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□ · House, 杏, "" "Jo 7th October 1979 Patent Minorie Nyafuji Hideo /"-˜ 5, list of attached
documents 1 ■ JP 50-E) 7632 internal office number 6 le 6555 Title of the book / invention
, Magnetic circuit of electro-acoustic transducer
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement
of non-straight distortion in the magnetic circuit of an electroacoustic transducer. . Usually, as
shown in FIG. 1 of this type of electroacoustic transducer, for example, dynamic speaker (2) L1, a
center pole (2) is disposed at the center position of the yoke (1) and the outer periphery of the
yoke (1) Magnet (3) and yoke play) (4)? Place the voice coil (6) in the gap (6) between the center
pole (2) and the yoke plate (4) and communicate it with the cone (8) with the bosu cons coil
'bobbin (7) The causes of non-linear distortion in the electroacoustic transducer can be roughly
divided into mechanical and electrical systems. The present invention improves the latter nonlinearity due to the electrical system. 2.) due to the magnetic non-linearity of the magnetic circuit
in close proximity to the scoil (6), the yoke plate (4) and the center pole (2). That is, the voice coil
(6) causes the cone (8) to vibrate approximately in proportion to the current as the signal current
flowing therethrough interacts with the DC magnetic field of the magnetic circuit. However, to be
precise, the amplitude of the vibration of the voice coil (6) is not in direct proportion to the
current value as the voice signal. This phenomenon is caused by the ferromagnetic material of
the gap (5) in which an AC magnetic field generated by the AC current of the voice coil (6)
approaches the coil (6), that is, the yoke (1) as a magnetic circuit. Normally, the gap density (5),
the yoke plate (4) and the magnetic flux density EndPage: 1I of this part. In order to increase the
efficiency of the speaker, ferromagnetic materials such as soft iron 1 are used. Therefore, the
magnetization curve of the magnetized ferromagnet becomes a minor rou 101 non-linear about
the bias of the DC magnetic field. For this reason, the voltage and the current of the voice coil
'cell (6) are in a proportional relationship in which the nonlinear magnetization curve is J
strained in a non-linear magnetization curve. Annular non-linear magnetization curves occur due
to losses due to the generation of eddy currents. Since a ferromagnetic material is a good
conductor at the same time, when an alternating magnetic flux passes through this material, an
eddy current is generated at that position in the direction to prevent the change of the magnetic
flux. Therefore, in this case, the primary side has a nonlinear component in the actance. Further,
the non-linear relationship between the voltage and the current means that a high-wave
component is generated in the current in consideration of the voltage.
The harmonics of the current are mostly the second and third harmonics. However, the harmonic
components that actually cause problems are the second harmonic components, and the firstorder JP-A! @ 50-67632 (The harmonic component is negligible compared to the same
component generated in the mechanical system. Now, the distortion component of the abovementioned current can be expressed by the following equation if it is theoretically determined
and the calculation process is omitted and the conclusion is shown. Second harmonic component
HD, in the end, R-") ω L j m Δ. The second harmonic component HD is included. Note that R is
the resistance of the magnetic circuit amount, L is the self inductance in the circuit, and μmΔ is
the so-called incremental permeability, and μmΔ ■, jm4 is a distortion component of the same
dimension as μ 寓 Δ 鳳Is a virtual quantity to represent From the above equation (1), reduction
of distortion of the electrical system of the electroacoustic transducer can be achieved by
reducing + '/ (1) L, (2) setting R> ωL, (a),, 4 . This can be achieved by any solution of reducing s
□ 6. The present invention provides an effective specific means corresponding to the solution
method (3) among the means described above. Conventionally, as a specific example of this type
of method, as shown in FIG. 3 and FIG. 3, the cross-sectional area of the surrounding magnetic
material facing the voice coil (6), specifically, the center pole (2) Reduce the magnetic flux
density of that part, ie, raise the operating point, bring it close to 1 sum 'q, reduce Q, and
consequently reduce the voice coil distortion. The However, in these methods, the center pole (2)
portion is structurally required to be cut, and a considerable increase in manufacturing cost is
inevitable. Moreover, the conventional speaker (6) shown in FIG. 2 has a special cross section as
a seat ring between the gap (5) removed from the vibration position of the voice coil (6)! Is a
structure in which the short-circuit cap (9) is interposed, so that bending of the short-circuit cap
(9) is difficult, and since it is out of the position of the voice coil (6), a sufficient reduction effect
is not expected And the range of vibration of the voice coil (6), that is, the amplitude is limited. In
addition, the conventional speaker shown in FIG. 3 is a structure in which a V-shaped copper cap
a1 is fitted on the inner and outer peripheral wall surfaces of the Yanter ball (2), so that it is
expensive. In order to obtain the reduction effect, the lateral vibration of the voice coil (6) is
limited, and strict accuracy is required at the time of assembly, and in order to secure the
specified gap (5), the presence of the copper cap αQ is required. As a result, the diameter of the
center ball (2) is reduced, and the magnet (3) is sufficiently reinforced to obtain the necessary
magnetic flux density.
Furthermore, complicated processes such as processing of the above-mentioned conventional
speakers (in the case of a conductive ring (9) (g) as a short ring) and fitting of the same to the
center ball (2) are required. There is a drawback to Therefore, the present invention is developed
in consideration of the above-mentioned drawbacks and problems in EndPage: 2, and the
technical means disclosed herein greatly contributes to the improvement of the non-linearity in
the magnetic circuit of the speaker. Above--will facilitate the 'design near gap position as
compared to the exemplary prior art. The magnetic circuit of the electro-acoustic transducer
according to the present invention is a magnetic circuit in a position opposite to the 1.7 ′ voice
coil, a magnetic circuit of the following outer peripheral surface or yoke, a phase or a center pole
and yoke. A material characterized by using a material having a saturation magnetic flux density
equal to the magnetic flux density of that portion on the inner and outer peripheral surfaces is
characterized in that the magnetic circuit of the present invention will be described below with
reference to FIG. . In the figure, the same reference numerals as in FIG. 1 denote the same
members, and the pole piece (-a) portion of the center pole (2) facing the voice coil (6) is equal to
the magnetic flux density of this portion. A material having a saturated 'magnetic flux density' is
used. However, 1) considering the permeance of this structure, i) permeance of gap 2P self-P, =
·················· · · · · · · · · (scan) t However, Af = cross-sectional area Lt = width of the gap of the gap)
around the gap permeance:, 2P. Co P, = 0 s co-gD + · · · · · · · · · · ························· (2)) 1) above, except
for the l) Permeance 2 PT (, P ++, 2 P snow) Therefore, the leakage coefficient f is = p
·························· ···· - ········· (3) P and however, the magnetic flux passing through the Am = magnet
cross-sectional area center pole outside the local then the magnetic field voice coil generates
exert the Borupi 3, current Assuming that the average diameter of the strained portion is D-s (≠
DP) and its thickness t-t, the magnetic flux density on the diameter D ′ ′ P reaches saturation.
As a result, svmA @, swhl is small, and the distortion component of the current flowing through
the voice coil is small. In addition, since the magnetic flux obtained by the above equation (5) is
actually focused on the center ball via another magnetic path, it is larger than the value obtained
by the equation (5), (6) Saturation is sufficient if B 'of the formula and BQ of the material are
approximately equal.
By the way, in the embodiment shown in the second drawing, as a specific example, 7%
permalloy (, 71% Ni 7 residual Fe, Mo) in the pole piece portion of the center pole. Using Coetc),
this effect is classified as first class strain resistance, and compared with the conventional Subei
in Figure 1 as shown in the graph of the characteristics in Figure 5. I got The admittance curve of
the ponne coil of the graph is the in of the voice coil. It supports the decrease of the inductance
L. Also, the harmonic distortion curve clearly shows that the present invention is improved as
compared to the prior art. Incidentally, the measurement circuit of this experiment is as shown in
FIG. The measurement conditions are RO> measured point 2, and in addition to the above
embodiment, the voice coil (6) and the entire upper surface of the center port-(2) facing each
other or the yoke plate (4) Alternatively, a material having a once-accumulated flux density equal
to the flux density of that portion may be used. As described above, the present invention can be
easily put into practical use with a partial configuration 11 that does not limit the amplitude of
the voice coil, and can reduce the nonlinearity of the magnetic circuit without reducing the
magnetic flux density of the magnetic circuit cap. If you try to reduce it now, you will have the
effect of making a difference. FIGS. 1 to 3 are a conventional example End page: 3 as a
conventional example and FIG. 3 are cross-sectional views of the main part of a conventional
speaker by distortion improvement. Fig. Q is a cross-sectional view of an essential part showing
an embodiment of the present invention. FIG. S is a graph showing characteristics of the
magnetic circuit according to experimental measurement results, and FIG. 6 is a measurement
circuit diagram. /・・・・・・・・・ヨーク2−0−8−1. −に7. - Bohr 3 ' "6 ......... voice
coil - patent applicant Sony Corporation representative patent attorney Akira Koike EndPage: 4
first 8m6. Other than the above inventor Seta ξ ξ Bay (1) Address Setagaya-ku, Tokyo, Japan 211 8-8 Fukuda 4 power name Fuku 1) Yu procedure correction (voluntary) Showa & Jan. 30, 9th
Secretary of Patent Office 粛Fuji Hide Longitudinal 1, Display of the case-Sum 48 years Patent ai
116 472 No. 2, Title of the invention 2, Name of the invention Magnetism of the electric-toelectricity converter-Path 3, Person who makes correction Related patent applicant 1 Name
representative Akio Morita number 0 agent
, Magnetic circuit of electro-acoustic transducer
6, the date of correction instruction Spontaneous 6, subject of 1111 only subject "−-detailed
description of the invention of the book-Ma", the contents of correction (two 1) on page 11 of the
second line of the specification "gap (5) Correct the ferromagnetism of sI, which forms the Jtr
gap (5). (Two 2) Circular ··· eO loss occurs in line 9 to line 10 of the specification. Jt-1 'jlJ
divide. (Mar. 3) Correct the "conductor Jtr conductor" of the specification, page 3, line 11. (? -1
Correct the 11th "calculation course" on page 2 of the specification into "calculation process". (? 5) The name which corrects as follows the specification of the 9th page 2nd line.
EndPage:5(? -6) Correct rRo> Measured in the specification, page 10, line lK4, to "RO
<Measured". JP 50-67632 (6) EndPage: 6