JPH0596821A - Printing head using a piezoelectric element as an actuator - Google Patents

Abstract

(57) [Abstract] [Purpose] In a print head using a piezoelectric element, it is possible to obtain a heat-dissipating effect that does not reduce the heat-dissipating effect and that does not reduce the expansion of the piezoelectric element. A piezoelectric element 25 is covered with a heat conductive material 59 having a low hardness, a plurality of printing units 17 having the piezoelectric element 25, and a heat radiation cover 1 for covering the printing unit 17.
The gap 5 is filled with a heat conductive material 47 having a high hardness to promote the heat dissipation function without hindering the expansion and contraction movement of the piezoelectric element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head used in an impact dot matrix printing apparatus, and more particularly to a print head using a piezoelectric element as an actuator.

[0002]

2. Description of the Related Art Conventionally, a print head utilizing the expansion / contraction characteristics of a piezoelectric element has a charge / discharge current applied to the piezoelectric element to expand / transmit the expansion / contraction motion of the piezoelectric element to move a printing wire forward / backward. Printing is performed on the paper facing the wire via an ink ribbon. A plurality of printing units including the piezoelectric elements are radially arranged to form one print head, which is arranged at a predetermined position of the printing apparatus. In this type of print head, it is possible to prevent heat generation in the piezoelectric element and its vicinity by repeating charging and discharging for expanding and contracting the piezoelectric element. However, since the piezoelectric element has a characteristic that it contracts when heated, this heat causes the piezoelectric element to contract, resulting in a decrease in printing striking force.

As one of the solutions, for example, as shown in Japanese Patent Laid-Open No. 63-17060, the elasticity is such that the expansion and contraction movement of the piezoelectric element is not hindered between the piezoelectric element and the base supporting the piezoelectric element. There is a method of radiating heat by filling a heat conductive synthetic resin having In addition, in order to make the heat radiation effect more effective, the entire space between the plurality of printing units and the heat radiation cover installed around these printing units is filled with a thermally conductive synthetic resin to form a piezoelectric element. It is also considered that the heat generated in the vicinity thereof can be more effectively released to the outside of the print head.

[0004]

However, in the print head driven by the expansion and contraction movement of the piezoelectric element,
In order to fill the thermally conductive synthetic resin in the details of the gaps between the plurality of printing units and the heat radiation cover that covers these printing units, it is necessary to use the thermally conductive synthetic resin having low viscosity. However, a heat conductive synthetic resin having a low viscosity usually has a property of increasing hardness after curing.
Therefore, the thermally conductive synthetic resin having a high hardness after curing contacts and surrounds the piezoelectric element, thereby reducing the amount of expansion of the piezoelectric element, which is the driving force of the print head, and reducing the speed of expansion / contraction operation. And the print hitting force is adversely affected. The present invention has been made to solve the above-mentioned problems, and provides a print head using a piezoelectric element as an actuator that achieves a more effective heat dissipation effect and that does not reduce the expansion and contraction action of the piezoelectric element. The purpose is to

[0005]

In order to achieve the above object, the present invention has a plurality of print units driven by a piezoelectric element which expands and contracts by charging and discharging, and has a heat radiation cover around the print units. In the arranged print head, the piezoelectric element is covered with a heat conductive material having a low hardness,
Moreover, a heat conductive material having high hardness is filled between the heat conductive material and the heat radiation cover.

[0006]

According to the above construction, the piezoelectric element which expands and contracts due to charging and discharging is covered with a heat conductive material having a low hardness, and a plurality of printing units having the piezoelectric element and a plurality of printing units arranged around these printing units are provided. A gap between the heat dissipation cover and the heat dissipation cover is filled with a heat conductive material having a hardness higher than that of the heat conductive material. As a result, the heat generated in the piezoelectric element and its vicinity is not accumulated, but is radiated to the outside through the heat conductive material and the heat dissipation cover, and the heat conductive material in contact with the piezoelectric element expands and contracts the piezoelectric element. Do not disturb

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A print head according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the structure of the present print head, and FIG. 2 is a side view showing the structure of a print unit 17 arranged in the print head. The print head is composed of a disk-shaped head main body 13 and a bottomed cylindrical heat dissipation cover 15, and has a cylindrical shape.
3 and the heat dissipation cover 15 are made of aluminum alloy. A predetermined number of printing units 17 are radially arranged inside the heat dissipation cover 15 on the back side of the head body 13.
A hollow nose portion 16 is provided at a substantially central position of the head body 13.
Are projected at a position facing an ink ribbon and a print sheet (not shown).

The printing unit 17 has a piezoelectric element 25 in which piezoelectric ceramics are laminated to each other, and a printing wire 21 for printing on a printing paper via an ink ribbon (not shown) by moving forward and backward in association with expansion and contraction of the piezoelectric element 25. And a motion transmission mechanism 14 for expanding and transmitting the expansion and contraction movement of the piezoelectric element 25,
It is composed of a support frame 27 that supports the motion transmitting mechanism 14 and the piezoelectric element 25. The support frame 27 is integrally formed in a U-shape by the main strut portion 27a, the sub strut portion 27b and the connecting rear end portion 27c so as to surround both side surfaces and the rear end portion of the piezoelectric element 25 in the stacking direction (longitudinal direction). Has been formed. The piezoelectric element 25 is applied to the main strut 2 by applying a voltage.
Along the 7a and the sub-column portion 27b, it expands and contracts in the stacking direction. Further, the temperature compensator 26 is fixedly inserted between the rear end portion of the piezoelectric element and the connecting rear end portion 27c of the support frame 27 so that the piezoelectric element 25 corrects only the reduced size due to the temperature rise. Is becoming The print wire 21 is arranged in the nose portion 16 of the head main body 13, and the nose portion 1
It is guided by a predetermined number of guide plates 23 provided in 6 so as to be movable back and forth.

The motion transmitting mechanism 14 has a print wire 2 at the tip.
1 has a plate-shaped arm 29 having a fixed shape, and first and second leaf springs 3 for expanding the displacement of the piezoelectric element 25.
1, 33 and a movable element 35 mounted on the front surface of the piezoelectric element 25 and transmitting the displacement of the piezoelectric element 25 to the second leaf spring 33.
It consists of and. First leaf spring 31 and second leaf spring 3
3 is the same material having elasticity and has the same shape. Further, the first leaf spring 31 and the second leaf spring 33 are installed in parallel with each other, and the tips thereof are continuously provided to form a U-shape, and the continuously provided portion 37 includes the printing wire 21 of the arm 29. Is fixed to the end opposite to the one end where is fixed. The base end of the first plate spring 31 is fixed to the side surface of the main support column 27a, and the base end of the second plate spring 33 is fixed to the side surface of the mover 35.

In the motion transmitting mechanism 14 having the above-mentioned structure, when a voltage is applied to the piezoelectric element 25 and the piezoelectric element 25 expands in the stacking direction, the mover 35 interlocks and moves in the forward direction. The second leaf spring 33 fixed to the mover 35 is
Since it tries to move in the forward direction relative to the leaf spring 31, the connecting portion 37 rotationally moves in the counterclockwise direction. As a result, the arm 29 is interlocked with the front direction (left direction in FIG. 1), and the print wire 21 fixed to one end of the arm 29 is projected,
The printing paper is hit through an ink ribbon (not shown), and dots are printed on the printing paper. When the voltage application is released, the piezoelectric element 25 contracts, and this contraction movement is transmitted to the arm 29 having the print wire 21,
The arm 29 returns to the non-acting position. The arm 29
An arm stopper 39a made of resin is provided at the non-acting position, and comes into contact with the stopper 39b of the sub strut 27b to stop.

Further, the main strut portion 27a and the sub strut portion 2
A 4-node link mechanism member 41 is provided so as to straddle 7b. The material of the four-bar linkage mechanism 41 is a plate material that is elastically deformable, and the wide side plate part 41a and the long narrow plate part 41b are connected to each other on the auxiliary column part 27b, and the shape thereof is a U-shape. Both ends of the plate portion 41b are main strut portions 27a
And the sub-column 27b. A notch hole 43 having a substantially H shape in a side view is formed in the plate portion 41a, and two sides sandwiching the notch hole 43 are fixed to the sub strut portion 27b and the mover 35, respectively. For this reason, when the piezoelectric element 25 expands and the mover 35 moves, the two sides of the plate portion 41a are elastically deformed into a parallelogram shape in a side view, and are configured not to hinder the mover 35 from moving. There is.

With the moment action of the connecting portion 37 of the motion transmitting mechanism 14 in the counterclockwise direction, the piezoelectric element 2 is moved.
5 may be bent in a direction intersecting the stacking direction,
Due to the configuration of the four-node link mechanism member 41, a moment in a direction of moving the mover 35 and the piezoelectric element 25 in the clockwise direction is generated, and thus the two opposite moments cancel each other out, and the piezoelectric element 25 is bent. It can be expanded and contracted linearly without doing.

In the printing unit 17, the piezoelectric element 25
In the gap between the support frame 27 and the support frame 27, the hardness of 30 which does not hinder the expansion and contraction movement of the piezoelectric element 25 and has thermal conductivity.
Silicone rubber 59 of about -50 (JIS-A) is filled. Further, in the gap between the predetermined number of printing units 17 and the heat dissipation cover 15, a synthetic resin having a low viscosity before curing and a hardness after curing of about 50-80 (JIS-A), which is excellent in thermal conductivity, such as silicone. It is filled with rubber 47. With the above configuration, heat generated in the piezoelectric element 25 and its vicinity is radiated to the outside from the heat dissipation cover 15 via the silicone rubber 59 and the silicone rubber 47, and it is possible to prevent the piezoelectric element 25 from contracting due to a temperature rise. Moreover, since the silicone rubber 59 contacting the piezoelectric element 25 has a hardness that does not hinder the expansion and contraction movement of the piezoelectric element 25, it does not adversely affect the printing operation.

This synthetic resin is used after the printing unit is assembled in the head main body and covered with a heat radiation cover.
The heat radiation cover is filled through the gap. Therefore, in order to expect a sufficient heat radiation effect, it is preferable to fill the heat radiation cover without bubbles or the like adhering to the printing unit. Therefore, it is also desired that the resin has a sufficiently low viscosity before curing. The applicant of the present invention, as the resin to be filled in the gap between the piezoelectric element 25 and the supporting frame, has a viscosity before curing of 4000 (25 degrees C poise) and a hardness of 4 after curing.
5 (JIS-A), elongation rate 200 (%), thermal conductivity 2.
0 * 10E-3 (cal / sec.cm.degree. C.) silicone rubber is used, and the printing unit 17 and the heat dissipation cover 1 are used.
In the gap with the No. 5, the viscosity before curing is 26.5 (25 degrees C po
ise), hardness after curing 69 (JIS-A), elongation 70
(%), Thermal conductivity 2.5 * 10E-3 (cal / sec
Good characteristics have been obtained using silicon rubber of cm.degree. C) (the above figures are all measured values).

In each printing unit 17, the front end portion (the left end portion in FIG. 1) of the main support column 27a is attached to the head body 13.
It is fixed to the head main body 13 by being fixed to the annular mounting piece 45 which is fixed to a predetermined position on the back surface portion with a screw (not shown) by a screw 19. In addition, each printing unit 17
A lead wire 51 for connecting the piezoelectric element 25 to a drive circuit is provided at a predetermined position on the rear end of the support frame 27 in
The substrate 5 supported on the back side of the bottom surface of the heat dissipation cover 15.
Connected to 7.

[0016]

As is apparent from the above description, according to the present invention, the piezoelectric element is covered with a heat conductive material having a low hardness,
Piezoelectric elements are manufactured by filling a gap between a plurality of printing units having piezoelectric elements and a heat radiating cover disposed around these printing units with a heat conductive material having a hardness higher than that of the heat conductive material in detail. It is possible to effectively dissipate the heat generated in the vicinity thereof and to prevent the expansion and contraction movement of the piezoelectric element from decreasing.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a configuration of a print head according to an embodiment of the present invention.

FIG. 2 is a side view of a print unit in a print head according to an embodiment of the present invention.

[Explanation of symbols]

 15 Heat Dissipation Cover 17 Printing Unit 25 Piezoelectric Element 47 Silicon Rubber 59 Silicon Rubber

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 8603-2C B41J 3/10 113 A

Claims (1)

[Claims] 1. In a print head in which a plurality of printing units driven by a piezoelectric element that expands and contracts due to charging and discharging are arranged, and a heat radiation cover is arranged around the printing unit, the piezoelectric element has a hardness of A print head using a piezoelectric element as an actuator, which is covered with a low thermal conductive material and is filled with a high thermal conductive material between the thermal conductive material and the heat radiation cover.