JP3740796B2 - Engine fuel injection valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine fuel injection valve that operates a needle valve by changing the fuel pressure before and after the needle valve via an electromagnetic strain actuator.
[0002]
[Prior art]
2. Description of the Related Art Some fuel injection valves and the like provided in automobile engines include a piezo actuator (piezoelectric element) that expands according to an applied voltage, and a needle valve (valve element) is opened via the piezo actuator. By driving the needle valve with a piezo actuator, the high-speed response of the fuel injection valve is enhanced, and the ratio of the maximum injection amount to the minimum injection amount (dynamic range) can be expanded to cope with higher engine output. In addition, since a small amount of fuel can be stably injected, it is possible to meet the demand for reducing fuel consumption of the engine.
[0003]
As this type of fuel injection valve, there is known a valve in which a needle valve is opened based on a differential pressure across it. A fuel pressure chamber and a differential pressure chamber are defined before and after the needle valve. Fuel is introduced into the fuel pressure chamber at a predetermined pressure, and the differential pressure chamber communicates with the fuel pressure chamber through an orifice. A piezo actuator is provided in the differential pressure chamber behind the needle valve, and the opening and closing operation of the needle valve is controlled by the expansion and contraction of the piezo actuator. That is, the pressure in the fuel pressure chamber and the differential pressure chamber before and after the needle valve is equalized through the orifice in a state where the piezoelectric actuator is extended by applying a voltage. At this time, the needle valve is held closed by the tension of the return spring. If both terminals of the piezo actuator are short-circuited from this state and the piezo actuator is instantaneously contracted, the volume of the differential pressure chamber behind the needle valve increases. At this time, since the differential pressure chamber communicates with the fuel pressure chamber in front of the needle valve via the orifice, the internal pressure of the differential pressure chamber temporarily decreases and a pressure difference in the valve opening direction is generated before and after the needle valve. To do. As a result, the needle valve is opened against the return spring, and the nozzle is opened to inject fuel. (For a known example of this type of fuel injection valve, see, for example, JP-A-6-280711.)
[0004]
[Problems to be solved by the invention]
By the way, in the conventional fuel injection valve using such a piezo actuator, when the needle valve is seated on the seat portion and the injection port is closed, the pressure in the fuel chamber rises instantaneously, and the fuel is injected at a time other than the predetermined injection timing. There was a possibility of causing secondary injection.
[0005]
Further, when the engine is started, the electric fuel pump is driven before the engine is started, and the fuel pressure led to the fuel pressure chamber is increased. Before starting the engine, the fuel is first introduced into the fuel pressure chamber, and then the fuel flows into the differential pressure chamber via the orifice. Due to the pressure difference, there is a possibility that initial fuel injection will occur when the needle valve is opened against the return spring at a time other than the predetermined injection timing and fuel is injected.
[0006]
On the other hand, there has been a demand for further increasing the responsiveness of opening and closing the needle valve and expanding the setting range of the fuel injection amount.
[0007]
The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent initial fuel injection in a fuel injection valve of an engine and improve the open / close response of a needle valve.
[0008]
[Means for Solving the Problems]
The engine fuel injection valve according to claim 1 is an electromagnetic strain actuator that contracts according to an applied voltage or magnetic field, a pressurizing spring that applies a compressive load to the electromagnetic strain actuator, and a contraction of the electromagnetic strain actuator. A piston that expands the differential pressure chamber, a fuel pressure chamber through which pressurized fuel is guided, a throttle passage that communicates the fuel pressure chamber and the differential pressure chamber, and a needle valve that is displaced according to the pressure difference between the fuel pressure chamber and the differential pressure chamber; An engine fuel injection valve comprising a return spring that urges the needle valve in a valve closing direction and an injection port that is opened and closed by the needle valve and ejects fuel in the fuel pressure chamber, wherein a pressurizing spring is provided between the piston and the needle valve. A transmission member for transmitting the urging force in the valve closing direction of the needle valve is interposed.
[0009]
According to a second aspect of the present invention, there is provided a fuel injection valve for an engine in which a protrusion projecting from a piston toward a needle valve is integrally formed as the transmission member according to the first aspect.
[0010]
According to a third aspect of the present invention, there is provided a fuel injection valve for an engine according to the first or second aspect, wherein the transmission member abuts on the needle valve in the initial stage of closing the needle valve, and the piston directly drives the needle valve. To do.
[0011]
A fuel injection valve for an engine according to claim 4 is provided with an adjusting mechanism for adjusting a position of a base end portion of an electromagnetic distortion actuator with respect to the needle valve in the invention according to any one of claims 1 to 3. It was.
[0012]
The fuel injection valve for an engine according to claim 5 is the fuel injection valve according to any one of claims 1 to 4, wherein an elastic restoring force of the pressurizing spring is applied by a fuel pressure applied to the needle valve before starting the engine. It was set to be larger and smaller than the load due to the fuel pressure applied to the piston after the engine was started.
[0013]
According to a sixth aspect of the present invention, there is provided a fuel injection valve for an engine according to any one of the first to fifth aspects, wherein the pressurizing spring is interposed between a tip portion of a magnetostrictive actuator and a piston. did.
[0014]
A fuel injection valve for an engine according to claim 7 is the casing according to any one of claims 1 to 5, wherein the pressurizing spring is accommodated in a base end portion of an electromagnetic strain actuator and an electromagnetic strain actuator. It was supposed to intervene between.
[0015]
Operation and effect of the invention
In the first aspect of the invention, when the engine is stopped, the electrostrictive actuator contracts and the pressures in the fuel pressure chamber and the differential pressure chamber both decrease, but the needle valve is elasticized by both the return spring and the pressurizing spring. The valve is closed by restoring force.
[0016]
When the low-pressure fuel pump and high-pressure fuel pump are driven before the engine is started and the fuel pressure led to the fuel pressure chamber rises, the needle valve will remain on until the fuel finishes flowing into the differential pressure chamber through the throttle passage. Although a pressure difference occurs between the front and the back, the needle valve is biased in the valve closing direction also by the elastic restoring force of the return spring, and is also biased in the valve closing direction by the elastic restoring force of the pressurizing spring. By increasing the urging force acting in the valve closing direction of the needle valve in this way, it is possible to prevent initial injection in which the needle valve opens at a timing other than the predetermined injection timing and fuel is injected, and start-up failure or the like can be prevented.
[0017]
The electromagnetic distortion actuator contracts when the applied voltage is cut off and short-circuited in synchronism with the engine rotation at the time of starting the engine and opening the fuel injection valve after starting. When the piston moves as the electromagnetic strain actuator contracts, the volume of the differential pressure chamber increases and the pressure decreases. Since the pressure drop in the fuel pressure chamber is transmitted through the throttle passage with a delay, a pressure difference is immediately generated between the differential pressure chamber and the fuel pressure chamber. Due to this pressure difference, the needle valve opens against the return spring, and high-pressure fuel guided to the fuel pressure chamber is injected into the combustion chamber of the engine through the nozzle.
[0018]
In the second aspect of the present invention, the movement of the piston can be reliably transmitted to the needle valve by integrally forming the protrusion protruding from the piston toward the needle valve as the transmission member.
[0019]
According to a third aspect of the present invention, when the fuel injection valve is closed, the electromagnetic strain actuator is extended by applying a voltage in synchronization with the engine rotation, and the piston is moved through the protrusion as the piston starts to move. To drive the needle valve directly in the closing direction. Thereby, the responsiveness at which the needle valve closes can be enhanced, and the setting range of the fuel injection amount can be expanded to cope with the high output of the engine.
[0020]
Since the transmission member is separated from the needle valve when the needle valve is closed, it is avoided that a reaction force when the needle valve is seated on the seat portion is transmitted to the piezo actuator via the transmission member. As a result, the durability of the piezoelectric actuator having low impact resistance can be ensured, and the wear between the needle valve and the seat portion of the nozzle body can be prevented from proceeding.
[0021]
In the invention according to claim 4, the valve opening characteristic of the needle valve can be easily adjusted by adjusting the position of the base end portion of the electromagnetic strain actuator with respect to the needle valve via the adjusting mechanism.
[0022]
In the invention according to claim 5, by setting the elastic restoring force of the pressurizing spring to be larger than the force of the needle valve to open before starting the engine, the needle valve opens at a timing other than the predetermined injection timing. The initial injection in which the fuel is injected can be prevented.
[0023]
By setting the elastic restoring force of the pressurizing spring to be smaller than the fuel pressure applied to the piston before starting the engine, as the fuel pressure driven to the fuel pressure chamber is increased by driving the fuel pump before starting the engine, Fuel flows into the differential pressure chamber through the throttle passage, and the piston compresses the pressurizing spring. As a result, the piston drives the needle valve to open and close following the expansion and contraction of the electromagnetic strain actuator.
[0024]
In the invention according to claim 6, the pressurizing spring is interposed between the tip portion of the electromagnetic strain actuator and the piston, and the needle valve is urged in the valve closing direction by its elastic restoring force. Prevents initial fuel injection that opens at other times.
[0025]
In the invention according to claim 7, the pressurizing spring is interposed between a base end portion of the electromagnetic strain actuator and a casing housing the electromagnetic strain actuator, and the needle valve is attached in the valve closing direction by the elastic restoring force. The needle valve is opened at a timing other than the predetermined injection timing to prevent initial fuel injection.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a fuel injection valve provided in an in-cylinder spark ignition engine will be described with reference to the accompanying drawings.
[0027]
As shown in FIG. 1, the fuel injection valve 7 causes the nozzle body 1 provided at the tip thereof to face a combustion chamber of an engine (not shown). The nozzle body 1 faces the combustion chamber from the ceiling wall of the combustion chamber of the engine, and fuel spray is ejected from a nozzle 1b opened at the tip of the nozzle body 1 toward the crown of the piston.
[0028]
A needle valve 2 is slidably housed inside the nozzle body 1. A fuel pressure chamber 3 is defined around the needle valve 2 inside the nozzle body 1. A nozzle hole 1 b opens at the tip of the nozzle body 1, and the nozzle hole 1 b is opened and closed by a needle valve 2.
[0029]
As shown in FIG. 3, the fuel stored in the fuel tank 59 is sucked up via the low pressure fuel pump 58 driven by the electric motor 54 and is pumped to the high pressure fuel pump 57.
[0030]
The high-pressure fuel pump 57 sends further pressurized fuel to the pressure accumulating chamber 56 and pumps the fuel from the pressure accumulating chamber 56 to the fuel injection valve 7 of each cylinder. A pressure regulator 55 is provided in the fuel return passage 52, and the fuel pressure guided to the fuel injection valve 7 is maintained at a predetermined value by returning the surplus fuel in the pressure accumulating chamber 56 to the fuel tank 59. In the high-pressure fuel pump 57, fuel pumped from a high-pressure fuel pump 57 driven by an electric motor (not shown) or the engine 50 is introduced into the fuel pressure chamber 3 from the fuel inlet passage 6, and the nozzle 1 b is accompanied with the lift of the needle valve 2. Is injected from.
[0031]
The needle valve 2 has a piston portion 2c on the base end side, and defines a throttle passage (orifice) 5 between the outer periphery of the piston portion 2c and the nozzle body 1. The fuel pressure chamber 3 communicates with a differential pressure chamber 8 described later via a throttle passage 5.
[0032]
A return spring 4 that urges the needle valve 2 in the valve closing direction is provided. The return spring 4 is interposed between the piston portion 2 c of the needle valve 2 and the casing 9 in a compressed state, and is disposed coaxially with the needle valve 2.
[0033]
A shim 17 is interposed between the proximal end side of the needle valve 2 and the casing 9, and the movement of the needle valve 2 in the axial direction is restricted by the shim 17. The shim 17 is formed in a disk shape. That is, the maximum lift amount of the needle valve 2 is determined by the thickness of the shim 17.
[0034]
Inside the casing 9, a piston 11 defining a differential pressure chamber 8 is slidably interposed. An O-ring 12 is interposed on the outer periphery of the piston 11. When the O-ring 12 is in sliding contact with the cylindrical inner wall surface of the casing 9, the differential pressure chamber 8 is sealed.
[0035]
A piezo actuator 10 that opens and closes the needle valve 2 via a piston 11 is provided. In the piezo actuator 10, a plurality of disk-shaped piezo elements are stacked with an internal electrode that is also disk-shaped in between.
[0036]
An end plate 15 is coupled to the moving end of the piezo actuator 10. The end plate 15 is in contact with the piston 11 so that the piston 11 follows the expansion and contraction operation of the piezo actuator 10.
[0037]
An end plate 14 is coupled to the fixed end of the piezo actuator 10. Adjust plates 21 and 22 are attached to the opening end of the casing 9. The end plate 14 abuts on the adjustment plate 21 and supports the base end of the piezo actuator 10.
[0038]
The piezoelectric actuator 10 expands when a voltage is applied to each piezoelectric element from a driving amplifier (not shown). At this time, the pressure in the differential pressure chamber 8 is increased and the needle valve 2 is closed. The piezoelectric actuator 10 contracts when the voltage applied to each piezoelectric element is cut off and short-circuited. At this time, the pressure in the differential pressure chamber 8 decreases with respect to the fuel pressure chamber 3, and the needle valve 2 moves in the valve opening direction against the return spring 4.
[0039]
Instead of the piezo actuator 10, a magnetostrictive actuator composed of a giant magnetostrictive element that expands and contracts according to the strength of the applied magnetic field may be used. Here, the piezo actuator and the magnetostrictive actuator are collectively referred to as an electromagnetic strain actuator.
A pulse signal corresponding to the fuel injection amount calculated by the controller 60 is generated, and a voltage corresponding to the pulse signal is applied to the piezo actuator 10 via the driving amplifier.
[0040]
The controller 60 inputs various signals for detecting engine operating conditions such as the rotational speed of the engine 50 and the intake air amount of the engine 50, and calculates the fuel injection amount in accordance with these engine operating conditions.
[0041]
A pressurizing spring 18 having a disc spring shape is interposed between the end plate 15 of the piezoelectric actuator 10 and the piston 11. The piezo actuator 10 is provided with a compressive load by the pressurizing spring 18 to ensure stable operability.
[0042]
At the same time, a projection 19 that projects from the piston 11 toward the needle valve 2 is integrally formed as a transmission member that transmits the urging force (reaction force) of the pressurizing spring 18 to the needle valve 2.
[0043]
The protrusion 19 protrudes in a cylindrical shape from the piston 11 and is provided so as to penetrate the casing 9 and the return spring 4. The protrusion 19 is disposed coaxially with the needle valve 2 and the piston 11.
[0044]
Since the displacement direction of the piezo actuator 10 and the displacement direction of the needle valve 2 coincide with each other in the fuel injection valve 7, the piezo actuator 10, the piston 11, the needle valve 2 and the return spring 4 are arranged in series to simplify the structure. Is peeled off.
[0045]
Before the engine is started and in the initial driving of the fuel pumps 57 and 58, the piston 11 is moved by the biasing force of the pressurizing spring 18 in the process in which the pressure in the differential pressure chamber 8 is increased by the discharge pressure of the fuel pumps 57 and 58. As shown, the protrusion 19 is held in contact with the needle valve 2. As a result, the needle valve 2 is held in the closed position by the urging force of the pressurizing spring 18 and the return spring 4, and the initial fuel injection can be prevented.
[0046]
The elastic restoring force of the pressurizing spring 18 is set to be larger than the force with which the needle valve 2 attempts to open with the pressure introduced from the fuel pumps 57 and 58 to the fuel pressure chamber 3 before the engine is started. That is, the pressure receiving area of the piston portion 2 c of the needle valve 2 is A ₁ , the pressure receiving area of the piston 11 is A ₂ , the area where the needle valve 2 is seated on the seat portion of the nozzle body 1 is A ₃ , and the elastic recovery of the pressurizing spring 18 is performed. If the force is F ₂ , the elastic restoring force of the return spring 4 is F ₁ , the fuel pressure sent from the fuel pumps 57 and 58 before starting the engine is PH, and the pressure in the differential pressure chamber 8 does not reach PH, The following relationship is established.
[0047]
(A ₁ −A ₃ ) × PH <F ₂ + F ₁ (1)
When time elapses from the above state and the high pressure fuel pressure PH acts on the differential pressure chamber 8, the piston 11 abuts against the end plate 15 against the urging force of the pressurizing spring 18 as shown in FIG. 19 is held in a state of not contacting the needle valve 2.
[0048]
The elastic restoring force of the pressurizing spring 18 is set to be smaller than the pressing force acting on the piston 11 when the differential pressure chamber 8 is filled with a predetermined pressure before starting the engine. That is, when the pressure receiving area of the piston 11 is A ₂ and the high pressure fuel pressure is PH, the following relationship is established.
[0049]
F ₂ <A ₂ × PH (2)
The length of the protrusion 19 is such that when the engine is in operation with the piston 11 in contact with the end plate 15, the needle valve 2 is closed by contacting the needle valve 2 only at the initial closing time of the needle valve 2 in which the piezo actuator 10 extends. Set to drive in the direction. That is, in a state where the needle valve 2 is open, the protrusion 19 comes into contact with the needle valve 2 when the piezo actuator 10 is extended. On the other hand, when the needle valve 2 is closed, the protrusion 19 does not contact the needle valve 2 even when the piezo actuator 10 is extended. As a result, the valve closing response of the needle valve 2 is improved, and the impact generated when the needle valve 2 is seated on the seat portion of the nozzle body 1 is avoided from being transmitted to the piezo actuator 10, thereby improving the durability of the piezo actuator 10. Can be maintained.
[0050]
Each adjustment plate 21, 22 is screwed to the inner periphery of the casing 9 and fastened together. By changing the screwing position of each adjustment plate 21, 22 with respect to the casing 9, the position of the protrusion 19 with respect to the needle valve 2 can be finely adjusted.
[0051]
It is comprised as mentioned above, Next, an effect | action is demonstrated.
[0052]
FIG. 1 shows the state of the fuel injection valve 7 when the engine is stopped. The piezo actuator 10 contracts, and the pressures in the fuel pressure chamber 3 and the differential pressure chamber 8 both decrease. At this time, the needle valve 2 is pressed against the seat portion of the nozzle body 1 by the elastic restoring force of the return spring 4, and the elastic restoring force of the pressurizing spring 18 is transmitted through the protrusion 19, and the elastic restoring force of the pressurizing spring 18 is transmitted. Is also pressed against the sheet portion of the nozzle body 1. Thus, the needle valve 2 is seated on the seat portion of the nozzle body 1 to prevent fuel from leaking from the nozzle 1b while the engine is stopped.
[0053]
When the engine 50 is started, before the engine 50 is started, the fuel pumps 57 and 58 are driven, and the fuel pressure led to the fuel pressure chamber 3 increases. At this time, a pressure difference is generated between the front and rear of the needle valve 2 until the fuel finishes flowing into the differential pressure chamber 8 through the throttle passage 5. However, when the needle valve 2 is pressed against the seat portion of the nozzle body 1 by the force obtained by combining the elastic restoring forces of the return spring 4 and the pressurizing spring 18, the needle valve 2 opens at a timing other than the predetermined injection timing. It is possible to prevent initial injection in which fuel is injected.
[0054]
FIG. 2 shows a state before the start in which the pressure in the differential pressure chamber 8 is increased. The piezoelectric actuator 10 is extended by applying a voltage, and the fuel pressure chamber 3 and the differential pressure chamber 8 generated before and after the piston portion 2c. Is equalized through the throttle passage 5. The piston 11 abuts against the end plate 15 against the pressurizing spring 18 by the pressure in the differential pressure chamber 8. That is, in a state in which the fuel is filled in the differential pressure chamber 8 with a predetermined pressure, the pressurizing spring 18 is compressed and the piston 11 is in close contact with the end plate 15.
[0055]
When the fuel injection valve 7 is opened when the engine is started and after the engine is started, the piezo actuator 10 contracts by cutting off and short-circuiting the voltage applied in synchronization with the engine rotation. When the piston 11 moves as the piezo actuator 10 contracts, the volume of the differential pressure chamber 8 increases, and fuel from the fuel pressure chamber 3 is supplied to the differential pressure chamber 8 through the throttle passage 5. At this time, the pressure drop in the fuel pressure chamber 3 is transmitted through the throttle passage 5 with a delay, so that a pressure difference immediately occurs between the differential pressure chamber 8 and the fuel pressure chamber 3. Due to this pressure difference, the needle valve 2 opens the nozzle hole 1b against the return spring 4, and high-pressure fuel guided to the fuel pressure chamber 3 is injected into the combustion chamber of the engine 50 through the nozzle hole 1b. Even when the pressure in the differential pressure chamber 8 decreases, the differential pressure chamber 8 is maintained at a pressure higher than atmospheric pressure, so that the pressurizing spring 18 is compressed and the piston 11 is in close contact with the end plate 18. Is maintained.
[0056]
When the fuel injection valve 7 is closed, the piezo actuator 10 is extended by applying a voltage in synchronization with the engine rotation, and the needle valve 2 is directly moved through the protrusion 19 as the piston 11 starts moving. Driven in the valve closing direction. As the piston 11 moves, the pressure in the differential pressure chamber 8 immediately recovers, and the needle valve 2 moves due to the pressure difference between the differential pressure chamber 8 and the fuel pressure chamber 3 and the urging force of the return spring 4, and the seat portion of the nozzle body 1. Sit on. When the needle valve 2 is seated on the seat portion, the nozzle hole 1b is closed, and fuel injection is stopped.
[0057]
In this way, when the needle valve 2 is directly driven in the valve closing direction via the protrusion 19 at the initial stage of closing the needle valve 2, the responsiveness that the needle valve 2 is closed is enhanced. As a result, the setting range of the fuel injection amount can be expanded to cope with high engine output.
[0058]
When the needle valve 2 is seated on the seat portion of the nozzle body 1, the protrusion 19 does not contact the needle valve 2 even if the piezo actuator 10 is extended. Thereby, it is avoided that the reaction force when the needle valve 2 is seated on the seat portion of the nozzle body 1 is transmitted to the piezo actuator 10 via the protrusion 19. As a result, sufficient durability can be ensured even with the piezo actuator 10 having low impact resistance, and the wear between the needle valve 2 and the seat portion of the nozzle body 1 can be prevented.
[0059]
That is, the protrusion 19 abuts on the needle valve 2 and is held closed when the discharge pressure of the fuel pumps 57 and 58 is not acting on the differential pressure chamber 8.
[0060]
Next, the embodiment shown in FIG. 4 will be described. In addition, the same code | symbol is attached | subjected to a corresponding part with FIG.
[0061]
The pressurizing spring 18 is interposed between the end plate 14 connected to the base end side of the piezo actuator 10 and the adjustment plate 21.
[0062]
The piston 11 is connected to the tip side of the piezo actuator 10. Also in this case, as a transmission member that transmits the urging force of the pressurizing spring 18 to the needle valve 2, a protrusion 19 that protrudes from the piston 11 toward the needle valve 2 is integrally formed.
[0063]
It is comprised as mentioned above, Next, an effect | action is demonstrated.
[0064]
FIG. 4 shows the state of the fuel injection valve 7 when the engine is stopped. The piezo actuator 10 contracts, and the pressures in the fuel pressure chamber 3 and the differential pressure chamber 8 both decrease. At this time, the needle valve 2 is pressed against the seat portion of the nozzle body 1 by the elastic restoring force of the return spring 4, and the elastic restoring force of the pressurizing spring 18 is passed through the end plate 14, the piezoelectric actuator 10, the piston 11 and the protrusion 19. It is transmitted and is pressed against the seat portion of the nozzle body 1 even by the elastic restoring force of the pressurizing spring 18. Thus, the needle valve 2 is seated on the seat portion of the nozzle body 1 to prevent fuel from leaking from the nozzle 1b while the engine is stopped.
[0065]
When the fuel pumps 57 and 58 are driven before the engine is started and the fuel pressure guided to the fuel pressure chamber 3 rises, the needle valve remains until the fuel has flown into the differential pressure chamber 8 through the throttle passage 5. A pressure difference occurs before and after 2. However, when the needle valve 2 is pressed against the seat portion of the nozzle body 1 by the force obtained by combining the elastic restoring forces of the return spring 4 and the pressurizing spring 18, the needle valve 2 opens at a timing other than the predetermined injection timing. It is possible to prevent initial injection in which fuel is injected.
[0066]
If the pressure in the fuel pressure chamber 3 and the differential pressure chamber 8 generated before and after the piston portion 2 c is equalized through the throttle passage 5 before the engine is started, the pressure in the differential pressure chamber 8 causes the piston 11, the piezoelectric actuator 10, and the end. The plate 14 moves to the left in the drawing, and the end plate 14 is brought into contact with the adjustment plate 21 against the pressurizing spring 18. Thereby, the base end of the piezo actuator 10 is supported by the adjustment plate 21, and the needle valve 2 can be prepared to open and close.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fuel injection valve before starting an engine according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the fuel injection valve after starting.
FIG. 3 is a system diagram of the same fuel supply system.
FIG. 4 is a cross-sectional view of a fuel injection valve before starting an engine according to another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Nozzle body 1b Injection hole 2 Needle valve 2c Piston part 3 Fuel pressure chamber 4 Return spring 5 Restriction passage 6 Fuel inlet 7 Fuel injection valve 8 Differential pressure chamber 9 Casing 10 Piezo actuator 11 Piston 18 Pressure spring

Claims (7)

An electrostrictive actuator that contracts in response to an applied voltage or magnetic field;
A pressurizing spring that applies a compressive load to the electromagnetic strain actuator;
A piston that expands the differential pressure chamber according to the contraction of the electromagnetic strain actuator;
A fuel pressure chamber through which pressurized fuel is guided;
A throttle passage communicating the fuel pressure chamber and the differential pressure chamber;
A needle valve that is displaced according to the pressure difference between the fuel pressure chamber and the differential pressure chamber;
A return spring that urges the needle valve in the closing direction;
A nozzle that is opened and closed by a needle valve to inject fuel in the fuel pressure chamber;
In a fuel injection valve of an engine comprising
A fuel injection valve for an engine, wherein a transmission member for transmitting an urging force of a pressurizing spring in a valve closing direction of the needle valve is interposed between the piston and the needle valve. The engine fuel injection valve according to claim 1, wherein a projection projecting from the piston toward the needle valve is integrally formed as the transmission member. The transmission member is brought into contact with the needle valve at the initial stage of closing the needle valve, and the piston directly drives the needle valve, and the transmission member is separated from the needle valve when the needle valve is closed. Item 3. The fuel injection valve for an engine according to Item 1 or 2. The engine fuel injection valve according to any one of claims 1 to 3, further comprising an adjustment mechanism that adjusts a position of a proximal end portion of the electromagnetic strain actuator with respect to the needle valve. The elastic restoring force of the pressurizing spring is set to be larger than the load due to the fuel pressure applied to the needle valve before starting the engine and smaller than the load due to the fuel pressure applied to the piston after starting the engine. The fuel injection valve for an engine according to any one of the above. The engine fuel injection valve according to any one of claims 1 to 5, wherein the pressurizing spring is interposed between a tip portion of an electromagnetic strain actuator and a piston. 6. The fuel injection valve for an engine according to claim 1, wherein the pressurizing spring is interposed between a base end portion of the electromagnetic strain actuator and a casing housing the electromagnetic strain actuator. .

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