JP3590191B2 - Thermal head - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a thermal head used in a thermal printer.
[0002]
[Prior art]
Thermal printers are classified into a thermal type and a thermal transfer type. The former thermal printer is a thermal printer in which thermal recording paper is heated by a thermal head to develop color on the thermal recording paper and thermally record dots. The latter thermal transfer types include a fusion type and a sublimation type. In these, the ink film is superimposed on the recording paper, the thermal head is pressed from behind the ink film and heated to transfer the ink of the ink film to the recording paper. Things.
[0003]
The thermal head used in the thermal printer as described above has a head portion in which a plurality of heating elements are arranged in a line, and the head portion is provided at one side of the other end while holding the head at one end. And a head holding plate which is supported by a support shaft and is swingable. Then, by the swinging of the head holding plate, the recording paper or the recording paper and the ink film are sandwiched between the head portion and the platen roller disposed facing the head portion, and the heating elements are transferred while transferring these line by line. Heat recording is performed by generating heat. In such a thermal head, in order to properly perform thermal recording on a recording sheet, the pressing force of the head portion against the recording sheet becomes important in addition to the management of the heat generation temperature of the heating element.
[0004]
[Problems to be solved by the invention]
In a conventional thermal head, a spring is interposed between a head portion and a head holding plate, the upper portion of the head holding plate is pressed by a cam-shaped pressing member, and the head portion is pressed by a spring by a spring via a recording paper. Pressed against However, since the heating elements of the head are arranged in a line in the main scanning direction, the pressing force may be different at both ends depending on the processing accuracy of each component. Conventionally, in order to balance the pressing force, the biasing force of the spring was changed or the pressing member was replaced.However, such an adjusting method is inefficient in work efficiency, and even if the both ends are balanced, the pressing distribution shape may be reduced. Sometimes changed. Further, there is a problem that the replacement of the pressing member is troublesome and that fine adjustment is difficult.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problem, and an object of the present invention is to provide a thermal head that can easily finely adjust a pressing balance in a width direction.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, the thermal head according to claim 1 uses a support member movably attached to a head holding plate , instead of at least one of the support portions, and uses the support member as a head. By adjusting the position of the head holding plate with respect to the support shaft by moving the head holding plate with respect to the holding plate, it is possible to adjust the pressing balance of the head portion to the platen roller in the width direction.
[0007]
The thermal head according to claim 2 wherein, one end is fixed to the head holding plate, and a mounting portion to which the other end is movable, and a bearing portion for bearing the support shaft is formed on the other end of the mounting portion And a supporting member. Further, in the thermal head according to the third aspect, the bearing portion for bearing the support shaft, one end portion fixed to the head holding plate, and the one end portion being elastically deformed to displace the position with respect to the head holding plate. And a mounting part having an end, and a supporting member is formed, and a bearing part is formed at the other end of the mounting part.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In FIG. 2, which shows the configuration of a thermal recording type thermal printer embodying the present invention, a thermal head 10 is provided with a heating element array 10a in which a large number of heating elements are arranged in a line. The thermal head 10 is swingable about a support shaft 11 and swings between a printing position on the platen roller 13 where the color thermosensitive recording paper 12 is pressed and a retracted position away from the platen roller 13. I do.
[0009]
As is well known, the color thermosensitive recording paper 12 is provided with a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer in this order on a support. The yellow thermosensitive coloring layer, which is the uppermost layer, has the highest thermal sensitivity and develops yellow with small heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity, and develops cyan with large heat energy. Further, the yellow thermosensitive coloring layer loses its coloring ability when irradiated with near-ultraviolet rays of 420 nm. The magenta thermosensitive coloring layer develops magenta color with a thermal energy intermediate between the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer, and loses its coloring ability when irradiated with 365 nm ultraviolet rays. For example, the color thermosensitive recording paper 12 may be provided with a black thermosensitive coloring layer to form a four-layer structure.
[0010]
A transport roller pair 15 is disposed downstream of the thermal head 10, and is rotated by a pulse motor 16 in forward and reverse directions. The transport roller pair 15 reciprocates by nipping the color thermosensitive recording paper 12.
[0011]
The platen roller 13 is rotatable, and rotates in the forward and reverse directions following the transfer of the color thermosensitive recording paper 12 by the transport roller pair 15. The platen roller 13 and the support shaft 11 of the thermal head 10 are supported by the same frame 24 (see FIG. 3).
[0012]
An optical fixing device 17 is arranged on the transport path of the color thermosensitive recording paper 12. The optical fixing device 17 includes an ultraviolet lamp 18 for yellow which emits near-ultraviolet light having an emission peak of 420 nm, an ultraviolet lamp 19 for magenta which emits ultraviolet light having an emission peak of 365 nm, and a reflector 20 which covers the back of these lamps. Have been. Reference numeral 22 denotes a position sensor that detects the leading end of the color thermosensitive recording paper 12.
[0013]
3 and 4 showing the configuration of the thermal head 10, the thermal head 10 has a head section 26 provided with a heating element array 10a, a head holding plate 27 for holding the head section 26, and an upper surface of the head section 26. And a heat radiating plate 28 attached to the radiating plate. FIG. 3 illustrates only one end of the thermal head 10 in the width direction, and the other end has a symmetrical shape and component configuration.
[0014]
The head section 26 has a form in which a silicon substrate on which the heating element array 10a is formed is mounted on the lower surface of a head mounting plate 30 formed of a material having a high thermal conductivity such as aluminum. The head mounting plate 30 transfers the heat of the heating element array 10a to the heat radiating plate 28 on which the plurality of fins 28a are formed, and cools the temperature so that the temperature does not rise more than necessary.
[0015]
The head holding plate 27 is formed of a substantially U-shaped thin plate, and holds the head 26 with two protruding arms 32 at one end of the head holding plate 27. In the vicinity of both side edges on the other end side of the head holding plate 27, the head holding plate 27 is mounted on the support shaft 11 and a support for adjusting the balance of the pressing force on the platen roller 13 in the width direction of the thermal head 10. A member 33 and a shaft pressing portion 34 for preventing the support member 33 and the support shaft 11 from coming off are attached.
[0016]
The support member 33 is formed by bending a thin metal plate having elasticity. The support member 33 is inserted into a mounting portion 36 mounted on the upper surface of the head holding plate 27 and a slit 37 formed in the head mounting plate 27 to hold the head. And a bearing 38 for receiving the support shaft 11 below the plate 27.
[0017]
A hole 36a through which the fixing screw 40 is inserted is formed at one end of the rectangular mounting portion 36. The fixing screw 40 inserted through the hole 36a is screwed into the screw hole 27a of the head holding plate 27. Thus, the support member 33 is attached to the upper surface of the head holding plate 27 with one end fixed. A screw hole 36b into which the adjusting screw 41 is screwed is formed on the other end side of the mounting portion 36. The tip of the adjusting screw 41 screwed into the screw hole 36b is inserted into a concave portion 27b formed on the upper surface of the head holding plate 27, and is used for positioning when the support member 33 is attached to the head holding plate 27. .
[0018]
The bearing portion 38 is provided below the other end of the mounting portion 36 where the screw hole 36b is provided, and has a cutout 38a that is open on the side of the head portion 26 side. The notch 38a holds the large-diameter portion 11a of the support shaft 11 from above and below. At this time, the distance between the head holding plate 27 and the support shaft 11 is L, and the head holding plate 27 and the support shaft 11 are in the state where they are farthest from each other.
[0019]
Then, when adjusting the pressing balance of the head portion 26 to the platen roller 13, the adjusting screw 41 is screwed into the screw hole 36b as shown in FIG. Then, the tip of the adjusting screw 41 presses the inside of the concave portion 27b, and the head holding member 27 moves downward accordingly. At this time, the mounting portion 36 of the support member 33 is elastically deformed to absorb the protrusion of the adjusting screw 41. Thereby, the support shaft 11 in the notch 38a of the bearing portion 38 and the head holding plate 27 approach each other, and the distance L1 is L> L1. Then, as the distance between the head holding plate 27 and the support shaft 11 becomes shorter, the pressing force of the platen roller 13 by the head unit 26 increases.
[0020]
Even when the adjusting screw 41 is fully tightened, the change in the pressing force at that time is so small that it falls within an allowable range. What is necessary is just to match with a direction.
[0021]
The shaft holding portion 34 includes a spring holding plate 43 formed by bending a thin metal plate, and a coil spring 44 held by the spring holding plate 43. A screw 45 is provided on the screw of the head holding plate 27 through a hole 43a. The spring holding plate 43 is attached to the upper surface of the head holding plate 27 by being screwed into the hole 27c. The coil spring 44 abuts the small-diameter portion 11b of the support shaft 11 from the side due to elasticity, and urges the support shaft 11 in a direction of pushing the support shaft 11 into the notch 38a.
[0022]
The head holding plate 27 is urged by a spring 46 around the support shaft 11 in the clockwise direction in the figure where the platen roller 13 is pressed by the head unit 26. When the color thermosensitive recording paper 12 is sandwiched between the heating element array 10a and the platen roller 13 or when the color thermosensitive recording paper 12 is moved backward, the support shaft is pressed against the bias of the spring 46 by a solenoid or the like. 11 is rotated counterclockwise in the figure and retracts from the platen roller 13. The coil spring 44 has a lower urging force than the spring 46 so as not to hinder the urging by the spring 46.
[0023]
Next, the operation of the above embodiment will be described. The balance adjustment of the pressing force on the platen roller 13 in the width direction of the thermal head 10 is performed after the thermal printer is assembled. The determination of the pressing force on the platen roller 13 by the thermal head 10 is performed by printing one color such as yellow over the entire surface of the color thermosensitive recording paper 12, Is measured. In this case, the higher the density, the stronger the pressing force on the platen roller by the thermal head, and the lower the density, the weaker the pressing force.
[0024]
For example, when one pressing force at one end in the width direction of the thermal head 10 is strong and the other pressing force is weak, the pressing force at the other end is made equal to the one pressing force. In order to increase the pressing force at the other end of the thermal head 10, as shown in FIG. 1, the adjusting screw screwed into the screw hole 36b of the support member 33 attached to the other end. Tighten 41. Then, since the tip of the adjusting screw 41 presses the inside of the concave portion 27b on the upper surface of the head holding plate 27, the head holding plate 27 moves downward. As a result, the distance between the head holding plate 27 and the support shaft 11 is reduced, and the pressing force on the other end is increased.
[0025]
After the adjustment of the pressing force by the support member 33, printing with one color is performed again, and the density is measured. As a result of this concentration measurement, if the pressing force is not yet balanced, the pressing force by the support member 33 is adjusted again. As described above, by performing the test printing several times and adjusting the support member 33 several times, the thermal head 10 in which the pressing forces at both ends are balanced can be obtained. Further, if the pressing force is measured using a pressure sensor, the pressing force balance can be adjusted without performing the test print.
[0026]
In the above embodiment, a thermal recording type thermal printer has been described as an example, but the present invention can also be applied to a thermal transfer type thermal printer. Further, the support members are provided on both sides of the head holding plate, but may be provided on only one of them.
[0027]
【The invention's effect】
As described above, according to the thermal printer of the present invention, at least one of the support portions supported by the support shaft and capable of swinging the head holding plate is a support member movable with respect to the head holding plate. By adjusting the position of the head holding plate with respect to the support shaft, the balance of the pressing force to the platen roller in the width direction of the head portion can be easily adjusted.
[0028]
In addition, a support member including a mounting portion having one end fixed to the head holding plate and the other end being movable, and a bearing portion formed on the other end side of the mounting portion and supporting the support shaft is used. Therefore, the configuration is simple and it can be adopted at low cost.
[Brief description of the drawings]
FIG. 1 is a side view of a thermal head at the time of pressing balance adjustment.
FIG. 2 is a schematic diagram showing a configuration of a thermal recording type color thermal printer.
FIG. 3 is an exploded perspective view illustrating a configuration of a thermal head.
FIG. 4 is a side view of the thermal head when the pressing balance is not adjusted.
[Explanation of symbols]
Reference Signs List 10 thermal head 11 support shaft 12 color thermal recording paper 13 platen roller 26 head unit 27 head holding plate 33 support member

Claims (3)

A head portion in which a plurality of heating elements are arranged in a line, and a support portion that holds the head portion on one end side and is provided on each of both side edges on the other end side is supported by a support shaft. In a thermal head including a print position for pressing the platen roller and a head holding plate that is swingable between a retracted position separated from the platen roller,
In place of at least one of the support portions, a support member movably attached to a head holding plate is used, and the support member is moved with respect to the head holding plate to position the head holding plate with respect to the support shaft. The thermal head is characterized in that the pressure balance on the platen roller in the width direction of the head portion is adjusted by adjusting the pressure. The support member, characterized in that it consists of one end fixed to the head holding plate, and a mounting portion to which the other end is movable, and is formed on the other end bearing portion for bearing the support shaft of the mounting portion The thermal head according to claim 1, wherein   The support member, a bearing portion for bearing the support shaft,
An end portion fixed to the head holding plate, and a mounting portion having another end portion that is elastically deformed with respect to the one end portion and displaces the position with respect to the head holding plate,
3. The thermal head according to claim 1, wherein a bearing portion is formed at the other end of the mounting portion.

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