JP2013044943A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To abbreviate output time for a first transfer material and reduce an impact sound at a time of contact operation of a first transfer roller.SOLUTION: An image forming apparatus comprises: a first separation mode in which a photoreceptor drum 1, an intermediate transfer belt 11 and a primary transfer roller 12 are separated from each other, and a second separation mode in which a separation distance between the photoreceptor drum 1 and the primary transfer roller 12 is smaller than that in the first separation mode. When the intermediate transfer belt 11 is driven in a state where the photoreceptor drum 1, the intermediate transfer belt 11 and the primary transfer roller 12 are separated from each other, the first separation mode is set, and the second separation mode is set for a standby time before transition to an image forming operation.

Description

  The present invention relates to an image forming apparatus using an electrophotographic system or an electrostatic recording system.

  Conventionally, as an image forming apparatus that outputs a color image, a tandem type in which a plurality of photosensitive drums 1a to 1d are arranged along an intermediate transfer belt 11 is known as shown in FIG. In the following drawings, the photosensitive drums 1 for yellow, magenta, cyan, and black are given reference numerals such as 1a, 1b, 1c, and 1d. There is also. The same applies to other members.

  In this type of image forming apparatus, toner images of different colors are formed on the respective photosensitive drums 1, and these toner images are sequentially superimposed on the intermediate transfer belt 11 and primarily transferred to obtain a color toner image.

  Thereafter, a color toner image is secondarily transferred to a transfer material 9 passing between the intermediate transfer belt 11 and a secondary transfer roller 25 that is in pressure contact with the intermediate transfer belt 11, thereby outputting a color image to the transfer material 9. To do.

  Such a color image forming apparatus generally has a full separation mode in which all the photosensitive drums 1 are separated from the intermediate transfer belt 11 as shown in FIG. Further, as shown in FIG. 5, a full color mode for forming an image using toners of four colors (yellow, magenta, cyan, and black) is provided. Further, as shown in FIG. 6, there are three modes of a mono mode in which an image is formed using one color toner (typically black).

  The all separation mode shown in FIG. 3 is mainly set when the power is turned off or during standby, immediately after the end of the image forming operation, or immediately after the end of the calibration operation. Immediately after the end of the image forming operation or the end of the calibration operation, the intermediate transfer belt 11 is driven in a state where all the photosensitive drums 1 are separated from the intermediate transfer belt 11 when residual toner on the intermediate transfer belt 11 is cleaned.

  When the intermediate transfer belt 11 is driven, if the primary transfer roller 12 as a primary transfer means is in contact with the intermediate transfer belt 11 even slightly, the primary transfer roller 12 rotates without obtaining an appropriate rotational force. Cause a defect. As a result, foreign matter or the like is generated due to wear of the roller portion, and therefore the station where the photosensitive drum 1 and the intermediate transfer belt 11 are separated is also separated from the intermediate transfer belt 11 and the primary transfer roller 12.

  This prevents unnecessary wear on the image forming components (for example, the photosensitive drum 1, the developing device 4, the cleaning device 8, the primary transfer roller 12, etc.) of the station not involved in image formation.

  In the full color mode shown in FIG. 5, all the photosensitive drums 1 are brought into contact with the intermediate transfer belt 11 to perform primary transfer. In the mono mode shown in FIG. 6, one photosensitive drum 1 (typically, the black station photosensitive drum 1d) is brought into contact with the intermediate transfer belt 11, and the other photosensitive drums 1a, 1b, 1c are set in the middle. Separated from the transfer belt 11.

  As described above, the contact and separation of the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 in the full separation mode shown in FIG. 3, the full color mode shown in FIG. 5, and the mono mode shown in FIG. Change over. As such a technique, there is a method of moving the primary transfer roller 12 that presses against the intermediate transfer belt 11 in a direction to contact or separate from the photosensitive drum 1 as disclosed in Patent Document 1.

  The color image forming apparatus shown in FIG. 1 transfers a toner image that has been primarily transferred from a plurality of photosensitive drums 1 serving as image carriers on the intermediate transfer belt 11 at a secondary transfer portion where a secondary transfer roller 25 faces. Secondary transfer is performed collectively on the material 9.

  3, 5, and 6 are schematic cross-sectional views illustrating the contact / separation operation of the photosensitive drum 1 and the intermediate transfer belt 11. FIG. 3 shows a state in which all the photosensitive drums 1, the intermediate transfer belt 11, and the primary transfer roller 12 are separated in the all separation mode. FIG. 5 shows a state in which the intermediate transfer belt 11 is in contact with all the photosensitive drums 1 in the full color mode. FIG. 6 shows a state in which the intermediate transfer belt 11 is separated from the photosensitive drum 1 other than black in the black monochromatic mode.

  In FIG. 5, the intermediate transfer belt 11 is stretched by a drive roller 13 and a tension roller 14 that are rotatably supported on a housing (not shown) of the intermediate transfer unit 5. The primary transfer roller 12 is rotatably supported at its longitudinal end by a bearing portion 123 of a bearing link member 121. The bearing link member 121 is supported so as to be swingable about a rotation shaft 120 with respect to a housing (not shown) of the intermediate transfer unit 5. Then, the primary transfer roller 12 is pressed by the transfer spring 122 with the intermediate transfer belt 11 sandwiched between the photosensitive drums 1 facing each other.

  The cam sliders 111a and 111b are provided so as to be movable with respect to a casing (not shown) of the intermediate transfer unit 5 in a direction perpendicular to the pressing direction of the transfer spring 122 (left and right direction in FIG. 3). Each of the cam sliders 111a and 111b has a cam slope 112 at a predetermined position. When the cam sliders 111a and 111b move in a predetermined direction, the engaging portion 119 of the bearing link member 121 abuts and slides on the cam inclined surface 112, and the bearing link member 121 is swung around the rotation shaft 120.

  The separation cams 113a and 113b shown in FIG. 9 are integrally formed and supported so as to be rotatable about a cam shaft 114 with respect to a housing (not shown) of the intermediate transfer unit 5. As shown in FIGS. 10 (b), 12 (b), and 13 (b), the separation cams 113a and 113b are arranged at the center of the portion where the sliding ends of the cam sliders 111a and 111b overlap. .

  The cam surfaces 113a1 and 113b1 of the separation cams 113a and 113b push the cam receiving surfaces 111a1, 111a2, 111b1, and 111b2 formed by the left and right wall surfaces at the sliding direction ends of the cam sliders 111a and 111b. As a result, the cam sliders 111a and 111b move in the left-right direction in FIG.

  10, 12, and 13 show the contact state between the separation cams 113 a and 113 b and the cam receiving surfaces 111 a 1, 111 a 2, 111 b 1, and 111 b 2 of the cam sliders 111 a and 111 b in all separation mode, full color mode, and mono mode. Show. Note that a position P shown in FIGS. 10, 12, and 13 indicates a contact position between the separation cams 113a and 113b and the cam receiving surfaces 111a1, 111a2, 111b1, and 111b2 of the cam sliders 111a and 111b in each mode. 10A, 10B, 12A, and 13A are views looking down from the upper side of each (b) in order to match the moving directions of the cam sliders 111a and 111b in each of (b) and (c) (rear view). ).

  The separation cams 113a and 113b are integrally driven by a motor 10 that is rotationally driven by a control unit 16 serving as control means. Then, the controller 16 selectively drives the position of the fully separated mode shown in FIGS. 3 and 10, the position of the full color mode shown in FIGS. 5 and 12, and the position of the mono mode shown in FIGS. Be controlled.

  The control unit 16 sends a command to switch from the state of the full separation mode shown in FIGS. 3 and 10 (at the time of standby in FIG. 8) to the full color mode shown in FIGS. Then, the separation cams 113a and 113b rotate 120 degrees clockwise about the cam shaft 114 in FIG. Then, as shown in FIG. 12 (a), the left cam receiving surface 111a1 of the cam slider 111a is pushed by the cam surface 113b1 of the separating cam 113b. Further, as shown in FIG. 12C, the left cam receiving surface 111b1 of the cam slider 111b is pushed by the cam surface 113a1 of the separation cam 113a. This pushes the cam sliders 111a and 111b in the left direction in FIG.

  At this time, the engaging portion 119 of the bearing link member 121 slides on the cam slope 112 of the cam sliders 111a and 111b in the upward direction of FIG. Rocks. At this time, the primary transfer roller 12 is pressed against the photosensitive drum 1 via the intermediate transfer belt 11 by the urging force of the transfer spring 122 and is brought into a contact state.

  Next, when the control unit 16 sends a command to switch from the full color mode shown in FIG. 5 to the mono mode shown in FIG. 6, the separation cams 113a and 113b further rotate 120 degrees in the clockwise direction of FIG. Then, as shown in FIG. 13A, the right cam receiving surface 111a2 of the cam slider 111a is pushed by the cam surface 113b1 of the separating cam 113b, and the cam slider 111a is pushed rightward in FIG. The engagement portion 119 slides downward in FIG. 6 along the cam slope 112 of the cam slider 111a pushed by the separation cam 113b, and the bearing link member 121 is rotated counterclockwise in FIG. Swing. The primary transfer rollers 12a, 12b, and 12c other than black are separated from the intermediate transfer belt 11.

  The intermediate transfer belt 11 pressed against the primary transfer rollers 12a, 12b, and 12c is also separated from the photosensitive drums 1a, 1b, and 1c other than black. At this time, a force for pressing and contracting the transfer spring 122 is always urged between the bearing link members 121a, 121b, and 121c and the cam slider 111a.

  Further, at the time of switching from the mono mode shown in FIG. 6 to the full separation mode shown in FIG. 3, the separation cams 113a and 113b further rotate 120 degrees in the clockwise direction of FIG. Then, as shown in FIG. 10C, the cam receiving surface 111b2 on the right side of the cam slider 111b is pushed by the cam surface 113a1 of the separating cam 113a, and the cam slider 111b moves in the right direction in FIG. The engaging portion 119d slides downward in FIG. 3 along the cam slope 112d of the cam slider 111b pushed by the separation cam 113a, and the bearing link member 121d swings around the rotation shaft 120d in the counterclockwise direction in FIG. Move. Then, the black primary transfer roller 12 d is separated from the intermediate transfer belt 11.

  The intermediate transfer belt 11 pressed against the primary transfer roller 12d is also separated from the black photosensitive drum 1d. At this time, also in the black station, a force for pressing and contracting the transfer spring 122d is always urged between the bearing link member 121d and the cam slider 111b.

JP 2008-129448 A

  However, the above-described conventional image forming apparatus has the following two problems.

  The first problem is that the first printout time which is the output time of the first sheet of the transfer material 9 takes a long time.

  In order to separate all the photosensitive drums 1, the intermediate transfer belt 11, and all the primary transfer rollers 12, in consideration of misalignment due to part shape variation and vibration during driving, the photosensitive drum 1 and the primary transfer roller 11 are separated. It was necessary to increase the distance from the transfer roller 12.

  In the standby state before shifting to the image forming operation, the all-separation mode shown in FIG. 3 is used. To perform image forming output, the full color mode shown in FIG. 5 or the mono mode shown in FIG. 6 must be changed. . Therefore, the time from the full separation mode shown in FIG. 3 to the full color mode shown in FIG. 5 or the mono mode shown in FIG. 6 is increased by the amount of separation between the photosensitive drum 1 and the primary transfer roller 12. It was hanging. For this reason, there is a problem that the first printout time becomes long.

  As a second problem, there was a problem of operation sound.

  In the contact operation for shifting from the full separation mode shown in FIG. 3 to the full color mode shown in FIG. 5, the transfer springs 122 compressed by the cam sliders 111a and 111b and the bearing link member 121 are simultaneously released. .

  For this reason, the primary transfer roller 12 vigorously abuts against the intermediate transfer belt 11 and the photosensitive drum 1, and a large impact sound is generated. If the transition time from the full separation mode shown in FIG. 3 to the full color mode shown in FIG. 5 or the mono mode shown in FIG. 6 is made longer, the impact sound is alleviated, but the first printout time described above becomes longer. There is.

  An object of the present invention is to provide an image forming apparatus capable of shortening the output time of the first sheet of transfer material and reducing the impact sound during the contact operation of the primary transfer roller. .

  In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes a plurality of image carriers that carry toner images, an endless belt that faces the plurality of image carriers, and the endless belt. A plurality of transfer means for transferring the toner image on the image carrier to the endless belt or transfer material, and pressing the transfer means toward the opposite image carrier, with the image carrier being sandwiched therebetween A pressing means; and a contact / separation means for selectively moving at least one or more of the transfer means to a transfer position where transfer is possible and a separation position where transfer is not possible; and the image carrier, the endless belt, A first separation mode in which the transfer means are separated from each other; and a second separation mode in which a separation amount between the image carrier and the transfer means is smaller than the first separation mode. An image carrier, the endless belt and The first separation mode is set when the endless belt is driven in a state where the transfer unit is separated from each other, and the second separation mode is set during standby before the image forming operation is started. It is characterized by doing.

  According to the present invention, at the time of standby before shifting to the image forming operation, the separation amount between the image carrier and the transfer unit is the first separation in which the image carrier, the endless belt, and the transfer unit are separated from each other. The second separation mode is set smaller than the separation amount between the image carrier and the transfer means in the mode. As a result, it is possible to shorten the time for shifting to the image forming operation from the standby time before shifting to the image forming operation, and to shorten the output time of the first sheet of the transfer material. Further, it is possible to reduce an impact sound when the transfer unit comes into contact with the image carrier or the endless belt.

1 is an explanatory cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention. It is a figure explaining the operation | movement process of the image forming apparatus which concerns on this invention. FIG. 6 is a schematic explanatory diagram illustrating a contact / separation state of a transfer unit in a full separation mode. It is a schematic explanatory drawing which shows the contacting / separating state of the transfer means at the time of the 2nd separation mode in 1st Embodiment. FIG. 6 is a schematic explanatory diagram illustrating a contact / separation state of a transfer unit in a full color mode. It is a schematic explanatory drawing which shows the contact-and-separation state of the transfer means at the time of mono mode. It is a schematic explanatory drawing which shows the contacting / separating state of the transfer means at the time of the 2nd separation mode in 2nd Embodiment. It is a figure explaining the operation | movement process of the conventional image forming apparatus. It is a schematic perspective view of a separation cam. It is an enlarged view which shows the contact state of the separation cam and cam slider at the time of all separation modes, (a) is a rear view, (b) is a top view, (c) is a front view. It is an enlarged view which shows the contact state of the separation cam and cam slider at the time of the 2nd separation mode in 1st Embodiment, (a) is a rear view, (b) is a top view, (c) is a front view. . It is an enlarged view which shows the contact state of the separation cam and cam slider at the time of a full color mode, (a) is a rear view, (b) is a top view, (c) is a front view. It is an enlarged view which shows the contact state of the separation cam and cam slider at the time of mono mode, (a) is a rear view, (b) is a top view, (c) is a front view.

  A case where the present invention is applied to an electrophotographic full-color laser beam printer as an example of an image forming apparatus according to the present invention will be described below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments can be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. The scope of the present invention is not limited only to the following embodiments.

[Entire configuration of image forming apparatus]
Referring to FIG. 1, the overall configuration of an image forming apparatus 100 composed of a full color laser beam printer is shown. The configuration of the image forming apparatus 100 is a tandem type intermediate transfer belt type electrophotographic color (multicolor image) printer in which a plurality of image bearing members that carry toner images are arranged in a substantially horizontal direction. is there. The image forming unit is roughly divided into an image forming unit, a feeding unit, a fixing unit, and a discharging unit. The image forming unit is located at the center of FIG. In addition, a feeding unit is located from the lower right hand to the middle of the right hand in FIG. 1, and a fixing unit and a discharging unit are located above the right hand.

<Image forming unit>
First, the image forming unit will be described. The image forming apparatus 100 includes drum-shaped electrophotographic photosensitive members (hereinafter referred to as “photosensitive drums”) 1 as four image carriers arranged in parallel in the horizontal direction. In the following drawings, the photosensitive drums 1 for yellow, magenta, cyan, and black are given reference numerals such as 1a, 1b, 1c, and 1d. There is also. The same applies to other members.

  These four photosensitive drums 1 are rotationally driven in the clockwise direction in FIG. 1 by driving means (not shown). Around the photosensitive drum 1, a charging roller 2 as a charging unit that uniformly charges the surface of the photosensitive drum 1 in order according to the rotation direction, and an exposure unit that irradiates a light image based on image information. A scanner unit 3 is arranged. The scanner unit 3 irradiates a laser beam based on image information to form an electrostatic latent image on the photosensitive drum 1 (on the image carrier).

  Around the photosensitive drum 1, there is provided a developing device 4 that attaches toner to the electrostatic latent image on the photosensitive drum 1 and develops it as a toner image. Further, an intermediate transfer unit 5 is provided for primarily transferring a toner image on the photosensitive drum 1 to an intermediate transfer belt 11 serving as an endless belt facing the plurality of photosensitive drums 1.

  In addition, the toner image on the intermediate transfer belt 11 (on the endless belt) is transferred from the primary transfer portion where the intermediate transfer unit 5 and the photosensitive drum 1 are in contact to the downstream side in the conveyance direction of the intermediate transfer belt 11 (right side in FIG. 1). A secondary transfer unit 24 for secondary transfer to the material 9 is arranged.

  Around the photosensitive drum 1, a cleaning blade 6 that removes transfer residual toner remaining on the surface of the photosensitive drum 1 after transfer is disposed.

  In this embodiment, the photosensitive drum 1, the charging roller 2, the developing device 4, and the cleaning blade 6 are integrated into a cartridge to form a process cartridge 7, which is attached to and detached from the main body of the image forming apparatus 100. It is configured freely.

  The intermediate transfer belt 11 is an endless belt having a circumferential length of about 700 mm and a thickness of about 150 μm. The intermediate transfer belt 11 is stretched around two rollers, a driving roller 13 and a tension roller 14. Then, the toner images formed on the photosensitive drums 1 of the respective colors are circulated and moved in the direction of arrow A in FIG. 1 so as to be transferred onto the transfer material 9 via the intermediate transfer belt 11.

  Inside the intermediate transfer belt 11, a plurality of transfer units are arranged to face the four photosensitive drums 1 across the intermediate transfer belt 11 and transfer the toner images on the photosensitive drum 1 to the intermediate transfer belt 11. The primary transfer roller 12 is arranged in parallel. A positive charge is applied from the primary transfer roller 12 to the intermediate transfer belt 11, and a negative toner image on the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 11 by an electric field generated by the charge.

  A secondary transfer roller 25 is disposed at a position facing the drive roller 13 of the intermediate transfer unit 5. As with the primary transfer roller 12, positive charges are applied from the secondary transfer roller 25 to the transfer material 9 conveyed to the secondary transfer unit. Due to the electric field due to this electric charge, the negative toner image on the intermediate transfer belt 11 that has been primarily transferred to the transfer material 9 in contact with the intermediate transfer belt 11 is secondarily transferred. As a result, the above-described intermediate transfer belt 11 circulates and moves, and the toner image formed on the photosensitive drum 1 is transferred to the transfer material 9.

  A cleaning device 15 serving as a cleaning unit for removing an unnecessary toner image remaining on the intermediate transfer belt 11 after the secondary transfer is disposed at a position facing the tension roller 14 of the intermediate transfer unit 5. The residual toner removed by the cleaning device 15 passes through a waste toner conveyance path (not shown) and is collected in a waste toner collection container.

<Transfer material feeding section>
The transfer material feeding unit feeds the transfer material 9 to a secondary transfer unit that transfers the toner image on the intermediate transfer belt 11 to the transfer material 9. A plurality of transfer materials 9 are stored in the feeding cassette 17.

  At the time of image formation, the feeding roller 18 feeds the uppermost transfer material 9 on the feeding cassette 17, and the leading edge of the transfer material 9 abuts against the registration roller pair 19 to temporarily stop to form a loop. Thereafter, the rotation of the intermediate transfer belt 11 and the image writing position are synchronized, and the sheet is fed by the registration roller pair 19 to the secondary transfer unit.

<Fixing part>
The fixing unit 20 serving as fixing means fixes a plurality of color toner images transferred to the transfer material 9. The image forming surface side includes a fixing roller 21 having a heat generating unit, and a pressure roller 22 as a pressure unit facing the fixing roller 21. The transfer material 9 is held between the fixing roller 21 and the pressure roller 22 by a pressure spring (not shown) and is pressed with a predetermined pressure. When the pressure roller 22 is driven to rotate, the image forming surface side is heated and pressed by the fixing roller 21 and the non-image forming surface side is heated and pressed to melt the toner image to form the toner image on the transfer material 9. Let it settle.

<Discharge unit>
Further, a discharge unit is formed on the downstream side of the fixing unit 20 in the transfer material conveyance direction, and a conveyance roller pair 231 and a discharge roller pair 232 on the downstream side in the transfer material conveyance direction are further provided. Drain outside.

<Image forming operation>
As the image forming operation, in the process cartridge 7, the photosensitive drum 1 is rotationally driven in the clockwise direction in FIG. Then, the scanner units 3 corresponding to all the process cartridges 7 are driven. During this rotation process, a charging bias is applied to the charging roller 2 from a power supply circuit (not shown), and the peripheral surface of the photosensitive drum 1 is subjected to primary charging uniformly to a predetermined polarity and potential.

  The scanner unit 3 performs optical image exposure on the peripheral surface of the photosensitive drum 1 in accordance with image patterns of yellow, magenta, cyan, and black, which are color separation component images of a full-color image, according to an image signal. An electrostatic latent image is formed on the peripheral surface of 1.

  The electrostatic latent image is transferred to the low potential portion of the electrostatic latent image by the developing roller 41 in each developing device 4, and yellow, magenta, cyan on the peripheral surface of each of the four photosensitive drums 1. Then, a black toner image is formed at a predetermined sequence control timing. Yellow, magenta, cyan, and black toner images, which are color separation component images of a full-color image, are formed on the peripheral surface of each of the four photosensitive drums 1 by an electrophotographic process.

  The toner images of the respective colors formed on the peripheral surface of the photosensitive drum 1 are superimposed and transferred onto an intermediate transfer belt 11 that is rotationally driven at approximately the same speed as the photosensitive drum 1 in synchronization with the image position. In the primary transfer portion on the intermediate transfer belt 11, the toner images of the respective colors formed on the peripheral surface of the photosensitive drum 1 by the primary transfer bias applied from the power supply circuit (not shown) to the primary transfer roller 12 are sequentially transferred to the intermediate transfer belt 11. It is superimposed and transferred on top.

  At this time, an unfixed full-color toner image (mirror image) is formed on the intermediate transfer belt 11 when the toner images of all colors are primarily transferred.

  In each of the image forming units, the transfer residual toner remaining on each photosensitive drum 1 after the primary transfer of the toner image to the intermediate transfer belt 11 is removed by the cleaning blade 6 of the cleaning device 8, and a storage unit in the cleaning device 8. It is stored in.

  Thereafter, the leading end of the full color toner image on the peripheral surface of the intermediate transfer belt 11 is rotated and conveyed to a point where the intermediate transfer belt 11 and the secondary transfer roller 25 face each other. At this timing, the registration roller pair 19 starts to rotate and feeds the transfer material 9 to the secondary transfer unit so that the image formation start position of the transfer material 9 coincides with the front end of the toner image on the intermediate transfer belt 11. .

  An electric field is formed between the intermediate transfer belt 11 and the secondary transfer roller 25 by a secondary transfer bias applied to the secondary transfer roller 25 from a power supply circuit (not shown), and the transfer material 9 is conveyed while being transferred. A full color toner image is transferred. The transfer residual toner remaining on the intermediate transfer belt 11 is removed by the cleaning blade of the cleaning device 15, and sent to a waste toner box (not shown) to be stored.

  Thereafter, the transfer material 9 onto which the full-color toner image has been transferred is conveyed from the secondary transfer portion to the fixing unit 20. After the toner image is heat-fixed by the fixing unit 20, the transfer material 9 is discharged out of the apparatus main body by the conveying roller pair 231 and the discharge roller pair 232 with the image forming surface facing down from the discharge portion.

<Internal mechanism of intermediate transfer unit>
Next, the internal mechanism of the intermediate transfer unit 5 which is characteristic in this embodiment will be described with reference to FIGS.

  The intermediate transfer belt 11 is stretched by a driving roller 13 and a tension roller 14 that are rotatably supported by a housing (not shown) of the intermediate transfer unit 5.

  The primary transfer roller 12 is rotatably supported at its longitudinal end by a bearing link member 121. The bearing link member 121 is supported so as to be swingable about a rotation shaft 120 with respect to a housing (not shown) of the intermediate transfer unit 5. The bearing link member 121 has an intermediate transfer belt 11 against the photosensitive drum 1 facing the primary transfer roller 12 by a transfer spring 122 serving as a pressing unit that presses the primary transfer roller 12 toward the photosensitive drum 1. Press between the two.

  The cam sliders 111a and 111b are configured to be movable with respect to a casing (not shown) of the intermediate transfer unit 5 in a direction perpendicular to the pressing force direction of the transfer spring 122 (left and right direction in FIG. 3).

  The cam sliders 111a and 111b have cam slopes 112 at predetermined positions. When the cam slider 111a moves in the left direction in FIG. 3, the engaging portion 119 of the bearing link member 121 abuts and slides along the cam slope 112 in the upward direction in FIG. 121 is swung in the clockwise direction of FIG.

  The separation cams 113a and 113b shown in FIG. 9 are integrally formed and supported so as to be rotatable in the clockwise direction of FIG. 3 about the cam shaft 114 with respect to a housing (not shown) of the intermediate transfer unit 5. The separation cams 113a and 113b selectively move to a contact position where the primary transfer roller 12 can be transferred and a separation position where transfer cannot be performed by moving the cam sliders 111a and 111b in the horizontal direction in FIG.

  The cam surfaces 113a1 and 113b1 of the separation cams 113a and 113b push the cam receiving surfaces 111a1, 111a2, 111b1, and 111b2 formed by the left and right wall surfaces of the slide direction end portions provided on the cam sliders 111a and 111b, respectively. As a result, the cam sliders 111a and 111b move in the left-right direction in FIG.

  As shown in FIG. 9, the separation cams 113 a and 113 b are one part configured with a shape in which a plurality of cams are overlapped. The cam sliders 111a and 111b have a shape in which a plurality of cams are overlapped so that the cam surfaces 113a1 and 113b1 to be used are different depending on the cam receiving surfaces 111a1, 111a2, 111b1, and 111b2 formed by the left and right wall surfaces at the ends in the sliding direction. In FIG. 3, the cam sliders 111a and 111b can be selectively moved by the separation cams 113a and 113b. In the present embodiment, the cam slider 111a is moved by the separation cam 113b, and the cam slider 111b is moved by the separation cam 113a.

  Contact / separation means for selectively moving at least one or more primary transfer rollers 12 between a contact position where transfer is possible and a transfer position where transfer is impossible by cam sliders 111a, 111b, separation cams 113a, 113b and bearing link member 121. Configure.

  The separation cams 113a and 113b are driven by a motor 10 controlled by a control unit 16 serving as control means. As shown in FIGS. 3 and 10, the control unit 16 controls the driving of the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 to the position of the full separation mode in which the first separation mode is separated from each other. Is done.

  Further, as shown in FIGS. 4 and 11, the drive control of the photosensitive drum 1 and the primary transfer roller 12 is controlled to the second separation mode position smaller than the first separation mode shown in FIG. . Further, as shown in FIGS. 5 and 12, all the primary transfer rollers 12 are driven and controlled to a full color mode position where the intermediate transfer belt 11 is in contact with the opposing photosensitive drum 1.

  Further, as shown in FIGS. 6 and 13, the black-only primary transfer roller 12d is driven and controlled to a mono mode position where the intermediate transfer belt 11 is in contact with the opposing photosensitive drum 1d. Then, drive control is selectively performed to these plurality of contact / separation mode positions.

  In the present embodiment, as shown in FIG. 4, a second separation mode position is provided in which the separation amount between the photosensitive drum 1 and the primary transfer roller 12 is smaller than the first separation mode shown in FIG. At that time, the engaging portion 119 of the bearing link member 121 is held at a predetermined position on the cam slope 112 of the cam sliders 111a and 111b.

  Then, the separation amount between the photosensitive drum 1 and the primary transfer roller 12 is smaller than that in the first separation mode shown in FIG. 3 in a state where the primary transfer roller 12d, the intermediate transfer belt 11, and the photosensitive drum 1 are not in contact with each other. Set to position.

  The control unit 16 selects the first separation mode shown in FIG. 3 based on the image forming operation status and the given print job. Further, the second separation mode shown in FIG. 4 is selected. Further, the full color mode shown in FIG. 5 is selected. Further, the mono mode shown in FIG. 6 is selected. The plurality of contact / separation modes are selected as appropriate, the rotational phase of the motor 10 is controlled, and the operations of the cam sliders 111a and 111b are controlled via the separation cams 113a and 113b.

<Contact / separation operation>
The contact / separation operation of the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 will be described below. The first separation mode shown in FIG. 3, which is the four contact / separation modes of the present embodiment, the second separation mode shown in FIG. 4, the full color mode shown in FIG. 5, and the mono mode shown in FIG. 6 will be described. Thereafter, which contact / separation mode is applied in the image forming operation process will be described with reference to FIG.

  In the first separation mode shown in FIG. 3, all the primary transfer rollers 12 are moved upward in FIG. 3, and the plurality of photosensitive drums 1, intermediate transfer belts 11, and primary transfer rollers 12 face each other. In this state, the contact / separation mode is greatly separated.

  In this embodiment, the amount of separation between the photosensitive drum 1 and the intermediate transfer belt 11 and the amount of separation between the intermediate transfer belt 11 and the primary transfer roller 12 in the first separation mode shown in FIG. When the intermediate transfer belt 11 is driven with the photosensitive drum 1, the intermediate transfer belt 11 and the primary transfer roller 12 being separated from each other, the controller 16 sets the first separation mode shown in FIG. Is done. For example, when the toner image on the intermediate transfer belt 11 is transferred to the transfer material 9 and the remaining toner remaining on the intermediate transfer belt 11 is cleaned by the cleaning device 15, the first separation mode shown in FIG. 3 is set. Then, the intermediate transfer belt 11 is driven to rotate.

  In order to prevent all the photosensitive drums 1, the intermediate transfer belt 11, and all the primary transfer rollers 12 from being rubbed and damaged when the intermediate transfer belt 11 is driven and rotated, the respective parts are increased in the separation amount. In the first separation mode, the rotation of all the photosensitive drums 1 is stopped. Thereby, in the first separation mode, the wear progress of each part can be delayed without sliding or rubbing each part of the image forming unit.

  In the second separation mode shown in FIG. 4, which is a characteristic configuration of this embodiment, the separation amounts of the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 with respect to the respective components are shown in FIG. This is a state of the contact / separation mode set to be smaller than the separation amount in the one separation mode.

  In the present embodiment, the separation amount between the photosensitive drum 1 and the intermediate transfer belt 11 in the second separation mode shown in FIG. 4 is set to 3 mm, and the separation amount between the intermediate transfer belt 11 and the primary transfer roller 12 is set to 1 mm. Yes.

  The second separation mode shown in FIG. 4 is set mainly when the image forming apparatus 100 is in a standby state during the operation process. In this contact / separation mode, the photosensitive drum 1 and the intermediate transfer belt 11 are not driven to rotate. Therefore, in the first separation mode shown in FIG. 3, the intermediate transfer belt 11 is rotationally driven to increase the separation amounts of the photosensitive drum 1, the intermediate transfer belt 11 and the primary transfer roller 12 with respect to the respective components. The separation amount with respect to each component is made smaller than in the one separation mode. Therefore, at the time of standby before shifting to the image forming operation, the control unit 16 sets the second separation mode shown in FIG.

  If the photosensitive drum 1 and the intermediate transfer belt 11 are left in contact with each other for a long period of time, the surface property of the photosensitive drum 1 in the contacted region is locally different from other regions. Image defects with periodically different color densities occur in other regions. For this reason, all the photosensitive drums 1 and the intermediate transfer belt 11 are configured to be surely separated from each other.

  FIG. 5 shows a full-color mode state in which a plurality of image forming units are all performing image formation. All the primary transfer rollers 12 are in contact with the corresponding photosensitive drums 1 with the intermediate transfer belt 11 interposed therebetween.

  FIG. 6 shows a mono mode state in which only the black color image is formed. Each station of the unused color moves the primary transfer roller 12 upward in FIG. 6, and the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 are separated from the corresponding parts. With this configuration, the parts of the image forming unit that are not used do not rub against each other, and the degree of wear progress of each part can be delayed.

<Operation Process of Image Forming Apparatus>
FIG. 2 shows an operation process diagram of the image forming apparatus 100. The contents of each operation process and the contact / separation modes of the photosensitive drum 1, the intermediate transfer belt 11, and the transfer roller 12 at that time are shown below.

(1) Pre-multi-rotation process (first separation mode shown in FIG. 3)
The pre-multi-rotation process is a startup operation period (warming period) of the image forming apparatus 100. When the main power switch of the image forming apparatus 100 is turned on, the image forming apparatus 100 is activated to execute a preparation operation for a required process device. This operation process is also the first separation mode shown in FIG.

(2) Standby state (second separation mode shown in FIG. 4)
After the predetermined activation operation period, the image forming apparatus 100 stops driving, and the image forming apparatus 100 is held in a standby state until a print job trigger (print job start signal) is input. In this operation process, conventionally, the first separation mode shown in FIG. 3 has been set.

(3) Pre-rotation process (full color mode shown in FIG. 5 or mono mode shown in FIG. 6)
The pre-rotation process is a period in which the image forming apparatus 100 is re-driven based on the input of the image forming trigger and a pre-print job operation of a required process device is executed. In this operation process, the full color mode shown in FIG. 5 or the mono mode shown in FIG.

  If an image forming trigger is input during the previous multi-rotation process (1), the pre-rotation process (3) continues without waiting for the (2) after the completion of the pre-multi-rotation process. Migrate to

(4) Print job execution (full color mode shown in FIG. 5 or mono mode shown in FIG. 6)
When the predetermined pre-rotation process is completed, the image forming process is executed, and the image-formed transfer material 9 is output. In this operation process, the full color mode shown in FIG. 5 or the mono mode shown in FIG.

  In the case of a continuous print job, the image forming process is repeated, and a predetermined number of image-formed transfer materials 9 are sequentially output.

(5) Inter-transfer material process (full color mode shown in FIG. 5 or mono mode shown in FIG. 6)
The inter-transfer material process is an interval process between the trailing edge of the first transfer material 9 and the leading edge of the next transfer material 9 in the case of a continuous print job. In this operation process, the full color mode shown in FIG. 5 or the mono mode shown in FIG.

(6) Post-rotation process (first separation mode shown in FIG. 3)
In the post-rotation process, in the case of a single print job, after the image-formed transfer material 9 is output (end of print job), the image forming apparatus 100 is continuously driven to perform a print job for a required process device. This is a period during which the post-operation is executed. Alternatively, in the case of a continuous print job, after the last image-formed transfer material 9 of the continuous print job is output (end of the print job), the image forming apparatus 100 is continuously driven to perform a print job of a required process device. This is a period during which the post-operation is executed.

  In this step, the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 are largely separated from each other in order to clean the residual toner on the intermediate transfer belt 11 after completion of the image forming process by the cleaning device 15.

  This prevents unnecessary wear of image forming parts (photosensitive drum 1, developing device 4, cleaning blade 6, etc.) that are not required after the image forming process is completed.

  The distances among the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 are increased. As a result, generation of foreign matter (such as roller scraping) caused by abrasion or rubbing due to contact between the primary transfer roller 12 and the intermediate transfer belt 11, and the photosensitive drum 1 and the intermediate transfer belt 11 generated when the intermediate transfer belt 11 is driven. Lost. This operation process is also the first separation mode shown in FIG.

(7) Standby state (second separation mode shown in FIG. 4)
After completion of the predetermined post-rotation process, the driving of the image forming apparatus 100 is stopped, and the image forming apparatus 100 is held in a standby state until the next print job trigger is input. In this step, the distance between the primary transfer roller 12 and the photosensitive drum 1 (the distance between the primary transfer roller 12 and the intermediate transfer belt 11) is reduced. In this operation process, conventionally, the first separation mode shown in FIG. 3 has been set.

  From the pre-rotation process to the post-rotation process is one image forming process, and when a print job trigger is input next, a new image forming process is executed.

  Next, the contact / separation operation of the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 in the pre-rotation process from the standby state will be described.

  When the controller 16 sends a command to switch from the second separation mode shown in FIGS. 4 and 11 to the full color mode shown in FIGS. 5 and 12, the separation cams 113a and 113b are moved in the clockwise direction in FIG. Rotate 60 degrees integrally.

  Then, as shown in FIG. 11A, the left cam receiving surface 111a1 of the cam slider 111a is pushed by the cam surface 113b1 of the separation cam 113b. Then, as shown in FIG. 11C, the left cam receiving surface 111b1 of the cam slider 111b is pushed by the cam surface 113a1 of the separation cam 113a. As a result, the cam sliders 111a and 111b are moved in the left direction in FIG.

  A position P shown in FIGS. 10 to 13 indicates a contact position between the separation cams 113a and 113b and the cam receiving surfaces 111a1, 111a2, 111b1, and 111b2 of the cam sliders 111a and 111b in each mode. Each of FIGS. 10 to 13 (a) is a view (rear view) looking down from the upper side of each (b) in order to match the moving direction of the cam sliders 111a and 111b in each (b) and (c). .

  The engaging portions 119 of the bearing link member 121 abut on and slide on the cam inclined surfaces 112 of the cam sliders 111a and 111b moved by the separation cams 113a and 113b, respectively, and the cam inclined surfaces 112 move upward in FIG. As a result, the spring force of the transfer spring 122 that has been compressed is released, and the bearing link member 121 rotates about the rotation shaft 120 in the clockwise direction in FIG. Abutting the photosensitive drum 1 with the transfer belt 11 in between.

  Here, as shown in FIG. 8, conventionally, when the image forming operation is started, the first separation mode shown in FIG. 3 in the standby state is directly switched to the full color mode shown in FIG. The rotation angle of the separation cams 113a and 113b necessary for the rotation was 120 degrees.

  Therefore, as in the present embodiment, the separation cam necessary for switching can be obtained by switching from the second full separation mode shown in FIG. 4 set during standby before shifting to the image forming operation to the full color mode shown in FIG. The rotation angles of 113a and 113b were reduced by 60 degrees. As a result, the image output time of the first transfer material 9 was shortened by 0.3 seconds by shortening the time until the transition from the standby state to the full color mode. The same applies when switching from the second separation mode shown in FIG. 4 to the mono mode shown in FIG.

  Further, the separation amount between the photosensitive drum 1 and the primary transfer roller 12 and the separation amount between the intermediate transfer belt 11 and the primary transfer roller 12 when shifting from the standby state to the full color mode are reduced. As a result, the moving distance and time during which the primary transfer roller 12 can be accelerated by gravity and the transfer spring 122 are shortened. As a result, when the primary transfer roller 12 is in contact with the photosensitive drum 1 or the intermediate transfer belt 11, the moving speed at the time of contact can be reduced, and the impact sound can be reduced.

  In the present embodiment, it has been described that the operation process for setting the first separation mode shown in FIG. 3 is mainly when the intermediate transfer belt 11 is cleaned by the cleaning device 15. The present invention is not limited to this, and can be applied to all the operation steps when driving the intermediate transfer belt 11 while stopping the image forming operation.

  In the mono mode shown in FIG. 6, when it is desired to increase the first printout time that is the output time of the first sheet of the transfer material 9, the rotation direction of the separation cams 113a and 113b is changed. Alternatively, the cam shapes of the separation cams 113a and 113b are changed. Then, the order of the contact / separation mode of the primary transfer roller 12 may be changed so that the mono mode shown in FIG. 6 comes after the second separation mode shown in FIG.

  In the present embodiment, an intermediate transfer belt type image forming apparatus 100 that transfers a toner image on the photosensitive drum 1 to an intermediate transfer belt 11 serving as an endless belt by a primary transfer roller 12 serving as a transfer unit will be described as an example. went. However, the present invention is not limited to this. For example, image formation using a transfer transfer system of a direct transfer system in which a toner image on the photosensitive drum 1 is transferred to a transfer material 9 transported by an endless belt by a transfer unit. It may be a device.

  Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. In addition, what was comprised similarly to the said 1st Embodiment attaches | subjects the same code | symbol, and abbreviate | omits the overlapping description.

  The separation amount in the second separation mode shown in FIG. 7 of the present embodiment is smaller than the separation amount in the second separation mode of the first embodiment shown in FIG. 4 and described above. Is set.

  The separation amounts in the second separation mode shown in FIG. 7 are the separation amounts of the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 with respect to the respective components. The separation amount in the second separation mode of the first embodiment described above with reference to FIG. 4 is the separation amount of the photosensitive drum 1, the intermediate transfer belt 11, and the primary transfer roller 12 with respect to the respective components.

  In the present embodiment, as shown in FIG. 7, the separation amount between the photosensitive drum 1 and the primary transfer roller 12 is in the second separation mode position smaller than the first separation mode shown in FIG. At that time, the engaging portion 119 of the bearing link member 121 is held at a predetermined position somewhat above the first embodiment on the cam slope 112 of the cam sliders 111a and 111b.

  At this time, the photosensitive drum 1 and the intermediate transfer belt 11 are separated from each other. The primary transfer roller 12 d is in contact with the intermediate transfer belt 11. In this state, the distance between the photosensitive drum 1 and the primary transfer roller 12 is smaller than that in the first separation mode shown in FIG. Furthermore, it is set to a position that is smaller than the second separation mode of the first embodiment shown in FIG.

  In FIG. 7, all the photosensitive drums 1 and the intermediate transfer belt 11 are separated from each other, and the intermediate transfer belt 11 and the primary transfer roller 12 are in contact with each other. In this embodiment, the amount of separation between the photosensitive drum 1 and the intermediate transfer belt 11 in the second separation mode shown in FIG. 7 is set to 2 mm.

  In the second separation mode shown in FIG. 7, the rotation of the photosensitive drum 1 and the intermediate transfer belt 11 is stopped. For this reason, the photosensitive drum 1 and the intermediate transfer belt 11 in the first separation mode shown in FIG. 3 are separated by the amount of the belt position fluctuation when the intermediate transfer belt 11 is driven in the first separation mode shown in FIG. The amount of separation between the photosensitive drum 1 and the intermediate transfer belt 11 was set smaller than the amount.

  In this embodiment, since the intermediate transfer belt 11 and the primary transfer roller 12 are in contact with each other, the separation amount between the photosensitive drum 1 and the intermediate transfer belt 11 is also the photosensitive member in the first separation mode shown in FIG. The distance between the drum 1 and the intermediate transfer belt 11 can be made smaller.

  As a result, the distance from the primary transfer roller 12 to the photosensitive drum 1 during standby before shifting to the image forming operation can be further reduced. The amount of rotation of the separation cams 113a and 113b necessary for switching from the second separation mode shown in FIG. 7 to the full color mode shown in FIG. 5 is reduced by 80 degrees compared to the prior art.

  As a result, the time required to shift to the full color mode was further shortened, and the time for outputting the first image of the transfer material 9 could be shortened by 0.4 seconds compared to the conventional case. The same applies when switching from the second separation mode shown in FIG. 7 to the mono mode shown in FIG.

  Further, when the second separation mode shown in FIG. 7 is switched to the full color mode shown in FIG. 5, the intermediate transfer belt 11 and the primary transfer roller 12 are already brought into contact with each other in the second separation mode shown in FIG. Further, the distance between the primary transfer roller 12 and the photosensitive drum 1 is further reduced. As a result, the moving distance and time during which the primary transfer roller 12 can be accelerated by gravity and the transfer spring 122 can be further shortened. As a result, it is possible to eliminate the impact noise that is generated when the primary transfer roller 12 that has been generated conventionally comes into contact with the intermediate transfer belt 11. Furthermore, the impact sound generated when the primary transfer roller 12 is in contact with the photosensitive drum 1 can be further reduced.

1, 1a, 1b, 1c, 1d ... photosensitive drum (image carrier)
11 ... Intermediate transfer belt (endless belt)
12, 12a, 12b, 12c, 12d ... primary transfer roller (transfer means)

Claims (3)

A plurality of image carriers that carry toner images;
An endless belt facing the plurality of image carriers;
A plurality of transfer means for transferring the toner image on the image carrier to the endless belt or a transfer material, relative to the image carrier across the endless belt;
A pressing unit that presses the transfer unit toward the opposite image carrier;
Contact / separation means for selectively moving at least one transfer means to a transfer position where transfer is possible and a separation position where transfer is impossible;
With
A first separation mode in which the image carrier, the endless belt, and the transfer unit are separated from each other;
A second separation mode in which a separation amount between the image carrier and the transfer unit is smaller than the first separation mode;
Have
When driving the endless belt in a state where the image carrier, the endless belt and the transfer unit are separated from each other, the first separation mode is set and a standby time before the image forming operation is started. Is set in the second separation mode. A cleaning means for removing an unnecessary toner image on the endless belt;
2. The image forming apparatus according to claim 1, wherein when the remaining toner on the endless belt is cleaned by the cleaning unit, the first separation mode is set. The image bearing member and the endless belt are separated from each other in the second separation mode, and the endless belt and the transfer unit are in contact with each other. Image forming apparatus.

Images