JPH0624942U - Thermal head - Google Patents

Abstract

(57) [Summary] [Purpose] To effectively prevent warping of the heat sink due to thermal expansion, and to obtain proper and good print quality. [Structure] An insulating substrate 1 having a heating resistor 2 and a flexible printed circuit board 3 are sandwiched and fixed by a heat radiating plate 4 and a pressing cover 5. Form the nut groove 20 on the heat sink 4,
A nut 21 is inserted and arranged in the groove 20. Set screw 6
Is inserted into the screw mounting holes 23 and 22 of the pressing cover 5 and the flexible printed circuit board 3, the tip end thereof is inserted into the nut groove 20, and the nut 21 is screwed into the tip end portion, so that the pressing cover 5 is radiated. Secure to plate 4.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a thermal head used in a printer or the like.

[0002]

[Prior art]

 Thermal heads used in printers, etc., have a large number of heating resistors arrayed and formed on an insulating substrate such as ceramics in a direction orthogonal to the feeding direction of the thermal recording paper, and these heating resistors are selected by applying a voltage. Information is printed by causing the color to react on the thermosensitive recording paper by causing heat to be generated. FIG. 3 shows a conventional example of such a thermal head. Briefly explaining it, 1 is an insulating substrate such as ceramic provided with a heating resistor 2, 3 is a flexible printed circuit board, 4 is a heat sink, and 5 is With the pressing cover, the insulating substrate 1 and the flexible printed circuit board 3 are pressed and fixed onto the heat sink 4 by the pressing cover 5. The heat dissipation plate 4 and the pressing cover 5 are made of aluminum alloy or the like and have a heat dissipation function. The holding cover 5 is fixed on the heat dissipation plate 4 by a plurality of setscrews 6. Reference numeral 7 is a driver IC, 8 is an elastic member such as silicon rubber, 9 is a thermal recording paper, and the recording paper 9 is heated by a transport mechanism such as a roller (not shown) at the time of printing and the heating resistor 2 and the platen roller 10 are used. It is fed between the heat generating resistor 2 and the heating resistor 2 and is printed.

[0003]

[Problems to be solved by the device]

 However, in the above-mentioned conventional thermal head, since the flat heat dissipation plate 4 is simply used and the set screw 6 is screwed into the screw hole of the heat dissipation plate 4 to fix the pressing cover 5, the heat dissipation plate 4 is caused by thermal expansion. There is a problem that the warp cannot be absorbed and the print quality is degraded. That is, the insulating substrate 1, the heat dissipation plate 4 and the pressing cover 5 thermally expand during long-term use, but the thermal expansion coefficients of these members are different, and the thermal expansion coefficient of the insulating substrate 1 is small and hardly expands. On the other hand, since the heat dissipation plate 4 has a large coefficient of thermal expansion and tends to expand greatly due to thermal expansion, the central portion in the longitudinal direction is curved in a convex shape on the side opposite to the platen roller 10, as shown in FIG. As a result, there is a problem that the gap between the heat generating resistor 2 in the central portion and the platen roller 10 is enlarged to cause a print fading phenomenon, which deteriorates print quality.

Therefore, as a method for solving the above-mentioned problems, for example, the following thermal print head has been proposed. That is, this thermal print head has a plurality of V-shaped grooves 11 (see FIG. 4) formed on the lower surface of the heat dissipation plate 4 and orthogonal to the longitudinal direction. Therefore, the amount of thermal expansion of the upper surface side and the lower surface side of the heat dissipation plate 4 is different, and since the expansion of the lower surface side is absorbed by the groove 11, the heat dissipation plate 4 can be curved so as to be convex toward the platen roller side, and print faintness may occur. It has the advantage that it can be prevented. However, when the groove 11 is formed, the strength of the heat dissipation plate 4 is reduced, and when the heat dissipation plate 4 is curved in a convex shape toward the platen roller side, the frictional force between the heat generating resistor 2 and the platen roller 10 is increased, which is large. There is a problem that not only the transporting force is required, but also the heat generating resistor 2 is worn quickly and the wear resistance is required.

Therefore, the present invention has been made in view of the above-described conventional problems, and an object thereof is to effectively prevent warping of a heat dissipation plate due to thermal expansion, and to perform proper and good operation. It is to provide a thermal head capable of obtaining print quality.

[0006]

[Means for Solving the Problems]

 In order to achieve this purpose, the thermal head according to the present invention is a thermal head in which an insulating substrate equipped with a heating resistor and a flexible printed circuit board are pressed and fixed on a heat dissipation plate by a pressing cover. A nut groove is formed in the longitudinal direction, a plurality of nuts are inserted and arranged in this nut groove, and a plurality of screw mounting holes are formed in the presser cover corresponding to the nut groove. Is inserted into the nut groove from each of the screw mounting holes, the nut is screwed into the tip end of the groove, and the pressing cover is fixed to the heat radiating plate.

[0007]

[Action]

 In the present invention, the heat radiating plate and the pressing cover sandwich and fix the insulating substrate and the flexible printed circuit board. The nut groove allows relative movement between the set screw and the nut and the heat sink, and causes slippage between the heat sink and the nut when the heat sink expands due to thermal expansion.

[0008]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. FIG. 1 is an exploded perspective view showing an embodiment of a thermal head according to the present invention, and FIG. 2 is a sectional view. The same components as those of the conventional head shown in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. In these drawings, in this embodiment, a nut groove 20 is formed near the rear end of the upper surface of the heat dissipation plate 4 over the entire length in the longitudinal direction, and a plurality of nuts 21 are inserted and arranged in the nut groove 20. The holding cover 5 is fixed to the heat radiating plate 4 by the set screw 6 screwed to the nut 21, and the insulating substrate 1 and the flexible printed circuit board 3 are held and fixed by the heat radiating plate 4 and the holding cover 5.

The heat dissipation plate 4 is made of an extruded material such as an aluminum alloy, and the nut groove 20 is formed at the same time as the extruding process. Since the nut groove 20 is formed in an inverted T-shape in cross section, the groove width of the opening is set to be narrower than that of the inner part, thereby preventing the nut 21 from slipping upward.

Reference numerals 22 and 23 denote screw mounting holes formed in the flexible printed circuit board 3 and the pressing cover 5 at regular intervals in the longitudinal direction. The set screws 6 are inserted into these holes from above, and their tips are provided. The nut 21 in the nut groove 20 is screwed to the portion. The other structure is the same as the conventional structure shown in FIG.

In the thermal head having such a structure, the warp due to the thermal expansion of the heat dissipation plate 4 can be absorbed. That is, as described above, the insulating substrate 1, the heat radiating plate 4, and the pressing cover 5 thermally expand during long-term use, but the thermal expansion coefficients of these members are different, and the thermal expansion coefficient of the insulating substrate 1 is small and almost no heat is generated. In contrast to the fact that it does not expand, the heat dissipation plate 4 and the pressing cover 5 have large thermal expansion coefficients and tend to expand greatly due to thermal expansion. Therefore, in the conventional device in which the set screw 6 is screwed into the heat sink 4 without the nut groove 20 and the pressing cover 5 is rigidly fixed to the heat sink 4, the entire head is as shown in FIG. It is curved so as to be convex on the side opposite to the platen roller 10. On the other hand, instead of screwing the set screw 6 directly into the heat sink 4 as in the present invention, a nut groove 20 is formed and a nut 21 to be screwed into the set screw 6 is inserted and arranged therein. That is, since the set screw 6 is movable in the longitudinal direction of the nut groove 20 with respect to the heat dissipation plate 4, when the heat dissipation plate 4 thermally expands, slippage occurs between the heat dissipation plate 4 and the nut 21. Occurs. Further, if the tightening force of the set screw 6 is adjusted so that the insulating substrate 1 and the heat sink 4 are slipped due to thermal expansion, the heat sink 4 will not warp upward or downward, Extends straight in the direction. Therefore, the distance between the heat-generating antibody 2 and the platen roller 10 can always be kept constant.

In this embodiment, since the heat sink 4 is made of an extruded aluminum alloy material, the nut groove 20 can be formed at the same time when the heat sink 4 is extruded. Easy and easy to manufacture. Further, since the nut 21 is used, there is an advantage that it is not necessary to form a screw hole by post-processing.

[0013]

[Effect of device]

 As described above, in the thermal head according to the present invention, the groove for accommodating the nut is formed on the upper surface of the heat dissipation plate, and the set screw for fixing the holding cover for holding and fixing the insulating board and the flexible printed board together with the heat dissipation plate to the heat dissipation plate. Since it is configured to be screwed into the nut in the groove, when the heat dissipation plate thermally expands during heat generation of the heat generating resistor, slippage may occur between the insulating substrate and the heat dissipation plate and between the heat dissipation plate and the nut. Therefore, the heat sink can be surely prevented from warping. Therefore, the distance between the heating resistor and the platen roller can be kept constant at all times, and the printing quality can be improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a thermal head according to the present invention.

FIG. 2 is a side sectional view of the head.

FIG. 3 is a side sectional view of a conventional thermal head.

FIG. 4 is a diagram showing thermal deformation of a conventional head.

[Explanation of symbols]

 1 Insulation board 2 Heating resistor 3 Flexible printed circuit board 4 Heat sink 5 Holding cover 6 Set screw 10 Platen roller 20 Groove for nut 21 Nut

Claims (1)

[Scope of utility model registration request] 1. A thermal head in which an insulating substrate having a heating resistor and a flexible printed circuit board are pressed and fixed onto a heat dissipation plate by a pressing cover, and a groove for a nut is formed in the longitudinal direction on the upper surface of the heat dissipation plate, and this nut is formed. Plural nuts are inserted and arranged in the groove for use, a plurality of screw mounting holes are formed in the presser cover corresponding to the nut grooves, and set screws are inserted into the nut grooves through the screw mounting holes. The thermal head is characterized in that the nut is screwed onto the tip of the lever and the pressing cover is fixed to a heat dissipation plate.