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JPS6125399

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DESCRIPTION JPS6125399
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone unit which is most suitable and inexpensively assembled when bandwidth limitation
is required for communications such as telephones. Prior Art Configuration and Its Problem FIG.
1 shows an example of a conventional microphone unit cut off m1. The configuration of this
conventional example will be described below with reference to the drawings. In FIG. 1, reference
numeral 1 denotes a metal case having a sound hole 1a on the top surface, and 2 denotes a
differential type microphone operated by the sound pressure difference between the front and
back of the built-in diaphragm. The front and back of the differential type microphone are
separated, and sound holes 30 provided in the insulator 3 are configured to ventilate the front
and back. Father, the chamber 5 is formed between the top surface of the metal case 1 and the
front portion of the insulator 3 via the rubber ring 4 for preventing leakage, and the back of the
insulator 3 is backed by the case 6 for the back air chamber. The air chamber 7 is configured. An
output lead 8 of the differential microphone 2 is connected to a metal terminal 9 a provided on
the external case 9. Leakage occurs by bonding the insulator 3 to the back air chamber case 6
and the contact portion of the differential microphone 2 and the penetration portion 8 a of the
back air chamber case 6 of the output lead wire 8 by bonding or the like. Prevent and seal. Each
of the above components is fixed by caulking the end portion 10 of the metal case. Next, the
operation of the conventional example configured as described above will be described. In the
case of a simple acoustic equivalent circuit, as shown in FIG. 2, ml and rl are sound holes 1a and
Sf is the front air chamber 5. m2. r2 is a sound hole 3a. sb back room 7. mo and So are
equivalent to the differential microphone 2. In FIG. 2, ml, rl and Sf and m2. It can be seen that r
and Sb each constitute an acoustic high cut filter. When microphones having characteristics as
shown in FIG. 3 are used as the differential microphone 2, the high cut frequency f1 of m, r, and
Sf is m7. If it is set higher than the high cut frequency f2 of r2 and sb, an example of band-
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limited characteristics as shown in FIG. 4 can be obtained. f, adjustment of Q of f2 part is sound
hole 1a. 3aK acoustic resistance cloth etc. can be added and adjusted. In the above-described
conventional example configured as described above, it has an advantage that characteristics
suitable for the case where band limitation is required for communications such as telephones
can be obtained, but the structure is complicated and it is difficult to assemble automatically.
There is a drawback that the cost increase can not be avoided. SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the disadvantages of the prior art, and to
provide a microphone unit which is inexpensive, has a structure suitable for mass production,
and is capable of band limitation.
In order to achieve the above object, the present invention reduces the number of parts and
simplifies the structure, inserts each part as a block into a cylindrical metal case, and inserts all
the inserted parts at the end of the metal case. It secures by caulking, and obtains the effect of
enabling automatic assembly. Description of the Embodiments The configuration of an
embodiment of the present invention will be described below with reference to the drawings. In
FIG. 5, the same parts as in FIG. 1 are indicated by the same reference numerals. In FIG. 5, the
insulator 3 separates the front and back of the differential microphone 2 and constitutes the
front air chamber 5 by the recess in the front and the top surface of the metal case l, and the
recess in the back and the printed circuit board 11 Back room 7 is configured. Reference
numeral 3a denotes one or more sound holes for ventilating the front air chamber 5 and the back
air chamber 7. The printed circuit board 11 also serves as an output terminal for taking out the
output of the differential type microphone 2 through the output lead wire 8... The output lead
wire 8 is connected. Differential microphones coupled as above. The insulator 3, the printed
circuit board 11 and the like are inserted into the metal case 1, and the end 10 of the metal case
1 is fixed by caulking. In the case of the present invention, the contact surface of the metal case
10 is in contact with the contact surface of the insulator 3 with a flat surface, and fixed by
caulking, so that a separate rubber ring or the like for preventing leakage is not necessary.
Moreover, the contact surface of the insulator 3 and the printed circuit board 11 is the same. FIG.
6 shows a second embodiment of the present invention, in which the differential microphone 2 is
inserted and fixed from the front side of the insulator 3. FIG. 7 shows a third embodiment, in
which a projection 3b is provided at the front of the insulator 3, thereby obtaining a noise
frequency f1 shown in FIG. It is like that. As described above, in the case of the present invention,
the number of parts is small and the insulator which is an insertion part. The differential
microphone 2 ° printed circuit board 11 or the like can be configured in advance as one block,
and this block can be fixed to the metal case 1 by caulking after being inserted into the metal
case 1, so that automatic assembly and the like is possible. There is an advantage that a
microphone unit having a different structure can be provided. The present invention is
configured as described above, and the following effects can be obtained. The back air chamber 7
is configured using a printed circuit board, and no rubber ring is required to form the front air
chamber, so that the number of parts can be significantly reduced compared to the prior art and
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automatic assembly is possible. Therefore, the microphone unit 7 can be provided at low cost and
with band limitation.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view showing a conventional microphone unit, FIG. 2 is an acoustic
equivalent circuit diagram in FIG. 1, and FIG. 3 is a frequency characteristic showing
characteristics of a differential microphone used in the microphone unit of FIG. 4 and 5 are
frequency characteristics showing the characteristics of the microphone unit in FIG. 1, FIG. 5 is a
sectional view showing the microphone unit in one embodiment of the present invention, and
FIG. 6 is a second embodiment of the present invention And FIG. 7 is a sectional view showing a
third embodiment.
1 metal case, 2 .. differential type microphone, 3. Insulator, 8. Lead wire for output, 11 printed
circuit board,], Ia Copper foil surface. Name of agent Attorney Nakao Toshio and 1 other person
Figure 1 Figure 3 Commissioned by 1-Number of members jLjz) Figure 4 Beast ≧ Figure 5
Figure 6 Figure 7
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