JP2017116695A - Fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device which suppresses the excessive temperature rise in a non-sheet passage region of a fixation member, has the excellent travel performance of the fixation member, and deals with sheets in a special size.SOLUTION: A fixation device includes: an endless fixation member that can rotate; a facing rotor which is provided on the outer side of the fixation member and faces the fixation member; a plurality of heat sources which are provided on the inner side of the fixation member and have the different heat distributions in the longitudinal direction; a nip formation member which is provided on the inner side of the fixation member and forms a fixation nip between the fixation member and the facing rotor; a plurality of end heat sources which are provided in the nip formation member and respectively heat both ends in the longitudinal direction of the fixation member; and a heat transfer auxiliary member which contacts the surfaces facing the fixation member of the nip formation member and the plurality of end heat sources and relaxes the temperature gradient in the longitudinal direction of the fixation member. The heat transfer auxiliary member has recesses on the surfaces facing the fixation member corresponding to portions with which the plurality of end heat sources are brought into contact.SELECTED DRAWING: Figure 7

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 thin endless belt with a low heat capacity and a thin film shape is directly heated without using a metal heat conductor also serving as a support, and good fixability is obtained even when mounted on a high-production image forming apparatus. A fixing device that can perform this is known (for example, see Patent Document 1). In this fixing device, the pressure roller disposed on the outer peripheral side of the endless fixing belt and the nip forming member fixedly disposed inside the fixing belt (in the loop) are brought into pressure contact with each other via the fixing belt. A fixing nip is formed.

  Various sizes of recording materials are used in the image forming apparatus. In order to support recording materials of various sizes, when fixing the fixing heat source (heater) of the fixing device to the maximum size of the recording material, when fixing a small size recording material, fixing that is a non-sheet passing portion The belt / roller end temperature rises. At the time of continuous paper feeding, the end portion is excessively heated, so it is necessary to reduce the productivity by, for example, slowing the recording material conveyance speed. Therefore, there is a problem that it is not possible to meet the market demand for energy saving and high speed.

  In order to cope with this problem, there is known a fixing device including a halogen heater having a dense light distribution at the center and a halogen heater having a dense light distribution near the end inside the fixing belt / roller. . In the case of a recording material of a small size, this fixing device performs fixing by turning on only a halogen heater having a dense light distribution in the center, and in the case of a recording material larger than a small size, turning on both halogen heaters. .

  By the way, although the recording material used in the image forming apparatus is rarely used, there is a case where the image is formed to the full standard size of the recording material. In this case, a recording material that is one size larger than the standard size of the recording material (for example, an A3 novi size that is one size larger than the A3 size) or a special size such as a 13-inch size is used. Therefore, further improvement has been desired to cope with these special-size recording materials.

  For such a problem, a plurality of halogen heaters having different light distributions in the belt width direction (paper width direction) are provided inside the endless belt, and at both ends in the longitudinal direction of the belt member, It has been proposed to provide an end heater in contact with the inner or outer surface of the belt at a position upstream of the nip in the belt rotation direction (see, for example, Patent Document 2).

  However, in the fixing device disclosed in Patent Document 2, in order to increase the heat transfer efficiency from the end heater to the fixing belt, if the contact pressure of the end heater with respect to the fixing belt is increased, the gap between the end heater and the fixing belt is increased. The frictional force increases. This may lead to poor running of the fixing belt, resulting in a decrease in reliability.

  On the other hand, the heat transfer assisting member provided with the sliding sheet is brought into contact with the fixing belt to prevent excessive temperature rise in the non-sheet passing region of the fixing member and reduce the sliding resistance between the fixing belt and the heat transfer assisting member. A configuration has been proposed (see, for example, Patent Document 3). Furthermore, by applying a lubricant between the heat transfer assisting member and the fixing belt, the sliding resistance can be further reduced, and poor running of the fixing belt can be prevented.

  However, since the lubricant used in such a fixing device has high fluidity, there is a problem in that the lubricant flows out from the end face of the fixing belt and increases the sliding resistance.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that suppresses an excessive temperature rise in a non-sheet passing region of a fixing member and is excellent in running performance of the fixing member and corresponding to a special size paper.

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 contacts a surface of the nip forming member and the plurality of end heat sources facing the fixing member and loosens a temperature gradient in the longitudinal direction of the fixing member,
The heat transfer assisting member has a recess on a surface facing the fixing member corresponding to a portion where the plurality of end heat sources are in contact with each other.

  According to the present invention, it is possible to provide a fixing device that can suppress the excessive temperature rise in the non-sheet passing region of the fixing member and that is excellent in the running performance of the fixing member and is compatible with special-size paper.

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 a fixing device according to an embodiment of the present invention. It is a perspective view which shows the basic composition of the nip formation unit in one Embodiment of this invention. It is a perspective view which shows the structure of the nip formation unit and halogen heater in one Embodiment of this invention. It is a schematic diagram which shows arrangement | positioning of the heat generating part of the halogen heater and end part heater in one Embodiment of this invention. It is a schematic diagram which shows the positional relationship of each heat-emitting part of the halogen heater and end part heater in one Embodiment of this invention. It is explanatory drawing explaining the heat transfer auxiliary member in 1st Embodiment of this invention. It is explanatory drawing explaining the heat transfer auxiliary member in 1st Embodiment of this invention. It is explanatory drawing explaining the heat transfer auxiliary member in 2nd Embodiment of this invention. It is explanatory drawing explaining the heat transfer auxiliary member in 3rd Embodiment of this invention. It is a figure explaining the position of the temperature detection part provided for the edge part heater in one Embodiment of this invention. It is a schematic diagram which shows a fixing device provided with two halogen heaters as a heat source.

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. In the center of the printer body, four image forming units 4Y, 4C, 4M, and 4K are provided side by side along the extending direction of the intermediate transfer belt 30. Yes. 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 an endless fixing belt 21 that is a thin and flexible cylindrical fixing member, and a pressure roller 22 that is a pressure member that abuts from the outer peripheral side of the fixing belt 21. ing. The fixing belt 21 is heated by 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 fixing heat sources arranged inside (in the loop). The halogen heater represents a radiant heat source as a fixing heat source which is 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 (398 W / mK), aluminum (236 W / mK), 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 lit, so that the width direction of the fixing belt 21, that is, the longitudinal direction of the heat transfer assisting member 27. The heat is positively transferred to the longitudinal temperature gradient.

  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, more preferably 0.16 mm or less, and the diameter is 30 mm. The following is desirable.

  As shown in FIG. 2, the stay member 25 having a T-shaped cross section has an upright portion 25a that is upright on the side opposite to the fixing nip N side. Halogen heaters 23A and 23B as main heat sources are separated by the upright portion 25a. Are arranged to be. One of the halogen heaters 23A and 23B has a heat generating portion at a longitudinal center portion corresponding to a small size paper, and the other has a heat generating portion at both longitudinal end portions corresponding to a 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 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. The positional relationship between the end heaters 26a and 26b and the halogen heaters 23A and 23B will be described later.

  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 can be 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, etc. provided on the surface of the elastic layer. It is configured. 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 sandwiched and rotated at the fixing nip N, and travels while being guided by side plate flanges disposed at both ends except for 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 assisting 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 surface 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 configuration of the heat transfer assisting member 27 and the nip forming member 24 may be provided with claws or the like, or may be bonded.

  On the surface of the nip forming member 24 facing the heat transfer assisting member 27, the accommodating portions 24a and 24b as stepped portions are formed at both ends in the longitudinal direction. The end heaters 26a and 26b are accommodated and fixed in the accommodating portions 24a and 24b. 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 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 surface of the end heaters 26a and 26b facing the inner peripheral surface of the fixing belt 21 and the surface of the nip forming member 24 facing the inner peripheral surface of the fixing belt 21 have the same height (on the same plane). Therefore, a sufficient pressing force by the pressure roller 22 is given through the heat transfer assisting member 27. Therefore, the fixing belt 21 is in contact with the end heaters 26a and 26b with sufficient contact pressure via the heat transfer assisting member 27, and good heating is maintained.

In the conventional fixing device, as shown in FIG. 12, a halogen heater 50A that heats the longitudinal center of the fixing belt 60 and a halogen heater 50B that heats both longitudinal ends of the fixing belt 60 are arranged in parallel. Has been placed. Therefore, there is a problem that the radiation efficiency of one halogen heater heats the other halogen heater and the heating efficiency is lowered.
The fixing device of this embodiment solves such a problem.

  FIG. 4 is a perspective view showing configurations of the stay member 25 and the halogen heaters 23A and 23B. 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 first and second halogen heaters 23A and 23B are shielded from each other by the standing portion 25a. Therefore, unlike the fixing device shown in FIG. 11, the glass tubes are not heated when the heater is turned on, so that 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. For example, the cross-sectional shape of the stay member 25 may be a shape that partitions the first and second halogen heaters 23A and 23B from each other, and the first member 25A and the second member 25B are curved in the longitudinal direction of the halogen heater. It may extend. 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. 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 formed by the heat generating portions 40A and 40B of both the halogen heaters 23A and 23B and the heat generating portions 42a and 42b of the both end heaters 26a and 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%. It is common to define.

  Further, as shown in the lower part of FIG. 6, the end heater 26 b also has a reduced heating output at the end portion in the longitudinal direction of the heat generating portion 42 b due to the heat generating pattern 37. 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 a risk of not.

  Therefore, in this 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 begins to decrease and the boundary Bc at which the heating output at the heat generating portion 42b of the end heater 26b begins to decrease. To match. 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 when projected. 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 nip forming unit has a heat transfer assisting member, there is a possibility that a so-called warm-up time from when the image forming apparatus can be used until image formation becomes possible may be extended.

  Specifically, the heat transfer auxiliary member 27 uses a material having high thermal conductivity such as copper and aluminum, and prevents the heat of the halogen heaters 23A and 23B and the end heaters 26a and 26b from staying locally, Heat is positively moved in the longitudinal direction of the heat transfer assisting member 27 to loosen the temperature gradient in the longitudinal direction.

  The plate thickness of the heat transfer auxiliary member 27 is about 0.3 to 1.0 mm, but the heat transfer performance improves as the thickness increases. For example, when the paper having a paper width smaller than or larger than the heat generation range W1 including the heat generating portions 40A and 40B of the halogen heaters 23A and 23B is continuously passed, the heat transfer assisting member 27 having an increased thickness causes the fixing belt 21 to be excessive. Alternatively, the temperature gradient in the axial direction of the fixing belt 21 is relaxed so as not to be heated excessively. On the other hand, since the heat transfer assisting member 27 having an increased thickness has a large heat capacity, there is a possibility that the warm-up time is extended and the usability of the user is deteriorated. Therefore, it is necessary to make the thickness compatible with the relaxation of the temperature gradient in the axial direction of the fixing belt 21 and the shortening of the warm-up time.

  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. As the lubricant applied to the belt sliding contact surface 27a and / or the inner surface of the fixing belt 21, for example, grease is used.

  By the way, the grease generally has a lower sliding torque as its viscosity is lower. A grease having a low viscosity has high fluidity and cannot be kept at a desired position. Therefore, mixing a thickener with the base oil may increase the viscosity and improve the retention. However, if the viscosity of the grease is increased more than necessary, the sliding torque between the heat transfer assisting member 27 and the fixing belt 21 increases, and it is necessary to increase the motor output in the apparatus and increase the drive gear strength. And there is a problem that the fixing belt runs poorly. Furthermore, since grease has a property of softening as the temperature rises, there is a problem that the grease softens more quickly when directly heated in the vicinity of the end heaters 26a and 26b.

Next, the heat transfer auxiliary member according to the first embodiment will be described.
As shown in FIGS. 3 and 7, the heat transfer assisting member 27 of the present embodiment is a belt-sliding contact surface 27 a, and concave portions 27 b and 27 c are formed in portions corresponding to the portions in contact with the end heaters 26 a and 26 b. Provide. In addition, since the recessed part 27b and the recessed part 27c are the same shapes, only the recessed part 27b is demonstrated and description about the recessed part 27c is abbreviate | omitted.

  The recess 27b has a rectangular shape and is formed to be approximately 0.05 mm to 0.2 mm lower than the belt sliding contact surface 27a that is not the recess 27b. As a result, the fixing belt 21 pressurized from the pressure roller 22 side is in close contact with the concave portion 27b of the heat transfer assisting member 27 and does not hinder desired heat conduction.

  A corner 27e is formed in the recess 27b by a bottom surface and a wall surface. In the state where the heat transfer assisting member 27 is installed in the fixing device 20, the contact pressure of the fixing belt 21 at the corner 27e is lower than the contact pressure of the fixing belt 21 at the recess 27b that is not the corner 27e.

  Therefore, the grease 46 applied to the concave portion 27b moves to the corner portion 27e having a low contact pressure, and is blocked by the wall surface. And the grease 46 thicker than the grease 46 formed in the part which is not the corner 27e is formed in the corner 27e. That is, the corner 27e forms a grease reservoir. As a result, even when the fixing belt 21 rotates, the sealing of the recesses 27b and 27c can be maintained, and the grease 46 can be prevented from moving from the recesses 27b and 27c.

Next, the heat transfer auxiliary member according to the second embodiment will be described.
The heat transfer assisting member 127 of the present embodiment is different from the heat transfer assisting member 27 of the first embodiment in that the shape of the recess is different. In addition, about the structure equivalent to the said embodiment, a corresponding code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  The heat transfer assisting member 127 is provided with recesses 127b and 127c in the belt sliding contact surface 127a corresponding to the portion that contacts the end heaters 26a and 26b. In addition, since the recessed part 127b and the recessed part 127c are symmetrical shapes, only the recessed part 127b is demonstrated and description about the recessed part 127c is abbreviate | omitted.

  The concave portion 127b is formed by a slope 127ba that is inclined in the longitudinal direction of the heat transfer assisting member 127, a wall surface 127bb that is formed in the longitudinal direction of the heat transfer assisting member 127, and two wall surfaces that are formed in the short direction. The inclined surface 127ba is gently inclined from the longitudinal end portion side of the heat transfer assisting member 127 toward the longitudinal central portion side, and is connected to the wall surface 127bb. That is, the concave portion 127 b is separated from the rotation axis of the fixing belt 21 as it goes toward the center in the axial direction of the fixing belt 21.

  As a result, the contact pressure of the fixing belt 21 decreases as the concave portion 127 b moves toward the axial center of the fixing belt 21. Therefore, the grease 46 applied to the recess 127b moves in the recess 127b toward the center in the axial direction of the fixing belt 21, and is blocked by the wall surface 127bb to form a thick layer. That is, the slope 127ba and the wall surface 127bb form a grease reservoir. As a result, even if the fixing belt 21 rotates, the sealing of the recess 127b can be maintained and the grease 46 can be prevented from moving from the recess 127b. The fixing belt 21 pressed from the pressure roller 22 side is also in close contact with the concave portion 127b of the heat transfer auxiliary member 127, and does not hinder desired heat conduction.

Next, the heat transfer auxiliary member according to the third embodiment will be described.
The heat transfer assisting member 227 of this embodiment is different from the heat transfer assisting member 27 of the first embodiment in that the shape of the recess is different. In addition, about the structure equivalent to the said embodiment, a corresponding code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  The heat transfer assisting member 227 is provided with recesses 227b and 227c in the vicinity of the belt sliding contact surface 227a corresponding to the portion in contact with the end heaters 26a and 26b. In addition, since the recessed part 227b and the recessed part 227c are symmetrical shapes, only the recessed part 227b is demonstrated and description about the recessed part 227c is abbreviate | omitted.

  The concave portion 227b is trapezoidal, is formed by one bottom surface and four wall surfaces, and is lower by about 0.05 mm to 0.2 mm than the belt sliding contact surface 227a that is not the concave portion 227b. As a result, the fixing belt 21 pressed from the pressure roller 22 side is in close contact with the concave portion 227b of the heat transfer assisting member 227 and does not hinder desired heat conduction.

  As shown in FIG. 10, among the four wall surfaces forming the recess 227 b, the wall surface 227 ba on the downstream side in the rotation direction (belt feeding direction) of the fixing belt 21 is in the elevation direction with respect to the longitudinal direction of the heat transfer auxiliary member 227. Extend. That is, the wall surface 227ba on the downstream side in the rotation direction of the fixing belt 21 is separated from the wall surface 227bb on the upstream side in the rotation direction of the fixing belt 21 as it goes toward the axial center of the fixing belt 21.

  The grease 46 applied to the recess 227b is heated by the end heater 26a. When the fixing belt 21 rotates, the grease 46 heated by the end heater 26a moves to the wall surface 227ba together with the fixing belt 21. The grease 46 moved to the wall surface 227ba moves toward the longitudinal direction center side (the deeper side of the inclination) of the heat transfer auxiliary member 227 by the inclination of the wall surface 227ba, and is blocked. That is, the wall surface 227ba forms a grease reservoir. As a result, even if the fixing belt 21 rotates, the grease 46 can be prevented from moving from the recess 227b.

  The present invention has been described based on the embodiments. The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the present invention. Moreover, you may combine each embodiment in the range which can be applied.

  In the above embodiment, the outer diameters of the recesses 27b and 27c are substantially matched to the outer diameters of the end heaters 26a and 26b, but the present invention is not limited to this mode. For example, you may comprise so that the outer diameter of the recessed parts 27b and 27c may fully cover the outer diameter of the edge part heaters 26a and 26b. That is, the recess 27b may be formed over the entire area of the end heater 26a, and the recess 27c may be formed over the entire area of the end heater 26b. Thereby, movement of grease can be prevented in a wide range.

  Further, the length of the pressure roller 22 in the longitudinal direction may be formed to the outside of the recesses 27b and 27c. That is, the pressure roller 22 may be formed across the concave portion 27b and the concave portion 27c in the longitudinal direction. Thereby, the end surface side of the heat transfer assisting member 27 is pressurized, and the adhesion can be enhanced and the sealing effect of grease can be enhanced.

  Next, a temperature detection unit different from the temperature sensor 29 shown in FIG. 2 that detects the temperature of the end heater 26 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 minute sliding contact mark may be generated at the contact position, or a minute gloss unevenness may occur 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 this embodiment, as shown in FIG. 11, temperature detectors 45a and 45b that detect the temperatures of the end heaters 26a and 26b (illustration is omitted because 45a is provided at the opposite end) The fixing belt 21 is provided outside the fixing belt 21 in the radial direction and outside the maximum standard size paper width and inside the nobi size paper width larger than the maximum standard size in the longitudinal direction of the fixing belt 21. Thereby, the temperature can be detected with high accuracy at low cost without revealing an abnormal image such as minute uneven gloss.

21 Fixing belt (an example of a fixing member)
22 Pressure roller (example of counter rotating body)
23A, 23B Halogen heater (example of heat source)
24 Nip forming member 26 End heater (end heat source)
27 Heat transfer auxiliary member 27b, 27c Concave portion N Fixing nip

JP 2010-32631 A JP 2014-178370 A JP-A-2015-102718

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 contacts a surface of the nip forming member and the plurality of end heat sources facing the fixing member and loosens a temperature gradient in the longitudinal direction of the fixing member,
The fixing device according to claim 1, wherein each of the heat transfer assisting members has a concave portion on a surface facing the fixing member corresponding to a portion where the plurality of end heat sources are in contact with each other.   The fixing device according to claim 1, wherein the concave portion has a slope that is separated from a rotation shaft of the fixing member toward the axial center of the fixing member.   The wall surface of the concave portion on the downstream side in the rotation direction of the fixing member is separated from the wall surface of the concave portion on the upstream side in the rotation direction of the fixing member as it goes toward the axial center of the fixing member. The fixing device according to 1 or 2.   The fixing device according to claim 1, wherein the concave portion is formed over the entire area of the end heat source.   The fixing device according to claim 1, wherein the counter rotating body is formed across all the concave portions in a longitudinal direction.   An image forming apparatus comprising the fixing device according to claim 1.

Images