JP2002188540A - Distribution type fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distribution type fuel injection pump which can reduce coupling noises while reducing an injection amount difference between each cylinder by reducing a fuel leak amount from a pressure chamber at force feed time. SOLUTION: This distribution type fuel injection pump suited for a diesel engine is formed with an equalizing leak circuit 4e passing from an equalizing port 4b formed in the periphery of a plunger 4 through its inside to lead to a communication opening 4d opened to a pump chamber, in the plunger, and the distribution type fuel injection pump is characterized by providing this communication opening in a side of a face cam 3 from an overlapped part of the plunger and a cylinder 13. This communication opening is preferably opened to almost the center of a surface of the face cam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution type fuel injection pump used for a diesel engine or the like in which a single plunger reciprocates while rotating and distributes and feeds fuel to each cylinder of the engine.

[0002]

2. Description of the Related Art With the development of diesel engines in passenger cars and commercial vehicles, distribution type fuel injection pumps have been developed as pumps which can be reduced in size, weight and speed. This eliminates the need for plungers for the number of cylinders as in the case of the row fuel injection, so that the size and weight can be reduced. The distribution type fuel injection pump is classified into a face cam type, an outer cam type, and an inner cam type depending on the cam type. The face cam type distribution pump is the most widely used at present.

FIG. 3 shows a pressure equalizing leak circuit at the time of pressure feeding of a conventional face cam type distribution type fuel injection pump. In this conventional face cam type distribution type fuel injection pump, the pressure equalizing port 4b of the plunger 4 is larger than the distribution port 4a in order to connect the pressure equalizing port 4b and the annular groove 4f which is a pressure equalizing leak circuit. Because it is necessary to make the shape, the injection pressure is reduced due to the fuel leak from the pressurized chamber at the time of fuel pumping, or the injection amount varies between the cylinders, thereby reducing the engine output,
Various problems such as an increase in engine vibration and a decrease in exhaust gas performance have occurred.

In the face cam type distribution type fuel injection pump, a drive shaft (drive shaft), a pump distribution member (face cam) which rotates together with the drive shaft and reciprocates in the axial direction, and a drive A cross-shaped coupling that couples the shaft to the pump distributing member, and a pair of claws facing each other are formed on the output side of the drive shaft and the input side of the pump distributing member. A coupling is provided between the claws. That is, the cross piece of the coupling for transmitting the driving torque from the pawl of the drive shaft to the pump distributing member is disposed between the pawl of the drive shaft and the pawl of the pump distributing member so as to be axially movable. Therefore, at the time of pumping the fuel by the pump distributing member, the cross piece of the coupling is entrained by the claw of the pump distributing member, and at the end of the pumping, it moves extra with respect to the claw of the pump distributing member due to its inertia, and The output side end face may repeatedly collide. For this reason, a coupling noise (Russell noise) that can be heard in the high rotation range of the pump may occur.

Conventionally, as a countermeasure against the abnormal noise of the coupling, Japanese Patent Publication No. 6-1065 and Japanese Unexamined Patent Publication No.
A method according to JP-A-22578 is known. That is,
The former method is provided with a compression coil spring to alleviate the impact at the time of the collision of the coupling on the drive shaft, the latter method, a sound reduction member that regulates the movement of the coupling to the drive shaft side, And a cushioning member for reducing transmission of the seating noise of the coupling to the drive shaft, which is disposed in a notch formed in the axial direction on the output side end face of the drive shaft. As described above, the conventional countermeasures against the abnormal noise of the coupling require an extra member for reducing noise, and the structure thereof is complicated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to reduce the amount of fuel leakage from a pressurizing chamber during pressure feeding and reduce the difference in injection amount between cylinders. Another object of the present invention is to provide a distribution type fuel injection pump in which an equalizing pressure leak circuit is formed by an inexpensive method. It is a further object of the present invention to provide a distribution type fuel injection pump having a simple structure and reduced coupling noise without requiring an extra member for reducing coupling noise.

[0007]

According to the present invention, as a means for solving the above-mentioned problems, there is provided a distribution type fuel injection pump according to each of the claims. The distribution type fuel injection pump according to claim 1, wherein the communication opening of the pressure equalizing leak circuit communicating from the pressure equalizing port to the pump chamber through the inside of the plunger is closer to the face cam than the overlapping portion of the plunger and the cylinder. This eliminates the need for the equalizing port of the plunger to have a larger shape than the distribution port in order to connect the equalizing port and the annular groove that is the equalizing leak circuit, as in the related art. The sliding area between the plunger and the cylinder can be increased, and the sealing performance can be improved. Therefore, it is possible to reduce the amount of fuel leak from the high-pressure chamber during pressure feeding.

According to a second aspect of the invention, there is provided a distribution type fuel injection pump in which a communication opening from a pressure equalizing port of a pressure equalizing leak circuit is provided substantially at the center of a face cam surface. As in the case of the fuel injection pump, the pressure equalizing port does not need to have a large shape, the sliding area between the plunger and the cylinder can be increased, the sealing performance can be improved, and the amount of fuel leakage can be reduced. Furthermore, in the configuration of the second aspect, since the pressure equalizing leak circuit extends to the face cam, a force acts on the high pressure fuel to push the coupling toward the drive shaft via the pressure equalizing leak circuit. This prevents the coupling from being pulled toward the face cam when the face cam is lifted, thereby eliminating noise (abnormal noise) when the coupling is seated.

A distribution type fuel injection pump according to an embodiment of the present invention will be described below with reference to the drawings. FIG.
1 shows an outline of an overall configuration of a distribution type fuel injection pump system. When the face cam 3 in contact with the roller 2 rotates, the distribution type fuel injection pump 1 reciprocates the plunger 4 by the waveform of the end cam 3 a on the surface thereof, and distributes the fuel to the injection nozzle 5. It is in the form of supply.

As shown in FIG. 2, in the distribution type fuel injection pump 1, fuel pumped up from a fuel tank 7 by a feed pump 6 through a filter 8 to a pump low pressure side passage is passed through a pump high pressure side passage into a pump housing 9 ( The high-pressure fuel whose injection timing and injection amount have been adjusted is pumped from the delivery valve 10 to the injection nozzle 5 of the diesel engine. A drive chamber 11 as a drive shaft is rotatably supported in a pump chamber inside the pump housing 9 of the fuel injection pump 1, and the drive shaft 11 is connected via a coupling 12 to a pump distribution member. It is connected to a disk-shaped face cam 3.

The face cam 3 is coupled to a plunger 4 slidably guided inside a cylindrical cylinder 13 built in the pump housing 9 and moves together with the plunger 4. Therefore, the face cam 3 and the plunger 4
Means that they rotate together and reciprocate. The face cam 3 has a number of end cams 3 a corresponding to the number of cylinders of the engine, and is in contact with the rollers 2 held inside a roller ring 15 fixed to the pump housing 9. The face cam 3 is urged by a plunger spring 17 via a yoke 16 and is pressed against the roller 2.

The coupling 12 is connected to the drive shaft 1.
1 is used for transmitting a rotational driving force from the first cam 1 to the face cam 3 and the plunger 4. The cross-shaped coupling 12 disposed between the drive shaft 11 and the face cam 3 is provided with four grooves of a predetermined width uniformly distributed on its peripheral surface. A claw 11b protruding in the axial direction from the flange 11a of the shaft 11 and a claw 3b protruding in the axial direction from the face cam 3 are engaged. Therefore, the coupling 12 connects the drive shaft 11 and the face cam 3 so as to be integrally rotatable around the axis.

Next, the fuel distribution structure of the plunger 4 of the distribution type fuel injection pump 1 which is a feature of the present invention will be described. The plunger 4 has a distribution port 4 a and a pressure equalizing port 4.
b, and a communication passage 4c that communicates the distribution port 4a with the pressurizing chamber 18 formed by the plunger 4 and the cylinder 13. Further, inside the plunger 4, a pressure equalizing leak circuit 4e is formed, and a communication opening 4d for communicating the pressure equalizing port 4b to a pump chamber in the pump housing 9 is provided at an overlapping portion (plunger) between the plunger 4 and the cylinder 13. (Where the cylinder and the cylinder 13 come into contact with each other). In FIG. 1, the communication opening 4 d opens substantially at the center of the face cam 3.

Therefore, when the solenoid valve (not shown) is opened and the plunger 4 is lowered (moves rightward in FIG. 1),
The pump chamber (in the pump housing 9) and the pressurizing chamber 18 communicate with each other to form a fuel suction passage 13a, and the fuel is sucked into the plunger 4 and the cylinder 13. This is the fuel intake stroke. In the fuel pumping process, the solenoid valve is closed, the plunger 4 is rotated, and the distribution port 4a of the plunger 4 is connected to the four distribution passages 13 in the cylinder 13.
Matches one place of b. The number of the distribution passages 13b is equal to the number of cylinders of the engine. When the plunger 4 further rotates, the end cam 3a of the face cam 3 rides on the roller 2, the plunger 4 enters a rising (moving leftward in FIG. 1) stroke, and the pressure in the pressurizing chamber 18 increases. The high-pressure fuel is pressure-fed from the distribution passage 13b to the delivery valve 10 and the nozzle 5, and is injected into the fuel chamber.

FIG. 1 shows an equalizing leak circuit 4e of the plunger 4 during the equalizing stroke. In the pressure equalizing process, the distribution passage 13b communicates with the inside of the pump housing 9 (pump chamber) to equalize the pressures of the four distribution passages 13b before pumping the fuel at a high pressure. This is provided to reduce the variation in the injection amount. In this equalizing stroke, the equalizing port 4b of the plunger 4 is
Communicates with the distribution passage 13b and the inside of the pump housing 9 through the communication opening 4d. Distribution passage 1
The fuel in 3b returns into the pump housing 9, and the inside of the distribution passage 13b is made equal to the pressure in the pump housing 9.

As described above, in the distribution type fuel injection pump according to the present invention, the plunger 4 is replaced with the annular groove 4f forming the equalizing pressure leak circuit in the conventional injection pump.
The pressure equalizing leak circuit 4e is provided in the inside, so that it is not necessary to form the pressure equalizing port 4b large in order to connect the pressure equalizing port 4b and the annular groove 4f as in the prior art. 4b can be made as small as the distribution port 4a. For this reason, the plunger 4 and the cylinder 13
Can be increased, and the sealing performance of the fuel is improved.

Further, since the pressure equalizing leak circuit 4e extends to the surface of the face cam 3, a force for pressing the coupling 12 toward the drive shaft 11 via the pressure equalizing leak circuit 4e is exerted. Become. As a result, when the face cam 3 moves up (moves leftward in FIG. 1), the coupling 12 is not pulled toward the face cam 3 side, and noise (unusual noise) when the coupling is seated does not occur.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a pressure equalizing leak circuit of a distribution type fuel injection pump according to an embodiment of the present invention.

FIG. 2 is a schematic overall configuration diagram of a distribution type fuel injection pump system.

FIG. 3 is a diagram illustrating a pressure equalizing leak circuit of a conventional distribution type fuel injection pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Distribution type fuel injection pump 3 ... Face cam 4 ... Plunger 4a ... Distribution port 4b ... Equalizing port 4c ... Communication path 4d ... Communication opening 4e ... Equalizing leak circuit 4f ... Annular groove 11 ... Drive shaft (drive shaft) 12 ... Coupling 13 ... Cylinder 13b ... Distribution passage 18 ... Pressure chamber

Claims (2)

[Claims] 1. A distribution type fuel injection pump in which one plunger reciprocates while rotating to distribute and pressure-feed fuel to each cylinder of an engine, wherein the plunger is connected to a pressure equalizing port formed around the plunger. A pressure equalizing leak circuit reaching the communication opening opened to the pump chamber through the inside of the plunger, and the communication opening is provided on the face cam side of the overlapping portion of the plunger and the cylinder. A distribution type fuel injection pump characterized in that: 2. The distribution type fuel injection pump according to claim 1, wherein the communication opening is provided substantially at the center of the face cam surface.