Patent Description:
Conventionally, a piezoelectric valve has been known that utilizes displacement of a laminated piezoelectric element to open and close the valve and discharge a compressed gas (see Patent Literature <NUM>).

The piezoelectric valve described in Patent Literature <NUM> utilizes characteristics of a laminated piezoelectric element with excellent high-speed response performance, and includes a piezoelectric actuator that utilizes displacement of the laminated piezoelectric element to open and close the valve element.

The piezoelectric actuator has a displacement enlargement mechanism that enlarges a small displacement of the laminated piezoelectric element based on the principle of leverage. At an end part of the displacement enlargement mechanism, a pair of leaf springs are provided symmetrically with respect to the longitudinal axis of the laminated piezoelectric element, and a valve element is provided between the pair of leaf springs.

In the piezoelectric valve, when a voltage is applied to the laminated piezoelectric element, the displacement of the laminated piezoelectric element in the extension direction is transmitted to the valve element via the displacement enlargement mechanism, and the valve element is rapidly moved to open the valve.

Conversely, in the piezoelectric valve, when the voltage is not applied to the laminated piezoelectric element, the restoring force of the laminated piezoelectric element that accompanies the restoration to the original state is transmitted to the valve element via the displacement enlargement mechanism, so that the valve element is promptly brought into contact with the valve seat to close the valve.

Meanwhile, to improve the strength of the laminated piezoelectric element against the tensile force in the piezoelectric actuator, a tensile load is applied to the laminated piezoelectric element mounted on the displacement enlargement mechanism in advance in the extension direction (longitudinal direction) of the laminated piezoelectric element.

However, in the piezoelectric actuator, the tensile load distorts the displacement enlargement mechanism, which deforms the front surface of the valve element provided between the pair of leaf springs. This generates a risk of air leakage due to weakening of the pressing force and airtightness of the valve element against the valve seat surface when the piezoelectric valve is assembled.

As described in Patent Literature <NUM>, it is possible to prevent air leakage when the valve is closed by pressing the valve element of the piezoelectric actuator against the valve seat surface with a compression margin when the piezoelectric valve is assembled. However, if the front surface of the valve element is deformed by tensile load, it is necessary to take a large compression margin. This makes the opening and closing operation of the valve element slow, and makes the movement amount of the valve element small. Therefore, the valve cannot open and close at high speed and with high accuracy, leading to a problem that deteriorates the performance of the piezoelectric valve. <CIT> concerns a piezoelectric valve. <CIT> concerns a fuel injection valve for an internal combustion engine.

It is an object of the present disclosure to provide a piezoelectric actuator that can reduce a risk of air leakage due to weakened pressing force against a valve seat surface of a valve element and airtightness, a piezoelectric valve using the piezoelectric actuator, and a method of manufacturing a piezoelectric actuator.

Aspects of the present invention are defined in the accompanying claims. According to a first 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 objectives, the present disclosure is
a piezoelectric actuator used for a piezoelectric valve that opens and closes a valve utilizing displacement of a laminated piezoelectric element, the piezoelectric actuator comprising:.

Preferably, the piezoelectric actuator of the present disclosure is such that
the tensile load is applied to the laminated piezoelectric element in a direction of the valve element.

Preferably, the piezoelectric actuator of the present disclosure is such that.

Preferably, the piezoelectric actuator of the present disclosure is such that
a surface of the valve element to be in contact with the valve seat of the piezoelectric valve is subjected to a lubricating treatment.

In addition, in order to achieve the above objectives, this disclosure is
a piezoelectric valve comprising:.

Preferably, the piezoelectric valve of the present disclosure further comprises.

Furthermore, in order to achieve the above objectives, the present disclosure is.

Preferably, the method of manufacturing the piezoelectric actuator of the present disclosure is such that.

The piezoelectric actuator of the present disclosure has the valve element to be in contact with the valve seat of the piezoelectric valve. The surface of the valve element is made flat and smooth in a state in which a tensile load is applied to the laminated piezoelectric element. Therefore, when the piezoelectric valve is assembled, it is possible to reduce a risk of air leakage due to the weakening of the pressing force of the valve element against the valve seat surface and airtightness.

In addition, the piezoelectric actuator of the present disclosure does not need to take a large compression margin in assembling the piezoelectric valve even when the valve element is pressed against the valve seat surface with a compression margin to prevent air leakage at a time of closing the valve. Thus, it is possible to open and close the valve at high speed and with high accuracy.

In the piezoelectric actuator of the present disclosure,
if the surface of the valve element to be in contact with the valve seat of the piezoelectric valve is subjected to a lubricating treatment, the surface of the valve element can have highly non-adhesive and lubricating properties. Therefore, when the piezoelectric valve is not operated for a long time after the piezoelectric valve is assembled, it is possible to prevent the valve element from adhering to the valve seat surface and becoming difficult to separate, resulting in malfunction.

In the piezoelectric valve of the present disclosure, a piezoelectric actuator having a valve element to be in contact with the valve seat is used. The surface of the valve element is made flat and smooth in a state in which a tensile load is applied to the laminated piezoelectric element. Thus, it is possible to reduce the risk of air leakage due to the weakening of the pressing force of the valve element against the valve seat surface and airtightness.

In addition, the piezoelectric valve of the present disclosure does not need to take a large compression margin in assembling the piezoelectric valve even when the valve element is pressed against the valve seat surface with a compression margin to prevent air leakage at a time of closing the valve. Thus, it is possible to open and close the valve at high speed and with high accuracy.

The method of manufacturing a piezoelectric actuator of the present disclosure is such that the surface of the valve element to be in contact with the valve seat of the piezoelectric valve is made flat and smooth, in a state in which a tensile load is applied to the laminated piezoelectric element. Therefore, it is possible to manufacture a piezoelectric actuator capable of reducing the risk of air leakage due to weakening of the pressing force of the valve element against the valve seat surface and airtightness.

In addition, the method of manufacturing a piezoelectric actuator of the present disclosure is such that the surface of the valve element to be in contact with the valve seat of the piezoelectric valve is made flat and smooth, in a state in which a tensile load is applied to the laminated piezoelectric element. Therefore, the method does not need to take a large compression margin in assembling the piezoelectric valve even when the valve element is pressed against the valve seat surface with a compression margin to prevent air leakage at a time of closing the valve, and can manufacture a piezoelectric actuator that can open and close a valve at high speed and with high accuracy.

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

<FIG> is a perspective view of an example of a piezoelectric valve. <FIG> is an exploded perspective view of the piezoelectric valve of <FIG>. <FIG> is an explanatory diagram of a piezoelectric actuator used for the piezoelectric valve of <FIG>. <FIG> is an explanatory diagram of a state in which the piezoelectric actuator is fixed to a valve seat plate used for the piezoelectric valve of <FIG>. <FIG> is a cross-sectional view of the piezoelectric valve of <FIG> and an explanatory diagram of a state in which the valve seat plate is disposed inside the valve main part.

The piezoelectric valve <NUM> shown in <FIG> includes a valve main part <NUM>, a valve seat plate <NUM> disposed inside the valve main part <NUM> and fixed to the valve main part <NUM>, and a piezoelectric actuator <NUM> fixed to both sides of the valve seat plate <NUM> with screws.

The valve main part <NUM> is a case whose front surface is open, and includes a gas pressure chamber inside that receives supply of compressed gas from an external compressed gas supply source (not shown).

Furthermore, a connector portion <NUM> is provided on the front surface of the valve main part <NUM>. A gas suction port <NUM> for sucking compressed gas into the valve main part <NUM> and a gas discharge port <NUM> for discharging compressed gas are opened on the front surface of the connector portion <NUM>.

A wiring board <NUM> for supplying power to a laminated piezoelectric element <NUM> (hereinafter referred to as "piezoelectric element") is disposed between the valve main part <NUM> and the connector portion <NUM>. A wiring connector <NUM> for supplying power to the piezoelectric element <NUM> via the wiring board <NUM> is disposed at one side end of the connector portion <NUM> and at a lateral position of the valve main part <NUM>.

The valve seat plate <NUM> is provided with attachment part for the piezoelectric actuator <NUM> on both sides, and has a valve seat <NUM> with which a valve element <NUM> to be described below of the piezoelectric actuator <NUM> is in contact. Furthermore, in a front protruding portion <NUM> of the valve seat plate <NUM>, gas discharge paths <NUM> is formed through which the valve seat surface of the valve seat <NUM> is in communication with the gas discharge port <NUM> of the connector portion <NUM>.

A lid member <NUM> that closes the opening of the valve main part <NUM> is attached to the front surface of the valve seat plate <NUM>. The lid member <NUM> is formed with an opening <NUM> into which the front protruding portion <NUM> of the valve seat plate <NUM> fits. The lid member <NUM> is formed with a gas suction path <NUM> through which the gas suction port <NUM> that opens on the front surface of the connector portion <NUM> is in communication with the inside of the valve main part <NUM>.

The valve seat plate <NUM> is molded from, for example, a synthetic resin material, and the wiring from the wiring board <NUM> to the piezoelectric element <NUM> is molded.

At the rear position of the valve seat plate <NUM>, there is exposed electrodes of the wiring connected to lead wires of the piezoelectric element <NUM> (not shown).

As shown in <FIG>, the piezoelectric actuator <NUM> includes the valve element <NUM>, a piezoelectric element <NUM> that generates a driving force required for operation of the valve element <NUM> as a displacement, and a displacement enlargement mechanism <NUM> that enlarges the displacement of the piezoelectric element <NUM> and causes it to act on the valve element <NUM>.

For the piezoelectric element <NUM>, for example, a resin-coated-type piezoelectric element can be used. The resin-coated-type piezoelectric element is thinly coated with epoxy resin over the entire peripheral surface including the side surface where the internal electrode layer is exposed.

For the valve element <NUM>, for example, nitrile rubber (NBR) or fluorine rubber (FKM, FEPM, FFKM) can be used. The nitrile rubber and fluorine rubber used for the valve element <NUM> are preferably those having a hardness of, for example, <NUM> ± <NUM>.

The valve element <NUM> can be subjected to a lubricating treatment such as a halogenation treatment at least on the surface to be in contact with the valve seat surface of the valve seat <NUM>.

If the piezoelectric valve <NUM> is not operated for a long time, the rubber valve element <NUM> may adhere to the valve seat surface of the resin valve seat <NUM> and be difficult to separate, which may cause malfunction. However, if at least the surface of the valve element <NUM> to be in contact with the valve seat is subjected to a lubricating treatment so that it has highly non-adhesive and lubricating properties, it would be possible to prevent malfunction.

The displacement enlargement mechanism <NUM> has a displacement enlargement portion <NUM> that enlarges the displacement of the piezoelectric element <NUM> and a displacement transmission portion <NUM> that transmits the displacement of the piezoelectric element <NUM> to the displacement enlargement portion <NUM>. The displacement enlargement portion <NUM> and the piezoelectric element <NUM> are respectively arranged symmetrically with respect to the axis in the operating direction of the valve element <NUM>, here, the straight line connecting the valve element <NUM> and the longitudinal axis of the piezoelectric element <NUM>.

The displacement transmission portion <NUM> has a U-shaped base board <NUM> to which one end of the piezoelectric element <NUM> is joined, and a cap member <NUM> to which the other end of the piezoelectric element <NUM> is joined. The piezoelectric element <NUM> is disposed in the space of the U-shaped base board <NUM>, so that the displacement enlargement mechanism <NUM> is arranged symmetrically with respect to the longitudinal axis of the piezoelectric element <NUM>.

Here, the piezoelectric element <NUM> is installed in the space of the U-shaped base board <NUM> between the U-shaped bottom portion <NUM> of the base board <NUM> and the cap member <NUM>, for example, via an adhesive. One end of the piezoelectric element <NUM> is joined to the U-shaped bottom portion <NUM> of the base board <NUM> and the other end is joined to the cap member <NUM>, by plastically deforming the U-shaped bottom portion <NUM> of the base board <NUM>. A tensile load is applied to the piezoelectric element <NUM> in the direction of the valve element <NUM> (the direction of pressing against the valve element <NUM>) by plastically deforming the U-shaped bottom portion <NUM> of the base board <NUM>.

The displacement enlargement portion <NUM> is configured of a first and second displacement enlargement portions 34a and 34b arranged symmetrically with respect to a straight line connecting the valve element <NUM> and the longitudinal axis of the piezoelectric element <NUM>.

The first displacement enlargement portion 34a has a first and second hinges <NUM> and <NUM>, a first arm <NUM>, and a first leaf spring <NUM>. The first arm <NUM> is integrated with one side end of the U-shaped base board <NUM> by a first hinge <NUM>. The first arm <NUM> is integrated with the cap member <NUM> by the second hinge <NUM>. One end of the first leaf spring <NUM> is joined to the outer end part of the first arm <NUM>.

On the other hand, the second displacement enlargement portion 34b has a third and fourth hinges <NUM> and <NUM>, a second arm <NUM>, and a second leaf spring <NUM>. The second arm <NUM> is integrated with the other side end of the U-shaped base board <NUM> by the third hinge <NUM>. The second arm <NUM> is integrated with the cap member <NUM> by the fourth hinge <NUM>. One end of the second leaf spring <NUM> is joined to the outer end part of the second arm <NUM>.

Here, the displacement enlargement mechanism <NUM> can be integrally formed by punching out a metal material such as a stainless steel material including an invar material, except for the first and second leaf springs <NUM> and <NUM>, for example.

The first leaf spring <NUM> and the second leaf spring <NUM> can be formed from, for example, one sheet of metal plate material. Here, the first leaf spring <NUM> and the second leaf spring <NUM> are respectively formed on opposite parts of one sheet of single metal plate material, which is symmetrical with respect to the longitudinal axis of the piezoelectric element <NUM> and is formed into a shape having an installation portion <NUM> of the valve element <NUM> in the central part. The installation portion <NUM> is, for example, a portion including a flat installation surface orthogonal to the longitudinal axis of the piezoelectric element <NUM>. One ends of the first and second leaf springs <NUM> and <NUM> are joined to the outer end parts of the first and second arms <NUM> and <NUM>, respectively. The valve element <NUM> is provided on the installation portion <NUM> located between the other ends of the first and second leaf springs <NUM> and <NUM> and on the longitudinal axis of the piezoelectric element <NUM>.

When the piezoelectric element <NUM> is energized in the valve closed state of the piezoelectric actuator <NUM>, the piezoelectric element <NUM> extends. In the displacement enlargement mechanism <NUM>, the displacement of the piezoelectric element <NUM> due to the extension is enlarged by the principle of leverage with the first and third hinges <NUM> and <NUM> serving as fulcrums, the second and fourth hinges <NUM> and <NUM> serving as efforts, and the outer end parts of the first and second arms <NUM> and <NUM> serving as loads, and this largely displaces the outer end parts of the first and second arms <NUM> and <NUM>.

Then, the displacement of the outer end parts of the first and second arms <NUM> and <NUM> separates the valve element <NUM> from the valve seat <NUM> via the first and second leaf springs <NUM> and <NUM>, and opens the gas discharge path <NUM>.

Conversely, the above piezoelectric actuator <NUM> works such that: when the piezoelectric element <NUM> is not energized, the piezoelectric element <NUM> contracts; the contraction causes the valve element <NUM> to be seated on the valve seat <NUM> via the displacement enlargement mechanism <NUM>; and this closes the gas discharge path <NUM>.

Note that it is also possible to: form the first leaf spring <NUM> and the second leaf spring <NUM> using separate members; and join one lateral end part of the valve element <NUM> to the other end of the first leaf spring <NUM> and join the other lateral end part of the valve element <NUM> to the other end of the second leaf spring <NUM> to provide the valve element <NUM> between the other ends of the first and second leaf springs <NUM> and <NUM>.

<FIG> is an enlarged view of part A of <FIG>, and is an explanatory diagram of the piezoelectric actuator in a state in which a tensile load is applied to the laminated piezoelectric element. <FIG> is an explanatory diagram of the piezoelectric actuator of <FIG> in which the surface of the valve element is made flat and smooth in a state in which a tensile load is applied to the laminated piezoelectric element.

In the piezoelectric actuator <NUM>, the U-shaped bottom portion <NUM> of the base board <NUM> is plastically deformed, so that a tensile load is applied to the piezoelectric element <NUM> in the direction of the valve element <NUM>. Therefore, the displacement enlargement mechanism <NUM> is distorted, and, for example, the front surface of the valve element <NUM> provided in the installation portion <NUM> between the other ends of the first leaf spring <NUM> and the second leaf spring <NUM> is deformed in a concave shape, as shown in <FIG>. This makes a risk in which air leakage occurs due to weakening of the pressing force of the valve element <NUM> against the valve seat surface and airtightness when the piezoelectric valve is assembled.

Then, in the embodiments of the present disclosure, the front surface of the valve element <NUM> in the piezoelectric actuator <NUM> is made flat and smooth so as to be orthogonal to the longitudinal axis of the piezoelectric element <NUM>, that is, the axis of the valve element <NUM> in the operating direction in a state in which a tensile load is applied to the piezoelectric element <NUM>.

For example, in the embodiment of the present disclosure, as shown in <FIG>, the piezoelectric actuator <NUM> can have the front surface of the concavely deformed valve element <NUM> made flat and smooth by polishing.

Alternatively, in the embodiments of the present disclosure, the piezoelectric actuator <NUM> can have the valve element <NUM> provided so as to be integrally formed with the installation portion <NUM> provided in the central part between the other ends of the first and second leaf springs <NUM> and <NUM>, in a state in which a tensile load is applied to the piezoelectric element <NUM>. In this way, the front surface of the valve element <NUM> can be made flat and smooth.

In the piezoelectric actuator in the embodiment of the present disclosure, the surface of the valve element <NUM> to be in contact with the valve seat <NUM> of the piezoelectric valve <NUM> is made flat and smooth in a state in which a tensile load is applied to the piezoelectric element <NUM>. Therefore, when the piezoelectric actuator is assembled to the piezoelectric valve <NUM>, it is possible to reduce the risk of air leakage due to weakening of the pressing force of the valve element <NUM> against the valve seat surface and airtightness.

In the piezoelectric actuator in the embodiment of the present disclosure, the valve element can also be pressed against the valve seat surface with a compression margin to assemble the piezoelectric valve, as described in Patent Literature <NUM>.

The piezoelectric actuator in the embodiment of the present disclosure does not need to take a large compression margin in assembling the piezoelectric valve even when the valve element is pressed against the valve seat surface with a compression margin to prevent air leakage at a time of closing the valve. Thus, it is possible to open and close the valve at high speed and with high accuracy.

The embodiments of the present disclosure are described above, but it goes without saying that the present disclosure is not limited to the above embodiments, and the configuration thereof can be appropriately changed as long as it does not deviate from the scope of the disclosure, the invention being defined by the appended claims.

Claim 1:
A method of manufacturing a piezoelectric actuator (<NUM>) configured to be used for a piezoelectric valve (<NUM>) that opens and closes a valve utilizing displacement of a laminated piezoelectric element (<NUM>),
the piezoelectric actuator (<NUM>) including: a valve element (<NUM>), the surface of which is configured to be in contact with a valve seat (<NUM>) of the piezoelectric valve (<NUM>); a laminated piezoelectric element (<NUM>) configured to generate a driving force as a displacement, and a displacement enlargement mechanism (<NUM>), the driving force being required for operation of the valve element (<NUM>), the displacement enlargement mechanism (<NUM>) configured to enlarge the displacement of the laminated piezoelectric element (<NUM>) and cause the enlarged displacement to act on the valve element (<NUM>), the method characterized by comprising:
making the surface of the valve element (<NUM>) flat and smooth by polishing it when it is in a state in which a tensile load is being applied to the laminated piezoelectric element (<NUM>) and a front surface of the valve element (<NUM>) is concavely deformed;
wherein the tensile load is applied to the laminated piezoelectric element (<NUM>) in a direction of the valve element (<NUM>).