Fixing apparatus and image forming apparatus

Abstract

The present invention provides a fixing device and an image forming apparatus that, even when a vapor chamber with high thermal conductivity is used as the nip forming member, effectively utilizes the heat of the reflector to prevent heat from being drawn away from the fixing member, thereby shortening the start-up time of the fixing device and improving energy saving effects. [Solution] The present invention comprises a rotatable endless fixing belt, a pressure roller rotatably mounted opposite the fixing belt, a heater mounted inside the fixing belt for heating the fixing belt, a nip-forming member mounted inside the fixing belt and including a vapor chamber that forms a nip portion opposite the pressure roller, a reinforcing member mounted inside the fixing belt for supporting the nip-forming member, and a reflector mounted between the heater and the reinforcing member for reflecting heat from the heater back onto the fixing belt, wherein the vapor chamber included in the nip-forming member and the reflector are in contact with each other by a heat-conducting member.

Description

Technical Field

[0001] The present invention relates to a fixing device and an image forming apparatus.

Background Art

[0002] In an electrophotographic fixing device, in order to enhance the thermal conductivity of a nip forming member that contacts the inside of a fixing member, a technique using a nip forming member made of metal (such as copper or aluminum) (see Patent Document 2), and further, a technique using a member in which a working fluid is enclosed in a hollow such as a heat pipe and the thermal conductivity is enhanced by repeating vaporization and liquefaction of the working fluid (see Patent Document 1) have been developed. Also, a technique of thermally contacting a nip forming member and a support member has been developed in order to suppress an increase in end portion temperature during passage of small-sized paper and enhance heat uniformity (see Patent Document 2).

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, in the above-described nip forming member, since the thermal conductivity is enhanced, during warm-up, the heat of the fixing member is taken away by the nip forming member and the heat escapes to the member holding the nip forming member.

[0004] <able> The present invention has been made in view of the above, and even when a vapor chamber having a high thermal conductivity is used for the nip forming member, the heat of the fixing member is not taken away by effectively utilizing the heat of the reflector, and it is possible to shorten the start-up time of the fixing device and improve the energy saving effect. An object of the present invention is to provide a fixing device and an image forming apparatus.

Means for Solving the Problems

[0005] To solve the above-mentioned problems and achieve the objective, the present invention comprises a rotatable endless fixing belt, a pressure roller rotatably provided opposite the fixing belt, a heater provided inside the fixing belt for heating the fixing belt, a nip-forming member provided inside the fixing belt and including a vapor chamber that forms a nip portion opposite the pressure roller, a reinforcing member provided inside the fixing belt for supporting the nip-forming member, and a reflector provided between the heater and the reinforcing member for reflecting heat from the heater onto the fixing belt, wherein the vapor chamber included in the nip-forming member and the reflector are in contact with each other by a heat-conducting member. [Effects of the Invention]

[0006] According to the present invention, even when a vapor chamber with high thermal conductivity is used as the nip forming member, the heat from the reflector is effectively utilized, preventing heat from being drawn away from the fixing member, thereby shortening the start-up time of the fixing device and improving energy saving effects. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows an example of the configuration of an image forming apparatus according to this embodiment. [Figure 2] Figure 2 is a diagram illustrating an example of a fixing device included in the image forming apparatus according to this embodiment. [Figure 3] Figure 3 is a diagram illustrating an example of a fixing device in the image forming apparatus according to this embodiment. [Figure 4] Figure 4 is a diagram illustrating an example of a fixing device included in the image forming apparatus according to this embodiment. [Figure 5] Figure 5 is a diagram illustrating an example of a fixing device included in the image forming apparatus according to this embodiment. [Figure 6] Figure 6 shows an example of a schematic cross-sectional configuration of a fixing device. [Figure 7] Figure 7 shows an example of a schematic cross-sectional configuration of the fixing device. [Figure 8] Figure 8 shows an example of a schematic cross-sectional configuration of a fixing device. [Figure 9] Figure 9 shows an example of a schematic cross-sectional configuration of a fixing device. [Figure 10] Figure 10 shows an example of a schematic cross-sectional configuration of a fixing device. [Figure 11] Figure 11 shows an example of a schematic cross-sectional configuration of a fixing device. [Figure 12] Figure 12 is a cross-sectional view of an example of a fixing device according to this embodiment. [Figure 13] Figure 13 is a diagram illustrating an example of a fixing device according to this embodiment. [Figure 14] Figure 14 is a diagram illustrating an example of a fixing device according to this embodiment. [Figure 15] Figure 15 is a diagram illustrating an example of a fixing device according to this embodiment. [Figure 16] Figure 16 is a diagram illustrating an example of a fixing device according to this embodiment. [Figure 17] Figure 17 is a diagram illustrating an example of a fixing device according to this embodiment. [Figure 18] Figure 18 is a diagram illustrating an example of a fixing device according to this embodiment. [Figure 19] Figure 19 is a diagram illustrating an example of a fixing device according to this embodiment. [Figure 20] Figure 20 is a diagram illustrating an example of a fixing device according to this embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the fixing device and the image forming apparatus will be described in detail below with reference to the attached drawings.

[0009] FIG. 1 is a diagram showing an example of the configuration of an image forming apparatus according to the present embodiment. FIGS. 2 to 5 are diagrams for explaining an example of a fixing device included in the image forming apparatus according to the present embodiment. FIGS. 6 to 11 are diagrams showing an example of a schematic cross-sectional configuration of the fixing device. First, the overall configuration and operation of the image forming apparatus 1 in FIG. 1 will be described. As shown in FIG. 1, the image forming apparatus 1 in the present embodiment is a tandem type color printer. In a bottle storage unit 101 above the main body of the image forming apparatus 1, four toner bottles 102Y, 102M, 102C, and 102K corresponding to each color (yellow, magenta, cyan, black) are detachably (replaceably) installed. Below the bottle storage unit 101, an intermediate transfer unit 85 is disposed. Image forming units 4Y, 4M, 4C, and 4K corresponding to each color (yellow, magenta, cyan, black) are arranged in parallel so as to face an intermediate transfer belt 78 of the intermediate transfer unit 85.

[0010] In each of the image forming units 4Y, 4M, 4C, and 4K, a photosensitive drum 5Y, 5M, 5C, or 5K is disposed. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge removing unit, etc. are disposed. Then, on the surface of each of the photosensitive drums 5Y, 5M, 5C, and 5K, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed, and an image of each color is formed on the surface of each of the photosensitive drums 5Y, 5M, 5C, and 5K.

[0011] The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in the clockwise direction of FIG. 1 by a motor. And at the position of the charging unit 75, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged (this is the charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser beam L emitted from the exposure unit 3, and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position (this is the exposure process).

[0012] Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the position facing the developing unit 76, and at this position, the electrostatic latent image is developed to form toner images of each color (this is the developing process). Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at this position, the toner images on the photoreceptor drums 5Y, 5M, 5C, and 5K are transferred onto the intermediate transfer belt 78 (this is the first transfer process). At this time, a small amount of untransferred toner remains on the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K.

[0013] Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the position facing the cleaning unit 77, and at this position, the untransferred toner remaining on the photoreceptor drums 5Y, 5M, 5C, and 5K is mechanically recovered by the cleaning blade of the cleaning unit 77 (this is the cleaning process). Finally, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the position facing the charge removal unit, and at this position, the residual potential on the photoreceptor drums 5Y, 5M, 5C, and 5K is removed. Thus, a series of image forming processes performed on the photoreceptor drums 5Y, 5M, 5C, and 5K are completed.

[0014] Thereafter, the toner images of each color formed on each photoreceptor drum through the developing process are transferred and overlapped onto the surface of the intermediate transfer belt 78. Thus, a color image is formed on the intermediate transfer belt 78. Here, the intermediate transfer unit 85 is composed of the intermediate transfer belt 78, four first transfer bias rollers 79Y, 79M, 79C, and 79K, the secondary transfer backup roller 82, the cleaning backup roller 83, the tension roller 84, the intermediate transfer cleaning unit 80, etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is endlessly moved in the direction of the arrow in FIG. 1 by the rotational drive of one roller 82.

[0015] The four primary transfer bias rollers 79Y, 79M, 79C, and 79K each have an intermediate transfer belt 78 sandwiched between them and the photoreceptor drums 5Y, 5M, 5C, and 5K to form a primary transfer nip. A transfer bias opposite to the toner polarity is then applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 then travels in the direction of the arrow, sequentially passing through the primary transfer nip of each primary transfer bias roller 79Y, 79M, 79C, and 79K. In this way, the toner images of each color on the photoreceptor drums 5Y, 5M, 5C, and 5K are superimposed onto the intermediate transfer belt 78 and primary transferred.

[0016] Subsequently, the intermediate transfer belt 78, on which the toner images of each color have been transferred in layers, reaches a position opposite the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between itself and the secondary transfer roller 89, forming a secondary transfer nip. The four toner images formed on the intermediate transfer belt 78 are then transferred onto the sheet P, which has been transported to the position of this secondary transfer nip. At this point, untransferred toner remains on the intermediate transfer belt 78. Subsequently, the intermediate transfer belt 78 reaches the intermediate transfer cleaning section 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected. Thus, the series of transfer processes performed on the intermediate transfer belt 78 is completed.

[0017] Here, the sheet P that is transported to the secondary transfer nip position is transported from the paper feed unit 12 located below the main body of the image forming apparatus 1, via the paper feed roller 97 and the pair of registration rollers 98 (timing roller pair). More specifically, the paper feed unit 12 stores multiple sheets of paper or the like stacked together. When the paper feed roller 97 is driven to rotate counterclockwise in Figure 1, the top sheet P is fed towards the space between the rollers of the pair of registration rollers 98.

[0018] The sheet P, transported to the register roller pair 98, temporarily stops at the position of the roller nip of the register roller pair 98, which has stopped its rotational drive. Then, in time with the color image on the intermediate transfer belt 78, the register roller pair 98 is driven to rotate, and the sheet P is transported toward the secondary transfer nip. In this way, the desired color image is transferred onto the sheet P.

[0019] Subsequently, the sheet P onto which the color image has been transferred at the secondary transfer nip is transported to the fixing device 20. At this location, the heat and pressure from the fixing belt 21 and pressure roller 31 fix the color image transferred to the surface of the sheet P (this is the fixing process). After that, the sheet P is discharged from the device through the rollers of the paper discharge roller pair 99. The sheets P discharged from the device by the paper discharge roller pair 99 are sequentially stacked on the stacking unit 100 as output images. In this way, a series of image forming processes in the image forming apparatus are completed.

[0020] Next, the configuration and operation of the fixing device 20, which is installed in the main body 1 of the image forming apparatus, will be described in detail using Figure 8. The fixing device 20 is a device that transports the sheet P (a sheet on which unfixed toner is carried) while heating it. As shown in Figures 8, 2, and 3, the fixing device 20 consists of a fixing belt 21 as a belt member, a nip forming member 26, a reinforcing member 23, a heater 25 as a heating means (heat source), a reflector 27, a pressure roller 31 as a pressure rotating body, a temperature detection sensor 40 as a temperature detection means, etc.

[0021] Here, the fixing belt 21 is an endless belt member that is in contact with the pressure roller 31 and rotates in a driven manner as the pressure roller 31 rotates. The fixing belt 21 is a thin-walled, flexible endless belt that rotates (driven rotation) in the direction of the arrow in Figure 8 (counterclockwise). In other words, the fixing belt 21 is an example of a rotatable endless fixing belt. The fixing belt 21 has a base layer, an elastic layer, and a release layer sequentially laminated from the inner circumferential surface (the sliding surface with the nip forming member 26), and its overall thickness is set to 1 mm or less. The base layer of the fixing belt 21 has a layer thickness of 30 to 50 μm and is made of a metal material such as nickel or stainless steel, or a resin material such as polyimide. The elastic layer of the fixing belt 21 has a layer thickness of 100 to 300 μm and is made of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber. By providing an elastic layer, minute irregularities are prevented from forming on the surface of the fixing belt 21 at the nip, allowing heat to be uniformly transferred to the toner image T on the sheet P, thereby suppressing the occurrence of orange peel-like images. The release layer of the fixing belt 21 has a layer thickness of 5 to 50 μm and is made of materials such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, and PES (polyethersulfone). By providing a release layer, release properties (peelability) from the toner T (toner image) are ensured.

[0022] On the inside (inner circumferential surface) of the fixing belt 21, a nip-forming member 26, a heater 25 (heating means), a reinforcing member 23, a reflector 27, etc. are installed. Here, the nip-forming member 26 presses against the pressure roller 31 via the fixing belt 21 on the inside (inner circumferential surface) of the fixing belt 21, forming a nip (fixing nip) on which the sheet P is conveyed. That is, the pressure roller 31 is an example of a pressure roller that is rotatably provided with respect to the fixing roller 21. The nip-forming member 26 is also installed so as to slide against the inner circumferential surface of the fixing belt 21. Then, the nip-forming member 26 presses against the pressure roller 31 via the fixing belt 21, forming a nip on which the sheet P is conveyed. The nip-forming member 26 is provided with a vapor chamber 26b on the nip side. That is, the nip-forming member 26 is an example of a nip-forming member that is provided on the inside of the fixing belt 21 and includes a vapor chamber 26b that forms a nip portion facing the pressure roller 31.

[0023] The fixing belt 21 is then directly heated by radiant heat from a heater 25 (heating means) installed inside it. In other words, the heater 25, as a heating means, heats the fixing belt 21 in order to heat the sheet P. The heater 25 is an example of a heater that is provided on the inside of the fixing belt 21 and heats the fixing belt 21. The heater 25 (heating means) is configured to heat a circumferential region of the fixing belt 21 that is different from the nip. Specifically, the heater 25 as a heating means is a halogen heater (or carbon heater), and both ends thereof are fixed to the side plate 43 (see Figure 2) of the fixing device 20. Then, the radiant heat from the heater 25 (heating means) whose output is controlled by the control unit heats a heating region on the fixing belt 21 that is different from the nip (primarily the region facing the heater 25). Furthermore, heat is applied to the toner image T on the sheet P from the heated surface of the fixing belt 21. The output control of the heater 25 is performed based on the detection result of the belt surface temperature by a temperature detection sensor 40 (temperature detection means) such as a thermopile or thermistor facing the surface of the fixing belt 21. In addition, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature by controlling the output of the heater 25 in this way. In this embodiment, two heaters 25 (heating means) are installed on the inner circumferential surface side of the fixing belt 21, but one or more heaters can also be installed on the inner circumferential surface side of the fixing belt 21. Furthermore, the position of the heater 25 and the shape of the reinforcing member 23, which will be described later, are not limited to those of this embodiment. For example, the heater 25 can be arranged to face the upstream side in the rotational direction of the fixing belt 21 compared to the one in Figure 8, and the shape of the reinforcing member 23 can be set accordingly.

[0024] Thus, in this embodiment, the fixing device 20 does not heat only a portion of the fixing belt 21 locally, but rather heats the fixing belt 21 over a relatively wide area in the circumferential direction. Therefore, even when the device is operated at high speed, the fixing belt 21 is sufficiently heated, preventing fixing failures. In other words, because the fixing belt 21 can be heated efficiently with a relatively simple configuration, the warm-up time and first print time are shortened, and the device can be made smaller. In particular, in this embodiment, the fixing device 20 is configured so that the fixing belt 21 is directly heated by the heater 25 (heating means), which further improves the heating efficiency of the fixing belt 21 and allows for further cost reduction and miniaturization of the fixing device 20.

[0025] As shown in Figure 3, the guide members 29 guide both ends of the fixing belt 21 in the width direction from the inner circumferential surface side so that the fixing belt 21 maintains a substantially cylindrical position. Specifically, the two guide members 29 are made of a heat-resistant resin material or the like and are fitted into the side plates 43 at both ends of the fixing device 20 in the width direction. The guide members 29 are provided with a guide portion 29a for holding the fixing belt 21 while maintaining the substantially cylindrical position of the fixing belt 21, and a stopper portion for restricting the movement of the fixing belt 21 in the width direction (towards the belt), etc. The guide members 29 are positioned at both ends in the width direction in a circumferential area excluding the nip so as not to interfere with the formation of a nip by the nip forming member 26.

[0026] In this embodiment, the only members that contact the inner circumferential surface of the fixing belt 21 are the guide member 29 that makes loose contact at both ends in the width direction and the nip forming member 26 (actually via the sheet-like member 22). There are no other members (belt guides) that contact the inner circumferential surface and guide the rotation of the fixing belt 21. Thus, in order to further improve the heating efficiency of the fixing belt 21 and to reduce the cost and size of the device, the fixing device 20 in this embodiment adopts a configuration in which the pipe-shaped heating member is removed and the fixing belt 21 is directly heated by the heating means (heater 25) without going through the pipe-shaped heating member.

[0027] In this embodiment, a reinforcing member 23 is installed inside the fixing belt 21 so as to contact the pressure roller 31 via the nip forming member 26 and the fixing belt 21. The reinforcing member 23 reinforces the strength of the nip forming member 26 that forms the nip, and is integrated with the nip forming member 26 by screw fastening or the like. That is, the reinforcing member 23 is an example of a reinforcing member that is provided inside the fixing belt 21 and supports the nip forming member 26. As shown in Figure 2, the reinforcing member 23 is formed so as to have a length in the width direction that is longer than the nip forming member 26, and both ends in the width direction are held on the side plate 43 of the fixing device 20 so as to be movable in the vertical direction in Figure 2 (the left-right direction in Figure 8). The reinforcing member 23 contacts the pressure roller 31 via the nip forming member 26 and the fixing belt 21, thereby preventing the nip forming member 26 from deforming significantly due to the pressure applied by the pressure roller 31 in the nip. In order to satisfy the functions described above, it is preferable that this reinforcing member 23 be made of a metal material with high mechanical strength, such as stainless steel or iron.

[0028] In this embodiment, a reflector 27 is fixed between the reinforcing member 23 and the heater 25. That is, the reflector 27 is an example of a reflector provided between the heater 25 and the reinforcing member 23 to reflect heat from the heater 25 to the fixing belt 21. As a result, the heat directed from the heater 25 toward the reinforcing member 23 (heat that heats the reinforcing member 23, which is infrared radiation) is reflected by the reflector 27 and used to heat the fixing belt 21, thereby further improving the heating efficiency of the fixing belt 21. Aluminum, stainless steel, etc. can be used as the material for the reflector. In addition, a similar effect can be obtained even if a part or all of the surface of the reinforcing member 23 facing the heater 25 is given a mirror finish or an insulating material is provided.

[0029] As shown in Figure 8, the pressure roller 31, which acts as a heating rotating body, has an elastic layer 33 provided on a core metal 32 (shaft portion), and is driven to rotate in a predetermined direction (clockwise in Figure 8) by a drive motor (driving means) not shown. The core metal 32 of the pressure roller 31 is a hollow structure made of a metal material. The elastic layer 33 of the pressure roller 31 is made of a material such as foamed silicone rubber, silicone rubber, or fluororubber. A thin release layer made of PFA, PTFE, etc. can also be provided on the surface of the elastic layer 33. The pressure roller 31 is pressed against the fixing belt 21 to form a desired nip between the two members. Also, as shown in Figure 2, a gear 45 that meshes with the drive gear of the drive motor is installed on the pressure roller 31, and the pressure roller 31 is driven to rotate in the direction of the arrow in Figure 8 (clockwise). Furthermore, both ends of the pressure roller 31 in the width direction are rotatably supported on the side plate 43 of the fixing device 20 via bearings 42.

[0030] If the elastic layer 33 of the pressure roller 31 is made of a sponge-like material such as foamed silicone rubber, the pressure acting on the nip can be reduced, thereby reducing the load on the nip forming member 26. Furthermore, the heat insulation of the pressure roller 31 is improved, making it difficult for heat from the fixing belt 21 to transfer to the pressure roller 31, thus improving the heating efficiency of the fixing belt 21.

[0031] As shown in Figure 9, the nip-forming member 26 that slides against the inner circumferential surface of the fixing belt 21 has a flat surface facing the pressure roller 31 (which is the sliding surface 26b2 of the vapor chamber 26b, described later). That is, the sliding surface 26b2 of the nip-forming member 26 (the surface facing the pressure roller 31) is formed to be flat. As a result, the shape of the nip becomes approximately parallel to the image plane of the sheet P, increasing the adhesion between the fixing belt 21 and the sheet P and improving fixing performance. Furthermore, because the curvature of the fixing belt 21 at the exit side of the nip is increased, the sheet P that has been fed out from the nip can be easily separated from the fixing belt 21.

[0032] The following briefly describes the normal operation of the fixing device 20 configured as described above. When the power switch of the device body 1 is turned on, power is supplied to the heater 25 and the rotational drive of the pressure roller 31 in the direction of the arrow in Figure 8 is started. As a result, the fixing belt 21 also rotates in the direction of the arrow in Figure 8 due to the frictional force with the pressure roller 31 at the nip. Subsequently, the sheet P is fed from the paper feeding section 12 and the unfixed color image is placed on (transferred) onto the sheet P at the position of the secondary transfer roller 89. The sheet P, on which the unfixed image T (toner image) is placed, is transported in the direction of arrow Y10 in Figure 8 while being guided by the guide plate and is fed into the fixing belt 21 and the nip of the pressure roller 31, which are in a pressed state. Then, the toner image T is fixed to the surface of the sheet P by the heating of the fixing belt 21 heated by the heater 25 and the pressing force between the nip forming member 26 reinforced by the reinforcing member 23 and the pressure roller 31. Subsequently, the sheet P, which was sent out from the nip, is transported in the direction of arrow Y11.

[0033] The characteristic configuration and operation of the fixing device 20 in this embodiment will be described in detail below. As previously explained using Figure 8, the fixing device 20 in this embodiment is equipped with a fixing belt 21, a nip forming member 26, etc. The fixing belt 21 is an endless belt member that is heated by a heater 25 as a heating means and rotates in a predetermined rotational direction (counterclockwise in Figure 8). The heater 25 is installed so as to face the inner circumferential surface of the fixing belt 21. The nip forming member 26 is arranged on the inner circumferential surface side of the fixing belt 21 and presses against the pressure roller 31, which is a pressure rotating body, via the fixing belt 21 to form a nip (fixing nip) on which the sheet P is conveyed.

[0034] Here, as shown in Figure 9 and other figures, the fixing device 20 in this embodiment is provided with a vapor chamber 26b on the nip-forming member 26 that slides against the inner circumferential surface of the fixing belt 21. More specifically, the nip-forming member 26 mainly consists of a holding portion 26a (nip-forming member body) and a vapor chamber 26b.

[0035] The holding portion 26a holds the vapor chamber 26b on the side away from the nip (fixing nip) (inside the belt) and has sufficient rigidity to prevent significant deflection even when subjected to pressure from the pressure roller 31. Resin materials (such as liquid crystal polymer (LCP), polyamide-imide (PAI), polyethersulfone (PES), polyphenylene sulfide (PPS), polyethernitrile (PEN), polyetheretherketone (PEEK), etc.) can be used to form the holding portion 26a. The holding portion 26a holds the vapor chamber 26b and is also held by the reinforcing member 23.

[0036] The vapor chamber 26b is a metal heat dissipation component that has a hollow section 26b1 filled with a working fluid such as water, and has the function of instantly transferring heat through the vaporization and condensation of the working fluid. The vapor chamber 26b is provided with a wick 26z (see Figure 4) in the hollow section 26b1. As shown in Figure 4, the vapor chamber 26b is provided with a wick 26z (a roughly gauze-like material with a fine internal structure) covering almost the entire surface of the inner wall surfaces 26b4 and 26b5. Due to the capillary action of this wick 26z, the liquefied working fluid in the hollow section 26b1 moves, and the vaporized working fluid moves, thereby achieving high thermal conductivity and uniform heating through heat exchange.

[0037] Furthermore, the roughly rectangular frame constituting the vapor chamber 26b is formed from a material with high thermal conductivity (for example, copper, aluminum, silver, graphite, etc.). In Figure 5, the sliding contact surface 26b2 of the vapor chamber 26b (the surface that directly contacts the inner circumferential surface of the fixing belt 21 and into which the fixing belt 21 slides) is formed in a planar shape.

[0038] As shown in Figure 4, in this embodiment, the sliding surface 26b2 of the vapor chamber 26b that slides against the fixing belt 21 is made of a low-friction material. More specifically, a thin film coating layer 26x made of a low-friction material such as fluororesin is formed on the sliding surface 26b2 of the vapor chamber 26b. By configuring it in this way, the frictional resistance due to sliding contact between the fixing belt 21 and the vapor chamber 26b is reduced, thereby reducing wear and deterioration of the fixing belt 21 and the vapor chamber 26b. In order to achieve the above-mentioned effect, it is sufficient to make at least the sliding surface 26b2 of the vapor chamber 26b from a low-friction material, but other parts can also be made from a low-friction material.

[0039] Here, as shown in Figures 4 and 5, in this embodiment, in the hollow portion 26b1 of the vapor chamber 26b, which is filled with working fluid, a columnar member 26b10 is installed between the nip-side inner wall surface 26b4 on the nip side and the non-nip-side inner wall surface 26b5 (the inner wall surface on the side of the reinforcing member 23) that is opposite to the nip-side inner wall surface 26b4. In other words, the hollow portion 26b1 of the vapor chamber 26b is not just a space through which the working fluid flows, but also has multiple columnar members 26b10 provided from the nip side to the non-nip side, in a range that does not hinder heat exchange due to the flow of the working fluid. In this embodiment, the columnar members 26b10 are integrally formed from the same material as the frame of the vapor chamber 26b. By providing the columnar member 26b10 in this way, the vapor chamber 26b, which has a hollow section 26b1 and lacks sufficient mechanical strength, becomes less prone to deformation even when the pressure of the pressure roller 31 is applied. As a result, the desired nip shape is more easily maintained, a good fixing process can be performed stably, and good heat exchange performance by the vapor chamber 26b is more easily maintained.

[0040] For example, the fixing device shown in Figure 6 is an example in which a heat pipe is used for the nip-forming member 26. Because the heat pipe has good thermal conductivity, during warm-up, heat from the fixing member is absorbed by the nip-forming member 26, and heat escapes to the member holding the nip-forming member 26.

[0041] For example, the fixing device shown in Figure 7 has a nip-forming member 26 made of metal, and is configured to improve the rise in end temperature by providing a location where the stay (reinforcement member 23) and the nip-forming member 26 can be thermally separated. Although the configuration allows for the thermal separation location to be blocked during warm-up, the part that holds the nip-forming member 26 is in contact with other members, so heat from the fixing belt 21 is taken away by the nip-forming member 26, and heat escapes to the member that holds the nip-forming member 26.

[0042] For example, the fixing device 20 shown in Figure 8 (overall cross-sectional view of the fixing device 20) and Figure 9 (partial cross-sectional view of the fixing device 20) is an example in which a vapor chamber 26b is used for the nip forming member 26. Because the vapor chamber 26b has good thermal conductivity, during warm-up, heat from the fixing belt 21 is absorbed by the nip forming member 26, and heat escapes to the member holding the nip forming member 26.

[0043] The fixing device 20 shown in Figure 10 is an improved version of the fixing device 20 shown in Figures 8 and 9. The aim is to suppress heat loss by reducing the contact area of ​​the contact portion of the holding portion 26a that holds the vapor chamber 26b, changing it from a flat surface to an uneven shape. However, the effect is insufficient, and during warm-up, heat from the fixing belt 21 is absorbed by the nip forming member 26, and heat escapes to the member holding the nip forming member 26.

[0044] The fixing device 20 shown in Figure 11 is the same example as in Figure 8, but the opening direction of the heater 25 is different. Hereafter, the description of this embodiment will proceed based on Figure 11. Note that this embodiment is also applicable to the fixing device 20 of the form shown in Figure 8.

[0045] Figure 12 is a cross-sectional view of an example of a fixing device according to this embodiment. In this embodiment, as shown in Figure 12, a transmission portion 26b1 is provided between the vapor chamber 26b and the reflector plate 27, thereby bringing the components into contact with each other. That is, the transmission portion 26b1 is an example of a heat conductive member that brings the vapor chamber 26b and the reflector plate 27 into contact. Before the warm-up operation, each component constituting the fixing device 20 is at room temperature. When the warm-up operation starts, a driving force is applied to the pressure roller 31, and the pressure roller 31 and the fixing belt 21 rotate in conjunction at a predetermined speed. At the same time, the heating member (heater 25) is energized and generates heat, so the inner circumferential surface of the fixing roller 21 receives heat from the heater 25 and the heat reflected by the reflector plate 27 while rotating, heating the entire circumference and rising towards the target temperature. At this time, the fixing belt 21 loses heat to the nip forming member 26 in contact with the inner circumference and the pressure roller 31 in contact with the outer circumference, so the temperature rise is slower.

[0046] In this embodiment, the heat absorbed by the nip-forming member 26 in contact with the inner circumference during the warm-up operation is reduced. The surface of the reflector 27 has surface properties that easily reflect light and heat from the heater 25, but because it receives heat from the heater 25 at close range, the temperature of the reflector 27 itself rises more rapidly than the surrounding members even during warm-up. In the conventional technology, the amount of heat given to the reflector 27 was dissipated naturally inside the fixing belt 21 or to contacting members such as the support member 23. In this embodiment, the amount of heat given to the reflector 27 is transferred to the vapor chamber 26b by making the reflector 27 and the vapor chamber 26b thermally contacted at the transfer part 26b1. Since the transfer part 26b1 and the vapor chamber 26b have good thermal conductivity, the heat given to the reflector 27 is rapidly and uniformly transferred to the vapor chamber 26b. As a result, while conventionally heat from the fixing belt 21 was absorbed by the vapor chamber 26b during warm-up, the vapor chamber 26b receives heat from the reflector 27 and quickly reaches a high temperature, reducing heat transfer from the fixing belt 21. Consequently, the fixing belt 21 reaches the predetermined temperature more quickly, shortening the warm-up time.

[0047] Figures 13 and 14 illustrate an example of a fixing device according to this embodiment. Figure 13 is a perspective view of an example of the vapor chamber 26b and transmission portion 26b1 in a cross-sectional view of the fixing device 20 shown in Figure 12. In the example shown in Figure 13, an L-shaped bend is provided on the lower side of the vapor chamber 26b. The end of the L-shaped bend, extending horizontally in the figure, corresponds to the transmission portion 26b1 shown in Figure 12. Its tip is not shown, but it is positioned to contact the reflector plate 27. That is, the transmission portion 26b1 is an example of a heat conductive member integrally formed with the nip forming member 26.

[0048] Figure 14 is a cross-sectional view of an example of a vapor chamber 26b and a transmission section 26b1. Since the vapor chamber 26b and the transmission section 26b1 are integrally formed, the hollow portion of the vapor chamber 26b, which is filled with working fluid, is connected to the hollow portion of the transmission section 26b1. As a result, the contact portion of the transmission section 26b1 with the reflector 27 is made of a highly thermally conductive material filled with working fluid. By thermally contacting the vapor chamber 26b and the reflector 27 at the transmission section 26b1, which has high thermal conductivity, the warm-up time of the fixing device 20 can be shortened and energy saving effects can be improved. In addition, although there are three transmission sections 26b1 in the example shown in Figure 13, the number, width, and position can be arbitrarily arranged as long as they are in contact with the reflector 27.

[0049] Figures 15-18 illustrate an example of a fixing device according to this embodiment. As shown in the schematic perspective view of Figure 18, a transmission member 28 can be provided as a separate component from the vapor chamber 26b. That is, the transmission member 28 is an example of a heat conductive member that brings the vapor chamber 26b and the reflector 27 into contact, and is formed separately from the nip forming member 26. Figure 15 shows an example in which the transmission member 28 is arranged on the side surface of the vapor chamber 26b, similar to the transmission portion 26b1 in the example shown in Figure 12. The effects are similar, but by making the vapor chamber 26b and the transmission member 28 separate components, the vapor chamber 26b does not require bending or complex shaping, making it easier to manufacture. Furthermore, simplifying the shape of the vapor chamber 26b is expected to improve heat conductivity, increase component productivity, and reduce component manufacturing costs. However, a mechanism for attaching the transmission member 28, a fixing method, etc., will be required separately, so the most suitable method for the fixing device 20 to which it will be mounted should be selected.

[0050] Figure 16 shows an example where the heat transfer member 28 is brought into contact with the flat surface on the back of the nip surface of the vapor chamber 26b, and into contact with the reflector 27 at an opposing position. Since the vapor chamber 26b has good thermal conductivity, heat will quickly spread throughout regardless of where the heat transfer member 28 is brought into contact, thus achieving a similar heat transfer effect. In order to position the heat transfer member 28 and to bring the vapor chamber 26b and the reflector 27 into thermal contact, the holding portion 26a and the support member 23 are partially provided with openings to secure a path for the heat transfer member 28, and to prevent heat from escaping by contacting the heat transfer member 28. Furthermore, if it is unavoidable to bring the heat transfer member 28 into contact with another member for holding purposes, it is preferable that the material and form have high thermal insulation properties and do not absorb heat.

[0051] Figure 17 is similar to Figure 16, but shows an example where the opening direction of the reflector 27 is different. The transmission member 28 is preferably made of a material with good thermal conductivity and heat resistance, and may be made of a common metal material such as copper alloy or aluminum. Alternatively, the transmission member 28 may be a processed product partially provided between the nip forming member 26 and the reflector 27.

[0052] Figure 18 is a schematic perspective view illustrating an example of a fixing device according to this embodiment. As shown in Figure 18, a transmission member 28 may be provided as a separate component from the vapor chamber 26b. To obtain sufficient effect, it is desirable that the transmission member 28 itself has high thermal conductivity. The vapor chamber 26b can be made of a vapor chamber or heat pipe, etc., which is made of a highly thermally conductive material with a hollow interior and a working fluid sealed inside. In Figure 18, the flat schematic diagram of the transmission member 28 represents a vapor chamber, and the cylindrical schematic diagram represents a heat pipe. That is, the transmission part 26b1 is an example of a thermal conductive member which is a paper chamber 26b or heat pipe containing a highly thermally conductive material with a working fluid (hydraulic agent) sealed inside.

[0053] As shown in the schematic perspective views of Figures 13, 18, 19, and 20, the number, width, and position of the transmission sections 26b1 and transmission members 28 can be arbitrarily arranged as long as the reflector 27 and the vapor chamber 26b are in contact with each other. The transmission section 26b1 shown in Figure 19 is an example in which the transmission sections 26b1 are integrally arranged with the vapor chamber 26b at both ends in the width direction of the sheet P. The transmission section 26b1 shown in Figure 20 is an example in which the transmission sections 26b1 are integrally arranged with the vapor chamber 26b both upstream and downstream in the conveying direction of the sheet P.

[0054] In either case, the thermal conductivity of the transfer portion 26b1 or the heat transfer member 28, which is integrally formed with the vapor chamber 26b, is good, making it possible to quickly equalize the heat throughout. Therefore, a heat equalization effect can be obtained by partially making thermal contact with any desired location. As a result, the warm-up time of the fixing device 20 can be shortened, and energy saving effects can be improved. It is also possible to make thermal contact between the vapor chamber 26b and the reflector 27 over the entire width of the sheet P, in which case an even faster heat equalization effect can be obtained. In other words, the transfer portion 26b1 is an example of a heat conductive member partially provided between the nip forming member 26 and the reflector 27.

[0055] As shown in the schematic perspective view of Figure 19, the transmission parts 26b1 are positioned on the upstream and downstream sides of the sheet P in the conveying direction. By positioning the transmission parts 26b1 on both the upstream and downstream sides of the sheet P, the holding part 26a is sandwiched between them, making it possible to position the vapor chamber 26b in the conveying direction of the sheet P. In this case, it is preferable to provide a highly heat-insulating material at the contact point between the transmission parts 26b1 and the holding part 26a to prevent heat leakage.

[0056] The number of transmission portions 26b1 in the upstream / downstream and widthwise directions of the sheet P in Figure 19 is arbitrary, but positioning is stabilized by arranging the transmission portions 26b1 near both ends in the widthwise direction of the vapor chamber 26b as shown in Figure 19. As shown in the schematic perspective view of Figure 20, the transmission portions 26b1 are arranged on the right and left sides in the widthwise direction of the sheet P in Figure 19, respectively. By arranging the transmission portions 26b1 on both ends in the widthwise direction of the sheet P, the holding portion 26a is sandwiched between them, making it possible to use them to position the vapor chamber 26b in the widthwise direction of the sheet P. In this case, it is preferable to provide a highly heat-insulating material at the contact area between the transmission portion 26b1 and the holding portion 26a to prevent heat leakage. That is, the transmission portion 26b1 is an example of a heat conductive member that has a positioning portion for the nip forming member 26.

[0057] Thus, according to the image forming apparatus and fixing apparatus 20 of this embodiment, even when a vapor chamber 26b with high thermal conductivity is used as the nip forming member 26, the heat from the reflector 27 is effectively utilized, preventing heat from being drawn from the fixing belt 21, thereby shortening the start-up time of the fixing apparatus 20 and improving energy saving effects.

[0058] In this embodiment, the present invention was applied to a fixing device 20 using a pressure roller 31 as the pressure rotating body. However, the present invention can also be applied to a fixing device using a pressure belt as the pressure rotating body. In such cases, the same effects as those in this embodiment can be obtained.

[0059] It is clear that the present invention is not limited to this embodiment, and that this embodiment can be modified as appropriate within the scope of the technical concept of the present invention, in addition to what is suggested here. Furthermore, the number, position, shape, etc. of the constituent members are not limited to this embodiment, and can be set to a number, position, shape, etc. that is suitable for carrying out the present invention.

[0060] In this specification, the term "width direction" is defined as the direction perpendicular to the conveying direction of the sheet P, and the same direction as the rotation axis direction of the fixing belt 21 and the pressure roller 31.

[0061] In the above embodiment, the image forming apparatus of the present invention is described using an example in which it is applied to a multifunction device having at least two functions from among a copy function, a printer function, a scanner function, and a facsimile function. However, it can be applied to any image forming apparatus such as a copier, printer, scanner, or facsimile device.

[0062] Examples of the present invention are as follows: <1> A rotatable, endless fixing belt, A pressure roller is rotatably mounted opposite the fixing belt, A heater is provided inside the fixing belt to heat the fixing belt, A nip-forming member including a vapor chamber provided inside the fixing belt and facing the pressure roller to form a nip portion, A reinforcing member provided on the inside of the fixing belt and supporting the nip forming member, The system includes a reflector provided between the heater and the reinforcing member, which reflects heat from the heater to the fixing belt, A fixing device in which the vapor chamber, which includes the nip-forming member, and the reflector plate are in contact with each other by a heat-conducting member. <2> The heat conductive member is integrally formed with the nip forming member. <1> The fixing device described above. <3> The heat conductive member is formed separately from the nip forming member. <1> The fixing device described above. <4> The heat conduction member is a vapor chamber or heat pipe containing a highly thermally conductive material with a hydrant sealed inside. <3> The fixing device described above. <5> The heat conductive member is partially provided between the nip forming member and the reflector. <1> from <4> A fixing device as described in any one of the following. <6> The heat conductive member includes a positioning portion for the nip forming member, <2> The fixing device described above. <7> <1> from <6> An image forming apparatus comprising a fixing device as described in any one of the following. [Explanation of Symbols]

[0063] 1. Image forming apparatus 20 Fixing device 21 Fixing belt 23 Reinforcement members 25 Heater 26 Nip forming member 26b Vapor Chamber 27 Reflector 31 Pressure roller [Prior art documents] [Patent Documents]

[0064] [Patent Document 1] Japanese Patent Publication No. 2020-86350 [Patent Document 2] Japanese Patent Publication No. 2022-37693

Claims

1. A rotatable, endless fixing belt, A pressure roller is rotatably mounted opposite the fixing belt, A heater is provided inside the fixing belt to heat the fixing belt, A nip-forming member including a vapor chamber provided inside the fixing belt and facing the pressure roller to form a nip portion, A reinforcing member provided on the inside of the fixing belt and supporting the nip forming member, The system includes a reflector provided between the heater and the reinforcing member, which reflects heat from the heater to the fixing belt, A fixing device in which the vapor chamber, which includes the nip-forming member, and the reflector plate are in contact with each other by a heat-conducting member.

2. The fixing device according to claim 1, wherein the heat conductive member is integrally formed with the nip forming member.

3. The fixing device according to claim 1, wherein the heat conductive member is formed separately from the nip forming member.

4. The fixing device according to claim 3, wherein the heat conducting member is a vapor chamber or heat pipe containing a highly thermally conductive material with a working agent sealed inside.

5. The fixing device according to any one of claims 1 to 4, wherein the heat conductive member is partially provided between the nip forming member and the reflector.

6. The fixing device according to claim 2, wherein the heat conductive member includes a positioning portion for the nip forming member.

7. An image forming apparatus comprising a fixing device according to any one of claims 1 to 4.

Images