JP2017161892A - Fixation device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device that deals with recording materials of a plurality of sizes, and suppresses a temperature unevenness in a longitudinal direction of a fixation belt.SOLUTION: A fixation device comprises: a rotatable endless fixation member; an opposite rotor that is provided outside the fixation member and oppose the fixation member; a plurality of heat sources that are provided inside the fixation member and have a thermal distribution different in a longitudinal direction; a nip formation member that is provided inside the fixation member and forms a fixation nip between the fixation member and the opposite rotor; a plurality of end part heat sources that are provided in the nip formation member and heat each of either end part in the longitudinal direction of the fixation member; and a heat transmission auxiliary member that is provided between the nip formation member and the fixation member and alleviates a temperature slope in the longitudinal direction of the fixation member. A surface opposing the heat transmission auxiliary member of the plurality of end part heat sources is configured to protrude further than a surface opposing the heat transmission auxiliary member of the nip formation member.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device and an image forming apparatus including the fixing device.

  In recent years, there has been a strong market demand for energy saving and high speed for image forming apparatuses such as copiers, printers, facsimiles, and multifunction machines having at least two of these functions.

  Among image forming apparatuses, the fixing apparatus has a large amount of power consumption and a large room for energy saving, and various proposals have been made. For example, a fixing device that has a configuration in which a thin endless fixing belt in a film shape with a low heat capacity is directly heated and can obtain good fixing properties even when mounted on a high-production image forming apparatus is known (for example, , See Patent Document 1). In the fixing device described in Patent Document 1, a pressure roller arranged on the outer peripheral side of an endless fixing belt and a nip forming member fixedly arranged inside the fixing belt (in the loop) are interposed via the fixing belt. The fixing nip is formed by pressure contact.

  Incidentally, recording materials of various sizes are used in the image forming apparatus. In order to handle recording materials of various sizes, when the length of the heat source (heater) of the fixing device is adjusted to the maximum size of the recording material, a fixing belt that is a non-sheet passing portion is used when fixing a small size recording material. There is a problem that the temperature of the end portion rises.

  To solve this problem, a plurality of halogen heaters having different light distributions in the width direction (longitudinal direction) of the fixing belt are provided inside the endless fixing belt, and at both ends in the longitudinal direction of the fixing belt. A configuration is disclosed in which an end heater is provided in contact with the inner or outer surface of the fixing belt at a position upstream of the nip in the rotation direction of the fixing belt (see, for example, Patent Document 2).

  However, since the fixing device disclosed in Patent Document 2 uses different heaters, the heat of the heater cannot be efficiently transmitted to the fixing belt, and there is a problem that temperature unevenness occurs in the longitudinal direction of the fixing belt.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that can cope with recording materials of a plurality of sizes and suppress temperature unevenness in the longitudinal direction of the fixing belt.

In order to solve the above-described problem, a fixing device according to a first aspect of the present invention includes:
A rotatable endless fixing member;
An opposing rotating body provided outside the fixing member and facing the fixing member;
A plurality of heat sources provided inside the fixing member and having different heat distributions in the longitudinal direction;
A nip forming member provided inside the fixing member and forming a fixing nip between the fixing member and the counter rotating body;
A plurality of end heat sources provided on the nip forming member and respectively heating both longitudinal ends of the fixing member;
A heat transfer auxiliary member that is provided between the nip forming member and the fixing member and loosens a temperature gradient in the longitudinal direction of the fixing member,
The surface of the plurality of end heat sources that faces the heat transfer assisting member protrudes from the surface of the nip forming member that faces the heat transfer assisting member.

  According to the present invention, it is possible to provide a fixing device that can cope with recording materials of a plurality of sizes and suppress temperature unevenness in the longitudinal direction of the fixing belt.

1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional configuration diagram illustrating an embodiment of a fixing device. It is a perspective view which shows the basic composition of a nip formation unit. It is a perspective view which shows the structure of a nip formation unit and a halogen heater. It is a schematic diagram which shows arrangement | positioning of the heat-emitting part of a halogen heater and an edge part heater. It is a schematic diagram which shows the positional relationship of each heat-emitting part of a halogen heater and an edge part heater. It is explanatory drawing explaining 1st Embodiment of a structure of a nip formation member, an edge part heater, and a heat transfer auxiliary member. It is explanatory drawing explaining 2nd Embodiment of a structure of a nip formation member, an edge part heater, and a heat transfer auxiliary member. It is explanatory drawing explaining 3rd Embodiment of a structure of a nip formation member, an edge part heater, and a heat transfer auxiliary member. It is explanatory drawing explaining 4th Embodiment of a structure of a nip formation member, an edge part heater, and a heat transfer auxiliary member. It is explanatory drawing explaining the modification of 4th Embodiment of a structure of a nip formation member, an edge part heater, and a heat transfer auxiliary member. It is explanatory drawing explaining the temperature detection part which detects the temperature of the location heated with the edge part heater of the fixing belt. It is a schematic diagram which shows the modification of the heat-generation pattern of a resistance heating element. FIG. 10 is an explanatory diagram illustrating a conventional fixing device.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 is a color laser printer, and four image forming units 4Y, 4C, 4M, and 4K are arranged in parallel in the center of the printer main body along the extending direction of the intermediate transfer belt 30. Each of the image forming units 4Y, 4C, 4M, and 4K stores developers of different colors of yellow (Y), cyan (C), magenta (M), and black (K) corresponding to the color separation components of the color image. Other than that, the configuration is the same.

  Specifically, each of the image forming units 4Y, 4C, 4M, and 4K constituting the image station includes a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoconductor 5, and A developing device 7 for supplying toner to the surface of the photoreceptor 5 and a cleaning device 8 for cleaning the surface of the photoreceptor 5 are provided. In FIG. 1, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4 </ b> K are assigned color codes, and the other image forming units 4 </ b> Y, 4 </ b> C, and 4 </ b> M The reference numerals are omitted.

  Below the image forming units 4Y, 4C, 4M, and 4K, an exposure device 9 that exposes the surface of the photoreceptor 5 is disposed. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 5 with laser light based on image data.

  A transfer device 3 is disposed above the image forming units 4Y, 4C, 4M, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as primary transfer means, and a secondary transfer roller 36 as secondary transfer means. Further, the transfer device 3 includes a secondary transfer backup roller 32, a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35.

  The intermediate transfer belt 30 is an endless belt and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, when the secondary transfer backup roller 32 is driven to rotate, the intermediate transfer belt 30 runs (rotates) in the direction indicated by the arrow in the figure.

  Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 with each photoconductor 5 to form a primary transfer nip. In addition, each primary transfer roller 31 is connected to a power source of a printer main body, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to each primary transfer roller 31. .

  The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Similarly to the primary transfer roller 31, the secondary transfer roller 36 is also connected to the power source of the printer main body, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 36. It has come to be.

  The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 30.

  A bottle container 2 is provided in the upper part of the printer main body, and four toner bottles 2Y, 2C, 2M, and 2K containing replenishing toner are detachably attached to the bottle container 2. As is well known, a replenishment path is provided between each toner bottle 2Y, 2C, 2M, 2K and each developing device 7, and each development from each toner bottle 2Y, 2C, 2M, 2K is performed via this replenishment path. The toner is supplied to the device 7.

  On the other hand, a lower portion of the printer main body is provided with a paper feed tray 10 that stores paper P as a recording material, a paper feed roller 11 that carries the paper P out of the paper feed tray 10, and the like. Here, in addition to plain paper, the recording material includes thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. Further, as is well known, a manual paper feed mechanism may be provided.

  In the printer main body, a transport path R is provided for discharging the paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus. In the transport path R, a pair of registration rollers (positioning rollers) 12 serving as transport means for transporting the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 36 in the paper transport direction. ing.

  Further, a fixing device 20 for fixing the unfixed image transferred onto the paper P is disposed downstream of the position of the secondary transfer roller 36 in the paper transport direction. Further, a pair of paper discharge rollers 13 for discharging the paper to the outside of the apparatus is provided downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R. In addition, a paper discharge tray 14 for stocking paper discharged outside the apparatus is provided on the upper surface of the printer main body.

  The basic operation of the printer according to this embodiment is as follows. When the image forming operation is started, the photoconductors 5 in the image forming units 4Y, 4C, 4M, and 4K are rotationally driven clockwise in the drawing, and the surface of each photoconductor 5 is set to a predetermined polarity by the charging device 6. Uniformly charged. The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9 to form an electrostatic latent image on the surface of each photoconductor 5. At this time, the image information to be exposed on each photoconductor 5 is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. In this way, toner is supplied to each electrostatic latent image formed on each photoconductor 5 by each developing device 7, whereby the electrostatic latent image is visualized (visualized) as a toner image. .

  When the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, and the intermediate transfer belt 30 is caused to run in the direction indicated by the arrow in the figure. 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 31. As a result, a transfer electric field is formed in the primary transfer nip between each primary transfer roller 31 and each photoconductor 5.

  Thereafter, when each color toner image on the photoconductor 5 reaches the primary transfer nip as each photoconductor 5 rotates, the toner image on each photoconductor 5 is formed by the transfer electric field formed in the primary transfer nip. The images are sequentially superimposed and transferred onto the intermediate transfer belt 30. Thus, a full color toner image is carried on the surface of the intermediate transfer belt 30. Further, the toner on each photoconductor 5 that could not be transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Thereafter, the surface of each photoconductor 5 is neutralized, and the surface potential is initialized.

  In the lower part of the image forming apparatus, the paper feed roller 11 starts to rotate, and the paper P is sent out from the paper feed tray 10 to the transport path R. The sheet P sent to the conveyance path R is timed by the registration roller 12 and is sent to the secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage having a polarity opposite to the toner charge polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip.

  Thereafter, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip as the intermediate transfer belt 30 rotates, the toner image on the intermediate transfer belt 30 is generated by the transfer electric field formed in the nip. Are collectively transferred onto the paper P. At this time, the residual toner on the intermediate transfer belt 30 that could not be transferred onto the paper P is removed by the belt cleaning device 35, and the removed toner is conveyed to a waste toner container placed in the printer body. To be recovered.

  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 13 and stocked on the paper discharge tray 14.

  The above description is an image forming operation when a full-color image is formed on a sheet. A single-color image can be formed using any one of the four image forming units 4Y, 4C, 4M, and 4K. Two or three image forming units can be used to form a two-color or three-color image.

  FIG. 2 is a schematic cross-sectional configuration diagram showing an embodiment of the fixing device 20. The fixing device 20 includes a fixing belt 21 that is an endless and cylindrical fixing member that is thin, flexible, and rotatable, and a pressure roller 22 that is an opposing rotating body that comes into contact with the fixing belt 21 from the outer peripheral side. And have. The fixing belt 21 is heated by the radiant heat of halogen heaters 23A and 23B (hereinafter also referred to as first halogen heater 23A and second halogen heater 23B) as a plurality of heat sources arranged inside (in the loop). The halogen heater represents a radiant heat source as a main heat source.

  Further, on the inner side (inside) of the fixing belt 21, a nip forming member 24 that forms a fixing nip N with the pressure roller 22 via the fixing belt 21, and a stay member 25 (supporting member) that supports the nip forming member 24. ) And are arranged. When the nip forming member 24 arranged in the width direction (longitudinal direction) of the fixing belt 21 is fixedly supported by the stay member 25, the nip forming member 24 is bent by the pressure from the pressure roller 22. Thus, a uniform nip width can be obtained in the axial direction (longitudinal direction) of the pressure roller 22. The nip forming member 24 is a heat-resistant member having high mechanical strength and a heat-resistant temperature of 200 ° C. or more, particularly heat-resistant resins such as polyimide (PI) resin, polyether ether ketone (PEEK) resin, and reinforced them with glass fiber. Is made up of. This prevents deformation of the nip forming member 24 due to heat in the toner fixing temperature range, ensures a stable fixing nip state, and stabilizes the output image quality. The stay member 25 and the halogen heaters 23A and 23B are fixedly held at both ends in the longitudinal direction by a side plate of the fixing device 20 or a separately provided holder. End heaters 26 as end heat sources different from the main heat source (fixing heat source) are integrally attached to both ends in the longitudinal direction of the nip forming member 24. As the end heater, a contact heat transfer type heat source that is a resistance heating element such as a ceramic saver is generally used.

  A heat transfer auxiliary member 27, also referred to as a heat equalizing member that loosens the temperature gradient in the longitudinal direction of the fixing belt, covers each surface of the nip forming member 24 and the end heater 26 that faces the inner peripheral surface of the fixing belt 21. Is arranged. The heat transfer auxiliary member 27 is made of a material having high thermal conductivity that enables heat transfer in a short time, such as copper, aluminum, silver, or the like. This prevents heat from staying in the end region of the fixing belt 21 when small-size paper is passed or when the end heater 26 is turned on, and actively moves heat in the longitudinal direction of the heat transfer auxiliary member 27. Thus, the temperature non-uniformity in the longitudinal direction of the fixing belt 21 is eliminated.

  In the depiction in FIG. 2, the surface of the heat transfer assisting member 27 that faces the inner peripheral surface of the fixing belt 21 is a surface that directly contacts the fixing belt 21 and is a nip forming surface that is formed in a flat shape. However, it may be a concave shape or other shapes. If the nip forming surface has a concave shape, the discharge direction at the front end of the paper is closer to the pressure roller, the separation is improved, and jamming is suppressed.

  As is well known, a temperature sensor 29 for detecting the belt temperature is provided at an appropriate position on the outer peripheral side of the fixing belt 21, for example, upstream of the fixing nip in the belt rotation direction, and downstream of the fixing device 20 in the sheet conveyance direction. On the side, a separating member 41 for separating the paper P from the fixing belt 21 is disposed. Further, releasable pressure means for pressing the pressure roller 22 to the fixing belt 21 is also provided.

  In order to achieve a low heat capacity, the endless fixing belt 21 which is thin and small in diameter like a film is composed of a base material on the inner peripheral side made of a metal material such as nickel or SUS, or a resin material such as polyimide, and a PFA. It is constituted by a release layer on the outer peripheral side formed of (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene). 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. When the thickness of the elastic layer is about 100 μm, when the unfixed toner is crushed and fixed, minute irregularities on the belt surface can be absorbed by the elastic deformation of the elastic layer, and uneven gloss can be avoided. From the viewpoint of reducing the heat capacity, the fixing belt 21 is set to a thickness of 1 mm or less and a diameter of 20 to 40 mm as a whole. The thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 21 are set in a range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm. Further, in order to reduce the heat capacity, the thickness of the entire fixing belt 21 is preferably 0.2 mm or less, and more preferably 0.16 mm or less, and the diameter is It is desirable to be 30 mm or less.

  The stay member 25 having a T-shaped cross section has an upright portion 25a standing upright on the side opposite to the fixing nip N side, and is arranged so that halogen heaters 23A and 23B as main heat sources are separated by the upright portion 25a. . One of the halogen heaters 23A and 23B has a heat generating portion at the center in the longitudinal direction corresponding to the small size paper, and the other has a heat generating portion at both longitudinal ends corresponding to the large size paper. The halogen heaters 23 </ b> A and 23 </ b> B are configured to generate heat by being output controlled by a power supply unit provided in the printer main body. The output control is performed on the belt surface by a temperature sensor 29 provided on the outer periphery of the fixing belt 21. This is performed based on the temperature detection result. By such heater output control, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature.

  Reflecting members 28A and 28B are disposed between the stay member 25 and the halogen heaters 23A and 23B. As a result, the heating efficiency of the halogen heaters 23A and 23B with respect to the fixing belt 21 is increased, and wasteful energy consumption due to the stay member 25 being heated by the radiant heat from the halogen heaters 23A and 23B can be suppressed. The same effect can be obtained by performing heat insulation or mirror treatment on the surface of the stay member 25 instead of providing the reflecting members 28A and 28B.

  The pressure roller 22 includes a cored bar, an elastic layer made of foamable silicone rubber or fluororubber provided on the surface of the cored bar, and a release layer made of PFA, PTFE or the like provided on the surface of the elastic layer. It is constituted by. At a location where the pressure roller 22 is pressed against the fixing belt 21 by a pressing means such as a spring and is pressed against the fixing belt 21, the elastic layer of the pressure roller 22 is crushed to form a fixing nip N having a predetermined width. The The pressure roller 22 is rotationally driven by a driving source such as a motor provided in the printer main body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 through the fixing nip N, and the fixing belt 21 is driven to rotate. The fixing belt 21 is. The roller is sandwiched and rotated by the fixing nip N, and travels by being guided by side plate flanges disposed at both ends other than the fixing nip N.

  In the present embodiment, the pressure roller 22 is a solid roller, but may be a hollow roller. In that case, a heat source such as a halogen heater may be disposed inside the pressure roller 22. The elastic layer may be solid rubber, but if there is no heat source inside the pressure roller, 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.

  FIG. 3 is a perspective view showing a basic configuration of the nip forming unit. As shown in FIG. 3, the nip forming unit includes a nip forming member 24, a stay member 25, a heat transfer auxiliary member 27, and end heaters 26a and 26b. In the nip forming unit, the surface of the nip forming member 24 opposite to the fixing nip N side is integrated with the plane of the stay member 25 on the fixing nip N side. At this time, uneven shapes such as bosses and pins may be formed on the respective surfaces, and these may be fitted in a shape-constrained manner. The heat transfer assisting member 27 is fitted and integrated so as to cover the surface of the substantially rectangular parallelepiped nip forming member 24 that faces the inner peripheral surface of the fixing belt 21. The integral structure of the heat transfer assisting member 27 and the nip forming member 24 may be provided by engaging with a nail or the like, but may be adhesive. Concave portions 24a and 24b as stepped portions are formed at both ends of the nip forming member 24 in the longitudinal direction, and end heaters 26a and 26b are accommodated and fixed at these portions. Note that the end heaters 26a and 26b are not limited to a mode in which the end heaters 26a and 26b are provided in the concave portion, and may be provided in a flat portion or a convex portion. The positional relationship between the end heaters 26a and 26b and the halogen heaters 23A and 23B will be described later.

  The surface of the heat transfer assisting member 27 that faces the inner peripheral surface of the fixing belt 21 is configured as a belt sliding contact surface 27a. However, in terms of mechanical strength, the nip forming surface is substantially the nip forming surface. This is a nip forming surface 24 c facing the pressure roller 22.

  As described above, in the present embodiment, the end heaters 26 a and 26 b are integrally provided on the nip forming member 24 necessary for forming the fixing nip, so that the end heaters 26 a and 26 b are provided on the fixing belt 21. It can be placed inside with space saving. Further, the heating portion of the fixing belt 21 by the end heaters 26a and 26b is in the nip region. Therefore, there is no problem of remelting of unfixed residual toner (degradation of quality) due to heating at a site different from the fixing nip N as in Patent Document 2.

By the way, in the conventional fixing device, as shown in FIG. 14, a halogen heater 23A for heating the longitudinal central portion of the fixing belt 21 and a halogen heater 23B for heating both longitudinal ends of the fixing belt 21 are arranged in parallel. Has been placed. Therefore, the radiant heat of one halogen heater heats the other halogen heater. Further, since the two halogen heaters 23A and 23B are surrounded by the reflection member 38, radiation due to reflection by the reflection member 38 is attenuated. Furthermore, as indicated by the bidirectional arrows, the angle at which the radiation from the halogen heaters 23A and 23B directly hits the fixing belt 21 is narrowed. Therefore, the problem that heating efficiency falls arises.
The fixing device of this embodiment solves such a problem.

  FIG. 4 is a perspective view showing configurations of the nip forming unit and the halogen heater. As shown in FIG. 4, the stay member 25 includes a first member 25 </ b> A and a second member 25 </ b> B having a substantially L-shaped section, and has a substantially T-shaped section. Therefore, the rigidity is high and the nip forming member 24 can be prevented from being bent by the stress from the pressure roller 22. The stay members 25 (the first member 25 </ b> A and the second member 25 </ b> B) extend linearly in the longitudinal direction of the nip forming member 24 and are fixed to the nip forming member 24. Therefore, a good nip forming surface can be maintained over the entire longitudinal direction of the fixing nip N.

  A first halogen heater 23 </ b> A and a second halogen heater 23 </ b> B are disposed on both sides of the standing portion 25 a in the short direction. That is, the heat generating portions of the first and second halogen heaters 23A and 23B have different distributions in the longitudinal direction (shaded portions in the drawing), and are separated from each other by the upright portions 25a that are support members. Therefore, since the glass tubes are not heated when the heater is turned on, the heating efficiency is not lowered. Further, since the first and second halogen heaters 23A and 23B are not surrounded by the stay member 25 (the center of each halogen heater 23 is outside the space surrounded by the stay member 25), the irradiation angles α and β (see FIG. 2) becomes obtuse and heating efficiency can be improved.

  The cross-sectional shape of the stay member 25 is not limited to a substantially T shape. The first and second halogen heaters 23A and 23B may be arranged so as to partition each other with the upright portion 25a interposed therebetween, and the first member 25A and the second member 25B extend in the longitudinal direction of the halogen heater in a curved manner. May be. Further, the first member 25A and the second member 25B may be raised in an oblique direction with respect to the nip forming surface of the nip forming member 24.

  Next, the arrangement of heat sources that can be used for recording materials of special sizes such as A3 Novi will be described. FIG. 5 is a schematic diagram showing the arrangement of the heating portions of the halogen heater and the end heater. As shown in FIG. 5, a first halogen heater 23A having a dense light distribution at the center in the longitudinal direction and a second halogen heater 23B having a dense light distribution at both ends in the longitudinal direction are arranged. Yes. That is, the first halogen heater 23 </ b> A heats the central range of the fixing belt 21, and the second halogen heater 23 </ b> B heats the side range of the fixing belt 21.

  The heat generating part 40A of the first halogen heater 23A corresponds to a recording material of a small size such as A4 vertical size, for example, and the heat generating part 40B of the second halogen heater 23B has an A3 vertical size that cannot be covered by the first halogen heater 23A. Covers the side area of the largest standard size recording material that can be used. That is, the heat generation range W1 composed of the heat generating portions 40A and 40B of both halogen heaters corresponds to the maximum standard size paper width and does not cover the nobi size paper width larger than the maximum standard size.

  On the other hand, the end heaters 26a and 26b have heating portions 42a and 42b that are located at positions corresponding to both ends in the longitudinal direction of the second halogen heater 23B and heat both ends of the nobi size paper width larger than the maximum regular size. Here, for convenience of explanation, the longitudinal heat generating regions 42a and 42b in the longitudinal direction of the fixing belt 21 are used as the heat generating portions of the end heaters 26a and 26b, but actually the longitudinal heat generating regions 42a and 42b are used. And the heat generating regions 43a and 43b in the width direction of the fixing belt 21 (regions where a resistance heating element 51 pattern (heat generating pattern 37) described later is formed) are generated by the end heaters 26a and 26b. Part. Further, part of the heat generating portions 42a and 42b of the end heaters 26a and 26b overlaps the heat generating portion 40B of the halogen heater 23B. As a result, the fixing device 20 can cope with both ends of the nobi size paper width larger than the maximum standard size. That is, the heat generation range W2 composed of the heat generating portions 40A, 40B of both the halogen heaters 23A, 23B and the heat generating portions 42a, 42b of the both end heaters 26a, 26b corresponds to a nobi size larger than the maximum standard size.

  Here, the amount of heat (heating output) actually output from the halogen heater and the end heater will be described. FIG. 6 is a schematic diagram showing the positional relationship between the heat generating portions of the second halogen heater 23B and the end heater 26b and the heating output of each heater. The upper part of FIG. 6 shows the state of the right end of the heat generating part of the second halogen heater 23B, and the lower part of FIG. 6 shows the state of the left side of the heat generating part of the end heater 26b.

  Generally, in the halogen heater, the heating output is reduced at the longitudinal end portion of the heat generating portion (portion where the filament is spirally wound). This also changes depending on the winding density of the filament, and is more likely to decrease if the winding density is sparse. As shown in the upper part of FIG. 6, the heat generating part 40B of the second halogen heater 23B ranges from a part that outputs a predetermined heating output of 100 (%) to a part where the heat output is reduced and the heating output becomes 50%. For example, it can be defined.

  Further, as shown in the lower part of FIG. 6, the end heater 26 b also has a reduced heating output at the end in the longitudinal direction of the heat generating part 42 b. In other words, 100% of the predetermined heating output is not output at the end, and the heating output is sag.

  For this reason, when a drop in heating output occurs at the ends of the second halogen heater 23B and the end heater 26b, good fixing is performed particularly at the end of a recording material having a larger size than the maximum standard size. There is no fear.

  Therefore, in the present embodiment, as shown in FIG. 6, the boundary Bh at which the heating output at the heat generating portion 40B of the second halogen heater 23B starts to decrease and the boundary at which the heating output at the heat generating portion 42b of the end heater 26b starts to decrease. Match Bc. In an actual apparatus, the second halogen heater 23B and the end heater 26b are spaced apart from each other in the space, so that the boundaries Bh and Bc coincide with each other in the longitudinal direction in the projected state. The same applies to the other end heater 26a.

  Thereby, in the area | region where the halogen heater 23B and the both-ends heaters 26a and 26b overlap, the heating output does not decrease and 100% of the predetermined heating output can be maintained. Therefore, it is possible to guarantee good fixing particularly at both ends of a recording material having a nobi size larger than the maximum standard size.

  In the present embodiment, the boundary Bh of the second halogen heater 23B matches the boundary Bc of the end heater 26b, but the present invention is not limited to this mode. Since the nip forming unit has the heat transfer assisting member 27 having a good thermal conductivity, it is possible to level out a drop in heating output to some extent. Therefore, a predetermined allowable range may be provided in the arrangement of the boundary where the heating output of the both end heaters 26a and 26b starts to decrease.

  By the way, if the heat transfer assisting member 27 made of a metal material is directly rubbed against the inner peripheral surface of the fixing belt 21, the frictional force between the heat transfer assisting member 27 and the fixing belt 21 is increased, the unit torque is increased, and fixing is performed. There is a problem that causes poor running of the belt.

  In this embodiment, a fluorine-based paint or coating such as PFA or PTFE is applied to the belt sliding contact surface 27a of the heat transfer assisting member 27 facing the inner peripheral surface of the fixing belt 21. Thereby, it is possible to suppress the frictional force between the heat transfer assisting member 27 and the fixing belt 21 and to maintain good slidability.

  Further, by applying a lubricant such as fluorine grease or silicone oil between the heat transfer assisting member 27 and the fixing belt 21, the sliding torque can be reduced over a long period of time.

  By the way, the surface of the end heaters 26a and 26b facing the inner peripheral surface of the fixing belt 21 and the nip forming surface 24c of the nip forming member 24 facing the inner peripheral surface of the fixing belt 21 have the same height. Even if it is designed to be (level), there is a risk that the target shape will not be achieved due to variations in parts. When the nip forming surface 24c facing the inner peripheral surface of the fixing belt 21 of the nip forming member 24 protrudes from the surface facing the inner peripheral surface of the fixing belt 21 of the end heater 26b, the end heaters 26a and 26b are moved. The heat transfer assisting member 27 is not contacted. Therefore, the heat from the end heaters 26 a and 26 b is not transmitted to the fixing belt 21 via the heat transfer auxiliary member 27, and there is a problem that temperature unevenness occurs in the longitudinal direction of the fixing belt 21. The present invention solves such a problem.

  Next, the configuration of the nip forming member, the end heater, and the heat transfer auxiliary member will be described.

[First Embodiment]
FIGS. 7A and 7B are explanatory views for explaining the first embodiment of the configuration of the nip forming member, the end heater, and the heat transfer auxiliary member, where FIG. 7A is a sectional view, FIG. 7B is a front view, and FIG. Is the same side view. Here, (a) is the figure which looked at the cross section cut | disconnected on the AA line of (b) from the paper conveyance direction. For convenience of explanation, only one end (end heater 26b) is shown in FIG. 7, but the end heater 26a has the same configuration.

  As shown in FIG. 7A, the end heater 26b supplies power to the base 50, the resistance heating element 51 formed on the base 50, for example, in a substantially U shape, and the resistance heating element 51. A resistance heating member having a plurality of electrodes 52 as electrode parts to be supplied. For example, as the end heater, a ceramic heater in which a resistance heating element (heating element) is disposed on a base material such as ceramic is used.

  As shown in FIG. 7B, the electrode 52 is disposed on the outside in the longitudinal direction of the longitudinal heat generation region 42 b of the end heater 26 b and is connected to both ends of the resistance heating element 51. When power is supplied to the electrode 52, the resistance heating element 51 generates heat, and the longitudinal heat generation region 42b in which the resistance heating element 51 is disposed becomes high temperature. By disposing the electrode 52 on the outer side in the longitudinal direction of the longitudinal heat generation region 42b of the end heater 26b, it is possible to prevent the electrode 52 from being overheated. As described above, the regions defined by the longitudinal heat generating regions 42a and 42b in the longitudinal direction of the fixing belt 21 and the width heat generating regions 43a and 43b in the width direction of the fixing belt 21 are the end heaters 26a, It becomes a heat generating part of 26b.

  The width direction heat generation region 43 b is smaller than the width of the heat transfer assisting member 27. As a method of connecting electrodes for supplying power to the resistance heating element 51, brazing and soldering are generally used. Since these bonding methods have low heat resistance itself, high-temperature solder or silver may be used.

  The heat transfer assisting member 27 is in contact with the base material 50 of the end heater 26b in the contact range 55, and the heat generating portion of the end heater 26b (region divided by the longitudinal heat generating region 42b and the width heat generating region 43b). It is provided to cover. In FIG. 7C, the heat transfer auxiliary member 27 is conceptually drawn, and the heat transfer auxiliary member 27 protrudes in the direction of the pressure roller 22 on the upstream side in the belt rotation direction near the nip outlet portion. It is good also as the shape made. Thereby, the releasability of the paper P at the nip outlet is improved.

  Although shown in a simplified manner in FIG. 7, the end heater 26 b is provided in a recess 24 b (see FIG. 3) formed at the end of the nip forming member 24 in the longitudinal direction of the nip forming member 24. The surface of the end heater 26 b that faces the inner peripheral surface of the fixing belt 21 is provided so as to protrude from the nip forming surface 24 c that faces the inner peripheral surface of the fixing belt 21 of the nip forming member 24. As a result, the end heaters 26 a and 26 b are reliably in contact with the heat transfer auxiliary member 27 in the contact range 55. As a result, the heat from the end heaters 26a and 26b is efficiently transmitted to the fixing belt 21 via the heat transfer assisting member 27, and the occurrence of temperature unevenness in the longitudinal direction of the fixing belt 21 is prevented.

[Second Embodiment]
FIGS. 8A and 8B are explanatory views for explaining a second embodiment of the configuration of the nip forming member, the end heater, and the heat transfer auxiliary member, where FIG. 8A is the same sectional view, FIG. 8B is the front view, and FIG. Is the same side view. Here, (a) is the figure which looked at the cross section cut | disconnected on the AA line of (b) from the paper conveyance direction. For convenience of explanation, only one end (end heater 26b) is shown in FIG. 8, but the end heater 26a has the same configuration.

  As shown in FIGS. 8A and 8B, the end heater 26b is generally a flat plate-like member. However, as shown in FIG. 8C, the cross-sectional shape of the heat transfer assisting member 27 is used. Are often formed with complex curves. When the flat surface is narrow on the side of the heat transfer auxiliary member 27 facing the end heater 26b, the portion where the end heater 26b and the heat transfer auxiliary member 27 are in contact with each other decreases.

  Therefore, in the present embodiment, as shown in FIGS. 8A and 8C, an intermediate member 53 is provided between the heat transfer auxiliary member 27 and the end heater 26b. The shape of the intermediate member 53 facing the heat transfer assisting member 27 is a shape corresponding to (combining with) the heat transfer assisting member 27, and the shape of the intermediate member 53 facing the end heater 26b is the end heater 26b. And corresponding (combined) shapes. It is desirable that the intermediate member 53 is provided corresponding to the size of the heat generating portion of the end heater 26b (region partitioned by the longitudinal heat generating region 42b and the width heat generating region 43b).

  The intermediate member 53 is made of, for example, copper, aluminum, or an alloy thereof, and it is desirable that the thermal conductivity is the same as or larger than that of the heat transfer auxiliary member 27. If the thermal conductivity of the intermediate member 53 is low, the heat transfer from the end heater 26b to the heat transfer auxiliary member 27 becomes worse (heat loss increases). However, by increasing the thermal conductivity of the intermediate member 53, the thermal efficiency decreases. Can be prevented.

  Further, by disposing an intermediate member 53 in contact with each other between the heat transfer assisting member 27 and the end heater 26b, heat transmitted from the end heater 26b to the electrode 52 via the fixing belt 21 is reduced. An excessive temperature rise of the electrode 52 due to heat can be prevented. The electrode 52 of the end heater 26 b having low heat resistance can be moved away from the fixing belt 21.

  Although shown in a simplified manner in FIG. 8, the end heater 26 b is provided in a recess 24 b (see FIG. 3) formed at the end of the nip forming member 24 in the longitudinal direction of the nip forming member 24. The surface of the intermediate member 53 that faces the inner peripheral surface of the fixing belt 21 is provided so as to protrude from the nip forming surface 24 c that faces the inner peripheral surface of the fixing belt 21 of the nip forming member 24. As a result, the end heaters 26 a and 26 b are reliably in contact with the heat transfer assisting member 27 through the intermediate member 53 in the contact range 55. As a result, the heat from the end heaters 26a and 26b is efficiently transmitted to the fixing belt 21 through the intermediate member 53 and the heat transfer assisting member 27, and the occurrence of temperature unevenness in the longitudinal direction of the fixing belt 21 is prevented.

[Third Embodiment]
FIG. 9 is an explanatory view illustrating a third embodiment of the configuration of the nip forming member, the end heater, and the heat transfer auxiliary member.

  This embodiment is different from the first embodiment in that the shape of the nip forming member is different.

  As shown in FIG. 9, the nip forming member 24 of the present embodiment is provided with a predetermined distance from the heat transfer assisting member 27. The shape of the nip forming surface 24c of the nip forming member 24 facing the heat transfer assisting member 27 is desirably a shape corresponding to the shape of the surface of the heat transfer assisting member 27 facing the nip forming member 24. The shape of the surface of the heat transfer assisting member 27 facing the nip forming member 24 may be a shape corresponding to the shape of the nip forming surface 24c of the nip forming member 24 facing the heat transfer assisting member 27.

  This prevents the heat transferred from the end heaters 26 a and 26 b to the heat transfer auxiliary member 27 from moving to the nip forming member 24. As a result, the heat from the end heaters 26a and 26b is efficiently transmitted to the fixing belt 21 via the heat transfer assisting member 27, and the occurrence of temperature unevenness in the longitudinal direction of the fixing belt 21 is prevented.

[Fourth Embodiment]
FIG. 10 is an explanatory diagram for explaining a fourth embodiment of the configuration of the nip forming member, the end heater, and the heat transfer assisting member.

  This embodiment is different from the first embodiment in that the shape of the nip forming member is different.

  As shown in FIG. 10, the nip forming surface 24c facing the heat transfer assisting member 27 of the nip forming member 24 of the present embodiment is shaped so that the central portion in the longitudinal direction protrudes from both ends in the longitudinal direction. In addition, it is good also considering the surface which opposes the nip formation member 24 of the heat transfer auxiliary member 27 as the shape where the longitudinal direction center part protruded from the longitudinal direction both ends. The nip forming member 24 is provided with a predetermined distance from the heat transfer assisting member 27.

  Thereby, when the nip forming member 24 is bent due to the pressure from the pressure roller 22, it is possible to prevent a decrease in the surface pressure at the central portion in the longitudinal direction of the fixing nip N.

  As shown in FIG. 11, the shape of the surface of the heat transfer assisting member 27 facing the nip forming member 24 corresponds to the shape of the nip forming surface 24c of the nip forming member 24 facing the heat transfer assisting member 27. It is good.

  This prevents the heat transferred from the end heaters 26 a and 26 b to the heat transfer auxiliary member 27 from moving to the nip forming member 24. As a result, the heat from the end heaters 26a and 26b is efficiently transmitted to the fixing belt 21 via the heat transfer assisting member 27, and the occurrence of temperature unevenness in the longitudinal direction of the fixing belt 21 is prevented.

  Next, a temperature detection unit different from the temperature sensor 29 shown in FIG. 2 that detects the temperature of the portion heated by the end heater 26 of the fixing belt 21 will be described. Using a contact-type sensor (for example, a thermistor) for detecting the temperature of the fixing belt 21 has the advantage of being inexpensive and highly accurate. However, there is a possibility that a fine sliding contact mark is generated at the contact position, or a minute gloss unevenness is generated in the image at the corresponding position. For this reason, especially in color image output machines, it is the mainstream not to use a contact type sensor within a standard size paper width.

  By the way, in the Nobi size recording material, the Novi part is the ear part when forming an image up to the edge of the maximum standard size paper edge, a line image called a register mark used for printing alignment, or a small area for color confirmation The solid patch is used as the part to be imaged. And it is often cut finally. Therefore, even if a contact mark is generated by the contact-type temperature detection unit, it can be said that minute gloss unevenness does not appear as an abnormal image.

  Therefore, in the present embodiment, as shown in FIG. 12, temperature detectors 45a and 45b (45a is provided at the opposite end portion) that detects the temperature of the portion heated by the end heaters 26a and 26b of the fixing belt 21. Therefore, in the longitudinal direction of the fixing belt 21, the paper is provided outside the maximum standard size paper width and inside the nobi size paper width larger than the maximum standard size. Thereby, the temperature can be detected with high accuracy at low cost without revealing an abnormal image such as minute uneven gloss.

  In the above-described embodiment, the resistance heating element pattern (heat generation pattern) formed in a U shape as viewed from the front is illustrated, but the present invention is not limited to this mode. For example, as shown in FIG. 13, the resistance heating element 51 may be formed by reciprocating a plurality of times on the surface of the substrate 50, and the length of the resistance heating element 51 may be made longer. Thereby, the heat output of the end heater 26 can be increased.

  The present invention has been described based on the embodiments. The present invention is not limited to the embodiments, and can be appropriately changed within the scope of the present invention. The image forming apparatus provided with the fixing device of the present invention is not limited to a copying machine or a printer, but may be a facsimile machine or a multifunction machine having a plurality of functions.

20 Fixing device 21 Fixing belt (fixing member)
22 Pressure roller (opposite rotating body)
23A, 23B Halogen heater (heat source)
24 Nip forming member 26a, 26b End heater (end heat source)
27 Heat transfer auxiliary member N Fixing nip

JP 2010-32631 A JP 2014-178370 A

Claims (6)

A rotatable endless fixing member;
An opposing rotating body provided outside the fixing member and facing the fixing member;
A plurality of heat sources provided inside the fixing member and having different heat distributions in the longitudinal direction;
A nip forming member provided inside the fixing member and forming a fixing nip between the fixing member and the counter rotating body;
A plurality of end heat sources provided on the nip forming member and respectively heating both longitudinal ends of the fixing member;
A heat transfer auxiliary member that is provided between the nip forming member and the fixing member and loosens a temperature gradient in the longitudinal direction of the fixing member,
The fixing device according to claim 1, wherein surfaces of the plurality of end heat sources facing the heat transfer auxiliary member protrude from a surface of the nip forming member facing the heat transfer auxiliary member.   The surface of the nip forming member facing the heat transfer assisting member is spaced from the surface of the heat transfer assisting member facing the nip forming member. Fixing device.   The shape of the surface of the nip forming member facing the heat transfer assisting member corresponds to the shape of the surface of the heat transfer assisting member facing the nip forming member. The fixing device according to 1.   The surface of the nip forming member facing the heat transfer assisting member, and the surface of the fixing member in the longitudinal direction protrudes from the surface of the fixing member in the longitudinal direction. The fixing device according to any one of claims 1 to 3. Between the end heat source and the heat transfer auxiliary member, an intermediate member that transmits heat of the end heat source to the heat transfer auxiliary member is provided,
The fixing device according to claim 1, wherein the intermediate member corresponds to a shape of the end heat source and the heat transfer auxiliary member.   An image forming apparatus comprising the fixing device according to claim 1.

Images