Patent Application
20110103853
During operation of an image-forming device such as a laser printer or copier, a fuser permanently affixes toner particles to a media sheet in the final stage of a non-impact image-forming process. When fusing toner onto a substrate, the toner is heated to a point where the toner coalesces and appears tacky. The heat allows the toner to flow, thereby enabling it to coat the fibers or pores of the substrate. With the addition of pressure, an improved contact between the substrate and toner can be obtained. The heat and pressure required for fusing are achieved by a heated member and a pressure roller that under an applied force form a nip. Heat from the fuser melts the toner particles, while the applied pressure allows for absorption thereof into the media. Subsequent cooling of the toner, while it is in intimate contact with the substrate, allows it to adhere to the sheet.
The heater of the fuser may be mounted within a movable belt. During operation, stick-slip friction between the heating element and the belt introduces vibration and noise that prematurely wear the components and can affect image quality. While lubrication between the heater and belt can reduce the vibration and noise, it may be difficult to retain such lubrication in the desired location over time, under the heat and pressure of the components during ongoing operation of the device.
This problem is exacerbated over the life of the printer, as over time, the fuser lubricant migrates away from any high-pressure areas present on the heater glass.
One factor that has a significant effect on belt vibration noise is any uneven areas of the heater external surface which is in contact with the belt. Uneven areas of the heater can scrape the grease off the inside of the fuser belt and reduce the film thickness in the areas with high pressure contact. In addition, if the amount of waviness and/or unevenness in the outer surface of the heater is greater than the grease thickness, areas of contact between the outer heater surface and the fuser belt may undesirably operate with boundary layer lubrication and stick-slip may occur, thereby causing vibration and noise.
The conventional screening method used to make ceramic heaters leaves raised portions on the surface in the areas of the resistive traces.
Referring now to
Published references pertaining to fusers, ceramic heaters and related technology include U.S. Pat. Nos. 6,157,806, 6,818,290, 6,865,351, 6,870,140, 6,879,803, and 7,193,180, which are assigned to the assignee of the present application and hereby incorporated by reference into the application in their entirety.
Although the known fuser assemblies have some utility for their intended purposes, a need still exists in the art for an improved heater for a fuser assembly usable in electrophotography, as well as to methods of making such an improved heater.
Exemplary embodiments of the present invention provide an improved heater for a fuser assembly usable in electrophotography, as well as methods of making such an improved heater. An improved heater according to the exemplary embodiments exhibit improved flatness of an exterior surface thereof which comes into contact with a belt of the fuser.
The fuser includes a heater having a base component with at least one heating element disposed thereon. The heater further includes a covering layer covering the at least one heating element providing an outer surface to abut a belt. In addition, any unevenness on the outer surface is reduced by providing a filler material in low portions of the covering layer. The unevenness remaining in the outer surface of the heater is less than about 10 μm.
The features and advantages of the various exemplary approaches of this disclosure, and the manner of attaining them, will become more apparent and better understood by reference to the accompanying drawings, wherein:
It is to be understood that the following disclosure and claims are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrations. The disclosure is capable of other exemplary approaches and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.
In addition, it should be understood that exemplary approaches described herein include both hardware and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one would recognize that, in at least one exemplary approach, the electronic based aspects of the disclosure may be implemented in software. As such, it should be noted that a plurality of hardware and software-based devices, as well as a plurality of different structural components may be utilized to implement the exemplary approaches described herein. Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings merely provide exemplary approaches and that other alternative mechanical configurations are possible.
As shown in
The cartridges 22 include the same sub-elements and are only distinguished by the color of the toner contained therein. As depicted, the image-forming device 10 includes four cartridges 22, with colors black (K), magenta (M), Cyan (C), and yellow (Y). Each cartridge forms an individual mono-color image that is combined in a layered manner with images from the other cartridges to create the final multi-colored image. Each cartridge 22, which may be individually removable, includes a reservoir holding a supply of toner and a developer roller for applying toner to the respective photo-conductive drum 18. The photo-conductive drum 18 may be an aluminum hollow-core drum coated with one or more layers of light-sensitive organic photo-conductive materials. The drum 18 may be charged over its entire surface allowing for the imaging device 20 to discharge a portion of the surface with a laser beam 23, or the like. The discharged portion of the drum 18 corresponds to the image layer that will be covered with toner from the respective cartridge 22.
Toner is drawn by electrostatic force from the developer roll of the cartridge 22 to the discharged area of the drum 18. The endless intermediate transfer belt 24 rotates continuously in cooperation with the drums 18. A potential difference between the belt 24 and the drums 18 forces the toner particles from each of the drums onto the belt 24. The belt 24 and drums 18 are synchronized so that the toner from each drum precisely aligns to form the layered multi-colored image.
Media may be drawn from either the manual feeder 16 or the media tray 14 and delivered along the media path to the secondary transfer point 26. The timing of the media arrival is synchronized with the portion of the belt 24 carrying the completed image in order to transfer the toner from the belt to the media. At the secondary transfer point 26, the toner and the media move through an electric field at the exact point of transfer, or transfer nip 28, created between a positively-biased second transfer roller and a grounded backup roller. At the transfer nip 28, the negatively charged toner particles become sandwiched between the belt 24 and the media. The electric field between the second transfer roller and the backup roller, which form secondary transfer point 26, forces the toner to be released from the belt 24 and transferred onto the media. Subsequent to the toner transfer, the media passes through the fuser 34, which applies heat and pressure to permanently affix the toner to the media. A waste toner cleaner 36 removes any residual toner particles from the belt 24.
The above-described printing process may be controlled by a controller such as an electronic processor 38. While not depicted in detail, the processor 38 includes a processing unit and associated memory, and may be formed as one or more Application Specific Integrated Circuits (ASIC). The memory may be, for example, random access memory (RAM), read only memory (ROM), and/or non-volatile RAM (NVRAM). Alternatively, the memory may be in the form of a separate electronic memory (e.g., RAM, ROM, and/or NVRAM), a hard drive, a CD or DVD drive, or any memory device convenient for use with the processor 38. Regardless of the particular implementation, the memory provides a computer readable medium that may be encoded with computer instructions for controlling the processor 38 to carryout the printing process as well as the methods described below. The processor 38 may further include an I/O controller and I/O ports for communicating with an external computing or processing device. Moreover, computer instructions for implementing the image-forming process and the methods described herein may be provided to the device 10 via the I/O ports from a computer readable medium associated with the external processing device.
The belt 40 is an endless tube, which is continuously rotated by contact with the pressing roller 42 for fixing a toner image to a media substrate. The belt 40 is typically made of a highly heat resistive and durable material having good parting properties. The belt 40 typically has total thickness of not more than about 100 microns, and may be less than about 55 microns. The belt 40 is usually electrically conductive. It is understood that belt 40 may have any of a number of different layers and compositions, the details of which will not be further described herein for reasons of simplicity.
As shown in
A thin covering layer 62 (shown in
To facilitate the contact between the belt 40 and the surface of covering layer 62 of the heater assembly 50, a thin layer of grease (not shown) is disposed on the inner surface of the belt 40. The amount of grease is thin in relation to total thickness of belt 40, and is applied only in sufficient amounts within the fusing nip over the life of the fuser. In one exemplary approach, the full amount for that purpose may be applied during manufacture on the surface of covering layer 62.
Pressing roller 42 and heater assembly 50 of belt fuser 34 may be controlled by the processor 38. Heating assembly 50 may be operated at a temperature necessary to melt the toner in the fixing nip N, with the heat thereof transferring through the belt 40. The pressure from the pressure roller 42 causes the melted toner to substantially permanently adhere to the media sheet. As the media sheet exits the fixing nip N, the belt 40 peels away from the media, leaving the image deposited on the media, and the belt 40 then continues around the heater holder 52.
It is considered advantageous if the surface of heater assembly 50 that abuts belt 40 is substantially even in order to reduce stick-slip vibration noise. The substantially even surface should not have any areas of unevenness greater than about 10 μm valley-to-peak. In one exemplary embodiment hereof, the extent of unevenness present has a height in the range of about 0.1 μm to about 7 μm.
As stated above with respect to prior heater assemblies, the surface of heater assemblies has a level of unevenness which may undesirably cause vibration and noise and adversely impact the lifetime of the fuser belt. Referring now to
To compensate for the inevitable unevenness produced in the covering layer 62 due to the presence of heating elements 56 on base member 54, an additional unevenness reduction step may be performed. In particular, a filler material 70 may be added to the outer external surface of the covering layer 62. The filler material 70 fills low points in the outer surface of heater 150 and thereby reduces the amount of surface unevenness. Use of filler material 70 has been seen to reduce the amount of surface unevenness to a range of about 0.1 μm to about 7 μm. In one exemplary approach, as shown in
The filler material 70 may have a number of different compositions. For example, filler material 70 may be glass, a high temperature polymeric material, e.g., polyimide, or other suitable high-strength, heat tolerant and heat conductive materials known in the art.
In another exemplary approach, filler material 70 is added to all uneven surface regions along the surface of heater 150, as illustrated in
In still another exemplary approach, as shown in
Optionally, the above exemplary techniques may be combined, i.e., the peaks may be reduced or removed in an initial step, as described in the preceding paragraph, and then any remaining regions of unevenness may be filled in or covered over with an added exterior coating of filler material 70.
Accordingly, an improved heater for a belt-based fuser of an image-forming device 10 has been disclosed. In particular, the external surface of the heater which contacts the belt 40 should provide a substantially even surface. Any regions of unevenness which are present may be reduced by adding a step to the production of the heater assembly 50. Regardless of the particular approach selected, remaining regions of unevenness have been seen to be less than about 10 μm, and in particular between about 0.1 μm and about 7 μm.
The foregoing description of methods and exemplary approaches has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the below-listed claims to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the disclosure be defined by the claims appended hereto.
