JP2707639B2 - Drive mechanism of image forming apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a driving mechanism for an image forming apparatus.
More specifically, for example, a multi-color image forming apparatus such as an electrophotographic copying machine or a printer drives an image forming apparatus for the purpose of preventing relative color misregistration between respective colors to obtain high definition halftone image quality. It concerns the mechanism.

2. Description of the Related Art In general, as shown in FIG. 4, a cylindrical transfer means a (transfer drum) having an insulating flexible transfer medium is used as a multicolor image forming apparatus for electrophotographing a color document. A plurality of image carriers b1, b2, b3, and b4 (photoconductors) arranged at equal intervals on the peripheral surface of the transfer drum a have respective chargers c1, c2, and c on the peripheral surface.
3, c4, a plurality of image forming units g1 including an optical system d1, d2, d3, d4 as electrostatic latent image forming means, developing units e1, e2, e3, e4 and cleaners f1, f2, f3, f4. An electrophotographic copying machine including g2, g3, and g4 is known. According to this conventional image forming apparatus, the optical systems d1, d2, d3, of the image forming units g1, g2, g3, g4
d4, and yellow in the developing units e1, e2, e3, e4, etc.
Reproduces magenta, cyan or black, and
Each image forming unit g1, g2, g3, g4 for the transfer drum a
The transfer corotrons h1, h2, h3, and h4 confront each other.

On the other hand, the paper i to be transferred is sent out from the paper feeding unit k by the feed roll j, and waits on the registration roll l.
At a predetermined timing, the leading end of the sheet is conveyed from the registration roll 1 to the transfer corotron while being gripped by a gripper (not shown) provided on the transfer drum a, and a visible image lead already formed on the photoconductor is read. The transfer corotrons h1, h2, h3, and h4 sequentially transfer multiple images corresponding to yellow, magenta, cyan, and black while aligning the timing with the edge, and then are conveyed to the fixing unit n via the release guide m and fixed. After the unfixed image is fixed in the portion n, the image is discharged to a discharge tray o.

In the image forming apparatus configured as described above, since the plurality of image forming units g1, g2, g3, and g4 are arranged in tandem on the peripheral surface of the transfer drum a, the diameter of the transfer drum a is several hundred mm. , So that the inertial load and the load fluctuation increase. Therefore, in order to obtain high-definition halftone image quality, it is important to prevent relative color shift between colors.

[Problems to be Solved by the Invention] However, in the conventional main image forming apparatus, generally, the photosensitive members b1, g2, g3, and g4 of the image forming units g1, g2, g3, and g4
b2, b3, b4 are independently rotated by the drive motor, and
Since it is controlled by the combination with the electrostatic latent image formation by the optical systems d1, d2, d3, and d4, accurate control cannot be performed, and the photosensitive members b1, b2, and the photosensitive members b1, b2, and g4 of the image forming units g1, g2, g3, and g4 are not provided. There is a possibility that the phases of b3 and b4 are shifted. In addition, a drive system in which the photoconductors b1, b2, b3, and b4 or the photoconductors b1, b2, b3, and b4 and the transfer drum a are interlocked by a gear train is also considered. In this drive system, the photoconductors b1 and b2 are also used. , b3, b4 may be out of phase. As shown in FIG. 5, the phase shift of the photoconductors b1, b2, b3, b4 causes the second rotation of the first photoconductor b1 for one rotation. Photoconductor
The phase of one rotation of b2 is shifted, and the color shift caused by the two times of multiple transfer appears in the hatched area shown in FIG. 6, resulting in a decrease in image quality.

Further, as another means for solving the relative color shift between the respective colors, it is conceivable to adjust the write timing (write margin time) of the optical systems d1, d2, d3, d4. The lead edge of the visible image formed on the photoconductors b1, b2, b3, and b4 can be matched to a certain extent with the lead edge of the paper i. There is a problem that can not be.

In view of the above circumstances of the present invention, the object is to match the moving angle of the transfer drum and the photoconductor, that is, the angular velocity, and to reproduce color misregistration to match the phase and the fluctuation level between each color. It is an object of the present invention to provide a driving mechanism of an image forming apparatus in which a relative color shift between respective colors is prevented by providing a driving mechanism.

[Means for Solving the Problems] In order to achieve the above object, a driving mechanism of the present invention comprises:
A cylindrical transfer unit having an insulative flexible transfer medium, and at least an electrostatic latent image forming unit and a developing unit on a peripheral surface of each of a plurality of image carriers arranged at equal intervals on the peripheral surface of the transfer unit An image forming apparatus comprising a plurality of image forming units comprising: a transfer unit drive gear and an image carrier drive gear formed on a transfer unit and an image carrier, respectively, wherein the transfer unit drive gear is a first intermediate gear. And the image carrier driving gear meshes with each other via the second intermediate gear, and meshes with the common driving gear to transfer the power from the common driving gear to the transfer unit and the image carrier. In addition to the transmission, the rotation angle of the image carrier is synchronized with the transfer movement angle of the transfer means.

In the present invention, any one may be used as long as the rotation angle of the image carrier is synchronized with the transfer movement angle of the transfer means. The speed ratio and the speed ratio between the common drive gear, the image carrier drive gear, and the second intermediate gear are each set to an integer ratio, and the integral rotation of the image carrier is used to transfer the transfer movement angle between adjacent image carriers in the transfer unit. It is preferable to tune the transfer angle, and more preferably, to make one rotation of the common drive gear coincide with the transfer movement angle between the adjacent image carriers of the transfer means.

Further, the types of the common drive gear, the first and second intermediate gears, and the image carrier driving gear for transmitting the power from the driving source to the transfer unit and each image carrier are not limited, and spur gears, Any type of gear, such as a helical gear, a worm gear, or a spiral gear, can be used, and the drive mechanism can be formed by a gear train in which various gears are arbitrarily combined.

Further, the transfer unit driving gear and the image carrier driving gear may be mounted on a rotation shaft of the transfer unit and the image carrier, respectively, or may be formed integrally with the direct transfer unit and the image carrier. Any of these may be used.

[Operation] As described above, the transfer unit drive gear and the image carrier drive gear are formed on the transfer unit and the image carrier, respectively, and the transfer unit drive gear meshes with the common drive gear via the first intermediate gear. The image carrier drive gears mesh with each other via a second intermediate gear and mesh with the common drive gear to transmit power from a drive source to the transfer means and the image carrier via the common drive gear. Can be. Further, since the rotation angle of the image carrier is synchronized with the transfer movement angle of the transfer unit, it is possible to prevent a relative color shift of a visible image formed by each image forming unit.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view when an image forming apparatus having a drive mechanism of the present invention is applied to a full-color digital printer, and FIG. 2 is a schematic view of the drive mechanism of the present invention.

The full-color digital printer having the driving mechanism of the present invention includes a plurality of (four in the drawing) image forming units 1 on the outer peripheral surface of a transfer drum 10 as a transfer unit.
1, 12, 13, and 14 are arranged at equal intervals, and the transfer corotrons 21, 22, 23, and are opposed to the image forming units 11, 12, 13, and 14, respectively.
24 are arranged. In this case, the transfer drum 10 has a structure in which an insulating mesh or an insulating synthetic resin film is adhered to an opening corresponding to the maximum paper length opened in an aluminum cylinder having a diameter of about 400 mm. Each of the image forming units 11, 12, 13, 14 includes a photoconductor 31, which is an image carrier.
32, 33, 34 sequentially, chargers 41, 42, 43, 44, optical systems 51, 52, 53, 54 as electrostatic latent image forming means, developing units 61, 62, 63, developing means. 64 and cleaners 71, 72, 73, 74. In this case, the optical systems 51, 52, 53, 54
Is a laser 55 for irradiating a laser beam corresponding to the image information.
And a polygon mirror 56 for deflecting the laser beam from the laser 55 in the scanning direction and an imaging lens 5 for imaging the beam deflected by the polygon mirror 56 on the photoconductors 31, 32, 33, and 34.
It is composed of seven.

In the printer configured as described above, for example, yellow is reproduced by the photoreceptor 31, the charger 41, the optical system 51, the developing device 61, and the cleaner 71 of the image forming unit 11, and is transferred to a sheet by the transfer corotron 21. Magenta is reproduced by the photoreceptor 32, the charger 42, the optical system 52, the developing device 62 and the cleaner 72 of the image forming unit 12, and the transfer corotron
Transferred to paper at 22. Similarly, the photoconductor 33, the charging device 43, the optical system 53, the developing device 63, and the cleaner of the image forming unit 13
The cyan is reproduced by 73, transferred by the transfer corotron 23, and the photosensitive member 34 of the image forming unit 14 and the charger
The black color is reproduced by 44, the optical system 54, the developing device 64 and the cleaner 74, and is transferred by the transfer corotron 24.

As shown in FIG. 2, the drive mechanism of the present invention that constitutes the drive unit of the printer configured as described above includes a rotation shaft of the transfer drum 10 or a transfer unit drive mounted on or integrally formed with the transfer drum 10. A gear 1, a rotating shaft of each of the photoconductors 31, 32, 33, 34 or an image carrier driving gear 2 attached to or integrally formed with the photoconductors 31, 32, 33, 34; A common drive gear 4 meshed via a first intermediate gear 3
And a second intermediate gear 5 interposed between and meshed with the adjacent image carrier driving gear 2, and receives power from a driving source (not shown) via the common driving gear 4. The power is transmitted to the transfer drum 10 and the photoconductors 31, 32, 33, and 34. The angle formed by the line segment connecting the center of each photoconductor 31, 32, 33, 34 and the center of the transfer drum 10 is set to 60 °, and each gear 1, 2, 3, 4, 5 is helical. It is formed by gears (tooth right angle module M _n = 1, helix angle α = 15 °). The transfer means the number of teeth Z1 = 360 of the driving gear 1, the number of teeth Z ₂ = 60 for each image carrier driving gear 2, the number of teeth Z ₃ = 30 of common drive gear 4, the number of teeth of the first intermediate gear 3 Z ₄ = 30, the number of teeth of the second intermediate gear 5 Z ₅ = 120, and the gear ratio Z ₂ / Z ₃ = 2 between the image carrier driving gear 2 and the common driving gear 4; The gear ratio Z ₄ / Z ₃ = 1 of the second intermediate gear 5 with the common drive gear 4 and the gear ratio Z ₅ / Z ₃ = 4 of the second intermediate gear 5 with the common drive gear 4 are integers. And 360 °
/ (Z ₁ / Z ₂ ) = 60 °, and the above photosensitive members 31, 32, 33, 34
And the angle formed by the line segment connecting the center of the transfer drum 10 and the center of the transfer drum 10 (an integer ratio of 1). Therefore, the rotation of the photoconductors 31, 32, 33, and 34 makes the transfer drum 10 rotate.
Are rotated by a transfer movement angle of 60 °, so that the transfer movement angles of the photoconductors 31, 32, 33, and 34 and the transfer drum 10 can be synchronized. To explain this more specifically, in FIG.
When the lead edge of the paper is at the point, assuming that the lead edge of the visible image on the photoreceptor connected to the image carrier driving gear 2 also coincides at the point, the lead edge of the paper Is moved to the point (60 in terms of the number of teeth), the image carrier driving gear 2 is
By rotating, the visible images of the photoconductors 31, 32, 33, and 34 are transferred onto the paper. That is, the transfer movement angle up to the next transfer point and the rotation angles of the photoconductors 31, 32, 33, and 34 are synchronized, and the reproducibility of each color at each transfer point is maintained (see FIG. 3). In this case, the large positional fluctuation basically occurring is caused by the transfer drum 10
(E.g., cumulative pitch error, tooth groove runout, etc.) and the position error component of the first and second intermediate gears 3, 5 are main components. However, since the correlation of each gear is represented by an integer ratio, ,
At the transfer point,..., The node is a node for every two rotations of the first and second intermediate gears 3,5. Of course, since the transfer unit drive gear 1 is also synchronized with the image carrier drive gear 2, reproducibility from each transfer point is maintained. The first intermediate gear 3 rotates 12 times during one rotation of the transfer drum 10 (see FIG. 3). In order to provide reproducibility even at the position error fluctuation level, for example, the image carrier driving gears 2, 2,. An arbitrary point may be marked so that the phases of the four gears 2, 2,.

As described above, if the reproducibility of each color at each transfer point is maintained, the relative color shift between the four colors is reduced, and the adverse effect due to the color shift can be prevented.

On the other hand, the paper 80 is sent out by the feed roll 82, forms a curl at the registration roll 84, waits, receives a timing signal from a sensor (not shown), passes through the paper guide 86 from the registration roll 84 to the transfer drum 10, and The paper is circulated, and the leading end of the sheet is gripped by a gripper (not shown) provided on the transfer drum 10. And paper
80 is a gripper for each image forming unit 11, 12, 13, 14
Of the photoconductors 31, 32, 33, and 34
The transfer corotrons 21, 22, 23, and 24 sequentially perform multiple transfer corresponding to yellow, magenta, cyan, and black while adjusting the timing with the lead edge of the visible image formed thereon. The paper 80 having the full-color print unfixed image formed in this way is sent to a fixing device 90 via a release guide 88, and after the unfixed toner image transferred onto the paper 80 by the fixing device 90 is fixed, Paper 80 is the output tray
Collected at 92.

In the above embodiment, the image forming units 11, 12, 13, 14
Has been described, but the number of image forming units 11, 12, 13, and 14 does not necessarily have to be four. For example, three image forming units that reproduce yellow, magenta, and cyan may be used.

[Effects of the Invention] Since the present invention is configured as described above, the following effects can be obtained.

According to the driving mechanism of the first aspect, 1) the transfer unit and the image carrier are connected via a gear train, and the rotation of the image carrier is synchronized with the transfer movement angle of the transfer unit. And the relative color shift between the colors can be prevented.

2) Since there is no need to provide a drive source for each of the transfer means and each image carrier, there is no need for synchronous positioning as compared with the conventional independent driving method, and the device can be manufactured at low cost.

3) Since the indirect drive system is employed, the effects of inertia load and load fluctuation on the load side can be reduced.

Further, according to the driving mechanism of the present invention, since one rotation of the image carrier is made to coincide with the transfer movement angle between the adjacent image carriers in the transfer means, a multicolor image can be formed more quickly. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an image forming apparatus provided with a drive mechanism of the present invention, FIG. 2 is a schematic view of the drive mechanism of the present invention, and FIG. FIG. 4 is a schematic sectional view of a conventional image forming apparatus.
FIG. 5 is a characteristic curve showing the deviation of the image carrier from the ideal position, and FIG. 6 is a characteristic curve showing the relative color shift between the colors. Description of Symbols (1) ... Transfer unit driving gear (2) ... Image carrier driving gear (3) ... First intermediate gear (4) ... Common driving gear (5) ... Second intermediate gear ( 10) Transfer drum (transfer means) (11, 12, 13, 14) Image forming unit (21, 22, 23, 24) Transfer corotron (31, 32, 33, 34) Photoconductor (Image carrier) (41, 42, 43, 44) Charger (51, 52, 53, 54) Optical system (electrostatic latent image forming means) (61, 62, 63, 64) Developing device (developing means)

Claims (2)

(57) [Claims] 1. A cylindrical transfer means having an insulative flexible transfer medium, and at least an electrostatic latent image formed on a peripheral surface of each of a plurality of image carriers arranged at equal intervals on a peripheral surface of the transfer means. In an image forming apparatus comprising a plurality of image forming units including a forming unit and a developing unit, a transfer unit driving gear and an image carrier driving gear are formed on the transfer unit and the image carrier, respectively, and the transfer unit driving gear is formed. Are meshed with a common drive gear via a first intermediate gear, and the image carrier drive gears are meshed with each other via a second intermediate gear, and are meshed with the common drive gear, so that power from a drive source is And the rotation of the image carrier is synchronized with the transfer movement angle of the transfer device, via the common drive gear. 2. The speed ratio of the common drive gear to the first intermediate gear and the speed ratio of the common drive gear to the image carrier drive gear and the second intermediate gear are each set to an integer ratio, and the speed ratio of the image carrier is adjusted. 2. A drive mechanism for an image forming apparatus according to claim 1, wherein one rotation is made to coincide with a transfer movement angle between adjacent image carriers in the transfer means.