JP4341338B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and the like, and more particularly to a fixing device used in an image forming apparatus using an electrophotographic system.

  In an image forming apparatus such as a copying machine or a printer using an electrophotographic method, for example, a photosensitive member formed in a drum shape is uniformly charged, and the photosensitive member is exposed to light controlled based on image information. An electrostatic latent image is formed on the photoreceptor. The electrostatic latent image is converted into a visible image (toner image) with toner, and the toner image is further transferred onto a recording sheet and fixed by a fixing device to form an image.

  In the fixing device used in such an image forming apparatus, as shown in FIG. 7, a heating source 113 is provided inside a cylindrical metal core 111, and a release layer 112 is formed on the outer peripheral surface of the metal core 111. The fixing roll 110 was pressed against the fixing roll 110, and a heat-resistant elastic body layer 122 and a release layer 123 made of a heat-resistant resin film or heat-resistant rubber film were formed on the outer peripheral surface of the core metal 121. It is composed of a pressure roll 120. Then, the recording paper carrying the unfixed toner image is passed between the fixing roll 110 and the pressure roll 120, and the unfixed toner image is heated and pressed to thereby apply the toner to the recording paper. The image is fixed. Such a fixing device is called a heating roll method and is generally widely used.

By the way, when it is intended to increase the speed of the heating roll type fixing device, it is necessary to widen the nip width in proportion to the fixing speed in order to supply a sufficient amount of heat to the toner and the recording paper. As a method of widening the nip width, there are a method of increasing the load between the fixing roll and the pressure roll, a method of increasing the thickness of the elastic body, and a method of increasing the roll diameter.
However, in the method of increasing the load and the method of increasing the thickness of the elastic body, the uneven nip width and paper wrinkle occur because the shape of the nip width due to the deflection of the roll becomes non-uniform along the roll axis. This causes image quality problems such as Further, the method of increasing the roll diameter has problems that the apparatus is increased in size and that the time until the roll is raised from room temperature to the fixable temperature (warm-up time) becomes longer.

  Therefore, in order to solve these problems and realize a fixing device corresponding to the speedup of the image forming apparatus, the applicant of the present invention has a rotatable heating roll whose surface is elastically deformed and remains in contact with the heating roll. A travelable endless belt and a pressure pad arranged in a non-rotating state inside the endless belt. The pressure pad presses the endless belt against the heating roll so that a contact surface with the heating roll is formed. And a belt nip so that the sheet can pass between the endless belt and the heating roll, and a fixing device configured to locally elastically deform the exit side of the sheet on the surface of the heating roll The technique regarding this is proposed (for example, refer patent document 1).

  In the technique described in Patent Document 1, the endless belt is pressed against the heating roll using a pressure pad in place of the pressure roll in the conventional heating roll type fixing device. By adopting such a configuration, the width of the belt nip formed by the heating roll and the endless belt can be easily made larger than the width of the conventional roll nip between the heating roll and the pressure roll. It is easy to reduce the size of the apparatus.

  In particular, the heat capacity of the endless belt brought into pressure contact with the heating roll is small, and furthermore, the heat transmitted from the heating roll is hardly dissipated because the pressure pad is arranged in a non-rotating state. Therefore, even if rotation of the heating roll is started, the amount of heat taken away from the heating roll to the endless belt side is small, the efficiency of using heat for melting the toner is increased, and the amount of temperature decrease at the belt nip is also small. There is an advantage that the fixing property of the toner can be improved.

Japanese Patent No. 3298354 (pages 4-7)

By the way, in the fixing device of the type in which the endless belt is pressed against the heating roll using the pressure pad, when the endless belt is pressed against the heating roll by the pressure pad, the sliding property between the pressure pad and the endless belt is ensured. In addition, a low friction member is interposed between them or a lubricant is applied.
However, temperature change at the nip due to increase / decrease in the number of recording sheets that are continuously passed for each job of the image forming apparatus, change in sheet passing speed due to the thickness of the recording sheet, and passage of time, etc. As a result, the amount of lubricant applied between the pressure pad and the endless belt becomes unstable. For this reason, a phenomenon may occur in which the contact resistance (sliding resistance) between the pressure pad and the endless belt increases. When such a phenomenon occurs, the movement of the endless belt becomes difficult to respond to the heating roll, and accordingly, the conveyance of the recording paper becomes unsatisfactory and may cause image defects such as paper wrinkles and image misalignment. There is.

  Accordingly, the present invention has been made to solve the technical problems as described above. The object of the present invention is to stabilize the recording paper conveyance capability in the fixing device, and thereby to make the paper wrinkle over a long period of time. In other words, it is possible to form a high quality image while suppressing occurrence of image misalignment and the like.

  For this purpose, the fixing device according to the present invention is disposed inside a rotation member that can rotate, an endless belt that can move while contacting the rotation member, and rotates the endless belt. A pressure member that forms a nip through which the recording material passes between the rotating member and the endless belt by being in pressure contact with the member. In addition, a lubricant is applied to the inner peripheral surface of the endless belt. And a coating amount control member for controlling the coating amount of the lubricant applied to the inner peripheral surface of the endless belt by the lubricant coating member.

Here, the pressure member may be characterized by locally elastically deforming the downstream side in the conveyance direction of the recording material among the surface of the rotating member.
Further, the application amount control member can be disposed in the vicinity of the upstream side in the moving direction of the endless belt at the nip portion. Furthermore, the application amount control member can be arranged on the downstream side of the lubricant application member in the moving direction of the endless belt.
Further, it is preferable that the application amount control member is configured to have a lower lubricant absorption capacity than the lubricant application member.
Furthermore, a sliding member that reduces sliding resistance between the endless belt and the pressure member may be further provided between the endless belt and the pressure member. In particular, the sliding member is preferably configured so as not to infiltrate the lubricant.

  The fixing device of the present invention has a heat generating source, a rotatable fixing roll whose surface is elastically deformed, an endless belt that can move while contacting the fixing roll, an inner endless belt, and an endless belt. A pressure member that forms a nip through which the recording material passes between the endless belt and the fixing roll by pressing the belt against the fixing roll, and in addition, is arranged in contact with the inner peripheral surface of the endless belt The first porous member formed and the second porous member disposed in contact with the inner peripheral surface of the endless belt, on the downstream side in the moving direction of the endless belt of the first porous member and in the vicinity of the upstream side of the nip portion. The porous member is provided.

  Here, the first porous member may be characterized by being impregnated with a lubricant. Moreover, it is preferable that the second porous member has a lower lubricant absorption capacity than the first porous member.

Further, the fixing device of the present invention has a pressure roll that is elastically deformed and connected to a driving source and is rotatable, an endless belt that has a heat generation source and can be driven while being in contact with the pressure roll, A pressure member that is disposed inside the endless belt, presses the endless belt against the pressure roll, and forms a nip portion through which the recording material passes between the endless belt and the pressure roll. A first porous member disposed in contact with the inner peripheral surface of the endless belt, and an inner end of the endless belt on the downstream side of the first porous member in the moving direction of the endless belt and in the vicinity of the upstream side of the nip portion. And a second porous member disposed in contact with the peripheral surface.
Here, the endless belt can use a resistance heating element or an electromagnetic induction heating element as a heat source. As long as the heat source can heat the belt, a method and a configuration are arbitrary. Specifically, the heat generation source may be a resistance heating layer provided in the endless belt, or separately from the endless belt, for example, the endless belt and the pressure roll are brought into pressure contact with the pressure roll. The pressure member forming the nip portion through which the recording material passes may be formed of a resistance heating element.

Further, the present invention is regarded as an image forming apparatus. The image forming apparatus of the present invention includes a toner image forming unit that forms a toner image, and a transfer unit that transfers the toner image formed by the toner image forming unit onto a recording material. A fixing means for fixing the toner image transferred onto the recording material to the recording material, the fixing means comprising a rotatable rotating member, an endless belt movable while contacting the rotating member, and an endless A pressure member that is disposed inside the belt, presses the endless belt against the rotating member, and forms a nip portion through which the recording material passes between the rotating member and the endless belt. A first porous member disposed in contact with the inner peripheral surface of the belt, and an inner end of the endless belt on the downstream side of the first porous member in the moving direction of the endless belt and in the vicinity of the upstream side of the nip portion. It is characterized in that a second porous members disposed surface and in contact with.
Here, the fixing unit may be characterized in that the pressure member locally elastically deforms the downstream side of the rotation direction of the recording material in the conveyance direction of the recording material. Further, the toner image forming means may form a color toner image.

  As an effect of the present invention, it is possible to provide an image forming apparatus capable of forming a high-quality image while suppressing the occurrence of paper wrinkles and image misalignment over a long period of time by stabilizing the recording paper conveyance capability in the fixing device. It became possible to do.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[Embodiment 1]
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus to which the exemplary embodiment is applied. The image forming apparatus shown in FIG. 1 is an intermediate transfer type image forming apparatus generally called a tandem type, and includes a plurality of image forming units 1Y, 1M, 1C, on which toner images of respective color components are formed by electrophotography. 1K, a primary transfer unit 10 for sequentially transferring (primary transfer) each color component toner image formed by each image forming unit 1Y, 1M, 1C, 1K to the intermediate transfer belt 15, and a superimposition transferred on the intermediate transfer belt 15 A secondary transfer unit 20 that batch-transfers (secondary transfer) toner images to a sheet P that is a recording material (recording sheet), and a fixing device 60 that fixes the secondary-transferred image on the sheet P are provided. Moreover, it has the control part 40 which controls operation | movement of each apparatus (each part).

  In the present embodiment, each of the image forming units 1Y, 1M, 1C, and 1K includes a charger 12 and a photosensitive drum around which the photosensitive drum 11 is charged around the photosensitive drum 11 that rotates in the arrow A direction. A laser exposure device 13 (an exposure beam is indicated by a symbol Bm in the drawing) in which an electrostatic latent image is written on the image 11, each color component toner is accommodated, and the electrostatic latent image on the photosensitive drum 11 is visualized with toner. Developing unit 14, primary transfer roll 16 for transferring each color component toner image formed on photosensitive drum 11 to intermediate transfer belt 15 in primary transfer unit 10, and residual toner on photosensitive drum 11 are removed. Electrophotographic devices such as a drum cleaner 17 are sequentially arranged. These image forming units 1Y, 1M, 1C, and 1K are arranged in a substantially straight line from the upstream side of the intermediate transfer belt 15 in the order of yellow (Y), magenta (M), cyan (C), and black (K). Has been.

The intermediate transfer belt 15 as an intermediate transfer member is constituted by a film-like endless belt in which an appropriate amount of an antistatic agent such as carbon black is contained in a resin such as polyimide or polyamide. And the volume resistivity is formed so that it may become 10 < ⁶ > -10 < ¹⁴ > (omega | ohm) cm, The thickness is comprised by about 0.1 mm, for example. The intermediate transfer belt 15 is circulated and driven (rotated) at a predetermined speed in the direction B shown in FIG. 1 by various rolls. As these various rolls, a drive roll 31 that is driven by a motor (not shown) having excellent constant speed and rotates the intermediate transfer belt 15, and an intermediate that extends substantially linearly along the arrangement direction of the photosensitive drums 11. A support roll 32 that supports the transfer belt 15, a tension roll 33 that functions as a correction roll that applies a constant tension to the intermediate transfer belt 15 and prevents meandering of the intermediate transfer belt 15, and a backup provided in the secondary transfer unit 20. A cleaning backup roll 34 provided in a cleaning unit for scraping off residual toner on the roll 25 and the intermediate transfer belt 15 is provided.

The primary transfer unit 10 includes a primary transfer roll 16 that is disposed to face the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. The primary transfer roll 16 includes a shaft and a sponge layer as an elastic layer fixed around the shaft. The shaft is a cylindrical bar made of metal such as iron or SUS. The sponge layer is a sponge-like cylindrical roll formed of a blend rubber of NBR, SBR and EPDM containing a conductive agent such as carbon black and having a volume resistivity of 10 ^7.5 to 10 ^8.5 Ωcm. The primary transfer roll 16 is placed in pressure contact with the photosensitive drum 11 with the intermediate transfer belt 15 in between, and the primary transfer roll 16 has a voltage (with negative polarity; the same applies hereinafter) having a polarity opposite to that of the toner. (Primary transfer bias) is applied. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 so as to form superimposed toner images on the intermediate transfer belt 15.

The secondary transfer unit 20 includes a secondary transfer roll 22 disposed on the toner image carrying surface side of the intermediate transfer belt 15 and a backup roll 25. The backup roll 25 is composed of a tube of EPDM and NBR blend rubber with carbon dispersed on the surface, and EPDM rubber inside. And it is formed so that the surface resistivity may be 10 ⁷ to 10 ¹⁰ Ω / □, and the hardness is set to, for example, 70 ° (Asker C: manufactured by Kobunshi Keiki Co., Ltd., the same shall apply hereinafter). The backup roll 25 is disposed on the back side of the intermediate transfer belt 15 to form a counter electrode of the secondary transfer roll 22, and a metal power supply roll 26 to which a secondary transfer bias is stably applied is disposed in contact with the backup roll 25. ing.

On the other hand, the secondary transfer roll 22 includes a shaft and a sponge layer as an elastic layer fixed around the shaft. The shaft is a cylindrical bar made of metal such as iron or SUS. The sponge layer is a sponge-like cylindrical roll formed of a blend rubber of NBR, SBR and EPDM containing a conductive agent such as carbon black and having a volume resistivity of 10 ^7.5 to 10 ^8.5 Ωcm. The secondary transfer roll 22 is disposed in pressure contact with the backup roll 25 with the intermediate transfer belt 15 interposed therebetween. Further, the secondary transfer roll 22 is grounded, and a secondary transfer bias is formed between the secondary transfer roll 22 and the backup roll 25. The toner image is secondarily transferred onto the paper P conveyed to the transfer unit 20.

  Further, on the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, an intermediate transfer belt that removes residual toner and paper dust on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15. A cleaner 35 is provided so as to be able to contact and separate. On the other hand, on the upstream side of the yellow image forming unit 1Y, a reference sensor (home position sensor) 42 that generates a reference signal serving as a reference for taking image forming timings in the image forming units 1Y, 1M, 1C, and 1K. It is arranged. Further, an image density sensor 43 for adjusting image quality is disposed on the downstream side of the black image forming unit 1K. The reference sensor 42 recognizes a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. In response to an instruction from the control unit 40 based on the recognition of the reference signal, each image forming unit. 1Y, 1M, 1C, and 1K are configured to start image formation.

  Further, in the image forming apparatus according to the present embodiment, as a paper transport system, a paper tray 50 that stores paper P, a pickup roll 51 that picks up and transports the paper P accumulated in the paper tray 50 at a predetermined timing, and a pickup After secondary transfer is performed by the transport roll 52 that transports the paper P fed by the roll 51, the transport chute 53 that feeds the paper P transported by the transport roll 52 to the secondary transfer unit 20, and the secondary transfer roll 22. A conveyance belt 55 that conveys the conveyed paper P to the fixing device 60 and a fixing entrance guide 56 that guides the paper P to the fixing device 60 are provided.

  Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described. In the image forming apparatus as shown in FIG. 1, image data output from an image reading device (IIT) not shown or a personal computer (PC) not shown is subjected to predetermined image processing by an image processing device (IPS) not shown. Is applied, the image forming operation is executed by the image forming units 1Y, 1M, 1C, and 1K. In IPS, the input reflectance data is subjected to predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, moving editing, and other various image editing. Is done. The image data that has undergone image processing is converted into color material gradation data of four colors, Y, M, C, and K, and is output to the laser exposure unit 13.

  The laser exposure unit 13 irradiates the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K, for example, with an exposure beam Bm emitted from a semiconductor laser in accordance with the input color material gradation data. Yes. In each of the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K, the surface is charged by the charger 12, and then the surface is scanned and exposed by the laser exposure unit 13 to form an electrostatic latent image. The formed electrostatic latent images are developed as toner images of respective colors Y, M, C, and K by the respective image forming units 1Y, 1M, 1C, and 1K.

  The toner images formed on the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K are transferred onto the intermediate transfer belt 15 at the primary transfer unit 10 where the photosensitive drums 11 and the intermediate transfer belt 15 come into contact with each other. Is transcribed. More specifically, in the primary transfer unit 10, a voltage (primary transfer bias) having a polarity opposite to the charging polarity (minus polarity) of the toner is applied to the base material of the intermediate transfer belt 15 by the primary transfer roll 16. Primary transfer is performed by sequentially superimposing images on the surface of the intermediate transfer belt 15.

  After the toner images are sequentially primary transferred onto the surface of the intermediate transfer belt 15, the intermediate transfer belt 15 moves and the toner image is conveyed to the secondary transfer unit 20. When the toner image is transported to the secondary transfer unit 20, in the paper transport system, the pick-up roll 51 rotates in accordance with the timing at which the toner image is transported to the secondary transfer unit 20, and the paper of a predetermined size is transferred from the paper tray 50. P is supplied. The paper P supplied by the pickup roll 51 is transported by the transport roll 52 and reaches the secondary transfer unit 20 via the transport chute 53. Before reaching the secondary transfer unit 20, the paper P is temporarily stopped, and a registration roll (not shown) rotates in accordance with the movement timing of the intermediate transfer belt 15 on which the toner image is carried. And the position of the toner image are aligned.

  In the secondary transfer unit 20, the secondary transfer roll 22 is pressed against the backup roll 25 via the intermediate transfer belt 15. At this time, the sheet P conveyed at the same timing is sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22. At this time, when a voltage (secondary transfer bias) having the same polarity as the toner charging polarity (negative polarity) is applied from the power supply roll 26, a transfer electric field is formed between the secondary transfer roll 22 and the backup roll 25. Is done. The unfixed toner image carried on the intermediate transfer belt 15 is collectively electrostatically transferred onto the paper P by the secondary transfer unit 20 pressed by the secondary transfer roll 22 and the backup roll 25. The

Thereafter, the sheet P on which the toner image has been electrostatically transferred is transported as it is while being peeled off from the intermediate transfer belt 15 by the secondary transfer roll 22, and transported downstream of the secondary transfer roll 22 in the sheet transport direction. It is conveyed to the belt 55. The conveyance belt 55 conveys the paper P to the fixing device 60 in accordance with the optimum conveyance speed in the fixing device 60. The unfixed toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by being subjected to a fixing process by heat and pressure by the fixing device 60. Then, the paper P on which the fixed image is formed is conveyed to a paper discharge placement unit provided in a discharge unit of the image forming apparatus.
On the other hand, after the transfer onto the paper P is completed, the residual toner remaining on the intermediate transfer belt 15 is conveyed to the cleaning unit as the intermediate transfer belt 15 rotates, and the cleaning backup roll 34 and the intermediate transfer belt cleaner 35 are transferred. Is removed from the intermediate transfer belt 15.

  Next, the fixing device 60 used in the image forming apparatus of the present embodiment will be described. FIG. 2 is a side sectional view showing a configuration of the fixing device 60 of the present embodiment. The fixing device 60 includes a fixing roll 61 as an example of a rotating member, an endless belt 62, and a pressure pad 64 as an example of a pressure member pressed from the fixing roll 61 via the endless belt 62. .

The fixing roll 61 is configured by laminating a heat-resistant elastic layer 612 and a release layer 613 around a metal core (cylindrical core) 611.
Inside the fixing roll 61, a halogen lamp 66 is disposed as a heat source. On the other hand, a temperature sensor 69 is disposed in contact with the surface of the fixing roll 61. The control unit 40 of the image forming apparatus controls lighting of the halogen lamp 66 based on the temperature measurement value by the temperature sensor 69 so that the surface temperature of the fixing roll 61 is maintained at a predetermined set temperature (for example, 170 ° C.). It is adjusted to.
The endless belt 62 is rotatably supported by a pressure pad 64 and a belt traveling guide 63. The nip portion N is disposed in pressure contact with the fixing roll 61.

  The pressure pad 64 is disposed inside the endless belt 62 while being pressed against the fixing roll 61 via the endless belt 62, and forms a nip portion N with the fixing roll 61. In the pressure pad 64, a pre-nip member 64a for securing a wide nip portion N is disposed on the inlet side of the nip portion N, and a peeling nip member 64b for distorting the fixing roll 61 is disposed on the outlet side of the nip portion N. Is arranged. Further, in order to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64, a low resistance sheet 68 is provided on the surface of the pre-nip member 64a and the peeling nip member 64b in contact with the endless belt 62. The pressure pad 64 and the low resistance sheet 68 are held by a metal holder 65.

  Furthermore, a belt traveling guide 63 is attached to the holder 65 so that the endless belt 62 can smoothly rotate. That is, the belt running guide 63 is made of a material having a small static friction coefficient in order to rub against the inner peripheral surface of the endless belt 62. Further, the belt running guide 63 is formed of a material having low thermal conductivity so that it is difficult to remove heat from the endless belt 62.

  The fixing roll 61 is rotated in the direction of arrow C by a drive motor (not shown), and the endless belt 62 is also rotated by this rotation. The sheet P on which the toner image is electrostatically transferred in the secondary transfer unit 20 of the image forming apparatus shown in FIG. 1 is guided by the fixing inlet guide 56 and conveyed to the nip N. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the fixing roll 61. In the fixing device 60 of the present embodiment, since the nip portion N can be configured widely by the concave pre-nip member 64a that substantially follows the outer peripheral surface of the fixing roll 61, stable fixing performance can be ensured.

In addition, in the fixing device 60 of the present embodiment, the separation nip member 64 b is disposed so as to protrude from the outer peripheral surface of the fixing roll 61, so that the fixing roll 61 has an outlet region (peeling nip portion). It can also be configured such that the distortion is locally increased. If the separation nip member 64b is arranged in this way, the fixed paper P passes through the locally formed distortion when passing through the separation nip portion, and therefore is wound around the fixing roll 61. This makes it possible to more effectively peel off the paper P.
In particular, by locally increasing the distortion of the fixing roll 61, it is possible to obtain high peeling performance with a small amount of distortion. Therefore, even when a thin heat-resistant resin is used as the release layer 613 of the fixing roll 61, the occurrence of paper wrinkles on the paper P can be suppressed. Further, peeling between the heat-resistant elastic layer 612 and the release layer 613 hardly occurs, and the reliability of the component performance over a long period can be improved together with maintaining the peeling performance.

Furthermore, since the distortion amount of the fixing roll 61 can be reduced, the heat-resistant elastic body layer 612 of the fixing roll 61 can be thinned. Therefore, since the heat capacity of the fixing roll 61 can be reduced, the warm-up time can be shortened and the power consumption can be reduced. Further, since the heat-resistant elastic body layer 612 having a low thermal conductivity can be thinned, the thermal resistance between the inner surface and the outer surface of the fixing roll 61 can be reduced and the thermal responsiveness can be improved. It is also suitable for conversion.
Note that a peeling member 70 may be disposed on the downstream side of the nip portion N of the fixing roll 61 as an auxiliary means for peeling. The peeling member 70 is held by a holder 72 in a state in which the peeling sheet 71 is close to the fixing roll 61 in a direction (counter direction) facing the rotation direction of the fixing roll 61.

Next, each member constituting the fixing device 60 will be described in detail. First, in the fixing roll 61, the core 611 is formed of a cylindrical body made of a metal having high thermal conductivity such as iron, aluminum, and SUS. The outer diameter and thickness of the core 611 can be reduced in diameter and thickness in the fixing device 60 of the present embodiment because the pressing force of the pressure pad 64 is small.
Any material can be used for the heat-resistant elastic layer 612 as long as it is an elastic body having high heat resistance. In particular, it is preferable to use an elastic body such as rubber or elastomer having a rubber hardness of about 25 to 40 ° (JIS-A), and specific examples thereof include silicon rubber and fluorine rubber.

  The release layer 613 may be any resin as long as it is a heat-resistant resin. For example, a silicon resin, a fluororesin, or the like can be used. From the viewpoint of safety, a fluororesin is suitable. As the fluororesin, PFA, PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene hexafluoropropylene copolymer), or the like can be used. The thickness of the release layer 613 is preferably 5 to 30 μm, more preferably 10 to 20 μm. If the thickness of the release layer 613 is less than 5 μm, the paper P tends to be wrinkled due to the distortion of the fixing roll 61, while if it exceeds 30 μm, the release layer 613 becomes hard and the image has defects such as uneven gloss. This is because there is an increase in the possibility of the occurrence of both.

  The endless belt 62 is an endless belt whose original shape is formed in a cylindrical shape. The endless belt 62 includes a base layer and a release layer coated on the surface or both surfaces of the base layer on the fixing roll 61 side. The base layer is formed of a polymer such as polyimide, polyamide, or polyimideamide, or a metal such as SUS, nickel, or copper, and has a thickness of 30 to 200 μm, preferably 50 to 125 μm, and more preferably about 75 to 100 μm. The release layer coated on the surface of the base layer is formed of a fluororesin such as PFA, PTFE, or FEP, and has a thickness of about 5 to 100 μm, preferably about 10 to 30 μm.

As described above, the pressure pad 64 includes the pre-nip member 64a, the peeling nip member 64b, the low resistance sheet 68 as an example of the sliding member, and the holder 65. The prenip member 64 a can use an elastic body such as silicon rubber or fluororubber, a leaf spring, or the like, and the surface on the fixing roll 61 side is formed in a concave shape that substantially follows the outer peripheral surface of the fixing roll 61.
The peeling nip member 64b is formed of a heat-resistant resin such as PPS (polyphenylene sulfide), polyimide, polyester, polyamide, or a metal such as iron, aluminum, or SUS. As the shape of the peeling nip member 64b, the outer surface shape in the nip portion N is formed in a convex curved surface shape having a constant radius of curvature.

  The low resistance sheet 68 is provided to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64, and a material having a low friction coefficient and excellent wear resistance and heat resistance is suitable. Specifically, a sintered molded PTFE resin sheet, a glass fiber sheet impregnated with Teflon (trade name), and the like can be used. The low resistance sheet 68 may be configured separately from the pre-nip member 64a and the peeling nip member 64b, or may be configured integrally with the pre-nip member 64a and the peeling nip member 64b.

Further, as described above, the belt running guide 63 is made of a material having a low coefficient of friction and a low thermal conductivity so that heat is not easily taken from the endless belt 62 because it slides on the inner peripheral surface of the endless belt 62. A heat resistant resin such as PFA or PPS is used.
A lubricant application member 67 is disposed in the belt traveling guide 63 along the longitudinal direction of the fixing device 60. The lubricant application member 67 supplies a suitable amount of a lubricant such as dimethyl silicone oil to the inner peripheral surface of the endless belt 62, thereby reducing the sliding resistance between the endless belt 62 and the pressure pad 64 via the low resistance sheet 68. Further reduction is made, and the endless belt 62 is smoothly rotated.

  Further, in the fixing device 60 of the present embodiment, the lubricant is applied by the lubricant applying member 67 inside the endless belt 62 and in the vicinity of the upstream side in the moving direction of the endless belt 62 with respect to the arrangement position of the pressure pad 64. As an example of a coating amount control member that temporarily holds the lubricant and constantly supplies a constant amount of lubricant uniformly across the width direction to the sliding portion between the endless belt 62 and the pressure pad 64. It is characterized in that the lubricant control member 80 is provided.

  As described above, the paper P on which the toner image has been electrostatically transferred passes through the nip portion N of the fixing device 60, whereby the toner image is fixed to the paper P, but when the paper P passes through the nip portion N. Is received from the fixing roller 61 on the driving side. That is, the paper P is conveyed by receiving a frictional force from the fixing roll 61 as the fixing roll 61 rotates.

  On the other hand, in a state where the sheet P is not conveyed to the nip portion N, the driven endless belt 62 is also rotated by receiving a frictional force from the fixing roll 61 as the fixing roll 61 rotates. However, when the paper P is conveyed to the nip portion N and the paper P is nipped by the nip portion N, the endless belt 62 receives the conveying force from the fixing roll 61 via the paper P. Accordingly, when viewed from the sheet P side, when the sheet P passes through the nip portion N, the sheet P receives a conveying force from the fixing roll 61 and a force in the direction opposite to the conveying direction from the endless belt 62 side. (Reverse conveying force) will act.

By the way, since the pressure pad 64 is pressed in the nip portion N of the endless belt 62, a force in the direction opposite to the rotation direction acts as a sliding resistance from the pressure pad 64. Therefore, as described above, the low resistance sheet 68 is interposed between the endless belt 62 and the pressure pad 64, and a lubricant is applied from the lubricant applying member 67 to the inner peripheral surface of the endless belt 62, so The sliding resistance between the belt 62 and the pressure pad 64 is configured to be reduced as much as possible.
Therefore, in the normal state, the endless belt 62 receives a very small sliding resistance from the pressure pad 64 and can rotate smoothly. Therefore, the endless belt 62 can rotate at the same speed as the paper P. . In this case, the reverse conveying force received by the paper P is small enough to be ignored because of the sliding resistance from the pressure pad 64 via the endless belt 62. Therefore, the paper P is stably conveyed at the same speed as the fixing roll 61.

  However, since the number of sheets to be passed is different for each job of the image forming apparatus, a temperature change occurs in the nip portion N, or in the configuration in which the sheet passing speed is changed according to the thickness of the sheet P to be passed, Since the moving speed of the endless belt 62 also changes, the amount of lubricant applied between the pressure pad 64 and the endless belt 62 may change in an unstable manner. Further, when the fixing device 60 is used for a long period of time, component deterioration also occurs in the lubricant such as silicon oil supplied from the lubricant application member 67. In particular, in the fixing device 60, since the lubricant is used in a high temperature state, component deterioration is easily promoted. Therefore, between the endless belt 62 and the pressure pad 64, the sliding resistance of both may fluctuate and a state where the sliding resistance becomes high may occur.

  When the sliding resistance between the endless belt 62 and the pressure pad 64 increases, the reverse conveying force that the sheet P receives from the pressure pad 64 via the endless belt 62 when the sheet P is conveyed through the nip portion N is ignored. become unable. Further, if the sliding resistance between the endless belt 62 and the pressure pad 64 becomes excessive, the reverse conveyance force acting on the paper P increases, and the conveyance of the paper P cannot follow the rotation of the fixing roll 61, and the paper P And the fixing roll 61 slip. Therefore, the smooth conveyance of the paper P is hindered, causing image shift and paper wrinkles on the paper P.

  In particular, the nip portion N has a so-called crown shape in which the outer diameter of the fixing roll 61 is formed to increase from the center portion to both end portions, or the pressing force between the peeling nip member 64b and the fixing roll 61 is increased from the center portion to both ends. It is set so as to increase over the part. By setting in this way, a force is always applied to the paper P in the width direction from the center to both ends, thereby preventing the paper P from wrinkling. Such a balance of subtle forces acting in the width direction of the paper P increases the sliding resistance between the endless belt 62 and the pressure pad 64, so that the paper P cannot follow the conveyance of the fixing roll 61. As a result, the sheet P collapses, and a paper wrinkle is generated on the paper P or an image shift occurs.

  Therefore, in the fixing device 60 of the present embodiment, the lubricant control member 80 is disposed inside the endless belt 62 and in the vicinity of the upstream side in the moving direction of the endless belt 62 with respect to the position where the pressure pad 64 is disposed. ing. A constant amount of lubricant is always applied to the sliding portion between the endless belt 62 and the pressure pad 64 while the lubricant applied from the lubricant application member 67 is temporarily held by the lubricant control member 80. By being configured to supply uniformly, an increase in sliding resistance between the endless belt 62 and the pressure pad 64 is suppressed. As a result, the paper P can be stably conveyed at a constant speed with the fixing roll 61, and the occurrence of image misalignment and paper wrinkles on the paper P can be suppressed.

Here, the operation of the lubricant control member 80 will be described in detail. First, as described above, the lubricant application member 67 constantly supplies a lubricant such as dimethyl silicone oil to the inner peripheral surface of the endless belt 62. Here, as the lubricant, in addition to a liquid material such as dimethyl silicone oil, a grease obtained by mixing a solid substance and a liquid can be used, or a combination thereof can be used.
The lubricant applied by the lubricant application member 67 is carried to the sliding portion between the endless belt 62 and the pressure pad 64 as the endless belt 62 moves. At that time, in the vicinity of the upstream side of the sliding portion between the endless belt 62 and the pressure pad 64, the endless belt 62 is disposed in contact with the inner peripheral surface of the endless belt 62 uniformly in the width direction with a predetermined pressing force. The lubricant control member 80 temporarily holds the lubricant.

  The lubricant held by the lubricant control member 80 is supplied again from the lubricant control member 80 to the inner peripheral surface of the endless belt 62 by a certain amount. That is, the lubricant control member 80 replenishes when the amount of lubricant applied by the lubricant application member 67 is insufficient, and removes excess lubricant when the amount of supply is excessive. Thus, the amount of lubricant applied to the sliding portion between the endless belt 62 and the pressure pad 64 is controlled. Therefore, a constant amount of lubricant can always be uniformly supplied to the sliding portion between the endless belt 62 and the pressure pad 64. In particular, since the lubricant control member 80 is disposed in the vicinity of the upstream side in the moving direction of the endless belt 62, the uniformly applied lubricant can be supplied to the sliding portion as it is without being disturbed. .

  As described above, the lubricant control member 80 always provides a constant amount between the endless belt 62 and the pressure pad 64 regardless of the difference in the number of sheets passed for each job of the image forming apparatus or the change in the sheet passing speed. Since the lubricant can be supplied uniformly, the fluctuation of the sliding resistance between them can be suppressed, and the sliding resistance can always be kept substantially constant. Therefore, the endless belt 62 can be smoothly rotated, and the endless belt 62 and the paper P can be rotated at a constant speed. As a result, the paper P can be stably conveyed at the same speed as the fixing roll 61, and the occurrence of paper wrinkles and image displacement can be suppressed.

  Further, the lubricant control member 80 is disposed inside the endless belt 62 and in the vicinity of the upstream side in the moving direction of the endless belt 62 with respect to the position where the pressure pad 64 is disposed, so that the endless belt 62 and the belt traveling guide are arranged. Since wear powder generated by sliding with 63 or the like is prevented from entering the sliding portion between the endless belt 62 and the pressure pad 64, an increase in sliding resistance due to the inclusion of foreign matter between the two is prevented. It can also be suppressed.

  By the way, the lubricant application member 67 and the lubricant control member 80 are formed of a porous material so as to hold the lubricant. A porous material refers to a material that has a hole and can hold a lubricant, such as a substance having a large number of pores or a substance having a structure in which fine fibers are entangled. Specifically, a sponge or foam is used. Body resin, felt, woven fabric, film made porous by stretching, and the like are included.

In particular, in the fixing device 60 of the present embodiment, the lubricant absorption capability of the lubricant control member (second porous member) 80 is greater than the lubricant absorption capability of the lubricant application member (first porous member) 67. Is also configured to be low. Further, the lubricant application member 67 is disposed in the belt traveling guide 63 that is farthest from the nip portion N that is a heat source.
In this way, by disposing the lubricant application member 67 that also serves as a lubricant storage part at a position away from the nip portion N, it is possible to suppress heat from being applied to the lubricant held by the lubricant application member 67, and Since the lubricant absorption capacity of the lubricant control member 80 is set low, the amount of lubricant that is disposed in the vicinity of the nip portion N and is held by the lubricant control member 80 that easily receives heat can be reduced. The amount of lubricant that undergoes deterioration due to heat from the nip portion N is minimized, and thermal deterioration of the lubricant as a whole can be suppressed.

Note that the absorption capacity of the lubricant is measured by sufficiently filling the lubricant in the member and then hanging it in free space and measuring the weight of the filled lubricant by measuring the weight after a certain period of time. Can do.
Further, a plurality of lubricant application members 67 may be provided so as to contact the inner peripheral surface of the endless belt 62 in order to supply the lubricant over a long period of time. Even in this case, it is preferable that the lubricant application member 67 is disposed away from the nip portion N.

  On the other hand, the low resistance sheet 68 disposed between the inner peripheral surface of the endless belt 62 and the pressure pad 64 is desirably formed of a material that does not have a hole on the surface and does not have invasiveness. If it is a material having no infiltration property, an uneven shape may be formed on the surface thereof. When the low resistance sheet 68 is formed of a material having an infiltrating property such as a porous material, the endless belt 62 and the pressure pad are formed by the lubricant entering the hole portion under a high pressure, or even entering the back surface. 64, there is a disadvantage that a uniform layer of lubricant cannot be formed. Therefore, by forming the low resistance sheet 68 with a material that has no holes on the surface and does not have infiltration, the lubricant is held only on the surface of the low resistance sheet 68, and a uniform layer is formed on the surface of the low resistance sheet 68. It becomes possible to form. For this reason, it becomes easy to slide the endless belt 62 and the pressure pad 64 smoothly.

Next, in the fixing device 60 of the present embodiment provided with the lubricant control member 80, an experiment on the generation of paper wrinkles on the paper P was performed. In this experiment, a PTFE resin fiber having a thickness of 400 denier stretched on the surface of the endless belt 62 on the substrate of an FEP (tetrafluoroethylene hexafluoropropylene copolymer) resin sheet as the lubricant control member 80. A woven fabric twilled and heat-pressed was used. The lubricant application member 67 is a felt having a thickness of 4 mm, a width of 7 mm, and a length of 310 mm, impregnated with 3 cc of dimethyl silicone oil having a kinematic viscosity of 300 mm ² / s in advance.

  The fixing roll 61 includes an aluminum core 611 covered with a heat-resistant elastic layer 612 made of silicon rubber having a thickness of 0.6 mm and a release layer 613 made of PFA resin having a thickness of 0.03 mm. The surface temperature of the fixing roll 61 was set to 170 ° C. The endless belt 62 used was a polyimide resin having an outer diameter of 30 mm and a thickness of 0.075 mm coated with a 0.01 mm PFA resin. Further, the pressure pad 64 includes a pre-nip member 64a made of silicon rubber, a peeling nip member 64b made of aluminum, and a low resistance sheet 68 coated with a sintered PTFE resin on the sliding surface side of the endless belt 62 side. What was done was used.

Then, the fixing device 60 performed a non-sheet-passing operation for 20 hours at a process speed of 194 mm / s, and caused pseudo deterioration with time. This fixing device 60 uses A3 size Fuji Xerox Co., Ltd. P paper (product name), carries an unfixed toner image on the endless belt 62 side, and fixes the toner image fixed on the fixing roll 61 side. Ten sheets of paper P on which the paper wrinkles easily occur were passed, and the number of paper wrinkles generated was counted. As a result, no paper wrinkle was observed.
On the other hand, as a comparative example, a similar experiment was performed using a fixing device without the lubricant control member 80. As a result, generation of paper wrinkles was confirmed in 8 out of 10 sheets. The configuration of the fixing device is the same as that of the fixing device 60 of the present embodiment described above except for the presence or absence of the lubricant control member 80.
Thus, the superiority in the fixing device 60 of the present embodiment was confirmed.

  As described above, in the fixing device 60 used in the image forming apparatus of the present embodiment, the lubricant control member 80 causes a difference in the number of sheets to be passed for each job of the image forming apparatus, a change in the sheet passing speed, and the like. Regardless of this, since a constant amount of lubricant can be supplied uniformly between the endless belt 62 and the pressure pad 64, fluctuations in the sliding resistance between them can be suppressed, and the sliding resistance can be kept small at all times. be able to. Therefore, the endless belt 62 can be smoothly rotated, and the endless belt 62 and the paper P can be rotated at a constant speed. As a result, the paper P can be stably conveyed at the same speed as the fixing roll 61, and the occurrence of paper wrinkles and image displacement can be suppressed.

  Further, the lubricant control member 80 is disposed inside the endless belt 62 and in the vicinity of the upstream side in the moving direction of the endless belt 62 with respect to the position where the pressure pad 64 is disposed, so that the endless belt 62 and the belt traveling guide are arranged. Since it is also possible to suppress wear powder or the like generated by sliding with 63 or the like from entering the sliding portion between the endless belt 62 and the pressure pad 64, sliding resistance due to contamination of foreign matter between the two can be suppressed. This also has the effect of suppressing the increase of the sheet P and stabilizing the conveyance of the paper P and the fixing roll 61.

[Embodiment 2]
In the first embodiment, an image forming apparatus in which a fixing roll using a fixing roll as a heating unit and an endless belt with a pressure pad pressed as a pressing unit is mounted has been described. In the second embodiment, a fixing device mounted on the image forming apparatus shown in FIG. 1, which uses an endless belt with a heat generation source pressed as a heating unit and uses a pressure roll as a pressing unit. explain. In addition, about the structure similar to Embodiment 1, the same code | symbol is used and the detailed description is abbreviate | omitted here.

FIG. 3 is a side sectional view showing the configuration of the fixing device 91 according to the present embodiment. As shown in FIG. 3, in the fixing device 91 of the present embodiment, the endless belt 62 is arranged on the toner image carrying surface side of the paper P. A ceramic heater 82, which is a resistance heating element as an example of a heat source, is disposed inside the endless belt 62, and heat is supplied from the ceramic heater 82 to the nip portion N.
The ceramic heater 82 is formed in a concave shape in which the surface on the pressure roll 81 side substantially follows the outer peripheral surface of the pressure roll 81, and is disposed in a state of being pressed against the pressure roll 81 via the endless belt 62. N is formed. Therefore, the ceramic heater 82 also functions as a pressure member. The ceramic heater 82 is configured such that the thickness increases toward the exit region (peeling nip portion) of the nip portion N, and a larger nip pressure is formed in the peeling nip portion, and the radius of curvature of the endless belt 62 in the peeling nip portion is smaller. It is comprised so that it may become. As a result, when the paper P after fixing passes through the peeling nip portion, the paper P can be peeled off without being wound around the endless belt 62 due to the small radius of curvature of the endless belt 62.
Further, a low resistance sheet 68 is disposed between the inner peripheral surface of the endless belt 62 and the ceramic heater 82. The low resistance sheet 68 may be configured separately from the ceramic heater 82 or may be configured integrally with the ceramic heater 82.

On the other hand, the pressure roll 81 is disposed so as to face the endless belt 62, and is configured to rotate in the direction of arrow D by a drive motor (not shown), and the endless belt 62 is driven to rotate by this rotation. The pressure roll 81 includes a core (cylindrical core) 811, a heat-resistant elastic body layer 812 coated on the outer peripheral surface of the core 811, and a release layer 813 made of a heat-resistant resin coating or a heat-resistant rubber coating. Has been configured.
Further, as an auxiliary means for peeling, a peeling member 70 can be disposed on the downstream side of the nip portion N of the endless belt 62. The peeling member 70 is held by the holder 72 in a state in which the peeling sheet 71 is close to the endless belt 62 in a direction (counter direction) opposite to the rotation direction of the endless belt 62.

  The sheet P on which the toner image has been electrostatically transferred in the secondary transfer unit 20 of the image forming apparatus shown in FIG. 1 is guided to the nip N of the fixing device 91 by the fixing inlet guide 56. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the ceramic heater 82 on the endless belt 62 side. Also in the fixing device 91 of the present embodiment, since the nip portion N can be widely configured by the concave ceramic heater 82 that substantially follows the outer peripheral surface of the fixing roll 61, stable fixing performance can be ensured.

  Here, in the fixing device 91 of the present embodiment, a lubricant application member 67 is disposed in the belt traveling guide 63 along the longitudinal direction of the fixing device 91, and the lubricant application member 67 is provided in the endless belt 62. An appropriate amount of lubricant such as dimethyl silicone oil is supplied to the peripheral surface. Further, a lubricant control member 80 is disposed inside the endless belt 62 and in the vicinity of the upstream side in the moving direction of the endless belt 62 from the position where the ceramic heater 82 is disposed. Then, the lubricant applied from the lubricant application member 67 is temporarily held by the lubricant control member 80, and a constant amount of lubricant is always applied to the sliding portion between the endless belt 62 and the low resistance sheet 68. Is supplied uniformly.

  With this configuration, as in the first embodiment, the endless belt 62 and the low-resistance sheet 68 can be connected regardless of the difference in the number of sheets to be passed for each job of the image forming apparatus or the change in the sheet passing speed. Since a certain amount of lubricant can be supplied uniformly in the meantime, fluctuations in the sliding resistance between the endless belt 62 and the ceramic heater 82 can be suppressed, and the sliding resistance can always be kept small. Therefore, the endless belt 62 can be smoothly rotated, and the endless belt 62 and the paper P can be rotated at a constant speed. As a result, the paper P can be stably conveyed at the same speed as the fixing roll 61, and the occurrence of paper wrinkles and image displacement can be suppressed.

[Embodiment 3]
In the second embodiment, a fixing device mounted on the image forming apparatus shown in FIG. 1, which uses an endless belt with a heat generation source pressed as a heating unit and uses a pressure roll as a pressing unit. explained. In the third embodiment, a fixing device using an electromagnetic induction heating element as a heat generation source in the heating means will be described. In addition, about the structure similar to Embodiment 2, the same code | symbol is used and the detailed description is abbreviate | omitted here.

FIG. 4 is a side sectional view showing a configuration of the fixing device 92 in the present embodiment. As shown in FIG. 4, in the fixing device 92 of the present embodiment, the endless belt 62 is disposed on the toner image carrying surface side of the paper P. An electromagnet 83 constituting a part of an electromagnetic induction heating element that generates an alternating magnetic field substantially orthogonal to the surface of the endless belt 62 is disposed outside the endless belt 62. It is configured to supply heat.
On the other hand, the pressure roll 81 is disposed so as to face the endless belt 62, and is configured to rotate in the direction of arrow D by a drive motor (not shown), and the endless belt 62 is driven to rotate by this rotation.

The endless belt 62 is an endless belt whose original shape is formed in a cylindrical shape. In the fixing device 92 of the present embodiment, the layer structure of the endless belt 62 is laminated on the base material layer 621 and the base material layer 621 made of a sheet-like member having high heat resistance, as shown in FIG. At least three layers of a conductive layer 622 constituting a part of the electromagnetic induction heating element and a release layer 623 which is the uppermost layer are basically provided.
The base material layer 621 of the endless belt 62 is formed of a sheet having a high heat resistance with a thickness of 10 to 100 μm, more preferably 50 to 100 μm (for example, 75 μm). For example, polyester, polyethylene terephthalate, polyethersulfone, polyether What consists of synthetic resins with high heat resistance, such as a ketone, polysulfone, a polyimide, a polyimide amide, polyamide, can be used.

  The conductive layer 622 of the endless belt 62 is a layer that generates heat by the electromagnetic induction effect of an alternating magnetic field generated by the electromagnet 83, and is made of metal such as iron, cobalt, nickel, SUS, aluminum, copper, chromium, silver, and the like in the range of about 1 to 100 μm. What was formed with the thickness of is used. Here, in the case of a metal having a high electrical conductivity such as aluminum, copper, or silver, the apparent resistance value is increased in order to increase the Joule heat caused by the eddy current. That is, since the resistance value R is represented by R = ρl / S (ρ: resistivity, l: length, S: cross-sectional area), the cross-sectional area S is reduced by forming the conductive layer 622 thin. If it is made smaller, the apparent resistance value can be increased. Therefore, when a metal having high electrical conductivity is used as the conductive layer 622, the thickness of the conductive layer 622 is several μm, for example, 5 to 10 μm. On the other hand, in the case of a metal having a relatively low electrical conductivity such as iron, cobalt, nickel, and SUS, the material itself has a certain high resistivity ρ, so that the thickness of the conductive layer 622 is formed to 30 to 100 μm, for example. Is done.

  Further, the release layer 623 of the endless belt 62 needs to use a material having good release properties. Examples of the material constituting the release layer 623 include PFA, PTFE, silicon copolymer, or a composite layer thereof. The release layer 623 is a layer appropriately selected from these materials and provided on the uppermost layer of the endless belt 62 with a thickness of 1 to 100 μm.

The electromagnet 83 is a member formed in a horizontally long shape having a direction orthogonal to the moving direction of the endless belt 62 as a longitudinal direction, and maintains a gap of about 0.5 to 2 mm from the endless belt 62 that is a member to be heated. The outer belt 62 is disposed outside the endless belt 62.
FIG. 6 is a side sectional view for explaining the configuration of the electromagnet 83. As shown in FIG. 6, the electromagnet 83 is provided on the side opposite to the endless belt 62 with respect to the exciting coil 831 that generates a magnetic field, a magnetic core 832 made of a ferromagnetic material that forms a magnetic path, and the exciting coil 831. The magnetic field shielding member 833 and the excitation circuit 834 for supplying a current to the excitation coil 831 are formed.

As the exciting coil 831, for example, a coil in which a predetermined number of litz wires in which 16 copper wires having a diameter of 0.5 mm that are insulated from each other are bundled in a straight line is arranged in parallel is used.
An alternating current having a predetermined frequency is applied to the excitation coil 831 by an excitation circuit 834. As a result, an alternating magnetic field H is generated around the exciting coil 831. When the AC magnetic field H crosses the conductive layer 622 of the endless belt 62, an eddy current B is generated in the conductive layer 622 so as to generate a magnetic field that prevents the change of the AC magnetic field H by electromagnetic induction. The frequency of the alternating current applied to the exciting coil 831 is set to 10 to 50 kHz, for example, but is set to 30 kHz in the present embodiment.
Thus, when the eddy current B flows through the conductive layer 622 of the endless belt 62, Joule heat is generated due to the electric power W (W = B ² R) proportional to the resistance value R of the conductive layer 622, and the endless belt 62. Is to heat.

  The magnetic core 832 is made of ferrite or the like that is a ferromagnetic material. Since the magnetic flux generated by the exciting coil 831 forms a magnetic path passing through the inside of the magnetic core 832, the magnetic flux can be concentrated efficiently and the heating efficiency for the endless belt 62 can be increased. Therefore, it is possible to set the frequency of the high-frequency power source for applying an alternating current to the excitation coil 831 in the excitation circuit 834 low, and to set the number of windings of the excitation coil 831 to be small. Can be reduced in size and cost.

As described above, in the fixing device 92 of the present embodiment, the endless belt 62 can be directly heated by the electromagnet 83, so that a sufficient amount of heat for fixing the toner in the nip portion N can be supplied from the endless belt 62. It becomes possible.
In addition, a concave pressure pad 64 that substantially follows the outer peripheral surface of the pressure roll 81 is disposed in the nip portion N while being pressed against the pressure roll 81 via the endless belt 62. The pressure pad 64 is configured to increase in thickness toward the outlet region (peeling nip portion) of the nip portion N, and forms a larger nip pressure in the peeling nip portion, and the radius of curvature of the endless belt 62 in the peeling nip portion is smaller. It is comprised so that it may become. As a result, the paper P after fixing can be peeled off without being wound around the endless belt 62 by the small radius of curvature of the endless belt 62 when passing through the peeling nip portion. In addition, since the nip portion N can be widely configured by the concave pressure pad 64 that substantially follows the outer peripheral surface of the pressure roll 81, stable fixing performance can be ensured.
Furthermore, in order to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64, a low resistance sheet 68 is provided on the surface of the pressure pad 64 that contacts the endless belt 62.

  Here, in the fixing device 92 according to the present embodiment, a lubricant application member 67 is disposed in the belt traveling guide 63 along the longitudinal direction of the fixing device 92, and the lubricant application member 67 is provided in the endless belt 62. An appropriate amount of lubricant such as dimethyl silicone oil is supplied to the peripheral surface. Further, a lubricant control member 80 is disposed inside the endless belt 62 and in the vicinity of the upstream side in the moving direction of the endless belt 62 with respect to the position where the pressure pad 64 is disposed. Then, the lubricant applied from the lubricant application member 67 is temporarily held by the lubricant control member 80, and a constant amount of lubricant is always applied to the sliding portion between the endless belt 62 and the low resistance sheet 68. Is supplied uniformly.

  With this configuration, as in the first embodiment, the endless belt 62 and the low-resistance sheet 68 can be connected regardless of the difference in the number of sheets to be passed for each job of the image forming apparatus or the change in the sheet passing speed. Since a constant amount of lubricant can be supplied uniformly in the meantime, fluctuations in the sliding resistance between the endless belt 62 and the pressure pad 64 can be suppressed, and the sliding resistance can always be kept small. Therefore, the endless belt 62 can be smoothly rotated, and the endless belt 62 and the paper P can be rotated at a constant speed. As a result, the paper P can be stably conveyed at the same speed as the fixing roll 61, and the occurrence of paper wrinkles and image displacement can be suppressed.

  As an application example of the present invention, application to an image forming apparatus such as a copying machine or a printer using an electrophotographic method, for example, application to a fixing apparatus that fixes an unfixed toner image carried on a recording paper (paper). is there. Further, there is application to an image forming apparatus such as a copying machine or a printer using an ink jet method, for example, to a fixing device that dries an undried ink image carried on a recording paper (paper).

1 is a schematic configuration diagram showing an image forming apparatus of the present invention. 2 is a side cross-sectional view illustrating a configuration of a fixing device according to Embodiment 1. FIG. FIG. 4 is a side sectional view illustrating a configuration of a fixing device according to a second embodiment. FIG. 6 is a side cross-sectional view illustrating a configuration of a fixing device according to a third embodiment. It is a sectional side view explaining the layer structure of an endless belt. It is a sectional side view explaining the structure of an electromagnet. FIG. 10 is a side sectional view showing a configuration of a conventional fixing device.

Explanation of symbols

1Y, 1M, 1C, 1K ... image forming unit, 11 ... photosensitive drum, 12 ... charger, 13 ... laser exposure device, 14 ... developing device, 15 ... intermediate transfer belt, 16 ... primary transfer roll, 17 ... drum cleaner , 20 ... secondary transfer part, 60, 91, 92 ... fixing device, 61 ... fixing roll, 62 ... endless belt, 63 ... belt running guide, 64 ... pressure pad, 64a ... pre-nip member, 64b ... peeling nip member, 65 DESCRIPTION OF SYMBOLS ... Holder, 66 ... Halogen heater, 67 ... Lubricant application member, 68 ... Low resistance sheet, 69 ... Temperature sensor, 70 ... Release member, 80 ... Lubricant control member, 81 ... Pressure roll, 82 ... Ceramic heater, 83 …electromagnet

Claims (7)

A rotatable fixing roll having a heat source and elastically deforming the surface;
An endless belt movable while contacting the fixing roll;
A pressure member disposed inside the endless belt, and press-contacting the endless belt to the fixing roll to form a nip portion through which a recording material passes between the endless belt and the fixing roll;
A sliding member that reduces sliding resistance between the endless belt and the pressure member between the endless belt and the pressure member;
A first porous member disposed in contact with the inner peripheral surface of the endless belt, impregnated with a lubricant, and applying the lubricant to the inner peripheral surface of the endless belt;
The first porous member is disposed on the downstream side in the moving direction of the endless belt and in the vicinity of the upstream side of the sliding member in contact with the inner peripheral surface of the endless belt, and is arranged by the first porous member. A second porous member that absorbs and holds the lubricant applied to the inner peripheral surface of the endless belt and supplies the held lubricant again to the inner peripheral surface of the endless belt. A fixing device. The second porous member, fixing device according to claim 1, wherein the low lubricant absorption capacity than the first porous member. A pressure roll that is elastically deformed and is connected to a drive source and rotatable;
An endless belt that has a heat source and can be driven while in contact with the pressure roll;
A pressure member that is disposed inside the endless belt, and that presses the endless belt against the pressure roll to form a nip portion through which a recording material passes between the endless belt and the pressure roll;
A sliding member that reduces sliding resistance between the endless belt and the pressure member between the endless belt and the pressure member;
A first porous member disposed in contact with the inner peripheral surface of the endless belt, impregnated with a lubricant, and applying the lubricant to the inner peripheral surface of the endless belt;
The first porous member is disposed on the downstream side in the moving direction of the endless belt and in the vicinity of the upstream side of the sliding member in contact with the inner peripheral surface of the endless belt, and is arranged by the first porous member. A second porous member that absorbs and holds the lubricant applied to the inner peripheral surface of the endless belt and supplies the held lubricant again to the inner peripheral surface of the endless belt. A fixing device. The fixing device according to claim 3 , wherein the heat generation source of the endless belt is a resistance heating element or an electromagnetic induction heating element. Toner image forming means for forming a toner image;
Transfer means for transferring the toner image formed by the toner image forming means onto a recording material;
Fixing means for fixing the toner image transferred onto the recording material to the recording material,
The fixing means is
A pivotable pivot member;
An endless belt movable while contacting the rotating member;
A pressure member that is disposed inside the endless belt, presses the endless belt against the rotating member, and forms a nip portion through which the recording material passes between the rotating member and the endless belt;
A sliding member that reduces sliding resistance between the endless belt and the pressure member between the endless belt and the pressure member;
A first porous member disposed in contact with the inner peripheral surface of the endless belt, impregnated with a lubricant, and applying the lubricant to the inner peripheral surface of the endless belt;
The first porous member is disposed on the downstream side in the moving direction of the endless belt and in the vicinity of the upstream side of the sliding member in contact with the inner peripheral surface of the endless belt, and is arranged by the first porous member. A second porous member that absorbs and holds the lubricant applied to the inner peripheral surface of the endless belt and supplies the held lubricant again to the inner peripheral surface of the endless belt. An image forming apparatus. 6. The image forming apparatus according to claim 5 , wherein the fixing unit locally elastically deforms the pressure member on a downstream side in the transport direction of the recording material on the surface of the rotating member. The image forming apparatus according to claim 5 , wherein the toner image forming unit forms a color toner image.

Images