JPH0810035B2 - Piezoelectric valve - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric valve that controls the flow of fluid with a piezoelectric element that bends when a voltage is applied.

2. Description of the Related Art As shown in FIG. 7, a conventional piezoelectric valve of this type is provided with a valve element 2 on a valve actuating plate 1 having a cantilevered support structure composed of a pair of laminated ferroelectric materials. The valve seat 3 is configured so as to oppose the valve seat 3. The voltage applied to the valve seat 1 causes the valve seat 1 to bend due to the electrostrictive lateral effect, and the valve body 2 changes the lift a of the valve seat 3. Therefore, the flow rate was controlled. (For example, Japanese Examined Patent Publication No. 55-30143) However, in the above configuration, the dynamic pressure stress due to the flow of the fluid acting on the valve element 2 is received in the thickness direction of the valve actuating plate 1 and cantilevered. Since it is a support structure, there is a problem that the rigidity of the valve operating plate 1 is weak against the dynamic pressure of the flow and the flow rate characteristic with respect to the voltage is distorted as shown in FIG. That is, the flexural strain is easily influenced by the dynamic pressure of the flow other than the flexure of the valve operating plate 1 due to the applied voltage. In addition, since the valve operating plate 1 has a bimorph structure, when a DC voltage is applied for a long time, there is a problem that polarization deterioration of one of the bonded piezoelectric bodies is caused. The reason for polarization deterioration is that one of the two piezoelectric bodies that are bonded together causes an electric field to act in the direction of expansion and contraction of the other, which causes displacement. Will work. When an electric field in the opposite direction to the polarization is continuously applied, polarization is a characteristic of the piezoelectric body. However, this problem can be avoided if it is driven by an AC voltage.

Further, as shown in FIG. 9, the displacement amount is enlarged by connecting the two bimorph type piezoelectric elements 4 and 5 with the spacers 6 at both ends, and the passage is performed by the valve body 7 which interlocks with the center of the lower piezoelectric element 5. There was a thing which adjusts the opening degree of the valve opening 9 provided in 8. (For example, Japanese Patent Laid-Open No. 61-236974) In this configuration as well, since the bimorph piezoelectric element is used, when a DC voltage is applied to drive the piezoelectric element, polarization deterioration of the piezoelectric body occurs as described above, and valve characteristics There is a problem that changes. In addition to this, since the two piezoelectric elements 5 and 6 are connected by the spacer 7, the displacement and force generated in the piezoelectric element are lost in the spacer and its linking portion, so that an extra voltage is applied or the piezoelectric element is enlarged. There were problems such as having to do it.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention solves the above-mentioned problems of the related art. The piezoelectric element has sufficient rigidity, is not easily affected by dynamic pressure due to fluid flow, and can be driven by a DC voltage. An object is to provide a piezoelectric valve with less force loss.

Means for Solving the Problems In order to solve the above problems, the piezoelectric valve of the present invention is a unimorph element in which a piezoelectric body is attached to one surface of a thin metal plate, and an outer peripheral edge portion of the unimorph element and a fitting gap. With a ring-shaped support body sandwiching the unimorph element, the front surface and the back surface of the unimorph element are opposed to each other, and the displacement unit abutting against the support element and the central portion of one of the pair of unimorph elements are in contact with each other. A piezoelectric valve is provided to provide a valve body that is supported and connected to the other central portion.

Action The present invention, by the above configuration, when a voltage is applied, the unimorph element bends in the plate thickness direction, and the outer peripheral edge portion of the unimorph element is supported with a support and play,
In the pair of unimorph elements, the force of the bending and the bending of the pair of unimorph elements smoothly act to act on the valve element as the displacement of the displacement unit to control the valve element. The displacement amount of the displacement unit changes depending on the magnitude of the voltage, and the opening degree of the valve opening also changes. When a predetermined voltage is turned on and off, the valve body opens and closes accordingly. Since the unimorph element supports the outer peripheral edge portion, the rigidity against bending stress is larger than that of the cantilever support, so that a piezoelectric valve that is not easily affected by dynamic pressure can be obtained.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIGS. 1 to 5, reference numerals 10, 11, 12, and 13 are disc-shaped unimorph elements made of a piezoelectric ceramic material, and outer peripheral portions of these unimorph elements are supported by supports 14 and 15 with play. Has been done. A pair of unimorph elements 10/11
The support so that they face each other and bend in opposite directions.
Set to 14 to form a displacement unit 16. Similarly, the unimorph elements 12 and 13 and the support 15 constitute a displacement unit 17.

The disassembled perspective view of the displacement unit 16 is shown in FIG. The unimorph elements 10 and 11 are made of a 42% nickel-iron alloy plate 18 with a thickness of 0.1 mm and a 0.1% thickness.
A piezoelectric ceramic plate 19 made of lead zirconate titanate having a plate thickness of millimeter is laminated, and a hole 20 is formed at the center of the substrate.
The edge of the piezoelectric body is formed slightly outside the edge of the
21 ・ 22 ・ 23 are joined with nickel solder. Support 14
Has a hole 24 and a groove 25 for allowing a molded product of a thermoplastic polyacetal resin to pass through the lead wire.

A perspective view of the displacement unit 16 is shown in FIG. After inserting and setting the unimorph element into the support 4, the three edges of the support 14 made of a thermoplastic resin are melted by heat and crushed, and the unimorph element is semi-fixed while having play in the radial direction. In the embodiment of the present invention shown in FIGS. 1 and 2, the valve body 26
Displacement unit 16 for the purpose of increasing the stroke of
The structure is such that 17 is connected in two stages via the connecting body 27.
FIG. 5 shows a perspective view of the connector 27.

Returning to FIG. 1 and continuing the description, the pressure balance piston 28 is brought into contact with the center of the unimorph element 10, and the magnet 29
The valve body 26 is provided via the. The valve body 26 is formed by baking a nitrile rubber 31 on a magnetic shaft rod 30 in a spherical shape, and has excellent closing performance when it comes into contact with the valve seat 32. Shaft rod
The contact surface of the magnet 30 with the magnet 29 is formed in a spherical shape, and the valve body 26
The swingability of the is improved, and a more secure closure is secured. Further, the spring 33 acts on the valve body 26 in the direction biased by the valve seat 32.

The magnet 29 is fixed in the pressure balance piston 28, and not only has the function of adsorbing and holding the spherical surface of the shaft rod 30, but also adsorbing and holding the magnetic fluid 34 in the groove portion of the outer circumference of the balance piston 28 of polyacetal resin, and forming the fluid passage 35. Displacement unit chamber 36
A magnetic fluid seal is provided between and. In addition, an inlet 38 and an outlet 39 are formed in the body case 37, and an upper lid 40 and a lower lid 41 are attached.

An adjusting screw 42 is screwed into the center of the lower lid 41, abuts on the center of the unimorph element 13, and adjusts and fixes the fixed position of the unimorph element 13.

In the above configuration, when the applied voltage is zero, the unimorph elements 10, 11, 12, 13 are flat as shown in FIG. 1, and the valve body 26 closes the valve seat 32. Therefore, the fluid flow is blocked. When a voltage is applied to the unimorph element 10/11/12/13, the unimorph element 10
・ Displacement unit as the deflection of 11/12/13 changes
The displacement of 16 and 17 also changes and the valve element 26 opens as shown in FIG.
Since the valve body 26 changes the opening degree with the valve seat 32 according to the displacement amount of the displacement units 16 and 17, it acts to change the fluid flow rate, and its characteristics are as shown in FIG.

In this case, the fluid flow can be controlled even if the inlet 35 and the outlet 36 are reversed. In this case, according to the test results, the slope (gain) and the position (voltage value) of the characteristics were slightly changed. Further, since the displacement units 16 and 17 have sufficient rigidity, the effect of dynamic pressure due to the fluid flow does not appear in the characteristics at all, which is good. The rigidity of the unimorph element is sufficient even if it is a strip shape, but if it is a disk shape, even greater rigidity can be obtained. In addition, the disc shape has a simple shape and is easy to mass produce, and has advantages in terms of an assembly jig and assemblability.

In addition, since the unimorph elements that are displaced in opposite directions are made to face each other, a sufficient displacement magnifying effect is obtained, and rigidity is obtained because the outer peripheral edge of the unimorph element is supported by a support. Since there is play in the support of the peripheral portion, there is an effect that there is no loss in force and displacement, and smooth and good characteristics can be obtained. This is because there is no backlash in the direction of the flexure axis, and there is no resistance against the outer peripheral edge of the unimorph element flexibly moving in the radial direction.

Also, as already explained, since it is a unimorph element, there is no concern that the polarization of the element will deteriorate even if it is driven by a DC voltage, and there is an effect that it can be used safely without being changed in characteristics for a long time by incorporating it in household appliances etc. is there. In addition, the fact that it can be driven with a DC voltage means that a piezoelectric valve with significantly less discharge loss and lower power consumption can be realized, compared to the case where an element is repeatedly charged and discharged like an AC voltage and loss is caused by the amount of discharge. It has a unique effect.

Furthermore, since a plurality of displacement units can be connected through a connecting body, the displacement unit can be easily applied to a large flow rate piezoelectric valve that requires a large force and displacement. Also connected
If 27 is made of a conductive material, there is an effect that the lead wire 23 becomes unnecessary and the assembling becomes easier.

Generally, a silver electrode is often used as the electrode of the piezoelectric element, but by using a nickel electrode and connecting the lead wire with nickel solder, silver migration during soldering or DC voltage driving, There is an effect that it is possible to prevent problems such as partial disappearance of electrodes and poor conduction due to so-called migration.

The unimorph element has a structure in which a piezoelectric ceramic of lead zirconate titanate and an iron-nickel plate are laminated, and the thermal expansion coefficients of these laminated materials are close to each other, so the effect of temperature can be reduced. There is.

Furthermore, the displacement unit has a structure in which the support body is made of a thermoplastic resin, and after inserting the unimorph element, a part of the support body is melted by heat to partially fix the outer peripheral edge portion of the unimorph element with play. Therefore, the support can be lightened with resin first, which is advantageous because it does not hinder extra force loss and response in the operation of the unimorph element. Moreover, only a part of the resin is melted with a hot iron, and no extra parts are required, and the work is easy.

Further, by forming the hole 4 or the groove 25 for passing the lead wire in a part of the support, the work of wiring the lead wire is easy, and the wiring position is fixed, so that problems such as electrical insulation and leak short circuit hardly occur. There is.

Further, in the unimorph element, the adjustment screw is in contact with the fixed portion on the side opposite to the side where the valve element is provided, and the position of the displacement unit can be easily adjusted, and the operating position or non-energized position of the valve element can be finely adjusted. This has the effect of compensating for variations in characteristics due to parts and other factors after assembly or installation of equipment.
Specifically, by adjusting the adjusting screw, it is possible to change the voltage characteristics such as the voltage value at which the valve body begins to open and the voltage value at which the maximum flow rate is reached, or to set the valve opening so that the minimum flow rate is maintained when there is no energization. A unique effect can be obtained.

Further, since the unimorph element has a hole 20 formed at the center of the substrate and a piezoelectric wire is formed at a position slightly outside the edge of the hole 20, the stress acting on the center supporting portion of the unimorph element is not applied to the substrate. Even if it acts directly, it will act indirectly and weakly on the piezoelectric body, and since it can prevent the piezoelectric body from cracking or cracking, a piezoelectric valve with higher long-term durability and reliability is realized. There is an effect that can be done.

Effects of the Invention As described above, according to the piezoelectric valve of the present invention, the following effects can be obtained.

A displacement unit including a pair of plate-shaped unimorph elements that face each other and are displaced in opposite directions, and a support unit that supports the outer peripheral edge portions of the pair of unimorph elements with play, and the pair of unimorph elements Since a part of one of them is fixed and a valve body is provided on the other, (1) First, since the unimorph elements that are displaced in opposite directions are opposed to each other, a sufficient displacement magnifying effect can be obtained.

(2) Since the outer peripheral edge portion of the unimorph element is supported by the support body, rigidity is obtained, and the influence of dynamic pressure due to the flow of fluid is scarcely exerted.

(3) Further, since the support of the outer peripheral portion has a play, there is an effect that there is no loss in force and displacement, and smooth and good characteristics can be obtained. This is because there is no backlash in the direction of the flexure axis, and there is no resistance against the outer peripheral edge of the unimorph element flexibly moving in the radial direction.

(4) Since it is a unimorph element, there is no concern that the polarization of the element will deteriorate even if it is driven by a DC voltage, and there is an effect that it can be incorporated into household appliances and the like and can be used with peace of mind without long-term characteristic changes.

(5) In addition, the fact that it can be driven by a DC voltage means that a piezoelectric valve with significantly less discharge loss and lower power consumption is compared to the case where the element is repeatedly charged and discharged like an AC voltage, resulting in loss of discharge. There is a unique effect that can be realized.

(6) Compared with a valve that uses electromagnetic force or a motor, the configuration is simple, the number of parts is small, the power consumption is extremely small, and the flow rate is continuously variable or open / close control is widely used.

[Brief description of drawings]

FIG. 1 is a front sectional view of a piezoelectric valve according to an embodiment of the present invention,
2 is a front sectional view showing an open state of the piezoelectric valve, FIG. 3 is an exploded perspective view of the displacement unit of the piezoelectric valve, FIG. 4 is a perspective view of the displacement unit of the piezoelectric valve, and FIG. FIG. 6 is a perspective view of a piezoelectric valve connecting body, FIG. 6 is a representative flow rate characteristic diagram of the piezoelectric valve, FIG. 7 is a front sectional view of a conventional piezoelectric valve, and FIG. 8 is a representative flow rate characteristic diagram of the piezoelectric valve. The figure is a front sectional view of another conventional piezoelectric valve. 10/11/12/13 ... Unimorph element, 14/15 ... Support, 16/17 ... Displacement unit, 26 ... Valve body, 27 ... Coupling body, 42 ... Adjusting screw.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-4682 (JP, A) JP-A-60-65968 (JP, A) Actually open Sho-60-114499 (JP, U) Actual-open Sho-60- 160187 (JP, U)

Claims (10)

[Claims] 1. A front surface and a back surface of the unimorph element sandwiching a unimorph element in which a piezoelectric body is provided on one surface of a thin metal plate and a ring-shaped support having a fitting gap with an outer peripheral edge portion of the unimorph element. A piezoelectric valve provided with a displacement unit which is opposed to each other and abuts against the support, and a valve body which abuts and supports a central part of one of the pair of unimorph elements and is connected to the other central part. 2. A piezoelectric valve according to claim 1, wherein a plurality of displacement units are connected via a connecting body. 3. The piezoelectric valve according to claim 2, wherein the connecting body is made of a conductive material. 4. The piezoelectric valve according to claim 1, wherein the unimorph element has a disk shape. 5. The piezoelectric valve according to claim 1, wherein the unimorph element has a hole at the center of the substrate and an edge of the piezoelectric body is formed at a position slightly outside the edge of the hole. 6. The piezoelectric element according to claim 1, wherein the unimorph element has a structure in which a piezoelectric ceramic and an iron-nickel plate are bonded together, a nickel electrode is formed on the piezoelectric ceramic, and lead wires are joined by nickel solder. valve. 7. The piezoelectric valve according to claim 1, wherein the unimorph element is driven by applying a DC voltage. 8. A displacement unit, in which a unimorph element having a support made of a thermoplastic resin is inserted, a part of the support is melted by heat, and an outer peripheral edge portion of the unimorph element is semi-fixed with play. The piezoelectric valve according to claim 1. 9. The piezoelectric valve according to claim 1, wherein an adjusting screw is brought into contact with a fixed portion of the unimorph element on the side opposite to the side where the valve body is provided. 10. The piezoelectric valve according to claim 1, wherein a hole or a groove through which the lead wire is passed is formed in a part of the support.