Abstract:
A temperature sensing system for use in an electrographic printing machine senses temperature on a surface of a moving member. An intermediate roller is placed in operative contact with the surface of the moving member at a first location. A temperature sensor is then placed in operative connection with the intermediate roller at a location distanced and/or isolated from the moving member. A bias member is placed in operative contact with the temperature sensor to provide a force to the temperature sensor, resulting in the temperature sensor being biased against the intermediate roller, the temperature sensor thereby sensing the surface temperature of the moving member indirectly through the intermediate roller.

Description:
BACKGROUND 
       [0001]    The present application relates to an image reproduction machine such as an electrophotographic copying machine or printer and, more particularly, to a temperature sensing/controlling system of the image reproduction machine. 
         [0002]    In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface of the member. The charged portion of the member is exposed to selectively dissipate charges on the irradiated areas. This records an electrostatic latent image on the member. After the electrostatic latent image is recorded, the latent image is developed by bringing a developer material, such as toner, into contact with the latent image. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are heated to permanently affix the powder image to the copy sheet. 
         [0003]    In order to fix or fuse the toner material, it is necessary to elevate the temperature of the toner material to a point at which constituents of the toner material coalesce and become tacky. This action causes the toner to flow to some extent onto the fibers or pores of the copy sheet. Thereafter, as the toner material cools, solidification of the toner material occurs causing the toner material to be bonded firmly to the copy sheet. 
         [0004]    One approach to thermal fusing of toner material images onto the copy sheet has been to pass the copy sheet with the unfused toner images thereon between a pair of opposed roller members at least one of which is internally heated. During operation of a fusing system of this type, the copy sheet to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the heated fuser roll to thereby affect heating of the toner images within the nip. 
         [0005]    In order to insure a fuser functions at desired operating temperatures, a temperature sensing/controlling system including a thermistor or some other type temperature sensing device is employed. Conventionally, the temperature sensing/controlling device or devices physically engage the surface of the fuser member which most commonly comprises a pair of roller members. One such fuser utilizes an internally heated fuser roll. As will be appreciated, the heated fuser member may be heated using an external source. 
         [0006]    The physical engagement of the temperature sensor/controller to a cylindrical roller, such as a fuser roller results in a friction, such as a sliding friction, on the surface of the cylindrical roller. Such friction causes wear on the surface of the roller and leads in one instance to printing artifacts and necessitates replacement of the roller or other parts. 
         [0007]    Following is a discussion of prior art, incorporated herein by reference, which may bear on the patentability of the present application. In addition to possibly having some relevance to the question of patentability, these references, together with the detailed description to follow, may provide a better understanding and appreciation of the present concepts. 
         [0008]    U.S. Pat. No. 4,821,062 granted to Katoh et al. on Apr. 11, 1989 discloses a heat fixing device which includes a temperature sensing element and temperature control element which are integrally combined. 
         [0009]    U.S. Pat. No. 5,019,692 granted to Nbedi et al. on May 28, 1991 discloses a thermostatic device including a rotatable roller mountable in rolling engagement with a moving surface. 
         [0010]    U.S. Pat. No. 5,281,793 granted to Gavin et al. on Jan. 25, 1994 discloses an apparatus with a resistance reducing mechanism, interposed between the apparatus and a moving object or roller, for reducing frictional resistance between the apparatus and the moving object. 
         [0011]    U.S. Pat. No. 5,475,200 granted to Amico et al on Dec. 12, 1995 discloses a thermistor assembly wherein a wear resistant member is loosely disposed about a thermistor in contact with a thermistor bead such that it is between the bead and a heated fuser member and completely surrounds the components of the thermistor. The wear resistant member is in the form of a strap or tape having an opening adjacent one end through the opposite end is insertable. 
         [0012]    U.S. Pat. No. 5,666,593 granted to Amico et al. on Sep. 9, 1997 discloses a temperature sensor with one or more Resistance Temperature Detector (RTD) sensors embedded in a polyimide material. 
       BRIEF DESCRIPTION 
       [0013]    A temperature sensing system for use in an electrographic printing machine senses temperature on a surface of a moving member. An intermediate roller is placed in operative contact with the surface of the moving member at a first location. A temperature sensor is then placed in operative connection with the intermediate roller at a location distanced and/or isolated from the moving member. A bias member is placed in operative contact with the temperature sensor to provide a force to the temperature sensor, resulting in the temperature sensor being biased against the intermediate roller, the temperature sensor thereby sensing the surface temperature of the moving member indirectly through the intermediate roller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a cross-sectional view of a heat sensing device of the prior art; 
           [0015]      FIG. 2  is a side-view of another embodiment of a heat sensing device of the prior art; 
           [0016]      FIG. 3  is a cross-sectional view of one of the heat sensors of  FIG. 2 ; 
           [0017]      FIG. 4  is a schematic view of a heat sensing device of the present application; 
           [0018]      FIG. 5  is a side view of the system of  FIG. 4 ; 
           [0019]      FIG. 6  is a schematic view of another embodiment of a heat sensing device of the present application; 
           [0020]      FIG. 7  is a schematic view of still another embodiment of a heat sensing devise of the present application; and 
           [0021]      FIG. 8  is a schematic view of a temperature sensing system of the present application used in connection with a belt system. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  is a cross-sectional view of a prior art temperature sensing device  10  for an image reproduction machine such as an electrophotographic copying machine or printer. 
         [0023]    The temperature sensing system  10  of  FIG. 1  is shown in use with a moving member such as a cylindrical heat roller (fuser roller)  12  coated with a heat resistive resin such as Teflon or the like. Within the cylindrical roller  12 , an inner heater  14  is provided for generating heat to the cylindrical roller  12 . A second roller (not shown) coated with, for example, a silicone rubber is forced against the cylindrical roller  12 . A copied paper passes through the clearance between the cylindrical roller  12  and the second roller, during which a toner image is heat fixed onto the copied paper. 
         [0024]    Provided at the peripheral surface of the cylindrical roller  12 , as part of temperature sensing system  10 , is a temperature sensing element  16 , such as a thermistor, for sensing the temperature of the heat fixing device. 
         [0025]    A temperature control element such as a thermostat  20  is integrally combined with the thermistor  16 . The thermostat  20  is for preventing an abnormal temperature increase in the fixing device. The thermostat  20  is secured on a plate  22  for stressing the thermostat  20  and the thermistor  16  toward the surface of the cylindrical roller  12 . The plate  22  is supported by a body frame  24  of the image reproduction machine and can electrically move toward the cylindrical roller  12 . A pair of springs  24  are provided for forcing the combination of the thermistor  16  and the thermostat  20  toward the cylindrical roller  12 . 
         [0026]      FIG. 2  illustrates another embodiment of an existing temperature sensing system  30  of a copying machine or printer including moving members such as a fusing roller  32  and a pressure roller  34  (not shown in  FIG. 1 ). The rollers or moving members typically have surfaces which have good release characteristics and may be coated with silicone oil to prevent offset of toner onto either roller. Pressure roller  34  is shown as a hard metallic roller which is internally heated. Fusing roller  32  has a somewhat compliant outer layer or layers  36  made of a material such as silicone rubber or other material which is compliant enough to form a nip of some width with pressure roller  34 . Outer layer or layers  36  are positioned on a core  38  which generally is of aluminum, glass or similar hard material. Because the compliant material layer or layers  36  do not conduct heat as well as metallic pressure roller  34 , the surface of fusing roller  32  is heated by a pair of metallic heating rollers or moving members  40  and  42  which are heated internally by lamps  44  and  46 . 
         [0027]    With continuing attention to  FIG. 2  temperature sensing system  30 , includes a roller type temperature sensor  48  carried on carrier  50 , and where sensor  48  is configured with internal components to sense and control the temperature of rollers  34 ,  40  and  42 . Turning to  FIG. 3 , shown is an internal view of the roller temperature sensor  48 , along with carrier  50 . The configuration includes heat insulative support  52 , along with a ceramic pin  54  positioned in a hole in support  52 , with an end which rests directly against the inner surface of roller  48 . The other end of ceramic pin  54  engages part of a switch  56  held by pin  54  in an open condition in  FIG. 3 . Support  52  includes end extensions  58  and  60  which have cylindrical outer bearing surfaces  62  and  64  coaxial with roller  48 . 
         [0028]    Support arms  66  and  68  include ball bearings  70  and  72  which engage bearing surfaces  62  and  64  on extensions  58  and  60  and hold support  52  for rotation with respect to arms  66  and  68 . 
         [0029]    Switch  56  is made up of first and second switching members  74  and  76  which are held in slots in support  52  in positions in which they are resiliently urged toward a closed position. The ends of members  74  and  76  away from their contacts include contact elements  78  and  80  positioned on outside lateral faces of extensions  58  and  60 . Although contact elements  78  and  80  are shown as separate metallic elements in electrical contact with switch members  74  and  76 , they could, of course, be made from single pieces with members  74  and  76  appropriately folded. Arms  66  and  68  contain arm contacts  82  and  84  resiliently urged by means not shown into contact with contact members  78  and  80 . 
         [0030]    Turning to  FIG. 4 , a temperature sensing system  90  according to the present application is provided and configured to eliminate dragging type friction known to damage moving members, such as cylindrical roller  12 . In the embodiment of  FIG. 4 , temperature sensing system  90  includes elements similar to the device of  FIG. 1 , including temperature sensing element  16 , which may be a thermistor or other appropriate component for sensing the temperature of cylindrical roller  12 . In addition, thermistor  16  may be attached to thermostat  20 . Thermostat  20  is secured to plate  22  in a manner to stress thermostat  20  and thermistor  16  toward the surface of cylindrical roller  12 . Plate  22  is supported by body frame  24 . An additional configuration in connection with temperature sensing system  90  of  FIG. 4  is the inclusion of intermediate, rotatable cylindrical element  92  interposed between temperature sensing element  16  and the surface of cylindrical roller  12 . As may be appreciated from the foregoing discussion of  FIG. 1 , undesirable artifacts and other damage may be caused to the surface of cylindrical roller  12  when the temperature sensing element  16  is in contact to the surface of cylindrical roller  12 , as movement of cylindrical roller  12  results in a rubbing contact of temperature sensing element  16  with the moving surface, causing wear on the surface of cylindrical roller  12 . 
         [0031]    By interposing intermediate roller  92 , this rubbing contact, which causes sliding friction, is replaced with a rolling friction, resulting in much less stress being placed upon the surface of cylindrical roller  12 . Thus, in this embodiment the temperature sensor, e.g., thermistor  16 , is placed in an arrangement to contact the intermediate roller  92  and to measure the temperature of the surface of cylindrical roller  12  indirectly through intermediate roller  92 . The arrangement of  FIG. 4  also illustrates temperature sensor  16  and cylindrical roller  12  are distanced and/or isolated from each other. 
         [0032]    This embodiment uses a simple configuration of the intermediate cylindrical roller. There are no internal mechanisms or components within intermediate roller  92 . Rather, the transmission of the sensed temperature is undertaken by others of the previously noted components. 
         [0033]    A benefit of this embodiment therefore is the simplicity with which it may be incorporated into existing systems as a retrofit. For example, as shown in  FIG. 5 , the intermediate roller  92  may be integrated into the system by a simple shaft  94  and pin  96  arrangement, where the intermediate roller  92  is held in place by its interconnection to shaft  94  extending from a bracket  98 . 
         [0034]    Turning to  FIG. 6 , illustrated is another embodiment of the concepts according to the present application. In this embodiment, the temperature sensor  100  is formed to match the circumference of the intermediate roller  92 . 
         [0035]    Turning to  FIG. 7 , depicted is a further embodiment where the temperature sensor  102  is a bead type heat sensing component. In this design, bead portion  102  is placed in contact with the intermediate roller  92 . 
         [0036]    Turning to  FIG. 8 , depicted is still a further embodiment of the present application, wherein the temperature sensing device  16  is used to sense the temperature of a moving belt  104 , indirectly through intermediate roller  92 . 
         [0037]    It is to be appreciated that the embodiments shown in the Figures are not intended to limit the concepts of the present application, but use of an intermediate cylindrical roller to transform a system imparting the sliding friction on a moving member during a sensing operation to a rolling friction may be implemented in a number of embodiments. As also mentioned, due to the simple construction of the system, for example, the uncomplicated design of the intermediate roller  92 , retrofitting of existing systems is simplified, as well as incorporation of the present components into existing designs of newly manufactured systems. 
         [0038]    It is also to be appreciated that intermediate roller  92  may be composed of a number of different materials, including a plastic coated with an outer surface of metal, a ceramic roller, or a roller with a metal interior having a silicon outer surface, among others. Whichever materials are used, they would preferably permit heat transferred from the moving surface of the machine, e.g., cylindrical roller  12 , to be measured indirectly through the heat absorbed by intermediate roller  92 . It is to be appreciated that in some instances the heat or temperature of the intermediate roller  92  may be a percentage of the heat or temperature on the surface of cylindrical roller  12 . In these cases, the percentage may be obtained through simple trial-and-error testing. However, many materials which may be used to configure the intermediate roller  92  will cause a de minimus heat loss. In these designs the heat or temperature sensed on the intermediate roller  92  may be directly used. Also the temperatures of interest in many uses are within a range and the exact temperature of cylindrical roller  12  is not needed. Additionally, intermediate roller  92  may be configured in a cylindrical form, spherical form, or other configuration, which provides rolling friction to the surface of the cylindrical roller  12 , or other appropriate roller. 
         [0039]    It is also to be appreciated while the foregoing discussion has focused on the use of the temperature sensing systems of the present application in connection with an electrophotographic device and fuser rollers of such a device, the concepts are equally applicable to other rollers within a copy machine or printer. 
         [0040]    It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.