JPH0945972A - Actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an actuator having simple structure which can be produced at lower cost than a magnetostrictive element and can expand/contract more than a piezoelectric element by employing a low cost piezoelectric material for the first layer and a conductive magnetostrictive material for the second layer. SOLUTION: A positive voltage is applied to each second positive layer 2a having conductivity and a negative voltage is applied to each second negative layer 2b having conductivity thus applying an electric field to each first layer 1. Consequently, the first piezoelectric layer 1 expands/contracts in the laminating direction of a multilayer element depending on the level of voltage applied through the second positive and negative layers 2a, 2b. When a magnetic field is applied to the element part 10 in the laminating direction by conducting a coil, each second positive and negative layers 2a, 2b also exhibiting magnetostrictive effect expand/contract in the laminating direction depending on the strength of magnetic field. Consequently, the layer of element 5 at the element part 10 is elongated when a positive voltage is applied to the positive electrode 12 and a negative voltage is applied to the negative electrode 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an actuator that produces a linear displacement, and can be applied to, for example, a positioning device or a pump driving device.

[0002]

2. Description of the Related Art Conventionally, an electromagnetic motor has been generally used as a positioning device or a driving device for a pump. However, in order to realize higher precision, high responsiveness and downsizing, a driving part is used. Those using a piezoelectric element or a giant magnetostrictive alloy have been developed. As an example of using the piezoelectric element, Journal of the Japan Society of Mechanical Engineers (C edition), Volume 60, 571 (1994-3), p. 9
There is a piezoelectric pump shown at 56. In addition, as an example of using the above giant magnetostrictive material, Journal of the Japan Society of Mechanical Engineers (C edition), 59, 5
63 (1993-7) P. There are servo valves and the like shown in 2112.

[0003]

However, since the amount of displacement generated by the piezoelectric element is very small, it is necessary to improve the processing accuracy of the parts used and the output range is limited. Therefore, as a means for structurally magnifying the displacement, Japanese Patent Application Laid-Open No. 62-230069 discloses a device for magnifying the displacement by a piezoelectric element by utilizing the resonance of a spring and a weight. It is known to use the principle or the relationship between cross-sectional area and pressure. However, even in these cases, as the actuator is used as a positioning device, a drive device for a pump, etc., the cost is high, the device becomes large, and the force that can be generated further increases the expansion rate for expanding the displacement of the piezoelectric element. There was a problem of becoming smaller.

Further, although the amount of displacement generated in the giant magnetostrictive element is larger than that in the piezoelectric element, the giant magnetostrictive material such as terphenol D having a large magnetostrictive effect contains an expensive rare earth element as a main component. There is a problem that the material cost becomes high. In particular, the amount of displacement is not required to use a giant magnetostrictive element, and even when the amount of displacement is small when using the piezoelectric element, there is no choice but to use an expensive giant magnetostrictive material, and the material cost is high. Was becoming.

[0005]

The present invention has been made to solve the above problems, and has a first layer having a piezoelectric effect and a magnetostrictive effect having conductivity. An element part formed by alternately laminating the first layer and the second layer so that at least one first layer is sandwiched between the second layer and the second layer; and the element part. A voltage controller for applying a voltage to the second layer of the first layer to apply a desired electric field to the first layer, an electromagnetic coil for forming a magnetic field parallel to the stacking direction of the element portion, and the electromagnetic coil. And an electric current control unit for controlling an electric current, wherein an electric field is applied to the first layer and a magnetic field is applied to the second layer to displace the element unit. , Each of the first layers expands and contracts due to the piezoelectric effect,
Since each of the second layers expands and contracts due to the magnetostrictive effect, the displacement of the element portion can be increased by adding the expansion and contraction action of each of the layers.

Therefore, by using a low-cost piezoelectric material for the first layer and a magnetostrictive material having conductivity for the second layer, the magnetostrictive material can be formed with a simple structure. It is possible to obtain an actuator which is lower in cost than the used magnetostrictive element and has a larger expansion / contraction amount than the piezoelectric element. For example, cost reduction can be achieved when an expansion amount larger than that of the piezoelectric element and smaller than that of the magnetostrictive element is required.

In the invention described in claim 2 of the present application, each second layer of the above-mentioned claim 1 is provided with an electrode for applying a voltage, and the internal electrode of the first layer is provided. The voltage control unit applies a positive voltage to every other electrode of the second layer and applies a negative voltage to the electrodes of the other second layers to apply the negative voltage to the electrodes of the other second layers. Characterized by applying an electric field to the layer of, by using a conductive magnetostrictive material for the internal electrodes that were essential in the conventional multilayer piezoelectric element but did not contribute to expansion and contraction, in all layers of the element part The expansion and contraction action can be efficiently obtained.

The invention according to claim 3 of the present application comprises at least one first layer having a piezoelectric effect and a second layer having an electroconductivity and a magnetostriction effect. The first layer and the second layer are alternately laminated so that the first layer is sandwiched by the second layer, an electric field is applied to the first layer, and a magnetic field is applied to the second layer in the laminating direction. In addition, the first
And an actuator characterized by displacing a second layer, wherein each of the first layers expands and contracts by a piezoelectric effect, and each of the second layers expands and contracts by a magnetostrictive effect. The displacement can be increased by adding the stretching action of each layer.

Therefore, by using a low-cost piezoelectric material for the first layer and a magnetostrictive material having conductivity for the second layer, the magnetostrictive material can be formed with a simple structure. It is possible to obtain an actuator which is lower in cost than the used magnetostrictive element and has a larger expansion / contraction amount than the piezoelectric element. For example, cost reduction can be achieved when an expansion amount larger than that of the piezoelectric element and smaller than that of the magnetostrictive element is required.

In the invention described in claim 4 of the present application, each second layer of claim 3 is provided with an electrode for applying a voltage, and the internal electrode of the first layer is provided. And applying a positive voltage to every other electrode of the second layer and applying a negative voltage to the electrodes of the other second layers to apply an electric field to the first layer. Characterized by
By using a conductive magnetostrictive material for the internal electrodes, which is essential in the conventional laminated piezoelectric element but does not contribute to expansion and contraction, it is possible to efficiently expand and contract in all the layers of the element part.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic view showing a structural example of a laminated element used for the actuator of the present invention. In FIG. 1, a first layer 1 made of a piezoelectric material having a piezoelectric effect and a second layer 2 made of a magnetostrictive material having both conductivity and magnetostrictive effect are alternately and repeatedly laminated. That is, the laminated element 5 includes at least one first
Layers 1 are alternately laminated so as to be sandwiched by the second layers 2, and the second layers 2 are each formed by the first layer 1 described above.
It also serves as an internal electrode.

In the laminated element 5, the green sheet of each of the first layers 1 made of the raw material powder of the piezoelectric material and the binder is prepared by, for example, the tape casting method, and also in each of the second layers 2 to be the electrodes. , A green sheet made of powder of a material having a magnetostrictive effect is prepared, and after drying each green sheet, the carrier film is peeled off and cut into a rectangular plate shape having a predetermined size, and then, as described above. They are stacked in this order and integrally fired. The manufacturing method is publicly known, and detailed description thereof is omitted here.

FIG. 2 is a schematic view showing an example of the structure of an element portion used in the actuator of the present invention by forming electrodes on the laminated element shown in FIG. In FIG. 2, the element unit 1
Reference numeral 0 denotes the laminated element 5, the insulating material 11, the positive electrode 12 to which a positive voltage is applied, and the negative electrode 1 to which a negative voltage is applied.
3 and 3. The second layers 2 are alternately used as a positive second layer 2a which is a layer to which a positive voltage is applied and a negative second layer 2b which is a layer to which a negative voltage is applied, That is, the first layer 1 is laminated so as to be sandwiched between the positive second layer 2a and the negative second layer 2b. Glass powder is attached to each of the negative second layers 2b exposed on the stacking surface forming the positive electrode 12 on the stacking surface of the stacking element 5 facing each other by, for example, electrophoresis.
A glass insulator, which is the above-mentioned insulating material 11, is formed by performing heat treatment.

Similarly, glass powder is applied to each of the positive second layers 2a, which is exposed on the laminated surface on which the negative electrode 13 is formed and is opposed to the laminated surface on which the positive electrode 12 is formed, by an electrophoresis method. The glass insulators, which are the above-mentioned insulating materials 11, are respectively formed by adhering them and performing heat treatment.
Furthermore, on each of the above laminated surfaces on which the glass insulator 11 is formed,
A conductive metal paste is applied by a printing method or the like to form the positive electrode 12 and the negative electrode 13 which are external electrodes. The above-mentioned electrophoresis method is publicly known and its detailed description is omitted here.

FIG. 3 is a schematic configuration diagram of an actuator using the element section 10. In FIG. 3, the actuator 20 includes the element unit 10 and the voltage control circuit 21.
And a coil 22 and a current control circuit 23, and a positive voltage is applied to the positive electrode 12 of the element portion 10 by the negative electrode 13
Is connected to a voltage control circuit 21 so that a negative voltage is applied to the device. Further, in order to generate a magnetic field in the stacking direction of the stacked device 5, the device part 10 is provided on the outer periphery of the stacked surface. A coil 22 is installed so as to surround 10, and the coil 22 is connected to a current control circuit 23 that controls a current flowing through the coil 22.

In the above structure, a positive voltage is applied to each positive second layer 2a having conductivity, and a negative voltage is applied to each negative second layer 2b having conductivity. As a result, an electric field is applied to each of the first layers 1 described above. As a result, the first layer 1 having the piezoelectric effect expands and contracts in the stacking direction of the stacked element 5 according to the voltage value applied via the positive second layer 2a and the negative second layer 2b. Further, by energizing the coil 22 and applying a magnetic field in the stacking direction of the element portion 10, a magnetic field to which each of the positive second layers 2a and the negative second layers 2b having a magnetostrictive effect is applied respectively. Stretches in the stacking direction according to the strength of the. From these facts, in the element portion 10, the positive voltage is applied to the positive electrode 12 and the negative electrode 1
By applying a negative voltage to 3 and energizing the coil 22, all layers of the laminated element 5 are stretched.

As described above, in the actuator 20 according to the present embodiment, by using the magnetostrictive material for the internal electrodes, which are indispensable in the conventional laminated piezoelectric element, but do not contribute to the expansion and contraction, all of the laminated element 5 can be obtained. It is possible to obtain an actuator in which the layers are efficiently expanded and contracted. Further, in the actuator 20 of the present embodiment, the laminated element 5
Since each first layer 1 of FIG. 2 expands and contracts by the piezoelectric effect and each second layer 2 expands and contracts by the magnetostrictive effect,
As 0, the expansion and contraction action of each layer can be added.

Generally, a laminated piezoelectric element has several hundred ppm
The amount of elongation is 200, and the magnetostrictive material such as terphenol is 200
An elongation amount of 0 ppm or more is shown. However, although the magnetostrictive material such as terphenol has a large amount of expansion and contraction, it is mainly composed of rare earth elements such as terbium and dysprosium.
It will be very expensive. The actuator of the present invention is
It is possible to obtain an actuator which is lower in cost than the magnetostrictive element using the magnetostrictive material and has a larger expansion / contraction amount than the piezoelectric element according to various purposes, for example, when an expansion amount of 1400 ppm is required.

FIG. 4 is a schematic structural diagram showing an example of a plunger pump using the actuator shown in FIG. In FIG. 4, the plunger 51 disposed at the end of the element portion 10 in the displacement direction is preloaded by the fixed spring 53 provided in the working chamber 52. The working chamber 52
When the element part 10 is extended and the plunger 51 is operated, the liquid is discharged from the discharge valve 54 constituting the check valve in the direction of flowing out from the operation chamber 52, and the element part 10
The plunger 5 by preloading the fixed spring 53.
When 1 operates, the liquid flows in from the suction valve 55 that constitutes the check valve in the direction of flowing into the working chamber 52. As described above, the actuator of the present invention can be applied to a drive source of a pump such as a plunger pump that linearly expands and contracts.

In FIG. 4, the discharge valve 54 is
It comprises a discharge spring 54a and a discharge ball 54b, the discharge ball 54b forms a valve, and the discharge spring 54a applies a preload to the discharge ball 54b. Similarly, the suction valve 55 includes a suction spring 55a and a suction ball 55b, and the suction ball 55b constitutes a valve.
Serves to preload the suction ball 55b. Furthermore,
Reference numeral 56 is an O-ring, and 57 is a body of the plunger pump 50.

Further, in the above embodiment, a metal paste made of a material having a magnetostrictive effect is applied to the green sheet of the first layer 1 by a printing method or the like, and the second layer 2 is applied.
May be produced. As described above, various modifications are conceivable, and it goes without saying that the present invention is not limited to the above-described embodiment and should be defined by the scope of the claims.

[0022]

EXAMPLES Next, examples of the actuator of the present invention will be described. A PZT-based material is used for the first layer 1 and a TbDyFe-based material is used for the second layer 2, and green sheets of each layer having approximately the same thickness are alternately laminated by two hundred and several tens layers and integrally fired. Then, the laminated element 5 is manufactured. The laminated element 5 produced by firing had a cross section of 10 mm × 10 mm and a shape of 50 mm in the expansion / contraction direction. The coil 22 was formed concentrically with the element unit 10 so that a magnetic field parallel to the expansion and contraction direction of the laminated element 5 was generated, and the actuator 20 was operated under the following conditions. Pre-load on the element part 10: 100 (kgf) (expanding and contracting direction of the laminated element 5) Magnetic field applied to the second layer 2: 2000 (Oe) Voltage applied to the first layer 1: 150 (V)

As a result, the element portion 10 of the actuator 20 expanded and contracted substantially in proportion to the applied electric field or magnetic field, and showed a maximum elongation of 70 μm, that is, 1400 ppm when the electric field and magnetic field were applied simultaneously. In this way, it was possible to obtain an element that exceeds the displacement amount shown by the conventional piezoelectric element at a relatively low cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a structural example of a laminated element 5 used for an actuator of the present invention.

FIG. 2 is an element portion 1 used in the actuator of the present invention.
It is the schematic which showed the structural example of 0.

FIG. 3 is a schematic configuration diagram showing an embodiment of an actuator of the present invention.

FIG. 4 is a schematic view of a plunger pump using the actuator shown in FIG.

[Explanation of symbols]

 1 1st layer 2 2nd layer 2a Positive 2nd layer 2b Negative 2nd layer 5 Laminated element 10 Element part 11 Insulating material 12 Positive electrode 13 Negative electrode 20 Actuator 21 Voltage control circuit 22 Coil 23 Current control circuit

Claims (4)

[Claims] 1. A first layer having a piezoelectric effect and a second layer having an electroconductivity and a magnetostriction effect, wherein the at least one first layer is sandwiched between the second layers. 1
And a voltage controller for applying a voltage to the second layer of the element to apply a desired electric field to the first layer. An electromagnetic coil that forms a magnetic field parallel to the stacking direction of the element section, and a current control section that controls a current flowing through the electromagnetic coil. An electric field is applied to the first layer and the second layer is added. An actuator characterized by applying a magnetic field to displace the element portion. 2. The actuator according to claim 1, wherein each of the second layers is provided with an electrode for applying a voltage to form an internal electrode of the first layer, and the voltage control unit includes: , Applying a positive voltage to every other electrode of the second layer and applying a negative voltage to the electrodes of the other second layers to apply an electric field to the first layer. Characteristic actuator. 3. A first layer having a piezoelectric effect and a second layer having an electroconductivity and a magnetostriction effect, wherein the at least one first layer is sandwiched between the second layers. 1
Layers and the second layer are alternately laminated, an electric field is applied to the first layer, and a magnetic field is applied to the second layer in the laminating direction to displace the first and second layers. Characteristic actuator. 4. The actuator according to claim 3, wherein each of the second layers is provided with an electrode for applying a voltage to form an internal electrode of the first layer,
An actuator characterized in that every other positive electrode is applied to the electrode of the second layer, and a negative voltage is applied to the other electrodes of the second layer to apply an electric field to the first layer.