JPH07112317B2 - Electromagnetic induction type speaker - Google Patents

Description

Detailed Description of the Invention

[001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction type speaker.

[002]

2. Description of the Related Art Conventionally, a magnetic circuit section for generating a DC magnetic field, a diaphragm made of a conductive material vibratably supported in the DC magnetic field, and an electromagnetic induction coil arranged on the magnetic circuit side. An electromagnetic induction speaker that is provided with a signal current to the electromagnetic induction coil to generate an AC magnetic field and induce an induction current in the diaphragm to vibrate the diaphragm to perform sound reproduction. Is proposed.

As this type of electromagnetic induction type speaker, a speaker configured as shown in FIG. 6 is known. The electromagnetic induction speaker shown in FIG. 6 has a magnetic circuit section 1 for generating a DC magnetic field, a diaphragm 2 made of a conductive material oscillatingly supported in the DC magnetic field, and a magnetic circuit section 1 arranged on the magnetic circuit section 1 side. The electromagnetic induction coil 3 is provided. The magnetic circuit unit 1 includes a yoke 4, a pole piece 5 arranged so as to stand in the center of the yoke 4, and a ring-shaped magnet 6 arranged on the yoke 4 so as to surround the pole piece 5. It is arranged on the magnet 6 and is composed of a ring-shaped top plate 7. The magnetic circuit portion 1 constitutes a ring-shaped magnetic gap 8 for generating a DC magnetic field with an air gap between the top plate 7 and the pole piece 5 facing each other. The vibrating plate 2 is formed in a ring shape corresponding to the magnetic gap 8 and is movably supported so as to be located in the magnetic gap 8. That is, the diaphragm 2
The outer peripheral edge is supported on the inner peripheral surface of the top plate 7 via the viscoelastic support 9, and the inner peripheral edge is supported on the outer peripheral surface of the pole piece 5 via the viscoelastic support 9. By doing so, the magnetic gap 8 is oscillatably supported. Further, the electromagnetic induction coil 3 for inducing an induced current in the diaphragm 2 is located on the back side of the diaphragm 2 and is arranged to face the diaphragm 2.

In the electromagnetic induction type speaker constructed as described above, the ring-shaped diaphragm 2 made of a conductive material functions as a short-circuit coil, and the electromagnetic induction coil 3 receives a signal current corresponding to a predetermined acoustic signal. When supplied, an induced current is induced in the diaphragm 2. This induced current is applied to the diaphragm 2
Flows in the circumferential direction of. Then, the induced current acts on the DC magnetic field in the magnetic gap 8 to vibrate the diaphragm 2 and radiate reproduced sound.

[0095]

In the electromagnetic induction type speaker constructed as described above, it is necessary to prevent the diaphragm 2 and the electromagnetic induction coil 3 from coming into contact with each other when the diaphragm 2 vibrates. Yes, the diaphragm 2 and the electromagnetic induction coil 3
It is necessary to provide a required space between and. Further, since the electromagnetic induction coil 3 is disposed only on the back surface side of the diaphragm 2, the distance between the electromagnetic induction coil 3 and the electromagnetic induction coil 3 is changed when the diaphragm 2 vibrates, and the diaphragm 2 and the electromagnetic induction coil 3 are varied. The electromagnetic coupling between the three is not constant, and the vibration of the diaphragm 2 according to the signal current supplied to the electromagnetic induction coil 3 is not performed.

Further, since the electromagnetic induction type speaker has a structure in which the diaphragm 2 is arranged in the magnetic gap 8, if the area of the diaphragm 2 is increased, the gap between the magnetic gaps 8 is increased. The magnetic flux density in the magnetic gap 8 becomes small. Therefore, in the electromagnetic induction type speaker as described above, sufficient sound pressure output characteristics cannot be obtained, and good sound reproduction cannot be performed.

Therefore, the present invention has been proposed for the purpose of providing an electromagnetic induction speaker capable of obtaining a sufficient sound pressure output characteristic with high efficiency and enabling good sound reproduction.

[0085]

In order to achieve the above-mentioned object, an electromagnetic induction type loudspeaker according to the present invention has a ring-shaped magnetic circuit part for generating a DC magnetic field in a ring-shaped magnetic gap and a ring-shaped conductive material. And a first and a second diaphragms, which are disposed in close proximity to the front side and the rear side of the diaphragm, with the diaphragm sandwiched between the diaphragm and the diaphragm that is vibratably supported in the magnetic gap. An electromagnetic induction coil is provided, and by supplying a common signal current from the common signal source to the first and second electromagnetic induction coils, an in-phase AC magnetic field is generated in these coils.

[0109]

In the electromagnetic induction type speaker according to the present invention, the common signal is applied to the first and second electromagnetic induction coils which are arranged close to the front side and the back side of the diaphragm with the diaphragm sandwiched therebetween. By supplying a common signal current from the sources, an in-phase AC magnetic field is generated in these coils, the diaphragm is driven, and the reproduced sound is emitted.

[0101]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an electromagnetic induction type loudspeaker according to the present invention includes a magnetic circuit section 11 for generating a DC magnetic field, a diaphragm 12 made of a conductive material vibratably supported in the DC magnetic field, and the vibration. 1st which is arrange | positioned near the front side and the back side, respectively, sandwiching the plate 12
The electromagnetic induction coil 13 and the second electromagnetic induction coil 14 of FIG.

The magnetic circuit section 11 includes a yoke 15 made of a magnetic material, a pole piece 16 made of the same magnetic material arranged so as to stand at the center of the yoke 15, and the pole piece 15. A ring-shaped magnet 1 arranged on the yoke 15 so as to surround it.
7 and a top plate 18 formed on the magnet 17 and made of a ring-shaped magnetic material. The magnetic circuit portion 11 constitutes a ring-shaped magnetic gap 19 for generating a DC magnetic field with the air gap between the top plate 18 and the pole piece 16 facing each other.

The vibrating plate 12 is made of a light conductive material such as aluminum foil.
Is formed in a ring shape corresponding to, and a corrugation is formed concentrically on the main surface portion.
The vibrating plate 12 has its outer peripheral edge supported by the top plate 18 via the support ring 20 and its inner peripheral edge supported by the pole piece 16 via the support ring 21 as well. It is supported so that it can vibrate freely.

By the way, in this electromagnetic induction type speaker, the diaphragm 12 is arranged so as to be mounted on the top plate 18 and the pole piece 16, so that it can be arranged in the magnetic gap 19. It is equipped with. That is, notch steps 22 and 23 are formed at the corners of the top plate 18 and the pole piece 16 on the magnetic gap 19 side.
Since these notch steps 22 and 23 are formed facing the outer side of the upper surface of the magnetic circuit section 11 as shown in FIG.
The diaphragm 12 is arranged in the magnetic gap 19 by arranging the outer peripheral side and the inner peripheral side from the upper surface side of the magnetic circuit section 12 so as to be respectively placed on the notch step portions 22 and 23. Further, the support rings 20 and 21 respectively supporting the outer peripheral edge side and the inner peripheral edge side of the vibration plate 12 are also disposed in the notch step portions 22 and 23 by arranging them from the upper surface side of the magnetic circuit portion 12.

The notched step portions 22 and 23 are formed to a depth such that the vibration plate 12 supported here can be positioned substantially at the center of the magnetic gap 19. In addition, each of the support rings 20 and 21 is attached to the notch step portions 22 and 2 by an adhesive.
It is fixed to 3 and supports the diaphragm 12. Further, the support rings 20, 21 facing the magnetic gap 19 are provided.
Is made of a ferromagnetic material in order to improve the transmission of magnetic flux.

Then, the first electromagnetic induction coil 13 is
The pole piece 16 is fitted on the outer peripheral side of the pole piece 16 and is supported on the upper end side of the coil holding cylinder 24 provided on the yoke 15 so as to be close to the back surface of the diaphragm 12. The coil holding cylinder 24 has its mounting position in the horizontal direction restricted by fitting the base end of the coil holding cylinder 24 into the mounting position restricting protrusion 15a protruding from the yoke 15. Further, the second electromagnetic induction coil 14 is supported on the lower surface side of the coil support projecting piece 26 provided on the outer peripheral side of the equalizer 25 arranged on the upper end surface side of the pole piece 16 so as to be supported by the diaphragm 1.
It is arranged so as to be close to the front surface of 2. A plurality of, for example, three coil support protrusions 26 are radially provided on the outer peripheral side of the equalizer 25 at equal intervals.

By the way, the first and second electromagnetic induction coils 13 and 14 are arranged so as to face each other, and cannot contact the vibrating plate 12 when the vibrating plate 12 is driven to vibrate. The diaphragms 12 are arranged close to each other with a gap. In addition, the first and second electromagnetic induction coils 13 and 14 have substantially no cross-sectional shape because they do not generate unnecessary resonance when the diaphragm 12 is vibrationally driven and do not become an acoustic load. It is wound in a circular shape.

Then, the first and second electromagnetic induction coils 1
A common signal current is supplied to the signals 3 and 14 from a common signal source through a predetermined signal supply line. These coils 13, 1
By supplying a common signal current to the four, in-phase AC magnetic fields are generated.

Further, a concave portion 27 is formed on the outer periphery of the pole piece 16 constituting the magnetic circuit portion 11 and at the portion facing the first electromagnetic induction coil 13. The concave portion 27 widens the gap between the first electromagnetic induction coil 13 and the pole piece 16, and the diaphragm 12
When the vibration is driven, the viscous resistance of the air flow generated in the magnetic circuit portion 11 on the back side of the diaphragm 12 is reduced.

Inside the magnetic circuit portion 11, a sound absorbing material 28 for absorbing the reproduced sound radiated on the back side of the diaphragm 12 is arranged.

The electromagnetic induction type loudspeaker configured as described above is short-circuited by the AC magnetic field when the first and second electromagnetic induction coils 13 and 14 are supplied with a signal current such that an AC magnetic field of the same phase is generated. Vibration plate 12 that functions as a coil
An induced current is induced in. The induced current flows in the circumferential direction of the diaphragm 12 and vibrates the diaphragm 12 due to the interaction with the DC magnetic field in the magnetic gap 19. Further, this speaker has the first and second electromagnetic induction coils 13 and 14 arranged close to and opposed to the front side and the back side of the diaphragm 12, respectively.
Even when 2 vibrates and the position in the magnetic gap 19 is changed, the distance between the diaphragm 12 and the first electromagnetic induction coil 13 and the distance between the diaphragm 12 and the second electromagnetic induction coil 14 is It will always be constant. As a result, the diaphragm 12 and the first
Also, the electromagnetic coupling state with the second electromagnetic induction coils 13 and 14 becomes constant. Further, since the first and second electromagnetic induction coils 13 and 14 are supplied with a signal current such that an in-phase AC magnetic field is generated, the diaphragm 12 is responsive to the supplied signal current. Induction of stable induction current is performed, and the diaphragm 12 can be accurately vibrated in accordance with the supplied signal current. The sound pressure frequency characteristics of this speaker show the characteristics shown in FIG. 3, and can be sufficiently put to practical use.

By the way, since the second electromagnetic induction coil 14 arranged on the front surface side of the diaphragm 12 functions as an equalizer, the shape of the coil 14 and the size of the coil 14 can be changed as appropriate. It is possible to adjust the frequency characteristic and the directivity of the reproduced sound radiated through. In addition,
The signal line on the input side of the speaker, that is, the first and second signal lines
As shown in FIG. 4, the resistor 30 is connected to the signal supply line for supplying the signal current from the signal source to the electromagnetic induction coils 13 and 14 of FIG.
By connecting the capacitor 31 and the capacitor 31 in parallel, the electrical impedance characteristic shown in the electrical impedance characteristic diagram shown in FIG. 3 can be obtained, and the nominal impedance can be lowered.

FIG. 5 shows another embodiment of the present invention, in which a horn is provided and the second electromagnetic induction coil arranged on the front side of the diaphragm 12 is divided. It is configured by. In the speaker shown in FIG. 5, a horn 40 is provided on the sound output surface side of the diaphragm 12, and in addition to the equalizer 25 arranged on the pole piece 16, two equalizers 41, 42 are further provided around the equalizer 25. Is provided. And each of the above equalizers 4
Second electromagnetic induction coils 14a and 14b that are divided so as to be integrated with 1, 1 and 42 are provided. That is, the divided second electromagnetic induction coils 14a and 14b are
The equalizers 41, 42 are arranged on the lower end surfaces of the equalizers 41, 42. In this speaker, the reproduced sound radiated from the front side of the diaphragm 12 is radiated from the opening side of the horn 40 through the horn 40 and the equalizers 25, 41, 42.

Even in the structure as shown in FIG. 5, the sound pressure frequency characteristic similar to that of the speaker can be obtained, and it can be sufficiently put into practical use.

[0242]

As described above, the electromagnetic induction type loudspeaker according to the present invention is arranged such that the diaphragm is sandwiched between the first side and the second side, which are arranged close to the front side and the back side of the diaphragm, respectively.
By supplying a common signal current from the common signal source to these electromagnetic induction coils, an in-phase AC magnetic field is generated in these coils to drive the diaphragm, and the diaphragm vibrates. Even if the distance from the first and second electromagnetic induction coils is changed, a stable induction current is induced in the diaphragm according to the signal current supplied to each coil, and the diaphragm is supplied to each coil. It is possible to accurately vibrate according to the applied signal current. As a result, it is possible to obtain an electromagnetic induction speaker having high efficiency and sufficient sound pressure frequency characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view of an electromagnetic induction speaker according to the present invention.

FIG. 2 is a plan view of the electromagnetic induction speaker.

FIG. 3 is a characteristic diagram showing sound pressure frequency characteristics and impedance characteristics of the electromagnetic induction speaker.

FIG. 4 is a circuit diagram showing a circuit configuration of an input side of the speaker.

FIG. 5 is a sectional view showing another embodiment of the electromagnetic induction speaker according to the present invention.

FIG. 6 is a sectional view of a conventional electromagnetic induction speaker.

[Explanation of symbols]

 11 ... Magnetic circuit part 12 ... Diaphragm 13 ... 1st electromagnetic induction coil 14 ... 2nd electromagnetic induction coil 19 ... Magnetic gap 22,23 ... Notch step part

Claims (1)

[Claims] 1. A magnetic circuit unit for generating a DC magnetic field in a ring-shaped magnetic gap, a ring-shaped diaphragm formed of a conductive material, and vibratably supported in the magnetic gap, and the diaphragm. A first and a second electromagnetic induction coil which are arranged close to the front side and the back side of the diaphragm, respectively, with a common signal source for the first and second electromagnetic induction coils. Or
Supply a common signal current from
An electromagnetic induction type speaker that generates an in-phase AC magnetic field in the speaker.