Star Micronics Company Limited

Takahiro Sone

Yoshio Imahori

Naoyuki Kigawa

Kazushige Tajima

Mitsuhiro Masuda

Hiroshi Fujinami

Tomonari Suzuki

Katsuyuki Sano

Isao Fushimi

Kazushi Suzuki

Yoshiharu Oishi

Yasuharu Tsuchiya

Fumihito Ishimura

Speaker

An electroacoustic transducer includes a base made of a magnetic material; a magnetic core made of a magnetic material and upstanding on the base ; a diaphragm made of a magnetic material and spaced from a leading end of the magnetic core; a magnetic field generating member cooperating with the base , the magnetic core and the diaphragm to constitute a magnetic circuit, for supplying a static magnetic field; a coil placed around the magnetic core, for supplying an oscillating magnetic field to the magnetic circuit. The magnetic field generating member constitutes a multiplex ring structure in which a magnet a and a support ring are integrated together, whose faces opposing the diaphragm have respectively magnetic poles of the same polarity.

Electroacoustic transducer

An electroacoustic transducer adapted to be mounted on a printed circuit board in which a coil spring is accommodated and supported in a cylindrical recess of a frame while it is fixed to neither a terminal plate nor the frame. Particularly, a protruding pin of the coil spring is passed through a though hole of the terminal plate to allow a leading portion of the protruding pin to be hooked thereon. When the electroacoustic transducer is mounted on the printed circuit board, any horizontal displacement between the compressed spring and the printed circuit board would not cause stress concentration on the coil spring since the coil spring is onlly horizontally shifted in the cylindrical recess until a coil portion of the coil spring hits against the wall of the cylindrical recess.

An electroacoustic transducer is provided with a diaphragm which is made of a magnetic material, and to which a magnetic piece is fixed; a magnetic core which is placed in proximity to the diaphragm ; a coil which supplies an oscillating magnetic field to the magnetic core ; a housing which accommodates the diaphragm , the magnetic core , and the coil , and which has a sound release opening in a top plate opposed to the diaphragm , the sound release opening being larger than the magnetic piece . A beam portion is formed integrally with the housing which extends from a peripheral portion of the sound release opening to another peripheral portion passing above the magnetic piece . A gap Ga between the diaphragm and the magnetic core , and a gap Gb between the magnetic piece and the beam portion satisfy relationships of Ga&lE;Gb&lE;5Ga.

The invention provides an electroacoustic transducer capable of preventing degradation in its acoustic performance as a result of the reflow soldering process applied. With the electroacoustic transducer, variation in the minimum resonance frequency Fo of a diaphragm is restrained, stabilizing the acoustic performance by causing a decrease in the minimum resonance frequency Fo of the diaphragm due to irreversible demagnetization of the magnet caused by the reflow soldering temperatures to cancel out an increase in the minimum resonance frequency Fo of the diaphragm due to thermal contraction of a holder member caused by the reflow soldering temperatures.

The present invention provides an electroacoustic transducer which realizes an optimum characteristic thereof utilizing heat caused by reflow soldering without being influenced by the same heat. The electroacoustic transducer includes a magnetic driving portion composed of a base, a core provided upright on the base and a coil wound around the core, wherein a height of the coil at the manufacturing time is set lower by a height which corresponds to thermal expansion of the coil in reflow soldering, and a projection length of the core exposed from the coil at the manufacturing time is set larger by the height which corresponds to thermal expansion of the coil in reflow soldering.

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Shizuoka, Japan

Takahiro Sone