Abstract:
A linear vibration motor has a movable element including a magnet and a weight, and an elastic member are inserted into a frame. The frame supports the movable element so the movable element can freely slide axially; a coil fixed to the frame and drives the magnet axially; and an elastic member applying, to the movable element, an elastic force against the driving force of the magnet. The frame has a bottom surface plate with a bottom surface affixing the coil; an upper surface plate has an upper surface opposing the bottom surface; and a front surface plate facing the axially and supports the elastic member. The bottom surface plate has partial side surface portions that are respectively bent from both side edges of the bottom surface portion and in which an opening is formed in a central part of the partial side surface portions in the axial direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a U.S. national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/JP2015/074744, filed Aug. 31, 2015, and claims benefit of priority to Japanese Patent Application No. 2014-181445, filed Sep. 5, 2014. The entire contents of these applications are hereby incorporated by reference. 
     
    
     FIELD OF TECHNOLOGY 
       [0002]    The present invention relates to a linear vibration motor for generating a vibration through causing a movable element to undergo reciprocating vibration linearly through a signal input. 
       BACKGROUND 
       [0003]    A vibration motor (or a vibration actuator) is that which communicates, to a user of a communication device or to an operator who is holding any of a variety of electronic devices, the state of an input signal through a vibration, through generating a vibration through an incoming call on a communication device or through the transmission of an alarm on any of a variety of electronic devices, and is built into any of a variety of electronic devices, such as mobile information terminals, including mobile telephones. 
         [0004]    Among the various forms of vibration motors that are under development, there are known linear vibration motors that are able to generate relatively large vibrations through linear reciprocating vibrations of a movable element. This linear vibration motor comprises a coil that is disposed within a frame, and a weight, which is vibrated linearly, by a magnet, along a vibrational axis within the frame, through cooperation with a magnet that is surrounded by this coil, and which vibrates together with the magnet along the vibrational axis, where a coil spring is disposed between an end portion of the weight and an inner surface of the frame, so that the elastic force of the coil spring repels the driving force of the coil and the magnet, to cause the movable element, made from the magnet and the weight, to vibrate within the frame (for example, Japanese Unexamined Patent Application Publication 2014-028349). 
       SUMMARY 
       [0005]    In a conventional linear vibration motor, an elastic member (a coil spring) is disposed within the frame, to produce a linear vibration along the axial direction through causing both the driving force that is produced by the coil and the magnet, and the elastic force of the elastic member (the coil spring), to act in the same axial direction. At this time, the elastic member is disposed positioned by a protruding portion that is formed within the frame and a recessed/raised portion that is formed on an end portion of the weight, but in the prior art wherein the elastic member and the movable element that is made from the magnet and the weight are built in advance into a frame that is formed into a box shape, it is not possible to check, in the end, whether or not the elastic member is assembled into the frame in an appropriate state, requiring more careful operations at the time of assembly, and thus there is a problem in that simple asemblability is not possible. 
         [0006]    In the present invention, the handling of such problems is an example of the problem to be solved. That is, the object of the present invention is to enable simple asemblability, through the ability to carry out the assembly operation while confirming the proper state of attachment of the elastic member, in a linear vibration motor wherein an elastic member and a movable element that is made from a magnet and a weight are built into a frame. 
         [0007]    In order to achieve such an object, the linear vibration motor of the present invention is equipped with the following structures: 
         [0008]    a linear vibration motor comprising: a movable element equipped with a magnet and a weight; a frame for supporting the movable element so as to be able to slide along the axial direction; a coil, secured to the frame, for driving the magnet along the axial direction; and an elastic member for applying, to the movable element, an elastic force that opposes the driving force that is applied to the magnet, wherein: a bottom plate that has a bottom face portion whereon the coil is secured; a top face plate that has a top face portion that faces the bottom face portion; and end face plates, facing the axial direction, for supporting the elastic member, wherein: the bottom plate has a partial side face portion that is bent from a side edge of the bottom face portion, wherein an open portion is formed in a center part along the axial direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is an explanatory diagram (an assembly perspective diagram) illustrating the overall structure of a linear vibration motor according to an example according to the present invention. 
           [0010]      FIG. 2  is an explanatory diagram (a plan view diagram showing the internal structure) illustrating the overall structure of a linear vibration motor according to an example according to the present invention. 
           [0011]      FIG. 3  is an explanatory diagram (a perspective view showing the attached state) illustrating the overall structure of a linear vibration motor according to an example according to the present invention. 
           [0012]      FIG. 4  is an explanatory diagram (a perspective view showing the state after assembly has been completed) illustrating the overall structure of a linear vibration motor according to an example according to the present invention. 
           [0013]      FIG. 5  is an explanatory diagram illustrating the electronic device (a mobile information terminal) equipped with a linear vibration motor according to an example according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    A linear vibration motor according to an example according to the present invention comprises: a movable element that is provided with a magnet and a weight; a frame that supports the movable element so as to be able to slide along an axial direction; a coil, secured to the frame, for driving the magnet along the axial direction; and an elastic member for applying, to the movable element, an elastic force that repels the driving force that acts on the magnet. Here the structure wherein the frame supports the movable element so as to be able to oscillate may be of any shape. For example, the form may be one wherein a single shaft, a plurality of shafts, or a guide is provided in the axial direction within the frame, where the movable element is supported so as to be able to slide along the shaft or guide, or a form may be used wherein the movable element within the frame is constrained to the axial direction, without the provision of a shaft or guide. 
         [0015]    The frame of the linear vibration motor according to an example according to the present invention comprises: a bottom face plate that has a bottom face portion whereon the coil is secured; a top face plate that has a top face portion that faces the bottom face portion; and perpendicular face plates, facing the axial direction, for supporting the elastic member, wherein: the bottom face plate has a partial side face portion that is bent from a side edge of the bottom face portion, wherein an open portion is formed in a center part along the axial direction. 
         [0016]    In the linear vibration motor having such distinguishing features, the frame being provided with the bottom face plate, the top face plate, and the perpendicular face plates enables assembly through joining the perpendicular face plates with edges of the bottom face plate in a state wherein the coil is secured to the bottom face portion of the bottom face plate, and the movable element and the elastic members to be assembled to the bottom face plate in an open state, followed by joining the bottom face plate and the top face plate together. In this way, this enables simple and accurate assembly through the ability to join, at the end, the bottom face plate and the top face plate together after checking the appropriate assembly of the elastic members. 
         [0017]    Moreover, because the bottom face plate to which the movable element and the elastic member are assembled has a partial side face portion wherein an open portion is formed in the center part along the axial direction, the operation for joining together the magnet and the weights can be carried out through an easy operation through the use of the open portion in a state wherein the magnets are inserted into openings of the coil that is secured to the bottom face portion. At this time, the magnet and the weights are joined together in a state wherein the magnets are inserted into the coil, enabling relative freedom in the size and shape of the weights, making it possible to achieve a linear vibration motor that uses little energy, through the use of large weights. 
         [0018]    An example according to the present invention will be explained below in reference to the drawings (where in different drawings below, identical reference symbols indicate identical positions, and redundant explanations in the individual drawings are omitted.)  FIG. 1  through  FIG. 4  illustrate the overall structure of a linear vibration motor according to one example according to the present invention (where  FIG. 1  is an exploded perspective diagram,  FIG. 2  is a plan view that illustrates the internal structure,  FIG. 3  is a perspective diagram that illustrates the assembled state, and  FIG. 4  is a perspective diagram illustrating the state wherein the assembly has been completed). The X direction in each of the drawings indicates the direction of vibration (the axial direction), the Y direction indicates the width direction, and the Z direction indicates the thickness (height) direction. The example that is illustrated is one example according the present invention, and the present invention is not limited thereto. In particular, the structure wherein the movable element is supported slidably on the frame is not limited to the example that is illustrated. 
         [0019]    The linear vibration motor  1  comprises: a movable element  10  that is equipped with a magnet  11  and a weight  12 ; a frame  2  for supporting the movable element  10  so as to be able to slide along the axial direction; a coil  4  that is secured to the frame  2 , for driving the magnet  11  along the axial direction; and an elastic member  6  for applying, to the movable element  10 , an elastic force for repelling the driving force that acts on the magnet  11 . 
         [0020]    The frame  2  comprises a bottom face plate  20 , a top face plate  21 , and perpendicular face plates  22 , where these are joined together to form the frame  2 . The bottom face plate  20 , the top face plate  21 , and the end face plates  22  are each formed through machining (pressing processes, or the like) respective metal plates. More specifically, the bottom face plate  20  and the top face plate  21  that structure a magnetic circuit in respect to the coil  4  can be formed from, for example, stainless steel plates of a magnetic material, where the pair of end face plates  22  that do not structure a magnetic circuit may be formed from stainless steel plates of a non-magnetic material. 
         [0021]    The bottom face plate  20  has a bottom face portion  20 A to which the coil  4  is secured, a partial side face portion  20 B that is bent from the side edge of the bottom face portion  20 A, and an open portion  20 C, wherein the center part along the axial direction (the X direction in the figure, which is the direction of vibration) is open on a side edge of the bottom face portion  20 A. The top face plate  21  has a top face portion  21 A that faces the bottom face portion  20 A, and a partial side face portion  21 B that is bent from the side face of this top face portion  21 A. The end face plates  22  are provided in a pair that is mutually facing in the axial direction (the X direction in the figure, which is the direction of vibration), and have supporting portions  22 A for supporting the elastic members  6 . 
         [0022]    Here, in the example that is illustrated, the bottom face portion  20 A of the bottom face plate  20  and the top face portion  21 A of the top face plate  21  are formed in rectangular shapes wherein the lengthwise direction is the axial direction (the X direction in the figure), where the partial side face portions  20 B and  21 B, along the long edges thereof, are formed bent so as to be essentially perpendicular to the bottom face portion  20 A or top face portion  21 A. Given this, the end face plates  22  are formed in rectangular shapes having outer peripheral edges depending on the short edges of the bottom face portion  20 A and the top face portion  21 A, and the height of the partial side face portion  20 B. 
         [0023]    The partial side face portion  21 B of the top face plate  21  is formed so as to cover the open portion  20 C of the bottom face plate  20 , where a protruding portion  21 P for engaging with a recessed portion  20 S that is formed on a side edge of the bottom face portion  20 A in the open portion  20 C is formed on the bottom edge of the partial side face portion  21 B. Moreover, protruding portions  20 P for engaging with recessed portions  21 S,  20 S that are formed on edges of the top face plate  21  and the bottom face plate  20  are formed on the top and bottom edges of the end face plates  22 . 
         [0024]    In regards to such a frame  2 , the coil  4  is secured to the bottom face portion  20 A, and a driving portion is structured from the coil  4  that is secured to the frame  2  and the magnet  11  that is a portion of the movable element  10 . Lorentz forces that act on the magnet  11  through the application of the electric current to the stationary coil  4  act as driving forces that cause the movable element  10  to vibrate along the axial direction (the X direction in the figure). 
         [0025]    As illustrated in  FIG. 11 , in the magnet  2 , two flat rectangular magnet pieces  11 A and  11 B that have polarities along the axial direction (the X direction in the figure) are disposed with identical poles facing each other, connected with a spacer yoke  11 C interposed therebetween. If necessary, a reinforcing plate  11 D is secured to a side face of the magnet  11  to increase the rigidity of the magnet  11  thereby. 
         [0026]    The coil  4  is a wire wrapped, along the Y and Z directions, around the magnet  11  wherein the direction of the magnetic pole faces in the X direction. The securing of the coil  4  to the bottom face portion  20 A may be through securing directly to the bottom face portion  20 A, or may be through winding the coil  4  onto a coil bobbin and securing the coil bobbin onto the bottom face portion  20 A. 
         [0027]    In the example that is illustrated, in the movable element  10 , weights  12  are connected to both end portions of the magnet  11  in the axial direction (the X direction in the figure). The weight  12  may be structured through, for example, a metal material with a high specific gravity, and, in the example that is illustrated, has a shape that is a rectangular prism that has a Z-direction height that is greater than the thickness of the magnet  11 , and a width in the Y direction that is greater than the width of the magnet  11 . 
         [0028]    The movable element  10  is provided with a pair of shaft portions  5  that protrude in mutually opposing directions along the axial direction (the X direction in the figure). The shaft portions  5  are provided protruding in cantilever shapes from both axial-direction end portions of the movable element  10 . In the example that is illustrated, shaft portions  5  protrude from within recessed portions  12 B of respective weights  12  that are connected to both axial-direction end portions of the magnet  11 , where here one end side of the shaft portion  5  is inserted and secured in a shaft supporting portion  12 B 1  that is provided in the weight  12 . 
         [0029]    Bearing portions  3  for supporting respectively, the pair of shaft portions  5  are provided on the bottom face portion  20 A of the bottom face plate  20 . The movable element  10  is supportive slidably, relative to the frame  2 , through the bearing portions  3  supporting the pair of shaft portions  5  so as to be able to slide. The bearing portion  3  is structured from a bearing  3 A and a bearing supporting member  3 B, where the bearing supporting member  3 B is attached to the bottom face portion  20 A of the bottom face plate  20 , and the bearing  3 A is attached to the standing portion of the bearing supporting member  3 B. A positioning protrusion  20 A 1  that protrudes for positioning is provided in the bottom face portion  20 A, where the bearing supporting member  3 B is attached to this positioning protrusion  20 A 1 . 
         [0030]    The recessed portion  12 B of the weight  12  wherein the shaft portion  5  protrudes has a width that enables insertion of the bearing portion  3 . The provision of such a recessed portion  12 B enables the X-direction length of the linear vibration motor  1  to be kept short, while enabling a large vibrational amplitude for the movable element  10 . 
         [0031]    Elastic members  6  are disposed off-axis from, and in parallel to, the pair of shaft portions  5 , to apply, to the movable element  10 , an elastic force that opposes the driving force that is produced by the magnet  11  and the coil  4 . In the example that is illustrated, compression coil springs that extend and compress along the axial direction (the X direction) are used as the elastic members  6 , where on one side two elastic members  6  are disposed between the end portion  12 A of the weight  12  and the end face plate  22 . A supporting portion (a supporting protrusion)  12 A 1 , for supporting one end side of the elastic member  6 , is provided on an end portion  12 A of the weight  12 , and a supporting portion (a supporting protrusion)  22 A, for supporting the other end side of the elastic member  6 , is provided on the inner surface side of the end face plate  22 . 
         [0032]    The operation of such a linear vibration motor  1  will be explained. When not driven, the movable element  10  stands still in the vibration center position wherein the elastic forces of the elastic members  6  are in equilibrium. When an electric current of a vibration generation signal is inputted into the coil  4 , a driving force is applied to the magnet  11  in the X direction, and the movable element  10  undergoes reciprocating vibration along the axial direction (the X direction in the drawing) through the driving force and the elastic repulsive force of the elastic member  6 . 
         [0033]    If necessary, sliding protrusions  12 D for making sliding contact with the bottom face portion  20 A and the top face portion  21 A, are provided on the surface of the weight  12  in the movable element  10 . The provision of such sliding protrusions  12 D, and the formation of the location of sliding contact between the bottom face portion  20 A and the top face portion  21 A from a resin material, or the like, enables suppression of noise at the time of vibration of the movable element  10 , and enables a stabilized vibration. At this time, the location of sliding contact may be provided instead on the weight  12  surface side, and the sliding protrusions may be provided instead on the bottom face portion  20 A and the top face portion  21 A. 
         [0034]    The method for assembling such a linear vibration motor  1  (the manufacturing method thereof) will be explained. As illustrated in  FIG. 3 , the assembly of each of the parts is performed in a state wherein the bottom face portion  20 A of the bottom face plate  20  is open. First the coil  4  is secured to the bottom face portion  20 A of the bottom face plate  20 . The coil  4  is secured to the bottom face portion  20 A through an adhesive agent, or the like. 
         [0035]    Given this, a weight  12 , in a state wherein the shaft portion  5  is attached, is joined in advance to one end side of the magnet  11  in the axial direction (the X direction in the figure), and after the other end side, in the axial direction, of the magnet  11  is inserted into the opening of the coil  4 , a weight  12 , in a state wherein the shaft portion  5  is attached, is joined to the other end side, in the axial direction, of the magnet  11 . The joining of the magnet  11  and the weight  12  is through, for example, inserting end portion of the magnet  11  into a joining portion  12 C of the weight  12  and welding. At this time, the joining together of the magnet  11  and the weight  12 , which is carried out in a state wherein the other end side, in the axial direction, of the magnet  11  has been inserted into the opening of the coil  4 , can be carried out through a joining operation in a state wherein the junction portion  12 C is exposed by the open portion  20 C, enabling the operation to be performed easily. 
         [0036]    Thereafter, respective bearings  3 A of bearing portions  3  are inserted into/slid onto the pair of shaft portions  5 , and the bearing supporting members  3 B of the bearing portions  3  engage with the positioning protrusions  20 A 1  on the bottom face portion  20 A, to be secured to the bottom face portion  20 A. At this time, both the end face plate sides of the bottom face plate  20  are open, and thus the operation for securing the bearing supporting member  3 B to the bottom face portion  20 A can be carried out easily. 
         [0037]    Following this, the two end face plates  22  are joined to the end face side edges of the bottom face plate  20  (the perpendicular face side edges of the bottom face portion  20 A and the partial side face portion  20 B). Moreover, four elastic members  6  are disposed between the pair of end face plates  22  and the end portions  12 A of the weights  12 , where both end portions of the elastic members  6  are attached, respectively, to the supporting portions  12 A 1  and the supporting portions  22 A. 
         [0038]    This state is one wherein the bottom face plate  20  is still open, making it possible to check the state of attachment of the elastic members  6 , and the like. Given this, after it has been confirmed that the state of attachment of the elastic members  6 , and the like, is correct, the top face portion  21 A is turned to face the bottom face portion  20 A, and the top face plate  21  is placed over the bottom face plate  20 , so that the partial side face portion  21 B of the top face plate  21  will block the open portion  20 C of the bottom face plate  20 , and the bottom face plate  20  and the top face plate  21 , or the end face plates  22  and the top face plate  21 , are joined together.  FIG. 4  shows the state wherein the assembly has been completed by joining together the bottom face plate  20 , the top face plate  21 , and the end face plates  22 . In this state, the movable element  10 , the bearing portions  3 , the coil  4 , and the elastic members  6  are enclosed within the frame  2  that is formed from the bottom face plate  20 , the top face plate  21 , and the end face plates  22 . 
         [0039]    Note that while the example described above illustrates an example wherein the bottom face plate  20  and the end face plates  22  are formed from separate members, instead the end face plates (the end face portions)  22  may be formed through bending from the perpendicular face edges of the bottom face portion  20 A that are portions of the bottom face plate  20 . 
         [0040]    As explained above, in the linear vibration motor  1  according to an example according to the present invention the coil  4 , the movable element  10 , the bearing portions  3 , the elastic members  6 , and the like, are assembled onto the bottom face portion  20 A with the bottom face portion  20 A in an open state, where the bottom face plate  20  and the top face plate  21  are joined together after this assembly has been completed, to enclose the coil  4 , the movable element  10 , the bearing portions  3 , the elastic members  6 , and the like, within the frame  2 . This makes it possible to join the bottom face plate  20  and the top face plate  21  together after confirming that the assembly of the elastic members  6 , and the like, is in the correct state. Moreover, the center part on the side face side of the bottom face portion  20 A is open, through the open portion  20 C, at the time of the operations for assembling the various portions onto the bottom face portion  20 A, and the perpendicular face sides of the bottom face portion  20 A are open until the end face plates  22  are attached, enabling the assembly operation to be carried out easily. 
         [0041]      FIG. 5  shows a mobile information terminal  100  as an example of an electronic device equipped with a linear vibration motor  1  according to an example according to the present invention. The mobile information terminal  100  that is equipped with the linear vibration motor  1  that can produce a stabilized vibration and for which the thickness can be reduced and which can be made more compact in the width direction enables the user to be notified through a stabilized vibration that does not tend to produce noise, when there is an incoming call in a communication function or at the beginning or end of an operation such as an alarm function. Moreover, this makes it possible to produce a mobile information terminal  100  with high mobility and which facilitates design performance, through the linear vibration motor  1  having reduced thickness and being more compact in the width direction. Furthermore, because the linear vibration motor  1  is of a compact shape wherein the various components are contained within a frame  2  of a rectangular shape wherein the thickness is suppressed, it can be mounted, with excellent space efficiency, within a thinner mobile information terminal  100 . 
         [0042]    While examples according to the present invention were described in detail above, referencing the drawings, the specific structures thereof are not limited to these examples, but rather design variations within a range that does not deviate from the spirit and intent of the present invention are also included in the present invention.