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JP2009111484

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2009111484
An object of the present invention is to enable reproduction of a bass region with a sufficiently
large amplitude and a uniform driving force within a driving range even if the magnet spacing is
increased. A first magnet array layer is formed by arranging a plurality of rod permanent
magnets having a width Wm, a thickness Tm, and a predetermined length alternately in parallel
on a plane with mutually different magnetic poles facing each other at a constant pole pitch τp.
Forming the same arrangement of the first magnet arrangement layer and the rod-like
permanent magnet, opposing the same magnetic pole to each other in the vertical direction with
the first magnet arrangement layer, and separating the distance 2 × lg between the opposing
magnet surfaces Between the opposing magnet surfaces, forming a second magnet array layer,
and forming a coil of a conductor pattern of meandering shape in the gap portion between
adjacent rod-like permanent magnets of the first and second magnet array layers; The rod-like
permanent magnets were disposed so as to be positioned at an intermediate position, and when
α = τp / lg, β = Wm / τp, and γ = Tm / lg, β ≦ 0.15α × 10. [Selected figure] Figure 1
Electromagnetic converter
[0001]
The present invention relates to an electromagnetic transducer which has a coil pattern on the
surface of a vibrating film provided between permanent magnets arranged vertically and which
reproduces sound from an audio signal.
[0002]
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1
Among rectangular electromagnetic transducers using a permanent magnet plate and a vibrating
membrane, there is one in which the permanent magnet plate and the vibrating membrane are
disposed opposite to each other, and a buffer material is disposed between the permanent
magnet plate and the vibrating membrane.
The permanent magnet plate, the vibrating membrane and the shock absorbing material are
covered with a member such as a frame and attached to, for example, a speaker housing. The
permanent magnet plate has band-like magnetized portions alternately changed in polarity at
regular intervals. In addition, the vibrating membrane has a meandering shape that acts as an
electromagnetic coil, making the gap between the permanent magnet plate alternately
magnetized and opposite to a portion called a so-called magnetized neutral zone A body pattern
is provided on the film surface of the vibrating film (see, for example, Patent Document 1). When
the current of the audio signal flows to the coil pattern formed on the vibrating film, the
conductor pattern acting as an electromagnetic coil and the magnetized pattern of the permanent
magnet are electromagnetically coupled, and the vibration having the above-mentioned
conductor pattern according to Fleming's law The membrane vibrates. Sound waves generated by
this vibration are emitted through sound emission holes drilled in the permanent magnet plate
and the frame to perform audio reproduction. In addition, there is an ultra thin speaker
“gamouson type” with the same configuration as the above electromagnetic converter (see, for
example, Non-Patent Document 1). This is one in which the above-mentioned permanent magnet
plate is made into a bar-like magnet, and the other members are made of the same one. The rodshaped magnet has the same poles (N and N poles, or S and S poles) facing each other, and the
poles are alternately arranged in the arrangement direction perpendicular to the rods. According
to the configuration of this electromagnetic converter, the sound generation operation of audio
reproduction is also the same as that at the beginning.
[0003]
Patent No. 3192372 Gazette supervision Tamon Saeki, Speaker & enclosure encyclopedia,
Section 2-25, Seibundo Shinkosha (May, 1999 issue)
[0004]
With any of the conventional electromagnetic transducers, it is difficult to obtain a vibrating
membrane that vibrates with a large amplitude, and there has been a problem that the
reproduced sound pressure level in the bass region is low accordingly.
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The main reason is that the distance between opposing permanent magnets can not be increased.
This is because the magnetic flux density at the position of the coil pattern (the position of the
vibrating film) where the driving force is obtained decreases if the distance between the opposing
permanent magnets is easily extended. Also, if the magnet thickness is simply increased to
increase the magnetic flux density, the magnetic flux density near the magnet surface increases,
and the larger the amplitude of the vibrating film, that is, the closer the vibrating film is to the
magnet surface, the larger the driving force becomes. Also, the vibrating film comes in contact
with the permanent magnet and causes distortion or abnormal sound.
[0005]
The present invention has been made to solve the above-mentioned problems, and it is an
electromagnetic converter which enables reproduction of a bass region with a sufficiently large
amplitude even with a large magnet distance and a uniform driving force within the drive range.
The purpose is to get.
[0006]
In the electromagnetic converter according to the present invention, a plurality of rod permanent
magnets each having a width Wm, a thickness Tm, and a predetermined length are arrayed at a
constant pole pitch τp, with different magnetic poles facing each other alternately in parallel on
a plane. Of the first magnetic array layer and the rod-like permanent magnet, the same magnetic
pole is opposed to the first magnetic array layer in the vertical direction, and the distance
between the opposing magnet surfaces A coil of a meander-shaped conductor pattern formed so
as to form a second magnet array layer separated by 2 × lg and facing the gap between adjacent
rod permanent magnets in the first and second magnet array layers A vibrating film formed over
the entire surface corresponding to the magnet arrangement layer is disposed so as to be located
in the middle between the opposing magnet surfaces, and α = τp / lg, β = Wm / τp, and γ =
Tm / lg. In the above case, the above-mentioned rod-like permanent magnet is set so that .beta. It
is obtained by placing a.
[0007]
According to the present invention, by optimizing the cross-sectional dimension and the
arrangement pitch of the rod-like permanent magnets, even if the magnet interval between the
two magnet array layers is increased, a sufficient driving force and uniform driving force within
the drive range can be obtained. It enables the reproduction of the obtained low range.
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That is, a large amplitude can be realized, and a loud bass region can be reproduced.
[0008]
Embodiment 1
FIG. 1 is a perspective view showing a structure of an electromagnetic converter according to
Embodiment 1 of the present invention. In the figure, the electromagnetic converter has a
plurality of rod-like permanent magnets 10 each having a width Wm, a thickness Tm, and a
predetermined length, which are arranged parallel to each other in parallel on a plane, with
different magnetic poles facing each other at a constant pole pitch τp. The magnet arrangement
layer of Further, the electromagnetic transducer has the same arrangement of the first magnet
arrangement layer and the rod-like permanent magnet 10, has the same magnetic pole opposed
to each other in the vertical direction with the first magnet arrangement layer, and the distance
between the opposing magnet surfaces It has a second magnet layer formed 2 × 1 g apart. The
rod-like permanent magnets 10 of the first and second magnet arrangement layers are fixed to a
yoke 40 of a magnetic body, and the yoke 40 is supported by a frame (not shown) together with
a vibrating film 20 described later. The magnetic flux emitted from one rod-like permanent
magnet 10 is mainly directed in the right or left direction, and in a space where the magnets face
each other vertically, it draws an arc-shaped magnetic flux line and reaches the other pole.
[0009]
The sheet-like vibrating film 20 is disposed at an intermediate position between the opposing
magnet surfaces of the first and second magnet array layers in the vertical relationship, that is, at
the same distance lg from the opposing magnet surfaces. In the vibrating film 20, coils 21 of a
meandering conductor pattern formed facing the gap between different magnetic poles of the
first and second magnet arrangement layers are formed over the entire surface corresponding to
each magnet arrangement layer. It is done. Therefore, the pattern of the coil 21 is disposed at a
position where the magnetic flux exhibited by the upper and lower rod-like permanent magnets
10 in FIG. 1 is horizontal. With such a configuration, when a drive current flows through the coil
21, a force is generated in the upward or downward direction of FIG. 1 by the orthogonal
magnetic fluxes. This force vibrates the entire vibrating membrane 20 up and down, and
generates a sound through the slit 30 provided in the yoke 40.
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[0010]
In the above magnetic circuit configuration, it is important for the electromagnetic converter to
generate a large level of sound, and in particular, it is necessary to increase the magnetic flux
density in the place where the coil 21 is located. To do this, use a permanent magnet with strong
magnetic energy, or reduce the magnetic flux density by reducing the distance between the
upper and lower magnets (at a distance 2 × lg between the magnet surfaces, twice the distance
from the surface of the vibrating film 20). Countermeasures for raising can be considered.
However, narrowing the distance between the upper and lower magnets restricts the vibration of
the vibrating membrane 20, and a large sound pressure can not be obtained particularly in the
low sound range where the vibration amplitude is large. Therefore, in the present invention, as
described below, a structure is provided in which a sufficient driving force can be obtained by
securing sufficient magnetic flux density even if the distance between the upper and lower
magnets is increased and optimizing the dimensions and arrangement of the permanent magnets.
. Furthermore, even if the vibrating membrane 20 vibrates with a large amplitude, the change in
magnetic flux density is reduced in the vibrating direction (the direction perpendicular to the
vibrating membrane surface) to maintain the driving force.
[0011]
First, the parameters defining the configuration will be described. Let α, β and γ be α = τp /
lg, β = Wm / τp and γ = Tm / lg. Further, assuming that the magnetic flux density in the
direction parallel to the magnet surface (left and right direction in FIG. 1) is Bmax, and the
magnetic flux density in the same direction of the conductor portion of the coil 21 is Bmin
“(Bmax−Bmin) / Br × 100, the ratio of the magnetic flux density Bmin of the coil conductor to
the residual magnetic flux density Br of the magnet, ie, the proportion of the conductor at a
position where the conductor is not vibrating Let Bmin / Br × 100. Based on the above
conditions, electromagnetic field analysis is performed for various magnetic circuit
configurations. The calculation result of the above-mentioned "percentage of variation" is shown
in FIG. 2, and the calculation result of "percentage of conductor portion" is shown in FIG. In the
figure, let γ = Tm / lg be the parameter (γ = 0.67, 1.00, 1.33, 1.67), the horizontal axis be α =
τp / lg, and the vertical axis β = Wm / τp. It is a distribution map.
[0012]
A small value is desirable for the "variation ratio" (Bmax-Bmin) / Br x 100 in FIG. The reason is
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that the smaller the difference in magnetic flux density between the coil position and the magnet
position, the smaller the change in magnetic flux density, and even if the vibrating membrane 20
vibrates significantly and approaches the permanent magnet, the same degree as the original coil
position This is because if there is a magnetic flux density, the driving force can be maintained. In
FIG. 2, the value of the “variation ratio” is generally reduced below the diagonal line D, and
becomes an area of several percent. However, for γ = 0.67, a region T exceeding 3% appears in
the lower right corner of FIG. 2A, which is not desirable. From this, in the present invention,
γγ1.0, and the thickness Tm of the magnet is larger than the distance lg between the rod-like
permanent magnet 10 and the vibrating film 20. Further, the diagonal line D entered in FIG. 2
has a relationship of straight line β = 0.15α / 10.1, and the range defining α (= τp / lg) and β
(= Wm / τp) is β It is set that ≦ 0.15α × 10.
[0013]
On the other hand, with regard to the “proportion of conductor portion” Bmin / Br × 100 in
FIG. 3, it is desirable that the residual magnetic flux density Br, which is the original performance
of the magnet, effectively appears in the coil conductor portion. What can be read from FIG. 3 is
that the “proportion of conductor” is larger as it goes to the upper right of the figure. That is,
the pole pitch τp is preferably large (α: large), and the magnet width Wm relative to the pole
pitch τp is preferably large (β: large). The magnetic flux density near the magnet surface is
considered to be 1/3 of the residual magnetic flux density, and in the present invention,
“proportion of conductor” Bmin / Br × 100 is 35% or more.
[0014]
In many current electromagnetic transducers, the distance between the permanent magnet and
the vibrating membrane is often 0.5 mm or less. In this state, a vibrating film collides with the
surface of the permanent magnet to generate noise when a large amount of human power is
applied in the low frequency range. As a countermeasure, a shock absorbing material may be
inserted between the permanent magnet and the vibrating membrane. Since this cushioning
material is disposed in contact with the permanent magnet and the vibrating membrane, it is
obvious that the vibration of the vibrating membrane is limited. That is, the reproduction of the
low frequency range is limited, and the electromagnetic converter speaker has a reproduction
range of the middle frequency range or more close to 500 Hz to 1 kHz. However, by adopting the
present invention, it is possible to increase the distance lg between the rod-like permanent
magnet 10 and the vibrating film 20. Therefore, for example, a distance of 1.0 mm to 1.5 mm or
more may be adopted. it can. Since this interval lg can be made large, it is possible to eliminate
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the need for a shockproof cushioning material.
[0015]
In the example of FIG. 1 described above, the electromagnetic transducer constituted by the
magnet array layer in which the rod-like permanent magnet 10 is fixed to the yoke 40 of the
magnetic body and the vibrating film 20 has been described, but it is not limited thereto.
Although the electromagnetic converter shown in FIG. 4 is another example of the present
invention, it is assumed here that there is no yoke, and the rod-like permanent magnet 10 and
the vibrating membrane 20 are directly held by frames (not shown) provided on the front and
rear ends of the electromagnetic converter.・ It has a fixed structure. In addition, although the
slit 30 of the yoke 40 of FIG. 1 showed the rectangular-shaped hole of an eccentric length in the
length direction of the rod-shaped permanent magnet 10, it does not interfere with magnetic
path formation, and the vibrating film 20 It may be of a structure in which the generated sound
is radiated to the outside without being attenuated. For example, circular or square holes may be
arranged between the rod-like permanent magnets 10, or holes such as ovals or polygons may be
used.
[0016]
As described above, according to the first embodiment, by optimizing the cross-sectional
dimension and the arrangement pitch of the rod-like permanent magnets, a sufficient size and
drive can be obtained even if the magnet interval between the two magnet arrangement layers is
increased. A uniform driving force can be obtained within the range to enable reproduction of the
low range. That is, a large amplitude can be realized, and a loud bass region can be reproduced.
[0017]
It is a perspective view which shows the structure of the electromagnetic converter by
Embodiment 1 of this invention. It is a distribution map which shows "the ratio of a variation"
concerning Embodiment 1 of this invention. It is a distribution map which shows "the ratio of a
conductor part" which concerns on Embodiment 1 of this invention. It is a perspective view
which shows the structure of the other electromagnetic transducer by other Embodiment 1 of
this invention.
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Explanation of sign
[0018]
10 bar permanent magnets, 20 diaphragms, 21 coils, 30 slits, 40 yokes, Wm magnet width, Tm
magnet thickness, τp pole pitch, lg diaphragms distance from magnet surface
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