JP3376533B2 - Transfer member driving device for electrophotographic apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus for transferring a toner image formed on an image forming body onto a transfer material by rotating a transfer roller or a transfer belt. And a transfer member driving device. 2. Description of the Related Art A transfer belt or a transfer roller used as a transfer member in an image transfer apparatus in an image forming apparatus such as an electrophotographic copying machine has a peripheral speed equal to that of an image forming body carrying an image in the same direction. And the transfer material is brought into close contact with the image forming body to transfer the image. Therefore, if a slight difference occurs in the peripheral speed, the transfer material may be displaced with respect to the peripheral surface of the image forming member during the transfer of the image, thereby damaging the image. The motor is driven by a high-precision gear train using a common motor as a power source so that the peripheral speeds coincide with each other. [0004] However, the permissible difference in the peripheral speed of the transfer member with respect to the image forming body must be 1% or less in order to obtain a high-quality transferred image. It has been. However, the gear used as the driving means has a rotary shaft hole H having a center O of a pitch circle PC as shown in FIG.
In many cases, the eccentricity of the transfer member is slightly eccentric, and as a result, a peripheral speed difference corresponding to δ shown in FIG. The present invention has solved and improved the above points,
It is an object of the present invention to provide a transfer member driving device for an electrophotographic apparatus, which can drive a transfer member at a constant peripheral speed even with an eccentric gear of a rotary shaft hole. An object of the present invention is to provide a transfer member driving device for an electrophotographic apparatus for transferring a toner image on an image forming body onto a transfer material by the action of a rotating transfer member. The members are structured so that the driving force can be given by the gear train.
And a tooth fixed to a drive shaft for driving the transfer member
The eccentricity of the rotating shaft hole of the car and the gear meshing with it with the same number of teeth
Gears with the same amount, the eccentric direction of each rotating shaft hole is
The present invention is achieved by a transfer member driving device of an electrophotographic apparatus, which is assembled so as to mesh with each other at positions facing each other . FIG. 1 shows an embodiment of the structure of an electrophotographic image forming apparatus provided with a transfer member driving device according to the present invention. In FIG. 1, reference numeral 10 denotes a photosensitive drum serving as an image carrier, which is obtained by coating an OPC photosensitive layer on the drum, is grounded, and is driven to rotate clockwise. 12 is a scorotron charger, a uniform charging of the V _H the photosensitive drum 10 peripheral surface V _G
Is provided by a corona discharge by a grid and a corona discharge wire which is held at a potential. This scorotron charger
Prior to the charging by 12, the photosensitive member is exposed to light by a PCL 11 using a light emitting diode or the like in order to eliminate the history of the photosensitive member up to the previous print, thereby removing the charge on the peripheral surface of the photosensitive member. After the photosensitive member is uniformly charged, the image exposure means 13 performs image exposure based on the image signal. Image exposure means
Reference numeral 13 denotes a reflection mirror 1 via a polygon mirror 131 rotating with a laser diode (not shown) as a light source, an fθ lens, and the like.
The optical path is bent by 32 to perform scanning, and a latent image is formed by rotation (sub-scan) of the photosensitive drum 10.
In the present embodiment, a character portion is exposed to form a reversal latent image such that the character portion has a lower potential _VL . On the periphery of the photosensitive drum 10, yellow (Y),
Developing devices each containing a built-in developer composed of a toner and carrier such as magenta (M), cyan (C), black (K), etc.
First, development of the first color is performed by a developing sleeve 141 which rotates with a built-in magnet and holding a developer. The developer is a carrier coated with an insulating resin around a ferrite core, a pigment and a charge control agent according to the color with polyester as the main material,
It consists of a toner added with silica, titanium oxide, etc.
It is conveyed to the development zone while being regulated to a layer thickness of 600600 μm. The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is 0.4 to larger than the layer thickness (developer).
As 1.0mm, D of AC Baaisu and V _DC of V _AC during this time
A C bias is superimposed and applied. V _DC and V _H, for charging the toner are the same polarity, the toner given the opportunity to leave from the carrier by V _AC is not adhere to a portion of the high V _H of potential than V _DC, potential than V _DC Adhered to the low V _L portion, and visualization (reversal development) is performed. After the visualization of the first color is completed, the image forming process for the second color is started, and the uniform charging is again performed by the scorotron charger 12, and a latent image based on the image data of the second color is formed by the image exposure means 13. Is done. At this time, the charge removal by the PCL 11 performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to a sharp drop in the surrounding electric potential. Again, V is applied over the entire surface of the photosensitive drum 10
A latent image similar to that of the first color is formed and developed on a portion of the photoconductor having the potential of _H where there is no image of the first color. the part for a latent image of V _M 'is formed by the charge possessed by the shading of the toner itself by the toner adhering the first color, V _DC
And development according to the potential difference between V _M ′ and V _M ′. In the overlapping portion of the first color image and the second color image, the development of the first color is performed by V _L
When the latent image of the first color is formed, the balance between the first color and the second color is lost, so that the exposure amount of the first color is reduced and V _H > V _M > V
_It may be an intermediate potential that becomes _L. An image forming process similar to that for the second color is performed for the third color and the fourth color, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10. On the other hand, the recording paper PA, which is the transfer material fed from the paper feed cassette 21 by the paper feed mechanism 22, is transferred by a transfer belt.
The multi-color image on the peripheral surface of the photosensitive drum 10 is collectively transferred onto the recording paper PA by the transfer belt device 30 having the transfer belt device 30 stretched over. The transfer belt 31 has a thickness of 0.46 having a resistance of 10 ⁶ to 10 ¹⁴ Ω · cm, on which an outer FLC layer of a urethane rubber substrate is formed.
If it is an endless rubber belt of about 1.0 mm and provided with a static elimination mechanism or the like, it may be a high resistance belt such as a film such as PET or the one coated with these. The holding roller 3 which stretches the transfer belt 31
For the axis 32a of the upstream-side holding roller 32 of 2, 33 are applied a voltage of V _PC, as charging unit to the recording sheet PA is in a position to place through the transfer belt 31 to the shaft 32a The conductive brush 34 is grounded or grounded via a non-linear element resistor. The fed recording paper PA enters between the brush 34 and the transfer belt 31, charges are injected into the recording paper PA from the brush 34, and the recording paper PA and the transfer belt 31 are transferred.
An adsorbing force is generated between this and 31. Thereafter, the recording paper PA enters a nip (transfer area) 35 formed by the photoreceptor drum 10 and the transfer belt 31, and the corona discharger enters from the back of the transfer belt 31.
The transfer electric field is applied by the bias roller 36 or, alternatively, the multicolor image is transferred onto the recording paper PA. Recording paper PA separated from photosensitive drum 10
Is the axis of the downstream holding roller 33 that stretches the transfer belt 31.
After the charge is removed by the AC corona discharge using the 33a as a counter electrode, the transfer belt 31 is separated from the transfer belt 31 while receiving the AC corona discharge. 37 removes toner adhered to the transfer belt 31 rotated by the cleaning blade. During the formation of a multicolor image, the transfer belt 31 of the transfer belt device 30 rotates around the shaft 33a of the holding roller 33 on the downstream side as the rotation center.
More distant. The recording paper PA holding the multicolor image separated from the transfer belt device 30 is conveyed to a fixing device 23 composed of at least two pressure rollers having a heater inside one of the rollers, and between the pressure rollers. The applied toner is melted by application of heat and pressure, is fixed on the recording paper PA, and is discharged out of the apparatus. The residual toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is subjected to static elimination by a static eliminator 15 using an AC corona discharger, and then enters a cleaning device 16 or from a rubber material in contact with the photoreceptor. The toner is scraped into the cleaning device 16 by the cleaning blade 16a, discharged by a screw or the like, and stored in a collection box. It should be noted that the above static eliminator 15 can also serve as static elimination of the recording paper depending on its arrangement. The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 16 is uniformly charged by the scorotron charger 12 after being exposed by the PCL 11,
The next image forming cycle is started. During the formation of the multicolor image, the cleaning blade 16a is separated from the photoreceptor surface,
The AC neutralization by 15 is kept in the OFF state. FIG. 2 shows a transfer belt device provided with a roller 39. The roller 39 is located on the inner side of the transfer belt 31 upstream of the nip (transfer area) 35 where the photosensitive drum 10 and the transfer belt 31 having the corona discharger 36 on the back surface are in contact with each other. The belt is pressed against the drum. The transfer belt device 30 is mounted at a position where the outer periphery of the roller 39 projects outside the belt beyond a common tangent line between the roller 39 and the photosensitive drum 10. FIG.
In (b), the outer periphery of the roller 39 is further held by the holding rollers 32 and 33.
The transfer belt device 30 installed at a position protruding from a common tangent line connecting the outer circumferences of the
The transfer belt 31 is capable of swinging about the rotation center a, and the transfer belt 31 is in a posture separated from the photosensitive drum 10 during the formation of the multicolor image as shown in FIG. FIG. 2A shows the posture at the time of transfer, and the transfer belt 31 is pressed between the photoconductor drum 10 and at least the upstream side from the nip 35 by the newly provided roller 39. By having the contact area, the air between the photoreceptor drum 10 and the transfer belt 31 is removed, so that a better contact state is obtained, and the recording sheet PA is not affected by irregularities on the surface of the recording paper PA or carrier adhesion. As a result, uniform transferability can be obtained. The holding roller 33 for transporting the photosensitive drum 10 and the transfer belt 31 is driven and rotated in the direction of the arrow by the power of a common motor M provided as a power source shown in FIG. The photosensitive drum 10 has a gear G fixed to the side end.
Meshes with the final gear G1 of the gear train T1 connected to the pinion P of the motor M, while the shaft 33a of the holding roller 33 is connected to the final gear G of the gear train T2 connected to the pinion P of the motor M.
2 are coaxially integrated. The gear trains T1 and T2 are configured such that the photosensitive drum 10 and the transfer belt 31 rotate in the same direction at the same peripheral speed. The gears G2 and G constituting the gear train T2
Reference numeral 3 denotes a completely common gear made of, for example, a hard plastic or a sintered metal formed by the same mold,
Therefore, as shown in FIG. 4, a rotary shaft hole H is provided which is eccentric by an amount equivalent to △ and equal to the pitch circle PC having the same pitch. The gears G2 and G3 are both provided with a rotary shaft hole H.
The index S is indicated by molding on the periphery of the gear on the opposite side in the eccentric direction. The above-mentioned gears G2 and G3 are assembled as shown in FIG.
As shown in (a), the above-mentioned indices S are meshed after setting the interval between the rotating shafts at positions facing each other, and the gear G3 is placed in a state of transmitting the peripheral speed to the gear G2 at a correct 1: 1. On the other hand at the position where the gears G2 and G3 are rotated a half turn, the pitch circle P of both gear as shown in FIG. 4 (b)
Since the center O of C moves outward, the depth of meshing becomes shallow, but when the amount of eccentricity is small, the meshing state is maintained and the gear G3 is 1: 1 with respect to the gear G2 in the same manner as described above. Can transmit the rotation. That is, by the meshing described above, the phase of the change in the peripheral speed with respect to the rotation angle within one rotation of both gears is matched, the change in the peripheral speed δ of both gears is canceled out, and the gear G2 becomes Always driven at a constant rotational speed,
The rotation unevenness of the holding roller 33 to which the gear G2 is fixed is eliminated.
The transfer belt 31 is moved in synchronization with the peripheral speed of the photosensitive drum 10 .
It is possible to transport without any irregularities. [0032] The present inventors have, as shown in FIG. 5 (a), the times
For a gear pair consisting of the gear A and the gear B having the amounts of change δ1 and δ2 of the peripheral speed with respect to the turning angle, when the unevenness of the transmitted rotation speed was measured by frequency analysis,
For example, when the gear A and the gear B are meshed with the eccentric direction on the same side without specifying the meshing position, when the output of the frequency and the vibration component is displayed by the voltage, the rotation unevenness is shown in FIG.
Although the magnitude was equivalent to the output of 60 mV as shown in (b), when the meshing position was specified by the present invention, the output was equivalent to 15 mV as shown in FIG.
It has been confirmed that it can be reduced by a factor of one. According to the present invention, the transfer member is driven and transported at a high speed and at a high precision with respect to the toner image on the image forming body. As a result, a high-quality image without transfer deviation and deformation is obtained. And a transfer member driving device for an electrophotographic apparatus capable of transferring an image.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus shown in an embodiment. FIG. 2 is a configuration diagram of a transfer device of the apparatus. FIG. 3 is a perspective view illustrating a configuration of a transfer member driving device of the present invention. FIG. 4 is an explanatory view showing the meshing state of the gear according to the present invention. FIG. 5 is an explanatory diagram showing the stability of the peripheral speed of the gear according to the present invention. FIG. 6 is an explanatory diagram showing a change in peripheral speed due to eccentricity of a gear. [Description of Signs] 10 Photoconductor drum 31 Transfer belt 32, 33 Holding roller 32a, 33a Shaft 35 Nip (transfer area) 36 Corona discharger G1, G2, G3 Gear PC Cut circle H Rotating shaft hole M Motor P Pinion

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/00 550 F16H 51/00-55/30

Claims (1)

(57) Claims 1. In a transfer member driving device of an electrophotographic apparatus for transferring a toner image on an image forming body onto a transfer material by the action of a rotating transfer member, the transfer member is Depending on gear series
A drive force is provided to drive the transfer member.
The gear fixed to the drive shaft and the gear meshing with it
Gears with the same number of teeth and the same amount of eccentricity of the rotary shaft hole
Meshing at positions where the eccentric directions of these rotary shaft holes are opposed to each other
A transfer member driving device for an electrophotographic apparatus, wherein the transfer member driving device is assembled as described above .