JP2522073Y2 - Thermal head cooling device - Google Patents

Description

The present invention relates to a cooling device for a thermal head.

2. Prior Art First, FIGS. 4 to 9 show a prior art. FIG. 4 is a horizontal sectional view of the thermal head, FIG. 5 is a longitudinal sectional front view taken along the line BB in FIG. 4, and FIG. 6 is C in FIG.
It is a vertical side view of the -C line part. As shown in these figures, the thermal head 20 is formed by joining an insulating support plate 3 in which a large number of heating elements 2 are linearly arranged and a substrate 21. The common flow path 5 through which the coolant flows from one side to the other side along the arrangement direction of the heating elements is formed in the substrate 21, and the end of the upstream area 5a and the downstream area 5b of the common flow path 5 are adjacent to each other. The common flow path 5 is communicated with the individual flow paths 6 located immediately below the heating elements 2, and a cooling liquid inlet 11 and a cooling liquid outlet 12 are formed at both ends of the common flow path 5. The depth of the individual flow path 6 is determined to be smaller than the depth of the common flow path 5. Further, the downstream area 5b of the common flow path 5 is a thin partition wall.
The discharge passages 5c and 5d which are continuous in a U-shape are divided by 22.

In such a configuration, during printing, the temperature of the thermal head 20 rises due to the heat generated by the heating element 2, but the temperature can be lowered by the coolant flowing from the upstream area 5 a to the downstream area 5 b of the common flow path 5. Here, let us consider a state where the rightmost heating element 2 generates heat in FIG. The coolant that has cooled the rightmost heating element 2 flows to the left along the discharge path 5c in the downstream area 5b, and further flows to the right along the discharge path 5d. At this time, the temperature of the coolant in the discharge path 5c is higher rightward and lower as going to the left, and the temperature of the coolant in the discharge path 5d gradually decreases as going from the left to the right. That is, the heat gradient of the discharge passages 5c and 5d is reversed, but the temperature of the coolant in the discharge passages 5c and 5d is transmitted to the thin partition wall 22, so that there is no heat gradient in the entire downstream region 5b. Therefore, the thermal head
20 can be made uniform, and accordingly, it is possible to prevent the print density from being varied depending on the position of the heating element 2.

Next, FIG. 7 shows a structure of a main part of the thermal printer. A heat exchange unit 25 having a cooler 24 and a magnet 26 are provided on the back surface of the thermal head 20 facing the platen 23. The platen 23 includes a non-metallic roller 27, a ring-shaped magnet 28, and a ring-shaped elastic body 29 around a drive shaft 27a.
Are formed by laminating. Magnet 28
Is magnetized in the radial direction from the inside, where the inside is N
The poles and the outside are south poles, but the polarity may be reversed. The polarity of the magnet 26 is opposite to the polarity of the ring-shaped magnet 28. Further, the heat exchange unit 25 includes an element that can be electrically heated and cooled, such as a Peltier element, and a temperature sensor 30 is provided between the heat exchange unit 25 and the thermal head 20. I have.

Here, the cooling liquid will be described. The cooling liquid is a magnetic fluid in which a magnetic material such as magnetite or ferrite is made into fine particles of about 100 mm, mixed with a liquid, and dispersed in a colloidal state. This coolant has the property that the magnetic force decreases with temperature and loses the magnetic force at a certain temperature or higher. Therefore, in a state where printing is not performed, the coolant near the heating element 2 maintains a normal temperature and has a predetermined magnetic force.
Due to the action of 26, the gradient magnetic field works and does not move while staying there. When the printing operation is performed, the temperature of the heating element 2 rapidly rises, and the cooling fluid (magnetic fluid) loses its interaction with the magnet 26 because the magnetic force decreases due to the temperature rise, and acts on the cooling fluid in the unheated portion. The cooling liquid that is pushed by the force and moves at a low temperature is supplied to the heat-generating portion by the heat-generating element 2, and the heat-generating portion is cooled. As shown in FIG. 8, the cooling liquid is applied with pressure by the pump 31 so as to return to the common flow path 5 of the thermal head 20, discharged from the cooling liquid discharge port 17, and temporarily collected by the recovery unit 32.
After being collected, the ink is supplied to the thermal head 20 again.

Further, the operation of the heat exchange unit 25 will be described with reference to FIG. The temperature of the thermal head 20 is determined by the temperature sensor
Detected at 30. The operational amplifier 33, which has received the signal voltage from the temperature sensor 30, compares the signal voltage with the reference voltage and outputs a plus or minus voltage according to the difference. This output is further amplified by the amplifier 34 and applied to the heat exchange unit 25. By the heating or cooling action of the heat exchange section 25, the temperature of the cooling liquid (magnetic fluid) is automatically maintained at a constant temperature.

Problems to be Solved by the Invention In the prior art described above, the temperature of the thermal head 20 is made uniform by the heat exchange action of the partition wall 22 in the downstream area 5b of the common flow path, and therefore, the speed of making the temperature uniform is slow. In addition to the purpose of cooling the thermal head 20, when printing by preheating the thermal head 20 by the heat exchange unit 25, the cooling is performed from the cooling liquid inlet 11 toward the inside of the thermal head 20. There is a problem that the temperature of the liquid becomes low, the difference occurs in the temperature distribution, and the print density varies.

Means for Solving the Problems According to the invention of claim 1, a thermal head in which a number of heating elements are arranged on one surface, and cooling from one side along the arrangement direction of the heating elements formed on the thermal head and from the other side. A flow path through which the liquid flows, a cooling liquid inlet and a cooling liquid outlet formed at an end of the flow path, and a thermal liquid head provided in the thermal head along a direction in which the heating elements are arranged downstream of the flow path. And a heat pipe.

According to a second aspect of the present invention, in the first aspect, the thermal head is provided with a heat pipe in the upstream area of the flow path along the arrangement direction of the heating elements.

The invention according to claim 3 comprises a magnet provided in the vicinity of the flow path along the flow path, and a cooling liquid supply means for supplying a cooling liquid to the flow path, wherein a magnetic fluid is used as the cooling liquid. It is.

According to the invention of claim 1, when the purpose of cooling the thermal head is to be used (when the thermal head is used without preheating), when the cooling liquid that has absorbed the heat generation temperature of the heating element flows through the downstream area of the flow path, the cooling is performed. The heat pipes located along the downstream area can quickly absorb the heat of the cooling liquid and disperse it over a wide area, so that the temperature of each part of the thermal head can be made uniform.

According to the invention of claim 2, when the thermal head is preheated and used, the temperature of the coolant that is supplied to the upstream area of the flow path and preheated is reduced by the heat pipe provided along the upstream area. It can be rapidly absorbed and dispersed over a wide range, so that the temperature of each part of the thermal head can be made uniform.

According to the third aspect of the present invention, a low-temperature coolant is always present in the vicinity of the heating element, whereby the thermal head can be rapidly cooled.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 4 to 8 are denoted by the same reference numerals, and description thereof is omitted. FIG. 2 is a plan view of the thermal head 1 and the insulating support plate 3 of the thermal head 1.
Has a large number of heating elements 2 arranged in a straight line. First
FIG. 2 is a vertical cross-sectional side view taken along line AA in FIG. 2, and a substrate 4 on which a thermal head 1 is formed together with an insulating support plate 3 is provided with a cooling liquid from one side along the arrangement direction of the heating elements 2 to the other side. The common flow path 5 which is a flow path through which the fluid flows is formed. 5a shows the upstream area of the common flow path 5, and 5b shows the downstream area. The upstream region 5a and the downstream region 5b are communicated by an individual flow path 6 formed in the substrate 4 immediately below the adjacent heating elements 2. Thus, on the back surface of the substrate 4, two grooves 7 are formed along the upstream area 5a and the downstream area 5b of the common flow path 5, and these grooves 7 are made of heat such as silicon grease or silicon rubber. Heat transfer auxiliary member 8 with high conductivity
The heat pipe 9 wrapped in the heat pipe 9 is fitted, and a holding plate 10 for holding the heat pipe 9 is attached to the back surface of the substrate 4.

FIG. 3 is a plan view of the substrate 4, in which a coolant injection port 11 is formed at an end of an upstream area 5a of the common flow path 5 and a downstream area 5b is formed.
A cooling liquid outlet 12 is formed at an end of the cooling liquid.

In such a configuration, when the thermal head 1 is used without preheating, a coolant (magnetic fluid) having substantially the same temperature as room temperature is supplied to the common flow channel 5 from the upstream region 5a. This cooling liquid absorbs the heat of the heating element 2 accompanying the printing in the process of flowing through the downstream area 5b of the common flow path 5 toward the cooling liquid outlet 12, but the heat transmitted to the cooling liquid in the downstream area 5b. Is this downstream area
The heat pipe 9 is rapidly transmitted to the heat pipe 9 provided along 5b, and the heat pipe 9 having a high thermal conductivity disperses the transmitted heat in a wide range and quickly and transmits the heat to the substrate 4 of the thermal head 1.

When using the thermal head 1 with preheating,
8 and FIG. 8, the coolant is supplied from the upstream region 5a of the common flow path 5 to the constant temperature by the heat exchange unit 25. The heat of the coolant supplied to the upstream region 5a is supplied to the upstream region 5a. The heat pipe 9 having a high thermal conductivity is rapidly transmitted to the heat pipe 9 disposed along the base, and spreads the transmitted heat over a wide area and quickly and transmits the heat to the substrate 4 of the thermal head 1. Even when the thermal head 1 is used with preheating, the temperature in the vicinity of the heating element 2 that is energized with the printing operation rises.
This heat is cooled by the coolant flowing through the downstream area 5 b of the common flow path 5 toward the coolant outlet 12. At this time, the heat transmitted to the coolant is rapidly transmitted to the heat pipe 9 provided along the downstream area 5b, and the heat pipe 9 having a high thermal conductivity disperses the transmitted heat over a wide area and rapidly. To the substrate 4 of the thermal head 1.

Therefore, no matter which usage mode is selected, the temperature distribution of the thermal head 1 can be rapidly dispersed and maintained at a constant temperature, so that the printing density can be made uniform and high-speed printing can be performed. .

As described above, the invention of claim 1 provides a thermal head in which a large number of heating elements are arranged on one surface, and cooling from one side along the arrangement direction of the heating elements formed on the thermal head to the other side. A flow path through which the liquid flows, a cooling liquid inlet and a cooling liquid outlet formed at an end of the flow path, and a thermal liquid head provided in the thermal head along a direction in which the heating elements are arranged downstream of the flow path. In the case where the thermal head is to be cooled (when used without preheating), the cooling liquid having absorbed the heat generation temperature of the heating element flows through the downstream area of the flow path. Sometimes
The heat pipes along the downstream area can quickly absorb the heat of the coolant and disperse it over a wide area.
As a result, the temperature of each part of the thermal head can be rapidly made uniform, so that the printing density can be made uniform and the printing speed can be increased.

As described above, in the invention of claim 2, in claim 1,
By providing a heat pipe along the upstream area of the flow path to the thermal head, when the thermal head is preheated and used, the temperature of the coolant that is supplied to the upstream area of the flow path and preheated is set to the upstream area. The heat pipes arranged along the direction in which the heating elements are arranged can quickly absorb the heat of the coolant and disperse the heat over a wide area, thereby rapidly uniforming the temperature of each part of the thermal head. In addition, there is an effect that the printing density can be made uniform and the printing speed can be increased.

According to the third aspect of the present invention, a low-temperature coolant is always present in the vicinity of the heat generating element, which has an effect that the thermal head can be rapidly cooled.

[Brief description of the drawings]

1 to 3 show an embodiment of the present invention.
FIG. 1 is a longitudinal sectional side view taken along the line AA in FIG.
The figure is a plan view, FIG. 3 is a plan view of a substrate of a thermal head,
4 to 8 show the prior art, FIG. 4 is a horizontal sectional view, FIG. 5 is a vertical sectional front view taken along the line BB in FIG. 4, and FIG. 6 is C in FIG. FIG. 7 is a front view showing the structure of the main part of the thermal printer with a partial cross section, and FIG. 8 is a block diagram showing the structure of the heat exchange unit. DESCRIPTION OF SYMBOLS 1 ... Thermal head, 2 ... Heating element, 5 ... Flow path, 5a ... Upstream area, 5b ... Downstream area, 9 ... Heat pipe, 11 ... Coolant inlet, 12 ... Coolant outlet

Claims (3)

(57) [Scope of request for utility model registration] A thermal head in which a number of heating elements are arranged on one surface; a flow path formed in the thermal head for flowing a coolant from one side to the other side along the arrangement direction of the heating elements; A cooling liquid inlet and a cooling liquid outlet formed at an end of the flow path, and a heat pipe provided in the thermal head along a direction in which the heating elements are arranged in a downstream area of the flow path. Characteristic thermal head cooling device. 2. The thermal head cooling device according to claim 1, wherein a heat pipe is provided in the thermal head in an upstream area of the flow path along a direction in which the heating elements are arranged. 3. A magnet provided near the flow path along the flow path, and cooling liquid supply means for supplying a cooling liquid to the flow path, wherein a magnetic fluid is used as the cooling liquid. The cooling device for a thermal head according to claim 1, wherein