JP2008055800A - Image forming device and gear unit suitable for its recording paper conveyance mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device having a recording sheet conveying mechanism excellent in assembling work performance and capable of eliminating the backlash of a gear, and a gear unit suitable for its recording paper conveyance mechanism. <P>SOLUTION: Driven gears 51, 52 mounted at the rotary shafts of conveying rollers 22, 23 of the recording sheet conveying mechanism are constituted by two gear parts 61, 62 superposed in the axial direction of a rotary shaft 60 and one spring 63 provided between these two gear parts 61, 62. Bottomed holes 64, 65 superposed partly are formed on the opposed surfaces of the respective gear parts 61, 62, and openings 66, 67 penetrating in a rotary axial direction are formed near the end of the opening 65 with the bottom of the gear parts 62 disposed at an outside. Whether the spring 63 is correctly engaged with the superposed parts of the holes 64, 65 with the bottoms can be visually recognized by the openings 66, 67, and the spring 63 can be fitted in a normal state by inserting a tool from the openings 66, 67. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a thermal printer in which recording paper is reciprocally conveyed in the conveying direction and a gear device suitable for the recording paper conveying mechanism.

  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, especially sublimation thermal printers that use ink ribbons, can always obtain a print with a constant image quality even if they have not been used for a long time. Economical.

  In an inkjet printer, inks of a plurality of colors, for example, Y (yellow), M (magenta), and C (cyan) can be simultaneously applied to the recording paper, so that the recording paper is conveyed only in one direction. In contrast, thermal printers cannot simultaneously form images of multiple colors, including not only the above-described sublimation thermal printers but also thermal printers using thermal recording paper such as the TA (Thermo-Autochrome) method. An image must be formed while a sheet of recording paper is reciprocated several times with respect to the thermal head. Therefore, conventionally, a device for eliminating gear backlash (play) has been devised for the recording paper transport mechanism of the thermal printer.

  For example, in Patent Document 1, a driven gear 100 that is normally composed of a single gear component is replaced with two gear components 101 and 102 that are stacked in the direction of the rotation axis as shown in FIG. 6 and these two gears. The compression coil springs 111 and 112 are provided between the parts 101 and 102. Since the two gear parts 101 and 102 try to rotate in the opposite directions around the rotation shaft 105 by the biasing force of the compression coil springs 111 and 112, the two gear parts 101 and 102 mesh with the tooth gaps of the other gears without any gaps. Is resolved.

  According to the conventional configuration shown in FIG. 6, rectangular through holes 103 and 104 are formed in the two gear parts 101 and 102, respectively, and the through holes 103 and 104 of the gear parts 101 and 102 are overlapped. Thus, the compression coil springs 111 and 112 are fitted into the through holes 103 and 104, respectively. When one gear part 101 rotates relative to the other gear part 102, the through holes 103 and 104 of the gear parts 101 and 102 are displaced from each other, and the compression coil springs 111 and 112 are compressed and deformed. However, since the compression coil springs 111 and 112 are not constrained in a direction parallel to the rotation shaft 105, the compression coil springs 111 and 112 may jump out of the through holes 103 and 104 during assembly or rotation of the driven gear 100. .

  In order to prevent the compression coil springs 111 and 112 from jumping out of the through holes 103 and 104, for example, as shown in FIG. 7, bottomed holes 113 and 114 are formed on the opposing surfaces of the gear parts 101 and 102, respectively. It is also conceivable to constrain the compression coil springs 111 and 112 in a direction parallel to the rotation shaft 105. However, in that case, the operator cannot visually recognize the alignment of the compression coil springs 111 and 112 and the bottomed holes 113 and 114 during the assembly work, and must make a frustration. Therefore, the assembly workability of the driven gear 100 becomes very poor, and when the compression coil springs 111 and 112 are sandwiched between the opposing surfaces of the gear parts 101 and 102, as shown in FIG. 111 and 112 may be deformed and become unusable.

JP-A-4-345184

  The present invention has been made to solve the above-described problems of the conventional example, and has an image forming apparatus having a recording paper transport mechanism that is excellent in assembling workability and can eliminate gear backlash, and the recording paper thereof. An object of the present invention is to provide a gear device suitable for a transport mechanism.

In order to achieve the above object, the invention of claim 1
A housing,
A paper feed tray 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 tray, pulls it into the housing, and reciprocates the recording paper in a predetermined transport direction inside the housing;
An image is formed on the recording paper transported by the recording paper transport mechanism, including a thermal head that is provided at a predetermined position facing the recording paper transport mechanism and in which minute heating elements are arranged in a direction orthogonal to the transport direction. An image forming unit,
In the transport direction, provided on the opposite side of the housing from the paper feed tray, an image is formed by the image forming unit, and the recording paper discharged from the housing by the recording paper transport mechanism is placed In an image forming apparatus provided with a paper discharge tray,
The recording paper transport mechanism rotates about a direction orthogonal to the transport direction as a rotation shaft, and contacts the recording paper to reciprocate the recording paper in the transport direction, and a rotation shaft of the transport roller. A driving force transmission mechanism including an attached driven gear, a motor for generating a driving force, and at least one gear for transmitting the driving force of the motor to the driven roller;
The driven gear is constituted by two gear parts stacked in the rotation axis direction of the transport roller and one compression coil spring or tension coil spring provided between the two gear parts, and the compression gear The two gear parts are rotated relative to each other around the rotation axis of the conveying roller by the biasing force of the coil spring or the tension coil spring, so that the driven gear is independent of the rotation direction of the driven gear. And the backlash between the at least one gear and
The opposed surfaces of the two gear parts are each formed with a bottomed hole that is arc-shaped and partially overlaps with the rotation axis of the transport roller, and the compression coil is formed at the overlapping part of the bottomed hole. A spring or a tension coil spring is fitted, thereby restraining the compression coil spring or the tension coil spring in a direction parallel to the rotation axis and restricting a relative rotatable angle of the two gear parts. A stopper is provided,
Out of the two gear parts, at least one of the arc-shaped end portions of the bottomed hole of the gear part located outside the rotation axis direction of the conveyance roller penetrates in the rotation axis direction of the conveyance roller. An opening is formed, which makes it possible to visually check whether the compression coil spring or the tension coil spring is correctly fitted in the overlapping portion of the bottomed hole, and allows the tool to be removed from the opening. By inserting, the compression coil spring or the tension coil spring can be fitted in a normal state without being sandwiched between the opposing surfaces of the two gear parts.

The invention of claim 2
In an image forming apparatus provided with a recording paper transport mechanism for reciprocally transporting recording paper in its transport direction,
The recording paper transport mechanism rotates about a direction orthogonal to the transport direction as a rotation shaft, and contacts the recording paper to reciprocate the recording paper in the transport direction, and a rotation shaft of the transport roller. A driving force transmission mechanism including an attached driven gear, a motor for generating a driving force, and at least one gear for transmitting the driving force of the motor to the driven roller;
The driven gear is composed of two gear parts stacked in the rotation axis direction of the transport roller and at least one spring provided between the two gear parts, and the compression coil spring or the tension coil The two gear parts are rotated relative to each other around the rotation axis of the transport roller by the biasing force of the spring, so that the driven gear and the at least one of the at least one gear are rotated regardless of the rotation direction of the driven gear. Eliminates backlash between the gears,
The opposed surfaces of the two gear parts are each formed with a partially overlapping bottomed hole, and the spring is fitted into the overlapping part of the bottomed hole, whereby the spring is attached to the rotating shaft. A stopper is provided for restraining the relative rotation angle of the two gear parts while restraining in a parallel direction,
An opening penetrating in the rotation axis direction of the conveying roller is formed in the vicinity of at least one end of the bottomed hole of the gear component located outside the conveying roller in the rotation axis direction of the two gear components. It is possible to visually check whether the spring is correctly fitted in the overlapping portion of the bottomed hole by the opening, and by inserting a tool from the opening, the spring It is characterized in that it can be fitted in a normal state without being sandwiched between opposing surfaces of two gear parts.

The invention of claim 3
A driven gear that meshes with another gear and receives a rotational force from the other gear to be reciprocally rotated around its rotation axis, regardless of the direction of rotation of the driven gear. In the gear device that can eliminate the backlash between the gears of
The driven gear is composed of two gear parts stacked in the direction of the rotation axis of the transport roller and at least one spring provided between the two gear parts,
The opposed surfaces of the two gear parts are each formed with a partially overlapping bottomed hole, thereby constraining the spring in a direction parallel to the rotational axis and relative to the two gear parts. A stopper is provided to regulate the typical rotatable angle,
An opening penetrating in the rotation axis direction of the conveying roller is formed in the vicinity of at least one end of the bottomed hole of the gear component located outside the conveying roller in the rotation axis direction of the two gear components. It is possible to visually check whether the spring is correctly fitted in the overlapping portion of the bottomed hole by the opening, and by inserting a tool from the opening, the spring It is characterized in that it can be fitted in a normal state without being sandwiched between opposing surfaces of two gear parts.

  According to the first aspect of the present invention, in a thermal printer (including a sublimation ink ribbon type and a thermal paper use type) that reciprocates the recording paper in the transport direction, the recording paper is attached to the rotation shaft of the transport roller of the recording paper transport mechanism. Since the driven gear is constituted by two gear parts stacked in the direction of the rotation axis of the conveying roller and one compression coil spring or tension coil spring provided between the two gear parts, the compression coil The biasing force of the spring or tension coil spring can cause the two gear parts to rotate relative to the rotation axis of the transport roller, so that the driven gear and at least Backlash between one gear can be eliminated.

  In addition, the opposed surfaces of the two gear parts are each formed with a circular hole centered on the rotation axis of the conveying roller and partially overlapped with a bottomed hole. Alternatively, since the tension coil spring is constrained in the direction parallel to the rotation axis, one gear part rotates relative to the other gear part, the bottomed holes of each gear part shift from each other, and the compression coil spring Even if it is compressed or the tension coil spring is pulled and deformed, the compression coil spring or the tension coil spring does not jump out of the bottomed hole and come off.

  Further, of the two gear parts, an opening penetrating in the rotation axis direction of the conveyance roller is provided in the vicinity of at least one of the arc-shaped end portions of the bottomed holes of the gear parts located outside the rotation axis direction of the conveyance roller. Therefore, it is possible to visually check whether the compression coil spring or the tension coil spring is correctly fitted in the overlapping portion of the bottomed hole through the opening. Furthermore, by inserting a tool such as tweezers through this opening, it is possible to fit the compression coil spring or tension coil spring in a normal state without being sandwiched between the opposing surfaces of the two gear parts. . As a result, the deformation of the compression coil spring or the tension coil spring is prevented and the assembling work is facilitated.

  According to the second aspect of the present invention, the driven gear and the at least one gear are not limited to the thermal printer, and the entire image forming apparatus is the same as in the first aspect, regardless of the rotational direction of the driven gear. The backlash between the two can be eliminated, the spring is prevented from jumping out of the bottomed hole and coming off, the deformation of the spring is prevented, and the assembly work is facilitated. The type of spring is not limited to a compression coil spring or a tension coil spring, and may be a leaf spring or the like. Furthermore, the shape of the bottomed hole is not limited to the arc shape, and may be a rectangle or the like.

  According to the third aspect of the present invention, the driven gear is the same as the first or second aspect for all devices in which backlash with other gears is a problem regardless of the rotational direction of the driven gear. And at least one gear can be eliminated, and the spring can be prevented from being deformed without jumping out of the bottomed hole and being easily assembled.

  An image forming apparatus according to an embodiment of the present invention and a gear device suitable for the recording paper transport mechanism will be described with reference to the drawings. FIG. 1 shows a configuration of a sublimation 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 is provided on a housing 10, for example, a back side of the housing 10, and a recording tray 2 on which recording paper 2 is placed. Recording paper conveyance provided with a pickup roller 21 that picks up the paper 2 one by one and pulls it into the housing 10 and conveyance rollers 22 and 23 that reciprocate the recording paper 2 in the predetermined conveyance direction X inside the housing 10 The thermal head 31 is provided at a predetermined position facing the mechanism 20 and the recording paper transport mechanism 20 and in which minute heating elements are arranged in a direction orthogonal to the transport direction X (a direction perpendicular to the paper surface: hereinafter referred to as Y direction). The recording paper 2 conveyed by the recording paper conveyance mechanism 20 includes a first reel 33 on which an unused ink ribbon roll 32 is mounted, a second reel 34 on which a used portion of the ink ribbon 35 is wound up, and the like. And an image forming unit 30 that forms an image on the opposite side (for example, the front side) of the housing 10 in the transport direction X, the image forming unit 30 forms an image, and the recording paper It is composed of a paper discharge tray 12 on which the recording paper 2 discharged from the housing 10 by the transport mechanism 20 is placed.

  The pickup roller 21 and the transport rollers 22 and 23 of the recording paper transport mechanism 20 rotate about a rotation axis 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 rotates only in one direction, and after the recording paper 2 is picked up from the paper supply tray 11 and drawn into the housing 10, the rotation is stopped. On the other hand, while the image forming unit 30 forms an image on the recording paper 2, the transport rollers 22 and 23 reciprocate the recording paper 2 a plurality of times in the transport direction inside the housing 10. The recording paper transport mechanism 20 further includes driven gears 51 and 52 attached to the rotation shafts 60 of the transport rollers 22 and 23, a motor 53 that generates a driving force, and a driving force of the motor 53. And a gear train 50 for transmitting a driving force.

  The distance between the axes of the two transport 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 an image is formed on the recording paper 2 by the image forming unit 30, the leading edge of the recording paper 2 is transported to a predetermined reference position P in the transporting direction X, and the rectangular coated on the leading edge of the recording paper 2 and the ink ribbon 35 is used. Align each area of the shape. 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, the recording paper 2 is raised to a predetermined position so as not to hinder the movement of the recording paper 2.

  As described above, in the sublimation thermal printer 1, in order to form an image on one sheet of recording paper 2, the recording sheet 2 must be reciprocated a plurality of times within the housing 10. If the tip is displaced from the reference position, the displacement directly leads to a decrease in image quality. Therefore, the recording paper transport mechanism 20 is configured to minimize the backlash of the gear, and more preferably not to generate backlash.

  Next, a configuration for eliminating gear backlash in the recording paper transport mechanism 20 will be described. FIG. 2 is a partially cutaway front view of the driven gears 51 and 52, and FIG. 3 is a side sectional view thereof. As shown in each figure, the driven gears 51 and 52 are composed of two first gear parts 61 and second gear parts 62 that are superposed in the axial direction of the rotation shaft 60 of the transport rollers 22 and 23, respectively. A single compression coil spring 63 is provided between the gear parts 61 and 62. A cylindrical fitting protrusion 61 a that protrudes outward is formed at the center of the first gear component 61 located inside the rotation shaft 60 of the transport rollers 22 and 23. In addition, a circular opening 62 a that fits with the fitting protrusion 61 a of the first gear part 61 is formed at the center of the second gear part 62. Further, an engagement protrusion 61b protruding in the radial direction is formed on the outer periphery of the fitting protrusion 61a of the first gear part 61, and this engagement is formed on the inner periphery of the circular opening 62a of the second gear part 62. A notch 62b that engages with the protrusion 61b is formed. The dimension of the notch 62b around the rotating shaft 60 is set to be slightly larger than the dimension of the engaging protrusion 61b, and the rotating shaft 60 is within the range of the dimension difference between the notch 62b and the engaging protrusion 61b. The first gear part 61 and the second gear part 62 rotate relatively with respect to each other. The notch 62b and the engagement protrusion 61b function as a stopper for restricting the relative rotatable angle of the two gear parts 61 and 62.

  The opposed surface 61c of the first gear component 61 and the opposed surface 62c of the second gear component 62 are arcuate and centering on the rotation shaft 60 of the conveying rollers 22 and 23, respectively, and have a bottomed hole 64 that partially overlaps. , 65 are formed. The compression coil spring 63 is fitted in a space formed in the overlapping portion of these two bottomed holes 64 and 65. One end portion of the compression coil spring 63 is in contact with the end surface of the bottomed hole 64 on the first gear component 61 side, and the other end surface is in contact with the end surface of the bottomed hole 65 on the second gear component 62 side. Therefore, the first gear part 61 and the second gear part 62 are each urged to rotate in opposite directions by the urging force of the compression coil spring 63. In other words, in order to generate the urging force by the compression coil spring 63, the phase of the bottomed hole 64 of the first gear component 61 is the phase of the bottomed hole 65 on the second gear component 62 side around the rotation shaft 60. It is not.

  Of the first gear part 61 and the second gear part 62, in the vicinity of the arc-shaped end of the bottomed hole 65 of the second gear part 62 located outside the rotation shaft 60 of the transport rollers 22 and 23 in the axial direction. Are formed with openings 66 and 67 penetrating in the direction of the rotary shaft 60. When the driven gears 51 and 52 are assembled, these openings 66 and 67 are used to correctly fit the compression coil spring 63 in a space formed in the overlapping portion of the two bottomed holes 64 and 65. Specifically, as shown in FIG. 4, the compression coil spring 63 is fitted in the bottomed hole 64 on the first gear component 61 side in advance, and the second gear component is fitted from above. As described above, since the phases of the bottomed hole 64 of the first gear part 61 and the bottomed hole 65 on the second gear part 62 side are shifted, the first gear part 61 and the second gear part 62 are fitted as they are. If it is forced to fit, the end portion of the compression coil spring 63 is sandwiched between the facing surface 61c of the first gear component 61 and the facing surface 62c of the second gear component 62, Transformed. Therefore, a tool 70 such as tweezers or a screwdriver is inserted from the opening 66 or 67, and the compression coil spring 63 is inserted into the bottomed hole 65 on the second gear part 62 side while being compressed and deformed. As a result, the compression coil spring 63 is fitted in a normal state without being sandwiched between the opposing surfaces of the two gear parts 61 and 62. Further, the openings 66 and 67 are also used to confirm whether or not the compression coil spring 63 is correctly fitted after the driven gears 51 and 52 are assembled. The openings 66 and 67 may be provided only in the vicinity of one end of the bottomed hole 65 according to the phase shift direction of the bottomed holes 64 and 65.

  In this manner, the driven gears 51 and 52 attached to the rotation shaft 60 of the conveyance rollers 22 and 23 of the recording paper conveyance mechanism 20 are connected to the two gear components 61 and 62 that are stacked in the axial direction of the rotation shaft 60, and Since it is constituted by one compression coil spring 63 provided between these two gear parts, the two gear parts 61 and 62 are relatively rotated around the rotation shaft 60 by the urging force of the compression coil spring 63. Accordingly, backlash between the driven gears 51 and 52 and the gear 54 or the gear train 50 can be eliminated regardless of the rotation direction of the driven gears 51 and 52.

  Further, on the opposing surfaces 61c and 62c of the two gear parts 61 and 62, bottomed holes 64 and 65 that are arc-shaped around the rotation shaft 60 of the transport rollers 22 and 23 and partially overlap are formed. The bottomed holes 64 and 65 restrain the compression coil spring 63 in a direction parallel to the rotation shaft 60, so that one gear part 61 or 62 is relative to the other gear part 62 or 61. Even if the bottomed holes 64 and 65 of the gear parts 61 and 62 are displaced from each other and the compression coil spring 63 is compressed and deformed, the compression coil spring 63 protrudes from the bottomed holes 64 and 65. It will not come off.

  Further, at least one of the arcuate ends of the bottomed hole 65 of the second gear part 62 located outside the rotation axis 60 of the conveyance rollers 22 and 23 penetrates in the rotation axis direction of the conveyance roller. Since the openings 66 and 67 are formed, it is possible to visually check whether or not the compression coil spring 63 is correctly fitted in the overlapping portions of the bottomed holes 64 and 65 through the openings 66 and 67. Further, by inserting a tool such as tweezers through the openings 64 and 65, the compression coil spring 63 is fitted in a normal state without being sandwiched between the opposing surfaces 61c and 62c of the two gear parts 61 and 62. Is possible. As a result, the deformation of the compression coil spring 63 is prevented and the assembling work is facilitated.

  Next, a modification of this embodiment will be described. In the modification shown in FIG. 5, a tension coil spring 68 is used instead of the compression coil spring 63. Bosses 64a and 65a for spring application are formed in the bottomed holes 64 and 65 of the gear parts 61 and 62, respectively. When assembling the driven gears 51 and 52, one end of the tension coil spring 68 is hooked on the boss 65 a on the second gear part 62 side, and a tool 70 such as tweezers is inserted from the opening 67 to the other end. May be pulled to the boss 64a on the first gear part 61 side. Thus, even if the compression coil spring 63 is changed to the tension coil spring 68, the same effect as described above can be obtained.

  In the above embodiment, a sublimation type thermal printer has been described as an example of an image forming apparatus. However, the present invention is not limited to this, and an electrophotographic system such as a thermal printer using thermal paper or a laser beam printer may be used. Needless to say, the present invention can also be applied to an image forming apparatus. Furthermore, in the said embodiment, although the circular-shaped thing was illustrated as a shape of the bottomed holes 64 and 65, it is not limited to this, Like a prior art example shown in FIG. 6, rectangular and other shapes It may be. Furthermore, although the compression coil spring 63 and the tension coil spring 68 are illustrated as the springs that generate the urging force, the present invention is not limited to this, and a leaf spring having a substantially V-shaped cross section may be used.

1 is a diagram illustrating a configuration of a sublimation thermal printer as an example of an image forming apparatus according to an embodiment of the present invention. The front view which shows the structure of the driven gear used for the recording paper conveyance mechanism in the said one Embodiment. Side part sectional drawing which shows the structure of the said driven gear. Side part sectional drawing which shows the assembly procedure of the said driven gear. FIG. 7 is a side cross-sectional view showing a configuration of a modified example of a driven gear used for the recording paper transport mechanism in the embodiment. The front view which shows the structure of the driven gear conventionally used for the image forming apparatus. Side part sectional drawing which shows the structure of the other driven gear conventionally proposed. Side sectional drawing which shows the problem in the structure of said other driven gear.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sublimation type thermal printer 2 Recording paper 10 Housing | casing 11 Paper feed tray 12 Paper discharge tray 20 Recording paper conveyance mechanism 22, 23 Conveyance roller 30 Image formation part 31 Thermal head 51, 52 Driven gear 60 Rotating shaft (of conveyance roller) 61 First gear part 61c First gear part facing surface 62 Second gear part 62c Second gear part facing surface 63 Compression coil springs 64, 65 Bottomed holes 66, 67 Opening 68 Tension coil spring 70 Tool

Claims (3)

A housing,
A paper feed tray 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 tray, pulls it into the housing, and reciprocates the recording paper in a predetermined transport direction inside the housing;
An image is formed on the recording paper transported by the recording paper transport mechanism, including a thermal head that is provided at a predetermined position facing the recording paper transport mechanism and in which minute heating elements are arranged in a direction orthogonal to the transport direction. An image forming unit,
In the transport direction, provided on the opposite side of the housing from the paper feed tray, an image is formed by the image forming unit, and the recording paper discharged from the housing by the recording paper transport mechanism is placed In an image forming apparatus provided with a paper discharge tray,
The recording paper transport mechanism rotates about a direction orthogonal to the transport direction as a rotation shaft, and contacts the recording paper to reciprocate the recording paper in the transport direction, and a rotation shaft of the transport roller. A driving force transmission mechanism including an attached driven gear, a motor for generating a driving force, and at least one gear for transmitting the driving force of the motor to the driven roller;
The driven gear is constituted by two gear parts stacked in the rotation axis direction of the transport roller and one compression coil spring or tension coil spring provided between the two gear parts, and the compression gear The two gear parts are rotated relative to each other around the rotation axis of the conveying roller by the biasing force of the coil spring or the tension coil spring, so that the driven gear is independent of the rotation direction of the driven gear. And the backlash between the at least one gear and
The opposed surfaces of the two gear parts are each formed with a bottomed hole that is arc-shaped and partially overlaps with the rotation axis of the transport roller, and the compression coil is formed at the overlapping part of the bottomed hole. A spring or a tension coil spring is fitted, thereby restraining the compression coil spring or the tension coil spring in a direction parallel to the rotation axis and restricting a relative rotatable angle of the two gear parts. A stopper is provided,
Out of the two gear parts, at least one of the arc-shaped end portions of the bottomed hole of the gear part located outside the rotation axis direction of the conveyance roller penetrates in the rotation axis direction of the conveyance roller. An opening is formed, which makes it possible to visually check whether the compression coil spring or the tension coil spring is correctly fitted in the overlapping portion of the bottomed hole, and allows the tool to be removed from the opening. By inserting, the compression coil spring or the tension coil spring can be fitted in a normal state without being sandwiched between the opposing surfaces of the two gear parts. Forming equipment. In an image forming apparatus provided with a recording paper transport mechanism for reciprocally transporting recording paper in its transport direction,
The recording paper transport mechanism rotates about a direction orthogonal to the transport direction as a rotation shaft, and contacts the recording paper to reciprocate the recording paper in the transport direction, and a rotation shaft of the transport roller. A driving force transmission mechanism including an attached driven gear, a motor for generating a driving force, and at least one gear for transmitting the driving force of the motor to the driven roller;
The driven gear is composed of two gear parts stacked in the rotation axis direction of the transport roller and at least one spring provided between the two gear parts, and the compression coil spring or the tension coil The two gear parts are rotated relative to each other around the rotation axis of the transport roller by the biasing force of the spring, so that the driven gear and the at least one of the at least one gear are rotated regardless of the rotation direction of the driven gear. Eliminates backlash between the gears,
The opposed surfaces of the two gear parts are each formed with a partially overlapping bottomed hole, and the spring is fitted into the overlapping part of the bottomed hole, whereby the spring is attached to the rotating shaft. A stopper is provided for restraining the relative rotation angle of the two gear parts while restraining in a parallel direction,
An opening penetrating in the rotation axis direction of the conveying roller is formed in the vicinity of at least one end of the bottomed hole of the gear component located outside the conveying roller in the rotation axis direction of the two gear components. It is possible to visually check whether the spring is correctly fitted in the overlapping portion of the bottomed hole by the opening, and by inserting a tool from the opening, the spring An image forming apparatus characterized in that it can be fitted in a normal state without being sandwiched between opposing surfaces of two gear parts. A driven gear that meshes with another gear and receives a rotational force from the other gear to be reciprocally rotated around its rotation axis, regardless of the direction of rotation of the driven gear. In the gear device that can eliminate the backlash between the gears of
The driven gear is composed of two gear parts stacked in the direction of the rotation axis of the transport roller and at least one spring provided between the two gear parts,
The opposed surfaces of the two gear parts are each formed with a partially overlapping bottomed hole, thereby constraining the spring in a direction parallel to the rotational axis and relative to the two gear parts. A stopper is provided to regulate the typical rotatable angle,
An opening penetrating in the rotation axis direction of the conveying roller is formed in the vicinity of at least one end of the bottomed hole of the gear component located outside the conveying roller in the rotation axis direction of the two gear components. It is possible to visually check whether the spring is correctly fitted in the overlapping portion of the bottomed hole by the opening, and by inserting a tool from the opening, the spring A gear device characterized in that it can be fitted in a normal state without being sandwiched between opposing surfaces of two gear parts.

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