JP2002147310A - Accumulator type fuel injector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injector 1 structured at a low cost. SOLUTION: A spring seat 21a is formed on one axial end face of an annular member 21 having an annular shape, and the other axial end face of the annular member 21 is so structured as to abut on a shaft end on the opposite side to the nozzle hole of a needle 20c, that is a shaft end face 12j of a large-diameter part 12h. Both the needle 20c and a control piston 20a are brought in contact with each other through an annular inside diameter part 21b of the annular member 21 without interlaying the annular member 21. Specifically, this injector is so structured that a small-diameter part 12i of the needle 20c is freely fitted to the annular inside diameter part 21b, thereby the control piston 20a always abuts on the needle 20c, and only the control of the respective axial sizes of both the needle 20c and the control piston 20a, that is to say, the machining accuracy such as the parallelism and the flatness/roughness of the surfaces abutting on each other of the needle 20c and the control piston 20a should be controlled, so that the low-cost injector 1 can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure accumulating fuel injection device for an internal combustion engine for injecting fuel directly into a cylinder (hereinafter, "internal combustion engine" is referred to as an engine).

[0002]

2. Description of the Related Art Conventionally, a pressure-accumulation type fuel injection device has been known in which high-pressure fuel is supplied from a fuel supply pump and the fuel is directly injected into an engine cylinder as disclosed in Japanese Patent Application Laid-Open No. 8-296521. ing. This accumulator type fuel injection device can freely lift the needle by controlling the energization of the control valve provided in the accumulator type fuel injection device with the aim of reducing harmful substances emitted in exhaust gas and improving fuel efficiency. Is controlled.

[0003] As shown in FIG. 3, this accumulator type fuel injection device is provided slidably in the axial direction within a nozzle body 101 and has a needle 103 for opening and closing an injection hole 102. In the nozzle body 101, there is provided a fuel reservoir 105 for receiving high-pressure fuel from a fuel supply pump (not shown) via a high-pressure fuel passage 104. The shaft end of the needle 103 on the side opposite to the injection hole is in contact with the pressure pin 106. This pressure pin 106
Is a spring 1 for urging the needle 103 in the valve closing direction.
And a spring seat 106a for receiving a biasing force of 07. Further, the shaft end of the pressure pin 106 on the side opposite to the needle is in contact with one end of the control piston 108. At the other end of the control piston 108, there is disposed a pressure chamber (not shown) for controlling the force in the valve closing direction of the control piston 108 by supplying fuel and the force in the valve opening direction of the control piston 108 by discharging fuel. ing. The pressure chamber is provided with a control valve (not shown) for switching between supply and discharge of high-pressure fuel from a fuel supply pump.

[0004] The accumulator type fuel injection device 100 having the above-described configuration.
Is a force that presses the injection hole in the opening direction by the fuel pressure introduced into the fuel reservoir chamber 105 against the needle 103, a force that the pressure pin 106 receiving the urging force of the spring 107 pushes the injection hole in the injection hole closing direction, and The fuel pressure acts on the control piston 108 to control the injection based on the magnitude relationship between the three forces and the force pushing in the nozzle hole closing direction.

[0005]

However, in the conventional pressure-accumulating fuel injection device 100, the needle 103, the pressure pin 106, and the control piston 108 are arranged in series in the axial direction. , And during the valve closing process, the three axial end faces come into contact with each other. In the pressure-accumulation type fuel injection device having such a configuration, if the lengths in the entire axial direction in a state where the three members are in contact with each other vary, the following problem occurs. Here, a case where the total axial length is shorter than, for example, a specified length will be described.

First, at the maximum lift position by opening the valve, the axial length of the pressure chamber located at the other end of the control piston 108 is determined because the total axial length of the three members is shorter than the specified length. Is shorter than the length specified by the three parties. This has the consequence of increasing the volume of the pressure chamber. Thus, when the volume of the pressure chamber increases,
In the stroke from the maximum lift position by opening the valve to the valve closing position, extra time is required to supply fuel to the pressure chamber. That is, it affects the injection characteristics of the injection from the injection hole. Specifically, the change in the injection rate in the latter half of the injection becomes slower, and the injection amount tends to increase.

Further, in the stroke from the valve closing position to the maximum lift position by opening the valve, it takes time to discharge extra fuel by an amount corresponding to the increase in the volume of the pressure chamber. That is, it affects the injection characteristics of the injection from the injection hole. Specifically, there is a tendency that the change in the injection rate in the first half of the injection is slowed down and the injection amount is reduced. Thus, the needle 103, the pressure pin 106, the control piston 10
If the lengths of the three members 8 in the axial direction vary when they come into contact with each other, the injection rate is changed and the injection amount is affected, so that the harmful substances discharged in the exhaust gas are reduced. As a result, the fuel efficiency improving effect is impaired.

In order to improve the accuracy of the three dimensions of the needle 103, the pressure pin 106, and the control piston 108 in the axial direction, the processing accuracy of the three abutting surfaces, such as parallelism and flatness, is adjusted. Although it is necessary to improve it, this increases the processing cost and is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pressure accumulating fuel injection device having a low cost configuration in view of the above points.

[0010]

According to a first aspect of the present invention, there is provided a pressure-accumulation type fuel injection device, comprising: a nozzle having an injection hole for injecting fuel and a fuel reservoir for receiving high-pressure fuel. A body, a needle slidably provided in the nozzle body in the axial direction for opening and closing the injection hole, a pressure chamber in which the inside is switched between high pressure and low pressure, a control valve for switching the pressure of the pressure chamber, and a pressure chamber. A control piston capable of receiving pressure and liftable in cooperation with the needle, an abutting portion that abuts on the shaft end on the side opposite to the injection hole of the needle, and receives a biasing force of a spring that biases the needle in the valve closing direction. A spring receiving portion, and an annular member having an annular inner diameter portion that penetrates in the axial direction and that can always contact the shaft end on the side opposite to the injection hole of the needle and the control piston. is there.

According to this, both the needle and the control piston are always in contact with the shaft end of the needle through the annular inner diameter portion of the annular member without through the annular member, and cooperate with each other. In other words, the configuration is such that both the needle and the control piston (two members) are in contact with each other and are arranged in series in the axial direction.

In the structure between the needle and the control piston, a mechanism for setting the lift of the needle is not provided around the needle, and the structure around the needle and the control piston is always brought into contact with each other, thereby simplifying the structure around the needle. In addition, as described above, the following effects are exhibited by combining the abutment structure of both the needle and the control piston (two members) without interposing the annular member.

This effect can be achieved only by controlling the axial dimensions of both the needle and the control piston, that is, by controlling the processing accuracy such as the parallelism and flatness of the surfaces of the needle and the control piston that come into contact with each other. It is possible to provide a pressure accumulating fuel injection device having a low cost configuration.

According to a second aspect of the present invention, in the pressure accumulating fuel injection device according to the first aspect, the needle and the control piston are brought into contact with each other within the annular inner diameter portion. It is assumed that.

According to this, the shaft diameters of the needle and the control piston are disposed at positions within the annular inner diameter, and the shaft diameters of the needle and the control piston are guided to the inner wall of the annular inner diameter. This makes it possible to easily obtain a configuration in which the contact between both the needle and the control piston is stabilized.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an injector 1 as an accumulator type fuel injection device according to an embodiment of the present invention will be described in detail with reference to the drawings. 1 and 2 show a configuration of an injector 1 according to an embodiment of the present invention. FIG.
FIG. 1 is an overall sectional view showing an injector 1 of the present invention. FIG.
FIG. 2 is a partial sectional view showing a part of the injector 1 shown in FIG.

The injector 1 is mounted on an engine head of an engine (not shown), and is configured to directly inject fuel into each cylinder of the engine. Fuel supply pump 2
The high pressure fuel discharged from the pressure accumulator is accumulated at a predetermined pressure in the accumulator of the accumulator 3 and supplied to the fuel inlet 60 of the injector 1. The fuel supply pump 2 adjusts the fuel discharge pressure in accordance with the engine speed, load, or intake fuel pressure, intake air amount, and coolant temperature.

The main body of the injector 1 is formed by fastening the nozzle body 12 and the holder body 11 with a retaining nut 14 and fastening the holder body 11 and the control valve 30 with a retaining nut 52.

The nozzle body 12 has a needle accommodation hole 12
e is formed, and the needle 20c is inserted into the needle storage hole 12e.
It is supported reciprocally inside. In addition, nozzle body 1
2, a fuel passage 12d, a fuel reservoir 12c, and an injection hole 12b are formed, and communicate with the needle storage hole 12e in the fuel reservoir 12c. Needle storage hole 12e
Communicates with a not-shown cylinder space of the engine through the injection hole 12b.

The needle 20c has a seat portion 12a, a small diameter portion 12f, a tapered portion 12g, and a large diameter portion 12a from the side of the injection hole 12b.
h, constituted by a small diameter portion 12i. Large diameter part 12h
Is supported on the inner wall of the needle accommodating hole 12e in a reciprocating manner and in a substantially liquid-tight manner. The tapered portion 12g is formed so as to receive upward pressure in FIG. 2 from the fuel in the fuel storage chamber 12c. Outer wall of small diameter portion 12f and needle storage hole 1
A circumferential gap is formed between the inner wall 2e and the inner wall 2e. The seat portion 12a has a shape capable of sitting on the valve seat 12a and closing the injection hole 12b.

A piston housing hole 11 is provided in the holder body 11.
d is formed, and the control piston 20a is
It is reciprocally movable and substantially liquid-tightly supported on the inner wall 1d. When the needle 20c is closed, the shaft end surface of the control piston 20a is configured to abut the shaft end surface of the small-diameter portion 12i on the side opposite to the injection hole of the needle 20c. Further, the piston housing hole 1 is provided in the holder body 11.
A leak passage 11c communicating with 1d is formed.

Nozzle body 12 of piston receiving hole 11d
On the side, a storage hole 11 having a larger diameter than the piston storage hole 11d.
e is formed, and the annular member 21 is disposed on the inner wall of the storage hole 11e so as to be reciprocally movable. A stepped portion 11f is formed at the boundary between the piston storage hole 11d and the storage hole 11e having different inner diameters.

The annular member 21 has an annular shape, and a spring seat 21a as a spring receiving portion is formed on one end surface of the annular member 21 in the axial direction. Further, the other end surface of the annular member 21 in the axial direction is a shaft end of the needle 20c on the side opposite to the injection hole,
That is, it is configured to contact the shaft end surface 12j of the large diameter portion 12h, and constitutes the contact portion according to claim 1.

The needle 20c and the control piston 20
Both a are configured to always contact the shaft end of the needle 20c through the annular inner diameter portion 21b of the annular member 21 without the intervention of the annular member 21, and to cooperate with each other. Specifically, the small diameter portion 12i of the needle 20c is loosely fitted to the annular inner diameter portion 21b, and the control piston 20a and the needle 20c are arranged in series in the axial direction as described above,
Always in contact. In the present embodiment, the abutment surfaces of the two are located at the annular inner diameter portion 21b, and the control piston 20a is formed so as to be loosely fitted to the annular inner diameter portion 21b.

Thus, the shaft diameter portions of the needle 20c and the control piston 20a are disposed at positions inside the annular inner diameter portion 21b, and the shaft diameter portions of the needle 20c and the control piston 20a are connected to the inner wall of the annular inner diameter portion 21b. And the contact between the needle 20c and the control piston 20a is stabilized.

However, the control piston 20a and the needle 2
The position at which the control piston 20a contacts the needle 20c can be in contact with the control piston 20a even at a position above the annular member 21 in FIG.

The inner diameter of the storage hole 11e and the control piston 20a
A coil-shaped spring 15 is provided in a space sandwiched by the outer diameters of the coils. One end of the spring 15 in the axial direction contacts the spring seat 21a, and the other end of the spring 15 in the axial direction is a spacer 15a for adjusting the set load of the spring.
Is in contact with the stepped portion 11f. Then, the urging force of the spring 15 is applied to the needle 2 via the annular member 21.
0c.

The pressure chamber 16c has an outer wall at the end of the control piston 20a, an inner wall surface of the piston housing hole 11d,
1 (see FIG. 1). By supplying the fuel to the pressure chamber 16c, the force of the control piston 20a in the valve closing direction (downward in FIG. 1), and by discharging the fuel, the force of the control piston 20a in the valve opening direction (upward in FIG. 1). Control.

The holder body 11 has a fuel inlet 6
A fuel passage 11b communicating with the nozzle body 12 is formed, and communicates with a fuel passage 12d formed in the nozzle body 12.
Further, the fuel passage 11b communicates with a pressure chamber 16c via a throttle 16b formed in the plate 16.

The control valve 30 is configured to switch between supply and discharge of high-pressure fuel from the fuel supply pump 2 to the pressure chamber 16c. Specifically, an EC (not shown)
U, a terminal 38 to which a drive current is supplied, an exciting coil 32 electrically connected to the terminal 38, and a stator 3 which is excited by the exciting coil 32 to generate an exciting force.
1. Armature 41 attracted by exciting force from stator 31, valve member 40 connected to armature 41
b, and a valve hole 18a or the like in which fuel in the pressure chamber 16c is sealed or opened by the valve member 40b. Note that a valve member 40b is provided above the control valve 30 with a valve hole 18a.
Is opened, the fuel discharge passage 3 for discharging the fuel in the pressure chamber 16c to the outside of the injector 1 through the valve hole 18a.
9 are formed. The fuel discharge passage 39 is connected to a fuel tank (not shown).

Next, the fuel injection operation of the injector 1 will be described.

The fuel is discharged from the fuel injection pump 2 and sent to the accumulator 3. The high-pressure fuel accumulated at a predetermined constant pressure in the accumulator of the accumulator 3 is supplied to the fuel inlet 60.
In addition, a drive current according to the operating condition of the engine is generated by an ECU (not shown) and supplied to the exciting coil 32. When a drive current flows through the exciting coil 32, the stator 31
A suction force is generated. Armature 4
1 and the valve member 40b connected to the armature 41 move upward in FIG. With this movement, the valve hole 18a is opened, and the fuel in the pressure chamber 16c is guided and discharged to the fuel discharge passage 39 on the low pressure side, and returns to the fuel tank (not shown).

When fuel is discharged from the pressure chamber 16c through the valve hole 18a, the fuel pressure in the pressure chamber 16c starts to decrease because the amount of fuel flowing out of the valve hole 18a is larger than that of fuel flowing in from the throttle 16b. The fuel pressure in the pressure chamber 16c decreases, and the force in the injection hole closing direction, which is the combined force of the urging force of the spring 15 and the force received from the fuel pressure in the pressure chamber 16c, is applied in the opening direction of the injection hole 12b received from the fuel pressure in the fuel reservoir 12c. When the force becomes smaller than the force, the needle 20c starts moving in the opening direction of the injection hole 12b, that is, upward in FIG. When the needle 20c separates from the valve seat, the injection hole 1
2b is opened and fuel is injected from the injection hole 12b.

When the supply of the drive current to the exciting coil 32 is cut off, the attraction force of the stator 31 disappears, and the valve member 40b connected to the armature 41 moves in the closing direction of the injection hole 12b. Even after the valve hole 18a is closed, the pressure chamber 1
Since fuel continues to flow from the throttle 16b into 6c, the fuel pressure in the pressure chamber 16c starts to rise. The fuel pressure in the pressure chamber 16c increases, and the urging force of the spring 15 and the pressure chamber 1
The injection hole 12b, which is a combined force of the force received from the fuel pressure of the fuel reservoir 6c and the force in the closing direction, is received from the fuel pressure of the fuel reservoir 12c
When the force becomes larger than the force in the opening direction 2b, the needle 20c starts to move in the closing direction of the injection hole 12b, that is, downward in FIG. When the needle 20c is seated on the valve seat 12a, the injection hole 12
b is closed and the fuel injection ends.

Here, in the injector 1 of the present invention, both the needle 20c and the control piston 20a always contact the shaft end of the needle 20c through the annular inner diameter portion 21b of the annular member 21 without passing through the annular member 21. With
It is a configuration that cooperates with each other. In other words, the configuration is such that both the needle 20c and the control piston 20a (two members) abut on each other and are arranged in series in the axial direction.

The control piston 2 is moved from the needle 20c to the control piston 2.
0a, the mechanism for setting the lift of the needle 20c is not provided around the needle 20c.
c, the control piston 20a is always in contact with the control piston 20a, so that the surroundings of the needle 20c are simplified, and the needle 20c does not pass through the annular member 21 as described above.
The following effects are exhibited by combining the two (two) contact configurations of the control piston 20a and the control piston 20a.

This effect is achieved only by controlling the axial dimensions of both the needle 20c and the control piston 20a, that is, by controlling the processing accuracy such as the parallelism and flatness of the surfaces of the needle 20c and the control piston 20a that abut each other. As a result, the injector 1 having a low-cost configuration can be provided.

In addition to the above-described arrangement of the spring 15 for bringing both the needle 20c and the control piston 20a into contact with each other and applying a biasing force to the needle 20c in the valve closing direction, for example, a spring seat is provided on the control piston. Although a method of forming a stepped portion is conceivable, machining a control piston having a stepped portion increases machining cost for the following reasons.

That is, the control piston is located in the piston storage hole 1
High machining accuracy such as cylindricity, coaxiality, and shaft diameter of the shaft surface is required over the entire shaft portion in contact with 1d. If a stepped portion having a different shaft diameter is formed in the middle of the shaft portion, the process, processing time, and the like required for processing the shaft portion in contact with the piston housing hole 11d are increased, and the processing cost is increased. On the other hand, the annular member 21 used for disposing the spring for applying the biasing force of the present invention is separated from the control piston 20a, so that the control piston 20a can be easily processed and the annular member 21 Since the processing is easy, the injector 1 that can reduce the processing cost can be provided.

[Brief description of the drawings]

FIG. 1 is an overall sectional view showing an injector of the present invention.

FIG. 2 is a partial sectional view showing a part of the injector shown in FIG.

FIG. 3 is a cross-sectional view showing a conventional pressure accumulating fuel injection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injector (accumulation type fuel injection device) 2 Fuel supply pump 12 Nozzle body 12b Injection hole 12c Fuel reservoir 12j Shaft end face (contact part) 15 Spring 16c Pressure chamber 20a Control piston 20c Needle 21 Ring member 21a Spring seat (spring seat) Part) 21b annular inner diameter part 30 control valve

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G066 AB02 AC09 AD12 BA54 BA61 CC06T CC08T CC14 CC26 CC51 CC61 CC67 CC68U CE13 CE22 DC00 DC01 DC09 DC14 DC18

Claims (2)

[Claims] 1. A nozzle body having an injection hole for injecting fuel and having a fuel reservoir for receiving high-pressure fuel, and an injection hole provided slidably in an axial direction in the nozzle body. A pressure chamber that switches between high pressure and low pressure, a control valve that switches the pressure of the pressure chamber, and a control piston that receives the pressure of the pressure chamber and lifts in cooperation with the needle. A contact portion that contacts the shaft end of the needle on the side opposite to the injection hole, a spring receiving portion that receives the urging force of a spring that urges the needle in the valve closing direction, penetrates in the axial direction, and the shaft end portion; An accumulator-type fuel injection device, comprising: an annular member having an annular inner diameter portion capable of constantly contacting the control piston. 2. The control piston according to claim 1, wherein the needle and the control piston are in contact with each other within the annular inner diameter portion.
3. An accumulator type fuel injection device according to claim 1.