JPH0794797A - Piezoelectric device actuator - Google Patents

Abstract

PURPOSE:To circulate coolant to cool the center part of the main body of a piezoelectric device actuator without requiring a pump, etc., by a method wherein a first linkage path is provided on the upper end side of the main body and a second linkage path is provided on the lower end side of the main body and a coolant circulation path between the inside space of the main body and around the outer circumference of the main body. CONSTITUTION:The inside space 15 of the main body 1 of a piezoelectric device actuator is composed of the inner holes of respective piezoelectric devices 1a. The inside space 15 and the predetermined space 3 outside the main body 1 are linked with each other by the first linkage path 5c of a first shim 5 and the second linkage path 6c of a second shim 6. A circulation path through which insulating oil in the inside space 15 is circulated and returned to the inside space 15 is composed of the first linkage path 5c, the predetermined space 3 and the second linkage path 6c. Two valves 11 and 12 which can be opened in the direction of the circulation are provided in the circulation path. If heat is generated in the main body 1 of the piezoelectric device actuator, the insulating oil is circulated by the expansion and contraction of the main body 1 and the center part is cooled to make the temperature distribution uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element actuator.

[0002]

2. Description of the Related Art It has already been proposed that a piezoelectric element that expands and contracts when a voltage is applied is used as a highly responsive actuator in a fuel injection valve of an internal combustion engine. Since the displacement amount of such a piezoelectric element actuator changes in accordance with the temperature thereof, cooling is performed for heat generated during operation, and temperature correction is generally performed for drive control. In order to make the drive control including this temperature correction accurate, the piezoelectric element actuator must be cooled so as to have a uniform temperature distribution. There is described one in which a cooling liquid is caused to flow through a cooling liquid passage formed around an element by using a pump or the like.

[0003]

In the above-mentioned prior art, since the piezoelectric element generally has a low heat transfer coefficient, its outer peripheral portion is cooled uniformly, but its central portion is not cooled so much.
It is not possible to realize sufficient uniform temperature distribution cooling in the piezoelectric actuator. Further, since a supply means such as a pump for supplying the cooling liquid is provided, a considerable increase in cost is required.

Therefore, an object of the present invention is to provide a piezoelectric element actuator which can circulate a refrigerant without requiring a pump or the like and cool it to a uniform temperature including its central portion.

[0005]

A piezoelectric element actuator according to the present invention has a body of a piezoelectric element actuator formed by laminating ring-shaped piezoelectric elements, and a predetermined gap is formed around the outer periphery of the body. A housing surrounding the upper end of the main body, supporting the upper end of the main body, a plunger penetrating the housing in the axial direction of the main body and contacting the lower end of the main body, a refrigerant filled in the housing, and the refrigerant. A first series passage on the upper end side of the main body and a second communication passage on the lower end side of the main body for forming a refrigerant circulation passage that returns from the inner space of the main body to the inner space through the predetermined gap. However, at least two same-direction check valves installed in the refrigerant circulation passage are used to form a section whose volume increases and decreases as the main body expands and contracts.

[0006]

In the above-mentioned piezoelectric element actuator, the refrigerant filled in the housing is moved from the inner space of the main body to the outer periphery thereof by the first series passage on the upper end side of the piezoelectric element actuator and the second communication passage on the lower end side. A refrigerant circulation passage is formed that returns to the internal space through a predetermined gap around the section, and the volume of the refrigerant circulation passage increases and decreases as the main body expands and contracts by using at least two same-direction check valves installed in the refrigerant circulation passage. Therefore, when the volume of this compartment is reduced, the refrigerant is discharged from this compartment to the other compartment through one check valve,
When the volume of this section increases, the refrigerant is supplied from this section to the section via the other check valve, so that the refrigerant circulates along the refrigerant circulation passage by utilizing the expansion and contraction of the main body.

[0007]

1 is a sectional view of a piezoelectric element actuator according to the present invention. 1 is a ring-shaped piezoelectric element (for example, PZ
T) is a main body of the piezoelectric element actuator formed by laminating 1a, and 2 is a housing that surrounds the main body 1 so that a predetermined gap 3 around the outer periphery thereof is formed.
A through hole 2a is formed at the lower end of the housing 2, and an oiltightly sealed plunger 4 is inserted through the through hole 2a. The upper end of the main body 1 contacts the inner upper wall of the housing 2 via the first shim 5, and the lower end contacts the position adjusting plate 7 provided on the upper portion of the plunger 4 via the second shim 6. ing.

Reference numerals 8a and 8b denote lead wires covered with an insulating material for supplying a voltage to the main body 1 of the piezoelectric element actuator. Via battery (not shown)
Connected to. Insulating coatings are removed from the ends of the lead wires 8a and 8b on the piezoelectric element side, and in order to maintain insulation with respect to the housing 2, an insulating layer 9 is formed around the main body 1 of the piezoelectric element actuator. The inside of the housing 2 is filled with insulating oil such as silicone oil.

The first shim 5 has a ring-shaped piezoelectric element 1a.
Is formed with a through hole 5a which is concentric with the inner hole portion and has substantially the same inner diameter, and further has a counterbore hole 5b having a larger inner diameter, and the counterbore hole 5b and the above-mentioned predetermined gap 3 on the surface of the housing 2 side. To communicate with each other, a first series of passages 5c composed of a plurality of radial passages is provided. The second shim 6 is provided with a through hole 6a similar to the first shim 5 and a second communication passage 6c on the surface of the position adjusting plate 7 side.

A counterbore hole 2b is formed in the housing 2 so as to face the counterbore hole 5b of the first shim 5, and the counterbore hole 2 is formed.
b is a through hole 5a in the counterbore 5b of the first shim 5
A poppet-shaped first valve body 11 urged by a first spring 10 so as to close is inserted. A through hole 11a is provided in the wall portion of the first valve body 11 so that the insulating oil can surely enter the counterbore hole 2b of the housing 2.

The position adjusting plate 7 of the second shim 6
A step portion 6d is formed on the side surface, and the plate-shaped second valve body 12 is formed.
Is urged by the second spring 13 so that the perforated bottom plate abuts the upper surface of the step 6d, and the tubular side plate has an outer diameter substantially the same as the inner side wall of the housing 2 It is placed in contact. In order to enable the above assembly, the housing 2 has a through hole 2a.
Is divided into a bottom portion and a base portion, each of which has a pair of male screw member 14a and female screw member 1 that surround the housing 2.
It is surely connected by fitting with 4b.

Piezoelectric actuators are used, for example, as very responsive actuators for fuel injection valves in internal combustion engines. When fuel injection is stopped, a set positive voltage of about several hundred volts is applied to the main body 1 of the piezoelectric element actuator, and each piezoelectric element 1a is charged and expanded, so that a spring (provided on the fuel injection valve side ( (Not shown), the plunger 4 is pushed down to the position shown in FIG. 1 to close the fuel injection valve. on the other hand,
When the fuel injection is started, the piezoelectric element 1a is discharged by the application of the set negative voltage or the application of the voltage is stopped, and the piezoelectric element 1a contracts. Therefore, the plunger 4 is pushed up from the position shown in FIG. Open the valve.

In the piezoelectric element actuator of this embodiment, as described above, the internal space 15 in the main body 1 of the piezoelectric element actuator formed by the inner hole of each piezoelectric element 1a and the predetermined gap 3 outside the main body 1 are provided. Are communicated with each other by the first series passage 5c of the first shim 5 and the second communication passage 6c of the second shim 6, so that the insulating oil in the internal space 15 becomes
A circulation passage is formed which allows circulation to return to the internal space 15 through the first series passage 5c, the predetermined gap 3, and the second communication passage 6c, and the circulation passage can be opened only in this circulation direction. Two valve bodies 11 and 12 are arranged.

Since the first compartment including the internal space of the main body 1 in the circulation passage divided by these two valve bodies 11 and 12 includes the vicinity of the end of the main body 1 on the plunger 4 side, its large displacement is utilized. By doing so, it is possible to remarkably increase or decrease the volume according to the expansion and contraction of the main body 1. In the present embodiment, the plate-shaped second valve body 12 is used as a means for effectively utilizing this displacement. To be done.

When the main body 1 of the piezoelectric element actuator contracts, the second spring 13 raises the second valve body 12 accordingly, so that the volume of the first compartment increases and the second compartment of the other compartment increases. The volume of is reduced. As a result, the pressure of the insulating oil in the first compartment decreases and the pressure in the second compartment increases, and the spring constant of the second spring 13 is set to be relatively small.
Is easily opened by the pressure difference between the two compartments, the insulating oil flows from the second compartment to the first compartment through the second valve body 12, and when the two compartments have almost the same pressure, the second spring 13
Closed by. At this time, a similar pressure difference acts on the first valve body 11, but it is not opened because the pressure on the second partition side is higher.

From this state, when the main body 1 of the piezoelectric element actuator expands, the second valve body 12 descends accordingly, so that the volume of the first compartment decreases and the volume of the other second compartment increases. The volume increases. As a result, the insulating oil pressure in the first compartment increases and the pressure in the second compartment decreases, and the spring constant of the first spring 10 is set to be relatively small. Is easily opened by the pressure difference between the first compartment and the insulating oil flows from the first compartment to the second compartment through the first valve element 11, and when both compartments have almost the same pressure, the first spring 10 closes the valve. It At this time, a similar pressure difference acts on the second valve body 12, but it is not opened because the pressure on the first partition side is higher.

As described above, due to the expansion and contraction of the main body 1 of the piezoelectric element actuator, the insulating oil returns from the internal space 15 to the internal space 15 through the first series passage 5c, the predetermined gap 3 and the second communication passage 6c. Main body 1 of the piezoelectric element actuator that generates heat during operation because it circulates along the circulation passage
The insulating oil thus circulated is cooled so as to have a uniform temperature distribution including its central portion. As a result, it is possible to make accurate drive control including temperature correction, which is generally executed for the piezoelectric element actuator whose displacement amount changes according to the temperature. Further, by realizing such a uniform temperature distribution, the piezoelectric element 1a
It is possible to prevent thermal stress from being generated inside and improve its durability.

In this embodiment, the circulation of the refrigerant (insulating oil) for cooling the main body 1 of the piezoelectric element actuator is automatically performed by the expansion and contraction of the main body 1, such as an electric pump. Since the device is not used, the device itself is simplified and the cost is not increased.

In this embodiment, the second valve body 12 is the main body 1
It is configured to move up and down according to the expansion and contraction of the first partition, and is used to change the volume of the above-mentioned first section, but this does not particularly limit the present invention, and for example, the specific height of the predetermined gap 3 is It is also possible to replace the reed valve that can close the entire circumference in the S position, and in this case, the volume of the section corresponding to the above-mentioned first section is, for example, the difference between the sectional area of the main body 1 and the sectional area of the plunger 4. By using, it is possible to decrease or increase when the main body 1 extends and increase or decrease when the main body 1 contracts, and to realize similar refrigerant circulation without causing the opposite volume change in the other compartment. It is possible.

Further, the positions of the two valve bodies 11 and 12 in the circulation passage are not limited to the positions of this embodiment, and they are designed to open in the same direction, and the positions of the sections divided by them are divided. If the volume is increased or decreased according to the expansion and contraction of the main body 1 of the piezoelectric element actuator, the piezoelectric element actuator can be freely arranged. Further, although the insulating oil is used as the refrigerant in the present embodiment, it is possible to use the refrigerant having the better cooling performance by completely insulating the insulating layer 9.

[0021]

As described above, according to the piezoelectric element actuator of the present invention, the refrigerant filled in the housing by the first series passage on the upper end side and the second communication passage on the lower end side of the body of the piezoelectric element actuator. A refrigerant circulation passage is formed from the internal space of the main body to the internal space through a predetermined gap around the outer periphery of the main body, and at least two same-direction check valves installed in the refrigerant circulation passage are used to expand and contract the main body. As a result, a compartment whose volume increases and decreases is formed, so when the volume of this compartment decreases, the refrigerant is discharged from this compartment to the other compartment via one check valve, and when the volume of this compartment increases, the other Refrigerant is supplied from other compartments to this compartment through a stop valve, so that the refrigerant can be supplied to the main body without using an electric pump or the like that increases the cost and complexity of the piezoelectric actuator. By using the stretch circulated along the refrigerant circulation passage, it is possible to cool the central portion and the peripheral portion of the piezoelectric element actuator uniform temperature.

[Brief description of drawings]

FIG. 1 is a sectional view of a piezoelectric element actuator according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Main body of piezoelectric element actuator 2 ... Housing 3 ... Predetermined gap 4 ... Plunger 5 ... First shim 5c ... First series passage 6 ... Second shim 6c ... Second communication passage 11 ... First valve body 12 ... Second valve Body 15 ... Internal space

Claims (1)

[Claims] 1. A main body of a piezoelectric element actuator formed by stacking ring-shaped piezoelectric elements, and a housing surrounding the main body so as to form a predetermined gap around the outer peripheral portion thereof and supporting an upper end portion of the main body. A plunger that penetrates the housing in the axial direction of the main body and contacts the lower end of the main body; a refrigerant filled in the housing; and the refrigerant passing through the predetermined gap from the internal space of the main body A first series passage on the upper end side of the body and a second communication passage on the lower end side of the body for forming a refrigerant circulation passage returning to the space; and at least two installed in the refrigerant circulation passage. A piezoelectric element actuator, wherein two same-direction check valves are used to form a section whose volume increases and decreases as the main body expands and contracts.