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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional front view of a conventional
electro-acoustic transducer, FIG. 2 is a cross-sectional front view of an electro-acoustic
transducer in one embodiment of the present invention, FIG. 3 agbt cFi same conversion It is a
figure for device explanation. 1 ...... permanent magnet, 2: ----- York, 3 ...... Giyatsua 4 ...... coil, 5
...... i pole piece, 9 ... · · · · Center hole, 10 · · · · · · · · Conductive spacer.
DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electro-acoustic
transducer that has a high conversion efficiency and high productivity. An example of a
conventional configuration of this type of converter is shown in FIG. In FIG. 1, 1 is a permanent
magnet, 2 is a yoke of a magnetic circuit, 3 is a gear tab of a magnetic circuit, 4 is a coil for
passing an AC signal current, 5 is a soft magnetic pole piece, 6 is a vibrating film, 7 is a case,
Reference numeral 8 is a spacer in which the vibrating membrane 6 is inserted between the
cases and A is inserted. 9 is a center 1 'correction of the yoke 2 and 2 is a pole 5 as shown in FIG.
1, a magnetic circuit is constituted by the permanent magnet 1 and the yoke 2 as shown in FIG.
Pass signal current. In the magnetic circuit, a DC magnetic flux from the permanent magnet 1
and a signal current (AC magnetic flux from C flow. In the gap 3, DC and AC magnetic flux flows,
and at the same time, leakage magnetic flux is generated on the upper surface of the gear knob
3. The leakage flux reaches the pole piece 5 to excite the pole piece 6. However, in such a
configuration, most of the magnetic flux flows through the gear knob 3, the leakage flux on the
top of the gap is extremely small, and the electrode conversion efficiency is poor. Further, in the
configuration 1 of the gap 3, it is necessary to form a narrow gap uniformly, and it is timeconsuming to insert a spacer at the time of manufacture, assemble it, assemble a magnetic
circuit, and remove the spacer. The present invention is intended to provide an electroacoustic
transducer having a high electromagnetic conversion efficiency and a high productivity. One
embodiment of the present invention will be described below with reference to the drawings. -4
An embodiment of the present invention is shown in FIG. The same elements as in FIG. 1 are
assigned the same reference numerals as in FIG. The feature of the present invention resides in
that the conductive spacer 10 is inserted in the gap 3. The configuration of the conductive spacer
10 is, for example, a structure in accordance with the gear knob 3 made of Cu, and the yoke 2
and center pole at the time of assembling the magnetic circuit. You should fit to 9. If the accuracy
of the conductive spacer 10 and the accuracy of the yoke 2 and the center pole 9 are sufficiently
set by such assembly, the uniformity of the gap, the shift of the center, the center pole 9 and the
yoke which were difficult in the conventional assembly Assembling of the upper surface of 2 or
the like can improve the assembly accuracy. Therefore, in the conventional example, the
nonuniformity of the magnetic field occurs due to the nonuniformity of the gear knob 3 and the
blur of the center, etc., and the single sided adsorption and the like occur when the gap 3 is
narrowed. It is possible to construct an efficient converter without having to Further, in the
electromagnetic converter, as described above, since the leakage flux on the upper surface of the
gear knob 3 is used, it is desirable 4 to increase the leakage flux on the upper surface of the gear
knob 3.
In the present invention (one gear knob 3 is filled with a conductive material to increase leakage
flux. As described above, magnetic flux of direct current and alternating current flows in the
magnetic circuit. The conductive material inserted in the gap 3 of the magnetic circuit (it does
not affect the direct current magnetic field at all, but an eddy current is generated with respect to
the alternating magnetic field (signal), and the eddy current generates a magnetic field. The
magnetic field acts to intensify the leakage magnetic field on the upper surface of the gear tube
3, and leakage magnetic flux can be effectively generated with respect to the AC magnetic field.
The situation is shown in FIG. FIG. 3d shows that in the case of the conventional air gap, when
the conductive spacer 1o is inserted in the gap of the present invention, b shows an a field at the
conductive spacer 1 ° and a demagnetizing field is generated. In the conventional air gap 3,
leaked magnetic flux occurs in a semicircular shape (point portion) as shown in a. However, when
the conductive spacer 10 is inserted as in the present invention, the magnetic flux in the gap 3
has a sharp mountain shape (dotted line ). As shown in C, when a magnetic field is applied to the
conductive spacer 10 in the direction of the dotted arrow, a current flows in the direction of the
arrow A in the conductor, and a magnetic field is generated in the direction of the dotted arrow B
by this 'direct current'. Do. Therefore, in the gap, a magnetic field is generated in the opposite
direction to the externally applied magnetic field, a gap with high magnetic resistance is formed,
and the magnetic field becomes taxed as shown in FIG. The fact that the peak of the leakage flux
is sharp in this way can effectively extract the leakage flux of the gap to the outside. Magnetic
flux and the like that conventionally flowed from the yoke angle of the gap portion to the center
pole angle could not be used because the pole pieces and the center pole could not be brought
close enough, but they can be effectively used by making them like the present invention. . As
described above, according to the present invention, it is possible to obtain an electroacoustic
transducer having high electroacoustic conversion efficiency and high productivity.