JP2007093780A - Image forming apparatus and image forming method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a means for peeling a foreign matter adhering to the edge part of a cleaner blade with simple constitution and to achieve the simplification of the constitution of an image forming apparatus and the reduction of cost. <P>SOLUTION: In the image forming method for making the image forming apparatus selectively carry out a color mode and a monochrome mode, color transfer members 85Y, 85M and 85C are positioned on an image forming station side once (thrust stage) if necessary after performing the monochrome mode, and then the color transfer members 85Y, 85M and 85C are separated from the image forming station (thrust release stage), whereby a transfer belt 81 is moved in a reverse direction to a conveying direction D81 at a position where the cleaner blade 711 abuts on the transfer belt 81. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tandem type image forming apparatus provided with a cleaner blade for cleaning the surface of a transfer belt by bringing the leading end thereof into contact with the surface of a moving transfer belt, and an image forming method in the apparatus.

  As an image forming apparatus such as a copying machine, a printer, or a facsimile, for example, an image forming station that forms toner images of different colors along a transfer belt conveyed in a predetermined direction as disclosed in Patent Document 1 below. There is known a so-called tandem type image forming apparatus in which a plurality of image forming devices are arranged. In such an image forming apparatus, a color image is formed by superimposing toner images of different colors formed by a plurality of image forming stations on the surface of a transfer belt. The color image formed on the belt surface is transferred to a transfer medium such as paper.

  In such an image forming apparatus, a cleaner blade may be provided to remove toner remaining on the surface of the transfer belt. The cleaner blade removes residual toner from the surface of the transfer belt by bringing its tip into contact with the surface of the transfer belt conveyed in a predetermined direction.

  However, there are cases where foreign matters such as paper dust adhere to the transfer belt surface in addition to the residual toner. Most of such foreign matter is removed from the transfer belt surface by the cleaner blade in the same manner as the residual toner. However, some foreign matter adheres to the tip of the cleaner blade and is between the tip of the cleaner blade and the transfer belt surface. It may get caught. As a result, a gap is formed between the cleaner blade and the surface of the transfer belt, and the residual toner may slip through the gap, so that the residual toner may not be removed satisfactorily.

  The above-described problem in the configuration in which the cleaner blade is brought into contact with an image carrier that moves in a predetermined direction such as a transfer belt to clean the surface of the image carrier is also pointed out in, for example, Patent Document 2 below. Yes. For this problem, for example, in the invention described in Patent Document 2, the rotation direction of the image carrier is controlled. That is, the image carrier is driven to rotate in the opposite direction to the rotation direction of the image carrier during image formation. By this reverse driving, the foreign matter sandwiched between the surface of the image carrier and the tip of the cleaner blade is moved upstream in the rotation direction during image formation, and the foreign matter is peeled off from the tip of the cleaner blade. .

JP 2003-015378 A (paragraph 0022, FIG. 1) Japanese Patent Laying-Open No. 2004-102178 (paragraphs 0005, 0011, 0012)

  However, when the invention described in Patent Document 2 is applied to an apparatus that cleans the transfer belt surface with a cleaner blade, it is necessary to newly provide a reverse rotation mechanism in the drive system of the transfer belt, which complicates the configuration of the drive system. Invite. As a result, there arises a problem that the cost is increased and the size of the apparatus is increased.

  The present invention has been made in view of the above problems, and it is possible to effectively remove a foreign matter adhering to a cleaner blade with a simpler configuration, and to realize a technique for realizing cost reduction and downsizing of an apparatus. It is intended to provide.

  A first aspect of the image forming method according to the present invention includes a driving roller, a blade facing roller that is a driven roller that is urged in a direction away from the driving roller by an urging unit and reciprocates in the urging direction, and at least A transfer belt that is stretched between two rollers, a driving roller and a blade-opposed roller, and is rotated and conveyed in a predetermined conveying direction, and is integrally formed with the blade-opposing roller and can reciprocate in a biasing direction along with the blade-opposing roller. A cleaner blade that cleans the surface of the transfer belt by bringing its tip into contact with the blade facing roller via the transfer belt, and arranged in the transport direction downstream of the blade facing roller in the transport direction and upstream of the drive roller in the transport direction M image forming stations (M ≧ 2) arranged to form toner images of different colors from each other; In an image forming apparatus provided with M transfer members arranged to face each image forming station with a transfer belt interposed therebetween, the transfer belt is positioned by positioning the M transfer members on the image forming station side. Is pressed and brought into contact with M image forming stations to form a color image by performing primary transfer so that toner images of different colors formed at each of the M image forming stations are superimposed on the surface of the transfer belt. The color mode and the monochrome transfer member among the M transfer members are positioned on the monochrome image forming station side facing the monochrome transfer member, and the monochrome transfer member is removed from the M transfer members (M-1). Move the transfer belt to the monochrome image forming station by moving the individual color transfer members away from the image forming station. This is an image forming method in which an image forming apparatus selectively executes a monochrome mode in which only a toner image formed by a monochrome image forming station by pushing and abutting is primarily transferred onto the surface of a transfer belt to form a monochrome image. In order to achieve the above object, after the monochrome mode is completed, the following pushing process and pushing cancellation process are executed as necessary. Here, in the pushing process, among the (M-1) color transfer members, N color transfer members (M-1 ≧ N ≧ 1) are positioned on the image forming station side, and the N color transfer members are positioned. This is a step of pushing the transfer belt to the image forming station by a member. In the pushing removal process, the N color transfer members positioned on the image forming station side by the pushing step are moved away from the image forming station and moved to N pieces. This is a step of rotating the blade facing roller in the direction opposite to the conveyance direction while moving the blade facing roller in the urging direction by the urging force from the urging means by eliminating the pushing state of the transfer belt by the color transfer member.

  The image forming apparatus according to the present invention includes a drive roller, a blade facing roller that is a driven roller that is urged in a direction away from the drive roller by an urging unit and reciprocates in the urge direction, and at least the drive roller And a transfer belt that is stretched around two rollers of the blade facing roller and rotated and transported in a predetermined transport direction, and is configured integrally with the blade facing roller and reciprocates in the urging direction along with the blade facing roller. A cleaner blade that cleans the surface of the transfer belt by bringing the tip portion into contact with the blade facing roller via the transfer belt, and arranged side by side in the transport direction downstream of the blade facing roller in the transport direction and upstream of the drive roller in the transport direction. M image forming stations (M ≧ 2) for forming toner images of different colors, and M images An image forming apparatus comprising: M transfer members arranged to face each of the forming stations with a transfer belt on a one-to-one basis; and a control unit for controlling the positions of the M transfer members. In order to achieve the above, the control means positions the M transfer members on the image forming station side to push the transfer belt against the M image forming stations so as to contact each other to form each of the M image forming stations. A color mode in which a color image is formed by primary transfer so that the toner images of different colors are superimposed on the surface of the transfer belt, and a monochrome transfer member facing the monochrome transfer member of the M transfer members. While positioning to the image forming station side, (M-1) color transfer members, excluding the monochrome transfer member, of the M transfer members, The monochrome mode in which the transfer belt is pushed and brought into contact only with the monochrome image forming station by moving it away from the application to primarily transfer only the toner image formed at the monochrome image forming station onto the surface of the transfer belt to form a monochrome image. After the monochrome mode is completed, N color transfer members (M−1 ≧ N ≧ 1) of (M−1) color transfer members are moved to the image forming station side as necessary. After positioning and pushing the transfer belt to the image forming station by the N color transfer members, the N color transfer members are moved away from the image forming station to transfer the transfer belt by the N color transfer members. By removing the pushing state, the blade facing roller is moved in the urging direction by the urging force from the urging means, and the conveying direction It is characterized by being driven and rotated in the opposite direction.

  The invention (image forming method and image forming apparatus) configured as described above includes a transfer belt that is stretched around at least two rollers, that is, a driving roller and a blade-opposing roller that is driven to rotate, and is rotated and conveyed in a predetermined direction. In addition, M (M ≧ 2) image forming stations that form toner images of different colors are arranged side by side in the transport direction downstream of the blade facing roller in the transport direction and upstream of the drive roller in the transport direction. . A color mode in which toner images of different colors formed at each of the M image forming stations are primarily transferred to the surface of the transfer belt to form a color image; and a monochrome image forming station among the M image forming stations. It is possible to selectively execute the monochrome mode in which only the toner image formed in step 1 is primarily transferred onto the surface of the transfer belt to form a monochrome image.

  When executing the color mode, the transfer belt is pushed and brought into contact with all the M image forming stations, while when executing the monochrome mode, the transfer belt is pushed only against the monochrome image forming station. The transfer belt is separated from the (M−1) image forming stations other than the monochrome image forming station. The belt separation operation associated with the switching between the color mode and the monochrome mode is realized as follows.

  The invention configured as described above includes M transfer members arranged to face each of the M image forming stations with the transfer belt interposed therebetween. Further, in the invention configured as described above, the blade facing roller, which is a driven roller, is urged by the urging means and is configured to reciprocate in the urging direction. Therefore, the blade facing roller functions as a so-called tension roller, and applies tension to the transfer belt. When the color mode is executed, the M transfer members are positioned on the image forming station side against the urging force applied to the blade facing roller on the transfer belt applied with the tension by the blade facing roller. As a result, the transfer belt is pushed and brought into contact with the image forming station. On the other hand, when executing the monochrome mode, the monochrome transfer member among the M transfer members is positioned on the monochrome image forming station side opposed to the monochrome transfer member, and the monochrome transfer member is removed from the M transfer members. (M-1) The color transfer members are moved away from the image forming station. When the (M-1) color transfer members are moved away from the image forming station in this way, the pushing state of the transfer belt by the (M-1) pieces is eliminated. Thus, the blade is separated from the image forming station while being pulled by the blade-opposing roller biased in this manner. As a result, when the monochrome mode is executed, the transfer belt comes into contact with only the monochrome image forming station.

  In the present invention, as described above, the transfer belt is brought into contact with or separated from the image forming station in accordance with the switching between the color mode and the monochrome mode, and foreign matter such as toner remaining on the surface of the transfer belt. Is removed as follows. That is, the front surface of the cleaner blade is brought into contact with the blade facing roller via the transfer belt to clean the surface of the transfer belt. Therefore, as described above, foreign matters such as paper dust adhere to the tip of the cleaner blade, and as a result, there may be a cleaning failure in which residual toner cannot be removed satisfactorily.

  In order to deal with such a problem, in the present invention, the urging direction of the blade facing roller by the urging means is set to the direction in which the blade facing roller is separated from the driving roller, and is necessary after the monochrome mode is finished in the direction away from the driving roller. In response, the next pushing process and pushing cancellation process are executed. That is, of the (M-1) color transfer members, N color transfer members (M-1 ≧ N ≧ 1) are positioned on the image forming station side, and the transfer belt is imaged by the N color transfer members. After pushing the forming station, the pushing process of rotating the blade facing roller in the conveying direction while moving the blade facing roller against the urging force from the urging means in the direction opposite to the urging direction is performed. The N color transfer members positioned on the image forming station side are moved away from the image forming station to eliminate the pushing state of the transfer belt by the N color transfer members, thereby energizing the blade facing roller. A pushing elimination process is performed in which the urging force is rotated in the direction opposite to the conveyance direction while being moved in the urging direction.

  As described above, when the monochrome mode is executed, only the monochrome transfer member is positioned on the image forming station side, and the transfer belt is separated from the image forming stations other than the monochrome image forming station. In the present invention, when such a monochrome mode is finished, the (M-1) color transfer members are resisted against the urging force applied to the blade facing roller by a pushing process as necessary. Of these, N color transfer members are positioned on the image forming station side. At this time, the N color transfer members are opposed to each other while pulling the transfer belt separated from the image forming station at the end of monochrome against the urging force applied to the blade facing roller. Push it into contact with the image forming station. At this time, the blade facing roller moves in the direction opposite to the urging direction by the amount of the N color transfer members that have pulled the transfer belt, and approaches the drive roller.

  In the present invention, after the transfer belt is once pushed and brought into contact with the image forming station by the pushing process as described above, the pushing state is eliminated by executing the pushing cancellation process. The transfer belt is moved in the direction opposite to the conveying direction at the contact position where the tip of the cleaner blade contacts the transfer belt. This operation will be described in detail.

  In the pushing removal process, the N color transfer members positioned on the image forming station side in the pushing process are moved away from the image forming station to eliminate the pushing state of the transfer belt by the N transfer members. . At this time, the blade facing roller moves while pulling the transfer belt in the urging direction by the urging force from the urging means in accordance with the cancellation of the pushing state of the transfer belt. It will be separated from.

  Since the moving direction of the blade facing roller is a direction away from the driving roller, the circumferential length of the transfer belt from the driving roller to the blade facing roller in the transfer belt conveying direction (the circumferential length on the opposite side of the image forming station) is increased. Thus, the circumferential length (image forming station side circumferential length) of the transfer belt from the drive roller to the blade facing roller in the direction opposite to the transfer belt conveyance direction is shortened. At this time, since the driving roller is stationary and a relatively high frictional force exists between the driving roller and the transfer belt, the transfer belt does not move with respect to the driving roller. On the other hand, since the blade-opposing roller is a driven roller, the blade is rotated by being pulled by the transfer belt in the direction opposite to the transfer belt conveyance direction by the length of the circumference on the opposite side of the image forming station. In addition, the cleaner blade is configured integrally with the blade facing roller, and the cleaner blade moves together with the movement of the blade facing roller. Therefore, the relative positions of the blade facing roller and the cleaner blade are the same. The relationship does not change. Therefore, when the blade facing roller rotates in the direction opposite to the conveying direction by the variation in the circumferential length opposite to the image forming station, the transfer belt is moved by the circumferential length variation at the contact position where the cleaner blade tip contacts the transfer belt. Will move in the direction opposite to the transport direction.

  As described above, in the present invention, after the monochrome mode is completed, the pushing process is executed as necessary to push the transfer belt once against the image forming station and then the pushing cancellation process is executed. By eliminating the pushing state of the transfer belt, the transfer belt is moved in the direction opposite to the conveying direction at the cleaner blade contact position. Therefore, even when foreign matter is attached to the tip of the cleaner blade, the foreign matter can be peeled off as the transfer belt moves. Therefore, for example, unlike the invention described in Patent Document 2, it is not necessary to separately provide a drive mechanism for rotating the transfer belt in the reverse direction, and the drive system is simplified. That is, according to the present invention, the foreign matter adhering to the tip of the cleaner blade can be effectively peeled off with a simpler configuration, and the cost and size of the apparatus can be reduced.

  Further, the monochrome transfer member may be arranged on the most downstream side in the transport direction among the M transfer members. Such a configuration is preferable from the viewpoint of protecting the image forming station, the transfer member, and the transfer belt as compared with the case where the monochrome transfer member is arranged at a position other than the most downstream in the transport direction. The reason for this will be described next.

  When the monochrome transfer member is disposed at a position other than the most downstream in the transport direction, at least one color transfer member is disposed on the downstream side in the transport direction from the monochrome transfer member. The color transfer member is separated from the image forming station when switching from the color mode to the monochrome mode. With the separation operation, the transfer belt moves from the image forming station on the downstream side in the transport direction from the monochrome transfer member. Separate. At this time, the circumferential length of the transfer belt from the driving roller to the monochrome transfer member in the reverse direction of the conveyance direction is shortened, and the blade facing roller as a tension roller pulls the transfer belt in response to the variation in the circumferential length. It will move in the energizing direction. Accordingly, the transfer belt on the downstream side in the transport direction of the monochrome transfer member and on the upstream side in the transport direction of the drive roller is separated from the image forming station while being pulled by the blade facing roller. During the transfer belt separation operation, the monochrome transfer member is in contact with the monochrome image forming station with the transfer belt interposed therebetween. Therefore, the transfer belt that performs the separation operation downstream of the monochrome transfer member in the transport direction and upstream of the drive roller in the transport direction passes between the monochrome transfer member and the monochrome image forming station that are in contact with each other, and passes through the monochrome transfer member. It moves to the upstream side in the transport direction. Therefore, there may be a problem that the image forming station or the transfer member and the transfer belt rub against each other and are damaged. On the other hand, when the monochrome transfer member is arranged on the most downstream side in the transport direction among the M transfer members, with the switching from the color mode to the monochrome mode, on the downstream side of the monochrome transfer member in the transport direction and from the drive roller. There cannot be a situation in which the transfer belt is separated from the image forming station on the upstream side in the conveyance direction. Therefore, it is possible to suppress the occurrence of the above problem, which is preferable.

  When the foreign matter is peeled from the tip of the cleaner blade by the pushing process and the pushing cancellation process as described above, the movement amount of the transfer belt in the reverse direction in the conveyance direction at the contact position where the cleaner blade tip comes into contact with the transfer belt The larger the is, the more effectively the foreign matter can be peeled off. As can be seen from the above description, the amount of movement of the transfer belt is the amount of change in the peripheral length of the image forming station (or the peripheral length on the opposite side of the image forming station) when the transfer belt is separated due to the cancellation of the pushing state. Is substantially the same.

  Therefore, in order to increase the amount of movement of the transfer belt in the direction opposite to the conveyance direction at the cleaner blade contact position, the following configuration may be used. That is, in the pushing process, among the (M-1) color transfer members, L color transfer members (M-1 ≧ L ≧ 1) including the most upstream color transfer member located at the most upstream in the transport direction are imaged. The L color transfer member is positioned on the forming station side and the transfer belt is pushed to the image forming station by the L color transfer members, and the pushing release process is positioned on the image forming station side by the pushing process. The L color transfer members are moved away from the image forming station to eliminate the pushing state of the transfer belt by the L color transfer members, so that the blade facing roller is biased by the biasing force from the biasing means. You may comprise so that it may be a process of following and rotating in the direction opposite to a conveyance direction, moving it.

  In this configuration, the L transfer members including the most upstream color transfer member positioned at the most upstream in the transport direction are once positioned on the image forming station side and transferred by the L transfer members by the pushing process. The belt is pushed and brought into contact with the image forming station. And the pushing state of the transfer belt by the L transfer members is eliminated by the pushing elimination process. Therefore, the fluctuation amount of the image forming station side circumference (or the image forming station opposite side circumference) at the time of separation of the transfer belt accompanying the cancellation of the pushing state can be increased. As a result, it is possible to increase the amount of movement of the transfer belt in the direction opposite to the conveyance direction at the contact position where the cleaner blade tip is in contact with the transfer belt, and it is preferable because foreign matter can be peeled off more reliably.

  Further, the pushing process is performed by positioning the most upstream color transfer member located on the most upstream side in the transport direction among the (M-1) color transfer members on the image forming station side, and using the most upstream color transfer member to transfer the transfer belt. It is configured so that it is a process of pushing to the image forming station, and the pushing process is performed by moving the most upstream color transfer member positioned on the image forming station side away from the image forming station by moving away from the image forming station. By eliminating the pushing state of the transfer belt by the transfer member, the blade facing roller is driven in the direction opposite to the conveying direction while being moved in the urging direction by the urging force from the urging means. May be.

  In the invention configured as described above, only the most upstream color transfer member positioned at the most upstream in the conveying direction is positioned on the image forming station side by the pushing process, and the transfer belt is pushed and brought into contact with the image forming station. Then, the pushing state is released by separating the most upstream transfer member from the image forming station. Therefore, before the pushing elimination process is executed, the transfer belt is pushed against and contacted with the image forming station by only the most upstream transfer member and the monochrome transfer member. Therefore, the separation operation of the transfer belt accompanying the cancellation of the pushing state in the pushing cancellation process is not limited by the color transfer member existing between the most upstream color transfer member and the monochrome transfer member. The belt separating operation can be performed quickly. Therefore, it is preferable because the foreign matter adhering to the cleaner blade tip can be peeled off more reliably.

  Further, in the pushing-out canceling process, as the color transfer member is moved away from the image forming station, the monochrome transfer member is moved away from the image forming station so that the pushing state of the transfer belt is eliminated. The roller may be configured to be driven and rotated in the direction opposite to the conveying direction while being moved in the urging direction by the urging force from the urging means.

  In the invention configured as described above, not only the color transfer member but also the monochrome transfer member is separated from the image forming station by the pushing elimination process. Therefore, the fluctuation amount of the image forming station side circumference (or the image forming station opposite side circumference) at the time of separation of the transfer belt accompanying the cancellation of the pushing state can be increased. As a result, it is possible to increase the amount of movement of the transfer belt in the direction opposite to the conveyance direction at the contact position where the cleaner blade tip is in contact with the transfer belt, and it is preferable because foreign matter can be peeled off more reliably.

  According to a second aspect of the image forming method of the present invention, there is provided a driving roller, a blade facing roller that is a driven roller that is urged in a direction away from the driving roller by the urging means and reciprocates in the urging direction, and at least A transfer belt that is stretched between two rollers, a driving roller and a blade-opposed roller, and is rotated and conveyed in a predetermined conveying direction, and is integrally formed with the blade-opposing roller and can reciprocate in the urging direction along with the blade-opposing roller. A cleaner blade that cleans the surface of the transfer belt by bringing its tip into contact with the blade facing roller via the transfer belt, and arranged in the transport direction downstream of the blade facing roller in the transport direction and upstream of the drive roller in the transport direction M image forming stations (M ≧ 2) arranged to form toner images of different colors, and M M transfer members disposed one-on-one facing each image forming station with a transfer belt interposed therebetween, and among the M transfer members, the upstream side in the transport direction and the downstream side in the transport direction of the blade facing roller. In an image forming apparatus provided with an upstream guide roller disposed inside a transfer belt, M transfer members are positioned on the image forming station side and at the most upstream in the transport direction in a state where the M transfer members are positioned. By positioning the upstream guide roller so as to contact the transfer belt on a common inscribed line between the transfer member positioned and the image forming station facing the transfer member, the transfer belt is pushed against the M image forming stations. 1 so that toner images of different colors formed on each of the M image forming stations in contact with each other are superimposed on the surface of the transfer belt. A color mode for transferring and forming a color image, and positioning the monochrome transfer member at the most downstream in the transport direction among the M transfer members on the monochrome image forming station side facing the monochrome transfer member, and M transfer members (M-1) of the color transfer members excluding the monochrome transfer member are moved away from the image forming station and the upstream guide roller is moved inwardly from the positioning position in the color mode to move the transfer belt. The image forming apparatus selectively executes a monochrome mode in which only a toner image formed by the monochrome image forming station is pushed and brought into contact with only the monochrome image forming station and is primarily transferred onto the surface of the transfer belt to form a monochrome image. In order to achieve the above object, an image forming method, after the monochrome mode ends, It is characterized by performing the following pushing process and pushing cancellation process as necessary. Here, the pushing process is a process in which the upstream guide roller is positioned at the positioning position in the color mode and the transfer belt is pushed to the image forming station by the upstream guide roller, and the pushing cancellation process is performed by the pushing process. The upstream guide roller positioned at the positioning position in the color mode is moved inward from the positioning position toward the inside of the transfer belt to eliminate the pushing state of the transfer belt by the upstream guide roller, thereby biasing the blade facing roller. This is a step of rotating in the direction opposite to the conveying direction while moving in the urging direction by the urging force from.

In the invention configured as described above, among the (M-1) color transfer members, the most upstream color transfer member located upstream in the transport direction is upstream of the transport direction and the downstream of the blade facing roller in the transport direction. And an upstream guide roller disposed inside the transfer belt. The upstream guide roller positions the M transfer members on the image forming station side, and the most upstream color transfer member in a state where the transfer members are positioned, and the image forming station that the most upstream color transfer member faces. The upstream guide roller can be positioned so as to be in contact with the transfer belt on the common inscribed line, and can be moved inwardly of the transfer belt from the positioning position. Therefore, the transfer belt can be pushed and brought into contact with the image forming station by positioning the upstream guide roller at the positioning position or by moving it from the positioning position to the inside of the transfer belt. It is also possible to eliminate the pushing state. When the monochrome mode is executed, the upstream guide roller is moved to the inside of the transfer belt from the positioning position.

  Therefore, in the second aspect of the image forming method according to the present invention, in the pushing process, after the monochrome mode is finished, the upstream guide roller is positioned at the positioning position, so that the transfer belt is moved to the image forming station only by the upstream guide roller. While pushing and abutting, in the pushing cancellation process, the upstream guide roller is moved from the positioning position to the inside of the transfer belt to cancel the pushing state of the transfer belt. Then, in response to the cancellation of the pushing state of the transfer belt, the blade facing roller moves while pulling the transfer belt in the biasing direction by the biasing force from the biasing means. As a result, the circumferential length on the opposite side of the image forming station becomes longer, and the blade facing roller, which is a driven roller, rotates in the direction opposite to the conveyance direction by the variation in the circumferential length. Therefore, since the transfer belt moves in the reverse direction of the conveying direction at the cleaner blade contact position, even if foreign matter adheres to the tip of the cleaner blade, the foreign matter is moved along with the movement of the transfer belt. Can be peeled off. Therefore, for example, unlike the invention described in Patent Document 2, it is not necessary to separately receive a drive mechanism for rotating the transfer belt in the reverse direction, and the drive system is simplified. That is, according to the present invention, the foreign matter adhering to the tip of the cleaner blade can be effectively peeled off with a simpler configuration, and the cost and size of the apparatus can be reduced.

  Further, in the present invention, the upstream guide roller positioned further upstream than the most upstream color transfer member pushes the transfer belt to the image forming station and eliminates the pushing state. Therefore, compared with the case where such a process is executed by the color transfer member as described above, it is preferable that the movement amount of the transfer belt can be increased.

  Further, in the present invention, in the pushing process, the transfer belt is pushed and brought into contact with the image forming station only by the upstream guide roller, and in the pushing cancellation process, the pushing state is canceled only by the upstream guide roller. Therefore, before the pushing elimination process is performed, the transfer belt is pushed against and contacted with the image forming station only by the upstream guide roller and the monochrome transfer member. Therefore, the transfer belt separating operation due to the cancellation of the pushing state in the pushing removal process is not limited by the color transfer member existing between the upstream guide roller and the monochrome transfer member. The operation can be performed quickly. Therefore, it is preferable because the foreign matter adhering to the cleaner blade tip can be peeled off more reliably.

  Also, in the push-out elimination process, the monochrome transfer member is moved away from the image forming station as the upstream guide roller is moved from the positioning position in the color mode toward the inside of the transfer belt, thereby eliminating the push-up state of the transfer belt. By doing so, the blade opposing roller may be configured to be driven and rotated in the direction opposite to the conveying direction while being moved in the urging direction by the urging force from the urging means.

  In the invention configured as described above, not only the upstream side guide roller but also the monochrome transfer member is separated from the image forming station by the pushing elimination process. Therefore, the fluctuation amount of the image forming station side circumference (or the image forming station opposite side circumference) at the time of separation of the transfer belt accompanying the cancellation of the pushing state can be increased. As a result, it is possible to increase the amount of movement of the transfer belt in the direction opposite to the conveyance direction at the contact position where the cleaner blade tip is in contact with the transfer belt, and it is preferable because foreign matter can be peeled off more reliably.

  Further, the transfer member may be a transfer roller that is driven to rotate. In such a configuration, friction between the transfer belt and the transfer member (transfer roller) when the transfer belt is separated from the image forming station in accordance with the cancellation of the belt pushing state by the separation contact means is reduced. Can do. As a result, the separating operation of the transfer belt can be performed quickly, and the foreign matter adhering to the tip of the cleaner blade can be peeled off more effectively.

<First Embodiment>
FIG. 1 is a diagram showing a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram showing an electrical configuration of the image forming apparatus of FIG. This apparatus uses a color mode in which four color toners of black (K), cyan (C), magenta (M), and yellow (Y) are superimposed to form a color image, and only black (K) toner is used. Thus, the image forming apparatus can selectively execute a monochrome mode for forming a monochrome image. FIG. 1 corresponds to when the color mode is executed. In this image forming apparatus, when an image forming command is given to the main controller 510 from an external device such as a host computer, the engine controller 520 controls each part of the engine unit EG in accordance with the command from the main controller 510, and a predetermined image. The forming operation is executed, and an image corresponding to the image forming command is formed on a sheet such as copy paper, transfer paper, paper, and an OHP transparent sheet.

  In the housing main body 3 of the image forming apparatus according to the first embodiment, an electrical component box 5 that houses a power circuit board, a main controller 510 and an engine controller 520 is provided. An image forming unit 7, a transfer belt unit 8, and a paper feeding unit 11 are also disposed in the housing body 3. In FIG. 1, a secondary transfer unit 12, a fixing unit 13, and a sheet guide member 15 are disposed on the right side in the housing body 3. The paper feeding unit 11 is configured to be detachable from the apparatus main body 1. The paper feed unit 11 and the transfer belt unit 8 can be removed and repaired or exchanged.

  The image forming unit 7 includes four image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality of images of different colors. Each of the image forming stations Y, M, C, and K is provided with a photosensitive drum 21 on which a toner image of each color is formed. Each photosensitive drum 21 is connected to a dedicated drive motor and is driven to rotate at a predetermined speed in the direction of arrow D21 in the figure. A charging unit 23, an image writing unit 29, a developing unit 25, and a photoconductor cleaner 27 are disposed around the photoconductive drum 21 along the rotation direction. Then, a charging operation, a latent image forming operation, and a toner developing operation are executed by these functional units. As will be described later, in the first embodiment and the second to seventh embodiments described below, the image forming station K functions as a “monochrome image forming station” in the present invention. Therefore, when the color mode is executed, the toner images formed at all the image forming stations Y, M, C, and K are superimposed on the transfer belt 81 of the transfer belt unit 8 to form a color image, and the monochrome mode is executed. In some cases, a monochrome image is formed using only the toner image formed at the image forming station K. In FIG. 1, the image forming stations of the image forming unit 7 have the same configuration, and therefore, for convenience of illustration, only some image forming stations are denoted by reference numerals, and the other image forming stations are omitted. .

  The charging unit 23 includes a charging roller whose surface is made of elastic rubber. The charging roller is configured to rotate in contact with the surface of the photosensitive drum 21 at the charging position, and at a peripheral speed in the driven direction with respect to the photosensitive drum 21 as the photosensitive drum 21 rotates. Followed rotation. The charging roller is connected to a charging bias generator (not shown). The charging roller is supplied with the charging bias from the charging bias generator and is charged at the charging position where the charging unit 23 and the photosensitive drum 21 come into contact with each other. The surface of 21 is charged.

  The image writing unit 29 is an array writing in which elements such as a liquid crystal shutter including a light emitting diode and a backlight are arranged in a line in the axial direction of the photosensitive drum 21 (direction perpendicular to the paper surface of FIG. 1). The head is used and is spaced from the photosensitive drum 21. From such an element, the surface of the photosensitive drum 21 charged by the charging unit 23 is irradiated with light to form a latent image on the surface. The array-like writing head has a shorter optical path length and is more compact than the laser scanning optical system. Therefore, it can be disposed close to the photosensitive drum 21 and has the advantage that the entire apparatus can be reduced in size.

  In the first embodiment, the photosensitive drum 21, the charging unit 23, the developing unit 25, and the photosensitive cleaner 27 of each of the image forming stations Y, M, C, and K are combined with the photosensitive cartridges 17Y, 17M, 17C, and 17K ( It is unitized as FIG. Each of the photoconductor cartridges 17Y, 17M, 17C, and 17K is provided with nonvolatile memories 910, 920, 930, and 940 for storing information related to the photoconductor cartridge. The transmission / reception units 530Y, 530M, 530C, and 530K provided on the respective photosensitive cartridges and the transmission / reception units 5220Y, 5220M, 5220C, and 5220K provided on the main body side are arranged close to each other, and Wireless communication is performed with the memories 910, 920, 930, and 940. In this way, information on each photoconductor cartridge is transmitted to the CPU 5210, and information in each memory 910, 920, 930, 940 is updated and stored.

  The developing unit 25 has a developing roller 251 on which toner is carried. The charged toner is developed at a developing position where the developing roller 251 and the photosensitive drum 21 come into contact with each other by a developing bias applied to the developing roller 251 from a developing bias generator (not shown) electrically connected to the developing roller 251. Is moved from the developing roller 251 to the photosensitive drum 21, and the electrostatic latent image formed by the image writing unit 29 becomes obvious.

  The toner image that has been made visible at the development position in this way is conveyed in the rotational direction D21 of the photosensitive drum 21, and then the primary transfer position TR1 where the transfer belt 81, which will be described in detail later, and each photosensitive drum 21 come into contact with each other. 1 is primarily transferred to the transfer belt 53.

  In this embodiment, a photoreceptor cleaner 27 is provided in contact with the surface of the photoreceptor drum 21 on the downstream side of the primary transfer position TR1 in the rotation direction D21 of the photoreceptor drum 21 and on the upstream side of the charging unit 23. It has been. The photoconductor cleaner 27 abuts on the surface of the photoconductor drum to remove the toner remaining on the surface of the photoconductor drum 21 after the primary transfer.

  The transfer belt unit 9 includes a driving roller 82, a driven roller 83 (blade facing roller) disposed on the left side of the driving roller 82 in FIG. 1, and a stretched direction of these rollers in the direction indicated by an arrow D81 (conveying direction). And a transfer belt 81 that is driven to circulate. Further, the transfer belt unit 8 is disposed on the inner side of the transfer belt 81 so as to be opposed to each of the photosensitive drums 21 included in the image forming stations Y, M, C, and K when the photosensitive cartridge is mounted. Four primary transfer rollers 85Y, 85M, 85C, and 85K (transfer members) are provided. These primary transfer rollers 85 are electrically connected to a primary transfer bias generator 5250, respectively. As will be described in detail later, when the color mode is executed, as shown in FIG. 1, all the primary transfer rollers 85Y, 85M, 85C, 85K are positioned on the image forming stations Y, M, C, K side. Then, the transfer belt 81 is pushed and brought into contact with the photosensitive drum 21 of each of the image forming stations Y, M, C, and K, and the primary transfer position TR1 is set between each photosensitive drum 21 and the transfer belt 81. Form. The primary transfer bias is applied from the primary transfer bias generator 5250 to all the primary transfer rollers 85 at an appropriate timing, so that the toner images formed on the surfaces of the respective photosensitive drums 21 are respectively displayed. Is transferred to the surface of the transfer belt 81 at the primary transfer position TR1 corresponding to the color image to form a color image.

  On the other hand, as will be described in detail later, among the four primary transfer rollers 85, the color primary transfer rollers 85Y, 85M, and 85C (color transfer members) among the four primary transfer rollers 85 are opposed to each other at the image forming stations Y and Y. Only the monochrome primary transfer roller 85K (monochrome transfer member) is brought into contact with the image forming station K while being separated from M and C, so that only the monochrome image forming station K is brought into contact with the transfer belt 81. As a result, the primary transfer position TR1 is formed only between the monochrome primary transfer roller 85K and the image forming station K. Then, by applying a primary transfer bias from the primary transfer bias generator 5250 to the monochrome primary transfer roller 85K at an appropriate timing, the toner image formed on the surface of each photosensitive drum 21 is converted into a primary image. A transfer image is transferred to the surface of the transfer belt 81 at the transfer position TR1 to form a monochrome image.

  Further, the transfer belt unit 8 includes a downstream guide roller 86 disposed on the downstream side of the monochrome primary transfer roller 85K and on the upstream side of the driving roller 82. The downstream guide roller 86 is formed between the primary transfer roller 85K and the photosensitive drum 21 at the primary transfer position TR1 formed by the monochrome primary transfer roller 85K contacting the photosensitive drum 21 of the image forming station K. It is configured to contact the transfer belt 81 on a common inscribed line.

  The drive roller 82 circulates and drives the transfer belt 81 in the direction of the arrow D81 in the figure, and also serves as a backup roller for the secondary transfer roller 121. A rubber layer having a thickness of about 3 mm and a volume resistivity of 1000 kΩ · cm or less is formed on the peripheral surface of the driving roller 82, and secondary transfer is omitted by grounding through a metal shaft. The conductive path of the secondary transfer bias supplied from the bias generation unit via the secondary transfer roller 121 is used. When the rubber layer having high friction and shock absorption is provided on the driving roller 82 in this way, the sheet enters the contact portion (secondary transfer position TR2) between the driving roller 82 and the secondary transfer roller 121. Is difficult to be transmitted to the transfer belt 81, and image quality deterioration can be prevented.

  The paper feed unit 11 includes a paper feed unit having a paper feed cassette 77 capable of stacking and holding sheets and a pickup roller 79 for feeding sheets one by one from the paper feed cassette 77. The sheet fed from the sheet feeding unit by the pickup roller 79 is fed to the secondary transfer position TR2 along the sheet guide member 15 after the sheet feeding timing is adjusted by the registration roller pair 80.

  The secondary transfer roller 121 is provided so as to be able to come into contact with and separate from the transfer belt 81 and is driven to come into contact with and separate from a secondary transfer roller drive mechanism (not shown). The fixing unit 13 includes a heating roller 131 that includes a heating element such as a halogen heater and is rotatable, and a pressure unit 132 that presses and biases the heating roller 131. The sheet on which the image has been secondarily transferred is guided to a nip formed by the heating roller 131 and the pressure belt 1323 of the pressure unit 132 by the sheet guide member 15, and in the nip, a predetermined value is formed. The image is heat-fixed at temperature. The pressure unit 132 includes two rollers 1321 and 1322 and a pressure belt 1323 stretched between them. A nip portion formed by the heating roller 131 and the pressure belt 1323 is formed by pressing the belt tension surface stretched by the two rollers 1321 and 1322 out of the surface of the pressure belt 1323 against the peripheral surface of the heating roller 131. Is configured to be widely taken. Further, the sheet thus subjected to the fixing process is conveyed to a paper discharge tray 4 provided on the upper surface portion of the housing body 3.

  Further, in this apparatus, a cleaner portion 71 is disposed to face the blade facing roller 83. The cleaner unit 71 includes a cleaner blade 711 and a waste toner box 713. The cleaner blade 711 removes foreign matters such as toner and paper dust remaining on the transfer belt after the secondary transfer by bringing the tip of the cleaner blade 711 into contact with the blade facing roller 83 via the transfer belt 81. The foreign matter removed in this way is collected in a waste toner box 713. Further, the cleaner blade 711 and the waste toner box 713 are integrally formed with the blade facing roller 83. Therefore, when the blade facing roller 83 moves as will be described in detail later, the cleaner blade 711 and the waste toner box 713 also move together with the blade facing roller 83.

  Further, as shown in FIG. 2, the apparatus includes a display unit 540 that is controlled by the CPU 5110 of the main controller 510. This display unit 540 is configured by, for example, a liquid crystal display, and in accordance with a control command from the CPU 5110, the operation guidance to the user, the progress of the image forming operation, the occurrence of an abnormality in the apparatus, the replacement timing of any unit, etc. A predetermined message for notification is displayed.

  In FIG. 2, reference numeral 5130 denotes an image memory provided in the main controller 510 for storing an image given from an external device such as a host computer via the interface 5120. Reference numeral 5230 is a ROM for storing a calculation program executed by the CPU 5210, control data for controlling the engine unit EG, and the like. Reference numeral 5240 is a RAM for temporarily storing a calculation result in the CPU 5210 and other data. is there.

  3 and 4 are diagrams showing switching between the color mode and the monochrome mode in the first embodiment. In the first embodiment, the blade facing roller 83 is urged in the direction D83 away from the driving roller 82 by the urging means 99 and is configured to reciprocate in the urging direction D83. Therefore, the blade facing roller 83 functions as a so-called tension roller, and applies tension to the transfer belt 81. The three color primary transfer rollers 85Y, 85M, and 85C (color transfer members) from the upstream side in the transport direction D81 to the third are rotatably supported by the first support member 95, and The first support member 95 is fixedly supported by the first solenoid S1. Further, the first solenoid S1 is electrically connected to the first solenoid control unit 5260 of FIG. Accordingly, by giving an appropriate signal from the first solenoid control unit 5260 to the first solenoid S1, the first support member 95 and the primary transfer rollers 85Y, 85M, and 85C are moved in the stroke direction D (S1) of the first solenoid S1. Can be moved back and forth. The monochrome primary transfer roller 85K (monochrome transfer member) located at the most downstream side in the transport direction D81 is rotatably supported by a second support member 97, and the second support member 97 is a second solenoid. It is fixedly supported by S2. Further, the second solenoid S2 is electrically connected to the second solenoid control unit 5270 of FIG. Therefore, by giving an appropriate signal to the second solenoid S2 from the second solenoid controller 5270, the second support member 97 and the primary transfer roller 85K are reciprocated in the stroke direction D (S2) of the second solenoid S2. be able to. Thus, in the first embodiment, the first solenoid control unit 5260 and the second solenoid control unit 5270 function as “control means” in the present invention.

  When the color mode is executed, the first solenoid control unit 5260 and the second solenoid control unit 5270 give contact signals to the solenoids S1 and S2. Then, as shown in FIG. 3, the four primary transfer rollers 85Y, 85M, and 85C are applied to the transfer belt 81 applied with the tension from the blade facing roller 83 against the urging force applied to the blade facing roller 83. , 85K are positioned on the four image forming stations Y, M, C, and K, so that the photosensitive drums 21 of the image forming stations Y, M, C, and K are pushed and brought into contact with the primary transfer position. TR1 is formed. As described above, the toner images formed at the respective image forming stations Y, M, C, and K are primarily transferred onto the surface of the transfer belt 81 at the primary transfer position TR1.

  On the other hand, when executing the monochrome mode, the first solenoid control unit 5260 gives a separation signal to the solenoid S1, and the second solenoid control unit 5270 gives a contact signal to S2. Then, as shown in FIG. 4, the monochrome primary transfer roller 85K (monochrome transfer member) is positioned on the monochrome image forming station K side, and the color primary transfer rollers 85Y, 85M, 85C (color transfer member) are respectively set. It is separated from the opposing image forming stations Y, M, and C. Therefore, when the monochrome mode is executed, the state where the transfer belt 81 is pushed by the color primary transfer rollers 85Y, 85M and 85C is canceled. Accordingly, the transfer belt 81 is pulled by the blade facing roller 83 biased by the biasing means 99 and is separated from the image forming stations Y, M, and C. As a result, the transfer belt 81 contacts only the monochrome image forming station K when the monochrome mode is executed.

  In the present invention, as shown in FIGS. 3 and 4, the tip of the cleaner blade 711 is brought into contact with the blade-opposing roller via the transfer belt 81 when performing either the color mode or the monochrome mode. Thus, the surface of the transfer belt 81 is cleaned. In the image forming apparatus configured as described above, as shown in FIG. 4, foreign matter adheres to the tip of the cleaner blade 711 during execution of the monochrome mode, so that the tip of the transfer belt 81 and the cleaner blade 711 are transferred. In some cases, the surface of the transfer belt 81 cannot be satisfactorily cleaned. Therefore, in the first embodiment, the “pushing process” and the “pushing cancellation process” to be performed next are executed as necessary after execution of the monochrome mode.

  FIG. 5 is a diagram illustrating a pushing process in the first embodiment. In the pushing process, a contact signal is given to the solenoid S1 from the first solenoid control unit 5260 as necessary after the monochrome mode shown in FIG. Upon receiving the contact signal, the solenoid S1 causes the color primary transfer rollers 85Y, 85M, and 85C (color transfer members) to contact the image forming stations Y, M, and C facing each other. At this time, the color primary transfer rollers 85Y, 85M, and 85C push and abut the image forming stations Y, M, and C while pulling the transfer belt 81 against the urging force applied to the blade facing roller 83. At this time, the blade facing roller 83 moves in the direction opposite to the urging direction D83 according to the amount of the primary color transfer rollers 85Y, 85M, and 85C that pulled the transfer belt, and approaches the drive roller 82. At this time, the foreign matter remains attached to the tip of the cleaner blade 711. As described above, after the primary transfer belt 81 is pushed and brought into contact with the image forming stations Y, M, and C by the pushing process, the pushing cancellation process shown below is executed.

  FIG. 6 is a diagram illustrating a pushing elimination process in the first embodiment. In the pushing elimination process, a separation signal is given from the first solenoid controller 5260 to the solenoid S1. Upon receiving the separation signal, the solenoid S1 moves the color transfer members 85Y, 85M, 85C away from the image forming stations Y, M, C, and pushes the transfer belt 81 by the color transfer members 85Y, 85M, 85C. Cancel the condition. At this time, according to the cancellation of the pushing state of the transfer belt 81, the blade facing roller 83 moves while pulling the transfer belt in the urging direction D83 by the urging force from the urging means 99. As a result, the transfer belt 81 is separated from the image forming stations Y, M, and C.

  Since the moving direction of the blade facing roller 83 is a direction away from the driving roller 82, the transfer belt 81 a moving from the driving roller 82 toward the blade facing roller in the transport direction D 81 of the transfer belt 81 with the separation operation of the transfer belt 81. While the circumferential length L1 (the circumferential length L1 on the opposite side of the image forming station) becomes longer, the circumferential length L2 (image formation) of the transfer belt 81b from the driving roller 82 toward the blade facing roller 83 in the direction opposite to the conveying direction D81 of the transfer belt 81. The station side circumference L2) will be shortened.

  At this time, the driving roller 82 is stationary, and the surface of the driving roller 82 has a high frictional force as described above, so that the transfer belt 81 does not move with respect to the driving roller 82. On the other hand, since the blade facing roller 83 is a driven roller, it is pulled and rotated by the transfer belt 81 in the direction opposite to the transfer direction D81 of the transfer belt 81 by the length of the circumference L1 on the opposite side of the image forming station. Become. Further, as described above, the cleaner blade 711 is formed integrally with the blade facing roller 83, and the cleaner blade 711 moves together with the movement of the blade facing roller 83. Therefore, the relative position of the cleaner blade 711 and the blade facing roller 83 does not change. Therefore, when the blade facing roller 83 rotates in the direction opposite to the conveyance direction D81 by the variation ΔL2 of the image forming station side circumferential length L2, the peripheral edge is at the contact position where the tip of the cleaner blade 711 contacts the transfer belt 81. The transfer belt 81 moves in the direction opposite to the conveyance direction D81 by the length variation ΔL2. Therefore, in the state of FIGS. 4 and 5, the foreign matter adhering to the tip of the cleaner blade 711 separates the primary transfer rollers 85Y, 85M, and 85C from the image forming stations Y, M, and C, so that FIG. As shown, it moves in the direction opposite to the conveyance direction D81 by the circumference variation ΔL2. As a result, the foreign matter adhering to the tip of the cleaner blade 711 is peeled off.

  As described above, in the first embodiment, after the monochrome mode is completed, the “pushing process” is performed as necessary, and the transfer belt 81 is once pushed and brought into contact with the image forming stations Y, M, and C. By executing the “pushing elimination process” to eliminate the pushing state of the transfer belt 81, the transfer belt 81 is moved in the direction opposite to the conveyance direction D81 at a position where the cleaner blade 711 contacts the transfer belt 81. ing. Therefore, even if foreign matter adheres to the tip of the cleaner blade 711, the foreign matter can be peeled off as the transfer belt 81 moves. Therefore, it is not necessary to separately provide a drive mechanism for rotating the transfer belt 81 in the reverse direction with respect to the transport direction D81, and the drive system is simplified. That is, according to the first embodiment, the foreign matter adhering to the tip of the cleaner blade 711 can be effectively peeled off with a simpler configuration, and the cost and size of the apparatus can be reduced.

  In the first embodiment, the monochrome primary transfer roller 85K (monochrome transfer member) is arranged on the most downstream side in the transport direction D81 among the four primary transfer rollers 85Y, 85M, 85C, and 85K (transfer member). ing. Therefore, the image forming stations Y, M, C, K, the primary transfer roller 85 and the transfer belt 81 are protected as compared with the case where the monochrome primary transfer roller 85K is disposed at a position other than the most downstream position in the transport direction D81. It is preferable from the viewpoint. The reason for this will be described next.

  When the monochrome primary transfer roller 85K is disposed at a position other than the most downstream in the transport direction D81, at least one color primary transfer roller is disposed downstream of the monochrome primary transfer roller 85K in the transport direction. The color primary transfer roller is separated from the image forming station when switching from the color mode to the monochrome mode. However, the color primary transfer roller is transported from the monochrome primary transfer roller 85K in accordance with the separation operation of the color primary transfer roller. The transfer belt 81 is also separated from the image forming station on the downstream side in the direction D81. At this time, the circumferential length of the transfer belt 81 from the driving roller 82 to the monochrome primary transfer roller 85K in the direction opposite to the transport direction D81 is shortened, and the tension roller is opposed to the blade corresponding to the variation in the circumferential length. The roller 83 moves in the urging direction D83 while pulling the transfer belt 81. Accordingly, the transfer belt 81 downstream of the monochrome primary transfer roller 85K in the transport direction D81 and upstream of the drive roller 82 in the transport direction D81 is separated from the image forming station while being pulled by the blade facing roller 83.

  Further, during the separation operation of the transfer belt 81, the monochrome primary transfer roller 85K is in contact with the monochrome image forming station K with the transfer belt 81 interposed therebetween. Therefore, the transfer belt 81 that performs the separation operation downstream of the monochrome primary transfer roller 85K in the transport direction D81 and upstream of the drive roller 82 in the transport direction D81 is in contact with the monochrome primary transfer roller 85K and the monochrome image. It passes through the forming station K and moves to the upstream side in the transport direction D81 from the monochrome primary transfer roller. Therefore, there may be a problem that the image forming station K or the monochrome primary transfer roller 85K and the transfer belt 81 are rubbed against each other and damaged. On the other hand, when the monochrome primary transfer roller 85K is arranged on the most downstream side in the transport direction D81 among the four primary transfer rollers 85Y, 85M, 85C, 85K, the color mode is switched to the monochrome mode. There cannot be a situation in which the transfer belt 81 is separated from the image forming station on the downstream side of the monochrome primary transfer roller 85K in the transport direction D81 and on the upstream side of the drive roller 82 in the transport direction D81. Therefore, it is possible to suppress the occurrence of the above problem, which is preferable.

Second Embodiment
As in the first embodiment, the transfer belt 81 is moved in the direction opposite to the conveyance direction D81 at the contact position where the tip of the cleaner blade 711 contacts the transfer belt 81, thereby removing foreign matter from the tip of the cleaner blade 711. In this case, the larger the amount of movement of the transfer belt 81, the more effectively the foreign matter can be peeled off. In the above-described embodiment, as the primary transfer roller 85 moves away, the peripheral length L1 on the opposite side of the image forming station becomes longer, while the peripheral length L2 on the side of the image forming station becomes shorter. That is, the peripheral length on the opposite side of the image forming station is increased by the amount (ΔL2) of the peripheral length on the image forming station side. Such a circumferential variation ΔL2 is the amount of movement of the transfer belt 81 in the direction opposite to the conveyance direction at the contact position where the tip of the cleaner blade 711 contacts the transfer belt. Therefore, as the fluctuation amount ΔL2 of the peripheral length on the image forming station side is increased, the movement amount of the transfer belt 81 in the direction opposite to the conveyance direction D81 is increased. On the other hand, the fluctuation amount ΔL2 of the image forming station side circumference depends on the degree to which the transfer belt 81 is separated from the image forming stations Y, M, C, and K.

  Therefore, the second embodiment described below may be configured. Since the basic configuration of the apparatus is the same as that of the first embodiment, only the characteristic parts of the second embodiment will be described here, and the other components are denoted by the same reference numerals as those of the first embodiment and the description thereof is omitted. To do.

  In the first embodiment, only the three primary transfer rollers 85Y, 85M, and 85C (color transfer members) from the upstream side in the transport direction to the third among the four primary transfer rollers are used in the pushing elimination process. The image forming stations Y, M, and C are separated from each other by the first solenoid S1. On the other hand, in the “pushing elimination process” in the second embodiment, the primary transfer roller 85K is separated from the image forming station K by the second solenoid simultaneously with the separation operation by the first solenoid S1, as shown in FIG. I am letting. Thus, in the second embodiment, the first solenoid control unit 5260 and the second solenoid control unit 5270 function as “control means” in the present invention. That is, the first solenoid control unit 5260 (FIG. 2) issues a separation signal to the first solenoid S1, and at the same time, the second solenoid control unit 5270 (FIG. 2) issues a separation signal to the second solenoid S2. The primary transfer rollers 85Y, 85M, 85C, and 85K are separated from the image forming stations Y, M, C, and K. Therefore, the fluctuation amount ΔL2 of the peripheral length L2 on the image forming station is larger than when only the three primary transfer rollers 85Y, 85M, and 85C are separated from the image forming stations Y, M, and C from the upstream side in the transport direction. I can take it. As a result, it is possible to increase the amount of movement of the transfer belt 81 in the direction opposite to the conveyance direction at the contact position where the tip of the cleaner blade 711 contacts the transfer belt. Therefore, the foreign matter adhering to the tip of the cleaner blade 711 can be more reliably removed, which is preferable.

<Third Embodiment>
Next, a third embodiment of the apparatus according to the present invention will be described. Since the basic configuration of the apparatus is the same as that of the first embodiment, only the features of the third embodiment will be described here, and the other components will be denoted by the same reference numerals as those of the first embodiment and description thereof will be omitted. To do.

  8 and 9 are diagrams showing switching between the color mode and the monochrome mode in the third embodiment. In the third embodiment, the monochrome primary transfer roller 85K (monochrome transfer member) and the downstream guide roller 86 located on the most downstream side in the transport direction D81 are rotatably supported by the second support member 97, and The second support member 97 is fixedly supported by the second solenoid S2. Further, the second solenoid S2 is electrically connected to the second solenoid control unit 5270 of FIG. Therefore, by giving an appropriate signal to the second solenoid S2 from the second solenoid controller 5270, the second support member 97, the primary transfer roller 85K, and the downstream guide roller 86 are moved in the stroke direction D (S2 of the second solenoid S2). ).

  When the color mode is executed, the first solenoid control unit 5260 and the second solenoid control unit 5270 give contact signals to the solenoids S1 and S2. As shown in FIG. 8, the four primary transfer rollers 85Y, 85M, and 85C are applied to the transfer belt 81 applied with the tension from the blade facing roller 83 against the urging force applied to the blade facing roller 83. , 85K are positioned on the four image forming stations Y, M, C, and K, so that the photosensitive drums 21 of the image forming stations Y, M, C, and K are pushed and brought into contact with the primary transfer position. TR1 is formed. As described above, the toner images formed at the respective image forming stations Y, M, C, and K are primarily transferred onto the surface of the transfer belt 81 at the primary transfer position TR1.

  On the other hand, when executing the monochrome mode, the first solenoid control unit 5260 gives a separation signal to the solenoid S1, and the second solenoid control unit 5270 gives a contact signal to S2. Then, as shown in FIG. 9, the monochrome primary transfer roller 85K (monochrome transfer member) is positioned on the monochrome image forming station K side, and the color primary transfer rollers 85Y, 85M, and 85C are respectively (color transfer members). It is separated from the opposing image forming stations Y, M, and C. Therefore, when the monochrome mode is executed, the state where the transfer belt 81 is pushed by the color primary transfer rollers 85Y, 85M and 85C is canceled. Accordingly, the transfer belt 81 is pulled away from the image forming stations Y, M, and C by being pulled by the blade facing roller urged by the urging means 99. As a result, the transfer belt 81 contacts only the monochrome image forming station K when the monochrome mode is executed.

  In the present invention, as shown in FIGS. 8 and 9, the tip of the cleaner blade 711 is brought into contact with the blade-facing roller via the transfer belt 81 when performing either the color mode or the monochrome mode. Thus, the surface of the transfer belt 81 is cleaned. In the image forming apparatus configured as described above, as shown in FIG. 9, the foreign matter adheres to the tip of the cleaner blade 711 during execution of the monochrome mode, so that the tip of the transfer belt 81 and the cleaner blade 711. In some cases, the surface of the transfer belt 81 cannot be satisfactorily cleaned. Therefore, in the third embodiment, the following “pushing process” and “pushing cancellation process” are executed as necessary after the monochrome mode is executed.

  FIG. 10 is a diagram illustrating a pushing process in the third embodiment. In the pushing process, a contact signal is given to the solenoid S1 from the first solenoid control unit 5260 as necessary after the monochrome mode shown in FIG. Upon receiving the contact signal, the solenoid S1 causes the color primary transfer rollers 85Y, 85M, and 85C (color transfer members) to contact the image forming stations Y, M, and C facing each other. At this time, the color primary transfer rollers 85Y, 85M, and 85C push and abut the image forming stations Y, M, and C while pulling the transfer belt 81 against the urging force applied to the blade facing roller 83. At this time, the blade facing roller 83 moves in the direction opposite to the urging direction D83 according to the amount of the primary color transfer rollers 85Y, 85M, and 85C that pulled the transfer belt, and approaches the drive roller 82. At this time, the foreign matter remains attached to the tip of the cleaner blade 711. As described above, after the primary transfer belt 81 is pushed and brought into contact with the image forming stations Y, M, and C by the pushing process, the pushing cancellation process shown below is executed.

  FIG. 11 is a diagram illustrating a pushing elimination process in the third embodiment. In the pushing process in the third embodiment, the primary transfer roller 85K is separated from the image forming station K by the second solenoid simultaneously with the separation operation by the first solenoid S1, as shown in FIG. That is, the first solenoid control unit 5260 (FIG. 2) issues a separation signal to the first solenoid S1, and at the same time, the second solenoid control unit 5270 (FIG. 2) issues a separation signal to the second solenoid S2. The primary transfer rollers 85Y, 85M, 85C, and 85K are separated from the image forming stations Y, M, C, and K, and the downstream guide roller 86 is also moved to the inside of the transfer belt 81. Thus, in the third embodiment, the first solenoid control unit 5260 and the second solenoid control unit 5270 function as “control means” in the present invention. Therefore, compared with the case where only the primary transfer rollers 85Y, 85M, 85C, and 85K are separated from the image forming stations Y, M, C, and K, the fluctuation amount ΔL2 of the image forming station side circumferential length L2 can be increased. As a result, it is possible to increase the amount of movement of the transfer belt 81 in the direction opposite to the conveyance direction at the contact position where the tip of the cleaner blade 711 contacts the transfer belt. Therefore, the foreign matter adhering to the tip of the cleaner blade 711 can be more reliably removed, which is preferable.

<Fourth embodiment>
Next, a fourth embodiment of the image forming method according to the present invention will be described. Since the basic configuration of the apparatus is the same as that of the first embodiment, only the features of the fourth embodiment will be described here, and the other components will be denoted by the same reference numerals as those of the first embodiment and description thereof will be omitted. To do.

  FIG. 12 is a block diagram illustrating an electrical configuration of the apparatus according to the fourth embodiment, and FIGS. 13 to 16 are diagrams illustrating an operation of the apparatus according to the fourth embodiment. Also in the fourth embodiment, the blade facing roller 83 is urged in the direction D83 away from the drive roller 82 by the urging means 99 and is configured to reciprocate in the urging direction D83. Further, the cleaner blade 711 is formed integrally with the blade facing roller 83 and can reciprocate along with the blade facing roller 83. A primary transfer roller 85Y (most upstream color transfer member) positioned at the most upstream in the transport direction D81 is rotatably supported by a first support member 95, and the first support member 95 is a first support member 95. It is fixedly supported by the solenoid S1. Further, the first solenoid S1 is electrically connected to the first solenoid control unit 5260 of FIG. Accordingly, by giving an appropriate signal from the first solenoid controller 5260 to the first solenoid S1, the first support member 95 and the primary transfer roller 85Y are reciprocated in the stroke direction D (S1) of the first solenoid S1. be able to.

  The two color primary transfer rollers 85M and 85C (color transfer members) located second and third from the upstream side in the transport direction D81 are rotatably supported by the second support member 97, and The second support member 97 is fixedly supported by the second solenoid S2. Further, the second solenoid S2 is electrically connected to the second solenoid control unit 5270 of FIG. Therefore, by giving an appropriate signal from the second solenoid controller 5270 to the second solenoid S2, the second support member 97, the primary transfer rollers 85M and 85C, and the second solenoid S2 are moved back and forth in the stroke direction D (S2). Can be made.

  The monochrome primary transfer roller 85K (monochrome transfer member) located at the most downstream side in the transport direction D81 is rotatably supported by a third support member 98, and the third support member 98 is a third solenoid. Fixed and supported by S3. Further, the third solenoid S3 is electrically connected to the third solenoid control unit 5280 in FIG. Therefore, by giving an appropriate signal to the third solenoid S3 from the third solenoid controller 5280, the third support member 98 and the monochrome primary transfer roller 85K reciprocate in the stroke direction D (S3) of the third solenoid S3. Can be made. Thus, in the fourth embodiment, the first solenoid control unit 5260, the second solenoid control unit 5270, and the third solenoid control unit 5280 function as “control means” in the present invention.

  When the color mode is executed, the first solenoid control unit 5260, the second solenoid control unit 5270, and the third solenoid control unit 5280 give contact signals to the solenoids S1, S2, and S3. Then, as shown in FIG. 13, the four primary transfer rollers 85Y, 85M, and 85C are applied to the transfer belt 81 applied with the tension from the blade facing roller 83 against the urging force applied to the blade facing roller 83. , 85K are positioned on the four image forming stations Y, M, C, and K, so that the photosensitive drums 21 of the image forming stations Y, M, C, and K are pushed and brought into contact with the primary transfer position. TR1 is formed. As described above, the toner images formed at the respective image forming stations Y, M, C, and K are primarily transferred onto the surface of the transfer belt 81 at the primary transfer position TR1.

  On the other hand, when the monochrome mode is executed, the first solenoid control unit 5260 and the second solenoid control unit 5270 give separation signals to the solenoids S1 and S2, and the third solenoid control unit 5280 gives a contact signal to the solenoid S3. Then, as shown in FIG. 14, the monochrome primary transfer roller 85K (monochrome transfer member) is positioned on the monochrome image forming station K side, and the color primary transfer rollers 85Y, 85M, and 85C (color transfer member) are respectively provided. It is separated from the opposing image forming stations Y, M, and C. Therefore, when the monochrome mode is executed, the state where the transfer belt 81 is pushed by the color primary transfer rollers 85Y, 85M and 85C is canceled. Accordingly, the transfer belt 81 is pulled away from the image forming stations Y, M, and C by being pulled by the blade facing roller urged by the urging means 99. As a result, the transfer belt 81 contacts only the monochrome image forming station K when the monochrome mode is executed.

  In the present invention, as shown in FIGS. 13 and 14, the tip of the cleaner blade 711 is brought into contact with the blade-opposing roller via the transfer belt 81 when performing either the color mode or the monochrome mode. Thus, the surface of the transfer belt 81 is cleaned. In the image forming apparatus configured as described above, as shown in FIG. 14, foreign matter adheres to the tip of the cleaner blade 711 during execution of the monochrome mode, so that the tip of the transfer belt 81 and the cleaner blade 711. In some cases, the surface of the transfer belt 81 cannot be satisfactorily cleaned. Therefore, in the fourth embodiment, the following pushing process and pushing process are performed as necessary after execution of the monochrome mode.

  FIG. 15 is a diagram illustrating a pushing process in the fourth embodiment. In the pushing process, after the monochrome mode shown in FIG. 14 is finished, a contact signal is given from the first solenoid control unit 5260 to the solenoid S1 as necessary. Upon receiving the contact signal, the solenoid S1 brings the color primary transfer roller 85Y (the most upstream color transfer member) into contact with the image forming station Y. At this time, the color primary transfer roller 85Y pushes and contacts the image forming stations Y, M, and C while pulling the transfer belt 81 against the urging force applied to the blade facing roller 83. At this time, the blade facing roller 83 moves in the direction opposite to the urging direction D83 and approaches the driving roller 82 in accordance with the amount of the primary color transfer roller 85Y that has pulled the transfer belt 81. At this time, the foreign matter remains attached to the tip of the cleaner blade 711. As described above, after the primary transfer belt 81 is pushed and brought into contact with the image forming stations Y, M, and C by the pushing process, the pushing cancellation process shown below is executed.

  FIG. 16 is a diagram illustrating a pushing elimination process in the fourth embodiment. In the pushing elimination process in the fourth embodiment, as shown in FIG. 16, a separation signal is output from the first solenoid controller 5260 (FIG. 12) to the first solenoid S1, and the primary transfer roller 85Y is moved to the image forming station Y. Separate from. At this time, the blade facing roller 83 moves in the urging direction D83 while pulling the transfer belt 81 away from the image forming stations Y, M, and C, and is driven to rotate in the direction opposite to the conveying direction D81. Accordingly, since the transfer belt 81 moves in the direction opposite to the conveyance direction D81 at the contact position of the cleaner blade 711, the foreign matter attached to the tip of the cleaner blade 711 moves by ΔL2 upstream in the conveyance direction D81.

  As described above, in the fourth embodiment, the “pushing process” is executed as necessary after the monochrome mode is completed, and the transfer belt 81 is once pushed to the image forming stations Y, M, and C by the primary transfer roller 81Y. After the contact is made, the “pushing canceling process” is executed to cancel the pushing state of the transfer belt 81, so that the transfer belt 81 is moved in the transport direction D81 at the position where the cleaner blade 711 contacts the transfer belt 81. And move it in the opposite direction. Therefore, even if foreign matter adheres to the tip of the cleaner blade 711, the foreign matter can be peeled off as the transfer belt 81 moves. Therefore, it is not necessary to separately provide a drive mechanism for rotating the transfer belt 81 in the reverse direction with respect to the transport direction D81, and the drive system is simplified. That is, according to the fourth embodiment, the foreign matter attached to the tip of the cleaner blade 711 can be effectively peeled off with a simpler configuration, and the cost and size of the apparatus can be reduced.

  In the fourth embodiment, the separation operation of the transfer belt 81 from the image forming stations Y, M, and C in the “pushing elimination process” is only the separation operation of the primary transfer roller 85Y (the most upstream color transfer member). Done. That is, when starting the separation operation of the transfer belt 81, the primary transfer rollers 85M and 85C are separated from the image forming stations M and C. Therefore, the separation operation of the transfer belt 81 in the “pushing elimination process” is not limited by the primary transfer rollers 85M and 85C. Accordingly, since the transfer belt 81 can be quickly separated from the image forming stations Y, M, and C, the transfer belt 81 is moved quickly in the direction opposite to the conveyance direction D81 at the contact position of the tip of the cleaner blade 711. Can do. Therefore, it is preferable that the foreign matter attached to the tip of the cleaner blade 711 can be more reliably peeled off.

<Fifth Embodiment>
As in the fourth embodiment, the transfer belt 81 is moved in the direction opposite to the conveyance direction D81 at the contact position where the tip of the cleaner blade 711 contacts the transfer belt 81, so that the foreign matter is separated from the tip of the cleaner blade 711. In this case, the larger the amount of movement of the transfer belt 81, the more effectively the foreign matter can be peeled off. Therefore, it may be configured as in a fifth embodiment described below. Since the basic configuration of the apparatus is the same as that of the first or fourth embodiment, only the features of the fifth embodiment will be described here, and the other components are denoted by the same reference numerals as those of the first or fourth embodiment. A description thereof will be omitted.

  In the fourth embodiment, the primary transfer roller 85Y (the most upstream color transfer member) is separated from the image forming stations Y, M, and C by the first solenoid S1 in the pushing elimination process. On the other hand, in the “pushing elimination process” in the second embodiment, the primary transfer roller 85K is separated from the image forming station K by the third solenoid simultaneously with the separation operation by the first solenoid S1, as shown in FIG. I am letting. Thus, in the fifth embodiment, the first solenoid control unit 5260, the second solenoid control unit 5270, and the third solenoid control unit 5280 function as “control means” in the present invention. That is, the first solenoid control unit 5260 (FIG. 12) issues a separation signal to the first solenoid S1, and at the same time, the third solenoid control unit 5280 (FIG. 12) issues a separation signal to the third solenoid S3. The transfer rollers 85Y and 85K are separated from the image forming stations Y and K. Therefore, as compared with the case of the fourth embodiment, the fluctuation amount ΔL2 of the image forming station side circumference L2 can be increased. As a result, the amount of movement of the transfer belt 81 in the direction opposite to the conveyance direction D81 at the contact position where the tip of the cleaner blade 711 contacts the transfer belt 81 can be increased. Therefore, the foreign matter adhering to the tip of the cleaner blade 711 can be more reliably removed, which is preferable.

<Sixth Embodiment>
Next, a sixth embodiment of the image forming apparatus according to the present invention will be described. Since the basic configuration of the apparatus is the same as that of the first embodiment, only the features of the sixth embodiment will be described here, and the other components will be denoted by the same reference numerals as those of the first embodiment and description thereof will be omitted. To do.

  18-21 is a figure which shows operation | movement of the apparatus in 6th Embodiment. In the sixth embodiment, the blade facing roller 83 is urged in the direction D83 away from the driving roller 82 by the urging means 99, and is configured to reciprocate in the urging direction D83. Further, the cleaner blade 711 is formed integrally with the blade facing roller 83 and can reciprocate along with the blade facing roller 83. Further, the apparatus in the sixth embodiment does not have the downstream guide roller 86 existing in the first to fifth embodiments, but on the downstream side in the conveyance direction D81 of the blade facing roller 83 and the conveyance of the primary transfer roller 85Y. An upstream guide roller 87 is disposed upstream in the direction D81. The upstream guide roller 87 is positioned inside the transfer belt 81, and in the state where the four primary transfer rollers 85Y, 85M, 85C, and 85K are positioned on the image forming stations Y, M, C, and K sides, The transfer belt 81 is stretched by being positioned so as to contact the transfer belt 81 on a common inscribed line between the next transfer roller 85Y and the image forming station Y.

  The upstream guide roller 87 is rotatably supported by a first support member 95, and the first support member 95 is fixedly supported by a first solenoid S1. Further, the first solenoid S1 is electrically connected to the first solenoid control unit 5260 of FIG. Therefore, by giving an appropriate signal to the first solenoid S1 from the first solenoid controller 5260, the first support member 95 and the upstream guide roller 87 are reciprocated in the stroke direction D (S1) of the first solenoid S1. Can do.

  The primary transfer rollers 85Y, 85M, and 85C (color transfer members) are rotatably supported by a second support member 97, and the second support member 97 is fixedly supported by a second solenoid S2. Yes. Further, the second solenoid S2 is electrically connected to the second solenoid control unit 5270 of FIG. Therefore, by giving an appropriate signal to the second solenoid S2 from the second solenoid controller 5270, the second support member 97 and the primary transfer rollers 85Y, 85M, 85C (color transfer member) are moved to the stroke of the second solenoid S2. It can be reciprocated in the direction D (S2).

  The primary transfer roller 85K (monochrome transfer member) is rotatably supported by a third support member 98, and the third support member 98 is fixedly supported by a third solenoid S3. Further, the third solenoid S3 is electrically connected to the third solenoid control unit 5280 in FIG. Accordingly, by giving an appropriate signal from the third solenoid control unit 5280 to the third solenoid S3, the third support member 98 and the primary transfer roller 85K (monochrome transfer member) are moved in the stroke direction D (S3 of the third solenoid S3). ). Thus, in the sixth embodiment, the first solenoid control unit 5260, the second solenoid control unit 5270, and the third solenoid control unit 5280 function as “control means” in the present invention.

  When the color mode is executed, the first solenoid control unit 5260, the second solenoid control unit 5270, and the third solenoid control unit 5280 give contact signals to the solenoids S1, S2, and S3. Then, as shown in FIG. 18, the four primary transfer rollers 85Y, 85M, 85C, and 85K are positioned on the four image forming stations Y, M, C, and K sides, and the upstream guide roller 87 transfers the transfer belt. 81 is stretched and the transfer belt 81 is pushed and brought into contact with the photosensitive drum 21 of the image forming stations Y, M, C, and K to form the primary transfer position TR1. As described above, the toner images formed at the respective image forming stations Y, M, C, and K are primarily transferred onto the surface of the transfer belt 81 at the primary transfer position TR1.

  On the other hand, when the monochrome mode is executed, the first solenoid control unit 5260 and the second solenoid control unit 5270 give separation signals to the solenoids S1 and S2, and the third solenoid control unit 5280 gives a contact signal to the solenoid S3. Then, as shown in FIG. 19, the monochrome primary transfer roller 85K (monochrome transfer member) is positioned on the monochrome image forming station K side, while the color primary transfer rollers 85Y, 85M, 85C (color transfer member) are respectively positioned. The upstream guide roller 87 is moved inward of the transfer belt 81 while being separated from the opposing image forming stations Y, M, and C. Therefore, when the monochrome mode is executed, the state where the transfer belt 81 is pushed by the color primary transfer rollers 85Y, 85M and 85C is canceled. Accordingly, the transfer belt 81 is pulled away from the image forming stations Y, M, and C by being pulled by the blade facing roller urged by the urging means 99. As a result, the transfer belt 81 contacts only the monochrome image forming station K when the monochrome mode is executed.

  In the present invention, as shown in FIGS. 18 and 19, the tip of the cleaner blade 711 is brought into contact with the blade facing roller 83 via the transfer belt 81 when performing either the color mode or the monochrome mode. In this manner, the surface of the transfer belt 81 is cleaned. In the image forming apparatus configured as described above, as shown in FIG. 18, foreign matter adheres to the tip of the cleaner blade 711 during execution of the monochrome mode, so that the tip of the transfer belt 81 and the cleaner blade 711 In some cases, the surface of the transfer belt 81 cannot be satisfactorily cleaned. Therefore, in the sixth embodiment, the following “pushing process” and “pushing cancellation process” are executed as necessary after the monochrome mode is executed.

  FIG. 20 is a diagram illustrating a pushing process in the sixth embodiment. In the pushing process, a contact signal is given to the solenoid S1 from the first solenoid control unit 5260 as necessary after the monochrome mode shown in FIG. Upon receiving the contact signal, the solenoid S1 positions the upstream guide roller 87 at the positioning position when the color mode is executed. At this time, the upstream guide roller 87 stretches the transfer belt 81 against the urging force applied to the blade facing roller 83 and pushes the transfer belt 81 against the image forming stations Y, M, and C. Make contact. At this time, the blade facing roller 83 moves in the direction opposite to the urging direction D83 in accordance with the amount of the upstream guide roller 87 that has pulled the transfer belt 81, and approaches the driving roller 82. At this time, the foreign matter remains attached to the tip of the cleaner blade 711. As described above, after the primary transfer belt 81 is pushed and brought into contact with the image forming stations Y, M, and C by the pushing process, the pushing cancellation process shown below is executed.

  FIG. 21 is a diagram illustrating a pushing elimination process in the sixth embodiment. In the pushing process in the sixth embodiment, as shown in FIG. 21, a separation signal is output from the first solenoid control unit 5260 (FIG. 12) to the first solenoid S1, and the upstream guide roller 87 is moved inward of the transfer belt 81. Move to. At this time, the blade facing roller 83 moves in the urging direction D83 while pulling the transfer belt 81 away from the image forming stations Y, M, and C, and is driven to rotate in the direction opposite to the conveying direction D81. Accordingly, since the transfer belt 81 moves in the direction opposite to the conveyance direction D81 at the contact position of the cleaner blade 711, the foreign matter attached to the tip of the cleaner blade 711 moves by ΔL2 upstream in the conveyance direction D81.

  As described above, in the sixth embodiment, the “pushing process” is performed as necessary after the monochrome mode is completed, and the transfer belt 81 is once moved to the image forming stations Y, M, C, and K by the upstream guide roller 87. After the pushing contact, the “pushing cancellation process” is executed to cancel the pushing state of the transfer belt 81, so that the transfer belt 81 is moved in the conveying direction at a position where the cleaner blade 711 contacts the transfer belt 81. It is moved in the opposite direction to D81. Therefore, even if foreign matter adheres to the tip of the cleaner blade 711, the foreign matter can be peeled off as the transfer belt 81 moves. Therefore, it is not necessary to separately provide a drive mechanism for rotating the transfer belt 81 in the reverse direction with respect to the transport direction D81, and the drive system is simplified. That is, according to the first embodiment, the foreign matter adhering to the tip of the cleaner blade 711 can be effectively peeled off with a simpler configuration, and the cost and size of the apparatus can be reduced.

  In the sixth embodiment, the separation operation of the transfer belt 81 from the image forming station in the “pushing elimination process” is performed only by the separation operation of the upstream guide roller 87. That is, when the separation operation of the transfer belt 81 is started, the primary transfer rollers 85Y, 85M, and 85C are separated from the image forming stations Y, M, and C. Therefore, the separation operation of the transfer belt 81 in the “pushing elimination process” is not limited by the primary transfer rollers 85Y, 85M, and 85C. Accordingly, since the transfer belt 81 can be quickly separated from the image forming stations Y, M, and C, the transfer belt 81 is moved quickly in the direction opposite to the conveyance direction D81 at the contact position of the tip of the cleaner blade 711. Can do. Therefore, it is preferable that the foreign matter attached to the tip of the cleaner blade 711 can be more reliably peeled off.

<Seventh embodiment>
As in the sixth embodiment, the transfer belt 81 is moved in the direction opposite to the conveyance direction D81 at the contact position where the tip of the cleaner blade 711 contacts the transfer belt 81, thereby removing foreign matter from the tip of the cleaner blade 711. In this case, the larger the amount of movement of the transfer belt 81, the more effectively the foreign matter can be peeled off. Therefore, a seventh embodiment described below may be configured. Since the basic configuration of the apparatus is the same as that of the first or sixth embodiment, only the features of the seventh embodiment will be described here, and the other components are denoted by the same reference numerals as those of the first or seventh embodiment. A description thereof will be omitted.

  In the sixth embodiment, the upstream guide roller 87 is moved inward of the transfer belt 81 by the first solenoid S1 in the pushing elimination process. On the other hand, in the “pushing elimination process” in the seventh embodiment, as shown in FIG. 22, the primary transfer roller 85K is separated from the image forming station K by the third solenoid simultaneously with the separation operation by the first solenoid S1. I am letting. Thus, in the seventh embodiment, the first solenoid control unit 5260, the second solenoid control unit 5270, and the third solenoid control unit 5280 function as “control means” in the present invention. That is, at the same time when the first solenoid control unit 5260 (FIG. 12) issues a separation signal to the first solenoid S1, a third solenoid control unit 5280 (FIG. 12) issues a separation signal to the third solenoid S3, and the upstream guide. The roller 87 is moved inward of the transfer belt 81 and 85K is separated from the image forming station K. Therefore, as compared with the case of the sixth embodiment, the fluctuation amount ΔL2 of the image forming station side circumference L2 can be increased. As a result, the amount of movement of the transfer belt 81 in the direction opposite to the conveyance direction D81 at the contact position where the tip of the cleaner blade 711 contacts the transfer belt 81 can be increased. Therefore, the foreign matter adhering to the tip of the cleaner blade 711 can be more reliably removed, which is preferable.

<Others>
The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the image forming stations Y, M, C, and K are arranged in this order from the upstream side in the transport direction D81. However, the arrangement order of the image forming stations is not limited to this and can be changed as appropriate. is there.

  In the above embodiment, the monochrome primary transfer roller (monochrome transfer member) and the monochrome image forming station K are arranged on the most downstream side in the transport direction D81 of the transfer belt 81. However, these arrangement positions are limited to this. Instead, it may be arranged at a position other than the most downstream in the transport direction D81. However, as described above, from the viewpoint of preventing the transfer belt and the monochrome primary transfer roller or the monochrome image forming station K from switching between the color mode and the monochrome mode from rubbing each other, the monochrome primary transfer roller and the monochrome image formation are performed. The station K is preferably arranged on the most downstream side in the transfer direction D81 of the transfer belt 81.

  In the above-described embodiment, in the monochrome mode, monochrome image formation is executed using only black (K). However, monochrome image formation may be executed using only cyan (C), for example.

  In the first embodiment, in the pushing process, the three primary transfer rollers 85Y, 85M, and 85C including the primary transfer roller 85Y positioned upstream from the upstream side in the transport direction D81 are connected to the image forming station Y, Positioned on the M and C sides. However, the combination of the primary transfer rollers 85 positioned on the image forming station side in the pushing process is not limited to this, and may be, for example, only 85M and 85C. However, from the viewpoint of increasing the amount of movement ΔL2 of the transfer belt 81 in the reverse direction of the transfer direction D81 at the contact position of the cleaner blade 711 in the pushing-out elimination process, at least the primary located at the most upstream in the transfer direction D81. The transfer roller 85Y is preferably positioned on the image forming station Y side in the pushing process and separated from the image forming station Y in the pushing cancellation process.

  In the above embodiment, the primary transfer roller that is driven and rotated is used as the transfer member. However, the usable transfer member is not limited to this, and a transfer member that is not driven and rotated, for example, may be used. However, when the transfer member is a driven roller, the friction between the transfer belt and the transfer member (transfer roller) when the transfer belt is separated from the image forming station with the cancellation of the belt pushing state by the separation contact means. Can be reduced. As a result, the separating operation of the transfer belt can be performed quickly, and the foreign matter adhering to the tip of the cleaner blade can be peeled off more effectively.

1 is a diagram illustrating a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. The figure which shows operation | movement of the apparatus in 1st Embodiment of this invention. The figure which shows operation | movement of the apparatus in 1st Embodiment of this invention. The figure which shows operation | movement of the apparatus in 1st Embodiment of this invention. The figure which shows operation | movement of the apparatus in 1st Embodiment of this invention. The figure which shows operation | movement of the apparatus in 2nd Embodiment of this invention. The figure which shows operation | movement of the apparatus in 3rd Embodiment of this invention. The figure which shows operation | movement of the apparatus in 3rd Embodiment of this invention. The figure which shows operation | movement of the apparatus in 3rd Embodiment of this invention. The figure which shows operation | movement of the apparatus in 3rd Embodiment of this invention. FIG. 3 is a block diagram showing another electrical configuration of the image forming apparatus in FIG. 1. The figure which shows operation | movement of the apparatus in 4th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 4th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 4th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 4th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 5th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 6th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 6th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 6th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 6th Embodiment of this invention. The figure which shows operation | movement of the apparatus in 7th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Housing box main body, 5 ... Electrical component box, 5260, 5270, 5280 ... Solenoid control part (control means), 7 ... Image forming unit, 8 ... Transfer belt unit, 21 ... Photoconductor drum, 71 ... Cleaner part, 711 DESCRIPTION OF SYMBOLS ... Cleaner blade 81 ... Transfer belt 82 ... Drive roller 83 ... Driven roller (blade facing roller) 85, 85Y, 85M, 85C, 85K ... Primary transfer roller 86 ... Downstream guide roller 87 ... Upstream guide roller 95 ... first support member, 97 ... second support member, 98 ... third support member, 99 ... biasing means, Y, M, C, K ... image forming station, D21 ... photosensitive drum rotation direction, TR1 ... Primary transfer position, D81 ... transport direction, D83 ... biasing direction, D (S1), D (S2), D (S3) ... stroke direction, ΔL2 Variation amount of the transfer belt circumference, S1, S2, S3 ... solenoid

Claims (9)

A driving roller, a blade-opposing roller that is energized in a direction away from the driving roller by an urging means and reciprocates in the energizing direction, and at least two rollers, the driving roller and the blade-opposing roller A transfer belt that is stretched around and rotated and conveyed in a predetermined conveyance direction, and is configured integrally with the blade-opposing roller and reciprocates in the urging direction along with the blade-opposing roller. A cleaner blade that contacts the blade facing roller via a belt to clean the surface of the transfer belt; and a downstream side of the blade facing roller in the transport direction and an upstream side of the drive roller in the transport direction in the transport direction. M image forming stations (M) that are arranged side by side and form toner images of different colors. And 2), in an image forming apparatus having a M number of transfer members are opposed one on one across the transfer belt with respect to the M image forming stations each,
Different colors formed in each of the M image forming stations by positioning the M transfer members on the image forming station side so that the transfer belt is pushed and brought into contact with the M image forming stations. A color mode in which a toner image is primarily transferred so as to be superimposed on the surface of the transfer belt to form a color image;
Among the M transfer members, the monochrome transfer member is positioned on the monochrome image forming station side to which the monochrome transfer member faces, and (M-1) of the M transfer members excluding the monochrome transfer member. By moving the color transfer member away from the image forming station, only the toner image formed at the monochrome image forming station is brought into contact with the surface of the transfer belt by pushing and contacting the transfer belt only with the monochrome image forming station. An image forming method for causing the image forming apparatus to selectively execute a monochrome mode for forming a monochrome image by primary transfer.
An image forming method characterized in that after the monochrome mode is completed, a pushing process and a pushing cancellation process described below are executed as necessary.
In the pushing process, N color transfer members (M-1 ≧ N ≧ 1) among the (M-1) color transfer members are positioned on the image forming station side to transfer the N color transfer members. A step of pushing the transfer belt to the image forming station by a member;
In the pushing elimination step, the N color transfer members positioned on the image forming station side in the pushing step are moved away from the image forming station, and the transfer belt is moved by the N color transfer members. In this step, the blade facing roller is driven to rotate in the direction opposite to the conveying direction while the blade facing roller is moved in the urging direction by the urging force from the urging means by eliminating the pushing state.   2. The image forming method according to claim 1, wherein the monochrome transfer member is a transfer member located on the most downstream side in the transport direction among the M transfer members. The pushing process includes L color transfer members (M-1 ≧ L ≧ 1) including the most upstream color transfer member located at the most upstream in the transport direction among the (M−1) color transfer members. Positioning on the image forming station side and pushing the transfer belt to the image forming station by the L color transfer members;
In the pushing elimination step, the L color transfer members positioned on the image forming station side in the pushing step are moved away from the image forming station, and the transfer belt is moved by the L color transfer members. The step of rotating the blade facing roller in the direction opposite to the conveying direction while moving the blade facing roller in the urging direction by the urging force from the urging means by eliminating the pushing state. Image forming method. In the pushing step, the most upstream color transfer member positioned on the most upstream side in the transport direction among the (M-1) color transfer members is positioned on the image forming station side, and the most upstream color transfer member A step of pushing the transfer belt to the image forming station;
In the pushing elimination step, the transfer belt is pushed by the most upstream color transfer member by moving the most upstream color transfer member positioned on the image forming station side by the pushing step away from the image forming station. 3. The image formation according to claim 2, wherein the state is canceled and the blade facing roller is driven to rotate in a direction opposite to the transport direction while being moved in the biasing direction by a biasing force from the biasing unit. Method.   In the pushing-out canceling step, the monochrome transfer member is moved away from the image forming station as the color transfer member is moved away from the image forming station to cancel the pushing state of the transfer belt. 5. The image forming method according to claim 2, wherein the blade facing roller is driven and rotated in a direction opposite to the transport direction while being moved in the biasing direction by a biasing force from the biasing unit. . A driving roller, a blade-opposing roller that is energized in a direction away from the driving roller by an urging means and reciprocates in the energizing direction, and at least two rollers, the driving roller and the blade-opposing roller A transfer belt that is stretched around and rotated and conveyed in a predetermined conveyance direction, and is configured integrally with the blade-opposing roller and reciprocates in the urging direction along with the blade-opposing roller. A cleaner blade that contacts the blade facing roller via a belt to clean the surface of the transfer belt; and a downstream side of the blade facing roller in the transport direction and an upstream side of the drive roller in the transport direction in the transport direction. M image forming stations (M) that are arranged side by side and form toner images of different colors. 2) M transfer members disposed one-to-one facing the M image forming stations with the transfer belt interposed therebetween, and the upstream of the M transfer members in the transport direction and An image forming apparatus including an upstream guide roller disposed inside the transfer belt at a downstream side of the blade facing roller in the transport direction;
The M transfer members are positioned on the image forming station side, and the transfer member positioned on the most upstream side in the transport direction in the state where the M transfer members are positioned and the image forming station facing the transfer member. By positioning the upstream guide roller so as to come into contact with the transfer belt on a common inscribed line, the transfer belt is pushed and brought into contact with the M image forming stations so that each of the M image forming stations A color mode for forming a color image by performing primary transfer so that the formed toner images of different colors are superimposed on the surface of the transfer belt;
Among the M transfer members, the monochrome transfer member on the most downstream side in the transport direction is positioned on the monochrome image forming station side facing the monochrome transfer member, and the monochrome transfer member is excluded from the M transfer members. (M-1) The color transfer member is moved away from the image forming station and the upstream guide roller is moved inward from the positioning position in the color mode to move the transfer belt to the monochrome image. The image forming apparatus selectively selects a monochrome mode in which only a toner image formed by the monochrome image forming station is pushed and brought into contact with only the forming station and is primarily transferred to the surface of the transfer belt to form a monochrome image. An image forming method to be executed,
After the monochrome mode is completed, the following pushing process and pushing cancellation process are executed as necessary.
The pushing step is a step of positioning the upstream guide roller at a positioning position in the color mode and pushing the transfer belt to the image forming station by the upstream guide roller.
In the pushing cancellation process, the upstream guide roller positioned at the positioning position in the color mode by the pushing process is moved inward from the positioning position toward the inside of the transfer belt to push the transfer belt by the upstream guide roller. In this step, the blade facing roller is driven to rotate in the direction opposite to the conveying direction while the blade facing roller is moved in the urging direction by the urging force from the urging means by eliminating the feeding state.   In the pushing-out eliminating step, the monochrome transfer member is moved away from the image forming station to move the upstream guide roller away from the image forming station as the upstream guide roller is moved inward from the positioning position in the color mode. 7. The image according to claim 6, wherein the blade counter roller is driven and rotated in a direction opposite to the conveying direction while the blade facing roller is moved in the urging direction by the urging force from the urging means by eliminating the feeding state. Forming method.   The image forming method according to claim 1, wherein the transfer member is a transfer roller that is driven to rotate. A driving roller, a blade-opposing roller that is energized in a direction away from the driving roller by an urging means and reciprocates in the energizing direction, and at least two rollers, the driving roller and the blade-opposing roller A transfer belt that is stretched around and rotated and conveyed in a predetermined conveyance direction, and is configured integrally with the blade-opposing roller and reciprocates in the urging direction along with the blade-opposing roller. A cleaner blade that contacts the blade facing roller via a belt to clean the surface of the transfer belt; and a downstream side of the blade facing roller in the transport direction and an upstream side of the drive roller in the transport direction in the transport direction. M image forming stations (M) that are arranged side by side and form toner images of different colors. 2), M transfer members arranged to face each of the M image forming stations in a one-to-one relationship with the transfer belt interposed therebetween, and control means for controlling the positions of the M transfer members. In the provided image forming apparatus,
The control means positions the M transfer members on the image forming station side to push the transfer belt against and contact the M image forming stations to form each of the M image forming stations. A color mode for forming a color image by performing primary transfer so that the toner images of different colors are superimposed on the surface of the transfer belt;
Among the M transfer members, the monochrome transfer member is positioned on the monochrome image forming station side to which the monochrome transfer member faces, and (M-1) of the M transfer members excluding the monochrome transfer member. By moving the color transfer member away from the image forming station, only the toner image formed at the monochrome image forming station is brought into contact with the surface of the transfer belt by pushing and contacting the transfer belt only with the monochrome image forming station. Selectively executing a monochrome mode in which primary transfer forms a monochrome image;
After completion of the monochrome mode, N color transfer members (M-1 ≧ N ≧ 1) among the (M-1) color transfer members are positioned on the image forming station side as necessary. After the transfer belt is pushed to the image forming station by the number of color transfer members, the N color transfer members are moved away from the image forming station to transfer the transfer belt by the N color transfer members. By eliminating the pushing state, the image forming apparatus is characterized in that the blade facing roller is driven to rotate in the direction opposite to the conveying direction while being moved in the urging direction by the urging force from the urging means. .

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