Patent Publication Number: US-2023140711-A1

Title: Actuator

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present invention claims priority under 35 U.S.C. § 119 to Japanese Application No. 2021-176108 filed Oct. 28, 2021, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     Field of the Invention 
     At least an embodiment of the present invention relates to an actuator that vibrates a movable body. 
     Description of the Background Art 
     Japanese Patent Laid-Open No. 2020-102901 (JPA 2020-102901) discloses an actuator that has a movable body including magnets and a support body including coils, and that vibrates the movable body with respect to the support body by applying a drive current to the coil. Such a type of actuator uses an elastic or viscoelastic body as a connecting body that connects the support body and the movable body. When the movable body vibrates, a reaction force corresponding to the vibration of the movable body is applied to the support body through the connecting body. As a result, a user who is touching the support body can feel the vibration. 
     In the actuator of JPA 2020-102901, the support body has a coil holder. The coil is an air core coil and is disposed in a coil placement hole in the coil holder. The movable body includes a first yoke facing the coil from one side and a second yoke facing the coil from the other side, and magnets are fixed to the first and second yokes. The first yoke includes two connecting portions that bend and extend from the two ends of the first yoke toward the second yoke, and the connecting sections of the first yoke are welded or otherwise joined to the two ends of the second yoke. Such a structure constitutes a magnetic circuit through which the magnetic fluxes of the two magnets facing the coil from the two sides pass. 
     When an actuator is used as a tactile device that causes a user who touches the support body to sense vibration, the acceleration of the vibration of the movable body should be increased in order to cause the user to sense strong vibration. For example, it has been proposed to increase the acceleration of vibration of a movable body by increasing the weight of the movable body. In the configuration of JPA 2020-102901, the weight of the movable body can be readily increased by increasing the thickness of the first yoke and the second yoke. 
     However, to increase the thickness of the yokes, it is necessary to use magnetic plates of a different thickness than that of the general-purpose product, which increases the cost. In addition, simply increasing the thickness of the plates will increase the size of the movable body, which is detrimental to the miniaturization of the actuator. That is, in the yokes of JPA 2020-102901, not only does the height of the movable body (the dimension in the direction in which the magnets and coils face each other) increases due to the increased thickness of the flat plate portions to which the magnets are fixed, but the width of the movable body (the dimension in the direction of the vibration of the movable body) becomes larger due to the increased thickness of the connecting portions at the edges of the flat plate portions. 
     If the gap between the flat plate portion of the first yoke and the flat plate portion of the second yoke is reduced to suppress the increase in the height of the movable body due to the increased thickness of the flat plate portions, the space for the connecting body to be joined to the flat plate portion of the first yoke and the flat plate portion of the second yoke becomes narrower. Thus, the thickness of the connecting body must be reduced, which affects vibration characteristics. If the gap between the connecting portions is made narrower to reduce the increase in the width of the movable body due to the increased thickness of the connecting portions, the space for the movable body to vibrate cannot be secured. 
     At least an embodiment of the present invention increases the weight of the movable body and suppresses the influence on vibration characteristics and the enlargement of the movable body. 
     SUMMARY 
     An actuator according to at least an embodiment of the present invention includes: a movable body; a support body including a case that accommodates the movable body; a connecting body connected to the movable body and the support body; and a magnetic drive circuit including a coil and a magnet facing the coil in a first direction, the magnetic drive circuit causing the movable body to vibrate relative to the support body in a second direction intersecting the first direction. The movable body includes: a first yoke including a first inner member and a first outer member, the first inner member being stacked on the coil from a first side in the first direction, the first outer member being stacked on the first inner member from the first side in the first direction; and a second yoke including a second inner member and a second outer member, the second inner member being stacked on the coil from a second side in the first direction, the second outer member being stacked on the second inner member from the second side in the first direction. The magnets are fixed to at least one of the first inner member and the second inner member. The first outer member includes: a first flat plate portion to which the first inner member is fixed; and two first connecting plate portions extending from both ends of the first flat plate portion to the second side in the first direction. The second outer member includes: a second flat plate portion to which the second inner member is fixed; and two second connecting plate portions extending from both ends of the second flat plate portion to the first side in the first direction. The two first connecting plate portions are bonded to the two second connecting plate portions. 
     According to at least an embodiment of the present invention, the first yoke and the second yoke each includes two members (an inner member and an outer member) that are stacked on each other in the first direction. The outer members (the first outer member, the second outer member) of the first yoke and the second yoke each include connecting plate portions (the first connecting plate portions, the second connecting plate portions) extending in the first direction. When the first yoke and the second yoke are assembled, the connecting plate portions are bonded for assembly. With such a configuration, since the thickness of the portion opposing the coil in the first direction is increased as a result of the stacking of the two members, the weight of the yoke can be increased. The connecting plate portions disposed on both sides of the coil in the direction intersecting the first direction have the same plate thickness as when each yoke consist of one member. This can avoid an increase in the width of the movable body. Since narrowing of the gap between the connecting plate portions can be avoided, narrowing of the space for the movable body to vibrate can be avoided. Thus, the weight of the movable body can be increased, and the influence on the vibration characteristics and the enlargement of the movable body can be suppressed. 
     Since the weight of the yoke can be increased by using members having a plate thickness of a general-purpose product, a cost increase can be avoided. 
     In at least an embodiment of the present invention, a third direction intersects the first direction and the second direction; the two first connecting plate portions are disposed at both ends of the first flat plate portion in the second direction; the two second connecting plate portions are disposed at both ends of the second flat plate portion in the second direction; at least one of the first inner member and the second inner member includes a flat magnet fixing portion to which the magnet is fixed; at least one of the first flat plate portion and the second flat plate portion includes two connecting body fixing portions extending to both sides of the magnet fixing portion in the third direction, and the magnet fixing portion is fixed to a surface of the at least one of the first flat plate portion and the second flat plate portion facing the coil; and the connecting body is bonded to each of the two connecting body fixing portions. As described above, in at least one of the first yoke and the second yoke, portions (the connecting body fixing portions) to which the connecting bodies are bonded include only outer members, and thus, the thickness is not increased. Thus, it is possible to avoid a decrease in the placement space of the connecting bodies by increasing the weight of the movable body. Therefore, the influence on the vibration characteristics can be suppressed. 
     In at least an embodiment of the present invention, at least one of the first inner member and the second inner member has two cut-away portions formed by cutting away both ends of the magnet fixing portion in the third direction, and the connecting bodies are disposed in the two cut-away portions. Thus, by cutting away only the areas where the connecting bodies are disposed, the enlargement of the movable body can be suppressed and the weight of the movable body can be increased without narrowing the placement space of the connecting bodies. The edges of the cut-away portions also serve as guides for positioning the connecting bodies. Thus, the positional accuracy of the connecting bodies can be improved. 
     In at least an embodiment of the present invention, the first inner member and the second inner member each include the magnet fixing portion; the magnet includes a first magnet fixed to the magnet fixing portion of the first inner member and a second magnet fixed to the magnet fixing portion of the second inner member; and the connecting bodies include two first connecting bodies bonded to the two connecting body fixing portions disposed on the first flat plate portion at both ends of the first magnet in the third direction, and two second connecting bodies bonded to the two connecting body fixing portions disposed on the second flat plate portion at both ends of the second magnet in the third direction. Thus, by disposing magnets on both sides of the coil in the first direction, the weight of the movable body can be increased and the driving force of the magnetic drive mechanism can be increased. Since the first yoke and the second yoke are each connected to the support body via a connecting body, the movement of the movable body can be suppressed in a direction different from the vibration direction. In both the first yoke and the second yoke, portions (the connecting body fixing portions) to which the connecting bodies are bonded include only outer members, and thus, the thickness is not increased. Thus, it is possible to avoid a decrease in the placement space of the connecting bodies by increasing the weight of the movable body, and the influence on the vibration characteristics can be suppressed. 
     In at least an embodiment of the present invention, the support body includes a metallic first plate stacked on the coil from the first side in the first direction; and a metallic second plate stacked on the coil from the second side in the first direction; the coil is fixed to the case via the first plate and the second plate; the first connecting bodies connect the connecting body fixing portions disposed on the first flat plate portion to the first plat; and the second connecting bodies connect the connecting body fixing portions disposed on the second flat plate portion and the second plate. In this way, the two sides in the first direction of the coil are covered with metal plates, and the metal plates and the yokes are connected by the connecting bodies on the inner side of the yokes. Since it is not necessary to secure a space for placing the connecting bodies in the gaps between the case and the yokes, the dimension of the actuator in the first direction can be reduced. 
     In at least an embodiment of the present invention, at least one of the first inner member and the second inner member includes two raised portions extending from edges of both sides of the magnet fixing portion in the second direction to a side on which the coil is disposed. In this way, the weight of the movable body is increased by the raised portions. Thus, the weight of the movable body can be increased. 
     In at least an embodiment of the present invention, one of the two first connecting plate portions and the two second connecting plate portions are press-fitted to an inner side of the other one of the two first connecting plate portions and the two second connecting plate portions. 
     In this way, since the length of the first connecting plate portions and the second connecting plate portions in the first direction can be increased, the weight of the movable body can be increased. Since the first yoke and the second yoke can be easily assembled, and the formation of gaps between the first connecting plate portions and the second connecting plate portions can be avoided, the generation of chattering noise during vibration can be prevented or suppressed. 
     In at least an embodiment of the present invention, since the thickness of the portions of the yokes of the movable body opposing the coil in the first direction is increased as a result of the stacking of the two members, the weight of the yokes can be increased. The connecting plate portions disposed on both sides of the coil in the direction intersecting the first direction have the same plate thickness as when each yoke consist of one member. This can avoid an increase in the width of the movable body. Since narrowing of the gap between the connecting plate portions can be avoided, narrowing of the space for the movable body to vibrate can be avoided. Thus, the weight of the movable body can be increased, and the influence on the vibration characteristics and the enlargement of the movable body can be suppressed. Since the weight of the yoke can be increased by using members having a plate thickness of a general-purpose product, a cost increase can be avoided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several figures, in which: 
         FIGS.  1 A and  1 B  are perspective views of an actuator to which at least an embodiment of the present invention is applied when viewed from a Z2 direction and a Z1 direction. 
         FIG.  2    is a cross-sectional view of the actuator taken along the longitudinal direction or line A-A in  FIG.  1   . 
         FIG.  3    is a cross-sectional view of the actuator taken along a direction orthogonal to the longitudinal direction or line B-B in  FIG.  1   . 
         FIG.  4    is an exploded perspective view of a movable body viewed from the Z2 direction. 
         FIG.  5    is an exploded perspective view of a movable body viewed from the Z1 direction. 
         FIG.  6    is a side view of a first yoke and a second yoke disassembled. 
     
    
    
     DETAILED DESCRIPTION 
     An actuator according to at least an embodiment of the present invention will now be described with reference to the drawings. 
     Overall Configuration 
       FIG.  1 A  is a perspective view of an actuator  1  according to at least an embodiment of the present invention viewed from a Z2 direction. 
       FIG.  1 B  is a perspective view of an actuator  1  according to at least an embodiment of the present invention viewed from a Z1 direction.  FIG.  2    is a cross-sectional view of the actuator  1  taken along the longitudinal direction or line A-A in  FIG.  1 A .  FIG.  3    is a cross-sectional view of the actuator  1  taken along a direction orthogonal to the longitudinal direction or line B-B in  FIG.  1 A . 
     The actuator  1  is used as a tactile device that transmits information through vibration. As illustrated in  FIGS.  1 A and  1 B , the external shape of the actuator  1  is rectangular. The actuator  1  generates vibration in a transverse direction of its external shape. In the following description, the transverse direction in which vibration occurs is the X direction (second direction); the longitudinal direction of the actuator  1  that is orthogonal to the X direction is the Y direction (third direction); and the direction of the thickness of the actuator  1  (height direction), which is orthogonal to the X and Y directions, is the Z direction (first direction). One side of the X direction is an X1 direction and the other side is an X2 direction. One side of the Y direction is a Y1 direction and the other side is a Y2 direction. One side of the Z direction is a Z1 direction and the other side is a Z2 direction. 
     As illustrated in  FIGS.  1 A,  1 B,  2 , and  3   , the actuator  1  includes a support body  3  including a case  2  that defines the external shape, and a movable body  5  that is accommodated inside the case  2 . The actuator  1  further includes connecting bodies  4  that connects the support body  3  and the movable body  5 , and a magnetic drive circuit  6  that moves the movable body  5  in the X direction relative to the support body  3  (see  FIGS.  2  and  3   ). 
     Support Body 
     As illustrated in  FIGS.  2  and  3   , the support body  3  includes a coil  10 , a first plate  11  stacked in the Z1 direction of the coil  10 , and a second plate  12  stacked in the Z2 direction of the coil  10 . The coil  10  is positioned in the center of the case  2  in the Z direction. The coil  10  is a flat air core coil having its thickness direction oriented in the Z direction. The coil  10  has an oval shape long in the Y direction, and has two long sides  10   a  and  10   b  (see  FIG.  3   ) that extend parallel to each other in the Y direction. A central hole  10   c  extending in the Y direction is disposed between the two long sides. 
     As illustrated in  FIG.  2   , the support body  3  includes a first holder member  15  disposed on the Y1 side of the coil  10  and a second holder member  16  disposed on the Y12 side of the coil  10 . The first holder member  15  and the second holder member  16  are composed of resin. The first holder member  15  has a first coil holding portion  151  disposed between the first plate  11  and the second plate  12 , and a first side plate portion  152  extending from the Y1 side end of the first coil holding portion  151 , from the Z1 direction to the Z2 direction. The second holder member  16  has a second coil holding portion  161  disposed between the first plate  11  and the second plate  12 , and a second side plate portion  162  extending from the Y1 side end of the second coil holding portion  161 , from the Z1 direction to the Z2 direction. The coil  10  is disposed between the first coil holding portion  151  and the second coil holding portion  161 . 
     The first plate  11  and the second plate  12  are composed of a non-magnetic material. As illustrated in  FIG.  3   , the two ends of the first plate  11  and the second plate  12  are bent in the X direction at a substantially right angle and cover the outer circumferential surface of the coil  10  in the X direction. The first plate  11  is stacked on the Z1 side of the first coil holding portion  151  and the second coil holding portion  161 , and is fixed to the first coil holding portion  151  and the second coil holding portion  161 . The second plate  12  is stacked on the Z2 side of the first coil holding portion  151  and the second coil holding portion  161 , and is fixed to the first coil holding portion  151  and the second coil holding portion  161 . 
     A power feed substrate  14  is fixed to the Y1 direction end of the first holder member  15 . In the present embodiment, the power feed substrate  14  is a flexible printed circuit board. The power feed substrate  14  may be a rigid substrate. The coil  10  includes two coil wires led out in the Y1 direction, and the coil wires are connected to a wiring pattern on the surface of the power feed substrate  14 . Power is supplied to the coil  10  via the power feed substrate  14 . 
     When the support body  3  is assembled, the second plate  12  is fixed to the first holder member  15  and the second holder member  16  from the Z1 side, the coil is disposed between the first coil holding portion  151  and the second coil holding portion  161 , and the power feed substrate  14  is fixed to the first holder member  15 . Subsequently, the central hole  10   c  of the coil  10  is filled with an adhesive agent, and the first plate  11  is assembled from the Z2 side. This completes the assembly of an assembled body including the coil  10 , the first plate  11 , the second plate  12 , the power feed substrate  14 , the first holder member  15 , and the second holder member  16 . As illustrated in  FIGS.  2  and  3   , an adhesive layer  13  composed of the cured adhesive agent is formed in the central hole  10   c  of the coil  10 . 
     As illustrated in  FIGS.  1 A,  1 B,  2 , and  3   , the case  2  includes a first case member  31  and a second case member  32  stacked in the Z direction. The first case member  31  is assembled to the first holder member  15  and the second holder member  16  from the Z1 direction. The second case member  32  is assembled to the first holder member  15  and the second holder member  16  from the Z2 direction. As illustrated in  FIG.  1 A , the power feed substrate  14  is led out through a cut-away portion in the center in the X direction of the first holder member  15  to the Y1 direction side of the case  2  and bent in the Z1 direction. 
     Movable Body 
     The movable body  5  includes magnets  7  and yokes  8 . As illustrated in  FIGS.  2  and  3   , the magnets  7  oppose the coil  10  in the Z direction. The coil  10  and the magnets  7  constitute the magnetic drive circuit  6 . The movable body  5  includes a first magnet  71  and a second magnet  72  as the magnets  7 . The first magnet  71  is positioned in the Z1 direction of the coil  10 . The second magnet  72  is positioned in the Z2 direction of the coil  10 . 
     The first magnet  71  and the second magnet  72  are polarized into two in the X direction. As illustrated in  FIG.  3   , when the movable body  5  and the support body  3  are assembled, the long sides  10   a  and  10   b  of the coil  10  oppose the first magnet  71  in the Z1 direction and the second magnet  72  in the Z2 direction. 
       FIG.  4    is an exploded perspective view of the movable body  5  viewed from the Z2 direction.  FIG.  5    is an exploded perspective view of the movable body  5  viewed from the Z1 direction.  FIG.  6    is a side view of a first yoke  81  and a second yoke  82  in a disassembled state. In the present embodiment, the yokes  8  are composed of a magnetic material. As illustrated in  FIGS.  2  to  6   , the yokes  8  consist of the first yoke  81  and the second yoke  82 . The first yoke  81  includes a first inner member  83  stacked on the coil  10  in the Z1 direction and a first outer member  84  stacked on the first inner member  83  in the Z1 direction. The second yoke  82  includes a second inner member  85  stacked on the coil  10  in the Z1 direction and a second outer member  86  stacked on the second inner member  85  in the Z1 direction. 
     As illustrated in  FIGS.  4  and  5   , the first outer member  84  includes a first flat plate portion  841  long in the Y direction and two first connecting plate portions  842  extending in the Z2 direction from the central portion in the Y direction of the two ends of the first flat plate portion  841  in the X direction. The two ends of the first flat plate portion  841  in the Y direction are provided with two connecting body fixing portions  843  disposed at the two ends of the first connecting plate portions  842  in the Y direction. The ends of the two sides in the X direction of each of the connecting body fixing portions  843  are provided with raised portions  844  bent in the Z2 direction. 
     As illustrated in  FIG.  2   , each of the connecting body fixing portions  843  is connected to the first plate  11  through a first connecting body  9 A. 
     The first inner member  83  includes a magnet fixing portion  831  long in the Y direction and two raised portions  832  bent in the Z2 direction from the two ends of the magnet fixing portion  831  in the X direction. The magnet fixing portion  831  is fixed to the Z1 side of the first flat plate portion  841 . As illustrated in  FIG.  3   , the two raised portions  832  are disposed on the inner sides of the two first connecting plate portions  842  and surround the two X direction sides of the first magnet  71  fixed to the magnet fixing portion  831 . 
     As illustrated in  FIGS.  4  and  5   , the first inner member  83  has two cut-away portions  833  formed by cutting away the center in the Y direction of the two ends of the magnet fixing portion  831  in the Y direction. Each of the cut-away portions  833  has a rectangular shape long in the X direction, and is disposed in the center of the magnet fixing portion  831  in the Y direction. As illustrated in  FIG.  2   , the first connecting body  9 A disposed on the Y1 side of the first magnet  71  and the first connecting body  9 A disposed on the Y2 side of the first magnet  71  are placed in cut-away portions  833 . 
     As illustrated in  FIGS.  4  and  5   , the second outer member  86  includes a second flat plate portion  861  long in the Y direction and two second connecting plate portions  862  extending in the Z1 direction from the central portion in the Y direction of the two ends of the second flat plate portion  861  in the X direction. The two ends of the second flat plate portion  861  in the Y direction are provided with two connecting body fixing portions  863  disposed at the two ends of the second connecting plate portions  862 . The ends of the two sides in the X direction of each of the connecting body fixing portions  863  are provided with raised portions  864  bent in the Z1 direction. As illustrated in  FIG.  2   , each of the connecting body fixing portions  863  is connected to the second plate  12  through a second connecting body  9 B. 
     The second inner member  85  includes a magnet fixing portion  851  long in the Y direction and two raised portions  852  bent in the Z2 direction from the two ends of the magnet fixing portion  851  in the X direction. The magnet fixing portion  851  is fixed to the Z2 side of the second flat plate portion  861 . As illustrated in  FIG.  3   , the two raised portions  852  are disposed on the inner sides of the two second connecting plate portions  862  and surround the two X direction sides of the second magnet  72  fixed to the magnet fixing portion  851 . 
     As illustrated in  FIGS.  4  and  5   , the second inner member  85  has two cut-away portions  853  formed by cutting away the center in the Y direction of the two ends of the magnet fixing portion  851  in the Y direction. Each of the cut-away portions  853  has a rectangular shape long in the X direction, and is disposed in the center of the magnet fixing portion  851  in the Y direction. As illustrated in  FIG.  2   , the second connecting body  9 B disposed on the Y1 side of the second magnet  72  and the second connecting body  9 B disposed on the Y2 side of the second magnet  72  are placed in cut-away portions  853 . 
     The first yoke  81  is assembled by welding together the first inner member  83  and the first outer member  84 . The second yoke  82  is assembled by welding together the second inner member  85  and the second outer member  86 . The yokes  8  are assembled in a shape surrounding the outer circumferential sides of the coil  10 , the first plate  11 , and the second plate  12  by press-fitting and fixing two second connecting plate portions  862  of the second yoke  82  to the inner sides of the two first connecting plate portions  842  of the first yoke  81 . 
     Connecting Body 
     As illustrated in  FIG.  2   , the connecting bodies  4  consist of the first connecting bodies  9 A and the second connecting bodies  9 B. The first connecting bodies  9 A and the second connecting bodies  9 B each have a rectangular shape long in the X direction. The first connecting bodies  9 A are positioned in the Z1 direction of the coil  10 . The second connecting bodies  9 B are positioned in the Z2 direction of the coil  10 . The first connecting bodies  9 A are disposed at two locations on the Y1 side and the Y2 side of the first magnet  71 , and are each composed of two members of the same shape. The second connecting bodies  9 B are disposed at two locations on the Y1 side and the Y2 side of the second magnet  72 , and are each composed of two members of the same shape. The first connecting bodies  9 A and the second connecting bodies  9 B have at least one of elasticity and viscoelasticity. 
     The first connecting bodies  9 A are disposed between the first yoke  81  and the first plate  11 . The first connecting bodies  9 A are disposed in the two cut-away portions  833  provided at the end portion in the Y1 direction of the first yoke  81  and the end portion in the Y2 direction of the first yoke  81 . The first connecting bodies  9 A on the Y1 side are disposed between the connecting body fixing portions  843  provided at the end in the Y1 direction of the first outer member  84  and the end portion in the Y1 direction of the first plate  11 . The first connecting bodies  9 A on the Y2 side are disposed at two locations between the connecting body fixing portions  843  provided at the end in the Y2 direction of the first outer member  84  and the end portion in the Y2 direction of the first plate  11 . The first connecting bodies  9 A are compressed in the Z direction between the connecting body fixing portions  843  and the first plate  11 . 
     The second connecting bodies  9 B are disposed between the second yoke  82  and the second plate  12 . The second connecting bodies  9 B are disposed in the two cut-away portions  853  provided at the end portion in the Y1 direction of the second yoke  82  and the end portion in the Y2 direction of the second yoke  82 . The second connecting bodies  9 B on the Y1 side are disposed between the connecting body fixing portions  863  provided at the end in the Y1 direction of the second outer member  86  and the end portion in the Y1 direction of the second plate  12 . The second connecting bodies  9 B on the Y2 side are disposed at two locations between the connecting body fixing portions  863  provided at the end in the Y2 direction of the second outer member  86  and the end portion in the Y2 direction of the second plate  12 . The second connecting bodies  9 B are compressed in the Z direction between the connecting body fixing portions  863  and the second plate  12 . 
     In the present embodiment, the first connecting bodies  9 A and the second connecting bodies  9 B are gel-like members composed of silicone gel. Silicone gel is a viscoelastic body whose spring constant when it deforms in an expanding/contracting direction is approximately three times larger than the spring constant when it deforms in a shear direction. Deformation of the viscoelastic body in a direction (shear direction) that intersects a thickness direction is deformation in the direction in which the viscoelastic body is pulled and stretched. Thus, the viscoelastic body has deformation characteristics in which a linear component is larger than a nonlinear component. When the viscoelastic body deforms due to pressing and compressing in the thickness direction, the viscoelastic body has expanding/contracting characteristics in which the nonlinear component is larger than the linear component, whereas when the viscoelastic body is pulled and stretched in the thickness direction, the viscoelastic body has expanding/contracting characteristics in which the linear component is larger than the nonlinear component. 
     Alternatively, the first connecting bodies  9 A and the second connecting bodies  9 B may be composed of various rubber materials such as natural rubber, diene rubber (e.g., styrene butadiene rubber, isoprene rubber, butadiene rubber, chloroprene rubber, acrylonitrile butadiene rubber, etc.), non-diene rubber (e.g., butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, urethane rubber, silicone rubber, fluoro rubber, etc.), and thermoplastic elastomers, and their modified materials. 
     Operation of Actuator 
     When a current in a predetermined direction is supplied to the coil  10  via the power feed substrate  14 , the movable body  5  supported by the support body  3  moves in one of the X directions relative to the support body  3  by the driving force of the magnetic drive circuit  6 . Then, when the direction of the electric current is reversed, the movable body  5  moves in the other of the X directions relative to the support body  3 . The repeated reversal of the direction of the current supplied to the coil  10  vibrates the movable body  5 . When the movable body  5  vibrates in the X direction, the first connecting bodies  9 A and the second connecting bodies  9 B deform in the shear direction. 
     Main Advantageous Effects of Present Embodiment 
     As described above, the actuator  1  according to the present embodiment includes a movable body  5 , a support body  3  including a case  2  that accommodates the movable body  5 , a connecting body  4  connected to the movable body  5  and the support body  3 , a magnetic drive circuit  6  including a coil  10  and magnets  7  (first magnet  71  and second magnet  72 ) facing the coil  10  in the Z direction and causing the movable body  5  to vibrate in the X direction intersecting the Z direction relative to the support body  3 . The movable body  5  includes a first yoke  81  including a first inner member  83  stacked on the coil  10  from the Z1 direction and a first outer member  84  stacked on the first inner member  83  from the Z1 direction, and a second yoke  82  including a second inner member  85  stacked on the coil  10  from the Z2 direction and a second outer member  86  stacked on the second inner member  85  from the Z2 direction. The magnets  7  are first magnet  71  fixed to the magnet fixing portion  831  of the first inner member  83  and a second magnet  72  fixed to the magnet fixing portion  851  of the second inner member  85 . The first outer member  84  includes a first flat plate portion  841  to which the first inner member  83  is fixed and two first connecting plate portions  842  extending in the Z2 direction from the two ends of the first flat plate portion  841 . The second outer member  86  includes a second flat plate portion  861  to which the second inner member  85  is fixed and two second connecting plate portions  862  extending in the Z1 direction from the two ends of the second flat plate portion  861 . The two second connecting plate portions  862  are bonded to the two first connecting plate portions  842 . 
     According to the present embodiment, the first yoke  81  and the second yoke  82  each include two members (an inner member and an outer member) that are stacked on each other in the Z direction. The outer members (the first outer member  84 , the second outer member  86 ) of the first yoke  81  and the second yoke  82  each include connecting plate portions (the first connecting plate portions  842 , the second connecting plate portions  862 ) extending in the Z direction. When the first yoke  81  and the second yoke  82  are assembled, the connecting plate portions are bonded for assembly. Since the thickness of the portions of the yokes  8  opposing the coil  10  in the Z direction is increased as a result of the stacking of the two members, the weight of the movable body  5  is increased. The portions disposed on the two sides of the coil  10  in the direction intersecting the Z direction are composed only of the outer members, and the thickness is the same as each of the first yoke  81  and the second yoke  82  composed of one member. This can avoid an increase in the width of the movable body  5  in the X direction. Since the thickness of the connecting plate portions does not increase, narrowing of the gap between the connecting plate portions can be avoided. Thus, narrowing of the space for the movable body  5  to vibrate can be avoided. Thus, the weight of the movable body  5  can be increased, and the influence on the vibration characteristics and the enlargement of the movable body  5  can be suppressed. The weight of the yoke can be increased by using members having a plate thickness of a general-purpose product by stacking the two members to increase the weight. Thus, a cost increase can be avoided. 
     In the present embodiment, the two first connecting plate portions  842  are disposed at the two ends of the first flat plate portion  841  in the X direction, and the two second connecting plate portions  862  are disposed at the two ends of the second flat plate portion  861  in the X direction. The first inner member  83  includes flat magnet fixing portion  831  to which the first magnet  71  is fixed, and the second inner member  85  includes a flat magnet fixing portion  851  to which the second magnet  72  is fixed. The first flat plate portion  841  has a Z2 side surface (the surface opposing the coil  10 ) to which the magnet fixing portion  831  is fixed and has two connecting body fixing portions  843  that extend to the two ends of the magnet fixing portion  831  in the Y direction. The second flat plate portion  861  has a Z1 side surface (the surface opposing the coil  10 ) to which the magnet fixing portion  851  is fixed and has two connecting body fixing portions  863  that extend to the two ends of the magnet fixing portion  851  in the Y direction. The connecting bodies  4  consist of first connecting bodies  9 A connected to the two connecting body fixing portions  843  and second connecting bodies  9 B bonded to the two connecting body fixing portions  863 . As described above in the present embodiment, in each of the first yoke  81  and the second yoke  82 , portions (the connecting body fixing portions  843 ,  863 ) to which the connecting bodies  4  are bonded include only outer members, and the thickness is not increased. Thus, the placement space for the connecting bodies  4  is not narrowed by the increase in the weight of the movable body  5 , and the thickness of the connecting bodies  4  in the Z direction need not be reduced. Therefore, the influence on the vibration characteristics can be suppressed. 
     In the present embodiment, the first inner member  83  has two cut-away portions  833  formed by cutting away the two ends of the magnet fixing portion  831  in the Y direction, and the first connecting bodies  9 A are disposed in the two cut-away portions  833 . The second inner member  85  has two cut-away portions  853  formed by cutting away the two ends of the magnet fixing portion  851  in the Y direction, and the second connecting bodies  9 B are disposed in the two cut-away portions  853 . In such a configuration, the first yoke  81  and the second yoke  82  are both designed so that their weight is increased without increasing the thickness of the portions where the connecting bodies  4  (the first connecting bodies  9 A, the second connecting bodies  9 B) are disposed. Therefore, the enlargement of the movable body  5  can be suppressed, and to the weight of the movable body  5  can be increased. 
     The present embodiment includes the first magnet  71  and the second magnet  72  as the magnets  7 . Alternatively, the present embodiment may include one of the first magnet  71  and the second magnet  72 . In such a case, only one of the first inner member  83  and the second inner member  85  may include a magnet fixing portion. It is possible to adopt a configuration in which only one of the first connecting bodies  9 A and the second connecting bodies  9 B are provided as the connecting bodies  4 . In such a case, of the first inner member  83  and the second inner member  85 , whichever is disposed on the same side as the connecting bodies  4  relative to the coil  10  can be provided with cut-away portions at the two ends in the Y direction. In the first inner member  83  and the second inner member  85 , the cut-away portions may be provided only on one of the Y1 side end and the Y2 side end. 
     In the present embodiment, the support body  3  includes a first plate  11  that is composed of metal and stacked the coil  10  from the Z1 direction and a second plate  12  that is composed of metal and is stacked on the coil  10  from the Z2 direction. The coil  10  is fixed to a case  2  via the first plate  11  and the second plate  12 ; first connecting bodies  9 A connect connecting body fixing portions  843  provided on a first flat plate portion  841  to the first plate  11 ; and the second connecting bodies  9 B connect connecting body fixing portions  863  provided on a second flat plate portion  861  to the second plate  12 . In this way, the two sides of the coil  10  in the Z direction are covered with metal plates, and the yokes  8  and the plates are connected inside the yokes  8  that surround the metal plates by the connecting bodies  4 . Since it is not necessary to secure a space for placing the connecting bodies  4  in the gaps between the case  2  and the yokes  8 , the dimension of the actuator in the Z direction can be reduced. 
     In the present embodiment, the first inner member  83  includes two raised portions  832  extending from the edges on the two sides of the magnet fixing portion  831  in the X direction to the side (Z2 side) on which the coil  10  is disposed. The second inner member  85  includes two raised portions  852  extending from the edges on the two sides of the magnet fixing portion  851  in the X direction to the side (Z1 side) on which the coil  10  is disposed. Thus, the weight of the yokes  8  is increased by the amount of the raised portions  832  and  852 , so that the weight of the movable body  5  weight can be increased. 
     Alternatively, the raised portions may be provided with neither the first inner member  83  nor the second inner member  85 . Alternatively, the raised portions may be with only one of the first inner member  83  and the second inner member  85 . 
     In the present embodiment, the two second connecting plate portions  862  are disposed on the inner side of the two first connecting plate portions  842 , and the first connecting plate portions  842  and the second connecting plate portions  862  are stacked on and bonded to each other. Since the length of the first connecting plate portions  842  and the second connecting plate portions  862  in the Z direction can be increased, the weight of the movable body  5  can be increased. This configuration facilitates the assembly of the first yoke  81  and the second yoke  82 . Alternatively, a configuration may be adopted in which the two second connecting plate portions  862  are disposed on the outer side and the two first connecting plate portions  842  are disposed between the two second connecting plate portions  862 . 
     In the present embodiment, the two second connecting plate portions  862  are press-fitted and fixed between the two first connecting plate portions  842  to assemble the first yoke  81  and the second yoke  82  into a single unit. For example, the two second connecting plate portions  862  are formed to have a shape that slightly tilts in the direction in which the distance in the X direction increases toward the Z1 side. Alternatively, the two second connecting plate portions  862  may each have a protrusion protruding from the surface facing outward in the X direction, or the two first connecting plate portions  842  may each have a protrusion protruding from the surface facing inward in the X direction. By adopting such a shape, the two second connecting plate portions  862  are press-fitted when they are inserted between the two first connecting plate portions  842 . The press-fit state prevents gaps from being formed between the first connecting plate portions  842  and the second connecting plate portions  862 . Thus, chattering noise can be prevented or suppressed when the movable body  5  vibrates. 
     Alternatively, a configuration may be adopted in which the two second connecting plate portions  862  are inserted, not press-fitted, between the two first connecting plate portions  842  and fixed by welding or an adhesive agent. 
     In the present embodiment, all the members constituting the yokes  8  are magnetic, but, alternatively, only the members in contact to the magnets  7  may be magnetic. For example, the first inner member  83  and the second inner member  85  may be magnetic bodies, and the first outer member  84  and the second outer member  86  may be composed of a material different from that of the first inner member  83  and the second inner member  85 . For example, as the first outer member  84  and the second outer member  86 , magnetic bodies or non-magnetic bodies having a higher specific gravity than that of the first inner member  83  and the second inner member  85  may be used to provide a function as weights. This can increase the weight of the movable body  5 .