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−(、。 L name of invention
Carbon transmitter electrode
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode for a
carbon microphone that has good life characteristics and is easy to manufacture. In carbon
microphones, the diaphragm vibrates by sound and the vibration is transmitted to the movable
electrode attached to the diaphragm, resulting in the movement of carbon powder filled between
the movable electrode and the fixed electrode. Therefore, the resistance between the two
electrodes changes and the change is taken out as a voltage change, so that the movable and
fixed electrodes of the carbon microphone have sufficient mechanical properties to withstand
vibration and shock in use Although it is necessary, it is further required that the contact
resistance with carbon powder be low, and be stable over time and have good conductivity. In a
carbon microphone, the electrode and the carbon powder come in contact with or separate from
each other while being electrically energized 1 due to the structure, so that an arc 5 is generated,
and the surface of the electrode is easily oxidized. If the electrode surface is oxidized for some
reason, the contact resistance between the electrode and the carbon powder changes, which
changes the dynamic resistance, sensitivity and noise of the transmitter. Currently. In order to
improve conductivity, copper is used as a material, and movable and fixed electrodes having a
gold-plated structure that is oxidation-stable on the front surface 10 are widely used for carbon
transmitters. This type of electrode and carbon transmitter using it have stable electrical and
mechanical properties and no problem, but their manufacturing includes machining and plating
processes such as pressing, 15 impressions, and cutting. It is time consuming to manufacture,
and expensive to use gold. It is conceivable to replace gold plating with other metal plating. Not
only improvement in the process can not be obtained, but precious metal 20EndPage: 1 is
expensive as gold as gold, metallic plating other than precious metal can not obtain sufficient
stability against oxidation, and deterioration of characteristics with time is acceptable It will not
be possible. On the other hand, a pressure electrode has also been proposed by cutting graphite,
but the mechanical strength of the graphite electrode is inferior, and the breakage results from
drop impact and the like. Furthermore, although it is preferable to make the electrode surface
portion in contact with the carbon powder a smooth spherical surface, it is not easy to machine a
smooth spherical surface for cutting. Therefore, the main object of the present invention is to
provide a movable and fixed electrode for a carbon microphone which has mechanical and
electrical characteristics comparable to those of the conventional gold-plated electrode and
which can be manufactured inexpensively and easily. The object of the present invention is
achieved by the electrode for a carbon transmitter according to the present invention, which is
formed by molding a conductive resin containing 30 to 95 weight carbon.
By firing the formed electrode in an inert gas, it is possible to lower the initial dynamic
resistance. Referring to the attached drawings, FIG. 1 is a partially cutaway side view showing the
structure of a typical carbon microphone. The illustrated nine carbon transmitter has a fixed
electrode 1. Carbon powder 2 ° movable electrode 8. Fixed electrode terminal Vibrating plate 5.
Terminal 6 ° insulating plate 7. Inner frame 8. カバー9. Carbon chamber insulator 10. The
protective plate 11 and the outer frame 12 are provided. In the present invention, one or both of
the fixed electrode 1 and the movable electrode 8 of such a transmitter are the same as those
described above. Using a molding material obtained by mixing and crushing a carbon material
such as carbon black, graphite powder, carbon fiber etc. and a resin material such as phenol resin
lO oil, epoxy resin etc in various ratios, predetermined shape and size In order to achieve the
electrical characteristics as a transmitter electrode, the carbon ratio should be 80% by weight
upwind 15 to achieve the electrical characteristics as a transmitter electrode, and the carbon
ratio should be 95 weight or less in terms of formability. What should be done is that although
the dynamic resistance decreases as the use ratio of carbon increases, the temporal
characteristics are stable almost regardless of the carbon ratio. And it was found that the
influence of the type of carbon and the type of resin 111 was almost zero. Furthermore, if the
formed electrode is fired at a high temperature of at least 800 ° C., preferably about 500 ° C.
to about 1200 ° C. in an inert gas, for example, in a nitrogen stream, the conductivity of the
electrode is improved and the transmitter is improved. It turned out that the dynamic resistance
of can be reduced. In the carbon transmitter shown in FIG. 1, an electrode (a sample α) obtained
by plating a copper material which is generally used at present with gold, and an electrode
formed by a molding material composed of an epoxy resin containing a weight of 60 carbon (a
sample b) And molded into a molding material consisting of a phenolic resin containing 80 parts
by weight of carbon resin and then baked for 2 hours in a nitrogen stream at 800 ° C. for 1
hour to incorporate electrodes (sample C), and measured the time-dependent characteristics of
their microphones. . The results are shown in FIGS. 2 and 3. In the exam. Supply current a 50 mA
with accelerated standing conditions of a temperature of 60 ° C. and a relative humidity of 90-
95%. The noise is 80 horns and friends. At the start of leaving (the sun the moon). A friend who
measures the dynamic resistance and sensitivity on the 10th, 20th, 20th, 80th and 50th. Figures
2 and 8 show the time course of the kinetic resistance and sensitivity, respectively, in which
curves 1 a, b and C are for samples α, b and C respectively.
According to the illustrated results, it is understood that the electrode of the present invention 9
has no inferiority to the conventional gold plated electrode 5 in the temporal stability of its
characteristics. In addition, as already stated, the electrode of the present invention can be
manufactured inexpensively and easily.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a partial cutaway 10 of a typical
carbon microphone, and FIG. 2 is a dynamic resistance of a microphone incorporating various
carbon microphone electrodes. FIG. 3 is a graph showing a time-dependent change, and FIG. 3 is
a graph showing a time-dependent change of sensitivity of a transmitter incorporating various
carbon transmitter electrodes. In FIG. 1, reference numeral 115 denotes a solid electrode and 3
denotes a movable electrode. 0EndPage: 2 Fig. 1 Fig. 2 6 6 List of attached documents (1)
Request 1 copy (2) 1 specification (3) 1 drawing (4) 1 letter of attorney (5) application
examination 1 bill, 7 other inventor, patent applicant or agent Address same place 3) Agent
address Address number 13 Shiba Kampeicho, Minato-ku, Tokyo Shikkoh Toranomon Pino Name
Patent Attorney EndPage: 3
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