JP7151829B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to image forming apparatuses such as copiers, printers, facsimiles, or multi-function machines thereof, and fixing devices installed therein.

2. Description of the Related Art Conventionally, in image forming apparatuses such as copiers and printers, there have been known fixing devices that have a short warm-up time and first print time and are less likely to cause defective fixing even when the speed of the apparatus is increased (for example, See Patent Document 1.).

Specifically, the fixing device described in FIGS. 2, 4, etc. of Patent Document 1 includes a fixing belt (reference numeral 21) and a pipe-shaped fixing device fixed so as to face the inner peripheral surface of the fixing belt except for the nip portion. A heating member (reference numeral 22), a heater (reference numeral 25) provided in the heating member for heating the heating member, and a pressure roller (reference numeral 31) through the fixing belt to form a nip portion. It is composed of a fixing member (reference numeral 26) installed inside the fixing belt, a substantially plate-like reinforcing member (reference numeral 23) that reinforces the fixing member by coming into contact with the fixing member, and the like. The substantially plate-like reinforcing member has a relatively narrow width (the length in the conveying direction) so as to abut on a part of the surface of the fixing member.
Then, the fixing belt is heated by a pipe-shaped heating member heated by a heater, and the toner image on the recording medium conveyed toward the nip portion is subjected to heat and pressure at the nip portion to be transferred onto the recording medium. It will be established.

In the fixing device disclosed in Japanese Patent Laid-Open No. 2002-200000, the fixing member is installed so as to be fitted into the concave portion of the pipe-shaped heating member. Even if the balance of the force that the fixing member receives from the reinforcing member becomes unbalanced, the fixing member does not fall.

On the other hand, in the fixing device disclosed in Patent Document 1, etc., the pipe-shaped heating member is removed and the pipe-shaped heating member is interposed for the purpose of further improving the heating efficiency of the fixing belt and reducing the cost and size of the device. A conceivable measure is to employ a configuration in which the fixing belt is directly heated by a heating means without the heating means.
However, in that case, since there is no heating member (recess) to prevent the fixing member from falling, it becomes impossible to hold the fixing member in a state in which the reinforcing member is pressed against it in a well-balanced manner, and there is a possibility that the fixing member will fall. There is If the fixing member is tilted in such a manner, a desired nip cannot be formed, resulting in poor fixing of the output image or poor conveyance of the recording medium.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. To provide a fixing device and an image forming apparatus in which a fixing member in a state of pressure contact does not fall down.

The fixing device according to the first aspect of the present invention is a flexible endless fixing belt, and the fixing belt is disposed inside the fixing belt, and the fixing belt is sandwiched between a pressurizing rotating body. a nip forming member that forms a nip portion between the fixing belt and the pressurizing rotator in which a recording medium is conveyed; a heat source that faces the fixing belt and heats the fixing belt; and the fixing belt. and a reinforcing member having a facing surface that contacts the nip forming member, and a pair of guide members that guide both ends of the fixing belt in the width direction, wherein the nip forming member is a recording medium. an upstream contact portion that contacts the facing surface on the upstream side in the conveying direction, a downstream contact portion that contacts the facing surface on the downstream side in the conveying direction, the upstream contact portion and the downstream side a non-contact portion that does not contact the facing surface between the contact portion and the pair of guide members, each of the pair of guide members having an insertion portion inside the fixing belt; They are separated from each other inside the fixing belt.

In the present application, a state in which the fixing member and the reinforcing member are "fixed" is defined as a state in which the fixing member and the reinforcing member are held non-rotatably without being rotationally driven. Therefore, for example, even when the fixing member is biased toward the nip portion by biasing means such as a spring, the fixing member is "fixed" as long as the fixing member is held non-rotatably. state.

Further, in the present application, the “conveyance direction” of the recording medium is the same direction as the tangential direction of the nip portion when the fixing belt and the pressure rotating body are in contact with each other in an ideal circular arc without deformation at the nip portion. be defined as
Further, in the present application, the "width direction" is defined as a direction orthogonal to the conveying direction, which is the same direction as the rotation axis direction of the fixing belt and the pressure rotating member.

In the present invention, the fixing member is provided with a plurality of rows of protrusions that protrude toward the reinforcing member so as to come into contact with the reinforcing member along the conveying direction. As a result, even when the warm-up time and the first print time are short and the apparatus is speeded up, there is no fixing failure, etc., and the fixing member that is in pressure contact with the reinforcing member does not fall down. An apparatus and an image forming apparatus can be provided.

1 is an overall configuration diagram showing an image forming apparatus according to Embodiment 1 of the present invention; FIG. 2 is a configuration diagram showing a fixing device; FIG. 3 is a side view of the fixing device as viewed in the width direction; FIG. It is an enlarged view showing the vicinity of the nip portion. 4 is a cross-sectional side view showing a fixing belt held by a holding member; FIG. 4 is a schematic front view showing a state in which a fixing belt and a reinforcing member are held by a holding member; FIG. It is (A) a side view and (B) a bottom view showing the fixing member in a state where the sheet-like member is covered. In FIG. 7A, (A) a schematic cross-sectional view showing the X1-X1 cross section, (B) a schematic cross-sectional view showing the X2-X2 cross section, and (C) a schematic cross-sectional view showing the X3-X3 cross section. be. It is (A) a side view and (B) a bottom view showing a fixing member. FIG. 4 is an exploded view showing a sheet-like member; It is a top view which shows a plate-shaped member. FIG. 2 is a configuration diagram showing a fixing device according to Embodiment 2 of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant description thereof will be appropriately simplified or omitted.

Embodiment 1.
Embodiment 1 of the present invention will be described in detail with reference to FIGS. 1 to 11. FIG.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
As shown in FIG. 1, the image forming apparatus 1 according to the first embodiment is a tandem color printer. Four toner bottles 102Y, 102M, 102C, and 102K corresponding to respective colors (yellow, magenta, cyan, and black) are detachably (exchangeably) installed in the bottle storage unit 101 above the image forming apparatus main body 1. ing.
An intermediate transfer unit 85 is arranged below the bottle accommodating portion 101 . Imaging units 4Y, 4M, 4C, and 4K corresponding to respective colors (yellow, magenta, cyan, and black) are arranged side by side so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85 .

Photoreceptor drums 5Y, 5M, 5C and 5K are arranged in the image forming units 4Y, 4M, 4C and 4K, respectively. Further, a charging section 75, a developing section 76, a cleaning section 77, a neutralizing section (not shown), and the like are arranged around each of the photosensitive drums 5Y, 5M, 5C, and 5K. Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoreceptor drums 5Y, 5M, 5C, and 5K, and each photoreceptor drum 5Y, 5M, 5C, An image of each color is formed on 5K.

The photosensitive drums 5Y, 5M, 5C, and 5K are rotated clockwise in FIG. 1 by a driving motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging section 75 (charging step).
After that, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position. (This is the exposure process.)

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

After that, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning portion 77, and at this position the untransferred toner remaining on the photosensitive drums 5Y, 5M, 5C, and 5K is removed by the cleaning portion. It is mechanically recovered by the cleaning blade of 77 (cleaning process).
Finally, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach a position facing the static elimination unit (not shown), and the residual potential on the photoreceptor drums 5Y, 5M, 5C, and 5K is removed at this position. be.
Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K are completed.

After that, the toner images of each color formed on each photosensitive drum through the development process are superimposed and transferred onto the intermediate transfer belt 78 . A color image is thus formed on the intermediate transfer belt 78 .
Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning section 80. , etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 79Y, 79M, 79C and 79K sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C and 5K respectively to form primary transfer nips. A transfer bias opposite in polarity to the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K.
The intermediate transfer belt 78 runs in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are superimposed on the intermediate transfer belt 78 and primarily transferred.

After that, the intermediate transfer belt 78 on which the toner images of each color have been superimposed and transferred reaches a position facing the secondary transfer roller 89 . At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 with the secondary transfer roller 89 to form a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 78 is transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78 .
After that, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning station 80 . At this position, untransferred toner on the intermediate transfer belt 78 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 78 are completed.

Here, the recording medium P conveyed to the position of the secondary transfer nip passes through a paper feed roller 97, a pair of registration rollers 98 (a pair of timing rollers), etc. transported through
Specifically, a plurality of recording media P such as transfer paper are stored in the paper feeding unit 12 in a piled manner. When the paper feed roller 97 is rotated counterclockwise in FIG. 1, the uppermost recording medium P is fed between the rollers of the registration roller pair 98 .

The recording medium P conveyed to the registration roller pair 98 temporarily stops at the roller nip position of the registration roller pair 98 whose rotational drive is stopped. Then, the registration roller pair 98 is rotationally driven in time with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. A desired color image is transferred onto the recording medium P in this manner.

After that, the recording medium P onto which the color image has been transferred at the position of the secondary transfer nip is conveyed to the position of the fixing section 20 . At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure from the fixing belt 21 and pressure roller 31 .
After that, the recording medium P passes between the rollers of the paper ejection roller pair 99 and is ejected to the outside of the apparatus. The recording medium P ejected to the outside of the apparatus by the paper ejection roller pair 99 is sequentially stacked on the stack section 100 as an output image.
Thus, a series of image forming processes in the image forming apparatus are completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS. 2 to 11. FIG.
2 to 4, fixing device 20 includes fixing belt 21 (belt member) as a fixing member, fixing member 26 (nip portion forming member), reinforcing member 23, and heater 25 (heat source) as heating means. ), a pressure roller 31 as a pressure rotating member, a temperature sensor 40, a sheet-like member 22, a screw 24, a plate-like member 28 (fixed plate), a reflecting member 27, and the like.

Here, the fixing belt 21 is a thin flexible endless belt, and rotates (runs) in the direction of the arrow (counterclockwise) in FIG. The fixing belt 21 has a base material layer, an elastic layer, and a release layer, which are sequentially laminated from the inner peripheral surface 21a (the surface in sliding contact with the fixing member 26), and the total thickness is 1 mm or less. is set to
The base material layer of the fixing belt 21 has a layer thickness of 30 to 50 μm, and is made of a metal material such as nickel or stainless steel or a resin material such as polyimide.
The elastic layer of the fixing belt 21 has a layer thickness of 100 to 300 μm and is made of a rubber material such as silicone rubber, foamed silicone rubber, fluororubber, or the like. By providing the elastic layer, minute unevenness is not formed on the surface of the fixing belt 21 at the nip portion, and heat is evenly transferred to the toner image T on the recording medium P, thereby suppressing the generation of the orange peel image.
The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm and is made of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES ( polyether sulfide), etc. By providing the release layer, the releasability (releasability) of the toner T (toner image) is ensured.

Further, the diameter of the fixing belt 21 is set to be 15 to 120 mm. In addition, in Embodiment 1, the inner diameter of the fixing belt 21 is set to 30 mm.
A fixing member 26, a heater (heating means), a reinforcing member 23, a reflecting member 27, a sheet-like member 22, a screw 24, a plate-like member 28 (fixing plate), etc. is fixed.
Here, the fixing member 26 is fixed so as to be in sliding contact with the inner peripheral surface 21 a of the fixing belt 21 . The fixing member 26 presses against the pressure roller 31 via the fixing belt 21 to form a nip portion where the recording medium P is conveyed. 3 and 5, the fixed member 26 is held at both ends in the width direction by flanges 29 (holding members) fixedly supported by the side plates 43 of the fixing device 20 . Further, the fixing belt 21 is rotatably held by flanges 29 at both ends in the width direction. The configurations of the fixing member 26 and the flange 29 will be described later in more detail.
The fixing belt 21 is directly heated by radiant heat from a heater 25 (heating means) installed therein.

The heater 25 as heating means is a halogen heater (or a carbon heater), and both ends thereof are fixed to the side plates 43 of the fixing device 20 (see FIG. 3). A portion of the fixing belt 21 except for the nip portion is mainly heated by radiant heat from the heater 25 (heating means) whose output is controlled by the power supply section of the apparatus main body 1 . Furthermore, heat is applied to the toner image T on the recording medium P from the heated surface of the fixing belt 21 . The output control of the heater 25 is performed based on the detection result of the belt surface temperature by a temperature sensor 40 such as a thermistor facing the surface of the fixing belt 21 . Further, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature by controlling the output of the heater 25 in this manner.
Although one heater 25 is installed on the inner peripheral surface side of the fixing belt 21 in the first embodiment, a plurality of heaters may be installed on the inner peripheral surface side of the fixing belt 21 .

As described above, in the fixing device 20 according to Embodiment 1, the fixing belt 21 is heated over a relatively wide range in the circumferential direction, rather than only a part of the fixing belt 21 is locally heated. Therefore, even when the speed of the apparatus is increased, the fixing belt 21 is sufficiently heated, and the occurrence of fixing failure can be suppressed. That is, since the fixing belt 21 can be efficiently heated with a relatively simple configuration, the warm-up time and the first print time can be shortened, and the size of the apparatus can be reduced.
In particular, since the fixing device 20 in Embodiment 1 is configured such that the fixing belt 21 is directly heated by the heater 25 (heating means), the heating efficiency of the fixing belt 21 is further improved. The fixing device 21 can be further reduced in cost and size.

Here, referring to FIGS. 5 and 6, two flanges 29 as holding members are made of a heat-resistant resin material or the like, and are fitted to side plates 43 at both ends in the width direction of fixing device 20, respectively. there is The flange 29 includes a guide portion 29a for holding the fixing belt 21 while maintaining the circular posture of the fixing belt 21, a stopper portion 29b for restricting movement of the fixing belt 21 in the width direction (belt deviation), and the like. is provided.
Further, on the inner peripheral surface 21a of the fixing belt 21, sliding portions (surrounded by broken lines in FIG. 5) with the guide portions 29a of the flanges 29 are provided at both ends in the width direction (right and left direction in FIG. 5). A low-friction portion 21a1 is formed to reduce the sliding resistance at this portion. Specifically, the low-friction portion 21a1 is formed by coating the surface of the base material layer with a low-friction material such as fluororesin. With such a configuration, even if the fixing belt 21 and the flange 29 (the guide portion 29a) are in sliding contact with each other due to the rotation (running) of the fixing belt 21, the wear and deterioration of the fixing belt 21 and the flange 29 (the guide portion 29a) are less likely to occur. .
In the first embodiment, the members that come into contact with the inner peripheral surface 21a of the fixing belt 21 are only the flanges 29 at both ends in the width direction and the fixing member 26, and other members that come into contact with the inner peripheral surface 21a. There is no member (belt guide) that guides the rotation of the fixing belt 21 by doing so.

Here, in Embodiment 1, the reinforcing member 23 that reinforces the strength of the fixing member 26 that forms the nip portion is fixed to the inner peripheral surface of the fixing belt 21 . Referring to FIG. 3 , reinforcing member 23 is formed to have the same length in the width direction as fixing member 26 , and both ends in the width direction are held by flanges 29 (holding members) of fixing device 20 . It is Specifically, the reinforcing member 23 is sandwiched between the flange 29 and the fixing member 26 to determine its position. In the first embodiment, as shown in FIG. 6, the end surfaces (reference surfaces 23b) of the two standing portions 23c of the reinforcing member 23 (the portions that stand in the direction away from the facing surface 23a) contacts a holding portion 29c (see FIG. 6) of the flange 29 to hold the reinforcing member 23. As shown in FIG. On the other hand, the reinforcing member 23 can be held in contact with the side plate 43 instead of the holding portion 29 c of the flange 29 .
The reinforcing member 23 abuts against the pressure roller 31 via the fixing member 26 and the fixing belt 21, thereby preventing the fixing member 26 from receiving the pressure of the pressure roller 31 at the nip portion and being greatly deformed. ing. In Embodiment 1, the reinforcing member 23 is a substantially U-shaped plate-like member formed so that the recess faces the side where the heater 25 is located. In order to satisfy the functions described above, the reinforcing member 23 is preferably made of a metal material having high mechanical strength such as stainless steel or iron.
In addition, the structure of the reinforcing member 23 will be described later in more detail.

Further, in Embodiment 1, a reflecting member 27 (reflecting plate) is fixed to the surface of the reinforcing member 23 facing the heater 25 . As a result, heat directed from the heater 25 toward the reinforcing member 23 (heat for heating the reinforcing member 23) is reflected by the reflecting member 27 and used to heat the fixing belt 21, so that the heating efficiency of the fixing belt 21 increases. It will improve further.
Similar effects can be obtained even if part or all of the surface of the reinforcing member 23 facing the heater 25 is mirror-finished or provided with a heat-insulating member.

Referring to FIG. 2, a pressure roller 31 as a pressure rotating body that abuts against the outer peripheral surface of the fixing belt 21 at the position of the nip portion has a diameter of 30 mm, and has an elastic layer on a cored bar 32 having a hollow structure. 33 was formed. The elastic layer 33 of the pressure roller 31 (pressure rotating body) is made of a material such as foamed silicone rubber, silicone rubber, or fluororubber. A thin release layer made of PFA, PTFE, or the like may be provided on the surface layer of the elastic layer 33 . The pressure roller 31 presses against the fixing belt 21 to form a desired nip portion between the two members. 3, the pressure roller 31 is provided with a gear 45 that meshes with a driving gear of a drive mechanism (not shown), and the pressure roller 31 moves in the direction of the arrow (clockwise) in FIG. rotationally driven. Further, the pressure roller 31 is rotatably supported by side plates 43 of the fixing device 20 via bearings 42 at both ends in the width direction thereof. A heat source such as a halogen heater may be provided inside the pressure roller 31 .

If the elastic layer 33 of the pressure roller 31 is made of a sponge-like material such as foamed silicone rubber, the pressure acting on the nip portion can be reduced. can be mitigated. Furthermore, the heat insulation of the pressure roller 31 is enhanced, and the heat of the fixing belt 21 is less likely to move to the pressure roller 31 side, so that the heating efficiency of the fixing belt 21 is improved.
Further, in Embodiment 1, the fixing belt 21 is formed so that the diameter of the fixing belt 21 is substantially equal to the diameter of the pressure roller 31 . can also be formed. In this case, since the curvature of the fixing belt 21 at the nip portion is smaller than the curvature of the pressure roller 31 , the recording medium P delivered from the nip portion is easily separated from the fixing belt 21 .

Referring to FIG. 4 , fixing member 26 that slides on inner peripheral surface 21 a of fixing belt 21 has a surface facing pressure roller 31 (sliding surface) that is concave so as to follow the curvature of pressure roller 31 . is formed in As a result, since the recording medium P is delivered from the nip portion so as to follow the curvature of the pressure roller 31, it is possible to prevent the problem that the recording medium P after the fixing process is attracted to the fixing belt 21 and is not separated. be able to.
In Embodiment 1, the shape of the fixing member 26 forming the nip portion is formed in a concave shape, but the shape of the fixing member 26 forming the nip portion can also be formed in a flat shape. That is, the sliding contact surface of the fixed member 26 (the surface facing the pressure roller 31) can be formed in a planar shape. As a result, the shape of the nip portion becomes substantially parallel to the image surface of the recording medium P, and the adhesion between the fixing belt 21 and the recording medium P is increased, thereby improving the fixability. Furthermore, since the curvature of the fixing belt 21 on the exit side of the nip portion is large, the recording medium P delivered from the nip portion can be easily separated from the fixing belt 21 .

As a material for forming the fixing member 26, a resin material or a metal material can be used. A resin material having a heat insulating property (liquid crystal polymer, polyamideimide, etc.) is suitable. In Embodiment 1, liquid crystal polymer (LCP) is used as the material of the fixing member 26 .

Further, the fixed member 26 is covered with a sheet-like member 22 made of a low-friction material such as PTFE in order to reduce sliding resistance with the fixing belt 21 . Specifically, the sheet-like member 22 is interposed in the width direction between the fixing member 26 and the fixing belt 21 at the position of the nip portion. It is installed so as to cover the periphery of the member 26). Further, the sheet-like member 22 in Embodiment 1 is made of a fibrous material (a cloth member made of PTFE) impregnated with a lubricant such as silicone oil. As a result, the lubricant is retained on the contact surface between the fixing member 26 and the fixing belt 21 . Therefore, the inconvenience that both the members 21 and 26 are worn due to the sliding contact between the fixing member 26 and the fixing belt 21 can be reduced.
The structure of the sheet-like member 22 and the fixing member 26 will be described later in more detail.

Here, in Embodiment 1, the reinforcing member 23 (and the reflecting member 27) is installed so as to separate the space between the fixing member 26 and the heater 25 (heating means).
In Embodiment 1, the heater 25 is installed so as to face a relatively wide range in the circumferential direction of the fixing belt 21 (inner peripheral surface 21a). The belt 21 can be heated in the circumferential direction without temperature unevenness. Therefore, after receiving a print request, the print operation can be performed quickly. At this time, in a conventional on-demand fixing device (see, for example, Japanese Patent No. 2884714), if heat is applied to the pressure roller while it is deformed in the nip portion while waiting for heating, the rubber of the pressure roller will be deformed. Depending on the material of the roller, heat deterioration may occur, shortening the life of the pressure roller, or permanent compression strain may occur in the pressure roller. increase by joining). When compression set occurs in the pressure roller, a portion of the pressure roller becomes dented and the desired nip width cannot be obtained, resulting in poor fixing and abnormal noise during rotation. do.
On the other hand, in Embodiment 1, the reinforcing member 23 (and the reflecting member 27) is installed between the fixing member 26 and the heater 25 so as to block the heat of the heater 25. Heat is less likely to reach the fixing member 26 during standby. Therefore, it is possible to reduce the problem that the pressure roller 31 is heated to a high temperature in a deformed state during standby for heating, thereby preventing the above-described problem from occurring.

Furthermore, the lubricant applied between the fixed member 26 and the fixing belt 21 to reduce the frictional resistance between the two members deteriorates due to use under high temperature conditions in addition to high pressure conditions at the nip portion, and the fixing belt 21 There is a possibility that problems such as slippage may occur.
In contrast, in Embodiment 1, since the reinforcing member 23 (and the reflecting member 27) is installed between the fixing member 26 and the heater 25 so as to block the heat of the heater 25, the heater The heat of 25 is less likely to reach the lubricant in the nip. Therefore, deterioration of the lubricant due to high temperature is reduced, and the occurrence of the above-described problems can be suppressed.

Further, in Embodiment 1, since the reinforcing member 23 (and the reflecting member 27) is installed between the fixing member 26 and the heater 25 so as to block the heat of the heater 25, the fixing member 26 is Heat insulation prevents the fixing belt 21 from being actively heated at the nip portion. Therefore, the temperature of the recording medium P fed into the nip portion is lowered when it is delivered from the nip portion. That is, at the exit of the nip portion, the temperature of the toner image fixed on the recording medium P is lowered, the viscosity of the toner is lowered, and the adhesive force of the toner to the fixing belt 21 is reduced. It is separated from the fixing belt 21 . Therefore, the recording medium P immediately after the fixing process is prevented from being jammed by being wound around the fixing belt 21, and the fixation of toner to the fixing belt 21 is also suppressed.

The normal operation of the fixing device 20 configured as described above will be briefly described below.
When the power switch of the apparatus main body 1 is turned on, power is supplied to the heater 25 and the pressure roller 31 is started to rotate in the direction of the arrow in FIG. As a result, the fixing belt 21 is also driven (rotated) in the direction of the arrow in FIG.
After that, the recording medium P is fed from the paper feeding unit 12 , and the unfixed color image is carried (transferred) on the recording medium P at the position of the secondary transfer roller 89 . The recording medium P bearing the unfixed image T (toner image) is conveyed in the direction of arrow Y10 in FIG. 2 while being guided by a guide plate (not shown). It is fed into the nip.
Then, the toner image T is fixed on the surface of the recording medium P by heating by the fixing belt 21 heated by the heater 25 and pressing force between the fixing member 26 reinforced by the reinforcing member 23 and the pressing roller 31 . . After that, the recording medium P delivered from the nip portion is conveyed in the direction of arrow Y11.

The configuration and operation characteristic of the fixing device 20 according to the first embodiment will be described in detail below.
As described above, the fixing device 20 according to the first embodiment is fixed to the inner peripheral surface of the fixing belt 21 and pressed against the pressure roller 31 via the fixing belt 21 to form a nip portion. and a reinforcing member 23 that is fixed to the inner peripheral surface of the fixing belt 21 and contacts the fixing member 26 from the inside of the fixing belt 21 to reinforce the fixing member 26 .
Here, in the first embodiment, as shown in FIG. 4, projecting portions 26a and 26b projecting toward the facing surface 23a of the reinforcing member 23 so as to abut against the reinforcing member 23 are provided on the fixing member 26 so as to form a recording medium. A plurality of rows are provided along the conveying direction of the medium P (or the rotating direction of the fixing belt 21). Specifically, as the plurality of rows of protrusions, an upstream protrusion 26a that protrudes toward the facing surface 23a of the reinforcing member 23 so as to abut against the reinforcing member 23 on the upstream side in the conveying direction of the recording medium P, A downstream projecting portion 26b projecting toward the facing surface 23a of the reinforcing member 23 so as to abut on the reinforcing member 23 on the downstream side with respect to the conveying direction of P is formed. That is, the fixing member 26 has two rows of protrusions 26a and 26b (the distance between the upstream end and the downstream end is set to B) spaced apart in the conveying direction on the side facing the reinforcing member 23. ) are provided, and these two rows of protrusions 26a and 26b come into surface contact with the facing surface 23a of the reinforcing member 23, respectively.

With such a configuration, even if a pipe-shaped heating member for fitting and fixing the fixing member 26 is not installed, the fixing member 26 is held in a well-balanced state in which the reinforcing member 23 is pressed against. 26 is prevented from falling down. Then, a desired nip is formed with high accuracy, and problems such as poor fixing of an output image and poor conveyance of a recording medium can be prevented.
That is, when the fixing member 26 comes into contact with the reinforcing member 23 biased toward the upstream side in the conveying direction or the downstream side in the conveying direction, or when the contact width (distance B) of the fixing member 26 contacting the reinforcing member 23 is narrow. 4, the fixing member 26, which receives the pressure contact force at the nip portion, tends to rotate (fall down) in the clockwise or counterclockwise direction in FIG. . On the other hand, in the present embodiment, the contact width ( Since the distance B) is set sufficiently large, the fixing member 26 that receives the pressure contact force at the nip portion is supported by the reinforcing member 23 in a well-balanced manner, and the fixing member 26 falls down with the contact portion with the reinforcing member 23 as a fulcrum. become difficult.

Furthermore, in the first embodiment, only the portion of the fixing member 26 divided into the upstream protruding portion 26a and the downstream protruding portion 26b is configured to abut against the reinforcing member 23. Since the contact area between the reinforcing member 23 and the fixing member 26 can be reduced compared to the case where one flat surface formed in a wide range from the side to the downstream side contacts the reinforcing member 23, the fixing member 26 less heat is transferred to That is, the heat transmitted from the fixing belt 21 to the reinforcing member 26 through the fixing member 26 in the nip portion can be reduced (the amount of heat escaping from the fixing belt 21 to the reinforcing member 23 via the fixing member 26 is reduced). can be reduced.). In particular, when the thickness of the fixing belt 21 is made thin (for example, when the thickness is set to 160 μm or less) or when the nip width is set wide, heat is easily transferred from the fixing belt 21 to the fixing member 26 . Therefore, the configuration in which the contact area between the reinforcing member 23 and the fixing member 26 is reduced as in the first embodiment is useful.

7 and 9, the fixing member 26 according to Embodiment 1 has a plurality of rows of protrusions (upstream protrusions 26a and downstream protrusions 26b) each having a It is divided into a plurality of parts at intervals in the width direction (right and left direction in FIGS. 7 and 9). Specifically, in the first embodiment, eight upstream protruding portions 26a and eight downstream protruding portions 26b are formed at approximately equal intervals in the width direction. With such a configuration, the contact area between the reinforcing member 23 and the fixing member 26 can be further reduced, so that the above-described effects can be exhibited more reliably.
In the first embodiment, the plurality of rows of protrusions 26a and 26b are configured to come into surface contact with the facing surface 23a of the reinforcing member 23. The projecting portions 26a and 26b can also be configured to make line contact or point contact (or close contact) with the facing surface 23a of the reinforcing member 23, respectively. In addition, in the first embodiment, two rows of the upstream protrusion 26a and the downstream protrusion 26b are provided as the plurality of rows of protrusions, but three or more rows of protrusions are provided as the plurality of rows of protrusions. can also be set.

Further, in the first embodiment, referring to FIG. 4, when the fixing member 26 is viewed in a cross section perpendicular to the width direction, an imaginary straight line (see FIG. 4, which is a straight line indicated by the dashed dotted line in Fig. 4).
With such a configuration, the fixing member 26 that receives pressure contact force at the nip portion can be more easily supported by the reinforcing member 23 in a well-balanced manner, and the fixing member 26 is even less likely to collapse.

Further, in the first embodiment, as shown in FIG. 4, the length (nip width) of the nip portion with respect to the conveying direction of the recording medium is A, and the fixing member 26 and the reinforcing member 23 contact each other on the upstream side in the conveying direction. B is the length from the contacting upstream side contact portion to the downstream side contacting portion where the fixing member 26 and the reinforcing member 23 contact on the downstream side in the conveying direction, and the opposite side of the reinforcing member 23 facing the fixing member 26 in the conveying direction When the length of the surface 23a is C,
A<B<C
It is formed so that the relationship of
Further, the range of the nip portion (range A in FIG. 4) is the range from the upstream side contact portion to the downstream side contact portion (range B in FIG. 4) with respect to the conveying direction. ), and the range from the upstream side contact portion to the downstream side contact portion (the range of B in FIG. 4) is the range of the facing surface 23a of the reinforcing member 23 (the range of C in FIG. 4) ) is formed to be included in
In other words, the range of the nip width is included within the range in the conveying direction (vertical direction in FIG. 4) of the fixing member 26 that contacts the reinforcing member 23 . Furthermore, the range in the transport direction of the fixing member 26 that contacts the reinforcing member 23 is included within the range in the transport direction of the facing surface 23 a of the reinforcing member 23 .
With such a configuration, the fixing member 26 that receives pressure contact force at the nip portion can be more easily supported by the reinforcing member 23 in a well-balanced manner, and the fixing member 26 is even less likely to collapse.

Here, with reference to FIGS. 7 to 11, the sheet-like member 22 has a plurality of holes that fit into a plurality of rows of protrusions (the upstream protrusions 26a and the downstream protrusions 26b). 22b are formed. The sheet-like member 22 is installed so as to closely adhere to the fixing member 26 along the circumferential direction at positions excluding the plurality of rows of protrusions 26a and 26b.
Specifically, as shown in FIG. 10, the sheet-like member 22 has a rectangular shape when unfolded as a single component. At both ends of the rectangular sheet-shaped member 22, a plurality of holes 22a and 22b (holes to be fitted to the projecting portions 26a and 26b) and screw holes 22c (for screws 24) are provided. ) are formed.
When the sheet-shaped member 22 is covered with the fixing member 26, both ends of the rectangular shape are folded between the upstream projections 26a and the downstream projections 26b (between the plurality of rows of projections) and overlapped. A portion (a region surrounded by a dashed line in FIG. 8 and a hatched region in FIG. 10) is formed. Then, as shown in FIG. 8, a plate-like member 28 (fixing plate) is fixed to a fixing member 26 with a plurality of screws 24 so as to sandwich the overlapped portion of the sheet-like member 22 . Specifically, a plate-like member 28 is placed on a fixing member 26 via the overlapping portion so as to sandwich the overlapping portion of the sheet-like member 22, and screw holes 28c of the plate-like member 28 (see FIG. 11). ) and the screw hole 22c of the sheet-like member 22, and the threaded portion of the screw 24 is screwed into the female threaded portion 26c of the fixing member 26 (see FIG. 9B). Here, the plurality of screws 24 are formed so that the height of the screw head exceeds the height of the protrusions 26 a and 26 b and does not come into contact with the reinforcing member 23 .

In this manner, the sheet-like member 22 is fixed and held on the fixing member 26 at the end corresponding to the upstream side in the conveying direction and the end corresponding to the downstream side in the conveying direction when unfolded. Therefore, in addition to the case where the sheet-shaped member 22 receives a frictional force between it and the fixing belt 21 running toward the downstream side (during a normal fixing process), the sheet-shaped member 22 moves toward the upstream side. Even if frictional force is applied between the fixing belt 21 and the running fixing belt 21 (such as when the fixing belt 21 and the pressure roller 31 are manually reversely rotated during jam processing), the sheet-like member 22 Therefore, it is possible to prevent problems such as gaps and wrinkles from occurring due to deviation of the fixing member 26.例文帳に追加
In particular, in this embodiment, the overlapped portion of the sheet-like member 22 is sandwiched between the plate-like members 28, and the plate-like members 28 are fastened to the fixing member 26 with a plurality of screws 24 arranged substantially evenly in the width direction. Therefore, compared to other fixing and holding methods (for example, bonding the overlapped portion with an adhesive or hooking the overlapped portion to the projecting portions 26a and 26b, etc.), the fixing member 26 The sheet-like member 22 can be stably and firmly fixed to the .

Further, the holes 22a and 22b of the sheet-like member 22 are fitted to the projecting portions 26a and 26b of the fixing member 26, and the plate-like member 28 and the screw 24 are inserted between the projecting portions 26a and 26b (central portion in the conveying direction). Since it is installed, the fixing member 26 with the sheet-like member 22 installed can be made compact.
In addition, since the fixing member 26 with the sheet-like member 22 installed can be managed in units of one sub-assembled part, parts management and assembly are improved during manufacturing and maintenance. be able to.
In addition, since the sheet-like member 22 is held by being fitted to the plurality of projecting portions 26a and 26b that are divided at approximately equal intervals in the width direction, even if the sheet-like member 22 receives a sliding contact force, the plurality of hole portions can be held. Force is likely to be evenly applied to 22a and 22b, and the problem of damage to sheet-like member 22 due to localized stress concentration can be reduced.

As described above, in the first embodiment, the fixing member 26 is provided with the protrusions 26a and 26b that protrude toward the reinforcing member 23 so as to come into contact with the reinforcing member 23 in a plurality of rows along the conveying direction. It is As a result, even when the warm-up time and the first print time are short and the speed of the apparatus is increased, there is no fixing failure or the like, and the fixing member 26 that is in pressure contact with the reinforcing member 23 is less likely to collapse. can do.

In Embodiment 1, the multi-layered fixing belt 21 is used as the fixing belt, but an endless fixing film made of polyimide, polyamide, fluororesin, metal, or the like can also be used as the fixing belt. Also in this case, the same effect as in the first embodiment can be obtained.

Embodiment 2.
Embodiment 2 of the present invention will be described in detail with reference to FIG.
FIG. 12 is a configuration diagram showing a fixing device according to the second embodiment, and corresponds to FIG. 2 according to the first embodiment. The fixing device of the second embodiment differs from that of the first embodiment in that the fixing belt 21 is heated by electromagnetic induction.

As shown in FIG. 12, a fixing device 20 according to the second embodiment also includes a fixing belt 21 (belt member), a fixing member 26, a reinforcing member 23, and a pressure roller 31 (as in the case of the first embodiment). heating rotating body), temperature sensor 40, sheet-like member 22, screw 24, plate-like member 28 (fixing plate), and the like.
Further, in the second embodiment, as in the first embodiment, a plurality of rows of projections (upstream parts) projecting toward the facing surface 23a of the reinforcing member 23 so as to abut against the reinforcing member 23 are provided on the fixing member 26. side projecting portion 26a and downstream projecting portion 26b) are formed.

Here, instead of the heater 25, the fixing device 20 in the second embodiment is provided with an induction heating section 50 as a heating means. The fixing belt 21 in the second embodiment is heated by electromagnetic induction by the induction heating section 50, unlike the fixing belt 21 in the first embodiment which is heated by the radiant heat of the heater 25. FIG.

The induction heating unit 50 is composed of an excitation coil, a core, a coil guide, and the like. The exciting coil is a Litz wire bundled with fine wires extending in the width direction (perpendicular to the paper surface of FIG. 12) so as to partially cover the fixing belt 21 . The coil guide is made of a highly heat-resistant resin material or the like, and holds the excitation coil and core. The core is a semicylindrical member made of a ferromagnetic material (having a relative magnetic permeability of about 1000 to 3000) such as ferrite. A side core is provided. The core is installed so as to face the exciting coil extending in the width direction.
On the other hand, in the fixing belt 21, apart from the base material layer, the elastic layer, and the release layer described in the first embodiment, a heating layer (for example, an elastic layer and a release layer) which is heated by electromagnetic induction by the induction heating unit 50 is provided. layer, or the substrate layer can be used as a heat-generating layer.) is formed. As materials for the heat generating layer, nickel, stainless steel, iron, copper, cobalt, chromium, aluminum, gold, platinum, silver, tin, palladium, alloys composed of a plurality of these metals, and the like can be used.

The fixing device 20 configured in this way operates as follows.
When the fixing belt 21 is driven to rotate in the direction of the arrow in FIG. More specifically, by passing a high-frequency alternating current through the excitation coil, magnetic lines of force are formed around the fixing belt 21 so as to alternately switch between two directions. At this time, an eddy current is generated on the surface of the heat generating layer of the fixing belt 21, and Joule heat is generated by the electrical resistance of the heat generating layer itself. The Joule heat heats the heating layer by electromagnetic induction, thereby heating the fixing belt 21 .
In order to efficiently heat the fixing belt 21 by electromagnetic induction, it is preferable to configure the induction heating section 50 so as to face the entire circumference of the fixing belt 21 .

As described above, in the second embodiment, similarly to each of the above-described embodiments, the fixed member 26 has projections 26a and 26b projecting toward the reinforcing member 23 so as to come into contact with the reinforcing member 23. , are formed in a plurality of rows along the conveying direction. As a result, even when the warm-up time and the first print time are short and the speed of the apparatus is increased, there is no fixing failure or the like, and the fixing member 26 that is in pressure contact with the reinforcing member 23 is less likely to collapse. can do.

Although the fixing belt 21 is heated by electromagnetic induction heating in the second embodiment, the fixing belt 21 can also be heated by the heat of a resistance heating element. Specifically, a resistance heating element is brought into contact with part or all of the inner peripheral surface or the outer peripheral surface of the fixing belt 21 . The resistance heating element is a planar heating element such as a ceramic heater, and power supply units are connected to both ends thereof. Then, when a current is passed through the resistance heating element, the temperature of the resistance heating element rises due to the electric resistance of the resistance heating element itself, and heats the fixing belt 21 in contact with the resistance heating element.
Even in such a case, by providing the fixing member 26 with the upstream projecting portion 26a and the downstream projecting portion 26b, the same effect as in the second embodiment can be obtained.

It should be noted that the present invention is not limited to each of the above-described embodiments, and that each of the above-described embodiments can be appropriately modified within the scope of the technical idea of the present invention, other than what is suggested in each of the above-described embodiments. is clear. Further, the number, position, shape, etc. of the constituent members are not limited to those in the above-described embodiments, and the number, position, shape, etc., can be set to be suitable for carrying out the present invention.

(Appendix)
(Appendix 1)
an endless fixing belt that travels in a predetermined direction, heats and melts the toner image, and has flexibility;
a fixing member that is fixed to the inner peripheral surface of the fixing belt and presses against the pressure rotating body through the fixing belt to form a nip portion where the recording medium is conveyed;
a reinforcing member that is fixed to the inner peripheral surface of the fixing belt and contacts the fixing member from the inside of the fixing belt to reinforce the fixing member;
with
The fixing device according to claim 1, wherein the fixing member includes a plurality of rows of protruding portions protruding toward the facing surface of the reinforcing member so as to abut on the reinforcing member along the conveying direction of the recording medium.
(Appendix 2)
The plurality of rows of protrusions include upstream protrusions protruding toward the facing surface of the reinforcing member so as to contact the reinforcing member on the upstream side in the conveying direction, and the reinforcing member on the downstream side in the conveying direction. and a downstream projecting portion projecting toward the facing surface of the reinforcing member so as to abut on the fixing device according to appendix 1.
(Appendix 3)
3. The fixing device according to appendix 1 or appendix 2, wherein each of the plurality of rows of protrusions is divided into a plurality of rows at intervals in the width direction.
(Appendix 4)
A sheet-shaped member made of a low-friction material and covering the fixing member along the circumferential direction so as to be interposed in the width direction between the fixing member and the fixing belt at the position of the nip portion. ,
The sheet-shaped member has a plurality of holes that fit into the plurality of rows of protrusions, and is installed so as to be in close contact with the fixing member along the circumferential direction at positions excluding the plurality of rows of protrusions. The fixing device according to any one of Appendices 1 to 3, characterized in that:
(Appendix 5)
The sheet-like member has a rectangular shape when it is unfolded as a single component, and when covered with the fixing member, both ends of the rectangular shape are folded between the plurality of rows of protrusions to form an overlapped portion. formed,
5. The fixing device according to claim 4, wherein a plate-like member is fixed to the fixing member by a plurality of screws so as to sandwich the overlapped portion of the sheet-like member.
(Appendix 6)
The fixing device according to appendix 4 or appendix 5, wherein the sheet-like member is formed of a fiber material impregnated with a lubricant.
(Appendix 7)
The fixing member is formed so as to be symmetrical with respect to an imaginary straight line passing through the center of the nip portion in the conveying direction and perpendicular to the conveying direction when viewed in a cross section perpendicular to the width direction. The fixing device according to any one of appendices 1 to 6.
(Appendix 8)
a holding member that holds both ends of the fixing belt in the width direction;
a heating unit that faces or contacts the fixing belt and heats the fixing belt;
The fixing device according to any one of appendices 1 to 7, further comprising:
(Appendix 9)
An image forming apparatus comprising the fixing device according to any one of Appendices 1 to 8.

(Appendix)
(Appendix 11)
a flexible endless fixing belt;
a fixing member disposed on the inner peripheral surface side of the fixing belt and forming a nip portion where the recording medium is conveyed by being pressed against the pressure rotating body through the fixing belt;
a heater that directly faces at least a portion of the fixing belt other than the nip portion and heats the fixing belt;
a reinforcing member disposed between the fixing member and the heater on the inner peripheral surface side of the fixing belt and abutting against the fixing member to reinforce the fixing member;
a holding member that holds both ends of the fixing belt in the width direction;
with
the reinforcing member is not in contact with the fixing belt when the fixing belt rotates;
The fixing member has a plurality of rows of protruding portions protruding toward the facing surface of the reinforcing member so as to abut on the reinforcing member along the conveying direction of the recording medium, and a low-friction sheet-like member extending in the width direction. a fixing device that contacts the fixing belt through a fixing device.
(Appendix 12)
The plurality of rows of protrusions include upstream protrusions that contact the facing surface on the upstream side in the conveying direction, and downstream protrusions that contact the facing surface on the downstream side in the conveying direction. 12. The fixing device of claim 11, characterized in that:
(Appendix 13)
13. The fixing device according to appendix 11 or 12, wherein each of the plurality of rows of protrusions is divided into a plurality of rows at intervals in the width direction.
(Appendix 14)
The low-friction sheet-like member has a plurality of holes,
14. The fixing device according to attachments 11 to 13, wherein the plurality of holes are fitted in the plurality of rows of projections.
(Appendix 15)
The low-friction sheet-like member has a rectangular shape when unfolded as a single component, and when covered with the fixing member, both ends of the rectangular shape are folded and overlapped between the plurality of rows of protrusions. part is formed,
15. The fixing device according to Supplementary Note 14, further comprising a contact member that contacts the fixing member via the overlapping portion between the plurality of rows of protrusions.
(Appendix 16)
16. The fixing device according to appendix 14 or 15, wherein the low-friction sheet-like member is made of a fiber material impregnated with a lubricant.
(Appendix 17)
The fixing member is formed so as to be symmetrical with respect to an imaginary straight line passing through the center of the nip portion in the conveying direction and perpendicular to the conveying direction when viewed in a cross section perpendicular to the width direction. The fixing device according to any one of appendices 11 to 16.
(Appendix 18)
The reinforcing member includes an upstream side wall portion provided on the upstream side with respect to the facing surface and substantially perpendicular to the direction opposite to the fixing member, and an upstream side wall portion provided on the downstream side with respect to the facing surface and the fixing member. 18. The fixing device according to any one of appendices 11 to 17, further comprising a downstream side wall portion provided substantially perpendicularly in a direction opposite to the upstream side wall portion and facing the upstream side wall portion.
(Appendix 19)
Assuming that the length of the nip portion with respect to the conveying direction of the recording medium is A, the fixing member is located downstream in the conveying direction from an upstream contact portion where the fixing member and the reinforcing member abut on the upstream side in the conveying direction. When the length to the downstream contact portion where the reinforcing member abuts is B,
A<B
As the relationship is established,
19. Any one of appendices 11 to 18, wherein the range of the nip portion is formed so as to be included in the range from the upstream side contact portion to the downstream side contact portion with respect to the conveying direction. A fixing device as described.
(Appendix 20)
19. The fixing device according to any one of attachments 11 to 19, wherein each of the plurality of rows of protrusions is formed so as to be in line contact or point contact with the facing surface of the reinforcing member.
(Appendix 21)
The reinforcing member has a heat insulating member provided on part or all of the surface facing the heater,
21. The fixing device according to any one of attachments 11 to 20, wherein the fixing member is made of a heat insulating material.
(Appendix 22)
An image forming apparatus comprising the fixing device according to any one of appendices 11 to 21.

1 image forming apparatus main body (apparatus main body),
20 fixing device,
21 fixing belt (fixing member),
22 sheet-shaped member,
23 reinforcing member,
24 screw (fixing screw),
25 heater (heating means),
26 fixing member,
26a upstream projection, 26b downstream projection,
28 plate-like member (fixing plate),
29 flange (holding member),
31 pressure roller (pressure rotating body);

Japanese Patent No. 2010-96782

Claims (17)

a flexible endless fixing belt;
A nip forming member disposed inside the fixing belt and sandwiching the fixing belt with a pressure rotating body to form a nip portion in which a recording medium is conveyed between the fixing belt and the pressure rotating body. When,
a heat source that faces the fixing belt and heats the fixing belt;
a reinforcing member disposed inside the fixing belt and having a facing surface that abuts against the nip forming member;
a pair of guide members that guide both ends of the fixing belt in the width direction;
with
The nip forming member includes an upstream contact portion that contacts the facing surface on the upstream side in the conveying direction of the recording medium, a downstream contact portion that contacts the facing surface on the downstream side in the conveying direction, and the upstream contact portion. a non-contact portion that does not contact the facing surface between the side contact portion and the downstream side contact portion;
The pair of guide members each have an insertion portion inside the fixing belt,
The fixing device, wherein the insertion portions are separated from each other inside the fixing belt. 2. The fixing device according to claim 1, wherein the heat source is a radiant heat source. 3. The fixing device according to claim 2, wherein the radiant heat source is a halogen heater. The reinforcing member is arranged between the nip forming member and the heat source inside the fixing belt,
4. The fixing device according to claim 1, further comprising a reflecting member provided between said reinforcing member and said heat source. The reinforcing member includes an upstream side wall portion provided on the upstream side with respect to the facing surface and substantially perpendicular to the direction opposite to the nip forming member, and an upstream side wall portion provided on the downstream side with respect to the facing surface and the nip forming member. 5. The fixing device according to any one of claims 1 to 4, further comprising a downstream side wall portion provided substantially perpendicularly in a direction opposite to the forming member and facing the upstream side wall portion. 6. The fixing device according to claim 5, wherein the upstream side contact portion and the downstream side contact portion are provided between the upstream side wall portion and the downstream side wall portion in the conveying direction. . 7. The facing surface is a surface facing the nip forming member and extends further downstream than the downstream contact portion in the conveying direction. The fixing device according to . The nip forming member has an upstream protruding portion protruding toward the opposing surface and a downstream protruding portion protruding toward the opposing surface,
The upstream projecting portion has the upstream contact portion,
The fixing device according to any one of claims 1 to 7, wherein the downstream projecting portion has the downstream contact portion. A surface facing the facing surface of the upstream projecting portion is the upstream contact portion,
9. The fixing device according to claim 8, wherein a surface of the downstream projecting portion facing the facing surface is the downstream contact portion. A plurality of the upstream protrusions are arranged in the longitudinal direction of the nip forming member,
10. The fixing device according to claim 8, wherein a plurality of said downstream protrusions are arranged in the longitudinal direction of said nip forming member. The fixing device according to any one of claims 1 to 10, wherein a sheet-like member is interposed between the nip forming member and the fixing belt. 12. The fixing device according to claim 11, wherein the nip forming member is covered with the sheet member. The sheet-like member covering the nip forming member has a plurality of holes,
11. The fixing device according to any one of claims 8 to 10, wherein the plurality of holes are fitted with the upstream projecting portion or the downstream projecting portion. The fixing device according to any one of claims 11 to 13, wherein the sheet member is made of a low-friction material. 15. The fixing device according to any one of claims 11 to 14, further comprising a member fixed to the nip forming member so as to sandwich the overlapped portion of the sheet member. 16. The fixing device according to any one of claims 1 to 15, wherein the nip forming member has a plurality of locations in contact with the facing surface in a direction orthogonal to the conveying direction. An image forming apparatus comprising the fixing device according to any one of claims 1 to 16.

Images