Patent Publication Number: US-2007115527-A1

Title: Light deflecting apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims all benefits accruing under 35 U.S.C. §119 from Korean Patent Application No. 2005-112040, filed on Nov. 22, 2005, in the Korean Intellectual Property Office, the content of which is incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an image forming device, and more particularly, relates to a light deflecting apparatus adapted to be used in a light scanning unit of an image forming device, such as a printer, a copier, a facsimile machine or a multi-functional product.  
      2. Related Art  
      In general, an image forming device, such as a printer, a copier, a facsimile machine or a multi-functional product, is provided with a light scanning unit such as a laser scanning unit to form an electrostatic latent image on a photoconductive body such as a photoconductive drum. The light scanning unit has a light deflecting apparatus such as a polygon motor arranged to deflect a light such as a laser beam radiated from a light source such as a laser diode to a scanning lens with a certain angle of image, thereby to form the electrostatic latent image on a photoconductive body.  
       FIG. 1  shows an example of a general light deflecting apparatus provided in an image forming device. As shown in  FIG. 1 , the light deflecting apparatus  10  is provided with a sleeve  3 , an axis  2 , a core  4 , and a rotor frame  5 . The sleeve  3  is installed at a printed circuit board (PCB)  1 . The axis  2  is supported in the sleeve  3  by a bearing  3   a . The core  4  in which coils  4   a  are wound is disposed around the sleeve  3 . The rotor frame  5  is fixed to a top end of the axis  2  to mount a rotary polygon mirror  7  thereon.  
      At a under surface of the rotor frame  5  is disposed a rotor housing  6  configured to surround the core  4 , and at an inner surface of the rotor housing  6  is disposed a magnet  6   a  that generates a magnetic force. The magnetic force of the magnet  6   a  produces a torque for rotating the rotor housing  6  in cooperation with an electromagnetic force of the coils  4   a.    
      Further, at an upper side of the rotor frame  5  on which the rotary polygon mirror  7  is mounted is installed a fixing spring  8  to immovably support the rotary polygon mirror  7 .  
      In the conventional light deflecting apparatus  10  constructed as shown in  FIG. 1 , the most important component that has influence on a performance of the light deflecting apparatus  10 , that is, a light scanning performance, is the rotary polygon mirror  7 . Accordingly, to enhance the performance of the light deflecting apparatus  10 , a stable support of the rotary polygon mirror  7  together with a precise manufacturing of such the rotary polygon mirror  7  are essential.  
      To stably support the rotary polygon mirror  7 , the rotor frame  5  which supports the rotary polygon mirror  7  must be manufactured in a high precision. In addition, the rotor housing  6  which has influence on the rotation of the rotary polygon mirror  7  must also be manufactured to have a minimum unbalance of weight.  
      However, the rotor frame  5  is usually manufactured by machining a cylindrical body formed of metal such as aluminum or brass. As a result, material waste is large and the manufacturing process can be difficult, so that a manufacturing cost is increased.  
      In addition, the rotor housing  6  is usually manufactured by pressing a disc formed of metal such as stainless steel. As a result, a high level of precision of a press working technique to manufacture the rotor housing  6  having a proper balance of weight, is required.  
      Moreover, at the inner surface of the rotor housing  6  is fixed the magnet  6   a  formed of a compound in which rubber, plastic or rare earth, and magnetic material are mixed. As a result, a high level of precision is required to fix the magnet  6   a  to the inner surface of the rotor housing  6  to avoid generating the unbalance of weight and an assembly deviation between the magnet  6   a  and the rotor housing  6 .  
      Furthermore, the rotor housing  6  is usually fixed to the rotor frame  5  by a caulking process. However, such a caulking process does not uniformly fix the rotor housing  6  to the rotor frame  5  in a circumferential direction due to its working characteristic, so that the rotor housing  6  may not have a proper balance of weight after fixed to the rotor frame  5 . In this case, the light deflecting apparatus  10  may not stably scan a light on the photoconductive body due to the unbalance of weight at the rotor housing  6  during an initial operation, thereby deteriorating a quality in electrostatic latent image that is formed on the photoconductive body by the light deflecting apparatus  10 .  
     SUMMARY OF THE INVENTION  
      Several aspects and example embodiments of the present invention provide a light deflecting apparatus in which a rotor frame and/or a rotor housing is formed of a plastic material, thereby facilitating a manufacturing, reducing a manufacturing cost, and maintaining a stable performance.  
      Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
      In accordance with an aspect of the present invention, a light deflecting apparatus is provided with a rotor housing and a magnet attached thereto are integrally formed by a single part of a plastic material, thereby facilitating a manufacture, reducing a manufacturing cost, and maintaining a stable performance.  
      In accordance with an embodiment of the present invention, a light deflecting apparatus comprises a stator having a sleeve disposed at a printed circuit board (PCB), and a core disposed around the sleeve, to which coils are wound; a rotor having a rotor frame connected to an axis which is rotatably supported in the sleeve, and a rotor housing fixed to the rotor frame to surround the core; and a polygon mirror supported on the rotor frame. At least one of the rotor frame and the rotor housing is formed of a plastic material.  
      According to an aspect of the present invention, the plastic material may be selected from a group consisting of polyamide, polyester, polycarbonate, polybutylene terephthalate (PBT), and polyphenylene oxide (PPO). The housing may further be formed of a magnetic material, and such a magnetic material may be composed of a ferrite power. In this case, the rotor housing may have a magnetized part disposed opposite to the core in which the magnetic material formed therein is magnetized to have a plurality of magnetic polarities.  
      According to an aspect of the present invention, the rotor frame and the rotor housing may be fixed with each other by an ultrasonic fusing. In this case, the rotor housing may have at least one fusing projection, and the rotor frame may have at least one projection receiving groove to receive the fusing projection.  
      In addition to the example embodiments and aspects as described above, further aspects and embodiments of the present invention will be apparent by reference to the drawings and by study of the following descriptions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      A better understanding of the present invention will become apparent from the following detailed description of example embodiments and the claims when read in connection with the accompanying drawings, all forming a part of the disclosure of this invention. While the following written and illustrated disclosure focuses on disclosing example embodiments of the invention, it should be clearly understood that the same is by way of illustration and example only and that the invention is not limited thereto. The spirit and scope of the present invention are limited only by the terms of the appended claims. The following represents brief descriptions of the drawings, wherein:  
       FIG. 1  is a sectional view illustrating a general light deflection apparatus;  
       FIG. 2  is a sectional view illustrating a light deflection apparatus in accordance with an embodiment of the present invention; and  
       FIG. 3  is a sectional view illustrating example rotor of the light deflection apparatus illustrated in  FIG. 2 . 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
      Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
       FIG. 2  is a view schematically illustrating an example light deflection apparatus  100  according to an embodiment of the present invention. As shown in  FIG. 2 , the light deflection apparatus  100  comprises a printed circuit board (PCB)  101 , a stator  110 , a rotor  120 , and a rotary polygon mirror  107 .  
      The printed circuit board (PCB)  101  has a light source (not shown) such as a laser diode forming a light scanning unit (not shown) such as a laser scanning unit, and all sorts of circuit chips (not shown) for driving the light source, which are mounted thereon.  
      The stator  110  is provided with a sleeve  103  and a core  104 . The sleeve  103  is disposed at the printed circuit board (PCB)  101 . The core  104  is installed around the sleeve  103 . At an inside surface of an upper portion of the sleeve  101  is installed a washer  103   b  to prevent oil leakage, i.e., oil from being dispersed from a bearing  103   a . At the core  104  is formed a plurality of slots, for example, 9 slots (not shown), each to which a coil  104   a  is wound to generate an electromagnetic force of corresponding magnetic polarity when applied thereto with an electric current.  
      The rotor  120  includes an axis  102  and a rotor frame  105 . The axis  102  is rotatably in the sleeve  103  by the bearing  103   a . The rotor frame  105  is fixed to a top end of the axis  102  to hold the rotary polygon mirror  107 .  
      The rotor frame  105  is formed by injection-molding an engineering plastic material, such as polyamide, polyester, polycarbonate, polybutylene terephthalate (PBT), or polyphenylene oxide (PPO), which has a good thermal resistance and a good impact-resisting property. Accordingly, the rotor frame  105  can be uniformly manufactured without a loss in time, manpower and materials. Such a motor frame  105  can also be generated according to mechanically machining a metal cylindrical body in a high precision as in the rotor frame  5  of the conventional light deflecting apparatus  10 , as shown in  FIG. 1 , so that a manufacture cost can be reduced. In addition, because a weight of the rotor frame  105  is reduced, an initial starting time, which takes until the rotor  120  reaches a normal speed, can be reduced compared with the conventional light deflecting apparatus  10 , as shown in  FIG. 1 .  
      At an under surface of the rotor frame  105  is fixed a rotor housing  106  which is configured to surround the core  104 .  
      The rotor housing  106  is formed by injection-molding a magnetic material, such as a ferrite powder and an engineering plastic material, such as polyamide, polyester, polycarbonate, polybutylene terephthalate (PBT), or polyphenylene oxide (PPO), which has a good thermal resistance and a good impact-resisting property. Accordingly, during manufacturing, there is little possibility to produce a poor rotor having an unbalance of weight that is influenced by the precision of the press working for a metal disc as in the rotor housing  6  of the conventional light deflecting apparatus  10 , as shown in  FIG. 1 . Thus, an amount in the unbalance of weight which is caused by the rotor housing  106  to result in an unstable scanning of light during an initial operation of the light deflecting apparatus  100  is greatly reduced, and thereby a performance of the light deflecting apparatus  100  is enhanced. In addition, because a weight of the rotor housing  106  is reduced, an initial starting time, which takes until the rotor  120  reaches a normal speed, can be reduced compared with the conventional light deflecting apparatus  10 , as shown in  FIG. 1 .  
      At a lower portion  106   b  of the rotor housing  106  is formed a magnetized part  111 , which generates a magnetic force. The magnetic force of the magnetized part  111  produces a torque for rotating the rotor  120  in cooperation with the electromagnetic force of the coils  104   a.    
      The magnetized part  111  is composed of a plurality of magnetic portions, for example,  6  magnetic portions, which are circumferentially formed opposite to the core  104  at the lower portion  106   b  of the rotor housing  106 . The  6  magnetic portions are disposed to alternate N polarities with S polarities. Positions of such magnetic polarities are identical to those of the magnet  6   a  of the conventional light deflecting apparatus  10 , as shown in  FIG. 1 , or the magnet known in the art, detailed descriptions thereof will be omitted for the sake of brevity.  
      The magnetized part  111  is magnetized in the  6  magnetic portions by a magnetizing process using a known magnetizing device (not shown) before or after the rotor housing  106  is fixed to the rotor frame  105  by an ultrasonic fusing which will be described later.  
      A stopper  109  is disposed above a side of an outer end  106   c  of the lower portion  106   b  of the rotor housing  106 . The stopper  109  is fixed on the printed circuit board (PBC)  101  to prevent the rotor  120  detachably installed to the stator  110  from being separated from the stator  110  when an impact from the outside is imparted on the rotor  120 .  
      The rotor frame  105  and the rotor housing  106  are fixed with each other by the ultrasonic fusing process using an ultrasonic fusing device (not shown). To assist the ultrasonic fusing between the rotor frame  105  and the rotor housing  106 , the rotor housing  106  has at least one fusing projection  106   a , and the rotor frame  105  has at least one projection receiving groove  105   a  to receive the fusing projection  106   a.    
      Hereinafter, the ultrasonic fusing process of fixing the rotor housing  106  to the rotor frame  105  according to an embodiment of the present invention will now be described herein below.  
      First, as illustrated in  FIG. 3 , the rotor frame  105  is placed on a bed (not shown) of the ultrasonic fusing device.  
      Subsequently, the rotor housing  106  is placed on the rotor frame  105 , so that the fusing projection  106   a  is inserted into the projection receiving groove  105   a.    
      Under this state, a jig (not shown) attached to the ultrasonic fusing device is decent onto portions of the rotor housing  106  and the rotor frame  105 , between which adjoin each other in the vicinity of the fusing projection  106   a  and the projection receiving groove  105   a . Then, the ultrasonic fusing device applies a vibration energy converted from an ultrasonic energy in range of 15-20 Khz on the adjoining portions of the rotor housing  106  and the rotor frame  105  through the jig for a predetermined time.  
      As a result, the adjoining portions of the rotor housing  106  and the rotor frame  105  generate a friction heat in a moment due to the powerful vibration energy, so that the fusing projection  106   a  and the projection receiving groove  105   a  are fused and fixed with each other.  
      The rotary polygon mirror  107  is mounted on an upper surface  105   c  of the rotor frame  105 . After the rotor frame  105  is injection-molded, the upper surface  105   c  of the rotor frame  105  is preferably polished through a grinding treatment and the like to have a required assembly precision, so that it is precisely joined with the rotary polygon mirror  107  during assembling.  
      The rotary polygon mirror  107  is formed in, for example, a hexagon shape having six reflective surfaces  107   a , so that a light radiated from the light source reflects to a scanning lens of the light scanning unit with a certain angle of image when it is rotated by the rotor  120 . However, such a rotary polygon mirror  107  may be formed in different shapes and having different reflective surfaces to reflect a light from the light source to the scanning lens of the light scanning unit.  
      At an upper side of the rotor frame  105  on which the rotary polygon mirror  107  is mounted is installed a fixing spring  108  to immovably hold the rotary polygon mirror  107 .  
      Hereinafter, an operation of the light deflecting apparatus  100  according to an embodiment of the present invention constructed as shown in  FIG. 2 , will now be described in detail.  
      At first, when the coils  104   a  are supplied with an electric current, the coils  104   a  generate an electromagnetic force, and the electromagnetic force of the coils  104   a  produce a torque for rotating the rotor housing  106  in cooperation with a magnetic force of the magnetized part  111 . As a result, the rotor housing  106  is rotated at a high speed.  
      As the rotor housing  106  is rotated at a high speed, the rotor frame  105  joined with the rotor housing  106  and the rotary polygon mirror  107  fixed on the rotor frame  105  are rotated at a high speed together with the rotor housing  106 .  
      While the rotary polygon mirror  107  is rotated, a light radiated to the rotary polygon mirror  107  from the light source is reflected to the scanning lens of the light scanning unit with a certain angle of image by the reflective surfaces  107   a.    
      The light reflected to the scanning lens is again reflected by a reflective mirror (not shown) of the light scanning unit, and scanned onto a photoconductive body (not shown) of an image forming device. As a result, an electric potential is lowered at a portion of a surface of the photoconductive body on which the light is scanned, so that an electrostatic latent image is formed on the surface of the photoconductive body.  
      According to the present invention as described above, the light deflecting apparatus  100  has the rotor frame and/or the rotor housing formed of a plastic material. So, when the light deflecting apparatus  100  is manufactured, an operation of requiring a high precision such as a mechanical machining and a press working is not needed. As a result, the manufacture of such a light deflecting apparatus is simpler and easier; and, likewise, a working time and an exhaustion of manpower are reduced, so that a manufacturing cost is reduced. Moreover, an unbalance of weight at the rotor frame and/or the rotor housing, which is influenced by a working precision thereof, is minimized, so that the light deflecting apparatus may maintain a stable performance. Also, because a weight of the rotor comprising the rotor frame and the rotor housing is reduced, an initial starting time, which takes until the rotor reaches a normal speed, can be reduced compared with the conventional light deflecting apparatus, as shown in  FIG. 1 .  
      Further, according to an embodiment of the present invention as shown in  FIG. 2  and  FIG. 3 , the light deflecting apparatus has a rotor housing and a magnet attached thereto integrally formed by a single part of a plastic material including a magnetic material therein. So, precisely manufacturing a rotor housing and a magnet to allow the magnet to be assembled to the rotor housing without generating an assembly deviation therebetween, as well as assembling the magnet to the rotor housing, is not needed. Accordingly, a manufacturing comes to be easy, and a manufacturing cost is reduced. Also, an unbalance of weight at the rotor housing, which can be caused as a result of assembling the magnet to the rotor housing, is not produced. Thus, an amount in the unbalance of weight, which results in an unstable scanning of light during an initial operation of the light deflecting apparatus, is greatly reduced, and thereby a performance of the light deflecting apparatus is enhanced.  
      The foregoing embodiment and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the embodiment of the present invention is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.  
      While the light deflecting apparatus of the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention. For example, components of a light scanning unit (LSU) can be arranged differently. In addition, other light sources can also be provided. Moreover, the operating part and the light deflecting mirror can be constructed differently as long as the rotor frame and/or the rotor housing, as wel as the rotor housing and the magnet attached thereto are formed in the manner as described with reference to  FIG. 2  to  FIG. 3 . Accordingly, it is intended, therefore, that the present invention not be limited to the various example embodiments disclosed, but that the present invention includes all embodiments falling within the scope of the appended claims.