JP6801325B2 - Rotating member for fixing, fixing device and image forming device - Google Patents

Description

The present invention relates to a rotating member for fixing, a fixing device, and an image forming device.

The fixing device of Patent Document 1 uses a roller having an inverted crown shape in which the outer diameter of the central portion in the longitudinal direction is smaller than the outer diameter of both end portions as the roller for forming the nip portion to be fixed.

JP-A-2002-333789

There is a rotating member for fixing in which the outer diameters of both ends in the axial direction are larger than the outer diameter of the central portion. In the fixing device in which the rotating member for fixing is pressurized to form the nip portion, the nip width in the transport direction of the recording medium is wider at both ends than the central portion in the axial direction. In other words, since the contact area between the fixing rotating member and the recording medium increases at both ends in the axial direction, the recording medium is likely to be wrapped around the fixing rotating member, so that the recording medium from the fixing rotating member The peelability of the product may decrease.

According to the present invention, in a rotating member for fixing in which the outer diameters of both ends in the axial direction are larger than the outer diameter of the central portion, the peelability of the recording medium is improved as compared with a configuration in which uneven portions are not formed on the outer peripheral surface. With the goal.

Fixing rotation member according to claim 1 of the present invention has an outer diameter of both ends of the axial Rutotomoni is a shape larger than the outer diameter of the central portion, an uneven portion on the outer peripheral surface, the uneven portions The difference in height along the radial direction between the concave portion and the convex portion gradually increases from the central portion side to the both end portions side .

The fixing rotating member according to claim 2 of the present invention is the fixing rotating member according to claim 1, and the maximum value of the height difference between the concave portion and the convex portion at both ends thereof is 2 μm or more. It is 10 μm or less.

The fixing device according to claim 3 of the present invention is arranged so as to face the fixing rotating member according to claim 1 or 2 and the fixing rotating member, and sandwiches a recording medium together with the fixing rotating member. It has a facing member, a rotating member for fixing, and a heating source for heating at least one of the facing members, and melts and pressurizes the developer to fix it on a recording medium.

The image forming apparatus according to claim 4 of the present invention is a claim for fixing a developer image forming means for forming a developer image on a recording medium and a developer image formed by the developer image forming means on the recording medium. It has the fixing device according to item 3 .

The invention of claim 1 is a removability of a recording medium in a rotating member for fixing in which the outer diameters of both ends in the axial direction are larger than the outer diameter of the central portion, as compared with a configuration in which uneven portions are not formed on the outer peripheral surface. Can be enhanced.

Further, the invention of claim 1 can improve the peelability in a plurality of types of recording media having different widths, as compared with a configuration in which there is a step between the central portion and both end portions in the axial direction.

According to the second aspect of the present invention, deterioration of image quality after fixing can be suppressed as compared with a configuration in which the maximum value of the height difference between the concave portion and the convex portion at both ends is lower than 2 μm or higher than 10 μm. ..

The invention of claim 3 can suppress peeling failure of the recording medium in the fixing rotating member as compared with the configuration without the fixing rotating member according to claim 1 or 2 .

The invention of claim 4 can suppress image defects after fixing as compared with the configuration without the fixing device according to claim 3 .

It is a block diagram which shows the image forming apparatus which concerns on this embodiment. (A) It is explanatory drawing which shows the state before pressurization of the fixing roll and the pressurizing roll which concerns on this embodiment. (B) It is explanatory drawing which shows typically the vertical cross section of the fixing roll which concerns on this embodiment. It is sectional drawing of the fixing apparatus which concerns on this embodiment (the cross section of line 3-3 of FIG. 2A). It is a graph which shows the relationship between the axial position at the time of forming the elastic layer of the fixing roll which concerns on this embodiment, and the discharge amount of a coating liquid. (A) It is explanatory drawing which shows the state of the outer peripheral part of the fixing roll when the paper enters the nip part of the fixing device which concerns on this Embodiment. (B) It is explanatory drawing which shows the state of the outer peripheral part of the fixing roll when the paper advances from the nip part of the fixing device which concerns on this Embodiment.

An example of the fixing rotating member, the fixing device, and the image forming device according to the present embodiment will be described.

〔overall structure〕
FIG. 1 shows the image forming apparatus 10 of the present embodiment. In the following description, the direction indicated by the arrow Y in FIG. 1 is the device height direction, and the direction indicated by the arrow X is the device width direction. Further, the direction (indicated by Z) orthogonal to each of the device height direction and the device width direction is defined as the device depth direction. Then, when the image forming apparatus 10 is viewed from the front, the device height direction, the device width direction, and the device depth direction are described as Y direction, X direction, and Z direction. Further, when it is necessary to distinguish one side and the other side of each of the X direction, the Y direction, and the Z direction, the image forming apparatus 10 is viewed from the front, the upper side is the Y side, the lower side is the −Y side, and the right side is the right side. The X side, the left side is described as -X side, the back side is described as Z side, and the front side is described as -Z side.

The image forming apparatus 10 has a box-shaped housing 11. Further, the image forming apparatus 10 includes, as an example, a conveying unit 12, an image forming unit 14 as an example of the developer image forming means, a control unit 16, and a fixing device 20. The transport unit 12 is configured to include the roll pair 13, and transports the paper P along the transport path A. The control unit 16 controls the operation of each unit of the image forming apparatus 10.

The image forming unit 14 has four image forming units 15 as an example. Further, the image forming unit 14 performs each step of charging, exposure, developing, and transferring, which is a known electrophotographic method, to form a toner image G on the paper P conveyed by the conveying unit 12 by using the toner T. Form. Paper P is an example of a recording medium. Toner T is an example of a developer. The toner image G is an example of a developer image. The fixing device 20 heats and pressurizes the toner image G formed by the image forming unit 14 and fixes it on the paper P. The details of the fixing device 20 will be described later.

[Main part composition]
Next, the fixing device 20 will be described.

The fixing device 20 shown in FIG. 3 has a fixing roll 22 as an example of a rotating member for fixing, a pressure roll 32 as an example of an opposing member, and a heating unit 42 as an example of a heating source. The fixing roll 22, the pressure roll 32, and the heating unit 42 are housed in a rectangular parallelepiped housing (not shown) which is the main body of the fixing device 20.

<Fixing roll>
As an example, the fixing roll 22 has a structure including a cylindrical core metal 24, an elastic layer 26 formed on the outer peripheral surface of the core metal 24, and a mold release layer 28 formed on the outer peripheral surface of the elastic layer 26. Has been done. Further, the fixing roll 22 is rotatably arranged around the toner image G side (X side) with the Z direction as the axial direction with respect to the transport path A of the paper P. That is, the fixing roll 22 rotates with the Z direction orthogonal to the conveying direction of the paper P as the axial direction. The fixing roll 22 is rotationally driven by a motor (not shown) at the Z-side end of the core metal 24.

FIG. 2A shows a non-pressurized state in which the pressurizing roll 32 is not pressed against the fixing roll 22. The fixing roll 22 has a shape in which the outer diameter d2 of both end portions 22A in the Z direction is larger than the outer diameter d1 of the central portion 22B when viewed in the Y direction. Further, the fixing roll 22 is formed in a so-called inverted crown shape in which the outer diameter gradually increases from the central portion 22B toward both end portions 22A along the Z direction. Further, in FIG. 2A, the difference between the outer diameter d1 and the outer diameter d2 is exaggerated. Here, the region representing the outer peripheral surface of the end portion on the −Z side, which is a part of the fixing roll 22, is surrounded by the alternate long and short dash line K. Hereinafter, this region will be referred to as region K. Since the end portion on the Z side has a symmetrical arrangement and the same configuration as the −Z side, the description thereof will be omitted.

(Core metal)
As an example, the core metal 24 is made of an aluminum cylinder extending in the Z direction as an axial direction. Further, the core metal 24 has substantially the same outer diameter d0 from the Z-side end to the −Z-side end in the Z direction. Outer diameter d0 <outer diameter d1. Further, the outer diameters of the portions of the core metal 24 in the Z direction in which the elastic layer 26 is not formed are smaller than the portions where the elastic layer 26 is formed.

(Elastic layer)
As an example, the elastic layer 26 is made of silicone rubber and covers the outer peripheral surface of the core metal 24. Further, the elastic layer 26 has an annular cross section when viewed in the Z direction. Further, the elastic layer 26 has an inverted crown shape in which the thickness gradually increases from the central portion 22B toward both end portions 22A. In order to form the elastic layer 26 having a shape in which the thickness gradually increases on the core metal 24, the amount of the coating liquid discharged [g] while the core metal 24 is rotated and the nozzle (not shown) is moved in the axial direction. / S] may be changed.

FIG. 4 is a graph G1 showing the relationship between the axial position and the discharge amount of the coating liquid as an example of changing the discharge amount of the coating liquid when the elastic layer 26 (see FIG. 3) is formed. The coating liquid contains, for example, a liquid silicone rubber. The discharge amount LB is set at the position A (one end) in the axial direction, the discharge amount LA (<LB) is set at the position B (center), and the discharge amount LB is set at the position C (the other end). Further, from position A to position B, the discharge amount is set to gradually decrease (stepwise) as it approaches position B, and from position B to position C, it gradually decreases (stairs) as it approaches position C. It is set to increase the discharge amount. In this way, by changing the discharge amount of the coating liquid according to the axial position, elastic layers 26 having different thicknesses in the axial direction are formed on the outer peripheral surface of the core metal 24 (see FIG. 3).

(Release layer)
The release layer 28 is formed of PFA (perfluoroalkyl vinyl ether copolymer) as an example. The thickness of the release layer 28 is substantially the same (35 [μm] as an example) in each portion in the Z direction.

FIG. 2B shows an enlarged vertical cross section of a part of the region K of the fixing roll 22 of FIG. 2A. Since the elastic layer 26 is formed by applying the coating liquid while rotating the core metal 24 while changing the discharge amount of the coating liquid in the axial direction, the entire elastic layer 26 is spirally wound around the outer peripheral surface of the core metal 24. It is in a state of being. Specifically, the elastic layer 26 is composed of a plurality of convex portions whose thickness (height) gradually increases from the central side in the Z direction toward the −Z side. Here, as an example, three convex portions are designated with reference numerals, and the convex portion 26A, the convex portion 26B, and the convex portion 26C are sequentially shown from the central side in the Z direction toward the −Z side. It is formed. As described above, the elastic layer 26 is formed with a plurality of convex portions arranged in the axial direction, so that the uneven portions 27 are formed on the outer peripheral surface of the fixing roll 22.

In the uneven portion 27, on the outer peripheral surface of the fixing roll 22, a plurality of concave portions 31 recessed in the radial direction of the core metal 24 and a plurality of convex portions 29 protruding in the radial direction of the core metal 24 alternate in the Z direction. It is said to be arranged. In FIG. 2B, the concave portions 31A, the concave portions 31B, and the concave portions 31C forming a part of the plurality of concave portions 31, and the convex portions 29A, the convex portions 29B, and the convex portions 29C forming a part of the plurality of convex portions 29. It is shown. These are arranged in the order of the concave portion 31A, the convex portion 29A, the concave portion 31B, the convex portion 29B, the concave portion 31C, and the convex portion 29C from the central side in the Z direction toward the −Z side.

The lowest position of the recess 31A in the radial direction of the fixing roll 22 is B1, the lowest position of the recess 31B is B2, and the lowest position of the recess 31C is B3. Further, the highest position of the convex portion 29A in the radial direction of the fixing roll 22 is P1, the highest position of the convex portion 29B is P2, and the highest position of the convex portion 29C is P3. Since the elastic layer 26 has an inverted crown shape, the heights of the respective positions are B1 <B2 <B3 and P1 <P2 <P3. Further, the radial height difference h1 between the position B1 and the position P1, the radial height difference h2 between the position B2 and the position P2, and the radial height difference h3 between the position B3 and the position P3. To do. Here, in the fixing roll 22, h1 <h2 <h3.

That is, in the fixing roll 22, the difference in height between the concave portion 31 and the convex portion 29 of the concave-convex portion 27 in the radial direction is that the both end portions 22A side in the Z direction are compared with the central portion 22B (see FIG. 2A) side. It's getting bigger. Further, the height difference h between the concave portion 31 and the convex portion 29 gradually increases from the central portion 22B side to the both end portions 22A side. Further, in the present embodiment, as an example, the maximum value of the height difference h between the concave portion 31 and the convex portion 29 at both end portions 22A of the fixing roll 22 is 2 [μm] or more and 10 [μm] or less. ..

The fact that the height difference h is larger on both end portions 22A than on the central portion 22B side is formed between the paper P and the fixing roll 22 when the paper P and the outer peripheral surface of the fixing roll 22 come into contact with each other. It means that the size of the space to be created is larger at both end portions 22A than at the central portion 22B.

<Pressurized roll>
As an example, the pressure roll 32 shown in FIG. 3 has a cylindrical core metal 34 made of aluminum, an elastic layer 36 made of silicone rubber formed on the outer peripheral surface of the core metal 34, and an outer peripheral surface of the elastic layer 36. It is configured to have a mold release layer 38 made of fluororesin formed. Further, the pressure roll 32 is rotatably arranged around the transfer path A of the paper P on the side (−X side) opposite to the toner image G side with the Z direction as the axial direction. ..

Further, the pressure roll 32 is arranged so as to face the fixing roll 22 in the X direction with the transport path A interposed therebetween, and is pressed toward the fixing roll 22 by a retract mechanism portion including a spring (not shown) to nip. Part N is formed. That is, the pressure roll 32 can be switched between a pressure state in which the fixing roll 22 is pressed and a retracted state in which the fixing roll 22 is not pressed by being driven by a retract mechanism unit (not shown). Then, the pressurizing roll 32 presses the paper P together with the fixing roll 22 in the pressurized state. The pressurizing roll 32 is configured to rotate (driven rotation) in synchronization with the rotation of the fixing roll 22.

As shown in FIG. 2 (A), as an example, the pressure roll 32 has a shape (flat shape) in which the outer diameter dB at both ends in the Z direction is substantially equal to the outer diameter dA at the center portion, and is formed on the outer peripheral surface. The above-mentioned uneven portion 27 (see FIG. 2B) is not formed.

<Heating part>
As an example, the heating unit 42 shown in FIG. 3 has a halogen heater 44, a halogen heater 46, and a power source (not shown) of the image forming apparatus 10 (see FIG. 1).

The halogen heater 44 is provided inside the core metal 24 in a non-contact state with the core metal 24 with the Z direction as the axial direction. Further, the halogen heater 44 generates heat when energized from a power source (not shown), and heats the core metal 24 to heat the entire fixing roll 22. Whether or not the halogen heater 44 is energized is determined based on the detection result of a temperature sensor (not shown) that detects the temperature of the outer peripheral surface of the fixing roll 22.

The halogen heater 46 is provided inside the core metal 34 in a non-contact state with the core metal 34 with the Z direction as the axial direction. Further, the halogen heater 46 generates heat when energized from a power source (not shown), and heats the core metal 34 to heat the entire pressure roll 32. Whether or not the halogen heater 46 is energized is determined based on the detection result of a temperature sensor (not shown) that detects the temperature of the outer peripheral surface of the pressurizing roll 32.

<Manufacturing method of fixing roll>
Next, an example of a method for manufacturing the fixing roll 22 will be described. In addition, FIG. 2 (A), (B), FIG. 3 and FIG. 4 are referred to.

An aluminum (A-5052) core metal 24 having an outer diameter of φ = 25.015 [mm] whose surface was adhesively treated was installed on a turntable including a motor (not shown). In the turntable, the axial direction of the core metal 24 is kept substantially horizontal, and the core metal 24 can rotate in the circumferential direction. Then, in a state where the core metal 24 is rotated at 460 [rpm], a nozzle (not shown) is moved in the Z direction and the discharge amount [g / s] of the coating liquid is changed as shown in FIG. The coating liquid for the layer 26 was spirally applied to the outer peripheral surface of the core metal 24.

The coating liquid for the elastic layer 26 is composed of a liquid silicone rubber coating liquid as an example. The liquid silicone rubber coating liquid contains 85 [mass%] of silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd .: X-34-2086A / B) in butyl acetate as a solvent. The moving speed of the nozzle is set at 23.4 [mm / s] as an example. The outer peripheral surface of the coating liquid applied to the core metal 24 was smoothed with a flat plate-shaped SUS (stainless steel) plate having a thickness of 0.1 [mm] (not shown).

Subsequently, in a drying furnace (not shown), a drying step of 110 [° C.] for 20 minutes was performed in a state where the core metal 24 having the outer peripheral surface of the coating liquid smoothed was rotated at 50 [rpm]. Then, after the drying was completed, a vulcanization step of 210 [° C.] for 1 hour was performed in a heating furnace (not shown).

Subsequently, a PFA tube (thickness 35 [μm]) having an outer diameter 2 [%] smaller than the maximum outer diameter of the tubular body on which the elastic layer 26 is formed is prepared, and the inner diameter is 0 than the outer diameter of the tubular body. 8.8 [%] This PFA tube was placed on the inner circumference of a large outer mold. Then, by removing the PFA tube from the outer mold with the above-mentioned tubular body inserted inside the PFA tube, the outer peripheral side of the elastic layer 26 was coated with PFA. Further, the tubular body coated with PFA was left at room temperature (25 [° C.]) for 24 hours and then heated at 200 [° C.] for 30 minutes to form a release layer 28 having a thickness of 35 [μm]. .. By the above steps, the fixing roll 22 was obtained.

[Action]
Next, the operation of this embodiment will be described.

In the fixing device 20 shown in FIG. 3, the fixing roll 22 and the pressure roll 32 rotate while being heated by the heating unit 42 to heat and melt the toner image G on the paper P that has entered the nip portion N. Pressurize to fix the toner image G on the paper P. At the nip portion N, the outer peripheral surface of the fixing roll 22 and the paper P are in contact with each other.

As shown in FIG. 2A, the outer diameter d2 of both end portions 22A of the fixing roll 22 is larger than the outer diameter d1 of the central portion 22B. Therefore, as shown in FIG. 5A, in the nip portion N, the pressure NP1 acting on the paper P on both end portions 22A side is higher than the pressure NP2 acting on the paper P on the central portion 22B side. Become. As a result, both ends of the paper P in the Z direction are pulled toward the Z side and the −Z side, so that the pressure acting on both ends of the paper P in the Z direction is the same as the pressure acting on the central portion. The slack of the paper P is suppressed, and the occurrence of wrinkles is suppressed.

In the fixing roll 22, since the uneven portion 27 is formed on the outer peripheral surface, a plurality of gaps S are formed between the paper P and the uneven portion 27. Further, the difference h in the radial height between the concave portion 31 and the convex portion 29 in the concave-convex portion 27 (see FIG. 2B) is larger on both end portions 22A side in the Z direction than on the central portion 22B side. .. That is, the volume of the gap S is larger on both ends 22A side where the pressure acting on the paper P is higher than on the central portion 22B side.

Here, as shown in FIGS. 5A and 5B, when the paper P is ejected from the nip portion N, even if the pressure acting on both ends of the paper P in the Z direction is high, the paper P is fixed. The gap S between the outer peripheral surface of the roll 22 and the paper P is larger than that in the configuration in which the uneven portion 27 is not formed. Therefore, the amount of air between the outer peripheral surface of the fixing roll 22 and the paper P increases on the discharge side of the paper P of the nip portion N. That is, in the fixing roll 22, the contact area between the fixing roll 22 and the paper P is reduced as compared with the configuration in which the outer peripheral surface has no uneven portion 27, so that the paper P discharged from the nip portion N is peeled off from the fixing roll 22. The sex is enhanced.

Further, in the fixing roll 22, the height difference h between the concave portion 31 and the convex portion 29 (see FIG. 2B) gradually increases from the central portion 22B side to the both end portions 22A side. Therefore, when the toner image G (see FIG. 1) is fixed on a plurality of types of paper P having different widths in the Z direction, the peeling action due to the gap S is performed at both ends of the paper P in the Z direction. Obtained to the same extent. That is, the peelability is improved in a plurality of types of paper P having different widths, as compared with the configuration in which a step is formed on the outer peripheral surface between the central portion 22B and both end portions 22A.

Further, in the fixing roll 22, the maximum value of the height difference h between the concave portion 31 and the convex portion 29 at both end portions 22A is 2 [μm] or more and 10 [μm] or less. Therefore, as compared with the configuration in which the maximum value of the height difference h is lower than 2 [μm] or higher than 10 [μm], the peelability of the paper P from the fixing roll 22 is enhanced, and the peelability after fixing is improved. Deterioration of image quality (image unevenness as an example) of the toner image G (see FIG. 1) is suppressed. The results of various evaluations using the fixing rolls 22 having different height differences h will be described later.

In the fixing device 20, the wrapping of the paper P around the fixing roll 22 (poor peeling of the paper P) is suppressed as compared with the configuration without the fixing roll 22.

In the image forming apparatus 10, excessive heating of the toner image G due to poor peeling of the paper P is suppressed in the fixing device 20, so that the toner after fixing to the paper P is compared with a configuration without the fixing device 20. Image defects (image unevenness as an example) of image G are suppressed.

[Various evaluations]
Next, various evaluations using the fixing roll 22 of the present embodiment and the fixing roll of the comparative example will be described.

In the present embodiment, by increasing or decreasing the discharge amount [g / s] when forming the elastic layer 26, the maximum height difference between the concave portion 31 and the convex portion 29 is 1 [μm], 2 [μm], 6 [. Fixing rolls 22 of μm, 10 [μm], and 11 [μm] were prepared. The maximum height difference was measured using a surface roughness meter (Surfcom 2000DX3 manufactured by Tokyo Seimitsu Co., Ltd.).

On the other hand, as a comparative example, an aluminum (A-5052) core metal having an outer diameter of φ = 25.015 [mmmm] having an adhesive treatment on the surface was installed in a tapered iron mold. Then, an addition reaction type liquid silicone rubber having a viscosity of 200 [Pa · s] was injected into the gap between the aluminum core metal and the PFA tube at a pressure of 4 [MPa] from the lower front part of the mold. Then, a vulcanization step was carried out at 120 [° C.] for 1 hour to prepare a fixing roll of a comparative example having no uneven portion 27 (see FIG. 2B).

Here, paper peeling evaluation, paper wrinkle evaluation, and image quality evaluation were performed on the fixing rolls 22 of the five types (Examples 1, 2, 3, 4, 5) of the present embodiment and the fixing rolls of the comparative example.

In the paper peeling evaluation, Fuji Xerox Co., Ltd. Docuplint CP400 was used as an image forming apparatus. A solid image using black toner is formed on P paper (A4 size) manufactured by Fuji Xerox Office Supply Co., Ltd. with the fixing roll 22 of the present embodiment or the fixing roll of the comparative example mounted on the fixing device of the image forming device. And fixed. Then, the paper in which the P paper is discharged without being wrapped around the fixing roll 22 is designated as rank A, and the paper in which the paper is slightly wrapped around the fixing roll 22 but is discharged is designated as rank B. Was wrapped around the fixing roll and was not discharged, and was judged as rank C. In the solid image, the margins from the tip of the P paper in the transport direction are formed in 6 patterns of 0, 1, 2, 3, 4, 5 [mm]. Moreover, as the evaluation result, the one with the lowest evaluation among these 6 patterns is adopted.

In the paper wrinkle evaluation, the P paper discharged in the paper peeling evaluation was visually confirmed and ranked according to the degree of wrinkle occurrence. Those without wrinkles at the visual level were judged as A rank, and those with wrinkles were judged as B rank.

In the image quality evaluation, the solid image of the P paper discharged in the paper peeling evaluation was visually confirmed and ranked according to the degree of occurrence of image unevenness. A rank is for those with no image unevenness at the visual level, B rank is for those with slight image unevenness, C rank is for those with clear image unevenness, and D rank is for those with marked image unevenness. Judged. Here, the evaluation results are summarized in Table 1.

As shown in Table 1, it was confirmed that the fixing roll 22 of the present embodiment was evaluated higher than the fixing roll of the comparative example in terms of paper peeling evaluation and image unevenness evaluation. Further, in the fixing roll 22 of the present embodiment, it was confirmed that the evaluation result of paper peeling is good when the maximum height difference between the concave portion 31 and the convex portion 29 is 2 [μm] or more. Further, in the fixing roll 22 of the present embodiment, it was confirmed that the evaluation result of image unevenness is good when the maximum height difference is 10 [μm] or less. Regarding the evaluation of paper wrinkles, no difference was observed between this embodiment and the comparative example. It is considered that this is because the effect of the inverted crown shape of the fixing roll is large for the paper wrinkles.

The present invention is not limited to the above embodiment.

The fixing rotating body is not limited to the roll, and may be an endless belt. Further, the fixing rotating body having the uneven portion formed is not limited to the fixing side rotating body such as the fixing roll 22, but may be a pressing side rotating body. For example, the pressure roll 32 may have an inverted crown shape, and the pressure roll 32 may have an uneven portion 27.

The facing member is not limited to a rotating member such as the pressure roll 32, and may be a non-rotating member such as a pad. The pressure roll 32 is not limited to a flat shape having substantially the same outer diameter in the axial direction, but also has a crown shape in which the outer diameter of the central portion is larger than the outer diameter of both ends, and the outer diameter of both ends is larger than the outer diameter of the central portion. May also have a large inverted crown shape. Further, when the fixing rotating body is a member on the pressurizing side, the opposing member is a member on the fixing side.

When there are few types of widths of the usable paper P in the Z direction, even if the height difference h between the concave portion 31 and the convex portion 29 has a stepped shape that greatly changes between the central portion 22B and both end portions 22A. Good.

The maximum value of the height difference h between the concave portion 31 and the convex portion 29 at both end portions 22A may be smaller than 2 [μm] or larger than 10 [μm].

The heating unit 42 may be one that heats only the fixing roll 22 or one that heats only the pressure roll 32.

10 Image forming apparatus 14 Image forming unit (an example of developing agent image forming means)
20 Fixing device 22 Fixing roll (an example of rotating member for fixing)
22A Both ends 22B Central part 27 Concavo-convex part 29 Concave part 31 Convex part 32 Pressurized roll (example of facing member)
42 Heating part (example of heating source)

Claims (4)

The outer diameter of the both end portions in the axial direction and shape larger than the outer diameter of the central portion Rutotomoni has an uneven portion on the outer peripheral surface, the height of which along the radial direction of the concave portion and the convex portion of the concavo-convex portion A rotating member for fixing in which the difference gradually increases from the central portion side to the both end portions side . The rotating member for fixing according to claim 1, wherein the maximum value of the height difference between the concave portion and the convex portion at both ends is 2 μm or more and 10 μm or less . The fixing rotating member according to claim 1 or 2,
An opposing member that is arranged to face the fixing rotating member and sandwiches the recording medium together with the fixing rotating member.
A heating source that heats at least one of the fixing rotating member and the opposing member,
Have,
A fixing device that melts the developer and pressurizes it to fix it on the recording medium . A developer image forming means for forming a developer image on a recording medium,
The fixing device according to claim 3, wherein the developer image formed by the developer image forming means is fixed to the recording medium.
An image forming apparatus having .