JP2007232968A - Drive device for image carrier or the like - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive device suitable for driving the image carrier of an image forming apparatus such as a copying machine, a printer, and a facsimile machine, in which nonuniform drive is eliminated and drive torque for the image carrier is reduced. <P>SOLUTION: The drive device includes a first drive system X that rotates an image carrier at a speed substantially equal to the set speed of the image carrier, and a second drive system Y that rotates the image carrier at a speed higher than the driving speed of the driving speed of the first driving system. The first drive system is provided with a transmission device 20 that includes a traction mechanism. The second drive system drives the image carrier via frictional force. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a driving device suitable for use in an image forming apparatus such as a copying machine to drive a photosensitive drum or the like as an image carrier.

  In an image forming apparatus such as an electrophotographic copying machine, a printer, or a facsimile, a toner image formed on a photosensitive drum as an image carrier is transferred to a recording paper as a transfer material (recording medium), and It is fixed on the recording paper by applying heat and pressure.

In this type of image forming apparatus, printing apparatus, and the like, a photosensitive drum that forms a latent image, an intermediate transfer belt that transfers an image on the photosensitive drum, and a sheet that is conveyed and conveyed while contacting the photosensitive drum. An image carrier such as a transfer conveyance belt for transferring the image is provided. These image carriers need to be driven so as not to cause unevenness in speed in order to obtain high image quality. For this reason, in the conventional apparatus, as a means for reducing drive fluctuations that cause rotation unevenness, a traction mechanism that is transmitted by frictional force is used to separate the drive system or eliminate unevenness that occurs due to gear meshing. Drive system is adopted. Examples of this type of driving device include those disclosed in Patent Documents 1 and 2 below.
JP 09-146325 A JP 2002-115751 A

  On the other hand, since the traction mechanism uses frictional force, there is a limit to the transmission torque, and if a motor equipped with a reduction device based on the traction mechanism is employed to eliminate uneven rotation of the image carrier, the torque is insufficient. There is a problem. In addition, if a planetary gear type reduction gear is used to obtain high torque by using an elastic member such as rubber on the planetary roller for cost reduction, the roller will wrinkle when it stops, causing uneven rotation. There is a problem of becoming.

  Such a problem can be solved at once by reducing the torque of the drive system of the image carrier and interposing the traction mechanism in the transmission path. However, in the conventional traction mechanism, None of them considered reducing the driving torque.

  Accordingly, the present invention is a driving device suitable for driving an image carrier of an image forming apparatus, and reduces driving torque by reducing the driving torque of the traction mechanism while adopting the traction mechanism, thereby reducing costs. It aims at providing the device which can also plan.

  In order to solve the above problems, the present invention employs the following configuration. That is, the drive device of the first aspect of the present invention is a drive device that drives the image carrier of the image forming apparatus, and includes a traction reduction mechanism, and applies a drive force at a speed substantially equal to the rotational speed of the image carrier. A first drive system for transmitting to the image carrier and a second drive system for transmitting a driving force higher than the drive speed of the first drive system to the image carrier; It is characterized in that the image carrier is driven by the cooperation of two drive systems.

  According to a second aspect of the present invention, in the drive device according to the first aspect of the present invention, the first drive system and the second drive system are configured to be driven by separate drive sources. It is said.

  Furthermore, a third aspect of the present invention is the drive apparatus according to the first aspect of the present invention, wherein the first drive system and the second drive system are configured to be driven by a common drive source. It is a feature.

  Furthermore, a fourth aspect of the present invention is the driving apparatus according to the third aspect of the present invention, wherein the image carrier obtains a driving force from the driving source via the first driving system and the second driving. A driving force is obtained from the driving source via a system.

  According to a fifth aspect of the present invention, in the driving device according to any one of the first to fourth aspects, the second driving system transmits a driving force to the image carrier via a gear train. It has been done.

  According to a sixth aspect of the present invention, in the drive device according to any one of the first to fourth aspects of the present invention, the second drive system is interposed via a rubbing roller that rotates in contact with the outer peripheral surface of the image carrier. The image carrier is configured to be driven.

  According to a seventh aspect of the present invention, in the drive device according to any one of the first to fourth aspects, the second drive system is connected to an output shaft of the first drive system via a gear train and a torque limiter. It is configured to transmit.

  According to the present invention, while adopting a traction mechanism, by reducing the driving torque of the traction mechanism, a drive device suitable for driving an image carrier of an image forming apparatus that eliminates drive unevenness and reduces costs can be realized. can do.

  Hereinafter, an embodiment of an image forming apparatus provided with a driving device according to the present invention will be specifically described. FIG. 1 illustrates a configuration of a copying machine as an example of an image forming apparatus. The image forming apparatus 1 includes a photosensitive drum 2 that is an image carrier, and a transfer belt 3 that conveys a recording paper (transfer material) S is provided below the photosensitive drum 2. The photosensitive drum 2 is a drum having a surface of a metal drum coated with a photosensitive layer. For example, the photosensitive drum 2 is an 80 mm diameter drum using an a-Si photosensitive member, and rotates in the direction of arrow A in the figure.

  A main charger 4 for uniformly charging the surface of the photosensitive drum 2, a laser irradiation device 5 for irradiating a photosensitive laser beam, and a developing device 7 are rotated in the outer peripheral portion of the photosensitive drum 2. Are arranged in order. A static eliminator 10 for the photosensitive drum 2 is located downstream of the position (transfer portion) T where the photosensitive drum 2 and the recording paper S conveyed by the transfer belt 3 are in contact with each other in the rotational direction of the photosensitive drum 2. Is provided.

  The laser irradiation device 5 includes a laser emission unit (not shown) and an optical device such as a mirror and a lens. Laser light is applied to the surface of the photosensitive drum 2 in accordance with an image signal from a CCD camera (not shown in FIG. 1). To form an electrostatic latent image on the surface of the photosensitive drum.

  The developing device 7 is for attaching toner to a latent image formed on the surface of the photosensitive drum 2 to form a toner image. The developing device 7 supplies an appropriate amount of toner in the toner container to the surface of the photosensitive drum. Is attached only to the charged portion of the surface of the photosensitive drum 2.

  The transfer belt 3 is an endless belt stretched between the driving roller 12 and the driven roller 13, and includes a NBR base material controlled in resistance to improve the recording paper adsorbability on the surface and the toner on the surface. In order to ensure releasability, a PTFE coating dispersed in a high-resistance urethane binder is applied.

  The driving roller 12 and the driven roller 13 are supported in parallel with each other in rotation axis and in parallel with the axis of the photosensitive drum 2. When the drive roller 12 is driven to rotate, the transfer belt 3 circulates in a predetermined direction (in the direction of arrow B in the figure) at a predetermined speed. The rotational speed (peripheral speed V2) of the photosensitive drum 2, the rotational speed (peripheral speed V12) of the drive roller 12, the moving speed (V3) of the transfer belt 3, and the transfer material S held on the transfer belt 3 by suction. Are designed to be equal to each other (V2 = V12 = V3 = Vs). In addition to the driving roller 12 and the driven roller 13, a belt cleaner for removing excess toner adhering to the transfer belt 3 is provided downstream of the driving roller 12 in the belt moving direction. In addition, a belt charger for charging the belt and electrostatically adsorbing the recording paper S is provided on the upstream side of the transfer portion T of the transfer belt 3 in the moving direction, and is driven downstream of the transfer position. In front of the roller 12, a static eliminator is provided for removing the charging of the transfer belt.

  A bias applying transfer roller 15 is provided at a position facing the photosensitive drum 2 with the transfer belt 3 interposed therebetween. The transfer roller applies a charge having a polarity opposite to that of the toner on the surface of the photosensitive drum 2 to the transfer belt 3, and causes the toner image on the photosensitive drum 2 to be transferred to the recording paper S on the surface of the transfer belt 3 by this charge. Thus, a high voltage is applied from the high voltage power source 16 and the spring 17 is pressed against the back surface of the transfer belt 3.

  The image forming apparatus 1 is provided with two drive systems, a first drive system X and a second drive system Y, for driving the photosensitive drum 2. FIG. 2 shows these drive systems. As shown in FIG. 2, a first drive motor 18 and a second drive motor 19 are provided as power sources for driving the respective drive systems. . The first drive motor 18 for driving the first drive system X is configured as a traction motor, and is output from the output shaft 22 via a reduction device 20 of a traction mechanism that transmits using frictional force. The photosensitive drum 2 is driven to rotate through the coupling 23. The reduction device 20 of the traction mechanism is a planetary gear type reduction device, and the rotation shaft of the drive motor 18 is a sun gear. The planetary gear decelerates the rotational power due to the frictional force of the rollers provided on the outer periphery of the planetary gear and transmits it to the output shaft 22. In the present embodiment, it is assumed that the first drive motor 18 is not included in the first drive system X.

  On the other hand, the second drive system Y passes from the drive shaft 25, which is the output shaft of the second drive motor 19 as a power source, through the gear train of the drive gear 26 and the intermediate gears 27, 28, via the coupling 29. The rubbing roller 30 is rotationally driven. The rubbing roller 30 has the same length as that of the photosensitive drum 2, and rotates while being in pressure contact with the outer peripheral portion of the photosensitive drum 2. The rubbing roller 30 also serves as a cleaner that removes toner remaining on the surface of the photosensitive drum 2. As shown in FIG. 1, a screw 32 is provided adjacent to the rubbing roller 30 to discharge the toner removed by the rubbing roller 30 to the outside. Reference numeral 34 in the drawing denotes a blade that scrapes off foreign matters such as toner from the surface of the photosensitive drum 2. In the present embodiment, it is assumed that the second drive motor 19 is not included in the second drive system Y.

  The first drive system X drives the photosensitive drum 2 at a set speed (process speed), but the rubbing roller 30 of the second drive system Y is driven by the rotational speed (circumferential speed) of the photosensitive drum 2. Is designed to rotate at a slightly higher speed (peripheral speed). The peripheral speed ratio of the rubbing roller 30 to the photosensitive drum 2 is preferably about 1.15 to 1.25, and it is most effective to be 1.2 in the experimental results. If this peripheral speed ratio is made too large, slip becomes large and an unreasonable force acts on the drive system, and problems such as early wear occur, which is not preferable. Further, if the peripheral speed ratio is reduced, a sufficient rubbing effect cannot be obtained.

  In this driving apparatus, the photosensitive drum 2 as an image carrier is rotationally driven by the cooperation of the first driving system X and the second driving system Y. In the first drive system X, the rotational force of the first drive motor 18 is decelerated by the traction type reduction device 20 to drive the photosensitive drum 2. Further, in the second drive system Y, the rotational force of the second drive motor 19 is transmitted to the rubbing roller 30 via the gear train, and the rubbing friction that is in press contact with the outer peripheral surface of the photosensitive drum 2 is performed. A rotational force is transmitted to the photosensitive drum 2 by the frictional force of the roller 30.

  In this case, since the rotational speed of the rubbing roller 30 is slightly higher than the rotational speed of the photosensitive drum 2, the photosensitive drum 2 is driven to rotate while a slight slip occurs between them, and the outer periphery of the photosensitive drum 2 is also rotated. Toner etc. adhering to the surface is removed. In this way, in addition to the first drive system X which is the original drive system, a second drive system Y is separately provided and the photosensitive drum 2 is rotationally driven in an auxiliary manner. Thus, the torque of the traction reduction device 20 can be reduced.

  In addition, the second drive system Y uses a gear train to reduce the rotational speed of the second drive motor 19 without using a traction reduction mechanism, so that a large traction motor is used as the second drive motor 19. This is advantageous in terms of cost.

  Next, FIG. 3 shows an embodiment slightly different from FIG. 2. In this embodiment, the second drive system Y is not provided with a drive motor 19 as a power source, and the drive of the first drive system X is performed. The rotational power of the motor 18 is branched and transmitted to the second drive system Y. In other words, the pulley 40 is provided on the rotating shaft of the first drive motor 18, and transmission is transmitted from the pulley 40 to the pulley 41 attached to the drive shaft 25 of the second drive system Y via the belt 42. Other parts are the same as those in the above embodiment, and the same parts are denoted by the same symbols. This embodiment is economical because it does not require a separate drive motor.

  FIG. 4 shows still another embodiment, in which the rotational power of the second drive motor 19 passes through the meshing of the gears 26, 27, 45, 46, 47 and the output shaft of the first drive system X. 22 is transmitted. In this embodiment, the last gear 47 of the gear train is attached to the drive side of the torque limiter 50. The driven side of the torque limiter 50 is attached to the output shaft 22 of the first drive system X, and the driving force of the second drive system Y is transmitted through the torque limiter 50 by friction. Yes. Although the second drive system Y is transmitted by a gear train, since a frictional torque limiter 50 is interposed, a smooth and stable driving force is transmitted to the photosensitive drum 2.

  Although the rubbing roller 30 is also provided in the embodiment of FIG. 4, the rubbing roller only needs to exhibit the function as an original cleaner, and therefore has a peripheral speed faster than the peripheral speed of the photosensitive drum 2. It is not necessary to rotate, and for example, it may be rotated at a speed of about 0.8 times the peripheral speed of the photosensitive drum 2. In some cases, the rubbing roller 30 can be omitted. Further, the motor 19 is not provided, and the pulley 41 and the belt 42 shown in FIG. 3 are provided, and the rotational power of the drive motor 18 of the first drive system X is branched and transmitted to the second drive system Y. It may be.

  Next, the operation of the image forming apparatus 1 will be described. The image forming apparatus 1 is uniformly charged on the surface of the photosensitive drum 2 by the main charger 4 while being driven so that the peripheral speed of the photosensitive drum 2 and the moving speed of the transfer belt 3 are the same. . The laser irradiation device 5 scans the surface of the photosensitive drum with laser light that is turned on and off so as to correspond to a predetermined image, and forms a latent image in a charged state corresponding to the image signal on the surface of the photosensitive drum.

  The portion where the latent image is formed reaches the position of the developing device 7 along with the rotation of the photosensitive drum 2, where toner is supplied to the entire surface, but this toner is electrostatically applied to the surface of the photosensitive drum in the charged portion. It adheres and does not adhere on uncharged parts.

  On the other hand, the recording sheet S as a transfer material is supplied onto the transfer belt 3 so as to be synchronized with the above operation. This recording paper S is fed in synchronization with the rotation of the photosensitive drum 2 in a state of being electrostatically adsorbed to the transfer belt 3 charged by the belt charger so that the toner image is transferred onto the recording paper S. . At the transfer portion T sandwiched between the photosensitive drum 2 and the transfer belt 3, the toner image is transferred to a predetermined location on the recording paper S. In this transfer portion T, since the reverse polarity charge is applied by the bias applying transfer roller 15, the toner image on the photosensitive drum 2 is transferred from the surface of the photosensitive drum 2 to the surface of the recording paper S. It is.

  The recording sheet S to which the image has been transferred is sent as it is in the direction of arrow B by the transfer belt 3, but the transfer belt 3 is discharged by the charge eliminator before the drive roller 12, so that the recording sheet S is adsorbed to the transfer belt 3. The transfer belt 3 is separated from the transfer belt 3 at a separation position where the transfer belt 3 changes its moving direction downward. The recording paper S separated from the transfer belt 3 is sent to a fixing device (not shown), and the image is fixed on the recording paper by heating and pressing.

  The driving device that drives the photosensitive drum 2 that is the image carrier of the image forming apparatus includes the second driving system that drives the photosensitive drum 2 in addition to the first driving system X that is the original driving system. Since the drive system Y is provided, the torque of the traction reduction device 20 of the first drive system X can be reduced. For this reason, since not a metal but an inexpensive material such as rubber can be used as the planetary roller of the speed reduction mechanism, the cost can be reduced. Further, since the power is transmitted by the frictional force, uniform transmission can be performed and uneven rotation of the photosensitive drum 2 can be suppressed as much as possible. As a result, a high quality image can be obtained.

  The torque of the photosensitive drum was measured using the apparatus shown in FIG. The peripheral speed ratio of the rubbing roller 30 was 1.2, and the torque was 0.196 N · m (2 kgf · cm). Further, the use torque (Max) of the traction motor was 0.421 N · m (4.3 kgf · cm). However, the roller inside the traction reduction gear 20 used a metal roller. When the peripheral speed ratio of the rubbing roller 30 was 0.8, the torque was 0.294 N · m (3 kgf · cm).

  A state in which the second drive system Y is provided to reduce the torque of the traction motor is as shown in FIG. A graph indicated by a broken line in FIG. 5 represents the conventional torque, and a solid line graph represents the torque according to the present invention. That is, according to the present invention, the torque can be reduced by the amount indicated by A in the figure from the conventional torque, and the entire torque is within the range of B.

  Further, by transmitting the driving force via the torque limiter 50 shown in FIG. 4, the torque can be reduced by the amount indicated by D in the figure, and the entire torque is within the range of C.

  FIG. 6 shows the relationship between the speed ratio of the rubbing roller 30, the wear amount of the rubbing roller 30, and the driving torque of the photosensitive drum 2 in the configuration of FIG. 2. As can be seen from the figure, in order to reduce the torque of the photosensitive drum 2, the speed ratio needs to be 1.1 or more, but considering the wear amount of the rubbing roller 30, the speed ratio is 1. It is considered preferable to set it to 3 or less.

  In addition, the substantially equal speed of the present invention is a speed that is considered to be equal for social reasons.

  The drive device according to the present invention can be effectively used as a drive device for an image carrier for an image forming apparatus such as an electrophotographic copying machine, a printer, or a facsimile.

1 is a front view schematically showing an outline of an image forming apparatus. It is a top view which represents typically the structure of a drive device. It is a top view showing different embodiment. It is a top view showing different embodiment. It is a figure which shows the graph showing the drive torque of a photoconductor drum. It is a figure which shows the graph showing the relationship between speed ratio, the abrasion amount of a rubbing roller, and the drive traction of a photosensitive drum.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum (image carrier)
DESCRIPTION OF SYMBOLS 3 Transfer belt 4 Main charger 5 Laser irradiation apparatus 7 Developing apparatus 12 Drive roller 13 Drive roller 15 Bias application transfer roller 18 First drive motor 19 Second drive motor 20 Traction reduction device 22 Output shaft 25 Drive shaft 30 Sliding Friction roller 40 Pulley 41 Belt 42 Pulley 50 Torque limiter X First drive system Y Second drive system

Claims (7)

  A driving device that rotationally drives an image carrier of an image forming apparatus, and includes a traction deceleration mechanism, and transmits a driving force having a speed substantially equal to a set speed of the image carrier to the image carrier. And a second drive system that transmits a driving force higher than the drive speed of the first drive system to the image carrier, and the image carrier is supported by the cooperation of the first and second drive systems. An apparatus for driving an image carrier, wherein the apparatus is configured to drive the body.   The image carrier driving apparatus according to claim 1, wherein the first driving system and the second driving system are configured to be driven by separate driving sources.   The image carrier driving apparatus according to claim 1, wherein the first driving system and the second driving system are configured to be driven by a common driving source.   The image carrier according to claim 3, wherein the image carrier obtains a driving force from the driving source via the first driving system and obtains a driving force from the driving source via the second driving system. Body drive device.   5. The image carrier driving apparatus according to claim 1, wherein the second driving system transmits a driving force to the image carrier through a gear train. 6.   The second drive system includes a rubbing roller that rotates in contact with an outer peripheral surface of the image carrier, and drives the image carrier through the rubbing roller. The image carrier driving apparatus according to the description.   5. The image carrier driving apparatus according to claim 1, wherein the second drive system is transmitted to an output shaft of the first drive system via a gear train and a torque limiter.

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