Patent Application
20230108172
The present exemplary embodiment relates to a fixing device that is mounted on an image forming apparatus, such as an electrophotographic recording type printer or copying machine, and fixes a toner image formed on a recording medium onto the recording medium.
An example of fixing devices is a film heating type fixing device having an excellent on-demand property. Such a fixing device is discussed in Japanese Patent Application Laid-Open No. 2016-114621.
In general, a conventional film heating type fixing device has a fixing nip portion that is formed between a film unit provided with a heater in an internal space of a tubular film and a pressure roller. The film heating type fixing device heats and fixes an unfixed toner image on a recording medium to the recording medium while pinching and conveying the recording medium by the fixing nip portion.
Both end portions of the film unit and the pressure roller are supported by a frame of the fixing device, and each of the both end portions of the film unit is urged toward the pressure roller with a spring, whereby the fixing nip portion is formed. A shaft of the pressure roller is rotatably supported by the frame, and a gear that receives a driving power from a motor is attached to a portion of the shaft outside the frame.
The present exemplary embodiment is directed to providing a fixing device having a frame with a specific structure.
According to an aspect of the present disclosure, a fixing device for fixing a toner image formed on a recording medium to the recording medium includes a film unit including a tubular film that is configured to rotate while being in contact with the recording medium, a roller configured to be in contact with an outer surface of the tubular film, wherein the roller and the film unit form a fixing nip portion configured to pinch and convey the recording medium on which the toner image is formed, and a frame that includes a first side frame configured to hold one end portion of the film unit in a longitudinal direction of the fixing device and includes a second side frame configured to hold the other end portion of the film unit in the longitudinal direction, wherein at least one of the first side frame and the second side frame includes a first plate configured to hold at least one of the film unit and the roller, and a second plate disposed substantially parallel to the first plate and having a surface facing the film unit, and wherein the first plate is fixed to the second plate and is disposed on a side of the surface of the second plate orthogonal to the longitudinal direction.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The desirable embodiments for carrying out the present disclosure will be illustrated as an example in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative locations of components described in the exemplary embodiments should be appropriately changed depending on a configuration of a device to which the present disclosure is applied and various conditions, and are not intended to limit the scope of the present disclosure to the following forms.
An overall configuration of an image forming apparatus 1 will be described with reference to
The image forming apparatus 1 includes a recording medium feeding unit and an image forming unit. In the recording medium feeding unit, recording media P are stacked in a cassette 2, and a recording medium P on the top of the recording media P is picked up one by one by a paper feed roller 3 and sent to a registration unit. After a posture of the recording medium P is aligned in a conveyance direction in the registration unit including a registration roller 4 and a registration driven roller 5, the recording medium P is fed to an image forming unit.
The image forming unit includes a photosensitive drum 6, a charge device 7 for charging the photosensitive drum 6, a development unit 8 for developing an electrostatic latent image formed on the photosensitive drum 6 with a toner, and a cleaner 9 for removing a residual toner on the photosensitive drum 6. The photosensitive drum 6 is rotationally driven in a direction indicated by an arrow in
The recording medium P on which the toner image is transferred is conveyed to a fixing device 13. The toner image on the recording medium P is heated and fixed to the recording medium P by the fixing device 13.
The recording medium P having passed through the fixing device 13 is discharged to a recording medium stacking unit 15 disposed on the top of the image forming apparatus 1 by a discharge roller pair 14.
The film unit 28 includes the film 20 in a tubular form, a heater 21 in a plate shape disposed in an internal space of the film 20, a heater holder 17, formed of a heat-resistant resin, such as a liquid crystal polymer and the like, for holding the heater 21, and a stay 22, formed of metal, for reinforcing the heater holder 17. The film unit 28 further includes two flanges F100 (see
The heater 21 is a ceramic substrate on which a heat generation resistor is printed. The heater 21 can be configured such that a surface of a metal substrate is insulated with a glass layer or the like and a heat generation resistor is provided on the glass layer or the like. A metal plate or the like can be interposed between the heater 21 and the film 20. The pressure roller 16 includes a shaft portion 18 and a rubber layer 19.
The fixing device 13 heats and fixes an unfixed toner image T on the recording medium P to the recording medium P while pinching and conveying the recording medium P by the fixing nip portion N in a recording medium conveyance direction indicated by an arrow A.
As illustrated in
Next, configurations around the side frames 23 and 24 will be described with reference to
An encoder 31 is disposed coaxially with the idler gear 30, and the encoder 31 rotates with rotation of the idler gear 30. An encoder sensor 32 is disposed in the fixing device 13 and detects a rotation speed of the pressure roller 16. The spring 34 for forming the fixing nip portion N urges the film unit 28 toward the pressure roller 16 via a pressurizing plate 33. The pressurizing plate 33 and the spring 34 are also disposed on the side of the side frame 24. An urging force of the spring 34 is applied to the pressurizing plate 33, the flanges F100, the stay 22, the heater holder 17, the heater 21, the film 20, and the pressure roller 16 in this order.
A cam 35 is disposed at a position opposite to a side of the pressurizing plate 33 on which the spring 34 is disposed. The cam 35 is coupled to a cam gear 36 and is fixed together with the cam gear 36 such that the cam 35 and the cam gear 36 do not rotate with respect to a cam shaft 37. A driving force is transmitted to the cam gear 36 from the main body of the image forming apparatus 1, and when the cam gear 36 rotates, the cam 35 pushes up the pressurizing plate 33 against the urging force of the spring 34. As a result of the pressurizing plate 33 being pushed up, a pressure applied to the fixing nip portion N is reduced (or eliminated). This makes it possible for a user to easily perform jam clearance of the recording medium P near the fixing nip portion N.
A cam 38 is also disposed on the side frame 24 illustrated in
A configuration of the side frames 23 and 24 having a specific structure according to the present exemplary embodiment will be described below.
As illustrated in
Due to an urging force of the spring 34, the bearings B100 abut against the edges 101C each forming a bottom surface of the corresponding U-shaped fitting portion.
Next, the side frames 23 and 24 will be described in detail with reference to
When the side frame 23 is assembled, each of fixing holes 102, 103, and 104 of the support frame 100, and each of fixing holes 201, 202, and 203 of the first main frame 200 are threaded on shafts of an assembly tool to position the support frame 100 and the first main frame 200 in a thickness direction. Further, while the support frame 100 and the first main frame 200 are pressed in the thickness direction of the frames, a laser is irradiated to weld the welded portions W. Similarly, when the side frame 24 is assembled, each of fixing holes 102, 103, and 104 of the support frame 100, and each of fixing holes 301, 302, and 303 of the second main frame 300 are threaded on shafts of an assembly tool to position the support frame 100 and the second main frame 300 in the thickness direction. Further, while the support frame 100 and the second main frame 300 are pressed in the thickness direction of the frames, a laser is irradiated to weld the welded portions W. While, in the present exemplary embodiment, the frames are positioned using the shafts provided in the assembly tool, any method can be used as long as accurate positioning can be performed, in a manner, for example, that positioning between the support frame 100 and the first main frame 200 and positioning between the support frame 100 and the second main frame 300 are performed by embossing and fitting holes.
According to the configuration of the present exemplary embodiment, it is possible to prevent heat generated from the fixing nip portion N from being transmitted to the pressure roller gear 29 and the idler gear 30, which are driving force transmission units disposed on the outside of the side frames 23 and 24. Specifically, the support frame 100, the first main frame 200, and the second main frame 300 are formed of galvanized steel plates, and a surface layer of each of the frames is an organic film. For example, a description is given of a case using a steel plate having the thermal conductivity of 60 Watts per meter-Kelvin (W/mK) in 1.0 millimeter (mm) thickness with an organic film having the thermal conductivity of 0.3 W/mK in 0.1 mm thickness on one side. Compared with a case where one galvanized steel plate is used, an amount of heat energy transferred outside the side frames 23 and 24 out of the amount of the heat energy generated from the fixing nip portion N is one-half (½) in the configuration according to the present exemplary embodiment. Further, due to an air gap between the support frame 100 and the first main frame 200 resulting from surface roughness of the support frame 100 and the first main frame 200 and an air gap between the support frame 100 and the second main frame 300 resulting from surface roughness of the support frame 100 and the second main frame 300, an actual contact area between the support frame 100 and the first main frame 200 and an actual contact area between the support frame 100 and the second main frame 300 are each reduced. As a result, contact thermal resistance is generated, the amount of heat energy transfer is further reduced, and thus, it is possible to prevent the heat from transferring to the pressure roller gear 29 and the idler gear 30.
In the present exemplary embodiment, the frames are welded to each other with fiber laser performed on limited areas, and thus, as compared to the case using continuous welding, it is possible to retain a large area of the organic film of the galvanized steel plate and further possible to increase a heat transfer prevention effect. A heat insulating structure is provided by the support frame 100 and the first main frame 200, and the support frame 100 and the second main frame 300 disposed in the vicinity of the fixing nip portion N, whereby heat diffusion can be efficiently suppressed or reduced. On the contrary, if the support frame 100 is disposed between the driving force transmission unit and the first main frame 200, the heat of the fixing nip portion N is transferred to the support frame 100 and is directly transferred to the driving force transmission unit.
While, in the present exemplary embodiment, the galvanized steel plates are used for the support frame 100, the first main frame 200, and the second main frame 300, a resin can also be used. While the support frame 100, the first main frame 200, and the second main frame 300 are welded by fiber laser, using screwing, crimping, bonding, engaging, or the like can be sufficient as long as the frames are fixed. However, to effectively utilize the contact thermal resistance, it is desirable to limit a close contact area between the frames. In the configuration of the present exemplary embodiment, the encoder sensor 32, the cam 35, the cam 38, and the flag sensor 40 are disposed on the side frames 23 and 24, and the support frame 100 is provided in each of the side frames 23 and 24, which is effective at preventing sensor malfunction and suppressing or reducing a cam abrasion. In a case where a member, such as the flag sensor 40 and the like, is not disposed on the outside of the side frame 24, the support frame 100 and the second main frame 300 can be configured as one frame without being separated. While, in the present exemplary embodiment, the pressure roller 16 is driven by the driving force transmission unit, a heat roller, if the film unit 28 is a high-rigidity heat roller, can be driven, for example.
Next, a configuration of a side frame according to a second exemplary embodiment will be described. In the present exemplary embodiment, as illustrated in
With the above-described configuration, it is possible to suppress or reduce heat transfer from the support frame 100 to the third main frame 400 by the air gap provided by the offset portion 401. Because air of the air gap is non-convective, the air gap can be used as a heat insulating layer. The air gap formed by the offset portion 401 is 0.3 mm in thickness and has an air thermal conductivity of 0.02 watts per meter-kelvin (W/mK). Compared with the first exemplary embodiment, the amount of heat energy transferred outside the side frame 41 out of the amount of heat energy generated in the fixing nip portion N is about one-twelfth ( 1/12). While, in the present exemplary embodiment, the third main frame 400 is provided with the offset portion 401, the support frame 100 can also have an offset shape to have an air gap.
Next, a configuration of a side frame according to a third exemplary embodiment will be described. In the present exemplary embodiment, as illustrated in
Even with such a configuration, if it is not possible to form the heat insulating structure around the pressure roller 16, heat insulation is still effective due to the support frame 500 and the support frame 600 positioning the film unit 28. In the present exemplary embodiment, a thickness of the air gap formed in the offset portions 702 and 703 is increased to 0.6 mm, which is twice the thickness of the air gap of the second exemplary embodiment, so that, even if the heat insulating area is reduced, the thickness of the heat insulating layer is increased, and thus, it is possible to suppress or reduce heat transfer to the driving transmission unit.
In the present exemplary embodiment, only the film unit 28 is supported by the support frame 500 and the support frame 600, which are separate components from the fourth main frame 700. Alternatively, a support frame configured to support only the pressure roller 16 can be provided as the support frame, and the support frame can be fixed to a surface of the fourth main frame 700 on the fixing nip portion N side. In addition, depending on an amount of heat generated from the fixing nip portion N, a convection direction of an air in the fixing device 13, and the like, only one of the support frame 500 and the support frame 600 according to the present exemplary embodiment and the fourth main frame 700 can be used to position the film unit 28.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure 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. 2021-163199, filed Oct. 4, 2021, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-163199 | Oct 2021 | JP | national |
