JP4843510B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus in which a drive unit having a gear train for transmitting power to a plurality of rollers for conveying paper is detachably attached to a main body.

  In an image forming apparatus such as a copying machine or a printer that employs an electrophotographic system, a recording material such as paper is transported along a transport path in the main body by a plurality of transport rollers, and an image is formed in the process. The plurality of transport rollers are rotationally driven by power transmitted from an electric motor as a drive source through a gear train.

By the way, there has been proposed an image forming apparatus that employs a configuration in which gear trains that transmit power to conveyance rollers are combined into a unit as a drive unit, and the drive unit is detachably attached to a side portion of the main body (see, for example, Patent Document 1). ).
JP 11-133744 A

  However, in the image forming apparatus employing the above configuration, it is not easy to position the plurality of gears in the drive unit, and it is not easy to accurately position the drive unit with respect to the apparatus main body.

  Accordingly, a first object of the present invention is to provide an image forming apparatus capable of easily and accurately positioning a gear in a drive unit and positioning the drive unit with respect to the apparatus main body.

  In the conventional drive unit, a pin that rotatably supports the gear is used as a metal cutting pin, and this is caulked to a metal plate. This increases the number of assembly steps and increases the cost. There was a problem that positioning was not easy.

  Accordingly, a second object of the present invention is to provide an image forming apparatus capable of positioning a gear shaft supporting a gear of a drive unit with high accuracy and easily mounting at a low cost.

  In order to achieve the above object, the invention according to claim 1 is an image forming apparatus in which a drive unit having a gear train for transmitting power to a plurality of rollers for conveying paper is detachably attached to a main body. The drive unit is divided into two parts, the main unit side unit and the non-main unit side unit, and the positioning boss projecting from the non-main unit side unit is fitted into the positioning hole formed in the main unit unit so that both units are positioned and joined. The drive unit is positioned and fixed to the main body by fitting a positioning protrusion formed on the main body into the positioning hole formed in the main body side unit of the drive unit.

  According to a second aspect of the present invention, in the first aspect of the invention, one end of the gear shaft is fixed to the fitting hole of the resin holder formed in the main body side unit by concave and convex fitting, and is inserted through the gear shaft. The gear shaft is supported at both ends by fitting the other end of the gear shaft protruding from the end face of the gear toward the main body into a fitting hole formed in the main body.

  According to a third aspect of the present invention, in the second aspect of the present invention, the convex portion protruding from the inner circumference of the fitting hole of the resin holder is fitted into a concave groove formed at one outer circumference of the gear shaft. Thus, one end of the gear shaft is fixed to the resin holder.

  According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the convex portion that protrudes from the inner periphery of the one end of the boss portion of the gear is fitted into the concave groove formed in the outer periphery of the other end of the gear shaft. By combining, the gear inserted into the gear shaft is temporarily fixed.

  According to the first aspect of the present invention, the drive unit is divided into the main body side unit and the non-main body side unit, and the positioning protrusions protruding from the anti-main body side unit are fitted into the positioning holes formed in the main body side unit. Thus, the positioning of the plurality of gears supported by both units is facilitated and highly accurate. Further, since the positioning projection formed on the main body is fitted into the positioning hole formed in the main unit of the drive unit, the drive unit can be easily and highly accurately positioned with respect to the apparatus main body.

  According to the second aspect of the present invention, since the gear shaft is fixed to the main body side unit of the drive unit by fitting one end of the gear shaft into the fitting hole of the resin holder by concave and convex fitting, the gear shaft that supports the gear of the drive unit. Can be positioned with high accuracy and easily attached at low cost. In addition, the other end of the gear shaft protruding from the end face of the gear inserted through the gear shaft to the main body side is fitted into the fitting hole formed in the main body, so that the gear shaft is securely supported by both ends. In addition, the gear supported by the gear shaft can be positioned with high accuracy with respect to the main body. Particularly, since the positioning projection on the main body side is fitted into the positioning hole formed in the main body side unit of the drive unit, the positioning of the gear supported by the main body side unit of the drive unit with respect to the main body is performed accurately.

  According to the third aspect of the present invention, one end of the gear shaft is fitted by fitting a convex portion projecting on the inner circumference of the fitting hole of the resin holder into a concave groove formed on one outer circumference of the gear shaft. Can be easily fixed to the resin holder with one touch.

  According to the fourth aspect of the present invention, the convex portion provided on the inner periphery of the one end of the boss portion of the gear is fitted into the concave groove formed on the outer periphery of the other end of the gear shaft, thereby being inserted into the gear shaft. Since the gear is temporarily fixed, the gear does not fall off the gear shaft when the drive unit is assembled into the main body, and the assemblability of the drive unit to the main body is improved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a front sectional view of a color image forming apparatus according to the present invention. The illustrated image forming apparatus is a tandem type color image forming apparatus, and a magenta image forming unit 1M is provided at the center of a main body 100 thereof. The cyan image forming unit 1C, the yellow image forming unit 1Y, and the black image forming unit 1BK are arranged in a line at regular intervals.

  Each of the image forming units 1M, 1C, 1Y, and 1BK is provided with photosensitive drums 2a, 2b, 2c, and 2d as image carriers, and a primary charger is provided around each of the photosensitive drums 2a to 2d. 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d as primary charging means, and cleaning devices 6a, 6b, 6c, 6d are arranged, respectively.

  Here, the photosensitive trams 2a to 2d are drum-shaped photosensitive members, and are driven to rotate at a predetermined process speed in a direction indicated by an arrow (clockwise) by a driving device (not shown). The primary chargers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

  Further, the developing devices 4a to 4d contain magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (BK) toner, respectively, and are formed on the photosensitive drums 2a to 2d. In addition, the toner of each color is attached to each electrostatic latent image to visualize each electrostatic latent image as a toner image of each color.

  The transfer rollers 5a to 5d as primary transfer means are disposed so as to be in contact with the photosensitive drums 2a to 2d via the intermediate transfer belt 7 in each primary transfer portion. Here, the intermediate transfer belt 7 is stretched between the secondary transfer counter roller 8 and the tension roller 9 and is disposed on the upper surface side of each of the photosensitive drums 2a to 2d. The roller 8 is disposed so as to be in contact with the secondary transfer roller 10 via the intermediate transfer belt 7 in the secondary transfer portion. A belt cleaning device 11 is provided in the vicinity of the tension roller 9. As a material for the intermediate transfer belt 7, for example, a dielectric resin such as polycarbonate, polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), or the like is selected.

  By the way, above the image forming units 1M, 1C, 1Y, and 1BK in the apparatus main body 100, toner containers 12a, 12b, 12c, and 12d for supplying toner to the developing units 4a to 4d are arranged in a line. It is installed.

  In addition, a laser scanner unit (LSU) 13 is disposed below the image forming units 1M, 1C, 1Y, and 1BK in the apparatus main body 100, and a paper feed cassette 14 is detachably attached to the bottom of the main body 100 below the image forming units. is set up. A plurality of sheets (not shown) are stacked and accommodated in the paper feed cassette 14, and a pickup roller 15 for taking out the paper one by one from the paper feed cassette 14 is taken out in the vicinity of the paper feed cassette 14. A feed roller 16 and a retard roller 17 are provided for feeding the fed paper to the transport path L.

  The conveyance path L extending in the vertical direction on the side of the apparatus main body 100 includes a conveyance roller 18 that conveys the sheet, and the secondary transfer counter roller 8 and the secondary transfer roller at a predetermined timing after temporarily waiting the sheet. A registration roller 19 is provided to supply to a secondary transfer portion that is a contact portion with the transfer roller 10. Next to the transport path L, another transport path L ′ used for forming an image on both sides of the sheet is formed, and a plurality of transport rollers 20 are suitable for this transport path L ′. It is provided at intervals.

  By the way, the transport path L arranged in the vertical direction on one side of the apparatus main body 100 extends to the paper discharge tray 21 provided on the upper surface of the apparatus main body 100, and the fixing device 22 and a plurality of them are in the middle. The paper discharge rollers 23 and 24 are provided.

  Next, an image forming operation by the color image forming apparatus having the above configuration will be described.

  When an image formation start signal is issued, the photosensitive drums 2a to 2d are driven to rotate at a predetermined process speed in the direction of the arrow in FIG. 1 (clockwise) in each of the image forming units 1M, 1C, 1Y, and 1BK. The drums 2a to 2d are uniformly charged by the primary chargers 3a to 3d. The laser scanner unit 13 emits a laser beam modulated by a color image signal for each color, irradiates the surface of the photosensitive drums 2a to 2d with each laser beam, and irradiates each color on the photosensitive drums 2a to 2d. An electrostatic latent image corresponding to the color image signal is formed.

  First, magenta toner is attached to the electrostatic latent image formed on the photosensitive drum 2a of the magenta image forming unit 1M by the developing device 4a to which a developing bias having the same polarity as the charging polarity of the photosensitive drum 2a is applied. The electrostatic latent image is visualized as a magenta toner image. This magenta toner image is transferred to the arrow shown in FIG. 1 by the action of the transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied at the primary transfer portion (transfer nip portion) between the photosensitive drum 2a and the transfer roller 5a. Primary transfer is performed on the intermediate transfer belt 7 which is rotationally driven in the direction.

  The intermediate transfer belt 7 on which the magenta toner image has been primarily transferred as described above moves to the next cyan image forming unit 1C. In the cyan image forming unit 1C as well, the cyan toner image formed on the photosensitive drum 2b is transferred to the magenta toner image on the intermediate transfer belt 7 in the primary transfer portion in the same manner as described above.

  Similarly, yellow and black toners respectively formed on the photosensitive drums 2c and 2d of the yellow and black image forming units 1Y and 1BK on the magenta and cyan toner images superimposed and transferred on the intermediate transfer belt 7, respectively. The images are sequentially superimposed at each primary transfer portion, and a full-color toner image is formed on the intermediate transfer belt 7. The transfer residual toner that is not transferred onto the intermediate transfer belt 7 and remains on the photosensitive drums 2a to 2d is removed by the cleaning devices 6a to 6d, and the photosensitive drums 2a to 2d are prepared for the next image formation. .

  Then, the pickup from the paper feed cassette 14 is performed in accordance with the timing at which the front end of the full color toner image on the intermediate transfer belt 7 reaches the secondary transfer portion (transfer nip portion) between the secondary transfer counter roller 8 and the secondary transfer roller 10. The sheet fed to the conveyance path L by the roller 15, the feed roller 16 and the retard roller 17 is conveyed to the secondary transfer unit by the registration roller 19. Then, a full-color toner image is collectively transferred from the intermediate transfer belt 7 to the sheet conveyed to the secondary transfer unit by the secondary transfer roller 10 to which a secondary transfer bias having a polarity opposite to that of the toner is applied. .

  Thus, the sheet on which the full-color toner image has been transferred is conveyed to the fixing device 22, and the sheet on which the full-color toner image has been fixed by being heated and pressurized and thermally fixed on the surface of the sheet. Then, the paper is discharged onto the paper discharge tray 21 by the paper discharge rollers 23 and 24 to complete a series of image forming operations. The transfer residual toner that is not transferred onto the sheet and remains on the intermediate transfer belt 7 is removed by the belt cleaning device 11, and the intermediate transfer belt 7 is prepared for the next image formation.

  By the way, in the color image forming apparatus according to the present embodiment, a drive unit 25 described later is detachably assembled to the apparatus main body 100, and the pickup roller 15, feed roller 16, and retard roller 17 are driven by the drive unit 25. Various rollers such as the transport roller 18, the registration roller 19, the transport roller 20, and the paper discharge rollers 23 and 24 are rotationally driven. Details of the drive unit 25 will be described below with reference to FIGS.

  2 is a perspective view of the drive unit, FIG. 3 is an exploded perspective view of the drive unit, FIG. 4 is an exploded perspective view of the drive unit and the apparatus main body, FIG. 5 is a sectional perspective view of the positioning unit of the drive unit and the apparatus main body, and FIG. FIG. 7 is a perspective view of a resin holder and a gear shaft, FIG. 8 is a partial cross-sectional view showing a support state of the gear shaft, and FIG. 9 is a line AA in FIG. It is sectional drawing.

  2 and 3, the drive unit 25 is divided into a main body side unit 25A and a non-main body side unit 25B, and the surface of the main body side unit 25A facing the apparatus main body 100 (see FIGS. 1 and 2). A plurality of gears G are rotatably supported on the front surface), and these constitute a gear train that transmits power to various rollers. Similarly, a plurality of gears G are rotatably supported on the surface of the non-main body side unit 25B facing the main body side unit 25A, and these constitute a gear train that transmits power to various rollers.

  As shown in FIG. 3, a pair of left and right cylindrical positioning bosses 26 project from the main body unit 25 </ b> A toward the main body unit 25 </ b> A. A pair of left and right positioning holes 27 for fitting the positioning bosses 26 projecting from 25B are formed.

  Thus, as shown in FIG. 5, the positioning boss 26 protruding from the non-main body side unit 25B is fitted into the positioning hole 27 formed in the main body side unit 25A, and both the units 25A and 25B are positioned. By joining, the drive unit 25 is assembled as shown in FIG.

  Further, as shown in FIG. 4, a pair of left and right cross-shaped positioning bosses 28 project from the surface of the apparatus main body 100 to which the drive unit 25 is attached. As described above, the main body side unit 25A and the opposite main body side unit are provided. The drive unit 25 formed by joining and integrating 25B is assembled to the apparatus main body 100. At this time, the positioning boss of the apparatus main body 100 is inserted into the positioning hole 27 formed in the main unit 25A of the drive unit 25 as shown in FIG. Thus, the drive unit 25 is positioned with respect to the apparatus main body 100. Therefore, the positioning boss 26 of the non-main body side unit 25B and the positioning boss 28 of the apparatus main body 100 are fitted together in the positioning hole 27 formed in the main body side unit 25A of the drive unit 25.

  As described above, in the present embodiment, the drive unit 25 is divided into the main body side unit 25A and the non-main body side unit 25B, and the positioning boss 26 protruding from the non-main body side unit 25B is formed on the main body side unit 25A. Since the units 25A and 25B are positioned by being fitted into the positioning holes 27, the positioning of the plurality of gears G supported by the units 25A and 25B can be performed easily and with high accuracy.

  Further, since the positioning projections 28 provided on the apparatus main body 100 are fitted into the positioning holes 27 formed in the main unit 25A of the drive unit 25, the drive unit 25 can be easily and accurately positioned relative to the apparatus main body 100. The position of the gear (not shown) that transmits the rotational force to the roller that is provided in the apparatus main body 100 and is driven to rotate and the gear G that is provided in the drive unit 25 can be maintained with high accuracy.

  By the way, as shown in FIG. 6, a plurality of gear shafts 29 for rotatably supporting the gear G are provided by a resin holder 30 on the surface of the main body side unit 25 </ b> A of the drive unit 25 facing the apparatus main body 100. It is installed.

  As shown in FIG. 7, the resin holder 30 is integrally formed in a ring shape with resin, and a D-cut portion 30b is formed in a part of the fitting hole 30a, and the D-cut portion 30b is excluded. A convex portion 30c is integrally formed on the inner peripheral portion.

  The gear shaft 29 is made of a metal or a resin excellent in slidability and wear resistance, and a flat D-cut portion 29a is formed on a part of the outer periphery at one end in the axial direction. A concave groove 29b is formed in the outer peripheral portion excluding the cut portion 29a. A concave groove 29c is formed on the outer periphery of the other end portion in the axial direction of the gear shaft 29 over the entire periphery.

  Thus, the gear shaft 29 has a D-cut portion 29 a formed at one end in the axial direction thereof aligned with a D-cut portion 30 b formed in the fitting hole 30 a of the resin holder 30, and one end in the axial direction is aligned with the resin holder 30. 8, the convex portion 30 c formed on the inner periphery of the resin holder 30 is fitted into the concave groove 29 b formed on the outer periphery of one end in the axial direction of the gear shaft 29, as shown in FIG. 8. Therefore, the gear shaft 29 can be easily attached to the main unit 25A with one touch. In addition, as shown in FIG. 8, since the meat steal 30d is formed in the outer peripheral part of the resin holder 30 over the perimeter, the resin holder 30 is easy to elastically deform. For this reason, when the gear shaft 29 is fitted, the diameter of the resin holder 30 is easily increased, and the fitting hole 30a can be moved over the convex portion 30c of the resin holder 30. The meat stealing 30d is provided on the outer periphery of the convex portion 30c formed on the inner periphery.

  When the gear shaft 29 is attached to the main unit 25A as described above, the gear G is inserted into and supported by the gear shaft 29. As shown in FIGS. A plurality of (three in the present embodiment) convex portions g2 are integrally projected on the inner periphery of the end portion of the end portion of the gear shaft 29. When the gear G is passed through the gear shaft 29, these convex portions g2 The gear G is temporarily fixed to the gear shaft 29 by fitting into a concave groove 29c formed in the portion.

  In the state where a plurality of gears G are temporarily fixed to the gear shaft 29 as described above, an end portion of the gear shaft 29 that protrudes from the end face of the gear G toward the device body 100 side is formed in the device body 100 as shown in FIG. When fitted into the fitted hole 100a, the gear shaft 29 can be supported at both ends by the drive unit 25 and the apparatus main body 100, and the gear G can be reliably supported by the supported gear shaft 29. Can do.

  As described above, in the present embodiment, the gear shaft 29 is fixed to the main body side unit 25A of the drive unit 25 by fitting one end of the gear shaft 29 into the fitting hole 30a of the resin holder 30 by the concave and convex fitting. The gear shaft 29 that supports the 25 gears G can be positioned with high accuracy and easily attached at low cost.

  Further, since the end of the gear shaft 29 protruding from the end face of the gear G toward the apparatus main body 100 is fitted into the fitting hole 100a formed in the apparatus main body 100, the gear shaft 29 is securely supported by both ends. In addition, the gear G supported by the gear shaft 29 can be positioned with high accuracy with respect to the apparatus main body 100. Particularly, since the positioning boss 28 on the apparatus main body 100 side is fitted into the positioning hole 27 formed in the main body side unit 25A of the drive unit 25, the apparatus main body 100 of the gear G supported by the main body side unit 25A of the drive unit 25 is provided. Is accurately positioned.

  Furthermore, in the present embodiment, the convex portion 30c protruding from the inner circumference of the fitting hole 30a of the resin holder 30 is fitted into the concave groove 29b formed on the outer circumference of one end of the gear shaft pin 29. One end of the gear shaft 29 can be easily fixed to the resin holder 30 with one touch.

  In addition, a gear g2 inserted into the gear shaft 29 is fitted into a groove 29c formed on the outer periphery of the other end of the gear shaft 29 by fitting a convex portion g2 protruding from the inner periphery of the boss portion g1 of the gear G. Since G is temporarily fixed, the gear G is not dropped from the gear shaft 29 when the drive unit 25 is assembled into the apparatus main body 100, and the assembling property of the drive unit 25 to the apparatus main body 100 is improved.

  In this embodiment, an example in which the present invention is applied to a color image forming apparatus has been described. However, the present invention can be applied not only to color image formation but also to a monochrome image forming apparatus. Of course.

1 is a front sectional view of an image forming apparatus (color image forming apparatus) according to the present invention. 1 is a perspective view of a drive unit of an image forming apparatus according to the present invention. 1 is an exploded perspective view of a drive unit of an image forming apparatus according to the present invention. 1 is an exploded perspective view of a drive unit and an apparatus main body of an image forming apparatus according to the present invention. FIG. 3 is a cross-sectional perspective view of a drive unit of the image forming apparatus according to the present invention and a positioning portion of the apparatus body. 3 is a partial perspective view showing a gear shaft erected on a main body side unit of the image forming apparatus according to the present invention. FIG. It is a perspective view of a resin holder and a gear shaft of the image forming apparatus according to the present invention. FIG. 3 is a partial cross-sectional view showing a supported state of a gear shaft in the image forming apparatus according to the present invention. It is the sectional view on the AA line of FIG.

Explanation of symbols

1M Magenta image forming unit 1C Cyan image forming unit 1Y Yellow image forming unit 1BK Black image forming unit 2a to 2d Photosensitive drum (image carrier)
3a to 3d Primary charger 4a to 4d Developer 5a to 5d Transfer roller 6a to 6d Cleaning device 7 Intermediate transfer belt 8 Secondary transfer counter roller 9 Tension roller 10 Secondary transfer roller 11 Belt cleaning device 12a to 12d Toner container 13 Laser Scanner unit (LSU)
DESCRIPTION OF SYMBOLS 14 Paper feed cassette 15 Pickup roller 16 Feed roller 17 Retard roller 18 Conveyance roller 19 Registration roller 20 Conveyance roller 21 Paper discharge tray 22 Fixing device 23, 24 Paper discharge roller 25 Drive unit 25A Main body side unit 25B Non-main body side unit 26 Positioning boss ( Positioning protrusion)
27 Positioning hole 28 Positioning boss (positioning protrusion)
29 Gear shaft 29a Gear shaft D-cut portion 29b, 29c Gear shaft concave groove 30 Resin holder 30a Resin holder fitting hole 30b Resin holder D-cut portion 30c Resin holder convex portion 30d Resin holder meat stealing 100 Device body 100a Device body fitting hole G Gear g1 Gear boss g2 Gear convex L, L 'Conveyance path

Claims (4)

In an image forming apparatus in which a drive unit having a gear train for transmitting power to a plurality of rollers for conveying paper is detachably attached to a main body.
The drive unit is divided into a main body side unit and an anti-main body side unit, and a positioning boss protruding from the anti-main body side unit is fitted into a positioning hole formed in the main body side unit so that both units are positioned and joined. As a result, the drive unit is assembled and the positioning of the drive unit is fixed to the main body by fitting the positioning protrusion formed on the main body into the positioning hole formed in the main body side unit of the drive unit. Image forming apparatus.   One end of the gear shaft is fixed to the fitting hole of the resin holder formed in the main body side unit by concave and convex fitting, and the other end of the gear shaft protruding from the end face of the gear inserted through the gear shaft to the main body side is the main body. The image forming apparatus according to claim 1, wherein the gear shaft is supported at both ends by being fitted into a fitting hole formed in the inner wall.   Fixing one end of the gear shaft to the resin holder by fitting a convex portion protruding from the inner periphery of the fitting hole of the resin holder into a concave groove formed on one outer periphery of the gear shaft; The image forming apparatus according to claim 3.   Temporarily fixing the gear inserted through the gear shaft by fitting a convex portion protruding from the inner periphery of one end of the boss portion of the gear into a groove formed on the outer periphery of the other end of the gear shaft. The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus.

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