JP2005180299A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device having a simplified structure.
An injector 300 is connected to an injector body 40 having an internal space 40i, an opening / closing valve 6 for opening / closing a fuel injection port 41, a control valve 5 for controlling the operation of the opening / closing valve 6, and a control valve 5. A transmission member 45, and an actuator 1 connected to the transmission member 45 and having a piezoelectric element 2d. The control valve 5, the transmission member 45, and the actuator 1 are provided substantially coaxially in the internal space 40i.
The surface of the actuator 1 that contacts the transmission member 45 holds the transmission member 45 so as to absorb the vibration of the transmission member 45 in the direction orthogonal to the axis.
[Selection] Figure 3

Description

  The present invention relates to a fuel injection device, and more particularly to a fuel injection device using a piezoelectric element or a magnetostrictive element.

Conventionally, a fuel injection device using a piezoelectric element as an actuator is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-13352 (Patent Document 1).
Japanese Patent Application Laid-Open No. 2002-13452

  In the conventional fuel injection device, a coil spring or the like is used because the piezoelectric element must be operated with a compressive load. However, a large space is required, which is disadvantageous for downsizing.

  Further, since the displacement of the piezoelectric element is small, a displacement expansion chamber structure or the like must be used in order to take out the displacement effectively, so that a complicated structure is required and displacement transmission loss increases.

  Further, due to its complexity, loss is increased in transmitting displacement from the piezo unit to the control valve, and accuracy as an injection control device is also deteriorated.

  In addition, the fuel in the displacement transmission chamber leaks and flows out during operation, but requires a function to replenish it in a timely manner. However, when bubbles are mixed in, it may not be easily removed and a malfunction may occur.

  A piezoelectric element is a brittle material, and unless it is operated by a compressive load, the fatigue life is significantly reduced. For this purpose, it is necessary to apply a load in advance. In addition, since the thermal expansion coefficient of the element is remarkably smaller than that of the surrounding material, a stable compressive load cannot always be applied unless a coil spring or the like is used.

  In addition, since the displacement of the piezoelectric element is small and the coefficient of thermal expansion is small, it is necessary to adopt a displacement expansion chamber structure for absorbing the difference in thermal expansion from the material for fixing the piezoelectric element.

  Furthermore, since the displacement of the piezoelectric element is small, if the coaxiality, vibration, roughness, etc. between the elements that transmit the drive from the piezoelectric element to the control valve are large, the displacement transmission loss becomes large and the control accuracy is also deteriorated.

  Further, when the seat of the check valve is on the top side, the fuel escapes through the passage and it is difficult to replenish the fuel.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a fuel injection device having a simplified structure.

  A fuel injection device according to the present invention is connected to a body having an internal space and a fuel injection port, an open / close valve that opens and closes the fuel injection port, a control valve that controls the operation of the open / close valve, and the control valve. A transmission member, and an actuator connected to the transmission member and having a piezoelectric element or a magnetostrictive element. The control valve, the transmission member, and the actuator are provided substantially coaxially in the internal space.

  In the fuel injection device configured as described above, the control valve, the transmission member, and the actuator are provided substantially coaxially in the internal space. Therefore, the arrangement thereof can be simplified, and the configuration of the fuel injection device is simplified. be able to.

  Preferably, the surface of the actuator that comes into contact with the transmission member holds the transmission member so as to absorb the deflection of the transmission member in the direction orthogonal to the axis. In this case, even if the shaft centers of the actuator and the transmission member are deviated, this deviation can be absorbed, the force can be transmitted without waste, and the displacement can be reliably transmitted.

  Preferably, the internal space is filled with high-pressure fuel injected from the injection port and low-pressure fuel having a pressure lower than that of the high-pressure fuel. The transmission member includes a piston provided on the actuator side and a cylinder provided on the control valve side and forming a displacement transmission chamber filled with low-pressure fuel between the piston. The cylinder is provided with a check valve that allows low pressure fuel to flow into the displacement transmission chamber and prevents the low pressure fuel from flowing out of the displacement transmission chamber.

  In this case, since the check valve is provided, the pressure in the displacement transmission chamber rises and the air in the displacement transmission chamber is discharged from the gap between the piston and the cylinder. When the pressure in the displacement transmission chamber decreases, the check valve operates to fill the displacement transmission chamber with low-pressure fuel. As a result, the air in the displacement transmission chamber can be discharged and the displacement transmission chamber can always be filled with low-pressure fuel.

  More preferably, the contact surface between the control valve and the cylinder is a spherical surface. In this case, even if the degree of coaxiality between the piston and the actuator is shifted and tilted, this shake can be absorbed even if the cylinder is shaken in various directions on the control valve. As a result, the displacement can be reliably transmitted.

  Preferably, the actuator has a housing having a thermal expansion coefficient substantially the same as that of the piezoelectric element or the magnetostrictive element, and the piezoelectric element is accommodated in advance by the casing. . In this case, since the casing has a thermal expansion coefficient comparable to that of the piezoelectric element or magnetostrictive element, a compressive load is always stably applied to the piezoelectric element or magnetostrictive element even if the temperature of the material changes. As a result, durability is ensured. In addition, since the conventional coil spring is not used, the fuel injection device can be configured in a small space.

  According to the present invention, a fuel injection device with a simplified structure can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
1 is a block diagram of a fuel injection mechanism according to Embodiment 1 of the present invention. Referring to FIG. 1, a fuel injection mechanism 1000 includes an ECU 100 as a control unit, an EDU 200 that receives a signal from the ECU, and an injector 300 as a fuel injection device connected to the EDU 200. ECU 100 has map data related to fuel injection. The ECU and EDU are connected by control signal lines for the charge switch and the discharge switch. A plurality of injectors 300 corresponding to the number of cylinders are connected to the EDU 200.

  FIG. 2 is a circuit diagram showing a circuit in the EDU in FIG. Referring to FIG. 2, in EDU 200, DC-DC coil 201 connected to a power source, DC-DC diode 202 connected to DC-DC coil 201, DC connecting DC-DC coil 201 and ground are connected. A DC switch 203; A DC-DC field capacitor 205 is provided between the DC-DC diode 202 and ground. A charge switch 206 is provided so as to be connected to the DC-DC electric field capacitor 205. A discharge switch 208 is provided between the charge switch 206 and ground.

  An actuator 1 and a cylinder selection switch 321 are provided for each injector.

  FIG. 3 is a cross-sectional view of an injector according to the present invention. FIG. 4 is an enlarged sectional view showing the piston 3, the displacement transmission cylinder 4 and the control valve 5 in FIG. Referring to FIGS. 3 and 4, an injector 300 as a fuel injection device according to the first embodiment of the present invention includes an injector body 40 having an internal space 40 i and an on-off valve 6 that opens and closes a fuel injection port 41. A control valve 5 for controlling the operation of the on-off valve 6, a transmission member 45 connected to the control valve 5, and an actuator 1 connected to the transmission member 45 and having a piezoelectric element 2d. The control valve 5, the transmission member 45, and the actuator 1 are provided substantially coaxially on the shaft 5c in the internal space 40i.

  The surface 2f of the actuator 1 that contacts the transmission member 45 holds the transmission member 45 so as to absorb the vibration of the transmission member 45 in the direction orthogonal to the shaft 5c.

  The internal space 40 i is filled with the high-pressure fuel 9 injected from the injection port 41 and the low-pressure fuel 10 having a pressure lower than that of the high-pressure fuel 9. The transmission member 45 includes a piston 3 provided on the actuator 1 side and a displacement transmission cylinder 4 provided on the control valve 5 side and forming a displacement transmission chamber 8 filled with the low-pressure fuel 10 between the piston 3. Including. The displacement transmission cylinder 4 is provided with a ball valve 7 as a check valve that allows low pressure fuel to flow into the displacement transmission chamber 8 and prevents the low pressure fuel 10 from flowing out of the displacement transmission chamber 8. The spherical surface 5a of the control valve 5 and the spherical surface 4f of the displacement transmission cylinder 4 are in contact with each other. The actuator 1 has a housing 2b having substantially the same thermal expansion coefficient as that of the piezoelectric element 2d, and a compressive load is applied to the piezoelectric element 2d by the housing.

  The actuator 1 includes a housing 2b made of a material having a low thermal expansion coefficient and lids 2a and 2c for sealing the housing 2b. The casing 2b is welded to the lid 2a and 2c in a state where a compressive load is applied to the piezoelectric element 2d so as to apply a preload to the lids 2a and 2c. As a result, since the casing 2b has a thermal expansion coefficient comparable to that of the piezoelectric element 2d, the preload is always stably maintained even when the material temperature changes, and a compressive load is applied to the piezoelectric element 2d, resulting in durability. Is secured. In addition, since a conventional coil spring for applying a load is not used, the actuator 1 can be stored in a small space.

  A guide 2g is provided in the housing 2b in order to freely hold the piston 3 for transmitting the displacement on a plane. As a result, even if the axes of the housing 2b and the piston 3 are displaced, the axis of the displacement transmission cylinder 4 in which the piston 3 is accommodated can coincide with the axis of the control valve 5, and the displacement can be transmitted without waste.

  In order to absorb the difference in coefficient of thermal expansion between the injector body 40 and the piezoelectric element 2d, a displacement transmission chamber 8 is provided between the displacement transmission cylinder 4 and the piston 3. In order to always replenish the displacement transmission chamber 8 with the low-pressure fuel 10, the ball valve 7 is configured to face the lower seat. The suction passage 4 a is provided below the ball valve 7. By configuring the ball valve 7 downward, the ball valve 7 is seated when the actuator 1 is operated even if the low pressure fuel 10 in the displacement transmission chamber 8 is removed. And air is discharged from the gap between the displacement transmission cylinders 4. When the piezoelectric element 2d contracts, the pressure in the displacement transmission chamber 8 decreases. As a result, the ball valve 7 moves upward, and the low pressure fuel 10 is filled in the displacement transmission chamber 8.

  The surface for transmitting the displacement to the control valve 5 is a spherical surface 5a, and the displacement transmitting cylinder 4 is also provided with a receiving surface for the spherical surface 4f. As a result, even if the coaxiality between the piston 3 and the housing 2b is shifted and inclined, a biased load is not applied from the displacement transmission cylinder 4 to the control valve 5, and the displacement can be transmitted reliably.

  A spring 11 is provided between the piston 3 and the displacement transmission cylinder 4 to urge the displacement transmission cylinder 4 in a direction away from the piston 3. Further, a spring 12 is provided on the lower surface of the control valve 5, and the spring 12 biases the control valve 5 toward the actuator 1. A spring 13 is provided so as to contact the opening / closing valve 6, and the spring 13 biases the opening / closing valve 6 toward the injection port 41.

  Next, the operation of the actuator 1 shown in FIGS. 3 and 4 will be described. FIG. 5 is a cross-sectional view showing the control valve when the injection is stopped. 3 to 5, no voltage is applied to actuator 1 when injection is stopped. As a result, the actuator 1 is in a contracted state. At this time, the control valve 5 is pressed against the actuator 1 by the spring 12. Thereby, as shown in FIG. 5, the space between the high pressure fuel 9 and the low pressure fuel 10 is closed. As a result, the high pressure fuel 9 does not move to the low pressure fuel 10 side. In the fuel pressure chamber 44, since the opening / closing valve 6 is pushed toward the injection port 41 by the spring 13, the high-pressure fuel 9 is not ejected from the injection port 41.

  FIG. 6 is a cross-sectional view showing a control valve during fuel injection. Referring to FIG. 6, a voltage is applied to actuator 1 from EDU 200 during injection. Specifically, the charging switch 206 in the EDU 200 is turned on. Thereby, the electric charge in the DC-DC electric field capacitor 205 flows into the piezoelectric element 2 d constituting the actuator 1. The piezoelectric element 2d expands. The piston 3, the displacement transmission cylinder 4 and the control valve 5 connected to the actuator 1 move toward the injection port 41. As a result, when the control valve 5 is lifted as shown in FIG. 6, a gap is formed, and the high-pressure fuel 9 flows to the low-pressure fuel 10 side through the gap as indicated by an arrow 4j. As a result, the pressure of the high-pressure fuel 9 decreases and the opening / closing valve 6 moves in a direction approaching the spring 13. At this time, the high-pressure fuel 9 is injected from the injection port 41 where the injection port 41 is opened.

  Injector 300 configured as described above according to the first embodiment of the present invention can be simplified in structure and reduced in size as compared with a conventional injector.

  Although the embodiments of the present invention have been described above, the embodiments described herein can be variously modified. First, the piezoelectric element is shown as the material constituting the actuator 1 in the embodiment, but the present invention is not limited to this, and the actuator can be composed of a magnetostrictive element. Further, the present invention can be applied as an injector of a diesel engine using a common rail. The present invention can also be applied as an injector for a gasoline engine.

  Furthermore, the piston 3 can be composed of two pistons, a large diameter piston and a small diameter piston, and fluid can be filled between the large diameter piston and the small diameter piston. Thereby, the displacement of the large diameter piston can be enlarged and transmitted to the small diameter piston.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be used in the field of automobile fuel injection devices.

It is a block diagram of the fuel-injection mechanism according to Embodiment 1 of this invention. It is a circuit diagram which shows the circuit in EDU in FIG. It is sectional drawing of the injector according to this invention. It is sectional drawing which expands and shows the piston 3, the displacement transmission cylinder 4, and the control valve 5 in FIG. It is sectional drawing which shows the control valve at the time of an injection stop. It is sectional drawing which shows the control valve at the time of fuel injection.

Explanation of symbols

  1 Actuator, 2a, 2c Lid, 2b Housing, 2d Piezoelectric element, 3 Piston, 4 Displacement cylinder, 4f Spherical surface, 5 Control valve, 5a Spherical surface, 6 Open / close valve, 9 High pressure fuel, 10 Low pressure fuel, 40 Body, 41 injection port, 300 injector.

Claims (5)

A housing having an internal space;
An on-off valve that opens and closes the fuel injection port;
A control valve for controlling the operation of the on-off valve;
A transmission member connected to the control valve; and an actuator connected to the transmission member and composed of a piezoelectric element or a magnetostrictive element;
The fuel injection device, wherein the control valve, the transmission member, and the actuator are provided substantially coaxially in the internal space.   2. The fuel injection device according to claim 1, wherein a surface of the actuator that contacts the transmission member holds the transmission member so as to absorb a vibration of the transmission member in a direction orthogonal to the axis.   The internal space is filled with high-pressure fuel injected from the injection port and low-pressure fuel whose pressure is lower than that of the high-pressure fuel, and the transmission member includes a piston provided on the actuator side, and the control A cylinder that is provided on a valve side and forms a displacement transmission chamber filled with low-pressure fuel between the piston and the piston, and the cylinder transmits the low-pressure fuel into the displacement transmission chamber, and the displacement transmission chamber The fuel injection device according to claim 1, further comprising a check valve that prevents the low-pressure fuel from flowing out of the fuel.   The fuel injection device according to any one of claims 1 to 3, wherein a contact surface between the control valve and the cylinder is a spherical surface.   The actuator has a casing having a thermal expansion coefficient substantially the same as that of a piezoelectric element or a magnetostrictive element, and the piezoelectric element or the magnetostrictive element is preliminarily applied to the piezoelectric element or the magnetostrictive element by the casing. The fuel injection device according to any one of claims 1 to 4.

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