JP2005352122A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus for forming an image of high quality by changing the driving velocity of an intermediate transfer body with a simple constitution, without causing irregularities in a toner image on the intermediate transfer body. <P>SOLUTION: In the case of reducing the driving velocity of the intermediate transfer body 64 after primarily transferring each color toner image to the intermediate transfer body 64 at a normal velocity, the driving velocity is reduced after the toner image (maximum image forming area A) primarily transferred on the intermediate transfer body 64 passes through a contact area R of the body 64 with an image carrier 50. Besides, a velocity changing period of reducing the driving velocity is continued during an operation of secondarily transferring a toner image and fixing the toner image, and is ended when a prescribed time passes after the aforesaid operation. By changing the driving velocity of the intermediate transfer body 64 at the aforesaid timing, irregularities in the toner image caused by changing the driving velocity of the intermediate transfer body 64 in a period when the toner image on the intermediate transfer body 64 passes through the contact area R (primary transfer position T1) are avoided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus. More specifically, the present invention relates to an intermediate transfer body type in which a toner image formed on a photoreceptor is primarily transferred to an intermediate transfer body, and the toner image on the intermediate transfer body is secondarily transferred to a sheet. The present invention relates to an image forming apparatus.

In an image forming apparatus using electrophotographic technology such as an electrophotographic copying machine or a laser printer, a toner image formed on a photosensitive member is primarily transferred to an intermediate transfer member such as an intermediate transfer belt, and a toner image on the intermediate transfer member. In the intermediate transfer body type device that transfers the toner image onto the paper, in order to obtain a high-quality image by sufficiently melting and fixing the toner image on the paper in full color image formation, the toner image that has been primarily transferred is retained. A technique has been proposed in which the peripheral speed of the intermediate transfer member is decelerated in accordance with the peripheral speed of the fixing device while the intermediate transfer member is idled by one rotation, and the secondary transfer is performed at that low speed for fixing. For example, see Patent Document 1). Also, when fixing a toner image by forming an image on OHT (overhead transparencies) paper or thick paper, the fixing speed of the fixing device and the intermediate transfer member is released after separating the intermediate transfer member from the photosensitive member and releasing the primary transfer nip. There has been proposed a technique for decelerating (see, for example, Patent Document 2).
JP-A-4-67174 JP 2000-267474 A

  However, in the technique of Patent Document 1 described above, since the driving speed (circumferential speed) is reduced while the toner image on the intermediate transfer member passes through the primary transfer position, the toner image (image) is reduced along with the deceleration. There is a problem that is disturbed. Further, the technique of Patent Document 2 requires a large-scale mechanism for separating the intermediate transfer member from the photosensitive member, which complicates the apparatus configuration.

  In consideration of the above-described facts, the present invention provides an image forming apparatus that can form a high-quality image by changing the driving speed of the intermediate transfer member without disturbing the toner image on the intermediate transfer member with a simple configuration. The task is to do.

  In order to achieve the above object, the invention according to claim 1 is provided on an image carrier, provided to maintain an image carrier on which a toner image is formed, and in contact with the image carrier. In the image forming apparatus having an intermediate transfer body in which the toner image is primarily transferred and the toner image is secondarily transferred to a recording medium and the driving speed can be changed, the change in the driving speed of the intermediate transfer body is The toner image that is primarily transferred onto the intermediate transfer member is located at a position excluding the contact area between the image carrier and the intermediate transfer member.

  In the first aspect of the present invention, for example, a toner image is recorded on the recording medium until the toner image primarily transferred from the image bearing member to the intermediate transfer member is secondarily transferred from the intermediate transfer member to the recording medium. When the driving speed of the intermediate transfer member is changed in accordance with the fixing speed of the fixing means for fixing, the toner image primarily transferred onto the intermediate transfer member has a contact area between the image carrier and the intermediate transfer member. The drive speed of the intermediate transfer member is changed when it is in the removed position. By changing the driving speed of the intermediate transfer member at this timing, that is, when the toner image is located in the contact area between the image carrier and the intermediate transfer member, the driving speed of the intermediate transfer member is not changed. It is possible to avoid the disturbance of the toner image caused by changing the driving speed of the intermediate transfer body while the toner image on the body passes through the contact area (primary transfer position). Further, in order to avoid such disturbance of the toner image, it is not necessary to provide a mechanism for separating the intermediate transfer member from the image carrier when changing the driving speed of the intermediate transfer member. It can be installed by a simple holding mechanism (attachment mechanism) that maintains the contact state with the carrier.

  In this way, even when the drive speed of the intermediate transfer member is changed in image formation on the recording medium, the drive speed of the intermediate transfer member is changed without disturbing the toner image on the intermediate transfer member with a simple configuration, and high quality. An image can be formed.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the change in the driving speed of the intermediate transfer member is a deceleration.

  According to the second aspect of the present invention, for example, when an image is formed on a recording medium such as an OHP sheet or a postcard paper in which the heating time for melting and fixing the toner image is longer than that of plain paper, the toner image is The driving speed of the intermediate transfer member is reduced according to the capability (fixing speed) of the fixing means for fixing on the recording medium. As a result, the toner image can be satisfactorily secondarily transferred from the intermediate transfer member to the recording medium for fixing.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the change in the driving speed of the intermediate transfer member is an increase.

  According to the third aspect of the present invention, for example, when an image is formed on a recording medium in which the heating time for melting and fixing the toner image is shorter than that of plain paper, the fixing means for fixing the toner image to the recording medium is provided. The driving speed of the intermediate transfer member is increased according to the capability (fixing speed). As a result, the processing time for secondary transfer and fixing of the toner image onto the recording medium from the intermediate transfer member can be shortened, and the productivity can be increased while forming a high-quality image.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the non-image forming area excluding the maximum image forming area provided on the intermediate transfer member is an intermediate transfer. It is larger than the contact area in the driving direction of the body, and the drive speed of the intermediate transfer body is changed in the non-image forming area.

  In the invention according to claim 4, by changing the driving speed of the intermediate transfer member in the non-image forming region provided larger than the contact region between the image carrier and the intermediate transfer member on the intermediate transfer member, It is possible to eliminate dot (pixel) unevenness and density unevenness of the toner image generated in the contact area.

  Since the image forming apparatus of the present invention has the above-described configuration, it is possible to form a high-quality image by changing the driving speed of the intermediate transfer member without disturbing the toner image on the intermediate transfer member with a simple configuration.

  An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIGS. 1 and 2, the image forming apparatus 10 according to the present embodiment includes an image forming apparatus main body 12, and an opening / closing cover that is rotatable about a hinge portion 14 at the top of the image forming apparatus main body 12. 16 is provided, and, for example, a one-stage sheet feeding unit 18 is disposed below the image forming apparatus main body 12.

  The paper feed unit 18 includes a paper feed tray 22 that stores paper. A feed roll 24 that feeds paper from the paper feed tray 22 and a paper to be fed are provided in an upper portion near the rear end of the paper feed tray 22. The retard rolls 26 are arranged one by one.

  The conveyance path 28 is a sheet path from the feed roll 24 to the discharge port 30, and this conveyance path 28 is in the vicinity of the back side (right side in FIG. 1) of the image forming apparatus main body 12 and will be described later from the sheet feeding unit 18. The fixing device 90 is formed substantially vertically. A secondary transfer roll 80 and a secondary transfer backup roll 72, which will be described later, are disposed on the upstream side of the fixing device 90 in the conveyance path 28, and on the upstream side of the secondary transfer roll 80 and the secondary transfer backup roll 72, respectively. A resist roll 32 is disposed. In addition, a discharge roll 34 is disposed in the vicinity of the discharge port 30 in the conveyance path 28.

  Accordingly, the sheet fed from the sheet feeding tray 22 of the sheet feeding unit 18 by the feed roll 24 is turned by the retard roll 26 and only the uppermost sheet is guided to the conveyance path 28 and is temporarily stopped by the registration roll 32. The toner image is transferred between a secondary transfer roll 80 and a secondary transfer backup roll 72, which will be described later, and the transferred toner image is fixed by the fixing device 90, and the discharge port 34 discharges the discharge port 30. Are discharged to a discharge portion 36 provided on the upper portion of the opening / closing cover 16. The discharge portion 36 has a low discharge port portion and is inclined so as to gradually increase toward the front direction (left direction in FIG. 1).

  The image forming apparatus main body 12 is provided with a rotary developing device 38 at a substantially central portion. The rotary developing device 38 includes developing units 42a to 42d that respectively form toner images of four colors of yellow, yellow, magenta, cyan, and black in the developing unit main body 40, and rotate. It rotates counterclockwise around the support shaft 44 (counterclockwise in FIG. 1). The developing units 42a to 42d are respectively provided with developing rolls 46a to 46d, and are pressed in the normal direction of the developing unit main body 40 by elastic bodies 48a to 48d such as coil springs.

  The rotary developing device 38 is arranged so as to rotate about a rotation support shaft 49 so that an image carrier 50 made of a photosensitive member comes into contact therewith, and the developing rolls 46 a to 46 d are in contact with the image carrier 50. In the absence, a part of each outer periphery protrudes slightly (for example, 2 mm) from the outer periphery of the developing device main body 40 in the radial direction. A tracking roll (not shown) having a diameter slightly larger than the diameter of the developing rolls 46a to 46d is provided at both ends of each of the developing rolls 46a to 46d so as to rotate coaxially with the developing rolls 46a to 46d. ing. In other words, the developing units 42 a to 42 d are arranged on the outer periphery of the developing unit main body 40 at intervals of 90 ° around the rotation support shaft 44, and the tracking rolls of the developing rolls 46 a to 46 d are provided at both ends of the image carrier 50. The latent image on the image carrier 50 is developed with toner of each color while abutting against a flange (not shown) formed and forming a predetermined gap between the developing rolls 46a to 46d and the image carrier 50. To do.

  Below the image carrier 50, a charging device 52 including a charging roll that uniformly charges the image carrier 50 is provided. Further, the image carrier 50 is provided with an image carrier cleaner 54 so as to hang from the rotation support shaft 49, and the image carrier 50 and the image carrier cleaner 54 are integrated. The image carrier cleaner 54 includes a cleaning blade 56 that scrapes residual toner remaining on the image carrier 50 after primary transfer, and a toner collection bottle 58 that collects waste toner scraped by the cleaning blade 56. A rib or the like is formed on the back side (right side in FIG. 1) of the toner collection bottle 58, and is curved to form a part of the conveyance path 28 so that the paper is smoothly conveyed.

  On the lower back side of the rotary developing device 38, an exposure device 60 for writing a latent image on the image carrier 50 charged by the charging device 52 with a light beam such as a laser beam is disposed. Further, an intermediate transfer device 62 is provided above the rotary developing device 38. The toner image visualized by the rotary developing device 38 is primarily transferred at the primary transfer position T1 and conveyed to a secondary transfer position T2, which will be described later. .

  The intermediate transfer device 62 includes an intermediate transfer member 64 such as an elastic intermediate transfer belt, a primary transfer roll 66, a wrap-in roll 68, a wrap-out roll 70, a secondary transfer backup roll 72, a scraper backup roll 74, and a brush backup roll 76. It has.

  The intermediate transfer member 64 is stretched substantially flat so as to have a long side and a short side above the rotary developing device 38. The long side on the upper surface side of the intermediate transfer member 64 is stretched so as to be substantially parallel to the discharge unit 36 provided on the upper portion of the image forming apparatus main body 12. Further, as shown in FIG. 3, the intermediate transfer body 64 is disposed below the long side of the intermediate transfer body 64 and a wrap-in roll 68 disposed upstream of the primary transfer roll 66 and downstream of the primary transfer roll 66. A contact region (primary transfer portion) R that contacts the image carrier 50 in a wrap shape with the wrap-out roll 70 is wrapped around the image carrier 50 by a predetermined range and driven by the rotation of the image carrier 50. To do. As described above, the intermediate transfer member 64 is primarily transferred by the primary transfer roll 66 so that the toner image on the image carrier 50 is superposed in the order of yellow, magenta, cyan, and black, and the first transferred toner image is described later. It is conveyed toward the next transfer roll 80. Note that the wrap-in roll 68 and the wrap-out roll 70 are separated from the image carrier 50.

  Thus, the intermediate transfer body 64 is stretched by five rolls of the wrap-in roll 68, the wrap-out roll 70, the secondary transfer backup roll 72, the scraper backup roll 74, and the brush backup roll 76, and the primary transfer roll 66, the toner image on the image carrier 50 is transferred.

  Further, a flat portion (short side) is formed on the back side (right side surface in FIG. 1) of the intermediate transfer member 64 by a wrap-out roll 70 and a secondary transfer backup roll 72, and this flat portion is the secondary transfer portion. It faces the conveyance path 28.

  In the secondary transfer portion, the wrap-out roll 70 is arranged so that the intermediate transfer body 64 and the conveyance path 28 are at an angle of 12 °, for example.

  The scraper backup roll 74 assists the scraper 84 described later to scrape off transfer residual toner remaining on the intermediate transfer body 64 after the secondary transfer, and the brush backup roll 76 remains on the intermediate transfer body 64 after the secondary transfer. A brush roll 86 described later assists in scraping off the transfer residual toner.

  Above the long side of the intermediate transfer member 64, a sensor 78 such as a reflective photosensor is provided by being fixed to the back surface (inside) of the opening / closing cover 16. The sensor 78 reads a toner patch formed on the intermediate transfer body 64, detects the position of the intermediate transfer body 64 in the rotation direction, and detects the toner density.

  A secondary transfer roll 80 is opposed to the secondary transfer backup roll 72 of the intermediate transfer device 62 with the conveyance path 28 interposed therebetween. That is, the secondary transfer position T2 in the secondary transfer portion is between the secondary transfer roll 80 and the secondary transfer backup roll 72, and the secondary transfer roll 80 is assisted by the secondary transfer backup roll 72. The toner image primarily transferred to the intermediate transfer member 64 is secondarily transferred to the sheet at the secondary transfer position T2. Here, the secondary transfer roll 80 is separated from the intermediate transfer body 64 while the intermediate transfer body 64 rotates three times, that is, while the toner images of three colors of yellow, magenta, and cyan are transported. When the image is transferred, it comes into contact with the intermediate transfer member 64. Note that a predetermined potential difference is generated between the secondary transfer roll 80 and the secondary transfer backup roll 72. For example, when the secondary transfer port 80 is set to a high voltage, the secondary transfer roll 80 has a secondary voltage. The transfer backup roll 72 is connected to a ground (GND) or the like.

  An intermediate transfer body cleaner 82 is provided at the end of the intermediate transfer body 64 on the side opposite to the image carrier. The intermediate transfer body cleaner 82 includes a scraper 84, a brush roll 86, a toner collection bottle 88, and a rotation support shaft 89. The intermediate transfer body cleaner 82 swings about the rotation support shaft 89 and can contact and separate from the intermediate transfer body 64. .

  The scraper 84 provided on the intermediate transfer body cleaner 82 is made of a thin plate such as a SUS material, and a negative voltage (for example, −200 V) having the same polarity as the negatively charged toner is applied to the intermediate transfer body after the secondary transfer. The transfer residual toner remaining on the body 64 is scraped off to be thinned, and the polarity of the transfer residual toner is made negative (positive polarity). The brush roll 86 is made of a brush made of an acrylic resin or the like that has been subjected to a conductive treatment, and is applied with a positive voltage (for example, +2.3 kV) having a polarity opposite to that of the negatively charged toner. The transfer residual toner remaining on the transfer body 64 is further scraped off and the transfer residual toner is positively charged (reverse polarity). The toner collection bottle 88 collects the toner scraped by the scraper 84 and the brush roll 86. While the intermediate transfer member 64 conveys the toner image, the scraper 84 and the brush roll 86 are separated from the intermediate transfer member 64 so that they come into contact with the intermediate transfer member 64 at a predetermined timing. Has been.

  A fixing device 90 is disposed above the secondary transfer position. The fixing device 90 includes a heating roll 92 and a pressure roll 94, fixes the toner image secondarily transferred to the sheet by the secondary transfer roll 80 and the secondary transfer backup roll 72, and directs the toner image to the discharge roll 34. Transport.

  The intermediate transfer device 62, the image carrier 50, the charging device 52, the image carrier cleaner 54, and the intermediate transfer member cleaner 82 described above are integrated to form an image forming unit 96. In the apparatus 10, the image forming unit 96 is detachable from the image forming apparatus main body 12.

  FIG. 2 shows a state where the image forming unit 96 is removed from the image forming apparatus main body 12.

  As shown in FIG. 2, when the image forming unit 96 is removed from the image forming apparatus main body 12, the open / close cover 16 of the image forming apparatus main body 12 is rotated around the rotation fulcrum 14 to Open the top of 12. Here, the image forming unit 96 is disposed such that the intermediate transfer device 62 and the image carrier 50 are positioned between the fixing device 90 and the rotary developing device 38. Through the space, the image forming apparatus main body 12 can be removed so as to be drawn obliquely forward (left obliquely upward in FIG. 2). In addition, the image forming unit 96 is detached from the image forming apparatus main body 12, the intermediate transfer unit 97 in which the intermediate transfer device 62 and the intermediate transfer body cleaner 82 are integrated, the image carrier 50, and the charging device 52. The image carrier cleaner 54 is integrated with the image carrier unit 98.

  Next, a color image forming operation by the image forming apparatus 10 of the present embodiment configured as described above will be described.

  When an image forming signal is input to the image forming apparatus 10, the image carrier 50 is uniformly charged by the charging device 52, and the charged image carrier 50 is supplied to the charged image carrier 50 from the exposure device 60 based on the image forming signal. A light beam is emitted. Light rays from the exposure device 60 expose the surface of the image carrier 50 to form a latent image. The latent image of the image carrier 50 formed by the exposure device 60 is developed with yellow, magenta, cyan, and black toner images by the rotary developing device 38, and is primarily transferred onto the intermediate transfer member 64 at the primary transfer position T1. The In the primary transfer, the transfer residual toner remaining on the image carrier 50 is scraped off by the cleaning blade 56 of the image carrier cleaner 54 and collected in the toner collection bottle 58.

  On the other hand, the paper stored in the paper feed tray 22 by a paper feed signal or the like is sent out by the feed roll 24, is turned by the retard roll 26, is guided to the transport path 28, is temporarily stopped by the registration roll 32, and the timing is reached. As a result, it is guided between the secondary transfer roll 80 and the secondary transfer backup roll 72. When the sheet is guided between the secondary transfer roll 80 and the secondary transfer backup roll 72, the toner image primarily transferred to the intermediate transfer body 64 is secondarily transferred by the secondary transfer roll 80 and the secondary transfer backup roll 72. Secondary transfer is performed on the sheet at the next transfer position T2. The sheet on which the toner image is transferred is guided to the fixing device 90, and the toner image is melted and fixed by the thermal pressure of the heating roll 92 and the pressure roll 94. The paper on which the image is formed by fixing the toner image is discharged from the discharge port 30 to the discharge unit 36 by the discharge roll 34.

  Further, the transfer residual toner remaining in the image area of the intermediate transfer body 64 after the secondary transfer is scraped off by the scraper 84 and the brush roll 86 of the intermediate transfer body cleaner 82 and recovered in the toner recovery bottle 88. Further, when the apparatus is stopped after image formation, the drive system including the image carrier 50 and the intermediate transfer member 64 that is driven to rotate by the image carrier 50 has the intermediate transfer member 64 driven by the intermediate transfer member cleaner 82. After the image area cleaning operation, the driving is stopped after the driving is continued for a predetermined time. As a result, the transfer residual toner remaining on the intermediate transfer member 64 without being separated by the intermediate transfer member cleaner 82 is reversed from the intermediate transfer member 64 to the image carrier 50 by the intermediate transfer member cleaning operation accompanying the apparatus stop operation. The image is copied and removed by the image carrier cleaner 54.

  Through the above operation, a color image is formed on the sheet by the image forming apparatus 10.

  Next, an operation for changing the driving speed (toner image conveying speed) of the intermediate transfer body 64 in the image forming operation by the image forming apparatus 10 of the present embodiment will be described.

When the image forming apparatus 10 forms an image on an OHP sheet, a postcard paper, or the like in which the heating time for melting and fixing the toner image is longer than that of plain paper, the OHP is transferred after the primary transfer of the toner image. Secondary transfer and fixing processing are performed by reducing the driving speed of the intermediate transfer body 64 in accordance with the fixing speed of the fixing device 90 that fixes the toner image on a sheet, a postcard paper, or the like. In the case of the image forming apparatus 10 according to the present embodiment, the fixing speed for each sheet is the fixing speed for a thick sheet such as a postcard sheet, where (V ₁ ) is a normal fixing speed for plain paper or the like by the fixing device 90. (V ₂ ) is set to “V ₂ = 1/2 · V ₁ ”, and the fixing speed (V ₃ ) for the OHP sheet is set to “V ₃ = 1/3 · V ₁ ”.

  FIG. 4 shows a timing chart relating to the control timing of the drive speed changing operation of the intermediate transfer body 64 in the image forming operation by the image forming apparatus 10. As shown in FIG. 4, the toner images of the respective colors are primarily transferred to the intermediate transfer body 64 at a normal speed, and the reduction of the driving speed of the intermediate transfer body 64 is caused by the toner image primarily transferred onto the intermediate transfer body 64. Is performed after passing through the contact region R between the intermediate transfer member 64 and the image carrier 50. The speed change period in which the drive speed is reduced is continued during the secondary transfer and fixing process of the toner image, and is ended when a predetermined time has elapsed after the operation. Then, the drive speed of the intermediate transfer body 64 is returned to the original normal speed, and the process proceeds to the next image forming operation or apparatus stop operation.

  In FIG. 5, the intermediate transfer body 64 is developed in the rotation direction (rotational length L), and the maximum image forming area A and the non-image forming area B excluding the maximum image forming area A provided on the intermediate transfer body 64 are illustrated. 4 is a development view of the intermediate transfer member 64 showing the relationship of the contact area R between the intermediate transfer member 64 and the image carrier 50. FIG. As shown in FIG. 5, the non-image forming area B is made larger than the contact area R in the driving direction of the intermediate transfer body 64 (in the direction of arrow C in the figure). Here, the deceleration (shift period) of the driving speed of the intermediate transfer member 64 described above is a non-image of the intermediate transfer member 64 that is rotationally driven after the primary transfer of the toner image, as shown in FIGS. When the formation area B is located in the contact area R with the image carrier 50, that is, when the toner image (maximum image formation area A) primarily transferred onto the intermediate transfer body 64 is in a position excluding the contact area R. Is going to.

  Next, an effect of the operation for changing the driving speed of the intermediate transfer body 64 in the image forming operation by the image forming apparatus 10 described above will be described.

  In the image forming apparatus 10 of the present embodiment, when an image is formed on an OHP sheet or a postcard paper, the toner image primarily transferred from the image carrier 50 to the intermediate transfer member 64 is secondarily transferred from the intermediate transfer member 64 to the paper. In the case where the driving speed of the intermediate transfer body 64 is changed according to the fixing speed of the fixing device 90 until transfer, the toner image primarily transferred onto the intermediate transfer body 64 is transferred to the image carrier 50 and the intermediate transfer body. The drive speed of the intermediate transfer body 64 is changed when the position is in a position excluding the contact region R with the 64, and the toner image on the intermediate transfer body 64 is changed by changing the drive speed of the intermediate transfer body 64 at this timing. Can be prevented from being disturbed by changing the driving speed of the intermediate transfer member 64 while the toner passes through the contact region R (primary transfer position T1). Further, in order to avoid such disturbance of the toner image, it is not necessary to provide a mechanism for separating the intermediate transfer member 64 from the image carrier 50 when the driving speed of the intermediate transfer member 64 is changed. The body 64 can be installed by a simple holding mechanism (attachment mechanism) that maintains the contact state with the image carrier 50. Therefore, even when the driving speed of the intermediate transfer member is changed in image formation on an OHP sheet or a postcard paper, the driving speed of the intermediate transfer member 64 is changed without disturbing the toner image on the intermediate transfer member 64 with a simple configuration. In addition, a high quality image can be formed.

  Further, in the image forming apparatus 10 of the present embodiment, when an image is formed on a recording medium in which the heating time required for melting and fixing the toner image is shorter than that of plain paper, the image forming apparatus 10 corresponds to the fixing speed of the fixing device 90. It is also possible to increase the driving speed of the intermediate transfer member 64. Also in this case, the drive speed is changed at the speed change timing of the intermediate transfer body 64 described with reference to FIGS. 3 to 5 to increase the intermediate transfer body 64 from the normal speed, and after the secondary transfer and fixing processing operations, a predetermined value is obtained. When the time has elapsed, the drive speed of the intermediate transfer member 64 is returned to the original normal speed.

  Accordingly, it is possible to shorten the processing time for secondary transfer and fixing of the toner image from the intermediate transfer member 64 to the recording medium, and it is possible to increase the productivity while forming a high quality image.

  In the present embodiment, the driving speed of the intermediate transfer member 64 is changed in the non-image forming region B provided on the intermediate transfer member 64 larger than the contact region R between the image carrier 50 and the intermediate transfer member 64. By doing so, dot (pixel) unevenness and density unevenness of the toner image generated in the contact region R can be eliminated.

  As mentioned above, although this invention was demonstrated in detail by specific embodiment mentioned above, this invention is not limited to it, Various other embodiment is possible within the scope of the present invention.

1 is a configuration diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram illustrating a schematic configuration in a state where an image forming unit is removed from the image forming apparatus main body in the image forming apparatus of FIG. 1. FIG. 6 is an operation explanatory diagram illustrating a position where the drive speed of the intermediate transfer member is changed during an image forming operation in the image forming apparatus according to the embodiment of the present invention. 6 is a timing chart illustrating control timing for changing the driving speed of the intermediate transfer member during an image forming operation in the image forming apparatus according to the embodiment of the present disclosure. FIG. 3 is a development view illustrating a relationship between a contact area and a maximum image forming area and a non-image forming area provided on the intermediate transfer body by developing the intermediate transfer body according to an embodiment of the present invention in the rotation direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 50 Image carrier 64 Intermediate transfer body A Maximum image forming area B Non-image forming area R Contact area T1 Primary transfer position T2 Secondary transfer position

Claims (4)

An image carrier on which a toner image is formed and a toner image formed on the image carrier are primarily transferred so that the toner image is secondarily transferred to a recording medium. In an image forming apparatus having an intermediate transfer body that is transferred and whose driving speed can be changed,
Changing the driving speed of the intermediate transfer member is performed when the toner image primarily transferred onto the intermediate transfer member is at a position excluding the contact area between the image carrier and the intermediate transfer member. apparatus.   The image forming apparatus according to claim 1, wherein the change in the driving speed of the intermediate transfer member is a deceleration.   2. The image forming apparatus according to claim 1, wherein the drive speed of the intermediate transfer member is increased.   The non-image forming area excluding the maximum image forming area provided on the intermediate transfer body is made larger than the contact area in the driving direction of the intermediate transfer body, and the change in the driving speed of the intermediate transfer body is the non-image forming area The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus is configured as described above.

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