JP6191916B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the fixing device.

  As a fixing device used in various image forming apparatuses such as a copying machine, a printer, a facsimile, or a composite machine thereof, a fixing device having a thin fixing belt made of a metal base and an elastic rubber layer is known. As described above, by providing the thin fixing belt having a low heat capacity, the energy required for heating the fixing belt can be greatly reduced, and the warm-up time and the first print time can be shortened.

  In the fixing device described in Patent Document 1, an endless fixing belt, a pressure roller in contact with the outer peripheral surface of the fixing belt, and an inner peripheral side of the fixing belt are in contact with the pressure roller via the fixing belt. A fixing nip portion is formed between the fixing belt and the pressure roller by the nip forming member.

  A heater, which is a heating means for heating the fixing belt, is provided on the inner peripheral side of the fixing belt, and the surface of the fixing belt is detected based on the detection result of the contact-type temperature detection sensor that detects the surface temperature of the fixing belt. Electric power is supplied to the heater so that the temperature becomes the target temperature. The toner image on the paper is fixed on the paper by heat and pressure at the fixing nip portion.

  Generally, flanges as guide members are inserted at both ends in the width direction of the fixing belt, and both ends in the width direction of the fixing belt are rotatably held by the flanges. Thus, the fixing belt can be rotated stably by guiding both ends of the fixing belt in the width direction with the flange and rotating the fixing belt along a predetermined locus.

  In addition, by using only the nip forming member and the flange as the members that come into contact with the inner peripheral surface of the fixing belt, the fixing belt can be directly heated by the heat from the heater other than the location where the nip forming member or the flange is disposed. The heat transfer efficiency from the heater to the fixing belt is greatly improved.

  However, at least when the fixing belt rotates, the fixing belt has a cross-sectional shape due to the influence of the bending of the fixing belt at both ends of the fixing belt in the width direction guided by the guide member and the central portion in the width direction of the fixing belt not guided by the guide member. Different.

  For this reason, when a plurality of temperature detection sensors are arranged side by side in the fixing belt width direction so that the temperature of the fixing belt can be accurately adjusted in the fixing belt width direction, the contact state with the fixing belt may differ among the temperature detection sensors. There is.

  When the temperature of the fixing belt is detected using a contact-type temperature detection sensor, the contact state between the surface of the fixing belt and the temperature detection sensor greatly affects the detection accuracy. If the state is different, a temperature detection error occurs in the fixing belt width direction.

  The present invention has been made in view of the above problems, and an object thereof is to provide a fixing device that can suppress a temperature detection error in the fixing belt width direction, and an image forming apparatus including the fixing device. .

  In order to achieve the above object, the invention of claim 1 is directed to a rotatable endless fixing belt, a contact member that contacts an outer peripheral surface of the fixing belt, and an inner peripheral side of the fixing belt. A nip forming member that forms a nip by contacting the contact member via a belt, a heating unit that directly or indirectly heats the fixing belt, and an inner peripheral surface at both widthwise ends of the fixing belt can be contacted. Provided with a guide member for guiding the rotation of the fixing belt, and a plurality of temperature detecting means arranged in the fixing belt width direction for contacting the fixing belt and detecting the temperature of the fixing belt. The detecting means is arranged at a position in contact with the surface of the fixing belt in the same contact state in accordance with at least the bending shape of the fixing belt when the fixing belt rotates. A.

  As described above, according to the present invention, there is an excellent effect that a temperature detection error in the fixing belt width direction can be suppressed.

(A) Schematic view of the fixing device viewed from above the device (in the direction of arrow A in FIG. 1C), (b) When the fixing device is viewed from the fixing belt side to the pressure roller side (of FIG. 1C) The figure which showed the shape of the fixing belt in the case where it sees from the arrow B direction, (c) The schematic diagram when the fixing device is seen from the fixing belt width direction. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 3 is a diagram illustrating an example of a conventional fixing device that indirectly heats a fixing belt via a metal heat conductor. 1 is a schematic configuration diagram illustrating an example of a fixing device according to an embodiment. FIG. 6 is a diagram illustrating another configuration of the fixing device. FIG. 6 is a diagram illustrating still another configuration of the fixing device. The top view of a shielding member. FIG. 3 is a perspective view of a fixing device showing a state where a shielding member is moved to a shielding position for small-size paper. FIG. 6 is a cross-sectional view of the fixing device showing a state where the shielding member is moved to a shielding position for small-size paper. FIG. 3 is a perspective view of a fixing device showing a state where a shielding member is moved to a shielding position for large-size paper. FIG. 4 is a cross-sectional view of the fixing device showing a state where the shielding member is moved to a shielding position for large-size paper. Explanatory drawing explaining the installation position of the temperature detection sensor. FIG. 6 is an explanatory diagram of an installation position of a stay member provided in the fixing device and a sensor bracket on which a temperature detection sensor is installed. The schematic diagram which showed the other shape of the sensor bracket.

  Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings for explaining the embodiments of the present invention, constituent elements such as members and components having the same function or shape are described once by giving the same reference numerals as much as possible. Then, the explanation is omitted.

FIG. 2 is a schematic configuration diagram of the image forming apparatus 100 according to the present embodiment.
An image forming apparatus 100 shown in FIG. 2 is a tandem color laser printer, and includes an image forming section (four image forming sections in the illustrated example) that forms a plurality of color images at the center of the apparatus main body. An image station is provided.

  The plurality of image forming units are juxtaposed along the extending direction of the intermediate transfer belt 11 as an endless belt-like intermediate transfer member. The configuration is the same except that developers of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image are accommodated. .

  In FIG. 2, the image forming apparatus 100 includes a plurality of photosensitive drums 120Y, 120C, 120M, and 120Bk as image bearing members corresponding to colors separated into yellow, cyan, magenta, and black, respectively. ing.

  A toner image, which is a visible image of each color, formed on each photoconductor drum 120Y, 120C, 120M, and 120Bk is an intermediate transfer that can move in the direction of arrow A1 while facing each photoconductor drum 120Y, 120C, 120M, and 120Bk. A primary transfer process is performed on the belt 11. As a result, the toner images of the respective colors are superimposed and transferred onto the intermediate transfer belt 11. Thereafter, the toner images of the respective colors superimposed and transferred onto the intermediate transfer belt 11 are collectively transferred onto the paper P by performing a secondary transfer process on the paper P as a recording material.

  Around the photosensitive drums 120Y, 120C, 120M, and 120Bk, various devices for image forming processing are arranged according to the rotation of the photosensitive drum 120.

  Here, the photosensitive drum 120Bk that performs black image formation will be described. Around the photosensitive drum 120Bk, there are a charging device 30Bk, a developing device 40Bk, a primary transfer roller 112Bk as a primary transfer unit, and a cleaning device 50Bk that perform image forming processing along the rotation direction of the photosensitive drum 120Bk. Has been placed. For writing of the electrostatic latent image performed on the photosensitive drum 120Bk after charging, the optical writing device 6 as an exposure unit that exposes the surface of the photosensitive drum 120Bk is used.

  The optical writing device 6 includes a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, a rotating polygon mirror (polygon mirror) as an optical deflecting unit, and the like. The optical writing device 6 irradiates the surface of each of the photosensitive drums 120Y, 120C, 120M, and 120Bk with writing light (laser light) Lb based on the image data, and statically irradiates the photosensitive drums 120Y, 120C, 120M, and 120Bk. An electrostatic latent image is formed.

  In the superimposing transfer to the intermediate transfer belt 11, when the intermediate transfer belt 11 moves in the direction A1 in the figure, visible images (toner images) formed on the photosensitive drums 120Y, 120C, 120M, and 120Bk are transferred to the intermediate transfer belt 11. It is performed so that it is transferred to the same position.

  More specifically, a primary transfer bias is applied to each of a plurality of primary transfer rollers 112Y, 112C, 112M, and 112Bk disposed to face the respective photosensitive drums 120Y, 120C, 120M, and 120Bk with the intermediate transfer belt 11 interposed therebetween. Applied. By the primary transfer rollers 112Y, 112C, 112M, and 112Bk to which the primary transfer bias is applied, the toner images formed on the respective photosensitive drums 120Y, 120C, 120M, and 120Bk are superimposed with the timing shifted in the intermediate transfer belt rotation direction. Transcribed.

  The plurality of primary transfer rollers 112Y, 112C, 112M, and 112Bk sandwich the intermediate transfer belt 11 with the corresponding photosensitive drums 120Y, 120C, 120M, and 120Bk to form a primary transfer nip. Further, a power source (not shown) is connected to each primary transfer roller 112Y, 112C, 112M, 112Bk. A primary transfer bias composed of at least one of a predetermined direct current voltage (DC) and alternating current voltage (AC) is applied to each primary transfer roller 112Y, 112C, 112M, 112Bk by this power source.

  The photosensitive drums 120Y, 120C, 120M, and 120Bk are arranged in this order from the upstream side in the A1 direction in the drawing. Each of the photosensitive drums 120Y, 120C, 120M, and 120Bk is provided in the plurality of image forming units that respectively form yellow, cyan, magenta, and black images.

  In addition to the plurality of image forming units, the image forming apparatus 100 includes a transfer belt unit 10, a secondary transfer roller 5, a transfer belt cleaning device 113, and an optical writing device 6.

  The transfer belt unit 10 includes a plurality of belt support members such as an intermediate transfer belt 11 and a plurality of primary transfer rollers 112Y, 112C, 112M, and 112Bk, as well as a driving roller 72 and a driven roller 73 around which the intermediate transfer belt 11 is wound. It has. By driving the drive roller 72 to rotate, the intermediate transfer belt 11 rotates in the direction indicated by the arrow A1 in the drawing.

  The drive roller 72 also functions as a secondary transfer backup roller that faces the secondary transfer roller 5 via the intermediate transfer belt 11. The driven roller 73 also functions as a cleaning backup roller that faces the transfer belt cleaning device 113 via the intermediate transfer belt 11. Further, since the driven roller 73 also has a function as a tension urging unit for the intermediate transfer belt 11, the driven roller 73 is provided with an urging unit using a spring or the like. The transfer device 71 is configured to include the transfer belt unit 10, the primary transfer rollers 112 </ b> Y, 112 </ b> C, 112 </ b> M, and 112 </ b> Bk, the secondary transfer roller 5, and the transfer belt cleaning device 113.

  The secondary transfer roller 5 is disposed so as to face the intermediate transfer belt 11 and is driven by the intermediate transfer belt 11. Further, the secondary transfer roller 5 sandwiches the intermediate transfer belt 11 with a driving roller 72 that also functions as a secondary transfer backup roller, thereby forming a secondary transfer nip.

  Similarly to the primary transfer rollers 112Y, 112C, 112M, and 112Bk, the secondary transfer roller 5 is also connected to a power source (not shown), and receives at least one of a predetermined direct current voltage (DC) and alternating current voltage (AC). The secondary transfer bias is applied to the secondary transfer roller 5.

  The transfer belt cleaning device 113 is disposed so as to face the driven roller 73 with the intermediate transfer belt 11 interposed therebetween, and cleans the surface of the intermediate transfer belt 11. In the illustrated example, the transfer belt cleaning device 113 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 11. A waste toner transfer hose (not shown) extending from the transfer belt cleaning device 113 is connected to an inlet portion of a waste toner container (not shown).

  Further, the image forming apparatus 100 includes a sheet feeding device 61 on which sheets P as recording materials are stacked and accommodated, a pair of registration rollers 4 as recording material feeding means, and a sheet leading edge (not shown) as recording material leading edge detection means. And a sensor.

  The sheet feeding device 61 is provided at the lower part of the main body of the image forming apparatus 100 and has a feeding roller 3 as a recording material feeding unit that comes into contact with the upper surface of the uppermost sheet P. Then, the uppermost sheet P is fed toward the registration roller pair 4 by the feeding roller 3 being driven to rotate counterclockwise in the drawing.

  In the image forming apparatus main body, a paper transport path is provided for discharging the paper P from the paper feeding device 61 through the secondary transfer nip to the outside of the device. A registration roller pair 4 that conveys the sheet P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 5 in the sheet conveyance path in the sheet conveyance direction.

  The registration roller pair 4 and the secondary transfer roller 5 are in contact with the secondary transfer roller 5 at a predetermined timing in accordance with the toner image formation timing of the paper P conveyed from the paper feeding device 61 by the image station including the plurality of image forming units. It is fed out toward the secondary transfer nip with the intermediate transfer belt 11. The paper leading edge sensor detects that the leading edge of the paper P has reached the registration roller pair 4.

  Here, the paper P as the recording material includes, in addition to plain paper, thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, recording sheet, and the like. . In addition to the paper feeding device 61, a manual paper feed mechanism may be provided so that the paper P can be manually fed.

  Further, the image forming apparatus 100 includes a fixing device 20 as a fixing unit for fixing the toner image on the paper P on which the toner image is transferred, a paper discharge roller pair 7 as a recording material discharging unit, and a recording material stacking unit. As a paper discharge tray 17. The paper discharge roller pair 7 discharges the fixed paper P to the outside of the main body of the image forming apparatus 100. The paper discharge tray 17 is disposed on the upper part of the main body of the image forming apparatus 100 and stacks and stores the paper P discharged to the outside of the main body of the image forming apparatus 100 by the pair of paper discharge rollers 7.

  Further, the image forming apparatus 100 includes toner bottles 9Y, 9C, 9M, and 9Bk as a plurality of toner containers. Each of the plurality of toner bottles 9Y, 9C, 9M, and 9Bk is filled with toner of each color of yellow, cyan, magenta, and black. It is detachably attached to each bottle housing part.

  Further, a replenishment path (not shown) is provided between each toner bottle 9Y, 9C, 9M, 9Bk and each developing device 40Y, 40C, 40M, 40Bk. The toner is supplied from the toner bottles 9Y, 9C, 9M, and 9Bk to the corresponding developing devices 40Y, 40C, 40M, and 40Bk through the supply path.

  Although not shown in detail, the transfer belt cleaning device 113 provided in the transfer device 71 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 11.

  The cleaning brush and the cleaning blade scrape and remove foreign matters such as residual toner on the intermediate transfer belt 11 to clean the intermediate transfer belt 11. The transfer belt cleaning device 113 has a discharge means (not shown) for carrying out and discarding the residual toner removed from the intermediate transfer belt 11.

Next, the basic operation of the image forming apparatus 100 will be described.
When the image forming operation is started in the image forming apparatus 100, the photosensitive drums 120Y, 120C, 120M, and 120Bk in the respective image forming units are rotationally driven clockwise in the drawing by a driving device (not shown). The surfaces of the photosensitive drums 120Y, 120C, 120M, and 120Bk are uniformly charged to a predetermined polarity by the charging devices 30Y, 30C, 30M, and 30Bk.

  The surface of each charged photoconductive drum 120Y, 120C, 120M, and 120Bk is irradiated with laser light from the optical writing device 6, and the surface of each photoconductive drum 120Y, 120C, 120M, and 120Bk is electrostatic latent. An image is formed. At this time, the image information exposed on each of the photoconductive drums 120Y, 120C, 120M, and 120Bk is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black.

  The toner is supplied to the electrostatic latent images formed on the photosensitive drums 120Y, 120C, 120M, and 120Bk in this way by the developing devices 40Y, 40C, 40M, and 40Bk, so that the electrostatic latent images become toners. The image is visualized (visualized).

  When the image forming operation is started, the driving roller 72 is driven to rotate counterclockwise in FIG. 2, and the intermediate transfer belt 11 is rotated in the direction of the arrow A1 in the drawing. Then, a constant voltage or a constant current-controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 112Y, 112C, 112M, 112Bk. As a result, a predetermined transfer electric field is formed in the primary transfer nip between each primary transfer roller 112Y, 112C, 112M, 112Bk and each photosensitive drum 120Y, 120C, 120M, 120Bk.

  Thereafter, the toner images on the photosensitive drums 120Y, 120C, 120M, and 120Bk are sequentially superimposed and transferred onto the intermediate transfer belt 11 by the transfer electric field formed in the primary transfer nip, and full color is transferred onto the surface of the intermediate transfer belt 11. The toner image is carried.

  Further, the toner on each of the photosensitive drums 120Y, 120C, 120M, and 120Bk that could not be transferred to the intermediate transfer belt 11 is removed by the cleaning devices 50Y, 50C, 50M, and 50Bk. Thereafter, the surface of each of the photosensitive drums 120Y, 120C, 120M, and 120Bk is neutralized by a neutralizing device (not shown), and the surface potential is initialized.

  In the lower part of the image forming apparatus 100, the feeding roller 3 starts to rotate, and the paper P is sent from the paper feeding device 61 to the conveyance path. The sheet P sent to the conveyance path is timed by the registration roller pair 4 and sent to the secondary transfer nip between the drive roller 72 and the secondary transfer roller 5 that also functions as a secondary transfer backup roller. It is done. At this time, a transfer voltage having a polarity opposite to the toner charge polarity of the toner image on the intermediate transfer belt 11 is applied to the secondary transfer roller 5, and a predetermined transfer electric field is formed in the secondary transfer nip. .

  Thereafter, when the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip as the intermediate transfer belt 11 rotates, the toner on the intermediate transfer belt 11 is generated by the transfer electric field formed in the secondary transfer nip. The images are transferred onto the paper P at once.

  At this time, the residual toner on the intermediate transfer belt 11 that could not be transferred onto the paper P is removed by the transfer belt cleaning device 113, and the removed toner is conveyed to a waste toner container (not shown) and collected.

  Thereafter, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged out of the apparatus by the paper discharge roller pair 7 and stocked on the paper discharge tray 17.

  The above description is an image forming operation when a full-color image is formed on the paper P. A single-color image is formed using any one of the four image forming units, or two or three. It is also possible to form a two-color or three-color image using two image forming units.

  The image forming apparatus shown in FIG. 2 is a color printer that uses a tandem method in which image forming units for forming a plurality of color images are juxtaposed along the belt extending direction. However, the present invention is not limited to this method. It is also possible to target not only printers but also copying machines and facsimiles.

  Here, as is well known, an electrophotographic image forming apparatus outputs a copy image through the following steps. That is, the electrostatic latent image formed on the photosensitive member, which is a latent image carrier, is subjected to visible image processing with toner, and the toner image is transferred to a recording material such as paper and fixed, whereby a copy image is obtained. Is output.

  Examples of the fixing method used in the image forming apparatus include a heat roller fixing method, a belt fixing method, a film fixing method, and an electromagnetic induction heating fixing method.

  In the heat fixing roller system, a fixing roller and a pressure roller that are in contact with each other with a sheet conveyance path interposed therebetween are used. In this system, the toner image is melted and penetrated into the sheet by the action of heat from a heat source provided in the fixing roller and pressure corresponding to the pressure applied from the pressure roller. The phenomenon that the toner image melts and penetrates the paper is the same in the fixing method having the following configuration.

  In the belt fixing method, a fixing belt serving as a heat good conductor, a pressure roller, a roller equipped with the belt, and a heating source for the belt are used instead of the fixing roller (for example, Patent Document 2).

  In the film fixing method, a fixing belt serving as a good heat conductor, a pressure roller, a roller equipped with the belt, and a heating source for the belt are used instead of the fixing roller (for example, Patent Document 3).

  In the electromagnetic induction heating and fixing method, a configuration in which an electromagnetic induction coil that enhances heat generation efficiency is provided on a heating member is used (for example, Patent Document 2).

The fixing system has the following required issues.
It is to reduce the warm-up time, and further to reduce the first print time. The warm-up time is a time required from a normal temperature state to a predetermined printable temperature (reload temperature) such as when the power is turned on. The first print time is a time required from when a print request is received to when a print operation is performed through a print preparation and paper discharge is completed.

In the fixing device, fixing failure may occur for the following reason.
The image forming apparatus is an apparatus that can perform high-speed processing. When the number of fixed sheets per unit time, that is, the number of sheets passing through the fixing device is increased by high-speed processing, the amount of heat supplied to the sheet moving at high speed must be increased. This is because the amount of heat necessary for fixing is given to the sheet as the time for the sheet to pass through the fixing device becomes shorter.

  However, if the amount of heat required at the beginning of continuous printing is not secured, the temperature will drop greatly, and if the paper is passed without reaching the required amount of heat during high-speed continuous printing, there is a possibility that fixing failure will occur. .

  In addition, as the speed of image forming apparatuses increases, the number of sheets passed per unit time increases and the required heat quantity increases, so the so-called temperature drop, which is a shortage of heat quantity especially at the beginning of continuous printing, may be a problem. There is a problem that fixing failure occurs when the speed is increased.

  On the other hand, in addition to the above-described fixing methods, there is a fixing method called a surf fixing method using a ceramic heater.

  The surf fixing method uses a configuration in which only the nip portion is locally heated and the other portions are not heated. In this fixing method, since the heat capacity can be reduced and the size can be reduced as compared with the belt-type fixing device, it is possible to rise to a predetermined temperature and shorten the first print time, but there are the following problems.

  In other words, the surf fixing method is not heated in any part other than the local area, so that there is a problem that the fixing belt is in the coldest state at the entrance of the nip sheet and the like, and fixing failure is likely to occur. In particular, in a high-speed machine, there is a problem that a fixing failure is more likely to occur because the fixing belt rotates quickly and the heat radiation of the belt outside the nip increases.

  Therefore, in order to deal with such problems, a fixing device has been proposed in which a fixing belt can be used to obtain a good fixing property even if it is mounted on a high-production image forming apparatus. For example, Patent Document 4).

  In the fixing device disclosed in Patent Document 4, the configuration shown in FIG. 3 is used. The fixing belt 21, the pipe-shaped metal heat conductor 200 disposed in the fixing belt 21, the heat source 300 disposed in the metal heat conductor 200, and the metal heat conductor 200 via the fixing belt 21. Is provided with a pressure roller 400 that forms a fixing nip N.

  The fixing belt 21 is rotated by the rotation of the pressure roller 400. At this time, the metal heat conductor 200 guides the movement of the fixing belt 21. Further, the fixing belt 21 is heated by the heat source 300 in the metal heat conductor 200 via the metal heat conductor 200, so that the entire fixing belt 21 can be heated. This makes it possible to shorten the first print time from the heating standby time and to solve the shortage of heat during high-speed rotation.

  However, in order to further save energy and improve the first print time, it is necessary to further improve the thermal efficiency.

  Therefore, a configuration is adopted in which the fixing belt is directly heated rather than indirectly heated via a metal heat conductor (a member denoted by reference numeral 200 in FIG. 3). As a result, power consumption can be reduced, and the first print time from the heating standby time can be further shortened. Moreover, the cost reduction by not providing a metal heat conductor can also be anticipated.

FIG. 4 is a schematic configuration diagram illustrating an example of the fixing device 20 according to the present embodiment.
The fixing device 20 includes a fixing belt 21 as a fixing member that is a surface endless moving body having a hollow inside, and a pressure roller as a pressing member that is provided so as to be opposed to the fixing belt 21 so as to be rotatable. 22.

  Inside the fixing belt 21, a halogen heater 23 as a heat source for heating the fixing belt 21, a pressure roller 22 opposed via the fixing belt 21, and a nip forming member 24 that forms a fixing nip portion N are provided. ing. Further, a stay 25 as a support member that supports the nip forming member 24 and a reflection member 26 that reflects light emitted from the halogen heater 23 to the fixing belt 21 are provided inside the fixing belt 21.

  The fixing device 20 includes a temperature detection sensor (not shown) as a temperature detection unit that detects the temperature of the fixing belt 21, a separation member 28 as a recording medium separation unit that separates the paper P from the fixing belt 21, and pressure. A pressing means (not shown) for pressing the roller 22 to the fixing belt 21 is provided.

  In addition, flanges as guide members (not shown) are inserted into both ends of the fixing belt 21 in the width direction, and the fixing belt 21 is rotatably held while being guided by the flanges. The halogen heater 23, stay 25, flange, and the like are fixedly supported by a pair of side plates (not shown) of the fixing device 20.

  The fixing belt 21 is a thin and flexible endless belt member (including a film).

  The fixing belt 21 has a base material on the inner peripheral side formed of a metal material such as nickel or stainless steel or a resin material such as polyimide (PI).

  In addition, a release layer on the outer peripheral side formed of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or polytetrafluoroethylene (PTFE) is provided.

  Further, an elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material and the release layer.

  The pressure roller 22 includes a cored bar 22a, an elastic layer 22b, and a release layer 22c. The elastic layer 22b is disposed on the surface of the cored bar 22a, and foamable silicone rubber, silicone rubber, fluorine rubber, or the like is used. The release layer 22c is provided on the surface of the elastic layer 22b, and PFA, PTFE, or the like is used.

  The pressure roller 22 is in contact with the nip forming member 24 via the fixing belt 21 by being pressed toward the fixing belt 21 by a pressing unit (not shown).

  At the location where the pressure roller 22 and the fixing belt 21 are in pressure contact, the elastic layer 22b of the pressure roller 22 is crushed to form a fixing nip portion N having a predetermined width.

  The pressure roller 22 is rotationally driven by a drive source (not shown) such as a motor provided in the printer body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the fixing nip portion N, and the fixing belt 21 is driven to rotate.

  In the present embodiment, the pressure roller 22 is a solid roller, but may be a hollow roller. In that case, a heating source such as a halogen heater may be disposed inside the pressure roller 22. Further, when there is no elastic layer, the heat capacity is reduced and the fixability is improved.

  However, when the unfixed toner is crushed and fixed, minute irregularities on the belt surface may be transferred to the image, resulting in uneven gloss on the solid portion of the image. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 [μm] or more.

  By providing an elastic layer having a thickness of 100 [μm] or more, minute irregularities can be absorbed by elastic deformation of the elastic layer, so that occurrence of uneven gloss can be avoided. The elastic layer 22b may be solid rubber, but if there is no heat source inside the pressure roller 22, sponge rubber may be used.

  Sponge rubber is more preferable because heat insulation is enhanced and heat of the fixing belt 21 is less likely to be taken away. Further, the fixing rotator and the counter rotator are not limited to being brought into pressure contact with each other, and may be configured to simply contact each other without applying pressure.

  Both ends of the halogen heater 23 are fixed to a side plate (not shown) of the fixing device 20. The output of the halogen heater 23 is controlled by a power supply unit disposed in the printer main body, and generates heat. The output control is performed based on the detection result of the surface temperature of the fixing belt 21 by a temperature detection sensor (not shown).

  By such output control of the halogen heater 23, the temperature of the fixing belt 21 (fixing temperature) can be maintained at a desired temperature. In addition to the halogen heater, an IH (electromagnetic induction), a resistance heating element, a carbon heater, or the like may be used as a heating source for heating the fixing belt 21.

  The nip forming member 24 is a member that determines the shape of the fixing nip portion N in response to the pressure applied by the pressure roller 22. For this reason, it is arranged in parallel with the axial direction of the fixing belt 21 or the axial direction of the pressure roller 22 and is fixedly supported by a stay 25 used as a support member of the nip forming member 24.

  In this way, by supporting the nip forming member 24 with the stay 25, it is possible to suppress the nip forming member 24 from being bent by the pressure of the pressure roller 22, and to be uniform in parallel with the axial direction of the pressure roller 22. A nip width is obtained.

  The stay 25 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the bending prevention function of the nip forming member 24. However, the stay 25 may be made of resin. Is possible.

  In this embodiment, the fixing nip portion N has a flat shape, but may have a concave shape or other shapes. When the fixing nip portion N has a concave shape, the discharge direction of the leading edge of the paper P is closer to the pressure roller 22 and the separation is improved, so that the occurrence of jam is suppressed.

  The reflecting member 26 is disposed between the stay 25 and the halogen heater 23 using aluminum, stainless steel, or the like whose surface can be used as a reflecting surface.

  Here, since the reflecting member 26 is directly heated by the halogen heater 23, it is desirable that the reflecting member 26 be formed of a high melting point metal material or the like.

  Since the reflecting member 26 is disposed between the stay 25 and the halogen heater 23, the light emitted from the halogen heater 23 toward the stay 25 is reflected to the fixing belt 21. As a result, the amount of light applied to the fixing belt 21 can be increased, and the fixing belt 21 can be efficiently heated.

  Further, since it is possible to suppress the radiant heat from the halogen heater 23 from being transmitted to the stay 25 and the like, energy saving can be achieved.

  Further, without providing the reflecting member 26 as in the present embodiment, the surface on the halogen heater 23 side of the stay 25 may be subjected to a mirror surface treatment such as polishing or painting to form a reflecting surface.

  However, the shape and material of the stay 25 cannot be freely selected in order to ensure its strength. For this reason, if the reflecting member 26 is separately provided as in the present embodiment, the degree of freedom in selecting the shape and material is increased, and the reflecting member 26 and the stay 25 can be specialized in their functions.

  Further, since the reflecting member 26 is provided between the halogen heater 23 and the stay 25, the position of the reflecting member 26 with respect to the halogen heater 23 becomes close, so that the fixing belt 21 can be efficiently heated.

  The fixing device 20 according to the present embodiment has various contrivances in the configuration in order to further improve energy saving and first print time.

  Specifically, the fixing belt 21 can be directly heated by a halogen heater 23 at a place other than the fixing nip portion N (direct heating method).

  In the present embodiment, radiant heat from the halogen heater 23 is directly applied to the fixing belt 21 at a position where the halogen heater 23 and the fixing belt 21 face each other.

In order to reduce the heat capacity of the fixing belt 21, the fixing belt 21 is thin and has a small diameter.
In this embodiment, the diameter of the pressure roller 22 is set to 20 [mm] to 40 [mm], and the diameter of the fixing belt 21 and the diameter of the pressure roller 22 are equal. However, it is not limited to this configuration.

  For example, the fixing belt 21 may be formed so that the diameter thereof is smaller than the diameter of the pressure roller 22. In that case, since the curvature of the fixing belt 21 at the fixing nip N is smaller than the curvature of the pressure roller 22, the recording medium discharged from the fixing nip N is easily separated from the fixing belt 21.

  In this embodiment, the only members that contact the inner peripheral surface of the fixing belt 21 are the flange and the nip forming member 24. Besides these members, the members contact the inner peripheral surface of the fixing belt 21 to guide the rotation. There is no belt guide.

  Hereinafter, the basic operation of the fixing device 20 according to the present embodiment will be described with reference to FIG.

  When the power switch of the printer main body is turned on, power is supplied to the halogen heater 23, and the pressure roller 22 starts to rotate clockwise in FIG. As a result, the fixing belt 21 is driven to rotate counterclockwise in FIG. 4 by the frictional force with the pressure roller 22.

  Thereafter, the paper P carrying the unfixed toner image T in the image forming process described above is conveyed in the direction of the arrow F1 in FIG. 4 while being guided by a guide plate (not shown), It is fed into the fixing nip N of the pressure roller 22.

  Then, the toner image T is fixed on the surface of the paper P by heat from the fixing belt 21 heated by the halogen heater 23 and pressure applied between the fixing belt 21 and the pressure roller 22.

  The paper P on which the toner image T is fixed is carried out from the fixing nip portion N in the direction of arrow F2 in FIG. At this time, the paper P is separated from the fixing belt 21 by the leading edge of the paper P coming into contact with the leading edge of the separation member 28. Thereafter, the separated paper P is discharged out of the apparatus by the paper discharge roller pair 7 (see FIG. 2) and stocked on the paper discharge tray 17 (see FIG. 2) as described above.

FIG. 5 shows another configuration of the fixing device 20.
The fixing device 20 shown in FIG. 4 has one halogen heater 23 as a heat source, whereas the fixing device 20 shown in FIG. 5 differs in that there are three halogen heaters 23 as heat sources.

  As described above, since the number of the halogen heaters 23 is three, it is possible to heat the fixing belt 21 in a range corresponding to various widths of the paper by varying the heat generation region for each halogen heater 23. Therefore, excessive heat supply can be suppressed, leading to improved energy saving.

  The other configuration of the fixing device 20 shown in FIG. 5 is substantially the same as that of the fixing device 20 shown in FIG.

FIG. 6 shows still another configuration of the fixing device 20.
Also in the fixing device 20 illustrated in FIG. 6, the pressure roller 22 is brought into contact with the nip forming member 24 provided on the inner peripheral side of the fixing belt 21 via the fixing belt 21. A fixing nip portion N is formed between the two.

  The nip forming member 24 is supported on the inner peripheral side of the fixing belt 21 by a stay 25 which is a support member in which both end portions in the longitudinal direction are fixed to the side plate of the apparatus main body.

  The stay 25 has at least a parallel portion parallel to the conveyance direction of the paper P at the fixing nip portion N and a rising portion that rises vertically from the parallel portion in a direction away from the fixing nip portion N. The cross section in the direction perpendicular to the longitudinal direction is a closed shape. Thereby, the strength of the stay 25 is increased.

  In the fixing device shown in FIG. 6, two halogen heaters 23 are arranged on the downstream side in the rotation direction of the fixing belt 21 with respect to the rising portion. By arranging the halogen heater 23 in this way, the halogen heater 23 and the stay 25 can be accommodated in the fixing belt 21 in a compact manner.

  Further, by disposing the halogen heater 23 as a heating source at a position close to the fixing nip portion N, it is possible to further reduce the heat radiation from the fixing belt 21 from the heating position to the nip position, thereby saving energy. improves. At the same time, the accuracy of temperature control at the fixing nip N can be improved.

  Between the fixing belt 21 and the halogen heaters 23A and 23B, between the shield position that shields the radiant heat from the halogen heaters 23A and 23B to the non-sheet passing area of the fixing belt 21 and the retracted position that is retracted from the shield position. A movable shielding member 29 is disposed.

  Thereby, in particular, an excessive temperature rise in the non-sheet passing region of the fixing belt 21 during continuous sheet feeding can be suppressed, and deterioration or damage of the fixing belt 21 due to heat can be prevented.

  The moving operation of the shielding member 29 between the shielding position and the retracted position is performed by a driving force from a driving source included in a driving device (not shown) which is a driving unit controlled by a control unit (not shown). Is called.

  The shielding member 29 is configured by forming a metal plate having a thickness of 0.1 [mm] to 1.0 [mm] into an arcuate cross-sectional shape along the inner peripheral surface of the fixing belt 21. Further, the shielding member 29 is movable in the circumferential direction of the fixing belt 21.

  In the fixing device 20 shown in FIG. 6, in the circumferential region of the fixing belt 21, there is a direct heating region in which the halogen heater 23 heats directly facing the fixing belt 21. In addition, there is a non-direct heating region in which other members (stay 25, nip forming member 24, reflecting member 26, etc.) other than the shielding member 29 are interposed between the halogen heater 23 and the fixing belt 21.

  When it is necessary to perform heat shielding, the shielding member 29 is directly positioned at the shielding position on the heating region side. On the other hand, when heat shielding is not performed, the shielding member 29 can be moved from the shielding position to the retracted position on the non-direct heating region side, and the shielding member 29 can be retracted to the back side of the reflecting member 26 and the stay 25. ing.

  In the present embodiment, in order to change the heating area according to the paper size, the lengths and arrangement positions of the heat generating portions of the halogen heaters 23A and 23B are varied. In other words, the heat generating portion of the halogen heater 23A is disposed on the center side in the longitudinal direction, and the heat generating portion of the halogen heater 23B is disposed on both ends in the longitudinal direction.

  The heat generating portion of the halogen heater 23A corresponds to a range that is not less than the sheet passing width W1 of the small size sheet and less than the sheet passing width W2 of the medium size sheet. Further, the heat generating portion of the halogen heater 23A is disposed in a range that is equal to or larger than the sheet passing width W2 for medium size paper and includes the sheet passing width W3 for large size paper.

  FIG. 7 shows a plan view of the shielding member 29. In the shielding member 29 shown in FIG. 7, the shielding portions 48 on both end sides are each formed in a shape having three step portions. That is, each shielding part 48 is comprised by the 1st shielding area part 48a, the 2nd shielding area part 48b, and the 3rd shielding area part 48c. Further, the third shielding region portions 48 c of the shielding portions 48 are connected to each other through a connecting portion 49.

  The shielding member 29 shown in FIG. 7 corresponds to at least three types of paper: “postcard” as a small size paper, “B4 size” as a medium size paper, and “A3 size” as a large size paper. The example of the paper size is not limited to this.

  FIG. 8 is a perspective view of the fixing device 20 showing a state in which the shielding member 29 is moved to the shielding position for small size paper. FIG. 9 is a cross-sectional view of the fixing device 20 showing a state in which the shielding member 29 is moved to the shielding position for small size paper.

  The sheet passing width W1 of the small size sheet is in a range smaller than the length of the heat generating portion of the halogen heater 23A. Therefore, when small-size paper is passed, only the halogen heater 23A generates heat. However, in this case, since the range of the fixing belt 21 heated by the halogen heater 23A exceeds the sheet passing width W1 of the small size paper, the shielding member 29 is moved to the shielding position for the small size paper.

  That is, as shown in FIG. 8, the third shielding area 48c is moved to a position facing the heat generating part of the halogen heater 23A. As a result, the third shielding area 48c can cover the outer area from the vicinity of the end of the sheet passing width W1 of the small size sheet, so that the temperature rise of the fixing belt 21 can be suppressed in the non-sheet passing area.

  Next, when the medium-size paper is passed, both the halogen heater 23A and the halogen heater 23B generate heat. In this case, if the halogen heater 23A and the halogen heater 23B generate heat, the heated range of the fixing belt 21 exceeds the sheet passing width W2 of the medium size sheet.

  Therefore, when passing the medium size paper, the shielding member 29 is moved to the shielding position for the medium size paper. That is, the first shielding area 48a and the second shielding area 48b are moved to positions facing the heat generating parts of the halogen heaters 23A and 23B. As a result, the outer area from the vicinity of the end of the sheet passing width W2 of the medium-sized sheet can be covered by the first shielding area 48a and the second shielding area 48b. Temperature rise can be suppressed.

  FIG. 10 is a perspective view of the fixing device 20 showing a state in which the shielding member 29 is moved to the shielding position for large size paper. FIG. 11 is a cross-sectional view of the fixing device 20 showing a state in which the shielding member 29 is moved to the shielding position for large size paper.

  When passing a large-size sheet, both the halogen heater 23A and the halogen heater 23B generate heat. In this case, if the halogen heater 23A and the halogen heater 23B generate heat, the heated range of the fixing belt 21 exceeds the sheet passing width W3 of the large size paper.

  Therefore, when passing large-size paper, the shielding member 29 is moved to the shielding position for large-size paper. That is, as shown in FIG. 10, the second shielding region portion 48b and the third shielding region portion 48c are not exposed to the halogen heaters 23A and 23B side, and the first shielding region portion 48a is mainly used as the heat generating portion of the halogen heater 23B. The shielding member 29 is moved to the facing position.

  As a result, since the first shielding area 48a can cover the outer area from the vicinity of the end of the sheet passing width W3 of the large size sheet, the temperature rise of the fixing belt 21 can be suppressed in the non-sheet passing area.

  8, 9, 10, and 11, illustration of the pressure roller 22 and the like is omitted as appropriate.

  As described above, by providing the shielding member 29, even when a sheet having a width smaller than that of the halogen heaters 23A and 23B is continuously passed in the fixing belt width direction, the non-sheet passing region of the fixing belt 21 is overheated. It can be suppressed. Thus, it is not necessary to perform control such as reducing productivity in order to cancel the excessive temperature rise region. Accordingly, the number of halogen heaters 23 can be reduced from three to two in the fixing device 20 shown in FIG.

  Next, features of the fixing device 20 provided in the image forming apparatus 100 according to the present embodiment will be described.

  The change in the position of the fixing belt 21 and the installation position of the temperature detection sensor 12 will be described with reference to FIG. FIG. 1A is a schematic view of the fixing device 20 as viewed from above the device (in the direction of arrow A in FIG. 1C). FIG. 1B is a diagram showing the shape of the fixing belt 21 when the fixing device 20 is viewed from the pressure belt side from the fixing belt side (when viewed from the direction of arrow B in FIG. 1C). . FIG. 1C is a schematic diagram when the fixing device 20 is viewed from the fixing belt width direction.

  Reference numeral 8 in FIG. 1 denotes a flange that is a guide member that holds both ends of the fixing belt 21 in the width direction and guides rotation thereof. Reference numeral 12 in FIG. 1 denotes a contact type that detects the temperature of the fixing belt 21. It is a temperature detection sensor.

  Here, since the fixing belt 21 is held only at both ends in the width direction by the flange 8, the cross-sectional shape (orbital position) in the direction orthogonal to the width direction at both ends in the width direction of the fixing belt 21 is that of the flange 8. Depends on shape.

  On the other hand, the cross-sectional shape (orbital position) in the direction perpendicular to the width direction of the central portion in the width direction of the fixing belt 21 depends on the positions and shapes of the nip forming member 24, the pressure roller 22, the flange 8, and the like.

  For example, in order to suppress the generation of wrinkles, the pressure roller 22 often has a drum shape in which the central portion in the axial direction is recessed from both end portions in the axial direction, as shown in FIG.

  Further, the nip forming member 24 makes the fixing nip portion N uniform in the axial direction, so that the nip forming member 24 has a drum shape of the pressure roller 22 or a pressure applied from the pressure roller 22 via the fixing belt 21. The shape takes into account bending. For this reason, as shown in FIG. 1A, the fixing belt width direction center portion is often a convex shape protruding toward the pressure roller 22 side than the width direction end portion.

  In this case, the central portion in the width direction of the fixing belt 21 extends in a direction perpendicular to the nip surface of the fixing nip portion N as shown by reference numeral 21b in FIG. 1B and FIG. On the other hand, it becomes an elliptical shape contracted in the parallel direction.

  Since the durability of the fixing belt 21 is remarkably lowered due to an increase in distortion or repetition of uneven curvature, it is desirable that the fixing belt 21 has a substantially circular shape as indicated by reference numeral 21a in FIG.

  In order to improve durability, when the end portion in the width direction of the fixing belt 21 is held in a substantially perfect circle shape by the flange 8, the shape of the fixing belt 21 is a substantially perfect circle shape (reference numeral 21a) at the end portion in the fixing belt width direction. Gradually changes to an elliptical shape (reference numeral 21b) toward the center in the fixing belt width direction.

  Here, when the temperature of the fixing belt 21 is detected by the contact-type temperature detection sensor 12, the contact state of the temperature detection sensor 12 with respect to the fixing belt 21 greatly affects the detection accuracy.

  The fixing belt 21 provided in the fixing device 20 of the present embodiment has a different cross-sectional shape (orbit position) in a direction perpendicular to the width direction of the fixing belt 21 in the fixing belt width direction.

  For this reason, if the end temperature detection sensor 12A and the center temperature detection sensor 12B are installed at the same position in the direction perpendicular to the fixing belt width direction at each of the width direction end portion and the center portion of the fixing belt 21, the fixing belt is used in both. The contact state with 21 will be different. As a result, a temperature detection error occurs in the fixing belt width direction.

  Therefore, in the fixing device 20 of the present embodiment, the fixing belt surface and the temperature detection sensors 12A and 12B are in contact with each other in a desired contact state according to the shape of the fixing belt 21 at least when the fixing belt rotates. Temperature detection sensors 12A and 12B are provided.

  In other words, the temperature detection sensors 12A, 12A, 12A, 12B, 12C, 12C, 12C, and 12D are temperature detection sensors 12A, 12B, so that the contact state of the temperature detection sensors 12A, 12B with the fixing belt 21 differs in the fixing belt width direction. 12B is installed.

  For example, the temperature detection sensor 12 is provided on the downstream side of the fixing nip N in the sheet conveyance direction from the fixing belt width direction end toward the fixing belt width direction center. That is, as shown in FIG. 1C, the center temperature detection sensor 12B is provided at the downstream side in the sheet conveyance direction in the fixing nip portion N rather than the end temperature detection sensor 12A.

  Accordingly, the positions of the temperature detection sensors 12A and 12B are optimized at the end portion in the fixing belt width direction and the central portion in the fixing belt width direction at least according to the bending shape at the time of fixing belt rotation. That is, even if the bending shape (cross-sectional shape) of the fixing belt 21 is different between the fixing belt width direction end portion and the fixing belt width direction center portion, the temperature detection sensors 12A and 12B and the fixing belt 21 at each position in the fixing belt width direction The contact state can be made the same.

  Therefore, by arranging the temperature detection sensors 12A, 12B and the fixing belt 21 so that the contact state is the same at least when the fixing belt rotates, the occurrence of temperature detection errors in the fixing belt width direction is suppressed. be able to.

  In this way, by suppressing the temperature detection error in the fixing belt width direction, the fixing belt 21 can be heated at an appropriate temperature, and good image formation can be performed while suppressing poor fixing.

  Further, the end temperature detection sensor 12 </ b> A and the center temperature detection sensor 12 </ b> B are arranged on the upstream side in the sheet conveyance direction of the fixing nip portion N and at an acute angle position with respect to the nip surface of the fixing nip portion N.

  The fixing belt 21 has a positional fluctuation (shake), and the positional fluctuation (shake) becomes smaller as it approaches the fixing nip portion N. Each of the temperature detection sensors 12A and 12B determines the contact pressure with leaf spring-like detection parts (heat sensitive parts) 12a and 12b that protrude from the sensor body. In order to suppress the contact pressure deviation (improve the wear durability), it is desirable to arrange the detection units 12a and 12b so as to be in contact with the fixing belt 21 at a position where the position fluctuation (shake) is small.

  For this reason, in this embodiment, the fixing nip portion N is located closer to the fixing nip portion N than the intersection of the substantially circular shape (reference numeral 21a) and the elliptical shape (reference numeral 21b) in FIG. The temperature detection sensor 12 is provided in contact with the fixing belt 21 at a close position. Further, when the fixing belt 21 is brought into contact with the plate spring-like detection portions 12a and 12b of the temperature detection sensors 12A and 12B and the fixing belt 21, a virtual plane on the same plane as the nip surface of the fixing nip portion N is obtained. The detector is inclined at an acute angle. The “acute angle” angle range and the like are appropriately set according to the spring rate and the like.

  FIG. 12B is a schematic diagram when the installation positions of the end temperature detection sensor 12A and the center temperature detection sensor 12B are the same in the direction orthogonal to the fixing belt width direction. FIG. 12B is a schematic diagram in a case where the installation positions of the end temperature detection sensor 12A and the center temperature detection sensor 12B are different in the direction perpendicular to the nip surface of the fixing nip portion N. In addition, the code | symbol P in a figure is a position where the detection parts 12a and 12b of each temperature detection sensor 12A and 12B and the fixing belt 21 contact.

  As shown in FIG. 12A, when the installation positions of the end temperature detection sensor 12A and the center temperature detection sensor 12B are the same in the direction orthogonal to the fixing belt width direction, each temperature detection sensor 12 and the fixing belt 21 The contact state of is as follows. That is, the end portion in the width direction of the fixing belt 21 having the shape of the reference numeral 21a in the drawing and the detecting portion 12a of the end portion temperature detecting sensor 12A are in contact with each other at the optimum position P1. On the other hand, the central portion in the width direction of the fixing belt 21 having the shape of the reference numeral 21b in the drawing and the detection portion 12b of the central temperature detection sensor 12B are in contact with each other at a position P1 'that is not the optimum position P2.

  The areas of the detection units 12a and 12b of the temperature detection sensors 12A and 12B are determined, and it is necessary to install the temperature detection sensors 12A and 12B so that the contact pressure and the contact angle are the same. Further, the contact pressure and the contact angle are different between the position P1 and the position P1 ', leading to a temperature detection error.

  Therefore, the temperature detection sensor 12 is provided on the nip surface side of the fixing nip portion N as it goes from the fixing belt width direction end portion toward the fixing belt width direction center portion. That is, as shown in FIG. 12B, the center temperature detection sensor 12B is shifted from the end temperature detection sensor 12A by a distance L on the nip surface side.

  As a result, the center of the fixing belt 21 in the width direction at the optimum position P2 where the contact pressure and the contact angle between the end portion in the width direction of the fixing belt 21 and the detecting portion 12a of the end temperature detecting sensor 12A are the same at the position P1. And the detection part 12b of the center temperature detection sensor 12B come into contact with each other.

  Therefore, even if the cross-sectional shape of the fixing belt 21 is different between the end portion in the fixing belt width direction and the center portion, the contact state between the temperature detection sensors 12A and 12B and the fixing belt 21 at the respective positions in the fixing belt width direction is the same. be able to. Therefore, it is possible to suppress the occurrence of temperature detection errors due to the difference in the contact state between the temperature detection sensors 12A and 12B and the fixing belt 21 in the fixing belt width direction.

  Note that the center temperature detection sensor 12B is shifted in the sheet conveyance direction with respect to the end temperature detection sensor 12A as shown in FIG. 1C, and the nip surface side is shifted as shown in FIG. 12B. In this case, there is no particular difference in operation and effect, and it is sufficient to use them according to layout constraints.

  Referring to FIG. 13, the end sensor bracket 13a and the center sensor bracket 13b for holding the end temperature detection sensor 12A and the center temperature detection sensor 12B on the stay member 14 provided in the fixing device 20 are installed. explain.

  The stay member 14 that is long in the fixing belt width direction has an L-shaped end sensor bracket 13a and a center sensor bracket 13b on which the end temperature detection sensor 12A and the center temperature detection sensor 12B are installed. It is fixed.

  Further, the heights of the portions fixed by the end sensor bracket 13a and the center sensor bracket 13b of the stay member 14 in the direction perpendicular to the fixing belt width direction (thickness direction of the stay member 14) are varied in the fixing belt width direction. Yes.

  That is, as shown in FIG. 13, a throttle portion S having a height H is provided at a portion where the end sensor bracket 13 a of the stay member 14 is fixed. Then, by fixing the end sensor bracket 13 a to the throttle portion S, the positions of the end sensor bracket 13 a and the center sensor bracket 13 b are made different in the thickness direction of the stay member 14.

  As a result, the position of the central temperature detection sensor 12B installed in the central sensor bracket 13b is fixed by the height H of the throttle portion than the position of the end temperature detection sensor 12A installed in the end sensor bracket 13a. The nip portion N can be shifted to the nip surface side.

  Moreover, the shift amount (distance L) to the nip surface side of the center part temperature detection sensor 12B can be adjusted by changing the height H of the throttle part S provided in the stay member 14. As a result, the end sensor bracket 13a and the center sensor bracket 13b can be shared, and an increase in cost can be suppressed.

FIG. 14 is a schematic view showing another shape of the sensor bracket 13.
As shown in FIG. 13, when the sensor bracket 13 is installed in the diaphragm portion S of the stay member 14, the dimensional accuracy of the diaphragm portion S is difficult to achieve, so that the stacking error increases and the detection accuracy may be reduced. Further, in order to ensure dimensional accuracy, adding a processing step such as correction may increase the cost.

  Therefore, the end temperature detection sensor 12A and the center are mounted on one sensor bracket 13 so that the position of the center temperature detection sensor 12B can be shifted in the sheet conveyance direction or the nip surface side from the position of the end temperature detection sensor 12A. A temperature sensor 12B is installed.

  Thereby, a detection error and a cost increase can be suppressed without providing the diaphragm member S as shown in FIG.

  For example, as shown in FIG. 14A, the sensor bracket 13 is provided with a step in the sheet conveyance direction at the fixing nip N, and the end temperature is set at the installation position corresponding to the fixing belt width direction end. A detection sensor 12A is installed. Then, the central part temperature detection sensor 12B is installed at the installation position corresponding to the central part in the fixing belt width direction, which is the lower step.

  Accordingly, by fixing the sensor bracket 13 to the stay member 14, the center temperature detection sensor 12B can be shifted and positioned in the sheet conveyance direction with respect to the end temperature detection sensor 12A.

  Further, as shown in FIG. 14B, the center temperature detection sensor 12B is placed on the sensor mounting surface of the sensor bracket 13 with respect to the sensor bracket width direction (the same direction as the fixing belt width direction) rather than the end temperature detection sensor 12A. ) And shifted in the direction orthogonal to the distance L.

  Thus, by fixing the sensor bracket 13 to the stay member 14, the center temperature detection sensor 12B can be shifted to the nip surface side relative to the end temperature detection sensor 12A.

  By using the sensor bracket 13 as shown in FIGS. 14 (a) and 14 (b), the stop portion S as shown in FIG. 13 can be eliminated from the stay member 14, and the detection error can be suppressed while suppressing an increase in cost. Can be suppressed.

  The present invention has been described based on the preferred embodiments. However, the present invention is not limited to those described in the above embodiments, and various modifications can be made without departing from the scope of the present invention.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
In a fixing device such as the fixing device 20, a fixing belt such as a rotatable endless fixing belt 21, a contact member such as a pressure roller 22 that contacts an outer peripheral surface of the fixing belt, and an inner peripheral side of the fixing belt A nip forming member such as a nip forming member 24 that contacts the contact member via the fixing belt and forms a nip portion, and a heating means such as a halogen heater 23 that heats the fixing belt directly or indirectly. A fixing member that is provided so as to be in contact with inner peripheral surfaces at both ends in the width direction of the fixing belt, guides rotation of the fixing belt, and the like, and a temperature of the fixing belt in contact with the fixing belt; A plurality of temperature detection means such as temperature detection sensors 12A, 12B arranged in the fixing belt width direction, and the temperature detection means includes at least the temperature detection means In accordance with the deflection shape of the fixing belt at the time of wearing the belt rotates, it is disposed at a position in contact with the contact state of the same the surface of the fixing belt.
In (Aspect A), a plurality of temperature detection means are provided in accordance with the bending shape (cross-sectional shape) of the fixing belt at each position in the fixing belt width direction. As a result, even if the bending shape (cross-sectional shape) of the fixing belt differs at the fixing belt width direction end portion or the width direction center portion, the contact state between each temperature detecting means and the fixing belt surface at each position in the fixing belt width direction Can be the same. Therefore, it is possible to suppress the occurrence of temperature detection errors in the fixing belt width direction due to different contact states between the temperature detection means and the fixing belt surface.
(Aspect B)
In (Aspect A), the installation positions of the plurality of temperature detection units in a direction orthogonal to the fixing belt width direction are different. According to this, as described in the above embodiment, the position of each temperature detection means can be changed in accordance with the shape of the fixing belt, and the installation position of each temperature detection means can be optimized.
(Aspect C)
In (Aspect A) or (Aspect B), the temperature detecting means is provided on the nip surface side of the nip portion as it goes from the end portion in the fixing belt width direction toward the center portion in the fixing belt width direction. According to this, as described in the above embodiment, the installation position of each temperature detection unit can be optimized according to the cross-sectional shape of the fixing belt at each position in the fixing belt width direction.
(Aspect D)
In (Aspect A) or (Aspect B), the temperature detecting means is provided on the nip surface side from the end in the fixing belt width direction toward the center in the fixing belt width direction. According to this, as described in the above embodiment, the installation position of each temperature detection unit can be optimized according to the cross-sectional shape of the fixing belt at each position in the fixing belt width direction.
(Aspect E)
In (Aspect D), a plurality of holding members such as an end sensor bracket 13a and a center sensor bracket 13b that hold each temperature detection means, and a stay that is long in the fixing belt width direction to which the plurality of holding members are fixed. The fixing member such as the member 14 is provided, and the height of the portion of the fixing member to which each holding member is fixed is different in the direction perpendicular to the fixing belt width direction in the fixing belt width direction. According to this, as explained about the above-mentioned embodiment, the holding member which holds each temperature detection means can be made common, and an increase in cost can be suppressed.
(Aspect F)
In (Aspect A), (Aspect B), (Aspect C), or (Aspect D), a holding member such as a sensor bracket 13 that holds the temperature detection unit is provided, and the holding member is in the fixing belt width direction. A plurality of temperature detecting means installing portions corresponding to at least two portions of the end portion and the central portion in the fixing belt width direction are provided. According to this, as described in the above embodiment, temperature detection errors and cost increases can be suppressed.
(Aspect G)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E) or (Aspect F), the temperature detecting means is a holding part such as a sensor main body held by the holding member. And detection units such as leaf spring detection units 12a and 12b that protrude from the holding unit, and the temperature of the fixing belt is detected by bringing the detection unit into contact with the surface of the fixing belt. When the temperature detecting means having such a configuration is used, it is possible to suppress the temperature detection error more effectively.
(Aspect H)
An image carrier such as a photosensitive drum 120, a toner image forming unit such as a developing device 40 that forms a toner image on the image carrier, and a transfer belt that transfers the toner image from the image carrier onto a recording material. In an image forming apparatus including a transfer unit such as the unit 10 and a fixing unit such as a fixing device 20 for fixing the toner image transferred onto the recording material to the recording material, the fixing unit (Aspect A) The fixing device of (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F) or (Aspect G) is used. According to this, as described in the above embodiment, it is possible to suppress a temperature detection error in the fixing belt width direction and to perform a good image formation by suppressing a fixing defect.

DESCRIPTION OF SYMBOLS 3 Feed roller 4 Registration roller pair 5 Secondary transfer roller 6 Optical writing device 7 Paper discharge roller pair 8 Flange 9 Toner bottle 10 Transfer belt unit 11 Intermediate transfer belt 12 Temperature detection sensor 12A End temperature detection sensor 12a Detection section 12B Central temperature detection sensor 12b detection unit 13 sensor bracket 13a end sensor bracket 13b central sensor bracket 14 stay member 17 paper discharge tray 20 fixing device 21 fixing belt 22 pressure roller 22a cored bar 22b elastic layer 22c release layer 23 halogen Heater 23A Halogen heater 23B Halogen heater 24 Nip forming member 25 Stay 26 Reflecting member 27 Temperature sensor 28 Separating member 29 Shielding member 30 Charging device 40 Developing device 48 Shielding portion 48a First shielding region portion 48c Third shielding region portion 8b Second shielding area 49 Linking unit 50 Cleaning device 61 Paper feeding device 71 Transfer device 72 Drive roller 73 Driven roller 100 Image forming device 112 Primary transfer roller 113 Transfer belt cleaning device 120 Photosensitive drum 200 Metal thermal conductor 300 Heat source 400 Pressure roller

JP 2012-145703 A JP 2004-286922 A JP 2010-79309 A JP 2007-334205 A

Claims (8)

A rotatable endless fixing belt;
A contact member in contact with the outer peripheral surface of the fixing belt;
A nip forming member disposed on the inner peripheral side of the fixing belt and contacting the contact member via the fixing belt to form a nip portion;
Heating means for directly or indirectly heating the fixing belt;
A guide member provided so as to be able to come into contact with the inner peripheral surfaces of both ends in the width direction of the fixing belt, and for guiding the rotation of the fixing belt;
A plurality of temperature detecting means arranged in the width direction of the fixing belt for detecting the temperature of the fixing belt in contact with the fixing belt;
The fixing device according to claim 1, wherein the temperature detecting means is arranged at a position in contact with the surface of the fixing belt in the same contact state in accordance with at least a bending shape of the fixing belt when the fixing belt is rotated. The fixing device according to claim 1.
A fixing device characterized in that installation positions of the plurality of temperature detection units in a direction orthogonal to a fixing belt width direction are different. The image forming apparatus according to claim 1 or 2,
The fixing device is characterized in that the temperature detection unit is provided on the downstream side of the nip portion in the sheet conveyance direction from the fixing belt width direction end portion toward the fixing belt width direction central portion. The fixing device according to claim 1 or 2,
The fixing device, wherein the temperature detecting means is provided on the nip surface side of the nip portion from the end portion in the fixing belt width direction toward the center portion in the fixing belt width direction. The fixing device according to claim 4.
A plurality of holding members for holding each temperature detection means;
A fixing member elongated in the fixing belt width direction to which the plurality of holding members are fixed;
A fixing device characterized in that a height of a portion of the fixing member fixed by each holding member in a direction perpendicular to the fixing belt width direction is varied in the fixing belt width direction. The fixing device according to claim 1, 2, 3 or 4.
A holding member for holding the temperature detecting means;
The fixing device includes a plurality of temperature detection means installation portions corresponding to at least two locations of an end portion in the fixing belt width direction and a central portion in the fixing belt width direction. The fixing device according to claim 1, 2, 3, 4, 5 or 6.
The temperature detection means has a holding portion held by a holding member and a leaf spring-like detection portion protruding from the holding portion, and the detection portion is brought into contact with the surface of the fixing belt so that the fixing belt A fixing device that performs temperature detection. An image carrier;
Toner image forming means for forming a toner image on the image carrier;
Transfer means for transferring the toner image from the image carrier onto a recording material;
An image forming apparatus comprising: a fixing unit that fixes the toner image transferred onto the recording material to the recording material;
An image forming apparatus using the fixing device according to claim 1, as the fixing unit.

Images