Abstract:
A vibration generator making a closed loop of a magnetic circuit of a permanent magnet to obtain a high vibrating force while kept small in size, including a reciprocating vibrator having a ring-shaped permanent magnet in a center hole of a ring-shaped weight, a first and second plate springs supporting this reciprocating vibrator at a recessed case and end plate to be able to elastically displace in a thickness direction spanning a first and a second end faces, a tubular toroidal coil passing through a center hole of the permanent magnet and generating a reciprocating vibrating magnetic field for reciprocatingly driving the permanent magnet in the thickness direction, and a columnar core passing through this toroidal coil, the ring-shaped permanent magnet being magnetized in the thickness direction, and the toroidal coil having a lower toroidal coil and an adjoining reversely wound series connected upper toroidal coil coaxial with the same.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2010, 031208, filed on Feb. 16, 2010, and the prior Japanese Patent Application No. 2011, 006513, filed on Jan. 15, 2011, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vibration generator which is built into a mobile phone etc., more particularly relates to the structure of a vibration generator by which a high vibrating force is obtained. 
     2. Description of the Related Art 
     As shown in  FIG. 17 , the vibration linear actuator  51  disclosed in Japanese Patent Publication (A) No. 2003-154314 is provided with a ring-shaped external yoke  54  as a weight having a cylindrical permanent magnet  55  at its inner circumference side, a first plate spring  57  fastened to a first end face  54   a  of this external yoke  54  by elastically deforming an outer circumference side hanging part  57   a , a second plate spring  56  the same as this first plate spring  57  and fastened to a second end face  54   b  of this external yoke  54  by elastically deforming an outer circumference side hanging part  56   a , and a stator supporting the first and second plate springs  57  and  56  and having a coil  52  which generates a reciprocating vibration magnetic field at an inner circumference side of the permanent magnet  55 , wherein this stator is provided with a plastic base  59  at a bottom surface of which a power feed land  61  is arranged and from which a shaft  58  stands and, with an internal yoke  53  on this base  59  having the shaft  58  at its center and forming also a coil bobbin of the coil  52 . An inner circumference side  57   b  of the first plate spring  57  mates with a first projection  53   a  of the internal yoke  53 , while an inner circumference side  56   b  of the second plate spring  56  mates with a second projection  53   b  of the internal yoke  53  and is sandwiched between the base  59  and internal yoke  53 . 
     In the state with no power fed to the coil  52 , the external yoke  54  serving as the weight remains at a standstill at an illustrated neutral position in the axial direction where the elastic recovery force outward at the first end face  54   a  side due to the first plate spring  57  and the elastic recovery force outward at the second end face  54   b  side due to the second plate spring  56  are balanced, but due to the alternating current flowing through the coil  52 , an S-pole and an N-pole are alternately generated at the two ends of the internal yoke  53  in the axial direction, so the ring-shaped permanent magnet  55  magnetized in the radial direction, solely receives a magnetic attraction/repulsion action in the axial direction due to the strong magnetic pole at the inner circumferential surface side close to the internal yoke  53  rather than the magnetic pole at the outer circumferential surface side, so the first plate spring  57  and the second plate spring  56  alternately are restored to the free state of their planar shapes in a repeated operation and the external yoke  54  engages in reciprocating linear motion in the thrust direction resulting in reciprocating vibration. 
     As related art, there is Japanese Patent Publication A No. 2003-154314 (FIG. 1). 
     However, in the above vibration linear actuator  51 , due to the alternating current flowing through the coil  52 , the two ends of the internal yoke  53  across the axial direction alternately switch between the S-pole and the N-pole, but the outer circumferential surface of the external yoke  54  has the opposite magnetic pole to the magnetic pole of the inner circumferential surface of the permanent magnet  55 . The magnetic pole of the outer circumferential surface of the external yoke  54  has the effect of suppressing linear reciprocating vibration of the permanent magnet  55 , so it is necessary to lengthen the diametrical direction distance from the inner circumferential surface of the permanent magnet  55  to the outer circumferential surface of the external yoke  54  so as to weaken that effect. The longer the outer diameter of the external yoke  54  is set, the more this runs counter to the reduction of size of the vibration linear actuator of course, the magnetic circuit of the permanent magnet  55  becomes an open loop, and the vibration force becomes weaker. Obtaining the required vibration force leads to a larger size due to the increased number of turns of the coil  52  or an increase in the power consumption due to the increase in the alternating current. 
     SUMMARY OF THE INVENTION 
     Therefore, in view of the above problem, an object of the present invention is to provide a vibration generator which forms the magnetic circuit of the permanent magnetic carried in a mechanical vibrator into a closed loop so as to keep the size small while obtaining a high vibrating force. 
     The vibration generator according to the present invention has a mechanical vibrator having a first ring-shaped permanent magnet with a front and back comprised of an N pole face and an S pole face, a fastening part supporting the mechanical vibrator in a plate thickness direction spanning the N pole face and the S pole face through a suspension spring means, a magnetic core member supported by the fastening part and passing through a center hole of the first ring-shaped permanent magnet, and a first toroidal coil fitting over an outer circumferential surface of the magnetic core member and facing an inner circumferential surface of the center hole, wherein the mechanical vibrator is provided with a first ring-shaped pole piece superposed over at least one magnetic pole face among the N pole face and the S pole face, the first ring-shaped pole piece having an inner circumferential edge approaching an outer circumferential surface of the first toroidal coil. 
     In this structure, the magnetization direction of the first ring-shaped permanent magnet is the axial direction parallel to the magnetic core member, the magnetic force lines from the N pole face to the S pole face form a short circuit closed loop of a low magnetic resistance including a first concentrated flux path crossing across the current flowing through the first toroidal coil between the inner circumferential edge of the first ring-shaped pole piece and the outer circumferential surface of the magnetic core member to generate an electromagnetic force, an air gap flux path with the outer circumferential surface of the magnetic core member at the magnetic pole face without a ring-shaped pole piece, and a low magnetic resistance path in the magnetic core member, so at the first concentrated flux path, the electromagnetic force which is applied to the ring-shaped permanent magnet along with the alternation of current which is fed to the first toroidal coil switches between forward and reverse in the axial direction, so compared with the conventional case of drive by magnetic attraction/repulsion, drive is possible with a high vibrating force. Further, among the N pole face and S pole face, the magnetic force lines at the outer circumference side part of the first ring-shaped permanent magnet are short circuited at the thickness direction of the ring-shaped permanent magnet, so there is no adverse effect on the first concentrated flux path or the air gap flux path, therefore a reduction in the size of the device can be realized. 
     Preferably, the mechanical vibrator is provided with a second ring-shaped pole piece superposed over one of the pole faces of the first ring-shaped permanent magnet, the magnetic polarity of the one of the pole faces is opposite to the magnetic polarity of the first ring-shaped pole piece, and the second ring-shaped pole piece has an inner circumferential edge approaching the outer circumferential surface of the magnetic core member. In this case, due to the provision of the second ring-shaped pole piece, the path between the other magnetic pole face and the outer circumferential surface of the magnetic core member also forms a second concentrated flux path, so it is possible to further lower the magnetic resistance. This leads to strengthening of the vibrating force. 
     Further, preferably the vibration generator has a second toroidal coil adjoining the first toroidal coil, fitting over the outer circumferential surface of the magnetic core member, and facing the inner circumferential surface of the center hole, the inner circumferential edge of the second ring-shaped pole piece approaching an outer circumferential surface of said second toroidal coil. Depending on the direction of feed of current to the second toroidal coil, at the second concentrated flux path as well, it is possible to generate an electromagnetic force of the same direction as the electromagnetic force in the first concentrated flux path. This contributes to magnification of the vibrating force and reduction of size of the device. 
     The first toroidal coil and second toroidal coil may be connected in parallel, but to decrease the number of feed terminals, the first toroidal coil and second toroidal coil are preferably connected in series by windings wound in reverse directions. 
     The fastening part has a recessed case and an end plate fastened to an open side of the recessed case, the first toroidal coil being stacked over the second toroidal coil in the same diameter, the second toroidal coil being mounted on a printed circuit board, and the end plate has a through hole of a size enabling passage of said first toroidal coil and said second toroidal coil. After obtaining the assembly of the recessed case and end plate, it is possible to simply inject a magnetic fluid for functioning as a damper of the mechanical vibrator via the through hole of the end plate so as to coat the inner circumferential surface of the ring-shaped permanent magnet. Not only this, after this, it is possible to insert the first and second toroidal coils from this through hole and fasten the printed circuit board to the back surface of the end plate and thereby possible to facilitate manufacture. 
     To prevent the generation of electrical noise from the vibration generator, it is necessary to ground and shield the outer housing having the recessed case and end plate. As the structure for feeding a ground potential to the end plate, preferably the end plate has a current carrying projection which contacts a conductive rubber piece, which is adhered to a back surface of the printed circuit board, through a notch formed in the printed circuit board. This is not a connection structure of the end plate and a pattern on the printed circuit board, but a direct connection structure of a current carrying projection of the end plate and a conductive rubber piece. Therefore, it is possible to obtain the current carrying projection at the time of press forming the end plate and possible to realize lower cost. 
     Preferably, the first ring-shaped pole piece overlaps the S pole face of the first ring-shaped permanent magnet, the second ring-shaped pole piece overlaps the N pole face of the first ring-shaped permanent magnet, and the magnetic core member has a center iron core member spanning in the inside of the first toroidal coil and the second toroidal coil, a first permanent magnet core member having an S pole face overlapped on one end face of the center iron core member in the first toroidal coil, and a second permanent magnet core member having an N pole face overlapped on another end face of the center iron core member in the second toroidal coil. In this configuration, the magnetic force lines running from the second ring-shaped pole piece through the second toroidal coil to the magnetic core member, even with alternation of the current fed to the toroidal coil, run from the magnetization direction of the second permanent magnet core member through the magnetization direction of the center iron core member over the magnetization direction of the first permanent magnet core member to pass through the first toroidal coil and flow into the first ring-shaped pole piece, so it is possible to further decrease the magnetic resistance in the magnetic core member. This contributes to strengthening of the vibrating force and reduction of size of the device. 
     On the other hand, it is also possible to employ a configuration where the first ring-shaped pole piece overlaps the S pole face of the first ring-shaped permanent magnet, the second ring-shaped pole piece overlaps the N pole face of the first ring-shaped permanent magnet, and the magnetic core member has a center iron core member which spanning in the inside of the first toroidal coil and the second toroidal coil, the center iron core member having a magnetization direction of a reverse direction to the magnetization direction of the first ring-shaped permanent magnet, a first iron core member overlapping the N pole face of the center permanent magnet core member in the first toroidal coil, and a second iron core member overlapping the S pole face of the center permanent magnet core member in the second toroidal coil. In this configuration as well, the magnetic force lines running from the second ring-shaped pole piece through the second toroidal coil to the magnetic core member, even with alternation of the current fed to the toroidal coil, run from the magnetization direction of the second permanent magnet core member through the magnetization direction of the center iron core member over the magnetization direction of the first permanent magnet core member to pass through the first toroidal coil and flow into the first ring-shaped pole piece, so it is possible to further decrease the magnetic resistance in the magnetic core member. This contributes to strengthening of the vibrating force and reduction of size of the device. 
     As another configuration of the mechanical vibrator, in addition to the first ring-shaped permanent magnet and first ring-shaped pole piece, the mechanical vibrator has a second ring-shaped permanent magnet including an N pole end face and an S pole end face, and the magnetic pole faces of the same poles of the first ring-shaped permanent magnet and the second ring-shaped permanent magnet sandwich the first ring-shaped pole piece. In this configuration, the flux density at the first concentrated flux path is substantially doubled, so this contributes to the strengthening of the vibrating force. 
     Further, preferably the mechanical vibrator is provided with a second ring-shaped pole piece and a third ring-shaped pole piece superposed over one of the pole faces of the first ring-shaped permanent magnet and the second ring-shaped permanent magnet, the magnetic polarity of the one of the pole faces being opposite to the magnetic polarity of the first ring-shaped pole piece, the second ring-shaped pole piece and the third ring-shaped pole piece having inner circumferential edges approaching the outer circumferential surface of the magnetic core member. The path between the inner circumferential edge of the second ring-shaped pole piece and the outer circumferential surface of the magnetic core member forms a second concentrated flux path, while the path between the inner circumferential edge of the third ring-shaped pole piece and the outer circumferential surface of the magnetic core member forms a third concentrated flux path, so it is possible to further lower the magnetic resistance. This leads to an increase of the vibrating force. 
     When the mechanical vibrator has three toroidal coils, preferably the vibration generator has second and third toroidal coils adjoining the first toroidal coil, the first toroidal coil being provided between the second and third toroidal coils, fitting over the outer circumferential surface of the magnetic core member, and facing the inner circumferential surface of the center hole, the inner circumferential edges of the second and third ring-shaped pole pieces approaching corresponding outer circumferential surfaces of the second and third toroidal coils. Depending on the direction of feed of current to the second and third toroidal coils, it is also possible, in the second and third concentrated flux paths as well, to cause the generation of an electromagnetic force of the same direction as the electromagnetic force in the first concentrated flux path, so it is possible to realize a stronger vibrating force. 
     The first toroidal coil, the second toroidal coil, and the third toroidal coil may also be connected in parallel, but to reduce the number of the feed terminals, the first toroidal coil and the second toroidal coil are preferably connected with each other in series by windings wound in reverse directions, while the first toroidal coil and the third toroidal coil are preferably connected with each other in series by windings wound in reverse directions. 
     Further, preferably the first ring-shaped pole piece overlaps the N pole face of the first ring-shaped permanent magnet, the second ring-shaped pole piece overlaps the S pole face of the first ring-shaped permanent magnet, the third ring-shaped pole piece overlaps the S pole face of the second ring-shaped permanent magnet, and the magnetic core member has a center iron core member spanning in the inside of the first toroidal coil, the second toroidal coil and the third toroidal coil, a first permanent magnet core member having an S pole face overlapped on one end face of the center iron core member in the second toroidal coil, and a second permanent magnet core member having an S pole face overlapped on another end face of the center iron core member in the second toroidal coil. 
     In this configuration, the magnetic force lines running from the first ring-shaped pole piece through the first toroidal coil to the magnetic core member, even with alternation of the current fed to the toroidal coil, run from the center iron core member through the magnetization direction of the first permanent magnet core member through the second toroidal coil and flow into the second ring-shaped pole piece and also run from the center iron core member through the magnetization direction of the second permanent magnet core member through the third toroidal coil and flow into the third ring-shaped pole piece, so it is possible to further decrease the magnetic resistance in the magnetic core member. This contributes to strengthening of the vibrating force and reduction of size of the device. 
     Further, conversely, it is possible to employ a configuration wherein the first ring-shaped pole piece overlaps the S pole face of the first ring-shaped permanent magnet, the second ring-shaped pole piece overlaps the N pole face of the first ring-shaped permanent magnet, the third ring-shaped pole piece overlaps the N pole face of the second ring-shaped permanent magnet, and the magnetic core member has a center iron core member spanning in the inside of the first toroidal coil, the second toroidal coil and the third toroidal coil, a first permanent magnet core member having an N pole face overlapped on one end face of the center iron core member in the second toroidal coil, and a second permanent magnet core member having an N pole face overlapped on another end face of the center iron core member in the third toroidal coil. 
     On the other hand, it is also possible to employ configuration wherein the first ring-shaped pole piece overlaps the N pole face of the first ring-shaped permanent magnet, the second ring-shaped pole piece overlaps the S pole face of the first ring-shaped permanent magnet, the third ring-shaped pole piece overlaps the S pole face of the second ring-shaped permanent magnet, and the magnetic core member has a center iron core member accommodated in the inside of the first toroidal coil, a first permanent magnet core member having an S pole face overlapped on one end face of the center iron core member in the first toroidal coil and second toroidal coil, a second permanent magnet core member having an S pole face overlapped on another end face of the center iron core member in the first toroidal coil and the third toroidal coil, a first end iron core member overlapping an N pole face of the first permanent magnet core member in the second toroidal coil, and a second end iron core member overlapping an N pole face of second permanent magnet core member in the third toroidal coil. 
     In this configuration as well, the magnetic force lines running from the first ring-shaped pole piece through the first toroidal coil to the magnetic core member, even with alternation of the current fed to the toroidal coil, run from the center iron core member through the magnetization direction of the first permanent magnet core member and the magnetization direction of the first end iron core member through the second toroidal coil and flow into the second ring-shaped pole piece and also run from the center iron core member through the magnetization direction of the second permanent magnet core member and the magnetization direction of the second end iron core member through the third toroidal coil and flow into the third ring-shaped pole piece, so it is possible to further decrease the magnetic resistance in the magnetic core member. This contributes to strengthening of the vibrating force and reduction of size of the device. 
     Further, conversely, it is possible to employ a configuration where the first ring-shaped pole piece overlaps the S pole face of the first ring-shaped permanent magnet, the second ring-shaped pole piece overlaps the N pole face of the first ring-shaped permanent magnet, the third ring-shaped pole piece overlaps the N pole face of the second ring-shaped permanent magnet, and the magnetic core member has a center iron core member accommodated in the inside of the first toroidal coil, a first permanent magnet core member having an N pole face overlapped on one end face of the center iron core member in the first toroidal coil and second toroidal coil, a second permanent magnet core member having an N pole face overlapped on another end face of the center iron core member in the first toroidal coil and the third toroidal coil, a first end iron core member overlapping an S pole face of the first permanent magnet core member in the second toroidal coil, and a second end iron core member overlapping an S pole face of second permanent magnet core member in the third toroidal coil. 
     The outer circumferential surface of the toroidal coil is preferably covered by a protective tube. At the time of impact upon being dropped etc., the inner circumferential surface of the ring-shaped permanent magnet is prevented from striking the outer circumferential surface of the toroidal coil so the device can be protected from coil breakage. 
     Further, when the gap between the outer circumferential surface of the protective tube and the inner circumferential surface of the center hole of the ring-shaped permanent magnet is filled with a magnetic fluid, even if an outside impact force is given, the magnetic fluid acts as a buffer material, so it is possible to effectively suppress sudden collision of the ring-shaped permanent magnet with the protective tube. 
     Summarizing the advantageous effects of the present invention, in the present invention, the magnetization direction of the ring-shaped permanent magnet is the axial direction parallel to the magnetic core member, and, in the first concentrated flux path by the first ring-shaped pole piece, along with alternation of the feed of current to the first toroidal coil, the electromagnetic force which is applied to the ring-shaped permanent magnet switches to forward and reverse with respect to the axial direction, so compared with the conventional drive by magnetic attraction/repulsion, drive by a high vibrating force is possible. The magnetic force lines of the outer circumference side part of the ring-shaped permanent magnet are short circuited at the thickness direction of the ring-shaped permanent magnet, so it is possible to realize a reduced size of the vibration generator without a detrimental effect on the first concentrated flux path etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein 
         FIG. 1A  is a perspective view showing the appearance of a vibration linear actuator according to a first embodiment of the present invention, while  FIG. 1B  is a perspective view showing an inverted state of the vibration linear actuator; 
         FIG. 2  is a longitudinal cross-sectional view of the vibration linear actuator; 
         FIG. 3  is an assembled perspective view of the vibration linear actuator seen from above; 
         FIG. 4  is an assembled perspective view of the vibration linear actuator seen from below; 
         FIG. 5A  is a perspective view showing a combination of a case side structure and a lid side structure of the vibration linear actuator, while  FIG. 5B  is a perspective view showing a combination of the case side structure and the back lid side structure; 
         FIG. 6  is a longitudinal cross-sectional view showing a combination of the case side structure and the back lid side structure; 
         FIG. 7A  is a front view of the back lid side structure,  FIG. 7B  is a bottom view of the back lid side structure, and  FIG. 7C  is a plan view of the back lid side structure; 
         FIGS. 8A and 8B  are schematic views which explain a vibration mode of a vibration linear actuator according to a first embodiment; 
         FIGS. 9A and 9B  are schematic views which explain a vibration mode of a vibration linear actuator according to a second embodiment; 
         FIGS. 10A and 10B  are schematic views which explain a vibration mode of a vibration linear actuator according to a third embodiment; 
         FIGS. 11A and 11B  are schematic views which explain a vibration mode of a vibration linear actuator according to a fourth embodiment; 
         FIGS. 12A and 12B  are schematic views which explain a vibration mode of a vibration linear actuator according to a fifth embodiment; 
         FIGS. 13A and 13B  are schematic views which explain a vibration mode of a vibration linear actuator according to a sixth embodiment; 
         FIGS. 14A and 14B  are schematic views which explain a vibration mode of a vibration linear actuator according to a seventh embodiment; 
         FIGS. 15A and 15B  are schematic views which explain a vibration mode of a vibration linear actuator according to an eighth embodiment; 
         FIGS. 16A and 16B  are schematic views which explain a vibration mode of a vibration linear actuator according to a ninth embodiment; and 
         FIG. 17  is a longitudinal cross-sectional view showing a conventional vibration linear actuator. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, embodiments of the present invention will be explained with reference to the attached drawings. 
     First Embodiment 
     The vibration linear actuator  1  of this embodiment is provided with a ring-shaped permanent magnet  3  which is fit in a center hole H of a ring-shaped weight  2  and which is magnetized by a single pole in a thickness direction between a top end face (S pole face)  3   a  and bottom end face (N pole face)  3   b , a ring-shaped top pole piece  4  which is adhered to the top end face  3   a  by an adhesive, a ring-shaped bottom pole piece  5  which is adhered to the bottom end face  3   b  by an adhesive, a top plate spring  6  having an inner circumference side hanging part  6   a  fastened to the top pole piece plate  4  by for example spot welding, adhesion, or another means and having an outer circumference side hanging part  6   b  fastened to a bottom surface of a recessed case  9 , a bottom plate spring  7  having an inner circumference side hanging part  7   a  fastened to the bottom pole piece plate  5  and having an outer circumference side hanging part  7   b  fastened to an end plate  10  fastened to an opening side of the recessed case  9 , a columnar core (iron core)  8  which is a magnetic core member passing through a center hole h of the ring-shaped permanent magnet  3  and fastened standing up at the bottom surface of the recessed case  9 , a cylindrically shaped toroidal coil L standing up on a printed circuit board  11  adhered to the back surface of the end plate  10  and fit from a through hole  10   a  of the end plate  10  over the columnar core  8 , a plastic protective tubular member  12  standing up on the printed circuit board  11  and fit over the toroidal coil L, a magnetic fluid  13  filled in the space between the inner circumferential surface of the ring-shaped permanent magnet  3  and the outer circumferential surface of the protective tubular member  12  sandwiched between the top pole piece plate  4  and the bottom pole piece plate  5 , a rubber damper  14  adhered on the printed circuit board  11  and buffering against sharp impact of an inner circumference side hanging part  7   a  of the bottom plate spring  7  on the printed circuit board  11 , a pair of spiral spring terminals S 1 , S 2  connected to the back surface of the printed circuit board  11 , a soft crescent-shaped conductive rubber piece  15  bonded to the back surface of the printed circuit board  11  while straddling a notch  11   a  and contacting a conductive projection  10   b  of the end plate  10  through the notch  11   a , and a hard, substantially T-shaped rubber sheet  6  bonded with the back surface of the printed circuit board  11  for being closely held in a holding space (not shown) of the vibration linear actuator  1  itself, and a double-sided tape  17  with a peeloff sheet  17   a  adhered to the recessed case  9 . 
     The toroidal coil L includes a cylindrically shaped lower stage toroidal coil L 2  and a coaxial, superposed, cylindrically shaped, oppositely wound series upper stage toroidal coil L 1 . The second winding terminal T 2  bulging out from the end face of the lower stage toroidal coil L 2  is soldered to a second coil connection pattern P 2  on the printed circuit board  11 , while the first winding terminal T 1  bulging out from the end face of the lower stage toroidal coil L 2  from the upper stage toroidal coil L 1  to the lower stage toroidal coil L 2  at the inner circumferential side is soldered to a first coil connection pattern P 1  on the printed circuit board  11 . The method of production of this toroidal coil L is to wind a wire from the second winding terminal T 2  side in one direction in several layers to form the lower stage toroidal coil L 2 , then wind it in the opposite direction in several layers to form the upper stage toroidal coil L 1 , run a cross wire G (see  FIG. 6 ) along the base line direction of the lower stage toroidal coil L 2  at the inner circumferential surface, and cause the first winding terminal T 1  to bulge out from the end face. Note that, this cross wire G can be pulled around to the outer circumferential surface of the toroidal coil L and brought to the end face of the lower stage toroidal coil L 2 . 
     In this example, the inner circumferential edge of the top pole piece plate  4  bulges out somewhat from the inner circumferential surface of the ring-shaped permanent magnet  3  to the upper stage toroidal coil L 1  side and the inner circumferential edge of the bottom pole piece plate  5  bulges out from the inner circumferential surface of the ring-shaped permanent magnet  3  to the lower stage toroidal coil L 2  side. 
     The top plate spring  6  has spiral elastic wires  6   c  and  6   d  extending in an approximately 360° spiral shape from 180° rotationally symmetric positions of the outer circumferential side edges of the ring-shaped inner circumference side hanging part  6   a  and connecting to the inner circumference side edge of the ring-shaped outer circumference side hanging part  6   b . The bottom plate spring  7  also has spiral elastic wires  7   c  and  7   d  extending in an approximately 360° spiral shape from 180° rotationally symmetric positions of the outer circumferential side edges of the ring-shaped inner circumference side hanging part  7   a  and connecting to the inner circumference side edge of the ring-shaped outer circumference side hanging part  7   b.    
     The stainless steel or SPCC end plate  10  is recessed at the back surface side for accommodation of the printed circuit board  11 . It has a positioning piece  10   c . At the opposite side, a conductive projection  10   b  bulging out to the back surface side is press-formed. A through hole  10   a  is not a true circle, but has a straight edge N forming a chord for leaving room for forming the conductive projection  10   b.    
     The printed circuit board  11  is provided, at its front surface side, with not only a first coil connection pattern P 1  and a second coil connection pattern P 2 , but also a ring-shaped coil receiving pattern M mounting the toroidal coil L and fan-shaped reinforcement patterns f 1  to f 3  surrounding this coil receiving pattern M in three directions and is provided, at its back surface side, with a first terminal connection pattern Q 1  and second terminal connection pattern Q 2  for connection via the through holes to the first coil connection pattern P 1  and second coil connection pattern P 2 , and soldering to the conical bottom surface sides of the spring terminals S 1  and S 2  and a reinforcement pattern F surrounding the notch  11   a  and extending between the first terminal connection pattern Q 1  and second terminal connection pattern Q 2 . 
     In the present example, the end plate  10  is provided with the through hole  10   a  so as to thereby, as shown in  FIG. 5A  to  FIG. 7C , enable the case side structure  20  and the back lid side structure  30  to be assembled and a vibration linear actuator  1  to be obtained. The case side structure  20  is formed by assembling the recessed case  9 , the columnar core  8  fastened implanted at the bottom surface of this recessed case  9 , the ring-shaped weight  2 , ring-shaped permanent magnet  3 , the top pole piece plate  4 , the bottom pole piece plate  5 , the top plate spring  6 , the bottom plate spring  7 , and the end plate  10 , then injecting the magnetic fluid  13  through the through hole  10   a  of the end plate  10  to coat the inner circumferential surface of the ring-shaped permanent magnet  3 . On the other hand, the back lid side structure  30  includes the toroidal coil L, the protective tubular member  12 , and the rubber damper  14  mounted on the printed circuit board  11  and the spring terminals S 1  and S 2  connected to the back surface of the printed circuit board  11  and bonded to the rubber sheet  16 . The columnar core  8  of the case side structure  20  is fit through the through hole  10   a  of the end plate  10  and into the hollow part of the toroidal coil L, and the printed circuit board  11  is bonded to the recess at the back surface side of the end plate  10 . After this, the crescent-shaped conductive rubber piece  15  is bonded to the back surface of the printed circuit board  11 , and a double-sided tape  17  is stuck to the recessed case  9 . 
     In this embodiment, as shown in  FIGS. 8A and 8B , almost all of the magnetic field lines emerging from the bottom end face (N pole face)  3   b  run through the bottom pole piece  5  to pass from the inner circumferential edge through the lower toroidal coil L 2  and enter the columnar core  8 , then run in the axial direction, pass through the upper toroidal coil L 1  to jump to the inner circumferential edge of the top pole piece  4 , run through the inside of it, and return to the top end face (S pole face)  3   a . For this reason, by the concentrated flux path between the inner circumferential edge of the bottom pole piece  5  and the columnar core  8  and the concentrated flux path between the inner circumferential edge of the top pole piece  4  and columnar core  8 , electromagnetic forces are generated. In the state where the direction of current flowing through the lower toroidal coil L 2  and the upper toroidal coil L 1  is as shown in  FIG. 8A , a counteraction force to the electromagnetic force occurs in the arrow direction and the ring-shaped permanent magnet  3  is made to vibrate, while in the state shown in  FIG. 8B  where the current direction switches, a counteracting force occurs in the arrow direction and the ring-shaped permanent magnet  3  is made to vibrate in the reverse direction. This contributes to improvement of the vibration intensity or lower power consumption. 
     Further, in the state of  FIG. 8A , the end face of the columnar core  8  at the upper toroidal coil L 1  side is the S pole, while the end face of the columnar core  8  at the lower toroidal coil L 2  side is also the S pole, so the magnetic attraction and repulsion force with the ring-shaped permanent magnet  3  acts in the same direction as the above-mentioned counteracting force. In the state of  FIG. 8B , the end face of the columnar core  8  at the upper toroidal coil L 1  side is the N pole and the end face of the columnar core  8  at the lower toroidal coil L 2  side is also the N pole, so the magnetic attraction and repulsion force with the ring-shaped permanent magnet  3  acts in the same direction as the above counteracting force. Such a magnetic attraction and repulsion force is superposed on the electromagnetic force, so this contributes even more to the improvement of the vibrating strength or lower power consumption. However, the magnetic force lines pass through the inside of the columnar core  8  by a short-circuit magnetic path, so it is possible to lower the magnetic resistance, but in the state of  FIG. 8A , since the center part in the columnar core  8  becomes the N pole, the magnetic resistance of the path from the lower toroidal coil L 2  side toward this center part in the magnetization direction is extremely low, while the magnetic resistance of the path from the center part toward the upper toroidal coil L 1  side in the counter magnetization direction is high. In the state of  FIG. 8B , since the center part ins the columnar core  8  becomes the S pole, the magnetic resistance of the path from the lower toroidal coil L 2  side toward this center part in the counter magnetization direction is high, while the magnetic resistance of the path from the center part toward the upper toroidal coil L 1  side is extremely low. 
     The magnetized direction of the ring-shaped permanent magnet  3  is substantially parallel to the direction of the columnar core  8  in the toroidal coil L. In the flux emerging from the first end face  3   a  or second end face  3   b  of the ring-shaped permanent magnet  3 , the flux sneaking around to the inner circumference side jumps over the gap to the outer circumferential surface of the columnar core  8  and passes through the inside of the columnar core  8 , so the magnetic fluid  13  interposed in the clearance between the outer circumferential surface of the protective tubular member  12  and the inner circumferential surface of the ring-shaped permanent magnet  3  is sealed in state by the flux jumping over the gap. Regardless of the posture of the reciprocating vibration generator, it is therefore possible to prevent leakage of magnetic fluid  13 . Further, due to the magnetic fluid  13  acting as this buffer layer, even if external force of impact is given, it is possible to effectively keep the reciprocating vibrator from sharply striking the toroidal coil L and therefore possible to prevent damage to the toroidal coil L. It is also possible to not use the magnetic fluid  13  and instead cover the toroidal coil L with the protective tubular member  12  so as to protect the toroidal coil L from damage due to being sharply struck by the reciprocating vibrator. Since there is the protective tubular member  12 , the gap with the ring-shaped permanent magnet  3  can be made very small. This contributes to the reduction of size of the reciprocating vibration generator. Further, since the gap is very small, it is not necessary to use a high viscosity magnetic fluid  13  which is not excellent in low temperature characteristics. It is sufficient to use low viscosity, inexpensive magnetic fluid  13  which is excellent in low temperature characteristics. Note that, this protective tubular member  12  is preferably made of a slippery material. It may be a metal material or plastic material of course and may also be a heat shrinkable tube. 
     The top pole piece plate  4  is superposed at the top end face  3   a  of the ring-shaped permanent magnet  3 , while the bottom pole piece plate  5  is superposed at the bottom end face  3   b  of the ring-shaped permanent magnet  3 , so the inner circumferential surface of the top pole piece plate  4  trapping the flux at the top end face  3   a  side and the inner circumferential surface of the bottom pole piece plate  5  trapping the flux at the bottom end face  3   b  side approach the outer circumferential surface of the columnar core  8  whereby the magnetic resistance is lowered. Further, the flux density for jumping over this gap becomes high, so it is possible to further improve the vibration strength or lower the power consumption and it is possible to rapidly attenuate the vibration. Further, the sealing ability of the magnetic fluid  13  is improved. 
     In particular, in the present example, the inner circumferential surfaces of the top pole piece plate  4  and the bottom pole piece plate  5  bulge out from the inner circumferential surface of the ring-shaped permanent magnet  3  to the protective tubular member  12  side, so the flux density for jumping the gap between the inner circumferential surfaces of the pole piece plates  4  and  5  and the outer circumferential surface of the columnar core  8  becomes higher, so the ability to seal in the magnetic fluid  13  is raised. 
     Further, the outer circumferential surface of the toroidal coil L is covered by the protective tubular member  12  such as a heat-shrinkable tube or other member, so at the time of impact due to being dropped etc., it is possible to prevent the inner circumferential surface of the ring-shaped permanent magnet  3  from sharply striking the outer circumferential surface of the toroidal coil L and possible to protect the actuator from coil breakage problems. 
     Magnetic fluid  13  is interposed between the outer circumferential surface of the protective tubular member  12  and the inner circumferential surface of the ring-shaped permanent magnet  3 , so even if an external force of impact is applied, the magnetic fluid  13  becomes a buffer material, so it is possible to effectively suppress sharp impact of the ring-shaped permanent magnet  3  to the protective tubular member  12 . Note that, even when there is no protective tubular member  12 , since magnetic fluid  13  is interposed between the outer circumferential surface of the toroidal coil L and the inner circumferential surface of the ring-shaped permanent magnet  3 , it is possible to keep the inner circumferential surface of the ring-shaped permanent magnet  3  from striking the outer circumferential surface of the toroidal coil L. 
     In the assembled structure of the vibration linear actuator  1 , the end plate  10  has a through hole  10   a  of a size enabling passage of the toroidal coil L, so not only is it possible to simply inject magnetic fluid  13  through this through hole  10   a  to coat the inner circumferential surface of the ring-shaped permanent magnet  3 , but also, after this, it is possible to insert the toroidal coil L from this through hole  10   a  and fasten the printed circuit board  11  to the back surface of the end plate  10  and possible to try to facilitate production. 
     To prevent the generation of electromagnetic interference from the vibration linear actuator  1 , it is necessary to ground and shield the outer housing having the recessed case  9  and the end plate  10 . As the structure for feeding a ground potential to the end plate  10 , the end plate  10  has the conductive projection  10   b  contacting the conductive rubber piece  15  adhered to the back surface of the printed circuit board  11  through the notch  11   a  framed in the printed circuit board  11 . This is not a structure where the end plate  10  contacts a pattern of the printed circuit board  11 , but a structure directly connecting the conductive projection  10   b  of the end plate  10  and the conductive rubber piece  15 , so it is possible to obtain the conductive projection  10   b  when press-forming the end plate  10  and possible to realize lower cost. 
     Note that, in this example, the series connection lower stage toroidal coil L 1  and upper stage toroidal coil L 2  were explained, but a parallel connection structure of the two coils may also be employed for reducing the resistance loss. Further, as the mechanical vibrator, it is also possible to eliminate the ring-shaped weight  2  and just use the large ring-shaped permanent magnet  3 . 
     Second Embodiment 
     The point of difference of the vibration linear actuator of the second embodiment shown in  FIGS. 9A and 9B  from the vibration linear actuator of the first embodiment 1 lies in the configuration of a columnar core  18 . The columnar core  18  has a center core (center iron core member)  18   a  which fits inside the lower toroidal coil L 2  and the upper toroidal coil L 1  straddling the two, a bottom permanent magnet (permanent magnet core member)  18   c  which has an N pole face provided in an inside the lower toroidal coil L 2  and overlaid on one end face of the center core  18   a , and a top permanent magnet  18   b  which has an S pole face provided in an inside the top toroidal coil L 1  and overlaid on another end face of the center core  18   a . Note that the rest of the configuration is the same as the first embodiment. 
     In such a configuration of the columnar core  18 , even if the feed of current to the toroidal coils L 1  and L 2  alternates, the magnetization direction of the center core  18   a  is determined by the magnetization of the bottom permanent magnet  18   c  and the top permanent magnet  18   b , so the magnetic force lines which run from the bottom pole piece  5  through the lower toroidal coil L 2  to the columnar core  18  run from the magnetization direction of the bottom permanent magnet  18   c  through the magnetization direction of the center core  18   a  and through the magnetization direction of the top permanent magnet  18   b  to pass through the top toroidal coil L 1  and flow into the top pole piece  4 , so it is possible to further decrease the magnetic resistance in the columnar core  18 . This contributes to strengthening of the vibrating force and reduction in size of the device. 
     Third Embodiment 
     A columnar core  28  of a vibration linear actuator of the third embodiment shown in  FIGS. 10A and 10B , opposite to the configuration of the columnar core  18  of the second embodiment, has a center permanent magnet  28   a  which fits inside the lower toroidal coil L 2  and the upper toroidal coil L 1  straddling the two and which has a magnetization direction of the reverse direction from the magnetization direction of the ring-shaped permanent magnet  3 , a bottom core (iron core member)  28   c  provided in an inside the lower toroidal coil L 2  and overlaps the S pole face of the center permanent magnet  28   a , and a top core  28   b  provided in an inside the upper toroidal coil L 1  and overlaps the N pole face of the center permanent magnet  28   a . The magnetization directions of the bottom core  28   c  and top core  28   b  match the magnetization direction of the center permanent magnet  28   a , so the magnetic force lines which run from the bottom pole piece  5  through the lower toroidal coil L 2  to enter the columnar core  28  run through the magnetization direction of the bottom core  28   c  through the magnetization direction of the top core  28   b  to pass through the top toroidal coil L 1  and flow into the top pole piece  4 . For this reason, it is possible to further decrease the magnetic resistance inside the columnar core  28 . This contributes to strengthening of the vibrating force and reduction in size of the device. 
     Fourth Embodiment 
     A vibration linear actuator of the fourth embodiment shown in  FIGS. 11A and 11B  is configured simplified over the vibration linear actuator of the first embodiment shown in  FIGS. 8A and 8B . Instead of the ring-shaped permanent magnet  3 , it has a thin top ring-shaped permanent magnet  23  having an N pole face on which a sole ring-shaped pole piece  25  is overlaid. Further a sole center toroidal coil L 0  is fit over the columnar core  8 . 
     The magnetic force lines from the N pole face  23   b  to the S pole face  23   a  form a short-circuit closed loop with a low magnetic resistance. The short-circuit closed loop includes a concentrated flux path W 0  for generating electromagnetic force which runs across the current flowing through the center toroidal coil L 0  between the inner circumferential edge of the pole piece  25  and the outer circumferential surface of the columnar core  8 , an air gap flux path W 1  between the outer circumferential surface of the columnar core  8  and the S pole face  23   a  with no pole piece, and a low magnetic resistance path in the columnar core  8 . For this reason, at the top ring-shaped permanent magnet  23 , a counteracting force of the electromagnetic force is alternately generated. 
     Further, the magnetic force lines at the outer circumference side part of the top ring-shaped permanent magnet  23  among the N pole face  23   b  and the S pole face  23   a  are short-circuited in the thickness direction of the top ring-shaped permanent magnet  23 , so there are no detrimental effects on the concentrated flux path W 0  or the air gap flux path W 1 . Therefore, a reduction of size of the device can be realized. 
     Fifth Embodiment 
     A vibration linear actuator of the fifth embodiment shown in  FIGS. 12A and 12B  is configured as the vibration linear actuator of the fourth embodiment shown in  FIGS. 11A and 11B  plus a bottom ring-shaped permanent magnet  24 . The ring-shaped pole piece  25  is sandwiched between the N pole face of the top ring-shaped permanent magnet  23  and the N pole face of the bottom ring-shaped permanent magnet  24 . The magnetic force lines coming from the inner circumferential edge of the ring-shaped pole piece  25  run through the concentrated flux path W 0  to pass through the center toroidal coil L 0  where they are then branched into two. One part passes through the columnar core  8  toward the top and runs through the air gap flux path W 1  to jump to the S pole face of the top ring-shaped permanent magnet  23 , while the other passes through the columnar core  8  toward the bottom and runs through the air gap flux path W 2  to jump to the S pole face of the bottom ring-shaped permanent magnet  24 . In this configuration as well, electromagnetic force is generated by the concentrated flux path W 0  from the inner circumferential edge of the pole piece  25 . Inside the columnar core  8 , the magnetic resistance is low, so drive with a high vibrating force is possible. Further, the magnetic force lines at the outer circumference side parts of the top ring-shaped permanent magnet  23  and bottom ring-shaped permanent magnet  24  are short-circuited in the thickness direction, so there are no detrimental effects on the concentrated flux path W 0  or the air gap flux paths W 1  and W 2 . Therefore, a reduction of size of the device can be realized. 
     Sixth Embodiment 
     A vibration linear actuator of the sixth embodiment shown in  FIGS. 13A and 13B  is configured as the vibration linear actuator of the fifth embodiment shown in  FIGS. 12A and 12B  plus the ring-shaped top pole piece  4  and the bottom pole piece  5 . By the addition of the top pole piece  4  and the bottom pole piece  5 , it is possible to make the air gap flux paths W 1  and W 2  in  FIGS. 12A and 12B  to be the concentrated flux paths W 1 ′ and W 2 ′ between the inner circumferential edges of the top pole piece  4  and bottom pole piece  5  and the columnar core  8 , possible to lower the magnetic resistance, and possible to drive the device with a high vibrating force. 
     Seventh Embodiment 
     A vibration linear actuator of the seventh embodiment shown in  FIGS. 14A and 14B  is configured as the vibration linear actuator of the sixth embodiment shown in  FIGS. 13A and 13B  plus the lower toroidal coil L 2  and the upper toroidal coil L 1 . The center toroidal coil L 0  and the lower toroidal coil L 2  are wound oppositely and connected in series, while the center toroidal coil L 0  and upper toroidal coil L 1  are wound oppositely and connected in series. The magnetic force lines emerging from the inner circumferential edge of the ring-shaped pole piece  25  run through the concentrated flux path W 0  and pass through the center toroidal coil L 0  where they are then branched into two. One part passes through the inside of the columnar core  8  toward the top and runs through the concentrated flux W 1 ′ to jump to the inner circumferential edge of the top pole piece  4 , while the other passes through the inside of the columnar core  8  toward the bottom and runs through the concentrated flux W 2 ′ to jump to the inner circumferential edge of the bottom pole piece  5 . For this reason, by the concentrated flux paths W 1 ′ and W 2 ′ also, electromagnetic force is generated, so the drive force is strengthened. Furthermore, in the current carrying state of  FIG. 14A , the top end face of the columnar core  8  is the S pole face and the top pole piece  4  is the S pole face, so the two magnetically repulse each other, while the bottom end face of the columnar core  8  is the N pole face and the bottom pole piece  5  is the S pole face, so the two magnetically attract each other. From the viewpoint of magnetic attraction and repulsion, as well, the drive force is augmented. Further, in the current carrying state of  FIG. 14B , the top end face of the columnar core  8  is the N pole face and the top pole piece  4  is the S pole face, so the two magnetically attract each other, while the bottom end face of the columnar core  8  is the S pole face and the bottom pole piece  5  is the S pole face, so the two magnetically repulse each other. From the viewpoint of magnetic attraction and repulsion, as well, the drive force is augmented. 
     However, in the current carrying state of  FIG. 14A , the magnetic flux which passes through the inside of the columnar core  8  downward is opposite in direction from the magnetization direction of the electromagnet, so the magnetic resistance is high. Further, in the current carrying state of  FIG. 14B , the magnetic flux which passes through the inside of the columnar core  8  upward is opposite in direction from the magnetization direction of the electromagnet, so the magnetic resistance is high. 
     Eighth Embodiment 
     A vibration linear actuator of the eighth embodiment shown in  FIGS. 15A and 15B  is an improvement of the vibration linear actuator of the seventh embodiment shown in  FIGS. 14A and 14B . Instead of the columnar core  8  of  FIGS. 14A and 14B , a columnar core  29  includes a center core  29   a  which spans the lower toroidal coil L 2  and the upper toroidal coil L 1  and which has a center at the inside of the center toroidal coil L 0 , a bottom permanent magnet  29   c  which has an S pole face overlaid on the bottom end face of the center core  29   a  inside the lower toroidal coil L 2 , and a top permanent magnet  29   b  which has an S pole face overlaid on the top end face of the center core  39   a  inside the upper toroidal coil L 1 . 
     The magnetic force lines emerging from the inner circumferential edge of the ring-shaped pole piece  25  run through the concentrated flux path W 0  and pass through the center toroidal coil L 0  where they are then branched into two. The magnetic flux branched downward runs through the almost completely nonmagnetized state center core  29   a  and passes through the magnetization direction of the bottom permanent magnet  29   c  to head toward the lower toroidal coil L 2 , while the magnetic flux branched upward runs through the almost completely nonmagnetized state center core  29   a  and passes through the magnetization direction of the top permanent magnet  29   b  to head toward the upper toroidal coil L 1 , so compared with the case of the seventh embodiment of  FIGS. 14A and 14B , the magnetic resistance becomes lower, so the drive force is increased. Further, in both of the current carrying states of  FIG. 15A  and  FIG. 15B , the electromagnetic forces generated by the concentrated flux paths W 1 ′, W 2 ′ are balanced. 
     However, even in the current carrying state of  FIG. 15A  and  FIG. 15B , the N pole face of the top permanent magnet  29   b  and the top pole piece  4  magnetically attract each other and, the N pole face of the bottom permanent magnet  29   c  and the bottom pole piece  5  magnetically attract each other, so addition of drive force from the point of magnetic attraction and repulsion cannot be expected. 
     Ninth Embodiment 
     A vibration linear actuator of the ninth embodiment shown in  FIGS. 16A and 16B  is a separate structure from the vibration linear actuator of the eighth embodiment shown in  FIGS. 15A and 15B . A columnar core  31  has a center core  31   a  which is fit inside the center toroidal coil L 0 , a bottom permanent magnet  31   c  provided in an inside of this center toroidal coil L 0  and the lower toroidal coil L 2  and having an S pole face overlapping a bottom end face of the center core  31   a , a top permanent magnet  31   b  provided in an inside the center toroidal coil L 0  and upper toroidal coil L 1  and having an S pole face overlapping the center core  31   a , a bottom end core  31   e  which overlaps an N pole face of the bottom permanent magnet  31   c  inside the lower toroidal coil L 2 , and a top end core  31   d  which overlaps an N pole face of the top permanent magnet  31   b  inside the upper toroidal coil L 1 . 
     In the vibration linear actuator of this ninth embodiment, in the same way as the vibration linear actuator of the eighth embodiment, the magnetic resistance is decreased. 
     Note that the illustrated polarities of the permanent magnets  3 ,  18   b ,  18   c ,  28   a ,  23 ,  24 ,  29   b ,  29   c ,  31   b , and  31   c  of  FIG. 3  to  FIGS. 16A and 16B  may be reversed in assembly as well. 
     While the invention has been described with reference to specific embodiments chosen for purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.