SPECIFICATION
`
`TITLE OF THE INVENTION:
`
`LINEAR VIBRATION MOTOR
`
`FIELD OF TECHNOLOGY
`
`[0001]
`The present invention relates to a linear vibration motor.
`PRIOR ART
`
`[0002]
`Vibration motors (or "vibration actuators") are built into mobile electronic devices,
`and are broadly used as devices to communicate to the user, through a vibration, that
`there is an incoming call, or that a signal, such as an alarm, has been generated, and have
`become indispensable devices in wearable devices, which are carried on the body of the
`user. Moreover, in recent years vibration motors have been of interest as devices by
`which to achieve haptics (skin-sensed feedback) in the human interfaces such as touch
`panels.
`[0003]
`Among the various forms of vibration motors that are under development, there is
`interest in linear vibration motors that are able to generate relatively large vibrations
`through linear reciprocating vibrations of a movable element. A conventional linear
`motor is provided with a weight and a magnet on a movable element side, where an
`electric current is applied to a coil that is provided on the stator side to cause the Lorentz
`forces that act on the magnet to form a driving force, to cause the movable element,
`which is elastically supported along the direction of vibration, to undergo reciprocating
`vibrations in the aXial direction (referencing Patent Document 1, below).
`PRIOR ART DOCUMENTS
`
`PATENT DOCUMENTS
`
`[0004]
`Patent Document 1: Japanese Unexamined Patent Application Publication 2016-
`13 5 54
`
`SUMIVIARY OF THE INVENTION
`
`PROBLEM SOLVED BY THE PRESENT INVENTION
`
`[0005]
`Because the linear vibration motors are built into spaces within thin mobile electronic
`devices or wearable electronic devices, there is the need for a shape that is thin in the
`thickness direction, relative to the width direction that is perpendicular to the vibration
`direction. At this time, if the movable element were to rotate or pivot around the aXis that
`is the direction of vibration, both side portions of the movable element in the width
`direction would strike the frame (case) that covers the movable element, resulting in a
`drawback in that this would produce a noise during vibration. In linear vibration motors
`that are to provide silent notification, to the operator, that a signal has occurred there is
`the need to suppress the production of operating noise insofar as is possible.
`[0006]
`The linear vibration motor according to the present invention is to handle such a
`situation, and the object thereof is to provide a thin linear vibration motor that suppresses
`the production operating noise.
`Means for Solving the Problem
`
`

`

`[0007]
`In order to solve such a problem, the linear vibration motor according to the present
`invention is provided with the following structures:
`[0008]
`A linear vibration motor comprising: a stationary element, a movable element that is
`supported elastically, so as to enable vibration along an axial direction, on the stationary
`element, and a driving portion for causing the movable element to undergo reciprocating
`vibration along the axial direction, through the provision of a coil on the stationary
`element, the provision of a driving magnet on the movable element, and the application
`of an electric current to the coil while the driving magnet is attracted by magnetic
`material that is provided on the stationary element side of the coil, wherein: the stationary
`element is provided with a stationary magnet that is magnetized in a direction that is
`perpendicular to the axial direction, and the movable element is provided with a movable
`magnet that opposes, while repelling, the stationary magnet.
`[0009]
`FIG. 1 is an exploded perspective diagram illustrating one example of a linear
`vibration motor according to an embodiment according to the present invention.
`FIG. 2 is an assembly oblique view (without the case) of the example depicted in
`FIG. 1.
`
`FIG. 3 is a front view of FIG. 2.
`
`FIG. 4 is an explanatory diagram depicting the magnetization directions of the
`magnets (the driving magnet, the stationary magnet, and the movable magnet) equipped
`in the linear vibration motor according to the present invention.
`FIG. 5 is an explanatory diagram illustrating a mobile electronic device in which is
`provided a linear vibration motor according to an embodiment according to the present
`invention.
`
`Most Preferred Form for Carrying out the Invention
`[0010]
`Embodiments according to the present invention will be explained below in reference
`to the drawings. In the descriptions below, identical reference symbols in the different
`drawings below indicate positions with identical functions, and redundant explanations in
`the various drawings are omitted as appropriate. In each figure, the arrow in the X
`direction indicates the direction of vibration of the movable element, the arrow in the Y
`direction indicates the width direction of the movable element, and the arrow in the Z
`direction indicates the thickness direction of the movable element.
`
`[0011]
`FIG. 1 through FIG. 3 illustrate one example of a linear vibration motor according to
`an embodiment according to the present invention. The linear vibration motor 1
`comprises a stationary element 10, a movable element 20, and a driving portion 30. The
`stationary element 10, in the example in the figure, is equipped with a supporting plate 11
`and a case 12. The movable element 20 is borne slidably in relation to the stationary
`element 10, and is supported elastically so as to enable vibration along the axial direction
`(the X direction in the figure). The movable element 20, in the example in the figure, is
`equipped with a weight portion 21, a pair of coil springs 22 that extend and retract along
`the X direction in the figure, where a spring supporting portion 2lT, for supporting one
`
`

`

`end side of the coil spring 22, is provided on the weight portion 21, and a yoke 33 and
`driving magnets 32 of the driving portion 30, described below, are attached.
`[0012]
`The driving portion 30 comprises a coil 31 that is attached to the stationary element
`10 (a supporting plate 11), and driving magnets 32 that are provided on the movable
`element 20 (the weight portion 21). In this driving portion 30, a coil 31 is arranged in a
`magnetic circuit that is formed from a pair of magnets 32, a yoke 33 on the movable
`element 20 side for coupling with this pair of driving magnets 32, and a supporting plate
`11, made from a magnetic material, that serves as a yoke on the stationary element 10
`side, where the application of a driving signal to the coil 31 through a flexible circuit
`board 34 causes the movable element 20 to vibrate, reciprocating along the axial direction
`(the X direction in the figure) while the driving magnets 32 are attracted by the
`supporting plate 11 of the magnetic material. The driving signal that is applied to the coil
`31 is a pulse signal or an alternating current signal, or the like, of the resonant frequency
`(the natural frequency) that is determined by the spring constant of the coil springs 22
`and the mass of the movable element 20 (the weight portion 21). While, in the
`explanation above, the supporting plate 11 was of a magnetic material to serve as a yoke
`on the stationary element 10 side, instead the supporting plate 11 may be a non-magnetic
`body, and a separate yoke may be provided between the supporting plate 11 and the coil
`3 1, so that the driving magnets 32 will be attracted by this yoke.
`[0013]
`The linear vibration motor 1 comprises a guide shaft 13. The guide shaft 13 is
`provided extending in the axial direction (the X direction in the figure), and the movable
`element 20 is borne so as to enable sliding along the guide shaft 13. In the example in the
`figure, the guide shaft 13 is secured on both ends to the stationary element 10 (the case
`12), and a bearing 23 is provided so as to bear the guide shaft 13 slidably on the movable
`element 20 side, however, the guide shaft 13 may be provided instead on the movable
`element 20 side, and the bearing may be provided so as to support the guide shaft 13
`slidably on the stationary element 10 side.
`[0014]
`Moreover, in this linear motor 1, the stationary element 10 side is equipped with a
`stationary magnet 14, and the movable element 20 side is equipped with a movable
`magnet 24. Here the stationary magnet 14 is magnetized in a direction (the Z direction in
`the figure) that is perpendicular to the axial direction (the X direction in the figure), and
`is secured over the supporting plate 11, which is of a magnetic material. Moreover, the
`stationary magnet 14 extends along the axial direction (the X direction in the figure. In
`contrast, the movable magnet 24 is magnetized in the opposite direction of that of the
`stationary magnet 14. Through this, the driving magnets 32 are attracted to the supporting
`plate 11 side, which is a magnetic material, but the movable magnet 24 is in opposition,
`repelling the stationary magnet 14. Because of this, the movable magnet 24 that is
`secured to the movable element 20 is subject to the repelling magnetic force from the
`stationary magnet 14, so as to vibrate in a non-contacting state.
`[0015]
`FIG. 4 depicts the magnetization directions of the driving magnets 32 of the driving
`portion 30, the stationary magnet 14, and the movable magnet 24. The pair of driving
`magnets 32 are magnetized, in mutually opposing directions, along the Z direction in the
`
`

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`figure, where the linear part, extending in the Y direction in the figure, of the coil 31 that
`is disposed within the magnetic circuit that is structured from the pair of driving magnets
`32, the yoke 33, and the supporting plate 11 of the magnetic material has magnetic flux
`passtherethrough in the Z direction in the figure, and thus a driving force in the X
`direction in the figure is applied to the driving magnets 32.
`[0016]
`In contrast, the stationary magnet 14 and the movable magnet 24 are magnetized, in
`mutually opposing directions, along the direction of the Z direction in the figure. The
`movable magnet 24 that is provided on the movable element 20 is disposed so as to face
`the stationary magnet 14 that extends along the X direction in the figure, and, similarly,
`the driving magnets 32 that are disposed on the movable element 20 are disposed in
`positions that do not interfere with the stationary magnet 14. Note that, in the example in
`the figure, while the stationary magnet 14 is provided extending in the X direction in the
`figure, and the movable magnet 24 opposes the stationary magnet 14, instead, conversely,
`the movable magnet 24 may extend in the X direction in the figure, and the stationary
`magnet 14 may oppose the movable magnet 24.
`[0017]
`Given such a linear vibration motor 1, when the movable element 20 vibrates
`reciprocating along the axial direction, the movable magnet 24 that is provided on the
`movable element 20 vibrates while maintaining a constant spacing, in what is always a
`non-contacting state, over the stationary magnet 14 that is provided on the stationary
`element 10. Through this, the movable element 20 is not only able to vibrate while
`suppressing the operating noise extremely, but is also able to vibrate in the axial direction
`in a steady state wherein a rotation or pivoting around the axis is suppressed. This enables
`suppression of the operating noise, eliminating the drawback of the noise that would be
`produced through the movable element 20 contacting the supporting plate 11 or the case
`12.
`
`[0018]
`In the example depicted in FIG. 1 through FIG. 3, the movable element 20 is of a thin
`shape wherein the dimension in the thickness direction thereof (the Z direction in the
`figure) is less than the dimension in that the width direction (the Y direction in the
`figure). Additionally, a bearing 23 is provided for bearing the guide shaft 13, on one end,
`in the Y direction in the figure, of the movable element 20, and a movable magnet 24 is
`provided on the other end side, in the Y direction in the figure, of the movable element
`20. Through this, the movable element 20 is able to vibrate along the axial direction
`while being supported fiat by the movable magnet 24 that is held by the guide shaft 13
`and over the stationary magnet 14, making it possible to achieve a stabilized vibration
`with parallel movement along the X-Y plane.
`[0019]
`The stationary magnet 14 that is secured to the stationary element 10 side has a length
`that is at least equal to the amplitude of the movable element 20 along the axial direction.
`A recessed portion 21A, recessed in the Z direction in the figure (the thickness direction
`of the movable element 20) is provided in the weight portion 21 of the movable element
`20, and the movable magnet 24 is provided in this recessed portion 21A. Moreover, a
`recessed portion 21B, which is recessed in the Z direction in the figure, and which is
`provided extending in the X direction in the figure, is provided in the weight portion 21,
`
`

`

`so that the stationary magnet 14 will be located within the recessed portion 21B when the
`movable element 20 vibrates. The provision of the recessed portions 21A and 21B in this
`way in the weight portion 21 enables the stationary magnet 14 and the movable magnet
`24 to be provided while still suppressing the thickness (the height in the Z direction in the
`figure) of the linear vibration motor 1.
`[0020]
`FIG. 5 illustrates a mobile information terminal 100 as one example of a mobile
`electronic device equipped with a linear vibration motor 1 according to an embodiment
`according to the present invention. The mobile information terminal 100, provided with
`the linear vibration motor 1 is able to convey silently, to a user, an incoming call in a
`communication function, an alarm function, or the like. Moreover, this makes it possible
`to produce a mobile information terminal 100 that facilitates superior mobility and design
`quality through making the linear vibration motor 1 thinner and smaller. Furthermore,
`because the linear vibration motor 1 is of a compact shape wherein the various
`components are contained within a case 11 [sic - "12"?] of a rectangular shape wherein
`the thickness is suppressed, it can be mounted, with excellent space efficiency, within a
`thinner mobile information terminal 100.
`
`[0021]
`While embodiments according to the present invention were described in detail
`above, referencing the drawings, the specific structures thereof are not limited to these
`embodiments, 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.
`Moreover, insofar as there are no particular contradictions or problems in purposes or
`structures, or the like, the technologies of the various embodiments described above may
`be used together in combination.
`EXPLANATION OF CODES
`
`[0022]
`1: Linear Vibration Motor
`
`10: Stationary Element
`11: Supporting Plate
`12: Case
`
`13: Guide Shaft
`
`14: Stationary Magnet
`20: Movable Element
`
`21: Weight Portion
`21A, 21B: Recessed Portions
`21T: Spring Supporting Portion
`22: Coil Spring
`23: Bearing
`24: Movable Magnet
`30: Driving [Portion]
`31: Coil
`
`32: Driving Magnet
`33: Yoke
`
`34: Flexible Circuit Board
`
`100: Mobile Information Terminal (Mobile Electronic Device)
`
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