JP2023165131A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can prevent abnormal deformation of a reflecting member and prevent an abnormal high temperature of the reflecting member, and an image forming apparatus.SOLUTION: A fixing device 40 comprises: a rotating fixing member such as a fixing belt; a pressure member such as a pressure roller that is in contact with an outer peripheral surface of the fixing member to form a nip part and applies pressure to a recording material passing through the nip part; and heat sources that are arranged inside the fixing member. The fixing device further comprises a reflecting member such as a reflector in which a reflecting part reflecting radiation heat radiated from the heat sources toward an inner peripheral surface of the fixing member and a pressure receiving part 48b receiving the pressure applied by the pressure member through the fixing member are integrated with each other or thermally connected with each other. The pressure receiving part 48b extends from one end to the other end of the fixing member, and the pressure receiving part 48b is provided with slits 48c.SELECTED DRAWING: Figure 6

Description

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

Conventionally, a fixing device includes a rotating fixing member, a pressure member that presses a recording material passing through a nip formed by contacting the outer peripheral surface of the fixing member, and a heat source disposed inside the fixing member. The device is known.

Patent Document 1 discloses that the fixing device includes a first reflecting member that reflects radiant heat from a first heat source to a fixing member, the fixing device having a heat generating region at the center in the axial direction, and a heat generating region at the end in the axial direction. A second reflecting member that reflects radiant heat from the second heat source to the fixing member is described. Each reflecting member has a reflecting portion that reflects radiant heat emitted from the heat source toward the inner circumferential surface of the fixing member, and a pressure receiving portion that receives the pressing force of the pressure member via the fixing member. , it is described that thermal efficiency can be improved by transferring the heat from the heat source absorbed by the reflection part to the fixing member by the pressure receiving part.

Further, Patent Document 1 discloses an example of a device in which the pressure receiving portion of each reflecting member extends from one end side of the fixing member to the other end side, and the pressure receiving portion of the first reflecting member is located at the center in the axial direction. , an example of a device in which the pressure receiving portions of the second reflecting member are provided at both ends in the axial direction is described.

However, with the configuration of Patent Document 1, there is a possibility that either abnormal deformation of the reflecting member or abnormal high temperature of the reflecting member cannot be suppressed.

In order to solve the above-mentioned problems, the present invention provides a rotating fixing member, a pressure member that presses a recording material passing through a nip portion formed by contacting an outer peripheral surface of the fixing member, and a heat source disposed inside the fixing member; a reflecting portion that reflects radiant heat emitted from the heat source toward an inner circumferential surface of the fixing member; The pressure receiving part has a reflecting member integrally or thermally connected to the pressure receiving part that is received through the fixing member, and the pressure receiving part extends from one end side of the fixing member to the other end side, and the pressure receiving part It is characterized in that a notch is provided in the receiving part.

According to the present invention, abnormal deformation of the reflective member and abnormal high temperature of the reflective member can be suppressed.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram of a fixing device in this embodiment. FIG. 3 is a perspective view showing a reflector, a nip forming member, and a fixing stay. FIG. 1 is a schematic configuration diagram of a conventional fixing device. FIG. 7 is a schematic configuration diagram showing another configuration example of the fixing device. FIG. 3 is a schematic perspective view showing a plurality of notches in the pressure receiving part. A schematic diagram showing formation positions of a plurality of notches. FIG. 7 is a diagram illustrating heat transfer in the axial direction of the pressure receiving portion and temperature distribution on the surface of the fixing belt when there is no notch and when there is a notch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a laser printer (hereinafter referred to as a "printer") which is an electrophotographic image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of an image forming apparatus 1 of this embodiment. The image forming apparatus 1 includes an image forming section 100 that forms an image on paper P, which is a recording material. The image forming section 100 includes image forming sections 10Y, 10M, 10C, and 10K for each color of yellow (Y), magenta (M), cyan (C), and black (K), which are connected to an intermediate transfer belt 20 as an intermediate transfer body. This is a tandem-type image forming apparatus arranged along the rotation direction. Each of the image forming units 10Y, 10M, 10C, and 10K includes photoreceptors 11Y, 11M, 11C, and 11K as latent image carriers, respectively.

Further, each of the image forming units 10Y, 10M, 10C, and 10K includes a charging device as a charging means and an optical writing device 9 as an electrostatic latent image forming means around the photoreceptors 11Y, 11M, 11C, and 11K. , and a developing device as a developing means. Furthermore, a primary transfer device as a primary transfer means and a cleaning device as a cleaning means are also provided around the photoreceptors 11Y, 11M, 11C, and 11K. The charging device uniformly charges the surface of the photoreceptor to a predetermined potential, and the optical writing device 9 exposes the surface of the photoreceptor uniformly charged by the charging device to static electricity according to image information. It is used to write an electric latent image. The developing device creates a toner image through a developing process in which toner of each color (Y, M, C, K) is attached to an electrostatic latent image on a photoreceptor. The primary transfer device transfers the toner image on the photoreceptor onto the intermediate transfer belt 20, and the cleaning device removes and cleans the photoreceptor toner remaining after transfer.

The toner images of each color formed on each of the photoreceptors 11Y, 11M, 11C, and 11K are primarily transferred onto the intermediate transfer belt 20 so as to overlap with each other by a primary transfer device, and a color toner image is formed on the intermediate transfer belt 20. be done. The color toner image on the intermediate transfer belt 20 is conveyed to an area facing the secondary transfer device 30 (secondary transfer area) as the intermediate transfer belt 20 rotates.

On the other hand, below the image forming section 100, a paper feed cassette 60 serving as a feeding section that feeds the paper P to be held is arranged. Paper P is fed one by one from a paper feed cassette 60 by a pickup roller 61. Then, the paper P is transported to the secondary transfer area by the registration roller pair 62 along the transport path.

The color toner image on the intermediate transfer belt 20 is secondarily transferred by the second transfer device 30 onto the paper P conveyed by the pair of registration rollers 62 at a predetermined timing in the second transfer area. The paper P on which the color toner image has been formed is then conveyed to a fixing device 40 as a fixing means, and the color toner image is fixed onto the paper P by the action of heat and pressure. After fixing, the paper P is conveyed along the conveyance path and is discharged to the paper discharge tray 50 by the paper discharge roller 63.

FIG. 2 is a schematic configuration diagram of the fixing device 40 in this embodiment.
The fixing device 40 includes a pressure roller 41 as a pressure member, a fixing belt 42 as a fixing member, and a heat source 43 (a halogen heater in the illustrated example), and performs fixing by heating and pressing.
A nip forming member 45 held by a fixing stay 44 serving as a stay member is disposed within the fixing belt 42 .

The nip forming member 45 is composed of a heat equalizing member 45a which is a sliding member and a heat transfer member disposed on the nip surface, and a resin pad 45b which supports this. One of the roles of the resin pad 45b is heat insulation, which suppresses heat absorption of the fixing belt 42 to the fixing stay 44 via the nip forming member 45, thereby suppressing an increase in warm-up time and TEC value. The heat equalizing member 45a has a pad shape, for example, extending in the width direction of the fixing belt 42. The heat equalizing member 45a is arranged to average the temperature of the fixing belt in the axial direction. That is, heat is taken away from the high-temperature parts of the fixing belt 42 and transferred to the low-temperature parts of the fixing belt 42, thereby making the temperature of the fixing belt 42 uniform in the axial direction.

Although the configuration of FIG. 2 has a flat shape, the nip portion may have a concave shape or other shapes. By forming the concave nip, the ejection direction of the leading edge of the paper is moved closer to the pressure roller, and the separability of the paper from the fixing belt 42 is improved, thereby suppressing the occurrence of jams.

The heat equalizing member 45a is a highly thermally conductive metal member such as aluminum or copper with a thermal conductivity of 50 [W/m·K] or more, and the surface of the heat equalizing member 45a has a coating with excellent sliding performance. It has been subjected. Coating materials include those based on resins such as polyimide resins, fluororesins, polyphenylene sulfide resins, or saturated polyester resins. Alternatively, such a resin-based coating material may be mixed with glass fiber, carbon, graphite, fluorinated graphite, carbon fiber, molybdenum disulfide, fluororesin, or the like.

Moreover, metal-based materials can also be used as coating materials. Examples of metal-based coating materials include molybdenum disulfide, nickel, and composite plating of nickel and fluororesin. Further, examples of metal-based coating materials include alumite or alumite impregnated with resin or metal. Moreover, ceramic can also be used as a coating material. Examples of the ceramic used as the coating material include silicon carbide ceramic, silicon chamber ceramic, alumina ceramic, and mixtures thereof with molybdenum disulfide, fluororesin, and the like.

In addition, an alumite layer is formed on the surface layer of the heat equalizing member 45a made of aluminum or an aluminum alloy, and molybdenum disulfide generated by secondary electrolysis is applied to the micropores of the alumite layer from the deepest part of the micropores to the outermost layer. It is also effective to fill the area over the entire range.

The pressure roller 41 has a silicone rubber layer provided on the outer periphery of a metal roller, and a release layer (PFA or PTFE layer) is provided on the surface of the silicone rubber layer to obtain release properties. Further, the pressure roller 41 is pressed against the fixing belt side by a spring or the like, and has a predetermined nip width by compressing and deforming the rubber layer.

The pressure roller 41 is rotated by a driving force transmitted through a gear from a driving source such as a motor provided in the image forming apparatus. The fixing belt 42 rotates together with the driving force transmitted from the pressure roller 41 at the nip portion.

The pressure roller 41 may be a solid roller, but a hollow roller is preferable because it has less heat capacity. Further, the pressure roller 41 may include a heat source such as a halogen heater. The silicone rubber layer may be solid rubber, but if there is no heater inside the pressure roller, sponge rubber may be used. Sponge rubber is more desirable because it has better heat insulation and makes it difficult for the fixing belt to lose heat.

The fixing belt 42 is an endless belt (or film) whose base material is a metal belt such as nickel or SUS, or a resin material such as polyimide. The surface layer of the fixing belt 42 has a release layer such as a PFA or PTFE layer, and is provided with release properties to prevent toner from adhering.

An elastic layer formed of a silicone rubber layer or the like may be provided between the base material of the fixing belt 42 and the release layer. If there is no silicone rubber layer, the heat capacity will be smaller and the fixing performance will be improved, but when the unfixed image is crushed and fixed, subtle irregularities on the belt surface will be transferred to the image, resulting in a yuzu skin-like appearance in the solid areas of the image. This causes the problem of leaving marks. To improve this, it is necessary to provide a silicone rubber layer with a thickness of 100 μm or more. By deforming the silicone rubber layer, subtle irregularities are absorbed and the Yuzu skin image is improved.

The fixing stay 44 is a hollow pipe-shaped metal body made of metal such as aluminum, iron, or stainless steel. In this embodiment, the fixing stay 44 has a square shape, but may have other cross-sectional shapes. This prevents the nip forming member 45 from being bent when it receives pressure from the pressure roller 41, so that a uniform nip width can be obtained in the axial direction.

Two heat sources for raising the temperature of the fixing belt 42 are provided inside the fixing belt 42 . In this embodiment, the heat source 43 is a halogen heater, and the fixing belt 42 is directly heated by radiant heat from the heat source 43 from the inner peripheral side. Here, the heat source 43 only needs to be able to heat the fixing belt 42, and may be an IH coil, a resistance heating element, a carbon heater, or the like.

Furthermore, in order to reduce the loss of radiant heat from the heat source 43 as much as possible, a reflector 48 is disposed within the fixing belt 42 as a reflective member that reflects heat toward the fixing belt. The reflector 48 is made of high-brightness aluminum, which is made of a high-purity aluminum material as a metal member and has a plurality of reflection-enhancing films and protective films formed on its surface. Also, depending on the configuration, an aluminum plate with silver vapor-deposited on it to further improve the reflectance may be used.

The reflector 48 of this embodiment includes a reflecting portion 48a that reflects radiant heat toward the fixing belt, and a pressure receiving portion 48b that receives the pressing force of the pressure roller 41. The reflecting portion 48a is arranged between the heat source 43 and the fixing stay 44. The pressure receiving portion 48b is disposed to be sandwiched between a heat equalizing member 45a, which is a sliding member, and a resin pad 45b.

FIG. 3 is a perspective view showing the reflector 48, the nip forming member 45, and the fixing stay 44.
As shown in FIG. 3, the reflector 48 is held by the pressure receiving part 48b being sandwiched between the heat equalizing member 45a and the resin pad 45b, and other parts other than the pressure receiving part 48b are not in contact with other members. It has become.

FIG. 4 is a schematic configuration diagram of a conventional fixing device.
As shown in FIG. 4, in the past, the reflector 148 did not have the pressure receiving part 48b.
The reflectance of the reflector 148 is about 95 to 98%, and it cannot reflect 100% of the radiant heat from the heat source 143, and since the reflector itself absorbs a small amount of radiant heat, the temperature gradually increases. In particular, in the conventional fixing device shown in FIG. 4, when a large amount of paper is continuously passed, the temperature of the reflector 148 rises to about 300° C. to 400° C. If a heat load above a certain level is applied to the reflector 148, the aluminum or silver layer of the reflector 148 will discolor. If this happens, not only will the reflectance decrease and the original performance cannot be achieved, but in the worst case, it will develop into a safety problem. Therefore, in the past, it was only possible to achieve productivity that did not reach that temperature range, which became a bottleneck in improving machine productivity.

On the other hand, in the present embodiment, as explained using FIGS. 2 and 3, the reflector 48 is a region that receives the pressing force from the pressure roller 41 between the heat equalizing member 45a and the resin pad 45b. It has a pressure receiving part 48b extending to . As described above, the reflector 48 is made of aluminum, which is a metal member with good thermal conductivity, so that the heat absorbed by the reflective portion 48a is quickly conducted to the entire component. Then, the heat of the reflector 48 is transferred from the pressure receiving part 48b that is in contact with the heat equalizing member 45a to the heat equalizing member 45a, and an increase in the temperature of the reflector 48 can be suppressed. Further, the heat of the reflector 48 transferred to the heat equalizing member 45a is transmitted to the fixing belt 42 through the heat equalizing member 45a, and is used for melting the toner. As a result, compared to the case where the heat of the reflector 48 is exhausted to other members such as the fixing stay 44, the heat of the reflector 48 can be used more effectively, the lighting time of the heat source 43 can be shortened, and the power consumption It is possible to reduce the

Further, the pressure receiving portion 48b is located in a pressure region that receives the pressure of the pressure roller 41. Thereby, the adhesion between the heat equalizing member 45a and the pressure receiving part 48b is improved, the heat transferability can be improved, and the heat exhaust efficiency of the reflector 48 can be improved. Furthermore, since the heat equalizing member 45a and the reflector 48 are metal members with good thermal conductivity, the heat of the reflector 48 can be efficiently exhausted to the fixing belt 42.

Further, the pressure receiving portion 48b of this reflector 48 extends from one end side to the other end side of the fixing belt 42, and this pressure receiving portion 48b is in direct contact with the heat equalizing member 45a. Furthermore, the base material of the reflector itself is a metal body with high thermal conductivity such as aluminum. Therefore, like the heat equalizing member 45a, the pressure receiving part 48b is also capable of equalizing heat by absorbing heat from a place with a high temperature in the axial direction and moving it to a place with a low temperature in the axial direction to equalize the temperature in the axial direction. Has a function. Therefore, this pressure receiving portion 48b can have a function of assisting the temperature equalization member 45a in equalizing the temperature in the axial direction of the fixing belt 42.

Further, as shown in FIGS. 2 and 3, the bent portion of the heat equalizing member 45a and the fixing stay 44 are provided with a clearance and are not in contact with each other. Thereby, it is possible to prevent heat transfer to the bent portion of the soaking pad and the fixing stay, which is unnecessary from the viewpoint of effective use of heat.

With the above configuration, it is possible to obtain a fixing device that can prevent the temperature of the reflector 48 from rising, can effectively utilize the heat of the reflector 48, and can also suppress power consumption.

Further, as described above, the heat equalizing member 45a is coated with a coating having excellent sliding performance, and the friction coefficient of the surface of the pressure receiving portion 48b against the inner circumferential surface of the fixing belt 42 indicates that The coefficient of friction against As a result, compared to the case where the pressure receiving part 48b of the reflector 48 is brought into contact with the inner peripheral surface of the fixing belt 42 and the heat of the reflector 48 is exhausted to the fixing belt 42 without going through the heat equalizing member 45a, the fixing The sliding resistance of the belt can be reduced. Thereby, an increase in the torque for rotating the fixing belt 42 can be suppressed, and wear on the inner circumferential surface of the fixing belt 42 can also be suppressed.

Note that if the pressure receiving part 48b of the reflector 48 is coated with a coating having excellent sliding performance so that the pressure receiving part 48b is brought into contact with the inner circumferential surface of the fixing belt 42, the following problems are expected. Ru. That is, if the coating material with excellent sliding performance adheres to the reflective portion 48a of the reflector 48, the reflectance may decrease. Therefore, it is necessary to prevent the coating material having excellent sliding performance from adhering to the reflective part 48a by, for example, masking the reflective part 48a. When applying masking to the reflective part 48a, a process of applying masking, a process of peeling off the masking, a process of removing the masking adhesive adhering to the reflective part 48a, etc. are required. Furthermore, it would be difficult to perform these steps using a machine or the like, and even if it could be done, it would be costly.

On the other hand, as in the present embodiment, by transmitting the heat of the reflector 48 to the fixing belt 42 via the heat equalizing member 45a, the reflector 48 has good slidability on the inner circumferential surface of the fixing belt 42. There is no need to provide functions. As a result, it becomes necessary to apply a coating with excellent sliding performance to the pressure receiving portion 48b, and an increase in manufacturing difficulty and cost can be suppressed.

FIG. 5 is a schematic configuration diagram showing another configuration example of the fixing device.
The fixing device shown in FIG. 5 has a concave shape when viewed from the direction of the rotation axis of the fixing stay 44, and a heat source 43 is disposed in the concave portion of the fixing stay 44. Similarly to the embodiment, the reflective portion 48a of the reflector 48 is disposed between the fixing stay 44 and the heat source 43. A pressure receiving part 48b extends from the lower side of the reflecting part 48a in the figure and is sandwiched between the resin pad 45b and the heat equalizing member 45a.

In the fixing device shown in FIG. 5 as well, the heat of the reflector 48 can be exhausted to the fixing belt 42 via the heat equalizing member 45a, and the heat of the reflector 48 can be used for melting the toner.

Furthermore, in the above description, the heat equalizing member 45a is disposed between the pressure receiving portion 48b of the reflector 48 and the fixing belt 42, but a member disposed between the pressure receiving portion 48b and the fixing belt 42 Any material may be used as long as it has better sliding properties on the inner circumferential surface of the fixing belt 42 than the reflector. For example, although the heat dissipation property to the fixing belt 42 is inferior to that of the heat equalizing member 45a, the space between the pressure receiving part 48b and the fixing belt 42 is made of fibers such as PTFE impregnated with a lubricant such as silicone oil. A sliding sheet may be arranged as a sliding member. This sliding sheet is arranged, for example, so as to be wrapped around the resin pad 45b, and is fixed with screws or the like on the back side (fixing stay side) of the resin pad 45b.

The reflective part 48a of the reflector, which directly receives heat from the heat source, has a higher temperature than the pressure receiving part 48b, which discharges the heat of the reflector 48 to the heat equalizing member 45a, and there is a gap between the reflecting part 48a and the pressure receiving part 48b. A temperature difference occurs. This temperature difference causes a difference in thermal expansion in the axial direction between the reflecting portion 48a and the pressure receiving portion 48b, and there is a possibility that the reflector 48 may be abnormally deformed.

Therefore, in this embodiment, as shown in FIG. 6, a plurality of notches 48c are provided in the pressure receiving portion 48b along the rotational direction of the fixing belt.
In this way, by providing the notch 48c, the difference in the amount of thermal expansion in the axial direction between the pressure receiving part 48b and the reflecting part 48a is absorbed by the notch 48c of the pressure receiving part 48b expanding in the axial direction. can. Thereby, abnormal deformation of the reflector 48 can be suppressed.

Note that even if the notch 48c is provided in the reflective part 48a, the difference in the amount of thermal expansion in the axial direction between the pressure receiving part 48b and the reflective part 48a is reduced by narrowing the width of the notch in the reflective part 48a in the axial direction. Abnormal deformation of the reflector 48 can be suppressed. However, if the reflective portion 48a is provided with a notch, the radiant heat from the heat source 43 cannot be reflected at the notch, and there is a risk that the temperature of the part of the fixing belt 42 corresponding to the notch decreases. There is a possibility that heating may not be uniform in all directions. Therefore, it is possible to uniformly heat the fixing belt 42 in the axial direction while suppressing abnormal deformation of the reflector 48, so it is preferable to provide the notch 48c in the pressure receiving portion 48b.

Further, a notch 48c is provided in the pressure receiving portion 48b, and has a shape similar to that cut with a knife, and the gap in the axial direction opened by the notch 48c is narrow. Therefore, even if the notch 48c is provided, the pressure receiving portion 48b has a sufficient area at both axial ends and at the axial center. Therefore, even if both ends of the fixing belt 42 become hot during continuous printing of small-sized paper and the heat of the reflector 48 cannot be exhausted from both axial ends of the pressure receiving part 48b, the heat from the reflector 48 cannot be exhausted from the axial center of the pressure receiving part 48b. Can exhaust heat. As a result, even during continuous printing on small-sized paper, the temperature rise of the reflector 148 can be suppressed, and the aluminum or silver layer of the reflector 148 can be suppressed from discoloring.

Further, even when the pressure receiving portion 48b is provided with the notch 48c, the heat can be moved in the axial direction by bypassing the notch 48c, and the temperature in the axial direction of the fixing belt 42 of the heat equalizing member 45a can be averaged. Supporting functions can be maintained.

Further, the thickness of the reflector 48 is 0.3 to 1.2 mm, more preferably 0.5 to 0.7 mm. When the thickness of the reflector 48 exceeds 1.2 m, the amount of heat transferred in the axial direction at the pressure receiving portion decreases, and the function of assisting in equalizing the temperature of the fixing belt 42 in the axial direction described above decreases. There is a risk. On the other hand, when the thickness of the reflector 48 is less than 0.3 mm, the rigidity of the reflector decreases, and abnormal deformation due to the difference in thermal expansion between the reflecting part 48a and the pressure receiving part 48b is likely to occur, and the reflector 48 due to the notch 48c There is a possibility that abnormal deformation of the material cannot be suppressed.

Furthermore, as shown in FIG. 7, the notch 48c is preferably provided at a location corresponding to the edge in the width direction of a sheet of a predetermined size. In the example shown in FIG. 7, the notch 48c is provided at a position corresponding to the edge in the width direction of the paper of A6 portrait size and a position corresponding to the edge in the width direction of the paper of B4 portrait size. Note that this is just an example, and the paper size to which the notch 48c corresponds may be determined as appropriate based on the heat distribution characteristics of the two heat sources 43, etc.

In this embodiment, as described above, the pressure receiving part 48b and the heat equalizing member 45a remove heat from the high-temperature areas of the fixing belt 42 and transfer the removed heat to the low-temperature areas of the fixing belt 42. The temperature of the fixing belt 42 in the axial direction is made uniform. As a result, when small-sized paper is continuously fed, the heat in the non-sheet passing area on the end side of the fixing belt where heat is not absorbed by the paper is transferred to the center in the axial direction using the pressure receiving part 48b and the heat equalizing member 45a. The fixing belt 21 can be moved to the paper passing area, thereby suppressing abnormal high temperatures in the non-paper passing area of the fixing belt 21.

However, as the high temperature heat in the paper non-passing area is transferred to the paper passing area by the pressure receiving part 48b and the heat equalizing member 45a, the temperature near the end of the paper passing area of the fixing belt 42 becomes higher than the fixing temperature. turn into. As a result, hot offset (hereinafter referred to as edge hot offset) may occur in the image in the edge area of the paper.

FIG. 8(a) is a diagram showing heat transfer and the temperature distribution of the fixing belt 42 when there is no notch 48c, and FIG. 8(b) is a diagram showing the heat transfer when the notch 48c is not provided, and FIG. 8(b) is a diagram showing the heat transfer when the notch 48c is not provided, and FIG. 3 is a diagram showing heat transfer and temperature distribution of the fixing belt 42 in the case of FIG.
As shown in FIG. 8(a1), if there is no notch 48c near the edge in the width direction of the paper, the fixing belt 42 that has moved to the pressure receiving part 48b of the reflector 48 via the heat equalizing member 45a does not pass the paper. A part of the heat in the area moves to near the end of the paper passing area of the fixing belt 42 via the heat equalizing member 45a near the end of the paper passing area. As a result, as shown in FIG. 8(a2), the temperature near the end of the paper passing area of the fixing belt 42 becomes high, and end hot offset may occur.

On the other hand, when the notch 48c is provided in the pressure receiving part 48b, the heat of the fixing belt 42 that has moved to the pressure receiving part 48b via the heat equalizing member 45a is transferred to the notch 48c as shown in FIG. 8(b1). move in the axial direction, bypassing the Specifically, part of the heat in the non-paper passing region of the fixing belt 42 that has been transferred to the pressure receiving portion 48b of the reflector 48 via the heat equalizing member 45a is transferred to the notch 48c, where it is transferred in the paper conveyance direction. Moving. The heat that has moved to the notch 48c moves to the connection portion that connects the reflecting portion 48a and the pressure receiving portion 48b of the reflector 48, and after going around the notch 48c, moves to the pressure receiving portion 48b again. A part of the heat that has moved to the pressure receiving part 48b returns to the fixing belt 42 via the heat equalizing member 45a. In this way, the heat that bypasses the notch 48c provided near the edge in the width direction of the paper is returned to the fixing belt 42 via the heat equalizing member 45a at a position X mm inside from the end of the paper passing area of the fixing belt 42. . In this way, a part of the heat at the axial end of the fixing belt 42 that has moved to the pressure receiving part 48b via the heat equalizing member 45a bypasses the notch 48c, thereby increasing the paper passing area of the fixing belt 42. Move inward by Xmm from the end. Therefore, it is possible to reduce the heat in the non-sheet passing area that is returned to the vicinity of the end of the sheet passing area of the fixing belt 42 via the pressure receiving part 48b, and as shown in FIG. 8(b2), the fixing belt It is possible to suppress the temperature rise near the end of the paper passing area 42. In this way, by providing the notches 48c according to the size of the sheet in the width direction, edge hot offset can be suppressed.

Note that the pressure receiving portion 48b of the reflector 48 may be brought into direct contact with the inner circumferential surface of the fixing belt 42, although this may increase manufacturing costs.

What has been described above is just an example, and each of the following aspects has its own unique effects.
(Aspect 1)
A fixing member such as a rotating fixing belt 42, a pressure member such as a pressure roller 41 that presses a recording material passing through a nip portion formed by contacting the outer peripheral surface of the fixing member, and a pressure member disposed inside the fixing member. The fixing device includes a heat source 43 and a reflecting portion 48a disposed inside the fixing member to reflect radiant heat emitted from the heat source 43 toward the inner circumferential surface of the fixing member; The pressure receiving part 48b that receives pressure via the fixing member has a reflecting member such as a reflector 48 that is integrated with or thermally connected to the pressure receiving part 48b, and the pressure receiving part 48b extends from one end side of the fixing member to the other end side. A notch 48c is provided in the pressure receiving portion 48b.
In the device example (hereinafter referred to as conventional example 1) in which the pressure receiving portion of each reflecting member extends from one end side to the other end side of the fixing member described in Patent Document 1, the reflecting member There is a risk of abnormal deformation. In other words, the temperature of the reflecting part that directly receives heat from the heat source is higher than that of the pressure receiving part, which dissipates heat from the reflecting member to the fixing member in the contact area, and there is a temperature difference between the reflecting part and the pressure receiving part. occurs. This temperature difference causes a difference in thermal expansion in the axial direction between the reflecting part and the pressure receiving part, which may cause abnormal deformation of the reflecting member.
On the other hand, the pressure receiving part of the first reflecting member described in Patent Document 1 is located at the center in the axial direction, and the pressure receiving part of the second reflecting member is provided at both ends in the axial direction (hereinafter, conventional Regarding Example 2), at least for the second reflecting member, the axial distance between the pressure receiving part on one axial end side and the pressure receiving part on the other end side is increased, so that the reflecting part and the pressure receiving part It is thought that the difference in the amount of thermal expansion in the axial direction between the two can be absorbed and abnormal deformation of the reflective member can be suppressed. However, in this conventional example 2, the following problem may occur due to the absence of a pressure receiving portion at the axial center of the second reflecting member.
In other words, when passing a recording material whose length in the axial direction is slightly longer than the heat generating area of the first heat source that has a heat generating area in the center, the length of the recording material that is slightly longer in the axial direction than the heat generating area of the first heat source and the second heat source that has heat generating areas on both sides in the axial direction. Both are turned on to perform the fixing process. In this case, most of the heated area of the fixing member heated by the second heat source becomes a non-sheet passing area. In the non-sheet passing area, heat is not absorbed by the recording material passing through the nip portion. Therefore, when recording material whose length in the axial direction is slightly longer than the heat generating area of the first heating source is continuously passed through, the end of the fixing member becomes high temperature, and the temperature of the end of the fixing member increases due to the pressure applied by the second reflective member. The temperature may become higher than that of the receiving part. When the temperature of the end of the fixing member becomes higher than the temperature of the pressure receiving part of the second reflecting member, the heat absorbed by the reflecting part of the second reflecting member is transferred to the fixing member via the pressure receiving part (hereinafter referred to as heat transfer). (This is referred to as exhaust heat.) Not only is this not possible, but on the contrary, heat is transferred from the fixing member to the pressure receiving portion of the second reflective member. As a result, the second reflective member becomes abnormally high in temperature, which may cause discoloration of the second reflective member, resulting in a decrease in reflectance.
In aspect 1, a notch is provided in the pressure receiving portion provided from one end side to the other end side of the fixing member. In this way, since the pressure receiving part is provided with a notch, the difference in thermal expansion in the axial direction between the reflecting part and the pressure receiving part can be absorbed by the widening of the notch, which prevents abnormal deformation of the reflecting member. It can be suppressed.
Further, in the first embodiment, the pressure receiving portion is provided from one end side to the other end of the fixing member, and the reflecting member also has a pressure receiving portion at the center in the axial direction. As a result, even if the temperature at both ends of the fixing member becomes higher than the temperature at both ends of the pressure receiving part and the heat absorbed by the reflecting part cannot be exhausted through both ends of the pressure receiving part, this heat can be dissipated. Heat can be exhausted through the axial center of the pressure receiving part. Moreover, when the temperature at both ends of the fixing member becomes higher than the temperature at both ends of the pressure receiving part, the heat that moves from both ends of the fixing member to both ends of the pressure receiving part also bypasses the notch and is transferred to the pressure receiving part. Heat can be exhausted through the axial center of the section. Specifically, the heat that has moved from both ends of the fixing member to both ends of the pressure receiving section moves from both ends of the pressure receiving section to the connection section that connects the reflecting section and the pressure receiving section of the reflecting member. After moving toward the center in the axial direction at this connecting portion, the heat is moved to the center in the axial direction of the pressure receiving portion, and heat is exhausted to the fixing member via the center in the axial direction of the pressure receiving portion. As can be seen from these, in aspect 1, the fixing member has the pressure receiving part at the center in the axial direction, unlike the second reflecting member of the conventional example 2, which does not have the pressure receiving part in the center in the axial direction. Even if both ends of the fixing member become high in temperature, the heat of the reflecting member can be efficiently exhausted to the fixing member, and abnormal high temperatures of the reflecting member can be suppressed. Furthermore, as described above, by discharging the heat that has moved from both ends of the fixing member to both ends of the pressure receiving part through the axial center of the pressure receiving part, the temperature in the axial direction of the fixing member can be reduced. Uniform heating can also be achieved.

(Aspect 2)
In the first aspect, the notch 48c is provided along the rotational direction of the fixing member such as the fixing belt 42.
According to this, the difference in the amount of thermal expansion in the axial direction between the pressure receiving part 48b and the reflecting part 48a can be satisfactorily absorbed by the notch 48c.

(Aspect 3)
In embodiment 1 or 2, the notch 48c is provided at a position corresponding to the size of the recording material such as paper P.
According to this, as described in the embodiment, the heat that has moved from both ends of the fixing member such as the fixing belt 42 to both ends of the pressure receiving part 48b bypasses the notch 48c, thereby allowing the sheet to pass through the fixing member. Heat can be exhausted to the fixing member closer to the center in the axial direction than the end portions of the region. Thereby, it is possible to suppress the temperature rise at the end of the paper passing area of the fixing member, and it is possible to suppress the occurrence of edge hot offset.

(Aspect 4)
In any one of aspects 1 to 3, the thickness of the reflective member such as the reflector 48 is 0.3 mm or more and 1.2 mm or less.
According to this, as described in the embodiment, a decrease in the amount of movement of heat in the axial direction in the pressure receiving part 48b is suppressed, and the difference in the amount of thermal expansion between the pressure receiving part 48b and the reflecting part 48a is suppressed. It is possible to suppress abnormal deformation due to

(Aspect 5)
In aspect 4, the thickness of the reflective member such as the reflector 48 is 0.5 mm or more and 0.7 mm or less.
According to this, it is possible to further suppress a decrease in the amount of heat movement in the axial direction in the pressure receiving part 48b, and to prevent abnormal deformation due to the difference in thermal expansion between the pressure receiving part 48b and the reflecting part 48a. Can be suppressed.

(Aspect 6)
In an image forming apparatus including an image forming section that forms an image on a recording material and a fixing device that fixes the image formed on the recording material to the recording material, the fixing device according to any one of Aspects 1 to 5 is used as the fixing device. Using.
According to this, it is possible to prevent the temperature of the reflective member such as the reflector 48 from rising, while effectively utilizing unnecessary heat, thereby suppressing power consumption and suppressing abnormal deformation of the reflective member.

1: Image forming device 40: Fixing device 41: Pressure roller 42: Fixing belt 43: Heat source 44: Fixing stay 45: Nip forming member 45a: Heat equalizing member 45b: Resin pad 48: Reflector 48a: Reflector 48b: Pressure Receiving part 48c: Notch P: Paper

JP 2017-11129 Publication

Claims (6)

a rotating fixing member;
a pressure member that presses a recording material passing through a nip formed in contact with an outer peripheral surface of the fixing member;
A fixing device comprising: a heat source disposed inside the fixing member;
A reflecting portion that reflects radiant heat emitted from the heat source toward the inner circumferential surface of the fixing member and a pressure receiving portion that receives the pressing force of the pressure member via the fixing member are integrated or thermally a reflective member connected to the
The fixing device is characterized in that the pressure receiving portion extends from one end of the fixing member to the other end, and a notch is provided in the pressure receiving portion. The fixing device according to claim 1,
The fixing device is characterized in that the cut is provided along the rotational direction of the fixing member. The fixing device according to claim 1,
A fixing device characterized in that the notch is provided at a position corresponding to the size of the recording material. The fixing device according to claim 1,
A fixing device characterized in that the thickness of the reflective member is 0.3 mm or more and 1.2 mm or less. The fixing device according to claim 4,
A fixing device characterized in that the thickness of the reflective member is 0.5 mm or more and 0.7 mm or less. an image forming unit that forms an image on a recording material;
An image forming apparatus including a fixing device that fixes an image formed on the recording material to the recording material,
An image forming apparatus characterized in that the fixing device according to claim 1 is used as the fixing device.

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