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US3783311A - Magnetic device for use in acoustic apparatus - Google Patents

Magnetic device for use in acoustic apparatus Download PDF

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Publication number
US3783311A
US3783311A US3783311DA US3783311A US 3783311 A US3783311 A US 3783311A US 3783311D A US3783311D A US 3783311DA US 3783311 A US3783311 A US 3783311A
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Prior art keywords
magnetic
pole
center
gap
yoke
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
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Inventor
T Sato
T Ebihara
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SHINKO MAGNET KK
CORAL AUDIO CORP
Original Assignee
SHINKO MAGNET KK
CORAL AUDIO CORP
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02Details
    • H04R9/025Magnetic circuit
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00Magnets
    • H01F7/02Permanent magnets [PM]
    • H01F7/0273Magnetic circuits with PM for magnetic field generation
    • H01F7/0289Transducers, loudspeakers, moving coil arrangements
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02KDYNAMO-ELECTRIC MACHINES
    • H02K33/00Motors with reciprocating, oscillating or vibrating magnet, armature or coil system
    • H02K33/18Motors with reciprocating, oscillating or vibrating magnet, armature or coil system with coil systems moving upon intermittent or reversed energisation thereof by interaction with a fixed field system, e.g. permanent magnets
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2209/00Details of transducers of the moving-coil, moving-strip, or moving-wire type covered by H04R9/00 but not provided for in any of its subgroups
    • H04R2209/022Aspects regarding the stray flux internal or external to the magnetic circuit, e.g. shielding, shape of magnetic circuit, flux compensation coils

Abstract

This invention relates to a magnetic device comprising a magnet, a center pole secured to an upper surface of said magnet, a yoke enclosing said magnet and said center pole such that a gap is formed between said yoke and said center pole, a voice coil wound on a bobbin loosely received in said gap, and a metallic member which permits the lines of magnetic force to move substantially in one direction only. Said magnetic member is mounted either on the center pole or the yoke in the vicinity of the surface of the north pole or south pole.

Description

United States Patent 1191 Sato etal. Jan. 1, 1974 [5 MAGNETIC DEVICE FOR USE IN 2,380,616 7/1945 Snoek et al. 335/231 ACOUSTIC APPARATUS 3,549,830 12/1970 Hofman. 179/117 3,129,298 4/1964 Hofman.... 179/120 Inventors: Tadao Sato, Asaka; Toshio Ebihara, 3,550,051 12/1970 Parker 179/117 x Ichikawa, both of Japan 2,930,914 3/1960 Johnson.... 310/27 3,593,239 7 1971 H f 179 217 X [73] Assignees: Coral Audio (Forpolzatio 2,774,000 1211956 3101217 x Kawaguchi C1ty; Shmko Magnet lgatlilusltillkl Kaisha, Narashmo City, Primary Examiner-D F gg 2933,31??? An0rneyStevens, Davis, Miller & Mosher [22] Filed: Dec. 13, 1971 [21] Appl. No.: 207,081 [57] ABSTRACT This invention relates to a magnetic device comprising [30] Foreign Application Priority Data a magnet, a center pole secured to an upper surface of Dec. 19, 1970 Japan 45/114666 Said magnet, a Y enclosing Said magnet and Said center pole such that a gap is formed between said 521 U.S. c1 310/27, 179/115.5 R, 179 117 yoke and Said Center P919, 8 voice coil wound on a 51 1111.01. H02k 33/18 1 bobbin looselv'received in said p and a metallic [58] Field of Search 310/13, 27, 217; member which Permits the of magnetic force to 7 155 H9 120, 7 55 335/231 move substantially in one direction only. Said mag netic member is mounted either on the center pole or 5 References Cited the yoke in the vicinity of the surface of the north pole UNITED STATES PATENTS 3,134,057 5/1964 Tsungo et al. 179/117 X 1 Claim, 8 Drawing Figures PAIENIEDJM nan 3.733.311 SHEET 10F 2 I mmw-mm PAIENTED AN 1 i974 3,783.31 1

' saw an; 2

FIG. 7 FIG. 8

MAGNETIC DEVICE FOR USE IN ACOUSTIC APPARATUS This invention relates to magnetic devices, such as a speaker and microphone, etc., in an acoustic apparatus, and more particularly it is concerned with a magnetic device which can reduce distortions of the vibration system due to the unbalance of magnetic field intensity in an effective air gap.

Generally, a distortion in the ranges of medium and high loudness levels of sound is believed to be caused by non-lineality of the vibration system in the split vibration zone. However, the major portion of the distortion of higher harmonics occurring in the ranges of medium and high loudness levels of sound is caused by non-lineality of the magnetic device.

In a conventional magnetic device or a speaker, for example, the magnetic field extending from a center pole 1 to a yoke 2 comprises a magnetic flux 3 in an effective gap flux and a stray flux 4 in the interior and exterior of the yoke 2, and all the flux does not pass through the effective gap. Such magnetic device has a very low efficiency.

A principal object of this invention is to reduce distortions in high harmonics, low harmonics and ampli tude, etc. caused by non-lineality of the magnetic device.

Another object of this invention is to improve the efficiency of magnetic flux in the air gap by preventing the leakage of the magnetic flux 4 which strays in the portions other than the effective air gap.

A further object of this invention is to achieve a maximum efficiency of a magnetic device at low cost.

In order to accomplishthe aforementioned objects, this invention provides a magnetic device which comprises at least one member made of a metal which permits the lines of magnetic force to move, substantially in one direction and which has low iron loss, such metallic member being provided in the vicinity of the surfaces of the north pole or the south pole of the magnetic device juxtaposed to a gap so that a unidirectional magnetic field is produced and the leakage of an internal or external stray magnetic flux from the effectivegap is markedly reduced by the action of said metallic member, whereby the efficiency of the magnetic flux in the effective gap can be improved and a distortion of higher harmonics in the audio band can be eliminated.

Additional objects as well as features and advantages of this invention will be evident from the description set forth hereinafter when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a view in explanation of a conventional mag netic device;

FIG. 2 is a sectional view of one embodiment of the magnetic device according to this invention;

FIG. 3 is a sectional view, on an enlarged scale, of essential portions of the magnetic device of FIG. 2; and

FIG. 4 to FIG. 8 are sectional views of the other embodiments of this invention.

In FIG. 2, there is shown a magnet 5. A center pole 1 is secured to the upper portion of the magnet 5. The magnet 5 and center pole 1 are secured to a yoke 2 such that they are enclosed by the [Ll-shaped yoke 2. The upper end portion of the center pole l is received in a circular opening 6 formed in the yoke with a gap 7 being formed therebetween.

A uni-directional metallic member 8 is disposed in the vicinity of the surfaces of the yoke 2 and center pole l opposed to each other. As the uni-directional metallic member 8, a silicon-steel plate may be used, for example, which is adapted to cause the lines of magnetic force to move substantially in one direction only by having its crystals oriented in the direction and which has high specific resistance and low iron loss.

The center pole 1 is supported by a centering 9 secured to the underside of a top plate of the yoke 2. A bobbin 11 having a voice coil 10' wound thereon is loosely mounted in the gap 7 for vertical movement.

A conical frame 12 is secured to an upper surface of the yoke 2, and a cone 14 is fitted between an upper marginal portion of the frame 12 and a packing 13. The cone 14 is bonded at its center lower end portion to the bobbin 11 at its outer side surface. A damper 15 is secured at its inner peripheral edge to the outer side surface of the bobbin 11, and at its outer marginal edge to the frame 12. A dust prevention cover 16 is mounted on an upper portion of the bobbin l1.

Leads 17 of the voice coil 10 extend through the cone l4 and frame 12 to outside.

The uni-directional metallic member 8 may have, for example, a property such that it permits the lines of magnetic force to move substantially crosswise thereof. It may be mounted in doughnut shape on upper and lower surfaces of the yoke 2 in disk shape on an upper surfaces of the enter pole l, and cylindrically in a lower portion of the yoke 2 except for a surface thereof which is juxtaposed to the circular opening 6. Alternatively, the members 8 may be mounted in a plurality of these positions.

It will be appreciated that, in the present invention, the uni-directional metallic member 8 which has low iron loss and permits the lines of magnetic force to move substantially in one direction only is provided in the vicinity of the surfaces of the north pole and the south pole of a magnetic device which are juxtaposed to each other so that the eddy current loss is reduced, the specific magnetic permeability is increased and the inner and outer stray magnetic flux is eliminated. The magnetic field in the magnetic device is substantially confined to the magnetic field 3 that passes through the effective gap 7, with a result that a distortion of higher harmonics in the audio band is reduced and efficiency is markedly increased.

FIG. 4 shows an embodiment in which the center pole 1 is made of a material of high magnetic permeability. The use of a material of high magnetic permeability is conducive to increased magnetic flux density but not conducive to the elimination of a distortion of higher harmonics. The provision of the uni-directional metallic member 8 on an upper surface of the center pole 1 thus permits to markedly eliminate a stray magnetic flux.

FIG. 5 shows an embodiment in which the unidirectional metallic member 8 is only provided on an upper marginal portion of the yoke 2.

In the embodiment shown in FIG. 6, the unidirectional metallic members 8 are provided on the surfaces of the yoke 2 and center pole 1 respectively which are opposed to each other with the effective gap 7 being interposed therebetween, so that the movement of the lines of magnetic force horizontally between the yoke and center pole is facilitated. Alternatively, the unidirectional metallic member 8 may be only provided on the surface of the yoke 2 or the surface of the center pole 1.

FIG. 7 shows an embodiment in which the magnet itself serves as a center pole, and the uni-directional metallic members 8 on an upper surface of the yoke 2 and on an upper surface of the magnet 5 respectively. The manner of mounting the members 8 in this embodiment is not limited to the one illustrated, and the member or members 8 may be mounted in any position or positions as desired as shown in the embodiments of 10 FIGS. 3 to 6.

In FIG. 8, there is shown an embodiment in which the center pole 1 is made of the same material as the unidirectional metallic member. The center pole 1 is formed such that it is in an inverted cone shape and bent inwardly so that the center pole 1 may face a direction which agrees with the direction of movement of the lines of magnetic force.

From the foregoing description, it will be appreciated that the magnetic device according to this invention comprises at least one uni-directional metallic member disposed in the vincity of the surfaces of the north pole and south pole of the magnetic device which are juxtaposed to the gap either on the north pole side or the south pole side so that the leakage of an internal or external stray magnetic flux from the effective gap is prevented. This arrangement is effective to make the best use of the energy of the magnet and increase the efficiency of the magnetic device, whereby non-linear distortions and various other distortions occurring in a magnetic device used as an electro-acoustic or acoustico-electric transducer with a speaker or microphone can be eliminated. The magnetic device provided by this invention has an additional advantage in that it is simple in construction and low in cost.

What is claimed is:

1. A magnetic device, comprising: means forming a magnetic circuit and defining a magnetic gap between two opposed surfaces thereof, said magnetic circuit forming means including a magnet,

a center pole secured to an upper surface of said magnet, and

a yoke enclosing said magnet and said center pole such that said magnetic gap is formed between said yoke and said center pole; acoustic vibration producing means disposed in said gap; at least one uni-directional metallic member composed of silicon steel, having low iron loss and permitting movement of magnetic lines of force generated by said magnetic circuit substantially in only one direction, mounted on at least one of said two opposed surfaces adjacent said magnetic gap, wherein the magnetic field generated by said magnetic circuits is confined substantially to that field which passes directly between said opposed surfaces defining said magnetic gap and wherein said at least one metallic member is disposed on the top surface of said center pole adjacent said gap; further metallic members disposed on opposed surfaces of said yoke adjacent said gap; and a still further metallic member disposed on a side surface of said center pole adjacent to and outside said gap.

Claims (1)

1. A magnetic device, comprising: means forming a magnetic circuit and defining a magnetic gap between two opposed surfaces thereof, said magnetic circuit forming means including a magnet, a center pole secured to an upper surface of said magnet, and a yoke enclosing said magnet and said center pole such that said magnetic gap is formed between said yoke and said center pole; acoustic vibration producing means disposed in said gap; at least one uni-directional metallic member composed of silicon steel, having low iron loss and permitting movement of magnetic lines of force generated by said magnetic circuit substantially in only one direction, mounted on at least one of said two opposed surfaces adjacent said magnetic gap, wherein the magnetic field generated by said magnetic circuits is confined substantially to that field which passes directly between said opposed surfaces defining said magnetic gap and wherein said at least one metallic member is disposed on the top surface of said center pole adjacent said gap; further metallic members disposed on opposed surfaces of said yoke adjacent said gap; and a still further metallic member disposed on a side surface of said center pole adjacent to and outside said gap.
US3783311A 1970-12-19 1971-12-13 Magnetic device for use in acoustic apparatus Expired - Lifetime US3783311A (en)

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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3830986A (en) * 1971-12-17 1974-08-20 Pioneer Electronic Corp Magnetic circuit for an electro-acoustic converter
US3867587A (en) * 1971-12-17 1975-02-18 Pioneer Electronic Corp Magnetic circuit for an electro-acoustic converter
US3922501A (en) * 1971-12-17 1975-11-25 Pioneer Electronic Corp Moving voice coil electro-acoustic converter with laminated magnetically anisotropic poles
US4259550A (en) * 1978-04-15 1981-03-31 Yoshiro Nakamatsu Acoustic device with floating vibrating means
US4498023A (en) * 1983-10-31 1985-02-05 Motorola, Inc. Voice coil linear motor with integral capacitor
US4652779A (en) * 1984-10-30 1987-03-24 Magnetic Peripherals Inc. Center pole for rotary actuator coil with lowered inductance
US4980921A (en) * 1985-07-17 1990-12-25 Willi Studer Ag Magnetic system for dynamic loudspeaker
WO1991005447A1 (en) * 1989-10-02 1991-04-18 Jbl, Incorporated Improved electrodynamic loudspeaker
WO1999048329A1 (en) * 1998-03-19 1999-09-23 Jbl Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
WO2001006523A2 (en) * 1999-07-20 2001-01-25 New Transducers Limited Magnet assembly
US20030190052A1 (en) * 1998-03-19 2003-10-09 Jbl Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
US6636612B1 (en) * 2000-11-03 2003-10-21 Algo Sound, Inc. Speaker for use in confined spaces
US6774510B1 (en) 2000-10-25 2004-08-10 Harman International Industries, Inc. Electromagnetic motor with flux stabilization ring, saturation tips, and radiator
US20060061442A1 (en) * 2004-05-20 2006-03-23 Elliot Brooks Eddy current inductive drive electromechanical linear actuator and switching arrangement
US20120062049A1 (en) * 2010-09-10 2012-03-15 Minebea Co., Ltd. Electromechanical energy converter
US20140169615A1 (en) * 2011-05-04 2014-06-19 Dali A/S Electromagnetic drive unit

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2380616A (en) * 1940-06-20 1945-07-31 Snock Jacob Louis Magnetic system
US2774000A (en) * 1955-06-29 1956-12-11 Westinghouse Electric Corp Oriented-steel stator-cores
US2930914A (en) * 1957-05-28 1960-03-29 Gen Dynamics Corp Vibration hand tool
US3129298A (en) * 1960-05-10 1964-04-14 Philips Corp Electro-dynamic conical loudspeaker
US3134057A (en) * 1960-07-11 1964-05-19 Sumitomo Metal Ind Magnetic circuit for the deflection of flux leakage
US3550051A (en) * 1969-03-14 1970-12-22 Gen Electric Speaker magnet having curved preferred direction of magnetization
US3549830A (en) * 1967-01-07 1970-12-22 Philips Corp Magnet configuration for a loudspeaker
US3593239A (en) * 1968-03-01 1971-07-13 Philips Corp Magnetic system

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2380616A (en) * 1940-06-20 1945-07-31 Snock Jacob Louis Magnetic system
US2774000A (en) * 1955-06-29 1956-12-11 Westinghouse Electric Corp Oriented-steel stator-cores
US2930914A (en) * 1957-05-28 1960-03-29 Gen Dynamics Corp Vibration hand tool
US3129298A (en) * 1960-05-10 1964-04-14 Philips Corp Electro-dynamic conical loudspeaker
US3134057A (en) * 1960-07-11 1964-05-19 Sumitomo Metal Ind Magnetic circuit for the deflection of flux leakage
US3549830A (en) * 1967-01-07 1970-12-22 Philips Corp Magnet configuration for a loudspeaker
US3593239A (en) * 1968-03-01 1971-07-13 Philips Corp Magnetic system
US3550051A (en) * 1969-03-14 1970-12-22 Gen Electric Speaker magnet having curved preferred direction of magnetization

Cited By (29)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3830986A (en) * 1971-12-17 1974-08-20 Pioneer Electronic Corp Magnetic circuit for an electro-acoustic converter
US3867587A (en) * 1971-12-17 1975-02-18 Pioneer Electronic Corp Magnetic circuit for an electro-acoustic converter
US3922501A (en) * 1971-12-17 1975-11-25 Pioneer Electronic Corp Moving voice coil electro-acoustic converter with laminated magnetically anisotropic poles
US4259550A (en) * 1978-04-15 1981-03-31 Yoshiro Nakamatsu Acoustic device with floating vibrating means
US4498023A (en) * 1983-10-31 1985-02-05 Motorola, Inc. Voice coil linear motor with integral capacitor
US4652779A (en) * 1984-10-30 1987-03-24 Magnetic Peripherals Inc. Center pole for rotary actuator coil with lowered inductance
US4980921A (en) * 1985-07-17 1990-12-25 Willi Studer Ag Magnetic system for dynamic loudspeaker
WO1991005447A1 (en) * 1989-10-02 1991-04-18 Jbl, Incorporated Improved electrodynamic loudspeaker
WO1999048329A1 (en) * 1998-03-19 1999-09-23 Jbl Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
US20030190052A1 (en) * 1998-03-19 2003-10-09 Jbl Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
US6847726B2 (en) * 1998-03-19 2005-01-25 Harman International Industries, Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
US6768806B1 (en) * 1998-03-19 2004-07-27 Harman International Industries, Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
WO2001006523A2 (en) * 1999-07-20 2001-01-25 New Transducers Limited Magnet assembly
WO2001006523A3 (en) * 1999-07-20 2001-07-19 Graham Bank Magnet assembly
US7012345B2 (en) 2000-10-25 2006-03-14 Harman International Industries, Inc. Electromagnetic motor with flux stabilization ring, saturation tips, and radiator
US20040239193A1 (en) * 2000-10-25 2004-12-02 Jerry Moro Electromagnetic motor with flux stabilization ring, saturation tips, and radiator
US7057314B2 (en) 2000-10-25 2006-06-06 Harman International Industries, Inc. Electromagnetic motor system capable of removing heat away from its magnetic gap
US20050179326A1 (en) * 2000-10-25 2005-08-18 Harman International Industries Incorporated Electromagnetic motor with flux stabilization ring, saturation tips, and radiator
US6774510B1 (en) 2000-10-25 2004-08-10 Harman International Industries, Inc. Electromagnetic motor with flux stabilization ring, saturation tips, and radiator
US6636612B1 (en) * 2000-11-03 2003-10-21 Algo Sound, Inc. Speaker for use in confined spaces
US20060061442A1 (en) * 2004-05-20 2006-03-23 Elliot Brooks Eddy current inductive drive electromechanical linear actuator and switching arrangement
US7777600B2 (en) 2004-05-20 2010-08-17 Powerpath Technologies Llc Eddy current inductive drive electromechanical liner actuator and switching arrangement
US20110068884A1 (en) * 2004-05-20 2011-03-24 Powerpath Technologies Llc Electromechanical actuator
US8134438B2 (en) 2004-05-20 2012-03-13 Powerpath Technologies Llc Electromechanical actuator
US20090212889A1 (en) * 2005-05-20 2009-08-27 Elliot Brooks Eddy current inductive drive electromechanical linear actuator and switching arrangement
US8134437B2 (en) 2005-05-20 2012-03-13 Powerpath Technologies Llc Eddy current inductive drive electromechanical linear actuator and switching arrangement
US20120062049A1 (en) * 2010-09-10 2012-03-15 Minebea Co., Ltd. Electromechanical energy converter
US20140169615A1 (en) * 2011-05-04 2014-06-19 Dali A/S Electromagnetic drive unit
US9036859B2 (en) * 2011-05-04 2015-05-19 Dali A/S Electromagnetic drive unit

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