JPH0717072B2 - Thermal print head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head which is capable of accurately defining a positional relationship with a platen and of which a contact state with the platen can be made constant along the longitudinal direction. Regarding

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional thermal print head of this type has a base board a made of aluminum and having a rectangular shape in plan view.
A head cover b and a connecting board c for connecting to an external circuit are attached to the top of the base board a from above the connecting board c, and a pressing cover d for pressing an overlapping portion of a terminal portion described later is provided. It has a structure that is superimposed on.

The head substrate b has a large number of heating dots e arranged in a line in the longitudinal direction on its surface and its driving circuit f, and one side thereof has a comb-teeth shape over almost the entire length. The terminal part g is formed. On the other hand, the connection board c has a flexible circuit board i made of a resin film and a comb-shaped terminal portion h corresponding to the terminal portion g of the head substrate b formed on the back surface of one side, and the flexible circuit board. It is composed of a reinforcing plate j made of glass epoxy or the like that reinforces the substrate i from the back surface. Then, as shown in FIG.
The head substrate b and the connecting substrate c are electrically connected by polymerizing the both terminal portions g and h.

Further, the pressing cover d is fixed by stacking it on the base board a together with the connecting board c by a mounting screw l inserted through the mounting holes m provided at a predetermined interval over the entire length thereof. The cord-shaped pressing rubber k held on the back surface presses the terminal portions g and h against each other.

By the way, in the conventional thermal print head as described above, since the pressing cover d is superposed and fixed by the plurality of screws l over substantially the entire length of the base substrate a and the head substrate b, the head substrate a is pressed. In order to prevent the print head from being warped temporarily and changing the print quality due to the temperature rise before the cover d, the thickness of the base substrate a is increased to reduce its section modulus. It has to be as large as possible, which has led to increased overall thickness and weight of the printhead.

Further, the print head having the above-mentioned structure is used to feed the recording paper backed up by the platen p while pressing it against the heat-generating dots e when it is incorporated in the printer, and Loading,
Also, for convenience of maintenance of the head itself, it is usual to attach one of the print head and the platen p to the chassis of the printer, and the other to a member capable of rotating and opening and closing with respect to the chassis. Therefore, when the opening / closing member is closed, the positioning bracket o is attached to the print head side so that the side edge busbars of the platen p accurately correspond to the heating dots e arranged in rows.

The positioning bracket o is provided with a guide groove q which stands up in an L shape from a base portion s which is applied to the back surface of the base substrate a of the print head and which can be engaged with the spindle end portion of the platen p. It is formed by bending a plate material so as to have a main body portion r, and as shown in FIG.
Are fixed to both ends of the back surface of the device with screws t.

By the way, as described above, the base substrate a to which the positioning bracket o is fixed is usually made of an aluminum plate or the like having a high section modulus in order to prevent the warp of the entire print head. On the other hand, since the positioning bracket o is required to have mechanical strength in order to repeatedly engage with the shaft of the platen, it cannot be formed of an iron-based material. Also, it is necessary to manufacture the positioning bracket o as a separate member from the above, and the positioning bracket o, which requires an accurate positional relationship of the engagement groove q with respect to the heating dot e, must be attached to the back surface of the base substrate a with a screw, which is a work difficulty. there were.

The present invention was devised under the above circumstances, and there are two problems in the above-mentioned conventional thermal print head, that is, an increase in size due to the need to increase the section modulus of the base substrate a. , The problem of weighting,
Also, a new thermal print capable of solving the problems of an increase in the number of parts and an increase in work cost due to the need to attach the positioning bracket o formed separately from the base board a to the base board at once by a simple configuration. The challenge is to provide a head.

[0010]

In order to solve the above problems, the present invention takes the following technical means. That is, the present invention comprises a base substrate and a head substrate which is superposed and supported on the base substrate and arranged in rows in a row, and a head substrate provided with a driving circuit for the heating dots. In a thermal print head that performs printing by guiding and passing a recording paper between the platen and the platen, the base substrate is formed of an iron-based thin sheet metal member, which allows mutual pressing force with the platen. Is provided with flexibility that allows the platen to adhere to the platen evenly over the entire length in the longitudinal direction, and is guided and engaged with both ends of the base substrate by the shaft of the platen or a member having a fixed relationship with the shaft. It is characterized in that a positioning piece having an engaging groove is formed integrally with a bend.

[0011]

First, according to the present invention, the thermal print head itself is positively provided with flexibility by forming the base substrate with an iron-based thin sheet metal member. Therefore, when the entire head is pressed against the surface of the platen by, for example, a plurality of springs, the heating dots are averaged in all the portions in the longitudinal direction of the array without being affected by the mounting accuracy of the platen and the roundness of the surface. It can be brought into contact with the surface of the platen with a sufficient pressing force. In other words, when pressed toward the surface of the platen, in the thermal print head of the present invention, by deforming along the surface of the platen, the entire length in the longitudinal direction is increased by the average pressing force. Can be brought into contact with.

It should be noted that due to the difference in the coefficient of thermal expansion between the head substrate and the base substrate, there is a tendency that the entire head tends to warp and deform due to the bimetal effect associated with the temperature rise. Since the entire structure is provided with flexibility, if the thermal print head of the present invention is configured to be pressed against the surface of the platen in its entire longitudinal direction by a plurality of springs, it is possible to prevent warpage due to the bimetal effect as described above. Instead, it becomes possible to press the heating dot row on the surface of the platen with an average pressing force at various points in the longitudinal direction.

Moreover, in the present invention, the positioning pieces for the platen are provided by integrally bending the base plate made of the iron-based thin plate metal member at both ends. Therefore, since the positioning bracket, which is a separate body from the related art, is integrated with the base substrate, the cost can be reduced by reducing the number of parts. Then, the problem of ensuring the positional accuracy between the engagement groove of the positioning piece and the heating dot on the head substrate can be treated as a problem of the positioning accuracy of the head substrate with respect to the base substrate, and the head with respect to the base substrate can be treated. The problem is solved simply by aligning the substrate in the same manner as in the past. Therefore, unlike the conventional case, the troublesome work of screwing the bracket from the back surface of the base substrate while recognizing the positional relationship between the heating dots on the head substrate and the guide engagement groove of the positioning bracket from the front surface side is eliminated. .

As described above, according to the thermal print head of the present invention, the heat generation dots on the head substrate are averaged over the entire length in the longitudinal direction while accurately defining the positional relationship with respect to the platen with a simple structure. It becomes possible to press against the surface of the platen, the print quality can be improved, and the base substrate can be made thin, so that the thermal print head itself can be made smaller and lighter.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be specifically described 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 the figure, on the base substrate 1 of the thermal print head, the heating dots 2 arranged in rows and the driving circuit 3 for the heating dots 2 are provided, and the comb-teeth-shaped terminal portion 4 is formed on one side surface. A ceramic head substrate 5,
An external connection circuit board 8 having a comb-teeth-shaped terminal portion 6 corresponding to the comb-teeth-shaped terminal portion 4 of the head substrate 5 on the back surface of one side and lined with a reinforcing substrate 7 made of glass epoxy, The comb-teeth-shaped terminal portions 4 and 6 are arranged so as to overlap each other. Further, the pressing cover 11 is arranged along the side edge of the head substrate 5, presses and fixes the overlapping portion 9 of both the terminal portions 4 and 6, and has the cover portion 10 extending above the drive circuit 3. Is the base substrate 1
Is fixed against.

In the pressing cover 11 in the present embodiment, the comb-teeth-shaped terminal portions 4 and 6 are centrally arranged in the central portion in the longitudinal direction of the head as will be described later, so that the fixing portion to the base substrate is also adjusted accordingly. It has been shortened and only the cover 10 extends laterally so as to protect all drive circuits 8.

In the head substrate 5 of this embodiment, the comb-teeth-shaped terminal portions 6 are arranged centrally in the longitudinal direction by devising a circuit pattern to be formed therein.
Correspondingly, the length of the external connection circuit board 8 itself in the longitudinal direction of the head is also shortened.

In the present invention, as well shown in FIG. 1, the base substrate 1 is formed by press-molding an iron-based thin sheet metal member, and positioning pieces are provided at both ends thereof. 12 is integrally formed by bending. The positioning piece 12 is formed with an engaging groove 14 that can be guided and engaged with a shaft end portion of the platen 13 or a member having a fixed positional relationship with the shaft of the platen. As described in the section of "Prior Art and Problems to be Solved by the Invention", in a printer, a member that can mount one of a thermal print head and a platen on the chassis of the printer and rotate the other on the chassis with respect to the chassis. The positioning piece 12 is for always controlling the positional relationship between the thermal print head and the platen to be constant when the rotating member is closed. Normally, the above positional relationship is determined so that the side surface busbars of the platen accurately follow the heating dot rows 2 of the print head.

The head substrate 5 is attached to the base substrate 1 by adhesion or the like, and the base substrate 1 to which the head substrate 5 is fixed in advance, the external connection substrate 8 and the pressing cover 11 are connected to each other with the pressing cover 11. This is performed by screwing a fixing screw 16 inserted into a screw hole 15 formed at a predetermined position of the external connection substrate 8 into a screw hole 17 of the base substrate 1.

At this time, the string-like elastic body 19 held in the holding groove 18 formed on the back surface of the pressing cover 11 causes the terminal portion 4 of the head substrate 5 and the terminal portion 6 of the external connection circuit substrate 8 to overlap with each other. 9 is elastically pressed from above to ensure their electrical continuity. In FIG. 1, reference numeral 20 indicates a positioning hole provided in each of the base board 1, the external connection circuit board 8 and the pressing cover 11 for mutual positioning with a knock pin (not shown).

By the way, in the present invention, as described above, by using the base substrate 1 formed of an iron-based thin sheet metal member, the entire head is flexibly provided with flexibility. Therefore, as shown in FIG. 4, when the entire area in the longitudinal direction of the print head is biased toward the platen 13 by using a plurality of springs 21 or the like, the mounting accuracy of the platen 13 and the surface roundness are affected. The heat generating dots 2 are applied to the platen 1 with an average force in all parts in the longitudinal direction of the array without receiving the heat.
It can be pressed against the surface of 3.

Further, since the base board 1 is integrally formed with the positioning piece 12 for positioning with respect to the platen, a positioning bracket separately formed as in the conventional case is screwed to the back surface of the base board 1. However, it is not necessary to fix the head substrate 5 while performing a predetermined positioning with respect to the base substrate 1, and the heating dot row 2 which becomes a problem in the positional relationship with respect to the platen.
The positional accuracy between the positioning groove 12 and the engaging groove 14 of the positioning piece 12 is automatically ensured. Such positioning of the head substrate 5 with respect to the base substrate 1 can be easily performed from both sides of the print head by using a recognition table provided in a circuit pattern of the head substrate 5, for example.

In this embodiment, in particular, the comb-teeth-shaped terminal portions 4 provided on the head substrate 5 are centrally arranged in the central portion of the head substrate 5 in the longitudinal direction, and the corresponding external connection circuit substrate 8 is provided. Shorten and hold down cover 11
Thus, the portions of the head substrate 5 and the circuit board 8 for external connection that press the terminals 4, 6 are limited to the center of the head in the longitudinal direction. Therefore, even if the temperature of the base substrate 1 is increased in the early stage of the operation, it is possible to effectively prevent the entire print head from being warped due to thermal stress.

As described above, according to the present invention, since the base substrate is formed by using the iron-based thin plate metal member, and thereby the entire head is flexibly provided, the platen is applied to the platen. As a result, it is possible to bring the respective parts in the longitudinal direction into contact with each other with a uniform pressing force, so that the printing quality is improved and the positioning with respect to the platen can be easily performed while reducing the cost.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an embodiment of a thermal print head of the present invention.

FIG. 2 is an assembled sectional view corresponding to a section taken along the line II-II in FIG.

FIG. 3 is an assembled sectional view corresponding to a section taken along the line III-III in FIG.

FIG. 4 is a cross-sectional view showing an example of a state of being incorporated in a printer.

FIG. 5 is an exploded perspective view of a conventional example.

6 is an assembled sectional view corresponding to a section taken along line VI-VI in FIG.

[Explanation of symbols]

 1 base substrate 2 heating dot 3 driving circuit 12 positioning piece 13 platen

Claims (1)

[Claims] 1. A base substrate and a head substrate which is superposed and supported on the base substrate and arranged in a row in a row, and a head substrate provided with a driving circuit for the heating dots, the head substrate being pressed against the head substrate. In the thermal print head for printing by guiding the recording paper between the platen and the platen, the base substrate is formed of an iron-based thin sheet metal member, whereby a mutual pressing force is applied between the platen and the platen. When provided, it has flexibility so that it can be adhered to the platen evenly over the entire length in the longitudinal direction, and is engaged at both ends of the base substrate with a shaft of the platen or a member having a fixed relationship with the shaft. A thermal print head characterized in that a positioning piece having a mating groove is integrally formed by bending.