Fixing device including shutter pivotable about axis positioned downstream of nipping region in sheet conveying direction

A fixing device includes a first rotatable body, a second rotatable body, a frame, and a shutter. The frame supports the first rotatable body and the second rotatable body. The first rotatable body and the second rotatable body provide a nipping region therebetween where a sheet is configured to be conveyed in a conveying direction. The sheet is configured to pass through an opening of the frame to be conveyed toward the nipping region. The shutter is pivotally movable about a first axis between a closed position where the shutter closes the opening and an open position where the shutter opens the opening. The first axis is positioned downstream of the nipping region in the conveying direction.

REFERENCE TO RELATED APPLICATIONS

This application claims priorities from Japanese Patent Application Nos. 2022-104689 filed on Jun. 29, 2022 and 2022-104688 filed on Jun. 29, 2022. The entire contents of the priority applications are incorporated herein by reference.

BACKGROUND ART

There has been known a fixing device for fixing an image on a sheet. One conventional fixing device includes a shutter configured to open and close a sheet inlet of a housing of the fixing device. The shutter is pivotally movable about a pivot axis that is positioned near the sheet inlet of the housing.

There has been also known a conventional fixing device of another type that includes a mechanism for changing a nipping pressure between a heat roller and a pressure roller, in addition to the shutter. The nipping pressure changing mechanism includes a pressure arm configured to urge the pressure roller toward the heat roller in cooperation with a spring, and a cam configured to urge the pressure arm against an urging force of the spring for reducing the nipping pressure.

DESCRIPTION

In the above-descried conventional fixing device, the pivot axis is positioned in the vicinity of a portion of the shutter which closes the shutter inlet. Accordingly, the shutter is required to pivotally move by a relatively larger amount than otherwise for opening and closing the sheet inlet.

Further, according to the above-descried conventional fixing device provided with the nipping pressure changing mechanism, an image forming apparatus incorporating the fixing device may become bulky if a pivot axis of the cam is arranged at a different position from the pivot axis of the shutter.

In view of the foregoing, it is an object of the disclosure to provide a fixing device capable of reducing a pivotally moving amount of the shutter.

It is another object of the disclosure to provide a fixing device capable of suppressing an increase in size of the image forming apparatus incorporating the fixing device that includes the shutter and the nipping pressure changing mechanism.

In order to attain the above and other objects, according to one aspect, the disclosure provides a fixing device including a first rotatable body, a second rotatable body, a frame supporting the first rotatable body and the second rotatable body, and a shutter. The first rotatable body and the second rotatable body provide a nipping region therebetween where a sheet is configured to be conveyed in a conveying direction. The frame has an opening to allow the sheet to pass through the opening to be conveyed toward the nipping region. The shutter is pivotally movable about a first axis between a closed position where the shutter closes the opening and an open position where the shutter opens the opening. The first axis is positioned downstream of the nipping region in the conveying direction.

According to the configuration, a portion of the shutter for closing the opening can be positioned farther away from the first axis, thereby reducing a pivotally moving amount of the shutter required for opening and closing the shutter.

Further, since the pivot axis of the shutter (the first axis) is coincident with a pivot axis of a cam that is provided for changing a nipping pressure at the nipping region, a mechanical component defining the pivot axis of the shutter need not be provided at the frame, in addition to a component constituting the pivot axis of the cam. Accordingly, the image forming apparatus incorporating the fixing device of the disclosure can be made compact.

ONE EMBODIMENT

Hereinafter, a fixing device1according to one embodiment of the present disclosure will be described with reference to accompanying drawings.

1. Overview of the Laser Printer100

Referring toFIG.2, a laser printer100includes a housing120, a sheet supplying portion130, an exposing device140, a process cartridge150, the fixing device1according to the embodiment, and a controller500.

The housing120includes a front cover121, a manual insertion tray122, a rear cover123, and a discharge tray124.

The front cover121is configured to open and close a first opening H1of the housing120. The first opening H1has such a size that the process cartridge150can pass through the first opening H1. The manual insertion tray122is used for performing printing on a sheet S (for example, a thick sheet such as a postcard) that is conveyed along a linear conveying passage (see a bold break line inFIG.1). In the following description, printing performed through the linear conveying passage will be referred to as “straight printing”.

The rear cover123is configured to open and close a second opening H2of the housing120. The second opening H2is an opening through which the sheet S is configured to be discharged from the fixing device1during the straight printing. The rear cover123is opened to support the sheet S discharged out of the second opening H2at the time of performing the straight printing. The discharge tray124is configured to support the sheet S discharged out of the housing120in a state where the rear cover123is closed.

The laser printer100further includes a cover sensor SE1configured to detect whether the rear cover123is closed. The cover sensor SE1is electrically connected to the controller500to transmit information detected by the cover sensor SE1to the controller500.

The sheet supplying portion130is configured to supply a sheet S toward a photosensitive drum151(described later). The sheet supplying portion130includes a sheet tray131, a lifter plate132, and a sheet pick-up mechanism133. The sheet tray131is configured to accommodate the sheets S therein. The sheets S on the sheet tray131are lifted upward by the lifter plate132, and are separated one by one by the sheet pick-up mechanism133such that an uppermost sheet S is supplied toward the process cartridge150by the sheet pick-up mechanism133.

The exposing device140includes a laser light source, a polygon mirror, lenses, and a reflection mirror all of which are not illustrated. The exposing device140is configured to expose a peripheral surface of the photosensitive drum151to a laser beam that is configured to be emitted from the laser light source based on image data.

The process cartridge150is attachable to and detachable from the housing120through the first opening H1. The process cartridge150includes the photosensitive drum151, a charger152, a developing roller153, and a transfer roller154.

The charger152is configured to charge the peripheral surface of the photosensitive drum151to form an electrostatic latent image on the peripheral surface.

The developing roller153is configured to supply toner in the process cartridge150to the electrostatic latent image formed on the peripheral surface of the photosensitive drum151, thereby forming a toner image on the peripheral surface of the photosensitive drum151. The toner image on the photosensitive drum151is then configured to be transferred onto the sheet S while the sheet S conveyed by the sheet supplying portion130passes through a position between the photosensitive drum151and the transfer roller154.

2. Detailed Structure of the Fixing Device1

The fixing device1is configured to fix a toner image to the sheet S. The sheet S to which the toner image has been fixed is then configured to be conveyed to the discharge tray124by a pair of discharge rollers125.

As illustrated inFIG.2A, the fixing device1includes a heating unit2, a pressure roller3, and a frame4supporting the heating unit2and the pressure roller3.

The pressure roller3is a rotatable roller. The pressure roller3includes a solid cylindrical shaft3A, and a hollow cylindrical roller portion3B. The shaft3A is made from metal, and the roller portion3B is made from rubber, for example. The roller portion3B covers a part of the shaft3A. The pressure roller3and the heating unit2provide a nipping region NP (seeFIG.2B) therebetween. Specifically, the pressure roller3and a belt BT (described later) of the heating unit2provide the nipping region NP therebetween.

As illustrated inFIGS.2A and2B, the heating unit2includes a heater10, a holder20, a heat conduction member30, a stay ST, the belt BL, and a temperature sensor SE2.

The heater10is configured to heat the belt BL for heating the sheet S through the belt BL. The temperature sensor SE2is configured to detect a temperature of the heater10and transmit the detected temperature to the controller500. The temperature sensor SE2is in contact with the heat conduction member30.

The heater10is a so-called ceramic heater. As illustrated inFIG.2B, the heater10includes a substrate11, a pair of resistance heating elements12mounted on the substrate11, and a cover13.

The substrate11is in a form of an elongated rectangular plate made from a ceramic material such as aluminum oxide. The substrate11has a surface11aon which the resistance heating elements12are formed by printing. As illustrated inFIG.3A, two resistance heating elements12are formed on the surface11aof the substrate11in the present embodiment. The two resistance heating elements12extend parallel to each other in a longitudinal direction of the substrate11, and are spaced apart from each other in a short direction perpendicular to the longitudinal direction. The short direction with respect to the substrate11is coincident with a direction in which the sheet S at the nipping region NP is configured to be conveyed. In other words, the two resistance heating elements12are arranged on the substrate11such that the resistance heating elements12are arrayed with each other in the conveying direction of the sheet S. In the following description, the conveying direction of the sheet S at the nipping region NP will be simply referred to as “conveying direction”.

Referring toFIG.3A, each resistance heating element12has one end12A connected to one end of a lead wire19A. Each lead wire19A has another end provided with a power feed terminal18configured to supply power to the corresponding resistance heating element12.

Each of the power feed terminals18is electrically connected to the corresponding resistance heating element12through the corresponding lead wire19A. The power feed terminal18is positioned at one end portion11E of the substrate11in the longitudinal direction thereof. As illustrated inFIG.3C, a connector C is connected to the power feed terminals18for supplying power to the heater10. The connector C is attachable to and detachable from one end portion of the heater10in a longitudinal direction thereof. The power feed terminals18are configured to receive power from the connector C attached to the heater10. Incidentally, inFIG.3C, the resistance heating elements12, the cover13and the belt BL are not illustrated to facilitate understanding.

As illustrated inFIG.3A, each resistance heating element12has another end12B opposite the one end12A in the longitudinal direction. The other ends12B of the resistance heating elements12are connected to each other through a lead wire19B.

Incidentally, the resistance heating elements12need not be two and may be arbitrary. Further, the resistance heating elements12may be configured of two resistance heating elements: a first resistance heating element and a second resistance heating element elongated in the longitudinal direction. The first resistance heating element may have a longitudinal center portion configured to generate a heat quantity greater than that generated at longitudinal end portions thereof, and the second resistance heating element may have longitudinal end portions configured to generate a heat quantity greater than that generated at a longitudinal center portion thereof. The first and second resistance heating elements may be controlled individually in order to control distribution of heat generation with respect to the longitudinal direction.

As illustrated inFIG.2C, the cover13covers the resistance heating elements12. The cover13is made from glass, for example.

As illustrated inFIG.2A, the holder20supports the heater10. The holder20is configured to guide the belt BL. The holder20is made from resin, for example.

The stay ST supports the holder20. The stay ST is made from metal, for example.

The belt BL is an endless belt, and is made from metal or resin. The belt BL is circularly movable around the heater10while the belt BL is being guided by the holder20. The belt BL has an inner peripheral surface in contact with the heater10, and an outer peripheral surface configured to contact the pressure roller3or the sheet S (as a target to be heated).

The heat conduction member30is configured to conduct heat generated by the heater10in the longitudinal direction thereof to provide uniform temperature along the entire length of the heater10in the longitudinal direction. The heat conduction member30has a plate like shape and is positioned between the heater10and the holder20. The heat conduction member30is provided at a surface11bof the substrate11opposite the surface11a(seeFIG.2B). In a state where the sheet S is nipped between the heating unit2and the pressure roller3at the nipping region NP, the heat conduction member30is interposed between the heater10and the holder20. The heat conduction member30is made from aluminum, for example.

As illustrated inFIGS.3A and3B, the one end12A and the other end12B of each resistance heating element12are positioned outward of a maximum width W1of the sheet S applicable to the heating unit2with respect to the longitudinal direction. The one end12A and the other end12B of each resistance heating element12are also positioned inward of one end and another end30B of the heat conduction member30in the longitudinal direction, respectively. That is, with respect to the longitudinal direction, the heat conduction member30has a length greater than a length of each resistance heating element12.

The substrate11has a length greater than the length of the heat conduction member in the longitudinal direction. The one end30A of the heat conduction member30is positioned inward of one end11A of the substrate11in the longitudinal direction. The other end of the heat conduction member30is positioned inward of another other end11B of the substrate11in the longitudinal direction.

As illustrated inFIG.4A, the fixing device1further includes a nipping pressure changing mechanism NM. The nipping pressure changing mechanism NM is configured to change a nipping pressure at the nipping region NP between a first nipping pressure and a second nipping pressure lower than the first nipping pressure.

The nipping pressure changing mechanism NM includes a shaft SF, a pair of pressure arms60, a pair of pressure springs70, and a pair of cams80. The frame4supports the shaft SF. The frame4also pivotally movably supports the pair of pressure arms60, and the pair of cams80.

One of the pressure arms60, one of the pressure springs70, and one of the cams80are provided at each end portion of the frame4in an axial direction of the pressure roller3. In the following description, the axial direction of the pressure roller3will be simply referred to as “axial direction”. The pressure arm60, the pressure spring70, and the cam80positioned at one end portion of the frame4in the axial direction are identical to those positioned at another end portion of the frame4in the axial direction in the present embodiment. Hence, for simplifying description, only the pressure arm60, the pressure spring70, and the cam80positioned at the one end portion of the frame4in the axial direction will be described.

As illustrated inFIG.6, the shaft SF extends in the axial direction. The shaft SF is made from, for example, metal. The shaft SF is rotatably supported by the frame4. The shaft SF is rotatable about a first axis X1(seeFIG.4A). The shaft SF has each end in the axial direction to which the cam80is fixed. The cam80is pivotable in accordance with the rotation of the shaft SF.

The pressure arm60is configured to urge the heating unit2toward the pressure roller3. The pressure arm60is pivotally movably supported by the frame4.

The pressure spring70is a tension coil spring configured to urge the pressure arm60toward the pressure roller3. The pressure spring70has one end connected to the pressure arm60, and another end connected to the frame4.

The cam80is configured to apply pressure to the pressure arm60against an urging force of the pressure spring70. Specifically, the cam80is pivotable about the first axis X1between a first position (illustrated inFIG.4A) and a second position (illustrated inFIG.5A). The cam80is pivotable upon receipt of a driving force from a motor (not illustrated) through the shaft SF. Alternatively, the cam80may be configured to pivot through a linking mechanism (not illustrated) that can be actuated in interlocking relation to opening/closing operations of the rear cover123for opening and closing the second opening H2.

The nipping pressure at the nipping region NP becomes the first nipping pressure when the cam80is at the first position. The nipping pressure at the nipping region NP becomes the second nipping pressure lower than the first nipping pressure when the cam80is at the second position.

FIGS.4B and5Bshow a nipping width Ln which is a length of the nipping region NP in the conveying direction when the first nipping pressure is applied to the nipping region NP and when the second nipping pressure is applied to the nipping region NP, respectively. InFIGS.4B and5B, E1designates a most downstream end of the resistance heating element12in the conveying direction, and E2designates a most upstream end of the resistance heating element12in the conveying direction. Further Lr designates a length between the most downstream end E1and the most upstream end E2.

As illustrated inFIG.4B, the nipping width Ln is greater than the length Lr when the first nipping pressure is applied to the nipping region NP. The two resistance heating elements12are positioned within a range of the nipping region NP in the conveying direction.

As illustrated inFIG.5B, the nipping width Ln is smaller than the length Lr when the second nipping pressure is applied to the nipping region NP. The nipping region NP is positioned within a range defined between the most downstream end E1and the most upstream end E2in the conveying direction.

As illustrated inFIG.5A, a side guide SG is positioned at each end portion of the heating unit2in the axial direction. Each side guide SG supports a corresponding end portion of the stay ST in the axial direction. The side guides SG are movably supported by the frame4. The pressure arm60is configured to press the corresponding side guide SG toward the pressure roller3.

As illustrated inFIG.6, the fixing device1further includes a shutter50. The shutter50is pivotally movably supported by the shaft SF. Hence, the shutter50is pivotally movable about the first axis X1, as illustrated inFIGS.7and8.

Referring toFIGS.7and8, the frame4has an opening4A through which the sheet S conveyed toward the nipping region NP is configured to pass. The opening4A is positioned upstream relative to the nipping region NP in the conveying direction.

The shutter50is pivotally movable between a closed position illustrated inFIG.7and an open position illustrated inFIG.8. The shutter50closes the opening4A when the shutter50is at the closed position. The shutter50opens the opening4A when the shutter50is at the open position.

The first axis X1(i.e., a pivot center of the shutter50) is positioned downstream relative to the nipping region NP in the conveying direction. Specifically, the first axis X1is positioned downstream relative to the belt BL of the heating unit2. Further, the first axis X1is positioned closer to the belt BL than to the nipping region NP in a facing direction in which the belt BL and the pressure roller3face each other.

Hereinafter, the facing direction is assumed to be a direction from the heating unit2toward the pressure roller3, as indicated by arrows inFIGS.7and8.

The shutter50includes a shutter body51and a shutter arm52.

The shutter body51is a part configured to open and close the opening4A. The shutter body51extends in parallel to the first axis X1.

The shutter arm52has one end portion pivotably supported by the shaft SF. The shutter arm52has another end portion integrally connected to the shutter body51. The shutter arm52extends from the shutter body51to the shaft SF. The shutter arm52extends in a direction parallel to the first axis X1. The shutter arm52is curved to be convex away from the nipping region NP. The heating unit2is positioned between the shutter arm52and the pressure roller3in the facing direction.

The fixing device1also includes a sheet guide G1configured to guide the sheet S toward the nipping region NP. The sheet guide G1is positioned upstream of the nipping region NP in the conveying direction. The sheet guide G1has a most upstream end G11in the conveying direction. The most upstream end G11is positioned closer to the pressure roller3than to the nipping region NP in the facing direction. In the present embodiment, an entirety of the sheet guide G1is positioned closer to the pressure roller3than to the nipping region NP in the facing direction.

The sheet guide G1is so positioned that the sheet S can pass through a gap between the sheet guide G1and a tip end51A of the shutter50when the shutter50is at the open position. The tip end51A of the shutter50is a most downstream end of the shutter50in a pivotally moving direction of the shutter50when the shutter50pivots from the open position to the closed position.

The tip end51A of the shutter50is positioned closer to the sheet guide G1when the shutter50is at the at the closed position than at the open position. The tip end51A of the shutter50is positioned more downstream in the conveying direction when the shutter50is at the closed position50than at the open position. The tip end51A of the shutter50is positioned downstream of the most upstream end G11of the sheet guide G1in the conveying direction when the shutter50is at the closed position. The shutter body51extends from the shutter arm52obliquely toward downstream in the conveying direction when the shutter50is at the closed position.

More specifically, when the shutter50is at the closed position, the shutter body51extends to slope relative to the conveying direction such that an outer surface51B of the shutter body51(the outer surface opposite an inner surface facing the heating unit2) extends obliquely toward downstream in the conveying direction as approaching toward the sheet guide G1in the facing direction. The tip end51A of the shutter50is on the outer surface51B of the shutter body51.

As illustrated inFIGS.1,7and8, the laser printer100further includes a wall160and a sheet guide G2positioned in the housing120.

The wall160is positioned between the process cartridge150(attached to the housing120) and the fixing device1in the conveying direction. The wall160extends generally in an up-down direction. The sheet guide G2of the housing120is a guide configured to guide the sheet S toward the sheet guide G1of the fixing device1. The sheet guide G2is positioned adjacent to and upstream of the sheet guide G1in the conveying direction.

The sheet guide G2of the housing120is positioned spaced apart from the wall160in the up-down direction. The wall160and the sheet guide G2provide a space therebetween such that the sheet S can pass through the space in the conveying direction. The tip end51A of the shutter50is positioned closer to the sheet guide G2of the housing120when the shutter50is at the closed position than at the open position.

Specifically, the tip end51A of the shutter50is positioned above a lowermost end161of the wall160in the up-down direction when the shutter50is at the open position. The tip end51A of the shutter50is positioned below the lowermost end161of the wall160in the up-down direction when the shutter50is at the closed position.

In other words, when the shutter50is at the open position, the tip end51A of the shutter50is positioned farther away from the sheet guide G2than the lowermost end161of the wall160is from the sheet guide G2in an extending direction of the wall160. Further, when the shutter50is at the closed position, the tip end51A of the shutter50is positioned closer to the sheet guide G2than the lowermost end161of the wall160is to the sheet guide G2in the extending direction of the wall160.

In the following description, an upstream edge of the sheet S in the conveying direction will be referred to as a trailing edge of the sheet S. In a case where the sheet S is curled and jammed at the fixing device1, the trailing edge of the sheet S may not be observed by a user since the trailing edge of the sheet S is positioned above the lowermost end161of the wall160, as illustrated inFIG.8. Even in this case, according to the configuration of the embodiment, the tip end51A of the shutter50can press the jammed sheet S from above by the pivotal movement of the shutter50from the open position to the closed position, as illustrated inFIG.7, thereby moving the trailing edge of the sheet S to the space between the wall160and the sheet guide G2. Hence, a user can visually observe the trailing edge of the jammed sheet S.

As illustrated inFIG.9, the fixing device1further includes a shutter actuation mechanism90for opening and closing the shutter50. Specifically, as illustrated inFIG.10, the shutter actuation mechanism90includes a linking arm91, an arm cam92, and a spring93. The linking arm91and the arm cam92are made from resin. The spring93is made from metal.

A first boss52A protrudes outward in the axial direction from the shutter arm52. The first boss52A is positioned offset from the first axis X1.

The linking arm91is connected to the first boss52A to pivotally move the shutter50between the closed position and the open position. The linking arm91is pivotally movable about the first axis X1, independent of the pivoting of the cam80. The linking arm91has a first hole91A and a second hole91C, and a second boss91B.

The first hole91A receives the first boss52A of the shutter50. The linking arm91is pivotally movably connected to the shutter50by the first boss52A and the first hole91A. In other words, the linking arm91is pivotally movable about the first boss52A relative to the shutter50.

The second boss91B protrudes outward in the axial direction. The second boss91B is positioned between the first hole91A and the second hole91C.

The second hole91C receives a third boss92A (described later) of the arm cam92, as will be described later.

The spring93is a torsion spring including a coil part93A, a first arm part93B extending from one end of the coil part93A, and a second arm part93C extending from another end of the coil part93A. The first arm part93B and the second arm part93C are configured to make contact with the second boss91B of the linking arm91in a pivotally moving direction of the linking arm91(seeFIGS.11B and12B).

The arm cam92is pivotably movable about the first axis X1to urge the linking arm91at a position offset from the first axis X1to pivotally move the linking arm91. The arm cam92has the third boss92A, an elongated slot92B, and a pressure part92C (illustrated inFIG.11B).

The third boss92A is rotatably supported by the shaft SF. The third boss92A extends through the coil part93A for supporting the coil part93A. Further, the third boss92A extends through the second hole91C of the linking arm91for pivotally movably supporting the linking arm91. Accordingly, the linking arm91and the arm cam92are pivotally movably connected to each other through the second hole91C and the third boss92A.

The second boss91B of the linking arm91extends through the elongated slot92B. The elongated slot92B has an arcuate shape centered on the first axis X1.

As illustrated inFIG.11B, the pressure part92C is positioned between the first arm part93B and the second arm part93C of the spring93in a pivotally moving direction of the arm cam92. The arm cam92is pivotable between a cam closing position (illustrated inFIG.11A) and a cam opening position (illustrated inFIG.12A). When the arm cam92is at the cam closing position, the shutter50is at the closed position. When the arm cam92is at the cam opening position, the shutter50is at the open position.

As the arm cam92pivots from the cam opening position to the cam closing position, the pressure part92C presses the second arm part93C of the spring93to pivotally move the spring93in a counterclockwise direction inFIG.11B. The first arm part93B of the spring93then presses the second boss91B of the linking arm91to pivotally move the linking arm91in the counterclockwise direction inFIG.11B. In this way, the arm cam92pivotally moves the shutter50about the first axis X1from the open position to the closed position through the spring93and the linking arm91.

As illustrated inFIGS.11A and11B, when the shutter50is at the closed position, the pressure part92C is in contact with the second arm part93C, and the first arm part93B of the spring93is in contact with the second boss91B of the linking arm91. That is, the arm cam92presses the linking arm91through the spring93to place the shutter50at the closed position.

As the arm cam92pivots from the cam closing position to the cam opening position, the pressure part92C presses the first arm part93B of the spring93to pivotally move the spring93in a clockwise direction inFIG.12B. The second arm part93C of the spring93thus presses the second boss91B of the linking arm91to pivotally move the linking arm91in the clockwise direction inFIG.12B. Accordingly, the arm cam92pivotally moves the shutter50about the first axis X1from the closed position to the open position through the spring93and the linking arm91.

As illustrated inFIGS.12A and12B, when the shutter50is at the open position, the pressure part92C is in contact with the first arm part93B of the spring93, and the second arm part93C of the spring93is in contact with the second boss91B of the linking arm91. That is, the arm cam92presses the linking arm91through the spring93to place the shutter50at the open position.

The arm cam92is caused to pivotally move by an interlocking mechanism (not illustrated) operable in interlocking relation to attachment/detachment operations of the process cartridge150relative to the housing120. The interlocking mechanism may be configured of a plurality of links, for example. The interlocking mechanism may be configured to contact a part of the process cartridge150during the attachment operation of the process cartridge150to the housing120, so that a force applied to the process cartridge150can be transmitted to the arm cam92to pivotally move the arm cam92from the cam closing position to the cam opening position. Further, the interlocking mechanism may be configured to contact a part of the process cartridge150during the detachment operation of the process cartridge150from the housing120, so that a force applied to the process cartridge150can be transmitted to the arm cam92to pivotally move the arm cam92from the cam opening position to the cam closing position.

As illustrated inFIG.8, in a case where a curled sheet S is jammed at the fixing device1, the trailing edge of the sheet S may be positioned above the lowermost end161of the wall160. Even in such a case, in accordance with a user's detachment operation of the process cartridge150from the housing120, the arm cam92is pivotally moved from the cam closing position to the cam opening position upon receipt of the force from the interlocking mechanism (not illustrated). As such, the arm cam92pushes the shutter50through the spring93and the linking arm91to pivotally move the shutter50from the open position to the closed position.

As the shutter50pivots from the open position to the closed position, the tip end51A of the shutter50moves downward to slidingly push the sheet S downward, as illustrated inFIG.7. The trailing edge of the sheet S is thus moved downward to a position lower than the lowermost end161of the wall160. Accordingly, a user can reach the trailing edge of the jammed sheet S after detachment of the process cartridge150from the housing120to remove the jammed sheet S from the housing120through the first opening H1.

3. Operational and Technical Advantages of the Embodiment

The shutter50is configured to pivot about the first axis X1which is coincident with the pivot axis of the cam80. With this configuration, a mechanical component constituting the pivot center of the shutter50is not necessary to be provided at the frame4of the fixing device1, in addition to the component constituting the pivot axis of the cam80. Accordingly, the laser printer100can be made compact.

In the fixing device1according to the embodiment, the shaft SF (a single member) supports the shutter50as well as the cam80. With this configuration, a smaller number of parts are required to constitute the fixing device1than otherwise.

The first axis X1is positioned downstream relative to the nipping region NP in the conveying direction. This configuration can enlarge the distance between the shutter body51and the first axis X1, thereby reducing the pivotally moving amount of the shutter50that is required for opening and closing the shutter50.

In particular, according to the present embodiment, since the first axis X1is positioned downstream relative to the heating unit2in the conveying direction, the shutter body51can be located farther away from the first axis X1. Accordingly, this configuration of the embodiment can further reduce the pivotally moving amount of the shutter50that is required for opening and closing the shutter50.

Further, in the fixing device1according to the embodiment, the tip end51A of the shutter50is positioned closer to the sheet guide G1when the shutter50is at the closed position than at the open position. With this structure, even if a sheet S is jammed at the nipping region NP and a trailing edge of the jammed sheet S is curved in a direction away from the sheet guide G1, simply closing the shutter50can push the jammed sheet S toward the sheet guide G1. As such, a user can easily grasp the jammed sheet S pushed against the sheet guide G1and remove the same, without damaging working efficiency in addressing a paper jam.

According to the above-described embodiment, the first axis X1is positioned closer to the heating unit2than to the nipping region NP in the facing direction, and the most upstream end G11of the sheet guide G1in the conveying direction is positioned closer to the pressure roller3than to the nipping region NP in the facing direction. Therefore, the shutter50can be made more compact in comparison with a structure where the first axis X1is positioned closer to the pressure roller3than to the nipping region NP in the facing direction.

According to the above-described embodiment, the tip end51A of the shutter50is positioned more downstream in the conveying direction when the shutter50is at the closed position than at the open position. That is, the tip end51A of the shutter50moves toward downstream in the conveying direction in accordance with the pivotal movement of the shutter from the open position to the closed position. With this configuration, upon occurrence of a paper jam of the sheet S at the nipping region NP, the tip end51A of the shutter50can slide along the surface of the sheet S and push the sheet S gently in accordance with the pivotal movement of the shutter50from the open position to the closed position.

When the shutter50is at the closed position, the shutter body51slopes relative to the conveying direction such that the shutter body51extends from the shutter arm52diagonally toward downstream in the conveying direction. Therefore, the sheet S jammed at the nipping region NP is less likely to be hidden by the shutter50, compared to a structure where the shutter body51extends from the shutter arm52toward upstream in the conveying direction.

Further, the tip end51A of the shutter50is positioned downstream of the most upstream end G11of the sheet guide G1when the shutter50is at the closed position. This configuration can reduce a gap distance between the tip end51A of the shutter50and the most upstream end G11of the sheet guide G1to reliably suppress accidental insertion of a user's finger into the opening4A of the frame4.

In the above-described embodiment, the shutter body51is integral with the shutter arm52. However, a shutter body and a shutter arm of the disclosure may be prepared as separate members.

Further, in the above-described embodiment, the arm cam92is configured to operate in interlocking relation to the attachment/detachment operations of the process cartridge150. Alternatively, the arm cam92may be configured to operate in interlocking relation to opening/closing motions of the front cover121.

Further, the spring93need not be a torsion spring, but may be a leaf spring or a coil spring.

In the embodiment, the endless belt BL is employed an example of a first rotatable body of the disclosure. Alternatively, the first rotatable body of the disclosure may be a heat roller configured of a cylindrical metal tube.

In the embodiment, the pressure roller3is employed as an example of a second rotatable body of the disclosure. Alternatively, the second rotatable body of the disclosure may be a belt of a pressure unit including a pressure pad. In this case, the belt as the second rotatable body may be nipped between the pressure pad and the first rotatable body.

Still alternatively, the first rotatable body of the disclosure may be a pressure roller or a belt of a pressure unit. The second rotatable body of the disclosure may be a belt configured to be heated by a heater, or a heat roller.

The heater of the disclosure need not be a ceramic heater, but may be a halogen lamp. In the latter case, a heat unit may include a belt, a nipping plate configured to nip the belt in cooperation with a pressure roller, and a heater configured to heat the nipping plate.

The parts and components employed in the above-described embodiment and modifications thereto may be suitably selected and combined together.

REMARKS

The fixing device1is an example of a fixing device. The belt BL is an example of a first rotatable body. The pressure roller3is an example of a second rotatable body. The nipping region NP is an example of a nipping region. The frame4is an example of a frame. The opening4A is an example of an opening of the frame. The shutter50is an example of a shutter. The first axis X1is an example of a first axis. The sheet guide G1is an example of a sheet guide. The most upstream end G11is an example of a most upstream end of the sheet guide. The tip end51A is an example of a tip end of the shutter. The shutter body51is an example of a shutter body of the shutter. The shutter arm52is an example of a shutter arm of the shutter. The pressure arm60is an example of a pressure arm. The cam80is an example of a cam. The shaft SF is an example of a shaft. The linking arm91is an example of a linking arm. The arm cam92is an example of an arm cam. The spring93is an example of a spring. The heater10is an example of a heater.