JPH0332236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a piezoelectric actuator whose actuation source is the curvature displacement of a piezoelectric element piece.

[Conventional technology]

Conventionally, as this type of piezoelectric actuator, one shown in FIG. 6 is known. The piezoelectric element piece 101 used here has a laminated structure in which a thin piece 104 of a conductive material such as brass is inserted between piezoelectric layers 102 and 103 made of electrically polarized PZT or the like. , 103 are coated with a thin layer 105,1 of conductive material such as silver or nickel.
Covered by 06. This piezoelectric element piece 101 supports the base end portions of the piezoelectric layers 102 and 103 in a cantilevered manner.

On the other hand, the upper thin layer 105 is connected via the terminal 107.
While connected to a relatively high voltage power source, on the order of 160 volts, the lower lamina 106 is connected to ground. The center lamella 104 is then selectively connected to either a high positive potential or ground potential via a double pole double throw switch 108.

Now, selectively toggling the double-pole, double-throw switch 108 connects the lamina 104 to a high positive potential or to ground potential, either to the upper piezoelectric layer 102 or to the lower piezoelectric layer 1.
An operating voltage is applied to 03. That is, when a positive voltage is applied to the upper piezoelectric layer 102, the piezoelectric element piece 101 is curved upward with its base end serving as a fulcrum P. Conversely, the piezoelectric element piece 101 where the positive voltage is downward
, the piezoelectric element piece 101 is bent downward with its base end as a fulcrum P. In response to this curved displacement, the movable piece fixed to the free end of the piezoelectric element piece 101 moves in the vertical direction.

[Problem that the invention seeks to solve]

In the above conventional technology, the piezoelectric layers 102, 10
Since the proximal end of the piezoelectric element 3 is fixed and supported in a cantilever manner, the movement of the piezoelectric element piece is suppressed and there is a problem in that sufficient bending displacement and operating force cannot be obtained. In particular, when conventional piezoelectric actuators are applied to so-called Braille cells that display Braille characters by converting electrical signals into mechanical motions, it is difficult to obtain sufficient initial pressing force, and even when touched lightly, In this case, the fingertips do not have sufficient tactile sensation, making it impossible to read Braille characters accurately. Furthermore, since there is no means for specifically regulating the amount of curved displacement of the piezoelectric element piece, there is a problem in that the characteristics of the piezoelectric element piece are uniquely determined.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a piezoelectric actuator that can obtain a large initial actuation force and bending displacement, and can arbitrarily set the actuation force and the amount of bending displacement. With the goal.

[Means and actions for solving problems]

As shown in FIG. 1, a piezoelectric element piece 4 is constructed by laminating piezoelectric layers 2 and 3 made of piezoelectric material on both plate surfaces of a thin piece 1 made of an elastic conductive material, and the base of this piezoelectric element piece 4 is Base end 1 of the thin piece 1 located on the end side
A is fixed by a fixing means 5, and a substantially central portion of the piezoelectric element piece 4 is supported by a supporting means 6 with a degree of freedom in curvature displacement.

The piezoelectric actuator of this invention has a piezoelectric element piece 4
By applying an external electric field to the piezoelectric layer 2,
3 is strained, causing the base end of the thin piece 1 and the piezoelectric element piece 4 to
Displaces in a curved manner using the approximate center of the fulcrum as a fulcrum. At this time, by moving the supporting means 6 toward the free end side or the base end side and shifting the fulcrum, the operating force and amount of bending displacement of the piezoelectric element piece 4 can be adjusted.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, 11 is a piezoelectric element piece, and this piezoelectric element piece 11 is a laminated layer in which a thin piece 14 made of an elastic conductive material such as phosphor bronze or Kovar is inserted between piezoelectric layers 12 and 13 made of a piezoelectric material, for example, PZT. The outer surfaces of the piezoelectric layers 12 and 13 are covered with thin layers 15 and 16 made of a conductive material such as silver, and the ends of the piezoelectric layers 12 and 13 are short-circuited with a thin silver piece 17. There is. In this embodiment, the piezoelectric element piece 11 has a width of 2 mm, a thickness of 0.96 mm, and a total length of
A piece with a narrow width of about 91 mm, a thick wall, and a relatively long length is used. This piezoelectric element piece 11 is fixed by electrically connecting the base end 14a of the thin piece 14 protruding from the base end side to the wiring pattern of the printed circuit board using a fixing means such as solder 18 or the like. moreover,
A substantially central portion of the piezoelectric element piece 11 is supported by support means, such as a U-shaped fulcrum member 19 having protrusions 19a and 19b formed on opposing surfaces, with a degree of freedom in curvature displacement. In this case, the piezoelectric element piece 11 is placed at a position where the fulcrum position P of the fulcrum member 19 is 50.2 mm from the tip of the thin piece 14 on the base end side, that is, a position slightly shifted to the right in the drawing from the center of the piezoelectric element piece 11 (total length 91 mm). It has been experimentally confirmed that the balance between the curved displacement and the operating force is optimal.

A power supply circuit (not shown) is connected to the thin piece 14 of the piezoelectric element piece 11, and a grounding circuit (not shown) is connected to the piezoelectric layer 13. A polarized DC voltage is supplied.

Such piezoelectric actuators are used, for example, in Braille cells for displaying Braille characters. In the case of a so-called Braille cell, as shown in the figure, a piezoelectric element piece 1
A tactile pin 20 is provided as a movable piece at the tip of the free end of 1.
is installed. As shown in FIGS. 3a and 3b, the so-called Braille cell has four grooves 33 formed on both sides of the support plate 32 constituting the base 31.
By setting the piezoelectric element pieces 11 of the piezoelectric actuator 34 described above in a stepwise manner in 3, the tactile scanning section 3
The neck portions 20a of eight tactile pins 20 are provided so as to be able to protrude from the surface of 5, and 4×2 Braille characters can be displayed. In this case, the heads of the tactile pins 20 are aligned at the same height, and each piezoelectric element piece 1
It is held movable in the vertical direction according to the curved displacement of 1. Here, in order to absorb variations in upward or downward deflection due to the manufacture of the piezoelectric element 11, a direct current voltage of opposite polarity is applied to the piezoelectric element piece 11, and the tactile pin 20 is bent downward. The height is adjusted so that the head does not protrude beyond the surface of the tactile scanning section 35. Thereafter, the thin piece 14 of the piezoelectric element piece 11 is fixed onto the wiring pattern of a printed circuit board 36 that is integrally provided with the base body 31 and has electronic circuit components mounted thereon.

By applying a DC voltage of opposite polarity to each piezoelectric actuator 34 of the braille cell configured in this manner and pre-energizing it, each piezoelectric element piece 11 is activated by using the fulcrum member 19 as a fulcrum and the head of the tactile pin 20. The tactile scanning section 35 is curved downward so as not to protrude from the surface of the tactile scanning section 35. In this state, when a positive DC voltage is applied to the piezoelectric actuator 34 selected by the braille character designation circuit (not shown), the piezoelectric element piece 11
is bent upward using the fulcrum member 19 as a fulcrum, and the head of the tactile pin 20 protrudes from the surface of the tactile scanning section to display the desired Braille character.

According to the piezoelectric actuator 34, when a DC voltage of opposite polarity is applied to the piezoelectric element piece 11, the fourth
It is curved downward as shown by the solid line in the figure. Further, when a positive DC voltage is applied to the piezoelectric element piece 11, the piezoelectric element piece 11 is curved upward as shown by the dashed line in FIG. At this time, the fulcrum member 19 located approximately in the center of the piezoelectric element piece 11 suppresses its curved displacement, so that the reaction force at that time is applied to the thin piece 14 and the elastic force of the thin piece 14 is applied to the base of the piezoelectric element piece 11. The actuating force on the free end side is increased. At the same time, due to the elasticity of the thin piece 14, the piezoelectric element piece 1
1 degree of freedom is increased, allowing for larger curved displacements than conventional ones.

By the way, when we prepared a piezoelectric actuator according to the present invention and a conventional piezoelectric actuator and investigated the relationship between pressing force and bending displacement, we found that the conventional piezoelectric actuator, which is a cantilever type with a fulcrum at the lower center, was found to have the same characteristics as shown in Fig. 5. a
The characteristics shown in FIG. 5B were obtained for the product of the present invention.

As a result, it can be seen that the product of the present invention can obtain a larger initial pressing force and bending displacement than the conventional product.

Moreover, in the product of the present invention, the pressing force and the amount of bending displacement can be adjusted by moving the fulcrum member 19 left and right. That is, moving the fulcrum member 19 toward the free end increases the pressing force, and moving the fulcrum member 19 toward the proximal end increases the bending displacement. In the case of the embodiment, 50.2 from the base end of the thin piece 14
A piezoelectric actuator with a well-balanced pressing force and bending displacement at a point of mm can be obtained.

Therefore, according to the piezoelectric actuator having such a configuration, by causing the piezoelectric element piece 11 to bend and displace using the base end of the thin piece 14 and the fulcrum member 19 as fulcrums, a large bending is caused to the free end side of the piezoelectric element piece 11. Since a moment can be applied, stable bending displacement and actuation force can be obtained, and in the case of a Braille cell, high-quality Braille display can be performed via the tactile pin 20. Furthermore, by moving the fulcrum member 19 from side to side around the best position, the pressing force and the amount of bending displacement can be arbitrarily adjusted, so that design specifications can be varied.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist.

For example, in the above embodiment, the present invention was applied to a Braille cell, but it can be applied to any actuator that can convert electrical changes into a dynamic system.

〔Effect of the invention〕

As described above, the present invention has the advantage that a large initial actuation force and bending displacement can be obtained, and the actuation force and the amount of bending displacement can be set arbitrarily.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a piezoelectric actuator of the present invention, Fig. 2 is a schematic block diagram showing an embodiment of the present invention, and Figs. 3 a and b show a Braille cell constructed using the same embodiment. a is a front view, b is a plan view, FIG. 4 is an explanatory diagram for explaining the operation of the same embodiment, FIGS. 5 a and b are characteristic diagrams showing the characteristics of the conventional example and the same embodiment, respectively, and FIG. 6 1 is a configuration diagram showing a conventional piezoelectric actuator. 1, 14... thin piece, 1a... proximal end, 2, 3, 1
2, 13... Piezoelectric layer, 4, 11... Piezoelectric element piece, 5...
Fixing means, 6... Supporting means, 15, 16... Thin layer, 1
7... thin piece, 18... solder, 19... fulcrum member, 19
a, 19b... protrusion, 20... tactile pin, 20a...
Neck, 31... Base, 32... Support plate, 33... Groove,
34...Piezoelectric actuator, 35...Touch scanning unit,
36...Printed circuit board.

Claims (1)

[Claims] 1. A piezoelectric element piece in which a piezoelectric layer made of a piezoelectric material is laminated on both plate surfaces of a thin piece made of an elastic conductive material, and a fixing means for fixing the base end of the thin piece located on the base end side of the piezoelectric element piece; A piezoelectric actuator comprising: support means for supporting a substantially central portion of the piezoelectric element piece with a degree of freedom in curvature displacement.