GB2120900A

GB2120900A - Transmitter microphone

Info

Publication number: GB2120900A
Application number: GB08310040A
Authority: GB
Inventors: Yasushi Endou
Original assignee: Kureha Corp
Current assignee: Kureha Corp
Priority date: 1982-04-13
Filing date: 1983-04-13
Publication date: 1983-12-07
Also published as: DE3313408A1; FR2525062A1; GB8310040D0; SE8302029L; SE8302029D0; JPS58178700A

Abstract

A transmitter microphone is provided wherein a tip 2a of a diaphragm 2 is fixed to one leg 3a of a substantially U-shaped spring 3 whose other leg 3b is fixed, and a piezoelectric body 6 with electrodes is attached to a substantially central portion 3c of the spring, so that an output may be obtained from the piezoelectric body. <IMAGE>

Description

SPECIFICATION Transmitter microphone The present invention relates to a transmitter microphone for producing a signal which utilizes a body formed of a piezoelectric material.

Description of the prior art A transmitter microphone has been proposed which uses for a diaphragm a film of a polymeric piezoelectric material such as PVDF (polyvinylidene fluoride), having electrodes formed at two surfaces thereof. Studies are being made for practical use of such a transmitter microphone. Although many types of transmitter microphone are known, they all use a piezoelectric body in the expansion/contraction mode. For this reason, the vibration amplitude of such a diaphragm is small and the output is also small.

According to the invention there is provided a microphone comprising: a resilient member comprising a first, substantially arcuate, portion, a second, fixed, portion and a leg portion extending from the first portion; a diaphragm having a tip connected to the leg portion of the resilient member; and a piezoelectric body provided with electrodes and attached to the first, substantially arcuate, portion of the resilient member.

The invention will be further described by way of example with reference to the drawings in which: Figure lisa side sectional view of a transmitter microphone for a telephone set in accordance with an embodiment of the present invention, together with a circuit diagram of a receiver circuit; and Figure 2 is an enlarged view of part of the microphone shown in Figure 1.

Figure 1 shows an embodiment of the present invention as applied to a transmitter microphone for a telephone set.

A conical diaphragm 2 is disposed inside a casing 1 such that its periphery is fixed to the side walls of the casing 1. The diaphragm 2 may be a metallic or plastic diaphragm which is conventionally used for a carbon microphone or the like. Atip 2A of the diaphragm 2 is fixed to one leg 3a of the U-shaped spring 3 of phosphor bronze or the like through a damper 4 by adhesion or the like. The end of the other leg 3b of the spring 3 is fixed by a support member 5. A body 6 formed of a piezoelectric material is adhered to a central arcuate portion 3c of the spring 3. The piezoelectric body 6 preferably comprises a flexible material such as a polymeric piezoelectric material, e.g., PVDF, as described above. The piezoelectric body 6 is formed into a thin plate-like shape as shown in Figure 2, and electrodes 7 and 8 are formed at two surfaces of the piezoelectric body 6.Lead wires 9 and 10 extend from the electrodes 7 and 8 and are connected to terminals 11 and 12, respectively, which extend through a side wall of the casing 1. The terminals 11 and 12 are connected to input terminals 16 and 17 of an external receiver circuit 15 through lead wires 13 and 14, respectively. The receiver circuit 15 has a configuration as shown in Figure 1 incorporating an FET (field-effect transistor) 18 and produces an output signal Eo at its output terminals 19 and 20. A plurality of holes 21 for receiving a voice are formed in the surface of the casing 1 which is opposed to the diaphragm 2.

With the microphone of the above configuration, when the conical diaphragm 2 receives a sound pressure of the voice received through the holes 21, the total displacement of the diaphragm 2 is concentrated at the tip 2a. Upon reception of the displacement of the diaphragm 2, the leg 3a of the spring 3 moves vertically in the direction indicated by arrow a. Then, the piezoelectric body 6 is deformed to produce a voltage. The voltage from the piezoelectric body 6 is amplified by the FET 18 to obtain the output signal E,.

In this case, since the piezoelectric body 6 is displaced in a deformed mode, a large output may be obtained. In the case of the configuration of this embodiment, since the piezoelectric body 6 is not subject to adverse effects of electromagnetic waves, the S/N ratio may be improved. Furthermore, since the piezoelectric body 6 may be placed at substantially the centre of a flat spring material and the spring material may then be bent in a U-shape, element processing is easy and the manufacturing steps of the microphone are thus simplified.

In the embodiment described above, the diaphragm 2 is of conical shape. However, the diaphragm 2 may be of a shape (inverted dome-shape) constituting a part of a sphere. Thus, the shape of the diaphragm 2 needs only to be such that the displacement thereof upon reception of a sound pressure may be concentrated at its tip. The damper 4 may be omitted. However, when a sound pressure of high frequency is received, it may bounce between the diaphragm 2 and the spring 3. Therefore, the damper 4 is used to eliminate this. If the receiver circuit 15 is housed inside the casing 1 with the output terminals 19 and 20 extending outside the casing 1, the S/N ratio is further improved.

1. A microphone comprising: a resilient member comprising a first, substantially arcuate, portion, a second, fixed, portion and a leg portion extending from the first portion; a diaphragm having a tip connected to the leg portion of the resilient member; and a piezoelectric body provided with electrodes and attached to the first, substantially arcuate, portion of the resilient member.

2. A transmitter microphone according to claim 1, wherein the resilient member is substantially U-shaped.

3. A transmitter microphone according to claim 1 or 2, wherein the piezoelectric body comprises a polymeric piezoelectric material.

4. Atransmitter microphone according to any preceding claim, wherein the diaphragm is of a conical shape.

5. A transmitter microphone according to any of claims 1 to 3, wherein the diaphragm is of an inverted dome-shape.

6. A transmitter microphone according to claim

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Transmitter microphone The present invention relates to a transmitter microphone for producing a signal which utilizes a body formed of a piezoelectric material. Description of the prior art A transmitter microphone has been proposed which uses for a diaphragm a film of a polymeric piezoelectric material such as PVDF (polyvinylidene fluoride), having electrodes formed at two surfaces thereof. Studies are being made for practical use of such a transmitter microphone. Although many types of transmitter microphone are known, they all use a piezoelectric body in the expansion/contraction mode. For this reason, the vibration amplitude of such a diaphragm is small and the output is also small. According to the invention there is provided a microphone comprising: a resilient member comprising a first, substantially arcuate, portion, a second, fixed, portion and a leg portion extending from the first portion; a diaphragm having a tip connected to the leg portion of the resilient member; and a piezoelectric body provided with electrodes and attached to the first, substantially arcuate, portion of the resilient member. The invention will be further described by way of example with reference to the drawings in which: Figure lisa side sectional view of a transmitter microphone for a telephone set in accordance with an embodiment of the present invention, together with a circuit diagram of a receiver circuit; and Figure 2 is an enlarged view of part of the microphone shown in Figure 1. Figure 1 shows an embodiment of the present invention as applied to a transmitter microphone for a telephone set. A conical diaphragm 2 is disposed inside a casing 1 such that its periphery is fixed to the side walls of the casing 1. The diaphragm 2 may be a metallic or plastic diaphragm which is conventionally used for a carbon microphone or the like. Atip 2A of the diaphragm 2 is fixed to one leg 3a of the U-shaped spring 3 of phosphor bronze or the like through a damper 4 by adhesion or the like. The end of the other leg 3b of the spring 3 is fixed by a support member 5. A body 6 formed of a piezoelectric material is adhered to a central arcuate portion 3c of the spring 3. The piezoelectric body 6 preferably comprises a flexible material such as a polymeric piezoelectric material, e.g., PVDF, as described above. The piezoelectric body 6 is formed into a thin plate-like shape as shown in Figure 2, and electrodes 7 and 8 are formed at two surfaces of the piezoelectric body 6.Lead wires 9 and 10 extend from the electrodes 7 and 8 and are connected to terminals 11 and 12, respectively, which extend through a side wall of the casing 1. The terminals 11 and 12 are connected to input terminals 16 and 17 of an external receiver circuit 15 through lead wires 13 and 14, respectively. The receiver circuit 15 has a configuration as shown in Figure 1 incorporating an FET (field-effect transistor) 18 and produces an output signal Eo at its output terminals 19 and 20. A plurality of holes 21 for receiving a voice are formed in the surface of the casing 1 which is opposed to the diaphragm 2. With the microphone of the above configuration, when the conical diaphragm 2 receives a sound pressure of the voice received through the holes 21, the total displacement of the diaphragm 2 is concentrated at the tip 2a. Upon reception of the displacement of the diaphragm 2, the leg 3a of the spring 3 moves vertically in the direction indicated by arrow a. Then, the piezoelectric body 6 is deformed to produce a voltage. The voltage from the piezoelectric body 6 is amplified by the FET 18 to obtain the output signal E,. In this case, since the piezoelectric body 6 is displaced in a deformed mode, a large output may be obtained. In the case of the configuration of this embodiment, since the piezoelectric body 6 is not subject to adverse effects of electromagnetic waves, the S/N ratio may be improved. Furthermore, since the piezoelectric body 6 may be placed at substantially the centre of a flat spring material and the spring material may then be bent in a U-shape, element processing is easy and the manufacturing steps of the microphone are thus simplified. In the embodiment described above, the diaphragm 2 is of conical shape. However, the diaphragm 2 may be of a shape (inverted dome-shape) constituting a part of a sphere. Thus, the shape of the diaphragm 2 needs only to be such that the displacement thereof upon reception of a sound pressure may be concentrated at its tip. The damper 4 may be omitted. However, when a sound pressure of high frequency is received, it may bounce between the diaphragm 2 and the spring 3. Therefore, the damper 4 is used to eliminate this. If the receiver circuit 15 is housed inside the casing 1 with the output terminals 19 and 20 extending outside the casing 1, the S/N ratio is further improved. CLAIMS

6. A transmitter microphone according to claim f,wherein the diaphragm, the resilient member and the piezoelectric body are housed in a casing, which has terminals from which the output from the piezoelectric body may be obtained.

7. Atransmitter microphone according to claim 5, wherein a circuit for amplifying the output from the piezoelectric body is arranged inside the casing.

8. Atransmitter microphone according to claim 1, wherein a damper is interposed between the diaphragm and the resilient member.

9. Atransmitter microphone substantially as described with reference to the drawings.