JP3785735B2 - Engine fuel injection valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine fuel injection valve that opens and closes a needle valve by changing the fuel pressure before and after the needle valve via an actuator such as a piezoelectric element or a magnetostrictive element.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a fuel injection valve provided in an automobile engine, a needle valve (valve element) is opened and closed by an actuator having a piezoelectric element that changes in volume according to an applied voltage and a magnetostrictive element that changes in volume according to a change in magnetic field. What is known is that by driving the needle valve with these actuators, the responsiveness of the fuel injection valve can be improved, the range of injection can be expanded to support higher engine output, and a small amount of fuel can be stabilized This makes it possible to inject fuel and reduce the fuel consumption of the engine.
[0003]
As such a fuel injection valve, for example, one disclosed in Japanese Patent Laid-Open No. 6-88559 is known, and a piezoelectric actuator composed of a piezoelectric element is used as an actuator, and the opening and closing of the needle valve is made to have a differential pressure before and after. Based on this.
[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 increases in volume according to the expansion and contraction of the piezoelectric actuator. The opening / closing operation of the needle valve is controlled by the differential pressure across the needle valve accompanying this volume change. That is, when the voltage is applied to the piezo actuator and extended, the pressure in the back pressure chamber becomes larger, the needle valve closes and fuel injection stops, while the back pressure is reduced when the piezo actuator contracts. Since the volume of the chamber increases, the internal pressure decreases and the needle valve is driven to open.
[0005]
[Problems to be solved by the invention]
However, the conventional fuel injection valve as described above has a structure in which the voltage applied to the piezo actuator is cut off and the needle valve is opened. When the supply voltage decreases, the needle valve opens as the piezo actuator contracts, and fuel may be temporarily injected at times other than the predetermined injection timing.
[0006]
Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to prevent temporary fuel injection at the time of disconnection or the like in an engine fuel injection valve.
[0007]
[Means for Solving the Problems]
A first invention includes a fuel pressure chamber through which pressurized fuel is guided, a needle valve that is displaced according to a differential pressure between the fuel pressure chamber and the differential pressure chamber, a nozzle that is opened and closed by the needle valve and injects fuel in the fuel pressure chamber, Fuel injection of an engine comprising an elastic member that urges the needle valve in the valve closing direction, an actuator composed of a piezoelectric element or a magnetostrictive element, and a piston that increases or decreases the pressure in the differential pressure chamber according to the expansion and contraction of the actuator In the valve, the differential pressure chamber is defined on the back side of the piston portion formed on the proximal end side of the needle valve, and is formed on the open end side of the casing having an open end on the substantially opposite side to the injection port. The actuator is housed in the space, and a piston is attached to the actuator end on the opening end side, and is defined between the casing and the piston to increase the volume when the actuator is extended, while the volume is set when the actuator is contracted. The To form a pressure chamber for small, 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.
[0008]
Moreover, 2nd invention sets the pressure receiving area A1 of the said piston larger than the pressure receiving area A2 of the piston part back surface of a needle valve in the said 1st invention.
[0009]
Further, according to a third aspect, in the first aspect, the piston includes a cylindrical portion surrounding the actuator, and the casing is formed with an annular groove for accommodating the cylindrical portion from the opening end side. The pressure chamber is defined between the end surface of the cylindrical portion of the piston and the annular groove.
[0010]
According to a fourth aspect of the present invention, in the third aspect of the present invention, a seal member is interposed between the annular groove and the inner periphery and the outer periphery of the tubular portion, and the piston chamber and the opening end side are sandwiched between the pressure chambers. Define the outside.
[0011]
In a fifth aspect based on the first aspect, the urging means comprises a second fuel pressure chamber that is defined on the opening end side of the piston and into which the pressurized fuel is guided.
[0012]
【The invention's effect】
According to a first aspect of the present invention, the valve opening operation of the fuel injection valve is performed by extending the actuator against the urging means according to the voltage applied to the actuator, and the piston opens as the actuator extends. Since the displacement of the pressure chamber suddenly increases and the pressure suddenly decreases and the pressure in the differential pressure chamber communicating with the pressure chamber via the communication path also decreases sharply, the needle valve piston part has a longitudinal difference. Pressure is generated and the needle valve is displaced against the elastic member in a direction in which the volume of the differential pressure chamber decreases, the needle valve is opened, and the pressurized fuel in the fuel pressure chamber is injected from the nozzle into the combustion chamber. On the other hand, the closing operation of the fuel injection valve is performed by cutting off the voltage application to the actuator and driving it to contract. The actuator contracts and is displaced to the most contracted position by the urging force of the urging means. The chamber volume decreases rapidly and the pressure increases rapidly. For this reason, since the pressure in the differential pressure chamber communicating with the pressure chamber via the communication passage also increases rapidly, 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. The valve can be closed against the fuel pressure applied to the fuel pressure chamber, and this valve closing operation works in the same way even when the application of voltage is interrupted due to disconnection of the energization path to the actuator, etc. It is possible to ensure fail-safe at the time of failure of the electric system, and it is possible to surely prevent the fuel from being temporarily injected due to disconnection of the wiring as in the conventional example, and the piezoelectric element In addition, the reliability of the fuel injection valve using the actuator including the magnetostrictive element can be improved.
[0013]
In the second aspect of the invention, 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. Therefore, even if the displacement of the actuator is very small, the needle valve necessary for fuel injection is opened. The valve amount can be secured, and the degree of freedom in designing the fuel injection valve can be improved.
[0014]
According to a third aspect of the present invention, a cylindrical portion provided on the piston is accommodated in an annular groove formed on the opening end side of the casing, and the actuator is surrounded by the cylindrical portion and the annular groove. By defining a pressure chamber between the end face of the shaped part and the annular groove, the assembly of the actuator, piston and urging means can be performed from the opening end side of the casing, so that the work can be easily performed. It is possible to improve productivity, and further, it is possible to easily perform maintenance of the actuator, piston and urging means from the opening end side even after being mounted on the engine. This can greatly improve the maintainability and productivity.
[0015]
In addition, since the seal member is interposed between the annular groove and the inner periphery and the outer periphery of the cylindrical portion, the fourth invention can seal the space for housing the actuator and block the outside air from entering and exiting, This prevents the actuator made of the magnetostrictive element from coming into contact with the outside air, reliably avoids a short circuit due to condensation or the like, and further improves the reliability of the fuel injection valve.
[0016]
In the fifth aspect of the invention, since the means for urging the piston in the contracting direction of the actuator is configured by the second fuel pressure chamber, the actuator may have a driving force that extends and contracts against the fuel pressure applied to the piston. The load due to the fuel pressure is always constant, and the load does not fluctuate as in the case of using a spring, so the needle valve can be reliably opened and closed with a smaller force, and the actuator can be downsized. As a result, 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 INVENTION
Hereinafter, an embodiment in which the present invention is applied to a fuel injection valve disposed in a direct injection spark ignition engine will be described with reference to the accompanying drawings.
[0018]
In FIG. 1, the fuel injection valve is provided with a nozzle body 1 that faces a combustion chamber of an engine (not shown) at the tip end (partition wall 9a side) of the casing 9, and this nozzle body 1 has a nozzle hole 1a that opens at the tip, The fuel spray is formed to be injected toward the combustion chamber.
[0019]
Inside the nozzle body 1, a valve body 2a is formed on the side of the nozzle hole 1a, and on the other end, a needle valve 2 formed with a piston portion 2c slidably in contact with the inner periphery of the nozzle body 1 is slidably mounted. A rod portion 2b having a small outer diameter is formed between the valve body 2a and the piston portion 2c.
[0020]
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 2 b of the needle valve 2, and the nozzle 1 a is opened and closed by the needle valve 2 as dictated. The fuel inlet 6 opens to the side surface of the nozzle body 1 and is connected to fuel supply means (not shown).
[0021]
The needle valve 2 is disposed with the piston portion 2c side facing the partition wall 9a constituting the tip of the casing 9, and a differential pressure between the back surface of the piston portion 2a (the surface facing the partition wall 9a) and the partition wall 9a. Chamber 8 is defined.
[0022]
In the differential pressure chamber 8, a return spring 4 that biases the needle valve 2 in the valve closing direction is interposed as an elastic member between the back surface of the piston portion 2c and the partition wall 9a.
[0023]
In addition, a throttle passage 21 formed by a gap or the like is provided between the piston portion 2 c and the inner periphery of the nozzle body 1, and the pressurized fuel supplied to the fuel pressure chamber 3 passes through the throttle passage 21 and has a differential pressure. It is gradually supplied to the chamber 8.
[0024]
The casing 9 is formed in a cylindrical shape with the partition wall 9a as the bottom, and the piezoelectric actuator 10 made of a piezoelectric element is provided in the inner circumferential space 90 with the opening end 9b facing the right side in the figure opposite to the nozzle body 1. It is retractable in the axial direction (left and right in the figure). And the sealing member 16 is arrange | positioned by the opening end 9b (right side in the figure) of the casing 9, and the inside of the casing 9 is sealed.
[0025]
The piezo actuator 10 is formed by laminating a number of members in which piezoelectric elements made of PZT (lead zirconate titanate) ceramic, PMN (lead magnesium niobate) ceramic, etc. are formed in a disk shape. Electrodes (not shown) are interposed between and at both ends, and the piezo actuator 10 expands and contracts in the axial direction in response to an applied voltage from a controller (not shown).
[0026]
One end of the piezoelectric actuator 10 housed in the casing 9 is in contact with the partition wall 9 a, and the other end is attached with a piston 11 via a plate-like spacer 14, and between the piston 11 and the sealing member 16. A space 18 is defined, and a disc spring-like return spring 22 is interposed in the space 18 as a biasing means that biases the piezo actuator 10 in the contracting direction via the piston 11.
[0027]
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 the top surface 11a faces the space 18 side, while the cylindrical portion 11b. (Cylindrical part) is accommodated in the casing 9 with the nozzle body 1 side facing.
[0028]
The top surface 11a of the piston 11 contacts the return spring 22 as described above, while the cylindrical portion 11b is formed in an annular groove 9c formed at a predetermined depth from an inner peripheral end surface 9d formed inside the opening end 9b. To be stowed. 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 surface 9d is disposed at a predetermined depth from the opening end 9b so as not to contact the inner side of the top surface 11a of the sliding piston 11.
[0029]
And the end surface of the cylindrical part 11b of the piston 11 accommodated in the annular groove 9c defines the pressure chamber 7 between the bottom part of the annular groove 9c, and the annular groove facing the inner periphery and the outer periphery of the cylindrical part 11b. O-rings 12 and 12 are interposed as seal members on the inner periphery of 9c to define the pressure chamber 7, the space 18 and the internal space 90 of the casing 9 housing the piezoelectric actuator 10. Note that the O-ring 12 is disposed at a position that can be slidably contacted with the inner and outer circumferences of the cylindrical portion 11b even when the piezo actuator 10 is extended to the maximum. The piezo actuator 10 is sealed by preventing the fuel from leaking and preventing the atmosphere from entering and leaving the space 90 from the space 18 on the sealing member 16 side.
[0030]
Next, the pressure chamber 7 defined between the end surface of the cylindrical portion 11 b of the piston 11 and the annular groove 9 c is connected to the back surface of the piston portion 2 c of the needle valve 2 via the communication passage 17 formed in the casing 9. It communicates with the differential pressure chamber 8 defined in FIG.
[0031]
Here, when 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 V1 of the pressure chamber 7 is
V1 = A1 × S1 (1)
It is represented by
[0032]
On the other hand, when 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
V2 = A2 × S2 (2)
And assuming that V1 = V2, from the above equations (1) and (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
A1> A2 (4)
As a result, the stroke S2 of the needle valve 2 can be increased as compared to the minute stroke S1 of the piezo actuator 10.
[0033]
Next, the operation will be described.
[0034]
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 contracts and is urged by the return spring 22 to the maximum contracted position. Therefore, the stroke S1 becomes the minimum value, and the volume V1 of the pressure chamber 7 becomes the minimum from the above equation (1).
[0035]
At this time, the pressure in the fuel pressure chamber 3, the differential pressure chamber 8 and the pressure chamber 7 is equalized by the throttle passage 21 provided between the piston portion 2 c of the needle valve 2 and the inner periphery of the cylinder body 1. No differential pressure is generated in the second piston portion 2c. 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 from the above equation (2).
[0036]
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 nozzle 1a while the engine is stopped.
[0037]
In order to start the engine, when fuel is pumped from a 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 has finished flowing into the differential pressure chamber 8 and the pressure chamber 7 through the throttle passage 21 of the piston portion 2c, a differential pressure is generated in the piston portion 2c with the needle valve 2, but the pressure chamber 7, the piezoelectric actuator 10 contracts and the piston 11 is also urged in the contracting direction by the return spring 22, so that the volume V 1 remains at a minimum, and the needle valve 2 is driven 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 at a timing other than the predetermined injection timing.
[0038]
The 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.
[0039]
As the piezo actuator 10 extends, the piston 11 is displaced toward the sealing member 16, so that the stroke S <b> 1 increases, the volume V <b> 1 of the pressure chamber 7 increases rapidly, and the pressure rapidly decreases.
[0040]
Accordingly, the pressure in the differential pressure chamber 8 communicating with the pressure chamber 7 via the communication path 17 is also suddenly reduced. Therefore, 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 is reduced. In the direction, the piston portion 2c is displaced against the urging force of the return spring 4, and the needle valve 2 is opened. When the needle valve 2 is opened, the pressurized fuel in the fuel pressure chamber 3 is injected from a nozzle 1a into a combustion chamber (not shown).
[0041]
The stroke S2 when the needle valve 2 is opened is set so that 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 shown in the above expression (4). Therefore, even if the stroke S1 of the piezo actuator 10 is small, the stroke S2 of the needle valve 2 can be increased according to the ratio of the pressure receiving area, so that the stroke necessary for opening the needle valve 2 can be easily secured. It can be done.
[0042]
Next, the closing operation of the fuel injection valve is performed by cutting off the application of voltage to the piezo actuator 10 and driving it to contract.
[0043]
The piezo actuator 10 contracts when the voltage is interrupted, and is displaced to the most contracted position by the urging force of the return spring 22, and the volume V1 of the pressure chamber 7 becomes the minimum value again.
[0044]
As the piezo actuator 10 contracts, the piston 11 is displaced toward the needle valve 2, so that the stroke S1 is reduced, the volume V1 of the pressure chamber 7 is rapidly reduced, and the pressure is rapidly increased.
[0045]
Accordingly, the pressure in the differential pressure chamber 8 communicating with the pressure chamber 7 via the communication path 17 also increases rapidly, so that a differential pressure is generated in the piston portion 2c of the needle valve 2 and the volume V2 of the differential pressure chamber 8 increases. Since the piston portion 2c is displaced in the direction and 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 is connected to the nozzle body 1. The fuel injection from the fuel pressure chamber 3 to the combustion chamber is stopped by contacting the seat portion and sealing the nozzle hole 1a.
[0046]
Since the valve closing operation operates in the same manner even when the application of voltage is interrupted due to disconnection of the energization path to the piezo actuator 10, fail-safe in the event of failure of the electrical system can be ensured. .
[0047]
Thus, the piston portion 2c is formed on the proximal end side of the needle valve 2, and the differential pressure chamber 8 is defined between the back surface of the piston portion 2c and the partition wall 9a of the casing 9, and through the piston portion 2c. A return spring 4 for biasing in the valve closing direction is provided, and a space 90 that supports the base end of the piezo actuator 10 on the partition wall 9a side is defined on the inner periphery of the casing 9 that opens at the end opposite to the partition wall 9a. Further, an annular groove 9c is formed so as to surround the end portion of the space 90, and the pressure chamber 7 is defined between the cylindrical portion 11b of the piston 11 attached to the other end of the piezoelectric actuator 10 and the annular groove 9c. In addition, since the differential pressure chamber 8 and the pressure chamber 7 are communicated with each other via the communication passage 17, the piezo actuator 10 is driven to extend when energized, thereby generating a differential pressure across the piston portion 2c to generate a needle valve. When the current is cut off, the actuator 10 contracts and the pressure applied to the piston 2c increases, and the return spring 4 can reliably close the valve. When the piezo actuator contracts, it is possible to reliably prevent the fuel from being temporarily injected, and the reliability of the fuel injection valve using the piezo actuator 10 can be improved.
[0048]
And since the assembly of the piezo actuator 10, the piston 11 and the return spring 22 can be performed from the open end 9b side of the casing 9, it becomes possible to work easily and improve productivity. In addition, even after mounting on the engine, the piezo actuator 10, the piston 11 and the return spring 22 can be easily maintained by simply removing the sealing member 16, greatly improving the maintainability of the fuel injection valve. It can be improved.
[0049]
Further, since the pressure receiving area A1 of the piston 11 is set larger than the pressure receiving area A2 of the piston portion 2c, the opening amount of the needle valve 2 necessary for fuel injection is ensured even if the displacement amount of the piezo actuator 10 is very small. Therefore, the degree of freedom in designing the fuel injection valve can be improved.
[0050]
Further, the O-rings 12 and 12 provided in the annular groove 9c seal the space 90 in which the piezo actuator 10 is accommodated, and reliably separate the space 18 on the sealing member 16 side from the annular pressure chamber 7. Therefore, contact with the outside air of the piezo actuator 10 can be prevented, so that a short circuit due to dew condensation can be avoided reliably, and the reliability of the fuel injection valve using the piezo actuator 10 can be further improved.
[0051]
FIG. 2 shows a second embodiment, in which the space 18 defined between the top surface 11a of the piston 11 and the sealing member 16 in the first embodiment is communicated with the fuel inlet 6 to form the second fuel pressure chamber 20. In addition, the disc spring-like return spring 22 is eliminated, and other configurations are the same as those in the first embodiment.
[0052]
A second fuel pressure chamber 20 defined between the top surface 11 a of the piston 11 and the sealing member 16 communicates with the fuel inlet 6 through a fuel pressure supply passage 19 formed in the casing 9.
[0053]
When the engine is stopped, as in the first embodiment, 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, and the valve body 2 is reliably closed. The fuel is prevented from leaking from the nozzle hole 1a.
[0054]
In order to start the engine, when fuel is pumped from a fuel supply means (not shown) to the fuel inlet 6 at a predetermined fuel pressure Pf, first, the fuel pressure Pf is led to the fuel pressure chamber 3 and the second fuel pressure chamber 20 to increase the pressure. The fuel pressure Pf applied to the second fuel pressure chamber 20 urges the piston 11 in the contraction direction of the piezoelectric actuator 10 in place of the return spring 22 of the first embodiment, and the fuel pressure Pf applied to the piston 11 and the return spring 4. The needle valve 2 can be kept closed by the urging force.
[0055]
When a voltage is applied to the piezo actuator 10 in synchronism with the engine rotation to open the fuel injection valve, the piezo actuator 10 expands against the fuel pressure Pf in the second fuel pressure chamber 20, and the piston is the same as described above. The needle valve 2 is driven to open by generating a differential pressure across the portion 2c.
[0056]
Similarly, the closing operation of the fuel injection valve is performed by cutting off the application of voltage to the piezo actuator 10 and driving it to contract.
[0057]
The piezo actuator 10 contracts when the voltage is cut off, 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 to minimize the volume V1 of the pressure chamber 7, which is the same as in the first embodiment. Similarly, 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 to close the nozzle 1a, and the fuel injection from the fuel pressure chamber 3 to the combustion chamber is stopped. To do.
[0058]
In this case, the piezo actuator 10 only needs to have a driving force that expands and contracts against the fuel pressure Pf applied to the piston 11, and the load due to the fuel pressure Pf is always constant, and the return spring 22 of the first embodiment. Thus, since the load fluctuation does not occur, the needle valve 2 can be reliably opened and closed with a smaller force, and the piezo actuator 10 can be reduced in size, thereby reducing the manufacturing cost. Further, the degree of freedom in designing the fuel injection valve can be further improved.
[0059]
In the above embodiment, the piezoelectric actuator 10 made of a piezoelectric element is used as the actuator for driving the piston 11. However, although not shown, magnetostriction using a magnetostrictive element that expands and contracts according to the strength of the magnetic field is shown. The same applies when an actuator or a giant magnetostrictive actuator is employed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fuel injection valve showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a fuel injection valve showing a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Nozzle body 1a Injection hole 2 Needle valve 2a Valve body 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 portion (tubular portion)
12 O-ring 17 Communication passage 18 Space 19 Fuel pressure supply passage 20 Second fuel pressure chamber (biasing means)
21 Restriction passage 22 Return spring (biasing means)
90 spaces

Claims (5)

A fuel pressure chamber through which pressurized fuel is guided;
A needle valve that is displaced according to the differential pressure between the fuel pressure chamber and the differential pressure chamber;
A nozzle that is opened and closed by a needle valve to inject fuel in the fuel pressure 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;
In a fuel injection valve of an engine provided with a piston that increases or decreases the pressure in a differential pressure chamber according to expansion and contraction of an actuator,
The differential pressure chamber is defined on the back side of the piston portion formed on the proximal end side of the needle valve, and the casing having an open end on the substantially opposite side of the injection port is in a space formed on the open end side. Pressure that accommodates the actuator and attaches a piston to the actuator end on the open end side, and is defined between the casing and the piston, and expands the volume when the actuator extends, while reducing the volume when contracting An engine fuel injection valve characterized in that a chamber is formed, and a biasing means for biasing the piston in a contracting direction of the actuator and a communication passage communicating the pressure chamber and the differential pressure chamber are provided. 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. The piston is provided with a cylindrical portion that surrounds the actuator, while the casing is formed with an annular groove that accommodates the cylindrical portion from the opening end side, and the pressure chamber is annularly connected to the end surface of the cylindrical portion of the piston. The engine fuel injection valve according to claim 1, wherein the fuel injection valve is defined between the groove and the groove. 4. A seal member is interposed between the annular groove and the inner periphery and the outer periphery of the cylindrical portion, and the inside of the piston and the outside on the open end side are defined with the pressure chamber interposed therebetween. The fuel injection valve of the described engine. 2. The fuel injection valve for an engine according to claim 1, wherein the urging unit includes a second fuel pressure chamber that is defined on an opening end side of the piston and into which pressurized fuel is guided.

Images