JP2005215126A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of canceling image distortion and color shifts regardless of the degrees of the rotational angle of a photoreceptor drum from exposure to transfer. <P>SOLUTION: In the image forming apparatus, a latent image formed at an exposure position on the photoreceptor drum rotated by receiving driving transmitted from a driving source through a gear train is developed to a visible image by a developing device, and the visible image is transferred to a transfer material carried to a transfer position. The apparatus has the gear train 18a, 18b, 17a, 17b, 16, 15 and 14 where a plurality of gears are meshed successively in order to transmit driving force from a motor 12 to drum gears 11Y, 11M, 11C and 11K provided coaxially to the rotary shaft of the photoreceptor drum, and the respective gears 18a, 18b, 17a, 17b, 16, 15 and 14 constituting the gear train are respectively rotated by integral times while the photoreceptor drum is rotated from the exposure position to the transfer position. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus, and more specifically, a latent image formed at an exposure position on an image carrier rotated by driving transmission from a driving source via a gear train is made a visible image by a developing device, The present invention relates to an image forming apparatus that transfers a visible image onto a transfer material conveyed to a transfer position.

  In the conventional technology, in order to eliminate color misregistration in the image forming apparatus, the drive from the motor is transmitted by a gear train, the drive is transmitted between the pulleys using a timing belt, and the gear for driving the drum is transferred from exposure to transfer. Some pulleys are configured to rotate an integer number of times.

  For example, a latent image is formed immediately above a rotating cylindrical photosensitive drum, developed while the photosensitive drum is half-rotated to form a visible image, and the visible image is transferred to a transfer material conveyed directly under the photosensitive drum. In transferring the toner, there is one in which the photosensitive drum rotates 180 degrees when the pulley rotates an integer (see Patent Document 1).

  In this way, even if there is rotation unevenness in the drive system, the effect of rotation unevenness is absorbed between the image formation on the photosensitive drum and the image transfer to the transfer material, and an image that does not cause image distortion or the like is obtained. Can do.

Japanese Patent Laid-Open No. 7-140732

  In recent years, not only monochrome images but also color images have been required to have higher image quality. When a belt is used as the means for driving the image carrier, it is necessary to consider the speed unevenness due to the expansion and contraction of the belt when transmitting the drive. For this reason, using a belt with less expansion and contraction causes a high cost. End up.

  Further, in the case of an image forming apparatus using a photosensitive drum, the degree of freedom in design is reduced in consideration of exposure reflection prevention and process factors in order to make the rotation angle of the image carrier from exposure to transfer exactly 180 degrees. End up.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an image forming apparatus capable of canceling image distortion and color misregistration regardless of the rotation angle of the image carrier from exposure to transfer. To do.

  A typical means in the present invention for solving the above-described problem is that a latent image formed at an exposure position on a rotating image carrier is transmitted by a drive source via a gear train from a drive source to be a visible image by a developing device. In the image forming apparatus for transferring the visible image to the transfer material conveyed to the transfer position, a plurality of driving forces are transmitted from the driving source to the image carrier gear provided coaxially with the rotation shaft of the image carrier. Each gear constituting the gear train rotates an integer number while the image carrier rotates from the exposure position to the transfer position.

  According to the present invention, even if the angle at which the image carrier rotates from the exposure position to the transfer position is not 180 degrees, the front gear that meshes with the image carrier gear that drives the image carrier between exposure and transfer. Since it rotates an integer number of times, even if there is rotation unevenness in the previous gear, rotation unevenness at the time of exposure and transfer appears in the same way, so that no image distortion or color shift appears in the image on the transfer material.

  Next, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the drawings. 1 is an explanatory view showing a drive gear train of the image forming apparatus, FIG. 2 is a schematic explanatory view of the configuration of the image forming apparatus, and FIG. 3 is a perspective explanatory view showing a photosensitive drum and a conveying belt in the image forming apparatus. FIG. 4 is an explanatory diagram showing exposure and transfer positions on the photosensitive drum.

{Overall configuration of image forming apparatus}
First, the overall configuration of the image forming apparatus will be schematically described with reference to FIGS. Transfer materials are stored in a feeding tray 1 loaded in the lower part of the apparatus main body, and the transfer materials are separated and fed one by one by a feeding roller 2. The fed transfer material is adsorbed by an endless conveying belt 4 suspended from a driving roller 3a and a driven roller 3b, and is conveyed upward as the conveying belt 4 rotates.

  On the other hand, four process cartridges 5Y, 5M, 5C, and 5K serving as image forming means for forming each color image of yellow (Y), magenta (M), cyan (C), and black (K) are provided on the conveying belt 4. Arranged along the direction of rotation. The process cartridges 5Y, 5M, 5C, and 5K are provided so that the photosensitive drums 6Y, 6M, 6C, and 6K as image carriers can be rotated by receiving drive transmission from a motor that is a drive source provided in the apparatus main body. In addition, process means such as charging means and developing means are disposed around the photosensitive drums 6Y, 6M, 6C, and 6K. When forming an image, the surface of the rotating photosensitive drums 6Y, 6M, 6C, and 6K is selectively exposed from the exposure unit to form an electrostatic latent image, and the latent image is developed with toner by a developing unit (not shown). To make a visible image. Then, the toner image is transferred to a transfer material conveyed by the conveying belt 4 as the photosensitive drum rotates, thereby forming an image. Further, the transfer material onto which the toner image has been transferred is conveyed to the fixing means 7 to fix the toner image by applying heat and pressure, and then discharged by a discharge roller 8 to a discharge portion 9 at the top of the apparatus. .

{Driving force transmission configuration}
As shown in FIG. 4, the image forming apparatus of the present embodiment rotates the photosensitive drum in the direction of the arrow from the exposure position where the laser beam 10 from the scanner is incident on the photosensitive drum 8d, thereby generating a toner image. The drum rotation angle θ up to the transfer position for transfer to the transfer material is set to 194 degrees. In this type of image forming apparatus, the rotation angle of the drum from the exposure position to the transfer position is not exactly 180 degrees but a little shifted due to prevention of reflection of incident light, arrangement of exposure means, process factors, etc. Often has become.

  In order to transfer a high-quality image without distortion or color misregistration on the transfer material, the photosensitive drum is not affected by rotational irregularities when the toner image is transferred from the exposure position to the transfer position. Must be. In the present embodiment, the drive transmission to the photosensitive drums 6Y, 6M, 6C, and 6K is configured as follows, so that the influence of the rotation unevenness due to the drive transmission is canceled.

  In this embodiment, the four photosensitive drums 6Y, 6M, 6C, and 6K, the driving roller 3a that drives the conveyance belt, and the developing roller in the developing unit (not shown) are driven by a motor that is one driving source. Yes. As shown in FIG. 1, the driving force is transmitted from the motor to the photosensitive drums 6Y, 6M, 6C, and 6K by a gear train.

  That is, drum gears 11Y, 11M, 11C, and 11K as image carrier gears are fixed to one end portion of the rotation shaft of each of the photosensitive drums 6Y, 6M, 6C, and 6K. The drum gears 11Y, 11M, and 11C are fixed. , 11K, the driving force from the motor 12 is transmitted to rotate the photosensitive drums 6Y, 6M, 6C, 6K.

  The gear train in this embodiment is attached to the right side from the front of the main body as shown in FIG. That is, the motor 12 is attached to the side plate 13 for fixing the rotation shaft of the gear, the driving force from the pinion gear 14 fixed to the motor shaft is transmitted to the adjacent meshing gear 15, and the gear 15 is a step gear. The drive is transmitted to 16 large gears. On the other hand, the small gear portion of the step gear 16 meshes with the gears 17a and 17b having the same number of teeth to transmit driving. The gear 17a transmits the drive to the drum front gear 18a that is the front gear that meshes with the drum gears 11C and 11K, and the gear 17b similarly transmits the drive to the drum front gear 18b that is the front gear that meshes with the drum gears 11Y and 11M. . Thus, the driving force from the motor 12, which is a driving source, is transmitted to the drum gears 11Y, 11M, 11C, and 11K through the gear train, and the four photosensitive drums 6Y, 6M, 6C, and 6K are driven to rotate.

  Here, the rotation of the photosensitive drum and the rotation of the gear train will be described. Here, the drive transmission to the photosensitive drum 6K will be described as an example, but the drive transmission from the gear train to the four photosensitive drums 6Y, 6M, 6C, and 6K is similarly performed.

  As described above, in the image forming apparatus of this embodiment, the drum rotation angle from exposure to transfer is set to 194 degrees. The gear ratio is determined so that the front gear 5a meshing with the drum gear 11K rotates an integer number of times while the photosensitive drum 6K and the drum gear 11K rotate. That is, if the drum rotation angle from the exposure position to the transfer position to the photosensitive drum 6K is θ ° and the number of teeth of the drum gear 11K is Z1, the number of teeth Z2 when the front gear 5a rotates n times is Z2 = Z1 × (θ / 360n).

  In this embodiment, since the number of teeth of the drum gear 11K is 98 and the drum rotation angle θ between exposure and transfer is 194 degrees, the number of teeth Z2 of the front gear 5a is Z2 = 98 × (194/360) = 52.81. Thus, when the number of teeth is 53, the front gear 5a rotates once.

  Further, all the gear trains from the front gears 18a and 18d to the pinion gear 14 of the drive source are assembled at an integer ratio, and the gear trains 17a, 17b, 16, 15, and 14 up to the motor 12 are rotated while the front gear 18a rotates once. By combining the gears so that they rotate an integer number of times, it is possible to cancel the rotation unevenness of the drive system from the pinion gear 14 to the preceding gears 18a and 18d.

  In this embodiment, the gear ratio of the gears 17a and 17b meshing with the front gears 18a and 18d is 1: 1, and the gear ratio of the gears 17a and 17b and the small gear portion of the gear 16 is 3: 1. The gear ratio between the large gear portion of the step gear 16 and the gear 15 is 1: 1, and the gear ratio between the gear 15 and the pinion gear 14 is 9: 1. As a result, the gear ratio between the front-stage gears 18a and 18d and the pinion gear 14 is 27 to 1, and while the photosensitive drums 6Y, 6M, 6C, and 6K are rotated from the exposure position to the transfer position, the front-stage gears 18a and 18d to the pinion gear. All gears up to 14 rotate an integer number of times. For this reason, even if rotation unevenness occurs in the front gears 18a and 18d due to the rotation unevenness of the motor 12 or other gear accuracy, the rotation unevenness at the time of exposure and transfer is the same, so color misregistration on the transfer material is cancelled. And high-quality images can be obtained.

  As described above, when the drum rotation angle from the exposure position of the photosensitive drum to the transfer position is not 180 degrees, the gear train in which the gears after the preceding gear rotate an integer number of times while the photosensitive drum rotates at that angle. By assembling, it is possible to obtain a high-quality image by canceling color misregistration of an image transferred to a transfer material while simplifying the structure by increasing the degree of freedom of design when assembling subsequent gear trains. Further, it is not necessary to consider the elongation of the belt as in the case of using a timing belt.

  In addition, since the front gear that meshes with the drum gear that rotates integrally with the photosensitive drum is a step gear, even if one gear portion of the step gear is determined by the number of teeth of the drum gear, The number of teeth can be set freely. For this reason, it becomes easy to set all the gear trains to the drive source to integer rotations, and the drive train structure can be simplified.

It is explanatory drawing showing the drive gear train of an image forming apparatus. 1 is a schematic explanatory diagram of a configuration of an image forming apparatus. 2 is a perspective explanatory view showing a photosensitive drum and a conveyance belt in the image forming apparatus. FIG. It is explanatory drawing showing the exposure and transfer position on a photoconductive drum.

Explanation of symbols

5Y, 5M, 5C, 5K ... Process cartridge 6Y, 6M, 6C, 6K ... Photoconductor drum
10… Laser light
11Y, 11M, 11C, 11K ... drum gear
12 ... Motor
14… pinion gear
15… Gear
16 ... Step gear
17a, 17b ... Gear
18a, 18d ... Drum front gear

Claims (4)

The latent image formed at the exposure position on the rotating image carrier that is driven and transmitted through the gear train from the drive source is converted into a visible image by the developing device, and the visible image is transferred to the transfer material conveyed to the transfer position. In the image forming apparatus,
A gear train in which a plurality of gears are sequentially meshed in order to transmit a driving force from a driving source to an image carrier gear provided coaxially with the rotation axis of the image carrier;
Each of the gears constituting the gear train rotates an integer number while the image carrier rotates from the exposure position to the transfer position. 2. The image forming apparatus according to claim 1, wherein a rotation angle at which the image carrier rotates from the exposure position to the transfer position is not 180 degrees. 3. The image forming apparatus according to claim 1, wherein the front gear that meshes with the image carrier gear is formed of a step gear having a first gear portion and a second gear portion that rotate coaxially. 4. . The image carrier is arranged in a plurality along the transfer direction of the transfer material, and a driving force is transmitted to each image carrier from the single drive source via the gear train. Item 4. The image forming apparatus according to Item 3.

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