JP4894230B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including power transmission means for transmitting power from a driving source to a driving shaft of a developing device.

  Each color toner image formed on an image carrier such as a photosensitive drum is sequentially primary transferred (multiple transfer) to an intermediate transfer belt, and each color toner image is superimposed on the intermediate transfer belt to form a color toner image. 2. Description of the Related Art Image forming apparatuses that form a color image by secondarily transferring the color toner image from an intermediate transfer belt to a recording sheet are conventionally known.

  In such an image forming apparatus, a flywheel is generally provided on the drive shaft of the image carrier in order to reduce banding (streaks caused by shading) caused by uneven rotation of the image carrier. ing. However, in recent years, banding often occurs due to uneven rotation of the developing device due to improvement in developability of the developing device.

  The cause of uneven rotation of the developer unit is due to the backlash of the clutch that stops the rotation of the developer unit in order to extend the life of the developer, the meshing error of the reduction gear train of the power transmission system, etc. is there. As countermeasures, the gears are eliminated as much as possible from the driving system of the developing device and the image carrier, and the driving is performed by a timing belt (for example, see Patent Document 1), or a sliding member is provided around the developing device. In addition, a configuration for imparting a braking effect (for example, see Patent Document 2) or a configuration for improving the connection relationship of the drive gear train of the developing device (for example, see Patent Document 3) has been proposed.

However, in order to obtain an image with less banding, the above-described configuration cannot be said to have a sufficient effect. In order to obtain a sufficient effect, it is desirable to attach a flywheel having a large inertia effect to the drive shaft of the developing device. However, in a general image forming apparatus, there is an image carrier next to the developing device. Since priority is given to attaching the flywheel to the drive shaft of the image carrier, a space for attaching the flywheel to the drive shaft of the developing device cannot be secured.
JP 2000-347472 A JP 2001-356603 A JP 2003-280322 A

  SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides an image forming apparatus that can reduce uneven rotation on the drive shaft of the developing device and reduce the occurrence of banding without securing a space for mounting the flywheel on the drive shaft of the developing device. The purpose is to obtain.

In order to achieve the above object, an image forming apparatus according to claim 1 according to the present invention is disposed on a downstream side in a power transmission direction of a drive source, and a reduction gear train to which power is transmitted from the drive source; A first transmission shaft that is disposed downstream of the reduction gear train in the power transmission direction, transmits power from the reduction gear train, and has a flywheel attached thereto, and upstream of the first transmission shaft in the power transmission direction A clutch that turns on / off power transmission from the drive source to the first transmission shaft, a drive pulley fixed to the first transmission shaft, and a timing from the drive pulley without using a gear train. A driven pulley to which power is transmitted via a belt, a second transmission shaft to which the driven pulley is fixed, and a coupling that is provided on the second transmission shaft and transmits power to the drive shaft of the developing device. Preparation It is characterized in that was.

According to the first aspect of the present invention, an inertia effect can be imparted to the drive shaft of the developer without securing a space for mounting the flywheel on the drive shaft of the developer .

In addition, since a clutch for turning on / off the power transmission is arranged upstream of the first transmission shaft in the power transmission direction, the clutch is not affected by rattling of the clutch, and the drive shaft of the developing device is not affected. An inertia effect can be imparted.

Therefore, it is possible to reduce the rotation unevenness in the developing unit of the drive shaft, it is possible to reduce the occurrence of banding.

  As described above, according to the present invention, it is possible to reduce uneven rotation on the drive shaft of the developing device and reduce the occurrence of banding without securing a space for mounting the flywheel on the drive shaft of the developing device. Can be provided.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for carrying out the present invention will be described below in detail based on the embodiments shown in the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus 10 according to the present invention. The image forming apparatus 10 performs image processing based on color image information sent from an image data input device such as a computer (not shown), and forms a color image on the recording paper P by an electrophotographic method.

  The image forming apparatus 10 includes an image forming apparatus main body 12, a paper feeding device 14, and a paper discharging device 16. The image forming apparatus main body 12 includes a control unit 18 that controls the entire image forming apparatus 10 and an operation panel (not shown) that displays various information of the image forming apparatus 10 and performs various operations.

  The image forming apparatus main body 12 includes image forming units 20Y, 20M, 20C, and 20K that form toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K). ing. In the following, when it is necessary to distinguish Y, M, C, and K, it is necessary to add Y, M, C, and K letters after the code to distinguish Y, M, C, and K. If there is no such character, the description will be made with the Y, M, C, K alphabets omitted.

  The image forming apparatus main body 12 has an endless intermediate transfer belt 30 stretched by a backup roll 34 and a plurality of stretch rolls 32, and the intermediate transfer belt 30 is moved in the traveling direction (indicated by an arrow B). On the other hand, the image forming units 20Y, 20M, 20C, and 20K are arranged in this order.

  The intermediate transfer belt 30 is disposed so as to face the image carriers (hereinafter also referred to as “photosensitive drums”) 22Y, 22M, 22C, and 22K of the image forming units 20Y, 20M, 20C, and 20K. Are inserted between the primary transfer rolls 36Y, 36M, 36C, and 36K. The intermediate transfer belt 30 is made of polyimide and has a thickness of about 80 μm.

  Next, the configuration of each of the image forming units 20Y, 20M, 20C, and 20K and the image forming operation on the intermediate transfer belt 30 will be described using the image forming unit 20Y that forms a yellow toner image as an example. First, the surface of the photosensitive drum 22Y as an image carrier is uniformly charged by the charger 24Y. Next, image exposure corresponding to the yellow image is performed by the exposure device 25Y, and an electrostatic latent image corresponding to the yellow image is formed on the surface of the photosensitive drum 22Y.

  The electrostatic latent image corresponding to the yellow image is developed by the developing device 26Y to become a yellow toner image. The yellow toner image is transferred onto the intermediate transfer belt 30 by the pressing force of the primary transfer roll 36Y and electrostatic attraction by the transfer bias applied to the primary transfer roll 36Y.

  After the primary transfer, the untransferred residual yellow toner remaining on the photosensitive drum 22Y is scraped off and removed by the cleaning blade 29Y of the photosensitive drum cleaning device 28Y. The surface of the photosensitive drum 22Y is neutralized by a neutralization device (not shown) and then charged again by the charger 24Y for the next image forming cycle.

  Such an image forming process is similarly performed in the other image forming units 20M, 20C, and 20K at a timing that takes into consideration the relative position difference between the image forming units 20Y, 20M, 20C, and 20K. The Y, M, C, and K color toner images are sequentially superimposed on the transfer belt 30 to form a full color toner image.

  The full-color toner image formed on the intermediate transfer belt 30 is pressed against the recording paper P conveyed to the secondary transfer position A at a predetermined timing and the backup roll 34 that supports the intermediate transfer belt 30 and the backup roll 34. The image is transferred by a pressure contact force with the secondary transfer roll 38 and an electrostatic attraction force by a transfer bias applied to the secondary transfer roll 38.

  The recording paper P is accommodated in a paper feed cassette 40 of the paper feed device 14 disposed on the side of the image forming apparatus main body 12. The recording paper P is fed from the paper feed cassette 40 by the paper feed mechanism 42. The recording paper P fed by the paper feed mechanism 42 is sent to the secondary transfer position A at a predetermined timing by a plurality of transport rolls 46 and registration rolls 48 of the transport mechanism 44.

  Then, as described above, the full color toner images are collectively transferred from the intermediate transfer belt 30 to the recording paper P by the backup roll 34 and the secondary transfer roll 38. The recording paper P on which the full color toner image is transferred from the intermediate transfer belt 30 is separated from the intermediate transfer belt 30 and is conveyed to the fixing device 50 by the conveyance belt 31 disposed on the downstream side of the secondary transfer position A. Is done.

  The fixing device 50 includes a heat fixing roll 52 including a heat source such as a halogen lamp inside a metal core having high thermal conductivity. A fixing belt 56 stretched around the fixing belt roll 54 is wrapped around the heat fixing roll 52. Then, the recording paper P having the surface carrying the full-color toner image on the side of the heat-fixing roll 52 is gripped and conveyed by the heat-fixing roll 52 and the fixing belt 56. At this time, the full-color toner image is It is fixed on the recording paper P by pressure.

  Note that a release agent such as silicone oil is applied to the heat fixing roll 52 by a release agent application device 58. Therefore, a so-called offset in which the full color toner image on the recording paper P is transferred to the heat fixing roll 52 is prevented. The recording paper P on which the full color toner image is fixed by the fixing device 50 is sent to the paper discharge device 16. The recording paper P sent to the paper discharge device 16 is discharged to the paper discharge tray 62 via the paper discharge processing device 60.

  On the other hand, the untransferred residual toner on the intermediate transfer belt 30 that has not been transferred to the recording paper P by the backup roll 34 and the secondary transfer roll 38 is scraped and removed by the cleaning blade 65 of the intermediate transfer belt cleaning device 64. Is done.

  The image forming apparatus 10 reverses the recording paper P having a full-color toner image fixed on one side, transports the recording paper P to the secondary transfer position A again, and also intermediates the other side. A new full-color toner image is transferred from the transfer belt 30 (images are formed on both sides of the recording paper P), and a so-called double-sided printing function is provided.

  Specifically, the recording paper P is reversed by the paper discharge processing device 60 so that the other side faces the intermediate transfer belt 30 side, and then conveyed to the conveyance mechanism 44 through the reverse conveyance path 66, and again. The paper is fed to the secondary transfer position A at a predetermined timing by the transport mechanism 44. Then, the recording paper P on which the full color toner image is transferred to the other side is fixed with the full color toner image on the other side by the fixing device 50 in the same manner as described above. 62 is discharged.

  In the image forming apparatus 10 having the above configuration, the drive system (power transmission means) of the image carrier (photosensitive drum) 22 and the developing device 26 will be described next. As shown in FIG. 2, the rotational driving force from the drive motor 70 as a drive source is transmitted to the transmission shaft 86 via the reduction gear train 72. That is, a gear 74 is provided at the tip of the rotation shaft 70 </ b> A of the drive motor 70, and the gear 74 meshes with a gear 76 provided at one end of the rotation shaft 80 </ b> A in the clutch unit 80.

  A gear 78 is provided at the other end of the rotary shaft 80 </ b> A, and a gear 82 is engaged with the gear 78. The gear 82 is provided below a transmission shaft 86 (a transmission shaft 86 to which a flywheel (not shown) is attached) provided in the flywheel portion 84. A driving pulley 88 is fixed to the lower end of the transmission shaft 86, and a timing belt 90 is wound around the driving pulley 88.

  The timing belt 90 is also wound around a driven pulley 92 disposed at a predetermined position. The timing belt 90 includes a pulley 96 that slidably contacts the timing belt 90 from the inner side and a pulley 98 that slidably contacts the outer side. In a state of being bent at approximately 90 degrees in plan view, it is bridged between the driving pulley 88 and the driven pulley 92. A tension pulley 94 is pressed against the timing belt 90 from the outside in the vicinity of the driven pulley 92.

  As shown in FIG. 3, the driven pulley 92 is fixed to one end of the transmission shaft 102, and the coupling 100 is attached to the other end of the transmission shaft 102. A driving shaft 26A of the developing device 26 is attached (held) to the coupling 100, and the developing device 26 is driven.

  The drive shaft 22A of the photosensitive drum 22 is configured to be rotated by a drive motor (not shown) provided in the housing 68 shown in FIG. That is, the rotational driving force by the drive motor is transmitted to the transmission shaft 104 via a reduction gear train and a flywheel portion (not shown), and a coupling 106 is attached to the other end of the transmission shaft 104. A drive shaft 22A of the photosensitive drum 22 is attached (held) to the coupling 106 so that the photosensitive drum 22 is driven.

  Next, the operation of the power transmission means having such a configuration will be described. The rotational driving force from the drive motor 70 is transmitted to the transmission shaft 86 of the flywheel unit 84 through the gears 74, 76, 78, 82 that constitute the reduction gear train 72. A driving pulley 88 is fixed to the transmission shaft 86 of the flywheel portion 84, and a timing belt 90 is wound between the driving pulley 88 and the driven pulley 92.

  Therefore, the rotational driving force transmitted to the drive pulley 88 via the transmission shaft 86 is transmitted to the driven pulley 92 by the timing belt 90 and is transmitted to the transmission shaft 102 to which the driven pulley 92 is fixed. Since the transmission shaft 102 is provided with a coupling 100 that transmits power to the drive shaft 26A of the developing device 26, the rotational unevenness of the drive shaft 26A is reduced by the rotational driving force transmitted to the transmission shaft 102. It can rotate in the state.

  That is, since the rotational driving force from the drive motor 70 can be transmitted to the drive shaft 26A of the developing device 26 via the flywheel portion 84, an inertia effect is given to the drive shaft 26A of the developing device 26. It becomes possible. Therefore, the rotation unevenness in the drive shaft 26A of the developing device 26 can be reduced, and the banding caused by the rotation unevenness can be sufficiently reduced.

  In addition, since the reduction gear train 72 is disposed upstream of the flywheel portion 84 in the transmission direction of the rotational driving force, adverse effects caused by the meshing error generated by the reduction gear train 72 are eliminated. Further, the downstream side of the flywheel portion 84 in the direction of transmission of the rotational driving force is configured to transmit the rotational driving force by the timing belt 90 and the coupling 100, and to transmit the rotational driving force using a gear. Therefore, it is possible to eliminate uneven rotation due to a meshing error when transmission is performed using a gear as in the prior art.

  Further, the clutch portion 80 for turning ON / OFF the power transmission from the drive motor 70 to the drive shaft 26A of the developing device 26 is disposed upstream of the flywheel portion 84 (transmission shaft 86) in the transmission direction of the rotational driving force. Therefore, the adverse effect of the rotation unevenness due to the rattling of the clutch unit 80 can be attenuated by the flywheel unit 84. Therefore, even in the drive system in which the clutch unit 80 is provided, the banding generated due to uneven rotation of the drive shaft 26A of the developing device 26 can be sufficiently reduced.

  As described above, in the conventional image forming apparatus, it is difficult to dispose the flywheel (providing the inertia effect) with respect to the drive shaft 26A of the developing device 26, but according to the present invention. According to the image forming apparatus 10, an inertia effect can be imparted to the drive shaft 26 </ b> A of the developing device 26. Therefore, the rotation unevenness in the drive shaft 26A can be reduced. The flywheel is preferably made of a metal such as SUS.

  The image forming apparatus 10 according to the present invention is not limited to the above-described embodiment. In the above embodiment, the image forming apparatus 10 using four color toners of Y, M, C, and K has been described as an example. However, the image forming apparatus 10 is not limited to four colors, and other colors such as light magenta are used. It can also be applied to an image forming apparatus having five or more colors added. Also, the present invention can be applied to an image forming apparatus having three colors or less.

1 is a schematic configuration diagram schematically showing an image forming apparatus according to the present invention. Schematic perspective view showing drive system of developing device and photosensitive drum Schematic perspective view showing drive system of developing device and photosensitive drum

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 20 Image forming unit 22 Photosensitive drum (image carrier)
22A Drive shaft 26 Development device (developer)
26A Drive shaft 70 Drive motor (drive source)
72 Reduction gear train 80 Clutch part 84 Flywheel part 86 Transmission shaft (first transmission shaft)
88 Driving pulley 90 Timing belt 92 Driven pulley 94 Tension pulley 100 Coupling 102 Transmission shaft (second transmission shaft)

Claims (1)

A reduction gear train disposed downstream of the drive source in the direction of power transmission, to which power is transmitted from the drive source;
A first transmission shaft that is disposed downstream of the reduction gear train in the power transmission direction, transmits power from the reduction gear train, and has a flywheel attached thereto ;
A clutch disposed upstream of the first transmission shaft in the power transmission direction and configured to turn on / off power transmission from the drive source to the first transmission shaft;
A drive pulley fixed to the first transmission shaft;
A driven pulley in which power is transmitted from the driving pulley via a timing belt without using a gear train ;
A second transmission shaft to which the driven pulley is fixed;
A coupling provided on the second transmission shaft for transmitting power to the drive shaft of the developing device ;
An image forming apparatus comprising:

Images