JPH0480229B2 - - Google Patents

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 amount of displacement of the piezoelectric element to obtain a stable injection amount in a fuel injection valve using a piezoelectric element.

[Conventional technology]

The use of a piezoelectric element as a drive source for an actuator for operating a fuel injection valve of an internal combustion engine or for controlling a fuel injection device is disclosed in, for example, Japanese Patent Application Laid-Open No. 59/1989.
This is proposed by Publication No. -206668. This is because a piezoelectric element causes almost instantaneous displacement when a voltage is applied, so a piezoelectric actuator can control a fuel injection valve or fuel injection device with more precise timing than an electromagnetic actuator.

In its simplest construction, a piezoelectric actuator comprises a hollow casing in which a generally cylindrical piezoelectric element is arranged. This piezoelectric element is generally made of piezoelectric material, e.g.
It is made up of approximately 100 thin disks stacked together. A thin interlayer electrode made of metal 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 approximately 400V between both electrodes, each disk will elongate in the thickness direction, and the end of the cylindrical piezoelectric element will have a thickness of 40 to 50μ.
An axial displacement of the order of m occurs. This displacement is taken out to the outside by an output means such as an output rod or a piston, and is used to open and close the flow path and the injection hole.

[Problem 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 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 a means for enlarging the displacement, such as increasing the number of laminated piezoelectric materials or implementing a displacement enlarging mechanism. The fuel injection system constructed in this way is large and heavy, and therefore has the problem of not being able to be made smaller and lighter.

The present invention has been made by focusing on such conventional problems, and uses a piezoelectric element to obtain high-speed valve opening and closing responses. The purpose of the present invention is to provide a small and lightweight piezoelectric fuel injection valve that can secure a large amount of displacement and perform 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 shoulders of the metal member into contact with the inner surface of the casing and is movable within the casing using this 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 casing.

[Effect]

Its action is such that when the piezoelectric element is displaced against the restraining force within the substantially U-shaped metal member due to the application of high voltage, the direction of the displacement and force moves toward the fulcrum that contacts the valve case. The displacement is directed from the radial direction to the axial direction through the radial direction, and the amount of displacement is increased 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 cross-sectional view 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 this casing 1, and has a fuel passage hole 3 and a fuel filter 4 inside, and is used for attaching a fuel pipe (not shown). It consists of a fuel pipe joint 5, a lead wire outlet 6, and a seal member 7 for sealing the lead wire outlet 6 and preventing fuel leakage to the outside. Further, inside the casing 1, on the side facing the fuel pipe joint 5, there is a rectangular cavity 8 with one side open, and a side groove 8a communicating with the fuel passage hole 3 on both sides of the long side of the cavity 8. is provided. 9 is a substantially U-shaped metal member inserted into the cavity 8 in the casing 1;
The shoulder portion 9a of the metal member 9 is inserted and fixed in line contact with both bottom corners of the cavity portion 8. Metal member 9
freely moves within this 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 compressive force.
The columnar piezoelectric element 10 is constructed by laminating a large number of thin plates (not shown) with a thickness of 0.1 to 0.5 mm made of a piezoelectric material whose main component is lead zirconate titanate. When a voltage of several hundred volts is applied to the electrode, an axial displacement of about 50 μm occurs. As is well known, positive side electrode foils and negative side electrode foils (both not shown) are alternately sandwiched between the piezoelectric thin plates, and each lead wire 1
Connected to 1. Reference numeral 12 denotes a shaft rod integrally attached to the center of the metal part 9, and this shaft rod 12 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 inserted into the large-diameter portion 14a of this casing 14 via an O-ring 15, and then the upper edge 14b of the casing 14 is attached to the actuator casing 1 side. It is fixed by tightening it. At this time, the shaft rod 12 that is integrally connected to the metal member 9
is inserted into the guide hole 1b provided in the casing 14 with a slight gap. The tip of this shaft rod 12 is located in the cavity 17 within the small diameter portion 14c of the casing 14. Further, a valve device 18 is connected to the small diameter portion 14c via a spacer 20 and an O-ring 21 provided to a stepped portion 19 provided in the cavity 17 to prevent fuel leakage to the outside.
It is fixed by caulking the lower edge 14d of c toward the valve device 18 side.

This valve device 18 is a generally used outward-opening seat valve, and a tip tapered portion 22a of a nozzle body 22 is connected to a tip tapered portion 23a of a plunger 23.
are in line contact. 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 the figure. The plunger 23 has a fuel passage groove 26
A plurality of holes are provided and communicate with the fuel passage hole 3 in the large diameter portion 14a.

When this valve device 18 is crimped onto the small diameter portion 14c of the casing 14 as described above, the rod shaft 12
The spacer 20 is used to adjust the tip end of the plunger 23 and the head 23b of the plunger 23 so that they are in contact with each other or are positioned with a very small gap between them.

Next, the operation of the piezoelectric fuel injection valve of the present invention will be explained. When a pulsed high voltage is applied to the lead wire 11 from a control circuit (not shown), the pulsed voltage is
When ON, the piezoelectric element 10 expands against the restraining force of the metal member 9. In the figure, it is displaced in a radial direction. Due to this displacement of the piezoelectric element 10, the metal member 9 moves in the radial direction on the side that contacts the piezoelectric element 10, while the other side moves in the axial direction, using the shoulder portion 9a as a fulcrum.

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. 12 is an explanatory diagram three-dimensionally depicting the relative positional relationship of 12. FIG. That is, as the columnar piezoelectric element 10 is displaced, the shoulder portion 9a of the metal member 9, P shown in the figure.
Using the point as a fulcrum, move in the _Q1 direction via the arm _L1 . Therefore, the other arm l ₂ is Q ₂ with P point as the fulcrum.
direction, i.e. moving down the axis. As is clear from the figure without going into detail, this amount of movement is amplified relative to the amount of displacement of the piezoelectric element 10 approximately equal to the arm length ratio l ₂ /l ₁ .

The columnar piezoelectric element 10 used in this example has a thickness of
It is made by laminating about 200 thin sheets of 0.1 mm. The relationship between force and displacement when a voltage of 400V is applied is shown in Figure 4. That is, piezoelectric element 1
0 changes by about 50μm with free displacement, and when this is restrained, a force of about 80Kg can be obtained. Now, the displacement is 25μ
If the metal member 9 is restrained at a force of 40 kg, the metal member 9 will receive a force of about 40 kg. This force is propagated from the arm _l1 to _l2 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 columnar piezoelectric element 1
The displacement and force of 0 are properly propagated to the shaft rod 12 which is 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. The tip tapered portion 22a of the nozzle body 22 corresponds to the tip tapered portion 23 of the plunger 23.
It separates from a and secures a gap that allows the passage of fuel. At this time, fuel pressurized by a fuel pump (not shown) is supplied from the fuel passage hole 3 to the side groove 8a provided in the cavity 8, to the small diameter portion 14c of the valve casing 14.
The fuel is injected and supplied to the outside through the inner cavity 17 and fuel passage 26.

On the other hand, when the pulse voltage applied to the columnar piezoelectric element 10 is turned off, 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 integrally connected thereto is subject to the force and displacement that push down the plunger 23 of the valve device 18. In order to eliminate the plunger 23, the coiled spring 24
With its restoring force, it quickly returns to its original position and stops fuel injection. Therefore, the fuel injection supply ends.

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 make smooth line contact within the casing side plate 2, and the tapered portion 51a is provided on the inner surface of the casing side plate 2 of the casing 1. It is designed to allow for exercise. This embodiment also provides the same functions and effects as the first embodiment.

The amount of fuel injected in such a piezoelectric fuel injection valve is controlled by adjusting the ON/OFF ratio of the pulse voltage, and the reciprocating movement of the plunger 23 is reliably performed by the high-speed movement of the piezoelectric element 10. Moreover, since the movement is performed by a large amount of movement, there are 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, which relates to an inward-opening seat valve using a needle valve. In the figure, 100 is a valve casing with a valve guide cylinder 101 and an actuator cylinder 1.
02 integrally. Reference numeral 103 denotes an upper casing side plate inserted and fixed into the portion 100a of the valve casing 100, and 104 denotes a guide portion 1 for coaxially sliding with extremely high precision within the valve guide cylinder 101.
Needle valve with 04a, 104b, 10
5 is a columnar piezoelectric element provided in the actuator cylinder 102, and 106 is a piston provided on the movable end side of the piezoelectric element 105, which 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. The leg portion 107 has a spherical tip portion 107a, and the tip portion 107a is tightly inserted into an annular groove 100b provided in the valve casing 100. 108 is a leaf spring 109 which is biased to press the piston 106 against the piezoelectric element 105 within the actuator cylinder 105;
is a support member provided at one end of the piezoelectric element 105,
It has a conical groove 109a. 110 is a spherical part 110
1 of the actuator cylinder 102 with a fixed plate having a
It is inserted and fixed into the 02a section. The spherical portion 110a is connected and fixed to the conical groove 109a of the support member 109, and holds the piezoelectric element 105 coaxially within the actuator cylinder 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. 113 is the spring adjuster 112 and the end portion 10 of the needle valve 104.
4c, the distal end portion 104d of the needle valve 104 is inserted into the valve seat 10 in the valve guide cylinder 101.
It is a coiled spring that is seated on 1a. In addition, 1
14 is a lead wire, and 115 is a packing.

Next, the operation will be explained. When a voltage is applied to the piezoelectric element 105 from a control circuit (not shown), the piezoelectric element 105 is displaced against the restoring force of the leaf spring 108, and the piston 106 is moved to the left in the figure.
As the piston 106 moves, the leg 107 made of an elastic member that is integrally connected to the piston 106 moves to the left at the same time, but the tip 107a of the leg 107 is previously inserted into the annular groove 100b of the valve casing 100.
Because it is in close contact with the body, 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, the base of the leg 107 that is integrally connected to the piston 106 is at point a, and the tip 1
If part 07a is point b and the center position of leg 107 is point P, then point a becomes Δx due to the displacement of piezoelectric element 105.
Move to the left, 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, and this movement amount x is approximately several times the displacement Δx.

Returning to FIG. 6, the end 104c of the needle valve 104 connected to the leg 107 is connected to the leg 107.
7, the distal end 104d of the needle valve 104 separates from the valve seat 101a of the valve guide cylinder 101, thereby securing a gap through which fuel can pass.

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,
Guide parts 104a, 104 of needle valve 104
b and reaches the tip portion 104d through the gap between the valve guide cylinder 101. Here, 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. Along with this, 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, the needle valve 104 is pushed downward by the restoring force of the coiled spring 113, and the tip end 104d seats on the valve seat 101a of the valve guide cylinder 101, and the injection supply of fuel is stopped.

As described above, the needle valve 104 is moved by a large amount of movement of the leg portion 107 made of an elastic member integrally connected to the piston 106, so that a stable amount of displacement can be obtained and accurate injection amount control can be achieved. It is possible. 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 the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line -- in FIG. FIG. 4 is a characteristic diagram of a piezoelectric element used in an embodiment of the present invention, FIG. 5 is a vertical cross-sectional view showing another embodiment of the present invention, and FIG.
The figure 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... Valve casing, 18... Valve device.

Claims (1)

[Scope of Claims] 1. A piezoelectric fuel injection valve that uses a piezoelectric element as an actuator and injects and supplies fuel by opening and closing a plunger of a valve device by displacement of the piezoelectric element, in which a casing of the injection valve is provided. A valve device is provided, one end of a shaft rod is connected to the plunger of the valve device in the direction of movement thereof, a displacement member for displacing the shaft rod in the axial direction is connected to the other end of the shaft rod, and the displacement member is connected to the other end of the shaft rod in the direction of movement thereof. A piezoelectric element for displacing the member is connected to the member, and the displacement member includes a first displacement portion disposed substantially perpendicular to the axis of the shaft so as to apply the axial displacement to the shaft; a second displacement part provided perpendicularly to both ends of the first displacement part so as to give displacement to the displacement part; and a connecting part between the first displacement part and the second displacement part to the casing. a fulcrum part supported as a displacement fulcrum, the piezoelectric element passing through the shaft rod and disposed between the second displacement part of the displacement member. 2. In a piezoelectric fuel injection valve that uses a piezoelectric element as an actuator and injects and supplies fuel by opening and closing a plunger of a valve device by displacement of the piezoelectric element, the valve device is provided in the casing of the injection valve, and the valve device is provided in the casing of the injection valve, One end of a shaft rod is connected to the plunger of the valve device in its moving direction, a displacement member for displacing the shaft rod in the axial direction is connected to the other end of the shaft rod, and the displacement member is connected to the shaft rod. The displacement member is provided with a displacement part that is connected to be substantially orthogonal to the axis of the shaft rod so as to provide the axial displacement, one end of the displacement part of the displacement member is supported by a casing, and the other end of the displacement part is moved to the casing. A piezoelectric fuel injection valve, characterized in that the piezoelectric element is disposed between the other end of the displacement portion and the casing.