Patent Publication Number: US-6223005-B1

Title: Multi-level oiling device and process for a fuser system

Description:
BACKGROUND OF THE INVENTION 
     1. Related Applications 
     This application relates to contemporaneously filed applications Ser. No. 09/548,922, entitled “Constant Displacement Oil Web System and Method of Operating the Same”, and Ser. No. 09/548,922, entitled “Multi-Level Oiling Device Drive Mechanism”, both of which are expressly incorporated herein by reference. 
     2. Field of the Invention 
     The present invention relates to an electrophotographic imaging apparatus, and more particularly to a fuser oiling apparatus and the associated method involved with its use and operation. 
     3. Description of the Related Art 
     In an imaging apparatus, such as a laser printer using the electrophotographic process, an electrostatic image is created upon a photosensitive member, such as a roll or belt. Visible electroscopic marking particles, commonly referred to as toner, are applied to the electrostatic image on the photosensitive material. Thereafter, the toner is transferred to the desired media, which may include paper, transparency sheets or the like. 
     The toner image applied to the media is not permanent, however, until the toner is fixed by the application of heat. The toner is elevated in temperature sufficiently to cause constituents of the toner to become tacky, and flow into the pores or interstices between fibers of the media. Upon cooling, the toner again solidifies, causing the toner to adhere to the media. Pressure may be applied to enhance the flow of the toner, and thereby improve the subsequent bonding of the toner to the media. 
     Thermally fixing the electroscopic toner images commonly has been accomplished by passing the media, with the toner image thereon, through a nip formed by opposed rolls, at least one of which is heated internally. The heated roll, transferred thereafter elsewhere in the apparatus. The presence of wayward toner particles in the imaging apparatus can degrade the quality of the printed sheets. 
     To reduce sticking and toner offset to the fuser roll, fusers of the type described above commonly employ an apparatus for applying a release fluid to the surface of the fuser roll. The release fluid creates a weak boundary between the heated roll and the toner, thereby substantially minimizing the offset of toner to the fuser roll, which occurs when the cohesive forces in the toner mass are less than the adhesive forces between the toner and the fuser roll. Silicone oils having inherent temperature resistance and release properties suitable for the application are commonly used as release fluids. Polydimethylsiloxane is one such suitable silicone oil that has been used advantageously in the past. 
     Several methods and apparatuses have been used to supply oil to the fuser hot roll, including oil wicking systems, oil delivery rolls and oil webs. Oil wicking systems include reservoir tanks of the desired release agent or oil, and a piece of fabric wick material having one end mounted in the reservoir and the other end spring biased against the hot roll. Oil from the reservoir is drawn through the fabric wick by capillary action, and is deposited against the roll surface. While a wicking system can be effective in supplying oil to the fuser roll, surface deposit of the oil on the roll can be inconsistent, and the replenishment or replacement of the oil and/or system can be difficult and messy. Further, oil wicking systems can be designed only for a single oil delivery rate, determined by the rate of capillary action of the oil through the wick. By necessity, the delivery rate must be for the maximum oil demand for the print processes to be performed, and the media types to be used in the imaging apparatus. This can result in the over-application of oil under some conditions. 
     Oil delivery roll systems used in the past commonly include a roll nipped against the hot fuser roll, and either freely rotating against the fuser roll or driven against the fuser roll through a gear train. Oil delivered to the surface of the oil delivery roll is deposited on the hot fuser roll as the rolls rotate against each other. Various structures have been used for providing oil to the surface of the oil delivery roll, including reservoirs at the center of the roll, which may include a hollow tube filled with oil, providing oil to the surface through small tubes or via capillary action through the outer material. Felts or metering membranes may be used in the oil delivery roll to control the oil flow through the roll. Another style of oil delivery roll, referred to as a web-wrapped roll, includes high temperature paper or non-woven material saturated with oil, and wrapped around a metal core. Similarly to oil wicking systems, oil delivery rolls can be designed for a single delivery rate only, and can create excessive oil application under some operating conditions of the imaging apparatus. 
     Conventional oil web systems include a supply spool of web material, generally being a fabric of one or more layers saturated with the desired oil. Commonly, the web material is a non-woven fabric of polyester and aramid fibers, such as Nomex® manufactured by DuPont. A take-up spool is provided for receiving the used web. A web path, commonly including one or more guide rolls, extends from the supply spool to the take-up spool. A portion of the web path brings the web material into contact with the hot fuser roll, either by wrapping a portion of the web around the hot roll, or by utilizing a spring- loaded idler roll to nip the web material against the fuser roll. As the fuser roll rotates against the web in contact therewith, oil is transferred from the web to the fuser roll. Periodically, a drive mechanism for the take-up spool activates, rotating the spool and advancing web material from the supply spool to the take-up spool, thereby bringing a fresh section of web material into contact with the fuser roll. 
     Such conventional oil web systems can be used to deliver oil at a relatively constant rate with good uniformity. However, the oil flow is dependent on the amount of material brought into contact with the fuser roll over a given period of time. In oil web systems utilized heretofore, the simplified drive systems for the take-up roll have been operated for consistent durations at constant intervals throughout the life of the web system. Therefore, as spent material passes onto the take-up spool, and the diameter of the take-up spool increases, the linear length of material brought into contact with the fuser roll increases during each web advancement, thereby increasing the amount of oil deposited on the fuser roll. 
     An improved oil web system is described in our co-pending patent application entitled “Constant Displacement Oil Web System, And Method For Operating The Same” filed on even date herewith. In the improved system described therein, the problem of the incremental increase in the linear advancement of the web as the take-up spool diameter increases has been solved by adjustment of the drive mechanism operating cycle. However, the oil web system described therein also provides only a single oil application rate, regardless of the media type being printed. The design oil application rate must meet the maximum demand for oil required by the imaging apparatus design parameters, and can result in excess oil application under some conditions. 
     Excess oil on the fuser roll has undesirable effects. Since the paper passing through the fuser system generally carries away a portion of the oil deposited on the fuser roll, an excess amount of oil on the fuser roll, when picked up by the paper or other media, can cause an undesirable glossy appearance to the media. In duplexing systems, oil carried on the first printed side can be transferred to other areas of the imaging apparatus, when the media passes again through the apparatus for printing on the second side. Excessive amounts of oil deposited in other sections of the imaging apparatus can decrease print quality and otherwise produce undesirable operating effects. Additionally, unnecessary advancement of the web is wasteful, and shortens the useful life of the oiling system, necessitating replacement. 
     While excessive amounts of oil can result in problems and difficulties as mentioned above, controlling the amount of oil applied to the fuser roll can alter the appearance of the image on the printed sheet. It is often desirable that the printed image has glossiness similar to the glossiness of the media on which it is printed. Glossiness of the toner image is partially determined by the ease of release of the toner from the fuser roll. Therefore, if slightly more oil is applied to the fuser roll, a higher gloss can be achieved for the printed image as release of the toner from the fuser roll would be enhanced, and roughness of the toner image would be minimized. Conversely, if a duller or matte appearance is desired for the printed image, the use of slightly less oil on the fuser roll would result in a slightly increased tendency of the toner to adhere to the fuser roll, thereby creating the matte or dull look to the print. However, an adjustable oiling apparatus to control glossiness has not been available heretofore. 
     What is needed is a multi-level oiling device for an imaging apparatus fuser drum in which the application rate of oil can be varied, to more closely meet the requirements of the imaging apparatus operating conditions. More specifically, what is needed is an oil web system for an imaging apparatus in which the indexing increment length and frequency of the oil web can be varied to meet release demands of the media being processed, or the user preferences for printed appearance of the media. 
     SUMMARY OF THE INVENTION 
     The present invention provides an imaging apparatus having an oil web system employing a multi-level oil displacement rate for applying oil on the fuser roll. 
     The invention comprises, an oil carrying web provided on a supply spool; a take-up spool for spent web from which the oil has been transferred to the fuser roll; a drive mechanism for rotating the take-up spool; and one or more web guiding members defining a web path such that, along at least a portion of the path, the web material is brought into contact with the fuser roll. In accordance with one feature of the invention, a drive mechanism control receives input regarding the media type being processed through the imaging apparatus, and controls operation of the drive mechanism to minimize over-application of oil on the fuser roll. Media type information can be provided from media supply cassette data entered for each media supply cassette, from user input at the control panel or from media sensor data generated in the imaging apparatus. 
     In accordance with a second feature of the invention, the drive mechanism control receives input with respect to print copy glossiness preferences, and controls operation of the drive mechanism to apply more or less oil, to achieve the desired level of glossiness. The glossiness preferences can be pre-established or from preference data entered by the user at an interface panel. 
     An advantage of the present invention is the reduction of waste in the oil web system and the resulting prolonged life of the system. 
     Another advantage of the present invention is the control of printed sheet glossiness characteristics in response to user preferences. 
     Yet another advantage of the present invention is the minimization of oil dumps and, therefore, the reduction of oil carry over by printed media and resulting contamination of other portions in the imaging apparatus. 
    
    
     BRIEF DESCRIPTON OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a simplified schematic representation of an imaging apparatus in which the present invention may be used advantageously; 
     FIG. 2 is a simplified schematic representation of an oil web system; 
     FIG. 3 is a cross-sectional view of the oil web system shown in FIG. 2, taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a flow diagram schematic representation of a process control for an oil web system accordance with one aspect of the present invention; and 
     FIG. 5 is a flow diagram schematic representation of a process control for an oil web system in accordance with a second aspect of the present invention. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now more specifically to the drawings, and to FIG. 1 in particular, an imaging apparatus in the form of a laser printer  10  is shown, in which a multilevel oiling device and process of the present invention may be used advantageously. Laser printer  10  includes a fuser  12  and an oil web system  14  (FIG.  2 ), which is operated in accordance with a media requirements control process  16  shown in FIG. 4, a glossiness preference control process  18  shown in FIG. 5, or a combination thereof. 
     Laser printer  10  includes a printhead  20 , which, in known fashion, creates an electrostatic image on an image transfer belt  22 . Media from a media supply tray  24  or  36  is moved along a media path, which is indicated in the drawings by the arrows  26 , and includes processing through an image transfer nip  28  and fuser  12 . The media path includes a plurality of guide surfaces or belts  30  and guide rolls  32  to direct the media through printer  10 , ending at a media receiving zone  34 . The media path may further include a duplexing side path including an alternate path indicated by the arrows  38 . 
     Those skilled in the art will readily understand the manner in which printhead  20  creates an electrostatic image on a photosensitive member, such as the image transfer belt  22 . The image is further processed by the attachment of toner particles, which in a color printer may include particles of different colors. Thereafter, the toner image is transferred to the media sheets at image transfer nip  28 , and the sheet is processed through fuser  12 , wherein the image is fixed through the application of heat and pressure. 
     Fuser  12  includes a hot roll  42  and a backing roll  44 , creating a fuser nip  46  through which the media passes. Heat and pressure are applied to the media as it passes through fuser nip  46 . Oil web system  14  is provided to prevent sticking between the media and hot roll  42 , and to minimize toner offset to hot roll  42 . Oil web system  14  applies a release agent, such as silicone oil, to the surface of hot roll  42 . Oil on the surface of fuser hot roll  42  minimizes the sticking and toner off-set problems that can be encountered. 
     It should be recognized that the laser printer  10  shown in FIG. 1 is merely the representation of a suitable apparatus in which the present invention may be used advantageously. It should be further understood that other types of laser printers, other types of printers generally, and other types of imaging apparatus may advantageously use the present invention as well. Printer  10 , shown in FIG. 1, is merely one such device provided and described herein for ease of understanding the use of the present invention, and should not be considered as a limitation on the invention, nor on the claims to follow. 
     Oil web system  14  (FIG. 2) includes a material web  52  of suitable material for holding release agent. A non-woven fabric of polyester and aramid fibers, such as Nomex® manufactured by and available from DuPont, has been used advantageously in the past. The material is coated or saturated with a release agent, such as a silicone oil of polydimethylsiloxane or the like. Web  52  is a relatively thin elongated band of material stored on a supply spool  54  prior to its use in oil web system  14 . A take-up spool  56  is provided for receiving used or spent portions of web  52 . Between supply spool  54  and take-up spool  56 , material web  52  extends along a web path which is indicated in the drawings by arrows  58 . The web path is defined by web guiding members, which may include supply spool  54 , take-up spool  56  and other rolls or surfaces influencing the position of web  52 . Along at least a portion of the web path, web  52  is brought into contact with hot roll  42  of fuser  12 . Release agent is transferred from web  52  to hot roll  42  at an oil transfer nip  60 . In the embodiment shown, oil transfer nip  60  is created by the close proximity of a spring-loaded biasing roll  62  to hot roll  42 , which holds web  52  against hot roll  42  at oil transfer nip  60 . It should be understood that other arrangements may be used advantageously to bring portions of web  52  into contact with hot roll  42 . For example, two or more rolls may be used to position web  52  such that a segment of web  52  wraps a portion of hot roll  42 . Alternatively, the relative positions of a single idler roll and take-up pool  56  may be such as to cause a portion of web  52  to wrap a portion of hot roll  42 . 
     In oil transfer nip  60 , or other transfer area at which oil is deposited on hot roll  42 , the surface of hot roll  42  and web  52  move in opposite directions. As a result, tension is applied to web  52  between biasing roll  62  and take-up spool  56 , and, therefore, the roll up of the web  52  on take-up spool  56  is under tension. Tension in the roll-up creates a neat, clean wind up of web  52  on take-up spool  56 . Further, tension is relieved from the segment of web  52  between supply spool  54  and biasing roll  62 , to prevent an unintentional unwind of supply spool  54  and the resultant over application of oil on fuser hot roll  42 . 
     To effect transfer of web  52  from supply spool  54  to take-up spool  56 , a drive mechanism  64  is provided, which may include an independent, dedicated prime mover and gear train, a gear train from a common drive for other apparatus in the printer, a direct drive prime mover, or the like. The prime mover may be a stepper motor, a solenoid, or other positional activator. Such drive mechanisms are known in the industry, and will not be described in further detail herein. Operation of drive mechanism  64  is controlled by drive controller  66 , which transmits signals to drive mechanism  64 , including start and stop signals, via a signal pathway  68 . 
     In accordance with one embodiment of the aforementioned co-pending patent application entitled “Constant Displacement Oil Web System And Method Of Operating The Same” a web advancement sensor system  70  is provided. Web advancement sensor system  70  includes an idler shaft  72 , a web engagement portion  74  of idler shaft  72  and an encoder wheel  76  connected thereto. Idler shaft  72  is journaled in suitable bearings and/or bushings (not shown) to allow its relatively free rotation therein. Idler shaft  72  and engagement portion  74  are positioned in oil web system  14  such that engagement portion  74  is partially wrapped by web  52 . Commonly, this will be in the segment of web  52  between biasing roll  62  and take-up spool  56 , such that the tensioned portion of web  52  rotates the idler shaft as linear advancement of the web  52  occurs. 
     Encoder wheel  76  is connected to idler shaft  72 , or to engagement portion  74 , for rotation therewith. Encoder wheel  76  includes surface indicia, holes or the like, movement of which may be detected by an appropriate sensor. In the embodiment shown, a band or region  78  is provided near the periphery of encoder wheel  76 . Within the band or region  78 , a hole or opening  80  (FIG.  3 ), or a plurality thereof are provided, and may be in specific patterns or orientations. Although band or region  78  is shown in FIG. 2 as only a small segment on encoder wheel  76 , band or region  78  may extend along a greater portion or entirely around encoder wheel  76 , near the periphery thereof. A transmissive sensor of known design is used, and includes an emitter  82  disposed on one side of encoder wheel  76 , and a receiver  84  disposed on the side of encoder wheel  76  opposite emitter  82 . In known fashion, emitter  82  emits a beam of light, or the like, and receiver  84  is positioned to receive the emitted beam as it passes through hole or holes  80 . Thus, emitter  82  and receiver  84  are used to detect movement of encoder wheel  76 , as evidenced by the passage of hole or holes  80  through the area between emitter  82  and receiver  84 . From the frequency of passage of hole or holes  80 , or the recognition of the pattern of passing between emitter  82  and receiver  84 , the web advancement sensor system  70  provides a signal representative of the linear advancement of web  52 . 
     The structures and operations of appropriate sensors that may be used in the present invention, to ascertain the pattern or frequency of hole  80  passings are known for other uses, and will not be described in further detail herein. 
     Other types of web movement sensors may be used advantageously in the present invention. A system using an encoder wheel  76 , emitter  82 , and receiver  84  as shown and described is a preferred, low cost and accurate alternative. 
     In accordance with a first aspect of the present invention, advancement of web  52 , and application of oil to fuser hot roll  42 , are controlled with consideration to characteristics of the media being printed, as shown in media requirements control process  16 , shown schematically in FIG.  4 . In accordance with a second aspect of the present invention, advancement of web  52 , and application of oil to fuser hot roll  42 , are controlled with consideration to preferences for glossiness of the printed image, as shown in glossiness preference control process  18  in FIG.  5 . In each of processes  16  and  18 , drive controller  66  receives a web advancement data signal via a signal pathway  86  from the web advancement sensor system  70 , and processes the signal to determine the actual linear advancement of web  52 . Drive controller  66  transmits drive control signals via a drive control signal pathway  88  to drive mechanism  64 , to start and stop drive mechanism  66  for rotation of take-up spool  56 . 
     In media requirements control process  16  shown schematically in FIG. 4, drive controller  66  additionally receives data signals regarding the media type to be used. Different media have different print characteristics, and different tendencies to stick to the fuser hot roll  42 . Therefore, the need for oil on roll  42  differs from one media type to another. The media type information can be user entered data signals received by drive controller  66  via a signal pathway  90  from a user interface control panel  92 . Control panel  92  can be on the printer  10 , or may be a workstation or personal computer transmitting print job instructions from word processing software. Additionally, the media type information can be memory resident or stored data transmitted to drive controller  66  via a signal pathway  94  from a memory device  96 , such as encoded or stored information regarding the content of media supply tray  24 . As yet another alternative, the media type information can be sensor data signals transmitted to drive controller  66  via a signal pathway  98  from a media sensor  100  disposed in media path  26 . Controller  66  processes user entered data signals received on signal pathway  90 , memory resident or stored data signals received on signal pathway  94  and sensor data signals received on signal pathway  98 , together with stored look-up tables or the like, to determine the preferred oil application rate for the media being processed. Thus, release characteristics of the media can be considered in determining the need for oil application on fuser hot roll  42 . In conjunction with data signals received from signal pathway  86  regarding actual linear advancement of web  52 , drive controller  66  determines the appropriate interval and duration for indexing web  52 , and transmits drive control signals  88  to drive mechanism  64  based thereon. 
     In the glossiness preference control process  18  shown schematically in FIG. 5, drive controller  66  receives data signals regarding the desired glossiness of the image on the media being processed. The data may be user entered glossiness data signals transmitted via a signal pathway  102  from a user interface control panel  104 , similar to control panel  92 . Stored glossiness preference data signals also may be transmitted via a signal pathway  106  from a memory device  108  to apply preferences on glossiness characteristics that are established as part of equipment set-up. Drive controller  66  utilizes user entered glossiness data signals received via signal pathway  102 , and stored glossiness data signals received via signal pathway  106 , with stored information in the nature of look-up tables or the like, to determine the rate at which oil should be applied to fuser hot roll  42  to achieve the desired glossiness level. Encoder wheel signals received via signal pathway  86  are used to determine the actual performance of drive mechanism  64 . The actual performance data is used to generate drive control signals transmitted via signal pathway  88  relating to the frequency and duration of web advancement steps. 
     It should be understood that media requirements control process  16  and glossiness preference control process  18 , may be used independently of each other. Alternatively, for greater print quality control, the two control processes may be combined in a single process control, such that the appropriate indexing frequency and duration is determined by the drive controller  66  based on both the media type being used and the desired glossiness of the image. The individual characteristics of the media, as they affect both glossiness and sheet release from fuser hot roll  42  can be considered in determining the need for oil application. 
     Through use of the present invention, desired glossiness characteristics can be achieved and the appropriate amount of release agent can be applied for the media being processed and the desired level of glossiness on the media. Waste is reduced and machine contamination through over application of oil is minimized. 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.