JP2012098610A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent image staining from occurring at a conveyance direction downstream side from a nip part.SOLUTION: A separation unit is configured so as to be provided with a separation plate 76, a separation belt 74 or the like. The separation belt 74 is configured so as to cover the separation plate 76 and around a belt sliding surface of a driving roller 73, and slides and moves on an outer surfaces of parts including a separated end 76a, which is the closest part to a fixing roller 20 on a surface of the separation plate 76, by a rotational driving of the driving roller 73. A sliding direction of the separation belt 74, belt conveyance direction, is a contact part between the surface of the separation plate 76 and a recording medium P and is the same as a conveyance direction of the recording medium P.

Description

  The present invention relates to a fixing device used in an electrophotographic image forming apparatus such as an electronic copying machine or a facsimile, and an image forming apparatus using the same.

  In general, in an image forming apparatus, as a device for fixing a toner image transferred onto the surface of a recording medium such as transfer paper, a fixing roller heated by an IH (Induction Heating) heater or the like, and a pressure for pressing the fixing roller A heat roller fixing system in which a recording medium having an unfixed toner image is sandwiched and conveyed by a nip formed by a roller and heated and pressurized is known and widely used.

  In such a heat roller fixing method, since the toner image fused to the recording medium comes into contact with the fixing roller, the fixing roller is coated on the surface with a fluororesin excellent in releasability, and further has a separating member. Often doing.

  As the separation member, in the case of a monochrome image forming apparatus, since the fixing roller is made of metal, a configuration in which the separation claw is in contact with the roller is known. However, in the case of a color image forming apparatus, in order to improve the color developability, the surface layer is a fluorine-coated silicone rubber (generally, PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether of about several tens of microns). Polymer) tube is used) or a silicone rubber surface coated with oil. In such a configuration, the surface layer is soft and easily damaged. If the surface layer is scratched, streaky scratches are formed on the fixed image. Therefore, in recent color image forming apparatuses, contact means such as a separation claw are hardly used, and most are non-contact separation.

  In the non-contact separation, if the adhesive force between the toner and the fixing roller is high, the recording medium after fixing is wound around the roller, so that a winding jam may easily occur. In particular, in color image formation, multiple layers of colors are laminated, and the adhesive strength is increased, so that there is a possibility that winding jam is likely to occur.

For this reason, the following methods are mainly employed in the separation of the recording medium in the fixing device of a recent color image forming apparatus.
[1] A non-contact separation plate system that uses a separation plate that has a small gap (about 0.2 to 1 mm) between the fixing roller and extends in parallel to the longitudinal direction (axial direction) of the fixing roller.
[2] A non-contact separation claw system in which a minute gap (about 0.2 to 1 mm) is provided between the fixing roller and separation claw arranged at a predetermined interval.
[3] An air separation method in which the recording medium and the roller are separated by blowing compressed air to the recording medium separation position.
[4] A self-stripping method in which the recording medium itself, such as paper or film, is naturally peeled by the stiffness of the recording medium itself and the curvature of the fixing roller.

  As such a separation system, [1] and [2] are particularly widely used because of their low cost.

  In addition, by controlling the feeding speed of the transfer belt for transferring the toner image and the feeding speed by the fixing roller, the transportability of the recording medium is stabilized, and the toner image when the recording medium is peeled off from the transfer belt is stabilized. Some attempt to prevent disturbance (see, for example, Patent Document 1).

  In addition, as an image forming apparatus that performs double-sided printing by using an intermediate transfer body, a spur member is provided between the intermediate transfer body and the fixing device, and a spur member forms a loop on the recording medium and is fixed from the intermediate transfer body. There is one that attempts to prevent the spur member from being soiled by being conveyed to the apparatus (see, for example, Patent Document 2).

  However, the above recording medium separation methods [1] and [2] have the following problems as shown in FIGS.

  First, as shown in FIG. 4, when used for a long period of time, paper dust and dust accumulate in a minute gap between the fixing roller and the separation plate.

Further, as shown in FIG. 5, when the surface of the recording medium and the separation plate are rubbed, the toner on the surface of the recording medium moves to and adheres to the separation plate. When this happens many times, toner accumulates on the separation plate, and the accumulated toner may contaminate the recording medium.
Further, the oil component contained in the toner may be condensed on the surface of the separation plate.

  Further, when the problems shown in FIGS. 4 and 5 occur, the print image on the recording medium has a problem of streaking in the conveyance direction of the recording medium.

  Further, the above-mentioned Patent Documents 1 and 2 are for preventing print image contamination upstream of the nip portion in the conveyance direction of the recording medium, and are considered to prevent image contamination downstream of the nip portion. It was not what was done.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device and an image forming apparatus that can prevent image smearing on the downstream side in the conveyance direction from the nip portion.

  In order to achieve such an object, a fixing device according to the present invention includes a heating rotary member that heats a recording medium carrying an unfixed image, and a pressure rotary member that presses against the heating rotary member to form a nip portion. A separating unit that is provided for at least one of the heating rotating member and the pressure rotating member and separates the recording medium conveyed by the rotation of the rotating member from the surface of the provided rotating member. The means includes a separation member provided at a separation position for separating the recording medium to be conveyed, and a belt member that slides at least a portion of the separation member including a separation tip portion closest to at least one rotating member. The belt member is configured to be slid in the conveyance direction of the recording medium at a contact portion with the recording medium.

  The image forming apparatus according to the present invention includes an unfixed image forming unit that forms an unfixed image on the surface of the recording medium and the fixing device according to the present invention described above. The unfixed image formed is fixed on the recording medium by a fixing device.

  As described above, according to the present invention, it is possible to prevent image smearing on the downstream side in the transport direction from the nip portion.

1 is a longitudinal sectional view illustrating a configuration example of an image forming apparatus as an embodiment of the present invention. 2 is a longitudinal sectional view illustrating a configuration example of a fixing device in the image forming apparatus. FIG. FIG. 4 is a longitudinal sectional view illustrating a configuration example of a separation unit 43 in the fixing device. FIG. 10 is a diagram illustrating a first problem in the conventional fixing device. FIG. 10 is a diagram illustrating a second problem in the conventional fixing device. It is a longitudinal cross-sectional view which shows the other structural example of the separation unit 43 by embodiment of this invention.

  Next, an embodiment to which a fixing device and an image forming apparatus according to the present invention are applied will be described in detail with reference to the drawings.

First, the configuration of the entire image forming apparatus as the present embodiment will be described with reference to FIG.
In FIG. 1, reference numeral 1 is a main body of a tandem color copying machine as an image forming apparatus, reference numeral 2 is a writing unit that emits laser light based on input image information, and reference numeral 4 is a document reading unit that reads image information of a document D. Reference numeral 7 denotes a paper feeding unit that accommodates a recording medium P such as transfer paper, and reference numerals 11Y, 11M, 11C, and 11BK denote photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed. Reference numeral 12 denotes a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK. Reference numeral 13 denotes a developing unit that develops an electrostatic latent image formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Reference numeral 15 denotes a cleaning unit that collects untransferred toner on the photosensitive drums 11Y, 11M, 11C, and 11BK.

  Reference numeral 16 denotes an intermediate transfer belt cleaning unit for cleaning the intermediate transfer belt 17, reference numeral 17 denotes an intermediate transfer belt on which toner images of a plurality of colors are transferred, and reference numeral 18 denotes a color image formed on the intermediate transfer belt 17. Is a secondary transfer roller for transferring the toner image onto the recording medium P. Reference numeral 19 denotes an electromagnetic induction heating type fixing device for fixing a toner image (unfixed image) on the recording medium P.

Next, an operation during normal color image formation in the image forming apparatus will be described.
First, image information of the document D placed on the contact glass 5 is optically read by the document reading unit 4. Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

  On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK rotate in the clockwise direction in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams. In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  The laser beam corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side in FIG. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left in FIG. 1, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left in FIG. 1, and an electrostatic latent image of the cyan component is formed. The black component laser light is irradiated on the surface of the fourth photosensitive drum 11BK from the left in FIG. 1, and an electrostatic latent image of the black component is formed.

  Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development process). .)

  Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the intermediate transfer belt 17, respectively. Here, a transfer bias roller (not shown) is installed at each facing portion so as to abut on the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photoconductive drums 11Y, 11M, 11C, and 11BK are sequentially transferred to the intermediate transfer belt 17 at the position of the transfer bias roller (primary transfer process). .)

  Then, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the primary transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (this is a cleaning process).

  Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

  Thereafter, the intermediate transfer belt 17 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 18. At this position, the secondary transfer backup roller sandwiches the intermediate transfer belt 17 between the secondary transfer roller 18 and forms a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 17 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip (secondary transfer process). At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 17.

Thereafter, the intermediate transfer belt 17 reaches the position of the intermediate transfer cleaning unit 16. At this position, the untransferred toner on the intermediate transfer belt 17 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 17 is completed.

  Here, the recording medium P transported to the position of the secondary transfer nip passes through a transport path K1 in which a paper feed roller 8, a registration roller, and the like are installed from a paper feed unit 7 disposed below the apparatus main body 1. It was transported via. Specifically, a plurality of recording media P are stored in the paper supply unit 7 in a stacked manner. When the paper feed roller 8 is rotationally driven counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the transport path K1.

  The recording medium P transported to the transport path K1 temporarily stops at the position of the roller nip of the registration roller (not shown) that has stopped rotating. Then, the registration roller is driven to rotate in synchronization with the color image on the intermediate transfer belt 17, and the recording medium P is conveyed toward the secondary transfer nip. Thus, a desired color image (unfixed image) is transferred onto the recording medium P.

  Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 19. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.

  Then, the recording medium P after the fixing process is discharged as an output image by the paper discharge roller 9 to the outside of the apparatus main body 1 (moving in the direction of the broken line arrow in FIG. 1), and a series of image forming processes is completed. To do.

  Next, the configuration and operation of the fixing device 19 installed in the image forming apparatus main body 1 will be described in detail with reference to FIG.

  As shown in FIG. 2, the fixing device 19 includes an induction heating unit 25 (magnetic flux generating unit), a fixing roller 20 (heating rotating member) as a fixing member facing the induction heating unit 25, and a pressure that presses against the fixing roller 20. A pressure roller 30 (pressure rotating member), an inlet guide plate 41, a spur guide plate 42, a separation unit 43 (separation means), an outlet guide plate 50, thermistors 61 and 62, and the like are configured as members.

  Here, the fixing roller 20 as a fixing member is formed by sequentially laminating a heat insulating elastic layer 22 made of foamed silicone rubber or the like and a sleeve layer 21 on a cored bar 23 made of iron or stainless steel, The outer diameter is about 40 mm.

  The sleeve layer 21 of the fixing roller 20 is a multilayer structure in which a base material layer, a first antioxidant layer, a heat generating layer, a second antioxidant layer, an elastic layer, and a release layer are sequentially laminated from the inner peripheral surface side. Specifically, the base material layer is formed of stainless steel having a layer thickness of about 40 μm, and the first antioxidant layer and the second antioxidant layer are formed by strike plating treatment of nickel having a layer thickness of 1 μm or less. The heating layer is made of copper having a layer thickness of about 10 μm, the elastic layer is made of silicone rubber having a layer thickness of about 150 μm, and the release layer has a layer thickness of about 30 μm. It is formed of PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer).

  In the fixing roller 20 configured as described above, the heat generating layer of the sleeve layer 21 is electromagnetically heated by the magnetic flux generated from the induction heating unit 25. The configuration of the fixing roller 20 is not limited to that of the present embodiment. For example, the sleeve layer 21 can be separated without being bonded to the heat insulating elastic layer 22 (fixing auxiliary roller). However, when the sleeve layer 21 (fixing sleeve) is separated, it is preferable to install a member for preventing the sleeve layer 21 from moving in the width direction (thrust direction) during operation.

  Here, a spur guide plate 42 in which a plurality of spurs are juxtaposed in the width direction is installed at a position facing the fixing roller 20 and upstream of the nip portion (upstream in the transport direction). The spur guide plate 42 is disposed at a position facing the fixing surface (the surface on which the image is fixed) of the recording medium P fed into the nip portion, and guides the recording medium P to the nip portion. It is. The spur guide plate 42 has a saw-tooth peripheral surface so that even if the spur contacts the unfixed image T on the recording medium P, the image does not rub.

  A separation unit 43 is installed at a position facing the fixing roller 20 and facing the fixing surface of the recording medium P sent from the nip (on the downstream side in the conveyance direction of the nip). ing. The separation unit 43 is for preventing a problem that the recording medium P after the fixing process sent out from the nip portion is attracted to and wound around the fixing roller 20. That is, when the recording medium P after the fixing process is attracted to the fixing roller 20, the separation unit 43 comes into contact with the leading end of the recording medium P, and the recording medium P is forcibly separated from the fixing roller 20.

  Further, a thermistor 62 as a contact-type temperature detection sensor that contacts the fixing roller 20 is disposed upstream of the nip (on the upstream side in the conveyance direction of the recording medium P) and close to the nip. It is installed. The thermistor 62 is disposed at the end in the width direction on the drive unit side, and detects the surface temperature of the end in the width direction of the fixing roller 20.

  A thermopile 34 (a non-contact type temperature detection sensor) is disposed at a position facing the central portion in the width direction of the fixing roller 20. A thermopile is an element that measures the temperature of an object from infrared rays emitted from the object. The infrared rays emitted from the object are absorbed by the heat conversion film inside the thermopile and converted to heat. Thereafter, the temperature is detected by a large number of micro thermocouples formed on the film.

  The temperature (fixing temperature) on the fixing roller 20 is detected by the thermistor 62 and the thermopile 34, and the heating amount by the induction heating unit 25 is adjusted based on the detection result by the thermistor 62 and the thermopile 34. In the present embodiment, the induction heating unit 25 is controlled so that the fixing temperature during the fixing process (when passing paper) is 160 to 165 ° C.

  Referring to FIG. 2, a pressure roller 30 as a pressure member is formed on a cylindrical member 32 made of steel, aluminum or the like, an elastic layer 31 made of silicone rubber or the like, a release layer made of PFA or the like (not shown). Is formed). The elastic layer 31 of the pressure roller 30 is formed to have a thickness of 1 to 5 mm. The release layer of the pressure roller 30 is formed so that the layer thickness is 20 to 200 μm. The pressure roller 30 is in pressure contact with the fixing roller 20. Then, the recording medium P is conveyed to a pressure contact portion (nip portion) between the fixing roller 20 and the pressure roller 30.

  In the present embodiment, a heater 33 such as a halogen heater is provided in the pressure roller 30 in order to increase the heating efficiency of the fixing roller 20. By supplying electric power to the heater 33, the pressure roller 30 is heated by the radiant heat of the heater 33, and the surface of the fixing roller 20 is heated via the pressure roller 30.

  A thermistor 61 as a contact-type temperature detection sensor that contacts the pressure roller 30 is located upstream of the nip portion (on the upstream side in the conveyance direction of the recording medium P) and close to the nip portion. It is arranged. The thermistor 61 is disposed at the end in the width direction on the drive unit side and detects the surface temperature of the end in the width direction of the pressure roller 30.

  A thermopile 34 (non-contact temperature detection sensor) is disposed at a position facing the central portion in the width direction of the pressure roller 30. Then, the temperature on the pressure roller 30 is detected by the thermistor 61 and the thermopile 34, and the heating amount by the heater 33 is adjusted based on the detection result by the thermistor 61 and the thermopile 34.

  Here, at a position facing the pressure roller 30 and a position facing the non-fixing surface of the recording medium P fed into the nip portion (on the upstream side of the nip portion), the inlet guide plate 41. Is installed. The inlet guide plate 41 guides the recording medium P fed into the nip portion to the nip portion.

  Further, an exit guide plate 50 is installed at a position facing the pressure roller 30 and facing the non-fixing surface of the recording medium P sent from the nip portion (on the downstream side of the nip portion). Has been. The exit guide plate 50 is for guiding the recording medium P after the fixing process sent from the nip portion toward the conveyance path after the fixing process.

  The induction heating unit 25 includes a coil unit 26 (excitation coil), a core unit 27 (excitation coil core), a coil guide 28, and the like. The coil portion 26 extends in the width direction (vertical direction in FIG. 2) by winding a litz wire bundled with thin wires on a coil guide 28 disposed so as to cover a part of the outer peripheral surface of the fixing roller 20. It is a thing.

  The coil guide 28 is made of a highly heat-resistant resin material such as PET (polyethylene terephthalate) containing about 45% of a glass material, and holds the coil portion 26 facing the outer peripheral surface of the fixing roller 20. In the present embodiment, the gap between the opposing surface of the coil guide 28 (induction heating unit 25) and the outer peripheral surface of the fixing roller 20 is set to 2 ± 0.1 mm.

The core portion 27 is made of a ferromagnetic material such as ferrite (having a relative magnetic permeability of about 2500), and is used to form an efficient magnetic flux toward the heat generating layer of the fixing roller 20, and includes an arch core and a center core. It is composed of a side core and the like.
The smoke cylinder portion 35 is formed on the back side of the hollow portion of the coil, and is installed for the purpose of circulating the airflow from the fixing device to the coil side.

  Next, the separation unit 43 which is a main configuration of the present embodiment will be described with reference to FIG.

The separation unit 43 includes a separation plate 76 (separation member), a separation belt 74, and the like.
The separation plate 76 is a plate-like member disposed at a separation position for separating the recording medium conveyed from the nip portion from the fixing roller 20 and guiding the recording medium downstream in the conveyance direction.
The separation belt 74 is configured to cover the belt sliding surface of the separation plate 76 and the drive roller 73 (rotation drive member), and the fixing roller on the surface of the separation plate 76 is driven by the rotation of the drive roller 73. The portion including the separation tip 76a, which is the portion closest to 20, is slid. As shown in FIG. 3, the sliding direction of the separation belt 74 (belt conveyance direction) is the same as the conveyance direction of the recording medium P at the contact portion with the recording medium P on the surface of the separation plate 76.

  The conveyance speed of the nip composed of the pressure roller 30 and the fixing roller 20 described above and the conveyance speed of the paper discharge roller 9 on the downstream side thereof are slightly higher for the paper discharge roller 9. This is because no slack is generated in the recording medium P. The conveyance speed of the separation belt 74 is faster than the conveyance speed of the nip and is slower than the paper discharge roller 9.

  The cleaning brush 71 is in contact with the separation belt 74, and a cleaning mechanism that removes dirt on the surface of the separation belt 74 by rotating in a reverse direction at the contact portion with the separation belt 74 by a driving unit (not shown).

  The oil application roller 72 is also in contact with the separation belt. The oil application roller 72 contains oil, and rotates in the same direction at the contact portion with the separation belt 74 to constitute an oil application mechanism that applies oil to the surface of the separation belt 74.

  The separation belt 74 is a polyimide belt having a thickness of 60 μm, and the surface is coated with a 10 μm fluororesin. The cleaning brush 71 is made of BTCF and is flocked around the roller. The bristles are used to remove dirt.

The oil application roller 72 contains silicone oil, and by applying this to the surface of the separation belt 74, the toner fixing property to the belt is kept low. Although not shown, the oil application roller 72 is always urged downward in FIG. 3 by a spring, thereby maintaining the belt tension and preventing the belt from slackening.
Further, a small gap is formed between the separation tip 76a, which is the nip side tip of the separation plate 76, and the surface of the fixing roller 20.

  Next, the effect of the separation unit 43 according to the present embodiment will be described.

  In the conventional configuration shown in FIG. 4, a separation plate is installed at the position of the separation unit, and is used for separation (peeling) of the recording medium and the fixing roller. The smaller the gap between the tip of the separation plate and the roller, the higher the separation performance. However, the narrower the gap, the more easily paper dust and dust in the air accumulate. Further, when wax oil is used in the toner used, the evaporated wax oil may condense on the separation plate. If these deposits, the recording medium after printing may become dirty.

  On the other hand, according to the above-described embodiment, the configuration in which the separation belt 74 is slidably moved can prevent paper dust, dust, wax oil, and the like from accumulating between the gaps. Paper dust or the like to be deposited is attached to the separation belt 74 and then removed by the cleaning brush 71. Thereby, the gap can be kept constant and clean.

  Further, in this embodiment, in addition to always cleaning the separation belt 74, since the oil is always applied by the oil application roller 72, the tip of the separation unit 43 (the separation belt 74) may come into contact with the fixing roller 20. However, the fixing roller is not easily damaged.

Conventionally used separation plates are composed of highly accurate parts so that a gap is always formed because the fixing roller is damaged when the separation plate and the fixing roller come into contact with each other. In the configuration of the present embodiment, the fixing roller is not easily damaged. Therefore, if the contact pressure is low, the gap is not necessarily required, and the parts accuracy as in the conventional case is not required. In addition, since the minute gap between the separation tip 76a and the surface of the fixing roller 20 can be reduced as compared with the prior art, highly reliable separation is possible.
Alternatively, the separation plate 76 may be urged so that the separation tip 76a is pressed against the surface of the fixing roller with a predetermined pressure.

  Further, as shown in FIG. 5, in the conventional configuration, a separation plate is installed at the position of the separation unit, and is used for separation (peeling) of the recording medium and the fixing roller. When a large amount of toner adheres to the recording medium, the recording medium is conveyed so as to rub against the separation plate at the nip exit. Since the recording medium is immediately after passing through the nip, the toner is not completely solidified, and there is a possibility that the toner adheres to and accumulates on the separation plate when rubbed. The toner adhering to the surface of the separation plate may transfer the toner from the separation plate to the recording medium when another recording medium rubs against the separation plate, and may contaminate the recording medium.

  On the other hand, according to the above-described embodiment, since the toner is removed by the cleaning brush 71 even if the toner adheres to the separation belt 74, it is possible to prevent such a problem of image smearing from occurring.

  Further, as shown in FIG. 5, in the conventional configuration, the toner adheres to and accumulates on the separation plate as described above, so that the recording medium to be conveyed is rubbed (streaks). was there.

  On the other hand, according to the above-described embodiment, the separation belt 74 is conveyed at the contact portion with the recording medium in the same direction and at almost the same speed as the recording medium. It is possible to prevent the occurrence of rubbing, and hence no rubbing trace (streaks).

As described above, the above-described embodiment has the following features.
As a first feature, the fixing device of the above-described embodiment includes a heating rotating member that heats a recording medium that carries an unfixed image, a pressure rotating member that contacts the heating rotating member and forms a nip portion, A separation unit provided for at least one of the heating rotation member and the pressure rotation member, and the separation unit is biased so that an end is pressed against the surface of the rotation member, A separation plate that separates and guides the sheet-like recording medium that has passed through the nip portion from the surface of the at least one rotating member, and a belt member that slides on the surface of the separation plate. To do.

  According to the 1st characteristic, a separation unit can be made clean by conveying a separation belt. For this reason, it is possible to prevent the recording medium from being smudged or rubbed on the downstream side in the transport direction from the nip portion.

As a second feature, the fixing device according to the above-described embodiment includes a cleaning mechanism for cleaning the belt member.
According to the second feature, the separation belt can be kept clean.

As a third feature, the fixing device of the above-described embodiment is characterized in that the belt member is an endless belt.
According to the third feature, the separation belt can be used repeatedly.

As a fourth feature, the fixing device according to the above-described embodiment includes an oil application mechanism that applies oil for sheet peeling onto the belt member.
According to the fourth feature, the separation property of the separation belt against dirt can be maintained.

Further, as a fifth feature, the fixing device of the above-described embodiment can be configured to discharge a pulsed compressed gas from the separation member to the nip portion.
In recent years, the recording medium is often separated by ejecting compressed air to the outlet from the nip (the outlet of the recording medium being conveyed). By using the above-described embodiment together with the compressed air ejection mechanism, the recording medium can be more reliably separated.

  Thus, according to the fifth feature, it can be used in combination with an air separation type separation mechanism that discharges compressed air.

  Each of the above-described embodiments is a preferred embodiment of the present invention, and the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, in the above-described embodiment, the configuration example in which the separation belt 74 is an endless belt has been described. However, the configuration is not limited to this configuration, and for example, the configuration may be configured as illustrated in FIG.
In the configuration example of FIG. 6, the separation belt 74 is stored in a state in which the separation belt 74 is wound around the belt bank 77 in advance. The front end of the separation belt 74 is connected to a belt winding device 78, and the separation belt 74 therebetween is wound so as to stick to the surface of the part including the separation front end 76a of the separation plate 76.

The separation belt 74 is in a stationary state during printing, and as it is printed, the gap between the separation plate and the fixing roller and the rubbing portion with the recording medium become dirty.
For this reason, in the configuration example of FIG. 6, the winding operation is performed on the separation belt 74 every time a predetermined number (for example, 500 pages) is printed. Thereby, the separation unit 43 can be kept in a clean state.

  In the above-described embodiment, the separation unit 43 is described as being provided with respect to the fixing roller 20. However, the present invention is not limited to this configuration, and in the case where the recording medium needs to be separated from the pressure roller 30, The separation unit 43 may be provided for the pressure roller 30.

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Writing part 4 Document reading part 5 Contact glass 7 Paper feed part 8 Paper feed roller 9 Paper discharge roller 11 Photosensitive drum 12 Charging part 13 Developing part 15 Cleaning part 16 Intermediate transfer belt cleaning part 17 Intermediate transfer belt 18 2 Next transfer roller 19 Fixing device 20 Fixing roller 21 Sleeve layer 22 Thermal insulation elastic layer 23 Core metal 25 Induction heating unit 26 Coil unit 27 Core unit 28 Coil guide 30 Pressure roller 31 Elastic layer 32 Cylindrical member 33 Heater 34 Thermopile 41 Inlet guide plate 42 spur guide plate 43 separation guide plate 50 outlet guide plate 61, 62 thermistor 71 cleaning brush 72 oil application roller 73 separation belt drive roller 74 separation belt 75 idler roller 76 separation plate 76a separation tip 77 belt bank 78 bell Winding device

Japanese Patent No. 3434056 Japanese Patent Laid-Open No. 11-265095

Claims (6)

A heating rotating member for heating a recording medium carrying an unfixed image;
A pressure rotating member that is pressed against the heating rotating member to form a nip portion; and
Separation means provided for at least one of the heating rotary member and the pressure rotary member, and separating a recording medium conveyed by rotation of the rotary member from the provided rotary member surface;
The separating means includes
A separation member provided at a separation position for separating the recording medium to be conveyed;
A belt member that slidably moves at least a portion of the separation member including a separation tip portion closest to the at least one rotating member;
The fixing device, wherein the belt member is configured to slide in a conveyance direction of the recording medium at a contact portion with the recording medium.   The fixing device according to claim 1, wherein the separation unit includes a cleaning mechanism that cleans the surface of the belt member. The separating means includes a rotation drive member that slides the belt member,
The fixing device according to claim 1, wherein the belt member is an endless belt provided so as to slidably cover at least sliding surfaces of the separation member and the rotation driving member. .   The fixing device according to claim 1, wherein the separating unit includes an oil application mechanism that applies oil to a surface of the belt member.   The fixing device according to claim 1, wherein the separation unit includes a discharge unit that discharges compressed gas to the nip portion. Unfixed image forming means for forming an unfixed image on the surface of the recording medium;
A fixing device according to any one of claims 1 to 5,
An image forming apparatus configured to fix an unfixed image formed on a surface of a recording medium by the unfixed image forming unit to the recording medium by the fixing device.

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