JP2008068989A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To earth the three axes of a feed roller, a platen roller, and a press roller by a simple structure in an image forming device. <P>SOLUTION: A metal spring member 57 for electrically connecting feed roller 22, a platen roller 25, a press roller 27, and a chassis 41 to each other is installed on a press roller 27. The torsion coil part 57a of the spring member 57 is wound around the rotating shaft part 27a of the press roller 27. The engagement part 57d of a first arm part 57b is engaged with the rotating shaft part 25a of the platen roller 25. The contact part 57e of a second arm part 57c is brought into contact with the rotating shaft part 22a of the feed roller 22. The end portion 57f of the arm part 57c is brought into contact with a chassis 41. When a recording paper is fed, the static electricity charged on the feed roller 22, the platen roller 25, and the press roller 27 is discharged to the chassis 41 through the spring member 57. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a thermal sublimation type image forming apparatus.

  In recent years, with the spread of digital still cameras, various printers have been proposed so that color printing can be easily performed at home. By the way, if the ink jet printer has not been used for a long time, the ink may dry and the nozzles of the print head may be clogged. And when ink clogging occurs, not only is the recording paper wasted due to printing failure, but a large amount of ink is consumed to eliminate clogging of the ink, that is, to clean the print head. End up. For this reason, the inkjet printer has a problem that it is not economical because it requires a running cost for a user who is less frequently used. On the other hand, thermal transfer printers, particularly thermal sublimation type image forming apparatuses using ink ribbons, are used less frequently because prints with a constant image quality can always be obtained even if they have not been used for a long time. It is economical for the user.

  A thermal head used in a thermal sublimation type image forming apparatus usually includes a plurality of minute heating elements. Further, a platen roller for supporting the recording paper at the time of image formation is provided at a position facing the thermal head, and on the upstream side thereof, a recording roller is fed to the feed roller and the feed roller for feeding the recording paper. A press roller for pressing is provided. Each roller is grounded to the chassis via an independent metallic spring member in order to discharge the static electricity charged with the conveyance of the recording paper to the metal chassis.

As a technique related to the grounding of a roller using such a metal spring member, Patent Document 1 discloses a static electricity that is mounted on a rotating shaft of a platen roller and urges the platen roller in the axial direction and is charged on the platen roller. An image forming apparatus having a coil spring for discharging the battery to the chassis is shown. Japanese Patent Application Laid-Open No. 2004-228561 discloses a printer configured to connect two rollers with three spring members and ground the rollers. Patent Document 3 discloses an image forming apparatus provided with a torsion coil spring capable of preventing the clutch from being detached from the roller shaft and grounding the roller shaft.
JP 2004-250174 A JP 2005-26094 A JP 2006-35612 A

  However, in the image forming apparatuses disclosed in Patent Documents 1 to 3, a plurality of independent spring members are required to ground a plurality of rollers, which causes an increase in the number of parts of the apparatus. The number of man-hours required for assembly also increases, and the cost cannot be reduced.

  SUMMARY An advantage of some aspects of the invention is to provide an image forming apparatus capable of reducing the cost by allowing a plurality of rollers to be grounded with a simple configuration.

In order to achieve the above object, the invention of claim 1
A housing,
A paper feed cassette provided in the housing and on which recording paper is placed;
A recording paper transport mechanism that picks up recording paper one by one from the paper feed cassette, pulls it into the housing, and reciprocates the recording paper in a predetermined transport direction inside the housing;
Including a thermal head in which minute heating elements are arranged in a direction orthogonal to the transport direction, and an image forming unit that forms an image on a recording paper transported by the recording paper transport mechanism,
The recording paper transport mechanism is disposed between a pickup roller that picks up recording paper placed in a paper feed cassette, the thermal head, and the pickup roller, and the recording paper picked up by the pickup roller is A feed roller that conveys to the vicinity of the thermal head; a press roller that presses the recording paper toward the feed roller; and a platen roller that supports the recording paper on which an image is formed by the thermal head from the back side. ,
In the image forming apparatus further comprising: a resin bearing that rotatably supports the feed roller, the press roller, and the platen roller at both ends; and a metal chassis that supports the bearing;
A metal spring member for electrically connecting the feed roller, press roller and platen roller to the chassis;
The spring member includes a torsion coil portion wound around a rotation shaft portion of the press roller, a first arm portion and a second arm portion extending from both ends of the torsion coil portion, and the first arm portion. An engagement portion engaged with the rotation shaft portion of the platen roller, and a contact portion contacted with the rotation shaft portion of the feed roller in the second arm portion;
The engagement portion of the spring member is curved in a U shape, and is engaged with an engagement groove formed in the circumferential direction in the rotation shaft portion of the platen roller, and the second arm portion is the contact portion. Is further bent in the shape of a crank on the tip side, and its tip portion is in contact with the chassis,
The torsion coil portion urges the engagement portion in the direction of the rotation shaft portion of the platen roller and the contact portion in the direction of the rotation shaft portion of the feed roller,
The first arm portion and the second arm portion urge the tip portion of the second arm portion toward the chassis,
The feed roller, the press roller and the platen roller are grounded to the chassis by a single component so that the cost can be reduced.

The invention of claim 2
A paper feed cassette on which recording paper is placed;
A recording paper transport mechanism for reciprocally transporting recording paper from the paper feed cassette in a predetermined transport direction;
Image forming means for forming an image on recording paper conveyed by the recording paper conveyance mechanism;
The recording paper transport mechanism includes a feed roller that transports a recording paper placed in a paper feed cassette to the vicinity of the image forming unit, a press roller that presses the recording paper toward the feed roller, and the image forming A platen roller for supporting the recording paper on which an image is formed by means from the back side,
In the image forming apparatus further comprising: a resin bearing that rotatably supports the feed roller, the press roller, and the platen roller at both ends; and a metal chassis that supports the bearing;
A metal spring member that electrically connects the feed roller, press roller, and platen roller to the chassis is further provided.

The invention of claim 3
The image forming apparatus according to claim 2.
The image forming unit includes a thermal head in which minute heating elements are arranged in a direction orthogonal to the transport direction.

The invention of claim 4
The image forming apparatus according to claim 3.
The spring member includes a torsion coil portion wound around a rotation shaft portion of the platen roller, a first arm portion and a second arm portion extending from both ends of the torsion coil portion, and a tip of the first arm portion. An engagement portion that is engaged with the rotation shaft portion of the press roller in the portion, and a contact portion that is contacted with the rotation shaft portion of the feed roller in the second arm portion,
The engagement portion of the spring member is curved and engaged with an engagement groove formed in the circumferential direction in the rotation shaft portion of the platen roller, and the second arm portion is further distal than the contact portion. Is bent in a crank shape on the side, and its tip is in contact with the chassis,
The torsion coil portion and the two arm portions urge the engagement portion in the direction of the rotation shaft portion of the press roller and the contact portion in the direction of the rotation shaft portion of the feed roller, respectively. Urging the press roller in the direction of the feed roller;
The first arm and the second arm urge the tip of the other end toward the chassis,
The feed roller, the press roller and the platen roller are grounded to the chassis by a single component so that the cost can be reduced.

  According to the first aspect of the present invention, since the feed roller, the press roller and the platen roller are electrically connected to the chassis by a single spring member, each of the three-axis rollers is grounded to the chassis with a simple configuration. It is possible to reduce the cost of the apparatus by reducing the number of parts and the number of assembly steps. Further, since the torsion coil portion of the spring member is wound around the rotary shaft portion of the press roller, the spring member can be accommodated in the device in a compact manner, and the device can be miniaturized. Further, since the engaging portion of the spring member is curved in a U shape, the posture of the platen roller and the spring member is kept constant while the engaging portion is engaged with the engaging groove of the platen roller. The platen roller and the spring member can be easily assembled. Further, the torsion coil portion of the spring member urges the engaging portion in the direction of the rotation shaft portion of the platen roller and the contact portion in the direction of the rotation shaft portion of the feed roller, so that the feed roller, the press roller, and the platen Even if vibration occurs with the rotation of the rollers, the conduction between each roller and the spring member is sufficiently ensured. Further, since the first and second arm portions of the spring member urge the second tip portion in the direction of the chassis, the spring member and the chassis are sufficiently connected even if vibration occurs as the rollers rotate. Secured. Further, since the second arm portion of the spring member is bent in a crank shape, the contact pressure between the tip portion of the second arm portion and the chassis is optimized regardless of the positional relationship between the torsion coil portion and the chassis. be able to.

  According to the invention of claim 2, since the feed roller, the press roller and the platen roller are electrically connected to the chassis by a single spring member, each of the three-axis rollers is grounded to the chassis with a simple configuration. It is possible to reduce the cost of the apparatus by reducing the number of parts and the number of assembly steps.

  According to the invention of claim 3, the cost of a sublimation type image forming apparatus including a thermal head can be reduced.

  According to the invention of claim 4, since the torsion coil portion of the spring member is wound around the rotating shaft portion of the platen roller, the spring member can be accommodated in the device in a compact manner, and the device can be miniaturized. be able to. Further, the torsion coil portion of the spring member urges the engaging portion in the direction of the rotation shaft portion of the press roller and the contact portion in the direction of the rotation shaft portion of the feed roller, so that the feed roller, the press roller, and the platen Even if vibration occurs with the rotation of the rollers, the conduction between each roller and the spring member is sufficiently ensured. In addition, since the press roller is pressed against the feed roller at the same time, an elastic member (for example, the tension coil spring 55 in FIG. 2) separately required for pressing the press roller in the direction of the feed roller can be omitted. Further cost reduction can be achieved. In addition, since the first and second arm portions of the spring member urge the tip portion of the second arm portion toward the chassis, even if vibration occurs with the rotation of the rollers, the spring member and the chassis are electrically connected. Is sufficiently secured. Further, since the second arm portion of the spring member is bent in a crank shape, the contact pressure between the tip portion of the second arm portion and the chassis is optimized regardless of the positional relationship between the torsion coil portion and the chassis. be able to.

(Embodiment 1)
An image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a mechanical configuration of a thermal printer 1 as an example of an image forming apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the sublimation thermal printer 1 includes a housing 10, a paper feed cassette 11 provided on the front side of the housing 10, on which the recording paper 2 is placed, and the recording paper from the paper feed cassette 11. 2 is picked up one sheet at a time, and the recording paper transport is provided with a pickup roller 21 that pulls the paper 2 into the housing 10 and feed rollers 22, 23 that reciprocate the recording paper 2 in the predetermined transport direction X inside the housing 10. Micro heating elements are arranged in a predetermined position facing the mechanism 20 and the recording paper transport mechanism 20, and are arranged in a direction perpendicular to the transport direction X (a direction perpendicular to the paper surface: hereinafter referred to as a Y direction (see FIG. 2)). And a second reel 34 on which a used portion of the ink ribbon 35 is wound up, and the like. An image forming unit (image forming unit) 30 for forming an image on the recording paper 2 to be formed and an upper surface of the paper feed cassette 11, an image is formed by the image forming unit 30, and the recording paper transport mechanism 20 A recording paper tray 12 on which the recording paper 2 discharged from the body 10 is placed is configured.

  The pickup roller 21 and the feed rollers 22 and 23 of the recording paper transport mechanism 20 rotate about the rotation direction 60 in the Y direction orthogonal to the transport direction X, and contact the recording paper 2 to transport the recording paper 2 in the transport direction. . The pickup roller 21 picks up the recording paper 2 from the paper feed cassette 11. The feed rollers 22 and 23 reciprocate the recording paper 2 a plurality of times in the conveying direction inside the housing 10 while the image forming unit 30 forms an image on the recording paper 2. The recording paper transport mechanism 20 is further driven at a position facing the thermal head 31 by a platen roller 25 that supports the back surface of the recording paper on which an image is formed, and driven shafts attached to the rotation shafts of the feed rollers 22 and 23. A gear (not shown), a motor 26 for generating a driving force, a driving gear (not shown) for transmitting the driving force of the motor 26 to the driven gear, and a position facing the feed rollers 22 and 23 are provided. And press rollers 27, 28 for pressing the recording paper against the feed rollers 22, 23. The thermal head 31 and the motor 26 are controlled by the CPU 40 of the sublimation thermal printer 1.

  The distance between the axes of the two feed rollers 22 and 23 in the transport direction X determines the minimum size in the transport direction X of the recording paper 2 that can be printed by the sublimation thermal printer 1. On the other hand, the arrangement length of the minute heating elements of the thermal head 31 in the Y direction orthogonal to the transport direction X is the maximum size in the Y direction orthogonal to the transport direction X of the recording paper 2 that can be printed by the sublimation thermal printer 1. decide. Generally, since the size of the recording paper is determined by a standard such as JIS, the maximum size and the minimum size of the recording paper 2 that can be printed are determined from the standard. On the other hand, as a dedicated printer for outputting an image photographed by a digital still camera, for example, a printer compatible only with the L size of a photo size has been commercialized.

  For example, three types of inks of three primary colors (Y, M, and C) and an overcoat coating agent are sequentially arranged on a ribbon having a width corresponding to the arrangement length of the micro heating elements of the thermal head 31. The ink is applied in a rectangular shape corresponding to the maximum size of the recording paper 2 that can be printed by the sublimation type thermal printer 1 (not shown because it is publicly known). Actually, the size of each rectangular area on the ink ribbon 35 is set to be slightly larger than the size of the recording paper 2 in consideration of the margin. The number of ink colors on the ink ribbon 35 is not limited to the above three colors, and may be four colors including B (black) or five or more colors including an intermediate color.

  When the image forming unit 30 forms an image on the recording paper 2, the rear end of the recording paper 2 is transported to a predetermined reference position P in the transport direction X, and is applied onto the leading end of the recording paper 2 and the ink ribbon 35. Align each rectangular area. Then, while conveying both in the same direction at the same speed, the heating / non-heating of each heating element of the thermal head 31 is controlled using the image data, and the ink on the ink ribbon 35 is transferred onto the recording paper 2. For example, when a Y-color image is formed on the recording paper 2, the recording paper transport mechanism 20 is driven in the reverse direction while the ink ribbon 35 is stopped at the same position, and the leading edge of the recording paper 2 is moved to the reference position. Match. Then, the next M color image is formed on the recording paper 2 in the same procedure. When images are formed on the recording paper 2 for all colors, the entire surface of the recording paper 2 is finally overcoated, and image formation is completed.

  The thermal head 31 can move up and down in the Z direction orthogonal to both the transport direction X and the Y direction orthogonal to the transport direction X, and the image is formed on the recording paper 2 transported in a predetermined direction by the image forming unit 30. Is formed so as to be in close contact with the recording paper 2 with the ink ribbon 35 interposed therebetween. On the other hand, when the recording paper 2 is conveyed in the reverse direction to the reference position P, the recording paper 2 is raised to a predetermined position so as not to disturb the movement of the recording paper 2.

  2 to 4 show the configuration of the feed roller 22, the platen roller 25, the press roller 27 and their surroundings. 4 is a perspective view of the chassis 41 indicated by the alternate long and short dash line. The feed roller 22 and the platen roller 25 are supported by the chassis 41 via bearing members 51 and 52 made of synthetic resin. The press roller 27 is supported by the chassis 41 via a synthetic resin bearing member 53 and a metal arm member 54. The arm member 54 is rotatably supported by a rotation shaft 41a formed on the chassis 41, and a bearing member 53 is provided at one end thereof, and a tension coil for urging the press roller 27 at the other end thereof. Each of the springs 55 is mounted. The arm member 54 is urged in the arrow Z direction by the tension coil spring 55, and the press roller 27 is pressed in the direction of the feed roller 22.

  The feed roller 22, the platen roller 25, and the press roller 27 are insulated from the chassis 41 by bearing members 51, 52, and 53 made of synthetic resin having insulation properties. Accordingly, the press roller 27 is provided with a feed roller 22, a platen roller 25, and a metal spring member 57 for electrically connecting the press roller 27 and the chassis 41. Static electricity charged on the feed roller 22, the platen roller 25 and the press roller 27 as the recording paper is conveyed is discharged to the chassis 41 by the spring member 57.

  The spring member 57 is formed of a metal wire, and the torsion coil portion 57a wound around the rotation shaft portion 27a of the press roller 27, the first arm portion 57b and the second arm portion 57b extending from both ends of the torsion coil portion 57a. The arm portion 57c, the engagement portion 57d engaged with the rotation shaft portion 25a of the platen roller 25, and the contact portion 57e contacted with the rotation shaft portion 22a of the feed roller 22 are provided. The engaging portion 57d is provided at the distal end portion of the first arm portion 57b, and the abutting portion 57e is provided at a substantially central portion of the second arm portion 57c.

  The engaging portion 57 d of the spring member 57 is curved in a U shape and is engaged with an engaging groove 25 b formed in the circumferential direction on the rotating shaft portion 25 a of the platen roller 25. The contact portion 57 e of the spring member 57 is in contact with the rotation shaft portion 22 a of the feed roller 22. The second arm portion 57c is bent in a crank shape on the distal end side with respect to the contact portion 57e, and the distal end portion 57f is in contact with the chassis 41.

  The torsion coil portion 57a of the spring member 57 has the engagement portion 57d of the spring member 57 in the direction of the rotation shaft portion 25a of the platen roller 25 (arrow S1 direction) and the contact portion 57e of the rotation shaft portion 22a of the feed roller 22. Each is urged in the direction (arrow T1 direction). The first arm portion 57b and the second arm portion 57c of the spring member 57 urge the tip portion 57f of the spring member 57 in the direction of the chassis 41 (the direction of the arrow U1). The engaging portion 57d of the spring member 57 is engaged with the engaging groove 25b of the platen roller 25, and the first arm portion 57b and the second arm portion 57c move the distal end portion 57f in the direction of the chassis 41 (the direction of the arrow U1). It becomes a fulcrum when energizing.

  According to the present embodiment configured as described above, the feed roller 22, the press roller 27, and the platen roller 25 are electrically connected to the chassis 41 by the single spring member 57. The rollers 22, 25, and 27 can be grounded to the chassis 41, and the cost of the apparatus can be reduced by reducing the number of parts and the number of assembly steps. Further, since the torsion coil portion 57a of the spring member 57 is wound around the rotation shaft portion 27a of the press roller 27, the spring member 57 can be accommodated in the device in a compact manner, and the device can be miniaturized. it can. Further, since the engagement portion 57d of the spring member 57 is curved in a U shape, the platen roller 25 and the engagement portion 57d of the spring member 57 are engaged with the engagement groove 25b of the platen roller 25. The spring member 57 can be incorporated into the chassis 41 while keeping the posture of the spring member 57 constant. Thereby, the assembly of the platen roller 25 and the spring member 57 can be facilitated.

  Further, the torsion coil portion 57a of the spring member 57 biases the engaging portion 57d in the direction of the rotating shaft portion 25a of the platen roller 25 and the contact portion 57e in the direction of the rotating shaft portion 27a of the feed roller 22. Even if vibration occurs with the rotation of the feed roller 22, the press roller 27, and the platen roller 25, the continuity between the rollers 22, 25, 27 and the spring member 57 is sufficiently ensured. Further, since the first arm portion 57b and the second arm portion 57c of the spring member 57 urge the tip portion 57f in the direction of the chassis 41, even if vibration is generated as the rollers 22, 25, 27 are rotated. Sufficient conduction between the spring member 57 and the chassis 41 is ensured. Further, since the second arm portion 57c of the spring member is bent in a crank shape, the contact pressure between the tip portion 57f and the chassis 41 is optimized regardless of the positional relationship between the torsion coil portion 57a and the chassis 41. Can do.

(Embodiment 2)
Next, another embodiment of the sublimation thermal printer 1 will be described with reference to FIGS. FIG. 7 is a perspective view of the chassis 41 indicated by the alternate long and short dash line. The present embodiment is different from the first embodiment in the configuration of the spring member 61 and the arm member 62. The spring member 61 is formed of a metal wire, and the torsion coil portion 61a wound around the rotation shaft portion 25a of the platen roller 25, the first arm portion 61b and the second arm portion extending from both ends of the torsion coil portion 61a. The arm portion 61c, the engaging portion 61d engaged with the rotation shaft portion 27a of the press roller 27, and the contact portion 61e contacted with the rotation shaft portion 22a of the feed roller 22 are provided. The engaging portion 61d is provided at the tip portion of the first arm portion 61b, and the contact portion 61e is provided at the central portion of the second arm portion 61c. In the present embodiment, the press roller 27 can be pressed toward the feed roller 22 by the elastic force of the torsion coil portion 61a of the spring member 61. Therefore, the tension coil mounted on the arm member 54 in the first embodiment. The spring 55 is eliminated.

  The engaging portion 61 d of the spring member 61 is curved and is engaged with an engaging groove 27 b formed in the circumferential direction on the rotating shaft portion 27 a of the press roller 27. The contact portion 61 e of the spring member 61 is in contact with the rotation shaft portion 22 a of the feed roller 22. The second arm portion 61c is bent in a crank shape on the distal end side with respect to the contact portion 61e, and the distal end portion 61f is in contact with the chassis 41.

  The torsion coil portion 61a of the spring member 61 has the engaging portion 61d in the direction of the rotation shaft portion 27a of the press roller 27 (direction of arrow S2) and the contact portion 61e in the direction of the rotation shaft portion 22a of the feed roller 22 (arrow T2). Direction). The first arm portion 61b and the second arm portion 61c of the spring member 61 urge the tip portion 61f of the spring member 61 in the direction of the chassis 41 (the direction of the arrow U2). The engaging portion 61d of the spring member 61 is engaged with the engaging groove 25b of the platen roller 25, and the first arm portion 61b and the second arm portion 61c move the tip portion 61f toward the chassis 41 (direction of arrow U2). It becomes a fulcrum when energizing.

  According to the present embodiment configured as described above, the feed roller 22, the press roller 27, and the platen roller 25 are electrically connected to the chassis 41 by the single spring member 61. The rollers 22, 25, and 27 can be grounded to the chassis 41, and the cost of the apparatus can be reduced by reducing the number of parts and the number of assembly steps. Further, since the torsion coil portion 61a of the spring member 61 is wound around the rotating shaft portion 25a of the platen roller 25, the spring member 61 can be accommodated in the apparatus in a compact manner, and the apparatus can be miniaturized. it can.

  Further, the torsion coil portion 61a of the spring member 61 biases the engaging portion 61d in the direction of the rotating shaft portion 27a of the press roller 27 and the contact portion 61e in the direction of the rotating shaft portion 22a of the feed roller 22 respectively. Even if vibration is generated as the feed roller 22, the press roller 27, and the platen roller 25 rotate, the rollers 22, 25, 27 and the spring member 61 are sufficiently connected to each other, and the press roller 27 is connected to the feed roller. It is pressed in the direction of 22. As a result, the tension coil spring 55 (see FIG. 2 and the like) that is separately required for urging the press roller 27 in the direction of the feed roller 22 in the first embodiment can be omitted, and further cost reduction can be achieved. be able to. Further, since the first arm portion 61b and the second arm portion 61c of the spring member 61 urge the distal end portion 61f of the second arm portion 61c in the direction of the chassis 41, as the rollers 22, 25, and 27 are rotated. Even if vibration occurs, the electrical connection between the spring member 61 and the chassis 41 is sufficiently ensured. Further, since the spring member 61 is bent in a crank shape, the contact pressure between the tip portion 61f and the chassis 41 can be optimized regardless of the positional relationship between the torsion coil portion 61a and the chassis 41.

  The present invention is not limited to the configuration of the above-described embodiment, and at least the feed roller 22, the press roller 27, the platen roller 25, and the chassis 41 are electrically connected by a conductive metal spring member. It only has to be configured. The sublimation thermal printer 1 using an ink ribbon has been described as an example of an image forming apparatus. However, other types of image forming apparatuses that form images using a thermal head, such as a TA (Thermo Autochrome) type, are used. The present invention can be widely applied to an image forming apparatus or an inkjet image forming apparatus.

The figure which shows the structure of the sublimation type thermal printer by one Embodiment of this invention. FIG. 3 is a perspective view of a configuration of a feed roller, a platen roller, a press roller, and their surroundings in the printer. The sectional side view of the structure. The perspective view which looked at the same structure from the other side of FIG. 2 on both sides of the chassis. The perspective view of the structure of the feed roller, platen roller, press roller, and its periphery in the sublimation type thermal printer by another embodiment of this invention. The sectional side view of the structure. The perspective view which looked at the same structure from the other side of FIG. 5 across the chassis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sublimation type thermal printer 22 Feed roller 25 Platen roller 27 Press roller 31 Thermal head 41 Chassis 57 Spring member 57a Torsion coil part 57b 1st arm part 57c 2nd arm part 57d Engagement part 57e Contact part 57f Tip part

Claims (4)

A housing,
A paper feed cassette provided in the housing and on which recording paper is placed;
A recording paper transport mechanism that picks up recording paper one by one from the paper feed cassette, pulls it into the housing, and reciprocates the recording paper in a predetermined transport direction inside the housing;
Including a thermal head in which minute heating elements are arranged in a direction orthogonal to the transport direction, and an image forming unit that forms an image on a recording paper transported by the recording paper transport mechanism,
The recording paper transport mechanism is disposed between a pickup roller that picks up recording paper placed in a paper feed cassette, the thermal head, and the pickup roller, and the recording paper picked up by the pickup roller is A feed roller that conveys to the vicinity of the thermal head; a press roller that presses the recording paper toward the feed roller; and a platen roller that supports the recording paper on which an image is formed by the thermal head from the back side. ,
In the image forming apparatus further comprising: a resin bearing that rotatably supports the feed roller, the press roller, and the platen roller at both ends; and a metal chassis that supports the bearing;
A metal spring member for electrically connecting the feed roller, press roller and platen roller to the chassis;
The spring member includes a torsion coil portion wound around a rotary shaft portion of the press roller, a first arm portion and a second arm portion extending from both ends of the torsion coil portion, and the first arm portion. An engagement portion engaged with the rotation shaft portion of the platen roller, and a contact portion contacted with the rotation shaft portion of the feed roller in the second arm portion;
The engagement portion of the spring member is curved in a U shape, and is engaged with an engagement groove formed in the circumferential direction in the rotation shaft portion of the platen roller, and the second arm portion is the contact portion. Is further bent in the shape of a crank on the tip side, and its tip portion is in contact with the chassis,
The torsion coil portion urges the engagement portion in the direction of the rotation shaft portion of the platen roller and the contact portion in the direction of the rotation shaft portion of the feed roller,
The first arm portion and the second arm portion urge the tip portion of the second arm portion toward the chassis,
An image forming apparatus characterized in that the feed roller, press roller, and platen roller are grounded to the chassis by a single component so that the cost can be reduced. A paper feed cassette on which recording paper is placed;
A recording paper transport mechanism for reciprocally transporting recording paper from the paper feed cassette in a predetermined transport direction;
Image forming means for forming an image on recording paper conveyed by the recording paper conveyance mechanism;
The recording paper transport mechanism includes a feed roller that transports a recording paper placed in a paper feed cassette to the vicinity of the image forming unit, a press roller that presses the recording paper toward the feed roller, and the image forming A platen roller for supporting the recording paper on which an image is formed by means from the back side,
In the image forming apparatus further comprising: a resin bearing that rotatably supports the feed roller, the press roller, and the platen roller at both ends; and a metal chassis that supports the bearing;
An image forming apparatus, further comprising: a metal spring member that electrically connects the feed roller, press roller, platen roller, and the chassis.   The image forming apparatus according to claim 2, wherein the image forming unit includes a thermal head in which minute heating elements are arranged in a direction orthogonal to the transport direction. The spring member includes a torsion coil portion wound around a rotation shaft portion of the platen roller, a first arm portion and a second arm portion extending from both ends of the torsion coil portion, and a tip of the first arm portion. An engagement portion that is engaged with the rotation shaft portion of the press roller in the portion, and a contact portion that is contacted with the rotation shaft portion of the feed roller in the second arm portion,
The engagement portion of the spring member is curved and engaged with an engagement groove formed in the circumferential direction in the rotation shaft portion of the platen roller, and the second arm portion is further distal than the contact portion. Is bent in a crank shape on the side, and its tip is in contact with the chassis,
The torsion coil portion and the two arm portions urge the engagement portion in the direction of the rotation shaft portion of the press roller and the contact portion in the direction of the rotation shaft portion of the feed roller, respectively. Urging the press roller in the direction of the feed roller;
The first arm and the second arm urge the tip of the other end toward the chassis,
The image forming apparatus according to claim 3, wherein the feed roller, the press roller, and the platen roller are grounded to the chassis by a single component so that the cost can be reduced.

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