JPS6193255A - Fuel-injection control timing device in diesel engine - Google Patents

Abstract

PURPOSE:To improve the exhaust characteristic of a Diesel engine to provide optimum injection timing, by providing a detection means for detecting the speed of variation in the opening degree of an accelerator, and by a hold means for holding the fuel injection timing for a predetermined time. CONSTITUTION:A step S4 the speed of variation theta' in the opening degree of an accelerator is calculated. Upon acceleration the control of compensation for injection timing is carried out in the direction of spark advance through steps S6 through S10. When an accelerator is not rapidly closed, at step S13 the duty ratio of a control signal to obtain optimum injection timing in accor dance with the operating condition of the engine. When the accelerator is rapidly closed, a countermeasure to a delay in response is controlled through steps S14 through S16. With this arrangement it is possible to improve the exhaust characteristic of the engine and to obtain optimum injection timing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a fuel injection timing control device for a diesel engine that controls fuel injection timing according to the rotational speed of the engine and the opening degree of the accelerator pedal. .

(Prior art) For example, as shown in Japanese Utility Model Application Publication No. 57-112041, the timing of fuel injection from a fuel injection pump provided in a diesel engine depends on the engine rotation speed, load, or accelerator pedal opening. It is customary to control according to the In other words, as the engine speed increases, the time required to pump fuel from the fuel injection pump to the fuel injection nozzle becomes relatively longer. In addition, as shown in Figure (b), the injection timing is advanced in order to secure the required output in the high load area, and in the low load area (■), the injection timing is controlled to In order to reduce NOx, it is customary to delay the timing, but even more so in the low load region (2), the injection timing may be advanced in order to completely burn the fuel (to reduce emissions of C, etc.).

On the other hand, the above-mentioned injection timing control in a fuel injection pump is usually performed by changing the phase between the input shaft of the pump and the camshaft that drives the plunger using a timer piston. According to the control method, it takes some time for the pressure that activates the timer piston to be adjusted to the pressure that corresponds to the engine rotational speed and load at that time. On the other hand, there will be a delay in the response of the ejection timing control.As a result, the following problems will occur, especially when the load changes suddenly, such as when changing gears.

In other words, as shown in Fig. 6(a), the accelerator pedal is quickly returned to the zero opening state during a gear change, and then is depressed again after the gear change is completed, and as a result, for example, the load on the engine is reduced. In Fig. 5 (Fig. 5), if the BL injection timing shifts from the region (■) where the injection timing is delayed to the region (■ where the injection timing is advanced at extremely low loads) and then returns to the above region (■), the actual fuel injection timing is controlled. Due to the delay in the response, as shown in FIG.
In case 2, the control to delay the injection timing is delayed. As a result, the normal injection timing characteristics set as shown in Figure 5 (bl) for the load cannot be obtained, and especially after the accelerator pedal is depressed again, the timing returns to region 14I [where the timing should originally be delayed]. Despite this, a situation occurs in which the injection timing is advanced, as indicated by symbol (b), and during this period, the amount of NOx discharged increases.

(Object of the Invention) The present invention is intended to deal with the above-mentioned actual situation regarding fuel injection timing in diesel engines. By canceling advanced angle and retard angle control, it is possible to prevent a situation where the injection timing does not correspond to the load due to a delay in control response.
The first objective is to improve exhaust performance during gear changes and the like.

Furthermore, the present invention not only cancels the temporary injection timing control that accompanies a sudden change in the accelerator pedal opening as described above, but also controls the injection timing during the cancellation when the accelerator pedal is returned. By anticipating the accompanying decrease in engine rotation speed, the timing is set to correspond to the decreased rotation speed, so that when the accelerator pedal is depressed again, injection timing that corresponds to both the engine load and rotation speed can be obtained. The second purpose is to

(Structure of the Invention) In order to achieve the above object, the present invention is characterized by the following structure.

That is, it is configured to detect the accelerator pedal opening degree and the engine rotational speed, change the fuel injection timing according to the accelerator pedal opening degree, and change the timing in the advance direction according to the increase in the engine rotational speed. In the fuel injection timing control device for a diesel engine, the detection means for detecting the rate of change in the accelerator pedal opening;
．． A correction means is provided for correcting and controlling the injection timing when the detection means detects a state in which the rate of change in the return direction of the accelerator pedal is equal to or higher than a predetermined speed, that is, sudden closing of the accelerator pedal. Specifically, when the sudden closing of the accelerator pedal is detected, this correction means cancels the control to advance the injection timing due to the sudden closing, and also adjusts the injection timing by a predetermined amount further than the timing at the time of detecting the sudden closing. It operates by setting and holding at a delayed timing. Therefore, temporary and sudden changes in the injection timing caused by sudden closing and closing of the accelerator pedal during gear changes etc. are prevented, and when the accelerator pedal is depressed again, injection timing that correctly corresponds to the load can be obtained immediately. The timing is a predetermined delay from the timing immediately before the accelerator pedal is suddenly closed, taking into account the amount of decrease in engine rotation speed, so the injection timing after the accelerator pedal is depressed again will be a timing that correctly corresponds to the engine rotation speed. .

(Example) Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 1, the fuel system of the diesel engine 1 includes fuel injection nozzles 2...2 provided in each cylinder.
, a fuel injection pump 3 that intermittently pressure-feeds fuel to these nozzles 2...2 and injects it into cylinder C, and a fuel injection amount and injection timing from the fuel pump 3 according to the operating state of the engine 1. Control unit 4 to control
It is composed of. This control unit 4 receives a rotation signal a from a rotation sensor 5 that detects the rotation speed of the fuel injection pump 3 (corresponding to the rotation speed of the engine 1), and a rotation signal a corresponding to the rotation signal a from the position of the control lever on the pump 3. An accelerator opening signal a from an accelerator opening sensor 6 that detects the opening of the accelerator pedal is input.

The fuel injection amount and injection timing are set based on the engine rotational speed and the accelerator pedal opening indicated by b, and the control signal C is output to the fuel injection pump 3 so as to match the injection purpose and injection timing. There is.

Now, to explain the variable injection timing mechanism in the fuel injection pump 3, as shown in FIG. 2, a timer piston 8 is slidably provided in the casing 7 of the pump 3, Pressure fluid (fuel) in the casing 7 is introduced into the pressure 9 formed through a passage 8a formed in the piston 8, and a screw 1 is inserted so as to face the pressure of this fluid. - A spring 1o that biases the spring 8 is provided. Then, as the piston 8 moves due to the balanced relationship between this fluid pressure and the spring 1o, the engaging member 11.1
The cam disc 13 is rotated in the A direction or the B direction via the shaft 2.

Although not shown, this cam disc 13 changes the phase of the input shaft of the fuel injection pump 3 that is linked to the output shaft of the engine 1 and the cam shaft that reciprocates the plunger provided in the pump 3. When the plunger rotates in the direction B, the lift timing of the plunger, that is, the fuel injection timing is delayed.
When it rotates in the direction, the timing is advanced.

The pressure chamber 9 is provided with a relief passage 14, and a control valve 15 which is duty-controlled by a control signal d from the control unit 4 is installed on the passage 14. By adjusting the fluid pressure in the pressure chamber 9 according to the duty ratio (° opening/closing time ratio) of 15, the timer piston 8
The position of the cam disc 13 is set so that the fuel injection timing is determined according to the duty ratio of the control signal d. Here, the control unit 4 sets the basic timing of fuel injection according to the engine rotation speed and the accelerator pedal distance indicated by the rotation signal a and the accelerator opening signal, and also It has a detection section that detects the rate of change in the opening degree of the accelerator pedal, and performs correction control of the basic timing according to the rate of change in the opening degree of the accelerator pedal detected by the detection section.

In this embodiment, the control unit 4 controls the exhaust gas recirculation of the engine 1. That is, as shown in FIG.
and the exhaust passage 17, a part of the exhaust gas is passed through an intake passage,
Exhaust gas recirculation passages 18 and 19 for recirculating the exhaust gas to 16 are provided,
A reflux control valve 20 on said passage 18,19 to control the flow rate.
．． 21 are respectively installed, and a negative pressure passage 24.2 that introduces negative pressure to a negative pressure diaphragm type actuator 22.23 that operates these reflux control valves 20.21.
1st on top of 5. Second negative pressure control valves 26 and 27 are installed, respectively. Further, an intake throttle valve 28 is installed upstream of the opening of the exhaust gas recirculation passage 18, 19 in the intake passage 16, and a negative pressure introduction passage to a negative pressure diaphragm type actuator 29 that opens and closes the intake throttle valve 28. 3rd on 30
A negative pressure control valve 31 is installed. And the control
The control unit 4 controls the first to third negative pressures based on the signals a and b from the rotation sensor 5 and the accelerator opening sensor 6, and the water temperature signal e from the water temperature sensor 32 provided in the water jacket of the engine 1. Output control signals r, g, h to valves 26, 27, 31. As a result, the recirculation control valves 20 and 21 and the intake throttle valve 28 are opened and closed depending on the engine operating state (rotational speed, accelerator pedal opening, cooling water temperature), and exhaust recirculation is controlled. .

Next, the operation of the control unit 4 regarding fuel control will be explained according to the flowchart shown in FIG.

First, the control unit 4 performs steps 81 to S3.
Accordingly, the rotation signal a and the accelerator opening signal S from the rotation sensor 5 and the accelerator opening sensor 6 are input, and the engine rotation speed and accelerator pedal opening are calculated as shown in FIG.
a) Set the basic timing To of the fuel injection timing with the characteristics shown in lb+. And then step S
a, calculate the rate of change of the accelerator pedal opening from the accelerator opening signal according to Ss, and determine whether the speed is correct, that is, whether or not the accelerator pedal is being pressed during acceleration; During acceleration, correction control of the advance direction of the injection timing is performed in steps 86 to Sho. That is, in step S6, it is determined whether the rate of change of the accelerator opening is greater than a predetermined value α, and when b>α, that is, when there is sudden acceleration, step S7. A relatively large correction ff1Kt in the advance direction is set according to S8, and the basic timing To is corrected using this correction ff1K+ to calculate the first correction timing T1. Further, when b≦α, that is, when the acceleration is slow, step S9. The above correction flEI according to S10
Set a correction ff1K2 in the advance angle direction that is smaller than K1, and use this correction ff1K2 to set the basic timing TO.
is corrected to calculate the second correction timing T2.

Further, the control unit 4 controls steps Sn, S+
2, the rate of change in the opening degree of the accelerator pedal is calculated again, and it is determined whether the rate of change is smaller than a predetermined negative value -β, that is, whether the accelerator pedal is suddenly closed during a gear change or the like. . If the accelerator pedal is not closed suddenly, step S1 is performed.
3, so that the injection timing becomes the basic timing To corresponding to the engine rotational speed and accelerator pedal opening obtained in step $3, or step Sa,
The duty ratio of the aill f11 signal d is set so that the basic timing To is corrected in the advance direction according to the acceleration state obtained in S1o, and the duty ratio of the aill f11 signal d is set. Output to. As a result, the timer piston 8 in the pump 3
The fluid pressure acting on the piston 8 is regulated and the piston 8
or the position of the cam disc 13 is set and the pump 3
The fuel injection timing from then becomes the basic timing To or the corrected timing T1 or T2, and the engine 1
The injection timing is such that the required output or good exhaust performance can be obtained depending on the operating state of the engine.

On the other hand, when the accelerator pedal is suddenly closed during a gear change, etc., the control unit 4 performs the step S described above.
12 to steps 814 to 816 to control response delay countermeasures. In this control, first, step S1
In step 4, the timing at which the sudden closing of the accelerator pedal is detected is corrected using the correction f2tK3 in the retard direction, and the retard correction timing T3 is obtained. Then, the duty ratio of the control signal d corresponding to this timing T3 is set, and control is performed to fix the duty ratio to this duty ratio in step S15, and in step S16, the time [from the sudden closing of the accelerator pedal] is changed to the set time 0. The control signal d fixed at the duty ratio is output until it is determined that the duty ratio has elapsed. Therefore, when the accelerator pedal is suddenly closed at time t1 as shown in FIG. 4, the load region changes from the region ■ where the injection timing is delayed to the region ■ shown in FIG. 5(b) due to this sudden closing. Even if the timing is shifted to , the control to advance the timing as shown by the chain line (c) in FIG. This corrected timing T3 is held for a set time of 0. As a result, when the accelerator pedal is depressed again due to the completion of a gear change, etc., and the load area returns to the injection A and mink delay area ■,
It is now possible to obtain injection timing that correctly corresponds to the load at that time, and as a result, even after entering the region where the injection timing is delayed due to the control response delay as shown by the chain line (c) in Figure 4 (b). This prevents the problem that the timing is advanced and NOx in the exhaust gas increases during this time. In addition, while the accelerator pedal is closed, the engine speed decreases, but the injection timing is corrected in the retarded direction in response to this decrease, so when the accelerator pedal is pressed again, the injection timing The timing corresponds to the load as described above, and at the same time corresponds correctly to the engine rotation speed.

(Effects of the Invention) As described above, according to the present invention, in the fuel injection timing control device for a diesel engine that controls the fuel injection timing in correspondence with the engine rotation speed and the accelerator pedal opening, the gear When the accelerator pedal is suddenly closed or opened at the time of change, the temporary advance or retard control of the injection timing is canceled, and the timing is delayed by a predetermined amount from the timing immediately before the accelerator pedal is suddenly closed. Since the timing is fixed, it is possible to prevent an injection timing state that does not correspond to the load from occurring due to a delay in injection timing control in response to a sudden change in the opening degree of the accelerator pedal. Furthermore, since the fuel injection timing is corrected in a retarded direction in response to a decrease in engine rotational speed while the accelerator pedal is closed, the timing also correctly corresponds to the engine rotational speed. This prevents deterioration of exhaust gas, such as an increase in the amount of NOx discharged, due to a situation in which the fuel injection timing does not correspond to the load or engine rotational speed, such as during a gear change.

[Brief explanation of the drawing]

Figures 1 to 4 show embodiments of the present invention, with Figure 1 being a control system diagram and Figure 2 being a sectional view of the main parts of the fuel injection pump.
FIG. 3 is a flowchart showing the operation of the control unit, and FIGS. 4(a) and 4(b) are time charts showing the action. In addition, Fig. 5 fa) and (b) are graphs showing the control characteristics of injection timing, and Fig. M6 fa) lb>
is a time chart diagram illustrating the conventional problems. 1... Engine, 2... Fuel injection nozzle, 3...
Fuel injection pump, 4... Control unit, 5.
...Rotation sensor, 6...Accelerator opening sensor.

Claims (1)

[Claims] (1) The accelerator pedal opening degree and the engine rotational speed are detected, and the fuel injection timing is changed according to the accelerator pedal opening degree, and the timing is changed in the advance direction according to the increase in the engine rotational speed. In the diesel engine fuel injection timing control device configured, a detection means for detecting the rate of change of the accelerator pedal opening;
Correction for setting the fuel injection timing to a timing delayed by a predetermined amount from the timing at the time of detection and holding this timing for a predetermined time when the detection means detects a state in which the rate of change in the return direction of the accelerator pedal is equal to or higher than a predetermined speed. 1. A fuel injection timing control device for a diesel engine, comprising: means.