JPH08121261A - Controller of engine - Google Patents

Abstract

PURPOSE: To enable the exhaust gas recirculation(EGR) of proper amount of exhaust gas even if aged deterioration occurs in an EGR passage by comparing actual EGR amount with the target EGR amount and increasing a difference between suction pressure and exhaust pressure when actual EGR amount is smaller than the target EGR amount. CONSTITUTION: In a controller 18 in which signals from an O2 sensor 16 and the detected signals such as the number of revolutions of an engine, a degree of opening of an accelerator, water temperature, etc., are input, an injection time setting means 20 which sets the target injection time in accordance with the operation condition of the engine is provided, and a fuel injection pump 12 is controlled through an injection time adjusting means 22 so that a predetermined amount of fuel is injected at the target injection time. Moreover, an EGR amount setting means 24 which sets the target EGR amount in accordance with the operation condition in a predetermined EGR region is provided, and an EGR control valve 14 is controlled through an opening degree adjusting means 26 in accordance with the target EGR amount. On this occasion, the fuel injection time is compensated so that a difference between suction pressure and exhaust pressure is increased and decreased under certain operation conditions by a differential pressure control means 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device configured to recirculate (EGR) exhaust gas introduced into an exhaust passage of an engine to an intake passage.

[0002]

2. Description of the Related Art Conventionally, for the purpose of reducing the amount of NOx in exhaust gas discharged from an engine, a part of the exhaust gas is recirculated (EGR) into intake air to lower the temperature of combustion gas of the engine, thereby reducing NOx. There is known an engine that suppresses the generation of the engine (Japanese Patent Laid-Open No. 2-123272).

In such an engine, an EG for recirculating exhaust gas derived from the intake passage of the engine to the intake passage
An EGR control valve is installed in the R passage, and the opening degree of the EGR control valve is controlled according to the engine speed or the like to improve the composition of exhaust gas without impairing the drivability of the engine. Has been done.

[0004]

However, when the engine is operated for a long period of time, impurities such as carbon contained in the exhaust gas adhere to the EGR control valve and the wall surface in the EGR passage. The control valve may not be opened or closed properly, or it may be difficult to appropriately recirculate the exhaust gas according to the opening degree of the EGR control valve, and as a result, the effect of improving the composition of the exhaust gas may be reduced. Occurs.

Therefore, in an engine configured to recirculate the exhaust gas discharged into the exhaust passage into the intake passage, even if the above-described secular change occurs in the exhaust gas recirculation system, an appropriate amount of exhaust gas is generated. It is desirable to allow reflux.

Further, in controlling the engine, when the engine is in a specific state such as a cold operation state, it is detected to advance the fuel injection timing or the plug ignition timing to advance the engine control. Although complete combustion is promoted, in this case, if the opening degree of the EGR control valve is set to the same opening degree during normal operation (during warm time etc.), the opening degree of the EGR control valve will be constant. However, since the actual EGR amount may be excessive or insufficient, it is also necessary to suppress such a variation in the EGR amount.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an engine control device capable of appropriately controlling the recirculation amount of exhaust gas.

[0008]

According to a first aspect of the present invention, there is provided an engine control system, wherein an EGR control valve is installed in an EGR passage for returning exhaust gas discharged into an exhaust passage of the engine to an intake passage. The EGR amount setting means for setting the target EGR amount according to the operating state of the vehicle, the opening adjusting means for opening and closing the EGR control valve based on the set target EGR amount, and the information indicating the actual EGR amount is detected. EGR amount detection means, target EGR amount and actual EGR
And a differential pressure control means for controlling the engine so as to increase the differential pressure between the intake pressure and the exhaust pressure when the actual EGR amount is smaller than the target EGR amount.

According to a second aspect of the present invention, there is provided an engine control apparatus according to the first aspect, wherein the engine is an exhaust turbocharged engine and the differential pressure control means is provided in an exhaust passage. The combustion state of the engine is controlled so that the exhaust gas temperature decreases.

According to a third aspect of the present invention, in the engine control device according to the second aspect, the engine is a diesel engine, and the differential pressure control means controls the fuel injection timing in advance.

According to a fourth aspect of the present invention, in the engine control device according to the second aspect, the engine is a gasoline engine, and the differential pressure control means controls the ignition timing in advance.

According to a fifth aspect of the present invention, in the engine control device according to any one of the first to fourth aspects, the above E
The GR amount detecting means is an O ₂ sensor provided in the exhaust passage.

According to a sixth aspect of the present invention, in an engine in which an EGR control valve is installed in an EGR passage that recirculates the exhaust gas led to the exhaust passage of the engine to the intake passage, a target EGR amount is set according to the operating state of the engine. EG to set
R amount setting means, opening adjustment means for opening and closing the EGR control valve based on the set target EGR amount, and correction means for correcting the opening degree of the EGR control valve based on the combustion state of the engine are provided. It is a thing.

According to a seventh aspect of the present invention, in the engine control apparatus according to the sixth aspect, the engine is a diesel engine with an exhaust turbocharger, and the correction means controls the advance of the fuel injection timing. If the above E
The opening adjusting means is controlled so as to correct the GR control valve in the closing direction.

The invention according to claim 8 is the engine control device according to claim 6, wherein the engine is a gasoline engine with an exhaust turbocharger, and the correcting means is
When the ignition timing is advanced, the opening adjusting means is controlled so as to correct the EGR control valve in the closing direction.

[0016]

According to the first aspect of the present invention, when the actual EGR amount becomes smaller than the target EGR amount during engine operation, the engine is controlled so that the differential pressure between the intake pressure and the exhaust pressure increases. As a result, the EGR amount can be increased even under the condition where the opening degree of the EGR control valve is kept constant, and the adjustment range of the EGR amount is expanded.

According to the second aspect of the present invention, the temperature of the exhaust gas in the exhaust passage is lowered and the pressure of the exhaust gas (exhaust pressure) is lowered, so that the supercharging efficiency of the supercharger is reduced. The intake pressure drops. At this time, since the intake pressure decreases more than the decrease of the exhaust pressure, the differential pressure between the intake pressure and the exhaust pressure can be effectively increased.

According to the third aspect of the present invention, when the engine is a diesel engine, advance combustion control of the fuel injection timing promotes complete combustion in the engine, thereby lowering the exhaust gas temperature. As it becomes, the exhaust pressure becomes lower.

According to the fourth aspect of the present invention, when the engine is a gasoline engine, the ignition timing is advanced to promote complete combustion in the engine, thereby lowering the exhaust gas temperature. At the same time, the exhaust pressure decreases.

According to the invention described in claim 5, EGR
When the amount is small, while the O ₂ concentration in the exhaust gas increases in improved combustion efficiency of the engine, when the EGR amount is small, O ₂ in the exhaust gas combustion efficiency of the engine is reduced
Since the concentration becomes high, the actual EGR amount is detected by detecting the O ₂ concentration in the exhaust gas. Particularly, in the case of a gasoline engine, the existing O ₂ sensor can be used together, which is advantageous in terms of structure.

According to the sixth aspect of the present invention, although the operating conditions are the same, it is possible to suppress an error in the EGR amount caused by a difference in predetermined conditions such as during cold and warm conditions.

According to the invention described in claim 7, the engine is a diesel engine with an exhaust turbocharger,
When the fuel injection timing is advanced, the EGR control valve is controlled in the closing direction to prevent excessive recirculation of exhaust gas.

According to the invention described in claim 8, when the engine is a gasoline engine with an exhaust turbocharger and the ignition timing is advanced, the EGR control valve is controlled to be closed. This prevents the exhaust gas from being excessively recirculated.

[0024]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows a diesel engine to which a first embodiment of a control device according to the present invention is applied. A diesel engine (hereinafter abbreviated as an engine) shown in the figure includes an engine body 2 having a combustion chamber, an intake passage 4 for supplying air to the engine body 2, and an exhaust passage 6 for exhausting exhaust gas after combustion. The turbocharger 8 includes a compressor 8a and a turbine 8b, and an EGR passage 10 that recirculates a part of exhaust gas to the intake side.

The upstream end of the intake passage 4 and the downstream end of the exhaust passage 6 are connected to the turbocharger 8, respectively. The turbine 8a is rotated by the pressure of the exhaust gas so that compressed air is taken in by the compressor 8b. It is supposed to be sent to 4. Further, an O ₂ sensor 16 is provided in the upstream portion of the exhaust passage 6 so that the O ₂ concentration contained in the exhaust gas can be detected.

The engine body 2 has a fuel injection pump 1 for injecting a predetermined amount of fuel into the compressed air in the combustion chamber.
2 is installed. The fuel injection pump 12 is, for example, a so-called electronically controlled FIP whose fuel injection timing can be adjusted by moving a timer piston, and the fuel injection timing is controlled by a control device 18 described later. . Further, the fuel injection pump 12 is provided with a position detection sensor for the timer piston, and fuel injection timing management is performed based on the sensor output.

One end of the EGR passage 10 is connected to the intake passage 4 and the other end thereof is connected to the exhaust passage 6, and an EGR control valve 14 is provided at a portion connected to the intake passage 4. . Although not shown, the EGR control valve 14 includes a poppet that closes the EGR passage 10 and an actuator that adjusts the lift amount of the poppet, and the opening degree is controlled by the control device 18 described later. ing. The EGR control valve 14 is provided with a lift amount detection sensor that detects the lift amount of the poppet, and the opening degree of the EGR control valve 14 is managed based on the sensor output.

Further, the engine is provided with a control device 18 having a microcomputer as a constituent element, and the fuel injection pump 12 and the EGR control valve 14 are all electrically connected to the control device 18 and are integrally controlled. At the same time, a signal from the O ₂ sensor 16 and signals indicating the engine speed, the engine speed, the accelerator opening, the water temperature, the oil temperature, etc. are input to the control device 18.

The control device 18 has an injection timing setting means 20 for setting a target injection timing of fuel according to an operating state of the engine, and the fuel injection for injecting a predetermined amount of fuel at the set target injection timing. A target recirculation exhaust gas amount (target EGR amount) according to an operating state of the engine in a predetermined EGR region and an injection timing adjusting unit 22 that controls the pump 12.
EGR amount setting means 24 for setting
The opening adjusting means 26 for controlling the opening of the EGR control valve 14 according to the amount, and the fuel injection by the fuel injection pump 12 to increase or decrease the pressure difference between the intake pressure and the exhaust pressure under a constant operating condition. A differential pressure control means 28 for correcting the timing is provided.

The injection timing setting means 20 and the EGR amount setting means 24 each have a table of target fuel injection timing and target EGR amount corresponding to the operating state of the engine, and the various signals indicating the operating state of the engine. Based on the input, the target fuel injection timing and the target EGR amount corresponding to the operating state are read out from each table, and the signals corresponding to these are output to the injection timing adjusting means 22 and the opening adjusting means 26, respectively. There is. The EGR amount setting means 24 reads out the target EGR amount only when the operating state of the engine is in a predetermined EGR region.

The injection timing adjusting means 22 has a table of the timer piston position of the fuel injection pump 12 set corresponding to the target fuel injection timing, and the injection timing setting means 20 sets the target of the fuel injection pump 12 as described above. When the signal indicating the fuel injection timing is input, the position of the timer piston corresponding to this signal is read out, and the EGR control valve 14 is adjusted so that the position of the timer piston of the EGR control valve 14 coincides with this position.
A control signal is output to.

The opening adjusting means 26 is configured to operate the target EGR.
It has a table of the opening degree of the EGR control valve 14 set corresponding to the amount, that is, the lift amount of the poppet, and when the signal indicating the target EGR amount is input from the EGR amount setting means 24 as described above. The opening degree corresponding to this signal is read out, and a control signal is output to the EGR control valve 14 so that the opening degree of the EGR control valve 14 coincides with this opening degree.

The differential pressure control means 28 determines the actual EGR amount based on the O ₂ concentration in the exhaust gas detected by the O ₂ sensor 16, and the EGR amount and E
The target EGR amount set by the GR amount setting means 24 is compared, and when there is a difference between the target EGR amount and the actual EGR amount, the fuel is set by a preset amount in a direction to correct the difference. A control signal is output to the injection timing adjusting means 22 in order to correct the injection timing.

Next, the control of the engine by the control device 18 constructed as above will be described with reference to the flow chart shown in FIG.

When the control shown in the figure is started, first, information indicating the operating state of the engine such as the engine speed and the accelerator opening is read, and based on these information, whether the engine is in the EGR region or not is read. It is determined (steps S1 to S3).

When the engine is in the EGR region (YES in step S3), the target EGR amount is set by the EGR amount setting means 24, and the EGR control valve 14 opens according to the target EGR amount. (Step S4).

When EGR is started, the above O ₂
The actual EGR amount is calculated based on the O ₂ concentration in the exhaust gas detected by the sensor 16, and the actual EGR amount is calculated.
It is determined whether the GR amount and the target EGR amount match (steps S5 and S6). Here, when the actual EGR amount and the target EGR amount match (YES in step S6)
It is assumed that EGR is properly performed in step S1.
Will be returned to.

On the other hand, if the actual EGR amount does not match the target EGR amount (NO in step S6), step S
After the shift to 7 and the fuel injection timing is detected, it is determined in step S8 whether the actual EGR amount is smaller than the target EGR amount, that is, whether the EGR amount is insufficient. Then, if the actual EGR amount is small (YES in step S8), the fuel injection timing of the fuel injection pump 12 is advanced by a preset amount, and then the process returns to step S1.

That is, when the fuel injection timing is corrected in advance in this way, the complete combustion in the engine is promoted, and the so-called afterburn phenomenon is suppressed, and the exhaust gas temperature and the exhaust gas in the exhaust passage 6 are suppressed. Therefore, the pressure (exhaust pressure) decreases. However, since the efficiency of the turbocharger 8 is greatly influenced by the exhaust gas temperature and the exhaust pressure, when both the exhaust gas temperature and the exhaust pressure decrease as described above, the supercharge efficiency of the turbocharger 8 is increased accordingly. Is significantly reduced.
Therefore, the intake pressure is reduced more than the exhaust pressure is reduced, which effectively increases the differential pressure between the intake pressure and the exhaust pressure. When the pressure difference between the intake pressure and the exhaust pressure thus increases, the amount of exhaust gas that recirculates to the intake passage 4 via the EGR passage 10 increases, and as a result, the shortage of the EGR amount is effective. Will be compensated for.

On the other hand, in step S8, the actual EGR
When the amount is large (NO in step S8), step S
In 10, the fuel injection timing of the fuel injection pump 12 is retarded by a preset amount, and step S1 is performed.
Will be returned to. That is, by correcting the fuel injection timing in this manner, the pressure difference between the intake pressure and the exhaust pressure is reduced by the principle opposite to the above (step S9).
Excessive supply of the EGR amount with respect to the target EGR amount is suppressed.

As described above, according to the engine control, the EGR is performed by utilizing the change in the pressure difference between the intake pressure and the exhaust pressure.
Since the amount is adjusted, for example, impurities such as carbon contained in the exhaust gas may be contained in the EGR control valve 14 or the EG.
For example, the EGR control valve 14 is fully opened and the EGR amount becomes insufficient due to adhesion to the inside of the R passage 10, or the EGR control valve 14 is fully opened.
This is effective when the R control valve 14 does not open beyond a certain opening, that is, when the EGR passage 10 and the EGR control valve 14 change over time.

That is, in the conventional engine in which the EGR amount is adjusted only by the EGR control valve, when the above-described secular change occurs in the exhaust gas recirculation system, the optimum EGR amount according to the operating state of the engine is obtained. It becomes difficult or impossible to maintain the above, which may lead to deterioration of the exhaust gas composition. However, the engine of the above embodiment can prevent such a situation from occurring. Therefore, for example, if the above-described control is executed when the engine has been used or the mileage of the vehicle exceeds the distance for a predetermined period, the exhaust gas composition of the engine can be appropriately adjusted over a long period of time. It is possible to maintain.

By the way, the above-mentioned control for adjusting the EGR amount by adjusting the fuel injection timing and utilizing the change in the pressure difference between the intake pressure and the exhaust pressure caused by the fuel injection timing is performed in the EGR passage 10 and the EGR control valve 14. It is effective not only as a measure against aging, but also when applied to normal engine control. That is,
As shown in FIG. 3, if the fuel injection timing is controlled to advance in a predetermined EGR region, the EGR amount in the EGR region can be increased, thereby more effectively suppressing the generation of NOx. be able to.

In the first embodiment described above, an example in which the control device of the present invention is applied to a diesel engine has been described, but it is of course applicable to a gasoline engine. In this case, in the gasoline engine, the combustion timing changes depending on the ignition timing of the spark plug, so instead of the injection timing setting means 20 and the injection timing adjusting means 22 of the first embodiment, the ignition timing setting means and the ignition timing adjustment are performed. Means may be provided to adjust the ignition timing.

Further, in the first embodiment, the O ₂ sensor 16 is applied as a means for detecting the actual EGR amount, but the O ₂ sensor 16 does not necessarily have to be used, and instead of this, the flow rate sensor is used. May be used. However, since the O ₂ concentration in the exhaust gas significantly reacts to the change in the EGR amount, the O ₂ sensor 16 as in the above-described embodiment is used.
Is more reliable and structurally advantageous. In particular, in the case of a gasoline engine, an O ₂ sensor is preliminarily provided in the exhaust passage due to its structure, which is advantageous in that an existing O ₂ sensor can be used.

Further, in the above first embodiment, the control device of the present invention is applied to an engine with an exhaust turbocharger,
By changing the combustion state of the engine by advancing or retarding the fuel injection timing by the fuel injection pump 12, the change in the pressure difference between the intake pressure and the exhaust pressure resulting from this is used to adjust the EGR amount. However, this is because the characteristics of the supercharger have the advantage that the pressure difference between the intake pressure and the exhaust pressure can be greatly increased or decreased by slightly adjusting the fuel injection timing. Of course, it is also possible to apply to an engine without a supercharger. In this case, a device that mechanically changes the intake pressure or the exhaust pressure may be provided in either the intake passage 4 or the exhaust passage 6. For example, a variable silencer may be provided in the exhaust passage 6. It is possible to adopt a structure in which the variable silencer is connected to increase or decrease the distance of the exhaust gas passage.
According to this, while keeping the intake pressure substantially constant, by changing the distance of the exhaust gas passage to change the exhaust pressure, the EGR amount can be adjusted by increasing or decreasing the pressure difference between the intake pressure and the exhaust pressure. .

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 4 schematically shows a diesel engine to which a second embodiment of the control device according to the present invention is applied.

The diesel engine (hereinafter abbreviated as "engine") shown in the second embodiment basically has the same structure as the engine of the first embodiment. In the following description, the first embodiment will be described. Only the differences from the example will be briefly described. It should be noted that components having the same functions as those of the first embodiment will be described with the same reference numerals.

The engine of the second embodiment also includes an engine body 2, an intake passage 4, an exhaust passage 6, a turbocharger 8 and an EGR.
It is common to the engine of the first embodiment in that it has a passage 10, a fuel injection pump 12, an EGR control valve 14 and a control device 18. However, they are different in that the O ₂ sensor 16 is not provided in the exhaust passage 6 and that the correction device 30 is provided in the control device 18 instead of the differential pressure control device 28.

In the control device 18 of the second embodiment, the correcting means 30 controls the advance of the fuel injection timing of the fuel injection pump 12 while the engine is in a predetermined cold operation state or a predetermined transition period. In this case, for example, a control signal is output to the opening degree adjusting means 26 so as to operate the EGR control valve 14 in a direction to be closed by a preset amount immediately after the engine is started or during acceleration.

Next, the control of the engine by the control device 18 of the second embodiment will be described with reference to the flow chart shown in FIG.

When the control shown in the figure starts, first,
Information indicating the operating state of the engine, such as engine speed, accelerator opening, fuel injection timing, etc., is read, and the target fuel injection timing and EGR are set in the injection timing setting means 20 and EGR amount setting means 24 based on these information. The amount is set (steps S11 to S15).

Then, information such as water temperature and oil temperature relating to the engine temperature is read, and it is judged based on this information whether or not the engine is in a cold operation state (step S1).
6, S17). Then, when it is determined that the engine is in the cold operation state (YES in step S17), advance combustion control of the fuel injection timing promotes complete combustion in the engine, and further the preset amount is set. Only EGR
The EGR amount is suppressed by closing the control valve 14 (steps S18 and S19). Then, after that, the process proceeds to step S20, various correction controls are performed here, and then the process returns to step S11.

On the other hand, if it is determined in step S17 that the engine is not in the cold operation state (NO in step S17), the process proceeds to step S21 to determine whether the engine is in a predetermined transition period. Is determined.
If it is determined that the engine is in the predetermined transition period (YES in step S21), step S
The routine proceeds to 18 and the fuel injection timing is advanced. On the other hand, when it is determined that the engine is not in the transition period (NO in step S21), the process proceeds to step S20 and then returns to step S11.

According to the control of the second embodiment, the following effects can be obtained. When the engine is in a cold operation state or during a predetermined transition period such as acceleration,
Although it has been conventionally performed to advance the fuel injection timing by advancing the complete combustion, in the conventional engine, even if the fuel injection timing is advanced as described above, the EGR control valve The opening degree is set to the same opening degree during warm operation or during operation other than during the transition period, so that the exhaust gas may be excessively recirculated.

That is, when the fuel injection timing is advanced and the complete combustion is promoted as described above, the pressure difference between the intake pressure and the exhaust pressure increases as described in the first embodiment.
Along with this, the amount of exhaust gas recirculated to the intake passage 4 via the EGR passage 10 increases. Therefore, in the conventional engine in which the opening degree of the EGR control valve is set to be the same during the cold operation and the warm operation of the engine, or during the predetermined transient period and the operation other than the transient period, excessive exhaust gas recirculation is prevented. Will be invited.

On the other hand, according to the engine of the second embodiment, when the fuel injection timing is advanced when the engine is in a cold operation state or during a predetermined transition period such as acceleration, As shown in the flow chart of FIG.
Is closed by a preset amount to suppress the EGR amount, which effectively suppresses the occurrence of excessive recirculation of exhaust gas as in conventional engines, and as a result, it is possible to prevent deterioration of the exhaust gas composition. Becomes

In the second embodiment, an example in which the control device of the present invention is applied to a diesel engine has been described, but it is of course applicable to a gasoline engine. In this case, in the gasoline engine, instead of the injection timing setting means 20 and the injection timing adjusting means 22 of the second embodiment, an ignition timing setting means and an ignition timing adjusting means may be provided.

[0061]

As described above, according to the present invention, in an engine in which an EGR control valve is installed in an EGR passage that recirculates the exhaust gas led to the exhaust passage of the engine to the intake passage, the target EGR amount and actual When the actual EGR amount is smaller than the target EGR amount by comparing with the EGR amount, the differential pressure between the intake pressure and the exhaust pressure is increased so that the opening degree of the EGR control valve is kept constant. E even at the bottom
Since it is possible to increase the GR amount, the EG
Even if the R passage is aged or the like, an appropriate amount of exhaust gas can be EGR'd, whereby the initial exhaust gas composition can be more reliably maintained.

Particularly, in such a structure, when the engine is an engine with an exhaust turbocharger, a differential pressure control for controlling the combustion state of the engine so as to lower the exhaust gas temperature in the exhaust passage. By providing a means,
The characteristic of the supercharger can be utilized to effectively increase the pressure difference between the intake pressure and the exhaust pressure.

At this time, as a specific example of the differential pressure control means, if the engine is a diesel engine, the one for advancing the fuel injection timing can be applied, and if the engine is a gasoline engine, the ignition timing can be adjusted. Those that control the advance angle can be applied.

Further, as the EGR amount detecting means, O ₂
If a sensor is provided in the exhaust passage, the detected O
_{2 It} is possible to accurately detect the actual EGR amount based on the _two concentrations. Particularly, in the case of a gasoline engine, the existing O ₂ sensor can be used together, which is advantageous in terms of structure.

Further, according to the present invention, the EG is provided in the EGR passage for recirculating the exhaust gas led to the exhaust passage of the engine to the intake passage.
In the engine in which the R control valve is installed, the correction means for correcting the opening degree of the EGR control valve based on the combustion state of the engine is provided. Therefore, the operating state of the engine is the same, It is possible to effectively suppress an error in the EGR amount caused by a difference in a predetermined operating condition such as a short time.

At this time, when the engine is an exhaust turbocharged diesel engine, the EGR control valve is closed when the fuel injection timing is advanced, and
When the engine is a gasoline engine with an exhaust turbocharger, the EGR control valve is configured to be corrected in the closing direction when the ignition timing is advanced,
It is possible to effectively suppress the error in the EGR amount caused by the difference in operating conditions.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a diesel engine to which a control device according to a first embodiment of the present invention is applied.

FIG. 2 is a flowchart showing an example of control of the engine of FIG.

FIG. 3 is a graph showing an example of normal engine control.

FIG. 4 is a schematic diagram showing a diesel engine to which a control device according to a second embodiment of the present invention is applied.

5 is a flowchart showing an example of control of the engine of FIG.

[Explanation of symbols]

2 engine body 4 intake passage 6 exhaust passage 8 turbocharger 10 EGR passage 12 fuel injection pump 14 EGR control valve 16 O ₂ sensor 18 controller 20 injection timing setting means 22 injection timing adjusting means 24 EGR amount setting means 26 opening Adjusting means 28 Differential pressure controlling means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichi Toyokawa, 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Hideo Yamashita, 3-1-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Shares In-house (72) Inventor Masashi Naono 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (8)

[Claims] 1. An EGR amount setting for setting a target EGR amount according to an operating state of an engine in an engine in which an EGR control valve is installed in an EGR passage for recirculating exhaust gas discharged to an exhaust passage of the engine to an intake passage. Means, opening adjustment means for opening and closing the EGR control valve based on the set target EGR amount, EGR amount detecting means for detecting information indicating the actual EGR amount, target EGR amount and actual EGR
And a differential pressure control means for controlling the engine so as to increase the differential pressure between the intake pressure and the exhaust pressure when the actual EGR amount is smaller than the target EGR amount. Control device for the engine. 2. The engine is an engine with an exhaust turbocharger, and the differential pressure control means controls the combustion state of the engine so that the temperature of the exhaust gas in the exhaust passage decreases. The engine control device according to claim 1. 3. The engine control device according to claim 2, wherein the engine is a diesel engine, and the differential pressure control means controls the fuel injection timing in advance. 4. The engine control device according to claim 2, wherein the engine is a gasoline engine, and the differential pressure control means controls the ignition timing in advance. 5. The engine control device according to claim 1, wherein the EGR amount detecting means is an O ₂ sensor provided in the exhaust passage. 6. An EGR amount setting for setting a target EGR amount according to an operating state of an engine in an engine having an EGR control valve installed in an EGR passage for recirculating exhaust gas led to an exhaust passage of the engine to an intake passage. Means, opening adjustment means for opening and closing the EGR control valve based on the set target EGR amount, and correction means for correcting the opening degree of the EGR control valve based on the combustion state of the engine. Characteristic engine control device. 7. The engine is a diesel engine with an exhaust turbocharger, and the correcting means corrects the EGR control valve in a closing direction when the fuel injection timing is advanced. 7. The engine control device according to claim 6, wherein the control device controls the degree of opening adjustment. 8. The engine is a gasoline engine with an exhaust turbocharger, and the correction means opens the engine so as to correct the EGR control valve in a closing direction when the ignition timing is advanced. 7. The engine control device according to claim 6, which controls the degree adjusting means.