JP4963565B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that is detachably attached to an image forming apparatus main body and includes an image forming unit.

  In recent years, image forming apparatuses such as copiers, printers, facsimile machines, and multifunction machines having at least two of these functions have been required to have high image quality without density unevenness for single colors and color unevenness for colors. Further, as shown in Patent Documents 1 and 2, in many image forming apparatuses, when the developing unit is mounted on the apparatus body, the driving gear on the apparatus body side meshes with the driven gear on the developing unit side, The provided developing roller or the like is configured to be driven.

JP 2002-287494 A JP 2005-114159 A

  In such an image forming apparatus, the photosensitive member is a unit that is positioned based on the main reference of the apparatus main body, whereas the developing roller is a sub-standard unit that is positioned relative to the position of the photosensitive member. Since the developing unit, which is the sub-standard, is driven by gear engagement, the gap between the developing roller and the photosensitive member fluctuates periodically during image formation, resulting in density unevenness for a single color and color unevenness for each color. There was a problem that occurred. Furthermore, the vibration is caused by the meshing component of one tooth of the driving gear and the driven gear, which causes rotation unevenness in the photosensitive member, and the vibration is propagated to the folding mirror of the writing unit, thereby causing banding. It has become.

  For example, in the image forming apparatus described in Patent Document 1, since the gear for driving the developing roller is not fixed, the meshing pitch becomes unstable at the time of meshing, and banding is likely to occur. In addition, there are a large number of components, and there is a concern that the swing bracket that supports the gear may vibrate and adversely affect the image.

  Further, since the image forming apparatus described in Patent Document 2 has a configuration in which the gear for driving the developing roller has a degree of freedom (a configuration in which it operates), there is a concern about the occurrence of banding due to meshing vibration.

  The present invention eliminates the above-mentioned conventional problems, and suppresses banding caused by gear gap variation and gear meshing between the image carrier and the image forming unit positioned with respect to the image carrier with a simple configuration. An object of the present invention is to provide an image forming apparatus capable of performing the above.

In order to solve the above problems, the present invention provides an image forming unit that is detachably attached to an image forming apparatus main body and positioned with respect to an image carrier, and is provided in the image forming apparatus main body. In the image forming apparatus having a drive source for rotationally driving the driven body and a drive gear for transmitting drive from the drive source to the image forming unit, the image forming unit is mounted on the image forming apparatus main body. A driven gear that meshes with the driving gear, and the driven gear is an idler gear that meshes with the driven gear provided coaxially with the driven body , and the image forming apparatus main body includes an idler gear of the idler gear. to the axis, to regulate the movement in the radial direction of the drive gear, to provide flexibility in movement in the circumferential direction, and movable between said driven member gear and the driving gear That the insertion hole is provided, when the image forming unit is mounted to the image forming apparatus main body, the idler shaft of the idler gear is proposed an image forming apparatus characterized by being inserted into the insertion hole.

The present invention is effective when the insertion hole is a long hole extending in the circumferential direction of the concentric circle of the drive gear.
Furthermore, the present invention is effective when the longitudinal direction of the elongated hole extends along a concentric arc of the drive gear.

Furthermore, the present invention is effective when the longitudinal direction of the elongated hole extends in parallel substantially along the concentric circle of the drive gear.
Furthermore, the present invention is effective when the driving gear and the driven gear are helical gears.

Furthermore, the present invention is effective when the insertion hole is provided in a member for positioning the image carrier.
Furthermore, according to the present invention, the spatial frequency on the image carrier per tooth when the driven gear on the image forming unit side and the driving gear on the image forming apparatus main body side are engaged is 0.9 or more. Is effective.

  It is effective when the driven body of the image forming unit is engaged with the driven gear or a drive train connected thereto.

  According to the present invention, it is possible to suppress the gap fluctuation between the photosensitive member and the developing roller with a simple configuration and to suppress the banding generated by the developing drive gear.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an example of a dandem type image forming apparatus.
The image forming unit 1 includes a plurality of drum-shaped photoconductors 2a, 2b, 2c, and 2d configured as image carriers, and toner images of different colors are formed on the respective photoconductors. The In the illustrated example, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are formed on the surfaces of the photoreceptors 2a to 2d, respectively. The photoconductors 2a to 2d are arranged in parallel with each other at a predetermined interval, and an intermediate transfer belt 3 configured as an intermediate transfer body is arranged facing the upper portions of the photoconductors 2a to 2d. Although a drum can be used as the intermediate transfer member, an endless belt that is wound around a plurality of support rollers 4 and driven in the direction of the arrow is used in the illustrated example.

  Although not shown around each of the photoconductors 2a to 2d, a charging device that performs a charging process on the surface of the photoconductor, a writing device that writes image information on the surface of the photoconductor with a laser beam, and a photoconductor 2 by optical writing. A developing unit that visualizes the electrostatic latent image formed on the surface of the toner, a transfer device disposed opposite to the photoreceptor 2 via the intermediate transfer belt 3, and the surface of the photoreceptor 2 after being transferred to the intermediate transfer belt 3. A cleaning device that removes and collects residual toner is provided. Reference numerals 5a to 5d denote developing rollers of a developing unit disposed so as to face the photoreceptors 2a to 2d via a predetermined gap.

  In such an image forming apparatus, latent images are formed on the photoreceptors 2a to 2d by light beams of respective colors irradiated by a writing device (not shown), and the photoreceptors 2a to 2d are developed by developing rollers 5a to 5d of the respective colors. A toner image is formed on top. Thereafter, the formed toner images are sequentially transferred onto the intermediate transfer belt 3 in the order of the yellow photosensitive member 2d, the cyan photosensitive member 2c, the magenta photosensitive member 2b, and the black photosensitive member 2a. Is transcribed.

FIG. 2 is a top view of a drive train of the drive system of the developing rollers 5a to 5d, and FIG. 3 is a perspective view of the drive train.
2 and 3, the developing clutch 10a is connected to the gears 8a to 8d and 9a to 9d engaged with the gears of the output shafts of the motors 7a to 7d by the motors 7a to 7d, which are driving sources, and releases the connection of the driving. It is drivingly connected to a gear of -10d. Gears 11a to 11d are provided on the same axis as the developing clutches 10a to 10d, and the gears 11a to 11d and later are selectively driven by turning the developing clutches 10a to 10d on and off. The gears 11a to 11d are further engaged with gears 12a to 12d, and the gears 12a to 12d are drive gears that transfer to and from the developing unit 17 not shown in the drawing (hereinafter referred to as drive gears 12).

  FIG. 4 is a perspective view of the side plate of the driving system of the developing unit as viewed from the motor side, FIG. 5 is a perspective view of the side plate as viewed from the drive delivery side to the developing unit 17, and FIG.

  4 to 6, the driving system of the developing unit is supported by a driving side plate 13 including a caulking shaft serving as a driving center of the developing gears 8, 9, and 12. Driving gears 8 and 9 and a developing clutch 10 are held outside the driving side plate 13 shown in FIG. 4, and driving gears 11 and 12 are supported inside the driving side plate 13 shown in FIG. Further, the drive side plate 13 also supports a housing 14 including a positioning hole 16 at the center of a photoreceptor (not shown) and an insertion hole 15 into which a central axis of a gear on the developing unit 17 meshing with the drive gear 12 is inserted.

  FIG. 7 is a perspective view of the developing unit 17, and FIGS. 8 and 9 are perspective views of the process cartridge 24 including the developing unit 17 and the photoreceptor 2. 10 and 11 are detailed perspective views of the developing drive system, and FIG. 12 is a perspective view of the photosensitive member drive system.

  As shown in FIGS. 10 and 11, the developing unit 17 includes a driven gear 18 that meshes with the driving gear 12, and the driven gear 18 drives a gear 20 that drives the developing roller 5 and a developing screw 24. The gears 25 are engaged with each other to transmit the driving force. When the developing unit 17 is attached to the apparatus main body, the central shaft 19 of the driven gear 18 that meshes with the driving gear 12 is inserted into the insertion hole 15 of the housing 14.

  On the other hand, as shown in FIG. 12, the photosensitive member 2 is driven by the large-diameter gear 21 by decelerating the motor 7 which is the same drive source as the development drive, and transmits the drive. A bearing 22 is disposed coaxially with the large-diameter gear 21 and is inserted into the positioning hole 26 of the housing 14 and positioned. Further, a coaxial coupling with the bearing engages with a coupling 27 coaxial with the photosensitive member 2 in the process cartridge 24 shown in FIGS.

  In the image forming apparatus configured as described above, when the developing unit 17 is mounted on the apparatus main body, the driven gear 18 on the developing unit 17 side meshes with the driving gear 12 on the housing side. At this time, the developing unit 17 is a sub-standard unit whose position is determined with respect to the photoconductor 2, and when the sub-standard unit is driven and transmitted by meshing the gear, the gap between the developing roller 5 and the photoconductor 2 is periodically changed. If it fluctuates, density unevenness, color unevenness, or banding may occur.

  Therefore, in the present invention, when the developing unit 17 is mounted on the apparatus main body, the central shaft 19 of the driven gear 18 is inserted into the insertion hole 15 formed in the housing 14 shown in FIG. At this time, the shape of the insertion hole 15 is formed so as to restrict the movement of the driving gear 12 in the radial direction with respect to the central axis 19 of the driven gear 18 and to give freedom in movement in the circumferential direction. That is, the insertion hole 15 is formed as an arc-shaped long hole extending in the circumferential direction of the concentric circle of the drive gear 12. The insertion hole 15 of the embodiment shown in FIG. 13 is a long hole whose longitudinal direction extends along a concentric arc of the drive gear 13, and the insertion hole 15 of another embodiment shown in FIG. Although the direction extends in the arc direction of the concentric circle of the drive gear 12, it is a track-like long hole that extends in a straight line in parallel, not an arc.

  Next, when the insertion hole 15 is an arc-shaped elongated hole, a track-shaped elongated hole, or a circular hole, the gap between the photosensitive member 2 and the developing roller 5 when the drive gear meshes directly with the gear 20 of the developing roller. The variation of the gap G was examined. FIG. 15 shows the measurement method, and the gap variation was measured from the direction of arrow E with a laser displacement meter. The result is shown in FIG.

  In the case where the insertion hole 15 is a round hole, in addition to the influence of the shake of the developing roller 5, a fluctuation corresponding to one rotation of the driven gear 18 is added to increase the amplitude. On the other hand, when the insertion hole 15 is an arc-shaped or track-shaped long hole, there is almost no influence of one rotation of the driven gear 18, and the dynamic gap G is determined only by the influence of the deflection of the developing roller 5. . Thus, it can be seen that by forming arc-shaped or track-shaped long holes, there is an effect of reducing image density unevenness in a single color and color unevenness in multiple colors. In particular, it is effective in suppressing color unevenness in a tandem type image forming apparatus as shown in FIG.

  Further, when the drive gear 12 is directly meshed with the developing roller gear 20 and driven, the fluctuation of the dynamic gap G becomes large. Therefore, it is preferable that the driving force of the developing roller 5 is not directly driven by the driving gear 12 but is transmitted through the driven gear 18 as an idler gear.

  Further, according to the present invention, the gears 11, 12, 18, 20, and 25 shown in FIGS. 10 and 11 are helical gears, thereby suppressing the occurrence of banding due to the meshing period of one tooth on the image. it can. Further, the drive gear 12 shown in FIGS. 10 and 11 is preferably chamfered so as to be inclined in the fitting direction so as to be easily fitted with the driven gear 18.

  Further, in the present invention, positioning is performed by inserting the bearing 26 of the photosensitive drum 2 of the process cartridge 24 in FIG. 8 into the hole 16 of the housing 14 shown in FIG. The housing 14 is also provided with an insertion hole 15 into which the central shaft 19 of the driven gear 18 is inserted. Therefore, the hole 16 and the insertion hole 15 are formed of the same component, and have a positional relationship. It is easy to configure.

  The spatial frequency on the photosensitive member 2 per tooth when the driven gear 18 on the developing unit 17 side and the driving gear 12 are meshed is set to 0.9 or more. By downsizing the module, the gear meshing rate is increased and the pitch on the image is made finer to make it less visible, thereby reducing human perception banding. For this, an experiment was conducted in which the gear module was shaken by 0.05, and an image rank was determined. Note that the image rank is determined by creating step samples in increments of 0.05 from rank 1 to rank 5 and comparing them with actual output images. As a result, as shown in FIG. 17, when the spatial frequency is 0.9 or more, the bad image is less noticeable.

  In the present invention, the developing unit 17 has been described as the sub-standard image forming unit positioned with respect to the image carrier. However, the sub-standard image forming unit has a member driven by the engagement of the drive gear. There is a unit, and the present invention can also be applied to such a cleaning unit. The present invention can also be applied to a process cartridge having a developing unit 17 that is separate from the photosensitive member 2 and independent, and can also be applied to a process cartridge having the photosensitive member 2 and the developing unit 17.

1 is a schematic configuration diagram illustrating an example of a dandem type image forming apparatus. FIG. 3 is a diagram showing a drive train of a developing roller drive system from above. FIG. 6 is a perspective view showing a drive train of a developing roller drive system. It is the perspective view which looked at the side plate of the drive system of the image development part from the motor side. It is the perspective view which looked at the side plate of the drive system of a development part from the drive delivery side with a development unit. It is a front view of the side plate of the drive system of a development part. It is a perspective view of a developing unit. FIG. 4 is a perspective view of a process cartridge including a developing unit and a photoreceptor. FIG. 4 is a perspective view of a process cartridge including a developing unit and a photoreceptor. It is a detailed perspective view showing a development drive system. It is a detailed perspective view showing a development drive system. It is a perspective view which shows a photoreceptor drive system. It is explanatory drawing which shows one Embodiment of this invention. It is explanatory drawing which shows other embodiment of this invention. It is a figure which shows the measuring method of the fluctuation | variation of the gap between a photoconductor and a developing roller. It is a graph which shows the measurement result of the gap between a photoconductor and a developing roller. It is a graph which shows the relationship between the spatial frequency on a photoconductor and an image rank.

Explanation of symbols

2 Photosensitive member 5 Developing roller 7 Motor 12 Driving gear 15 Insertion hole 17 Developing unit 18 Driven gear 19 Central axis of driven gear 24 Process cartridge

Claims (8)

An image forming unit that is detachably mounted on the image forming apparatus main body and positioned with respect to the image carrier, and a drive source that is provided in the image forming apparatus main body and that rotationally drives a driven body of the image forming unit. An image forming apparatus having a drive gear for transmitting drive from the drive source to the image forming unit;
The image forming unit includes a driven gear that meshes with the driving gear when attached to the image forming apparatus main body,
The driven gear is an idler gear that meshes with a driven body gear provided coaxially with the driven body ;
In the image forming apparatus main body, the drive gear and the driven body gear are arranged so as to restrict the movement of the drive gear in the radial direction relative to the idler shaft of the idler gear and to give freedom in movement in the circumferential direction . With an insertion hole that can move between
When the image forming unit is attached to the main body of the image forming apparatus, an idler shaft of the idler gear is inserted into the insertion hole.   The image forming apparatus according to claim 1, wherein the insertion hole is a long hole extending in a circumferential direction of a concentric circle of the drive gear.   The image forming apparatus according to claim 2, wherein the long hole extends in a longitudinal direction along a concentric arc of the drive gear.   The image forming apparatus according to claim 2, wherein the long hole extends in parallel in a longitudinal direction substantially along a concentric circle of the drive gear.   5. The image forming apparatus according to claim 1, wherein the driving gear and the driven gear are helical gears.   The image forming apparatus according to claim 1, wherein the insertion hole is provided in a member for positioning the image carrier.   2. The spatial frequency on the image carrier per tooth when the driven gear on the image forming unit side and the driving gear on the image forming apparatus main body side are engaged with each other is 0.9 or more. 5. The image forming apparatus according to any one of 4 to 4.   The image forming apparatus according to claim 1, wherein the driven body of the image forming unit is engaged with the driven gear or a driving train connected thereto.

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