JP2019082733A - Image heating device - Google Patents

Abstract

To satisfy durability of a fixing film throughout its life in a film heating type fixing device (image heating device and even in a high-speed machine in which shift force applied to the fixing film is large and a long life is required.SOLUTION: Relief tapered portions Tj, Tk are provided on the film longitudinal regulation surface 40a of a flange 40 so that a contact region Jr between the inner periphery of a fixing film and a guide surface 40b of the flange 40 and a contact region Zr between an end surface 25d of the fixing film and the film longitudinal regulation surface 40a of the flange 40 are located in substantially the same position. The contact region Jr and the second contact region Zr are provided together from the upstream side toward the downstream side in the conveyance direction A1 of a recording material P in a nip part N.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image heating apparatus suitable for use as a fixing device mounted on an image forming apparatus such as a copying machine, a printer, a fax machine, and a multifunction machine having a plurality of these functions.

  As a fixing device (image heating device) used in an electrophotographic image forming apparatus, a film (belt) heating type device is known. Specifically, it has a highly heat-resistant cylindrical film, a ceramic heater (hereinafter referred to as a heater) in contact with the inner surface of the film, and a pressure roller forming a nip with the heater via the film. Then, the recording material carrying the toner image is heated at the nip portion while being conveyed, and the toner image is fixed on the recording material. Since the heater and film used in this apparatus have low heat capacity, there is an advantage that power saving and shortening of weight time (quick start) are possible.

  In this device, when the film is rotated, the film may be deviated in the longitudinal direction (thrust direction), and it is difficult to control the deviation with high accuracy. Therefore, it has been proposed to install a regulating member (hereinafter referred to as a flange) for receiving the longitudinal end of the film and for suppressing deviation, at the film end. This flange contacts the inner circumferential surface and the end face of the film. The contact with the inner peripheral surface suppresses the inclination of the film in the recording material conveyance direction, and the contact with the end surface restricts the movement of the film in the longitudinal direction.

  However, in the case where the film is regulated by a flange, a phenomenon in which the end of the film may be broken or cracked (hereinafter referred to as film end breakage) may occur when the shift force of the film becomes large. As a result, there is the possibility of deterioration of the fixed image, poor running of the film, and shortening of the durable life. As a countermeasure, it has been taken to increase the film thickness of the film, to increase the strength by mixing additives with the material, and the like.

  In addition, it is necessary to appropriately manage the relationship between a region (hereinafter referred to as a guide surface) in contact with the inner circumferential surface of the film in the flange and a contact region (hereinafter referred to as a control surface) with the end surface of the film. When the film end surface contacts the control surface of the flange in a region not in contact with the inner circumferential surface of the film, a phenomenon in which the film is broken at the end portion (hereinafter referred to as end portion breakage) occurs. In the film in which the end portion is broken, the traveling locus becomes unstable, which may cause an image failure or a conveyance failure of the recording material. In addition, the end of the film may be damaged.

  The countermeasure which devises a flange shape is proposed with respect to the subject of film edge part bending (patent document 1). The features of this proposed configuration are as follows. When the flange is divided into two on the upstream side and the downstream side in the recording material conveyance direction with respect to the nip center, on the upstream side, the flange is in contact with the inner circumferential surface and the end face with respect to the film. And the area | region where a film inner peripheral surface and a guide surface contact is larger than the area | region where a film end surface and a control surface contact. On the other hand, at the downstream side, the flange is not in contact with the film with the inner circumferential surface and the end surface.

  By setting it as the said structure, in the area | region where the inner peripheral surface of a film and the guide surface of a flange are not contacting, it can prevent that the film end surface contacts the control surface of a flange, and can prevent an end part breakage.

JP 2012-252186 A

  However, in the above-mentioned prior art, there has been a problem that the shift force of the film is increased with the recent trend of speeding up and downsizing of the apparatus. That is, in the case where the film inner circumferential surface and the guide surface of the flange and the film end surface and the restriction surface of the flange are in contact only at the upstream side, the shift force that the film receives becomes large. The reason is shown below.

  In the above-mentioned conventional configuration, on the downstream side of the flange, a gap is generated between the inner circumferential surface of the film and the guide surface of the flange. When such a gap is present, the film is inclined in the recording material conveyance direction. When the film is inclined with respect to the pressure roller, a difference occurs in the vectors in the respective rotational directions of the film and the pressure roller, and an offset force is generated at the end of the film according to the difference. When the vector difference in the rotational direction is increased and the deviating force is increased, there is a possibility that the traveling path of the film may be disturbed or the film end may be broken.

  As a solution to this problem, a method is employed in which the inner circumferential surface of the film is brought into contact with the guide surface of the flange also on the downstream side by means of enlarging the guide surface of the flange or reducing the film diameter. As described above, by bringing the inner circumferential surface of the film and the guide surface of the flange into contact also on the downstream side, it is possible to suppress the inclination of the film in the transport direction with respect to the pressure roller and reduce the shift force.

  In addition, even when the film end face and the control surface of the flange contact each other only on the upstream side, there is a problem that the shift force per unit area received by the film is large with respect to a predetermined shift force. . In order to solve this problem, means for reducing the film shift force per unit area by bringing the film end face into contact with the control surface of the flange also on the downstream side and increasing the contact area is adopted.

  As described above, it is necessary to prevent the end of the film from being broken also in the apparatus in which the film inner circumferential surface and the guide surface of the flange and the film end surface and the restriction surface of the flange are in contact on the downstream side.

  Therefore, an object of the present invention is to provide an image heating apparatus which reduces the film shift force without occurrence of breakage of the film end and satisfies the durability performance of the film even in the apparatus having the above-mentioned configuration. It is.

  A typical configuration of an image heating apparatus according to the present invention for achieving the above object is an image heating apparatus that holds and conveys a recording material on which a toner image is formed in a nip portion and heats the recording material. Contacting the hollow first rotating body, the second rotating body forming the nip portion in contact with the outer surface of the first rotating body, and the end face of the longitudinal end of the first rotating body Therefore, there is a control member having a control surface for controlling the movement of the first rotating body in the longitudinal direction and a guide surface for supporting the inner peripheral surface of the longitudinal end of the first rotating body from the inside. The restricting member is a first contact area in which the restricting surface and the end face of the first rotating body are in sliding contact with each other when the first rotating body rotates, the guide surface and the first rotating body A second contact region in sliding contact with the inner peripheral surface of the end portion of the first portion substantially at the same position in the circumferential direction of the first rotating body And the first contact area and the second contact area are both upstream in the conveyance direction of the recording material in the nip portion. It is characterized in that it is provided from the side to the downstream side.

  According to the present invention, it is possible to reduce the shift force of the first rotating body without occurrence of breakage of the end portion of the hollow first rotating body (film) having flexibility, and thus to improve the durability performance of the first rotating body. Can be provided.

Structure of the flange in the fixing device of Embodiment 1 Structure of the flange in the fixing device of Example 2 Structure of the flange in the fixing device of Example 3 Schematic diagram of an example of an image forming apparatus Front view of fixing device example Vertical front view of the device Partial cutaway front view of the apparatus of FIG. 5 Transverse right side schematic diagram of the same device (A) is an exploded perspective view of the film unit, (b) is a view showing the layer structure of the film, (c) is a cross-sectional view of the heater Structural explanation of the flange Control system block diagram Illustration of shift movement of film An illustration of the guide area of the film and the running track Illustration of film breakage An explanatory view of a flange provided with a tapered portion Explanatory drawing of the flange of comparative example 1 and 2

  Hereinafter, with reference to the drawings, the best mode for carrying out the present invention will be exemplarily described in detail based on the embodiments.

Example 1
[Image forming apparatus]
FIG. 4 is a schematic view showing a schematic configuration of an example of an image forming apparatus A in which an image heating apparatus according to the present invention is mounted as a fixing apparatus C. As shown in FIG. The image forming apparatus A is a monochrome printer using an electrophotographic process, and image information is input to the control unit D from an external device (not shown) such as a host computer. The control unit D executes a predetermined image formation control sequence.

  The image forming portion B for forming a toner image on a recording material (hereinafter referred to as a sheet or paper) P has a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a drum) 1 rotationally driven in the clockwise direction of the arrow. . Around the drum 1, a charging roller 2, a laser scanner 3, a developing device 4, a transfer roller 5, and a cleaning device 6 are disposed in order along the drum rotation direction. The image forming operation (electrophotographic process) of the image forming unit B described above is well known, so detailed description will be omitted.

  The sheets P stored in the cassette 7 are fed one by one by the rotation of the feed roller 8. Then, the sheet P is introduced at a predetermined control timing to the transfer nip portion 11 formed by the drum 1 and the transfer roller 5 by the conveyance path 10 having the top sensor 9 to receive the transfer of the toner image on the drum 1 side. The sheet P having passed through the transfer nip portion 11 is sent to the fixing device (fixing portion) C along the conveyance path 12 and is subjected to heat and pressure fixing processing of the toner image. The sheet P which has exited the fixing device C passes through the conveyance path 13 and is discharged by the discharge roller 14 onto the discharge tray 15 as an image-formed product (consumable).

[Fixing device]
Regarding the fixing device C, the front side is the inlet side of the sheet P, and the back side is the same outlet side. The left and right are the left (one end side) or the right (the other end side) when the apparatus C is viewed from the front. Up and down are up and down in the direction of gravity. The upstream side and the downstream side are the upstream side and the downstream side in the sheet conveyance direction (recording material conveyance direction). Further, the axial direction of the pressure roller or the direction parallel to this is taken as the longitudinal direction, and the direction orthogonal to this is taken as the transverse direction.

  The fixing device C is a film (belt) heating type image heating device (OMF: on-demand fixing device) capable of shortening a start-up time and reducing power consumption. 5 is a schematic front view of the apparatus C, FIG. 6 is a longitudinal cross-sectional schematic view of the apparatus C, and FIG. 7 is a schematic front view of the apparatus C of FIG. FIG. 8 is a schematic cross-sectional side view of the apparatus C. The fixing device C is roughly divided into a film unit (belt unit) 50, an elastic pressure roller 26 as a pressure member, and an apparatus frame (housing) 60 accommodating these.

(1) Film unit 50
The film unit 50 is a flexible hollow (endless, endless belt-like, cylindrical) first rotary body which is loosely fitted to the inner assembly (internal component: internal member) in a loose manner. A fixing film (fixing belt: hereinafter referred to as a film) 25 is provided. Inside the film 25 is a heater 20 as a heating body, a guide member (holding member) 29 for holding the heater 20 and guiding the rotation of the film, and a pressurized rigid stay 30 made of, for example, iron for holding the guide member. It is arranged as FIG. 9A is an exploded perspective view of the film unit 50.

  The heater 20, the guide member 29, and the stay 30 are all members longer in length than the width (length) of the film 25, and one end side (left side) and the other end side (right side) are respectively from both ends of the film 25 It protrudes outward. Further, flanges (film holding members) 40 (L and R) at one end side and the other end side are fitted to the outward projecting portions 30a at one end side and the other end side of the stay 30, respectively. That is, the flanges 40 (L and R) are disposed at both ends of the film 25 in the longitudinal direction.

1) Film 25
The flexible film 25 has a cylindrical shape with a diameter of 24 mm in its free state due to its elasticity. The film 25 is loosely fitted around a guide member 29 having a substantially semicircular arc cross section. FIG. 9B is a schematic cross-sectional view showing the layer structure of the film 25 in the present example, and it comprises three composite layers of a base layer 25a, an elastic layer 25b and a surface layer 25c in order from the inside to the outside.

  As the material of the base layer 25a, heat-resistant resin materials with low heat capacity such as polyimide, polyamideimide, PEEK, PES, etc. are used in many fixing devices, but in order to enhance thermal conductivity and durability, thin materials such as SUS, Ni, etc. Metals can also be used. Since it is necessary to satisfy the mechanical strength as well as the heat capacity of the base layer 25a to reduce the heat capacity and to satisfy the quick start property, the thickness is preferably 15 μm or more and 50 μm or less. The base layer 25a of this example was a cylindrical polyimide base layer having a thickness of 70 μm.

  The elastic layer 25 b is made of silicone rubber. By providing the elastic layer 25b, it is possible to wrap the toner image T and apply heat uniformly, so it is possible to obtain a high-quality image having high glossiness and no unevenness. In addition, since the elastic layer 25b has low thermal conductivity when using only silicone rubber, securing 1.2 W / mk or more by means of adding a thermally conductive filler such as alumina, metal silicon, silicon carbide or zinc oxide good.

  In the present embodiment, metal silicon which is a heat conductive filler is added to dimethylpolysiloxane which is a rubber material in the elastic layer 25b, and the thermal conductivity thereof is set to 1.2 W / mk. The thickness of the elastic layer 25b is 210 μm.

  The surface layer 25c is required to have high abrasion resistance and high releasability to toner as a release layer. As the material, fluorine resin such as PFA, PTFE, FEP or the like mentioned above is used. It is formed of a coating layer obtained by firing a resin dispersion, or a tube layer. In addition, a conductive material such as carbon may be added to the fluorine resin. The surface layer 25c of the present example was made of PFA as a fluorocarbon resin and had a thickness of 15 μm as a coating layer.

2) Heater 20
Generally, a ceramic heater is used as the heater 20. (C) of FIG. 9 is a cross-sectional schematic diagram of the ceramic heater 20 in a present Example. The heater 20 has a heat resistant heater substrate (ceramic substrate) 20a made of aluminum nitride, alumina or the like. Then, on the surface of the heater substrate 20a, a resistor pattern 20b as a heating resistance layer (resistance heating element) that generates heat by energization is formed along the longitudinal direction of the heater substrate 20a by printing, for example. Then, the surface of the resistor pattern 20b is covered with a glass layer 20c as a protective layer.

  Further, a thermistor 24 as a temperature detection member for detecting the temperature of the heater 20 is disposed on the back surface (surface opposite to the nip portion N) of the heater substrate 20a.

3) Guide member 29
The guide member 29 is a member formed of a heat resistant resin, and supports the heater 20 and also serves as a rotational guide of the film 25. A groove is formed in the lower surface of the guide member 29 along the longitudinal direction, and the heater 20 is supported by being fitted to the groove with the surface side facing outward. As a material of the guide member 29, a heat resistant resin such as liquid crystal polymer, phenol resin, PPS, PEEK, etc. is used.

4) Flange 40
The flanges 40 (L and R) disposed at both ends in the longitudinal direction of the film 25 are molded articles made of heat-resistant resin which are symmetrical in the left-right direction. In the following description, “flange 40L” is a left side (one end side) flange, “flange 40R” is a right side (other end side) flange, “flange 40” or “flange 40 (L · R)” is both left and right It shall be a flange.

  (A), (b), (c) of FIG. 10 is the figure which looked at the flange 40 from the inner surface side, the side surface side, and the top | upper surface side, respectively. (D) is a longitudinal cross-sectional view. As shown in these figures, the flange 40 has a regulation surface (regulation portion, seat: first surface) 40a, a guide surface (guide portion: second surface) 40b, a pressure receiving portion 40c, and a fitting portion 40d, has a fitting longitudinal groove 40e.

  The restricting surface 40a faces the end face 25d of the longitudinal end of the film 25, and serves to restrict movement (shift) when the film 25 moves in the longitudinal direction, and the film 25 is at a predetermined position in the longitudinal direction. I am trying to stay. That is, when deviation occurs in the film 25, the film end face 25d abuts against the control surface 40a of the flange 40, and the deviation is regulated.

  The guide surface 40 b guides the inner surface of the rotating film 25 in the longitudinal end region of the film 25. That is, the guide surface 40 b plays a role of making the film 25 draw a desired rotational trajectory by supporting the inner peripheral surface of the longitudinal end of the film 25 from the inside. The contact area between the guide surface 40b and the inner surface of the film end is indicated by hatched portions (shaded portions) S1 and Sr in FIG.

  When the end inner surface of the rotating film 25 slides against the guide surface 40 b of the flange 40, the flange 40 takes away heat necessary for fixing the toner. Therefore, the guide surface 40b of the flange 40 is provided outside the conveyance area Wmax of the sheet of the maximum width size that can be used for the apparatus C.

  The fitting portion 40 d is a portion to be fitted to the outward projecting portion 30 a of the stay 30. The pressure receiving portion 40c is in direct contact with the outward projecting portion 30a of the stay 30, and plays a role of pressing down the stay 140 by the compression spring 48 (L · R) provided in a contracted state. As the flange 40 is excellent in heat resistance, relatively low in thermal conductivity, and excellent in slip resistance, glass fiber-containing resin such as PPS, liquid crystal polymer, PET, PA, etc. is used. Uses PPS.

(2) Pressure roller 26
The pressure roller 26 as a second rotating body is a drive rotating body for forming a nip portion N with the heater 20 with the film 25 interposed therebetween, and for rotationally driving the film 25. The pressure roller 26 is an elastic roller having an elastic layer 26b on the outer periphery of the core shaft 26a and a surface layer 26c on the outer periphery of the elastic layer 26b, and having an outer diameter of about 30 mm.

  The core shaft portion 26a is made of a solid or hollow metal material such as aluminum or iron. In the present embodiment, solid aluminum is used as the core metal material. The elastic layer 26 b is made of heat insulating silicone rubber, and is made conductive by adding an electric conductive material such as carbon. The surface layer 26 c is a 10 to 80 μm thick releasable tube made of a fluorine resin such as PFA, PTFE, or FEP. In the present embodiment, the layer 26c is a PFA tube with a thickness of 30 μm.

  Here, PFA is an abbreviation of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, PTFE is an abbreviation of polytetrafluoroethylene (tetrafluorination), and FEP is an abbreviation of tetrafluoroethylene-hexafluoropropylene copolymer (4,6 fluorination) It is.

  The pressure roller 26 is rotatably disposed such that one end side and the other end side of the core shaft portion 26a are rotatably supported between the side plates 61L and 61R of the apparatus frame 60 via the bearing member 62, respectively. It is done. Further, a drive gear 47 is disposed concentrically and integrally on the other end side of the core shaft portion 26a. The driving force of the motor M controlled by the control unit (engine controller) D (FIG. 11) is transmitted to the gear 47 via a drive transmission unit (not shown), whereby the pressure roller 26 serves as a drive rotating body. In FIG. 8, it is rotationally driven at a predetermined peripheral speed in the direction of arrow R26.

  The film unit 50 is disposed between the side plates 61L and 61R of the apparatus frame 60 substantially in parallel with the pressure roller 26 on the upper side of the pressure roller 26 with the heater 20 facing downward. The flanges 40L and 40R of the film unit 50 are engaged with the longitudinal edges of the vertical guide slits 63 and 63 provided with the fitting longitudinal grooves 40e in the side plates 61L and 61R, respectively.

  Thus, the flanges 40L and 40R are held slidably in the vertical direction with respect to the side plates 61L and 61R. That is, the film unit 50 has a degree of freedom movable along the vertical guide slits 63, 63 between the side plates 61L, 61R in the direction approaching and away from the pressure roller 26.

(3) Pressure Mechanism The pressure springs 48L and 484R are in contact with the pressure receiving portions 40c of the flanges 40L and 40R. The pressure spring 48L is compressed between the spring receiving portion 67L on one end side of the top plate 66 of the device frame 60 and the pressure receiving portion 40c of the flange 40L. The pressure spring 48R is compressed between the spring receiving portion 67R on the other end side of the top plate 66 of the device frame 60 and the pressure receiving portion 40c of the flange 40R.

  Due to the reaction force of the compression springs 48L and 48R described above, predetermined equivalent pressing forces are applied to the outward projecting portions 30a and 30a on one end side and the other end side of the stay 30 of the film unit 50 via the flanges 40L and 40R. Is working.

  As a result, the guide member 29 having the heater 20 and the pressure roller 26 press against the elasticity of the elastic layer 26 b of the pressure roller 26 with the film 25 interposed therebetween with a predetermined pressure. In the fixing device C of this embodiment, the heater 20 or a part of the heater 20 and the guide member 29 functions as a sliding member (backup member) in contact with the inner surface of the film 25. Therefore, as shown in FIG. 8, a nip portion N having a predetermined width is formed between the film 25 and the pressure roller 26 in the sheet conveyance direction A1.

(4) Fixing Operation As described above, the driving force of the motor M controlled by the control unit D is transmitted to the gear 47 of the pressure roller 26 through the drive transmission unit, whereby the pressure roller 26 is driven to rotate. The body is rotationally driven at a predetermined peripheral speed in the direction of arrow R26 in FIG. The rotation of the pressure roller 26 causes a rotational force to act on the film 25 by the frictional force with the pressure roller 26 at the nip portion N. Thereby, the film 25 slides on the inner surface thereof in close contact with the surface of the heater 20 and a part of the outer surface of the guide member 29 at the nip portion N, substantially corresponding to the rotational peripheral speed of the pressure roller 26 in the direction of arrow R25. Follows and rotates at circumferential speed.

  On the other hand, the heater 20 receives power supply from a power supply unit (triac) 51 controlled by the control unit D via a power supply path (not shown) and generates heat sharply. The temperature of the heater 20 is detected by the thermistor 24 disposed in contact with the rear surface of the heater, and the detected temperature information is input to the control unit D. The control unit D appropriately controls the current flowing from the power supply unit 51 to the heater 20 according to the input detected temperature information, thereby raising the temperature of the heater 20 to a predetermined temperature and maintaining the temperature thereof. Adjust.

  The thermistor 24 is an element for detecting the temperature of the central portion in the longitudinal direction of the heater 20. The temperature detected by the thermistor 24 is input to the control unit D. The thermistor 24 is an NTC (Negative Temperature Coefficient) thermistor, and the resistance value decreases as the temperature rises. The temperature of the heater 20 is monitored by the control unit D, and the power supplied to the heater 20 is adjusted by comparing it with the target temperature set inside the control unit. Thus, the power supplied to the heater is controlled such that the heater maintains the target temperature.

  As described above, the pressure roller 26 is driven to rotate, and the film 25 is driven and rotated accordingly, and the heater 20 is not heated from the image forming portion B side in a state where the temperature is raised to a predetermined temperature and regulated. The sheet P carrying the toner image T is conveyed to the nip portion N. The sheet P is introduced into the nip portion N so as to face the film 25 on which the toner image T is carried, and is nipped and conveyed. Thus, the unfixed toner image T on the sheet is heated and pressurized to be fixed as a fixed image. The sheet P having passed through the nip portion N is separated by curvature from the surface of the film 25 and is discharged and conveyed from the fixing device C.

(Contact area of the inner circumference of the film and shift force)
As described above, the pressure roller 26 is rotationally driven by the drive gear 47 and rotationally driven in the direction of the arrow R26 in FIG. The film 25 is rotationally driven by the pressure roller 26 at the nip portion N, and is driven to rotate in the direction of the arrow R25. When the film 25 is rotated, an offset may occur on either the left or right side in the longitudinal direction. Flanges 40 (L and R) are provided on both end sides of the film 25 in order to regulate the shift. When deviation occurs in the film 25, the film end face 25d abuts on the control surface 40a of the flange 40 so that the deviation is regulated.

  The flange 40 also has a guide surface 40 b in contact with the inner surface of the end of the film 25 and guides the inner surface of the end of the film 25 in the longitudinal end region of the film 25. That is, the film 25 is guided by the guide surface 40b of the flange 40 on the inner surface in the vicinity of both ends. When the contact areas Sl and Sr (FIG. 7) between the guide surface 40b and the inner surface of the film end become smaller, there arises a problem that the shift force becomes larger.

  The reason is shown below using FIG. FIG. 12 is a schematic view of the top surface side of the film unit 50 and the pressure roller 26 in the fixing device C, and the film 25 is shown by a broken line. Also, the stay 30 is omitted. When the pressure roller 26 and the film 25 are rotating normally, the pressure roller 26 applies a uniform force to the film 25 in the longitudinal direction.

  FIG. 12A is a schematic view in the case where the film 26 is rotated by receiving a uniform force in the longitudinal direction. The conveying force of the pressure roller 26 at the nip portion N is divided into right and left in the longitudinal direction, the conveying force on the drive gear 47 side (right side) is Hr, and the conveying force on the opposite side (left side) is Hl.

  The conveying forces Hr and Hl are equal forces, so that no deviating force is generated on the film 25, and the film end face 25d and the regulating surface 40a of the flange 40 are not in contact with both left and right sides. Further, on both left and right sides, a gap on the left side between the inner surface on the downstream side of the film 25 and the guide surface 40b is dl, and a gap on the right side is dr. At this time, the gap dl and dr are equal intervals.

  On the other hand, when the left and right conveyance forces Hl and Hr are not uniform, the film 25 generates a shift force in either the left or right direction. The reason why the right and left conveying forces Hl and Hr become uneven is that there is a difference between the outer diameter of the pressure roller 26 and the difference between the pressure of the pressure springs 48L and 48R and the film 25. There is a case where the alignment of the pressure roller 26 is shifted left and right.

  (B) of FIG. 12 is a schematic view in the case where the transport force Hr is larger than the same Hl. The inner surface of the film 25 is guided on the upstream side of the guide surface 40a of the flange 40R on the drive gear 47 side (right side), and is guided on the downstream side of the guide surface 40a on the flange 40L opposite to the longitudinal direction (left side) ing. As a result, the film 25 is inclined to the downstream side at the drive gear 47 side where the conveying force is large, and to the upstream side at the opposite side.

  When the film 25 is inclined by an angle θy with respect to the sheet conveyance direction A1, the component force Fy acts on the film 25 on the drive gear 47 side. Here, the component force Fy increases as the angle θy increases. As a result, the film 25 is shifted to the side of the drive gear 47 where the transport force is large, and the shift is restricted by the control surface 40a of the flange 40R.

  Here, the shift force which the end of the film 25 receives is proportional to the component force Fy. That is, as the tilt θy of the film 25 is larger, the shift force is larger. As described above, since the inclination of the film 25 is provided by the guide surface 40b of the flange 40, the larger the gap dr between the guide surface 40b of the flange 40 and the inner surface of the film, the larger the inclination θy. Therefore, the shift force can be reduced by reducing the gap dr (dl).

  In order to reduce the gap dr (dl), it is necessary to reduce the difference between the inner periphery of the film 25 and the guide surface 40b of the flange 40. FIG. 13 is a schematic view of a cross section of a unit formed by the flange 40R on the drive gear 47 side (right side), the heater holder 29, and the heater 21. As shown in FIG. 13 to 16 and FIGS. 1 to 3 illustrate the shapes of the flanges 40 and the like in a deformed manner for convenience of explanation, and in comparison with the flanges 40 and the like in FIGS. And dimensional proportions are not consistent.

  The right side of the drawing with respect to the sheet conveyance direction A1 at the nip portion N is the upstream side (the upstream side when the flange 40 is divided into two with the sheet conveyance direction A1 upstream and downstream with respect to the nip center). The inner peripheral surface of the film 25 is guided by the guide surface 40b of the flange 40R, the heater holder 29, and the heater 20, and the guide region is the hatched portion G in (a). Further, a state in which the film 25 is stretched in the guide area G is shown in (b). F indicated by a thick line of (b) is a region (film traveling track) where the inner periphery of the film 25 travels.

  An area where the film 25 is not guided by the guide surface 40b is generated on the downstream side, and a distance (gap distance) between a point at which the film 25 protrudes the most downstream side of the guide surface 40b and the film traveling track F is taken as dr. The smaller the difference between the inner circumferential length of the film, that is, the total length of the film traveling path F, and the total length of the guide region G, the smaller the distance dr.

  Here, the total length of the guide region G is Lg, the inner circumferential length of the film 25 is Lf, and Lg divided by Lf is Rgf (hereinafter, Rgf will be referred to as an inner use rate).

Rgf = Lg / Lf
By increasing the inner peripheral use rate Rgf, the interval dr can be reduced, and as a result, the shift force of the film 25 can be reduced.

  On the other hand, if the inner circumference utilization ratio Rgf becomes too large, the sliding resistance between the film inner circumference and the guide surface 40b becomes large, so that the torque increases, and further, the outer insertion insertion itself to the inner assembly of the film 25 becomes It can be difficult.

  Therefore, it is necessary to set the inner circumference utilization rate Rgf to an appropriate range. As a result, it is desirable to set the inner circumference utilization ratio Rgf in the range of 95 to 99.8%, and more desirably in the range of 98 to 99%. In the first embodiment, the inner circumference utilization ratio Rgf is set to be 98.5%. As a result, in the contact region between the film 25 and the guide surface 40b of the flange 40R, the region indicated by the arrow Jr in (b) (when the film 25 rotates, the guide surface 40b and the inner peripheral surface of the end of the film 25 slide Contact region in contact: hereinafter referred to as a second contact region). The case of the flange 40L is the same as the case of the flange 40R.

(Regulated surface of flange and broken film)
Subsequently, the restriction surface 40a of the flange 40R and the film breakage will be described. FIG. 14 shows an enlarged view when the end face 25d of the film 25 abuts against the restriction surface 40a of the flange 40R and the cross-sectional view of the guide surface 40b when the flange 40 of the reference example is used. When the film 25 rotates, the inner surface of the film 25 and the guide surface 40b of the flange 40R are in contact with each other in the second contact area Jr described in (b) of FIG.

  In the film 25, the film end is folded inward (bent) in a state where the inner surface of the end portion is not in contact with the guide surface 40 b, that is, in a region having a gap dr in F and G downstream of the second contact region Jr. A phenomenon may occur.

  For example, when the film end face 25d abuts against the control surface 40a due to the occurrence of a shift force in the direction of the arrow in the drawing, there is a possibility that the film end may be folded inward. (A) is a schematic diagram of the film edge part in the downstream area | region, being in the state in which it was folded inward by offset force. When the film is broken, the traveling of the film 25 may be disturbed to cause conveyance failure of the sheet or an image failure, or stress may be concentrated on the bent portion of the film 25 and the end of the film 25 may be damaged.

  On the other hand, as shown in (b), in the second contact area Jr in which the film end inner surface is guided by the guide surface 40b, the film 25 generates a shift force in the arrow direction in the figure and the film end face 25d is restricted. Even if it strikes the surface 40a, the phenomenon of breaking does not occur. This is because the inner surface of the film is guided by the guide surface 40b. The case of the flange 40L is the same as the case of the flange 40R.

  In order to solve the problem of the film breakage, it is effective to provide a tapered portion for relief on the restriction surface 40a of the flange 40R. FIG. 15 is an enlarged schematic view of the vicinity of the end portion of the film when the tapered portion 40f is provided on the downstream side of the restriction surface 40a of the flange 40R. With this configuration, the film end face 25d does not contact the regulating surface 40a in the region where the tapered portion 40f is provided, so that the phenomenon of being folded inward can be prevented. The case of the flange 40L is the same as the case of the flange 40R.

  However, if the tapered portion 40f is too wide, the contact area between the film end face 25d and the restriction surface 40a becomes small, and the deviation force per unit area received by the film 25 becomes large. As a result, problems such as buckling of the film end without being able to endure the offset force occur.

(Flange shape of Example 1)
As described above, in order to prevent the film 25 from being broken and to satisfy the durability of the fixing device C, it is necessary to satisfy the following two points.

  The first point is "preventing the end of the film from being broken" and the second point is "to reduce the offset force per unit area of the film." The conditions regarding the shape where the flange 40 is required to satisfy these conditions are the first point: "The area where the film inner periphery is not guided in the guide surface is such that the film end face does not contact the control surface", second point Is to "take a wide contact area between the end face of the film and the control surface".

  The flange 40 of Example 1 can satisfy these conditions and can satisfy the durability of the film 25. The view of the central portion of FIG. 1 is a schematic cross-sectional view of the flange 40R of the first embodiment. The schematic view shown on the right side of the figure is the flange 40R viewed from the upstream side in the sheet conveyance direction A1 (the upstream side when the flange 40R is divided into two with respect to the sheet conveyance direction A1 upstream and downstream with respect to the nip center) The left side is viewed from the downstream side (also downstream side).

  An area Jr indicated by an arrow and a hatched portion in the drawing is the above-described second contact area in which the inner peripheral surface of the film 25 is in contact with the guide surface 25b. In the flange 40R of the first embodiment, the inner peripheral usage rate Rgf is 98.5%, and as a result, as shown in FIG. 1, the second contact area Jr is present not only on the upstream side but also on the downstream side. It has become. With such a configuration, the first requirement can be satisfied. That is, by widening the second contact area Jr, the gap dr on the downstream side can be reduced, and as a result, the shift force received by the film 25 can be suppressed to 400 gf or less.

In addition, the restriction surface 40a of the flange 40R of the first embodiment has a shape portion (hereinafter referred to as a tapered shape portion) in which the upstream side and the downstream side are inclined in the direction away from the end of the film 25 respectively.
It has Tj and Tk. The start positions of the upstream and downstream tapered portions Tj and Tk are indicated by 40cj on the upstream side and 40ck on the downstream side.

  At the start positions 40cj and 40ck of the tapered portions Tj and Tk, in order to prevent the film end face 25d and the control surface 40a from being strongly hit locally, a shape (R shape) whose inclination is changed continuously is provided. Is desirable. That is, it is desirable that the shape of the tapered portions Tj and Tk apart from the film end face 25d is a shape such that the inclination does not change discontinuously. In the flange 40R of the first embodiment, the taper start positions 40cj and 40ck have a gentle R shape on both the upstream and downstream sides.

  The relief angles of the tapered portions Tj and Tk are indicated by the upstream side θTj and the downstream side θTk in the figure. The clearance angle θTj of the upstream tapered portion Tj and the clearance angle θTk of the downstream tapered portion Tk are different. In the first embodiment, the angle θTk of the downstream tapered portion Tk is smaller than the angle θTj of the upstream tapered portion Tj. In other words, θTj is set to be larger than θTk. By doing this, local contact of the film 25 can be prevented in the vicinity of the relief taper portion.

  The start positions 40cj and 40ck of the tapered portions Tj and Tk are asymmetric on the upstream side and the downstream side, and the downstream side is disposed at a position closer to the apex. That is, the flange 40R has tapered portions Tj and Tk on the upstream and downstream sides in the sheet conveyance direction A1 with the nip portion N in between, and the upstream tapered portion Tj is closer to the downstream tapered portion Tk Also near the nip portion N.

  The film end face 25d is in contact with the control surface 40a in a region Zr sandwiched by the start positions 40cj and 40ck of the upstream and downstream tapered portions Tj and Tk. That is, the region Zr is a contact region (hereinafter, referred to as a first contact region) in which the control surface 40a and the end face 25d of the film 25 come in sliding contact with each other when the film 25 rotates. The first contact area Zr is substantially at the same position as the above-described second contact area Jr.

  That is, in the flange 40R, the regulating surface 40a is separated from the film end face 25d such that the first contact area Zr and the second contact area Jr become substantially the same position in the circumferential direction of the film 25 when the film 25 rotates. It has shape parts Tj and Tk. The first contact area Zr and the second contact area Jr are both provided from the upstream side to the downstream side in the conveyance direction A1 of the sheet P in the nip portion N.

  By thus making the first contact area Zr and the second contact area Jr substantially in the same position, the first and second requirements can be satisfied. That is, since the film end face and the control surface 40a contact each other only at the inner peripheral guide portion, breakage can be prevented, and by widening the second contact area Jr, the force received by the film per unit area can be reduced. . Further, since the restriction surface and the guide surface are provided from the upstream side to the downstream side in the sheet conveyance direction (recording material conveyance direction), the posture of the film is stabilized.

  The case of the flange 40L is the same as the case of the flange 40R. As described above, by using the flange 40 (L · R) of the first embodiment, the durability of the film 25 can be satisfied throughout the life even in a high-speed machine requiring higher durability performance. .

(Comparison result of fixing device of Example 1 and fixing device of Comparative Example)
In order to demonstrate the effect of the fixing device of Example 1, the results of comparison experiments with the fixing devices of Comparative Examples 1 and 2 will be shown. The fixing device of the first embodiment uses the flange 40 shown in FIG. 1 described above. On the other hand, in the fixing devices of Comparative Examples 1 and 2, the flanges 40 shown in (a) and (b) of FIG. 16 are used, respectively. The configuration of the other comparative examples 1 and 2 is the same as that of the first embodiment, and thus the description thereof is omitted. Although (a) of Drawing 16 and (b) are flange 40R, respectively, flange 40F is also the same.

  FIG. 16A is a schematic cross-sectional view of the flange 40R used in the first comparative example. The difference between the flange 40R of the first comparative example and the flange 40R (FIG. 1) of the first embodiment is that the start position 40ck of the downstream tapered portion Tk provided on the restriction surface 40a is shifted further downstream. It is a point.

  The flanges 40R of the first comparative example are provided at positions where the start positions 40cj and 40ck of the tapered portions Tj and Tk on the upper and lower sides are symmetrical on the upper and lower sides with respect to the top of the guide portion 40b. At this time, a first contact region in which the end face 25d of the film 25 and the restriction surface 40a come in sliding contact with each other is a region indicated by Zr in the drawing, and a second contact region Jr in which the inner periphery of the film 25 and the guide surface 40b come in sliding contact. It becomes a wider area than that. As a result, the film end face 25d is pressed against the control surface 40a in the first contact area Zr in the area not in contact with the inner periphery of the film 25 (outside the area of the second contact area Jr). Occurs.

  FIG. 16B is a schematic cross-sectional view of the flange 40 used in Comparative Example 2. The difference between the flange 40 of the comparative example 2 and the first embodiment is that the start position 40 ck of the downstream tapered portion Tk provided on the restriction surface 40 a is shifted more upstream.

  The flange 40R of the comparative example 2 is formed such that the taper start position 40ck of the downstream tapered portion Tk is parallel to the nip line from the top of the guide portion 40b of the flange 40R. At this time, the first contact area in which the end face 25d of the film 25 and the restriction surface 40a of the flange 40 come in sliding contact with each other is the area indicated by the arrow Zr in FIG. The area is narrower than the contact area Jr. As a result, the deviation force per unit area applied to the film 25 becomes large, and buckling of the film 25 tends to occur.

  Next, the configuration of another fixing device is shown. The other configurations of the fixing device are the same in the first embodiment and the first and second comparative examples. The pressing force of the film 25 and the pressing roller 26 is 186.2 N (19 kgf), and the nip width is 9 mm. The printing speed of the image forming apparatus is 60 sheets / minute (A4 size: transverse feeding), and the life of the fixing device C is 200 k sheets. The environment under which the test was conducted was a temperature of 23 ° C. and a humidity of 50%, and the evaluation paper used CS-680 (A4 size 68 g / cm 2).

  Under this condition, in the image forming apparatus using the fixing devices of Example 1 and Comparative Examples 1 and 2, 200 k sheets were made durable in the single-sided continuous sheet passing mode, and problems associated with the durability were evaluated.

  Table 1 is a table of the results showing the durability of the fixing device in the image forming apparatus using the fixing device of Example 1 and Comparative Examples 1 and 2. The symbols indicating the level of durability in Table 1 will be described. O in the table indicates that the durability of the film 25 is good without any problem. The symbol “x” in the table indicates that a problem relating to the durability of the film 25 has occurred, an image defect resulting therefrom has occurred, and there is a problem in practical use.

  According to Table 1, in the fixing device of Comparative Example 1, when printing of 100 k sheets is performed, the end of the film 25 is cut into a ring at a width of about 2 mm, and the longitudinal length of the film 25 is shortened. The As a result, the running performance of the film 25 becomes unstable, paper conveyance is disturbed, and image defects occur.

  The reason why the phenomenon of tearing in a ring shape with a width of 2 mm occurs is the breakage of the film end. In the film 25, the film is broken at the downstream side and broken at the inside of the nip and at the upstream side, so that the film 25 is fatigue-broken due to the repetition of the bending and the cancellation.

  Further, in the fixing device of Comparative Example 2, when 150 k sheets of printing were performed, a plurality of cracks were inserted in the longitudinal direction at the end of the film 25 and spread like a trumpet. As a result, the traveling of the film 25 becomes unstable, the paper conveyance is disturbed, and an image defect occurs. The reason for the trumpet-like spread is that a large offset force is applied to the end of the film per unit area. Due to the progress of abrasion of the base layer due to durability and the deterioration due to heat, the strength of the film is reduced, and buckling occurs in the latter half of durability.

  On the other hand, in the fixing device of Example 1, no problem regarding durability occurred over the life of 200 k. The reason is that the second contact area Jr in sliding contact with the film end inner periphery and the guide surface 40b and the first contact area Zr in sliding contact with the film end face 25d and the control surface 40a are substantially the same position. Can prevent the end of the At the same time, the offset force per unit area of the film end could be reduced.

  As described above, it is understood that when the fixing device of Example 1 is used, the effects and advantages not obtained in Comparative Examples 1 and 2 can be obtained. That is, also in the fixing device in which the film inner peripheral surface and the guide surface of the flange and the film end surface and the restriction surface of the flange contact each other on the downstream side, the film edge force is reduced without generation of film edge breakage. It will be possible to satisfy the endurance performance.

  Although the second contact area Jr and the first contact area Zr are substantially at the same position in the first embodiment, it is difficult to achieve the same position in all in consideration of the variation. In this case, the first contact area Zr is slightly smaller than the second contact area Jr so that the first contact area Zr does not become wider than the second contact area Jr even when the tolerance deviates to the maximum. It is desirable that the film be set to prevent the end of the film from being broken.

Example 2
The configuration of the second embodiment will be described. The difference between the second embodiment and the first embodiment is only the flange 40, and the other configuration is the same as that of the first embodiment, so the description will be omitted. The cross-sectional schematic diagram which showed the flange 40 of Example 2 is shown in FIG. The flange 40 according to the second embodiment is characterized in that the control surface 40a has an eaves portion 40g.

  The eaves portion 40g plays a role of restricting the deformation from the surface side of the film 25 when the film 25 is largely deformed by, for example, a jam treatment. Therefore, it is necessary to set the film 25 so as not to be too far from the film traveling path F so that the film 25 can not be deformed significantly.

  On the other hand, if the film 25 contacts the eaves portion 40g at the time of normal printing, problems such as abrasion of the surface layer and torque increase may occur. That is, there is a possibility that a problem may occur if the eaves portion 40g is too far or too far from the traveling path F of the film 25.

  Therefore, in the flange 40 of the second embodiment, the distance between the eaves 40g and the guide surface 40b is different between the distance dj on the upstream side and the distance dk on the downstream side. Specifically, there is a constant interval dj between the upstream tapered shape start position 40cj of the restricting surface 40a and the downstream tapered shape start position 40ck. On the other hand, on the downstream side of the tapered shape start position 40 ck on the downstream side, the interval dk is larger than the above-mentioned interval dj.

  That is, the flange 40 has an eave-shaped portion 40 g covering the outer periphery of the end of the film 25. Further, the distance between the eaves-shaped portion 40g and the second contact region Jr between the downstream tapered portion Tk and the upstream tapered portion Tj is denoted by dj. The distance between the eaves-shaped portion 40g and the second contact region Jr in the region downstream of the downstream tapered portion Tk is dk. The distance dj is smaller than the distance dk.

  With such a configuration, even in the downstream area where the film traveling track F is separated from the guide area G, the film traveling track F and the eaves shape 40 g fall within a predetermined distance. As a result, it is possible to supply a good fixed image without causing a problem both at the time of printing and at the time of jam processing.

Example 3
In order to obtain a good image, a bias (potential) opposite in polarity (here, plus) to the charged polarity (here, minus) of the toner is applied to the conductive base layer 25a (FIG. 9B) of the film 25 Means are effective. By applying a bias to the film 25, the force of the electric field acts in the direction of pressing the unfixed toner T against the sheet P. The force of the electric field can suppress the phenomenon that the toner T scatters to the rear of the sheet P.

  In the third embodiment, therefore, the conductive base layer 25a is exposed in the circumferential direction of the film at the end of the film 25 in the fixing device of the first embodiment. Then, the control unit D (FIG. 11) controls the base layer exposed portion to apply a predetermined bias from the bias application unit 53 via a feeding means (feeding mechanism) 52 such as a conductive brush.

  FIG. 3 is a schematic cross-sectional view showing the flange 40R and the feeding mechanism 52 in the present embodiment. In the third embodiment, the negative bias is fed from the surface side of the film 25 by the brush type feed mechanism 52. At this time, if power is supplied in a region where the film end inner surface and the guide portion 40b are not in contact with each other, the contact point of the brush power supply mechanism 52 and the film 25 becomes unstable due to rotational movement and noise is generated. It can not be applied to the film.

  Therefore, in the third embodiment, the feed mechanism 52 is installed in the second contact area Jr in which the inner surface of the film end portion and the guide surface 40b are in contact with each other. That is, the feed mechanism 52 is installed in a region between the taper start position 40cj of the upstream tapered portion Tkj and the taper start position 40ck of the downstream tapered portion Tk. By doing this, even when the film 25 rotates, power can be stably supplied, and the occurrence of image defects can be prevented.

  The feed mechanism 52 can be provided also in the flange 40 having the eaves 40 g described in the second embodiment. In this case, it is necessary not to provide the eaves portion 40g in the region where the power supply mechanism 52 is installed. That is, the feeding mechanism 52 for applying a potential to the surface of the film 25 in the second contact area Jr is provided, and the eaves-shaped portion 40g is not provided in the area where the feeding mechanism 52 is located.

<< Other matters >>
(1) The pressure configuration of the film unit 50 and the pressure roller 26 for forming the nip portion N may be an apparatus configuration for pressing the pressure roller 26 against the film unit 50. Alternatively, the film unit 50 and the pressure roller 26 may be configured to press each other. That is, the pressing mechanism may be configured to press at least one of the film unit 50 and the pressing roller 26 toward the other.

  (2) The sliding member (backup member) inside the film 25 may be a member other than the heater 20.

  (3) The heating means of the film 25 is not limited to the heater 20 of the embodiment. An appropriate heating configuration such as an internal heating configuration, an external heating configuration, a contact heating configuration, or a non-contact heating configuration using other heating means such as a halogen heater or an electromagnetic induction coil can be adopted.

  (4) In the embodiment, although the flanges 40 are disposed on both ends of the one end side and the other end side of the film 25, the apparatus is configured such that the shift movement of the film 25 occurs exclusively on one end side or the other end side, Alternatively, the flange 40 may be disposed only on the side of the shift movement.

  (5) The film 25 may be used as a drive rotating body, and the pressure roller 26 may be driven to rotate by the rotation of the film 25.

  (6) In the embodiment, as the image heating device, the fixing device which heats and fixes the unfixed toner image formed on the recording material is described as an example, but the invention is not limited thereto. The present invention can also be applied to a device (glossiness improvement device) that reheats a toner image fixed or temporarily attached to a recording material to increase the gloss of the image.

  (7) The image forming apparatus is not limited to the one that forms a monochrome image as in the embodiment. The image forming apparatus may form a color image. Further, the image forming apparatus can be implemented in various applications such as a copying machine, a fax machine, and a multifunction machine having a plurality of these functions in addition to necessary equipment, equipment, and housing structure.

  C · · Image heating device (fixing device), P · · · · · · · · · · · · · · · · · · · · · · · · · · · 1st rotating body (film), 25d · · · · · · · · · 2 rotating body (pressure roller) 40 .. regulating member (flange) 40 a. Regulating surface 40 b guide surface Zr first contact area Jr second contact area Tj · · · Shaped part on the upstream side, · · · Shaped part on the downstream side

Claims (1)

An image heating apparatus that nips, conveys, and heats a recording material on which a toner image is formed at a nip portion, and is a flexible hollow first rotating body;
A second rotating body in contact with the outer surface of the first rotating body to form the nip portion;
The inner circumferential surface of the longitudinal end portion of the first rotating body and the control surface which regulates the movement of the first rotating body in the longitudinal direction by contacting the end surface of the longitudinal end portion of the first rotating body And a restriction member having a guide surface supported from the inside.
The restricting member is a first contact area in which the restricting surface and the end face of the first rotating body are in sliding contact with each other when the first rotating body rotates, and the guide surface and the end of the first rotating body And the restriction surface is configured to be separated from the end face of the first rotating body so that the second contact region in sliding contact with the inner circumferential surface of the portion is substantially the same position in the circumferential direction of the first rotating body Have
An image heating apparatus, wherein the first contact area and the second contact area are both provided from the upstream side to the downstream side in the conveyance direction of the recording material in the nip portion.

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