JPS60195367A - Exhaust gas circulation control device in diesel engine - Google Patents

Abstract

PURPOSE:To improve the running performance of an engine even upon speed change, particularly to improve the response and acceleration abilities of the engine, and as well to reduce the rate of black smoke, etc. contained in exhaust gas, by returning and recirculating exhaust gas into an intake-air system in accordance with the operating condition of the engine, and as well by rapidly restraining or stopping exhaust gas circulation. CONSTITUTION:A control unit 100 delivers a fuel injection timing control signal Ct to a valve 25 and an exhaust gas recirculation control signal Ce to a vacuum pressure control valve 41 in accordance with various detection signals which indicate the operating condition of the engine. Further, the range in which exhaust gas recirculation is carried out is limited to a range in which an accelerator is depressed in a certain amount and the rotational speed of the engine has a certain value. Further upon exhaust gas recirculation a vacuum supply port 42 is communicated with a vacuum port 43 and an atmospheric air suction port 46, alternately at a time rate in accordance with the duty ratio of the signal Ce. The larger the duty ratio, the more the effective opening area of a port 32 increases so that the amount of exhaust gas recirculation increases. Meanwhile, in a speed shift phase by a speed change gear unit exhaust gas recirculation is forced to be stopped for a predetermined period.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention aims to purify exhaust gas from a diesel engine by returning a portion of the exhaust gas to the intake system depending on the operating state of the engine. The present invention relates to an exhaust recirculation control device for a diesel engine that allows recirculation.

(Prior technology) As a measure to purify the exhaust gas of automobiles equipped with diesel engines, the main purpose is to reduce NOx components, which are harmful substances in the exhaust gas. Exhaust gas recirculation (EGR) is carried out to return the exhaust gas to the exhaust system. Unlike gasoline engines, diesel engines inject fuel from the fuel pump without controlling intake air h'.
By regulating the fuel pumped into the engine, the operating conditions of the engine are controlled. Therefore, the excess air that is not required for complete combustion of the fuel in the combustion chamber of an easel engine depends on the type of fuel injected during an intake stroke. In a diesel engine with exhaust gas recirculation control, the fuel injection amount is increased in response to an increase in engine load, so the engine is heated to 9. When the engine is in the load operation range, control is performed to reduce the flow rate of exhaust gas recirculated compared to when the engine is in the low load or medium load operation range, or to stop the exhaust gas recirculation. As a result, it is possible to achieve both purification of exhaust gas and improvement of engine operating performance.

In a vehicle equipped with a diesel engine that performs such exhaust recirculation control, when the transmission changes gear ranges, that is, when changing gears, the accelerator pedal is released due to clutch operation, and then the accelerator pedal is released. When the engine is re-depressed, the engine is rapidly shifted from a low-load operating range to a high-load operating range, and a large amount of combustion air is required due to the sudden increase in fuel injection. Therefore, it is desirable to rapidly reduce the amount of exhaust gas recirculation or to quickly stop exhaust gas recirculation.

However, normally, on the exhaust recirculation side 411, for example, a diaphragm type exhaust recirculation amount control valve is interposed in the exhaust recirculation passage whose both ends are connected to the intake passage and the exhaust passage.
The exhaust gas recirculation boat is opened and closed according to the operating condition of the engine to control the amount of exhaust gas recirculation, that is, the EGR rate (exhaust gas recirculation amount/exhaust gas recirculation amount + intake air amount).
Therefore, if the accelerator pedal is pressed down significantly from the released state during gear shifting, a transient response such as a mechanical delay in the negative pressure supply section for operating the diaphragm of the exhaust gas recirculation control valve may occur. Due to the delay, there is an inconvenience that undesirable IJP gas is returned even in high-load operating conditions. As a result, the amount of intake air required for complete combustion of fuel (actually, the amount of oxygen
Due to the lack of air, running performance, especially responsiveness and acceleration, deteriorates.
There is a problem in that the proportion of smoke, etc. increases, and fuel efficiency deteriorates accordingly.

By the way, for a gasoline engine that performs exhaust recirculation control for one engine during gear shifting, for example,
As disclosed in Japanese Unexamined Patent Publication No. 57-116151, the opening degree of the exhaust recirculation boat of the exhaust recirculation amount control valve is maintained large for a certain period of time after the gear shift is performed.
Some proposals have been made to reduce NOx components in exhaust gas, but even in diesel engines, where the exhaust recirculation mode is different from that in gasoline engines, there are methods to reduce the amount of NOx in the exhaust gas. Exhaust gas recirculation control is desired.

(Purpose of the Invention) In view of the above, the present invention has an exhaust gas recirculation amount control means that returns and recirculates an amount of exhaust gas according to the operating state of the engine to the intake system, thereby purifying the exhaust gas and improving engine operation. In addition, when the gear range is changed by the transmission, the high speed reduction due to the transient response delay of the 1-no-1 airflow control 11 means, etc. An object of the present invention is to provide an exhaust gas recirculation control device for a diesel engine that can prevent an undesired amount of exhaust gas from being recirculated under load.

(Structure of the Invention) The exhaust gas recirculation control device 11 for a diesel engine according to the present invention includes an exhaust gas recirculation means for returning and recirculating a part of the exhaust gas to the intake system in a diesel engine, and a system for recirculating the exhaust gas by the exhaust gas recirculation means. Exhaust gas recirculation amount control means for controlling the flow rate according to the operating state of the engine, gear change detection means for detecting a change in gear range by the transmission, and detection of a change in gear range by the transmission by the shift detection means In particular, the exhaust gas flow suppressing means for forcibly suppressing or stopping the recirculation of exhaust gas by the exhaust gas recirculation means for a predetermined period after the start of the gear range switching operation by the transmission. Ru. With this configuration, the recirculation of exhaust gas is suppressed or stopped in response to the change of the gear range, and the engine can be operated from a low load operating range to a high load operation due to the change of the gear range. This ensures that a sufficient amount of air is supplied to the combustion chamber even during rapid transitions to the combustion chamber.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of the exhaust recirculation control device for a diesel engine according to the present invention together with a diesel engine to which the device is applied. In FIG. 1, a diesel engine 1 is, for example, an in-line four-cylinder type swirl chamber two engine, and each of the four combustion chambers 2 is connected to a branch part of an intake passage 4 and an exhaust passage 5. . Each combustion chamber 2 is connected to a cylinder block 6 as shown in FIG.
゜Cylinder head 7, piston 8. It consists of a main combustion chamber 11 surrounded by an intake valve 9 and an exhaust valve (not shown), and a swirl chamber (auxiliary combustion chamber) 13 that communicates with the main combustion chamber 11 through a nozzle hole 12. A temperature Ts of cooling water related to the temperature state of the chamber 2 is detected by a water temperature sensor SS mounted on the cylinder block 6. Vortex chamber I3
A ceramic Nayansha member 14 fitted in a cavity provided in the cylinder head 7 is used for the circumferential wall of the cylinder head 7, so that the Chinchuan part shrine 14 is made of steel (some ordinary swirl chamber type). "CItJ" compared to diesel engine
It has a high thermal effect and a fast combustion rate. The vortex chamber 13 faces the heat generating portion 16a of the glow plug 16 mounted on the cylinder head l'7 and warms up, and a fuel injection nozzle 17 is also provided. This fuel injection nozzle 17 is configured to inject a predetermined amount of fuel into the swirl chamber 13 according to the operating state of the diesel engine, which is pumped from a fuel injection pump 18 every intake stroke.

The fuel injection pump 18 is, for example, an electronically controlled distribution type injection pump, and has a drive shaft 19 that rotates synchronously with the diesel engine 1 by being given rotational driving force from the crankshaft of the diesel engine 1. A rotation speed sensor NS that detects the rotation speed of the rotating body in correlation with the rotation speed of the drive shaft 19 is arranged at a predetermined position. The fuel injection pump 18 also includes a governor device 2.
0 is provided, and the fuel to be pumped to the fuel injection nozzle 17 is adjusted 41 according to its operation. Furthermore, this fuel injection pump 18 has a fuel injection function that advances or retards the injection timing of the fuel injected from the fuel injection nozzle 17 into the swirl chamber 13! An electronic timer 23 is built in as an IJI adjustment means, and this electronic timer 2
The operation of the plunger 24 of No. 3 is controlled by the injection timing control valve 25.
is controlled by. Furthermore, an accelerator sensor AS is installed at a lever portion of the accelerator pedal 21 to detect an accelerator pedal depression IAccp corresponding to the engine load Le.

- The intake air introduced into the above-mentioned combustion chamber 2 from the intake passage 4 flows into the swirl chamber I3 during the pressure*iif stroke, forms a swirl, and mixes and burns the fuel injected therefrom from the fuel injection nozzle 17. After that, it becomes gas and is discharged to the exhaust passage 5, but a part of this exhaust gas flows into the intake passage 4.
Due to the difference in negative pressure between the exhaust passage 5 and the exhaust passage 5, both ◇: 11 are connected to the intake passage 4 and the exhaust passage 5, respectively (throat air is returned to the intake passage 4 through the recirculation passage 30 and is recirculated. An exhaust gas recirculation control valve 3 is located in the middle of the recirculation passage 30.
1 is interposed. This exhaust recirculation control valve 31 is
a partition wall 33 formed with an exhaust recirculation boat 32 that communicates the intake passage 4 side and the exhaust passage 5 side of the exhaust gas recirculation passage 30;
It has a valve element 34 that opens and closes the exhaust gas recirculation boat 32 in cooperation with the partition wall 33, and a diaphragm mechanism 36 that drives the valve element 34 via a valve rod 35. The diaphragm mechanism 36 is
Negative pressure is introduced via a conduit 39 into a negative pressure introducing chamber 38 defined by a diaphragm 37 that connects and holds the diaphragm 35.
Apply a predetermined seven-stroke load to 7: 1 il spring 40
has been reduced. Further, a lift type of the valve element 34,
Therefore, a lift sensor R3 for detecting the effective opening area of the air return boat 32 is arranged in the diaphragm mechanism 36.

The negative pressure source side of the m pipe 39 that introduces negative pressure into the negative pressure introduction chamber 38 is connected to the negative pressure control valve 41 (11) ("j pressure 4j (" The ports 1-43 are connected, for example, via a conduit 45 to a pump 44 rotatably driven by a crankshaft (not shown) of a diesel engine 1.The negative pressure control valve 4 is connected to In addition to the negative pressure supply boat 42 and the vacuum boat 43, it has an atmosphere suction boat 46 that communicates with the atmosphere, and as shown in FIG.
When both side solenoids 48 are not energized, the valve elements 49 and 50 are connected to the spring member 5.
1 and 52 are pressed down,
The negative pressure supply boat 42 and the atmospheric suction boat 46 are communicated with each other, and the vacuum boat 43 is closed.
8 are both electrically excited by 1llll, the valve elements 49 and 50 are pulled up against the elasticity of the spring members 51 and 52, so that they communicate with the negative pressure supply boat 42 or the vacuum boat 43. It is being done.

A control unit 100 with a built-in timer is provided in order to perform actuation side JILT of each part configured as described above, and this control unit 100 includes a water temperature sensor SS.
A detection signal Ss corresponding to the temperature 1's of the cooling water related to the heating failure of the diesel engine 1 from , a detection signal Sn corresponding to the rotation speed of the diesel engine 1 from the rotation speed sensor NS, and a detection signal Sn corresponding to the rotation speed of the diesel engine 1 from the rotation speed sensor NS. Accelerator pedal depression IAccp, therefore engine negative ('+: J L
Detection signal Sa corresponding to e and lift sensor R3
A detection signal S[ corresponding to the effective opening area of the exhaust gas recirculation boat 32 from the
Further, a detection signal sb corresponding to a change in the primary voltage from the battery BS, a detection signal Sd corresponding to the atmospheric pressure from the atmospheric pressure sensor I), etc. are manually generated.

Then, the control unit 100 generates an injection timing control signal that controls the fuel injection timing of the diesel engine 1 based on the various detection signals Ss, Sn, Sa, Sr, Sb, Sd, etc. described above. Ct to the injection timing control valve 25,
An exhaust recirculation control signal Ce for controlling the amount of recirculation of exhaust gas is sent to the negative pressure control valve 41, and a heating control voltage Cg for heating the glow plug 16 and the glow resistor 59 provided in the intake passage 4 is sent.

As described above, the control signals Ce and Ct and the control voltage C
Under the control of the control unit 100 that sends out g,
Exhaust recirculation control in an example of the exhaust recirculation control device for a diesel engine according to the present invention is performed as described above.

The control signal Ce sent from the control unit 100 to the negative pressure control valve 41 is a pulse signal as shown in FIG.
ft+II control), the solenoid 47 and solenoid 48 of the negative pressure control valve 41 are energized and excited a1 every unit cycle with a pulse width t corresponding to the operating state of the engine, and when exhaust recirculation control is not performed ( (When EGR is stopped), the pulse width L1 of the 1-control control Ce is set to zero.

In addition, the region (r
i GR R area) is the accelerator pedal M included W A
Ccp and engine speed N (set in relation to ε,
For example, as shown by diagonal lines in FIG. 5, only in the range where the accelerator pedal depression NAccp is in the range of 5 to 60% with the limit depression amount as 100%, and the engine speed Ne is in the range of 600 to 3000 rpm. Exhaust gas recirculation is carried out, and therefore, when the engine is in a high load operating range and at very low engine loads, no exhaust gas recirculation is carried out.

Then, according to the control signal Ce (when non-air recirculation control is performed), the negative pressure supply boat 42 of the negative pressure control valve 41 is connected to the partneam boat 43 and the popular suction boat 46.
A system for each of them? Duty of No. 1118 Ce (11/
Therefore, the negative pressure in the negative pressure introduction chamber 38 of the diaphragm mechanism 36 in the exhaust recirculation control valve 31 is equal to the duty (L) of the control signal Ce.
l/L) is larger, its absolute value is increased, and accordingly, the diaphragm 37 is pulled up against the elasticity of the coil spring 40, and the effective opening area of the air return bow 132 is increased. Therefore, the flow rate (exhaust) is increased.

On the other hand, when the pulse width L1 of the control signal Ce is the limit and the exhaust gas recirculation control is not performed, communication between the negative pressure supply boat 42 and the vacuum boat 43 is cut off, and the communication between the negative pressure supply boat 42 and the atmospheric suction boat 46 is cut off. The absolute value of the negative pressure in the negative pressure introducing chamber 38 is reduced, the diaphragm 37 is pushed down by the elasticity of the coil spring 40, the exhaust gas recirculation boat 32 is closed, and the exhaust gas recirculation is stopped.

Furthermore, the control unit 100 detects information indicating that the gear range is to be changed by the transmission of the automobile equipped with the diesel engine exhaust recirculation control device according to the present example. Detection of this information is also carried out based on the detection signal Sn obtained from the rotational speed sensor NS.

When the gear range is changed by the transmission, the accelerator pedal is once released and then depressed again in conjunction with the operation of the clutch. At 911, the accelerator pedal depression 1 Accp and the engine rotational speed Ne sharply decrease, and then rapidly rise again, and the fuel injection amount increases.

The accelerator pedal is released and the accelerator pedal is pressed 1.
] When Accp suddenly decreases and the engine speed Ne also rapidly decreases in conjunction with this, the rate of decrease of the detection signal Sn rapidly increases accordingly. In this way, the Sn-th detection signal obtained from the rotational speed sensor NS indicates a change in the gear range by the transmission, and by detecting that the rate of decrease is rapidly increasing, the change in the gear range by the transmission is detected. It detects what is being done.

At the point in time shown in FIGS. 6A and 6B when it is detected that the gear range is changed by the transmission, the control unit 100 controls the negative pressure to stop the exhaust gas recirculation. The control No. 48 Ce sent to the valve 41 is changed to the subsequent depression amount of the accelerator pedal Ccp and the engine rotation speed N.
Regardless of the situation of e, a predetermined period of time, e.g.
"X (for example, for 2 to 3 seconds), the pulse width 1. shall be zero.

This period Tx is determined by, for example, starting a timer built in the control unit 7) 100 for a predetermined period of time at 1.1 when it is detected that the gear range is changed by the transmission. It is set by counting the remaining time of the timer so that it decreases as the time elapses, and setting the remaining time of the timer to zero. Therefore, during the period TxO, even if the accelerator pedal depression 1tAccp and the engine speed Ne are both in the EGR region, the negative pressure supply boat 42 of the negative pressure control valve 41 and the vacuum boat 4
The communication with the exhaust recirculation boat continues to be cut off, and atmospheric air is introduced from the negative pressure supply boat 42 into the negative pressure introduction chamber 38 for the diaphragm mechanism 36 in the exhaust recirculation control valve 31. As a result, the exhaust recirculation boat 32 is closed to stop exhaust gas recirculation. In this way, information indicating that the transmission will change the gear range is detected, and the exhaust gas recirculation is forcibly stopped for a predetermined period after the transmission starts changing the gear range. Due to the transient response delay of the exhaust recirculation control valve 31, etc., exhaust gas is not allowed to flow into the intake passage 4 in the high load range beyond the EGR range when the fuel injection amount increases rapidly after changing the gear range by the transmission. A situation where the water is returned to the desired state and refluxed is avoided.

The control unit 100 that operates as described above is configured using, for example, a microcomputer, and the central processing unit (CP) of the microcomputer in such a case is
An example of a program for exhaust gas recirculation control executed by U) will be described with reference to the flowchart in FIG.

An example of this program starts when the starting switch of a car equipped with the exhaust gas recirculation control device for a diesel engine according to the present example is turned on, and after starting, first, in process 101, information is obtained from the rotation speed sensor NS. The data of the engine rotational speed Ne and the accelerator pedal depression FIAcp obtained from the accelerator sensor AS are input. In the subsequent decision 102, it is determined whether or not it is in the EGR region. For this determination, as shown in FIG. 5, the vertical axis represents the amount of depression of the accelerator pedal
and taking the engine speed Ne on the horizontal axis, for example, the accelerator pedal depression ACcp is in the range of 5 to Gθ% when the limit depression amount is 100%, and,
An EGR region map is used in which the region where the engine speed he is in the range of 600 to 3000 rpm is the region where exhaust gas recirculation is to be performed.

Then, by comparing this EG R74 area map with the accelerator pedal depression IAccp and engine speed Ne input in process 101, the accelerator pedal depression ff is determined.
If the 1A c c p and the engine speed Ne are within the above-mentioned range where exhaust gas recirculation should be carried out, the process advances to decision 103, and if it is outside the range where exhaust gas recirculation should be carried out, in that case, for example, in a high load operating range. Since it is desirable to shut off the recirculation of exhaust gas and draw a large amount of air with high oxygen concentration into the combustion chamber 2, the process proceeds to process 104 to stop the recirculation of exhaust gas.

In the process 104, the control unit 100 or the pulse width [
, is the exhaust recirculation control signal Ce set to zero? Sends out to J11 valve 41 and returns to the original state. As a result, the exhaust gas recirculation boat 32 is closed, and the recirculation of exhaust gas is stopped.

On the other hand, in the decision 103 that proceeds when it is determined in the dino John 102 that the accelerator pedal depression fft A c c p and the engine rotational speed NG are in the range where exhaust gas recirculation is performed, the control unit 100 sets a built-in timer. It is determined whether the remaining time Tx' is greater than zero. As a result, if the remaining time Tx' of the timer is not greater than zero, the process proceeds to decision 105, and if the remaining time Tx' of the timer is greater than zero, the process determines that it is necessary to continue stopping the exhaust gas recirculation. 104-
, proceed, and as in the case of Dii, the control unit 100
sends an exhaust gas recirculation control signal Ce with a pulse width t1 of zero to the negative pressure control valve 41.

On the other hand, in decision 105, it is determined whether or not the gear range has been changed by the transmission. Here, for example, as described in FIG. 6) 3, the rate of decrease in the detection signal Sn obtained from the rotation speed sensor NS, that is, the rate of decrease in the engine rotation speed Ne is detected, and the rate of decrease in the detection signal Sn is detected. When there is a sudden increase in the rate of decrease, it is determined that the transmission should change the gear range.

Here, if it is determined that the transmission will change the gear range, that is, change, the process proceeds to process 106, where the control unit (LOO) gives a set time Tx (for example, 2 seconds) to a built-in timer. and start it. After starting this timer, the remaining time "X" of the timer decreases toward zero as time passes. After starting the timer in process 106, the process proceeds to process 104, where, as in the previous case, the control unit software l-100 is the pulse width t
The exhaust recirculation control signal Ce with 1 set to zero is sent to the negative pressure control valve 4.
Send to 1 and return. As a result, the exhaust recirculation boat 3
2 is closed and the recirculation of exhaust gas is stopped.

On the other hand, if it is determined in process 105 that the gear range will not be changed by the transmission, the process proceeds to process 107, in which the control unit 100 uses the detection signals obtained from each sensor. In order to recirculate exhaust gas at an EGR rate according to the operating state of the engine, an exhaust recirculation control signal Ce with a duty (it/l) according to a predetermined EGR control map is sent to the negative pressure control valve 41. do. As a result, the negative pressure introduction chamber 38 of the diaphragm mechanism 36 in the exhaust gas recirculation control valve 31
The negative pressure of the exhaust gas recirculation boat 32 is adjusted so that the effective opening area of the exhaust gas recirculation boat 32 corresponds to the operating condition of the engine, and a predetermined amount of exhaust gas is returned to the intake passage 4 and recirculated.

In the above example, the switching of the gear range of the transmission is detected based on the rate of decrease in the engine speed Nc.
For example, it may be detected directly from the movement of a shift lever of a transmission.

Furthermore, although the above example is a case in which a change in gear range by a manually operated transmission is detected, in the case of an automatic transmission, the change in gear range is also determined based on the rate of decrease in engine speed and acceleration. It can also be detected based on the rate of decrease in pedal depression.

Furthermore, in the above example, the recirculation of exhaust gas is stopped when the transmission changes to the i* gear range, but the recirculation of exhaust gas is not completely stopped, but the amount of recirculation is reduced. It may also be controlled to reduce the amount of water.

(Effects of the Invention) As is clear from the above description, according to the exhaust recirculation control device for a diesel engine according to the present invention, exhaust gas is returned to the intake system and recirculated according to the operating state of the engine. When a vehicle equipped with this diesel engine exhaust recirculation control device shifts gears, the gear shifting operation is detected, and the detection results are used to reduce the amount of exhaust gas. Since the recirculation is quickly suppressed or stopped, it is possible to prevent an undesirable amount of exhaust gas from recirculating during high loads due to a transient response delay of the exhaust recirculation control means, etc. Even when the amount of fuel injected into the combustion chamber increases rapidly, sufficient oxygen can be supplied to the combustion chamber. Therefore, an automobile equipped with the exhaust recirculation control device for a diesel engine according to the present invention has good driving performance, especially responsiveness and acceleration, even when changing gears, and also reduces black smoke etc. in IJF gas. This makes it possible to reduce the ratio and further improve fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of the exhaust recirculation control device for a diesel engine according to the present invention together with a diesel engine to which the device is applied; FIG. 2 is a partial sectional view of the main body of the diesel engine shown in FIG. 1; FIG. 3 is a sectional view of the negative pressure control valve shown in FIG. 1, FIGS. 4 to 6 are waveform charts and characteristic diagrams used to explain the operation of the example shown in FIG. 1, and FIG. 7 is a sectional view of the negative pressure control valve shown in FIG. 2 is a flowchart showing an example of an operating program of a microcomputer in an example of a control unit used in the example of FIG. 1; In the figure, 1 is a diesel engine, 2 is a combustion chamber, 4 is an intake passage, 5 is an exhaust passage, 30 is an exhaust recirculation passage, 31 is an exhaust recirculation control valve, 32 is an exhaust recirculation boat, 36 is a diaphragm mechanism, and 41 is a negative Pressure control valve, 100 is a control unit, AS is an accelerator sensor, NS is a rotation speed sensor, R
3 is a lift sensor. Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] Exhaust gas recirculation means for returning and recirculating a part of exhaust gas to an intake system in a diesel engine, and exhaust gas recirculation amount control means for controlling the amount of exhaust gas recirculated by the exhaust gas recirculation means in accordance with the operating state of the diesel engine. and a speed change detection means for detecting a change in the speed range by the transmission; An exhaust recirculation control device for a diesel engine, comprising an exhaust recirculation suppressing means for forcibly suppressing or stopping the recirculation of UL gas by the exhaust recirculation means for a predetermined period after the start of the exhaust gas recirculation.