WO2010095252A1

WO2010095252A1 - Fuel injection device

Info

Publication number: WO2010095252A1
Application number: PCT/JP2009/053134
Authority: WO
Inventors: 大前和広
Original assignee: トヨタ自動車株式会社
Priority date: 2009-02-23
Filing date: 2009-02-23
Publication date: 2010-08-26
Also published as: JPWO2010095252A1; JP5071582B2

Abstract

A fuel injection device (100) comprises a fuel injection valve (1) and an ECU (12). The fuel injection valve (1) comprises a nozzle body (2) having a nozzle hole (4) and a seat part (5) at the end, and a needle (7) which is provided with a support part (7a) slidably supported on the inner peripheral wall (2a) of the nozzle body (2), which is so disposed in the nozzle body (2) that a fuel storage chamber (6) is formed in the nozzle body (2) on the tip end side than the support part (7a), and which opens and closes the nozzle hole by approaching and separating from the seat part (5). The fuel injection valve (1) further comprises a piezo actuator (10) which is so disposed on the proximal end side than the needle (7) that a needle upper chamber (8) is formed between the piezo actuator (10) and the support part (7a), and which moves the needle (7) in the valve closing direction when a voltage is applied thereto. The ECU (12) so gradually lowers the voltage applied to the piezo actuator (10) that the closed state of the needle (7) is maintained when an internal combustion engine is stopped.

Description

Fuel injection device

The present invention relates to a fuel injection device.

Conventionally, various types of fuel injection valves have been proposed. For example, in an injection valve that uses a piezoelectric element as an actuator, an injection valve has been proposed that aims to simplify the structure and suppress variations in fuel injection amount. Specifically, the needle that opens and closes the nozzle hole by contacting and separating from the seat surface in which the nozzle hole is opened, the biasing means that biases the needle in the valve opening direction, and the needle is directly expanded by being extended by the applied voltage. An injection valve including a piezoelectric element that is driven in a valve closing direction has been proposed (see Patent Document 1). Such an injection valve has a simple configuration, and by releasing the voltage applied to the piezoelectric element, the needle is moved in the valve opening direction to inject fuel.

Japanese Patent Laid-Open No. 10-159675

However, as described above, when a piezoelectric element that extends by an applied voltage and directly drives the needle in the valve closing direction, the following phenomenon is considered to be a problem.
That is, when the internal combustion engine is stopped and the voltage application to the piezoelectric element is released, the needle moves in the valve opening direction, which may cause unintended fuel injection.

Therefore, an object of the present invention is to avoid fuel injection when the internal combustion engine is stopped in a fuel injection valve that moves the needle in the valve opening direction by releasing the voltage applied to the piezoelectric element.

In order to solve the above-described problems, a fuel injection device disclosed in the present specification includes a nozzle body provided with a nozzle hole and a seat portion at a tip portion, and a support portion that is slidably supported on an inner peripheral wall of the nozzle body A needle that is disposed in the nozzle body so as to form a fuel storage chamber on the tip side of the support portion in the nozzle body, and that opens and closes the nozzle hole in contact with and away from the seat portion; A piezoelectric element which is disposed on the proximal end side of the needle so as to form a needle upper chamber between the support portion and moves the needle in a valve closing direction by application of a voltage, and a high pressure in the fuel storage chamber A fuel supply valve for supplying fuel; and a control means for controlling application of a voltage to the piezoelectric element. The control means closes the needle when the internal combustion engine is stopped. Status It is characterized by gradually lowering the voltage applied to the piezoelectric element so as to maintain.

Thus, when the internal combustion engine is stopped, the voltage applied to the piezoelectric element is gradually reduced so that the closed state of the needle is maintained, thereby gradually reducing the expansion / contraction amount of the piezoelectric element. Thereby, the volume in the needle upper chamber is gradually increased, and the pressure of the fuel in the needle upper chamber is gradually decreased accordingly. At this time, high-pressure fuel is still stored in the fuel storage chamber. That is, the pressure in the fuel storage chamber is higher than the fuel pressure in the needle upper chamber. As a result, a static fuel leak occurs between the sliding portion separating the fuel storage chamber and the needle upper chamber, that is, the inner peripheral wall of the nozzle body and the support portion of the needle, and the fuel in the fuel storage chamber gradually flows into the needle upper portion. Flows into the chamber. Here, the pressure receiving area of the needle on the fuel storage chamber side is smaller than the pressure receiving area on the needle upper chamber side by an area corresponding to the seat portion. For this reason, even if the pressure in the fuel storage chamber is slightly higher than the pressure in the needle upper chamber, the needle can be kept closed.

Thus, by gradually releasing the voltage application to the piezoelectric element, the closed valve state of the needle can be maintained even when the voltage is released when the internal combustion engine is stopped.

The control means in such a fuel injection device can perform pressure reduction control for reducing the pressure in the fuel supply path after reducing the voltage applied to the piezoelectric element. For example, the control means can perform pressure reduction control for reducing the pressure in the fuel supply path by opening a pressure reduction valve mounted on the common rail. When the internal combustion engine is stopped, it is common to reduce the pressure of the common rail. However, by performing such pressure reduction control, it is possible to satisfy the demand for pressure reduction of the common rail. Here, the reason why the pressure reduction control is performed at such timing is as follows.

The static leakage of fuel from the fuel storage chamber to the needle upper chamber as described above occurs when the pressure in the fuel storage chamber is higher than the pressure in the needle upper chamber. If the piezoelectric element has already been shrunk and the expansion of the volume in the needle upper chamber has been completed, then the pressure drop in the needle upper chamber due to the volume expansion of the needle upper chamber will not occur. If the expansion of the volume of the needle upper chamber accompanying the fuel replenishment due to the static fuel leak is completed, no further static leak is necessary. Therefore, the pressure in the fuel supply path is reduced after the expansion of the volume of the needle upper chamber is completed. If the pressure in the fuel storage chamber is reduced by this, it is possible to satisfy the request for maintaining the needle closed state and the pressure reduction of the common rail.

The fuel injection valve in such a fuel injection device may further include an urging means for urging the needle in the valve closing direction.

In order to maintain the valve closed state of the needle, the force acting on the needle from the needle upper chamber side must exceed the force acting on the needle from the fuel storage chamber side. On the other hand, in order to cause a static leak of fuel from the fuel storage chamber side to the needle upper chamber side, the pressure on the fuel storage chamber side must be higher than the pressure on the needle upper chamber side. Here, the larger the difference between the pressure on the fuel storage chamber side and the pressure on the needle upper chamber side, the greater the amount of static leak and the faster the fuel is supplied to the needle upper chamber. Therefore, it is easy to follow the rapid expansion of the volume of the needle upper chamber. For this reason, the speed at which the voltage applied to the piezoelectric element is lowered can also be increased.

Here, if a biasing means for biasing the needle in the valve closing direction is provided, the pressure in the needle upper chamber can be further reduced. This is because the biasing means can compensate for the decrease in the force acting on the needle due to the pressure in the needle upper chamber being lowered.

The control means in such a fuel injection device can apply a voltage to the piezoelectric element before starting the internal combustion engine when starting the internal combustion engine.

When the fuel injection valve provided in the fuel injection device disclosed in this specification is in a closed state, a voltage is applied to the piezoelectric element. However, the fuel injection valve when the internal combustion engine is stopped has the needle closed while no voltage is applied to the piezoelectric element. For this reason, when starting the internal combustion engine, a voltage must be applied to the piezoelectric element, and the needle must be closed with the piezoelectric element extended. Therefore, when the internal combustion engine is started, voltage is applied to the piezoelectric element before the internal combustion engine is started. Thereby, it will be in the state which can inject a fuel by canceling the application of the voltage to a piezoelectric element.

The fuel injection valve may include a fuel discharge path for discharging fuel from the needle upper chamber, and a check valve disposed in the fuel discharge path and discharging fuel in the needle upper chamber.

The needle upper chamber when the internal combustion engine is stopped is filled with fuel flowing from the fuel storage chamber. If the piezoelectric element is extended in this state filled with fuel, the pressure in the needle upper chamber will increase too much. In some cases, the needle is pressed against the nozzle body, and the fuel injection valve may be damaged.

Therefore, a rise in pressure in the needle upper chamber is suppressed by providing a fuel discharge path for discharging the fuel from the needle upper chamber and a check valve disposed in the fuel discharge path for discharging the fuel in the needle upper chamber. In addition, the piezoelectric element can be in an extended state.

In the fuel injection valve that moves the needle in the valve opening direction by releasing the voltage applied to the piezoelectric element, it is possible to avoid fuel injection when the internal combustion engine is stopped.

FIG. 1 is an explanatory diagram showing a schematic configuration of the fuel injection device. FIG. 2A is an explanatory diagram of a cross-sectional dimension of the support portion of the needle. FIG. 2B is an explanatory diagram of the cross-sectional dimensions of the tip of the needle. FIG. 3 is an explanatory view showing a state of the fuel injection valve waiting for fuel injection. FIG. 4 is an explanatory diagram showing the state of the fuel injection valve during fuel injection. FIG. 5 is a graph showing the relationship between the voltage applied to the piezo actuator, the needle upper chamber pressure, and the needle lift amount when the internal combustion engine is in operation. FIG. 6 is an explanatory diagram showing the state of the fuel injection valve when the ignition is turned off. FIG. 7 is an explanatory view showing, in an enlarged manner, the periphery of the support portion of the needle when the ignition is turned off. FIG. 8 is a graph showing changes in voltage per unit time of the needle upper chamber volume due to the voltage applied to the piezo actuator, the needle upper chamber pressure, the static leak amount, and the piezo displacement when the ignition is turned off. FIG. 9 is an explanatory diagram showing the state of the fuel injection valve when the ignition is turned on. FIG. 10 is an explanatory view showing a schematic configuration of another fuel injection valve.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram showing a schematic configuration of the fuel injection device 100. The fuel injection device 100 includes a fuel injection valve 1. The fuel injection valve 1 includes a nozzle body 2 having a nozzle hole 4 and a seat portion 5 provided at the tip. The nozzle body 2 is provided with a sac chamber 3 at the tip, and a nozzle hole 4 is provided so that the sac chamber 3 communicates with the outside. The seat portion 5 is located at the upper edge of the sack chamber 3.

The fuel injection valve 1 includes a needle 7. The needle 7 includes a support portion 7 a that is slidably supported on the inner peripheral wall 2 a of the nozzle body 2. Further, the needle 7 is disposed in the nozzle body 2 so as to form the fuel storage chamber 6 on the tip side of the support portion 7 a in the nozzle body 2. Then, the needle 7 opens and closes the nozzle hole 4 with its tip end being in contact with and separating from the seat portion 5. The diameter of the support portion 7a of the needle 7 is set to Dn as shown in FIGS. 1 and 2A. Moreover, the diameter of the part which contact | abuts the sheet | seat part 5 of the needle 7 is set to Ds, as shown in FIG. 1, FIG. 2 (B). The support part 7a is the thickest part. For this reason, the area of the support part 7a is the needle cross-sectional area, and the needle cross-sectional area is An calculated from Dn. Further, the sheet cross-sectional area is As calculated from Ds.

A spring 9 is disposed on the proximal end side of the needle 7. The spring 9 is sandwiched between the needle 7 and the nozzle body 2 and urges the needle 7 in the valve closing direction. The spring 9 is an example of an urging unit in the present invention. The spring force of the spring 9 is set to F.

The fuel injection valve 1 includes a piezoelectric actuator 10 in which piezoelectric elements are stacked. The piezo actuator 10 is disposed on the base end side of the needle 7 so that the needle upper chamber 8 is formed between the piezo actuator 10 and the support portion 7a. The piezoelectric actuator 10 moves the needle 7 in the valve closing direction by applying a voltage. Such a piezo actuator 10 is connected to a piezo drive circuit 11. The piezo drive circuit 11 is electrically connected to an ECU (Electronic Control Unit) 12 corresponding to the control means in the present invention. That is, the ECU 12 controls the application of voltage to the piezo actuator 10. More specifically, the ECU 12 issues a control command to the piezo drive circuit 11, and the piezo drive circuit 11 applies a voltage to the piezo actuator 10 based on the control command of the ECU 12.
The diameter of the piezo actuator 10 is set to Dp, and the cross-sectional area of the piezo actuator 10 is set to Ap.

The fuel injection valve 1 includes a fuel supply path 13 for supplying high-pressure fuel to the fuel storage chamber 6. The fuel supply path 13 is connected to the common rail 15. The common rail 15 includes a pressure reducing valve 15a. The pressure reducing valve 15a is electrically connected to the ECU 12. When the ECU 12 opens the pressure reducing valve 15a, the pressure reducing control in the present invention is executed. That is, by opening the pressure reducing valve 15a and reducing the pressure in the common rail 15, the pressure in the fuel supply path 13, and hence the pressure in the fuel storage chamber 6, can be reduced.

The needle upper chamber 8 and the fuel supply path 13 are connected by a fuel discharge path 14. The fuel discharge path 14 is provided for discharging fuel from the needle upper chamber 8. The fuel discharge path 14 is provided with a check valve 14a. The check valve 14a is arranged so as to allow only the fuel flowing in the direction discharged from the needle upper chamber 8.

The operation of the fuel injection device 100 as described above will be described with reference to the drawings.

First, the state where the fuel injection valve 1 is waiting for fuel injection when the internal combustion engine is operating will be described with reference to FIG. The piezo actuator 10 provided in the fuel injection valve 1 of the present embodiment moves the needle 7 in the valve closing direction, that is, the distal end side by applying a voltage.

The fuel storage chamber 6 is replenished with high-pressure fuel from the common rail 15 shown in FIG. Here, the common rail pressure is Pc. On the other hand, since the piezo actuator 10 to which a voltage is applied from the piezo drive circuit 11 is extended, the fuel in the needle upper chamber 8 is in a pressurized state. In the state shown in FIG. 3, the needle upper chamber pressure Pup is the common rail pressure Pc at the maximum, and the high pressure fuel at the common rail pressure Pc is flowing in the fuel supply path 13, so that the check valve 14 a is opened. There is nothing.

Here, the valve opening pressure Pup_op, that is, the needle upper chamber pressure Pup when the valve is opened is determined as follows.

The force to move the needle 7 in the valve opening direction is
Pc × (An−As) + Psac × (As)
The force to move the needle 7 in the valve closing direction is
Pup × An + F
Pc: Common rail pressure An: Needle cross-sectional area As: Seat cross-sectional area Psac: Suck chamber pressure Pup: Needle upper chamber pressure F: Spring force From the above, the needle valve opening conditions are
Pc × (An−As) + Psac × (As)
= Pup × An + F
From this, the valve opening pressure Pup_op is
Pup_op
= (Pc × (An−As) + Psac × (As) −F) / An
It becomes.

When the piezo drive circuit 11 applies a voltage to the piezo actuator 10 and the piezo actuator 10 extends thereby, the needle upper chamber pressure Pup is higher than the valve opening pressure Pup_op, the valve closing state is maintained.

Next, a state in which the fuel injection valve 1 performs fuel injection when the internal combustion engine is operating will be described with reference to FIG. The piezo actuator 10 provided in the fuel injection valve 1 of the present embodiment moves the needle 7 in the valve opening direction, that is, the base end side by releasing the application of voltage.

The fuel storage chamber 6 is replenished with high-pressure fuel from the common rail 15 shown in FIG. On the other hand, the volume of the needle upper chamber 8 is expanded by the contraction of the piezoelectric actuator 10 from which the voltage application from the piezoelectric drive circuit 11 is released. Along with this, the needle upper chamber pressure Pup decreases.

Then, when the reduced needle upper chamber pressure Pup reaches the valve opening pressure Pup_op, the needle 7 moves in the valve opening direction, whereby the fuel in the sac chamber 3 and the fuel storage chamber 6 is injected from the injection hole 4. . In the state shown in FIG. 4 as well, the needle upper chamber pressure Pup is the common rail pressure Pc at the maximum, and the high pressure fuel of the common rail pressure Pc is circulating in the fuel supply path 13, so that the check valve 14a is opened. Never do.

The fuel injection valve 1 performs fuel injection by performing the above operation.
Here, the movement of the needle 7 is organized with reference to FIG. The piezo drive circuit 11 first releases the voltage at the time t1 from the state where the voltage is applied to the piezo actuator 10. Here, the voltage applied to the piezo actuator 10 and the amount of expansion / contraction of the piezo actuator 10 are in a corresponding relationship. When the voltage is released at time t1, the piezo actuator 10 starts to contract. Along with this, the needle upper chamber pressure Pup also decreases.

At time t2, once the needle 7 starts to move, the contraction amount of the piezo actuator 10 and the needle lift amount are synchronized. For this reason, the needle upper chamber pressure Pup is kept constant during the time t2 to t3. Here, the time t3 indicates the time when the needle lift amount reaches the maximum, that is, reaches the full lift.

The voltage drop to the piezo actuator 10 continues after time t3. Therefore, the needle upper chamber pressure Pup decreases again during the time t3 to t4. At time t4, the piezoelectric actuator 10 is in the most contracted state. From this time t4 to t5, the needle upper chamber pressure Pup is constant.

From time t5, the piezo drive circuit 11 starts applying a voltage to the piezo actuator 10. Then, since the piezo actuator 10 starts to expand, the needle upper chamber pressure Pup starts to increase. However, the needle upper chamber pressure Pup between times t5 and t6 has not yet reached the pressure at which the needle 7 can be moved. Therefore, the needle lift amount does not change between times t5 and t6.

At time t6, once the needle 7 starts to move, the extension amount of the piezo actuator 10 and the needle lift amount are synchronized. For this reason, the needle upper chamber pressure Pup is kept constant during the time t6 to t7. Here, time t <b> 7 indicates the time when the needle lift amount is minimum, that is, the needle 7 is seated on the seat portion 5.

After the time t7, the voltage increase to the piezo actuator 10 continues. For this reason, the needle upper chamber pressure Pup rises again during the time t7 to t8. At time t8, the piezoelectric actuator 10 is in the most extended state. From this time t7 to t8, the needle upper chamber pressure Pup is constant. The above is the movement of the needle 7.

In the fuel injection valve 1 operating as described above, the application of voltage to the piezo actuator 10 is released when the internal combustion engine is stopped. In general, measures are also taken to reduce the common rail pressure Pc. Here, if the voltage of the piezo actuator 10 is suddenly released after the common rail pressure Pc is reduced, the following inconveniences can be considered.

When the common rail pressure Pc is lowered, the pressure in the fuel storage chamber 6 is also lowered accordingly. In this state, if the voltage applied to the piezo actuator 10 is suddenly released, the volume of the needle upper chamber 8 is expanded, and the needle upper chamber pressure Pup is reduced, bubbles are generated in the fuel in the needle upper chamber 8. Is concerned. If air bubbles are present in the needle upper chamber 8, it is considered that fuel injection at the next start of the internal combustion engine becomes unstable, and it becomes difficult to secure a predetermined amount of fuel injection.

Therefore, in the fuel injection device 100 of the present embodiment, the following control is performed. That is, the ECU 12 gradually decreases the voltage applied to the piezo actuator 10 so that the closed state of the needle 7 is maintained when the internal combustion engine is stopped.

FIG. 6 is an explanatory diagram showing the state of the fuel injection valve 1 when the ignition is turned off when the internal combustion engine is stopped. FIG. 7 shows an enlarged view of the periphery of the support portion 7a of the needle 7 when the ignition is turned off. FIG. 8 is a graph showing the transition of the voltage applied to the piezo actuator 10 when the ignition is turned off, the needle upper chamber pressure, the amount of static leak, and the volume change amount of the needle upper chamber due to piezo displacement.

First, when the ECU 12 detects an ignition off signal, the ECU 12 issues a command to the piezo drive circuit 11 to reduce the voltage. Here, the rate of voltage decrease is set so that the amount of contraction of the piezoelectric actuator 10 becomes ΔL per unit time as shown in FIG. Thereby, the amount of change per unit time of the volume of the needle upper chamber 8 changes to a constant after reaching ΔL × Ap.

Thus, when the contraction amount per unit time of the piezoelectric actuator 10 is ΔL, the volume Vp of the needle upper chamber 8 changes by Ap × ΔL per unit time. Along with this, the change amount ΔPup per unit time of the needle upper chamber pressure Pup is:

ΔPup = −K × Ap × ΔL / Vp
K: Fuel bulk modulus

It becomes.

Due to such a decrease in the needle upper chamber pressure Pup, the fuel in the fuel storage chamber 6 flows into the needle upper chamber 8. This will be described with reference to FIG. The support portion 7a of the needle 7 is slidably fitted to the inner peripheral wall 2a of the nozzle body 9, and there is a clearance between them. When the pressure in the fuel storage chamber 6, that is, the common rail pressure Pc and the needle upper chamber pressure Pup satisfy predetermined conditions, the fuel storage chamber 6 moves to the needle upper chamber 8 as shown by an arrow 20 in FIG. A static fuel leak occurs. That is, the fuel in the fuel storage chamber 6 flows into the needle upper chamber 8 and is filled in the needle upper chamber 8.

The clearance leak amount Qleak flowing from the fuel storage chamber 6 into the needle upper chamber 8 is

Qleak = (Pc−Pup) ³ × C
C: Coefficient

It is defined as
This Qleak increases as time passes, as shown in FIG. When this Qleak is equal to ΔL × Ap, the needle upper chamber pressure Pup is stabilized.
Note that the coefficient C is a numerical value in consideration of a clearance variation due to a pressure variation.

As described above, when the voltage applied to the piezo actuator 10 is gradually reduced when the internal combustion engine is stopped, the needle upper chamber 8 is gradually filled with fuel. Thereby, it can suppress that needle upper chamber pressure Pup reduces until it reaches valve opening pressure Pup_op, and the valve 7 closed state of needle 7 is maintained. In this manner, the application of voltage to the piezo actuator 10 can be canceled while maintaining the state where the needle 7 shown in FIG. 6 is seated on the seat portion 5.
Further, since the needle upper chamber 8 is filled with fuel, it is possible to suppress the generation of bubbles in the needle upper chamber 8. As a result, stable fuel injection can be ensured when the internal combustion engine is restarted.

The ECU 12 performs a pressure reduction control for reducing the pressure in the fuel supply path 13 after the release of the voltage application of the piezoelectric actuator 10 is completed. Specifically, the pressure reducing valve 15 a attached to the common rail 15 is opened to reduce the pressure of the common rail 15. As a result, the pressure in the fuel supply path 13 connected to the common rail 15 decreases.

The fuel injection device 100 that operates as described above when the internal combustion engine is stopped operates as follows when the internal combustion engine is started.

When starting the internal combustion engine, the ECU 12 applies a voltage to the piezo actuator 10 before starting the internal combustion engine. Specifically, when the ECU 12 detects an ignition ON signal, the ECU 12 issues a command to apply a voltage to the piezo drive circuit 11.

In response to this command, the piezoelectric actuator 10 to which voltage is applied starts to expand. Thereby, the fuel in the needle upper chamber 8 is compressed, and the needle upper chamber pressure Pup increases. Then, as shown in FIG. 9, the fuel in the needle upper chamber 8 opens the check valve 14 a and is discharged to the fuel supply path 13 through the fuel discharge path 14 as indicated by an arrow 21. Thereby, the fuel injection valve 1 can shift to a state in which a voltage is applied to the piezo actuator 10 while the needle 7 is closed.

Here, when the fuel in the needle upper chamber 8 is discharged to the fuel discharge path 14, an excessive increase in the needle upper chamber pressure Pup can be suppressed.

As described above, according to the fuel injection device 100 of the present embodiment, the internal combustion engine is stopped in the fuel injection valve 1 that moves the needle 7 in the valve opening direction by releasing the voltage applied to the piezoelectric actuator 10. It is possible to avoid the fuel injection in the state of being performed. Further, it is possible to suppress the generation of bubbles in the needle upper chamber 8 when the internal combustion engine is stopped.

The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited to these embodiments. Various modifications of these embodiments are within the scope of the present invention, and further, It is apparent from the above description that various other embodiments are possible within the scope.

For example, as shown in FIG. 10, a groove 30 may be provided in the support portion 7 a to adjust the amount of static fuel leak from the fuel storage chamber 6 to the needle upper chamber 8.

Claims

A nozzle body provided with a nozzle hole and a seat at the tip,
A support portion that is slidably supported on the inner peripheral wall of the nozzle body, and is arranged in the nozzle body so as to form a fuel storage chamber on the tip side of the support portion in the nozzle body; A needle that opens and closes the nozzle hole in contact with and away from the seat portion;
A piezoelectric element that is disposed on the proximal side of the needle so as to form a needle upper chamber between the support portion and moves the needle in a valve closing direction by application of a voltage;
A fuel supply path for supplying high-pressure fuel to the fuel storage chamber;
A fuel injection valve comprising:
Control means for controlling the application of voltage to the piezoelectric element;
With
The control means gradually lowers the voltage applied to the piezoelectric element so that the closed state of the needle is maintained when the internal combustion engine is stopped.
2. The fuel injection device according to claim 1, wherein the control means performs pressure reduction control for reducing the pressure in the fuel supply path after reducing the voltage applied to the piezoelectric element.
3. The fuel injection device according to claim 1 or 2, wherein the fuel injection valve further includes an urging means for urging the needle in a valve closing direction.
The fuel injection device according to any one of claims 1 to 3, wherein when the internal combustion engine is started, the control means applies a voltage to the piezoelectric element before the internal combustion engine is started.
A nozzle body provided with a nozzle hole and a seat at the tip,
A support portion that is slidably supported on the inner peripheral wall of the nozzle body, and is arranged in the nozzle body so as to form a fuel storage chamber on the tip side of the support portion in the nozzle body; A needle that opens and closes the nozzle hole in contact with and away from the seat portion;
A piezoelectric element that is disposed on the proximal side of the needle so as to form a needle upper chamber between the support portion and moves the needle in a valve closing direction by application of a voltage;
A fuel supply path for supplying high-pressure fuel to the fuel storage chamber;
A fuel injection valve comprising:
Control means for controlling the application of voltage to the piezoelectric element;
With
The fuel injection device according to claim 1, wherein when the internal combustion engine is started, the control means applies a voltage to the piezoelectric element before the internal combustion engine is started.
The fuel injection valve includes a fuel discharge path for discharging fuel from the needle upper chamber, a check valve disposed in the fuel discharge path and discharging fuel in the needle upper chamber,
The fuel injection device according to claim 4 or 5, further comprising: