JP5541612B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed therein.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, the inner peripheral surface of a fixing belt has been used as a fixing device that is less likely to cause poor fixing even when the warm-up time or first print time is short and the speed of the device is increased. There is known a technique of installing a resistance heating element so as to be opposed to (see, for example, Patent Documents 1 and 2).

Specifically, the fixing device disclosed in Patent Documents 1 and 2 includes a fixing belt as a fixing member, a substantially cylindrical heating member (resistance heating element) fixed so as to face the inner peripheral surface of the fixing belt, and pressure. A roller (pressure rotator), a contact member (fixing member) that presses against the pressure roller via a fixing belt to form a nip portion, and the like are configured.
Then, the fixing belt is heated by the resistance heating element (heating member), and the toner image on the recording medium conveyed toward the nip portion is fixed on the recording medium by receiving heat and pressure at the nip portion. It will be.

Although the fixing device described in Patent Documents 1 and 2 described above is a device in which warm-up time and first print time are short and fixing failure is hardly caused even when the speed of the device is increased, a fixing belt is further provided. There has been a demand for efficient heating without variation.
In particular, the heat generating member is not completely in close contact with the fixing belt, and the gap between the heat generating member and other portions of the fixing belt is different because the inlet side of the nip portion becomes the tension side of the fixing belt. As a result, the heating state of the fixing belt may vary accordingly. When such variation becomes large, there is a possibility that fixing failure such as fixing unevenness may occur in the fixed image.

  The present invention has been made to solve the above-described problems. The warm-up time and the first print time are short, and the fixing belt is more efficient without causing fixing defects such as uneven fixing on the fixed image. It is an object of the present invention to provide a fixing device and an image forming apparatus that can be heated without variation.

  According to a first aspect of the present invention, there is provided a fixing device that travels in a predetermined direction to heat and melt a toner image, and has an endless fixing belt having flexibility, and an inner peripheral surface of the fixing belt. A fixing member that is fixed to the side and forms a nip portion that is pressed against the pressure rotator through the fixing belt to convey the recording medium, and an inner periphery of the fixing belt at a position different from the nip portion. A heating member that heats the fixing belt and is divided into a plurality of pieces along the circumferential direction of the fixing belt so as to contact or face the surface. The first heat generating member disposed upstream of the fixing belt in the running direction with respect to the nip portion is disposed so as to be adjacent to the fixing member, and includes a plurality of the first heat generating member and the first heat generating member. Other heating elements divided into Wherein the second heating member adjacent to the first heating member, in a position corresponding to between the, in which further comprising temperature detecting means for detecting a temperature of the fixing belt.

  According to a second aspect of the present invention, there is provided the fixing device according to the first aspect, wherein the first heat generating member is different from the other heat generating members divided into the plurality of heat generating members. The calorific value is controlled based on the detection result.

  According to a third aspect of the present invention, in the fixing device according to the second aspect, when the temperature detected by the temperature detecting means is low, the first heat generating member is detected by the temperature detecting means. The amount of heat generation is controlled to be larger than when the detected temperature is high.

  According to a fourth aspect of the present invention, there is provided the fixing device according to any one of the first to third aspects, wherein the first heating member is a conveyance speed of the recording medium conveyed to the nip portion. When the recording medium is slow, the amount of heat generation is controlled to be smaller than when the recording medium is transported at a high speed.

  The fixing device according to a fifth aspect of the present invention is the fixing device according to any one of the first to fourth aspects, wherein the first heat generating member is a basis weight of the recording medium conveyed to the nip portion. When any one of the thickness and density is large, the heat generation amount is controlled to be larger than when any of the basis weight, thickness and density of the recording medium is small.

  The fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the first heat generating member is a sheet passing area in a recording medium having a different size in the width direction. The first heat generating member divided into a plurality of portions in the width direction corresponding to the non-sheet passing region is heated based on the size in the width direction of the recording medium conveyed to the nip portion. The amount is to be controlled.

  The fixing device according to a seventh aspect of the present invention is the fixing device according to the sixth aspect, wherein the other heat generating members divided into a plurality of the heat generating members and the non-sheet passing regions in the recording media having different sizes in the width direction are provided. The other heat generating member divided into a plurality of parts in the width direction corresponding to the sheet passing area has a heat generation amount based on the size in the width direction of the recording medium conveyed to the nip portion. It is to be controlled.

  According to an eighth aspect of the present invention, there is provided the fixing device according to any one of the first to seventh aspects, wherein the fixing device faces the inner peripheral surface of the fixing belt via the heat generating member. It further includes a heat insulating member formed so as to support only the heat generating member.

  The fixing device according to a ninth aspect of the present invention is the fixing device according to any one of the first to eighth aspects, wherein the fixing member is the nip portion when viewed in a cross section perpendicular to the width direction. And the range along the running direction of the fixing belt is the range along the running direction of the fixing belt at the nip portion. A gap is formed between the nip portion and the fixing belt at a position upstream of the fixing belt in the running direction, and the first heat generating member includes the fixing member and the fixing belt. And so as to enter the gap.

  A fixing device according to a tenth aspect of the present invention is the fixing device according to any one of the first to ninth aspects, wherein the fixing device is fixed to an inner peripheral surface side of the heat generating member and abuts on the fixing member. And a reinforcing member for reinforcing the fixing member.

  According to an eleventh aspect of the present invention, in the fixing device according to any one of the first to tenth aspects, the fixing member is formed of a nonconductor.

  A fixing device according to a twelfth aspect of the present invention is the fixing device according to any one of the first to eleventh aspects, wherein the heat generating member divided into the plurality of members includes the first heat generating member and the second heat generating member. A heat generating member, wherein the second heat generating member is fixed so as to face the inner peripheral surface of the fixing belt at a position excluding the nip portion and the first heat generating member.

  A fixing device according to a thirteenth aspect of the present invention is the fixing device according to any one of the first to twelfth aspects of the present invention, wherein a part or all of the heat generating members divided into a plurality are each made of a resistor. It is formed of a heating element.

  An image forming apparatus according to a fourteenth aspect of the present invention includes the fixing device according to any one of the first to thirteenth aspects.

In the present application, the “sheet passing area” is defined as a range in the width direction of the recording medium to be passed by the image forming apparatus (a direction perpendicular to the sheet passing direction). The “paper passing area” is defined as an area outside the range of the “paper passing area”.
In the present application, the “width direction” is defined as a direction orthogonal to the conveyance direction of the recording medium.

  Further, in the present application, the state in which the fixing member or the reinforcing member is “fixed” is defined as a state in which the fixing member or the reinforcing member is held in a non-rotating manner without being driven to rotate. Therefore, for example, even when the fixing member is biased toward the nip portion by a biasing member such as a spring, the fixing member is “fixed” if the fixing member is held non-rotating. It becomes a state.

  According to the present invention, the heat generating member facing the inner peripheral surface of the fixing belt is divided into a plurality along the circumferential direction of the fixing belt, and the first heat generating member disposed on the upstream side of the nip portion is adjacent to the fixing member. It is arranged. Further, a temperature detecting means for detecting the temperature of the fixing belt is provided between the first heat generating member and the second heat generating member adjacent to the first heat generating member. As a result, a fixing device and an image forming apparatus in which the warm-up time and the first print time are short, fixing defects such as fixing unevenness do not occur in the fixed image, and the fixing belt is efficiently heated without variation. Can be provided.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram illustrating a fixing device installed in the image forming apparatus of FIG. 1. FIG. 3 is a diagram in which the fixing device of FIG. 2 is viewed in the width direction. It is an enlarged view which shows the vicinity of a nip part. 3 is a graph showing a fixing temperature at a passing position of a fixing belt. 6 is a graph showing a fixing temperature at a passing position of a fixing belt when a process linear velocity is varied. 7 is a graph showing a fixing temperature at a passing position of a fixing belt when different types of recording media are passed. It is a block diagram which shows the fixing device of another form. It is the top view which looked at the heat generating member in Embodiment 2 of this invention along the running direction of the fixing belt. It is a block diagram which shows the fixing device in Embodiment 3 of this invention. It is a perspective view which shows a heat insulation member. FIG. 10 is an enlarged view showing the vicinity of a nip portion of a fixing device according to Embodiment 4 of the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
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 type color printer. Four bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceable) installed in the bottle housing portion 101 above the image forming apparatus main body 1. ing.
An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge eliminating unit (not shown), and the like are disposed. Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K. An image of each color is formed on 5K.

The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in a clockwise direction in FIG. 1 by a drive motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (a charging process).
Thereafter, 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 electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (It is an exposure process.)

Thereafter, 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 toner images of each color (developing process). .)
Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions, the photoconductive drums 5Y, 5M. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. 77 is mechanically collected by a cleaning blade (cleaning process).
Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing a neutralization unit (not shown), and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. The
Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is 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 unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by the 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, thereby forming primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K.
The intermediate transfer belt 78 travels 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 primarily transferred while being superimposed on the intermediate transfer belt 78.

Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are 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.
Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97 and the registration roller pair 98. It is a thing.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in an overlapping manner. When the paper feed roller 97 is rotationally driven in the counterclockwise direction 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 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotationally driven in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing belt 21 and the pressure roller 31.
Thereafter, the recording medium P is discharged out of the apparatus through a pair of paper discharge rollers 99. The transferred P discharged from the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image.
Thus, a series of image forming processes in the image forming apparatus is 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.
As shown in FIGS. 2 to 4, the fixing device 20 includes a fixing belt 21 (belt member) as a fixing member, a fixing member 26, heating members 22 a and 22 b, a reinforcing member 23, and a pressure roller as a pressure rotator. 31 and a temperature sensor 40 as temperature detecting means.

Here, the fixing belt 21 is a thin and flexible endless belt, and rotates (runs) in an arrow direction (counterclockwise) in FIG. The fixing belt 21 has a base material layer, an elastic layer, and a release layer sequentially laminated from the inner peripheral surface 21a (sliding contact surface with the fixing member 26) side, and its 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 formed 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 formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber. By providing the elastic layer, minute irregularities on the surface of the fixing belt 21 in the nip portion are not formed, and heat is uniformly transmitted to the toner image T on the recording medium P, thereby suppressing the generation of a scum skin image. In the first embodiment, silicone rubber having a layer thickness of 200 μm is used as the elastic layer of the fixing belt 21.
The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm, and includes PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES ( Polyether sulfide) and the like. By providing the release layer, the releasability (peelability) for the toner T (toner image) is secured.

Further, the diameter of the fixing belt 21 is set to be 15 to 120 mm. In the first embodiment, the inner diameter of the fixing belt 21 is set to 30 mm.
A fixing member 26, heat generating members 22a and 22b, a reinforcing member 23, and the like are fixedly provided inside the fixing belt 21 (inner peripheral surface side). Although not shown, a lubricant is interposed (applied) between the fixing belt 21 and the heat generating members 22a and 22b.
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 is pressed against the pressure roller 31 via the fixing belt 21 to form a nip portion where the recording medium P is conveyed. Referring to FIG. 3, both ends of the fixing member 26 in the width direction are fixedly supported by the side plates 43 of the fixing device 20. The configuration of the fixing member 26 will be described in detail later.

Referring to FIG. 2, the heating members 22a and 22b are arranged along the circumferential direction of the fixing belt 21 so as to face (or lightly contact) the inner circumferential surface of the fixing belt 21 at a position different from the nip portion. It is divided into two.
Specifically, of the heat generating members 22a and 22b divided into two, the first heat generating member 22a disposed on the inlet side of the nip portion (on the upstream side in the 21 running direction of the fixing belt with respect to the nip portion). The fixing member 26 is disposed so as to be in contact with the fixing member 26. Further, the other second heat generating member 22b is located at a position excluding the nip portion and the first heat generating member 22a (a relatively wide range from the nip portion outlet side to the vicinity of the nip portion inlet side along the traveling direction of the fixing belt 21). In other words, the fixing belt 21 is fixed so as to face the inner peripheral surface.
Referring to FIG. 3, the heat generating members 22 a and 22 b are fixedly supported by the side plates 43 of the fixing device 20 at both ends in the width direction. In addition, flanges 29 are provided at both ends of the metal member 22 to limit the displacement of the fixing belt 21 (movement in the width direction).

Here, each of the heat generating members 22a and 22b is formed with a heat generating layer made of a resistance heat generating element. Although illustration is omitted, each of the heat generating members 22a and 22b has a base material layer, a heat generating layer, and a protective layer (insulating layer) sequentially laminated from the inner peripheral surface side.
The base material layers of the heat generating members 22a and 22b are made of aluminum oxide (alumina), aluminum nitride, or the like.
The heat generating layers of the heat generating members 22a and 22b are made of resistance heating elements. The resistance heating element is a planar heating element made of ceramic or the like, and a power supply unit (not shown) is connected to both ends in the width direction. When a current flows through the heat generation layer (resistance heating element) of the heat generation members 22a and 22b, the heat generation layer (resistance heating element) is heated by the electric resistance of the heat generation layer (resistance heating element) itself, and contact ( Alternatively, the fixing belt 21 which is opposed) is heated. The heating layer (resistance heating element) is not limited to that of the first embodiment as long as it is a device having a heating function such as a metal-dispersed resin having a moderately adjusted resistance value. be able to.
The protective layers (insulating layers) of the heat generating members 22 a and 22 b are made of an insulating material such as glass, and prevent the current applied to the heat generating members 22 a and 22 b from flowing to the fixing belt 21.

In the first embodiment, the heat generating members 22a and 22b generate heat by themselves and heat the fixing belt 21 by heat transfer. Then, heat is applied to the toner image T on the recording medium P from the surface of the heated fixing belt 21.
Note that current is applied to the two heat generating members 22a and 22b from separate power sources (not shown). The output control of these power supplies is performed based on the detection result of the belt surface temperature by the temperature sensor 40 (temperature detection means) such as the thermistor and the thermopile 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 such output control of the power source. As shown in FIG. 3, the temperature sensor 40 (temperature detection means) is disposed at a position corresponding to the paper passing area Dmin of the recording medium P of the minimum size that can pass paper (the range in FIG. 3). “Dmax” indicates the sheet passing area of the maximum size of the recording medium P that can be passed.
In the first embodiment, the heat generating members 22a and 22b are formed as a multilayer structure, and a heat generating layer (resistance heating element) is formed in a part thereof. On the other hand, the heat generating members 22a and 22b can be formed as a single layer structure, and all of them can be formed as a heat generating layer (resistance heating element).

  As described above, in the fixing device 20 according to the first embodiment, not only a part of the fixing belt 21 is locally heated, but the fixing belt 21 is almost entirely heated in the circumferential direction by the metal member 22. 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 are shortened, and the size of the apparatus is reduced.

Here, the two heat generating members 22a and 22b are respectively fixed so as to face the inner peripheral surface of the fixing belt 21 (a position excluding the nip portion) with a clearance. A clearance amount δ (a gap at a position excluding the nip portion) between the fixing belt 21 and the heat generating members 22a and 22b is set to be larger than 0 mm and equal to or smaller than 1 mm (0 mm <δ ≦ 1 mm). As a result, the area in which the heat generating members 22a and 22b and the fixing belt 21 are in sliding contact with each other is prevented, and the problem that the wear of the fixing belt 21 is accelerated is suppressed. A problem that the heating efficiency of the belt 21 is reduced can be suppressed. Furthermore, since the heat generating members 22a and 22b are arranged close to the fixing belt 21, the circular posture of the flexible fixing belt 21 is maintained to some extent, so that deterioration and breakage due to deformation of the fixing belt 21 can be reduced. Can do.
Further, a lubricant such as fluorine grease or silicone oil is applied to the inner peripheral surface of the fixing belt 21 so that the wear of the fixing belt 21 is reduced even if the heat generating members 22a and 22b and the fixing belt 21 are in sliding contact with each other. ing.

Here, in the first embodiment, 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 side of the fixing belt 21. Referring to FIG. 3, the reinforcing member 23 is formed so that the length in the width direction (the left-right direction in FIG. 3 and the direction perpendicular to the paper in FIG. 2) is equal to that of the fixing member 26. Both end portions in the width direction are fixedly supported on the side plate 43 of the fixing device 20. The reinforcing member 23 abuts against the pressure roller 31 via the fixing member 26 and the fixing belt 21, thereby preventing a problem that the fixing member 26 is greatly deformed by the pressure applied by the pressure roller 31 in the nip portion. ing.
In order to satisfy the above-described function, the reinforcing member 23 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron.

  Referring to FIG. 2, a pressure roller 31 as a pressure rotator that contacts the outer peripheral surface of the fixing belt 21 at the position of the nip portion has an outer diameter of about 25 mm and is placed on a hollow core metal 32. The elastic layer 33 (layer thickness is about 3 mm) is formed. The elastic layer 33 of the pressure roller 31 (pressure rotator) is formed of a material such as foamable silicone rubber, silicone rubber, or fluororubber. A thin release layer made of PFA, PTFE or the like can be provided on the surface layer of the elastic layer 33. The pressure roller 31 is pressed against the fixing belt 21 to form a desired nip portion between both members. Referring to FIG. 3, the pressure roller 31 is provided with a gear 45 that meshes with a drive gear of a drive mechanism (not shown), and the pressure roller 31 is in the direction of the arrow (clockwise) in FIG. Driven by rotation. Further, both ends of the pressure roller 31 in the width direction are rotatably supported by the side plates 43 of the fixing device 20 via bearings 42.

Note that when the elastic layer 33 of the pressure roller 31 is formed of a sponge-like material such as foamable silicone rubber, the pressure applied to the nip portion can be reduced. Further reduction can be achieved. Furthermore, since the heat insulation of the pressure roller 31 is enhanced and the heat of the fixing belt 21 is difficult to move to the pressure roller 31 side, the heating efficiency of the fixing belt 21 is improved.
In the first embodiment, the diameter of the fixing belt 21 and the diameter of the pressure roller 31 can be formed to be substantially equal.

Referring to FIG. 4, fixing member 26 slidably contacting inner peripheral surface 21 a of fixing belt 21 has a surface layer formed on a base layer. The fixing member 26 is formed in a concave shape so that the curvature of the surface facing the pressure roller 31 (the curvature at the nip portion) is smaller than the curvature of the pressure roller 31 when viewed in a cross section orthogonal to the width direction. ing. Further, the range M along the traveling direction of the fixing belt 21 in the fixing member 26 is formed so as to include the range N along the traveling direction of the fixing belt 21 at the nip portion. With such a configuration, since the recording medium P is sent from the nip portion so as to follow the curvature of the pressure roller 31, the recording medium P after the fixing process is not attracted to the fixing belt 21 and separated. Can be suppressed.
In the first embodiment, the shape of the fixing member 26 that forms the nip portion is formed in a concave shape, but the shape of the fixing member 26 that forms the nip portion can also be formed in a flat shape. That is, the sliding contact surface of the fixing 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 is 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, so that the fixing property is improved. Further, since the curvature of the fixing belt 21 on the exit side of the nip portion is increased, the recording medium P sent from the nip portion can be easily separated from the fixing belt 21.

In addition, the material for forming the base layer of the fixing member 26 is formed of a material having a certain degree of rigidity so that it does not bend greatly even if it receives pressure applied by the pressure roller 31. As the base layer, a nonconductor such as ceramic, glass, or an insulating resin material can be used.
The surface layer of the fixing member 26 is formed of a low friction elastic material such as fluoro rubber. By providing such a surface layer, a problem that both the members 21 and 26 wear due to the sliding contact between the fixing member 26 and the fixing belt 21 is reduced, and a desired nip is provided between the both members 21 and 26. A part will be formed. In addition, the surface layer of the fixing member 26 can be impregnated with a lubricant in advance. As a result, the fixing member 26 is in a state where the lubricant is held on the surface in contact with the fixing belt 21, and the problem that both the members 21 and 26 are worn is further reduced.
The fixing member 26 is preferably formed of a nonconductor as a whole. As a result, even if the first heat generating member 22 a is disposed so as to contact the fixing member 26, the current applied to the first heat generating member 22 a can be prevented from flowing to the fixing member 26.

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 heat generating members 22a and 22b (resistance heating elements), and a driving force is transmitted from a driving motor (not shown) to show the pressure roller 31 in FIG. Rotation drive in the direction of the arrow is started. Accordingly, the fixing belt 21 is also driven (rotated) in the direction of the arrow in FIG. 2 by the frictional force with the pressure roller 31 in the nip portion.
Thereafter, the recording medium P is fed from the paper supply unit 12, and an unfixed color image is carried (transferred) on the recording medium P at the position of the secondary transfer roller 89. The recording medium P carrying 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), and the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. It is fed into the nip part.
The surface of the recording medium P is heated by the fixing belt 21 heated by the heating members 22a and 22b (resistance heating elements) and the pressing force of the fixing member 26 reinforced by the reinforcing member 23 and the pressure roller 31. The toner image T is fixed to the toner image. Thereafter, the recording medium P delivered from the nip portion is conveyed in the direction of arrow Y11.

Hereinafter, a characteristic configuration and operation of the fixing device 20 according to the first embodiment will be described in detail.
Referring to FIGS. 2 and 4, in fixing device 20 according to the first exemplary embodiment, the heat generating member inscribed in the inner peripheral surface of fixing belt 21 is divided into two along the circumferential direction of fixing belt 21. Yes.
Specifically, of the heat generating members 22a and 22b divided into two, the first heat generating member 22a disposed on the inlet side of the nip portion (on the upstream side in the 21 running direction of the fixing belt with respect to the nip portion). The fixing member 26 is disposed so as to be in contact with the fixing member 26. The second heat generating member 22b is disposed adjacent to the first heat generating member 22a with a gap therebetween, and faces the inner peripheral surface of the fixing belt 21 at a position excluding the nip portion and the first heat generating member 22a. It is fixed to do. The first heat generating member 22 a is disposed in a relatively narrow range (less than ¼ of the circumferential length) with respect to the circumferential length of the inner circumferential surface of the fixing belt 21.
A temperature sensor 40 is installed as a temperature detecting means for detecting the temperature of the fixing belt 21 at a position corresponding to between the first heat generating member 22a and the second heat generating member 22b.

Here, the first heat generating member 22a has a heat generation amount based on the detection result of the temperature sensor 40 (temperature detecting means) separately from the second heat generating member 22b (other heat generating members divided into a plurality of members). Be controlled. Specifically, the first heat generating member 22a and the second heat generating member 22b are respectively connected to different power sources, and output control is separately performed based on the detection result of the temperature sensor 40, respectively.
Specifically, when the temperature detected by the temperature sensor 40 does not reach the predetermined fixing target temperature, current is applied to the second heat generating member 22b from the power source, and the temperature detected by the temperature sensor 40 reaches the predetermined fixing target temperature. Control (on / off control) is performed so that no current is applied from the power source.
On the other hand, the first heat generating member 22a is controlled so that the amount of generated heat is larger when the temperature detected by the temperature sensor 40 is lower than when the temperature detected by the temperature sensor 40 is high. The Specifically, the first heat generating member 22a is configured to be able to adjust the heat generation amount in several stages such as “strong”, “medium”, and “weak”. Then, referring to FIG. 5, when the temperature detected at the position of temperature sensor 40 substantially matches the fixing target temperature (the target value in the temperature control), it is shown in graph S0. As described above, the amount of heat generated by the first heat generating member 22a is controlled to be “medium” level. On the other hand, when the temperature detected at the position of the temperature sensor 40 is lower than the fixing target temperature, as shown in the graph S2, the amount of heat generated by the first heat generating member 22a becomes the “strong” level. And the fixing belt 21 is positively heated on the inlet side of the nip portion. When the temperature detected at the position of the temperature sensor 40 is higher than the target fixing temperature, as shown in the graph S1, the amount of heat generated by the first heat generating member 22a is at the “weak” level (or zero). In this way, heat dissipation of the fixing belt 21 is promoted on the nip entrance side. In this way, as shown in FIG. 5, when the fixing belt 21 reaches the position of the nip portion (fixing member 26) (the position where the fixing process is performed), the surface temperature of the fixing belt 21 is set to a desired temperature. The fixing target temperature can be made uniform.

In particular, since the position of the second heat generating member 22b is not on the nip portion entrance side but on the side where the fixing belt 21 is relatively loose (side where the belt tension is small), there is a gap variation between the second heating member 22b and the fixing belt 21. As a result, the heating state of the fixing belt 21 tends to vary. On the other hand, the position of the first heat generating member 22a is on the inlet side of the nip portion and on the tension side of the fixing belt 21 (the side on which the belt tension is large). The surface temperature of the fixing belt 21 is varied with good responsiveness when the amount of heat generated by the first heat generating member 22a is varied by being in contact. Therefore, the temperature sensor 40 detects the temperature at the most downstream position of the second heat generating member 22b, determines whether the heating state of the fixing belt 21 is good, and finally the temperature sensor 40 at the position of the first heat generating member 22a. By performing the fixing temperature correction based on the detection result, the fixing belt 21 can be efficiently heated without variation. Therefore, a problem that fixing failure such as fixing unevenness occurs in the fixed image is greatly reduced.
In the first embodiment, since the downstream end portion of the first heat generating member 22a is in contact with the fixing member 26, the fixing belt 21 is heated by the first heat generating member 22a until just before reaching the nip portion. As a result, the heating efficiency of the fixing belt 21 is increased.

Here, in the first embodiment, the first heat generating member 22a generates more heat when the transport speed of the recording medium P transported to the nip portion is slower than when the transport speed of the recording medium P is fast. Is controlled to be small.
Specifically, the image forming apparatus 1 according to the first embodiment performs recording when the temperature of the fixing belt 21 cannot be maintained near the fixing target temperature during continuous paper passing (when the heating of the fixing belt 21 cannot catch up). The “low speed mode” is set in which the image forming operation is performed while the transport speed (process linear speed) of the medium P is lower than normal. When such a “low speed mode” is executed, the heating time of the fixing belt 21 is also increased by the first heat generating member 22a, so that the temperature profile is normally as shown in the graph Q1 of FIG. However, it will change to a temperature profile as shown in the graph Q2 of FIG. Therefore, when the “low speed mode” is executed in the control unit, the control is performed so that the level of the heat generation amount of the first heat generating member 22a set based on the temperature detected by the temperature sensor 40 is lowered by one step. ing. Thereby, even when the “low speed mode” is executed, the fixing belt 21 can be efficiently heated without variation.

In the first embodiment, the first heating member 22a has a basis weight and thickness of the recording medium P when the basis weight, thickness, or density of the recording medium P conveyed to the nip portion is large. The amount of heat generated is controlled to be larger than when either one of the densities is small. This is because the amount of heat taken away by the fixing belt 21 in the fixing process increases as the basis weight, thickness, and density of the recording medium P to be passed increase. Therefore, when the basis weight, thickness, and density of the recording medium P to be passed are large, the fixing belt 21 is moved by the first heat generating member 22a as compared to when the basis weight, thickness, and density of the recording medium P to be passed is small. It is necessary to apply a high amount of heat to.
Specifically, referring to FIG. 7, when the recording medium P to be passed is plain paper, the amount of heat generated by the first heat generating member 22a is set to the “medium” level as shown in the graph R0. Control. On the other hand, when the recording medium P to be passed is thin paper, the amount of heat generated by the first heat generating member 22a is controlled to be “weak” level as shown in the graph R3. Further, when the recording medium P to be passed is thick paper, the amount of heat generated by the first heat generating member 22a is controlled to be “strong” level as shown in the graph R1. Further, when the recording medium P to be passed is a medium that requires a larger amount of heat such as an envelope or OHP, the amount of heat generated by the first heat generating member 22a is “strongest” as shown in the graph R2. Control to level. By performing such control, the fixing belt 21 can be efficiently heated without variation regardless of the type of the recording medium P to be passed.
Information about the basis weight, thickness, and density of the recording medium P is obtained indirectly based on information about the recording medium P input by the user from an operation panel (not shown) of the apparatus main body 1 or the like. It can also be obtained directly based on information detected by a paper thickness sensor or the like installed in the conveyance path of the recording medium P in the apparatus main body 1. The amount of heat generated by the first heat generating member 22a is controlled based on information on the basis weight, thickness, and density of the recording medium P thus obtained.

Here, in the first embodiment, the temperature sensor 40 as the temperature detecting unit is located at a position corresponding to the space between the first heat generating member 22a and the second heat generating member 22b and is applied to the outer peripheral surface of the fixing belt 21. It installed in the position which touches (or opposes).
On the other hand, as shown in FIG. 8, the temperature sensor 40 as the temperature detecting means is located at a position corresponding to between the first heat generating member 22a and the second heat generating member 22b, and the inner circumference of the fixing belt 21. It can also be installed at a position that abuts (or faces) the surface. In such a case, the same effect as in the first embodiment can be obtained. In particular, when the temperature sensor 40 is installed on the inner peripheral surface side of the fixing belt 21, even if a contact type temperature sensor such as a thermistor is used as the temperature sensor 40, the fixing belt 21 has an outer peripheral surface. Since no damage is given, a good fixed image can be obtained over time.

  As described above, in the first embodiment, the heat generating member facing the inner peripheral surface of the fixing belt 21 is divided into a plurality along the circumferential direction of the fixing belt, and disposed on the upstream side of the nip portion. The first heat generating member 22 a is disposed adjacent to the fixing member 26. Further, a temperature sensor 40 (temperature detection means) for detecting the temperature of the fixing belt 21 is provided between the first heat generating member 22a and the second heat generating member 22b adjacent to the first heat generating member 22a. As a result, the warm-up time and the first print time are short, and fixing defects such as fixing unevenness do not occur in the fixed image, and the fixing belt 21 can be efficiently heated without variation.

  In the first embodiment, the heat generating member is divided into the first heat generating member 22a and the second heat generating member 22b along the circumferential direction of the fixing belt 21, but the heat generating member is divided in the circumferential direction of the fixing belt 21. The first heat generating member 22a and the two or more second heat generating members 22b can be divided along the line. Even in this case, the same effect as in the first embodiment can be obtained by installing the first heat generating member 22a and the temperature sensor 40 as in the first embodiment.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 9 is a plan view of the heat generating member viewed along the traveling direction of the fixing belt 21 in the fixing device according to the second embodiment. The fixing device in the second embodiment is different from that in the first embodiment in that the first heat generating member and the second heat generating member are each divided into a plurality of parts in the width direction.

  Similarly to the first embodiment, the fixing device 20 according to the second embodiment also has a fixing belt 21 (belt member), a fixing member 26, and heat generating members 22a1, 22a2, and 22b1 divided into two in the circumferential direction. 22b2, a reinforcing member 23, a pressure roller 31 (pressure rotator), temperature sensors 40a and 40b (temperature detection means), and the like. Similarly to the first embodiment, the fixing device 20 according to the second embodiment is also provided with temperature sensors 40a and 40b at positions corresponding to the two heating members 22a and 22b. The first heat generating members 22a1, 22a2 are output-controlled separately from the second heat generating members 22b1, 22b2 based on the detection results of the temperature sensors 40a, 40b.

Here, in the second embodiment, as shown in FIG. 9, the first heat generating members 22a1 and 22a2 have widths corresponding to the sheet passing area and the non-sheet passing area in the recording medium P having different sizes in the width direction. It is divided into a plurality of directions. Specifically, the first heat generating member 22a1 installed at the central portion in the width direction is disposed corresponding to the paper passing area of the recording medium P of the minimum size through which paper can be passed. On the other hand, the first heat generating members 22a2 installed at both end portions in the width direction have a non-sheet-passing area of the recording medium P of the minimum size that can be passed (the sheet passing area of the recording medium P of the maximum size that can be passed). ).
The second heat generating members 22b1 and 22b2 are also divided into a plurality in the width direction corresponding to the sheet passing area and the non-sheet passing area in the recording medium P having different sizes in the width direction. Specifically, the second heat generating member 22b1 installed in the central portion in the width direction is disposed corresponding to the paper passing area of the recording medium P of the minimum size that can pass paper. On the other hand, the second heat generating members 22b2 installed at both end portions in the width direction have a non-sheet-passing area of the recording medium P having the smallest size that can be passed (the sheet-passing area of the recording medium P having the largest size that can be passed). ).

The first heat generating members 22a1 and 22a2 and the second heat generating members 22b1 and 22b2 divided into a plurality of portions in the width direction generate heat based on the size in the width direction of the recording medium P conveyed to the nip portion. The amount is controlled. Specifically, when the maximum size recording medium P is passed, control is performed so that current is applied to all the first heat generating members 22a1, 22a2 and the second heat generating members 22b1, 22b2. On the other hand, when the recording medium P of the minimum size is passed, current is applied to the first heat generating member 22a1 and the second heat generating member 22b1 at the center in the width direction, and the first heat generation at both ends in the width direction. Control is performed so that no current is applied to the member 22a2 and the second heat generating member 22b2.
By performing such control, even when the recording medium P of the minimum size is passed, the non-sheet passing area of the fixing belt 21 is overheated without being actively deprived of heat by the recording medium P. The problem of warming will be reduced.

  In the second embodiment, as shown in FIG. 9, between the first heat generating members 22a1 and 22a2 and the second heat generating members 22b1 and 22b2, the width direction central portion and the width direction both end portions are respectively provided. Temperature sensors 40a and 40b are installed. And based on the temperature sensor 40a installed in the center part in the width direction, the heat generation amount of the first heat generating member 22a1 installed in the center part in the width direction is controlled. Furthermore, based on the temperature sensor 40b installed at both ends in the width direction, the amount of heat generated by the first heat generating member 22a2 installed at both ends in the width direction is controlled. As a result, even when variations in the width direction occur in the heating state of the fixing belt 21, the variations are detected by the temperature sensors 40a and 40b, and a plurality of divisions divided in the width direction based on the detection information. By separately controlling the output of the first heat generating members 22a1 and 22a2, the fixing belt 21 can be heated more efficiently and without variation.

  In the second embodiment, the first heat generating member and the second heat generating member are respectively arranged in the width direction center portion and the width direction end portions corresponding to the minimum size recording medium P and the maximum size recording medium P. And divided. On the other hand, the number of divisions in the width direction of the first heat generating member and the second heat generating member can be set to be larger corresponding to three or more different size recording media P.

  As described above, also in the second embodiment, as in the first embodiment, the heat generating member facing the inner peripheral surface of the fixing belt 21 is divided into a plurality along the circumferential direction of the fixing belt, The first heat generating members 22 a 1 and 22 a 2 disposed on the upstream side of the nip portion are disposed adjacent to the fixing member 26. Further, temperature sensors 40a and 40b (temperature detection) for detecting the temperature of the fixing belt 21 between the first heat generating members 22a1 and 22a2 and the second heat generating members 22b1 and 22b2 adjacent to the first heat generating members 22a1 and 22a2. Means). As a result, the warm-up time and the first print time are short, and fixing defects such as fixing unevenness do not occur in the fixed image, and the fixing belt 21 can be efficiently heated without variation.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 10 is a configuration diagram illustrating the fixing device according to the third embodiment, and corresponds to FIG. 2 according to the first embodiment. FIG. 11 is a perspective view showing the heat insulating member 27.
The fixing device according to the third embodiment is different from that according to the first embodiment in that a heat insulating member 27 is provided on the inner peripheral surface side of the heat generating members 22a and 22b.

  As shown in FIG. 10, the fixing device 20 according to the fourth embodiment is also divided into a fixing belt 21 (belt member), a fixing member 26, and two in the circumferential direction, as in the first embodiment. The heat generating members 22a and 22b, the reinforcing member 23, the pressure roller 31 (pressure rotating body), the temperature sensor 40 (temperature detecting means), and the like are configured. Similarly to the first embodiment, the fixing device 20 according to the third embodiment is also provided with a temperature sensor 40 at a corresponding position between the heat generating members 22a and 22b divided into two, and the temperature Based on the detection result of the sensor 40, the output of the first heat generating member 22a is controlled separately from the second heat generating member 22b.

  Here, in the third embodiment, a substantially pipe-shaped heat insulating member 27 made of a heat insulating material such as ceramic (see FIG. 11) so as to face the inner peripheral surface of the fixing belt 21 via the heat generating members 22a and 22b. Can be referred to.) Is installed. The heat insulating member 27 is supported by side plates 43 shown in FIG. 3 at both ends in the width direction. By installing the heat insulating member 27 on the inner peripheral surface side of the heat generating members 22a and 22b, the heat of the heat generating members 22a and 22b is not easily dissipated to the inner peripheral surface side. Efficiency will be increased.

  The heat insulating member 27 is formed so as to support only the heat generating members 22 a and 22 b without supporting the fixing member 26 and the reinforcing member 23. Specifically, as shown in FIG. 11, the heat insulating member 27 is provided with an opening 27a, and the fixing member 26 and the reinforcing member 23 are disposed with a gap at the position of the opening 27a. It will be. Thereby, even if the fixing member 26 and the reinforcing member 23 are deformed due to the pressure at the nip portion, it is possible to reliably prevent a problem that the heat generating members 22a and 22b are deformed via the heat insulating member 27 due to the deformation. it can.

  The heat insulating member 27 also has a function of supporting the heat generating members 22a and 22b and reinforcing the mechanical strength of the heat generating members 22a and 22b. As a result, even when the heat generating members 22a and 22b are thinned, it is possible to suppress a problem that the heat generating members 22a and 22b are deformed and the gap with the fixing belt 21 is widened.

  As described above, also in the third embodiment, the heating member facing the inner peripheral surface of the fixing belt 21 is divided into a plurality along the circumferential direction of the fixing belt, as in the above-described embodiments. The first heat generating member 22 a disposed on the upstream side of the nip portion is disposed adjacent to the fixing member 26. Further, a temperature sensor 40 (temperature detection means) for detecting the temperature of the fixing belt 21 is provided between the first heat generating member 22a and the second heat generating member 22b adjacent to the first heat generating member 22a. As a result, the warm-up time and the first print time are short, and fixing defects such as fixing unevenness do not occur in the fixed image, and the fixing belt 21 can be efficiently heated without variation.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 12 is an enlarged view showing the vicinity of the nip portion of the fixing device according to the fourth embodiment, and corresponds to FIG. 4 in the first embodiment. The fixing device according to the fourth embodiment is different from that according to the first embodiment in that the first heat generating member 22a is installed so as to enter a recessed portion formed in the fixing member 26.

  Referring to FIG. 12, the fixing device 20 according to the fifth embodiment is also divided into a fixing belt 21 (belt member), a fixing member 26, and two in the circumferential direction, as in the first embodiment. The heat generating members 22a and 22b, the reinforcing member 23, the pressure roller 31 (pressure rotating body), the temperature sensor 40 (temperature detecting means), and the like are configured. Similarly to the first embodiment, the fixing device 20 in the fourth embodiment is also provided with a temperature sensor 40 at a corresponding position between the heat generating members 22a and 22b divided into two, and the temperature Based on the detection result of the sensor 40, the output of the first heat generating member 22a is controlled separately from the second heat generating member 22b.

Here, in the fourth embodiment, as shown in FIG. 12, the fixing member 26 and the fixing belt 21 are positioned upstream of the nip portion (on the upstream side of the nip portion in the running direction of the fixing belt 21). Is formed with a gap (a portion surrounded by a broken line in FIG. 12). Specifically, a recessed portion is provided at the end of the fixing member 26 (the end on the upstream side of the nip).
The first heat generating member 22a is formed so as to enter the gap (the recessed portion of the fixing member 26) between the fixing member 26 and the fixing belt 21 described above.

  With such a configuration, the downstream end portion of the first heat generating member 22a is further disposed near the nip portion, and the fixing belt 21 is heated by the first heat generating member 22a until just before reaching the nip portion. As a result, the heating efficiency of the fixing belt 21 is further increased.

  As described above, also in the fourth embodiment, as in each of the above embodiments, the heat generating member facing the inner peripheral surface of the fixing belt 21 is divided into a plurality along the circumferential direction of the fixing belt, The first heat generating member 22 a disposed on the upstream side of the nip portion is disposed adjacent to the fixing member 26. Further, a temperature sensor 40 (temperature detection means) for detecting the temperature of the fixing belt 21 is provided between the first heat generating member 22a and the second heat generating member 22b adjacent to the first heat generating member 22a. As a result, the warm-up time and the first print time are short, and fixing defects such as fixing unevenness do not occur in the fixed image, and the fixing belt 21 can be efficiently heated without variation.

In each of the above embodiments, the fixing belt 21 having a multilayer structure is used as the fixing belt. However, an endless fixing film made of polyimide, polyamide, fluororesin, metal, or the like may be used as the fixing belt. In this case, the same effects as those of the above embodiments can be obtained.
In each of the above embodiments, the present invention is applied to a fixing device using a pressure roller as a pressure rotator, but also to a fixing device using a pressure belt or the like as a pressure rotator. The present invention can be applied. In this case, the same effects as those of the above embodiments can be obtained.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing belt (fixing member),
22a 1st heat generating member (heat generating member),
22b Second heat generating member (heat generating member),
23 reinforcing members,
26 fixing member,
27 heat insulation member,
31 Pressure roller (pressure rotating body),
40, 40a, 40b Temperature sensor (temperature detection means), P recording medium.

Japanese Patent No. 2008-216928 Japanese Patent No. 2008-158482

Claims (14)

An endless fixing belt having flexibility and running in a predetermined direction to heat and melt the toner image;
A fixing member fixed on the inner peripheral surface side of the fixing belt and forming a nip portion for conveying a recording medium in pressure contact with the pressure rotator via the fixing belt;
A heating member that heats the fixing belt and is divided into a plurality of pieces along the circumferential direction of the fixing belt so as to contact or face the inner peripheral surface of the fixing belt at a position different from the nip portion. When,
With
Of the heat generating members divided into a plurality, the first heat generating member disposed on the upstream side in the running direction of the fixing belt with respect to the nip portion is disposed adjacent to the fixing member. ,
Temperature detection for detecting the temperature of the fixing belt at a position corresponding to between the first heat generating member and a second heat generating member adjacent to the first heat generating member among the other heat generating members divided into a plurality of parts. A fixing device further comprising means.   2. The fixing device according to claim 1, wherein a heat generation amount of the first heat generating member is controlled based on a detection result of the temperature detecting unit separately from the other heat generating members divided into the plurality of heat generating members. .   The first heat generating member is controlled such that when the temperature detected by the temperature detecting means is low, the amount of generated heat is larger than when the temperature detected by the temperature detecting means is high. The fixing device according to claim 2.   The first heat generating member is controlled so that the amount of heat generated when the conveyance speed of the recording medium conveyed to the nip portion is low is smaller than when the conveyance speed of the recording medium is high. The fixing device according to any one of claims 1 to 3.   The first heat generating member is when any of the basis weight, thickness, and density of the recording medium conveyed to the nip portion is large, and any of the basis weight, thickness, and density of the recording medium is small. 5. The fixing device according to claim 1, wherein the fixing device is controlled so that the amount of generated heat is larger than that of the fixing device. The first heat generating member is divided into a plurality in the width direction corresponding to a sheet passing area and a non-sheet passing area in recording media having different sizes in the width direction,
6. The heat generation amount of the first heating member divided into a plurality of parts is controlled based on a size in a width direction of a recording medium conveyed to the nip portion. The fixing device according to any one of the above. The other heat generating member divided into a plurality is divided into a plurality in the width direction corresponding to the sheet passing area and the non-sheet passing area in the recording medium having different sizes in the width direction,
The fixing device according to claim 6, wherein the heat generation amount of the other heat generating member divided into a plurality is controlled based on a size in a width direction of the recording medium conveyed to the nip portion. .   The heat insulating member is further provided so as to face the inner peripheral surface of the fixing belt through the heat generating member and to support only the heat generating member. A fixing device according to claim 1. The fixing member is formed such that a curvature at the nip portion is smaller than a curvature at the nip portion of the pressure rotator when viewed in a cross section orthogonal to the width direction, and the traveling direction of the fixing belt Is formed so as to include a range along the traveling direction of the fixing belt at the nip portion, and is located between the fixing belt at a position upstream of the nip portion in the traveling direction of the fixing belt. A gap is formed,
The fixing device according to claim 1, wherein the first heat generating member is formed so as to enter the gap between the fixing member and the fixing belt.   The reinforcing member according to any one of claims 1 to 9, further comprising a reinforcing member that is fixed to an inner peripheral surface side of the heat generating member and abuts on the fixing member to reinforce the fixing member. Fixing device.   The fixing device according to claim 1, wherein the fixing member is made of a non-conductor. The plurality of heat generating members divided into the first heat generating member and the second heat generating member,
12. The first heat generating member according to claim 1, wherein the second heat generating member is fixed so as to face the inner peripheral surface of the fixing belt at a position excluding the nip portion and the first heat generating member. The fixing device according to any one of the above.   13. The fixing device according to claim 1, wherein each of the plurality of divided heating members is formed of a resistance heating element.   An image forming apparatus comprising the fixing device according to claim 1.

Images