Fixing device and image forming apparatus

Abstract

To improve film thickness uniformity compared with a case in which powder coating is performed.SOLUTION: A method for manufacturing a heating roll executes the steps of: heating a surface of a metal substrate (11) with an electrically-insulating and heat-shrinkable polyether ether ketone resin (21) coated on a surface to form an insulating part (12) on the surface of the substrate (11); and forming a heat generation part (13) that generates heat upon energization on a surface of the insulating part (12).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to Fixing device and image forming apparatus .

Background Art

[0002] Regarding a fixing device for fixing unfixed developer transferred onto a medium in an image forming apparatus, the techniques described in the following Patent Documents 1 and 2 are known. Japanese Patent Application Laid-Open No. 10-3226 as Patent Document 1 describes a heating roller (10) in which an insulating film material (14) made of a polyimide resin is disposed on the inner surface of a roller body (11), and a heating element (15) is disposed further inside the insulating film material (14).

[0003] Japanese Patent Application Laid-Open No. 2001-201970 as Patent Document 2 describes a heat-generating fixing roll (10) in which an insulating layer (2) made of a water-repellent resin such as a fluororesin is formed on the inner peripheral surface of a cylindrical core metal (1), and a resistance heating element (3) is formed further inside the insulating layer (2). In Patent Document 2, a toner adhesion preventing layer (4) made of a water-repellent resin such as a fluororesin is also formed as a release layer on the outer peripheral side of the core metal (1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technical problem of the present invention is to improve the uniformity of film thickness as compared with the case of performing powder coating.

Means for Solving the Problems

[0006] To solve the above technical problem, the fixing device of the invention according to claim 1 is Endless belt-like means, supporting the belt-like means and heating the belt-like means a heating roll and and heating means having the same, a pressing means disposed opposite to the heating means , pressurizing the medium passing between the belt-like means and is provided with a fixing device for fixing a developer as a medium passing between the heating means and the pressing means, wherein the heating roll is composed of a metal base material and a heat generating portion made of a material that generates heat when energized resistance and is disposed between the base material and the resistance heat generating portion, and is an insulating portion that electrically insulates between the base material and the resistance heat generating portion, and the insulating portion is a tubular polyether ether ketone resin heat-shrinkingly fixed to the outer surface of the base material First and First has a second insulating portion disposed on the opposite side of the insulating portion across the heat generating portion and having a smaller thermal resistance than the resistance insulating portion First and First is characterized in that it has and the second insulating portion contacts the belt-like means while rotating this .

[0007] To solve the above technical problem, the fixing device of the invention according to claim 2 is Endless belt-like means, supporting the belt-like means and heating the belt-like means a heating roll and and heating means having the same, a pressing means disposed opposite to the heating means , pressurizing the medium passing between the belt-like means and is provided with a fixing device for fixing a developer as a medium passing between the heating means and the pressing means, wherein the heating roll is composed of a metal base material and a heat generating portion made of a material that generates heat when energized resistance and is disposed between the base material and the resistanceDisposed between the heat generating part, between the base material and the resistance electrically insulates between the heat generating part First an insulating part, the insulating part in which a tubular polyether ether ketone resin is fixed to the outer surface of the base material by heat shrinkage First and, the resistance heat generating part is sandwiched, and is disposed on the opposite side of the insulating part from the First insulating part, is composed of polyether ether ketone resin and First a second insulating part having a smaller thickness than the insulating part, having and the second insulating portion contacts the belt-like means while rotating and is characterized by this.

[0010] To solve the above technical problem, Claim 3 the image forming apparatus according to the invention described in image holding means, latent image forming means for forming a latent image on the image holding means, developing means for developing the latent image of the image holding means, transfer means for transferring the image of the image holding means to a medium, the fixing device according to claim 1 for fixing the image of the medium or 2 described in and is characterized by comprising.

Effect of the Invention

[0011] According to the inventions described in claims 1 and 2 ,3 compared with the case of performing powder coating, the uniformity of the film thickness can be improved. Further, according to the invention described in claim 1, compared with the case where the thermal resistance of the second insulating part is First larger than that of the insulating part, the heat transfer efficiency can be increased. Furthermore, according to the invention described in claim 2, compared with the case where the thickness of the second insulating part is First larger than that of the insulating part, the heat transfer efficiency can be increased. Also, Claims 1, 2 According to the invention described in

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0013] Next, examples as specific examples of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples. For the sake of easy understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and the directions or sides indicated by the arrows X, -X, Y, -Y, Z, -Z are the front, rear, right, left, upper, lower, or front side, rear side, right side, left side, upper side, lower side, respectively. Also, in the drawings, those with "·" in "○" mean arrows from the back to the front of the paper surface, and those with "×" in "○" mean arrows from the front to the back of the paper surface. In addition, in the following description using the drawings, for the sake of easy understanding, illustrations other than the members necessary for the description are appropriately omitted.

Examples

[0014] FIG. 1 is an overall explanatory view of the image forming apparatus according to Embodiment 1 of the present invention. In FIG. 1, a copying machine U as an example of the image forming apparatus has an operation unit UI, a scanner device U1 as an example of an image reading device, a paper feeding device U2, a printer unit U3 as an example of an image recording device, and a paper discharging unit U4.

[0015] The operation unit UI has a power button, a copy start key, a copy number setting key, a numeric keypad, etc. as an example of an input unit, and a display unit, etc. The scanner device U1 reads a document (not shown) and converts it into image information, and inputs the image information to the printer unit U3. The paper feeding device U2 has a plurality of paper feeding trays TR1 to TR4 as an example of a paper feeding unit. Recording paper S as an example of a medium is accommodated in each of the paper feeding trays TR1 to TR4. A paper feeding path SH1 as an example of a conveyance path of the medium extends from each of the paper feeding trays TR1 to TR4 toward the printer unit U3.

[0016] In FIG. 1, the printer unit U3 has a control unit C, a power circuit E that is controlled by the control unit C to supply power to each member of the printer unit U3, etc. The control unit C receives the image information of the document read by the scanner device U1 and the image information transmitted from a personal computer as an example of an information transmission device (not shown) connected to the copying machine U. The control unit C processes the received image information into information for printing in Y: yellow, M: magenta, C: cyan, and K: black, and outputs the processed information to a laser drive circuit D as an example of a drive circuit of a latent image writing device. The laser drive circuit D outputs the laser drive signal input from the control unit C to exposure devices ROSy, ROSm, ROSc, and ROSk as an example of latent image forming means for each color at a preset timing.

[0017] Below each of the exposure devices ROSy to ROSk, image holding body units Uy, Um, Uc, and Uk for Y, M, C, and K are arranged. In FIG. 1, K: The black image carrier unit Uk includes a photosensitive drum Pk as an example of an image holding means, a charging corotron CCk as an example of a charging means, and a photosensitive cleaner CLk as an example of a cleaning means for the image holding means. And the image carrier units Uy, Um, Uc of the other colors Y, M, C also include photosensitive drums Py, Pm, Pc, charging corotrons CCy, CCm, CCc, and photosensitive cleaners CLy, CLm, CLc. In Example 1, the photosensitive drum Pk of the K color, which is frequently used and has a lot of surface wear, is configured to have a larger diameter than the photosensitive drums Py, Pm, Pc of the other colors, and is compatible with high-speed rotation and has a longer lifespan.

[0018] The photosensitive drums Py, Pm, Pc, Pk are each uniformly charged by the charging corotrons CCy, CCm, CCc, CCk, and then, by laser beams Ly, Lm, Lc, Lk as an example of the latent image writing light output by the exposure devices ROSy, ROSm, ROSc, ROSk, an electrostatic latent image is formed on the surfaces of the photosensitive drums Py to Pk. The electrostatic latent images on the surfaces of the photosensitive drums Py, Pm, Pc, Pk are developed into toner images of each color of Y: yellow, M: magenta, C: cyan, and K: black by a developing roll R0 as an example of a developing member provided in developing devices Gy, Gm, Gc, Gk as an example of developing means.

[0019] The toner images on the surfaces of the photosensitive drums Py, Pm, Pc, Pk are sequentially transferred and overlapped onto an intermediate transfer belt B as an example of an intermediate transfer means and an example of an image holding means in a primary transfer region Q3 by primary transfer rolls T1y, T1m, T1c, T1k as an example of primary transfer means, and a multicolor image, that is, a so-called color image, is formed on the intermediate transfer belt B. The color image formed on the intermediate transfer belt B is conveyed to a secondary transfer region Q4. In the case of only black image data, only the photosensitive drum Pk of K: black and the developing device Gk are used, and only a black toner image is formed. After primary transfer, the residual toner remaining on the surfaces of the photosensitive drums Py, Pm, Pc, Pk is cleaned by the photosensitive cleaners CLy, CLm, CLc, CLk. Each of the image holding unit Uy, Um, Uc, Uk and the developing devices Gy, Gm, Gc, Gk constitutes a toner image forming member Uy + Gy, Um + Gm, Uc + Gc, Uk + Gk as an example of a visible image forming unit.

[0020] Above the printer unit U3, a toner dispenser U3a is arranged as an example of replenishing means, and toner cartridges Ky, Km, Kc, Kk are detachably mounted on the toner dispenser U3a as an example of accommodating means for the developer. When toner is consumed in the developing devices Gy to Gk during image formation, toner is supplied from each toner cartridge Ky to Kk to each developing device Gy to Gk.

[0021] The intermediate transfer belt B disposed below the photosensitive drums Py to Pk is provided with an intermediate drive roll Rd as an example of a driving means for the intermediate transfer means, an intermediate tension roll Rt as an example of a tension applying means for applying tension to the intermediate transfer belt B, an intermediate steering roll Rw as an example of a first deviation correction means for correcting the deviation and meandering of the intermediate transfer belt B, a plurality of intermediate idler rolls Rf as an example of a driven means, and a backup roll T2a as an example of an opposing means for the secondary transfer region, and is stretched by them. And the intermediate transfer belt B is supported so as to be rotatable and movable in the direction of arrow Ya by the drive of the intermediate drive roll Rd. The intermediate drive roll Rd, the intermediate tension roll Rt, the intermediate steering roll Rw, the intermediate idler rolls Rf, the backup roll T2a, the primary transfer rolls T1y to T1k, the intermediate transfer belt B, etc. constitute a belt module BM as an example of an intermediate transfer device. Note that the belt module BM of the first embodiment is constituted by a unit that can be detached and replaced with respect to the printer unit U3.

[0022] Below the backup roll T2a, a secondary transfer unit Ut, which is an example of transfer and conveyance means, is arranged. The secondary transfer unit Ut has a secondary transfer roll T2b as an example of a transfer member. The secondary transfer roll T2b is arranged to face the backup roll T2a. A secondary transfer area Q4 is formed by the area where the secondary transfer roll T2b faces the intermediate transfer belt B. Further, a contact control T2c, which is an example of contact means for voltage application, is in contact with the backup roll T2a. A secondary transfer voltage having the same polarity as the charging polarity of the toner is applied to the contact control T2c from a power supply circuit E controlled by a control unit C at a preset time. The rolls T2a to T2c constitute a secondary transfer device T2, which is an example of secondary transfer means. Further, an intermediate transfer belt B, primary transfer rolls T1y to T1k, a secondary transfer device T2, etc. constitute a transfer device B+T1+T2, which is an example of transfer means.

[0023] Below the belt module BM, a paper conveyance path SH2 is arranged. The recording paper S fed from the paper feed path SH1 of the paper feed device U2 is conveyed to the paper conveyance path SH2 by a conveyance roll Ra, which is an example of conveyance means. The recording paper S on the paper conveyance path SH2 is sent out by a registration roll Rr, which is an example of sending-out means, at a timing when the toner image is conveyed to the secondary transfer area Q4, and is guided by paper guides SG1 and SG2, which are examples of medium guiding means, and is conveyed to the secondary transfer area Q4. The toner image on the intermediate transfer belt B is transferred to the recording paper S by the secondary transfer device T2 when passing through the secondary transfer area Q4. In the case of a color image, the toner images primarily transferred on the surface of the intermediate transfer belt B are collectively secondarily transferred to the recording paper S. After secondary transfer, the intermediate transfer belt B is cleaned, that is, cleaned, by a belt cleaner CLB, which is an example of cleaning means for the intermediate transfer means.

[0024] The recording paper S on which the toner image has been secondarily transferred is sent to a medium conveyance belt BH as an example of a conveyance means. The medium conveyance belt BH conveys the recording paper S to a fixing device F. The fixing device F as an example of a fixing means has a heating unit Fh as an example of a heating means and a pressure roll Fp as an example of a pressure means, and a fixing area Q5 is formed by a region where the heating unit Fh and the pressure roll Fp face and contact each other. The toner image on the recording paper S is heat-fixed by the fixing device F when passing through the fixing area Q5. The recording paper S on which the toner image has been fixed by the fixing device F is discharged to a discharge tray TRh as an example of a discharge unit. A paper conveyance path SH is constituted by the symbols SH1, SH2, etc. Further, a paper conveyance device SU is constituted by the symbols SH, Ra, Rr, SG1, SG2, BH, etc.

[0025] (Explanation of the fixing device) In FIG. 1, the heating unit Fh of the fixing device F of Example 1 has an endless fixing belt 1 as an example of a belt-like means. The fixing belt 1 of Example 1 is supported by a heating roll 2 as an example of a heat-generating member, a driving roll 3 as an example of a driving means, and a fixing pad 4 as an example of an opposing means. The heating roll 2 generates heat during the image forming operation to heat the fixing belt 1. The driving roll 3 rotates the fixing belt 1 during image formation. The fixing pad 4 opposes the fixing belt 1 to the pressure roll Fp in the fixing area Q5.

[0026] (Explanation of the heating roll) FIG. 2 is a schematic explanatory view of the heating roll of Example 1. FIG. 3 is a cross-sectional view of the main part of the heating roll of Example 1. In FIGS. 2 and 3, the heating roll 2 of Example 1 has a core metal 11 as an example of a base material. The core metal 11 of Example 1 is made of a conductive metal material. The core metal 11 is preferably made of aluminum as an example, but it is also possible to use a conductive alloy such as iron or stainless steel. Further, the core metal 11 of Example 1 is formed in a cylindrical shape extending in the rotation axis direction. An insulating layer 12, which is an example of an insulating portion, is formed on the outer periphery of the core metal 11. The insulating layer 12 of Example 1 is an electrical insulating material and is made of polyether ether ketone (PEEK) resin as an example of a material having a lower water absorption rate and moisture content than polyimide resin. The water absorption rate is measured by immersing a test piece in water at 23°C for 24 hours as defined in JIS K7209. As an example, the PEEK resin has a water absorption rate of 0.04%, the polyimide resin has 0.8%, the polyamide resin has about 0.4%, the polyamideimide resin has about 0.3%, and PFA (perfluoroalkoxy alkane resin), which is an example of a fluororesin, has 0.01%.

[0027] A heating layer 13, which is an example of a heat generating portion, is formed on the outer surface side of the insulating layer 12. The heating layer 13 is composed of a resistive heating element that generates heat when energized. The resistive heating element is described in, for example, Patent Documents 1, 2, etc. and is conventionally known, so detailed description is omitted. A surface layer 14, which is an example of an outer layer, is formed on the outer surface side of the heating layer 13. The surface layer 14 of Example 1 is preferably made of an insulating material. If the surface layer 14 is made of a conductive material, current easily flows from the heating layer 13, and it is necessary to increase the power supply capacity of the power supply circuit E, or there are problems such as leakage to the fixing belt 1. Therefore, the surface layer 14 is preferably made of an electrically insulating material. As the electrically insulating material, for example, polyimide resin, glass resin, PEEK resin, fluororesin, polyamide resin, polyimideamide resin, PEKK (polyether ketone ketone) resin, etc. can be used.

[0028] Also, the surface layer 14 of Example 1 is preferably made of a wear-resistant material in response to contact and wear with the fixing belt 1. Examples of the wear-resistant material include polyimide resin, glass resin, PEEK resin, and fluororesin. Furthermore, from the perspective of the heat transfer efficiency to the fixing belt 1, it is desirable that the surface layer 14 of Example 1 has a lower (thermal resistance) = (thermal conductivity) × (thickness) than the insulating layer 12. That is, among the insulating layer 12 and the surface layer 14 sandwiching the heating layer 13, since heat is more likely to be transferred when the thermal resistance is smaller, it is desirable that the thermal resistance of the surface layer 14 on the fixing belt 1 side is smaller. Therefore, when the surface layer 14 is made of the same PEEK resin as the insulating layer 12, it is possible and preferable to lower the thermal resistance by making the thickness of the surface layer 14 thinner than the thickness of the insulating layer 12. In FIG. 2, for the heating roll 2 of Example 1, the length in the rotation axis direction is such that the length L1 of the core metal 11 is the longest, and for the length L2 of the insulating layer 12, the length L3 of the heating layer 13, and the length L4 of the surface layer 14, it is set as L1 > L2 > L3 ≧ L4. Note that silver paste 16 for power supply is applied to both axial ends of the heating layer 13.

[0029] (Explanation of the manufacturing method of the heating roll) FIG. 4 is an explanatory diagram of the manufacturing method of the heating roll of Example 1. FIG. 4A is an explanatory diagram of the state before covering the base material with PEEK resin, FIG. 4B is an explanatory diagram of the state after covering the base material with PEEK resin from the state of FIG. 4A, FIG. 4C is an explanatory diagram of the state after thermally shrinking the PEEK resin from the state of FIG. 4B, and FIG. 4D is an explanatory diagram of the state after fixing the heating part from the state of FIG. 4C. In FIG. 4, when manufacturing the heating roll 2 of Example 1, as shown in FIG. 4A, a cylindrical body 21 made of a cylindrical PEEK resin having an inner diameter larger than the outer diameter of the core metal 11 is prepared. The cylindrical body 21 is formed into a cylindrical shape by extrusion molding in a state where the bulk (solidified) PEEK resin is heated to a high temperature of 200°C or higher. At this time, when forming from the bulk state into a cylindrical shape, it is possible to solidify it into a cylindrical shape with residual stress and residual strain remaining by expanding while cooling. The cylindrical body 21 in a state where residual strain remains shrinks when reheated, but it is preferable to mold it so that the shrinkage rate in the radial direction of the cylindrical body 21 is larger than the shrinkage rate in the length direction (axial direction) of the cylindrical body 21. Also, from the perspective of ensuring insulation, the wall thickness of the cylindrical body 21 is preferably about 10 μm to 50 μm, and about 30 μm is suitable.

[0030] In FIG. 4B, after covering the cylindrical body 21 around the core metal 11, the cylindrical body 21 and the core metal 11 are heated to 160° C. or higher. When the core metal 11 and the cylindrical body 21 are heated, the cylindrical body 21 thermally contracts and adheres and fixes to the core metal 11, and as shown in FIG. 4C, the insulating layer 12 is formed. Then, in FIGS. 4C and 4D, the heating layer 13 is fixed to the outer periphery of the insulating layer 12. When the surface layer 14 is provided, the surface layer 14 is formed by thermal contraction of a cylindrical body similar to the insulating layer 12, painting, or the like, and the heating roll 2 is manufactured.

[0031] (Operation of Example 1) In the copying machine U of Example 1 having the above configuration, when the image forming operation is started, the heating layer 13 is energized, the heating layer 13 generates heat, the heating roll 2 heats the fixing belt 1, and the fixing area Q5 is heated to a predetermined fixing temperature. Then, the recording paper S passing through the fixing area Q5 is heated to fix the toner.

[0032] In the heating roll using the heating layer 13 or the sheet-like or film-like resistive heating element as shown in Example 1 and Patent Documents 1 and 2, an insulating layer for electrically insulating between the resistive heating element and the core metal is required as in Example 1 and Patent Documents 1 and 2. When polyimide is used as the insulating layer as in the configuration described in Patent Document 1, the moisture in the polyimide with high water absorption and moisture content expands due to heating, and unevenness occurs on the surface, causing uneven heating and uneven fixing. As in the configuration described in Patent Document 2, the problem of uneven fixing can be solved by using a fluororesin with low moisture content as the insulating layer, but the fluororesin has high releasability. That is, even when trying to fix the heating layer to the surface of the insulating layer, the wettability and adhesiveness are low, and uneven adhesion of the heating layer occurs, resulting in unevenness in the overall film thickness of the heating roll 2. Therefore, when using a fluororesin as the insulating layer, the film thickness homogeneity and film thickness uniformity decrease, and there is a risk of uneven fixing. In contrast, for these, in the heating roll 2 of Example 1, as the insulating layer 12, a PEEK resin that is electrically insulating, has a low water absorption rate, and has high wettability and adhesiveness such as the heating layer 13 is used. Therefore, compared with the case of using a fluororesin as the insulating layer, it is possible to fix the heating layer 13 uniformly on the surface of the insulating layer 12. Therefore, compared with the case of using a fluororesin, it is possible to improve the film thickness uniformity, and the fixing unevenness is suppressed.

[0033] Also, in Example 1, the surface layer 14 is made of an insulating material. Compared with the case of being made of a conductive material, problems such as an increase in the capacity of the power supply circuit and leakage to the fixing belt 1 are suppressed. Furthermore, in Example 1, the surface layer 14 is made of a wear-resistant material. Compared with the case of not being made of a wear-resistant material, the wear resistance of the heating roll 2 in contact with the fixing belt 1 is improved, and the service life is extended. Also, in Example 1, the surface layer 14 is configured to have a lower thermal resistance than the insulating layer 12. Compared with the case of having a high thermal resistance, the heat transfer efficiency to the fixing belt 1 is improved. Furthermore, in Example 1, regarding the axial lengths L1 to L4 of the core metal 11, the insulating layer 12, the heating layer 13, and the surface layer 14, they are set to L1 > L2 > L3 ≥ L4. In the case of L2 < L3, the insulation between the core metal 11 and the heating layer 13 becomes insufficient, but this is prevented in Example 1. Also, in the case of L3 < L4, power supply to the heating layer 13 becomes difficult, but this is prevented in Example 1.

[0034] In Example 1, when forming the insulating layer 12, a tubular (tube-shaped) cylinder 21 is put on the mandrel 11 and heat-shrunk and fixed. Currently, in coating processing for producing a coating film with a PEEK material, powder coating is common. Specifically, PEEK particles with a diameter of about 10 μm to 50 μm are used. After spraying the PEEK particles in a dry state, they are baked, or after applying a dispersion liquid in which the PEEK particles are dispersed, they are baked to form a coating film of the PEEK resin. However, when producing the insulating layer 12 with a film thickness of 30 μm to 50 μm using PEEK particles with a diameter of 10 μm to 50 μm, irregularities remain on the surface of the insulating layer 12, and it is difficult to obtain a uniform film thickness. Therefore, there is a problem that it also has an adverse effect on the film thickness of the outer heating layer 13 and the surface layer 14. If the film thickness of the insulating layer 12 is increased, this problem can be solved. However, when the film thickness increases, the amount of PEEK material used increases, the material cost rises, and the overall heat capacity of the heating roll 2 increases, resulting in a longer time required to reach the target temperature and a problem that it takes a long time until the start of the image forming operation.

[0035] In contrast, in Example 1, the cylindrically formed cylinder 21 is heat-shrunk, and compared with the case of using particles, the uniformity and homogeneity of the film thickness are improved. Therefore, the overall film thickness of the heating roll 2 is also improved in terms of uniformity and homogeneity compared with the case of performing powder coating, and it can be made thinner. In addition, in Example 1, the shrinkage rate in the axial direction of the cylinder 21 is formed to be smaller than the shrinkage rate in the radial direction. When the shrinkage rate in the axial direction is higher, there is a problem that during heat shrinkage, the shrinkage in the axial direction becomes large and wrinkles are likely to occur on the surface of the insulating layer 12. In contrast, in Example 1, the shrinkage rate in the radial direction is larger, and the occurrence of wrinkles on the surface of the insulating layer 12 is suppressed.

Example

[0036] Next, Example 2 of the present invention will be described. In the description of this Example 2, components corresponding to the components of the above Example 1 are denoted by the same reference numerals, and detailed descriptions thereof are omitted. Although Example 2 is different from Example 1 in the following points, it is configured in the same manner as Example 1 in other points.

[0037] FIG. 5 is an explanatory diagram of the image forming apparatus of Example 2 and corresponds to FIG. 1 of Example 1. In FIG. 5, the heating means Fh′ of the copying machine U of Example 2 is composed of a heating roll Fh′ as an example of a heating roll, different from the heating unit Fh of Example 1. The heating roll Fh′ of Example 2 has a core metal 11, an insulating layer 12, and a heating layer 13, similar to the heating roll 2 of Example 1, and has a surface layer 14′ different from the surface layer 14 of Example 1. A fluororesin with high releasability is used for the surface layer 14′ of Example 2.

[0038] (Operation of Example 2) In the heating roll Fh′ of Example 2 having the above configuration, in the heating roll Fh′ directly facing the pressure roll Fp, PEEK resin is used for the insulating layer 12, and fixing unevenness is suppressed. In particular, a fluororesin with good releasability is used for the surface layer 14′ that directly contacts the unfixed toner on the surface of the recording paper S. Therefore, compared with the case of using a polyimide resin or the like having poor releasability compared to the fluororesin, in the heating roll Fh′ of Example 2, toner hardly adheres to the surface. Thus, it is reduced that the surface of the heating roll Fh′ is soiled by the adhered toner, and it is suppressed that the toner on the surface of the heating roll Fh′ re-adheres to the recording paper S and the recording paper S is soiled.

[0039] (Modification Example) Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. Modification examples (H01) to (H09) of the present invention are exemplified below. (H01) In the above embodiment, a copying machine as an example of an image forming apparatus is exemplified, but it is not limited thereto. For example, it can also be configured by a FAX, a printer, or a multifunction machine.

[0040] (H02) In the above embodiment, as the image forming apparatus, a configuration in which four-color developers are used was exemplified, but the present invention is not limited thereto. For example, it is also applicable to a monochromatic image forming apparatus or a multicolor image forming apparatus having three or less or five or more colors. (H03) In the above embodiment, a configuration in which the insulating layer 12 is directly disposed on the surface of the core metal 11 and the heating layer 13 is directly disposed on the surface of the insulating layer 12 was exemplified, but the present invention is not limited thereto. For example, a configuration in which another layer is interposed between the insulating layer 12 and the heating layer 13, such as a case where a primer layer for improving wettability and adhesiveness is applied, is also possible. (H04) In the above embodiment, it is desirable to provide the surface layer 14, but a configuration without providing it is also possible.

[0041] (H05) In the above embodiment, it is desirable that the surface layer 14 be made of an insulating material, but it is also possible to be made of a conductive material. (H06) In the above embodiment, it is desirable that the surface layer 14 be made of a wear-resistant material, but for example, it is also possible to be made of a material that is easily worn, emphasizing releasability. (H07) In the above embodiment, it is desirable that the surface layer 14 has a low thermal resistance, but a configuration with a high thermal resistance is also possible. (H08) In the above embodiment, the axial lengths L1 to L4 of each part are preferably the configurations exemplified in the embodiment, but can be appropriately changed according to the design, specifications, etc.

[0042] (H09) In the above embodiment, a case where the insulating layer 12 is formed using the cylindrical body 21 was exemplified, but the present invention is not limited thereto. For example, a configuration in which a thin film or film of PEEK resin is wound around the core metal and heat-shrunk to be adhered is also possible. However, when winding the film, joints will occur, so it is preferable to use the cylindrical body 21.

Explanation of Reference Numerals

[0043] 1... Belt-like means, 2, Fh′... Heating roll, 11... Substrate, 12... Insulating part, 13... Heating part, 14... Outer layer, 21... Polyetheretherketone resin, B + T1 + T2... Transfer means, F... Fixing device, Fh, Fh′... Heating means, Fp... Pressing means, Gy, Gm, Gc, Gk... Developing means, L1... Length of the substrate in the rotational axis direction, L2... Length of the insulating part in the rotational axis direction, L3... Length of the heating part in the rotational axis direction, L4... Length of the outer layer in the rotational axis direction, Py, Pm, Pc, Pk... Image holding means, ROSy, ROSm, ROSc, ROSk... Latent image forming means, S... Medium, U... Image forming apparatus.

Claims

Claim 1: A fixing device comprising: endless belt-like means; and a heating roll that supports the belt-like means and heats the belt-like means. Pressing means that is disposed opposite to the heating means and presses a medium passing between the pressing means and the belt-like means. Comprising: A fixing device that fixes a developer of a medium passing between the heating means and the pressing means, wherein the heating roll has a metal base material, a resistive heating portion composed of a material that generates heat when energized, a first insulating portion that is disposed between the base material and the resistive heating portion and electrically insulates between the base material and the resistive heating portion, and the first insulating portion is a cylindrical polyether ether ketone resin heat-shrinkingly fixed to the outer surface of the base material, a second insulating portion that is disposed on the opposite side of the first insulating portion with the resistive heating portion interposed therebetween and has a lower thermal resistance than the first insulating portion, and the second insulating portion contacts the belt-like means while rotating. A fixing device characterized by the above. Claim 2: A fixing device comprising: endless belt-like means; and a heating roll that supports the belt-like means and heats the belt-like means. Pressing means that is disposed opposite to the heating means and presses a medium passing between the pressing means and the belt-like means. Comprising: A fixing device that fixes a developer of a medium passing between the heating means and the pressing means, wherein the heating roll has a metal base material, a resistive heating portion composed of a material that generates heat when energized, a first insulating portion that is disposed between the base material and the resistive heating portion and electrically insulates between the base material and the resistive heating portion, and the first insulating portion is a cylindrical polyether ether ketone resin heat-shrinkingly fixed to the outer surface of the base material, a second insulating portion that is disposed on the opposite side of the first insulating portion with the resistive heating portion interposed therebetween, is composed of polyether ether ketone resin, and is configured to have a smaller thickness than the first insulating portion, and the second insulating portion contacts the belt-like means while rotating. A fixing device characterized by the above. Claim 3 Image holding means, Latent image forming means for forming a latent image on the image holding means, Developing means for developing the latent image of the image holding means, Transferring means for transferring the image of the image holding means to a medium, and the fixing device according to claim 1 or 2 for fixing the image of the medium. An image forming apparatus characterized by comprising the above.

Images