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DESCRIPTION JP2002507873

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DESCRIPTION JP2002507873
[0001]
FIELD OF THE INVENTION The present invention relates to the field of electromagnetic
transducers and actuators, in particular an improvement of the type having dual voice coils
axially located in corresponding dual annular magnetic air gaps on a common axis A spectral
driver.
[0002]
2. Description of the Related Art In order to solve the basic design problem of dual voice coil dual
magnetic gap speaker as related to a conventional single voice coil drive, the inventor of the
present invention is a dual voice coil dual. It has been discovered that gap types offer advantages
in terms of linearity, efficiency, effective voice coil excursions, power consumption, heat
dissipation, and maximum sound pressure output capability. Furthermore, the inventor has
discovered that certain advantages of the dual coil dual gap scheme can be further enhanced by
introducing a short circuit ring in the two magnetic gap areas near the voice coil.
[0003]
Japanese Laid-Open Patent Application No. 61-137496 of Okada introduces a conductive
annular plate of a speaker magnet structure for preventing voice coil burnout and for preventing
eddy current adversely affecting voice coil current. doing.
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1
[0004]
No. 5,381,483 to Grau, a minimum inductance electrodynamic transducer having a
ferromagnetic shunt ring that is coated with a high conductivity material to increase the induced
current carrying capacity of the transducer. Is disclosed.
[0005]
Yamamuro US Pat. No. 3,830,986 discloses a magnet for an electroacoustic converter having an
air gap formed of a magnetic material laminated with a conductive layer acting as a short circuit
ring to reduce the inductance of the voice coil. A circuit is disclosed.
[0006]
Japanese Patent Publication WO 81/02501 discloses a magnetic circuit for a magnetic circuit for
an electro-mechanical transducer of the dynamic electrical type, wherein a compensating coil or
conductor in the magnetic gap disturbs the magnetic field. Signal current is provided to block.
[0007]
Japanese Patent No. 198,208 discloses an electromagnetic converter, in which the magnetic ring
is located in the air gap, whereby the magnetic ring is magnetized with different magnetic poles
in the center and the outer periphery. The hollow disk permanent magnet can be moved axially
between the circumferential yoke and the central yoke to provide good conversion efficiency.
[0008]
No. 3,783,311 to Sato discloses a magnetic device for use in an acoustic device, wherein the
metal members in the voice coil gap have magnetic lines in one direction for strain reduction.
Allow only to move.
[0009]
Rotshtein's Soviet Union Patent No. 587645 / SU 197801 for electromagnetic speaker magnetic
circuits has a magnetic shunt of soft magnetic material located over one core pole piece to
increase acoustic pressure by reducing the reluctance It is disclosed.
[0010]
The aforementioned patent specification is limited to the general speaker driver / actuator
structure having only one gap and one voice coil.
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[0011]
Patents disclosing dual voice coil dual magnetic gap drivers / actuators are US Pat. No.
4,612,592 to Frandsen, US Pat. No. 5,231,336 to Van Namen, and French Patent No. 1,180,456
to Kritter. Although included, they do not disclose the use of shorting rings.
[0012]
In Kato et al.'S US Pat. No. 4,914,707 for a mobile mobile speaker system, in order to make the
impedance of the rear speakers higher than the impedance of the front speakers, instead of
connecting a resistor in series with the rear speakers, It is proposed to attach a shorting ring to
the coil of the dual coil dual gap front speaker of the vehicle to reduce the frequency impedance.
[0013]
SUMMARY OF THE INVENTION A primary object of the present invention is to provide an
improvement to a dual voice coil / dual magnetic gap type transducer that reduces harmonic
distortion in the acoustic output.
[0014]
Yet another object of the present invention is to implement the aforementioned improvement to
reduce even harmonic distortion, particularly including second harmonic distortion.
[0015]
Yet another object of the present invention is to implement the aforementioned improvement to
reduce odd harmonic distortion, particularly including third harmonic distortion.
[0016]
SUMMARY OF THE INVENTION The foregoing objects are achieved by the present invention and
the advantages thereof are realized by the present invention.
According to the present invention, a dual voice coil / dual magnetic gap type speaker by adding
one or more shorting rings of high conductivity metal strategically placed near two magnetic
gaps near the voice coil And other transducer characteristics are improved.
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[0017]
The shorting ring does not affect the steady constant magnetic field, but changes in the flux
density or displacement of the field lines as occurs under the load imposed when the voice coil is
driven hard by the audio frequency current. Acts in reverse.
The position of the shorting ring determines its effect, ie a position close to the voice coil reduces
the inductance of the voice coil and the second harmonic and further if all of the shorting ring is
located inside the center line of the flux loop Promotes reduction of high-order even harmonic
distortion and promotes reduction of third harmonic and high-order odd harmonic distortion
when centered on the centerline of the flux loop, ie, at the center of the magnetic gap, At
locations outside of the centerline but close to the voice coil, it generally operates to reduce
harmonic distortion.
Thus, multiple rings can be placed at different locations to optimally suppress both even and odd
harmonic distortion and to reduce voice coil inductance.
[0018]
The foregoing and further objects, features, and advantages of the present invention will be more
fully understood from the following description taken in conjunction with the accompanying
drawings.
FIGS. 1-12 are basic functional representations in which a half of a dual gap dual voice coil
speaker drive having a voice coil assembly 10 is shown in cross section, wherein the voice coil
assembly 10 has the north pole of the magnet M as shown in FIG. A permanent magnet M
disposed between the steel pole piece N of No. 1 and the second steel pole piece S of the S pole of
the magnet M and a pair of magnetic air gaps formed between the yoke 12 Supports the voice
coils 10A and 10B, and the yoke 12 is made of a magnetic material and can be considered as
defining a pair of pole pieces that mirrors the N and S connected pole pieces of the magnet M. ,
And thus form two magnetic gaps.
[0019]
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The magnetic system of the above-described construction places flux loops in the path shown by
the dashed line, ie flux loop centerline 14, which typically is centered within each magnetic gap
and within each voice coil 10A and 10B. It is located in
[0020]
The voice coil assembly 10 is constrained by the well-known spring-suspended diaphragm
structure (not shown), whereby it moves axially and, typically, the right hand well-known in
electro-magnetic mechanisms. According to the law of the speaker, in the usual way of the
loudspeaker, in response to the AC (alternating current) currents applied to the coils 10A, 10B,
drive a common loudspeaker cone diaphragm (not shown), the two coils thus being in phase
Connected
[0021]
The cross-sectional views of the halves shown in FIGS. 1-12 represent coaxial speaker motor
structures which can have either of the following two basic structures which are mutually
inverse.
(1) The ring M is coaxial with the center line CL1 having the magnet M inside the annular voice
coil structure 10, whereby the magnet M having the pole pieces N and S is cylindrical and the
yoke 12 encloses the voice coil assembly 10 Tubular shape.
(2) Coaxial with the center line CL2 having the cylindrical yoke 12 inside the voice coil assembly
10, the magnet M and the pole pieces N and S are annular in shape and surround the voice coil
assembly 10.
[0022]
A common inherent drawback to speakers is that the magnetic flux in the voice coil region is
subject to pattern deformation or modulation in response to the drive current of the voice coil,
which distorts the acoustic output, causing the coil winding to Increase the inductance and
change the frequency response characteristics.
[0023]
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As indicated in the previous description of the related prior art, it is desirable to introduce a high
conductivity metal short / shunt ring such as copper near the magnetic air gap of a conventional
single coil drive. It has been discovered that advantages can be provided by acting to stabilize the
flux against disturbances from such modulation due to voice coil current.
Such a short-circuit ring does not affect the flux pattern as long as it is constant and stationary,
but the ring does not affect the flow of internal current as opposed to the change in flux pattern
caused by the drive current of the voice coil. In response to this, it reduces the distortion in the
acoustic output.
Also, shorting rings located near the voice coil tend to reduce the inductance of the voice coil.
[0024]
The inventors have identified in the research on the improvement of dual gap dual coil
transducer drives, particularly the main position and structure of such a shorting ring with
regard to the reduction of strain, the second and / or third harmonics. Such locations and
structures have been developed to selectively reduce wave distortion.
[0025]
FIGS. 1 to 3 are located in the flux loop defined by the center line 14 of the flux loop, and
therefore to reduce even harmonic distortion, which in particular comprises second harmonic
distortion, in accordance with the invention. The position of the short-circuit ring of the tubular
shape which operates with.
[0026]
In FIG. 1, the tubular shorting ring 16A is positioned adjacent to the permanent magnet M and
extends generally between the two pole pieces N and S at a location adjacent to the voice coil
assembly 10 and generally Inside the flux loop which is defined by the center line 14.
In FIG. 2, the tubular shorting ring 16B is embedded in the recessed area of the yoke 12 and
extends essentially between the two yoke pole pieces at a location adjacent to the voice coil
assembly 10 and is generally defined by the centerline 14 In the flux loop.
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In FIG. 3, two rings are provided in the drive as in ring 16A of FIG. 1 and ring 16B of FIG. 2, and
both rings are located in the flux loop defined by center line 14 Even harmonic distortion
suppression is greater than in FIG. 1 or FIG.
[0027]
FIGS. 4 and 5 show the position of the annular shorting rings 16D and 16E as a disk with an edge
located near the voice coil of the assembly 10, which is outside the center line 14 of the flux
loop. Positioned to operate to reduce harmonic distortion and reduce voice coil inductance in
accordance with the present invention.
[0028]
In FIG. 4, the first pair of shorting rings 16C is located on the outer surface of pole pieces N and
S, respectively, and the second pair of shorting rings 16D is located on each end of yoke 12, all in
assembly. It has an edge close to ten voice coils.
The shorting rings 16C and 16D are annular disc shapes, ie flat washers, but depending on the
shape, ie at the center of the axis depending on whether CL1 or CL2 is at the central axis The
pair of shorting rings does not have to have a central hole and is therefore shaped as a simple
circular disc.
[0029]
In FIG. 5, the two shorting rings 16E are secured to the outer corners of the yoke 12 close to the
voice coil of the assembly 10, but outside the flux loop defined by the center line 14.
[0030]
FIGS. 6 and 7 show a structure having a shorted ring position near the voice coil both inside and
outside the flux loop defined by the center line 14 and thus mainly the second harmonic And to
suppress even higher harmonics and to reduce voice coil inductance.
[0031]
In FIG. 6, two shorting rings 16F 'are located at the inner corners of each pole piece N and S in
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the flux loop, operating mainly with even harmonics, and the two rings 16F These four rings
located at the outer corner of S, two rings 16E located at the outer corner of the yoke as in FIG. 5
and located outside the flux loop but close to the voice coil of assembly 10 are therefore It
operates to reduce harmonic distortion and to reduce the inductance of the voice coil.
[0032]
In FIG. 7, a total of eight rings, ie a pair of shorting rings 16G and 16G 'embedded in each of the
pole pieces N and S as shown, and the corresponding positions of the yoke 12 There are
provided two pairs of corresponding short circuit rings 16H and 16H ′ embedded in, so that
four rings are in the flux loop and the other four rings are outside the flux loop.
[0033]
FIGS. 8 to 10 show a short circuit ring substantially centered on the flux loop centerline 14, ie,
this is the optimum position for suppressing odd harmonics, in particular the third harmonic. .
[0034]
In FIG. 8, the shorting rings 16J and 16K are embedded in the center position, and the respective
shorting rings of all four pole pieces defining two magnetic gaps are at the center of the flux loop
centerline 14.
[0035]
In FIG. 9, the entire end faces of the N and S poles are made up of stacked shorted ring structures
16L, and the corresponding stacked shorted ring structures 16M are shown adjacent to the voice
coil as shown. It is embedded in the 12 upper pole piece areas.
These laminated short circuit ring structures 16L and 16H consist of sheets of conductive metal
(typically copper or aluminum) sandwiched with magnetic grade steel laminates.
This method reduces acoustic distortion, both the second and third harmonics and higher
harmonics, and represents the closest possible method to ideal conditions for reducing voice coil
inductance, and is stacked Because the shorting ring operates in the manner of a plurality of
individual shorting rings, some are located in the flux loop, some are centered above it, and some
are located outside the flux loop, but all Are positioned close to the voice coil.
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This type of shorting ring is particularly effective at high audio frequencies.
[0036]
FIG. 10 basically shows a non-laminated variant of that of FIG. 9, with a tubular shorting ring 16P
attached to the underside of the pole pieces N and S, and the yoke 12 slightly more than the ring
16P. A long tubular shaped embedded shorting ring 16Q is mounted and thus extends inwardly
from the outer corner beyond the voice coil of the assembly 10 to reduce voice coil inductance
and to optimally reduce harmonic distortion Operate.
[0037]
In FIG. 11, a single tubular shorting ring 16R extends the entire length of the magnet assembly
and includes a surface layer applied to the front of the pole pieces N and S near the voice coil,
thus the voice coil It operates to reduce inductance and reduce harmonic distortion.
[0038]
FIG. 12 basically shows a variant of FIG. 11 with the tubular shorting ring 16S deployed as a
surface layer extending the entire length along the upper surface of the yoke 12, the yoke 12
being a voice coil And its pole region, thus further reducing the voice coil inductance.
[0039]
Alternative viable combinations of FIGS. 10-12 include a ring 16R (FIG. 11) deployed in place of
the ring 16P of FIG. 10 and a ring 16S deployed in place of the ring 16Q of FIG. 12) and the ring
16S (FIG. 12) deployed in the yoke 12 of FIG.
[0040]
With various shorted ring patterns, harmonic distortion suppression is usually more effective
when the rings are larger and / or more.
[0041]
The shorted ring is most effective in reducing harmonic distortion in the audio frequency range
200 to 2,000 Hertz.
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[0042]
Typical results for strain reduction were measured as follows.
Frequency: 200 Hz 500 Hz 1 kHz 1.
Ring structure combining FIG. 1 and FIG. 5 second harmonic reduction 5 dB 6 dB 14 dB third
harmonic reduction 11 dB 10 dB 2 dB2.
Ring Structure FIG. 5 Second harmonic reduction No noticeable reduction Third harmonic
reduction 9 dB 4 dB 2 dB The invention may be practiced and practiced in other specific forms
without departing from its basic characteristics.
Therefore, the embodiments of the present invention are considered in all respects as illustrative
and do not limit the technical scope.
The technical scope of the present invention is indicated not by the above description but by the
claims.
Therefore, all variations, substitutions and alterations within the scope of the claims are intended
to be included here.
Drawing Description: BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of a shorting
ring located in a flux loop to reduce even harmonic distortion.
FIG. 2 is a diagram of a shorting ring located in a flux loop to reduce even harmonic distortion.
FIG. 3 is a diagram of a shorting ring located in a flux loop to reduce even harmonic distortion.
FIG. 4 is a diagram of a shorting ring located outside the flux loop.
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FIG. 5 is a diagram of a shorting ring located outside the flux loop.
FIG. 6 is a view of at least two shorting rings located in a flux loop.
FIG. 7 is a view of at least two shorting rings located outside the flux loop.
FIG. 8 is a diagram of a shorting ring centered on the flux loop for best suppression of odd
harmonics.
FIG. 9 is a diagram of a shorting ring centered on the flux loop for best suppression of odd
harmonics.
FIG. 10 is a diagram of a shorting ring centered on the flux loop for best suppression of odd
harmonics.
FIG. 11 is a view of a shorting ring in tubular form extending through both gaps; FIG. 12 is a view
of a shorting ring in tubular form extending through both gaps;
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