Fixing device

Abstract

The present invention provides a configuration that facilitates jamming even when a separation plate 71 is included. [Solution] The discharge unit 60 has a separation plate 71 that can separate the sheet that has passed through the fixing nip from the fixing belt 31, and a separation guide 74 that supports the separation plate 71 so that it can move between a separation position and a retracted position. The separation plate moving mechanism 700 can move the separation plate 71 between the separation position and the retracted position. The pressure roller 22 can move between a contact position in contact with the fixing belt and a separation position away from it. When the pressure roller is in the contact position, the separation plate 71 is in the separation position, and in conjunction with the movement of the pressure roller 22 from the contact position to the retracted position, the separation plate 71 moves from the separation position to the retracted position.

Description

Technical Field

[0001] The present disclosure relates to a fixing device that heats a toner image carried on a recording material and fixes it to the recording material.

Background Art

[0002] Image forming apparatuses such as copiers, printers, facsimiles, and multifunction devices having a plurality of these functions have a fixing device that fixes a toner image carried on a recording material to the recording material. As a fixing device, a configuration in which a toner image on a recording material is conveyed while being heated in a nip portion formed by two rotating bodies has been conventionally known (Patent Document 1).

[0003] Patent Document 1 describes a configuration including a separating member that is disposed on the downstream side of the nip portion and separates the recording material that has passed through the nip portion from the rotating body. Since the separating member is required to be positioned with high precision with respect to the rotating body, Patent Document 1 has a configuration in which a part of the rotating body abuts on an end portion of the separating member to ensure a gap between the separating member and the rotating body.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, a nip section is formed by sandwiching the belt between a pressure roller and a pressure pad. The pressure pad is supported by a rigid stay so that it can withstand the pressure from the pressure roller. The stay has a shape in which the center protrudes slightly compared to the ends in the axial direction of the pressure roller, and is configured to withstand the pressure from the pressure roller. As a result, the belt's trajectory changes when the pressure roller is in contact with the belt and when it is separated from the belt. Furthermore, even when the pressure roller is separated, the belt rotates if heating continues at the heating roller. Therefore, there is a problem that the rotating belt and the separating member come into contact at the separated position, causing the belt to break.

[0006] To remove jammed recording material in the nip section, one might consider moving a unit including a separating member located downstream of the nip section away from the rotating body to create space for removing the jammed recording material (jamming). However, the separating member protrudes toward the rotating body downstream of the nip section, and is positioned so that a predetermined gap exists between the rotating body and the separating member. Therefore, in a configuration with a separating member, even if the unit is moved away from the rotating body to perform jamming, the protruding separating member makes it difficult to secure space for jamming, resulting in difficulties in performing jamming. [Means for solving the problem]

[0007] This disclosure provides a configuration having a separating member such that the belt and the separating member do not come into contact even when the belts are separated.

[0008] One aspect of the present disclosure is a fixing device for heating and fixing a toner image supported on a recording material, comprising: a first rotating body; a second rotating body that contacts the first rotating body and forms a nip portion between itself and the first rotating body for clamping and transporting the recording material; a separating member positioned downstream of the nip portion with respect to the transport direction of the recording material and capable of separating the recording material that has passed through the nip portion from the first rotating body; a separating member support portion that supports the separating member so as to be movable between a first position and a second position; a first moving mechanism that allows the separating member to move between a first position and a second position; and a second rotating body that is movable between a contact position in contact with the first rotating body and a separated position separated from the first rotating body. The fixing device comprises a moving mechanism, wherein the first position is a position in which, when the second rotating body is in the contact position, the tip of the separating member faces the first rotating body with a predetermined gap between them, and the separating member can separate the recording material that has passed through the nip portion from the first rotating body; the second position is a position in which, when the second rotating body is in the separation position, the tip of the separating member is further away from the first rotating body than from the first position; and the fixing device is characterized in that, in conjunction with the movement of the second rotating body from the contact position to the separation position by the second moving mechanism, the separating member moves from the first position to the second position by the first moving mechanism. [Effects of the Invention]

[0009] According to this disclosure, in a configuration having a separating member, it is possible to prevent contact between the belt and the separating member even when the belts are separated. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic cross-sectional view of the image forming apparatus according to the embodiment. [Figure 2] A control block diagram of an image forming apparatus according to an embodiment. [Figure 3] A schematic cross-sectional view of the fixing device according to the embodiment. [Figure 4] A perspective view of the discharge unit according to the embodiment, seen from above. [Figure 5]A perspective view of the discharge unit according to the embodiment, seen from the side. [Figure 6] A schematic cross-sectional view showing a part of the fixing device is provided to illustrate the positioning configuration of the separating member according to the embodiment. [Figure 7] A schematic cross-sectional view of the fixing device showing the state in which the separating member according to the embodiment is positioned at the separation position. [Figure 8] A schematic cross-sectional view of the fixing device showing the state in which the separation member according to the embodiment is in the retracted position. [Figure 9] A schematic cross-sectional view of the fixing device showing the discharge unit of the comparative example in the open position. [Figure 10] A schematic cross-sectional view of the fixing device showing the discharge unit according to the embodiment in the open position. [Modes for carrying out the invention]

[0011] Embodiments will be described using Figures 1 to 10. First, the schematic configuration of the image forming apparatus of this embodiment will be described using Figure 1.

[0012] [Image forming apparatus] In this embodiment, a tandem-type full-color printer is described as an example of an image forming apparatus 1. However, the image forming apparatus is not limited to a tandem type, and may be mounted on an image forming apparatus of another type. Furthermore, it is not limited to full color, and may be monochrome or monocolor. Moreover, it can be implemented in various applications such as image forming apparatuses, printers, various printing machines, copiers, fax machines, and multifunction devices.

[0013] As shown in FIG. 1, the image forming apparatus 1 includes an apparatus main body 10, a sheet feeding unit (not shown), an image forming unit 40, and a control unit 90. The image forming apparatus 1 can form a four-color full-color image on a recording material according to an image signal from a host device such as a document reading apparatus (not shown), a personal computer, or an external device such as a digital camera or a smartphone. Note that the sheet S as the recording material is one on which a toner image is to be formed. Specific examples thereof include plain paper, a synthetic resin sheet that is a substitute for plain paper, thick paper, an overhead projector sheet, and the like.

[0014] [Image forming unit] The image forming unit 40 can form an image as an unfixed toner image on the sheet S fed from the sheet feeding unit based on image information. The image forming unit 40 includes image forming units 50y, 50m, 50c, 50k, toner bottles 41y, 41m, 41c, 41k, exposure devices 42y, 42m, 42c, 42k, an intermediate transfer unit 44, a secondary transfer unit 45, and a fixing device 20. Note that the image forming apparatus 1 of the present embodiment is compatible with full color, and the image forming units 50y, 50m, 50c, 50k are provided separately with the same configuration for each of the four colors of yellow (y), magenta (m), cyan (c), and black (k). For this reason, in FIG. 1, an identifier of the color is attached after the same reference numeral for each of the four-color configurations, but in the specification, there may be cases where only the reference numeral is used for description without attaching the identifier of the color.

[0015] The image forming unit 50 includes a photosensitive drum (photoconductor) 51 which is an example of an image carrier that carries and rotates a toner image, a charging roller (charging member) 52, a developing device (developer) 53, and a cleaning blade (not shown). The image forming unit 50 is unitized integrally as a process cartridge and is configured to be detachable from the apparatus main body 10, and forms a toner image on an intermediate transfer belt 44b described later.

[0016] The photosensitive drum 51 is rotatable and carries an electrostatic latent image used for image formation. In this embodiment, the photosensitive drum 51 is a negatively charged organic photoreceptor (OPC) with an outer diameter of 30 mm, and is rotationally driven in the direction of the arrow at a predetermined process speed (peripheral speed) by a motor (not shown). The charging rollers 52y, 52m, 52c, and 52k use rubber rollers that contact the surface of each photosensitive drum 51 and rotate passively, and uniformly charge the surface of the photosensitive drum 51. The exposure device 42 is a laser scanner and emits laser light according to the color-separated image information output from the control unit 90.

[0017] The developing devices 53y, 53m, 53c, and 53k have developing sleeves 54y, 54m, 54c, and 54k, and develop the electrostatic latent image formed on the photosensitive drum 51 with toner when a developing bias is applied. The developing device 53 stores the developer supplied from the toner bottle 41 and develops the electrostatic latent image formed on the photosensitive drum 51. The developing sleeve 54 is made of a non-magnetic material such as aluminum or non-magnetic stainless steel, and is made of aluminum in this embodiment. Inside the developing sleeve 54, a roller-shaped magnet roller is fixedly installed in a non-rotating state with respect to the developing container. The developing sleeve 54 carries a developer containing non-magnetic toner and magnetic carrier and conveys it to the developing area facing the photosensitive drum 51.

[0018] The toner image developed on the surface of the photosensitive drum 51 is primarily transferred to the intermediate transfer unit 44. That is, the photosensitive drum 51 can carry the toner image by supplying toner to the intermediate transfer belt 44b. After the primary transfer, the toner remaining on the photosensitive drum 51 without being transferred to the intermediate transfer unit 44 is removed by a cleaning blade provided in contact with the photosensitive drum 51, in preparation for the next image forming process.

[0019] The intermediate transfer unit 44 includes tension rollers such as a drive roller 44a, a driven roller 44d, and a secondary transfer inner roller 45a, as well as a plurality of rollers such as primary transfer rollers 47y, 47m, 47c, and 47k, and an intermediate transfer belt 44b that is wrapped around these rollers and carries and moves the toner image. The driven roller 44d is a tension roller that controls the tension of the intermediate transfer belt 44b to be constant. The driven roller 44d is subjected to a force that pushes the intermediate transfer belt 44b toward the surface by the biasing force of a biasing spring (not shown). The primary transfer rollers 47y, 47m, 47c, and 47k are positioned opposite the photosensitive drums 51y, 51m, 51c, and 51k, respectively, and come into contact with the intermediate transfer belt 44b, primarily transferring the toner image from the photosensitive drum 51 to the intermediate transfer belt 44b. That is, the intermediate transfer belt 44b carries and moves (rotates) the toner image.

[0020] The intermediate transfer belt 44b contacts the photosensitive drum 51 to form a primary transfer section, and when a primary transfer bias is applied, the toner image formed on the photosensitive drum 51 is transferred in the primary transfer section. By applying a positive primary transfer bias to the intermediate transfer belt 44b using the primary transfer roller 47, the toner images with different negative polarities on the photosensitive drum 51 are sequentially transferred to the intermediate transfer belt 44b. The intermediate transfer belt 44b is equipped with a belt cleaning device 56 for cleaning any remaining toner on the intermediate transfer belt 44b.

[0021] The secondary transfer section 45 includes a secondary transfer inner roller 45a and a secondary transfer outer roller 45b. The secondary transfer outer roller 45b contacts the intermediate transfer belt 44b, and a secondary transfer bias with opposite polarity to the toner is applied at the nip portion with the intermediate transfer belt 44b. As a result, the secondary transfer outer roller 45b transfers the toner image carried on the intermediate transfer belt 44b to the sheet S supplied to the nip portion in one go.

[0022] The fixing device 20 includes a fixing belt 31 and a pressure roller 22. The sheet S is held between the fixing belt 31 and the pressure roller 22 and transported in the sheet transport direction. As a result, the toner image formed in the image forming unit 40 and transferred to the sheet S is heated and pressurized to fix it to the sheet S. The fixing device 20 is driven by a drive motor M1 (see Figure 2) housed within the fixing device 20. Details of the fixing device 20 will be described later.

[0023] [Control Unit] As shown in Figure 2, the control unit 90 is composed of a computer, and includes, for example, a CPU 91, a ROM 92 for storing programs that control each part, a RAM 93 for temporarily storing data, and an input / output circuit (I / F) 94 for inputting and outputting signals to and from the outside. The CPU 91 is a microprocessor that oversees the entire control of the image forming apparatus 1 and is the main component of the system controller. The CPU 91 is connected to the operation unit, sheet feeding unit, image forming unit 40, etc., via the input / output circuit 94, and exchanges signals with each part and controls its operation. The drive motor M1 of the fixing unit 20 is connected to the control unit 90, and the operation of the fixing unit 20 can be controlled. The ROM 92 stores image forming control sequences for forming an image on the sheet S, etc.

[0024] [Image Formation Process] Next, the image forming operation in the image forming apparatus 1 configured in this way will be described. When the image forming operation starts, the photosensitive drum 51 first rotates and its surface is charged by the charging roller 52. Then, the exposure apparatus 42 emits laser light onto the photosensitive drum 51 based on the image information, and an electrostatic latent image is formed on the surface of the photosensitive drum 51. Toner adheres to this electrostatic latent image, causing it to be developed and visualized as a toner image, which is then transferred to the intermediate transfer belt 44b.

[0025] Meanwhile, in parallel with the toner image formation process, a sheet S is supplied and, in time with the toner image on the intermediate transfer belt 44b, the sheet S is transported to the secondary transfer unit 45 via the transport path. Furthermore, the sheet S, on which the image has been transferred from the intermediate transfer belt 44b, is transported to the fixing device 20. In the fixing device 20, the unfixed toner image is heated and pressurized to fix it to the surface of the sheet S. The sheet S with the fixed toner image is then discharged from the main body 10 of the device.

[0026] [Fusing device] Next, the fixing device 20 will be described in detail using Figures 3 to 10. As shown in Figure 3, the fixing device 20 is a belt heating type heating device and is formed in a cartridge shape that can be attached to and detached from the device body 10 (see Figure 1). The fixing device 20 has a housing 21, a heating unit 30, a pressure roller 22, and a discharge unit 60. The heating unit 30 has a fixing belt 31 as a rotatable first rotating body, a pressure pad 32 as a nip part forming member, a heating roller 33, a steering roller 34, a stay 35 as a support member, and a unit side plate 36 that integrates these into a cartridge shape.

[0027] The fixing belt 31, as an endless belt, is a thin-walled cylindrical belt member that can contact the sheet S and heat the sheet S, and possesses thermal conductivity and heat resistance. In this embodiment, the fixing belt 31 has a three-layer structure with a base layer, an elastic layer on the outer circumference of the base layer, and a release layer on the outer circumference of the elastic layer. The base layer is 30 μm thick and made of polyimide resin (PI), the elastic layer is 300 μm thick and made of silicone rubber, and the release layer is 30 μm thick and made of PFA as a fluororesin. The fixing belt 31 is stretched by a pressure pad 32, a heating roller 33, and a steering roller 34.

[0028] The pressure pad 32 is positioned inside the fixing belt 31 and facing the pressure roller 22 via the fixing belt 31, forming a fixing nip portion N between the fixing belt 31 and the pressure roller 22 for gripping and conveying the sheet S. The pressure pad 32 is pressed against the pressure roller 22 with the fixing belt 31 in between. The fixing nip portion N is formed by the contact between the fixing belt 31 and the pressure roller 22. A lubricating sheet or lubricant is interposed between the pressure pad 32 and the fixing belt 31, so that the fixing belt 31 slides smoothly against the pressure pad 32.

[0029] The heating roller 33 is a 1 mm thick stainless steel pipe with a halogen heater (not shown) installed inside, capable of generating heat to a predetermined temperature. The fixing belt 31 is heated by the heating roller 33 and controlled to a predetermined target temperature according to the sheet type based on temperature detection by a thermistor. A gear (not shown) is fixed to one end of the heating roller 33 in the direction of its rotation axis (hereinafter also referred to as the width direction W), and is connected to a drive motor M1 (see Figure 2) via the gear to rotate. The fixing belt 31 rotates in accordance with the rotation of the heating roller 33. The width direction W is the direction of the rotation axis of the pressure roller 22, which is perpendicular to the conveying direction of the sheet S after it has passed through the fixing nip section N.

[0030] The steering roller 34 has a pivot point approximately vertically at one end in the direction of the rotation axis or near the center, and rotates relative to the fixing belt 31 to generate a tension difference in the main scanning direction (width direction W), thereby adjusting the position of the fixing belt 31 in the width direction W. The steering roller 34 is biased by a biasing spring (not shown) supported by the frame of the heating unit 30, and also functions as a tension roller that applies a predetermined tension to the fixing belt 31.

[0031] The pressure pad 32 is made of liquid crystal polymer (LCP) and is supported by a stay 35 which serves as a support member. The surface of the pressure pad 32 on the side facing the pressure roller 22 is a smooth curved surface that is convex toward the pressure roller 22, and has a crown shape with a radius of curvature of 700 μm in the width direction W. The stay 35 is made of stainless steel and is supported at both ends in the width direction W by the fixing frame 23 of the housing 21 of the fixing device 20.

[0032] The pressure roller 22, acting as the second rotating body, contacts the fixing belt 31 opposite it, forming a pressurized fixing nip portion N between itself and the fixing belt 31. The pressure roller 22 is a roller with an elastic layer on the outer circumference of its shaft and a release layer on the outer circumference of the elastic layer. Stainless steel is used for the shaft, the elastic layer is 3 mm thick and made of conductive silicone rubber, and the release layer is 30 μm thick and made of PFA as a fluororesin. The pressure roller 22 is supported by a pressure frame 25, and a gear is fixed to one end in the direction of the rotation axis. The gear is connected to a drive motor M1 (see Figure 2) and rotated.

[0033] In the fixing nip section N formed between the fixing belt 31 and the pressure roller 22, the sheet carrying the toner image is held and heated while being transported. In this way, the fixing device 20 fixes the toner image to the sheet while holding and transporting it. Therefore, it is necessary to balance the functions of applying heat and pressure with the function of transporting the sheet.

[0034] The fixing frame 23 is fixed to both sides of the housing 21 in the width direction W and is provided with a guide portion 24, a pressure frame 25, a pressure spring 26, and a pressure cam 27. The stay 35 of the heating unit 30 is inserted into the guide portion 24 and fixed to the guide portion 24 by a fixing member (not shown). After the stay 35 is fixed to the guide portion 24, the pressure frame 25 moves toward the heating unit 30 by a drive source (not shown) and the pressure cam 27, thereby pressurizing the pressure roller 22 against the pressure pad 32 via the fixing belt 31.

[0035] The guide section 24 has a support surface (support part) 24a, a positioning surface (positioning part) 24b, and a sliding surface 24c. In Figure 3, the heating unit 30 is in the mounting position. The support surface 24a is formed on the side opposite the pressure roller 22 along the sheet conveying direction and supports the reaction force that the fixing belt 31 receives from the pressure roller 22 on the inner circumference side of the fixing belt 31 when the heating unit 30 is in the mounting position. The positioning surface 24b is formed substantially vertically at the innermost part of the guide section 24 in the direction in which the heating unit 30 is inserted and positions the heating unit 30 by contacting it in the insertion direction when the heating unit 30 is in the mounting position. The sliding surface 24c is formed opposite the support surface 24a along the sheet conveying direction and guides the stay 35 by sliding it when inserting or removing the heating unit 30.

[0036] [Discharge Unit] Next, the discharge unit 60, which has a separation plate 71 (described later), will be explained. Downstream of the fixing nip section N in the sheet S conveying direction, there is a discharge unit 60 for discharging the sheet S that has passed through the fixing nip section N to the outside of the fixing device 20. The discharge unit 60 is equipped with a separation unit 70 that guides the sheet S that has been peeled off from the fixing belt 31 after passing through the fixing nip section N, a discharge lower guide 61, and a pair of conveying rollers 62 as a conveying section for discharging the peeled sheet S to the outside of the fixing device 20. The pair of conveying rollers 62 is positioned approximately 40 mm downstream from the fixing nip section N in the conveying direction.

[0037] The discharge unit 60 is rotatable around a pivot shaft 84 (see Figures 7-10) provided on the fixing frame 23, and when a sheet S becomes jammed at the outlet of the fixing nip section N, it can rotate in the direction of arrow A to expose the fixing nip section N and remove the jammed sheet S. In other words, as will be described in detail later, the discharge unit 60 is movable by an opening / closing mechanism 600 as a third movement mechanism, between a closed position (third position) where the separation plate 71 faces the fixing belt 31, and an open position (fourth position) where the separation plate 71 is further away from the fixing nip section N than in the closed position, and the jammed sheet S at the fixing nip section N can be removed. The closed position is the position in which the discharge unit 60 does not open the downstream side of the fixing nip section N with respect to the conveying direction of the sheet S, and the open position is the position in which the discharge unit 60 opens the downstream side of the fixing nip section N with respect to the conveying direction of the sheet S. In the following, when simply referred to as "downstream," it means downstream with respect to the conveying direction of the sheet S.

[0038] The opening / closing mechanism 600 includes a pivot shaft 84 that rotatably supports the discharge unit 60, a lock shaft 82 provided on the fixing frame 23, and a locking member 63 provided on the discharge unit 60. The discharge unit 60 is positioned relative to the fixing frame 23 by engaging the locking member 63 with the lock shaft 82. In this state, the discharge unit 60 is in the closed position. On the other hand, by disengaging the locking member 63 from this state and rotating the discharge unit 60 around the pivot shaft 84 in the direction away from the fixing nip portion N (direction of arrow A), the discharge unit 60 is positioned in the open position. Then, in this state, jamming is performed.

[0039] [Separation Unit] Next, the separation unit 70 will be described in detail using Figures 4, 5, and 6. The separation unit 70 is provided in the discharge unit 60 (see Figure 3). The separation unit 70 of this embodiment includes a separation plate 71 as a separation member, a separation plate support member 72 that supports the separation plate 71, a separation plate restricting part 73 that restricts the direction of movement of the separation plate 71, a separation guide 74 as a separation member support part that supports the separation plate support member 72, and a torsion coil spring 75 as a biasing part. The separation plate 71 is made of a metal plate and is formed by attaching fluorine-based tape to prevent toner adhesion from the sheet and damage to the image due to sliding.

[0040] The separation plate support member 72 is provided with a separation plate restricting portion 73, which serves to restrict the direction of movement of the separation plate 71 relative to the separation guide 74. The separation plate restricting portion 73 has a first guide shaft 73a and a second guide shaft 73b on both sides in the width direction W, which serve as engagement portions on the separation member side. In addition, spring attachment portions 73c are provided on both sides in the width direction W of the separation plate support member 72, which engage with the ends of the torsion coil spring 75.

[0041] On the other hand, the separation guide 74 has a guide groove 74a in which the first guide shaft 73a and the second guide shaft 73b roughly engage with a predetermined gap, and a fastening portion 74b which is a fastening surface with the discharge unit 60. The first guide shaft 73a and the second guide shaft 73b provided on the separation plate support member 72 that supports the separation plate 71 engage with the guide groove 74a provided on the separation guide 74, so that the separation plate 71 can move between a separation position (first position) and a retracted position (second position) relative to the separation guide 74. That is, the guide groove 74a, which serves as a guide portion on the support side, guides the first guide shaft 73a and the second guide shaft 73b to the separation position and the retracted position. The side portion 73d is provided substantially vertically at both ends in the width direction W of the separation plate support member 72. The first guide shaft 73a and the second guide shaft 73b are provided extending outward from the side portion 73d, with their width direction W and axial center aligned, and are arranged side by side in the sheet conveying direction.

[0042] The direction in which the separation plate 71 is moved by the first guide shaft 73a and the second guide shaft 73b is determined by the guide groove 74a of the separation guide 74. The separation unit 70 is biased by the torsion coil spring 75 in the direction of arrow B, which is approximately the same as the determined direction of movement, so that the first guide shaft 73a of the separation unit 70 comes into contact with the contact surface 37a (Figure 6) of the separation positioning part 37, which is a positioning member provided on the stay 35 of the heating unit 30. This makes it possible to position the separation plate 71 in the separation position.

[0043] Furthermore, retractable arms 76 are provided at both ends of the separation guide 74 in the width direction W, and are pivotally supported on a retractable arm shaft 77 which is rotatably supported by the separation guide 74. A retractable lever 78 is rotatably provided at one end of the discharge unit 60 in the width direction W, and is biased by a torsion coil spring 79 acting as a biasing part in the direction of contacting the end of the retractable arm 76. When the retractable lever 78 is biased by the torsion coil spring 79, the retractable arm 76 that is in contact with the retractable lever 78 is biased in the direction of arrow C, and further the retractable arm 76 biases the spring attachment part 73c provided on the separation plate support member 72 in the direction of arrow C.

[0044] In this embodiment, as will be described in detail later, the mechanism including the torsion coil spring 75, retraction arm 76, retraction lever 78, torsion coil spring 79, and separation movement cam 29 corresponds to the separation plate movement mechanism 700 as a first movement mechanism capable of moving the separation plate 71 between the separation position and the retraction position. In the above description, the biasing part is described as a torsion coil spring, but it is not limited to this, and equivalent effects can be obtained with other biasing members such as tension springs or compression springs. Furthermore, the biasing part for biasing the separation plate 71, such as the torsion coil spring 79, may be provided outside the separation unit 70, for example, on the fixing frame 23.

[0045] [Separation and positioning section of the heating unit] Next, the positioning configuration of the separation plate 71 provided in the heating unit 30 will be described in detail with reference to Figure 6. The stay 35 is provided with a separation positioning section 37 as a positioning member for positioning the separation plate 71 in the separation position. The separation positioning section 37 is engageable with a first guide shaft 73a and a second guide shaft 73b provided in the separation plate support member 72, and has a guide groove 37b as a guide that guides the separation plate 71, supported by the separation plate support member 72, to the separation position and the retracted position, which will be described later. The position of the separation unit 70 relative to the fixing belt 31 is determined by the engagement of the first guide shaft 73a and the second guide shaft 73b with the guide groove 37b of the separation positioning section 37.

[0046] Specifically, as shown in Figure 6, the separation plate 71 is positioned toward the fixing belt 31 at the point where the first guide shafts 73a at both ends of the separation plate support member 72 engage with the contact surface 37a of the guide groove 37b. Furthermore, the engagement of the second guide shaft 73b with the guide groove 37b prevents the separation plate 71 from rotating. This enables the positioning of the separation unit 70 having the separation plate 71 with the stay 35. It should be noted that the manner in which the guide groove 37b of the separation positioning section 37 engages with the first guide shaft 73a and the second guide shaft 73b is not limited to the above configuration, and other configurations can be applied as appropriate.

[0047] [Movement configuration of the separation plate] Next, the movement configuration of the separation plate 71 will be explained in detail using Figures 7 and 8. Figure 7 shows the separation plate 71 in the separation position, and Figure 8 shows the separation plate 71 in the retracted position. As described above, the separation plate 71 can move between a separation position, which is the first movement mechanism, and a retracted position, which is the second position, by the separation plate movement mechanism 700, which is the first movement mechanism. The separation position is the position in which, with the discharge unit 60 in the closed position, the tip of the separation plate 71 faces the fixing belt 31 with a predetermined gap between them, and the sheet that has passed through the fixing nip N can be separated from the fixing belt 31 by the separation plate 71. The retracted position is the position in which, with the discharge unit 60 in the closed position, the tip of the separation plate 71 is further from the fixing belt 31 than in the separation position. The separation plate moving mechanism 700 includes a torsion coil spring 75 as a biasing part, a retraction arm 76, a retraction lever 78, a torsion coil spring 79, a separation moving lever 28, a torsion coil spring 83, and a separation moving cam 29.

[0048] The separation plate support member 72, which supports the separation plate 71, is provided with a spring attachment portion 73c on which a torsion coil spring 75 is attached. The torsion coil spring 75 biases the separation plate 71 in the direction from the retracted position to the separated position via the spring attachment portion 73c. ​​The retraction arm 76 is rotatably supported with respect to the separation guide 74 (Figure 5), which serves as a separation member support portion. The retraction arm 76 can also contact the spring attachment portion 73c, and as will be described later, when the retraction arm 76 is pushed by the retraction lever 78, the retraction arm 76 pushes the spring attachment portion 73c, causing the separation plate support member 72 to move against the biasing force of the torsion coil spring 75. As a result, the separation plate 71 moves from the separated position to the retracted position together with the separation plate support member 72.

[0049] The retraction lever 78 is rotatably supported on the side plate of the discharge unit 60 and is biased by a torsion coil spring 79 to contact the end of the retraction arm 76. In the state shown in Figure 7, the retraction lever 78 is pushed by the separation movement lever 28 and rotates in a direction against the biasing force of the torsion coil spring 79, so the retraction lever 78 is not in contact with the retraction arm 76. As a result, the separation plate 71 is positioned in the separation position due to the biasing force of the torsion coil spring 75.

[0050] The separation and movement lever 28 is rotatably supported with respect to a link pivot center 81 provided on the side plate of the discharge unit 60, and is capable of contacting the retraction lever 78. A torsion coil spring 83 biases the separation and movement lever 28 away from the retraction lever 78. The separation and movement cam 29 is supported on the frame of the fixing device 20 (for example, the fixing frame 23 (Figure 3)) and rotates together with the pressure cam 27, which will be described later. The separation and movement cam 29 is also capable of engaging with the separation and movement lever 28, and as shown in Figure 7, when engaged with the separation and movement lever 28, it rotates the separation and movement lever 28 against the biasing force of the torsion coil spring 83. In this state, the separation and movement lever 28 rotates the retraction lever 78 in the direction of arrow D, preventing the retraction lever 78 from contacting the retraction arm 76.

[0051] In this embodiment, the pressure roller 22 is moved by a second moving mechanism, a pressure cam 27. The pressure cam 27 can move the pressure roller 22 between a contact position (Figure 7) where the pressure roller 22 is in contact with the fixing belt 31 and a separated position (Figure 8) where the pressure roller 22 is separated from the fixing belt 31. The separation plate moving mechanism 700 moves the separation plate 71 from the separated position to the retracted position in conjunction with the movement of the pressure roller 22 from the contact position to the separated position by the pressure cam 27. That is, the separation moving cam 29 of the separation plate moving mechanism 700 has the same pivot point as the pressure cam 27 and is configured to rotate together with the pressure cam 27. Therefore, when the pressure cam 27 is rotated by a drive source (not shown), the separation moving cam 29 also rotates together with the pressure cam 27. Note that even when the pressure roller 22 is separated from the fixing belt 31, the fixing belt 31 continues to rotate while the heating roller 33 heats the belt. A detailed explanation follows below.

[0052] As shown in Figure 7, when the separation plate 71 is in the separation position, the pressure frame 25 moves toward the heating unit 30 by a drive source (not shown) and a pressure cam 27, so that the pressure roller 22 is pressed against the pressure pad 32 via the fixing belt 31, forming a fixing nip portion N. The fixing nip portion N is normally almost flat across its entire width when the media is fixed, by adjusting the crown shape of the pressure pad 32 and the contact pressure of the pressure roller 22.

[0053] At this time, the separation movement lever 28 provided on the link pivot center 81 rotates together with the pressure cam 27 by the separation movement cam 29, and the retraction lever 78 rotates in the direction of arrow D. When the retraction lever 78 rotates in the direction of arrow D, the separation plate regulating part 73 moves in the direction of arrow B together with the separation plate 71 due to the biasing force of the torsion coil spring 75. Then, the first guide shaft 73a of the separation plate regulating part 73 engages with the contact surface 37a of the separation positioning part 37 provided on the stay 35. In other words, the separation plate movement mechanism 700 allows the separation plate 71 to be biased by the torsion coil spring 75 and positioned in the separation position while the pressure roller 22 is in the contact position. As a result, the separation plate 71 is positioned such that the gap (a predetermined gap) between the fixing belt 31 and the tip of the separation plate 71 is G1, and since the fixing nip portion N is almost flat throughout the width direction, a gap of approximately 500 μm can be guaranteed throughout the width direction.

[0054] In this way, when the separation plate 71 is in the separation position, the gap G1 between the fixing belt 31 and the separation plate 71 is guaranteed to be approximately 500 μm across the entire width direction, thereby guiding the various media peeled off from the fixing belt 31 from the outlet of the fixing nip section N to the transport roller pair (discharge roller pair) 62 without causing them to become clogged in the gap with the separation plate 71.

[0055] As shown in Figure 8, when the separation plate 71 is in the retracted position, the pressure frame 25 moves away from the heating unit 30 by a drive source (not shown) and a pressure cam 27, so that the pressure roller 22 does not come into contact with the fixing belt 31. At this time, the separation movement lever 28 provided on the link pivot center 81 moves away from the separation movement lever 29, which is provided coaxially with the pressure cam 27, and the separation movement lever 28 rotates in the direction of arrow E by the biasing force of the torsion coil spring 83.

[0056] When the separation lever 28 rotates in the direction of arrow E, the retraction lever 78 rotates in the direction of arrow F due to the biasing force of the torsion coil spring 79. As the retraction lever 78 rotates in the direction of arrow F, the retraction arm 76 rotates against the biasing force of the torsion coil spring 75, moving the separation plate 71 in the direction of arrow C via the spring attachment portion 73c. ​​Then, the separation plate regulating portion 73 moves together with the separation plate 71 in the direction of arrow C by the retraction arm 76, so that the second guide shaft 73b of the separation plate regulating portion 73 comes into contact with the guide groove 74a of the separation guide 74.

[0057] When the second guide shaft 73b is in contact with the guide groove 74a, the first guide shaft 73a is retracted by a predetermined amount (20 mm in this embodiment) from the contact surface 37a while engaged with the guide groove 37b of the separation positioning part 37 provided on the stay 35. That is, the separation plate moving mechanism 700 moves the separation plate 71 to the retracted position against the biasing force of the torsion coil spring 75 while the pressure roller 22 is in the separated position. In this way, the separation plate 71 moves from the separated position to the retracted position in conjunction with the movement of the pressure roller 22 to the separated position. When the separation plate 71 is in the retracted position, a gap G2 larger than the gap G1 is formed between the tip of the separation plate 71 and the fixing belt 31.

[0058] To remove jammed recording material in the fixing nip section N, it is conceivable to move the discharge unit 60, which includes a separation plate 71 located downstream of the fixing nip section N, away from the fixing belt 31 to create space for removing the jammed recording material (jamming). However, the separation plate 71 protrudes toward the fixing belt 31 downstream of the fixing nip section N and is positioned so that a predetermined gap exists between the fixing belts 31. Therefore, in the configuration with the separation plate 71, even if the discharge unit 60 is moved away from the fixing belt 31 to perform jamming, it is difficult to secure space for jamming due to the protrusion of the separation plate 71, and thus jamming is difficult to perform.

[0059] In this embodiment, when jamming is detected in the fixing nip section N, the pressure roller 22 moves to a retracted position, and furthermore, the opening / closing mechanism 600 is configured to rotate the discharge unit 60 from a closed position to an open position capable of jamming in order to remove the jammed sheet in the fixing nip section N. As shown in Figures 7 and 8, when the discharge unit 60 is in the closed position, at least the first guide shaft 73a of the first guide shaft 73a and the second guide shaft 73b is engaged with the guide groove 37b of the separation positioning section 37. Then, when the discharge unit 60 moves from the closed position to the open position, the engagement between the first guide shaft 73a and the second guide shaft 73b and the guide groove 37b is released, as shown in Figure 10, which will be described later. In this case, the first guide shaft 73a and the second guide shaft 73b engage with the guide groove 74a of the separation guide 74, and the spring attachment portion 73c is biased by the torsion coil spring 75 via the retraction arm 76, thereby maintaining the separation plate 71 in the retracted position.

[0060] Thus, even if the discharge unit 60 is rotated from the closed position to the open position while the separation plate 71 is in the retracted position, the separation plate 71 remains in the retracted position. In other words, the separation plate moving mechanism 700 can position the separation plate 71 in the separated position or the retracted position regardless of the operation of the opening and closing mechanism 600. When jamming is performed, the pressure roller 22 is usually moved to the separated position before moving the discharge unit 60 to the open position. For this reason, the separation plate 71 is in the retracted position when the discharge unit 60 is in the open position.

[0061] [Effect of expanding jam processing space by retracting the separation plate] Next, as described above, the effect of expanding the jam processing space by moving the separation plate 71 to the retracted position will be explained in detail using Figures 9 and 10. Figure 9 shows the comparative example with the discharge unit 60 opened for jam processing (moved to the open position). The comparative example shown in Figure 9 is configured such that the separation plate 71 does not move to the retracted position. As the discharge unit 60 rotates in the H direction around the pivot axis 84, a jam processing space M appears between the discharge unit 60 and the fixing belt 31. At this time, since the separation plate 71 is biased to the separated position by the torsion coil spring 75, the separation plate 71 remains protruding toward the fixing nip portion N. Therefore, sufficient space M for removing jammed sheets during jam processing cannot be secured, and there is a possibility that the user may touch the separation plate 71.

[0062] In particular, when jamming, the sheet is removed by reaching in from above the space M, so if the separation plate 71 remains protruding, as in the comparative example, it becomes difficult to remove the sheet. Specifically, let the virtual surface L be the extension of the nip surface of the fixing nip section N (the surface formed between the pressure roller 22 and the fixing belt 31 when the pressure roller 22 is pressed against the fixing belt 31) along the direction in which the sheet is discharged from the fixing nip section N. In this case, when the discharge unit 60 is in the open position, the position of the tip of the separation plate 71 is vertically above the virtual surface L. Therefore, if the separation plate 71 remains protruding, the space M becomes smaller, making it difficult to remove the sheet.

[0063] On the other hand, Figure 10 shows the discharge unit 60 in the configuration of this embodiment with the discharge unit 60 opened for jam processing. As the discharge unit 60 rotates in the H direction around the pivot axis 84, a jam processing space M appears between the discharge unit 60 and the fixing belt 31. At this time, the separation plate 71 is moved to the retracted position by being biased with a stronger force than the torsion coil spring 75 by the retraction lever 78 and the torsion coil spring 79. As a result, the separation plate 71 is located about 20 mm away from the fixing nip, and sufficient space M for removing jammed sheets during jam processing is secured. In addition, by retracting the separation plate 71 inside the frame of the discharge unit 60, the possibility of the user touching the separation plate 71 is reduced.

[0064] Furthermore, in this embodiment, when the separation plate 71 is in the retracted position and the discharge unit 60 is in the open position, the tip of the separation plate 71 is located vertically above the virtual plane L. However, unlike the comparative example, since the separation plate 71 is in the retracted position, even if the tip of the separation plate 71 is above the virtual plane L, sufficient space M can be secured. Therefore, it is easy to remove the sheet by reaching in from above the space M.

[0065] As described above, according to the fixing device 20 of this embodiment, the separation plate 71 is movable between the separation position and the retracted position, and when the discharge unit 60 is in a state where it can be opened and closed, the separation plate 71 is in the retracted position, which makes it possible to secure space for jam processing. Therefore, jam processing is easy even with a configuration that includes a separation plate 71.

[0066] [Other embodiments] In the above-described embodiment, the discharge unit 60 was moved to the open position during jam processing. However, during jam processing, the discharge unit 60 may remain in the closed position, and the separation plate 71 may be moved to the retracted position in conjunction with the operation of separating the pressure roller from the fixing belt 31.

[0067] In the embodiments described above, a configuration was described in which a halogen heater is provided on the heating roller as a heating element for heating the fixing belt. However, the heating element may be provided on other tensioning members instead of the heating roller. It may also be provided on the pad member. For example, a plate-shaped heating element such as a ceramic heater may be provided on the fixing belt side of the pad member. Alternatively, the fixing belt may be heated by electromagnetic induction (IH). Furthermore, in each of the embodiments described above, instead of a heating element placed inside the roller, an external heating method may be adopted in which another heating element is brought into contact with the belt or roller from the outside to heat it.

[0068] Furthermore, in the embodiments described above, a configuration using a pressure roller as the driving rotating body was explained. However, the driving rotating body may also be an endless belt that is stretched by a plurality of tension rollers and driven by any of the tension rollers. Also, in each of the embodiments described above, the pressure roller as the driving rotating body is pressed against the belt in order to form the nip portion, but the configuration may also be one in which the belt is pressed against the driving rotating body. Furthermore, in each of the embodiments described above, a configuration using a fixing pad as the nip portion forming member was explained, but the nip portion forming member may also be a roller.

[0069] Furthermore, in the above-described embodiment, the first moving mechanism is a separation plate moving mechanism 700 having multiple arms or levers, but any configuration that allows the separation plate 71 to move may be a conventional link mechanism, cam mechanism, or a combination thereof. In addition, it is preferable that the first moving mechanism is configured to be linked with a second moving mechanism, which is a mechanism that separates the second rotating body from the first rotating body, but it is not necessary for it to be linked with the second moving mechanism. Also, the first moving mechanism may be linked with a third moving mechanism that moves the unit to the jamming position. In short, it is sufficient that the separation member is in the second position (retracted position) when the unit is in the fourth position (open position).

[0070] Furthermore, although the first rotating body is a fixing belt in the above embodiment, the first rotating body may be a roller. Also, although the second rotating body is a pressure roller, the second rotating body may be an endless belt. In other words, the first and second rotating bodies may be rollers or belts. Also, although the separating member is a metal plate in the above embodiment, it may be a resin plate member or a sheet-like member. Also, although the separating member is a plate-shaped separating plate in the above embodiment, the separating member may be, for example, a roughly rectangular parallelepiped with a rectangular cross-section, and the recording material may be separated by bringing the corners of this member close to the first rotating body. [Explanation of Symbols]

[0071] 20. Fixing device 22. Pressure roller (second rotating body) 27. Pressurized cam (second movement mechanism) 31. Fixing belt (first rotating body) 32. Pressure pad (nipple forming member) 35...Stay (support member) 37. Separation positioning section (positioning member) 37b... Guide groove (guide section) 60... Discharge Unit (Unit) 62...Conveyor roller pair (conveyor section) 71...Separation plate (separation member) 73a...First guide shaft (engaging portion on the separation member side) 73b...Second guide shaft (engaging part on the separation member side) 74. Separation guide (support part for separation member) 84...Rotating shaft 600...Opening / closing mechanism (third movement mechanism) 700... Separation plate moving mechanism (first moving mechanism)

Claims

1. A fixing device that heats a toner image supported on a recording material to fix it to the recording material, The first rotating body and, A second rotating body that contacts the first rotating body and forms a nip portion between itself and the first rotating body for gripping and transporting the recording material, A separation member is positioned downstream of the nip section with respect to the direction of transport of the recording material, and is capable of separating the recording material that has passed through the nip section from the first rotating body, A separation member support portion that supports the separation member so that it can move between a first position and a second position, A first moving mechanism that allows the separating member to move between the first position and the second position, The second rotating body comprises a second moving mechanism that allows it to move between a contact position where it is in contact with the first rotating body and a separated position where it is separated from the first rotating body. The first position is a position in which, when the second rotating body is in the contact position, the tip of the separating member faces the first rotating body with a predetermined gap between them, and the separating member can separate the recording material that has passed through the nip portion from the first rotating body. The second position is a position where, when the second rotating body is in the separated position, the tip of the separating member is further away from the first rotating body than the first position. In conjunction with the movement of the second rotating body from the contact position to the separation position by the second moving mechanism, the first moving mechanism moves the separating member from the first position to the second position. A fixing device characterized by the following features.

2. The unit, including the separating member and the separating member support, is equipped with a third moving mechanism that allows it to move between a third position in which the downstream side of the nip portion is not opened and a fourth position in which the downstream side of the nip portion is opened, with respect to the transport direction of the recording material. The separating member is located in the second position when the unit is in the fourth position. The fixing device according to feature 1.

3. When the unit is in the third position, the first moving mechanism moves the separating member from the first position to the second position. The fixing device according to feature 2.

4. The unit is positioned downstream in the direction of transport of the recording material and has a transport section that transports the recording material that has passed through the nip section. The fixing device according to feature 2.

5. The first moving mechanism has a biasing section that biases the separating member toward the first position, and allows the separating member to be biased by the biasing section to be in the first position when the second rotating body is in the contact position, and moves the separating member to the second position against the biasing force of the biasing section when the second rotating body is in the separated position. The fixing device according to feature 1.

6. The first rotating body is an endless belt, A nip-forming member is positioned inside the belt and facing the second rotating body via the belt, and forms the nip portion between the belt and the second rotating body. A support member is positioned inside the belt and supports the nip portion forming member, A positioning member provided on the support member for positioning the separation member at the first position, and further comprising The fixing device according to feature 2.

7. The positioning member has a guide portion that guides the separating member to the first position and the second position when the unit is in the third position. The fixing device according to feature 6.

8. The unit has a separating member-side engaging portion that engages with the guide portion when the unit is in the third position, and disengages from the guide portion when the unit moves from the third position to the fourth position. The fixing device according to feature 7.

9. The engagement portion on the separation member side is movable together with the separation member between the first position and the second position. The separation member support portion has a support portion side guide portion that guides the separation member side engagement portion to the first position and the second position. The fixing device according to feature 8.

10. The third moving mechanism has a pivot shaft that rotatably supports the unit, and the unit is rotatable between the third position and the fourth position about the pivot shaft. When the separating member is located in the second position and the unit is located in the fourth position, the position of the tip of the separating member is vertically above a virtual plane that extends the nip surface of the nip portion in the direction from which the recording material is discharged from the nip portion. The fixing device according to feature 2.

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