JP5541096B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

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

For example, Patent Document 1 discloses a fixing device that includes a plurality of external heating rolls that are pressed against the surface of a heat fixing member and heats the surface of the heat fixing member from the outside. There is disclosed a fixing device comprising contact / separation means for pressing and separating from the surface and adjusting means for uniformly pressing a plurality of external heating rolls to the surface of the heat fixing member.
Further, for example, Patent Document 2 discloses an image forming unit that forms an image on a recording material, an image heating unit that heats an image on the recording material at a nip portion, and a recovery unit that recovers the surface property of the image heating unit. The image forming apparatus includes: an execution unit configured to execute a recovery operation of the recovery unit based on an instruction from an operator.

JP 2004-37555 A JP 2008-20790 A

  Here, if the surface state of the member pressed against the paper in the fixing device is not good, it is difficult to ensure uniform image quality after fixing the image transferred onto the paper.

  An object of the present invention is to provide a fixing device or the like that can ensure uniform image quality after fixing an image transferred to a sheet.

The invention according to claim 1 is a heating member provided with a heating unit, a pressure member that is provided opposite to the heating member, and that fixes the toner image transferred to the paper together with the heating member to the paper, and the heating An external heating member that is arranged so as to be able to contact and separate from the member and that supplies heat by contacting the heating member, and a polishing that is arranged so as to be able to contact and separate from the heating member and that contacts the heating member and polishes the heating member A drive mechanism unit that includes a member and a motor, and performs contact and separation operations of the external heating member and the polishing member with respect to the heating member; and the external heating member contacts the heating member and the polishing member The first state of the drive mechanism section is changed so as to mutually change between a first state in which the heating member is separated and a second state in which the external heating member is separated from the heating member and the polishing member is in contact with the heating member. Control the motor A control unit, a fixing device including a.
According to a second aspect of the present invention, the drive mechanism section includes a single motor, and when the rotation direction of the motor is different, the contact and separation operations of the external heating member and the polishing member with respect to the heating member are different. The fixing device according to claim 1.
According to a third aspect of the present invention, when the single motor rotates in one direction, the drive mechanism unit causes both the external heating member and the polishing member to make contact with and separate from the heating member. 3. The fixing device according to claim 2, wherein when the motor rotates in the other direction, one of the external heating member and the polishing member performs a contact / separation operation with respect to the heating member.
According to a fourth aspect of the present invention, the control unit mutually changes the first state, the second state, and the third state in which the external heating member and the polishing member are separated from the heating member. 4. The fixing device according to claim 1, wherein the motor of the drive mechanism is controlled.

According to a fifth aspect of the present invention, a toner image forming unit that forms a toner image, a transfer unit that transfers the toner image formed by the toner image forming unit onto a recording material, and the toner image that has been transferred onto the recording material Fixing means for fixing a toner image on the recording material, the fixing means provided with a heating member provided with a heating unit, and the toner image provided on the heating member and transferred to a sheet. And a pressure member that fixes to the paper, an external heating member that is in contact with and away from the heating member, and supplies heat by contacting the heating member, and a heating member that is in contact with and away from the heating member. A driving member that includes a motor and a polishing member that contacts the member and polishes the heating member; and a motor that performs contact and separation of the external heating member and the polishing member with respect to the heating member; and the external heating member Heating A first state in which the polishing member is separated from the heating member in contact with a material and a second state in which the external heating member is separated from the heating member and the polishing member is in contact with the heating member are mutually And a controller that controls the motor of the drive mechanism so as to be changed.
According to a sixth aspect of the present invention, the drive mechanism section includes a single motor, and when the rotation direction of the motor is different, the contact and separation operations of the external heating member and the polishing member with respect to the heating member are different. The image forming apparatus according to claim 5.
According to a seventh aspect of the present invention, when the single motor rotates in one direction, the drive mechanism unit causes both the external heating member and the polishing member to make contact with and separate from the heating member. 7. The image forming apparatus according to claim 5, wherein when the motor rotates in the other direction, one of the external heating member and the polishing member performs a contact / separation operation with respect to the heating member.
According to an eighth aspect of the present invention, the control unit mutually changes the first state, the second state, and the third state in which the external heating member and the polishing member are separated from the heating member. The image forming apparatus according to claim 5, wherein the motor of the drive mechanism unit is controlled.

According to the first aspect, compared to the case where the present invention is not adopted, it is possible to ensure uniform image quality after fixing of the image transferred onto the paper.
According to claim 2, it is possible to realize downsizing and cost reduction of the apparatus as compared with the case where the present invention is not adopted.
According to claim 3, it is possible to simplify the contents of the control as compared with the case where the present invention is not adopted.
According to the fourth aspect, as compared with the case of the first aspect, it is possible to ensure uniform image quality after fixing of the image transferred to the paper.
According to the fifth aspect, compared with the case where the present invention is not adopted, it is possible to ensure uniform image quality after fixing of the image transferred onto the paper.
According to the sixth aspect, compared with the case where the present invention is not adopted, it is possible to realize downsizing and cost reduction of the apparatus.
According to the seventh aspect, it is possible to simplify the contents of the control as compared with the case where the present invention is not adopted.
According to the eighth aspect, compared to the case of the fifth aspect, it is possible to ensure uniform image quality after fixing of the image transferred to the paper.

1 is a schematic configuration diagram showing a color image forming apparatus according to the present embodiment. FIG. 4 is a diagram illustrating a pair of rolls included in the fixing device. FIG. 3 is a diagram illustrating a configuration around a fixing roll of a fixing device. It is a figure explaining the drive mechanism part which drives an external heating roll and a refresh roll. It is a figure explaining the drive mechanism part which drives an external heating roll and a refresh roll. It is a figure explaining the drive mechanism part between an external heating roll and a cam shaft. It is a figure explaining the drive mechanism part between an external heating roll and a cam shaft. It is a figure explaining the drive mechanism part between a refresh roll and a cam shaft.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing a color image forming apparatus according to the present embodiment.
The color image forming apparatus according to the present embodiment is provided with a photosensitive drum 11 as an image holding member that is rotatably arranged in an arrow A direction, and a photosensitive drum 11 that is rotatably arranged in an arrow B direction. And an intermediate transfer belt 20 as a transfer material for sequentially transferring (primary transfer) and holding the respective color component toner images formed thereon. The color image forming apparatus also includes a secondary transfer unit 30 that batch-transfers (secondary transfer) the superimposed toner image transferred onto the intermediate transfer belt 20 to a sheet P that is a recording material, and a secondary transferred image. Are fixed on the paper P, and a control unit 60 that controls each mechanism unit of the color image forming apparatus is provided.

  Around the photosensitive drum 11, there are a charging roll 12 as a contact charging member for charging the photosensitive drum 11, and a laser exposure device 13 as a latent image forming unit on which an electrostatic latent image is written on the photosensitive drum 11. (The exposure beam is indicated by a symbol Bm in the drawing) The yellow (Y), magenta (M), cyan (C), and black (K) color component toners are accommodated to form an electrostatic latent image on the photosensitive drum 11. Each developing device 14Y, 14M, 14C, 14K as a developing unit that visualizes with a toner is mounted on a rotary developing device 14 rotatably mounted in the direction of arrow C, and each color component toner image formed on the photosensitive drum 11. An electrophotographic device such as a primary transfer roll 15 serving as a transfer unit that transfers the toner onto the intermediate transfer belt 20 and a refresher 16 that temporarily collects residual toner on the photosensitive drum 11 are sequentially disposed. In other words, the rotary developing device 14 according to the present embodiment includes six accommodating portions that are equally divided in the circumferential direction, and is configured such that a developing device can be attached to each of the six accommodating portions. . In the rotary developing device 14 according to the present embodiment, four developing devices 14Y, 14M, 14C, and 14K are attached. However, for example, a developing device such as a special color may be attached to the remaining two storage units. Conceivable.

  Here, the charging roll 12 is formed by coating the surface of the metal shaft with an epichlorohydrin rubber layer and further coating the surface of the epichlorohydrin rubber layer with a polyamide containing tin oxide conductive powder by about 3 μm.

  Further, the photosensitive drum 11 is formed by forming an organic photosensitive layer on the surface of a metal thin cylindrical drum, and the organic photosensitive layer is made of a material that is negatively charged. The development by the developing units 14Y, 14M, 14C, and 14K is performed by a reversal development method. Accordingly, the toner used in the developing units 14Y, 14M, 14C, and 14K is of the negative charge type. A charging bias power source (not shown) for applying a charging bias to the charging roll 12 and a developing bias (not shown) for applying a developing bias to each of the developing devices 14Y, 14M, 14C, and 14K to the rotary developing device 14 are provided. A primary transfer bias power source (not shown) for applying a primary transfer bias is connected to the primary transfer roll 15. The rotary developing device 14 is provided with a developing device drive motor (not shown) for causing the developing device to face the photosensitive drum 11 by rotation. The photosensitive drum 11 is grounded.

The intermediate transfer belt 20 is stretched over a plurality of (six in this embodiment) rolls 21 to 26. Among these, the rolls 21 and 25 are driven rolls, the roll 22 is a metal idle roll used for positioning the intermediate transfer belt 20 and forming a flat primary transfer surface, and the roll 23 has a constant tension of the intermediate transfer belt 20. The tension roll used for this purpose, the roll 24 is a drive roll for the intermediate transfer belt 20, and the roll 26 is a backup roll for secondary transfer described later. Further, the intermediate transfer belt 20 is made of a resin such as polyimide, polycarbonate, polyester, polypropylene, polyethylene terephthalate, acrylic, vinyl chloride, or various rubbers containing carbon black as a conductive agent, and has a surface resistivity. ^{10 11 Ω / □, 10 11} Ω · cm in volume resistivity, and used after a 150μm thickness.

  The secondary transfer unit 30 includes a secondary transfer roll 31 disposed on the toner image holding surface side of the intermediate transfer belt 20, a backup roll 26, and the like. The backup roll 26 is a tube of EPDM and NBR blend rubber in which carbon is dispersed on the surface, the inside is made of EPDM rubber, and the surface resistivity is 7 to 10 logΩ / □, and the hardness is, for example, 70 ° ( Asuka C). The backup roll 26 is connected to a secondary transfer bias power source (not shown) for applying a secondary transfer bias, while the secondary transfer roll 31 is grounded. A paper transport guide 32 that guides the transported paper P to the secondary transfer unit 30 is attached to the upstream side of the secondary transfer unit 30.

  On the other hand, on the downstream side of the secondary transfer unit 30, a belt cleaner 27 is provided as a cleaner for removing residual toner adhering to the intermediate transfer belt 20 after the secondary transfer, and the intermediate transfer belt 20 is interposed therebetween. A sheet metal member 28 is disposed along the inner surface of the intermediate transfer belt 20 at a position facing the belt cleaner 27. The belt cleaner 27 includes a scraper 41 that is formed of a stainless steel plate or the like and is disposed on the image holding surface side of the intermediate transfer belt 20, and a cleaner housing 42 in which the scraper 41 is accommodated. Further, one end side of the scraper 41 is fixed by being sandwiched between blocks 43, and this block 43 is attached to a holder 44 that swings about a shaft 44a. Further, a spring 45 that urges the scraper 41 toward the intermediate transfer belt 20 is attached between a recess 44b provided on the lower end side of the holder 44 and a bulging portion provided at a lower portion of the cleaner housing 42. A film seal 46 is attached on the upstream side of the moving direction of the intermediate transfer belt 20 as viewed from the scraper 41 to prevent the removed foreign matter from scattering to the outside.

  The holder 44 can be urged or released in a direction opposite to the urging direction of the spring 45 by a cam (not shown) connected to a cleaner drive motor (not shown). The transfer belt 20 can be contacted and separated. In this embodiment, when a color image composed of a plurality of colors is formed, the secondary transfer roll 31 and the toner image before the final color pass through the secondary transfer roll 31 and the belt cleaner 27. A belt cleaner 27 is separated from the intermediate transfer belt 20.

  The fixing unit 50 further includes a fixing roll (heating roll) 51 containing a heating source such as a halogen lamp, and a pressure roll 52 disposed in pressure contact with the fixing roll 51. Fixing is performed by passing the paper P on which the toner image is transferred through a fixing nip area formed between the pressure roll 52 and the pressure roll 52.

  Next, the toner and developer used in the present embodiment will be described in detail. The toner used in the present embodiment has a polarity that is negatively charged as described above, and may be polyester, styrene acrylic, etc. by suspension polymerization, emulsion aggregation and coalescence, dissolution suspension, or the like. Fine particles obtained by internally adding a colorant and wax to the binder resin. As a result of measurement with a Coulter counter (manufactured by Coulter Co., Ltd.), the volume average particle size was about 5 μm, and the particle size distribution index (GSD) was 1.23. The toner shape (degree of sphere) is represented by a shape factor, and an enlarged photograph of the toner obtained with an optical microscope (microphoto FXA: manufactured by Nikon Corporation) is subjected to image analysis using an image analyzer Luzex3 (manufactured by Nireco Corporation), and the following formula Calculated with

  This expression is expressed as a ratio of the projected area of the toner to the area of the circle circumscribing the toner, and is 100 for a true sphere, and the number increases as the shape moves away from the sphere. If the shape factor is small, the amount of toner (residual toner) that remains without being transferred during transfer decreases, so the shape factor of the toner is preferably about 100 to 140. In this embodiment, The shape factor of each color component toner of yellow, magenta, cyan, and black was in the range of 129 to 134. To this toner, inorganic fine particles such as silica and titania having an average particle diameter of 5 to 200 nm were externally added as external additives, and mixed with a carrier made of ferrite beads having an average particle diameter of 35 μm to obtain a two-component developer.

  Next, an image forming process of the color image forming apparatus according to the present embodiment will be described. When a start switch (not shown) is turned on, an image forming process is executed. First, the surface of the photosensitive drum 11 is charged to a predetermined potential by the charging roll 12, and then an electrostatic latent image corresponding to the image is written by the laser exposure unit 13, and the corresponding developing units 14Y, 14M, 14C, 14K. The electrostatic latent image is developed by either of the above. For example, if the electrostatic latent image written on the photosensitive drum 11 corresponds to yellow, the electrostatic latent image is developed by the yellow developing device 14Y containing yellow toner, and the photosensitive drum A yellow toner image is formed on 11. The toner image formed on the photoconductive drum 11 is transferred from the photoconductive drum 11 by the primary transfer bias applied to the primary transfer roll 15 at the primary transfer position where the photoconductive drum 11 and the intermediate transfer belt 20 are in contact with each other. Primary transfer is performed on the belt 20. On the other hand, the toner remaining on the photosensitive drum 11 after the primary transfer is mechanically leveled by the refresher 16. In this embodiment, since so-called spherical toner is used, transfer efficiency is very high, and almost no residual toner is generated. Therefore, it is possible to form a good image without providing a drum cleaner. It has become.

  At this time, when forming a single color image, the toner image primary-transferred to the intermediate transfer belt 20 is immediately secondary-transferred to the paper P, but a color image is formed by superimposing a plurality of color toner images. In this case, the toner image formation on the photosensitive drum 11 and the primary transfer process of the toner image formed on the photosensitive drum 11 are repeated for the number of colors. For example, when a full color image is formed by superimposing four color toner images, yellow, magenta, cyan, and black toner images are sequentially formed on the photosensitive drum 11, and the toner images of these colors are sequentially transferred to the intermediate transfer belt. 20 is primarily transferred. On the other hand, the intermediate transfer belt 20 rotates in the same cycle as the photosensitive drum 11 while holding the primary transferred toner image, and magenta, cyan, and black toner images are formed on the intermediate transfer belt 20 for each rotation. Transcribed and overlaid.

  The toner image primarily transferred to the intermediate transfer belt 20 in this way is conveyed to the secondary transfer position as the intermediate transfer belt 20 rotates. On the other hand, the paper P is supplied to a secondary transfer position via a paper conveyance guide 32 at a predetermined timing by a resist roll (not shown), and the secondary transfer roll with respect to the intermediate transfer belt 20 (backup roll 26). 31 nips the paper P. Then, at the secondary transfer position, the toner image held on the intermediate transfer belt 20 is transferred to the sheet P by the action of the secondary transfer electric field that acts between the secondary transfer roll 31 that is the secondary transfer unit 30 and the backup roll 26. Electrostatic transfer (secondary transfer). Thereafter, the sheet P on which the toner image has been transferred is conveyed to the fixing unit 50, where the toner image on the sheet P is heated and pressurized and fixed, while remaining on the intermediate transfer belt 20 that has passed through the secondary transfer position. The toner is removed by the belt cleaner 27.

Next, the fixing unit 50 (hereinafter sometimes referred to as a fixing device) will be described.
FIG. 2 is a diagram illustrating a pair of rolls included in the fixing device 50.
As shown in FIG. 2, the fixing device 50 is a two-roll type including a fixing roll 51 and a pressure roll 52. The fixing roll 51 includes a core 51a, an elastic layer 51b that covers the core 51a, a release layer 51c that further covers the elastic layer 51b, and a heater (heat source) 51d provided at the center of the core 51a. I have. The pressure roll 52 includes a core 52a, an elastic layer 52b covering the core 52a, a release layer 52c further covering the elastic layer 52b, and a heater (heat source) provided at the center of the core 52a. 52d.

That is, the fixing roll 51 and the pressure roll 52 cover, for example, the surfaces of aluminum cores 51a and 52a having a thickness of 4 mm and a length of 350 mm with elastic body layers 51b and 52b made of heat-resistant silicone rubber, and further elastic layer The surface of 51b, 52b is formed by covering release layers 51c, 52c made of a 30 μm thick PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) tube.
The fixing roll 51 and the pressure roll 52 have, for example, a substantially outer diameter of 50 mm. Inside the fixing roll 51, for example, a heater 51 d such as a 570 W halogen lamp is provided. In addition, a heater 52 d such as a 470 W halogen lamp is provided inside the pressure roll 52. Heating is performed from the inside so that the surface temperatures of the fixing roll 51 and the pressure roll 52 become predetermined temperatures (depending on the melting temperature of the toner, about 100 to 190 ° C. in this embodiment).
The rubber of the elastic layer 51b of the fixing roll 51 has a hardness of 33 ° (JIS-A) and a thickness of 3 mm. The rubber layer 52b of the pressure roll 52 has a rubber hardness of 45 ° and a thickness of 2 mm. As a result, the fixing (primary fixing) nip has a shape in which the pressure roll 52 bites into the fixing roll 51. For this reason, even when the toner image is melted and brought into contact with the fixing roll 51 at the time of fixing, the toner image is easily peeled off.

  The fixing roll 51 and the pressure roll 52 configured as described above have the following operations. That is, the paper P conveyed by the conveyance belt 57 is pressed against the fixing roll 51 by the pressure roll 52 at a pressure of 0.1 to 0.8 MPa, for example. Then, the toner resin of the toner image held on the paper P is heated and melted and fixed on the paper P.

FIG. 3 is a diagram illustrating a configuration around the fixing roll 51 of the fixing device 50. (A) of the figure shows a state in which the external heating roll 53 is in contact with the fixing roll 51 while the refresh roll 54 is separated, and is an example of the first state. (B) is a state in which the external heating roll 53 is separated from the fixing roll 51 while the refreshing roll 54 is in contact, and is an example of a second state. (C) is a state in which the external heating roll 53 and the refresh roll 54 are separated from the fixing roll 51, and is an example of a third state. The fixing roll 51 is an example of a heating member, the pressure roll 52 is an example of a pressure member, the external heating roll 53 is an example of an external heating member, and the refresh roll 54 is an example of a polishing member.
As shown in the figure, the fixing roll 51 includes an external heating roll 53 that can come into contact with and separate from the fixing roll 51 and a refresh roll 54 that can come into contact with and separate from the fixing roll 51.
As will be described later, neither the external heating roll 53 nor the refreshing roll 54 is in contact with the fixing roll 51 at the same time, and either one of the external heating roll 53 or the refreshing roll 54 is in contact with the fixing roll 51. . In the present embodiment, as will be described later, the contact / separation operation of the external heating roll 53 and the refresh roll 54 with respect to the fixing roll 51 is realized by a single drive source.

  The external heating roll 53 is for supplying heat to the fixing roll 51 as necessary because the heat transfer speed of the elastic body layer 51b of the fixing roll 51 is low. That is, when the unfixed transfer paper passes through the fixing roll 51, the heat replenishment from the heater 51d of the fixing roll 51 is performed against the speed at which the heat of the surface of the fixing roll 51 is taken away by the unfixed transfer paper. The speed supplied to the surface of 51 is slow, and the surface of the fixing roll 51 may temporarily decrease in temperature. Therefore, in this embodiment, when the unfixed transfer paper enters the fixing nip, the external heating roll 53 is pressed against the fixing roll 51 and heat is supplied to the fixing roll 51 from the outside. As a result, the surface temperature of the fixing roll 51 is kept constant, and a uniform image quality can be generated.

The refresh roll 54 is for rotating the surface of the fixing roll 51 in contact with the surface to polish cracks on the surface. That is, when a large number of thick papers are run, the surface of the fixing roll 51 is cracked due to burrs at the time of cutting the paper P, so that a streak may appear in the fixed image on the paper P. As a measure for preventing such a phenomenon, it is conceivable to dispose the sheet deburring device on the upstream side of the fixing device in the image forming apparatus. However, the size of the apparatus increases, leading to an increase in cost. Therefore, in the present embodiment, the above-mentioned phenomenon is reduced by providing the external heating roll 53 that smoothes the unevenness by pressing the refreshing roll 54 against the fixing roll 51 and polishes it so as not to cause streaking in the image. This prevents the increase in size and cost.
Control of the refresh operation by the refresh roll 54 may be performed automatically at the end of printing after traveling the specified number of sheets, or may be activated by a user pressing a manual button.

More specifically, the external heating roll 53 comes into contact with the fixing roll 51 as shown in FIG. 3A when the unfixed transfer paper enters the fixing nip. As shown in FIG. 3B, the external heating roll 53 is separated from the fixing roll 51 in consideration of the service life as a component.
In addition, when the refresh roll 54 does not enter the fixing nip, in other words, when the print job is finished, as shown in FIG. Is what you do. When the refresh operation is completed, the refresh roll 54 is separated from the fixing roll 51 in order to prevent plastic deformation of the elastic layer 51b of the fixing roll 51, as shown in FIG.
By performing the separating operation of the external heating roll 53 and the refresh roll 54 with respect to the fixing roll 51 as described above, it is possible to prevent the life of the external heating roll 53 as a component from being shortened as described above. Further, it is difficult to stably secure the fixing nip due to plastic deformation of the fixing roll 51, and the possibility of causing vibration and fixing failure is prevented. Further, the circumferential temperature of the surface of the fixing roll 51 is made uniform. It is prevented that it becomes difficult to achieve uniform image quality because it cannot be maintained.

  Note that the timing for switching to the state (home position) shown in FIG. 3C may be a standby state in which a print instruction is waited after printing is completed. In addition, for example, a case where the power is turned on is also conceivable. That is, when the power of the image forming apparatus is turned from OFF to ON, an operation (initializing operation) for separating the external heating roll 53 and the refresh roll 54 from the fixing roll 51 is performed. With this operation, as shown in FIG. 3C, the external heating roll 53 and the refresh roll 54 are set to the home position.

Next, a drive transmission system in the fixing device 50 will be described.
4 and 5 are diagrams illustrating the drive mechanism unit 70 that drives the external heating roll 53 and the refresh roll 54. 4 is a schematic plan view, and FIG. 5 is a schematic front view seen from the stepping motor 71 side of FIG. 4, and the illustration of the stepping motor 71 is omitted.
As shown in FIGS. 4 and 5, the drive mechanism unit 70 includes a single stepping motor 71 that is driven and controlled by the control unit 60, and a motor shaft that is coaxially fixed to the drive shaft 71 a of the stepping motor 71. A gear 72, an idler gear 73 that meshes with the motor shaft gear 72, and an idler gear 74 that is coaxially fixed to the shaft member of the idler gear 73 are provided. In addition, the drive mechanism unit 70 includes an idler gear 75 that meshes with the idler gear 74, a camshaft gear 76 that meshes with the idler gear 75, and a camshaft gear 78 that meshes with the idler gear 74. And.
The camshaft gear 76 is coaxially fixed and attached to a camshaft 77 for transmitting a driving force to the external heating roll 53. The camshaft gear 78 is coaxially fixedly attached to a camshaft 79 for transmitting a driving force to the refresh roll 54.

The stepping motor 71 operates in synchronization with the pulse power, and can rotate so as to be switched between a forward rotation direction and a reverse rotation direction. The motor shaft gear 72, idler gears 73, 74, 75 and cam shaft gears 76, 78 are spur gears. The drive shaft 71a of the stepping motor 71, the shaft member of the idler gear 73, and the cam shafts 77 and 79 are arranged in parallel to each other.
When the stepping motor 71 rotates, the motor shaft gear 72, the idler gear 75, and the cam shaft gear 78 rotate in the same direction as the rotation direction of the stepping motor 71, while the idler gears 73, 74 and the cam shaft gear 76 are stepped. The motor 71 rotates in the direction opposite to the rotation direction.
The cam shaft gear 76 for the external heating roll 53 and the cam shaft gear 78 for the refresh roll 54 rotate in directions opposite to each other.

More specifically, the camshaft gear 78 is attached to the camshaft 79 via a one-way clutch 78a that transmits a driving force only in one direction and blocks it without transmitting a driving force in the other direction. More specifically, when the stepping motor 71 rotates forward, the driving force is transmitted from the camshaft gear 78 to the camshaft 79 via the one-way clutch 78a, whereby the camshaft gear 78 and the camshaft 79 are stepped. The motor 71 rotates in the same direction as the rotation direction. However, when the stepping motor 71 rotates in the reverse direction, the driving force is not transmitted from the camshaft gear 78 to the camshaft 79 via the one-way clutch 78a, and therefore the camshaft gear 78 is in the same direction as the rotation direction of the stepping motor 71. However, the cam shaft 79 does not rotate. In this specification, when the driving force of the stepping motor 71 is transmitted from the camshaft gear 78 to the camshaft 79 via the one-way clutch 78a, the rotation direction of the stepping motor 71 is set to normal rotation. The rotation direction of the stepping motor 71 when the driving force is not transmitted to the cam shaft 79 due to the action of the one-way clutch 78a is reverse rotation.
Therefore, when the stepping motor 71 rotates forward, the cam shaft 77 for the external heating roll 53 rotates in a direction opposite to the rotation direction of the stepping motor 71, and the cam shaft 79 for the refresh roll 54 rotates with the stepping motor 71. It rotates in the same direction as the rotation direction. However, when the stepping motor 71 rotates in the reverse direction, the cam shaft 77 for the external heating roll 53 rotates in the direction opposite to the rotation direction of the stepping motor 71, but the cam shaft 79 for the refresh roll 54 does not rotate.

6 and 7 are diagrams illustrating the drive mechanism unit 70 between the external heating roll 53 and the cam shaft 77. 6 is a longitudinal sectional view, and FIG. 7 is a perspective view.
As described above, the cam shaft gear 76 (see FIG. 4 or 5) for the external heating roll 53 is fixedly attached to the cam shaft 77 shown in FIGS. A cam 81 for the external heating roll 53 is fixedly attached to the cam shaft 77.
The cam 81 is an eccentric plate cam (cam) whose distance from the center of rotation to the circumferential surface varies depending on the position of the circumferential surface of the cam 81. A circular member 82 arranged coaxially with the external heating roll 53 is in pressure contact with the cam 81. For example, a bearing may be used as the circular member 82.
Due to such a configuration, the circular member 82 is displaced with respect to the cam shaft 77 following the rotation of the cam 81. In other words, when the cam 81 is rotated by the cam shaft 77, the circular member 82 is displaced with respect to the fixing roll 51 in accordance with the position on the circumferential surface of the cam 81 where the circular member 82 is pressed. Then, in conjunction with the displacement of the circular member 82, the external heating roll 53 is displaced. Therefore, when the cam 81 rotates, the circular member 82 is displaced according to the position of the cam 81, whereby the external heating roll 53 is displaced with respect to the fixing roll 51.
The position of the external heating roll 53 is detected by a position sensor (not shown), and the detection result is output to the control unit 60. 6 and 7 illustrate a state where the external heating roll 53 is in contact with the fixing roll 51.

FIG. 8 is a diagram illustrating the drive mechanism unit 70 between the refresh roll 54 and the cam shaft 79. FIG. 8 is a perspective view.
As described above, the cam shaft gear 78 for the refresh roll 54 is fixedly attached to the cam shaft 79 shown in FIG. A cam 83 for the refresh roll 54 is fixedly attached to the cam shaft 79. Like the cam 81, the cam 83 is a plate cam, and is configured such that the amount of eccentricity is increased by forming a recess in a portion of the circumferential surface where the distance from the rotation center to the circumferential surface is short. The cam 83 is in pressure contact with a circular member 84 such as a bearing. The circular member 84 is attached to a plate-like member 85 to which the refresh roll 54 is attached. In the plate-like member 85, one end (lower end) 85a is held on the apparatus main body side as a fulcrum, and the other end (upper end) 85b is urged by a compression coil spring in a direction in which the circular member 84 is pressed against the cam 83. Has been.
With this configuration, when the cam 83 is rotated by the cam shaft 79, the circular member 84 moves relative to the fixing roll 51 according to the position on the circumferential surface of the cam 83 to which the circular member 84 comes into pressure contact. . When the circular member 84 moves with respect to the fixing roll 51, the plate-like member 85 moves in conjunction therewith, whereby the refresh roll 54 is displaced with respect to the fixing roll 51.
The position of the refresh roll 54 is detected by a position sensor (not shown), and the detection result is output to the control unit 60. FIG. 8 illustrates a state where the refresh roll 54 is in contact with the fixing roll 51.

  Here, when the stepping motor 71 rotates forward, the external heating roll 53 and the refresh roll 54 are displaced with respect to the fixing roll 51 by the driving force. That is, the cam 81 (see FIG. 6 or FIG. 7) for the external heating roll 53 is rotated by the driving force of the stepping motor 71 that rotates in the forward direction, and the circular member 82 is displaced with respect to the fixing roll 51. Is displaced with respect to the fixing roll 51. Further, the driving force of the stepping motor 71 that rotates forward is transmitted to the cam 83 (see FIG. 8) for the refresh roll 54 without being interrupted by the one-way clutch 78a (see FIG. 4), and the circular member 84 is fixed. By being displaced with respect to the roll 51, the plate-like member 85 rotates around the one end portion 85 a, and the refresh roll 54 is displaced with respect to the fixing roll 51.

  On the other hand, when the stepping motor 71 rotates in the reverse direction, the external heating roll 53 is displaced with respect to the fixing roll 51 by the driving force, and the refresh roll 54 is not displaced with respect to the fixing roll 51. The driving force of the reversely rotating stepping motor 71 is interrupted by the one-way clutch 78a (see FIG. 4) and is not transmitted to the cam shaft 79 for the refresh roll 54.

Thus, when the stepping motor 71 is rotated forward, the external heating roll 53 and the refresh roll 54 change the positional relationship with respect to the fixing roll 51. For this reason, in the case of normal rotation, the external heating roll 53 and the refresh roll 54 repeat contact and separation with the fixing roll 51. In addition, when the stepping motor 71 is rotated in the reverse direction, the external heating roll 53 changes the positional relationship with respect to the fixing roll 51, but the refresh roll 54 is not displaced with respect to the fixing roll 51. For this reason, in the case of reverse rotation, the external heating roll 53 repeats contact and separation with the fixing roll 51, but the refresh roll 54 maintains the positional relationship with the fixing roll 51.
The contact / separation operation of the external heating roll 53 and the refresh roll 54 with respect to the fixing roll 51 differs depending on whether the stepping motor 71 rotates forward or reverse.

The control unit 60 (see FIG. 1) controls the stepping motor 71 to perform the state shown in FIG. 3A as an example of the first state and the state shown in FIG. 3B as an example of the second state. The state shown in FIG. 3C as an example of the state and the third state are mutually changed.
Next, control of the stepping motor 71 by the control unit 60 (see FIG. 1) will be described.
At the beginning of power-on, the control unit 60 does not grasp the contact / separation state of the external heating roll 53 and the refresh roll 54 with respect to the fixing roll 51, and determines whether the state shown in FIG. It is unclear whether it is in the state of b) or even the state of (c) in FIG. Therefore, when the power is turned on, the control unit 60 sets the external heating roll 53 and the refresh roll 54 to the home position as an initial operation of the fixing device 50 (see FIG. 3C). That is, the control unit 60 rotates the stepping motor 71 forward until it receives a signal from a position sensor (not shown) indicating that the refresh roll 54 is at a position away from the fixing roll 51.
When the control unit 60 receives a signal indicating that the refresh roll 54 is in a position away from the fixing roll 51, the control unit 60 temporarily stops the rotation of the stepping motor 71 and then reversely rotates the stepping motor 71. The controller 60 rotates the stepping motor 71 in reverse until it receives a signal from a position sensor (not shown) indicating that the external heating roll 53 is at a position away from the fixing roll 51. At this time, the refresh roll 54 remains at a position separated from the fixing roll 51 by the action of the one-way clutch 78a (see FIG. 4).
When the control unit 60 receives a signal that the external heating roll 53 is in a position away from the fixing roll 51, the control unit 60 stops the rotation of the stepping motor 71. Thereby, the external heating roll 53 and the refresh roll 54 are set to the home position (see (c) of FIG. 3).

From the state of the home position (see FIG. 3C), the control unit 60 brings the external heating roll 53 into contact with the fixing roll 51 and separates the refresh roll 54 from the fixing roll 51 (FIG. 3A). In the case of reference), the stepping motor 71 is rotated in the reverse direction.
Further, the control unit 60 separates the external heating roll 53 from the fixing roll 51 and brings the refresh roll 54 into contact with the fixing roll 51 from the home position (see FIG. 3C) (see FIG. 3 ( In step b), the stepping motor 71 is first rotated forward to bring the refreshing roll 54 into contact with the fixing roll 51, and then the stepping motor 71 is rotated reversely until the external heating roll 53 is separated from the fixing roll 51.

Further, when changing from (a) to (b) in FIG. 3, the control unit 60 first rotates the stepping motor 71 to bring the refreshing roll 54 into contact with the fixing roll 51, and then the stepping motor 71 is changed. The external heating roll 53 is separated from the fixing roll 51 by rotating in the reverse direction.
Further, when changing from (b) to (a) in FIG. 3, the control unit 60 rotates the stepping motor 71 in the forward direction to move the refresh roll 54 away from the fixing roll 51 and then reverses the stepping motor 71. The external heating roll 53 is rotated and brought into contact with the fixing roll 51.
Thus, when changing the relative positional relationship between the external heating roll 53 and the refresh roll 54 with respect to the fixing roll 51, the refresh roll capable of transmitting / disconnecting the driving force by the action of the one-way clutch 78a (see FIG. 4). After the position is determined for 54, the position of the external heating roll 53 that is displaced according to the forward / reverse rotation of the stepping motor 71 is determined.

Here, various modifications of the present embodiment can be considered. That is, in the present embodiment, the one-way clutch 78a (see FIG. 4) is disposed in the drive transmission system on the refresh roll 54 side, but instead is disposed in the drive transmission system on the external heating roll 53 side. This is a modification example.
In another modification, the first one-way clutch is disposed in the drive transmission system on the refresh roll 54 side, and the second one-way clutch is such that transmission and interruption of driving force is opposite to the first one-way clutch. Is arranged in the drive transmission system on the external heating roll 53 side. In this case, when the stepping motor 71 is rotated forward, only the refresh roll 54 changes the relative positional relationship with the fixing roll 51, and when the stepping motor 71 is rotated reversely, the relative position with respect to the external heating roll 53 is changed. The relationship is changed.
Further, in this embodiment, the stepping motor 71 is used as an example of a single motor that performs the contact and separation operation of the external heating roll 53 and the refresh roll 54 with respect to the fixing roll 51. A modification using a plurality of motors is also conceivable, although there are concerns about the use of multiple motors.

DESCRIPTION OF SYMBOLS 50 ... Fixing device, 51 ... Fixing roll, 52 ... Pressure roll, 53 ... External heating roll, 54 ... Refresh roll, 60 ... Control part, 70 ... Drive mechanism part, 71 ... Stepping motor, 71a ... Drive shaft, 72 ... Motor shaft gear, 73, 74, 75 ... idler gear, 76, 78 ... cam shaft gear, 77, 79 ... cam shaft, 78a ... one-way clutch, 81, 83 ... cam, 82, 84 ... circular member, 85 ... plate shape Element

Claims (8)

A heating member comprising a heating unit;
A pressure member provided opposite to the heating member and fixing the toner image transferred to the paper to the paper together with the heating member;
An external heating member that is arranged so as to be able to contact and separate from the heating member, and that supplies heat in contact with the heating member;
A polishing member that is disposed so as to be capable of contacting and separating from the heating member, and that contacts the heating member and polishes the heating member;
A drive mechanism unit that includes a motor and performs contact and separation operations of the external heating member and the polishing member with respect to the heating member;
A first state in which the external heating member contacts the heating member and the polishing member separates from the heating member, and a first state in which the external heating member separates from the heating member and the polishing member contacts the heating member. A control unit for controlling the motor of the drive mechanism unit so as to mutually change the state of 2;
Including a fixing device.   2. The drive mechanism according to claim 1, wherein the drive mechanism unit includes the single motor, and when the rotation direction of the motor is different, the contact and separation operations of the external heating member and the polishing member with respect to the heating member are different. The fixing device described.   When the single motor rotates in one direction, the drive mechanism unit causes both the external heating member and the polishing member to make contact with and separate from the heating member, and when the single motor rotates in the other direction, The fixing device according to claim 2, wherein any one of the external heating member and the polishing member performs a contact / separation operation with respect to the heating member.   The control unit is configured to change the first state, the second state, and the third state in which the external heating member and the polishing member are separated from the heating member to each other. The fixing device according to claim 1, wherein the motor is controlled. 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;
Including
The fixing means is
A heating member comprising a heating unit;
A pressure member provided opposite to the heating member and fixing the toner image transferred to the paper to the paper together with the heating member;
An external heating member that is arranged so as to be able to contact and separate from the heating member, and that supplies heat in contact with the heating member;
A polishing member that is disposed so as to be capable of contacting and separating from the heating member, and that contacts the heating member and polishes the heating member;
A drive mechanism unit that includes a motor and performs contact and separation operations of the external heating member and the polishing member with respect to the heating member;
A first state in which the external heating member contacts the heating member and the polishing member separates from the heating member, and a first state in which the external heating member separates from the heating member and the polishing member contacts the heating member. A control unit for controlling the motor of the drive mechanism unit so as to mutually change the state of 2;
An image forming apparatus including:   The said drive mechanism part is provided with the said single motor, and the contact / separation operation | movement with respect to the said heating member of the said external heating member and the said polishing member differs if the rotation directions of the said motor differ. The image forming apparatus described.   When the single motor rotates in one direction, the drive mechanism unit causes both the external heating member and the polishing member to make contact with and separate from the heating member, and when the single motor rotates in the other direction, The image forming apparatus according to claim 5, wherein one of the external heating member and the polishing member performs a contact / separation operation with respect to the heating member.   The control unit is configured to change the first state, the second state, and the third state in which the external heating member and the polishing member are separated from the heating member to each other. The image forming apparatus according to claim 5, wherein a motor is controlled.

Images