JPS58138663A - Thermal head for heat-sensitive recording - Google Patents

Abstract

PURPOSE:To improve the temperature control of heating elements by a method in which a heat pipe is thermally connected with the heating elements and a thermister to control applied voltage to the heating elements according to the variations in the temperature of a base plate is thermally connected to the heat pipe. CONSTITUTION:A groove 7 is provided linearly and continuously in the longitudinal direction of a base metal plate 4 at the widthwise center of the upside of the base metal plate 4. A heat pipe 8 is housed in the groove 7 along a heating element 2, and a belt-shaped elastomer 9 of silicone rubber, etc., is put between the heat pipe 8 and the bottom of the groove 7. Also, a thermal compound is beforehand coated on one or both sides of the contact part between the heat pipe 8 and a ceramic base plate 1. The preferred shape of the heat pipe 8 is angular or circular form in cross section, but angular form is most preferable. A thermister 6 is thermally connected with one end of the heat pipe 8.

Description

[Detailed description of the invention] The present invention relates to a thermal head for heat-sensitive recording.

As an example of a conventional thermal head of this type, one shown in FIGS. 1 and 2 and constructed as 1J is known. That is, on the upper surface of the strip-shaped ceramic substrate 1, at the center in the width direction, there is a heating element (heating resistor) 2 made of ceramic!
It is provided by continuous printing in a straight line in the longitudinal direction of the ill. The ceramic substrate 1 is provided on a base metal plate 4 provided on a frame 3. A recess 5 is provided in the center of the upper surface of the base metal plate 4, and a thermistor 6 is provided in the recess 5. Then, by selectively energizing and heating the heating element 2 according to the image information, the information is recorded on thermal recording paper (or ordinary recording paper via an ink donor sheet). At this time, the temperature of the heating element 2 is controlled by the thermistor 6 to make the density in the recording uniform.

To explain this in more detail, if the temperature of the heating element 2 rises above a desired value, the recording will become darker. Therefore, when the temperature of the heating element 2 rises above a desired value, the thermistor 6 detects this and reduces the voltage applied to the heating element 2 via the control circuit, thereby suppressing the temperature rise of the heating element 2. It is designed to equalize the density within the recording.

By the way, in the conventional thermal head mentioned above,
If the recording paper is partially continuously recorded, the heat distribution of the heating element 2 will become uneven, but since the thermistor 6 is provided only at the lower center of the linear heating element 2, the heat of the heating element 2 will be uneven. It is not possible to deal with non-uniformity of the pores, and temperature control over the entire heating element 2 becomes impossible. For example, when recording is performed continuously only on the center of the recording paper, the temperature of only the center of the heating element 2 rises above the desired value, and the thermistor 6 detects this and reduces the voltage applied to the entire heating element 2. Reduce voltage. Therefore, when recording is subsequently performed on the edges of the recording paper, the rise of heat generation at the edges of the heating element 2 is slow due to the above-mentioned drop in applied voltage, and as a result, the density of the recording at the edges of the recording paper is lower than that at the center. There was a problem that it became thinner than before and uneven density occurred.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to quickly correct the heat distribution of the heating element to be approximately uniform, and also to perform temperature control over the entire heating element favorably (which may cause density unevenness in the recording). It is an object of the present invention to provide a thermal head for heat-sensitive recording that can be prevented from occurring.

To achieve this objective, the present invention provides a heat pipe along the heating element, the heat pipe thermally coupled to the heating element, and a thermistor thermally coupled to the heat pipe. This is what I did.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. In addition, in these figures, the first
Components that are the same as those of the conventional example shown in the figures and FIG.

A groove 7 is provided on the upper surface of the base metal plate 4 at the center in the width direction so as to be continuous in a straight line in the longitudinal direction of the base metal plate 4. The seven wheels are housed so that the heat pipe 8 runs along the heating element 2. A band-shaped elastic body 9 made of silicone rubber or the like is interposed between the heat pipe 8 and the bottom of the groove 7. The heat pipe 8 is urged upward by the elastic force of the elastic body 9 and brought into close contact with the lower surface of the ceramic substrate 1. As a result, the heat pipe 8 transfers heat to the heating element 2 via the ceramic substrate 1. Although not shown, a thermal compound is applied to one or both of the contact parts between the heat pipe 8 and the ceramic substrate 1 in order to improve thermal conductivity. .Furthermore, the cross-sectional shape of the heat pipe 8 is round.
Any shape such as a corner may be used, but in consideration of thermal conductivity, a shape that has a large contact area with the ceramic substrate 1, such as a corner, is preferable. Further, a thermistor 6 is provided at one end of the heat pipe 8 and is thermally coupled thereto.

With the above configuration, even if the heat distribution of the heating element 2 becomes uneven when partially continuous recording is performed on the recording paper,
This can be quickly dispersed by the heat pipe 8 via the ceramic substrate 1 and the like, so that the heat distribution of the heating element 2 can be quickly corrected to be approximately uniform. Moreover, since the temperature of the heating element 2 is detected by the thermistor 6 via the heat pipe 8, the temperature of the entire heating element 2 can be well controlled, which causes unevenness in the recording session. Never.

In addition, in the above embodiment, the heating element 2 was explained as being linearly continuous, but the heating element 2 is not limited to this, and may be linearly discontinuous.

As explained above, according to the thermal head for heat-sensitive recording according to the present invention, the thermal head for heat-sensitive recording can be moved along the heating element. In addition to providing a heat pipe, this heat pipe is thermally coupled to a heating element,
Further, a thermistor is provided to be thermally coupled to the heat pipe. Therefore, the heat distribution of the heating element can be quickly corrected to be approximately uniform, and the temperature of the entire heating element can be well controlled, thereby making it possible to prevent density unevenness from occurring in the recording session. It has the following effects.

4. Brief explanation of the drawings;

Figure 1 is a perspective view showing an example of a conventional thermal recording head, and Figure 2 is a perspective view taken along the line ■-■ in Figure 1.
A top view, FIG. 3 is a perspective view showing one embodiment of the thermal head for thermosensitive recording according to the present invention, and FIG.
It is a longitudinal cross-sectional view along the line.・1...Ceramic substrate 2...Heating element 4...Base metal plate 6...Thermistor 7...Groove 8...・・Heat pipe 9・・・・Applicant for elastic body Umeo Yamauchi Representative of Fuji Xerox Co., Ltd. Patent attorney Figure 1 ? figure

Claims (1)

[Claims] There's a heating element on the board! In the thermal head for heat-sensitive recording provided in the shape of an illumination, a heat pipe is provided along the heating element 47, and the heat pipe is thermally coupled to the heating element, so that the heat pipe is thermally coupled to the heating element, and the heat pipe is thermally connected to the heating element, so that the temperature of the substrate changes depending on the temperature change of the substrate. A thermal head for thermosensitive recording, characterized in that a thermistor for controlling the voltage applied to the heating element is thermally coupled to the heat pipe.