Abstract:
A rotary actuator includes a roller having a center shaft protruding along a center axis, a bearing for supporting the center shaft of the roller to allow the roller to rotate about the center axis, a ring magnet fixed to the center shaft of the roller, an elastic member having a ring shape provided between the center shaft of the roller and the bearing, and a fixed magnet facing the ring magnet. The ring magnet is alternately magnetized to an S-pole and an N-pole with predetermined angular intervals. This rotary actuator has a simple structure and operates with a preferable operation feeling.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a rotary actuator to be used for operating various electronic devices, and to an input device using the rotary actuator. 
     BACKGROUND OF THE INVENTION 
     As various electronic apparatuses, such as mobile phones and video cameras, have recently had small sizes and high functions, rotary actuators and input devices have been demanded to perform various operations of the apparatuses with a preferable feeling during operation. 
       FIGS. 4 and 5  are a front sectional view and an exploded perspective view of a conventional rotary actuator  6 , respectively. Roller  1  has a substantially columnar shape and is made of metal or insulating resin. An outer circumferential surface of roller  1  has recesses. Roller  1  has center shafts  1 A protruding from both ends of roller  1 . Ring magnet  2  is alternately magnetized to S-poles and N-poles with predetermined angular pitches. Ring magnet  2  is fixed to each end of center shafts  1 A of roller  1 . Roller  1  is accommodated between upper cover  3  and lower cover  4  while center shafts  1 A are rotatably supported by bearings  3 A and  4 A having substantially arcuate shapes. Plural fixed magnets  5  face ring magnets  2  by predetermined gaps provided at both ends of roller  1  with magnetic poles of ring magnet  2  and fixed magnet  5  having the same polarity face each other, thus providing rotary actuator  6 . 
       FIG. 6  is side sectional view of input device  501  including rotary actuator  6 . Plural wiring patterns are formed on upper and lower surfaces of wiring board  7 . Wiring board  7  is located under rotary actuator  6 . Magnetic detector  8 , such as a Hall element, is mounted on the upper surface of wiring board  7 . Magnetic detectors  8  face ring magnets  2  with predetermined gaps, thus providing input device  501 . 
     Input device  501  is mounted to an operating section of an electronic device, such as a mobile phone, including a display, such as a liquid crystal display, and magnetic detector  8  is electrically connected to an electronic circuit of the electronic device via the wiring patterns. 
     An operation of input device  501  will be described below. While plural menus, such as names, or a cursor, are displayed on the display of the electronic device, roller  1  is rotated in left or right directions to rotate ring magnets  2 . Since two ring magnets  2  are alternately magnetized to S-poles and N-poles deviating slightly from each other in angle by a predetermined angular phase difference, ring magnets  2  produce magnetic fields changing in different phases according to the rotation. Magnetic detectors  8  detect the change of the magnetic fields, generate pulse signals having phases different from each other, and send the signals to the electronic circuit of the electronic device. 
     The electronic circuit detects the direction and angle of the rotation of roller  1  based on the pulse signals, and moves the cursor on the menus on the display in vertical or horizontal directions, thereby allowing the menus, such as names, to be selected. 
     When roller  1  is rotated, this rotation produces attractive repulsive forces between ring magnet  2  and fixed magnet  5  facing each other. The attractive and repulsive forces provide generate click feeling, thus providing preferable, clear operation feeling. 
     Roller  1  rotates while center shaft  1 A of roller  1  is supported by bearings  3 A and  4 A of upper cover  3  and lower cover  4 , a friction produced between center shaft  1 A and bearings  3 A and  4 A may cause a user to feel that roller  1  rubs. 
     Ring magnet  2  producing a larger magnetic field allows magnetic detector  8  to detect the direction and angle of the rotation of roller  1  more accurately, but also increases the attractive and repulsive forces between ring magnet  2  and fixed magnet  5 . This may cause a rotation noise due to a shock when roller  1  is operated. Thus, conventional rotary actuator  6  can hardly operate with a preferable operation feeling. 
     BRIEF SUMMARY OF THE INVENTION 
     A rotary actuator includes a roller having a center shaft protruding along a center axis, a bearing for supporting the center shaft of the roller to allow the roller to rotate about the center axis, a ring magnet fixed to the center shaft of the roller, an elastic member having a ring shape provided between the center shaft of the roller and the bearing, and a fixed magnet facing the ring magnet. The ring magnet is alternately magnetized to an S-pole and an N-pole with predetermined angular intervals. 
     This rotary actuator has a simple structure and operates with a preferable operation feeling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front sectional view of a rotary actuator according to an exemplary embodiment of the present invention. 
         FIG. 2  is an exploded perspective view of the rotary actuator according to the embodiment. 
         FIG. 3  is a side sectional view of an input device according to the embodiment. 
         FIG. 4  is a front sectional view of a conventional rotary actuator. 
         FIG. 5  is an exploded perspective view of the conventional rotary actuator. 
         FIG. 6  is a side sectional view of an input device including the conventional rotary actuator. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  are a front sectional view and an exploded perspective view of rotary actuator  15  according to an exemplary embodiment of the present invention, respectively. Roller  11  is made of metal, such as aluminum, or insulating resin and has substantially a columnar shape having center axis  11 A. Grooves  11 C extending in parallel to center axis  11 A are provided in outer circumferential surface  11 B of roller  11 . Center shafts  111 A and  111 B protrude from end surfaces  11 D and  11 E along center axis  11 A of roller  11 , respectively. 
     Ring magnet  2 A is alternately magnetized to S-poles and N-poles with predetermined angular intervals. Ring magnet  2 B is alternately magnetized to S-poles and N-poles with angular intervals identical to those of ring magnet  2 A. Ring magnets  2 A and  2 B are fixed to center shafts  111 A and  111 B, respectively, while the positions of the S-poles and the N-poles are deviated by a predetermined angular phase difference. 
     Upper cover  3  and lower cover  4  are made of metal, such as magnetic steel, to prevent leakage magnetic field. Center shaft  111 A is rotatably supported by bearings  3 A and  4 A having substantially arcuate shapes. Center shaft  111 B is rotatably supported by bearings  13 A and  14 A having arcuate shapes. Roller  11  is accommodated between upper cover  3  and lower cover  4  rotatably about center axis  11 A. Bearings  3 A and  4 A surrounds center shaft  111 A. Bearings  13 A and  14 A surrounds center shaft  111 B. 
     Elastic members  12 A and  12 B made of elastic material, such as fluorine rubber, silicone rubber, urethane rubber, or elastomer, has substantially ring shapes. Elastic member  12 A is mounted to center shaft  111 A of roller  11 , and has an outer circumferential surface thereof contacting bearings  3 A and  4 A of upper cover  3  and lower cover  4 . Elastic member  12 B is mounted to center shaft  111 B of roller  11 , and has an outer circumferential surface thereof contacting bearings  13 A and  14 A of upper cover  3  and lower cover  4 . Elastic members  12 A and  12 B are made preferably of fluorine rubber to smoothly slide on bearings  3 A,  4 A,  13 A, and  14 A. Fluorine powders having a small powder diameter may be attached on surfaces of elastic members  12 A and  12 B. Elastic members  12 A and  12 B are immersed in solution including solvent and the fluorine powders dispersed therein. Then, elastic members  12 A and  12 B are taken out of the solution, and the solvent attached to the members is evaporated, thereby attaching the fluorine powders to elastic members  12 A and  12 B. 
     Fixed magnets  5 A and  5 B face ring magnets  2 A and  2 B with predetermined gaps in between, respectively, providing rotary actuator  15 . Magnetic poles of fixed magnet  5 A face magnetic poles of ring magnet  2 A having polarities identical to polarities of magnetic poles of fixed magnet  5 A. Magnetic poles of fixed magnet  5 B face magnetic poles of ring magnet  2 B having polarities identical to polarities of magnetic poles of fixed magnet  5 B. The positions and shapes of fixed magnets  5 A and  5 B may be determined to stop roller  11  stably while an attractive force and a repulsive force produced between fixed magnets  5 A and  5 B and ring magnets  2 A and  2 B are balanced. 
       FIG. 3  is a side sectional view of input device  1001  including rotary actuator  15 . Wiring board  7  made of phenolic paper or glass epoxy has plural wiring patterns provided on upper surface  7 A and lower surface  7 B of wiring board  7  and is located under rotary actuator  15 . Magnetic detectors  8 A and  8 B, such as Hall elements, are mounted onto upper surface  7 A of wiring board  7 . Magnetic detectors  8 A and  8 B face ring magnets  2 A and  2 B with predetermined gaps in between, respectively, providing input device  1001 . 
     Input device  1001  is mounted to an operating section of an electronic device, such as a mobile phone, including a display, such as a liquid crystal display, and magnetic detectors  8 A and  8 B are electrically connected to an electronic circuit of the electronic device via the wiring patterns. 
     While plural menus, such as names, or a map, or a cursor or a pointer are displayed on the display, roller  11  is rotated in left direction  1001 A or right direction  1001 B about center axis  11 A, and ring magnets  2 A and  2 B each of which is alternately magnetized to the S-poles and the N-poles are rotated, accordingly. Since ring magnets  2 A and  2 B are fixed by the predetermined angular phase difference and since each of magnets  2 A and  2 B is magnetized to the S-poles and the N-poles by an identical angular intervals, magnetic detectors  8 A and  8 B output pulse signals having phases different from each other to the electronic circuit of the electronic device according to the rotation of ring magnets  2 A and  2 B, i.e., roller  11 . 
     The electronic circuit of the electronic device detects the direction and angle of the rotation of roller  11  based on the pulse signals, moves the cursor or pointer on the menus vertically or horizontally, thereby allowing a user to select the menus, such as the names, or the map. 
     When roller  11  is rotated, attractive and repulsive forces are generated between ring magnet  2 A and fixed magnet  5 A and between ring magnet  2 B and fixed magnet  5 B according to the rotation. These attractive and repulsive forces provide a preferable, clear operation feeling with a click feeling during the rotation of roller  11 . When roller  11  stops, the attractive and repulsive forces between ring magnet  2 A and fixed magnet  5 A and between ring magnet  2 B and fixed magnet  5 B are balanced, thereby holding roller  11  stably. 
     In rotary actuator  15  according to this embodiment, ring magnets  2 A and  2 B are fixed to center shafts  111 A and  111 B of roller  11 , respectively, while the magnetic poles of ring magnets  2 A and  2 B deviate by a predetermined angular phase difference. Magnetic detectors  8 A and  8 B output the pulse signals having phases different from each other. In another rotary actuator according to the embodiment, ring magnets  2 A and  2 B may be fixed to roller  11  while the magnetic poles of ring magnets  2 A and  2 B coincide with each other, and magnetic detectors  8 A and  8 B may be located at positions deviating with respect to ring magnets  2 A and  2 B, thereby outputting pulse signals having different from each other. For example, in the case that ring magnets  2 A and  2 B are magnetized to the S-poles and the N-poles with angular intervals of 60 degrees, one pulse is output at each rotation angle of 120 degrees. If magnetic detectors  8 A and  8 B are located at positions deviating by, for example, 30 degrees from each other with respect to ring magnets  2 A and  2 B, pulse signals having a phase difference of ¼ cycle, namely, 90 degrees, may be obtained. In still another rotary actuator according to this embodiment, ring magnets  2 A and  2 B are fixed to center shafts  111 A and  111 B of roller  11 , respectively, while the magnetic poles of ring magnets  2 A and  2 B deviate by a predetermined angular phase difference, and magnetic detectors  8 A and  8 B are located at positions deviating with respect to ring magnets  2 A and  2 B, providing the same effects. 
     Roller  11  is rotated while center shafts  111 A and  111 B of roller  11  do not contact bearings  3 A,  13 A,  4 A, and  14 A of upper cover  3  and lower cover  4 , elastic member  12 A mounted to center shaft  111 A contacts bearings  3 A and  4 A, and elastic member  12 B mounted to center shaft  111 B contacts bearings  13 A and  14 A. The outer circumferential surface of elastic member  12 A having the ring shape elastically contacts bearings  3 A and  4 A, and an inner circumferential surface of elastic member  12 A elastically contacts shaft  111 A. Similarly, the outer circumferential surface of elastic member  12 B having the ring shape elastically contacts bearings  13 A and  14 A, and an inner circumferential surface of elastic member  12 B elastically contacts shaft  111 A. Elastic forces with which the outer circumferential surfaces of elastic members  12 A and  12 B elastically contact bearings  3 A,  4 A,  13 A, and  14  B are larger than elastic forces with which the inner circumferential surfaces of elastic members  12 A and  12 B elastically contact shafts  111 A and  111 B. This arrangement allows shafts  111 A and  111 B to slide on the inner circumferential surfaces of elastic members  12 A and  12 B, and prevents elastic members  12 A and  12 B from rubbing on bearings  3 A,  4 A,  13 A, and  14 A, while roller  11  is rotated. 
     The elastic members  12 A and  12 B prevent center shafts  111 A and  111 B from generating a rubbing feeling due to a friction produced when center shafts  111 A and  111 B contacts bearings  3 A,  4 A,  13 A, and  14 A. A simple structure, such as elastic members  12 A and  12 B allows a user to rotate roller  11  with a smooth, sticky comfortable sliding feeling. 
     Elastic members  12 A and  12 B prevent center shafts  111 A and  111 B from directly colliding with bearings  3 A,  4 A,  13 A, and  14 A due to the attractive and repulsive force generated between ring magnets  2 A and  2 B and fixed magnets  5 A and  5 B while roller  11  is rotated, and reduces a shock to reduce a rotation noise due to the shock.