 detected by the intake negative pressure sensor 19 and the engine speed detected by the rotation speed sensor 20 are taken into the control device 30 as a signal Pm and a signal Ne, respectively, and It is used for calculating a target value when controlling the opening degree of the exhaust gas recirculation control valve 6.

A storage device 31 is connected to the control device 30. The storage device 31 includes a target value map, which will be described later, for the opening degree of the exhaust gas recirculation control valve 6 (the lift amount of the valve body 7) and a control device 30 configured as an arithmetic logic operation circuit by a microcomputer. A control program and the like are stored in advance.

In FIG. 1, for convenience, the so-called fuel supply system for supplying fuel (gasoline) to the engine 1 is omitted. FIG. 2 shows a specific configuration example of the control device 30. Next, the configuration and function of the control device 30 will be described in more detail with reference to FIG.

The control device 30 includes the CPU 301,
Data memory 302, map memories 303, 304 and 305, input interface 306, output interface 307, analog multiplexer 308, A /
It comprises a D converter 309 and a counter 310.

Of these, the input interface 306
Is for inputting the engine speed signal Ne detected by the engine speed sensor 20, and the output interface 307 is a drive signal (duty control signal) for the negative pressure solenoid valve 12 and the atmospheric solenoid valve 15. Is for outputting.

Also, the analog multiplexer 308 is
The opening degree signal Ps of the exhaust gas recirculation control valve 6 detected by the lift amount sensor 18 and the intake negative pressure signal Pm detected by the intake negative pressure sensor 19 are selectively fetched. These captured signals Ps or Pm are
Through the A / D converter 309, it is converted into a digital signal which can be directly handled by the control device 30.

The counter 310 is for counting the number of pulses of the engine speed signal Ne input as a pulse signal. By counting the number of pulses, the engine speed Ne of the engine 1 is controlled by the counter 310. It becomes to be grasped by 30.

Further, the CPU 301 and the data memory 30
2, the map memories 303 to 305, the input interface 306, the output interface 307, the A / D converter 309, and the counter 310 are connected to each other by the address / data bus 311. Address signals and data are exchanged between these elements through the address / data bus 311.

Similarly, the CPU 301, the data memory 302, the map memories 303 to 305, the input interface 306, the output interface 307, the analog multiplexer 308, and the counter 310 are mutually connected by the control bus 312. Between each of these elements, through the control bus 312,
Control signals will be exchanged with each other.

On the other hand, the storage device 31 is also connected to the CPU 301 via the address / data bus and the control bus, and the control program, map data, etc. stored therein are accessed by the CPU 301 so that the control device 30 stores the stored control programs and map data. The data is read by the (CPU 301).

By the way, the storage device 31 previously stores a lift amount target value map as shown in FIG. This lift amount target value map is obtained by the current engine speed Ne of the engine 1 detected by the engine speed sensor 20 and the current intake negative pressure Pm detected by the intake negative pressure sensor 19. A target opening degree Pr of the exhaust gas recirculation control valve 6 corresponding to the optimum exhaust gas recirculation amount is incorporated. That is, the lift amount target value Pr of the valve body 7 for applying the operating negative pressure corresponding to the target exhaust gas recirculation amount to the negative pressure chamber 10 is stored. It should be noted that in this map, the target value P of the lift amount is arranged in a matrix for each predetermined engine speed Ne and each predetermined intake negative pressure Pm.
r is prepared.

The map memory 303 also stores the solenoid drive map shown in FIG. As shown in FIG. 4, in this solenoid drive map, the deviation P (P = Pr−Ps) between the target value Pr of the opening degree of the exhaust gas recirculation control valve 6 and the current detected opening degree Ps, and the negative pressure Solenoid valve 12
The relationship with the duty ratio of the atmospheric solenoid valve 15 is stored. This duty ratio is set to increase as the absolute value of the deviation value P increases. Further, this solenoid drive map shows a dead zone (-) in which the exhaust gas recirculation control valve 6 is held in the state at that time when the detected value Ps regarding the opening degree of the exhaust gas recirculation control valve 6 is close to the target value Pr. aa). The presence of such a dead zone region not only stabilizes the control but also improves the durability of the solenoid valves 12 and 15.

Further, the map memory 304 has a lift amount target value map at the time of failure diagnosis as shown in FIG. 5, and the map memory 305 has a lift amount at the time of deceleration fuel cut as shown in FIG. A target value map is stored.

In the apparatus of this embodiment, when the deceleration fuel cut for the purpose of improving the fuel consumption is being executed, the malfunction of the exhaust gas recirculation control valve 6 is diagnosed and the deposits on the exhaust gas recirculation control valve 6 are removed. Do the action for.

First, regarding the failure diagnosis of the exhaust gas recirculation control valve 6, for example, when the change in the engine speed Ne per unit time is small, it is determined that the condition for carrying out the failure diagnosis is satisfied,
Perform fault diagnosis. In this failure diagnosis, there is no failure depending on whether the exhaust gas recirculation control valve 6 is changed from the “fully closed state” to the “open”, and the change amount of the intake pipe internal pressure (intake negative pressure) Pm at that time is equal to or more than a predetermined value. Alternatively, the presence is determined. In such a failure diagnosis, the target value of the opening when the exhaust gas recirculation control valve 6 is changed from the “fully closed state” to the “open” is the map memory 30 as the lift amount target value map (FIG. 5) in the failure diagnosis.
Registered in 4. Incidentally, the lift amount target value map at the time of this failure diagnosis is set such that a smaller value is selected as the opening degree of the exhaust gas recirculation control valve 6 as the engine speed Ne is higher, as shown in FIG. Specifically, (1) The exhaust gas recirculation control valve 6 is opened from "fully closed state".
Then, the intake pipe pressure (intake negative pressure) Pm changes. (2) The exhaust gas recirculation control valve 6 is opened from the "fully closed state".
The amount of change in the intake pipe internal pressure Pm at this time is constant regardless of the engine speed Ne. The map matching condition is set so that Note that the opening degree information of the exhaust gas recirculation control valve 6 selected through this map is a value corresponding to the target value Pr for the opening degree of the exhaust gas recirculation control valve 6 set through the lift amount target value map shown in FIG. Has become.

On the other hand, when the conditions for carrying out the failure diagnosis are not satisfied, or when it is determined through the failure diagnosis that the exhaust gas recirculation control valve 6 is normal, the exhaust gas recirculation control valve 6 is
An operation is performed to remove deposits on the surface. To remove such deposits, the exhaust gas recirculation control valve 6 is forcibly opened.
And the same reflux control valve 6 at that time
The target value of the opening when "open" is registered in the map memory 305 as the lift amount target value map (FIG. 6) at the time of deceleration fuel cut. As shown in FIG. 6, the lift amount target value map at the time of deceleration fuel cut is also set such that a smaller value is selected as the opening degree of the exhaust gas recirculation control valve 6 as the engine speed Ne is higher. However, in the case of the map, in detail, (1) during deceleration fuel cut, when the engine speed Ne is high, it is the minimum to remove the deposit without causing drivability defects such as engine braking not being effective. Obtaining a limited air flow. (2) During the same deceleration fuel cut, the minimum air flow for removing the deposits is obtained even if the engine speed Ne is low. The map matching condition is set so that The opening degree information of the exhaust gas recirculation control valve 6 selected through this map is also a value corresponding to the target value Pr for the opening degree of the exhaust gas recirculation control valve 6 set through the lift amount target value map shown in FIG. Has become.

FIGS. 7 and 8 show the exhaust gas recirculation control procedure by the exhaust gas recirculation control device of this embodiment. Next, referring also to FIGS. 7 and 8, the device of the same embodiment will be described. The operation of will be described in detail.

In the exhaust gas recirculation control device of this embodiment, the exhaust gas recirculation control routines listed below are started every predetermined time. First, step 1001 and step 1002
At, it is determined whether the engine speed Ne is a predetermined value or more and the throttle valve 4 is fully closed. That is, it is determined whether or not the deceleration fuel cut condition is satisfied. The opening of the throttle valve 4 is detected by a well-known throttle sensor or the like.

When it is determined that the deceleration fuel cut condition is not satisfied, the normal exhaust gas recirculation control 1100 is executed under the normal fuel injection. That is, in this normal exhaust gas recirculation control 1100, in step 1101, the engine speed Ne is read based on the output of the engine speed sensor 20, and the value is stored in the storage area M1 of the data memory 302 (FIG. 2). .

Similarly, in step 1102, the intake negative pressure Pm is read from the output of the intake negative pressure sensor 19, and the value (digital conversion value) is stored in the storage area M2 of the data memory 302.

Next, at step 1103, based on the engine speed Ne and the intake negative pressure Pm, the storage device 3
The target opening degree (lift amount) Pr of the exhaust gas recirculation control valve 6 is obtained from the lift amount target value map (FIG. 3) stored in No. 1 by using the interpolation method, and is stored in the storage area M3 of the data memory 302. .

Then, in step 1104, the drive control of the exhaust gas recirculation control valve 6 based on the obtained target value Pr is executed. The drive control of the exhaust gas recirculation control valve 6 is executed in the following procedure based on the drive control routine of the exhaust gas recirculation control valve shown in FIG.

First, at step 101, the current opening degree (lift amount) Ps of the exhaust gas recirculation control valve 6 is obtained based on the output of the lift amount sensor 18, and this is stored in the storage area M4 of the data memory 302, and the next In step 102, the target value P
A deviation value P (= Pr-Ps) between r and the detected value Ps is calculated.

Next, at step 103, it is judged if the deviation value P is within a predetermined range (-a≤P≤a).
As a result, when it is determined that the deviation value P is within the predetermined range, the negative pressure solenoid valve 12 and the atmospheric solenoid valve 15 are both maintained as they are in the dead zone region to stabilize the control system. At the same time, the durability of those solenoid valves is secured.

When it is determined in step 103 that the opening degree (lift amount) of the exhaust gas recirculation control valve 6 is not in the dead zone, the deviation value P is set to the lower limit of the dead zone in step 110. It is determined whether it is smaller than "-a". That is, it is determined whether the lift amount of the exhaust gas recirculation control valve 6 should be reduced or increased, in other words, whether the atmosphere or the negative pressure should be introduced into the negative pressure chamber 10.

As a result, when the deviation value P is smaller than the lower limit value "-a" of the dead zone, it is judged that the negative pressure should be introduced, and the negative pressure introducing process 120 to the negative pressure chamber 10 is executed. Run. In this negative pressure introduction process 120, step 12
At 1, the time information tp corresponding to the same deviation value P is read from the solenoid drive map (FIG. 4) registered in the map memory 303, and at step 122, the negative pressure solenoid valve 12 is opened for this time tp. Yes (duty control). At that time, the atmospheric solenoid valve 15 is kept closed.

As a result of the judgment, if the deviation value P is larger (not smaller) than the lower limit value "-a" of the dead zone, it is judged that the atmosphere should be introduced, and the atmosphere to the negative pressure chamber 10 is judged. The introduction process 130 is executed. In this atmosphere introduction process 130, in step 131, the time information ta corresponding to the deviation value P is read from the solenoid drive map (FIG. 4) registered in the map memory 303, and step 13
At 2, the atmospheric solenoid valve 15 is opened for this time ta (duty control). At this time, the negative pressure solenoid valve 12 is kept closed.

On the other hand, the above steps 1001 and 1002
In step 1, if it is determined that the engine speed Ne is equal to or higher than a predetermined value and the throttle valve 4 is fully closed, the deceleration fuel cut condition is satisfied.
The deceleration fuel cut is implemented as 200.

Then, in step 1201, it is determined whether or not the above-described failure diagnosis execution condition for the exhaust gas recirculation control valve 6 is satisfied. The conditions for performing the failure diagnosis are as described above: The change in the engine speed Ne per unit time is small (the change is within a predetermined value). In addition, -The intake negative pressure sensor 19 has not failed. Etc. When it is determined in step 1201 that the condition for performing the failure diagnosis is satisfied, the failure diagnosis process 1210 is executed in the following manner.

In this failure diagnosis processing 1210, first, at step 1211, the current intake negative pressure Pm is read, and this is set as the intake negative pressure P1, and the storage area M of the data memory 302 is read.
Store in 5.

Next, at step 1212, the engine speed Ne is read based on the output of the engine speed sensor 20, and the value is stored in the storage area M1 of the data memory 302. The opening target value Pr of the exhaust gas recirculation control valve 6 to be set is set (selected) based on the lift amount target value map (FIG. 5) registered in the map memory 304 at the time of the failure diagnosis, and this is set in the data memory 30.
The data is stored in the second storage area M3 (step 1213). The drive of the exhaust gas recirculation control valve 6 is controlled based on the set and stored target value Pr (step 1214). After such processing, the exhaust gas recirculation control valve 6 is opened. The drive control of the exhaust gas recirculation control valve 6 in step 1214 is executed in the same procedure as the procedure described above with reference to FIG.

After opening the exhaust gas recirculation control valve 6 in this way, as a step 1215, a predetermined time elapses until the intake negative pressure Pm settles to a constant value, and then a step 121
At 6, the current intake negative pressure Pm is read again. Regarding the intake negative pressure Pm read again, this is set to the intake negative pressure P2.
Is separately stored in the storage area M6 of the data memory 302.

Then, in step 1217, the difference between the intake negative pressures P1 and P2 stored in the storage areas M5 and M6 of the data memory 302, that is, when the exhaust gas recirculation control valve 6 is changed from "fully closed" to "open" It is determined whether or not the amount of change in the intake pipe pressure (intake negative pressure) Pm is equal to or greater than a predetermined value.

Here, if the difference between the intake negative pressures P1 and P2, that is, the amount of change in the intake negative pressure Pm is less than the predetermined value, an abnormality determination is made in step 1218, and the processing ends. In this way, when the abnormality determination for the exhaust gas recirculation control valve 6 is performed, thereafter, the target value Pr of the opening degree is set to "0",
That is, it is possible to take measures such as suspending execution of the exhaust gas recirculation control until the cause is eliminated by maintaining the valve "fully closed".

If it is determined in step 1217 that the amount of change in the intake negative pressure Pm (P2-P1) is equal to or greater than the predetermined value, then the exhaust gas recirculation control valve 6 is determined to be normal. Assuming that, the process proceeds to execution of the exhaust gas recirculation control 1220 at the time of the next deceleration fuel cut.

In this failure diagnosis processing 1210, when the exhaust gas recirculation control valve 6 is opened through the drive control (FIG. 8) in the above step 1214, (1) the exhaust gas recirculation control valve 6 is in the “fully closed state”. When changing from "open" to "open", the intake pipe internal pressure (intake negative pressure) Pm changes. (2) The amount of change in the intake pipe internal pressure Pm when the exhaust gas recirculation control valve 6 is changed from the “fully closed state” to the “open” is constant regardless of the engine speed Ne. The target value Pr of the opening degree is set based on the lift amount target value map (FIG. 5) at the time of the failure diagnosis.

Therefore, the threshold value for the failure diagnosis, that is, the "predetermined value" set for the change amount (P2-P1) of the intake negative pressure Pm may be a single value. Highly reliable failure diagnosis can be performed using the "predetermined value" as a threshold.

On the other hand, when it is judged in the step 1201 whether or not the failure diagnosis execution condition is satisfied, it is judged that the execution condition is not satisfied, or the failure diagnosis processing 121.
As a result of 0, when it is determined that the exhaust gas recirculation control valve 6 is normal, the exhaust gas recirculation control 1220 at the time of deceleration fuel cut is further executed according to the following procedure.

First, at step 1221, the engine speed Ne is read based on the output of the engine speed sensor 20, and the value is stored in the storage area M1 of the data memory 302.

Next, at step 1222, the opening target value Pr of the exhaust gas recirculation control valve 6 corresponding to the stored engine speed Ne is registered in the map memory 305 and the lift amount target at the time of deceleration fuel cut is registered. It is set based on the value map (FIG. 6), and this is set in the storage area M3 of the data memory 302.
To store.

Then, in step 1223, the exhaust gas recirculation control valve 6 is set based on the set and stored target value Pr.
Drive control. The drive control of the exhaust gas recirculation control valve 6 is also
The procedure is similar to the procedure described above with reference to FIG.

As described above, in the exhaust gas recirculation control 1220 at the time of deceleration fuel cut by the device of the embodiment, when the exhaust gas recirculation control valve 6 is opened through the drive control of the above step 1223 (FIG. 8), (1) During deceleration fuel cut, when the engine speed Ne is high, a minimum air flow for removing the deposits is obtained without causing a drivability defect such as engine braking not being effective. (2) During the same deceleration fuel cut, the minimum air flow for removing the deposits is obtained even if the engine speed Ne is low. The target value Pr of the opening is set based on the lift amount target value map (FIG. 6) at the time of deceleration fuel cut that satisfies the above condition.

For this reason, the exhaust gas recirculation amount during the deceleration fuel cut is maintained at a substantially constant amount that can remove the deposits on the exhaust gas recirculation control valve 6 regardless of the engine speed Ne. As a result, the drivability failure such as the engine brake not being effective due to too large a pressure difference between the upstream and downstream of the exhaust gas recirculation control valve 6 will not occur.
In addition, the deposits on the exhaust gas recirculation control valve 6 and the recirculation passage 5 can be accurately removed regardless of the engine speed Ne. By properly removing the adhering matter in this manner, the exhaust gas recirculation control valve 6 is prevented from sticking and changes in the flow rate characteristics in the exhaust gas recirculation control are prevented.

In the system of this embodiment, in the exhaust gas recirculation control 1220 at the time of deceleration fuel cut, when the exhaust gas recirculation control valve 6 is opened to the target value Pr, step 1
It is assumed that the exhaust gas recirculation control valve 6 is directly driven to the target opening degree through 223. However, the driving of the exhaust gas recirculation control valve 6 to the target opening degree may be controlled in a gradual change manner, for example, in the mode illustrated in FIG.

That is, in the exhaust gas recirculation control valve gradual change control routine 1223 at the time of deceleration fuel cut shown in FIG. 9, the current opening degree of the exhaust gas recirculation control valve 6 based on the output of the lift amount sensor 18 in step 201 ( The lift amount Ps is calculated and stored in the storage area M4 of the data memory 302. In step 202, a deviation value P (= Pr-Ps) between the target value Pr and the detected value Ps is calculated. -In step 203, this deviation value P is within a predetermined range (-a ≤
P (≦ a)) is determined. After performing such processing, execution of the gradual change processing 210 is started under the condition that it is determined that the deviation value P is not within the predetermined range.

In the gradual change process 210, first, in step 211, it is determined whether or not desired time data is stored in the memory area M7 which is the seventh memory area of the data memory 302. In the first stage of the gradual change process 210, this time data is not stored. Therefore, first, in step 212, the corresponding time information tp is read from the solenoid drive map (FIG. 4). In step 213, the read time tp is divided by the number K of gradual changes to obtain gradual change time data Δtp, and the obtained time data Δtp is stored in the storage area M7 of the data memory 302. After performing such processing, in step 214, the negative pressure solenoid valve 12 is opened for this time Δtp (duty control). Of course, at that time, the atmospheric solenoid valve 15
Is kept closed.

After that, the processes of steps 201 to 203 are repeated until the deviation value P falls within the predetermined range, after which it is determined that the desired time data is stored in the storage area M7. (Step 211), only the negative pressure solenoid valve drive processing for each time Δtp in Step 214 is repeated.

Then, at step 203, when it is judged that the deviation value P is within the predetermined range,
The storage area M7 of the data memory 302 is cleared (step 220), and the gradual change control 1223 is ended.

By executing such a gradual change control of the exhaust gas recirculation control valve 6 during deceleration fuel cut, the exhaust gas recirculation control device is expected to have a new effect as shown in FIG. Become.

That is, assuming that the deceleration fuel cut is executed at the timing shown in FIG. 10A, for example, if the gradual change control is not performed, FIG.
While the exhaust gas recirculation control valve 6 is “open” in the mode shown by the solid line A in FIG.
In the mode shown by the broken line B in FIG. 10B, the exhaust gas recirculation control valve 6 gradually opens.

Corresponding to such behavior of the exhaust gas recirculation control valve 6, the amount of air passing through the exhaust gas recirculation control valve 6 is changed to the form shown by a solid line A in FIG. In contrast to this, when the gradual change control is executed, it gradually changes in the mode shown by the broken line B in FIG.

Therefore, it is expected that the feeling of deceleration due to the engine brake will be suddenly sensed in the manner shown by the solid line A in FIG. 10 (d) when the gradual change control is not performed. When the gradual change control is executed, it is expected that the shock will be reduced by the amount indicated by the diagonal lines, as indicated by the broken line B in FIG. That is, the drivability is further improved by executing such gradual change control. The mode of such gradual change control is not limited to the example illustrated in FIG. 9 and is arbitrary.

In addition, for example, step 21 in FIG.
By omitting the processing of No. 1 and executing the calculation such as Δtp = tp / K (the number of gradual changes) with respect to the gradually shortening time tp, a more detailed gradual change control can be realized. Become.

Further, in all of these, the duty control time for the negative pressure solenoid valve 12 is divided to gradually change the drive of the exhaust gas recirculation control valve 6, but in addition, the exhaust gas recirculation control valve 6 is opened. The same gradual change control is also realized by setting the degree target value Pr itself stepwise.

Further, in the apparatus of the above embodiment, the lift amount target value Pr at the time of failure diagnosis and at the time of deceleration fuel cut is obtained from the map shown in FIG. 5 and the map shown in FIG. No need to use maps. Alternatively, for example, it is of course possible to set appropriate functions corresponding to those characteristics and execute the calculation using these functions to obtain the target value Pr at each time.

The lift amount target value map at the time of failure diagnosis and deceleration fuel cut, or the function thereof, may be shared depending on the characteristics set therein. If this kind of sharing becomes possible,
The exhaust gas recirculation control device can be configured as a simpler device.

As the engine operating condition for obtaining the lift amount target value at the time of the failure diagnosis and the deceleration fuel cut, the engine speed is adopted in the apparatus of the above-mentioned embodiment. The pipe pressure and the like can be appropriately adopted as the operating condition for obtaining the same lift amount target value.

Further, in the L-JETRO system having no intake pipe negative pressure sensor, the ratio Q / Ne of the intake air amount Q and the rotation speed Ne may be used instead of the intake pressure Pm. Furthermore, in the above embodiment, the device having both the function of executing the exhaust gas recirculation control at the time of the deceleration fuel cut and the function of performing the failure diagnosis at the same time of the deceleration fuel cut is exemplified.
The exhaust gas recirculation control device according to the present invention may be any device as long as it has a function of executing exhaust gas recirculation control at least during deceleration fuel cut.

[0099]

As described above, according to the present invention, it is possible to properly remove the deposits on the exhaust gas recirculation control valve and the recirculation passage while maintaining the drivability appropriately. By properly removing the adhering matter in this way, the exhaust gas recirculation control valve is prevented from sticking and changes in the flow rate characteristics of the exhaust gas recirculation control are prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an exhaust gas recirculation control device for an internal combustion engine according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a control device shown in FIG.

FIG. 3 is a graph showing an example of a map mode of a lift amount target value map of an exhaust gas recirculation control valve used for exhaust gas recirculation control in a normal state by the apparatus of the embodiment.

FIG. 4 is a graph showing an example of a map mode of a solenoid drive map used by the apparatus of the embodiment to determine the drive amounts of the atmospheric solenoid and the negative pressure solenoid.

FIG. 5 is a graph showing an example of a map mode of an opening degree control (lift amount target value) map of the exhaust gas recirculation control valve used by the device of the embodiment for failure diagnosis.

FIG. 6 is a graph showing an example of a map mode of an opening degree control (lift amount target value) map of the exhaust gas recirculation control valve used by the apparatus of the embodiment for deceleration fuel cut.

FIG. 7 is a flowchart showing a procedure for determining the opening degree of the exhaust gas recirculation control valve by the apparatus of the embodiment.

FIG. 8 is a flowchart showing a drive control procedure of an exhaust gas recirculation control valve by the apparatus of the embodiment.

FIG. 9 is a flow chart showing an example of a control procedure in the case of gradually changing the opening of the exhaust gas recirculation control valve during deceleration fuel cut, as another embodiment of the exhaust gas recirculation control device for an internal combustion engine according to the present invention.

FIG. 10 is a timing chart exemplifying the effect in the case where the exhaust gas recirculation control valve is controlled to be gradually changed at the time of deceleration fuel cut.

[Explanation of symbols]

1 ... Engine, 2 ... Intake passage (intake pipe), 3 ... Exhaust passage (exhaust pipe), 4 ... Throttle valve, 5 ... Exhaust gas recirculation passage, 6 ... Negative pressure responsive exhaust recirculation control valve, 7 ... Valve body, 8 ...
Diaphragm, 9 ... Rod, 10 ... Negative pressure chamber (diaphragm chamber), 11 ... Atmosphere chamber, 12 ... Negative pressure solenoid valve, 13
... Negative pressure introduction passage, 14 ... Negative pressure outlet, 15 ... Atmosphere solenoid valve, 16 ... Atmosphere introduction passage, 17 ... Compression coil spring, 18 ... Lift amount sensor, 19 ... Intake negative pressure sensor,
20 ... Engine speed sensor, 30 ... Control device, 31 ...
Storage device, 301 ... CPU, 302 ... Data memory, 3
03, 304, 305 ... Map memory, 306 ... Input interface, 307 ... Output interface, 30
8 ... Analog multiplexer, 309 ... A / D converter,
310 ... Counter, 311 ... Address / data bus, 3
12 ... Control bus.

Claims (6)

[Claims] 1. A recirculation passage for recirculating a part of exhaust gas of an internal combustion engine to an intake system of the engine, an exhaust gas recirculation control valve for opening and closing the recirculation passage, and a deceleration fuel cut of the internal combustion engine, wherein: A control means for forcibly opening the exhaust gas recirculation control valve and variably controlling the opening degree of the internal combustion engine in order to maintain the exhaust gas recirculation amount during the same deceleration fuel cut at a constant amount. An exhaust gas recirculation control device for an internal combustion engine, comprising: 2. The control means decreases the opening degree of the exhaust gas recirculation control valve as the rotation speed increases, and decreases the opening degree of the exhaust gas recirculation control valve as the rotation speed decreases, according to the rotation speed of the internal combustion engine. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, which largely controls the exhaust gas recirculation control device. 3. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, further comprising: forcibly opening the exhaust gas recirculation control valve during deceleration fuel cut of the internal combustion engine, and opening the exhaust gas recirculation control valve. And a failure diagnosis means for diagnosing whether or not there is a failure of the exhaust gas recirculation control valve based on the difference in intake pressure before and after, and according to the operating condition of the internal combustion engine in order to keep the difference in intake pressure constant during the diagnosis. An exhaust gas recirculation control device for an internal combustion engine, comprising: diagnostic condition control means for variably controlling the opening degree of the exhaust gas recirculation control valve. 4. The diagnostic condition control means reduces the opening degree of the exhaust gas recirculation control valve as the rotational speed increases and opens the exhaust gas recirculation control valve as the rotational speed decreases, according to the rotational speed of the internal combustion engine. The exhaust gas recirculation control device for an internal combustion engine according to claim 3, wherein the exhaust gas recirculation control device largely controls the degree. 5. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, further comprising the step of gradually changing the opening of the exhaust gas recirculation control valve from an opening of 0 at the start of deceleration fuel cut of the internal combustion engine. An exhaust gas recirculation control device for an internal combustion engine, comprising: a gradual change control means for gradual change control up to an opening controlled by the means. 6. A recirculation passage for recirculating a part of exhaust gas of the internal combustion engine to an intake system of the engine, an exhaust gas recirculation control valve for opening and closing the recirculation passage, an internal combustion engine during deceleration fuel cut, and Control means for forcibly opening the exhaust gas recirculation control valve and variably controlling the opening degree of the internal combustion engine in order to maintain the exhaust gas recirculation amount during the deceleration fuel cut at a constant amount; A gradual change control means for gradually changing the opening degree of the exhaust gas recirculation control valve from an opening degree of 0 to an opening degree controlled by the control means at the start of deceleration fuel cut of the engine; A failure diagnosis means for diagnosing whether or not the exhaust gas recirculation control valve has a failure based on a difference in intake pressure before and after opening the exhaust gas recirculation control valve forcibly. During the diagnosis, the intake pressure difference should be kept constant. Exhaust gas recirculation control system for an internal combustion engine, characterized in that it comprises a diagnostic condition control means for variably controlling the opening degree of the exhaust gas recirculation control valve in accordance with the operating conditions of the internal-combustion engine.