Fixing device and image forming apparatus including the same

Abstract

To provide a fixing device capable of maintaining a shutter member for preventing contact with a fixing member in a closed state, and to provide an image forming apparatus including the same.SOLUTION: The fixing device includes: a heated rotary body; a pressure rotary body which is brought into pressure contact with the heated rotary body to form a fixing nip part; a housing; a sheet entry port; a shutter member; and a biasing member. The shutter member slides between a first position for opening the sheet entry port provided at the housing and a second position for closing the sheet entry port. The biasing member biases the shutter member in a direction toward the second position. The shutter member has a hook portion where an engaging claw that faces an engaged portion of the housing when the shutter member is disposed at the second position is formed. When an external force toward the inside of the housing is applied to the shutter member disposed at the second position, the engaging claw and the engaged portion are engaged with each other to regulate the movement of the shutter member to the first position.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine thereof, and to an image forming apparatus equipped with the fixing device. [Background technology]

[0002] In image forming apparatuses using electrophotography, a fixing device equipped with a fixing member in which a fixing roller or fixing belt (a heated rotating body) and a pressure roller (a pressure rotating body) are in pressure contact with each other is widely used to fix a toner image onto paper. In this fixing device, the paper is passed through the fixing nip formed by the fixing roller or fixing belt and the pressure roller, and heat and pressure are applied to the toner image to melt and fix it onto the paper.

[0003] In a belt fixing type fixing device that uses a fixing belt as a heated rotating body, a primary current flows through the fixing belt. Therefore, according to the Industrial Safety and Health Regulations, workers must not touch the fixing belt when clearing a jam or performing maintenance on the fixing device. In addition, touching the fixing belt may cause damage to the fixing belt or cause image degradation due to dirt on the fixing belt.

[0004] Therefore, a configuration has been proposed that includes an openable and closable shutter member that covers the heated rotating body. For example, Patent Document 1 discloses a cover opening and closing mechanism that includes a cover that can be moved between an open position that exposes the fixing roller and the pressure roller and a closed position that covers them, and a lock lever that can be switched between a locked position that fixes the cover in the closed position and an unlocked position that allows the cover to be moved without engaging with the cover.

[0005] Patent document 2 discloses an image forming device that includes an opening / closing member that can be opened and closed relative to the image forming device main body, a shutter member that moves in conjunction with the opening / closing member to prevent contact with a fixing means of the image forming device, and a detection unit that detects the open / closed state of the opening / closing member and the shutter member. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-64423 A [Patent Document 2] JP 2015-141252 A Summary of the Invention [Problem to be solved by the invention]

[0007] The configurations of Patent Documents 1 and 2 have many parts for opening and closing the shutter member and parts for locking and unlocking the shutter member, resulting in a complex configuration. This leads to problems such as increased cost of the fixing device due to the increased number of parts and reduced assembly workability. In addition, the mechanism for maintaining the locked state when an attempt is made to intentionally open the shutter member is insufficient.

[0008] In view of the above problems, the present invention aims to provide a fixing device and an image forming apparatus equipped with the same that can maintain a shutter member in a closed state when an attempt is made to intentionally open the shutter member, which prevents contact with the fixing member. [Means for solving the problem]

[0009] In order to achieve the above object, a first configuration of the present invention is a fixing device that includes a heated rotating body, a pressurizing rotating body, a housing, a sheet inlet, a shutter member, and an urging member, and that heats and pressurizes a sheet passing through a fixing nip portion to melt and fix an unfixed toner image on the sheet. The pressurizing rotating body is pressed against the heated rotating body to form a fixing nip portion. The housing accommodates the heated rotating body and the pressurizing rotating body. The sheet inlet is provided in the housing, and a sheet conveyed to the fixing nip portion passes through the sheet. The shutter member is supported by the housing and slides between a first position that opens the sheet inlet and a second position that closes the sheet inlet. The urging member urges the shutter member in a direction toward the second position. The shutter member has a hook portion formed with an engagement claw that faces the engaged portion of the housing when the shutter member is disposed at the second position. When an external force toward the inside of the housing is applied to the shutter member disposed at the second position, the engagement claw and the engaged portion engage with each other to restrict the movement of the shutter member to the first position. Effect of the Invention

[0010] According to the first configuration of the present invention, when an external force toward the inside of the housing is applied to the shutter member disposed at the second position, the engaging claw of the hook portion provided on the shutter member engages with the engaged portion. Therefore, when an attempt is made to intentionally open the shutter member disposed at the second position, it is possible to reliably prevent the shutter member from moving to the first position. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an overall configuration of an image forming apparatus 100 according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a partial cross-sectional view of the paper transport path 19 and the double-sided transport path 20 in the image forming apparatus 100 according to the present embodiment. [Diagram 3] FIG. 1 is a perspective view of the fixing device 14 as seen from the upstream side in the conveying direction of the transfer paper P, showing a state in which the shutter member 33 is disposed in the open position. [Figure 4]FIG. 1 is a perspective view of the fixing device 14 as seen from the upstream side in the conveying direction of the transfer paper P, showing a state in which the shutter member 33 is disposed in the closed position. [Diagram 5] A perspective view of the shutter member 33. [Figure 6] A side cross-sectional view of one end of the fixing device 14 in the longitudinal direction. [Figure 7] A partially enlarged view of the lower periphery of the side plate 31a from the outside. [Figure 8] FIG. 7 is a side cross-sectional view showing a state in which the opening / closing cover 21 is opened from the state shown in FIG. 6 and the shutter member 33 is placed in a closed position. [Figure 9] 1 is an enlarged perspective view of the tip of the support portion 332 of the shutter member 33 viewed from the inside. [Figure 10] FIG. 11 is a side cross-sectional view showing a state in which the shutter member 33 is placed in a closed position. [Figure 11] FIG. 3 is a diagram for explaining a mechanism for maintaining the locked state by the hook portion 332b when the shutter member 33 placed in the closed position is manually opened. [Figure 12] FIG. 2 is a diagram illustrating a mechanism by which the shutter member 33, which is placed in the closed position, is unlocked by the opening / closing cover 21. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing the internal structure of an image forming apparatus 100 according to one embodiment of the present invention. Inside the main body of the image forming apparatus 100 (here, a color printer), four image forming sections Pa, Pb, Pc, and Pd are arranged in order from the upstream side in the transport direction (the left side in Fig. 1). These image forming sections Pa to Pd are provided corresponding to images of four different colors (yellow, cyan, magenta, and black), and sequentially form images of yellow, cyan, magenta, and black through the respective processes of charging, exposing, developing, and transferring.

[0013] In these image forming units Pa to Pd, photoconductor drums (image carriers) 1a, 1b, 1c, and 1d carrying visible images (toner images) of each color are disposed. Furthermore, an intermediate transfer belt (intermediate transfer body) 8, which rotates in a counterclockwise direction in FIG. 1 by a belt drive motor (not shown), is provided adjacent to each image forming unit Pa to Pd. The toner images formed on these photoconductor drums 1a to 1d are sequentially primarily transferred and superimposed on the intermediate transfer belt 8, which moves while contacting each of the photoconductor drums 1a to 1d. Thereafter, the toner images primarily transferred onto the intermediate transfer belt 8 are secondarily transferred onto a transfer paper P, which is an example of a recording medium, by a secondary transfer roller 9. Furthermore, the transfer paper P to which the toner image has been secondarily transferred is discharged from the main body of the image forming apparatus 100 after the toner image is fixed in a fixing device 14. While the photoconductor drums 1a to 1d are rotated in a clockwise direction in FIG. 1, an image forming process is performed for each of the photoconductor drums 1a to 1d.

[0014] The transfer paper P onto which the toner image is secondarily transferred is stored in a paper cassette 16 arranged at the bottom of the main body of the image forming apparatus 100, and is transported along a paper transport path 19 to a nip between a secondary transfer roller 9 and a drive roller 11 of the intermediate transfer belt 8 via a paper feed roller 12 and a pair of registration rollers 13. A sheet made of dielectric resin is used for the intermediate transfer belt 8, and a seamless belt is generally used. In addition, a blade-shaped belt cleaner 25 is arranged downstream of the secondary transfer roller 9 to remove toner and the like remaining on the surface of the intermediate transfer belt 8.

[0015] Next, the image forming units Pa to Pd will be described. Around and below the rotatably arranged photoconductor drums 1a to 1d, there are provided charging devices 2a, 2b, 2c, and 2d that charge the photoconductor drums 1a to 1d, an exposure device 5 that exposes image information onto each of the photoconductor drums 1a to 1d, developing devices 3a, 3b, 3c, and 3d that form toner images on the photoconductor drums 1a to 1d, and cleaning devices 7a, 7b, 7c, and 7d that remove developer (toner) and the like remaining on the photoconductor drums 1a to 1d.

[0016] When image data is input from a host device such as a personal computer, first, the surfaces of the photoconductor drums 1a-1d are uniformly charged by the charging devices 2a-2d. Next, the exposure device 5 irradiates light according to the image data, and electrostatic latent images corresponding to the image data are formed on the photoconductor drums 1a-1d. The developing devices 3a-3d are filled with a predetermined amount of two-component developer containing yellow, cyan, magenta, and black toner, respectively. When the ratio of toner in the two-component developer filled in each of the developing devices 3a-3d falls below a specified value due to the formation of a toner image described later, toner is replenished from the toner containers 4a-4d to each of the developing devices 3a-3d. The toner in the developer is supplied onto the photoconductor drums 1a-1d by the developing devices 3a-3d and electrostatically adheres to them. As a result, a toner image corresponding to the electrostatic latent image formed by exposure from the exposure device 5 is formed.

[0017] Then, an electric field is applied between the primary transfer rollers 6a-6d and the photoconductor drums 1a-1d by the primary transfer rollers 6a-6d at a predetermined transfer voltage, and the yellow, cyan, magenta, and black toner images on the photoconductor drums 1a-1d are primarily transferred onto the intermediate transfer belt 8. These images are formed with a predetermined positional relationship. Thereafter, in preparation for the subsequent formation of a new electrostatic latent image, the toner and the like remaining on the surfaces of the photoconductor drums 1a-1d after the primary transfer are removed by the cleaning devices 7a-7d.

[0018] The intermediate transfer belt 8 is stretched over a driven roller 10 on the upstream side and a driving roller 11 on the downstream side. When the intermediate transfer belt 8 starts to rotate counterclockwise with the rotation of the driving roller 11 by a belt driving motor (not shown), the transfer paper P is transported at a predetermined timing from the pair of registration rollers 13 to a secondary transfer nip N (see FIG. 2) between the driving roller 11 and a secondary transfer roller 9 provided adjacent thereto. Then, the toner image on the intermediate transfer belt 8 is secondarily transferred onto the transfer paper P passing through the secondary transfer nip N.

[0019] The transfer paper P onto which the toner image has been secondarily transferred is transported to the fixing device 14. The fixing device 14 has a fixing belt 14a, a pressure roller 14b, and a heater 14c arranged inside the fixing belt 14a (see FIG. 2 for all of these). The fixing belt 14a is heated by the heater (heating device) 14c. The pressure roller 14b is pressed against the fixing belt 14a to form a fixing nip portion, and applies a rotational driving force to the fixing belt 14a. Note that an induction heating portion may be provided on the outside of the fixing belt 14a instead of the heater 14c.

[0020] The transfer paper P conveyed to the fixing device 14 is heated and pressurized by the fixing belt 14a and the pressure roller 14b, so that the toner image is fixed to the surface of the transfer paper P, and a predetermined full-color image is formed. The transfer paper P on which the full-color image has been formed is then directed to a different conveying direction by a branching section 15 which branches into multiple directions, and is discharged directly to a discharge tray 18 by a pair of discharge rollers 17 (or after being sent to a double-sided conveying path 20 and having images formed on both sides).

[0021] 2 is a partial cross-sectional view of the vicinity of paper transport path 19 and duplex transport path 20 in image forming apparatus 100 of this embodiment. Openable cover 21 constitutes side surface 102 of image forming apparatus 100, and is rotatably supported by cover spindle 21a provided below the main body of image forming apparatus 100. The inner surface of openable cover 21 constitutes one (outer) transport surface of duplex transport path 20.

[0022] A handle portion 22 is provided on the side of the opening / closing cover 21. One end of the handle portion 22 engages with an engagement pin (not shown) provided on the front frame and rear frame of the main body of the image forming apparatus 100, thereby holding the opening / closing cover 21 in a closed state. When opening / closing cover 21, the handle portion 22 is rotated to release the engagement with the engagement pin.

[0023] A transport unit 23 is disposed inside the opening / closing cover 21. The transport unit 23 is supported on the main body of the image forming apparatus 100 so as to be rotatable about a unit shaft 23a, and constitutes a part of the transport surface of the double-sided transport path 20 and the paper transport path 19. The double-sided transport path 20 extends in the vertical direction along the side surface 102 of the image forming apparatus 100 between the inner surface of the opening / closing cover 21 and the outer surface of the transport unit 23, and is configured to be curved in a substantially C-shape to merge with the paper transport path 19. On the inner surface of the transport unit 23, one roller 13b constituting the registration roller pair 13 and the secondary transfer roller 9 are provided in this order from the upstream side (lower side in FIG. 2) in the transport direction of the transfer paper P.

[0024] By rotating only the opening / closing cover 21 in the opening direction relative to the image forming apparatus 100 to set it in an open state, a wide area of ​​the duplex conveying path 20 is exposed. Also, by rotating the opening / closing cover 21 together with the conveying unit 23 in the opening direction, the conveying unit 23 moves away from the main body of the image forming apparatus 100 to expose a wide area of ​​the paper conveying path 19. On the other hand, by rotating the opening / closing cover 21 together with the conveying unit 23 in the closing direction to set it in a closed state, the conveying unit 23 comes into contact with the main body of the image forming apparatus 100, and the secondary transfer roller 9 is pressed against the drive roller 11 via the intermediate transfer belt 8.

[0025] Next, the configuration of the fixing device 14 will be described. Figures 3 and 4 are perspective views of the fixing device 14 as seen from the upstream side in the transport direction of the transfer paper P (the lower side in Figure 2), respectively, and show the states in which the shutter member 33 is disposed in the open position and the closed position. Figure 5 is a perspective view of the shutter member 33. Figure 6 is a side cross-sectional view of one longitudinal end of the fixing device 14 (cross-sectional view taken along the arrow AA in Figure 3).

[0026] The fixing device 14 has a housing 30 and side plates 31a, 31b fixed to both longitudinal ends of the housing 30. A fixing belt 14a and a pressure roller 14b are contained within the housing 30. A paper entrance 30a is formed on the bottom surface of the housing 30. The transfer paper P that has passed through the secondary transfer nip N (see FIG. 2) passes through the paper entrance 30a and is guided to the fixing nip formed by the fixing belt 14a and the pressure roller 14b.

[0027] A drive input gear 32 is disposed on the side plate 31b. The drive input gear 32 is fixed to the rotation shaft of the pressure roller 14b. A rotational drive force is transmitted from a fixing drive motor (not shown) to the pressure roller 14b via the drive input gear 32, and the pressure roller 14b rotates at a predetermined speed. As a result, the fixing belt 14a, which is pressed against the pressure roller 14b, also rotates following the pressure roller 14b.

[0028] A shutter member 33 is attached to the housing 30. As shown in Fig. 5, the shutter member 33 has a flat body portion 331 that overlaps the paper entrance 30a, and a pair of support portions 332 formed at both longitudinal ends of the body portion 331. The shutter member 33 is slidably attached to the lower surface of the housing 30. The shutter member 33 is selectively positioned at an open position (first position, see Fig. 3) where the paper entrance 30a of the housing 30 is opened, and at a closed position (second position, see Fig. 4) where the paper entrance 30a is closed.

[0029] As shown in Fig. 6, a coil spring (biasing member) 35 is disposed between the inner side surface of the housing 30 and the support portion 332. The shutter member 33 is biased in a direction from the open position toward the closed position (from left to right in Fig. 6) by the biasing force of the coil spring 35. A guide groove 332a extending along the sliding direction of the shutter member 33 is formed on the side surface of the support portion 332.

[0030] 7 is a partially enlarged view of the lower periphery of side plate 31a as viewed from the outside. Side plate 31b has a similar configuration, so its description is omitted. An engagement protrusion 40 is formed on the lower end of side plates 31a, 31b. The engagement protrusion 40 is formed by bending a part of side plates 31a, 31b inward, and engages with a guide groove 332a (see FIG. 6) formed on the side surface of support portion 332.

[0031] Further, a rail portion 41 (see FIG. 6) is formed on the inner side of the side plates 31a and 31b so as to face the upper side of the support portion 332. The shutter member 33 slides between an open position and a closed position while being held in a horizontal position by the engaging protrusion 40 that engages with the guide groove 332a and the rail portion 41.

[0032] A restricting protrusion 50 is formed on the inner surface of the opening / closing cover 21 at a position facing the support portion 332. When the opening / closing cover 21 is in the closed state as shown in FIG. 6, the restricting protrusion 50 abuts against the support portion 332. As a result, the shutter member 33 is placed in the open position against the biasing force of the coil spring 35.

[0033] 6 is rotated clockwise to the open state, the restricting projection 50 moves away from the support portion 332 as shown in Fig. 8. As a result, the shutter member 33 moves from the open position to the closed position by the biasing force of the coil spring 35.

[0034] 8 is rotated counterclockwise to the closed state, the restricting projection 50 presses the support portion 332 toward the open position. As a result, the shutter member 33 moves from the closed position to the open position while compressing the coil spring 35.

[0035] According to the above configuration, the shutter member 33 is selectively disposed in an open position or a closed position in conjunction with the opening and closing operation of the opening and closing cover 21. Therefore, when the opening and closing cover 21 is opened, the shutter member 33 is reliably disposed in the closed position, so there is no risk of an operator touching the fixing belt 14a when clearing a jam or performing maintenance on the fixing device 14. In addition, when the opening and closing cover 21 is closed, the shutter member 33 is reliably disposed in the open position, so there is no risk of forgetting to open the shutter member 33.

[0036] Next, a mechanism for locking the shutter member 33 in the closed position will be described. Fig. 9 is an enlarged perspective view of the vicinity of the tip of the support part 332 of the shutter member 33 as viewed from the inside. As shown in Fig. 9, a hook part 332b is formed at the tip of the support part 332, extending along the inner side surface of the support part 332. The hook part 332b has an engagement claw 60 that protrudes upward. Also, an inclined surface 332c is formed at the tip of the support part 332, which is inclined downward toward the downstream side in the movement direction (from left to right in Fig. 9) of the shutter member 33 from the open position to the closed position.

[0037] 10 is a side cross-sectional view showing a state in which the shutter member 33 is arranged at the closed position. As shown in FIG. 10, when the shutter member 33 is arranged at the closed position by the biasing force of the coil spring 35, the engagement claw 60 (see FIG. 9) of the hook portion 332b faces the corner portion 41a of the rail portion 41.

[0038] Here, the base end side (left end side in FIG. 10) of the shutter member 33 adjacent to the coil spring 35 is restricted from moving in the vertical direction by the engagement between the engagement protrusion 40 and the guide groove 332a (see FIG. 11). On the other hand, the tip end side (right end side in FIG. 10) of the shutter member 33 is a free end. Therefore, in the state of FIG. 10, the tip end side of the shutter member 33 is inclined downward due to its own weight, and the engagement claw 60 of the hook portion 332b and the corner portion 41a of the rail portion 41 are not engaged.

[0039] Fig. 11 is a diagram illustrating a mechanism by which the locked state is maintained by the hook portion 332b when the shutter member 33 disposed in the closed position is manually opened. The surface of the shutter member 33 is not formed with an uneven shape that a finger can hook. Therefore, when trying to open the shutter member 33 disposed in the closed position with a finger, it is necessary to apply a force in the upward direction (the direction of the white arrow) in Fig. 11.

[0040] As a result, the tip side of the shutter member 33 swings upward (in the direction of the black arrow) with the engagement protrusion 40 as a fulcrum. That is, the shutter member 33 swings in a direction in which the engagement claw 60 of the hook portion 332b engages with the corner portion 41a of the rail portion 41. With the above configuration, the shutter member 33 cannot be opened even if an attempt is made to open it with a finger.

[0041] In addition, the tip of the support part 332 is protected by a cover part (not shown) formed on the housing 30. The cover part has a slit through which the restricting protrusion 50 of the opening and closing cover 21 can pass, but is configured so that a finger cannot enter the slit. Therefore, an operator cannot press the tip of the support part 332 to open the shutter member 33.

[0042] When the hand is released from the shutter member 33, the force of the coil spring 35 presses the shutter member 33 toward the closed position (to the right in Figure 11), and the tip side of the shutter member 33 tilts downward due to its own weight, causing the engagement claw 60 of the hook portion 332b to disengage from the corner portion 41a of the rail portion 41.

[0043] 12 is a diagram illustrating a mechanism by which the shutter member 33, which is placed at the closed position, is released from the locked state by the opening / closing cover 21. Since an inclined surface 332c is formed at the tip of the support portion 332 of the shutter member 33, the restricting protrusion 50 presses the inclined surface 332c diagonally downward (in the direction of the arrow in FIG. 12) when the opening / closing cover 21 is closed. As a result, a force is applied to the shutter member 33 in a direction in which the engagement claw 60 is disengaged from the corner portion 41a of the rail portion 41. Therefore, even if the engagement claw 60 does not disengage from the corner portion 41 only by the biasing force of the coil spring 35 and the weight of the shutter member 33, the shutter member 33 can be reliably moved from the closed position to the open position when the opening / closing cover 21 is closed.

[0044] In addition, the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the present invention. For example, in the above embodiment, the fixing device 14 of the belt heating type having the endless fixing belt 14a as the heated rotating body is exemplified, but the present invention is also applicable to a fixing device having a heated rotating body other than the fixing belt 14a, such as a fixing roller. If the fixing roller is touched with a hand, fingerprints or dirt may adhere to the fixing roller, which may adversely affect the image, so it is effective to apply the present invention.

[0045] In addition, in the above embodiment, a color printer as shown in FIG. 1 has been used as an example of image forming apparatus 100; however, the present invention is not limited to color printers and can be applied to image forming apparatuses equipped with a fixing device, such as color copiers, color multifunction machines, monochrome printers, and monochrome copiers. [Industrial Applicability]

[0046] The present invention can be used in an image forming apparatus equipped with a fixing device. By using the present invention, it is possible to provide an image forming apparatus in which a shutter member for preventing contact with a fixing member can be opened and closed with a simple configuration, and locked and unlocked in a closed state. [Explanation of symbols]

[0047] Pa~Pd Image forming section 14 Fixing device 14a Fixing belt (heated rotating body) 14b Pressure roller (pressure rotating body) 14c Heater 19 Paper transport path 21 Opening and closing cover 23 Transport unit 30 Housing 30a Paper entrance (sheet entrance) 31a, 31b side plate 33 Shutter parts 331 Main body 332 Support part 332a Guide groove 332b Hook part 332c slope 35 Coil spring (biasing member) 40 Engagement protrusion 41 Rail section 41a Corner (engaged part) 50 Regulating protrusion 60 Engagement claw 100 Image forming device P Transfer paper (recording medium)

Claims

1. A heated rotating body; a pressure rotating body that is pressed against the heated rotating body to form a fixing nip portion; a housing that accommodates the heated rotating body and the pressurizing rotating body; a sheet entrance provided in the housing through which a sheet passes to be conveyed to the fixing nip portion; a shutter member supported by the housing and slidable between a first position for opening the sheet entrance and a second position for closing the sheet entrance; a biasing member that biases the shutter member in a direction toward the second position; a fixing device for melting and fixing an unfixed toner image on the sheet by applying heat and pressure to the sheet passing through the fixing nip portion, the shutter member has a hook portion on which an engaging claw is formed that faces an engaged portion of the housing when the shutter member is disposed at the second position; A fixing device characterized in that when an external force toward the inside of the housing is applied to the shutter member disposed at the second position, the engaging claw and the engaged portion engage with each other to restrict movement of the shutter member to the first position.

2. The shutter member is A flat body portion overlapping the sheet entrance; A pair of support portions formed at both ends of the main body in the longitudinal direction; having The pair of support portions each have a guide groove extending along a sliding direction of the shutter member and engaging with an engaging protrusion of the housing, The fixing device according to claim 1, characterized in that when an external force toward the inside of the housing is applied to the shutter member disposed in the second position, the shutter member swings with the engagement protrusion as a fulcrum in a direction in which the engagement claw and the engaged portion engage with each other.

3. 2. The fixing device according to claim 1, wherein the heated rotating body is a fixing belt.

4. an image forming unit that forms a toner image on a sheet; a fixing device according to claim 1 , which melts and fixes the toner image formed by the image forming unit onto the sheet; In an image forming apparatus comprising: an opening / closing cover that configures a side surface of the image forming apparatus and is supported rotatably between a closed state in which the opening / closing cover faces the fixing device and an open state in which the opening / closing cover is spaced apart from the fixing device; The opening / closing cover is formed with a restricting protrusion that contacts the shutter member in the closed state, When the opening / closing cover is in the closed state, the shutter member is pressed by the restricting protrusion and is disposed at the first position against the biasing force of the biasing member, When the opening / closing cover is in the open state, the shutter member is disposed at the second position by the biasing force of the biasing member.

5. The seat entrance is formed in a lower surface of the housing, the shutter member is supported so as to be horizontally slidable between the first position and the second position, 5. The image forming apparatus according to claim 4, wherein a sloping surface is formed in the portion of the shutter member with which the regulating protrusion comes into contact, the sloping surface being inclined downward as it approaches the downstream side in the movement direction from the first position to the second position.

Images