JP2018101036A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent loss of a lubrication function due to an increase in viscosity resulting from mixing of abrasion powder in lubricant occurring through rubbing between a fixing belt and a nip forming member, and reduce a phenomenon for a long period in which torque generated when driving to rotate the fixing belt is increased.SOLUTION: A belt contact surface 24c (27a) of a nip forming member 24 (or heat transfer auxiliary member 27) is provided with a continuous concave part shape (continuous concave parts) that is formed of a plurality of concave parts 51 extending in a belt conveyance direction and communication concave parts 52 connecting the respective concave parts 51. Abrasion powder is mixed with lubricant attached to the inside of a fixing belt to increase the viscosity of the lubricant; however, a liquid portion of the lubricant is caused to flow in the longitudinal direction (belt width direction) from the concave parts 51 through the communication concave parts 52 to be circulated inside the fixing belt in order to suppress an increase in torque over time.SELECTED DRAWING: Figure 7

Description

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

  In recent years, in the image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine having at least two of these functions, market demands for energy saving and high speed are increasing.

  Among image forming devices, the fixing device consumes a lot of power and has a lot of room for energy saving.Therefore, various proposals have been made.For example, a thin endless belt with a low heat capacity and a metal heat that also serves as a support. There has been known a fixing device that can directly heat without using a conductor and can obtain good fixing properties even when mounted on a high-production image forming apparatus (for example, Patent Document 1). In the fixing device described in Patent Document 1, a pressure roller arranged on the outer peripheral side of an endless fixing belt and a nip forming member fixedly arranged inside the fixing belt (in a loop) The fixing nip is formed by pressure contact.

  On the other hand, in an image forming apparatus in which recording materials of various sizes are used, in order to cope with recording materials of various sizes, when the length of the fixing heat source (heater) of the fixing device is adjusted to the maximum size of the recording material, a small size is obtained. When fixing the recording material, the temperature of the fixing belt / roller end, which is a non-sheet passing portion, rises. Since the end portion is excessively heated during continuous paper feeding, for example, measures are taken such as slowing the recording material conveyance speed to reduce productivity.

  In order to cope with this, a halogen heater having a dense light distribution in the center so as to correspond to, for example, the A4 vertical paper width (210 mm) inside the fixing belt / roller, and the A4 vertical paper width of the A3 vertical paper width. There is known a fixing device including a halogen heater having a dense light distribution near an end portion excluding a portion corresponding to the above (ie, excluding a central 210 mm portion of a 297 mm width). 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. .

  The fixing device using such a plurality of heat sources has the following problems. FIG. 19 is a schematic diagram illustrating an example of a fixing device including two halogen heaters as heat sources. The halogen heater 50 </ b> A is a central heater that heats the longitudinal center portion of the fixing belt 60, and the halogen heater 50 </ b> B is a side heater that heats both longitudinal portions of the fixing belt 60. As shown in FIG. 19, since the two halogen heaters 50 (A, B) are arranged in parallel, the radiant heat of one halogen heater heats the other halogen heater, and the heating efficiency decreases. End up. In particular, when the endless fixing belt is reduced in size with the downsizing of the fixing device and the distance between the halogen heaters in the cross section of the fixing device is shortened, such a problem is serious. Further, since the two heaters are arranged inside the fixing belt having a reduced diameter so as to be surrounded by the reflecting member 70 disposed on the surface of the support member, the irradiation angle of each heater to the fixing belt is narrowed. In this respect, the heating efficiency is lowered.

  On the other hand, for example, Patent Document 2 discloses a configuration in which a plurality of halogen heaters are disposed on both sides sandwiched by reflectors to prevent thermal interference between the plurality of halogen heaters that are heated to each other.

  However, when the heat capacity of the member is lowered in order to realize energy saving and first print time improvement, a new problem has occurred. In the fixing device, when a recording material (small size paper) having a width smaller than the heating width of the heat source for heating the fixing belt is passed, at a temperature in the width direction of the fixing belt (a direction perpendicular to the paper conveyance direction). A so-called edge temperature rise occurs in which the temperature rise in the region outside the sheet passing range becomes significant. This is because the heat transfer in the width direction of the fixing belt is hindered by the thinning of the fixing belt. In addition, a member constituting the fixing device such as a pressure roller / belt may reach a temperature higher than the heat resistance temperature, and the temperature outside the sheet passing range must be suppressed to protect the member. There was a problem (CPM down) that the productivity of passing paper had to be reduced. Further, there is a problem that the toner is hot-offset near the end of the recording material (near the end in the width direction) due to the rise in the end temperature. In order to cope with this problem, for example, Patent Document 3 proposes a configuration in which a good heat conducting member is arranged in the fixing nip so as to alleviate the temperature gradient in the axial direction (width direction) at the fixing nip.

  In order to increase the temperature uniformity in the axial direction at the fixing nip, it is preferable to use a good heat conduction member such as copper or aluminum as the heat transfer auxiliary member. However, because of the good heat conductivity when warming up from room temperature, There is a problem that the heat of the fixing belt is absorbed by the entire moving auxiliary member, the temperature rise of the fixing belt is delayed, and the warm-up time is delayed. Since the above-mentioned temperature rise at the end is longer than the warm-up time as a time axis, if a thin thermal resistance layer is provided on the surface of the heat transfer assisting member, a significant delay in the warm-up time can be prevented. This is a negative factor in ensuring the uniformity of the axial temperature.

  The fixing nip is a part for fixing the toner to the recording material by the applied pressure, and a sliding resistance is generated between the fixing belt and the heat transfer assisting member, so it is necessary to reduce the friction. Conventionally, a sliding contact sheet made of a material such as fluorine is provided on the surface of the heat transfer auxiliary member. Such means can lower the sliding resistance, but if the adhesion to the heat transfer auxiliary member is poor, the temperature gradient relaxation function may be impaired. Furthermore, as a thin-film sliding contact sheet, it is known that a low-torque can be maintained over a long period of time by holding a lubricant in a porous or fibrous sliding contact material. Because of the high heat conductivity. On the other hand, the non-porous material has a problem that the retention of the lubricant is poor, and the lubricant flows out from the end face of the fixing belt and the driving torque increases with time.

  Among these problems, the adhesion problem can be solved by coating the heat transfer auxiliary member with a low friction material, but for the retention of the lubricant, it is necessary to provide a lubricant supply member separately, Further, there is a problem that a low-viscosity lubricant tends to flow out from the end face of the fixing belt, and a high-viscosity lubricant does not stabilize the outflow from the lubricant supply member. In addition, the sliding contact surface at the fixing nip is liable to generate wear powder over time, and when the lubricant and the wear powder are mixed, there is a problem that the viscosity increases and the drive torque increases.

  In addition, the heat transfer auxiliary member is not necessary in any configuration. For example, in the low productivity (low ppm) model, the heat transfer in the axial direction can be achieved in the fixing belt. A configuration with only the nip forming member without providing the auxiliary member may be used.

  In view of the conventional problems as described above, the present invention prevents the wear powder generated by the rubbing between the fixing belt and the nip forming member from being mixed and impairs the lubrication function due to the increase in viscosity. It is an object of the present invention to provide a fixing device and an image forming apparatus that can suppress a phenomenon in which the torque generated in the above increases.

  In order to solve this problem, the present invention provides a rotatable fixing member, a heating source that heats the fixing member, a pressure member that is provided outside the fixing member and faces the belt, and an interior of the fixing member. And a nip forming member that forms a fixing nip by contacting the pressure member via the fixing member, and a plurality of recesses are formed on a contact surface of the nip forming member with the fixing member. A continuous recess having a continuous shape is formed, and the continuous recess is provided in a range where at least the nip forming member is in contact with the fixing member and pressed against the pressure member. To do.

  According to the present invention, the liquid component of the lubricant adhering to the inside of the fixing belt is caused to flow through the continuous concave portion having a shape in which a plurality of concave portions are continuous, and is circulated through the fixing belt, thereby increasing the torque over time. Can be suppressed.

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 two halogen heaters. 6 is a graph showing a relationship between a weight ratio of wear powder contained in a lubricant and a driving rotational torque of a fixing belt. It is a block diagram which shows the recessed part shape provided in the belt contact surface of a nip formation member or a heat transfer auxiliary member. It is a figure which shows another form of the recessed part shape provided in the nip formation member or the heat transfer auxiliary member belt contact surface. It is the elements on larger scale explaining the feature of the crevice shape. It is a figure which shows another form of the recessed part shape provided in the nip formation member or the heat transfer auxiliary member belt contact surface. It is a figure which shows another form of the recessed part shape provided in the nip formation member or the heat transfer auxiliary member belt contact surface. It is the elements on larger scale explaining the feature of the crevice shape. It is a figure which shows the whole recessed part shape provided in the belt contact surface. FIG. 9 is a front sectional view of a nip forming member in the configuration of FIG. 7 or FIG. 8. It is sectional drawing which shows the inclined surface provided in the upstream of the recessed part shape. It is a figure which shows another form of the recessed part shape provided in the nip formation member or the heat transfer auxiliary member belt contact surface. It is a figure which shows another form of the recessed part shape provided in the nip formation member or the heat transfer auxiliary member belt contact surface. It is a figure which shows another form of the recessed part shape provided in the nip formation member or the heat transfer auxiliary member belt contact surface. FIG. 2 is a schematic diagram illustrating an example of a fixing device including two halogen heaters as a heat source.

Hereinafter, embodiments of the present invention will be described in detail with reference to the 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 power supply of the printer main body is also connected to the secondary transfer roller 36, and a predetermined DC voltage (DC) or AC voltage (AC) is applied to the secondary transfer roller 36. It is like that.

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 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 includes a plurality of halogen heaters 23A and 23B (hereinafter also referred to as a first halogen heater 23A and a second halogen heater 23B) serving as a plurality of fixing heat sources (heating sources) disposed inside (in the loop). Heated by radiant heat. The halogen heater represents a radiant heat source as a fixing 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 a heat-resistant resin such as polyimide (PI) resin, polyether ether ketone (PEEK) resin, or liquid crystal polymer (LCP) resin. These are made of glass fiber reinforced. 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.

  In this embodiment, a heat transfer assisting member 27, which is also referred to as a heat equalizing member that relaxes the temperature gradient in the longitudinal direction of the fixing belt, is disposed so as to cover the surface of the nip forming member 24 that faces the inner peripheral surface of the belt. Further, it is possible to prevent heat from staying in the end region of the fixing belt 21 when passing small-size paper, and to positively move the heat in the width direction of the fixing belt 21, that is, in the longitudinal direction of the heat transfer auxiliary 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 substantially L-shaped cross section and composed of a first member 25A and a second member 25B and having a T-shaped cross section as a whole has an upright portion 25a that stands upright on the side opposite to the fixing nip N side. The halogen heaters 23A and 23B as fixing heat sources are arranged so as to be separated by the standing portion 25a, and also function as a partition member. 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. As is well known, the elastic layer of the pressure roller 22 is crushed at a location where the pressure roller 22 is pressed against the fixing belt 21 by the spring of the pressure means and is in pressure contact with the fixing belt 21, thereby fixing the fixing nip having a predetermined width. N is formed. 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, and a heat transfer assisting member 27. 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.

  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. For the purpose of forming the nip only, the heat transfer auxiliary means 27 is not necessarily required and can be omitted.

  FIG. 4 is a perspective view showing configurations of the nip forming unit and the halogen heater. As shown in FIG. 4 and as described above with reference to FIG. 2, 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 23A and a second halogen heater 23B are disposed on both sides of the standing portion 25a in the short direction. That is, the first halogen heater 23A and the second halogen heater 23B are shielded from each other by the standing portion 25a. Therefore, unlike the fixing device shown in FIG. 19, since the glass tubes are not heated when the heater is turned on, the heating efficiency is not lowered. Further, since the first halogen heater 23A and the second halogen heater 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 angle α, β (see FIG. 2) becomes an obtuse angle, and the heating efficiency can be improved.

  The cross-sectional shape of the stay member 25 is not limited to a substantially T shape. The halogen heaters 23A and 23B may be arranged so as to be partitioned from each other with the upright portion 25a interposed therebetween, and the first member 25A and the second member 25B may be curvedly extended in the longitudinal direction of the halogen heater. 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. In addition, this structure is one Embodiment, The arrangement | positioning of a halogen heater, 23A, 24B, and the shape of the stay member 25 are not limited.

  As can be seen from FIGS. 4 and 5, the first halogen heater 23A has a heat generating portion (a portion in which the filament is spirally wound and the light distribution is dense) at the center in the longitudinal direction, and is fixed. The central range of the belt 21 is heated and corresponds to a small size paper such as A4 vertical size. On the other hand, the second halogen heater 23B has heat generating portions at both ends in the longitudinal direction, and heats the side region of the fixing belt 21. For example, when passing a large size paper such as A3 vertical size, not only the first halogen heater 23A but also the second halogen heater 23B is turned on to correspond to the large size paper. The halogen heaters 23 </ b> A and 23 </ b> B are configured to generate heat by being output controlled by a power supply unit provided in the printer 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.

  In this way, the two halogen heaters 23A and 23B correspond to different sizes of paper. However, when different sizes of paper are used, the paper passing area is deprived of heat by the paper, while the non-paper passing area. In this embodiment, the heat transfer auxiliary member 27 made of a material having high heat conductivity is used to positively fix the fixing belt. The heat is transferred in the width direction 21, that is, in the longitudinal direction of the heat transfer auxiliary member 27, thereby eliminating the temperature non-uniformity in the longitudinal direction.

  However, since the heat transfer assisting member 27 is in sliding contact with the inner peripheral surface of the fixing belt 21, a friction coefficient is increased when a material having high thermal conductivity such as copper or aluminum is brought into sliding contact with the inner peripheral surface of the fixing belt 21 as it is. There are problems such as a large unit torque and a shortened device life. Therefore, it is also 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 subjected to a low friction process. Specifically, fluorine-based paint or coating such as PFA or PTFE is applied.

  Further, the sliding resistance is reduced by interposing a lubricant between the heat transfer assisting member 27 and the inner peripheral surface of the fixing belt 21. That is, as shown in FIG. 2, the lubricant 240 adheres to the inner peripheral surface of the fixing belt 21, and the fixing belt 21 is rotated by the rotation of the pressure roller 22, thereby It also adheres to the surface. As the lubricant, a fluorine oil such as polytetrafluoroethylene or silicone oil, an additive, and a grease containing a solid lubricant, PTFE, etc. as a thickener are used as the lubricant. Oil is used. Low torque is maintained by using semi-fluid or extremely soft grease having a consistency of about 0 to 0. Since the structure using fluorine oil as the base oil has higher heat resistance and is chemically stable than when silicone oil is used, even if there is a heat source in the fixing belt 21, volatilization loss and alteration can be suppressed. it can.

  FIG. 6 shows the relationship between the weight ratio (wt%) of the wear powder contained in the lubricant and the driving torque of the fixing belt 21. As the wear powder mixing ratio increases, the viscosity increases and the driving rotational torque increases. This is because the abrasion powder is added to the liquid base oil and the solid thickening component, so that the solid content is increased and the viscosity is increased.

  FIG. 7 is a view of the contact surface of the nip forming member 24 or the heat transfer assisting member 27 with the fixing belt 21 (hereinafter also referred to as a belt contact surface) viewed from the nip direction. “C” in the figure is the center (conveyance center) in the direction (belt width direction) orthogonal to the belt conveyance direction (vertical direction in the figure).

  The belt contact surface of the nip forming member 24 or the heat transfer assisting member 27 has a plurality of recesses (conveyance direction recesses) 51 extending in the belt transport direction and a non-transport direction recess 52 connecting the respective transport direction recesses 51 (contact). It has a continuous recess shape (continuous recess) formed by the recess). The bottom surface of the recess is configured to be approximately 0.05 to 0.5 mm lower than the belt contact surfaces 24c and 27a of the nip forming member 24 or the heat transfer assisting member 27 (so as to be recessed from the belt contact surface) and does not directly contact the fixing belt 21. It has a configuration. The concave portions 51 and 52 are previously formed on the nip forming member 24 or the heat transfer auxiliary member 27 by press working or the like, and in the case of resin, a sliding layer may be applied by coating or the like after forming an uneven surface on the mold. You may give an uneven | corrugated process by press work after providing a layer.

  As described above, the lubricant 240 adhering to the inside of the fixing belt 21 reduces the contact friction resistance with the nip forming member 24 or the heat transfer assisting member 27 and suppresses the wear generated from both members. However, wear of the members cannot be completely prevented due to long-term contact friction, and wear powder is generated and circulates in the fixing belt 21 (inner peripheral surface) and simultaneously mixes with the lubricant 240. The mixed and thickened lubricant 240 accumulates when entering the concave portion 51 in the conveyance direction, but the liquid component of the base oil easily flows due to the heat from the fixing belt 21, and the low friction of the sliding portion contributes to the liquid component. Can be maintained. Further, the wear generated in the fixing belt 21 is not uniform in the longitudinal direction. For example, the wear is likely to occur in a place where a load is high due to a high load at the nip portion, a large amount of wear, a paper passing paper size, and a paper thickness. The place where wear occurs is not specified by the user's usage of the device, environment, or conditions, so it is difficult to predict where the wear powder accumulates. Therefore, in order to reflow the lubricant at the place where the wear powder is accumulated, the liquid component of the lubricant 240 is caused to flow in the longitudinal direction (belt width direction) in the non-conveyance direction recess (connection recess) 52. Thereby, the lubricant can be circulated inside the fixing belt, and an increase in torque over time can be suppressed.

  FIG. 8 is a view showing another embodiment of the concave shape provided on the belt contact surface of the nip forming member 24 or the heat transfer assisting member 27. This form is an example in which the longitudinal recess 51B is inclined symmetrically about the conveyance center C (disposed obliquely). A plurality of concave portions (longitudinal concave portions 51B) are connected by a communication concave portion 52 to form a continuous concave portion.

  As shown in FIG. 9, the inclination angle of the longitudinal recess 51B is as follows. When the longitudinal recess width is d, the recess spacing is e, the recess transport direction length is f, and the tilt angle of the recess with respect to the transport direction is θ, tan θ> By setting (d + e) / f, the inner surface of the fixing belt 21 always passes through the longitudinal recess 51B in the belt conveyance direction, so that the abrasion powder only at a specific portion is not collected, and the lubricant 240 is also specified. The structure is such that the wear is not partially accelerated due to lack of locations. Further, by increasing the conveyance direction length f than the conveyance direction contact width g between the fixing belt 21 and the nip forming member 24 or the heat transfer assisting member 27, the lubricant 240 can easily flow into the inner portion, and a low friction state is obtained. be able to.

  Still another embodiment of the belt contact surface of the nip forming member 24 or the heat transfer assisting member 27 is shown in FIGS. In this embodiment, the belt contact surfaces 24c, 27a of the nip forming member 24 or the heat transfer assisting member 27 have a plurality of polygonal shapes, in this example, a rhombus shape which is an example of a polygon, and the belt contact surfaces 24c, The continuous recessed part 53 is comprised by the continuous concave surface so that 27a may be enclosed. In this example, the rhombic belt contact surfaces 24c and 27a are arranged such that the corners of the rhombus face the belt moving direction and the direction perpendicular to the belt moving direction, respectively. In this embodiment, the plurality of concave portions constituting the continuous concave portion 53 have a shape extending in an oblique direction so as to repeat branching and merging toward the downstream side in the belt moving direction.

  The inclination angle of the recess 53 with respect to the belt conveyance direction is smaller in θ2 in the configuration in FIG. 11 than in θ1 in the configuration in FIG. 10, and the contact angle in the conveyance direction of the fixing belt is smaller. This is desirable because it can be made smaller. Further, in the configuration of FIG. 10, the lubricant easily flows in the longitudinal direction (the width direction of the fixing belt 21), so that the lubricant 240 easily flows out of the fixing belt 21.

  Therefore, as shown in FIG. 12, the concave portion width j on the side toward the conveyance center may be made wider than the concave width k on the outer side of the conveyance center so that the lubricant 240 does not easily flow to the outside. The bold arrows in the figure indicate the direction of movement of the lubricant along the vertical recess. 12 shows the configuration of FIG. 11, the configuration of FIG. 10 is also the same.

  FIG. 13 shows the entire longitudinal direction (width direction of the fixing belt 21). As can be seen from FIG. 13, the entire longitudinal direction is symmetrical about the transport center C. Although FIG. 13 shows the configuration of FIG. 10, the configuration of FIG. 11 is also the same.

  FIG. 14 is a front sectional view including the conveyance direction recess 51 and the longitudinal recess 51B of the nip forming member 24 in the configuration of FIG. 7 or FIG. The fixing belt 21 is conveyed in contact with the nip forming member 24 while pressure is applied. At that time, the fixing belt 21 has a concave portion due to the relationship between the length of the concave portion (the length of the concave portion in the belt conveyance direction or the vertical direction is the length) and the width of the concave portion (the size is a direction perpendicular to the length). When entering, the corners of the recesses in the length direction and the fixing belt 21 may easily come into contact with each other, which not only increases the frictional resistance but also increases wear powder. Therefore, as shown in FIG. 15, an increase in frictional resistance can be prevented by providing an inclined surface 54 at a downstream portion in the length direction of the recess. As a result, it is possible to maintain a low coefficient of friction and suppress an increase in wear powder.

Still another form of the belt contact surface of the nip forming member 24 or the heat transfer assisting member 27 is shown in FIGS.
In the form shown in FIG. 16, the belt contact surfaces 24c and 27a of the nip forming member 24 or the heat transfer assisting member 27 have a polygonal shape, and the continuous recess 53 is continuous so as to surround the belt contact surfaces 24c and 27a. Consists of a concave surface. The polygonal shape may be a square or rectangular quadrangle, or other polygons such as a pentagon or a hexagon. In this example, polygonal belt contact surfaces 24c and 27a are arranged side by side in a fixing belt moving direction and a direction orthogonal to the fixing belt moving direction.

  In the form shown in FIG. 17, the belt contact surfaces 24c and 27a of the nip forming member 24 or the heat transfer assisting member 27 have a circular shape, and a concave surface in which continuous concave portions 53 are continuous so as to surround the belt contact surfaces 24c and 27a. It consists of The belt contact surfaces 24c and 27a are not limited to a circle but may be an ellipse. In the case of an ellipse, it may be arranged obliquely. In this example, the belt contact surfaces 24c and 27a having a circular shape or an elliptical shape are arranged side by side in a fixing belt moving direction and a direction orthogonal to the fixing belt moving direction.

  FIG. 18 is a view showing still another form of the belt contact surface of the nip forming member 24 or the heat transfer assisting member 27. In this embodiment, the belt contact surfaces 24c and 27a of the nip forming member 24 or the heat transfer assisting member 27 have a circular shape, and the positions of the belt contact surfaces 24c and 27a are perpendicular to the belt conveyance direction (width direction). ) Are arranged in a straight line, and are shifted laterally (in the width direction) in a direction (width direction) orthogonal to the belt conveyance direction. The belt contact surfaces 24c and 27a are arranged to be shifted in the direction orthogonal to the belt conveying direction and provided with the shift amounts h and i so that the lubricant 240 does not easily flow to the outside. The belt contact surfaces 24c and 27a may be elliptical.

  In the configuration having the polygonal belt contact surfaces 24c and 27a shown in FIG. 16, the belt contact surfaces 24c and 27a are shifted in the direction (width direction) perpendicular to the belt conveying direction as shown in FIG. It is also possible to adopt the configuration described above.

  In each of the embodiments described above, the continuous recess 53 is provided at least within a range where the nip forming member 24 or the heat transfer auxiliary member 27 is in contact with the fixing belt 21 and pressed against the pressure roller 22 (fixing belt). 21 may be provided outside the range that comes into contact with the pressure roller 21 and is pressed by the pressure roller 22).

Further, the upstream side of the continuous recess 53 in the fixing belt moving direction may be provided to the upstream side of the range where the nip forming member 24 or the heat transfer auxiliary member 27 contacts the fixing belt 21.
When the heat transfer assisting member 27 is provided, each of the recesses is provided not on the nip forming member 24 but on the surface of the heat transfer assisting member 27 (surface on the fixing belt contact surface side).

  As described above, in the present invention, the continuous concave portion is formed on the contact surface of the nip forming member or the heat transfer assisting member with the fixing member, and the continuous concave portion is pressed by at least the nip forming member contacting the fixing member. By being provided within the range that is pressed by the member, it is possible to prevent a decrease in lubricity due to an increase in viscosity due to contamination of wear powder generated by rubbing between the fixing member and the nip forming member or the heat transfer auxiliary member, and fixing. An increase in torque for driving the member can be suppressed for a long time.

Although the present invention has been described based on the illustrated examples, the present invention is not limited to this and can be appropriately changed within the scope of the present invention.
As the fixing device and the image forming apparatus, any configuration can be adopted as long as the present invention is applicable. For example, the heating source of the fixing device is not limited to the halogen heater, and an appropriate heating unit can be employed. The image forming apparatus is not limited to a printer, and may be a copier, a facsimile machine, or a multifunction machine having a plurality of functions.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 4C, 4K, 4M, 4Y Image forming part 20 Fixing apparatus 21 Fixing belt (fixing member)
22 Pressure roller (Pressure member)
23 Halogen heater (heating source)
24 Nipping member 24c Fixing belt contact surface 25 Stay member 27 Heat transfer assisting member 27 Fixing belt contact surface 28 Reflecting member 51 Conveyance direction recess 51B Vertical recess 52 Non-conveyance recess (connection recess)
53 Continuous recess 54 Inclined surface C Conveying center N Fixing nip P Paper (recording material)
θ, θ1, θ2 Inclination angle

JP 2010-32631 A JP 2010-78839 A JP2015-99352A

Claims (13)

A rotatable fixing member, a heating source for heating the fixing member, a pressure member provided outside the fixing member and opposed to the belt, and disposed inside the fixing member via the fixing member. In a fixing device including a nip forming member that contacts a pressure member to form a fixing nip,
On the contact surface of the nip forming member with the fixing member, a continuous recess having a shape in which a plurality of recesses are continuous is formed,
The fixing device is characterized in that the continuous concave portion is provided in a range where at least the nip forming member comes into contact with the fixing member and is pressed by the pressure member.   The fixing device according to claim 1, wherein the continuous recess includes a plurality of recesses extending in the fixing member moving direction and a communication recess connecting the plurality of recesses. The continuous recess comprises a plurality of recesses arranged obliquely with respect to the fixing member moving direction, and a communication recess connecting the plurality of recesses,
The plurality of concave portions are arranged obliquely so that a downstream side in the fixing member moving direction faces a conveyance center which is a central portion in a direction orthogonal to the fixing member moving direction. The fixing device according to 1. When the width of the concave portions is d, the interval between the concave portions is e, the length of the concave portions in the fixing member moving direction is f, and the inclination angle of the concave portions with respect to the fixing member moving direction is θ,
tan θ> (d + e) / f
The fixing device according to claim 3, wherein   5. The fixing device according to claim 1, wherein the plurality of recesses have inclined end surfaces on the downstream side in the fixing member moving direction. 6. The contact surface of the nip forming member with the fixing member is provided in a plurality of polygonal shapes,
The fixing device according to claim 1, wherein the continuous concave portion is configured by a concave surface that is continuous so as to surround the plurality of polygonal shapes. The contact surface of the nip forming member with the fixing member is provided in a plurality of rhombus shapes,
The fixing device according to claim 6, wherein the continuous concave portion provided around the rhombus shape is provided so as to repeat branching and merging toward the downstream in the fixing member moving direction.   The contact surface of the nip forming member with the fixing member is provided in a plurality of quadrangular shapes, and the quadrangular shapes are arranged side by side in a direction orthogonal to the fixing member moving direction and the fixing member moving direction. The fixing device according to claim 6. The contact surface of the nip forming member with the fixing member is provided in a plurality of circular or elliptical shapes,
The fixing device according to claim 1, wherein the plurality of concave portions are configured as concave surfaces that are continuous so as to surround the plurality of circular shapes or elliptical shapes.   The plurality of circular shapes or elliptical shapes are arranged side by side in a direction orthogonal to the fixing member moving direction, and are shifted in the direction orthogonal to the fixing member moving direction in the fixing member moving direction. The fixing device according to claim 9, characterized in that:   The upstream side of the continuous concave portion in the fixing member moving direction is provided up to an upstream side of a range where the nip forming member is in contact with the fixing member. The fixing device according to 1.   When the heat transfer auxiliary member having high thermal conductivity is provided on the contact surface side of the nip forming member with the fixing member, the concave portion is not the nip forming member but the contact surface of the heat transfer auxiliary member with the fixing member. The fixing device according to claim 1, wherein the fixing device is provided on a side surface. An image forming apparatus comprising the fixing device according to claim 1.

Images