JP2017037141A - Coated roll, transfer device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress unevenness in hardness in a circumference direction of a coated roll compared with a case where a coating member includes portions having a projection formed thereon and portions not having a projection formed thereon in its circumferential direction.SOLUTION: A coated roll comprises: an elastic roll 70; a cylindrical coating member 80 that coats an outer periphery of the elastic roll 70; and a projection 86 that is formed on an inner peripheral surface of the coating member 80, has a linear shape having an angle with respect to the axial direction of the coating member 80 when seen in the radial direction of the coating member 80, and projects over the entire periphery in a circumferential direction of the coating member 80.SELECTED DRAWING: Figure 5

Description

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

  Patent Document 1 discloses a conductive porous elastic roller in which a conductive porous elastic layer is provided on the outer peripheral surface of a conductive metal shaft, and a conductive tube that covers the outer peripheral surface of the conductive porous elastic roller. , A conductive roller is disclosed. In the conductive roller of Patent Document 1, a convex portion along the axial direction of the conductive tube is formed on the inner peripheral surface of the conductive tube.

JP 2014-170158 A

  In some coated rolls in which an elastic roll is coated with a coating member such as a tube, ribs or other convex portions are formed on the inner peripheral surface of the coated member in order to improve the adhesion between the coated member and the elastic roll. In the case where there are a portion where the convex portion is formed and a portion where the convex portion is not formed in the circumferential direction of the covering member, hardness unevenness may occur in the circumferential direction of the covering roll.

  An object of this invention is to suppress the hardness nonuniformity in the circumferential direction of a coating | coated roll compared with the case where there exists a part in which the convex part was formed in the circumferential direction of the coating | coated member, and the part in which the convex part is not formed.

  The invention according to claim 1 is an elastic roll, a cylindrical covering member covering an outer periphery of the elastic roll, and an inner peripheral surface of the covering member, and the covering is seen in a radial direction of the covering member. And a convex portion that is formed in a linear shape having an angle with respect to the axial direction of the member and protrudes in the entire circumferential direction of the covering member.

  According to a second aspect of the present invention, the convex portion protrudes at a plurality of locations separated in the axial direction on the entire circumference in the circumferential direction of the covering member.

  According to a third aspect of the present invention, the convex portion has a spiral shape that circulates a plurality of times along the axial direction.

  According to a fourth aspect of the present invention, the convex portion is a spiral-shaped first convex portion that circulates a plurality of times along the axial direction, and a spiral shape that circulates a plurality of times in a reverse direction from the first convex portion. And a second convex portion.

  In the invention of claim 5, the convex portion is formed in an annular shape having an angle with respect to the axial direction of the covering member when viewed in the radial direction of the covering member, and a plurality of the convex portions are arranged from one end side to the other end side in the axial direction. Has been.

  In the invention of claim 6, the ratio of the convex portion in the axial direction is constant over the entire circumference in the circumferential direction.

  The invention of claim 7 includes the coating roll according to any one of claims 1 to 6 as a transfer roll.

  According to an eighth aspect of the invention, there is provided an image forming portion that forms an image, and a transfer device according to the seventh aspect that transfers an image formed by the image forming portion to a medium.

  According to the configuration of the first aspect of the present invention, the hardness unevenness in the circumferential direction of the coating roll is smaller than that in the case where there are a portion where the convex portion is formed and a portion where the convex portion is not formed in the circumferential direction of the covering member. Can be suppressed.

  According to the structure of Claim 2 of this invention, compared with the case where a convex part protrudes only in one place of the axial direction of a coating | coated member, the hardness nonuniformity in the axial direction of a coating | coated roll can be suppressed.

  According to the structure of Claim 3 of this invention, compared with the case where a convex part is cyclic | annular, the hardness nonuniformity of the axial direction of a coating roll can be suppressed.

  According to the configuration of the fourth aspect of the present invention, the covering member is less likely to be displaced in the circumferential direction and the axial direction with respect to the elastic roll as compared with the case where a spiral convex portion that circulates only on one side is formed.

  According to the configuration of the fifth aspect of the present invention, the covering member is less likely to be displaced in the axial direction with respect to the elastic roll, as compared with the case where a spiral convex portion is formed on only one side.

  According to the structure of Claim 6 of this invention, compared with the case where the ratio of the convex part in an axial direction varies in the circumferential direction of a coating | coated member, the hardness unevenness of the circumferential direction of a covering roll can be suppressed.

  According to the configuration of the seventh aspect of the present invention, the transfer unevenness in the circumferential direction of the transfer roll is reduced as compared with the case where there are a portion where the convex portion is formed in the circumferential direction of the covering member and a portion where the convex portion is not formed. Can be suppressed.

  According to the configuration of the eighth aspect of the present invention, image defects in the circumferential direction of the transfer roll are reduced as compared with the case where there are a portion where the convex portion is formed in the circumferential direction of the covering member and a portion where the convex portion is not formed. Can be suppressed.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment. It is a perspective view which shows the structure of the secondary transfer roll which concerns on this embodiment. It is sectional drawing of a tube and a convex part when it sees along the axial direction of a tube. It is a side view which shows a convex part when it sees along the radial direction of a tube. It is a perspective view which shows the structure of an elastic roll and a tube. It is a side view which shows the structure of the convex part which concerns on a 1st modification. It is a side view which shows the structure of the convex part which concerns on a 2nd modification. It is a perspective view which shows the structure of the tube which concerns on a comparative example. It is a table | surface which shows an evaluation result.

  Below, an example of an embodiment concerning the present invention is described based on a drawing.

(Image forming apparatus 10)
First, the configuration of the image forming apparatus 10 will be described. FIG. 1 is a schematic diagram illustrating a configuration of the image forming apparatus 10.

  As shown in FIG. 1, the image forming apparatus 10 includes a toner image forming unit 12 (an example of an image forming unit) that forms a toner image, and a toner image formed by the toner image forming unit 12 on a recording medium P (medium And a transfer device 30 for transferring to (an example). Further, the image forming apparatus 10 controls the operations of the fixing device 60 that fixes the toner image transferred to the recording medium P to the recording medium P, the conveying device 16 that conveys the recording medium P, and each part of the image forming apparatus 10. And a control unit 20 that performs.

  The transport device 16 includes a storage unit 14 that stores a recording medium P such as paper, a delivery roll 46 that sends out the recording medium P stored in the storage unit 14, and a secondary recording medium P that is sent out by the delivery roll 46. And a plurality of transport rolls 50 transported to the transfer position T2.

  The toner image forming unit 12 includes image forming units 22Y, 22M, 22C, and 22K (hereinafter referred to as 22Y to 22K) that form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K). Is indicated).

  The image forming units 22Y to 22K are arranged along the horizontal direction. Each of the image forming units 22Y to 22K has a photoreceptor 32 that rotates in one direction (for example, the counterclockwise direction in FIG. 1). Since the image forming units 22Y to 22K are configured in the same manner, the reference numerals of the respective portions in the image forming units 22M, 22C, and 22K are omitted in FIG.

  Around each photoconductor 32, an electrostatic latent image formed on the photoconductor 32 is developed by a charging device 23 for charging the photoconductor 32 and an exposure device 36 described later in order from the upstream side in the rotation direction of the photoconductor 32. Thus, a developing device 38 for forming a toner image and a removing device 40 for removing the toner remaining on the photoconductor 32 in contact with the photoconductor 32 are provided.

  The developing devices 38 of the image forming units 22Y to 22K are supplied with yellow, magenta, cyan, and black toners accommodated in toner cartridges 23Y, 23M, 23C, and 23K.

  Below the image forming units 22Y to 22K, an exposure device 36 that exposes the photoreceptors 32 of the image forming units 22Y to 22K to form an electrostatic latent image on the photoreceptor 32 is provided.

  The exposure device 36 is configured to form an electrostatic latent image based on the image signal sent from the control unit 20. Examples of the image signal sent from the control unit 20 include an image signal acquired by the control unit 20 from an external device.

  The transfer device 30 transfers the intermediate transfer belt 24 (intermediate transfer member), a primary transfer roll 26 that primarily transfers the toner images formed by the image forming units 22Y to 22K to the intermediate transfer belt 24, and the intermediate transfer belt 24. And a secondary transfer roll 28 for secondary transfer of the toner image to the recording medium P.

  The intermediate transfer belt 24 is formed in an annular shape and is disposed below the image forming units 22Y to 22K. On the inner peripheral side of the intermediate transfer belt 24, winding rolls 41 and 42 around which the intermediate transfer belt 24 is wound are provided. For example, the intermediate transfer belt 24 rotates (rotates) in one direction (for example, the clockwise direction in FIG. 1) while being in contact with the photoreceptor 32 when the winding roll 42 is driven to rotate. The winding roll 41 is an opposing roll that faces the secondary transfer roll 28.

  The primary transfer roll 26 sandwiches the intermediate transfer belt 24 with the photoreceptor 32. A region (nip region) in which the intermediate transfer belt 24 is sandwiched between the primary transfer roll 26 and the photosensitive member 32 is a primary transfer position T1 at which the toner image formed on the photosensitive member 32 is transferred to the intermediate transfer belt 24. Yes.

  The primary transfer roll 26 is applied with a primary transfer voltage (primary transfer current) having a polarity opposite to the toner polarity. As a result, a transfer electric field is formed between the photoconductor 32 and the primary transfer roll 26, an electrostatic force acts on the toner image formed on the photoconductor 32, and the toner image is intermediate at the primary transfer position T1. The image is transferred to the transfer belt 24.

  The secondary transfer roll 28 and the winding roll 41 sandwich the intermediate transfer belt 24 with a predetermined nip pressure. The intermediate transfer belt 24 is sandwiched between the secondary transfer roll 28 and the winding roll 41 (nip area), and the secondary transfer in which the toner image transferred to the intermediate transfer belt 24 is transferred to the recording medium P. The position is T2.

  A secondary transfer voltage (secondary transfer current) having a polarity opposite to the toner polarity is applied to the secondary transfer roll 28. As a result, a transfer electric field is formed between the winding roll 41 and the secondary transfer roll 28, and an electrostatic force acts on the toner image on the intermediate transfer belt 24.

  Therefore, the recording medium P passing through the secondary transfer position T2 has an intermediate transfer belt due to the nip pressure between the secondary transfer roll 28 and the winding roll 41 and the electrostatic force acting on the toner image on the intermediate transfer belt 24. The toner image is transferred from 24. Note that a voltage (current) having the same polarity as the toner polarity may be applied to the winding roll 41 to form a transfer electric field. A specific configuration of the secondary transfer roll 28 will be described later.

  The fixing device 60 is disposed on the downstream side in the transport direction with respect to the secondary transfer position T2. The fixing device 60 includes a heating roll 61 and a pressure roll 62. In the fixing device 60, the toner image transferred to the recording medium P is fixed to the recording medium P by heating by the heating roll 61 and pressing by the pressure roll 62. The recording medium P on which the toner image is fixed by the fixing device 60 is discharged to the discharge unit 18 by the discharge roll 52.

(Image forming operation)
Next, an image forming operation for forming an image on the recording medium P in the image forming apparatus 10 according to the present embodiment will be described.

  In the image forming apparatus 10 according to the present embodiment, the recording medium P sent out from the storage unit 14 by the sending roll 46 is sent to the secondary transfer position T2 by the plurality of conveying rolls 50.

  On the other hand, in the image forming units 22 </ b> Y to 22 </ b> K, the photoconductor 32 charged by the charging device 23 is exposed by the exposure device 36 to form an electrostatic latent image on the photoconductor 32. The electrostatic latent image is developed by the developing device 38 to form a toner image on the photoreceptor 32. The toner images of the respective colors formed by the image forming units 22Y to 22K are transferred to the intermediate transfer belt 24 by the primary transfer roll 26 at the primary transfer position T1, and a color image is formed. The color image formed on the intermediate transfer belt 24 is transferred to the recording medium P by the primary transfer roll 26 at the secondary transfer position T2.

  The recording medium P to which the toner image has been transferred is conveyed to the fixing device 60, and the transferred toner image is fixed by the fixing device 60. The recording medium P on which the toner image is fixed is discharged to the discharge unit 18 by the discharge roll 52. As described above, a series of image forming operations are performed.

(Secondary transfer roll 28)
Next, a specific configuration of the secondary transfer roll 28 will be described. FIG. 2 is a perspective view showing the configuration of the secondary transfer roll 28.

  As shown in FIG. 2, the secondary transfer roll 28 includes an elastic roll 70 and a cylindrical tube 80 (an example of a covering member) that covers the outer periphery of the elastic roll 70 and has conductivity. . The elastic roll 70 includes a cylindrical or columnar support 72 (shaft) having conductivity, and a conductive elastic layer 74 provided on the outer peripheral surface of the support 72. Hereinafter, specific configurations of the support 72, the elastic layer 74, and the tube 80 will be described.

(Support 72)
Examples of the support 72 include metal members such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, nickel, and the like.

  Further, as the support 72, for example, a member (for example, a resin or a ceramic member) whose outer surface is plated may be used, or a member in which a conductive agent is dispersed (for example, a resin or a ceramic member).

(Elastic layer 74)
The elastic layer 74 includes, for example, a rubber material (elastic material) and a foaming agent, and if necessary, a conductive agent and other additives.

  Examples of the rubber material include so-called elastic materials having a double bond in at least a chemical structure. Specific examples of the rubber material include isoprene rubber, chloroprene rubber, epichlorohydrin rubber (ECO), butyl rubber, polyurethane, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, and epichlorohydrin. -Ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber, etc., and these were mixed Rubber.

  Among these rubber materials, polyurethane, ECO, EPDM, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, NBR, and rubbers obtained by mixing them are preferable.

  Examples of the blowing agent include benzenesulfonyl hydrazide, azodicarbonamide (ADCA), N, N′-dinitrosopentamethylenetetramine, dinitrosopentamethylenetetraamine (DPT), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, oxybis Benzenesulfonyl hydrazide (OBSH), ammonium bicarbonate generating carbon dioxide, sodium bicarbonate, ammonium carbonate, nitrososulfonylazo compound generating nitrogen, N, N′-dimethyl-N, N′-dinitrosophthalamide, toluene Examples thereof include sulfonyl hydrazide, P-toluenesulfonyl semicarbazide, P, P′-oxy-bis (benzenesulfonyl semicarbazide) and the like.

  Among these foaming agents, benzenesulfonyl hydrazide and azodicarbonamide are desirable in view of ease of foam control. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as a form of a foaming agent, According to the objective, it selects suitably from particulate form, liquid form, a capsule form, etc.

  The conductive agent is used as necessary when the rubber material has low conductivity or when the rubber material does not have conductivity. Examples of the conductive agent include an electronic conductive agent and an ionic conductive agent.

  Examples of the electronic conductive agent include carbon black such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, and stainless steel; tin oxide, indium oxide, and titanium oxide. And various conductive metal oxides such as tin oxide-antimony oxide solid solution, tin oxide-indium oxide solid solution; and the like. An electronic conductive agent may be used independently and may be used in combination of 2 or more type.

  The content of the electronic conductive agent is, for example, preferably from 1 part by weight to 30 parts by weight, and more preferably from 15 parts by weight to 25 parts by weight with respect to 100 parts by weight of the rubber material.

  Examples of the ionic conductive agent include quaternary ammonium salts (for example, lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, perchlorates such as modified fatty acid and dimethylethylammonium urine, Chlorates, borofluorides, sulfates, etosulphate salts, benzyl halide salts (eg, benzyl bromide salts, benzyl chloride salts, etc.), aliphatic sulfonates, higher alcohol sulfates, higher Alcohol ethylene oxide addition sulfate ester salt, higher alcohol phosphate ester salt, higher alcohol ethylene oxide addition phosphate ester salt, various betaines, higher alcohol ethylene oxide, polyethylene glycol Fatty acid esters, polyhydric alcohol fatty acid esters. An ionic conductive agent may be used independently and may be used in combination of 2 or more type.

  The content of the ionic conductive agent is, for example, preferably in the range of 0.1 parts by weight or more and 5.0 parts by weight or less, and preferably 0.5 parts by weight or more and 3.0 parts by weight with respect to 100 parts by weight of the rubber material. It is set as the range below a mass part.

  Examples of other additives include foaming aids, softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, antioxidants, surfactants, coupling agents, fillers (silica, calcium carbonate) And the like, which can be added to a normal elastic layer.

  From the viewpoint of image quality, the volume resistivity of the elastic layer 74 is preferably 6 (LogΩ · cm) or more and 8 (LogΩ · cm) or less, and 6.5 (LogΩ · cm) or more and 7.5 (LogΩ · cm). cm) or less is more desirable. The volume resistivity of the elastic layer 74 is adjusted by, for example, the type and amount of the conductive agent to be blended.

  The hardness of the elastic layer 74 is, for example, 20 or more and 50 or less, and desirably 30 or more and 40 or less. The hardness in the present embodiment is a hardness measured based on the Asker C method.

  The thickness of the elastic layer 74 is, for example, not less than 2 mm and not more than 20 mm, desirably not less than 2 mm and not more than 15 mm.

(Tube 80)
Examples of the material of the tube 80 include resin materials such as polyimide, polyphenylene sulfide, polyether sulfide, polyether imide, and polyarylate. Among these, polyimide is particularly desirable from the viewpoints of strength, heat resistance, and dimensional stability.

  More specific polyimide resin materials include, for example, thermosetting resins such as polypyromellitic imide based polyimide resin materials, polybiphenyltetracarboxylic imide based resin materials, polybenzophenone tetracarboxylic imide based resin materials, poly A thermoplastic polyimide resin such as an etherimide resin may be used.

  As the conductive agent included in the tube 80, in consideration of the fact that there is little fluctuation in electrical resistance value in a high temperature and high humidity environment of 30 ° C / 85% RH and a low temperature and low humidity environment of 10 ° C / 15% RH, It is desirable to use an electron conductive conductive agent that exhibits electrical conductivity. Specific examples of the electron conductive conductive agent include carbon black.

  The volume resistivity of the tube 80 is different from the volume resistivity of the elastic layer 72. For example, the common logarithmic value is 6.0 (LogΩ · cm) or more and 13.0 (LogΩ · cm) or less. It is set to 0 (LogΩ · cm) or more and 12.0 (LogΩ · cm) or less. The volume resistivity of the tube 80 is adjusted by, for example, the type and amount of the conductive agent to be blended.

  The hardness of the tube 80 is different from the hardness of the elastic layer 74. Specifically, the hardness of the tube 80 is harder than that of the elastic layer 74 and is, for example, Young's modulus 2000 MPa or more and 4500 MPa or less, and preferably 3000 MPa or more and 4000 MPa or less.

  The thickness of the tube 80 is, for example, in the range of 0.02 mm to 0.2 mm, and preferably in the range of 0.05 mm to 0.10 mm.

  Here, a convex portion 86 (rib) is formed on the inner peripheral surface of the tube 80 as shown in FIGS. The inner diameter R1 (see FIG. 3) of the circle formed by the top of the convex portion 86 is smaller than the outer diameter R1 (see FIG. 5) of the elastic roll 70 (elastic layer 74). Thereby, the convex part 86 bites into the elastic layer 74.

  Further, as shown in FIG. 4, the convex portion 86 has a linear shape having an angle with respect to the axial direction of the tube 80 when viewed in the radial direction of the tube 80. Specifically, as shown in FIG. 4 and FIG. 5, the convex portion 86 turns around a plurality of times (two or more times) along the axial direction of the tube 80 from one end to the other end in the axial direction of the tube 80. It is a continuous spiral.

  The above-mentioned “linear” may be a line having a length in a direction having an angle with respect to the axial direction of the tube 80, and may be a straight line or a meandering curve. .

  As described above, since the convex portion 86 is formed in a spiral shape, the convex portion 86 gradually shifts from the one end side in the axial direction of the tube 80 toward the other end side in the axial direction of the tube 80. It is formed to progress.

  Moreover, the convex part 86 protrudes in the several places distant from the axial direction of the tube 80 in the circumferential direction perimeter of the tube 80 because the spiral of the convex part 86 circulates a plurality of times (two or more rounds). The convex portions 86 are arranged at equal intervals in the axial direction of the tube 80 at predetermined intervals.

  Furthermore, the height (projection amount) H (see FIG. 3) of the convex portion 86 is, for example, 0.01 mm or more and 0.5 mm or less. Moreover, the width (length along the axial direction of the tube 80) W (see FIG. 4) of the convex portion 86 is, for example, not less than 0.01 mm and not more than 0.5 mm.

  Further, the height H of the convex portion 86 is a constant height from one end of the tube 80 to the other end. Further, the width W of the convex portion 86 is a constant width from one end of the tube 80 to the other end. Further, the same number of convex portions 86 are arranged in the axial direction of the tube 80 on the entire circumference of the tube 80. Therefore, the ratio of the convex portions 86 in the axial direction of the tube 80 is constant over the entire circumference of the tube 80 in the circumferential direction.

  Here, “constant” means that the ratio of the convex portions 86 is constant as a design value (target value). Therefore, a case where the ratio of the convex portion 86 varies within a range of 95% or more and 105% or less due to a manufacturing error or the like is also included in the present configuration.

(Method for producing secondary transfer roll 28)
The elastic roll 70 is manufactured using an extrusion molding apparatus. In the extrusion molding apparatus, for example, the support 72 is transported in the axial direction, and the elastic layer 74 is extruded in a cylindrical shape and attached to the outer periphery of the support 72. Thereby, the elastic roll 70 is formed.

  The tube 80 is formed as follows, for example. That is, first, a cylindrical mold in which a spiral groove for forming the convex portion 86 is formed on the outer peripheral surface is prepared. A coating solution containing the constituent material of the tube 80 is applied to the outer peripheral surface of the mold by a spiral coating method, and the coating film is cured by heating or the like to form the tube 80.

  The elastic roll 70 is inserted into the tube 80 as shown in FIG. 5 while expanding the diameter of the tube 80 by supplying air, for example. Then, by stopping the supply of air into the tube 80, the outer periphery of the elastic roll 70 is covered with the tube 80, and the secondary transfer roll 28 is manufactured.

(Operation according to this embodiment)
In the present embodiment, the convex portion 86 formed on the inner peripheral surface of the tube 80 bites into the elastic layer 74. For this reason, it is suppressed that the tube 80 slips (slips) with respect to the elastic layer 74, and the adhesiveness of the elastic layer 74, the tube 80, and the elastic layer 74 increases. Thereby, the tube 80 is less likely to be displaced with respect to the elastic layer 74 in the circumferential direction and the axial direction of the secondary transfer roll 28 (elastic roll 70). Therefore, wrinkles and breakage of the recording medium P that occur when the recording medium P is conveyed at the secondary transfer position T2 due to the displacement of the tube 80 with respect to the elastic layer 74 are suppressed.

  Further, in the present embodiment, the convex portion 86 protrudes at a plurality of locations separated in the axial direction of the tube 80 in the entire circumferential direction of the tube 80.

  Here, in the case of having a portion where the convex portion 86 is formed in the circumferential direction of the tube 80 and a portion where the convex portion 86 is not formed (Comparative Example (see FIG. 8)), the portion where the convex portion 86 is formed. Since the hardness of the secondary transfer roll 28 varies between the portions where the convex portions 86 are not formed, hardness unevenness in the circumferential direction of the secondary transfer roll 28 occurs. Further, in the case of having a portion where the convex portion 86 is formed and a portion where the convex portion 86 is not formed in the circumferential direction of the tube 80 (comparative example (see FIG. 8)), the portion where the convex portion 86 is formed; Since the volume resistivity of the secondary transfer roll 28 changes between the portions where the convex portions 86 are not formed, electrical resistance unevenness in the circumferential direction of the secondary transfer roll 28 occurs.

  On the other hand, in this embodiment, the convex part 86 protrudes in the perimeter of the tube 80, and the part in which the convex part 86 is not formed in the circumferential direction of the tube 80 does not exist. For this reason, compared with the case where it has the part in which the convex part 86 was formed in the circumferential direction of the tube 80, and the part in which the convex part 86 is not formed (comparative example), the hardness nonuniformity in the circumferential direction of the secondary transfer roll 28, and Uneven electrical resistance is suppressed.

  Moreover, since the convex part 86 protrudes in the several places distant in the axial direction of the tube 80 in the circumferential direction perimeter of the tube 80, when the convex part 86 protrudes only in one place of the axial direction of the tube 80 (comparison) Compared to Example), uneven hardness and uneven electrical resistance in the axial direction of the secondary transfer roll 28 are suppressed.

  Further, in the present embodiment, the convex portion 86 is formed in a spiral shape. That is, the convex portion 86 is formed so as to proceed from the one axial end side of the tube 80 toward the other axial end side of the tube 80 while gradually shifting in the circumferential direction. For this reason, compared with the case where the convex part 86 is cyclic | annular, the hardness nonuniformity and electrical resistance nonuniformity of the circumferential direction of the secondary transfer roll 28 and an axial direction are suppressed.

  In the present embodiment, the ratio of the convex portions 86 in the axial direction of the tube 80 is constant over the entire circumference in the circumferential direction of the tube 80. For this reason, compared with the case where the ratio of the convex part 86 in an axial direction varies in the circumferential direction of the tube 80, the hardness unevenness and electrical resistance unevenness of the secondary transfer roll 28 in the circumferential direction and the axial direction are suppressed.

  As described above, in this embodiment, unevenness in hardness in the circumferential direction and the axial direction of the secondary transfer roll 28 is suppressed, so that the secondary transfer roll 28 has a nip pressure with respect to the recording medium P at the secondary transfer position T2. Generation of unevenness is suppressed in the circumferential direction and the axial direction.

  Further, since uneven electrical resistance in the circumferential direction and the axial direction of the secondary transfer roll 28 is suppressed, the recording medium P generated by applying a secondary transfer voltage (secondary transfer current) to the secondary transfer roll 28 is prevented. In the electrostatic force, the occurrence of unevenness is suppressed in the circumferential direction and the axial direction of the secondary transfer roll 28.

  As described above, in the nip pressure at the secondary transfer position T2 and the electrostatic force to the recording medium P, the occurrence of unevenness in the circumferential direction and the axial direction of the secondary transfer roll 28 is suppressed. Transfer unevenness in the circumferential direction and the axial direction is suppressed. Accordingly, image defects due to transfer unevenness are suppressed.

(First modification)
Instead of the convex portion 86, the convex portion 190 may be formed on the inner peripheral surface of the tube 80 as shown in FIG. 6. The convex portion 190 is a spiral-shaped first convex portion 191 that circulates a plurality of times along the axial direction of the tube 80, and the first convex portion 191 is a spiral that circulates a plurality of times in a reverse winding. Part 192.

  Specifically, the first convex portion 191 is a continuous spiral that circulates a plurality of times (two or more times) along the axial direction of the tube 80 from the axial center of the tube 80 to one axial end of the tube 80. It is said that.

  Specifically, the second convex portion 192 is wound a plurality of times in the reverse direction from the first convex portion 191 along the axial direction of the tube 80 from the axial central portion of the tube 80 to the other axial end of the tube 80 ( (2 or more laps) It is a continuous spiral.

  Thus, the convex part 190 is comprised similarly to the convex part 86 except having the 1st convex part 191 and the 2nd convex part 192 reversely wound from the 1st convex part 191. ing.

  In the first modification, since the first convex portion 191 and the first convex portion 191 have a second convex portion 192 that is reversely wound, the convex portion 190 has a spiral shape that circulates only in one direction. Compared to the case (comparative example), the tube 80 is less likely to rotate relative to the elastic roll 70. For this reason, in the first modification, relative movement of the tube 80 in the circumferential direction and the axial direction of the elastic roll 70 is also suppressed as compared with the comparative example. Therefore, the tube 80 is less likely to be displaced in the circumferential direction and the axial direction of the elastic roll 70 with respect to the elastic roll 70.

  The first convex portion 191 and the second convex portion 192 may overlap (overlap) in the axial direction of the tube 80 when viewed in the radial direction of the tube 80.

(Second modification)
Instead of the convex portion 86, the convex portion 290 may be formed on the inner peripheral surface of the tube 80 as shown in FIG. 7. The convex portion 290 has a plurality of convex portions 292 that are annular and have an angle (specifically, 90 °) with respect to the axial direction of the tube 80 when viewed in the radial direction of the tube 80.

  A plurality of convex portions 292 are arranged at equal intervals in the axial direction of the tube 80 at predetermined intervals from one end side to the other end side in the axial direction of the tube 80. The convex portion 290 is not spiral, but is configured in the same manner as the convex portion 86 except that it has a plurality of annular convex portions 292.

  Here, in the case where the convex portion 190 has a spiral shape that circulates only on one side (comparative example), when the rotational force that rotates the tube 80 acts on the elastic roll 70, the elastic roll 70 is caused by the spiral of the convex portion 190. It is converted into a moving force in the axial direction.

  On the other hand, in the second modified example, since the convex portion 292 is annular, even if a rotational force that rotates the tube 80 acts on the elastic roll 70, the axial direction of the tube 80 with respect to the elastic roll 70 The relative movement to is suppressed.

  Note that the convex portion 86 may be inclined rather than perpendicular to the axial direction of the tube 80 when viewed in the radial direction of the tube 80.

(Other variations)
In the present embodiment, each of the convex portion 86, the first convex portion 191 and the second convex portion 192 is a continuous spiral, but may be divided in the middle.

  Moreover, in this embodiment, although the convex part 86, the 1st convex part 191 and the 2nd convex part 192 were each made into the single spiral, you may be comprised by the two or more spiral.

  Further, in the present embodiment, the convex portions 86, 190, and 290 are provided on the tube 80 of the secondary transfer roll 28 as an example of the transfer roll, but the present invention is not limited thereto. For example, as an example of the transfer roll, the primary transfer roll 26 may be used, and the primary transfer roll 26 may be configured similarly to the secondary transfer roll 28. In this case, the intermediate transfer belt 24 functions as an example of a medium. Further, as an example of the transfer roll, a transfer roll of a direct transfer type image forming apparatus that does not have an intermediate transfer member may be used.

  Further, the covering roll is not limited to the transfer roll, and may be a conductive roll such as a developing roll or a charging roll, and may be a covering roll in which a covering member is covered with an elastic roll.

  The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made without departing from the spirit of the present invention. For example, the modification examples described above may be appropriately combined.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the following, “part” represents a mass standard unless otherwise specified.

[Example 1]
(Production of elastic roll 70)
By containing an ethylene oxide group, 60 parts of epichlorohydrin rubber (ECO, Epichromer CG-102 manufactured by Daiso Corporation) and 30 parts of acrylonitrile-butadiene rubber (NBR, Nipol DN-219 manufactured by Nippon Zeon Co., Ltd.) excellent in ion conductivity are contained. 1 part of sulfur as a vulcanizing agent (200 mesh manufactured by Tsurumi Chemical Co., Ltd.), 1.5 part of a vulcanization accelerator (Noxera-M manufactured by Ouchi Shinsei Chemical Industrial Co., Ltd.), and benzenesulfonyl as a blowing agent 6 parts of hydrazide was added and kneaded with an open roll to obtain a rubber mixture.

  Next, this rubber mixture was formed into a roll shape on the outer peripheral surface of a SUS support roll (support 72) having a diameter of 12 mm and a length of 350 mm by extrusion molding, and was polished. As a result, an elastic roll 70 having an elastic layer 74 having an outer diameter of 20.5 mm and a length of 320 mm was obtained.

(Production of tube 80)
-Preparation of coating solution-
First, a polyamic acid N-methyl-2-pyrrolidone (NMP) solution containing biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) (Uimide KX manufactured by Unitika Ltd./solid content concentration 20% by mass) Carbon black (SPECIAL Black 4, manufactured by Evonik Degussa Japan Co., Ltd.) is charged in an amount of 8% by mass in terms of solid content, and dispersed (200 N / mm2, 5 passes) using a JETMILL disperser (Genus PY). It was. The obtained carbon black-dispersed polyamic acid solution was passed through a stainless steel 20 μm mesh to remove foreign substances and carbon black aggregates. Further, vacuum degassing was performed for 15 minutes with stirring to prepare a final solution. This was used as a coating solution for forming the tube 80.

-Production of cylindrical mold-
A cylindrical cylindrical mold made of SUS304 having an outer diameter of 20.3 mm and a length of 400 mm is prepared, and the outer peripheral surface of the cylindrical mold is roughened. At this time, a spiral groove is formed on the outer peripheral surface of the cylindrical mold. Formed.

-Production of tube 80-
A coating solution was applied to the outer peripheral surface of the above-described mold by a spiral coating method to form a coating film. Thereafter, the coating film was dried at 180 ° C. for 20 minutes, and reacted by heating at 200 ° C. for 30 minutes and at 300 ° C. for 30 minutes to cure the coating film. Thereafter, the cured coating film was extracted from the mold to obtain a tube 80 in which a spiral convex portion 86 was formed on the inner peripheral surface.

(Preparation of secondary transfer roll 28)
The aforementioned elastic roll 70 is inserted into the tube 80 while expanding the diameter of the tube 80 by supplying air, for example. As a result, the outer periphery of the elastic roll 70 was covered with the tube 80 to obtain the secondary transfer roll 28.

[Example 2]
On the outer peripheral surface of the cylindrical mold, a spiral first groove is formed from the axial central portion of the cylindrical mold to one axial end, and the first groove extends from the axial central portion of the cylindrical mold to the other axial end. A reverse wound spiral second groove was formed. By using this cylindrical mold, a tube 80 in which a first convex portion 191 and a second convex portion 192 that is reversely wound with the first convex portion 191 are formed on the inner peripheral surface is obtained (see the first modified example). ). The other points produced the secondary transfer roll 28 in the same manner as in Example 1.

Example 3
A plurality of grooves formed in an annular shape along the circumferential direction of the cylindrical mold were formed on the outer peripheral surface of the cylindrical mold along the axial direction of the cylindrical mold. By using this cylindrical mold, a tube 80 having a plurality of convex portions 292 formed on the inner peripheral surface was obtained (see the second modified example). The other points produced the secondary transfer roll 28 in the same manner as in Example 1.

[Comparative Example 1]
The tube which does not have a convex part in an inner peripheral surface was obtained by using the cylindrical metal mold | die in which the groove | channel is not formed in the outer peripheral surface. The other points produced the secondary transfer roll 28 in the same manner as in Example 1.

[Comparative Example 2]
A plurality of grooves along the axial direction of the cylindrical mold were formed on the outer peripheral surface of the cylindrical mold along the circumferential direction of the cylindrical mold. By using this cylindrical mold, as shown in FIG. 8, a tube 80 was obtained in which a plurality of convex portions 386 along the axial direction were formed on the inner circumferential surface along the circumferential direction. The other points produced the secondary transfer roll 28 in the same manner as in Example 1.

[Evaluation]
(Adhesion, crease, wrinkle durability test)
The produced secondary transfer roll 28 was mounted on DocuCentre-V C7775 (manufactured by Fuji Xerox) as the image forming apparatus 10, and after printing 100,000 sheets, the tube 80 of the secondary transfer roll 28 was visually observed.

The adhesion was evaluated by the presence or absence of displacement of the tube 80 in the axial direction with respect to the elastic roll 70 (elastic layer 74).
A: There is a displacement of the tube 80 B: There is no displacement of the tube 80

  Further, when the tube 80 is bent or wrinkled, the back surface of the paper may be stained due to poor cleaning of the tube surface. Therefore, the presence or absence of wrinkles or bends on the tube surface was evaluated.

(Volume resistance unevenness)
The prepared secondary transfer roll 28 is placed on a metal flat plate, 500 g weights are placed on both ends of the support 72, a voltage of +1000 V is applied to the support 72 of the secondary transfer roll 28, and a resistance measuring instrument is used. The volume resistance was measured. Measurement was carried out every 10 ° in the circumferential direction of the roller, and volume resistance unevenness was evaluated based on the difference (Δ) between the maximum value and the minimum value of resistance.
A: Δ0.05 logΩ or less B: Δ0.10 logΩ or less C: Δ0.20 logΩ or less D: Greater than Δ0.20 logΩ

(Hardness unevenness)
Using the ASK-C hardness meter (manufactured by Kobunshi Keiki Co., Ltd.), the secondary transfer roll 28 thus manufactured was measured at 108 points, with a load of 4.9 N, 3 points in the axial direction and 36 points in the circumferential direction every 10 °. The hardness unevenness was evaluated by the difference (Δ) between the maximum value and the minimum value of hardness.
A: Δ2 ° or less B: Δ3 ° or less C: Δ5 ° or less D: Greater than Δ5 °

(Evaluation results)
As a result of this evaluation, as shown in the table of FIG. 9, in Example 1 and Example 2, no wrinkles or creases occurred on the tube surface, and the evaluation was A in adhesion, resistance unevenness, and hardness unevenness. .

  In Example 3, no wrinkles or creases occurred on the tube surface, and the evaluation was A for adhesion and resistance unevenness and B for hardness unevenness.

  In addition, in the structure used as the object of this evaluation, any of Example 1, Example 2, and Example 3 did not cause the displacement of the tube 80 in the axial direction with respect to the elastic roll 70 (elastic layer 74). . When the material in which the tube 80 is slidable with respect to the elastic layer 74 is used, as described in the first modification and the second modification described above, the configurations of the second and third embodiments are higher than those of the first embodiment. It is considered that the effect of suppressing the displacement of the tube 80 in the axial direction with respect to the elastic layer 74 is higher.

  In Comparative Example 1, wrinkles and creases occurred on the tube surface, and A evaluation was obtained for B evaluation, resistance unevenness, and hardness unevenness in adhesion.

  In Comparative Example 2, wrinkles and creases occurred on the tube surface, and the evaluation was A evaluation for adhesion, resistance evaluation, and hardness evaluation for D.

  Thus, compared with the comparative examples 1 and 2, in Examples 1-3, a wrinkle and a crease | fold did not generate | occur | produce on the tube surface but evaluation became high in adhesiveness, resistance nonuniformity, and hardness nonuniformity.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Toner image forming part (an example of image forming part)
28 Secondary transfer roll (an example of a transfer roll, an example of a coating roll)
30 Transfer device 70 Elastic roll 80 Tube (an example of a covering member)
86 convex portion 190 convex portion 191 first convex portion 192 second convex portion 290 convex portion P Recording medium (an example of medium)

Claims (8)

An elastic roll;
A cylindrical covering member covering the outer periphery of the elastic roll;
A convex portion that is formed on the inner peripheral surface of the covering member, has a linear shape with an angle with respect to the axial direction of the covering member when viewed in the radial direction of the covering member, and protrudes in the entire circumferential direction of the covering member When,
A coating roll comprising: The coating roll according to claim 1, wherein the convex portion protrudes at a plurality of locations separated in the axial direction along the entire circumference of the coating member. The coating roll according to claim 2, wherein the convex portion has a spiral shape that circulates a plurality of times along the axial direction. The convex portion is
A first convex portion that is spirally wound around the axial direction a plurality of times;
The first convex portion is a second convex portion that is spirally wound around in multiple turns in a reverse winding,
The coating roll according to claim 3. The convex portion is
The coating roll according to claim 2, wherein the coating roll has an annular shape having an angle with respect to the axial direction of the coating member when viewed in the radial direction of the coating member, and a plurality of coating rolls are arranged from one end side to the other end side in the axial direction. The coating roll according to any one of claims 1 to 5, wherein a ratio of the convex portions in the axial direction is constant over the entire circumference in the circumferential direction.   The transfer apparatus provided with the coating roll of any one of Claims 1-6 as a transfer roll. An image forming unit for forming an image;
The transfer device according to claim 7, wherein the image formed by the image forming unit is transferred to a medium;
An image forming apparatus comprising:

Images