JPH057187B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to thermal print heads.

[Conventional technology and issues to be solved]

As shown in FIG. 5, a conventional thermal print head of this type has a head substrate b mounted on an aluminum base substrate a that is rectangular in plan view.
In addition to attaching a board c for connection to an external circuit, a presser cover d for pressing the overlapping portion of the terminal portion, which will be described later, is superimposed on the base board a from above the board c for connection. . The head board b has a large number of heat generating dots e arranged in a row in the longitudinal direction on its surface, and a drive circuit f for the heat generating dots e, and has a comb-shaped terminal section on one side thereof over almost its entire length. g is molded. On the other hand, the connection board c includes a flexible circuit board i made of a resin film on which a comb-shaped terminal part h corresponding to the terminal part g of the head board b is formed on the back surface of one side, and a flexible circuit board i made of a resin film. It consists of a reinforcing plate j made of glass epoxy or the like that reinforces the substrate i from the back side. As shown in FIG. 6, the head substrate b and the connection substrate c are electrically connected by overlapping the terminal portions g and h. Further, the holding cover d is stacked on the base board a together with the connection board c by means of mounting screws l inserted through mounting holes m provided at predetermined intervals along its entire length. It is fixed;
A string-like pressing rubber k held on the back side presses both terminals g and h against each other. By the way, when the print head configured as described above is installed in a printer, the platen p
The printer is used to feed the recording paper backed up by the printer while pressing it against the heating dot e, and for the convenience of loading the recording paper and maintenance of the head itself, one of the print head and platen p is connected to the printer. The other side is usually attached to a member that can be rotated to open and close the chassis. Therefore, a positioning bracket o is attached to the print head side so that the side generatrix of the platen p accurately corresponds to the row of heating dots e when the opening/closing member is closed. The positioning bracket o extends from the base s applied to the back surface of the base board a of the print head to L.
It is made by bending a plate material so as to have a main body part r that stands up in the shape of a letter and is equipped with a guide groove q that can be engaged with the end of the support shaft of the platen p, and as shown in FIG. The base s is fixed to both ends of the back surface of the base substrate a with screws t, respectively. In the print head to which the positioning bracket o as described above is attached, mechanical strength is required to repeatedly engage the shaft of the platen, so the positioning bracket o must be separately formed from iron-based material. Aluminum base board a
The above positioning bracket o, which has a large number of parts and requires an accurate positional relationship of the engagement groove q with respect to the heat generating dot e, is attached to the base board a.
It was difficult to attach it to the back side of the camera with screws. In addition, in conventional thermal print heads, the presser cover d is superimposed and fixed with multiple screws l over almost the entire length of the base substrate a and the head substrate b, so that the head substrate a is placed before the presser cover d. In order to prevent the printing quality from changing due to temporary warping of the entire print head due to temperature rise, it is necessary to increase the thickness of the base substrate a and increase its section modulus as much as possible. This resulted in an increase in the overall thickness and weight of the print head. This invention was devised under the above circumstances, and it solves the two problems of the conventional art, namely, the increase in the number of parts and the increase in work cost due to the installation of the positioning bracket o, and An object of the present invention is to provide a thermal print head that can solve the problems of increasing size and weight due to the need to increase the section modulus of the base substrate a with a simple structure.

[Means to solve the problem]

In order to solve the above problems, the present invention takes the following technical measures. That is, the present invention includes a head substrate having heating dots arranged in a row and a driving circuit thereon on a base substrate, and a terminal portion formed on the back surface of one side of the head substrate. a circuit board for external connection that is connected to the terminal portions in an overlapping manner; In a thermal print head that prints by guiding recording paper between a platen that is brought into pressure contact with the head board at a predetermined pressure and is provided with a presser cover that protects the head board, the terminals of the head board are provided. By arranging the parts centrally in the longitudinal direction of the head board, the overlapping part of the external connection circuit board and the terminal part of the head board is pressed and fixed in the center part of the base board, and the presser cover is placed in the center of the base board. The positioning piece is fixed to the base substrate at the base plate, and positioning pieces are bent and integrally formed at both ends of the base plate, each having an engagement groove that is guided and engaged with the shaft of the platen or a member having a fixed relationship therewith. Features.

[Action and effect]

In the present invention, positioning pieces for the platen are integrally bent at both ends of the base substrate. Therefore, since the positioning bracket, which was conventionally separate, is integrated into the base board, costs can be reduced by reducing the number of parts. The problem of ensuring positional accuracy between the engagement groove of the positioning piece and the heat generating dot on the head board can be treated as a problem of positioning accuracy of the head board with respect to the base board. This problem can be solved simply by aligning the substrates using the same conventional method. Therefore, the troublesome task of screwing the bracket from the back side of the base board while recognizing the positional relationship between the heat generating dot on the head board and the guide engagement groove of the positioning bracket from the front side, as in the conventional case, is eliminated. be done. Next, in the present invention, the terminal portions to be provided on the head substrate are concentrated in the longitudinal direction thereof. Therefore, the terminal portions of the external connection circuit board to be overlapped thereon and the pressing portions to which these are to be superimposed and fixed may be only a small portion limited to the longitudinal center portion of the print head. This means that the part where the presser cover should be fixed to the base board can be limited to the central part in the longitudinal direction, and therefore, the conventional example in which the base board and the presser cover are fixed to each other over the entire length. The problem of warping due to temperature rise, which existed in the previous model, is resolved. This eliminates the need to increase the cross-sectional modulus of the base board so much, and for example, it becomes possible to form the base board from a thin iron-based plate material that can be processed into sheet metal, making the print head thinner and lighter. can. The configuration of the present invention has even more important meaning. In other words, the conventional thermal print head is
In order to ensure printing quality, the premise is that the bending rigidity must not be large, in other words, that it must not bend due to thermal stress or external force, but the present invention breaks this premise. It is. As described above, in the present invention, the base substrate and the presser cover are substantially connected to each other only at the central portion in the longitudinal direction, but this means that even if the base substrate is heated first, the thermal stress In addition to the first meaning that warping does not occur in the entire head, there is no negative effect on the operation as a thermal head, that is, heating the predetermined heating dots according to the printed information. It becomes possible to form the entire head so that it can be bent flexibly without causing any damage. That is, according to the thermal print head of the present invention, the direction of the longitudinal axis of the head with respect to the axis of the platen is defined by the positioning pieces integrally formed at both ends, and the entire head is fixed to the platen by, for example, a plurality of springs. By pressing toward the surface, the heat-generating dots are pressed against the platen surface with a uniform pressing force in all parts of the longitudinal direction of the array, without being affected by the mounting accuracy or surface roundness of the platen. This makes it possible to improve print quality and to avoid changes in print quality over time as much as possible.

[Explanation of Examples]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is an exploded perspective view of an embodiment of a thermal print head according to the present invention. As shown in this figure, a base substrate 1 of the thermal print head has heating dots 2 arranged in a row and a driving circuit 3 therefor, and a comb-shaped terminal portion 4 is formed on the surface of one side. The head board 5 is made of ceramic and has a comb-shaped terminal part 6 on the back surface of one side thereof corresponding to the comb-shaped terminal part 4 of the head board 5, and an outer surface lined with an auxiliary plate 7 made of glass epoxy. A connecting circuit board 8 is arranged such that both comb-shaped terminal portions 4 and 6 are overlapped with each other. A presser cover 11 is disposed along the side edge of the head board 5, presses and fixes the overlapping portion 9 of the terminal portions 4 and 6, and has a cover portion 10 extending upwardly from the drive circuit 3. is fixed to the base substrate 1. As will be described later, in the presser cover 11, since the comb-shaped terminal portions 4 and 6 are arranged centrally in the longitudinal direction of the head, the portion fixed to the base board is also shortened accordingly. Only the cover part 10 extends to both wings so as to protect all the drive circuits 3. By devising a circuit pattern built into the head board 5, the comb-like terminal portions 6 are concentrated in the center in the longitudinal direction, and correspondingly, the external connection circuit board 8 itself The longitudinal length of the head is also shortened. As clearly shown in Figure 1, the base substrate 1
For example, a press-formed plate-shaped member made of iron is employed, and positioning pieces 12 are bent and integrally formed at both ends thereof. Positioning piece 12
An engagement groove 14 is formed that can be guided and engaged with the shaft end of the platen 13 or a member having a fixed positional relationship with the shaft of the platen. As explained in the "Prior Art and Problems to be Solved" section, in printers, one of the thermal print head and platen is attached to the chassis of the printer, and the other is attached to a member that can be rotated to open and close with respect to the chassis. However, the positioning piece 12 is for regulating the positional relationship between the thermal print head and the platen to always be constant when the rotating member is closed. Usually, the above-mentioned positional relationship is determined so that the side generatrix of the platen is precisely aligned with the row of heating dots 2 of the print head. The head board 5 is attached to the base board 1 by adhesion or the like, and the head board 5 is fixed in advance to the base board 1 and the external connection circuit board 8.
The presser cover 11 is coupled to the presser cover 11 by screwing into the screw hole 17 of the base board 1 a fixing screw 16 that is inserted into a screw hole 15 formed in a predetermined portion of the presser cover 11 and the external connection circuit board 8. It will be done. At this time, the string-like elastic body 19 held in the holding groove 18 formed on the back surface of the presser cover 11 presses the overlapping part 9 of the terminal part 4 of the head board 5 and the terminal part 6 of the external connection circuit board 8 from above. They are pressed elastically to ensure electrical continuity. In FIG. 1, the reference numeral 20 indicates a positioning hole provided in the base board 1, the external connection circuit board 8, and the holding cover 11 for mutual positioning using a dowel pin (not shown). In the above configuration, the base substrate 1 has a positioning piece 12 for positioning it with respect to the platen.
Since the head board is bent and formed in one piece, there is no need to screw a separately formed positioning bracket to the back surface of the base board 1 as in the past. 5, the positional accuracy between the heat generating dot array 2 and the engagement groove 14 of the positioning piece 12, which is a problem in the positional relationship with respect to the platen, is automatically ensured. Such positioning of the head board 5 with respect to the base board 1 can be easily performed from the front side of the print head using, for example, a recognition mark provided on the circuit pattern of the head board 5. Then, the comb-teeth terminal portions 4 provided on the head board 5 are arranged centrally in the longitudinal center of the head board 5, and the corresponding external connection circuit board 8 is also shortened. Since the portion that presses both terminal portions 4 and 6 of the head board 5 and the external connection circuit board 8 is limited to the center in the longitudinal direction of the head, even if the base board
Even if the temperature is raised first, it is possible to avoid warping of the entire print head due to thermal stress. Therefore, it is no longer necessary to increase the section modulus of the base substrate 1 as in the conventional case, and it is also possible to construct the base substrate 1 from an iron-based plate material as in the embodiment. In this way, the weight of the base substrate 1, which accounts for a large portion of the weight of the print head, can be significantly reduced and the overall weight can be reduced, and at the same time, the size of the print head can be reduced in the thickness direction. In addition, by constructing the base substrate 1 from an iron-based plate material suitable for press forming,
It becomes easier to form the positioning piece 12 which should be integrally bent. Then, as described above, the overlapping part 9 of both the terminal parts 4 and 6 of the head board 5 and the external connection circuit board 8 is arranged limited to the central part in the longitudinal direction of the head, and the overlapping part 9 is closed by the presser cover 11. Limiting the pressing portion to the central portion in the longitudinal direction also means that even if the entire head is flexible and can be bent with a relatively small force, it will not have any adverse effect on the electrical characteristics of the head substrate. That is, if the base substrate 1 is made of an iron-based plate material as in the embodiment, its section modulus will be significantly smaller than that of the conventional one, and it will be able to be elastically bent relatively easily by external force. This allows the printer to be configured as follows. That is, as shown in FIG. 4, the entire length of the print head is biased toward the platen 13 by using a plurality of springs 21 or the like. In this case, since the entire print head can be bent, the heating dots 2 can be pressed against the surface of the block 13 with a uniform force in all parts in the longitudinal direction of the arrangement, without being affected by the mounting accuracy of the platen 13 or the roundness of the surface. Furthermore, since there is no deformation due to thermal stress, printing quality is fundamentally improved and changes over time can be avoided.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of the thermal print head of the present invention, FIG. 2 is an assembled sectional view corresponding to the - line cross section in FIG. 1, and FIG. 3 is an assembled sectional view corresponding to the - line cross section in FIG. 1. , FIG. 4 is a cross-sectional view showing an example of a state in which it is installed in a printer head, and FIG.
The figure is an exploded perspective view of a conventional example, and FIG. 6 is an assembled sectional view corresponding to the - line cross section in FIG. 1...Base board, 2...Heating dot, 3...
Drive circuit, 4... terminal section (of head board), 5...
...Head board, 6...Terminal section (of flexible circuit board), 8...External connection circuit board, 9...
Overlapping portion, 11... Presser cover, 12... Positioning piece, 13... Platen.

Claims (1)

[Scope of Claims] 1. A head substrate having heat generating dots arranged in a row and a driving circuit thereof on a base substrate, and a terminal portion formed on the back surface of one side of the head substrate, formed on the surface of one side of the head substrate. A circuit board for external connection is formed along the side edge of the head board, and is connected to the terminal part by pressing the overlapping part of both the terminal parts, and a circuit board for external connection is connected to the terminal part by overlapping the terminal part. Equipped with a presser foot cover that extends to protect it.
In a thermal print head that performs printing by guiding recording paper between a platen that is pressed into contact with the head board at a predetermined pressure, the terminal portions of the head board are centrally arranged in the longitudinal center of the head board. By this, while pressing and fixing the overlapping part of the external connection circuit board and the terminal part of the head board at the center of the base board, the presser cover is fixed to the base board at its center, while the base A thermal print head characterized in that positioning pieces having engagement grooves that are guided and engaged with the shaft of a platen or a member having a fixed relationship therewith are integrally formed by bending at both ends of a substrate.