JPH0546915Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to the structure of a heat dissipation device for a thermal head used in facsimiles, printers, various measurement recorders, and the like.

[Conventional technology]

In facsimiles, printers, various measurement recorders, etc., there is a so-called thermal head that converts information sent as electrical signals onto heat-sensitive recording paper and records and fixes it as graphic information such as characters and images.

As shown in FIGS. 5 and 6, the thermal head 20 has heating elements 21 made of thick-film or thin-film resistors formed on the surface of a ceramic substrate 22 in a horizontal line or at appropriate intervals vertically and horizontally. The heat-sensitive recording paper 24 is pressed against the heating element section 21 (the surface of which is usually covered with an abrasion-resistant layer) via the platen roller 23, and pulses are applied to the heating element at appropriate locations. When a voltage is applied, the coloring layer on the recording paper 24 develops color in dots. By repeating the pulsed heating while moving the recording paper 24 with respect to this thermal head, a predetermined figure such as a character can be obtained by the arrangement of colored points.

Conventionally, the ceramic substrate 22 of this type of thermal head 20 is equipped with a ceramic substrate as shown in FIG. As shown in FIG. 7, a heat dissipating plate 25 made of metal such as aluminum having a high heat transfer coefficient was attached by adhesive or the like on the back side opposite to the side on which the heating element portion 21 was formed.

[Problem that the invention attempts to solve]

According to this configuration, in a high temperature state during use, the metal heat sink 25 having a large coefficient of thermal expansion extends against the ceramic substrate 22 having a small coefficient of thermal expansion, so that a so-called bimetal phenomenon occurs.

For example, if the ceramic substrate 22 and the heat dissipation plate 25 are bonded together in a straight plane at a low temperature such as room temperature, then at a high temperature the long thermal head 20 will be formed along the longitudinal direction of the platen roller 23.
In this case, the thermal expansion of the heat sink 25 along the longitudinal direction has a large influence, and due to the thermal stress, the longitudinal center portion A of the platen roller 23 in FIG.
The entire thermal head 20 is warped due to thermal deformation so that the gap between the part and the heating element 21 becomes larger, and the recording paper 24 pressed through the platen roller 23 and the heating element 21 become warped. The contact pressure of the platen roller 23 varies along the longitudinal direction of the platen roller 23, and the density of the print at the central part A of the platen roller 23 is light, and the density of the print at the left and right ends B and C is high. The sharpness of printing along the longitudinal direction of the platen roller 23 varies.

As a countermeasure against this, as shown in FIG. 7, deformation is performed in the opposite direction to the thermal deformation, that is, the heating element portion 21 approaches the central portion A of the platen roller 23, and the left and right end portions B of the platen roller 23 are deformed in the opposite direction. It is conceivable to deform the heat dissipating plate 25 in advance such that the heating element part 11 separates at locations C, and then attach the ceramic substrate 22 thereto.

However, if the heat dissipation plate 25 is previously given a deformation in the opposite direction to the warpage deformation at high temperatures, and if the thermal head is guaranteed to have an optimal shape (straight line) at high temperatures due to continuous use of the thermal head, on the contrary, at low temperatures Sometimes the platen roller 2
The contact with the points B and C at both left and right ends of the platen roller 3 becomes weak, and the contact at the center point A becomes too strong. Therefore, the printing condition at this low temperature is
3, the density of the print at point A in the center is light, and the density of the print at points B and C at both left and right ends is higher. There was a problem in that it was not possible to eliminate variations in the clarity of printing under both conditions and high temperatures.

The present invention aims to easily solve such conventional problems.

[Means for solving problems]

Therefore, in the present invention, a heat sink made of a metal plate is attached to the back side of a ceramic substrate with a heating element formed on the front side, and a reinforcing plate is arranged on the back side of the heat sink.
The reinforcing plate is fixed to the heat radiating plate at both left and right ends in the longitudinal direction, and between the heat radiating plate and the reinforcing plate, a suitable place between the fixing points at the left and right ends is provided in a high temperature range. A shape-memory alloy deformation imparting member that returns to its original shape and functions to appropriately elastically deform the heat sink is inserted, thereby correcting the warping deformation caused by heat between the ceramic substrate and the heat sink. It is something.

〔Example〕

Next, an embodiment of the present invention will be explained with reference to the drawings. In FIG. A heat sink 4 made of a metal plate having approximately the same dimensions as the ceramic substrate 2 in 1 is mounted on the back side of the ceramic substrate 2, and a reinforcing plate 5 is disposed on the back side of the heat sink 4, and the reinforcing plate 5 is The heat dissipation plate 4 is located at both left and right end portions in the longitudinal direction.
While fixing the heat sink plate 4 with tightening bolts 10, etc.
A deformation imparting member 9 made of a shape memory alloy is inserted between the reinforcing plate 5 and the reinforcing plate 5 at an appropriate location midway between the fixed locations on both the left and right ends.

One embodiment in which the deformation imparting member 9 made of a shape memory alloy is inserted is shown in FIG. That is, the reinforcing plate 5 has a groove 1 having a U-shaped cross section.
1 is formed to be long in a direction substantially perpendicular to the longitudinal direction of the heat sink 4, and a deformation imparting member 9 having a substantially semicylindrical cross section is inserted into the groove 11 along the longitudinal direction. At this time, the left and right end edges of the deformation imparting member 9 were brought into contact with the left and right bottom edges of the groove 11, and the midway portion of the semi-cylindrical outer peripheral surface of the deformation granting member 9 was brought into contact with the back surface of the heat sink 4. It is inserted depending on the situation.

Code 6 is a cover body, code 7 is a connector, code 8
1 is a mounting screw portion for attaching the thermal head 1 to an external component; the reference numeral 13 indicated by a dashed line in FIGS. .

The shape memory alloy deformation imparting member 9 inserted between the back surface of the heat sink 4 and the reinforcing plate 5 memorizes its shape as follows.

That is, in the high temperature range when the thermal head 1 is in use, the ceramic substrate 2 and the heat sink 4 are separated from the central part A of the platen roller 13 in FIG. 3 due to thermal stress, and the left and right ends B, Assuming that a warp approaches point C, the shape memory is applied in advance in the high-temperature region so that a warp shape in the opposite direction to counter this warp deformation is given from the back side of the heat dissipation plate 4. It is stored in the deformation imparting member 9 made of alloy.

In one form, as shown in FIG. 4, the semi-cylindrical cross section of the deformation imparting member 9 becomes vertically high in a high temperature state, and the distance between the left and right edges becomes narrower in the longitudinal direction of the heat sink 4. The approximately central portion is pressed toward the surface so that a convex curve is formed in that direction.

Next, in a low temperature range such as room temperature, the shape memory alloy deformation imparting member 9 is processed and deformed to have a substantially semi-cylindrical cross section, and in the low temperature range, the heat dissipation plate 4 and the reinforcing plate 5 are formed into a flat shape. The upper and lower parts of the deformation imparting member 9 made of shape memory alloy are brought into contact with the heat sink 4 and the reinforcing plate 5, but the heat sink 4 and the reinforcing plate 5 are both made in such a way that no warping occurs. The reinforcing plate 5 is inserted into the groove 11 of the reinforcing plate 5, and the right and left ends of the reinforcing plate 5 are fixed to the back ring side of the heat dissipation plate 4 with bolts 10.

When the heating element part 3 of the thermal head 1 configured in this way is pressed against the circumferential surface of the platen roller 13 with the recording paper 14 in between and a current is applied in pulses according to an appropriate external signal, the heating element part 3 is heated. Printing will occur on the recording paper 14 due to the temperature rise of the heating element at the predetermined position.

According to the present invention, when the temperature of the entire thermal head 1 immediately after the start of use is relatively low, each of the ceramic substrate 2, the heat dissipation plate 4, and the reinforcing plate 5 becomes flat as described above. Therefore, the heating element part 3 on the surface side of the ceramic substrate is located at the central part A of the platen roller 13 and at both left and right ends B,
The contact pressure at location C can be made substantially equal, and printing can be performed with substantially the same density over the entire width direction of the recording paper 14 along the circumferential surface of the platen roller 13.

Through continuous use, the thermal head 1
When the temperature reaches a high temperature, due to the difference in thermal expansion between the ceramic substrate 2 and the heat sink 4, the platen roller 13 separates from the central portion A of the platen roller 13.
Thermal stress (arrow X1 in Fig.
However, due to the heat transferred to the deformation imparting member 9 made of a shape memory alloy inserted between the heat dissipation plate 4 and the reinforcing plate 5, the deformation imparting member 9 is deformed, and the heat dissipation plate 4 and In other words, the heat dissipation plate 4 is deformed so as to be warped in the direction of the arrow Y, which is opposite to the direction of the arrow X, so that a gap with the reinforcing plate 5 opens, and the thermal stress of the heat dissipation plate 4 is reduced. The warping deformation caused by the deformation and the warping deformation given to the heat dissipation plate 4 by the deformation imparting member 9 are balanced, so that the heating element portion 3 of the thermal head 1 is maintained in a flat planar shape even in a high temperature range, and is Similarly, it is possible to print with uniform density along the axial direction of the platen roller 13.

In other embodiments, the left and right end portions of the reinforcing plate 5 made of ordinary metal may be fixed to the back surface of the heat sink 4 with an adhesive or the like, and the heat sink 4 and the reinforcing plate 5 may be bonded together. The deformation imparting member 9 inserted between the reinforcing plates 5 may be inserted at a plurality of arbitrary appropriate locations in between, instead of at the longitudinally central portion of the reinforcing plate 5.

Furthermore, the grooves 11 for positioning the deformation imparting members 9 made of each shape memory alloy can be formed not only in the reinforcing plate 5 but also in the heat dissipation plate 4 side, and the cross section of the deformation imparting members 9 can be convexly curved. The direction may be toward the reinforcing plate 5 side. Furthermore, the cross-sectional convex curve direction of the deformation imparting member 9 may be oriented laterally along the reinforcing plate 5, and a spring-like member may be used.

It goes without saying that the deformation imparting member 9 has reversibility to return to its original shape (FIG. 3) in a low temperature range.

[Functions and effects of the idea]

In summary, according to the present invention, the shape memory imparted to the deformation imparting member 9 made of a shape memory alloy inserted between the reinforcing plate and the back surface of the heat sink on the side opposite to the side where the heating element is provided is the heat dissipation. It is only when the plate 4 reaches a high temperature range that it attempts to return to its shape in a direction that counters the warping deformation of the heat sink 4 due to thermal stress, and the shape recovery force of the deformation imparting member 9 and the heat of the heat sink 4 in the high temperature range Due to the balance with the stress, the heating element portion 3 of the thermal head can be maintained in a flat shape in the high temperature range.

In the present invention, since the heat dissipation plate 4 and the reinforcing plate 5 are held flat in a low temperature range such as room temperature, the warpage in the opposite direction to the warp deformation that occurs in a high temperature range as in the conventional case Compared to the case where deformation is given in advance at room temperature, the heating element 3 in the thermal head 1 of the present invention can be kept flat in almost the entire temperature range of the usage condition from the low temperature range to the high temperature range, and its warping deformation can be minimized. It can be reduced.

Therefore, fluctuations in printing pressure due to warping deformation caused by thermal stress, as well as fluctuations in printing density, can be extremely reduced, and stable printing can be performed from a room temperature range to a high temperature range.

In addition, since the deformation imparting member 9 made of the shape memory alloy only needs to be inserted into any part of the heat dissipation plate 4 or the reinforcing plate 5 in the longitudinal direction, the amount of expensive shape memory alloy used can be extremely reduced. This also has the effect of reducing the cost of the thermal head.

[Brief explanation of drawings]

1 to 4 show embodiments of the present invention, in which FIG. 1 is a side view of the thermal head taken along the - line in FIG. 2, FIG. 2 is a plan view, and FIG.
Figure 4 is an enlarged sectional view of the main part viewed from the - line, Figure 4 is an explanatory diagram of the operation, Figures 5 to 7 show the prior art, and Figure 5 shows the prior art.
6 is a plan view of the thermal head, FIG. 6 is a cross-sectional view taken along the line -2 in FIG. 5, and FIG. 7 is a cross-sectional view showing a pre-warped state. 1, 20... Thermal head, 2, 22... Ceramic substrate, 3, 21... Heating element part, 13, 2
3...Platen roller, 14, 24...Recording paper,
4, 25... Heat dissipation plate, 5... Reinforcement plate, 9... Deformation imparting member made of shape memory alloy, 11... Concave groove, 10
...Tightening bolt.

Claims (1)

[Scope of utility model registration request] A heat sink made of a metal plate is attached to the back side of a ceramic substrate with a heating element formed on the front side, a reinforcing plate is arranged on the back side of the heat sink, and the reinforcing plate is attached to both left and right sides in the longitudinal direction. While the end portions are fixed to the heat sink, between the heat sink and the reinforcing plate, a heat sink is installed at an appropriate location midway between the fixing points at both left and right ends, and the heat sink returns to its original shape when the temperature reaches the high temperature range. A heat dissipation device for a thermal head, characterized in that a deformation imparting member made of a shape memory alloy that functions to impart appropriate elastic deformation to the ceramic substrate and the heat dissipation plate is inserted to correct warping deformation due to heat between the ceramic substrate and the heat dissipation plate. .