JPH10184484A - Fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce impulsive sound emitted out of a pump housing by installing a barrier pear the outlet of a cutoff port of a plunger in a distributor type fuel injection pump, and receiving a jet stream of high pressure fuel with this barrier. SOLUTION: With the rotation and reciprocating motion of a plunger 9, an inlet port 7 is interconnected to an inlet passage 6, forming a supply passage ranging from a pump case 21 to a high pressure chamber 22. Likewise, a distributing hole 10 is interconnected to a distributive passage 12, forming a discharge passage ranging from the high pressure chamber 22 to a delivery valve 11. In succession, a part of the rear end of a plunger barrel 8 is extendedly installed at the side of a cutoff port 14, surrounding the periphery of an outlet of this port 14 and thereby forming a barrier 18 receiving the fuel jetted out of the cutoff port 14. In this case the fuel is returned to the pump case 21 after receiving the high pressure fuel injection at the completion of fuel discharge with this barrier 18. Thus, the discharged fuel is prevented from directory colliding with a pump hosing 20, so that impulicive sound emitting from the pump housing is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-noise type fuel injection pump mainly used for an engine for a vehicle or the like, in which an impact sound is prevented.

[0002]

2. Description of the Related Art In a diesel engine such as an automobile, in order to reduce the size and weight, a single plunger repeatedly reciprocates by the number of cylinders during one rotation to distribute the injected fuel to each cylinder. Lightweight distributed fuel injection pumps are used. As shown in FIGS. 3 and 4, the distribution type fuel injection pump has a pump housing 20.
The pump chamber 21 and the supply pump 17 are disposed inside the fuel cell, and the fuel from the fuel tank 30 is fed into the pump chamber 21 via the fuel filter 31 by the supply pump 17 driven by the drive shaft 1 linked to the engine. The fuel is filled, the pressure is increased by a plunger pump including a plunger barrel 8 and a plunger 9 provided in the pump chamber 21, and the fuel is injected into each combustion chamber via the delivery valve 11 and the fuel injection nozzle 32. It is configured as follows.

Further, the face cam 3 of the cam disk 15 provided at the rear end of the plunger 9 is pressed against the cam roller 16 interlocking with the advancing device 35 on the pump housing 20 side, so that the plunger 9 reciprocates simultaneously with rotation. By moving, the suction hole 7, the distribution hole 10, and the cut-off port (spill port) 14 are communicated with the suction passage 6, the distribution passage 12, and the pump chamber 21 on the plunger barrel 8 side, respectively, in a timely manner. Pressurization, discharge to each delivery valve 11, and discharge stop are performed.

[0004] Then, the discharge is stopped by the plunger 9.
In the forward pressurization process, the cutoff port 14 which is the outlet of the return fuel is opened to the pump chamber 21, the pressure applied to the high pressure chamber 22 and to the delivery valve 11 is reduced, and the delivery valve 11 is closed. Done. And the adjustment of the fuel discharge amount
Through the governor mechanism, the control sleeve 4 fitted to the outer periphery of the plunger 9 is slid in the axial direction by the movement of the accelerator lever or the engine rotation speed to change the opening position of the cut-off port 14 and discharge the fuel. This is performed by changing the pressure feeding stroke from the start until the cutoff port 14 is opened.

[0005]

However, in the structure of the prior art fuel injection pump, since the cutoff port 14 faces directly into the pump chamber 21, the cutoff port 14 is controlled at the end of the fuel discharge. When released from the sleeve 4, the fuel in the high-pressure chamber 22, which is in a high-pressure state, is ejected directly into the pump chamber 21 to control the fuel injection amount.

Therefore, when the high-pressure jet collides with the inner wall of the pump housing, there is a problem that the inner wall of the pump housing vibrates to generate an impact sound and generate noise. In order to solve this problem, Japanese Utility Model Laid-Open Publication No.
According to the publication, an inclined guide portion is formed in a portion of the control sleeve facing the cutoff port to diffuse the injected fuel, or the fuel passage of the cutoff port in the plunger is formed to be inclined. A fuel injection pump has been proposed which prevents the jet flow of the jet fuel from directly hitting the inner wall of the pump housing by causing the flow to collide with the rear end of the plunger barrel, thereby suppressing the generation of noise.

However, the fuel to be jetted is, for example, 8
At a high pressure of 0 MPa, a very intense jet flow is generated. Therefore, it is not enough to simply diffuse or change the jet direction by expanding the discharge range of the jet fuel, and the diffuse flow and the reflected flow collide with the inner wall of the pump housing. Cannot be prevented, and vibration and noise cannot be sufficiently prevented. In addition, since the pump chamber is full of fuel, when high-pressure fuel is injected into the pump chamber, an impulsive pressure change occurs in the fuel in the pump chamber, which is transmitted to the inner wall of the pump housing by pressure propagation. Due to vibration, the fuel injection pump having the structure disclosed in the above publication cannot reduce the impact pressure caused by the pressure propagation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has as its object to provide a barrier around an outlet of a cut-off port of a plunger of a distribution type fuel injection pump to provide a fuel. An object of the present invention is to provide a low-noise fuel injection pump that receives a jet flow of high-pressure fuel at the end of discharge by this barrier, thereby alleviating the impact on the inner wall of the pump housing and reducing the impact noise generated from the pump housing. .

[0009] Further, in the buffer chamber partly including the barrier,
Surrounding the periphery of the cut-off port outlet, high-pressure fuel is received in the buffer chamber, the pressure is reduced by the orifice effect of the gap as the outlet of the buffer chamber, and the fuel is returned to the pump chamber. An object of the present invention is to provide a low-noise fuel injection pump that further reduces impact.

[0010]

According to a first aspect of the present invention, there is provided a fuel injection pump having a suction hole, a distribution hole, a suction passage, and a distribution passage. A plunger having a cut-off port and a center hole is fitted therein, and further, a control sleeve for changing an opening position of the cut-off port is provided. The plunger is rotated by a drive shaft and reciprocated in an axial direction by a cam. Further, in the distribution type fuel injection pump for sucking, increasing the pressure, and discharging the fuel, a barrier surrounding the outlet of the cut-off port and receiving the fuel injected from the cut-off port is provided.

With this barrier, it is possible to prevent the inner wall of the pump housing forming the pump chamber from directly receiving high-pressure jet fuel. And the barrier is formed by extending the rear end of the plunger barrel, and the buffer, the rear end of the plunger barrel and the front end of the control sleeve form a buffer chamber, or The barrier is formed by extending the front end of the control sleeve, and the buffer, the front end of the control sleeve, and the rear end of the plunger barrel form a buffer chamber.

With this buffer chamber, once the high-pressure jet fuel is received, the fuel flow can be reduced by reducing the flow of the fuel in the gap connecting the buffer chamber and the pump chamber, and then returned to the pump chamber.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. At the rear end side of a pump housing 20 forming a pump chamber 21, a drive shaft 1 interlocked with an engine via a drive gear 3 is provided.
The supply pump 17 is provided. The supply pump 17 is, for example, a vane type, and is driven by the rotation of the drive shaft 1.
The fuel is filled into the pump chamber 21 from the fuel tank 30.

A plunger 9 is inserted into a plunger barrel 8 provided in the pump chamber 21 to form a high-pressure chamber 22. The plunger barrel 8 has pump chambers 21 corresponding to the number of fuel injection nozzles for supplying fuel.
And a distribution passage 12 communicating with each delivery valve 11.

The plunger 9 has a center passage 23 which opens to the high-pressure chamber 22 on the front end side and extends to the rear end side, communicates with the center passage 23, and has an outer periphery of the plunger 9. , A suction hole 7, a distribution hole 10, and a cutoff port (plunger spill port) 14 are sequentially provided from the front end side. Further, at the rear end of the plunger 9, there is provided a cam disk 15 in which face cams 3 of the same number as the number of cylinders are formed at equal intervals, and when the cam disk 15 rotates, the cam face 3 is moved by the advancing device 35. The plunger 9 comes into contact with the cam roller 16 interlocked with FIG. 3 and reciprocates in the axial direction BB ′ in the plunger barrel 8 against the urging force of the plunger spring 13.

By the rotation and reciprocating motion of the plunger 9, the suction hole 7 communicates with the suction passage 6 to form a supply passage from the pump chamber 21 to the high-pressure chamber 22, and the distribution hole 10 is distributed. The discharge passage from the high-pressure chamber 22 to the discharge valve 11 is formed in communication with the passage 12. Also, the center hole
A control sleeve 4 is provided around the outer periphery of the plunger 9 where the cut-off port 14 provided at the rear end of the plunger 23 is open.
The fuel injection amount is controlled by moving the control sleeve 4 in the axial direction by operating a control lever to change the opening position of the cutoff port 14.

As shown in FIG. 1, a part of the rear end of the plunger barrel 8 extends toward the cut-off port 14 and is formed, for example, in a cylindrical shape to surround the outlet of the cut-off port 14. In addition, a barrier 18 for receiving fuel ejected from the cutoff port 14 is formed. Further, as shown in FIG. 2, the barrier 18 may be provided so as to extend a part of the front end of the control sleeve 4 and form, for example, a cylindrical shape to surround the opening of the cutoff port 14.

The barrier 18 has a cylindrical shape surrounding the opening of the cut-off port 14 in the circumferential direction, effectively receives the jet flow, and combines the jet reflected by the barrier 18 with the original jet. It is preferable to use a structure in which the jet flow is reduced by colliding or colliding with the plunger 9. Furthermore, any structure that does not completely surround the entire periphery of the outlet can be used as long as the jet flow from the cutoff port 14 can be blocked and the impact pressure can be reduced at this position.

In the distribution type fuel injection pump configured as described above, the plunger 9 is driven to rotate by the drive shaft 1, and reciprocates in the axial direction by the face cam 3 of the cam disk 15 and the cam roller 16. At each timing, the fuel is sucked by connecting the suction hole 7 and the suction passage 6 to each other. After compression, the fuel is discharged to each delivery valve 11 by connecting the distribution hole 10 and the distribution passage 12 to each other.

At the end of the discharge stroke, the cut-off port 14 is disengaged from the control sleeve 4 and opened, and when high-pressure fuel is ejected toward the barrier 18 via the center hole 23 and the cut-off port 14, Since the pressure of the fuel in the chamber 22 and the distribution passage decreases, the pressure for pressing the delivery valve 11 decreases and closes to stop the fuel supply to the fuel injection nozzle 32.

Further, the control of the control sleeve 4 fitted on the outer periphery of the plunger 9 in the axial direction by the movement of the accelerator lever and the engine rotation speed via the governor mechanism is performed to adjust the fuel discharge amount. Change the opening position of port 14 and cut off port 14 from the start of fuel discharge.
This is performed by changing the pressure feeding stroke until the opening is made. As described above, the barrier 18 is provided in a portion facing the outlet of the cutoff port 14, and the high pressure fuel jet at the end of the fuel discharge is once received by the barrier 18 surrounding the outlet, and then the fuel is pumped. The pump housing
The jet fuel can be prevented from directly colliding with the jet 20. Also, by forming the barrier 18 into a cylindrical shape, the reflected flow from the barrier 18 can collide with the jet flow, or the plunger 9 can be interposed between the plunger 9 and the barrier 18. Since the reflection can be repeated, the jet flow can be prevented from colliding with the pump housing 20 and the momentum of the jet flow can be reduced.

Next, in order to further reduce the impact of the high-pressure fuel ejected from the cut-off port 14, as a more preferable structure, as shown in FIG. 1 or FIG. At the front end of the control sleeve 4, a buffer chamber 19 surrounding the outlet of the cut-off port 14 is provided.
At this time, a gap having a size that preferably has an orifice effect between the barrier 18 and the control sleeve 4 or the plunger barrel 8 and that can reduce the pressure of the fuel in the buffer chamber 19 and return the fuel to the pump chamber 21 is provided. The fuel in the buffer chamber 19 is formed so as to flow out to the pump chamber 21 through the gap.

Since the control sleeve 4 moves, the tip of the control sleeve 4 in FIG. 1 and the tip of the plunger barrel 8 in FIG. It is formed so that it can penetrate. According to this structure, the shock pressure generated by the pressure propagation when the high-pressure fuel is injected into the pump chamber 21 is once received by the buffer chamber 19, which is the first decompression chamber, and the shock pressure fluctuation is alleviated. Since an orifice effect is generated in the gap between the buffer chamber 19 and the outlet, and a decompression effect can be obtained,
The fuel can be returned to the pump chamber 21 after the ejected fuel has a relatively low pressure.

Therefore, the impact of the fuel injection pump on the pump housing 20 can be reduced, so that the vibration and noise of the engine caused by the vibration of the pump housing 20 can be reduced, and the durability of the fuel injection pump can be reduced. Can be improved. Also, if the barrier 18 is provided with a circumferential wall by extending the plunger barrel 8 and the control sleeve 4, the barrier 18 can be formed by concentric processing using a lathe or the like, so that the processing becomes easy and the optimum for the orifice effect is obtained. A small gap amount can be easily formed with high accuracy.

[0025]

As described above, in the present invention, a barrier is provided around the outlet of the cut-off port of the plunger of the distribution type fuel injection pump, and high-pressure fuel at the end of fuel discharge is received by the barrier surrounding the outlet. The structure reduces the impact force of the jet flow and returns it to the pump chamber, so that the jet flow directly hits the inner wall of the pump housing and the secondary jet reflected by the barrier or plunger barrel collides. As a result, the impact noise generated from the pump housing can be reduced.

Further, the barrier is formed by extending a plunger barrel or a control sleeve, and the buffer, the plunger barrel and the control sleeve form a buffer chamber surrounding the cut-off port outlet.
The orifice effect of the gap between the buffer chamber and the outlet makes it possible to return the jet fuel to the pump chamber after the pressure of the ejected fuel is reduced to a relatively low pressure. Therefore, the impact on the inner wall of the pump housing can be remarkably reduced.

Therefore, the vibration and noise of the engine caused by the vibration of the pump housing can be reduced, and the durability of the fuel injection pump can be improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a part of a fuel injection pump according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a part of a fuel injection pump according to another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a configuration of a fuel injection pump and its surroundings.

FIG. 4 is a side sectional view of a portion of a prior art fuel injection pump.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drive shaft 2 ... Drive gear 3 ... Face cam 4 ... Control sleeve 5 ... Magnet valve 6 ... Suction passage 7 ... Suction hole 8 ... Plunger barrel 9 ... Plunger 10 ... Distribution hole 11 ... Delivery valve 12 ... Distribution passage 13… Plunger spring 14… Cut-off port 15… Cam disk 16… Cam roller 17… Supply pump 18… Barrier 19… Buffer chamber 20… Pump housing 21… Pump chamber 22… High pressure chamber 23… Center hole 30… Fuel tank 31… Fuel filter 32… Fuel injection nozzle 33… Control lever 34… Stop lever 35… Advance angle device 36… Cam rolling

Claims (3)

[Claims] 1. A plunger having a suction hole, a distribution hole, a cut-off port, and a center hole is inserted into a plunger barrel opened in a pump chamber and having a suction passage and a distribution passage. A dispensing type fuel injection pump that has a control sleeve that changes the opening position of the plunger, the plunger is rotated by a drive shaft, and reciprocates in the axial direction by a cam to perform suction, pressure increase, and discharge of fuel. A fuel injection pump provided with a barrier surrounding the outlet of the cut-off port and receiving the fuel injected from the cut-off port. 2. The method according to claim 1, wherein the barrier is formed by extending a rear end of the plunger barrel, and a buffer chamber is formed by the barrier, a rear end of the plunger barrel, and a front end of the control sleeve. Item 2. The fuel injection pump according to Item 1. 3. The barrier according to claim 1, wherein the barrier is formed by extending a front end of the control sleeve, and the barrier, a front end of the control sleeve, and a rear end of the plunger barrel form a buffer chamber. 2. The fuel injection pump according to claim 1.