JP3807626B2 - Gear mechanism of image forming apparatus - Google Patents

Description

  The present invention is attached to a gear mechanism of an image forming apparatus, in particular, a chassis equipped with a feed roller of an image forming apparatus and a printing element for printing on a sheet, and transmits power of a motor to a feed roller or the like. The present invention relates to a gear mechanism.

  In a thermal transfer type image forming apparatus that transfers the color of an ink ribbon to printing paper sent by a feed roller by the action of a printing element such as a thermal head, a gear train that transmits rotation to a feed roller is unitized to form a gear mechanism, When such a gear mechanism is assembled to a chassis equipped with a feed roller, a thermal head, etc., there is an advantage that the assembly process can be simplified. Further, the gear train may include a path for transmitting power to other movable members provided in the chassis, for example, a pickup roller or a platen roller for feeding printing paper from the cassette.

  FIG. 6 is a side view of a main part of a gear mechanism as a comparative example constituted by unitized gear trains. In this case, a resin plate in which a support shaft 2 is integrally formed with a side plate portion 1 of a sheet metal chassis. The intermediate gear 4 included in the gear train of the gear mechanism is rotatably fitted and supported by the support shaft 2, and a motor (not shown) as a drive source is The plate 5 is fixed to the resin plate 3 and attached to the plate 5 made of sheet metal disposed opposite to the resin plate 3.

  According to this gear mechanism, the gear train including the intermediate gear 4 is accommodated together in the space S between the resin plate 3 and the sheet metal plate 5, so that the gear mechanism can be accommodated well and attached to the chassis. Only by fixing the resin plate 3 to the side plate portion 1 of the chassis with the gear 4 fitted to the support shaft 2 or the other gear fitted to another support shaft protruding from the resin plate 3. There is an advantage that the gear mechanism can be assembled to the chassis and the assemblability is improved.

On the other hand, conventionally, there has been proposed a technique for preventing rotation unevenness due to inconsistent meshing of constituent gears by taking measures to use all internal gears in the gear train from the drive source of the image forming apparatus to the transfer roller (for example, patents). Reference 1). In addition, a technique for improving the assembly method of an image forming apparatus using a process cartridge has been proposed, and when the process cartridge is mounted on the apparatus main body, the drive shaft on the main body side has an inclined portion on the cartridge side. A technique has also been proposed in which the drive shaft is fitted into the fitting hole of the inclined portion after being bent in the thrust direction (see, for example, Patent Document 2 and Patent Document 3).
JP-A-8-312727 JP-A-6-130745 Japanese Patent Laid-Open No. 6-194892

  However, in the gear mechanism described with reference to FIG. 6, the support shaft protruding from the resin plate 3 is supported by the resin plate 3 only at one end portion thereof, and the other end portion is a free end. Therefore, the support shaft 2 is bent and deformed by the bending force applied to the support shaft 2 in accordance with the meshing rotation with the other gear (not shown) of the intermediate gear 4, and the intermediate gear 4 and the other gear are engaged. May become unstable. If the meshing between the intermediate gear 4 and the other gear becomes unstable, rotation irregularities occur in the intermediate gear 4 or other gears meshing with the intermediate gear 4, and the rotation irregularities are transmitted to the feed roller to feed the printing paper. There is a possibility that a situation may occur in which the state becomes unstable, which adversely affects the print quality and lowers the print quality.

  On the other hand, the technology described in each of the above-mentioned patent documents supports the case where the intermediate gear of the gear train is supported by a support shaft protruding in a cantilever manner from a resin plate fixed to the chassis. The problem that the support shaft bends and deforms due to the bending force applied to the shaft and uneven rotation occurs cannot be improved.

  The present invention has been made in view of the above problems and circumstances, and by taking measures only to add a simple configuration, the support shaft protrudes in a cantilever manner from a resin plate fixed to the chassis. Even when the intermediate gear of the gear train is supported, it is possible to prevent the support shaft from being bent and deformed by the bending force applied to the support shaft as the gears mesh with each other, and this causes uneven rotation of the intermediate gear. It is an object of the present invention to provide a gear mechanism of an image forming apparatus capable of improving the stability of the feeding state of the printing paper by the feed roller and improving the printing quality.

  A gear mechanism of an image forming apparatus according to the present invention includes a gear train that is assembled to a chassis that includes a feed roller that applies a feeding force to a sheet and a printing element that performs printing on the sheet and transmits rotation to the feed roller. ing. An intermediate gear included in the gear train is rotatably attached to a support shaft integrally formed in a protruding manner on a resin plate provided with a bearing that supports the feed roller. The support hole is fitted and supported in a support hole provided in a plate made of sheet metal fixed to the plate, and the support hole is a cantilevered support piece having elasticity cut out in the plate made of sheet metal. The supporting shaft is elastically pressed in the axial direction by the elasticity of the support piece.

  With this configuration, the support shaft, which is integrally formed with the resin plate and protrudes in a cantilevered manner from the plate, is fitted and supported in the support hole provided in the plate made of sheet metal even at the tip. Therefore, even if a bending force is applied to the support shaft, the support shaft is not easily bent and deformed. In addition, the support hole portion is provided in a cantilevered support piece having elasticity cut out in a plate made of sheet metal, and the support shaft is elastically pressed in the axial direction by the elasticity of the support piece. Is less likely to rattle in the axial direction, which helps to improve the rotational stability of the intermediate gear rotatably attached to the support shaft. For this reason, uneven rotation is unlikely to occur in the intermediate gear, and the stability of the feeding state of the printing paper by the feed roller is improved, and the printing quality is improved.

  In the present invention, it is desirable that the protruding direction from the base portion of the cantilevered support piece is along the direction of the bending force applied to the support shaft by meshing rotation with the other gear of the intermediate gear. . According to this, since the bending force applied to the support shaft acts in the direction of pulling the cantilevered support piece, a force in the direction of twisting or bending the support piece due to the bending force is added. Absent. Therefore, the tip of the support shaft is positioned without wobbling by the support piece, which helps to improve the rotational stability of the intermediate gear.

  In the present invention, the hole edge of the support hole portion is in contact with the inclined surface of the outer periphery of the tapered portion of the tip end portion of the support shaft at the fitting position between the support hole portion and the tip end portion of the support shaft. Is desirable. According to this, the centering action of the support shaft is exhibited at the fitting portion between the support hole and the tip end portion of the support shaft, which helps to improve the rotational stability of the intermediate gear.

  A gear mechanism of an image forming apparatus according to the present invention includes a gear train that is assembled to a chassis that includes a feed roller that applies a feeding force to a sheet and a printing element that performs printing on the sheet and transmits rotation to the feed roller. In the gear mechanism of the image forming apparatus, a resin plate provided with a bearing for supporting the feed roller is fixed to the side plate portion of the chassis so as to overlap, and an intermediate gear included in the gear train is integrally formed so as to protrude from the plate. A support hole is provided in a plate made of a sheet metal that is rotatably attached to the support shaft, and the tip end portion of the support shaft is fixed to the plate and accommodates the gear train in a space between the plate and the support shaft. The support hole is provided in a cantilevered support piece having elasticity cut out in the plate made of sheet metal. The support shaft is elastically pressed in the axial direction by the elasticity of the support piece, and the cantilevered support piece in the direction of the bending force applied to the support shaft by meshing rotation with the other gear of the intermediate gear In the projecting direction from the base portion of the support shaft, and at the fitting position between the support hole portion and the tip end portion of the support shaft, the support hole portion is formed on the inclined surface of the tapered portion of the tip end portion of the support shaft. It is further embodied by adopting a configuration in which the hole edges are in contact. The operation of the present invention will be described in detail with reference to embodiments described later.

  As described above, according to the gear mechanism of the image forming apparatus according to the present invention, not only can the assembling workability when the gear train is unitized and assembled to the chassis be improved, but also with the meshing rotation of the gears. The bending force applied to the support shaft prevents the support shaft from being bent and deformed, so that there is no rotation unevenness in the intermediate gear. As a result, the stability of the feeding state of the printing paper by the feed roller is improved and the printing quality is improved. The effect of becoming

  1 is a schematic perspective view of an essential part of an image forming apparatus employing a gear mechanism A according to the present invention, FIG. 2 is a view taken along the arrow II of the gear mechanism A shown in FIG. 1, and FIG. 4 is a schematic side view of the gear mechanism A when viewed from above, FIG. 4 is a cross-sectional view of a main part of the gear mechanism A, and FIG. 5 is a cross-sectional view of a part of FIG.

  In FIG. 1, reference numeral 10 denotes a sheet metal chassis formed in a substantially U shape. The chassis 10 is fed with a feed roller 21 and a pinch roller 22 for applying a feeding force to the printing paper, and for feeding the printing paper from the cassette. In addition to the pickup roller 25, printing elements necessary for printing on printing paper are provided. The printing element includes a thermal head 23 for transferring the color of an ink ribbon of an ink ribbon cartridge (not shown), an operating mechanism 24 thereof, a platen roller not shown in the drawing, and the like.

  The gear mechanism A is assembled to the outside of the side plate portion 12 on one side of the chassis 10. The gear mechanism A in the figure includes a gear train in which a plurality of gears are engaged with each other and assembled, and the end of the feed roller 21 is rotatable as schematically shown in part in FIG. A support shaft 32 is protruded outward in a cantilever manner from a resin plate (resin plate) 30 having a feed roller bearing 31 supported on the side plate 12 and fixed to the outer surface of the side plate portion 12 in an overlapping manner. Moreover, an intermediate gear 33 included in the gear train of the gear mechanism A is attached to the support shaft 32 so as to be rotatable by fitting the shaft hole. Although only one support shaft 32 protruding from the resin plate 30 is shown in FIG. 2, support shafts protrude from the resin plate 30 at a plurality of locations, and the gear train is connected to these support shafts. The gear which forms is attached rotatably.

  As shown in FIG. 1, the gear mechanism A includes a sheet metal plate (sheet metal plate) 40 to which a motor M is attached, and the sheet metal plate 40 protrudes from an appropriate position of the resin plate 30. The boss portion 34 is used for screwing. The gear train is accommodated in a space S <b> 1 formed between the sheet metal plate 40 and the resin plate 30. The gear 34 shown in FIG. 3 exemplifies an output gear fixed to the rotating shaft of the motor M, and this gear 34 is also accommodated in the space S1 to form the starting gear of the gear train. 2 and 3 show another gear meshing with the intermediate gear 32, and the gear 36 shown in FIG. 2 is a feed roller that protrudes into the space S1 through the feed roller bearing 31. A gear fixed to the support shaft is illustrated, and this gear 36 forms the terminal gear of the gear train. The power of the motor M is transmitted to the movable members such as the feed roller 21, the thermal head 23, and the pickup roller 25 through the gear train of the gear mechanism A.

  According to the image forming apparatus configured as described above, the printing paper fed out from the cassette by the action of the pickup roller 25 shown in FIG. 1 is pressed against the feed roller 21 by the pinch roller 22, and the feeding force by the feed roller 21. Receive. The color of the ink ribbon (not shown) is transferred to the printing paper that has reached the platen roller (not shown) by the action of the thermal head 23. In this printing process, the printing paper is reciprocally moved in both the forward and reverse directions by switching the rotation direction of the feed roller 21, and is applied to the printing paper using the color zones such as yellow, magenta, and cyan formed on the ink ribbon. High-quality printing is performed.

  Here, as shown in FIG. 3, the intermediate gear 33 is engaged with the gear 34 fixed to the rotation shaft of the motor M to transmit the rotation of the gear 34, and the rotation of the intermediate gear 33 is engaged with it. Since it is transmitted to the other gear 35, a bending force directed in one direction is applied to the support shaft 32 supporting the intermediate gear 33 by meshing rotation with the gear 34 and the other gear 35. Is done. In FIG. 3, the rotation directions of the gears 34, 35 and the intermediate gear 33 are indicated by arrows R 1, R 2, R 3, and the bending force applied to the support shaft 32 and the direction of the bending force are indicated by the arrow F. Moreover, the support shaft 32 to which the bending force F is applied is made of resin integrally formed with the resin plate 30 and is projected in a cantilever manner from the resin plate 30, so that the bending force F is applied. If the support shaft 32 is bent and deformed, the intermediate gear 33 is unevenly rotated, and the feed state of the printing paper by the feed roller 21 becomes unstable and the printing quality is deteriorated. Fall into.

  Therefore, in this embodiment, the measures described below are taken. That is, as shown in FIG. 1, FIG. 4 or FIG. 5, a circular support hole portion 42 is formed in the sheet metal plate 40, and the tip end of the support shaft 32 formed as a conical tapered portion 37 in the support hole portion 42. The parts are fitted and supported. Further, the support hole portion 42 is formed at the tip end portion of the cantilevered support piece 43 having elasticity cut out in the sheet metal plate 40, whereby the support shaft 32 is axially moved by the elasticity of the support piece 43. To repress. Further, the protruding direction of the support piece 43 from the base portion 43a coincides with the direction of the bending force F applied to the support shaft 32, or is along the direction of the bending force F.

  If such measures are taken, the support hole portion of the sheet metal plate 40 is also formed at the tip portion where the support shaft 32 protruding in a cantilever manner from the resin plate 30 is formed as a conical tapered portion 37. Since it is fitted and supported by 42, even if a bending force is applied to the support shaft 32, the support shaft 32 is not easily bent and deformed. In addition, since the support piece 43 elastically presses the support shaft 32 in the axial direction due to its elasticity, a situation in which the support shaft 32 does not rattle in the axial direction does not occur. Furthermore, when the direction of the bending force F applied to the support shaft 32 coincides with or follows the direction in which the cantilevered support piece 43 protrudes from the base portion 43a, the bending force F applied to the support shaft 32 is increased. This acts in the direction of pulling the cantilevered support piece 43 (arrow P in FIG. 5). Therefore, the force in the direction of twisting or bending the support piece 43 is not applied to the support piece 43 due to the influence of the bending force acting on the support shaft 32, and as a result, the tip end of the support shaft 32 is not wobbled by the support piece 43. Will be positioned. As a result of the synergistic effects described above, the rotational stability of the intermediate gear 33 is improved, and uneven rotation of the intermediate gear 33 is less likely to occur, and the stability of the feeding state of the printing paper by the feed roller 21 is improved. Quality will be improved.

  In particular, if such measures are taken, as shown in FIG. 5, the outer periphery of the tapered portion 37 of the distal end portion of the support shaft 32 at the fitting position between the support hole portion 42 and the distal end portion of the support shaft 32. Since the hole edge 42a of the support hole portion 42 comes into contact with the inclined surface 37a, the centering action of the support shaft 32 is exhibited at the fitting position between the support hole portion 42 and the tip end portion of the support shaft 32. This also helps to improve the rotational stability of the intermediate gear 33.

  In this embodiment, the support hole 42 is formed by performing a burring process on the sheet metal plate 40, and a small-diameter outward ring formed at the hole edge 42a of the support hole 42 by the burring process. A curved root portion inner peripheral surface of the portion 44 is provided. In this way, the curved inner peripheral surface of the outward ring portion 44 comes into contact with the tapered portion 37 of the support shaft 32, so that even if the support shaft 32 is made of resin, the tapered portion 37 is damaged or scraped off. It becomes difficult to do.

1 is a schematic perspective view of a main part of an image forming apparatus employing a gear mechanism according to the present invention. It is an II arrow view about the gear mechanism of FIG. FIG. 3 is a schematic side view of the gear mechanism as viewed from the direction of arrow III in FIG. It is sectional drawing of the principal part of a gear mechanism. It is sectional drawing to which a part of FIG. 4 was expanded. It is a side view of the principal part of the gear mechanism comprised by the united gear train as a comparative example.

Explanation of symbols

A Gear mechanism F Bending force 10 Chassis 12 Side plate portion of chassis 21 Feed roller 23 Thermal head (printing element)
30 Plate made of resin 31 Feed roller bearing 32 Support shaft 33 Intermediate gear 34 Gear (other gear)
35 Other gear 37 Tapered portion 37 at the tip of the support shaft 37a Inclined surface of the tapered portion 40 Plate made of sheet metal 42 Support hole portion 42a Hole edge of the support hole portion 43 Support piece 43a Base portion of the support piece

Claims (4)

In a gear mechanism of an image forming apparatus provided with a gear train that is assembled to a chassis equipped with a feed roller that applies feeding force to a sheet and a printing element that performs printing on the sheet, and transmits rotation to the feed roller.
A resin plate having a bearing for supporting the feed roller is fixed to the side plate portion of the chassis in an overlapping manner, and an intermediate gear included in the gear train is rotatable on a support shaft integrally formed in a protruding manner on the plate. The tip end portion of the support shaft is fixed to the plate and fitted and supported in a support hole provided in a plate made of sheet metal that accommodates the gear train in a space between the plate and the plate. In addition, the support hole portion is provided in a cantilevered support piece having elasticity cut out in the plate made of sheet metal, and the support shaft is elastically pressed in the axial direction by the elasticity of the support piece,
The direction of the bending force applied to the support shaft by meshing rotation with the other gear of the intermediate gear is along the protruding direction from the base portion of the cantilevered support piece, and the support hole portion The gear of the image forming apparatus, wherein a hole edge of the support hole portion is in contact with an inclined surface of an outer periphery of the tapered portion of the tip end portion of the support shaft at a fitting position with the tip end portion of the support shaft. mechanism. In a gear mechanism of an image forming apparatus provided with a gear train that is assembled to a chassis equipped with a feed roller that applies feeding force to a sheet and a printing element that performs printing on the sheet, and transmits rotation to the feed roller.
An intermediate gear included in the gear train is rotatably attached to a support shaft integrally formed in a protruding manner on a resin plate provided with a bearing that supports the feed roller, and a tip portion of the support shaft is attached to the plate. It is fitted and supported in a support hole provided in a fixed sheet metal plate, and the support hole is provided in a cantilevered support piece having elasticity cut out in the plate made of sheet metal. And the support shaft is elastically pressed in the axial direction by the elasticity of the support piece. The image according to claim 2, wherein a projecting direction from the base portion of the cantilevered support piece is along a direction of a bending force applied to the support shaft by meshing rotation with the other gear of the intermediate gear. The gear mechanism of the forming device. The hole edge of the said support hole part is contact | abutting to the inclined surface of the outer periphery of the taper part of the front-end | tip part of the said spindle in the fitting location of the said support hole part and the front-end | tip part of the said spindle. Item 4. The gear mechanism of the image forming apparatus according to Item 3.

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