JP2005329683A - Image formation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image formation apparatus which can uniformly press a sheet across its entirety in the width direction while suppressing increase in the number of parts, and can release the pressing against the sheet when printing is not performed. <P>SOLUTION: This image formation apparatus has a turning member 5a, a screw coil spring 7a for pressing one end side of a thermal head 2 against a platen roller 3, a turning member 5b, a screw coil spring 7b for pressing the other end of the thermal head 2 against the platen roller 3, and a coupling shaft 6 for coupling the turning member 5a and the turning member 5b such that they can be synchronized. A head attachment arm 2b of the thermal head 2 includes an opening 2f. The turning member 5a includes a lifting part 5g which is engaged with the opening 2f of the thermal head 2 and integrally formed with the turning member 5a for lifting the thermal head 2, along with turning of the turning member 5a, in the direction in which it gets away from the platen roller 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a print head for performing printing.

  Conventionally, an image forming apparatus provided with a print head for performing printing is known (see, for example, Patent Document 1).

  Patent Document 1 discloses a printer that performs printing by sequentially pressing a predetermined portion of an ink ribbon against a sheet while moving a print head (thermal head) biased by a torsion coil spring along the sheet width direction. Has been.

  However, since the printer disclosed in Patent Document 1 cannot be pressed at once by the print head over the entire width direction of the paper, it is not possible to simultaneously perform printing for one row along the width direction of the paper. There is an inconvenience.

  Therefore, conventionally, various printers that can be pressed at once by the print head over the entire width direction of the paper have been proposed in order to eliminate the inconvenience of the printer according to Patent Document 1 (for example, Patent Document 2). And Patent Document 3).

  The printer proposed in Patent Document 2 presses the central portion of a print head provided so as to extend over the entire width direction of the paper by a pressurizing body urged by a torsion coil spring, thereby reducing the width of the paper. It is configured to be pressed at once by the print head over the entire direction.

  The printer proposed in Patent Document 3 above urges both ends in the width direction of a print head (thermal head) provided so as to extend over the entire width direction of the paper by two torsion coil springs. The print head is configured to be pressed at a time over the entire width direction of the paper.

  FIG. 12 is a top view showing an entire configuration of a conventional thermal transfer printer that can be pressed by a thermal head at once over the entire width direction of a sheet. FIG. 13 is a perspective view showing a heating portion and a pressing member of the thermal transfer printer according to the conventional example shown in FIG. 14 and 15 are side sectional views for explaining the operation of the conventional thermal transfer printer shown in FIG. Referring to FIG. 12, a conventional thermal transfer printer includes a frame 101, a platen roller 102, a heating unit 103, a pressing member 104, a motor 105, two intermediate gears 106, and a drive gear 107. I have.

  The frame 101 is provided with two support shafts 108 for rotatably supporting two opposite side surfaces of the heating unit 103. A torsion coil spring 108 a is mounted on one side of the two support shafts 108. The torsion coil spring 108a is provided to urge the heating unit 103 to rotate in the direction of arrow N in FIG. As shown in FIG. 13, the heating unit 103 includes a thermal head 109, a pair of head support arms 110, two compression coil springs 111, and a heat dissipation member 112.

The thermal head 109 is configured so that it can be pressed at once over the entire width direction of the paper. The thermal head 109 is a head unit 1 for printing on paper.
09a and a pair of head attachment arms 109b attached to the head portion 109a. Two spring mounting boss portions (not shown) are provided on the upper surface of the head portion 109a. Further, the pair of head mounting arms 109b are rotatably mounted on the support shaft 108. The pair of head mounting arms 109b has an arm pressing portion 109c. The arm pressing portion 109c is provided to suppress the movement of the head support arm 110 that is biased so as to rotate in the direction of arrow N in FIG.

  The pair of head support arms 110 is provided so as to sandwich the pair of head mounting arms 109b from the outside, and is rotatably attached to the support shaft 108. The head support arm 110 has a boss portion 110a and a spring pressing portion 110b. The boss portion 110a is provided on the side surface near one end of the head support arm 110 so as to protrude outward. The spring pressing portion 110b is provided so as to protrude inward from the upper portion of the head support arm 110.

  Further, the two compression coil springs 111 are respectively fitted between two spring mounting bosses (not shown) on the upper surface of the head portion 109a and the spring pressing portions 110b of the pair of head support arms 110. The two compression coil springs 111 urge the head portion 109a of the thermal head 109 in a direction to press the platen roller 102 (see FIG. 12). The heat radiating member 112 is disposed on the upper surface of the head portion 109a and has a function of radiating heat from the head portion 109a.

  The pressing member 104 is configured to move the heating unit 103 toward the platen roller 102 by pressing the boss portions 110 a of the pair of head support arms 110. The pressing member 104 includes resin-made rotating members 104a and 104b and a connecting shaft 104c. The rotating member 104b has a gear engaging portion 104d. The gear engaging portion 104 d of the rotating member 104 b is disposed so as to engage with the drive gear 107. The connecting shaft 104c connects the rotating member 104a and the rotating member 104b. The connecting member 104c transmits the driving force obtained from the driving gear 107 engaged with the gear engaging portion 104d of the rotating member 104b to the rotating member 104a.

Next, with reference to FIGS. 12, 14, and 15, the operation of a conventional thermal transfer printer will be described. First, the pressing member 104 is rotated in the direction of arrow L in FIG. 14 by the driving force transmitted from the motor 105 (see FIG. 12) via the two intermediate gears 106 and the driving gear 107. Accordingly, the boss portions 110a of the pair of head support arms 110 of the heating unit 103 are pushed down by the rotating member 104a and the rotating member 104b (see FIG. 12) of the pressing member 104, respectively. For this reason, the heating part 103 is rotated in the direction of arrow O in FIG. As a result, the head portion 109a of the thermal head 109 prints on the paper by pressing the platen roller 102 so as to sandwich the ink sheet (not shown) and the paper (not shown) as shown in FIG. Is done. Thereafter, as the pressing member 104 rotates in the direction of arrow M in FIG. 15, the heating unit 103 biased by the torsion coil spring 108a (see FIG. 12) rotates in the direction of arrow N in FIG. Is done. As a result, as shown in FIG. 14, the pressing force of the head portion 109 a of the thermal head 109 against the platen roller 102 is released, and the head portion 109 a is separated from the platen roller 102.
Japanese Patent Laid-Open No. 3-120069 JP-A-8-132706 JP-A-4-276460

  However, the conventional thermal transfer printer shown in FIG. 12 requires a torsion coil spring 108a for biasing the head portion 109a of the thermal head 109 in a direction away from the platen roller 102 and a pair of head support arms 110. Therefore, there is a problem that the number of parts increases.

  Further, in the printer disclosed in Patent Document 2, the paper is pressed by the print head by applying pressure to the center of the print head. Therefore, the paper is pressed uniformly by the print head over the entire width direction of the paper. There is a problem that it is difficult.

  Further, the printer disclosed in Patent Document 3 is not provided with a mechanism for releasing the press by the print head, so that it is difficult to release the press against the paper when printing is not performed. is there.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to press uniformly over the entire width direction of the sheet while suppressing an increase in the number of parts. In addition, an object of the present invention is to provide an image forming apparatus capable of releasing the pressure on the paper when printing is not performed.

Means for Solving the Problems and Effects of the Invention

  In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention is configured to face a print head for printing on a sheet that is rotatably mounted around a predetermined fulcrum. In the image forming apparatus comprising a platen roller disposed on the platen, a pressing mechanism for pressing the printing head against the platen roller, and a driving mechanism for driving the pressing mechanism, the printing head is rotatable about a predetermined axis. A first arm part and a second arm part that are attached and are arranged to face each other, each of the first arm part and the second arm part includes a positioning hole, and the first arm part is The pressing mechanism further includes an opening formed on a side surface in the vicinity of the head portion, and the pressing mechanism applies a first rotating member made of a metal plate and a direction in which one end of the print head is pressed against the platen roller. The first pressing portion including a first torsion coil spring that is biased in a direction parallel to the paper transport direction, a second rotating member made of a metal plate, and the other end side of the print head are pressed against the platen roller. In addition to the direction, the second pressing portion including a second torsion coil spring that is urged in a direction parallel to the paper conveyance direction, and the first rotating member and the second rotating member are connected in a synchronizable manner. And a metal connecting shaft including a mounting portion having a D-shaped cross section formed at both ends, and each of the first rotating member and the second rotating member is one end of the connecting shaft. The print head includes a first positioning engagement portion to which the pressing end side of the first torsion coil spring is engaged, and a pressing force of the second torsion coil spring. A second positioning engagement portion with which the end side is engaged, The moving member is further engaged with the opening of the first arm portion and is formed integrally with the first rotating member, and the head portion is moved to the platen as the first rotating member rotates. The drive mechanism includes a holding portion for lifting in a direction away from the roller and a cam pin provided so as to protrude, and the drive mechanism has a cam groove that engages the cam pin on one side surface and a first rotation. A drive gear for rotating the member is included.

In the image forming apparatus according to the first aspect, as described above, the first pressing portion including the first torsion coil spring that biases the one end side of the print head in the direction of pressing the platen roller, and the other end of the print head. By providing the second pressing portion including a second torsion coil spring that urges the platen roller in the direction of pressing the platen roller, the printhead can be pressed uniformly against the platen roller across the width direction. Thus, the sheet can be uniformly pressed over the entire width direction of the sheet. In addition, an opening is formed in the first arm portion of the print head and is engaged with the opening to lift the print head away from the platen roller as the first rotating member rotates. By integrally forming the upper portion of the printing head on the first rotating member, the print head is separated from the platen roller without separately providing a spring member or the like for biasing the print head in the direction of separating from the platen roller. Since it can be lifted in the direction, it is possible to release the pressure of the print head against the paper when printing is not performed without increasing the number of parts. In addition, the first torsion coil spring and the second torsion coil spring are configured to urge the print head in a direction parallel to the paper transport direction in addition to the direction in which the print head is pressed against the platen roller. While the print head is pressed against the platen roller by the coil spring and the second torsion coil spring, it is possible to suppress the displacement of the print head in the direction parallel to the paper transport direction.

  In the image forming apparatus according to the first aspect, the attachment portions having a D-shaped cross section are formed at both ends of the connecting shaft, and the first rotation member and the second rotation member are respectively made of metal. Engage with the first rotating member and the second rotating member of the connecting portion of the connecting shaft by engaging the connecting portion of the connecting shaft with the plate and forming a D-shaped engaging hole. The length of the portion to be made is the length of the thickness of the first rotating member and the second rotating member made of a metal plate, so that compared to the case where a resin-made rotating member is used, the connecting shaft mounting portion The length of the portion engaged with the first rotating member and the second rotating member can be reduced. As a result, the length of the attachment portion having a D-shaped cross section of the connecting shaft can be reduced as compared with the case where a resin-made rotating member is used. Even when the attachment portion having the shape is formed, it is possible to suppress a significant increase in the manufacturing time of the connecting shaft. In addition, a first positioning engagement portion that engages the pressing end side of the first torsion coil spring with the print head and a second positioning engagement portion that engages the pressing end side of the second torsion coil spring are formed. Therefore, the positioning of the first arm portion with respect to the first torsion coil spring and the positioning of the second arm portion with respect to the second torsion coil spring can be easily performed, so that the position where the thermal head is installed is easily positioned. be able to. In addition, the cam pin is formed on the first rotating member so as to protrude, the drive mechanism has a cam groove with which the cam pin is engaged on one side surface, and a driving gear for rotating the first rotating member. By comprising so that the first rotating member can be easily rotated by rotating the driving gear of the driving mechanism.

  An image forming apparatus according to a second aspect of the present invention includes a print head for printing on a sheet that is rotatably mounted around a predetermined fulcrum, a platen roller disposed to face the print head, A first pressing member including a first rotating member and a first torsion coil spring that presses one end of the print head against the platen roller; a second rotating member; and the other end of the print head is pressed against the platen roller. A second pressing portion including a second torsion coil spring, and a connecting member that synchronizesly connects the first rotating member and the second rotating member, and the print head includes a rotating member engaging portion. The first rotating member is engaged with the rotating member engaging portion of the print head and is formed integrally with the first rotating member, and printing is performed as the first rotating member rotates. Lift the head away from the platen roller Including lifting part for.

In the image forming apparatus according to the second aspect, as described above, the first pressing portion including the first torsion coil spring that biases the one end side of the print head in the direction of pressing the platen roller, and the other end of the print head. By providing the second pressing portion including a second torsion coil spring that urges the platen roller in the direction of pressing the platen roller, the printhead can be pressed uniformly against the platen roller across the width direction. It is possible to press more uniformly over the entire width direction of the paper. In addition, a rotation member engaging portion is formed in the print head, and the print head is separated from the platen roller as the first rotation member is rotated by being engaged with the rotation member engaging portion. By forming the holding portion for lifting the print head integrally with the first rotating member, the print head can be moved to the platen roller without separately providing a spring member or the like for urging the print head in a direction away from the platen roller. Therefore, it is possible to release the pressure of the print head against the paper when printing is not performed, without increasing the number of parts.

  In the image forming apparatus according to the second aspect, preferably, the first torsion coil spring and the second torsion coil spring are attached in a direction parallel to the sheet conveyance direction in addition to the direction in which the print head is pressed against the platen roller. To force. According to this configuration, the print head can be prevented from being displaced in a direction parallel to the paper transport direction while pressing the print head against the platen roller by the first torsion coil spring and the second torsion coil spring. .

  In the image forming apparatus according to the second aspect, preferably, the connecting member includes a mounting portion having a non-circular cross section formed at both end portions, and the first rotating member and the second rotating member are These are each made of a metal plate and have a non-circular engagement hole portion that is engaged with the attachment portion at one end portion of the connecting member. If comprised in this way, the length of the part engaged with the 1st rotation member and the 2nd rotation member of the attachment part of a connection member is the length of the 1st rotation member and 2nd rotation member which consist of a metal plate. Since the length is equal to the thickness of the first side surface portion, compared with the case where a resin-made rotating member is used, the portion of the coupling member that is engaged with the first rotating member and the second rotating member of the attachment portion The length can be reduced. As a result, the length of the attachment portion having a non-circular cross-section of the connecting member can be reduced as compared with the case where a resin-made rotating member is used. Even when the attachment portion having a shape is processed, it is possible to suppress a significant increase in the manufacturing time of the connecting member.

  In the image forming apparatus according to the first aspect, preferably, the print head is engaged with a first positioning engagement portion to which a pressing end side of the first torsion coil spring is engaged and a pressing end side of the second torsion coil spring. And a second positioning engaging portion. If comprised in this way, since positioning of the 1st arm part with respect to a 1st torsion coil spring and positioning of a 2nd arm part with respect to a 2nd torsion coil spring can be performed easily, a print head can be installed easily. Positioning can be performed.

  The image forming apparatus according to the second aspect preferably further includes a drive mechanism for rotating the first rotation member, and the first rotation member is formed so that a cam pin protrudes, and the drive mechanism. Includes a drive gear for rotating the first rotation member while forming a cam groove to which the cam pin is engaged on one side surface. If comprised in this way, a 1st rotation member can be easily rotated by rotating the drive gear of a drive mechanism.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a thermal transfer printer will be described as an example of an image forming apparatus according to the present invention.

  FIG. 1 is a perspective view showing the overall configuration of a thermal transfer printer according to an embodiment of the present invention. FIG. 2 is a top view of the thermal transfer printer according to the embodiment shown in FIG. 3 to 7 are views showing the detailed structure of the thermal transfer printer according to the embodiment shown in FIG. First, the structure of a thermal transfer printer according to an embodiment of the present invention will be described with reference to FIGS.

As shown in FIGS. 1 and 2, the thermal transfer printer according to the embodiment of the present invention rotates a metal frame 1, a thermal head 2 for printing on a sheet, a platen roller 3, and a platen roller 3. The platen roller bearing 4 that can be supported, the metal rotating members 5a and 5b, the connecting shaft 6 for connecting the rotating member 5a and the rotating member 5b, and the rotating member 5a. A torsion coil spring 7a mounted on the connecting shaft 6, a torsion coil spring 7b mounted on the connecting shaft 6 so as to correspond to the rotating member 5b, and the rotating member 5a.
A resin drive gear 8, a motor 9 having a motor shaft gear portion 9a, a metal motor bracket 10, a large-diameter gear portion 11a and a drive gear engaged with the motor shaft gear portion 9a. 8 and an intermediate gear 11 having a small-diameter gear portion 11 b that engages with the gear 8. The thermal head 2 is an example of the “print head” in the present invention. The rotating member 5a is an example of the “first rotating member” in the present invention, and the rotating member 5b is an example of the “second rotating member” in the present invention. The torsion coil spring 7a is an example of the “first torsion coil spring” in the present invention, and the torsion coil spring 7b is an example of the “second torsion coil spring” in the present invention.

  As shown in FIG. 1, an ink sheet insertion portion 1c for attaching an ink sheet (not shown) is provided on the other surface 1b of the frame 1 opposite to the one surface 1a to which the motor bracket 10 is attached. It has been. Further, the one surface 1a and the other surface 1b of the frame 1 are provided with insertion holes 1d into which both end portions of the connecting shaft 6 are rotatably inserted. The thermal head 2 is attached to the inside of both side surfaces of the frame 1 so as to be rotatable about a support shaft 1f. The thermal head 2 is attached to a head portion 2a for transferring ink of an ink sheet (not shown) onto a sheet and an upper surface of the head portion 2a, and is rotatably attached to a support shaft 1f so as to face each other. And a pair of head mounting arms 2b and 2c. The head mounting arm 2b is an example of the “first arm portion” in the present invention, and the head mounting arm 2c is an example of the “second arm portion” in the present invention. Further, the support shaft 1 f is provided so as to protrude in the direction A in FIG. 2 at a portion bent and raised so as to extend along the vertical direction with respect to the lower surface of the frame 1. The head mounting arms 2b and 2c of the thermal head 2 are respectively mounted by being inserted into the support shaft 1f from the direction B in FIG. The head mounting arms 2b and 2c are formed separately from the head portion 2a and are screwed to the upper surface of the head portion 2a. Thereby, it is comprised so that the attachment position with respect to the head attachment arms 2b and 2c of the head part 2a can be adjusted. The head mounting arms 2b and 2c are provided with positioning holes 2d and 2e, respectively, as shown in FIGS. The positioning hole portion 2d is an example of the “first positioning engagement portion” in the present invention, and the positioning hole portion 2e is an example of the “second positioning engagement portion” in the present invention. . The positioning holes 2d and 2e are formed in portions bent and raised along the direction perpendicular to the upper surfaces of the head portions 2a of the head mounting arms 2b and 2c. An opening 2f is formed on the side surface of the head mounting arm 2b near the head portion 2a. The opening 2f is an example of the “rotating member engaging portion” in the present invention.

  Further, the rotating members 5a and 5b are respectively attached to the end portion on the A direction side in FIG. 2 of the connecting shaft 6 and the end portion on the B direction side in FIG. Each of the end portion on the A direction side and the end portion on the B direction side of the connecting shaft 6 has a D-shaped cross section formed by cutting the end portion of the connecting shaft 6 made of a metal rod. Attachment portions 6a and 6b are provided. Further, an intermediate portion 6 c having a circular cross section is formed between the attachment portions 6 a and 6 b of the connecting shaft 6. The rotating member 5a is formed by bending a metal plate having a thickness of about 1.2 mm. As shown in FIG. 5, the rotating member 5a is provided so as to face the side surface portion 5d having the D-shaped engagement hole portion 5c and the side surface portion 5d, and the circular engagement hole portion 5e is formed. And a side surface portion 5f. In addition, one attachment portion 6a of the connection shaft 6 is engaged with the D-shaped engagement hole 5c, and an intermediate portion 6c of the connection shaft 6 is inserted into the circular engagement hole 5e. Has been.

Here, in this embodiment, as shown in FIG. 5, the head portion 2a (see FIG. 1) is provided on the side surface portion 5d of the rotating member 5a as the rotating member 5a rotates upward. A lifting portion 5g for lifting the platen roller 3 away from the platen roller 3 is integrally formed. The holding portion 5g is engaged with the opening 2f of the head mounting arm 2b of the thermal head 2 (see FIG. 3). Further, a cam pin 5h is provided on the outer side surface of the side surface portion 5d so as to protrude. The cam pin 5h is engaged with a cam groove 8a of a drive gear 8 (see FIG. 1) described later. Further, as shown in FIG. 5, the rotating member 5a is provided along a direction orthogonal to the side surface portions 5d and 5f, and faces the side surface portion 5j having a U-shaped cutout portion 5i and the side surface portion 5j. And a side surface portion 5l having a U-shaped cutout portion 5k. Further, one end of the torsion coil spring 7a attached to the connecting shaft 6 is engaged with the notch 5i of the side surface portion 5j, and the other end is engaged with the notch portion 5k of the side surface portion 5l. Thereby, the torsion coil spring 7a is positioned in the A and B directions in FIG. Further, the rotating member 5b attached to the end of the connecting shaft 6 on the B direction side is configured in the same manner as the rotating member 5a except that it does not have the holding portion 5g and the cam pin 5h. Further, the torsion coil spring 7b provided so as to correspond to the rotating member 5b is configured in the same manner as the torsion coil spring 7a.

  In the present embodiment, the end of the torsion coil spring 7a engaged with the notch 5k of the rotating member 5a is inserted into the positioning hole 2d of the head mounting arm 2b (see FIG. 3). The end of the torsion coil spring 7b engaged with the notch 5k of the rotating member 5b is inserted into the positioning hole 2e of the head mounting arm 2c (see FIG. 4). Thereby, the thermal head 2 is positioned in the A and B directions in FIG. 2 and the pressing positions of the torsion coil springs 7a and 7b with respect to the thermal head 2 are positioned. In this embodiment, the thermal head 2 is positioned so that the head mounting arms 2b and 2c are moved in the direction B in FIG. 2 so that the head mounting arms 2b and 2c do not come off the support shaft 1f (see FIG. 2). Has been. The ends of the torsion coil springs 7a and 7b are in contact with the upper surfaces of the head mounting arms 2b and 2c via the positioning holes 2d and 2e, respectively, and the head 2a is pressed against the platen roller 3. 2 is configured to be urged in the direction of arrow C in FIG. Thereby, the thermal head 2 is pressed against the platen roller 3 with a predetermined pressing force, and is prevented from being displaced in the C and D directions in FIG.

  In the present embodiment, as shown in FIG. 7, a cam groove 8 a that engages with the cam pin 5 h of the rotating member 5 a is formed on one side surface of the drive gear 8. The drive gear 8 is attached to the one surface 1a of the frame 1 and is engaged with the small-diameter gear portion 11b of the intermediate gear 11 (see FIG. 2). As a result, when the driving gear 8 is rotated by transmitting the driving force of the motor 9 via the motor shaft gear 9 a and the intermediate gear 11, the rotating member 5 a rotates around the connecting shaft 6. It is configured to move. Further, as shown in FIG. 7, the cam groove 8a has a direction (arrow) in which the rotating member 5a tries to rotate about the connecting shaft 6 by a reaction force transmitted from the thermal head 2 to the rotating member 5a when pressed. E direction) and the surface (F surface) where the cam pin 5h contacts the cam groove 8a are formed perpendicular to each other. Further, the surface (F surface) where the cam pin 5h contacts the cam groove 8a when pressed is formed to be substantially flat. Thus, unlike the case where the cam pin 5h contacts the curved surface portion of the cam groove 8a when pressed, the cam pin 5h is moved to the cam groove immediately after the drive gear 8 is rotated in the G direction in FIG. It is configured not to slip within 8a. The rotation center 8 b of the drive gear 8 is disposed on a tangent line (H line) in a direction in which the rotation member 5 a attempts to rotate about the connecting shaft 6.

8 to 11 are side sectional views for explaining the pressing operation of the thermal head of the thermal transfer printer according to the embodiment of the present invention with respect to the platen roller. Next, with reference to FIGS. 2 and 8 to 11, the pressing operation of the thermal head 2 of the thermal transfer printer according to the present embodiment with respect to the platen roller 3 will be described. First, in this embodiment, as shown in FIGS. 8 and 9, as an initial state, the rotating member 5 a is rotated to a position where the torsion coil spring 7 a does not press the thermal head 2, and the thermal head 2 The thermal head 2 is rotated in a direction away from the platen roller 3 by lifting the head portion 2a by the holding portion 5g of the rotating member 5a. At this time, the rotating member 5b (see FIG. 2) is also rotated to a position where the torsion coil spring 7b does not press the thermal head 2, similarly to the rotating member 5a. From this state, the driving force of the motor 9 (see FIG. 2) is changed from the motor shaft gear portion 9a to the large-diameter gear portion 11a and the small-diameter gear portion 11b of the intermediate gear 11, the drive gear 8, and the cam groove of the drive gear 8. It is transmitted to the rotating member 5a through the cam pin 5h of the rotating member 5a engaged with 8a. As a result, the rotating member 5a is rotated from the state shown in FIG. 8 to the state shown in FIG. 10 in the direction of arrow I in FIG. 10 and connected to the rotating member 5a by the connecting shaft 6. The moving member 5b (see FIG. 2) is also rotated in the arrow I direction. Along with this, the thermal head 2 is rotated in the direction of arrow J in FIG. 9 to change from the state shown in FIG. 9 to the state shown in FIG. As a result, the head portion 2a of the thermal head 2 contacts the platen roller 3, and one ends of the torsion coil springs 7a and 7b contact the upper surfaces of the head mounting arms 2b and 2c of the thermal head 2, respectively. For this reason, the head portion 2a of the thermal head 2 is pressed against the platen roller 3 by the urging forces of the torsion coil springs 7a and 7b.

  At this time, in the present embodiment, as shown in FIG. 2, the one end side and the other end side of the head portion 2 a are pressed by the torsion coil springs 7 a and 7 b, respectively. The platen roller 3 is uniformly pressed over the entire direction (A and B directions in FIG. 2). Thereafter, when the pressing force of the head portion 2a against the platen roller 3 is released, the driving gear 8 rotates in the direction opposite to that during pressing, so that the rotating member 5a rotates in the K direction in FIG. To do. Accordingly, the head portion 2a of the thermal head 2 is lifted upward by the holding portion 5g of the rotating member 5a engaged with the opening portion 2f of the head mounting arm 2b. As shown, it is separated from the platen roller 3.

  In the present embodiment, as described above, the torsion coil spring 7a that presses one end side of the head portion 2a of the thermal head 2 against the platen roller 3, and the other end side of the head portion 2a of the thermal head 2 presses against the platen roller 3. By providing the torsion coil spring 7b, the head portion 2a of the thermal head 2 can be uniformly pressed against the platen roller 3 across the width direction, so that the head portion 2a of the thermal head 2 can apply the entire width direction of the paper. It can be pressed evenly across. In addition, an opening 2f is formed in the head mounting arm 2b of the thermal head 2, and the head 2a is separated from the platen roller 3 as the rotating member 5a rotates by being engaged with the opening 2f. By forming the holding portion 5g for lifting in the direction integrally with the rotating member 5a, there is no need to separately provide a spring member or the like for urging the head portion 2a away from the platen roller 3. Since 2a can be lifted away from the platen roller 3, the number of parts is not increased and the pressing of the head portion 2a of the thermal head 2 against the paper can be released when printing is not performed.

  Further, in the present embodiment, the torsion coil spring 7a and the torsion coil spring 7b are configured to urge in the direction C in FIG. 2 in addition to the direction in which the head portion 2a of the thermal head 2 is pressed against the platen roller 3. Thus, while the head portion 2a of the thermal head 2 is pressed against the platen roller 3 by the torsion coil spring 7a and the torsion coil spring 7b, the thermal head 2 is parallel to the paper transport direction (directions C and D in FIG. 2). It is possible to suppress the occurrence of positional deviation.

Moreover, in this embodiment, while attaching part 6a (6b) which has a D-shaped cross section in the edge part of connection shaft 6, turning member 5a (5b) is a metal which has a thickness of about 1.2 mm. The rotating member of the attachment portion 6a (6b) of the connection shaft 6 is formed by the plate so as to be engaged with the attachment portion 6a (6b) of the connection shaft 6 and to have a D-shaped engagement hole 5c. The length of the portion engaged with 5a (5b) is the side surface portion 5d of the rotating member 5a (5b) made of a metal plate.
Therefore, it is engaged with the rotating member 5a (5b) of the mounting portion 6a (6b) of the connecting shaft 6 as compared with the case where a resin rotating member is used. The length of the portion to be reduced can be reduced. This makes it possible to reduce the length of the attachment portion 6a (6b) having a D-shaped cross section of the connecting shaft 6 as compared with the case where a resin-made rotating member is used, and therefore requires a long processing time. Even when the D-shaped attachment portion 6a (6b) is formed by cutting, it is possible to suppress a significant increase in the manufacturing time of the connecting shaft 6.

  Further, in the present embodiment, the rotating member 5a (5b) is provided along the direction orthogonal to the side surface portion 5d, and the side surface portion having the cutout portion 5i with which one end of the torsion coil spring 7a (7b) is engaged. 5j and a side surface portion 5l that is provided so as to face the side surface portion 5j and has a notch portion 5k with which the other end of the torsion coil spring 7a (7b) is engaged, respectively. Further, the mounting position of the torsion coil spring 7a (7b) can be prevented from being shifted by the notch 5k.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above-described embodiment, the thermal transfer printer is shown as an example of the image forming apparatus. However, the present invention is not limited to this and can be applied to an image forming apparatus other than the thermal transfer printer.

Moreover, in the said embodiment, although the engaging part of the rotation member for engaging one end and the other end of a torsion coil spring was formed as a U-shaped notch part, this invention is not restricted to this, The engaging portion of the member may be formed in another shape such as a through hole.
Moreover, in the said embodiment, although the head part and head attachment arm of the thermal head were formed separately, this invention is not limited to this, You may form a head part and a head attachment arm integrally.

  Moreover, in the said embodiment, in order to connect the rotation member 5a and the rotation member 5b synchronously, while attaching the attachment parts 6a and 6b of the connection shaft 6 so that it may have a D-shaped cross section, it is connected. Although the engaging holes 5c of the rotating members 5a and 5b that engage with the mounting portions 6a and 6b of the shaft 6 are formed in a D-shape, the present invention is not limited to this, and the rotating members 5a and 5b are not limited thereto. In order to connect them in synchronization with each other, the connecting portion between the rotating member 5a and the rotating member 5b and the connecting shaft 6 may be formed in a non-circular shape other than the D-shape. For example, the connecting portion may be formed in an oval shape.

1 is a perspective view showing an overall configuration of a thermal transfer printer according to an embodiment of the present invention. FIG. 2 is a top view of the thermal transfer printer according to the embodiment shown in FIG. 1. FIG. 2 is a perspective view showing the vicinity of one head mounting arm of a thermal head of the thermal transfer printer according to the embodiment shown in FIG. 1. FIG. 2 is a perspective view showing the vicinity of the other head mounting arm of the thermal head of the thermal transfer printer according to the embodiment shown in FIG. 1. It is the disassembled perspective view which showed the attachment structure with respect to the connection shaft of one rotation member used for the thermal transfer printer by one Embodiment shown in FIG. It is the disassembled perspective view which showed the attachment structure with respect to the connection shaft of the other rotation member used for the thermal transfer printer by one Embodiment shown in FIG. FIG. 2 is a cross-sectional view for explaining in detail a structure of a rotating member and a drive gear of the thermal transfer printer according to the embodiment shown in FIG. 1. It is a sectional side view for demonstrating pressing operation | movement with respect to the platen roller of the thermal head of the thermal transfer printer by one Embodiment of this invention. It is a sectional side view for demonstrating pressing operation | movement with respect to the platen roller of the thermal head of the thermal transfer printer by one Embodiment of this invention. It is a sectional side view for demonstrating pressing operation | movement with respect to the platen roller of the thermal head of the thermal transfer printer by one Embodiment of this invention. It is a sectional side view for demonstrating pressing operation | movement with respect to the platen roller of the thermal head of the thermal transfer printer by one Embodiment of this invention. It is the top view which showed the whole structure of the thermal transfer printer by an example of the past. It is the perspective view which showed the heating part and the pressing member of the thermal transfer printer by an example of the prior art shown in FIG. FIG. 13 is a side sectional view for explaining the operation of the thermal transfer printer according to the conventional example shown in FIG. 12. It is a side view for demonstrating operation | movement of the thermal transfer printer by an example of the prior art shown in FIG.

Explanation of symbols

1 frame 2 thermal head (printing head)
2a Head part 2b Head mounting arm (first arm part)
2c Head mounting arm (second arm)
2d positioning hole (first positioning engaging portion)
2e Positioning hole (second positioning engaging portion)
2f Opening (rotating member engaging part)
3 Platen roller 5a Rotating member (first rotating member)
5b Rotating member (second rotating member)
5c Engagement hole 5g Lifting upper part 5h Cam pin 6 Connection shaft (connection member)
6a, 6b Mounting portion 7a Torsion coil spring (first torsion coil spring)
7b Torsion coil spring (second torsion coil spring)
8 Drive gear 8a Cam groove

Claims (6)

A print head for printing on a sheet that is rotatably mounted around a predetermined fulcrum, a platen roller disposed so as to face the print head, and a pressing mechanism that presses the print head against the platen roller And an image forming apparatus provided with a driving mechanism for driving the pressing mechanism,
The print head is rotatably attached to a predetermined shaft, and includes a first arm portion and a second arm portion arranged to face each other,
The first arm portion and the second arm portion each include a positioning hole,
The first arm portion further includes an opening formed on a side surface in the vicinity of the head portion,
The pressing mechanism biases the first rotating member made of a metal plate and a direction parallel to the paper transport direction in addition to a direction of pressing one end of the print head against the platen roller. In addition to a first pressing part including a torsion coil spring, a second rotating member made of a metal plate, and a direction in which the other end side of the print head is pressed against the platen roller, a direction parallel to the paper transport direction A second pressing portion including a second torsion coil spring that is biased to the first rotation member and the second rotation member are connected in a synchronizable manner, and are formed in D-shapes formed at both ends. A metal connecting shaft including a mounting portion having a cross section of
The first rotating member and the second rotating member are respectively
Including a D-shaped engagement hole engaged with a mounting portion at one end of the connection shaft;
The print head includes a first positioning engagement portion that engages a pressing end side of the first torsion coil spring and a second positioning engagement portion that engages a pressing end side of the second torsion coil spring. ,
The first rotating member is further engaged with the opening of the first arm portion, and is formed integrally with the first rotating member, so that the first rotating member rotates. And a holding portion for lifting the head portion in a direction away from the platen roller, and a cam pin provided so as to protrude,
The drive mechanism is an image forming apparatus in which a cam groove to which the cam pin is engaged is formed on one side surface and a drive gear for rotating the first rotation member. A print head for printing on a paper that is rotatably mounted around a predetermined fulcrum;
A platen roller disposed to face the print head;
A first pressing portion including a first rotating member and a first torsion coil spring that presses one end side of the print head against the platen roller;
A second pressing portion including a second rotating member and a second torsion coil spring that presses the other end side of the print head against the platen roller;
A connecting member that connects the first rotating member and the second rotating member in a synchronizable manner;
The print head includes a rotating member engaging portion,
The first rotating member is engaged with the rotating member engaging portion of the print head, and is formed integrally with the first rotating member, so that the first rotating member rotates. Accordingly, the image forming apparatus includes a holding portion for lifting the print head in a direction in which the print head is separated from the platen roller.   3. The first torsion coil spring and the second torsion coil spring urge each of the first torsion coil spring and the second torsion coil spring in a direction parallel to the sheet conveyance direction in addition to a direction in which the print head is pressed against the platen roller. Image forming apparatus. The connecting member includes a mounting portion having a non-circular cross section formed at both ends.
Each of the first rotation member and the second rotation member is made of a metal plate, and has the non-circular engagement hole that is engaged with an attachment portion at one end of the connection member. The image forming apparatus according to claim 2 or 3.   The print head includes a first positioning engagement portion that engages a pressing end side of the first torsion coil spring and a second positioning engagement portion that engages a pressing end side of the second torsion coil spring. The image forming apparatus according to any one of claims 2 to 4. A drive mechanism for rotating the first rotation member;
The first rotating member is formed so that a cam pin protrudes,
7. The drive mechanism according to claim 1, wherein a cam groove that engages the cam pin is formed on one side surface, and includes a drive gear for rotating the first rotation member. The image forming apparatus described in 1.

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