JP2002310030A - Fuel injector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injector having a structure for reducing the winding number of coils, and reducing an outer diameter of the coils while allowing operation under a high fuel pressure. SOLUTION: A movable body 23 is mechanically connected to a nozzle needle 13 capable of abutting to a valve seat 16 of a valve body 12, and is a cylindrical shape, and has a large diameter sliding part 24 having an outer wall guided to an inner wall of a guide hole 28 of a pipe 22, and a small diameter cylindrical part 25 formed on the nozzle needle side of this large diameter sliding part 24. There is a through-hole 27 as a restricting part formed in the small diameter cylindrical part 25 to generate pressure larger in inlet side pressure of the movable body 23 than outlet side pressure in the fuel flowing direction at valve opening operation time. Thus, a preset load of a compression coil spring 33 can be reduced while maintaining fuel maximum pressure in a large value. Minimum movable voltage applied to a coil 34 can be reduced while maintaining the fuel maximum pressure large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, it has been required to increase the pressure of fuel in a fuel injection device for an internal combustion engine. In a conventional fuel injection device, a nozzle needle is accommodated in a valve body so as to be reciprocally movable, and is closed when the nozzle needle is seated on a valve seat. The nozzle needle is urged in the closing direction by a coil spring, and the nozzle needle is opened by moving away from the valve seat by energizing the electromagnetic coil in a direction against the coil spring. In the fuel injection device provided with such an electromagnetic valve, the magnetic attraction force is increased by increasing the number of turns of the coil, thereby enabling operation at a high fuel pressure.

[0003]

In such a conventional fuel injection device, when the outer diameter of the valve body is increased, the weight of the nozzle needle is increased, and the amount of electricity supplied to the coil is increased. Further, in order to ensure the valve-closing responsiveness of the nozzle needle, it is essential to increase the coil spring force. As the number of turns of the coil increases, the outer diameter of the wound coil increases.

An object of the present invention is to provide a fuel injection device having a structure capable of reducing the number of turns of a coil and reducing the outer diameter of the coil while enabling operation under a high fuel pressure. With the goal. Another object of the present invention is to provide a fuel injection device having a structure capable of achieving both reduction in the size of the device main body and operation under high fuel pressure.

[0005]

According to the fuel injection device of the first aspect, the movable body mechanically connected to the nozzle needle that can be brought into contact with the valve seat of the valve body has a cylindrical shape and has an outer wall. Has a large-diameter sliding portion guided by the inner wall of the guide hole of the valve body, and a small-diameter cylindrical portion formed on the nozzle needle side of the large-diameter sliding portion. In addition, due to the throttle portion formed in the movable body, the structure has a structure in which the pressure on the inlet side of the movable body generates a pressure greater than the pressure on the outlet side during the valve opening operation in the fuel flow direction. Therefore, the set load of the urging means can be reduced while maintaining the fuel maximum pressure at a large value. Further, it is possible to reduce the minimum movable voltage applied to the coil while maintaining the maximum pressure of the fuel large.

[0006] During the valve opening operation, the voltage applied to the coil can be reduced. When the voltage applied to the coil at the time of the valve opening operation is made constant, the maximum operating fuel pressure by the constant voltage can be increased. During the valve closing operation, the assist force in the valve closing direction can be increased. Therefore, assuming that the maximum fuel pressure is constant, the fuel injection device of the present invention can reduce the set load of the urging means.

According to the second aspect of the present invention, since the throttle portion is a through-hole communicating the fuel passage inside the small-diameter cylindrical portion with the outer wall of the small-diameter cylindrical portion, the narrow portion is provided in the small-diameter cylindrical portion of the movable body in the radial direction. By forming the through holes, it is possible to make a structure that can reduce the size of the apparatus main body and operate under high fuel pressure. According to the fuel injection device of the third aspect, since the throttle portion is formed of a groove extending in the axial direction of the movable body, by forming a groove parallel to the axial direction of the movable body, the physical size of the device main body can be reduced and high pressure can be reduced. It is possible to make a structure compatible with operation under fuel pressure.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a fuel injection device according to a first embodiment of the present invention. The fuel injection device 1 includes a valve unit and an electromagnetic drive unit. The valve portion includes a valve body 12 fixed in a holder 14, a nozzle needle 13, and a movable body 23. The electromagnetic drive unit includes a coil 34, a compression coil spring 33 as biasing means, and an adjustment pipe 32.

With respect to the valve portion, a nozzle needle 13 can contact or separate from a valve seat 16 of a valve body 12 fixed to a holder 14. The nozzle needle 13 is
It is movable in the axial direction with respect to the valve body 12. The valve body 12 has an injection hole 15 and communicates the inside and the outside of the valve body 12.

As for the electromagnetic drive unit, a cylindrical pipe 2
2, a connector 31 is fixed by press-fitting. On the nozzle needle 13 side of the connector 31, a large-diameter sliding portion 24 of a movable body 23 is accommodated inside a pipe 22 so as to be able to reciprocate in the axial direction. The movable body 23 includes a cylindrical large-diameter sliding portion 24 and a small-diameter cylindrical portion 25. The large-diameter sliding portion 24 is slidable in the axial direction on the inner wall forming the guide hole 28 of the pipe 22. The small-diameter cylindrical portion 25 is mechanically connected to the end 131 of the nozzle needle 13 opposite to the injection hole. The small-diameter cylindrical portion 25 is formed with a through-hole 27 as a throttle portion communicating in the radial direction. Through hole 2 as this throttle
7 is a fuel passage 2 formed in the direction of the central axis of the movable body 23.
It communicates with 6. The connector 31 has a fuel passage 70 formed in the axial direction. An adjust pipe 32 is fixed to an inner wall of the connector 31.

Compression coil spring 3 as urging means
3 has one end in contact with the large-diameter sliding portion 24 of the movable body 23 and the other end in contact with the adjustment pipe 32. This allows
The movable body 23 is urged so as to contact the valve body 12 in the direction of the valve seat 16. The compression coil spring 33 is set to a predetermined load. This set load becomes a load at the time of the valve opening operation of the movable body 23, and limits the operation of the high fuel pressure. A connector 41 is fixed to the pipe 22 on the side opposite to the injection hole. The connector 41 has a fuel passage 70 that communicates with the inside in the axial direction, and a filter 42 is attached to an inner wall forming the fuel passage 70. A coil 34 is arranged around the pipe 22 inside the valve housing 21. The coil 34 is excited by a current supplied through a terminal 35.

The magnetic circuit of the electromagnetic drive section includes a movable body 23, a connector 31, a pipe 22, a valve housing 21, and a holder 14. Part of the pipe 22 covered by the coil 34 is made non-magnetic. When a current is supplied from a drive circuit (not shown) to the coil 34 through the terminal 35, the movable body 23 is attracted to the connector 31 by the magnetic attraction force against the compression coil spring 33. Thereby, the nozzle needle 13 is separated from the valve seat 16. When the current supplied to the coil 34 is cut off,
The magnetic attraction decreases, and the movable body 23 moves downward in FIG. 1 away from the connector 31, whereby the nozzle needle 13 comes into contact with the valve seat 16. Thereby, the valve is closed.

Hereinafter, the function of the first embodiment will be described in detail. (1) When the coil 34 is not energized, the movable body 23 is urged in the valve closing direction by the urging force of the compression coil spring 33,
Thereby, the nozzle needle 13 is connected to the valve seat 1 of the valve body 12.
6 abuts. This state is the valve closed state. (2) When the coil 34 is energized from this closed state, the movable body 23 moves upward in FIG.
At this time, the pressure on the fuel passage 26 side of the throttle portion 27 becomes relatively large, and the pressure on the nozzle needle side becomes relatively small. Therefore, the assisting force of the nozzle needle 13 acting in the valve closing direction increases. The presence of the throttle portion 27 can reduce the set load of the compression coil spring 33 of the fuel injection device.

(3) No fuel flow occurs in the throttle section 27 until immediately before the valve is moved from the closed state to the valve opening operation.
No differential pressure is generated between the movable body 23 and the inlet and outlet sides of the movable body 23, and the set load of the compression coil spring 33 can be relatively reduced. For this reason, the valve opening response is improved,
This has the effect of expanding the dynamic range. When the set load of the compression coil spring 33 is reduced, the responsiveness during the valve opening operation can be improved. Further, the valve opening / closing operation can be performed at a high fuel pressure.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
Shown in The second embodiment is an example in which the throttle portions 51 and 52 communicating with the axial direction are formed in the tubular thick portion of the cylindrical connector 31. An adjusting member 53 is fixed to the hollow portion of the connector 31 by press-fitting. Adjusting member 53
Is for adjusting the set force of the compression coil spring 33. The urging force of the compression coil spring 33 is determined according to the position of the adjusting member 53 in the axial direction with respect to the connector 31. Restrictor 5 communicating in the axial direction of connector 31
Reference numerals 1 and 52 denote linear throttle passages that communicate the space on the inlet side and the space on the outlet side of the connector 31.

As shown in FIG. 3, grooves 56, 57, 58, 5
9 are formed. In the second embodiment, the first
Compared to the embodiment, in addition to the above-described effects (1) and (2), the grooves 56, 57, 58, and 59 as the throttle portion are provided until immediately before the valve closing state is shifted to the valve opening operation. Since no fuel flow occurs in the compression coil spring 3, no differential pressure is generated between the movable body 23 and the movable body 23 at the inlet side and the outlet side.
The set load of No. 3 can also be made relatively low. Therefore, there is an effect that the valve opening response is improved and the dynamic range is expanded. When the set load of the compression coil spring 33 is reduced, the responsiveness during the valve opening operation can be improved. Further, the valve opening / closing operation can be performed at a high fuel pressure. In the second embodiment, the throttle section is provided on the outer periphery of the movable body. However, in the present invention, the throttle section may be provided inside the movable body.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view taken along line III-III of a movable body according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 fuel injection device 12 valve body 13 nozzle needle 14 holder 15 injection hole 16 valve seat 21 valve housing (valve body) 22 pipe (valve body) 23 movable body 24 large-diameter sliding portion 25 small-diameter cylindrical portion 26 fuel passage 27 throttle portion DESCRIPTION OF SYMBOLS 31 Connector 32 Adjust pipe 33 Compression coil spring (biasing means) 34 Coil 51 Throttle section 52 Throttle section 56, 57, 58, 59 Groove (throttle section)

Claims (3)

[Claims] A valve body having an injection hole, a guide hole, and a valve seat; a nozzle needle for switching to a valve closed state or a valve open state by contacting or separating from the valve seat; A movable body connected to the seat side and slidable in the axial direction on the inner wall of the guide hole; a biasing means for biasing the movable body in a valve closing direction; and when energized, excited to generate an electromagnetic attraction force A movable member having a cylindrical shape, an outer wall of which is guided by an inner wall of the guide hole; A fuel injection device comprising: a small-diameter cylindrical portion formed on a nozzle needle side; and a throttle portion communicating between an inlet side and an outlet side of fuel. 2. The fuel injection device according to claim 1, wherein the throttle portion is a through hole that communicates a fuel passage inside the small-diameter cylindrical portion with an outer wall of the small-diameter cylindrical portion. 3. The fuel injection device according to claim 1, wherein the throttle portion comprises a groove extending in the axial direction of the movable body.