Image forming apparatus

Abstract

To fix a heater of a fixing device to a certain position and reduce wear of a fixing member in the fixing device.SOLUTION: A fixing unit 5b has a plurality of first engagement parts 553 that are engaged with a plurality of first parts to be engaged 542 to restrict the movement of a heating unit 5a in a third direction intersecting a first direction and a second direction. A fixing unit 32 has a second engagement part 321 that is engaged with a second part to be engaged 544 to restrict the movement of the heating unit 5a in the first direction. The fixing unit 5b comprises a movable unit 56, a support 55, and a reciprocating mechanism 57. The support 55 movably supports the movable unit 56 along the first direction. The reciprocating mechanism 57 causes the movable unit 56 to reciprocate. The reciprocating mechanism causes the movable unit 56 to reciprocate once every time a plurality of sheets pass through between a first rotating body and a second rotating body.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electrophotographic image forming apparatus including a heating unit and a fixing unit.

Background Art

[0002] An electrophotographic image forming apparatus transfers a toner image from an image carrier to a sheet and fixes the toner image to the sheet by a fixing device. The fixing device includes a heater, a fixing member, and a pressure roller.

[0003] The fixing member and the pressure roller are each a rotating body. The heater heats the fixing member. The pressure roller biases the sheet against the fixing member.

[0004] The fixing device may be divided into a heating unit having the heater and a fixing unit having the fixing member and the pressure roller (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, portions of the fixing member that rub against both side ends of the sheet are more likely to wear than other portions of the fixing member.

[0007] Further, in order for the fixing member to be stably heated by the heater, it is desirable that the heater be fixed at a certain position. When an electromagnetic induction heating type heating device is employed as the heater, the influence of a change in the position of the heater on the heating performance is particularly large.

[0008] The object of the present invention is to provide an image forming apparatus that can fix the heater of the fixing apparatus in a fixed position and reduce wear of the fixing member in the fixing apparatus. [Means for solving the problem]

[0009] An image forming apparatus according to one aspect of the present invention comprises a heating unit, a fixing unit, a unit biasing unit, and a fixing unit. The heating unit has a heater and is arranged in a first direction within the main body. The fixing unit has a first rotating body heated by the heater and a second rotating body that biases a sheet toward the first rotating body, and is arranged in a first direction alongside the heating unit within the main body. The fixing unit is fixed to the main body. The unit biasing unit biases the heating unit toward the fixing unit. The unit biasing unit maintains the position of the heating unit relative to the fixing unit in a second direction which is the arrangement direction of the heating unit and the fixing unit. The heating unit has a plurality of first engaging parts and a plurality of second engaging parts. The fixing unit has a plurality of first engaging parts that restrict the movement of the heating unit in a third direction intersecting the first and second directions by engaging with the plurality of first engaging parts. The fixing unit has a second engaging part that restricts the movement of the heating unit in the first direction by engaging with the second engaging part. Furthermore, the fixing unit comprises a movable unit, a support, and a reciprocating mechanism. The movable unit includes the first rotating body and the second rotating body. The support provides support for the movable unit so that it can move along the first direction. The reciprocating mechanism causes the movable unit to reciprocate along the first direction. The reciprocating mechanism causes the movable unit to reciprocate once each time a plurality of the sheets pass between the first rotating body and the second rotating body. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an image forming apparatus that can fix the heater of the fixing apparatus in a fixed position and reduce wear of the fixing member in the fixing apparatus. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a configuration diagram of an image forming apparatus according to an embodiment. [Figure 2] Figure 2 shows the configuration of the main part of the fixing device in the image forming apparatus according to the embodiment. [Figure 3] Figure 3 is a perspective view of the main frame of the image forming apparatus according to this embodiment. [Figure 4] Figure 4 is a side view showing the configuration of the heating unit and its surrounding parts in an image forming apparatus according to an embodiment. [Figure 5] Figure 5 is a plan view showing the configuration of the heating unit and its surrounding area in an image forming apparatus according to an embodiment. [Figure 6] Figure 6 shows the configuration of the reciprocating mechanism in the image forming apparatus according to this embodiment. [Figure 7] Figure 7 is a perspective view of the peripheral portion of the fixing unit and cover member in the image forming apparatus according to the embodiment. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments are merely examples of the present invention and do not limit the technical scope of the present invention.

[0013] [Configuration of the image forming apparatus 10] The image forming apparatus 10 according to this embodiment performs printing using an electrophotographic method. The printing process is the process of forming an image on a sheet 900.

[0014] As shown in FIG. 1, the image forming apparatus 10 includes a sheet storage unit 2, a sheet conveyance device 3, and a printing device 4. The sheet conveyance device 3 and the printing device 4 are housed in the main body 1 which is a housing.

[0015] The sheet storage unit 2 can store a plurality of sheets 900. The sheet conveyance device 3 includes a sheet feeding device 30 and a plurality of sets of conveyance roller pairs 31.

[0016] The sheet feeding device 30 feeds the sheets 900 in the sheet storage unit 2 one by one into the conveyance path 300. The conveyance path 300 is the passage of the sheet 900.

[0017] The plurality of sets of conveyance roller pairs 31 convey the sheet 900 along the conveyance path 300. The plurality of sets of conveyance roller pairs 31 includes a discharge roller pair 31a (see FIG. 1). The discharge roller pair 31a discharges the sheet 900 with an image formed thereon from the conveyance path 300 onto the discharge tray 1a.

[0018] The printing device 4 performs the printing process on the sheet 900 conveyed along the conveyance path 300. The image formed on the sheet 900 is a toner image.

[0019] The printing device 4 includes an optical scanning unit 40, one or more image forming units 4x, a transfer device 45, and a fixing device 5. The image forming unit 4x includes a photoreceptor 41, a charging device 42, a developing device 43, and a drum cleaning device 44.

[0020] The charging device 42 charges the surface of the photoreceptor 41. The optical scanning unit 40 scans the surface of the charged photoreceptor 41 with a beam of light. Thereby, the optical scanning unit 40 forms an electrostatic latent image on the surface of the photoreceptor 41.

[0021] The developing device 43 develops the electrostatic latent image into a toner image by supplying toner to the surface of the photoreceptor 41. The transfer device 45 transfers the toner image formed on the surface of the photoreceptor 41 to the sheet 900.

[0022] The transfer device 45 transfers the electrostatic latent image to the sheet 900 at the transfer position P1 in the transport path 300.

[0023] In this embodiment, the printing apparatus 4 is a tandem-type color printing apparatus equipped with multiple image forming units 4x. The transfer apparatus 45 includes an intermediate transfer belt 450, multiple primary transfer devices 451, a secondary transfer device 452, and a belt cleaning device 453.

[0024] In the example shown in Figure 1, the printing device 4 comprises four image forming units 4x corresponding to four toner colors: yellow, magenta, cyan, and black. The transfer device 45 comprises four primary transfer units 451 corresponding to the four image forming units 4x.

[0025] The intermediate transfer belt 450 is rotatably supported by a plurality of support rollers 454. One of the support rollers 454 is rotated by a belt drive device (not shown), thereby causing the intermediate transfer belt 450 to rotate.

[0026] Each primary transfer device 451 transfers the toner image formed on the surface of the photoreceptor 41 in each image forming unit 4x to the surface of the intermediate transfer belt 450. As a result, a composite toner image, formed by combining the four toner images, is created on the surface of the intermediate transfer belt 450.

[0027] The intermediate transfer belt 450 rotates while carrying the synthesized toner image. The secondary transfer device 452 transfers the synthesized toner image formed on the surface of the intermediate transfer belt 450 to the sheet 900 at the transfer position P1.

[0028] The drum cleaning device 44 removes primary waste toner from the surface of the photoreceptor 41. The primary waste toner is the toner remaining on the surface of the photoreceptor 41 that has passed through the primary transfer device 451.

[0029] The belt cleaning device 453 removes secondary waste toner from the surface of the intermediate transfer belt 450. The secondary waste toner is the toner remaining on the surface of the intermediate transfer belt 450 that has passed through the secondary transfer device 452.

[0030] The fixing device 5 heats and pressurizes the synthesized toner image on the sheet 900 at the fixing position P2 in the transport path 300. This causes the fixing device 5 to fix the synthesized toner image to the sheet 900. The fixing position P2 is located downstream of the transfer position P1 in the sheet transport direction.

[0031] As shown in Figure 2, the fixing device 5 includes a heater 51, a fixing belt 52, a fixing roller 520, a pressure roller 53, and a sheet separating member 5200.

[0032] The fixing belt 52 is a flexible cylindrical member that encloses the fixing roller 520. The fixing belt 52 is heated by the heater 51.

[0033] The fixing roller 520 is a cylindrical member that supports the fixing belt 52 from the inside. The fixing roller 520 has a cylindrical core portion 521 and an elastic portion 522 formed on the outer circumference of the core portion 521.

[0034] The fixing roller 520 is rotatably supported. The fixing belt 52 is rotatable together with the fixing roller 520.

[0035] The fixing belt 52 has a conductive base material, an elastic layer formed on the outer periphery of the base material, and a release layer formed on the outer periphery of the elastic layer.

[0036] The heater 51 is positioned opposite the outer circumferential surface of the fixing belt 52. In this embodiment, the heater 51 is an electromagnetic induction heating device. The heater 51 primarily heats the base material of the fixing belt 52 by electromagnetic induction.

[0037] The pressure roller 53 is rotatably supported. Like the fixing roller 520, the pressure roller 53 also has a cylindrical core portion 531 and an elastic portion 532 formed on the outer circumference of the core portion 531.

[0038] The pressure roller 53 is driven and rotated by a drive device (not shown). The fixing belt 52 and fixing roller 520 rotate in conjunction with the pressure roller 53.

[0039] The fixing belt 52 heats the toner image formed on the sheet 900. The pressure roller 53 applies pressure to the toner image toward the sheet 900.

[0040] The fixing belt 52 is an example of a first rotating body heated by the heater 51. The pressure roller 53 is an example of a second rotating body that biases the sheet 900 onto the fixing belt 52.

[0041] The sheet separation member 5200 separates the sheet 900 from the fixing belt 52 when the sheet 900 adheres to the fixing belt 52.

[0042] The discharge roller pair 31a can discharge the sheet 900 that has passed between the fixing belt 52 and the pressure roller 53 to the discharge tray 1a (see Figure 1).

[0043] In this embodiment, the fixing device 5 is divided into a heating unit 5a and a fixing unit 5b (see Figures 4 and 5). The heating unit 5a includes a heater 51. The fixing unit 5b includes a fixing belt 52 and a pressure roller 53. The fixing unit 5b is located next to the heating unit 5a.

[0044] Furthermore, the discharge unit 32 is positioned above the fixing unit 5b (see Figure 1). The discharge unit 32 includes a pair of discharge rollers 31a and a sheet guide member. The sheet guide member guides the sheet 900 as it is transported from the fixing device 5 to the pair of discharge rollers 31a.

[0045] The discharge unit 32 is fixed to the main frame 1x. The discharge unit 32 is an example of a fixed unit.

[0046] The heating unit 5a is positioned within the main body 1 along the first direction D1. The fixing unit 5b is also positioned within the main body 1 along the first direction D1.

[0047] In this embodiment, the first direction D1 is the depth direction of the image forming apparatus 10. When the fixing unit 5b is mounted on the main body 1, the first direction D1 is the direction along the centerline of rotation of the fixing belt 52 and the pressure roller 53.

[0048] The heating unit 5a and the fixing unit 5b are arranged side by side in the second direction D2. That is, the second direction D2 is the direction in which the heating unit 5a and the fixing unit 5b are arranged. The second direction D2 intersects the first direction D1.

[0049] By moving the heating unit 5a to a position away from the fixing unit 5b, the fixing unit 5b can be pulled out from inside the main body 1.

[0050] The exterior member 100 has an opening 101 and a cover member 102 (see Figure 7). The opening 101 is a portion in which an opening is formed that opens one end of the fixing unit 5b in the first direction D1.

[0051] The cover member 102 is supported by a pivot shaft 102x. This allows the cover member 102 to rotate around the pivot shaft 102x. The cover member 102 is rotatable between a closed position that closes the opening 101 and an open position that opens the opening 101.

[0052] When the fixing unit 5b is pulled out from inside the main body 1, the fixing unit 5b can pass through the opening 101 of the exterior member 100.

[0053] By the way, the parts of the fixing belt 52 that rub against both ends of the sheet 900 are more prone to wear than other parts of the fixing belt 52.

[0054] Furthermore, in order for the fixing belt 52 to be stably heated by the heater 51, it is desirable that the heater 51 be fixed in a certain position. When an electromagnetic induction heating device is used as the heater 51, changes in the position of the heater 51 have a particularly large impact on the heating performance.

[0055] The image forming apparatus 10 includes a configuration for fixing the heater 51 in a fixed position and reducing wear on the fixing belt 52. The configuration will be described below.

[0056] [Configuration of heating unit 5a and fixing unit 5b] The heating unit 5a includes a heater 51 and a first support 54. The first support 54 is a member that supports the heater 51.

[0057] The fixing unit 5b includes a second support 55 and a movable unit 56 (see Figures 4 and 6). The movable unit 56 includes a movable support 560, a fixing belt 52, a fixing roller 520, and a pressure roller 53.

[0058] The movable support 560 rotatably supports the fixing roller 520 and the pressure roller 53. The fixing roller 520 supports the fixing belt 52. That is, the fixing belt 52 is supported by the movable support 560 via the fixing roller 520.

[0059] The second support 55 supports the movable unit 56 so that it can move along the first direction D1. For example, the second support 55 has a plurality of support shafts 556 arranged along the first direction D1 (see Figures 4 and 6). The plurality of support shafts 556 support the movable support 560 so that it can slide along the first direction D1.

[0060] The fixing unit 5b further includes a reciprocating mechanism 57 that moves the movable unit 56 back and forth along the first direction D1 (see Figure 6). The configuration of the reciprocating mechanism 57 will be described later.

[0061] [Mechanism for positioning the heating unit 5a and the fixing unit 5b] The image forming apparatus 10 comprises a main frame 1x and an exterior member 100 (see Figures 3 and 7). The main frame 1x forms the skeleton of the main body 1. The exterior member 100 forms the exterior of the main body 1.

[0062] The main frame 1x is composed of a combination of multiple metal pipes (see Figure 3). The heating unit 5a and the fixing unit 5b are supported by the main frame 1x.

[0063] The exterior component 100 is attached to the main frame 1x (see Figure 9). The exterior component 100 forms the exterior of the image forming apparatus 10.

[0064] The multiple metal pipes that make up the main frame 1x have two support columns 11 and two beam columns 12 (see Figure 3).

[0065] The two support columns 11 are formed extending in the vertical direction D3 and are spaced apart in the first direction D1 (see Figure 3). The vertical direction D3 is the up and down direction.

[0066] The two support columns 11 are formed extending in the vertical direction D3 next to the anchoring unit 5b (see Figures 4 and 9).

[0067] The two support columns 11 include a first support column 11a located on the front side of the image forming apparatus 10 and a second support column 11b located on the rear side of the image forming apparatus 10 (see Figure 3).

[0068] The two beam sections 12 are formed extending laterally below the heating unit 5a and the fixing unit 5b, and are spaced apart in the first direction D1 (see Figures 3 and 4). The lateral direction is the width direction of the image forming apparatus 10.

[0069] Each of the two beam sections 12 is connected to two support sections 11 (see Figure 3). For example, each of the two beam sections 12 is connected to two support sections 11 by welding.

[0070] The two beam sections 12 include a first beam section 12a located on the front side of the image forming apparatus 10 and a second beam section 12b located on the rear side of the image forming apparatus 10 (see Figure 3).

[0071] The fixing unit 5b is positioned between the heating unit 5a and the two support columns 11 (see Figure 3).

[0072] The first support 54 of the heating unit 5a is supported on the two beams 12, with the support spanning across them. Similarly, the second support 55 of the fixing unit 5b is supported on the two beams 12, with the support spanning across them.

[0073] In other words, neither the heating unit 5a nor the fixing unit 5b is fixed to the main frame 1x by screws or other fasteners.

[0074] The heating unit 5a and the fixing unit 5b are each mounted on two beam sections 12 with their longitudinal directions aligned with the first direction D1 (see Figures 7 and 8).

[0075] The image forming apparatus 10 further comprises an operating member 6, a first spring 60, and an interlocking mechanism 7 (see Figures 4, 5, 7, and 8). The operating member 6 and the first spring 60 are located within the main body 1.

[0076] The first support 54 of the heating unit 5a has a plurality of first engagement portions 542 and second engagement portions 544 (see Figures 4 and 5). Furthermore, the first support 54 has a plurality of unit contact portions 543 (see Figure 4).

[0077] The second support 55 of the fixing unit 5b has a plurality of first engaging portions 553 corresponding to a plurality of first engaged portions 542 (see Figure 4). Furthermore, the second support 55 has a plurality of contact portions 554 corresponding to a plurality of unit contact portions 543 (see Figure 4).

[0078] In this embodiment, the first support 54 has a pair of first engaging portions 542 formed at two locations spaced apart in the first direction D1. The second support 55 has a pair of first engaging portions 553 formed at two locations corresponding to the pair of first engaging portions 542.

[0079] In this embodiment, each of the first engaged portions 542 is concave, opening in the second direction D2 (see Figure 4). Each of the first engaged portions 553 is convex, fitting into each of the first engaged portions 542.

[0080] Each of the first engaged portions 542 may be convex. In this case, each of the first engaged portions 553 is concave, opening in the second direction D2.

[0081] Furthermore, the discharge unit 32 has a second engaging portion 321 that corresponds to the second engaged portion 544 (see Figures 4 and 5). The discharge unit 32 is an example of a fixed unit fixed to the main body 1.

[0082] The pair of first engaging portions 553 restrict the movement of the heating unit 5a in the vertical direction D3 by engaging with the pair of first engaged portions 542. The vertical direction D3 is an example of a third direction that intersects the first direction D1 and the second direction D2.

[0083] The second engaging portion 321 of the discharge unit 32 engages with the second engaged portion 544, thereby restricting the movement of the heating unit 5a in the first direction D1.

[0084] In this embodiment, the second engaging portion 321 is convex along the second direction D2 (see Figures 4 and 5). The second engaged portion 544 is a pair of upright portions facing each other in the first direction D1 (see Figure 5). The second engaging portion 321 is inserted between the pair of upright portions in the second engaged portion 544. As a result, the second engaging portion 321 engages with the second engaged portion 544.

[0085] The first spring 60 is an example of an elastic member. The first spring 60 is located within the main body 1 on the side opposite to the fixing unit 5b relative to the heating unit 5a (see Figure 4). For example, the first spring 60 is supported by a projection 546 of the first support 54.

[0086] The working member 6 has a first spring 60 sandwiched between it and the heating unit 5a (see Figure 4). The first spring 60 elastically biases the first support 54 toward the second support 55 (see Figure 4). As a result, the first spring 60 maintains the position of the heating unit 5a relative to the fixing unit 5b in the second direction D2. The first spring 60 is an example of a unit biasing member.

[0087] The biasing force F1 of the first spring 60 on the first support 54 is greater than the static frictional force of the heating unit 5a and the fixing unit 5b on the two beam sections 12 (see Figure 4).

[0088] The first support 54 has one or more ribs 541 that are in contact with the upper surfaces of the two beam sections 12. Similarly, the second support 55 has multiple ribs 551 that are in contact with the upper surfaces of the two beam sections 12. The ribs 541 of the first support 54 and the ribs 551 of the second support 55 are provided to reduce the static friction force.

[0089] The first spring 60 biases the first support 54, thereby bringing the first support 54 into contact with the second support 55.

[0090] In this embodiment, the pair of first engaged portions 542 contact the pair of first engaged portions 553 due to the biasing force of the first spring 60. Specifically, the inner surfaces of the concave portions of each of the pair of first engaged portions 542 contact each of the pair of first engaged portions 553 (see Figure 4).

[0091] Furthermore, the pair of unit contact portions 543 contact the pair of contacted portions 554 due to the biasing force of the first spring 60. In this embodiment, each of the pair of unit contact portions 543 is a curved surface. Each of the pair of contacted portions 554 is convex along the first direction D1.

[0092] The pair of unit contact portions 543 are formed at two locations separated by a vertical D3 from the pair of first engaged portions 542 (see Figure 4). That is, the pair of first engaged portions 542 and the pair of unit contact portions 543 contact the fixing unit 5b at four locations. As a result, the posture of the heating unit 5a is stabilized.

[0093] Furthermore, the first spring 60 biases the first support 54, thereby bringing the second support 55 into contact with the two support columns 11. In other words, the first spring 60 biases the second support 55 via the first support 54.

[0094] Furthermore, the second support 55 has a plurality of column contact portions 552 that protrude toward the two support columns 11 (see Figures 4 and 5). The plurality of column contact portions 552 abut against the sides of the two support columns 11.

[0095] When the second engaging portion 321 engages with the second engaged portion 544, the heating unit 5a is positioned at the desired position in the first direction D1.

[0096] Furthermore, the heating unit 5a and the fixing unit 5b are positioned at the desired location in the second direction D2 by being sandwiched between the first spring 60 and the two support columns 11.

[0097] Furthermore, the first spring 60 biases the heating unit 5a toward the fixing unit 5b by elastic force. This prevents the mechanical play of the interlocking mechanism 7, which will be described later, from adversely affecting the positioning of the heating unit 5a.

[0098] Furthermore, the heating unit 5a is positioned at the desired location in the vertical direction D3 by the engagement of the pair of first engaging portions 553 with the pair of first engaged portions 542.

[0099] The interlocking mechanism 7 moves the operating member 6 along the second direction D2 in response to an operation on a predetermined operating part. For example, the cover member 102 also serves as the operating part.

[0100] The interlocking mechanism 7 moves the operating member 6 from one of the first position and the second position to the other in conjunction with the movement of the operating unit.

[0101] When the working member 6 is in the first position, the heating unit 5a is positioned in a reference position in the second direction D2 by the biasing force of the first spring 60. The second position is further from the fixing unit 5b than the first position.

[0102] The interlocking mechanism 7 moves the operating member 6 from the first position to the second position in response to a first operation on the operating unit. For example, the first operation is to move the cover member 102 from the closed position to the open position.

[0103] The first support 54 of the heating unit 5a has an engaged portion 545 that engages with a part of the working member 6 (see Figure 4).

[0104] The operating member 6 has an engaging portion 62 that can engage with the engaged portion 545 of the first support 54 (see Figure 4). As the operating member 6 moves from the first position to the second position, the engaging portion 62 engages with the engaged portion 545.

[0105] When the working member 6 moves from the first position to the second position, the heating unit 5a receives a force from the working member 6 through the engaging portion 62 and moves from the reference position to the retracted position. The retracted position is a position further away from the fixing unit 5b than the reference position.

[0106] When the heating unit 5a is in the retracted position, the fixing unit 5b can be pulled out from inside the main body 1 in the removal direction D11 (see Figure 5). The fixing unit 5b is pulled out from inside the main body 1 without coming into contact with the heating unit 5a. The removal direction D11 is the direction along the first direction D1.

[0107] Furthermore, the interlocking mechanism 7 moves the operating member 6 from the second position to the first position in response to a second operation on the operating unit. For example, the second operation is to move the cover member 102 from the open position to the closed position.

[0108] When the working member 6 moves from the second position to the first position, the heating unit 5a receives the biasing force of the first spring 60 and moves from the retracted position to the reference position.

[0109] As the heating unit 5a moves from the retracted position to the reference position, the second engaging portion 321 engages with the second engaged portion 544. Furthermore, when the heating unit 5a reaches the reference position, the pair of first engaging portions 553 engage with the pair of first engaged portions 542.

[0110] Furthermore, when the heating unit 5a reaches the reference position, the pair of unit contact portions 543 come into contact with the pair of contacted portions 554. This positions the heating unit 5a at the reference position.

[0111] Furthermore, the image forming apparatus 10 is further equipped with a cover biasing mechanism 8 attached to the inner surface of the cover member 102 (see Figure 5). In addition, the second support 55 of the fixing unit 5b has a beam contact portion 555 that protrudes downward from the bottom surface (see Figures 4 and 7).

[0112] The cover biasing mechanism 8 comprises a second spring 80, a spring case 81, and a cap portion 82 (see Figure 7).

[0113] The spring case 81 houses the second spring 80. The cap portion 82 is movably attached to the spring case 81. The second spring 80 is an example of an elastic fixing unit biasing member.

[0114] The second spring 80 is sandwiched between the cover member 102 and the second support 55 of the fixing unit 5b when the cover member 102 is in the closed position. In this embodiment, the second spring 80 and the cap portion 82 are sandwiched between the cover member 102 and the second support 55.

[0115] The second spring 80 is sandwiched between the cover member 102 and the second support member 55, thereby elastically biasing the second support member 55 in the mounting direction D12 (see Figure 5). The mounting direction D12 is the opposite direction to the removal direction D11.

[0116] Furthermore, when the cover member 102 is in the closed position, the force received by the second support 55 from the second spring 80 causes the beam contact portion 555 to contact one side of the two beam portions 12. In this embodiment, the beam contact portion 555 contacts the side of the second beam portion 12b.

[0117] The anchoring unit 5b is positioned in the first direction D1 by the action of the second spring 80 and the beam contact portion 555.

[0118] The cover biasing mechanism 8 may also be attached to the second support 55 of the fixing unit 5b.

[0119] As mentioned above, the reciprocating mechanism 57 moves the movable unit 56 back and forth along the first direction D1. The image forming apparatus 10 also includes a drive mechanism 9 located within the main body 1 (see Figure 6). The drive mechanism 9 is fixed to the main body frame 1x.

[0120] The drive mechanism 9 comprises a reduction gear mechanism 91 including an output gear 911 and an output engagement part 92. The output engagement part 92 is formed integrally with the output gear 911. The output engagement part 92 rotates at the same speed as the output gear 911.

[0121] The reduction gear mechanism 91 transmits the rotational force of a motor (not shown) to the output gear 911 while reducing its speed. The output engagement part 92 is a rotating body that transmits rotational force to the fixing unit 5b. The output engagement part 92 is an example of a driving rotating body.

[0122] The reciprocating mechanism 57 comprises an input engagement portion 571 and a cylindrical cam 572. The input engagement portion 571 engages with the output engagement portion 92. The input engagement portion 571 transmits the rotational force of the output engagement portion 92 to the cylindrical cam 572.

[0123] The movable unit 56 of the fixing unit 5b has a cam engaging portion 561 that engages with the cylindrical cam 572. As the cylindrical cam 572 rotates, the cam engaging portion 561 reciprocates along the first direction D1.

[0124] As the cam engagement portion 561 reciprocates along the first direction D1, the entire movable unit 56 reciprocates along the first direction D1. In other words, the reciprocating mechanism 57 converts the rotational motion of the output engagement portion 92 into the reciprocating motion of the movable unit 56.

[0125] The reciprocating mechanism 57 moves the movable unit 56 back and forth once each time multiple sheets 900 pass between the fixing belt 52 and the pressure roller 53.

[0126] For example, the range of movement of the movable unit 56 in the first direction D1 is approximately 3 to 10 millimeters.

[0127] For example, the reciprocating mechanism 57 moves the movable unit 56 by approximately 0.02 to 0.08 millimeters each time a sheet 900 passes through the fixing device 5.

[0128] By employing the image forming apparatus 10, the heating unit 5a, including the heater 51, is fixed in a fixed position. Furthermore, the reciprocating mechanism 57 causes the position where the fixing belt 52 rubs against both ends of the sheet 900 to change as needed. As a result, wear on the fixing belt 52 is reduced. [Explanation of Symbols]

[0129] 1: Main unit 1a: Output tray 1x: Main frame 4: Printing device 5: Fixing device 5a: Heating unit 5b: Fixing unit 6: Operating Member 7: Interlocking mechanism 8: Cover biasing mechanism 9: Drive mechanism 10: Image forming apparatus 11: Support section 11a: 1st pillar part 11b:Second pillar part 12:Beam part 12a: 1st beam part 12b: 2nd beam part 30: Sheet feeding device 31: Conveyor rollers 31a: Discharge roller pair 51: Heater 52: Fixing belt 53: Pressure roller 54: 1st support 55:Second support 56: Movable Unit 57: Reciprocating mechanism 60: First spring (unit biasing member) 62: Engaging part 80: Second spring 81: Spring case 82: Cap part 91: Reduction gear mechanism 92: Output engagement part 321: Second engaging part 520: Fixing roller 542: First engaged part 543: Unit contact part 544: Second engaged part 545: Engaged part 552: Column contact part 553: First engaging part 554: Abutted part 555: Beam contact part 556: Support shaft 560: Movable support 561: Cam engagement part 571: Input engagement part 572: Cylindrical cam 911: Output gear

Claims

1. A heating unit having a heater and arranged along a first direction within the main body, A fixing unit having a first rotating body heated by the heater and a second rotating body that biases the sheet to the first rotating body, and positioned within the main body next to the heating unit along the first direction, A unit biasing unit that biases the heating unit toward the fixing unit, The main body comprises a fixing unit, The unit biasing unit maintains the position of the heating unit relative to the fixing unit in a second direction which is the arrangement direction of the heating unit and the fixing unit. The heating unit has a plurality of first engaged parts and second engaged parts, The fixing unit has a plurality of first engaging portions that restrict the movement of the heating unit in a third direction intersecting the first and second directions by engaging with a plurality of first engaging portions. The fixing unit is a discharge unit having a pair of discharge rollers capable of discharging the sheet that has passed between the first rotating body and the second rotating body to a discharge tray. The fixing unit has a second engaging portion that restricts the movement of the heating unit in the first direction by engaging with the second engaged portion. Furthermore, the fixing unit, A movable unit including the first rotating body and the second rotating body, A support that enables the movable unit to move along the first direction, The movable unit is further provided with a reciprocating mechanism that moves the movable unit back and forth along the first direction, The reciprocating mechanism of the image forming apparatus causes the movable unit to move back and forth once each time a plurality of sheets pass between the first rotating body and the second rotating body.

2. The main body is further equipped with a drive mechanism having a drive rotating body that transmits rotational force to the fixing unit, The image forming apparatus according to claim 1, wherein the reciprocating mechanism converts the rotational motion of the drive rotating body into the reciprocating motion of the movable unit.

3. The heating unit has a pair of first engaging portions formed at two locations spaced apart in the first direction, The fixing unit has a pair of first engaging portions formed at two locations corresponding to the pair of first engaging portions, The heating unit has a pair of contact portions formed at two locations spaced apart in the third direction relative to the pair of first engaged portions, The pair of first engaged portions abut against each other due to the biasing force of the unit biasing portion, The image forming apparatus according to claim 1 or claim 2, wherein the pair of contact portions contact the fixing unit by the biasing force of the unit biasing portion.

4. The image forming apparatus according to any one of claims 1 to 3, wherein the heater is an electromagnetic induction heating device.

Images