JPH06255111A - Temperature detector of thermal ink jet head - Google Patents

Abstract

PURPOSE:To improve the yield at a time of mass production while keeping temp. detection capacity well and to achieve the decrease in cost accompaned by the reduction of the number of manufacturing processes. CONSTITUTION:A thermal ink jet head is equipped with a head main body 1 having ink emitting nozzles 2 arranged thereto at a predetermined pixel pitch and having heating elements 3 forming ink emitting heat energy built in the nozzles, the radiation member 4 attached to the head main body 1 and discharging the excessive heat of the head main body 1 to the outside and the print substrate 5 arranged on the radiation member 4 and supplying the drive signal corresponding to the image signal from the outside to the respective heating elements 3 of the head main body 1. A temp. detection element 6 is provided on the print substrate 5 arranged in close vicinity to the head main body 1 and connected to the radiation member 4 by a thermal connection means 7 good in heat conductivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detecting device for a thermal ink jet head.

[0002]

2. Description of the Related Art Generally, as shown in FIGS. 10 and 11, in a thermal ink jet head, ink ejection nozzles 101 are arranged at a predetermined pixel pitch and each nozzle 1
Heating element 1 for generating thermal energy for ink ejection in 01
Head main body 100 that incorporates 02, and this head main body 1
Radiating member 103 attached to No. 00 to radiate excess heat of the head main body 100 to the outside, and each heat generating element 102 of the head main body 100 arranged on the heat radiating member 103 according to an external image signal. And a printed circuit board 104 that supplies a drive signal. Reference numeral 105 is a bonding wire (not shown in FIG. 10) that electrically connects the heating element 102 and the printed circuit board 104, and 106 is an ink supply member that supplies the ink from the ink tank (not shown) to the head main body 100. In such a thermal inkjet head, since the ink ejection performance depends on the temperature, it is necessary to control the temperature of the head body 100 within a certain range from the viewpoint of stabilizing the ink ejection performance. become. For example, the head body 10
When the temperature of 0 rises too much, the head unit 1 is forcedly cooled by a cooling fan or naturally cooled.
The temperature of 00 is lowered.

In such a technical background, the thermal ink jet head is usually provided with a temperature detecting device. In a conventional temperature detecting device of this type, in order to detect the temperature of the head main body 100 with high accuracy, for example, a cutout 107 is provided in a part of the printed board 104, and the head main body 100 is utilized by utilizing the area of the cutout 107. A temperature detecting element 108 such as a thermistor is attached to the heat radiating member 103 near the heat radiating member 103, or the temperature detecting element 108 is embedded in the heat radiating member 103. No. 155951).

[0004]

However, in such a conventional temperature detecting device, the heat radiating member 10 is provided as a post-process after the printed circuit board 104 is mounted on the heat radiating member 103.
3, the temperature detecting element 108 must be positioned and installed, and in order to take out the output of the temperature detecting element 108 to the outside, the temperature detecting element 108 and the printed board 104
There is a need to connect between and by bonding wire 109 or soldering with a lead wire. In this case, there arises a technical problem that the yield is deteriorated during mass production, and the cost is increased due to an increase in the number of production steps.

The present invention has been made in order to solve the above technical problems, and improves yield in mass production and reduces the number of production steps while maintaining good temperature detection performance. The present invention provides a temperature detecting device for a thermal ink jet head, which is intended to reduce costs.

[0006]

That is, the present invention is
As shown in FIG. 1, a head body 1 in which nozzles 2 for ejecting ink are arranged at a predetermined pixel pitch and a heating element 3 for generating thermal energy for ejecting ink is built in each nozzle 2.
A heat radiating member 4 attached to the head main body 1 to radiate extra heat of the head main body 1 to the outside; and a heat radiating member 4 disposed on the heat radiating member 4 to the heat generating elements 3 of the head main body 1 from the outside. In a thermal inkjet head including a printed circuit board 5 that supplies a drive signal according to an image signal, a temperature detection element 6 is provided on the printed circuit board 5 close to the head body 1, and the temperature detection element 6 and the heat dissipation member 4 are provided.
It is characterized in that the space between and is coupled by the thermal coupling means 7 having good thermal conductivity.

In such technical means, the temperature detecting device is used not only for controlling the temperature of the head main body 1 during printing within a predetermined range, but for example, when the ambient temperature is extremely high. When the temperature is low, the ink in the nozzle 2 may be solidified. In such a case, the temperature detected by the temperature detection device is used when the thermal inkjet head is initially operated. The head body 1 may be heated by a heater or the like until the temperature reaches a possible temperature, and the aggregated ink in the nozzles 2 may be removed by blank ejection, so that appropriate selection may be made.

As the temperature detecting element 6, a well-known one such as a thermistor or a thermocouple may be appropriately selected.
Further, as the heat coupling means 7, if the temperature detecting element 6 and the heat radiation member 4 can be coupled with each other with a heat transfer path having good thermal conductivity, a through hole is provided in the printed circuit board 5. The protrusion of the heat dissipation member may be disposed through the through hole so that the protrusion is brought into contact with the temperature detecting element 6, or the through hole is provided in the printed circuit board 5 so as to have a good thermal conductivity. Alternatively, the two may be combined with each other by interposing, or a through hole may be provided in the printed circuit board 5, a metal foil pattern may be formed on the peripheral wall of the through hole, and the two may be bonded via this metal foil pattern. It can be selected as appropriate. Particularly, in consideration of thermal conductivity, it is preferable to use the thermal coupling means 7 in which the metal foil pattern is formed on the peripheral wall of the through hole formed in the printed circuit board 5. In this type, the through-hole in which the metal foil pattern is formed is used. The aspect in which a plurality of holes are provided in parallel is preferable in that the heat transfer resistance between the temperature detection element 6 and the heat dissipation member 4 can be further reduced.

[0009]

According to the technical means as described above, the temperature detecting element 6 is arranged on the printed circuit board 4, so that the temperature detecting element 6 is directly mounted on the printed circuit board 5 by soldering or the like. The step of attaching the temperature detection element 6 as a post-step of mounting the printed circuit board 5 on the heat dissipation member 4 becomes unnecessary. Further, since the temperature detecting element 6 on the printed board 5 is thermally coupled to the heat radiating member 4 through the thermal coupling means 7, the heat from the head body 1 is detected through the heat radiating member 4 and the thermal coupling means 7. It is immediately transmitted to the element 6.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the accompanying drawings. 2 and 3 show an embodiment of a temperature detecting device for a thermal ink jet head to which the present invention is applied. In the figure, the basic structure of the thermal ink jet head is similar to the conventional one, in which the ink ejection nozzles 11 are arranged at a predetermined pixel pitch and the ink ejection heat energy is generated in each nozzle 11.
2, a head main body 10 having a built-in 2; a heat radiating member 13 that is adhesively fixed to the head main body 10 to radiate excess heat of the head main body 10 to the outside; Each heating element 102 is provided with a printed circuit board 14 made of, for example, an epoxy resin and having a thickness of 0.3 mm, which supplies a drive signal according to an image signal from the outside. Reference numeral 15 is a bonding wire (not shown in FIG. 2 and FIG. 4 described later) that electrically connects the heating element 12 and the printed circuit board 14, and 16 supplies ink from an ink tank (not shown) to the head body 10. Ink supply member, 17
Is a common ink chamber that communicates with each nozzle 11 of the head body 10.

In such a thermal ink jet head, the printed circuit board 14 close to the head body 10 is used.
A temperature detecting element 20 including a thermistor is mounted on the upper side by soldering. Then, this temperature detecting element 20
Are thermally coupled to the heat dissipation member 13 via the thermal coupling element 30. In this embodiment, on the printed circuit board 14,
As shown in FIG. 4, a ground electrode 41 and a voltage extracting electrode 42 that contact both terminals of the temperature detecting element 20 are provided, and the temperature detecting element 20 is arranged at a position 3 mm from the end of the head body 10. ing.

Further, the thermal coupling element 30 according to this embodiment
Is the printed circuit board 1 close to the ground electrode 41.
A total of eight through holes 31 each having a diameter of 0.5 mm are provided in two rows of four in four, and a part which is formed around the upper opening edge of each through hole 31 and is partially connected to the ground electrode 41. One copper foil pattern 32, a second copper foil pattern 33 formed on the peripheral wall of each through hole 31, and a third copper foil pattern 34 formed around the lower opening edge of each through hole 31. It is configured. In this embodiment, the through hole 31 is arranged at a position 2 mm from the end of the head body 10, and the first to third copper foil patterns 32 to 34 are one of ordinary fine processing techniques. It is formed by etching. Particularly, in this embodiment, the thermal coupling element 30 has eight through holes 31.
The copper foil patterns 32 to 34 are formed on the heat dissipation member 1 between the head body 10 and the thermal coupling element 30 of the printed circuit board 14 as shown in FIG.
If the thermal resistance of 3 is R1 and the thermal resistance corresponding to each through hole 31 is R2 (1) to R2 (8) = R2, the thermal resistance R between the head body 10 and the temperature detecting element 20 is ( 1 / R) =
(1 / R1) + {(1 / R2) × 8}, and the thermal resistance of the entire thermal coupling element 30 is suppressed to 1/8 of the thermal resistance of one through hole 31. A plurality of, for example, linear copper foil patterns 35 are provided on the back surface of the printed circuit board 14 so as to be separated from the third copper foil pattern 34, so that the printed board 14 can be stably installed on the heat dissipation member 13. Has been planned.

Next, the performance of the temperature detecting device for the thermal ink jet head according to this embodiment will be evaluated. As the evaluation method, the temperature detecting element 20 when the energy under the standard condition (15 W) is applied to the heating element 12 of the head body 10 is used.
The change in the measured temperature was measured, and the speed of its response was evaluated. The temperature detecting element 2 is provided on the printed circuit board 14.
The one in which 0 is simply installed (without the thermal coupling element 30) is taken as a comparative example, and the one in which the temperature detecting element 20 is installed on the heat dissipating member 13 is used as a reference example (the temperature change of the head body 10 is passed through the heat dissipating member 13 Example of detection).

FIG. 7 shows changes in the detected temperature in Examples, Comparative Examples and Reference Examples. In the figure, in Comparative Example 1 (indicated by a dotted line in the figure), the detection time is significantly delayed compared to the reference example (indicated by a dashed line in the figure), and a temperature difference occurs. Compared with the reference example, there is almost no detection time delay and there is almost no temperature difference. Looking at more specific numbers,
In Comparative Example 1, the rising delay with respect to the reference example is 10 to 20 seconds and the temperature difference is 3 to 5 degrees, whereas in the embodiment, the rising delay with respect to the reference example is 0 to 1 second. It was confirmed that the temperature difference was improved to about 0 degree. Further, in this embodiment, the thickness of the printed circuit board 14 is, from the viewpoint of enhancing thermal coupling,
It can be said that it is desirable to be thin, but in the embodiment, the thickness of the printed circuit board 14 is set to 0.3 mm. However, by providing the thermal coupling element 30 described above, the printed circuit board 14 is provided.
It was confirmed that the temperature detection performance of the temperature detection element 20 is sufficiently accurate even when the thickness is 1 mm or more.

The heat coupling element 30 is not limited to the one shown in the above embodiment, and for example, as shown in FIG. 8, a through hole 51 is provided in the printed circuit board 14 and a part of the heat dissipation member 13 is provided. A boss 52 is formed on the upper surface of the through hole 51 so as to project to the vicinity of the upper opening end.
2 and the temperature detecting element 20 are bonded to each other via an adhesive 53 having good thermal conductivity, or as shown in FIG. 9, a through hole 51 is provided in the printed board 14 and the through hole 51 is provided in the through hole 51. The temperature detecting element 20 and the heat dissipation member 13 are filled with a thermal coupling material 54 such as solder having good thermal conductivity.
It can be selected as appropriate, for example, by joining and.

[0016]

As described above, according to the invention of claim 1, the temperature detecting element can be directly mounted on the printed circuit board by soldering or the like.
Eliminating the process of mounting the temperature detection element as a post process after mounting the printed circuit board on the heat dissipation member, effectively avoiding the situation that the yield becomes worse during mass production and the cost increases due to the increase in the number of production processes. can do. Further, since the heat from the head body is promptly transferred to the temperature detecting element via the heat radiating member and the thermal coupling means, the heat is almost the same as that when the temperature detecting element is arranged on or inside the heat radiating member. Responsiveness can be obtained, and accordingly, temperature detection performance with good responsiveness can be exhibited.

In particular, when the metal foil pattern is formed on the peripheral wall of the through hole as the heat coupling means, the thermal conductivity between the temperature detecting element and the heat radiating member can be kept extremely good. Furthermore, by providing a plurality of through holes in which the metal foil pattern is formed in parallel, it is possible to further reduce the heat transfer resistance and to further improve the thermal conductivity between the temperature detection element and the heat dissipation member. You can keep good.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a temperature detecting device for a thermal inkjet head according to the present invention.

FIG. 2 is a perspective view showing a temperature detecting device for a thermal inkjet head according to an embodiment.

FIG. 3 is a cross-sectional explanatory diagram corresponding to the line III-III in FIG. 4 of the temperature detecting device for the thermal inkjet head according to the embodiment.

FIG. 4 is a plan view of FIG.

FIG. 5 is an explanatory diagram showing a back surface state of the printed circuit board according to the embodiment.

FIG. 6 is a schematic explanatory view showing the function of the thermal coupling element according to the example.

FIG. 7 is a graph showing changes in measured temperature of the temperature detecting element according to the example.

FIG. 8 is a cross-sectional explanatory view corresponding to FIG. 3 showing a modified example of the temperature detecting device according to the embodiment.

FIG. 9 is a cross-sectional explanatory view corresponding to FIG. 3 showing another modification of the temperature detecting device according to the embodiment.

FIG. 10 is a perspective view showing an example of a conventional temperature detecting device for a thermal inkjet head.

FIG. 11 is a cross-sectional explanatory view thereof.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Head main body, 2 ... Ink ejection nozzle, 3 ... Heating element, 4 ... Heat dissipation member, 5 ... Printed circuit board, 6 ... Temperature detection element, 7 ... Thermal coupling means

Claims (1)

[Claims] 1. A head body (1) in which ink ejection nozzles (2) are arranged at a predetermined pixel pitch and a heating element (3) for generating thermal energy for ink ejection is built in each nozzle (2). A heat radiating member (4) attached to the head main body (1) to radiate excess heat of the head main body (1) to the outside, and the head main body (1) provided on the heat radiating member (4). In the thermal ink jet head, the printed circuit board (5) for supplying a driving signal according to an image signal from the outside to each heating element (3) of (3), the printed circuit board (5) close to the head body (1). A temperature detecting element (6) is provided on the upper part, and the temperature detecting element (6) and the heat dissipation member (4) are coupled by a thermal coupling means (7) having good thermal conductivity. Inkjet head temperature detector.