JP4742709B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile machine, and a multifunction machine in which two or more of these are combined.

An electrophotographic image forming apparatus is a monochrome image forming apparatus and a color image forming apparatus capable of forming an image using two or more toners (typically a full color image forming apparatus) from the viewpoint of the color of toner used for development. Can be broadly divided.
In a monochrome image forming apparatus, generally, a visible toner image formed on an image carrier is directly transferred and fixed on a recording medium.

  In a color image forming apparatus, an intermediate transfer member is usually employed, and a visible toner image formed on an image carrier is primarily transferred onto the intermediate transfer member and secondarily transferred from the intermediate transfer member to a recording medium. Is fixed.

  Among such color image forming apparatuses, a plurality of developing units are arranged for one image carrier, and toner images of different colors are formed on the image carrier using the developing units, and the different color toners are formed. A device that sequentially superimposes and transfers an image onto an intermediate transfer member is called a four-cycle color image forming apparatus.

  In addition, a plurality of image carriers are sequentially arranged along the intermediate transfer member, and a developing device is provided for each image carrier, and a toner image is formed on the image carrier using a corresponding developing device. At the same time, a tandem type color image forming apparatus is known in which a toner image formed on the image carrier is sequentially transferred onto an intermediate transfer member.

  In any case, in a color image forming apparatus that employs an image carrier and an intermediate transfer member, generally, on the image carrier as the toner image is first transferred from the image carrier to the intermediate transfer member. A cleaner that cleans the primary transfer residual toner that may remain in the toner, or a secondary transfer that may remain on the intermediate transfer member due to the secondary transfer of the toner image from the intermediate transfer member to the recording medium A cleaner for cleaning the remaining toner is also provided.

The image bearing member is generally a drum-type photosensitive member that is driven to rotate. However, a photosensitive belt that is wound around a plurality of belt winding members and is driven to rotate may be employed.
As an intermediate transfer member, an intermediate transfer belt that is wound around a plurality of belt winding members and is driven to rotate can be cited as a representative example, and the intermediate transfer belt is rotated on the image carrier. The toner images are successively transferred onto the intermediate transfer belt in order.
Examples of the cleaner for cleaning the transfer residual toner may include a cleaning blade that cleans the transfer residual toner by being disposed in contact with the surface of the member to be cleaned.

  When the cleaner that cleans the transfer residual toner by being arranged in contact with the intermediate transfer member that is driven to rotate is always in contact with the intermediate transfer member, for example, the primary transfer is performed first on the intermediate transfer member, and further, When the next color toner image is overlaid on the toner image and then transferred primarily, the previous toner image is disturbed by contact with the cleaner. Separated from the member.

  Then, the cleaner is attached to the intermediate transfer member so that the time from the end of one image formation to the start of the next image formation can be efficiently formed without increasing the time for cleaning the intermediate transfer member by the cleaner. Even if the contact is started, there is no fear that the primary transfer toner image on the intermediate transfer member will be disturbed by contact with the cleaner, and the cleaner from the middle of the primary transfer of the last color toner image to the intermediate transfer member. Is often started to contact the intermediate transfer member.

  An example of such a cleaner is shown in FIG. The cleaner CL ′ in FIG. 8 cleans the intermediate transfer belt B. The belt B is wound around a plurality of belt winding rollers including the roller R and is driven to rotate. The cleaner CL 'has a cleaning blade BL that contacts the belt B and cleans the belt.

The blade BL is held by a blade support member F that can swing around an axis Fa.
When viewed from the side, the support member F has a vertical portion and an integral horizontal portion (portion following the cam) at the top as shown in the figure. The end of the lateral portion far from the belt B is biased by a spring S, whereby the entire support member F is a belt portion around which the blade BL is wound around the roller R around the axis Fa. It can be rotated in the direction in which it contacts. A cam CM rotated by a drive motor (not shown) is in contact with the other end of the horizontal portion.

In this cleaner CL ′, the center of the swing axis Fa of the blade support member F is arranged on a straight line Li connecting the center of the belt winding roller R facing the blade BL and the blade tip BLa when contacting the belt BL. Has been.
At the beginning of the primary transfer of the toner image onto the transfer belt B, the large radius portion of the cam CM abuts against the support member F as shown by the broken line in FIG. Thus, the blade BL is separated from the belt B by being rotated counterclockwise in the drawing.
In this state, for example, a toner image formed on an image carrier (not shown) is sequentially superimposed on the intermediate transfer belt B and is primarily transferred, and then secondarily transferred from the belt B onto a recording medium (not shown). .

  Then, at a predetermined timing before the secondary transfer residual toner on the belt B reaches the position facing the cleaner blade BL (typically, the toner image of the last color is being primarily transferred to the belt B. And at the timing when the primary transfer toner image on the belt B is not disturbed by contact with the blade BL), the cam CM is rotated in a direction to release the support member F. While receiving the spring S force, it follows the cam CM around the axis Fa and rotates in the clockwise direction CW in the figure, and thus the tip BLa of the blade BL starts to contact the belt B.

At this time, the blade tip BLa starts to contact the belt B from a substantially tangential direction of the roller R, and then further moves to a predetermined pressure contact position (predetermined biting position) to the belt B for cleaning residual toner.
Since the blade tip BLa is in pressure contact with the belt B in a range where the belt B is wound around the roller R, the blade tip BLa also approaches the belt B from a substantially tangential direction and is moved to a predetermined pressure contact position for cleaning.

  At this time, since the movement of the blade tip BLa from the start of contact with the belt B to the predetermined pressure contact position is in a substantially tangential direction of the belt B, the blade is brought into contact with the belt portion wound around the roller R from the normal direction. In comparison, the movement time from the start of contact of the blade BL to the belt B to the predetermined pressure contact position (predetermined bite position) becomes longer.

  For this reason, the gradient of the increase in the load fluctuation of the belt due to the cleaner contact with the belt B becomes gentler, and the rapid speed fluctuation of the belt B is suppressed accordingly. By suppressing the speed fluctuation in this way, for example, even if the cleaner starts to contact the intermediate transfer belt B in the middle of the primary transfer of the last color toner image to the intermediate transfer belt B, the intermediate transfer belt B Deviation (so-called color misregistration) between toner images transferred on top of each other is suppressed, so that good image formation can be performed.

A cleaner of the type described above is described in, for example, Japanese Patent Application Laid-Open No. 9-311522.
JP-A-9-311522

  However, according to the cleaner having the structure as shown in FIG. 8, when the blade BL moves from the contact start position with the belt B to the predetermined pressure contact position for cleaning, the moving speed of the blade tip BLa is changed to the belt B of the blade BL. The blade BL decreases with an increase in the amount of biting (the amount by which the blade tip BLa bends due to contact with the belt B). The blade BL is a friction force between the blade BL and the belt B. Stops at a position where the total pressing force by the urging member is balanced.

  For this reason, when the moving speed of the blade BL for contact with the belt B is high or when the blade hardness is high, the load fluctuation of the belt B due to the blade contact cannot be reduced, and the blade BL stops its movement. Sometimes a large impact is generated, which may cause the belt running speed to fluctuate rapidly and cause the color shift.

  Further, in a small image forming apparatus, when a small roller is used as the roller R due to the space in the apparatus, if the blade BL is pressed against the belt B from the substantially tangential direction of the roller, the blade bites against the curvature of the roller. Where the amount must be increased, there may be cases where such a sufficient bite amount cannot be ensured. In addition, since the diameter of the roller is small, the amount of belt wound around the roller is small, and belt speed fluctuations easily affect the color shift.

  JP-A-9-311522 discloses a brake device that constantly applies a constant load to the roller R shown in FIG. 8 or a load applied to the roller R before contact with the cleaner, and the load applied when the cleaner contacts. Although it is also disclosed that the load change of the belt at the time of contact with the cleaner is suppressed by adopting a brake device etc. that releases the brake, the installation of such a brake device is a large-scale and hinders downsizing of the image forming apparatus become.

  The above problem relating to the cleaner for cleaning the transfer residual toner is not only the cleaner for the intermediate transfer member, but also a belt in which the image carrier is wound around a plurality of belt winding members. When cleaning the primary transfer residual toner remaining on the image carrier belt after the primary transfer of the toner image to the toner, the same phenomenon occurs when a cleaner of the type shown in FIG. 8 is employed.

  For example, if the cleaner is brought into contact with the image carrier belt during the primary transfer of the toner image of the last color to the intermediate transfer member in order to perform image formation efficiently, the speed of the belt may fluctuate. A color shift occurs in the toner image primarily transferred to the intermediate transfer member, and in order to efficiently perform image formation, a cleaner is formed while the last color toner image is being formed on the image carrier belt. Is brought into contact with the image carrier belt, the toner image formed on the belt is distorted due to speed fluctuations of the belt, and as a result, the toner image is transferred onto the intermediate transfer member on which the toner image is primarily transferred. Color misregistration occurs.

Accordingly, the present invention provides a plurality of developing devices having different color toners,
An image carrier on which a toner image is formed by the developing device;
An intermediate transfer member on which a toner image formed on the image carrier is primarily transferred;
A primary transfer device that sequentially superimposes and transfers toner images formed on the image carrier onto the intermediate transfer member;
A secondary transfer device for secondary transfer of the multiple toner image primarily transferred onto the intermediate transfer member to the recording medium;
At least one of the image carrier and the intermediate transfer member is a belt wound around a belt winding member, and a transfer residual toner remaining on the belt after transfer of the toner image on the belt A cleaner and a cleaner driving device are provided, and the cleaner is a cleaner that cleans the residual toner by being disposed in contact with the belt, and the cleaner driving device removes the cleaner. An image forming apparatus that is a driving device that contacts and separates from the belt, and the speed variation of the belt at the moment of cleaner contact with the belt is easily and surely suppressed, and the images are transferred onto the intermediate transfer member in an overlapping manner. An object of the present invention is to provide an image forming apparatus capable of suppressing color misregistration between toner images.

In order to solve the above problems, the present invention provides a plurality of developing units having different color toners,
An image carrier on which a toner image is formed by the developing device;
An intermediate transfer member on which a toner image formed on the image carrier is primarily transferred;
A primary transfer device that sequentially superimposes and transfers toner images formed on the image carrier onto the intermediate transfer member;
A secondary transfer device for secondary transfer of the multiple toner image primarily transferred onto the intermediate transfer member to the recording medium;
At least one of the image carrier and the intermediate transfer member is a belt wound around a belt winding member, and a transfer residual toner remaining on the belt after transfer of the toner image on the belt A cleaner and a cleaner driving device are provided, and the cleaner is a cleaner that cleans the residual toner by being disposed in contact with the belt, and the cleaner driving device removes the cleaner. A drive device for contacting and separating the belt, and at a moment when the cleaner starts to contact the belt, a belt tangential velocity component of the cleaner at a site where the cleaner and the belt start to contact each other A cleaner urging portion for bringing the cleaner into contact with the belt so as to be equal to a belt speed at a mutual contact start portion; Later, for the belt of the cleaner, to provide an image forming apparatus and a cleaner reduction unit that moves while decelerating to a final contact position for belt cleaning.

In general, when the cleaner is brought into pressure contact with the belt, the difference in speed between the belt and the blade at the moment of pressure contact causes fluctuations in the load of the belt, and hence the running speed of the belt.
In this regard, according to the image forming apparatus of the present invention, the cleaner that cleans the transfer residual toner on the belt is driven to contact and separate from the belt by the cleaner driving device, but the cleaner biasing portion of the cleaner driving device is At the moment when the belt starts to contact the belt, the cleaner is brought into contact with the belt so that the belt tangential speed component of the cleaner at the contact start portion of the cleaner and the belt becomes equal to the belt speed at the contact start portion of the belt. . Therefore, the load fluctuation of the belt at the moment of contact of the cleaner with the belt is suppressed to a small level, and the speed fluctuation of the belt is also suppressed to a small extent.

  Also, if the speed at which the cleaner starts to contact the belt and then moves to the contact position for cleaning the belt is large, the pressure contact force that the cleaner exerts on the belt increases rapidly, and the load fluctuation of the belt increases accordingly. In the cleaner driving apparatus, the cleaner decelerating unit moves the cleaner while decelerating it to the final contact position for cleaning the belt after the moment of contact start, so that the load fluctuation of the belt is suppressed and the speed fluctuation of the belt is reduced. Is also reduced by that much.

  As a result, color misregistration between toner images primarily transferred onto the intermediate transfer member is suppressed, and a good image can be formed accordingly.

Specific examples of the image forming apparatus according to the present invention include the above-described four-cycle color image forming apparatus and tandem color image forming apparatus.
Regardless of the type of image forming apparatus, the case where the intermediate transfer member of the image carrier and the intermediate transfer member is a belt wound around the belt winding member can be exemplified. .

  In this case, the cleaner and the cleaner driving device can be provided for the intermediate transfer belt. By doing so, for example, even if the cleaner starts to contact the intermediate transfer belt, the primary transfer toner image on the intermediate transfer belt is not in contact with the cleaner and disturbed so that an image can be formed efficiently. Even if the cleaner starts to contact the intermediate transfer belt in the middle of the primary transfer of the toner image of the last color to the intermediate transfer belt, color misregistration between the toner images on the intermediate transfer belt is suppressed.

In the four-cycle color image forming apparatus, the image carrier of the image carrier and the intermediate transfer member can be a belt wound around a belt winding member.
On the image carrier belt, toner images of different colors can be sequentially formed by the developing device. The cleaner and cleaner driving device may be provided for the belt.

  By providing the cleaner and the cleaner driving device for the image carrier belt, for example, in order to efficiently form an image, even if the cleaner starts to contact the image carrier belt, a toner image is formed on the belt. Even if the cleaner is brought into contact with the image carrier belt in the middle of the formation of the toner image of the last color on the belt, the formation of a toner image on the image carrier belt can be suppressed. Color misregistration between toner images that are primarily transferred onto the transfer member can be suppressed.

  The image carrier and the intermediate transfer member may both be belts wound around the belt winding member. In this case, toner images of different colors may be sequentially formed on the belt as the image carrier by the developing device. The cleaner and the cleaner driving device may be provided for each belt.

As described above, according to the present invention, a plurality of developing devices having different color toners,
An image carrier on which a toner image is formed by the developing device;
An intermediate transfer member on which a toner image formed on the image carrier is primarily transferred;
A primary transfer device that sequentially superimposes and transfers toner images formed on the image carrier onto the intermediate transfer member;
A secondary transfer device for secondary transfer of the multiple toner image primarily transferred onto the intermediate transfer member to the recording medium;
At least one of the image carrier and the intermediate transfer member is a belt wound around a belt winding member, and a transfer residual toner remaining on the belt after transfer of the toner image on the belt A cleaner and a cleaner driving device are provided, and the cleaner is a cleaner that cleans the residual toner by being disposed in contact with the belt, and the cleaner driving device removes the cleaner. An image forming apparatus that is a driving device that contacts and separates from the belt, and the speed variation of the belt at the moment of cleaner contact with the belt is easily and surely suppressed, and the images are transferred onto the intermediate transfer member in an overlapping manner. An image forming apparatus capable of suppressing color misregistration between toner images can be provided.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a four-cycle full-color image forming apparatus provided with an example of a cleaning apparatus according to the present invention.
This image forming apparatus includes a drum-type photosensitive member 1 that is rotationally driven as an image carrier, and the surface of the photosensitive member 1 is uniformly charged to a predetermined potential by a charging charger 2, and an image exposure device is provided in the charged region. 3 is subjected to image exposure to form an electrostatic latent image, and the latent image is developed by the developing device 4 to form a visible toner image.

  The developing device 4 includes a holder 4H that is rotationally driven, and a yellow developing device 4Y, a magenta developing device 4M, a cyan developing device 4C, and a black developing device 4K. An electrostatic latent image corresponding to each color can be sequentially formed on the photoreceptor 1 based on image data for each color of yellow, magenta, cyan, and black, and the latent image corresponding to one color is formed each time the latent image is formed. The latent image is developed by a developing unit corresponding to the color among the four developing units.

  The toner images of the respective colors sequentially formed on the photoreceptor 1 in this way are primarily transferred to an intermediate transfer belt (an example of an intermediate transfer member) 5 each time one toner image is formed, The toner image transferred onto the toner image is transferred onto the toner image. The multiple toner images formed on the intermediate transfer belt 5 in this way are supplied one by one from the recording medium supply unit 6 by the supply roller 61, and sent in synchronization with the multiple toner image by the timing roller pair 62. The toner image is secondarily transferred to the recording medium S such as transfer paper, and fixed on the recording medium by the fixing device 7. The recording medium S on which the toner image is fixed in this manner is discharged onto the discharge tray 8 by the discharge roller pair 81.

  After the primary transfer, untransferred toner remaining on the photoreceptor 1 is cleaned by a cleaner 9 including a cleaning blade 91 pressed against the photoreceptor 1. The toner remaining on the intermediate transfer belt 5 due to the secondary transfer is transferred to the cleaner 9 at a predetermined timing, in the present example, while the last color toner image is being transferred from the photoreceptor 1 to the intermediate transfer belt 5. And cleaning begins. The cleaner 9 will be described in detail later.

  The above is the case of full-color image formation, but it is also possible to form a monochrome image using only the black developing device 4K, for example.

The intermediate transfer belt 5 and the cleaner 9 will be further described.
The intermediate transfer belt 5 is a rotationally driven drive roller 51, a primary transfer roller 52 disposed opposite to the photoreceptor 1, a roller 53 that contacts the photoreceptor 5 in cooperation with the roller 52, a driven roller 54, and It is wound around a roller group consisting of tension rollers 55.

  The primary transfer roller 52 primarily transfers the toner image on the photosensitive member 1 to the intermediate transfer belt 5 by applying a primary transfer voltage. The secondary transfer roller 10 is opposed to the drive roller 51, and the secondary transfer roller 10 is applied with a secondary transfer voltage to the recording medium S passed between the rollers 51 and 10 on the belt 5. The toner image is secondarily transferred.

  The secondary transfer roller 10 is separated from the belt 5 until the primary transfer of the predetermined toner image onto the belt 5 is completed. When the primary transfer of the predetermined toner image is completed, or 1 of the last color toner image. It is pressed toward the belt 5 from the middle of the next transfer.

As shown in FIG. 2, the cleaner 9 has a cleaning blade 91 that is in pressure contact with a portion of the intermediate transfer belt 5 that is wound around the belt-wrapped driven roller 54. The blade 91 is supported by a blade support member 92. The support member 92 can reciprocate linearly along a guide member 93 attached to a frame (not shown), and is biased downward in the figure by a tension spring 94. A cam 95 is in contact with the support member 92.
These spring 94, cam 95, etc. constitute a cleaner driving device.

  The cam 95 is rotationally driven at a predetermined timing around the cam shaft 95a by a drive motor (not shown). By rotating the cam in the counterclockwise direction CCW in FIG. 2, the support member 92 can be lifted against the spring 94 and the blade 91 can be pressed against the belt 5. The blade 91 can be separated from the belt 5 by turning clockwise from this state.

  FIG. 3 shows details of the cam 91. The peripheral surface (cam surface) of the cam 95 includes a contact side cam surface that can contact the blade support member 92 and a separation side cam surface that does not contact the support member 92. The contact side cam surface includes a separation portion, a constant velocity portion, a deceleration portion, and a pressure contact portion.

The separation portion is a portion that contacts the blade support member 92, but is a portion where the support member 92 is lowered by the spring 94 and the blade 91 is separated from the belt 5.
The constant velocity part pushes up the support member 92 at a constant velocity against the spring 94, thereby moving the blade 91 at a constant velocity (Va) to contact the belt 5, and the blade tip 91a to the belt 5 A belt tangential velocity component Va · cosφ (φ is an angle formed by the direction of the blade tip speed Va and the belt tangential direction) of the blade tip 91a at the contact point between the blade tip 91a and the belt 5 at the moment of contact. It is a part for making it correspond to the speed (circumferential speed) Vb. The constant velocity portion and the like constitute a cleaner urging portion of the cleaner driving device.

  Thus, at the moment of contact of the blade 91 with the belt 5, the belt tangential velocity component Va · cosφ of the blade tip 91 a becomes equal to the belt speed Vb, and therefore the load of the belt when the blade 91 starts to contact the belt 5. The fluctuation, and hence the rapid speed fluctuation of the belt 5 is suppressed.

After the blade 91 starts to contact the belt 5 (after the moment of contact), the speed reduction unit decelerates and moves the blade 91 to the final contact position for cleaning the secondary transfer residual toner on the belt 5. The blade 91 is decelerated as the amount of biting of the blade 91 into the belt 5 increases, whereby the load fluctuation of the belt 5 and consequently the rapid speed fluctuation of the belt 5 can be suppressed.
Such a speed reduction part constitutes a cleaner speed reduction part of the cleaner driving device.

  The pressure contact portion is a portion that maintains the blade 91 at the final contact position for cleaning the secondary transfer residual toner.

  In FIG. 3, a1, a2, and a3 indicate positions on the cam surface that come into contact with the blade support member 92, a1 is a contact start position of the cam 95 to the blade support member 92, and a2 is a blade The position where the tip 91a is switched to the speed reducing portion after the moment of contact with the belt 5 is a position corresponding to the blade 91 reaching the final contact position on the belt 5 for cleaning the secondary transfer residual toner.

  4 shows a cam diagram of the cam 95, and FIG. 5 shows the relationship between the rotation angle of the cam 95 and the moving speed of the cleaner 9 (more precisely, the blade 91) for pressing against the belt 5. ing.

  By adopting such a constant speed part and a speed reducing part, it is possible to suppress a rapid speed fluctuation of the belt 5 due to the press contact of the cleaner 9 to the belt 5, so that, for example, the last color of the last color can be efficiently performed. Even when the blade 91 is pressed against the belt 5 for cleaning the secondary transfer residual toner on the belt 5 from the middle of the primary transfer of the toner image from the photoreceptor 1 to the intermediate transfer belt 5, the belt 5 The occurrence of color misregistration between the multiple toner images can be easily and reliably suppressed.

  The cam 95 is switched from the constant velocity portion to the deceleration portion after the blade 91 contacts the belt 5. In this example, the deceleration unit decelerates the moving speed of the blade 91 at a constant acceleration, but other deceleration patterns such as a quadratic curve may be employed.

Further, the separation position of the blade 91 from the belt 5 may be determined by position regulation of the cleaner 9 such as the blade support member 92. In this case, the separation part in the cam 95 can be omitted.
According to the cam 95 of the illustrated example, the blade 91 shows the same behavior, although the order is opposite, when the blade 91 is pressed against the belt 5 and when the blade 91 is separated from the belt 5. You may employ | adopt the cam which the cleaner 9 shows the behavior which changes with time.

  In the cleaner 9 described above, the cleaning blade 91 is employed. However, the cleaning member in the cleaner is not limited to the blade, and any cleaning member that can clean the transfer residual toner by pressure contact may be used. It is also possible to employ a type cleaning member (for example, a cleaning member such as a roller type or a brush type, or a pressing type cleaning member made of felt or the like).

Next, another example of the cleaner for cleaning the transfer residual toner will be described with reference to FIGS.
The cleaner 9 ′ in FIG. 6 has a cleaning blade 91 that is in pressure contact with a portion of the intermediate transfer belt 5 that is wound around the belt-wrapped driven roller 54. The blade 91 is supported by a blade support member 92 ′. The support member 92 ′ can swing around a fixed position shaft 92a ′, and is biased by a tension spring 94 ′ in a direction away from the belt 5 in the drawing. A cam 95 is in contact with the support member 92 '.

  The cam 95 is the same cam as the cam 95 in the cleaner 9 shown in FIG. By rotating the cam 95 in the counterclockwise direction CCW in FIG. 6, the support member 92 ′ can be rotated in the counterclockwise direction CCW against the spring 94 ′, thereby bringing the blade 91 into pressure contact with the belt 5 Can do. The blade 91 can be separated from the belt 5 by turning clockwise from this state.

  Also in this cleaner 9 ′, the cam 95 is provided with a constant velocity portion, so that the belt of the blade tip 91 a at the contact point between the blade tip 91 a and the belt 5 at the moment of contact of the blade tip 91 a with the belt 5. The tangential speed component can be made to coincide with the speed (circumferential speed) of the belt 5, thereby suppressing the load fluctuation of the belt at the start of contact of the blade 91 with the belt 5, and hence the rapid speed fluctuation of the belt 5. Accordingly, the color shift of the toner image on the intermediate transfer belt 5 can be suppressed.

  Further, since the cam 95 includes a speed reducing portion, the blade 91 is decelerated as the amount of biting of the blade 91 into the belt 5 increases, thereby suppressing the load fluctuation of the belt 5 and consequently the rapid speed fluctuation of the belt 5. As a result, the rapid speed fluctuation of the belt 5 can be suppressed, and the color shift of the toner image on the intermediate transfer belt 5 can be suppressed accordingly.

  The cleaner 9 ″ in FIG. 7 has a cleaning blade 91 that is pressed against a portion of the intermediate transfer belt 5 that is wound around the belt-wrapped driven roller 54. The blade 91 is supported by a blade support member 92 ″. Has been. The support member 92 ″ can swing about a fixed-position shaft 92a ″, and is urged by a tension spring 94 ″ in a direction in which the blade 91 is pressed against the belt 5. The support member 92 ″ The cam 95 ″ is in contact. The damper 96 is also in contact at the timing described later.

  According to the cam 95 ″ of the cleaner 9 ″, by rotating it in the clockwise direction CW in FIG. 7, the support member 92 ″ is also rotated in the clockwise direction CW, and the blade 91 can be moved toward the belt 5. The moving speed of the blade 91 at this time depends on the force of the spring 94 ″, the configuration of the cleaner 9 ″, the sliding resistance of the shaft 92a ″ of the support member 92 ″, etc., but depends on the cam 95 ″ here. Then, at the moment when the blade 91 is pressed against the belt 5, the belt tangential speed component of the blade tip 91 a at the mutual contact portion between the blade tip 91 a and the belt 5 matches the speed (circumferential speed) of the belt 5. . As a result, the belt load fluctuation at the start of the contact of the blade 91 with the belt 5 and the rapid speed fluctuation of the belt 5 are suppressed, and the color shift of the toner image on the intermediate transfer belt 5 can be suppressed accordingly.

Further, after the blade tip 91a starts to press against the belt 5 (after the moment of pressing), the damper 96 comes into contact with the support member 92 ″, and the blade 91 is decelerated by the action of the damper to clean the residual toner. Move to the final contact position and stop.
In this way, after the moment of pressure contact of the blade 91 to the belt 5, the blade 91 is decelerated as the amount of biting of the blade 91 into the belt 5 increases, thereby causing a load fluctuation of the belt 5 and a sudden speed fluctuation of the belt 5. Therefore, the color shift of the toner image on the intermediate transfer belt 5 can be suppressed accordingly.

  The image forming apparatus described above is a so-called four-cycle color image forming apparatus, but the present invention can also be applied to a tandem type color image forming apparatus. In the four-cycle color image forming apparatus described above, the image carrier is a drum-type photosensitive member. However, a belt-type photosensitive member can also be used. It is also possible to employ the same cleaner as described above for cleaning the transfer residual toner.

  INDUSTRIAL APPLICABILITY The present invention can be used for forming a good image by suppressing color shift of a toner image caused by the operation of a cleaner for cleaning residual toner on a belt such as an intermediate transfer belt in color image formation. .

1 is a diagram schematically illustrating a configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a view showing a cleaner for an intermediate transfer belt in the image forming apparatus of FIG. 1. It is an enlarged side view of the cam of the cleaner drive device of the cleaner of FIG. FIG. 4 is a cam diagram of the cam of FIG. 3. FIG. 4 is a diagram showing the relationship between the cam rotation angle of FIG. 3 and the pressure contact speed of the blade to the belt. It is a figure which shows the other example of a cleaner. It is a figure which shows the further another example of a cleaner. It is a figure which shows the prior art example of a cleaner.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging charger 3 Image exposure apparatus 4 Developing apparatus 4Y Yellow developing unit 4M Magenta developing unit 4C Cyan developing unit 4K Black developing unit 5 Intermediate transfer belt 51 Driving roller 52 Primary transfer roller 53 Roller 54 Followed roller 55 Tension roller 6 Recording medium supply unit 61 Supply roller S Recording medium 62 Timing roller pair 7 Fixing device 8 Discharge tray 81 Discharge roller pair 10 Secondary transfer rollers 9, 9 ', 9 "Cleaner 91 Cleaning blade 91a Tips 92, 92' of blade 91 92 "blade support member 92a ', 92a" support member shaft 93 guide members 94, 94', 94 "spring 95, 95" cam 95a cam shaft 96 damper Va / cosφ belt tangential speed component Vb at blade tip Vb belt speed

Claims (4)

A plurality of developing devices having different color toners;
An image carrier on which a toner image is formed by the developing device;
An intermediate transfer member on which a toner image formed on the image carrier is primarily transferred;
A primary transfer device that sequentially superimposes and transfers toner images formed on the image carrier onto the intermediate transfer member;
A secondary transfer device for secondary transfer of the multiple toner image primarily transferred onto the intermediate transfer member to the recording medium;
At least one of the image carrier and the intermediate transfer member is a belt wound around a belt winding member, and a transfer residual toner remaining on the belt after transfer of the toner image on the belt A cleaner and a cleaner driving device are provided, and the cleaner is a cleaner that cleans the residual toner by being disposed in contact with the belt, and the cleaner driving device removes the cleaner. A drive device for contacting and separating the belt, and at a moment when the cleaner starts to contact the belt, a belt tangential velocity component of the cleaner at a site where the cleaner and the belt start to contact each other A cleaner urging portion for bringing the cleaner into contact with the belt so as to be equal to a belt speed at a mutual contact start portion; Later, the image forming apparatus characterized by for the belt the cleaner, and a cleaner reduction unit that moves while decelerating to a final contact position for belt cleaning.   The intermediate transfer member of the image carrier and the intermediate transfer member is a belt wound around the belt winding member, and the cleaner and a cleaner driving device are provided on the belt. Item 2. The image forming apparatus according to Item 1.   Among the image carrier and the intermediate transfer member, the image carrier is a belt that is wound around the belt winding member, and the belt that is the image carrier has different colors depending on the developing device. The image forming apparatus according to claim 1, wherein the image forming apparatus is a belt on which a toner image is formed, and the cleaner and a cleaner driving device are provided for the belt.   The image carrier and the intermediate transfer member are both belts wound around the belt winding member, and toner images of different colors are sequentially formed on the belt as the image carrier by the developing device. The image forming apparatus according to claim 1, wherein the cleaner and the cleaner driving device are provided for each belt.