JP2019159251A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device capable of suppressing a temporal increase in torque in a nip part of a fixing belt at a low cost and prolonging service life thereof even when mounted on a high production image forming apparatus.SOLUTION: The fixing device includes an endless fixing belt 21 which is rotatably provided, a pressure member 22 which is rotatably provided and pressurizes the fixing belt 21 from an outer peripheral side, a nip forming member 24 which presses the fixing belt 21 from an inner peripheral side through a soaking member 29 made of metal and forms a fixing nip part N between the fixing belt 21 and the pressure member 22, and a heat source 23 which heats the fixing belt 21. In the fixing nip part N, a lubricant is interposed between the soaking member 29 and the fixing belt 21. The soaking member 29 has a film 40 on a contact surface with the fixing belt 21 and a plurality of recesses 50. The recesses 50 have an inclined surface whose inclination direction and inclination angle are different between an upstream side and a downstream side in the rotational direction of the fixing belt.SELECTED DRAWING: Figure 2

Description

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

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a toner image is formed on an image carrier based on image information, and the toner image is transferred onto a recording medium such as paper or an OHP sheet. Thereafter, the unfixed toner image carried on the recording medium is fixed on the recording medium by the fixing device.

  The fixing device is provided with a fixing rotator constituted by opposing rollers or belts, or a combination thereof. A recording sheet as a recording medium is sandwiched at a nip portion, and a toner image is placed on the recording sheet by heat and pressure. To settle.

  A fixing device having a thin fixing belt is known. By providing a thin fixing belt with a low heat capacity, the energy required to heat the fixing belt can be greatly reduced, and the warm-up time (predetermined temperature that can be printed from room temperature, such as when the power is turned on ( The time required until the (reload temperature)) and the first print time (the time from when a print request is received to when the print operation is performed and the paper discharge is completed) can be shortened.

  However, when the fixing belt is thinned for the purpose of shortening the warm-up time or the first print time, the heat conduction is not good due to the thin belt, so that the temperature difference increases depending on the location of the fixing belt when heated by a heat source. . For example, an excessive temperature rise in a non-sheet passing region at the end in the width direction of the fixing belt may cause a problem.

  Further, when the sliding resistance between the nip forming member and the fixing belt is large, the fixing belt may not be rotated by the pressure roller and may slip. When such a slip occurs, the recording medium stops and an excessive amount of heat is generated, thereby causing a hot offset. In addition, the temperature distribution of the fixing belt itself becomes abnormal, and the fixing quality deteriorates.

In order to keep the sliding resistance between the nip forming member and the fixing belt low and to maintain high heat equalization performance against these problems, a heat equalizing member made of a metal having high heat conductivity is provided on the inner peripheral side of the fixing belt. In addition, a configuration is proposed in which a dispersion plating film of a fluororesin is formed on the surface of the heat equalizing member facing the inner peripheral surface of the fixing belt (see, for example, Patent Document 1).
By using a soaking member having high thermal conductivity for the nip forming member that forms the nip part or a part of the nip forming member, it is possible to diffuse heat and suppress an excessive temperature rise.

On the other hand, in order to reduce the frictional load between the nip forming member or the soaking member and the fixing belt, it is common to apply a lubricant to the inner peripheral surface side of the nip portion of the fixing belt.
However, since the lubricant applied to the inner peripheral surface of the fixing belt is scraped off by the nip forming member at the entrance and exit of the fixing nip, the amount of lubricant adhering to the inner peripheral surface of the fixing belt decreases with time. Since the friction load increases, the fixing belt may be damaged or the member that rotates the fixing belt may be damaged.

On the other hand, Patent Document 2 discloses an image heating apparatus in which a lubricant diffusion portion having a concavo-convex shape is formed on a surface on the recording material intrusion side of a support member that supports a flat heater. .
Further, in Patent Document 3, the surface unevenness has a groove shape having continuity, and the groove shape having the continuity has a predetermined interval with respect to the sliding direction and the sliding direction on the surface to be contacted. Provided with a linear inclination from the end in the parallel direction to the center line in the sliding direction, and the 10-point average roughness Rz in the sliding direction of the surface is 10-point average roughness in the direction perpendicular to the sliding direction. A sliding member for an electrophotographic apparatus having a thickness larger than the surface roughness Rz is disclosed.
Furthermore, Patent Document 4 includes a sheet-like sliding member as a member interposed between the resin film tubular body and the pressing member, and the sheet-like sliding member includes at least a sliding surface containing a heat-resistant resin. There is disclosed a fixing device comprising a non-porous sheet and a non-porous sheet provided on a substrate having irregularities on the surface.

  In addition to such an uneven surface, the patent document 5 has a first member such as a film guide member and a second member such as a fixing film that slides on the first member. A heating device is disclosed in which a plurality of independent recesses for holding a lubricant are provided in a sliding portion of the first member with the second member.

In the technology for forming the unevenness on the sliding member provided in the sliding portion to hold the lubricant, reducing the sliding resistance, and realizing sliding with a low torque, the shape of the unevenness due to wear over time (for example, (Ra value) changes. If the amount of the lubricant that can be retained is reduced due to wear of the unevenness over time, the torque is increased.
Further, since the amount of the lubricant retained in the concave portion decreases with time unless there is a mechanism for recovering the lubricant, the torque similarly increases with time.

In order to achieve both the optimization of the shape of the unevenness and the suppression of the torque increase, there are problems that the design conditions are extremely narrow and the manufacturing cost of the parts is increased.
In particular, as a fixing device applied to a high-speed machine with high productivity, it is preferable that the lifetime is low and the cost is low, but it is difficult to achieve both of them in the above-described conventional technology.

  Accordingly, the present invention provides a fixing device that can suppress an increase in torque over time at the nip portion of the fixing belt at a low cost and can achieve a long life even when mounted on a high-production image forming apparatus. With the goal.

  In order to solve the above problems, a fixing device of the present invention includes an endless fixing belt that is rotatably provided, a pressure member that is rotatably provided and presses the fixing belt from the outer peripheral side, and a metal. A nip forming member that presses the fixing belt from the inner peripheral side through a heat equalizing member and forms a fixing nip portion between the fixing belt and the pressure member, and a heat source that heats the fixing belt, In the fixing nip portion, a lubricant is interposed between the heat equalizing member and the fixing belt, and the heat equalizing member has a film on a contact surface with the fixing belt, and has a plurality of concave portions. The concave portion has inclined surfaces having different inclination directions and inclination angles on the upstream side and the downstream side in the rotation direction of the fixing belt.

  According to the present invention, it is possible to provide a fixing device that can suppress an increase in torque over time at a nip portion of a fixing belt at low cost and can achieve a long life even when mounted on a high-production image forming apparatus. Can do.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus including a fixing device according to the present invention. 1 is a cross-sectional view illustrating a configuration of an embodiment of a fixing device according to the present invention. It is sectional drawing (A) and a perspective view (B) which show an example of a soaking | uniform-heating member typically. It is sectional drawing (A) and a top view (B) which show an example of the recessed part of a soaking | uniform-heating member. It is a top view explaining an example of arrangement | positioning of the recessed part of a soaking | uniform-heating member. 6 is a graph showing an effect of an embodiment of a fixing device according to the present invention. 6 is a graph showing an effect of an embodiment of a fixing device according to the present invention. 6 is a graph showing an effect of an embodiment of a fixing device according to the present invention. 1 is a cross-sectional view illustrating a configuration of an embodiment of a fixing device according to the present invention. 1 is a cross-sectional view illustrating a configuration of an embodiment of a fixing device according to the present invention.

  Hereinafter, a fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.

  FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus including a fixing device according to the present invention, and shows an example in which the image forming apparatus is applied to a color laser printer.

  In FIG. 1, the image forming apparatus 1 includes a bottle storage unit 2, a transfer device 3, four image forming units 4 </ b> Y, 4 </ b> M, 4 </ b> C, and 4 </ b> K, a paper feeding unit 10, and a fixing device 20. .

The four image forming units 4Y, 4M, 4C, and 4K are provided in the center of the apparatus main body of the image forming apparatus 1. Each of the image forming units 4Y, 4M, 4C, and 4K contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. The configuration is the same except that.
Specifically, each of the image forming units 4Y, 4M, 4C, and 4K has a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoconductor 5, and a surface of the photoconductor 5. A developing device 7 that supplies toner and a cleaning device 8 that cleans 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 denoted by reference numerals. In the other image forming units 4 </ b> Y, 4 </ b> M, and 4 </ b> C, The reference numerals are omitted.

  Under the image forming units 4Y, 4M, 4C, 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, 4M, 4C, 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 FIG.

  Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 with each photoconductor 5 to form a primary transfer nip. Each primary transfer roller 31 is connected to a power source, and a predetermined direct current voltage (DC) and / or alternating current 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, a power source is connected to the secondary transfer roller 36 so that a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the secondary transfer roller 36. It has become.

  The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 30. The waste toner transfer hose extending from the belt cleaning device 35 is connected to the entrance of the waste toner container.

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

  A lower part of the printer main body is provided with a paper feeding unit 10 that stores a recording medium P such as transfer paper, a paper feeding roller 11 that carries the recording medium P out of the paper feeding unit 10, and the like. Here, the recording medium P includes, in addition to plain paper, thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. A manual paper feed mechanism may be provided.

  In the printer main body, a conveyance path R is provided for discharging the recording medium P from the paper supply unit 10 through the secondary transfer nip to the outside of the apparatus. As conveying means for conveying the recording medium P to the secondary transfer nip, in the conveying path R, upstream of the position of the secondary transfer roller 36 in the conveying direction of the recording medium P (hereinafter simply referred to as “conveying direction”). A pair of registration rollers 12a and 12b is provided.

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

FIG. 2 is a diagram illustrating the configuration of the fixing device 20.
As shown in FIG. 2, the fixing device 20 according to the present invention includes an endless fixing belt 21 that is rotatably provided, and a pressure member that is rotatably provided and pressurizes the fixing belt 21 from the outer peripheral side. The nip forming member 24 forms a fixing nip portion N between the fixing belt 21 and the pressure member 22 by pressing the fixing belt 21 from the inner peripheral side via a pressure roller) 22 and a soaking member 29 made of metal. And a heat source 23 for heating the fixing belt 21.
Furthermore, a stay 25 as a supporting member, a reflecting member 26, and a separating member 28 are provided.

In the fixing nip portion N, a lubricant is interposed between the heat equalizing member 29 and the fixing belt 21.
As will be described in detail later, the heat equalizing member 29 has a coating 40 on the contact surface with the fixing belt 21 and a plurality of recesses 50 formed as shown in FIG. There are inclined surfaces with different inclination directions and inclination angles on the upstream side and the downstream side in the rotation direction. (In FIG. 2, the recess 50 is omitted.)

  The fixing belt 21 is a thin and flexible endless belt (or film), and is provided so as to be rotatable in the direction of the arrow in FIG. Here, the endless shape means a state in which both ends of the belt are joined and no joint exists.

  The fixing belt 21 has a thin and small-diameter laminated structure in order to reduce the heat capacity, and a base material layer and a release layer are sequentially laminated from the inner peripheral surface side, and the total thickness is The diameter is set to 1 mm or less, and the diameter is set to 20 to 40 mm. This is an exemplification, and the present invention is not limited to this.

  The base material layer of the fixing belt 21 has a layer thickness of 20 to 50 μm. For example, a metal material such as nickel or SUS (stainless steel), or a resin material such as polyimide (PI) or polyamideimide (PAI) is used. It is formed. This is an exemplification, and the present invention is not limited to this.

  The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm and is formed of a material such as ethylene tetrafluoride / perfluoroalkyl vinyl ether copolymer resin (PFA) or tetrafluoroethylene resin (PTFE). Yes. By providing such a release layer, the fixing belt 21 is secured with respect to the toner image T on the recording medium P. This is an exemplification, and the present invention is not limited to this. Moreover, the mold release means that the bonded objects are peeled off, and the mold release property means the ease of peeling between the objects.

  There may be an elastic layer formed of silicone rubber or the like between the base material layer and the release layer of the fixing belt 21. When there is no elastic layer, the heat capacity is reduced and the fixability is improved. There is a possibility that a defect in which luster unevenness (coconut skin image) remains on the part remains. Here, the cocoon skin image means an image in which a number of minute irregularities are formed on the surface. In order to improve this, an elastic layer of silicone rubber is provided to 100 μm or more. Due to the deformation of the elastic layer, minute irregularities are absorbed, and the cocoon skin image can be improved.

  The pressure roller 22 is a roller having a diameter of about 20 to 40 mm provided so as to contact the outer peripheral surface of the fixing belt 21 at the position of the fixing nip portion N and press the fixing belt 21 from the outer peripheral side. In the pressure roller 22, an elastic layer 22b is formed on a core bar 22a having a heat-resistant solid structure, and a thin release layer 22c is formed on the surface of the elastic layer 22b. This is an exemplification, and the present invention is not limited to this.

  The pressure roller 22 is pressed against the fixing belt 21, the heat equalizing member 29, and the nip forming member 24 by a pressure mechanism such as a spring, so that the elastic layer 22b is crushed. Thereby, in the fixing device 20, a desired fixing nip portion N in which the recording medium P is conveyed is formed between the pressure roller 22 and the fixing belt 21.

  The pressure roller 22 is rotationally driven in a direction indicated by an arrow in FIG. 2 by a driving mechanism such as a motor provided in the image forming apparatus main body, and transmits a driving force to the fixing belt 21 at the fixing nip portion N. Is driven to rotate.

  The elastic layer 22b of the pressure roller 22 is formed of a material such as foamable silicone rubber, silicone rubber, or fluororubber, and has a thickness set to 100 μm or more. Further, the release layer 22c of the pressure roller 22 is formed of a material such as PFA or PTFE. This is an exemplification, and the present invention is not limited to this.

  Since the elastic layer 22b has a thickness of 100 μm or more, the fixing device 20 absorbs minute irregularities on the surface of the fixing belt 21 due to elastic deformation of the elastic layer 22b and fixes the color image on the recording medium P. Generation of a skin image can be prevented.

  The pressure roller 22 may be a hollow roller, and may have a heat source such as a halogen heater inside the pressure roller 22. The elastic layer 22b may be solid rubber, but if there is no heater inside the pressure roller 22, sponge rubber may be used. Use of sponge rubber is more preferable because heat insulation is enhanced and heat of the fixing belt 21 is not easily taken.

As the heat source 23 for heating the fixing belt 21, a halogen heater, an IH heater, a resistance heating element, a carbon heater, or the like can be used.
Hereinafter, an aspect in which the heat source 23 is a halogen heater will be described.

Both ends of the halogen heater 23 are fixed to the side plate of the fixing device 20 and are configured to generate heat when output is controlled by a power supply unit provided in the printer body.
The halogen heater 23 includes a halogen lamp in which a glass tube containing a gas containing xenon or krypton as a main component (hereinafter also referred to as “enclosed gas”) as an inert gas. Xenon or krypton, which is a component of the enclosed gas, is a gas having a higher molecular weight than argon.

  The halogen heater 23 is provided in the fixing belt 21 so as to face a reflection member 26 described later, and directly heats the fixing belt 21 from the inner peripheral side at a place other than the fixing nip portion N by generating radiant heat. It is configured as follows.

  As a result, the fixing device 20 improves the heating efficiency of the fixing belt 21 by the halogen heater 23, so that it is excellent in energy saving and can shorten the first print time. The first print time means a time required for printing the first sheet on the recording medium P after receiving the print start instruction and discharging the recording medium P to the outside of the image forming apparatus 1.

The nip forming member 24 is disposed so as to press the pressure roller 22 from the inner peripheral side of the fixing belt 21 and form a fixing nip portion N between the fixing belt 21 and the pressure roller 22.
The nip forming member 24 is non-rotating and is in contact with the inner peripheral surface of the fixing belt 21 via a heat equalizing member 29 described later, and slides indirectly with the inner peripheral surface of the fixing belt 21.

Note that a lubricant is interposed in order to reduce wear of the fixing belt 21 and the heat equalizing member 29 that is pressed by the nip forming member 24 and contacts the inner peripheral surface.
As the lubricant, those containing a fluorine compound or a silicon compound are preferable, and examples thereof include fluorine oil and fluorine grease containing a fluorine compound, fluorine grease using fluorine particles as a thickener, and silicone grease.

  In the configuration of FIG. 2, the fixing nip portion N has a flat shape, but may have a curved shape or other shapes. When the curved fixing nip portion N is formed, the separation direction of the recording medium P with respect to the fixing belt 21 is improved by making the discharge direction of the recording medium tip closer to the pressure roller 22, so that jamming is suppressed. The

  Since the shape of the nip forming member 24 is complicated, it is desirable that the nip forming member 24 is an injection-molded product of a heat-resistant resin. desirable. This is an exemplification, and the present invention is not limited to this.

  Since the nip forming member 24 is made of a heat-resistant resin material, the fixing device 20 can prevent the deformation of the nip forming member 24 due to heat in the toner fixing temperature region and ensure a stable state of the fixing nip portion N. The output image quality can be stabilized.

  The nip forming member 24 is provided such that the axial direction of the fixing belt 21 is the longitudinal direction, and a contact portion 24b protruding from the base portion 24a in the thickness direction of the recording medium P (hereinafter simply referred to as “thickness direction”). Is fixedly supported by the stay 25 by contacting the stay 25.

  By fixing and supporting the nip forming member 24 to the stay 25, the fixing device 20 is prevented from being bent by the pressure by the pressure roller 22, and has a uniform nip width in the longitudinal direction. Obtainable.

  The nip forming member 24 is formed smaller than the stay 25 in order to ensure the mechanical strength of the stay 25.

  Furthermore, it is assumed that a protrusion is formed on the nip exit side of the nip forming member 24. This protruding portion is not in contact with the pressure roller 22 via the fixing belt 21, and the recording medium P after fixing at the fixing nip portion N is lifted from the fixing belt 21, thereby improving the separation of the recording medium P. It is something to enhance.

  The stay 25 reinforces and supports the nip forming member 24 that forms the fixing nip portion N, and is held and fixed to the side plate at both ends in the axial direction and positioned. The stay 25 presses the pressure roller 22 via the nip forming member 24, the heat equalizing member 29, and the fixing belt 21, so that the nip forming member 24 receives the pressure of the pressure roller 22 at the fixing nip portion N. Therefore, the occurrence of defects that cause large deformations is suppressed.

  The stay 25 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron alloy in order to satisfy the above-described function, but may be formed of a resin material.

  The reflection member 26 is fixed between the stay 25 and provided between the stay 25 and the halogen heater 23. The reflecting member 26 is a concentric circle centering on the halogen heater 23 that reflects the radiant heat and radiant light (hereinafter simply referred to as “radiant heat”) emitted from the halogen heater 23 toward the reflecting member 26 toward the fixing belt 21. The reflecting surface 26a is formed on the surface. Further, since the reflecting member 26 is directly heated by the halogen heater 23, the reflecting member 26 is formed of a metal material having a high melting point.

  The reflection surface 26a of the reflection member 26 has a reflectance set to 90% or more. In addition, this is an illustration and this invention is not limited to this.

  By providing the reflection member 26, the fixing device 20 can increase the radiant heat applied to the fixing belt 21, and can efficiently heat the fixing belt 21. Further, since the fixing device 20 can suppress the radiant heat from the halogen heater 23 from being transmitted to the stay 25 and the like, energy saving can be achieved. Here, instead of providing the reflecting member 26, the same effect can be obtained by subjecting the surface of the stay 25 to heat insulation treatment or mirror treatment.

  The separation member 28 is fixed to the fixing device 20 and separates the recording medium P from the surface of the fixing belt 21 by coming into contact with the recording medium P on which the color image is fixed at the fixing nip N.

Hereinafter, the soaking member 29 will be described.
The heat equalizing member 29 is a heat conductive member made of metal disposed so as to cover the nip side surface of the nip forming member 24, and the metal is a metal material having high heat conductivity such as copper, aluminum, aluminum alloy, or the like. Is mentioned.

When the base material of the fixing belt 21 is a metal such as nickel or SUS, the soaking member 29 has a copper-based material (for example, thermal conductivity 381 W / m · K) or an aluminum-based material (for example, thermal conductivity 236 W / m). -It is preferable to use a material having a high thermal conductivity such as K).
When a resin material such as polyimide (thermal conductivity 0.29 W / m · K) is used for the fixing belt base material, an iron-based SUS material (for example, thermal conductivity 19 W / m · K) is used as the soaking member 29. Metal materials such as) can also be used.

  By providing the heat equalizing member 29, for example, when small-size paper is continuously passed, even if the fixing member temperature rises in the vicinity of the end of the paper passing area or in the non-paper passing area, the heat in the longitudinal direction ( It can be efficiently moved and diffused in the paper width direction), and heat is hardly accumulated on the surface. Therefore, it is possible to effectively suppress the so-called edge temperature rise during continuous paper feeding.

The heat equalizing member 29 has a film 40 on the contact surface with the fixing belt 21.
As the film | membrane 40, what contains a fluororesin or a silicone resin is mentioned, for example.
The contact surface that slides with the fixing belt 21 is preferably provided with irregularities to hold the lubricant.

In the present embodiment, an example in which the film 40 is formed by a fluororesin coat (polyimide amide system / PTEF + PAI) will be described. The film 40 preferably has a surface roughness of Ra = 0.1 to 5.0 depending on the coating conditions (coating amount, temperature, etc.), but is not limited thereto.
A known method can be applied to the coating conditions in which the Ra value is in a desired range. For example, a method of spraying a fluororesin on the metal material of the heat equalizing member 29 (spray coating) can be used. .
Moreover, it can be set as the dispersion plating film | membrane of the fluororesin described in patent document 1 (Unexamined-Japanese-Patent No. 2017-125922). The dispersion plating film is, for example, one obtained by dispersing a fluororesin in a Ni—P matrix and precipitation hardening at 280 to 320 ° C.

In the conventional example in which the means for retaining the lubricant is only the unevenness of the film, when the surface roughness value of the unevenness of the film 40 is small (for example, Ra <0.1), the amount of lubricant retained is small and the torque is reduced. If the surface roughness value is large (for example, Ra> 5.0), even if the amount of lubricant retained is sufficient, the progress of wear over time will be accelerated, and the torque will increase significantly over time. Will occur.
In particular, in a fixing device mounted on a system having a high rubbing speed, such as a high-production image forming apparatus (high-speed machine), the range in which both the wear amount and the torque increase are reduced is extremely low. It is difficult to deal with unevenness alone.

In contrast, in the fixing device according to the present embodiment, as shown in FIG. 3, a plurality of concave portions 50 are formed as a structure different from the concave and convex portions formed on the film 40 of the heat equalizing member 29.
FIG. 3A is a cross-sectional view of the soaking member 29, and FIG. 3B is a perspective view of the soaking member 29.
By providing the recess 50, even when the coating 40 is worn and the amount of lubricant retained decreases, the decrease in the supply amount can be suppressed, and the increase in torque over time can also be suppressed.
Thereby, the range of Ra of the applicable film | membrane 40 can be expanded, a yield can improve and manufacturing cost can be reduced. That is, even when the surface roughness Ra of the coating 40 is less than 0.1 or more than 5.0, the effect of extending the life can be obtained by suppressing the torque increase with time.

The recess 50 has inclined surfaces having different inclination directions and inclination angles on the upstream side and the downstream side in the rotation direction of the fixing belt 21.
An example of the recess 50 is shown in FIG. 4A is a cross-sectional view of the heat equalizing member 29 in the rotation direction of the fixing belt 21, and FIG. 4B is a top view of the heat equalizing member 29.

The “inclined surface” of the recess 50 is a surface that is not parallel or perpendicular to the contact surface of the heat equalizing member 29 with the fixing belt 21.
Of the wall surfaces constituting the recess 50, a surface that is continuous along the rotation direction of the fixing belt 21 is composed of at least two inclined surfaces, and the inclination direction and the inclination angle are upstream and downstream of the two inclined surfaces. The cross-sectional shape is not limited to that shown in FIG.
For example, a flat surface may be provided between the upstream inclined surface and the downstream inclined surface, and the upstream inclined surface or the downstream inclined surface is composed of a plurality of inclined surfaces having the same inclination direction and different inclination angles. May be.
Further, the configuration of the wall surface in the width direction of the fixing belt 21 constituting the concave portion 50 can be appropriately selected within a range in which the object of the present invention can be achieved, and one or both of the pair of opposing wall surfaces are inclined. It may be a plane or a non-tilted vertical plane.

As shown in FIG. 4A, the recess 50 has inclined surfaces having different inclination directions and inclination angles on the upstream side and the downstream side in the rotation direction (traveling direction) D of the fixing belt 21. In the figure, the inclination angle of the downstream inclined surface is indicated by θ1, and the inclination angle of the upstream inclined surface is indicated by θ2.
A film 40 is formed on the surface of the soaking member 29.
A lubricant (for example, silicon grease) is applied to the film 40, and the lubricant is interposed between the fixing belt 21.
The lubricant held in the recess 50 is supplied to the inner peripheral surface of the fixing belt 21 and the surface of the heat equalizing member 29 by sliding of the fixing belt 21.

As shown in FIG. 4, it is preferable that the inclination angle θ2 of the upstream inclined surface in the rotation direction of the fixing belt 21 of the recess 50 of the heat equalizing member 29 is larger than the inclination angle θ1 of the downstream inclined surface. That is, it is preferable that the upstream inclined surface is steeper than the downstream inclined surface.
Accordingly, the lubricant can be supplied in the downstream direction by the flow indicated by the arrow d1 in FIG. 4A, and the lubricant can be recovered by the flow indicated by the arrow d2, so that a trace amount of the lubricant is continuously stabilized. Can be supplied.

Further, the maximum depth of the recess 50 of the heat equalizing member 29 is preferably equal to or greater than the thickness of the coating 40 of the heat equalizing member 29.
In the embodiment shown in FIG. 4, the maximum depth t <b> 2 of the recess 50 is larger than the thickness t <b> 3 of the coating 40. As a result, even when the film 40 disappears due to wear over time or the like, the concave portion 50 remains and the function of supplying the lubricant is not lost, so that a rapid torque increase can be suppressed.

  The maximum depth of the formed recess 50 can be measured by a surface shape measuring device using a laser or the like.

The recess 50 can be formed by pressing or stamping.
For example, the recess 50 can be formed on the heat equalizing member 29 so as to have a desired shape and arrangement by pressing.

FIG. 5 is a top view for explaining an example of the arrangement of the concave portions 50 of the heat equalizing member 29 (on the contact surface side with the fixing belt 21). In FIG. 5, arrow D indicates the rotation direction (traveling direction) of the fixing belt 21, W indicates the nip width, and Nc indicates the center of the nip width.
As shown in FIG. 5, one recess 50 of the heat equalizing member 29 is preferably adjacent to another recess 50 in the rotation direction of the fixing belt 21.
With such an arrangement of the recess 50, the lubricant can be supplied to the entire area in the longitudinal direction (width direction) of the fixing belt 21.

In addition, one recess 50 of the heat equalizing member 29 has at least one of the recess 50 and another recess 50 adjacent in the rotation direction of the fixing belt 21 with another recess 50 on both sides in the rotation direction of the fixing belt 21. Adjacent is preferred.
As a result, the lubricant can be stably supplied over the long term to the entire region in the longitudinal direction (width direction) of the fixing belt 21.

  It should be noted that a plurality of ridge lines of the concave portion 50 are not overlapped on the line segment L in the rotation direction of the fixing belt 21 (for example, line segments represented by L1, L2 and L3, and arbitrary line segments parallel thereto). This prevents the occurrence of streaks that occur when pressure unevenness overlaps.

As shown in FIG. 5, it is preferable that the recess 50 of the heat equalizing member 29 is formed more on the upstream side than on the downstream side in the rotation direction of the fixing belt 21. Specifically, it is preferable that the number of the recessed portions 50 formed on the upstream side is larger than the number of the recessed portions 50 formed on the downstream side with respect to the central portion Nc of the nip portion.
The lubricant supplied from the concave portion 50 spreads in the direction indicated by d3 and d4 in the figure as the fixing belt 21 slides, and is aligned and applied downstream of the fixing nip portion N. Thus, uneven supply of the lubricant depending on the part can be reduced.

Hereinafter, the effects of reducing the increase in torque with time and extending the life of the fixing device according to the present embodiment will be described with reference to FIGS.
6 to 8 are graphs showing the results of intermittent printing of A4Y size transfer paper at 3 P / J, 10 [second] intervals. The vertical axis indicates the unit torque value (unit: Nm), and the horizontal axis indicates the number of sheets (k).
In the graph, the limit torque in this embodiment is indicated by “T”, and the target life is indicated by “L”.

The film 40 was formed by spray coating so that the surface roughness Ra had a desired value.
The concave portion 50 was formed by pressing so as to have inclined surfaces with different inclination directions and inclination angles on the upstream side and the downstream side in the rotation direction of the fixing belt 21.
The unit torque value was measured using a general-purpose torque measuring device.

  FIG. 6 shows the result when the surface roughness Ra of the coating 40 formed on the heat equalizing member 29 is around 0.05. The value of the present embodiment in which the recess 50 is formed is indicated by a solid line. The values of the conventional example indicated by ▲ and not having the recess 50 are indicated by broken lines and Δ.

  As shown in FIG. 6, in the conventional example in which the recess 50 is not formed, the lubricant is depleted early and a rapid torque increase is observed. On the other hand, in this embodiment, exhaustion of the lubricant is prevented by the effect of the formed recess 50, and an increase in torque due to use over time can be suppressed.

  FIG. 7 shows the result when the surface roughness Ra of the film 40 formed on the heat equalizing member 29 is around 2.0. The value of the present embodiment in which the recess 50 is formed is indicated by a solid line. The values of the conventional example where the concave portion 50 is not formed are indicated by broken lines and ◯.

  As shown in FIG. 7, in the conventional example in which the recess 50 is not formed, the torque increase is suppressed to the vicinity of the target life L due to the appropriate value of the surface roughness Ra of the coating 40, When the lubricant is depleted due to wear, a rapid torque increase is observed. On the other hand, in the present embodiment, the effect of the formed recess 50 prevents the lubricant from being depleted even when the coating 40 is worn, and can suppress a rapid torque increase, thereby extending the life. Can be realized.

  FIG. 8 shows the result when the surface roughness Ra of the coating 40 formed on the heat equalizing member 29 is around 8.0. The value of the present embodiment in which the recess 50 is formed is indicated by a solid line. The values of the conventional example shown by (2) and not having the recess 50 are shown by broken lines and □.

When Ra is about 8.0, the surface area is large, and the amount of the additive that protrudes from the coating 40 increases, so that the amount of wear on the inner peripheral surface of the fixing belt 21 increases. For this reason, although there are more surface irregularities than the above-mentioned Ra of about 2.0 (FIG. 7), in the conventional example, a decrease in the viscosity of the lubricant due to powder caused by wear, or irregularities such as powder The torque increases with time due to the accumulation on the part.
On the other hand, in the present embodiment, due to the effect of the formed recess 50, the supply of the lubricant can be continued without being affected by the powder or the like caused by wear, and the powder can be taken into the recess 50. A sudden increase in torque can be suppressed, and a longer life can be realized.

  As described above, according to the fixing device of this embodiment, regardless of the value of the surface roughness Ra of the film 40 formed on the surface of the heat equalizing member 29, the torque increases with time due to the effect of the recess 50. It is possible to suppress (stabilize the torque) and realize a long life even when applied to a high-speed machine at a low cost.

Hereinafter, other configuration examples of the fixing device 20 are shown in FIGS.
The fixing device 20 shown in FIG. 9 is the same as the fixing device shown in FIG. 2 except that the heat source includes three halogen heaters 23a, 23b, and 23c. The fixing device 20 shown in FIG. 10 is the same as the fixing device shown in FIG. 2 except that the heat source includes two halogen heaters 23a and 23b.
By increasing the number of halogen heaters 23, fixing corresponding to various paper widths of the recording medium P can be performed without reducing productivity.
(In addition, in FIG.9 and FIG.10, the recessed part 50 of the soaking | uniform-heating member 29 is abbreviate | omitted.)

  In the fixing device of FIG. 9, a protrusion 27 is formed on the nip exit side of the nip forming member 24. The protrusion 27 is not in contact with the pressure roller 22 via the fixing belt 21 and improves the separation of the recording medium P.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20 Fixing apparatus 21 Fixing belt 22 Pressure member (Pressure roller)
23 Heat source (halogen heater)
24 Nip forming member 29 Heat equalizing member 40 Film 50 Recessed portion N Fixing nip portion

JP 2017-125922 A Japanese Patent No. 3254117 Japanese Patent No. 4251048 Japanese Patent No. 4543670 Japanese Patent No. 3634679

Claims (10)

An endless fixing belt provided rotatably;
A pressure member that is rotatably provided and pressurizes the fixing belt from an outer peripheral side;
A nip forming member that presses the fixing belt from an inner peripheral side through a heat equalizing member made of metal and forms a fixing nip portion between the fixing belt and the pressure member;
A heat source for heating the fixing belt,
In the fixing nip portion, a lubricant is interposed between the heat equalizing member and the fixing belt,
The soaking member has a film on the contact surface with the fixing belt, and a plurality of recesses are formed.
The fixing device according to claim 1, wherein the concave portion has inclined surfaces having different inclination directions and inclination angles on an upstream side and a downstream side in a rotation direction of the fixing belt.   The fixing device according to claim 1, wherein an inclination angle of an upstream inclined surface of the concave portion of the heat equalizing member in a rotation direction of the fixing belt is larger than an inclination angle of a downstream inclined surface.   The fixing device according to claim 1, wherein a maximum depth of the concave portion of the heat equalizing member is equal to or greater than a thickness of a film of the heat equalizing member.   4. The fixing device according to claim 1, wherein one recess of the heat equalizing member is adjacent to the other recess in the rotation direction of the fixing belt. 5.   At least one of the concave portion and the other concave portion adjacent in the rotation direction of the fixing belt is adjacent to the other concave portion on both sides in the rotation direction of the fixing belt. The fixing device according to claim 1, wherein   6. The fixing device according to claim 1, wherein the concave portion of the heat equalizing member is formed more on the upstream side than on the downstream side in the rotation direction of the fixing belt.   2. The fixing device according to claim 1, wherein the heat source is a halogen heater including a halogen lamp, and a gas sealed in the halogen lamp is mainly composed of either xenon or krypton. The fixing device according to claim 6.   The fixing device according to claim 1, wherein the heat source is an IH heater. The lubricant includes a fluorine compound or a silicon compound,
The fixing device according to claim 1, wherein the film formed on the heat equalizing member includes a fluororesin or a silicone resin.   An image forming apparatus comprising the fixing device according to claim 1.