JP2009053564A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device where a separation pawl or a non-contact separation guide is separated from a fixing roller or a pressure roller with inexpensive simple constitution, so that damage of the roller is suppressed. <P>SOLUTION: The fixing device 30 having the fixing roller 31, the pressure roller 32, halogen heaters 33 and 34, and a separation guide unit 80 guiding a sheet S passing through a nip part N includes: a motor; a cam shaft 50 rotated by the motor; a nip separation mechanism to make the fixing roller 31 and the pressure roller 32 press-contact with and separate from each other by rotation of the cam shaft 50; and a guide retreat mechanism to make the separation guide unit 80 come close to and retreat from the fixing roller 31 or the pressure roller 32 by the rotation of the cam shaft 50. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

  Conventionally, as a fixing device mounted on an electrophotographic image forming apparatus such as a copying machine or a laser printer, a fixing roller, a heater for heating the fixing roller disposed in the fixing roller, and the fixing roller are also in pressure contact with each other in the nip. And a pressure roller that forms the portion. The sheet carrying the unfixed toner image is heated and melted while being nipped and conveyed at the nip portion of the fixing device, whereby the toner image on the sheet is fixed to the sheet.

  Normally, the fixed sheet that has passed through the nip is conveyed without being wound around the fixing roller by the waist of the sheet, but when the adhesion force of the fixed toner image to the fixing roller exceeds the peeling force by the waist of the sheet There is a possibility of being wound around the fixing roller. For this reason, there are some which prevent the winding by bringing the separation claw into contact with the fixing roller.

  Here, if the separation claw is kept in contact with the fixing roller at all times, dirt may accumulate on the abutting portion or the surface of the fixing roller may be scratched. A device that is separated from the fixing roller is known (see Patent Document 1).

  In addition, with recent improvements in image quality of image forming apparatuses, there are some that prevent fine scratches and dirt on the surface of the fixing roller from affecting the printed image. In this image forming apparatus, the separation claw is not brought into contact with the fixing roller, and the non-contact separation guide is arranged as close to the fixing roller as possible to suppress winding (see Patent Document 2).

Japanese Patent Laying-Open No. 2005-99426 (FIG. 3) JP-A-8-314305 (FIG. 1)

  However, since the fixing device described in Patent Document 1 requires an actuator such as a solenoid as the separation claw separation mechanism, the configuration tends to be complicated and the cost tends to increase as a whole.

  Further, in the fixing device described in Patent Document 2, it is necessary to reduce the gap between the leading end of the separation guide and the surface of the fixing roller as much as possible in order to prevent wrapping around the fixing roller. However, if this gap is small, the separation guide may come into contact with the fixing roller and scratch the surface of the fixing roller when the image forming apparatus is transported or installed, or when handling the fixing device such as jam processing. There is also a risk.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that can separate a separation claw and a non-contact separation guide from a fixing roller or a pressure roller with a low-cost and simple configuration and suppress damage to the roller.

  In order to solve the above-described problems, a typical configuration of the fixing device according to the present invention includes a fixing rotator, a pressure rotator that forms a nip portion in contact with the fixing rotator, the fixing rotator, and the adder. A heating means for heating at least one of the pressure rotator and a recording medium that has passed through the nip portion is scooped up so as not to be wound around the fixing rotator or the pressure rotator and guided in the downstream direction. A fixing unit that heats a toner image on the recording medium while nipping and conveying the recording medium at the nip portion, a driving source, a rotating shaft that is rotated by the driving source, and the rotating shaft A nip separation mechanism that presses and separates the fixing rotator and the pressure rotator by rotation, and the guide means with respect to the fixing rotator or the pressure rotator by rotation of the rotation shaft. A guide retraction mechanism for contact and retreated, characterized by having a.

  According to the present invention, the separation claw and the non-contact separation guide can be separated from the fixing roller or the pressure roller with a low cost and simple configuration, and damage to the roller can be suppressed.

[First embodiment]
A first embodiment of a fixing device according to the present invention will be described with reference to the drawings.

(1) Image Forming Apparatus FIG. 1 is a configuration diagram of an image forming apparatus equipped with a fixing device according to the present embodiment. As shown in FIG. 1, the image forming apparatus is an electrophotographic full-color laser printer (hereinafter simply referred to as “printer”).

  The printer includes a sheet supply device 20 below a printer main body (image forming apparatus main body) 100 constituting a housing of the printer. In the sheet supply apparatus 20, a sheet S such as recording paper as a recording medium stored in the sheet supply cassette 21 is sent out from the cassette 21 as the pickup roller 22 rotates counterclockwise in the drawing. The fed sheets S are separated and fed one by one to the registration roller pair 25 through the feeding roller 23 and the retard roller 24. The separately fed sheet S is conveyed to the secondary transfer unit 17 by the registration roller pair 25 at a predetermined timing.

  An image forming unit 8 is provided above the sheet supply apparatus 20 in the printer main body 100. In the image forming unit 8, four drum-type electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) 1a, 1b, which correspond to yellow, magenta, cyan, and black colors in the substantially horizontal direction as image carriers. 1c and 1d. The photosensitive drum 1 is rotated clockwise in the figure by driving means (not shown).

  Around the photosensitive drum 1, charging devices 2a, 2b, 2c, and 2d and scanner units 3a, 3b, 3c, and 3d are arranged in order according to the rotation direction. Further, developing devices 4a, 4b, 4c and 4d and cleaning devices 6a, 6b, 6c and 6d are arranged.

  The charging device 2 uniformly charges the outer peripheral surface (surface) of the photosensitive drum 1. An electrostatic latent image is formed on the charged surface of the photosensitive drum 1 by irradiating the charged surface on the surface of the photosensitive drum 1 with a laser beam based on the image information of each color by the scanner unit 3. The developing device 4 develops the electrostatic latent image as a toner image (developed image) by attaching toners (developers) of yellow, magenta, cyan, and black to the electrostatic latent image on the photosensitive drum 1.

  Here, the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 are integrally formed as a cartridge to form process cartridges 7a, 7b, 7c, and 7d. The cartridge 7 is detachably attached to the printer main body 100.

  An intermediate transfer device 10 is disposed at the opposite portion of the photosensitive drum 1 so that the intermediate transfer belt 11 is in contact with each photosensitive drum 1. The intermediate transfer belt 11 is formed of a thin film member having a predetermined volume specific resistance. The intermediate transfer belt 11 is stretched around three rollers of a driving roller 12 and driven rollers 13 and 14 and rotates counterclockwise in the drawing.

  Inside the intermediate transfer belt 11, primary transfer rollers 15a, 15b, 15c, and 15d that face the four photosensitive drums 1 and abut against the inner surface of the intermediate transfer belt 11 are arranged in parallel. The primary transfer roller 15 transfers yellow, magenta, cyan, and black toner images from the surface of the photosensitive drum 1 to the surface of the intermediate transfer belt 11 at a primary transfer portion that is in contact with the inner surface of the intermediate transfer belt 11.

  The surface of the photosensitive drum 1 to which the toner image has been transferred is cleaned by the transfer device 6 after removal of the transfer residual toner, and is repeatedly used for the next image formation.

  A secondary transfer roller 16 is disposed at a position facing the drive roller 12 of the intermediate transfer device 10, and is pressed against the surface of the intermediate transfer belt 11 with a predetermined pressure to form a secondary transfer portion 17. The secondary transfer roller 16 transfers yellow, magenta, cyan, and black toner images from the surface of the intermediate transfer belt 11 to the sheet S surface in the secondary transfer unit 17.

  The sheet S to which the toner image has been transferred in the secondary transfer unit 17 is conveyed and introduced to the fixing device 30 through the conveyance guide 18 and undergoes heating and pressure fixing processing of the toner image.

  The sheet S that has passed through the fixing device 30 is conveyed to the discharge roller pair 29 through the conveyance guide 28. The discharge roller pair 29 discharges the sheet onto a sheet discharge tray 101 provided on the upper portion of the printer main body 100.

(2) Fixing device 30
2 to 4 are cross-sectional views of the fixing device 30. FIG. 2 is a cross-sectional view in the vicinity of the longitudinal center, showing a state in which the pressure roller 32 is in pressure contact with the fixing roller 31. FIG. 3 is a cross-sectional view showing the nip separation mechanism A and the guide retraction mechanism B, and shows a state where the pressure roller 32 is in pressure contact with the fixing roller 31. FIG. 4 is also a cross-sectional view showing the nip separation mechanism A and the guide retraction mechanism B, and shows a state in which the pressure roller 32 is separated from the fixing roller 31. FIG. 5 is a perspective view of the separation guide unit 80. FIG. 6 is a configuration diagram of a drive transmission mechanism unit of the fixing device 30.

  As shown in FIG. 2, the fixing device 30 includes a fixing roller 31 as a fixing rotator, a pressure roller 32 as a pressure rotator, and heating provided in each of the fixing roller 31 and the pressure roller 32. As means, halogen heaters 33 and 34 are provided.

  The fixing device 30 includes fixing inlet guides 37 and 38 for guiding the sheet S to the nip portion N on the sheet inlet side, and conveyance for further conveying the sheet S downstream on the outlet side of the nip portion N. Rollers 35 and 36 are provided. The fixing device 30 includes a separation guide unit 80 as guide means on the fixing roller 31 side on the exit side of the nip portion N. The fixing device 30 includes a pressure guide 39 on the pressure roller 32 side on the exit side of the nip portion N.

  The fixing roller 31 includes, in order from the inside, a metal pipe-shaped core 31a and an elastic layer 31b made of heat-resistant silicon rubber, and a release layer 31c made of a fluorine-based resin such as PFA on its surface. Yes. As shown in FIGS. 3 to 6, both longitudinal end portions 31 </ b> A of the cored bar 31 a are formed to have a smaller diameter than the longitudinal central portion, and are rotatably held by the fixing frame 40 via bearings (not shown) such as bearings. ing.

  Similarly to the fixing roller 31, the pressure roller 32 includes a metal pipe-shaped cored bar 32 a and an elastic layer 32 b made of heat-resistant silicon rubber in order from the inside, and the surface thereof is made of a fluorine-based resin such as PFA. A release layer 32c is provided. As shown in FIGS. 3 and 4, both longitudinal end portions 32 </ b> A of the cored bar 32 a are formed with a smaller diameter than the longitudinal central portion, and a pressure arm 41 disposed on the inner side of the frame 40 is provided with a bearing such as a bearing. It is supported rotatably.

  The pressure arm 41 is rotatably supported by the frame 40 via a shaft 42 so that the pressure roller 32 can be brought into contact with and separated from the fixing roller 31. A pressure spring 43 is provided between the pressure arm 41 and the frame 40 on the opposite side of the shaft 42, and the pressure arm 41 is urged toward the fixing roller 31 by the pressure spring 43. Due to this urging force, the pressure roller 32 is pressed against the fixing roller 31 to form a nip portion (fixing nip portion) N having a predetermined width with the fixing roller 31.

  Here, if the fixing roller 31 and the pressure roller 32 are left in pressure contact, the elastic layers 31b and 32b of the rollers 31 and 32 may be permanently deformed in the nip portion N. Therefore, the fixing device 30 also includes a nip separation mechanism A that separates the pressure roller 32 from the fixing roller 31.

a) Nip separation mechanism A
As shown in FIGS. 3 to 6, the nip separation mechanism A includes a roller 44 provided on the pressure arm 41 and a pressure release cam (first cam member) 51 provided on the cam shaft (rotary shaft) 50. And comprising. The separation operation of the pressure roller 32 is performed by the rotational movement of the cam shaft 50 that receives driving from a motor 70 as a driving source described later.

  The cam shaft 50 is disposed above the fixing roller 31 in parallel with the fixing roller 31, and both longitudinal ends thereof are rotatably supported by the frame 40 via bearings 55. A pressure release cam 51 as a first cam means is fixedly held near the end of the cam shaft 50 inside the frame 40. A roller 44 is rotatably supported by a shaft 45 at a portion of the pressure arm 41 facing the pressure release cam 51.

  In the nip separation mechanism A, the roller 44 is in rolling contact with the outer peripheral surface (large diameter portion) of the pressure release cam 51. Then, the pressure arm 41 rotates counterclockwise about the shaft 42 to separate the pressure roller 32 from the fixing roller 31 (state shown in FIG. 4).

b) Separation guide unit 80
The separation guide unit 80 is guide means for scooping up the sheet S wound around the fixing roller 31 and conveying it in the direction of the conveying rollers 35 and 36 (downstream in the conveying direction) as shown in FIG. The winding of the sheet S occurs when the force of the toner T that adheres to the surface of the fixing roller 31 is stronger than the waist of the sheet. That is, the sheet S on which the toner T has been fixed on one side by the nip N is normally conveyed as it is in the direction of passing through the nip N. However. When the force of the toner T that adheres to the surface of the fixing roller 31 is stronger than the waist of the sheet, the leading edge of the sheet S may be carried out along the surface of the fixing roller 31 as shown in FIG. .

  The separation guide unit 80 includes a separation guide frame 82 and a separation guide 81 attached to the separation guide frame 82, and shafts 83 at both ends are rotatably supported by the fixing frame 40. Further, the abutting members 84 provided at both end portions of the lower surface of the separation guide frame 82 are in contact with the camshaft 50 to determine the position of the separation guide frame 82 in the height direction.

  As shown in FIG. 5, the separation guide 81 is fixed to the separation guide frame 82 at two locations in the longitudinal direction by screws 85, and the attachment position in the direction of arrow A3 is adjusted in the assembly process. Thereby, the gap G between the separation guide 81 and the fixing roller 31 can be set to a predetermined distance. The smaller the gap G is, the greater the effect of preventing the occurrence of a wrap around the fixing roller 31. On the other hand, the tip of the separation guide 81 comes into contact with the surface of the fixing roller 31 and is damaged. The possibility that it will end up also increases. For this reason, the gap G is adjusted to be 0.6 to 1.0 mm in consideration of thermal expansion of the fixing roller 31, fluctuation of the outer diameter, other component accuracy, and the like.

c) Guide retraction mechanism B

  The fixing device 30 includes a guide retracting mechanism that retracts the separation guide unit 80 from the fixing roller 31. The guide retraction mechanism B includes a cam shaft 50 and a separation guide cam (second cam member) 52.

  As with the nip separation mechanism A, the guide retraction mechanism B is performed by the rotational movement of the cam shaft 50. In the vicinity of both end portions of the cam shaft 50, a separation guide cam 52 as second cam means is fixedly held inside the pressure release cam 51. As the cam shaft 50 rotates about 180 °, the outer peripheral surface (large diameter portion) of the separation guide cam 52 contacts the lower surface of the separation guide frame 82. Then, the separation guide unit 80 can be rotated counterclockwise about the shaft 83 to retract the separation guide 81 from the surface of the fixing roller 31 (state shown in FIG. 4). The gap G1 at this time is about 3 mm.

  As a result, even if the gap G is set as small as possible, when an unexpected force is applied except during printing, the leading end of the separation guide 81 comes into contact with the fixing roller 31 and is damaged due to deflection of each part. There is nothing. For example, even when the separation guide unit 80 is pushed during vibrations during transportation or installation of the printer 100 or when a jam sheet is removed by the user, the leading end of the separation guide 81 is sufficiently separated from the fixing roller 31. Damage to the roller 31 can be suppressed.

d) Driving Mechanism of Fixing Roller 31 and Cam Shaft 50 In FIG. 6, a motor 70 that is the only driving source for driving each part of the fixing device 30 is fixed to the main body frame 71. The rotational drive of the motor 70 is transmitted from the motor gear 70 a to the gear 72 and the gear shaft 73. One-way gears 74 and 75 are fitted on the gear shaft 73. In the one-way gears 74 and 75, one-way clutches 74a and 75a are incorporated so that the locking directions are opposite to each other.

  With this configuration, when the motor 70 rotates in the direction of the solid arrow A1 (first direction), the one-way clutch 74a is locked and the one-way clutch 75a is free, so that the drive is transmitted only to the one-way gear 74. The The driving of the one-way gear 74 is transmitted to the gear 78 fixed to the one end 31A of the core 31a of the fixing roller 31 through the gear 76, and the fixing roller 31 is rotated in the direction in which the sheet S is conveyed. Due to the rotation of the fixing roller 31, a rotational force acts on the pressure roller 32 by the frictional force between the surface of the fixing roller 31 and the surface of the pressure roller 32 in the nip portion N. The pressure roller 32 has a rotational peripheral speed of the fixing roller 31. The sheet S is driven and rotated at substantially the same peripheral speed.

  On the contrary, when the motor 70 rotates in the direction of the broken arrow A2 (second direction opposite to the first direction), the one-way clutch 75a is locked and the one-way clutch 74a becomes free. Drive is transmitted only to 75. The drive of the one-way gear 75 is transmitted to the gear 79 attached to one end of the cam shaft 50 through the gear 77, and the cam shaft 50 is rotated.

  A flag 65 for detecting the amount of rotation of the cam shaft 50 is attached to one end side of the cam shaft 50, and a photo sensor 66 is provided on the fixing frame 40. FIG. 7 is an explanatory diagram of the flag 65 and the sensor 66.

  As shown in FIG. 7, the flag 65 is provided with a notch 65a for detecting the rotation amount of the camshaft 50. The notch 65a is detected by the sensor 65, and the detection signal Sa is used as a control means. The CPU 110 is inputting. The CPU 110 controls the operations of the nip separation mechanism A and the guide retracting mechanism B by outputting a drive control signal Sb to the motor 70 based on the detection signal Sa.

e) Description of operation of the fixing device 30 and the printer 100 When the non-image is formed, the pressure roller 32 is separated from the fixing roller 31 in order to prevent permanent deformation of the elastic layers 31b and 32b of the fixing roller 31 and the pressure roller 32. (State of FIG. 4). In this separated state, the separation guide unit 80 is also retracted from the fixing roller 31. The non-image forming time includes when the printer 100 is turned off, when there is no print job for a predetermined time even when the power is turned on, warm-up, standby, jam processing, and the like.

  When the image forming apparatus forms an image, the print signal is received in a separated state, the cam shaft 50 rotates, the pressure roller 32 comes into pressure contact with the fixing roller 31, and the separation guide unit 80 also approaches the fixing roller 31 (non- Contact state) and a state where printing is possible (state shown in FIG. 3).

  When the fixing device 30 is ready for printing, in FIG. 1, the sheet feeding device 20 separates and feeds the sheets S one by one, and the registration sensor 26 provided immediately after the nip portion of the registration roller pair 25 causes the leading edge of the sheet S to be fed. When the sheet is detected, sheet feeding is temporarily stopped. On the other hand, the process cartridges 7 are also sequentially driven to form the respective color toner images and sequentially transfer them onto the intermediate transfer belt 11, thereby completing the superposition of the four color toner images. Then, sheet feeding is resumed by the registration roller pair 25 in accordance with the timing of the toner image on the intermediate transfer belt 11, and the toner image is transferred to the sheet S by the secondary transfer unit 17.

  Thereafter, the sheet S is conveyed upward along the leading edge of the conveyance guide 18, guided to the fixing device 30, and nipped and conveyed by the nip portion N to the heated fixing roller 31 and pressure roller 32. The toner image is fixed on the sheet S surface. The sheet S that has passed through the nip portion N is conveyed by the conveying rollers 35 and 36 and is discharged onto the sheet discharge tray 101 by the discharge roller pair 29.

  Here, even when a sheet that is easily wound around the fixing roller 31, such as a sheet on which a large amount of toner is transferred near the front end or a sheet with low stiffness, is picked up by the separation guide 81 and discharged without causing jamming. .

  If there is no next print job for a predetermined time after printing, the fixing nip N is separated again, and the separation guide unit 80 is also retracted. Further, even when a jam occurs due to some cause, the fixing nip portion N is similarly separated, and even if there is a sheet that has been transported and stopped while being sandwiched between the fixing nip portion N, the sheet can be easily removed. it can.

  As described above, the separation guide unit 80 is also moved toward and away from the fixing roller 31 by using the rotation of the cam shaft 50 that performs the pressure contact / separation operation between the fixing roller 31 and the pressure roller 32. I can do things. Therefore, the non-contact separation guide unit 80 can be retracted from the fixing roller 31 with a low cost and simple configuration without providing an actuator or the like, and damage to the fixing roller 31 can be suppressed.

[Second Embodiment]
Next, a second embodiment of the fixing device according to the present invention will be described with reference to the drawings. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

Is omitted.

  FIG. 8 is an explanatory diagram of the separation guide unit 130 according to the present embodiment. As shown in FIG. 8, the fixing device of the present embodiment is provided with a fixing roller 121 instead of the fixing roller 31, and a separation guide unit 130 instead of the separation guide unit 80.

  The fixing roller 121 is of a type having no elastic layer, and the release layer 121c is formed directly on the surface of the cored bar 121a. Therefore, the heat capacity is small, the heat conduction speed is high, and the warm-up time can be shortened. There is. On the other hand, since the fixing roller 121 does not have an elastic layer, there is a demerit such that the glossiness of the image is difficult to be obtained. Therefore, the fixing roller 121 is often used mainly for a monochrome printer that does not require high image quality.

  The separation guide unit 130 brings the leading end of the separation claw 131 into contact with the fixing roller 121 and peels the sheet that is about to be wound around the fixing roller 121. The separation guide unit 130 has a plurality of separation claws 131 attached to the tip of a short separation guide 132. The separation claw 131 is rotatable about a shaft 131a and is urged by a compression spring 133 with a very small force in a direction in contact with the fixing roller 121 (clockwise direction in FIG. 8).

  Therefore, as shown in FIG. 8A, when the separation guide unit 130 is close to the fixing roller 121, the vicinity of the tip of the separation claw 131 always follows the surface of the fixing roller 121 and abuts. The sheet S that is about to be wound can be surely scooped up.

  As shown in FIG. 8B, the separation guide unit 130 can be retracted from the fixing roller 121 around the shaft 134 and the separation claw 131 can be separated from the fixing roller 121. The retraction operation of the separation guide unit 130 can be performed simultaneously with the separation of the pressure roller by the rotational movement of the cam shaft 50, as in the first embodiment.

  As a result, even if the separation claw 131 is in contact with the fixing roller 121, the separation claw 131 can be separated as much as possible except during printing to prevent the surface of the fixing roller 121 from being damaged. Further, it is possible to suppress the surface of the fixing roller 121 from being damaged by inadvertently pushing the separation claw 131 even during jam processing.

1 is a configuration diagram of an image forming apparatus equipped with a fixing device according to a first embodiment. FIG. 3 is a cross-sectional view of the fixing device. FIG. 3 is a cross-sectional view of the fixing device. FIG. 3 is a cross-sectional view of the fixing device. It is a perspective view of a separation guide unit. FIG. 4 is a configuration diagram of a drive transmission mechanism unit of the fixing device. It is explanatory drawing of a flag and a sensor. It is explanatory drawing of the separation guide unit which concerns on 2nd embodiment.

Explanation of symbols

G ... Gap N ... Nip part S ... Sheet Sa ... Detection signal Sb ... Drive control signal T ... Toner 1 ... Photoconductor drum 2 ... Charging device 3 ... Scanner unit 4 ... Developing device 6 ... Cleaning device 7 ... Process cartridge 8 ... Image Forming unit 10 ... intermediate transfer device 11 ... intermediate transfer belt 12 ... drive rollers 13 and 14 ... driven roller 15 ... primary transfer roller 16 ... secondary transfer roller 17 ... secondary transfer unit 18 ... transport guide 20 ... sheet feeding device 21 Sheet feed cassette 22 Pickup roller 23 Feed roller 24 Retard roller 25 Registration roller pair 26 Registration sensor 28 Conveying guide 29 Discharge roller pair 30 Fixing device 31 Fixing roller (fixing rotator)
31A, 32A ... Longitudinal ends 31a, 32a ... Core bars 31b, 32b ... Elastic layers 31c, 32c ... Release layer 32 ... Pressure roller (pressure rotator)
33, 34 ... Halogen heaters 35, 36 ... Conveying rollers 37, 38 ... Fixing inlet guide 39 ... Pressure guide 40 ... Fixing frame 41 ... Pressure arms 42, 45 ... Shaft 43 ... Pressure spring 44 ... Roller 50 ... Cam shaft 51 ... Pressure release cam 52 ... Separation guide cam 65 ... Flag 65a ... Notch 66 ... Photo sensor 70 ... Motor 70a ... Motor gear 71 ... Body frame 72 ... Gear 73 ... Gear shafts 74, 75 ... One-way gears 74a, 75a ... One-way Clutch 76 to 79 ... Gear 80 ... Separation guide unit 81 ... Separation guide 82 ... Separation guide frame 83 ... Shaft 84 ... Abutting member 100 ... Printer body 101 ... Sheet discharge tray 110 ... CPU
121: fixing roller 130 ... separation guide unit 131 ... separation claw 131a ... shaft 132 ... separation guide 133 ... compression spring

Claims (8)

A fixing rotator, a pressure rotator that forms a nip portion in contact with the fixing rotator, a heating unit that heats at least one of the fixing rotator and the pressure rotator, and passes through the nip portion. Guide means for scooping up the recording medium so that the recording medium does not wrap around the fixing rotator or the pressure rotator and guiding the recording medium downstream in the conveying direction. In the fixing device that heats the toner image on the recording medium,
A driving source;
A rotating shaft rotated by the drive source;
A nip separation mechanism for performing pressure contact and separation between the fixing rotator and the pressure rotator by rotation of the rotation shaft;
A guide retraction mechanism that causes the guide means to approach and retreat with respect to the fixing rotator or the pressure rotator by rotation of the rotation shaft;
A fixing device. The nip separation mechanism has a first cam member provided on the rotating shaft,
The fixing device according to claim 1, wherein the guide retracting mechanism includes a second cam member provided on the rotating shaft.   In a state where the fixing rotator and the pressure rotator are separated by the nip separation mechanism, the guide means is also evacuated from the fixing rotator or the pressure rotator by the guide retracting mechanism. The fixing device according to claim 1 or 2.   The fixing device according to claim 1, wherein the driving source is the same as a driving source that rotationally drives the fixing rotator or the pressure rotator. When the drive source rotates in the first direction, the fixing rotator or the pressure rotator is rotationally driven, and the rotational drive is not transmitted to the rotational shaft,
When the drive source rotates in a second direction opposite to the first direction, no rotation drive is transmitted to the fixing rotator or the pressure rotator, and a rotation drive is applied to the rotation shaft. The fixing device according to claim 4, wherein the fixing device is transmitted.   The fixing device according to claim 1, wherein the guide unit is always in a non-contact state with respect to the fixing rotator or the pressure rotator.   The guide means is in contact with the fixing rotator or the pressure rotator when the guide evacuation mechanism comes close to the fixing rotator or the pressure rotator, and in the retracted state, the guide rotator or The fixing device according to claim 1, wherein the fixing device is not in contact with the pressure rotating body. At least when the image forming apparatus forms an image, the fixing rotator and the pressure rotator are in pressure contact with each other by the nip separation mechanism, and the guide means is used to fix the fixing rotator or the pressure by the guide retracting mechanism. In close proximity to the rotating body,
When the image forming apparatus does not form an image, the fixing rotator and the pressure rotator are in a separated state by the nip separation mechanism, and the guide means is the fixing rotator or the pressure rotation by the guide retracting mechanism. The fixing device according to claim 1, wherein the fixing device is retracted from the body.

Images