Abstract:
An image forming device, a process cartridge engageable with the same and a method for firmly positioning the process cartridge in the image forming device. The image forming device includes a main frame and a main frame driving gear, wherein a guide rail is respectively arranged on left and right sides of the inside of the main frame. An installation section is arranged at a tail end of each guide rail and the installation section and guide rail respectively define a reverse hook-shape. Lugs formed at both ends of a housing of the process cartridge are driven by a radial component of driving force of the image forming device to the process cartridge to closely bear against walls of installation sections at the tail ends of the guide rails when the process cartridge is in an operating state in the image forming device.

Description:
This application is a national stage entry in the United States of PCT/CN11/77304 filed Jul. 19, 2011 and claims priority to Chinese application 201010234519.8 filed Jul. 22, 2010. 
     FIELD OF THE INVENTION 
     The invention relates to an image forming device, a process cartridge engaged with the same and a method for firmly positioning the process cartridge in the image forming device. 
     BACKGROUND OF THE INVENTION 
     The electrophotographic image forming device is a device for forming an image on a recording material by electrophotographic imaging processing, for example, an electrophotographic copier, an electrophotographic printer (a laser printer, an LED printer, etc.), a facsimile apparatus, a word processor and the like. 
       FIG. 1  is a schematic diagram illustrating the engagement of the traditional process cartridge and image forming device. The traditional image forming device comprises a main frame  1  for the image forming device and a process cartridge  10  slideably coupled to the main frame  1 , wherein the process cartridge  10  comprises components (not shown in the figure) among a developer, a developing roller, a supply roller, a doctor blade, a photosensitive drum and the like, and a photosensitive drum driving gear  15  engaged with a main frame driving gear  5  for transmitting driving force; first lugs  11  coaxially arranged with the photosensitive drum and second lugs  12  positioned at the downstream side of the first lugs  11 , relative to the installation direction of the process cartridge, are formed on the surfaces of the opposite end parts of both sides of the process cartridge; the first lugs  11  and the second lugs  12  on the end parts of both sides of the process cartridge  10  are slideably coupled to the main frame  1  along curved guide rails  2  on two sidewalls of the main frame  1 ; the guide rails  2  guide the process cartridge  10  to enter into first lug installation positions  2   a  and second lug installation positions  2   b ; the shape of the guide rails  2  is as shown in  FIG. 2 ; and tail ends  2   c  of the guide rails  2  are horizontal. When the first lugs of the process cartridge  10  are positioned at the installation positions  2   a  at the tail ends  2   c  of the guide rails  2 , the first lugs  11  of the process cartridge  10 , at the axial direction of the photosensitive drum, is under the action of the elastic pressure of stop components (such as springs, not shown in the figure), so that the process cartridge  10  is accurately positioned. Meanwhile, the photosensitive drum driving gear  15  of the process cartridge  10  is engaged with the main frame driving gear  5  on the main frame  1  for the image forming device, when the process cartridge  10  is assembled into the main frame. 
     The force condition of the process cartridge  10  when the image forming device is in the operating state is as shown in  FIG. 2 . When the process cartridge  10  is in the operating state, the photosensitive drum driving gear  15  of the process cartridge is engaged with the main frame driving gear  5 ; gear driving force F is transmitted from the main frame driving gear  5  to the process cartridge  10 ; the photosensitive drum driving gear  15  of the process cartridge is under the action of tangential force F t  along the tangential direction of the photosensitive drum driving gear  15  and radial force F n  along the direction of a line that links centers of the photosensitive drum driving gear  15  and the main frame driving gear  5 , which are resolved by the gear driving force F; the tangential force F t  drives the photosensitive drum gear  15  to rotate; and the radial force F n  pushes the process cartridge  10  off an installation position. Therefore, elastic forcible pushing components (such as springs, not shown in the figure) are usually required to be arranged at the installation positions  2   a  of the first lugs  11 , coaxially arranged with the photosensitive drum of the process cartridge, so that the process cartridge  10  is prevented from being disengaged. As the elastic forcible pushing components are required to be able to prevent the process cartridge  10  from being disengaged from the guide rails  2  and prevent the process cartridge  10  from rotating, the component, namely the radial force F n , of the gear driving force F can be resolved into a horizontal component F nx  and a vertical component F ny  in the horizontal direction and the vertical direction respectively, as shown in  FIG. 2 . By adoption of the shape design, the guide rails of the traditional image forming device can only restrain the vertical component F ny  of the radial force F n  and cannot restrain the horizontal component F nx  of the radial force F n , so the elastic forcible pushing components (such as the springs) are required for preventing the process cartridge from being disengaged from the guide rails. However, the position bears large thrust force; the performance requirement of the springs is relatively high; and the positioning accuracy of the process cartridge in the image forming device is affected. Moreover, although the engagement mode of the traditional image forming device and process cartridge is simple, the process cartridge  10  can be driven to be disengaged from the installation position when the photosensitive drum driving gear  15  of the process cartridge  10  is under the action of the driving force of the main frame driving gear  5  of the image forming device, and consequently the image quality is poor. 
     SUMMARY OF THE INVENTION 
     The invention provides an image forming device, a process cartridge engaged with the same and a method for firmly positioning the process cartridge in the image forming device, to solve the technical problem that the image quality is affected by the low positioning accuracy of the process cartridge in the traditional image forming device. 
     The image forming device, comprising a main frame and a main frame driving gear, wherein a guide rail is respectively arranged on the left and right sides of the inside of said main frame; an installation section is arranged at the tail end of each guide rail; and said installation section and said guide rail approximately form a barb. 
     A second guide rail is also respectively arranged on the left and right sides of the inside of said main frame. 
     Said installation sections are provided with vertexes B which are higher than intersection points C of said installation sections and guide rails. 
     End points O of path centerlines of said installation sections are higher than starting points A thereof. 
     Lower parts DB of said installation sections are circular-arc. 
     Said installation sections are also provided with elastic forcible pushing components. 
     A process cartridge engaged with the image forming device, comprising a housing and a photosensitive drum, wherein lugs engaged with the installation sections at the tail ends of said guide rails are formed on said housing; said lugs and said photosensitive drum coaxially arranged; said photosensitive drum comprising a photosensitive drum gear; intersection points of an extension of a line that links centers of said photosensitive drum gear and said main frame driving gear and CB segments of said installation sections being higher than or level with the intersection points C of said installation sections and said guide rails. 
     Wherein second lugs engaged with said second guide rails are formed on said housing. 
     Wherein the diameter of said lugs is less than the distance from the starting points A to the end points O of the path centerlines of said installation sections. 
     A method for firmly positioning a process cartridge in an image forming device, comprising the following steps of: firstly, arranging installation sections which approximately form barbs with guide rails at the tail ends of said guide rails, which are arranged on the left and right sides of the inside of a main frame of said image forming device; and secondly, pushing said process cartridge, in which lugs engaged with said guide rails are formed at both ends of a housing, into said main frame, so that said lugs are engaged with said installation sections and a photosensitive drum gear of said process cartridge is engaged with a main frame driving gear in the radial direction for receiving driving force from said main frame driving gear. 
     Wherein said installation sections are provided with vertexes B which are higher than intersection points C of said installation sections and said guide rails. 
     Wherein the first step also comprises the following steps of respectively arranging a second guide rail on the left and right sides of the inside of said main frame and respectively forming a second lug engaged with said second guide rail at both ends of said housing; and the second step also comprises the following step of making said second lugs to be engaged with said second guide rails. 
     Wherein the first step also comprises the following step of arranging elastic forcible pushing components on said installation sections for forcibly pushing said lugs. 
     By adoption of the technical proposal, as installation sections are arranged at the tail ends of guide rails and the installation sections and the guide rails approximately form barbs, lugs formed at both ends of a housing of the process cartridge are driven by a radial component of driving force of the image forming device to the process cartridge to always closely lean against the walls of the installation sections at the tail ends of the guide rails when the process cartridge is in the operating state in the image forming device. Therefore, not only the installation is convenient but also the positioning is reliable; the vibration of the photosensitive drum during the image forming is reduced; and the technical problem that the image quality is affected by the low positioning accuracy of the process cartridge in the traditional image forming device is solved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating the engagement of the traditional process cartridge and image forming device; 
         FIG. 2  is a schematic diagram illustrating the force condition of the traditional process cartridge when the image forming device is in the operating state; 
         FIG. 3  is a schematic diagram illustrating the engagement of a process cartridge and an image forming device, provided by the invention; 
         FIG. 4  is a structure diagram of a guide rail in the invention; 
         FIG. 5  is a perspective view of the process cartridge provided by the invention; 
         FIG. 6  is a structure diagram of the end part of the process cartridge provided by the invention; 
         FIG. 7  is a schematic diagram illustrating the state when the process cartridge provided by the invention is in the first installation phase; 
         FIG. 8  is a schematic diagram illustrating the state when the process cartridge provided by the invention is in the second installation phase; and 
         FIG. 9  is a schematic diagram illustrating the position deflection of the process cartridge provided by the invention at different phases. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As illustrated in  FIGS. 3 and 4 , the image forming device comprises a main frame  30  and guide rails  400  which are arranged on the left and right sides of the inside of the main frame  30 , wherein first guide rails  410  and second guide rails  420  are arranged on the guide rails  400 ; the guide rails approximately adopt top-down design; circular-arc installation sections  411  are arranged at the tail ends of the first guide rails  410 ; the installation sections  411  and the first guide rails  410  approximately form barbs; vertexes B of the installation sections  411  are higher than intersection points C of the installation sections  411  and the first guide rails  410 , so the barbs are formed; and end points O of path centerlines AO of the installation sections  411  are higher than starting points A thereof. 
     Lower parts DB of the installation sections  411  are circular arcs of which the curvature is different from that of the guide rails. Due to the arrangement of the circular arcs, the process cartridge is smoother and more convenient to be assembled and disassembled. 
     The installation sections  411  of the first guide rails  410  can also be provided with elastic forcible pushing components. The elastic forcible pushing components in the embodiment are torsion springs and of course can be other elastic forcible pushing components with the same function. 
     Installation sections  421  are arranged at the tail ends of the second guide rails  420  and also provided with elastic forcible pushing components. The elastic forcible pushing components in the embodiment are torsion springs  50  and of course can be other elastic forcible pushing components with the same function. 
     A process cartridge  60  comprises a photosensitive drum, a charging roller, a developing roller, an end cover, a toner hopper and a waste bin (not shown in the figure), as shown in  FIGS. 5 and 6 . First lugs  61  and second lugs  62 , which are engaged with the first guide rails  410  and the second guide rails  420  respectively, are formed on two end parts of the process cartridge  60 . The first lugs  61  and the photosensitive drum are coaxially arranged, and the second lugs  62  are positioned at the downstream side of the first lugs  61 , relative to the installation direction of the process cartridge. 
     The process of assembling the process cartridge  60  into the main frame  30  in the embodiment is as illustrated in  FIGS. 7 and 8 . The process cartridge  60  is assembled into the main frame  30  in the direction perpendicular to the axial direction of the photosensitive drum. When the process cartridge  60  is inserted into the image forming device, the first lugs  61  and the second lugs  62  formed on the two end parts of the process cartridge  60  are combined with the first guide rails  410  and the second guide rails  420  of the guide rails  400  respectively. Under the action of definite installation pressure, the first lugs  61  of the process cartridge arrive at the first installation sections  411  along the first guide rails  410 , and the second lugs  62  of the process cartridge arrive at the second installation sections  421  along the second guide rails  420 , at which the second lugs  62  are clamped by the torsion springs  50 . The torsion springs  50  push the second lugs  62  of the process cartridge  60  with definite elastic force, so as to limit the rotation of the process cartridge  60 , thus stable positioning of the process cartridge  60  in the main frame  30  is realized. 
     When the process cartridge  60  is arranged at the installation sections  411  in the image forming device, intersection points of an extension of a line that links centers of a photosensitive drum gear  64  and a main frame driving gear  34  and CB segments of the installation sections are higher than or level with the intersection points of the installation sections  411  and the guide rails  410 . 
     Moreover, for the installation sections of the guide rails to be barbed and the process cartridge to be smoothly assembled into or disassembled from the image forming device, the diameter of the lugs  61  of the process cartridge  60  should be less than the distance of the path centerlines AO of the installation sections  411 . 
     After the first lugs  61  and the second lugs  62  of the process cartridge  60  arrive at the first installation sections  411  and the second installation sections  421  along the first guide rails and the second guide rails respectively, the forward speed of the first lugs  61  of the process cartridge is relatively slow while the forward speed of the second lugs  62  of the process cartridge is relatively fast; and the rotation angle of the first lugs  61  is more than that of the second lugs  62 . The process cartridge  60  is rotated by a certain angle (in the embodiment, as illustrated in  FIG. 9 , the rotation angle of a handle  63  of the process cartridge  60  is about 22 DEG from the time when the process cartridge  60  is assembled into the main frame  30  to the time when the photosensitive drum gear  64  of the process cartridge  60  is engaged with the main frame driving gear  34 ), so that the photosensitive drum gear  64  of the process cartridge is engaged with the main frame driving gear  34  of the image forming device. The rotation effectively utilizes the inner space of the image forming device, so materials are saved and the miniaturization of the image forming device is realized. When the process cartridge  60  is disassembled, the handle  63  of the process cartridge  60  is directly held, and the process cartridge  60  can be disassembled just after the first lugs  61  and the second lugs  62  of the process cartridge  60  move outward along the guide rails  400 . The mode of assembly and disassembly of the process cartridge is very simple. 
     The image forming device is in the operating state when the photosensitive drum gear  64  of the process cartridge is positioned at a position at which the photosensitive drum gear  64  is engaged with the main frame driving gear  34  and receives driving force transmitted by the main frame driving gear  34 . The force condition of the process cartridge  60  when the image forming device is in the operating state is as illustrated in  FIG. 8 . When the image forming device is in the operating state, the photosensitive drum gear  64  is engaged with the main frame driving gear  34 ; the driving force F is transmitted from the main frame driving gear  34  to the photosensitive drum gear  64  of the process cartridge; the photosensitive drum gear  64  of the process cartridge is under the action of tangential force Ft along the tangential direction of the photosensitive drum gear  64  and radial force Fn along the direction of the line that links centers of the photosensitive drum gear  64  and the main frame driving gear  34 , which are resolved by the driving force F; the tangential force Ft drives the photosensitive drum gear  64  to rotate; and the radial force Fn pushes the process cartridge  60  off the installation position and can be resolved into a horizontal component Fnx and a vertical component Fny in the horizontal direction and the vertical direction respectively. 
     In the embodiment, the installation sections  411  are arranged at the tail ends of the first guide rails; the vertexes B of the installation sections  411  are higher than the intersection points C of the installation sections and the guide rails; and both the installation sections and the guide rails form the barbs. When the process cartridge  60  is positioned at the installation sections  411  in the image forming device, the intersection points of the extension of the line that links centers of the photosensitive drum gear  64  and the main frame driving gear  34  and the CB segments of the installation sections are higher than or level with the intersection points C of the installation sections  411  and the guide rails. When the process cartridge  60  is under the action of the radial force Fn along the centerline of the photosensitive drum gear  64  and the main frame driving gear  34 , the horizontal component Fnx and the vertical component Fny of the radial force Fn can be effectively restrained by adoption of the structure, so that the first lugs, coaxially arranged with the photosensitive drum, of the process cartridge are pushed against the walls of the installation sections, thus the vibration of the photosensitive drum in the operating process is extremely effectively reduced, consequently the image quality is guaranteed and the stop force required of the elastic forcible pushing components is further reduced a great extent. Therefore, in the embodiment, the elastic forcible pushing components of the image forming device are the torsion springs  50  arranged at the second installation positions  421  of the second guide rails  420 . The torsion springs  50  are used for preventing the process cartridge  60  from rotating, and small force can be applied for the accurate positioning of the process cartridge  60 . Compared with the technical proposal in the prior art that the first lugs  11  coaxially arranged with the photosensitive drum are pushed by the torsion springs to determine the position of the process cartridge  10 , the invention can reduce the requirements on the stop elastic force of the elastic forcible pushing components and the performances of stop components and consequently reduce the cost, improve the positioning accuracy and guarantee the image quality finally. 
     According to one aspect of the patent, when the first lugs  61 , coaxially arranged with the photosensitive drum, on the two end parts of the process cartridge  60 , arrive at the walls of the installation sections  411  of the first guide rails  410 , the intersection points of the extension of the line that links centers of the photosensitive drum gear  64  and the main frame driving gear  34  and the CB segments of the installation sections are higher than or level with the intersection points C of the installation sections  411  and the guide rails  410 , so that the radial force F n  of the gear driving force F can be effectively restrained. As illustrated in  FIG. 8 , in the embodiment, the intersection points of the extension of the line that links centers of the photosensitive drum gear and the main frame driving gear and the CB segments of the installation sections are level with the intersection points C of the installation sections  411  and the guide rails  410 . 
     According to one aspect of the patent, the elastic forcible pushing components can be arranged at the first installation positions of the first guide rails or the second installation positions of the second guide rails or can be simultaneously arranged at the two installation positions. No matter how the installation mode is changed, the invention can effectively reduce the elastic stop force, at the installation position of the process cartridge, required for preventing the process cartridge from being disengaged from the guide rails, and thus improve the positioning accuracy of the process cartridge and consequently improve the image quality. 
     As described above, the process cartridge can be stably and conveniently assembled or disassembled, so the positioning accuracy of the process cartridge can be improved, thus the service performances of users and the image quality can be improved.