JP2000206760A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely drive an intermediate transfer body by driving the intermediate transfer body without having the surface of an image carrier in between but directly from a driving source, when precision is not required for superimposing each toner image. SOLUTION: In this image forming device, when primary transfer of a multiple number of toner images are carried out in sequence from an image carrier consisting of a photoreceptor 11 to the intermediate transfer body 17, the intermediate transfer body 17 is driven by driving force that is immediately received from the surface of the image carrier consisting of the photoreceptor 11. Then, the transmission of the driving force from the driving source to the intermediate transfer body 17 is intermittently controlled at a period, when the primary transfer of the multiple number of toner images to the intermediate transfer body 17 is finished, that is from an appropriate time after the completion, and the driving force is transmitted to the intermediate transfer body 17 without going through the surface of the image carrier. In this case, an electromagnetic clutch is operated so that the intermediate transfer body 11 is driven by a drive motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate image forming apparatus in which toner images of different colors are sequentially formed on the surface of an image carrier driven so as to move, and the toner image is driven while being in contact with the surface of the image carrier. Image formation in which the toner images formed on the surface of the image carrier are sequentially superimposed and primary-transferred onto the surface of a transfer body, and the superimposed toner images are collectively and secondarily transferred onto a recording medium to obtain a recorded image. The apparatus, when the toner image is primarily transferred to the surface of the intermediate transfer member, separates from the surface of the intermediate transfer member, and ends the primary transfer of the plurality of toner images from the image carrier to the intermediate transfer member. The present invention relates to an image forming apparatus having a contact / separation member that comes into contact with the surface of an intermediate transfer member at a time after a time point.

[0002]

2. Description of the Related Art An image forming apparatus of the above-mentioned type constituted as an electronic copying machine, various printers, a facsimile or a multifunction machine having at least two of these functions has been conventionally known. This type of image forming apparatus sequentially primary-transfers each toner image sequentially formed on the surface of an image carrier onto a surface of an intermediate transfer body that is in contact with the surface of the image carrier, and transfers toner of each color onto the surface of the intermediate transfer body. Since the images are configured to be superimposed, the toner images of the respective colors are superimposed with high accuracy,
It is necessary to suppress color misregistration of the color toner image primarily transferred on the surface of the intermediate transfer member and improve the image quality. However, the image carrier is affected by the eccentricity of the transmission element and the like, and the surface speed of the image carrier fluctuates, though slightly, whereby the contact portion between the image carrier and the intermediate transfer body causes both. There is a possibility that a slight difference is made in the surface linear velocity of the toner image, and a color shift occurs in the superimposed toner image transferred to the intermediate transfer member.

Therefore, in this type of conventional image forming apparatus, both the image bearing member and the intermediate transfer member are driven by a driving source, and each transmission element is driven so that mechanical eccentricity of each transmission element is eliminated. In order to improve the processing accuracy of the image carrier and the intermediate transfer body, the phases at the time of operation of the two are made the same so that the image carrier and the intermediate transfer body are not affected by the eccentricity of the transmission element. The speed difference is reduced as much as possible to prevent color shift of the color toner image on the intermediate transfer member.

According to this method, the periods of minute speed fluctuations of the image carrier and the intermediate transfer body are made to coincide with each other at a contact portion between the two.
The purpose is to make the surface linear velocities of the two portions coincide at the contact portion. However, since this method drives both the image carrier and the intermediate transfer member, it is difficult to completely match the surface linear velocities at the contact portion between the two.

Therefore, an image forming apparatus has been proposed in which the intermediate transfer body is driven by a driving force directly received from the surface of the image carrier (JP-A-6-301263, JP-A-6-301263).
258897 and JP-A-6-214446. In this type of image forming apparatus, an image carrier and an intermediate transfer member are electrostatically attracted, for example, and the intermediate transfer member is driven by the movement of the surface of the image carrier. According to this method, the intermediate transfer member is driven by the image carrier by the driving force received from the image carrier.
Even if a slight fluctuation occurs in the surface linear velocity of the image carrier due to the eccentricity of the transmission element, the intermediate transfer body is also driven while changing the surface linear velocity in synchronization with the fluctuation. The speed of the image carrier and the speed of the intermediate transfer body can be accurately synchronized by eliminating the influence of the speed fluctuation of the image carrier.

However, in this type of image forming apparatus, as described at the beginning, when the toner image is primarily transferred onto the surface of the intermediate transfer member, the toner image separates from the surface and moves from the image carrier to the intermediate transfer member. Since there is a contact / separation member that comes into contact with the surface of the intermediate transfer member at a time after the time when the primary transfer of the plurality of toner images is completed, for example, a cleaning member that cleans the surface of the intermediate transfer member, By adopting a configuration in which the intermediate transfer member is driven by being driven by the image carrier, a braking force is applied to the intermediate transfer member when the contact member comes into contact with the intermediate transfer member, whereby the intermediate transfer member is reliably driven by the image carrier. When the braking force is large, the intermediate transfer member may be stopped.

The contact width between the image carrier and the intermediate transfer body in the surface moving direction of the image carrier is set to be large, and even when the contact / separation member is in contact with the surface of the intermediate transfer body, the image on the intermediate transfer body can be maintained. It is also conceivable to employ a configuration in which the carrier can be driven by a large force. However, if the contact width between the two becomes excessively large, the primary transfer of the toner image from the image carrier to the intermediate transfer member is unavoidable, and the toner image may be disturbed. Is not preferred.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to effectively suppress the color misregistration of each toner image primary-transferred onto the surface of an intermediate transfer member without causing the above-mentioned conventional disadvantages, and to obtain a high-quality image. An object of the present invention is to provide an image forming apparatus of the type described at the beginning which can be formed.

[0009]

According to the present invention, in order to achieve the above object, in an image forming apparatus of the type described at the beginning, when a toner image is primarily transferred from the image bearing member to an intermediate transfer member, The intermediate transfer body is driven by a driving force directly received from the surface of the image carrier, and at a time after the time when the primary transfer of the plurality of toner images from the image carrier to the intermediate transfer body is completed, a timing from the drive source is changed. The driving force is transmitted to the intermediate transfer member without passing through the surface of the image carrier, and the transmission of the driving force from the driving source to the intermediate transfer member is intermittently controlled so that the intermediate transfer member is driven by the driving source. An image forming apparatus provided with a switching unit is proposed (claim 1).

At this time, when the toner image is primarily transferred from the image bearing member to the intermediate transfer member, the switching means transmits the driving force of the drive source without passing through the surface of the image bearing member to the intermediate transfer member. A clutch that operates to transmit the driving force of the driving source to the intermediate transfer member without passing through the image carrier surface at a time before the time when the contact / separation member contacts the surface of the intermediate transfer member. It is advantageous (claim 2).

In the image forming apparatus according to the first aspect of the present invention, the switching means may be configured such that the contacting / separating member comes into contact with the surface of the intermediate transfer member, and a braking force acts on the intermediate transfer member, thereby causing the image to be changed. It is advantageous to provide a one-way clutch that operates to transmit the driving force of the driving source to the intermediate transfer member without passing through the surface of the carrier (claim 3).

4. The image forming apparatus according to claim 3, wherein the surface linear velocity of the image carrier is VP, and the surface line of the intermediate transfer member driven by the driving source without passing through the surface of the image carrier. When the speed is VT, it is advantageous to set VP> VT (claim 4).

Further, in the image forming apparatus according to claim 4, when the surface linear velocity VP of the image carrier is set to 1, the intermediate transfer driven by the drive source without passing through the surface of the image carrier. It is advantageous to set the surface linear velocity VT of the body between 0.97 and 0.99 (claim 5).

Further, in the image forming apparatus according to any one of claims 1 to 5, a single toner image is formed on the surface of the image carrier, and the contact / separation member is brought into contact with the surface of the intermediate transfer member. When the single toner image is primarily transferred to the surface of the intermediate transfer member as it is, and the single toner image on the surface of the intermediate transfer member is secondarily transferred to a recording medium to obtain a recorded image, the single image on the surface of the image carrier is Even when the primary transfer of one toner image to the surface of the intermediate transfer member or after the primary transfer of the single toner image is completed, the driving force of the drive source without passing through the surface of the image carrier It is advantageous to configure the switching means so that the intermediate transfer member is driven by the switching means.

Further, in the image forming apparatus according to any one of claims 1 to 6, it is advantageous that the driving source for driving the intermediate transfer member and the driving source for driving the image carrier are the same driving source. (Claim 7).

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view showing the internal structure of the image forming apparatus. The image forming apparatus illustrated here has a drum-shaped photoconductor 11 as an example of an image carrier, and the photoconductor 11 has a structure in which an organic optical semiconductor layer is laminated on a surface of an aluminum drum. 1 is rotatably supported by an image forming apparatus main body not shown (see FIG. 3).

A developing device 13 is provided adjacent to the photoreceptor 11, and includes a black developing device 13A, a cyan developing device 13B, and a magenta developing device 13C.
And a yellow developing device 13 </ b> D, and these developing devices can rotate about the shaft 12. Further, developers (not shown) of black, cyan, magenta, and yellow are provided in the developing units 13A, 13B, 13C, and 13D, respectively.
Are accommodated respectively. As the developer, a two-component developer having a toner and a carrier or a one-component developer having no carrier is used. In the illustrated example, a powdery developer is used. Each developing device is provided with a developer carrying member composed of developing rollers 13a, 13b, 13c and 13d.

During the image forming operation, the photosensitive member 11 is driven to rotate in a counterclockwise direction (direction of arrow A) in FIG. 1 by a drive source composed of a drive motor described later. Photoconductor 11
Is driven to move its surface,
At this time, the surface of the photoreceptor is uniformly charged to a predetermined polarity by a charging charger 14 which is an example of a charging device, and the charged surface thereof is a laser writing device 15 which is an example of an image exposure device
And a first electrostatic latent image is formed on the surface of the photoconductor. Laser beam L
Is controlled to blink in accordance with the recording image signal.

At this time, the black developing device 13A of the developing device 13 occupies the developing position facing the photoreceptor 11, and the developing roller 13a carries and carries the black developer while rotating. The latent image is electrostatically transferred to the first electrostatic latent image, and the latent image is visualized as a black toner image.

On the other hand, an intermediate transfer member 17 composed of an endless belt is disposed opposite to the photoreceptor 11, and the intermediate transfer member 17 includes a driving roller 18, a transfer opposing roller 19, a cleaning opposing roller 20, The intermediate transfer member between the cleaning opposing roller 20 and the bias roller 21 is wound around the roller 21 and is in contact with the surface of the photoconductor 11. The intermediate transfer body 17 is driven to rotate in the direction of arrow B in a manner described later.

When the black toner image formed on the surface of the photoconductor 11 reaches the contact portion between the photoconductor 11 and the intermediate transfer member 17 as described above, the bias roller 21 applies the toner of the toner forming the toner image. A bias voltage having a polarity opposite to the charging polarity is applied, whereby the black toner image on the surface of the photoconductor is electrostatically and primarily transferred to the surface of the intermediate transfer body 17. As described above, the contact portion between the photoconductor 11 and the intermediate transfer body 17 forms a primary transfer section that primarily transfers the toner image from the photoconductor 11 to the intermediate transfer body 17.

The transfer residual toner adhering to the surface of the photoreceptor after the transfer of the toner image is scraped off by a cleaning member including a cleaning blade 22 pressed against the surface of the photoreceptor 11, and the surface of the photoreceptor is cleaned. The potential of the photoconductor surface thus cleaned is initialized by a static elimination action by a static eliminator (not shown), and then the photoconductor surface is uniformly charged again by the charging charger 14, and the charged surface is subjected to laser writing. The laser beam L generated by the device 15 is irradiated to form a second electrostatic latent image on the surface of the photoconductor.

When the second electrostatic latent image passes through the developing device 13, the rotation of the developing device 13 causes the cyan developing device 1 to rotate.
3B occupies a developing position facing the photoconductor 11, and the second electrostatic latent image is visualized as a cyan toner image by the cyan developer carried on the developing roller 13b. This toner image is also primary-transferred onto the surface of the intermediate transfer body 17 on which the black toner image has been previously transferred, in the same manner as described above. The surface of the photoconductor after the transfer of the cyan toner image is also cleaned by the cleaning blade 22.

In order to superimpose the cyan toner image on the black toner image already transferred to the surface of the intermediate transfer member for primary transfer, the position of the toner image formed on the surface of the photosensitive member is adjusted and controlled. This position adjustment is performed by detecting the reference mark 23 attached to the back surface of the intermediate transfer body 17 by the optical sensor 24 and forming an electrostatic latent image on the surface of the photoconductor at a predetermined timing by the control of the optical sensor 24. Will be

In exactly the same manner as described above, a magenta toner image and a yellow toner image are sequentially formed on the photoreceptor surface by a magenta developing device 13C and a yellow developing device 13D, respectively. The image is superimposed on the previously transferred toner image on the surface of the intermediate transfer body 17 and sequentially primary-transferred. The cleaning blade 22 removes the transfer residual toner from the surface of the photoreceptor every time each toner image is transferred, and cleans the surface. Thus, a full-color toner image is formed on the surface of the intermediate transfer body 17.

On the other hand, a recording medium 27 made of transfer paper or a plastic sheet is stacked on a paper feeding cassette 25 set at a lower portion of the main body of the image forming apparatus. The recording medium 27 is sent out, and is conveyed to a registration roller pair 29 through a conveyance path 28. The registration roller pair 29 is
The rotation is started at the timing when the recording medium is aligned with the superimposed toner image on the intermediate transfer body 17, and the recording medium is fed.

At this time, the transfer means including the transfer roller 30 which has been separated and opposed to the intermediate transfer body portion wound around the transfer opposed roller 19 is raised by the operation of the solenoid 16 and is shown in FIG. As described above, the transfer roller 30 is rotated in the counterclockwise direction in FIG. As described above, the intermediate transfer body 17 and the transfer roller 30 come into contact with each other, and a secondary transfer portion is formed at the contact portion. At the same time or at a timing slightly later than this, the solenoid 35 is operated, whereby the cleaning member 34 composed of the cleaning blade which has been separated from the surface of the intermediate transfer member up to that time as shown in FIG. It comes into pressure contact with the surface of the intermediate transfer member 17. Instead of the transfer roller 30, a transfer unit including a transfer charger that is always separated from the surface of the intermediate transfer body is used,
Alternatively, a cleaning member made of a fur brush which comes into contact with and separates from the surface of the intermediate transfer member can be used.

The recording medium sent out from the pair of registration rollers 29 is sent between the intermediate transfer body 17 and the transfer roller 30 which are in contact with each other, and passes therethrough. A bias voltage having a polarity opposite to that of the toner of the toner image on the body is applied, whereby the superimposed color toner image on the surface of the intermediate transfer member is collectively electrostatically and secondarily transferred onto the surface of the recording medium. The recording medium that has passed through the secondary transfer section is conveyed by a conveying belt 31 and passes between a pair of fixing rollers 32. At this time, a toner image is fixed on the surface of the recording medium by the action of heat and pressure. Next, the recording medium is discharged out of the apparatus by a discharge roller pair 33. The transfer residual toner adhering to the surface of the intermediate transfer member after the transfer of the toner image to the recording medium in the secondary transfer portion is removed by the cleaning member 34 in contact with the surface of the intermediate transfer member.

If the transfer roller 30 and the cleaning member 34 are in contact with the surface of the intermediate transfer member even during the primary transfer operation of the toner image, the toner image sequentially transferred on the surface of the intermediate transfer member is disturbed, or Since the toner image is removed from the surface of the intermediate transfer member, the transfer roller 30 and the cleaning member 34 are supported so as to be able to come into contact with and separate from the surface of the intermediate transfer member. When secondary transfer is performed on the recording medium, the transfer roller 30 contacts the surface of the intermediate transfer member via the recording medium, and the cleaning member 34 presses against the surface of the intermediate transfer member. As described above, the transfer roller 30 and the cleaning member 34 constitute a contact / separation member that comes into contact with / separates from the surface of the intermediate transfer member, and the contact / separation member primarily transfers the toner image onto the surface of the intermediate transfer member 17. The photosensitive member 1 is separated from the surface of the intermediate transfer member.
1 comes into contact with the surface of the intermediate transfer member at a time after the primary transfer of the plurality of toner images from the image carrier to the intermediate transfer member 17 is completed.

As described above, the image forming apparatus of this embodiment sequentially forms toner images of different colors on the surface of the image carrier composed of the photoconductor 11 driven so that the surface moves.
The toner image formed on the surface of the image carrier is sequentially superimposed on the surface of the intermediate transfer body 17 driven while being brought into contact with the surface of the image carrier, and the primary image is transferred onto the recording medium. And a transfer roller 30 and a cleaning member 34, which are one example of a contact / separation member that comes into contact with / separates from the surface of the intermediate transfer member 17 as described above. ing.

Here, in the image forming apparatus shown in FIGS. 1 and 2, a plurality of toner images on the photoreceptor are primary-transferred sequentially onto the surface of the intermediate transfer member 17, and are superposed on the intermediate transfer member. Because it forms an image, the photoreceptor itself,
If the positions of the toner images of the respective colors primary-transferred on the surface of the intermediate transfer member are shifted from each other due to fluctuations in the surface linear velocity of the intermediate transfer member and the photosensitive member due to the eccentricity of the transmission element, etc. Color misregistration occurs and the image quality deteriorates. From this point of view, in the conventional image forming apparatus, as described above, various configurations for preventing the misregistration of the toner images of each color on the surface of the intermediate transfer member are employed. I could not escape such a problem.

Therefore, in the image forming apparatus of this embodiment,
When a plurality of toner images are sequentially primary-transferred from the image carrier composed of the photoconductor 11 to the intermediate transfer body 17, the driving force that the intermediate transfer body 17 directly receives from the surface of the image carrier composed of the photoconductor 11 At the time after the primary transfer of the plurality of toner images from the image carrier to the intermediate transfer member 17 is completed, that is, at a time after the completion of the primary transfer, the driving force from the drive source is applied to the image carrier. The intermediate transfer body 17 is transmitted from the driving source to the intermediate transfer body 17 so that the intermediate transfer body 17 is driven by the driving source without passing through the surface.
There is provided switching means for intermittently controlling the transmission of the driving force to the driving motor 7.

The switching means can be embodied in various forms. To clarify specific examples, first, an example of a drive system for the photosensitive member 11 and the intermediate transfer member 17 will be described.

FIG. 3 is a partial cross-sectional plan view of the drive system, and FIG. 4 is an explanatory view of the arrangement of the components when viewed from the front. As shown in FIG. 3, one back end of a photoconductor drive shaft 51 for fixedly supporting the photoconductor 11 has a back side plate 40 of the image forming apparatus main body and an auxiliary side plate integrally fixed thereto. The shaft 41 is rotatably supported by bearings 53, 53 on a shaft support member 52 fixed to the shaft 41. The other front end of the photoconductor drive shaft 51 is also rotatably supported by a front side plate (both not shown).

The intermediate transfer member 17 shown in FIGS.
Each end of the plurality of rollers 18, 19, 20, 21 around which is wound is rotatably supported by a support 42 of an intermediate transfer unit mounted on the image forming apparatus main body, as shown in FIG. FIG. 3 shows a driving roller 1 of these rollers.
8, only one end side is shown.

As shown in FIGS. 3 and 4, a drive source comprising a drive motor 56 is fixedly supported on the auxiliary side plate 41 on the back side of the image forming apparatus main body, and a pulley 55 is fixed on the output shaft thereof. . Further, a photoconductor driving pulley 54 is fixed to a rear end of the photoconductor driving shaft 51. further,
An intermediate shaft 61 is rotatably supported by the rear side plate 40 and the auxiliary side plate 41 via a bearing, and an intermediate transfer member driving pulley 57 is fixed to a rear end of the intermediate shaft 61. An endless timing belt 60 is wound around these pulleys 55, 54, 57.

An intermediate transfer member driving shaft 62 is rotatably supported on the rear side plate 40 and the auxiliary side plate 41 via bearings. The front end of the driving shaft 62 and the rear end of the driving roller 18 are supported. The parts are detachably connected via a joint 64.

Further, a gear 58 is provided on the intermediate shaft 61 via an electromagnetic clutch 59, and the gear 58 is provided on the intermediate transfer member driving gear 6 fixed to the intermediate transfer member driving shaft 62.
3 is engaged.

When the drive motor 56 rotates, the pulley 55 fixed to the output shaft rotates counterclockwise as shown by the arrow in FIG.
0, the driving force is transmitted to the intermediate transfer member drive pulley 57 and the photosensitive member drive pulley 54, and these pulleys 57, 54 rotate in the directions indicated by arrows in FIG. By rotating the photoconductor drive pulley 54 in this manner, the photoconductor 11 is driven to rotate in the direction indicated by the arrow A in FIGS. 1, 2 and 4, whereby the photoconductor 11 is first turned to FIG. 1 and FIG. A predetermined image forming operation is performed as described.

On the other hand, the rotation of the intermediate transfer member driving pulley 57 rotates the intermediate shaft 61. As described above, a plurality of toner images of different colors on the photosensitive member are primarily transferred to the surface of the intermediate transfer member. When the power is on, the electromagnetic clutch is not operated, and therefore, the rotation of the intermediate shaft 61 is not transmitted to the gear 58, and the intermediate transfer body 17 is driven by a transmission element such as the timing belt 60 and the gear 58. It is not driven by the motor 56. The driving force of the driving motor 56 is not transmitted to the intermediate transfer body 17 via the transmission element.

At this time, since the photosensitive member 11 is rotating while contacting the surface of the intermediate transfer member 17 as shown in FIG. 1, the intermediate transfer member 17 receives a driving force from the surface of the photosensitive member, and The vehicle is driven to run following movement of the body surface. The intermediate transfer member 17 is driven via the surface of the photoconductor 11. At this time, not only the frictional force but also the electrostatic force acts between the photoreceptor 11 and the intermediate transfer body 17, so that
The intermediate transfer body 17 is driven at the same surface linear velocity as the surface linear velocity of the photoconductor 11. For this reason, Japanese Patent Application Laid-Open No. 6-301263
JP-A-6-258897 and JP-A-6-258897
As disclosed in Japanese Patent No. 214446 and the like, the intermediate transfer member 17 is not affected by the fluctuation of the surface linear velocity of the photosensitive member 11 due to various transmission elements for the photosensitive member 11 and the eccentricity of the photosensitive member itself. The photosensitive member 11 is driven in synchronization with the surface linear velocity. As a result, a plurality of toner images can be correctly positioned and primarily transferred on the surface of the intermediate transfer member, and the occurrence of color misregistration in the superimposed toner image on the surface of the intermediate transfer member can be prevented.

As described above, the intermediate transfer member 17 is
, The rollers 18, 19, 20, 21 around which the intermediate transfer member 17 is wound are rotated. The rotation of the drive roller 18 is rotated via the joint 64 shown in FIG. The power is transmitted to the intermediate transfer member drive shaft 62, and the intermediate transfer member drive gear 63 and the gear 58 meshing therewith rotate. At this time, the gear 58 is rotatably supported by the intermediate shaft 61. Can rotate.

On the other hand, it is a time after the completion of the primary transfer of a plurality of toner images (four color toner images in the example of FIG. 1) from the photoreceptor 11 to the intermediate transfer member 17, and the transfer roller 30 and the cleaning roller The electromagnetic clutch 59 is activated at a time before the time when the contacting / separating member of the member 34 that first contacts the surface of the intermediate transfer member 17 contacts the surface of the intermediate transfer member 17. Thus, the gear 58 is connected to the intermediate shaft 6.
1, the rotation of the intermediate shaft 61 is transmitted to the intermediate transfer member drive shaft 62 via the gears 58 and 63, and the rotation of the intermediate transfer member drive shaft 62 is transmitted to the drive roller 18 via the joint 64. The intermediate transfer body 17 is driven to travel in the direction indicated by the arrow B in FIG. The driving force of the drive motor 56 is transmitted to the intermediate transfer member 17 without passing through the surface of the photoconductor 11, and the electromagnetic clutch 59 is operated so that the intermediate transfer member 17 is driven by the drive motor 56. In this example, almost at the same time when the transfer roller 30 comes into contact with the intermediate transfer member 17, the electromagnetic clutch 59 is operated, and the rotation of the drive motor 56 is transmitted to the intermediate transfer member 17. Driven by the driving force of the driving motor 56 via the transmission element, regardless of the driving force from the motor.

As described above, after the contact member comes into contact with the intermediate transfer member, the intermediate transfer member 17 is forcibly driven by the drive motor 56 without the intermediary of the photosensitive member 11, so that the intermediate transfer member Even if a braking force is applied to the intermediate transfer member 17 by the contact / separation member contacting the member 17, the intermediate transfer member 1
No trouble such as the stop of 7 occurs. Even if the contact width between the photosensitive member 11 and the intermediate transfer member 17 in the rotation direction of the photosensitive member 11 is not excessively increased, the intermediate transfer member 17 can be reliably driven to travel.

As a transfer means for secondarily transferring the toner image on the surface of the intermediate transfer member to a recording medium, the intermediate transfer member 1 is used as described above.
7, a fur brush or the like can be used as a cleaning member for removing transfer residual toner on the surface of the intermediate transfer member. However, as in the transfer roller shown in FIGS. Intermediate transfer member 1
The use of a transfer unit in contact with the surface of No. 7 can suppress the generation of ozone, and the use of a cleaning blade as a cleaning member can improve the cleaning performance of the intermediate transfer member. However, since the transfer roller 30 and the cleaning blade apply a larger braking force to the intermediate transfer member 17 than when a transfer charger or a fur brush is used, the intermediate transfer member is driven only by the driving force from the photosensitive member. In a conventional image forming apparatus, if a transfer roller or a cleaning blade is used, there is a possibility that the intermediate transfer member stops when the transfer roller or the cleaning blade comes into contact with the intermediate transfer member. However, in the image forming apparatus of the present embodiment, when the cleaning member 34 including the transfer roller 30 and the cleaning blade is in contact with the intermediate transfer body 17, the intermediate transfer body 17 is driven by the drive motor 56 without the photoconductor. , The intermediate transfer member 17 does not stop or its driving state does not become unstable. Therefore, the cleaning member 34 including the transfer roller 30 and the cleaning blade can be used without any trouble.

The surface linear velocity of the photosensitive member 11 is VP, and the surface of the intermediate transfer member 17 when the transfer roller 30 and the cleaning member 34 are in contact with the intermediate transfer member 17 and the intermediate transfer member 17 is driven by the drive motor 56 When the linear velocity is VT, when the intermediate transfer body 17 is driven by the driving force from the photoconductor 11, the intermediate transfer body 17 is driven at the surface linear velocity of VP. At that time, VP = VT, VP> VT or V
The transmission ratio and the like of each transmission element may be set so as to satisfy any one of P <VT. However, when the intermediate transfer body 17 is driven by the drive motor 56 without passing through the photoconductor surface, When the surface linear velocity VT of No. 17 decreases, the image forming speed decreases. Therefore, the respective surface linear velocities are set so that VP ≦ VT, the image forming speed is increased, and the image forming processing time can be reduced. It is advantageous to do so. The transfer roller 30 in contact with the intermediate transfer body 17 is driven to rotate at the same surface linear velocity VT as the surface linear velocity VT of the intermediate transfer body 17 at this time.

As described above, in the image forming apparatus of this embodiment, the intermediate transfer member 1 is
The aforementioned switching means for intermittently controlling the transmission of the driving force to
A clutch 59 is provided, and the clutch 59 is
When the toner image is primarily transferred from the image carrier to the intermediate transfer member 17, the driving force of the drive source that does not pass through the surface of the image carrier is not transmitted to the intermediate transfer member, and the contact / separation member is not transferred. It operates so as to transmit the driving force of the driving source, which does not pass through the surface of the image carrier, to the intermediate transfer body 17 before the point of contact with the body surface. At that time, a clutch other than the electromagnetic clutch can be used.

Next, in the embodiment shown in FIG.
The above-mentioned switching means for intermittently controlling the transmission of the driving force from the driving source to the intermediate transfer member includes a one-way clutch. That is, the electromagnetic clutch 59 shown in FIG. 3 is not provided, and the gear 58 is fixed to the intermediate shaft 61, and between the intermediate transfer member driving gear 63 meshing with the gear 58 and the intermediate transfer member driving shaft 62. A one-way clutch 65 is interposed in such a manner that the driving force can be transmitted to the intermediate transfer body driving shaft 62 in only one direction. Further, in the image forming apparatus shown in FIG. 5, the surface linear velocity of the photoconductor 11 is VP, and the intermediate transfer body 17 is driven by the drive motor 56 without passing through the photoconductor surface. Assuming that the surface linear velocity is VT, VP> VT is set. Other configurations are the same as those described above with reference to FIGS. Therefore, among the elements shown in FIG. 5, the same or corresponding elements as those shown in FIG. 3 are denoted by the same reference numerals as those shown in FIG. 1 and 2 will be referred to in the description of the image forming apparatus shown.

As described above with reference to FIG. 1, when the toner images of different colors formed on the surface of the photoreceptor 11 are sequentially superimposed on the surface of the intermediate transfer member and primarily transferred, The body 11 is rotationally driven by a drive motor 56 shown in FIG. 5 in a direction indicated by an arrow A in FIG. 1, and the rotation of the drive motor 56 is controlled by a central shaft 61, a gear 58 fixed thereto, and a Is transmitted to the intermediate transfer member drive gear 63 meshing with. At this time, the rotation of the intermediate transfer member drive gear 63 is not transmitted to the intermediate transfer member drive shaft 62 by the action of the one-way clutch 65. For this reason, the intermediate transfer body 17 electrostatically attracted to the surface of the photoconductor 11 at the contact portion with the photoconductor 11 is driven in the direction of arrow B by the driving force directly received from the photoconductor 11, and the rollers 18, 19, 20, 21
Is driven by the intermediate transfer member 17. Therefore, the intermediate transfer member 17 has the same surface linear velocity VT as the surface linear velocity VP of the photosensitive member.
It is driven to run. For this reason, even in the same manner as in the previous embodiment, even if the surface linear velocity of the photoconductor 11 fluctuates slightly due to eccentricity of the transmission element or the like, the intermediate transfer body 17 that is driven in contact with the photoconductor 11 is The photoconductor 11 is driven at the same surface linear speed as the surface linear speed of the photoconductor 11 while changing the speed following the speed fluctuation of the photoconductor 11. As described above, by synchronizing the surface linear velocities of the photoconductor 11 and the intermediate transfer member 17, the positional deviation of the toner image of each color transferred onto the intermediate transfer member 17 can be improved.
That is, the occurrence of the color shift can be effectively suppressed.

Next, as described above, the transfer roller 30 abuts on the surface of the intermediate transfer member 17 directly or via a recording medium, and the cleaning member 34 holds the intermediate member. It comes into contact with the surface of the transfer body 17,
When one of these contacting / separating members that first contacts the intermediate transfer member contacts the intermediate transfer member 17, the intermediate transfer member 1
A large braking force acts on 7. Therefore, the intermediate transfer member drive shaft 62 attempts to stop, but at this time, the drive motor 5 is driven by the action of the one-way clutch 65 shown in FIG.
The rotation of the intermediate transfer member drive gear 63, which is rotationally driven by 6, is transmitted to the intermediate transfer member drive shaft 62. Then, this rotation is transmitted to the drive roller 18 via the joint 64,
As a result, the intermediate transfer member 17 is driven at the surface linear velocity of the VT in the direction indicated by the arrow B in FIG. Thus, the contact member of the intermediate transfer member 17 comes into contact with the intermediate transfer member 17 and
Even if a large load is applied, the intermediate transfer body 17 is reliably driven, and does not stop or run unstable.

As described above, in the image forming apparatus shown in FIG. 5, the above-mentioned switching means for controlling the transmission of the driving force from the driving source constituted by the driving motor 56 to the intermediate transfer body 17 is a contact / separation member. When the transfer roller 30 and the cleaning member 34, which are one example, contact the surface of the intermediate transfer member and a braking force acts on the intermediate transfer member 17, the driving force of the drive source without passing through the image carrier surface To the intermediate transfer member 17
And a one-way clutch 65 operable to transmit to the clutch.

At this time, the surface linear velocity VP of the image carrier composed of the photoreceptor 11 and the intermediate transfer body 1 driven by the drive source composed of the drive motor 56 without passing through the surface of the image carrier.
By setting the relationship of the surface linear velocity VT so as to satisfy VP> VT as described above, the above-described operation can be reliably obtained. Hereinafter, a more specific configuration example related to this and the one-way clutch 65 will be described.

The speed ratio between the drive of the photosensitive member and the drive of the intermediate transfer member by the drive system shown in FIG. On the other hand, the photoconductor 11
Is D1, the diameter of the drive roller 18 for the intermediate transfer member 17 is D2, and when D1 / D2 = N2, N2> N
The ratio of the number of teeth of the gears shown in FIG. 5, the diameter of the photosensitive member and the diameter of the drive roller 18 and the like are set so as to be 1. The rotation speed of the photoconductor driving pulley 54 driven by the driving motor 56 is represented by R.

Now, when the intermediate transfer member drive shaft 62 is driven at a rotational speed smaller than the rotational speed RT (= N1 × R) of the intermediate transfer member drive gear 63, the intermediate transfer member drive shaft 62 The rotation of the intermediate transfer member driving gear 63 is determined by its rotation speed RT.
(= N1 × R), and the intermediate transfer member drive shaft 62
When the intermediate transfer member drive gear 63 is driven at a rotation speed greater than the rotation speed RT (= N1 × R), the one-way rotation is performed so that the rotation of the intermediate transfer member drive gear 63 is not transmitted to the intermediate transfer member drive shaft 62. The clutch 65 operates.

The one-way clutch 65 is shown in FIGS.
As shown in FIG. 7, the roller 65A includes a plurality of rollers 65A located around the intermediate transfer member driving shaft 62 and an annular member 65B around the roller 65A. The annular member 65B is fixed to the intermediate transfer member driving gear 63. As shown in FIG. 6, when the intermediate transfer member drive gear 63 rotates clockwise at RT and the inner intermediate transfer member drive shaft 62 rotates at a rotation speed equal to or lower than RT, the roller 65A And the intermediate transfer member drive shaft 62 rotates at the rotation speed RT of the intermediate transfer member drive gear 63. In this way,
The rotation of the intermediate transfer member drive gear 63 is
Is transmitted to

On the other hand, as shown in FIG. 7, the intermediate transfer member drive gear 63 rotates clockwise at RT, and the inner intermediate transfer member drive shaft 62 rotates clockwise at RP (N2 × R).
When T <RP, the roller 65A moves to the outside of the inclined surface 65C and is released from the wedge portion, and the intermediate transfer member drive gear 63 and the intermediate transfer member drive shaft 62 rotate at RT and RP, respectively. The rotation of 63 is not transmitted to the intermediate transfer member drive shaft 62.

When each toner image on the photosensitive member is primarily transferred onto the intermediate transfer member, the intermediate transfer member 17 is driven by the photosensitive member 11, the surface linear velocity is VP, and the drive roller 18 is driven by the intermediate transfer member. Driven by body 17. The rotation speed is RP (N2 × R), and the intermediate transfer member drive shaft 62 is driven by the rotation speed RP (N2 × R
Rotate at a rotational speed equal to R). Accordingly, the intermediate transfer member drive shaft 62 is driven by the rotation speed RT (N1
XR), the drive from the drive motor 56 is not transmitted to the intermediate transfer member drive shaft 62. That is, the intermediate transfer member drive shaft 62
Rotates at RP (N2 × R).

When the transfer roller 30 and the cleaning member 34 come into contact with the intermediate transfer member 17, the intermediate transfer member drive shaft 62 tries to stop, but the one-way clutch 65 is in the state shown in FIG. Of the drive roller 18 via the one-way clutch 65, the intermediate transfer member drive shaft 62 and the joint 64
Is rotated at the rotation speed of RT (N1 × R), and the intermediate transfer body 17 is driven at the surface linear velocity of VT.

The linear velocity of the surface of the photoconductor varies depending on the eccentricity of the photoconductor itself or its transmission element.
Assuming that N2 = 1: 1, when the toner image on the photosensitive member is primarily transferred to the intermediate transfer member 17 and the speed of the photosensitive member increases, the intermediate transfer member 17 It follows and rotates. However, when the speed of the photoconductor 11 changes so that the speed of the photoconductor 11 decreases, the drive of the drive motor 56 is transmitted to the intermediate transfer member 17 via transmission elements such as a timing belt, a pulley, and a gear. The vehicle runs at a surface linear velocity different from that of the photoconductor 11. By setting the surface linear velocity VP of the photoconductor 11 and the surface linear velocity VT of the intermediate transfer body 17 driven by the drive motor 56 without passing through the surface of the photoconductor to VP> VT, the toner image on the photoconductor is set. Is primarily transferred to the intermediate transfer member 17, the intermediate transfer member 17 can be reliably driven by the photoconductor 11.

At this time, it is necessary to set the surface linear velocity VT of the intermediate transfer body 17 in consideration of the fluctuation of the surface linear velocity of the photoreceptor 11. Also, the surface linear velocity VT of the intermediate transfer body 17 is
If the surface linear velocity is set to be much lower than the surface linear velocity VP, the image forming speed is reduced. Therefore, it is advantageous to set VT to a value as close to VP as possible.

Normally, the variation of the surface linear velocity VP of the photosensitive member 11 is ± 1% to ± 2%. Therefore, taking into account some safety, the surface linear velocity VP of the image carrier composed of the photoreceptor 11
Is set to 1 when the intermediate transfer body 17 driven by the drive source including the drive motor 56 without passing through the surface of the image carrier has a surface linear velocity VT of 0.97 to 0.99. It is advantageous to set the linear velocity VT such that

In any of the above-described image forming apparatuses, when a single-color image is to be obtained, a single-color image is formed on the surface of the photosensitive member by any one of the plurality of developing units 13A, 13B, 13C, and 13D. Forming a single toner image of
The toner image is primary-transferred onto the intermediate transfer body 17 and then the toner image is secondarily transferred onto a recording medium. In this case, the contact / separation member including the transfer roller 30 and the cleaning member 34 is In contact with the surface. In this case, when the single toner image on the photosensitive member surface is primarily transferred to the intermediate transfer member 17 and thereafter, the intermediate transfer member 17 is driven not by the photosensitive member but without the photosensitive member. The electromagnetic clutch 59 or the one-way clutch 65
The switching means comprises: Thus, even when the contact member is always in contact with the intermediate transfer member 17, the intermediate transfer member 17 can be reliably driven in a stable state. Also,
Even in this case, since only a single toner image is primarily transferred to the intermediate transfer body 17, there is no possibility that a color shift occurs. In this manner, a single toner image is formed on the surface of the image carrier composed of the photoreceptor 11, and the single toner image is formed on the surface of the intermediate transfer member while the contact member is kept in contact with the surface of the intermediate transfer member. When a primary transfer is performed and a single toner image on the surface of the intermediate transfer member is secondarily transferred to a recording medium to obtain a recorded image, a single toner image on the surface of the image carrier is primarily transferred onto the surface of the intermediate transfer member. The switching means is configured such that the intermediate transfer member 17 is driven by the driving force of the driving source that does not pass through the surface of the image carrier, both at the time and after the primary transfer of the single toner image is completed. It constitutes.

In each of the above-described embodiments, the driving source for driving the intermediate transfer member 17 and the driving source for driving the image bearing member composed of the photosensitive member 11 are the same driving source, ie, the driving motor 56. Although only one driving source is required, the structure and cost of the image forming apparatus can be reduced, but the intermediate transfer member and the image carrier can be driven by different driving sources.

According to the configuration shown in FIG. 5, in addition to the functions and effects provided by the configuration shown in FIG. 3, an advantage of simplifying control of the apparatus can be obtained. That is, when the electromagnetic clutch 59 shown in FIG. 3 is used, it is necessary to control timing for switching the electromagnetic clutch 59. However, when the one-way clutch 65 shown in FIG. It can be done automatically by release.

The above-described configurations can be widely applied to image forming apparatuses other than those shown in FIGS. For example, as shown in FIG.
The image forming apparatus can be applied to an image forming apparatus including an endless belt wound around a plurality of rollers including an intermediate transfer member 117 in which the intermediate transfer member 117 is formed in a drum shape. Similarly, as shown in FIG. 9, the photosensitive member 211 is formed of an endless belt wound around a plurality of rollers including a driving roller 212, and the intermediate transfer body 217 is also wound around a plurality of rollers including a driving roller 218. The present invention can be applied to an image forming apparatus including an endless belt. Also in the image forming apparatus shown in FIGS. 8 and 9, the surfaces of the photoconductors 111 and 211 driven in the direction of arrow A
Toner images of different colors are sequentially formed by the developing device 13, and the respective toner images are primarily transferred to the intermediate transfer members 117 and 217 driven in the direction of arrow B, and the superimposed toner images are transferred by the action of the transfer roller 30. The image is secondarily transferred onto the recording medium 27. Other configurations and operations are shown in FIGS.
8 and 9 corresponding to the elements shown in FIGS. 1 and 2 are denoted by the same reference numerals as those in FIGS. 1 and 2. The description is omitted.

In the image forming apparatus shown in FIG. 8, the surface linear velocity VP of the photosensitive member 111 is equal to the diameter D of the driving roller 112.
1 and its rotation speed R. Intermediate transfer member 117
Runs at VP during the primary transfer of the toner image, but the transfer roller 30 and the cleaning member 34
, It rotates at the rotation speed RT (N1 × R) and is driven at the surface linear velocity of the VT.

In the image forming apparatus shown in FIG. 9, the surface linear velocity VP of the photosensitive member 211 is equal to the diameter D of the driving roller 212.
1 and its rotation speed R. Similarly, the intermediate transfer member 217 travels at the surface linear velocity of the VP during the primary transfer of the toner image, and when the transfer roller 30 and the cleaning member 34 are in contact with the intermediate transfer member 217, the rotation speed RT (N1 ×
R) and driven at the surface linear velocity of the VT.

[0069]

According to the image forming apparatus of the first aspect, in the step of primarily transferring the plurality of toner images formed on the surface of the image carrier to the intermediate transfer body, the intermediate transfer body contacts the intermediate transfer body. Since the toner image is driven from the image carrier, the toner images on the surface of the intermediate transfer member can be superposed with high accuracy. Also, when the contacting / separating member is in contact with the surface of the intermediate transfer member and there is no need for the superposition accuracy of each toner image, the intermediate transfer member is driven by the drive source without passing through the surface of the image carrier.
The intermediate transfer member can be reliably driven.

According to the image forming apparatus of the second aspect,
The above effects can be obtained with a simple configuration.

According to the image forming apparatus of the third aspect,
The switching control of the switching means can be simplified.

According to the image forming apparatus of the fourth aspect,
When the toner image on the surface of the image carrier is primarily transferred to the intermediate transfer body, the intermediate transfer body can be reliably driven and driven by the image carrier.

According to the image forming apparatus of the fifth aspect,
When the intermediate transfer member is driven by the driving source without passing through the image carrier, it is possible to prevent the speed of the intermediate transfer member from excessively decreasing, and to prevent the image forming speed from decreasing.

According to the image forming apparatus of the sixth aspect,
A single toner image can be formed without any trouble.

According to the image forming apparatus of the seventh aspect,
The configuration of the image forming apparatus can be simplified, and its cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus, and is a diagram illustrating a state when a toner image on a photosensitive member is primarily transferred onto an intermediate transfer member.

FIG. 2 is a schematic cross-sectional view illustrating a state when a transfer roller and a cleaning member of the image forming apparatus illustrated in FIG. 1 contact an intermediate transfer member.

FIG. 3 is a partial cross-sectional plan view of a drive system.

FIG. 4 is an explanatory diagram when the drive system is viewed from the front side.

FIG. 5 is a view similar to FIG. 3, showing an example different from the example shown in FIG. 3;

FIG. 6 is an explanatory diagram of a one-way clutch.

FIG. 7 is an explanatory diagram of a one-way clutch.

FIG. 8 is a schematic sectional view showing another example of the image forming apparatus.

FIG. 9 is a schematic sectional view showing still another example of the image forming apparatus.

[Explanation of symbols]

 17 Intermediate transfer member 27 Recording medium 59 Clutch 65 One-way clutch

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H030 AA01 AD17 BB02 BB23 BB24 BB42 BB53 2H032 AA05 BA01 BA03 BA09 BA16 BA18 BA19 CA01 CA13

Claims (7)

[Claims] 1. An image forming apparatus according to claim 1, wherein toner images of different colors are sequentially formed on the surface of the image carrier driven to move, and the surface of the intermediate transfer member driven while being in contact with the surface of the image carrier. An image forming apparatus, wherein the toner images formed on the surface of the image carrier are sequentially superimposed and primary transferred, and the superimposed toner images are collectively and secondarily transferred onto a recording medium to obtain a recorded image, During the primary transfer of the toner image to the surface of the intermediate transfer member, the toner image is separated from the surface of the intermediate transfer member, and the intermediate image is formed at a time after the completion of the primary transfer of the plurality of toner images from the image carrier to the intermediate transfer member. In an image forming apparatus having a contact / separation member in contact with a surface of a transfer member, when the toner image is primarily transferred from the image carrier to an intermediate transfer member, the intermediate transfer member is directly received from a surface of the image carrier. Driven by driving force, image bearing The driving force from the driving source is transmitted to the intermediate transfer member without passing through the surface of the image carrier at a time after the time when the primary transfer of the plurality of toner images from the An image forming apparatus comprising: a switching unit that intermittently controls transmission of a driving force from the driving source to an intermediate transfer member so that the transfer member is driven. 2. The image forming apparatus according to claim 1, wherein when the toner image is primarily transferred from the image bearing member to the intermediate transfer member, the switching means transmits a driving force of the drive source to the intermediate transfer member without passing through the surface of the image bearing member. A clutch operable to transmit a driving force of the driving source to the intermediate transfer member without passing through the surface of the image carrier at a time before the contacting / separating member contacts the surface of the intermediate transfer member. Item 2. The image forming apparatus according to Item 1. 3. The drive unit of the drive source, wherein the drive unit does not pass through the surface of the image carrier when the contact member comes into contact with the surface of the intermediate transfer member and a braking force is applied to the intermediate transfer member. The image forming apparatus according to claim 1, further comprising a one-way clutch that operates to transmit a driving force to the intermediate transfer member. 4. When the surface linear velocity of the image carrier is VP and the surface linear velocity of the intermediate transfer member driven by the driving source without passing through the surface of the image carrier is VT, VP> VT is set. The image forming apparatus according to claim 3. 5. When the surface linear velocity VP of the image carrier is 1, the surface linear velocity VT of the intermediate transfer body driven by the driving source without passing through the surface of the image carrier is 0.97 to 0. 5. The image forming apparatus according to claim 4, wherein the image forming apparatus is set to .99. 6. A single toner image is formed on the surface of the image carrier, and the contact member is kept in contact with the surface of the intermediate transfer member.
When the single toner image is primarily transferred onto the surface of the intermediate transfer member, and the single toner image on the surface of the intermediate transfer member is secondarily transferred onto a recording medium to obtain a recorded image, a single image on the surface of the image carrier is obtained. Even when the toner image is primarily transferred to the surface of the intermediate transfer member, or after the primary transfer of the single toner image is completed, the intermediate source is driven by the driving force of the driving source without passing through the surface of the image carrier. The image forming apparatus according to claim 1, wherein the switching unit is configured to drive the transfer member. 7. The drive source for driving an intermediate transfer member and the drive source for driving an image carrier are the same drive source.
7. The image forming apparatus according to any one of claims 1 to 6, wherein