(19) Japan Patent Office (JP) (12) JAPANESE UNEXAMINED PATENT
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`APPLICATION PUBLICATION (A)
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`(11) Patent Application
` Publication No.
` JP H8-196053
`
`(43) Publication Date: July 30, 1996 (Heisei 8)
`FI Basis for Classification
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`Ident. Code
`
`Internal Ref. No.
`
` (51) Int. Cl.6
` H02K 7/065
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` 33/02 A
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` Examination Request: Not yet Total No. of Claims: 3 OL (Total 8 pages)
`(21) Application No. JP H7-3356
`(71) Applicant 000112565
`
` Foster Electric Company, Ltd.
`(22) Date of Filing January 12, 1995
` 512 Miyazawa-cho,
` (Heisei 7)
` Akishima-shi, Tokyo-to
`
`
`
`(72) Inventor Minoru Ogusu
` C/o Foster Electric Company,
` Ltd.
` 512 Miyazawa-cho,
` Akishima-shi, Tokyo-to
`
`(74) Agent Toji Ijima, patent attorney
` (and 1 other)
`
`
`
`(54) [Title of Invention] VIBRATION ACTUATOR
`
`(57) [Abstract]
` [Object] To realize a vibration actuator having high
`vibration generation efficiency and high vibration
`transmission efficiency, which is capable of generating
`vibration at an arbitrary frequency and at an accurate
`amplitude.
`[Constitution] A vibration actuator comprising: a first
`and second coil wound so as to protrude above a base
`part; a spindle supported by a center part of the base part
`so as to be parallel to the two coils; a first yoke
`supported by the spindle via holding means so as to be
`movable in an axial direction and arranged so that one
`end forms a core of the first coil and another end
`opposes a side surface of the first coil; a second yoke
`supported by the spindle via holding means so as to be
`movable in an axial direction and arranged so that one
`end forms a core of the second coil and another end
`opposes a side surface of the second coil; a magnet
`provided on respective surfaces wherein the first and
`second yoke oppose the first and second coil and
`magnetized in an opposing direction; and an elastic
`body arranged between the holding means and the base
`part, the elastic body positioning the holding means so
`that the coil and the magnet are in opposing positions.
`
`
`
`
`
`Magnet 9b
`Second yoke 8b
`
`Holder 6
`
`First yoke 8a
`
`Magnet 9a
`
`3b Second coil
`
`3a Frame
`
`1 Base part
`
`7 Spring
`
`1c Hole
`4 Spindle
`
`2a Frame
`
`2b First coil
`
`Exhibit 1015 - Page 1 of 8
`
`

`

` (2)
`
` JP H8-196053
`
`[Scope of Patent Claims]
`[Claim 1] A vibration actuator comprising:
`a first and second coil wound so as to protrude above a
`base part;
`a spindle supported by a center part of the base part so as
`to be parallel to the two coils;
`a first yoke supported by the spindle via holding means
`so as to be movable in an axial direction and arranged so
`that one end forms a core of the first coil and another end
`opposes a side surface of the first coil;
`a second yoke supported by the spindle via holding
`means so as to be movable in an axial direction and
`arranged so that one end forms a core of the second coil
`and another end opposes a side surface of the second
`coil;
`and a magnet provided on respective surfaces wherein
`the first and second yoke oppose the first and second coil
`and magnetized in an opposing direction.
`[Claim 2] A vibration actuator comprising: a first and
`second coil wound so as to protrude above a base part;
`a spindle supported by a center part of the base part so as
`to be parallel to the two coils;
`a first yoke supported by the spindle via holding means
`so as to be movable in an axial direction and arranged so
`that one end forms a core of the first coil and another end
`opposes a side surface of the first coil;
`a second yoke supported by the spindle via holding
`means so as to be movable in an axial direction and
`arranged so that one end forms a core of the second coil
`and another end opposes a side surface of the second
`coil;
`a magnet provided on respective surfaces wherein the
`first and second yoke oppose the first and second coil
`and magnetized in an opposing direction; and
`an elastic body arranged between the holding means and
`the base part, the elastic body positioning the holding
`means so that the coil and the magnet are in opposing
`positions.
`[Claim 3] A vibration actuator comprising: a first and
`second coil wound so as to protrude above a base part;
`a spindle supported by a center part of the base part so as
`to be parallel to the two coils;
`a first yoke supported by the spindle via holding means
`so as to be movable in an axial direction and arranged so
`that one end forms a core of the first coil and another end
`opposes a side surface of the first coil;
`a second yoke supported by the spindle via holding
`means so as to be movable in an axial direction and
`arranged so that one end forms a core of the second coil
`and another end opposes a side surface of the second
`coil; and
`a magnet provided on respective surfaces wherein the
`first and second yoke oppose the first and second coil
`and magnetized in an opposing direction; wherein
`the holding means is arranged between the spindle and
`
`the yoke and is composed of a holder positioning the first
`and second yoke so that the coil and the magnet are in
`opposing positions; and a diaphragm.
`[Detailed Description of Invention]
`[0001]
`[Industrial Applicability] The present invention relates
`to a moving magnet-type vibration actuator, and more
`particularly to a moving magnet-type vibration actuator
`having low loss and high efficiency.
`[0002]
`[Conventional Art] A vibration actuator is a device that
`generates vibration in response to an externally supplied
`current. The vibration actuator is sometimes used as a
`vibration canceller which cancels out vibration of a main
`device by generating vibration in an opposite phase to
`that generated by the main device. It may also be used as
`vibration generation means for a pager.
`[0003] Herein, a description is given of the current state
`of vibration generation means in pagers and the
`problems therein. Two types of calling methods are used
`in pagers: sound-based calling and vibration-based
`calling. Sound-based calling is designed to generate
`sound intermittently and to gradually increase in volume.
`This is achieved by changing the current (voltage)
`supplied to a speaker, buzzer (oscillator), or the like.
`[0004] In vibration-based calling, a vibration motor with
`an unbalanced weight attached to the rotor is generally
`used as vibration generation means. The vibration motor
`generates
`the necessary vibration by rotating an
`unbalanced weight attached to a front end of the rotor. A
`small DC motor capable of being driven by a pager
`battery is used as the vibration motor.
`[0005]
`[Technical Problem]However, a vibration motor with
`the above configuration has the following problems.
`Cylindrical or flat type DC motors are used, but in order
`to generate sufficient vibration that can be felt by a user,
`it is necessary to use a motor that rotates at high speed
`and with sufficient torque. However, while the demand
`for thinner and smaller pagers necessitates the use of
`smaller motors, significantly smaller motors cannot
`generate sufficient vibration. Therefore, in order to
`generate sufficient vibration, motors which are
`somewhat larger must be used. For this reason, some
`extremely thin pagers do not offer a vibration-based
`calling mode, and only sound-based calling is available.
`[0006] Furthermore, since a DC motor is used as
`vibration generation means, brushes and other
`components have a certain lifespan. This makes it
`impossible to maintain stable performance over a long
`period of time. In practice, there are problems such as
`fluctuations in rotation speed over time. Furthermore,
`there is a problem with DC motors in that electrical noise
`from the brush parts is generated over a wide frequency
`band.
`
`Exhibit 1015 - Page 2 of 8
`
`

`

` (3)
`
` JP H8-196053
`
`[0007] Moreover, in DC motors, the rated speed is fixed,
`and it is difficult to arbitrarily change the rotation speed
`if the applied voltage is constant. Therefore, the
`vibration frequency is determined by the rotation speed,
`and this vibration frequency cannot be changed.
`Naturally, in addition to this, neither can the amplitude
`of vibration be changed. As such, it cannot be changed
`in any way, even when slow vibrations at low frequency
`or low amplitude are desired, or when it is desired to
`gradually increase the amplitude of vibration to ensure a
`reliable call. Generation of intermittent vibration and the
`like are also not supported. Thus, there are only a series
`of vibrations at a constant amplitude.
`[0008] Furthermore, since vibration is generated by
`rotation, it also includes vibration in directions other
`than
`those
`the user
`is sensitive
`to
`(directions
`perpendicular to the surface of the human body).
`Therefore, although
`the efficiency of converting
`electricity into rotational motion is high, the effective
`acting force from among the generated vibration is weak
`and vibration transmission efficiency is low.
`[0009] There are brushless motors which do not use
`brushes despite being driven by DC. However, it is not
`possible to change the rotation speed in brushless
`motors, either. Furthermore, these brushless motors
`require a dedicated electronic circuit for generating a
`rotating magnetic field, and are
`inefficient and
`unsuitable for pagers, which are required to be small and
`thin.
`[0010] A vibration actuator combining an electromagnet
`and a magnet using a solenoid coil may also be
`considered. In this case, a non-excitation holding force
`is exerted wherein the magnet tries to adhere to the iron
`core of the solenoid coil and stay at a predetermined
`position. Therefore, the vibration actuator begins to
`move only when a force greater than this non-excitation
`holding force is applied. This loss due to the non-
`excitation holding force has a significant effect when
`generating low-amplitude vibrations, and there is a
`problem in that it is difficult to obtain accurate vibrations
`for minute inputs.
`[0011] In view of the foregoing problems, an object of
`the present invention is to provide a vibration actuator
`having high vibration generation efficiency and high
`vibration transmission efficiency, which is capable of
`generating vibration at an arbitrary frequency and
`amplitude, and which responds accurately to minute
`inputs.
`[0012]
`[Solution to Problem] As a result of intensive research to
`improve defects expected in conventional vibration
`actuators, the inventor of the present application has
`arrived at a configuration capable of eliminating loss
`caused by non-excitation holding force and has
`completed the present invention.
`
`[0013] Accordingly, the present invention, which is
`means for solving the problem, is configured as
`described below.
`(1) Namely, the first means of solving the foregoing
`problem is a vibration actuator provided with: a first and
`second coil wound so as to protrude above a base part; a
`spindle supported by a center part of the base part so as
`to be parallel to the two coils; a first yoke supported by
`the spindle via holding means so as to be movable in an
`axial direction and arranged so that one end forms a core
`of the first coil and another end opposes a side surface of
`the first coil; a second yoke supported by the spindle via
`holding means so as to be movable in an axial direction
`and arranged so that one end forms a core of the second
`coil and another end opposes a side surface of the second
`coil; and a magnet provided on respective surfaces
`wherein the first and second yoke oppose the first and
`second coil and magnetized in an opposing direction.
`[0014] (2) Furthermore, the second means of solving the
`foregoing problem is a vibration actuator provided with:
`a first and second coil wound so as to protrude above a
`base part; a spindle supported by a center part of the base
`part so as to be parallel to the two coils; a first yoke
`supported by the spindle via holding means so as to be
`movable in an axial direction and arranged so that one
`end forms a core of the first coil and another end opposes
`a side surface of the first coil; a second yoke supported
`by the spindle via holding means so as to be movable in
`an axial direction and arranged so that one end forms a
`core of the second coil and another end opposes a side
`surface of the second coil; a magnet provided on
`respective surfaces wherein the first and second yoke
`oppose the first and second coil and magnetized in an
`opposing direction; and an elastic body arranged
`between the holding means and the base part, the elastic
`body positioning the holding means so that the coil and
`the magnet are in opposing positions.
`[0015] (3) Furthermore, the third means of solving the
`foregoing problem is a vibration actuator comprising: a
`first and second coil wound so as to protrude above a
`base part; a spindle supported by a center part of the base
`part so as to be parallel to the two coils; a first yoke
`supported by the spindle via holding means so as to be
`movable in an axial direction and arranged so that one
`end forms a core of the first coil and another end opposes
`a side surface of the first coil; a second yoke supported
`by the spindle via holding means so as to be movable in
`an axial direction and arranged so that one end forms a
`core of the second coil and another end opposes a side
`surface of the second coil; and a magnet provided on
`respective surfaces wherein the first and second yoke
`oppose the first and second coil and magnetized in an
`opposing direction; wherein the holding means is
`arranged between the spindle and the yoke and is
`composed of a holder positioning the first and second
`yoke so that the coil and the magnet are in opposing
`
`Exhibit 1015 - Page 3 of 8
`
`

`

` (4)
`
` JP H8-196053
`
`positions; and a diaphragm.
`[0016]
`[Effect] In the vibration actuator which is the first means
`of solving the problem, a magnetic circuit is formed by
`a path of: the magnet opposing the first coil - the first
`coil - the first yoke. Furthermore, a magnetic circuit is
`formed by a path of: the magnet opposing the second coil
`- the second coil - the second yoke.
`[0017] When an electric current is sent to the coil in this
`magnetic circuit, thrust is generated in the yoke on which
`the magnet is provided as a reaction to the thrust
`generated in the coil, and the yoke moves in the axial
`direction of the spindle via the holding means. If the
`current supplied to the coil is an alternating current, the
`yoke and base part vibrate according to the waveform of
`the current.
`[0018] In this configuration, the magnet and yoke are
`integrated in each magnetic circuit, so no non-excitation
`holding force is exerted, and accurate vibration is
`generated even for micro input. In the vibration actuator
`which is the second means of solving the problem, a
`magnetic circuit is formed by a path of: the magnet
`opposing the first coil - the first coil - the first yoke.
`Furthermore, a magnetic circuit is formed by a path of:
`the magnet opposing the second coil - the second coil -
`the second yoke.
`[0019] When an electric current is sent to the coil in this
`magnetic circuit, thrust is generated in the yoke on which
`the magnet is provided as a reaction to the thrust
`generated in the coil, and the yoke moves in the axial
`direction of the spindle via the holding means positioned
`by the elastic body. If the current supplied to the coil is
`an alternating current, the yoke and base part vibrate
`according to the waveform of the current.
`[0020] In this configuration, the magnet and yoke are
`integrated in each magnetic circuit, so no non-excitation
`holding force is exerted, and accurate vibration is
`generated even for micro input. In the vibration actuator
`which is the third means of solving the problem, a
`magnetic circuit is formed by a path of: the magnet
`opposing the first coil - the first coil - the first yoke.
`Furthermore, a magnetic circuit is formed by a path of:
`the magnet opposing the second coil - the second coil -
`the second yoke.
`[0021] When an electric current is sent to the coil in this
`magnetic circuit, thrust is generated in the yoke on which
`the magnet is provided as a reaction to the thrust
`generated in the coil, and the yoke moves in the axial
`direction of the spindle via the holder positioned by the
`diaphragm. If the current supplied to the coil is an
`alternating current, the yoke and base part vibrate
`according to the waveform of the current.
`[0022] In this configuration, the magnet and yoke are
`integrated in each magnetic circuit, so no non-excitation
`holding force is exerted, and accurate vibration is
`generated even for micro input.
`[0023]
`[Embodiments] An embodiment of the present invention
`
`will be described using drawings. FIG. 1 is a cross-
`sectional view of an embodiment of the present
`invention, and FIG. 2 is a front view of an embodiment
`of the present invention. FIG. 1 is a cross-sectional view
`illustrating cross section A-A in FIG. 2. FIG. 3 is a cross-
`sectional view illustrating cross section B-B in FIG. 1.
`[0024] In these drawings, a base part 1 is a member for
`holding the coil and spindle (described later) in a
`predetermined position. A hole 1c for mounting the
`spindle (described later) is provided near the center of
`the base part 1.
`[0025] A first coil 2b is a solenoid coil wound around a
`frame 2a. The frame 2a is fixed to one end of the base
`part 1. A second coil 3b is a solenoid coil wound around
`a frame 3a. The frame 3a is fixed to the other end of the
`base part 1.
`[0026] A spindle 4 is mounted in the hole 1c provided in
`the center part of the base part 1. A holder 6 is provided
`so as to be movable in an axial direction of the spindle 4
`via a bearing 5. Furthermore, the bearing 5 and the
`holder 6 constitute the holding means and hold the yoke
`(described later).
`[0027] A spring 7 is provided to maintain the holder 6 in
`a predetermined position (for example, magnetically
`neutral position) when it is not vibrating. Furthermore,
`the spring 7 can be replaced by an elastic substance (such
`as rubber, a coil spring, a plate spring, or an air spring)
`and is configured so as to be affixed to the holder 6 or to
`both of the holder 6 and the base part 1.
`[0028] A first yoke 8a and a second yoke 8b are
`composed of a plate-shaped magnetic body and are
`mounted on the holder 6. Furthermore, one end part of
`each yoke is provided so as to compose the core of the
`first coil 2 and the second coil 3, respectively. Moreover,
`the other end part of each yoke is provided so as to be in
`a position opposing a side surface of the first coil 2 and
`the second coil 3, respectively. In addition to a
`ferromagnetic metal, it is also possible to use various
`non-magnetic materials mixed with ferromagnetic
`powders as the material of the above magnetic body.
`[0029] A magnet 9a is provided on the first yoke 8a on a
`part opposing the first coil 2b and is magnetized in an
`opposing direction. A magnet 9b is provided on the
`second yoke 8b on a part opposing the second coil 3b
`and is magnetized in an opposing direction.
`[0030] Therefore, a magnetic circuit is formed by a path
`of: the magnet opposing the first coil - the first coil - the
`first yoke. Furthermore, a magnetic circuit is formed by
`a path of: the magnet opposing the second coil - the
`second coil - the second yoke. This magnetic flux is
`shown by broken lines in FIG. 1 and FIG. 5.
`[0031] Next, the operation of a vibration actuator having
`the above configuration will be described. When a
`current in a predetermined direction is sent to the first
`coil 2b and the second coil 3b, thrust is generated
`according to Fleming's left-hand rule in the first coil 2b
`and second coil 3b arranged in the magnetic circuit
`described above. Then, as a reaction to the thrust, the
`
`Exhibit 1015 - Page 4 of 8
`
`

`

` (5)
`
` JP H8-196053
`
`movable elements (the holder 6, the bearing 5, the yokes
`8a and 8b, and the magnets 9a and 9b) try to move.
`[0032] Therefore, when an alternating current is sent to
`the first coil 2b and the second coil 3b, the movable
`elements generate vibration according to a current
`waveform. Furthermore, since the movable elements
`have magnets and a certain amount of weight, the base
`part 1 side also generates vibration in a direction
`opposite to that of the movable elements.
`[0033] For example, by sending an alternating current of
`an audible frequency of about 3000 Hz to the first coil
`2b and the second coil 3b, the yokes 8a and 8b and the
`holder 6 act as a speaker diaphragm to generate sound.
`In this case, various sounds can be generated by
`changing the frequency and an amplitude thereof, or by
`generating sound intermittently. This allows for sound-
`based calling in a pager.
`[0034] Furthermore, the movable elements (the holder 6,
`the bearing 5, the yokes 8a and 8b, and the magnets 9a
`and 9b) vibrate when a current of a frequency lower than
`an audible frequency of about several dozen to 100 Hz is
`sent to the first coil 2b and the second coil 3b. However,
`because the movable elements have a certain amount of
`weight, the base part 1 also vibrates. The vibration of the
`base part 1 vibrates the entire pager and can transmit the
`vibration to the user. Furthermore, the vibration is only
`in a direction perpendicular to the base part 1, which is a
`direction in which the vibration is easily felt by the user
`when used in a thin pager. Therefore, use of the vibration
`is efficient.
`[0035] Thus, a single vibration actuator can be used in
`the pager to perform sound-based and vibration-based
`calling, and to generate efficient vibration.
`[0036] In this configuration, the magnet and yoke are
`integrated in each magnetic circuit, so no non-excitation
`holding force is exerted, and accurate vibration is
`generated even for micro input. Therefore, in the above
`case, it is suitable for generating various sounds and
`vibrations by changing the frequency and an amplitude
`thereof, or by intermittently generating an electric
`current, and the like.
`[0037] FIG. 4 is a waveform diagram illustrating a
`current waveform in this case. FIG. 4 (a) to (e) shows an
`example of a current waveform from a signal generating
`part. Known signal generators can be used as the signal
`generating part. FIG. 4 (a) is a current waveform when
`sound is generated, wherein a current of a frequency of
`several hundred to several thousand Hz is generated
`intermittently and with varying amplitudes. A current of
`such a waveform is supplied to the first coil 2 and the
`second coil 3 to ensure that the yoke 8 vibrates and a
`reliable call can be made wherein the sound gradually
`gets louder.
`[0038] FIG. 4 (b) is a current waveform when vibration
`is generated, wherein a current of a frequency of several
`dozen to several hundred Hz is generated continuously.
`A current of such a waveform is supplied to the first coil
`2 and the second coil 3 to ensure that the base part 1
`vibrates, thus enabling a call to be made. Note that
`
`although a sine wave is shown here, various other AC
`waveforms can be used.
`[0039] FIG. 4 (c) is a current waveform when vibration
`is generated, wherein a current of a frequency of several
`dozen to several hundred Hz is generated intermittently.
`A current of such a waveform is supplied to the first coil
`2 and the second coil 3 to ensure that the base part 1
`vibrates intermittently, thus enabling a reliable call to be
`made.
`[0040] FIG. 4 (d) is a current waveform when vibration
`is generated, wherein a current of a low frequency of
`around several dozen Hz is generated continuously. A
`current of such a waveform is supplied to the first coil 2
`and the second coil 3 to ensure that the base part 1
`vibrates slowly, thus enabling a call to be made by a soft
`vibration during the initial time of the call or the like.
`[0041] FIG. 4 (e) is a current waveform when vibration
`is generated, wherein a current of a low frequency of
`around several dozen to several hundred Hz is generated
`intermittently with varying amplitude. The base part 1
`vibrates intermittently and so that the amplitude
`gradually increases when a current of such a waveform
`is supplied to the first coil 2 and the second coil 3, and a
`reliable call can be made wherein vibrations are small in
`the initial stage of calling and vibrations are larger later
`on.
`[0042] Furthermore, although not shown in the FIGS., it
`is also possible to combine sound and vibration by
`superimposing the current waveform in FIG. 4 (a) and
`the current waveforms in FIG. 4 (b) onwards. Thus, by
`making
`the vibration
`intermittent, changing
`the
`frequency of the vibration, and changing the amplitude
`(intensity of the vibration), it is possible to make various
`changes to the vibration as in the case of sound.
`Additionally, various types of vibrations other than the
`above can be produced as desired by further combining
`the above current waveforms.
`[0043] These various vibrations can be switched at the
`user's choice by a selection in the pager's control unit.
`The vibration can also be configured to be selected
`arbitrarily according to settings from the caller side.
`[0044] Furthermore, use of a spring 7 that determines a
`position of the yoke when it is at rest allows quick
`convergence of the vibration of the yoke when the
`alternating current is no longer supplied. Efficiency is
`high in the configuration of the present embodiment
`since no non-excitation holding force is exerted as
`described above. However, it is necessary to hold the
`movable elements in place in a predetermined position.
`For this reason, the spring 7 is used. Additionally, the
`spring 7 acts without impairing efficiency even during
`micro vibration of the movable elements.
`[0045] In addition to the spring 7 and various elastic
`materials, it is also possible to use, for example, means
`for determining a stationary position of the yoke 8 using
`magnetic force. By using such stationary positioning
`means for determining a stationary position and not
`preventing movement, more accurate vibration in
`accordance with the current waveform can be achieved.
`
`Exhibit 1015 - Page 5 of 8
`
`

`

` (6)
`
` JP H8-196053
`
`[0046] Therefore, according to the above configuration,
`in terms of vibration transmission efficiency, use
`(transmission) of vibrations is highly efficient since,
`instead of
`rotation-based vibration, vibration
`is
`generated in a direction in which the vibration is directly
`felt by the user.
`[0047] Vibration generation efficiency: Since each yoke
`forms the magnetic loop having the shortest path, loss is
`small and higher efficiency can be obtained compared to
`a conventional device. Additionally, since no non-
`excitation holding force
`is exerted, efficiency
`is
`extremely high and accurate vibration can be generated
`even during generation of micro vibration.
`[0048] Thinness and smallness: Since the invention is
`composed of a coil on a base part and movable elements
`having yoke that also serves as a core of the coil, it is
`thinner, smaller, and lighter than motors and other
`devices. Therefore, it is suitable for thin pagers and
`vibration-based calling can be achieved even in very thin
`pagers in which only sound-based calling had been
`possible. Additionally, since a single vibration actuator
`generates both sound and vibration, there is no need for
`a dedicated sound generating means (such as a speaker)
`in the pager, thus enabling miniaturization. Furthermore,
`as a vibration canceller, it can be arranged precisely at a
`desired point due to its small size.
`[0049] Long life: An alternating current is only supplied
`to the coil, thus eliminating the need for high-speed
`sliding parts such as brushes, commutators, and the like
`to achieve a long lifespan. Therefore, stable sound and
`vibration can be generated over a long period of time,
`and no aging problems occur. In addition, DC motors
`generate electrical noise from brushes, but the present
`vibration actuator has no such problem.
`[0050] Vibration mode: By selecting the current
`waveform supplied to the coil, an arbitrary frequency
`and amplitude, and intermittent or continuous vibration
`can be generated. Accordingly, since arbitrary vibrations
`can be generated where in the conventional device
`vibration can only be turned on and off, it is possible to
`use the vibration to transmit a message determined upon
`in advance between the related parties.
`[0051] Note that while in the embodiment described
`above, the holding means is composed of the bearing 5
`and the holder 6, it is possible to use a material having a
`low friction coefficient as the holder 6 to provide a
`holding means which is movable in an axial direction
`with respect to the spindle 4, thereby eliminating the use
`of a bearing. Furthermore, a variation is also possible
`wherein the holder 6 and the spindle 4 are affixed to each
`other and the bearing 5 is provided between the spindle
`4 and the base part 1.
`[0052] FIG. 5 is a cross-sectional view of a vibration
`actuator in another embodiment of the present invention.
`The same parts as those in the embodiments already
`described using FIG. 1 to FIG. 4 are marked with the
`same numbers in FIG. 5, and overlapping descriptions of
`such are omitted. In the vibration actuator illustrated in
`FIG. 5, the spindle 4 is mounted in the hole 1c in the base
`
`part 1, and a disk-shaped diaphragm 11 constituting the
`elastic body is provided in the spindle 4. The holder 6 is
`attached to a periphery of the diaphragm 11.
`[0053] That is, in the present embodiment, the holder 6
`is configured so as to be movable in an axial direction by
`the diaphragm 11 instead of the spring 7 in the previous
`embodiment. Thus, the diaphragm 11 realizes the
`functions of the bearing and spring in the embodiment
`described above. A diaphragm made of metal, resin, or
`various other materials can be used as the diaphragm 11.
`[0054] In the present embodiment, the magnetic circuit
`having the shortest path is formed in each yoke, resulting
`in high efficiency. Furthermore, accurate micro
`vibrations can be obtained without exertion of a non-
`excitation holding force. In the present embodiment, the
`diaphragm 11 also functions to maintain the holder 6 in
`a predetermined position when the holder 6 is not
`vibrating. The diaphragm 11 may also be composed of
`various elastic materials (such as rubber, a coil spring, a
`plate spring, or an air spring) in addition to the
`diaphragm, and it is sufficient if the diaphragm 11 is
`capable of holding the spindle 4 and holder 6 in a
`predetermined position while allowing them to vibrate
`and allowing quick convergence of the vibration when
`the current is no longer supplied. This ensures accurate
`vibration in accordance with the current waveform.
`[0055] Accordingly, in the configuration illustrated in
`FIG. 5, when a current in a predetermined direction is
`sent to the first coil 2b and the second coil 3b, thrust is
`generated according to Fleming's left-hand rule in the
`first coil 2b and second coil 3b arranged in the magnetic
`circuit described above. Then, as a reaction to the thrust,
`the movable elements (the holder 6, the yokes 8a and 8b,
`and the magnets 9a and 9b) try to move. Therefore, when
`an alternating current is sent to the first coil 2b and the
`second coi