JP2003214280A - Hydraulic piston and fuel injection device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic piston which reduces leakage of hydraulic oil when hydraulic pressure in a hydraulic chamber increases and promotes flow of hydraulic oil to the hydraulic chamber when hydraulic pressure in the hydraulic chamber decreases without causing enlargement of the size and a fuel injection device using it. <P>SOLUTION: When a first piston 30 moves to the direction of the hydraulic chamber 50 along with extension of a piezo actuator 51, the hydraulic pressure in the hydraulic chamber 50 increases and a difference of the hydraulic pressure is generated between the hydraulic chamber 50 and a hydraulic acting part 38. A skirt part 33 is expanded to the outside of the radial direction and pressed to an inside wall of a first cylinder 31 by the difference of the hydraulic pressure. Leakage of fuel from the hydraulic chamber 50 to the side of the hydraulic acting part 38 is reduced thereby. Similarly, when the first piston 30 moves to the opposite direction of the hydraulic chamber along with contraction of the piezo actuator 51, the hydraulic pressure of the hydraulic chamber 50 is dropped and the skirt part 33 is contracted to inside of the radial direction. Fuel is supplied from the hydraulic acting part 38 to the hydraulic chamber 50 thereby. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydraulic piston and a fuel injection device using the same.

[0002]

2. Description of the Related Art A fuel injection device for injecting fuel into a combustion chamber of an internal combustion engine (hereinafter referred to as "engine") includes a nozzle needle for intermittently injecting fuel from an injection hole. For example, in the case of interrupting the flow of high-pressure fuel such as in a fuel injection device of a diesel engine, the nozzle needle is controlled by controlling the hydraulic pressure of the control chamber into which the fuel for urging the nozzle needle in the direction of closing the injection hole is introduced. Are driving.

For example, as a fluid control device for driving the hydraulic pressure in a control chamber by a piezoelectric element such as a piezo element via a hydraulic piston, one disclosed in US Pat. No. 6,142,443 is known. In this case, a hydraulic chamber into which hydraulic oil is introduced is formed on the side opposite to the piezoelectric element of the hydraulic piston, and the displacement of the piezoelectric element is enlarged by the hydraulic pressure of the hydraulic chamber and transmitted to the valve member.

[0004]

However, in the case of the technique disclosed in US Pat. No. 6,142,443, the hydraulic oil leaks from the drive portion of the hydraulic piston and the hydraulic pressure drops, so it is necessary to supplement the leaking hydraulic oil. There is. Therefore, in the case of the above technique, the check valve is installed to reduce the leak of hydraulic oil.

Further, in order to reduce the leakage of hydraulic oil, a technique disclosed in DE 19914713 in Germany is known. In this technique, an annular groove is formed on the outer peripheral side of a cylinder that houses a driven hydraulic piston, and hydraulic oil having the same pressure as the hydraulic pressure acting on the hydraulic piston is introduced into this groove. This compresses the cylinder in the direction of the hydraulic piston from the outer peripheral side of the cylinder to reduce the clearance formed between the hydraulic piston and the cylinder,
It reduces the leak of hydraulic oil through the clearance.

However, the technique disclosed in DE 19914713 restores the clearance between the hydraulic piston expanded by high pressure and the cylinder to the state of the clearance before the high pressure acts. for that reason,
This does not positively reduce the clearance formed between the hydraulic piston and the cylinder, but when the pressure applied to the hydraulic piston increases, considerable hydraulic oil leaks from the clearance between the hydraulic piston and the cylinder.

Installation of a check valve and reduction of leakage of hydraulic oil are indispensable for a hydraulic actuator that expands displacement by hydraulic pressure. However, forming the check valve and the leak reducing mechanism in the hydraulic actuator poses a problem of increasing the size of the hydraulic actuator and, in turn, the fuel injection device to which the hydraulic actuator is applied.

Therefore, an object of the present invention is to reduce the leakage of hydraulic fluid when the hydraulic pressure of the hydraulic chamber increases and to reduce the hydraulic pressure of the hydraulic chamber to the hydraulic chamber when the hydraulic pressure of the hydraulic chamber decreases without increasing the size of the hydraulic chamber. To provide a hydraulic piston for promoting the inflow of fuel and a fuel injection device using the same.

[0009]

According to the hydraulic piston of the first or second aspect of the present invention, a skirt portion is formed at the end of the main body on the hydraulic chamber side. A hydraulic acting portion is provided on the skirt portion on the side opposite to the hydraulic chamber. A hydraulic pressure lower than the maximum hydraulic pressure of the hydraulic chamber is introduced into the hydraulic acting portion. In the present specification, the maximum hydraulic pressure means the hydraulic pressure in the hydraulic chamber when the displacement amount of the hydraulic piston in the hydraulic chamber direction becomes maximum. Therefore, when the hydraulic pressure in the hydraulic chamber increases, the skirt portion expands radially outward due to the pressure difference between the hydraulic acting portion and the hydraulic chamber and is pressed against the inner wall of the cylinder. This reduces the clearance formed between the skirt and the inner wall of the cylinder. Therefore, it is possible to reduce the leakage of hydraulic oil from the hydraulic chamber.

According to the hydraulic piston of the third aspect of the present invention, the main body has the annular groove formed in an annular shape in the circumferential direction from the end portion on the hydraulic chamber side toward the counter hydraulic chamber. With this annular groove, a thin-walled cylindrical portion that serves as a skirt is formed on the outer peripheral side of the annular groove. The thin-walled cylinder portion formed on the outer peripheral side of the annular groove easily expands radially outward due to the pressure difference between the hydraulic chamber and the hydraulic acting portion. Therefore, the skirt portion can be easily deformed. Moreover, since the thin-walled tubular portion is formed by the annular groove to form the skirt portion, the physical size is not increased. Further, by forming the thin-walled tubular portion by the annular groove, the dead volume on the inner peripheral side of the annular groove is reduced. Therefore, even when high-pressure fuel is used as in a fuel injection device, for example, the operation loss can be reduced.

According to the hydraulic piston of the fourth or fifth aspect of the present invention, the skirt member serving as the skirt portion is formed separately from the main body. Therefore, the tolerance of the outer diameter of the main body can be absorbed by the skirt member. Therefore, the main body and the skirt member can be easily formed. According to the hydraulic piston of claim 6 of the present invention, the skirt member has an elastic force for urging the main body in the direction opposite to the hydraulic chamber. Therefore, for example, the disc spring installed in the hydraulic chamber can be eliminated.

According to the hydraulic piston of claim 7 of the present invention, a hydraulic pressure equal to or higher than the minimum hydraulic pressure of the hydraulic chamber is introduced into the hydraulic acting portion. In the present specification, the minimum hydraulic pressure means the hydraulic pressure in the hydraulic chamber when the displacement amount of the hydraulic piston in the hydraulic chamber direction becomes zero. Therefore, when the hydraulic pressure in the hydraulic chamber decreases, the skirt portion contracts radially inward due to the difference in hydraulic pressure between the hydraulic acting portion and the hydraulic chamber. Thereby, the clearance formed between the skirt portion and the inner wall of the cylinder is enlarged. Therefore, the skirt portion functions as a check valve, and can promote the inflow of hydraulic oil into the hydraulic chamber.

According to the hydraulic piston of the eighth aspect of the present invention, the end portion of the skirt portion on the hydraulic chamber side is bent toward the inner peripheral side of the main body. Accordingly, it is possible to reduce the interference between the skirt portion and the inner wall of the cylinder due to the reciprocating movement. Therefore, the movement inside the cylinder can be made smooth and the operation loss can be reduced.

According to the fuel injection device of the ninth or tenth aspect of the present invention, either one or both of the first piston and the second piston comprises the hydraulic piston according to any one of the first to eighth aspects. Therefore, when the pressure of the hydraulic oil in the hydraulic chamber rises, the leakage of the hydraulic oil from the clearance formed between the first piston or the second piston and the cylinder can be reduced. Therefore,
Operation loss due to leakage of hydraulic oil is reduced, and the drive unit can be downsized. Further, for example, by making the first piston or the second piston function as a check valve, the check valve can be eliminated, and an increase in the number of parts or an increase in size can be suppressed.

According to the fuel injection device of the eleventh aspect of the present invention, the hydraulic action portion communicates with the high pressure passage, and the high pressure fuel is supplied to the hydraulic action portion from the common rail. Therefore, for example, by urging the second piston toward the anti-hydraulic chamber with high-pressure fuel, it is possible to reduce the driving force generated from the drive unit. Therefore, the drive unit can be downsized.

According to the twelfth aspect of the fuel injection device of the present invention, the hydraulic action portion communicates with the low pressure passage, and the low pressure fuel is supplied to the hydraulic action portion from the low pressure side. Therefore, although a large driving force is required for the drive unit, fuel leakage from the hydraulic action unit is reduced. Therefore,
The flow rate of fuel that needs to be supplied to the fuel injection device can be reduced, and the load on the fuel supply device that supplies fuel to the fuel injection device, such as a fuel injection pump, can be reduced. According to the fuel injection device of the thirteenth aspect of the present invention, the drive portion has the piezoelectric element. Therefore, it is possible to improve the responsiveness of driving the nozzle needle via the driving force transmission unit. Further, the displacement amount of the piezoelectric element can be expanded by the hydraulic chamber and transmitted from the first piston to the second piston.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of embodiments showing the embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a fuel injection device to which a hydraulic piston according to a first embodiment of the present invention is applied. The fuel injection device according to this embodiment is applied to a common rail fuel injection system.

As shown in FIG. 1, the fuel injection device 1 includes a housing 10 and a housing 10 with a plate member 11, a plate member 12 and a control chamber forming member 13 interposed therebetween.
And a nozzle body 20 connected by a retaining nut 14. A nozzle hole 21 is formed at the tip of the nozzle body 20. Inside the nozzle body 20,
The nozzle needle 22 is housed so as to be reciprocally movable in the axial direction. At the tip of the nozzle needle 22, a sealing portion 22
a is formed, and the seal portion 22a is the nozzle body 2
Seat portion 20a formed on the inlet side of the injection hole 21 of No. 0
Can be contacted with. When the nozzle needle 22 moves upward in FIG. 1 and the seal portion 22a is separated from the seat portion 20a, fuel is injected from the injection hole 21. On the other hand, when the nozzle needle 22 moves downward in FIG. 1 and the seal portion 22a is seated on the seat portion 20a, fuel injection from the injection hole 21 is stopped. A back pressure chamber 23 is formed between the nozzle body 20 and the plate member 11 at the end portion on the side opposite to the injection hole. A spring 24 is accommodated in the back pressure chamber 23, and the nozzle needle 22 is closed in the injection hole closing direction, that is, the seal portion 22a is seated by the seat portion 20a by the high-pressure fuel stored in the back pressure chamber 23 and the urging force of the spring 24.
It is urged in the direction to sit down.

From a common rail (not shown) to the housing 1
The fuel supplied to the fuel passage 25 of the nozzle body 20 via the high-pressure fuel passage 15 formed in No. 0 passes through the fuel reservoir 26, the gap formed between the nozzle needle 22 and the nozzle body 20. Is supplied to the tip of the nozzle needle 22. A part of the fuel supplied from the common rail via the high pressure fuel passage 15 is formed in the control chamber forming member 13 via the high pressure port 121 of the plate member 12 installed on the side opposite to the injection hole of the nozzle body 20. It is supplied to the control room 16 in which it is located. The fuel supplied from the common rail (not shown) via the high-pressure fuel passage 15 is several MPa.
To several 100 MPa.

The first piston 30, the second piston 40, the valve member 17, the first cylinder 31, the second cylinder 41 and the hydraulic chamber 50 formed in the housing 10, the control chamber forming member 13 and the plate member 12 are formed. The control chamber 16 and the back pressure chamber 23 formed by the plate member 11 and the nozzle body 20 constitute a driving force transmission portion. The valve member 17 is formed in a hemispherical shape, and has a control chamber 16 formed in the control chamber forming member 13.
It is installed in. The valve member 17 is capable of reciprocating in the vertical direction of FIG. 1 inside the control chamber 16. The inner peripheral surface of the control chamber forming member 13 is formed in a tapered shape, and the valve seat portion 13a on which the valve member 17 can be seated is formed on the tapered inner peripheral surface. The control chamber forming member 13 is formed with a low pressure port 131 as a passage communicating with the low pressure side, and the valve member 17 is seated on the valve seat portion 13a so that the control chamber 16 is closed.
The communication between the low pressure port 131 and the low pressure port 131 is blocked. On the low voltage side,
It is composed of a low pressure chamber 101 formed in the housing 10 and low pressure passages 102 and 132 formed in the housing 10 and the control chamber forming member 13. The low-pressure passages 102 and 132 communicate with the outside of the fuel injection device 1, and the control chamber 16 or the back pressure chamber 23, etc.
The fuel that is no longer needed is discharged in each part of.

In FIG. 1, the outer diameter of the second piston 40 is shown to be larger than the seat diameter of the valve seat portion 13a of the low pressure port 131 for the sake of simplicity of explanation.
7 for urging the second piston 4 toward the valve seat portion 13a.
The outer diameter of 0 is smaller than the seat diameter of the valve seat portion 13a.

A high pressure port 121, which communicates with the high pressure side, communicates with the control chamber 16. The high pressure port 121 communicates with the high pressure fuel passage 15. A control hydraulic pressure passage 18 communicating with the back pressure chamber 23 communicates with the control chamber 16. The control hydraulic passage 18 communicates with the back pressure chamber 23 from the control chamber 16 via the plate member 12 and the plate member 11 via the orifice 231.

Piezo actuator 51 as a drive unit
Has a piezo element which is a piezoelectric element. The piezo actuator 51 is connected to a drive circuit (not shown),
Electric energy is supplied according to a command from an ECU (not shown). The piezo actuator 51 expands when electric energy is supplied, and contracts when the energy is released. The piezo actuator 51
It is housed in a piezoelectric housing chamber 19 formed in the housing 10. The piezo storage chamber 19 has a low-pressure communication passage 103.
Are in communication. The low-pressure communication passage 103 is provided in the housing 10.
Is formed so as to connect the piezo storage chamber 19 and the low pressure passage 102. The fuel leaked from the high pressure side to the piezo storage chamber 19 is supplied to the low pressure communication passage 103 and the low pressure passage 102.
Is discharged to the outside of the fuel injection device 1 via

The first piston 30 is in contact with the end of the piezo actuator 51 on the injection hole 21 side, and reciprocally slides inside the first cylinder 31 formed in the housing 10 as the piezo actuator 51 expands and contracts. To do. A hydraulic chamber 50 is formed on the side opposite to the piezoelectric element of the first piston 30. The volume of the hydraulic chamber 50 changes as the first piston 30 moves. A disc spring 52 is installed in the hydraulic chamber 50, and the disc spring 52 urges the first piston 30 toward the piezo actuator 51. This allows
When energy is released from the piezo actuator 51, the first piston 30 moves upward in FIG. Fuel as hydraulic oil is introduced into the hydraulic chamber 50.

The second piston 40 is housed in a second cylinder 41 formed in the housing 10 so as to be able to slide back and forth in the vertical direction of FIG. One end of the second piston 40 faces the hydraulic chamber 50, and the second piston 40 receives the hydraulic pressure of the hydraulic chamber 50 and can move downward in FIG. 1.
The other end of the second piston 40 faces the low pressure chamber 101. The end of the low pressure chamber 101 of the second piston 40 has a small diameter and is in contact with the valve member 17.

Next, the first piston 30, the second piston 40 and their surroundings will be described in detail. The first piston 30 can reciprocate in the axial direction inside the first cylinder 31 formed in the housing 10. The first piston 30 is formed in a cylindrical shape having an outer diameter substantially the same as the inner diameter of the first cylinder 31. The first piston 30 has a main body 32, and a skirt portion 33 is integrally formed on the hydraulic chamber 50 side of the main body 32. The first piston 30 includes a piezo actuator 51 from the end on the hydraulic chamber 50 side.
An annular groove 34 is formed to the end portion on the side. The annular groove 34 is continuously formed in the circumferential direction on the inner circumferential side of the first piston 30 as shown in FIG. 2. First piston 30
Is divided into an outer peripheral side skirt portion 33 and an inner peripheral side island portion 35 by the annular groove 34.

The skirt portion 33 is a thin-walled cylinder portion formed on the outer peripheral side of the annular groove 34. The annular groove 34 is formed halfway in the axial direction of the first piston 30. Annular groove 34
An outer groove 36 is formed on the piezo actuator 51 side rather than the end on the piezo actuator 51 side. The outer groove 36 is formed continuously on the outer peripheral side of the first piston 30 in the circumferential direction. The chamfered portion 3 having a curved shape is formed on the skirt portion 33 side of the outer groove 36, that is, the root portion of the skirt portion 33.
7 are formed. By partitioning the hydraulic chamber 50 side of the first piston 30 into the skirt portion 33 and the island portion 35 by the annular groove 34, the island portion 35 formed on the inner peripheral side of the annular groove 34.
Faces the hydraulic chamber 50. Therefore, the dead volume on the inner peripheral side of the skirt portion 33 is reduced, and the operation loss is reduced in the hydraulic device that uses high pressure such as the fuel injection device 1.

As shown in FIG. 1, an annular space is formed between the outer wall of the first piston 30 and the inner wall of the first cylinder 31 in a portion corresponding to the outer groove 36, and this space acts hydraulically. It becomes part 38. The hydraulic action section 38 has a high pressure communication passage 10
4 are in communication. The high-pressure communication passage 104 includes the housing 1
The hydraulic pressure acting portion 38 and the high pressure fuel passage 15 are communicated with each other through 0. The high-pressure fuel supplied from the common rail to the fuel injection device 1 is introduced into the hydraulic action section 38 via the high-pressure communication passage 104.

The second piston 40 can reciprocate in the axial direction inside the second cylinder 41 formed in the housing 10. The second piston 40 is the second cylinder 41.
Is formed in a cylindrical shape having an outer diameter substantially the same as the inner diameter of the. Similarly to the first piston 30, the second piston 40 has a main body 42,
Skirt portion 43, annular groove 44, island portion 45 and outer groove 46
have. Skirt portion 43, annular groove 44, island portion 45
Since the structure of the outer groove 46 is the same as that of the first piston 30, the description thereof will be omitted.

The outer wall of the second piston 40 and the second cylinder 4
An annular space is formed between the inner wall 1 and the outer wall 46 at a portion corresponding to the outer groove 46, and this space serves as a hydraulic pressure acting portion 48.
A high-pressure communication passage 105 communicates with the hydraulic action section 48.
The high-pressure communication passage 105 penetrates through the housing 10 to communicate the hydraulic pressure acting portion 48 and the high-pressure fuel passage 15. The high-pressure fuel supplied from the common rail to the fuel injection device 1 is introduced into the hydraulic action section 48 via the high-pressure communication passage 105.

Next, the operation of the fuel injection device 1 according to the first embodiment and the first piston 30 and the second piston 40.
The operation of will be described. When energy is not supplied to the piezo actuator 51, the first piston 30 moves upward in FIG. 1 due to the biasing force of the disc spring 52, and the first piston 30 stops at the position where the volume of the hydraulic chamber 50 becomes maximum. ing. Therefore, the force that drives the valve member 17 downward in FIG. 1 is not applied to the second piston 40. At this time, the valve member 17 is seated on the valve seat portion 13a because the valve member 17 receives an upward force in FIG. 1 due to the pressure of the high-pressure fuel supplied from the high-pressure fuel passage 15 to the control chamber 16. Further, fuel having the same pressure as the inside of the common rail is supplied to the hydraulic chamber 50 via the high-pressure fuel passage 15 and the hydraulic action portions 38 and 48.

Further, at this time, high pressure fuel is supplied to the back pressure chamber 23 from the high pressure fuel passage 15 through the control chamber 16 and the control hydraulic pressure passage 18. Also, the nozzle needle 2
High-pressure fuel is also supplied from the high-pressure fuel passage 15 around the second seal portion 22a. The force that the nozzle needle 22 receives in the nozzle hole opening direction by the fuel around the seal portion 22a of the nozzle needle 22 is the high pressure fuel stored in the back pressure chamber 23 and the spring 24.
Is smaller than the force received in the injection hole closing direction by the urging force of. Therefore, the seal portion 22a is seated on the seat portion 20a. Therefore, when energy is not supplied to the piezo actuator 51, fuel injection from the injection hole 21 is stopped.

When energy is supplied to the piezo actuator 51, the piezo actuator 51 extends downward in FIG. As the piezo actuator 51 extends, the first piston 30 moves toward the hydraulic chamber 50, and the volume of the hydraulic chamber 50 decreases. Therefore, the hydraulic pressure in the hydraulic chamber 50 increases. When the second piston 40 moves downward in FIG. 1 due to the increased hydraulic pressure in the hydraulic chamber 50, the second piston 4
The valve member 17 in contact with 0 is pressed downward in FIG. Then, when the force that the valve member 17 receives from the second piston 40 becomes larger than the force that the valve member 17 receives in the valve seat portion 13a direction by the hydraulic pressure of the control chamber 16, the valve member 17 separates from the valve seat portion 13a, The low pressure port 131 is opened.
As a result, the control chamber 16 communicates with the low pressure side, and the control chamber 1
The fuel in 6 is the low pressure chamber 101 and the low pressure passages 132, 10
It flows to 2.

When the energy supplied to the piezo actuator 51 increases, the displacement amount of the piezo actuator 51 also increases. Along with this, the hydraulic pressure of the hydraulic chamber 50 increases and the displacement amount of the second piston 40 also increases. Then, when the energy supplied to the piezo actuator 51 becomes maximum, the amount of displacement of the second piston 40 and the valve member 17 also becomes maximum, and the valve member 17 closes the high pressure port 121 formed in the plate member 12.
When the high-pressure port 121 is closed, the supply of high-pressure fuel to the control chamber 16 is stopped, so the pressure inside the control chamber 16 decreases. As a result, the pressure in the back pressure chamber 23 communicating with the control chamber 16 is also reduced, and the force for urging the nozzle needle 22 in the nozzle hole closing direction is reduced. Then, the force that the nozzle needle 22 receives in the injection hole opening direction by the high-pressure fuel supplied to the periphery of the seal portion 22a of the nozzle needle 22 is blocked by the fuel pressure in the back pressure chamber 23 and the biasing force of the spring 24. When it becomes larger than the force received in the direction,
The nozzle needle 22 is lifted upward in FIG. As a result, the seal portion 22a is separated from the seat portion 20a, and the fuel is injected from the injection hole 21.

When the energy supplied to the piezo actuator 51 increases, the hydraulic pressure in the hydraulic chamber 50 increases due to the movement of the first piston 30 accompanying the displacement of the piezo actuator 51. Therefore, in the case of the first piston 30, the hydraulic pressure of the hydraulic chamber 50 is the same as that of the hydraulic chamber 5 of the first piston 30.
It acts not only on the 0-side end surface but also on the outer wall of the annular groove 34.
Fuel having the same pressure as the inside of the common rail is supplied from the high-pressure fuel passage 15 to the hydraulic action portion 38. First piston 3
The pressure of the hydraulic chamber 50 when the displacement amount of 0 is 0 (hereinafter, the pressure of the hydraulic chamber 50 when the displacement amount of the first piston 30 is 0 is referred to as “minimum hydraulic pressure”) is the same as that inside the common rail. is there. Therefore, the pressure of the hydraulic chamber 50 becomes larger than the pressure of the hydraulic acting portion 38 due to the decrease in the volume of the hydraulic chamber 50 due to the displacement of the first piston 30. As the oil pressure in the oil pressure chamber 50 increases, a pressure difference occurs between the oil pressure chamber 50 and the oil pressure acting portion 38. Therefore, the skirt portion 33 is elastically deformed radially outward, that is, toward the inner wall of the first cylinder 31, by the fuel inside the annular groove 34. As a result, the skirt portion 33 expands radially outward and is pressed against the inner wall of the first cylinder 31. The chamfered portion 37 formed at the base of the skirt portion 33 allows the skirt portion 33 to be easily deformed and the concentration of stress to be reduced.

The skirt portion 33 is enlarged to expand the first cylinder 31.
By being pressed against the inner wall of the, the clearance formed between the outer wall of the skirt portion 33, that is, the outer wall of the first piston 30 and the inner wall of the first cylinder 31 is reduced. As a result, the hydraulic chamber 50 moves as the first piston 30 moves.
Even when the hydraulic pressure of the hydraulic pressure increases, the leakage of fuel from the hydraulic pressure chamber 50 to the hydraulic pressure acting portion 38 is reduced.

The second piston 4 as well as the first piston 30
As for 0, the skirt portion 43 is elastically deformed by the hydraulic pressure of the hydraulic chamber 50. Thereby, the second piston 40 and the second cylinder 4
The clearance formed between 1 and 1 is reduced. Therefore, when the hydraulic pressure in the hydraulic chamber 50 increases, fuel leakage from the hydraulic chamber 50 to the low pressure chamber 101 is reduced.

When energy is released from the piezo actuator 51, the piezo actuator 51 contracts upward in FIG. When the piezo actuator 51 contracts, the urging force of the disc spring 52 causes the first piston 3 to move.
0 moves upward in FIG. 1 and the volume of the hydraulic chamber 50 increases. Therefore, the hydraulic pressure in the hydraulic chamber 50 decreases. As a result, the second piston 40 moves upward in FIG. Then, the valve member 17 moves upward in FIG. 1 due to the pressure of the fuel flowing into the control chamber 16 from the high pressure port 121, and the valve seat portion 1 moves.
Sit on 3a. Therefore, the control chamber 16 communicates with the high-pressure side, and the pressure inside the control chamber 16 rises again. As a result, the pressure in the back pressure chamber 23 communicating with the control chamber 16 also increases, and the force that urges the nozzle needle 22 in the injection hole closing direction increases. Then, the nozzle needle 22 is attached to the seal portion 22.
When the force received by the nozzle needle 22 in the nozzle hole closing direction by the fuel in the back pressure chamber 23 and the biasing force of the spring 24 becomes larger than the force received by the fuel around the nozzle a in the nozzle hole opening direction, Move below 1,
The seal portion 22a is seated on the seat portion 20a. As a result, the fuel injection from the injection hole 21 ends.

The movement of the first piston 30 accompanying the contraction of the piezo actuator 51 reduces the hydraulic pressure in the hydraulic chamber 50. On the other hand, in the case of the first piston 30, fuel having the same pressure as the inside of the common rail is supplied to the hydraulic pressure acting portion 38 from the high pressure fuel passage 15. Therefore, a pressure difference occurs between the hydraulic chamber 50 and the hydraulic action portion 38, and the fuel pressure in the hydraulic action portion 38 becomes higher than the fuel pressure in the hydraulic chamber 50. As a result, the skirt portion 33 elastically deforms inward in the radial direction, that is, the inner peripheral side of the first piston 30 by the pressure of the fuel of the hydraulic action portion 38, and the skirt portion 33 contracts.

By reducing the skirt portion 33, the clearance formed between the outer wall of the skirt portion 33, that is, the outer wall of the first piston 30 and the inner wall of the first cylinder 31 is enlarged. As a result, when the hydraulic pressure in the hydraulic chamber 50 decreases as the first piston 30 moves, fuel flows from the hydraulic acting portion 38 into the hydraulic chamber 50, and the hydraulic chamber 50 is replenished with fuel. That is, the skirt portion 33 has the hydraulic chamber 5
It functions as a check valve according to the increase or decrease of the hydraulic pressure of 0.

Similarly, in the case of the second piston 40, the skirt portion 43 shrinks due to the difference between the pressure of the fuel supplied from the high pressure fuel passage 15 to the hydraulic pressure acting portion 48 and the pressure of the fuel in the hydraulic pressure chamber 50. Thereby, the clearance formed between the outer wall of the second piston 40 and the inner wall of the second cylinder 41 is enlarged. As a result, fuel flows into the hydraulic chamber 50 from the hydraulic acting portion 48, and the second piston 40 functions as a check valve.

As described above, according to the fuel injection device 1 of the first embodiment of the present invention, when the first piston 30 moves toward the hydraulic chamber 50 and the fuel pressure in the hydraulic chamber 50 increases, the skirt is increased. The portion 33 expands radially outward. Therefore, the clearance formed between the first piston 30 and the first cylinder 31 is reduced, and the leakage of fuel from the hydraulic chamber 50 to the hydraulic acting portion 38 can be reduced. Similarly, the clearance formed between the second piston 40 and the second cylinder 41 is reduced, so that the hydraulic chamber 50 moves to the low pressure chamber 1
It is possible to reduce the leakage of fuel to 01. Therefore, the operation loss due to fuel leakage is reduced, and the driving force can be efficiently transmitted from the first piston 30 to the second piston 40 via the hydraulic chamber 50. As a result, it is possible to reduce the driving force of the piezo actuator 51, reduce the size of the piezo actuator 51, and reduce the power consumption of the piezo actuator 51.

When the first piston 30 moves in the direction opposite to the hydraulic chamber and the hydraulic pressure in the hydraulic chamber 50 decreases, the skirt portion 3
3 contracts radially inward. Therefore, the skirt 33
Functions as a check valve, the clearance formed between the first piston 30 and the first cylinder 31 is enlarged, and fuel is replenished from the hydraulic action portion 38 to the hydraulic chamber 50. Therefore, it is not necessary to separately install a check valve in the fuel injection device 1, and it is possible to suppress an increase in the size of the fuel injection device 1 and an increase in the number of parts.

Further, by introducing the fuel having the same pressure as the common rail into the hydraulic chamber 50, the driving force required to drive the first piston 30, the second piston 40 and the valve member 17 is reduced. Therefore, the driving force required for the piezo actuator 51 can be reduced, and the piezo actuator 51 can be downsized.

(Second Embodiment) FIG. 3 shows a fuel injection device according to a second embodiment of the present invention. The same components as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 3, the fuel injection device 2 according to the second embodiment is
The hydraulic operating portion 38 of the first piston 30 and the hydraulic operating portion 48 of the second piston 40 communicate with the low pressure side. The hydraulic pressure acting portion 38 of the first piston 30 communicates with the low pressure communication passage 106, and the side of the low pressure communicating passage 106 opposite to the hydraulic pressure acting portion communicates with the low pressure passage 102. That is, the low pressure communication passage 10
Reference numeral 6 penetrates the housing 10 to connect the hydraulic pressure acting portion 38 and the low pressure passage 102. As a result, the hydraulic pressure acting portion 38
Is introduced into the rail at a pressure lower than the pressure inside the common rail.

The second piston 40 is formed with a cutout portion 49 which connects the hydraulic pressure acting portion 48 and the low pressure chamber 101. As a result, fuel having a pressure lower than the pressure inside the common rail is introduced from the low pressure chamber 101 into the hydraulic action portion 48. By introducing fuel at a pressure lower than the pressure inside the common rail into the hydraulic pressure acting portion 38 of the first piston 30 and the hydraulic pressure acting portion 48 of the second piston 40, when the hydraulic pressure chamber 50 is at the minimum hydraulic pressure, the hydraulic pressure chamber 50 and the hydraulic pressure chamber 50 are The acting portion 38 and the hydraulic acting portion 38 have the same pressure. Therefore, the pressure in the hydraulic chamber 50 is also lower than the pressure inside the common rail.

When high-pressure fuel is introduced into the hydraulic action section 38, the hydraulic action section 48, and the hydraulic chamber 50 as in the first embodiment, the generated force from the piezo actuator 51 can be reduced, but Fuel is the first piston 30
Leaks into the piezo accommodating chamber 19 via the clearance between the first cylinder 31 and the first cylinder 31, and the fuel in the hydraulic action portion 48 passes through the clearance between the second piston 40 and the second cylinder 41 to the low pressure chamber 101. Leaks. Hydraulic action part 3
Since high-pressure fuel is constantly introduced into the hydraulic pressure acting portion 8 and the hydraulic pressure acting portion 48, a leak to the piezo storage chamber 19 and the low pressure chamber 101 constantly occurs. Therefore, the amount of fuel leakage increases. Further, the low pressure communication passage 103 for discharging the fuel from the piezo storage chamber 19 to the low pressure side is required.

On the other hand, when a low pressure is introduced into the hydraulic action section 38 and the hydraulic action section 48 as in this embodiment, the control chamber 16
Due to the high pressure fuel filled in the valve member 17, a large force is applied to the valve member 17 in the direction of seating on the valve seat portion 13a.
Therefore, in order to overcome the hydraulic pressure of the control chamber 16 applied to the valve member 17 and drive the valve member 17, it is necessary to increase the generated force generated from the piezo actuator 51.
However, since the steady fuel leakage from the hydraulic action unit 38 and the hydraulic action unit 48 is reduced, the fuel injection device 2
It is possible to reduce the flow rate of fuel to be supplied to. As a result, for example, the capacity of the fuel injection pump for supplying fuel to the fuel injection device 2 and the load of the fuel injection pump can be reduced.

In the second embodiment, the piezo actuator 5
When 1 extends, the pressure of the fuel in the hydraulic chamber 50 becomes higher than the pressures of the hydraulic acting portion 38 and the hydraulic acting portion 48.
Therefore, similarly to the first embodiment, the skirt portion 33 of the first piston 30 and the skirt portion 43 of the second piston 40 are expanded radially outward, and fuel leakage from the hydraulic chamber 50 can be reduced. In addition, the piezo actuator 5
When 1 is contracted, the pressure of the fuel in the hydraulic chamber 50 becomes lower than the pressures of the hydraulic action portion 38 and the hydraulic action portion 48.
Therefore, the skirt portion 33 of the first piston 30 and the skirt portion 43 of the second piston 40 are reduced inward in the radial direction and function as a check valve, so that the hydraulic action portion 38 and the hydraulic action portion 48 transfer fuel to the hydraulic chamber 50. Can be replenished.

(Third Embodiment) The third embodiment is a modification of the first and second embodiments. In the third embodiment, FIG.
As shown in, the tip of the skirt portion 63 of the first piston 60, that is, the hydraulic chamber 50 side is slightly bent to the inner peripheral side of the first piston 60. As a result, the first piston 6
Even when the skirt portion 63 elastically deforms with the movement of 0, the interference with the inner wall of the first cylinder 31 is reduced. Similarly to the first piston 60 described above, the tip of the skirt portion of the second piston can be bent inward.

(Fourth Embodiment) FIG. 5 shows a fuel injection device according to a fourth embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In the fourth embodiment, the piezo actuator directly drives the valve needle. As shown in FIG. 5, the fuel injection device 3 according to the third embodiment includes a nozzle body 20, a nozzle needle 22, a first piston, a second piston, a housing (not shown), a piezo actuator 51, and the like. The nozzle body 20 is similar to that of the first embodiment described above.

The piezo actuator 51 is housed inside a first cylinder 71 formed in a housing (not shown). The main body 70 of the first piston can reciprocate in the axial direction inside the first cylinder 71. A hydraulic chamber 90 is provided on the anti-piezo actuator side of the first cylinder 71.
Are formed. The hydraulic chamber 90 accommodates a skirt member 72, which is separate from the main body 70 of the first piston. The hydraulic chamber 90 communicates with the control chamber 92 via a hydraulic passage 91. A low pressure passage 93 communicates with the first cylinder 71.

The main body 70 of the first piston has a large diameter portion 70.
1, having a small diameter portion 702 and a convex portion 703. An annular space is formed between the outer wall of the small diameter portion 702 and the first cylinder 71. This space is in communication with the low pressure passage 93 and serves as a hydraulic pressure acting portion 73 that applies hydraulic pressure to the side of the skirt member 72 opposite to the hydraulic pressure chamber.

The skirt member 72 is formed in a ring shape having a hole 72a at the center as shown in FIG.
The skirt member 72 has a tubular thin wall portion 721, and a flat plate portion 722 extending toward the inner peripheral side is connected to an end of the thin wall tubular portion 721. A hole 72a is formed in the center of the flat plate portion 722. The skirt member 72 is
It is installed on the hydraulic chamber 90 side of the main body 70 of the first piston, and the projection 703 is inserted into the hole 72a. The flat plate portion 722 of the skirt member 72 is in contact with the end portion of the small diameter portion 702 on the hydraulic chamber 90 side. Since the skirt member 72 is elastically deformable and is installed in the hydraulic chamber 90 in a state of being slightly compressed in the axial direction, the skirt member 72 urges the main body 70 of the first piston in the anti-hydraulic chamber direction.

As shown in FIG. 5, the nozzle needle 22 is
It is housed inside the nozzle body 20 so as to be capable of reciprocating in the axial direction. The nozzle needle 22 is formed with a seal portion 22a at an end portion on the injection hole 21 side, and the seal portion 22a can contact the seat portion 20a of the nozzle body 20.
The main body 80 of the second piston is integrally connected to the end of the nozzle needle 22 on the side opposite to the seat portion. The main body 80 of the second piston is formed in a tubular shape, and the spring 82 is housed in a spring chamber 81 formed inside. The spring 82 biases the main body 80 of the second piston in the injection hole closing direction, that is, in the direction in which the seal portion 22a is seated on the seat portion 20a. Second piston body 80
Are housed in a second cylinder 83 formed in a housing (not shown). The second cylinder 83 communicates with the high-pressure fuel passage 15, and high-pressure fuel is supplied from the common rail. A control chamber 92 is formed at the end of the second cylinder 83 on the injection hole 21 side. The control chamber 92 communicates with the hydraulic chamber 90 via the hydraulic passage 91. Control room 92
The skirt member 84 is housed in the. Since the skirt member 84 has the same structure as the skirt member 72 of the hydraulic chamber 90, the description thereof will be omitted. The skirt member 84 is elastically deformable and urges the main body 80 of the second piston toward the spring 82. The outer diameter of the main body 80 of the second piston is formed to be slightly smaller than the inner diameter of the second cylinder 83, and the fuel introduced into the second cylinder 83 is supplied to the side opposite to the control chamber of the skirt member 84. As a result, the side of the skirt member 84 opposite to the control chamber becomes the hydraulic pressure acting portion 85.

Next, the operation of the fuel injection device 3 according to the fourth embodiment will be described. When energy is not supplied to the piezo actuator 51, the body 70 of the first piston moves upward in FIG. 5 due to the urging force of the skirt member 72, and stops at the position where the volume of the hydraulic chamber 90 becomes maximum. At this time, the main body 80 of the second piston and the nozzle needle 22 integrated with the main body 80 of the second piston receive the downward force in FIG. 5 due to the high-pressure fuel introduced into the spring chamber 81 and the urging force of the spring 82. The seal portion 22a of the nozzle needle 22 is seated on the seat portion 20a. Therefore, when energy is not supplied to the piezo actuator 51, fuel injection from the injection hole 21 is stopped.

When energy is supplied to the piezo actuator 51, the piezo actuator 51 extends downward in FIG. With the extension of the piezo actuator 51, the main body 70 of the first piston moves toward the hydraulic chamber 90, and the volume of the hydraulic chamber 90 becomes smaller. Therefore, the hydraulic pressure in the hydraulic chamber 90 increases. In addition, there is always a pressure difference between the hydraulic chamber 90 and the hydraulic action portion 73 with the skirt member 72 sandwiched therebetween, whereby the skirt member 72 is elastically deformed outward in the radial direction, that is, toward the inner wall of the first cylinder 71, and is expanded. ing. As a result, the skirt member 72 is pressed against the inner wall of the first cylinder 71.

The skirt member 72 is expanded so that the first cylinder 7
The skirt member 7 is pressed by the inner wall of the skirt member 1.
The clearance formed between the second outer wall and the inner wall of the first cylinder 71 is reduced. As a result, fuel leakage from the hydraulic chamber 90 to the hydraulic action portion 73 is reduced even when the hydraulic pressure in the hydraulic chamber 90 increases normally or as the main body 70 of the first piston moves.

Like the skirt member 72, the skirt member 84 of the control chamber 92 is elastically deformed by the hydraulic pressure of the control chamber 92. As a result, the skirt member 84 and the second cylinder 83
The clearance formed between and is reduced. Therefore, when the hydraulic pressure in the control chamber 92 increases as the hydraulic pressure in the hydraulic chamber 90 increases, fuel leakage from the control chamber 92 to the hydraulic pressure acting portion 85 is reduced.

The hydraulic pressure increased by the movement of the main body 70 of the first piston is introduced from the hydraulic chamber 90 into the control chamber 92, and the pressure in the control chamber 92 increases. Due to the increased hydraulic pressure in the control chamber 92, the main body 80 of the second piston moves upward in FIG.
As a result, the nozzle needle 22 integrated with the main body 80 of the second piston moves upward in FIG. 1, and the seal portion 22a is separated from the seat portion 20a. As a result, fuel is injected from the injection hole 21.

When the energy of the piezo actuator 51 is released, the piezo actuator 51 contracts upward in FIG. When the piezo actuator 51 contracts, the body 70 of the first piston moves upward in FIG. 5 due to the biasing force of the skirt member 72, and the volume of the hydraulic chamber 90 increases. Therefore, the hydraulic pressure in the hydraulic chamber 90 decreases and the hydraulic pressure in the control chamber 92 also decreases. When the hydraulic pressure in the control chamber 92 decreases, the nozzle needle 22 integrated with the main body 80 of the second piston moves downward in FIG. 5 due to the urging force of the spring 82, and the seal portion 22a is seated on the seat portion 20a. As a result, the fuel injection from the injection hole 21 ends.

When the pressures in the hydraulic chamber 90 and the control chamber 92 drop, the skirt member 72 contracts radially inward due to the hydraulic pressure difference between the hydraulic acting portion 85 and the control chamber 92. Therefore, the skirt member 72 functions as a check valve as in the above-described embodiments, and the hydraulic chamber 90 and the control chamber 92 are provided.
Promote the supply of fuel to.

In the fourth embodiment, the skirt member 72 and the skirt member 84 are constructed separately from the main body 70 of the first piston or the main body 80 of the second piston, and the skirt member 72 and the skirt member 84 are provided with a biasing force. is doing. Therefore, the disc spring installed in the hydraulic chamber 90 or the control chamber 92 can be substituted by the skirt member 72 and the skirt member 84.

In addition, in the fourth embodiment, the fuel leak can be reduced by the skirt member 72 and the skirt member 84 as in the above-described plurality of embodiments. Furthermore, since the skirt member 72 and the skirt member 84 function as a check valve, it is possible to prevent the fuel injection device 3 from increasing in size.

In the above-described embodiments, the hydraulic piston of the present invention is applied to the fuel injection device. However, the hydraulic piston according to the present invention can be applied not only to the fuel injection device but also to other hydraulic devices such as a hydraulic pump that reduces a leak of hydraulic pressure and needs a check valve. Further, in the above-described plurality of embodiments, each embodiment is described individually, but the plurality of embodiments may be combined and applied.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a fuel injection device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a first piston of the fuel injection device according to the first embodiment of the present invention, (A) showing the same cross section as FIG. 1, and (B) showing (A). It is a figure which shows the cross section cut | disconnected by the BB line.

FIG. 3 is a schematic sectional view showing a fuel injection device according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a first piston of a fuel injection device according to a third embodiment of the present invention.

FIG. 5 is a schematic diagram showing a fuel injection device according to a fourth embodiment of the present invention.

FIG. 6 is a view showing a first piston of a fuel injection device according to a fourth embodiment of the present invention, in which (A) is a sectional view,
(B) is an arrow view seen from the arrow B direction of (A).

[Explanation of symbols]

1, 2, 3 fuel injection device 15 High-pressure fuel passage 20 nozzle body 21 injection holes 22 nozzle needle 30, 60 First piston 31 first cylinder 32 body 33 Skirt 34 annular groove 36 outer groove 38 Hydraulic Action Section 40 Second piston 41 Second cylinder 42 body 43 Skirt 44 annular groove 46 outer groove 48 Hydraulic action part 50 hydraulic chamber 51 Piezo actuator (drive unit) 60 First piston 63 Skirt 70 body 71 First cylinder 72 Skirt member 73 Hydraulic unit 80 body 83 Second cylinder 84 Skirt member 85 Hydraulic action part 90 Hydraulic chamber 93 Low pressure passage 102 low pressure passage 721 Thin-walled cylinder 722 Flat plate part

Claims (13)

[Claims] 1. A hydraulic piston capable of increasing / decreasing the hydraulic pressure of a hydraulic chamber by reciprocating in an axial direction inside a cylinder, the main body and a hydraulic piston provided at an end portion of the main body on the hydraulic chamber side. A skirt portion, which is elastically deformable by the hydraulic pressure in the chamber, expands radially outward when the hydraulic pressure in the hydraulic chamber increases and is pressed against the inner wall of the cylinder, and a skirt portion of the main body formed on the side opposite to the hydraulic chamber. A hydraulic pressure acting portion into which a hydraulic pressure lower than the maximum hydraulic pressure of the hydraulic chamber is introduced, and a hydraulic piston. 2. The hydraulic piston according to claim 1, wherein the skirt portion is formed integrally with the main body. 3. An annular groove formed in an annular shape in the circumferential direction from the end on the hydraulic chamber side to the side opposite to the hydraulic chamber, and a thin-walled cylinder portion formed on the outer peripheral side of the annular groove. The hydraulic piston according to claim 2. 4. The hydraulic piston according to claim 1, wherein the skirt portion has a skirt member formed separately from the main body. 5. The hydraulic pressure according to claim 4, wherein the skirt member has a tubular portion and a flat plate portion connected to an end portion of the tubular portion on the main body side and extending radially inward. piston. 6. The hydraulic piston according to claim 4, wherein the skirt member has an elastic force that urges the main body in the anti-hydraulic chamber direction. 7. A hydraulic pressure equal to or higher than a minimum hydraulic pressure of the hydraulic chamber is introduced into the hydraulic acting portion.
7. The hydraulic piston according to any one of items 1 to 6. 8. The hydraulic piston according to claim 1, wherein an end of the skirt portion on the hydraulic chamber side is bent toward an inner peripheral side of the main body. 9. A nozzle part having a nozzle hole and a nozzle needle for opening and closing the nozzle hole, a driving part for generating a driving force when power is supplied, and a driving force generated by the driving part. A drive generated by the drive unit, which has a first piston, a hydraulic chamber whose volume changes by the movement of the first piston, and a second piston driven by the hydraulic pressure that changes with the change of the volume of the hydraulic chamber. A driving force transmitting unit that is capable of driving the nozzle needle by force, and one or both of the first piston and the second piston are the hydraulic pistons according to any one of claims 1 to 8; A fuel injection device comprising: 10. The fuel injection device according to claim 9, wherein the second piston is connected to an end of the nozzle needle on the side opposite to the injection hole. 11. The fuel injection device according to claim 9, wherein the hydraulic pressure acting portion communicates with a high pressure passage for supplying the high pressure from the common rail to the nozzle portion with fuel. 12. The fuel injection device according to claim 9, wherein the hydraulic action portion communicates with a low pressure passage through which excess fuel is discharged. 13. The fuel injection device according to claim 9, wherein the drive unit has a piezoelectric element whose displacement amount changes according to the supplied electric power.