JPH07118554B2 - Multilayer piezoelectric device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL FIELD OF APPLICATION This invention is extended by applying a high voltage,
Further, the present invention relates to a laminated piezoelectric device which is controlled to be reduced by removing the applied voltage and is effectively used as an actuator that generates a mechanical driving force, for example.

BACKGROUND ART As a piezoelectric device used as an actuator, for example, a plurality of piezoelectric elements configured in a disk shape are laminated, and electrodes are set between the plurality of piezoelectric elements. There is known a structure in which a high voltage is selectively applied and controlled by connecting the plurality of piezoelectric elements in parallel with the electrodes.

That is, an electrode that is set to be interposed between each of the plurality of piezoelectric elements is formed in the same disk shape as the piezoelectric element, and the electrode is formed from the outer peripheral portion to the outside of the laminated piezoelectric elements. The protruding lead-out terminal is integrally formed. Then, the lead-out terminals are drawn out in two different directions alternately from each electrode laminated with the piezoelectric element, and the lead-out terminals taken out in the respective directions are collectively connected to form a plurality of lead-out terminals. The piezoelectric elements are connected in parallel.

When various experiments were performed on the laminated piezoelectric device having such a structure, the piezoelectric element is relatively easily broken when a large load is applied to both sides of the laminated piezoelectric device in the laminating direction. It has been found. For example, if it is about several hundred kg, there is no problem, but when a large load of 1 ton or more acts, a crack will occur in the piezoelectric element. Considering the cause of this crack, it was clarified that a large strain stress acts on the piezoelectric element due to the displacement between the center of the piezoelectric element and the center of the electrode plate.

FIG. 5 shows experimentally obtained results of the relationship between the amount of deviation of the center position between the piezoelectric element and the electrode plate and the crack occurrence rate when a load of, for example, 2 tons is applied. The occurrence of cracks is recognized when the thickness is 0.08 mm or more.

In order to solve such a point, an electrode plate having a sufficiently large area may be used for the piezoelectric element, and the piezoelectric elements may be concentrically stacked. When it is projected from the outer peripheral part of the electrode, a large potential difference is set between the adjacent electrodes, so that discharge occurs at this electrode part and it is impossible to control the applied voltage to the piezoelectric element. It will be in a state.

Further, if the electrode plate is made of a hard metal material such as stainless steel to withstand a large load, it is difficult to ensure sufficient adhesion between the electrode plate and the piezoelectric element. Therefore, the operating characteristics of the actuator deteriorate. If the electrode plate is made of a soft material such as copper in consideration of such a point, the strength of the electrode plate is insufficient and the electrode plate cannot withstand a large load.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-described points, and a breakage in which a piezoelectric element is cracked even when a large load acts in the stacking direction. It is possible to prevent the phenomenon from occurring while maintaining safety, and to enable the characteristics of an actuator with good responsiveness to be effectively exhibited by voltage control. It is intended to provide a piezoelectric device.

[Means for Solving the Problems] That is, the laminated piezoelectric device according to the present invention is configured in a thin plate shape, and an electrode plate is provided between each of a plurality of piezoelectric elements in which electrodes are not formed. In this case, the piezoelectric elements are stacked in a state of interposing, and in this case, the electrode plates are respectively formed on the surfaces of the metal plates which are in contact with the piezoelectric elements, and are made of an electrode material softer than the metal plates such as copper and silver. Are laminated.

[Operation] In the laminated piezoelectric device configured as described above, after lamination, the soft electrode formed on the electrode plate is made to function as an electrode of the piezoelectric element, and the piezoelectric element is first connected to the electrode. I try not to form. For this reason, it is possible to eliminate the factor that causes the electrode material to adhere to the side surface of the piezoelectric element and cause a short-circuit accident, thereby improving safety. Further, the mutual positional relationship between the plurality of piezoelectric elements and the electrode plates interposed between the piezoelectric elements is easily and concentrically set, and particularly, the center of the metal plate serving as a strength member of the electrode plate is set. Since the center position of the electrode material portion is accurately matched, it is possible to sufficiently withstand a large load, and it is possible to effectively prevent breakage of the piezoelectric element. Further, the contact portion between the electrode and the piezoelectric element can be brought into a close contact state by the electrode material portion, and the actuator characteristics can be stably set. For example, as a control member of a braking mechanism for an automobile, The piezoelectric device can be effectively used.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a part of the piezoelectric device in a disassembled state. This piezoelectric device has a plurality of thin disk-shaped piezoelectric elements 11.
The plurality of piezoelectric elements 11a, 1b, ...
1b, ... are set in a concentric stacking state. Here, each of the piezoelectric elements 11a, 11b, ...
It is composed of 15 mm and a thickness of 0.5 mm.

In addition, a plurality of piezoelectric elements 11a, 11 stacked as described above.
b, ... Between the respective electrodes, the electrode plates 12a, 12
b, ... are interveningly set, and these electrode plates 12a, 12b,
… Each has a smaller diameter than the piezoelectric element
It is composed of a 13 mm disc and its thickness is set to 20 μm.

The electrode plates 12a, 12b, ... As shown in FIG. 2 by picking out one thereof 12, are formed with, for example, three protrusions 13a to 13c at equal intervals on the outer peripheral portion of the disk-shaped main body. The protrusions 13a to 13c are bent at right angles at the portions corresponding to the outer peripheral edge of the piezoelectric element to form the locking claws 14a to 14c. That is, when laminated with a piezoelectric element,
The mutual positional relationship between the piezoelectric element and the electrode plate is determined by the above-mentioned locking claw.
14a to 14c are set so that the piezoelectric elements and the electrode plates are laminated so that their center positions coincide with each other.

Further, the electrode plate 12 has a thickness of an electrode material 16 such as copper, silver, or aluminum, which is sufficiently softer than the metal plate 15, on both sides of a metal plate 15 made of a relatively hard material such as stainless steel, which is a strength member. The thickness is 2 to 5 μm, and the layers are formed by plating or the like. That is, the electrode material 16 is brought into contact with the surface of the piezoelectric element.

The electrode plates 12a, 12b, ... Having such a structure are to be alternately laminated with the piezoelectric elements 11a, 11b, .. As shown in FIG. , ... are arranged such that the projections 13a to 13c are sequentially displaced from each other by 60 °. Therefore, the protrusions 13a to 13c of the electrode plates 12a, 12b, ... Respectively have the positions thereof aligned with each other, and the locking claws 14a to 14c formed by bending the protrusions 13a to 13c. Every other pair of electrode plates 12a, 12b, ... Will come into contact with each other.

Here, projecting pieces 17a to 17c projecting in the lateral direction are formed on the locking claws 14a to 14c, respectively, and the projecting pieces 17a to 17c are bent at a right angle and raised to have a width of 1 mm, for example. 50
If the micron metal ribbons 18a, 18b, ... Are connected by spot welding or seam welding, the electrode plate
Every other 12a, 12b, ... will be commonly connected. Then, if the metal ribbons at the opposite positions are taken out as the electrode lead-out lines 19 and 20, the plurality of piezoelectric elements 11a, 11b, ... Are connected in parallel, and the electrode lead-out lines 19 and 20 are connected. By controlling the application of a voltage between them, the piezoelectric device in which the piezoelectric elements 11a, 11b, ... Are laminated is controlled to expand and contract.

That is, in the piezoelectric device having the above-described structure, the electrode plates 12a, 12b, ... Have the center position of the electrode material 16 in contact with the metal plate 15 and the piezoelectric elements 11a, 11b ,. Is configured to be an exact match,
The metal plate 15, which is a strength member of the electrode plates 12a, 12b, ... Is brought into contact with the piezoelectric element through the electrode material 16 whose center position is matched, so that uniform pressure is effectively applied to this piezoelectric element. become.

Further, the electrode plates 12a, 12b, ... Have locking claws 14a, 14b ,.
The mutual positional relationship with each of the piezoelectric elements 11a, 11b, ... Is accurately set by the piezoelectric elements 11a, 1b.
The center positional relationship between each of the electrodes 1b, ... And each of the electrode plates 12a, 12b ,. Then, in such a laminated state, the electrode plates 12a, 12b, ... Are brought into contact with each other through the layer of the soft electrode material 16, and the electrode plates 12a, 1b
2b, ... and the piezoelectric elements 11a, 11b ,.
The strength of 2b, ... Is surely held by the metal plate 15. Therefore, it is possible to effectively suppress the strain stress from acting on the piezoelectric elements 11a, 11b, ... Even if a pressure load acts on the piezoelectric element. It is possible to effectively suppress the occurrence of accidents that cause cracks in 11b, ....

FIG. 3 shows another embodiment of the present invention, in which the electrode plates 21a, 21b, ... Are formed in a disk shape having the same diameter as the piezoelectric elements 11a, 11b ,. , 11b, ... And the electrode plates 21a, 21b, .. are alternately laminated in the same manner as in the above-mentioned embodiment, and are housed in a container 22 made of a cylindrical resin. In this case, the electrode plates 21a, 21
b, ... One locking claw 2 protruding from the outer peripheral edge
The container 22 is formed with a pair of guide grooves 24a, 24b parallel to the axis.

That is, when the electrode plates 21a, 21b, ... Which are alternately laminated with the piezoelectric elements 11a, 11b ,.
The engaging claws 23 of 21a, 21b, ... Are alternately inserted into the guide grooves 24a, 24b so as to be guided, and the engaging claws 23 allow the electrode plates 21a, 21b ,. , 11
The mutual positional relationship with b, ... is set accurately. Then, from the guide grooves 24a, 24b respectively
By connecting the locking claws 23 projecting to the outside of 22 in common, a lead-out terminal for controlling the supply of voltage to this piezoelectric device is configured.

That is, in the case of this embodiment, since the laminated structure is configured in the container 22, the electrode plates 21a, 21b, ... Can be configured to have the same diameter as the piezoelectric elements 11a, 11b ,. It is possible to set the contact area between the piezoelectric elements 11a, 11b, ... And the electrode plates 21a, 21b ,. Therefore, the setting control of the applied voltage to each of the piezoelectric elements 11a, 11b, ... Can be stably executed more reliably.

Here, an electrode layer made of a soft metal material such as silver or copper is formed on both surfaces of each of the piezoelectric elements 11a, 11b, ... By means of screen printing or the like, and an electrode plate interposed between the piezoelectric elements. It is conceivable to use a hard metal material for this, but with this method, the soft electrode material also adheres to the side surface of the piezoelectric element, causing a short circuit between adjacent electrodes. There is a risk that such an accident may occur. Then, in order to solve such a problem, when the layer made of the electrode material is formed so as to be limited to a range smaller than the diameter of the piezoelectric element, the center position of the layer made of the electrode material and the electrode plate is accurately set. It becomes difficult to set, and strain stress is easily applied to the piezoelectric element through the layer made of the electrode material. Therefore,
When a large load is applied, an accident is likely to occur in the piezoelectric element, which is not effective.

On the other hand, with the configuration as shown in the first and second embodiments, the center position of the metal plate that serves as the strength member of the electrode plate and the center position of the electrode material that serves as the contact member are accurately aligned. Since it is set, the state in which unnecessary strain stress acts on the piezoelectric element can be effectively eliminated.

FIG. 4 shows still another embodiment. In this embodiment, the plurality of laminated piezoelectric elements 11 are formed in a square plate shape. Then, the ribbon-shaped first and second electrode plates having a width slightly smaller than the width of one piece of the piezoelectric element 11 while being in contact with both surfaces of the piezoelectric element 11.
Set 25 and 26 so as to extend in a direction perpendicular to each other.

In this state, the next piezoelectric element is further laminated on the electrode plate 26, the first electrode plate 25 is bent corresponding to the line a, and is folded and laminated on the laminated piezoelectric element, Further, the next piezoelectric element is laminated on the folded electrode plate 25, and the second electrode plate 26 is folded and laminated along the line b on the piezoelectric element. That is, the first and second electrode plates 25
And 26 are arranged so that they are alternately returned and laminated, and square piezoelectric elements are interposed between the first and second electrode plates 25 and 26, respectively.

As described above, in the laminated piezoelectric device according to the present invention, since the soft electrode formed on the electrode plate functions as an electrode of the piezoelectric element after the lamination, the piezoelectric element is initially formed. The electrode is not formed on. For this reason, it is possible to eliminate the factor that causes the electrode material to adhere to the side surface of the piezoelectric element and cause a short-circuit accident, thereby improving safety. Further, the electrode plate interposed between each of the plurality of laminated piezoelectric elements is such that an electrode material layer is formed of a soft metal material on at least the surface of the metal plate acting as a strength member in contact with the piezoelectric element. Has become. Therefore, since the electrode plate is configured such that the center positions of the metal plate and the electrode material layer are exactly aligned with each other, the contact state between the electrode plate and the piezoelectric element is caused by the electrode material layer. Is brought into a close contact state, and it is easy to prevent a large strain stress from being applied to the piezoelectric element even when a large load is applied to this piezoelectric device. Therefore, this piezoelectric device has a structure capable of effectively withstanding a large load, and for example, a mechanism for generating a braking force in a vehicle braking device can be effectively configured. The actuator mechanism can be effectively used as various voltage-controlled actuator mechanisms.

[Brief description of drawings]

FIG. 1 is a partially exploded configuration diagram illustrating a laminated piezoelectric device according to the present invention, and FIG. 2 is a diagram showing an electrode plate used in the above-described embodiment, in which FIG. Plan view,
(B) is a cross-sectional view taken along line bb of (A), FIG. 3 and FIG.
The drawings are block diagrams respectively explaining other embodiments of the present invention.
FIG. 5 is a curve diagram for explaining a crack generation state of the piezoelectric element. 11, 11a, 11b, ... Piezoelectric element, 12, 12a, 12b, ..., 21a, 2
1b, 25, 26 ... Electrode plate, 13a-13c ... Protrusion, 14a-14c, 23 ...
Locking claw, 15 ... Metal plate, 16 ... Electrode material (soft).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Jun Niwa, 1-1, Showa-cho, Kariya city, Aichi, Nihon Denso Co., Ltd. (56) References JP-A-59-211819 (JP, A) JP-A-60 -98612 (JP, A) JP 59-2385 (JP, A) Actual development 58-172392 (JP, U) Actual public 54-30953 (JP, Y2)

Claims (3)

[Claims] 1. A plurality of piezoelectric elements having a plate shape and not having electrodes formed on both surfaces thereof, and an electrode layer having a plate shape and made of a soft metal on both surfaces of an electrode plate body. And a plurality of electrode plates made of a metal whose electrode plate body is harder than the electrode layers, wherein the plurality of electrode plates are interposed between the plurality of piezoelectric elements. A laminated piezoelectric device, wherein the plurality of piezoelectric elements are laminated and arranged, and the electrode layers of the electrode plates are in contact with the both surfaces of the piezoelectric element, respectively. 2. The electrode material forming the electrode layer is copper,
The laminated piezoelectric device according to claim 1, wherein the piezoelectric device is made of one of silver and aluminum. 3. The electrode plate has at least an area smaller than that of the piezoelectric element, and a locking claw bent at the outer peripheral portion of the laminated piezoelectric element is integrally formed on the outer peripheral portion thereof as an electrode lead wire. The laminated piezoelectric device according to claim 1, wherein the electrode plates are formed so as to be laminated with each other in a state where the electrode plates are set at the center positions of the piezoelectric elements.