Patent Publication Number: US-11664713-B2

Title: Rotary reciprocating drive actuator having magnets and coils, capable of attaching a movable object

Description:
RELATED APPLICATION 
     This application claims the benefit of priority of Japanese Patent Application No. 2019-225570 filed on Dec. 13, 2019, the contents of which are all incorporated by reference as if fully set forth herein in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to a rotary reciprocating drive actuator. 
     BACKGROUND ART 
     For example, a rotation drive actuator is used in a scanner in a multifunction peripheral, a laser beam printer and other apparatuses. Specifically, a rotary reciprocating drive actuator changes a reflection angle of a laser beam by rotating a mirror of the scanner in a reciprocating manner to realize optical scanning with respect to an object. 
     Conventionally, the scanner using a galvanometer motor as this type of the rotary reciprocating drive actuator is disclosed in such as PTL 1 and PTL 2. Various types of the galvanometer motor, such as a coil movable type in which a coil is attached to the mirror and a structure disclosed in PTL 1, are known. 
     Incidentally, PTL 1 discloses a beam scanner in which four permanent magnets are provided on a rotating shaft to which the mirror is attached so as to be magnetized in the radial direction of the rotating shaft, and a core having magnetic poles around which the coil is wound is disposed so as to sandwich the rotating shaft. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Application Laid-Open No. 2007-333873 
     PTL 2: Japanese Patent Application Laid-Open No. 2014-182167 
     SUMMARY OF INVENTION 
     Technical Problem 
     By the way, in the rotary reciprocating drive actuator of the coil movable type, heat generated by the coil during driving may adversely affect such as a surface state of the mirror, a bonding state of the mirror to the rotating shaft and a shape of the mirror including a warp. Further, in the rotary reciprocating drive actuator of the coil movable type, considering a heat generation of the coil at the time of energization, there are problems that an input current to the coil is difficult to increase and a size and an amplitude of the mirror to be a movable body are difficult to increase. Further, there is a problem that an assemblability is poor, because it is necessary to pull out wirings to the coil to a fixed body side with respect to the mirror to be the movable body. 
     In PTL 1, since the magnets are disposed on the movable body side, the above problem of the coil movable type can be solved. In PTL 1, however, two magnets per one core pole and a total of four magnets are required in order to make the magnet stationary at the neutral position with respect to the core, that is, in order to position a switching portion of the magnetic pole of the magnet at the center of the core. 
     Thereby, there is a problem that the amplitude of the movable body is reduced, that is, a swing range is reduced, as compared with the case where an equivalent rotary reciprocating drive actuator is configured by using two poles magnet, for example. Further, since at least four magnets are used, a number of parts is large, the structure is complicated and the assembly is difficult. 
     Further, in recent years, as a rotary reciprocating drive actuator used in a scanner, a rotary reciprocating drive actuator that has rigidity, impact resistance and vibration resistance, improves assemblability and can achieve high amplitude is desired on the assumption that the mirror to be the movable body is enlarged and the like. 
     Further, as also described in PTL 1, the rotary reciprocating drive actuator is provided with an angle sensor for detecting a rotation angle of the rotation shaft connected to the mirror. A scanning accuracy as a scanner greatly depends on a detection accuracy of the angle sensor. In order to improve the detection accuracy of the angle sensor, it is necessary to adjust a mounting position of the angle sensor with high accuracy so that the relative relationship between the angle sensor and the other components of the rotary reciprocating drive actuator such as the mirror becomes a determined relationship. Such requirements make it difficult to assemble the rotary reciprocating drive actuator. 
     The present invention has been made in consideration of the above points, and provides a rotary reciprocating drive actuator which can be easily assembled and can drive a movable object at a high amplitude. 
     Solution to Problem 
     According to one aspect of a rotary reciprocating drive actuator of the present invention, the rotary reciprocating drive actuator comprising:
         a base portion;   a movable magnet fixed to a shaft portion to which a movable object is connected; and   a drive unit having a core body and a coil body for generating a magnetic flux in the core body when current is supplied, and driving the movable magnet in a rotary reciprocating manner by an electromagnetic interaction between the magnetic flux generated from the core body and the movable magnet,   wherein the movable magnet is formed in a ring shape, and is configured by alternately magnetizing an even number of magnetic poles forming an S-pole and an N-pole at an outer periphery of the shaft portion;   a number of magnetic poles of the core body and a number of magnetic poles of the movable magnet are equal to each other;   an even number of magnetic poles of the core body is respectively arranged to face the movable magnet with an air gap therebetween on the outer peripheral side of the shaft portion;   the drive unit is provided with a magnet position holding portion which is a magnetic material provided to face the movable magnet and magnetically attracts the movable magnet to a reference position;   a pair of wall portions is erected on the base portion to rotatably support the shaft portion via a bearing, and the movable object is disposed between the pair of wall portions; and   the drive unit is attached to one wall portion of the pair of wall portions, and an angle sensor portion for detecting the rotation angle of the shaft portion is attached to the other wall portion of the pair of wall portions.       

     Advantageous Effects of Invention 
     According to the present invention, since the magnet position holding portion for magnetically attracting the movable magnet to the reference position is provided, even if the movable object is a large sized mirror, it can be driven at a high amplitude. Further, since the angle sensor portion is attached to the other wall portion with respect to the wall portion to which the drive unit is attached in the pair of wall portions, it can be easily assembled. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG.  1    is an external perspective view of a rotary reciprocating drive actuator of an embodiment; 
         FIG.  2    is an exploded perspective view of the rotary reciprocating drive actuator; 
         FIG.  3    is a side view of the rotary reciprocating drive actuator of  FIG.  1    viewed from a drive unit side; 
         FIG.  4    is a view for explaining an operation of a magnetic circuit of the rotary reciprocating drive actuator; 
         FIG.  5    is a view for explaining the operation of the magnetic circuit of the rotary reciprocating drive actuator; 
         FIG.  6    is a block diagram showing a configuration of main parts of a scanner system using the rotary reciprocating drive actuator; 
         FIG.  7    is an external perspective view showing an exemplary configuration of the scanner system; 
         FIG.  8    is an external perspective view showing another exemplary configuration of the scanner system; 
         FIG.  9    is an external perspective view of the rotary reciprocating drive actuator of another embodiment; and 
         FIG.  10    is an exploded perspective view of the rotary reciprocating drive actuator of another embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
     &lt;1&gt; Entire Configuration of a Rotary Reciprocating Drive Actuator 
       FIG.  1    is an external perspective view of rotary reciprocating drive actuator  100  of the embodiment.  FIG.  2    is an exploded perspective view of rotary reciprocating drive actuator  100 . 
     Rotary reciprocating drive actuator  100  is used, for example, in a LIDAR (Laser Imaging Detection and Ranging) apparatus. Note that, rotary reciprocating drive actuator  100  is also applicable to a scanner in a multifunction peripheral, a laser beam printer and other apparatuses. 
     Rotary reciprocating drive actuator  100  is roughly divided into base portion  110 ; mirror portion  120  rotatably supported by base portion  110 ; drive unit  200  for driving mirror portion  120  in a rotary reciprocating manner; and angle sensor portion  130  for detecting a rotational angle position of mirror portion  120 . 
     As can be seen from  FIG.  2   , mirror  121  is attached to one surface of substrate  122  in mirror portion  120 . Shaft portion  141  is inserted into insertion hole  122   a  of substrate  122 , and substrate  122  and shaft portion  141  are fastened. 
     Base portion  110  is a member having a substantially U-shaped cross section and having a pair of wall portions  111   a  and  111   b . Insertion hole  112  through which shaft portion  141  is inserted is formed in each of the pair of wall portions  111   a  and  111   b . Further, notched holes  113  communicating insertion holes  112  and the outer edges of wall portions  111   a  and  111   b  are formed in the pair of wall portions  111   a  and  111   b , respectively. 
     Thus, shaft portion  141  can be disposed at positions of insertion holes  112  through notched holes  113  in a state where mirror portion  120  is fastened to shaft portion  141 . In the case where notched holes  113  are not provided, a complicated assembly operation is required in which shaft portion  141  is inserted into both insertion holes  112  of wall portions  111   a ,  111   b  and insertion hole  122   a  of substrate  122  while mirror portion  120  is disposed between the pair of wall portions  111   a  and  111   b , and shaft portion  141  and substrate  122  are fastened. In contrast, in the present embodiment, since notched holes  113  are formed, shaft portion  141  to which mirror portion  120  is fastened in advance can be easily inserted into insertion holes  112 . 
     Ball bearings  151  are attached to both ends of shaft portion  141 . Ball bearings  151  are mounted to bearing mounting portions  114  formed at the positions of insertion holes  112  of the pair of wall portions  111   a  and  111   b . Thus, shaft portion  141  is rotatably attached to base portion  110  via ball bearings  151 , and mirror portion  120  to be the movable object is disposed between the pair of wall portions  111   a  and  111   b.    
     Further, movable magnet  161  is fastened to one end of shaft portion  141 . Movable magnet  161  is disposed inside of drive unit  200  and is driven in a rotary reciprocating manner by a magnetic flux generated by drive unit  200 . 
     As described above, in the present embodiment, shaft portion  141  to which mirror portion  120  to be the movable object is attached is pivotally supported by the pair of wall portions  111   a  and  111   b  of base portion  110  so as to support mirror portion  120  from both sides. Thus, mirror portion  120  is supported more firmly than the case where shaft portion  141  is pivotally supported in a cantilever manner, and a shock resistance and a vibration resistance are improved. 
     As can be seen from  FIG.  2   , drive unit  200  has core body  210  and coil body  220 . A coil is provided with a winding inside of coil body  220 . Core body  210  includes first core body  211  and second core body  212 . Similarly, coil body  220  includes first coil body  221  and second coil body  222 . Coil body  220  is mounted so as to be inserted into a part of core body  210 . Thus, when the coil of coil body  220  is energized, core body  210  is excited. 
     Core body  210  and coil body  220  are fixed to fixing plate  250 , and fixing plate  250  is fixed to wall portion  111   a  of base portion  110  via fastening members  251 . 
     Incidentally, in the present embodiment, drive unit  200  further includes bridging core  230  and magnet position holding portion  240 . Bridging core  230  has the same structure as core body  210 . Magnet position holding portion  240  is made of a magnet. A position of movable magnet  161  is magnetically attracted to a movement reference position by a magnetic force of magnet position holding portion  240 . This will be described in detail later. 
     In the example of the present embodiment, core body  210  and bridging core  230  are laminated cores, and are formed by laminating, for example, silicon steel plates. 
     Angle sensor portion  130  includes circuit board  131 ; optical sensor  132  and connector  133  mounted on circuit board  131 ; encoder disk  134 ; and case  135 . Circuit board  131  is fixed to case  135  by fastening members  136 . Case  135  is fixed to wall portion  111   b  by fastening members  137 . 
     Encoder disk  134  is mounted by fastening to shaft portion  141  via mounting member  138 , and rotates integrally with movable magnet  161  and mirror portion  120 . That is, mounting member  138  has an insertion hole through which shaft portion  141  is inserted and fastened, and a flange portion to which encoder disk  134  is abutted and fastened, and mounting member  138  is fixed to both shaft portion  141  and encoder disk  134 . As a result, a rotational position of encoder disk  134  is the same as a rotational position of shaft portion  141 . Optical sensor  132  emits light to encoder disk  134  and detects the rotational position (angle) of encoder disk  134  based on the reflected light. Thus, the rotational positions of movable magnet  161  and mirror portion  120  can be detected by optical sensor  132 . 
     In the rotary reciprocating drive actuator  100  of the present embodiment, the movable body having movable magnet  161  and shaft portion  141 , and drive unit  200  having coil body  220 , core body  210 , and the like are attached to an outer surface side of one wall portion  111   a  of the pair of wall portions  111   a  and  111   b  of base portion  110 . On the other hand, angle sensor portion  130  for detecting the rotation angle of shaft portion  141  is attached to an outer surface side of the other wall portion  111   b  of the pair of wall portions  111   a  and  111   b  of base portion  110 . 
     This makes it easy to remove angle sensor portion  130  and adjust an assembly position thereof. Since angle sensor portion  130  can be easily removed, angle sensor portion  130  can be easily replaced when a failure occurs in angle sensor portion  130 . Further, angle sensor portion  130  can be assembled at the final stage of assembly. As a result, the expensive angle sensor portion  130  can be assembled after it is confirmed that the assembly of the other components is normal. Therefore, a risk of wasting the expensive angle sensor portion  130  due to the assembly failure of the other components can be suppressed. 
     &lt;2&gt; Detailed Configuration and Operation of Rotary Reciprocating Drive Actuator 
     Next, detailed configuration and operation of rotary reciprocating drive actuator  100  will be described with reference to  FIGS.  3  to  5   . 
       FIG.  3    is a side view of rotary reciprocating drive actuator  100  of  FIG.  1    viewed from the left side of  FIG.  1   . That is, drive unit  200  is mainly shown in  FIG.  3   . 
     In rotary reciprocating drive actuator  100 , the movable body including movable magnet  161 , shaft portion  141  and other potions is rotatably held by the magnetic attraction force, that is, a magnetic spring, between magnet position holding portion  240  and movable magnet  161 , so that the movable body is positioned at the movement reference position in the normal state. Here, the normal state is a state where coil body  220  is not energized. 
     Positioning the movable body at the movement reference position means that movable magnet  161  is positioned at a neutral position with respect to magnetic poles  211   a  and  212   a  of core body  210  excited by coil body  220  in the present embodiment, and it is a position capable of rotating similarly in either one direction and the other direction around the shaft (normal rotation and reverse rotation viewed from shaft portion  141  side). In other words, the movement reference position at which magnet position holding portion  240  magnetically attracts movable magnet  161  is a rotational center position of the rotating reciprocation of movable magnet  161 . When the movable body is positioned at the movement reference position, magnetic pole switching portions  161   c  of movable magnet  161  are positioned at positions facing the magnetic poles of coil body  220  side. 
     By the cooperation of movable magnet  161  and coil body  220 , shaft portion  141  of the movable body rotates in one direction and in the other direction around the shaft from the movement reference position in a reciprocating manner with respect to base portion  110 . 
     Movable magnet  161  is formed in a ring shape, and has an even number of magnetic poles  161   a ,  161   b  in which an S-pole (a South pole) and an N-pole (a North pole) are alternately magnetized in a direction orthogonal to the rotational axis direction of shaft portion  141  at an outer periphery of shaft portion  141 . Although movable magnet  161  is magnetized to two poles in the present embodiment, it may be magnetized to two or more poles depending on an amplitude at the time of movement. 
     The even number of magnetic poles  161   a  and  161   b  has magnetization surfaces of different polarities facing opposite direction to each other across shaft portion  141 . In the present embodiment, magnetic poles  161   a  and  161   b  have different polarities in which a plane along the axial direction of shaft portion  141  is as a boundary thereof. 
     Further, the even number of magnetic poles  161   a  and  161   b  is configured to magnetize at equal intervals at the outer periphery of shaft portion  141 . 
     As described above, in movable magnet  161 , the even number of magnetic poles  161   a  and  161   b  forming the S-pole and the N-pole is alternately arranged at the outer periphery of shaft portion  141 , and the magnetic poles  161   a  and  161   b  are arranged at equal intervals. 
     More specifically, in movable magnet  161 , each of semicircular portions constitutes different magnetic poles  161   a  and  161   b . Arc shaped curved surfaces of the semicircular portions are magnetization surfaces of different magnetic poles  161   a  and  161   b , and the magnetization surfaces of different magnetic poles  161   a  and  161   b  are configured to extend in a circumferential direction around the shaft. In other words, the magnetization surfaces of magnetic poles  161   a  and  161   b  are arranged in a direction orthogonal to the axial direction of shaft portion  141 , and are rotated to be able to face to magnetic pole  211   a  of first core body  211  and magnetic pole  212   a  of second core body  212 , respectively. 
     A number of magnetic poles of movable magnet  161  is equal to a number of magnetic poles of core body  210 . 
     Magnetic pole switching portions  161   c  of magnetic poles  161   a  and  161   b  of movable magnet  161  are located at positions facing center positions in a width direction of magnetic pole  211   a  of first core body  211  and magnetic pole  212   a  of second core body  212  when coil body  220  is not energized. 
     First core body  211  and second core body  212  are parallel to each other, and have core portions  211   b  and  212   b  (see  FIG.  4   ) which are formed so as to sandwich movable magnet  161 . First coil body  221  and second coil body  222  are respectively extrapolated to core portions  211   b  and  212   b . Bridging core  230  is provided to be bridged between one end portions of core portions  211   b  and  212   b , and magnetic poles  211   a  and  212   a  are formed continuously on the other end portions of core portions  211   b  and  212   b.    
     As described above, core body  210  has core portions  211   b  and  212   b  to which first coil body  221  and second coil body  222  are extrapolated; magnetic poles  211   a  and  212   a ; and bridging core  230  provided to be bridged between the end portions opposite to magnetic poles  211   a  and  212   a . That is, core body  210  is configured from three split bodies. Among these split bodies, bridging core  230  is provided with magnet position holding portion  240 . 
     Two magnetic poles  211   a  and  212   b  are disposed to face each other so as to sandwich movable magnet  161  with air gap G between them and the outer periphery of movable magnet  161 . 
     Magnet position holding portion  240 , which is disposed to face movable magnet  161  with air gap G therebetween, is attached to bridging core  230  so as to project convexly toward movable magnet  161  side. 
     Magnet position holding portion  240  is, for example, a magnet whose opposing surface is magnetized to the N-pole (see  FIG.  4   ). Magnet position holding portion  240  may be formed integrally with bridging core  230 . 
     Magnet position holding portion  240  functions as a magnetic spring together with movable magnet  161  by the magnetic attraction force generated between it and movable magnet  161 , and positions and holds the position of rotating movable magnet  161  at the movement reference position. 
     Magnet position holding portion  240  is a magnet magnetized toward movable magnet  161 . Magnet position holding portion  240  positions magnetic pole switching portions  161   c  of movable magnet  161  at positions facing magnetic poles  211   a  and  212   a  when movable magnet  161  is positioned at the movement reference position. As described above, magnet position holding portion  240  and movable magnet  161  are attracted to each other, and magnet position holding portion  240  can position movable magnet  161  at the movement reference position. Thus, magnetic pole switching portions  161   c  of movable magnet  161  face magnetic pole  211   a  of first core body  211  and magnetic pole  212   a  of second core body  212 . At this position, drive unit  200  generates the maximum torque to stably drive the movable body. 
     Further, since movable magnet  161  is magnetized with two poles, the movable object can be easily driven at a high amplitude and vibration performance can be improved by cooperation with core body  210 . 
       FIGS.  4  and  5    are views for explaining an operation of a magnetic circuit of rotary reciprocating drive actuator  100 . 
     When coil body  220  ( 221 ,  222 ) is not energized, movable magnet  161  is positioned at the movement reference position by the magnetic attraction force between magnet position holding portion  240  and movable magnet  161 , that is, the magnetic spring. 
     In this movement reference position (hereinafter, the movement reference position may be referred to as a normal state), one of magnetic poles  161   a  and  161   b  of movable magnet  161  is attracted to magnet position holding portion  240 , and magnetic pole switching portions  161   c  are positioned at positions facing the center positions of magnetic pole  211   a  of first core body  211  and magnetic pole  212   a  of second core body  212 . 
     When coil body  220  is energized, coil body  220  ( 221 ,  222 ) excite first core body  211  and second core body  212 . 
     When coil body  220  is energized in the direction shown in  FIG.  4   , magnetic pole  211   a  is magnetized to the N-pole, and magnetic pole  212   a  is magnetized to the S-pole. 
     As a result, in first core body  211 , a magnetic flux is formed in which the magnetic flux is emitted from magnetic pole  211   a  magnetized to the N-pole to movable magnet  161 , flows through movable magnet  161 , magnet position holding portion  240 , and bridging core  230  in this order, and enters into core portion  211   b.    
     In second core body  212 , the magnetic flux is emitted from core portion  212   b  to bridging core  230  side, flows through bridging core  230 , magnet position holding portion  240 , and movable magnet  161  in this order, and enters magnetic pole  212   a.    
     As a result, magnetic pole  211   a  magnetized to the N-pole is attracted to the S-pole in movable magnet  161 , magnetic pole  212   a  magnetized to the S-pole is attracted to N-pole in movable magnet  161 , a torque in the F direction is generated around the axis of shaft portion  141  in movable magnet  161 , and movable magnet  161  rotates in the F direction. Accordingly, shaft portion  141  also rotates, and mirror portion  120  fixed to shaft portion  141  also rotates. 
     Next, as shown in  FIG.  5   , when the energization direction of coil body  220  is switched to the opposite direction, magnetic pole  211   a  is magnetized to the S-pole, magnetic pole  212   a  is magnetized to the N-pole, and the flow of the magnetic flux is also reversed. 
     As a result, magnetic pole  211   a  magnetized to the S-pole is attracted to the N-pole in movable magnet  161 , magnetic pole  212   a  magnetized to the N-pole is attracted to the S-pole in movable magnet  161 , a torque in the direction opposite to the F direction is generated around the axis of shaft portion  141  in movable magnet  161 , and movable magnet  161  rotates in the direction opposite to the F direction. Accordingly, shaft portion  141  also rotates in the opposite direction, and mirror portion  120  fixed to shaft portion  141  also rotates in the opposite direction. By repeating these motions, rotary reciprocating drive actuator  100  drives mirror portion  120  in a rotary reciprocating manner. 
     In practice, rotary reciprocating drive actuator  100  is driven by an alternating current wave input from a power supply unit (for example, corresponding to drive signal supply unit  303  in  FIG.  6   ) to coil body  220 . That is, the energization direction of coil body  220  is periodically switched, and the torque in the F direction around the axis and the torque in the direction opposite to the F direction (−F direction) alternately act on the movable body. Thus, the movable body is driven in a rotary reciprocating manner. 
     Incidentally, at the time of switching the energization direction, the magnetic attraction force between magnet position holding portion  240  and movable magnet  161  is generated, that is, magnetic spring torque FM ( FIG.  4   ) or −FM ( FIG.  5   ) is generated by the magnetic spring, and movable magnet  161  is urged to the movement reference position. 
     The driving principle of rotary reciprocating drive actuator  100  will be briefly described below. In rotary reciprocating drive actuator  100  of the present embodiment, when the moment of inertia of the movable body is J [kg·m 2 ] and the spring constant in the torsional direction of the magnetic spring (magnetic poles  211   a  and  212   a , magnet position holding portion  240 , and movable magnet  161 ) is K sp , the movable body vibrates (rotary reciprocates) with respect to base portion  110  at a resonance frequency F r  [Hz] calculated by the equation (1). 
                     F   r     =       1     2   ⁢   π       ⁢         K   sp     J                 [     Equation   ⁢         1     ]               
F r : Resonance frequency [Hz]
 
J: Moment of inertia [kg·m 2 ]
 
K sp : Spring constant [N·m/rad]
 
     Since the movable body constitutes a mass portion in a vibration model of a spring-mass system, when an alternating current wave having a frequency equal to the resonance frequency F r  of the movable body is inputted to coil body  220 , the movable body enters a resonance state. That is, by inputting the alternating current wave having a frequency substantially equal to the resonance frequency F r  of the movable body to coil body  220  from the power supply unit, the movable body can be efficiently vibrated. 
     A motion equation and a circuit equation showing the driving principle of rotary reciprocating drive actuator  100  are shown below. Rotary reciprocating drive actuator  100  is driven based on the motion equation expressed by the equation (2) and the circuit equation expressed by the equation (3). 
                     J   ⁢         d   2     ⁢     θ   ⁡   (   t   )         dt   2         =         K   t     ⁢     i   ⁡   (   t   )       -       K   sp     ⁢     θ   ⁡   (   t   )       -     D   ⁢       d   ⁢     θ   ⁡   (   t   )       dt       -     T   Loss               [     Equation   ⁢         2     ]               
J: Moment of inertia [kg·m 2 ]
 
θ(t): Rotation angle [rad]
 
K t : Torque constant [N·m/A]
 
i(t): Current [A]
 
K sp : Spring constant [N·m/rad]
 
D: Damping coefficient [N·m/(rad/s)]
 
T Loss : Load torque [N·m]
 
                     e   ⁡   (   t   )     =       Ri   ⁡   (   t   )     +     L   ⁢       di   ⁡   (   t   )     dt       +       K   e     ⁢       d   ⁢     θ   ⁡   (   t   )       dt                 [     Equation   ⁢         3     ]               
e(t): Voltage [V]
 
R: Resistance [Ω]
 
L: Inductance [H]
 
K e : Counter electromotive force constant [V/(rad/s)]
 
     That is, the moment of inertia J [kg·m 2 ], the rotation angle θ(t) [rad], the torque constant K t  [N·m/A], the current i(t) [A], the spring constant K sp  [N·m/rad], the damping coefficient D [N·m/(rad/s)], the load torque T Loss  [N·m], and the like of the movable body in rotary reciprocating drive actuator  100  can be appropriately changed within the range satisfying the equation (2). Further, the voltage e(t) [V], the resistance R [Ω], the inductance L [H], and the counter electromotive force constant K e  [V/(rad/s)] can be appropriately changed within the range satisfying the equation (3). 
     As described above, rotary reciprocating drive actuator  100  can efficiently obtain a large vibration output when the coil is energized by the alternating current wave corresponding to the resonance frequency F r  determined by the moment of inertia J of the movable body and the spring constant K sp  of the magnetic spring. 
     According to rotary reciprocating drive actuator  100  of the present embodiment, since a torque generation efficiency is high, heat is hard to transfer to mirror  121  which is the movable object, and as a result, a flatness of a reflection surface of mirror  121  can be ensured with high accuracy. Further, a manufacturing efficiency is high, an assembly accuracy is good, and even if the movable object is a large sized mirror, it can be driven at a high amplitude. 
     Note that, rotary reciprocating drive actuator  100  of the present embodiment can be driven by resonance, but can also be driven by non-resonance. 
     &lt;3&gt; Overview Configuration of Scanner System 
     Next, a configuration of a scanner system using rotary reciprocating drive actuator  100  will be briefly described. 
       FIG.  6    is a block diagram showing an essential configuration of scanner system  300 A using rotary reciprocating drive actuator  100 . 
     Scanner system  300 A includes laser emitting unit  301 ; laser control unit  302 ; drive signal supply unit  303 ; and position control signal calculation unit  304  in addition to rotary reciprocating drive actuator  100 . 
     Laser emitting unit  301  includes, for example, an LD (laser diode) to be a light source; a lens system for converging a laser beam output from the light source, and the like. Laser control unit  302  controls laser emitting unit  301 . The laser beam obtained by laser emitting unit  301  is incident on mirror  121  of rotary reciprocating drive actuator  100 . 
     Position control signal calculation unit  304  generates and outputs a drive signal for controlling shaft portion  141  (mirror  121 ) to be the target angular position with reference to the angular position of shaft portion  141  (mirror  121 ) acquired by angle sensor portion  130  and the target angular position. For example, position control signal calculation unit  304  generates a position control signal on the basis of the obtained angular position of shaft portion  141  (mirror  121 ) and a signal indicating the target angular position converted using sawtooth waveform data, and the like stored in a waveform memory which is not illustrated, and outputs the position control signal to drive signal supply unit  303 . 
     Based on the position control signal, drive signal supply unit  303  supplies the drive signal to coil body  220  of rotary reciprocating drive actuator  100  such that the angular position of shaft portion  141  (mirror  121 ) becomes a desired angular position. Thus, scanner system  300 A can emit a scanning light from rotary reciprocating drive actuator  100  to a predetermined scanning area. 
       FIG.  7    is an external perspective view showing an example of the configuration of the scanner system, in which the same reference signs are assigned to the corresponding parts in  FIG.  1   . In scanner system  300 C, laser unit  410  is provided on base portion  110 . Laser unit  410  includes laser emitting unit  411  and laser light receiving unit  412 . Thus, a laser beam emitted from laser emitting unit  411  is reflected by mirror portion  120  of rotary reciprocating drive actuator  100  to be a scanning light, and irradiated to a scanning object. The scanning light reflected by the scanning object is received by laser light receiving unit  412  through mirror portion  120 . Note that, in rotary reciprocating drive actuator  100  of scanner system  300 C, as compared with rotary reciprocating drive actuator  100  of  FIG.  1   , a bottom plate of base portion  110  is extended in a depth direction in the drawing, and laser unit  410  is installed in this extended portion. 
       FIG.  8    is an external perspective view showing another configuration example of the scanner system, in which the same reference signs are assigned to the corresponding parts in  FIG.  7   . Scanner system  300 D has the same configuration as scanner system  300 C except that laser unit  410  is disposed at a different position. 
     As shown in  FIGS.  7  and  8   , since laser unit  410  is provided in base portion  110  of rotary reciprocating drive actuator  100 , laser unit  410  can be easily and accurately attached to rotary reciprocating drive actuator  100 . 
     Here, if a function as a scanner is to be realized, laser unit  410  may not have laser light receiving unit  412  but may have only laser emitting unit  411 . However, in the present embodiment, since laser unit  410  also has laser light receiving unit  412 , and laser unit  410  is provided in base portion  110  of rotary reciprocating drive actuator  100 , as a result, laser light receiving unit  412  as the light detecting unit is a configuration in which laser light receiving unit  412  is directly attached to the scanner portion. Thus, the positioning accuracy of the laser light receiving unit to the scanner portion can be easily enhanced. 
     &lt;4&gt; Summary 
     As described above, rotary reciprocating drive actuator  100  of the present embodiment includes base portion  110 ; movable magnet  210  fixed to shaft portion  141  to which the movable object (mirror portion  120  in the example of the embodiment) is connected; and drive unit  200  having core body  210  and coil body  220  for generating the magnetic flux in core body  161  when the current is supplied, and driving movable magnet  161  in a rotary reciprocating manner by the electromagnetic interaction between the magnetic flux generated from core body  210  and movable magnet  161 . Further, in rotary reciprocating drive actuator  100 , movable magnet  161  is formed in the ring shape, and is configured by alternately magnetizing the even number of magnetic poles forming the S-pole and the N-pole at the outer periphery of shaft portion  141 ; the number of magnetic poles of core body  210  and the number of magnetic poles of movable magnet  161  are equal to each other; the even number of magnetic poles of core body  210  is respectively arranged to face movable magnet  161  with the air gap therebetween on the outer peripheral side of shaft portion  141 ; and drive unit  200  is provided with magnet position holding portion  240  which is a magnetic material provided to face movable magnet  161  and magnetically attracts movable magnet  161  to a reference position. 
     Thus, since movable magnet  161  is magnetically attracted to the neutral position (movement reference position) by magnet position holding portion  240  every time the energization direction is switched, good energy efficiency, good responsiveness, and high amplitude rotary reciprocating drive are realized. Further, compared with the rotary reciprocating drive actuator of the coil movable type, the heat generated by coil body  220  is hard to transfer to the movable object, and when the movable object is a mirror, it is possible to prevent adverse effects (bond deterioration, warpage, etc.) of the heat from affecting the mirror. 
     In addition, in rotary reciprocating drive actuator  100  of the present embodiment, the pair of wall portions  111   a  and  111   b  for rotatably supporting shaft portion  141  via bearings (ball bearings  151 ) are provided in base portion  110 , the movable object (mirror portion  120  in the example of the embodiment) is disposed between the pair of wall portions  111   a  and  111   b . Drive unit  200  is attached to the outer surface side of one wall portion  111   a  of the pair of wall portions  111   a  and  111   b , and angle sensor portion  130  for detecting the rotation angle of shaft portion  141  is attached to the outer surface side of the other wall portion  111   b  of the pair of wall portions  111   a  and  111   b.    
     This makes it easy to remove angle sensor portion  130  and adjust the assembly position thereof. Since angle sensor portion  130  can be easily removed, angle sensor portion  130  can be easily replaced when the failure occurs in angle sensor portion  130 . Further, angle sensor portion  130  can be assembled at the final stage of assembly. As a result, the expensive angle sensor portion  130  can be assembled after it is confirmed that the assembly of the other components is normal. Therefore, the risk of wasting the expensive angle sensor portion  130  due to the assembly failure of the other components can be suppressed. 
     In one aspect of the present invention, the reference position at which magnet position holding portion  240  magnetically attracts movable magnet  161  is the rotational center position of the rotating reciprocation of movable magnet  161 . 
     In one aspect of the present invention, in movable magnet  161 , the even number of magnetic poles is magnetized at equal intervals at the outer periphery of shaft portion  141 . 
     In one aspect of the present invention, magnet position holding portion  240  is disposed at the position between the even number of magnetic poles of core body  210  and at the position facing movable magnet  161  in the radial direction of movable magnet  161 . 
     These configurations can maximize a driving torque and stabilize a direction of the driving torque. 
     The above embodiments are merely specific examples for carrying out the present invention, and the technical scope of the present invention should not be construed to be limited by them. That is, the present invention can be implemented in a variety of ways without departing from the spirit or essential features thereof. 
     In the above embodiment, the case where wall portion  111   b  to attach angle sensor portion  130  is formed integrally with base portion  110  is described. A wall portion to attach angle sensor portion  130 , however, may not be formed integrally with base portion  110  but may be attached to the base portion later. 
     Specifically, as shown in  FIG.  9    in which the same reference signs are assigned to the corresponding portions in  FIG.  1    and FIG. in which the same reference signs are assigned to the corresponding portions in  FIG.  2   , rotary reciprocating drive actuator  100 A has an L shaped base portion  110 ′. In rotary reciprocating drive actuator  100 A, wall portion  111   c  to which angle sensor portion  130  is attached to the inner surface is attached to base portion  110 ′. In this configuration, since wall portion  111   c  can be removed from or relatively moved with respect to base portion  110 ′, angle sensor portion  130  can also be easily removed and the assembling position can be easily adjusted. However, as in the above embodiments, the configuration in which angle sensor portion  130  is attached to the outer surface side of wall portion  111   b  is easier to remove and adjust the assembling position of angle sensor portion  130 . 
     In the above embodiments, the case where ball bearings  151  are used as bearings for rotatably attaching shaft portion  141  to base portion  110  is described. The present invention, however, is not limited thereto, and an air bearing, an oil bearing and other bearings may be used as bearings. 
     In the above embodiments, the case where drive unit  200  is mounted on the outer surface side of wall portion  111   a  is described. The position of drive unit  200 , however, is not limited thereto. Dive unit  200  may be mounted, for example, on the inner surface side of wall portion  111   a.    
     In the above embodiments, the case where the movable object driven by rotary reciprocating drive actuator  100 , that is, the movable object attached to shaft portion  141  is mirror portion  120  is described. The movable object, however, is not limited thereto. For example, a camera or the like may be the movable object. 
     INDUSTRIAL APPLICABILITY 
     The present invention is suitable for a scanner, for example. 
     REFERENCE SIGNS LIST 
     
         
           100 ,  100 A Rotary reciprocating drive actuator 
           110 ,  110 ′ Base portion 
           111   a ,  111   b ,  111   c  Wall portion 
           112  Insertion hole 
           113  Notched hole 
           114  Bearing mounting portion 
           120  Mirror portion 
           121  Mirror 
           122  Substrate 
           122   a  Insertion hole 
           130  Angle sensor portion 
           131  Circuit board 
           132  Optical sensor 
           133  Connector 
           134  Encoder disk 
           135  Case 
           136 ,  137 ,  251  Fastening member 
           138  Mounting member 
           141  Shaft portion 
           151  Ball bearing 
           161  Movable magnet 
           161   c  Magnetic pole switching portion 
           200  Drive Unit 
           210  Core body 
           211  First core body 
           212  Second core body 
           220  Coil body 
           221  First coil body 
           222  Second coil body 
           230  Bridging core 
           240  Magnet position holding portion 
           250  Fixing Plate 
           300 A,  300 C,  300 D Scanner system 
           301 ,  411  Laser emitting unit 
           302  Laser control unit 
           304  Position control signal calculation unit 
           410  Laser Unit 
           412  Laser light receiving unit