as) United States
`a2) Patent Application Publication co) Pub. No.: US 2005/0275294 Al
`(43) Pub. Date: Dec. 15, 2005
`
`Izumiet al.
`
`US 20050275294A1
`
`(54) DRIVING UNIT
`
`(52) US. Che
`
`ecssessssctssssssistsntnssesvee 310/15; 318/119
`
`(76)
`
`Inventors: Tomohiro Izumi, Osaka-shi (JP);
`Yasuo Ibuki, Hikone-shi (JP); Mikihiro
`Yamashita, Echi-gun (JP); Hideaki
`Abe, Neyagawa-shi (JP)
`
`(57)
`
`ABSTRACT
`
`Correspondence Address:
`RADER FISHMAN & GRAUER PLLC
`LION BUILDING
`1233 20TH STREET N.W., SUITE 501
`WASHINGTON, DC 20036 (US)
`
`(21) Appl. No.:
`
`11/150,284
`
`(22)
`
`Filed:
`
`Jun. 13, 2005
`
`(30)
`
`Foreign Application Priority Data
`
`Jun. 14, 2004
`
`(IP) ee eeeecseessecssetessteneeenes 2004-176156
`
`Publication Classification
`
`A driving unit of the present invention comprises a moving
`element, an elastic body configured to support the moving
`element, a permanent magnetfixed on said moving element,
`an electromagnet disposed to be opposed to said permanent
`magnet, and a controller. The moving element andthe elastic
`body constitute a resonance system. The electromagnet
`includes a magnetic material and a coil wounded around the
`magnetic material. The controller magnetizes the magnetic
`material by feeding a current through the coil and gives a
`vibration force to the moving element by magnetic force
`acting between the magnetic material and the permanent
`magnet. The feature of the present invention resides in that
`the controller determines a current waveform necessary for
`an intended motion of the moving element, and applies a
`voltage to the coil intermittently so that a current in the form
`
`(S51)
`
`Int. Ch? ee H02K 33/00; HO2P 1/00
`
`of the current waveform flows through said coil.
`
`APPLE 1005
`
`1
`
`APPLE 1005
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 1 of 15
`
`US 2005/0275294 Al
`
`FIG. 1A CONTROLLER
` 61
`
`CURRENT
`
`WAVEFORM
`
`DECIDER
`
`
`
`
`
`ALTERNATING
`VOLTAGE
`
`OUTPUT PART
`
`CONTROLLER
`
`FIG. 2
`
`60
`
`2
`
`

`

`Patent Application Publication Dec. 15, 2005
`
`Sheet 2 of 15
`
`US 2005/0275294 Al
`
`FIG. 3A
`
`FIG. 3B
`
`FIG. 3C
`
`oD
`
`3
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 3 of 15
`
`US 2005/0275294 Al
`
`(terre-
`
`70
`
`72
`
`L
`
`FIG. 4
`
`QLual
`
`FIG. 5
`
`QO>E=oO.=<t
`
`Lu
`
`4
`
`
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 4 of 15
`
`US 2005/0275294 Al
`
`AMPLITUDE
`
`FIG. 6
`
`CURRENT
`
`FIG. 7A
`
`CURRENT
`
`FIG. 7B
`
`t
`
`CURRENT Ne t
`
`FIG. 7C
`CURRENT+
`
`|
`
`FIG. 7D
`
`CURRENT es t
`
`FIG. 7E
`
`CURRENT EN t
`
`5
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 5 of 15
`
`US 2005/0275294 Al
`
`FIG. 8
`
`CURRENT
`
`JVVAAL
`
`6
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 6 of 15
`
`US 2005/0275294 Al
`
`FIG. 9
`
`
`
`FIG. 70
`
`AMPLITUDE
`
`CURRENT
`
`coe
`
`:
`
`t
`
`,
`
`AMPLITUDE fo» -—
`CURRENT
`ALTERNATING
`JMNM... “nnnnapnil
`VOLTAGE ETTT
`si nnn
`so
`LL ~‘
`
`r
`
`Ton Ton
`Tph
`
`Tph
`
`7
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 7 of 15
`
`US 2005/0275294 Al
`
`FIG. 11A
`
`FIG. 11B
`
`$1, $2
`
`$1, $2
`
`t
`
`t
`
`t t
`
`t
`
`t
`
`t
`
`t
`
`!
`
`FIG. 12
`
`ALTERNATING
`VOLTAGE
`vi
`
`Ton
`
`—_
`
`T2
`
`T3
`
`8
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 8 of 15
`
`US 2005/0275294 Al
`
`VOLTAGE
`CURRENT #4L,
`
` FIG. 13A
`
`FIG. 13B
`
`CURRENT
`
`FIG. 13C
`
`CURRENT
`
`9
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 9 of 15
`
`US 2005/0275294 Al
`
`FIG. 14A
`
`CURRENT ?
`
`T1i11
`+t72
`
`(
`
`|
`
`t
`
`T3
`
`FIG. 14B
`
`CURRENT
`
`|
`
`|
`
`14+!
`I He 72
`I
`ti
`
`T3
`
`t
`
`FIG. 14C
`
`_t
`
`ott
`|
`
`CURRENT
`
`a4
`My tt
`
`T3
`
`10
`
`

`

`Patent Application Publication Dec. 15, 2005 Sheet 10 of 15
`
`US 2005/0275294 Al
`
`FIG. 15
` FIG. 16
`
`INDUCED
`ELECTROMOTIVE
`FORCE (E)
`
`AMPLITUDE
`
`11
`
`11
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 11 of 15
`
`US 2005/0275294 Al
`
`FIG. 17
`
`
`_NOLTAGE (V1)
`eeST _, CURRENT
`= wre _ 2)
`
`
`
`i =—.—1-e
`R.
`
`t
`
`-t
`
`V2= Vit E
`
`FIG. 18
`
`CURRENT
`
`INDUCTANCE (L)
`
`
`1.0[W]
`
`FIG. 19
`
`POWER
`
`2.0[W]
`
`1.6[W]
`
`—.1,—___” —_y—
`THIS EMBODIMENT PRIOR ART
`
`12
`
`12
`
`

`

`Patent Application Publication Dec. 15,2005 Sheet 12 of 15
`
`US 2005/0275294 Al
`
`FIG. 20
`
`55
`
`75 AMPLITUDE
`
`OUTPUT OF THE
`DETECTION COIL
`
`FIG. 22A
`
`13
`
`13
`
`

`

`Patent Application Publication Dec. 15, 2005 Sheet 13 of 15
`
`US 2005/0275294 Al
`
`FIG. 22B
`
`55
`+Vs
`Ls
`oo+
`
`|co | iy
`
`$1
`
`LIK
`
`Q1
`
`FIG. 22C
`
`Q1.
`
`+Vs
`
`$1
`
`\
`“HE
`
`CHE
`
`Q2 Vs
`
`55
`
`v
`
`we
`
`FIG. 22D
`
`FIG. 22E
`
`14
`
`14
`
`

`

`Patent Application Publication Dec. 15, 2005 Sheet 14 of 15
`
`US 2005/0275294 Al
`
`FIG. 23A
`
`AMPLITUDE
`
`h
`
`CURRENT
`
`_
`
`{
`
`v'
`
`A
`
`AMPLITUDE
`AAAAAdee
`
`CURRENT
`/
`Ol
`t
`ALTERNATING
`Donn Ls-ppnnnnnt
`VOLTAGE ertHN
`, {un =
`a i |
`
`Tph
`
`Tph
`
`FIG. 23B
`
`AMPLITUDE
`
`AMPLITUDE
`
`CURRENT
`
`ALTERNATING
`VOLTAGE
`
`V'
`
`15
`
`15
`
`

`

`Patent Application Publication Dec. 15, 2005 Sheet 15 of 15
`
`US 2005/0275294 Al
`
`FIG. 24
`
`AMPLITUDE
`
`CURRENT
`
`VELOCITY
`
`VOLTAGE
`
`16
`
`16
`
`

`

`US 2005/0275294 Al
`
`Dec. 15, 2005
`
`DRIVING UNIT
`
`TECHNICAL FIELD
`
`[0001] The present invention relates to a driving unit and
`a method for driving a resonance system comprising an
`elastic body and a moving element supported by the elastic
`body.
`
`BACKGROUND ART
`
`Japanese Patent Publication No. 3382061 discloses
`[0002]
`a driving unit for driving a resonance system comprising an
`elastic body and a moving element supported by the elastic
`body. The driving unit is used in an electric shaveras a linear
`actuator which reciprocates an inner cutter.
`
`[0003] The driving unit is energy efficient because the
`moving element reciprocates as the resonance system con-
`serves kinetic energy of the moving element and elastic
`energy of the elastic body and converts them to each other
`alternately. In actuality, since the energy is consumed by a
`load and so on,the driving unit has to give consumed energy
`to the moving element in order to keep the reciprocating
`motion.
`
`[0004] So, in this driving unit, as shown in FIG. 24, a
`controller of the driving unit gives an alternating voltage of
`arectangular waveto an electromagnet every half-cycle, and
`reciprocates the moving element with a constant amplitude
`by controlling an voltage application period (Ton) and a
`phase (Tph) of the alternating voltage.
`
`[0005] Explaining in more detail, when the rectangular
`voltage is applied to the electromagnet, a current in the form
`of a triangular wave, as shown in FIG.24, flows through a
`coil of the electromagnet. Vibration force which moves the
`moving element will increase or decrease in response to the
`amountofthe current flowing throughthe coil. For example,
`when the amount of the current flowing through the coil
`increases as shownbya dashed line in FIG.24,the vibration
`force will increase, and, on the other hand, when the amount
`of the current flowing through the coil decreases, the vibra-
`tion force will decrease. So, in this driving unit, the con-
`troller detects a motion of the moving element every half-
`cycle, and if the width of the moving elementis larger than
`a target width, the controller decreases the voltage applica-
`tion period, and if the width of the moving elementis shorter
`than the target width, the controller increases the voltage
`application period. Furthermore, the controller applies the
`voltage to the coil when the moving element goes a prede-
`termined phase (Tph) from a top dead center or a bottom
`dead center so as to apply the voltage at the right time in
`keeping with the moving direction of the moving element.
`
`[0006] As mentioned above, the conventional driving unit
`controls the moving unit by varying the voltage application
`period (Ton) and the phase (Tph) of the voltage in order to
`make the moving element do an intended motion, such as a
`reciprocating motion with constant amplitude. However,
`although the conventional control method can make the
`moving element do an intended motion,it does not take into
`consideration an influence of a waveform of the current
`
`flowing through the coil on energy efficiency. Therefore, in
`the conventional driving unit, a current in the form of the
`triangular wave having many harmonic components flows
`through the coil, as mentioned above, so that a momentary
`
`current becomes very high at the conclusion of the energi-
`zation. As a result, an energy loss due to resistances of the
`coil, control circuit, etc. increases, by which heating values
`of electronic components and coil increase, and total energy
`efficiency decreases.
`
`DISCLOSURE OF THE INVENTION
`
`In view of the above problem, the object of the
`[0007]
`present invention is to provide a driving unit and a method
`for driving a resonance system which can improve energy
`efficiency.
`
`[0008] The driving unit in accordance with the present
`invention comprises a moving element, an elastic body
`configured to support
`the moving element, a permanent
`magnet fixed on said moving element, an electromagnet
`disposed to be opposed to said permanent magnet, and a
`controller. The moving elementandthe elastic body consti-
`tute a resonance system in which kinetic energy of the
`moving element and elastic energy of the elastic body are
`conserved and converted to each other. The electromagnet
`includes a magnetic material and a coil wounded around the
`magnetic material. The controller magnetizes the magnetic
`material by feeding a current through the coil, and gives a
`vibration force to the moving element by magnetic force
`acting between the magnetic material and the permanent
`magnet. The feature of the present invention resides in that
`the controller determines a current waveform necessary for
`an intended motion of the moving element, and applies a
`voltage to the coil intermittently so that a current in the form
`of the current waveform flows through said coil. Therefore,
`an electric current
`in the form of a current waveform
`desirable for an intended motion of the moving element can
`flow through the coil, so that an energy loss due to an
`unnecessary current can be reduced and the energy effi-
`ciency can be improved.
`
`[0009] Preferably, the controller determines a shape and a
`phase of the current waveform necessary for the intended
`motion of the moving element. Or,it is also preferable that
`the controller determines a shape and an application time of
`the current waveform. The driving unit can be driven more
`efficiently by controlling the phase and the application time
`of the current waveform in addition to controlling the shape
`ofit.
`
`[0010] A desirable current waveform for the intended
`motion of the moving element varies depending on various
`factors, such as a state of the resonance system and an
`external load. Therefore,it is preferable that the driving unit
`further comprises a sensor configured to detect a behavior of
`the moving, element, and the controller determines the
`current waveform in response to the behavior of the moving
`element detected by the sensor. In this case, an optimal
`current waveform can be determined in response to the
`behavior of the moving element.
`
`Ina driving unit for driving such resonance system,
`{0011]
`it is most energy efficient when the moving elementrecip-
`rocates under a resonant condition where the reciprocating
`motion of the moving element is synchronous with a natural
`frequency determined by a mass of the moving element and
`an elasticity of the elastic body. Therefore, it is preferable
`that the controller determines the current waveform neces-
`sary for the moving element to reciprocate in a resonant
`condition.
`
`17
`
`17
`
`

`

`US 2005/0275294 Al
`
`Dec. 15, 2005
`
`[0028] FIG. 15 is a view showing a configuration of the
`controller and the coil.
`
`[0029] FIG. 16 is a view showing induced electromotive
`force.
`
`[0030] FIG. 17 is a view showing a relation between a
`current and a voltage.
`
`[0031] FIG. 18 is a view showing a change of inductance
`of the coil.
`
`[0032] FIG. 19 is a view showing a result of an energy
`comparison.
`
`[0033] FIG. 20 is a view for explaining a sensor.
`
`[0034] FIG.21 is a view showing an output of the sensor
`of FIG. 20.
`
`[0035] FIGS. 22A to 22E are views showing other
`examples of the circuit configuration of the alternating
`voltage output part.
`
`[0036] FIGS. 23A to 23B are time charts of the control
`signals.
`
`[0037] FIG. 24 is a time chart showing a current wave-
`form of the priorart.
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`[0038] Hereinafter, the present invention will be described
`in more detail with reference to the accompanying drawings.
`
`In order to form an intended current waveform
`{0012]
`precisely, it is preferable that the controller predicts induced
`electromotive force generated with the reciprocating motion
`of the moving element, and forms the current waveform
`using the induced electromotive force. And, it is also pref-
`erable that the controller predicts inductance or a change of
`the inductance which varies by a position of the moving
`element or a change of the position of the moving element
`1, and forms the current waveform while taking into con-
`sideration the inductance or the change of the inductance.
`Furthermore,it is also preferable that the controller changes
`the current waveform in response to a change of a power
`supply voltage.
`
`In order to apply the voltage to the coil intermit-
`[0013]
`tently, it is preferable that the controller controls ON-time
`and OFF-time of the voltage to be applied to the coil. Or,it
`is also preferable that
`the controller controls a ratio of
`ON-time to OFF-time of the voltage to be applied to the coil.
`Or,
`the controller may control a sum of ON-time and
`OFF-time of the voltage to be applied to the coil. Or, the
`controller may control a sum of ON-time and OFF-time of
`the voltage to be applied to the coil and a ratio of the
`ON-time to the OFF-time of the voltage. In these cases, the
`controller can form various shapes of the current waveforms,
`so that an intended current waveform can flow through the
`coil.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0014] FIGS. 1A and 1B are views showing a construc-
`tion of a driving unit in accordance with an embodimentof
`the present invention.
`
`{0015] FIG. 2 is a block diagram of a controller of the
`driving unit.
`
`FIGS. 3A to 3C are views showing an example of
`[0016]
`a sensor for detecting a behavior of a moving elementof the
`driving unit.
`
`[0018] FIG. 5 is a time chart showing an output of the
`circuit of FIG. 4.
`
`FIG.6 is a view showing an example of a current
`[0019]
`waveform determined by a current waveform decider.
`
`FIGS. 7A to 7E are views showing other examples
`[0020]
`of the current waveform.
`
`{0021]
`
`FIG.8 is a view showing fundamental waveforms.
`
`FIG.9 is a view showing one exampleofa circuit
`[0022]
`configuration of an alternating voltage outputpart.
`
`[0023]
`
`FIG. 10 is a time chart of the control signals.
`
`[0039] FIG. 1A showsa driving unit for driving a reso-
`nance system in accordance with an embodiment of the
`present invention. The driving unit is used in an electric
`shaver as a linear actuator for reciprocating an inner cutter
`100 fixed on a moving element 1. As shownin FIG.1A,the
`driving unit comprises a moving element 1 both sides of
`which are supported by coil springs 2 as elastic bodies, a
`permanent magnet 3 fixed on the moving element 1, an
`electromagnet 5 fixed on a stationary element 4 opposite to
`[0017] FIG.4 is a view showingacircuit configuration of
`
`the permanent magnet3, and a controller 6 which drives the
`the sensor of FIGS. 3A to 3C.
`moving element 1 by energizing the electromagnet 5. One
`end of each coil spring 2 is connected to the moving element
`1, and the other end ofit is fixed on a wall of a case. The
`moving element 1 can reciprocate in a horizontal direction,
`and the coil springs 2 give the moving element 1 force which
`makes the moving element 1 return to the center of a moving
`range. The electromagnet 5 comprises three magnetic mate-
`rials 50 to 52 spaced uniformly, and coils 55 wound between
`the magnetic materials. When the coils 55 are energized, the
`magnetic material 51 located at the center and the magnetic
`materials 50, 52 located at both ends are magnetized into
`opposite poles. The permanent magnet 3 hasa north pole and
`a south pole along the moving direction of the moving
`element 1, and the distance between the centers of the north
`pole and the south pole is nearly equal to the distance
`between the centers of the adjacent magnetic materials. The
`[0024] FIGS. 11A and 11B are views showing examples
`controller 6 gives an alternating voltage to the coils 55.
`of the control signal.
`Whenapositive voltage is given to the coils 55 by the
`[0025] FIG. 12 is a view showing an alternating voltage.
`controller 6, the magnetic material 51 located at the center
`is magnetized into a north pole and the magnetic materials
`50, 52 located at both ends are magnetized into a south pole,
`respectively, as shown in FIG. 1A, and the moving element
`1 is movedto the left in FIG. LA by magnetic forth acting
`between the magnetic materials 50, 51 and the permanent
`
`[0026] FIGS. 13A to 13C are views showing current
`waveforms.
`
`[0027] FIGS. 14A to 14C are views showing current
`waveforms.
`
`18
`
`18
`
`

`

`US 2005/0275294 Al
`
`Dec. 15, 2005
`
`magnet 3. On the other hand, when a negative voltage is
`given to the coils 55, the magnetic material 51 located at the
`center is magnetized into a south pole and the magnetic
`materials 50, 52 located at both ends are magnetized into a
`north pole, respectively, as shown in FIG. 1B, and the
`moving element 1 is moved to the right in FIG. 1B by a
`magnetic forth between the magnetic materials 51, 52 and
`the permanent magnet 3. While the coils 55 are not ener-
`gized, the moving element 1 is located at the center of the
`moving range by the force of the coil springs 2. The
`resonance system comprising the elastic body (the coil
`spring 2) and the moving element 1 supported by theelastic
`body like this is energy efficient because the moving element
`1 reciprocates while conserving kinetic energy of the mov-
`ing element and elastic energy of the elastic body and
`converting them to each other alternately.
`
`FIG.2 is a block diagram ofthe controller 6. The
`[0040]
`controller 6 is electrically connected to a sensor 7 for
`detecting a behavior of the moving element 1, and comprises
`a current waveform decider 60 which determines a current
`
`waveform necessary for an intended motion of the moving
`element 1 in response to the behavior of the moving element
`1 detected by the sensor7, and an alternating voltage output
`part 61 which applies a voltage to the coil 55 intermittently
`based on a control signal from the current waveform decider
`60 so thal a current in the form of the current waveform
`
`determined by the current waveform decider 60 will flow
`through the coil 55.
`
`[0041] The sensor 7 detects a behavior of the moving
`element 1, such as amplitude, velocity, acceleration, vibra-
`tion force, frequency, and a moving direction, and gives the
`detected information to the current waveform decider 60.
`
`cepted by the moving element 1, and the voltage (Va) of the
`collector becomes high, and the output (Vb) of the com-
`parator (COMP1) becomes low (see a period (Td) in FIG.
`5). On the other hand, when the moving element 1 begins to
`move from the other side toward the center position, the
`light receiving element 72 beginsto receive the light emitted
`from the light emitting element 71 through theslit 10 before
`the moving element 1 reaches the center position(at time 0,
`t2, and t4 in FIG. 5), and the light receiving element 72
`keeps receiving the light until the slit 10 passes the photo
`sensor. While the light receiving element 72 receives the
`light (a period Tv in FIG.5), the voltage (Va) of the collector
`is held at low level, and the output (Vb) of the comparator
`(COMPI)is held at high level. When the slit 10 passed
`through the photo sensor, the light emitted from the light
`emitting element 71 is intercepted by the moving element1,
`and the voltage (Va) of the collector becomes high, and the
`output (vibe) of the comparator (COMP1) becomeslow over
`a half period (a period Tw/2 in FIG. 5). By such an output
`from the comparator (COMP1), the behavior of the moving
`element 1, such as a position, a frequency (1/Tw),a velocity
`of a specific segment (W/Tv), and a moving directionof the
`moving element 1, can be detected (The moving direction
`can be detected by a comparisonofthe lengths of the periods
`Tw/2 and Td).
`[0043] The current waveform decider 60 calculates an
`optimal current waveform for an intended motion of the
`moving element 1 in response to the behavior of the moving
`element 1 detected by the sensor 7. For example, the current
`waveform decider 60 calculates an optimal current wave-
`form for a reciprocating motion of the moving element 1
`with constant amplitude under a resonance condition. The
`driving unit for an electric shaver is required to keep a
`constant amplitude regardless of any external load, and, in
`FIGS. 3A to 3C show one exampleof the sensor 7.
`[0042]
`the resonance system like this, it is most energy efficient
`This sensor 7 is a photo sensor 70 comprising a light
`when the moving element reciprocates under the resonant
`emitting element 71 andalight receiving element 72. In this
`condition where the reciprocating motion of the moving
`case, the moving element 1 has a slit 10 having a width W,
`element is synchronous with a natural frequency determined
`and the light emitting element 71 and the light receiving
`by a mass of the moving element and an elasticity of the
`element 72 are disposed on both sides of the slit 10. As
`elastic body. Therefore,
`it
`is preferable that
`the current
`shown in FIG.4, the light emitting element 71 is constituted
`waveform decider 60 calculates an optimal current wave-
`by a LED1, andthe light receiving element 72 is constituted
`form for the reciprocating motion of the moving element 1
`by a series circuit of a resistance R1 and a phototransistor
`with constant amplitude under a resonance condition. It
`PT1, a series circuit of resistances R2 and R3, and a
`should be noted that, because the vibration force of the
`comparator (COMP1) whose inverting input
`terminal
`is
`moving element1 is decided by magnetic force generated in
`connected to a connection point between the resistance R1
`response to an instantaneous value of the current waveform,
`and a collector of the phototransistor PT1 as well as whose
`determining the current waveform necessary for an intended
`noninverting input terminal is connected to a connection
`motion of the moving element 1 means determining a
`point between the resistance R2 and the resistance R3. As
`vibration force necessary for an intended motion of the
`shown in FIG. 3A, while the light emitted from the light
`moving element 1. Put another way, the current waveform
`emitting element 71 is intercepted by the moving element1,
`decider 60 calculates an optimal vibration force necessary
`the voltage (Va) of the collector of the phototransistor PT1
`for an intended motion of the moving element1 to drive the
`becomeshigh, as shown in FIG. 5, and then the output (Vb)
`moving element 1 efficiently.
`of the comparator (COMP1) becomeslow. And as shownin
`[0044] The current waveform that the current waveform
`FIG. 3B, when the moving element 1 begins to move from
`one side toward the center position and gets to the center
`decider 6 determines includes a phase and an application
`position (amplitude=0)(see at time t1, t3 in FIG.5), the light
`time of the current waveform as well as a shape of the
`current waveform. Thatis, the current waveform decider 60
`receiving element 72 beginsto receive the light emitted from
`the light emitting element 71 through the slit 10. While the
`calculates the phase and the application time of the current
`light receiving element 72 receives the light throughtheslit
`waveform as well as the shape of the current waveform. In
`10 (see a period (Tv) in FIG. 5), the voltage (Va) of the
`a control method for the resonance system,
`the moving
`collector is held at low level, so the output (Vb) of the
`element 1 can be driven efficiently if the coil is energized
`comparator (COMP1)is held at high level. Whenthe slit 10
`after a lapse of a certain period (Tph) from an inversion of
`passed through the photo sensor as shown in FIG. 3C, the
`the moving direction of the moving element 1. Furthermore,
`light emitted from the light emitting element 71 is inter-
`it is important for the control method for a resonance system
`
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`US 2005/0275294 Al
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`Dec. 15, 2005
`
`to give a current to the coil within a half-period of the
`moving element so that the vibration force will not become
`brake force. Therefore,
`the current waveform decider 60
`decides the phase of the current waveform,thatis, the time
`period (Tph) in FIG. 6, and an application time of the
`current waveform,that is, the time period (Ton) in FIG.6,
`as well as a shape of the current waveform, in response to
`the behavior of the moving element 1 detected by the sensor
`7 in order to make the moving element 1 do an intended
`motionefficiently. The moving element 1 can be driven more
`efficiently by controlling the phase and the application time
`of the current waveform in addition to controlling the shape
`of the current waveform.
`
`[0045] FIG. 6 shows one example of the current wave-
`form determined by the current waveform decider 60. The
`current waveform of FIG.6 is a sawtooth current waveform
`
`whose peakis kept low. The current waveform is applied to
`the coil during a certain application time (Ton) after a lapse
`of a certain period (Tph) from time point when the moving
`element 1 passed the maximum amplitude point (Pmax). A
`value of the current and the length of time periods (Tph),
`(Ton) are controlled appropriately in response to the behav-
`ior of the moving element1.
`
`tently during the application time (Ton). As a result, the
`intended current waveform, namely the sawtooth current
`waveform, can flow through the coil 55. The control signal
`may be a shape shown in FIG. 11A,or may be a complex
`waveshape of the shapes of FIG. 11A, as shown in FIG.
`11B.
`
`[0050] Hereinafter, the control method of the alternating
`voltage will be described in detail below. As shownin FIG.
`12, the current waveform decider 60 controls ON-time (T1)
`and OFF-time (T2) of the alternating voltage to be applied
`to the coil 55, respectively, by the control signals $1, $2.
`FIGS. 13A to 131C show a current waveform at the case
`where the ON-time (T1) and the OFF-time (T2) are changed
`respectively within a certain period (T3). As shown in FIGS.
`13A to 13C, the current increases during the ON-time, and
`decreases during the OFF-time. Therefore, the momentary
`current of the coil 55 can be controlled by changing the
`lengths of the ON-time (T1) and the OFF-time (T2), so that
`many kinds of the current waveforms can be formed as
`shown in FIGS. 14A to 14C.
`
`In order to form the intended current waveform
`{0051]
`precisely,
`it
`is preferable that
`the controller 6 predicts
`induced electromotive force generated with the reciprocat-
`ing motion of the moving element 1, and formsthe current
`waveform using the induced electromotive force. If the
`induced electromotive force is not taken into consideration,
`the current flowing through the coil is described by the
`following equation:
`
`[0046] Of course, the shape of the current waveform is not
`limited to the sawtooth current waveform shownin FIG.6.
`Since an optimal current waveform for giving vibration
`force to a resonance system differs depending on a structure
`of the resonance system or a load, the current waveform
`decider 60 determines the current waveform according to the
`structure of the resonance system, the load, the behavior of
`the moving element 1 and so on. Other examples of the
`current waveform are shown in FIGS. 7A to 7E. The current
`waveform shownin FIG.7A is in the form of an isosceles
`conee
`triangle, the current waveform shownin FIG.7B is in the
`1
`form of a half cycle, the current waveform shownin FIG.
`[0052] wherein“i”represents the current, “V,” represents
`7C is in the form ofa trapezoid, the current waveform shown
`alternating voltage, “R” represents a resistive component of
`in FIG. 7D is in the form of a half cycle having ripples, and
`a coil, “L” represents inductance, and “t” represents time.
`the current waveform shown in FIG.7E is in the form of a
`
`jo ae ty
`‘| R
`
`00)
`
`triangle having ripples. These waveforms can be formed by
`a combination of the fundamentals shown in FIG.8.
`
`Thealternating voltage output part 61 is controlled
`[0047]
`by control signals sent from the current waveform decider
`60, and it applies a voltage to the coil 55 intermittently so
`that a current in the form of the current waveform deter-
`mined by the current waveform decider 60 will flow through
`the coil 55.
`
`[0048] FIG. 9 shows one example of a circuit configura-
`tion ofthe alternating voltage output part 61. The alternating
`voltage output part 61 is constituted by a series circuit of
`switching elements Q1 and Q2 each of which is a NPN
`transistor connected between a control voltage (+Vs) and a
`control voltage (-Vs). The coil 55 is connected to a con-
`nection point between the switching elements Q1 and Q2
`and to the ground. The switching elements Q1 and Q2 are
`controlled by the control signals $1, S2 which are inputted
`into each of the base terminals of the switching elements Q1,
`Q2 by the current waveform decider 60.
`
`[0049] FIG. 10 shows a time chart of the control signals
`$1, S2 for forming the sawtooth current waveform shownin
`FIG. 6. As shown in FIG.10, the control signals $1, S2 are
`inputted into the switching elements Q1 and Q2 intermit-
`tently, so that the voltage is applied to the coil 55 intermit-
`
`in actuality, magnetic flux passing
`[0053] However,
`through the coil 55 varies with the movement of the per-
`manent magnet 3 which reciprocates with the moving ele-
`ment 1, so that
`induced electromotive force E will be
`generated, as shown in FIG. 15 (in FIG.15, the coil 55 is
`represented by a series circuit of the inductance L and the
`resistance R.). As the velocity of the moving element 1
`increases, the induced electromotive force E increases, and
`the induced electromotive force peaks when the amplitude
`of the moving element1 is zero, namely, the velocity of the
`moving element 1 reaches a maximum,as shownin FIG.16.
`Therefore, when the induced electromotive force is taken
`into consideration, the voltage V, across the coil 55 becomes
`V,=V,+E (wherein “V,” is a voltage outputted from the
`controller 6), as shown in FIG. 17, and the current flowing
`through the coil is described by the following equation:
`
`R
`
`_ (42)
`is lebt
`
`2)
`
`[0054] As is clear from FIG. 17 and the above equation
`(2), when the induced electromotive force is taken into
`consideration, the current is decreased. Therefore, when the
`controller 6 predicts the induced electromotive force in
`
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`US 2005/0275294 Al
`
`Dec. 15, 2005
`
`response to the behavior of the moving element 1 and forms
`the current waveform using the induced electromotive force,
`the intended current waveform can be formed precisely.
`
`Furthermore,it is also preferable that the controller
`[0055]
`6 predicts inductance or a change of the inductance of the
`coil 55 which varies in response to the position of the
`moving element 1, and forms the current waveform taking
`into consideration the inductance or the change of the
`inductance. FIG. 18 shows a current waveform flowing
`through the coil 55 and the inductance of the inductance of
`the coil 55 in the case where the moving element 1 moves.
`As shown in FIG. 18, the inductanceof the coil 55 varies in
`responseto the position of the moving element 1. Therefore,
`when the controller 6 predicts the inductance or the change
`of the inductance of the coil to form the current waveform,
`the controller 6 can form the intended current waveform
`
`more precisely.
`
`[0056] Also, as is clear from the above equation (2), the
`current flowing through the coil 55 will increase or decrease
`in response to the voltage across the coil 55. Since the
`driving unit of this embodimentis used in theelectric shaver,
`a battery may be used as a powersource. Therefore, in order
`to form the current waveform precisely, it is preferable that
`the controller 6 changes the current waveform in response to
`a power supply voltage (the voltage V in FIG. 15). For
`example, when the power supply voltage is low, the con-
`troller 6 increases the current flowing through the coil 55,
`and when the power supply voltage is high, the controller 6
`decreases the current. By this, the controller 6 can make the
`moving element 1 do an intended motion, for example a
`reciprocating motion with a constant amplitude, without
`relying on the power supply voltage.
`
`the driving unit of this
`[0057] As mentioned above,
`embodiment can give the resonance system optimal vibra-
`tion force which is neither too much nortoolittle for the
`
`intended motion of the resonance system by detecting the
`behavior of the moving element 1 by the sensor 7, and
`determining optimal current waveform for driving the reso-
`nance system by the current waveform decider 60 in
`response to the detected behavior, and outputting the
`momentary current necessary fo