JPH0647965B2 - Fuel injection rate controller for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a mechanism for electrically controlling the fuel injection rate in order to reduce noise and vibration at idle of a diesel engine and to increase output at high speed and high load. The present invention relates to a fuel injection rate control device.

[Conventional technology]

Diesel engines have a problem of large combustion noise vibration during idle operation, and as a countermeasure against this, it is known that it is effective to reduce the injection rate during idle operation and lengthen the combustion injection period (for example, JP-A-57-86532).

Generally, in a fuel injection device, it is necessary to control the injection timing, the injection amount, and the injection rate, but it is difficult to control the injection rate compared to the injection timing and the injection amount. The reason is that it is necessary to control the injection amount of high-pressure fuel within a very short period of time. Therefore, it is well known that the conventional injection rate control is based on the structure of the injection port of the injection nozzle. It is known that these change the effective opening area of the injection port in the process of opening the injection valve, have two types of injection valves with different diameters, and change the injection path in the early and late stages of injection. .

[Problems to be solved by the invention]

The present invention has been made in view of the above conventional device, and for example, can reduce the fuel injection rate during idling and light load, and can reduce noise and vibration while maintaining a stable rotation state. Further, another object of the present invention is to provide a fuel injection rate control device for a diesel engine, which can secure a sufficient output by maintaining the relief pressure at a value higher than the pump generated pressure and increasing the injection rate at high speed and high load.

[Means for solving problems]

In order to achieve the above object, the present invention, an operating condition detector that detects the operating conditions of a diesel engine as an electrical signal,
Control means for receiving a signal from the operating condition detector to calculate an injection amount command value of the engine and controlling the fuel injection amount of the fuel injection pump according to the injection amount command value, and based on the operating condition of the engine, An injection pressure control solenoid valve for controlling the injection pressure by varying the valve opening pressure of a relief valve that guides the fuel in the high pressure passage from the injection pump to the injection nozzle to the low pressure passage, and the injection pressure control solenoid valve The injection amount command value is changed according to the operation of.

〔Example〕

An apparatus according to the present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, in which a device according to the present invention is applied to a Bosch type distribution type fuel injection pump. 6 is a 4-cycle diesel engine, 5 is a fuel injection pump, 41 is a pump drive shaft, and in the case of a 4-cycle engine, a vane type pump driven at a rotational speed half of the crankshaft rotational speed is used. 6
The fuel having passed 3 is sucked in through the inlet 43 and discharged into the outlet 44. The fuel discharged from the outlet 44 is filled in the fuel reservoir 45 in the pump housing, the pressure is adjusted by the fuel pressure adjuster 46, and the excess fuel is returned to the fuel tank 62. Face cam 4
7 and the pump plunger 48 are integrated with each other, and the pump drive shaft 41 and the coupling 49 are coupled to each other to transmit the rotational force. Since the face cam 47 is pressed against the roller 51 by the plunger spring 50, the plunger 48 is rotated as the pump drive shaft 41 rotates.
Performs reciprocating motion and rotating motion, sucks the fuel from the suction port 52, and then performs distributed pressure feeding.

Reference numeral 70 is an injection pressure control solenoid valve that can electrically vary the relief pressure. Reference numeral 71 denotes its housing, which is a seat portion 71a that determines a pressure receiving area on which the internal pressure from the high pressure chamber 56 acts.
The fuel in the high pressure chamber 56 is supplied to the fuel reservoir 4 in the pump housing.
The flow path 71b for returning to 5 is provided. A plunger 72 is a movable core 72a made of a magnetic material, which is axially movable to a cylindrical circumferential portion 71c in the housing 71.
It is integrated with. 73 is a coil, which is an electric control circuit 2
The energization is controlled more. A return spring 74 presses the plunger 72 against the seat portion 71a by a force that is added to the electromagnetic force due to the current flowing through the coil and sets the relief pressure of the high pressure chamber 56.

The spring 72 and the air gap of the return spring are selected so that the force of the plunger 72 does not change much with respect to the lift change due to the relief of the high pressure fuel by the plunger. That is, as shown in FIG. 2, a return spring force F _S and an electromagnetic force F _E are applied to the lift of the plunger.
The set load F _R as the total of the above is approximately constant. Here, the relationship between the relief pressure P _R and the set load F _R is expressed as P _R = F _R × (4 / πd ² ), where d
Is the diameter of the seat portion 71a. A spring retainer 75 is a sealing O-ring 75a and a threaded portion 75c.
The spring set load is adjustable.
A valve end 76 is screwed and fixed to the housing 71.

The pressure feeding of fuel starts when the plunger 48 moves in the direction of arrow b and closes the suction port 52, exits the distribution passage 53 and the delivery valve 54, and is injected from the injection nozzle to each cylinder of the engine through the high pressure pipe. . When the pressure in the high pressure chamber 56 exceeds the relief pressure of the injection pressure control solenoid valve 70 with the movement of the plunger, the plunger 72 of the injection pressure control valve 70 is lifted and the maximum pressure in the high pressure chamber 56 becomes the relief set pressure. keep. Further, when the plunger 48 moves in the direction of the arrow b and the spill port 55 is opened to the fuel reservoir 45 from the right (b direction side) end surface of the spill ring 4 forming the fuel adjusting member, the pressure feeding of the fuel ends. Therefore spill ring 4
The fuel injection amount can be adjusted by moving the valve in the axial direction of the plunger 48.

An electromagnetic actuator 3 determines the position of the moving core 33 by balancing the force in the direction of arrow a generated by the current flowing through the coil 31 and the force generated by the spring 35 in the direction opposite to the direction of arrow a. The moving core 33 moves the spill ring 4 via the connecting rod 34 and the link mechanism 38 to adjust the fuel injection amount. Reference numeral 1b is a rotation speed detector for detecting the rotation speed of the engine, and includes a pump drive shaft 41
The rotation speed of the gear 1b1 directly connected to the electromagnetic pickup 1
It is detected from b2, and this electric signal is input to the electric control circuit 2 as an engine speed signal. Reference numeral 1a is an accelerator operation amount detector using a potentiometer, for example, and inputs an electric signal corresponding to the accelerator operation amount to the electric control circuit 2. 81 is battery voltage and starter is ON or OF
It is a key switch for detecting whether it is F or not.

The electric control circuit 2 receives detection signals from the engine speed detector 1b, the accelerator operation amount detector 1a, and the key switch 81, respectively, and calculates and outputs a target current value flowing through the injection pressure control solenoid valve 70. In the electric control circuit 2,
A current control circuit 21 is provided.

FIG. 6 shows a specific embodiment of the current control circuit 21. Two
Reference numeral 2 denotes a microcomputer, which calculates the target current value, a target injection amount, a target position, etc. described later. The calculated digital value of the target current value is input to the D / A converter 211 and becomes an analog voltage corresponding to the target current value. On the other hand, the current flowing through the solenoid valve 70 is detected by the current detection resistor 215, passed through the current detection amplifier 213, and input to the error correction amplifier 212 as an actual current signal. The error correction amplifier 212 controls the base current of the transistor 214 so that the target current value and the actual current signal match.
In this way, the current control circuit 21 works so that the target current value calculated by the microcomputer 22 and the actual current flowing through the solenoid valve 70 match. The capacitor 216 is for stably operating the above operation without oscillating.

On the other hand, the electric control circuit 2 calculates the target position of the spill ring 4 corresponding to the target injection amount of the fuel injection pump, compares the signal representing this target position with the actual position signal from the actual position detector 7, A signal is given to the electromagnetic actuator 3 based on these errors, and the electromagnetic actuator 3 is driven so as to correct the error. In this embodiment, the calculation of the target injection amount and the target position is performed, for example, in Japanese Patent Laid-Open No. 2052525/1982.
It is performed by the microcomputer 22 as shown in the publication.

FIG. 3 shows the relief pressure P _R with respect to the current of the injection pressure control valve 70, and P _N shows the injection nozzle opening pressure. The relief pressure when the current I is zero (left end) corresponds to the set load F _S of the return spring. Then, the set load corresponding to the electromagnetic force linearly increases due to the coil current. That is, the maximum injection pressure can be controlled by changing the current flowing through the coil according to the operating conditions of the engine, and the fuel injection rate can be freely changed.

Next, the operation of the present invention will be described with reference to the characteristic diagrams of FIGS. FIG. 4 shows the case where the injection rate control is not performed (the same characteristic as that of the conventional injection pump is obtained), that is, the current flowing through the coil 73 of the pressure control solenoid valve 70 is made sufficiently large and the maximum pressure generated by the injection pump or more (A) shows the injection pressure in the high pressure chamber 56 when the relief pressure P _R is set to. When the plunger 48 moves in the direction of arrow b, the pressure in the high pressure chamber 56 rises. Then, when the valve opening pressure P _N of the nozzle is exceeded, the nozzle opens at point t ₂ and fuel injection starts. Further, as the plunger 48 moves, the pressure in the high pressure chamber 56 rises as shown in FIG. 4 (a). Along with that, the nozzle lift is also increased and the fuel injection rate is also shown in FIG.
The waveform is as shown in (c). When the plunger is further moved to inject a predetermined injection amount, the spill port 55 is opened to the right end surface of the spill ring 4 and the pressure feeding is completed at t ₃ .

FIG. 5 shows the case where the injection rate control is performed. Same as Fig. 4
(a) shows the injection pressure in the high pressure chamber. P _N is the valve opening pressure of the nozzle. P _R is the relief pressure of the pressure control valve, and is due to the suction force generated by the current value output from the electric control circuit 2 to the coil 73 to obtain the injection rate determined by the set load of the return spring 74 and the operating condition of the engine. It is determined. Here, when the plunger 48 moves in the direction of the arrow, the pressure in the high pressure chamber rises. When the nozzle opening pressure P _N is exceeded, the nozzle opens at point t ₂ and fuel injection starts. When the plunger further moves, the pressure in the high pressure chamber 56 rises accordingly, but when the relief pressure is reached, the plunger 72 of the injection pressure control solenoid valve 70 is lifted and a part of the fuel is accumulated in the fuel reservoir 45 in the housing through the flow passage 71b. By-passing, the amount of fuel pumped to the fuel nozzle is reduced, the injection nozzle lift amount is suppressed, and the injection rate is also reduced as shown in FIG. When the plunger 48 is further moved to inject a predetermined injection amount, the spin port 55 is opened to the right end surface of the spill ring 4 and the pressure feeding is completed at t ₃ .

In the above example, the relief pressure corresponding to the spring set load of the injection pressure control solenoid valve 70 is set to the nozzle opening pressure P.
_Although it is slightly smaller than _N, it may be equal to or slightly larger than the nozzle opening pressure. Further, the same effect can be obtained by making the spring set load sufficiently small so that almost all the force corresponding to the relief pressure is electromagnetic force.

Further, although the pressure control solenoid valve 70 is integrated with the pump body, it may be separately provided between the pump and the high pressure passage from the injection nozzle.

By the way, as described above, in order to allow the fuel in the high pressure chamber to escape and to control the injection rate, the spill ring is moved to the fuel injection increasing side from the normal operation during the injection rate control to apparently increase the fuel injection amount. There is a need.

Therefore, in this embodiment, the injection rate control is performed during idle rotation control (during constant speed rotation control) to change the current value of the solenoid valve 70, and at the same time, to set the target injection amount command value for moving the spill ring 4. The target spill position is also changed at the same time. Then, the deviation of the rotation speed thereafter is carried out by feedback control of the idle rotation speed, and the idle rotation speed is kept at the target rotation speed.

FIG. 7 shows the operation of the microcomputer 22 as a flowchart.

When the electric control circuit 2 is powered on, the program is started, and in step 901 the program is initialized. At step 902, operating conditions of the engine, such as an accelerator signal and engine cooling water temperature, are captured. Step 9
At 03, the engine speed is calculated. In step 904, the injection amount control routine is executed. In step 905, the idle rotation control execution condition determination routine determines conditions such as those shown in FIG. Steps 110 and 11
1,112 accelerator 0% and engine speed N
_E is near idle speed N _L (rpm) <N _E <N _H (rpm)
It is determined whether or not the state of 2 has passed for 2 seconds or more, and it is determined in steps 113 and 114 whether the starter is OFF or the vehicle speed is 0 km / h. When all the conditions are satisfied, the routine proceeds to step 906, the idle speed control routine is executed, and the routine proceeds to next step 907 to the injection rate control routine. The idle speed control is performed, for example, as disclosed in JP-A-57-140531. If the condition is not satisfied at step 905, the idle speed control is stopped at step 908, the injection rate control is stopped at 909, that is, the governor pattern described later is switched and the current flowing to the solenoid valve 70 is set to a sufficiently large value. ,
Output the current command value. Step 907 or 909
Is completed, the process returns to step 902 and the program is repeated.

Next, FIG. 9 shows a detailed flowchart of the injection rate control routine in step 907 of FIG.

Step 101 is a determination condition for entering the injection rate control routine. For example, in the present embodiment, it is determined whether or not the idle speed control of step 906 has reached 2 seconds or more. In step 102, the idle governor pattern is shown in FIG.
Switch from pattern (a) to pattern (b). At this time, the governor pattern to be selected differs depending on the cooling water temperature, and the lower the water temperature, the larger the injection amount at the same rotation speed. In step 103, the delay time (t _D ) after switching the governor pattern is set. This is because the response of the linear solenoid that is the injection amount control actuator is the solenoid valve 7
This is because it is slower than 0, and the value of t _D is about 10-50 milliseconds. In step 104, the value of the current flowing through the solenoid valve is switched. Here, the switching flow value at the time of injection rate control is a function of the water temperature as shown in FIG. In step 105, idle speed control is performed as before injection rate control.

By repeating steps 101 to 105, the idle speed control routine controls the spill ring so as to keep the engine speed constant, and the spill ring is controlled to the target spill position, that is, the target injection rate.

[Other Examples]

In addition, although the example in which the electromagnetic actuator 3 is used for the injection amount control is shown in the present embodiment, it is applied to a system including the overflow electromagnetic valve 100 arranged in the high pressure passage as shown in FIG. Also has the same effect. Here, the injection amount control may be performed as shown in JP-A-58-187537. In the system using the overflow current valve, step 103 in FIG. 9 is unnecessary because there is no response delay of the electromagnetic actuator (linear solenoid). Further, as the operation performed when the governor pattern is switched, the overflow timing (energization timing) of the overflow solenoid valve is changed.

〔The invention's effect〕

As described above, according to the present invention, it is possible to directly control the injection pressure by controlling the valve opening pressure of the relief valve by the electromagnetic force, and the injection amount that changes with the change of the injection pressure is also interlocked. Therefore, the degree of freedom in controlling the injection rate is improved, and a sufficient output can be secured at the time of high load, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a characteristic diagram showing a relationship between a plunger lift amount and a plunger acting force of a pressure control solenoid valve, and FIG. 3 is a current flowing through the pressure control solenoid valve. FIG. 4 is a characteristic diagram showing the relationship between the pressure and the relief pressure, FIGS. 4 and 5 are waveform diagrams showing the control state of the injection rate, and FIG. 6 is an electric circuit diagram of the current control circuit in FIG. 1, and FIG. , 8th
FIGS. 9 and 10 are flowcharts showing the processing procedure in the control circuit of FIG. 1, FIG. 10 is a characteristic diagram showing an idle governor pattern with and without injection rate control, and FIG. 11 is with injection rate control. FIG. 12 is a characteristic diagram showing the solenoid valve current with respect to the cooling water temperature, and FIG. 1a ... Accelerator operation amount detector, 1b ... Rotation speed detector, 2 ... Electric control circuit, 3 ... Electromagnetic actuator, 5 ... Fuel injection pump, 6 ... Diesel engine, 7
0 ... pressure control solenoid valve, 100 ... overflow solenoid valve.

Claims (3)

[Claims] 1. An operating condition detector for detecting an operating condition of a diesel engine as an electric signal, an injection amount command value of the engine being calculated in response to a signal from the operating condition detector, and a fuel in accordance with the injection amount command value. Control means for controlling the fuel injection amount of the injection pump, and based on the operating conditions of the engine, an electromagnetic force is applied to the valve opening pressure of the relief valve that guides the fuel in the high pressure passage from the injection pump to the injection nozzle to the low pressure passage. And a fuel injection rate control device for a diesel engine, characterized in that the injection pressure control solenoid valve that controls the injection pressure by changing the injection pressure control solenoid valve and the injection amount command value is changed according to the operation of the injection pressure control solenoid valve. 2. A fuel injection rate control device for a diesel engine, wherein the electromagnetic force of the solenoid valve is controlled by a current value, and the current value is a function of a cooling water temperature of the engine. 3. A fuel injection rate control device for a diesel engine, wherein the amount of change of the injection amount command value is a function of the cooling water temperature of the engine.