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WO2000044084A2 - Moteur electrique - Google Patents

Moteur electrique Download PDF

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Publication number
WO2000044084A2
WO2000044084A2 PCT/SE2000/000138 SE0000138W WO0044084A2 WO 2000044084 A2 WO2000044084 A2 WO 2000044084A2 SE 0000138 W SE0000138 W SE 0000138W WO 0044084 A2 WO0044084 A2 WO 0044084A2
Authority
WO
WIPO (PCT)
Prior art keywords
acmator
stator
pole
winding
rotor
Prior art date
Application number
PCT/SE2000/000138
Other languages
English (en)
Other versions
WO2000044084A3 (fr
Inventor
Lennart Stridsberg
Original Assignee
Stridsberg Innovation Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from SE9900204A external-priority patent/SE9900204D0/xx
Priority claimed from SE9902726A external-priority patent/SE9902726D0/xx
Priority claimed from SE9902884A external-priority patent/SE9902884D0/xx
Priority claimed from SE9903025A external-priority patent/SE9903025D0/xx
Priority claimed from SE9903784A external-priority patent/SE9903784D0/xx
Priority claimed from SE9904188A external-priority patent/SE9904188D0/xx
Priority claimed from SE9904600A external-priority patent/SE9904600D0/xx
Priority claimed from SE0000068A external-priority patent/SE0000068D0/xx
Priority to US09/889,784 priority Critical patent/US6921999B1/en
Priority to AU23405/00A priority patent/AU2340500A/en
Application filed by Stridsberg Innovation Ab filed Critical Stridsberg Innovation Ab
Publication of WO2000044084A2 publication Critical patent/WO2000044084A2/fr
Publication of WO2000044084A3 publication Critical patent/WO2000044084A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K26/00—Machines adapted to function as torque motors, i.e. to exert a torque when stalled
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
    • G11B5/55—Track change, selection or acquisition by displacement of the head
    • G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
    • G11B5/5552—Track change, selection or acquisition by displacement of the head across disk tracks using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means

Definitions

  • the invention is concerned with electric motors having a very limited rotation, for example in the range of about ⁇ 12°.
  • Such motors are sometimes called galvanometers or rotary actuators.
  • U.S. patent 4,968,909 for Rand H. Hulsing, II discloses an actuator having two wound stator pole pairs in the centre and a soft magnetic rotor that can be attracted to either of the stator pole pairs.
  • the motor is fully symmetric around the rotor shaft. There are three separate windings and no permanent magnets.
  • U.S. 5,270,594 for the same inventor a similar basic design is disclosed.
  • U.S. patent 5,025,201 for Alexander Berger discloses a resolver having a ⁇ 10° range and a stator covering a sector of some 90°. There are no permanent magnets. As is normal for a resolver, there are two static and one moving phase winding, and the magnetic coupling between the moving and the static windings depends on the position of the rotor.
  • U.S. patent 5,038,062 for Manabu Shiraki discloses what can be described as an inverted voice coil arrangement.
  • a rotor having one or two flat coils located in the same plane moves in an air gap with an axial magnet field generated by two stator magnet sets.
  • the magnets face a smooth back iron over a radial air gap that is approximately of the same length in the direction of flux as are the permanent magnets and the single or dual rotor coil(s) move in this air gap.
  • the magnet sets are parallel to the rotor movement plane.
  • U.S. patent 5,038,062 a rotor with one magnet moves between two stator flat coil pairs parallel to the rotor movement plane.
  • the rotor magnet causes an axial flux in the air gap, and the flat coils are inserted in this air gap.
  • the four coils are connected to the same phase.
  • the published Japanese patent application 2-074143 for Fujitsu, inventor Hiroshi Maeta. discloses a design of a rotary actuator that also can be described as an inverted voice coil arrangement.
  • the magnets are moving also in this design but the air gap flux is radial.
  • the coils are inserted in the air gap between the moving magnets and a smooth back iron.
  • the basically two coils are static, and all coils are connected to the same phase.
  • the published European patent application 0 127 058 for BASF, inventors Klaus Manzke et al. discloses a similar arrangement having two coils in the radial air gap between four magnets and a smooth back iron. The two coils are connected to the same phase.
  • the published German patent application 19 816 201 for Seiko Instruments, inventors Takashi Ishida et al. discloses a rotary actuator having a rotor carrying permanent magnets creating a flux in the radial direction. Around the rotor at least two ironless coils are arranged. The coils are either wound around a common non-magnetic structure (for example made of a thermoplastic) or wound one by one and inserted in slots in a nonmagnetic stator coil fixture. All coils are connected to the same phase. The stator and rotor are symmetric around the shaft and covers a 360° sector.
  • U.S. patent 5,557, 152 for Raymond G. Gauthier discloses a rotary actuator having one or two coils in the stator.
  • Both coils are connected to the same phase.
  • the rotor carries one or two permanent magnets and the flux in the air gap is axial.
  • the rotor also carries the back iron required by these magnets.
  • stator poles made of a magnetically highly permeable material, and the stator coils are placed around these stator poles.
  • the design shown uses a very large air gap (about 2.5 mm) to reduce the otherwise enormous cogging torque that is inherent in the design.
  • An object of the invention is to provide a compact actuator having a high output power/loss ratio. Another object of the invention is to provide a compact actuator using feedback and having a low total length.
  • Another object of the invention is to provide an actuator that combines a thin air gap with a very low cogging torque. Another object of the invention is to provide an actuator comprising both a low inductance and a high motor constant and thus permitting a fast response.
  • Another object of the invention is to provide an actuator having both a low inductance and a high motor constant and thus permitting a fast response so that a low exciting voltage can create a fast current change resulting in a fast change of torque.
  • Another object of the invention is to provide an actuator system having both a low resistance, to permit low losses, and a short time constant, to permit a fast response.
  • Another object of the invention is to provide an efficient and compact actuator having a single phase winding and thus having a reduced required current bandwidth.
  • a single phase motor can in principle make a full step move with a single period of current change (as shown for example in conjunction with the discussion of Figs. 13a - 13e below), whereas a polyphase motor requires several periods (the motor shown in the cited Japanese application 61-124254 seems to require some 10 full periods for a full range step).
  • a single phase motor can therefore perform faster and achieve more precisely controlled movements for a given inductance and excitation voltage.
  • an electromagnetic rotary actuator is driven or controlled by a single voltage.
  • the actuator comprises a rotor which can move about an axis and which has a permanent magnet or permanent magnets comprising at least two pairs of radially located north-south poles.
  • the actuator further comprises a stator having pole teeth carrying at least one winding, the pole teeth preferably have the same angular pitch as the pairs of north- south poles of the permanent magnet(s).
  • An airgap is formed between facing surfaces of the permanent magnets and of the pole teeth, these facing surfaces being located close to each other to create a small airgap, which can be smaller than 0.5 mm and preferably smaller than 0.3 mm.
  • the permanent magnets are arranged, so that the magnetic flux lines derived therefrom extend in the airgap substantially in a radial direction from or towards the axis.
  • the airgap has a shape substantially corresponding to part of a cylindrical shell.
  • the stator is made of a magnetically permeable material, in particular a soft-iron material, and always has at least three pole teeth.
  • the at least one winding is applied around a central one of the pole teeth.
  • the actuator can comprise only three pole teeth and then the pole teeth can be arranged within an angle, taken from the axis, of at most somewhat more than a third of a full turn, in particular within an angle smaller than 140° or preferably smaller than 130°. In the case where the actuator comprises only five pole teeth the pole teeth can be arranged within an angle of at most somewhat more than half a full turn, in particular within an angle smaller than 225°.
  • a first angular sector between the two outmost ends of the stator pole parts which face the air gap can be substantially equal or advantageously wider than the sum of the angular range of the rotor movement, i.e. the peak to peak movement of the rotor, and the angular sector between the two outmost ends of the rotor magnet pole parts facing the air gap.
  • the angular sector between the two ends of a stator pole part facing the air gap can be longer than the sum of the peak to peak movement of the rotor and the angular sector from an end of the rotor magnet pole part facing the air gap and the nearest end of the adjacent rotor magnet pole part facing the air gap.
  • the normally part-cylindrical surface of at least one stator pole part such as the outer-most pole part which faces the rotor magnet pole parts to create the air gap can have an adjusted shape to reduce the cogging torque of the actuator, such as have a portion located outside said part-cylindrical surface, to reduce cogging torque of the actuator.
  • Each of the stator poles carrying winding coils can have a reduced height in the axial direction at places of the stator pole where the winding coil is located, thereby permitting a portion of the stator pole located at the airgap and at a radially inner surface of the stator pole to be longer in the axial direction than a portion of stator pole located inside the stator pole winding.
  • This special design of the stator poles can also be used in many other conventional electromagnetic rotary machines such as controllable polyphase motors and step motors.
  • An electronic circuit suitable for driving a single phase rotary actuator such as those of the kind described herein but also other devices of similar kinds, particularly an actuator having a long electric time constant, is then connected to a winding or windings of the actuator and has resistance changing means which are adapted to increase a resistance in series with the actuator winding or the series resistance of the actuator winding when a longer electric time constant is advantageous or required and to reduce the resistance in series with the actuator winding or the series resistance of the actuator winding when a short electric time constant is advantageous or required.
  • the resistance changing means can the advantageously comprise a first bridge leg directly connected to a terminal of the actuator winding and a second bridge leg connected through a resistor to the same terminal of the actuator coil.
  • the resistance changing means can comprise means for varying the impedance or resistance of a resistor of the type having controllable resistances such as MOSFETs. Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS
  • Fig. 1 is a schematic axial view of an electric rotary actuator having three stator poles, only one of which carries a winding, and an incremental encoder,
  • Fig. 2 is a view similar to that of Fig. 1 of an electric rotary actuator having five stator poles carrying windings, an analog tachometer and an incremental encoder,
  • FIG. 3 is a schematic axial view of a hard disc drive head actuator having five stator poles only three of which carrying winding,
  • - Fig. 4 is a view similar to that of Fig. 3 of a hard disc drive head actuator having three stator poles which all carry windings
  • - Fig. 5a is a fragmentary view of only the actuator of Fig. 4,
  • Fig. 5b is a sectional view taken along the line A-A of Fig. 5a
  • - Fig. 6a is a fragmentary view similar to that of Fig. 5a of a hard disc drive head actuator having three stator poles only a central one of which carries a winding and has a reduced height where the winding is located
  • - Fig. 6b is a sectional view taken along the line A-A of Fig. 6a,
  • Figs. 7a - 7e are time diagrams of speed, position, current, voltage and resistive loss respectively for a long step for a voice coil motor
  • - Figs. 8a - 8e are time diagrams of speed, position, current, voltage and resistive loss respectively for a short step for a voice coil motor
  • - Fig. 9 is a sectional view of an electric rotary actuator having short rotor magnets and three thin stator coils that fits into a single piece stator of laminated steel having five stator poles two of which thus do not carry any winding
  • - Fig. 10 is a schematic view similar to that of Fig. 9 showing the stator during assembly of the three coils
  • - Fig. 11a is a circuit diagram of a partly linear control electronic system for an actuator according to Fig. 9,
  • Fig. lib is a circuit diagram of another partly linear control electronic system for an actuator according to Fig. 9,
  • Fig. l ie is a circuit diagram of a switched control electronic system for a motor according to Fig. 9.
  • Figs. 12a - 12e are time diagrams of speed, position, current, voltage and resistive loss respectively for a long step for the actuator shown in Fig. 9 using conventional electronic drive circuits,
  • Figs. 13a - 13e are time diagrams of speed, position, current, voltage and resistive loss respectively for a high speed, long step for the actuator shown in Fig. 9 using more complex electronic drive circuits,
  • - Figs. 14a - 14e are time diagrams of speed, position, current, voltage and resistive loss respectively for a short step for the actuator shown in Fig. 9 using more complex electronic drive circuits
  • - Fig. 15 is a fragmentary axial view of an actuator having rectangular section magnets and an arrangement to reduce cogging torques
  • Fig. 16 a schematic view similar to that of Fig. 9 showing an actuator having five stator poles, two of which carry no windings, and a rotor carrying a single, specially magnetized permanent magnet having the shape of a cylindrical shell that is magnetised to have four magnet poles.
  • Fig. 1 a basic torque producing arrangement in an electric rotary actuator is shown.
  • the rotor 101 is rotatable around an axis 101' and carries two permanent magnets at its peripheral surface.
  • the rotor magnets are magnetised radially to have opposing polarities, as also shown in the embodiment of Fig. 2 to be discussed below. This means that if one permanent magnet has its north pole distant from the axis 101' the adjacent permanent magnet or magnets have their south pole located distant from the axis.
  • Three pole pieces 103, 104, 105 form a stator and they all have an identical shape, only the center pole carrying a winding or coil 102.
  • the pole pieces have substantially a T- shape with a web portion projecting towards said axis and two arms joined to the web at the end thereof distant of the axis. Arms of adjacent pole pieces are joined to each other or abut each other.
  • the low portion of the web, located closer to the axis carries small triangular peripheral projections, the free edges of these projections being located close to each other for adjacent pole pieces.
  • the coil 102 is wound around a portion of the web of the central pole piece which has a uniform width, located between the arms and the triangular projections.
  • a narrow airgap is formed, which has the shape of thin part-cylindrical shell having a uniform thickness.
  • the inner surfaces of the webs and the facing outer surfaces of the permanent magnets all have part-cylindrical shapes.
  • the permanent magnets can advantageously be made of a high energy material like FeNdB.
  • the rotor magnet poles have the same angular pitch as the stator poles. In Fig. 1, the pitch 108 is 26°.
  • the angular range of the movement 107 of the rotor from its centre position to any of its two end or extreme positions is 9°, i.e. its movement is from the centre position corresponding to 0° to the left end position at -9° and to the right end position at +9°.
  • the angular half-width 109 of the magnet poles (10.6°) is larger than the maximum rotor displacement 107 (9°) from its centre position.
  • margin 110 of (78-47.2)/2 15.4° from the outmost ends of a stator pole to the outmost end of the adjacent rotor pole.
  • the maximum rotor movement 107 is 9° in either direction from the centre position, there will always be a sector of a stator pole on both sides of each rotor magnet.
  • Fig. 1 the two extreme rotor positions, i.e. its left-most and right-most positions, are indicated by the thin contour lines 112 and 113. This geometry reduces cogging torque.
  • the centre stator pole 104 will always face at least a small pan of two rotor magnet poles. With the rotor 101 in the central position shown in Fig. 1. the total magnetic flux through the stator winding 102 will be zero as shown by the drawn flux lines. If the rotor
  • an optical receiver By attaching an encoder disc segment, not shown, to the rotor 101, an optical receiver
  • sensing the position of the segment can give encoded signals from which the position of the device can be determined.
  • Fig. 2 shows another embodiment of a rotary actuator having five stator poles 201 - 205 of the same basic shape as in Fig. 1 which all carry windings.
  • the rotor 206 then 5 carries four permanent magnets, one less than the number of stator poles, the magnets having, as indicated above, alternating magnetization directions, as seen when passing peripherally over the rotor.
  • the total flux through the stator windings of poles 201 and 205 will be 50% of the maximum value and the flux through the three central poles 202 - 204 will be zero as already illustrated for Fig. 0 1.
  • an optical receiver 207 sensing the position of the segment can give encoded signals from which the angular position of the rotor can be determined.
  • an analog tachometer signal can be obtained from which also the position of the rotor can be determined.
  • a hard disc drive head actuator is shown.
  • the disc head(s) for reading/writing the tracks on the disc(s) are mounted at the point(s) of the arm(s) 301 which can sweep over a 25° sector that covers the active surface of the disc(s) 302.
  • the disc rotates around a central motor 303.
  • the arm is moved by a motor/ actuator of the basic type as discussed above having five stator poles, the three central ones of which (like 306) carry windings and the two remaining extremal or outer poles (like 305) are unwound.
  • the four permanent rotor magnets 308 are mounted on two soft-iron pans like 307 attached to the arm at the rotary axis thereof.
  • the two unwound poles like 305 will reduce the stray flux from the coils of the wound stator poles.
  • Fig. 4 another embodiment of a hard disc drive head actuator is shown.
  • the disc head arm is moved by a motor/actuator having three stator poles two (405) of which are wound with a coil like 404 having a smaller cross-sectional area.
  • the centre pole 406 is wound with a coil 409 having a larger cross-sectional area.
  • the centre 409 coil has a cross-sectional area corresponding to 1.4 times the cross-sectional area of anyone of the side coils like 404, but can advantageously have a number of winding turns corresponding to 2.9 times the winding turns of each of the side coils. All three coils can be connected in series to be all energized by the same single-phase voltage.
  • the stator shown consists of five parts, the two side poles like 405, the centre pole 406 and two back iron parts like 410. This arrangement permits the poles 405 - 406 to be inserted into already wound coils.
  • the five pans are then assembled together.
  • the five pans can be made as laminations of punched electric steel, possibly using oriented steels.
  • Figs. 5a. 5b the actuator of Fig. 4 is shown in two projections.
  • the permanent magnets 408 and soft magnetic pans like 407, 405, 410 and 406 all have the same height, the height being measured parallel to the rotational axis; the total height of the actuator is given by the coils like 409.
  • FIGs. 6a, 6b two projections of another embodiment of a hard disc drive head actuator is shown.
  • This embodiment has like the actuator of Figs. 4 - 5b three stator poles one of which is wound and has a reduced height at the web ponion where the winding is located.
  • the two outer poles like 602 have the same height as the rotor magnets and the back iron 601.
  • the outer pans of the wound pole has also the same height 611 as the rotor magnets and back iron 601, so that only the portion inside the coil 609 has a reduced height 610.
  • the coil 609 is slightly higher than the height 611 of the permanent and soft iron pans to permit a direct contact with the top 613 and bottom 612 of the hard disc drive enclosure.
  • the soft iron pans 602 of the stator will flow practically parallel to the plane of the upper projection, they can advantageously be made from laminated electric steel.
  • the soft iron pan 601 of the rotor can be solid.
  • the flux moves in three dimensions and these parts can be made of compressed soft iron powder to reduce eddy currents.
  • they can be made of laminated steel.
  • Yet another alternative is to have the thinner part inside the coil made of a laminated FeCo-alloy and the outer parts of a soft iron metal powder.
  • Fig. 6 permits the use of a larger air gap flux, since it carries basically the same flux intensity but has a larger area due to the higher magnets, and a winding having a low resistance.
  • Conventional hard disc drives often use voice coil head actuators .
  • Such actuators have a coil similar to the tachometer coil 210 shown in Fig. 2.
  • the coil is rigidly connected to the disc head arm.
  • the magnets are fixed to the hard disc chassis.
  • the coil is therefore thermally insulated from the chassis by air gaps.
  • a voice coil actuator from a 100 x 145 x 23 mm hard disc drive was partly disassembled and measured.
  • the motor constant was measured to 0.139 Vs/radian, the voice coil inductance amounted to 3.7 mH and the coil resistance to 36.8 Ohms.
  • the inertia of the rotor of the voice coil actuator was estimated to 19.0 g-cm 2 and the inertia of the disk head arm was assumed to be 19.5 g-cm 2 .
  • Figs. 7a - 7e show time diagrams for the prior art disc drive motor described in the preceding paragraph.
  • the actuator is assumed to be driven by a voltage of + 11 V during acceleration and by -11 V during the retardation phase.
  • the movement shown is large: 0.2 radians are close to half the total movement range of the disk head arm.
  • the vertical scale of all Figs. 7a - 7e are normalised to the same peak-to-peak range.
  • Fig. 7a shows the angular speed.
  • Fig. 7b shows the angular distance travelled.
  • Fig. 7c shows the actuator coil current where the thin horizontal line represents zero current
  • Fig. 7d shows the acmator coil voltage
  • Fig. 7e shows losses due to the resistance of the acmator coil and serial resistors such as 1103. 1104 or 1121 of Figs. 11a. l ib or l ie to be described below.
  • Figs. 8a - 8e show similar diagrams for a short step of 0.004 radian (approximately 1 % of the total movement possible) for the prior art disc drive acmator described above.
  • Fig. 9 shows a hard disc drive head actuator similar to the one shown in Fig. 3.
  • the motor/ acmator has five stator poles, three of which 902 - 904 are wound and two of which 901 and 905 are unwound. Thus, there are three coils 906 - 908 shown as cross sections 906a - 908b.
  • the four permanent magnets such as 909 and 910 are mounted on a ferromagnetic (soft-iron) rotor support 912.
  • the acmator has been designed for a 2x12.5° peak-to-peak movement range. As each permanent magnet has an angular extension of 14.3°, each of the three centrally located magnets will for any rotor position simultaneously face pans of two rotor magnets.
  • the coils are thin, most of the height of the motor/actuator can be occupied by the laminated stator, thus permitting a relatively high rotor and high magnets and consequently a large torque constant.
  • the coils can be lightly pressed between the upper and lower disc drive encasement, not shown, and the stator lamination, thus permitting a low thermal impedance between the coils and the disc drive chassis.
  • FIG. 10 Another advantage of using thin coils is that they can be inserted around a stator pole through the air gap between adjacent poles as illustrated in Fig. 10. This permits a low assembly cost. It also permits the production of the whole stator as one single laminated part or unit.
  • the windings of the acmator have been adjusted to give the same motor constant as tor the voice coil acmator.
  • the inductance then becomes 3.3 mH (slightly less than for the voice coil acmator) and the resistance 3.66 Ohm, less than 10% of that of the voice coil acmator.
  • the rotor inertia is somewhat larger than that of the voice coil acmator, 27 g-cm .
  • Fig. 11a a diagram of an example of an electronic circuit suitable to drive an acmator according to Fig. 9 is shown.
  • the stator coils connected in series with each other are represented by the single coil 1101.
  • a first end of the combined coil is connected to the output terminal of a linear amplifier 1102 delivering the current controlling the current in the coil for positioning the rotor of the acmator in accordance with the current.
  • the other, second end of the combined acmator coil is through a first resistor 1103 and a first switch 1105 connected a positive supply or drive voltage of e.g. 12 V and through a second resistor 1104 and a second switch 1105 connected the ground potential.
  • the same end of the combined acmator coil is further through a third switch 1107 connected the positive supply voltage and through a fourth switch 1108 connected the ground potential.
  • the third and fourth switches are connected in parallel with diodes 1109, 1110 respectively.
  • the first end of the combined acmator coil is also connected to the supply voltage and the ground potential through diodes 1111, 1112 respectively.
  • a capacitor 1122 connects the line carrying the supply voltage with the ground potential.
  • the first and second switches 1105, 1106 can be called the high resistance switch set and the third and fourth switches 1107, 1108 together with their diodes 1 109. 1 1 10 connected in parallel a low resistance switch set.
  • the time constant is much longer.
  • the elements 1 107 - 1110 are deactivated and one or both of the two switches 1105 and 1106 are activated, the two resistors 1103 and/or 1104 will be connected in series with the motor coil 1101. Thereby the total resistance can be increased to give a time constant similar to that of a voice coil motor, which simplifies ⁇ o control of the current to be delivered to the coil in the final phase of positioning the rotor of the acmator.
  • a high motor resistance is only a disadvantage.
  • one of the switches 1107 or 1 108 can be enabled.
  • a movement can be initiated by setting the linear amplifier output to + 11.3 V and enabling is switch 1108, thus giving some 1 1 V over the combined acmator coil 1101.
  • the diodes 1111 and 1 112 permit a slow decay of the current through the acmator if the linear amplifier 1102 is set to have a high impedance output stage; current driven by the acmator coil inductance can then pass for example the switch 1108 and the diode 1112, thus meeting a low voltage.
  • An example of the operation is given in Fig. 13 which will be discussed below.
  • Fig. l ib shows a diagram of another example of a switched electronic circuit suitable to drive an acmator of the kind illustrated in Fig. 9 using a higher voltage for the low resistance switch set.
  • the higher voltage is generated by elements 1125 and 1126 which can be inductively or capacitively switched voltage multipliers.
  • the first resistor 1104 and the first switch 1105 are here also connected in series with a diode 1127 and the second resistor
  • the special elements 1125, 1126 have first terminals connected to the supply voltage line and the ground potential line respectively. Their opposite, second terminals then have voltages being somewhat more positive or somewhat more negative than the supply voltage and the ground potential respectively. To these second terminals are the third and fourth switches 1107, 1108 and
  • Fig. l ie shows a diagram of another example of a switched electronic system suitable to drive an acmator of the type shown in Fig. 9. It is generally a conventional H-bridge
  • the first and second resistors are here replaced by a single resistor 1121, which is thus at one end connected to the second of the coil 1101.
  • the other end of the resistor is connected to the supply line through a combination of a switch 1117 connected in parallel with a diode 1119 and to the ground line through a combination of a ⁇ o switch 1118 connected in parallel with a diode 1120.
  • the diodes 1115, 1116 in the lines connecting the first end of the coil 1001 to the supply line and the ground line are here connected in parallel with switches 1113, 1114.
  • one of the switches 1107 or 1108 can be enabled.
  • a movement can be initiated by enabling switches 1113 and 1108, thus giving is almost the full supply voltage over the combined acmator coil 1101.
  • the time constant of the acmator can be increased by disabling the switches 1107, 1108 connected directly to the second end of the coil and enabling the switches 1117, 1118 connected to the same end through the resistor 1121. Assuming that the current is low enough, the voltage caused by the acmator coil current
  • Figs. 11a - l ie only show examples of many possible alternative drive circuits.
  • the switches shown have bipolar transistor symbols; obviously any fast switch can be used.
  • the extra resistance used to reduce acmator time constant is shown as discrete resistors and
  • Figs. 12a - 12e show time diagrams for the actuator of Fig. 9 for the same step as that used for a voice coil acmator having the time diagrams of Figs. 7a - 7e.
  • the acmator is run with a constant resistance.
  • a possible driving circuit could then correspond to that of Fig.
  • Figs. 13a - 13e show time diagrams for the acmator of Fig. 9 for the same step as that used for a voice coil acmator having the time diagrams of Figs. 7a - 7e.
  • the diagrams illustrate the step time reduction which can be obtained using the acmator of Fig. 9 driven by the circuit shown in Fig. 11a.
  • the acmator is in this case run with an added resistance during the final positioning phase.
  • the driving voltage shown in Fig. 13d is positive, for example by having the linear power amplifier starting at + 11.3 V and having the switch 1108 enabled.
  • the current is driven by the energy in the acmator inductance and passes the switch 1108 and the diode 1112.
  • the acmator is accelerating even though no energy is supplied from the supply. This shows one of the advantages of providing a low resistance acmator coil.
  • the driving voltage is reversed and a negative current is increasing.
  • the energy stored in this way is then used with another phase of low driving voltage, switch 1 107 and diode 1111.
  • an extra resistance is connected by enabling switches 1105 and 1106 and disabling the two switches 1107 and 1 108.
  • the acmator current and the speed reach zero at the same time.
  • the time constant of the current is in this case much shorter.
  • the time constant of the acmator is similar to that of the prior art voice coil motor, and should also permit the same ease of control as prior art voice coil motors.
  • the driving voltage from the amplifier is only 0.5 V . This is arranged as a linear amplifier output of 6.5 V at the left end of the combined coil 1101 and 6.0 V in series with the parallel value of resistors 1103 and 1104 in the other end.
  • Figs. 14a - 14e show time diagrams for the acmator of Fig. 9 for the same short step as that used for a voice coil acmator as illustrated by the diagrams of Figs. 8a - 8e, see the discussion of Fig. l ib.
  • the acmator as depicted in Fig. 9 has been laid out rather randomly, and its winding has been selected to have the same motor constant as that of a randomly selected prior art voice coil acmator. Depending on the driving policy used, it permits a significant reduction of step time or of power consumption.
  • the improvement in the most critical parameter can probably be far larger than what has been shown above.
  • Fig. 15 shows a section through an actuator similar to that of Fig. 9 having non-cylindrical pole surfaces to reduce cogging torque.
  • the surface 1501 of an outermost stator pole 905 (and 901) is non-cylindrical.
  • the thin dotted line 1502 represents a cylindrical pole surface having the same radius as that of the adjacent, more centrally located pole 904.
  • Fig. 15 also shows magnets having a rectangular cross-section; it is often less expensive to produce such magnets than magnets having one side shaped as a circle segment as shown in the other figures.
  • the rectangular shape gives a slightly lower torque. o
  • the arrangement to reduce cogging torque is applicable also for other magnet shapes.
  • Fig. 16 an acmator is shown which has the magnet poles integrated in a single cylinder segment magnet.
  • the hard disc head acmators of Figs. 3. 4 and 9 permit the lower part of the acmator 5 coils to be in direct contact with the hard disc chassis.
  • the upper part of the coils can be in thermal contact with the hard disc outside case.
  • the torque available for a given copper loss 0 is also significantly higher than for conventional voice coil acmators. Combined, this permits significantly faster head accelerations.
  • the acmators described above are compact and have a high output power/loss ratio, in particular as compared to conventional voice coil acmators. Even though the embodiment shown in Fig. 9 uses coils having a very thin cross section and has the same dimensions and 5 the same motor constant as a conventional voice coil motor, the resistance is less than 10% of that of the voice coil motor. This permits more than three times more current at the same copper loss.
  • the hard disc head acmators illustrated in Figs. 3, 4 and 9 permit the upper and lower part of the acmator coils to be in direct contact with available heat sinks such as a hard disc chassis. This permits a very low thermal resistance to the ambient air.
  • the acmators described above also have a high flux density in the air gap. Assuming that all other factors are equal, a higher air gap flux increases efficiency. As can be seen for example in Fig. 2, the flux will pass only a thin air gap; the remaining flux path consists of soft iron or permanent magnets.
  • acmators described above combine a thin air gap with a very low cogging torque. This is primarily obtained by the inherently magnetically balanced design and is further improved by the compensation arrangement described with reference to Fig. 15.
  • the acmators described above have both a low inductance and a high motor constant thus permitting a fast response.
  • the improvement over a voice coil motor is small at very small currents and increases with current. This results from the fact that much of the excitation voltage is lost in the resistive voltage over the high resistance of a voice coil motor.
  • acmator systems as described above have both a low resistance giving low losses and a short time constant permitting a fast response, this being achieved when driving the acmators by the circuits depicted in Figs. 11a - l ie.
  • the invention can be modified in many ways.
  • the number of poles can be increased. This will however increase the complexity and (for a given volume) reduce the air gap radius and the copper area of the coils.
  • the rotor magnets can alternatively be placed on the periphery with the stator coils close to the centre. However, this will increase inertia. While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous additional advantages, modifications and changes will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative devices and illustrated examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within a true spirit and scope of the invention.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)

Abstract

L'invention concerne un actionneur rotatif électromagnétique entraîné par une tension monophasée. Des aimants permanents disposés sur un rotor interagissent, par l'intermédiaire d'un petit entrefer partiellement cylindrique, avec un stator en fer doux pourvu de dents polaires portant au moins un enroulement (906a, 906b; 907a, 907b; 908a, 908b), de façon à faire tourner le rotor à l'intérieur d'une plage angulaire limitée, l'entrefer possédant une densité de flux élevée. Les enroulements sont disposés autour des dents polaires centrales. Les aimants permanents et les pôles du stator ont le même pas angulaire. L'actionneur est compact, avec une faible longueur totale, et a un rapport puissance de sortie/pertes élevée qui lui permet de réagir rapidement. On peut lui donner une faible résistance thermique par rapport à une enceinte ou un boîtier en mettant les enroulements en contact mécanique direct avec ces derniers.
PCT/SE2000/000138 1999-01-21 2000-01-21 Moteur electrique WO2000044084A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU23405/00A AU2340500A (en) 1999-01-21 2000-01-21 An electric motor
US09/889,784 US6921999B1 (en) 1999-01-21 2000-01-21 Electric motor

Applications Claiming Priority (16)

Application Number Priority Date Filing Date Title
SE9900204A SE9900204D0 (sv) 1999-01-21 1999-01-21 Electric motor
SE9900204-0 1999-01-21
SE9902726A SE9902726D0 (sv) 1999-07-14 1999-07-14 Electric motor
SE9902726-0 1999-07-14
SE9902884A SE9902884D0 (sv) 1999-08-10 1999-08-10 "Electric motor"
SE9902884-7 1999-08-10
SE9903025A SE9903025D0 (sv) 1999-08-25 1999-08-25 "Electric motor"
SE9903025-6 1999-08-25
SE9903784-8 1999-10-17
SE9903784A SE9903784D0 (sv) 1999-10-17 1999-10-17 Electric motor
SE9904188-1 1999-11-17
SE9904188A SE9904188D0 (sv) 1999-11-17 1999-11-17 Electric motor
SE9904600A SE9904600D0 (sv) 1999-12-12 1999-12-12 Electric motor
SE9904600-5 1999-12-12
SE0000068A SE0000068D0 (sv) 2000-01-09 2000-01-09 Electric motor
SE0000068-7 2000-01-09

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WO2000044084A3 WO2000044084A3 (fr) 2000-11-02

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SG106624A1 (en) * 2000-09-27 2004-10-29 Seagate Technology Llc Magnetless actuator for disc drive
WO2005071817A1 (fr) 2004-01-23 2005-08-04 Heinz Leiber Moteur segmente
US7025774B2 (en) 2001-06-12 2006-04-11 Pelikan Technologies, Inc. Tissue penetration device
US7198606B2 (en) 2002-04-19 2007-04-03 Pelikan Technologies, Inc. Method and apparatus for a multi-use body fluid sampling device with analyte sensing
US7229458B2 (en) 2002-04-19 2007-06-12 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7232451B2 (en) 2002-04-19 2007-06-19 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7244265B2 (en) 2002-04-19 2007-07-17 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7291117B2 (en) 2002-04-19 2007-11-06 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7297122B2 (en) 2002-04-19 2007-11-20 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7331931B2 (en) 2002-04-19 2008-02-19 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7371247B2 (en) 2002-04-19 2008-05-13 Pelikan Technologies, Inc Method and apparatus for penetrating tissue
US7374544B2 (en) 2002-04-19 2008-05-20 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7410468B2 (en) 2002-04-19 2008-08-12 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7485128B2 (en) 2002-04-19 2009-02-03 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7491178B2 (en) 2002-04-19 2009-02-17 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7524293B2 (en) 2002-04-19 2009-04-28 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7547287B2 (en) 2002-04-19 2009-06-16 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7563232B2 (en) 2002-04-19 2009-07-21 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7648468B2 (en) 2002-04-19 2010-01-19 Pelikon Technologies, Inc. Method and apparatus for penetrating tissue
US7674232B2 (en) 2002-04-19 2010-03-09 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7717863B2 (en) 2002-04-19 2010-05-18 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7901362B2 (en) 2002-04-19 2011-03-08 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US8267870B2 (en) 2002-04-19 2012-09-18 Sanofi-Aventis Deutschland Gmbh Method and apparatus for body fluid sampling with hybrid actuation
US9034639B2 (en) 2002-12-30 2015-05-19 Sanofi-Aventis Deutschland Gmbh Method and apparatus using optical techniques to measure analyte levels
US9072842B2 (en) 2002-04-19 2015-07-07 Sanofi-Aventis Deutschland Gmbh Method and apparatus for penetrating tissue
US9089294B2 (en) 2002-04-19 2015-07-28 Sanofi-Aventis Deutschland Gmbh Analyte measurement device with a single shot actuator
US9248267B2 (en) 2002-04-19 2016-02-02 Sanofi-Aventis Deustchland Gmbh Tissue penetration device
US9261476B2 (en) 2004-05-20 2016-02-16 Sanofi Sa Printable hydrogel for biosensors
US9427532B2 (en) 2001-06-12 2016-08-30 Sanofi-Aventis Deutschland Gmbh Tissue penetration device
US9561000B2 (en) 2003-12-31 2017-02-07 Sanofi-Aventis Deutschland Gmbh Method and apparatus for improving fluidic flow and sample capture
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US9724021B2 (en) 2002-04-19 2017-08-08 Sanofi-Aventis Deutschland Gmbh Method and apparatus for penetrating tissue
US9795747B2 (en) 2010-06-02 2017-10-24 Sanofi-Aventis Deutschland Gmbh Methods and apparatus for lancet actuation
US9820684B2 (en) 2004-06-03 2017-11-21 Sanofi-Aventis Deutschland Gmbh Method and apparatus for a fluid sampling device
US9839386B2 (en) 2002-04-19 2017-12-12 Sanofi-Aventis Deustschland Gmbh Body fluid sampling device with capacitive sensor
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US7258693B2 (en) 2002-04-19 2007-08-21 Pelikan Technologies, Inc. Device and method for variable speed lancet
US9314194B2 (en) 2002-04-19 2016-04-19 Sanofi-Aventis Deutschland Gmbh Tissue penetration device
US7141058B2 (en) 2002-04-19 2006-11-28 Pelikan Technologies, Inc. Method and apparatus for a body fluid sampling device using illumination
WO2004112602A1 (fr) 2003-06-13 2004-12-29 Pelikan Technologies, Inc. Procede et appareil pour dispositif d'analyse sur le lieu de soin
US8282576B2 (en) 2003-09-29 2012-10-09 Sanofi-Aventis Deutschland Gmbh Method and apparatus for an improved sample capture device
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US9775553B2 (en) 2004-06-03 2017-10-03 Sanofi-Aventis Deutschland Gmbh Method and apparatus for a fluid sampling device
US9386944B2 (en) 2008-04-11 2016-07-12 Sanofi-Aventis Deutschland Gmbh Method and apparatus for analyte detecting device
US9375169B2 (en) 2009-01-30 2016-06-28 Sanofi-Aventis Deutschland Gmbh Cam drive for managing disposable penetrating member actions with a single motor and motor and control system
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US9248267B2 (en) 2002-04-19 2016-02-02 Sanofi-Aventis Deustchland Gmbh Tissue penetration device
US9907502B2 (en) 2002-04-19 2018-03-06 Sanofi-Aventis Deutschland Gmbh Method and apparatus for penetrating tissue
US7232451B2 (en) 2002-04-19 2007-06-19 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US9498160B2 (en) 2002-04-19 2016-11-22 Sanofi-Aventis Deutschland Gmbh Method for penetrating tissue
US9839386B2 (en) 2002-04-19 2017-12-12 Sanofi-Aventis Deustschland Gmbh Body fluid sampling device with capacitive sensor
US7229458B2 (en) 2002-04-19 2007-06-12 Pelikan Technologies, Inc. Method and apparatus for penetrating tissue
US7226461B2 (en) 2002-04-19 2007-06-05 Pelikan Technologies, Inc. Method and apparatus for a multi-use body fluid sampling device with sterility barrier release
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US9034639B2 (en) 2002-12-30 2015-05-19 Sanofi-Aventis Deutschland Gmbh Method and apparatus using optical techniques to measure analyte levels
US10034628B2 (en) 2003-06-11 2018-07-31 Sanofi-Aventis Deutschland Gmbh Low pain penetrating member
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