JP2017120390A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that prevents the generation of damage due to an excessive temperature rise of electrode parts of end heat sources.SOLUTION: A fixing device 20 comprises: a rotatable endless fixing member 21; a pressure member 22; a nip forming member 24 that is arranged inside the fixing member and forms a fixing nip N with the pressure member with the fixing member therebetween; a plurality of heat sources 23A and 23B on the inside of the fixing member; end heat sources 26a and 26b that are provided on both ends of the nip forming member and heat both ends in the longitudinal direction of the fixing member; and a heat transfer auxiliary member 27 that is held by the nip forming member and the inner periphery of the fixing member and transfers heat of the fixing member in the longitudinal direction. The end heat sources 26a and 26b are a resistance heating member including a base material 50, a resistor 51 formed on the base material, and an electrode part 52 feeding power to the register. The electrode parts 52 of the end heat sources are arranged on the outside in the longitudinal direction of heating parts 40B of the plurality of heat sources.SELECTED DRAWING: Figure 12

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.

  In Patent Document 1, a nip forming unit is provided inside a thin and flexible endless belt member that quickly rises to the fixing temperature, and the nip forming unit and the pressure roller are provided between the belt member and the pressure roller. A fixing device that forms a nip by contact pressure with a pressure roller is disclosed. Inside the belt member, a plurality of halogen heaters having different heat generation portions and light distributions in the longitudinal direction (paper width direction) of the belt member are provided.

  At both ends of the belt member in the longitudinal direction, end heaters capable of handling a large size paper are positioned in contact with the inner surface or outer surface of the belt member at a position upstream of the nip in the rotation direction of the belt member. Is provided. By adopting a configuration in which the end heater is partially provided, it is possible to cope with a large size paper with a simple configuration without adding a large size dedicated halogen heater.

  In the configuration described in Patent Document 1, power is supplied to the end heater. Brazing and soldering are generally used as an electrode coupling method for power supply. Since the heat resistance itself of these joints is low, the heat resistance of the electrode is also low. On the other hand, in the case of a fixing device that can handle a plurality of sheets, the end region may be excessively heated depending on the sheet size, and there is a risk of electrode damage due to excessive temperature increase.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device in which an electrode portion of an end heat source is not damaged due to excessive temperature rise.

  In order to solve this problem, a rotatable endless fixing member, a pressure member abutting from the outer peripheral side of the fixing member, and the pressure member disposed inside the fixing member via the fixing member A nip forming member that forms a fixing nip, a plurality of heat sources disposed inside the fixing member, and ends that heat both ends in the longitudinal direction of the fixing member. In the fixing device, comprising: a partial heat source; and a heat transfer auxiliary member that is sandwiched between the nip forming member and the inner periphery of the fixing member and moves the heat of the fixing member in the longitudinal direction. A resistance heating member having a base material, a resistor formed on the base material, and an electrode portion for supplying power to the resistor, wherein the electrode portion of the end heat source is a plurality of heat sources. Located on the outside in the longitudinal direction of the heat generating part That proposes a fixing apparatus characterized by.

  By disposing the electrode part of the end heat source on the outside in the longitudinal direction of the heat generating parts of the plurality of heat sources, it is possible to prevent overheating and damage of the electrode part having low heat resistance.

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 a graph (1st pattern) which shows the heating output of a 2nd halogen heater. It is a graph which shows the state of each heating output of the halogen heater which has a heat generating part near the center, and the halogen heater which has a heat generating part near the end. It is a graph (2nd pattern) which shows the heating output of a 1st, 2nd halogen heater. It is a graph (3rd pattern) which shows another example of the heating output of a 1st, 2nd halogen heater. It is a figure explaining the position of the temperature detection part provided for an edge part heater. It is a figure which shows the structure of a edge part heater, and arrangement | positioning (1st form) of an edge part heater and a heat transfer auxiliary member. It is a figure which shows the modification of a structure of an edge part heater, and arrangement | positioning (1st form) of an edge part heater and a heat transfer auxiliary member. It is a figure which shows the structure (2nd form) of a structure of an end part heater, and an end part heater and a heat transfer auxiliary member. It is a figure which shows the structure (3rd form) of a structure of an end part heater, and an end part heater and a heat transfer auxiliary member. It is a figure which shows the structure (4th form) of a structure of an end heater, and an end heater and a heat transfer auxiliary member. It is a schematic diagram which shows the modification of the heat-generation pattern of a resistance heating element.

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 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.

  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 a thin, flexible, rotatable endless and 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. And have. The fixing belt 21 is heated by radiant heat from 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, 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 (support member) that supports the nip forming member 24 are arranged inside the fixing belt 21. Has been. The nip forming member 24 arranged across the width direction of the fixing belt 21 is fixedly supported by the stay member 25, thereby preventing the nip forming member 24 from being bent by the pressure from the pressure roller 22, A uniform nip width is obtained over 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 a and 26 b as end heat sources different from the main heat source are integrally attached to both ends in the longitudinal direction of the nip forming member 24, and both ends in the longitudinal direction of the fixing belt 21 are heated. The end heat source is located within the range of the fixing nip N in the circumferential direction of the fixing belt 21. As a result, the belt end and the end heater are pressed against each other at the fixing nip N, and the belt end does not flutter at the fixing nip N even when the fixing belt is running. Are reliably in contact with each other, and the fixing belt does not run poorly. In addition, the residual toner on the fixing belt that has not been fixed to the recording material at the fixing nip is re-melted at the position of the end heater and does not cause a problem of quality deterioration such that it remains as a fixed toner. 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 assisting member 27, which is also referred to as a heat equalizing member that loosens the temperature gradient in the longitudinal direction of the fixing belt, covers each surface facing the inner peripheral surface of the fixing belt 21 of each of the nip forming member 24 and the end heater 26. This prevents the 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. The heat is moved in the longitudinal direction of the movement assisting member 27 to eliminate the temperature non-uniformity in the longitudinal direction. Therefore, the heat transfer auxiliary member 27 is formed of a material having high thermal conductivity that enables heat transfer in a short time, such as copper or aluminum. 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 flat. However, it may be a concave shape or other shapes. When the nip forming surface has a concave shape, the discharge direction at the front end of the sheet 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. In order to further 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.

  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, 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 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.

  Reflecting members 28A and 28B are disposed between the stay member 25 and the halogen heaters 23A and 23B. Accordingly, 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 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 facing the inner peripheral surface of the fixing belt 21. The heat transfer assisting member 27 and the nip forming member 24 may be integrated with each other by providing a claw or the like, but may be bonded or the like. Concave portions 24a and 24b as stepped portions are formed at both ends in the longitudinal direction of the nip forming member 24, and end heaters 26a and 26b are accommodated and fixed at these portions. 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 addition of the nip forming member 24. 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.

  In addition, the surface of the end heaters 26a and 26b that faces the inner surface of the fixing belt 21 and the surface of the nip forming member 24 that faces the fixing belt 21 are positioned at the same height (on the same plane). Sufficient pressure is applied through the heat transfer assisting member 27.

  As a result, the fixing belt 21 is in a state of being in intimate contact with the end heaters 26a and 26b, so that stable belt traveling can be performed. Further, the fixing belt 21 and the end heaters 26a and 26b are in contact with each other with a sufficient contact pressure, and good heating is maintained. With these configurations, the reliability of the fixing device 20 is improved.

  Further, the heating portion of the fixing belt 21 by the end heaters 26a and 26b is in the nip region. For this reason, the problem of re-melting of unfixed residual toner due to heating at a site different from the fixing nip N as in Patent Document 1 does not occur.

  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 generating unit 40 including the heat generating units 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.

  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 (the part where the heat generating pattern 37 is provided). In other words, 100% of the predetermined heating output is not output at the end, and the heating output is sag. An example of the heat generation pattern 37 is a region where a pattern of a resistor 51 as will be described later is formed.

  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.

  As described above, in the present embodiment, the boundary Bh of the second halogen heater 23B and the boundary Bc of the end heater 26b are matched. However, as described above, since the nip forming unit has the heat transfer assisting member 27 with good thermal conductivity, it is possible to level out a certain decrease in heating output. 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.

  Next, how to set the end of the end heater near the center of the heat generating portion (boundary Bc where the heating output starts to decrease) will be described in three patterns using a graph of the heating output. The position where the boundary Bc is set has a predetermined allowable range.

(First pattern)
FIG. 7 is a graph showing the heating output of the second halogen heater. The depiction of the graph shows the output at one end for convenience of explanation. In FIG. 7, the vertical axis represents the output ratio (%) with respect to the predetermined heating output, and the horizontal axis represents the position in the longitudinal direction of the second halogen heater 23B. The graph of the heating output draws a curve having a convex peak in the longitudinal direction.

  In the case of the heating output shown in FIG. 7, the boundary Bc of the end heater 26 (the boundary where the heating output near the center in the longitudinal direction in the heat generating part 42b starts to decrease) is closer to the end in the longitudinal direction in the second halogen heater. It is set to a range (a range indicated by A in the figure) from a location where the peak heating output is 40% to a location where the peak heating output is located 80% of the peak heating output. If the boundary Bc of the end heater 26 is set in such a range, the heating output at the end portions of the end heater 26 and the second halogen heater 23B can be within an allowable range.

(Second pattern)
FIG. 8 is a graph showing the heating output states of a halogen heater having a heat generating part in the central range and a halogen heater having a heat generating part in the side range. The heating output of the halogen heater having the heat generating portion in the central range corresponding to the first halogen heater 23A is shown by a broken line graph, and the heating output of the halogen heater having the heat generating portion in the side range corresponding to the second halogen heater 23B is shown by a solid line. It shows with. A plurality of halogen heaters having different light distributions in the longitudinal direction and thus having different heating output patterns can have different patterns of total heating output.

  FIG. 9 is a graph showing the heating output of the combined state of the first and second halogen heaters. As shown in FIG. 9, in the graph of the heating output, the output ratio rises to 100% in the vicinity of both end portions, and is gentle at almost 100% in the central region in the longitudinal direction.

  Here, the range where the heating output is approximately 100% is defined as length (B), and the range where the output ratio is approximately 100% to 40% is defined as length (C). At this time, the boundary Bc of the end heater 26 is arranged in a range from a position where the output ratio is 40% of the heating output to a length D that satisfies (C + B × 1/10) toward the center in the longitudinal direction. . If the boundary Bc of the end heater 26 is arranged in such a range, the heating output at the ends of the end heater 26 and the second halogen heater 23B can be within an allowable range.

(Third pattern)
FIG. 10 is a graph showing another example of the heating output of the first and second halogen heaters. As shown in FIG. 10, the central region of the graph is gentle, but both ends thereof are higher than the central region. When the filament of the heat generating part of the second halogen heater 23B is wound more densely than the filament of the heat generating part of the first halogen heater 23A, such a shape is obtained.

  Here, a range sandwiched between both ends where the heating output is approximately 100% is defined as length (B '), and a range where the output ratio is approximately 100% to 40% is defined as length (C). At this time, the boundary Bc of the end heater 26 is within a range from a position where the output ratio is 40% of the heating output to a length D ′ that satisfies (C + B ′ × 1/10) toward the center in the longitudinal direction. Be placed. If the boundary Bc of the end heater 26 is arranged in such a range, the heating output at the ends of the end heater 26 and the second halogen heater 23B can be within an allowable range.

Next, an advantageous configuration of the fixing device of the present invention will be described.
Since the heat transfer assisting member 27 is in sliding contact with the inner surface of the fixing belt 21, if a metal material such as copper or aluminum is used as it is, the friction coefficient increases. If the friction coefficient is large, the unit torque becomes large, causing problems such as shortening the life of the apparatus.

  Therefore, it is desirable that the belt sliding contact surface 27a (see FIG. 3) facing (contacting) the fixing belt 21 of the heat transfer assisting member 27 is smooth and further subjected to a low friction process. Specifically, the friction between the heat transfer assisting member 27 and the inner surface of the fixing belt 21 is reduced by applying fluorine-based paint or coating such as PFA or PTFE. It is also desirable to apply a lubricant such as fluorine grease or silicone oil between the heat transfer assisting member 27 and the inner surface of the fixing belt 21, and the friction can be further reduced.

  Next, a temperature detection unit different from the temperature sensor 29 shown in FIG. 2 for detecting the temperature of the fixing belt 21 heated by 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 45 a and 45 b (45 a is provided at the opposite end portion) that detects the temperature of the portion heated by the end heaters 26 a and 26 b of the fixing belt 21. Therefore, it is provided outside the fixing belt 21 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.

  Although the configuration for detecting the temperature of the portion heated by the end heater 26 of the fixing belt 21 has been described, a sensor for detecting the temperature of a part of the end heater itself is provided, and the end heater is controlled based on the detection result. It is also possible to apply this method.

  Next, four forms of the configuration of the end heater and the arrangement of the end heater and the heat transfer auxiliary member will be described.

(First form)
12A and 12B are diagrams showing the configuration of the end heater and the arrangement of the end heater and the heat transfer auxiliary member (first form), where FIG. 12A is the same cross-sectional view, and FIG. 12B is the same front view. c) is a side view of the same. 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. 12, but the end heater 26a has the same configuration.

  As shown in FIG. 12A, the end heater 26 b supplies electric power to the base material 50, the resistor 51 formed on the base material 50, for example, in a substantially U shape, and the resistor 51. This is a resistance heating member having a plurality of electrodes 52 as electrode portions. For example, as the end heater, a ceramic heater in which a resistor (heating element) is disposed on a base material such as ceramic is used. The end heater 26b is disposed in a non-contact manner with a small gap from the heat transfer assisting member 27. As shown in FIGS. 12A and 12B, the electrode 52 is disposed on the outer side in the longitudinal direction of the heat generating portion 40 </ b> B of the second halogen heater 23 </ b> B and is connected to both ends of the resistor 51. Therefore, when electric power is supplied to the electrode 52, the resistor 51 generates heat, and the heat generating portion 42b in which the resistor 51 is disposed becomes high temperature. In this configuration, when paper is passed in a size not using the end heater 26b, the relationship between the heat generating part 40B of the second halogen heater 23B and the paper P to be passed (from the heat generating part 40B of the second halogen heater 23B). When passing a narrow size), the end of the fixing belt 21 may become a non-sheet passing portion and the temperature may increase. At this time, if the electrode 52 of the end heater 26b is disposed in the region of the heat generating part 40B of the second halogen heater 23B, the heat resistance of the electrode 52 of the end heater is low, so There is a possibility that the electrode 52 may be damaged due to excessive heating due to heat. However, it is possible to prevent the electrode 52 from being overheated by disposing the electrode 52 on the outer side in the longitudinal direction of the heat generating portion 40B of the second halogen heater 23B.

  The heat generating portion 42 b is a region that extends in the longitudinal direction of the heat transfer assisting member 27, and has a width 43 in which the resistor 51 is disposed in the width direction of the heat transfer assisting member 27. The width 43 of the heat generating part 42 b is smaller than the width of the heat transfer assisting member 27. Brazing and soldering are generally used as a method for connecting electrodes for supplying power to the resistor. Since the heat resistance itself of these bonding methods is low, the heat resistance of the electrode is also low. For the purpose of improving heat resistance, high-temperature solder or silver may be used.

  The heating output and the heat generation area are shown in the upper part of FIG. This heating output and heat generation region corresponds to the heating output and heat generation unit 40B shown in the upper diagram of FIG. On the other hand, this heating output can also be viewed as a combined heating output of the first halogen heater 23A and the second halogen heater 23B as shown in FIGS. Also in this case, as described above, the electrode 52 may be disposed outside the heating portion 40B of the second halogen heater 23B until the heating output reaches 50%.

  The heat transfer assisting member 27 is provided so as to face the base material 50 of the end heater 26b and cover the heat generating portion 42b of the end heater 26b. Further, in FIG. 12C, the heat transfer auxiliary member 27 is conceptually drawn, and the heat transfer auxiliary member 27 has a shape protruding in the direction of the pressure roller 22 on the upstream side in the belt rotation direction in the vicinity of the nip outlet portion. It is good. This improves the releasability of the paper P at the nip exit. These characteristics are the same in the end heater 26a, and the heat transfer assisting member 27 is provided so as to face the base material 50 of the end heaters 26a and 26b and cover the heat generating part 42b of the end heaters 26a and 26b. It has been.

  The heat of the end heaters 26 a and 26 b is transmitted to the fixing belt 21 through the heat transfer auxiliary member 27. When a part of the heat generating part 42b of the end heaters 26a and 26b is not covered with the heat transfer assisting member 27, the heat of the part is not easily transmitted to the fixing belt 21, and the heating efficiency is deteriorated. Heating efficiency can be improved by covering at least the entire heat generating portions of the end heaters 26 a and 26 b with the heat transfer assisting member 27.

  FIGS. 13A and 13B are diagrams showing a modification of the configuration of the end heater and the arrangement of the end heater and the heat transfer auxiliary member (first form), where FIG. 13A is the same cross-sectional view, and FIG. 13B is the same front view. FIG. 3C is a side view of the same. Here, (a) is the figure which looked at the cross section cut | disconnected on the AA line of (b) from the paper conveyance direction. What is different from the first embodiment is the configuration of the heat transfer auxiliary member 27. That is, as shown in FIG. 13, the thickness of the heat transfer assisting member 27 (the length between the surface facing the inner peripheral surface of the fixing belt 21 and the surface facing the end heater 26) is increased to assist the heat transfer. The rigidity of the member 27 may be increased. Since the pressure acting on the fixing nip can be increased, the fixability of the image can be improved.

(Second form)
14A and 14B are diagrams showing the configuration of the end heater and the arrangement of the end heater and the heat transfer assisting member (second embodiment), where FIG. 14A is the same cross-sectional view, and FIG. 14B is the same front view. c) is a side view of the same. Here, (a) is the figure which looked at the cross section cut | disconnected on the AA line of (b) from the paper conveyance direction. 14, the same components as those in FIG. 12 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIGS. 14A and 14C, the side of the heat transfer assisting member 27 facing the end heater 26b is provided in contact with the heat generating portion 42b of the end heater 26b. That is, the contact range 55 is the same as or larger than the heat generating portion 42b of the end heater 26b. The same applies to the end heater 26a. In the portion where the heat transfer assisting member 27 does not come into contact with the heat generating portion 42b, heat transfer is deteriorated. The heating efficiency can be improved by the heat transfer assisting member 27 contacting at least the entire heat generating portions of the end heaters 26a and 26b.

(Third form)
FIGS. 15A and 15B are diagrams showing the configuration of the end heater and the arrangement of the end heater and the heat transfer auxiliary member (third embodiment), where FIG. 15A is the same sectional view, and FIG. c) is a sectional view of the same. Here, (a) is the figure which looked at the cross section cut | disconnected on the AA line of (b) from the paper conveyance direction. 15, the same components as those in FIGS. 12 to 14 are denoted by the same reference numerals, and detailed description thereof is omitted.
In this embodiment, on the base material 50 of the end heater 26 b, two conductors 56 that are non-heat generating portions are provided between both ends of the resistor 51 and the two electrodes 52. Two conductors 56 connect both ends of the resistor 51 and the two electrodes 52. In order to provide the conductor 56, the base material 50 is longer in the longitudinal direction than in the above-described embodiment. For this reason, although the heat resistance of the electrode 52 of the end heater is low, by interposing the conductor 56, the electrode 52 is further away from the heat generating portion 42b of the end heater, and the overheating of the electrode 52 having low heat resistance is ensured. Can be prevented.

  In this embodiment as well, the side of the heat transfer assisting member 27 that faces the end heater 26b is provided in contact with the heat generating part 42b of the end heater 26b. The entire width of the resistor 51 in the longitudinal direction is covered with the heat transfer auxiliary member 27. Therefore, the contact range 55 is the same as or larger than the heat generating portion 42b of the end heater 26b.

(4th form)
16A and 16B are diagrams showing the configuration of the end heater and the arrangement of the end heater and the heat transfer auxiliary member (fourth embodiment), where FIG. 16A is the same cross-sectional view, and FIG. 16B is the same front view. c) is a sectional view of the same. Here, (a) is the figure which looked at the cross section cut | disconnected on the AA line of (b) from the paper conveyance direction. In FIG. 16, the same components as those in FIG. 14 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIGS. 16A and 16B, the end heater 26b is generally a flat plate-like member. However, as shown in FIG. 16C, the cross-sectional shape of the heat transfer assisting member 27 is Often formed with complex curves. When the flat surface is narrow on the side facing the end heater 26b of the heat transfer assisting member 27, the portion where the heat generating part 42b of the end heater 26b and the heat transfer assisting member 27 overlap is reduced.

  Therefore, in this embodiment, as shown in FIG. 16C, an intermediate member 53 is provided between the heat transfer assisting member 27 and the end heater 26b. The side of the intermediate member 53 facing the heat transfer assisting member 27 has a shape corresponding to (combining with) the heat transfer assisting member 27, and the side of the intermediate member 53 facing the end heater 26b corresponds to the end heater 26b ( Shape). 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 heat generating portion 42b of the end heater 26b to the electrode 52 via the fixing belt 21 is reduced. Further, it is possible to prevent an excessive temperature rise of the electrode 52 due to this heat. The electrode 52 of the end heater 26 b having low heat resistance can be further away from the fixing belt 21. The same applies to the end heater 26a.

  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 assisting 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.

  By the way, although the said 1st-4th form (FIGS. 12-16) illustrated the resistor (heat generation pattern) formed in the U shape seeing from the front, it is not limited to this. For example, as shown in FIG. 17, the resistor 51 may be formed by reciprocating a plurality of times on the surface of the substrate 50, and the length of the resistor 51 may be made longer. In the case of this heat generation pattern, the heat output of the end heaters 26a and 26b 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 (Pressure member)
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 2014-178370 A

Claims (6)

A rotatable endless fixing member;
A pressure member abutting from the outer peripheral side of the fixing member;
A nip forming member disposed inside the fixing member and forming a fixing nip with the pressure member via the fixing member;
A plurality of heat sources arranged inside the fixing member;
An end heat source that is provided at both ends of the nip forming member and heats both ends in the longitudinal direction of the fixing member;
A heat transfer auxiliary member that is sandwiched between the nip forming member and the inner periphery of the fixing member and moves heat of the fixing member in the longitudinal direction;
In a fixing device having
The end heat source is a resistance heating member having a base material, a resistor formed on the base material, and an electrode portion for supplying power to the resistor,
The fixing device, wherein the electrode portion of the end heat source is disposed outside in a longitudinal direction of the heat generating portions of the plurality of heat sources.   The fixing device according to claim 1, wherein a conductor that is a non-heat generating portion is provided between the resistor and the electrode portion on the base of the end heat source.   An intermediate member is provided between the heat transfer assisting member and the end heat source, and the side of the intermediate member facing the heat transfer assisting member has a shape corresponding to the heat transfer assisting member, and the end heat source The fixing device according to claim 1, wherein the side of the intermediate member facing each other has a shape corresponding to the end heat source.   The fixing device according to claim 3, wherein the intermediate member is copper, aluminum, or an alloy thereof.   5. The fixing device according to claim 1, wherein the heat generating portions of the plurality of heat sources have different distributions in the longitudinal direction and are separated from each other by a support member. An image forming apparatus comprising the fixing device according to claim 1.

Images