JPH02223659A - Exhaust gas return control device for engine with supercharger - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a torque shock by providing a closing operation speed control means which outputs a low speed closing operation signal to an opening closing control means only when acceleration from a low load running state to a state in which running at an engine load exceeding a given value is effected is effected and controls so that an exhaust gas return valve is gradually closed. CONSTITUTION:When acceleration from a low load running state to a running state wherein an engine load exceeds a given value at which exhaust gas return is stopped is effected, a low speed closing operation signal is outputted to an opening closing control means 36 by a closing operation speed control means 38, an exhaust gas return valve 9 is gradually closed, and exhaust gas return is gradually stopped. Thereby, a differential pressure between an exhaust gas pressure and a supercharge pressure is temporarily increased. As a result, an exhaust gas return amount is temporarily increased, and since, even when engine torque is temporarily stopped, engine torque is gradually increased, exhaust gas return is stopped. This constitution prevents the occurrence of a torque shock, and prevents worsening of a running feeling.

Description

[Detailed description of the invention] Star! TECHNICAL FIELD The present invention relates to an exhaust gas recirculation control device for a supercharged engine, and more specifically, it has a simple structure, improves emissions, and reduces torque during acceleration from a low-load operating state. The present invention relates to an exhaust gas recirculation control device for a supercharged engine that can prevent shock and quickly obtain sufficient torque when accelerating from a high or low load operating state.

Exhaust recirculation of the Guangqiu Fu Nini engine is generally performed under operating conditions below the specified engine load, because if the engine load exceeds a specified level, sufficient engine torque may not be obtained due to exhaust recirculation, and smoke may occur. Exhaust gas recirculation is performed only in the engine, and when the engine load exceeds a predetermined value, the exhaust gas recirculation is controlled to be stopped.

Furthermore, in a supercharged engine, exhaust gas recirculation control is normally performed using the differential pressure between exhaust gas pressure and supercharging pressure.

However, in the exhaust gas recirculation control device for a supercharged engine that utilizes the differential pressure between the exhaust gas pressure and the supercharging pressure, during acceleration, the exhaust gas pressure increases and Since there is a time delay between the boost pressure increasing and the boost pressure increasing, it becomes difficult to control the exhaust gas recirculation as desired, and a torque shock may occur, which may deteriorate the driving feeling.

That is, in general, engine torque increases as the engine load increases, but the engine torque obtained when exhaust gas recirculation is performed is always smaller than when exhaust gas recirculation is not performed, regardless of the engine load. Therefore, when the engine load exceeds the predetermined value at which exhaust gas recirculation is stopped due to acceleration, and exhaust gas recirculation is stopped, it is inevitable that a larger torque fluctuation will occur than when exhaust gas recirculation is continued. Ta.

However, the fluctuation in torque caused by stopping the exhaust gas recirculation due to acceleration is not so great as to deteriorate the driving feeling, but it is possible to use the differential pressure between the exhaust gas pressure and the boost pressure mentioned above. In the exhaust gas recirculation control device for a supercharged engine, the exhaust gas pressure increases immediately during acceleration, but the supercharging pressure does not increase immediately.
- The differential pressure between the exhaust gas pressure and the boost pressure increases over time, increasing the amount of exhaust gas recirculation and causing a temporary decrease in engine torque. This results in a sudden increase in torque, and there is a problem in that compared to a normal engine, the torque shock when exhaust gas recirculation is stopped due to acceleration becomes larger, which may worsen the driving feeling.

However, in the case of acceleration from a high-load operating state, the boost pressure before acceleration is already sufficiently high, so the temporary increase in the differential pressure between the exhaust gas pressure and the boost pressure due to acceleration will not be that large. Also, since the temporary increase in the amount of exhaust gas recirculation is not so large, the temporary decrease in engine torque is also small. Therefore, even if exhaust gas recirculation is stopped immediately thereafter, the engine torque fluctuation will be the same as in a normal engine. There is no significant difference between the two, and the deterioration of driving feeling due to torque shock is not so much of a problem. However, when accelerating from a low-load operating state, the boost pressure is originally low, so if the exhaust gas pressure increases due to acceleration. , the temporary increase in the differential pressure between the exhaust gas pressure and boost pressure caused by acceleration becomes extremely large, and the temporary increase in the amount of exhaust gas recirculation also becomes extremely large, so the engine torque temporarily decreases significantly due to acceleration. Therefore, if the exhaust gas recirculation is stopped immediately thereafter, the torque shock becomes extremely large, resulting in a problem that the driving feeling is significantly deteriorated.

During such acceleration, the problem of a temporary drop in engine torque caused by the time delay between the rise in exhaust gas pressure and the rise in supercharging pressure in the exhaust gas recirculation control device of a supercharged engine is Although it is possible to prevent this by using a device that corrects the differential pressure between the exhaust gas pressure and the boost pressure, using a differential pressure correction device complicates the device and causes an increase in cost. , undesirable.

Dishes F and U The present invention provides an exhaust type supercharger, an exhaust recirculation passage, an exhaust recirculation valve that opens and closes the exhaust recirculation passage, an engine negative section detection means for detecting engine load, and an output of the engine load detection means. A supercharger equipped with an opening/closing control means that controls to open an exhaust recirculation valve when the engine load is below a predetermined value and to close the exhaust recirculation valve when the engine load exceeds a predetermined value based on a signal. This exhaust recirculation control system for engines with a simple structure improves emissions, prevents torque shock when accelerating from low-load operating conditions, and quickly provides sufficient control when accelerating from high-low-load operating conditions. It is an object of the present invention to provide an exhaust gas recirculation control device for a supercharged engine that can obtain torque.

The object of the present invention is to provide acceleration detection means for detecting the acceleration state of the engine, and an output signal from the engine load detection means and an output signal from the acceleration detection means. This is achieved by providing a closing operation speed control means that outputs a low-speed closing operation signal to the opening/closing control means and controls the exhaust recirculation valve to gradually close only when the engine accelerates to a state where the engine load exceeds . Ru.

According to the present invention, when the engine load accelerates from a low-load operating state to an operating state in which the engine load exceeds a predetermined value at which exhaust gas recirculation is stopped, the exhaust recirculation valve is gradually closed by the opening/closing control means, and the exhaust recirculation is gradually stopped. Because the engine is stopped, acceleration temporarily increases the differential pressure between exhaust gas pressure and boost pressure, resulting in a temporary increase in the amount of exhaust gas recirculation and a temporary decrease in engine torque. However, as the engine torque gradually increases, exhaust recirculation is stopped,
Torque shock is prevented from occurring, and the driving feeling is not deteriorated.

In a preferred embodiment of the present invention, engine speed detection means is further provided, and in addition to the output signals from the acceleration detection means and the engine load detection means, the low load and when the engine load accelerates from a low engine speed operating state until it exceeds a predetermined value at which exhaust gas recirculation is stopped, a low speed closing operation signal is output to the opening/closing control means to control the closing speed of the exhaust recirculation valve to a small value. It is configured as follows.

Even when the engine load is low and the engine speed is high, the exhaust gas energy is relatively high.
Therefore, since the boost pressure is also at a relatively high value, the differential pressure between the exhaust gas pressure and the boost pressure will not become so large due to acceleration, and therefore the temporary decrease in engine torque will not become so large. With this configuration, while maintaining good acceleration response,
It becomes possible to prevent deterioration of driving feeling due to torque shock.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is an overall schematic diagram of a supercharged diesel engine including an exhaust gas recirculation control device according to an embodiment of the present invention.

In FIG. 1, a diesel engine 1 has a cylinder 2
The piston 4 is provided with a piston 4 that slides vertically within the cylinder bore 3. A recess is provided on the top surface of the piston 4 within the cylinder bore 3, and this recess forms a combustion chamber 5. The cylinder bore 3 is connected to an intake passage 6 and an exhaust passage 7, and is provided with an exhaust recirculation passage 8 that branches from the exhaust passage 7 and can communicate with the intake passage 6, and an exhaust recirculation valve 9 that opens and closes the exhaust recirculation passage 8. It is being Inside the cylinder head 10, an intake valve 12 that opens and closes an intake port 11 of the intake passage 6 and an exhaust valve (not shown) that opens and closes an exhaust port (not shown) of the exhaust passage 7 are provided. Furthermore, a fuel injection nozzle 13 is provided that injects fuel into the highly compressed air in the combustion chamber 5 to cause spontaneous ignition. The intake passage 6 is arranged near the intake port 11 so that air is supplied along the inner surface of the cylinder bore 3 in the circumferential direction thereof, and generates an extremely strong swirl within the cylinder bore 3, which causes fuel injection. It is configured so that the fuel injected from the nozzle 13 and the intake air are sufficiently mixed.

A turbine 14 is provided on the downstream side of the branching part of the exhaust gas recirculation passage 8 of the exhaust passage 7, and a turbine 14 attached to the shaft of the turbine 14 is provided on the upstream side of the merging part of the exhaust gas recirculation passage 8 of the intake passage 6. A compressor 15 is provided to constitute a supercharger 16. As is well known, the supercharger 16 rotates the turbine 14 at high speed using the energy of the exhaust gas exhausted from the exhaust passage 7, and compresses the intake air with the compressor 15 attached to the end of the shaft of the turbine 14. However, it is configured to feed into the combustion chamber 5. Also,
The branch part of the exhaust gas recirculation passage 8 from the exhaust passage 7 is connected to the supercharger 16.
Since the joining part of the exhaust gas recirculation passage 8 to the intake passage 6 is provided on the downstream side of the supercharger 16, when the exhaust gas recirculation valve 9 opens the exhaust gas recirculation passage 8, Due to the pressure difference between the exhaust gas pressure in the exhaust passage 7 and the supercharging pressure of the intake air supercharged by the supercharger 16, the amount of exhaust gas returned from the exhaust passage 7 to the intake passage 6 via the exhaust recirculation passage 8 is increased. Exhaust recirculation personnel are to be determined.

The exhaust gas recirculation valve 9 is divided into a negative pressure chamber 21 and a valve side chamber 22 by a diaphragm 20, and the diaphragm 20 is always attached in the negative pressure chamber 21 in the direction in which the exhaust gas recirculation valve 9 closes the exhaust gas recirculation passage 8. Spring 23
is provided.

A negative pressure passage 24 is connected to the negative pressure chamber 21, and a three-way solenoid valve 25 is provided upstream of the negative pressure passage 24 to selectively connect the downstream side of the negative pressure passage 24 with a vacuum pump 26 and the atmosphere. A negative pressure passage throttle valve 27 is provided downstream of the three-way solenoid valve 25 to change the passage area of the negative pressure passage 24. 30 is a control unit.

FIG. 2 shows a block diagram of the exhaust recirculation control device; 31 according to the embodiment of the present invention provided in the control unit 30, and the exhaust recirculation control device 31 includes:
The memory 32 that stores the exhaust recirculation control map is accessible, and is based on the amount of depression of the accelerator pedal (not shown) or the opening degree of the fuel injection lever of the fuel injection pump (not shown) linked to the amount of depression of the accelerator pedal. Engine load sensor 33 that detects engine load
an engine load detection signal from the engine rotation speed sensor 34 that detects the engine rotation speed, and an engine coolant temperature sensor detection signal from the engine coolant temperature sensor 35 that detects the engine coolant temperature. are respectively input, and based on these input signals, outputs an exhaust recirculation ON signal or an exhaust recirculation OFF signal to the three-way solenoid valve 25 according to the exhaust recirculation control map stored in the memory 32, and turns the three-way solenoid valve 25 on. An opening/closing control means 36 that opens and closes, an acceleration detection signal from an acceleration sensor 37 that can access the memory 32 and detects the acceleration state of the engine, an engine load detection signal from the engine load sensor 33, and an engine rotation from the engine rotation speed sensor 34. Based on these input signals and according to the exhaust recirculation control map stored in the memory 32, the negative pressure passage throttling valve 27 is given a negative pressure passage throttling on signal or a negative pressure passage throttling valve off signal. A closing operation speed control means 38 is provided which outputs a signal and changes the passage area of the negative pressure passage 24.

FIG. 3 is an exhaust recirculation control map showing an operating region in which exhaust gas recirculation is performed and an operating region in which exhaust gas recirculation is not performed, which is stored in the memory 32 of the exhaust recirculation control device for a day cell engine with a supercharger according to the present embodiment. It is. In Fig. 3, the vertical axis shows the engine load, the horizontal axis shows the engine speed, the curve X shows the full load state, the shaded area A and the matte area B show the operating area where exhaust gas recirculation is performed, and , regions other than regions A and B indicate operating regions in which exhaust gas recirculation is not performed, and curve Y indicates a limit load line that determines whether or not exhaust gas recirculation is performed.

In this embodiment, as shown in FIG. 3, in the operating region where the engine speed is high compared to the operating region where the engine speed is low,
Exhaust gas recirculation is controlled to continue even when the engine load is higher. In order to improve emissions, it is desirable to perform exhaust gas recirculation even in high-load operating ranges, but in diesel engines, the excess air ratio decreases as the load increases, so during high-load operating There is a problem in that smoke is generated when exhaust gas recirculation is performed in the area where the exhaust gas is recirculated. When the diesel engine according to this embodiment is equipped with a combustion chamber 5 that generates swirl, the flow velocity of the swirl increases as the engine speed increases, so that the mixing of air and fuel is reduced. In the operating range where the engine speed is high,
This is based on the knowledge that smoke generation can be suppressed even if exhaust gas recirculation is performed even under operating conditions where the engine load is higher.

The opening/closing control means 36 of the exhaust gas recirculation control device 31 according to the present embodiment includes an engine load detection signal input from the engine load sensor 33, an engine rotation speed detection signal input from the engine rotation speed sensor 3 and 4, and an engine cooling water Based on the engine coolant temperature detection signal input from the temperature sensor 35, and according to the exhaust recirculation control map shown in FIG. It is determined whether the engine is in region A or region B of the map shown in FIG. On the other hand, when it is determined that the engine operating state is outside of region A and region B, an exhaust recirculation ON signal is output to the three-way solenoid valve 25. Further, the closing operation speed control means 38 includes an acceleration state detection signal inputted from the acceleration sensor 37, an engine load detection signal inputted from the engine load sensor 33, and an engine rotation speed sensor 3.
Based on the engine rotational speed detection signal input from 4, the engine accelerates to within region A or region B of the map in FIG. 3 according to the exhaust recirculation control map shown in FIG. From the operating state of
It is determined whether the operating state has changed to outside, and from area A,
When it is determined that the operating state has changed to a state outside of region A and region B by crossing the limit load line Y, a negative pressure passage throttle off signal is output to the negative pressure passage throttle valve 27, and on the other hand, from region B When it is determined that the load line Y has been crossed and the operating state has changed to a state outside of region A and region B, a negative pressure passage throttling ON signal is output to the negative pressure passage throttling valve 27.

When the three-way solenoid valve 25 receives an exhaust gas recirculation ON signal from the opening/closing control means 36 of the exhaust gas recirculation control device 31, the three-way solenoid valve 25 connects the downstream side of the negative pressure passage 24 to the vacuum pump 26, and as a result, it connects the downstream side of the negative pressure passage 24 to the negative pressure chamber 2I. Negative pressure is introduced from the vacuum pump 26, overcomes the biasing force of the spring 23, pushes the diaphragm 20 upward, and the exhaust gas recirculation valve 9 opens the exhaust gas recirculation passage 8, so that the exhaust gas is recirculated. On the other hand, when receiving the exhaust gas recirculation off signal from the opening/closing control means 36, the three-way solenoid valve 25 connects the downstream side of the negative pressure passage 24 to the atmosphere, and as a result, the negative pressure chamber 21 has a large Since atmospheric pressure is introduced, the biasing force of the spring 23 causes
The exhaust gas recirculation valve 9 closes the exhaust gas recirculation passage 8, and no exhaust gas recirculation is performed.

On the other hand, when the negative pressure passage throttling valve 27 receives a negative pressure passage throttling on signal from the closing operation speed control means 38, it throttles the passage area of the negative pressure passage 24 to a predetermined value and sends a negative pressure passage throttling off signal. When this occurs, the negative pressure passage 24 is controlled so that its passage area is fully opened.

As a result, the accelerator pedal (not shown) is depressed, and by acceleration, the engine load and engine speed are changed from the engine operating state within the region B of the exhaust recirculation control map shown in FIG. , when moving from a low engine speed operating state to an operating state outside region A and region B by crossing the limit load line Y, that is, to a high-load operating state, the fuel injection amount increases suddenly and the exhaust gas increases. As the gas energy increases, the exhaust gas pressure increases immediately, but the boost pressure has not increased yet, so the differential pressure between the exhaust gas pressure and the boost pressure increases temporarily, and - over time, the exhaust gas pressure increases. The amount of exhaust gas recirculated from the exhaust passage 7 to the intake passage 6 via the recirculation passage 8 increases, and the engine torque temporarily decreases, and then shifts to a high-load operating state with a large engine torque, but the negative pressure Since the passage area of the passage 24 is throttled to a predetermined value by the negative pressure passage throttle valve 27, the signal output from the opening/closing control means 36 to the three-way solenoid valve 25 changes from the exhaust recirculation on signal to the exhaust recirculation off signal. Change, three-way solenoid valve 2
5 changes the downstream side of the negative pressure passage 24 from being connected to the vacuum pump 26 to being connected to the atmosphere, the pressure within the negative pressure chamber 21 changes only gradually, and therefore the exhaust gas The closing speed of the exhaust gas recirculation passage 8 by the recirculation valve 9 is slow, and exhaust gas recirculation is gradually stopped, and the supercharging pressure also gradually increases during this period, so acceleration causes high-load operation in which exhaust gas recirculation is stopped. Even if the state moves to
Torque shock caused by stopping exhaust gas recirculation can be effectively prevented, and it is possible to maintain a good driving feeling while expanding the exhaust gas recirculation area to the high-load operation range where the amount of fuel injection is large. .

On the other hand, the accelerator pedal (not shown) is depressed, and as a result of acceleration, the engine load and engine speed change from the engine operating state within the region A of the exhaust recirculation control map shown in FIG. 3 to the limit load line Y. When shifting to an operating state outside of areas A and B, that is, a high-load operating state, 1. First, the amount of fuel injection increases rapidly, the exhaust gas energy increases, and the exhaust gas pressure immediately decreases. In contrast, the boost pressure does not increase immediately, but in the engine operating state within the region A, the exhaust energy is originally relatively high.
Since the boost pressure is also relatively high, the temporary increase in the differential pressure between the exhaust gas pressure and the boost pressure is not so large; Since the increase in the amount of exhaust gas recirculated to the intake passage 6 is not so large, there is little temporary drop in engine torque, and therefore the passage area of the negative pressure passage 24 is not restricted by the negative pressure passage throttle valve 27. (In the fully open state, the opening/closing control means 36 controls the three-way solenoid valve 25.
The signal output to changes from the exhaust recirculation on signal to the exhaust recirculation off signal, and the three-way solenoid valve 25 changes the downstream side of the negative pressure passage 24 from being connected to the vacuum pump 26 to being connected to the atmosphere. Even if it is changed, the fluctuation in torque due to stopping the exhaust gas recirculation will not be so large, and the problem of deteriorating the driving feeling will not occur.

According to this embodiment, it is possible to effectively prevent torque shock caused by stopping exhaust gas recirculation by acceleration, and maintain a good driving feeling. When accelerating from a rotational speed state to a high-load operating state where exhaust gas recirculation is stopped, the exhaust recirculation valve 9 is gradually closed, so that exhaust gas recirculation can be performed until the higher-load operating state. It is also possible to prevent deterioration of emissions when accelerating from a low engine speed state to a high load operating state where exhaust gas recirculation is stopped.

The present invention is not limited to the above-mentioned examples, but various modifications can be made within the scope of the invention described in the claims, and these are also included within the scope of the present invention. Needless to say.

For example, in the embodiment described above, an explanation has been added regarding an exhaust recirculation control device for a supercharged diesel engine, but the present invention is not limited to a supercharged diesel engine.
It goes without saying that the present invention can also be applied to a gasoline engine with a supercharger.

Furthermore, in the embodiment described above, an explanation has been added regarding an exhaust recirculation control device for a so-called direct injection type diesel engine that directly injects fuel into the combustion chamber 5, but the present invention provides an auxiliary combustion chamber that generates a swirl. Needless to say, it is also applicable to a supercharged diesel engine.

Furthermore, in the embodiment, when accelerating from a low load, low engine speed operating state to a high load operating state where exhaust gas recirculation is stopped, the closing operation speed control means 38 gradually closes the exhaust recirculation valve 9. However, regardless of the engine speed, when accelerating from a low load operating state to a high load operating state where exhaust gas recirculation is stopped, the closing operation speed control means 38 controls the exhaust gas recirculation. It is also possible to control the valve 9 to gradually close.

Furthermore, in the present invention, the opening/closing control means and the closing speed control means do not necessarily mean physical means,
The present invention also includes cases where the functions of each means are realized by software, and furthermore, even when the functions of each means are realized by one physical means, the functions of each means or one of the means are included. The present invention also includes cases where this is realized by two or more physical means.

According to the present invention, an exhaust type supercharger, an exhaust recirculation passage, an exhaust recirculation valve that opens and closes the exhaust recirculation passage, an engine load detection means for detecting an engine load, and an engine load detection means for detecting an engine load. Based on the output signal, the exhaust recirculation valve is controlled to open the exhaust recirculation valve when the engine load is below a predetermined value, and to close the exhaust recirculation valve when the engine load exceeds the predetermined value. The exhaust recirculation control device for a fed engine has a simple structure that improves emissions, prevents torque shock when accelerating from low-load operating conditions, and quickly It becomes possible to obtain an exhaust gas recirculation control device for a supercharged engine that can obtain sufficient torque.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of a supercharged diesel engine including an exhaust gas recirculation control device according to an embodiment of the present invention. FIG. 2 is a block diagram of an exhaust gas recirculation control device according to an embodiment of the present invention provided in a control unit. FIG. 3 is a graph showing the relationship between the operating range in which exhaust gas recirculation is performed, the engine load, and the engine speed. 1 diesel engine, 2 cylinder, 3 cylinder bore, 4' piston, 5' combustion chamber, 6' intake passage,
7-Exhaust passage, 8''-Exhaust recirculation passage, 9-Exhaust recirculation valve, 10-Cylinder head, 11...Intake port, 12-Intake valve, 13-Fuel injection nozzle, 14 Turbine, 15・'Compressor, 1
6° supercharger, 20- diaphragm, 21- negative pressure chamber, 22... valve side chamber, 23° spring, 24- negative pressure passage, 25° three-way solenoid valve, 26-- vacuum pump, 27° negative pressure passage throttle valve, 30-' control unit, 31'... exhaust recirculation control device, : 32 - memory, 3-... engine load sensor, 4-' engine speed sensor, 5- engine cooling Water temperature sensor, 6°-opening/closing control means, 37... Acceleration sensor, 8° closing operation speed control means.

Claims (1)

[Claims] An exhaust type supercharger, an exhaust gas recirculation passage, an exhaust recirculation valve that opens and closes the exhaust gas recirculation passage, an engine load detection means for detecting the engine load, and an engine load that is determined based on the output signal of the engine load detection means. Exhaust recirculation control for a supercharged engine, comprising an opening/closing control means that opens the exhaust recirculation valve when the engine load is below a predetermined value and closes the exhaust recirculation valve when the engine load exceeds a predetermined value. The device includes an acceleration detection means for detecting an acceleration state of the engine, and an engine load operation that exceeds the predetermined value from a low load operation state based on an output signal from the acceleration detection means and an output signal from the engine load detection means. A supercharged engine characterized in that a closing operation speed control means is provided for controlling the exhaust recirculation valve to gradually close by outputting a low speed closing operation signal to the opening/closing control means only when the engine accelerates to the above state. Exhaust recirculation control device.