JPS6043148A - Control apparatus for fuel injection pump - Google Patents

Abstract

PURPOSE:To attain optimum pilot injection of fuel and to vary the injection rate under exact control, by forming a leak passage in parallel to a fuel passage, and providing a first solenoid valve in the fuel passage while providing a second solenoid valve in the leak passage. CONSTITUTION:A high-pressure plunger pump 6 is reciprocated while rotating synchronously with rotation of an engine and feeds fuel drawn from a pump chamber 5 into a high-pressure chamber 6A via a fuel passage 36 to a plurality of cylinders under pressure. A first solenoid valve 38 closed during fuel feeding stroke of a plunger 7 is provided in the fuel passage 36 while a second solenoid valve 39 is provided in a leak passage 37. By the function of these solenoid valves 38, 39, it is enabled to attain optimum setting of pilot injection of fuel and a low injection rate of fuel. Therefore, the engine performance can be improved to a great extent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) 1. This invention relates to a control device for a fuel injection pump of a diesel engine or the like.

(Prior Art) Generally, in a diesel engine, the fuel injection amount is variably controlled according to the engine speed and required output (load).

An example of such control means is the distribution type fuel injection pump shown in Fig. 1, which is most widely used in practical use.
, 1980 Technical Manual [Diesel Engine] published June 1973).

First, fuel is sucked from an inlet 1 of a pump body by a feed pump 3 driven by a drive shaft 2 connected to an engine output shaft.

The fuel discharged from the feed pump 3 is supplied to the pump chamber 5 inside the pump housing 31 with the supply pressure controlled by the pressure regulating valve 4 .

The fuel in the pump chamber 5 lubricates the working parts and is simultaneously sent to the high pressure plunger pump 6 through the suction port 12.

A plunger 7 of this pump 6 is fixed to a cam disk 8 connected to a drive shaft 2, and is driven by the drive shaft 2 through two couplings in synchronization with the rotation of the engine.

The cam disk 8 has the same number of face cams 9 as the number of engine cylinders, and each time the face cams 9 ride over a roller 11 disposed on a roller ring 10 while rotating, the cam disk 8 reciprocates by a predetermined cam lift. do.

Therefore, the plunger 7 reciprocates while rotating, and by this reciprocating movement, the fuel sucked from the suction boat 12 is forced into the distribution boat 13 through the delivery pulp 14 to an injection nozzle (not shown).

On the other hand, the amount of fuel to be injected is determined by the position of the control sleeve 16 that covers the cut-off boat 15 formed on the plunger 7. For example, cut-off boat 15
When the opening of the plunger 7 passes the right end of the control sleeve 16 as the plunger 7 moves to the right, the fuel that had been pumped from the high pressure chamber 6A to the distribution boat 13 passes through the cutoff port 15'r. The water is then released to the low-pressure pump chamber 5, thus completing pressure feeding to the distribution boat 13.

Therefore, if the control sleeve 16 is displaced to the right relative to the plunger 7, the fuel injection end time will be delayed and the fuel injection amount will be increased, whereas if the control sleeve 16 is displaced to the left, the fuel injection end time will be brought forward. This results in a decrease in the amount of fuel injected.

The control sleeve 16 is supported by a link lever device 19 that is interlocked with an accelerator pedal (not shown), and is displaced according to the amount of depression. Correction control is performed to increase or decrease the fuel injection amount in order to always keep the engine speed constant depending on the accelerator opening.

This link lever device 19 includes a collector lever 21, a tension lever 22, a star lever 23, and a star lever 21.
- spring 24.

The collector lever 21 is rotatably supported by the pump housing 31 about a fulcrum B, and is held stationary by being pressed against a full load adjustment screw 26 by a compression spring 25.

In addition, the tension lever 22 and the star torque p<-23
The tension lever 22 is provided on the collector lever 21 so as to be rotatable about the fulcrum A, and the tension lever 22 is provided with the control shaft 2 as the control lever 20 is rotated.
A biasing force of a tension spring 28 that increases or decreases is applied via the start lever 24, and this biasing force is transmitted to the start lever 23 via the start spring 24.
It is pressed to f.

Then, attach the ball joint 1 to this start lever 23.
The control sleeve 16 is supported via 8g.

Therefore, if the lever 20 is rotated to increase the tension of the tension spring 28, the tension lever 22 will rotate in the counterclockwise direction, pushing the start lever 23 through the start spring 24, and moving the tension lever 23 around the fulcrum A. control sleeve 16. Move it all the way to the right to increase the fuel injection amount.

On the other hand, the governor mechanism 18 is built in the upper part of the injection pump main body, and a flyweight holder l, 8b is configured integrally with a gear 18a, and a flyweight 18c is rotatable around a joint point 18d. 9 was attached to it.

When the flyweight holder tab slides and rotates around the governor shirt 18e according to the rotation of the drive shaft 2 transmitted through the gear 18a, the flyweight 1
8c also expands due to rotational centrifugal force around the rotation 1 junction point 18d'i.

For example, if the rotational speed increases even though the accelerator opening does not change, the governor sleeper 18f, which fits into the governor shaft 18e and engages with the flyweight 18c, will
It is placed on the fly weight 18c and moves forward. As the governor sleeper 18f moves forward, the start lever 23 rotates around the fulcrum A against the pressing force of the start spring 24, and moves the control sleeve 16 to the left in the figure to adjust the fuel injection amount. reduce Therefore, the engine speed decreases and converges to the engine speed corresponding to the accelerator opening.

Further, the fuel injection timing is controlled by rotating the roller ring 10.

Specifically, the face cam 9 of the cam disk 8 is the roller 1.
Since fuel is injected when the face cam 9 runs onto the roller 11, for example, if the roller ring 10 is rotated in the opposite direction to the rotational direction of the cam disc 8, the time when the face cam 9 runs onto the roller 11 will be earlier. The injection timing is advanced relative to the engine crank angle.

For this purpose, the roller ring 10 is connected to the timer slide pin 2.
It is rotatably fitted to the timer piston 30 via 9.

The fuel pressure of the pump chamber 5 is guided through a passage 33 to a high pressure chamber 32 on the end face of the timer piston 30 sliding in the cylinder 30A, and a low pressure chamber 34 on the opposite side communicates with the suction side of the feed pump 3. However, the elastic force of the spring 350 pushes back the timer piston 30. Note that FIG. 1 shows a state in which the axis of the timer piston 30 is rotated 90 degrees, and in reality the roller ring 1
00 rotation corresponds to the tangential direction. Similarly, for convenience of explanation, the axis of the feed pump 3 is also shown rotated by 90 degrees in the same drawing.

Since the fuel pressure in the pump chamber 5 increases in proportion to the rotation speed of the feed pump 3, the timer piston 30 is pushed to the left as the engine rotation speed increases, and this causes the rotation of the cam disk 8 and It rotates the roller ring 10 in the opposite direction and acts to relatively advance the injection timing.

By the way, in this device, the injection rate (injection amount per unit crank angle) is uniquely determined by the plunger speed determined by the plunger diameter and the profile of the face cam 9, and it is possible to change the injection rate according to the operating conditions. I could not do it. For this reason, for example, if the injection rate is matched to the high-speed rotation range, the initial injection rate will be high in the low-speed rotation range, temporarily enriching the air-fuel mixture, increasing the heat release rate at the initial stage of combustion, and reducing the noise level and NOx emissions. On the other hand, when the increased engine level force is matched to a low speed rotation range, there is a problem in that smoke increases in the high speed rotation range.

For this reason, a device that variably controls the injection rate according to the engine operating condition without changing the profile of the face cam 9 of the cam disk 8 was developed in Japanese Patent Laid-Open No. 57-6.
No. 5857, JP-A-57-44744 and JP-A-57
Various proposals have been made as No.-41462.

In addition, as a countermeasure mentioned above, a so-called pilot injection device that pre-injects a certain amount of fuel prior to main injection has the advantage that it is possible to lower the maximum pressure in the cylinder while ensuring a predetermined injection rate and maintaining the custom engine output. It attracted a lot of attention and was also proposed as Japanese Patent Application Laid-Open No. 57-65852.

However, in all of the above conventional examples, the intended purpose is achieved by controlling the discharge oil or suction oil in the plunger pump, so the passage structure around the plunger pump is complicated9 and the number of machining increases, resulting in high costs. In addition, the reliability of the device was low, and K had the problem that it was not possible to obtain a very accurate injection rate or pilot injection.

(Objective of the Invention) An object of the present invention is to realize optimal pilot injection and accurate variable control of the injection rate depending on the operating state of the engine with a simple structure.

(Structure and operation of the invention) The present invention provides a fuel injection pump for a diesel engine in which a plunger performs a reciprocating motion while rotating and pumps and distributes fuel sucked from a pump chamber into a high pressure chamber via a fuel passage to each cylinder. A first leak passage is formed in parallel with the fuel passage, and the fuel passage is closed during the pumping stroke of the plunger.
A solenoid valve and a second solenoid valve that opens while the first solenoid valve is closed are respectively installed in the leak passage, and the closing timing and period of the first solenoid valve are adjusted depending on the engine load and rotation. There are provided means for controlling the valve opening timing and valve opening period of the second electromagnetic valve according to the number of rotations of the engine.

That is, by closing the fuel passage with the first solenoid valve, the pressure of the fuel in the high pressure chamber increases as the plunger compresses the pressure, and by opening the passage with the second solenoid valve during the pressure increase, A portion of the pressurized fuel is allowed to escape. - Accordingly, during the predetermined period when the first solenoid valve is closed, fuel is injected, and during the predetermined period when the second solenoid valve is open, the amount of fuel to be injected is reduced or the injection is interrupted. .

Therefore, the first. By controlling the opening/closing timing and opening/closing period of the second solenoid valve according to the engine load, rotation speed, etc., it is possible to obtain the appropriate injection timing and injection amount according to the operating state of the engine. If the opening timing of the solenoid valve is set at the early stage of injection, the optimum injection rate will be ensured at the initial injection amount, and if it is set at the middle stage of injection, a good pilot injection will be achieved. It is.

Embodiment) FIGS. 2 and 3 are a sectional view of a fuel injection pump and a block diagram of a control means, respectively, showing an embodiment of the present invention, in which 2 is a drive shaft, 3 is a feed pump, 8 is a cam disk, and 10 is a block diagram of a control means. is a roller ring, 6-hole high pressure plunger pump.

This high-pressure plunger pump 6 has a plunger 7 that reciprocates while rotating in synchronization with the rotation of the engine, as shown in FIG.
The pressure of the fuel sucked from the pump chamber 5 into the high pressure chamber 6A via the fuel passage 36 is increased by its compression operation, and the fuel is transferred from the distribution boats 1 and 3 of the plunger barrel 6B to the injection nozzle (not shown) of each cylinder via the delivery valve 14. ) to 2.

A leak passage 37 is formed in parallel with the fuel passage 36 connecting the pump chamber 5 and the high pressure chamber 6A, and a first electromagnetic valve 38 for opening and closing the passage 36 is provided in the middle of the fuel passage 36. A second electromagnetic valve 39 for opening and closing the passage 37 is installed in the middle of each passage.

The first electromagnetic valve 38 is constructed as shown in FIG. 4
1 moves back to open the fuel passage 36.

In the second electromagnetic valve 39, as shown in FIG. 5, when the coil is energized, the valve body 43 moves forward to open the leak passage 37, and when opened, the valve body 43 retreats to close the leak passage 37. Note that an orifice 44 having a predetermined small diameter is provided in this leak passage 37.

These solenoid valves 38 and 39 are connected to an accelerator sensor 45 that detects the opening degree of the accelerator pedal, as shown in FIG.
1 signal S2 from a unit pulse generator 46 that detects the crank angle and generates a unit pulse, and a reference pulse generator 47 that also generates a reference pulse.
Opening/closing is controlled by a signal from a control circuit 48 to which a reference signal S1 from the control circuit 48 is input.

This control circuit 48 includes an input interface 49, an arithmetic processing section 50, a storage section (ROM) 51, and a storage section (RAM) 5.
2 and an output interface 53, a high voltage power supply 55, and a drive circuit 56. The control signal generation circuit 54 determines the opening/closing timing of the solenoid valves 38 and 39 based on the input signal. , the opening/closing period is calculated, and the solenoid valve 38.
The solenoid valves 38 and 39 are commanded via the drive circuit 56 to open and close 39.

Specifically, the load signal, the 1-variable signal S2, and the reference signal S
, and the signal S1 or iS, the first rotational speed signal is used to close the first electromagnetic valve 38 for a predetermined period of time according to the rotational speed of the plunger 7. ,
The second solenoid valve 39 is controlled to open for a predetermined period of time depending on the number of rotations of the first solenoid valve 38 during closing. However, 57
is a battery.

That is, while the first electromagnetic valve 38 is closed, the pressure of the fuel in the high pressure chamber 6A of the high pressure plunger pump 6 is increased and injected from the injection nozzle, while a part of this high pressure fuel is transferred to the second electromagnetic valve 3.
It leaks into the pump chamber 5 while the valve 9 is open. In this case, the second solenoid valve 39 is set to open in the middle of the closing of the first solenoid valve 38 and in the middle of the injection of the pickled fuel, as shown in FIG.

As a result, the appropriate fuel injection timing and injection amount can be maintained according to the operating state of the engine, and pilot injection can be performed accurately prior to main injection as shown in FIG.

Therefore, compared to the case of only main injection, combustion does not occur suddenly, and as shown in Figure 8, the peak of the cylinder pressure due to combustion is alleviated, and as a result, especially in the low load and low rotation range. This makes it possible to sufficiently reduce noise and NQx in exhaust gas.

Note that the governor mechanism 18, control sleeve 16, etc. shown in FIG. 1 are of course unnecessary.

On the other hand, when lowering the injection rate at the initial stage of injection, the opening timing and opening period of the second electromagnetic valve 39 are set to coincide with the initial closing period of the first electromagnetic valve 38. Then, the diameter of the orifice 44 interposed in the leak passage 37 is made smaller to reduce the amount of fuel leaked due to opening of the second electromagnetic valve 39, and increase the fuel pressure in the high pressure chamber 6A. ! l
)' The orifice diameter is selected to loosen by a predetermined value.

According to this, it is possible to obtain a good injection rate with a low initial injection pressure and a small initial injection amount, and as with pilot injection, it is possible to sufficiently reduce noise, NOx, etc. by relaxing the peak pressure in the cylinder. I can do it. Note that in this case, it goes without saying that the injection start timing is delayed from the time of pilot injection.

Next, the detailed configuration and timing chart of the control circuit 48 when pilot injection is performed are shown in FIGS. 9 and 10.

The reference signal S from the reference pulse generator 47 is input to the counters 5s-, 6t, and when the counters 58-61 are set in response to the reference signal Sl, the counters 58-6
1 is a 1-variant signal S2 sent from the unit pulse generator 46
It starts counting and outputs a signal S according to the counted value.

This signal S, is sent to the corresponding comparator 62-65, and the output S4-S7 of the comparator 62-65 is sent to the counter 5, respectively.
The signal is input to reset terminals 8 to 61, and is sent to the set and reset terminals of flip-flops 67 and 68.

Further, the 1-variable signal S2 is converted into a rotation speed signal in the rotation speed calculation circuit 69, and this rotation speed signal is sent to the pilot injection timing calculation circuit 70, the pilot injection period correction calculation circuit 71, the main injection timing calculation circuit (ignition delay period Correction calculation circuit) 7
2. Main injection period calculation circuit (main injection amount calculation circuit)
At the same time, the load signal from the accelerator sensor 45 is sent to the pilot injection timing calculation circuit 70 and the main injection period calculation circuit 73.

The pilot injection timing calculation circuit 70 calculates the crank angle T1 (see FIG. 6) from the reference signal Sl to the start of the pilot injection based on the rotational speed signal and the load signal,
The pilot injection period correction calculation circuit 71 calculates the crank angle T corresponding to the period during which the pilot injection is performed based on the rotational speed signal.
, -T, and the main injection timing calculation circuit 72 calculates the crank angle T, -Tl- from the start of pilot injection to the start of main injection based on the rotational speed signal, and calculates the main injection timing calculation circuit 72. 73 is a crank angle T4 corresponding to the period during which main injection is performed based on the rotational speed signal and load signal.
− Calculate T.

Then, the crank angle T is determined by the comparator 62.
2-'r is added with T1 by the adder 74 and sent to the comparator 63, crank angle T, -T, is added with T1 by the adder 75 and sent to the comparator 64, and crank angle T, -T is added to the comparator 64. At 76, T is added and sent to the comparator 65.

Therefore, from the reference signal S1, the crank angles T, , Tt.

After Ts and Ta have elapsed, the outputs S4 to S7 of the comparators 62 to 65 momentarily reach the no-y level, and in response, the flip-flops 67 and 68 are sequentially switched.

When the output S4 of the comparator 62 goes high, the output S8 of the flip-flop 67 goes high, making the transistor 77 conductive and closing the first electromagnetic valve 38. Next, when the output S of the comparator 63 becomes /'l, the output S of the flip-flop 68 becomes high level, making the transistor 78 conductive and opening the second solenoid valve 39. When the output S of the comparator 64 becomes a high level, the flip-flop 68 is reset and the second solenoid valve 39 is closed, and when the output S7 of the comparator 65 becomes a low level, the flip-flop 67 is reset. This resets the first solenoid valve 38 and opens it.

As a result, the first and second electromagnetic valves 38 and 39 are controlled to open and close, and the injection timing and injection amount are appropriately controlled according to the operating state of the engine, and optimal pilot injection can be performed. .

As shown in FIG. 11, if the output S of the comparator 62 is used to start the counters 59 and 60, and the output S6 of the comparator 64 is used to start the counter 61, the adder 74
76 can be made unnecessary. Furthermore, when lowering the initial injection rate, the flip-flops 67 and 68 may be set by the output S4 of the comparator 62, and of course, in this case, the crank angles T, , T, ,
T is appropriately set according to the operating state of the engine.

(Effect of the invention) With the very simple configuration of the first solenoid valve and the second solenoid valve, pilot injection and low injection rate setting can be accurately realized, and the optimal fuel injection can be achieved according to the operating state of the engine. This has the effect of making injection control possible and greatly improving engine performance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional example, FIGS. 2 and 3 are sectional views of a fuel injection pump and a control means, respectively, showing an embodiment of the present invention. FIGS. 4 and 5 are sectional views of a fuel injection pump and a control means, respectively. , a sectional view and a partial sectional view of the second solenoid valve, FIG. 6 is a graph showing the opening and closing states of the eleventh second solenoid valve, FIGS. FIG. 9 and FIG. 10 are circuit diagrams showing detailed examples of the configuration of the control circuit of the present invention and their timing charts, and FIG. 11 is a circuit diagram showing an example of the configuration of the control circuit. 5... Pump chamber, 6... High pressure plunger pump, 6
A... High pressure chamber, 7... Plunger, 36... Fuel passage, 37... Leak passage, 38... First electromagnetic valve, 39... Second electromagnetic valve, 44...・Orifice, 4
5... Accelerator sensor, 46... Unit pulse generator, 47... Reference pulse generator, 48... Control circuit.

Claims (1)

[Claims] In a fuel injection pump for a diesel engine, the plunger performs reciprocating motion while rotating in synchronization with engine rotation, and the fuel sucked from the pump chamber into the high pressure chamber via the fuel passage is pumped and distributed to each cylinder, in parallel with the fuel passage. forming a leak passage, installing in the fuel passage a first solenoid valve that closes during a pressure feeding stroke of the plunger, and a second solenoid valve that opens while the first solenoid valve is closed in the leak passage; 1st
means for controlling the closing timing and closing period of a second solenoid valve in accordance with the operating condition based on the load and rotation speed of the engine, and the opening timing and valve opening period of a second solenoid valve depending on the engine rotation speed 1. A control device for a fuel injection pump, comprising means for controlling the fuel injection pump accordingly.