JPH09209798A - Exhaust gas recirculating device for engine and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a misfire and the deterioration of the operating property by detecting the quick deceleration state of an engine in the exhaust gas recirculation(EGR) state, and feeding auxiliary air to the engine with an auxiliary air feeding means while by-passing a throttle valve when the quick deceleration state is detected. SOLUTION: When a quick deceleration state detecting means 80 detects the quick deceleration state of an engine main body based on the change quantity of the throttle opening Th, an EGR rate correcting means 82 controls the auxiliary air feeding means 85 of an idle speed control(ISC) valve and an ISC passage and feeds auxiliary air to the engine main body. An auxiliary air quantity calculating means 83 refers to an EGR map 64 stored with the optimum EGR rate for each stationary operation state of the engine main body as a map and calculates the required auxiliary air quantity in response to the EGR rates before and after the occurrence of the quick deceleration state. An ignition timing correction quantity calculating means 84 calculates the spark delay quantity of the ignition timing required for canceling the torque change generated when the auxiliary air is fed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas recirculation system and method, and more particularly to an engine exhaust gas recirculation system equipped with a system for controlling the opening of the exhaust gas recirculation valve in accordance with operating state parameters such as throttle valve opening. The present invention relates to a device and a method thereof.

[0002]

2. Description of the Related Art General exhaust gas recirculation (hereinafter referred to simply as "EG
(R) system controls the opening degree of an EGR valve provided in the middle of the EGR passage that connects the exhaust passage and the intake passage to use the intake pipe negative pressure from the exhaust passage to the intake passage. And adjust the amount of exhaust gas to be recirculated. As a result, the combustion temperature is lowered to reduce the amount of NOx and the fuel consumption is improved. Here, as the EGR valve, there are a negative pressure type that uses a negative pressure in the intake pipe to displace the diaphragm, and an electronic control type that opens and closes the valve body using an electric motor. As the control type, it is known to use a pulse motor such as a stepping motor to control the valve lift amount, and to control the energization of the electromagnetic solenoid in a time proportional manner.

The negative pressure type EGR valve adjusts the EGR amount based on the throttle opening and controls the EGR rate, which is the ratio of the EGR amount to the intake air amount, and therefore its control range is naturally limited. Therefore, in recent years, a relatively large number of electronically controlled EGR valves have been proposed in order to realize an EGR rate most suitable for the operating state of the engine. In such a conventional EGR system, the number of pulse signals output to the stepping motor for driving the EGR valve is set to a value set according to each operating state parameter such as the intake air amount of the engine, the number of revolutions, and the intake pipe pressure. The lift amount of the EGR valve is controlled so as to realize the optimum EGR rate for the operating state by adjusting the opening degree by adjusting the.
The optimum EGR rate for each operating state of the engine is set by mapping in advance, and when the operating state of the engine changes, stepping is performed to realize the EGR rate according to the changed operating state. The required pulse signal is output to the motor.

Further, in Japanese Patent Laid-Open No. 2-5741, in order to prevent a torque change due to an operation delay of a negative pressure type EGR valve utilizing negative pressure of an intake pipe, a fuel injection amount is corrected according to the operation delay. The technology is disclosed.

Further, in Japanese Patent Application Laid-Open No. 2-233853, in the case of suppressing the torque change due to the operation delay of the negative pressure type EGR valve by correcting the fuel injection amount, the delay time of the actual air amount change and the intake pipe negative pressure are In view of the above correlation, a technique is disclosed in which the fuel injection amount is corrected after a predetermined delay time that changes due to the intake pipe negative pressure or the like.

[0006]

In the EGR system for controlling the EGR rate according to the operating state of the engine as described above, the optimum EGR rate can be maintained when the engine is in the steady state. However, in the case of a transient response state in which the operating state of the engine changes rapidly, the volume between the EGR valve and the combustion chamber and the EGR
Due to the delay in the valve operation, the actual EGR rate cannot be promptly dealt with, and there is a risk that a torque change will occur and the operating performance will deteriorate. In particular, when a stepping motor is used as the drive source of the EGR valve, the number of output pulses for realizing the optimum EGR rate is calculated after the operating state of the engine is changed, and then the stepping motor is actually driven. More responsiveness is needed.

As shown in FIG. 5, the EGR rate set in accordance with the engine operating state is high, for example, when the throttle valve is open and the engine is in a high load state because the combustion temperature is high and the NOx concentration is high. It is necessary to set the EGR rate high, and therefore, the higher the operating condition becomes, the higher the E
The opening of the GR valve is set large. It should be noted that when the throttle is fully opened at high rotation and high load, it is necessary to sufficiently produce the engine output, but in this case, since the suction pipe negative pressure is small and the EGR amount that is recirculated is also small, there is no problem. When the engine speed is low, such as when idling, the EGR rate is reduced to prevent misfire, while, for example, when the engine is running at medium speed and running at a constant speed of 60 to 80 km / hour, the combustion temperature is lowered to reduce the NOx amount. EG to reduce
The R rate is set high.

Therefore, when the throttle valve is rapidly closed to shift to the low load state (during rapid deceleration) from the operating state where the load is relatively high and the EGR rate is high, the load decreases as shown in FIG. As a result, the EGR rate will decrease, though there will be a delay (G1 → G2). However, immediately after the sudden deceleration, the engine load is immediately reduced, whereas the actual EGR rate in the combustion chamber depends on the delay in the operation of the EGR valve itself and the influence of the EGR gas remaining in the intake passage before transition. Therefore, it takes a predetermined time for the EGR rate to change from G1 to G2. As a result, intake air having an excessive EGR rate is supplied to the engine with a reduced load, which may cause a misfire, deterioration of drivability, and deterioration of exhaust emission. In particular, when the throttle opening is reduced near the idle, the intake air amount sharply decreases and the engine load immediately decreases, but the intake air having an excessive EGR rate is added to the combustion chamber.

In order to prevent such a drawback, in the techniques disclosed in the above-mentioned JP-A-2-5741 and JP-A-2-233853, the torque change due to the operation delay of the EGR valve is dealt with by correcting the fuel injection amount. I am trying. However, there is a slight time lag between the closing of the throttle valve and the change in the intake pipe pressure, and since the intake pipe pressure has pulsation, it takes time to establish the detected pressure. Since the fuel injection amount is corrected and calculated after detection, it is disadvantageous in terms of responsiveness, and there is a possibility that transient torque changes during sudden deceleration cannot be sufficiently prevented.

The present invention has been made in view of the above-mentioned various problems, and an object thereof is to perform an optimum exhaust gas recirculation control according to a steady operation state of an engine and a state where exhaust gas recirculation is performed. It is an object of the present invention to provide an exhaust gas recirculation device and a method thereof that can prevent excessive exhaust gas recirculation quickly even when the vehicle is suddenly decelerated, and thereby prevent misfires and deterioration of drivability.

[0011]

In order to achieve the above object, the exhaust gas recirculation system according to the present invention uses the engine rapid deceleration while EGR is being performed, as a timing criterion for correcting the EGR rate. The sudden deceleration state is detected by the sudden deceleration state detecting means, and when the sudden deceleration state is detected, E
In order to prevent the GR amount from becoming excessive, the auxiliary air supply means bypasses the throttle valve to quickly supply the auxiliary air to the engine.

Therefore, when the engine is rapidly decelerated from the state where the EGR rate is high, the auxiliary air is quickly supplied to the engine, so that the excessive state of the EGR amount can be promptly prevented from occurring.

When a rapid deceleration state occurs, the auxiliary air is supplied to the engine in an amount corresponding to the difference between the EGR rate before the occurrence of the rapid deceleration state and the EGR rate after the occurrence of the rapid deceleration state.
It becomes possible to prevent the high EGR value before the sudden deceleration state from occurring for a while.

Further, by retarding the ignition timing according to the amount of auxiliary air, it is possible to easily cancel the torque change due to the auxiliary air supplied to prevent excessive EGR.

Further, by reducing the amount of auxiliary air within the fixed time period every predetermined time, it is possible to prevent supply of an unnecessary amount of auxiliary air in correction of the EGR rate for sudden deceleration. In addition, the said fixed time means the transient time until the operation delay of an EGR system is eliminated.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the overall structure of an automobile engine device to which the EGR device according to the present invention is applied.
First, the intake passage 12 is provided in the horizontally opposed engine body 10.
And the exhaust passage 14 is in communication. An intake chamber 16 is opened upstream of the intake passage 12 toward the front of the vehicle body (not shown), and an intake pipe 22 branched from a surge tank 20 is connected to the downstream side of the intake passage 12 so as to correspond to each cylinder 18. , The downstream end of each intake pipe 22 is an intake port 24.
And communicates with each combustion chamber 26 via. On the other hand, the downstream side of the exhaust passage 14 is connected to a muffler 28 attached to the rear portion of the vehicle body, and the upstream side of the exhaust passage 14 is connected to an exhaust pipe 32 communicating with each combustion chamber 26 via each exhaust port 30. .

An air cleaner 3 for removing dust in the air is provided in the intake passage 12 in order from the upstream side thereof.
4. An air flow meter 36 for detecting the intake air amount Q and a throttle valve 38 for controlling the intake air amount according to the depression amount of an accelerator pedal (not shown) are provided.
The intake valve 12 bypasses the throttle valve 38.
An idle speed control (hereinafter, simply referred to as "ISC") passage 40 provided in the vehicle is provided with an ISC valve 42 for adjusting the passing air amount mainly for controlling the intake air amount during idling. The opening and closing of the ISC valve 42 is adjusted by the duty ratio. Further, an injector 44 is provided on the downstream side of each intake pipe 22 toward the intake port 24, and each injector 44 extends from the fuel pump 46 to the fuel pipe 4.
Fuel atomized and supplied via 8 is atomized and injected.

On the other hand, a catalyst 50 such as a three-way catalyst is provided near the engine body 10 side of the exhaust passage 14, and an upstream side of the catalyst 50 serves as an air-fuel ratio sensor for detecting the air-fuel ratio in the exhaust gas. O2 sensor 52 is provided.

The EGR passage 54 formed with a flow passage area having a diameter smaller than that of the intake pipe 22 and the exhaust pipe 32 is
The exhaust pipe 32 and the collecting portion of the intake pipe 22 are provided so as to communicate with each other, and an EGR valve 56 that is controlled to be opened and closed by using, for example, a stepping motor as a drive source is attached in the middle of the EGR passage 54. This EGR valve 56
By sending a pulse signal to the stepping motor of
The lift amount of the EGR valve 56 is controlled.

Further, the combustion chamber 26 is provided in the cylinder head 58.
A spark plug 60 is provided facing the inside of the combustion chamber 26. The spark plug 60 is powered by a high voltage supplied through an igniter 62 and an ignition coil 64.
Forcibly ignite the air-fuel mixture inside at a predetermined ignition timing.

In the figure, 66 is a crank angle sensor for detecting the crank angle and engine speed N, and 68 is a crank angle sensor.
Is a knock sensor that detects knocking of the engine body 10, 70 is a water temperature sensor that detects the temperature of the cooling water, 72 is a cam angle sensor that detects the rotation angle of a cam provided on the cam shaft 74, and 76 is the throttle valve 38. Opening T
A throttle opening sensor for detecting h.

An engine control unit (hereinafter simply referred to as "ECU") 78 that receives the drive control of each member and the detection signals from each sensor receives the signal from each sensor as shown in FIG. Input interface 78a for outputting, output interface 78b for outputting a drive control signal to each member, CP as a main processing unit
The bus line 7 includes a U 78c, a ROM 78d that stores a control program and preset fixed data, a RAM 78e that stores a detection signal from each sensor, a timer 78f, and the like.
It is configured as a microcomputer system which is connected to each other at 8 g.

Next, FIG. 3 shows each function realized by the ECU 78 for EGR rate correction. First, the rapid deceleration state detection means 80 rapidly decelerates the engine body 10 based on the amount of change in the throttle opening Th. When the condition is detected, EGR
The rate correction means 82 controls the auxiliary air supply means 85 including the ISC valve 42 and the ISC passage 40 to supply the auxiliary air to the engine body 10. Further, when supplying the auxiliary air, the auxiliary air amount calculation means 83 refers to the EGR map 84 in which the optimum EGR rate is mapped and stored for each steady operation state of the engine body 10 to refer to the rapid deceleration state. A necessary correction air amount is calculated according to the difference between the EGR rate before occurrence and the EGR rate after occurrence. Further, the ignition timing correction amount calculation means 84 calculates the ignition timing retard amount necessary to cancel the torque change caused by the supply of the auxiliary air.

Next, an operation routine for correcting the EGR rate according to one embodiment of the present invention using the engine device having the above-mentioned configuration will be described with reference to the flowchart of FIG.

First, in step (hereinafter simply referred to as "S") 101, the latest throttle opening Th detected by the throttle opening sensor 76 is read, and in S102, this read throttle opening Th is opened to the latest throttle opening Th. Degree T
It is set as the second throttle opening Th2 indicating h (n). Next, in S103, the throttle opening Th (n-1) read in the previous routine is read as the first throttle opening Th1. Then, in S104, the difference between the latest throttle opening Th2 and the previous throttle opening Th1 is calculated, and it is determined whether or not the difference between the two is larger than a preset first reference value Tha.

If the throttle opening is lower than the previous value by the predetermined reference value Tha or more (YES), it is judged that the rapid deceleration has started, and the routine proceeds to S105. At this S105,
It is determined whether the throttle opening Th2 read this time is smaller than a preset second reference value A or not. This second
The reference value A of E is the value E when the operating state of the engine body 10 is excessive.
This is for determining whether or not the load has shifted to a low load state in which GR should be prevented.

When it is determined that the load is low (Y
ES) reads the EGR map illustrated in FIG. 5 in S106, and EG corresponding to the first throttle opening Th1.
EG corresponding to R rate G1 and second throttle opening Th2
A correction amount ISC1 for the opening of the ISC valve 42 is calculated from the difference from the R ratio G2, and this correction amount ISC1 is adjusted to a normal I value according to the current engine load (low load in this case).
Add to SC valve opening value ISC0. As a result, the throttle valve 3
The air on the upstream side of No. 8 corresponds to the high EGR rate G1 before the rapid deceleration as the auxiliary air, and the ISC passage 40 and the ISC.
It is supplied through the valve 42, which prevents the EGR amount from becoming excessive.

Next, in order to prevent the output change due to the increase of the opening degree of the ISC valve 42, the correction amount ADV1 of the ignition timing for canceling the output increase by the auxiliary air is calculated in S107, and this ignition is performed. The correction amount ADV1 of the timing is set to the normal ignition timing AD according to the current operating state.
Subtract from V0 to retard. That is, the excessive EGR can be suppressed by increasing the supply of the auxiliary air, but if it is left as it is, it does not meet the intention of the driver who releases the accelerator pedal in order to reduce the output. Therefore, by retarding the ignition timing from the normal value, the output increase is suppressed to match the operation feeling of the driver.

After the auxiliary air is supplied by the ISC valve 42 and the ignition timing is retarded, at S108
It is determined whether or not the correction amount ISC1 for the SC valve 42 is "0", and when it is not "0" (YE
S), and then in S109, a predetermined value ΔI is calculated from the correction amount ISC1.
Decrease SC only. That is, the value of the correction amount ISC1 is decreased by ΔISC for each routine, and eventually becomes “0”, and when the supply of the auxiliary air by the ISC valve 42 is stopped, the EGR rate correction in the transient state is completed, It is determined to be "NO" in S108.
Similarly, in S110, it is determined whether or not the ignition timing correction amount ADV1 is "0", and if it is not "0" (YES), then in S111, the ignition timing correction amount ADV1 is determined for each routine. Decrease it by ΔADV until it reaches “0”.

Finally, when the correction amount ISC1 for the ISC valve 42 becomes "0", it is determined to be "NO" in S108 and the process proceeds to S112. In this S112, the valve opening degree of the ISC valve 42 is changed. It is set to a normal value ISC0 corresponding to the current engine load that has reached a steady state. Similarly, when the correction amount ADV1 of the ignition timing becomes "0", it is determined to be "NO" in S110 and is set to the normal ignition timing ADV0 corresponding to the engine load settled in the steady state in S113. .

If it is determined to be "NO" in S104, it means that the rapid deceleration state has not occurred.
Move to 2. Further, when it is determined to be "NO" in S105, it means that the rapid deceleration has started but the engine load has not decreased to a low load, and the EGR rate correction is not necessarily required. Therefore, the process proceeds to S112.

Note that FIG. 5 is an EGR rate map in which the optimum EGR rate in a steady engine operating state is set by the relationship between the engine speed N and the engine torque (load). As described above, the EGR rate becomes the maximum value in the medium load state where the engine load is relatively high.
This EGR rate map is set so that the GR rate gradually decreases.

As described above, at the time of rapid deceleration in which the opening of the throttle valve 38 is sharply narrowed and the engine load is rapidly reduced, the ISC valve 42 is quickly opened and the supply of auxiliary air is started to increase. The high EGR rate G1 set according to the relatively high load state before the sudden deceleration is maintained,
It is possible to prevent excessive EGR from occurring when the load is low, which leads to misfires, exhaust emission and deterioration of fuel efficiency.
Drivability can be prevented from lowering. In particular, since the excessive EGR is prevented by supplying the auxiliary air from the ISC valve 42 without depending on the correction of the fuel injection amount, it is possible to enhance the responsiveness and appropriately deal with the transient response characteristic of the EGR. It will be possible.

Further, since the ignition timing is retarded in accordance with the increase in the supply of the auxiliary air, it is possible to easily cancel the output change (torque change) due to the increase in the supply of the auxiliary air, and prevent deterioration of drivability. can do.

Further, since the correction amount of the auxiliary air and the correction amount of the ignition timing are reduced every predetermined time, after the transient state due to the sudden change of the engine load has passed and the steady state has been reached, the unnecessary EGR rate is corrected. It is possible to efficiently control the EGR rate without causing such a situation.

The present invention is not limited to the configuration of the above embodiment, and various modifications can be made within the scope of the gist of the invention. For example, the engine body 10 is not limited to a horizontally opposed engine, and may be another type such as an in-line engine or a V-type engine. The EGR valve 56 is not limited to a stepping motor in its drive system, and may be feedback-controlled using another electric motor such as a servo motor if necessary. Furthermore, the EGR valve 56 is a negative pressure EGR valve. May be.

If the throttle opening Th is used,
This is advantageous because a rapid deceleration state can be detected with high responsiveness, but the present invention is not limited to this, and is based on changes in parameters that reflect other operating states such as the engine speed N, the intake air amount Q, or the intake pipe pressure Pm. It is also possible to detect the occurrence of a sudden deceleration state. Further, the auxiliary air supply means is not limited to the ISC passage 40 and the ISC valve 42, and for example, an air conditioner bypass passage and an air conditioner valve for securing an engine load when the air conditioner is used may be used.

[0039]

As described above, according to the exhaust gas recirculation system of the present invention, excessive exhaust gas recirculation is transient when a rapid deceleration state occurs in which the engine load is rapidly reduced while the exhaust gas recirculation is high. Can be prevented by the supply of auxiliary air, and the output change due to the supply of auxiliary air can be canceled by appropriate correction of the ignition timing. As a result, it is possible to prevent misfire, deterioration of exhaust emission and fuel consumption, and deterioration of drivability in a transient state during rapid deceleration.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an overall configuration of an engine device to which an embodiment of the present invention is applied.

FIG. 2 is a configuration explanatory view showing an internal configuration of an ECU in FIG.

FIG. 3 is an explanatory diagram of a function realized by an ECU regarding exhaust gas recirculation in the embodiment.

FIG. 4 is a flowchart showing an EGR rate correction method according to an embodiment.

FIG. 5 is an explanatory diagram of an EGR rate map showing the relationship between the steady operating state of the engine and the EGR rate.

[Explanation of symbols]

 10 engine body 12 intake passage 38 throttle valve 40 ISC passage 42 ISC valve 54 EGR passage 56 EGR valve 78 ECU Th throttle opening Th1 previous throttle opening Th2 current throttle opening ISC0 normal ISC valve opening ISC1 ISC correction amount ΔISC Decrease in ISC correction amount ADV0 Normal ignition timing ADV1 Ignition timing correction amount ΔADV Decrease in ignition timing correction amount Tha First reference value for determining sudden deceleration state A Second reference for determining low load state value

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F02P 5/15 F02P 5/15 G

Claims (6)

[Claims] 1. An exhaust gas recirculation device that recirculates a part of exhaust gas to a downstream side of a throttle valve to control an exhaust gas recirculation rate according to an operating state of the engine, and bypasses the throttle valve to supply auxiliary air to the engine. Auxiliary air supply means capable of supplying, a rapid deceleration state detecting means for detecting a rapid deceleration state in which the engine rapidly decelerates while the exhaust gas recirculation is being performed, and the rapid deceleration state detecting means detects the rapid deceleration state. An exhaust gas recirculation system for an engine, comprising: an exhaust gas recirculation ratio correction means for correcting the exhaust gas recirculation ratio by supplying auxiliary air to the engine for a certain period of time by the auxiliary air supply device. 2. The exhaust gas recirculation rate correction means supplies the engine with an amount of auxiliary air according to the exhaust gas recirculation rate before the occurrence of the sudden deceleration state, through the auxiliary air supply means. Item 2. The engine exhaust gas recirculation device according to Item 1. 3. The exhaust gas recirculation system for an engine according to claim 1, wherein the exhaust gas recirculation rate correction means retards the ignition timing according to the amount of the auxiliary air. . 4. The exhaust gas recirculation system for an engine according to claim 1, wherein the exhaust gas recirculation rate correction means reduces the amount of the auxiliary air at predetermined time intervals during the fixed time period. apparatus. 5. An exhaust gas recirculation method in which a part of exhaust gas is recirculated to a downstream side of a throttle valve and the exhaust gas recirculation rate is controlled according to the operating state of the engine. The engine rapidly decelerates while exhaust gas recirculation is being performed. An exhaust gas recirculation method for an engine, wherein the exhaust gas recirculation rate is corrected by detecting the sudden deceleration state, and when the sudden deceleration state is detected, bypassing the throttle valve and supplying auxiliary air to the engine. 6. The exhaust gas recirculation method for an engine according to claim 5, wherein the ignition timing is retarded according to the amount of the auxiliary air.