JP2020086350A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device capable of effectively suppressing the end temperature rise of a fixing member by a high soaking property and to provide an image forming apparatus.SOLUTION: The fixing device includes an annular fixing belt 60, a nip forming member 45 which is arranged inside the fixing belt 60, a pressure roller 80 which is arranged to face the nip forming member 45 across the fixing belt 60 outside the fixing belt 60, and a halogen heater 90 which is arranged in a position away from the nip forming member 45 inside the fixing belt 60 and heats the inner peripheral surface 65 of the fixing belt 60. The nip forming member 45 includes a heat pipe 50 to which heat is transmitted from the inner peripheral surface 65 of the fixing belt 60 and a coating layer 56 which is formed between the heat pipe 50 and the inner peripheral surface 65 of the fixing belt 60 and made of a slide material.SELECTED DRAWING: Figure 2

Description

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

Conventionally, in a fixing device, when a recording material having a width narrower than the heating width of a heating element passes, it is known that the temperature of the fixing member rises in a range where the recording material does not pass, that is, a so-called edge temperature rise occurs. Has been.

Patent Document 1 is related to a technique for suppressing the rise in the end temperature. Patent Document 1 describes a heating means in which a heating element is printed on a substrate made of a plate-shaped heat pipe via an insulating layer, and the outermost surface is coated with the insulating layer.

As a method of suppressing the end temperature rise, it is conceivable to increase the thermal conductivity of the nip forming member that contacts the inside of the fixing member. However, if the area of the cross-sectional shape of the nip forming member is increased in order to improve the thermal conductivity, the volume is increased and the heat capacity is increased. Since the nip forming member is in contact with the fixing member, an increase in heat capacity leads to a longer warm-up time and a reduction in energy saving. Further, a sliding sheet is generally arranged between the fixing member and the nip forming member in order to ensure slidability, and this sliding sheet also transfers heat from the fixing member to the nip forming member. Was an obstacle to In this regard, in Patent Document 1, although a heat pipe having a low heat capacity is used, the heat pipe and the heating element are integrated. Therefore, the heat pipe is directly affected by the heating of the heating element, and there is room for improvement in that the soaking is effectively performed when the end temperature rises.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device and an image forming apparatus capable of effectively suppressing an end temperature rise of a fixing member due to high soaking property.

The present invention provides an annular fixing member, a nip forming member arranged inside the fixing member, and a pressure member arranged outside the fixing member so as to face the nip forming member with the fixing member interposed therebetween. A heating element disposed inside the fixing member and spaced apart from the nip forming member to heat the inner peripheral surface of the fixing member; and the nip forming member heats the inner peripheral surface of the fixing member. And a coating layer of a sliding material formed between the heat pipe and the inner peripheral surface of the fixing member.

According to the fixing device and the image forming apparatus of the present invention, it is possible to effectively suppress the temperature rise at the end portion of the fixing member due to the high heat uniformity.

FIG. 1 is a diagram illustrating an image forming apparatus including a fixing device according to an exemplary embodiment of the present invention. FIG. 3 is a diagram showing a fixing device of the present embodiment. It is a cross-sectional perspective view showing a heat pipe of the fixing device of the present embodiment. FIG. 4 is a schematic diagram showing a coating layer formed on the nip surface of the heat pipe of the fixing device of the present embodiment. It is a schematic diagram explaining the length of the hydraulic fluid space of the heat pipe of the fixing device of the present embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an electrophotographic laser printer 1 as an example of an image forming apparatus including a fixing device 10 according to an embodiment of the present invention. First, the overall configuration of the printer 1 will be described.

The printer 1 according to the present embodiment includes a sheet feeding unit 2 that accommodates a transfer sheet S as an example of a recording material, an image forming unit 3 that forms an image on the transfer sheet S supplied from the sheet feeding unit 2, and a transfer sheet. A fixing device 10 for fixing the image formed on S, and a paper discharge unit 4 for discharging the transfer paper S on which the image is fixed by the fixing device 10 are provided.

The sheet feeding unit 2 is a sheet feeding cassette that can store the transfer sheets S in a stacked manner. A paper feed roller 21 that sends the transfer paper S to the downstream side in the carrying direction is arranged in the paper feed unit 2. The transfer sheets S stored in the sheet feeding unit 2 are separated one by one by the rotation operation of the sheet feeding roller 21. The separated transfer paper S is sent to the image forming unit 3 at a predetermined timing by the registration roller pair 22 arranged on the downstream side of the paper feed roller 21 in the carrying direction.

The image forming unit 3 includes a plurality of image forming devices 30Y, 30M, 30C and 30K, a plurality of toner bottles 40Y, 40M, 40C and 40K, an optical writing unit 31, and a transfer unit 32.

The image forming devices 30Y, 30M, 30C and 30K and the toner bottles 40Y, 40M, 40C and 40K correspond to yellow, magenta, cyan and black which are toner colors forming a toner image. In FIG. 1, Y in the reference numeral corresponds to yellow, M to magenta, C to cyan, and K to black.

The image forming devices 30Y, 30M, 30C, and 30K have the same configuration except that the toner colors are different. Hereinafter, each component of the image forming apparatus 30 will be described by omitting the reference numerals indicating the toner colors in FIG. The image forming apparatus 30 according to the present embodiment includes a photosensitive drum 41 as an example of a latent image carrier, a charging device 42 that charges the surface of the photosensitive drum 41, and a toner supplied to the toner bottle 40 to the photosensitive drum. A developing device 43 that supplies the photosensitive drum 41 and a cleaning device 44 that cleans the photosensitive drum 41 are provided.

The optical writing unit 31 is a latent image forming unit including optical components such as a semiconductor laser as a light source, various lenses and mirrors. The optical writing unit 31 performs scanning exposure based on image information acquired from the outside by communication or the like.

The transfer unit 32 includes an endless transfer belt 33, a plurality of primary transfer rollers 35Y, 35M, 35C, 35K arranged inside the transfer belt 33, a tension roller 37 and a secondary transfer backup roller 38, and a transfer belt 33. The intermediate transfer cleaning device 39 and the secondary transfer roller 23, which are arranged outside the device, are provided. The primary transfer rollers 35Y, 35M, 35C, and 35K are arranged to face the photoconductor drums 41Y, 41M, 41C, and 41K with the transfer belt 33 interposed therebetween. The secondary transfer backup roller 38 is arranged to face the secondary transfer roller 23 via the transfer belt 33.

When the image formation is started, the photosensitive drum 41 rotates. The surface of the photosensitive drum 41 is uniformly charged by the charging device 42. The scanning exposure of the optical writing unit 31 forms an electrostatic latent image on the surface of the photoconductor drum 41. Toner as a developer is supplied from the developing device 43 to the electrostatic latent image formed on the surface of the photoconductor drum 41 to form a toner image as a visible image.

The toner image formed on the surface of the photosensitive drum 41 is primarily transferred to the transfer belt 33. The toner images of the photosensitive drums 41 of the respective colors are transferred onto the transfer belt 33 in an overlapping manner by the primary transfer nip formed by the photosensitive drum 41 and the primary transfer roller 35 via the transfer belt 33. The toner remaining on the surface of the photoconductor drum 41 is removed by the cleaning device 44, and the residual charge on the photoconductor drum 41 is removed by a charge eliminating lamp as a charge eliminating unit.

The registration roller pair 22 rotates at the timing when the transfer paper S is superposed on the toner image transferred onto the surface of the transfer belt 33. By the rotation of the registration roller pair 22, the transfer paper S is sent to the secondary transfer nip formed by the secondary transfer backup roller 38 and the secondary transfer roller 23 via the transfer belt 33. The transfer paper S to which the toner image is transferred at the secondary transfer nip is mechanically separated from the transfer belt 33 and then sent to the fixing device 10. The toner remaining on the surface of the transfer belt 33 after passing through the primary transfer nip is removed by the intermediate transfer cleaning device 39. The configuration of the image forming unit 3 can be changed as appropriate. For example, a charging unit having a different configuration from the charging device 42 or a latent image forming unit having a different configuration from the optical writing unit 31 may be used.

Next, the fixing device 10 of this embodiment will be described. FIG. 2 is a diagram showing the fixing device 10 of this embodiment. As shown in FIG. 2, the fixing device 10 includes a fixing belt 60 as a fixing member, a pressure roller 80 as a pressure member, a flange 61 as a holding member, and a stay disposed inside the fixing belt 60. A member 62, a plurality of halogen heaters 90 as heating elements, a reflecting member 70, and a nip forming member 45 are provided.

The fixing belt 60 is a flexible endless rotating body or cylinder. The fixing belt 60 of this embodiment includes a cylindrical base material having a hollow portion, an elastic layer coated on the surface of the base material, and a release layer formed on the surface layer of the elastic layer. The base material is made of a metal such as nickel, SUS (stainless steel) or aluminum, or a heat resistant resin such as PI (polyimide). The elastic layer is made of silicon rubber. The elastic layer made of silicone rubber deforms when the toner image formed on the transfer paper S is pressed, and absorbs minute unevenness on the surface, so that the formation of an image such as orange peel can be prevented. The thickness of the elastic layer made of silicone rubber is preferably 100 μm or more. The release layer is made of a fluorine-based resin such as PFA (tetrafluoroethylene/perfluoroalkyl vinyl ether copolymerization) or PTFE (polytetrafluoroethylene). The configuration of the fixing belt 60 can be changed as appropriate. For example, in the fixing belt 60, the elastic layer may be omitted or the cross-sectional shape may be formed in a polygonal shape other than a circular shape from the viewpoint of reducing the heat capacity.

The pressure roller 80 is arranged to face the outer peripheral surface of the fixing belt 60. The pressure roller 80 is rotated by a driving force transmitted from a driving source such as a motor and a transmission member (not shown) such as a gear. The pressure roller 80 is biased toward the fixing belt 60 by a biasing member (not shown) such as a spring. The pressure roller 80 of this embodiment includes a cylindrical base material having a hollow portion, an elastic layer coated on the surface of the base material, and a release layer formed on the surface layer of the elastic layer. The base material is made of metal such as nickel, SUS (stainless steel), and aluminum. The elastic layer is made of silicon rubber. The release layer is made of a fluorine-based resin such as PFA or PTFE. The configuration of the pressure roller 80 can be changed as appropriate. For example, the pressure roller 80 may be solid without a hollow portion. Further, a heat source such as a halogen heater may be arranged inside the pressure roller. The elastic layer 82 of the pressure roller 80 may be made of a material other than solid rubber such as silicon rubber. For example, sponge rubber having a high heat insulating property may be used in a configuration in which the pressure roller does not have a heat source. The heat transfer from the fixing belt 60 to the pressure roller 80 can be suppressed by using the sponge rubber having a high heat insulating property.

The flange 61 is a holding member that holds the fixing belt 60, the stay member 62, the nip forming member 45, the halogen heater 90, and the reflecting member 70. The flange 61 is fixed to the housing side of the printer 1 and holds both ends of the stay member 62 inside the apparatus.

The stay member 62 supports the nip forming member 45 inside the fixing belt 60. The pressing force applied by the pressure roller 80 is received by the stay member 62 via the fixing belt 60 and the nip forming member 45.

The plurality of halogen heaters 90 are heating elements that heat the inner peripheral surface 65 of the fixing belt 60. The halogen heater 90 is a component independent of the stay member 62 and the nip forming member 45. In this embodiment, two halogen heaters 90 are arranged. In addition to the halogen heater 90, an IH coil, a resistance heating element, a carbon heater, or the like may be used as the heating element.

The reflecting member 70 reflects the radiant heat of the halogen heater 90 to the inner peripheral surface 65 of the fixing belt 60. The reflecting member 70 is composed of a base material made of aluminum or the like, a mirror surface portion made of silver paste or the like applied to the surface of the base material, an antioxidant layer located on the outermost surface formed on the surface of the mirror surface portion, and the like.

The reflection member 70 is formed inside the fixing belt 60 so as to block the space between the stay member 62 and the halogen heater 90. The radiant heat applied to the stay member 62 side of the halogen heater 90 is reflected on the inner peripheral surface 65 of the fixing belt 60 by the reflecting member 70 without directly reaching the stay member 62. Accordingly, the stay member 62 is prevented from being heated, and the halogen heater 90 can efficiently heat the fixing belt 60.

The nip forming member 45 is arranged inside the fixing belt 60 so as to face the pressure roller 80 with the fixing belt 60 interposed therebetween. The nip forming member 45 is an assembly body based on the heat pipe 50. In the present embodiment, the nip forming member 45 is configured by combining the heat pipe 50 and the connecting component 46 and the like with the stay member 62 formed of resin or metal.

FIG. 3 is a sectional perspective view showing the heat pipe 50 of the fixing device 10 of the present embodiment. As shown in FIG. 3, the heat pipe 50 is elongated in the axial direction (longitudinal direction) of the fixing belt 60 and is made of a material having a high thermal conductivity, such as aluminum or copper. The axial direction of the fixing belt 60 indicates a direction parallel to the rotation axis of the fixing belt 60. Although the heat pipe 50 is preferably made of copper from the viewpoints of cost, workability, and strength, other materials such as silver and graphite may be used.

The heat pipe 50 has a nip surface 51 that contacts the inner peripheral surface 65 of the fixing belt 60. The ends 52 on both sides of the heat pipe 50 are bent toward the stay member 62, and the cross section of the heat pipe 50 is substantially U-shaped. The nip surface 51 is formed in a flat shape or a concave shape. From the viewpoint of suppressing the occurrence of jams, it is preferable to form the nip surface 51 in a concave shape that improves the separability because the discharge direction of the transfer sheet S is the pressure roller 80, but the shape is not limited thereto. It does not mean that The shape of the nip surface 51 is not limited to a flat surface or a concave surface, and can be changed as appropriate.

Inside the heat pipe 50, a working liquid space 53 in which the working liquid 55 is enclosed is formed. The working fluid space 53 is a space extending in the axial direction of the fixing belt 60, and water is filled as the working fluid 55. The hydraulic fluid space 53 of the present embodiment has a substantially U-shaped space that extends in the axial direction according to the shape of the heat pipe 50, but is not limited to this shape. The hydraulic fluid space 53 may be formed as a rectangular parallelepiped space. The hydraulic fluid 55 may be other than water.

FIG. 4 is a schematic view showing the coating layer 56 formed on the nip surface 51 of the heat pipe 50 of the fixing device of this embodiment. As shown in FIG. 4, a thin film coating layer 56 is formed on the nip surface 51 by coating the sliding material 57. As the sliding material 57 that forms the coating layer 56, for example, a resin material containing PTFE is preferable.

The coating layer 56 is formed on almost the entire area of the nip surface 51. The nip surface 51 on which the coating layer 56 is formed serves as a contact portion that contacts the inner peripheral surface 65 of the fixing belt 60. The range of the coating layer 56 is not limited to the nip surface 51. The range of the coating layer 56 may extend from the nip surface 51 of the heat pipe 50 to the end portion 52. Further, in the range of the coating layer 56, there may be a part where the coating layer is not formed.

The length of the hydraulic fluid space 53 of the heat pipe 50 will be described. FIG. 5 is a schematic diagram illustrating the length of the hydraulic fluid space 53 of the heat pipe 50 of the fixing device 10 of the present embodiment. The transfer paper S shown in FIG. 5 is the transfer paper S having the longest width b in the direction orthogonal to the transport direction among the transfer papers S set in the paper supply unit 2 of the printer 1.

The distance a in the longitudinal direction of the working fluid space 53 of the heat pipe 50 is formed to be longer than the width b of the transfer sheet S having the largest width in the direction orthogonal to the transport direction set in the printer 1.

Next, the fixing process of the fixing device 10 will be described. The pressure roller 80 is rotated by a driving source (not shown), and when the driving force is transmitted to the fixing belt 60 which is pressed by the pressure roller 80, the fixing belt 60 is rotated. At this time, the portion of the heat pipe 50 of the nip forming member 45 that contacts the inner peripheral surface 65 of the fixing belt 60 is the nip surface 51 on which the coating layer 56 is formed, so the fixing belt 60 rotates smoothly.

The heat of the portion of the fixing belt 60 that is nipped by the nip forming member 45 and the pressure roller 80 is equalized by the heat pipe 50 that extends in the axial direction, and the temperature distribution in the axial direction of the fixing belt 60 is made uniform. Therefore, even if the size of the transfer sheet S is small and the transfer sheet S does not contact the end portion of the fixing belt 60, the heat of the fixing belt 60 is uniformized by the heat pipe 50, and the end portion of the fixing belt 60 is It is possible to effectively suppress the occurrence of temperature rise in the end portion due to overheating.

When the transfer sheet S on which the toner image is formed in the image forming section 3 reaches the fixing device 10 as described above, the toner image is transferred by being pressed and heated by the fixing belt 60, the nip forming member 45 and the pressure roller 80. It is fixed on the paper S. The transfer sheet S, which has passed through the fixing device 10 and has the toner image fixed thereon, is ejected to the sheet ejecting section 4 by the sheet ejecting roller pair 24. The paper discharge unit 4 is a paper discharge tray on which the transfer paper S can be temporarily placed. The toner image formed on the transfer sheet S is fixed by heating and pressing.

As described above, the fixing device 10 includes the annular fixing belt 60, the nip forming member 45 arranged inside the fixing belt 60, and the nip forming member 45 sandwiching the fixing belt 60 outside the fixing belt 60. The pressure roller 80 is disposed to face each other, and the halogen heater 90 is disposed inside the fixing belt 60 at a position separated from the nip forming member 45 and heats the inner peripheral surface 65 of the fixing belt 60. The nip forming member 45 includes the heat pipe 50 to which heat is transferred from the inner peripheral surface 65 of the fixing belt 60, and the sliding member 57 formed between the heat pipe 50 and the inner peripheral surface 65 of the fixing belt 60. And a coating layer 56.

As a result, the heat pipe 50 has several times better thermal conductivity than when a coating layer is formed on a plate-shaped metal member made of the same material (for example, pure aluminum or pure copper). The heat transferred from the belt 60 can be effectively equalized. In addition, since the heat pipe 50 has a low heat capacity, it has an advantageous effect in terms of warm-up time and energy saving. Further, since the halogen heater 90 heats the inner peripheral surface of the fixing belt 60 and is arranged apart from the nip forming member 45, it moves from the fixing belt 60 regardless of the heating range of the halogen heater 90. The heat can be effectively soaked by the heat pipe 50. As a result, even if the edge temperature rises during continuous sheet feeding, heat unevenness can be transferred from the fixing belt 60 to the heat pipe 50, and uniform heat distribution can be performed quickly. Furthermore, since there is no air layer between the heat pipe 50 and the coating layer 56 that can be formed with a thickness of several tens of μm, the slidability can be ensured, so compared to the case where a sliding sheet with a thickness of several hundreds μm is used. The heat transfer from the fixing belt 60 to the heat pipe 50 can be dramatically improved. That is, the fixing device 10 of the present embodiment can realize both low friction due to the coating layer 56 and high soaking effect in the axial direction due to the heat pipe 50 without incurring a large cost.

Further, the heat pipe 50 of the present embodiment has a planar nip surface 51 that contacts the inner peripheral surface 65 of the fixing belt 60. As a result, a large contact area between the fixing belt 60 and the heat pipe 50 can be secured, heat can be efficiently transferred, and a higher soaking effect can be realized.

Further, the coating layer 56 of the present embodiment is formed on the surface of the heat pipe 50 on the nip surface 51 side. As a result, the coating layer 56 formed on the nip surface 51 in contact with the fixing belt 60 can realize slidability and thermal uniformity at a higher level.

Further, the heat pipe 50 of the present embodiment has a working fluid space 53 for enclosing the working fluid 55. The length a of the hydraulic fluid space 53 in the direction orthogonal to the transporting direction of the transfer sheet S is set to be equal to or larger than the maximum width b of the transported transfer sheet S. As a result, the uniform heating effect can be effectively exerted on the transfer sheets S of all sizes conveyed to the fixing device 10, so that the temperature rise at the end portion of the fixing belt 60 can be suppressed more reliably.

Further, the sliding material of the present embodiment is PAI or PI resin containing PTFE. Thereby, higher thermal uniformity and slidability can both be achieved.

Further, the fixing device 10 of the exemplary embodiment further includes a reflecting member 70 that is disposed inside the fixing belt 60 between the halogen heater 90 and the nip forming member 45 and that reflects the radiant heat of the halogen heater 90. Thereby, the radiant heat of the halogen heater 90 is reflected by the reflecting member 70 to the fixing belt 60 without being applied to the heat pipe 50 of the nip forming member 45. The influence of the heating range of the halogen heater 90 of the heat pipe 50 is further suppressed, and the rise in the end temperature can be prevented more reliably.

With the printer 1 including the fixing device 10 of the present embodiment, the warm-up time can be shortened and the energy can be saved with an inexpensive structure, and the temperature rise of the end portion of the fixing belt 60 during continuous sheet feeding can be effectively suppressed.

Each configuration of the fixing device 10 described above is an example, and the configuration can be appropriately changed according to circumstances. For example, at both ends of the fixing belt 60, according to the size of the transfer sheet S, a shielding member movable between a shielding position for shielding between the halogen heater 90 and the fixing belt 60 and a standby position for releasing the shielding is further arranged. You may. The shielding member is made of aluminum, iron, stainless steel or the like having high heat resistance. The shielding member can control the heating range of the fixing belt 60 by the halogen heater 90 according to the size of the transfer sheet S. By combining such a shielding member, the temperature rise at the end can be further suppressed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and modifications, and can be appropriately modified.

1 Printer (image forming device)
10 Fixing Device 45 Nip Forming Member 50 Heat Pipe 56 Coating Layer 57 Sliding Material 60 Fixing Belt (Fixing Member)
80 Pressure roller (pressure member)
90 Halogen heater (heating element)
S transfer paper (recording material)

JP, 2013-142834, A

Claims (7)

An annular fixing member,
A nip forming member arranged inside the fixing member,
A pressure member that is arranged outside the fixing member and faces the nip forming member with the fixing member interposed therebetween;
A heating element disposed inside the fixing member at a position separated from the nip forming member, for heating the inner peripheral surface of the fixing member;
Equipped with
The nip forming member is
A heat pipe to which heat is transferred from the inner peripheral surface of the fixing member;
A fixing device having a coating layer of a sliding material formed between the heat pipe and the inner peripheral surface of the fixing member.
The fixing device according to claim 1, wherein the heat pipe has a planar nip surface that contacts an inner peripheral surface of the fixing member.
The fixing device according to claim 2, wherein the coating layer is formed on a surface of the heat pipe on the nip surface side.
The heat pipe has a working fluid space for enclosing the working fluid,
The fixing device according to claim 1, wherein a length of the working fluid space in a direction orthogonal to a transport direction of the recording material is set to a length equal to or larger than a maximum width of the transported recording material.
The fixing device according to claim 1, wherein the sliding member is PAI or PI resin containing PTFE.
The fixing device according to claim 1, further comprising a reflecting member that is disposed inside the fixing member between the heating element and the nip forming member and that reflects radiant heat of the heating element.
An image forming apparatus comprising the fixing device according to claim 1.

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