Fixing apparatus and image forming apparatus

Abstract

In the fixing device, this prevents a portion of the elastic member forming the upstream nip from riding up onto the top surface of the raised portion forming the downstream nip. [Solution] The fixing device 5 comprises a rotating body (heating roll 51) having a heat source (halogen heater lamp 52), a tubular belt 53 that rotates in contact with the outer circumferential surface of the rotating body, an opposing member 56 positioned on the inner circumferential side of the belt 53 and having an opposing surface 57 facing the outer circumferential surface of the rotating body, a raised portion 58 that is raised at the end of the opposing surface 57 on the downstream side in the rotation direction A of the rotating body, pressing the belt 53 against the outer circumferential surface of the rotating body to form a downstream nip N1, and an elastic member 59 that is attached to the opposing surface 57 in contact with the side surface of the raised portion 58, pressing the belt 53 against the outer circumferential surface of the rotating body to form an upstream nip N2. The raised portion 58 is configured as a recessed corner portion 60 with a recessed corner on the opposing surface 57 side.

Description

Technical Field

[0004] , , , , , , , ,

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

Background Art

[0002] The following Patent Document 1 describes a fixing device having a heating roll, a fixing belt, a first pad, and a second pad. The heating roll is a roll having a heat source. The fixing belt is a rotating endless belt. The first pad is a hard pad that makes the nip pressure uniform in the axial direction on the inner belt support member. The second pad is a soft pad disposed on the inner belt support member on the upstream side in the rotation direction of the fixing belt with respect to the first pad. Also, the second pad has a larger coefficient of friction than the first pad.

[0003] The following Patent Document 2 describes a fixing device including a fixing belt, a fixing belt holding member, a pressure roller, a heat source, a nip forming member, and the like. The fixing belt holding member is a member that holds the fixing belt at both ends. The heat source is a halogen heater or the like that heats the fixing belt. The nip forming member is a pad that contacts the pressure roller through the fixing belt to form a nip. Also, the nip forming member is supported by a nip support member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to prevent a situation in which a part of the elastic member forming the upstream nip in a fixing device rides up onto the top surface of the raised portion forming the downstream nip. [Means for solving the problem]

[0006] A first aspect of the present invention is: A rotating body having a heat source, A tubular belt that rotates in contact with the outer surface of the rotating body, An opposing member is positioned on the inner circumferential surface side of the belt and has an opposing surface facing the outer circumferential surface of the rotating body, A raised portion is formed at the end of the opposing surface that is on the downstream side in the direction of rotation of the rotating body, pressing the belt against the outer circumferential surface of the rotating body to form a downstream nip, An elastic member is attached to the opposing surface in contact with the side surface of the raised portion, and presses the belt against the outer circumferential surface of the rotating body to form an upstream nip, Equipped with, This fixing device is configured such that the corner on the opposite side of the raised portion is a recessed corner.

[0007] A second aspect of the present invention is the fixing device of the first aspect described above, The recessed corner portion is a fixing device that is continuously formed in a direction along the axial direction of the rotating body.

[0008] A third aspect of the present invention is the fixing device of the second aspect described above, The aforementioned recessed corner portion is a fixing device whose cross-sectional shape is the same in the axial direction.

[0009] A fourth aspect of the present invention is the fixing device of the first aspect described above, The aforementioned recessed corner portion is a fixing device formed in a recessed shape on the downstream side in the rotational direction of the rotating body from the side surface of the raised portion.

[0010] A fifth aspect of the present invention is the fixing device of the fourth aspect described above, The aforementioned recessed corner portion is a fixing device in which a portion of the raised portion is recessed to a size of 1 / 3 or less of the height of the raised portion from the opposing surface of the opposing member.

[0011] A sixth aspect of the present invention is an image forming apparatus equipped with a fixing device according to any of the first to fifth aspects described above. [Effects of the Invention]

[0012] According to the fixing device of the first embodiment described above, it is possible to prevent a part of the elastic member that forms the upstream nip from riding up onto the top surface of the raised portion that forms the downstream nip.

[0013] According to the fixing device of the second embodiment described above, it is possible to prevent a part of the elastic member from riding up on the top surface of the raised portion even in the axial direction of the rotating body.

[0014] According to the fixing device of the third embodiment described above, compared to the case where the cross-sectional shape of the recessed corner portion is formed with a different shape in the axial direction, it is possible to reliably prevent a part of the elastic member from riding up on the top surface of the raised portion in the axial direction of the rotating body.

[0015] According to the fixing device of the fourth embodiment described above, even if a part of the elastic member deforms downstream in the rotational direction of the rotating body, the deformed portion of the elastic member can be temporarily accommodated in the recessed space of the recessed corner.

[0016] According to the fixing device of the fifth embodiment described above, compared to the case where the recessed corner is formed in a dimension greater than 1 / 3 of the height raised from the opposing surface of the opposing member of the raised portion, it is possible to keep the elastic member in contact with the side surface of the raised portion while preventing a part of the elastic member from riding up onto the top surface of the raised portion.

[0017] According to the image forming apparatus of the sixth aspect, in the fixing device, it is possible to prevent a part of the elastic member that forms the front pressure nip from riding on the top surface of the raised portion that forms the rear pressure nip, and it is also possible to prevent fixing defects and image quality defects caused by such riding.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic diagram of an image forming apparatus including a fixing device according to Embodiment 1. [Figure 2] It is a schematic cross-sectional view of a fixing device according to Embodiment 1. [Figure 3] It is a schematic cross-sectional view showing an enlarged part of the fixing device in FIG. 2. [Figure 4] (A) is a schematic cross-sectional view of the opposing member, and (B) is a schematic perspective view of a part of the opposing member in (A). [Figure 5] (A) is an explanatory diagram showing a recessed corner, and (B) is an explanatory diagram showing a modified example of the recessed corner. [Figure 6] It is an explanatory diagram showing the riding phenomenon of a part of the elastic member when a raised portion for comparison is adopted, and an enlarged view extracting only the raised portion.

Modes for Carrying Out the Invention

[0019] Hereinafter, modes for carrying out the present invention will be described.

[0020] Embodiment 1. In FIG. 1, an image forming apparatus 10 including a fixing device 5 according to Embodiment 1 is shown. In FIG. 2, the fixing device 5 according to Embodiment 1 is shown.

[0021] In this specification and the drawings, substantially the same components are denoted by the same reference numerals. Also, in this specification, duplicate descriptions of the same components are omitted. In Figure 1, etc., the arrow +X indicates the right direction when viewed from the front of the image forming apparatus 10, and the arrow -X indicates the left direction. Also, the arrow +Y indicates the upward direction of the image forming apparatus 10, and the arrow -Y indicates the downward direction. Furthermore, the symbol +Z indicates the depth direction when viewed from the front of the image forming apparatus 10, and the symbol -Z indicates the forward direction. In addition, the symbol with a "×" inside a "○" in Figure 1, etc., indicates the direction from the front to the back of the drawing. The symbol with a "·" inside a "○" indicates the direction from the back to the front of the drawing.

[0022] (1) Image forming apparatus The image forming apparatus 10 is a device that forms a predetermined image on a sheet of paper 19. An image is a representation that includes visible information such as characters, figures, photographs, and patterns. The image forming apparatus 10 has the image forming apparatus 20, paper feeding apparatus 40, fixing apparatus 5, etc., arranged in the internal space of the housing 11. Furthermore, a power supply device, a rotary drive device, a control device, etc. (not shown) are also arranged inside the housing 11. An operation panel, etc. (not shown) is located outside the housing 11.

[0023] The enclosure 11 is a box-shaped structure having a predetermined external shape and internal space. The enclosure 11 is composed of, for example, a frame, plates, exterior materials, etc. The housing 11 is provided with an output and storage section 12 at its top for ejecting and storing the paper 19 on which the image has been formed. In addition, an output port 13 is provided on the side portion that forms part of the output and storage section 12 for passing the paper 19 through and ejecting it.

[0024] The image forming apparatus 20 is a device capable of forming an unfixed image on the paper 19. As the image forming apparatus 20, for example, an apparatus employing an image forming method such as electrophotography is used. In this case, the image forming apparatus 20 includes an image holder, a charging device, an image exposure device, a developing device, a transfer device, a cleaning device, etc., which are not shown. Furthermore, this image forming apparatus 20 may be either a device that forms a monochrome (e.g., black) image or a device that forms a multicolor (color) image.

[0025] The image holder is a rotating structure, such as a photosensitive drum, that has an image-holding surface capable of holding an image. The charging device is a device that charges the image-holding surface of the image holder. The image exposure apparatus is a device that forms an electrostatic latent image by exposing the charged image-holding surface of an image holder to image information. The image information is information about an image that is input to the image forming apparatus 10 from an external source. A developing device is a device that develops the electrostatic latent image formed on the image-holding surface of an image holder using a developer to create an unfixed image. The unfixed image is, for example, the toner image obtained by development.

[0026] The transfer device is a device that transfers an unfixed image formed on an image holder onto a sheet of paper 19. The transfer device used may be either a direct transfer method or an intermediate transfer method. The direct transfer method is a method in which the unfixed image is directly transferred to the paper 19. The intermediate transfer method is a method in which the unfixed image is first transferred to an intermediate transfer medium and then secondarily transferred to the paper 19. In Figure 1, the portion that transfers the unfixed image to the paper 19 is shown as the transfer section 30. The transfer section 30 has a transfer position TP that transfers the unfixed image by passing it through the paper 19. The cleaning device is used to clean the image-holding surface of the image holder and the image-holding surface of the intermediate transfer body.

[0027] The paper supply device 40 is a device that stores a predetermined amount of paper 19 and supplies it to the image forming apparatus 20. The paper supply device 40 includes a container 41 for holding the paper 19, a feeder 43 for feeding the paper 19 one sheet at a time from the container 41, and the like. The container 41 and the feeder 43 are not limited to one set as illustrated in Figure 1, but may be provided in multiple sets. The paper 19 is a recording medium that can be transported inside the housing 11 and used to transfer unfixed images in the image forming apparatus 20. The paper 19 is mainly a sheet-shaped recording medium of a predetermined size.

[0028] The fixing device 5 is a device that fixes the unfixed image formed by the image forming device 20 onto the paper 19. The fixing device 5 is configured by arranging a heating roll 51, which is an example of a rotating body for heating, and a belt 53, which is an example of a rotating body for pressurizing, inside the fixing housing 50. In the fixing device 5, the contact area where the heating roll 51 and the belt 53 come into contact becomes the fixing position FP, where the paper 19 is passed through and the fixing process is performed. Details of the fixing device 5 will be described later.

[0029] A paper transport path 45, illustrated by a dashed line in Figure 1, is arranged within the internal space of the housing 11. The paper transport path 45 has a main transport path from the paper supply device 40 through the image forming device 20 and the fuser device 5 to the discharge port 13. Along this main transport path, the paper 19 is transported so as to pass through the transfer position TP of the image forming device 20 and the fixing position FP of the fuser device 5. The paper transport path 45 is composed of a predetermined number of pairs of transport rolls 46a, 46e and transport guide members (not shown).

[0030] (2) Image formation process The following image forming operations are performed in the image forming apparatus 10. Here, we will explain assuming that a monochrome image is formed in the image forming apparatus 20.

[0031] When a control device (not shown) receives a command to perform an image forming operation, the image forming apparatus 10 starts up the image forming apparatus 20, paper supply device 40, fixing device 5, etc.

[0032] At this time, the image carrier in the image forming apparatus 20 begins to rotate in a predetermined direction. The image forming apparatus 20 also performs charging, exposure, development, transfer, and cleaning operations on the rotating image carrier. Furthermore, the paper supply device 40 and the paper transport path 45 perform paper feeding operations in accordance with the timing of the transfer operation.

[0033] As a result, an unfixed image is formed on the image holder in the image forming apparatus 20. In addition, a predetermined sheet of paper 19, fed from the paper supply device 40, is supplied to the transfer section 30 of the image forming apparatus 20 via the paper transport path 45. Then, in the image forming apparatus 20, the unfixed image on the image holder is transferred to the paper 19 at the transfer position TP of the transfer unit 30.

[0034] In the fixing device 5, the heating roll 51 and the belt 53 begin to rotate. Also in the fixing device 5, the heating roll 51 is heated to a temperature at which fixing operation is possible. In the fixing device 5, the fixing operation is performed after the heating roll 51 reaches a temperature at which fixing is possible.

[0035] Then, in the fixing device 5, the paper 19 on which the unfixed image has been transferred is introduced into the fixing housing 50 and passed through the fixing position FP. As a result, in the fixing device 5, the unfixed image on the paper 19 is heated under pressure as it passes through the fixing position FP and fixed to the paper 19.

[0036] Finally, in the image forming apparatus 10, the paper 19 that has been fixed by the fixing device 5 is transported to the discharge port 13 via the paper transport path 45. The fixed paper 19 is then discharged from the discharge port 13 by a pair of transport rolls 46e and stored in the discharge storage section 12.

[0037] As a result of the above series of actions, the basic image formation process of forming an image on one side of a single sheet of paper 19 is completed.

[0038] (3) Fixing device The fixing device 5 has a fixing housing 50 (see Figure 2). Furthermore, the fixing device 5 includes a heating roll 51, a belt 53, an opposing member 56, an elastic member 59, and the like inside the fixing housing 50.

[0039] The fixing housing 50 is a box-shaped structure having a predetermined external shape and internal space. The fixing enclosure 50 has a paper input 50a and an output 50b for the paper 19. The fixing housing 50 has an internal space where an input guide member 50c, an output guide member 50d, and the like are arranged. In addition, a temperature sensor (not shown) for detecting the surface temperature of the heating roll 51 is also arranged inside the fixing housing 50. The fixing housing 50 is then fixed in a predetermined position within the housing 11 of the image forming apparatus 10.

[0040] The heated roll 51 is a roll with a structure in which necessary layers, such as a release layer, are laminated on the outer surface of a cylindrical roll base made of metal or the like. Furthermore, the heating roll 51 is rotatably mounted to the fixing housing 50 via bearings or the like at both ends in its axial direction J (see Figure 4(B)). The axial direction J is aligned with the depth direction Z of the image forming apparatus 10. Furthermore, the heating roll 51 receives power from a rotational drive device (not shown) via a passive gear (not shown) mounted on its far end in the axial direction J. As a result, when it is time for operation such as fixing, the heating roll 51 rotates in the direction indicated by arrow A.

[0041] Furthermore, a halogen heater lamp 52, which is an example of a heat source, is placed in the internal space of the heating roll 51. The halogen heater lamp 52 is positioned within the internal space of the heating roll 51 and fixed along the axial direction J of the heating roll 51. The halogen heater lamp 52 receives a predetermined power supply from a power supply device (not shown) and generates heat, thereby heating the heating roll 51.

[0042] The belt 53 is a tubular member that rotates in contact with the outer surface of the heating roll 51. The belt 53 is a component in which the necessary layers are formed on the outer surface of a cylindrical belt base material. The belt base material is made of a material such as polyimide resin. The necessary layers are, for example, heat-resistant release layers.

[0043] Furthermore, the belt 53 is rotatably held by a belt holding member 54, an opposing member 56, an elastic member 59, etc., which are arranged on its inner circumferential surface side.

[0044] The belt holding member 54 is a member positioned on the inner circumferential surface side of the belt 53, extending along the axial direction J of the heating roll 51. The belt holding member 54 has a belt holding surface 54a and a pressing surface 54b (see Figure 2). The belt holding surface 54a is a curved surface that slidably holds the inner circumferential surface of the belt 53 from below. The pressing surface 54b is a substantially flat surface that contacts a part of the opposing member 56 and pushes the opposing member 56. The part of the opposing member 56 becomes the pressing receiving surface 56a, which will be described later.

[0045] Furthermore, the belt holding member 54 is attached to the pressurizing mechanism 55 via the support member 551 (see Figure 2).

[0046] The support member 551 supports the belt holding member 54 and transmits the pressurizing action of the pressurizing mechanism 55 to the belt holding member 54. The support member 551 is a plate material that extends along the axial direction J of the heating roll 51. In Embodiment 1, the support member 551 is made of a metal plate material with a bent upper section.

[0047] The support member 551 is attached such that its bent upper portion is located inside the belt holding member 54 and fixed in place. The lower portion (bottom edge) of the support member 551 is fitted into an insertion groove 56e (see Figure 3) provided in the opposing member 56. Furthermore, both ends of the support member 551 in the longitudinal direction are attached to the swing arms 55a of the pressurizing mechanism 55, which will be described later.

[0048] The pressurizing mechanism 55 is a mechanism that includes a swinging arm 55a, pressurizing components (not shown), etc. The oscillating arm 55a is a member that oscillates around the support shaft 55c as a pivot point, and to which both ends of the support member 551 are attached. The oscillating arm 55a is a pair of arms positioned so as to straddle both ends of the heating roll 51 from above. The support shaft 55c is fixed, for example, to a part of the fixing housing 50. The pressurizing component is a component that applies a predetermined pressure F1 (see Figure 2) to cause the oscillating arm 55a to oscillate in a direction that brings it closer to the heating roll 51. The pressurizing component can be one or a combination of tension springs, compression springs, cams, etc.

[0049] The belt holding member 54 receives a predetermined pressure F1 generated by the pressurizing mechanism 55 through the support member 551. As a result, the belt holding member 54 presses against the opposing member 56 by its pressing surface 54b contacting the opposing member 56's pressing receiving surface 56a. At this time, the support member 551 directly applies pressure from the pressurizing mechanism 55 to the insertion groove 56e of the opposing member 56. As a result, the belt holding member 54 works in cooperation with the support member 551 to press the opposing member 56 in a direction that brings it closer to the heating roll 51.

[0050] The opposing member 56 is positioned on the inner circumferential side of the belt 53 and faces the outer circumferential surface of the heating roll 51. The opposing member 56 is configured as a plate-shaped member having a raised portion 58 and an opposing surface 57. The opposing member 56 is also a member having a pressing receiving surface 56a, a belt guiding portion 56b, and an insertion groove 56e.

[0051] The opposing member 56 can be obtained, for example, by molding it using a material such as synthetic resin. Furthermore, the opposing member 56 is attached to the fixing housing 50 so as to be displaceable at both ends in its longitudinal direction. In other words, the opposing member 56 is in a state where the opposing surface 57 and the raised portion 58 can be displaced in directions toward and toward the outer circumferential surface of the heating roll 51.

[0052] The raised portion 58 on the opposing member 56 is the raised part at the end of the opposing surface 57 that is downstream in the rotation direction A of the heating roll 51. Furthermore, the raised portion 58 is also the part that presses the belt 53 against the outer surface of the heating roll 51 to form a downstream nip N1 (see Figure 2). The nip is the part that makes contact under pressure.

[0053] The raised portion 58 rises from the opposing surface 57 of the opposing member 56 toward the heating roll 51 at a predetermined height H (see Figure 4(A)). Furthermore, the raised portion 58 is provided in a manner that is aligned with the axial direction J of the heating roll 51. Furthermore, the raised portion 58 has a roughly rectangular cross-section.

[0054] Furthermore, the raised portion 58 has a top surface 58a, an upstream side surface 58b, a downstream side surface 58c, and so on. The top surface 58a is the surface that presses the belt 53 against the outer circumferential surface of the heating roll 51, and is also the surface that forms the downstream nip N1. The top surface 58a is formed as a curved surface that is convex in the direction of elevation. The elevation portion 58 forms the downstream nip N1 when the top surface 58a contacts the heating roll 51 in the rotational direction A with a nip width Wn (see Figure 3). The upstream side surface 58b is the surface extending from the upstream end of the top surface 58a to the opposing surface 57. The downstream side surface 58c is the surface extending from the downstream end of the top surface 58a to the downstream end of the opposing member 56.

[0055] The opposing surface 57 of the opposing member 56 is the surface that faces the outer circumferential surface of the heating roll 51 with a predetermined distance S between them. The opposing surface 57 is formed to extend from the raised portion 58 of the opposing member 56 to the upstream side in the rotation direction A of the heating roll 51. Furthermore, the opposing surface 57 is formed as a curved surface that curves substantially along the outer circumferential surface of the heating roll 51.

[0056] The pressing surface 56a of the opposing member 56 is the surface that comes into contact with the pressing surface 54b of the belt holding member 54. The pressing surface 56a is formed on the portion of the opposing member 56 opposite to the opposing surface 57. Furthermore, the pressing surface 56a is formed as a planar surface that is substantially parallel to and facing the pressing surface 54b of the belt holding member 54.

[0057] The belt guide portion 56b in the opposing member 56 is the part that guides the rotating belt 53 to approach the heating roll 51 at a predetermined position. The belt guide portion 56b is formed to extend upstream in the rotational direction A from the portion of the opposing surface 57 to which the elastic member 59 is attached. As a result, the belt guide unit 56b guides the portion of the belt 53 that has passed the belt holding member 54 to approach the heating roll 51. At this time, the belt 53 is guided to approach the heating roll 51 at a position just before the upstream nip N2, which will be described later.

[0058] The insertion groove 56e in the opposing member 56 is a groove into which the lower part of the support member 551 is fitted. The insertion groove 56e is formed on the opposite side of the opposing member 56 from the raised portion 58. Furthermore, the insertion groove 56e is formed as a groove that extends linearly along the axial direction J of the heating roll 51. As a result, the insertion groove 56e exists on both the front and back surfaces of the opposing member 56 in a state that aligns with the raised portion 58.

[0059] The elastic member 59 is an elastically deformable member that is attached to the opposing surface 57 of the opposing member 56. Furthermore, the elastic member 59 also serves to press the belt 53 against the outer circumferential surface of the heating roll 51 to form the upstream nip N2 (see Figure 2).

[0060] The elastic member 59 is a plate-like member with a substantially rectangular cross-section having a predetermined thickness (height) and width Wa, and extending for a predetermined length. Furthermore, the elastic member 59 is positioned such that its longitudinal direction lies along the axial direction J of the heating roll 51. The width Wa of the elastic member 59 is a dimension that aligns with the rotation direction A of the heating roll 51 (see Figure 3). The width Wa of this elastic member 59 is set to match the required dimension as the width of the upstream nip N2. As the elastic member 59, an elastic material such as a silicone sponge is used.

[0061] The elastic member 59 is attached to the opposing surface 57 of the opposing member 56 by means of double-sided adhesive tape, adhesive, or the like. At this time, the elastic member 59 is attached with one end in contact with the upstream side surface 58b of the raised portion 58 (see Figure 3).

[0062] The fixing device 5 receives pressure from the belt holding member 54 and the support member 551 due to the pressurizing action of the pressurizing mechanism 55, causing the opposing member 56 to be subjected to pressure. In other words, in the fixing device 5, the pressure F1 generated by the pressurizing mechanism 55 is transmitted to the opposing member 56 via the belt holding member 54 and the support member 551. As a result, in the fixing device 5, the opposing member 56 is subjected to pressure in a direction that moves it toward the outer surface of the heating roll 51.

[0063] At this time, the raised portion 58 of the opposing member 56 is kept pressed against the outer surface of the heating roll 51 with the belt 53 in between. In other words, the raised portion 58 at this time is mainly pressed down by the support member 551. As a result, the raised portion 58 is pressed against the outer surface of the heating roll 51 with a predetermined pressure F2 (see Figure 2).

[0064] As a result, the raised portion 58 forms a downstream nip N1 between itself and the outer surface of the heating roll 51 with the belt 53 in between. The downstream nip N1 is formed by the raised portion 58 with a nip width Wn. The downstream nip N1, due to the raised portion 58, is the area that applies pressure F2 to the paper 19 and the unfixed image with a nip width Wn.

[0065] At this time, the elastic member 59 is kept pressed against the outer surface of the heating roll 51 with the belt 53 in between. In other words, at this time, the elastic member 59 is pressed against the outer surface of the heating roll 51 by the opposing surface 57 of the opposing member 56. As a result, the elastic member 59 is pressed against the outer surface of the heating roll 51 via the belt 53, causing it to undergo elastic deformation. Therefore, the elastic member 59 is used in a state where it is thinner than the thickness of the fixing device 5 before assembly (when unloaded).

[0066] As a result, the elastic member 59 forms an upstream nip N2 between itself and the outer surface of the heating roll 51 with the belt 53 in between. The upstream nip N2 is formed with a nip width that is approximately equivalent to the width Wa of the elastic member 59. The upstream nip N2 is formed by an elastically deformable elastic member 59. Therefore, the upstream nip N2 is the part that applies a smaller pressure to the paper 19 and the unfixed image than the pressure F2 at the downstream nip N1. On the other hand, the upstream nip N2 has a wider nip width (effective width Wa) than the downstream nip N1's nip width Wn. The nip width of the upstream nip N2 should be, for example, three times or more the nip width Wn of the downstream nip N1. Therefore, the upstream nip N2 is the part that applies heat and weak pressure to the paper 19 and the unfixed image for a longer period of time than the downstream nip N1.

[0067] (4) Fixing operation When the fixing device 5 receives a fixing command, the heating roll 51 begins to rotate in the rotation direction A. At this time, the belt 53 receives the rotational force of the heating roll 51 at the upstream nip N2 and the downstream nip N1 and rotates in the direction indicated by arrow B. The driven rotating belt 53 is held by the belt holding member 54 and guided by the belt guiding portion 56b of the opposing member 56. The driven rotating belt 53 moves in a circulating manner, contacting the outer circumferential surface of the heating roll 51 and passing through the upstream nip N2 and the downstream nip N1. At this time, the heating roll 51 is heated to a predetermined temperature by the heating action of the halogen heater lamp 52. The heated heating roll 51 prepares the upstream nip N2 and downstream nip N1 that it passes through for heating.

[0068] When the fixing device 5 is ready for fixing, it accepts the paper 19 on which the unfixed image It (see Figure 2) has been transferred into the fixing housing 50. At this time, the paper 19 is brought in with the side on which the unfixed image It has been transferred facing the heating roll 51. At this time, the paper 19 is guided by the loading guide member 50c and moves to a position where the heating roll 51 and the belt 53 begin to come into contact.

[0069] The paper 19 is then transported while sandwiched between the rotating heated roll 51 and the belt 53. In other words, the paper 19 is transported in such a way that it passes through the upstream nip N2 and the downstream nip N1 in that order.

[0070] As a result, the paper 19 on which the unfixed image It has been transferred is heated under pressure as it passes through the upstream nip N2 and the downstream nip N1. As a result, the unfixed image It is heated and melted and fixed to the paper 19.

[0071] At this time, the unfixed image It and the paper 19 are subjected to relatively weak pressure at the upstream nip N2. Subsequently, the unfixed image It and the paper 19 are subjected to relatively strong pressure (F2) at the downstream nip N1. Therefore, the fixing device 5 performs preliminary fixing at the upstream nip N2, and then performs the main fixing at the downstream nip N1.

[0072] In the fixing device 5, the paper 19 after the fixing process is completed is guided by the discharge guide member 50d and discharged to the outside of the fixing housing 50. At this point, the paper 19 is peeled off the heated roll 51 and discharged after passing through the downstream nip N1.

[0073] As a result of the above series of operations, the fixing operation of the fixing device 5 on one sheet of paper 19 is completed.

[0074] (5) Defects In this case, if the fixing device 5 employs the comparative raised portion 58X shown in Figure 6, the following problems may occur.

[0075] The raised portion 58X being compared has a corner 58e on the opposing surface 57 side that protrudes outward. The corner 58e has a shape where the top surface 58a of the raised portion 58X and the upstream side surface 58b intersect (ridge) is convex outward. When a raised portion 58X having this corner portion 58e is used, the elastic member 59 may deform and a part of it may ride up onto the top surface 58a of the raised portion 58X. In Figure 6, reference numeral 59p indicates a part of the elastic member 59 that rests on the top surface 58a of the raised portion 58X. In Figure 6, reference numeral 58f indicates the corner of the raised portion 58X opposite to the opposing surface 57. Corner 58f is the downstream corner, assuming that corner 58e is the upstream corner.

[0076] If a portion of the elastic member 59 rides up onto the top surface 58a of the raised portion 58X, the pressurizing force, particularly at the downstream nip N1, will deviate from the design value. As a result, the fixing device 5 may experience fixing failures and wrinkles in the paper 19 due to fluctuations in the applied pressure. The riding up of a portion of the elastic member 59 may also occur during the assembly stage of the anchoring device 5.

[0077] (6) Additional configuration of the fixing device Therefore, in the fixing device 5, the corner portion (58e: see Figure 6) on the opposite side of the raised portion 58 to the surface 57 is configured as a recessed corner portion 60.

[0078] The recessed corner portion 60 is a corner portion that has a shape that is recessed inward. "Inward recess" means that the recess is located inside the imaginary straight line or plane Q (see Figure 5(A)) connecting the top surface 58a and the upstream side surface 58b. The top surface 58a and the upstream side surface 58b are connected to the recessed corner 60. The recessed corner portion 60 does not include corners that are tapered by cutting a plane at an angle, or corners that are chamfered by processing a curved surface that bulges outwards.

[0079] Furthermore, the recessed corner portion 60 is formed continuously in the direction along the axial direction J of the heating roll 51 (see Figure 4(B)). The recessed corner portion 60 exists in the axial direction J with a length longer than the axial direction J of the elastic member 59.

[0080] In this case, the recessed corner 60 has the same cross-sectional shape in the axial direction J when cut by a plane perpendicular to the axial direction J. In other words, there is no part of the recessed corner 60 whose cross-sectional shape differs in the axial direction J.

[0081] Furthermore, the recessed corner portion 60 is formed in a shape that is recessed from the upstream side surface 58b of the raised portion 58 to the downstream side in the rotation direction A of the heating roll 51. In Embodiment 1, the recessed corner portion 60 is formed with a rectangular cross-sectional shape having a first surface 61 and a second surface 62. The first surface 61 is a surface that extends in the direction of recession from the upstream side surface 58b. The second surface 62 is a surface that extends from the recessed end of the first surface 61 toward the top surface 58a.

[0082] In this case, the recessed corner 60 is formed by a recess with a dimension h2 that is 1 / 3 or less of the height H of the raised portion 58 (see Figure 4(A)). The height H of the raised portion 58 is the dimension of the portion that rises from the opposing surface 57 of the opposing member 56. In Figure 4(A), the reference numeral h1 is the height of the upstream side surface 58b from the opposing surface 57. If the recessed corner 60 is formed in a dimension exceeding 1 / 3 of the height H of the raised portion 58, the degree of contact with the upstream side surface 58b of the elastic member 59 will decrease. This may make it easier to induce elastic deformation of the elastic member 59 into the recessed space of the recessed corner 60.

[0083] Furthermore, the recessed corner portion 60 should have a smaller recessed dimension k (see Figure 4(A)) downstream of the raised portion 58. The recessed dimension k is the dimension by which the recessed corner portion 60 is recessed downstream from the upstream side surface 58b in the rotation direction A of the heating roll 51. The depth of the recess on the downstream side of the recessed corner 60 is preferably set to 1 / 8 or less of the width of the top surface 58a (nip width Wn). For example, the depth of the recess should be set within a range of 1 mm or less.

[0084] In the fixing device 5 which employs a raised portion 58 having a recessed corner portion 60, even if a part of the elastic member 59 undergoes slight elastic deformation, the following occurs. In other words, in this fixing device 5, the elastically deformed portion of the elastic member 59 is temporarily housed within the recessed space of the recessed corner portion 60. Therefore, the fixing device 5 prevents a portion of the elastic member 59 from riding up onto the top surface 58a of the raised portion 58.

[0085] Furthermore, the fixing device 5 prevents a portion of the elastic member 59 from riding up onto the top surface 58a of the raised portion 58 in the axial direction J of the heating roll 51. Furthermore, the fixing device 5 has the following advantages compared to the case where the recessed corner portion has a different cross-sectional shape in the axial direction J. Specifically, the fixing device 5 reliably prevents a part of the elastic member 59 from riding up on the top surface 58a of the raised portion 58 in the axial direction J as well.

[0086] Furthermore, the fixing device 5 has the following advantages compared to a case where the recessed corner is formed by a recess exceeding 1 / 3 of the height of the raised portion 58. Specifically, the fixing device 5 keeps the elastic member 59 in contact with the upstream side surface 58b of the raised portion 58, while preventing a part of the elastic member 59 from riding up onto the top surface 58a of the raised portion 58.

[0087] Furthermore, in the image forming apparatus 10 equipped with the fixing device 5, the fixing device 5 prevents a portion of the elastic member 59 from riding up onto the top surface 58a of the raised portion 58. Therefore, the image forming apparatus 10 is also prevented from experiencing fixing failures or image quality defects caused by this overlapping.

[0088] Variant expression. The present invention is not limited to the configuration examples illustrated in the above embodiments. The present invention can be modified as necessary, as long as the gist of the invention described as a means of solving the problem is not altered. Therefore, the present invention also includes modifications as illustrated below.

[0089] The recessed corner portion 60 of the raised portion 58 may be a recessed corner portion 60B that curves inward, as illustrated in Figure 5(B). The recessed corner portion 60B at this time is formed by a single recessed surface 63 that is curved inward.

[0090] The heating roll 51 may use a heat source other than the halogen heater lamp 52. Examples of other heat sources include a heat-resistant layer, an electromagnetic induction heating layer, and an external heating device.

[0091] The fixing device 5 may use a rotating heating element consisting of a belt supported by multiple rolls instead of the heating roll 51.

[0092] (Note) (((1))) A rotating body having a heat source, A tubular belt that rotates in contact with the outer surface of the rotating body, An opposing member is positioned on the inner circumferential surface side of the belt and has an opposing surface facing the outer circumferential surface of the rotating body, A raised portion is formed at the end of the opposing surface that is on the downstream side in the direction of rotation of the rotating body, pressing the belt against the outer circumferential surface of the rotating body to form a downstream nip, An elastic member is attached to the opposing surface in contact with the side surface of the raised portion, and presses the belt against the outer circumferential surface of the rotating body to form an upstream nip, Equipped with, An anchoring device in which the corner on the opposite side of the raised portion is configured as a recessed corner. (((2))) The fixing device according to (((1))), wherein the recessed corner portion is formed continuously in a direction along the axial direction of the rotating body. (((3))) The fixing device according to (((1))) or (((2))), wherein the recessed corner portion is formed with the same cross-sectional shape in the axial direction. (((4))) The fixing device according to any one of (((1))) to (((3))), wherein the recessed corner portion is formed in a shape that is recessed from the side surface of the raised portion toward the downstream side in the rotational direction of the rotating body. (((5))) The fixing device according to (((4))), wherein the recessed corner portion is formed by recessing a portion of the raised portion that is 1 / 3 or less the height of the raised portion from the opposing surface of the opposing member. (((6))) An image forming apparatus equipped with a fixing device as described in any of (((1))) to (((5))).

[0093] According to the fixing device described in (((1))), it is possible to prevent a part of the elastic member that forms the upstream nip from riding up onto the top surface of the raised portion that forms the downstream nip. According to the fixing device described in (((2))), it is possible to prevent a part of the elastic member from riding up on the top surface of the raised portion in the axial direction of the rotating body. According to the fixing device of (((3))), compared to the case where the cross-sectional shape of the recessed corner is formed with a different shape in the axial direction, it is possible to reliably prevent a part of the elastic member from riding up on the top surface of the raised portion in the axial direction of the rotating body. According to the fixing device described in (((4))), even if a part of the elastic member deforms downstream in the direction of rotation of the rotating body, the deformed part of the elastic member can be temporarily accommodated in the recessed space of the recessed corner. The fixing device according to (((5))) is able to keep the elastic member in contact with the side surface of the raised portion while preventing a part of the elastic member from riding up onto the top surface of the raised portion, compared to the case where the recessed corner is formed in a dimension greater than 1 / 3 of the height raised from the opposing surface of the opposing member of the raised portion. According to the image forming apparatus described in (((6))), in the fixing apparatus, it is possible to prevent a part of the elastic member that forms the forward pressure nip from riding up on the top surface of the raised part that forms the rear pressure nip, and thus prevent fixing failures and image quality defects caused by such riding up. [Explanation of symbols]

[0094] 5. Fixing device 10…Image forming apparatus 51…Heated roller (an example of a rotating body) 52…Halogen heater lamp (an example of a heat source) 53... Belt 56… Opposing member 57… Opposite side 58...Protuberance 58b... Upstream side (an example of the side facing the opposite side) 59...Elastic member 60… recessed corner A...direction of rotation H...height J…Axis direction N1... Downstream nip N2... Upstream nip

Claims

1. A rotating body having a heat source, A tubular belt that rotates in contact with the outer surface of the rotating body, An opposing member is positioned on the inner circumferential surface side of the belt and has an opposing surface facing the outer circumferential surface of the rotating body, A raised portion is formed at the end of the opposing surface that is on the downstream side in the direction of rotation of the rotating body, pressing the belt against the outer circumferential surface of the rotating body to form a downstream nip, An elastic member is attached to the opposing surface in contact with the side surface of the raised portion, and presses the belt against the outer circumferential surface of the rotating body to form an upstream nip, Equipped with, An anchoring device in which the corner on the opposite side of the raised portion is configured as a recessed corner.

2. The fixing device according to claim 1, wherein the recessed corner portion is formed continuously in a direction along the axial direction of the rotating body.

3. The fixing device according to claim 2, wherein the recessed corner portion is formed to have the same cross-sectional shape in the axial direction.

4. The fixing device according to claim 1, wherein the recessed corner portion is formed in a shape that is recessed from the side surface of the raised portion toward the downstream side in the rotational direction of the rotating body.

5. The fixing device according to claim 4, wherein the recessed corner portion is formed by recessing a portion of the raised portion that is less than or equal to one-third of the height of the raised portion from the opposing surface of the opposing member.

6. An image forming apparatus comprising a fixing device according to any one of claims 1 to 5.

Images