JPS6125399A - Microphone unit - Google Patents

Abstract

PURPOSE:To reduce the number of parts and to assemble parts automatically by constituting a rear-air-chamber of a printed board and comprising its front-air- chamber without a rubber ring, etc. CONSTITUTION:An insulating material 3 separates a rear-part and front-part of a differential microphone 2. A front-air-chamber 5 and rear-air-chamber 7 are constituted of a group of a front recessed part and a top panel of a metallic case 1 and that of a rear recessed part and printed board 11, respectively. Said board 11 also serves as an output terminal for fetching an output of the microphone 2 through a lead wire 8, which is jointed to a copper foil surface 11a of the board 11 by soldering. The microphone 2 insulating material 3, substrate 11, etc. jointed in such a way, are inserted into the metallic case 1, and an end 10 of the case 1 is fixed by caulking. In this case, the jointed surface of the top panel of the case 1 and the insulating material 3 is flat, and therefore a rubber ring for preventing leakage is unnecessary. Moreover, the jointed surface of the insulating material 3 and substrate 11 is similar to said surface.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a microphone unit that is optimal and inexpensive to assemble when band limitation is required for communications such as telephones.

Structure of a conventional example and its problems FIG. 1 shows an example of a cross-sectional view of a conventional microphone unit. The configuration of this conventional example will be explained below with reference to the drawings. In Fig. 1, l is a metal case with a sound hole 1a on the top surface, 2 is a differential microphone that operates by the difference in sound pressure between the front and back of the built-in diaphragm, and the insulator 3 The front and back portions of the differential microphone are separated, and the front and back portions are configured to be ventilated through sound holes 30 provided in the insulator 3. The chamber 5 is formed between the top surface of the metal case 1 and the front part of the insulator 3 via a rubber ring 4 for preventing leakage, and the back air chamber case 6 is connected to the back of the insulator 3. It constitutes an air chamber 7. 8 is an output lead wire of the differential microphone 2;
It is connected to a metal terminal 9a provided on the external case 9. In addition, the connection part between the insulator 3 and the back air chamber case 6 and the differential microphone 2, and the back air chamber case 6 of the output lead wire 8.
The penetrating portion 8a is sealed by bonding or the like to prevent leakage. Each of the above parts is a metal case]
It is fixed by caulking the end 10 of.

Next, the operation of the conventional example configured as described above will be explained. When considering a simple acoustic equivalent circuit,
As shown in Fig. 2, ml and rl are the sound holes 1a, and Sf is the front air chamber 5. m2. r2 is the sound hole 3a.

sb is the back air chamber 7. mo and So are equivalent to the differential microphone 2. In Figure 2, ml, rl, Sf and m2
．． It can be seen that r and Sb each constitute an acoustic high-cut filter. When a microphone having characteristics as shown in Fig. 3 is used as the differential microphone 2, m,...
m7.r, and the high cut frequency f1 of Sf. r2 and sb
If you set it higher than the high cut frequency f2 of
As shown in the figure, an example of band-limited characteristics is obtained. f,, f2
Adjustment of the Q of the section is done through the sound hole 1a.

It can be adjusted by adding 3aK acoustic resistance surface cloth, etc.

The above-mentioned conventional example configured as described above has the advantage of obtaining characteristics suitable for communications such as telephones that require band limitation, but the structure is complex and automatic assembly is difficult, so it is not suitable for mass production. However, the drawback was that the cost was unavoidable.

OBJECTS OF THE INVENTION The present invention eliminates the drawbacks of the conventional example described above, and aims to provide a microphone unit that is inexpensive, has a structure suitable for mass production, and is capable of band limiting.

Structure of the Invention In order to achieve the above object, the present invention reduces the number of parts and simplifies the structure, inserts each part as one block into a cylindrical metal case, and inserts all the inserted parts into the end of the metal case. It is fixed by caulking, and has the effect of making automatic assembly possible.

DESCRIPTION OF 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 numbers. In FIG. 5, the insulator 3 separates the front and back parts of the differential microphone 2, and forms a front air chamber 5 with the recess in the front part and the top surface of the metal case l, and the recess in the back part and the printed circuit board 11. A back air chamber 7 is configured. 3a is one or more sound holes for ventilating the front air chamber 5 and the back air chamber 7. The printed circuit board 11 receives the output of the differential microphone 2 via the output lead wire 8.
The copper foil surface 11a of the printed circuit board 11 and the output lead wire 8 are connected by wires, etc., which also serve as output terminals for output. Differential microphones coupled as above 2. The insulator 3, printed circuit board 11, etc. are inserted into the metal case 1, and the end portion 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 and the insulator 3 are flat and are fixed by caulking, so there is no need for a rubber ring or the like to prevent leakage as in the conventional case. The same applies to the contact surfaces between the insulator 3 and the printed circuit board 11.

FIG. 6 shows a second embodiment of the present invention, in which a differential microphone 2 is inserted and fixed into an insulator 3 from the front side. Also, FIG. 7 shows a third embodiment,
This device is characterized in that a protrusion 3b is provided on the front part of the insulator 3, so that the normal frequency f1 shown in FIG. 4 can be obtained.

As described above, in the case of the present invention, the number of parts is small and the insulator 3. Differential microphone 2゜Printed circuit board 1
The first class can be configured in advance as one block, and this block can be fixed by caulking after being inserted into the metal case 1, so automatic assembly is possible, and the microphone unit and unit are inexpensive and have a structure suitable for mass production. It has the advantage of being able to provide

Effects of the Invention The present invention has the above-described configuration, and provides the following effects.

The back air chamber 7 is configured using a printed circuit board, and
No rubber ring is required when constructing the front air chamber, so
The number of parts can be significantly reduced compared to the conventional method, and since automatic assembly is possible, it is possible to provide a microphone unit 7 that is inexpensive and capable of band limiting.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional microphone unit, Fig. 2 is an acoustic equivalent circuit diagram of Fig. 1, and Fig. 3 is a sectional view of a conventional microphone unit.
FIG. 4 is a frequency characteristic diagram showing the characteristics of the differential microphone used in the microphone unit shown in FIG. 1. FIG. 5 is a frequency characteristic diagram showing the characteristics of the microphone unit in FIG. 6 is a sectional view showing a second embodiment of the present invention, and FIG. 7 is a sectional view showing a third embodiment. 1 Metal case, 2... Differential microphone, 3 Insulator, 8 Output lead wire, 11 Printed circuit board, ], I
a Copper foil surface. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 3: Number of times per cycle jLjz) Fig. 4: Beast ≧ Fig. 5: Fig. 6 Fig. 7

Claims (3)

[Claims] (1) A cylindrical metal case with a sound hole on the top surface, a differential microphone, and a front part and a back part of the differential microphone separated from each other, and one or more sound holes in the front part. and a printed circuit board connected to an output of the differential microphone, and all the inserted parts are fixed by caulking an end of a metal case. (2) A microphone unit according to claim 1, wherein a front air chamber is formed by the recess at the front of the insulator and the top surface of the metal case, and a back air chamber is formed by the recess at the back of the insulator and the printed circuit board. (3) The microphone unit according to claim 1 or 2, wherein an acoustic resistance surface cloth is attached to the sound hole portion of the insulator or the top sound hole portion of the metal case.