JPH0972253A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve treatment capacity of evaporative emission by judging deviation of a control air-fuel ratio in feedback control of the air-fuel ratio in the low temperature of an engine and correcting the feeding ratio between the evaporative emission and the fuel in the purge mixture in the air-fuel ratio feedback control based on this deviation. SOLUTION: When a control unit 6 judges that an exhaust gas temperature of an engine detected by an exhaust gas temperature sensor 34 is a temperature state lower than a prescribed temperature, the control unit 6 judges the deviation of a control air-fuel ratio as the deviation of a feedback correction factor based on the deviation of the exhaust gas temperature to the prescribed temperature. The control unit 6 calculates a correction factor of a purge mixture flow and the correction factor of a fuel injection amount by a fuel injection valve 5 based on this deviation. It also judges whether the value formed by multiplying the correction factor of the purge mixture flow by the feedback correction amount exceeds the upper limit or not, and calculates the purge rate based on the air-fuel ratio of the purge mixture and controls the purge control valve 23 by setting the purge mixture flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, which is equipped with a device for processing evaporated fuel from a fuel system and performs the evaporated fuel processing in combination with air-fuel ratio feedback control. The present invention relates to technology with improved processing capacity.

[0002]

2. Description of the Related Art In a conventional vaporized fuel processing apparatus for an internal combustion engine, vaporized fuel generated in a fuel tank or the like is temporarily adsorbed in a canister, and the adsorbed vaporized fuel is released under predetermined engine operating conditions for purging. The purge mixture, which is mixed with air, is sucked into the intake system of the engine while the flow rate is controlled by the purge control valve to prevent the evaporated fuel from evaporating to the outside air.

On the other hand, in an internal combustion engine equipped with an electronically controlled fuel injection device, feedback control may be performed by a feedback correction amount that is increased / decreased so that the air-fuel ratio approaches a target air-fuel ratio (theoretical air-fuel ratio) under predetermined operating conditions. Done.

[0004]

With the recent strengthening of air purification measures, it has been required to carry out the treatment of the vaporized fuel over a wide operating range, and ultimately over the entire operating range. Here, if the evaporated fuel is processed during the air-fuel ratio feedback control, it is possible to constantly process the evaporated fuel while maintaining the air-fuel ratio at the target air-fuel ratio. In order to suppress the fluctuation of the air-fuel ratio in the transient state, it is desirable to make the supply ratio of the fuel supplied from the fuel supply device and the evaporated fuel in the purge mixture constant.

Therefore, while the basic flow rate of the purged mixture is set in proportion to the intake air flow rate, the air-fuel ratio of the purged mixture is estimated based on (the average value of) the feedback correction amount in the air-fuel ratio feedback control. It has been considered that the basic flow rate is corrected on the basis of the air-fuel ratio of the purged air-fuel mixture, so that the supply ratio of the fuel and the evaporated fuel from the fuel supply means becomes constant.

However, even in the operating region where the air-fuel ratio feedback control is performed, the control point (controlled air-fuel ratio) may shift to the lean side because the air-fuel ratio sensor is not sufficiently activated when the engine temperature is low. . In that case, even if the feedback correction amount is the same, that is, even if the air-fuel ratio of the mixture of fuel and air injected from the fuel injection valve (hereinafter referred to as the main mixture) is the same, the air-fuel ratio of the purge mixture is the control air-fuel ratio. Since it is shifted to the lean side by the shift of the fuel ratio, the estimation of the air-fuel ratio of the purged air-fuel mixture based on the feedback correction amount is shifted, and it is estimated that it is richer than the actual air-fuel ratio.

Therefore, the flow rate of the purged air-fuel mixture is controlled to be reduced from the required amount based on the air-fuel ratio of the purged air-fuel mixture estimated to be richer than it actually is, and a sufficient amount of evaporated fuel cannot be processed. was there. Unnecessarily increasing the flow rate of the purged air-fuel mixture in order to secure the throughput of the evaporated fuel causes the exhaust purification performance to deteriorate due to the enrichment of the air-fuel ratio.

The present invention has been made in view of the above situation, and secures the ability to prevent the evaporation fuel from escaping to the outside air by avoiding the restriction of the processing amount of the evaporation fuel due to the deviation of the control point of the air-fuel ratio sensor. At the same time, it is an object of the present invention to maintain good air-fuel ratio feedback control and maintain good exhaust gas purification performance.

[0009]

Therefore, in the invention according to claim 1, as shown by the solid line in FIG. 1, the flow rate of the purge mixture obtained by mixing the evaporated fuel generated from the fuel system and the air is controlled. While including the evaporated fuel processing means for guiding and processing to the engine intake system, while detecting the air-fuel ratio of the air-fuel mixture supplied to the engine by the air-fuel ratio detection means, to bring the air-fuel ratio close to the target air-fuel ratio, In a control device for an internal combustion engine equipped with an air-fuel ratio feedback control means for performing feedback control of a fuel supply amount from a fuel supply means with a feedback correction amount, evaporation in a purge mixture based on a feedback correction amount at the time of air-fuel ratio feedback control. The purge mixture flow rate control means for controlling the flow rate of the purge mixture so that the supply ratio of the fuel and the fuel from the fuel supply means becomes constant, and the engine low rate. Low temperature state detecting means for detecting the state, when the low temperature state is detected, the control air-fuel ratio deviation amount estimating means for estimating the deviation amount of the control air-fuel ratio during the feedback control of the air-fuel ratio, the estimated And a fuel supply ratio correction means for correcting the supply ratio of the evaporated fuel in the purged air-fuel mixture and the fuel from the fuel supply means during the air-fuel ratio feedback control based on the deviation amount of the control air-fuel ratio. Characterize.

According to the air-fuel ratio control apparatus for an internal combustion engine of the first aspect of the present invention, since the air-fuel ratio detecting means is not sufficiently activated in the low temperature state, the air-fuel ratio controlled in the air-fuel ratio feedback control is lean. However, the control air-fuel ratio deviation amount is estimated by detecting the low temperature state. Then, when the control air-fuel ratio deviation amount is generated, it is controlled so that the supply ratio of the evaporated fuel in the purge mixture and the fuel from the fuel supply means becomes constant based on the feedback correction amount as it is. Therefore, the flow rate of the purged air-fuel mixture is reduced by the control air-fuel ratio deviation amount.

Therefore, the deviation of the control air-fuel ratio is generated by correcting the supply ratio of the evaporated fuel in the purge mixture to the fuel from the fuel supply means based on the estimated deviation amount of the control air-fuel ratio. It is possible to secure the same amount of purged air-fuel mixture flow as when it is not performed. As a result, the ability to prevent the evaporated fuel from evaporating to the outside air can be secured. On the other hand, since the air-fuel ratio feedback control is performed, the fuel supply amount from the fuel supply means is automatically reduced by the amount corresponding to the deviation amount of the control air-fuel ratio by the correction of the purge mixture flow rate.

The invention according to claim 2 is, as shown by the alternate long and short dash line in FIG. 1, when the air-fuel ratio feedback control and the evaporated fuel processing are performed at the same time, based on the feedback correction amount, the purge mixture is purged. The purge mixture air-fuel ratio estimation means for estimating the air-fuel ratio of the purge mixture mixture is provided, and the purge mixture mixture flow rate control means corrects the purge mixture mixture flow rate based on the estimated air-fuel ratio of the purge mixture mixture while supplying the fuel. The ratio correction means corrects the estimated value of the air-fuel ratio of the purged air-fuel mixture by correcting the feedback correction amount based on the deviation amount of the control air-fuel ratio estimated during the feedback control of the air-fuel ratio, thus purging While correcting the air-fuel mixture flow rate, fuel supply from the fuel supply means is suppressed so as to suppress a change in the feedback correction amount of the air-fuel ratio due to the correction of the purged air-fuel mixture flow rate. By setting a correction coefficient for correcting the amount, and correcting the fuel supply ratio.

According to the second aspect of the present invention, when the air-fuel ratio of the purged air-fuel mixture is rich (thin), the amount of fuel supply from the fuel supply means is reduced (increased) by the feedback correction amount. Is reduced (increased), the air-fuel ratio of the purged air-fuel mixture can be estimated based on the feedback correction amount.

When the control air-fuel ratio deviates in a low temperature state, the estimated air-fuel ratio estimated value of the purged air-fuel mixture also deviates, but feedback correction is performed based on the estimated amount of deviation of the control air-fuel ratio. By correcting the amount, the deviation of the estimated value of the air-fuel ratio can also be prevented. As a result, based on the correct estimated value of the air-fuel ratio of the purged air-fuel mixture, the correction is performed so that the same amount of the purged air-fuel mixture flow as when the control air-fuel ratio does not shift is obtained.

On the other hand, if the purge air-fuel mixture flow rate is corrected based on the deviation amount of the control air-fuel ratio as described above, the air-fuel ratio feedback control corrects the fuel supply amount from the fuel supply means by a corresponding amount, but the feedback is performed. The correction amount is
Since the basic fuel supply amount is set based on the operating state of the engine, the feedback correction amount is reduced and set for a constant basic fuel supply amount as it is.

In this case, the basic flow rate of the purged air-fuel mixture is reduced and set based on the reduced feedback correction amount, and the control air-fuel ratio deviation amount is corrected accordingly. Therefore, the amount is increased once. The corrected purge mixture flow rate may be returned to the original value, which may cause hunting such that the feedback correction amount increases again.

Therefore, if a correction coefficient for performing a decrease correction corresponding to the deviation amount of the control air-fuel ratio is set and the fuel supply amount is decreased and corrected by the correction coefficient, feedback correction by correction of the purge mixture flow rate is performed. Since the change in the amount is suppressed, the hunting can be prevented and stable control can be performed.
The invention according to claim 3 is characterized in that an upper limit value is set for the corrected purged mixture flow rate.

As a result, it is possible to prevent the purge mixture flow rate from becoming excessive due to some error factor, and to prevent the air-fuel ratio from deteriorating. Further, the invention according to claim 4 is on the lean side with respect to the air-fuel ratio of the mixture of fuel and air supplied from the fuel supply means, which is corrected by the correction coefficient for correcting the feedback correction amount of the air-fuel ratio. It is characterized by setting a limit value.

As a result, it is possible to prevent the amount of fuel supplied from the fuel supply means from being reduced too much to prevent stable fuel supply.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In FIG. 2 showing an embodiment, air is sucked into an internal combustion engine 1 through an intake passage 3 provided with a throttle valve 2 which works in conjunction with an accelerator pedal (not shown). An air flow meter 4 for detecting an intake air flow rate controlled by the throttle valve 2 is installed at an upstream portion of the intake passage 3, and an electromagnetic flow meter for each cylinder is provided at a downstream portion (manifold portion) of the intake passage 3. A fuel injection valve 5 of a type is provided to inject into the intake passage 3 fuel that is fed under pressure from a fuel pump (not shown) and is controlled to a predetermined pressure by a pressure regulator. The control of the fuel injection amount by the fuel injection valve 5 is performed by a control unit 6 (illustrated by a chain line) with a built-in microcomputer.

Further, the engine 1 is provided with an evaporated fuel processing device. In the evaporative fuel processing apparatus, an adsorbent such as activated carbon filled in a canister 21 as an adsorbing means adsorbs and collects the evaporative fuel of the fuel generated in a fuel tank (not shown), and the adsorbent is adsorbed on the adsorbent. The fuel is supplied to the intake passage 3 downstream of the throttle valve 2 via the purge passage 22.

An electromagnetically driven purge control valve 23 whose duty is controlled based on a control signal from the control unit 6 is interposed in the purge passage 22. Further, a rotation speed sensor 31 that detects the engine rotation speed N, a water temperature sensor 32 that detects the water temperature Tw, an air-fuel ratio sensor 33 that detects the air-fuel ratio based on the oxygen concentration in the exhaust gas, and an exhaust temperature that detects the exhaust gas temperature T. A sensor 34 is provided, and detection signals thereof are output to the control unit 6.

The control unit 6 controls the purge control valve 23 under a predetermined operating condition on the basis of signals from the various sensors to purge evaporated fuel into the intake system, and the fuel injection valve 5 The air-fuel ratio feedback control by controlling the injection amount is performed at the same time. Below, the routines of the purge processing control and the air-fuel ratio feedback control by the control unit 6 will be explained according to the flowchart of FIG.

Step (denoted by S in the figure. The same applies hereinafter) 1
Then, the exhaust temperature T of the engine detected by the exhaust temperature sensor 34
It is determined whether or not the temperature is lower than the predetermined temperature T ₀ . If it is determined that the temperature is low, go to step 2,
Deviation ΔT of exhaust temperature T from predetermined temperature T ₀ {= (T ₀
-T)} is calculated, and the deviation amount of the control air-fuel ratio is estimated as the deviation amount Δα of the feedback correction coefficient α based on the deviation ΔT.

In step 3, the correction coefficient KEV for the purge mixture flow rate and the fuel injection valve 5 are calculated based on the deviation amount Δα.
The correction coefficient KFI of the fuel injection amount from is calculated by the following equations, respectively. KEV = (α + Δα) / α KFI = (α−Δα) / α In step 4, the correction coefficient KE of the purged mixture flow rate is obtained.
It is determined whether or not the value KEV · α obtained by multiplying V by the feedback correction amount α exceeds the upper limit value KEVSL.

If the upper limit is not exceeded, step 5
To the corrected feedback correction amount KEV.
-Estimate the air-fuel ratio of the purge mixture based on α. That is, the air-fuel ratio of the purge mixture is the target air-fuel ratio (theoretical air-fuel ratio).
When it is darker (thinner) than, the feedback correction amount α decreases (increases) in order to decrease (increase) the fuel injection amount from the fuel injection valve accordingly, so feedback correction learned for each operating region is performed. It is possible to estimate the air-fuel ratio of the purge mixture based on the amount α. However, when the control air-fuel ratio of the entire air-fuel mixture supplied to the engine deviates to the lean side from the target air-fuel ratio due to the low temperature characteristics of the air-fuel ratio sensor, the same feedback correction amount, that is, the fuel injected from the fuel injection valve If the air-fuel ratio of the air-fuel mixture is the same as the air-fuel ratio of the air-fuel mixture, the concentration of the purge air-fuel mixture is shifted to the lean side by the deviation of the control air-fuel ratio. There is a gap in the estimation of the air-fuel ratio, and it is estimated that it is richer than the actual air-fuel ratio.

Therefore, the deviation of the feedback correction amount α due to the deviation of the control air-fuel ratio is corrected by being multiplied by the correction coefficient KEV, and the feedback correction amount KE thus increased is corrected.
By correcting the air-fuel ratio of the purged air-fuel mixture to a thinner side based on V · α, it is possible to estimate a value close to a correct value. When it is determined that the feedback correction amount KEV · α corrected in step 4 exceeds the upper limit value KEVSL, the process proceeds to step 6 and the air-fuel ratio of the purged mixture is estimated based on the upper limit value KEVSL. As a result of KEV · α becoming too large due to some error factor, the purge mixture concentration may be estimated to be too thin, and the purge mixture flow rate may be excessively controlled to deteriorate the air-fuel ratio, but this is limited by the upper limit value. This can prevent such a situation.

In step 7, the purge ratio is calculated based on the estimated air-fuel ratio of the purged air-fuel mixture, and the basic flow rate of the purged air-fuel mixture is set proportionally to the intake air flow rate separately detected by the air flow meter. , The purge ratio is multiplied to set the flow rate of the purged mixture, and the purge control valve is controlled so that the opening degree corresponds to the flow rate of the purged mixture.

As described above, even if the control air-fuel ratio is deviated in the low temperature state, the air-fuel ratio of the purged mixture can be estimated to be a correct value, so that the reduction of the purge rate due to erroneous estimation can be prevented and the processing capacity is matched. The purge mixture flow rate can be secured. Next, in step 8, it is determined whether or not the value obtained by multiplying the correction coefficient KFI calculated in step 4 by the feedback correction amount α is below the lower limit value KFISL.

The value of KFI · α is the lower limit value KFIS.
If L or more, the process proceeds to step 9 and the fuel injection amount T from the fuel injection valve 5 is set to KFI · α as a feedback correction amount.
Set _i as follows. T _i = T _P · COEF · KFI · α + T _S However, T _P : basic fuel injection amount COEF: various correction factors T _S : invalid injection amount Further, when the value of KFI · α is below the lower limit KFISL, step 10 Then, the fuel injection amount T _i is set as in the following equation with the lower limit value KFISL as the feedback correction amount.

T _i = T _P · COEF · KFISL + T _S That is, as a result of increasing and correcting the purge mixture flow rate according to the deviation of the control air-fuel ratio, the fuel injection amount from the fuel injection valve 5 is decreased and corrected by the air-fuel ratio feedback control. However, as it is, the reduction correction is performed by reducing the feedback correction amount α, and due to the reduction of the feedback correction amount, the air-fuel ratio of the purged air-fuel mixture is erroneously estimated to the rich side again. Hunting will occur.

Therefore, by correcting the feedback correction amount α with the correction coefficient KFI, it is possible to suppress the change of the feedback correction amount α due to the increase of the purge mixture flow rate, and to maintain the control in a stable state. You can

[0033]

As described above, according to the first aspect of the present invention, the deviation amount of the control air-fuel ratio in the air-fuel ratio feedback control which occurs when the air-fuel ratio detecting means is not sufficiently activated in the low temperature state is described. Since the estimated amount is corrected and the supply ratio of the evaporated fuel in the purged mixture to the fuel from the fuel supply means is corrected based on the estimated amount, the same amount of purged mixture as when the control air-fuel ratio is not changed is generated. The flow rate can be secured, and thus the ability to prevent the evaporated fuel from evaporating to the outside air can be secured.

Further, according to the second aspect of the present invention, by correcting the feedback correction amount based on the estimated deviation amount of the control air-fuel ratio, the deviation of the estimated value of the air-fuel ratio can be prevented and the correct purge can be performed. Based on the estimated value of the air-fuel ratio of the air-fuel mixture, correction is performed so that the same amount of purged air-fuel mixture flow as when the control air-fuel ratio is not displaced is obtained.

On the other hand, since the fuel supply amount is reduced by the correction coefficient for performing the reduction correction corresponding to the deviation amount of the control air-fuel ratio, the change of the feedback correction amount due to the correction of the purged mixture flow rate is suppressed. Hunting can be prevented and stable control can be performed. Further, according to the third aspect of the present invention, by setting the upper limit value of the purged mixture flow rate, it is possible to prevent the purged mixture flow rate from becoming excessive and prevent the air-fuel ratio from deteriorating.

According to the invention of claim 4, the lean side limit value is set for the air-fuel ratio of the mixture of the fuel and air supplied from the fuel supply means. It is possible to prevent the amount of fuel supplied from the fuel cell from being excessively reduced and failing to stably supply the fuel.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration of an embodiment of the present invention.

FIG. 3 is a flowchart showing an evaporated fuel processing and air-fuel ratio feedback control routine of the above embodiment.

[Explanation of symbols]

 1 Internal Combustion Engine 3 Intake Passage 4 Air Flow Meter 5 Fuel Injection Valve 6 Control Unit 21 Canister 22 Purge Passage 23 Purge Control Valve 31 Rotation Speed Sensor 33 Air-Fuel Ratio Sensor 34 Exhaust Temperature Sensor

Claims (4)

[Claims] 1. An evaporative fuel processing means for introducing and processing a purged air-fuel mixture, which is a mixture of evaporative fuel generated from a fuel system and air, into an engine intake system while controlling the flow rate, and is supplied to an engine. The air-fuel ratio of the air-fuel mixture is detected by the air-fuel ratio detection means, so that the air-fuel ratio approaches the target air-fuel ratio,
In a control device for an internal combustion engine having an air-fuel ratio feedback control means for feedback-controlling a fuel supply amount from a fuel supply means by a feedback correction amount, evaporation in a purge mixture is performed based on a feedback correction amount at the time of air-fuel ratio feedback control. Purge mixture flow rate control means for controlling the flow rate of the purge mixture so that the supply ratio of fuel and fuel from the fuel supply means is constant, low temperature state detection means for detecting the low temperature state of the engine, and the low temperature state When detected, the control air-fuel ratio deviation amount estimating means for estimating the deviation amount of the control air-fuel ratio during the feedback control of the air-fuel ratio, based on the deviation amount of the estimated control air-fuel ratio, the air-fuel ratio Fuel supply ratio correction for correcting the supply ratio of the evaporated fuel in the purge mixture during the feedback control and the fuel from the fuel supply means A control device for an internal combustion engine, characterized in that the control device includes: 2. A purge mixture air-fuel ratio estimating means for estimating an air-fuel ratio of a purge mixture based on a feedback correction amount when the air-fuel ratio feedback control and the evaporated fuel processing are performed simultaneously, the purge comprising: The air-fuel mixture flow rate control means corrects the purged air-fuel mixture flow rate based on the estimated air-fuel ratio of the purged air-fuel mixture, while the fuel supply ratio correction means controls the air-fuel ratio estimated by the air-fuel ratio feedback control. The estimated value of the air-fuel ratio of the purged air-fuel mixture is corrected by correcting the feedback correction amount based on the deviation amount of the air-fuel ratio, and thus the flow rate of the purged air-fuel mixture is corrected. By setting a correction coefficient for correcting the fuel supply amount from the fuel supply means so as to suppress the change in the feedback correction amount of The control apparatus according to claim 1, characterized in that to correct the feed ratio. 3. The air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein an upper limit value is set for the corrected purged air-fuel mixture flow rate. 4. A lean-side limit value is set for the air-fuel ratio of the mixture of fuel and air supplied from the fuel supply means, which is corrected by the correction coefficient for correcting the air-fuel ratio feedback correction amount. Claim 1 or claim 2 characterized in that
The air-fuel ratio control device described in.