JP2013152281A - Transfer roll and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer roll configured to prevent vibration to be generated when a recording medium enters in a transfer section.SOLUTION: The transfer roll includes a shaft body 63; a cover body 64 formed of a material containing air bubble, showing a cylindrical shape and covering the shaft body 63; and a meeting line 65 formed on the cover body 64, having air bubble of diameter smaller than the surroundings in the cover body 64, and formed in a linear shape so as to form an angle with an axial direction in side view.

Description

  The present invention relates to a transfer roll and an image forming apparatus.

  Patent Document 1 describes a technique in which a liquid foam containing bubbles formed by a mechanical floss method is injected into a mold cavity to form an elastic layer around a shaft.

  In Patent Document 2, as shown in FIG. 1, in a transfer roller 1 including a shaft 2 and an elastic layer 3 formed on the outer periphery of the shaft 2, a rubber component made of epichlorohydrin rubber and acrylonitrile butadiene rubber is 100 mass. A rubber composition comprising carbon black and 5 to 30 parts by mass of 4,4′-oxybisbenzenesulfonyl hydrazide (OBSH) is used for the elastic layer 3 with respect to the part, and the elastic layer 3 is 50 to 200 μm. A technique for having a cell diameter is described.

JP 2006-116793 A JP 2007-293086 A

  An object of the present invention is to provide a transfer roll that suppresses vibration caused by a recording medium entering a transfer portion.

  The transfer roll according to claim 1 of the present invention is composed of a shaft body, a material having air bubbles inside, is formed in a cylindrical shape, covers the shaft body, and is formed on the cover body. And a small-diameter bubble portion that is linearly formed so as to form an angle with respect to the axial direction in a side view of the covering body.

  A transfer roll according to a second aspect of the present invention is the transfer roll according to the first aspect, wherein the covering body is covered with the shaft body in a twisted state.

  The transfer roll according to a third aspect of the present invention is the transfer roll according to the first or second aspect, wherein the small diameter bubble portion extends in the axial direction at any position in the circumferential direction of the cover. The shaft body is covered in a twisted state so as not to appear in two or more places.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: a holder on which an electrostatic latent image is formed; a developing device that develops the electrostatic latent image formed on the holder with toner; And a transfer device having the transfer roll according to any one of claims 1 to 3 for transferring the toner image onto a recording medium.

  According to the transfer roll of the first aspect of the present invention, the vibration generated by the recording medium entering the transfer portion is more pronounced than in the case where the small diameter bubble portion is formed linearly along the axial direction in the covering. Can be suppressed.

  According to the transfer roll of claim 2 of the present invention, the small diameter bubble portion is formed in a straight line along the axial direction as compared with the case where the shaft body is not covered in a twisted state. It is possible to easily form the small-diameter bubble portion with respect to the body so as to form an angle with respect to the axial direction.

  According to the transfer roll described in claim 3 of the present invention, compared to the case where the shaft body is coated in a state where the cover body is twisted so that two or more small diameter bubble portions appear in the axial direction, in the transfer portion. It is possible to suppress vibration caused by the entry of the recording medium.

  According to the image forming apparatus of claim 4 of the present invention, an image having an excellent image quality can be used as a recording medium as compared with the case where the transfer apparatus having the transfer roll according to any one of claims 1 to 3 is not provided. Can be formed.

1 is a diagram illustrating a configuration of an image forming apparatus according to the present invention. It is a figure which shows the structure of the image forming unit of FIG. It is a figure which shows the structure of the secondary transfer roll of 1st Embodiment which concerns on this invention. It is a figure which shows the structure of the metal mold | die apparatus used for manufacture of the coating body of the secondary transfer roll of 1st Embodiment. It is a figure which shows the structure of the coating body manufactured by the metal mold | die apparatus of FIG. It is a figure which shows the structure of the secondary transfer roll as a comparative example with respect to the secondary transfer roll of 1st Embodiment. It is a figure which shows the aspect of the secondary transfer in a secondary transfer part at the time of employ | adopting the secondary transfer roll as a comparative example with respect to the secondary transfer roll of 1st Embodiment for a transfer apparatus. It is a figure which shows the assembly aspect of the secondary transfer roll of 1st Embodiment. It is a figure which shows the structure of the secondary transfer roll of 2nd Embodiment which concerns on this invention. It is a figure which shows the structure of the discharge head used for manufacture of the coating body of the secondary transfer roll of 2nd Embodiment. It is a figure which shows the structure of the coating body manufactured using the discharge head of FIG. It is a figure which shows the structure of the secondary transfer roll as a comparative example with respect to the secondary transfer roll of 2nd Embodiment. It is a figure which shows the aspect of the secondary transfer in a secondary transfer part at the time of employ | adopting the secondary transfer roll as a comparative example with respect to the secondary transfer roll of 2nd Embodiment to a transfer apparatus. It is a figure which shows the assembly aspect of the secondary transfer roll of 2nd Embodiment.

  Hereinafter, an example of an embodiment of a transfer roll and an image forming apparatus according to the present invention will be described with reference to the accompanying drawings.

(overall structure)
The image forming apparatus 10 according to the present invention forms a full-color image or a black-and-white image. As shown in FIG. 1, the image forming apparatus 10 accommodates a first processing unit constituting a horizontal one side (left side in FIG. 1). The first housing 10A, and the second housing 10B that is detachably connected to the first housing 10A and that houses the second processing unit that forms the horizontal direction + side (right side in FIG. 1). I have.

  An image signal processing unit 13 that performs image processing on image data sent from an external device such as a computer is provided on the second housing 10B.

  On the other hand, the first special color (V), second special color (W), yellow (Y), magenta (M), cyan (C), and black (K) toners are provided on the upper portion of the first housing 10A. Toner cartridges 14V, 14W, 14Y, 14M, 14C, and 14K are provided so as to be replaceable along the horizontal direction.

  The first special color and the second special color are appropriately selected from colors other than yellow, magenta, cyan, and black (including transparency). In the following description, the first special color (V), the second special color (W), yellow (Y), magenta (M), cyan (C), and black (K) are distinguished for each component. Is described with a letter followed by any letter of V, W, Y, M, C, or K. The first special color (V), the second special color (W), yellow (Y), magenta When not distinguishing (M), cyan (C), and black (K), V, W, Y, M, C, and K are omitted.

  Further, under the toner cartridge 14, six image forming units 16 corresponding to the respective color toners are provided along the horizontal direction so as to correspond to the respective toner cartridges 14.

  An exposure device 40 provided for each image forming unit 16 receives the image data subjected to the image processing by the image signal processing unit 13 from the image signal processing unit 13 and modulates the light beam L according to the image data. Is applied to the photosensitive drum 18 described below (see FIG. 2).

  As shown in FIG. 2, each image forming unit 16 includes a photosensitive drum 18 as an example of an image holding member that is rotationally driven in one direction (clockwise direction in FIG. 2). By irradiating each photoconductor drum 18 with the light beam L from each exposure device 40, an electrostatic latent image is formed on each photoconductor drum 18.

  Around each photosensitive drum 18, an electrostatic latent image formed on the photosensitive drum 18 by the corona discharge method (non-contact charging method) scorotron charger 20 that charges the photosensitive drum 18 and the exposure device 40 is displayed. A developing device 22 for developing with the developer, a blade 24 as a removing member for removing the developer remaining on the photosensitive drum 18 after the transfer, and a static elimination that performs neutralization by irradiating light to the photosensitive drum 18 after the transfer. A device 26 is provided.

  The scorotron charger 20, the developing device 22, the blade 24, and the charge removal device 26 are arranged in this order from the upstream side to the downstream side in the rotation direction of the photosensitive drum 18 so as to face the surface of the photosensitive drum 18. .

  The developing device 22 includes a developer accommodating member 22A that accommodates a developer G containing toner, and a developing roll 22B that supplies the developer G accommodated in the developer accommodating member 22A to the photosensitive drum 18. Has been. The developer accommodating member 22A is connected to the toner cartridge 14 (see FIG. 1) through a toner supply path (not shown), and the toner is supplied from the toner cartridge 14.

  As shown in FIG. 1, a transfer device 32 is provided below each image forming unit 16. The transfer device 32 is primarily transferred to the transfer belt 34 in contact with each photoconductor drum 18, a primary transfer roll 36 that primarily transfers the toner image formed on each photoconductor drum 18 to the transfer belt 34, and the transfer belt 34. And a secondary transfer roll 62 as an example of a transfer roll for secondary transfer of the toner image onto a recording medium P such as paper.

  The transfer belt 34 is formed in an annular shape, and is driven by a motor (not shown), a tension applying roll 41 that applies tension to the transfer belt 34, an opposing roll 42 that faces the secondary transfer roll 62, and a plurality of The roll 44 is wound around and is circulated and moved in one direction (counterclockwise direction in FIG. 1) by the drive roll 38.

  Each primary transfer roll 36 is disposed opposite to the photosensitive drum 18 of each image forming unit 16 with the transfer belt 34 interposed therebetween. Further, a transfer voltage having a polarity opposite to the toner polarity is applied to the primary transfer roll 36 by a power supply unit (not shown). With this configuration, the toner image formed on the photosensitive drum 18 is transferred to the transfer belt 34.

  A cleaning device 46 for cleaning the outer peripheral surface of the transfer belt 34 is provided in the vicinity of the drive roll 38.

  Below the transfer device 32, two recording medium accommodating portions 48 for accommodating a recording medium P such as paper are provided along the horizontal direction.

  Each recording medium accommodating portion 48 can be pulled out from the first housing 10A. Above one end side (the right side in FIG. 1) of each recording medium container 48, a delivery roll 52 that sends the recording medium P from each recording medium container 48 to the transport path 60 is provided.

  In each recording medium accommodating portion 48, a bottom plate 50 on which the recording medium P is placed is provided. The bottom plate 50 is lowered by an instruction of a control unit (not shown) when the recording medium accommodating portion 48 is pulled out from the first housing 10A. When the bottom plate 50 is lowered, a space in which the user replenishes the recording medium P is formed in the recording medium accommodating portion 48.

  When the recording medium accommodating portion 48 pulled out from the first housing 10A is attached to the first housing 10A, the bottom plate 50 is raised by an instruction from the control means. As the bottom plate 50 moves up, the uppermost recording medium P placed on the bottom plate 50 and the delivery roll 52 come into contact with each other.

  On the downstream side in the recording medium conveyance direction of the delivery roll 52 (hereinafter sometimes simply referred to as “downstream side”), a separation roll 56 that separates the recording media P delivered from the recording medium accommodating portion 48 one by one. Is provided. A plurality of transport rolls 54 that transport the recording medium P downstream in the transport direction are provided on the downstream side of the separation roll 56.

  The conveyance path 60 provided between the recording medium container 48 and the transfer device 32 folds the recording medium P sent out from the recording medium container 48 to the left side in FIG. It extends to the secondary transfer portion T between the secondary transfer roll 62 and the opposing roll 42 so as to be folded back to the right side in FIG.

  The secondary transfer roll 62 is applied with a transfer voltage having a polarity opposite to the toner polarity by a power supply unit (not shown). With this configuration, each color toner image primarily transferred to the transfer belt 34 is secondarily transferred to the recording medium P transported along the transport path 60 by the secondary transfer roll 62. Details of the configuration of the secondary transfer roll 62 will be described later.

  A preliminary path 66 extending from the side surface of the first housing 10 </ b> A is provided so as to join the second folding portion 60 </ b> B of the transport path 60. The recording medium P sent out from another recording medium accommodating portion (not shown) arranged adjacent to the first housing 10 </ b> A enters the conveyance path 60 through the spare path 66.

  On the downstream side of the secondary transfer portion T, a plurality of conveying belts 70 that convey the recording medium P on which the toner image has been transferred toward the second casing 10B are provided in the first casing 10A. A transport belt 80 that transports the transported recording medium P to the downstream side is provided in the second casing 10B.

  Each of the plurality of conveyor belts 70 and the conveyor belt 80 is formed in an annular shape and is wound around a pair of rolls 72. The pair of rolls 72 are respectively arranged on the upstream side and the downstream side in the conveyance direction of the recording medium P, and when one of them is rotated, the conveyance belt 70 (conveyance belt 80) is rotated in one direction (clockwise in FIG. 1). Direction). A suction device (not shown) that sucks the recording medium P is provided inside the conveying belt 70 and the conveying belt 80, and the conveying belt 70 and the conveying belt 80 convey the recording medium P while adsorbing the recording medium P to the surface. It has become.

  A fixing unit 82 for fixing the toner image transferred onto the surface of the recording medium P to the recording medium P with heat and pressure is provided on the downstream side of the conveyance belt 80.

  The fixing unit 82 includes a fixing belt 84 and a pressure roll 88 disposed so as to contact the fixing belt 84 from below. A fixing unit N is formed between the fixing belt 84 and the pressure roll 88 to fix the toner image by pressurizing and heating the recording medium P.

  The fixing belt 84 is formed in an annular shape and is wound around the drive roll 89 and the driven roll 90. The drive roll 89 faces the pressure roll 88 from above, and the driven roll 90 is disposed above the drive roll 89.

  Each of the driving roll 89 and the driven roll 90 includes a heating unit such as a halogen heater. As a result, the fixing belt 84 is heated.

  On the downstream side of the fixing unit 82, a conveyance belt 108 for conveying the recording medium P sent out from the fixing unit 82 to the downstream side is provided. The conveyor belt 108 is formed in the same manner as the conveyor belt 70.

  A cooling unit 110 that cools the recording medium P heated by the fixing unit 82 is provided on the downstream side of the conveyance belt 108.

  The cooling unit 110 includes an absorption device 112 that absorbs the heat of the recording medium P, and a pressing device 114 that presses the recording medium P against the absorption device 112. The absorption device 112 is disposed on one side (upper side in FIG. 1) with respect to the conveyance path 60, and the pressing device 114 is disposed on the other side (lower side in FIG. 1).

  The absorption device 112 includes an annular absorption belt 116 that contacts the recording medium P and absorbs the heat of the recording medium P. The absorption belt 116 is wound around a driving roll 120 that transmits a driving force to the absorption belt 116 and a plurality of rolls 118.

  A heat sink 122 made of an aluminum material that dissipates heat absorbed by the absorption belt 116 by contacting the absorption belt 116 in a planar shape is provided on the inner peripheral side of the absorption belt 116.

  Further, a fan 128 for removing heat from the heat sink 122 and discharging hot air to the outside is disposed on the back side of the second housing 10B (the back side of the paper surface shown in FIG. 1).

  The pressing device 114 that presses the recording medium P against the absorbing device 112 includes an annular pressing belt 130 that conveys the recording medium P while pressing the recording medium P against the absorbing belt 116. The pressing belt 130 is wound around a plurality of rolls 132.

  On the downstream side of the cooling unit 110, there is provided a correction device 140 that conveys the recording medium P and corrects the curl of the recording medium P.

  An in-line sensor 200 that detects a toner density defect, an image defect, an image position defect, and a position and shape of the recording medium P of the toner image fixed on the recording medium P is provided on the downstream side of the correction device 140. .

  On the downstream side of the inline sensor 200, a discharge roll 198 is provided for discharging the recording medium P having an image formed on one side thereof to a discharge unit 196 attached to the side surface of the second housing 10B.

  On the other hand, when images are formed on both sides, the recording medium P sent from the inline sensor 200 is conveyed to a reversing path 194 provided on the downstream side of the inline sensor 200.

  The reversing path 194 includes a branch path 194A that branches from the transport path 60, a paper transport path 194B that transports the recording medium P transported along the branch path 194A toward the first housing 10A, and a paper transport path. A reversing path 194C is provided for turning the recording medium P conveyed along 194B in the reverse direction to switch back and reversing it.

  With this configuration, the recording medium P that is switched back and conveyed by the reversing path 194C is conveyed toward the first housing 10A, and further enters the conveyance path 60 provided above the recording medium container 48, so that the secondary medium It is sent again to the transfer part T.

  Next, an image forming process of the image forming apparatus 10 will be described.

  The image data that has been subjected to image processing by the image signal processing unit 13 is sent to each exposure device 40. In each exposure device 40, each light beam L is emitted according to the image data, and exposed to each photosensitive drum 18 charged by the scorotron charger 20, thereby forming an electrostatic latent image.

  The electrostatic latent image formed on the photosensitive drum 18 is developed by the developing device 22 and is first special color (V), second special color (W), yellow (Y), magenta (M), cyan (C ) And black (K) toner images are formed.

  The toner images of the respective colors formed on the photosensitive drums 18 of the image forming units 16V, 16W, 16Y, 16M, 16C, and 16K are transferred to the transfer belt 34 by six primary transfer rolls 36V, 36W, 36Y, 36M, 36C, and 36K. The primary transfer is performed sequentially.

  The toner images of the respective colors that have been primary-transferred multiple times onto the transfer belt 34 are secondarily transferred onto the recording medium P conveyed from the recording medium container 48 by the secondary transfer roll 62. The recording medium P onto which the toner image has been transferred is transported toward the fixing unit 82 provided inside the second housing 10B by the transport belt 70.

  The toner images of the respective colors on the recording medium P are fixed on the recording medium P by being heated and pressurized by the fixing unit 82. Further, the recording medium P on which the toner image is fixed is cooled by passing through the cooling unit 110 and then sent to the correction device 140 to correct the curvature generated in the recording medium P.

  The recording medium P whose curvature is corrected is discharged to the discharge unit 196 by the discharge roll 198 after an image defect or the like is detected by the in-line sensor 200.

  On the other hand, when an image is formed on a non-image surface where no image is formed (in the case of double-sided printing), after passing through the inline sensor 200, the recording medium P is reversed by the reversing path 194 and above the recording medium container 48. And a toner image is formed on the back surface according to the above-described procedure.

  In the image forming apparatus 10, components for forming images of the first special color and the second special color (image forming units 16V and 16W, exposure devices 40V and 40W, toner cartridges 14V and 14W, primary transfer rolls 36V and the like). 36W) is configured to be attachable to the first housing 10A as an additional part by the user's selection. Accordingly, the image forming apparatus 10 does not include a part for forming the first special color and second special color images, and the image of any one of the first special color and the second special color. It is good also as a structure which has the components for forming.

(Secondary transfer roll)
(First embodiment)
Next, the configuration of the secondary transfer roll 62 according to the first embodiment of the present invention will be described.

  FIG. 3 shows the configuration of the secondary transfer roll 62 of the first embodiment.

  As shown in FIG. 3, the secondary transfer roll 62 according to the first embodiment includes, for example, a foam material such as urethane foam (with air bubbles inside) on a shaft body 63 made of a metal material such as aluminum or steel. A cylindrical covering 64 made of a material is covered. The covering 64 is an example of a linear small-diameter bubble portion that is a joint (described later) of the foamable material at the time of manufacture, and in which the cell diameter (bubble diameter) of the foamable material is smaller than the surroundings. The meet line 65 is formed. The meet line 65 is formed so as to form an angle with respect to the axial direction in a side view of the covering body 64, that is, in a spiral shape.

  FIG. 4 shows a configuration of a mold apparatus 73 used for manufacturing the covering body 64 of the secondary transfer roll 62 according to the first embodiment. 4A shows a longitudinal section of the mold apparatus 73, and FIG. 4B shows a transverse section of the mold apparatus 73. As shown in FIG.

  As shown in FIG. 4, the mold apparatus 73 includes a dummy core 74 and a mold 76 that forms a cylindrical cavity 75 with the dummy core 74 positioned at the center. In the lower wall of the mold 76, an injection port 77 for injecting into the cavity 75 a liquid foam (a mixture of gas in a liquid resin and dispersing bubbles) that is the basis of the foamable material is formed. Yes. The dummy core 74 is preliminarily coated with a release agent for improving releasability from the foamable material.

  The covering body 64 is manufactured using this mold apparatus 73. Specifically, first, a liquid foam is injected into the cavity 75 from the injection port 77, and the cavity 75 is filled with the liquid foam. Next, the mold apparatus 73 is placed in an appropriate heat treatment furnace (not shown) to heat the liquid foam and promote the curing reaction. After completion of the curing reaction, the mold is opened and the dummy core 74 is removed to obtain a cylindrical covering 64 made of a foamable material.

  When the liquid foam is injected from the injection port 77, as shown in FIG. 4B, the liquid foam is filled into the cavity 75 so as to go around the dummy core 74 from two directions. That is, a seam where liquid foams from two directions merge on the opposite side of the injection port 77 is formed along the axial direction.

  FIG. 5 shows the configuration of the covering 64 manufactured by the mold apparatus 73. FIG. 5A shows a longitudinal section of the covering body 64, and FIG. 5B shows a transverse section of the covering body 64.

  As shown in FIG. 5, a meat line 65 derived from the joint where the liquid foam joins is formed linearly along the axial direction on the covering 64. When the characteristics of the foamable material in the meet line 65 are analyzed, the cell diameter of the foamable material in the meet line 65 is smaller than the surrounding cell diameter, and the hardness of the foamable material in the meet line 65 is higher than the ambient hardness. It was discovered.

  FIG. 6 shows a configuration of a secondary transfer roll 92 as a comparative example with respect to the secondary transfer roll 62 of the first embodiment.

  As shown in FIG. 6, the secondary transfer roll 92 as a comparative example is configured by covering a shaft body 63 with a covering body 64, similarly to the secondary transfer roll 62 of the first embodiment. In 64, a meet line 65 is formed linearly along the axial direction.

  FIG. 7 shows a mode of secondary transfer in the secondary transfer portion T when a secondary transfer roll 92 as a comparative example is adopted in the transfer device 32.

  As shown in FIG. 7, in the secondary transfer portion T, the secondary transfer roll 92 rotates in synchronization with the movement of the transfer belt 34, and the cover 64 of the secondary transfer roll 92 extends along the axial direction. When the recording medium P enters the secondary transfer portion T at a timing when the formed meet line 65 faces the transfer belt 34, vibration (banding) occurs in the transfer belt 34 and the opposing roll 42. This is because the foaming material in the meet line 65 has a higher hardness than the surroundings, and the meet line 65 cannot absorb the impact when the recording medium P enters the secondary transfer portion T. is there. Therefore, when the recording medium P enters the secondary transfer portion T at such a timing, a transfer defect (banding defect) due to vibration occurs in the transfer belt 34 and the opposing roll 42, which causes deterioration in the image quality of the formed image. It becomes.

  On the other hand, in the secondary transfer roll 62 of the first embodiment, the meet line 65 is formed in the cover 64 so as to form an angle with respect to the axial direction in the side view of the cover 64. Are distributed in the circumferential direction. Therefore, in the transfer device 32 having the secondary transfer roll 62 according to the first embodiment, the vibration generated through the meet line 65 when the recording medium P enters the secondary transfer portion T is suppressed, and the transfer caused by the vibration is suppressed. As a result of suppressing the defects, the image quality of the formed image is improved.

  FIG. 8 shows an assembly mode of the secondary transfer roll 62 according to the first embodiment.

  As shown in FIG. 8, the secondary transfer roll 62 according to the first embodiment is assembled by fitting a shaft body 63 into a covering body 64 in which a meet line 65 is formed linearly along the axial direction. When the shaft body 63 is fitted into the covering body 64, the meat line 65 is formed at an angle with respect to the axial direction in the covering body 64 by twisting the covering body 64. That is, by covering the cover body 64 in which the meet line 65 is formed linearly along the axial direction with the cover body 64 being twisted, the meet line 65 is formed in the cover body 64. The secondary transfer roll 62 that forms an angle with respect to the axial direction is assembled.

  Further, the covering body 64 is twisted within a range of less than 360 ° so that the meat line 65 does not appear in two or more locations in the axial direction at any position in the circumferential direction of the covering body 64. Thereby, the meat line 65 can be dispersed without waste in the circumferential direction. Accordingly, vibrations caused by the recording medium P entering the secondary transfer portion T are suppressed. Moreover, the restoring force which tries to return from the state by which the coating | coated body 64 was twisted will be suppressed.

  A primer (adhesive) is applied in advance to the outer peripheral surface of the shaft body 63 so that the cover body 64 is maintained in a twisted state. If the outer diameter of the covering body 64 is shaken by twisting the covering body 64, the outer peripheral surface of the covering body 64 may be polished after the shaft body 63 is fitted into the covering body 64.

(Second Embodiment)
Next, the configuration of the secondary transfer roll 162 according to the second embodiment of the present invention will be described.

  FIG. 9 shows the configuration of the secondary transfer roll 162 of the second embodiment.

  As shown in FIG. 9, the secondary transfer roll 162 of the second embodiment includes, for example, epichlorohydrin rubber (ECO) and nitrile butadiene on a shaft body 163 similar to the shaft body 63 of the secondary transfer roll 62 of the first embodiment. A cylindrical covering 164 made of a foamable material obtained by mixing rubber (NBR) and vulcanizing and foaming is coated. Each of the four meet lines 165 is formed on the cover 164 so as to form an angle with respect to the axial direction in a side view of the cover 164.

  FIG. 10 shows a configuration of the ejection head 173 used for manufacturing the covering 164 of the secondary transfer roll 162 according to the second embodiment. 10A shows a longitudinal section of the ejection head 173, and FIG. 5B shows a transverse section of the ejection head 173. FIG. 10C is a perspective view of the ejection head 173.

  As shown in FIG. 10, the discharge head 173 includes a cylindrical base 174 and a columnar core 175 positioned at the center of the base 174. The core 175 is held on the base 174 by joints 176 extending from four locations (90 ° intervals) on the inner peripheral surface of the base 174.

  The covering body 164 is manufactured using the discharge head 173. Specifically, first, the discharge head 173 is attached to an appropriate extrusion molding machine (not shown), and unvulcanized rubber, which is the base of the foamable material, is discharged through the discharge head 173 to obtain a cylindrical rubber molded product. obtain. Next, this rubber molded product is placed in a suitable processing furnace (not shown) and vulcanized and foamed to obtain a cylindrical covering 164 made of a foamable material.

  FIG. 11 shows the configuration of the covering 164 manufactured using the discharge head 173. FIG. 11A shows a longitudinal section of the covering body 164, and FIG. 11B shows a transverse section of the covering body 164.

  As shown in FIG. 11, four meat lines 165 are formed on the covering 164 in a straight line along the axial direction. The meat lines 165 are formed at 90 ° intervals in the circumferential direction. These four meat lines 165 are not formed when unvulcanized rubber is once split at each of the four joints 176 in the discharge head 173 and discharged from the discharge head 173 while joining after passing through the joints 176. It corresponds to the joint of vulcanized rubber. That is, the number of the meet lines 165 depends on the number of the joints 176. When the core 175 is held by, for example, the three joints 176 in the discharge head 173, the three meet lines 165 are formed on the covering 164. It is formed.

  When the characteristics of the foamable material in the four meat lines 165 of the covering 164 are analyzed, the cell diameter of the foamable material in each meet line 165 is smaller than the surrounding cell diameter, and the foam material in each meet line 165 has a smaller cell diameter. It was found that the hardness was higher than the ambient hardness.

  FIG. 12 shows a configuration of a secondary transfer roll 192 as a comparative example with respect to the secondary transfer roll 162 of the second embodiment.

  As shown in FIG. 12, the secondary transfer roll 192 as a comparative example is configured by covering a shaft body 163 with a covering body 164 in the same manner as the secondary transfer roll 162 of the second embodiment. Four meat lines 165 are formed on the line 164 along the axial direction. The meat lines 165 are formed at 90 ° intervals in the circumferential direction.

  FIG. 13 shows a mode of secondary transfer in the secondary transfer portion T when a secondary transfer roll 192 as a comparative example is employed in the transfer device 32.

  As shown in FIG. 13, in the secondary transfer portion T, the secondary transfer roll 192 rotates in synchronization with the movement of the transfer belt 34, and the cover 164 of the secondary transfer roll 192 extends along the axial direction. When the recording medium P enters the secondary transfer portion T at a timing when any one of the four meet lines 165 formed faces the transfer belt 34, the transfer belt 34 and the opposing roll 42 are moved to each other. Vibration (banding) occurs. This is because the foaming material in the meet line 165 has a higher hardness than the surroundings, and therefore, the meet line 165 cannot absorb the impact when the recording medium P enters the secondary transfer portion T. is there. Therefore, when the recording medium P enters the secondary transfer portion T at such a timing, a transfer defect (banding defect) due to vibration occurs in the transfer belt 34 and the opposing roll 42, which causes deterioration in the image quality of the formed image. It becomes. As described above, when the secondary transfer roll 192 is used, the rotational position of the secondary transfer roll 192 is a rotational position where one of the four meet lines 165 faces the transfer belt 34 (for example, 0 °, 90 °). When the recording medium P enters the secondary transfer portion T when it is at (°, 180 °, 270 °), a transfer defect (banding defect) occurs.

  On the other hand, in the secondary transfer roll 162 of the second embodiment, four meat lines 165 are formed in the covering 164 so as to form an angle with respect to the axial direction in a side view of the covering 164, respectively. The lines 165 are configured to be dispersed in the circumferential direction. Therefore, in the transfer device 32 having the secondary transfer roll 162 according to the second embodiment, the vibration generated through the meet line 165 when the recording medium P enters the secondary transfer portion T is suppressed, and the transfer caused by the vibration is suppressed. As a result of suppressing the defects, the image quality of the formed image is improved.

  FIG. 14 shows an assembly aspect of the secondary transfer roll 162 of the second embodiment.

  As shown in FIG. 14, the secondary transfer roll 162 according to the second embodiment is configured such that the shaft body 163 is fitted into a covering body 164 in which four meat lines 165 are linearly formed along the axial direction. Assembled. When the shaft body 163 is fitted into the covering body 164, the four meet lines 165 are formed in the covering body 164 so as to form an angle with respect to the axial direction by twisting the covering body 164. That is, the four meat lines 165 are each formed in a straight line along the axial direction, and the cover body 164 is covered with the shaft body 163 while being twisted. Secondary transfer rolls 162 are assembled in which the lines 165 form an angle with respect to the axial direction in the covering 164.

  Further, the covering body 164 is twisted within a range of less than 90 ° so that the meat line 165 does not appear in two or more locations in the axial direction at any position in the circumferential direction of the covering body 164. Thereby, the meat line 165 can be dispersed without waste in the circumferential direction. Accordingly, vibrations caused by the recording medium P entering the secondary transfer portion T are suppressed. In addition, the restoring force for returning the covering body 164 from the twisted state is suppressed.

  Note that a primer (adhesive) is applied in advance to the outer peripheral surface of the shaft body 163 so that the cover 164 is kept in a twisted state. Further, in the case where the outer diameter of the covering body 164 is shaken by twisting the covering body 164, the outer peripheral surface of the covering body 164 may be polished after the shaft body 163 is fitted into the covering body 164.

  As described above, in the secondary transfer roll 62 of the first embodiment and the secondary transfer roll 162 of the second embodiment according to the present invention, the cylindrical coverings 64 and 164 made of a foamable material are provided. The shaft bodies 63 and 163 are covered, and the meat lines 65 and 165 in the covering bodies 64 and 164 are linearly formed so as to form an angle with respect to the axial direction in a side view of the covering bodies 64 and 164. Accordingly, vibrations caused by the recording medium P entering the secondary transfer portion T are suppressed.

  The covering bodies 64 and 164 are covered with the shaft bodies 63 and 163 in a twisted state. Therefore, the meet lines 65 and 165 can be easily formed at an angle with respect to the axial direction with respect to the coverings 64 and 164 in which the meet lines 65 and 165 are linearly formed along the axial direction. It becomes.

  The covering bodies 64 and 164 are twisted so that the meet lines 65 and 165 do not appear in two or more locations in the axial direction at any position in the circumferential direction of the covering bodies 64 and 164. Is covered. Accordingly, vibrations caused by the recording medium P entering the secondary transfer portion T are suppressed. Further, the restoring force for returning the coverings 64 and 164 from the twisted state is suppressed.

  Further, since the image forming apparatus 10 includes the transfer device 32 having the secondary transfer roll 62 of the first embodiment or the secondary transfer roll 162 of the second embodiment, an image with excellent image quality is formed on a recording medium. It becomes possible to do.

  In the above description, the secondary transfer rolls 62 and 162 of the transfer device 32 for primary transfer of the toner image from the photosensitive drum 18 to the transfer belt 34 and then secondary transfer from the transfer belt 34 to the recording medium P have been described. The technical idea of the present invention may be applied to a transfer roll of a transfer device that directly transfers an image from the photosensitive drum 18 to the recording medium P.

10 Image forming apparatus 18 Photosensitive drum (an example of an image carrier)
22 Developing device 32 Transfer device 34 Transfer belt 62 Secondary transfer roll (an example of a transfer roll)
63 Shaft body 64 Cover body 65 Meat line (an example of a small diameter bubble part)
73 Mold device 74 Dummy core 75 Cavity 76 Mold 77 Inlet 92 Secondary transfer roll 162 Secondary transfer roll (an example of a transfer roll)
163 Shaft body 164 Cover body 165 Meat line (an example of small diameter bubble part)
173 Discharge head 174 Base 175 Core 176 Joint P Recording medium T Secondary transfer unit

Claims (4)

A shaft,
It is composed of a material having bubbles inside, has a cylindrical shape, and a covering that covers the shaft,
A small-diameter bubble portion formed in the covering body, having bubbles with a smaller diameter than the surroundings in the covering body, and formed linearly so as to form an angle with respect to the axial direction in a side view of the covering body;
A transfer roll comprising:   The transfer roll according to claim 1, wherein the covering body is covered with the shaft body in a twisted state.   The said covering body is covered with the said shaft body in the state twisted so that the said small diameter bubble part may not appear two or more places over the axial direction in any position in the circumferential direction of the said covering body. The transfer roll according to claim 2. A holder on which an electrostatic latent image is formed;
A developing device for developing the electrostatic latent image formed on the holder with toner;
A transfer device having a transfer roll according to any one of claims 1 to 3, for transferring a toner image developed by the developing device to a recording medium,
An image forming apparatus comprising:

Images