JP2021110893A - Heating device and image forming apparatus - Google Patents

Abstract

To solve the problem in which: a metal member has a large rigidity and does not have flexibility in its shape.SOLUTION: A fixing device 6 comprises: a fixing belt 31; a pressure roller 32 that is opposite to the fixing belt 31; a nip forming member 50 that is provided inside the fixing belt 31 and forms a nip part N with the pressure roller 32 with the fixing belt 31 therebetween; and a heater 40 that heats the fixing belt 31. The nip forming member 50 has a metal member 33. The metal member 33 has a nip forming part 33a that extends in a sheet conveyance direction, and a bent part 33b that is provided on at least either one of the upstream side or the downstream side of the nip forming part 33a in the sheet conveyance direction, and in a direction intersecting with the sheet conveyance direction, is bent in a direction different from a longitudinal direction of the metal member 33. The metal member 33 includes a slit 33b1 in the bent part 33b.SELECTED DRAWING: Figure 5

Description

The present invention relates to a heating device and an image forming device.

As a heating device, there is a fixing device provided in an image forming device such as a printer. The fixing device includes a fixing belt as a rotating member, and a heating member for heating the fixing belt and a nip forming member for forming a fixing nip between the fixing belt and the pressure roller are provided inside the fixing belt.

There is a fixing device having a structure in which a nip forming member having a metal member formed of a sheet metal material slides directly on a fixing belt without using a sliding sheet or the like. When such a metal member is formed in a flat plate shape, the edge of the end portion in the paper transport direction may slide with the fixing belt and cause wear or damage of the fixing belt. Further, even when the sliding sheet is used, the sliding sheet may slide with the edge of the metal member, which may cause the sliding sheet to be worn or damaged.

As the above-mentioned countermeasure, there is a metal heat equalizing member having a structure in which both ends of the paper transport direction are bent in a direction intersecting the paper transport direction (for example, Patent Document 1). With such a configuration, the fixing belt slides on the curved surface portion of the heat equalizing member on both sides in the paper transport direction, and the fixing belt can be prevented from being worn or damaged.

There is a problem that the rigidity of the metal member is high and the shape is not flexible.

In order to solve the above problems, the present invention provides a nip between a rotating member, an opposing member facing the rotating member, and inside the rotating member via the rotating member. A heating device including a nip forming member forming a portion and a heating member for heating the rotating member. The nip forming member has a metal member, and the metal member is in a direction of transporting an object to be heated. The length of the nip forming member provided on at least one of the extending nip forming portion and the upstream side or the downstream side of the heated object conveying direction from the nip forming portion and intersecting the heated object conveying direction. It has a bent portion bent in a direction different from the direction, and the metal member is characterized in that the bent portion is provided with a rigidity reducing portion.

The rigidity of the metal member can be reduced.

It is a schematic block diagram of an image forming apparatus. It is a schematic block diagram of the fixing device which concerns on one Embodiment of this invention. It is a perspective view of a stay. It is a top view of the fixing device. It is a perspective view of a stay and a nip forming member. It is a figure which shows the positional relationship in the longitudinal direction between the slit of a bent part, and the support surface of a stay. It is a perspective view which shows the different form of the rigidity lowering part. It is a perspective view which shows the different form of the rigidity lowering part. It is a perspective view which shows the different form of the rigidity lowering part. It is a figure which shows the nip forming member which has a sliding sheet. It is a schematic block diagram of a different fixing device.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted. Hereinafter, in each embodiment, as an example of the heating device, a fixing device for fixing the toner by heat will be described.

In the center of the color image forming apparatus 1 shown in FIG. 1, an image forming unit 2 to which four process units 9Y, 9M, 9C, and 9K are detachably provided is arranged. Each process unit 9Y, 9M, 9C, 9K accommodates developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. It has the same configuration except that it is.

Specific process units 9 include a photoconductor drum 10 which is a drum-shaped rotating body capable of carrying toner as a developer on the surface, and a charging roller 11 which uniformly charges the surface of the photoconductor drum 10. And a developing device 12 having a developing roller that supplies toner to the surface of the photoconductor drum 10.

An exposure unit 3 is arranged below the process unit 9. The exposure unit 3 is configured to emit a laser beam based on the image data.

A transfer unit 4 is arranged above the image forming unit 2. The transfer unit 4 faces the endless intermediate transfer belt 16 stretched around the drive roller 14 and the driven roller 15 so as to be able to travel around the drive roller 14, and the photoconductor drum 10 of each process unit 9 with the intermediate transfer belt 16 sandwiched between them. It is composed of a primary transfer roller 13 and the like arranged at the position. Each primary transfer roller 13 presses the inner peripheral surface of the intermediate transfer belt 16 at each position, and a primary transfer nip is formed at a position where the pressed portion of the intermediate transfer belt 16 and each photoconductor drum 10 come into contact with each other. Has been done.

Further, a secondary transfer roller 17 is arranged at a position facing the drive roller 14 with the intermediate transfer belt 16 interposed therebetween. The secondary transfer roller 17 presses the outer peripheral surface of the intermediate transfer belt 16, and a secondary transfer nip is formed at a position where the secondary transfer roller 17 and the intermediate transfer belt 16 come into contact with each other. The drive roller 14, the intermediate transfer belt 16, and the secondary transfer roller 17 function as an image transfer unit that transfers an image onto paper.

The paper feed unit 5 is located at the lower part of the image forming apparatus 1, and is a paper feed cassette 18 containing the paper P as a recording medium or an object to be heated, or a paper feed roller for carrying out the paper P from the paper feed cassette 18. It consists of 19 mag.

The transport path 7 is a transport path for transporting the paper P carried out from the paper feed unit 5, and the transport roller pair is in the middle of the transport path 7 until the paper discharge section 8 described later is reached in addition to the pair of resist rollers 20. It is arranged appropriately in.

The fixing device 6 has a fixing belt 31 heated by a heating member, a pressure roller 32 capable of pressurizing the fixing belt 31, and the like.

The paper ejection unit 8 is provided at the most downstream side of the transport path 7 of the image forming apparatus 1. The paper ejection section 8 is provided with a pair of paper ejection rollers 21 for ejecting the paper P to the outside and a paper ejection tray 22 for stocking the ejected paper P.

Toner bottles 23Y, M, C, and K filled with toners of each color of yellow, cyan, magenta, and black are detachably provided on the upper part of the image forming apparatus 1. Then, the toner of each color is replenished to the developing device 12 of each color through the replenishment path provided between the toner bottles 23Y, M, C, K and the developing device 12.

Hereinafter, the basic operation of the image forming apparatus 1 will be described with reference to FIG.

When the image forming operation is started in the image forming apparatus 1, an electrostatic latent image is formed on the surface of the photoconductor drum 10 of each process unit 9Y, 9M, 9C, 9K. The image information exposed by the exposure unit 3 on each photoconductor drum 10 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information. An electrostatic latent image is formed on each photoconductor drum 10, and the toner stored in each developing device 12 is supplied to the photoconductor drum 10 by a drum-shaped developing roller, so that the electrostatic latent image becomes visible. It is visualized as a toner image (developer image) which is an image.

In the transfer unit 4, the intermediate transfer belt 16 is driven to travel in the direction of arrow A in the figure by the rotational drive of the drive roller 14. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 13. As a result, a transfer electric field is formed at the primary transfer nip, and the toner images formed on each photoconductor drum 10 are sequentially superimposed and transferred on the intermediate transfer belt 16 at the primary transfer nip.

On the other hand, when the image forming operation is started, in the lower part of the image forming apparatus 1, the paper feeding roller 19 of the paper feeding unit 5 is rotationally driven, so that the paper P housed in the paper feeding cassette 18 is moved to the transport path 7. Be sent out. The paper P sent out to the transport path 7 is timed by the resist roller 20 and sent to the secondary transfer nip between the secondary transfer roller 17 and the drive roller 14. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 16 is applied, and a transfer electric field is formed in the secondary transfer nip. The toner image on the intermediate transfer belt 16 is collectively transferred onto the paper P by the transfer electric field formed in the secondary transfer nip.

The paper P on which the toner image is transferred is conveyed to the fixing device 6, and the paper P is heated and pressed by the fixing belt 31 and the pressure roller 32 to fix the toner image on the paper P. Then, the paper P on which the toner image is fixed is separated from the fixing belt 31, is conveyed by the transport roller pair, and is discharged to the paper discharge tray 22 by the paper discharge roller 21 at the paper discharge unit 8.

The above description is an image forming operation when forming a full-color image on paper P, but a single-color image can be formed by using any one of four process units 9Y, 9M, 9C, and 9K. It is also possible to use two or three process units 9 to form a two-color or three-color image.

Next, a more detailed configuration of the fixing device 6 will be described with reference to FIG.

As shown in FIG. 2, the fixing device 6 includes a fixing belt 31 as a fixing member or a rotating member, a pressure roller 32 as a pressure member or an opposing member, a nip forming member 50, and a heater 40 as a heating member. A stay 35 as a support member, a holder 36 as a fixing member holding member, a side plate 37, and the like are provided. The nip forming member 50, the heater 40, and the stay 35 are provided on the inner peripheral surface side of the fixing belt 31. Further, the nip forming member 50, the heater 40 and the stay 35 are in the longitudinal direction of the fixing belt 31 (in the direction orthogonal to the paper surface in the figure, refer to the double-headed arrow D direction in FIG. , Which is also the width direction of the paper passed through the fixing device). Hereinafter, this direction is also simply referred to as a longitudinal direction. Further, the vertical direction in FIG. 2 is the lateral direction of the nip forming member 50 (or the metal member 33), and is also the paper transport direction (see arrow C1 in FIG. 2).

As shown in FIG. 2, the fixing belt 31 is composed of a thin and flexible endless belt member (including a film). Specifically, the fixing belt 31 includes a base material on the inner peripheral side formed of a metal material such as nickel or SUS or a resin material such as polyimide (PI). Further, it is composed of a release layer on the outer peripheral side formed of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE) or the like. Further, an elastic layer made of a rubber material such as silicone rubber, foamable silicone rubber or fluororubber may be interposed between the base material and the release layer.

The pressure roller 32 is separated from the core metal, an elastic layer made of foamable silicone rubber, silicone rubber, fluororubber, etc. provided on the surface of the core metal, and PFA, PTFE, etc. provided on the surface of the elastic layer. It is composed of mold layers. The pressure roller 32 is urged toward the fixing belt 31 by the urging means, and is in contact with the nip forming member 50 (metal member 33) via the fixing belt 31. At the position where the pressure roller 32 and the fixing belt 31 are in pressure contact with each other, the elastic layer of the pressure roller 32 is crushed to form a nip portion N having a predetermined width. The nip portion N is continuously formed in the longitudinal direction.

Further, the pressure roller 32 is configured to be rotationally driven in the arrow B1 direction by a drive source such as a motor provided in the image forming apparatus main body. Then, when the pressure roller 32 is rotationally driven, the driving force is transmitted to the fixing belt 31 by the nip portion N, and the fixing belt 31 is driven to rotate in the direction of arrow B2.

In the present embodiment, the nip forming member 50 is composed only of the metal member 33 formed of the metal material. However, as in the embodiment described later, the nip forming member 50 may have a resin base pad (resin member) and a metal member.

The metal member 33 is preferably made of a material having high thermal conductivity such as gold, silver, copper, and graphite in order to make the temperature distribution in the longitudinal direction of the fixing belt 31 uniform. Further, in order to reduce the sliding resistance of the metal member 33 with the fixing belt 31, the surface of the metal member 33 in contact with the fixing belt 31 is coated with a sliding agent such as grease.

The metal member 33 has a nip forming portion 33a and a bending portion 33b. The metal member 33 can be formed, for example, by bending a sheet metal material.

The nip forming portion 33a is a portion that comes into contact with the fixing belt 31 from the inner peripheral surface side thereof and forms the above-mentioned nip portion N with the pressure roller 32. The nip forming portion 33a extends in the paper transport direction (vertical direction in the drawing). However, the direction is not limited to the direction parallel to the paper transport direction, and in the present embodiment, the downstream portion of the nip forming portion 33a extends in a direction inclined with respect to the paper transport direction.

The nip forming portion 33a abuts on the portion of the fixing belt 31 facing the pressure roller 32 from the inner peripheral surface side thereof. By this contact, the metal member 33 forms the above-mentioned nip portion N with the pressure roller 32 via the fixing belt 31.

Bending portions 33b are provided at the upstream end and the downstream end of the nip forming portion 33a in the paper transport direction. That is, the metal member 33 has bent portions 33b bent to the left in the drawing in a direction intersecting the paper transport direction at its upstream end and downstream end in the paper transport direction. In other words, the metal member 33 has a bent portion 33b that is bent away from the pressure roller 32. The bent portion 33b is provided over most of the metal member 33 in the longitudinal direction.

The bent portion 33b includes a curved surface portion 33c and a tip portion 33d. The curved surface portion 33c is a portion that has a curved surface shape and changes the extending direction of the metal member 33. The tip portion 33d is a portion provided on the end portion side of the metal member 33 with respect to the curved surface portion 33c, and extends in the left-right direction in the drawing.

Unlike the configuration of the present embodiment, when the metal member 33 is formed in a flat plate shape, that is, in the case where the metal member 33 is not provided with the bent portions 33b on the upstream side and the downstream side in the paper transport direction, the paper transport of the metal member 33 The fixing belt 31 may be in sliding contact with the edge portion of the edge in the direction (vertical direction in the drawing), and the fixing belt 31 may be worn or damaged. On the other hand, by forming the curved surface portions 33c on the upstream side and the downstream side of the metal member 33 in the paper transport direction as in the present embodiment, the metal member 33 is fixed by the curved surface portions 33c at both ends in the paper transport direction. Sliding with 31. Therefore, the frictional force generated between the fixing belt 31 and the metal member 33 can be reduced, and wear or damage of the fixing belt 31 can be prevented.

The heater 40 of this embodiment is a halogen heater. The heater 40 is a heating member that heats the fixing belt 31 from the inner peripheral side by radiant heat by radiating infrared light. Further, the heater 40 may be an IH coil, a resistance heating element, a carbon heater, or the like.

The stay 35 supports the metal member 33 from the back surface side thereof. More specifically, the stay 35 abuts the support surface 35a against the metal member 33 from the side opposite to the pressure direction of the pressure roller 32 (left side in the drawing) over the longitudinal direction thereof. As a result, the bending of the metal member 33 due to the pressurization of the pressurizing roller 32 is suppressed over the longitudinal direction thereof, and a flatter nip portion N is formed between the fixing belt 31 and the pressurizing roller 32. In particular, when the stay 35 extends in the pressurizing direction (left-right direction in the figure), it has a horizontally long cross section extending in the pressurizing direction, the cross-sectional coefficient becomes large, and the pressing force of the pressurizing roller 32 increases. It is possible to effectively suppress the bending of the metal member 33 against the above.

The stay 35 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the bending prevention function of the metal member 33. At this time, it is desirable that each plate material of the stay 35 is produced by punching an iron steel plate. By being made of steel plate, it is possible to make a stay 35 which is inexpensive and has high rigidity.

The holders 36 are provided on both ends in the longitudinal direction of the fixing belt 31, and support the fixing belt 31 from the inner peripheral surface side thereof. The holder 36 comes into contact with the inner peripheral surface of the fixing belt 31 at a position where the fixing belt 31 faces the metal member 33 and a position excluding the vicinity thereof in the circumferential direction of the fixing belt 31. When the holder 36 supports the fixing belt 31 from the inner peripheral surface side thereof, the fixing belt 31 can maintain its tubular shape.

Side plates 37 are provided at both ends of the fixing device 6 in the longitudinal direction to hold the stay 35 and the holder 36. The stay 35 is supported by the side plate 37 by fitting the supported surface 35b into the hole portion 37a formed in the side plate 37. The side plate 37 is fixed to the housing of the fixing device 6.

Further, a reflector that reflects radiant heat from the heater 40 is arranged between the heater 40 and the stay 35. The reflector is fixed to the stay 35. Further, a temperature sensor as a temperature detecting means for detecting the temperature of the fixing belt 31 is provided facing the fixing belt 31.

Next, a more detailed configuration of the stay 35 will be described with reference to FIG.

As shown in FIG. 3, the stay 35 is composed of a stay upper 351 and a stay lower 352, and a stay right 353. The upper part 351 of the stay and the lower part 352 of the stay are formed of a sheet metal material. The lower end surfaces of the stay upper 351 and the stay lower 352 in FIG. 3 are formed by a linear shear plane having a uniform height over the longitudinal direction. The stay upper 351 and the stay lower 352 have protrusions provided intermittently in the longitudinal direction on the upper end surface side thereof. This protruding portion penetrates the stay right 353 in the vertical direction in the drawing, and the upper end surface of the protruding portion forms a support surface 35a which is one shear section. As shown in FIG. 4, the amount of protrusion of the support surface 35a gradually increases from both ends in the longitudinal direction toward the center. In other words, the support surface 35a forms a convex shape from both ends toward the center. In FIG. 4, members such as the fixing belt 31 are omitted, and the stay 35, the metal member 33, and the members around the stay 35 are mainly shown.

As shown in FIG. 3, the upper end surface of the stay lower 352 in FIG. 3 is separated from the upper end surface of the stay upper 351 by a predetermined distance due to the stay lower 352 being bent in the middle (see FIG. 2). There is. That is, the rows (support rows) in the longitudinal direction of the support surfaces 35a formed by the stay upper 351 and the stay lower 352 are provided apart by a predetermined distance in the paper transport direction (vertical direction in FIG. 2).

The stay upper 351 and the stay lower 352 are fixed by welding, adhesion, caulking, screwing, or the like. Further, the stays 351 and 352 are fixed to the right 353 of the stays by welding, adhesion, caulking, screwing, or the like. The lower end surfaces of the stays 351 and 352 form a supported surface 35b which is the other sheared surface.

The support surface 35a, which is a sheared cross section formed on the stay 35 made of sheet metal, can easily obtain its dimensional accuracy. Therefore, by supporting the metal member 33 by the support surface 35a, the metal member 33 can be positioned with high accuracy. As a result, it is possible to provide a fixing device capable of improving the reliability of parts and reducing the inspection cost.

By the way, as shown in FIG. 4, the stay 35 is easily bent on the central side in the longitudinal direction because of the configuration of the double-sided beam supported by the side plates 37 at both ends in the longitudinal direction. Due to such bending, the fixing belt 31 and the pressure roller 32 cannot be sufficiently pressed against each other on the central side in the longitudinal direction, and the nip width (width in the lateral direction of the nip portion N) becomes smaller on the central side in the longitudinal direction. There is a risk that it will end up. If the nip width becomes non-uniform in the longitudinal direction, the amount of heat given to the toner on the paper passing through the nip portion N becomes excessive or insufficient, which causes poor fixing.

However, in the present embodiment, as described above, the amount of protrusion of the support surface 35a from the stay right 353 increases from both ends in the longitudinal direction toward the center, so that the nip due to the bending of the stay 35 The deviation can be offset to obtain a nip portion N having a uniform nip width.

Further, by providing the support surface 35a of the stay 35 intermittently in the longitudinal direction, the contact area of the stay 35 with respect to the metal member 33 can be reduced. As a result, the amount of heat transferred from the metal member 33 to the stay 35 can be reduced, and the fixing device 6 can efficiently heat the fixing belt 31. That is, the fixing device 6 can be energy-saving and speed-up.

Further, by providing each support surface 35a intermittently, the shape of each support surface 35a can be individually set or finely adjusted, so that the reliability of parts can be easily improved.

By the way, like the metal member 33 of the present embodiment, by providing the bent portions 33b on both sides in the paper transport direction, the rigidity of the metal member 33 in the longitudinal direction (rigidity against deformation in the direction intersecting the longitudinal direction) is increased. Therefore, it becomes difficult for the metal member 33 to follow the convex shape (see FIG. 4) formed toward the center side of the support surface 35a of the stay 35 described above. If the metal member 33 does not sufficiently follow the support surface 35a, the nip width of the nip portion N becomes non-uniform. Further, the metal member 33 is twisted in the longitudinal direction, and the frictional force with the fixing belt 31 is locally increased to cause uneven wear, or the nip pressure on the paper passing through the nip portion N is locally applied. There is a problem that it becomes large and causes poor transportation such as paper wrinkles.

The configuration of the present embodiment for solving the above problems, specifically, the rigidity reducing portion provided on the metal member 33 will be described with reference to FIG. FIG. 5 is a perspective view showing the pressure roller 32 and the metal member 33 extracted.

As shown in FIG. 5, each of the bent portions 33b provided on both sides of the metal member 33 in the paper transport direction is provided with slits 33b1 as rigidity reducing portions in the middle of the longitudinal direction thereof.

The slit 33b1 is a notch portion provided at the tip end portion 33d and opened on the end end side (the left side in the drawing in a direction different from the longitudinal direction of the metal member 33) of the tip end portion 33d. The slits 33b1 are provided at a plurality of locations in the longitudinal direction. However, it may be in one place. Of the slits 33b1 shown in FIG. 5, the slit 33b1 on the upper left of the figure is formed at a substantially central position in the longitudinal direction of the metal member 33.

By providing the slit 33b1 in the middle of the tip portion 33d in the longitudinal direction, the bending rigidity of the metal member 33, particularly the bending rigidity in the longitudinal direction, is reduced, and the metal member 33 can easily follow the convex shape of the stay 35. Therefore, it is possible to prevent the nip width of the nip portion N from becoming non-uniform, and it is possible to prevent the above-mentioned fixing failure. Further, it is possible to prevent the metal member 33 from being twisted in the longitudinal direction.

Further, as shown in FIG. 5, the slits 33b1 provided in the bent portions 33b on the upstream side and the downstream side in the paper transport direction are preferably arranged at the same positions in the longitudinal direction. As a result, in the bent portion 33b, the positions having low rigidity in the longitudinal direction can be aligned, so that the metal member 33 can be more easily imitated with respect to the shape of the stay 35.

As shown in FIG. 6A, the slit 33b1 can be arranged at a position facing the support surface 35a of the stay 35 in the longitudinal direction (direction of the double-headed arrow D). As a result, the rigidity of the metal member 33 can be reduced at the position where the stay 35 abuts on the metal member 33 in the longitudinal direction, and the metal member 33 can be made easier to follow the convex shape of the stay 35. .. Further, as shown in FIG. 6B, the slit 33b1 can be arranged at a position different from the support surface 35a in the longitudinal direction. Since the slit 33b1 (or each rigidity lowering portion described later) is a portion of the metal member 33 in which the heat capacity is partially reduced, the slit 33b1 can be arranged at a position different from that of the support surface 35a in the longitudinal direction. , It is possible to prevent the amount of heat from becoming too small around the slit 33b1. Therefore, the temperature of the metal member 33 can be made uniform in the longitudinal direction, and the temperature of the fixing belt 31 can be made uniform in the longitudinal direction. However, one slit 33b1 can be arranged at the same position as the support surface 35a, and another slit 33b1 can be arranged at a position different from the support surface 35a. At each position in the longitudinal direction, either rigidity or thermalization is prioritized. It can be appropriately selected depending on whether or not it is to be used.

In the above metal member 33, the case where the slit 33b1 is provided at the tip portion 33d of the bent portion 33b is shown. For example, as shown in FIG. 7, the slit 33b1 spans the tip portion 33d, the curved surface portion 33c, and the nip forming portion 33a. May be provided. As a result, the rigidity of the metal member 33 can be made smaller, and the metal member 33 can be made easier to follow the convex shape of the stay 35.

In the present embodiment, the slit 33b1 is preferably provided with a width of 2 mm or less in the longitudinal direction. That is, when the slit 33b1 is provided over the curved surface portion 33c and the nip forming portion 33a, a partial opening is provided on the side of the nip forming portion 33a that comes into contact with the fixing belt 31 or in the vicinity thereof. Therefore, if the width of the slit 33b1 is too large, the fixing belt 31 may enter the slit 33b1. By setting the width of the slit 33b1 to 2 mm or less, such a problem can be prevented.

The slit 33b1 of the present embodiment is formed by press working as an example. When the slit 33b1 is provided over the curved surface portion 33c and the nip forming portion 33a as described above, the surface of the metal member 33 facing the fixing belt 31 is provided with a sagging portion by press working, and vice versa. It is preferable that the side surface is the side on which the burr is provided. In other words, it is preferable that the side of the metal member 33 facing the fixing belt 31 is the upstream side in the shearing direction during press working. Even if the fixing belt 31 enters the portion of the nip forming portion 33a where the slit 33b1 is formed, the metal member can be formed by setting the side facing the fixing belt 31 as the side on which the sagging portion is formed as described above. It is possible to prevent the fixing belt 31 from being worn or damaged by the burrs formed on the 33.

In the above description, the case where the rigidity lowering portion provided on the metal member 33 has the shape of a slit is shown, but the present invention is not limited to this.

For example, as shown in FIG. 8, the metal member 33 may be provided with a hole 33b2 as a rigidity reducing portion. The hole 33b2 penetrates in the thickness direction of the metal member 33 and does not open on the edge side of the tip 33d. In the present embodiment, the hole portion 33b2 is provided over the tip portion 33d, the curved surface portion 33c, and the nip forming portion 33a. However, the nip forming portion 33a, which easily contributes to the fixing quality, may be provided from the tip portion 33d to the curved surface portion 33c, or may be provided only on the curved surface portion 33c, without cutting out the nip forming portion 33a.

Further, as shown in FIG. 9, the metal member 33 may be provided with a thin-walled portion 33b3 as a rigidity reducing portion. In the present embodiment, the thin-walled portion 33b3 is provided from the edge of the upstream tip portion 33d to the edge of the downstream tip portion 33d, but only a part thereof may be thinned. In this case, it is more preferable to provide the thin portion 33b3 on the bent portion 33b because the rigidity can be effectively reduced. Further, since the nip forming portion 33a is in contact with the fixing belt 31, from the viewpoint of thermalization and the like, when only a part of the metal member 33 in the lateral direction is thinned, the bent portion 33b has a thinned portion 33b3. It is better to provide. As a result, the thermal conductivity of the metal member 33 can be prevented from being impaired as much as possible.

These rigidity-reducing portions can reduce the rigidity of the bent portion 33b of the metal member 33, particularly in the longitudinal direction, so that the metal member 33 can easily follow the convex shape of the stay 35. Therefore, it is possible to prevent the nip width of the nip portion N from becoming uneven and the metal member 33 from being twisted in the longitudinal direction.

Next, a fixing device having a structure in which the nip forming member 50 includes a metal member and a resin member will be described.

For example, as shown in FIG. 10A, in the present embodiment, the nip forming member 50 has a metal member 33 and a resin base pad 34 (resin member 34). Further, a sliding sheet 41 is provided between the nip forming member 50 and the fixing belt 31. Further, the metal member 33 of the present embodiment also has a nip forming portion 33a and a bending portion 33b as in the above-described embodiment.

The base pad 34 is provided on the side opposite to the nip portion N (left side in the drawing) with respect to the metal member 33. The contact surface 34a that comes into contact with the stay 35 of the base pad 34 is formed to be convex toward the center side in the longitudinal direction thereof, as in the support surface 35a (see FIG. 4) of the stay 35 of the above-described embodiment. Thereby, the deviation of the nip due to the bending of the stay 35 can be canceled out, and the nip portion N having a uniform nip width can be obtained.

The sliding sheet 41 can be formed, for example, by impregnating a material made of PTFE thread with a lubricant such as silicone oil. The sliding sheet 41 is provided from one end side to the other end side of the base pad 34 in the paper transport direction (vertical direction in the drawing), and covers the surface of the base pad 34 or the metal member 33 facing the fixing belt 31. By providing the sliding sheet 41, the slidability between the metal member 33 and the fixing belt 31 can be improved, and the wear of the fixing belt 31 can be suppressed.

Further, as shown in FIG. 10B or FIG. 10C, the metal member 33 may be provided from the upstream end of the nip forming member 50 in the paper transport direction to the middle of the downstream side. .. That is, in the present embodiment, the metal member 33 is not arranged on the downstream side of the nip forming member 50 in the paper transport direction, and the base pad 34 hits the fixing belt 31 via the sliding sheet 41 on the downstream side in the paper transport direction. In contact with each other, a nip portion N is formed between the fixing belt 31 and the pressure roller 32. In the present embodiment, the portion of the base pad 34 on the downstream side in the paper transport direction is convex toward the pressure roller 32 side (right side in the drawing). By making the metal member 33 not face the convex portion of the base pad 34, it is possible to facilitate the processing of the metal member 33.

In the case of the configuration in which the sliding sheet 41 is provided, since the metal member 33 does not come into direct contact with the fixing belt 31, a bent portion is provided on the downstream side portion of the nip forming portion 33a in the paper transport direction as shown in FIG. 10 (b). It can be configured not to form. However, even in this case, the rigidity-reducing portion described above can be formed in the bent portion 33b on the upstream side of the metal member 33 in the paper transport direction. Since the rotation of the fixing belt 31 generates a force on the metal member 33 from the upstream side in the paper transport direction to the downstream side, by providing the bending portion 33b on the upstream side in the paper transport direction of the metal member 33, the metal It is possible to prevent the member 33 from being displaced with respect to the base pad 34, and to reduce the frictional force generated between the metal member 33 and the sliding sheet 41 on the upstream side portion. However, as shown in FIG. 10C, a bent portion 33b may be formed on the downstream side of the metal member 33 in the paper transport direction, and the tip portion 33d may extend in a direction intersecting the paper transport direction. In this case, the rigidity lowering portion can be formed in the bent portions 33b on the upstream side and the downstream side in the paper transport direction. With these rigidity reducing portions, it is possible to reduce the rigidity of the metal member 33 in the longitudinal direction in particular, and to make it easier for the metal member 33 to follow the convex shape of the base pad 34. The rigidity lowering portion is not limited to the slit, and may be a hole portion or a thin-walled portion.

Further, the fixing device to which the present invention is applied is not limited to the above fixing device. For example, the present invention can be applied to the fixing device shown in FIG. 11 below.

As shown in FIG. 11, the fixing device 6 of the present embodiment has a fixing belt 31, a pressure roller 32, a nip forming member 50, a heater 40, a stay 35, and a holder 36, as in the above-described embodiment. And side plates etc. are provided. Further, the fixing device 6 includes a reflecting member 38, a temperature sensor 29 as a temperature detecting means for detecting the temperature of the fixing belt 31 facing the outer peripheral surface of the fixing belt 31, a separating member 42 for separating paper from the fixing belt 31 and the like. Have. The nip forming member 50 has a metal member 33 and a base pad 34. Further, a sliding sheet 41 is provided between the nip forming member 50 and the fixing belt 31.

The base pad 34 is made of a material that is hard to some extent to ensure strength and has a heat resistant temperature of 200 ° C. or higher. Examples of the material of the base pad 34 include polyethersulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyethernitrile (PEN), polyamideimide (PAI), and polyetheretherketone (PEEK). General heat-resistant resin such as can be used.

The contact surface of the base pad 34 that abuts on the stay 35 is formed to be convex toward the center side in the longitudinal direction as in the above-described embodiment.

In the present embodiment, the stay 35 comes into contact with the base pad 34 and extends in the paper transport direction (vertical direction in FIG. 2), and the ends of the base portion 35c on the upstream side and the downstream side in the paper transport direction. It has a rising portion 35d extending from the portion toward the contact direction of the pressure roller 32 (left side in FIG. 2). By providing the rising portion 35d, the stay 35 has a horizontally long cross section extending in the pressurizing direction of the pressurizing roller 32, the cross-sectional coefficient becomes large, and the mechanical strength of the stay 35 can be improved. It will be possible.

Further, the heater 40 is arranged in the recess formed between the base portion 35c and the rising portions 35d formed on both sides, and the reflective member 38 is arranged between the heater 40 and the stay 35. With such an arrangement, the space on the inner peripheral surface side of the fixing belt 31 can be effectively utilized, and the diameter of the fixing belt 31 can be reduced.

Also in the above fixing device 6, bending portions 33b are provided on both sides of the metal member 33 in the paper transport direction, and the tip portions 33d extend in a direction intersecting the paper transport direction. Then, by providing the above-mentioned rigidity lowering portion in the bending portion 33b, the bending rigidity of the metal member 33, particularly the bending rigidity in the longitudinal direction is reduced, and the metal member 33 can easily follow the convex shape of the base pad 34. Can be done. Therefore, it is possible to prevent the nip width of the nip portion N from becoming uneven and the metal member 33 from being twisted in the longitudinal direction.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, and may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine thereof.

Recording media include paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, transparencies, plastic films, prepregs, copper foil, etc. included.

Further, the present invention is not limited to the fixing device as described in the above embodiment, but also a drying device that dries the ink applied to the paper, and further, heats a film as a covering member to the surface of a sheet such as paper. It can also be applied to a heating device such as a laminator for thermocompression bonding and a thermocompression bonding device such as a heat sealer for thermocompression bonding the seal portion of a packaging material. By applying the present invention to such an inkjet image forming apparatus and a thermocompression bonding apparatus, it is possible to reduce the rigidity of the metal member particularly in the longitudinal direction. Therefore, it is possible to prevent the nip width of the nip portion N from becoming uneven and the metal member from being twisted in the longitudinal direction.

1 Image forming device 6 Fixing device (heating device)
31 Fixing belt (fixing member or rotating member)
32 Pressurizing roller (pressurizing member or opposing member)
33 Metal member 33a Nip forming part 33b Bending part 33b1 Slit (reduced rigidity part)
33b2 hole (reduced rigidity)
33b3 Thin wall part (rigidity reduction part)
33c Curved surface 33d Tip 34 Base pad (resin member)
35 stay (support member)
35a Support surface 35b Supported surface 40 Heater (heating member)
50 Nip forming member P paper (recording medium or object to be heated)

Japanese Unexamined Patent Publication No. 2016-99590

Claims (13)

With rotating members
With the opposing member facing the rotating member,
A nip forming member provided inside the rotating member and forming a nip portion between the rotating member and the opposing member via the rotating member.
A heating device including a heating member for heating the rotating member.
The nip forming member has a metal member and has a metal member.
The metal member is provided on at least one of a nip forming portion extending in the heated object transporting direction and an upstream side or a downstream side of the heated object transporting direction from the nip forming portion, and the metal member is provided in at least one of the heated object transporting directions. It has a bent portion that is bent in a direction different from the longitudinal direction of the nip forming member in the intersecting direction.
The metal member is a heating device characterized in that the bent portion is provided with a rigidity reducing portion. The heating device according to claim 1, wherein the bent portion is provided on the upstream side and the downstream side of the nip forming portion in the direction of transporting the object to be heated, and each of the bent portions has the rigidity lowering portion. The heating device according to claim 2, wherein the rigidity-reducing portions on the upstream side and the downstream side in the object to be transported direction are provided at the same positions in the longitudinal direction. The metal member is a pressed product of sheet metal material, and is
The heating device according to any one of claims 1 to 3, wherein a sagging portion by the press working is arranged on a surface side of the metal member facing the rotating member. The heating device according to any one of claims 1 to 4, wherein the rigidity reducing portion is a slit opened on the end side of the metal member. The heating device according to any one of claims 1 to 4, wherein the rigidity reducing portion is a hole portion penetrating in the thickness direction of the metal member. The heating device according to any one of claims 1 to 4, wherein the rigidity-reducing portion is a thin-walled portion. The heating device according to any one of claims 1 to 7, wherein the surface of the metal member in contact with the rotating member is coated with a sliding agent. The heating device according to any one of claims 1 to 7, wherein a sliding sheet is provided between the metal member and the rotating member. The heating device according to any one of claims 1 to 9, wherein the nip forming member further includes a resin member provided on the side opposite to the nip portion side with respect to the metal member. The heating device according to any one of claims 1 to 9, wherein the nip forming member is the metal member itself. The heating device according to any one of claims 1 to 11, which is a fixing device for fixing an image on a recording medium. An image forming apparatus comprising the heating apparatus according to any one of claims 1 to 12.

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