Abstract:
A speed control mechanism for a reproduction apparatus including a fuser assembly having pressure, applying members in nip relation to apply pressure to a receiver member bearing a marking particle image to fuse such marking particle image to such receiver member transported through the fuser assembly. The speed control mechanism has an input device for storing parameters required for fusing particular types of receiver members under various desired conditions, and a device for determining fuser control parameters, including overdrive effect, based on information from the input device and selection of a particular receiver member type and certain conditions. A fuser assembly controller then sets fusing parameters based on the determination by the determining device, and adjusts the transport speed of a receiver member through the fuser assembly to compensate for the determined overdrive effect.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates in general to a fuser assembly for an electrographic reproduction apparatus, and more particularly to a receiver member speed control through the fuser assembly.  
       BACKGROUND OF THE INVENTION  
       [0002]     In typical commercial reproduction apparatus (electrostatographic copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged charge-retentive or photoconductive member having dielectric characteristics (hereinafter referred to as the dielectric support member). Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric support member. A receiver member, such as a sheet of paper, transparency or other medium, is then brought into contact with the dielectric support member, and an electric field applied to transfer the marking particle developed image to the receiver member from the dielectric support member. After transfer, the receiver member bearing the transferred image is transported away from the dielectric support member, and the image is fixed (fused) to the receiver member by application of heat and pressure to form a permanent reproduction thereon.  
         [0003]     One type of fuser assembly for typical reproduction apparatus includes at least one heated roller, having an aluminum core and an elastomeric cover layer, and at least one pressure roller in nip relation with the heated roller. The fuser assembly rollers are rotated to transport a receiver member, bearing a marking particle image, through the nip between the rollers. The pigmented marking particles of the transferred image on the surface of the receiver member soften and become tacky in the heat. Under the pressure, the softened tacky marking particles attach to each other and are partially imbibed into the interstices of the fibers at the surface of the receiver member. Accordingly, upon cooling, the marking particle image is permanently fixed to the receiver member.  
         [0004]     In the fuser assembly, at least one of the fuser and pressure rollers is compliant. Further, one of the fuser and pressure rollers, is driven by a driving motor (designated as the driving roller), and the other roller is driven by the friction in the nip (designated the driven roller). In the nip region, the compliant, uncompressible materials on the fuser and/or the pressure rollers are stressed and strained under pressure. This causes a phenomenon called “overdrive,” in which a segment along a linear element on the compliant surface of the roller in the nip region goes faster than a segment along a linear element on the free surface of the roller. The thicker the compliant, uncompressible material on a roller, the more the overdrive. The overdrive causes the receiver member being transported in the nip to go faster than the roller free surface speed.  
         [0005]     Once the thickness of the compliant, uncompressible materials on the fuser and pressure rollers are determined, the factor that can affect the overdrive the most is the pressure applied to the fuser/pressure roller nip, or equivalently the nip width. In the process of fixing the toner image permanently to the receiver, it is sometime necessary to adjust nip width for different receiver member thickness, different image gloss level, and/or compensating temperature variation. This can cause varying receiver member speed through the fuser assembly. Because the reproduction apparatus process speed is usually fixed, this varying receiver member speed through the fuser assembly may cause speed mismatch with the surrounding reproduction apparatus sub-systems and components. The resultant speed mismatch problem may include pulling/pushing of the receiver member, distortion to the image and/or the receiver member, triggering false jam detection, or actually causing a jam. Therefore, there is a need to compensate for this speed variation at fusing station.  
       SUMMARY OF THE INVENTION  
       [0006]     It is the purpose of this invention to compensate for receiver member speed variation through a reproduction apparatus fuser assembly due to overdrive characteristics of the driving roller of the fuser assembly, obtained experimentally or analytically, by adjusting the driving motor speed based on the load (or pressure, nip width). A speed control mechanism is provided for a reproduction apparatus including a fuser assembly having pressure applying members in nip relation to apply pressure to a receiver member bearing a marking particle image to fuse such marking particle image to such receiver member transported through the fuser assembly. The speed control mechanism has an input device for storing parameters required for fusing particular types of receiver members under various desired conditions, and a device for determining fuser control parameters, including overdrive effect, based on information from the input device and selection of a particular receiver member type and certain conditions. A fuser assembly controller then sets fusing parameters based on the determination by the determining device, and adjusts the transport speed of a receiver member through the fuser assembly to compensate for the determined overdrive effect. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in which:  
         [0008]      FIG. 1  is a schematic illustration of an exemplary reproduction apparatus, with portions removed to facilitate viewing, such reproduction apparatus including a fuser assembly utilizing a receiver member speed compensation control according to this invention;  
         [0009]      FIG. 2  is a schematic side elevational view of the fuser assembly of  FIG. 1 , utilizing a receiver member speed compensation control;  
         [0010]      FIG. 3  is a graph of fuser assembly nip load vs. receiver member overdrive;  
         [0011]      FIG. 4  is a graph of fuser assembly nip width vs. receiver member overdrive; and  
         [0012]      FIG. 5  is a flow chart of the receiver member speed compensation control according to this invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     An exemplary reproduction apparatus, designated generally by the numeral  10 , is schematically shown in  FIG. 1 . The reproduction apparatus  10  includes a plurality of printing modules  12   a  through  12   d,  which enable the reproduction apparatus  10  to produce color prints. In each of the printing modules  12   a  through  12   d,  a uniform charge, is deposited by any suitable charging device  14  on a charge-retentive or photoconductive member having dielectric characteristics (hereinafter referred to as the dielectric support member  16 ). A latent image charge pattern (e.g., a color separation image) is formed on the uniformly charged dielectric support member  16  by any suitable exposure device, such as an LED print head  18 . Correspondingly colored pigmented marking particles in an associated developer station  20  are attracted to the latent image charge pattern to develop such image on the respective dielectric support member  16 . The developed image is transferred to an intermediate transfer member  22 . A receiver member R, such as a sheet of paper, transparency or other medium, is transported by a moving belt  24  into contact with the intermediate transfer member  22  of each of the printing modules  12   a  through  12   d,  and an electric field is applied to respectively transfer the marking particle developed images to the receiver member R from the intermediate transfer member to form a full color print.  
         [0014]     After transfer, a receiver member bearing the transferred composite image is transported by belt  24  away from the last printing module to a fuser assembly  26  where the composite image is fixed (fused) to the receiver member by application of heat and pressure to form a permanent reproduction thereon. The speed of the fuser roller is controlled by a drive motor  64 . A main reproduction apparatus controller  60  receives data from an input data storage device  60   a.  The input data includes parameters required for fusing particular receiver members under various conditions, and provides such parameters based on the particular receiver member, for transmission to a fuser assembly controller  62 . The parameters can include nip pressure, nip width, temperature, and transport speed, which may vary for each receiver member type and desired operating condition such as the desired gloss for example. The fuser assembly controller  62  can then get, or calculate, the load or nip required for proper fusing. The controllers  60  and  62  may be any suitable well-known microprocessor-based devices capable of processing input data, determining related operating parameters, and setting the required fuser assembly control based on the determined parameters. Of course, the controllers  60  and  62  could, alternatively, be combined into a single controller. Thereafter, the print is transported to a remote collection location by any suitable transport mechanism  28 .  
         [0015]     The fuser assembly  26  for the reproduction apparatus  10  is best shown in  FIG. 2 . The roller fuser assembly  26  includes a fuser roller  30 , a pressure roller  32 , and other necessary sub-systems and components (not shown). The fuser roller  30  (or both rollers  30  and  32 ) is heated internally (for example by respective lamps  34 ,  36 ), and/or externally for example by heater rollers (not shown), to pre-set temperatures. When fusing prints on receiver members R, the fuser roller  30  and the pressure roller  32  are pressed together to form a nip, and rotation of the rollers drive receiver member prints through the nip. In the nip, heat energy stored in the fuser roller  30  is transferred to the prints, and heats up and melts the marking particle image carried by a receiver member. Under the influence of the temperature and pressure, the marking particle print image is fixed on the receiver member R.  
         [0016]     Generally the fuser roller  30  has a metal core  38 , a compliant uncompressible base cushion  40 , and a thin release topcoat  42 . The base cushion  40  is formed of an elastomeric material. A thicker base cushion makes the geometry in the nip area more favorable for the receiver member R to be released from the fuser roller  30 , but makes the heat more difficult to transfer from the metal core  38  to the outer surface of the topcoat  42 .  
         [0017]     As noted above, because of the nature of the compliant, uncompressible materials of the fuser roller  30 , in the nip region, the fuser and/or the pressure rollers are stressed and strained under pressure. As a result, a receiver member passing through the nip is subject to overdrive due to the fact that a segment along a linear element on the compliant surface of the roller in the nip region goes faster than a segment along a linear element on the free surface of the roller. The thicker the compliant, uncompressible material on a roller, the more the overdrive effect. The overdrive effect causes the receiver member being transported through the nip to go faster than the roller free surface speed.  
         [0018]      FIG. 3  is a graph showing a load-overdrive curve  50  of one example case. As can be determined from the curve  50 , as the load in the fuser nip region increases, the overdrive effect increases. Particularly, a load in the nip of approximately 15 pounds per linear inch yields an overdrive effect increase of approximately 6%; and a load in the nip of approximately 60 pounds per linear inch yields an overdrive effect increase of approximately 13%. As stated above, pressure in the nip directly impacts the nip width. That is to say, as the pressure increases the nip width increases. Accordingly, as shown in  FIG. 4 , a curve  52  therein represents a nip width-overdrive effect relationship of one example case. Particularly, a nip width of approximately 0.55 inches yields an overdrive effect increase of approximately 6%; and a nip width of approximately 0.85 inches yields an overdrive effect increase of approximately 13.5%. Knowing the overdrive effect enables an equivalent speed compensation to be calculated.  
         [0019]     Referring to  FIG. 5 , a flow chart of the control process in order to compensate for receiver member speed variation through a reproduction apparatus fuser assembly due to the overdrive effect characteristics of the driving roller of the fuser assembly, designated generally by the numeral  200 , is shown. It is noted that other minor factors that may affect the overdrive effect, such as roller temperatures, oil amount, paper type and surface coat type, can also be included in the control process. When it is determined that a receiver member R is being transported to the fuser assembly  12  (step  201 ), a main reproduction apparatus controller  60  receives data from an input data storage device  62   a  for the physical characteristics of the particular receiver member (step  202 ) for transmission to a fuser assembly controller  62 . The fuser assembly controller  62  can then get, or calculate, the load or nip required for proper fusing (step  203 ). As noted above, the two controllers could be combined into a single controller. According to the determined nip load or nip width, the fuser assembly controller  62  calculates the overdrive effect compensation requirement (step  204 ).  
         [0020]     Once a previous receiver member has passed through the fuser assembly roller nip, and the fuser roller  32  and the pressure roller  34  are in direct nip contact (that is, are within the inter-frame between the previous receiver member and a subsequent receiver member (step  205 )), the fuser assembly controller  62  adjusts the speed of the fuser roller drive motor  64  (step  206 ) by decreasing the motor speed by an appropriate percentage, such as determined from the graphs of  FIG. 3  or  FIG. 4 . Of course, depending on operating parameters, and system geometry, overdrive speed compensation could require that the fuser roller drive motor increase the fuser roller speed. When such subsequent receiver member then arrives at the nip, it will be controlled to be transported at a proper (compensated) speed. It has been found that the overdrive compensation range needs to be controlled at least from about 6% to 14%. Additionally, other adjustments of the fuser roller assembly nip or other normal fuser assembly tasks, can be accomplished by the fuser assembly controller  62  substantially with the motor speed adjustment (step  207 ).  
         [0021]     As a result of the receiver member speed compensation control according to this invention, receiver members are transported smoothly through the fuser assembly. Reliability of the receiver member transport is markedly improved by substantially reducing the speed mismatch problem so that pulling/pushing of the receiver member is prevented, as is distortion to the image and/or the receiver member. Furthermore, there is no triggering of false jam detection, or actual jams.  
         [0022]     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.  
       Parts List  
       [0000]    
       
           10  Reproduction apparatus  
           12   a - 12   d  Printing modules  
           14  Charging device  
           16  Dielectric support member  
           18  LED print head  
           20  Developer station  
           22  Intermediate transfer member  
           24  Moving belt  
           26  Fuser Assembly  
           28  Transport mechanism  
           30  Fuser roller  
           32  Pressure roller  
           34 ,  36  Lamps  
           38  Metal core  
           40  Base cushion  
           42  Release topcoat  
           50  Load—overdrive curve  
           52  Nip width overdrive curve  
           60  Main reproduction apparatus controller  
           60   a  Input data storage device  
           62  Fuser assembly controller  
           64  Drive motor  
           200  Flow chart  
           201 - 207  Flow chart steps  
          R Receiver member