Linear vibration motor

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.

CROSS-REFERENCE TO RELATED APPLICATIONS

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

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

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.

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

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.

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.

In order to achieve such an object, the linear vibration motor of the present invention is equipped with the following structures:

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.

DETAILED DESCRIPTION

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.

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.

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.

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.

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. 1throughFIG. 4illustrate the overall structure of a linear vibration motor according to one example according to the present invention (whereFIG. 1is an exploded perspective diagram,FIG. 2is a plan view that illustrates the internal structure,FIG. 3is a perspective diagram that illustrates the assembled state, andFIG. 4is 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.

The linear vibration motor1comprises: a movable element10that is equipped with a magnet11and a weight12; a frame2for supporting the movable element10so as to be able to slide along the axial direction; a coil4that is secured to the frame2, for driving the magnet11along the axial direction; and an elastic member6for applying, to the movable element10, an elastic force for repelling the driving force that acts on the magnet11.

The frame2comprises a bottom face plate20, a top face plate21, and perpendicular face plates22, where these are joined together to form the frame2. The bottom face plate20, the top face plate21, and the end face plates22are each formed through machining (pressing processes, or the like) respective metal plates. More specifically, the bottom face plate20and the top face plate21that structure a magnetic circuit in respect to the coil4can be formed from, for example, stainless steel plates of a magnetic material, where the pair of end face plates22that do not structure a magnetic circuit may be formed from stainless steel plates of a non-magnetic material.

The bottom face plate20has a bottom face portion20A to which the coil4is secured, a partial side face portion20B that is bent from the side edge of the bottom face portion20A, and an open portion20C, 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 portion20A. The top face plate21has a top face portion21A that faces the bottom face portion20A, and a partial side face portion21B that is bent from the side face of this top face portion21A. The end face plates22are 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 portions22A for supporting the elastic members6.

Here, in the example that is illustrated, the bottom face portion20A of the bottom face plate20and the top face portion21A of the top face plate21are formed in rectangular shapes wherein the lengthwise direction is the axial direction (the X direction in the figure), where the partial side face portions20B and21B, along the long edges thereof, are formed bent so as to be essentially perpendicular to the bottom face portion20A or top face portion21A. Given this, the end face plates22are formed in rectangular shapes having outer peripheral edges depending on the short edges of the bottom face portion20A and the top face portion21A, and the height of the partial side face portion20B.

The partial side face portion21B of the top face plate21is formed so as to cover the open portion20C of the bottom face plate20, where a protruding portion21P for engaging with a recessed portion20S that is formed on a side edge of the bottom face portion20A in the open portion20C is formed on the bottom edge of the partial side face portion21B. Moreover, protruding portions20P for engaging with recessed portions21S,20S that are formed on edges of the top face plate21and the bottom face plate20are formed on the top and bottom edges of the end face plates22.

In regards to such a frame2, the coil4is secured to the bottom face portion20A, and a driving portion is structured from the coil4that is secured to the frame2and the magnet11that is a portion of the movable element10. Lorentz forces that act on the magnet11through the application of the electric current to the stationary coil4act as driving forces that cause the movable element10to vibrate along the axial direction (the X direction in the figure).

As illustrated inFIG. 11, in the magnet2, two flat rectangular magnet pieces11A and11B 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 yoke11C interposed therebetween. If necessary, a reinforcing plate11D is secured to a side face of the magnet11to increase the rigidity of the magnet11thereby.

The coil4is a wire wrapped, along the Y and Z directions, around the magnet11wherein the direction of the magnetic pole faces in the X direction. The securing of the coil4to the bottom face portion20A may be through securing directly to the bottom face portion20A, or may be through winding the coil4onto a coil bobbin and securing the coil bobbin onto the bottom face portion20A.

In the example that is illustrated, in the movable element10, weights12are connected to both end portions of the magnet11in the axial direction (the X direction in the figure). The weight12may 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 magnet11, and a width in the Y direction that is greater than the width of the magnet11.

The movable element10is provided with a pair of shaft portions5that protrude in mutually opposing directions along the axial direction (the X direction in the figure). The shaft portions5are provided protruding in cantilever shapes from both axial-direction end portions of the movable element10. In the example that is illustrated, shaft portions5protrude from within recessed portions12B of respective weights12that are connected to both axial-direction end portions of the magnet11, where here one end side of the shaft portion5is inserted and secured in a shaft supporting portion12B1that is provided in the weight12.

Bearing portions3for supporting respectively, the pair of shaft portions5are provided on the bottom face portion20A of the bottom face plate20. The movable element10is supportive slidably, relative to the frame2, through the bearing portions3supporting the pair of shaft portions5so as to be able to slide. The bearing portion3is structured from a bearing3A and a bearing supporting member3B, where the bearing supporting member3B is attached to the bottom face portion20A of the bottom face plate20, and the bearing3A is attached to the standing portion of the bearing supporting member3B. A positioning protrusion20A1that protrudes for positioning is provided in the bottom face portion20A, where the bearing supporting member3B is attached to this positioning protrusion20A1.

The recessed portion12B of the weight12wherein the shaft portion5protrudes has a width that enables insertion of the bearing portion3. The provision of such a recessed portion12B enables the X-direction length of the linear vibration motor1to be kept short, while enabling a large vibrational amplitude for the movable element10.

Elastic members6are disposed off-axis from, and in parallel to, the pair of shaft portions5, to apply, to the movable element10, an elastic force that opposes the driving force that is produced by the magnet11and the coil4. 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 members6, where on one side two elastic members6are disposed between the end portion12A of the weight12and the end face plate22. A supporting portion (a supporting protrusion)12A1, for supporting one end side of the elastic member6, is provided on an end portion12A of the weight12, and a supporting portion (a supporting protrusion)22A, for supporting the other end side of the elastic member6, is provided on the inner surface side of the end face plate22.

The operation of such a linear vibration motor1will be explained. When not driven, the movable element10stands still in the vibration center position wherein the elastic forces of the elastic members6are in equilibrium. When an electric current of a vibration generation signal is inputted into the coil4, a driving force is applied to the magnet11in the X direction, and the movable element10undergoes reciprocating vibration along the axial direction (the X direction in the drawing) through the driving force and the elastic repulsive force of the elastic member6.

If necessary, sliding protrusions12D for making sliding contact with the bottom face portion20A and the top face portion21A, are provided on the surface of the weight12in the movable element10. The provision of such sliding protrusions12D, and the formation of the location of sliding contact between the bottom face portion20A and the top face portion21A from a resin material, or the like, enables suppression of noise at the time of vibration of the movable element10, and enables a stabilized vibration. At this time, the location of sliding contact may be provided instead on the weight12surface side, and the sliding protrusions may be provided instead on the bottom face portion20A and the top face portion21A.

The method for assembling such a linear vibration motor1(the manufacturing method thereof) will be explained. As illustrated inFIG. 3, the assembly of each of the parts is performed in a state wherein the bottom face portion20A of the bottom face plate20is open. First the coil4is secured to the bottom face portion20A of the bottom face plate20. The coil4is secured to the bottom face portion20A through an adhesive agent, or the like.

Given this, a weight12, in a state wherein the shaft portion5is attached, is joined in advance to one end side of the magnet11in the axial direction (the X direction in the figure), and after the other end side, in the axial direction, of the magnet11is inserted into the opening of the coil4, a weight12, in a state wherein the shaft portion5is attached, is joined to the other end side, in the axial direction, of the magnet11. The joining of the magnet11and the weight12is through, for example, inserting end portion of the magnet11into a joining portion12C of the weight12and welding. At this time, the joining together of the magnet11and the weight12, which is carried out in a state wherein the other end side, in the axial direction, of the magnet11has been inserted into the opening of the coil4, can be carried out through a joining operation in a state wherein the junction portion12C is exposed by the open portion20C, enabling the operation to be performed easily.

Thereafter, respective bearings3A of bearing portions3are inserted into/slid onto the pair of shaft portions5, and the bearing supporting members3B of the bearing portions3engage with the positioning protrusions20A1on the bottom face portion20A, to be secured to the bottom face portion20A. At this time, both the end face plate sides of the bottom face plate20are open, and thus the operation for securing the bearing supporting member3B to the bottom face portion20A can be carried out easily.

Following this, the two end face plates22are joined to the end face side edges of the bottom face plate20(the perpendicular face side edges of the bottom face portion20A and the partial side face portion20B). Moreover, four elastic members6are disposed between the pair of end face plates22and the end portions12A of the weights12, where both end portions of the elastic members6are attached, respectively, to the supporting portions12A1and the supporting portions22A.

This state is one wherein the bottom face plate20is still open, making it possible to check the state of attachment of the elastic members6, and the like. Given this, after it has been confirmed that the state of attachment of the elastic members6, and the like, is correct, the top face portion21A is turned to face the bottom face portion20A, and the top face plate21is placed over the bottom face plate20, so that the partial side face portion21B of the top face plate21will block the open portion20C of the bottom face plate20, and the bottom face plate20and the top face plate21, or the end face plates22and the top face plate21, are joined together.FIG. 4shows the state wherein the assembly has been completed by joining together the bottom face plate20, the top face plate21, and the end face plates22. In this state, the movable element10, the bearing portions3, the coil4, and the elastic members6are enclosed within the frame2that is formed from the bottom face plate20, the top face plate21, and the end face plates22.

Note that while the example described above illustrates an example wherein the bottom face plate20and the end face plates22are formed from separate members, instead the end face plates (the end face portions)22may be formed through bending from the perpendicular face edges of the bottom face portion20A that are portions of the bottom face plate20.

As explained above, in the linear vibration motor1according to an example according to the present invention the coil4, the movable element10, the bearing portions3, the elastic members6, and the like, are assembled onto the bottom face portion20A with the bottom face portion20A in an open state, where the bottom face plate20and the top face plate21are joined together after this assembly has been completed, to enclose the coil4, the movable element10, the bearing portions3, the elastic members6, and the like, within the frame2. This makes it possible to join the bottom face plate20and the top face plate21together after confirming that the assembly of the elastic members6, and the like, is in the correct state. Moreover, the center part on the side face side of the bottom face portion20A is open, through the open portion20C, at the time of the operations for assembling the various portions onto the bottom face portion20A, and the perpendicular face sides of the bottom face portion20A are open until the end face plates22are attached, enabling the assembly operation to be carried out easily.

FIG. 5shows a mobile information terminal100as an example of an electronic device equipped with a linear vibration motor1according to an example according to the present invention. The mobile information terminal100that is equipped with the linear vibration motor1that 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 terminal100with high mobility and which facilitates design performance, through the linear vibration motor1having reduced thickness and being more compact in the width direction. Furthermore, because the linear vibration motor1is of a compact shape wherein the various components are contained within a frame2of a rectangular shape wherein the thickness is suppressed, it can be mounted, with excellent space efficiency, within a thinner mobile information terminal100.

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.