Patent Abstract:
Disclosed is a motor. The motor includes a rotor case, a ring member mounted on the rotor case and including an encoder on a bottom surface thereof extending outside of the rotor case, and an encoder sensor detecting speed information of the rotor case from the encoder such that the rotor case rotates at low speeds enabling a LightScribe operation.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2009-0123272 filed on Dec. 11, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a motor, and more particularly, to a motor capable of having a control function for low-speed rotation by including an encoder on the bottom surface of a ring member mounted on a rotor case, and an encoder sensor located corresponding to the encoder. 
     2. Description of the Related Art 
     In general, a spindle motor installed inside an optical disc drive rotates a disc so that an optical pickup mechanism can read data written to the disc. 
     Recently, an optical disc drive equipped with a LightScribe function has been increasingly released onto the market. Here, the LightScribe function allows users to print letters (characters) or images freely on the upper side of a disc such as a DVD, a CD or the like. 
     According to the related art, only LightScribe discs that support the LightScribe function by having a printed encoder generating an FG pulse for low-speed control are able to be used in order to implement the LightScribe function. Here, typical discs for recording cannot be used in realizing the LightScribe function. 
     That is, in order to use the LightScribe function, a spindle motor needs to rotate at a low speed of 40 rpm to 300 rpm or less. Thus, an encoder generating a separate FG pulse is printed on the side of a disc, since the FG pulse of the spindle motor itself, cannot be used for the LightScribe function. 
     However, the use of such LightScribe discs has limitations in that the discs are costly and are not easy to buy. 
     In addition, since LightScribe printing is performed on the opposite side to the read/write-side of a disc, the LightScribe disc is repetitively taken out from and put back into a chucking device. This may damage an encoder printed on the LightScribe disc. 
     Further, the encoder, when printed on a disc in a non-uniform manner, fails to perform precise low-speed control and impairs printing quality. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a motor capable of having a control function for low-speed rotation (hereinafter “low-speed rotation control”) by including an encoder on the bottom surface of a ring member mounted on a rotor case, and an encoder sensor located corresponding to the encoder. 
     According to an aspect of the present invention, there is provided a motor including: a rotor case; a ring member mounted on the rotor case and including an encoder on a bottom surface thereof extending outside of the rotor case; and an encoder sensor detecting speed information of the rotor case from the encoder such that the rotor case rotates at low speeds enabling a LightScribe operation. 
     The ring member may be fixed to a chucking device on which a disc is mounted. 
     The encoder may be inkjet-printed on the bottom surface of the ring member. 
     The encoder may be provided as an adhesive film and bonded with the bottom surface of the ring member. 
     The encoder may be formed uniformly on the bottom surface of the ring member. 
     The ring member may include, on a top surface thereof, a disc mounting portion on which a disc is mounted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic plan view illustrating a motor according to an exemplary embodiment of the present invention; 
         FIG. 2  is a schematic perspective view illustrating a motor according to an exemplary embodiment of the present invention; 
         FIG. 3  is a cross-sectional view illustrating a motor according to an exemplary embodiment of the present invention; 
         FIG. 4  is a schematic view illustrating the bottom of a ring member according to an exemplary embodiment of the present invention; and 
         FIGS. 5A and 5B  are schematic views illustrating how an encoder is formed on the bottom surface of a ring member according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. While those skilled in the art could readily devise many other varied embodiments that incorporate the teachings of the present invention through the addition, modification or deletion of elements, such embodiments may fall within the scope of the present invention. 
     The same or equivalent elements are referred to by the same reference numerals throughout the specification. 
       FIG. 1  is a schematic plan view illustrating a motor according to an exemplary embodiment of the present invention.  FIG. 2  is a schematic perspective view illustrating a motor according to an exemplary embodiment of the present invention.  FIG. 3  is a cross-sectional view illustrating a motor according to an exemplary embodiment of the present invention.  FIG. 4  is a schematic view illustrating the bottom of a ring member according to an exemplary embodiment of the present invention. 
     Referring to  FIGS. 1 through 4 , a motor  10 , according to an exemplary embodiment of the present invention, may include a rotor case  32 , a ring member  20  and an encoder sensor  25 . 
     As for the internal construction of the motor  10 , the motor  10  may include a base plate  70 , a rotor  30 , a stator  40 , a bearing assembly  60 , and a chucking device  80 . 
     The base plate  70  serves as a support that supports the stator  40 . A flexible circuit board  72  may be formed on the base plate  70 . The flexible printed circuit board  72  may be provided with a circuit pattern applying power to the motor  10 . 
     The encoder sensor  25  is a data detector that receives information regarding the rotation of a disc D. Notably, the encoder sensor  25  may detect speed information of the rotor case  32  from an encoder formed on the ring member  20 . 
     The rotor  30  includes a rotor case  32  having a cup shape. The rotor case  32  includes a ring-shaped magnet  35  provided on the inner circumferential portion of the rotor case  32  and corresponding to a coil  46  of the stator  40 . The magnet  35  is a permanent magnet that generates a predetermined level of magnetic force as N poles and S poles are alternately magnetized in a circumferential direction. 
     The rotor case  32  includes a rotor hub  34  press-fitted to a shaft  62 , and a magnet coupling portion  36  having an inner surface on which the ring-shaped magnet  35  is disposed. 
     The rotor hub  34  is bent in an axial direction along the upper portion of the shaft  62  in order to maintain an unmating force with the shaft  62 . The chucking device  80  on which a disc D is mounted is coupled with the outer surface of the rotor hub  34 . 
     The stator  40  includes a support portion  42  supported from the outside of a sleeve  66 , a plurality of cores  44  fixed to the support portion  42 , and a winding coil  46  wound around the cores  44 . 
     The magnet  35 , provided on the inner surface of the magnet coupling portion  36 , opposes the winding coil  46 . The rotor  30  is rotated by the electromagnetic interaction between the magnet  35  and the winding coil  46 . 
     Further, the bearing assembly  60  is disposed inside of the support portion  42  of the stator  40 , and includes the shaft  62  supporting the rotation of the rotor  30 , and the sleeve  66  in which the shaft  60  is rotatably installed. 
     Terms regarding directions are defined as follows: the axial direction refers to a vertical direction with reference to the shaft  62  in  FIG. 1 , and outer and inner diameter directions refer to a direction toward the outer edge of the rotor  20  from the shaft  62 , and a direction toward the center of shaft  62  from the outer edge of the rotor  30 , respectively. 
     The chucking device  80  is coupled and fixed to one end portion of the rotor hub  34 , and allows for the detachable mounting of a disc thereon. The chucking device  80  includes a chuck base  82 , a spring  84 , and a chuck chip  86 . 
     A center hole is formed in the center of the chuck base  82 . The one end portion of the rotor hub  34  may be inserted into the center hole and coupled with the motor  10 . 
     The chuck chip  86  is received in the chuck base  82 , and may protrude toward the outside of the chuck base  82 . The spring  84  may be provided to elastically support the chuck chip  82  in an outward direction of the chuck base  82 , thereby allowing the chuck chip  82  to protrude to the outside of the chuck base  82 . 
     The ring member  20  may be mounted on the top surface of the rotor case  32  by being inserted below the chucking device  80  in the axial direction. That is, the ring member  20  may be fixed to the chucking device  80 . 
     A disc D may be mounted on the top surface of the ring member  20 . A disc mounting portion  24  may be provided on the top surface of the ring member  20  such that the disc D can be mounted stably thereon. 
     An encoder  22  may be formed on a portion of the bottom surface of the rotor case  32  extending outside of the rotor case  32  in the outer diameter direction. 
     The encoder  22  is formed by alternating reflective and non-reflective patterns on the bottom surface of the ring member  20  along the circumference of the ring member  20 , such that the encoder  22  reflects light coming out of the encoder sensor  25  to allow the encoder sensor  25  to receive the reflected light. 
     The encoder sensor  25  absorbs light reflected from the encoder  22  to thereby obtain a pulse signal. The pulse signal is transferred to a controller (not shown) that controls a speed of the motor  10 , and the controller performs rotation control for a low speed of the motor  10 . 
       FIGS. 5A and 5B  are schematic views illustrating how the encoder  22  is formed on the bottom surface of the ring member  20  according to an exemplary embodiment of the present invention. 
     From  FIGS. 5A and 5B , it can be seen how the encoder  22  is formed on the bottom surface of the ring member  20 . 
     Referring to  FIG. 5A , the encoder  22  is inkjet-printed on the bottom surface of the ring member  20  by using an inkjet printer  100 . Referring to  FIG. 5B , the encoder  22  is provided in the form of an adhesive film  200  and is bonded with the bottom surface of the ring member  20 . 
     The motor, according to the present invention, eliminates the need for LightScribe discs, and is capable of low-speed control required for the LightScribe function even when typical discs for recording are used. 
     Also, the encoder, formed on the ring member, is not damaged even if a disc is repetitively taken out from and put back into the chucking device. 
     Since the encoder is printed uniformly, precise low-speed control is ensured, and printing quality is improved. 
     As set forth above, according to the motor according to exemplary embodiments of the invention, LightScribe discs are not necessary, and low-speed control required to implement the LightScribe function can be performed even when typical discs for recording are used. 
     Since the encoder is formed on the ring member, the encoder is prevented from being damaged even if a disc is repetitively placed in and out of the chucking device. 
     The uniform encoder print state allows for precise low-speed control, as well as the enhancement of printing quality. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.

Technology Classification (CPC): 7