Fixing device and image forming apparatus

Abstract

To suppress increase in a size of an image forming apparatus comprising a fixing device including a shutter arm for opening and closing a shutter.SOLUTION: A fixing device 1 comprises: a first rotating body; a second rotating body that forms a nip part with the first rotating body; a frame 4 that has an opening; a shutter 50 that opens and closes the opening; a nip pressure changing mechanism NM; a shutter arm 91; and an arm cam 92. The nip pressure changing mechanism NM has a pressure arm that presses the first rotating body against the second rotating body, and a cam 80 that presses the pressure arm. The cam 80 is rotatable centered on a second axis X2. The shutter arm 91 is connected with the shutter 50. The shutter arm 91 rotates centered on the second axis X2 independently of the cam 80 to open and close the shutter 50. The arm cam 92 rotates centered on the second axis X2 to push the shutter arm 91 at a position off the second axis X2, and thereby rotates the shutter arm 91.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a fixing device that fixes a toner image on a sheet, and an image forming apparatus that includes the fixing device. [Background technology]

[0002] Conventionally, there is known a device that includes a first housing, a second housing that slides relative to the first housing, a fixing device located within the first housing, a shutter that opens and closes the sheet entrance of the fixing device, and a shutter arm that opens and closes the shutter in conjunction with the movement of the second housing (see Patent Document 1). In this technology, the shutter arm is disposed so as to extend vertically between the fixing device and the process cartridge.

[0003] The shutter arm has a rotatable roller at its upper end. The second housing has a guide rail along which the roller can move relatively. The guide rail has an inclined portion for moving the roller up and down. As a result, when the second housing is slid, the shutter arm moves up and down, opening and closing the shutter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-47593 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional technology, the shutter arm is disposed between the fixing device and the process cartridge, which may increase the size of the image forming apparatus.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to prevent an image forming apparatus from becoming large in size in a configuration that includes a shutter arm for opening and closing the shutter of a fixing device. [Means for solving the problem]

[0007] In order to achieve the above object, a fixing device according to the present invention includes a first rotating body, a second rotating body, a frame, a shutter, a nip pressure changing mechanism, a shutter arm, and an arm cam. The second rotating body forms a nip portion between itself and the first rotating body. The frame has an opening through which a sheet conveyed toward the nip passes, and the frame supports the first rotating body and the second rotating body. The shutter is rotatable 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 nip pressure change mechanism changes the nip pressure at the nip portion and includes a pressure arm, a cam, and an arm cam. The pressure arm presses the first rotating body toward the second rotating body. The cam presses the pressure arm and is rotatable about a second shaft. The shutter arm is connected to the shutter and rotates about the second axis independently of the cam to rotate the shutter between the closed position and the open position. The arm cam rotates about the second axis, thereby pushing the shutter arm at a position offset from the second axis, causing the shutter arm to rotate about the second axis.

[0008] With this configuration, the rotation axis of the shutter arm is coaxial with the rotation axis of the cam, so the amount by which the shutter arm protrudes from the frame of the fixing device can be reduced, and the image forming apparatus can be prevented from becoming larger.

[0009] The fixing device may further include a shaft that supports the cam and is rotatable around the second axis, the arm cam having a cylindrical portion into which the shaft fits, and the shutter arm having a hole into which the cylindrical portion fits.

[0010] The shutter may have a protrusion, and the shutter arm may have an elongated hole into which the protrusion fits.

[0011] Furthermore, the protrusion of the shutter may be located on the nip portion side of a straight line connecting the first axis and the second axis when the shutter is in the closed position, and may be located on the opposite side of the straight line from the nip portion when the shutter is in the open position.

[0012] According to this configuration, the shutter can be opened and closed even if the length of the elongated hole in the shutter arm is shortened, so that the shutter arm can be prevented from becoming large.

[0013] The fixing device may further include a shaft that supports the cam and is rotatable around the second axis, the frame may include a first frame that supports the first rotating body and the second rotating body, and a second frame that is attached to the first frame and holds the shaft between the first frame and the second frame, and the shutter may be supported on the second frame via a boss.

[0014] In addition, the boss may be disposed upstream of the nip portion in the sheet transport direction.

[0015] In addition, the second shaft may be disposed downstream of the nip portion in the sheet transport direction.

[0016] The pressure arm may also have a first pressure arm arranged at one end of the frame in the longitudinal direction and a second pressure arm arranged at the other end of the frame in the longitudinal direction, and the shutter arm may be arranged on the opposite side of the first pressure arm from the second pressure arm in the longitudinal direction.

[0017] The fixing device may also include a heater having a substrate and a resistance heating element disposed on the substrate, and the first rotating body may be an endless belt heated by the heater and rotating around the heater.

[0018] The fixing device may further include a connector that supplies electricity to the heater, the heater further having a power supply terminal at at least one end of the substrate in the longitudinal direction to which electricity is supplied from the connector, the second rotating body may be a pressure roller that can rotate around a third axis, and the shutter arm may be positioned on the opposite side of the connector from the third axis.

[0019] The fixing device may further include a spring that can come into contact with the shutter arm, and the arm cam may press the shutter arm via the spring to position the shutter at the closed position.

[0020] The arm cam may contact the shutter arm to position the shutter at the open position.

[0021] An image forming apparatus according to the present invention includes a main body housing, a unit detachable from the main body housing, and the fixing device. The arm cam rotates about the second axis when the unit is attached to or detached from the main body housing. The shutter arm rotates the shutter from the closed position to the open position when the unit is attached to the main body housing, and rotates the shutter from the open position to the closed position when the unit is detached from the main body housing.

[0022] The image forming apparatus may also include a connecting link that is connected to the arm cam and that abuts against the unit when the unit is attached to the main body housing and is movable relative to the main body housing.

[0023] The image forming apparatus may further include a lock for holding the shutter in the open position or the closed position, the lock having a lock arm that abuts against the connecting link and a lock spring that urges the lock arm toward the connecting link, and the connecting link may have a link protrusion that protrudes toward the lock side.

[0024] The unit may have a unit shaft that abuts against the connecting link when attached to the main body housing, and the main body housing may have a guide rail that guides the unit shaft. [Effects of the Invention]

[0025] According to the present invention, in a configuration including a shutter arm for opening and closing the shutter of a fixing device, it is possible to prevent the image forming apparatus from becoming large. [Brief explanation of the drawings]

[0026] [Figure 1] 1A is a cross-sectional view showing a fixing device according to an embodiment, and FIG. 1B is an enlarged cross-sectional view showing the periphery of a heater. [Figure 2] (a) is a diagram showing the surface on which the heater's resistance heating element is arranged, (b) is a diagram of the heater and heat conduction member seen from the back side of the heater, and (c) is a cross-sectional view of the heater etc. cut longitudinally. [Figure 3] FIG. 4 is a cross-sectional view showing the nip pressure changing mechanism, illustrating a state in which the nip pressure becomes a first nip pressure. [Figure 4] FIG. 10 is a cross-sectional view showing the nip pressure changing mechanism, illustrating a state in which the nip pressure becomes a second nip pressure. [Figure 5] FIG. 2 is an exploded perspective view showing a frame and a part of a nip pressure change mechanism. [Figure 6] FIG. 2 is a perspective view of the fixing device as seen from the downstream side in the transport direction. [Figure 7] 4A and 4B are cross-sectional views of the fixing device, showing a state in which the shutter is located at a closed position, and FIG. 4B shows a state in which the shutter is located at an open position. [Figure 8] FIG. 2(a) is a perspective view of the shutter as seen from the first plate-shaped portion side, and FIG. 2(b) is a perspective view of the shutter as seen from the second plate-shaped portion side. [Figure 9] 10 is a perspective view of the fixing device with the shutter in a closed position, as viewed from the upstream side in the transport direction. FIG. [Figure 10] 10 is a perspective view of the fixing device with the shutter in an open position, as viewed from the upstream side in the transport direction. FIG. [Figure 11] FIG. 2 is an exploded perspective view showing the shutter operating mechanism. [Figure 12] 1A is a side view of the fixing device when the shutter is in the closed position, and FIG. 1B is an enlarged cross-sectional view of a spring contact portion. [Figure 13] 1A is a side view of the fixing device when the shutter is in the open position, and FIG. 1B is an enlarged cross-sectional view of a spring contact portion. [Figure 14] FIG. 10 is a perspective view showing the relationship between two pressure arms and a shutter arm. [Figure 15] FIG. 2 is a diagram showing a main body housing of an image forming apparatus in which a fixing device is installed. [Figure 16] FIG. 2 is a diagram showing a unit that can be attached to and detached from a main body housing. [Figure 17] 10A and 10B are diagrams illustrating the state of the connecting link when the unit is removed from the main body housing. [Figure 18] 10A and 10B are diagrams illustrating the state of the connecting link when the unit is being attached to the main body housing. [Figure 19] 10A and 10B are diagrams illustrating the state of the connecting link when the unit is attached to the main body housing. DETAILED DESCRIPTION OF THE INVENTION

[0027] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. As shown in Fig. 1(a), the fixing device 1 is a device that fixes a toner image on a sheet S. The fixing device 1 is installed in an image forming apparatus such as a printer. The fixing device 1 includes a heating unit 2, a pressure roller 3 as an example of a second rotating body, and a frame 4.

[0028] The pressure roller 3 is rotatable about a third axis X3, and is capable of nipping the sheet S between itself and the heating unit 2. The pressure roller 3 has a cylindrical shaft 3A and a cylindrical roller portion 3B. The shaft 3A is made of, for example, metal. The roller portion 3B is made of, for example, rubber. The roller portion 3B covers a portion of the shaft 3A. The pressure roller 3 forms a nip portion NP between itself and the heating unit 2.

[0029] The heating unit 2 includes a heater 10, a holder 20, a heat conduction member 30, a stay ST, and a belt BL as an example of a first rotating body. The heater 10 heats the belt BL, and heats the sheet S through the belt BL.

[0030] As shown in FIG. 1(b), the heater 10 has a substrate 11, a resistance heating element 12 disposed on the substrate 11, and a cover 13. The substrate 11 is an elongated rectangular ceramic plate made of aluminum oxide. The heater 10 is a so-called ceramic heater. The resistance heating element 12 is formed by printing on one surface of the substrate 11. As shown in FIG. 2(a), in this embodiment, two resistance heating elements 12 are provided. The two resistance heating elements 12 are each elongated in the longitudinal direction of the heater 10 and arranged parallel to each other and spaced apart in the lateral direction perpendicular to the longitudinal direction. A conductor 19A is connected to one end 12A of each resistance heating element 12, and a power supply terminal 18 is provided at each end of the conductor 19A to supply power to the resistance heating element 12.

[0031] The power supply terminal 18 is electrically connected to the resistance heating element 12 via a conductor 19A. The power supply terminal 18 is located at one longitudinal end 11E of the substrate 11. As shown in FIG. 2(c), a connector C that supplies electricity to the heater 10 is connected to the power supply terminal 18. The connector C is detachable from one longitudinal end of the heater 10. Electricity is supplied to the power supply terminal 18 from the connector C. For convenience, the resistance heating element 12, cover 13, and belt BL are not shown in FIG. 2(c).

[0032] The other ends 12B of the resistance heating elements 12 are connected to each other by conductive wires 19B. The number of resistance heating elements 12 is not particularly limited. Alternatively, a resistance heating element having a larger heat generation amount at the longitudinal center than at the longitudinal ends and a resistance heating element having a larger heat generation amount at the longitudinal ends than at the longitudinal center may be provided, and the heat generation distribution in the longitudinal direction may be adjusted by individually controlling each resistance heating element.

[0033] 1(b), the cover 13 covers the resistance heating element 12. The cover 13 is made of, for example, glass.

[0034] 1(a), the holder 20 has a function of supporting the heater 10 and guiding the belt BL. The holder 20 is made of, for example, resin.

[0035] The stay ST supports the holder 20. The stay ST is made of, for example, metal.

[0036] The belt BL is endless and made of metal or resin. The belt BL rotates around the heater 10 while being guided by the holder 20. The belt BL has an outer peripheral surface and an inner peripheral surface. The outer peripheral surface comes into contact with the pressure roller 3 or the sheet S to be heated. The inner peripheral surface comes into contact with the heater 10.

[0037] The heat conducting member 30 is a member that conducts heat in the longitudinal direction of the heater 10 to make the temperature of the heater 10 uniform in the longitudinal direction. The heat conducting member 30 is a plate-shaped member that is located between the heater 10 and the holder 20. When the heating unit 2 sandwiches the sheet S between itself and the pressure roller 3, the heat conducting member 30 is sandwiched between the heater 10 and the holder 20. The heat conducting member 30 is made of, for example, aluminum.

[0038] 2(a) and 2(b), one end 12A and the other end 12B of the resistance heating element 12 are located, in the longitudinal direction, outside the maximum width W1 of the sheet that can be used in the heating unit 2 and inside one end 30A and the other end 30B of the heat conducting member 30. In other words, the length of the heat conducting member 30 is longer than the length of the resistance heating element 12 in the longitudinal direction.

[0039] In the longitudinal direction, the length of substrate 11 is longer than the length of heat conduction member 30. One end 30A of heat conduction member 30 is located inside one end 11A of substrate 11 in the longitudinal direction. The other end 30B of heat conduction member 30 is located outside the other end 11B of substrate 11 in the longitudinal direction.

[0040] 5, the frame 4 has a first frame 41 and a second frame 42. The first frame 41 supports the heating unit 2 and the pressure roller 3. The second frame 42 is attached to the first frame 41 so as to cover the heating unit 2 from the side opposite the pressure roller 3.

[0041] The first frame 41 supports the pressure roller 3 via bearings BR. The bearings BR are disposed at both one end and the other end of the first frame 41 in the axial direction of the pressure roller 3.

[0042] The first frame 41 supports the heating unit 2 so that it can move in a predetermined direction. In the following description, the axial direction of the pressure roller 3 will also be simply referred to as the "axial direction." The conveying direction of the sheet S at the nip portion NP will also be simply referred to as the "conveying direction." In this embodiment, the conveying direction of the sheet S at the nip portion NP is perpendicular to the axial direction and the predetermined direction. In addition, in the drawings, arrows indicating directions will point to one side. In particular, the arrow indicating the conveying direction will point to the downstream side of the conveying direction.

[0043] 3, fixing device 1 further includes a nip pressure changing mechanism NM for changing the nip pressure at nip portion NP between heating unit 2 and pressure roller 3. Nip pressure changing mechanism NM includes shaft SF, pressure arm 60, pressure spring 70, and cam 80. First frame 41 supports pressure spring 70 and rotatably supports pressure arm 60 and cam 80.

[0044] 5, the pressure arm 60 and the cam 80 are respectively disposed at one end and the other end of the first frame 41 in the axial direction. Although not shown, the pressure spring 70 is also respectively disposed at one end and the other end of the first frame 41 in the axial direction. Since the structure of one side of the nip pressure change mechanism NM in the axial direction is substantially the same as the structure of the other side, the structure of one side in the axial direction will be mainly described below as a representative.

[0045] In the following description, the pressure arm 60 disposed at one end of the frame 4 in the longitudinal direction will also be referred to as the "first pressure arm 60A." The pressure arm 60 disposed at the other end of the frame 4 in the longitudinal direction will also be referred to as the "second pressure arm 60B." Here, the longitudinal direction of the frame 4 refers to the direction parallel to the axial direction.

[0046] The shaft SF extends in the axial direction. The shaft SF is made of, for example, metal. A cam 80 is fixed to each axial end of the shaft SF. In other words, the cam 80 has the shaft SF. The cam 80 rotates in conjunction with the rotation of the shaft SF. The first frame 41 has a support portion 41C that rotatably supports the shaft SF. The support portion 41C is disposed at each of one end and the other end of the first frame 41 in the axial direction. The support portion 41C has a hole H1 that rotatably supports the shaft SF.

[0047] The second frame 42 has a groove 42C that rotatably supports the shaft SF (see also FIG. 6). The groove 42C is disposed at each of one end and the other end of the second frame 42 in the axial direction. The second frame 42 holds the shaft SF between itself and the first frame 41.

[0048] As shown in FIG. 3, the shaft SF is supported by the frame 4 so as to be rotatable about a second axis X2.

[0049] The pressure arm 60 is an arm that presses the heating unit 2 toward the pressure roller 3. The first frame 41 has a first support portion 41D that supports the pressure arm 60 rotatably around an axis XA. The first support portion 41D is a substantially cylindrical protrusion. The axis XA, the second axis X2, and the third axis X3 are located at different positions. The axis XA, the second axis X2, and the third axis X3 are parallel to each other.

[0050] The pressure spring 70 is a tension coil spring that biases the pressure arm 60 toward the pressure roller 3. The biasing direction of the pressure spring 70 is approximately parallel to a predetermined direction. The first frame 41 has a first spring catch 41E on which one end of the pressure spring 70 is hooked.

[0051] The cam 80 is capable of pressing the pressure applying arm 60 against the biasing force of the pressure applying spring 70. Specifically, the cam 80 is capable of rotating between a first position shown in Fig. 3 and a second position shown in Fig. 4.

[0052] When the cam 80 is in the first position, the nip pressure is a first nip pressure, and when the cam 80 is in the second position, the nip pressure is a second nip pressure that is smaller than the first nip pressure.

[0053] The pressure arm 60 has a main body portion 61, a supported portion 62, a first tip portion 63, and a second tip portion 64. The first tip portion 63 has a base portion 63A made of metal and a cam follower 63B (see also FIG. 5) made of resin. The main body portion 61, the supported portion 62, the base portion 63A, and the second tip portion 64 are made of metal and are integrally formed. The cam follower 63B is fitted into the base portion 63A.

[0054] The main body 61 has a first end E1 and a second end E2. The main body 61 extends from the first end E1 to one side in a predetermined direction and then extends downstream in the conveyance direction, with the second end E2 being the downstream end in the conveyance direction. The main body 61 has a pressure surface F1 between the first end E1 and the second end E2 that presses the heating unit 2 against the pressure roller 3.

[0055] Here, the heating unit 2 has side guides SG at each end in the axial direction. The side guides SG support the ends of the stays ST in the axial direction. The side guides SG are movably supported by the first frame 41. The pressure surface F1 presses the side guides SG toward the pressure roller 3.

[0056] The supported portion 62 is located at the first end E1 of the main body portion 61. The supported portion 62 is supported by the first support portion 41D of the first frame 41.

[0057] The first tip portion 63 is located at the second end E2 of the main body portion 61. The first tip portion 63 has a pressed surface F2 that is pressed by the cam 80. More specifically, the base portion 63A extends in a direction inclined with respect to the conveying direction so as to be positioned on one side of a predetermined direction as it moves from the second end E2 of the main body portion 61 toward the downstream side in the conveying direction. The cam follower 63B attached to the base portion 63A has the pressed surface F2.

[0058] The second tip portion 64 is located at the second end E2 of the main body portion 61. The second tip portion 64 extends in a different direction from the first tip portion 63. The second tip portion 64 has a second spring hook 64A on which the other end of the pressure spring 70 is hooked.

[0059] 7, the frame 4 has an opening 4A. The opening 4A is an opening through which the sheet S passes as it is transported toward the nip portion NP. The opening 4A is located upstream of the nip portion NP in the transport direction.

[0060] The fixing device 1 further includes a shutter 50. The shutter 50 is rotatable about a first axis X1 between a closed position shown in FIG. 7(a) and an open position shown in FIG. 7(b). When the shutter 50 is in the closed position, it closes the opening 4A. When the shutter 50 is in the open position, it opens the opening 4A. The shutter 50 is rotatably supported by the second frame 42 via a boss 52 (described later). The boss 52 is located upstream of the nip portion NP in the transport direction. The shaft SF is located downstream of the nip portion NP in the transport direction. In other words, the second axis X2 is located downstream of the nip portion NP in the transport direction.

[0061] 8, the shutter 50 has a shutter main body 51, a boss 52, a connecting portion 53, and a protrusion 54. The shutter 50 is made of a material such as resin. The shutter main body 51, the boss 52, the connecting portion 53, and the protrusion 54 are integrally formed.

[0062] The shutter main body 51 has a first plate-shaped portion 51A, a second plate-shaped portion 51B, and multiple ribs 51C. The first plate-shaped portion 51A is a plate-shaped portion that is long in the axial direction. The first plate-shaped portion 51A has multiple holes H2. The multiple holes H2 are lined up in the short direction of the first plate-shaped portion 51A and also lined up in the long direction of the first plate-shaped portion 51A.

[0063] The second plate-shaped portion 51B is a plate-shaped portion that is long in the axial direction. The second plate-shaped portion 51B does not have a plurality of holes. The second plate-shaped portion 51B extends from one end in the short side direction of the first plate-shaped portion 51A.

[0064] The plurality of ribs 51C are disposed between the first plate-shaped portion 51A and the second plate-shaped portion 51B. The plurality of ribs 51C connect the first plate-shaped portion 51A and the second plate-shaped portion 51B.

[0065] The bosses 52 are disposed at one end and the other end in the axial direction of the shutter body 51. Each boss 52 is cylindrical. The center of each boss 52 coincides with the first axis X1.

[0066] The connecting portion 53 connects the boss 52 to the shutter main body 51. The connecting portion 53 is disposed on each of one end side and the other end side of the shutter main body 51 in the axial direction.

[0067] The protrusion 54 is disposed on one axial end side of the shutter main body 51. More specifically, the protrusion 54 extends in the axial direction from one axial end of the first plate-shaped portion 51A. The protrusion 54 is located at a position different from the boss 52 in a direction perpendicular to the axial direction.

[0068] The protrusion 54 has a retaining portion 54A. The retaining portion 54A is located at the tip of the protrusion 54. The retaining portion 54A protrudes from the outer peripheral surface of the protrusion 54.

[0069] 9 and 10, the fixing device 1 further includes a shutter operating mechanism 90 for opening and closing the shutter 50. As shown in Fig. 11, the shutter operating mechanism 90 includes a shutter arm 91, an arm cam 92, and a spring 93. The shutter arm 91 and the arm cam 92 are made of resin or the like. The spring 93 is made of metal or the like.

[0070] The shutter arm 91 rotates about the second axis X2, thereby rotating the shutter 50 between a closed position and an open position (see FIGS. 9 and 10). The shutter arm 91 has an arm main body 91A, a first connecting portion 91B, and a second connecting portion 91C. The arm main body 91A, the first connecting portion 91B, and the second connecting portion 91C are integrally formed.

[0071] The first connecting portion 91B has a hole H3 into which the cylindrical portion 92A of the arm cam 92 fits. The first connecting portion 91B is connected to the shaft SF via the cylindrical portion 92A. The first connecting portion 91B is rotatably supported on the shaft SF via the cylindrical portion 92A. This allows the shutter arm 91 to rotate about the second axis X2. Furthermore, the shutter arm 91 can rotate independently of the shaft SF.

[0072] The second connecting portion 91C has an elongated hole H4 into which the protrusion 54 of the shutter 50 fits. The second connecting portion 91C is connected to the protrusion 54 of the shutter 50 by the elongated hole H4.

[0073] The arm body 91A connects the first connecting portion 91B and the second connecting portion 91C. The arm body 91A has a boss B1.

[0074] As shown in Fig. 12(a), when the shutter 50 is in the closed position, the protrusion 54 of the shutter 50 is located on the nip portion NP side of the straight line L1 connecting the first axis X1 and the second axis X2. As shown in Fig. 13(a), when the shutter 50 is in the open position, the protrusion 54 of the shutter 50 is located on the opposite side of the straight line L1 from the nip portion NP. The shutter arm 91 is located on the opposite side of the connector C from the third axis X3.

[0075] As shown in FIG. 11 , the arm cam 92 rotates about the second axis X2, thereby pressing the shutter arm 91 at a position offset from the second axis X2 and causing the shutter arm 91 to rotate about the second axis X2. Specifically, the arm cam 92 presses the boss B1 of the shutter arm 91 in the circumferential direction. Here, the circumferential direction is the direction along a circle centered on the second axis X2. The arm cam 92 has a cylindrical portion 92A, a pressing portion 92B, the boss B2, and a connecting portion 92C. The cylindrical portion 92A, the pressing portion 92B, the boss B2, and the connecting portion 92C are integrally formed. The pressing portion 92B and the boss B2 are connected to the cylindrical portion 92A by the connecting portion 92C.

[0076] The cylindrical portion 92A has a hole H5 into which the shaft SF fits. The cylindrical portion 92A is rotatably supported by the shaft SF. This allows the arm cam 92 to rotate about the second axis X2. The arm cam 92 can rotate independently of the shaft SF. The cylindrical portion 92A fits into a hole H3 in the shutter arm 91. The cylindrical portion 92A rotatably supports the shutter arm 91.

[0077] The boss B2 is a portion to which a force is input from a connecting link 200 (see FIG. 17) described later. The boss B2 is located at a position different from the second axis X2 in a direction perpendicular to the axial direction.

[0078] The pressing portion 92B is located at a position offset from the second axis X2. The pressing portion 92B has an elongated hole H6 into which the boss B1 of the shutter arm 91 fits. The elongated hole H6 is arc-shaped with the second axis X2 as its center. The elongated hole H6 allows for displacement of the boss B1 of the shutter arm 91. The pressing portion 92B is cylindrical and conforms to the arc-shaped elongated hole H6. As shown in FIG. 9, the other axial end of the pressing portion 92B has a portion on one end side of the elongated hole H6 cut out, thereby forming a spring contact portion T that can come into contact with the spring 93 in the rotational direction of the arm cam 92.

[0079] As shown in Figure 12(b), the spring 93 is a torsion spring and has a coil portion 93A, a first arm portion 93B, and a second arm portion 93C. The cylindrical portion 92A of the arm cam 92 is contained within the coil portion 93A. The cylindrical portion 92A supports the coil portion 93A. The angle formed between the first arm portion 93B and the second arm portion 93C is an acute angle.

[0080] The spring contact portion T is located between the first arm portion 93B and the second arm portion 93C. The spring contact portion T has a first contact surface T1 and a recess T3. The first contact surface T1 is a surface that can come into contact with the first arm portion 93B in the rotation direction of the arm cam 92.

[0081] The recess T3 has a shape obtained by cutting out a portion of the elongated hole H6 shown in FIG. 12(a). The recess T3 opens toward the second arm portion 93C. The boss B1 of the shutter arm 91 is movable within the recess T3. The bottom surface of the recess T3 serves as a second contact surface T2 that can come into contact with the boss B1 of the shutter arm 91 in the rotation direction of the arm cam 92. In the rotation direction of the arm cam 92, the second contact surface T2 is located between the first contact surface T1 and the boss B1. In addition, the boss B1 is located between the second contact surface T2 and the second arm portion 93C in the rotation direction of the arm cam 92.

[0082] 12(a), when the shutter 50 is in the closed position, as shown in FIG. 12(b), the first contact surface T1 of the arm cam 92 comes into contact with the first arm portion 93B, and the second arm portion 93C comes into contact with the boss B1 of the shutter arm 91. The position at which the second arm portion 93C comes into contact with the boss B1 of the shutter arm 91 is offset from the second axis X2. As a result, the arm cam 92 presses the shutter arm 91 via the spring 93, thereby positioning the shutter 50 in the closed position.

[0083] As shown in Figure 13(a), when the shutter 50 is in the open position, as shown in Figure 13(b), the second contact surface T2 of the arm cam 92 comes into contact with the boss B1 of the shutter arm 91. The position at which the second contact surface T2 comes into contact with the boss B1 of the shutter arm 91 is offset from the second axis X2. As a result, the arm cam 92 comes into contact with the shutter arm 91, thereby positioning the shutter 50 in the open position.

[0084] 14, the shutter arm 91 is arranged on the opposite side of the first pressure arm 60A from the second pressure arm 60B in the axial direction. The shutter arm 91 is arranged between the arm cam 92 and the first pressure arm 60A in the axial direction.

[0085] 15 and 16, image forming apparatus 100 includes main body housing 110 as the image forming apparatus main body, unit 120, connecting link 200, and the above-described fixing device 1. Note that in FIG. 15, arm cam 92 of fixing device 1 is shown as a representative, and other parts of fixing device 1 are omitted.

[0086] As shown in Fig. 16, the unit 120 has a photosensitive drum 121. The photosensitive drum 121 has a drum shaft 122 as an example of a unit shaft. The drum shaft 122 is located at the rotation center of the photosensitive drum 121. The unit 120 is detachable from the main body housing 110. As shown in Fig. 15, the main body housing 110 has guide rails 111 that guide the drum shaft 122.

[0087] 17, the connecting link 200 is a mechanism that rotates the shutter 50 from a closed position to an open position when the unit 120 is attached to the main body housing 110, and rotates the shutter 50 from the open position to the closed position when the unit 120 is detached from the main body housing 110. The connecting link 200 includes a contact piece 210, a first rotating link 220, a linear motion link 230, and a second rotating link 240.

[0088] The contact piece 210 is movable while in contact with the drum shaft 122. The contact piece 210 is movably supported by a contact piece rail (not shown). The contact piece rail is provided on the main body housing 110 or the like.

[0089] The abutment piece 210 has a main body portion 211, a first protrusion 212, and a second protrusion 213. The first protrusion 212 and the second protrusion 213 protrude from the main body portion 211 in the axial direction.

[0090] The first protrusion 212 comes into contact with the drum shaft 122 when the unit 120 is attached to the main body housing 110. The second protrusion 213 comes into contact with the drum shaft 122 when the unit 120 is detached from the main body housing 110.

[0091] In this embodiment, the abutment piece 210 is configured to move in contact with the drum shaft 122, but the unit 120 may be configured to have a guide protrusion separate from the drum shaft 122, so that the abutment piece 210 moves in contact with the guide protrusion. In this case, the guide protrusion corresponds to the unit shaft.

[0092] The first rotating link 220 is a substantially linear member that is connected to the abutting piece 210 and the linear motion link 230. One end of the first rotating link 220 supports the main body 211 of the abutting piece 210 so that the main body 211 is rotatable.

[0093] The linear link 230 is a substantially linear member connected to the first rotary link 220 and the second rotary link 240. The linear link 230 is movable in the front-to-rear direction relative to the main body housing 110. One end of the linear link 230 rotatably supports the first rotary link 220. The other end of the linear link 230 has an elongated hole H7 extending in the vertical direction.

[0094] The second rotating link 240 is connected to the linear link 230, and is supported by the main body housing 110 so as to be rotatable about the fourth axis X4. The second rotating link 240 has a support portion 241 that is rotatably supported by the main body housing 110, a first arm 242 that extends substantially downward from the support portion 241, and a second arm 243 that extends substantially upward from the support portion 241.

[0095] The first arm 242 has a boss B3 that fits into the elongated hole H7 of the linear link 230. The second arm 243 has an elongated hole H8 that is arc-shaped with the fourth axis X4 as its center.

[0096] Boss B2 of arm cam 92 fits into long hole H8 of second rotating link 240. As a result, the force input to contact piece 210 is transmitted to arm cam 92 via first rotating link 220, linear link 230, and second rotating link 240.

[0097] The image forming apparatus 100 further includes a lock 300 for holding the shutter 50 in the open or closed position. Specifically, the lock 300 restricts the movement of the linear link 230 in the forward or backward direction by pressing the linear link 230. The lock 300 includes a lock arm 310 that abuts against the linear link 230, and a lock spring 320 that biases the lock arm 310 toward the linear link 230.

[0098] The lock arm 310 is supported by the main body housing 110 so as to be rotatable about a fifth axis X5. The linear link 230 has a link protrusion 231 that protrudes toward the lock 300. The tip end 311 of the lock arm 310 can overcome the link protrusion 231 against the biasing force of the lock spring 320 as the linear link 230 moves in the front-rear direction.

[0099] When the tip end 311 of the lock arm 310 is positioned behind the link protrusion 231, the rearward movement of the linear link 230 is restricted. When the tip end 311 of the lock arm 310 is positioned in front of the link protrusion 231, the forward movement of the linear link 230 is restricted.

[0100] Next, the operation of the shutter operating mechanism 90 and the connecting link 200 will be described. First, we will explain the operation of the shutter operating mechanism 90 and the connecting link 200 when the unit 120 is attached to the main body housing 110. In the following explanation, the position of the arm cam 92 when the shutter 50 is in the closed position will also be referred to as the "closed corresponding position," and the position of the arm cam 92 when the shutter 50 is in the open position will also be referred to as the "opened corresponding position."

[0101] 17, when the drum shaft 122 of the unit 120 is inserted into the guide rail 111 of the main body housing 110, the drum shaft 122 comes into contact with the first protrusion 212 of the abutment piece 210 and pushes the abutment piece 210 backward. As a result, as shown in FIG. 18, the force applied from the drum shaft 122 to the abutment piece 210 is transmitted to the second rotating link 240 via the first rotating link 220 and the linear-acting link 230, causing the second rotating link 240 to rotate clockwise in the figure.

[0102] When the second rotary link 240 rotates clockwise in the drawing, the second rotary link 240 presses the boss B2 of the arm cam 92, causing the arm cam 92 to rotate from the closed corresponding position to the open corresponding position.

[0103] In the process of the arm cam 92 rotating from the close corresponding position to the open corresponding position, as shown in Figure 13(b), the second contact surface T2 of the arm cam 92 presses the boss B1 of the shutter arm 91, causing the shutter arm 91 to rotate from the position shown in Figure 12(a) to the position shown in Figure 13(a). As a result, the shutter 50 connected to the shutter arm 91 rotates from the close position to the open position.

[0104] 19, when the unit 120 attached to the main body housing 110 is removed from the main body housing 110, the drum shaft 122 moves forward along the guide rail 111, thereby coming into contact with the second protrusion 213 of the abutment piece 210 and pushing the abutment piece 210 forward. As a result, the force applied to the abutment piece 210 from the drum shaft 122 is transmitted to the second pivot link 240 via the first pivot link 220 and the linear link 230, and the second pivot link 240 pivots counterclockwise in the figure.

[0105] When the second rotary link 240 rotates counterclockwise in the drawing, the second rotary link 240 presses the boss B2 of the arm cam 92, causing the arm cam 92 to rotate from the open corresponding position to the closed corresponding position.

[0106] In the process of the arm cam 92 rotating from the open corresponding position to the closed corresponding position, as shown in Figure 12(b), the first contact surface T1 of the arm cam 92 presses the boss B1 of the shutter arm 91 via the spring 93, causing the shutter arm 91 to rotate from the position shown in Figure 13(a) to the position shown in Figure 12(a). As a result, the shutter 50 connected to the shutter arm 91 rotates from the open position to the closed position.

[0107] As described above, the following effects can be obtained in this embodiment. As shown in Figure 11, the rotation axis of the shutter arm 91 is coaxial with the rotation axis of the cam 80, so the amount by which the shutter arm 91 protrudes from the frame 4 of the fixing device 1 can be reduced, and the image forming device 100 can be prevented from becoming larger.

[0108] As shown in Figures 12 and 13, when the shutter 50 is in the closed position, the protrusion 54 is located on the side of the nip portion NP relative to the straight line L1, and when the shutter 50 is in the open position, the protrusion 54 is located on the opposite side of the straight line L1 from the nip portion NP.This means that the shutter 50 can be opened and closed even if the length of the long hole H4 of the shutter arm 91 is shortened, thereby preventing the shutter arm 91 from becoming larger.

[0109] The present invention is not limited to the above-described embodiment, but can be used in various forms as exemplified below.

[0110] In the above embodiment, the shutter arm is configured to move in conjunction with the operation of attaching the unit to the main body housing. However, for example, the shutter arm may move in conjunction with the operation of a cover that opens and closes an opening in the main body housing for attaching and detaching the unit to and from the main body housing. In other words, the shutter arm may rotate the shutter from a closed position to an open position when the cover that opens and closes the opening in the image forming apparatus main body is closed. In this case, for example, the shutter arm and the cover may be linked using a cam or link so that the shutter is positioned in the closed position when the cover is opened and the shutter is positioned in the open position when the cover is closed.

[0111] In the above embodiment, the shutter has a boss. However, for example, the frame of the fixing device may have a boss, and the shutter may have a hole into which the boss fits.

[0112] In the above embodiment, when the shutter is in the closed position, the protrusion is located on the nip side of the line L1, and when the shutter is in the open position, the protrusion is located on the opposite side of the line L1 from the nip portion. However, for example, the protrusion may be located on the nip side of the line L1 regardless of whether the shutter is in the closed position or the open position, or the protrusion may be located on the opposite side of the line L1 from the nip portion regardless of whether the shutter is in the closed position or the open position.

[0113] The power supply terminals may be provided at both ends of the substrate in the longitudinal direction.

[0114] The spring is not limited to a torsion spring, but may be, for example, a leaf spring or a wire spring.

[0115] The first rotating body is not limited to a belt, and may be, for example, a heating roller having a cylindrical metal tube.

[0116] The second rotating body is not limited to a pressure roller, but may be, for example, a belt of a pressure unit having a pressure pad and a belt. In this case, the belt as the second rotating body may be sandwiched between the pressure pad and the first rotating body.

[0117] The first rotating body may be a pressure roller, a belt of a pressure unit, etc. The second rotating body may be a belt heated by a heater, a heating roller, etc.

[0118] The unit that is detachably attached to the main body of the image forming apparatus may have a developing roller or a container that contains toner. The unit may have at least one of the photosensitive drum, the developing roller, and the container.

[0119] The heater is not limited to a ceramic heater, and may be, for example, a halogen lamp, etc. In this case, the heating unit may be configured to include a belt, a nip plate that sandwiches the belt between the belt and the pressure roller, and a heater that heats the nip plate.

[0120] The elements described in the above-described embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0121] 1 Fixing device 2 heating units 3 Pressure roller 4 frames 4A aperture 10 Heater 50 Shutter 60 Pressure Arm 80 Cam 91 Shutter arm 92 Arm Cam NM nip pressure change mechanism NP nip section SF Shaft X1 1st axis X2 2nd axis

Claims

1. A first rotating body; a second rotating body that forms a nip portion between itself and the first rotating body; a frame having an opening through which a sheet conveyed toward the nip portion passes, the frame supporting the first rotating body and the second rotating body; a shutter that is rotatable about a first axis between a closed position that closes the opening and an open position that opens the opening; A nip pressure change mechanism that changes the nip pressure in the nip portion, a pressure arm that presses the first rotating body toward the second rotating body; a nip pressure change mechanism having a cam that presses the pressure arm and is rotatable about a second shaft; a shutter arm connected to the shutter, the shutter arm rotating about the second axis independently of the cam to rotate the shutter between the closed position and the open position; an arm cam that rotates around the second axis to push the shutter arm at a position offset from the second axis, thereby rotating the shutter arm around the second axis.

2. a shaft supporting the cam and rotatable about the second axis; the arm cam has a cylindrical portion into which the shaft is inserted, 2. The fixing device according to claim 1, wherein the shutter arm has a hole into which the cylindrical portion is inserted.

3. the shutter has a protrusion, 3. The fixing device according to claim 1, wherein the shutter arm has an elongated hole into which the protrusion is inserted.

4. The protrusion of the shutter is When the shutter is in the closed position, the shutter is located on the nip portion side with respect to a line connecting the first axis and the second axis, 4. The fixing device according to claim 3, wherein the shutter is located on the opposite side of the straight line from the nip portion when the shutter is in the open position.

5. a shaft supporting the cam and rotatable about the second axis; The frame is a first frame supporting the first rotating body and the second rotating body; a second frame attached to the first frame, the second frame holding the shaft between the first frame and the second frame; 5. The fixing device according to claim 1, wherein the shutter is supported by the second frame via a boss.

6. 6. The fixing device according to claim 5, wherein the boss is disposed upstream of the nip portion in the sheet conveying direction.

7. 7. The fixing device according to claim 1, wherein the second shaft is disposed downstream of the nip portion in the sheet transport direction.

8. The pressure arm is a first pressure arm disposed at one end side of the frame in the longitudinal direction; a second pressure arm disposed on the other end side of the frame in the longitudinal direction, 8. The fixing device according to claim 1, wherein the shutter arm is disposed on an opposite side of the first pressure arm from the second pressure arm in the longitudinal direction.

9. a heater having a substrate and a resistive heating element disposed on the substrate; 9. The fixing device according to claim 1, wherein the first rotating body is an endless belt that is heated by the heater and rotates around the heater.

10. a connector for supplying electricity to the heater; the heater further includes a power supply terminal, to which electricity is supplied from the connector, at at least one end of the substrate in the longitudinal direction; the second rotating body is a pressure roller that is rotatable about a third axis, The fixing device according to claim 9 , wherein the shutter arm is disposed on an opposite side of the connector from the third shaft.

11. a spring contactable with the shutter arm; 11. The fixing device according to claim 1, wherein the arm cam presses the shutter arm via the spring to position the shutter at the closed position.

12. 12. The fixing device according to claim 11, wherein the arm cam brings the shutter into the open position by contacting the shutter arm.

13. A main body housing; a unit detachable from the main body housing; The fixing device according to any one of claims 1 to 12; An image forming apparatus comprising: When the unit is attached to or detached from the main body housing, the arm cam rotates about the second shaft, The shutter arm is When the unit is attached to the main body housing, the shutter is rotated from the closed position to the open position; an image forming apparatus, wherein the shutter is rotated from the open position to the closed position when the unit is detached from the main body housing;

14. 14. The image forming apparatus according to claim 13, further comprising a connecting link connected to the arm cam, the connecting link contacting the unit when the unit is attached to the main body housing and being movable relative to the main body housing.

15. a lock for holding the shutter in the open or closed position; The lock has a lock arm that contacts the connecting link and a lock spring that urges the lock arm toward the connecting link, 15. The image forming apparatus according to claim 14, wherein the connecting link has a link protrusion that protrudes toward the lock side.

16. the unit has a unit shaft that abuts against the connecting link when attached to the main body housing, 16. The image forming apparatus according to claim 14, wherein the main body housing has a guide rail for guiding the unit shaft.

Images