JP4820141B2 - Image carrier driving apparatus and image forming apparatus - Google Patents

Description

The present invention relates to an image bearing member driving instrumentation 置及 beauty image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus using an optical writing method using the principle of electrophotography has been known as a digital copying apparatus, an optical printer, an optical plotter, a facsimile apparatus, or the like. Although these image forming apparatuses are also progressing in “colorization of formed images”, there is a strong demand for image forming speed, and “tandem-type image forming apparatuses capable of forming color images as fast as monochrome image formation” Is intended to be realized.

  In the tandem type image forming apparatus, electrostatic latent images are formed on a plurality of latent image carriers by optical writing, and each electrostatic latent image is developed with a different color toner image, and each latent image carrier has a different color. A toner image is formed, and the plurality of toner images are transferred onto a common sheet-like recording medium so as to overlap each other to be a color image or a multicolor image. For this reason, in the tandem type image forming apparatus, whether or not the plurality of toner images transferred to the same sheet-like recording medium overlap with each other greatly affects the image quality of the formed image.

  In order to perform such overlapping of toner images with high accuracy, how to accurately perform “resist alignment” that aligns the leading end portions of the toner images with each other becomes a major issue. In a tandem type image forming apparatus, the optical system for performing optical writing, the latent image carrier, and the transfer unit for transferring the toner image are separate from each other. There are many factors that cause “deviation” between toner images, such as the distance to the image. Such misregistration between a plurality of toner images is called “registration misregistration”.

  Moreover, even if the apparatus is completely adjusted to achieve zero registration deviation, changes in the optical characteristics of the resin lens due to temperature changes and expansion / contraction of the latent image carrier are inevitable. Causes “registration misregistration between toner images”.

  As a method of reducing “registration misalignment”, conventionally, “registration alignment marks” are written on each latent image carrier as electrostatic latent images, and toner images that visualize these electrostatic latent images are transferred onto a transfer belt. Then, the positional relationship between the mark images is optically read, and the optical writing start timing is controlled based on the read result. In this case, an optical writing means for deflecting the light beam by the rotating polygon mirror is provided for each latent image carrier, and the phase of rotation of the rotating polygon mirror corresponding to each latent image carrier is controlled to thereby control each latent image carrier. It has also been proposed to perform resist registration with high accuracy by controlling the start timing of optical writing with high accuracy.

  However, since the rotation of the rotary polygon mirror is extremely high speed, it is not easy to control the phase of the rotation, and an expensive control device is required, which tends to increase costs. On the other hand, a tandem-type image forming apparatus of a type in which a rotating polygon mirror is used in common for a light beam that optically scans a plurality of latent image carriers has also been proposed. The phase of rotation cannot be controlled corresponding to each latent image carrier, and there is a limit to the effect of reducing registration.

  Therefore, what is disclosed in Japanese Patent Application Laid-Open No. 2004-198630 is a technique for controlling the linear velocity of the image carrier to reduce registration deviation.

  In addition, when the period variation of the drive unit of each image carrier is performed by a technique (Japanese Patent Laid-Open No. 2000-187428) that performs phase alignment by controlling the stop position, the linear velocity of the image carrier is varied. In this case, when the number of continuous sheets increases, the stop operation is not performed, so that it becomes difficult to maintain the phase relation of each image carrier.

JP 2004-198630 A JP 2000-187428 A

  The present invention corrects the registration error by adjusting the rotation speed of the image carrier, and can eliminate the phase error during continuous paper feeding in the state where the phase adjustment between each color is performed. An object of the present invention is to provide an image carrier driving apparatus, a process cartridge, and an image forming apparatus in which positional deviation is reduced while maintaining the characteristics.

In order to solve the above problems, the invention described in claim 1 is characterized in that each electrostatic latent image formed by optical writing on a plurality of rotationally driven latent image carriers is incorporated in each station. to obtain a plurality of toner images visualized with a different color toner to each image bearing member, and transferred and overlaid on the same sheet-like recording medium a plurality of toner images from each of said image bearing member in the image bearing member driving device for rotating the latent image carrier when the image forming multiple-color image or a color image, the transfer to control the linear velocity of rotation of the plurality of the image bearing member by the rotation control means configuration and a second of the linear velocity of rotation of the image bearing member of each color variable in between sheets of paper-like recording medium first performing resist alignment between the toner image transferred in the initial stage of a configuration and the implementation of the first structure Said resist phase shift due to rotation speed fluctuation of the resist alignment, the implementation of the second configuration when the said transfer in accordance with the station pitch early between the colors that occur more each said image bearing member The rotational phase control of the latent image carrier is performed for each interval between the sheets so as to return to the initial value .

The invention described in claim 2 is the invention according to claim 1, only when more than a certain number of sheets is a sheet-like recording medium, the rotational phase control is characterized in that it is effective.

The invention described in claim 3, in the invention described in claim 2, wherein the image bearing member is a photosensitive drum, the end portion of the photosensitive drum, a rotary shaft for rotating the photosensitive drum It includes an engagement portion of the pawl member provided on the opposite side of the transmission member, the photosensitive from the rotational axis as possible to and away of the engagement portion by moving the photosensitive drum in the axial direction of the rotary shaft drum you wherein the removable.

Invention described in claim 4 is the invention according to claim 3, wherein the photosensitive drum, and a flange member fixed to each longitudinal end of the photosensitive drum, the engagement portion of said pawl member And a process cartridge in which a charging unit for charging the surface of the photosensitive drum is housed in a unit case and configured integrally.

The invention described in claim 5, and at least four comprising the process cartridge according to claim 4, which is an image forming apparatus, wherein the color image can be formed.

  According to the present invention, it is possible to correct the registration error by adjusting the rotation speed of the image carrier, and to eliminate the phase error at the time of continuous paper feeding in the state where the phase adjustment between the colors is performed. The positional deviation can be reduced while maintaining the productivity.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view illustrating a color printer which is an example of an image forming apparatus including the above-described coupling device.

  In the image forming apparatus main body 1, four image carriers (latent image carriers) 2Y, 2M, 2C, and 2BK configured as drum-shaped photoconductors are arranged along a transfer direction A1 of the transfer material S described later. It is arranged. In the illustrated example, a yellow toner image is formed on the surface of the image carrier 2Y on the most upstream side in the transport direction A1 of the transfer material S, and a magenta toner image is further formed on the surface of the next image carrier 2M. A cyan toner image is formed on the surface of the image carrier 2C, and a black toner image is formed on the surface of the next image carrier 2BK. These image carriers 2Y, 2M, 2C, 2BK are formed. Are driven to rotate in the direction of arrow B1 at each station.

  A transfer material transport device 3 is arranged opposite to the image carriers 2Y, 2M, 2C, 2BK. The transfer material transport device 3 includes support rollers 4, 5, 6, and 7 and a transfer belt 8 that is an endless belt wound around the support rollers 4, 5, 6, and 7. The transfer material S is rotationally driven in the conveyance direction A1. Each image carrier 2Y, 2M, 2C, 2BK abuts on the surface of the transfer belt 8, and the transfer device 8 is located at a position facing the image carrier 2Y, 2M, 2C, 2BK across the transfer belt 8. As an example, transfer brushes 9Y, 9M, 9C, and 9BK are arranged.

  On the other hand, a cassette 11 of the sheet feeding apparatus 10 is arranged at the lower part in the image forming apparatus main body 1, and a transfer material S made of transfer paper, for example, is stacked on a bottom plate 12 arranged in the cassette 11. Yes. When the feeding roller 13 in contact with the upper surface of the uppermost transfer material S is driven to rotate counterclockwise, the uppermost transfer material S is fed in the direction of arrow C. The fed transfer material S is fed toward a transfer portion between each image carrier 2Y, 2M, 2C, 2BK and the transfer belt 8 at a predetermined timing by the rotation of the registration roller pair 14. .

  Here, as described above, a yellow toner image is formed on the surface of the image carrier 2Y for yellow, and when the transfer material S passes through the transfer portion between the image carrier 2Y and the transfer belt 8, The yellow toner image formed on the surface of the image carrier 2Y is transferred onto the surface of the transfer material S by the action of the transfer brush 9Y.

  The transfer material S successively passes through each transfer portion between the transfer belt 8 and the magenta image carrier 2M, the cyan image carrier 2C, the black image carrier 2BK, and the transfer brush 9M. , 9C, and 9BK, the toner images of the respective colors on the image carriers 2M, 2C, and 2BK are sequentially transferred at each station while being superimposed on the yellow toner image that has already been transferred onto the transfer material S.

  The transfer material S on which the four-color superimposed toner image is transferred onto the surface as described above passes between the fixing roller 15 and the pressure roller 16, and at this time, the toner image is transferred by the action of heat and pressure. It is fixed on the surface of the material S. Next, the transfer material S is stacked on the paper discharge tray 17 as indicated by an arrow E.

  Each image carrier 2Y, 2M, 2C, 2BK and each element that forms a toner image on the surface thereof are configured as an integral process cartridge 18Y, 18M, 18C, 18BK in each station. Since the process cartridges 18Y, 18M, 18C, and 18BK have substantially the same configuration, the process cartridge 18Y having one yellow image carrier 2Y is described with reference to FIG. This will be explained as a representative.

  As shown in FIG. 2, the image carrier 2Y of the process cartridge 18Y is rotatably assembled to the unit case 19 and is driven to rotate in the direction of the arrow B1. A charging roller 20 rotatably supported on the unit case 19 contacts the surface of the image carrier 2Y while rotating, and the surface of the image carrier 2Y is charged to a predetermined polarity by the charging roller 20.

  On the other hand, as shown in FIG. 1, a laser writing unit 21 is disposed in the image forming apparatus main body 1 separately from the process cartridge 18Y. As shown in FIG. 2, the surface of the charged image carrier 2Y is exposed by the light-modulated laser beam L emitted from the unit 21, so that the electrostatic latent image for yellow image is exposed on the surface of the image carrier 2Y. An image is formed.

  The electrostatic latent image is visualized as a yellow toner image by the developing device 22. The developing device 22 includes a developing case 23 constituted by a part of the unit case 19 and a developing roller 24 that is rotatably supported by the developing case 23 and is driven to rotate counterclockwise. 23 stores a powdery two-component developer DY having a yellow toner and a carrier.

  The developer DY is carried and conveyed on the developing roller 24, and the amount of the developer DY is regulated by the regulating blade 26 and is carried to the developing region between the developing roller 24 and the image carrier 2Y, and the toner in the developer Is electrostatically transferred to the electrostatic latent image formed on the surface of the image carrier, and the electrostatic latent image is visualized as a yellow toner image.

  The yellow toner image is transferred onto the surface of the transfer material S as described above, and the transfer residual toner adhering to the surface of the image carrier 2Y after the transfer is removed by the cleaning device 27. The cleaning device 27 includes a cleaning case 28 constituted by a part of the unit case 19, a cleaning brush 29 rotatably supported by the cleaning case 28 and driven to rotate in an arrow direction, and a base end portion of the cleaning device 27. The cleaning brush 30 and the cleaning blade 30 are in contact with the surface of the image carrier 2Y to scrape and remove the transfer residual toner on the surface of the image carrier 2Y.

  Further, the process cartridge 18Y including the photosensitive drum is detachably attached to the image forming apparatus main body 1. FIG. 3 shows a state in which the process cartridge 18Y is mounted on the image forming apparatus main body 1. As shown in FIG. 3, the drum-shaped image carrier 2Y has a cylindrical image carrier main body 39. And the flange member 40 on the front side is rotatably supported by the unit case 19 via a bearing 42, and the flange member 41 on the back side is an image. It is detachably connected to a shaft 144 that is rotatably supported by the forming apparatus main body 1.

  The shaft 144 is rotatably supported via bearings 47 and 148 on a positioning holder 146 including a back side plate 31 of the image forming apparatus main body 1 and a support plate 32 fixedly fixed to the side plate 31. Yes. Further, the joint 50 fixed to the tip end portion of the shaft 144 is engaged with a center hole 49 formed in the rotation center portion of the flange member 41 on the back side. A protrusion is formed at the tip of the joint 50, and a hole is also formed in the inner peripheral surface of the center hole 49. The joint 50 and the center hole 49 are engaged with each other, and they are engaged with each other. It is configured to be transmitted to the body 2Y. In this state, the unit case 19 of the process cartridge 18Y is positioned and held with respect to the image forming apparatus main body 1.

  When the process cartridge 18Y is pulled toward the front side of the image forming apparatus main body 1, that is, in the direction indicated by the arrow F in FIG. 3, the joint 50 and the center hole 49 of the image carrier are removed, and the process cartridge 18Y including the image carrier 2Y is removed. Can be pulled out to the front side of the image forming apparatus main body 1. On the contrary, when the process cartridge 18Y is pushed into the back side of the image forming apparatus body 1, that is, in the direction opposite to the arrow F, the center hole 49 and the joint 50 of the image carrier 2Y are fitted as shown in FIG. Both teeth mesh with each other, and the drum-shaped image carrier 2Y and the shaft 144 are positioned concentrically.

  A rotary drive gear 153Y is fixed by a member 109 at the end opposite to the end where the joint 50 of the shaft 144 is fixed. The rotation drive gear 153Y is engaged with the drive gear 55Y of the drive motor 54Y, and the image carrier 2Y can be rotated by the operation of the drive motor Y.

  FIG. 4 is a schematic diagram of a drive unit according to the embodiment of the present invention. Each image carrier (corresponding to a photosensitive drum in the embodiment) 2BK, 2C, 2M, and 2Y has a drive transmission gear. Drive transmission gears 153BK, 153C, 153M, and 153Y are held so as to be rotatable coaxially with the photosensitive drum.

  As for each drive gear 53BK, 53C, 53M, 53Y, drive motor 54BK, 54C, 54M, 54Y is being fixed to the output shaft. The drive transmission gears 155BK, 155C, 155M, and 155Y are all configured with the same number of teeth and the same modules, and the drive gears 55BK, 55C, 54M, and 54Y of the drive motors 54BK, 54C, 54M, and 54Y have the same number of teeth and the same number of teeth for each color. It consists of modules.

  In addition, phase marks 100 are provided on the drive transmission gears 153BK, 153C, 153M, and 153Y of the respective photosensitive members, and the respective color sensors 4BK, 4C, 4M, and 4Y are provided for the respective photosensitive drums. It is controlled to stop at a certain time after passing. Further, resin drive gears are generally used for the drive transmission gears 153BK, 153C, 153M, and 153Y of each photoconductor. However, eccentricity occurs during molding, and the reason shown in FIG. As described above, there is a difference in the rotation cycle (T1, T2, T3, T4) of each photoconductor drum, and as a result, as shown in the lowermost stage of FIG.

  Therefore, by controlling the gear stop position so that the registration position misalignment between the stations is optimal, it becomes possible to cancel the registration position misalignment between the colors, and to suppress the minimum registration position misalignment. I can do it.

However, the time of the start of the rotation as shown in FIG. 6 by performing the linear speed fine tuning of the photosensitive drum, the phase state between the colors at the time of the end of the rotation is changed. As an example, the registration position is shifted by changing the rotational speed of the drive motor (C motor, 54C shown in FIG. 4) by ΔP on the basis of the drive motor shown in FIG. 6 (BK motor, 54BK shown in FIG. 4). In this case, the period variation of the image carrier 2BK (BK drum) and the period variation of the image carrier 2C (C drum) are initially in phase with each other, and the positional deviation of the resist is canceled. As the motor continuous drive time becomes longer due to paper passing or the like, the phase shift (ΔY) of the resist between the BK drum and the C drum increases, and the positional shift of the resist (ΔX) occurs between the BK drum and the C drum. .

  Therefore, by performing the motor rotation speed control shown in FIG. 7, it is possible to minimize the phase shift of the resist. That is, in the graph of the drive motor 54C (C motor) rotation speed of FIG. 7, when the registration position shift is corrected by delaying ΔP with respect to the reference rotation speed, the difference ΔP with respect to the reference rotation speed rises. Therefore, a difference is generated with respect to the rotational speed of the image carrier 2BK (BK drum) by the operation time from.

Therefore, by increasing the drive motor 54C (C motor) speed so as to exceed the reference rotational speed in the paper interval T at the C image formation timing of the image carrier 2C other than the BK image formation timing of the image carrier 2BK, 1 It is possible to return the phase shift caused by the image formation to the initial phase state. By performing this operation during continuous paper feed state, that Ki out to eliminate the phase shift over time in the resist during continuous printing.

  Further, in the embodiment of the present invention, the registration correction of 1 dot or less for writing is finely adjusted by the driving motor of the drum, and the amount of phase change per sheet is considerably small. In addition, when the phase offset is performed, a speed difference is generated between the transfer belt and the photosensitive drum, which has a considerable influence on the life.

Therefore, the phase offset operation at the paper interval T is performed every several or tens of sheets, or the image forming time changes depending on the paper size. Further, by reducing the number of phase offset operations, for example, by increasing the length, it is possible to reduce the frictional degradation between the photosensitive drum and the transfer belt, and to increase the unit life.
In the present embodiment, the image carrier is a photosensitive drum, and the configuration in which the photosensitive drum is detachable enables a user operation to be performed smoothly.

  In the present embodiment, by taking the form of a process cartridge, the user can easily attach and detach the image forming apparatus, which leads to a reduction in user load.

  In the present embodiment, by mounting the present invention on a color image forming apparatus, it is possible to stabilize the quality of a color image having a higher required image than a monochrome image.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  In this embodiment, there are four stations and four process cartridges, but two or more, three or less, or five or more may be used. In the example of FIG. 1, the four process cartridges are arranged in an oblique direction, but may be arranged in a horizontal direction.

1 is a schematic cross-sectional view illustrating a color printer according to an embodiment of the present invention. FIG. 2 is a diagram showing a process cartridge having one yellow image carrier according to the color printer of FIG. 1. FIG. 3 is a diagram illustrating a state in which a process cartridge is mounted on the image forming apparatus. It is the schematic of the drive part of this invention. It is a figure which shows the position shift shown to the position fluctuation | variation in each station. It is a figure which shows the case where a registration position is shifted by making (DELTA) P fluctuation | variation of the rotation speed of C drum motor on the basis of BK motor. It is a figure which shows the case where a registration gap is correct | amended by delaying (DELTA) P with respect to a reference | standard rotation speed in the graph of C motor rotation speed.

Explanation of symbols

1 Image forming apparatus body 2Y, 2M, 2C, 2BK Image carrier (latent image carrier)
18Y process cartridge 19 unit case
50 Joint 54BK, 54C, 54M, 54Y Drive motor 153BK, 153C, 153M, 153Y Drive transmission gear

Claims (5)

Each electrostatic latent image formed by optical writing on a plurality of rotationally driven latent image carriers is visualized with a different color toner for each latent image carrier incorporated in each station, and a plurality of toner images are obtained. was obtained, and a plurality of toner images are transferred and superimposed on the same sheet-like recording medium from the respective said image bearing member, the latent image carrier when the image forming multiple-color image or a color image in the image bearing member driving device for rotating the, first the resist alignment between the toner image transferred to the linear velocity of the rotation of the plurality of the image bearing member to an initial time of the transfer is controlled by the rotation control means 1 configuration of the linear speed of rotation of the image bearing member of each color in between sheets of the sheet-like recording medium and a second configuration in which a variable, each said image bearing the implementation of the first structure the resist alignment that occurs in the body Rotation resist the phase shift due to speed variations, wherein the latent image carried by the implementation of the second configuration between every the paper to return to its initial value when the initial of the transfer in accordance with the said station pitch between the colors of an image bearing member driving device which is characterized in that the rotational phase control of the body. 2. The image carrier driving apparatus according to claim 1, wherein the rotational phase control is effected only when a certain number of sheet-shaped recording media are present. It said latent image bearing member is a photosensitive drum, this is the end of the photosensitive drum, with the engagement portion of the pawl member provided on the opposite side of the transmission member of the rotary shaft for rotating the photosensitive drum, the photosensitive an image bearing member driving device according to claim 2, wherein the photosensitive drum from said rotational axis as possible to and away of the engagement portion by moving the body drum in the axial direction of the rotary shaft, wherein the removable . Wherein the photosensitive drum, the photosensitive flange member fixed to the longitudinal ends of the drum, and the engagement portion of said pawl member, houses a charging means for charging the surface of the photosensitive drum unit case an image bearing member driving device according to claim 3, characterized in that it comprises a process cartridge configured to integrally Te. And at least four comprising the process cartridge according to claim 4, the image forming apparatus, wherein the color image can be formed.

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