JP2012000818A - Image forming apparatus, head position adjusting mechanism, and head position adjusting member - Google Patents

Abstract

A head position adjustment range can be expanded and positioning can be performed with a small number of parts.
A cam main body for adjusting a relative pressure contact position between each heating element and the platen roller when the thermal head is pressed against the platen roller via the recording paper, and the cam main body. A cam bearing 115 that is attached to rotate the cam body 111 and a rotation support shaft that rotatably supports the cam bearing 115 are provided. The cam bearing 115 is provided so that the rotation center position of the cam body 111 can be changed. It has been.
[Selection] Figure 7

Description

  The present invention relates to an image forming apparatus, a head position adjusting mechanism, and a head position adjusting member that can adjust a relative pressure contact position between a heating element of a thermal head and a platen roller.

  Conventionally, as an image forming apparatus, a line-type thermal head in which a plurality of heating elements are arranged in a direction orthogonal to the conveyance direction of a recording medium, and a platen roller disposed so as to face each heating element of the thermal head, There is known a thermal printer comprising: This thermal printer includes an elevating device that elevates and lowers the thermal head relative to the platen roller. The elevating device presses the thermal head against the platen roller via the recording medium. An image is formed on the recording medium by conveying the recording medium while generating heat from each heating element of the thermal head.

  Here, if the pressure contact position between each heating element of the thermal head and the platen roller is not appropriate, the quality of the formed image will be adversely affected. For this reason, a technique is disclosed in which the pressure contact position can be adjusted. Specifically, the thermal head is fixed to the head mounting base, and a head position adjusting groove is formed on the head mounting base. Then, the head mounting base and the thermal head are moved together by pushing and moving the side surface of the head position adjusting groove by the head position adjusting cam (eccentric member), and the pressure contact position of each heating element with respect to the platen roller is adjusted. is doing.

JP-A-11-254715

  In the technique of the above-mentioned Patent Document 1, two cams each having a columnar adjustment portion protruding from the upper surface of the disc-shaped eccentric rotation portion and shifted from the rotation center axis are used. The moving position of the thermal head is adjusted by selectively rotating one or both of the two cams. For example, when one of the two cams is rotated and each heating element is in a positional relationship where it does not press against the platen roller, adjustment is performed by rotating the other cam.

However, when a plurality of cams are used, the parts inventory increases, causing problems in parts management and economy. There is also a problem that productivity deteriorates.
On the other hand, with only one cam, as described above, each heating element may not be in pressure contact with the platen roller, resulting in poor adjustment performance. Furthermore, in the cam disclosed in the above-mentioned Patent Document 1, the adjustment range of the moving position of the thermal head is determined by the amount of deviation of the adjustment unit from the rotation center axis of the eccentric rotation unit.

  Therefore, the problem to be solved by the present invention is to make it possible to expand the adjustment range of the head position and to perform alignment with a small number of parts.

The present invention solves the above-described problems by the following means.
According to the first aspect of the present invention, a line-type thermal head in which a plurality of heating elements are arranged in a direction orthogonal to the conveyance direction of the recording medium, and the heating elements of the thermal head are arranged so as to face each other. A platen roller, an elevating device for elevating the thermal head relative to the platen roller, and when the thermal head is pressed against the platen roller via the recording medium by the elevating device, A cam main body for adjusting a relative pressure contact position between each of the heating elements and the platen roller, a cam bearing attached to the cam main body for rotating the cam main body, and the cam bearing rotating An image forming apparatus provided so as to be capable of changing a rotation center position of the cam body. It is.

  According to a fifth aspect of the present invention, there is provided a print head for forming an image, a cam main body for adjusting the position of the print head, and a cam bearing attached to the cam main body for rotating the cam main body. And a rotation support shaft that rotatably supports the cam bearing, and the cam bearing is an image forming apparatus provided so as to change a rotation center position of the cam body.

  The invention according to claim 6 is a cam main body for adjusting a relative pressure contact position between the thermal head and the platen roller when the thermal head is pressed against the platen roller via the recording medium. And a cam bearing that is attached to the cam body and rotates the cam body, and a rotation support shaft that rotatably supports the cam bearing, wherein the cam bearing has a rotation center position of the cam body. It is a head position adjustment mechanism provided so that it can be changed.

  The invention according to claim 7 includes a cam main body for adjusting the position of the print head for forming an image, and a cam bearing attached to the cam main body for rotating the cam main body, The cam bearing is a head position adjustment member provided so that the rotation center position of the cam body can be changed.

(Function)
The invention according to claim 1, claim 5, claim 6 and claim 7 comprises a cam body and a cam bearing attached to the cam body for rotating the cam body. The cam bearing is provided so that the rotation center position of the cam body can be changed. Therefore, only by preparing one type of cam body and one type of cam bearing, the rotation center position of the cam body can be appropriately changed when the cam bearing is attached to the cam body.

  According to the present invention, if one kind of cam body and one kind of cam bearing are prepared, the rotation center position of the cam body can be changed by itself. As a result, a wide alignment is possible with a small number of parts.

1 is a side view showing a basic configuration of a thermal printer as an embodiment of an image forming apparatus of the present invention. It is a perspective view which shows the peripheral part of the thermal head in the thermal printer shown in FIG. It is a side view which shows the thermal head position adjustment mechanism as one Embodiment of the head position adjustment mechanism of this invention. It is a perspective view which shows the thermal head position adjustment member (1st Embodiment) as one Embodiment of the head position adjustment member of this invention. It is a perspective view which shows the cam main body in the thermal head position adjustment member shown in FIG. It is a perspective view which shows the cam bearing in the thermal head position adjustment member shown in FIG. It is a perspective view which shows the attachment method of the cam main body and cam bearing in the thermal head position adjustment member shown in FIG. FIG. 5 is an explanatory diagram showing a mounting relationship between a cam body and a cam bearing in the thermal head position adjusting member shown in FIG. 4. FIG. 5 is a perspective view showing an example of a mounting state of a cam body and a cam bearing in the thermal head position adjusting member shown in FIG. 4. It is explanatory drawing which shows the position adjustment state of the thermal head by the thermal head position adjustment member of the attachment state shown in FIG. FIG. 6 is a perspective view showing another example of a mounting state of the cam body and the cam bearing in the thermal head position adjusting member shown in FIG. 4. It is explanatory drawing which shows the position adjustment state of the thermal head by the thermal head position adjustment member of the attachment state shown in FIG. It is a perspective view which shows the thermal head position adjustment member (2nd Embodiment) as one Embodiment of the head position adjustment member of this invention. It is a perspective view which shows the cam main body in the thermal head position adjustment member shown in FIG. It is explanatory drawing which shows the attachment method of the cam main body and cam bearing in the thermal head position adjustment member shown in FIG. 13, and has shown the state which attached the cam main body and the cam bearing. It is explanatory drawing which shows the attachment method of the cam main body and cam bearing in the thermal head position adjustment member shown in FIG. 13, and has shown the state which changes the attachment relationship of a cam main body and a cam bearing.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
Here, the image forming apparatus according to the present invention is assumed to be a thermal printer 1 in the following embodiments. The head position adjusting mechanism in the present invention is assumed to be the thermal head position adjusting mechanism 100 of the thermal printer 1 in the following embodiments. Furthermore, the head position adjusting members in the present invention are assumed to be the thermal head position adjusting members 110 and 120 of the thermal head position adjusting mechanism 100 in the following embodiments.
The description will be given in the following order:

1. First embodiment (head position adjusting member: an example of a cam body and a cam bearing)
2. Second Embodiment (Head Position Adjustment Member: Another Example of Cam Body and Cam Bearing)

[Configuration example of image forming apparatus]

FIG. 1 is a side view showing a basic configuration of a thermal printer 1 as an embodiment of an image forming apparatus of the present invention.
As shown in FIG. 1, the thermal printer 1 includes a plurality of heating elements (not shown) in a direction orthogonal to the conveyance direction (right direction in FIG. 1) of the recording paper 41 (corresponding to the recording medium of the present invention). A line-type thermal head 10 is arranged. A platen roller 11 is disposed so as to face each heating element of the thermal head 10.

  Here, the recording paper 41 is wound in a roll shape, and is held by a paper holder 42 as shown in FIG. The paper holder 42 is set at a predetermined location in the thermal printer 1, and the recording paper 41 is pulled out from the paper holder 42 as needed by the pair of paper feed rollers 14.

Further, the drawn recording paper 41 is conveyed by a capstan roller 12 (driving roller) and a pinch roller 13 (driven roller). Specifically, the recording paper 41 is sandwiched between the capstan roller 12 and the pinch roller 13 and is guided toward the thermal head 10 by the rotational drive of the capstan roller 12. At this time, since the recording paper 41 is guided by the conveyance guide 15, the leading end portion of the recording paper 41 does not collide with the platen roller 11 and buckle, so that the recording paper 41 is reliably placed between the thermal head 10 and the platen roller 11. It is conveyed to.
Note that the platen roller 11 is not limited to a platen having a roller shape, and a platen having another shape such as a plate shape may be used.

  Furthermore, an ink ribbon 31 is also interposed between the thermal head 10 and the platen roller 11. The ink ribbon 31 is coated with a color ink color-coded for each color of yellow (Y), magenta (M), and cyan (C), and a transparent laminate ink (L). (Not shown). Then, after being unwound from the supply reel 32 of the ribbon cassette according to the color conversion processed gradation data and guided by the two guide rollers 19 so as to pass above the platen roller 11 and the recording paper 41, the ribbon cassette The take-up reel 33 is wound up.

  In order to form an image with such a thermal printer 1, the thermal head 10 that has been lifted away from the platen roller 11 is lowered and pressed against the platen roller 11. Specifically, the thermal head 10 is lowered by the head lifting device 20 from a standby position where the thermal head 10 is separated from the platen roller 11 to the printing position on the platen roller 11. Further, the platen roller 11 supports the ink ribbon 31, the recording paper 41, and the lowered thermal head 10. Therefore, the thermal head 10 presses the platen roller 11 through the ink ribbon 31 and the recording paper 41.

  In this state, the capstan roller 12 is driven to rotate clockwise, and the ink ribbon 31 is taken up by the take-up reel 33. Accordingly, the recording paper 41 and the ink ribbon 31 sandwiched between the thermal head 10 and the platen roller 11 are conveyed from the printing start point to the printing end point. If gradation data is input to the thermal head 10 during this time, a heating element (for example, a heating resistor) is selectively energized to generate heat energy. As a result, the yellow (Y) ink (first ink) on the ink ribbon 31 is sublimated and transferred onto the recording paper 41.

  Here, the ink ribbon 31 is strongly attached to the recording paper 41 by the pressure contact force of the thermal head 10 and the heat of the heating element after the ink transfer is completed. Therefore, a blade-like ribbon peeling member 16 is provided downstream of the thermal head 10 and the platen roller 11 in the conveyance direction of the recording paper 41. The leading end of the ribbon peeling member 16 is brought into contact with the back side of the ink ribbon 31 superimposed on the recording paper 41 between the thermal head 10 and the platen roller 11. As a result, the ink ribbon 31 is pulled away at a predetermined angle with respect to the conveyance direction of the recording paper 41, and the ink ribbon 31 is peeled off from the recording paper 41.

  After transferring yellow (Y) in this way, preparations are made for transferring the next magenta (M). Specifically, in the case of color printing, yellow (Y), magenta (M), and cyan (C) inks are transferred for each color. Therefore, whenever the transfer of one color is completed, the thermal head 10 that has been lowered by the head lifting device 20 is raised and returned to the original standby position away from the printing position, and the pressure contact of the recording paper 41 by the thermal head 10 is released. . Then, the capstan roller 12 is driven to rotate counterclockwise and the recording paper 41 is returned to the printing start point.

  Next, the second magenta (M) is transferred in the same manner as the yellow (Y) transfer. Specifically, the thermal head 10 is lowered (moved to the printing position) by the head lifting device 20, and the ink ribbon 31 and the recording paper 41 are sandwiched between the platen roller 11. Then, magenta (M) of the ink ribbon 31 is transferred while conveying the recording paper 41 to the end point of printing. Further, after the magenta (M) is transferred, the third cyan (C) is transferred in the same manner. Furthermore, in order to protect the image formed by each color ink (Y, M, C) from ultraviolet rays and improve light resistance, finally, the laminate ink (L) is transferred in the same manner.

  The recording paper 41 after printing on which the last laminate ink (L) has been transferred and a color image is formed is the direction of curling (rolling inward direction) applied to the recording paper 41 by the decurling roller 17. And bent in the opposite direction (upward in FIG. 1) to correct the curl. Thereafter, the recording paper 41 is cut into a predetermined length by the cutter 18 and discharged from a paper discharge port (not shown).

  As described above, the thermal head 10 sublimates the sublimation dye applied to the ink ribbon 31 by using the heat generation energy when the heat generating element is energized, and transfers it onto the recording paper 41 to form an image. It is configured. During the period from the start of the transfer of the first yellow (Y) ink to the end of the transfer of the fourth (last) laminate ink (L), the thermal head 10 is moved between the print position and the standby position by the head lifting / lowering device 20. 4 reciprocations. In other words, the thermal head 10 is brought into pressure contact with the platen roller 11 four times for each printing by the head lifting device 20 for moving the thermal head 10 up and down with respect to the platen roller 11.

  Here, when the thermal head 10 is brought into pressure contact with the platen roller 11 by the head elevating device 20, the pressure contact position between the heating element and the platen roller 11 becomes a problem. Specifically, depending on the positional relationship between the thermal head 10 (heating element) and the platen roller 11, a strong pressure may be applied to the recording paper 41 during printing, and the intended printing result may not be obtained. Further, the recording paper 41 may not be smoothly conveyed, and a stripe pattern called a stick may occur. Therefore, the position of the thermal head 10 must be accurately adjusted.

FIG. 2 is a perspective view showing a peripheral portion of the thermal head 10 in the thermal printer 1 shown in FIG.
As shown in FIG. 2, the thermal head 10 is provided with a plurality of arms 21 constituting a head lifting device 20 (see FIG. 1). Then, by lowering each arm 21, the thermal head 10 comes into pressure contact with the outer peripheral surface of the platen roller 11 via the ink ribbon 31 and the recording paper 41 (see FIG. 1). Further, the thermal head 10 can adjust the pressure contact position with respect to the platen roller 11 by the thermal head position adjusting mechanism 100.

[Configuration example of head position adjustment mechanism]

FIG. 3 is a side view showing a thermal head position adjusting mechanism 100 as an embodiment of the head position adjusting mechanism of the present invention.
As shown in FIG. 3, the thermal head position adjustment mechanism 100 adjusts the pressure contact position between the heating element 10 a and the platen roller 11 when the thermal head 10 is pressed against the platen roller 11. An adjustment member 110 is provided. The thermal head position adjusting member 110 includes a cam body 111 that determines a pressure contact position between the heating element 10 a and the platen roller 11.

  When determining the pressure contact position by the thermal head position adjusting mechanism 100, the optimum position changes depending on the size (horizontal width) of the recording paper 41 (see FIG. 1) and the like. While rotating the cam main body 111. Then, the pressure contact position between the heating element 10a and the platen roller 11 is adjusted so that an intended printing result can be obtained without generation of a stick or the like, and an optimum position is determined.

<1. First Embodiment>
[Configuration Example of Head Position Adjustment Member]

FIG. 4 is a perspective view showing a thermal head position adjusting member 110 (first embodiment) as an embodiment of the head position adjusting member of the present invention.
As shown in FIG. 4, the thermal head position adjusting member 110 includes a cam body 111 for adjusting the pressure contact position between the thermal head 10 and the platen roller 11 (see FIG. 3). Further, a cam bearing 115 is provided which is attached to the cam body 111 and rotates the cam body 111.
The cam bearing 115 is rotatably supported by a rotation support shaft (not shown).

  Here, the cam bearing 115 is provided so that the rotation center position of the cam main body 111 can be changed. The rotation center position of the cam body 111 is changed by adjusting the mounting position of the cam bearing 115 with respect to the cam body 111. An example of the attachment state of the cam body 111 and the cam bearing 115 is the state shown in FIG. 4. In the example shown in FIG. 4, the cam body center 112 that is the center of gravity of the cam body 111 and the center of gravity of the cam bearing 115. It is attached so that a certain cam bearing center 116 coincides. Therefore, the thermal head position adjusting member 110 in the state shown in FIG. 4 has a cam having a longest diameter a and a shortest diameter b, so that the position can be adjusted within the adjustment range ab.

FIG. 5 is a perspective view showing the cam body 111 in the thermal head position adjusting member 110 shown in FIG.
FIG. 6 is a perspective view showing the cam bearing 115 in the thermal head position adjusting member 110 shown in FIG.
FIG. 7 is a perspective view showing a method of attaching the cam body 111 and the cam bearing 115 in the thermal head position adjusting member 110 shown in FIG.

As shown in FIG. 5, the cam body 111 has a plurality of positioning holes 113 for positioning the cam bearing 115 as a fitting portion when the cam bearing 115 (see FIG. 6) is attached. A total of 20 positioning holes 113 (5 patterns of 43-1 to 113-5 × 4 locations) are formed so that the cam bearings 115 can be attached in 5 patterns.
If the position where the positioning hole 113 is formed is far away from the cam body center 112, the cam body 111 is deformed or damaged by the weight of the thermal head 10 or the force received from the platen roller 11 during printing (see FIG. 3). There is a risk of this. Therefore, it is preferable that the positioning position of each positioning hole 113 is 70% or less of the longest diameter a from the cam body center 112.

  As shown in FIG. 6, the cam bearing 115 has a positioning protrusion 117 having a size capable of being press-fitted into the positioning hole 113 (see FIG. 5) of the cam body 111. Then, four positioning protrusions 117 are provided so that they can be press-fitted and attached to four positions of the positioning hole 113, respectively.

  Furthermore, the cam bearing 115 has a rotation adjustment gear 118 for adjusting the rotation angle of the cam body 111 accompanying the rotation of the cam bearing 115 in a stepwise manner. The rotation adjusting gear 118 is provided on the outer peripheral portion of the cam bearing 115 and is positioned by meshing with a rotating support shaft (not shown) attached to the end of the thermal head 10 (see FIG. 3). The

  Therefore, as shown in FIG. 7, the cam bearing 115 can be attached to the cam body 111 by the positioning hole 113 that fits the positioning protrusion 117. Then, by selecting any one of the positioning holes 113-1 to 113-5 shown in FIG. 5, it can be attached in five patterns. The rotation angle of the cam body 111 can be adjusted by the rotation adjustment gear 118, and the pressure contact position of the heating element 10a (see FIG. 3) can be moved (adjusted) by 0.05 mm each time the gear is moved. Yes.

FIG. 8 is an explanatory diagram showing a mounting relationship between the cam main body 111 and the cam bearing 115 in the thermal head position adjusting member 110 shown in FIG.
As described above, the cam main body 111 has five patterns of fitting portions (positioning holes 113-1 to 113-5 shown in FIG. 5) that fit into the cam bearing 115.

  Here, at least one fitting portion of the cam body 111 has a cam bearing center 116 positioned on a straight line connecting the cam diameter maximum point A of the cam body 111 and the cam body center 112, as shown in FIG. It is provided as follows. In the example shown in FIG. 8, the cam bearing center 116 is positioned on the opposite side of the maximum point A with respect to the cam body center 112. Specifically, a positioning hole 113-2 shown in FIG. 5 may be used. By doing so, the longest diameter of the cam is increased by Δc compared to the state shown in FIG. 4 using the positioning hole 113-1, and the longest diameter usable for position adjustment of the thermal head 10 (see FIG. 3) is a + Δc. It becomes.

Further, at least one other fitting portion of the cam main body 111 has a cam bearing center 116 positioned on a straight line connecting the cam diameter minimum point B of the cam main body 111 and the cam main body center 112, as shown in FIG. It is provided to do. In another example shown in FIG. 8, the cam bearing center 116 is located on the minimum point B side with respect to the cam body center 112. Specifically, a positioning hole 113-3 shown in FIG. 5 may be used. By doing so, the shortest diameter of the cam is reduced by Δd as compared with the state shown in FIG. 4 using the positioning hole 113-1, and the shortest diameter usable for position adjustment of the thermal head 10 (see FIG. 3) is b. −Δd.
When the positioning hole 113-4 or 113-5 shown in FIG. 5 is used, the diameter that can be used for position adjustment of the thermal head 10 changes according to the positioning hole 113-4 or 113-5.

FIG. 9 is a perspective view showing an example of a mounting state of the cam main body 111 and the cam bearing 115 in the thermal head position adjusting member 110 shown in FIG.
FIG. 10 is an explanatory view showing the position adjustment state of the thermal head 10 by the thermal head position adjustment member 110 in the attached state shown in FIG.
The state shown in FIGS. 9 and 10 is a case where the longest diameter that can be used for position adjustment of the thermal head 10 is a + Δc in the mounting relationship shown in FIG.

  As shown in FIG. 9, when the longest cam diameter from the cam bearing center 116 of the thermal head position adjusting member 110 is a + Δc, the state shown in FIG. 10 is obtained by adjusting the position of the thermal head 10 by this longest diameter a + Δc. It becomes. Specifically, the portion of the cam body 111 having the longest diameter a + Δc comes into contact with one end portion (operation point) of the link member 101. As a result, the link member 101 rotates counterclockwise around the contact portion (fulcrum) with the platen roller 11, and the thermal head 10 connected to the other end portion (force point) of the link member 101 is conveyed. And move in the opposite direction. As a result, the pressure contact position between the heating element 10a and the platen roller 11 is adjusted to a position of -Δc when the rotation center of the platen roller 11 is the origin and the transport direction is positive.

FIG. 11 is a perspective view showing another example of the mounting state of the cam main body 111 and the cam bearing 115 in the thermal head position adjusting member 110 shown in FIG.
FIG. 12 is an explanatory view showing the position adjustment state of the thermal head 10 by the thermal head position adjustment member 110 in the attached state shown in FIG.
The state shown in FIGS. 11 and 12 is the case where the shortest diameter that can be used for position adjustment of the thermal head 10 is b−Δd in the mounting relationship shown in FIG.

  As shown in FIG. 11, when the shortest cam diameter from the cam bearing center 116 of the thermal head position adjusting member 110 is b−Δd, the position of the thermal head 10 can be adjusted by adjusting the shortest diameter b−Δd. The state shown in FIG. Specifically, the portion of the cam body 111 having the shortest diameter b−Δd comes into contact with one end portion (operation point) of the link member 101. As a result, the link member 101 rotates clockwise around the contact portion (fulcrum) with the platen roller 11, and the thermal head 10 connected to the other end portion (force point) of the link member 101 is moved in the transport direction. Move. As a result, the pressure contact position between the heating element 10a and the platen roller 11 is adjusted to a position of + Δd when the rotation center of the platen roller 11 is the origin and the transport direction is positive.

  Accordingly, the position adjustment state of the thermal head 10 shown in FIG. 10 (the state adjusted to the position of −Δc) and the position adjustment state of the thermal head 10 shown in FIG. 12 (the state adjusted to the position of + Δd) As a whole, the adjustment range is expanded by Δc + Δd. Therefore, one type of cam main body 111 and one type of cam bearing 115 are prepared, and a plurality of adjustment ranges can be obtained simply by changing the mounting state of both types as shown in FIG. 4, FIG. 9, or FIG. be able to.

  Further, since only one type of cam body 111 and one type of cam bearing 115 need be prepared, it is possible to reduce the inventory of parts, thereby improving economy and productivity. Furthermore, even if it is necessary to adjust the position of the thermal head 10 again after the product is shipped, the mounting relationship between the mounted cam body 111 and the cam bearing 115 without preparing a new cam of a different type. It becomes possible to deal with it simply by changing. As a result, repair parts can be reduced.

<2. Second Embodiment>
[Configuration Example of Head Position Adjustment Member]

FIG. 13 is a perspective view showing a thermal head position adjusting member 120 (second embodiment) as an embodiment of the head position adjusting member of the present invention.
FIG. 14 is a perspective view showing the cam body 121 in the thermal head position adjusting member 120 shown in FIG.
Further, FIG. 15 is an explanatory view showing a method of attaching the cam main body 121 and the cam bearing 125 in the thermal head position adjusting member 120 shown in FIG. 13, and shows a state in which the cam main body 121 and the cam bearing 125 are attached. ing.
Further, FIG. 16 is an explanatory view showing a mounting method of the cam main body 121 and the cam bearing 125 in the thermal head position adjusting member 120 shown in FIG. 13, in which the mounting relationship between the cam main body 121 and the cam bearing 125 is changed. Is shown.

The thermal head position adjusting member 120 of the second embodiment shown in FIGS. 13 to 16 is for adjusting the pressure contact position between the thermal head 10 (see FIG. 3) and the platen roller 11 (see FIG. 3). A cam body 121 is provided. Further, a cam bearing 125 is provided that is attached to the cam body 121 and rotates the cam body 121.
The cam bearing 125 is rotatably supported by a rotation support shaft (not shown).

  Here, the cam main body 121 has a plurality of positioning holes 123 for positioning the cam bearing 125 as a fitting portion when the cam bearing 125 is attached. A total of eight positioning holes 123 (4 patterns × 2 locations of 123-1 to 123-4 shown in FIG. 14) are formed so that the cam bearings 125 can be attached in four patterns. Each positioning hole 123 is connected in a cross shape by a connecting groove 124 (see FIG. 14) having a width smaller than the size of the positioning hole 123.

  The cam bearing 125 has a positioning projection 127 for fitting into the positioning hole 123 of the cam body 121. Two positioning protrusions 127 are provided so that they can be attached to two positions of the positioning hole 123, respectively.

  Here, as shown in FIGS. 15 and 16, the positioning protrusion 127 includes a positioning protrusion 127a, a guide protrusion 127b, and a retaining protrusion that are sized to be actually press-fitted into the positioning hole 123 (see FIG. 14) of the cam body 121. 127c. Then, as shown in FIG. 15, the cam bearing 125 can be attached to the cam body 121 by press-fitting the positioning protrusion 127 a into the positioning hole 123.

  The guide protrusion 127b is provided at the tip of the positioning protrusion 127a, and has a size that can move along the connecting groove 124 (see FIG. 14). Further, the retaining 127 c is provided at the tip of the guide protrusion 127 b and prevents the positioning hole 123 and the connecting groove 124 from coming off. Therefore, the cam main body 121 and the cam bearing 125 cannot be completely separated by the retaining member 127c. Thereby, careless loss of the cam body 121 or the cam bearing 125 can be prevented.

  Further, in the thermal head position adjusting member 120 of the second embodiment, the guide projection 127b is connected to the connecting groove 124 (see FIG. 16) in a state where the cam bearing 125 is pulled out from the cam body 121 (see FIG. 13). 14). Then, any one of the positioning holes 123-1 to 123-4 shown in FIG. 14 is selected, and the positioning projection 127a is press-fitted into the positioning hole 123 (see FIG. 14) as shown in FIG. And the cam bearing 125 can be changed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, The following various deformation | transformation are possible. For example,
(1) In the embodiment, the thermal printer 1 is taken as an example of the image forming apparatus. However, the image forming apparatus is not limited to this, and can be applied to an ink jet printer, a copying machine, a facsimile, and the like.

  (2) In the embodiment, the thermal head 10 is moved to adjust the pressure contact position between the heating element 10 a and the platen roller 11. However, the present invention is not limited to this, and the platen roller 11 may be moved, or the thermal head 10 and the platen roller 11 may be moved to adjust the pressure contact position between them.

  (3) In the embodiment, the positioning hole 113 is formed in the cam body 111, and the positioning protrusion 117 of the cam bearing 115 is press-fitted into the positioning hole 113. However, a positioning protrusion may be provided on the cam body, and a positioning hole may be formed on the cam bearing. Further, the mounting is not limited to the mounting by the positioning protrusion and the positioning hole, and it is only necessary that the cam bearing can be mounted so that the rotation center position of the cam body can be changed.

1 Thermal printer (image forming device)
DESCRIPTION OF SYMBOLS 10 Thermal head 10a Heating element 11 Platen roller 20 Head raising / lowering device 100 Thermal head position adjusting mechanism 110 Thermal head position adjusting member 111 Cam main body 112 Cam main body 113 Positioning hole 115 Cam bearing 116 Cam bearing center 117 Positioning protrusion 118 Rotation adjusting gear 120 Thermal head position adjustment member 121 Cam body 123 Positioning hole 124 Connection groove 125 Cam bearing 127 Positioning protrusion

Claims (7)

A line-type thermal head in which a plurality of heating elements are arranged in a direction perpendicular to the conveyance direction of the recording medium;
A platen roller arranged to face each of the heating elements of the thermal head;
A lifting device for lifting and lowering the thermal head relative to the platen roller;
A cam body for adjusting a relative pressure contact position between each of the heating elements and the platen roller when the thermal head is brought into pressure contact with the platen roller via the recording medium by the lifting device; ,
A cam bearing attached to the cam body for rotating the cam body;
A rotation support shaft that rotatably supports the cam bearing,
The image forming apparatus, wherein the cam bearing is provided so that a rotation center position of the cam body can be changed. The image forming apparatus according to claim 1.
The cam body has a plurality of fitting portions that fit with the cam bearing,
One said fitting part is on the straight line which connects the maximum point of the cam diameter of the said cam body, and the gravity center of the said cam body, Comprising: The rotation center of the said cam bearing is on the opposite side of the said maximum point with respect to the said gravity center. Is located so that
The other one of the fitting portions is on a straight line connecting the minimum point of the cam diameter of the cam body and the center of gravity of the cam body, and the cam bearing rotates on the side of the minimum point with respect to the center of gravity. An image forming apparatus provided such that the center is located. The image forming apparatus according to claim 1.
The cam body is
A plurality of positioning holes for positioning the cam bearing;
A connecting groove for connecting the positioning holes with a width smaller than the size of the positioning holes,
The cam bearing is
Positioning protrusions of a size that can be press-fitted into each of the positioning holes;
A guide protrusion provided at a tip of the positioning protrusion and having a size capable of moving along the connecting groove;
An image forming apparatus provided at a tip of the guide projection and having a stopper for preventing the positioning hole and the connecting groove from coming off. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the cam bearing has a rotation adjustment gear for adjusting a rotation angle of the cam body in a stepwise manner as the cam bearing rotates. A print head for forming an image;
A cam body for adjusting the position of the print head;
A cam bearing attached to the cam body for rotating the cam body;
A rotation support shaft that rotatably supports the cam bearing,
The image forming apparatus, wherein the cam bearing is provided so that a rotation center position of the cam body can be changed. A cam body for adjusting a relative pressure contact position between the thermal head and the platen roller when the thermal head is pressed against the platen roller via the recording medium;
A cam bearing attached to the cam body for rotating the cam body;
A rotation support shaft that rotatably supports the cam bearing,
The cam bearing is provided so that a rotation center position of the cam body can be changed. A cam body for adjusting the position of the print head for forming an image;
A cam bearing attached to the cam body for rotating the cam body,
The cam bearing is provided so that a rotation center position of the cam body can be changed.

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