JPH0339191B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation device for an engine, and particularly to an exhaust gas recirculation device using a negative pressure responsive actuator.

(Prior art) Automotive engines are equipped with an exhaust recirculation device that recirculates part of the exhaust gas to the intake passage in order to reduce NOx in the exhaust gas. It is composed of an exhaust gas recirculation passage that communicates the exhaust passage and the intake passage, and an exhaust gas recirculation control valve that is installed on the passage and controls the amount of exhaust gas recirculation. In addition, in the case of diesel engines that cannot recirculate exhaust gas into the intake passage using intake negative pressure, for example,
As shown in Publication No. 41453, an intake throttle valve is provided on the upstream side of the opening of the exhaust gas recirculation passage in the intake passage, and the valve is closed during exhaust gas recirculation to generate an intake negative pressure, so that the exhaust gas is inhaled. It is designed to ensure that the flow returns to the passageway.

However, as shown in the above publication, the exhaust recirculation control valve and the intake throttle valve are usually driven by a negative pressure responsive actuator, but this type of actuator is not responsive to control signals. Since the actuator is activated only after the magnitude of the negative pressure changes after the output, if this actuator is used, the operation of the exhaust gas recirculation control valve and the like will be delayed.

On the other hand, in a diesel engine, if exhaust gas recirculation is performed at a time of high load with a large amount of fuel supplied, there is a problem in that the combustion state deteriorates significantly and smoke is generated. Therefore, it is customary to perform exhaust recirculation only in the range below a predetermined load, and to stop exhaust recirculation when the predetermined load is exceeded, in relation to the opening degree of the accelerator pedal that controls the injection amount of the fuel injection pump. In that case, due to the delay in the exhaust gas recirculation control valve, the following problems occur, for example, when changing gears.

In other words, as shown in Fig. 5, during driving in the exhaust gas recirculation stop region (high load region) I, where the opening degree of the accelerator pedal is greater than the predetermined opening degree θ ₀ , the accelerator pedal is once fully closed for gear change. When stepping back to the above range after a gear change, the exhaust recirculation control valve first begins to open at _t1 when the accelerator pedal opening enters the exhaust recirculation area (low load area), and after the gear change, the exhaust recirculation control valve begins to open when the accelerator pedal opening enters the exhaust recirculation area (low load area). When entering the exhaust gas recirculation stop region, it begins to close at _t2 , but its opening and closing operations are delayed as shown by arrows a and b. Therefore, even after the engine returns to a high load state due to the delay in the closing operation shown by arrow b, exhaust gas recirculation will continue for a while.
During this time, smoke occurs.

(Object of the Invention) The present invention addresses the above-mentioned problems in an engine exhaust gas recirculation device that performs exhaust gas recirculation at low loads in relation to the accelerator pedal opening and stops exhaust gas recirculation at high loads. By keeping the exhaust recirculation control valve in the closed state from the beginning when the accelerator pedal is pressed down after being released once during a gear change, etc., it is possible to prevent the control valve from closing when the accelerator pedal is pressed again. The purpose is to prevent smoke from occurring due to delayed operation. In addition, when the accelerator pedal is depressed slowly, which is less affected by the delay in the operation of this control valve, exhaust gas recirculation is performed while the pedal opening is in the exhaust recirculation region, and the increase in NOx emissions during that period is suppressed. The purpose is to prevent.

(Structure of the Invention) That is, the present invention includes an exhaust gas recirculation passage and an exhaust gas recirculation control valve that is installed on the passage and controls the amount of exhaust gas recirculation, and the exhaust gas recirculation control valve is provided at least in relation to the accelerator pedal opening at a predetermined load or less. The exhaust gas recirculation system for an engine is configured to carry out exhaust gas recirculation and to stop the exhaust gas recirculation when a predetermined load is exceeded. and an exhaust recirculation control means for controlling the operation of the exhaust recirculation control valve according to the opening/closing speed of the accelerator pedal. This exhaust gas recirculation control means is
When the accelerator pedal is returned at a predetermined speed or higher from an exhaust gas recirculation stop region where the accelerator pedal opening degree is large, the exhaust recirculation control valve is held in the recirculation stop state for a predetermined period of time, and when the accelerator pedal is subsequently depressed, When the depression speed is less than or equal to a predetermined speed, the control valve operates to release the reflux stop state of the control valve. Therefore, if the accelerator pedal is suddenly released during a gear change, etc., the exhaust recirculation control valve will not open even if the exhaust gas recirculation region is entered, and accordingly, when the accelerator pedal is depressed again, the control valve will not open. This prevents smoke from occurring due to a delay in the closing operation. In addition, when the accelerator pedal is depressed gently, the closing operation of the exhaust recirculation control valve can follow the increase in load, and
Since the time in the exhaust gas recirculation region becomes longer, exhaust gas recirculation is performed in this case, and an increase in the amount of NOx emissions during this period is prevented.

(Example) Examples of the present invention will be described below.

As shown in FIG. 1, an engine 1 includes an intake passage 2 that supplies intake air to the combustion chamber of each cylinder, and an exhaust passage 3 that discharges exhaust gas generated by combustion to the outside.
An exhaust gas recirculation passage 4 is provided between the exhaust passage 3 and the intake passage 2 to recirculate part of the exhaust gas into the intake passage 2, and the passage 4 has an exhaust gas recirculation amount. A reflux control valve (hereinafter referred to as EGR valve) 5 is installed to control the EGR. A negative pressure diaphragm type actuator 6 for operating the EGR valve 5 is provided, and a negative pressure pump (not shown) and the actuator 6 are also provided.
A first negative pressure control valve 8 is installed in the negative pressure introduction passage 7 between the
The EGR valve 5 is controlled to open and close.

On the other hand, the exhaust gas recirculation passage 4 in the intake passage 2
An intake throttle valve 9 is provided on the upstream side of the opening, and a negative pressure diaphragm type actuator 10 for opening and closing the intake throttle valve 9 is provided. A second negative pressure control valve 12 is also provided in the negative pressure introduction passage 11 that introduces negative pressure into the actuator 10.
is installed, and the opening degree of the intake throttle valve 9 is controlled by controlling the negative pressure within the actuator 10 according to the open/closed state of the control valve 12.

Therefore, control signals A and B are sent from the control unit 13 to the first negative pressure control valve 8 that controls the EGR valve 5 and the second negative pressure control valve 12 that controls the intake throttle valve 9, respectively. At the same time, the control unit 13 detects the rotation signal C from the rotation sensor 15 provided in the fuel injection pump 14 and the opening degree of the accelerator pedal linked thereto from the position of the control lever on the pump 14. An accelerator opening signal D from an accelerator opening sensor 16 and a water temperature signal E from a water temperature sensor 17 provided in the water jacket of the engine 1 are input. Based on these input signals C, D, and E, the control signals A and B are adjusted depending on the operating state of the engine 1.
Output. Here, the fuel injection pump 14 is for pumping fuel to fuel injection nozzles (not shown) provided in each cylinder of the engine 1, and the injection amount depends on the rotational speed of the pump 14 (engine rotational speed). ) and the accelerator opening degree.

Next, the operation of this embodiment will be explained according to the flowchart shown in FIG.

First, the control unit ₁₃ receives the water temperature signal E from the water temperature sensor 17 shown in _FIG . input the accelerator opening signal D from , and these signals E,
Based on C and D, it is determined whether the operating state of the engine 1 is in a region where exhaust gas recirculation is performed. In other words,
For example, if the temperature of the cooling water in the water jacket is
The temperature is 80℃ or higher, and the engine speed is e.g. 900℃.
~3000RPM, and if the accelerator pedal opening or the load related to the opening is below a predetermined value, it is determined that the exhaust gas recirculation region is present,
Step S Perform the _following controls.

In this control, the control unit 1
3, in step _S5 , the opening/closing speed θ〓 of the accelerator pedal is calculated based on the accelerator opening degree signal D, and then in step _S6 , the speed θ〓 is equal to or less than a predetermined value −θ〓a, that is, the accelerator pedal is moved at a predetermined speed. With the above steps, it is determined whether or not the door was suddenly closed. If the accelerator _pedal is not suddenly closed, the first and second negative pressure control valves 8, Control signals A and B are sent to 12. As a result, during normal operation in the above-mentioned exhaust gas recirculation region, some exhaust gas is recirculated from the exhaust passage 3 to the intake passage 2 through the exhaust recirculation passage 4 and the EGR valve 5, and NOx emissions are reduced. become. In this case, as the intake throttle valve 9 closes as described above, the negative pressure around the opening of the exhaust gas recirculation passage 4 in the intake passage 2 increases,
This ensures that the exhaust gas is recirculated. Note that if it is determined in step _S4 that the exhaust gas is not in the predetermined exhaust gas recirculation region, the control to open the EGR valve 5 (and the control to close the intake throttle valve 9) is not performed, and no exhaust gas recirculation is performed.

On the other hand, if the accelerator pedal is suddenly closed when changing gears, steps _S6 to _S8 are performed.
is executed to set a predetermined time _T0 in the timer built in the control unit 13, and at the same time, in step _S9 , it is determined whether the opening/closing speed θ is positive or not, that is, after the accelerator pedal is suddenly closed, the accelerator pedal is pressed again. Determine whether or not it has been stepped on. Immediately after the accelerator pedal is suddenly closed, the gear change has not yet been completed, so the accelerator pedal remains closed, so the opening/closing speed θ is zero, and the control unit ₁₃ starts from step S9 above. step
Run _S10 . At this point, the above-mentioned predetermined time T ₀ has not yet elapsed, so step S ₁₁ is further performed.
and keep the EGR valve 5 closed.
As a result, as shown in Fig. 3, even if the accelerator opening changes from the exhaust recirculation stop region to the exhaust recirculation region due to a decrease in the accelerator opening, when the accelerator is suddenly closed and the opening decreases at a predetermined speed or higher, it is indicated by arrow c. like
The EGR valve 5 will not open, and exhaust gas recirculation will not occur. Then, when the gear change is completed and the accelerator pedal is depressed again, the opening/closing speed θ〓 becomes positive, so the control unit 13 next executes steps _S9 to _S12 described above, so that the depression speed θ〓 becomes a predetermined value. Determine whether or not θ〓b is greater. If the accelerator pedal is pressed rapidly (θ〓＞θ〓b), steps _S10 and _S11 are executed in the same way as in the case above, and EGR is continued until the time T from the sudden closing of the accelerator pedal exceeds the predetermined time _T0 . Keep valve 5 closed. and,
Normal control is returned to when the predetermined time T ₀ has elapsed, but at this point the accelerator opening has already returned to the exhaust recirculation stop region as shown by arrow d in Figure 3, so the EGR valve 5 is never opened. As a result, even if the engine operating state enters the exhaust recirculation region due to the accelerator pedal being temporarily fully closed during a gear change, if the accelerator pedal is rapidly depressed after the gear change, the exhaust recirculation will not occur. It will not be done. Therefore, when exhaust gas recirculation is performed during gear change as shown by the chain line in Fig. 3, the closing operation of the EGR valve 5 is delayed when the accelerator pedal is depressed again.
Even after entering the exhaust gas recirculation stop region (high load region), smoke generation due to exhaust gas recirculation is prevented.

On the other hand, if the accelerator pedal is depressed slowly after the gear change (0<θ〓<θ〓b), the control unit 13 executes steps _S9 , _S12 to _S13 , and turns the EGR valve 5 on. Control to open. In other words, in this case, as shown in FIG. 4, even before the predetermined time _T0 has elapsed, the EGR valve 5 opens from the time _t3 when it is detected that the accelerator pedal depression speed is below the predetermined speed. When the accelerator opening enters the exhaust gas recirculation stop region, it will begin to close. In this case as well, due to the delay in the closing operation of the EGR valve 5, exhaust gas recirculation will continue for a while even after entering the exhaust gas recirculation stop region, but in this case, as shown by arrow e, the accelerator is opened. Since the rate of increase in fuel consumption, that is, the rate of increase in load, is slow, the EGR valve 5 will be closed before the load becomes significantly high.Therefore, there is a problem of smoke generation due to exhaust gas recirculation under high load conditions. will not occur. In this case, the time T ₁ from entering the exhaust gas recirculation area to exiting the area becomes longer, and if no exhaust gas recirculation is performed during this period, a large amount of NOx will be emitted, but as described above, The EGR valve 5 opens from time _t3 when it is detected that the depression speed is below a predetermined speed, and exhaust gas recirculation is performed, thereby preventing the problem of NOx emissions.

The above explanation is for gear change, but the control unit 13
The EGR valve 5 operates in the same way when the accelerator pedal is operated other than when changing gears, and the EGR valve 5 when the accelerator pedal is depressed rapidly.
This prevents the problem of smoke generation due to a delay in the closing operation. Furthermore, the present invention is applicable not only to diesel engines but also to other engines that perform similar exhaust gas recirculation control.

(Effects of the Invention) As described above, according to the present invention, in the exhaust gas recirculation device for an engine that performs or stops exhaust gas recirculation in relation to the degree of opening of the accelerator pedal, rapid depression of the accelerator pedal after a gear change, etc. This prevents smoke from occurring due to a delay in stopping the exhaust gas recirculation. In addition, if the accelerator pedal is depressed gently, exhaust recirculation will occur while in the exhaust recirculation region, and NOx will be generated during this period.
This will prevent the amount of emissions from increasing.

[Brief explanation of drawings]

Figures 1 to 4 show examples of the present invention. Figure 1 is a control system diagram, Figure 2 is a flowchart showing the operation, and Figures 3 and 4 are time frames for exhaust gas recirculation control during gear changes, etc. Chart diagram, FIG. 5 is a time chart diagram showing the conventional problems. 1...Engine, 4...Exhaust recirculation passage, 5...
Exhaust recirculation control valve (EGR valve), 13...Exhaust recirculation control means (control unit), 16...Accelerator pedal opening/closing speed detection means (accelerator opening sensor).

Claims (1)

[Claims] 1 It has an exhaust gas recirculation passage and an exhaust gas recirculation control valve that is arranged on the passage and controls the amount of exhaust gas recirculation, and performs exhaust gas recirculation at a predetermined load or less according to at least a signal related to the accelerator pedal opening, and at a predetermined level. In an engine exhaust gas recirculation system configured to stop exhaust gas recirculation when the load exceeds the load, a detection means is provided to detect the opening/closing speed of the accelerator pedal, and when the accelerator pedal is returned from the exhaust recirculation stop area at a predetermined speed or higher, Exhaust recirculation control that holds the exhaust gas recirculation control valve in a recirculation stopped state for a predetermined period of time, and releases the recirculation stopped state of the exhaust recirculation control valve when the accelerator pedal is depressed at a predetermined speed or less thereafter. An exhaust gas recirculation device for an engine, characterized by comprising means.