US007005811B2
`
`a2) United States Patent
`US 7,005,811 B2
`(10) Patent No.:
`(45) Date of Patent:
`Feb. 28, 2006
`Wakudaetal.
`
`
`(54) BODILY SENSED VIBRATION GENERATOR
`SYSTEM
`
`(75)
`
`Inventors: Hiroshi Wakuda, Fukushima-ken (JP);
`Takahiro Kawauchi, Fukushima-ken
`(JP)
`
`....... 340/407.1
`10/1997 Hiroyoshiet al.
`5,682,132 A
`3/2002 Tierling et al. 0.0... 345/156
`2002/0030663 Al
`FOREIGN PATENT DOCUMENTS
`
`EP
`JP
`
`1199 111 Al
`09-205763
`
`4/2002
`8/1997
`
`(73)
`
`Assignee: Alps Electric Co., Ltd., Tokyo (JP)
`
`* cited by examiner
`
`Primary Examiner—Darren Schuberg
`Assistant Examiner—Judson H. Jones
`(*)
`Notice:|Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`(74) Attorney, Agent, or Firm—Brinks Hofer Gilson &
`Lione
`US.C. 154(b) by 181 days.
`
`(21)
`
`Appl. No.: 10/717,070
`
`(22)
`
`Filed:
`
`Nov. 19, 2003
`
`Prior Publication Data
`US 2004/0104625 Al
`Jun. 3, 2004
`
`(65)
`
`(30)
`
`Foreign Application Priority Data
`seseeeenesenesaneneeanecneees 2002-348993
`
`Nov. 29, 2002
`
`(JP)
`
`(51)
`
`(52)
`(58)
`
`(56)
`
`Int. Cl.
`(2006.01)
`H02K 3/00
`US. Che i ccccceecteseseteeteneeenes 318/128; 318/114
`Field of Classification Search ................ 318/114,
`318/126, 127, 128, 129
`See application file for complete search history.
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`(57)
`
`ABSTRACT
`
`Avibration generator system is capable of generating vibra-
`tions of a frequency that can be bodily sensed by humans,
`notwithstanding a small size, and making setting of a
`configuration of vibrations easy. When a drive signal com-
`posed of a set of an accumulation signal and a damping
`signal is given as a natural frequency of a movable body, a
`vibrational waveform of the movable body makes an enve-
`lope. Since a frequency of the envelope is in a lower
`frequency band than the natural frequency of the movable
`body, humans can surely sense vibrations. When the number
`of and a current quantity of excitation signals and reverse
`excitation signals included in the accumulation signal are
`changed and the number of and a current quantity of
`inhibition signals and reverse inhibition signals included in
`the damping signal are changed,
`the envelope can be
`changed in frequency and amplitude, so that it becomes
`possible to generate a variety of vibrations.
`
`3,573,514 A *
`
`4/1971 Race cece eeeeee 310/17
`
`13 Claims, 5 Drawing Sheets
`
`Ma / ’
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`ENVELOPE E
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`ACCUMULATION
`SIGNAL Sta
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`DAMPING SIGNAL S1b
`
`Al
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`AS
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`C2
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`DRIVE SIGNAL 81----
`
`APPLE 1005
`
`APPLE 1005
`
`1
`
`

`

`U.S. Patent
`
`Feb. 28, 2006
`
`Sheet 1 of 5
`
`US 7,005,811 B2
`
`FIG.
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`1A
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`

`

`U.S. Patent
`
`Feb. 28, 2006
`
`Sheet 2 of 5
`
`US 7,005,811 B2
`
`
`
`
`
`
`POSITION
`DETECTION
`MEANS
`
`VIBRATION
`CONTROL
`MEANS
`
`3
`
`

`

`U.S. Patent
`
`Feb. 28, 2006
`
`Sheet 3 of 5
`
`US 7,005,811 B2
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`CYCLE: T
`
`CYCLE: T=1/RESONANCE FREQUENCY
`
`DISPLACEMENT
`X2
`
`VIBRATIONAL om1
`WAVEFORM
`|
`
`
`DIRECTION
`
`DRIVE SIGNAL St ---b-4----}----}-----Po---f--deff 0
`
`REVERSE
`
`ACCUMULATION
`SIGNAL Sta
`
`DAMPING
`SIGNAL Sib
`
`4
`
`

`

`U.S. Patent
`
`Feb. 28, 2006
`
`Sheet 4 of 5
`
`US 7,005,811 B2
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`FIG. 5
`
`Te
`
`fe=1/Te
`
`ENVELOPE E
`
`VIBRATIONAL
`WAVEFORM
`
`UM
`
`ACCUMULATION
`SIGNAL Sta
`
`DAMPING
`SIGNAL Stb
`
`ACCUMULATION
`SIGNAL Sia
`
`DAMPING
`SIGNAL Sib
`
`Ci C2 C3}|A1 A2 AB
`
`DRIVE SIGNAL St ----/-+-
`
`Di D2 D3
`
`Bi B2 B3
`
`5
`
`

`

`U.S. Patent
`
`Feb. 28, 2006
`
`Sheet 5 of 5
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`US 7,005,811 B2
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`VIBRATIONAL
`WAVEFORM
`
`SIGNAL Sta
`
`ACCUMULATION
`
`6
`
`

`

`US 7,005,811 B2
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`1
`BODILY SENSED VIBRATION GENERATOR
`SYSTEM
`
`This application claims the benefit of priority to Japanese
`Patent Application No. 2002-348993, herein incorporated by
`reference.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to a bodily sensed vibration
`generator system mountable on small-sized information
`terminal devices, such as portable telephones, PDA,portable
`game equipments, and so on, and more particular, to a bodily
`sensed vibration generator system, which is small in size and
`capable of realizing a variety of vibrations.
`2. Description of Related Art
`For example, Patent document1 discloses an invention of
`a conventional vibration generator system.
`The vibration generator system may be used as a drive
`device for speakers, and in which a cylindrical-shaped coil
`is fixed on a side of a bottom surface of a housing and a
`magnetic field generator composed of a magnet and a yoke
`is elastically supported in a position opposed to an outer
`surface of the coil by a plate-shaped elastic body or a coil
`spring. When a drive signalis given to the coil, an electro-
`magnetic force acts between the magnetic field generator
`and the coil to vibrate the magnetic field generator.
`Also, a column of the prior art in Patent document 1
`describes a biased weight type vibration generator system as
`a general vibration generator system. With the biased weight
`type vibration generator system, a biased weight having a
`non-axisymmetric shape is provided on a tip end of a
`rotating shaft of a motor and vibrations are generated by
`making a center of gravity of the biased weight offset from
`a center of rotation when the rotating shaft is rotated.
`[Patent Document 1]
`JP-A-9-205763
`However,
`the vibration generator system described in
`Patent document 1 is directed to bodily sensing vibrations
`when the magnetic field generator generates natural vibra-
`tions. However, the numberof vibrations that can be bodily
`sensed by humansis in a relatively low frequency band. The
`natural frequency of mechanical vibration is inversely pro-
`portional to the square root of a mass of a movable part and
`proportional to the square root of a spring constant. Accord-
`ingly,
`in order to generate natural vibrations at that fre-
`quency, which can be bodily sensed by humans, the movable
`part must have a considerably large mass since the movable
`part is limited in stroke. A drive part must have a large
`volume correspondingly, so that in order to generate natural
`vibrations of that amplitude, which can be bodily sensed by
`humans, equipmentsis large.
`Also, while an increase in frequency of natural vibrations
`is conceivable for the sake of miniaturization,
`it
`is also
`difficult since the number of vibrations that can be bodily
`sensed by humansis in a relatively low frequency band.
`Also, while the vibration generator system can generate
`simple vibrations based on the frequency of natural vibra-
`tions continuously or intermittently,
`it is not possible to
`freely set a configuration of vibrations. Accordingly,it is not
`possible to mount the system on portable telephones or
`portable game equipments to generate a variety of effective
`vibrations.
`
`Meanwhile, the conventional biased weight type vibration
`generator system is constructed to have a motor and a biased
`weight and so becomes large-sized, and it becomes neces-
`
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`2
`sary to firmly fix the motor in a manner to withstand
`vibrations caused by rotation of the biased weight, so that
`miniaturization of the system is impeded. Also, since a large
`inertial force acts on the biased weight in rotation, it is hard
`to finely vary intensity (mode of vibration) of vibrations by
`giving various drive signals and modifying the rotating
`speed. That is, the biased weight type vibration generator
`system involves a problem of a poor follow-up property of
`the vibration system for drive signals.
`
`SUMMARYOF THE INVENTION
`
`Embodiments of the invention provide a vibration gen-
`erator system, which can generate vibrations at a frequency
`that can be bodily sensed by humans, while being small in
`size, and which makessetting of a configuration of vibra-
`tions easy.
`The invention has a feature in a vibration generator
`system, by which a movable bodyis vibrated according to
`a drive signal, characterized in that accumulation signals for
`excitation of the movable body to vibrations are included in
`the drive signal at intervals, and when the accumulation
`signals are given, the movable body perform motionsto be
`excited, to damp thereafter, and to repeat such excitation and
`damping, and that changes in an envelope, which connects
`peaks of amplitude of the movable body whenthe vibrations
`are excited and damped, are obtained as vibrations of a
`lower frequency than a frequency of the vibrations.
`With the vibration generator system, vibrations of the
`movable body themselvesare not bodily sensed but changes
`in an envelope, which connects peaks of amplitude of the
`movable body, are taken out as vibrations being bodily
`sensed by humans. A frequency of the envelope is in a lower
`band than a natural frequency. The envelope is varied
`whereby changes in intensity of vibrations are given to
`humans. Since changesin intensity of vibrations are easy to
`be bodily sensed as changes in feeling of pressure and the
`frequency of the envelopeis in a frequency band, which can
`be bodily sensed effectively, humans can surely detect
`vibrations. Also,
`in the case where the movable body is
`excited at the natural frequency, the natural frequency may
`be high and so the movable body can be decreased in mass
`and formed to be small-sized. Also, since a spring constant
`can be made large, the movable body can be controlled in
`amplitude by the energizing means and it becomes easy to
`control the envelope.
`In addition, while the vibration generator system accord-
`ing to the invention is suited to applications,
`in which
`vibrations are generated at a natural frequency determined
`by a mass of the movable body and a spring constant, it is
`notlimited to applications, in which vibrations are generated
`at a natural frequency, but also to applications, in which
`excitation is caused at a frequency close to a natural fre-
`quency.
`For example, the accumulation signals include excitation
`signals intermittently giving to the movable body a driving
`force in the same direction.
`Further,
`the accumulation signals may include reverse
`excitation signals provided between the excitation signals to
`give a driving force in a reverse direction to that of the
`driving force by the excitation signals.
`In this manner,
`the excitation signals and the reverse
`excitation signals are given alternately whereby excitation of
`the movable body can be increased in rise and amplitude.
`Further,
`the drive signal includes damping signals for
`damping of the movable body, which has been excited with
`the accumulation signals, after the excitation.
`
`7
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`

`

`US 7,005,811 B2
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`3
`While the drive signal may include only the accumulation
`signals, damping signals are included to thereby enable
`excitation and damping to shorten cycles of the envelope
`and to generate pointed vibrations.
`For example, the damping signals include inhibition sig-
`nals giving to the vibrating movable body a driving force in
`a reverse direction to a move direction thereof.
`
`Further, the damping signals preferably include reverse
`inhibition signals provided betweenthe inhibition signals to
`give a driving force in a reverse direction to that of the
`driving force by the inhibition signals.
`By giving the inhibition signals and the reverse inhibition
`signals alternately, it is possible to abruptly dampvibrations
`to set the envelope in a steep shape.
`Also,
`the control means can be configured to produce
`intervals of the accumulation signals in different patterns
`and can generate accumulation signals having different
`numbers of the excitation signals and different patterns.
`Likewise, it is preferably possible to freely vary intervals of
`the damping signals and the numberofthe inhibition signals
`in the damping signals.
`In this case, variableness may be achieved by beforehand
`preparing the accumulation signals and the dampingsignals
`in a plurality of patterns, or a multiplicity of patterns for
`combinations of the accumulation signals and the damping
`signals, enabling continuously varying intervals of the accu-
`mulation signals and the damping signals, and enabling
`continuously varying the number of the excitation signals
`and the inhibition signals.
`Also, the invention can make a configuration in which the
`movable body is supported on a support
`to be able to
`reciprocate in a range of a predetermined stroke, and which
`comprises energizing means for energizing the movable
`body toward a middle point of the stroke, magnetic drive
`means comprising a magnet provided on one of the movable
`body and the support and a coil provided on the other of the
`movable body andthe support and for giving to the movable
`body a driving force in a direction along the stroke, and
`control meansfor giving a drive signal to the coil to cause
`the movable body to generate vibrations of natural fre-
`quency.
`Such configuration is not limited to one as shown in the
`embodiment of the figure,
`in which the movable body
`reciprocates linearly but may be one, in which the movable
`body reciprocates in a rotational locus.
`The above configuration may be constructed such that
`position detection means is provided to detect
`that
`the
`movable body has reached a predetermined position of
`detection during vibration and cycles of the excitation
`signals are determined onthe basis of detection signals from
`the position detection means.
`Alternatively, the configuration may be constructed such
`that position detection means is provided to detect that the
`movable body has reached a predetermined position of
`detection during vibration and cycles of the inhibition sig-
`nals are determined onthe basis of detection signals from the
`position detection means.
`The provision of such detection means makesit possible
`to generate excitation signals and inhibition signals follow-
`ing fluctuation in natural frequency of the movable body,
`which is caused by mechanical wear and changes in envi-
`ronment.
`
`The movable body in the invention is movable along an
`axis, and the energizing means can be configured to com-
`prise a coil spring for biasing the movable body in different
`directions from both sides in the stroke direction.
`
`4
`Further, preferably, the support comprises a cylindrical
`casing and the axis is positioned on a central axis of the
`cylindrical casing, and wherein one of the magnet and the
`coil is provided on the support and the other of the magnet
`and the coil is provided on the cylindrical casing.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
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`15
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`FIG. 1 shows an embodiment of vibration generating
`means1A being a perspective, cross sectional view, and 1B
`being a cross sectional view;
`FIG. 2 is a partial, cross sectional view showing the facing
`relationship between a magnet and a coil;
`FIG. 3 is a block diagram showing control means;
`FIG. 4 showsgraphsillustrating an example of a drive
`signal given to the coil and vibrations of a movable body at
`that time;
`FIG. 5 is a view showingthe relationship between a signal
`composedof a set of an accumulation signal and an damping
`signal, and a vibrational waveform of the movable body; and
`FIG. 6 is a view showing an example of control for a
`vibrational waveform of an envelope.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`30
`
`FIG. 1 shows an embodiment of vibration generating
`means, 1A being a perspective, cross sectional view, and 1B
`being a cross sectional view.
`A vibration generator system according to the invention
`comprises vibration generating means 1 shown in FIG. 1 and
`control means shown in FIG. 3.
`
`The vibration generating means 1 shown in FIG. 1 com-
`prises a cylindrical-shaped casing 2 made of a magnetic
`substance as a support, and covers 3, 3 made of a non-
`magnetic substance and being mountable on both endsof the
`casing. A shaft 4 made of a non-magnetic substance is
`supported on inner surfaces of the covers 3, 3, the shaft 4
`being in agreement with an imaginary center line O—O,
`which extendscentrally of the casing 2 and the covers 3, 3.
`Acoil 5 is fixed to an inner wall of the casing 2. The coil
`5 is formed by winding a length of covered copper wire,
`such as enameled wire orthe like, in a cylindrical shape, and
`is fixed in a position somewhat to one (a X1 side in FIG. 1)
`of the covers 3 from a center of a length of the casing 2 in
`a direction X shown.
`
`A movable body 6 is provided inside the casing 2. The
`movable body 6 is provided at one end thereof (a X2 side)
`with a weight 7 made of a non-magnetic substance andat the
`other end thereof (a X1 side) with a magnet M. Also, the
`magnet M is provided on both end surfaces thereof with
`yoke members 8a, 8b, which are formed from a magnetic
`material. The weight 7, yoke member 8a, magnet M,and the
`yoke member 8b are column- or disk-shaped, and all outer
`peripheral surfaces thereof are positioned in circles concen-
`tric with a center of the shaft 4.
`
`A hole 6a@ extending in the X direction is formed centrally
`of the movable body 6, that is, centrally of the weight 7,
`yoke member 8a, magnet M, and the yoke member 8b, and
`has the shaft 4 inserted inside thereof. Therefore, the mov-
`able body 6 can reciprocate along the shaft 4 in a stroke
`within a predetermined range in the X direction shown.
`Since the shaft 4 is formed from a non-magnetic material,
`the movable body6 is not attracted to the shaft 4 by forces
`of the magnet and a moving load is small when the movable
`body 6 moves along the shaft 4.
`
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`6
`8a in the X direction is in agreement with, or substantially
`in agreement with a middle point of the coil 5 in an axial
`direction of winding.
`In the neutral state shown in FIG. 1, when current in a
`direction shown in FIG. 1Bis givento the coil 5, a magnetic
`force F is generated by the magnetic flux
`and the current
`in the X2 direction to be able to give to the movable body
`6 a driving force in the X2 direction. Also, a driving force
`In the embodiment, the magnet M and the coil 5 form a
`in the X1 direction can be given to the movable body 6 by
`moving-magnet type magnetic drive means. However, a
`feeding a reverse current to the coil 5.
`moving-magnet type magnetic drive means may be used,in
`Subsequently, control means for the vibration generator
`whicha coil is mounted on the movable body 6 and a magnet
`system will be described.
`opposedto the coil is provided on an innerperipheral surface
`FIG. 2 is a partial, cross sectional view showing the facing
`of the casing 2.
`relationship between the magnet and the coil, FIG. 3 is a
`Energizing members 9, 9 are provided between both ends
`block diagram showing the control means, and FIG. 4 are
`of the movable body6 and inner surfaces of the covers3, 3,
`graphsillustrating an example of a drive signal given to the
`and so oppositely directed biasing forces along an axial
`coil and vibrations of the movable body 6 at that time.
`direction are exerted on the movable body 6 by the ener-
`As shownin FIG. 2, one end (a leading end of winding)
`gizing members 9, 9. The energizing members 9, 9 prefer-
`of the coil 5 makes a terminal Tal, the other end(atrailing
`ably have the same spring constant to produce the same
`end of winding) makes a terminal Ta2, and a middle point(a
`elastic force when they have the same axial length. FIG. 1
`middle point of the coil 5) between the terminal Tal and the
`showsa state, in which the coil 5 is not energized, andat this
`terminal Ta2 makes a middle terminal Ta3.
`time, the movable body6is exerted by the biasing forces of
`the energizing members 9, 9 positioned on both sides thereof
`Control means 10 shown in FIG. 3 comprises position
`detection means 11 connected to the middle terminal Ta3,
`to be positioned in a middle point of the moving stroke.
`In FIG. 1B, the energizing members 9, 9 are cone coil
`signal generation means 12, drive means 13, and vibration
`springs. The cone coil springs have such characteristics that
`control means 14. The drive means13 is provided with two
`as they undergo compressive deformation,they are varied in
`output parts, one of which is connected to one of the
`terminals Tal of the coil 5 and the other of which is
`spring constant. The vibration generating means 1 vibrates
`connected to the other of the terminals Ta2 of the coil 5.
`the movable body6 at a natural frequency that is determined
`by spring constants of the respective energizing members 9,
`9 in a neutral state shown in FIG. 1 and a mass of the
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`US 7,005,811 B2
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`5
`Also, the magnet M and the yoke member 8b are formed
`to have a smaller outside diameter than those of the weight
`7 and the yoke member 8a and than an inside diameterof the
`coil 5. Therefore, when the movable body 6 moves along the
`shaft 4 in the X1 direction shown,portions of the magnet M
`and the yoke member 8b can move within an interior of the
`coil 5.
`
`The signal generation means 12 generates a drive signal
`S1 on the basis of a command from the vibration control
`
`movable body 6. However, when the cone coil springs are
`used, the cone coil springs disposed on both sides are varied
`in spring constant as the movable body 6 moves in the X1
`direction or the X2 direction. Therefore, as the movable
`body 6 moves much from the middle point shownin FIG. 1,
`the natural frequency is varied. Thereby, it is possible to
`restrain the movable body 6 from resonating at the natural
`frequency and moving at a larger amplitude than a stroke,
`whichis essentiality desired to control.
`That is, the energizing members 9, 9 making use of the
`cone coil springs function to determinethe natural frequency
`with their spring constants and can also display the function
`as dampers for suppressing movements when the movable
`body 6 becomeslarge in stroke. As energizing members, of
`which spring constants are varied with displacementin this
`manner, coil springs wound at variable pitch can be used as
`well as the cone coil springs. Alternatively, dampers may be
`separately provided inside the covers 3, 3 to restrain the
`movable body 6 from becoming excessive in amplitude.
`The magnet M is magnetized such that an end surface Ma
`in contact with the yoke member8a and an end surface Mb
`in contact with the yoke member8b have opposite magnetic
`poles. In the embodiment shown in FIG. 1, the end surface
`Mbassumesthe N pole and the end surface Ma assumesthe
`S pole. In this case, magnetic flux @ generated by the magnet
`M are output through one of the yoke members 85 in an
`outer peripheral direction to traverse the coil 5 perpendicu-
`larly to reach the casing 2. Further, the magnetic flux o form
`a magnetic path, along which the flux pass inside the casing
`2 made of a magnetic substance to be conductedto a position
`opposedto the other of the yoke members8a, and are output
`toward the yoke member8a from the position to reach the
`S pole of the magnet M.
`Also, as shown in FIG. 1, when the movable body 6 is
`positioned at the middle point of the moving stroke, a middle
`point of a widthwise dimension of one of the yoke members
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`means 14 to output the same to the drive means 13, and a
`drive current having a predetermined waveform is given to
`the terminal Tal and the terminal Ta2 of the coil 5 from the
`drive means 13. The signal generation means 12 stores the
`drive signals S1 having a plurality of patterns, and a drive
`signal $1 having a certain pattern is selected on the basis of
`a commandfrom the vibration control means 14 to be given
`to the drive means 13.
`The position detection means 11 detects that the movable
`body 6 has reached the neutral position shown in FIGS. 1
`and 2, that is, a middle point in the reciprocation stroke.
`Whena detection signal of the middle point detected by the
`position detection means11 is given to the signal generation
`means 12, the signal generation means 12 performscontrol,
`such as switching of current direction of the drive signal $1
`or the like, with the detection signal as a standard.
`In addition, while the position detection means 11 is not
`essential, the provision of the position detection means 11
`makes it possible to generate a drive signal S1 following
`large changesinelastic forces of the energizing members9,
`9 even in the case where the movable body 6 involves a large
`sliding load, or the movable body 6 gets out of order much
`in natural frequency due to such large changes in elastic
`forces.
`Also, a detected position in the position detection means
`11 is not limited to the middle point in the reciprocation
`stroke, at which the movable body 6 is positioned. For
`example, such detected position may be positions of maxi-
`mum amplitudes in the X1 and X2 directions, at which
`movements of the movable body 6 stop, or other predeter-
`mined detected positions.
`FIG. 4 shows a waveform of a drive signal S1. In the
`embodiment, while the drive signal S1 is given to the coil 5
`as a rectangular wave,
`the drive signal S1 may have a
`waveform such as a triangular wave or the like. In FIG. 4,
`a middle pointof the drive signal S1 is indicated by “0”, and
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`at this time the coil 5 is in a non-energized state. When the
`drive signal S1 rises in a forward direction, current flows
`through the coil 5 from the terminals Tal to the terminals
`Ta2. At this time, a driving force acts on the movable body
`6 in the X2 direction. Also, when the drive signal S1 shown
`in FIG. 4 is in a reverse direction, current flows through the
`coil 5 reversely to the above, andat this time a driving force
`is given to the movable body 6 in the X1 direction.
`As shown in FIG. 4, an accumulation signal Sla is
`includedin the drive signal S1. The accumulation signal Sla
`excites resonant vibrations at the natural frequency in the
`movable body 6. Excitation signals Al, A2, A3 are included
`in the accumulation signal Sla, and the excitation signals
`A1, A2, A3 give to the coil 5 current in a forward direction.
`In addition, in FIG. 4, the excitation signals A1, A2, A3 are
`constant in level, and intermittently give to the coil 5 a
`constant current quantity.
`FIG. 4 shows a vibrational waveform with the axis of
`ordinates representing displacements of the movable body 6
`in the X1 and X2 directions, as well as a waveform ofa drive
`signal $1. Om in the vibrational waveform meansthat the
`movable body 6 is positioned at the middle point shown in
`FIGS. 1 and 2. In addition, the axis of abscissas indicates
`time t in both graphs, which show a waveform of a drive
`signal S1 and displacements of the movable body 6.
`While the natural frequency (resonance frequency) of the
`movable body 6 is determined by a mass of the movable
`body 6 and the spring constants (spring constants in the
`neutral position shownin FIG. 1) of the energizing members
`9, 9, the excitation signals A1, A2, A3 are given every cycle
`T, which is the reciprocal of the natural frequency (reso-
`nance frequency) and an energization time is a half of the
`cycle T. More specifically, the excitation signals Al, A2, A3
`are given when the movable body 6 has a velocity in the X2
`direction and the excitation signals Al, A2, A3 are given to
`the coil 5 whereby a driving force in the X2 direction is
`further given to the movable body 6 having a velocity in the
`X2 direction. In addition,
`the excitation signal Al is a
`starting signal.
`The excitation signals Al, A2, A3 cause the movable body
`6 to begin vibrations, and vibrationsat the natural frequency
`are increased in amplitude with time.
`The accumulation signal S1a in the embodiment shown in
`FIG. 4 includes reverse excitation signals B1, B2 between
`adjacent excitation signals Al, A2, A3. The reverse excita-
`tion signals B1, B2 permit a reverse current to that with the
`excitation signal A to be given to the coil 5. ‘The reverse
`excitation signals B1, B2 are given to the coil 5 when the
`movable body 6 has a velocity in the X1 direction, and a
`driving force in the X1 direction is further given to the
`movable body 6.
`In this manner, the excitation signal A and the reverse
`excitation signal B are alternately given whereby amplitude
`of the movable body 6 is abruptly increased in a short time.
`In addition, it is not necessarily required that the accu-
`mulation signal Sla include the excitation signal A and the
`reverse excitation signal B, and so vibrations can be gener-
`ated in the movable body 6 and increased in amplitude only
`with the excitation signal A or the reverse excitation signal
`B. In this case, amplitude can be abruptly increased by
`increasing the excitation signal A or the reverse excitation
`signal B in current quantity.
`Also, amplitude can be maintained with resonant vibra-
`tions of the movable body 6 even whenthe excitation signal
`A and the reverse excitation signal B are given only in an
`initial period of time during that term, in which the accu-
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`mulation signal Sla is given, and for some time thereafter
`current is not given to the coil.
`Here, an increase in amplitude becomes maximum when
`a direction of driving is the same as a movedirection of the
`movable body 6 and frequency is in agreement with the
`resonance frequency.
`Methods of controlling an increasing rate (decreasing
`rate) of amplitude include a method of varying an input
`energy, and a method of staggering a drive signal S1. The
`former method of varying an input energy includes control
`through amplitude variation, in which a drive current (or a
`drive voltage) given to the coil 5 is varied in quantity, and
`PWM(Pulse Width Modulation) control, in which a drive
`current (or a drive voltage) is varied in energization time.
`Also,
`the latter method of staggering a drive signal S1
`includes one, in which phase is shifted, and one, in which
`frequency is shifted.
`With the PWM control, time, during which, for example,
`the excitation signal A is given, is made shorter than time
`half of the cycle T and excitation is made 0 in the remaining
`time for the accumulation signal Sla, whereby control is
`enabled to prevent an increase in amplitude of the movable
`body 6 from becoming excessive.
`Also, for the phase shift, signals are not varied in pulse
`width (time interval), and the excitation signal A is some-
`what advanced or delayed relative to time as a standard,
`wherebycontrol is enabled to prevent an increase in ampli-
`tude of the movable body 6 from becoming excessive.
`Further, for the frequency shift, an operation, in which a
`drive frequency of the movable body is made twice the
`resonance frequency and shifted to a high frequency from a
`low frequency, or shifted in a reverse direction, or shifted
`from a staggered frequency to be made in agreement with
`the resonance frequency and staggered from a state of
`agreement,
`is performed, whereby control
`is enabled to
`prevent an increase in amplitude of the movable body 6 from
`becoming excessive. With this method, since excitation is
`varied in efficiency and staggered in phase,it is possible to
`provide an excitation interval and an inhibition interval.
`The drive signal S1 includes a damping signal S1b. The
`damping signal $16 includesinhibition signals C1, C2, C3.
`The inhibition signals Cl, C2, C3 are staggered 180° in
`cycle relative to the excitation signals A1, A2, A3, and when
`the movable body 6 has a velocity in the X1 direction,
`current in a forward direction is given to the coil 5 to give
`a driving force to the movable body 6 in the reverse X2
`direction to a direction of the velocity. Thereby, vibrations of
`the movable body 6 at the natural frequency are damped.
`In the embodiment shown in FIG. 4, reverse inhibition
`signals D1, D2 are provided between the inhibition signals
`C1, C2, C3 to give to the coil 5 current in a reverse direction.
`The movable body 6 having a velocity in the X2 direction is
`given a driving force in the X1 direction, which cancels the
`velocity, by the reverse inhibition signals D1, D2. The
`inhibition signals C and the reverse inhibition signals D are
`alternately provided whereby the movable body6 is abruptly
`damped in amplitude.
`In addition, only one of the inhibition signals C and the
`reverse inhibition signals D may be provided in the damping
`signal S1b. Also, the inhibition signals C and the reverse
`inhibition signals D maybe provided only inthefirst half of
`the damping signal and may be gradually staggered in cycle.
`FIG. 5 showsa vibrational waveform of the movable body
`6 in the case where the accumulation signal Sla@ and the
`damping signal S1b are made consecutive and signals com-
`posed of a set of the accumulation signal Sla and the
`damping signal S1b are given at a cycle Te. In FIG. 5, the
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`that a counterelectromotive force (voltage) Va is induced
`numberof the excitation signals Al, A2, A3 in the accumu-
`between the terminal Tal and the middle terminal Ta3. Also,
`lation signal S1ais the sameasthat of the inhibition signals
`when the center of the yoke member 8b