JP7253134B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to fixing devices and image forming apparatuses.

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

Japanese Patent Application Laid-Open No. 2002-300000 describes a technique for suppressing the temperature rise at the end portion. 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 an insulating layer.

As a method for suppressing the temperature rise at the end portion, it is conceivable to increase the thermal conductivity of the nip forming member that contacts the inner side of the fixing member. However, if the cross-sectional area of the nip forming member is increased in order to improve the thermal conductivity, the volume increases, leading to an increase in heat capacity. Since the nip forming member is in contact with the fixing member, an increase in heat capacity lengthens the warm-up time and causes a decrease in energy saving. A sliding sheet is generally placed between the fixing member and the nip forming member to ensure slidability. This sliding sheet also contributes to heat transfer from the fixing member to the nip forming member. was a hindrance to In this regard, in Patent Document 1, although a heat pipe with 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 terms of effectively equalizing the temperature when the end temperature rises.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus capable of effectively suppressing an increase in temperature at the end of a fixing member by high uniformity of heat.

The present invention comprises an annular fixing member, a nip forming member arranged inside the fixing member, and a pressing member arranged outside the fixing member so as to face the nip forming member with the fixing member interposed therebetween; a heating element arranged inside the fixing member at a position spaced from the nip forming member to heat an inner peripheral surface of the fixing member; and arranged between the heating element and the nip forming member inside the fixing member. and a reflecting member that reflects the radiant heat of the heating element, the nip forming member has a heat pipe to which heat is transferred from the inner peripheral surface of the fixing member, and the heat pipe rotates. The fixing member has a nip surface that slides relative to the inner peripheral surface of the fixing member, and a working fluid space that encloses the working fluid , the nip surface being formed of a coating layer of a sliding material. The heat pipe is formed to have a U-shaped cross section by bending both upstream and downstream end portions of the heat pipe in the rotation direction of the fixing member in the direction opposite to the pressure member side. The liquid space relates to a fixing device having a U-shaped cross section corresponding to the shape of the heat pipe .

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 uniformity of heat.

1 is a diagram showing an image forming apparatus equipped with a fixing device according to an embodiment of the invention; FIG. 2 is a diagram showing a fixing device according to the embodiment; FIG. 2 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; FIG. 4 is a schematic diagram illustrating the length of the working fluid space of the heat pipe of the fixing device of the present embodiment; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION 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 equipped with a fixing device 10 according to one embodiment of the present invention. First, the overall configuration of the printer 1 will be described.

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

The paper feed unit 2 is a paper feed cassette capable of storing the transfer paper S in layers. A paper feed roller 21 is arranged in the paper feed unit 2 to feed the transfer paper S downstream in the transport direction. The transfer paper S accommodated in the paper feed section 2 is separated one by one by the rotation operation of the paper feed roller 21 . The separated transfer paper S is sent to the image forming section 3 at a predetermined timing by a pair of registration rollers 22 arranged downstream of the paper feed roller 21 in the conveying direction.

The image forming section 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, 30K and the toner bottles 40Y, 40M, 40C, 40K correspond to yellow, magenta, cyan, and black, which are toner colors for forming toner images. In FIG. 1, Y in the symbols indicates that it 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 configuration of the image forming apparatus 30 will be described while omitting the reference numerals indicating the toner colors in FIG. The image forming device 30 of 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 on the photosensitive drum. 41 and a cleaning device 44 for cleaning the photosensitive drum 41 .

The optical writing unit 31 is a latent image forming section composed of 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 by communication or the like from the outside.

The transfer unit 32 includes an endless transfer belt 33 , a plurality of primary transfer rollers 35 Y, 35 M, 35 C, and 35 K arranged inside the transfer belt 33 , a tension roller 37 and a secondary transfer backup roller 38 , and the transfer belt 33 . and a secondary transfer roller 23 . The primary transfer rollers 35Y, 35M, 35C and 35K are arranged to face the photosensitive drums 41Y, 41M, 41C and 41K with the transfer belt 33 interposed therebetween. A secondary transfer backup roller 38 is arranged to face the secondary transfer roller 23 with the transfer belt 33 interposed therebetween.

When image formation is started, the photosensitive drum 41 rotates. The charging device 42 uniformly charges the surface of the photosensitive drum 41 . An electrostatic latent image is formed on the surface of the photosensitive drum 41 by scanning exposure of the optical writing unit 31 . Toner as a developer is supplied from the developing device 43 to the electrostatic latent image formed on the surface of the photosensitive 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 onto the transfer belt 33 . The toner images of the respective colors on the photosensitive drum 41 are superimposed and transferred onto the transfer belt 33 by the primary transfer nip formed by the photosensitive drum 41 and the primary transfer roller 35 via the transfer belt 33 . Toner remaining on the surface of the photoreceptor drum 41 is removed by a cleaning device 44, and residual charges on the photoreceptor drum 41 are removed by a charge removing lamp as a charge removing unit.

The registration roller pair 22 rotates at the timing when the transfer paper S is superimposed on the toner image transferred on the surface of the transfer belt 33 . By the rotation of the registration roller pair 22 , the transfer sheet S is fed to the secondary transfer nip formed by the secondary transfer backup roller 38 via the transfer belt 33 and the secondary transfer roller 23 . The transfer paper S onto which the toner image has been transferred at the secondary transfer nip is mechanically separated from the transfer belt 33 and then sent to the fixing device 10 . An intermediate transfer cleaning device 39 removes toner remaining on the surface of the transfer belt 33 after passing through the primary transfer nip. Note that the configuration of the image forming section 3 can be changed as appropriate. For example, a charging section having a configuration different from that of the charging device 42 or a latent image forming section having a configuration different from that of 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 rotary 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 silicone rubber. The elastic layer made of silicone rubber is deformed when the toner image formed on the transfer sheet S is pressed, and absorbs minute irregularities on the surface, thereby preventing formation of an image like orange peel. The thickness of the elastic layer made of silicon rubber is preferably 100 μm or more. The release layer is made of a fluororesin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene). Note that the configuration of the fixing belt 60 can be changed as appropriate. For example, the fixing belt 60 may omit the elastic layer from the viewpoint of reducing the heat capacity, or may have a polygonal cross-sectional shape other than a circular shape.

The pressure roller 80 is arranged to face the outer peripheral surface of the fixing belt 60 . The pressure roller 80 is rotated by driving force transmitted from a drive source such as a motor and a transmission member (not shown) such as a gear. Further, the pressure roller 80 is urged toward the fixing belt 60 by an urging member (not shown) such as a spring. The pressure roller 80 of the present embodiment is composed of a cylindrical substrate having a hollow portion, an elastic layer covering the surface of the substrate, and a release layer formed on the surface 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 fluororesin such as PFA or PTFE. Note that the configuration of the pressure roller 80 can be changed as appropriate. For example, the pressure roller 80 can be configured solid without a hollow portion. Also, a heat source such as a halogen heater may be arranged inside the pressure roller. Also, the elastic layer 82 of the pressure roller 80 can be made of materials other than solid rubber such as silicon rubber. For example, in a configuration in which the pressure roller does not have a heat source, sponge rubber with high heat insulation may be used. Heat transfer from the fixing belt 60 to the pressure roller 80 can be suppressed by using sponge rubber with high heat insulation.

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 . A 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 .

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

The reflecting member 70 reflects the radiant heat from 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, and an anti-oxidation layer positioned on the outermost side formed on the surface of the mirror surface portion.

The reflecting member 70 is formed in a shape that blocks the space between the stay member 62 and the halogen heater 90 inside the fixing belt 60 . The radiant heat applied to the stay member 62 side of the halogen heater 90 is reflected by the reflecting member 70 to the inner peripheral surface 65 of the fixing belt 60 without reaching the stay member 62 directly. Thereby, heating of the stay member 62 is prevented, and the heating of the fixing belt 60 by the halogen heater 90 can be performed efficiently.

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 based on the heat pipe 50 . In the present embodiment, the nip forming member 45 is configured by combining the heat pipe 50 with the connecting part 46 and the like that connects the stay member 62 made of resin or metal.

FIG. 3 is a cross-sectional perspective view showing the heat pipe 50 of the fixing device 10 of this embodiment. As shown in FIG. 3, the heat pipe 50 elongates in the axial direction (longitudinal direction) of the fixing belt 60 and is made of a material with high thermal conductivity, such as aluminum or copper. Note that the axial direction of the fixing belt 60 indicates a direction parallel to the rotation axis of the fixing belt 60 . From the viewpoint of cost, workability, and strength, the heat pipe 50 is preferably made of copper, but 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 . Both ends 52 of the heat pipe 50 are bent toward the stay member 62, and the heat pipe 50 has a substantially U-shaped cross section. The nip surface 51 is formed flat or concave. From the viewpoint of suppressing the occurrence of jams, it is preferable to form the nip surface 51 in a concave shape, which improves the separability of the transfer sheet S because the discharge direction of the transfer sheet S is toward the pressure roller 80, but the shape is limited. does not mean The shape of the nip surface 51 is not limited to a flat surface or a concave surface, and can be changed as appropriate.

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

FIG. 4 is a schematic diagram 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 coating layer 56 is formed on the nip surface 51 by coating with a sliding material 57 . As the sliding material 57 forming the coating layer 56, for example, a resin material containing PTFE is preferable.

The coating layer 56 is formed over substantially the entire 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 . Note that the range of the coating layer 56 is not limited to the nip surface 51 alone. The coating layer 56 may extend from the nip surface 51 to the end 52 of the heat pipe 50 . Moreover, in the range of the coating layer 56, there may be a region in which no coating layer is formed.

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

The longitudinal distance a of the working fluid space 53 of the heat pipe 50 is longer than the width b of the transfer paper 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 pressed against the pressure roller 80, the fixing belt 60 rotates. At this time, since 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, the fixing belt 60 rotates smoothly.

The heat of the portion of the fixing belt 60 nipped by the nip forming member 45 and the pressure roller 80 is equalized by the heat pipe 50 extending 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 paper S is small and the end of the fixing belt 60 does not come into contact with the transfer paper S, the heat of the fixing belt 60 is uniformed by the heat pipe 50, and the end of the fixing belt 60 is heated. It is possible to effectively suppress the occurrence of overheating edge temperature rise.

When the transfer sheet S on which the toner image is formed by the image forming section 3 as described above reaches the fixing device 10, it is pressed and heated by the fixing belt 60, the nip forming member 45 and the pressure roller 80, and the toner image is transferred. It is fixed on the paper S. The transfer paper S on which the toner image has been fixed by passing through the fixing device 10 is discharged to the paper discharge section 4 by the paper discharge roller pair 24 . The paper discharge section 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 fixing belt 60 sandwiched between the fixing belt 60 and the nip forming member 45 outside the fixing belt 60 . A pressing roller 80 is arranged opposite to the fixing belt 60 , and a halogen heater 90 is arranged inside the fixing belt 60 at a position spaced apart 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 is several times more excellent in thermal conductivity than when a coating layer is formed on a plate-like metal member made of the same material (for example, pure aluminum or pure copper). The heat transferred from the belt 60 can be effectively uniformed. In addition, since the heat pipe 50 has a low heat capacity, there are advantageous effects 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 spaced apart from the nip forming member 45 , the halogen heater 90 is moved from the fixing belt 60 regardless of the heating range of the halogen heater 90 . Heat can be effectively uniformed by the heat pipe 50 . As a result, even if the edge temperature rises during continuous sheet feeding, the heat unevenness moves from the fixing belt 60 to the heat pipe 50, so that the heat can be uniformly heated quickly. Furthermore, since no air layer is interposed 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. Heat transfer from the fixing belt 60 to the heat pipe 50 can be dramatically improved. That is, with the fixing device 10 of the present embodiment, it is possible to achieve both low friction due to the coating layer 56 and high uniformity of heat in the axial direction due to the heat pipe 50 without incurring a large cost.

The heat pipe 50 of this embodiment also 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 can be secured between the fixing belt 60 and the heat pipe 50, and heat transfer can be efficiently performed to realize a higher heat equalizing effect.

Also, 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 that contacts the fixing belt 60 can achieve a higher level of slidability and heat uniformity.

Further, the heat pipe 50 of this embodiment has a working fluid space 53 that encloses the working fluid 55 . The length a of the hydraulic fluid space 53 in the direction perpendicular to the transport direction of the transfer paper S is set to be equal to or greater than the maximum width b of the transfer paper S to be transported. As a result, the temperature uniformity effect can be satisfactorily exhibited for all sizes of the transfer paper S 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. This makes it possible to achieve both higher temperature uniformity and slidability.

Further, the fixing device 10 of the present embodiment further includes a reflecting member 70 which is arranged between the halogen heater 90 and the nip forming member 45 inside the fixing belt 60 and reflects the radiant heat of the halogen heater 90 . Thereby, the radiant heat of the halogen heater 90 is reflected to the fixing belt 60 by the reflecting member 70 without being irradiated 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 occurrence of the end temperature rise can be prevented more reliably.

The printer 1 including the fixing device 10 of the present embodiment can shorten the warm-up time, save energy, and effectively suppress the temperature rise at the end of the fixing belt 60 during continuous sheet feeding with an inexpensive configuration.

Note that 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, a shielding member that can move between a shielding position for shielding between the halogen heater 90 and the fixing belt 60 according to the size of the transfer sheet S and a standby position for canceling the shielding is further arranged. You may The shielding member is made of highly heat-resistant aluminum, iron, stainless steel, or the like. A heating range of the fixing belt 60 by the halogen heater 90 can be controlled according to the size of the transfer sheet S by the shielding member. By combining such shielding members, it is possible to further suppress the temperature rise at the edge.

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 modified as appropriate.

1 Printer (image forming device)
REFERENCE SIGNS LIST 10 fixing device 45 nip forming member 50 heat pipe 56 coating layer 57 sliding member 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 (4)

an annular fixing member;
a nip forming member disposed inside the fixing member;
a pressing member arranged outside the fixing member 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 for heating an inner peripheral surface of the fixing member;
a reflecting member disposed between the heating element and the nip forming member inside the fixing member and reflecting the radiant heat of the heating element;
with
The nip forming member is
a heat pipe through which heat is transferred from the inner peripheral surface of the fixing member;
The heat pipe has a nip surface that slides relative to the inner peripheral surface of the rotating fixing member , and a working fluid space that encloses a working fluid ,
The nip surface is formed of a coating layer of a sliding material ,
Both upstream and downstream ends of the heat pipe in the rotation direction of the fixing member on the nip surface are bent to the side opposite to the pressure member side, so that the heat pipe is formed to have a U-shaped cross section. ,
The fixing device , wherein the working fluid space is formed to have a U-shaped cross section corresponding to the shape of the heat pipe . 2. The fixing device according to claim 1 , wherein the length of the hydraulic fluid space in the direction orthogonal to the conveying direction of the recording material is set to a length equal to or larger than the maximum width of the conveyed recording material. 3. The fixing device according to claim 1, wherein the sliding material is PAI or PI resin containing PTFE. An image forming apparatus comprising the fixing device according to claim 1 .

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