JPS61138837A - Fuel injection rate controller for diesel engine - Google Patents

Abstract

PURPOSE:To aim at prevention against an overrun, by overflowing high pressure fuel from a solenoid valve at the low pressure side at a time when an electric current for the solenoid valve, controlling relief pressure, is cut off. CONSTITUTION:A solenoid valve 70, controlling relief pressure with electromagnetic force, is installed in a high pressure flow passage ranging from a high pressure chamber 56 of a fuel injection pump to an injection nozzle. With movement of a plunger 48, when pressure in the high pressure chamber 56 exceeds the relief pressure of the solenoid valve 70, a plunger 72 lifts whereby it is kept up to the setting pressure. When an electric current to the solenoid valve 70 is cut off, pressure in the high pressure chamber 56 overcomes a return spring 74, opening a seat 71a, and passes through a passage 71b, thus it overflows in an oil sump 45. With this constitution, even if a fuel regulating member sticks there, an engine is stoppable and an overrun is preventable.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a mechanism for electrically controlling the fuel injection rate in order to reduce noise and vibration during idling of a diesel engine and increase output amplifier during high speed and high load. The present invention relates to a fuel injection rate control device having a fuel injection rate control device.

[Conventional technology]

Diesel engines have the problem of large combustion noise and vibration during idling operation, and it is known that as a countermeasure to this problem, it is effective to lower the injection rate during idling operation and lengthen the fuel injection period.

As an example of changing the injection rate by changing the pump's pressure feeding mechanism, there is a known example shown in Japanese Patent Laid-Open No. 57-97025, which has a structure in which a movable pressure regulating piston is provided in the high pressure chamber of the pump. The problem is that the mechanism is complicated.

[Problem that the invention seeks to solve]

The present invention has been developed in view of the above-mentioned conventional device, and it is possible to reduce noise and vibration by lowering the injection rate during idling, and to maintain a large injection rate at high speeds and high loads to ensure sufficient output. The purpose of this system is to enable easy injection rate control and to stop the engine with a simple structure.

[Means for solving problems]

In order to achieve the above object, the present invention includes an injection pressure control solenoid valve whose relief pressure can be electrically varied in a high-pressure fuel flow path from a fuel injection pump to an injection nozzle, and a large current flowing through the solenoid valve. By changing the maximum injection pressure in the high-pressure fuel flow path according to the operating condition and changing the injection rate, by cutting off the current flowing through the solenoid valve, all the fuel in the high-pressure flow path is removed from the solenoid valve. The valve allows overflow to the low-pressure side, eliminating fuel injection regardless of the position of the fuel adjustment member when current is cut off, making it possible to stop the engine.

〔Example〕

The apparatus according to the present invention will be explained below with reference to embodiments shown in the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, in which the device of the present invention is applied to a Bosch type distribution fuel injection pump. 6 is a 4-cycle diesel engine, 5 is a fuel injection pump, 41 is a pump drive shaft, and in a 4+ cycle engine, a vane type pump driven at 1/2 of the crankshaft rotation speed is used, and from the fuel tank 62. Fuel that has passed through the fuel filter 63 is taken in through the inlet 43 and discharged to the outlet 44. The fuel reservoir 45 inside the fuel pump housing that exits the outlet 44 is filled with fuel, the pressure is regulated by the fuel pressure regulator 46, and excess fuel is returned to the fuel tank 2. face cam 4
7 and the pump plunger 48 are integrated, and are connected to the pump drive shaft 41 by a compression ring 49 to transmit rotational force. Since this 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.
accompanies reciprocating motion and rotational motion, and after sucking fuel through the suction port 52, distributes and pressure-feeds the fuel.

70 is an injection pressure control solenoid valve whose relief pressure can be electrically varied. 71 is the housing, which includes a seat portion 71a that determines the pressure receiving area on which the internal pressure from the high pressure chamber 56 acts;
The fuel in the high pressure chamber 56 is transferred to the fuel reservoir 4 in the pump housing.
5 is provided. A plunger 72 is movable in the axial direction toward the cylindrical inner peripheral portion 71c of the housing 71, and is integrated with a moving core 72a made of a magnetic material. A coil 72 is energized and controlled by the electrical control circuit 2. A return spring 74 presses the plunger 72 against the seat portion 71a with a force added to the electromagnetic force caused by the current flowing through the coil, and the high pressure chamber 5
6 relief pressure is set.

The spring constant of the return spring and the air gap are selected so that the acting force of the plunger 72 does not change much with respect to changes in lift caused by the plunger relieving high-pressure fuel. That is, as shown in Fig. 2, the return spring force Fs and the electromagnetic force FE are
The cent load FR as a result of the above is made to be approximately constant.

Here, the relationship between relief pressure PR and set load Fp is PR
-FR×(4/πd2), where d is the diameter of the sheet portion 71a. A spring retainer 75 has a sealing O-ring 75a and a threaded portion 75c, and allows the spring set load to be adjusted in circumference. 7°6 is a valve end that is fixed to the housing 71 with screws.

Pressure feeding of fuel begins when the plunger 48 moves in the direction of the arrow and closes the intake port 52, exits the distribution passage 53 and delivery valve 54, passes through the high-pressure pipe, and is injected into each cylinder of the engine from the injection nozzle. . As the plunger moves, the pressure in the high pressure chamber 56 increases
When the pressure exceeds the JIJ-f pressure, the plunger 72 of the injection pressure control valve 70 lifts to maintain the maximum pressure in the high pressure chamber 56 at the relief set pressure. Further, the plunger 48 moves in the direction indicated by the arrow, and the spill boat 55 moves from the right (b direction side) end face of the spill ring 4, which serves as a fuel adjustment member, to the fuel reservoir 45.
When it is opened, the pumping of fuel ends. Therefore, by moving the spill ring 4 in the axial direction of the plunger 48, it is possible to adjust the fuel injection amount.

3 is an electromagnetic actuator which determines the position of the moving core 33 by balancing the force in the direction of the arrow a generated by the current flowing through the coil 31 and the force in the direction of the arrow 3 generated by the springs 35. This moving core 33 moves the spill ring 4 via a link mechanism 38 to adjust the fuel injection amount.

Reference numeral 1b denotes a rotation speed detector that detects the rotation speed of the engine, which detects the rotation speed of a gear lbl directly connected to the pump drive shaft 41 using an electromagnetic pickup 1b2, and uses this electrical signal as an engine rotation speed signal for electrical control. Input to circuit 2. Reference numeral 1a denotes an accelerator operation amount detector using, for example, a potentiometer, and inputs an electric signal corresponding to the accelerator operation amount to the electrical control circuit 2. 71 is a key switch that outputs the battery voltage and whether the starter is ON or FF.

The electrical control circuit 2 receives detection signals from the engine speed detector 1b, accelerator operation amount detector 1a, and key switch 71, and controls the injection pressure control solenoid valve to maintain the maximum injection pressure corresponding to the target injection rate. A target current value to be passed through 70 is calculated and output. The electrical control circuit 2 includes a current control circuit 21 .

FIG. 7 shows a specific embodiment of the current control circuit 21. 2
A microcomputer 2 calculates the target current value, a target injection amount, a target position, etc., which will be 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 electromagnetic valve 70 is detected by a current detection resistor 215, passed through a current detection amplifier 213, and input as an actual current signal to an error correction amplifier 2122. The error correction amplifier 212 controls the heath 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. Conden No. 216 is for stably operating the above operations without oscillation.

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, and 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 to correct the errors. In this embodiment, the calculation of the target injection amount and target position is performed using, for example, Japanese Patent Application Laid-Open No. 57-20525.
This is performed by a microcomputer 22 as shown in the publication. ' Fig. 3 shows the relief pressure PR with respect to the current of the injection pressure control valve 70, and PN shows the injection nozzle opening pressure. When the current I is zero (left end), the glue IJ + pressure corresponds to the cent load Fs of the return spring. Here, the relief pressure Pp determined only by the cent load Fs of the return spring 74 when the current is zero is set lower than the valve opening pressure of the nozzle as shown in FIG. If the fuel does not flow, no matter where the spill ring 4 is located, the fuel in the high pressure chamber 56 will hit the return spring and open the seat 71a.
It returns to the oil sump 45 through the passage 71b. Furthermore, when current is applied, the cent load corresponding to the electromagnetic force increases linearly with the coil current. That is, by changing the current flowing through the coil depending on the operating conditions of the engine, the maximum injection pressure can be controlled and the fuel injection rate can be freely changed.

Next, the operation of the present invention will be explained with reference to characteristic diagrams shown in FIGS. 4, 5, and 6. Figure 4 shows the case where injection rate control is not performed (
In other words, when the current flowing through the coil 73 of the pressure control potential valve 70 is set to be sufficiently large (and the relief pressure PR is set above the maximum pressure generated by the injection pump) , (al indicates the injection pressure within the high pressure chamber 56.

When the plunger 48 moves in the direction of the arrow, the pressure within the high pressure chamber 56 increases. Then, the nozzle opening pressure PN
When this point is exceeded, the nozzle opens at point t2 and starts injecting fuel.

Furthermore, as the plunger 48 moves, the pressure within the high pressure chamber 56 increases as shown in FIG. 4 f8). Correspondingly, the nozzle lift becomes even larger and the fuel injection rate takes on a waveform as shown in FIG. 4(C). When the plunger further moves and injects a predetermined injection amount, the spill port 55 is opened to the right end surface of the spill ring 4, and the pressure feeding ends at t3.

FIG. 5 shows a case where injection rate control is performed. Same as Figure 4i
a+ indicates the injection pressure in the high pressure chamber. PN is the nozzle opening pressure. PR is caused by the suction force generated by the current value output from the electric control circuit 2 to the coil 73 in order to obtain the injection rate determined by the leaf pressure of the pressure control valve, the cent load of the return spring 74, and the operating conditions 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 increases. When the nozzle opening pressure PN is exceeded, the nozzle opens at point t2 and starts injecting fuel. As the plunger moves further, the pressure in the high pressure chamber 56 increases, but when it reaches the IJ pressure, the plunger 72 of the injection pressure control solenoid valve 70 lifts and flows through the flow path 71b to the fuel reservoir 45 in the housing. Since a portion of the fuel is bypassed, the amount of fuel pumped to the injection nozzle decreases, suppressing the injection nozzle rift l, and the injection rate also decreases as shown in diagram (C). When the plunger 48 further moves and injects a predetermined amount, the spill port 55 is opened to the right end surface of the spill ring 4, and the pressure feeding ends at t3.

Further, Fig. 86 shows a case where the current of the pressure control solenoid valve 70 is set to zero, and regardless of the position of the spill ring 4, the pressure in the high pressure chamber 56 is such that the fuel overflows to the low pressure side with a sufficient flow area. Therefore, the pressure does not become higher than the relief pressure PR determined by the return spring of the electromagnetic valve, and therefore does not exceed the valve opening pressure of the nozzle, so that the injection amount becomes zero and the engine can be stopped.

〔Effect of the invention〕

As described above, the present invention is equipped with an injection pressure control solenoid valve whose relief pressure can be varied by electromagnetic force in the high-pressure flow path from the fuel injection pump that reciprocates the plunger to forcefully feed fuel to the injection nozzle. Since the maximum injection pressure is controlled by changing the current flowing depending on the engine operating condition, fine-grained injection rate control is possible.For example, by reducing the injection rate during idling and extending the injection period, idling noise and vibration can be reduced. In addition, at high speeds and high loads, by keeping the relief pressure above the pump generation pressure and increasing the injection rate, sufficient output can be ensured, and by cutting off the current of the pressure control valve, the position of the fuel adjustment member can be adjusted. Since the fuel in the high pressure chamber overflows through the pressure control valve and the injection amount of the nozzle is reduced to zero, even if the fuel adjustment member etc. becomes stained with foreign matter, the current of the pressure control solenoid valve is simply cut off. can stop the engine and prevent overrun. Therefore, it can have the same function as a fuel cut valve conventionally provided in a so-called Bosch type distribution pump, the fuel cant valve can be omitted, and the structure can be simplified.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram showing one embodiment of the present invention, Fig. 2 is a characteristic diagram showing the relationship between the plunge lift amount of the pressure control solenoid valve and the plunger acting force, and Fig. 3 is a current flowing through the pressure control solenoid valve. A characteristic diagram showing the relationship between value and relief pressure, Figures 4, 5, and 6 are waveform diagrams each showing the injection rate control state, and Figure 7 is an electric circuit diagram of the first current control circuit. It is. 1a... Accelerator operation amount detector, 1b... Rotation speed detector, 2... Electric control circuit, 3... Electromagnetic actuator, 5... Fuel injection pump, 6... Diesel engine , 21... Current control circuit, 45... Fuel reservoir,
70...Pressure control solenoid valve 271b...Flow path, 73...
...Coil 174...Return spring.

Claims (1)

[Claims] An injection pressure control solenoid valve whose relief pressure can be varied by electromagnetic force is installed in the high-pressure flow path from the fuel injection pump, which pumps the fuel by reciprocating the plunger, to the injection nozzle. and when the current of the solenoid valve is cut off, all of the fuel in the high pressure flow path overflows to the lower pressure side of the solenoid valve, and fuel injection from the nozzle is stopped. A fuel injection rate control device for a diesel engine, which is characterized by: