JP4293179B2 - Fixing apparatus and electrophotographic image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus (laser printer), and a fixing device that is detachably assembled thereto.

  In an electrophotographic image forming apparatus, a toner image is transferred to a recording medium by an image transfer unit, and then the toner transferred to the recording medium is heated by a heating roller of a fixing device to fuse the toner to the recording medium. The image is fixed on a recording medium.

  Incidentally, the transfer of the toner image and the heat fixing of the toner are continuously performed while the recording medium is being transported, but the recording medium may be clogged for some reason during the transport. Therefore, in the invention described in Patent Document 1, the fixing device is detachably assembled to the image forming apparatus.

That is, in the electrophotographic image forming apparatus described in Patent Document 1, since the fixing device is detachably assembled to the image forming apparatus, the recording medium is jammed in the conveyance path between the image transfer unit and the fixing device. In this case, the jammed recording medium can be easily removed by removing the fixing device from the image forming apparatus and exposing the conveyance path to the outside.
JP 2004-301999 A

  Incidentally, the housing of the fixing device is provided with a medium inlet opening on the image transfer unit side and a medium discharge port for discharging the recording medium that has been heated, but the recording medium discharged from the image transfer unit The media inlet has a relatively large opening to ensure introduction into the fixing device.

  In the invention described in Patent Document 1, the medium entrance is always open regardless of the fixing device assembly state, and therefore, the recording medium jammed in the conveyance path between the image transfer unit and the fixing device is removed. Therefore, if the fixing device is removed from the image forming apparatus, a finger or the like may enter the housing from the medium entrance, and the finger may touch the heating roller.

  SUMMARY OF THE INVENTION In view of the above, the present invention prevents, in a fixing device detachably assembled to an electrophotographic image forming apparatus, from touching a heating roller when the fixing device is removed from the image forming apparatus. With the goal.

In order to achieve the above object, the present invention can be detachably assembled to an electrophotographic image forming apparatus having an image transfer section (70) for transferring a toner image onto a recording medium, and the image transfer section (70). A fixing device that fixes toner onto a recording medium discharged from the recording medium, and is provided on a printing surface side of the recording medium and heats a toner image transferred to the recording medium, and a heating roller (81 ), A pressure roller (82) that presses the recording medium toward the heating roller (81), and rotatably supports the heating roller (81) and the pressure roller (82), and an image. A housing (83) provided with a medium inlet (83a) opened to the transfer unit (70) side, a medium outlet (83b) for discharging the recording medium after heating, and the image transfer unit (70) are discharged. Added recording media It has a function as a guiding means that leads to a nip point (P1) that is a contact point between the roller (81) and the pressure roller (82), and a function as a covering means that covers the medium inlet (83a) so as to be closed. A conveyance flap (84) rotatably assembled to the medium inlet (83a) side of the body (83), and a heating roller (81 on the opposite side to the recording medium guiding side of the end portion of the conveyance flap (84) ) Side and extending to the pressure roller (81) side, and provided on the front end side of the arm (84c), the conveying flap (84) has a force to close the medium inlet (83a). The urging means (84b) to be acted on and the image forming apparatus side in contact with the urging means (84b) causes the force to oppose the urging means (84b) to act on the conveying flap (84). Comprising abutments to function as a guide means wrap (84) and (84d), the axis of rotation of the transport flaps (84) (84a) is the end of the heating roller (81) side of the conveyor flap (84) provided further, the rotation center of the rotation shaft (84a) is characterized that you have been arranged on a common tangent line (L1) from the nip point (P1) side of the heating roller (81) and the pressure roller (82) It is said.

  Accordingly, in the present invention, when the fixing device is removed from the image forming apparatus, the force against the urging means (84b) disappears, and the medium inlet (83a) is closed by the conveying flap (84) by the urging means. Therefore, it is possible to prevent the heating roller (81) from being touched when the fixing device is removed from the image forming apparatus.

  In addition, the conveyance flap (84) functions as a guide unit in a state where the fixing device is assembled to the image forming apparatus, and therefore, compared with a case where a dedicated component for closing the medium inlet (83a) is separately provided. The number of parts of the fixing device can be reduced.

Therefore, according to the present invention, it is possible to prevent the heating roller (81) from being touched when removing the fixing device from the image forming apparatus while suppressing an increase in the manufacturing cost of the fixing device.
By the way, since the conveyance flap (84) is assembled | attached to the housing | casing (83) so that rotation is possible, it will move so largely that the part which is distant from the rotation center among conveyance flaps (84). For this reason, there exists a possibility that the components which the conveyance flap (84) adjoins, and conveyance flap (84) may interfere at the time of rotation of a conveyance flap (84).

  In order to prevent this interference, it is necessary to increase the distance between the transport flap (84) and the other parts. However, such a solution causes an increase in the size of the fixing device and the image forming apparatus. .

  In contrast, the present invention is characterized in that the rotation axis (84a) of the transport flap (84) is provided at the end on the heating roller (81) side of the transport flap (84). Even if the conveyance flap (84) rotates, the movement amount of the conveyance flap (84) in the vicinity of the heating roller (81) and the pressure roller (82) becomes small.

  Therefore, the conveyance flap (84), the heating roller (81), and the pressure roller (82) interfere with each other even if the conveyance flap (84) rotates without causing an increase in size of the fixing device and the image forming apparatus. Can be prevented.

  Here, “the rotation axis (84a) of the transport flap (84) is provided at the end of the transport flap (84) on the heating roller (81) side” is an end portion in a strict sense. Of course, it also includes the vicinity of the end.

  Further, the recording medium discharged from the image transfer section (70) is likely to be discharged toward the pressure roller (82) from the nip point between the heating roller (81) and the pressure roller (82). Therefore, if the transport flap (84) rotates from the pressure roller (82) side to the heating roller (81) side when the medium inlet (83a) is closed as in the present invention, the transport flap (84). Can be surely guided to the nip point by scooping up the recording medium discharged from the image transfer section (70).

In time and, in the image transfer section (70), the toner by applying a charge opposite to the charge the toner has charged from the back side of the recording medium is prevented from being scattered, the image transfer section (70 ) To the fixing device, since no charge is normally applied to the recording medium, there is a possibility that the toner may scatter before being heated and fixed by the fixing device.

  On the other hand, in the present invention, it is possible to apply a charge opposite to the charge carried by the toner transferred to the recording medium to the transport flap (84). It is possible to prevent the toner from scattering.

  In the present invention, the conductive portion (84e) made of metal is provided on the side of the transport flap (84) that contacts the recording medium, while the conductive portion (84e) of the transport flap (84) is opposite to the conductive portion (84e). Since the heat insulating portion (84f) made of a resin material is provided on the side, the conductive portion (84e) can be surely charged, and the medium inlet (83a) is closed. In this case, the heat of the heating roller (81) can be blocked by the heat insulating portion (84f) of resin.

In the electrophotographic image forming apparatus according to the present invention, an image transfer unit (70) for transferring a toner image onto a recording medium, and the fixing device (80) according to any one of claims 1 to 4. The image transfer unit (70) and the fixing means (80) are provided with a frame means (3) to which the fixing device (80) is fixed. It is possible to prevent the heating roller (81) from being touched when it is removed.

  According to the present invention, the fixing device side electrical connector (86) provided in the fixing device (80) and the main body side electrical connection provided on the frame means (3) side and connected to the fixing device side electrical connector (86). The connector (9) is provided, and one of the fixing device side electrical connector (86) and the main body side electrical connector (9) is configured to be movable with respect to the other connector. When the fixing device is assembled to the image forming apparatus, the electrical connection can be easily completed even if there is a slight misalignment between the two electrical connectors.

The present invention is effective when applied to a so-called tandem type image forming apparatus in which a plurality of image transfer sections (70) are arranged along the conveyance direction of the recording medium.
Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to specific means.

In the present embodiment, the fixing device according to the present invention is applied to an electrophotographic image forming apparatus (laser printer). Hereinafter, the present embodiment will be described with reference to the drawings.
1. FIG. 1 is a side sectional view showing the main part of a laser printer 1. The laser printer 1 is installed with the upper side of the paper as the upper side in the direction of gravity, and is normally used with the right side of the paper as the front.

  The housing 3 of the laser printer 1 is formed in a substantially box shape (cubic shape). On the upper surface side of the housing 3, paper, an OHP sheet, or the like that has finished printing and is discharged from the housing 3 is used. A paper discharge tray 5 on which a recording medium is placed is provided.

  In the present embodiment, a frame member made of metal, resin, or the like is provided inside the housing 3, and an image transfer unit 70 and a fixing unit 80 described later are provided inside the housing 3. The frame member is detachably assembled.

  Further, the paper discharge tray 5 is configured with an inclined surface 5a that is inclined so as to descend from the upper surface of the housing 3 toward the rear side, and printing is finished on the rear end side of the inclined surface 5a. A discharge unit 7 for discharging the recording medium is provided.

2. Configuration of Laser Printer The image forming unit 10 constitutes an image forming unit that forms an image on a recording medium, and the feeder unit 20 constitutes a part of a conveying unit that supplies the recording medium to the image forming unit 10. It is.

  The conveyance belt 30 is a conveyance unit that conveys the recording medium to the four image transfer units 70a to 70d constituting the image forming unit 10 with the recording medium placed thereon, and the intermediate conveyance roller 40 is the image forming unit 10 (fixing). The recording medium discharged from the unit 80) is transported to the discharge roller 50, and has a curl removing function for removing curl from the recording medium generated in the image forming unit 10. Then, the recording medium conveyed to the discharge roller 50 is discharged from the discharge unit 7 to the discharge tray 5.

2.1. Feeder unit The feeder unit 20 includes a paper feed tray 21 housed in the lowermost part of the housing 3, and a recording medium that is provided above the front end of the paper feed tray 21 and placed on the paper feed tray 21. A sheet feeding roller 22 that feeds (conveys) the sheet, and a separation pad 23 that is disposed at a portion facing the sheet feeding roller 22 to separate the recording medium one by one by applying a predetermined conveyance resistance to the recording medium. It is comprised.

  Then, the recording medium placed on the paper feed tray 21 makes a U-turn on the front side in the housing 3, and enters the image forming unit 10 disposed at a substantially central portion in the housing 3. Be transported. For this reason, in the conveyance path of the recording medium from the paper feed tray 21 to the image forming unit 10, the recording conveyed to the image forming unit 10 while curving in a substantially U shape at a portion that is turned in a substantially U shape. A conveyance roller 24 that applies a conveyance force to the medium is disposed.

  A pressure roller 25 that presses the recording medium against the conveyance roller 24 is disposed at a portion facing the conveyance roller 24 across the recording medium. The pressure roller 25 is an elastic means such as a coil spring 25a. Is pressed to the conveying roller 24 side.

2.2. Image Forming Unit The image forming unit 10 includes a scanner unit 60, an image transfer unit (process cartridge) 70, a fixing unit 80, and the like.

  Further, the image forming unit 10 according to the present embodiment is of a so-called direct tandem type capable of color printing. Specifically, four image transfer units 70a to 70d corresponding to four colors of black, cyan, magenta, and yellow are arranged in series along the conveyance direction of the recording medium.

2.2.1. Scanner Unit The scanner unit 60 is provided at the upper part in the housing 3 and forms an electrostatic latent image on the surface of the photosensitive drum 71 provided in each of the four image transfer units 70a to 70d. Includes a laser light source, a polygon mirror, an fθ lens, a reflecting mirror, a reflecting mirror, and the like.

  The laser beam emitted from the laser light source based on the image data is deflected by the polygon mirror, passes through the fθ lens, the optical path is folded back by the reflecting mirror, and the optical path is further bent downward by the reflecting mirror. As a result, the surface of the photosensitive drum 71 is irradiated and an electrostatic latent image is formed.

2.2.2. Image transfer unit (process cartridge)
Since the four image transfer units 70a to 70d are different in only the toner color, and the others are the same, the structure thereof will be described below by taking the image transfer unit 70d as an example. Hereinafter, the four image transfer units 70a to 70d are collectively referred to as an image transfer unit 70.

  The image transfer unit 70 is detachably disposed in the housing 3 below the scanner unit 60. The image transfer unit 70 includes a photosensitive drum 71, a charger (not shown), and a transfer roller 72. And a developing cartridge 73 and the like.

  The photosensitive drum 71 serves as an image carrying means for carrying an image to be transferred to a recording medium. The outermost layer is a cylindrical drum body 71a formed of a positively charged photosensitive layer made of polycarbonate or the like, In the axial center of this drum main body 71a, it has the drum axis | shaft 71b extended along the longitudinal direction of the drum main body 71a, and supporting the drum main body 71a rotatably.

  The charger is a charging unit that charges the surface of the photosensitive drum 71. The charger is disposed diagonally above the rear side of the photosensitive drum 71 so as not to contact the photosensitive drum 71 with a predetermined interval. Has been. Note that the charger according to the present embodiment employs a scorotron charger that charges the surface of the photosensitive drum 71 substantially uniformly using corona discharge.

  The transfer roller 72 is disposed opposite to the photosensitive drum 71 and rotates in conjunction with the rotation of the photosensitive drum 71, and is opposite to the charge charged on the photosensitive drum 71 when the recording medium passes near the photosensitive drum 71. Forming a transfer means for transferring the toner adhering to the surface of the photosensitive drum 71 to the printing surface of the recording medium by applying a negative charge (in this embodiment, a negative charge) to the recording medium from the side opposite to the printing surface. It is.

  The developing cartridge 73 includes a toner storage chamber 73a that stores toner, a toner supply roller 73b that supplies the toner to the photosensitive drum 71, a developing roller 73c, and the like.

  The toner stored in the toner storage chamber 73a is supplied to the developing roller 73c side by the rotation of the toner supply roller 73b, and the toner supplied to the developing roller 73c side is carried on the surface of the developing roller 73c. In addition, the thickness of the toner carried by the layer thickness regulating blade 73d is adjusted to be constant (uniform) at a predetermined thickness, and then supplied to the surface of the photosensitive drum 71 exposed by the scanner unit 60.

2.2.3. 2 is a perspective view of the fixing unit 80, FIG. 3 is a cross-sectional view of the fixing unit 80, and FIG. 4 is a cross-sectional view of the transport flap 84. As shown in FIG. 5 is a diagram showing the unit side electrical connector 86 and the main body side electrical connector 9, FIG. 6 is a diagram showing a state where both the connectors 9 and 86 are connected, and FIG. It is the figure seen from the unit side electrical connector 86 side, and FIG. 8 is AA sectional drawing of FIG.

  As shown in FIG. 1, the fixing unit 80 is disposed downstream of the photosensitive drum 71 in the conveyance direction of the recording medium, and heats and melts the toner transferred to the recording medium to fix it. The fixing unit 80 is detachably assembled to the frame member.

  Specifically, as shown in FIG. 3, the fixing unit 80 is disposed on the printing surface side of the recording medium and sandwiches the recording medium with a heating roller 81 that applies a conveying force to the recording medium while heating the toner. The pressure roller 82 is disposed on the opposite side of the heating roller 81 and presses the recording medium toward the heating roller 81.

  Incidentally, the heating roller 81 is driven by driving means such as a motor (not shown), while the pressure roller 82 is driven to rotate by receiving a rotational force from the heating roller 81 via a recording medium in contact with the heating roller 81.

  The heating roller 81 and the pressure roller 82 are rotatably supported in a housing unit 83 that forms the outer shell of the fixing unit 80. The housing unit 83 includes an image transfer unit 70 (image forming unit). A medium inlet 83a opened on the part 10) side and a medium outlet 83b for discharging the recording medium on which heat fixing has been completed are provided.

  Further, a conveyance flap 84 is rotatably mounted on the medium inlet 83a side of the housing unit 83, and the conveyance flap 84 is a recording discharged from the image transfer unit 70 as will be described later. It has a function as a guiding means for guiding the medium to a contact point P1 (hereinafter referred to as a nip point P1) between the heating roller 81 and the pressure roller 82, and a function as a covering means for covering the medium inlet 83a. .

  Further, as shown in FIG. 2, the transport flap 84 extends in a direction parallel to the axial direction of the heating roller 81, at both ends in the longitudinal direction thereof, and on the heating roller 81 side, a housing unit. A rotation shaft 84 a is rotatably provided in a shaft support hole (not shown) formed in 83.

  That is, in the present embodiment, the rotation shaft 84a is an end portion of the transport flap 84 in a direction parallel to the axial direction of the heating roller 81, and the rotation center O1 is heated as shown in FIG. The roller 81 and the pressure roller 82 are disposed so as to be positioned on the nip point P1 side from the common tangent line L1.

  As shown in FIG. 2, a coil spring 84b for applying an elastic force in the direction of closing the medium inlet 83a to the conveyance flap 84 is assembled to the image transfer unit 70 side of the longitudinal end portion of the conveyance flap 84. Yes.

  On the other hand, the heating roller 81 side (rotation shaft 84a side) of the conveyance flap 84 on the end side in the longitudinal direction is radially outward from the rotation shaft 84a to the pressure shaft 82 side (lower side). An arm 84c extending to the laser printer 1 (frame member) is provided at the distal end side of the arm 84c in a state where the fixing unit 80 is assembled to the laser printer 1 (frame member). By contacting the contact portion 3a (see FIG. 9), a force that opposes the elastic force of the coil spring 84b, that is, a force that opens the medium inlet 83a is applied to the transport flap 84 so that the transport flap 84 functions as a guide means. A contact portion 84d is provided.

  Further, as shown in FIG. 4, the transport flap 84 is provided with a conductive portion 84e made of metal such as SECC on the side contacting the recording medium, and on the other side of the transport flap 84 on the side opposite to the conductive portion 84e. Is provided with a heat insulating portion 84f made of a resin material such as PET.

  In this embodiment, as shown in FIG. 3, the bias application unit 85 causes a charge opposite to the charge carried by the toner transferred to the recording medium (in this embodiment, a negative charge) to be transferred to the transport flap 84 ( Applied to the conductive portion 84e).

  Incidentally, the fixing unit 80 is equipped with electric devices such as the heating roller 81 and the bias applying unit 85 that require a power source. The power supply to these electric devices and control electric signals are shown in FIGS. 6, the unit-side electrical connector 86 provided on one end side of the fixing unit 80 in the width direction (the axial direction of the heating roller 81), and the body-side electrical connector 9 provided on the frame member (housing 3) side This is done by connecting

  One of the unit-side electrical connector 86 and the body-side electrical connector 9 (in this embodiment, the body-side electrical connector 9) is connected to the other connector (in this embodiment, the unit-side electrical connector 86). It consists of a floating connector that can move.

  That is, as shown in FIG. 8, the main body side electrical connector 9 which forms a floating connector includes a connector holder 9a fixed to the frame member (housing 3) side in a non-movable state by fastening means such as bolts (screws). The connector main body 9b is detachably assembled to the connector holder 9a. The connector main body 9b is provided with a terminal portion for electrical connection with the unit-side electric connector 86. It has been.

  In the present embodiment, the connector holder 9a is provided with a locking hole, and the locking projection 5c fitted into the locking hole in the connector main body 9b and the locking projection 5c are fitted into the locking hole. An elastically deformable locking hook 9d that maintains the state is provided, and the size of the locking hole is made larger than the outer dimension of the locking projection 5c, and a predetermined distance is provided between the locking hole and the locking projection 5c. By generating the gap, the connector body 9b can be moved relative to the connector holder 9a.

2.2.4. Outline of Image Forming Operation In the image forming unit 10, an image is formed on a recording medium as follows.
In other words, the surface of the photosensitive drum 71 is uniformly positively charged by the charger as it rotates, and then exposed by high-speed scanning of the laser beam emitted from the scanner unit 60. As a result, an electrostatic latent image corresponding to the image to be formed on the recording medium is formed on the surface of the photosensitive drum 71.

  Next, when the developing roller 73c rotates, the positively charged toner carried on the developing roller 73c is formed on the surface of the photosensitive drum 71 when it contacts the photosensitive drum 71. The electrostatic latent image, that is, the surface of the photosensitive drum 71 that is uniformly positively charged, is supplied to an exposed portion exposed to a laser beam and having a lowered potential. As a result, the electrostatic latent image on the photosensitive drum 71 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 71.

  Thereafter, the toner image carried on the surface of the photosensitive drum 71 is transferred to a recording medium by a transfer bias applied to the transfer roller 72. Then, the recording medium to which the toner image has been transferred is conveyed to the fixing unit 80 and heated, and the toner transferred as the toner image is fixed to the recording medium, thereby completing the image formation.

3. FIG. 9 is a view showing a state in which the fixing unit 80 is assembled to the frame member (housing 3), and FIG. 10 is a diagram illustrating the fixing unit 80 being attached to the frame member (housing). It is a figure which shows the state removed from 3).

  As is apparent from FIG. 10, in this embodiment, when the fixing unit 80 is removed from the laser printer 1 (frame member), the contact portion 84d moves away from the frame contact portion 3a and opposes the coil spring 84b. Since the force is lost and the medium inlet 83a is closed by the conveyance flap 84 by the coil spring 84b, it is possible to prevent the heating roller 81 from being touched when the fixing unit 80 is removed from the image forming apparatus.

  In the state where the fixing unit 80 is assembled to the laser printer 1 (frame member), the transport flap 84 rotates (swings) toward the pressure roller 82 (downward) as shown in FIG. And opens the medium inlet 83a and functions as a guide means so as to bridge the medium inlet 83a and the image transfer section 70, so that compared with a case where a dedicated part for closing the medium inlet 83a is separately provided. In addition, the number of parts of the fixing unit 80 can be reduced.

  Therefore, in this embodiment, it is possible to prevent the heating roller 81 from being touched when the fixing unit 80 is removed from the laser printer 1 while suppressing an increase in the manufacturing cost of the fixing unit 80.

  By the way, since the conveyance flap 84 is assembled | attached to the housing | casing unit 83 so that rotation is possible, it will move so much as the site | part away from the rotation center among the conveyance flaps 84. FIG. For this reason, when the conveyance flap 84 rotates, there exists a possibility that the components which the conveyance flap 84 adjoins, and the conveyance flap 84 may interfere.

  In order to prevent this interference, it is necessary to increase the distance between the conveyance flap 84 and other components (for example, the image transfer unit 70). In such a solution, the fixing unit 80 and the image forming apparatus are used. It will increase the size.

  On the other hand, in the present embodiment, the rotation shaft 84a of the transport flap 84 is provided at the end of the transport flap 84 on the heating roller 81 side. Therefore, even if the transport flap 84 rotates, the heating roller 81 is rotated. And the movement amount of the conveyance flap 84 in the vicinity of the pressure roller 82 becomes small.

  Therefore, it is possible to prevent the conveyance flap 84, the heating roller 81, and the pressure roller 82 from interfering with each other even if the conveyance flap 84 rotates without causing an increase in size of the fixing unit 80 and the laser printer 1.

  Further, the recording medium discharged from the image transfer unit 70 is likely to be discharged from the nip point P1 between the heating roller 81 and the pressure roller 82 toward the pressure roller 82 (downward). 9 and FIG. 10, when the medium inlet 83a is closed, if the conveyance flap 84 rotates from the pressure roller 82 side to the heating roller 81 side, the conveyance flap 84 functions as a guide means. The recording medium discharged from the image transfer unit 70 can be reliably guided to the nip point P1 by scooping up.

  By the way, in the image transfer unit 70, the toner is prevented from scattering by applying a charge opposite to the charge carried by the toner from the back side of the recording medium. In the transport path to reach, usually, no charge is applied to the recording medium, so that the toner may be scattered before being heated and fixed by the fixing unit 80.

  On the other hand, in the present embodiment, since the opposite charge to the charge carried by the toner transferred to the recording medium is applied to the transport flap 84, the toner is scattered before the fixing unit 80 heats and fixes the toner. Can be prevented beforehand.

  In the present embodiment, a conductive portion 84e is provided on the side of the transport flap 84 that contacts the recording medium, while a heat insulating portion 84f is provided on the side of the transport flap 84 opposite to the conductive portion 84e. Therefore, the electric charge can be surely charged in the conductive portion 84e, and when the medium inlet 83a is closed, the heat of the heating roller 81 can be blocked by the heat insulating portion 84f.

  Since the main body side electrical connector 9 is a floating connector, when the fixing unit 80 is assembled to the laser printer 1, the electrical connection can be easily completed even if there is a slight misalignment between the two electrical connectors 9 and 86. Can be made.

4). Correspondence between Invention Specific Items and This Embodiment In this embodiment, the coil spring 84b corresponds to the urging means described in the claims, and the bias application unit 85 serves as the application means for applying a charge to the transport flap 84. The frame member and the housing 3 correspond to the frame means described in the claims, and the unit-side electrical connector 86 corresponds to the fixing device-side electrical connector described in the claims.

(Other embodiments)
In the above-described embodiment, the coil spring is used as the biasing means. However, the present invention is not limited to this, and for example, a torsion spring may be used.

  In the above-described embodiment, the rotation shaft 84a is arranged on the heating roller 81 side. However, the present invention is not limited to this, and on the contrary, the rotation shaft 84a is arranged on the image transfer unit 70 side. May be.

  In the above-described embodiment, the conductive portion 84e made of metal is provided on the side of the transport flap 84 that contacts the recording medium, while the heat insulation made of a resin material is provided on the side of the transport flap 84 opposite to the conductive portion 84e. Although the portion 84f is provided, the present invention is not limited to this. For example, the entire transport flap 84 may be made of a conductive resin.

Further, in the above-described embodiment, the opposite charge to the charge charged by the toner is applied to the transport flap 84, but the present invention is not limited to this.
In the above-described embodiment, when the medium inlet 83a is closed, the conveyance flap 84 rotates (swings) from the heating roller 81 side to the pressure roller 82 side. However, the present invention is not limited to this. However, conversely, when closing the medium inlet 83a, the transport flap 84 may rotate from the pressure roller 82 side to the heating roller 81 side.

  In the above-described embodiment, the rotation center O1 of the rotation shaft 84a is disposed on the nip point P1 side from the common tangent L1 of the heating roller 81 and the pressure roller 82. However, the present invention is not limited to this. Absent.

  In the above-described embodiment, the present invention is applied to a tandem color laser printer. However, the present invention is not limited to this. For example, the present invention is also applied to a 4-cycle color laser printer or a monochrome monochrome laser printer. Can be applied.

  Further, the present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

It is a sectional side view which shows the principal part of the laser printer 1 which concerns on this embodiment. 2 is a perspective view of a fixing unit 80 according to the present embodiment. FIG. It is AA sectional drawing of FIG. It is sectional drawing of the conveyance flap 84 which concerns on this embodiment. It is a figure which shows the unit side electrical connector 86 and the main body side electrical connector 9 which concern on this embodiment. It is a figure which shows the state in which the unit side electrical connector 86 and the main body side electrical connector 9 which concern on this embodiment were connected. It is the figure which looked at the main body side electric connector 9 concerning this embodiment from the unit side electric connector 86 side. It is AA sectional drawing of FIG. FIG. 6 is a view showing a state where the fixing unit 80 is assembled to a frame member (housing 3). FIG. 6 is a view showing a state where the fixing unit 80 is detached from the frame member (housing 3).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer, 3 ... Housing | casing, 3a ... Frame contact part, 5 ... Paper discharge tray,
5a ... Inclined surface, 5c ... Locking projection, 7 ... Discharge part, 9 ... Body side electrical connector,
9a ... Connector holder, 9b ... Connector body, 9d ... Locking hook,
DESCRIPTION OF SYMBOLS 10 ... Image formation part, 20 ... Feeder part, 21 ... Paper feed tray, 22 ... Paper feed roller,
24 ... Conveying roller, 25 ... Pressure roller, 30 ... Conveying belt, 40 ... Intermediate conveying roller,
50 ... discharge roller, 60 ... scanner unit, 70 ... image transfer unit, 70a ... image transfer unit,
71 ... photosensitive drum, 71a ... drum body, 71b ... drum shaft, 72 ... transfer roller,
73: Development cartridge, 73a: Toner storage chamber, 73b: Toner supply roller,
73c ... developing roller, 73d ... layer thickness regulating blade, 80 ... fixing unit,
81: heating roller, 82: pressure roller, 83: housing unit, 83a: medium inlet,
83b ... medium outlet, 84 ... conveying flap, 84a ... rotating shaft, 84b ... coil spring,
84c ... arm, 84d ... contact portion, 84e ... conductive portion, 84f ... heat insulating portion,
85: Bias applying unit, 86: Unit side electrical connector.

Claims (7)

A fixing device that can be detachably attached to an electrophotographic image forming apparatus having an image transfer portion for transferring a toner image to a recording medium, and fixes the toner to the recording medium discharged from the image transfer portion,
A heating roller that is disposed on the printing surface side of the recording medium and heats the toner image transferred to the recording medium;
A pressure roller disposed opposite to the heating roller and pressing the recording medium toward the heating roller;
A housing provided with a medium inlet opening to the image transfer unit side and a medium outlet for discharging the recording medium that has been heated, while rotatably supporting the heating roller and the pressure roller;
It has a function as a guide means for guiding the recording medium discharged from the image transfer section to a nip point that is a contact point between the heating roller and the pressure roller, and a function as a covering means for covering the medium entrance. And a transport flap that is rotatably mounted on the medium inlet side of the housing;
Urging means for applying a force in a direction to close the medium inlet to the transport flap;
An arm that is provided on the side of the heating roller opposite to the side that guides the recording medium in the end portion of the transport flap, and extends to the side of the pressure roller;
Provided on the tip end side of the arm and in contact with the image forming apparatus in a state assembled to the image forming apparatus, a force that opposes the urging means is applied to the transport flap to cause the transport flap to move. A contact portion that functions as the guide means ;
The rotation axis of the conveyance flap is provided at the end on the heating roller side of the conveyance flap,
Furthermore, the rotation center of the rotary shaft, the heating roller and the fixing device according to the common tangent line than have been arranged in the nip point side, wherein Rukoto of the pressure roller. The fixing device according to claim 1, wherein the conveyance flap rotates from the pressure roller side to the heating roller side when the medium inlet is closed . The fixing device according to claim 1 , wherein the conveyance flap is configured to be able to apply a charge opposite to a charge carried by the toner transferred to the recording medium . A conductive portion made of metal is provided on the side of the transport flap that contacts the recording medium, while a heat insulating portion made of a resin material is provided on the side of the transport flap opposite to the conductive portion. The fixing device according to any one of claims 1 to 3, wherein An image transfer unit for transferring a toner image to a recording medium;
A fixing device according to any one of claims 1 to 4 ,
An electrophotographic image forming apparatus comprising: an image transfer unit; and a frame unit to which the fixing device is fixed. A fixing device-side electrical connector provided in the fixing device;
A main body side electrical connector provided on the frame means side and connected to the fixing device side electrical connector;
6. The electrophotographic image forming apparatus according to claim 5 , wherein one of the fixing device side electrical connector and the body side electrical connector is configured to be movable with respect to the other connector. A plurality of the image transfer portions,
Further, an electrophotographic image forming apparatus according to claim 5 or 6 image transfer portion of said plurality is characterized in that arranged along the conveying direction of the recording medium.

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