Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuser device used with an imaging system for setting toner on a recording media, and more especially to a fuser device which can tension a film based on a control structure. 
     2. Description of Related Art 
     Fuser devices are used in electronic imaging apparatus such as laser printers, copier and so on for setting toner, which is coated on thermally conductive thin films, on paper under proper pressure at proper temperature. 
     Please refer to  FIG. 1  illustrating a fuser device for an imaging system disclosed in U.S. Pat. No. 5,525,775. The fuser device include a pressure roller  10   a,  a thin film guiding element  13  and a heater  19  disposed on a bottom of an insulating base  20   a.  The thin film guiding element  13  includes a flat-bottom portion  14 , a front supporting wall  15  and a rear supporting wall  16 . The front supporting wall  15  and the rear supporting wall  16  extend longitudinally from two ends of the flat-bottom portion  14  respectively and are arc-shaped. A thermally conductive thin film  21   a  covers the thin film guiding element  13 . 
     When printing, the pressure roller  10   a  turns in the anticlockwise direction and drives the thermally conductive thin film  21   a  to turn in the clockwise direction, thereby driving paper P to pass through the fuser area between the heater  19  and the pressure roller  10   a.  The heater  19  gives out heat and transfers the heat to the paper P and the toner Ta through the thermally conductive thin film  21   a  after electrodes (not shown) of the heater  19  are electrified. Under the influence of the heat and the pressure from the pressure roll  10   a,  the toner Ta melts to be set on the paper P. 
     In the course of printing, the thermally conductive thin film  21   a  contacts with the front supporting wall  15  in an area B. The contact in the large area causes the wear of the thermally conductive thin film  21   a  relative to the thin film guiding element  13 . 
     Additionally, the thermally conductive thin film  21   a  is affected by the tensile force only in the area A and the area B, and is in the tension relaxation state in the other areas. Since the tensile force on the thermally conductive thin film  21   a  varies, the movement of the thermally conductive thin film  21   a  is unstable, so that the portion of the thermally conductive thin film  21   a  which contacts with the paper P has unstable dynamic characteristics when it enters and leaves the fuser area, which affects the set quality of the toner. Also, the contact force between the thermally conductive thin film  21   a  and the thin film guiding element  13  is unstable, so the thermally conductive thin film  21   a  and the thin film guiding element  13  collide with each other, thereby their wear increases. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a fuser device used with an imaging system for setting toner on a recording media. The fuser device includes a control structure, and controls tension force of a thin film via the control structure to maintain contact force between the thin film and its supporting elements, so that the thin film can keep in a stable operating state during heating and printing to improve the print image quality and solve the problem that the set quality of the toner is affected by the wear of the thin film and the unstable state of the thin film caused by its tension force. 
     To achieving the above-mentioned object, a fuser device in accordance with the present invention is provided. The fuser device includes a heating element; a rolling piece for exerting pressure on the toner adhered on the recording media; a film for clamping the recording media with the rolling piece, the film being in the heat of the heating element to set the toner on the recording media; and a control structure having a base piece on which a first engaging portion and a second engaging portion are disposed, wherein the heating element, the first engaging portion and the second engaging portion form a loop and the film surrounds the loop. 
     Preferably, a connecting portion is disposed on the base piece, and the second engaging portion is located between the first engaging portion and the connecting portion; and the control structure further includes an elastic piece coupled with the connecting portion and the imaging system for exerting pressure on the base piece and controlling the contact force between the film and the heating element, and between the first engaging portion and the second engaging portion. 
     Preferably, the elastic piece is a spring. 
     Preferably, the first engaging portion is rotatably disposed on the base piece. 
     Preferably, the second engaging portion is rotatably disposed on the base piece. 
     Preferably, the first engaging portion has a flange protruding from a free end thereof. 
     Preferably, the second engaging portion has a flange protruding from a free end thereof. 
     Preferably, the heating element is a halogen lamp or a ceramic heater. 
     In the present invention, the elastic piece tensions the base piece based on a certain force all the time in order that the contact force between the thin film and the first engaging portion, the second engaging portion and the thermally conductive sleeve remains constant during printing, thereby the thin film keeps in a stable operating state during heating and printing to improve the print image quality. Furthermore, the contact area between the thin film and the first engaging portion and the second engaging portion is relative small, so the friction therebetween is reduced during the movement of the thin film and the wear of the thin film is reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a conventional fuser device; 
         FIG. 2  is a perspective view of a preferred embodiment of a fuser device according to the present invention; 
         FIG. 3  is an exploded perspective view of the preferred embodiment of the fuser device according to the present invention; 
         FIG. 4  is a cross-sectional view of the preferred embodiment of the fuser device with a control structure according to the present invention; 
         FIG. 5  is an exploded perspective view of another preferred embodiment of the fuser device with a control structure according to the present invention; and 
         FIG. 6  is a cross-sectional view of the preferred embodiment of the fuser device according to the present invention, illustrating two positions of an elastic piece. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 2 ,  FIG. 3  and  FIG. 4  respectively show a perspective view, an exploded perspective view and a cross-sectional view of a preferred embodiment of an image forming device according to the present invention. The image forming device  10  includes a frame unit  20 , a pressure roller  50  and a guiding assembly, the guiding assembly comprises a heating unit  30 , a thermally conductive sleeve  40 , a belt  170  and a belt tensioner assembly  60 . 
     The frame unit  20  includes two side boards  21  which are disposed relative to each other for positioning of the thermally conductive sleeve  40  and the belt tensioner assembly  60 . Each side board  21  has a slot  211  and an inner wall  212  defining the slot  211  (as shown in  FIG. 5 ). 
     The thermally conductive sleeve  40  is made of aluminum alloy material and disposed on the frame unit  20 . The thermally conductive sleeve  40  has the shape of a hollow long strip and includes a casing wall  41 , two locating surfaces  42 ,  43 , a contact surface  44 , two end faces  45 ,  46  located on the ends thereof and a receiving space  47  defined by the casing wall  41 , the two locating surfaces  42 ,  43  and the contact surface  44 . The casing wall  41  has a horizontal colliding surface  411 . The two locating surfaces  42 ,  43  are respectively located on the left side and the right side of the casing wall  41  relative to each other and extend from the middle portion to the two sides. The contact surface  44  is connected with the two locating surfaces  42 ,  43  under the casing wall  41 . When the belt  170  is immediately lean against the thermally conductive sleeve  40  the, the contact face  44  abuts against the inner surface of the belt  170 . 
     The pressure roller  50  includes two contact portions  51  and a pivot shaft  52 . The two contact portions  51  are respectively disposed on two ends of the pivot shaft  52  and the pivot shaft  52  passes through the slots  211  in the side boards  21  adjacent to the bottom of the slots  211 , whereby the pressure roller  50  is disposed on the frame unit  20 . The pressure roller  50  may be driven to turn by a motor (not shown), and then drive the belt  170  to turn. 
     The heating unit  30  may be a halogen lamp and disposed in the receiving space  47  of the thermally conductive sleeve  40 . The heating unit  30  includes a long lamp portion  31  and two electrode portions  32 . The lamp portion  31  is received in the receiving space  47  and the two electrode portions are disposed on the two ends of the lamp portion  31  and extend out of the thermally conductive sleeve  40 . Two power lines (not shown) are respectively connected with the two electrode portions  32  for providing wording power, so that the lamp portion  31  can heat the thermally conductive sleeve  40  via radiation heating. Alternatively, the heating unit  30  may be also a ceramic heater and isn&#39;t limited in the design of the halogen lamp in the embodiment. 
     The image forming device  10  further includes two blocking pieces  70 , two upper locating pieces  80 , two lower locating pieces  90 , two top boards  110 , two bearings  120  and two elastic pieces  130 . Each blocking piece  70  includes two contact lateral faces  71 ,  72 , a step face  73  and two through-holes  74 ,  75 , wherein the two contact lateral faces  71 ,  72  respectively contact with the two locating surfaces  42 ,  43  of the thermally conductive sleeve  40  to limit the longitudinal displacement of the thermally conductive sleeve  40 ; the step face  73  abuts against the end faces  45 ,  46  of the thermally conductive sleeve  40  to limit the transverse displacement of the thermally conductive sleeve  40 ; and the blocking piece  70  is connected with the corresponding side board  21  via the two through-holes  74 ,  75 . Each upper locating piece  80  has a horizontal contact surface  81  formed on the bottom thereof. Each lower locating piece  90  has a horizontal colliding surface  91  formed on the upper surface thereof. The top board  110  includes two through-holes  111 ,  112  for connecting the top board  110  with the corresponding side board  21 . Each bearing  120  includes an inner wall  121  abutting against the corresponding contact portion  51  of the pressure roller, and a contact surface  122  formed on the bottom of the bearing  120 . The contact surface  122  abuts against the slot  211  of the corresponding side board  21 . Each elastic piece  130  is a compression spring for exerting pressure on the thermally conductive sleeve  40 , of which two ends respectively abut against the colliding surface  91  of the lower locating piece  90  and the contact surface  81  of the upper locating piece  80 . 
     As shown in  FIG. 4  which is a cross-sectional view of the preferred embodiment of the image forming device, the belt tensioner assembly  60  includes a base piece  141 , a free end portion  142 , a pivot portion  143  and a connecting portion  144 . 
     Refer to  FIG. 5  simultaneously, the free end portion  142  may be a first supporting shaft  1421  protruding from the base piece  141  or a first supporting rolling wheel  1422  rotatably disposed on the base piece  141 . When the free end portion  142  is the first supporting rolling wheel  1422 , the base piece  141  has a protruding shaft  1423  passing through the first supporting rolling wheel  1422 . The pivot portion  143  has a similar structure to the free end portion  142  and may be also a second supporting shaft  1431  protruding from the base piece  141  or a second supporting rolling wheel  1432  rotatably disposed on the base piece  141 . When the pivot portion  143  is the second supporting rolling wheel  1432 , the base piece  141  has a protruding shaft  1433  passing through the second supporting rolling wheel  1432 . 
     Regardless of the structures, the supporting shaft or the supporting rolling wheel has a flange protruding from the free end thereof, which has a circumference greater than that of the supporting shaft or the supporting rolling wheel, thereby protecting the belt  170  from sliding down during rotation. 
     As shown in  FIG. 5  which is a partially schematic view of an embodiment of the image forming device with the control structure, the second engaging portion  143  may has a hole  1434  and a shaft  213 , wherein the hole  1434  is formed in the base piece  141  and the shaft  213  is disposed on an imaging system, corresponding to the hole  1434 , and the base piece  141  is disposed on the shaft  213  via the engagement of the hole  1434  and the shaft  213 . The second engaging portion  143  may also has a hole  1434  and a rolling wheel  1435 , wherein the hole  1434  is formed in the base piece  141  and the rolling wheel  1435  is disposed on the imaging system, corresponding to the hole  1434 , and the base piece  141  is disposed on the rolling wheel  1435  via the engagement of the hole  1434  and the rolling wheel  1435 . When the second engaging portion  143  has the hole  1434  and the rolling wheel  1435 , the rolling wheel  1435  may be disposed in the hole  1434  so that the outer surface of the rolling wheel  1435  contacts with the hole  1434 ; or, extend from the hole  1434  so that the end face of the rolling wheel contacts with the base piece  141 . Each of the shaft  213  and the rolling wheel  1435  has a flange protruding therefrom, which has a circumference greater than that of the shaft  213  or the rolling wheel  1435 . 
     In the image forming device of the present invention, the heating unit  30 , the free end portion  142  and the pivot portion  143  form a loop, and the belt  170  surrounds the loop, that is, surrounds the heating unit  30 , the free end portion  142  and the pivot portion  143  in a relaxation state, and the two ends of the belt  170  abut against the base portion respectively. However, during the rotation of the belt  170 , the tensile force on the belt  170  varies, so that the movement of the belt  170  is unstable, and the paper has unstable dynamic characteristics when it passes through the fuser area, which affects the set quality of the toner. Further, the contact force between the belt  170  and the first engaging portion  142  and the second engaging portion  143  is unstable, so the belt  170  and the first engaging portion  142  collide with each other, thereby the wear degree of the belt  170  increases. 
     Accordingly, as shown in  FIG. 6  which is a cross-sectional view of the preferred embodiment of the image forming device, the belt tensioner assembly  60  further includes an elastic piece which is a spring  150  disposed on position I. The spring  150  is disposed on the connecting portion  144  of the base piece  141  and the imaging system in a pulled state. Based on the tension force of the spring  150 , the end of the base piece  141  adjacent to the pivot portion  143  moves along the side adjacent a paper feeding surface  160  and the other end moves in the opposite direction (the direction of the solid arrow as shown in the figure), thereby the whole loop becomes longer and the belt  170  is tensioned. 
     Besides, the spring  150  may be also disposed on position II, then the end of the base piece  141  adjacent to the pivot portion  143  moves on the side far away from the paper feeding surface  160  and the other end moves in the opposite direction (the direction of the hollow arrow as shown in the figure), thereby the whole loop becomes longer and the belt  170  is also tensioned. 
     As shown in  FIG. 4 , when printing, the pressure roller  50  rotates in the anticlockwise direction and drives the belt  170  to move in the clockwise direction, thereby driving a piece of paper (not shown) to pass through the fuser area between the contact surface  44  of the thermally conductive sleeve  40  and the pressure roller  50 . In the course of the paper and the toner passing through the fuser area, the heat from the heating unit  30  is transferred to the belt  170  through the thermally conductive sleeve  40  to heat the paper and the toner. When heated to a certain temperature, the toner melts, and then is set on the paper under the effect of the contact force between the belt  170  and the pressure roller  50 . 
     In the process, the spring  150  tensions the base piece  141  based on a certain force all the time in order that the contact force between the belt  170  and the free end portion  142 , the pivot portion  143  and the thermally conductive sleeve  40  remains constant, thereby the belt  170  keeps in a stable operating state during heating and printing to improve the print image quality. Furthermore, the contact area between the belt  170  and the free end portion  142  and the pivot portion  143  is relative small, so the friction therebetween is reduced during the movement of the belt  170  and the wear of the belt  170  is reduced. 
     The present invention connects the elastic piece (that is, the spring  150 ) between the base piece  141  and the imaging system and drives the base piece  141  based on the elastic force caused by the deformation of the elastic piece to tension the belt  170  and maintain the contact force between the  170  and the base piece  141 , so that the belt  170  can keep in the stable operating state during heating and printing, thereby improving the print image quality.

Technology Category: 3