JP2002115617A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform precise control of an injection amount corresponding to a current-carrying pulse width by suppressing the vibration of a small- diameter piston member to suppress excess fuel injection due to a resuming valve opening for a control valve. SOLUTION: A displacement increasing chamber 3 filled with a working fluid is provided between a large-diameter piston 2 to be driven by a piezoactuator 1 and the small-diameter piston member 4 for driving a three-way valve 5. A ring member 8 is fitted into the displacement increasing chamber 3 so that one end face is opposed to the small-diameter piston member 4 to form a stopper part 81. Thus, the replacement of the small-diameter piston 4 to the displacement increasing chamber 3 is restricted for suppressing the vibration and a hole in the center of the ring member 8 is functioned as a damper 82 for assisting vibration damping.

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 In order to inject high-pressure fuel into a diesel engine or the like, a hydraulically driven fuel injection device using a piezo actuator or the like has been conventionally used. Such a fuel injection device generally includes a large-diameter piston member that is displaced in accordance with expansion and contraction of a piezo actuator, a displacement expansion chamber filled with hydraulic oil, and a small-diameter piston member that drives a control valve. The displacement of the large-diameter piston member can be hydraulically converted in the displacement expansion chamber, expanded, and transmitted to the small-diameter piston member.

In the above-described conventional fuel injection device, when the piezo actuator is extended, the small-diameter piston member descends via the large-diameter piston member and the displacement expansion chamber, and the control valve is opened. , The nozzle needle rises and fuel is injected from the injection hole. Thereafter, when the piezo actuator is contracted, the small-diameter piston member rises as the large-diameter piston member rises, and the control valve is closed to stop the fuel.

[0004]

However, in the above-described conventional fuel injection device, when the piezo actuator contracts, the control valve may be restarted and excessive fuel may be injected. This is because when the small diameter piston member rises,
Due to overshooting due to inertia, the control valve re-opens again due to the reaction, and the control valve is restarted. In the above-described structure having the displacement expansion chamber, the vibration is difficult to stop because the small-diameter piston member is in a floating state, and the amplitude of the vibration periodically increases and decreases with respect to the width of the energizing pulse applied to the piezo actuator. Therefore, the injection amount also increases and decreases. In other words, there is a problem that the injection amount that increases in proportion to the energization pulse width fluctuates under the influence of vibration, and controllability deteriorates.

The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress vibration of a small-diameter piston member, suppress excessive fuel injection by a reopening valve of a control valve, and respond to an energizing pulse width. It is an object of the present invention to enable accurate injection amount control.

[0006]

According to a first aspect of the present invention, there is provided a fuel injection device which operates between a large-diameter first piston member driven by an actuator and a small-diameter second piston member driving a control valve. Providing a displacement expansion chamber filled with fluid,
A fuel injection device that enlarges a displacement of the first piston member, transmits the displacement to the second piston member, and opens and closes the control valve with the second piston member to move a nozzle needle up and down; A stopper is provided for regulating the amount of movement of the second piston member toward the displacement expansion chamber.

By providing the stopper, the amount of upward movement of the second piston member at the end of the injection is limited, so that the amplitude of the vibration does not increase any more and the stopper comes into contact with the stopper. In addition, vibration is easily attenuated. Therefore, excessive fuel injection due to the restart of the control valve is suppressed, and accurate injection amount control can be performed.

According to a second aspect of the present invention, a damper portion for attenuating the vibration of the second piston member is provided in the displacement expansion chamber. By providing the damper portion in addition to the stopper portion, the effect of attenuating vibration is further increased, and more accurate injection amount control becomes possible.

According to a third aspect of the present invention, the damper portion is a hole of a ring-shaped member provided in the displacement expansion chamber. When the ring-shaped member is fixed or loosely fitted in the displacement expansion chamber, the vibration is attenuated when the fuel flows through the hole due to the displacement of the second piston member.

According to a fourth aspect of the present invention, a ring-shaped member having one end face opposed to the end face of the second piston member at a predetermined interval is fixed in the displacement enlargement chamber to form the stopper portion and the ring-shaped member. The hole at the center of the member is a damper part for damping the vibration of the second piston member. Specifically, if a ring-shaped member is used, the stopper portion and the damper portion can be formed of the same member, and the configuration is simplified.

According to the present invention, the large-diameter first cylinder accommodating the first piston member and the small-diameter second cylinder accommodating the second piston member are continuously and eccentrically moved. And the displacement expansion chamber is provided at a connection portion between the first cylinder and the second cylinder. And
If a step surface is formed at the connecting portion between the first cylinder and the second cylinder to serve as the stopper portion, there is no need to provide a separate member, so that a stopper function can be obtained with a simple configuration.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a common rail injection system for a diesel engine will be described below. FIG. 1 shows a first embodiment of a fuel injection device according to the present invention. The fuel injection device has a housing H1 in which a piezo actuator 1 is accommodated, and a flow path forming member H2, Nozzle body H4 through H3
And fixed oil-tight with a retainer H5. A high-pressure fuel passage 62 is formed in the housing H1 in a vertical direction, and communicates with an external common rail (not shown) through a fuel introduction pipe 63 protruding from an upper portion. Housing H1
A fuel outlet pipe 65 communicating with the drain passage 64 protrudes from the upper part, and the fuel flowing out of the fuel outlet pipe 65 is returned to a fuel tank (not shown).

The housing H1 is substantially cylindrical and has a vertical hole 61 eccentric with respect to the center axis.
Are removably inserted and disposed. The vertical hole 61 is provided parallel to the side of the high-pressure fuel passage 62, and the drain passage 64
Extends further downward through a gap between the vertical hole 61 and the piezo actuator 1. The piezo actuator 1 has a piezo stack 12 housed in a thin metal tube 11, a rod member 13 that moves up and down integrally with the piezo stack 12, and a plate-shaped displacement transmission member 14 driven by the rod member 13. Around the rod member 13, a bellows 15 extending from the lower end of the metal tube 11 extends and is connected to the outer periphery of the displacement transmitting member. Bellows 15
Makes the displacement transmitting unit 14 displaceable by expanding and contracting in the vertical direction following the displacement of the driving member 13,
A preload is applied to the piezo stack 12.

The piezo stack 12 is connected to lead wires 16a and 16b of a connector portion 16 fixed to the upper end of the metal tube 11, and is provided with an insulating member (not shown) on the outer periphery to be connected to the metal tube 11. Insulation is ensured. The piezo actuator 1 is fixed to the upper end of the vertical hole 21 by tightening a retaining nut 17 arranged on the outer periphery of the connector section 16. A ring-shaped shim 18 is interposed between the flange portion on the outer periphery of the connector portion 16 and the stepped portion of the vertical hole 61 to seal between them and adjust the mounting height of the piezo actuator 1. .

FIG. 2 is an enlarged view of the lower half of the fuel injection device. The displacement of the displacement transmitting member 14 of the piezo actuator 1 is transmitted to a large-diameter piston 2 as a first piston member via a rod 21. Below the large-diameter piston 2, a displacement expansion chamber 3, and a small-diameter piston 4 as a second piston member,
The valve element 51 of the three-way valve 5 which is a control valve is driven by the small-diameter piston 4 provided coaxially.
The large and small pistons 2 and 4 are slidably disposed in a cylinder member 66 having two different inner diameters corresponding to these outer diameters, and the displacement expansion chamber 3 has a space formed between the large and small pistons 2 and 4. Is filled with fuel as a working fluid. The displacement expansion chamber 3 hydraulically converts the displacement of the piezo actuator 1, enlarges the displacement by the diameter difference between the large and small pistons 2, 4, and transmits the displacement to the small diameter piston 4.

A check valve 22 is provided at the lower end of the large-diameter piston 2.
Are provided integrally. As shown in FIG. 3A, the check valve 22 includes a plate-shaped valve body 24, a disc spring 25 for urging the valve body 24 toward the large-diameter piston 2, and a check valve holder for holding these. The valve body 24 opens and closes the low-pressure passage 23 provided in the large-diameter piston 2 and communicating with the drain passage 64. The check valve holder 26 is fixed to the outer periphery of the lower end portion of the large-diameter piston 2 having a concave cross section and a convex cross section, and has a through hole 27 at the center for communicating the space inside the check valve holder 26 and the displacement expansion chamber 3. ing. When the pressure in the displacement expansion chamber 3 decreases due to a fuel leak or the like, the valve element 24 descends against the urging force of the disc spring 25, and the displacement expansion chamber 3
Is replenished with fuel. Thereby, it is possible to prevent the generation of bubbles in the displacement expansion chamber 3 and the like. The large-diameter piston 2 is urged toward the actuator 1 by a spring 28 provided around the rod 21, and the small-diameter piston 4
It is urged toward the valve body 51 by a spring 29 provided around the lower end.

The three-way valve 5 has a back pressure chamber 7 of the nozzle needle 7.
1 to the high pressure passage 53 or the low pressure passage 54
, The pressure in the back pressure chamber 71 is increased or decreased. The high-pressure passage 53 communicates with the high-pressure fuel passage 62, and the low-pressure passage 54 communicates with the drain passage 64. When the piezo actuator 1 is extended by the input of the energizing pulse, the displacement is transmitted to the large-diameter piston 2, and the displacement is enlarged and transmitted to the small-diameter piston 4 by using the fuel pressure in the displacement expansion chamber 3. As a result, when the valve element 51 moves down together with the small-diameter piston 4, the low-pressure passage 54 is opened, and the fuel in the back pressure chamber 71 flows out of the three-way valve 5 into the drain passage 64, and the nozzle needle 7 rises. Fuel is injected. On the other hand, when the energization is terminated and the piezo actuator 1 is contracted, the small-diameter piston 4 rises as the large-diameter piston 2 rises, and then the valve body 51 rises with the fuel pressure in the high-pressure passage 53, High-pressure fuel flows into the back pressure chamber 71 from the high-pressure fuel passage 62 and lowers the nozzle needle 7.

The passage 72 is a high-pressure passage that connects the high-pressure fuel passage 62 and the back pressure chamber 71 without passing through the three-way valve 5, and is provided through an orifice in the passage from the high-pressure fuel passage 62 to the high-pressure passage 53. Communicating. This passage allows the high-pressure fuel passage 62 and the back pressure chamber 71 to always communicate with each other, so that at the start of injection, the pressure in the back pressure chamber 71 is reduced, and the nozzle needle 7 is opened slowly. On the other hand, at the end of the injection, there is an effect that the pressure is immediately increased and the nozzle needle 7 is quickly closed.

In the present invention, a ring-shaped member 8 (FIG. 3 (b)) having a predetermined thickness whose central hole diameter is smaller than the outer diameter of the small-diameter piston 4 is press-fitted and fixed in the displacement expansion chamber 3, and one end face ( The lower end face) is opposed to the small-diameter piston 4 at a predetermined interval to form a stopper portion 81 that regulates the upward movement amount of the small-diameter piston 4 within a predetermined range. A hole in the center of the ring-shaped member 8 serves as a damper portion 82 that attenuates the vibration of the small-diameter piston 4 due to the flow of fuel. The upper end surface of the ring-shaped member 8 is at a position where it does not interfere with the large-diameter piston 2 and does not hinder its driving.

In the configuration in which the displacement expansion chamber 3 is provided between the large and small pistons 2 and 4, when the large and small pistons 2 move upward and are released from the driving without the stopper portion 81, the small diameter piston 4 moves in the sliding direction. Floating state. For this reason,
Although the small-diameter piston 4 vibrates again and descends again, and the re-opening of the three-way valve 5 is likely to occur, in the present invention, since the stopper portion 81 is provided, the amount of upward movement of the small-diameter piston 4 is restricted. As described above, vibration cannot be performed with a large amplitude. Therefore, the reopening of the three-way valve 5 by the small-diameter piston 4 is suppressed,
After the nozzle needle 7 starts to descend, it can be prevented from rising again due to a decrease in the pressure of the back pressure chamber 71, or from temporarily not descending, thereby preventing the injection amount from excessively increasing. Further, the fuel flows through the inside of the damper portion 82 formed of the small-diameter hole, whereby the vibration damping effect of the small-diameter piston 4 is enhanced.

FIG. 4 shows the effect of the present invention on the ring-shaped member 8.
FIG. 6 is a diagram illustrating a comparison with a conventional configuration in which no is provided. Originally, it is desirable that the injection amount on the vertical axis increases in proportion to the energizing pulse width on the horizontal axis. A phenomenon occurs in which the fuel is injected. In addition, the amplitude of the small-diameter piston 4 periodically increases and decreases with respect to the energizing pulse width due to the relationship between the mass of the peripheral parts and the spring constant. Therefore, as shown in FIG. Thus, while repeating this, the injection amount increased as a whole. On the other hand, the ring-shaped member 8
In the configuration according to the present embodiment, the injection amount increases more linearly with respect to the energizing pulse width because the vibration of the small-diameter piston 4 is suppressed and the damping is easily performed. Therefore,
There is an advantage that the variation in the injection amount between the injections, particularly the variation in the minute injection amount, is reduced.

FIG. 5 shows a second embodiment of the present invention.
As shown in FIG. 5A, in the present embodiment, a first cylinder 67 that slidably holds the large-diameter piston 2 is provided in the housing H1 so as to be coaxially continuous with the vertical hole 61, and a small-diameter piston is provided. A second cylinder 68 for holding the slidable holding member 4 is provided on the separate member H6. First cylinder 67
Is coaxial with the center axis of the housing H1, and the first cylinder 67 and the second cylinder 68 are provided continuously and eccentrically. The displacement expansion chamber 3 includes a first cylinder 6
7 is provided at a connection portion between the second cylinder 68 and the second cylinder 68.

At this time, the first and second cylinders 68 are arranged so that the outer peripheral edge thereof is located outside the outer peripheral edge of the first cylinder 67, that is, as shown in FIG. The opening area A of the connection portion between the second cylinders 67 and 68 is made smaller than the cross-sectional area of the second cylinder 68. In the present embodiment, a stepped surface formed at a connection portion between the first cylinder 67 and the second cylinder 68 and opposed to the upper end surface of the small-diameter piston 4 is referred to as a stopper portion 83. Even in this case, the same vibration prevention effect as in the first embodiment can be obtained.

Further, in this embodiment, the check valve holder 26 of the check valve 22 is not fixed to the large-diameter piston 2 but is loosely fitted in the displacement expansion chamber 3 (the lower end of the first cylinder 67). Let it. In this case, the check valve holder 26 does not rise following the large-diameter piston 2, so that the fuel flows through the through hole 27 with the displacement of the small-diameter piston 4, and can function as a damper portion. In addition, since the opening area of the connecting portion between the cylinders 67 and 68 is smaller than the cross-sectional area of the second cylinder, the damper effect can be obtained by flowing the fuel through the opening.

The function of the check valve 22 is the same as that of the first embodiment, and as shown in FIG.
When there is sufficient fuel, the force pressing the valve element 24 toward the large-diameter piston 2 [spring force of the disc spring 25 + hydraulic pressure (large)] is large even if the large-diameter piston 2 rises. Low pressure passage 2
3 is closed. On the other hand, when the displacement expansion chamber 3 does not have sufficient fuel, as shown in FIG. 6B, when the large-diameter piston 2 rises, the pressing force [spring force of the disc spring 25 + hydraulic pressure (small)] decreases. The valve element 24 moves away from the large-diameter piston 2. Therefore, the low-pressure passage 23 is opened, and the displacement expansion chamber 3 receives supply of fuel. The first cylinder 67 side and the second cylinder 68 side of the displacement enlargement chamber 3 communicate with each other by an outer peripheral clearance of the check valve holder 26 and a central through hole 27.

As described above, in this embodiment, since the stopper 83 is formed by the step surfaces of the cylinders 67 and 68, it is not necessary to separately provide and assemble the components of the stopper, and the number of parts and the assembly cost are reduced. Can be reduced.
Further, the small-diameter piston 4 is not provided in the vertical hole 61, and a separate member H
6, the length of the vertical hole 61 which is difficult to machine with an eccentric hole is shortened, and machining is facilitated. In the present embodiment, by changing the shape of the high-pressure fuel passage 62, the flow path forming members H2 and H3 are integrated into a flow path forming member H7, and the number of components is further reduced.

In the above embodiment, the piezo actuator is used. However, the present invention is not limited to the piezo type, and any actuator may be used as long as it generates a displacement when energized. Further, it is not necessary to use a three-way valve as the control valve, and a configuration in which the nozzle needle is opened and closed by another method may be used.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a fuel injection device according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a lower half part of the fuel injection device according to the first embodiment.

FIG. 3A is an enlarged view of a main part of the fuel injection device according to the first embodiment, and FIG. 3B is an overall perspective view of a tubular member.

FIG. 4 is a diagram for explaining an effect of the first embodiment.

FIG. 5A is an enlarged view of a lower half of a fuel injection device according to a second embodiment of the present invention, and FIG. 5B is an enlarged view of a main part thereof.

FIGS. 6A and 6B are enlarged views of a main part of a fuel injection device for explaining an operation of a check valve according to a second embodiment of the present invention.

[Explanation of symbols]

 H1 Housing 1 Piezo actuator (actuator) 11 Metal tube 12 Piezo stack 14 Displacement transmitting member 15 Bellows 2 Large diameter piston (first piston member) 22 Check valve 26 Check valve holder 27 Through hole (damper part) 3 Displacement enlargement Chamber 4 small-diameter piston (second piston member) 5 three-way valve (control valve) 51 valve body 61 vertical hole 62 high-pressure fuel passage 63 introduction pipe 64 drain passage 65 outlet pipe 67 first cylinder 68 second cylinder 7 nozzle needle 71 Back pressure chamber

Continued on the front page F term (reference) 3G066 AA07 AC09 AD07 BA11 BA22 BA61 CC01 CC08T CC08U CC56 CC63 CC70 CE13 CE27 CE34

Claims (5)

[Claims] 1. A large-diameter first piston member driven by an actuator, and a small-diameter second piston member driving a control valve.
A displacement expansion chamber filled with a working fluid is provided between the piston members, and the displacement of the first piston member is enlarged and transmitted to the second piston member, and the control is performed by the second piston member. A fuel injection device in which a nozzle needle is moved up and down by opening and closing a valve, wherein a stopper portion for restricting a movement amount of the second piston member toward the displacement expansion chamber side is provided. 2. The fuel injection device according to claim 1, wherein a damper section for damping vibration of the second piston member is provided in the displacement expansion chamber. 3. The damper part comprises a hole of a ring-shaped member fixed or loosely fitted in the displacement expansion chamber.
The fuel injection device according to claim 1. 4. A ring-shaped member having one end face opposed to an end face of the second piston member at a predetermined interval in the displacement expansion chamber to form the stopper portion, and a center of the ring-shaped member. 2. The fuel injection device according to claim 1, wherein said hole is a damper portion for attenuating vibration of said second piston member. 5. A large-diameter first cylinder accommodating the first piston member and a small-diameter second cylinder accommodating the second piston member are continuously and eccentrically arranged. The displacement enlarging chamber is provided at a connection portion between the first cylinder and the second cylinder, and a step surface formed at a connection portion between the first cylinder and the second cylinder is used as the stopper portion. Item 4. The fuel injection device according to any one of Items 1 to 3.