Fixing apparatus and image forming apparatus

Abstract

In a fixing device that presses an endless belt against a rotating body using an internally positioned pressure contact section, a holding section is provided to hold the belt upstream of the pressure contact section along the direction of belt movement. Compared to a case where the holding section holds the belt linearly along the width direction intersecting the direction of belt movement, this device suppresses the occurrence of wrinkles in the recording medium. [Solution] The device comprises a rotating body heated by a heat source, an endless belt that rotates in contact with the rotating body at a pressure contact portion, and a holding portion disposed inside the belt, which holds both ends of the belt upstream of the belt's movement direction at the pressure contact portion, along the width direction intersecting the movement direction, from the central portion upstream.

Description

[Technical Field]

[0001] This invention relates to a fixing apparatus and an image forming apparatus. [Background technology]

[0002] Conventionally, technologies related to fixing devices have already been proposed, such as those disclosed in Patent Document 1 and Patent Document 2.

[0003] Patent Document 1 describes a pressing member having different thicknesses in the rotation axis direction of the endless belt, with a first region where the thickness decreases from the center to the end, and a second region located outside the rotation axis direction of the first region, which is configured to be a predetermined thickness thicker than the thickness obtained by extending the thickness curve of the first region.

[0004] Patent Document 2 describes a configuration in which the holder has an upstream adjustment section on the upstream side in the rotational direction of the endless strip-shaped body, where the central part in the longitudinal direction is the most raised compared to other parts, and the surface becomes lower as it moves from the central part toward both ends. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2006-151687 [Patent Document 2] Japanese Patent Publication No. 2008-184245 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of this invention is to provide a fixing device that presses an endless belt against a rotating body using an internally positioned pressure contact portion, wherein the fixing device includes a holding portion that holds the belt upstream of the pressure contact portion along the direction of belt movement, thereby suppressing the occurrence of wrinkles in the recording medium compared to a case where the holding portion holds the belt linearly along the width direction intersecting the direction of belt movement. [Means for solving the problem]

[0007] The invention described in claim 1 comprises a rotating body heated by a heat source, An endless belt that rotates while being pressed against the aforementioned rotating body at the pressure contact portion, A holding portion is disposed inside the belt and, on the upstream side of the pressing portion along the direction of movement of the belt, holds both ends of the belt along the width direction intersecting the direction of movement, on the upstream side of the central portion. This is a fixing device equipped with [a specific feature].

[0008] The invention described in claim 2 is a fixing device according to claim 1, wherein the holding portion is integrally provided with the pressure contact portion on the upstream side of the pressure contact portion along the direction of movement of the belt.

[0009] The invention described in claim 3 is a fixing device according to claim 2, wherein the holding portion is arranged at the upstream end along the direction of movement of the belt, and the portion that holds the belt is formed in a concave shape.

[0010] The invention described in claim 4 is a fixing device according to claim 1, wherein the holding portion has a first portion that contacts both ends of the belt along the width direction and a second portion that contacts the central portion of the belt along the width direction, and the first portion is located upstream of the second portion along the direction of movement of the belt.

[0011] The invention described in claim 5 is a fixing device according to claim 4, wherein the holding portion is formed by connecting the first portion and the second portion with a curve.

[0012] The invention according to claim 6 is the fixing device according to claim 1, wherein the pressing portion has a first pressing portion that directly presses the belt against the rotating body at the downstream end along the moving direction of the belt, and a second pressing portion that presses the belt against the rotating body via an elastic member on the upstream side along the moving direction of the belt from the first pressing portion.

[0013] The invention according to claim 7 is the fixing device according to claim 6, wherein the holding portion is arranged on the upstream side along the moving direction of the belt of the second pressing portion.

[0014] The invention according to claim 8 is the fixing device according to claim 7, wherein the holding portion is arranged to be spaced outward in the radial direction with respect to the outer peripheral surface of the rotating body.

[0015] The invention according to claim 9 includes an image forming means for forming an image on a recording medium, fixing means for fixing the image on the recording medium, and is an image forming apparatus using the fixing device according to any one of claims 1 to 8 as the fixing means.

Advantages of the Invention

[0016] According to the invention described in claim 1, in a fixing device that presses an endless belt against a rotating body by a pressing portion disposed inside, a holding portion that holds the belt on the upstream side along the moving direction of the belt with respect to the pressing portion is provided, and compared with the case where the holding portion holds the belt linearly along the width direction intersecting the moving direction of the belt, it is possible to suppress the occurrence of wrinkles on the recording medium.

[0017] According to the invention described in claim 2, compared with the case where the holding portion is provided separately from the pressing portion, the position of the holding portion can be maintained with high accuracy.

[0018] According to the invention described in claim 3, the holding portion can hold the belt smoothly compared with the case where the portion for holding the belt is formed in a V shape.

[0019] According to the invention described in claim 4, the holding portion can more reliably prevent wrinkles from forming on the recording medium compared to the case where the first portion that contacts both ends along the width direction of the belt and the second portion that contacts the central part along the width direction of the belt are in the same position along the direction of movement of the belt.

[0020] According to the invention described in claim 5, the holding portion can more reliably prevent wrinkles from forming on the recording medium compared to the case where the first portion and the second portion are connected by a straight line.

[0021] According to the invention described in claim 6, the fixing nip portion can be set wider compared to the case in which only a first fixing portion that directly presses the belt against the rotating body at the downstream end along the direction of movement of the belt is provided, thereby improving fixing performance.

[0022] According to the invention described in claim 7, the holding portion can avoid being subjected to forces that deform the belt unstably, compared to the case where the holding portion is positioned at the same location as the second contact portion along the direction of movement of the belt.

[0023] According to the invention described in claim 8, the holding portion can suppress the buckling force acting on the belt compared to the case where it is positioned close to the outer surface of the rotating body.

[0024] According to the invention described in claim 9, wrinkles can be suppressed on the recording medium compared to the case in which the fixing device described in any of claims 1 to 8 is not used as the fixing means. [Brief explanation of the drawing]

[0025] [Figure 1] This is an overall configuration diagram showing an image forming apparatus to which the fixing device according to Embodiment 1 of this invention is applied. [Figure 2] This is a cross-sectional view showing a fixing device according to Embodiment 1 of the present invention. [Figure 3]This is a perspective view diagram showing the main parts of the fixing device according to Embodiment 1 of the present invention. [Figure 4] This is a cross-sectional view showing the main parts of the fixing device according to Embodiment 1 of the present invention. [Figure 5] This is a perspective view diagram showing the pressure-holding member. [Figure 6] This is a perspective view diagram showing the first and second support members. [Figure 7] This is a diagram illustrating the operation of a conventional fixing device. [Figure 8] This is a plan view showing the pressure-holding member of the fixing device according to Embodiment 1 of the present invention. [Figure 9] This is a diagram illustrating the operation of the fixing device according to Embodiment 1 of this invention. [Figure 10] This is a diagram illustrating an experimental example. [Modes for carrying out the invention]

[0026] The embodiments for carrying out this invention (hereinafter referred to as "embodiments") will be described below with reference to the drawings.

[0027] [Embodiment 1] Figure 1 shows a schematic overview of an image forming apparatus to which the fixing device according to Embodiment 1 is applied. In the figure, arrow X indicates the width direction along the horizontal, Y indicates the depth direction along the horizontal, and Z indicates the vertical direction.

[0028] <Overall configuration of the image forming apparatus> The image forming apparatus 1 is configured, for example, as a color printer. As shown in Figure 1, this image forming apparatus 1 includes a plurality of image forming devices 10, an intermediate transfer device 20, a paper feed device 50, a fixing device 40, etc. The image forming devices 10 form toner images that are developed with toner, which constitutes the developer. The intermediate transfer device 20 holds the toner images formed by each image forming device 10 and transports them to a secondary transfer position T2 where they are ultimately transferred to a recording paper 5, which is an example of a recording medium. The paper feed device 50 receives and transports the required amount of recording paper 5 to be supplied to the secondary transfer position T2 of the intermediate transfer device 20. The fixing device 40 fixes the toner images on the recording paper 5 that have been secondarily transferred by the intermediate transfer device 20. Here, the plurality of image forming devices 10 and the intermediate transfer device 20 constitute an image forming means for forming an image on the recording paper 5. The fixing device 40 is an example of a fixing means. Reference numeral 1a indicates the main body of the apparatus, which is formed by support structural members, outer covers, etc.

[0029] The imaging device 10 consists of four imaging devices 10Y, 10M, 10C, and 10K, each dedicated to forming toner images of four colors: yellow (Y), magenta (M), cyan (C), and black (K). These four imaging devices 10 (Y, M, C, K) are arranged in a single row within the internal space of the device body 1a, tilted with respect to the horizontal direction X.

[0030] Each imaging device 10 (Y, M, C, K) is equipped with a photoreceptor drum 11 as an example of a rotating image holding means, as shown in Figure 1. Around this photoreceptor drum 11 are a charging device 12, an exposure device 13, a developing device 14, a primary transfer device 15, a drum cleaning device 16, etc. The charging device 12 charges the image-forming surface (image-holding surface) of the photoreceptor drum 11 to the required potential. The exposure device 13 irradiates the charged surface of the photoreceptor drum 11 with light based on image information (signals) to form electrostatic latent images (for each color) with potential differences. The developing device 14 develops these electrostatic latent images with toners of the corresponding color (Y, M, C, K) to form toner images. The primary transfer device 15 transfers each of these toner images to an intermediate transfer device 20. The drum cleaning device 16 cleans the image-holding surface of the photoreceptor drum 11 by removing any toner or other deposits that remain after the primary transfer.

[0031] The photoreceptor drum 11 has an image-holding surface formed on the circumferential surface of a cylindrical or columnar substrate that is grounded, and the photoreceptor drum 11 has a photoconductive layer (photosensitive layer) made of a photosensitive material. The photoreceptor drum 11 is supported so as to rotate in the direction indicated by arrow A by a driving force transmitted from a drive device (not shown).

[0032] The charging device 12 consists of a contact-type charging roll positioned in contact with the photoreceptor drum 11. A charging voltage is supplied to the charging device (charging roll) 12. If the developing device 14 performs reverse development, the charging voltage supplied is a voltage or current with the same polarity as the charging polarity of the toner supplied from the developing device 14. A cleaning roll 121 for cleaning the surface of the charging device 12 is positioned in contact with the back side of the charging device 12.

[0033] The exposure apparatus 13 consists of an LED print head and the like, which irradiates the photoreceptor drum 11 with light corresponding to image information using multiple LEDs (Light Emitting Diodes) arranged along the axial direction of the photoreceptor drum 11 to form an electrostatic latent image. When latent image formation is in progress, the exposure apparatus 13 receives image information (signals) input to the image forming apparatus 1 by any means.

[0034] Each developing device 14, as shown in Figure 1, consists of a housing 140, a developing roll 141, agitation and conveying members 142 and 143, and a layer thickness regulating member 144. The housing 140 has an opening and a container for the developer. The developing roll 141 holds the developer and conveys it to the developing area facing the photoreceptor drum 11. The agitation and conveying members 142 and 143 consist of screw augers, etc., that convey the developer while agitating it as it passes through the developing roll 141. The layer thickness regulating member 144 regulates the amount of developer (layer thickness) held by the developing roll 141. In this developing device 14, a developing voltage is supplied between the developing roll 141 and the photoreceptor drum 11 from a power supply unit (not shown). The developing roll 141 and the agitation and conveying members 142 and 143 are rotated in the required direction by driving force transmitted from a drive unit (not shown). Furthermore, the developers used for the four colors (Y, M, C, K) are two-component developers containing non-magnetic toner and magnetic carriers.

[0035] The primary transfer device 15 is a contact-type transfer device equipped with a primary transfer roll to which a primary transfer voltage is supplied. At the primary transfer position T1, the primary transfer device 15 contacts the circumferential surface of the photoreceptor drum 11 via an intermediate transfer belt 21 and rotates. As the primary transfer voltage, a DC voltage exhibiting the opposite polarity to the charging polarity of the toner is supplied from a power supply device (not shown).

[0036] The drum cleaning device 16 consists of a container-shaped body 160, a cleaning blade 161, and a delivery member 162. The cleaning blade 161 is positioned at the opening of the container-shaped body 160 to remove residual toner and other deposits for cleaning. The delivery member 162 consists of a screw auger or the like that collects the toner and other deposits removed by the cleaning blade 161 and transports them to a collection system (not shown).

[0037] The intermediate transfer device 20 is positioned above each imaging device 10 (Y, M, C, K) along the vertical Z direction. This intermediate transfer device 20 mainly consists of an intermediate transfer belt 21, a plurality of belt support rolls 22-25, a secondary transfer device 30, and a belt cleaning device 26. The intermediate transfer belt 21 moves in a circular motion in the direction indicated by arrow B, passing through the primary transfer position T1, which is between the photoreceptor drum 11 and the primary transfer device 15. The plurality of belt support rolls 22-25 support the intermediate transfer belt 21 from its inner circumference, holding it in a desired state so that it can move in a circular motion. The secondary transfer device 30 is positioned on the outer circumferential surface (image holding surface) side of the intermediate transfer belt 21, which is supported by the belt support rolls 25, and transfers the toner image on the intermediate transfer belt 21 to the recording paper 5. The belt cleaning device 26 cleans the intermediate transfer belt 21 by removing any toner, paper dust, and other deposits that remain and adhere to the outer circumferential surface after passing through the secondary transfer device 30.

[0038] The intermediate transfer belt 21 is an endless belt made of a material in which a resistance modifier such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin. The belt support roll 22 is configured as a drive roll. The belt support roll 23 is configured as a surface-setting roll that holds the running position of the intermediate transfer belt 21. The belt support roll 24 is configured as a sensor roll on which a sensor (not shown) is opposed. The belt support roll 25 is configured as a backup roll for secondary transfer.

[0039] The secondary transfer device 30 includes a secondary transfer roll 31 that rotates at the secondary transfer position T2, which is the outer circumferential surface portion of the intermediate transfer belt 21 supported by the belt support roll 25 in the intermediate transfer device 20. A DC voltage with opposite or same polarity as the charge polarity of the toner is supplied to the secondary transfer roll 31 or the belt support roll 25 of the intermediate transfer device 20 as the secondary transfer voltage.

[0040] The fixing device 40 is composed of a heating roll 41 and a pressure belt 42, among other components. The heating roll 41 is heated by a heating source so that its surface temperature is maintained at a predetermined temperature. The pressure belt 42 rotates while in contact with the heating roll 41 at the required pressure. In this fixing device 40, the contact area where the heating roll 41 and the pressure belt 42 come into contact becomes the fixing processing unit N, which performs the required fixing process (heating and pressurization). The fixing device 40 will be described in detail later.

[0041] The paper feeder 50 is positioned below the image creation device 10 (Y, M, C, K) along the vertical Z direction. This paper feeder 50 mainly consists of a paper container 52 and a paper feeder 53. The paper container 52 stores recording paper 5 of the desired size and type, stacked on a stacking plate 51. The paper feeder 53 feeds the recording paper 5 one sheet at a time from the paper container 52. The paper container 52 is mounted so that it can be pulled out, for example, from the front side (the side that the user faces when operating) of the device body 1a.

[0042] Examples of recording paper 5 include thin paper such as plain paper or tracing paper used in electrophotographic copiers and printers, or OHP sheets made of a transparent film-like medium made of synthetic resin (such as PET). To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 5 be as smooth as possible. For this reason, so-called thick paper with a relatively large basis weight, such as coated paper made by coating the surface of plain paper with resin, or art paper for printing, can also be suitably used as recording paper 5.

[0043] A paper feed transport path 57 is provided between the paper feed device 50 and the secondary transfer device 30. The paper feed transport path 57 consists of one (or more) pairs of paper transport rolls 54 and transport guide members 55, 56 that transport the recording paper 5 fed from the paper feed device 50 to the secondary transfer position T2. ​​The pair of paper transport rolls 54 positioned immediately before the secondary transfer position T2 in the paper feed transport path 57 is configured, for example, as a register roll to adjust the transport timing of the recording paper 5.

[0044] Furthermore, a paper transport path 59 is provided between the secondary transfer device 30 and the fixing device 40. The paper transport path 59 consists of transport guide members 58 and the like that transport the recording paper 5 fed out from the secondary transfer device 30 to the fixing device 40.

[0045] A discharge transport path 65 is provided downstream of the fuser 40. The discharge transport path 65 includes a pair of paper transport rolls 61 and 62, as well as transport guide materials 63, 64, etc., for discharging the recording paper 5, on which the toner image has been fixed by the fuser 40, to the paper discharge section 60 located at the top of the main body 1a of the device.

[0046] In Figure 1, reference numeral 100 denotes a control device as an example of a control means that comprehensively controls the operation of the image forming apparatus 1.

[0047] <Basic operation of an image forming apparatus> The following describes the basic image forming operation of the image forming apparatus 1.

[0048] This section describes the image formation operation when forming a full-color image by combining four toner images (Y, M, C, K) using the four imaging devices 10 (Y, M, C, K). The image formation operation is basically the same when forming an image by combining monochrome or multi-color toner images using one or more of the four imaging devices 10 (Y, M, C, K).

[0049] When the image forming apparatus 1 receives command information requesting an image forming operation (printing), the control device 100 controls the four image forming devices 10 (Y, M, C, K), the intermediate transfer device 20, the secondary transfer device 30, the fixing device 40, etc. to start up.

[0050] Then, in each imaging apparatus 10 (Y, M, C, K), each photoreceptor drum 11 first rotates in the direction indicated by arrow A. Each charging apparatus 12 charges the surface of each photoreceptor drum 11 to the required polarity (negative polarity in Embodiment 1) and potential. Subsequently, the exposure apparatus 13 irradiates the charged surface of the photoreceptor drum 11 with light emitted based on the image signal obtained by converting the image information input to the image forming apparatus 1 into each color component (Y, M, C, K). Electrostatic latent images of each color component, each composed of a required potential difference, are formed on the surface of the photoreceptor drum 11.

[0051] Next, each developing device 14 supplies toner of the corresponding color (Y, M, C, K), which is charged with the required polarity (negative polarity), to the electrostatic latent image of each color component formed on the photoreceptor drum 11, and electrostatically deposits it to develop the image. Through this development, the electrostatic latent image of each color component formed on each photoreceptor drum 11 is revealed as four toner images of the corresponding colors (Y, M, C, K), which have been developed with the toner of the corresponding color.

[0052] Next, the toner images of each color formed on the photoreceptor drum 11 of each imaging device 10 (Y, M, C, K) are transported to the primary transfer position T1. Then, the primary transfer device 15 performs a primary transfer, sequentially overlapping the toner images of each color onto the intermediate transfer belt 21 of the intermediate transfer device 20, which rotates in the direction indicated by arrow B.

[0053] Furthermore, in each imaging apparatus 10 (Y, M, C, K) where the primary transfer has been completed, the drum cleaning device 16 cleans the surface of the photoreceptor drum 11 by scraping off any adhering material. This prepares each imaging apparatus 10 (Y, M, C, K) for the next imaging operation.

[0054] Next, the intermediate transfer device 20 holds the toner image transferred in the first stage by the rotation of the intermediate transfer belt 21 and transports it to the secondary transfer position T2. ​​Meanwhile, the paper feed device 50 feeds the required recording paper 5 into the paper feed transport path 57 in accordance with the image formation operation. In the paper feed transport path 57, a pair of paper transport rolls 54 acting as registration rolls feeds and supplies the recording paper 5 to the secondary transfer position T2 in accordance with the transfer timing.

[0055] At the secondary transfer position T2, the secondary transfer roll 31 transfers the toner image on the intermediate transfer belt 21 onto the recording paper 5 in one go. After the secondary transfer is completed, the belt cleaning device 26 in the intermediate transfer device 20 cleans the surface of the intermediate transfer belt 21 by removing any toner or other deposits remaining after the secondary transfer.

[0056] Next, the recording paper 5, on which the toner image has been secondarily transferred, is peeled off from the intermediate transfer belt 21 and the secondary transfer roll 31 and then transported along the paper transport path 59 to the fuser device 40. In the fuser device 40, the recording paper 5 after secondary transfer is introduced and passed through the fuser processing section N between the rotating heating roll 41 and the pressure belt 42. This performs the necessary fuser processing (heating and pressurizing) to fix the unfixed toner image to the recording paper 5. After the fuser is complete, the recording paper 5 is discharged via the discharge transport path 65 by a pair of paper discharge rolls 62 to the paper discharge section 60 located at the top of the device body 1a.

[0057] Through the above process, a full-color image is output, formed by combining toner images consisting of four toner colors (Y, M, C, K).

[0058] <Configuration of the fixing device> Figure 2 is a cross-sectional view showing the entire fixing device according to this embodiment 1. The fixing device 40 according to this embodiment 1 is a so-called free-belt nip fuser (FBNF) type fixing device.

[0059] As shown in Figure 2, the fixing device 40 includes a device housing 43 as an example of a housing. Inside the device housing 43, a heating roll 41 as an example of a rotating body and a pressure belt 42 as an example of an endless belt are arranged in a state of being pressed together at the fixing processing section N, which is a pressure contact section.

[0060] As shown in Figure 3, the apparatus housing 43 is composed of a first support frame 431, a second support frame 432, and an outer cover (not shown) that covers the outer circumference of the first and second support frames 431 and 432. The first support frame 431 rotatably supports both ends of the heating roll 41 along its axial direction. The second support frame 432 rotatably supports both ends of the pressure belt 42 along its longitudinal direction (width direction). The second support frame 432 is rotatably mounted to the first support frame 431 around a pivot point 433. In Figure 3, the numeral S indicates a coil spring provided between the second support frame 432 and the first support frame 431. The coil spring S is an example of a biasing means that presses the pressure belt 42, held by the second support frame 432, against the heating roll 41.

[0061] As shown in Figure 2, the device housing 43 has an inlet 434 on its lower end surface for introducing recording paper 5 on which an unfixed toner image T has been transferred. Inside the inlet 434, a guide plate 435 is positioned at an angle upward. The guide plate 435 guides the recording paper 5 to the fixing section N where the heating roll 41 and the pressure belt 42 make contact. The device housing 43 also has an outlet 436 at the left end of its upper end surface. The outlet 436 discharges the recording paper 5, which has been fixed by the heating roll 41 and the pressure belt 42, to the outside. An outlet roll (not shown) is rotatably provided in the outlet 436 as needed to transport the recording paper 5 to the outside of the device housing 43. The recording paper 5 is transported with the center along the depth direction Y, which intersects the transport direction, as the reference point (so-called center register).

[0062] A rod-shaped actuator 438 is provided in a transport passage 437 formed between the fixing section N and the discharge port 436 of the fixing device 40, so as to be rotatable clockwise around a pivot point 438a. The actuator 438 is rotated by the recording paper 5 passing through the transport passage 437 and is an example of a detection means for detecting the passage of the recording paper 5. The rotational movement of the actuator 438 is detected as the passage of the recording paper 5 by an optical sensor or the like (not shown).

[0063] As shown in Figure 2, the fixing device 40 is broadly composed of a heating roll 41 and a pressure unit 44 that holds a pressure belt 42 that is pressed against the heating roll 41.

[0064] As shown in Figure 4, the heating roll 41 has a cylindrical core 411, an elastic layer 412, and a release layer 413. The core 411 is made of a metal such as stainless steel, aluminum, or iron (thin-walled high-tensile steel pipe). The core 411 is formed in a relatively thin-walled cylindrical shape, and its heat capacity is set to be significantly small. The elastic layer 412 is made of a heat-resistant elastic material such as silicone rubber or fluororubber, which is coated on the outer circumference of the core 411. The elastic layer 412 is also formed in a relatively thin-walled cylindrical shape, which contributes to reducing the heat capacity of the heating roll 41. The release layer 413 is made of polytetrafluoroethylene (PTFE) or perfluoroalkoxyalkane (PFA), etc., which is thinly coated on the surface of the elastic layer 412. Inside the heating roll 41, two halogen lamps 414a and 414b are arranged as an example of a heat source. The two halogen lamps 414a and 414b are configured such that their heating regions differ along the depth direction Y perpendicular to the drawing. For example, halogen lamp 414a has a heating region set in the central part along the axial direction of the heating roll 41, corresponding to the length along the shorter side of an A4 size recording sheet 5. Halogen lamp 414b has heating regions set in areas corresponding to both ends along the axial direction of the heating roll 41. Note that the number of halogen lamps 414a and 414b is not limited to two; there may be only one.

[0065] As shown in Figure 3, the heating roll 41 is rotatably supported at both ends along its longitudinal direction (axial direction) by bearing members 439 on the first support frame 431 of the device housing 43. The heating roll 41 is rotated at a required speed in the direction of arrow C by a drive motor (not shown) on the device body 1a side, via a drive force transmission gear 415 (see Figure 2) that meshes with a drive gear (not shown) attached to one end along the axial direction. The pressure belt 42 rotates by being pressed against the rotating heating roll 41 at the fixing section N.

[0066] The rotation speed of the heating roll 41, i.e., the fixing speed, may be set to one of several speeds, such as high speed, medium speed, or low speed, depending on the basis weight and material of the recording paper 5.

[0067] The heating roll 41 has its surface temperature detected by a temperature sensor (not shown). Based on the temperature sensor's detection result, the power supply to the halogen lamps 414a and 414b is controlled by a temperature control circuit (not shown) using a triac or the like. As a result, the heating roll 41 is maintained so that its surface reaches the required fixing temperature.

[0068] On the other hand, the pressurizing unit 44, as shown in Figure 4, comprises a pressurizing belt 42, a pressure contact holding member 45, first and second support members 46, 47, a guide member 48, a sliding sheet 49, and first and second felt members 70, 71. The pressure contact holding member 45 combines the functions of a pressure contact portion and a holding portion. The pressure contact holding member 45 is positioned inside the pressurizing belt 42 and has a first pressure contact portion 451 that presses the pressurizing belt 42 against the surface of the heating roll 41. The pressure contact holding member 45 is also positioned inside the pressurizing belt 42 and has a holding portion 452 that holds the pressurizing belt 42 at its upstream end along the direction of movement of the pressurizing belt 42. The first and second support members 46, 47 support the pressure contact holding member 45 so that it can be pressed against the surface of the heating roll 41. The guide member 48 rotatably guides both ends of the pressurizing belt 42 along its longitudinal direction. The sliding sheet 49 is interposed between the pressure belt 42 and the pressure contact holding member 45 to reduce sliding resistance. The first and second felt members 70 and 71 are positioned inside the pressure belt 42 and hold the lubricant applied to the inner circumferential surface of the pressure belt 42.

[0069] The pressure belt 42 is made of a flexible material and, in its free shape before installation, is configured as an endless belt with a thin-walled cylindrical shape. The pressure belt 42 comprises, for example, a base layer, an elastic layer coated on the surface of the base layer, and a release layer coated on the surface of the elastic layer. Alternatively, the pressure belt 42 may consist of a base layer and a release layer directly coated on the surface of the base layer. The base layer is made of a heat-resistant synthetic resin such as polyimide, polyamide, or polyimidoamide, or a metal such as stainless steel, nickel, or copper. The elastic layer is made of an elastic material such as heat-resistant silicone rubber or fluororubber. The release layer is made of polytetrafluoroethylene (PTFE) or perfluoroalkoxyalkane (PFA), etc. The thickness of the pressure belt 42 can be set to, for example, about 50 to 200 μm.

[0070] As shown in Figure 5, the pressure-fitting holding member 45 is made of a heat-resistant synthetic resin that is integrally molded into the required shape by, for example, injection molding. Examples of heat-resistant synthetic resins include liquid crystal polymer (LCP), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyethersulfone (PES), polyamideimide (PAI), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), or composite materials thereof.

[0071] As shown in Figure 4, the pressure-contacting holding member 45 is positioned at the downstream end of the pressure belt 42 in the fixing section N along the rotational direction, and includes a first pressure-contacting portion 451 that presses the pressure belt 42 against the surface of the heating roll 41. As shown in Figure 5, the first pressure-contacting portion 451 is arranged along substantially the entire length in the longitudinal direction (width direction), which is the direction intersecting the movement direction of the pressure belt 42. The first pressure-contacting portion 451 protrudes toward the surface of the heating roll 41 and has a pressure-contacting surface 451a that is pressed against the heating roll 41 via the pressure belt 42 and the sliding sheet 49. The first pressure-contacting portion 451 is formed to be relatively thicker than other parts. A groove 453 is formed in the first pressure-contacting portion 451 along the longitudinal direction. The tip of the first support member 46 is fitted into the groove 453. The contact surface 451a of the first contact portion 451 is composed of a first contact surface 451a' and a second contact surface 451a''. The first contact surface 451a' is formed in a curved shape with a curved end on the downstream side along the direction of movement of the pressure belt. The second contact surface 451a'' is formed in a planar shape located upstream of the first contact surface 451a' along the direction of movement of the pressure belt 42.

[0072] The pressure-welding holding member 45 integrally includes a second pressure-welding portion 454 on the upstream side of the first pressure-welding portion 451 along the direction of movement of the pressure belt 42. The second pressure-welding portion 454 is formed in an arc-shaped or curved shape, spaced a required distance from the surface of the heating roll 41. As shown in Figure 4, a sheet-like elastic member 455 made of an elastic material such as silicone rubber foam having a required thickness is disposed on the inner surface of the second pressure-welding portion 454. The elastic member 455, together with the first pressure-welding portion 451, constitutes a fixing section N by pressing the pressure belt 42 against the surface of the heating roll 41.

[0073] In the fixing device 40 according to this embodiment 1, as described above, the fixing section N is composed of an elastic member 455 disposed on the first pressure contact portion 451 and the second pressure contact portion 454 of the pressure contact holding member 45. In particular, the elastic member 455 disposed on the second pressure contact portion 454 is provided along the surface of the heating roll 41 over a required central angle θ (40 to 60 degrees). Therefore, the fixing device 40 has a significantly larger area of ​​the fixing section N compared to conventional fixing devices. As a result, the fixing device 40 according to this embodiment 1 can obtain sufficient pressure contact force and achieve good fixing performance even when the pressure contact force per unit area in the fixing section N is reduced.

[0074] Furthermore, the pressure contact holding member 45 is positioned inside the pressure belt 42 on the upstream side of the second pressure contact portion 454 along the direction of movement of the pressure belt 42, and integrally includes a holding portion 452 that holds the pressure belt 42 at the upstream end of the first pressure contact portion 451 along the direction of movement of the pressure belt 42.

[0075] As shown in Figure 4, the holding portion 452 of the pressure-contacting holding member 45 is formed in an arc shape or curved shape so as to be spaced slightly radially outward from the surface of the heating roll 41, compared to the second pressure-contacting portion 454. The tip 452a of the holding portion 452 is formed in an arc shape in cross-section so as to be able to smoothly hold the inner circumferential surface of the pressure belt 42.

[0076] The first and second support members 46 and 47 are made of metal plates such as stainless steel, aluminum, or steel. In the illustrated embodiment, the first support member 46 is formed to be thicker than the second support member 47. As shown in Figures 4 and 6, the first support member 46 is formed in an L-shape in cross-section from a vertical plate portion 461 and a horizontal plate portion 462. The vertical plate portion 461 is positioned substantially perpendicular to the surface of the heating roll 41. The horizontal plate portion 462 is bent in a direction intersecting the base end of the vertical plate portion 461. The vertical plate portion 461 of the first support member 46 is positioned along a first straight line L1 that passes through the center O of the heating roll 41 and extends radially. The second support member 47 is formed in an L-shape in cross-section from a vertical plate portion 471 and a horizontal plate portion 472. The vertical plate portion 471 is positioned parallel to the vertical plate portion 461 of the first support member 46. The horizontal plate portion 472 is bent in a direction that intersects with the base end of the vertical plate portion 471. The horizontal plate portion 462 of the first support member 46 and the horizontal plate portion 472 of the second support member 47 are arranged to face each other with a gap in between.

[0077] As shown in Figures 3 and 6, the first and second support members 46 and 47 are fixed in place with protrusions 463, 464, 473, and 474, which are provided to protrude from both ends along the longitudinal direction of the vertical plate portions 461 and 471, fitted into the openings 432a and 432b of the second support frame 432.

[0078] As shown in Figures 3 and 4, the second support member 47 is positioned such that the tips of the vertical plate portions 461 and 471 abut against a plurality (eight in the illustrated example) of contact portions 456, 456... provided on the back surface of the second pressure contact portion 454 of the pressure contact holding member 45.

[0079] To explain further, the second pressure contact portion 454 of the pressure contact holding member 45 has a plurality of contact portions 456, 456... integrally provided on its back surface along the longitudinal direction. As shown in Figure 4, the pressure contact holding member 45 is positioned and fixed by fitting the tip of the vertical plate portion 461 of the first support member 46 into a groove 453 provided on the back surface of the first pressure contact portion 451.

[0080] Furthermore, as described above, the second pressure contact portion 454 of the pressure contact holding member 45 is pressed against the surface of the heating roll 41 via the elastic member 455, by the tip of the vertical plate portion 471 of the second support member 47 contacting the contact portions 456, 456...

[0081] As shown in Figure 4, the base end of the sliding seat 49 is locked to the tip of the contact portion 456, 456... of the pressure-contact holding member 45 by locking pins 457, 457...

[0082] Furthermore, the second pressure contact portion 454 of the pressure contact holding member 45 is provided with a plurality of guide portions 458, 458... (four in the illustrated example) as shown in Figures 3 and 5. The plurality of guide portions 458, 458... are positioned between adjacent contact portions 456, 456... of the pressure contact holding member 45. The plurality of guide portions 458, 458... guide the back surface of the base end of the sliding seat 49, whose base end is locked to the contact portion 456, 456..., away from the second pressure contact portion 454 and guide it to the holding portion 452 of the pressure contact holding member 45.

[0083] As shown in Figure 4, the horizontal plate portions 462 and 472 of the first and second support members 46 and 47 are provided with first and second felt members 70 and 71 on their outer surfaces by means of adhesion or other means. The first and second felt members 70 and 71 elastically deform when tension is applied to the pressure belt 42 by the driven rotation of the pressure belt 42, thereby supporting the pressure belt 42. For convenience, Figure 4 shows the rectangular cross-section of the first and second felt members 70 and 71 before elastic deformation.

[0084] The first and second felt members 70 and 71 are impregnated with a predetermined amount of lubricant to be supplied to the inner circumferential surface of the pressure belt 42. For example, an amino-modified silicone oil with a viscosity of 100 to 350 cs can be used as the lubricant. The lubricant is supplied to the inner circumferential surface of the pressure belt 42 by pre-impregnating the first and second felt members 70 and 71. However, this is not the only option; the system may be configured to supply the lubricant already applied to the inner circumferential surface of the pressure belt 42.

[0085] The sliding sheet 49 consists of an elongated, planar rectangular sheet. For example, the sliding sheet 49 may have a base layer made of a fluororesin such as polytetrafluoroethylene (PTFE), and a structure consisting of a woven or knitted fabric made of aramid fibers laminated on the surface or both sides of the base layer. As shown in Figure 4, the tip of the sliding sheet 49 extends to the upper part of the first pressure contact portion 451 of the pressure contact holding member 45.

[0086] Incidentally, in the conventional fixing device 40, as shown in Figure 7(a), the tip of the holding portion 452 of the pressure contact holding member 45 holds the pressure belt 42 in a straight line along the width direction intersecting the direction of movement of the pressure belt 42. In this fixing device 40, the recording paper 5 is transported perpendicular to the width direction intersecting the direction of movement of the pressure belt 42, so that the direction of travel of the recording paper 5 and the direction of movement of the pressure belt 42 coincide. At this time, the recording paper 5 is transported at a uniform transport speed in the width direction intersecting the direction of movement. Therefore, the recording paper 5 passes through the fixing processing unit N where the heating roll 41 and the pressure belt 42 are pressed together and undergoes fixing processing without any paper wrinkles occurring on the recording paper 5.

[0087] On the other hand, in conventional fixing devices 40, as shown in Figure 7(b), the recording paper 5 may be transported in a state inclined with respect to the width direction intersecting the direction of movement of the pressure belt 42 of the pressure contact holding member 45. In this case, in this fixing device 40, the direction of travel of the recording paper 5 before it enters the fixing processing unit N is different from the direction of travel of the recording paper 5 when it is transported through the fixing processing unit N by the pressure belt 42. As a result, the direction of travel of the recording paper 5 when it passes through the pressure contact holding member 45 is forcibly changed to a direction intersecting the previous direction of travel. Therefore, the recording paper 5 passing through the pressure contact holding member 45, which is the fixing processing unit N, is subjected to a compressive force F in a direction intersecting the direction of travel, resulting in a technical problem of paper wrinkling. This paper wrinkling of the recording paper 5 is particularly noticeable when the recording paper 5 is thin paper with relatively low basis weight, i.e., the rigidity of the recording paper 5.

[0088] Therefore, the fixing device according to this embodiment is configured to be positioned inside the belt and to include a holding portion that holds both ends of the belt in the width direction intersecting the direction of movement upstream of the belt in the direction of movement of the pressure contact portion, upstream of the central portion.

[0089] Furthermore, in this embodiment of the fixing device, the holding portion is configured to be integrally provided with the pressure-contact portion on the upstream side along the direction of movement of the belt of the pressure-contact portion.

[0090] Furthermore, in this embodiment of the fixing device, the holding portion is positioned at the upstream end along the direction of movement of the belt, and the portion that holds the belt is formed in a concave shape.

[0091] In other words, as shown in Figure 4, the fixing device 40 according to this embodiment 1 is positioned inside the pressure belt 42 and holds an elastic member 455 to press the pressure belt 42 against the heating roll 41, and also includes a pressure contact holding member 45 which is integrally provided with the pressure contact portions 451 and 454 on the upstream side of the first and second pressure contact portions 451 and 454 along the direction of movement of the pressure belt 42 and has a holding portion 452 for holding the pressure belt 42.

[0092] As shown in Figures 5 and 8, the holding portion 452 of the pressure-contact holding member 45 is formed in a concave shape at its tip 452a, which is the upstream end along the direction of movement of the pressure belt 42. At this tip 452a, both ends 452a', which are an example of a first portion along the width direction intersecting the direction of movement of the pressure belt 42, are connected by a curved line so that they are located upstream along the direction of movement of the pressure belt 42 compared to the central portion 452a'', which is an example of a second portion. The upstream tip 452a of the holding portion 452 is formed in a symmetrical concave shape with respect to the center along the width direction intersecting the direction of movement of the pressure belt 42. The concave shape of this holding portion 452 is set to have a required radius of curvature or curved shape.

[0093] As shown in Figure 4, the pressure belt 42 moves in the fixing section N while being pressed against the outer surface of the heating roll 41, thereby applying the required tension. The upstream end of the pressure belt 42, along its direction of movement, is held by the holding portion 452 of the pressure contact holding member 45. Therefore, as shown in Figure 8, when the pressure belt 42 moves through the fixing section N, its upstream end, along its direction of movement, conforms to the concave shape of the tip 452a of the holding portion 452 of the pressure contact holding member 45.

[0094] After passing through the holding portion 452 of the pressure contact holding member 45, the pressure belt 42 moves in the fixing processing unit N while being pressed against the surface of the heating roll 41 by the second pressure contact portion 454 and the first pressure contact portion 451 of the pressure contact holding member 45.

[0095] In this case, the tip 452a of the holding portion 452 of the pressure-contacting holding member 45 is formed in a concave shape, as shown in Figure 8. Therefore, when the pressure belt 42 passes through the fixing treatment section N, the distance that both ends along the longitudinal direction need to travel is longer than that of the central part, due to the concave shape of the holding portion 452 of the pressure-contacting holding member 45. As a result, the movement speed of both ends along the longitudinal direction of the pressure belt 42 is relatively faster than that of the central part.

[0096] <Operation of the fixing device> In the above configuration, the fixing device according to this embodiment 1 is a fixing device that presses an endless belt against a rotating body with a pressure contact portion arranged inside, and is provided with a holding portion that holds the belt upstream of the pressure contact portion along the direction of belt movement, and compared to the case in which the holding portion holds the belt linearly along the width direction intersecting the direction of belt movement, it is possible to suppress the occurrence of wrinkles in the recording medium.

[0097] In other words, as shown in Figure 4, when the fixing device 40 according to this embodiment 1 is started, the halogen lamps 414a and 414b placed inside the heating roll 41 are energized, and the surface of the heating roll 41 is heated to a predetermined fixing temperature.

[0098] When the heating roll 41 is rotated in the fixing device 40, the pressure belt 42, which is pressed against the surface of the heating roll 41 in the fixing unit N, is also rotated in conjunction with the rotation of the heating roll 41. The pressure belt 42 is pressed against the surface of the heating roll 41 by the first and second pressure contact portions 451 and 454 of the pressure contact holding member 45, and is also held by the holding portion 452 of the pressure contact holding member 45.

[0099] At this time, the holding portion 452 of the pressure contact holding member 45 is formed in a curved concave shape such that its tip 452a is located upstream along the direction of movement of the pressure belt 42, while both ends 452a' are located upstream along the direction of movement of the pressure belt 42, compared to the central portion 452a''. As a result, as the pressure belt 42 is pressed against the surface of the heating roll 41 from the tip 452a of the holding portion 452 of the pressure contact holding member 45 and moves to the second and first pressure contact portions 454 and 451, the movement speed of both ends is faster than that of the central portion, which is in the width direction intersecting the direction of movement.

[0100] Now, in the fixing device 40 according to this embodiment 1, let's assume that the recording paper 5 enters the fixing device 40 at an inclination relative to the pressure-holding member 45, as shown in Figure 9. Then, the recording paper 5 is held and transported by the heating roll 41 and the pressure belt 42 in the fixing section N formed by the pressure-holding member 45. At that time, the central part of the pressure belt 42, which is the width direction intersecting its direction of movement, moves at a speed V c Movement speed V at both ends E The paper moves in a way that increases speed. Therefore, as the recording paper 5 passes through the fixing processing unit N formed by the pressure-holding member 45, it is transported while an expanding force acts on it, causing it to expand from the center along the width direction towards both ends.

[0101] Therefore, in the fixing device 40 according to this embodiment 1, even when the recording paper 5 enters the fixing processing unit N at an angle, the occurrence of paper wrinkles on the recording paper 5 is prevented or suppressed.

[0102] Furthermore, in this embodiment 1, the fixing device 40 has a curved shape for the holding portion 452 of the pressure contact holding member 45 that holds the pressure belt 42. Therefore, compared to cases where the outer diameter of the heating roll 41 is made larger at both ends along the axial direction than at the center, or where the central part along the axial direction of the pressure contact portion that presses against the heating roll 41 protrudes more than at both ends, the shape of the fixing processing unit N is not affected. As a result, it is possible to avoid the image on the recording paper 5 being affected, such as the fixing performance of the central part along the axial direction of the heating roll 41 being reduced compared to both ends.

[0103] Furthermore, the fixing device 40 according to this embodiment 1 only requires changing the shape of the holding portion 452 of the pressure-contact holding member 45. Therefore, compared to cases where the outer diameter is changed by appropriately setting the thickness of the elastic layer 412 of the heating roll 41, it is possible to avoid an increase in the manufacturing cost of the heating roll 41 and the like.

[0104] <Example of experiment> The inventors conducted an experiment to confirm the effects of the fixing device 40 according to the above Embodiment 1. As the fixing device 40, as shown in FIGS. 4 and 5, a prototype in which the tip 452a of the holding portion 452 in the pressure-contact holding member 45 is formed in a curved shape was used. Also, as the recording paper 5, A4-sized tracing paper with a basis weight of 49 g / m 2 , 54 g / m 2 , 60 g / m 2 was used respectively. As shown in FIG. 9, the recording paper 5 was conveyed while being inclined obliquely with respect to the normal conveyance direction, and an experiment was conducted to check whether paper wrinkles occurred. Note that the basis weight of plain paper is usually 64 to 68 g / m 2 . Therefore, tracing papers with basis weights of 49 g / m 2 , 54 g / m 2 , and 60 g / m 2 correspond to so-called thin papers that are likely to develop paper wrinkles. Also, as a comparative example, as shown in FIG. 7, the presence or absence of paper wrinkle generation was confirmed using a conventional fixing device 40 in which the holding portion 452 of the pressure-contact holding member 45 is formed linearly along the width direction intersecting the conveyance direction of the recording paper.

[0105] FIG. 10 is a chart showing the results of the above experimental examples and comparative examples.

[0106] As is clear from FIG. 10, in the fixing device 40 according to this Embodiment 1, regardless of which tracing paper with a basis weight of 49 g / m 2 , 54 g / m 2 , or 60 g / m 2 was used, no paper wrinkles occurred.

[0107] On the other hand, in the fixing device 40 according to the comparative example, when tracing paper with a relatively large basis weight of 60 g / m 2 was used, no paper wrinkles occurred. However, when tracing papers with basis weights of 49 g / m 2 and 54 g / m 2 were used, paper wrinkles occurred.

[0108] Thus, in the case of the fixing device 40 according to Embodiment 1 described above, the basis weight is 49 g / m². 2 54g / m 2 60g / m 2 It was found that wrinkles in the paper could be prevented regardless of which tracing paper was used.

[0109] Although the above embodiment described the case where the method is applied to a full-color image forming apparatus, it goes without saying that it can also be applied to a monochrome image forming apparatus in the same way.

[0110] Furthermore, in the above embodiment, the holding portion of the pressure-contact holding member was described as having a first portion that contacts both ends along the width direction of the belt and a second portion that contacts the central portion along the width direction of the belt, connected by a curve. However, it is not limited to this, and the first portion and the second portion may be connected by a straight line, or by a combination of a straight line and a curve.

[0111] (Note) (((1))) A rotating body heated by a heat source, An endless belt that rotates while being pressed against the aforementioned rotating body at the pressure contact portion, A holding portion is disposed inside the belt and, on the upstream side of the pressing portion along the direction of movement of the belt, holds both ends of the belt along the width direction intersecting the direction of movement, on the upstream side of the central portion. A fixing device equipped with the following features. (((2))) The fixing device according to (((1))), wherein the holding portion is integrally provided with the pressure contact portion on the upstream side of the pressure contact portion along the direction of movement of the belt. (((3))) The fixing device according to (((2))), wherein the holding portion is arranged at the upstream end along the direction of movement of the belt, and the portion that holds the belt is formed in a concave shape. (((4))) The fixing device according to (((1))), wherein the retaining portion has a first portion that contacts both ends of the belt along the width direction and a second portion that contacts the central portion of the belt along the width direction, and the first portion is located upstream of the second portion along the direction of movement of the belt. (((5))) The fixing device according to (((4))), wherein the holding portion is formed by connecting the first portion and the second portion with a curve. (((6))) The fixing device according to (((1))), wherein the pressure contact portion has a first pressure contact portion that directly presses the belt against the rotating body at the downstream end of the belt in the direction of movement of the belt, and a second pressure contact portion that presses the belt against the rotating body via an elastic member upstream of the first pressure contact portion in the direction of movement of the belt. (((7))) The fixing device according to (((6))), wherein the holding portion is arranged upstream of the second pressure contact portion along the direction of movement of the belt. (((8))) The fixing device according to (((7))), wherein the holding portion is arranged to be spaced apart radially outward from the outer circumferential surface of the rotating body. (((9))) Image forming means for forming an image on a recording medium, Fixing means for fixing the image onto the recording medium, Equipped with, An image forming apparatus using a fixing device as described in any of (((1))) to (((8))) as the fixing means.

[0112] According to the fixing device described in (((1))), in a fixing device that presses an endless belt against a rotating body with a pressure contact portion arranged inside, the fixing device is equipped with a holding portion that holds the belt upstream of the pressure contact portion along the direction of belt movement, and compared to the case in which the holding portion holds the belt in a straight line along the width direction intersecting the direction of belt movement, it is possible to suppress the occurrence of wrinkles in the recording medium. According to the fixing device described in (((2))), the position of the holding part can be maintained with greater precision compared to the case in which the holding part is provided separately from the pressure contact part. According to the fixing device of (((3))), the holding portion can hold the belt more smoothly compared to the case where the portion that holds the belt is formed in a V shape. According to the fixing device of (((4))), the holding portion can more reliably prevent wrinkles from forming on the recording medium compared to the case where the first portion that contacts both ends along the width direction of the belt and the second portion that contacts the central part along the width direction of the belt are in the same position along the direction of movement of the belt. According to the fixing device of (((5))), the holding part can more reliably prevent wrinkles from forming on the recording medium compared to the case where the first part and the second part are connected in a straight line. According to the fixing device described in (((6))), the fixing nip portion can be set wider compared to the case in which the pressure contact portion is provided only with a first pressure contact portion that directly presses the belt against the rotating body at the downstream end in the direction of movement of the belt, thereby improving fixing performance. According to the fixing device of (((7))), the holding portion can avoid the application of a force that deforms the belt unstably, compared to the case where the holding portion is positioned at the same location as the second pressure contact portion along the direction of belt movement. According to the fixing device of (((8))), the holding part can suppress the buckling force acting on the belt compared to when it is positioned close to the outer surface of the rotating body. According to the image forming apparatus described in (((9))), wrinkles can be suppressed in the recording medium compared to the case in which no fixing apparatus described in any of (((1))) to (((8))) is used as the fixing means. [Explanation of Symbols]

[0113] 1…Image forming apparatus 1a...Main unit of the device 11…Photoconductor drum 40… Fixing device 41...Heated Roll 42…Compression belt 45...Pressure-welded holding member 451...First pressure-welded section 452...Holding part 452a...Tip of the holding part 454...Second pressure-welded section

Claims

1. A rotating body heated by a heat source, An endless belt that rotates while being pressed against the aforementioned rotating body at the pressure contact portion, A holding portion is disposed inside the belt and, on the upstream side of the pressing portion along the direction of movement of the belt, holds both ends of the belt along the width direction intersecting the direction of movement, on the upstream side of the central portion. A fixing device equipped with the following features.

2. The fixing device according to claim 1, wherein the holding portion is integrally provided with the pressure contact portion on the upstream side of the pressure contact portion along the direction of movement of the belt.

3. The fixing device according to claim 2, wherein the holding portion is positioned at the upstream end along the direction of movement of the belt, and the portion that holds the belt is formed in a concave shape.

4. The fixing device according to claim 1, wherein the retaining portion has a first portion that contacts both ends of the belt along the width direction and a second portion that contacts the central portion of the belt along the width direction, and the first portion is located upstream of the second portion along the direction of movement of the belt.

5. The fixing device according to claim 4, wherein the holding portion is formed by connecting the first portion and the second portion with a curve.

6. The fixing device according to claim 1, wherein the pressure contact portion comprises a first pressure contact portion that directly presses the belt against the rotating body at the downstream end of the belt in the direction of movement of the belt, and a second pressure contact portion that presses the belt against the rotating body via an elastic member upstream of the first pressure contact portion in the direction of movement of the belt.

7. The fixing device according to claim 6, wherein the holding portion is arranged upstream of the second pressure contact portion along the direction of movement of the belt.

8. The fixing device according to claim 7, wherein the holding portion is arranged to be spaced apart radially outward from the outer circumferential surface of the rotating body.

9. Image forming means for forming an image on a recording medium, Fixing means for fixing the image onto the recording medium, Equipped with, An image forming apparatus using the fixing device described in any one of claims 1 to 8 as the fixing means.

Images