JPH10325374A - Fuel injection unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damage caused by the cavitation erosion of a spill deflector by providing the spill deflector opened/closed by a plunger and declining one passage hole made in the spill deflector such that it gives a rotational force to the spill deflector. SOLUTION: When a plunger 1 is lifted and its reed 1a opens an oil supply port 2a, the high pressure in a plunger space 21 is released to an oil supply system. The fuel jetted at high speeds collides with the inner peripheral surface of a spill deflector 3 to reduce velocity energy and then is discharged into an oil discharge passage 221. Since the fuel always flows between two passage holes 31, 32 of the spill deflector 3 and the passage holes 31, 32 are declined in the circumferential direction, a rotational force is produced on the spill deflector 3 and the positions where cavitation erosion is generated are uniformly distributed in the inner circumference, which prevents the generation of uneven erosion at a specified position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection pump for an internal combustion engine, and more particularly to a fuel injection pump provided with a spill deflector for preventing cavitation erosion of a pump body.

[0002]

2. Description of the Related Art In a diesel engine, in order to increase combustion efficiency and purify exhaust gas, it is essential to inject the fuel in a short injection period with a short injection period and a good injection cutoff in order to purify the exhaust gas. Unit injectors are widely used as fuel injectors that meet demands.

FIG. 7 shows one such unit injector.
An example is shown. In FIG. 7, 6 is a main body of the unit injector, 2 is a plunger barrel fixed to the main body, 1 is a plunger which is reciprocally slidably and fluid-tightly fitted in the plunger barrel 2 and has a lead 1a,
15 is a tappet and 14 is a plunger spring.

A fuel injection valve 30 has a nozzle 25 at its tip.
, A needle valve 24 fitted reciprocally slidably in a fluid-tight manner within the nozzle 10, a nozzle nut 11 for fastening the nozzle 10, a needle valve spring 7 for pressing the needle valve 24, and the needle valve It comprises a spring cage 5 for accommodating the spring 7, a spring receiver 8 for the needle valve spring 7, a spacer 9, and the like.

Reference numeral 4 denotes a retaining nut for fastening the fuel injection valve 30 and the plunger barrel 2 to the main body 6 to integrate them. Reference numeral 12 denotes a control rack for adjusting the fuel injection amount, and reference numeral 13 denotes a pinion that meshes with the rack 12.

Reference numeral 21 denotes a plunger chamber, which is formed in the plunger barrel 2 so as to face the top 1b of the plunger 1. Reference numeral 2a denotes an oil supply / discharge hole formed in the plunger barrel 2, which communicates the plunger chamber 21 with an oil supply / discharge passage 22 provided in the retaining nut 4. Reference numeral 27 denotes a fuel injection valve 30 from the plunger chamber 21.
This is a fuel passage connected to the fuel reservoir 26 of FIG. Reference numeral 16 denotes an O-ring for sealing.

Reference numeral 3 denotes a spill deflector, which is made of a special steel material having a hard and high toughness and is formed in an annular shape. The spill deflector 3 is disposed with its inner peripheral surface facing the oil supply / discharge hole 2a of the plunger barrel 2, and is inserted and fixed between the outer periphery of the tip of the plunger barrel 2 and the inner periphery of the retaining nut. Have been. A fuel passage 311 is formed between the inner peripheral surface of the spill deflector 3 and the outer peripheral surface of the plunger barrel 2 where the oil supply / discharge hole 2a is opened.

During operation of the diesel engine equipped with the unit injector, the tappet 15 is moved by the lift of the fuel cam (not shown) so that the plunger spring 1
4 is depressed against the elasticity of the plunger 1
When b closes the oil supply / drain hole 2a, the fuel in the plunger chamber 21 is at a high pressure (for example, a high pressure of about 1200 kgf / cm ² ).
Pressurized. The high-pressure fuel enters the fuel reservoir 26 through the fuel passage 27, pushes up the needle valve 24 against the elasticity of the needle valve spring 7 to open the valve, and is injected from the injection port 25 into a combustion chamber (not shown). .

When the plunger 1 is further lifted and its lead 1a opens the oil supply / drain hole 2a, the high pressure in the plunger chamber 21 (high pressure of about 1200 kgf / cm ² as described above)
Rapidly lowers pressure (for example, 4 kgf /
is open to the oil supply system of the cm order of ^2), the high pressure fuel in the plunger chamber 21 is ejected to the oil supply side through the supply and discharge oil hole 2a,
The fuel flows back to the oil supply / discharge passages 22 and 23 through the fuel passage 311. At this time, the fuel injected at a high speed from the oil supply / drain hole 2a collides with the inner peripheral surface of the spill deflector 3.
Cavitation occurs near the outlet of the oil supply / drain hole 2a due to such collision or separation of the fuel flow. The spill deflector 3 is provided to protect each part of the unit injector by such cavitation, and the spill deflector 3 protects other components from cavitation erosion by being exposed to this cavitation state. I have. Therefore, the spill deflector 3 is periodically replaced.

[0010]

In the unit injector shown in FIG. 7, the spill deflector 3 is a relatively thin annular body, and the outer periphery of the tip of the plunger barrel 2 and the inside of the retaining nut 4 are formed. It is fixed in a form inserted between the circumference. However, the high-pressure fuel ejected from the oil supply / discharge holes 2 a is supplied to the oil supply / discharge holes 2 of the spill deflector 3.
The collision intensively occurs in the vicinity of the surface facing a. For this reason,
In the spill deflector 3, in the vicinity of the portion facing the oil supply / drain hole 2a due to the above phenomenon,
The cavitation is discharged together with the fuel, and the cavitation is destroyed at the same place, and cavitation erosion is intensively generated at such a location. This shortens the life of the spill deflector, increases the frequency of replacement, and increases the maintenance cost of the unit injector.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel injection device that reduces damage due to cavitation erosion of a spill deflector for a fuel injection pump, extends its life, and reduces maintenance costs.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first means of the invention is to reciprocate a fuel introduced into a plunger chamber from a fuel supply passage into a plunger barrel. The fuel is pressurized by the movably fitted plunger and sent to the fuel injection valve. When the plunger opens the oil supply / discharge hole of the plunger barrel, the fuel in the plunger chamber flows to the oil supply side via the oil supply / discharge hole. In the fuel injection device configured as described above, an annular spill deflector is provided to face the oil supply / discharge hole, and the spill deflector is provided with a passage hole communicating the oil supply / discharge oil side and the oil supply side, At least one of the passage holes is formed as an inclined hole for applying a rotational force to the spill deflector.

According to the above means, when fuel is supplied from the refueling system to the plunger chamber, the fuel is supplied from the refueling system to the plunger chamber through the passage hole of the spill deflector, and part of the fuel is supplied to the plunger chamber. Refluxed to When the oil supply / discharge hole is opened after the fuel injection, the fuel passing through the oil supply / discharge hole collides with the spill deflector and is discharged to the oil supply system through the passage hole. Therefore, fuel always flows through the passage hole of the spill deflector, and since the passage hole is inclined in the circumferential direction, when the fuel passes through the passage hole, the fuel is rotated by the velocity energy of the fuel to the spill deflector. Force is generated.

Due to this rotational force, the spill deflector is constantly rotated on the outer periphery of the plunger barrel during the operation of the fuel injection device, so that the cavitation discharge and the cavitation erosion due to its destruction occur in the spill deflector. Disperse evenly around the circumference. As a result, the erosion concentrates on a specific portion such as the vicinity of the portion facing the oil supply / discharge hole, and the portion is prevented from being eroded unevenly.

A second means is that, in the above-mentioned fuel injection device, an annular spill deflector is provided opposite to the oil supply / drain hole, and the spill deflector is inclined in the axial direction on the inner periphery thereof, and is provided with a fuel spill deflector. This is to provide a groove through which the liquid can flow. According to the above means, at the time of refueling when fuel is supplied from the refueling system to the plunger chamber, the fuel is supplied from the refueling system to the plunger chamber through the inside groove of the inner periphery of the spill deflector, and part of the fuel is supplied to the refueling system. The fuel is recirculated, and at the time of oil discharge, the fuel that has passed through the oil supply / discharge hole passes through the above-mentioned groove and is discharged to the oil supply system.

When fuel flows through the inclined groove of the spill deflector, a rotational force is generated in the spill deflector by the flow velocity of the fuel. As a result, as in the case of the first means, the locations where cavitation erosion occurs in the spill deflector are uniformly dispersed in the circumferential direction, and do not concentrate at one location.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. 1 is a longitudinal sectional view of a diesel engine unit injector according to a first embodiment of the present invention, FIG. 2 is an enlarged longitudinal sectional view near a spill deflector mounting portion, and FIG. 3 is a sectional view taken along line AA of FIG. is there.

In FIGS. 1 to 3, reference numeral 6 denotes a main body of the unit injector, 2 denotes a plunger barrel fixed to the main body, and 1 denotes a reciprocally slidable and fluid-tight fit in the plunger barrel 2 and a lead 1a. Plunger with 15
Is a tappet and 14 is a plunger spring.

Numeral 30 denotes a fuel injection valve, which has a nozzle 25 at its tip.
, A needle valve 24 fitted reciprocally slidably in a fluid-tight manner within the nozzle 10, a nozzle nut 11 for fastening the nozzle 10, a needle valve spring 7 for pressing the needle valve 24, and the needle valve It comprises a spring cage 5 for accommodating the spring 7, a spring receiver 8 for the needle valve spring 7, a spacer 9, and the like.

Reference numeral 4 denotes a retaining nut for tightening and integrating the fuel injection valve 30 and the plunger barrel 2 with the main body 6. Reference numeral 12 denotes a control rack for adjusting the fuel injection amount, and reference numeral 13 denotes a pinion that meshes with the rack 12.

Reference numeral 21 denotes a plunger chamber, which is formed so as to face the top 1b of the plunger 1 in the plunger barrel 2. Reference numeral 2a denotes an oil supply / drainage hole formed in the plunger barrel 2, and an oil supply / drainage passage 2 provided at two locations in the axial direction of the plunger chamber 21 and the retaining nut 4.
21 and 222 are communicated via a spill deflector 3 described later. Reference numeral 27 denotes a fuel passage connected from the plunger chamber 21 to the fuel reservoir 26 of the fuel injection valve 30. Reference numeral 16 denotes an O-ring for sealing. The above configuration is shown in FIG.
Is similar to the conventional unit injector shown in FIG.

In the present invention, the spill deflector provided on the outer periphery of the plunger barrel so as to face the oil supply / discharge hole is improved. That is, in FIGS. 1 to 3, reference numeral 3 denotes a spill deflector, which is made of a hard steel having high toughness and formed in an annular shape. Same spill deflector 3
The inner peripheral surface of the plunger barrel 2 has an oil supply / drain hole 2a.
And is rotatably fitted in a circumferential direction between the outer periphery of the distal end of the plunger barrel 2 and the inner periphery of the retaining nut 4. And this spill deflector 3
In the axial direction, the movement is restricted by being fitted between the plunger barrel 2 and the retaining nut 4.

The spill deflector 3 is provided with fuel passage holes 31, 32 in two stages (two places) in the axial direction. As shown in FIGS. 1 and 2, the passage holes 31 and 32 are provided one by one in the axial direction with the oil supply / discharge hole 2 a of the plunger barrel 2 interposed therebetween. (In this embodiment, four). As shown in FIG. 3, among the passage holes 31 and 32, at least one passage hole 32 has all the holes (four in this example) in the circumferential direction, and the center 41 of the unit injector is located in the circumferential direction. It is formed so as to be inclined in the same direction by an angle θ with respect to the center line of the oil supply / discharge hole 2a passing therethrough. The other hole 31 is a radial hole directed toward the center 41 of the unit injector.

In this embodiment, only the upper passage hole 32 is inclined as shown in FIG. 3, but the lower passage hole 31 may be inclined in the opposite direction to the upper passage hole. Alternatively, only the lower side may be inclined. still,
In the spill deflector 3, the passage hole is formed in the upper side 3
If one of the lower side 31 and the lower side 31 is inclined and the other side is not inclined and is formed as a hole facing the center 41 of the unit injector, the spill deflector 3 can function without any trouble even if it is assembled upside down.

A fuel passage 29 is formed on the inner peripheral side of the spill deflector 3 between the upper passage hole 32 and the lower passage hole 31 by cutting the outer periphery of the plunger barrel 2. . Further, the retaining nut 4 is provided with oil supply / discharge oil passages 221 and 222 at the same axial position as the passage holes 32 and 31 of the spill deflector, so that fuel flows through the passage holes 32 and 31. Easy going.

When the plunger 1 opens the oil supply / drainage hole 2a during operation of the unit injector constructed as described above, fuel is spilled from the oil supply / drain passage 222 as shown in FIG. It enters one passage hole 31 of the deflector 3, passes through the fuel passage 29, and
a to the plunger chamber 21, and a part thereof is returned from the fuel passage 29 to the supply / discharge oil passage 221 through the other passage hole 32.

The tappet 15 is pushed down by the lift of the fuel cam (not shown) against the elasticity of the plunger spring 14, and the top 1 b of the plunger 11 is filled with the oil supply / drain hole 2.
When a is closed, the fuel in the plunger chamber 21 is pressurized to a high pressure (for example, a high pressure of about 1200 kgf / cm ² ).
The high-pressure fuel enters the fuel reservoir 26 through the fuel passage 27, pushes up the needle valve 24 against the elasticity of the needle valve spring 7 to open the valve, and is injected from the injection port 25 into a combustion chamber (not shown). .

When the plunger 1 is further lifted and its lead 1a opens the oil supply / drain hole 2a, the high pressure in the plunger chamber 21 (high pressure of about 1200 kgf / cm ² as described above)
Rapidly lowers pressure (for example, 4 kgf /
(about ² cm ² ), and the high-pressure fuel in the plunger chamber 21 is ejected to the oil supply / drain hole 2 a. The fuel ejected at high speed from the oil supply / drain hole 2a is supplied to the spill deflector 3
After the velocity energy is reduced by colliding with the inner peripheral surface of the fuel cell 29, the fuel gas is discharged to the oil supply / drain passage 221 through the fuel passage 29 and most of the passage holes 32.

Cavitation occurs near the outlet of the oil supply / discharge hole 2a due to the collision with the inner peripheral surface or the separation of the fuel flow.

During this operation, fuel always flows between the two-stage passage holes 31 and 32 of the spill deflector 3 as shown by arrows in FIG. Since the passage holes 31 are inclined at an angle θ in the circumferential direction as shown in FIG.
When the spill deflector 3 passes through the spill deflector 3, a rotational force is generated by the velocity energy of the fuel. By this rotational force, the spill deflector 3 is constantly rotated on the outer periphery of the plunger barrel 2. For this reason, as described above, the discharge of the cavitation generated in the vicinity of the outlet of the oil supply / discharge hole 2a and the occurrence of cavitation erosion due to its destruction are concentrated near the oil supply / discharge hole 2a by the rotation of the spill deflector 3. Without dispersing, it is uniformly distributed on the inner periphery of the spill deflector 3. As a result, the location where cavitation erosion occurs in the spill deflector 3 is concentrated at a specific location near the location facing the oil supply / drain hole 2a, and such location is not biasedly eroded.

FIGS. 4 to 6 show a unit injector according to a second embodiment of the present invention. 4 to 6
In the inner periphery of the spill deflector 3 rotatably fitted between the outer periphery of the plunger barrel 2 and the inner periphery of the retaining nut 4, a twist angle α is provided at equal intervals in the circumferential direction.
Thus, a spiral groove 33 is formed. 34 is groove 3
3 is a land portion. Other configurations are the same as those of the first embodiment, and the same members are denoted by the same reference numerals.

In the second embodiment, the fuel supplied from the oil supply / discharge passage 222 on one side enters the fuel passage 29 on the inner peripheral side of the spill deflector 3, and is formed in a spiral shape provided on the inner periphery of the spill deflector 3. The oil is returned to the oil supply / discharge passage 221 on the other side through the groove 33. Also, at the time of oil drainage in which the oil supply / drainage hole 2a is opened by the lead 1a of the plunger 1,
Fuel from the oil supply / discharge hole 2a is discharged to the oil supply / discharge passage 221 through the groove 34.

When the fuel passes along the spiral groove 33 on the inner periphery of the spill deflector 3 as described above, a rotational force is generated in the spill deflector 3 by the flow rate of the fuel, and the spill deflector 3 Reference numeral 3 is constantly rotated as in the first embodiment.

In this embodiment, since a rotational force is generated by the plurality of spiral grooves 34 as a whole, a rotational force larger than that in the first embodiment can be obtained by appropriately selecting the twist angle α.

[0035]

The present invention is configured as described above.
The spill deflector is provided with an inclined hole as in claim 1,
Alternatively, the spill deflector can be constantly rotated by providing the groove inclined in the axial direction. As a result, the locations where cavitation erosion occurs in the spill deflector do not concentrate on a specific portion near the portion facing the oil supply / drain hole, but are uniformly distributed in the circumferential direction of the spill deflector, and the unevenness at the specific portion is reduced. Erosion is prevented. Therefore, when the operating conditions of the fuel injection device are the same, the erosion speed of the spill deflector becomes slow, the life of the spill deflector is extended, the replacement interval of the spill deflector can be extended, and the maintenance cost is reduced. Is done.

When the replacement interval of the spill deflector is set to be the same, in the present invention, as described above, even if the cavitation erosion point increases due to a higher injection pressure release speed, Since the locations where cavitation erosion occurs are uniformly distributed and the erosion resistance is high, the release speed of the injection pressure can be increased, and the injection period can be shortened. Thereby, the combustion efficiency of the engine is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a diesel engine unit injector according to a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view of the vicinity of a spill deflector mounting portion in the first embodiment.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is an equivalent view of FIG. 1 showing a second embodiment of the present invention.

FIG. 5 is a plan view of a spill deflector according to the second embodiment.

FIG. 6 is a sectional view taken along line BB of FIG. 5;

FIG. 7 is an equivalent view of FIG. 1 showing a conventional unit injector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plunger 1a Lead 1b Top 2 Plunger barrel 2a Oil supply / drain hole 3 Spill deflector 4 Retaining nut 5 Spring cage 6 Main body 7 Needle valve spring 8 Spring receiver 10 Nozzle 12 Control rack 13 Pinion 14 Plunger spring 15 Tappet 21 Plunger chamber 24 needle Valve 25 Injection port 26 Fuel reservoir 27 Fuel passage 29 Fuel passage 30 Fuel injection valve 31 Passage hole 32 Passage hole 33 Groove 34 Land portion 221, 222 Supply / discharge oil passage

Claims (2)

[Claims] A plunger, which is reciprocally slidably fitted into a plunger barrel, pressurizes a fuel introduced into a plunger chamber from a fuel supply passage and sends the pressurized fuel to a fuel injection valve. A fuel injection device configured such that when the oil drain hole is opened, fuel in the plunger chamber flows to the fuel supply side through the oil drain hole,
An annular spill deflector is provided to face the oil supply / discharge hole, and a passage hole is provided in the spill deflector to connect the oil supply / drain hole side to the oil supply side, and at least one of the passage holes is provided with the spill deflector. A fuel injection device comprising a slanted hole that applies a rotational force to the fuel injection device. 2. The fuel introduced into a plunger chamber from a fuel supply passage is pressurized by a plunger fitted reciprocally slidably in a plunger barrel and sent to a fuel injection valve, and the plunger is supplied to the plunger barrel. A fuel injection device configured such that when the oil drain hole is opened, fuel in the plunger chamber flows to the fuel supply side through the oil drain hole,
A fuel is characterized in that an annular spill deflector is provided facing the oil supply / discharge hole, and the spill deflector is provided on its inner periphery with a groove which is inclined in the axial direction and through which fuel can flow. Injection device.