JP2897258B2 - Piezo actuator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator, and more particularly, to a piezoelectric actuator serving as a driving source of an operating device such as a printer or a relay.

[Conventional technology]

2. Description of the Related Art Conventionally, electromagnetic actuators have been widely used as driving sources for operating devices such as printers and relays. This electromagnetic actuator is configured to generate a magnetic field by passing a current through a coil, and to drive a movable member using the magnetic force due to the magnetic field. For this reason, copper loss and iron loss occur, which not only requires large input energy, but also causes problems such as heat generation and magnetic interference.

Therefore, in recent years, there has been proposed a printing hammer for a printer using a piezoelectric element having a high electric-mechanical energy conversion efficiency, a low power consumption, and a piezoelectric element which generates little heat and has no magnetic interference. FIG. 3 is a side view of a printing hammer for a printer using a piezoelectric element as an example of the related art. As shown in FIG. 3, the print hammer is arranged such that a flight hammer 33 supported by a leaf spring 32 is in contact with the tip of the piezoelectric element 31 in the extension operation direction (the direction of arrow A). The flight hammer 33 is provided with a printing wire 34 for printing dots. In this printing hammer,
When a voltage is applied to the piezoelectric element 31, the flight hammer 33
Due to the high-speed extension operation of the piezoelectric element 31, the piezoelectric element 31 is accelerated by receiving a force from the piezoelectric element 31, and flies away from the piezoelectric element 31. Then, the print wire 34 collides with the platen 37 via the ink ribbon 35 and the paper 36 in front, and prints dots on the paper 36. Thereafter, the flight hammer 33 returns to the piezoelectric element 31 by the repulsive force from the platen 37 and the return force of the leaf spring 32. By repeating this operation, some characters and figures are represented by a set of dots.

[Problems to be solved by the invention]

In the printing hammer for the printer described above, in order to speed up the printing operation, it is necessary to increase the natural frequency of the vibration system including the leaf spring 32, the flight hammer 33, and the printing wire 34. Must increase the spring constant of the leaf spring 32. However, when the spring constant of the leaf spring 32 is increased, the proportion of the energy transmitted from the piezoelectric element 31 to the flight hammer 33 that is consumed for deformation of the leaf spring 32 increases, so that the kinetic energy of the flight hammer 33 decreases. However, there is a disadvantage that the density of the printed dots is reduced. Therefore, in order to achieve a high-speed printing operation without lowering the printing density, a flight hammer is required from the piezoelectric element 31.
It is necessary to increase the energy transmitted to 33. When the transmitted energy is increased, the spring constant of the leaf spring 32 is increased to increase the speed, and a required print density can be secured.
In order to increase the transmitted energy, the energy generated by the piezoelectric element 31 may be increased, and the applied voltage may be increased. However, when the applied voltage is increased, the acceleration of the piezoelectric element 3 is increased, the tensile stress generated by the inertial force of the piezoelectric element 31 itself is increased, the reliability is reduced, and there is a problem that the piezoelectric element 31 may be broken.

An object of the present invention is to provide a piezoelectric actuator that solves these problems.

[Means for solving the problem]

The feature of the present invention is that the piezoelectric element is disposed between a piezoelectric element, one end having a constricted portion projecting in one direction from the inside, and the other end facing the one end, and a frame shape surrounding the piezoelectric element. A piezoelectric actuator comprising: a frame; and pressing and fixing the piezoelectric element to the other end by crushing and plastically deforming a constricted portion of the frame to extend the one end in the one direction.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a piezoelectric actuator according to a first embodiment of the present invention. The piezoelectric actuator includes a piezoelectric element 11 and a frame 13 having a constricted portion 12. FIG. Also, by crushing the constricted portion 12 of the frame 13 in the direction of arrow B and deforming the composition, the connection surface of the piezoelectric element of the frame 13 is pushed out in the direction of arrow C, and the piezoelectric element 11 has both ends in the expansion and contraction direction (direction of arrow D). 13 Fixed inside. As a result, the piezoelectric element 11 fixed inside the frame 13 receives compressive stress from the frame 13,
The reliability of the piezoelectric element 11 is greatly improved. Further, since the applied voltage can be increased, the output energy can be increased. FIG. 2 is a schematic side view of a printing hammer for a printer using the piezoelectric actuator of the first embodiment shown in FIG. In the figure, the piezoelectric actuator is configured similarly to the embodiment of FIG. The print hammer is supported by a leaf spring 23 and connected to a print wire 24 by a flight hammer 25 in the direction of extension of the piezoelectric element 11 (arrow A).
(Direction) in contact with the frame 13 at one end. In this print hammer, when a voltage is applied to the piezoelectric element 11, the flight hammer 25 is accelerated by receiving the force from the piezoelectric element 11 due to the high-speed extension operation of the piezoelectric element 11, and leaves the frame 13. Then, the print wire 24 collides with the platen 28 via the ink ribbon 26 and the paper 27 in front, and prints dots on the paper 27. Then Flight Hammer 25
Returns to the frame 13 due to the repulsive force from the platen 28 and the return force of the leaf spring 23. According to the present embodiment, since the piezoelectric element 11 has received a compressive stress from the frame 13 in advance, the inertial force of the piezoelectric element 11 itself when the piezoelectric element 11 is performing the extension operation at the time of applying a voltage is also applied to the piezoelectric element 11. It does not act as a tensile stress, resulting in a highly reliable printing hammer. Further, since the output energy can be increased by increasing the voltage applied to the piezoelectric element 11, the speed can be increased by increasing the spring constant of the leaf spring 23.

As described above, the constricted portion of the frame surrounding the piezoelectric element is crushed and plastically deformed, and both ends of the piezoelectric element in the direction of expansion and contraction are fixed inside the frame, so that the piezoelectric element receives compressive stress from the frame. Also, even when a voltage is applied to the piezoelectric element and the piezoelectric element expands, the frame is elastically deformed, so that a compressive stress is always applied to the piezoelectric element. Piezoelectric elements are strong against compressive stress and very weak against tensile stress. In the piezoelectric actuator of the present invention, by fixing the piezoelectric element inside the frame, a compressive stress is always applied to the piezoelectric element, so that the reliability of the piezoelectric element is greatly improved. Therefore, the applied voltage can be increased as compared with the conventional case, and the output energy can be increased. Further, in the piezoelectric actuator of the present invention, the fixing between the piezoelectric element and the frame is performed by crushing the plastic part of the frame by crushing the constricted part of the frame. is there. Therefore, the manufacturing accuracy of the frame is not so required, and the cost is low.

〔The invention's effect〕

As described above, according to the present invention, by fixing a piezoelectric element with a frame so as to compress it, there is an effect that the reliability of the piezoelectric element is increased and a piezoelectric actuator that expands and contracts at a high speed can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a piezoelectric actuator showing one embodiment of the present invention, FIG. 2 is a side view showing a print hammer for a printer using the piezoelectric actuator of FIG. 1, and FIG. It is a side view of the printing hammer for printers using an element. 11,31… Piezoelectric element, 12… Constriction, 13… Frame, 23,32… Leaf spring, 25,33… Fly hammer, 24,3
4 …… Printing wire, 26,35 …… Ink ribbon, 27,36 ……
Paper, 28,37 …… Platen.

Claims (1)

(57) [Claims] A frame-like member surrounding said piezoelectric element, said piezoelectric element being disposed between a piezoelectric element, one end having a constricted portion projecting in one direction from the inside, and the other end facing said one end. A piezoelectric actuator, comprising: a frame, wherein the piezoelectric element is pressed and fixed to the other end by crushing and plastically deforming a narrow portion of the frame to extend the one end in the one direction.