Piezoelectric valve

Abstract

Provided is a piezoelectric valve (1) driven by a DC component, the piezoelectric valve (1) being provided with: a plurality of piezoelectric elements (12A, 12B) electrically connected in parallel via an electrode (14) formed from a metal plating film; a conductive vibrating plate (13) that is joined to the plurality of piezoelectric elements (12A, 12B) via an electrode (14); and a resistor (22) electrically connected to the plurality of piezoelectric elements (12A, 12B). The resistance value (R1) of the resistor (22) is smaller than the insulation resistance value (R2) of the piezoelectric elements (12A, 12B).

Description

Technical Field

[0001] This disclosure relates to piezoelectric valves. Background Technology

[0002] Piezoelectric elements, possessing the characteristic of deforming due to the inverse piezoelectric effect, are used as piezoelectric actuators that convert electrical signals into physical deformations (see, for example, Japanese Patent Application Publication No. 04-6885). Examples of applications for piezoelectric actuators include piezoelectric valves. Piezoelectric valves, for example, can be applied to compressed air regulators. Compressed air regulators are installed in compressed air piping used in factories, etc., and have the function of maintaining a constant pressure within that piping. Summary of the Invention

[0003] In piezoelectric valves, piezoelectric elements that utilize strain deformation are typically used. Such a piezoelectric valve, for example, comprises a piezoelectric element and a vibrating plate electrically connected to the piezoelectric element. The electrodes of the piezoelectric element are, for example, sintered electrodes using electrode materials such as Ag or AgPd alloys. However, in sintered electrodes using Ag or AgPd alloys as electrode materials, there is a problem of ion migration, leading to a decrease in reliability in piezoelectric valves driven by DC components.

[0004] Previous studies have addressed this problem by using stable metals such as Pt to form sintered electrodes and by sputtering stable metals such as Au to form coated electrodes. However, the former method tends to result in an increased thickness of the sintered electrode, which can hinder the deformation of the piezoelectric element. Furthermore, the latter method tends to result in inconsistent contact resistance values ​​of the piezoelectric element, potentially reducing the stability of the drive.

[0005] This disclosure was made to solve the aforementioned technical problems, and its purpose is to provide a piezoelectric valve that can sufficiently ensure the stability of the drive regardless of the inconsistency of the contact resistance value of the piezoelectric element.

[0006] The gist of this disclosure is as follows.

[0007] [1] A piezoelectric valve driven by a DC component, the piezoelectric valve comprising: a plurality of piezoelectric elements electrically connected in parallel via electrodes formed of a metal coating; a conductive vibrating plate engaged with the plurality of piezoelectric elements via the electrodes; and a resistor electrically connected to the plurality of piezoelectric elements, the resistance value of the resistor being less than the insulation resistance value of the piezoelectric elements.

[0008] In this piezoelectric valve, multiple piezoelectric elements are electrically connected in parallel via electrodes formed by a metal coating. When using electrodes formed by a metal coating, ion migration problems can be avoided even when the piezoelectric valve is driven by a DC component. While electrodes formed by a metal coating can be used to bond the electrodes of multiple piezoelectric elements to each other or to bond the piezoelectric elements to a vibrating plate using adhesives, inconsistencies in adhesive thickness can lead to inconsistencies in the contact resistance values ​​between the multiple piezoelectric elements or between the piezoelectric elements and the vibrating plate. Therefore, in this piezoelectric valve, a resistor is electrically connected to the multiple piezoelectric elements. The resistor functions as a protective resistor to suppress overcurrent flowing through the multiple piezoelectric elements. Furthermore, by making the resistance value of the resistor less than the insulation resistance value of the piezoelectric elements, the current flowing through the multiple piezoelectric elements can be stabilized regardless of inconsistencies in the contact resistance values ​​between them. Therefore, the stability of the piezoelectric valve's operation can be sufficiently ensured.

[0009] [2] As described in [1], in the piezoelectric valve, the resistance value of the resistor is greater than the contact resistance value between the vibrating plate and the electrode of the piezoelectric element. In this case, when viewed from the overall circuit including the piezoelectric element, the vibrating plate, and the resistor, the inconsistency in the contact resistance value between the vibrating plate and the electrode of the piezoelectric element can be relatively small. Therefore, the stability of the piezoelectric valve's actuation can be sufficiently ensured.

[0010] [3] As described in [1] or [2], the resistance value of the resistor is greater than the contact resistance value between the electrodes of the plurality of piezoelectric elements. In this case, when viewed from the overall perspective of the circuit including the piezoelectric elements, the vibrating plate, and the resistor, the inconsistency in the contact resistance values ​​between the electrodes of the plurality of piezoelectric elements can be made relatively small. Therefore, the stability of the piezoelectric valve's actuation can be sufficiently ensured.

[0011] [4] The piezoelectric valve as described in any one of [1] to [3], wherein the electrode is formed by sputtering or vapor deposition. In this case, even when the piezoelectric valve is driven by a DC component, the problem of ion migration can be reliably avoided, and the reliability of the piezoelectric valve can be improved.

[0012] [5] The piezoelectric valve as described in any one of [1] to [4], wherein the electrode is disposed in a region that is further inward than the outline of the piezoelectric element. In this case, the occurrence of short circuits caused by the electrode can be suppressed.

[0013] [6] The piezoelectric valve as described in any one of [1] to [5], wherein the plurality of piezoelectric elements are joined to each other by an adhesive member that does not contain conductive components, and one of the plurality of piezoelectric elements and the vibrating plate are joined by an adhesive member that does not contain conductive components. By using an adhesive member that does not contain conductive components, the adhesive members between the plurality of piezoelectric elements and between the piezoelectric elements and the vibrating plate can be formed relatively thinly. Therefore, it is possible to prevent the deterioration of characteristics caused by the thickness of the adhesive member. In addition, by using an adhesive member that does not contain conductive components, it is possible to suppress the occurrence of short circuits.

[0014] [7] The piezoelectric valve as described in [5], wherein the adhesive member is configured to protrude to the outside of the contour of the piezoelectric element. This improves the bonding strength between multiple piezoelectric elements and the bonding strength between the piezoelectric element and the vibrating plate.

[0015] [8] The piezoelectric valve as described in any one of [1] to [7], wherein one of the long sides of the vibrating plate is a fixed end and the other side is a free end. This ensures sufficient displacement of the free end of the vibrating plate due to strain deformation of the piezoelectric element. Therefore, the piezoelectric element and the vibrating plate can be appropriately used as the valve body of the piezoelectric valve.

[0016] [9] The piezoelectric valve as described in [8] includes a wiring portion electrically connected to the electrode and the vibrating plate, wherein the electrode and the wiring portion are joined by an adhesive member that does not contain conductive components, and the vibrating plate and the wiring portion are joined by an adhesive member that does not contain conductive components. By adopting such a structure, it is possible to avoid adverse conditions such as solder erosion. Furthermore, by using an adhesive member that does not contain conductive components, it is possible to suppress the occurrence of short circuits.

[0017]

[10] As described in [9], the piezoelectric valve has the wiring section located at the fixed end side of the piezoelectric element and the vibrating plate. By positioning the wiring section at the fixed end side, the influence of stress generated by the strain deformation of the piezoelectric element on the wiring section can be suppressed. Thus, wire breakage and the like can be appropriately prevented. Attached Figure Description

[0018] Figure 1 This is a perspective view of a piezoelectric valve according to one embodiment of the present invention.

[0019] Figure 2 yes Figure 1 The diagram shows an exploded perspective view of the piezoelectric valve.

[0020] Figure 3 yes Figure 1 The top view of the piezoelectric valve shown.

[0021] Figure 4 yes Figure 1 The cross-sectional view of the piezoelectric valve shown is shown in the diagram, where (a) is the closed state of the inlet orifice and (b) is the open state of the inlet orifice.

[0022] Figure 5 This is a 3D diagram of the piezoelectric component.

[0023] Figure 6 yes Figure 5 The side view of the piezoelectric part shown.

[0024] Figure 7 This is a diagram showing the circuit structure of the piezoelectric element. Detailed Implementation

[0025] Hereinafter, a preferred embodiment of a piezoelectric valve according to one aspect of the present invention will be described in detail with reference to the accompanying drawings.

[0026] Figure 1 This is a perspective view of a piezoelectric valve according to one embodiment of the present invention. Figure 2 This is an exploded 3D view of a piezoelectric valve. Figure 3 This is a top view of a piezoelectric valve. Figure 4 This is a cross-sectional view of a piezoelectric valve. Figure 3 For ease of explanation, a top view is shown with the cover of the housing removed.

[0027] Figures 1-4 The piezoelectric valve 1 shown is, for example, a device suitable for a compressed air regulator. The compressed air regulator is installed in the piping of compressed air used in factories, etc., and has the function of maintaining the pressure within that piping at a constant level. For example... Figures 1-4 As shown, the piezoelectric valve 1 has a housing 2 and a valve body 3.

[0028] The housing 2 is made of resin, for example, and has: a bottomed main body 4 with an opening on one side; and a cover 5 fixed to one side of the main body 4 to close the opening of the main body 4. The housing 2 is fixed to the main body 4 by the cover 5 via a sealing member (not shown), thereby becoming a generally rectangular box-shaped structure with an airtight internal space S. In the following description, the long side direction (along the long side when viewed from above) of the housing 2 is defined as the X direction, the short side direction (along the short side when viewed from above) of the housing 2 is defined as the Y direction, and the thickness direction of the housing 2 is defined as the Z direction.

[0029] An air inlet hole P1 and an air outlet hole P2 are formed in the housing 2 (see reference). Figure 3Both the inlet hole P1 and the outlet hole P2 are circular in cross-section and communicate with the internal space S of the housing 2. The inlet hole P1 is the part that allows air from the primary side to flow into the housing 2. For example, the inlet hole P1 is located at one end in the X direction and at the center in the Y direction at the bottom 4a of the main body 4. At the location of the inlet hole P1, a nozzle 6 protruding toward the cover 5 is provided in the internal space S.

[0030] The outlet hole P2 is the part that allows air inside the housing 2 to flow out to the secondary side. For example, the outlet hole P2 is located at the bottom 4a of the main body 4, at the center in the Y direction, on the end side further in the X direction than the inlet hole P1. There are no particular limitations on the inner diameters of the inlet hole P1 and the outlet hole P2, but in this embodiment, the inner diameter of the outlet hole P2 is larger than the inner diameter of the inlet hole P1.

[0031] Valve body 3 is disposed within housing 2, opening and closing the inlet port P1. For example... Figure 5 and Figure 6 As shown, the valve body 3 is composed of a piezoelectric section 11 including a plate-shaped piezoelectric element 12 and a vibrating plate 13 on which the piezoelectric element 12 is stacked. The piezoelectric section 11 is powered by a power source 21 (described later) Figure 7 DC drive is performed by supplying voltage to the piezoelectric element 12. Through DC drive, the piezoelectric element 12 and the vibrating plate 13 are strained and deformed towards the cover portion 5. This results in the vibrating plate 13 abutting against the front end face 6a of the nozzle 6 of the inflow hole P1 in a closed state (see reference). Figure 4 (a) and the open state of the vibrating plate 13 separated from the front end face 6a of the nozzle 6 of the inflow hole P1 (refer to) Figure 4 (b) is switched to open and close the inlet port P1.

[0032] The vibrating plate 13, when viewed from above, is, for example, rectangular in shape. The vibrating plate 13 is formed of a conductive material, such as metal. The constituent material of the vibrating plate 13 can be carbon fiber reinforced plastic, Alloy 42 (nickel-iron alloy), etc. The thickness of the vibrating plate 13 can be the same as the thickness of the piezoelectric element 12, or it can be slightly larger than the thickness of the piezoelectric element 12.

[0033] A notch may also be provided at any corner of the vibrating plate 13. The notch serves as a mark for visually confirming the interior and exterior of the vibrating plate 13, and helps improve the ease of installation when mounting the piezoelectric part 11 to the housing 2. The shape of the notch (the shape cut through the notch) can be various shapes such as triangular, rectangular, or arc-shaped.

[0034] In this embodiment, the piezoelectric part 11 is as follows Figure 5 and Figure 6As shown, there are multiple plate-shaped piezoelectric elements 12 (piezoelectric element 12A and piezoelectric element 12B). Each piezoelectric element 12 has a body 10 and a pair of electrodes 14. The body 10 does not have internal electrodes and is composed of a single-layer piezoelectric body layer. The piezoelectric body layer is formed of a piezoelectric material such as piezoelectric ceramic. Examples of piezoelectric ceramic materials include PZT [Pb(Zr,Ti)O3], PT (PbTiO3), PLZT [(Pb,La)(Zr,Ti)O3], or barium titanate (BaTiO3).

[0035] Electrodes 14 are respectively disposed on both sides of the piezoelectric element 12. Electrodes 14 are, for example, formed by sputtering, vapor deposition, or other metal coatings. That is, electrodes 14 are formed by sputtering or vapor deposition. Electrodes 14 can be composed of multiple layers of metal coatings. Examples of materials for electrodes 14 include stable metals such as chromium (Cr), copper-nickel alloy (Ni-Cu), gold (Au), and platinum (Pt). The planar shapes of the electrodes 14 on both sides of the piezoelectric element 12 are both rectangular shapes, for example, smaller than the planar shape of the body 10. When viewed from above, the electrodes 14 are positioned in a region closer to the outline of the piezoelectric element 12, and a frame-shaped electrode non-forming region is formed at the edge of the piezoelectric element 12.

[0036] The piezoelectric section 11 is constructed, for example, by stacking multiple piezoelectric elements 12 of different dimensions along their long side in descending order of size on the vibrating plate 13. Figure 5 and Figure 6 In this example, piezoelectric elements 12A and 12B are stacked parallel to each other on one side of the vibrating plate 13. One electrode 14 of piezoelectric element 12A contacts one side of the vibrating plate 13, and the other electrode 14 of piezoelectric element 12A contacts one electrode 14 of piezoelectric element 12B. Thus, the vibrating plate 13 and piezoelectric element 12A are electrically connected to each other, and piezoelectric elements 12A and 12B are electrically connected to each other. In this embodiment, the thickness of piezoelectric element 12A and the thickness of piezoelectric element 12B are the same. Alternatively, one of the thicknesses of piezoelectric element 12A and piezoelectric element 12B may be greater than the other.

[0037] The piezoelectric element 12A, which overlaps with the vibrating plate 13, is the element that mainly contributes to the displacement of the piezoelectric section 11. The dimension of the piezoelectric element 12A in the X direction is smaller than the dimension of the vibrating plate 13 in the X direction. Therefore, the position of the piezoelectric element 12A relative to the vibrating plate 13 can be arbitrarily adjusted in the X direction. In this embodiment, the piezoelectric element 12A is located at the opposite end in the X direction on one side of the vibrating plate 13. The length of the vibrating plate 13 protruding from one end of the piezoelectric element 12A in the X direction is greater than the length of the vibrating plate 13 protruding from the other end of the piezoelectric element 12A in the X direction. Furthermore, the dimension of the piezoelectric element 12A in the Y direction is slightly smaller than the dimension of the vibrating plate 13 in the Y direction. Due to this dimensional difference, the forming area of ​​the adhesive portion 15A, described later, is provided on one side of the vibrating plate 13.

[0038] The piezoelectric element 12B, which overlaps with the piezoelectric element 12A, is the element that primarily contributes to the power (torque) of the piezoelectric section 11. The dimension of piezoelectric element 12B in the X direction is smaller than that of piezoelectric element 12A in the X direction. Piezoelectric element 12B is offset to one end of piezoelectric element 12A in the X direction, to the extent that the electrode non-forming region at one end of piezoelectric element 12A is slightly exposed. Furthermore, the dimension of piezoelectric element 12B in the Y direction is slightly smaller than that of piezoelectric element 12A in the Y direction. Due to this dimensional difference, the forming region of the adhesive portion 15B (described later) is located in the electrode non-forming region of piezoelectric element 12A.

[0039] An adhesive portion 15 is provided for bonding the vibrating plate 13 to the piezoelectric element 12A, and for bonding the piezoelectric element 12A to the piezoelectric element 12B. From the viewpoint of preventing short circuits, the adhesive portion 15 is made of an adhesive material that does not contain conductive particles or other conductive components. Examples of adhesive materials constituting the adhesive portion 15 include thermosetting epoxy resin. When viewed from the Z-direction, the adhesive portion 15 is located in a region that is further inward than the outline of the piezoelectric element 12. Alternatively, when viewed from the Z-direction, the adhesive portion 15 may be positioned such that it protrudes further outward than the outline of the piezoelectric element 12.

[0040] In this embodiment, such as Figure 5 and Figure 6 As shown, the adhesive portion 15A for joining the vibrating plate 13 and the piezoelectric element 12A is disposed on the entire surface of one side of the piezoelectric element 12A, connecting one side of the vibrating plate 13 and the electrode 14 on one side of the piezoelectric element 12A. A portion of the adhesive portion 15A is arranged to protrude slightly outward from the outline of the piezoelectric element 12A and wrap around the side of the piezoelectric element 12A. Figure 5 and Figure 6In this example, the adhesive portion 15A protrudes outward from the entire end edge of the piezoelectric element 12A. The adhesive portion 15A may also protrude outward from a portion of the end edge of the piezoelectric element 12A. In this case, the adhesive portion 15A may, for example, protrude outward only from both end edges of the piezoelectric element 12A in the X direction, or it may protrude outward only from both end edges of the piezoelectric element 12A in the Y direction.

[0041] The adhesive portion 15B for joining piezoelectric element 12B and piezoelectric element 12A is disposed on the entire surface of one side of piezoelectric element 12B to connect the electrode 14 on the other side of piezoelectric element 12A and the electrode 14 on one side of piezoelectric element 12B. A portion of the adhesive portion 15B is arranged to protrude slightly outward from the outline of piezoelectric element 12B and to wrap around the side of piezoelectric element 12B. Figure 5 and Figure 6 In this example, the adhesive portion 15B protrudes outward from all end edges of the piezoelectric element 12B. The adhesive portion 15B may also protrude outward from only a portion of the end edges of the piezoelectric element 12B. In this case, the adhesive portion 15B may, for example, protrude outward only from both end edges of the piezoelectric element 12B in the X direction, or it may protrude outward only from both end edges of the piezoelectric element 12B in the Y direction.

[0042] The adhesive portion 15, as described above, is made of an adhesive material that does not contain conductive components. The driving voltage of the piezoelectric portion 11 includes, for example, a high voltage of several hundred volts. Therefore, even when using adhesive portions 15A and 15B made of an adhesive material that does not contain conductive components, the electrical connection between the vibrating plate 13 and the piezoelectric element 12A, and the electrical connection between the piezoelectric element 12A and the piezoelectric element 12B, can be maintained respectively.

[0043] like Figure 5 As shown, the piezoelectric section 11 has a wiring section 16 for driving the piezoelectric element 12. The wiring section 16 is electrically connected to one side of the vibrating plate 13, the electrode 14 on the other side of the piezoelectric element 12A, and the electrode 14 on the other side of the piezoelectric element 12B via a bonding section 17. The bonding section 17, like the adhesive section 15, is made of an adhesive material that does not contain conductive components. The bonding section 17 may also be made of solder, for example. In this case, Sn-Ag-Cu and the like can be listed as solder materials for the bonding section 17.

[0044] Figure 7 This is a diagram showing the circuit structure of the piezoelectric element. For example... Figure 7 As shown, the power supply unit 21 for driving is electrically connected to the piezoelectric unit 11. Piezoelectric elements 12A and 12B are connected in parallel. The vibrating plate 13 is connected in series with piezoelectric elements 12A and 12B. A resistor 22 is connected in series between the parallel-connected piezoelectric elements 12A and 12B and the power supply unit 21.

[0045] Resistor 22 functions as a protective resistor to suppress overcurrent flowing in piezoelectric elements 12A and 12B. In this embodiment, the resistance value R1 of resistor 22 is less than the insulation resistance value R2 of piezoelectric elements 12A and 12B. The resistance value R1 of resistor 22 is greater than the contact resistance value R3 between the vibrating plate 13 and the electrode 14 of the piezoelectric element 12 (here, piezoelectric element 12A). Furthermore, the resistance value R1 of resistor 22 is greater than the contact resistance value R3 between the electrodes 14 of the plurality of piezoelectric elements 12 (here, piezoelectric elements 12A and 12B).

[0046] The insulation resistance R2 of piezoelectric elements 12A and 12B is equivalent to the resistance of the base 10, which serves as the insulator. The contact resistance R3 between the vibrating plate 13 and the electrode 14 of piezoelectric element 12A is equivalent to the resistance between one side of the vibrating plate 13 and one side of the electrode 14 of piezoelectric element 12A via the adhesive portion 15A. The contact resistance R3 between the electrodes 14 of piezoelectric elements 12A and 12B is equivalent to the resistance between the other side of the electrode 14 of piezoelectric element 12A and one side of the electrode 14 of piezoelectric element 12B via the adhesive portion 15B. As an example, the insulation resistance R2 of piezoelectric elements 12A and 12B is 1 × 10⁻⁶. 9 The contact resistance R3 between the vibrating plate 13 and the electrode 14 of the piezoelectric element 12A, and between the electrodes 14 of the piezoelectric element 12A and the piezoelectric element 12B, is 1×10 Ω. 2 In the case of Ω, the resistance value R1 of resistor 22 is set to 1×10. 5 Ω.

[0047] When the piezoelectric part 11 is fixed inside the housing 2, as follows: Figure 4 (a) and Figure 4 As shown in (b), a stepped portion 31 is provided in the main body portion 4 of the housing 2. The stepped portion 31 is located at the bottom 4a of the main body portion 4 on the opposite end in the X direction. The top surface 31a of the stepped portion 31 is a flat surface and is rectangular in shape when viewed from above. The height of the stepped portion 31 from the bottom 4a is, for example, the same as the amount of protrusion of the nozzle 6 from the bottom 4a.

[0048] The piezoelectric part 11 is positioned on the stepped part 31 with adhesive parts 15A and 15B located on the stepped part 31, and the protruding portion 13a of the vibrating plate 13 protruding from one end of the piezoelectric element 12A in the X direction faces the nozzle 6. The other end of the vibrating plate 13 in the X direction is fixed to the top surface 31a of the stepped part 31 by bonding members such as adhesive or double-sided tape. Thus, the vibrating plate 13 becomes a cantilever support on the stepped part 31. The end of the vibrating plate 13 on the side of the inlet hole P1 becomes a free end, and the end of the vibrating plate 13 on the side opposite to the inlet hole P1 becomes a fixed end. The wiring part 16 is located on the fixed end side of the vibrating plate 13 by placing the connecting portion 17 on the stepped part 31.

[0049] In this embodiment, such as Figure 4 (a) and Figure 4 As shown in (b), the cover portion 5 of the housing 2, serving as a cantilever support for reinforcing the vibrating plate 13, is provided with a protrusion 32 protruding toward the stepped portion 31. The protrusion 32 is provided with a certain width extending in the Y-axis direction, and its front end is a flat surface. The protrusion 32 holds the fixed end side of the vibrating plate 13 by clamping the vibrating plate 13 and the piezoelectric element 12 (piezoelectric element 12A and piezoelectric element 12B described later) between itself and the stepped portion 31.

[0050] The inlet port P1 is opened and closed via the free end of the vibrating plate 13. In this embodiment, in the cantilevered vibrating plate 13, the protruding portion 13a of the vibrating plate 13 protruding from one end of the piezoelectric element 12A in the X direction abuts against the front end face 6a of the nozzle 6 that defines the inlet port P1. Figure 3 As shown, when viewed from the stacking direction (Z direction) of the piezoelectric element 12 in the piezoelectric section 11, the inlet hole P1 does not overlap with the piezoelectric element 12, but only with the vibrating plate 13. Figure 3 In the example, when viewed from the stacking direction (Z direction) of the piezoelectric element 12 in the piezoelectric section 11, the front end face 6a of the nozzle 6 does not overlap with either the piezoelectric element 12A or the piezoelectric element 12B, but only with the vibrating plate 13.

[0051] Regarding the portion of nozzle 6 that does not contact the vibrating plate 13, that is, the portion of nozzle 6 excluding the front end face 6a, when viewed from the stacking direction (Z direction) of the piezoelectric elements 12 in the piezoelectric section 11, does not overlap with either piezoelectric element 12A or piezoelectric element 12B, but only with the vibrating plate 13. Furthermore, regarding the portion of nozzle 6 excluding the front end face 6a, a portion of it, when viewed from the stacking direction (Z direction) of the piezoelectric elements 12 in the piezoelectric section 11, may overlap with piezoelectric element 12A, or with both piezoelectric elements 12A and 12B.

[0052] In addition, Figure 3 In the example, when viewed from the stacking direction (Z direction) of the piezoelectric elements 12 in the piezoelectric section 11, a portion of the outflow hole P2 overlaps with the vibrating plate 13, but the positional relationship between the outflow hole P2 and the piezoelectric section 11 is not particularly restricted. Alternatively, when viewed from the stacking direction (Z direction) of the piezoelectric elements 12 in the piezoelectric section 11, the entire outflow hole P2 overlaps with the vibrating plate 13. Alternatively, when viewed from the stacking direction (Z direction) of the piezoelectric elements 12 in the piezoelectric section 11, the outflow hole P2 overlaps with both the piezoelectric elements 12 and the vibrating plate 13.

[0053] At the position opposite to the inlet hole P1, separated by the vibrating plate 13, such as Figure 4 (a) and Figure 4 As shown in (b), a force-applying part 33 is provided to apply force to the vibrating plate 13 toward the inlet hole P1. In this embodiment, the force-applying part 33 is, for example, a spring member such as a coil spring. The force-applying part 33 is disposed in the internal space S between the cover 5 and the protruding portion 13a of the vibrating plate 13, facing the inlet hole P1 with the vibrating plate 13 in between. By using the force-applying part 33 to press the protruding portion 13a of the vibrating plate 13 against the front end face 6a of the nozzle 6, the inlet hole P1 can be kept closed without strain deformation of the piezoelectric element 12.

[0054] An elastic member 34 is disposed between the vibrating plate 13 and the inlet hole P1. The elastic member 34 is formed, for example, from an elastomer into a disk shape with a diameter larger than the inner diameter of the inlet hole P1. In this embodiment, the elastic member 34 is fixed to the nozzle 6 side of the protruding portion 13a of the vibrating plate 13 by a bonding member such as an adhesive or double-sided tape. The elastic member 34 functions as a sealing member to improve the airtightness when the inlet hole is closed. In addition, the elastic member 34 functions as a vibration absorption member to mitigate the vibration when the vibrating plate 13 hits the inlet hole P1 (the front end face 6a of the nozzle 6).

[0055] As explained above, in the piezoelectric valve 1, piezoelectric elements 12A and 12B are electrically connected in parallel via electrodes 14 formed of a metal coating. Using electrodes 14 formed of a metal coating avoids ion migration problems even when the piezoelectric valve 1 is driven by a DC component. When using electrodes 14 formed of a metal coating, the electrodes 14 of piezoelectric elements 12A and 12B can be bonded to each other or to the piezoelectric element 12A and the vibrating plate 13 using an adhesive or the like. However, it is believed that inconsistencies in the thickness of the adhesive can lead to inconsistencies in the contact resistance values ​​between piezoelectric elements 12A and 12B or between piezoelectric element 12A and the vibrating plate 13.

[0056] In this regard, in piezoelectric valve 1, resistor 22 is electrically connected to piezoelectric elements 12A and 12B. Resistor 22 functions as a protective resistor to suppress overcurrent flowing in piezoelectric elements 12A and 12B. Furthermore, by making the resistance value R1 of resistor 22 smaller than the insulation resistance value R2 of piezoelectric elements 12A and 12B, the current flowing in piezoelectric elements 12A and 12B can be stabilized regardless of the inconsistency of the contact resistance value R3 between piezoelectric elements 12A and 12B. Therefore, the stability of the actuation of piezoelectric valve 1 can be sufficiently ensured.

[0057] In this embodiment, the resistance value R1 of resistor 22 is greater than the contact resistance value R3 between the vibrating plate 13 and the electrode 14 of piezoelectric element 12A. Furthermore, in this embodiment, the resistance value R1 of resistor 22 is greater than the contact resistance value R3 between the electrodes 14 of piezoelectric elements 12A and 12B. Therefore, when viewed as a whole circuit including piezoelectric elements 12A and 12B, vibrating plate 13, and resistor 22, the inconsistency of the contact resistance value R3 between the vibrating plate 13 and the electrode 14 of piezoelectric element 12A is relatively small. Thus, the stability of the piezoelectric valve 1's actuation can be sufficiently ensured.

[0058] In this embodiment, electrode 14 is formed of sputtered film or vapor-deposited film. Therefore, even when the piezoelectric valve 1 is driven with a DC component, the problem of ion migration can be avoided more reliably, and the reliability of the piezoelectric valve 1 can be improved.

[0059] In this embodiment, electrode 14 is disposed in a region that is closer to the inner side of the contours of piezoelectric elements 12A and 12B. This allows for the suppression of short circuits caused by electrode 14.

[0060] In this embodiment, piezoelectric elements 12A and 12B are joined together by adhesive members that do not contain conductive components, and piezoelectric element 12A and vibrating plate 13 are joined by adhesive members that do not contain conductive components. By using adhesive members that do not contain conductive components, the adhesive members between piezoelectric elements 12A and 12B, and between piezoelectric element 12A and vibrating plate 13, can be formed relatively thinly. Therefore, it is possible to prevent the deterioration of characteristics caused by thickening of the adhesive members. Furthermore, by using adhesive members that do not contain conductive components, the occurrence of short circuits can be suppressed.

[0061] In this embodiment, the adhesive member is arranged to protrude to the outside of the contours of the piezoelectric elements 12A and 12B. This improves the bonding strength between the piezoelectric elements 12A and 12B, as well as the bonding strength between the piezoelectric element 12A and the vibrating plate 13.

[0062] In this embodiment, one of the long sides of the vibrating plate 13 is designated as the fixed end, and the other long side is designated as the free end. This ensures sufficient displacement of the free end of the vibrating plate 13 caused by the strain deformation of the piezoelectric elements 12A and 12B. Therefore, the piezoelectric elements 12A and 12B and the vibrating plate 13 can be appropriately used as the valve body 3 of the piezoelectric valve 1.

[0063] In this embodiment, a wiring portion 16 is provided that is electrically connected to the electrode 14 and the oscillating plate 13. The electrode 14 and the wiring portion 16 are joined by an adhesive member that does not contain conductive components, and the oscillating plate 13 and the wiring portion 16 are also joined by an adhesive member that does not contain conductive components. This structure avoids defects such as solder erosion. Furthermore, by using an adhesive member that does not contain conductive components, short circuits can be suppressed.

[0064] In this embodiment, the wiring section 16 is located on the fixed end side of the piezoelectric elements 12A, 12B and the vibrating plate 13. By positioning the wiring section 16 on the fixed end side, the influence of stress caused by the strain deformation of the piezoelectric elements 12A, 12B on the wiring section 16 can be suppressed. As a result, wire breakage and other defects in the wiring section 16 can be appropriately prevented.

[0065] This invention is not limited to the embodiments described above. For example, in the embodiments described above, the piezoelectric part 11 is composed of a stack of piezoelectric elements 12A and 12B with different dimensions along their long sides, but it is also possible for the piezoelectric elements 12A and 12B to have the same dimensions along their long sides. Furthermore, the number of piezoelectric elements 12 stacked on the vibrating plate 13 is not limited to two layers, and may be a single layer or three or more layers.

[0066] Furthermore, for example, in the above embodiment, the protrusion 32 is used to clamp the vibrating plate 13 and piezoelectric elements 12A and 12B disposed on the step portion 31 to the cover portion 5. However, it is also possible to adopt a structure in which an elastic member such as a leaf spring is disposed in the internal space S between the step portion 31 and the cover portion 5 instead of the protrusion 32, and the vibrating plate 13 and piezoelectric elements 12 (piezoelectric elements 12A and 12B described later) are pressed by the elastic member.

Claims

1. A piezoelectric valve, characterized in that, This piezoelectric valve is driven by DC component and has the following features: Multiple piezoelectric elements are connected in parallel via electrodes formed by metal coating; A conductive vibrating plate connected to the plurality of piezoelectric elements via the electrodes; and Resistors electrically connected to the plurality of piezoelectric elements, The resistance value of the resistor is less than the insulation resistance value of the piezoelectric element.

2. The piezoelectric valve as described in claim 1, characterized in that, The resistance value of the resistor is greater than the contact resistance value between the vibrating plate and the electrodes of the piezoelectric element.

3. The piezoelectric valve as described in claim 1 or 2, characterized in that, The resistance value of the resistor is greater than the contact resistance value between the electrodes of the plurality of piezoelectric elements.

4. The piezoelectric valve according to any one of claims 1 to 3, characterized in that, The electrode is formed by sputtering or vapor deposition.

5. The piezoelectric valve according to any one of claims 1 to 4, characterized in that, The electrode is disposed in a region that is inside the contour of the piezoelectric element.

6. The piezoelectric valve according to any one of claims 1 to 5, characterized in that, The plurality of piezoelectric elements are joined together by adhesive members that do not contain conductive components, and one of the piezoelectric elements and the vibrating plate are joined by adhesive members that do not contain conductive components.

7. The piezoelectric valve as described in claim 6, characterized in that, The adhesive member is configured to protrude outwards from the outline of the piezoelectric element.

8. The piezoelectric valve according to any one of claims 1 to 7, characterized in that, One side of the vibrating plate along its long side is designated as the fixed end, and the other side along its long side is designated as the free end.

9. The piezoelectric valve as described in claim 8, characterized in that, Includes a wiring section electrically connected to the electrodes and the vibrating plate. The electrode and the wiring portion are joined by an adhesive member that does not contain conductive components, and the vibrating plate and the wiring portion are joined by an adhesive member that does not contain conductive components.

10. The piezoelectric valve as described in claim 9, characterized in that, The wiring section is located on the fixed end side of the piezoelectric element and the vibrating plate.

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