Image forming apparatus

Abstract

To perform stable image formation by preventing pitch unevenness of an image and malfunction of a secondary transfer belt, while reducing an environmental load.SOLUTION: A transfer unit has a revolvable endless transfer belt and a plurality of rotatable support rollers that stretch the transfer belt, and at least an inner peripheral part of the transfer belt and an outer peripheral part of each support roller are portions not including an organic fluorine compound. The transfer unit further has separability improving parts that improve separability between an outer peripheral surface of at least any one support roller of the plurality of support rollers and an inner peripheral surface of the transfer belt.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] In recent years, in the field of image forming devices, there has been a growing demand for thinner recording media such as paper in order to reduce environmental impact. Accordingly, a belt system using a secondary transfer belt is sometimes adopted in the secondary transfer unit of an image forming device to ensure good separation from thin recording media. An example of an image forming device equipped with a belt-type secondary transfer unit is shown in Patent Document 1.

[0003] The belt-type secondary transfer unit has an endless secondary transfer belt that can rotate and can hold a recording medium in cooperation with an intermediate transfer belt that serves as an image carrier, and a plurality of rotatable support rollers around which the secondary transfer belt is supported. One of the support rollers is a secondary transfer roller that holds a recording medium via the secondary transfer belt in cooperation with the intermediate transfer belt. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-215511 Summary of the Invention [Problem to be solved by the invention]

[0005] The surroundings of the secondary transfer unit are filled with an atmosphere containing a large amount of toner, which tends to adhere to the outer circumferential surfaces of the support rollers and the inner circumferential surface of the secondary transfer belt. When toner is present between the outer circumferential surface of the secondary transfer roller and the inner circumferential surface of the secondary transfer belt, poor separation between the secondary transfer roller and the secondary transfer belt can occur at the end of the winding area around the secondary transfer roller. This can result in uneven image pitch (uneven images) or malfunction of the secondary transfer belt, making stable image formation difficult.

[0006] In particular, in image forming devices such as production printers, the temperature of the fixing section is high, so the toner interposed between the outer surface of the secondary transfer roller and the inner surface of the secondary transfer belt becomes hot, increasing the toner's adhesive force and making the above problem more pronounced.

[0007] On the other hand, it is conceivable that poor separation between the secondary transfer roller and the secondary transfer belt can be suppressed by including an organic fluorine compound with excellent releasability in the inner peripheral portion of the secondary transfer belt or the outer peripheral portion of the secondary transfer roller, but this is not desirable in terms of reducing the environmental impact.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus that can perform stable image formation by suppressing uneven image pitch and malfunction of the secondary transfer belt while reducing the environmental impact. [Means for solving the problem]

[0009] An image forming apparatus according to one aspect of the present invention includes: an image carrier that carries a toner image; a transfer unit capable of holding a recording medium in cooperation with the image carrier, for transferring a toner image on the image carrier to the recording medium; The transfer unit includes: a rotatable endless transfer belt; a plurality of rotatable support rollers on which the transfer belt is supported, At least the inner peripheral portion of the transfer belt and the outer peripheral portions of each support roller are portions that do not contain organic fluorine compounds, The transfer belt further includes a separation improvement portion that improves separation between the outer circumferential surface of at least one of the support rollers and the inner circumferential surface of the transfer belt. [Effects of the Invention]

[0010] According to the present invention, it is possible to reduce the environmental load while suppressing uneven image pitch and malfunction of the transfer belt, thereby performing stable image formation. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram of the secondary transfer unit and its surroundings. [Figure 3] FIG. 3 is a schematic diagram illustrating a separation claw as a separation improving portion according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram illustrating a cleaning blade as a separation improvement portion according to the second embodiment and an application portion as a separation improvement portion according to the third embodiment. [Figure 5] FIG. 5 is a schematic diagram illustrating a cleaning blade as a separation improvement portion according to a fourth embodiment and an application portion as a separation improvement portion according to a fifth embodiment. [Figure 6] FIG. 6 is a schematic diagram illustrating a blower fan as a separation improving portion according to the sixth embodiment. [Figure 7] FIG. 7 is a schematic diagram illustrating a cooling roller as a separation improvement section according to a seventh embodiment and a cooling plate as a separation improvement section according to an eighth embodiment. [Figure 8] FIG. 8 is a control block diagram of the image forming apparatus according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present embodiment will be described below with reference to the drawings. In the drawings, "front" refers to the front direction, "rear" refers to the rear direction, "left" refers to the left direction, "right" refers to the right direction, "up" refers to the up direction, and "down" refers to the down direction.

[0013] The overall configuration of an image forming apparatus 10 according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram showing the overall configuration of the image forming apparatus 10 according to this embodiment. Figure 2 is a schematic diagram of a secondary transfer unit 48 and its periphery.

[0014] 1, the image forming apparatus 10 is a so-called tandem image forming apparatus, and forms a toner image on a recording medium, namely, paper P. The image forming apparatus 10 includes a box-shaped apparatus main body 12.

[0015] An image forming section 24 that forms images by electrophotography is provided in the upper part of the apparatus main body 12. The image forming section 24 has four image forming units 26Y, 26M, 26C, and 26K that form images using color toners of Y (yellow), M (magenta), C (cyan), and K (black) components based on image data. The four image forming units 26Y, 26M, 26C, and 26K are arranged in the vertical direction.

[0016] The image forming units 26Y, 26M, 26C, and 26K for the Y, M, C, and K components have the same configuration. For ease of illustration and description, common components are denoted by the same reference numerals, and when distinguishing between them, the reference numerals are suffixed with Y, M, C, or K. In FIG. 1, only the components of the image forming unit 26Y for the Y component are designated with reference numerals, and the components of the other image forming units 26M, 26C, and 26K are not designated with reference numerals. Note that the image forming section 24 may also include an image forming unit (not shown) that forms images using special toners other than the four standard color toners (yellow toner, magenta toner, cyan toner, and black toner).

[0017] The image forming unit 26 includes a photosensitive drum 28, a charging section 30, an exposure section 32, a developing section 34, and a drum cleaning section 36 arranged around the photosensitive drum 28.

[0018] The photoreceptor drum 28 is a negatively charged organic photoreceptor having an undercoat layer, a charge generating layer, and a charge transport layer laminated in this order on the circumferential surface of a conductive cylinder made of aluminum, for example. The photoreceptor drum 28 is rotated at a constant peripheral speed by a rotary motor (not shown).

[0019] The charging unit 30 uniformly charges the outer peripheral surface of the photosensitive drum 28 to a negative polarity. The exposure unit 32 emits a laser beam as scanning light to expose and scan the outer peripheral surface of the photosensitive drum 28, thereby forming an electrostatic latent image on the outer peripheral surface of the photosensitive drum 28. The light amount of the laser beam emitted from the exposure unit 32 is modulated according to image data for each of the YMCK colors.

[0020] The developing unit 34 is, for example, a two-component developing unit. The developing unit 34 visualizes the electrostatic latent image on the outer peripheral surface of the photosensitive drum 28 by attaching toner of each color component to the outer peripheral surface of the photosensitive drum 28, thereby forming a toner image. The drum cleaning unit 36 ​​cleans the transfer residual toner remaining on the outer peripheral surface of the photosensitive drum 28 after the primary transfer. The drum cleaning unit 36 ​​has a drum cleaning blade that comes into sliding contact with the outer peripheral surface of the photosensitive drum 28, etc.

[0021] A primary transfer unit 38 for transferring a toner image onto paper P is provided at the upper part of the device main body 12. The primary transfer unit 38 has an endless intermediate transfer belt 40, a plurality of support rollers 42, a primary transfer roller 44, and a belt cleaning unit 46.

[0022] The intermediate transfer belt 40 is an image carrier that carries a toner image, and has a base material made of, for example, polyimide resin (PI). The intermediate transfer belt 40 extends in the vertical direction and is stretched over multiple support rollers 42. The intermediate transfer belt 40 rotates as the multiple support rollers 42 rotate. At least one of the multiple support rollers 42 is configured as a drive roller that is linked to a rotation motor (not shown), and the other support rollers 42 are configured as driven rollers (free rollers).

[0023] The primary transfer rollers 44 are disposed on the inner circumferential surface side of the intermediate transfer belt 40, facing the photosensitive drums 28 of each color component. The primary transfer rollers 44 cooperate with the photosensitive drums 28 to pinch the intermediate transfer belt 40. A primary transfer nip CN for transferring a toner image from the photosensitive drums 28 to the intermediate transfer belt 40 is formed between the outer circumferential surface of the primary transfer roller 44 and the outer circumferential surface of the photosensitive drums 28.

[0024] When the intermediate transfer belt 40 passes through the primary transfer nip CN, the toner images on the photosensitive drums 28 are primarily transferred onto the intermediate transfer belt 40 in a sequentially overlapping manner. Specifically, a primary transfer bias is applied to the primary transfer roller 44, and a charge of the opposite polarity to the toner is applied to the back side of the intermediate transfer belt 40 (the side that abuts against the primary transfer roller 44), so that the toner images are electrostatically transferred onto the intermediate transfer belt 40.

[0025] The belt cleaning unit 46 removes untransferred toner remaining on the surface of the intermediate transfer belt 40 after the secondary transfer. The belt cleaning unit 46 has a cleaning blade that comes into sliding contact with the surface of the intermediate transfer belt 40.

[0026] 1 and 2, a secondary transfer unit 48 serving as a transfer unit for transferring a toner image on the intermediate transfer belt 40 is provided below the intermediate transfer belt 40 within the device main body 12. The secondary transfer unit 48 has a secondary transfer belt 50 serving as an endless transfer belt and a plurality of support rollers 52. The plurality of support rollers 52 includes a secondary transfer roller 52C serving as a transfer roller, a drive roller 52D, and a steering roller 52S.

[0027] The secondary transfer belt 50 has a substrate made of, for example, polyimide resin. The secondary transfer belt 50 is stretched over multiple support rollers 52 and can rotate. The intermediate transfer belt 40 rotates by the rotation of the multiple support rollers 42. The secondary transfer belt 50 is made up of multiple layers, the thickest of which contains an ionic conductive agent. The innermost layer, which is the inner periphery of the secondary transfer belt 50, does not contain any organic fluorine compounds. The rotation speed of the secondary transfer belt 50 is set to 340 mm / s or more. The secondary transfer belt 50 may contain an electronic conductive agent instead of an ionic conductive agent. The secondary transfer belt 50 may be made up of a single layer instead of multiple layers.

[0028] As described above, the multiple support rollers 52 are rotatable members on which the secondary transfer belt 50 is stretched. The outermost layer, which is the outer periphery of each support roller 52, is a portion that does not contain organic fluorine compounds. The outermost layer of each support roller 52 may be made of solid rubber, solid resin, or metal.

[0029] The secondary transfer roller 52C is disposed opposite a predetermined support roller 42 with the intermediate transfer belt 40 and secondary transfer belt 50 between them. The secondary transfer roller 52C is pressed against the predetermined support roller 42 and holds the paper P via the secondary transfer belt 50 in cooperation with the intermediate transfer belt 40. The secondary transfer roller 52C is the support roller 52 with the largest outer peripheral surface area among the multiple support rollers 52. The outermost layer of the secondary transfer roller 52C is made of at least a metal such as stainless steel and is electrically grounded.

[0030] A secondary transfer nip TN for transferring a toner image from the intermediate transfer belt 40 to the paper P is formed between the secondary transfer roller 52C and the intermediate transfer belt 40 (predetermined support roller 42). When the paper P passes through the secondary transfer nip TN, the toner image on the intermediate transfer belt 40 is secondarily transferred to the paper P. Specifically, by applying a secondary transfer bias of the same polarity as the toner to the predetermined support roller 42 and imparting a charge of the same polarity as the toner to the back side of the intermediate transfer belt 40 (the side that abuts against the predetermined support roller 42), the toner image is electrostatically transferred to the paper P, and an image can be formed on the paper P.

[0031] The drive roller 52D is located on the leftmost side of the multiple support rollers 52, and is rotated by a motor (not shown), such as a stepping motor. The steering roller 52S is located below the drive roller 52D, and is connected to a steering mechanism (not shown). The steering mechanism tilts the rotation axis of the steering roller 52S relative to the rotation axes of the other support rollers 52, thereby preventing the secondary transfer belt 50 from meandering.

[0032] The secondary transfer unit 48 may have a cleaning device (not shown) that cleans the outer peripheral surface of the secondary transfer belt 50. The cleaning device has a known configuration, for example, as shown in Japanese Patent Application Laid-Open No. 2019-148779 and Japanese Patent Application Laid-Open No. 2021-39235.

[0033] 1, a fixing unit 54 for fixing the toner image onto the paper P is provided on the outlet side of the secondary transfer nip TN within the device main body 12. The fixing unit 54 has a heating roller 56, a fixing roller 58, an endless fixing belt 60, and a pressure roller 62.

[0034] Heating roller 56 has a hollow cylindrical core made of, for example, aluminum, iron, or SUS (stainless steel), and a heating device such as a halogen lamp provided inside the core. Furthermore, fixing roller 58 is disposed opposite heating roller 56. Fixing roller 58 has a hollow cylindrical core made of, for example, aluminum, iron, or SUS, and a surface layer made of, for example, silicone rubber or silicone sponge, provided on the outer periphery of the core. Fixing belt 60 is stretched between heating roller 56 and fixing roller 58 and can rotate. Fixing belt 60 has a base material made of, for example, polyimide resin.

[0035] Pressure roller 62 is disposed outside fixing belt 60 in a position facing fixing roller 58, and presses against fixing roller 58 with a predetermined fixing load. Pressure roller 62 has a hollow cylindrical core made of, for example, aluminum, iron, or SUS, an elastic layer made of, for example, silicone rubber, provided on the outer surface of the core, and a surface layer made of, for example, PFA tubing, provided on the surface of the elastic layer. In addition, a fixing nip FN is formed between fixing roller 58 and pressure roller 62 to transport paper P while applying heat and pressure.

[0036] The pressure roller 62 is rotated by a motor (not shown), which causes the fixing belt 60 to rotate accordingly. The rotation of the fixing belt 60 causes the heating roller 56 and the fixing roller 58 to rotate accordingly. As a result, the paper P is conveyed while being heated and pressurized in the fixing nip FN, and the toner image that has not yet arrived can be fixed to the paper P.

[0037] A main transport path 72 is provided within the device body 12. The main transport path 72 is a path along which the paper sheet P is transported when a toner image is formed on the front side of the paper sheet P. The main transport path 72 is a path along which the paper sheet P is transported via a plurality of transport roller pairs including a registration roller pair 74, a secondary transfer nip TN, and a fixing nip FN. Also provided within the device body 12 is a reversing transport path 76 that reverses the paper sheet P from front to back. The reversing transport path 76 is a path along which the paper sheet P is transported when a toner image is formed on the back side of the paper sheet P, and is connected to the main transport path 72.

[0038] Paper P stored in a paper feeder (not shown) or the like disposed on the right side of the apparatus main body 12 is transported toward the secondary transfer nip TN along the main transport path 72. At this time, the pair of registration rollers 74 corrects the inclination of the paper P and adjusts the transport timing of the paper P. Then, at the secondary transfer nip TN, the toner image on the intermediate transfer belt 40 is secondarily transferred all at once onto one side (front or back) of the paper P, and the toner image is fixed to the paper P at the fixing nip FN. The paper P on which the image has been formed is then ejected outside the apparatus main body 12.

[0039] Next, the separation improvement portion of the secondary transfer unit 48 will be described with reference to FIGS. 2 to 7. FIG. 3 is a schematic diagram illustrating a separation claw 78 as a separation improvement portion according to a first embodiment. FIG. 4 is a schematic diagram illustrating a cleaning blade 82 as a separation improvement portion according to a second embodiment and an application portion 84 as a separation improvement portion according to a third embodiment. FIG. 5 is a schematic diagram illustrating a cleaning blade 94 as a separation improvement portion according to a fourth embodiment and an application portion 96 as a separation improvement portion according to a fifth embodiment. FIG. 6 is a schematic diagram illustrating a blower fan 104 as a separation improvement portion according to a sixth embodiment. FIG. 7 is a schematic diagram illustrating a cooling roller 106 as a separation improvement portion according to a seventh embodiment and a cooling plate 108 as a separation improvement portion according to an eighth embodiment.

[0040] As shown in FIGS. 2 to 7, the secondary transfer unit 48 has a separation improvement portion that improves the separability between the outer circumferential surface of the secondary transfer roller 52C (the outer circumferential surface of the outermost layer) and the inner circumferential surface of the secondary transfer belt 50 (the inner circumferential surface of the innermost layer). The separation improvement portion improves the separability between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50 at the end side of the winding region in the circumferential direction of the secondary transfer roller 52C. The winding region is a region for winding the secondary transfer belt 50 around the secondary transfer roller 52C. In this embodiment, the secondary transfer unit 48 includes any of the separation improvement portions according to the first to eighth aspects, as follows.

[0041] As shown in FIGS. 2 and 3, a plate-shaped separation claw 78 is provided as a separation performance improving portion according to the first embodiment at the end of the winding region of the secondary transfer roller 52C on the inside of the secondary transfer belt 50. The separation claw 78 is capable of contacting the inner circumferential surface of the secondary transfer belt 50 at the end of the winding region of the secondary transfer roller 52C. The tip of the separation claw 78 faces in the opposite direction to the rotation direction of the secondary transfer roller 52C. The tip of the separation claw 78 may be close to or in contact with the outer circumferential surface of the secondary transfer roller 52C. The separation claw 78 is made of resin or metal.

[0042] The separation claws 78 are configured to be rotatable about the axis of a rotation shaft 80 extending in the front-rear direction, and the base ends of the separation claws 78 are integrally connected to the rotation shaft 80. The rotation shaft 80 is rotatably supported on a part of the device body 12 via a bracket or the like. Note that there may be a plurality of separation claws 78, and the base ends of the plurality of separation claws 78 may be integrally connected to the rotation shaft 80 at intervals in the front-rear direction.

[0043] According to the separability improving section of the first aspect, when the separation claw 78 comes into contact with the inner circumferential surface of the secondary transfer belt 50, the separation claw 78 pushes up the secondary transfer belt 50, and a mechanical peeling force acts between the secondary transfer belt 50 and the secondary transfer roller 52C. This improves the separability between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50 at the terminal end of the winding region in the circumferential direction of the secondary transfer roller 52C.

[0044] As shown in FIG. 4, a plate-shaped cleaning blade 82 serving as a separation improving section according to the second embodiment is provided on the inner side of the secondary transfer belt 50, at the end of the winding region of the secondary transfer roller 52C. The cleaning blade 82 is a cleaning section that cleans the outer circumferential surface of the secondary transfer roller 52C. The cleaning blade 82 cleans the outer circumferential surface of the secondary transfer roller 52C by scraping off toner T adhering to the outer circumferential surface of the secondary transfer roller 52C. The cleaning blade 82 extends in the front-rear direction, and the tip of the cleaning blade 82 faces in the direction opposite to the rotation direction of the secondary transfer roller 52C. The tip of the cleaning blade 82 abuts against the outer circumferential surface of the secondary transfer roller 52C. The cleaning blade 82 is made of resin, rubber material, or metal. When the cleaning blade 82 is made of resin, a thickness of 50 μm to 300 μm allows the cleaning blade 82 to maintain appropriate cleaning performance.

[0045] According to the separability improving unit of the second aspect, the cleaning blade 82 cleans the outer peripheral surface of the secondary transfer roller 52C, thereby reducing the adhesive force of the toner T between the secondary transfer roller 52C and the secondary transfer belt 50. This improves the separability between the outer peripheral surface of the secondary transfer roller 52C and the inner peripheral surface of the secondary transfer belt 50 at the terminal end side of the winding area in the circumferential direction of the secondary transfer roller 52C.

[0046] The cleaning unit (second separation improvement unit) is not limited to the cleaning blade 82, but may be a brush roller (not shown) that scrapes off the toner T adhering to the outer peripheral surface of the secondary transfer roller 52C. In this case, the brush roller rotates in the opposite direction to the rotation direction of the secondary transfer roller 52C.

[0047] 4, an applicator 84 that applies a lubricant to the outer circumferential surface of the secondary transfer roller 52C is provided as a separation improving section according to the third embodiment on the opposite side of the winding region of the secondary transfer roller 52C inside the secondary transfer belt 50. The applicator 84 includes a holder 86 that holds a solid lubricant SL, a brush roller 88, an elastic member 90, and a leveling blade 92.

[0048] The holder 86 is provided on the inside of the secondary transfer belt 50 on the opposite side of the winding area of ​​the secondary transfer roller 52C, and extends in the front-to-rear direction. The brush roller 88 is rotatably provided between the holder 86 and the secondary transfer roller 52C, and extends in the front-to-rear direction. The brush roller 88 scrapes the lubricant L from the solid lubricant SL and applies it to the outer circumferential surface of the secondary transfer roller 52C. The brush roller 88 rotates in the opposite direction to the rotation direction of the secondary transfer roller 52C by driving a brush motor (not shown).

[0049] The elastic member 90 is provided at the bottom of the holder 86 and presses the solid lubricant SL towards the brush roller 88. The leveling blade 92 is provided below the holder 86 and extends in the front-to-rear direction. The leveling blade 92 levels out the lubricant L applied to the outer circumferential surface of the secondary transfer roller 52C. The tip of the leveling blade 92 faces in the direction of rotation of the secondary transfer roller 52C while in contact with the outer circumferential surface of the secondary transfer roller 52C. The leveling blade 92 is made of resin, metal, or rubber.

[0050] According to the separability improving section of the third aspect, the brush roller 88 (application section 84) scrapes the lubricant L from the solid lubricant SL and applies it to the outer peripheral surface of the secondary transfer roller 52C, thereby reducing the adhesive force between the secondary transfer roller 52C and the secondary transfer belt 50. This makes it possible to improve the separability between the outer peripheral surface of the secondary transfer roller 52C and the inner peripheral surface of the secondary transfer belt 50 at the terminal end side of the winding region in the circumferential direction of the secondary transfer roller 52C.

[0051] As shown in FIG. 5 , a cleaning blade 94 is provided as a separation improving section according to the fourth embodiment at a position spaced apart from the secondary transfer roller 52C on the inner side of the secondary transfer belt 50. The cleaning blade 94 is a cleaning section that indirectly cleans the inner circumferential surface of the secondary transfer belt 50. The cleaning blade 94 indirectly cleans the inner circumferential surface of the secondary transfer belt 50 by scraping off toner T adhering to the outer circumferential surface of a predetermined support roller 52 other than the secondary transfer roller 52C. The cleaning blade 94 extends in the front-to-rear direction, and the tip of the cleaning blade 94 faces in the direction opposite to the rotational direction of the predetermined support roller 52. The tip of the cleaning blade 94 abuts against the outer circumferential surface of the predetermined support roller 52. The cleaning blade 94 is made of resin, rubber, or metal. The predetermined support roller 52 is, for example, the support roller 52 located immediately upstream of the secondary transfer roller 52C when viewed in the rotational direction of the secondary transfer belt 50.

[0052] According to the separability improving section of the fourth aspect, the cleaning blade 94 indirectly cleans the inner circumferential surface of the secondary transfer belt 50, thereby reducing the adhesive force of the toner T between the secondary transfer roller 52C and the secondary transfer belt 50. This improves the separability between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50 at the terminal end side of the winding area in the circumferential direction of the secondary transfer roller 52C.

[0053] 5, an applicator 96 that indirectly applies a lubricant to the inner circumferential surface of the secondary transfer belt 50 is provided as a separation improvement unit according to a fifth embodiment at a position spaced apart from a predetermined support roller 52 on the inner side of the secondary transfer belt 50. The applicator 96 includes a holder 98 that holds a solid lubricant SL, a brush roller 100, and an elastic member 102.

[0054] The holder 98 is provided inside the secondary transfer belt 50 at a position spaced apart from the predetermined support roller 52 and extends in the front-rear direction. The brush roller 100 is rotatably provided between the holder 98 and the predetermined support roller 52 and extends in the front-rear direction. The brush roller 100 scrapes the lubricant L from the solid lubricant SL and applies it to the outer circumferential surface of the predetermined support roller 52. The lubricant L applied to the outer circumferential surface of the predetermined support roller 52 moves to the inner circumferential surface of the secondary transfer belt 50. In other words, the brush roller 100 scrapes the lubricant L from the solid lubricant SL and indirectly applies it to the inner circumferential surface of the secondary transfer belt 50. The brush roller 100 rotates in the direction opposite to the rotation direction of the predetermined support roller 52 by driving a brush motor (not shown). The elastic member 102 is provided at the bottom of the holder 98 and presses the solid lubricant SL toward the brush roller 100.

[0055] According to the separability improving section of the fifth aspect, the brush roller 100 (application section 96) scrapes the lubricant L from the solid lubricant SL and indirectly applies it to the inner circumferential surface of the secondary transfer belt 50, thereby reducing the adhesive force between the secondary transfer roller 52C and the secondary transfer belt 50. This makes it possible to improve the separability between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50 at the terminal end side of the winding region in the circumferential direction of the secondary transfer roller 52C.

[0056] 6, a blower fan 104 is provided as a separation improving section according to a sixth embodiment on the inner side of the secondary transfer belt 50, opposite the winding area of ​​the secondary transfer roller 52C. The blower fan 104 is a cooling section that blows air toward the secondary transfer roller 52C to cool the outer circumferential surface of the secondary transfer roller 52C. The blower fan 104 has an impeller (not shown) that rotates when driven by a fan motor (not shown).

[0057] According to the separability improving unit of the sixth aspect, the blower fan 104 cools the outer peripheral surface of the secondary transfer roller 52C, thereby lowering the temperature of the toner T on the outer peripheral surface of the secondary transfer roller 52C and reducing the adhesive force (tackiness) of the toner T. This makes it possible to improve the separability between the outer peripheral surface of the secondary transfer roller 52C and the inner peripheral surface of the secondary transfer belt 50 at the terminal end side of the winding region in the circumferential direction of the secondary transfer roller 52C.

[0058] As shown in FIG. 7, a cooling roller 106 is rotatably provided as a separation improving section according to a seventh embodiment at the start end of the winding region of the secondary transfer roller 52C on the inside of the secondary transfer belt 50. The cooling roller 106 is a cooling section that cools the outer circumferential surface of the secondary transfer roller 52C. The cooling roller 106 extends in the front-rear direction and has a known configuration, for example, as disclosed in Japanese Patent Application Laid-Open No. 2016-186342. The interior of the cooling roller 106 is configured so that a refrigerant such as cooling water can be circulated and supplied by driving a pump (not shown). The cooling roller 106 rotates in the same direction and at the same speed as the rotational direction of the secondary transfer roller 52C while in contact with the outer circumferential surface of the secondary transfer roller 52C.

[0059] According to the separability improving unit of the seventh aspect, the cooling roller 106 cools the outer peripheral surface of the secondary transfer roller 52C, thereby lowering the temperature of the toner T on the outer peripheral surface of the secondary transfer roller 52C and reducing the adhesive force of the toner T. This makes it possible to improve the separability between the outer peripheral surface of the secondary transfer roller 52C and the inner peripheral surface of the secondary transfer belt 50 at the terminal end side of the winding region in the circumferential direction of the secondary transfer roller 52C.

[0060] As shown in FIG. 7 , a cooling plate 108 is provided as a separation improvement section according to the eighth aspect on the inner side of the secondary transfer belt 50, at the end of the winding region of the secondary transfer roller 52C. The cooling plate 108 is a cooling section that cools the inner circumferential surface of the secondary transfer belt 50. The cooling plate 108 extends in the front-to-rear direction and has a known configuration, for example, as disclosed in Japanese Patent Application Laid-Open No. 2014-178582. The inside of the cooling plate 108 is configured so that a refrigerant such as cooling water can be circulated and supplied by driving a pump. The cooling plate 108 is in contact with or close to the inner circumferential surface of the secondary transfer belt 50.

[0061] According to the separability improving unit of the eighth aspect, the cooling plate 108 cools the inner circumferential surface of the secondary transfer belt 50, thereby lowering the temperature of the toner T on the inner circumferential surface of the secondary transfer belt 50 and reducing the adhesive force of the toner T. This improves the separability between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50 at the terminal end side of the winding region in the circumferential direction of the secondary transfer roller 52C.

[0062] The control configuration of the image forming apparatus 10 according to this embodiment will be described with reference to Fig. 8. Fig. 8 is a control block diagram of the image forming apparatus 10 according to this embodiment.

[0063] 8, the image forming apparatus 10 includes a control unit 110 that controls the image forming unit 24, the primary transfer unit 38, the secondary transfer unit 48, the fixing unit 54, etc. The control unit 110 controls at least one of the separation improvement units 78 in the secondary transfer unit 48. The control unit 110 is responsible for controlling the entire image forming apparatus 10. The control unit 110 includes a CPU (Central Processing Unit) 112, a ROM (Read Only Memory) 114, and a RAM (Random Access Memory) 116. A storage unit 118 and a communication unit 120 are connected to the control unit 110.

[0064] The CPU 112 performs overall control of the overall operation of the image forming apparatus 10. The CPU 112 reads out various control programs and setting data stored in the ROM 114, stores them in the RAM 116, and executes the programs to perform various arithmetic processing. The RAM 116 provides the CPU 112 with working memory space and stores temporary data. Furthermore, when performing various arithmetic processing, the CPU 112 refers to various data stored in the storage unit 118. The storage unit 118 is configured, for example, by a non-volatile semiconductor memory or a hard disk drive.

[0065] The control unit 110 transmits and receives various data to and from an external device (e.g., a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 120. The control unit 110 receives image data transmitted from, for example, an external device, and forms a toner image on paper P based on this image data (input image data). The communication unit 120 is configured by, for example, a communication control card such as a LAN card.

[0066] According to the configuration of the image forming apparatus 10 of this embodiment, the innermost layer of the secondary transfer belt 50 is a portion that does not contain organic fluorine compounds. The outermost layer of each support roller 52 is a portion that does not contain organic fluorine compounds. Therefore, organic fluorine compounds do not flow out from the secondary transfer unit 48 to the outside of the image forming apparatus 10, thereby reducing the environmental impact.

[0067] According to the configuration of the image forming apparatus 10 of this embodiment, the secondary transfer unit 48 has a separation improvement portion 78 that improves the separation between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50. Therefore, the separation between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50 can be improved at the end side of the winding area in the circumferential direction of the secondary transfer roller 52C. This suppresses uneven pitch in the image and malfunction of the secondary transfer belt 50, enabling stable image formation.

[0068] In particular, when the outermost layer of the secondary transfer roller 52C is made of solid rubber, solid resin, or metal, it is possible to reduce the contact area between the secondary transfer roller 52C and the toner T. This makes it possible to further improve the separability between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50.

[0069] Furthermore, when the outermost layer of the secondary transfer roller 52C is electrically grounded, the inner circumferential surface of the secondary transfer belt 50 can be neutralized to reduce the electrostatic adhesion between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50. This further improves the separability between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50.

[0070] That is, according to this embodiment, it is possible to reduce the environmental load while suppressing uneven image pitch and malfunction of the secondary transfer belt 50, thereby performing stable image formation.

[0071] In particular, the support roller 52 targeted for improving the separability from the secondary transfer belt 50 (hereinafter referred to as the support roller 52 targeted for separation) is the support roller 52 (52C) ​​having the largest outer peripheral surface area among the multiple support rollers 52. In other words, the secondary transfer unit 48 targets the support roller 52 (52C) ​​that has a large contact area with the secondary transfer belt 50 and tends to have a large adhesive force with the secondary transfer belt 50 as the support roller 52 targeted for separation. Therefore, according to this embodiment, malfunctions of the secondary transfer belt 50 can be efficiently suppressed, enabling more stable image formation.

[0072] The support roller 52 to be separated is the secondary transfer roller 52C that cooperates with the intermediate transfer belt 40 to hold the paper P. In other words, the secondary transfer unit 48 uses the support roller 52 (52C) ​​that directly affects image quality as the support roller 52 to be separated. Therefore, according to this embodiment, uneven pitch in the image can be efficiently suppressed, enabling more stable image formation.

[0073] Furthermore, according to the configuration of the image forming apparatus 10 of this embodiment, the secondary transfer belt 50 contains an ion conductive agent. Therefore, by setting the resistance uniformity of the secondary transfer belt 50 to a high level, discharge is less likely to occur. As a result, according to this embodiment, the occurrence of white spots (white spots) in images can be suppressed, thereby improving image quality.

[0074] (Variation) A modification of this embodiment will be described with reference to FIGS.

[0075] As shown in FIG. 8, the control unit 110 controls the separation improvement unit 78 and the like as needed to enhance the function of improving the separability between the outer circumferential surface of the secondary transfer roller 52C and the inner circumferential surface of the secondary transfer belt 50 (hereinafter referred to as the separation improvement function). "Enhancing the separation improvement function" means to exert the separation improvement function. By enhancing the separation improvement function as needed, it is possible to reduce the power consumption associated with the separation improvement function and achieve energy conservation in the image forming apparatus 10. Specifically, the control unit 110 controls the separation improvement unit 78 and the like in the following manner.

[0076] The control unit 110 may control the separation improvement unit 78 etc. to strengthen the effect of improving separation when the environmental temperature is higher than a predetermined temperature (for example, 27°C) compared to when the environmental temperature is lower than the predetermined temperature. Furthermore, the control unit 110 may control the separation improvement unit 78 etc. to strengthen the effect of improving separation when the temperature of the secondary transfer unit 48 is higher than a predetermined temperature (for example, 50°C) compared to when the temperature of the secondary transfer unit 48 is lower than the predetermined temperature.

[0077] 2 and 8, when the cumulative usage period of the secondary transfer roller 52C is longer than a predetermined period, the control unit 110 may control the separation improvement unit 78 etc. to strengthen the separation improvement effect compared to when the cumulative usage period of the secondary transfer roller 52C is shorter than the predetermined period. The cumulative usage period of the secondary transfer roller 52C is meant to include a period that corresponds to (substitutes for) the cumulative usage period of the secondary transfer roller 52C.

[0078] The control unit 110 may control the separation improvement unit 78 etc. to strengthen the separation improvement effect when the cumulative usage period of the secondary transfer belt 50 is longer than a predetermined period, compared to when the cumulative usage period of the secondary transfer belt 50 is shorter than the predetermined period. The cumulative usage period of the secondary transfer belt 50 is meant to include a period corresponding to the cumulative usage period of the secondary transfer belt 50.

[0079] When the cumulative usage amount of toner T (see FIG. 3, etc.) is greater than a predetermined usage amount, the control unit 110 may control the separability improving unit 78, etc. to strengthen the separability improving effect compared to when the cumulative usage amount of toner T is less than the predetermined usage amount. The cumulative usage amount of toner T is meant to include the period corresponding to the cumulative usage amount of toner T. The control unit 110 may estimate the cumulative usage amount of toner T based on the size and coverage of the paper P.

[0080] The secondary transfer unit 48 and the control unit 110 have the following configuration in order to enhance the separation performance improvement effect of the separation performance improvement unit 78 and the like.

[0081] 3 and 8, the secondary transfer unit 48 may have a movement mechanism (not shown) that moves a separation claw 78, which serves as a separation performance improving unit according to the first embodiment, in a direction toward or away from the outer circumferential surface of the secondary transfer roller 52C. The movement mechanism has a known configuration, for example, as shown in JP 2023-28024 A or JP 2022-214544 A. When the separation performance improving effect of the separation claw 78 is to be strengthened, the control unit 110 may control the movement mechanism to move the separation claw 78 in a direction toward the outer circumferential surface of the secondary transfer roller 52C.

[0082] 4 and 8, the secondary transfer unit 48 may have a movement mechanism (not shown) that moves a cleaning blade 82, which serves as a separation improvement unit according to the second embodiment, in a direction toward or away from the outer circumferential surface of the secondary transfer roller 52C. The movement mechanism has a known configuration, for example, as shown in JP 2023-28024 A or JP 2022-214544 A. When the separation improvement effect of the cleaning blade 82 is to be strengthened, the control unit 110 may control the movement mechanism to move the cleaning blade 82 in a direction toward the outer circumferential surface of the secondary transfer roller 52C.

[0083] The application unit 84 serving as the separability improving unit according to the third embodiment may be configured to be able to adjust the rotation speed of the brush roller 88. When the effect of improving the separability by the application unit 84 is to be strengthened, the control unit 110 controls the brush motor to increase the rotation speed of the brush roller 88.

[0084] 5 and 8, the secondary transfer unit 48 may have a movement mechanism (not shown) that moves a cleaning blade 94, which serves as a separation improvement unit according to the fourth aspect, in a direction toward or away from the outer circumferential surface of a predetermined support roller 52. The movement mechanism has a known configuration, for example, as shown in JP 2023-28024 A or JP 2022-214544 A. When the separation improvement effect of the cleaning blade 94 is to be strengthened, the control unit 110 may control the movement mechanism to move the cleaning blade 94 in a direction toward the outer circumferential surface of a predetermined support roller 52.

[0085] The application unit 96 as the separability improving unit according to the fifth embodiment may be configured to be able to adjust the rotation speed of the brush roller 100. When the effect of improving the separability by the application unit 96 is to be strengthened, the control unit 110 controls the brush motor to increase the rotation speed of the brush roller 100.

[0086] 6 and 8, the blower fan 104 serving as the separation improvement unit according to the sixth embodiment may be configured to have an adjustable fan rotation speed. When the separation improvement effect of the blower fan 104 is to be strengthened, the control unit 110 may control the blower fan 104 to increase the fan rotation speed.

[0087] 7 and 8, the circulation speed of the refrigerant inside the cooling roller 106 serving as the separation improvement part according to the seventh embodiment may be adjustable. When the separation improvement effect of the cooling roller 106 is to be strengthened, the control unit 110 may control the pump to increase the circulation speed of the refrigerant inside the cooling roller 106.

[0088] The circulation speed of the coolant inside the cooling plate 108 as the separation improvement part according to the eighth aspect may be adjustable. When the separation improvement effect of the cooling plate 108 is to be strengthened, the control unit 110 may control the pump to increase the circulation speed of the coolant inside the cooling plate 108.

[0089] Although the present embodiment has been specifically described above, the present invention is not limited to the specific embodiment described above. For example, instead of using the secondary transfer roller 52C as the support roller 52 to be separated in the secondary transfer unit 48, a support roller 52 other than the secondary transfer roller 52 may be used as the support roller 52 to be separated. In addition, various modifications and changes can be made to the specific example described in the above embodiment within the scope of the gist of the present invention as set forth in the claims. [Industrial Applicability]

[0090] The present invention is useful as an image forming apparatus that can perform stable image formation by suppressing uneven image pitch and malfunction of the secondary transfer belt while reducing the environmental load. [Explanation of symbols]

[0091] 10 Image forming device 12 Device body 24 Image forming unit 26 Image forming unit 26Y Image forming unit 26M Image Forming Unit 26C Image forming unit 26K Image Formation Unit 28 Photosensitive drum 30 Charging section 32 Exposure section 34 Development section 36 Drum Cleaning Section 38 Primary transfer unit 40 Intermediate transfer belt 42 Support roller 44 Primary transfer roller 46 Belt cleaning section 48 Secondary transfer unit 50 Secondary transfer belt 52 Support roller 52C Secondary Transfer Roller 52D drive roller 52S steering roller 54 Fixing section 56 Heating Roller 58 Fuser roller 60 Fixing belt 62 Pressure roller 72 Main transport route 74 Zystrola vs. 76 Reversing conveyance path 78 Separation claw (separation improvement part) 80 Rotation axis 82 Cleaning blade (separation improvement part, cleaning part) 84 Application section (separability improvement section) 86 Holder 88 Brush Roller 90 Elastic member 92 Leveling Blade 94 Cleaning blade (separability improvement part, cleaning part) 96 Application section (separability improvement section) 98 Holder 100 brush rollers 102 Elastic member 104 Blower fan (separation improvement section, cooling section) 106 Cooling roller (separability improvement section, cooling section) 108 Cooling plate (separation improvement section, cooling section) 110 control section 112 CPU 114 ROM 116 RAM 118 Storage section 120 Communications Department CN Primary Transfer Nip TN Secondary Transfer Nip FN Fixing Nip P Paper (recording medium) T Toner L Lubricant SL Solid Lubricant

Claims

1. an image carrier that carries a toner image; a transfer unit capable of holding a recording medium in cooperation with the image carrier, for transferring a toner image on the image carrier to the recording medium; The transfer unit includes: a rotatable endless transfer belt; a plurality of rotatable support rollers on which the transfer belt is supported, At least the inner peripheral portion of the transfer belt and the outer peripheral portions of each support roller are portions that do not contain organic fluorine compounds, a separation improvement portion that improves separation between an outer circumferential surface of at least one of the plurality of support rollers and an inner circumferential surface of the transfer belt; Image forming device.

2. the separation improvement portion improves separation between an outer circumferential surface of any one of the support rollers and an inner circumferential surface of the transfer belt at a terminal end side of a winding region for winding the transfer belt around the any one of the support rollers in the circumferential direction. The image forming apparatus according to claim 1 .

3. the transfer belt contains an ion conductive agent; The image forming apparatus according to claim 1 .

4. the transfer belt is made up of a plurality of layers, and the thickest layer of the plurality of layers contains an ion conductive agent; The image forming apparatus according to claim 3 .

5. the separation performance improving portion is a separation claw that can come into contact with the inner circumferential surface of the transfer belt at a terminal end side of the winding region of any one of the support rollers. The image forming apparatus according to claim 2 .

6. the separation improvement unit is a cleaning unit that cleans the outer circumferential surface of any one of the support rollers or the inner circumferential surface of the transfer belt. The image forming apparatus according to claim 1 .

7. the separation improvement unit is an application unit that applies a lubricant to an outer circumferential surface of any one of the support rollers or an inner circumferential surface of the transfer belt. The image forming apparatus according to claim 1 .

8. the separation improvement unit is a cooling unit that cools the outer circumferential surface of any one of the support rollers or the inner circumferential surface of the transfer belt. The image forming apparatus according to claim 1 .

9. the separation improvement unit enhances the effect of improving the separation between the outer circumferential surface of any one of the support rollers and the inner circumferential surface of the transfer belt when the environmental temperature or the temperature of the transfer unit is high, compared to when the environmental temperature or the temperature of the transfer unit is low. The image forming apparatus according to claim 1 .

10. the separation improvement unit enhances the effect of improving the separation between the outer circumferential surface of the support roller and the inner circumferential surface of the transfer belt when the cumulative usage period of either the support roller or the transfer belt is long, compared to when the cumulative usage period is short. The image forming apparatus according to claim 1 .

11. the separation improvement unit enhances the effect of improving the separation between the outer circumferential surface of any one of the support rollers and the inner circumferential surface of the transfer belt when the cumulative amount of toner used is large, compared to when the cumulative amount of toner used is small. The image forming apparatus according to claim 1 .

12. Any one of the support rollers is a support roller having the largest outer peripheral surface area among the plurality of support rollers, The image forming apparatus according to claim 1 .

13. The outer periphery of any of the support rollers is made of solid rubber, solid resin, or metal. The image forming apparatus according to claim 1 .

14. The outer periphery of any one of the support rollers is electrically grounded. The image forming apparatus according to claim 1 .

15. any one of the support rollers is a transfer roller that cooperates with the image carrier to hold the recording medium via the transfer belt; The image forming apparatus according to claim 1 .

Images