JPS639091B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel control device for a diesel engine, and more particularly to a device for preventing the generation of black smoke during rapid acceleration.

In conventional diesel engines, the accelerator pedal is mechanically connected to the sleeve (60 in Figure 2) of the injection pump that controls the fuel injection amount, and the accelerator pedal position (tread angle) and sleeve position are directly connected. I was beginning to cope.

However, recently, the optimal fuel injection amount is calculated in response to various operating variables such as the accelerator pedal position, engine speed, and temperature, and the actuator (e.g., servo motor) that displaces the sleeve is adjusted according to the above calculated value. Electronically controlled fuel control devices have been developed that control the fuel injection amount through servo control.

In the above device, for example, as shown in Figure 3, the injection amount is set according to the rotational speed and the accelerator pedal position (the degrees in the figure indicate the accelerator pedal position with 90 degrees fully open). The value when the pedal is fully opened is set to the limit value that does not generate black smoke. However, the injection amount Q ₁ at startup is
In order to improve starting performance, the value is set to be greater than the value when the accelerator pedal is fully open, and therefore the range of movement of the sleeve is considerably wider than the value when the accelerator pedal is fully open.

Therefore, if the command signal that controls the servo motor increases rapidly during sudden acceleration, the sleeve position will overshoot the command signal value due to the inertia of the servo motor and sleeve, and the injection amount will exceed the value when fully opened.

In a diesel engine, when the amount of fuel is excessive, black smoke is generated and is emitted into the atmosphere from the exhaust pipe. For example, as shown in Fig. 4, when the accelerator pedal position A suddenly increases from the idle position to 4/5 load, the servo motor command signal B also changes to 4/5 load.
It increases rapidly up to 5 loads. However, as shown by the broken line C, the actual sleeve position changes with some response delay and overshoots, exceeding the value D when fully opened. In this case, in the shaded area beyond D, there is excess fuel and black smoke is generated. Note that the broken line E indicates the limit of movement of the sleeve.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel control device for a diesel engine that prevents the generation of black smoke during rapid acceleration.

In order to achieve the above object, in the present invention,
By setting a limit on the speed at which the command signal changes in the fuel increase direction, the servo motor is prevented from overshooting, and by preventing excessive fuel from being supplied even during sudden acceleration, it is configured to prevent the generation of black smoke. ing.

FIG. 8 is a block diagram showing the configuration of the present invention.

In FIG. 8, 200 is an actuator 20
2, and is calculated according to, for example, the depression angle of the accelerator pedal or the rotational speed of the engine.

201 is means for setting a predetermined upper limit value on the rate of change of the command signal 200 described above.

The actuator 202 is controlled by the command signal whose upper limit value of the rate of change is limited by the means 201 described above. The actuator 202 drives the fuel injection amount adjustment mechanism, and fuel is injected accordingly.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is an example diagram of a diesel engine control device to which the present invention is applied.

In Fig. 1, 1 is an air cleaner, 2 is an intake pipe, 3 is a main fuel chamber, 4 is a swirl chamber, 5 is a glow plug, 6 is an injection nozzle, 7 is an injection pump (details will be described later), 8 is an exhaust pipe, 9 is a throttle valve that adjusts the amount of intake air,
10 is a diaphragm valve that controls the throttle valve opening;
1 is an EGR valve that controls the amount of EGR recirculated from the exhaust pipe 8 to the intake pipe 2 (exhaust gas recirculation amount); 12 and 13;
is a solenoid valve. Further, 14 is a vacuum pump serving as a negative pressure source, and can be used in common with, for example, a brake servo pump. Further, 15 is a constant pressure valve that creates a constant negative pressure from the negative pressure given from the vacuum pump 14, 16 is a battery, 17 is a glow relay that controls energization to the glow plug 5, and 18 is a control unit that controls the fuel injection amount of the injection pump 7. A servo circuit 19 is a glow lamp that indicates the energization state of the glow plug 5. 20 is an accelerator position signal IS ₁ corresponding to the accelerator pedal position (depression angle)
The accelerator position sensor 21 outputs a reference pulse at every reference angle of crank angle (for example, 120°).
IS ₂ , unit pulse per unit angle (e.g. 1°)
A crank angle sensor that outputs IS ₃ , 22 a neutral switch that detects that the transmission is in the neutral position and outputs a neutral signal IS ₄ , and 23 a vehicle speed signal IS ₅ corresponding to the vehicle speed (transmission 24 is a temperature sensor that outputs a temperature signal IS ₆ corresponding to the engine cooling water temperature; 25 is an injection start signal every time the injection nozzle 6 starts fuel injection. A lift sensor outputting IS ₇ , for example a switch or a piezoelectric element actuated by fuel pressure. Further, 26 is an atmospheric density sensor that outputs an atmospheric density signal _IS8 corresponding to the temperature and pressure of the atmosphere. In addition, a sleeve position signal corresponding to the position of the sleeve that controls the fuel injection amount of the injection pump 7
Signals such as IS ₉ (details will be described later) and battery voltage signal IS ₁₀ are used.

Further, 27 is an arithmetic unit, such as a central processing unit (CPU) 28 and a read-only memory (ROM).
29. Readable and writable memory (RAM) 3
0, an input/output interface 31, and the like.

The computing device 27 receives signals IS ₁ to IS ₁₀ provided from the various sensors described above, a starter signal IS ₁₁ provided from a starter switch (not shown) (turned on when the starter motor is activated), a glow signal IS ₁₂ provided from a glow switch, etc. It inputs signals and outputs various control signals OS ₁ to _{OS 7} for optimally controlling the diesel engine.

First, throttle valve opening control signal OS ₁ and EGR control signal
OS ₂ is a pulse signal, and by changing the duty of these pulse signals and controlling the duty of the solenoid valves 12 and 13, the opening degree of the throttle valve 9 and
The opening degree of the EGR valve 11 is controlled.

Further, the fuel cutoff control signal OS ₃ controls opening and closing of a fuel cutoff valve 71 (for stopping the engine) in the injection pump 7.

Further, the fuel injection amount control signal OS ₄ and the sleeve position signal IS ₉ are given to the servo circuit 18, and the servo circuit 18 outputs the servo signal S ₁ so as to match both signals _. By controlling the sleeve position, the fuel injection amount is controlled.

Furthermore, by controlling the injection timing control mechanism in the injection pump 7 using the injection timing control signal OS ₅ ,
Controls fuel injection timing. Note that the injection timing is feedback-controlled using the injection start signal _IS7 from the lift sensor 25.

Furthermore, by controlling the glow relay 17 using the glow control signal OS ₆ , the energization of the glow plug 5 is controlled.

Further, the energization state of the glow plug 5 is displayed by controlling the flashing of the glow lamp 19 using the glow lamp control signal _OS7 . For example, the glow lamp 19 is turned on when energized, and turned off when not energized.

Next, FIG. 2 is a sectional view of an example of the injection pump 7. As shown in FIG.

In FIG. 2, fuel is first sucked from an inlet 32 of the pump body by a feed pump 34 driven by a drive shaft 33 connected to an engine output shaft.

The supply pressure of the fuel discharged from the feed pump 34 is controlled by a pressure regulating valve 35, and the fuel is supplied to a pump chamber 36 inside the pump housing.

The fuel in the pump chamber 36 lubricates the working parts and is simultaneously sent to the high pressure plunger pump 38 through the suction port 37.

A plunger 39 of this pump 38 is fixed to an eccentric disk 40 connected to a drive shaft 33, and is driven by the drive shaft 33 via a joint 41 in synchronization with the rotation of the engine.

The eccentric disk 40 has the same number of face cams 42 as the number of engine cylinders, and each time the face cams 42 pass over a roller 44 disposed on a roller ring 43 while rotating, the eccentric disk 40 reciprocates by a predetermined cam lift.

Therefore, the plunger 39 reciprocates while rotating, and due to this reciprocating movement, the fuel sucked from the suction port 37 is forced into the injection nozzle 6 of FIG. 1 through the distribution port 45 and the delivery valve 46. be done.

At that time, the fuel injection timing is determined by the roller ring 43.
can be freely adjusted by changing the relative position between the face cam 42 and the roller 44.

The roller ring 43 is connected to a plunger 48 via a driving pin 47.

In FIG. 2, for convenience of explanation, the axis of the plunger 48 is rotated by 90 degrees, and the axis of the feed pump 34 is also rotated by 90 degrees.

A cylinder 49 containing the plunger 48 is slidably housed inside the casing 50.
An oil chamber 51 is defined at the right end of the cylinder 49, and an oil chamber 52 is defined at the left end. Note that passages 49a and 50a are provided for communicating between the oil chamber 51 and the end face high pressure chamber 55 when the cylinder 49 moves to the right.

The oil chamber 51 communicates with the other oil chamber 52 and the suction side of the feed pump 34 through a fuel passage 53, and a solenoid valve 54 is provided at the connection between the oil chamber 5 and the fuel passage 53. .

Further, the fuel pressure in the pump chamber 36 is introduced to the end face high pressure chamber 55 of the plunger 48 sliding in the cylinder 49 through a passage 56, and the low pressure chamber 57 on the opposite side is communicated with the suction side of the feed pump 34. Although the pressure is close to negative, the elastic force of the spring 58 pushes back the plunger 48.

The fuel pressure in the pump chamber 36 is
4, so when the passage 49a is closed as shown in the figure, the plunger 48 is pushed to the left in the figure as the engine rotation speed increases, thereby causing the eccentric Since the roller ring 43 is rotated in the opposite direction to the rotational direction of the disk 40, the injection timing becomes earlier in accordance with the rotational speed.

Furthermore, when the cylinder 49 moves fully to the right in the drawing due to the rotational force of the eccentric disk 40 (at this time, the solenoid valve 54 is open), the passages 49a and 5
Since the oil chamber 51 and the end high pressure chamber 55 communicate with each other through the oil chamber 51 and the end high pressure chamber 55, the pressure in the end high pressure chamber 55 can be controlled by opening and closing the solenoid valve 54. Therefore, by duty-controlling the opening and closing of the solenoid valve 54 using the injection timing control signal _OS5 , the injection timing can be electrically controlled.

On the other hand, the amount of fuel to be injected is determined by the position of the sleeve 60 that covers the spill board 59 formed on the plunger 39. For example, when the opening of the spill port 59 passes the right end of the sleeve 60 due to the rightward movement of the plunger 39, the fuel that had been pumped from the plunger pump chamber 61 to the distribution port 45 passes through the spill port 59. The pump is then released into the pump chamber 36, thus ending the pumping.

That is, if the sleeve 60 is displaced rightward relative to the plunger 39, the fuel injection end time will be delayed and the fuel injection amount will be increased, and conversely, if the sleeve 60 is displaced leftward, the fuel injection end time will be brought forward. Therefore, the amount of fuel injection decreases.

The position control of the sleeve 60 described above is performed by a servo motor 62. That is, the shaft 63 of the servo motor 62 is threaded, and a slider 64 having a threaded hole in the center is screwed into the shaft 63 of the servo motor 62.

A link lever 65 is coupled to this slider 64 so as to be rotatable about a pin 66 as a fulcrum.

The link lever 65 is rotatably attached around a fulcrum 67, and is connected to the sleeve 60 via a pivot pin 72 at the tip of the link lever 65.
is locked.

Therefore, when the servo motor 62 rotates forward and backward, the slider 64 moves left and right, which causes the link lever 65 to rotate about the fulcrum 67 and move the sleeve 60 left and right.

The servo motor 62 is controlled by a servo signal _{S1 output from the servo circuit 18} in response to the fuel injection amount control signal _OS4 .

Therefore, there is no direct correspondence between the accelerator pedal and the fuel injection amount. In other words, the accelerator pedal "want to accelerate" or "want to decelerate"
The calculation device 27 calculates the optimal fuel injection amount according to the driving condition at that time, and performs optimal control using the fuel injection amount control signal OS ₄ . This is what we do.

Further, the shaft of the potentiometer 68 provided near the servo motor 62 is coupled to the shaft 63 of the servo motor 62 by gears 69 and 70, so that the signal from the potentiometer 68 is transmitted to the sleeve 63.
This will indicate the 0 position. This signal becomes the aforementioned sleeve position signal _IS9 .

On the other hand, the electromagnetic type fuel cutoff valve 71 is controlled to open and close by the fuel cutoff control signal OS ₃ , and when the fuel cutoff valve 71 is cut off, the intake port 37 is closed and the fuel is cut off, thereby stopping the engine. There is.

The fuel temperature sensor 73 also outputs a fuel temperature signal IS ₁₃ corresponding to the temperature of the fuel in the injection pump.

The present invention relates to the fuel injection amount control signal _OS4 that controls the servo circuit 18 of FIG.

This will be explained in detail below.

FIG. 5 is a block diagram of one embodiment of the present invention.

In FIG. 5, the basic injection amount calculation circuit 101
is, for example, a function generator that calculates the basic injection amount from the accelerator position signal IS ₁ corresponding to the accelerator pedal position and the engine rotation speed calculated from the unit pulse IS ₃ , and outputs the basic injection amount signal S ₂ . .

Further, the correction amount calculation circuit 102 performs the above-mentioned IS ₁ , IS ₃
Then, a correction amount of the injection amount is calculated according to the atmospheric density signal IS ₈ and the fuel temperature signal IS ₁₃ , and a correction amount signal S ₃ is output.

Next, the addition circuit 103 outputs an actual injection amount signal S ₄ that is the sum of the basic injection amount signal S ₂ and the correction amount signal S ₃ .

Next, the memory circuit 104 stores the value of the fuel injection amount control signal OS ₄ a certain period of time ago (the previous value if calculation is performed at certain intervals), and outputs a signal S ₅ corresponding to the value. .

Next, the subtraction circuit 105 outputs the actual injection amount signal _S4 and the signal _S5.
Calculate the difference ΔS=S ₄ −S ₅ .

Next, the comparison circuit 106 compares ΔS with a predetermined upper limit value ΔS ₀ of the amount of change, and outputs a signal S ₆ that becomes high level when ΔS>ΔS ₀ .

On the other hand, the adder circuit 108 outputs S ₅ +ΔS ₀ obtained by adding ΔS ₀ to the signal S ₅ .

Next, the switching circuit 107 outputs the actual injection amount signal S ₄ when the signal S ₆ is at a low level, and outputs S ₅ +ΔS ₀ when the signal S ₆ is at a high level. The output of this switching circuit 107 is the fuel injection amount control signal.
OS ₄ is applied to the servo circuit 109 (corresponding to 18 in Figure 1), and the servo circuit 109 drives the servo motor 110 (corresponding to 62 in Figure 2) to determine the position of the sleeve 60 and control the fuel injection amount. Control.

As described above, in the circuit shown in Fig. 5, even if the accelerator pedal is suddenly depressed during rapid acceleration and the actual injection amount signal _S4 increases rapidly, the fuel injection amount control signal _OS4 that is actually given to the servo circuit is The rate of change of is limited to ΔS ₀ or less per unit time.

Therefore, as shown in FIG. 6, even if the accelerator pedal position A suddenly increases from the idle position to 4/5 load, the command signal B (fuel injection amount control signal OS ₄ ) rises at a constant rate of change. Therefore, in the actual sleeve position, there is almost no overshoot as shown by the broken line, so no black smoke is generated.

In FIG. 5, more appropriate control can be achieved by changing the upper limit value ΔS ₀ of the amount of change in accordance with the rotational speed of the engine. In that case, the value of ΔS ₀ given to the comparator circuit 106 and the value of ΔS ₀ added by the adder circuit 108 may be changed in accordance with the rotation speed.

Further, the part surrounded by the broken line in FIG. 5 can be constructed by a microcomputer (27 in FIG. 1).

FIG. 7 is an embodiment of a flowchart of calculations when the control indicated by the broken line in FIG. 5 is performed by a microcomputer.

The calculation shown in FIG. 7 is repeated at regular intervals. First, in P ₁ , the basic injection amount, which is predetermined by table drawing, etc., is calculated according to the accelerator pedal position and rotation speed, and then in P ₂
The actual injection amount _K2 is calculated by adding various corrections.

Next, in _P3 , the difference ΔK=K2 _{−K1 between the value K1 output in the previous calculation and the current actual injection amount K2 is calculated .}

Next, in _P4 , a predetermined upper limit value ΔK ₀ of the amount of change is calculated according to the rotational speed.

Next, in P ₅ , determine whether ΔK is greater than or equal to ΔK ₀ , and YES
In the case of P ₆ , set K=K ₁ +ΔK ₀ , and in the case of NO, P ₇
Let K= _K2 .

Next, the K from P ₆ or P ₇ is stored as K ₁ for the next calculation, and then, in P ₉ , the K is output as the fuel injection amount control signal OS ₄ .

As explained above, according to the present invention, an upper limit is set on the rate of change of the signal that controls the fuel injection amount, and the sleeve position is prevented from overshooting even if the accelerator pedal position changes suddenly. It is possible to prevent the generation of black smoke.

[Brief explanation of the drawing]

Fig. 1 is a diagram of an example of a control device for a diesel engine to which the present invention is applied, Fig. 2 is a sectional view of an example of an injection pump, Fig. 3 is a diagram of the relationship between rotational speed, accelerator pedal position, and injection amount, and Fig. 4 5 is a diagram showing the relationship between the command signal and the sleeve position, FIG. 5 is a diagram showing an embodiment of the present invention, FIG. 6 is a diagram showing the relationship between the command signal and the sleeve position in the present invention, and FIG. 7 is a diagram showing the calculation of the present invention. FIG. 8 is a block diagram showing the structure of the present invention. Explanation of symbols, 1...Air cleaner, 2...Intake pipe,
3... Main combustion chamber, 4... Whirlpool chamber, 5... Glow plug,
6... Injection nozzle, 7... Injection pump, 8... Exhaust pipe,
9... Throttle valve, 10... Diaphragm valve, 11...
EGR valve, 12, 13... Solenoid valve, 14... Vacuum pump, 15... Constant pressure valve, 16... Battery, 17
... Glow relay, 18... Servo circuit, 19... Glow lamp, 20... Accelerator position sensor, 21... Crank angle sensor, 22... Neutral switch,
23...Vehicle speed sensor, 24...Temperature sensor, 25...Lift sensor, 26...Atmospheric density sensor, 27...Arithmetic unit, 28...CPU, 29...ROM, 30...RAM,
31...I/O interface, 32...Entrance, 33
...Drive shaft, 34...Feed pump, 3
5... Pressure regulating valve, 36... Pump chamber, 37... Suction port, 38... High pressure plunger pump, 39... Plunger, 40... Eccentric disk, 41
...Coupling, 42...Face cam, 43...Roller ring, 44...Roller, 45...Distribution port, 46...Delivery valve, 47...Driving pin, 48...
plunger, 49... cylinder, 49a... passage, 5
0... Casing, 50a... Passage, 51, 52... Oil chamber, 53... Fuel passage, 54... Solenoid valve, 55... End face high pressure chamber, 56... Passage, 57... Low pressure chamber, 58... Spring, 59... Spill port, 60 …sleeve,
61... Plunger pump chamber, 62... Servo motor, 63... Shaft, 64... Slider, 65... Link lever, 66... Pin, 67... Fulcrum, 68... Potentiometer, 69, 70... Gear, 71... Fuel cutoff valve ,
72... Pivot pin, 73... Fuel temperature sensor, 1
01... Basic injection amount calculation circuit, 102... Correction amount calculation circuit, 103... Addition circuit, 104... Memory circuit, 1
05...Subtraction circuit, 106...Comparison circuit, 107...Switching circuit, 108...Addition circuit, 109...Servo circuit, 110...Servo motor, IS ₁ ...Accelerator position signal, IS ₂ ...Reference pulse, IS ₃ ...Unit pulse, IS ₄ ...neutral signal, IS ₅ ...vehicle speed signal,
IS ₆ ...Temperature signal, IS ₇ ...Injection start signal, IS ₈ ...Atmospheric density signal, IS 9...Sleeve position signal, IS ₁₀ ...Battery voltage signal, IS ₁₁ ...Starter signal, IS _{12 ...} Glow signal, CS ₁ ...Aperture Valve opening control signal, CS ₂ ...EGR
Control signal, OS ₃ ...Fuel cutoff control signal, OS ₄ ...Fuel injection amount control signal, OS ₅ ...Injection timing control signal, OS ₆
...glow control signal, OS ₇ ...glow lamp control signal, S ₁ ...servo signal.

Claims (1)

[Scope of Claims] 1. In a fuel control device for a diesel engine that controls a fuel injection amount by controlling an actuator that drives a fuel injection amount adjustment mechanism using a command signal, A fuel control device for a diesel engine, comprising means for setting a predetermined upper limit on a rate of change. 2. The fuel control device for a diesel engine according to claim 1, wherein the above means changes the upper limit value of the rate of change in the fuel increasing direction in accordance with the engine rotation speed.