JP2005352297A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of obtaining expected transfer material carrying performance by two rotating bodies for fixing and surely preventing wrinkles and a waving phenomenon from occurring by fixing, and an image forming apparatus capable of surely yielding a high-quality image free from an image defect caused by the said trouble. <P>SOLUTION: The fixing device is equipped with a heating rotating body for fixing and a pressure rotating body for fixing which are brought into press-contact with each other to form a fixing nip part, and the heating rotating body and the pressure rotating body have such outside shape to attain a condition that press-contact force gets stronger from a center position toward the outside in a center part area, and it gets weaker toward the outside in an end area where the edge of transfer material is positioned in press-contact force distribution in a longitudinal direction in the fixing nip part. It is desirable to use the rotating bodies, for example, either of which has such outside shape in terms of outside diameter that the center part area is formed in inverted-crown shape and the end area is formed in straight shape. The image forming apparatus is equipped with the fixing device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile, and a fixing device used in the image forming apparatus.

  Conventionally, in an image forming apparatus using an electrophotographic method, an image is formed by fixing an unfixed toner image formed on a transfer material such as transfer paper, and fixing for performing a fixing process. As a device, for example, a device using a heat roller pressing method is widely used.

  Such a heat roller pressure fixing device includes, for example, a heating roller having a heating source disposed therein, and a pressure roller provided so as to form a fixing nip portion in pressure contact with the heating roller. By passing the transfer material through the fixing nip portion, the toner is melted and pressed by heat and pressure in the fixing nip portion. Here, the heating roller and the pressure roller have uniform outer diameters. For example, when the rotation shaft of the heating roller is fixed, the rotation shaft of the pressure roller is urged toward the heating roller. As a result, a fixing nip portion is formed.

In such a fixing device, since the transfer material conveyance speed in the longitudinal direction at the fixing nip portion is non-uniform, wrinkles extending along the transfer material conveyance direction are likely to occur at the central portion in the width direction of the transfer material. There's a problem.
As a means for solving such a problem, for example, at least one of the heating roller and the pressure roller is adjusted to have a specific outer shape by changing the outer diameter in the longitudinal direction. ing.
Specifically, for example, one or both of the pressure roller and the fixing roller have an inverted crown shape over the entire length of the roller, and the diameters satisfying a predetermined relationship at a plurality of arbitrarily set positions. The heating roller has a reverse crown shape over the entire area in the longitudinal direction, and the pressure roller has a regular crown shape over the entire area in the longitudinal direction. A core metal that forms at least one of a heating roller and a pressure roller is used as a shape in which the linear velocity distribution in the longitudinal direction in the portion is in a specific state (see Patent Document 2) or The diameter of the central portion in the direction is smaller than the diameter of the end, and the outer shape of the roller is a normal crown shape or a reverse crown shape (special Document 3 reference.) Have been proposed.

In addition, the above-mentioned problem is not limited to the heat roller pressure bonding type, and also occurs in, for example, a film heating type fixing device. For example, a heating heater supported by a heat insulating stay holder and a thin wall A fixing member composed of a film, and a pressure roller provided so as to form a fixing nip portion by being pressed against the fixing member. A configuration has been proposed in which the heating heater surface or the heating heater has a regular crown shape, and the normal crown amount of the heat insulating stay holder is set larger than the reverse crown amount of the pressure roller (Patent Document 4). reference.).
JP 2003-149773 A JP 2001-265146 A JP 2001-215832 A JP 09-197864 A

  However, if the outer shape of the fixing member forming the fixing nip portion is, for example, an inverted crown shape over the entire length in order to prevent the generation of wrinkles in the center portion of the transfer material, the fixing by the heat roller method In both the apparatus and the film-type fixing device, since the tensile force outward in the longitudinal direction of the fixing nip portion is applied to the transfer material, the end portion of the transfer material is easily extended in the transport direction. However, there is a problem that a so-called “ripple phenomenon” occurs at both ends of the transfer material. In addition, both ends of the transfer material are easily stretched due to differences in thermal conductivity with respect to the transfer material between the both ends and the center of the fixing nip portion, and the waviness phenomenon is noticeably generated.

The present invention has been made on the basis of the above-described circumstances, and can achieve the desired transfer material conveyance performance by the two fixing rotating bodies, and reliably generate wrinkles and wavy phenomena due to fixing. It is an object of the present invention to provide a fixing device that can be prevented.
Another object of the present invention is to provide an image forming apparatus that includes the above-described fixing device and can reliably obtain a high-quality image free from image defects due to wrinkles or wavy phenomena.

  The fixing device of the present invention includes a fixing heating rotator and a fixing pressure rotator arranged so as to be pressed against each other to form a fixing nip portion, and the fixing heating rotator and the fixing pressurizing member. In the rotating body, the pressure contact force distribution in the longitudinal direction at the fixing nip portion increases in the central region from the center position toward the axial direction outward, and the edge in the width direction of the transfer material is positioned. The end region has an outer shape in which the pressing force becomes smaller as it goes outward in the axial direction.

In the fixing device of the present invention, the fixing heating rotator and the fixing pressure rotator are composed of rollers, and one of the fixing heating rotator and the fixing pressure rotator has an inverted crown shape in the central region. The end region may have an outer shape that is a straight shape or a regular crown shape.
Further, in such a configuration, the other of the fixing heating rotator and the fixing pressure rotator has an outer shape in which the central region has a straight shape and the end region has a regular crown shape. Can be.

In the fixing device of the present invention, the size LA of the central region satisfies the relationship of 0.5B ≦ LA ≦ 0.9B, where B is the maximum width dimension of the transfer material. It is preferable that
Further, in the fixing device of the present invention, the crown amount of the fixing heating rotator and the fixing pressure rotator is preferably 0.03 to 0.50 mm.

  In the fixing device of the present invention, the first heating source having the main heat distribution region in the central region and the second heating having the main heat distribution region in the end region are provided inside the fixing heating rotator. When the size H1 of the main heat distribution region of the first heating source is LA and the size of the central region is LA, the relationship LA-10 ≦ H1 ≦ LA [mm] is satisfied. It is preferable that the size be In the case of such a configuration, the first temperature detecting means for detecting the temperature of the central portion of the fixing heating rotator and the second temperature detecting means for detecting the temperature of the end portion are provided. In the standby state, when the temperature difference (T2−T1) between the temperature T1 at the center of the fixing heating rotator and the temperature T2 at the end (T2−T1) is less than 5 ° C., the end region is mainly When the second heating source having the heat distribution region is operated and the temperature state between the central portion and the end portion is in the other state, the first heating having the main heat distribution region in the central portion region The source is preferably configured to be operated.

    An image forming apparatus according to the present invention includes the fixing device described above.

  According to the fixing device of the present invention, the pressure contact force distribution in the longitudinal direction at the fixing nip portion decreases in the central region from the center position toward the outside in the longitudinal direction, and in the end region, the pressure contact force decreases. Since the outer shape of the fixing heating rotator and the fixing pressure rotator is set so that the pressure contact force becomes smaller toward the direction, the transfer material at the fixing nip portion has a longitudinal outer side. Therefore, it is possible to reliably prevent wrinkles from being generated at the center of the transfer material, and to prevent the end region where the pressure contact force decreases toward the outside from the end of the transfer material. By transporting the edges so that they pass, it is possible to prevent the both ends of the transfer material from extending in the transport direction, so that it is ensured that the wavy phenomenon occurs at both ends of the transfer material. It is possible to prevent the.

  In addition, for example, two heating sources having different main heat distribution areas are disposed inside the fixing heating rotator, so that heating can be performed with a heat distribution according to the outer shape of the fixing heating rotator. Therefore, the temperature state in the fixing nip portion can be maintained in a uniform temperature distribution state in the longitudinal direction, and the both end portions of the transfer material can be more reliably prevented from being stretched, and a wavy phenomenon occurs. Can be reliably prevented.

  According to the image forming apparatus of the present invention, since the above-described fixing device is provided, it is possible to reliably form a high-quality image free from image defects due to wrinkling or wavy phenomenon of the transfer material due to fixing.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram showing an outline of a configuration in an example of an image forming apparatus of the present invention.
The image forming apparatus includes a drum-shaped photoreceptor 10 that is rotated, and a charging device 11, an exposure device 12, and development including toner in a rotation direction of the photoreceptor 10 in an outer peripheral surface region of the photoreceptor 10. A developing device 13 that performs development using an agent, a transfer device 14, a separation device 15, and a cleaning device 16 are arranged in the order of operation. A fixing device 20 for fixing an unfixed toner image formed on the transfer material P is disposed at a position downstream of the transfer region in the conveyance direction of the transfer material P. In FIG. 1, reference numeral 18 denotes a conveying unit for conveying the transfer material P on which an unfixed toner image is formed to the fixing device 20.

  The fixing device 20 is arranged in such a manner that two fixing rotators are pressed against each other so that a fixing nip portion is formed, and a heating source is provided in at least one fixing rotator. Specifically, for example, as shown in FIG. 2, a heating roller 21 that is a fixing heating rotator, and pressing and fixing by the heating roller 21 are used. It is constituted by a pressure roller 26 which is a pressure rotator for fixing and is arranged so that a nip portion N is formed.

The heating roller 21 is formed on the surface of the metal core 22 and a cylindrical metal core 22 made of metal that extends in the width direction of the transfer material P to be conveyed (in FIG. 2, the direction perpendicular to the paper surface). And a release layer 24 made of, for example, a fluororesin, formed on the surface of the elastic layer 23. Inside the cored bar 22, for example, two heat sources, for example, two Rod-shaped halogen heater lamps 30 and 31 are arranged to extend in the longitudinal direction (axial direction) of the cored bar 22.
In the heating roller 21, the core bar 22 has a uniform outer diameter and thickness in the longitudinal direction, and the thickness (covering amount) of the elastic layer 23 formed on the surface of the core bar 22 is adjusted. As shown in FIG. 3, the central region 21A has an inverted crown shape having a hyperbolic outer peripheral surface with the outer diameter increasing from the central position C toward the outer side in the longitudinal direction, and the central region 21A. The end region 21 </ b> B following the both ends is formed in a state having an outer shape that is a straight shape having a uniform outer diameter in the longitudinal direction.
The maximum value d of the crown amount, which is the difference between the maximum value and the minimum value of the outer diameter in the central region 21A having the inverted crown shape, is preferably 0.03 to 0.50 mm, for example. Thereby, in relation to the outer shape of the pressure roller 26, the fixing nip portion N in which the pressure contact force distribution in the longitudinal direction, which will be described later, is in a predetermined state is reliably obtained.

The metal constituting the metal core 22 is not particularly limited, and various metals can be used. Specific examples thereof include metals such as aluminum, iron, and copper, or alloys thereof.
The outer diameter and thickness of the cored bar 22 have sufficient mechanical strength, but from the viewpoint of reducing the power consumption by reducing the heat capacity, the outer diameter of the cored bar 22 is, for example, 20 to 65 mm. It is preferable that the thickness of the cored bar 22 is, for example, 0.5 to 5.0 mm.

The elastic body constituting the elastic layer 23 is not particularly limited, and examples thereof include various heat-resistant soft rubbers and sponge rubbers such as fluorine rubber and silicone rubber.
For example, the elastic layer 23 preferably has a JIS-A hardness of 1 to 20, more preferably 5 to 10. Thereby, sufficient flexibility (deformability) is obtained, and the fixing nip portion N having an expected shape can be obtained with certainty.
The elastic layer 23 preferably has a thermal conductivity of 0.40 to 0.51 W / m · ° C.
The thickness of the elastic layer 23 is appropriately set so that the pressure contact force distribution in the longitudinal direction at the fixing nip N, which will be described later, is in a predetermined state in relation to the outer shape of the pressure roller 26.

Examples of the fluororesin constituting the release layer 24 include polytetrafluoroethylene (PTFE), a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (PFA), and a copolymer of tetrafluoroethylene and hexafluoropropylene. (FEP) can be exemplified.
The thickness of the release layer 24 is preferably 20 to 50 μm, for example.

The pressure roller 26 includes a cylindrical cored bar 27 made of, for example, metal, an elastic layer 28 formed on the surface of the cored bar 27, and a release layer 29 formed on the surface of the elastic layer 28. In the cored bar 27, for example, a rod-shaped halogen heater lamp 25 as a heating source is arranged to extend in the longitudinal direction of the cored bar 27.
In the pressure roller 26, the core 27 has a uniform outer diameter and thickness in the longitudinal direction, and the thickness (covering amount) of the elastic layer 28 formed on the surface of the core 27 is adjusted. As shown in FIG. 4, the central region 26A has a straight shape with a uniform outer diameter in the longitudinal direction, and the end regions 26B following both ends of the central region 26A are directed outward in the longitudinal direction. It is formed in a state having an outer shape that is a regular crown shape with a reduced outer diameter.
The maximum value d of the crown amount, which is the difference between the maximum value and the minimum value of the outer diameter in the end region 26B having a regular crown shape, is preferably 0.03 to 0.50 mm, and more preferably. 0.03 to 0.08 mm. As a result, in relation to the outer shape of the heating roller 21, a predetermined pressure distribution in the longitudinal direction at the fixing nip portion N, which will be described later, is reliably obtained.

As materials constituting the core metal 27, the elastic layer 28, and the release layer 29, those exemplified as those constituting the heating roller 21 can be used.
The core metal 27 constituting the pressure roller 26 preferably has an outer diameter of, for example, 18 to 60 mm and a thickness of, for example, 0.5 to 5.0 mm.
The elastic layer 28 constituting the pressure roller 26 preferably has a JIS-A hardness of 1 to 20, for example.
The thickness of the elastic layer 28 can be appropriately set so that the pressure contact force distribution in the longitudinal direction at the fixing nip N, which will be described later, is in a predetermined state in relation to the outer shape of the heating roller 21.
The elastic layer 28 preferably has a thermal conductivity of 0.40 to 0.51 W / m · ° C.
The thickness of the release layer 29 is preferably 20 to 50 μm, for example.

As described above, the fixing nip portion N is formed by the heating roller 21 and the pressure roller 26 being pressed against each other. Specifically, for example, in a state where the rotating shaft 21C of the heating roller 21 is fixed, the rotating shaft 26C of the pressure roller 26 is placed on the heating roller 21 side (upper side in FIG. 2), and the pressing force is set to an appropriate magnitude. By being biased by the adjusted appropriate pressing means, a fixing nip portion N in which the pressure contact surface between the heating roller 21 and the pressure roller 26 is linear is formed.
As shown in FIG. 5, in the fixing nip portion N, the pressure contact force distribution in the longitudinal direction is directed from the center position C in the longitudinal direction of the fixing nip portion N to the longitudinally outward position in the central region. Accordingly, the pressure contact force increases and the pressure contact force at a position on the inner side of the edge position of the maximum transfer material width B of the transfer material P exhibits a peak value, and the end portion where the width direction edge of the transfer material P is located In the region, the pressure contact force decreases as it goes outward in the longitudinal direction, and the entire region is symmetric with respect to the central position C in the longitudinal direction. Here, the central region is a region formed by press-contacting the central region 21A of the heating roller 21 and the central region 26A of the pressure roller 26, and the end region is an end region of the heating roller 21. 21B is an area formed by press-contacting the end area 26B of the pressure roller 26 with the end area 26B.

The size LA of the central region 21A in which the outer shape of the heating roller 21 is an inverted crown shape and the size LA of the central region 26A in which the outer diameter shape of the pressure roller 26 is a straight shape are, for example, equivalent. It is preferable that the size is set so as to satisfy the following expression 1 in relation to the maximum width dimension (maximum transfer material width) B of the transfer material P.
(Formula 1) 0.5B ≦ LA ≦ 0.9B

In the pressure contact force distribution in the fixing nip N, the absolute value of the pressure force varies depending on the thickness of the elastic layer 23 in the heating roller 21 and the thickness of the elastic layer 28 in the pressure roller 26. It is preferable that the difference between the pressure contact force P2 at the position C and the pressure contact force P1 at the edge position of the central region showing the peak value is, for example, 0.01 to 0.05 MPa.
If the position where the pressure contact force shows the peak value is located within the maximum transfer material width B, a practically sufficient effect can be obtained, but for example, 15-30 mm inward from the edge position of the maximum transfer material width B It is preferable that the position is set on the side.

As described above, inside the heating roller 21, the two rod-shaped halogen heater lamps 30 and 31 that are heating sources are arranged.
The halogen heater lamps 30 and 31 have different main heat distribution areas, and the first halogen heater lamp 30 has a main heat distribution area H1 in the central area 21A (mainly heats the central area 21A). The second halogen heater lamp 31 has a main heat distribution region H2 in the end region 21B (mainly heats the end region 21B).
In the cross section of the heating roller 21, the surface temperature of the central region 21 </ b> A of the heating roller 21 is detected on the side where the first halogen heater lamp 30 is provided across the rotation center axis of the heating roller 21. For this purpose, for example, first temperature detection means 32 made of a thermistor is provided, and the surface temperature of the end region 21B of the heating roller 21 is detected on the side where the second halogen heater lamp 31 is provided. For this purpose, second temperature detection means 33 made of, for example, a thermistor is provided.

For example, during the image forming operation, the halogen heater lamps 30 and 31 are ON / OFF controlled so that the temperature state in the fixing nip portion N becomes a uniform temperature distribution state in the longitudinal direction.
During standby, the temperature T1 at the center of the heating roller 21 detected by the first temperature detection means 32 and the temperature T2 at the end of the heating roller 21 detected by the second temperature detection means 33 When the temperature difference (T2-T1) is less than 5 ° C., the second halogen heater lamp 31 is operated to heat the end region, and the temperature difference (T2-T1) is 5 ° C. or more. In this case, the first halogen heater lamp 30 is operated to heat the central region, and the temperature difference in the longitudinal direction of the fixing nip portion N is maintained in a uniform temperature distribution state within a range of 0 to 5 ° C., for example. ON-OFF control is performed.

  In the above image forming apparatus, an image is formed as follows. That is, the toner image is formed on the photosensitive member 10 by sequentially performing the charging process by the charging device 11, the exposure process 13 by the exposure device 12, and the developing process by the developing device 14, while the transfer material P that has been conveyed is transferred. Is introduced into the transfer region in a state of being synchronized with the toner image formed on the photoconductor 10 and is transferred by the transfer device 14 so that the toner image on the photoconductor 10 is transferred to the transfer material P. Then, a separation process by the separation device 15 and a fixing process by the fixing device 20 are sequentially performed to form a visible image. Here, after the transfer process by the transfer device 14 is performed, the cleaning process is performed by the cleaning device 16 to remove the toner remaining on the photoreceptor 10.

Thus, according to the image forming apparatus having the above-described configuration, the pressure contact force distribution in the longitudinal direction at the fixing nip portion N decreases in the central region from the center position toward the outside in the longitudinal direction. The partial area is provided with the fixing device 20 in which the outer shapes of the heating roller 21 and the pressure roller 26 are set so that the pressure contact force becomes smaller toward the outside. When the unfixed toner image is fixed, a force pulling outward in the longitudinal direction is applied to the transfer material P in the fixing nip portion N, so that wrinkles are surely generated in the central portion of the transfer material P. Further, both ends of the transfer material P are conveyed by being conveyed so as to pass through the end region where the pressure contact force becomes smaller as the end edge of the transfer material P goes outward in the longitudinal direction. It is possible to prevent the extending direction, it is possible to reliably prevent the waving phenomenon occurs at both ends of the transfer material P.
In addition, a heating source composed of, for example, two halogen heater lamps 30 and 31 having different main heat distribution areas is disposed inside the heating roller 21, so that the heat distribution according to the outer shape of the heating roller 21 is achieved. Since the heating can be performed, the temperature state in the fixing nip portion N can be maintained in a uniform temperature distribution state in the longitudinal direction, and the both end portions of the transfer material P can be more reliably prevented from extending. It is possible to prevent the undulation phenomenon from occurring.
Therefore, it is possible to reliably form a high-quality image free from image defects due to wrinkling or wavy phenomenon of the transfer material P due to fixing.

  In particular, the heating roller 21 has an outer diameter shape in which the central region 21A has an inverted crown shape and the end region 21B has a straight shape, and the pressure roller 26 has a straight shape in the central region 26A. The end region 26B has an outer shape with a regular crown shape, and during standby, the temperature difference between the temperature T1 at the center of the heating roller 21 and the temperature T2 at the end (T2-T1) Is lower than 5 ° C., the second halogen heater lamp 31 having the main heat distribution region in the end region is operated, and the temperature state in the fixing nip portion N is in a state other than the above, the central region Due to the operation of the first halogen heater lamp 30 having the main heat distribution region, it is caused by the thickness of the elastic layers 23 and 28 in the heating roller 21 and the pressure roller 26. Since the temperature distribution state in the longitudinal direction in the contact nip portion N is prevented from being non-uniform and maintained at a predetermined temperature state, the fixing nip portion can be surely lengthened by being heated to a predetermined temperature during warm-up. It becomes a state having a uniform temperature distribution state in the direction.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be added.
For example, in the fixing device using the heat roller pressure bonding method, the outer shape of the heating roller and the pressure roller may be that of the above embodiment as long as the pressure contact force distribution in the longitudinal direction at the fixing nip portion is in a predetermined state. It is not limited to things.
For example, as shown in FIG. 6, one of the heating roller and the pressure roller has a central region 41 in which a predetermined region including the central position is straight and a portion following the end region 45 is tapered. It can be set as the shape made into the reverse crown shape made into the shape and the outer diameter of an edge part large as compared with the center part. In the fixing roller member 40, the size of the straight-shaped region 42 in the central region 41 is secured to a predetermined size in the central region 41, and a sudden change in the outer diameter in the tapered region 43 occurs. Any configuration can be set as appropriate.
For example, as shown in FIG. 7, the central region 51 has an inverted crown shape, and the end region 52 that follows the central region 51 has a regular crown shape in which the outer diameter decreases toward the outside. The fixing roller member 50 having the above-described configuration may be used. In the fixing roller member 50, the maximum value d1 of the crown amount in the central region 51 having the inverted crown shape is preferably 0.03 to 0.50 mm, for example, and the end portion having the regular crown shape is used. The maximum value d2 of the crown amount in the region 52 is preferably 0.03 to 0.50 mm, for example. When such a fixing roller member 50 is used, the other fixing roller member in pressure contact with the fixing roller member 50 is, for example, a straight member having a uniform outer diameter in the longitudinal direction. Can do.
The size LA of the center regions 41 and 51 and the size LB of the end regions 45 and 52 are set in the same manner as shown in FIGS. 3 and 4, for example.

The present invention is not limited to a fixing device using a heat roller pressure bonding method, and can be applied to a fixing device using a film heating method or a belt fixing method, for example.
Furthermore, even when the present invention is applied to a color image forming apparatus, a practically sufficient effect can be obtained.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Fixing device manufacturing example 1]
A fixing device of the present invention (hereinafter referred to as “fixing device 1”) was manufactured according to the configuration shown in FIGS. A specific configuration of the fixing device 1 is as follows.
<Heating roller (21)>
Metal core (22): material: aluminum alloy, outer diameter: 27.5 mm, wall thickness: 0.8 mm, total length: 367 mm
Elastic layer (23): material; silicone rubber having a JIS-A hardness of 10 °, a thermal conductivity of 0.45 W / m · ° C., and a tensile strength of 0.7 MPa, the size of the central region (21A) (LA ); 240 mm, size of end region (21B) (LB); 120 mm (one side), outer diameter shape of central region; inverted crown shape having hyperbolic outer peripheral surface, outer shape of end region; straight shape , Outer diameter (D1) of the central portion; 64.94 mm, outer diameter of the end portion (D2); 65.0 mm, crown amount (d); 0.06 mm (d / 2 in FIG. 3 is 0.03 mm)
Release layer (24): material: tube made of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), thickness: 20 μm
<Pressure roller (26)>
Core metal (27): material: iron, outer diameter: 26 mm, wall thickness: 0.8 mm, total length: 367 mm
Elastic layer (28): material: silicone rubber having JIS-A hardness of 10 °, thermal conductivity of 0.45 W / m · ° C., and tensile strength of 0.7 MPa, size of central region (26A) (LA ); 240 mm, size of end region (26B) (LB); 63.5 mm, outer diameter shape of central region; straight shape, outer shape of end region; regular crown shape having hyperbolic outer peripheral surface; Center outer diameter (D1): 55 mm, end outer diameter (D2): 54.94 mm, crown amount (d): 0.06 mm (d / 2 in FIG. 4 is 0.03 mm)
Release layer (29): material: tube made of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), thickness: 50 μm
<Heat source>
First halogen heater lamp (30): rated power; 475 W, size of main heat distribution area (H1); 190 mm (LA-10 ≦ H1 ≦ LA)
Second halogen heater lamp (31): Rated power: 425 W, size of main heat distribution area: 200 mm
Halogen heater lamp (25) for heating the pressure roller: Rated power: 425 W, size of main heat distribution area: 390 mm
A thermistor is used as the first temperature detection means (32) and the second temperature detection means (33), and the voltage supply to the halogen heater lamp is controlled according to the temperature detected when the heating roller is stationary, so that the fixing temperature. Was maintained at 210 ° C.
<Fixing nip conditions>
Pressing force (total load) urged against the rotating shaft of the pressure roller; 1000 N, the pressing force (P2) at the central portion in the fixing nip portion is 0.37 MPa, and the pressing at the boundary position between the central region and the end region Force (P1) is 0.40 MPa, pressure at the end is 0.37 MPa, nip width: 7.4 mm, fixing linear velocity: 140 mm / sec

[Fixing device manufacturing example 2]
In the example of manufacturing the fixing device 1, a fixing device having the same configuration as the fixing device 1 except that the heating roller having the following configuration (see FIG. 7) is used (referred to as “fixing device 2”). ").
Elastic layer: outer shape of central region; inverted crown shape with hyperbolic outer peripheral surface, outer diameter of central portion (D1); 64.94 mm, outer diameter of end portion (D2); 65 mm, outer shape of end region Shape: a normal crown shape having a hyperbolic outer peripheral surface, an outer diameter (D3) of an end portion; 64.94 mm, a crown amount (d1) in a central region made an inverted crown shape; 0.06 mm (d1 in FIG. 7) / 2 is 0.03 mm), the crown amount (d2) of the end region having a regular crown shape; 0.06 mm (d2 / 2 in FIG. 7 is 0.03 mm), and the pressure contact force of the end portion in the fixing nip portion is Shape to be 0.37 MPa

[Fixing device manufacturing example 3]
In the manufacturing example of the fixing device 1, as the heating roller, an elastic layer is formed on the surface of the core metal with a uniform thickness of 1.5 mm in the longitudinal direction and the outer diameter shape is a straight shape. A comparative fixing device (this is referred to as a “comparison fixing device”) by using an elastic layer having a uniform thickness of 1.0 mm in the longitudinal direction on the surface of the core metal and having a straight outer diameter. 1 ”). In this comparative fixing device 1, the pressure contact force distribution in the fixing nip is uniform in the longitudinal direction.

[Fixing device fabrication example 4]
In the manufacturing example of the fixing device 1, a heating roller having an elastic layer formed on the surface of the core metal with a predetermined thickness so as to have an inverted crown shape having a hyperbolic outer peripheral surface over the entire length direction is used. As a pressure roller, an elastic layer formed on the surface of a core metal with a predetermined thickness so as to have a hyperbolic outer peripheral surface over the entire length direction is used. "Comparative fixing device 2") was prepared. The heating roller in the comparative fixing device 2 has an outer diameter of 64.94 mm at the center of the elastic layer, an outer diameter of 65 mm at the end, and a crown amount of 0.06 mm. The outer diameter is 55 mm at the center, the outer diameter is 54.94 mm, and the crown amount is 0.06 mm. In this comparative fixing device 2, the pressure contact force distribution in the fixing nip is uniform in the longitudinal direction.

[Live-action test]
In a normal temperature and humidity environment (temperature 25 ° C, relative humidity 45%), we evaluated the presence or absence of wrinkles on the transfer material by performing a live-action test in which the image forming operation for 50 copies was repeated three times. went. The results are shown in Table 1 below. Further, for each of the image forming apparatuses on which the fixing device 1, the fixing device 2, and the comparative fixing device 2 are mounted, the presence / absence of the undulation phenomenon was evaluated. The results are shown in Table 2 below.
As the image forming apparatus, a digital copying machine “8050” (manufactured by Konica Minolta Co., Ltd.) was used, and a modified machine equipped with the fixing devices 1 and 2 and the comparative fixing devices 1 and 2 was used.
As a transfer material, A3 size copy paper “CF paper” (manufactured by Konica Minolta Co., Ltd.) (this is referred to as “transfer material 1”) having 80 g / m ² and A3 size copy paper having 90 g / m ² is used. Copy paper “Color Copy Paper” (manufactured by Neusiedler) (hereinafter referred to as “transfer material 2”) was used. The maximum transfer material width (B) by the transfer material 1 and the transfer material 2 is 297 mm.
In the live-action test, after one image forming operation was completed, the image was not allowed to operate for 1 hour (standby state), and then the next image forming operation was performed. Here, in the standby state, the temperature difference between the temperature of the central portion of the heating roller detected by the first temperature detecting means and the temperature of the end portion of the heating roller detected by the second temperature detecting means is 5. If the temperature difference is less than 5 ° C., the second halogen heater lamp is activated to heat the end region, and if the temperature difference is 5 ° C. or more, the first halogen heater lamp is activated to activate the central portion. The region was heated, and the temperature difference in the longitudinal direction of the fixing nip portion was maintained in a uniform temperature distribution state within a range of 0 to 5 ° C.

〔Evaluation methods〕
(1) Wrinkle occurrence / non-existence The occurrence of wrinkle occurrence on the transfer material was confirmed by visual observation, and the number of wrinkles (50 sheets in total) generated for each image forming operation was measured.
(2) Presence / absence of undulation phenomenon A transfer material on which an image is formed is placed on a flat surface, and undulation is performed based on a cumulative value of the amount lifted upward with respect to the placement surface for the entire periphery of the transfer material. The phenomenon was evaluated. The case where the cumulative value was 50 mm or less was evaluated as “◯”, and the case where it was larger than 50 mm was evaluated as “×”. Here, the accumulated values of the transfer material 1 and the transfer material 2 before use are both about 30 mm, and if the accumulated value is 50 mm or less, it is determined that there is no practical problem.

As described above, according to the image forming apparatus including the fixing devices 1 and 2 according to the present invention, the generation of wrinkles due to the fixing process can be prevented, and the occurrence of the wavy phenomenon at both ends of the transfer material can be prevented. It was confirmed that it can be prevented.
On the other hand, in the image forming apparatus provided with the comparative fixing devices 1 and 2, it was confirmed that the generation of wrinkles in the transfer material could not be prevented. In particular, the comparative fixing device 2 was provided. In the image forming apparatus, it has been confirmed that the occurrence of the undulation phenomenon at the end of the transfer material cannot be prevented. In the image forming apparatus provided with the comparative fixing device 2, the reason that the waviness phenomenon becomes prominent as the number of copies increases is that the thickness of the elastic layer increases as it goes outward in the longitudinal direction. For this reason, it is considered that the temperature difference between the temperature of the central region and the temperature of the end region in the fixing nip portion is increased, and the end portion of the transfer material is easily stretched.

1 is an explanatory diagram showing an outline of a configuration in an example of an image forming apparatus of the present invention. FIG. 2 is an explanatory cross-sectional view illustrating an outline of a configuration in an example of a fixing device of the present invention. FIG. 3 is a plan view illustrating an example of a configuration of a heating roller in the fixing device illustrated in FIG. 2. FIG. 3 is a plan view illustrating an example of a configuration of a pressure roller in the fixing device illustrated in FIG. 2. FIG. 3 is an explanatory diagram schematically showing a pressure contact force distribution in a longitudinal direction at a fixing nip portion in the fixing device shown in FIG. 2. FIG. 10 is a plan view showing another configuration example of a fixing rotation member used in the fixing device of the present invention. FIG. 6 is a plan view showing still another configuration example of a fixing rotation member used in the fixing device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photoconductor 11 Charging device 12 Exposure device 13 Developing device 14 Transfer device 15 Separating device 16 Cleaning device 18 Conveying means 20 Fixing device 21 Heating roller 21A Central region 21B End region 21C Rotating shaft 22 Core metal 23 Elastic layer 24 Mold release Layer 25 Halogen heater lamp 26 Pressure roller 26A Central area 26B End area 26C Rotating shaft 27 Core metal 28 Elastic layer 29 Release layer 30, 31 Halogen heater lamp H1 Main heat distribution area H2 Main heat distribution area 32 First Temperature detection means 33 Second temperature detection means C Center position N Fixing nip portion P Transfer material B Maximum transfer material width 40 Fixing roller member 41 Center region 42 Straight shape region 43 Taper shape region 45 End region 50 Fixing roller Member 51 Central area 52 End area

Claims (8)

In a fixing device comprising a fixing heating rotator and a fixing pressure rotator arranged so as to be pressed against each other to form a fixing nip,
In the fixing heating rotator and the fixing pressure rotator, the pressure contact force distribution in the longitudinal direction at the fixing nip portion increases in the central region from the center position toward the axially outward direction. The fixing device is characterized in that the end region in which the edge in the width direction is positioned has an outer shape in which the pressure contact force becomes smaller toward the outside in the axial direction. The fixing heating rotator and the fixing pressure rotator are rollers,
One of the fixing heating rotator and the fixing pressure rotator has an outer shape in which a central region has an inverted crown shape and an end region has a straight shape or a regular crown shape. The fixing device according to claim 1.   3. The other of the fixing heating rotary member and the fixing pressure rotating member has an outer shape in which a central region has a straight shape and an end region has a regular crown shape. The fixing device according to 1.   2. The size LA of the central region satisfies the relationship of 0.5B ≦ LA ≦ 0.9B, where B is the maximum width dimension of the transfer material. The fixing device according to claim 3.   The fixing device according to any one of claims 2 to 4, wherein a crown amount of the fixing heating rotator and the fixing pressure rotator is 0.03 to 0.50 mm.   A first heating source having a main heat distribution region in the central region and a second heat source having a main heat distribution region in the end region are disposed inside the fixing heating rotator. The size H1 of the main heat distribution region of the heating source is a size satisfying the relationship of LA-10 ≦ H1 ≦ LA [mm] when the size of the central region is LA. The fixing device according to any one of claims 1 to 5. A first temperature detecting means for detecting the temperature of the central portion of the fixing heating rotator and a second temperature detecting means for detecting the temperature of the end;
In the standby state, if the temperature difference (T2−T1) between the temperature T1 at the center of the heating heating body for fixing and the temperature T2 at the end (T2−T1) is smaller than 5 ° C., the main heat distribution region is provided in the end region. When the second heating source is operated and the temperature state between the central portion and the end portion is other than that, the first heating source having the main heat distribution region in the central region is operated. The fixing device according to claim 6. An image forming apparatus comprising the fixing device according to claim 1.