JP6790150B2 - Fixing device - Google Patents

Description

The present invention is a copying machine, a printer, facsimile, and those concerning the fixing equipment to be mounted in an image forming apparatus such as a complex machine having a plurality of these functions.

As a fixing device (image heating device) used in an electrophotographic image forming device, a film (belt) heating type device is known. Specifically, it has a highly heat-resistant tubular film, a ceramic heater (hereinafter referred to as a heater) that contacts the inner surface of the film, and a pressure roller that forms a nip portion together with the heater via the film. Then, the recording material carrying the toner image is heated by the nip portion and fixed to the recording material. Since the heater and film used in this device have a low heat capacity, they have the advantages of saving power and shortening the wait time (quick start).

In this device, the film may be displaced in the longitudinal direction (thrust direction) when the film is rotated, and it is difficult to accurately control this displacement. Therefore, it has been proposed to install a regulating member (hereinafter referred to as a flange) at the end of the film, which receives the end in the longitudinal direction of the film and suppresses the deviation. This flange comes into contact with the inner and end faces of the film. The contact with the inner peripheral surface suppresses the inclination of the film in the recording material transport direction, and the contact with the end surface regulates the movement of the film in the longitudinal direction.

However, when the film is regulated by a flange, if the leaning force of the film becomes large, a phenomenon of breaking or cracking at the edge of the film (hereinafter referred to as film edge breakage) may occur. As a result, there is a possibility that the fixed image is deteriorated, the film runs poorly, and the durable life is shortened. As countermeasures, measures are taken such as increasing the film thickness and increasing the strength by mixing additives with the material.

Further, it is necessary to appropriately manage the relationship between the region of the flange in contact with the inner peripheral surface of the film (hereinafter referred to as the guide surface) and the contact region with the end surface of the film (hereinafter referred to as the regulation surface). When the end surface of the film comes into contact with the regulation surface of the flange in a region not in contact with the inner peripheral surface of the film, a phenomenon in which the film folds at the end (hereinafter referred to as end fold) occurs. In a film with broken edges, the traveling locus becomes unstable, which may cause image defects and poor transport of recording materials. In addition, the edge of the film may be damaged.

A measure to devise a flange shape has been proposed to solve the problem of film edge breakage (Patent Document 1). The features of this proposed configuration are: When the flange is divided into two parts, an upstream side and a downstream side in the recording material transport direction with respect to the center of the nip, the flange is in contact with the inner peripheral surface and the end surface of the film on the upstream side. The region where the inner peripheral surface of the film and the guide surface are in contact is larger than the region where the end surface of the film and the regulation surface are in contact with each other. On the downstream side, on the other hand, the flange is not in contact with the inner peripheral surface and the end surface of the film.

With the above configuration, it is possible to prevent the end surface of the film from contacting the regulation surface of the flange and prevent the end portion from being broken in the region where the inner peripheral surface of the film and the guide surface of the flange are not in contact with each other.

Japanese Unexamined Patent Publication No. 2012-252186

However, the above-mentioned conventional technique has a problem that the leaning force of the film increases with the recent trend of increasing speed and miniaturization of the apparatus. That is, in the case where the inner peripheral surface of the film and the guide surface of the flange and the end surface of the film and the regulation surface of the flange are in contact with each other only on the upstream side, the approaching force received by the film becomes large. The reason is shown below.

In the conventional configuration, a gap is formed between the inner peripheral surface of the film and the guide surface of the flange on the downstream side of the flange. If there is such a gap, the film is tilted in the recording material transport direction. When the film is tilted with respect to the pressure roller, a difference is generated in the vectors of the rotation directions of the film and the pressure roller, and a biasing force is generated at the end of the film according to the difference. If the vector difference in the rotation direction increases and the leaning force increases, the traveling locus of the film may be disturbed or the film may be damaged at the edge.

As a means for solving this problem, a method is adopted in which the inner peripheral surface of the film and the guide surface of the flange are brought into contact with each other even on the downstream side by means such as increasing the guide surface of the flange or reducing the diameter of the film. In this way, by bringing the inner peripheral surface of the film into contact with the guide surface of the flange even 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 leaning force.

Further, with respect to the contact between the end face of the film and the regulation surface of the flange, there is a problem that the leaning force per unit area received by the film becomes larger than the predetermined leaning force when the contact is made only on the upstream side. .. In order to solve this problem, a means is adopted in which the end face of the film and the regulation surface of the flange are brought into contact with each other even on the downstream side to increase the contact area to reduce the film leaning force per unit area.

As described above, it is necessary to prevent the edge of the film from being broken even in the device where the inner peripheral surface of the film and the guide surface of the flange and the end surface of the film and the regulation surface of the flange are in contact with each other on the downstream side.

Therefore, an object of the present invention is to provide a fixing device that reduces the film leaning force without causing breakage at the end of the film and satisfies the durability performance of the film even in the device having the above configuration. is there.

A typical configuration of the image heating device according to the present invention for achieving the above object is a nip portion that comes into contact with a tubular film and an outer surface of the film and sandwiches and conveys a recording material between the film. The roller to be formed, a guide surface which is arranged at a position facing the end surface of the film in the longitudinal direction, faces the inner surface of the end portion of the film in the longitudinal direction, and guides the rotation of the film, and the film. It has a facing surface facing the end face in the longitudinal direction, and when the film moves in the longitudinal direction, the end face of the film comes into contact with the facing surface to move the film in the longitudinal direction. When the fixing device is viewed in the longitudinal direction in a fixing device having a regulating member for fixing the image and fixing the image to the recording material while sandwiching and transporting the recording material on which the image is formed by the nip portion. The facing surfaces are located in a first region located on the downstream side of the line passing through the center of the nip portion in the transport direction of the recording material in the nip portion and on the upstream side of the first region in the transport direction. It has a second region, and in the longitudinal direction, the first region is retracted from the end face of the film with respect to the second region, and when the fixing device is viewed in the longitudinal direction, the opposite region is present. The second region of the surface and the contact region of the guide surface that contacts the inner surface of the film when the film rotates are both upstream to downstream of the line passing through the center of the nip portion. The portion of the nip portion on the upstream side of the line passing through the center of the nip portion is longer than the portion on the downstream side in the rotation direction of the film, and the fixing device is moved in the longitudinal direction. When viewed, the upstream end of the second region in the rotational direction is located at a position downstream of the upstream end of the contact region in the rotational direction or at the same position as the upstream end of the contact region in the rotational direction. It is characterized by.

According to the present invention, the leaning force of the first rotating body is reduced without causing end bending of the flexible hollow first rotating body (film), and the durability performance of the first rotating body is achieved. It is possible to provide a fixing device that satisfies the above.

Schematic diagram of the structure of the flange in the fixing device of the first embodiment Schematic diagram of the flange configuration in the fixing device of the second embodiment Schematic diagram of the structure of the flange in the fixing device of the third embodiment Schematic diagram of an example of an image forming apparatus Front schematic view of an example of fixing device Longitudinal front schematic view of the device Schematic diagram of the front of a partial notch of the device of FIG. Schematic diagram of the cross-sectional right side of the device (A) is a schematic view of an exploded perspective of a film unit, (b) is a schematic diagram showing a layer structure of a film, and (c) is a schematic cross-sectional view of a heater. Explanatory drawing of flange structure Control system block diagram Explanatory drawing of the movement of the film Explanatory drawing of the guide area and running track of the film Explanatory drawing of film breakage Explanatory drawing of a flange provided with a tapered shape portion Explanatory drawing of flanges of Comparative Examples 1 and 2

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

<< Example 1 >>
[Image forming device]
FIG. 4 is a schematic diagram showing a schematic configuration of an example of an image forming apparatus A equipped with an image heating apparatus according to the present invention as a fixing apparatus C. 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 unit B that forms a toner image on the recording material (hereinafter referred to as paper or paper) P has a drum-type electrophotographic photosensitive member (hereinafter referred to as a drum) 1 that is rotationally driven in the clockwise direction of the arrow. .. A charging roller 2, a laser scanner 3, a developing device 4, a transfer roller 5, and a cleaning device 6 are arranged around the drum 1 in this order along the drum rotation direction. Since the image forming operation (electrophotograph process) of the image forming unit B described above is well known, detailed description thereof will be omitted.

The paper P stored in the cassette 7 is fed out one by one by the rotation of the feeding roller 8. Then, the paper P is introduced into the transfer nip portion 11 formed by the drum 1 and the transfer roller 5 by the transport path 10 having the top sensor 9 at a predetermined control timing, and receives the transfer of the toner image on the drum 1 side. The paper P that has passed through the transfer nip portion 11 is sent to the fixing device (fixing portion) C along the transport path 12, and undergoes a thermal pressure fixing process of the toner image. The paper P that has exited the fixing device C passes through the transport path 13 and is discharged to the discharge tray 15 as an image forming product (deliverable product) by the discharge roller 14.

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

The fixing device C is a film (belt) heating type image heating device (OMF: on-demand fixing device) that can shorten the start-up time and reduce the power consumption. 5 is a schematic front view of the device C, FIG. 6 is a schematic front view of the vertical section of the device C, and FIG. 7 is a schematic front view of the device C of FIG. 5. The film of the film unit is cut out so that the inside of the unit can be seen through. FIG. 8 is a schematic view of the cross-sectional right side surface of the device C. The fixing device C is roughly classified into a film unit (belt unit) 50, an elastic pressure roller 26 as a pressure member, and a device frame (housing) 60 containing these.

(1) Film unit 50
The film unit 50 is a flexible hollow (endless belt-shaped, tubular-shaped) first rotating body that is loosely fitted to the internal assembly (internal body: internal member). It has a fixing film (fixing belt: hereinafter referred to as a film) 25. Inside the film 25, a heater 20 as a heating body, a guide member (holding member) 29 that holds the heater 20 and guides the rotation of the film, and a pressurized rigid stay 30 made of iron, for example, that holds the guide member are internally assembled. It is arranged as. FIG. 9A is an exploded perspective schematic view of the film unit 50.

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

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

As the material of the base layer 25a, a heat-resistant resin material having a low heat capacity such as polyimide, polyamide-imide, PEEK, or PES is used in many fixing devices, but a thin wall such as SUS or Ni is used to improve thermal conductivity and durability. Metal can also be used. Since it is necessary to reduce the heat capacity of the base layer 25a to satisfy the quick start property and at the same time to satisfy the mechanical strength, it is desirable that the thickness of the base layer 25a is 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 25b is made of silicone rubber. By providing the elastic layer 25b, the toner image T can be wrapped and heat can be uniformly applied, so that it is possible to obtain a high-quality image having high glossiness and no unevenness. Further, since the elastic layer 25b has low thermal conductivity with the silicone rubber alone, it is necessary to secure 1.2 W / mk or more by means such as adding a thermally conductive filler such as alumina, metallic silicon, silicon carbide, and zinc oxide. good.

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

As the release layer, the surface layer 25c is required to have high wear resistance and high release resistance to toner. As the material, the above-mentioned fluororesins such as PFA, PTFE and FEP are used. It is formed of a coating layer or a tube layer obtained by firing a dispersion of a resin. Further, a conductive material such as carbon may be added to the fluororesin. For the surface layer 25c of this example, PFA was used as the fluororesin, and the thickness was 15 μm to form a coating layer.

2) Heater 20
A ceramic heater is generally used for the heater 20. FIG. 9C is a schematic cross-sectional view of the ceramic heater 20 in this embodiment. The heater 20 has a heat-resistant heater substrate (ceramic substrate) 20a made of aluminum nitride, alumina, or the like. Then, a resistor pattern 20b as a heating resistance layer (resistance heating element) that generates heat when energized is formed on the surface of the heater substrate 20a 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, on the back surface of the heater substrate 20a (the surface opposite to the nip portion N), a thermistor 24 as a temperature detecting member for detecting the temperature of the heater 20 is arranged.

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

4) Flange 40
The flanges 40 (L and R) arranged at both ends of the film 25 in the longitudinal direction are molded products made of heat-resistant resin having a symmetrical shape. In the following description, "flange 40L" is the left side (one end side) flange, "flange 40R" is the right side (other end side) flange, and "flange 40" or "flange 40 (L / R)" is both left and right. It shall be a flange.

10 (a), (b), and (c) are views of the flange 40 as viewed from the inner surface side, the side surface side, and the top surface side, respectively. (D) is a vertical sectional view. As shown in these figures, the flange 40 has a regulation surface (regulation portion, flange seat: first surface , facing surface ) 40a, a guide surface (guide portion: second surface , guide surface ) 40b, and a pressure receiver. It has a portion 40c, a fitting portion 40d, and a fitting vertical groove portion 40e.

The regulation surface 40a faces the end surface 25d of the longitudinal end portion of the film 25, plays a role of restricting movement (closeness) when the film 25 moves in the longitudinal direction, and the film 25 is placed at a predetermined position in the longitudinal direction. I try to stay. That is, when the film 25 is displaced, the end surface 25d of the film abuts on the regulation surface 40a of the flange 40, and the displacement is regulated.

The guide surface 40b guides the inner surface of the rotating film 25 in the longitudinal end region of the film 25. That is, the guide surface 40b plays a role of causing the film 25 to draw a desired rotation locus by supporting the inner peripheral surface of the longitudinal end portion of the film 25 from the inside. The contact areas between the guide surface 40b and the inner surface of the film end are indicated by shaded portions (shaded portions) Sl and Sr in FIG.

When the inner surface of the end of the rotating film 25 and the guide surface 40b of the flange 40 slide in contact with each other, the heat required for fixing the toner is taken away by the flange 40. Therefore, the guide surface 40b of the flange 40 is provided in a region outside the transport region Wmax of the maximum width size paper that can be used in the device C.

The fitting portion 40d is a portion to be fitted to the outward protruding portion 30a of the stay 30. The pressure receiving portion 40c is in direct contact with the outward protruding portion 30a of the stay 30, and plays a role of pushing down the stay 140 by the contracted pressure spring 48 (LR). The flange 40 has excellent heat resistance, relatively poor thermal conductivity, and a glass fiber-containing resin such as PPS, liquid crystal polymer, PET, PA, etc. is used as a material having excellent anti-slip properties. Uses PPS.

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

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

Here, PFA is an abbreviation for tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, PTFE is an abbreviation for polytetrafluoroethylene (tetrafluoroethylene), and FEP is an abbreviation for tetrafluoroethylene / hexafluoropropylene copolymer (4,6 fluoride). Is.

The pressure roller 26 is rotatably arranged by bearing one end side and the other end side of the core shaft portion 26a between the side plates 61L and 61R on the one end side and the other end side of the device frame 60, respectively, via a bearing member 62. Has been done. Further, a drive gear 47 is concentrically arranged 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 the drive transmission unit (not shown), so that the pressurizing roller 26 acts as a drive rotating body. In FIG. 8, it is rotationally driven in the direction of arrow R26 at a predetermined peripheral speed.

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

As a result, the flanges 40L and 40R are held so as to be slidable in the vertical direction with respect to the side plates 61L and 61R, respectively. That is, the film unit 50 has a degree of freedom as a whole so that it can move between the side plates 61L and 61R in the direction closer to and farther from the pressure roller 26 along the vertical guide slits 63 and 63.

(3) Pressurizing mechanism Pressurizing springs 48L and 484R are in contact with the pressurizing receiving portions 40c of the flanges 40L and 40R, respectively. The pressure spring 48L is reduced between the spring receiving portion 67L on one end side of the top plate 66 of the apparatus frame 60 and the pressure receiving portion 40c of the flange 40L. The pressure spring 48R is reduced between the spring receiving portion 67R on the other end side of the top plate 66 of the apparatus frame 60 and the pressure receiving portion 40c of the flange 40R.

Due to the contraction reaction force of the pressure springs 48L and 48R, the outer protrusions 30a and 30a on one end side and the other end side of the stay 30 of the film unit 50 are pressed by the flanges 40L and 40R, respectively. Is working.

As a result, the guide member 29 having the heater 20 and the pressure roller 26 are pressed against each other with the film 25 sandwiched between them with a predetermined pressing force against the elasticity of the elastic layer 26b of the pressure roller 26. 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 , nip forming member ) that comes into 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 paper transport 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 via the drive transmission unit, so that the pressure roller 26 is driven and rotated. As a body, it is rotationally driven at a predetermined peripheral speed in the direction of arrow R26 in FIG. Due to the rotation of the pressure roller 26, a rotational force acts on the film 25 due to the frictional force with the pressure roller 26 at the nip portion N. As a result, the inner surface of the film 25 substantially corresponds to the rotational peripheral speed of the pressurizing roller 26 in the direction of arrow R25 while sliding 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. It makes a driven rotation at the peripheral speed.

On the other hand, the heater 20 receives electric power from the power feeding unit (triac) 51 controlled by the control unit D via a power feeding path (not shown) and generates heat steeply. The temperature of the heater 20 is detected by the thermistor 24 arranged in contact with the back 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 feeding unit 51 to the heater 20 according to the input detection temperature information, so that the temperature of the heater 20 is raised to a predetermined temperature and the temperature is maintained. To adjust.

The thermistor 24 is an element for detecting the temperature of the central portion of the heater 20 in the longitudinal direction. The temperature detected by the thermistor 24 is input to the control unit D. The thermistor 24 is an NTC (NegativeTemperatureCoerricient) thermistor, and its resistance value decreases as the temperature rises. The temperature of the heater 20 is monitored by the control unit D, and the electric power supplied to the heater 20 is adjusted by comparing with the target temperature set inside the control unit. As a result, the electric power supplied to the heater is controlled so that the heater maintains the target temperature.

In this way, in a state where the pressurizing roller 26 is rotationally driven, the film 25 is driven to rotate, and the heater 20 is raised to a predetermined temperature to control the temperature, it is undecided from the image forming portion B side. The paper P carrying the incoming toner image T is introduced into the nip portion N. The paper P is introduced into the nip portion N so that the supporting surface of the toner image T faces the film 25, and is sandwiched and conveyed. As a result, the unfixed toner image T on the paper is heated and pressed and fixed as a fixed image. The paper P that has passed through the nip portion N is separated from the surface of the film 25 by curvature and is discharged and conveyed from the fixing device C.

(Contact area and approach force on the inner circumference of the film)
As described above, the pressurizing roller 26 receives rotational drive from the drive gear 47 and is rotationally driven in the direction of arrow R26 in FIG. The film 25 is rotationally driven by the pressurizing roller 26 at the nip portion N, and is driven to rotate in the direction of arrow R25. When the film 25 is rotated, it may be displaced to the left or right in the longitudinal direction. Flange 40s (LR) are arranged on both end sides of the film 25 in order to regulate the deviation. When the film 25 is deviated, the end surface 25d of the film abuts on the regulation surface 40a of the flange 40, and the deviation is regulated.

Further, the flange 40 includes a guide surface 40b that comes into contact with the inner surface of the end portion of the film 25, and guides the inner surface of the end portion of the film 25 in the longitudinal end region of the film 25. That is, the inner surface of the film 25 is guided by the guide surface 40b of the flange 40 near both ends. Then, 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 approaching force increases.

The reason is shown below with reference to FIG. FIG. 12 is a schematic view of the top surface side of the portion 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. Moreover, the stay 30 is omitted. When the pressure roller 26 and the film 25 are normally rotated, the pressure roller 26 applies a uniform force to the film 25 in the longitudinal direction.

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

Since the transport force Hr and the same Hl are the same force, no leaning force is generated on the film 25, and the film end surface 25d and the regulation surface 40a of the flange 40 are not in contact with both the left and right ends. Further, on both left and right ends, the gap on the left side between the inner surface on the downstream side of the film 25 and the guide surface 40b is indicated by dl, and the gap on the right side is indicated by dr. At this time, the gap dl and the same dr are at the same interval.

On the other hand, when the left and right transport forces Hl and the same Hr are non-uniform, the film 25 generates a leaning force in either the left or right direction. The reason why the left and right transport forces Hl and the same Hr are non-uniform is that when there is a difference in the outer diameter of the pressure roller 26, there is a difference in the pressing force of the pressure springs 48L / 48R, there is a difference between the film 25 and the film 25. For example, the pressure roller 26 is misaligned on the left and right.

FIG. 12B is a schematic view when 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 on the opposite side (left side) in the longitudinal direction. ing. As a result, the film 25 is tilted to the downstream side on the drive gear 47 side having a large transport force and to the upstream side on the opposite side.

When the film 25 is tilted by an angle θy with respect to the paper transport direction A1, a component force Fy acts on the drive gear 47 side of the film 25. Here, the larger the angle θy, the larger the component force Fy. As a result, the film 25 is closer to the drive gear 47 side, which has a large carrying force, and is restricted by the regulation surface 40a of the flange 40R.

Here, the leaning force received by the end portion of the film 25 is proportional to the component force Fy. That is, the larger the inclination θy of the film 25, the larger the leaning force. As described above, since the inclination of the film 25 is brought about 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 leaning 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 circumference of the film 25 and the guide surface 40b of the flange 40. FIG. 13 is a schematic cross-sectional view of a unit formed by the flange 40R on the drive gear 47 side (right side), the heater holder 29, and the heater 21. For convenience of explanation, FIGS. 13 to 16 and 1 to 3 show the shapes of the flange 40 and the like in a deformed shape, and the shapes of the respective parts are shown in comparison with the flange 40 and the like in FIGS. 8 and 10. And dimensional ratios are not consistent.

The right side of the drawing with respect to the paper transport direction A1 in the nip portion N is the upstream side (the upstream side when the flange 40 is divided into the upstream side and the downstream side with respect to the paper transport direction A1 with respect to the center of the nip). 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 shaded portion G in (a). Further, a state in which the film 25 is stretched over the guide region G is shown in (b). F indicated by the thick line in (b) is the region (film traveling track) on which the inner circumference of the film 25 travels.

A region where the film 25 is not guided by the guide surface 40b is generated on the downstream side, and the distance (gap interval) between the most protruding point on the downstream side of the guide surface 40b and the film traveling track F is defined as dr. This interval dr becomes smaller as the difference between the inner peripheral length of the film, that is, the total length of the film traveling track F and the total length of the guide region G is smaller.

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

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

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

Therefore, it is necessary to set the inner circumference usage rate Rgf in an appropriate range. As a result, the inner circumference usage rate Rgf is preferably set in the range of 95 to 99.8%, and more preferably in the range of 98 to 99%. In Example 1, the inner circumference usage rate Rgf was set so as to be 98.5%. As a result, the contact region between the film 25 and the guide surface 40b of the flange 40R is the region indicated by the arrow Jr in (b) (when the film 25 is rotated, the guide surface 40b and the inner peripheral surface of the end portion of the film 25 slide together. Contact area: Hereinafter referred to as a second contact area). The case of the flange 40L is the same as that of the flange 40R.

(Regulatory surface of flange and film breakage)
Next, the regulation surface 40a of the flange 40R and the film breakage will be described. FIG. 14 shows an enlarged view when the end surface 25d of the film 25 abuts on the regulation surface 40a of the flange 40R when the flange 40 of the reference example is used, and a cross-sectional view of the guide surface 40b. When the film 25 is rotated, 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 region Jr described in FIG. 13 (b).

The film 25 bends (bends) inward in a state where the inner surface of the end portion is not in contact with the guide surface 40b, that is, in a region where there is a gap dr between F and G on the downstream side of the second contact region Jr. The phenomenon may occur.

For example, if a biasing force is generated in the direction of the arrow in the drawing and the film end surface 25d abuts on the regulation surface 40a, the film end may be bent inward. (A) is a schematic view of a state in which the end portion of the film is folded inward by a pulling force in the downstream region. When the film is broken, the running of the film 25 is disturbed, which may cause poor paper transport or poor image quality, or stress may be concentrated on the bent portion of the film 25, leading to damage to the edge of the film 25.

On the other hand, in the film 25, as shown in (b), in the second contact region Jr where the inner surface of the film end is guided by the guide surface 40b, a biasing force is generated in the direction of the arrow in the figure to regulate the film end surface 25d. Even if it hits the surface 40a, the phenomenon of folding 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 that of the flange 40R.

In order to solve the problem of film breakage, it is effective to provide a relief tapered shape portion on the regulation surface 40a of the flange 40R. FIG. 15 is an enlarged schematic view of the vicinity of the film end when the tapered shape portion 40f is provided on the downstream side of the regulation surface 40a of the flange 40R. With this configuration, in the region where the tapered shape portion 40f is provided, the film end surface 25d and the regulation surface 40a do not come into contact with each other, so that the phenomenon of inward folding can be prevented. The case of the flange 40L is the same as that of the flange 40R.

However, on the other hand, if the tapered shape portion 40f is made too wide, the contact region between the film end surface 25d and the regulation surface 40a becomes small, and the approaching force per unit area received by the film 25 increases. As a result, problems such as the end of the film not being able to withstand the leaning force and buckling occur.

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

The first point is "to prevent the edge of the film from breaking", and the second point is "to reduce the leaning force received per unit area of the film". The conditions regarding the shape in which the flange 40 is required to satisfy these conditions are as follows: "The film end face should not come into contact with the regulation surface in the region where the inner circumference of the film is not guided by the guide surface", and the second point. Is to "make a wide contact area between the end face of the film and the regulation surface".

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

The region Jr indicated by the arrow and the shaded portion in the figure is the above-mentioned second contact region in which the inner peripheral surface of the film 25 and the guide surface 25b are in contact with each other. The flange 40R of the first embodiment has an inner peripheral usage rate Rgf of 98.5%, and as a result, as shown in FIG. 1, a second contact region Jr is provided 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 region Jr, the gap dr on the downstream side can be reduced, and as a result, the leaning force received by the film 25 can be suppressed to 400 gf or less.

Further, the regulation surface 40a of the flange 40R of the first embodiment has a shape portion (hereinafter, referred to as a tapered shape portion) having an inclination in a direction away from the end portion of the film 25 on the upstream side and the downstream side, respectively.
It has Tj (third region) and Tk (first region) . The start positions of the tapered shape portions Tj and Tk on the upstream side and the downstream side are indicated by 40 cz on the upstream side and 40 ck on the downstream side.

At the start positions 40cj and 40ck of the tapered shape portions Tj and Tk, a shape (R shape) that continuously changes the inclination is provided in order to prevent the film end surface 25d and the regulation surface 40a from locally strongly hitting each other. Is desirable. That is, it is desirable that the shapes of the tapered shape portions Tj and Tk away from the film end face 25d are discontinuous and the inclination does not change. In the flange 40R of the first embodiment, the taper start positions 40cj and 40ck are provided with a gentle R shape both upstream and downstream.

The clearance angles (inclination angles) of the tapered shape portions Tj and Tk are indicated by θTj on the upstream side and θTk on the downstream side in the figure. The clearance angle θTj of the tapered shape portion Tj on the upstream side and the clearance angle θTk of the tapered shape portion Tk on the downstream side are different. In the first embodiment, the angle θTk of the tapered shape portion Tk on the downstream side is smaller than the angle θTj of the tapered shape portion Tj on the upstream side. In other words, θTj is set to be larger than θTk. By doing so, it is possible to prevent local contact of the film 25 in the vicinity of the relief taper portion.

The starting positions 40cj and 40ck of the tapered shape portions Tj and Tk are asymmetrical on the upstream side and the downstream side, and the downstream side is arranged at a position closer to the apex portion. That is, the flange 40R has tapered shape portions Tj and Tk on the upstream side and the downstream side in the paper transport direction A1 with the nip portion N in the middle, and the tapered shape portion Tj on the upstream side is from the tapered shape portion Tk on the downstream side. Is also close to the nip part N.

It is sandwiched between the upstream and downstream tapered shape portions Tj and Tk starting positions 40 cn (downstream end of the second region in the rotation direction of the film 25 ) and 40 ck (upstream end of the second region in the rotation direction of the film 25). The film end surface 25d and the regulation surface 40a come into contact with each other in the region Zr (second region) . That is, the region Zr is a contact region (hereinafter, referred to as a first contact region) in which the regulation surface 40a and the end surface 25d of the film 25 are in sliding contact with each other when the film 25 is rotated. The first contact region Zr is substantially at the same position as the above-mentioned second contact region Jr.

That is, the flange 40R is separated from the film end surface 25d so that the first contact region Zr and the second contact region Jr are substantially the same position in the circumferential direction of the film 25 when the film 25 is rotated. It has shaped parts Tj and Tk (retracted) . Both the first contact region Zr and the second contact region Jr are provided from the upstream side to the downstream side in the transport direction A1 of the paper P in the nip portion N.

By setting the first contact region Zr and the second contact region Jr at substantially the same position in this way, the requirements of the first and second points can be satisfied. That is, since the film end surface and the regulation surface 40a come into contact with each other only at the inner peripheral guide portion, breakage can be prevented, and the force received by the film per unit area can be reduced by widening the second contact area Jr. .. Further, since the regulation surface and the guide surface are provided from the upstream side to the downstream side in the paper transport direction (recording material transport direction), the posture of the film is stable.

The case of the flange 40L is the same as that of the flange 40R. In this way, by using the flange 40 (LR) of the first embodiment, the durability of the film 25 can be satisfied throughout the life even in a high-speed machine that requires higher durability performance. ..

(Comparison result of the fixing device of Example 1 and the fixing device of Comparative Example)
In order to explain the action and effect of the fixing device of Example 1, the results of comparative experiments with the fixing devices of Comparative Examples 1 and 2 are shown. The flange 40 shown in FIG. 1 described above is used for the fixing device of the first embodiment. On the other hand, in the fixing devices of Comparative Examples 1 and 2, the flanges 40 shown in FIGS. 16A and 16B are used, respectively. Since the configurations of the other Comparative Examples 1 and 2 are the same as those of the first embodiment, the description thereof will be omitted. 16 (a) and 16 (b) are flanges 40R, respectively, but the same applies to flanges 40F.

FIG. 16A is a schematic cross-sectional view of the flange 40R used in Comparative Example 1. The difference between the flange 40R of Comparative Example 1 and the flange 40R of Example 1 (FIG. 1) is that the start position 40ck of the tapered shape portion Tk on the downstream side provided on the regulation surface 40a is shifted to the downstream side. It is a point.

The flange 40R of Comparative Example 1 is provided at positions where the upstream and downstream tapered shape portions Tj and Tk start positions 40 jk and 40 ck are symmetrical with respect to the apex portion of the guide portion 40b. At this time, the first contact region in which the end surface 25d of the film 25 and the regulation surface 40a are in sliding contact is the region indicated by Zr in the drawing, and the second contact region Jr in which the inner circumference of the film 25 and the guide surface 40b are in sliding contact. It becomes a wider area than. As a result, the film end surface 25d is pressed against the regulation surface 40a in the first contact region Zr in the region not in contact with the inner circumference of the film 25 (outside the region of the second contact region Jr), and the film is broken. 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 Comparative Example 2 and the first embodiment is that the start position 40ck of the tapered shape portion Tk on the downstream side provided on the regulation surface 40a is shifted to the upstream side.

The flange 40R of Comparative Example 2 is formed so that the taper start position 40ck of the tapered shape portion Tk on the downstream side is parallel to the nip line from the apex of the guide portion 40b of the flange 40R. At this time, the first contact region (second region) in which the end surface 25d of the film 25 and the regulation surface 40a of the flange 40 are in sliding contact is the region indicated by the arrow Zr in the figure (the upstream end of the region Zr in the rotation direction of the film 25 ( 2nd region) . 40ck) is a region Zr) located downstream of the upstream end of the second contact region Jr in the rotation direction of the film 25, and the inner circumference of the film 25 and the guide surface 40b are in sliding contact with each other. The area is narrower than the contact area Jr. As a result, the leaning force applied to the film 25 per unit area becomes large, and buckling of the film 25 is likely to occur.

Next, the configurations of other fixing devices are shown. The configurations of the other fixing devices are the same in Example 1 and Comparative Examples 1 and 2. The pressing force of the film 25 and the pressure roller 26 is 186.2 N (19 kgf), and the nip width thereof is 9 mm. The printing speed of the image forming apparatus is 60 sheets / minute (A4 size: lateral feed), and the life of the fixing apparatus C is 200 k sheets. The environment in which the test was conducted was a temperature of 23 ° C. and a humidity of 50%, and CS-680 (A4 size 68 g / cm2) was used as the evaluation paper.

Under these conditions, in the image forming apparatus using the fixing devices of Example 1, Comparative Examples 1 and 2, 200 k sheets of paper were passed through in the single-sided continuous paper passing mode, and the 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 devices of Example 1 and Comparative Examples 1 and 2. The symbols indicating the level of durability in Table 1 will be described. ◯ in the table indicates that the durability of the film 25 is good without any problem. The x in the table indicates that a problem related to the durability of the film 25 has occurred, and an image defect has occurred due to the problem, which is a practical problem.

According to Table 1, in the fixing device of Comparative Example 1, when 100 k sheets were printed, the end portion of the film 25 was torn into a ring shape with a width of about 2 mm, and the longitudinal length of the film 25 was shortened. It was. As a result, the running performance of the film 25 becomes unstable, the paper transport is disturbed, and image defects occur.

The reason why the phenomenon of ring-shaped tearing with a width of 2 mm occurred is that the edge of the film is broken. Since the film 25 is broken on the downstream side and the break is eliminated in the nip and on the upstream side, the film 25 is fatigue-fractured by repeating the folding and the breaking.

Further, in the fixing device of Comparative Example 2 , the evaluation at the time when the problem occurred in the fixing device of Comparative Example 1 when 100 k sheets were printed was good (◯), and when 150 k sheets were printed , the evaluation was good. At the end of the film 25, a plurality of cracks were formed in the longitudinal direction and spread in a trumpet shape. As a result, the running of the film 25 became unstable, the paper transport was disturbed, and image defects occurred. The reason why it spreads like a trumpet is that the force applied to the edge of the film per unit area is large. The strength of the film is reduced due to the progress of wear of the base layer due to durability and deterioration due to heat, and buckling occurs in the latter half of durability.

On the other hand, in the fixing device of Example 1, no problem related to durability occurred throughout the life of 200 k. The reason is that the second contact region Jr where the inner circumference of the film edge and the guide surface 40b are in sliding contact and the first contact region Zr where the film end surface 25d and the regulation surface 40a are in sliding contact are set to substantially the same position. It is possible to prevent the end of the film from breaking. At the same time, it was possible to reduce the leaning force per unit area of the film edge.

As described above, it can be seen that by using the fixing device of Example 1, an action and effect not found in Comparative Examples 1 and 2 can be obtained. That is, even on the downstream side, even in the fixing device in which the inner peripheral surface of the film and the guide surface of the flange and the end surface of the film and the regulation surface of the flange are in contact with each other, the film approaching force is reduced without causing the film end to break, and the film It becomes possible to satisfy the durability performance.

In the first embodiment, the second contact region Jr and the first contact region Zr are set to substantially the same position, but it is difficult to set them to the same position in all cases in consideration of variation. In this case, the first contact region Zr is slightly smaller than the second contact region Jr so that the first contact region Zr does not become wider than the second contact region Jr even when the tolerance swings to the maximum. It is desirable to set it so as to prevent the edge of the film from breaking.

<< 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 configurations are the same as those of the first embodiment, so the description thereof will be omitted. FIG. 2 shows a schematic cross-sectional view showing the flange 40 of the second embodiment. The flange 40 of the second embodiment is characterized by having an eaves portion 40g on the regulation surface 40a.

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

On the other hand, if the film 25 comes into contact with the eaves portion 40 g during normal printing, problems such as scraping of the surface layer and torque increase may occur. That is, if the eaves portion 40g is too far or too close to the traveling track F of the film 25, a problem may occur.

Therefore, in the flange 40 of the second embodiment, the distance between the eaves portion 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 taper shape start position 40cc on the upstream side and the taper shape start position 40ck on the downstream side on the regulation surface 40a. On the other hand, on the downstream side of the taper shape start position 40ck on the downstream side, the interval dc is larger than the above interval dj.

That is, the flange 40 has a canopy-shaped portion 40 g that covers the outer periphery of the end portion of the film 25. Further, the distance between the eaves-shaped portion 40g and the second contact region Jr between the tapered-shaped portion Tk on the downstream side and the tapered-shaped portion Tj on the upstream side is defined as dj. Let dk be the distance between the eaves-shaped portion 40 g and the second contact region Jr in the region downstream of the tapered shape portion Tk on the downstream side. The distance dj is smaller than the distance dk.

With such a configuration, the film traveling track F and the eaves shape 40 g can be contained within a predetermined distance even in the downstream region where the film traveling track F is separated from the guide region G. As a result, a good fixed image can be supplied without causing a problem during both printing and jam processing.

<< Example 3 >>
In order to obtain a good image, a bias (potential) having a polarity (here positive) opposite to the charging polarity (here negative) of the toner is applied to the conductive base layer 25a ((b) in FIG. 9) of the film 25. The means to do so is effective. By applying a bias to the film 25, an electric field force acts in the direction of pressing the unfixed toner T against the paper P. The force of this electric field can suppress the phenomenon that the toner T scatters behind the paper P.

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

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

Therefore, in the third embodiment, the power feeding mechanism 52 is installed in the second contact region Jr where the inner surface of the film end and the guide surface 40b are in contact with each other. That is, the power feeding mechanism 52 is installed in the region sandwiched between the taper start position 40 cz of the tapered shape portion Tkj on the upstream side and the taper start position 40 ck of the tapered shape portion Tk on the downstream side. By doing so, even when the film 25 rotates, power can be stably supplied, and the occurrence of image defects can be prevented.

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

<< Other matters >>
(1) The pressurizing configuration of the film unit 50 and the pressurizing roller 26 for forming the nip portion N may be an apparatus configuration in which the pressurizing roller 26 pressurizes the film unit 50. It is also possible to form a structure in which both the film unit 50 and the pressure roller 26 are pressed against each other. That is, the pressurizing mechanism may be configured to pressurize at least one of the film unit 50 and the pressurizing 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, and 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, the flanges 40 are arranged on both ends of the film 25 on one end side and the other end side, but the device configuration is such that the film 25 moves toward the one end side or the other end side exclusively. It is also possible to configure the device so that the flange 40 is arranged only on the side of the moving side.

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

(6) In the embodiment, as the image heating device, a fixing device for heating and fixing an unfixed toner image formed on the recording material has been described as an example, but the present invention is not limited to this. The present invention can also be applied to an apparatus (glossiness improving apparatus) for increasing the gloss (glossiness) of an image by reheating a toner image fixed or hypothesized on a recording material.

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

C ... image heating device (fixing device), P ... recording material, T ... toner image, N ... nip part, 25 ... first rotating body (film), 25d ... end face, 26 ... 2 rotating body (pressurizing roller), 40 ... regulation member (flange), 40a ... regulation surface, 40b ... guide surface, Zr ... first contact area, Jr ... second contact area, Tj・ ・ Upstream side shape part, Tk ・ ・ Downstream side shape part

Claims (8)

With a tubular film
A roller that comes into contact with the outer surface of the film and forms a nip portion that sandwiches and conveys the recording material between the film and the roller.
A guide surface that is arranged at a position facing the end surface of the film in the longitudinal direction, faces the inner surface of the end portion of the film in the longitudinal direction, and guides the rotation of the film, and an end surface of the film in the longitudinal direction. A regulating member having a facing surface facing the film, and restricting the movement of the film in the longitudinal direction by contacting the end surface of the film with the facing surface when the film moves in the longitudinal direction. When,
In a fixing device that fixes the image to the recording material while sandwiching and transporting the recording material on which the image is formed by the nip portion.
When the fixing device is viewed in the longitudinal direction, the facing surfaces are a first region located downstream of a line passing through the center of the nip portion in the transport direction of the recording material in the nip portion, and the transport direction. Has a second region located upstream of the first region in the above.
In the longitudinal direction, the first region is recessed from the end face of the film more than the second region.
When the fixing device is viewed in the longitudinal direction, the second region of the facing surface and the contact region of the guide surface that contacts the inner surface of the film when the film rotates are both the nip. The portion of the nip portion that is provided from the upstream side to the downstream side of the line passing through the center of the portion and is upstream of the line passing through the center of the nip portion is the rotation direction of the film rather than the portion on the downstream side. Is long in
When the fixing device is viewed in the longitudinal direction, the upstream end of the second region in the rotation direction is a position downstream of the upstream end of the contact region in the rotation direction or the upstream end of the contact region and the rotation. Located in the same position in the direction,
A fixing device characterized in that. The fixing device according to claim 1, wherein the first region is inclined so as to approach the end face of the film as it goes downstream in the rotation direction. The facing surface further has a third region located downstream of the second region in the rotational direction, and in the longitudinal direction, the third region is the end face of the film with respect to the second region. The fixing device according to claim 1 or 2, wherein the film is retracted from. The first region is inclined so as to approach the end face of the film as it goes downstream in the rotation direction, and the third region separates from the end face of the film as it goes downstream in the rotation direction. The fixing device according to claim 3, wherein the film is inclined to. The fixing device according to claim 4, wherein the inclination angle of the first region is smaller than the inclination angle of the third region. The fixing device according to any one of claims 1 to 5, further comprising a nip forming member that comes into contact with the inner surface of the film and forms the nip portion together with the roller via the film. apparatus. When the fixing device is viewed in the longitudinal direction, the length of the contact region and the guide region G formed by the nip forming member in the rotation direction is Lg, and the length of the inner peripheral surface of the film is Lf. The fixing device according to claim 6, wherein the inner surface usage rate Rgf (= Lg / Lf) is in the range of 95 to 99.8%. The fixing device according to claim 6 or 7, wherein the nip forming member has a heater.

Images