JP2016020960A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to prevent vibration generated in a transfer nip from being transmitted to primary transfer means, with a simple configuration.SOLUTION: An intermediate transfer unit 30 includes a main unit 71 having a plurality of support rollers and primary transfer means, and a secondary-transfer facing unit 72 having at least one support roller. A secondary transfer device 80 includes a transfer member 22 arranged opposite to an intermediate transfer body 10 stretched on the support roller. A transfer nip is formed by a facing transfer member 16(intermediate transfer body 10) and the transfer member 22. The secondary-transfer facing unit 72 holding the facing transfer member 16 is held with an allowance by joining means 73 with respect to a main unit 71, not in contact with the main unit 71. The secondary-transfer facing unit 72 is fixed by the opposite secondary transfer device 80. The secondary-transfer facing unit 72 and the secondary transfer device 80 are in contact with each other via a buffer member 91.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof.

  In an intermediate transfer type image forming apparatus, an intermediate transfer belt that is an image carrier of an endless belt that is rotated while being stretched by a plurality of stretching rollers, and a transfer member that is in contact with the front surface of the intermediate transfer belt A secondary transfer nip is formed with a certain secondary transfer roller. However, when the transfer sheet enters or exits the secondary transfer nip, sudden speed fluctuations of the intermediate transfer belt and vibrations of the intermediate transfer unit that holds this occur. Then, this vibration is transmitted to the primary transfer nip between the photoreceptor and the intermediate transfer belt, and the image transferred on the intermediate transfer belt expands and contracts, or transfer blur occurs. For this reason, light and shade occurs in an image portion that should have a constant image density, and an abnormal image called a shock jitter occurs.

  In order to suppress shock jitter, a minute gap is formed between the intermediate transfer belt and the secondary transfer roller before the transfer paper enters the transfer nip, and the intermediate transfer immediately after the leading edge of the transfer paper enters the minute gap. A technique for bringing a belt into contact with a secondary transfer roller is known (Patent Document 1). As a result, during the transfer process, a sufficient transfer pressure is exerted at the secondary transfer nip to suppress the occurrence of transfer failure.

  However, the technology of bringing the intermediate transfer belt and the secondary transfer roller into contact immediately after the transfer paper leading edge enters the transfer nip is highly effective in reducing the speed fluctuation of the intermediate transfer belt, but reduces the vibration of the intermediate transfer unit. The effect is low. Conversely, if the gap between the intermediate transfer belt and the secondary transfer roller before the transfer paper enters is too wide than the paper thickness, the intermediate transfer unit may vibrate due to the impact at the time of contact, and shock jitter may occur. Therefore, a complicated apparatus is required to cope with various paper thicknesses.

  Patent Document 2 discloses a technique for correcting a positional deviation between the transfer device and the image carrier when the transfer device is positioned and brought into contact with the image carrier. In Patent Document 3, the secondary transfer device is held non-fixed in the sub-housing, and when the sub-housing is housed in the main housing, the secondary transfer device is applied to the intermediate transfer belt by the urging force of the urging means. An image forming apparatus positioned in this manner is disclosed.

  Accordingly, the present invention provides an image forming apparatus in which vibration generated in the transfer nip is not transmitted to the primary transfer unit with a simple configuration.

  In order to solve this problem, an intermediate transfer unit having a main unit having a plurality of support rollers and primary transfer means, and a secondary transfer counter unit having at least one support roller, can be rotated and conveyed around the support roller. An intermediate transfer member, and a secondary transfer device that is disposed to face the intermediate transfer member and includes a transfer member. The counter transfer member, which is one of the support rollers, and the transfer member serve as the intermediate transfer member. In the image forming apparatus for transferring the toner image on the intermediate transfer body onto a transfer sheet in a transfer nip formed by facing through the body, the secondary transfer facing unit holding the facing transfer member is It is held against the main unit with play and in non-contact with the main unit, before the secondary transfer opposing unit is opposed to the main unit. Is fixed by the second transfer device, the secondary transfer counter unit and the secondary transfer device proposed an image forming apparatus characterized by contacting via the cushioning member.

  The vibration generated in the transfer nip is not transmitted to the primary transfer means, and the occurrence of shock jitter is suppressed. Further, the vibration of the secondary transfer counter unit is attenuated by the buffer member, and the speed fluctuation of the intermediate transfer member is also reduced. Therefore, the image transfer quality and transfer paper transport quality can be improved with a simple configuration.

1 is a schematic front view showing an embodiment of an image forming apparatus. FIG. 2 is a schematic front view showing an intermediate transfer unit. It is a schematic perspective view which shows a secondary transfer apparatus. FIG. 3 is a schematic plan cross-sectional view of the secondary transfer counter unit viewed in the direction of the arrow in FIG. 2 in a state where the secondary transfer counter unit is positioned with respect to the secondary transfer apparatus. FIG. 3 is a schematic side sectional view of an intermediate transfer unit and a secondary transfer device. It is a schematic side sectional view of an intermediate transfer unit and a secondary transfer device showing different embodiments.

FIG. 1 is a schematic front view illustrating an embodiment of an image forming apparatus.
In the figure, reference numeral 100 denotes a tandem intermediate transfer type electrophotographic apparatus main body as an image forming apparatus, and 200 denotes a paper feed table on which the main body is placed. Subscripts Y, M, C, and K indicate yellow, magenta, cyan, and black (black) colors, respectively. Other reference numerals are directly referred to in the following description. In the image forming apparatus 100, an endless belt-like intermediate transfer belt 10 as an intermediate transfer member is provided near the center. The intermediate transfer belt 10 can be wound around a plurality of support rollers and rotated in the clockwise direction in the drawing. In the illustrated example, a cleaning device 17 for the intermediate transfer belt is provided on the left side of the secondary transfer counter roller 16 which is one of the support rollers and is a counter transfer member. The cleaning device 17 removes residual toner remaining on the intermediate transfer belt 10 after image transfer.

  The intermediate transfer belt 10 is stretched between the support roller 14 and the support rollers 15 and 15 '. On the intermediate transfer belt 10, four image forming units 18Y, 18M, 18C, and 18K (hereinafter, “18Y, M, C, and K”) of yellow, magenta, cyan, and black are abbreviated along the conveyance direction. Are arranged side by side to form a tandem image forming apparatus 20. Above the cleaning device 17, a tension roller 63 for adjusting the tension of the belt is provided. An exposure device 21 is further provided on the tandem image forming apparatus 20 as shown in FIG. Each image forming unit 18 of the tandem image forming apparatus 20 includes photosensitive drums 40Y, 40M, 40C, and 40K as image carriers that carry toner images of yellow, magenta, cyan, and black. Further, at the primary transfer position where the toner image is transferred from the photosensitive drums 40Y, 40M, 40C, and 40K to the intermediate transfer belt 10, the primary transfer unit faces the respective photosensitive drums with the intermediate transfer belt 10 interposed therebetween. Primary transfer rollers 62Y, M, C, and K are provided as constituent elements. The support roller 14 is a drive roller that rotationally drives the intermediate transfer belt 10. Therefore, when a black single color image is formed on the intermediate transfer belt 10, the support rollers 15 and 15 'other than the driving roller are moved by means not shown, and the yellow, magenta, and cyan photoconductors 40Y, 40M, and 40C are obtained. Can be separated from the intermediate transfer belt 10.

  A secondary transfer device (secondary transfer unit) is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming apparatus 20. The secondary transfer device 80 includes the secondary transfer roller 22 as a transfer member in the illustrated example, and details thereof will be described later. The secondary transfer device 80 transfers the image on the intermediate transfer belt 10 to a sheet S as transfer paper by pressing the secondary transfer roller 22 against the secondary transfer counter roller 16 and applying a transfer electric field. Next to the secondary transfer device 80, a fixing device 25 for fixing the transferred image on the sheet is provided. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt. A fixing nip is formed between the fixing belt 26 and the pressure roller 27, and the sheet after image transfer is conveyed to the fixing nip of the fixing device 25 by the conveyance belt unit 24, and the toner image on the sheet is generated by heat and pressure. To fix. In the illustrated example, below the secondary transfer device 80 and the fixing device 25, in parallel with the tandem image forming device 20 described above, a sheet reversing device 28 for reversing the sheet to record images on both sides of the sheet. It has.

  When the image forming apparatus 100 receives the image data and the image formation start signal, the image forming apparatus 100 rotates the support roller 14 by a drive motor (not shown) to rotate the other support rollers 15 and 15 ′ and the like to perform intermediate transfer. The belt 10 is rotated and conveyed. At the same time, the individual image forming units 18 form monochrome images of yellow, magenta, cyan, and black on the respective photoreceptors 40. Then, along with the conveyance of the intermediate transfer belt 10, these single color images are sequentially transferred by the primary transfer rollers 62 Y, M, C, and K to form a composite color image on the intermediate transfer body 10.

  Further, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet is fed out from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The fed sheets are separated one by one by the separation roller 45 and put into the paper feed path 46, conveyed by the conveyance roller 47, led to the paper feed path 48 in the image forming apparatus 100, and abutted against the registration roller 49. stop. Alternatively, the sheet feed roller 50 is rotated to feed out the sheets on the manual feed tray 51, separated one by one by the separation roller, put into the manual feed path 53, and abutted against the registration roller 49 and stopped. Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer belt 10, the sheet is fed between the intermediate transfer belt 10 and the secondary transfer roller 22, and is transferred by the secondary transfer roller 22. A color image is recorded on the sheet.

  The sheet after the image transfer is conveyed by the secondary transfer roller 22 and the conveyor belt unit 24 and sent to the fixing device 25. After fixing the transferred image by applying heat and pressure, the sheet is discharged by the discharge roller 56, Stack on the discharge tray 57. Alternatively, the conveyance path is switched by a switching claw (not shown), the sheet is put into the sheet reversing device 28, reversed there, and led again to the transfer position where the secondary transfer roller 22 is located. The paper is discharged onto a paper discharge tray 57 by a discharge roller 56. On the other hand, the residual toner remaining on the intermediate transfer belt 10 is removed from the intermediate transfer belt 10 after the image transfer by the intermediate transfer belt cleaning device 17 to prepare for the image formation by the tandem image forming apparatus 20 again.

FIG. 2 is a schematic front view showing the intermediate transfer unit.
The frame of the intermediate transfer unit 30 (hereinafter also referred to as “intermediate transfer frame”) is composed of two units, a main unit 71 and a secondary transfer counter unit 72. A primary transfer unit (not shown) including primary transfer rollers 62Y, 62M, 62C, and 62K and components (not shown) for holding them is fixed and held on the intermediate transfer frame. The main unit 71 includes support rollers 14, 15, 15 ′, and primary transfer rollers 62Y, 62M, 62C, 62K, etc. in a primary transfer unit (not shown). Under the main unit 71, a secondary transfer counter unit 72 is connected to a frame (solid line portion) of the main unit 71 by a stepped screw 73 as a connecting means. The intermediate transfer belt 10 is indicated by a dotted line. As will be described later, the secondary transfer opposing unit 72 is held with play in the front, rear, up, down, left and right with respect to the main unit 71 via a stepped screw 73 and is positioned on the secondary transfer device 80 to perform secondary transfer. The position of the facing unit 72 is fixed.

  The secondary transfer counter unit 72 holds a secondary transfer counter roller 16, a pre-transfer roller 74, and a transfer paper guide plate 75 as a transfer paper guide member therein, and positions the secondary transfer device 80 on the front side plate 92. Positioning pins 76 and 77.

  Further, the back surface of the secondary transfer counter unit 72 has the same configuration as the front surface, and the secondary transfer counter unit 72 has positioning pins 78 and 79 for positioning the secondary transfer device 80 on the rear plate 93. (FIGS. 4 and 5).

Further, a buffer member 91 is attached to the front plate 92 of the secondary transfer opposing unit 72 except for the positioning pins 76 and 77, and when the secondary transfer device 80 is mounted on the image forming apparatus 100, the buffer member. 91 contacts the front frame 81 of the secondary transfer device 80 (FIGS. 4 and 5).
As shown in FIG. 2, the secondary transfer counter unit 72 is disposed inside the intermediate transfer belt 10 that is stretched over a support roller provided in the main unit 71, and the secondary transfer counter roller 16 is in the middle. It is in contact with the transfer belt 10.

FIG. 3 is a schematic perspective view showing the secondary transfer apparatus. 3A is a view of the front side (front side of the image forming apparatus) of the secondary transfer device as viewed from the inside. FIG. 3B is a back side of the secondary transfer device (back side of the image forming apparatus) from the outside. FIG.
The secondary transfer device 80 includes a front frame 81, a rear frame 82, the secondary transfer roller 22 disposed between these frames, and the like. The front frame 81 is provided with holes 83 and 84 that are tapered outward, and the rear frame 82 is provided with holes 85 and 86 that are tapered inward.

  The secondary transfer device 80 is fixed on a drawer unit 90 that slides so as to be drawable from the main body of the image forming apparatus (FIG. 1). As shown in FIG. 4, when the drawer unit 90 holding the secondary transfer device 80 is stored in the main body, the positioning pins 76 and 77 of the front plate 92 of the secondary transfer opposing unit 72 are respectively connected to the secondary transfer device. It fits into the positioning holes 83 and 84 of the 80 front frame 81. Further, the positioning pins 78 and 79 of the rear plate 93 of the secondary transfer counter unit 72 are fitted into the positioning holes 85 and 86 of the rear frame 82 of the secondary transfer device 80. As a result, the secondary transfer opposing unit 72 that is held with play in the front, rear, up, down, left, and right with respect to the main unit 71 via the stepped screw 73 is positioned with respect to the secondary transfer device 80.

  FIG. 4 is a schematic plan cross-sectional view of the secondary transfer opposing unit 72 as viewed in the direction of the arrow in FIG. 2 in a state where the secondary transfer opposing unit 72 is positioned with respect to the secondary transfer device 80. Since the secondary transfer counter roller 16 is opposed to the secondary transfer roller 22 via the intermediate transfer belt 10, the secondary transfer roller 22 is not visible in this drawing. A pre-transfer roller 74 is disposed upstream of the secondary transfer counter roller 16 in the conveyance direction of the sheet S. The positioning pins 76 and 78 are formed substantially parallel to the axial direction of the secondary transfer opposing unit 72. Similarly, the positioning pins 77 and 79 are formed substantially parallel to the axial direction of the secondary transfer opposing unit 72. The positioning pins 76, 77, 78, 79 and the positioning holes 83, 84, 85, 86 are fitted, so that the secondary transfer opposing unit 72 is attached to the secondary transfer device 80 mounted on the image forming apparatus 100. Positioned against. However, as can be seen from FIGS. 3 and 5, the positioning holes 83 and 84 are formed at positions higher than the positioning holes 85 and 86, and the positioning pins 76 and 77 correspond to the positioning pins 78 and 79 correspondingly. Is also formed at a lower position. Accordingly, the secondary transfer roller 22 is positioned horizontally, and the secondary transfer counter roller 16 is also positioned horizontally so as to face the secondary transfer roller 22.

  Further, a buffer member 91 attached to the front surface of the front plate 92 of the secondary transfer counter unit 72 buffers the vibration between the secondary transfer counter unit 72 and the secondary transfer device 80. As the buffer member 91, rubber or a spring can be used. 3 and 4, the holes 83, 84, 85, 86 do not penetrate the front frame 81 and the rear frame 82, and the positioning pins 76, 77, 78, 79 are formed in the holes 83, 84, 85, 86. It is mated.

FIG. 5 is a schematic side cross-sectional view of the intermediate transfer unit 30 and the secondary transfer device 80.
As shown in the figure, the secondary transfer opposing unit 72 is not in contact with the main unit 71, and is attached to the main unit 71 with play by a stepped screw 73. The secondary transfer counter unit 72 is fixed by positioning pins 76, 77, 78, and 79 to the secondary transfer device 80 that is mounted and fixed to the frame of the image forming apparatus 100. A buffer member 91 is provided on the front surface of the front plate 92 of the secondary transfer counter unit 72, and the vibration of the secondary transfer counter unit 72 is attenuated and reduced by the buffer member 91. In FIG. 5, the holes 83, 84, 85, 86 pass through the front frame 81 and the rear frame 82, and the positioning pins 76, 77, 78, 79 pass through the holes 83, 84, 85, 86. Yes.

  Conventionally, since the primary transfer unit and the secondary transfer counter unit are held on the same intermediate transfer frame, vibration from the secondary transfer device side is transmitted to the primary transfer unit. In the case of a configuration in which the secondary transfer counter unit is held by the secondary transfer device, vibration from the secondary transfer device is not directly transmitted to the primary transfer unit, but the secondary transfer counter unit vibrates, so that the intermediate transfer belt Speed fluctuation became large, causing shock jitter.

  However, in this embodiment, since the secondary transfer opposing unit 72 is not in contact with the main unit 71 and is held by the secondary transfer device 80 fixed to the apparatus main body, the primary transfer is performed via the main unit 71. Vibration is not transmitted to the means. Further, since the secondary transfer counter unit 72 is held by the secondary transfer device 80 fixed to the apparatus main body via the buffer member 91, the vibration of the secondary transfer counter unit 72 is attenuated by the buffer member 91 and is intermediate. The speed fluctuation of the transfer belt 10 is also reduced. Therefore, the image transfer quality and transfer paper transport quality can be improved with a simple configuration.

  As shown in FIG. 2, the secondary transfer counter unit 72 holds a pre-transfer roller 74 upstream of the secondary transfer counter roller 16 in the conveyance direction of the sheet S. As described above, since the secondary transfer counter roller 16 and the pre-transfer roller 74 are integrally held, there is no left-right deviation of the transfer prenip, and a stable transfer prenip is obtained, so that high transfer quality is obtained.

  Further, the secondary transfer opposing unit 72 holds a transfer paper guide plate 75 upstream of the transfer nip in the transport direction of the sheet S. As described above, since the secondary transfer counter roller 16 and the transfer paper guide plate 75 are integrally held, the sheet S is accurately guided to the transfer nip, and abnormalities such as deviations in registration position and blurred images are suppressed. . It is possible to suppress the occurrence of an abnormal image due to an abnormal conveyance of the sheet S or an accuracy failure of the image forming position, and a high transfer quality can be obtained.

  Further, a sensor (not shown) that is a detecting means for detecting the toner image on the intermediate transfer belt 10 is positioned on the secondary transfer device 80 or the drawer unit 90 that supports the secondary transfer device. This sensor is, for example, an optical sensor. By installing the sensor in the secondary transfer device 80 or the drawer unit 90 in this way, it is possible to ensure high positional accuracy with respect to the secondary transfer unit, and the sensor detects and corrects the toner image position. Thus, the image position with respect to the sheet S can be corrected with high accuracy.

FIG. 6 is a schematic side cross-sectional view of the intermediate transfer unit 30 and the secondary transfer device 80 showing another embodiment.
In the following description, parts different from the above-described embodiment will be mainly described. As shown in the figure, the secondary transfer opposing unit 72 is not in direct contact with the main unit 71, and is attached to the main unit 71 with play by a stepped screw 73. The secondary transfer counter unit 72 is fixed by positioning pins 76, 77, 78, and 79 to the secondary transfer device 80 that is mounted and fixed to the frame of the image forming apparatus 100.

  Conventionally, the primary transfer unit and the secondary transfer counter unit are held on the same intermediate transfer frame. However, in this embodiment, the primary transfer unit (not shown) is held by the main unit 71, but the secondary transfer counter unit 72 is held by the secondary transfer device 80 and is in direct contact with the main unit 71. Therefore, vibration is not transmitted through the intermediate transfer frame. Further, since the secondary transfer counter roller 16 is positioned by the secondary transfer device 80, the pressure deviation between the secondary transfer roller 22 and the secondary transfer counter roller 16 can be reduced. Furthermore, since the secondary transfer device 80 is attached to the same drawer unit 90 as the conveying device such as the registration roller 49, the positional relationship (parallelism, etc.) between the secondary transfer roller 22 and other components can be obtained with high accuracy. it can. Therefore, the image transfer quality and transfer paper transport quality can be improved with a simple configuration.

  In this embodiment, the buffer member 91 is installed on the back surface of the front plate 92 of the secondary transfer counter unit 72, and the main unit 71 and the secondary transfer counter unit 72 are in contact with each other through the buffer member 91. The buffer member 91 is provided between the portions without the stepped screws 73, for example, the stepped screws 73, 73. It is desirable that the frame of the main unit 71 and the secondary transfer opposing unit 72 are completely in non-contact. However, if only a small gap can be secured between these units due to restrictions on the size of the device, the units come into contact with each other due to the vibration of the device, and abnormal images such as shock jitter and banding occur. Therefore, in this embodiment, the main unit 71 and the secondary transfer opposing unit 72 are brought into contact with each other via the buffer member 91. Accordingly, the vibration of the secondary transfer counter unit 72 is buffered by the buffer member 91 and is not easily transmitted to the main unit 71. Further, since the secondary transfer opposing unit 72 is positioned and held by the secondary transfer device 80, the transport quality and the image quality are not deteriorated. Therefore, the image transfer quality and transfer paper transport quality can be improved with a simple configuration.

  However, the buffer member 91 may also be installed on the front surface of the front plate 92 of the secondary transfer counter unit 72, thereby further attenuating and reducing the vibration of the secondary transfer counter unit 72.

10 Intermediate transfer belt (intermediate transfer member)
14, 15, 15 ', 16, 74 Support roller 16 Secondary transfer counter roller (counter transfer member)
22 Secondary transfer roller (transfer member)
30 Intermediate transfer unit 62Y, M, C, K Primary transfer roller (primary transfer means)
72 Secondary transfer counter unit 73 Stepped screw (connecting means)
80 Secondary transfer device 91 Buffer member 100 Image forming apparatus

JP 2011-133653 A JP 2002-296927 A JP 2004-144878 A

Claims (6)

An intermediate transfer unit having a main unit having a plurality of support rollers and primary transfer means, and a secondary transfer counter unit having at least one support roller;
An intermediate transfer member that is wound around the support roller and can be rotated and conveyed, and a secondary transfer device that is disposed to face the intermediate transfer member and includes a transfer member,
An image forming apparatus for transferring a toner image on the intermediate transfer body onto a transfer sheet in a transfer nip formed by an opposing transfer member that is one of the support rollers and the transfer member facing each other via the intermediate transfer body In
The secondary transfer counter unit that holds the counter transfer member is held with respect to the main unit with play by a connecting means and in non-contact with the main unit,
An image forming apparatus, wherein the secondary transfer opposing unit is fixed by the opposing secondary transfer device, and the secondary transfer opposing unit and the secondary transfer device are in contact via a buffer member. An intermediate transfer unit having a main unit having a plurality of support rollers and primary transfer means, and a secondary transfer counter unit having at least one support roller;
An intermediate transfer member that is wound around the support roller and can be rotated and conveyed, and a secondary transfer device that is disposed to face the intermediate transfer member and includes a transfer member,
An image forming apparatus for transferring a toner image on the intermediate transfer body onto a transfer sheet in a transfer nip formed by an opposing transfer member that is one of the support rollers and the transfer member facing each other via the intermediate transfer body In
The image forming apparatus, wherein the secondary transfer counter unit holding the counter transfer member is fixed by the opposing secondary transfer device and is not in direct contact with the main unit.   3. The image forming apparatus according to claim 1, wherein the secondary transfer facing unit holds a pre-transfer roller on the upstream side in the conveyance direction of the transfer paper with respect to the facing transfer member.   4. The image forming apparatus according to claim 1, wherein the secondary transfer counter unit includes a transfer paper guide member on an upstream side of the counter transfer member in a transport direction of the transfer paper. 5. .   The detection unit for detecting a toner image on the intermediate transfer member is positioned in the secondary transfer device or a drawer unit that supports the secondary transfer device. The image forming apparatus according to one item. The image forming apparatus according to claim 2, wherein the main unit and the secondary transfer counter unit are in contact with each other via a buffer member.

Images