JPH02112664A - Piezoelectric type fuel injection valve - Google Patents

Abstract

PURPOSE:To secure a requisite and proper displacement as well as to make stable injection quantity control performable by performing the on-off operation of a valve system through a shaft rod solidly connected to an almost U-shaped metal member supporting and fixing a piezoelectric element. CONSTITUTION:A piezoelectric element 10 is inserted into, and fixed to a groove 9b of a U-shaped metal member 9. A guide plate 13 makes both shoulders 9a of the metal member 9 contact with an inner surface of a casing 1, and is movably held in this casing 1 with the contact position as a fulcrum. In addition, a shaft rod 12 is solidly attached to a central part of the metal member 9, partially covering the piezoelectric element 10, and properly extended in the lower part. When high voltage is impressed on the piezoelectric element 10 hereat, it is displaced against restraint in the metal member 9, and the displacement and force direction are directed to the axial direction from the radial direction via a fulcrum contacting with the casing 1. With this constitution, the shaft rod 12 secures a sufficient displacement and moves in the lower part, so that on-off operation of a valve system 18 is properly performable.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel supply device for an internal combustion engine.

In particular, the present invention relates to a mechanism for amplifying the displacement of the piezoelectric element to obtain a stable number of injections in a fuel injection valve using a piezoelectric element.

[Conventional technology]

For example, Japanese Patent Laid-Open No. 59-206668 proposes the use of a pressure rod as a drive source for a seven-actuator for operating a fuel injection valve or controlling a fuel injection device of an internal combustion engine. Piezoelectric This is because the piezoelectric actuator can control the fuel injection valve or fuel injection device with more precise timing than an electromagnetic actuator because the element causes displacement almost instantaneously when a voltage is applied.

In its simplest configuration, a piezoelectric actuator comprises a hollow casing in which a generally cylindrical piezoelectric element is arranged. This pressure! The element is generally constructed by laminating a plurality of thin disks, for example about 100, made of piezoelectric material. A thin interlayer electrode made of gold X foil or the like is sandwiched between each disk. Every other electrode is connected to a positive lead and a negative lead. If an electric field is applied to each piezoelectric disk by applying a voltage of, for example, about 400 V between both electrodes, each disk will expand in the thickness direction, causing an axial displacement of about 40 to 50 μm at the end of the cylindrical piezoelectric element. occurs. This displacement is taken out to the outside by an output means such as an output rond or a piston, and is used to open and close the flow path and the injection hole.

[Problem M to be Solved by the Invention] However, as described above, since the amount of displacement of the piezoelectric actuator is minute, the shape of the nozzle is subject to significant restrictions. For this reason, there was a problem in that accurate injection amount control could not be performed. In addition, in order to avoid this and obtain a practically stable injection amount, it is necessary to use means for enlarging the displacement, such as increasing the number of laminated piezoelectric bodies, or installing a displacement enlarging device. A fuel injection valve constructed in this way is large and heavy, and therefore has the problem of not being able to be made smaller and lighter.

This invention was made by focusing on such conventional problems, and in a device that uses a piezoelectric element to obtain a high-speed valve opening and closing response, it is possible to obtain a necessary and appropriate amount of displacement with a simple structure. The purpose of the present invention is to provide a small and lightweight piezoelectric fuel injection valve that can ensure stable injection amount control.

[Means to solve the problem]

The above object is to provide a piezoelectric fuel injection valve that uses a piezoelectric element as an actuator, opens and closes a valve device by displacement of the piezoelectric element, and injects and supplies fuel. a metal member, a guide member that brings both shoulder portions of the metal member into contact with the inner surface of the casing and holds the metal member movably within the casing using the contact position as a fulcrum; This is achieved by opening and closing a valve device provided in a valve casing, the shaft rod being mechanically coupled to the surface casing.

[Effect]

The effect is that the piezoelectric element is m
When a U-shaped metal member is displaced against its restraining force, the direction of the displacement and force is directed from the radial direction to the axial direction via the fulcrum that contacts the valve case, and the amount of displacement is It is enlarged several times. As a result, the shaft rod integrally connected to the metal member can move downward with a sufficient amount of displacement to appropriately open and close the valve device.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of a piezoelectric fuel injection valve according to this invention. FIG. 2 is a sectional view taken along line I-1 of the first embodiment, and FIG. 3 is a schematic diagram showing the positional relationship between the piezoelectric element, which is the main part of the present invention, and a substantially U-shaped metal member.

In FIG. 1, 1 is a cylindrical actuator casing, 2 is a casing side plate integrally formed with the casing 1, and has fuel passage holes 3. A fuel pipe joint 5 having a fuel filter 4 and for attaching a fuel pipe (not shown); a lead wire outlet 6; and a sealing member 7 for sealing the lead wire outlet 6 and preventing fuel leakage to the outside. Consists of.

Inside the casing 1, on the side facing the fuel pipe joint 5, there is a rectangular cavity 8 whose negative side is open, and side grooves communicating with the fuel passage hole 3 on both sides of the long sides of the cavity 8. 8a is provided. Reference numeral 9 denotes a substantially U-shaped metal member inserted into the cavity 8 in the casing 1;
a is inserted and fixed to both corners of the bottom of the cavity 8 so as to make contact with the angle. The metal member 9 freely moves within the cavity 8 using the shoulder 9a as a fulcrum. Reference numeral 10 denotes a columnar piezoelectric element, which is inserted and fixed into the groove 9b of the metal member 9 with some compression force.

The columnar piezoelectric 1I47-io is constructed by laminating a large number of thin plates (not shown) with a thickness of 0.1 to 0.5 - made of piezoelectric material whose main component is lead zirconate titanate. When a voltage of several hundred volts is applied to both ends of each thin plate, an axial displacement of about 50 μm occurs.

As is well known, positive electrode foils and negative electrode foils (both not shown) are alternately held between the piezoelectric thin plates and are connected to lead wires 11, respectively. 12 is a shaft rod integrally attached to the center of the metal member 9;
2 partially covers the piezoelectric element 10 and extends downward as appropriate. Reference numeral 13 supports the piezoelectric element 10 to such an extent that it does not interfere with the operation of the piezoelectric element 10, and holds the shoulder portion 9a of the metal member 9 coupled thereto in a position where it contacts both bottom corners of the hollow portion 8 in the casing 1 without wobbling. A guide plate made entirely or partially of non-metallic material. 14 is a valve casing, and each member listed so far is the large diameter part 1 of this casing 14.
4a via the O-ring 15, and then fixed by caulking the upper edge 14b of the casing 14 to the actuator casing 1 side. At this time, the shaft rod 12 that is integrally connected to the metal member 9 is connected to the casing 14.
It is inserted into the guide hole 1b provided inside with a slight gap. The tip of this shaft rod 12 is connected to the small diameter portion 1 of the casing 14.
It is located in the cavity 17 within 4c. Also, this small diameter portion 14c
The valve device 18 is connected to a step 19 provided in the cavity 17.
A spacer 20 is attached to the lower edge 1 of the small diameter portion 14c via an O-ring 21 provided to prevent fuel leakage to the outside.
It is fixed by caulking 4d to the valve device 18 side.

This valve device 18 is a generally used outward-opening seat valve, and a tip tapered portion 23a of a plunger 23 is in line contact with a tip tapered portion 22a of a nozzle body 22. In order to obtain this contact force (seat force), the plunger 23 is pushed up against the nozzle body 22 via the coiled spring 24 and the spring seat 25, as shown in FIG. The plunger 23 has a fuel passage groove 2.
A plurality of fuel passage holes 3 are fixedly provided in the large diameter portion 14a.
Communicate with.

When this valve device 18 is crimped onto the small diameter portion 14c of the casing 14 as described above, the tip of the rod shaft 12 and the head 23b of the plunger 23 should be in contact with each other, or be positioned with a very small gap. This is adjusted using the spacer 20.

Next, the operation of the piezoelectric fuel injection valve of the present invention will be explained. 1. When a pulsed high voltage is applied to the lead wire 11 from a control circuit/circuit (not shown), when the pulse voltage is ON, the piezoelectric element 1
0 expands against the restraining force of the metal member 9. In the figure, it is displaced in the radial direction.

Due to this displacement of the piezoelectric element 10, the metal member 9 is moved to the shoulder portion 9a.
As a fulcrum, the other surface moves in the axial direction while the surface in contact with the piezoelectric element 10 moves in the radial direction.

This operation will be explained using FIG. 3. FIG. 3 shows a columnar piezoelectric element 10, a substantially U-shaped metal member 9, and a shaft rod that is integrally connected to the metal member 9, partially covers the piezoelectric element 10, and extends downward as appropriate. 6 is an explanatory diagram three-dimensionally depicting the relative positional relationship between the elements 12 and 12. In other words, with the displacement of the columnar piezoelectric element 10, the shoulder 9a of the metal member 9 and the arm Ql are and move in the Q1 direction. Therefore, the other arm QZ is Q with the point P as the fulcrum.
Move in the z force direction, ie down the axis.

As is clear from the figure without going into details, this amount of transfer IjlI is as follows.
This is amplified with respect to the displacement amount of the piezoelectric element 10, which is approximately the arm length ratio Qs/Q1.

The columnar piezoelectric element 10 used in this example has a thickness of 0 and an in.
It is made by laminating about 200 n thin plates. The relationship between force and displacement when a voltage of 400 V is applied is as shown in Figure 46. In other words, the piezoelectric element 10 has a free displacement of 50
It changes by about μm, and when it is restrained, a force of about 80 kg can be obtained. Now, if we restrict the displacement to 25 μm,
- The metal member 9 is subjected to a force of approximately 40 kg. This force is propagated from the arm Q+ to Ω2 via the fulcrum P, and as a result, the amount of movement in the R2 direction can be increased by about 5 times.

By the operation based on the above, the displacement and force of the columnar piezoelectric element 10 are accurately propagated to the shaft rod 12 integrally connected to the metal member 9. Therefore, the plunger 23 of the valve device 18, which is placed in contact with the tip of the shaft rod 12 or with a very small gap, is quickly pushed down against the repulsive force of the coiled spring 24, and the nozzle body 22 The tip tapered portion 22a of the plunger 23 is the tip tapered portion 22a of the plunger 23.
A is separated from a, and a gap is secured that allows the passage of fuel.

At this time, 1. Fuel pressurized and supplied by a fuel pump (not shown) is passed from the fuel passage hole 3 to the side groove 8a provided in the cavity 8, the cavity 17 in the small diameter part 14c of the valve casing 14, and the fuel passage 26 to the outside. Jet-fed.

On the other hand, the pulse voltage applied to the columnar piezoelectric cord 10 is O
When it becomes FF, the piezoelectric element 10 quickly contracts. Along with this, the metal member 9 quickly returns to its original shape in this case as well, and the shaft rod 12 that is connected to it inside the body eliminates the force and displacement that push down the plunger 23 of the valve device 18. Therefore, the plunger 23 quickly returns to its original position due to the restoring force of the coiled spring 24 and stops injecting fuel. Therefore, the fuel injection supply ends.6 FIG. 5 is a sectional view showing another embodiment of the present invention. The same symbols as in FIG. 1 indicate the same parts. In this embodiment, a U-shaped metal member 50 is disposed in the actuator casing 1, and a new cavity 51 is provided. That is, a tapered portion 51a that slopes toward the fuel passage hole 3 is provided on the inner surface of the casing side plate 2 of the casing 1 so that the shoulder portion 50a of the metal member 50 can smoothly and freely make line contact within the casing side plate 2. It is designed to allow for exercise. This embodiment also provides the same functions and effects as the first embodiment.

Fuel injection amount control in such a piezoelectric fuel injection valve is as follows:
The reciprocating motion of the plunger 23 is performed by adjusting the ON/OFF ratio of the pulse voltage, and the reciprocating motion of the plunger 23 is reliably performed in response to the high-speed operation of the piezoelectric element 10, and is performed by a large amount of movement. Manufacturing constraints (manufacturing accuracy.

(variations, etc.) are alleviated, and a stable injection amount can be obtained.

FIG. 6 is a longitudinal sectional view showing a third embodiment of the present invention,
In Figure 1 regarding an inward-opening seat valve using a needle valve, 100 indicates that the valve casing is connected to the valve guide cylinder 1.
01, has an actuator cylinder 102 integrally. 10
3 is an upper casing side plate that is inserted and fixed into the portion 100a of the valve casing 100, and 104 is the °valve guide tube 1.
A needle valve having guide portions 104a and 104b for sliding coaxially with extremely high precision within the actuator tube 102;
06 is a piston provided on the movable end side of the piezoelectric element 105, and is inserted coaxially into the actuator cylinder 102 with extremely high precision. A leg 107 is integrally connected to the piston 106 and is made of an elastic member. This leg 1
07, the tip portion 107a has a spherical shape, and the tip portion 107a is formed in an annular groove 100b provided in the valve casing 100.
07a is inserted closely. 108 is a leaf spring that is biased to press the piston 106 against the piezoelectric element 105 within the actuator cylinder 102, and 109 is a support member provided at one end of the piezoelectric element 105, which has a conical groove 109a. 1
Reference numeral 10 denotes a fixing plate having a spherical portion 110a, which is inserted and fixed into a portion 102a of the actuator cylinder 102. The spherical part 11
0a is connected and fixed to the conical groove 1098 of the support member 109, and holds the piezoelectric element 105 coaxially within the actuator tube 102. 111 is a seal member provided on the piston 106, and 112 is a spring adjuster provided in the upper casing side plate 103, which has a fuel introduction hole 112a. 11
3 is the spring adjuster 112 and the needle valve 10
The needle valve 104 is interposed between the ends 104c of the needle valve 104.
The tip end 104d of the valve seat 10 in the valve guide cylinder 101
It is a coiled spring that is seated on 1a. Note that 114 is a lead wire, and 115 is a packing.

Next, the operation will be explained. Pressure fI from a control circuit (not shown)! When a voltage is applied to the cord 105, the piezoelectric cord 1
05 is displaced against the restoring force of the leaf spring lO8, and the piston 1
06 to the left in the figure.

As the piston 106 moves, the leg 107 made of an elastic member integrally connected to the piston 106 moves to the left at the same time, but the tip 107a of the leg 107 is already in close contact with the annular groove 100b of the valve casing 100. The movement to the left is corrected and it is elastically deformed upward in the figure.

Here, this operation will be explained using the schematic diagram of FIG.

In the figure, if the root of the leg 107 that is integrally connected to the piston 106 is a point, the tip 1078 is a point b, and the center position of the leg 107 is a point P, the displacement of the piezoelectric element 105 causes a point a. moves to the left by ΔX, that is, to point a'. Since point b is a fixed end, the leg portion 107 is elastically deformed by the displacement ΔX, and its point P moves to point P'. That is, an upward movement amount X is obtained, which is approximately several times this movement amount or displacement ΔX.

Returning to FIG. 6, when the end portion 104c of the needle valve 104 connected to the two leg portions 107 moves due to upward elastic deformation of the one leg portion 107, the tip portion 104d of the needle valve 104 moves toward the valve guide tube 101. Valve seat 101a
A gap is secured to allow fuel to pass through.

On the other hand, high-pressure fuel pumped from a fuel pump (not shown) enters the fuel introduction hole 112a of the spring adjuster 112 via a fuel pipe. moreover.

It passes through the gap between the guide parts 104a, 104b of the needle valve 104 and the valve guide cylinder 101, and reaches the tip part 104d, where it is injected and supplied to the outside of the valve through a gap that is opened in advance.

Conversely, when the voltage applied to the piezoelectric element 105 is released, the piezoelectric element 105 quickly contracts and returns to its original position. Accordingly, the piston 106 quickly moves to the right in the figure and returns to its original position due to the restoring force of the leaf spring 108 and the restoring force of the leg portion 107 made of an elastic member. Therefore, needle valve 1
04 is pushed down by the restoring force of the coiled spring 113.

The tip/end portion 104d is the valve seat 101 of the valve guide cylinder 101
When the vehicle is seated at position a, the fuel injection supply stops.

J-As noted, the movement of the needle valve 104 is as follows.

Since this is performed by a large amount of movement of the leg portion 107 made of an elastic member integrally connected to the piston 106, a stable amount of displacement can be obtained and accurate control of the injection amount can be achieved. This embodiment also provides the same functions and effects as the first and second embodiments.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to amplify the displacement of the piezoelectric element with a simple configuration to perform stable injection amount control, and to provide a small and lightweight piezoelectric fuel injection valve.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line 1-1 in FIG. An explanatory diagram three-dimensionally depicting the relative positional relationship of metal members, FIG. 4 is a characteristic diagram of a piezoelectric element used in an embodiment of the present invention, and FIG. 5 is a longitudinal cross-sectional view showing another embodiment of the present invention. FIG. 6 is a longitudinal sectional view of still another embodiment of the present invention, and FIG. 7 is a detailed view of the piston in FIG. 6. DESCRIPTION OF SYMBOLS 1... Actuator casing, 9... U-shaped metal member, 10... Piezoelectric element, 12... Shaft rod, 14
・ ・ ・ Bam diagram + 4 -Ba Jefuk Ichishi ＞ ッ ッ 図 乙 乙 乙 乙 乙 乙 乙 乙 乙 乙 乙 乙 ・ ・ ・ ・ て ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ て ・

Claims (1)

[Claims] 1. In a piezoelectric fuel injection valve that uses a piezoelectric element as an actuator and injects and supplies fuel by opening and closing a valve device by displacement of the piezoelectric element, a U-shaped metal supporting and fixing the piezoelectric element; a guide member that brings both shoulders of the metal member into contact with the inner surface of the casing and is movable within the casing using the contact position as a fulcrum; and a guide member that is integrally coupled to the metal member and moves the piezoelectric element in the axial direction. What is claimed is: 1. A piezoelectric fuel injection valve, characterized in that the piezoelectric fuel injection valve is provided with an elongated shaft rod, and the shaft rod performs an opening/closing operation of a valve device provided in a valve casing that is mechanically coupled to the casing.