Patent Description:
A piezoelectric valve is conventionally known in which the valve is opened/closed utilizing a displacement of a laminated piezoelectric element to eject compressed gas (see Patent Literature <NUM>).

The piezoelectric valve described in Patent Literature <NUM> utilizes properties of the laminated piezoelectric element having excellent high-speed response performance, and includes a displacement enlarging mechanism that enlarges a small displacement of the laminated piezoelectric element based on the principle of leverage.

In the piezoelectric valve, application of a voltage to the laminated piezoelectric element causes a displacement of the laminated piezoelectric element in an extending direction, the displacement is transmitted to a valving element via the displacement enlarging mechanism, and the valving element is immediately moved to open the valve.

Moreover, in the piezoelectric valve, cancellation of voltage application to the laminated piezoelectric element causes a return force associated with return of the laminated piezoelectric element to an original state, the return force is transmitted to the valving element via the displacement enlarging mechanism, and the valving element is immediately brought into contact with a valve seat to close the valve.

The laminated piezoelectric element has excellent features such as low consumption energy associated with the operation, suitability for high-speed operation, and compactness.

However, the laminated piezoelectric element has a piezoelectric ceramic layer, and is thus structurally fragile, which may cause broken pieces to be ejected together with compressed gas when the piezoelectric valve is used.

Moreover, the laminated piezoelectric element is vulnerable to a highly-humid environment. Thus, in a case of using the piezoelectric valve in a highly-humid environment, moisture may enter the laminated piezoelectric element to shorten the life of the piezoelectric valve.

Thus, the inventors of the present invention have proposed coating a surface of the laminated piezoelectric element with a polyolefin-based resin (see Patent Literature <NUM>).

A piezoelectric valve described in Patent Literature <NUM> utilizes a laminated piezoelectric element coated with a polyolefin-based resin having properties of small Young's modulus and excellent flexibility and having properties of small moisture permeability and excellent water resistance. This prevents broken pieces of the laminated piezoelectric element from being ejected together with compressed gas when using the piezoelectric valve. Moreover, even in a case of usage in a highly-humid environment, moisture will not enter the laminated piezoelectric element to shorten the life.

Ejection of broken pieces of the laminated piezoelectric element is prevented by coating the surface of the laminated piezoelectric element thinly with a polyolefin-based resin. However, in order to prevent reduction in insulation resistance of the laminated piezoelectric element in a high-temperature, highly-humid environment, the surface of the laminated piezoelectric element needs to be coated with a polyolefin-based resin thickly to some extent. In that case, the movement of the laminated piezoelectric element may be interfered with to reduce the stroke or to cause a failure to perform a correct operation.

<CIT> concerns a piezoelectric actuator.

<CIT> concerns an actuator using an electrochemical transducer.

<CIT> concerns an apparatus driven by a smart material actuator.

Thus, the present disclosure has an object to provide a piezoelectric valve that can prevent broken pieces of a laminated piezoelectric element from being ejected together with compressed gas when in use, can prevent moisture from entering the laminated piezoelectric element to shorten the life even in a case of usage in a highly-humid environment, and can prevent the movement of the laminated piezoelectric element from being interfered with to reduce the stroke or to cause a failure to perform a correct operation, and to provide a method of manufacturing the piezoelectric valve.

Aspects of the present invention are defined in the accompanying claims. According to a first aspect there is provided a piezoelectric valve in accordance with claim <NUM>. According to a second aspect there is provided a method in accordance with claim <NUM>.

Advantageous optional features are defined in the dependent claims.

In order to achieve the above object, the present disclosure is a piezoelectric valve in which the valve is opened/closed utilizing a displacement of a laminated piezoelectric element, including: a valve main body having a gas pressure chamber that receives compressed gas supplied externally; and an actuator having a valving element, the laminated piezoelectric element that generates a driving force required for operating the valving element as the displacement, and a displacement enlarging mechanism that enlarges the displacement of the laminated piezoelectric element to be acted on the valving element, the actuator being disposed in the valve main body, in which a surface of the laminated piezoelectric element is coated with silicone in a state in which the laminated piezoelectric element is integrated into the actuator.

In the present disclosure, , the surface of the laminated piezoelectric element is coated with silicone filled between a pair of projecting pieces positioned on both sides of the laminated piezoelectric element along a longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces.

In the present disclosure, preferably, the piezoelectric valve further includes a plate disposed in the valve main body, the actuator being fixed to the plate and disposed in the valve main body together with the plate, in which the pair of projecting pieces are provided on a surface of the plate, the pair of projecting pieces being positioned on both the sides of the laminated piezoelectric element along the longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces when the actuator is fixed to the plate, and the surface of the laminated piezoelectric element is coated with the silicone filled between the pair of projecting pieces in a state in which the actuator is fixed to the plate.

Herein, in the present disclosure, silicone means a low-viscosity silicone rubber, and preferably a silicone rubber having a viscosity of more than or equal to <NUM> Pa·s and less than or equal to <NUM> Pa·s, and more preferably, a silicone rubber having a viscosity of <NUM> Pa·s can be used.

Moreover, considering workability, a one-component room temperature curing silicone rubber is preferably used. For example, a low-viscosity silicone rubber "KE-<NUM> (product name)" manufactured by Shin-Etsu Chemical Co. or the like is preferably used.

In the present disclosure, the displacement enlarging mechanism is formed of a metallic material, and an interconnection line for supplying power to the laminated piezoelectric element is molded in a plate formed of a resin material, and an electrode of the interconnection line exposed from the plate is coated with an insulation material in a state in which the electrode is connected to a lead line of the laminated piezoelectric element.

In the present disclosure, preferably, the displacement enlarging mechanism is formed of a metallic material, and a lead line of the laminated piezoelectric element is arranged on an insulating film bonded to a surface of the displacement enlarging mechanism.

Moreover, in order to achieve the above object, the present disclosure is a method of manufacturing a piezoelectric valve in which the valve is opened/closed utilizing a displacement of a laminated piezoelectric element, the piezoelectric valve including a valve main body having a gas pressure chamber that receives compressed gas supplied externally, and an actuator having a valving element, the laminated piezoelectric element that generates a driving force required for operating the valving element as the displacement, and a displacement enlarging mechanism that enlarges the displacement of the laminated piezoelectric element to be acted on the valving element, the actuator being disposed in the valve main body. The method includes supplying silicone onto a surface of the laminated piezoelectric element integrated into the actuator to coat the surface of the laminated piezoelectric element with the silicone.

In the present disclosure, the silicone is supplied onto the surface of the laminated piezoelectric element integrated into the actuator to coat the surface of the laminated piezoelectric element with the silicone filled between a pair of projecting pieces positioned on both sides of the laminated piezoelectric element along a longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces.

In the present disclosure, preferably, the piezoelectric valve further includes a plate disposed in the valve main body, the actuator being fixed to the plate and disposed in the valve main body together with the plate, the pair of projecting pieces are provided on a surface of the plate, the pair of projecting pieces being positioned on both the sides of the laminated piezoelectric element along the longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces when the actuator is fixed to the plate, and after the laminated piezoelectric element is integrated into the actuator and the actuator is fixed to the plate, the silicone is supplied onto the surface of the laminated piezoelectric element to coat the surface of the laminated piezoelectric element with the silicone filled between the pair of projecting pieces.

In the piezoelectric valve of the present disclosure, the surface of the laminated piezoelectric element is coated with silicone having properties excellent in water resistance and water proofness. This can prevent broken pieces of the laminated piezoelectric element from being ejected together with compressed gas when in use, and can prevent moisture from entering the laminated piezoelectric element to shorten the life even in a case of usage in a highly-humid environment.

Moreover, in the piezoelectric valve of the present disclosure, the surface of the laminated piezoelectric element is coated with silicone having properties whose elasticity and compressibility are greater than those of a conventional polyolefin-based resin. This can prevent the movement of the laminated piezoelectric element from being interfered with to reduce the stroke or to cause a failure to perform a correct operation even in a case where the surface of the laminated piezoelectric element is coated with silicone thickly to some extent in order to prevent reduction in insulation resistance of the laminated piezoelectric element in a high-temperature, highly-humid environment.

In the piezoelectric valve of the present disclosure, the entire circumferential surface of the laminated piezoelectric element can be easily coated with silicone since the surface of the laminated piezoelectric element is coated with silicone filled between the pair of projecting pieces positioned on both sides of the laminated piezoelectric element along the longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces.

In the piezoelectric valve of the present disclosure, the entire circumferential surface of the laminated piezoelectric element can be easily coated with silicone since the piezoelectric valve further includes a plate disposed in the valve main body, the actuator being fixed to the plate and disposed in the valve main body together with the plate, and the pair of projecting pieces are provided on the surface of the plate, the pair of projecting pieces being positioned on both the sides of the laminated piezoelectric element along the longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces element when the actuator is fixed to the plate, and the surface of the laminated piezoelectric element is coated with the silicone filled between the pair of projecting pieces in a state in which the actuator is fixed to the plate.

In the method of manufacturing a piezoelectric valve of the present disclosure, silicone is supplied onto the surface of the laminated piezoelectric element integrated into the actuator to coat the surface of the laminated piezoelectric element with the silicone. This prevents an assembling failure when integrating the laminated piezoelectric element into the actuator from occurring even in a case where silicone spreads out and adheres to a place other than the surface of the laminated piezoelectric element.

In the method of manufacturing a piezoelectric valve of the present disclosure, the entire circumferential surface of the laminated piezoelectric element can be easily coated with silicone since silicone is supplied onto the surface of the laminated piezoelectric element integrated into the actuator to coat the surface of the laminated piezoelectric element with the silicone filled between the pair of projecting pieces positioned on both the sides of the laminated piezoelectric element along the longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces.

In the method of manufacturing a piezoelectric valve of the present disclosure, an assembling failure when fixing the actuator into which the laminated piezoelectric element has been integrated to the plate does not occur even in a case where silicone spreads out and adheres to a place other than the surface of the laminated piezoelectric element since the piezoelectric valve further includes a plate disposed in the valve main body, the actuator being fixed to the plate and disposed in the valve main body together with the plate, the pair of projecting pieces are provided on the surface of the plate, the pair of projecting pieces being positioned on both the sides of the laminated piezoelectric element along the longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces when the actuator is fixed to the plate, and after the laminated piezoelectric element is integrated into the actuator and the actuator is fixed to the plate, the silicone is supplied onto the surface of the laminated piezoelectric element to coat the surface of the laminated piezoelectric element with the silicone filled between the pair of projecting pieces.

Moreover, in the method of manufacturing a piezoelectric valve of the present disclosure, the pair of projecting pieces positioned on both the sides of the laminated piezoelectric element along the longitudinal direction of the laminated piezoelectric element with gaps between the pair of projecting pieces when the actuator is fixed to the plate are provided on the surface of the plate. This enables the entire circumferential surface of the laminated piezoelectric element to be easily coated with silicone filled between the pair of projecting pieces.

An embodiment of the present disclosure will be described with reference to the drawings.

<FIG> shows a cross-sectional view of a representative example of a laminated piezoelectric element (hereinafter referred to as a "piezoelectric element").

A piezoelectric element <NUM> shown in <FIG> has a laminate <NUM> obtained by alternately laminating piezoelectric ceramic layers <NUM> and inner electrode layers <NUM>. The inner electrode layers <NUM> are exposed at side surfaces of the laminate <NUM>. The exploded side surfaces of the respective inner electrode layers <NUM> are coated with an insulation layer <NUM> in every other layer. The laminate <NUM> further has an external electrode <NUM> that covers the insulation layer <NUM> and conducts with the inner electrode layers <NUM> that are not coated with the insulation layer <NUM>.

<FIG> shows a perspective view of an example of a piezoelectric valve. <FIG> shows an assembly exploded view of the piezoelectric valve in <FIG>. <FIG> shows an explanatory view of an actuator. <FIG> shows an explanatory view in a state in which the actuator is fixed to a valve seat plate. <FIG> shows a sectional view of the piezoelectric valve, which is an explanatory view in a state in which the valve seat plate is disposed in a valve main body.

A piezoelectric valve <NUM> shown in <FIG> includes a valve main body <NUM>, a valve seat plate <NUM> disposed in the valve main body <NUM> and fixed to the valve main body <NUM>, and actuators <NUM> fixed to both surfaces of the valve seat plate <NUM> with screws.

The valve main body <NUM> is a case whose front surface is openable, and includes therein a gas pressure chamber to be supplied with compressed gas from an external compressed gas supply source (not shown).

Moreover, a connector part <NUM> is provided on the front surface of the valve main body <NUM>. A gas inlet <NUM> for taking in compressed gas into the valve main body <NUM> and a gas outlet <NUM> for discharging compressed gas are open in the front surface of the connector part <NUM>.

An interconnection line substrate <NUM> for supplying power to the piezoelectric element <NUM> is disposed between the valve main body <NUM> and the connector part <NUM>. An interconnection line connector <NUM> for supplying power to the piezoelectric element <NUM> via the interconnection line substrate <NUM> is disposed on one side end of the connector part <NUM> and at a lateral position of the valve main body <NUM>.

The valve seat plate <NUM> includes attachment portions for the actuators <NUM> on both of the surfaces, and has a valve seat <NUM> with which a valving element <NUM> which will be described later of the actuator <NUM> is to be brought into contact. Moreover, a lid member <NUM> for closing the opening of the case is attached to the front surface of the valve seat plate <NUM>. A gas discharge path that communicates from a valve seat plane of the valve seat <NUM> to the outlet <NUM> that is open in the front surface of the connector part <NUM> is formed in the lid member <NUM>. Furthermore, a gas inlet path that communicates from the inlet <NUM> that is open in the front surface of the connector part <NUM> into the valve main body <NUM> is formed in the lid member <NUM>.

The valve seat plate <NUM> is molded with a synthetic resin material, for example, and interconnection lines from the interconnection line substrate <NUM> to the piezoelectric element <NUM> are molded.

Moreover, electrodes <NUM> of interconnection lines to be connected to the lead lines <NUM> of the piezoelectric element <NUM> as will be described later using <FIG> are exposed at a rear position of the valve seat plate <NUM>.

The actuator <NUM> includes the valving element <NUM> made of rubber, preferably smooth rubber, a piezoelectric element <NUM> that generates a driving force required for operating the valving element <NUM> as a displacement, and a displacement enlarging mechanism <NUM> that enlarges the displacement of the piezoelectric element <NUM> to be acted on the valving element <NUM>, as shown in <FIG>.

The piezoelectric element shown in <FIG> can be used for the piezoelectric element <NUM>. Alternatively, a resin-coated piezoelectric element whose entire circumferential surface including the side surfaces at which the inner electrode layers <NUM> are exposed is coated thinly with epoxy resin can also be used for the piezoelectric element <NUM>.

The displacement enlarging mechanism <NUM> has a displacement enlarging section <NUM> that enlarges a displacement of the piezoelectric element <NUM>, and a displacement transmitting section <NUM> that transmits the displacement of the piezoelectric element <NUM> to the displacement enlarging section <NUM>. The displacement enlarging mechanism <NUM> is arranged symmetrically with respect to an axial line in an operating direction of the valving element <NUM>, herein, a straight line (hereinafter referred to as a "center line") connecting the valving element <NUM> and a longitudinal axial line of the piezoelectric element <NUM>.

The displacement transmitting section <NUM> has a U-shaped base substrate <NUM> to which one end of the piezoelectric element <NUM> is connected, and a cap member <NUM> to which the other end of the piezoelectric element <NUM> is connected. Since the piezoelectric element <NUM> is disposed in a space of the U-shaped base substrate <NUM>, the displacement enlarging mechanism <NUM> has an arrangement symmetric about the longitudinal axial line of the piezoelectric element <NUM>.

Herein, the piezoelectric element <NUM> is incorporated into the space of the U-shaped base substrate <NUM> and between the bottom of the U-shaped base substrate <NUM> and the cap member <NUM>. By plastically deforming the bottom of the U-shape base substrate <NUM>, the piezoelectric element <NUM> has one end joined to the bottom of the U-shape base substrate <NUM> and the other end joined to the cap member <NUM>.

The displacement enlarging section <NUM> is composed of first and second displacement enlarging sections 34a, 34b arranged symmetrically with respect to the center line.

The first displacement enlarging section 34a has first and second hinges <NUM>, <NUM>, a first arm <NUM>, and a first plate spring <NUM>. One end of the first hinge <NUM> is integrated with one side leading end of the U-shaped base substrate <NUM>, and one end of the second hinge <NUM> is integrated with the cap member <NUM>. One end of the first plate spring <NUM> is joined to an outer leading end portion of the first arm <NUM>, and one side end portion of the valving element <NUM> is joined to the other end of the first plate spring <NUM>.

On the other hand, the second displacement enlarging section 34b has third and fourth hinges <NUM>, <NUM>, a second arm <NUM>, and a second plate spring <NUM>. One end of the third hinge <NUM> is integrated with the other-side leading end of the U-shaped base substrate <NUM>, and one end of the fourth hinge <NUM> is integrated with the cap member <NUM>. One end of the second plate spring <NUM> is joined to an outer leading end portion of the second arm <NUM>, and the other side end portion of the valving element <NUM> is joined to the other end of the second plate spring <NUM>.

Herein, the displacement enlarging mechanism <NUM> can be formed integrally by punching a metallic material such as a stainless material including an invar material, for example.

In the above-described actuator <NUM>, the piezoelectric element <NUM> is elongated when applying a current to the piezoelectric element <NUM> in a valve-closed state. A displacement associated with the elongation of the piezoelectric element <NUM> is enlarged in accordance with the principle of leverage in the displacement enlarging mechanism <NUM> using the first and third hinges <NUM>, <NUM> as a fulcrum, the second and fourth hinges <NUM>, <NUM> as a point of effort, and the outer leading end portions of the first and second arms <NUM>, <NUM> as a point of load to greatly displace the outer leading end portions of the first and second arms <NUM>, <NUM>.

Then, the displacement of the outer leading end portions of the first and second arms <NUM>, <NUM> moves the valving element <NUM> away from the valve seat <NUM> via the first and second plate springs <NUM>, <NUM> to open the gas discharge path.

On the other hand, when current application to the piezoelectric element <NUM> is stopped in the above-described actuator <NUM>, the piezoelectric element <NUM> contracts, and the contraction causes the valving element <NUM> to be seated on the valve seat <NUM> via the displacement enlarging mechanism <NUM> to close the gas discharge path.

<FIG> shows a plan view of the actuator included in the piezoelectric valve according to an embodiment of the present disclosure.

In the actuator shown in <FIG>, the surface of the piezoelectric element <NUM>, that is, at least the side surfaces of the piezoelectric element <NUM> at which the inner electrode layers are exposed are coated with a silicone <NUM> in a state in which the piezoelectric element <NUM> is integrated.

In the piezoelectric valve according to an embodiment of the present disclosure, for example, a piezoelectric element <NUM> of the type shown in <FIG> whose surface is coated with the silicone <NUM> can be integrally incorporated into the actuator <NUM>.

Moreover, in the piezoelectric valve according to an embodiment of the present disclosure, the silicone <NUM> can also be supplied onto the surface of the piezoelectric element <NUM> in the state in which the piezoelectric element <NUM> is integrated into the actuator <NUM> with a dispenser, brush, or the like to coat the surface of the piezoelectric element <NUM> with the silicone <NUM>.

The piezoelectric valve according to an embodiment of the present disclosure eliminates the concern of an occurrence of assembling failure when integrating the piezoelectric element <NUM> into the actuator <NUM> even in a case where the silicone <NUM> spreads out and adheres to a place other than the surface of the piezoelectric element <NUM> since the silicone <NUM> is supplied onto the surface of the piezoelectric element <NUM> in the state in which the piezoelectric element <NUM> is integrated into the actuator <NUM> to coat the surface of the piezoelectric element <NUM> with the silicone <NUM>.

The surface of the piezoelectric element <NUM> is coated with the silicone <NUM> in the state in which the piezoelectric element <NUM> is integrated into the actuator <NUM>, and the piezoelectric valve according to an embodiment of the present disclosure can be assembled by fixing the actuator <NUM> to the valve seat plate.

Herein, it is sufficient that at least the side surfaces of the piezoelectric element <NUM> at which the inner electrode layers are exposed be coated with the silicone <NUM>, and preferably, it is sufficient that all the side surfaces (the entire circumferential surface) including the side surfaces at which the inner electrode layers are exposed be coated with the silicone <NUM>.

Moreover, in a case of using a resin-coated piezoelectric element whose entire circumferential surface is coated thinly with epoxy resin for the piezoelectric element <NUM>, it is preferable to coat the entire circumferential surface with the silicone <NUM>.

<FIG> shows a plan view in a state in which the actuator is fixed to the valve seat plate included in the piezoelectric valve according to an embodiment of the present disclosure. <FIG> shows a cross-sectional view taken along A-A in <FIG>.

In the piezoelectric valve according to an embodiment of the present disclosure, a pair of projecting pieces <NUM> are provided at attachment portions of the actuator <NUM> on the surface of the valve seat plate <NUM>. The pair of projecting pieces <NUM> are positioned between the piezoelectric element <NUM> and the displacement transmitting section <NUM> and on both sides along the longitudinal direction (elongating/contracting direction) of the piezoelectric element <NUM> with gaps between the pair of projecting pieces <NUM> when the actuator <NUM> is fixed with screws.

Moreover, as shown in <FIG>, the pair of projecting pieces <NUM> are formed to be higher than the height of the surface of the piezoelectric element <NUM> of the actuator <NUM> fixed to the valve seat plate <NUM>.

The piezoelectric valve according to an embodiment of the present disclosure is the actuator <NUM> shown in <FIG>, and the entire circumferential surface of the piezoelectric element <NUM> can be coated with the silicone <NUM> filled between the pair of projecting pieces <NUM> by supplying the silicone <NUM> onto the surface of the piezoelectric element <NUM> after fixing the piezoelectric element <NUM> whose side surfaces at which the inner electrode layers are exposed have been coated with the silicone <NUM> to the valve seat plate <NUM>.

Moreover, in the piezoelectric valve according to an embodiment of the present disclosure, the entire circumferential surface of the piezoelectric element <NUM> can also be coated with the silicone <NUM> filled between the pair of projecting pieces <NUM> by integrating the piezoelectric element <NUM> whose surface has not been coated with the silicone <NUM> into the actuator <NUM>, fixing the actuator <NUM> to the valve seat plate <NUM>, and then supplying the silicone <NUM> onto the surface of the piezoelectric element <NUM>.

In the piezoelectric valve according to an embodiment of the present disclosure, the pair of projecting pieces <NUM> positioned on both the sides of the piezoelectric element <NUM> along the longitudinal direction of the piezoelectric element <NUM> with gaps between the pair of projecting pieces <NUM> when the actuator <NUM> is fixed to the valve seat plate <NUM> are provided on the surface of the valve seat plate <NUM>. This enables the entire circumferential surface to be easily coated with the silicone <NUM> filled between the pair of projecting pieces <NUM>.

Note that the piezoelectric valve according to an embodiment of the present disclosure eliminates the concern of an occurrence of an assembling failure when fixing the actuator <NUM> to the valve seat plate <NUM> even in a case where the silicone <NUM> spreads out and adheres to a place other than the surface of the piezoelectric element <NUM> by integrating the piezoelectric element <NUM> whose surface has not been coated with the silicone <NUM> into the actuator <NUM>, fixing the actuator <NUM> to the valve seat plate <NUM>, and then supplying the silicone <NUM> onto the surface of the piezoelectric element <NUM> to coat the entire circumferential surface of the piezoelectric element <NUM> with the silicone <NUM> filled between the pair of projecting pieces <NUM>.

Herein, in the present disclosure, the silicone <NUM> indicates a low-viscosity silicone rubber, and preferably a silicone rubber having a viscosity of more than or equal to <NUM> Pa·s and less than or equal to <NUM> Pa·s, and more preferably, a silicone rubber having a viscosity of <NUM> Pa·s can be used.

Moreover, considering workability, a one-component room temperature curing silicone rubber is preferably used, and for example, a low-viscosity silicone rubber "KE-<NUM> (product name)" manufactured by Shin-Etsu Chemical Co. or the like is preferably used.

In <FIG>, the electrodes <NUM> of interconnection lines molded for supplying power to the piezoelectric element <NUM> are exposed at a rear position of the valve seat plate <NUM>, and are connected to the lead lines <NUM> of the piezoelectric element <NUM> by soldering. The electrodes <NUM> of the interconnection lines are coated with an insulation material not shown in a state in which the electrodes <NUM> is connected to the lead lines <NUM>. An insulation resin material such as silicone, for example, can be used as the insulation material.

Moreover, as shown in <FIG>, the actuator <NUM> has an insulating film <NUM> bonded at a rear position on the surface of the displacement transmitting section <NUM> in the displacement enlarging mechanism <NUM>.

In <FIG>, the interconnection lines from the interconnection line substrate <NUM> to the piezoelectric element <NUM> are molded in the valve seat plate <NUM> to which the actuator <NUM> is attached. The lead lines <NUM> of the piezoelectric element <NUM> are arranged on the insulating film <NUM> so as to be prevented from being in contact with the metallic material constituting the displacement enlarging mechanism <NUM> of the actuator <NUM>. The lead lines <NUM> of the piezoelectric element <NUM> are connected, by soldering, to the electrodes <NUM> of the interconnection lines exposed at the rear position of the valve seat plate <NUM>.

Herein, a low moisture-permeable film, for example, can be used as the insulating film <NUM>.

In the present disclosure, the low moisture-permeable film refers to a resin film made of a material having a moisture permeability of less than or equal to <NUM>/m<NUM>·24hr in <NUM>-mm thickness in an environment at a temperature of <NUM> and a relative humidity of <NUM>%.

A resin film made of a low moisture-permeable material such as, for example, a polyolefin-based resin film of polyethylene, polypropylene, polyethylene terephthalate, or the like can be used as the low moisture-permeable film. Alternatively, a resin film subjected to moisture permeability reducing treatment such as being coated with a moisture permeability reducing agent such as fluorine can also be used as the low moisture-permeable film.

The piezoelectric valve according to an embodiment of the present disclosure described above is provided with the pair of projecting pieces <NUM> on the surface of the valve seat plate <NUM>. In a case of directly attaching the actuator <NUM> to the valve main body <NUM>, a pair of projecting pieces can also be provided on an inner wall surface of the valve main body. In that case, by fixing the actuator to the valve main body, and then supplying the silicone <NUM> onto the surface of the piezoelectric element, the entire circumferential surface of the piezoelectric element <NUM> can be coated with the silicone <NUM> filled between the pair of projecting pieces <NUM>.

In the piezoelectric valve of the present disclosure, the surface of the piezoelectric element is coated with silicone having properties excellent in water resistance and water proofness. This can prevent broken pieces of the piezoelectric element from being ejected together with compressed gas when in use, and can prevent moisture from entering the piezoelectric element to shorten the life even in a case of usage in a highly-humid environment.

Moreover, in the piezoelectric valve of the present disclosure, the surface of the piezoelectric element is coated with silicone having properties whose elasticity and compressibility are greater than those of a conventional polyolefin-based resin. This can prevent the movement of the piezoelectric element from being interfered with to reduce the stroke or to cause a failure to perform a correct operation even in a case of coating the surface of the piezoelectric element with silicone thickly to some extent in order to prevent reduction in insulation resistance of the piezoelectric element in a high-temperature, highly-humid environment.

<FIG> shows a graph indicating an ejection pressure property of air ejected from the piezoelectric valve, which is a graph in which a case where the surface of the piezoelectric element is coated with silicone and a case where the surface of the piezoelectric element is not coated with silicone are compared. Note that a coating thickness in the case where the surface of the piezoelectric element is coated with silicone is about <NUM>, and reduction in insulation resistance in a high-temperature, highly-humid environment can be prevented.

Experiments were conducted based on the method described in [Example] in <CIT>. Experimental conditions were as follows:.

In <FIG>, the broken line indicates a result of a piezoelectric valve in which the surface of the piezoelectric element is coated with silicone. Moreover, the solid line indicates a result of a piezoelectric valve in which the surface of the piezoelectric element is not coated with silicone.

Comparing them, they substantially agree in air ejection pressure property, and in the piezoelectric valve according to an embodiment of the present disclosure, it was confirmed that the movement of the piezoelectric element was not interfered with even in a case of coating the surface of the piezoelectric element with silicone thickly to some extent in order to prevent reduction in insulation resistance of the piezoelectric element in a high-temperature, highly-humid environment.

The present disclosure is not limited to the above-described embodiment, and can obviously be modified as appropriate in configuration within the range of the disclosure.

Claim 1:
A piezoelectric valve (<NUM>) in which the valve is opened/closed utilizing a displacement of a laminated piezoelectric element (<NUM>, <NUM>), comprising:
a valve main body (<NUM>) having a gas pressure chamber that receives compressed gas supplied externally; and
an actuator (<NUM>) having a valving element (<NUM>), the laminated piezoelectric element (<NUM>, <NUM>) configured to generate a driving force required for operating the valving element (<NUM>) as the displacement, a displacement enlarging mechanism (<NUM>) that enlarges the displacement of the laminated piezoelectric element (<NUM>, <NUM>) to be acted on the valving element (<NUM>), the actuator (<NUM>) being disposed in the valve main body (<NUM>), wherein:
a surface of the laminated piezoelectric element (<NUM>, <NUM>) is coated with silicone in a state in which the laminated piezoelectric element (<NUM>, <NUM>) is integrated into the actuator (<NUM>);
the displacement enlarging mechanism (<NUM>) is formed of a metallic material, and an interconnection line for supplying power to the laminated piezoelectric element (<NUM>, <NUM>) is molded in a plate (<NUM>) formed of a resin material;
an electrode (<NUM>) of the interconnection line exposed from the plate (<NUM>) is coated with an insulation material in a state in which the electrode (<NUM>) is connected to a lead line (<NUM>) of the laminated piezoelectric element (<NUM>, <NUM>);
characterized in that
the surface of the laminated piezoelectric element (<NUM>, <NUM>) is coated with silicone filled between a pair of projecting pieces (<NUM>) positioned on both sides of the laminated piezoelectric element (<NUM>, <NUM>) along a longitudinal direction of the laminated piezoelectric element (<NUM>, <NUM>) with gaps between the pair of projecting pieces (<NUM>).