JPH10288118A - Fuel injection valve of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent temporary fuel injection at the time of breaking of wire by contracting an actuator by interrupting voltage impression on the actuator, reducing volume of a pressure chamber in company with energizing force, causing rapid pressure increase into pressure chamber and rapid pressure increase in a differential pressure chamber via a communicating path, resulting in closing of a valve against the fuel pressure. SOLUTION: When opening a valve, a piezoactuator 10 is driven to elongate against a return spring 22 according to voltage impressed by synchronizing with an engine revolution. When closing the valve, the piezoactuator is contracted by interrupting voltage impression on the piezoactuator 10. According to this contraction, volume of a pressure chamber 7 is reduced by energizing force of the return spring 22 and the pressure in the pressure chamber 7 rapidly increases. The pressure in a differential pressure chamber 8 which is communicated with the pressure chamber 7 via a communicating path 17 rapidly increased, energizing force of the return spring 4 is added and a needle valve 2 is closed against fuel pressure of a fuel pressure chamber 3. Thus, fuel injection can be prevented because valve closing operation is performed when voltage impression is interrupted due to breaking of wire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for an engine in which the needle valve is opened and closed by changing the fuel pressure before and after the needle valve via an actuator such as a piezoelectric element or a magnetostrictive element.

[0002]

2. Description of the Related Art Conventionally, in a fuel injection valve provided in an automobile engine, a needle valve (valve) is provided by an actuator having a piezoelectric element whose volume changes according to an applied voltage and a magnetostrictive element whose volume changes according to a change in a magnetic field. The opening and closing of the body is known. By driving the needle valve with these actuators, the responsiveness of the fuel injection valve can be improved, the injection range can be expanded and the engine output can be increased, It is possible to stably inject a small amount of fuel, thereby reducing the fuel consumption of the engine.

[0003] As such a fuel injection valve, for example, a fuel injection valve disclosed in Japanese Patent Application Laid-Open No. 6-88559 is known. A piezo actuator composed of a piezoelectric element is used as an actuator, and a needle valve is opened and closed before and after that. This is performed based on the differential pressure.

[0004] To explain this, a fuel pressure chamber and a back pressure chamber are defined before and after the needle valve, fuel is introduced into the fuel pressure chamber at a predetermined pressure, and the back pressure chamber responds to expansion and contraction of a piezo actuator. The opening / closing operation of the needle valve is controlled by the pressure difference between the front and rear of the needle valve accompanying the change in the volume. That is, when the piezoelectric actuator is extended by applying a voltage, the pressure in the back pressure chamber becomes larger, the needle valve closes and fuel injection is stopped, while the back pressure is reduced when the piezoelectric actuator contracts. Since the volume of the chamber increases, the internal pressure decreases and the needle valve is driven to open.

[0005]

However, in the conventional fuel injection valve as described above, the needle valve is opened by cutting off the voltage applied to the piezo actuator. If the supply voltage drops due to disconnection of the supply line, the needle valve opens as the piezo actuator contracts, and fuel may be injected temporarily even at times other than the predetermined injection timing. there were.

Accordingly, the present invention has been made in view of the above problems, and has as its object to prevent a fuel injection valve of an engine from temporarily injecting fuel at the time of disconnection or the like.

[0007]

According to a first aspect of the present invention, there is provided a fuel pressure chamber into which pressurized fuel is introduced, a needle valve which is displaced in accordance with a differential pressure between the fuel pressure chamber and a differential pressure chamber, and a fuel pressure chamber which is opened and closed by the needle valve. An injection port for injecting fuel in the chamber, an elastic member for urging the needle valve in the valve closing direction, an actuator composed of a piezoelectric element or a magnetostrictive element, and increasing and decreasing the pressure in the differential pressure chamber in accordance with expansion and contraction of the actuator In a fuel injection valve of an engine having a piston, the differential pressure chamber is defined on the back side of a piston portion formed on the base end side of the needle valve, and has an open end substantially opposite to the injection port. In the casing, the actuator is housed in a space formed on the open end side, and a piston is attached to the actuator end on the open end side, while being defined between the casing and the piston, when the actuator is extended. Volume While large, to form a pressure chamber to reduce the volume during contraction, and urging means for urging said piston to contraction direction of the actuator, provided with a communicating path communicating the pressure chamber and the differential room.

In a second aspect based on the first aspect, the pressure receiving area A1 of the piston is set larger than the pressure receiving area A2 on the back surface of the piston portion of the needle valve.

According to a third aspect of the present invention, in the first aspect, the piston includes a tubular portion surrounding the actuator, and the casing accommodates the tubular portion from the opening end side. A groove is formed to define the pressure chamber between the end surface of the cylindrical portion of the piston and the annular groove.

In a fourth aspect based on the third aspect, a seal member is interposed between the annular groove and the inner and outer peripheries of the cylindrical portion, and an opening is formed between the inside of the piston and the pressure chamber. The outside of the end is defined.

In a fifth aspect based on the first aspect, the biasing means comprises a second fuel pressure chamber defined on an open end side of the piston and through which pressurized fuel is guided. .

[0012]

According to the first aspect of the present invention, the valve opening operation of the fuel injector is performed by extending the actuator in response to the voltage applied to the actuator against the urging means. Since the piston is displaced to the open end side, the volume of the pressure chamber rapidly increases and the pressure suddenly decreases, and the pressure of the differential pressure chamber communicating with the pressure chamber through the communication passage also rapidly decreases. The needle valve is displaced against the elastic member in the direction where the volume of the differential pressure chamber decreases, the needle valve is opened, and the pressurized fuel in the fuel pressure chamber flows from the injection port to the combustion chamber. Injected to On the other hand, the valve closing operation of the fuel injection valve is performed by interrupting the application of the voltage to the actuator and causing the actuator to contract, and the actuator contracts and is displaced to the most contracted position by the urging force of the urging means, and the pressure is reduced. The volume of the chamber decreases sharply and the pressure increases sharply. For this reason, the pressure in the differential pressure chamber communicating with the pressure chamber via the communication passage also rapidly increases,
The needle valve is displaced in the direction in which the volume of the differential pressure chamber increases, and at the same time, the urging force of the elastic member is applied. Therefore, the needle valve can be closed against the fuel pressure applied to the fuel pressure chamber. The same operation is performed even when the application of the voltage is cut off due to a disconnection of the current supply path to the actuator, so that fail-safe at the time of failure of the electric system can be ensured. It is possible to reliably prevent the fuel from being temporarily injected due to disconnection or the like, and to improve the reliability of a fuel injection valve using an actuator including a piezoelectric element or a magnetostrictive element. .

In the second invention, the pressure receiving area A1 of the piston is set to be larger than the pressure receiving area A2 on the back surface of the piston portion of the needle valve. Therefore, even if the displacement of the actuator is very small, the needle required for fuel injection is required. The valve opening amount can be ensured, and the degree of freedom in designing the fuel injection valve can be improved.

According to a third aspect of the present invention, there is provided a structure in which a cylindrical portion provided on a piston is accommodated in an annular groove formed on an opening end side of a casing, and the actuator is surrounded by the cylindrical portion and the annular groove. By defining a pressure chamber between the end surface of the cylindrical portion of the piston and the annular groove, the assembly of the actuator, the piston and the biasing means can be performed from the open end side of the casing, so that the work can be easily performed. It is possible to do,
It is possible to improve productivity, and even after mounting on the engine, it becomes possible to easily perform maintenance of the actuator, the piston and the biasing means from the open end side,
The maintenance and productivity of the fuel injection valve can be greatly improved.

According to the fourth aspect of the present invention, since the seal member is interposed between the annular groove and the inner and outer circumferences of the tubular portion, the space for accommodating the actuator can be sealed to block the inflow and outflow of outside air. By preventing the actuator composed of the piezoelectric element and the magnetostrictive element from coming into contact with the outside air, a short circuit due to dew condensation or the like can be reliably avoided, and the reliability of the fuel injection valve can be further improved.

In the fifth invention, the means for urging the piston in the contracting direction of the actuator is constituted by the second fuel pressure chamber. Therefore, the actuator is provided with a driving force for extending and contracting against the fuel pressure applied to the piston. Since the load due to fuel pressure is always constant and does not fluctuate as in the case of using a spring, it is possible to reliably open and close the needle valve with a smaller force, thus miniaturizing the actuator. By reducing the manufacturing cost, the manufacturing cost can be reduced, and the degree of freedom in designing the fuel injection valve can be further improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a fuel injection valve provided in a direct injection type spark ignition engine will be described below with reference to the accompanying drawings.

In FIG. 1, a fuel injection valve has a casing 9.
A nozzle body 1 facing the combustion chamber of an engine (not shown) is provided at the tip (partition wall 9a side) of the nozzle body. This nozzle body 1 injects fuel spray from an injection port 1a opened at the tip toward the combustion chamber. It is formed as follows.

Inside the nozzle body 1, a valve body 2a is formed on the side of the injection port 1a, while a needle valve 2 having a piston portion 2c slidably in contact with the inner periphery of the nozzle body 1 is slidably housed at the other end. A rod portion 2b having a small outer diameter is formed between the valve body 2a and the piston portion 2c.

Inside the nozzle body 1, a fuel pressure chamber 3 communicating with the fuel inlet 6 is defined so as to surround the rod portion 2b of the needle valve 2, and the injection port 1a is opened and closed by the needle valve 2 as described. You. The fuel inlet 6 opens to the side of the nozzle body 1 and is connected to fuel supply means (not shown).

The needle valve 2 has a piston 9 on the side of the casing 9.
A differential pressure chamber 8 is defined between the rear surface of the piston portion 2a (the surface facing the partition wall 9a) and the partition wall 9a.

The differential pressure chamber 8 has a piston 2
A return spring 4 for urging the needle valve 2 in the valve closing direction is interposed between the rear surface of the valve c and the partition 9a as an elastic member.

A throttle passage 21 formed by a gap or the like is provided between the piston portion 2c and the inner periphery of the nozzle body 1. Pressurized fuel supplied to the fuel pressure chamber 3 passes through the throttle passage 21. The pressure is gradually supplied to the differential pressure chamber 8.

The casing 9 is formed in a cylindrical shape with the partition 9a as the bottom, and the opening end 9b is directed to the right side in FIG. The actuator 10 is housed so as to be able to expand and contract in the axial direction (left and right directions in the figure). And the casing 9
A sealing member 16 is provided at the open end 9b (right side in the figure) of the casing 9 to seal the inside of the casing 9.

The piezo actuator 10 has a PZ
A large number of disc-shaped piezoelectric elements made of T (lead zirconate titanate) ceramic, PMN (lead magnesium niobate) ceramic, etc. are laminated,
Electrodes (not shown) are interposed between the piezoelectric elements and both ends, and the piezo actuator 10 expands and contracts in the axial direction according to a voltage applied from a controller (not shown).

One end of the piezo actuator 10 housed in the casing 9 abuts against the partition wall 9a, and the other end is provided with a piston 11 via a plate-like spacer 14. Space 1 between
8 is defined, and a disc spring-shaped return spring 2 is provided in this space 18 as urging means for urging the piezo actuator 10 in the contracting direction via the piston 11.
2 are interposed.

Here, the piston 11 has a U-shaped radial cross section, is formed of a cylindrical member whose side facing the space 18 is sealed, and has the top surface 11a facing the space 18 side. The cylindrical part 11 b (cylindrical part) is housed in the casing 9 with the nozzle body 1 facing the nozzle body 1.

The top surface 11a of the piston 11 contacts the return spring 22 as described above, while the cylindrical portion 1
1b is housed in an annular groove 9c formed at a predetermined depth from an inner peripheral end face 9d formed inside the open end 9b. The inner peripheral end surface 9d is formed at a predetermined depth from the opening end 9b toward the partition wall 9a, and the annular groove 9c is formed as an annular groove portion having a predetermined depth on the outer peripheral side of the inner peripheral end surface 9d. The inner peripheral end face 9 d is the top face 11 of the sliding piston 11.
It is arranged at a predetermined depth from the opening end 9b so as not to come into contact with the inside of a.

The end face of the cylindrical portion 11b of the piston 11 accommodated in the annular groove 9c defines a pressure chamber 7 between the cylindrical portion 11b and the bottom of the annular groove 9c, and faces the inner and outer circumferences of the cylindrical portion 11b. O-rings 12, 1 are provided on the inner periphery of the annular groove 9c.
2 is interposed as a seal member to define the pressure chamber 7 and the space 18 and the internal space 90 of the casing 9 in which the piezo actuator 10 is accommodated. The O-ring 12 is disposed at a position where the O-ring 12 can be in sliding contact with the inner and outer circumferences of the cylindrical portion 11b even when the piezo actuator 10 is fully extended. The sealing member 1 prevents fuel from leaking.
The piezo actuator 10 is hermetically sealed while preventing air from entering and leaving the space 90 from the space 18 on the sixth side.

Next, the pressure chamber 7 defined between the end face of the cylindrical portion 11b of the piston 11 and the annular groove 9c communicates with the piston portion of the needle valve 2 through a communication passage 17 formed in the casing 9. It communicates with a differential pressure chamber 8 defined on the back of 2c.

Here, assuming that the pressure receiving area of the piston 11 facing the pressure chamber 7 is A1, and the stroke (axial displacement) of the piezo actuator 10 is S1, the volume V of the pressure chamber 7 is
1 is represented by V1 = A1 × S1 (1)

On the other hand, assuming that the pressure receiving area of the piston portion 2c facing the differential pressure chamber 8 is A2 and the stroke of the needle valve 2 is S2, the volume V2 of the differential pressure chamber 8 is as follows: V2 = A2 × S2. 2) and V1 = V2, assuming (1),
From the formula (2), S2 = A1 / A2 × S1 (3). Therefore, the relationship between the pressure receiving area A1 of the piston 11 and the pressure receiving area A2 of the piston portion 2c of the needle valve 2 is represented by A1> A2. By setting (4), the stroke S2 of the needle valve 2 is smaller than the minute stroke S1 of the piezo actuator 10.
Can be increased.

The operation is described below, with the above configuration.

FIG. 1 shows the state of the fuel injection valve when the engine is stopped. Since no voltage is applied from a controller (not shown), the piezo actuator 10
Is contracted and urged by the return spring 22 to be in the most contracted position, so that the stroke S1 becomes the minimum value, and the volume V1 of the pressure chamber 7 becomes the minimum according to the above equation (1).

At this time, the pressures in the fuel pressure chamber 3, the differential pressure chamber 8 and the pressure chamber 7 are made uniform by the throttle passage 21 provided between the piston portion 2c of the needle valve 2 and the inner periphery of the cylinder body 1. In addition, there is no front-back differential pressure in the piston portion 2c of the needle valve 2. Therefore, the needle valve 2 is closed by the urging force of the return spring 4, the stroke S2 of the needle valve 2 becomes the maximum value, and the volume V2 of the differential pressure chamber 8 becomes the maximum according to the above equation (2).

That is, the urging force of the return spring 4 presses the valve body 2a of the needle valve 2 against the seat portion of the nozzle body 1 to reliably close the valve, thereby preventing fuel from leaking from the injection port 1a while the engine is stopped. You.

In order to start the engine, when fuel is fed from the fuel supply means (not shown) to the fuel inlet 6 at a predetermined fuel pressure Pf, first, the fuel pressure Pf is guided to the fuel pressure chamber 3 to increase the pressure. Until the pressurized fuel passes through the throttle passage 21 of the piston portion 2c into the differential pressure chamber 8 and the pressure chamber 7, a differential pressure is generated in the piston portion 2c with the needle valve 2. 7, the piezo actuator 10 is contracted, and the piston 11 is also urged in the contracting direction by the return spring 22. Therefore, the volume V1 remains minimum, and the needle valve 2 is actuated by the urging force of the return spring 4. By pressing the valve body 2a against the seat portion of the nozzle body 1, it is possible to reliably prevent the needle valve 2 from opening other than at a predetermined injection timing.

The valve opening operation of the fuel injection valve at the start of the engine and after the start is performed by the piezo actuator 10 being extended and driven against the return spring 22 in accordance with the voltage applied in synchronization with the engine rotation. Will be

With the extension of the piezo actuator 10, the piston 11 is displaced toward the sealing member 16 so that the stroke S1 increases, the volume V1 of the pressure chamber 7 increases rapidly, and the pressure decreases rapidly.

Therefore, the pressure chamber 7 is connected via the communication passage 17.
The pressure in the differential pressure chamber 8 communicating with the needle valve 2 also sharply decreases, so that a front-back differential pressure is generated in the piston portion 2c of the needle valve 2, and the volume V2 of the differential pressure chamber 8
The piston portion 2c is displaced against the urging force of the return spring 4 in the direction in which the needle valve 2 decreases, and the needle valve 2 opens. Needle valve 2
, The pressurized fuel in the fuel pressure chamber 3 is injected from the injection port 1a into a combustion chamber (not shown).

The stroke S2 when the needle valve 2 is opened is
Since the pressure receiving area A1 of the piston 11 is set larger than the pressure receiving area A2 of the piston portion 2c of the valve 2 as in the above equation (4), the piezo actuator 1
Since the stroke S2 of the needle valve 2 can be increased in accordance with the pressure receiving area ratio even if the stroke S1 of 0 is minute, the stroke required for opening the needle valve 2 can be easily secured. It is.

Next, the closing operation of the fuel injection valve is performed by interrupting the application of the voltage to the piezo actuator 10 and driving the piezo actuator 10 to contract.

The piezo actuator 10 contracts due to the interruption of the voltage, and is displaced to the most contracted position by the urging force of the return spring 22, and the volume V of the pressure chamber 7 is reduced.
1 becomes the minimum value again.

With the contraction of the piezo actuator 10, the piston 11 is displaced toward the needle valve 2, so that the stroke S1 is reduced, and the volume V1 of the pressure chamber 7 is rapidly reduced.
Pressure surges.

Therefore, the pressure chamber 7 is
The pressure in the differential pressure chamber 8 communicating with the needle valve 2 also increases rapidly, so that a front-rear differential pressure is generated in the piston portion 2c of the needle valve 2, and the volume V2 of the differential pressure chamber 8
The piston portion 2c is displaced in a direction in which
Since the urging force of the return spring 4 is applied, the needle valve 2 can be closed against the fuel pressure Pf applied to the fuel pressure chamber 3, and the valve body 2a contacts the seat portion of the nozzle body 1 to seal the injection port 1a. By stopping, the fuel injection from the fuel pressure chamber 3 to the combustion chamber is stopped.

The valve closing operation is performed by the piezo actuator 1
The same operation is performed even when the application of the voltage is interrupted due to disconnection of the current supply path to 0, etc., so that fail-safe at the time of failure of the electric system can be ensured.

In this manner, the piston 2
c to form a differential pressure chamber 8 between the back surface of the piston 2c and the partition 9a of the casing 9, and a return spring 4 for urging in the valve closing direction via the piston 2c. On the other hand, a space 90 that supports the base end of the piezo actuator 10 on the partition 9a side is defined on the inner periphery of the casing 9 having an open end opposite to the partition 9a.
Further, the annular groove 9 is formed so as to surround the end of the space 90.
c to form a pressure chamber 7 between the cylindrical portion 11b of the piston 11 attached to the other end of the piezo actuator 10 and the annular groove 9c, and the differential pressure chamber 8 and the pressure chamber 7, the piezo actuator 10 is driven to extend when energized, so that the piston 2
While the needle valve 2 is opened by generating a pressure difference between the front and rear, the actuator 10 contracts when the power is cut off, the pressure applied to the piston part 2c increases, and the valve can be reliably closed by the return spring 4. In the case where the piezo actuator contracts due to disconnection of the wiring or the like as in the conventional example, it is possible to reliably prevent the fuel from being temporarily injected, and the fuel injection valve using the piezo actuator 10 Reliability can be improved.

Since the piezo actuator 10, the piston 11, and the return spring 22 can be assembled from the opening end 9b side of the casing 9, the work can be easily performed, and the productivity is improved. Further, even after mounting on the engine, the piezo actuator 1
Thus, maintenance of the piston 11, the return spring 22 and the piston 11 can be easily performed, and the maintainability of the fuel injection valve can be greatly improved.

Since the pressure receiving area A1 of the piston 11 is set larger than the pressure receiving area A2 of the piston portion 2c,
Even if the displacement of the piezo actuator 10 is very small,
The amount of opening of the needle valve 2 necessary for fuel injection can be secured, and the degree of freedom in designing the fuel injection valve can be improved.

Further, the O-ring 1 provided in the annular groove 9c
The space 90 for accommodating the piezo actuator 10 is sealed by the parts 2 and 12, and the space 18 on the sealing member 16 side and the annular pressure chamber 7 can be reliably separated from each other. Therefore, a short circuit due to dew condensation or the like can be prevented, and the reliability of the fuel injection valve using the piezo actuator 10 can be further improved.

FIG. 2 shows a second embodiment. In the first embodiment, the top surface 11a of the piston 11 and the sealing member 1
A space 18 defined between the first embodiment and the second embodiment is communicated with the fuel inlet 6 to form the second fuel pressure chamber 20, and a disc spring-shaped return spring 22 is omitted. The same is true.

The top surface 11a of the piston 11 and the sealing member 16
Is communicated with the fuel inlet 6 via a fuel pressure supply passage 19 formed in the casing 9.

In the stopped state of the engine, the valve body 2a of the needle valve 2 is pressed against the seat portion of the nozzle body 1 by the urging force of the return spring 4 to close the valve reliably, as in the first embodiment. This prevents fuel from leaking from the injection port 1a during stoppage.

When the fuel is fed at a predetermined fuel pressure Pf from a fuel supply means (not shown) to the fuel inlet 6 to start the engine, first, the fuel pressure Pf is supplied to the fuel pressure chamber 3 and the second fuel pressure chamber 20.
Are respectively introduced to increase the pressure, and the fuel pressure Pf applied to the second fuel pressure chamber 20 urges the piston 11 in the contracting direction of the piezo actuator 10 instead of the return spring 22 of the first embodiment, and the piston 11 The needle valve 2 can be kept in the closed state by the fuel pressure Pf applied to the needle and the urging force of the return spring 4.

When a voltage is applied to the piezo actuator 10 in synchronization with the rotation of the engine in order to open the fuel injection valve, the piezo actuator 10 extends against the fuel pressure Pf of the second fuel pressure chamber 20, and Similarly, the piston portion 2c
, The needle valve 2 is driven to open.

Similarly, the valve closing operation of the fuel injection valve is performed by interrupting the application of the voltage to the piezo actuator 10 and driving the piezo actuator 10 to contract.

The piezo actuator 10 contracts due to the interruption of the voltage, and is displaced to the most contracted position by the fuel pressure Pf applied to the second fuel pressure chamber 20 via the piston 11, thereby minimizing the volume V1 of the pressure chamber 7, and As in the embodiment, the valve body 2a is brought into contact with the seat portion of the nozzle body 1 by the urging force of the return spring 4, and
By closing a, the valve is closed, and fuel injection from the fuel pressure chamber 3 to the combustion chamber is stopped.

In this case, the piezo actuator 10
Need only be provided with a driving force that expands and contracts against the fuel pressure Pf applied to the piston 11, the load due to the fuel pressure Pf is always constant, and the return spring 2 of the first embodiment is used.
2, the needle valve 2 can be reliably opened and closed with a smaller force, and the size of the piezo actuator 10 can be reduced, thereby reducing the manufacturing cost. At the same time, the degree of freedom in designing the fuel injection valve can be further improved.

In the above embodiment, the piston 1
Although a case where a piezoelectric actuator 10 composed of a piezoelectric element is employed as an actuator for driving the actuator 1 is shown, although not shown, a magnetostrictive actuator or a giant magnetostrictive actuator using a magnetostrictive element that expands and contracts according to the strength of a magnetic field is employed. It is the same as above.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fuel injection valve showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a fuel injection valve according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle body 1a Injection port 2 Needle valve 2a Valve element 2c Piston part 3 Fuel pressure chamber 4 Return spring (elastic member) 6 Fuel inlet 7 Pressure chamber 8 Differential pressure chamber 9 Casing 9a Partition wall 9b Open end 9c Annular groove 10 Piezo actuator 11 Piston 11a Top surface 11b Cylindrical part (cylindrical part) 12 O-ring 17 Communication path 18 Space 19 Fuel pressure supply path 20 Second fuel pressure chamber (biasing means) 21 Throttle path 22 Return spring (biasing means) 90 Space

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 41/12 H01L 41/08 C (72) Inventor Takashi Fukuda 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (5)

[Claims] 1. A fuel pressure chamber into which pressurized fuel is introduced, a needle valve displaced in accordance with a differential pressure between the fuel pressure chamber and the differential pressure chamber, an injection port opened and closed by the needle valve to inject fuel in the fuel pressure chamber, and a needle. A fuel injection valve for an engine, comprising: an elastic member for urging a valve in a valve closing direction; an actuator constituted by a piezoelectric element or a magnetostrictive element; and a piston for increasing or decreasing the pressure in a differential pressure chamber according to expansion and contraction of the actuator. In the above, the differential pressure chamber is defined on the back side of a piston portion formed on the base end side of the needle valve, and a casing having an open end substantially opposite to the injection port has a space formed on the open end side. While the actuator is housed in the housing and a piston is attached to the actuator end on the open end side, a volume is defined between the casing and the piston to expand the volume when the actuator is extended and increase the volume when the actuator is contracted. A fuel injection valve for an engine, comprising: a biasing means for forming a pressure chamber that reduces pressure and biasing the piston in a contraction direction of an actuator; and a communication passage communicating the pressure chamber and the differential pressure chamber. . 2. The fuel injection valve for an engine according to claim 1, wherein the pressure receiving area A1 of the piston is set larger than the pressure receiving area A2 on the back surface of the piston portion of the needle valve. 3. The piston is provided with a cylindrical portion surrounding the actuator, and the casing is formed with an annular groove for accommodating the cylindrical portion from an open end side, and the pressure chamber is formed as a cylinder of the piston. 2. The fuel injection valve for an engine according to claim 1, wherein the fuel injection valve is defined between the end face of the shape and the annular groove. 4. A seal member is interposed between the annular groove and the inner and outer peripheries of the cylindrical portion to define the inside of the piston and the outside on the open end side with a pressure chamber interposed therebetween. Claim 3
The fuel injection valve for an engine according to claim 1. 5. The engine according to claim 1, wherein said biasing means comprises a second fuel pressure chamber defined on an open end side of said piston and through which pressurized fuel is guided. Fuel injection valve.