Patent Application
20210356888
The present invention relates to an image heating apparatus for fixing a toner image transferred onto a recording material in an image forming apparatus that adopts an electrophotographic system or an electrostatic recording system, and the image forming apparatus.
Hitherto, in an image forming apparatus adopting an electrophotographic system, an electrostatic latent image formed on a photosensitive drum serving as an image bearing member is developed using toner to form a toner image and the toner image is transferred to a recording material before the toner image is fixed to the recording material in a fixing unit, which is one example of an image heating apparatus. One example of a fixing unit used widely is a heat-pressure type unit that includes a heating rotary member and a pressing rotary member that applies pressure to the heating rotary member, wherein a fixing nip portion formed between the heating rotary member and the pressing rotary member nips and conveys the recording material, by which the toner borne on the recording material is fixed thereto by heat and pressure.
Processing speed of electrophotographic image forming apparatuses is increasing, and in response thereto, the size of the heating rotary member in the fixing unit is increased. Therefore, a fixing unit has been developed in which the heating rotary member stretched across a fixing roller and a heating roller is formed of a thin belt member (refer to Japanese Patent Application Laid-Open Publication No. 2011-123181). According to the fixing unit disclosed in Japanese Patent Application Laid-Open Publication No. 2011-123181, for example, a heating unit including the heating rotary member can be replaced with respect to a frame member such as a casing of the fixing unit to facilitate maintenance and extend service life of the heating rotary member forming the fixing nip portion.
However, according to the fixing unit disclosed in the above-mentioned Japanese Patent Application Laid-Open Publication No. 2011-123181, a cover of the frame member provided in the fixing unit is designed to open to a direction toward which the heating unit is removed. Therefore, when removing the heating unit from the frame member for replacement, the opened cover may be in the way of with the heating unit and hinder the replacement operation of the heating unit.
The present invention provides an image heating apparatus and an image forming apparatus that enables to improve workability of attaching and detaching the heating unit to and from the frame member.
According to a first aspect of the present invention, an image heating apparatus includes a first rotary member configured to heat a toner image formed on a recording material, a second rotary member configured to contact the first rotary member and form a fixing nip portion with the first rotary member for conveying the recording material, a frame member configured to support the first rotary member and the second rotary member, a guide portion configured to guide the first rotary member to be moved upstream in a conveyance direction of the recording material when the first rotary member is being removed, and a cover attached to the frame member and configured to turn around a rotation shaft to open and close the guide portion. The cover is configured to turn in a direction toward the conveyance direction to open the guide portion.
According to a second aspect of the present invention, an image forming apparatus configured to form an image on a recording material includes the image heating apparatus, and a drawer portion configured to support the image heating apparatus and be drawn out from the image forming apparatus.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
An embodiment of the present invention will be described in detail with reference to
As illustrated in
An image forming process will be described. At first, the image forming units PY, PM, PC, and PK will be described. In the present embodiment, the image forming units PY, PM, PC, and PK adopt approximately the same configuration except for the differences in toner colors, which are yellow, magenta, cyan, and black. The image forming unit PY of yellow toner will be described hereafter as an example, and descriptions of other image forming units PM, PC, and PK are omitted.
The image forming unit PY is mainly composed of a photosensitive drum 2, a charging apparatus 3, an exposing unit 4, and a developing apparatus 5. A surface of the photosensitive drum 2 serving as an example of an image bearing member being driven to rotate is uniformly charged in advance by the charging apparatus 3, and thereafter, an electrostatic latent image is formed thereon by the exposing unit 4 driven based on an image information signal. That is, an electrostatic latent image is formed on the photosensitive drum 2. The electrostatic latent image formed on the photosensitive drum 2 is developed by toner in the developing apparatus 5 and visualized as toner image. Toner in the developer consumed by image formation is replenished together with carrier from a toner cartridge not shown.
Thereafter, a predetermined pressurizing force and primary transfer bias are applied by a primary transfer roller 6 arranged opposed to the photosensitive drum 2 interposing the intermediate transfer belt 7, and the toner image formed on the photosensitive drum 2 is primarily transferred to the intermediate transfer belt 7. Transfer residual toner remaining slightly on the photosensitive drum 2 after primary transfer is removed by a cleaning device 8 to prepare the photosensitive drum 2 for a subsequent image forming process.
The intermediate transfer belt 7 is stretched across a tension roller 10, a secondary transfer inner roller 11 and a drive roller 12. The intermediate transfer belt 7 is driven to move in a direction of arrow R1 in the drawing by the drive roller 12. Image forming processes of respective colors performed by the above-mentioned image forming units PY, PM, PC, and PK are carried out at timings set so that toner images are sequentially superposed to a toner image previously formed upstream in the direction of movement on the intermediate transfer belt 7 via primary transfer. As a result, a full-color toner image is finally formed on the intermediate transfer belt 7 and conveyed to a secondary transfer portion T2. The secondary transfer portion T2 is a transfer nip portion formed between the intermediate transfer belt 7 stretched on the secondary transfer inner roller 11 and a secondary transfer outer roller 13. Transfer residual toner that remains after passing through the secondary transfer portion T2 is removed from the intermediate transfer belt 7 by a transfer cleaner device 14.
A conveyance process of the recording material S to the secondary transfer portion T2 is performed at a similar timing as a forming process of toner image that has been conveyed to the secondary transfer portion T2. In the conveyance process, the recording material S is fed from a sheet cassette and the like not shown and sent to the secondary transfer portion T2 at a matched timing with the forming of image. At the secondary transfer portion T2, secondary transfer voltage is applied to the secondary transfer inner roller 11.
As described, toner image is secondarily transferred from the intermediate transfer belt 7 to the recording material S at the secondary transfer portion T2 by the image forming process and the conveyance process. Thereafter, the recording material S is conveyed to a fixing unit 30 and subjected to heat and pressure by the fixing unit 30, according to which the toner image is melted and fixed to the recording material S. The fixing unit 30 is an example of the image heating apparatus for fixing an unfixed toner image formed by the image forming unit to the recording material S. The recording material S to which toner image has been fixed is discharged to a sheet discharge tray not shown by a sheet discharge roller.
The image forming apparatus 1 includes the control unit 20 for performing various controls such as the image forming operation described above. The operations of various units of the image forming apparatus 1 are controlled by the control unit 20 provided in the image forming apparatus 1. The series of image forming operations are controlled by the control unit 20 based on various input signals entered through an operation portion provided on an upper side of the apparatus body or via a network.
As illustrated in
Next, the fixing unit 30 will be described in detail with reference to
Meanwhile, according to the present embodiment, the fixing unit 30 is supported by a drawer portion 100 that can be drawn out of the image forming apparatus 1, as illustrated in
The heating unit 40 includes the fixing belt 41 serving as a first rotary member that is a rotatable endless belt, a pressure pad 42 serving as a fixing member, a heating roller 43, a steering roller 44, a stay 45, and unit side plates 46 that integrate these members as a cartridge. The heating unit 40 is attached in a detachable manner to the casing 31.
The fixing belt 41 is a thin, cylindrical belt member having thermal conductivity and heat resisting property, and can abut against and heat the recording material S. In the present embodiment, the fixing belt 41 adopts a three-layer structure including a base layer, an elastic layer formed on a circumference of the base layer, and a releasing layer formed on a circumference of the elastic layer. The base layer is formed of polyimide resin (PI) and has a thickness of 30 μm, and the elastic layer is formed of silicone rubber and has a thickness of 300 μm. The releasing layer is formed of PFA (tetrafluoro-ethylene-perfluoro alkoxy ethylene copolymer resin) as fluororesin and has a thickness of 30 μm. The fixing belt 41 is stretched across the pressure pad 42, the heating roller 43 and the steering roller 44. An outer diameter of the fixing belt 41 is, for example, 120 mm.
The pressure pad 42 is supported by the stay 45 and pressed by the pressure roller 32 interposing the fixing belt 41. The stay 45 is formed of stainless steel, and both ends in the rotational axis direction of the stay 45 are supported by fixing frames 33 of the casing 31 of the fixing unit 30. The stay 45 includes a separation plate positioning portion 45a. A fixing nip portion N is formed by a contact portion of the fixing belt 41 and the pressure roller 32. The rotational axis direction refers to a direction orthogonal to a sheet conveyance direction X of the recording material S that had passed through the fixing nip portion N.
The pressure pad 42 is formed, for example, of LCP (liquid crystal polymer) resin. A lubricating sheet 47 is interposed between the pressure pad 42 and the fixing belt 41. A PI (polyimide) sheet being coated with PTFE (polytetrafluoroethylene) with a thickness of 100 μm is used as the lubricating sheet 47. The PI sheet has 100-μm projections formed at 1-mm intervals to reduce a contact area with the fixing belt 41, to thereby reduce sliding resistance. A lubricant is applied to an inner side of the fixing belt 41 so that the fixing belt 41 slides smoothly on the pressure pad 42. The lubricant can be, for example, a silicone oil.
The heating roller 43 is a stainless-steel pipe with a thickness of 1 mm and having the heater 48 (refer to
The steering roller 44 has a pivot axis that is arranged approximately in a vertical direction at a first end or near a center portion in the rotational axis direction, and pivots with respect to the fixing belt 41 to create a tension difference in the main scanning direction and adjust the position of the fixing belt 41 in the main scanning direction. Further, the steering roller 44 is urged by a spring not shown supported by a frame of the heating unit 40 and serves as a tension roller for applying predetermined tension to the fixing belt 41.
The pressure roller 32 is opposed to and abuts against the fixing belt 41, forming the fixing nip portion N where pressure is applied between the pressure roller 32 and the fixing belt 41. The pressure roller 32 is a roller in which an elastic layer is formed on a circumference of a shaft and a releasing layer is formed on a circumference of the elastic layer. In the pressure roller 32, the shaft is formed of stainless steel, and the elastic layer is formed of conductive silicon rubber having a thickness of 3 mm. The releasing layer is formed of PFA (tetrafluoro-ethylene-perfluoro alkoxy ethylene copolymer resin) as fluororesin having a thickness of 30 μm. The pressure roller 32 is axially supported by the fixing frames 33 on the casing 31 of the fixing unit 30, and a gear is fixed to a first end of the pressure roller 32 in the rotational axis direction, wherein the pressure roller is connected through the gear to the drive motor M1 (refer to
The recording material S (refer to
The separation unit 50 is provided on the fixing frames 33 and includes a separation plate 51, and a guide shaft 52 and a rotation shaft 53 which are protruded toward either side in the rotational axis direction. The separation unit 50 is axially supported in a swingable manner by the rotation shaft 53 on the fixing frames 33. The separation plate 51 is provided to separate the recording material S having passed through the fixing nip portion N from the fixing belt 41, and it is formed by adhering a fluorine-based tape on a metal plate to prevent adhesion of toner and damaging of image on the recording material S by slide movement. The guide shaft 52 is arranged upstream in the sheet conveyance direction (direction D1 in the drawing) X of the rotation shaft 53.
The fixing frames 33 are arranged in a fixed manner on both side portions of the casing 31 with respect to the rotational axis direction, and each fixing frame 33 is provided with a guide portion 34, a pressing frame 35 and a pressurizing spring 36. The stay 45 of the heating unit 40 is inserted to the guide portion 34, pressed against and fixed to the guide portion 34 by a pressing portion 80 described later. After fixing the stay 45 to the guide portion 34, the pressing frame 35 is moved toward the heating unit 40 by a drive source and a cam not shown, by which the pressure roller 32 is pressed against the pressure pad 42 via the fixing belt 41. The pressurizing force of the pressure roller 32 to the pressure pad 42 during image forming operation is set to 1000 N, for example.
The guide portion 34 includes a support surface 34a, a positioning surface 34b serving as an example of a positioning portion, a sliding surface 34c and an opening portion 34d. The support surface 34a is formed on an opposing side of the pressure roller 32 along an attachment direction D1 for inserting the heating unit 40, and in a state where the heating unit 40 is positioned at the attachment position illustrated in
When attaching the heating unit 40 to the casing 31, the guide portion 34 guides and causes the heating unit 40 to be attached from an insertion start position (refer to
In the present embodiment, the attachment direction D1 for inserting the heating unit 40 is a direction along the sheet conveyance direction of the recording material S nipped by the fixing nip portion N, which is set parallel in the illustrated example. However, the attachment direction D1 is not limited to being completely parallel with the sheet conveyance direction X at the fixing nip portion N, and it can be approximately parallel, or the attachment direction D1 and the sheet conveyance direction X can be set to opposite directions.
Further, in a state where the heating unit 40 is positioned at the attachment position as illustrated in
The unit side plates 46 are provided on both sides in the rotational axis direction. Each unit side plate 46 includes a first abutment surface 46a and a second abutment surface 46b. The second abutment surface 46b is arranged along the attachment direction D1 and disposed continuously with the first abutment surface 46a but with a different angle value. The details of the first abutment surface 46a and the second abutment surface 46b will be described later.
Next, the cover 60 will be described in detail. The cover 60 is provided to cover the opening portion of the casing 31 and the heating unit 40 attached to the casing 31 to thereby protect and shield heat from the heating unit 40. The cover 60 includes a cover body 61, a cleaning unit 70 and the pressing portion 80.
The cover body 61 can cover the upper portion of the casing 31, both end portions in the rotational axis direction thereof, and both upstream and downstream side portions in the attachment direction D1 thereof. Both end portions in the rotational axis direction of the cover body 61 are axially supported pivotably on the fixing frame 33 through a swing shaft 62, which is an example of a rotation shaft. In the present embodiment, the swing shaft 62 is arranged downstream in the attachment direction D1 of the heating unit 40 positioned at the attachment position. That is, the cover body 61 is provided in a swingable manner with a swinging center regarding the casing 31 arranged downstream in the attachment direction D1 of the heating unit 40 positioned at the attachment position or the fixing nip portion N. The swing shaft 62 is not limited to being arranged downstream in the attachment direction D1 of the heating unit 40 positioned at the attachment position, and for example, even if the swing shaft 62 is not arranged downstream in the attachment direction D1 of the heating unit 40, the cover 60 should merely be openable in the attachment direction D1.
The cover body 61 includes an opening/closing engagement shaft 63 provided on both sides in the rotational axis direction on an outer diameter side of the swing shaft 62. The opening/closing engagement shaft 63 engages with the fixing frame 33 when the cover 60 is closed, by which the position of the cover 60 in the swinging direction with respect to the fixing frame 33 is determined.
The cover body 61 is movable by swinging motion between a first position and a second position. The first position is a position where the cover 60 covers the heating unit 40 positioned at the attachment position, as illustrated in
The cover body 61 includes a shielding portion 64 positioned upstream in the attachment direction D1 of the heating unit 40 in the first position, as illustrated in
The cleaning unit 70 is an example of a contact portion, and it is provided to clean the surface of the fixing belt 41. The cleaning unit 70 is arranged to abut against the fixing belt 41 of the heating unit 40 positioned at the attachment position when positioned at the first position as illustrated in
The pressing portion 80 is provided to press the stay 45 of the heating unit 40 attached to the casing 31 against the positioning surface 34b and position the heating unit 40 at the attachment position. The pressing portion 80 is a lock mechanism that stabilizes the position of the heating unit 40 with respect to the fixing unit 30 by pressing the heating unit 40 against the fixing frame 33 in a state where the cover 60 is closed and positioned at the first position. The pressing portion 80 includes a pressing arm 81, a swing shaft 82, a pressing roller 83, a pressing spring 84, and a stopper 85.
The pressing arm 81 is axially supported in a swingable manner by the swing shaft 82 on both side portions in the rotational axis direction of the cover body 61. The pressing roller 83 is axially supported in a rotatable manner by the pressing arm 81. The pressing spring 84 is formed of a tension coil spring, for example, and the pressing roller 83 urges the pressing arm 81 toward the direction to press the heating unit 40. Further, as illustrated in
Next, an operation for removing the heating unit 40 from the fixing unit 30 according to the present embodiment will be described with reference to
When removing the heating unit 40 from the guide portion 34, the removal direction D2 is regulated by the sliding surface 34c, as illustrated in
When the stay 45 exits through the opening portion 34d to the exterior, the heating unit 40 can be removed from the fixing unit 30, as illustrated in
Therefore, the operator will not have to take an unreasonable posture of working with the cover 60 placed therebetween and can work in a natural posture, so that deterioration of workability due to the presence of the cover 60 or occurrence of excessive operation of removing the cover 60 can be prevented. In a state where the cover 60 is positioned at the second position, the cleaning roller 73 is separated from the fixing belt 41 and moved to a retracted position in the removal direction D2 of the heating unit 40. Thereby, during the removal operation and the attaching operation of the heating unit 40, the risk of the cleaning roller 73 being in contact with the fixing belt 41 and damaging the fixing belt 41 can be suppressed.
Next, the operation for attaching the heating unit 40 to the fixing unit 30 according to the present embodiment will be described with reference to
As illustrated in
As illustrated in
The angle formed by the first abutment surface 46a with the attachment direction D1 should be close to 90 degrees to press the heating unit 40 effectively against the fixing frame 33. Therefore, the first abutment surface 46a preferably forms an angle of 45 degrees or greater and 90 degrees or smaller with the attachment direction D1.
The second abutment surface 46b and the first abutment surface 46a have different inclination angles but are arranged continuously. Thus, the pressing roller 83 can contact the second abutment surface 46b and apply rotational force by the pressing spring 84 while moving to the first abutment surface 46a, so that the pressing portion 80 can press the heating unit 40 after coming into contact therewith. If the heating unit 40 is merely attached to place by the user, there may be a gap between the stay 45 of the heating unit 40 and the positioning surface 34b of the guide portion 34. In contrast, by having the pressing roller 83 contact the first abutment surface 46a, a force pressing the stay 45 against the positioning surface 34b can be generated, and the position and posture of the heating unit 40 can be set preferably.
As described, according to the fixing unit 30 of the present embodiment, in a state where the cover 60 is opened and positioned at the second position, the cover 60 is positioned downstream in the attachment direction D1 than when the cover 60 is closed and positioned at the first position. Therefore, by positioning the cover 60 at the second position that is retracted to the opposite direction as the removal direction D2 for removing the heating unit 40, the entire body of the cover 60 can be retracted from the work area Ar2 (refer to
According to the fixing unit 30 of the present embodiment, the cover 60 includes the pressing portion 80. Therefore, when attaching the heating unit 40, the heating unit 40 can be pressed toward the attachment direction D1 by simply closing the cover 60, and the heating unit 40 can be accurately positioned and attached to the fixing unit 30.
Further according to the fixing unit 30 of the present embodiment, the cover 60 includes the cleaning unit 70. Therefore, when attaching and detaching the heating unit 40, members and mechanisms that contact the surface of the fixing belt 41 can be retracted, and the attaching and detaching of the heating unit 40 can be facilitated.
According further to the fixing unit 30 of the present embodiment, the second abutment surface 46b and the first abutment surface 46a are arranged continuously with different inclination angles. Therefore, the contact and pressing operations of the pressing roller 83 to the heating unit 40 can be performed continuously, and the heating unit 40 can be positioned smoothly to the attachment position.
The fixing unit 30 of the present embodiment described above has been illustrated of a case where both the heating roller 43 and the pressure roller 32 are driven by driving the drive motor M1, but the present technique is not limited thereto. For example, it is possible to have the pressure roller 32 driven by the drive motor M1 and the fixing belt 41 rotated following the rotation of the pressure roller 32. In that case, the heating unit 40 is pressed toward the sheet conveyance direction X, so that it is advantageous from the point of view of force to attach the heating unit 40 in the sheet conveyance direction X. According to the fixing unit 30 of the present embodiment, the attachment direction D1 of the heating unit 40 is set to a direction parallel to the sheet conveyance direction X of the recording material S nipped by the fixing nip portion N, so that it is also preferable in the case mentioned above.
Further, the fixing unit 30 of the present embodiment described above has been illustrated of a case where the cleaning unit 70 and the pressing portion 80 are provided to the cover 60, but the present technique is not limited thereto, and these members can be omitted. According further to the fixing unit 30 of the present embodiment described above, the cover 60 has been opened and closed by swinging motion, but the present technique is not limited thereto. For example, the cover 60 can be opened and closed by sliding motion.
Even further, the fixing unit 30 of the present embodiment described above has been illustrated using a belt as the first rotary member, but the present technique is not limited thereto, and for example, the first rotary member can be a roller. Moreover, the heating roller 43 can be omitted, and the heating source for heating the heating unit 40 can adopt a configuration of heating the first rotary member from an outer side of the heating unit 40.
Furthermore, the fixing unit 30 of the present embodiment described above has adopted a configuration where the heating unit 40 is attached to and detached from the fixing unit 30 independently from the pressing roller 32, but the present technique is not limited thereto, and a configuration can be adopted where the heating unit 40 and the pressure roller 32 are integrally attached to and detached from the fixing unit 30.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2020-083700, filed May 12, 2020 which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-083700 | May 2020 | JP | national |
