JPH0519910B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric actuator, and particularly to a piezoelectric actuator that serves as a drive source for drive devices such as printers and relays.

[Conventional technology]

Conventionally, electromagnetic actuators have been widely used as drive sources for printers, relays, and the like. This electromagnetic actuator generates a magnetic field by passing a current through the coil, and uses that magnetic force to drive the movable member, which not only requires a large amount of energy due to copper loss and iron loss, but also generates heat. There were also problems such as magnetic interference. Therefore, in recent years, electrical/mechanical energy conversion efficiency has improved,
A printing hammer for printers as shown in Figure 5, which uses a piezoelectric element with low power consumption, low heat generation, and no magnetic interference, has been reported (IEICE Mechanical Components Study Group material)
EMC 84−49).

FIG. 5 is a schematic side view of a printing hammer for a printer showing an example of a conventional piezoelectric actuator.

In the same figure, the printing hammer is attached to a plate spring 32 at the tip of the piezoelectric element 31 in the direction of extension (direction of arrow A).
The flight hammers 33 supported by the two are arranged so as to be in contact with each other. 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
1 receives a force from the piezoelectric element 31 and is accelerated, leaves the piezoelectric element 31 and flies. Then, the printing wire 34 collides with the platen 37 via the ink ribbon 35 and paper 36 in front, and prints a dot on the paper 36. After that, the flight hammer 33 receives the repulsive force from the platen 37 and the leaf spring 32.
It returns to the piezoelectric element 31 due to the restoring force.
By repeating this action, characters and figures are expressed as a collection of dots.

[Problem that the invention seeks to solve]

In the conventional printing hammer for printers described above, in order to speed up the printing operation, a leaf spring 3 is used.
2, the flight hammer 33, and the printing hammer 34, it is necessary to increase the natural frequency of the vibration system, and for this purpose, the spring constant of the leaf spring 32 must be increased. However, when the spring constant of the leaf spring 32 is increased, the energy transmitted from the piezoelectric element 31 to the flight hammer 33 is absorbed by the leaf spring 32.
Since the proportion spent on the deformation of the dot 2 increases, the kinetic energy of the flight hammer 33 decreases, and the density of the printed dots becomes thinner.

Therefore, in order to achieve faster printing operations without reducing print density, it is necessary to increase the energy transmitted from the piezoelectric element 31 to the flight hammer 33. When this transmitted energy is increased,
By increasing the spring constant of the leaf spring 32, the speed can be increased and the required printing density can be ensured.

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 voltage element 31 increases, and the internal stress generated by the chronic force of the piezoelectric element 31 itself increases, reducing reliability and causing a problem that it may break.

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

[Means for solving problems]

The piezoelectric actuator of the present invention includes a piezoelectric element;
A frame that surrounds part or all of the piezoelectric element, and due to the residual strain generated by polarizing the piezoelectric element, both ends of the piezoelectric element in the expansion and contraction direction are fixed inside the frame, and the piezoelectric element is is subjected to compressive stress.

[Effect]

FIG. 6 shows the relationship between applied voltage and displacement of the piezoelectric element. When a voltage is applied to the unpolarized piezoelectric element (point A) and the voltage is increased, the displacement increases along the curve until it reaches point B, and the piezoelectric element is polarized. When the voltage is lowered from point B, the displacement decreases along the curve and reaches point C. When the voltage is applied again from point C and raised, the displacement rises along the curve and reaches point B. When the voltage is lowered from point B, the displacement decreases along the curve and reaches point C. Return to Therefore, under normal use, the piezoelectric element is at point C and point B.
It rises and falls along the curve between. Therefore, if a voltage is applied to an unpolarized piezoelectric element up to point B to polarize it, residual strain will occur between points AC.

Therefore, when an unpolarized piezoelectric element is inserted inside a frame that is slightly larger inside than the piezoelectric element and polarized, the piezoelectric element generates residual strain and both ends of the piezoelectric element in the expansion and contraction direction are fixed to the inside of the frame. .

As a result, the piezoelectric element fixed inside the frame receives a compressive force from the frame. Further, even when the piezoelectric element is expanded by applying a voltage, the frame is elastically deformed, so a compressive force is always applied to the piezoelectric element.

Piezoelectric elements are strong against compressive stress but very weak against tensile stress. In the piezoelectric actuator of the present invention, by fixing the piezoelectric element inside the frame, a compressive force is always applied to the piezoelectric element, so the reliability of the piezoelectric element is greatly improved. Therefore, the applied voltage can be increased compared to the conventional case, and the output energy can be increased.

Furthermore, in the piezoelectric actuator of the present invention, the piezoelectric element is fixed to the frame by utilizing the residual strain generated by polarizing the piezoelectric element.
No special jig is required, making it simple.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic side view showing a first embodiment of the present invention, in which a piezoelectric actuator is composed of a piezoelectric element 11 and a U-shaped frame 12. An unpolarized piezoelectric element 11 is placed inside a frame 12 whose inner length is larger than the length of the unpolarized piezoelectric element 11.
The piezoelectric element 11 is fixed to the inside of the frame 12 by fitting and processing to generate residual strain in the piezoelectric element 11.

As a result, the piezoelectric element 11 fixed inside the frame 12 receives compressive stress from the frame 12, and the reliability of the piezoelectric element 11 is greatly improved. Furthermore, since the applied voltage can be increased, output energy can be increased.

FIG. 2 is a schematic side view showing a second embodiment of the present invention, in which the piezoelectric actuator is composed of a piezoelectric element 23 and a square-shaped frame 28. An unpolarized piezoelectric element 23 is placed inside the frame 28, the length of which is larger than the length of the unpolarized piezoelectric element 23.
The piezoelectric element 23 is fixed inside the frame 28 by the residual strain of the piezoelectric element 23.

As a result, the piezoelectric element 23 fixed inside the frame 28 receives compressive stress from the frame 28, and the reliability of the piezoelectric element 23 is greatly improved. Furthermore, since the applied voltage can be increased, output energy can be increased.

FIG. 3 is a schematic side view of a printing hammer for a printer showing an example of use of the first embodiment shown in FIG.

In the figure, the piezoelectric actuator is composed of a piezoelectric element 11 and a U-shaped frame 12, and the piezoelectric element 11 is fixed inside the frame 12 by utilizing residual strain caused by polarization processing. Further, the printing hammer is supported by a leaf spring 13,
The flight hammer 15 to which the printing wire 14 is connected is directed in the direction of extension of the piezoelectric element 11 (direction of arrow A).
It is arranged so as to be in contact with the frame 12 at one end.

In this printing hammer, when a voltage is applied to the piezoelectric element 11, the flight hammer 15
1 is accelerated by the force from the piezoelectric element 11, and flies away from the frame 12. Then, the application wire 14 collides with the platen 18 via the ink ribbon 16 and paper 17 in front, and prints dots on the paper 17. Thereafter, the flight hammer 15 returns to the frame 12 due to the repulsive force from the flatten 18 and the return force of the leaf spring 13.

According to this usage example, the piezoelectric element 11 is
Since the piezoelectric element 11 receives compressive stress in advance from the piezoelectric element 2, the inertial force of the piezoelectric element 11 itself when the piezoelectric element 11 is expanding when a voltage is applied does not act on the piezoelectric element 11 as a tensile stress, resulting in highly reliable printing. It becomes a hammer. Further, since the output energy can be increased by increasing the voltage applied to the piezoelectric element 11, the speed can be increased.
Furthermore, no special jig is required for fixing the piezoelectric element 11 to the frame 12.

Next, FIG. 4 is a schematic side view of a latch type relay showing an example of use of the second embodiment shown in FIG. 2.

In the same figure, the piezoelectric actuator has first and second piezoelectric elements 23 and 24, and a square-shaped first and second piezoelectric element 23, 24.
It is composed of frames 28 and 29, and has a first frame and a second frame.
The piezoelectric elements 23 and 24 are fixed inside the first and second frames 28 and 29, respectively, using the residual strain caused by the polarization process. Also,
In the latch type relay, a reversing spring 21 provided with a flying member 20 is inserted into the mounting portions 22a and 22b of the mounting member 22 and curved, and a first and a second reversing spring 21 are placed opposite the flying member 20 and on both sides of the reversing spring 21, respectively. piezoelectric elements 23 and 24 are arranged, and a movable contact 25 that is interlocked with the operation of the reversing spring 21 and first and second fixed contacts 26 and 27 that are opposed to the movable contact 25 are connected to the mounting member 22. The first and second piezoelectric elements 23 and 24 are fixed by first and second frames 28 and 29, respectively, and the first and second frames 28 and 29 are connected to the mounting member 22.

This latch-type relay flies the flying member 20 by the force generated by the first or second piezoelectric element 23 or 24, causes the reversing spring 21 to perform a reversing action, and moves the movable contact 25, from a to b or b in FIG. a
Switch to the state shown in

According to this usage example, the first and second piezoelectric elements 2
3 and 24 are the first and second frames 28, respectively.
Since compressive stress is previously received from the piezoelectric element 29, the inertial force of the piezoelectric element itself when the first or second piezoelectric element 23 or 24 is expanding when a voltage is applied does not act on the piezoelectric element as a tensile stress. A highly reliable latch type relay. In addition, by increasing the applied voltage, the first and second piezoelectric elements 23,
Since the flight distance of the flight member 20 can be increased by increasing the energy generated by the relay 24, a long stroke of the movable contact 25 can be realized, resulting in a high-power latch relay. Furthermore, the first and second piezoelectric elements 2
There is also no need for a special jig to fix the parts 3 and 24 to the first and second frames 28 and 29.

〔Effect of the invention〕

As explained above, by using the piezoelectric aketuator of the present invention, it is possible to achieve high speed and long stroke, and there is an effect that a highly reliable printing hammer, relay, etc. can be obtained.

[Brief explanation of the drawing]

1 and 2 are the first and second embodiments of the present invention, respectively.
FIG. 3 is a schematic side view of a printing hammer for a printer showing an example of the use of the first embodiment shown in FIG. FIG. 5 is a schematic side view of a printing hammer for a printer showing an example of a conventional piezoelectric actuator, and FIG. FIG. 3 is a diagram showing the relationship between applied voltage and displacement. 11, 23, 24, 31...piezoelectric element, 12,
28, 29... Frame, 13, 32... Leaf spring, 14, 34... Printing wire, 15, 33...
Flight hammer, 16,35...ink ribbon,
17,36...paper, 18,37...platen, 2
0... Flight member, 21... Reversing spring, 22... Mounting member, 25... Movable contact, 26, 27... Fixed contact.

Claims (1)

[Claims] 1 Consisting of a piezoelectric element and a frame surrounding part or all of the piezoelectric element, both ends of the piezoelectric element in the expansion and contraction direction are fixed inside the frame due to residual strain caused by polarizing the piezoelectric element. A piezoelectric actuator characterized in that compressive stress is applied to the piezoelectric element.