JPH0471280A - Manufacture of laminated piezoelectric element - Google Patents

Abstract

PURPOSE:To equalize the wall thickness or protective layers by a method wherein a laminated body is covered with a transparent tube while an ultraviolet ray setting resin is set in a tube type cavity in almost even thickness formed between the tube and the laminated body. CONSTITUTION:Disc-shaped piezoelectric bodies 10 are formed by molding and baking the solid solution powder of PbZrO3 and PbTiO3 and then electrodes 11 are formed on both surface and rear surface to manufacture a piezoelectric disc 1. Besides, a copper sheet is stamped to manufacture the electrode sheets 2 comprising a disc type base 20 and a tongue piece part 21. Next, a pair of piezoelectric discs 1 adjoining to each other through the intermediary of an electrode sheet 2 arranged making the polarities of the surface and rear surface oppose to each other besides the electrode sheets 2 are laminated making the tongue piece parts 21 alternately protrude from both sides while the tongue piece parts 21 are connected to lead bodies 30, 31 and then lead wires 32, 33 are provided to form a laminated body 3. Next, the end of a transparent tube 5 is inserted into a fixing base 4 to be fixed for vertically arranging the laminated body 3 in the tune 5. Next, the tube 5 is filled up with a liquid ultraviolet ray setting resin 6 so as to bury the laminated body 3 in the tube 5 and then the laminated body 3 is irradiated with ultraviolet rays from the peripheral surface of the tube 5 to form protective layers 7. Through these procedures, thermosetting insulating layers in even thickness can easily be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a laminated piezoelectric element used as a piezoelectric actuator.

[Prior Art] In recent years, piezoelectric actuators that utilize piezoelectric effects have been frequently used in place of actuators that utilize electromagnetic force. This piezoelectric actuator is small and can be driven at high speed.
It also holds great promise as a variety of mechanical drive elements. Since the mechanical displacement caused by the piezoelectric effect is essentially extremely small, a stacked piezoelectric element having a structure in which piezoelectric plates and electrode plates are alternately stacked is used as a piezoelectric actuator in order to obtain a large amount of displacement.

However, if the piezoelectric plates and electrode plates are simply stacked alternately, discharge may occur on the outer peripheral surface because the electrode plates are very close to each other. Therefore, it is necessary to cover the outer peripheral surface of the laminate with an insulator, and conventionally, as seen in Japanese Patent Application Laid-Open Nos. 62-88382 and 1-108959, thermosetting resin is used to cover the laminate with an insulator. A protective layer is formed to cover the outer peripheral surface for insulation.

[Problems to be Solved by the Invention] In order to obtain a reliable insulation effect, it is necessary to form a protective layer with a uniform thickness over the entire outer peripheral surface of the laminate. This is because if there are parts where the wall thickness is thin, the insulation may be poor in that part and electric discharge may occur. However, when the protective layer is formed from a thermosetting resin, the thermosetting resin softens during heating and curing, resulting in a decrease in viscosity, which may cause sagging and uneven film thickness. Also, it takes a long time (approximately 150℃ x approximately 30 minutes) to heat cure,
There is also the problem of poor productivity. On the other hand, if a thermoplastic resin is used, productivity is improved, but the piezoelectric element generates heat when used under high load or high speed operation, making it unusable.

The present invention overcomes these problems and aims to easily form a thermosetting insulating layer of uniform thickness in a short time.

[Means for Solving Problem 111] The method for manufacturing a laminated piezoelectric element of the present invention includes a first step of alternately laminating piezoelectric plates and electrode plates to form a laminated body, and a transparent layer on the outside of the laminated body. a second step of covering the cylindrical body coaxially and forming a gap of a substantially uniform distance between the laminate and the cylindrical body; a third step of filling the gap with an ultraviolet curing resin; It is characterized by comprising a fourth step of irradiating ultraviolet rays from above to cure the ultraviolet curable resin filled in the gap to form a protective layer of uniform thickness.

The first step is a step of alternately stacking piezoelectric plates and electrode plates in multiple layers to form a laminate. Here, the piezoelectric plate refers to a plate that generates strain or stress when voltage is applied, and includes 3al'-i03 and PbT i03 with a perovskite crystal structure.
or solid solution with CaT i 03, PbZro3 and Pb
A plate-shaped material similar to the conventional one formed from piezoelectric ceramics such as a solid solution of TiO3 (PZT) is used.

Usually, it has electrode parts printed and baked with silver paste on both the front and back surfaces.

Further, the electrode plate is not particularly limited as long as it can be used as an electrode, and conventional materials such as a copper plate can be used. The piezoelectric plates are stacked with electrode plates in between so that the polarities of the front and back sides are opposite to each other. The number of laminated piezoelectric plates and electrode plates is not particularly limited.

In the second step, a transparent cylinder is coaxially coated on the outside of the laminate. At this time, the distance between the outer circumferential surface of the laminate and the inner circumferential surface of the cylinder is made to be a substantially uniform distance throughout. The cylindrical body is not particularly limited as long as it is transparent and transmits ultraviolet rays, and can be formed from various resins, glasses, and the like. Particularly preferably, it is formed from heat-shrinkable tubing, as described below.

In the third step, the cylindrical gap formed between the laminate and the cylindrical body is filled with an ultraviolet curable resin.

The filling method is not particularly limited. Note that it is desirable to use a method of filling under reduced pressure so that no air remains inside, or a method of reducing pressure after filling.

In the fourth step, ultraviolet rays are irradiated from the outside of the cylinder. As a result, the ultraviolet curable resin inside is irradiated with ultraviolet rays through the cylinder, and the ultraviolet curable resin is cured to form a protective layer with a substantially uniform thickness. In other words, since the ultraviolet curable resin is cured within a cavity with a substantially uniform thickness formed by the inner peripheral surface of the cylinder and the outer peripheral surface of the laminate, a protective layer with a substantially uniform thickness can be formed in a short time. can do.

The ultraviolet curable resin is not particularly limited as long as it is cured by ultraviolet rays in a short time and has insulating properties after curing, and any known resin can be used as is.

The obtained laminated piezoelectric element may be used with the cylindrical body covering the outer surface of the protective layer, or may be used by removing the cylindrical body after forming the protective layer.

In addition, when the cylindrical body is formed from a heat-shrinkable tube, it is desirable to heat the entire body to shrink the cylindrical body after the fourth step in which the ultraviolet curable resin is cured.

In this way, the force of contraction acts on the protective layer to reduce its diameter, and the protective layer is pressed against the laminate. Therefore, the effect of further preventing interfacial peeling between the protective layer and the laminate is produced, and the occurrence of electric discharge is further prevented.

[Operations and Effects of the Invention 1 Although it is possible to coat the surface of the laminate by applying an ultraviolet curable resin by dipping, etc., it is necessary to apply a particularly thick layer of protection when electrode leads protrude from the outer periphery of the laminate. layers are required. On the other hand, when ultraviolet curable resin is irradiated with ultraviolet rays, curing progresses from the surface, and heat is also added during irradiation, so if it is attached to a thick wall, the internal viscosity decreases and sagging occurs. Become.

However, in the method for manufacturing a laminated piezoelectric element of the present invention,
The laminate is covered with a transparent cylindrical body, and the ultraviolet curable resin is cured within a cylindrical cavity with a substantially uniform thickness formed between the cylindrical body and the laminate. Therefore, even if the viscosity decreases when irradiated with ultraviolet rays, no sagging occurs, so the thickness of the protective layer can be reliably made substantially uniform and thick.
Discharge can be reliably prevented. Furthermore, the time required to form the protective layer is extremely short compared to the conventional method since it is an ultraviolet curing reaction. Therefore, the number of man-hours can be reduced.

In addition, in the manufacturing method of the present invention, even if you touch the UV-curable resin in an uncured state after the third step, the uncured UV-curable resin will stick to your hand because the outside is covered with the cylindrical body. There are no such problems. Therefore, it is easy to handle and has good workability.

Furthermore, by forming the cylindrical body from a heat-shrinkable tube and adding a step of heating the entire body after the UV-curable resin has hardened, the protective layer will come into close contact with the laminate due to the shrinkage of the heat-shrinkable tube, further preventing electrical discharge. can do.

[Example] This will be explained in detail below using examples.

(Example 1) (1) First step Solid solution (PZT) powder of PbZro3 and PbTi03 is molded and fired to form a disk-shaped piezoelectric body 10 with a diameter of 15 mm and a thickness of 0.5 mm. Ag paste was printed on the surface and baked to form electrodes 11 to obtain the piezoelectric plate 1 shown in FIG. 2.

In addition, a copper plate with a thickness of 0.03 mm is hammered and processed to form a disc-shaped base 20 with a diameter of 15 mm and a base 2 as shown in FIG.
An electrode plate 2 consisting of a tongue portion 21 protruding from the electrode plate 2 was obtained.

The piezoelectric plate 1 and the electrode plate 2 are arranged alternately as shown in FIG.
00 layers are laminated. At this time, a pair of piezoelectric plates 1 adjacent to each other with one electrode plate 2 in between are stacked so that the polarities of the front and back sides are opposite to each other. Further, the electrode plates 2 are stacked so that the tongue portions 21 alternately protrude to both sides in opposite directions by 180 degrees. Then, the tongue pieces 21 protruding on both sides are connected to lead plates 30, respectively.
．． 31 and lead wires 32 and 33 are provided to form the laminate 3 shown in FIG.

(2) Second step Next, a fixing table 4 with a diameter of 16 mm is prepared, and the tip of a transparent Teflon tube 5 with a diameter of 16 mm is inserted into the fixing table 4 and fixed. Then, the tube 5 is held vertically with the fixing base 4 facing downward, and the laminate 3 is placed inside the tube 5 with its axial direction perpendicular. At this time, the upper end of the tube 5 is
It is located above the top of the . Further, the distance between the outer circumferential surface of the laminate 3 and the inner circumferential surface of the tube 5 is determined by the lead plate 3.
They are arranged to have the same Q and 5 mm throughout except for the 0.31 part.

(3) Third step Next, as shown in FIG. 1, the gap between the tube 5 and the laminate 3 is filled with liquid ultraviolet curable resin 6 (epoxy type) so that the laminate 3 is buried. .

Since one end of the tube 5 is fixed to the fixed base 4, the ultraviolet curing resin 6 will not leak from inside the tube 5. At this time, if the viscosity of the ultraviolet curable resin 6 is high, the air in the filled ultraviolet curable resin 6 may be removed by placing the whole in a tank with a reduced pressure atmosphere or by heating to lower the viscosity. It is desirable to remove.

(4) In the fourth step, using an 80W ultraviolet lamp, ultraviolet rays are irradiated for 10 seconds from a distance of 5 cm from the outer peripheral surface of the tube 5 to harden the filled ultraviolet curable resin 6 and protect the protective layer 7. was formed.

Then, both ends of the fixing table 4 and the tube 5 are cut and removed, and as shown in cross section in FIG.
A laminated piezoelectric element was obtained in which a protective layer 7 with a uniform thickness of m and a tube 5 were fixed coaxially and integrally.

In this embodiment, the protective layer 7 is covered with the tube 5 as a product, but the tube 5 may be removed after the fourth step.

(Example 2) This example is the same as Example 1 except that a transparent Teflon heat-shrinkable tube was used as the tube 5, and a heating step was performed as a fifth step after the fourth step.

That is, after the ultraviolet curable resin 6 has hardened to form the protective layer 7, the whole is heated to 150° C., and the heat-shrinkable tube 5 is shrunk. Due to this contraction, the preservation is maintained! Stress is applied to l17 from the tube 5, and the protective layer 7 is brought into close contact with the laminate 3. This further prevents discharge.

The UV-curable resin has a Young's modulus of 1okQ,
It is desirable to use a material with a low elastic modulus of , 'mm2 or less. In this way, the protective layer 7 is easily deformed when the heat-shrinkable tube 5 contracts, and it becomes easier to follow the shape of the laminate 3, so that higher insulation can be obtained. Further, since the heat-shrinkable tube 5 contracts and strongly presses the surface of the protective layer 7, deformation of the protective layer is prevented and the occurrence of cracks is also prevented.

By the way, as an ultraviolet curing resin, the Young's modulus is i kg
/mm2, a pulse voltage (1 kv) is applied to the obtained multilayer piezoelectric element.

When 100 Hz> was applied, no abnormality was observed even after 108 operations. However, if a heat-shrinkable tube or one that does not have a cylindrical body and is simply coated with a low elastic modulus ultraviolet curable resin similar to the above and cured,
A crack appeared in the protective layer 7. Also, without providing a cylinder,
If a laminate is simply coated with a high modulus ultraviolet curable resin with a Young's modulus of 100 kQ/mm and cured,
The protective layer peeled off from the laminate after 107 cycles, and the creeping discharge was 1!
It was noticed.

[Brief explanation of the drawing]

The drawings relate to a manufacturing method according to an embodiment of the present invention; FIG. 1 is an explanatory diagram showing a state in which the third step is performed, FIG. 2 is a perspective view of a piezoelectric plate, FIG. 3 is a perspective view of an electrode plate, FIG. 4 is an explanatory view showing the lamination method in the first step, FIG. 5 is a perspective view of the laminate after the first step, and FIG. 6 is a sectional view of the obtained laminated piezoelectric element. 1... Piezoelectric plate 2... Electrode plate 3... Laminated body 4... Fixing base 5... Tube (cylindrical body) 6... Ultraviolet curing resin 7... Protective layer
11...〇Electrode 21...tongue part 30.
31...Lead plate patent applicant Toyota Motor Corporation representative Patent attorney Hiroshi Okawa Figure 1

Claims (1)

[Claims] (1) A first step in which piezoelectric plates and electrode plates are alternately laminated to form a laminate, and a transparent cylindrical body is coaxially coated on the outside of the laminate and the laminate and the cylindrical body are bonded together. a second step of forming a gap of a substantially uniform distance between the tubes; a third step of filling the gap with an ultraviolet curable resin; and a step of irradiating ultraviolet rays from outside the cylindrical body and applying the ultraviolet rays filled in the gap. A method for manufacturing a laminated piezoelectric element, comprising a fourth step of curing a curable resin to form a protective layer having a substantially uniform thickness.