JPH09236063A - Fuel injection control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control valve by which fuel oil is prevented from being penetrated into a pump chamber when a valve is opened, by certain ly closing the ejection opening of a distance piece by the upper end formed in a curved surface of a nozzle needle when an ejection opening is opened. SOLUTION: When an electrostrictive actuator 2 is shrunk when fuel injection is started, a pump chamber 28 is enlarged so as to generate negative pressure. Hereupon, a nozzle needle 3 is lifted so that fuel is ejected from a jet opening 26. While the ejection opening is closed, the upper end spherical surface 33 of the nozzle needle 3 is automatically aligned toward the ejection opening 27 of a distance piece 1, and tightly stuck to the ejection opening 27 so as to close the ejection opening 27. Therefore, the ejection opening 27 is easily sealed so that fuel oil is certainly prevented from being penetrated into the pump chamber 28 while the jet opening 26 is opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a fuel injection control valve of a type in which an electrostrictive actuator opens and closes the fuel injection control valve via hydraulic pressure.

[0002]

2. Description of the Related Art As an electrostrictive operation type fuel injection valve for controlling a back pressure chamber via hydraulic pressure, an injection valve disclosed in Japanese Patent Publication No. 54065/1994 is known (see FIG. 9). In FIG. 9, the injection valve is a nozzle body 10 having an injection port 101.
2, a nozzle needle 103 housed in the nozzle body 102, an electrostrictive actuator 105, an end surface of the electrostrictive actuator 105, and the nozzle needle 1.
And a pump chamber 106 facing the end surface of the nozzle chamber 03, and the electrostrictive effect causes the electrostrictive actuator 105 to expand and contract to change the pressure in the pump chamber 106 to reciprocate the nozzle needle 103 in the axial direction. When the valve is closed, the oil pressure of the fuel is applied to the end surface of the nozzle needle 103 via the throttle passage 107 to maintain the valve closed and the pump chamber 106. The distance piece 108 is provided between the end surface of the nozzle needle 103 and the end surface of the nozzle needle 103 is brought into close contact with the distance piece 108 when the valve is opened, so that the opening of the nozzle needle 103 is maintained.

Next, the operation of the injection valve will be briefly described. First, the actuator 105 is contracted to reduce the pressure of the pump chamber 106 via the pump piston 110, and the nozzle needle 103 is moved to the nozzle needle 103.
The valve is lifted and opened by overcoming the acting force of the hydraulic pressure applied to.
During the injection period, the discharge hole 111 is closed by the upper end surface of the nozzle needle 103 and the pump chamber 106 is kept in a depressurized state, so that the nozzle needle 103 is held in a pulled-up state. Next, when the valve is closed, the actuator 105 is extended to increase the pressure in the pump chamber 106 via the pump piston 110, and a downward acting force is applied to the nozzle needle 103, and the nozzle needle 103 descends and sits down. To do. During the injection period, if the upper end surface of the nozzle needle 103 and the lower end surface of the distance piece 108 contact each other and the discharge hole 111 is not sealed, the pump chamber 1 is depressurized.
Through the clearance 107 between the large diameter portion 112 of the nozzle needle and the large diameter portion 113 of the nozzle body 102,
Upper end face of nozzle needle 103 and distance piece 1
Fuel oil enters through the discharge hole 111 from the gap between the lower end surface of 08. Therefore, the longer the injection period is, and the higher the temperature is when the viscosity of the fuel oil decreases with respect to the environment, the more the amount of infiltration of the fuel oil increases, and it becomes impossible to secure the decompression for raising and holding the nozzle needle 103. When used in such a situation, there is a problem that it is necessary to increase the decompression amount of the pump chamber in advance, and the driving energy must be increased in order to increase the expansion / contraction amount of the actuator 105.

However, the conventional fuel injection valve described in the above publication is characterized in that the end face of the nozzle needle 103 is brought into close contact with the distance piece 108 to maintain the valve opening of the nozzle needle 103, which is realized. Therefore, in the embodiment, the upper end surface of the nozzle needle 103 and the distance piece 108 are polished to form a smooth flat surface. However, in order to maintain this close contact state in a high temperature environment, considerable accuracy is required for the flatness of the upper end portion of the nozzle needle 103, the surface roughness, the perpendicularity of the needle shaft, and the like, which raises the problem of cost increase. is there.

The present invention has been made in view of the above problems of the present invention, and its purpose is to ensure that the discharge hole of the distance piece is reliably formed at the curved upper end surface of the nozzle needle during opening of the injection port. The purpose of the present invention is to provide a fuel injection control valve that can prevent fuel oil from entering the pump chamber during valve opening by closing the valve.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the means described in claim 1 can be adopted. According to this means, when the nozzle needle rises to open the nozzle,
A curved sealing surface formed on the upper end of the nozzle needle closes the discharge hole provided in the distance piece. At this time, since the upper end of the nozzle needle is curved, it is automatically aligned and closely adheres to the discharge hole, so that the discharge hole is easily sealed. Therefore, it is possible to reliably prevent the fuel oil from entering the pump chamber during the opening of the injection port.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a fuel injection control valve of the present invention will be described with reference to FIGS. In the figure, the casing 5 of the fuel injection valve 1 is composed of a nozzle holder 6 and a retaining nut 7. The nozzle holder 6 has a cylindrical space 8 formed therein. Also, a cylindrical space 9 having a large inner diameter is formed. The male screw 10 of the nozzle holder 6 and the female screw 11 of the retaining nut 7 are connected to each other to form a stepped cylindrical space inside. In this space, from the upper side of FIG. 1, the electrostrictive actuator 2, the pump piston 12,
Belleville spring 13, distance piece 14, nozzle body 4
Is stored.

The nozzle body 4 has a stepped cylindrical shape, and a thin cylindrical portion 15 thereof projects below a lower end portion of the retaining nut 7. The nozzle needle 3 is housed in a stepped cylindrical space inside the nozzle body 4. The nozzle needle 3 also has a stepped cylindrical shape, and the small diameter portion 16 is housed in the small diameter portion 17 of the nozzle body 4 and the large diameter portion 18 thereof is housed in the large diameter portion 19 of the nozzle body 4 and can slide in the axial direction. It is like this. The range of motion of the nozzle needle 3 is about 1
00 μm, and the lower end is limited by the valve seat 20 provided on the nozzle body 4.

The clearance 22 between the small-diameter portions 16 and 17 has a diameter of about 1 mm, and the clearance 21 between the large-diameter portions 18 and 19.
Is about 20 μm in diameter. The connecting portion between the large diameter portion 19 and the small diameter portion 17 of the stepped cylindrical space of the nozzle body 4 is an annularly expanded space and forms a fuel pool 23. The fuel pool 23 is a fuel passage 24 that connects the nozzle body 4, the distance piece 14, and the nozzle holder 6 to each other.
And the fuel passage 24 opens into the inlet port 25 at the upper end of the nozzle holder 6. The fuel in the fuel pool 23 should pass through the clearance 22 and be injected and supplied to the internal combustion engine from the injection port 26 provided at the lower end of the nozzle body 4, but when the nozzle needle 3 is located at the lowest end, The seat 20 is closed and the fuel does not reach the injection port 26.

As shown in an enlarged view in FIGS. 2 and 3, the upper end surface of the nozzle needle 3 has a circumferential seal surface formed in a curved surface, for example, a spherical surface portion 33, and the distance piece 14 has Is formed by chamfering a stepped cylindrical through hole that penetrates in the axial direction, that is, a discharge hole 27. The large diameter portion of the discharge hole 27 is a spherical portion 33 on the nozzle needle 3 side.
2 and face each other at a predetermined interval, as shown in FIG. 2, but during fuel injection, as shown in FIG. The spherical portion 33 of the nozzle needle 3 is brought into close contact with the large diameter portion of the nozzle 27 to close the discharge hole 27 and seal it.

The upper end surface of the distance piece 14 and the lower end surface of the pump piston 12 face each other with a gap, and the gap forms a pump chamber 28. The discharge hole 27 penetrating the distance piece 14 is electrically connected to the pump chamber 28. Further, inside the pump chamber 28, there is a disc spring 13 for urging the pump piston 12 upward. The pump piston 12 is driven by the expansion and contraction of the electrostrictive actuator 2 above the pump piston 12 to cause a pump action in the pump chamber 28, but an O-ring 29 is used for sealing. The electrostrictive actuator 2 has a cylindrical shape by stacking about 50 thin disk-shaped electrostrictive elements.

The electrostrictive element is a ceramic called PZT, which contains lead zirconate titanate as a main component and which extends 1 μm when a voltage of 500 V is applied in its thickness direction.
Fifty of these are laminated and 500 V is applied in the thickness direction of each element.
When applied, an overall elongation of 50 μm is obtained. If this voltage is released or a slight negative voltage is applied, 50μ
It contracts m and returns to its original length. Application and release of voltage is performed by an external controller via the lead wire 30.

A knock pin 31 is used to secure the fuel passage 24 by regulating the relative positions of the nozzle holder 6, the distance piece 14 and the nozzle body 4. or,
An accumulator 32 is used to supply fuel to the fuel injection valve 1. Fuel of 200 atm is accumulated in the accumulator 32 by a pump, a pressure setting valve, and the like, which are not shown, and continues to be maintained.

The operation of the first embodiment having the above configuration will be described. When a voltage of 500 V is applied to the electrostrictive actuator 2 at the time when the fuel injection should be stopped, the electrostrictive actuator 2 expands by about 50 μm and the pump piston 12
Since the fuel in the pump chamber 28 is compressed to a high pressure and acts on the upper end surface of the nozzle needle 3 through the discharge hole 27 to lower it, the lower end of the nozzle needle 3 is pressed against the valve seat 20. This is closed and the fuel supply to the injection port 26 is cut off. The high-pressure fuel that has acted on the upper end of the nozzle needle 3 leaks to the fuel pool 23 through the clearance 19, but naturally does not fall below the fuel pressure of the fuel pool 23, that is, the fuel pressure of the accumulator 32, and is at least 200 atm. Fuel pressure is nozzle needle 3
Continues to act on the entire top surface of. Although the fuel pressure of 200 atm of the fuel pool 23 acts upward on the area corresponding to the difference in cross-sectional area between the large diameter portion 18 and the small diameter portion 16 of the nozzle needle 3, the difference force is inferior to the downward force. The lower end of the nozzle needle 3 is continuously pressed against the valve seat 20. That is, the fuel injection valve 1 continues to be closed. At this time, as shown in FIG. 2, the discharge hole 27 of the distance piece 14 faces the spherical surface portion 33 of the nozzle needle 3 side with a predetermined space.

Next, a slight negative voltage is applied to the electrostrictive actuator 2 at the time when fuel injection should be started, and
When the voltage of 0V is released, the electrostrictive actuator 2
Contracts about 50 μm, and the pump piston 12 is a disc spring 13
The pump chamber 28 expands to generate a negative pressure, and the pressure acting on the upper end surface of the nozzle needle 3 via the discharge hole 27 is reduced. Therefore, the nozzle needle 3 is pushed up by the fuel pressure of the fuel pool 23 of 200 atm. At this time, as shown in FIG. 3, the upper end spherical surface portion 33 of the nozzle needle 3 has the discharge hole 27 of the distance piece 14.
The self-alignment is performed toward the discharge hole 27 and the discharge hole 27 is brought into close contact with the discharge hole 27 to close the discharge hole 27. In this state, there is no fuel leakage into the pump chamber 28, and the depressurized state of the pump chamber 28 is maintained, so that the nozzle needle 3 is connected to the fuel reservoir 23 and the pump chamber 2.
Due to the pressure difference of 8, the force continues to be upward and stays at the upper end position, and the injection port 26 conducts with the fuel pool 23 to continue fuel injection. That is, the fuel injection valve 1 is continuously opened.

Thereafter, the operation for stopping the fuel injection is as described above, and the fuel is injected only at an arbitrary time and for an arbitrary period according to the request of the internal combustion engine even in a high temperature environment where the viscosity of the fuel oil decreases. be able to.

The present invention is characterized in that the discharge hole 27 of the pump chamber 28 is closed by the upper end portion of the nozzle needle 3, and the configuration can be changed as follows.
FIG. 4 shows a second embodiment of the present invention. First
In the embodiment, the upper end portion of the nozzle needle 3 is a curved surface portion, but in the present embodiment, the upper end portion is a conical portion 35. Further, by attaching the same reference numerals to the structural parts common to the above-described first embodiment,
A duplicate description will be omitted. The same applies to other embodiments described below.

FIG. 5 shows a third embodiment of the present invention. In this embodiment, the upper end of the nozzle needle 3 is a truncated cone 36.

FIG. 6 shows a fourth embodiment of the present invention. In this embodiment, the upper end portion of the nozzle needle 3 is a spherical projection 37. In any of the above-described embodiments, the discharge hole 27 can be closed with a circumferential seal.

FIG. 7 shows a fifth embodiment of the present invention. In the previous embodiments, the discharge hole 27 of the distance piece 14 was a stepped cylindrical through hole, but in the present embodiment it is. The tapered through hole 38 is formed.

FIG. 8 shows a sixth embodiment of the present invention, in which a spring 40 acting downward with respect to the nozzle needle 3 is housed in the stepped portion of the discharge hole 27 of the distance piece 14. is there. The spring 40 is for urging the nozzle needle 3 downward to prevent gas intrusion from the inside of the engine cylinder when the fuel is filled and when the fuel runs out.
However, since the discharge hole 27 is closed by self-alignment, the spring 40 can be effectively operated without being affected by the centering of the spring 40.

[Brief description of drawings]

FIG. 1 is a sectional view taken along a central axis of a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the first embodiment of the present invention, showing a normal state.

FIG. 3 is an enlarged cross-sectional view of a main part of the first embodiment of the present invention, showing a state during fuel injection.

FIG. 4 is an enlarged cross-sectional view of a main part of a second embodiment of the present invention.

FIG. 5 is an enlarged sectional view of a main part of a third embodiment of the present invention.

FIG. 6 is an enlarged cross-sectional view of a main part of a fourth embodiment of the present invention.

FIG. 7 is an enlarged cross-sectional view of essential parts of a fifth embodiment of the present invention.

FIG. 8 is an enlarged sectional view of an essential part of a sixth embodiment of the present invention.

FIG. 9 is a sectional view taken along the central axis of a conventional fuel injection control valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve 2 ... Electrostrictive actuator 3 ... Nozzle needle 5 ... Casing 14 ... Distance piece 26 ... Injection port 27 ... Discharge hole 28 ... Pump chamber 33 ... Spherical part 35 ... Conical part 36 ... Frustum 37 ... Spherical projection Portion 38 ... Tapered through hole 40 ... Spring

Claims (4)

[Claims] 1. A fuel injection control valve that opens and closes an injection port by moving a nozzle needle in an axial direction by operating an electrostrictive actuator provided in a casing. The fuel injection control valve is formed at a lower end of the electrostrictive actuator. A distance piece having a discharge hole is provided between the pump chamber and the upper end of the nozzle needle, and when the nozzle of the nozzle is opened, a curved circumferential sealing surface formed on the upper end of the nozzle needle is used. A fuel injection control valve characterized by closing the discharge hole. 2. The shape of the upper end of the nozzle needle is
The fuel injection control valve according to claim 1, wherein the fuel injection control valve has one shape selected from a spherical shape, a conical shape, a truncated cone shape, and a spherical projection shape. 3. The fuel injection control valve according to claim 1, wherein the discharge hole is a stepped cylindrical through hole or a tapered through hole. 4. The fuel injection control valve according to claim 1, wherein a spring is provided inside the stepped portion of the discharge hole.