JPH0476029B2 - - Google Patents

Description

[Detailed Description of the Invention] <<Industrial Application Field>> The present invention supplies fuel measured in accordance with the operating state of the engine to the plunger pressurizing chamber of a plunger pump, and uses the plunger to supply the supplied fuel. The present invention relates to a fuel injection device for a diesel engine that supplies pressurized fuel to a fuel injector.

[Prior art] Fuel is supplied from a fuel pressure pump to the plunger pressurizing chamber of a plunger pump, and the amount of fuel is supplied according to the operating condition of the engine, and this plunger is driven by a fuel injection timing setting cam directly or via a rocker arm. As a fuel injection device for injecting fuel into a combustion chamber from a fuel injector, there is a device previously proposed by the present applicant in Japanese Patent Application No. 1986-86782.

<<Problems to be Solved>> In the prior application, fuel is supplied to the plunger pressurizing chamber of the plunger pump according to the operating condition of the engine, and the plunger is pushed back by the supplied fuel. Therefore, the amount of pushback of the plunger varies depending on the amount of fuel supplied.

However, since the plunger stroke of the plunger pump is set based on the most recent fuel injection amount, in operating conditions where the injection amount is small, the return stroke of the plunger is only equal to the next injection amount. A problem arises in that a gap is created between a cam follower such as an input section of the mechanism and a fuel injection cam, and the fuel injection cam and cam follower collide during fuel injection, generating noise.

<Means for Solving the Problems> The present invention provides a fuel injection device that supplies a metered amount of fuel to a plunger pressurizing chamber of a plunger pump, in which the plunger is moved by the maximum stroke regardless of the amount of injected fuel. Although it pushes back and prevents a gap from forming between the fuel injection cam and the cam follower, it allows injection of only the metered amount of fuel that has been pumped from the pressure pump. A check valve is interposed between the pump and the plunger pressurizing chamber, and downstream of this check valve, the pressure regulating spring chamber of the fuel injector is constructed in an airtight structure, and the pressure regulating chamber of this airtight structure is By communicating the spring chamber with the plunger pump chamber through an inlet valve, the pressure regulating spring chamber is formed into a fuel pressure accumulator, and fuel is pressurized from this fuel pressure accumulator into the plunger pressurizing chamber to push the plunger back by the entire stroke. At the same time, the metered amount of fuel is injected from the pressure pump, and the forced valve opening means attached to the inlet valve of the plunger pump is switched and activated by changes in the internal pressure of the fuel pressure accumulator. When the internal pressure of the fuel accumulator is below a certain pressure, the inlet valve is maintained in an open state by the forced valve opening means, and when the internal pressure of the fuel pressure accumulator reaches the certain pressure, the operation of the forced valve opening means is released and the inlet valve is closed. At the beginning of the plunger's advance operation, the fuel in the plunger pressurizing chamber is sent back to the fuel pressure accumulator, and when the internal pressure of the pressure accumulator reaches the set pressure, the inlet valve is closed and the fuel pressure pump is activated into the plunger pressurizing chamber. This is characterized in that only the metered amount of fuel that has been supplied remains.

<<Operation>> In the present invention, a hydraulic pressure command type inlet valve opening means is attached to the inlet valve disposed between the fuel pressure accumulation chamber formed by the pressure regulating spring chamber of the fuel injector and the plunger pressurization chamber, and this inlet Since the valve opening means is configured to operate when the internal pressure of the pressure accumulator is below the set pressure to keep the inlet valve open, the fuel stored in the fuel pressure accumulator is released from the inlet valve by the plunger using the accumulated pressure. A prescribed amount (Q ₀ ) is inserted into the pressurizing chamber to push the plunger of the plunger pump back from the maximum extended position to the maximum retracted position, that is, the entire stroke. At this time, in the fuel pressure accumulator, as the fuel expands in volume according to the bulk modulus of the fuel,
The accumulated pressure decreases.

When the plunger enters, the volume of the plunger pressurizing chamber increases, so the accumulated pressure in the fuel pressure accumulator communicating with the plunger pressurizing chamber via the inlet valve decreases, and the inlet valve opening means is activated. The inlet valve remains open.

Then, when the metered amount of fuel is injected from the pressure pump, the metered amount (Q ₁ ) flows into the pressure accumulator,
The pressure inside the pressure accumulator increases. If this metered amount is equal to the maximum injection amount, the internal pressure of the pressure accumulator will reach the set pressure of the pressure accumulator, but if the metered amount is less than the maximum injection amount, the internal pressure of the pressure accumulator will not reach the set pressure. Therefore, the inlet valve opening means remains in an activated state, that is, the inlet valve remains open.

When the plunger pump starts discharging, the inlet valve opening means is configured to switch and operate based on the internal pressure of the fuel accumulator in the early stage of the plunger's advancing operation, so until the internal pressure of the accumulator reaches the set pressure. In this case, the fuel in the plunger pressurizing chamber will flow back into the pressure accumulator. When the sum of the check flow rate (Q ₂ ) of fuel to the pressure accumulator and the metered amount (Q ₁ ) reaches the specified amount (Q ₀ ), the internal pressure in the pressure accumulator and the plunger pressurizing chamber returns to the setting of the pressure accumulator. Since the pressure will be reached, the inlet valve opening means will be deactivated to close the inlet valve. As a result, an amount of fuel equivalent to the metered amount (Q ₁ ) remains in the plunger pressurizing chamber. Then, by advancing the plunger after closing the inlet valve, the remaining amount of fuel (Q ₁ ) remaining in the plunger pressurizing chamber is injected from the fuel injector into the combustion chamber of the engine.

《Example》 Figure 1 is a partially cutaway cross-sectional view of a pressure accumulator unit injector, Figure 2 is a vertical sectional view of the main parts of a diesel engine, Figure 3 is an enlarged view of the main parts of Figure 1, and Figure 4 is a cross-sectional view of the main parts of the diesel engine. 1 is a schematic system diagram showing a fuel supply system of the present invention.

In the figure, reference numeral 1 indicates the entire engine, and this engine 1 has a cylinder head 4 above a cylinder block 3 formed integrally with a crankcase 2.
The engine body 6 is constructed by placing and fixing the head cover 5 and the head cover 5 in this order.

A piston 8 is accommodated in the cylinder block 3 so as to be able to slide up and down within the cylinder 7. A combustion chamber 1 is provided above the piston 8 and between the cylinder head 4 and the nozzle 9a of the unit injector 9.
0 is formed.

As shown in FIG. 3, in this unit injector 9, a holding block 12 that holds a fuel injector 11 is formed with an egress hole 14 for a plunger 13, and the plunger 13 is airtightly slid into the plunger egress hole 14. The plunger pressurizing chamber 16 of the plunger pump 15 is formed into a plunger pump 15 by being freely inserted into the fuel inlet 1 formed in the fuel injector 11.
7. It communicates with the accumulator 20 via the inlet chamber 18 and the cylindrical check valve body 19. Inside the accumulator 20 is a nozzle valve 21 that closes the fuel nozzle 9a.
The valve shaft 22 of the nozzle valve 21 vertically passes through the inside of the accumulator 20, and its upper end passes through the upper wall 23 of the inlet chamber 18 to form a nozzle spring chamber 24 in an airtight manner on the upper side. is entering. A spring receiving plate 28 that receives the lower end of the nozzle spring 27 that sets the closing force of the nozzle valve 21 is in contact with the upper end of the nozzle valve shaft 22 .

Additionally, a nozzle valve shaft 22 located within the inlet chamber 18
A flange portion 29 is protruded from the flange portion 29, and the cylindrical check valve 19 is in contact with the lower surface of the flange portion 29.

A fuel introduction passage 30 is formed in a cross shape in the plunger 13 of the plunger pump 15, and a ball valve is formed at the lower end of the vertical passage of this fuel introduction passage 30, that is, at the end on the side of the plunger pressurizing chamber 16. An inlet valve 31 is arranged. In the vertical passage, an inlet valve 31 is placed in contact with a ball valve 32 of the inlet valve 31.
A rod 33 is inserted through the valve to forcibly open the valve. The rod 33 has a large diameter portion located above the intersection of the cross-shaped fuel introduction passage 30, and this large diameter portion is fitted in the vertical passage in an airtight and slidable manner. Further, the upper end of the rod 33 is in contact with the lower end of the inlet valve closing setting spring 34, and is elastically biased downward by the inlet valve closing pressure setting spring 34, which sets the inlet valve closing pressure. The spring 34 and the rod 33 constitute an inlet valve forced opening means 35.

One end of the horizontal passage of the cross-shaped fuel introduction passage 30 is
It communicates with a fuel pressure pump 38 via a check valve 36 and a fuel filter 37, and the other end of the horizontal passage connects to a fuel communication passage 39 formed in the holding block 12 and the wall of the fuel injector 11. It communicates with the nozzle spring chamber 24 of the fuel injector 11 through the nozzle spring chamber 24 of the fuel injector 11. Therefore, the fuel pressure-fed from the fuel pressure-feeding pump 38 flows into the plunger pressurizing chamber 16 and also into the nozzle spring chamber 24. Since this nozzle spring chamber 24 is formed in an airtight manner, when fuel is pressurized, air is sealed in the nozzle spring chamber 24, and this sealed air acts as a pressure accumulating member. The nozzle spring chamber 24 serves as a fuel pressure accumulator 40
becomes. The inlet valve forced opening means 35 receives the pressure in the fuel introduction passage 30 at the large diameter portion of the rod 33, and the internal pressure of the fuel introduction passage 30 becomes greater than the spring pressure of the inlet valve closing pressure setting spring 34. At this stage, the rod 33 is pulled up to close the inlet valve 31. Therefore, the internal pressure of the nozzle spring chamber 24 also becomes equal to the spring pressure of the inlet valve closing pressure setting spring 34, and the nozzle spring chamber 24 acts as a fuel pressure accumulator 40.

In the figure, reference numeral 41 is a fuel metering device, and the fuel metered by this fuel metering device is supplied to the fuel pressure pump 3.
8, it is fed into a plunger pump 15.

In the fuel injection device configured as described above, fuel at a constant pressure is always stored in the fuel pressure accumulator 40, so when the plunger 13 enters the return stroke after being pushed all the way and discharging the fuel, Since the internal pressure of the plunger pressurizing chamber 16 decreases, the inlet valve 31 opens due to the difference between the internal pressures of the fuel inlet passage 30 and the fuel pressure accumulator 40, and the inlet valve 31 opens from the fuel inlet passage 30 and the fuel accumulator 40 to the plunger pressurizing chamber. Fuel will flow into 16 and push plunger 13 back a full stroke. At this time, in the fuel pressure accumulator 40, the fuel expands in volume according to the bulk elastic modulus of the fuel, and an amount of fuel (Q ₀ ) corresponding to the volume of the plunger pressurizing chamber 16 flows out. 40 internal pressure decreases. Then, when the metered fuel is pumped from the fuel pressure pump 38, the pressurized fuel amount (Q ₁ ) flows into the fuel pressure accumulator 40, and the internal pressure of the fuel pressure accumulator 40 is adjusted to the metered fuel flow rate (Q1). ₁ ), the primary pressure will be boosted to the extent that it corresponds to 1). However, since the metered injection amount (Q ₁ ) is smaller than the specified amount (Q ₀ ) corresponding to the volume of the plunger pressurizing chamber 16, the internal pressure of the fuel introduction passage 30 and fuel accumulator 40 is set to the inlet valve closing pressure. It becomes smaller than the spring pressure of the spring 34, and the inlet valve 31 is forcibly opened.

Next, when the plunger pump 15 enters the pressurizing stroke, since the plunger pressurizing chamber, the fuel introduction passage 30, and the fuel pressure accumulator 40 are in communication with each other, the internal pressure of these parts increases to the pressure of the inlet valve closing pressure setting spring 34. Until the spring pressure is reached, the fuel in the plunger pressurizing chamber 16 flows back to the fuel pressure accumulator 40 side. Then, the amount (Q ₂ ) whose sum with the metered press-in amount (Q 1 ) is a specified amount (Q ₀ ) equal to _the volume of the plunger pump chamber 16.
When the fuel flows back into the fuel pressure accumulator 40, the internal pressure of the fuel pressure accumulator 40 and the fuel introduction passage 30 reaches the spring pressure of the inlet valve closing pressure setting spring 34, and the inlet valve 31 is closed.

Therefore, an amount of fuel equal to the amount of metered fuel (Q ₁ ) pressurized by the pressure pump 38 remains in the plunger pressurizing chamber 16, and the inlet valve 31
By pressurizing the plunger 13 after closing, the remaining fuel is pressurized and discharged to the fuel injector 11.

Further, the present invention can be applied not only to a pressure accumulation type unit injector but also to a normal unit injector in which a nozzle valve is opened by discharge pressure from a plunger pump.

<<Effects>> In the present invention, a pressure accumulator is disposed between the fuel pressure pump and the inlet valve of the plunger pump, and a hydraulic pressure command type inlet valve opening means is attached to the inlet valve, and the inlet valve opening means is connected to the pressure accumulator. It is configured to operate when the internal pressure of the accumulator is below the set pressure to keep the inlet valve open, so the fuel stored in the pressure accumulator is transferred from the inlet valve to the plunger pressurizing chamber in a specified amount ( _Q0 )
Once pressed in, the plunger of the plunger pump is pushed back from the maximum extended position to the maximum retracted position. Therefore, a gap does not occur between the plunger drive cam and the cam follower, making it possible to prevent collision noise and reduce wear.

Furthermore, although the plunger pump's plunger is returned to its full stroke, the effective pumping stroke of the plunger is after the inlet valve closes, so the fuel discharged to the fuel injector is metered by the metering device. The injection amount is equal to the amount that was pressurized into the plunger pump by the pressure pump, and the injection amount can be ensured with high accuracy. In addition, in the lift-down stroke of the plunger drive cam, the accumulated pressure of the fuel pressure accumulator is used as a means to push back the plunger to prevent a gap from forming between this cam and the cam follower, so the powerful large size There is no need for a plunger push-back spring or a device for attaching this spring, and the structure of the plunger push-back means can be downsized.
Can be simplified.

Furthermore, since the fuel pressure accumulation chamber is formed using the pressure regulating spring chamber of the fuel injector, the pressure accumulation tank can be omitted, and the structure of the fuel injection device can be further downsized and simplified, and manufacturing costs can also be reduced. can.

[Brief explanation of drawings]

Figure 1 is a partially cutaway cross-sectional view of the pressure accumulator unit injector, Figure 2 is a longitudinal sectional view of the main parts of the diesel engine, Figure 3 is an enlarged view of the main parts of Figure 1, and Figure 4 is It is a schematic system diagram showing a fuel supply system. 11...Fuel injector, 15...Plunger pump,
16...Plunger pressurizing chamber, 31...15 inlet valve,
35... Inlet valve opening means, 36... Check valve, 38... Fuel pressure pump, 40, Pressure accumulator, 41... Metering device.

Claims (1)

[Claims] 1. The fuel injector 11 and the plunger pump 15 are integrated, and the fuel metered by the fuel metering device 41 is supplied from the pressure pump 38 to the plunger pressurizing chamber 16 of the plunger pump 15. In the fuel injection system for a diesel engine, from the pressure pump 38 to the plunger pressurizing chamber 16.
A check valve 36 is interposed between the fuel injector 11 and the fuel injector 11 on the downstream side of the check valve 36.
The pressure regulating spring chamber 24 is configured to have an airtight structure, and the pressure regulating spring chamber 24 is communicated with the plunger pressurizing chamber 16 via the inlet valve 31, thereby forming a fuel pressure accumulation chamber 40 in the pressure regulating spring chamber 24. , A fluid pressure command type inlet valve opening means 35 is attached to the inlet valve 31 disposed between the pressure regulating spring chamber 24 and the plunger pressurizing chamber 16. The inlet valve 31 is maintained in an open state while the internal pressure is lower than a predetermined pressure, and when the internal pressure of the pressure regulating spring chamber 24 reaches the predetermined pressure, the opening maintaining operation of the inlet valve 31 is canceled and the inlet valve 31 is closed. A fuel injection device for a fuel injection engine, characterized in that: