This application is based on and claims the benefit of priority from Japanese Patent Application No. 2023-209480 filed on Dec. 12, 2023, the contents of which are hereby incorporated by reference.
The present disclosure relates to fixing devices incorporated in image forming apparatuses such as multifunction peripherals, printers, facsimile machines, and multifunction peripherals having their functions integrated together, and to image forming apparatuses provided with such a fixing device.
In electrophotographic type image forming apparatuses, to fix a toner image to a sheet, wide use is made of a fixing device including a fixing member configured with a fixing roller or a fixing belt (a heated rotating member) and a pressing roller (a pressing rotating member) kept in pressed contact with each other. This fixing device passes the sheet through a fixing nip portion formed between the fixing roller or the fixing belt and the pressing roller, and heats and presses the toner image to fuse and fix the toner image to the sheet.
With the fixing device described above, the heated rotating member and the pressing rotating member are kept in pressed contact with each other, and this necessitates a configuration that can relieve the pressure for removal of the sheet when a jam occurs.
According to one aspect of the present disclosure, a fixing device includes a fixing member, a housing, a side cover, a pressing mechanism, and a unit side gear, and heats and presses a sheet passing through a fixing nip portion to fuse and fix an unfixed toner image on the sheet. The fixing member is configured with a heated rotating member and a pressing rotating member kept in pressed contact with the heated rotating member to form the fixing nip portion. The housing houses the fixing member. The side cover is fitted to at least one end of the housing in the longitudinal direction. The pressing mechanism adjusts the pressure between the heated rotating member and the pressing rotating member. The unit side gear is coupled with a main body side gear provided on a main body of an image forming apparatus, and transmits a driving force to the fixing member or the pressing mechanism. The side cover has a first positioning portion that positions the unit side gear and a second positioning portion that positions the main body side gear.
Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.
In these image forming portions Pa to Pd are arranged photosensitive drums (image carrying member) 1a, 1b, 1c, and 1d, which carry visible images (toner images) of the different colors. An intermediate transfer belt (intermediate transfer member) 8 that rotates counterclockwise in
The transfer sheets P to which toner images will be secondarily transferred are stored inside a sheet cassette 16 arranged in a lower part of the main body of the image forming apparatus 100. The transfer sheet P is conveyed via a sheet feed roller 12 and a pair of registration rollers 13 along a sheet conveyance passage 19 to the nip between the secondary transfer roller 9 and a driving roller 11 for the intermediate transfer belt 8. Used as the intermediate transfer belt 8 is a sheet of a dielectric resin, typically a belt with no seam (a seamless belt). Downstream of the secondary transfer roller 9, a blade-form belt cleaner 25 for removing toner and the like left on the surface of the intermediate transfer belt 8 is provided.
Next, the image forming portions Pa to Pd will be described. Around and under the photosensitive drums 1a to 1d, which are rotatably arranged, there are provided charging devices 2a, 2b, 2c, and 2d which electrostatically charge the photosensitive drums 1a to 1d, an exposure device 5 which exposes the photosensitive drums 1a to 1d to light conveying image information, developing device 3a, 3b, 3c, and 3d which form toner images on the photosensitive drums 1a to 1d, and cleaning devices 7a, 7b, 7c, and 7d which remove developer (toner) and the like left on the photosensitive drums 1a to 1d.
When image data is fed in from a host device such as a personal computer, first, the charging devices 2a to 2d electrostatically charge the surfaces of the photosensitive drums 1a to 1d uniformly. Next, the exposure device 5 irradiates the photosensitive drums 1a to 1d with light according to image data to form on them electrostatic latent images according to the image data. The development devices 3a to 3d are loaded with predetermined amounts of two-component developer containing toner of different colors, namely yellow, cyan, magenta, and black respectively. When, as image formation proceeds as will be described later, the proportion of the toner in the two-component developer in the development devices 3a to 3d falls below a prescribed value, toner is supplied from toner containers 4a to 4d to the development devices 3a to 3d. The toner in the developer is fed from the development devices 3a to 3d to the photosensitive drums 1a to 1d and electrostatically adhere to them. Thus, toner images are formed according to the electrostatic latent images formed by exposure to light from the exposure device 5.
Then, primary transfer rollers 6a to 6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d, and thereby the yellow, cyan, magenta, and black toner images on the photosensitive drums 1a to 1d are primarily transferred to the intermediate transfer belt 8. These images are formed with a predetermined positional relationship. After that, in preparation for the subsequent formation of new electrostatic latent images, the toner and the like remaining on the surfaces of photosensitive drums 1a to 1d after primary transfer are removed by cleaning devices 7a to 7d.
The intermediate transfer belt 8 is wound around a driven roller 10, arranged upstream, and the driving roller 11, arranged downstream. As the driving roller 11 is rotated by the belt driving motor (not illustrated), the intermediate transfer belt 8 starts rotating counterclockwise, and the transfer sheet P is conveyed with predetermined timing from the pair of registration rollers 13 to a secondary transfer nip portion N1 (see
The transfer sheet P having the toner images secondarily transferred to it is conveyed to the fixing device 14. The fixing device 14 has a fixing belt 14a and a pressing roller 14b (see
The transfer sheet P conveyed to the fixing portion 14 is heated and pressed by the fixing belt 14a and the pressing roller 14b; thus the toner images are fixed to the surface of the transfer sheet P and a predetermined full-color image is formed. The transfer sheet P with the full-color image formed on it is conveyed via a pair of fixing discharge rollers 24 (see
The side face of the open/close cover 21 is provided with a grip portion 22. The grip portion 22 keeps the open/close cover 21 closed with one end part of the grip portion 22 engaging with engagement pins (not illustrated) provided on a front frame and a rear frame of the main body of the image forming apparatus 100. To open the open/closed cover 21, the grip portion 22 is pivoted to disengage from the engagement pins.
Inward of the open/close cover 21 is arranged a conveyance unit 23. The conveyance unit 23 is supported on the main body of the image forming apparatus 100 so as to be pivotable about a unit shaft 23a and the conveyance unit 23 constitutes part of the conveyance face of the duplex conveyance passage 20 and the sheet conveyance passage 19. The duplex conveyance passage 20 extends between the inner side surface of the open/close cover 21 and the outer side surface of the conveyance unit 23 along the side face 102 of the image forming apparatus 100 in the up-down direction, then curves substantially in a C-shape to join the sheet conveyance passage 19. The inner side surface of the conveyance unit 23 is fitted with, in order from upstream (bottom in
As the open/close cover 21 alone is pivoted to open in the opening direction with respect to the image forming apparatus 100, the duplex conveyance passage 20 is exposed over a wide range. As the open/close cover 21 is pivoted together with the conveyance unit 23 in the opening direction, the conveyance unit 23 moves away from the main body of the image forming apparatus 100 and the sheet conveyance passage 19 is exposed over a wide range. By contrast, as the open/close cover 21 is pivoted together with the conveyance unit 23 to close in the closing direction, the conveyance unit 23 makes contact with the main body of the image forming apparatus 100, the secondary transfer roller 9 is pressed against the driving roller 11 with the intermediate transfer belt 8 in between to form a secondary transfer nip N1.
Next, the configuration of the fixing device 14 will be described.
The fixing device 14 has a housing 30, side covers 31a and 31b, and a stay 31c. The housing 30 houses the fixing belt 14a and the pressing roller 14b. Above the housing 30 is supported one-side (left side in
The side covers 31a and 31b are fixed to side plates 30a and 30b arranged at the opposite ends of the housing 30 in the longitudinal direction. The stay 31c is made of metal and is a plate-form member fixed to the housing 30 along the longitudinal direction. At the opposite ends of the stay 31c in the longitudinal direction, a pair of spring brackets 40 are formed, each to support one end (lower end) of a pressing spring 35 (see
At the side cover 31a side, there are arranged a driving input gear 60 and a depressurizing gear 61. The driving input gear 60 meshes with a roller driving gear 142 (see
Inside the fixing belt 14a are arranged a nip forming member 41 and a belt guide 42. The nip forming member 41 makes contact with the pressing roller 14b via the fixing belt 14a to form a fixing nip portion N2 through which the transfer sheet P is inserted. The nip forming member 41 is made of a heat-resistant resin such as a liquid crystal polymer or an elastic material such as silicone rubber and an elastomer may be arranged on the surface facing the fixing belt 14a for enhanced sliding properties.
The belt guide 42 is in the shape of an arc in a sectional view and makes contact with the inner circumferential surface of the fixing belt 14a except on the surface facing the nip forming member 41. The belt guide 42 applies a predetermined tension to the fixing belt 14a and holds the fixing belt 14a in the shape of an arc from inside it. The belt guide 42 is formed of a metal plate that extends along the axial direction of the fixing belt 14a over substantially the same length as the fixing belt 14a.
A pair of pressing mechanisms 32 are provided at the opposite ends of the fixing belt 14a and the pressing roller 14b in the axial direction. Each pressing mechanism 32 has a pressing plate 33, a pressing spring 35, and an eccentric cam 37.
The pressing plate 33 is arranged opposite belt holder 143 that supports the opposite ends of the fixing belt 14a, the nip forming member 41, and the belt guide 42 in the longitudinal direction. The pressing plate 33 has a fulcrum portion 33a supported on the housing 30 (see
The pressing spring 35 urges the belt holder 143 in a direction toward the pressing roller 14b. Specifically, one end of the pressing spring 35 is supported in the spring bracket 40 (see
The eccentric cam 37 is arranged at the same side (right side in
When the eccentric cam 37 rotates a predetermined amount from the state in
The first bearing portion 311 is a circular through-hole in which is inserted a drive transmission shaft 61a (see
The second bearing portion 312 is a U-shaped groove with a cutout portion 312a formed in part of the circumference of a through-hole in a cylindrical shape. In the second bearing portion 312 is inserted a rotation shaft 81a (see
The third bearing portion 313 is a circular through-hole in which is inserted a coupling (not illustrated) that drives the roller 24a (see
The gear cover portion 314 is in a cylindrical shape and covers the driving input gear 60 (see
The positioning pin 315 is inserted into a positioning hole (not illustrated) in the side plate 30a (see
Thus, the first bearing portion 311 in the side cover 31a and the driving transmission shaft 61a on the housing 30 are positioned with each other. The driving transmission shaft 61a has a D-cut shaped section and supports the depressurizing gear 61 such that this is movable in the thrust direction but not rotatable in the circumferential direction.
The depressurizing gear 61 is coupled with the depressurizing gear 61 at the other side (side cover 31b side) by the driving transmission shaft 61a. A rotational driving force fed from the depressurizing input gear 81 to the depressurizing gear 61 is transmitted via the drive transmission shaft 61a to the depressurizing gear 61 and the eccentric cam 37 at the other side.
The gear cover portion 314 in the side cover 31a and the driving input gear 60 in the housing 30 are positioned with each other and the driving input gear 60 is housed in the gear cover portion 314. On the side face of the driving input gear 60 (the face facing the driving output gear 80) input coupling teeth 60a are formed. The input coupling teeth 60a are exposed through the opening 314a in the gear cover portion 314.
When the fixing device 14 is mounted in the main body of the image forming apparatus 100, the open/close cover 21 (see
As the fixing device 14 is inserted, as shown in
As shown in
With the configuration described above, the positioning accuracy between the depressurizing gear 61 on the fixing device 14 and the depressurizing input gear 81 on the main body of the image forming apparatus 100 is improved and the inter-axial distance (gear pitch) is kept constant; this helps prevent meshing failure (tooth skipping) on the depressurizing gear 61 and the depressurizing input gear 81 and prevent abnormal noise.
Only with the side cover 31a, the depressurizing gear 61 and the depressurizing input gear 81 can be positioned relative to each other, and this helps reduce the number of the components of the fixing device 14. It is thus possible to reduce the size and the weight of the fixing device 14.
As shown in
The shaft 60d of the driving input gear 60 has a long protruding length relative to the housing 30 and so is prone to axis inclination. The gear cover portion 314 holding the driving input gear 60 also helps prevent axis inclination of the shaft 60d.
The present disclosure is not limited to the above embodiment and can be carried out with any modifications made without departure from the spirit of the present disclosure. For example, while the above embodiment takes up as an example a belt heating-type fixing device 14 that includes an endless fixing belt 14a as a heated rotating member, the present disclosure is applicable also to fixing devices including a heated rotating member other than a fixing belt 14a, such as a fixing roller.
While the embodiment described above deals with, as an example of an image forming apparatus 100, a color printer as shown in
The present disclosure finds applications in fixing devices incorporated in image forming apparatuses such as copiers, printers, facsimile machines, and multifunction peripherals having their functions integrated together. Based on the present disclosure, it is possible to enhance the positioning accuracy of a driving member with a simple configuration and to provide a fixing device that can prevent problems such as coupling failure and abnormal noise caused by displacement of a coupling portion, and to provide an image forming apparatus provided with such a fixing device.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-209480 | Dec 2023 | JP | national |