JPH067712B2 - Speaker - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a speaker, and more particularly to a speaker in which a small amplitude of a vibration source such as a voice coil is amplified by an amplitude amplification means and transmitted to a vibration width. It is about.

2. Description of the Related Art In recent years, audio equipment is required to be smaller and have higher performance, and speaker systems are also becoming smaller, but there is a problem in bass reproduction. On-axis sound pressure (Pr) and amplitude of speaker
(X) is expressed by the following equation.

Where ρ _{o is the} air density, ω is the vibration angular frequency, a is the effective radius of the diaphragm, r is the distance between the speaker and the microphone, V is the speed of the diaphragm, X is the amplitude of the diaphragm, and A is the force coefficient. , E: input voltage of the signal, _{R E:} electrical resistance of the speaker, _{M s:} vibration system mass of the loudspeaker, _{M a:} load mass of air, _{Q o:} sharpness of the _{resonance, o:} minimum resonance frequency, f: frequency Is.

Therefore, the efficiency decreases as the effective radius of the diaphragm decreases. The amplitude of the diaphragm from the formula (2), increases in the low frequency range to inversely proportional the square of the frequency in the above _o.

However, if the winding width of the voice coil is reduced in order to improve efficiency, the amplitude range of the voice coil is narrowed, so that a distortion component is generated in the low frequency range. There is a speaker that uses a long voice coil as a method capable of large amplitude, but there is a contact point where the utilization rate of the voice coil deteriorates and the efficiency decreases. Therefore, in order to improve efficiency and reduce distortion, it is necessary to amplify a small amplitude of the voice coil and transmit it to the diaphragm. As a conventional technique, for example, there is one using a hydraulic transmission device using a cylinder and a piston as shown in Japanese Patent Publication No. 56-131298.

Hereinafter, a conventional speaker as described above will be described with reference to the drawings.

FIG. 2 is a schematic cross-sectional view of a conventional speaker using an amplitude amplification mechanism by a liquid pressure transmission device. In FIG. 2, 1
Is a center pole, 2 is a plate, 3 is a magnet, 4
Is a voice coil whose lower end is inserted into a gap of a magnetic circuit composed of a center pole 1, a plate 2, and a magnet 3, 5 is a piston having a cross-sectional area S ₁ formed at the upper end of the voice coil, and 6 is a lower end of a diaphragm 9. Area S ₂ formed in the section
, A cylinder 7 having a piston 5 on the input side and a piston 6 on the output side, a fluid pressure transmission device 8 composed of the cylinder 7 and the pistons 5 and 6, and a diaphragm 9
Is an edge obtained by adhering the inner peripheral edge to the outer peripheral edge and fixing the outer peripheral edge to a frame (not shown).

The operation of the conventional speaker configured as above will be described below.

When a signal current flows through the voice coil 4 in the magnetic gap formed by the center pole 1, the plate 2, and the magnet 3, a force acts on the voice coil 4 according to Fleming's left-hand rule to vibrate vertically. At this time, the piston 5 formed in the voice coil 4 also vibrates, and the vibration of the piston 6 is amplified by S ₁ / S ₂ times that of the piston 5 by the hydraulic transmission 8. Therefore, the vibration plate 9 fixed to the piston 6 is amplified by S ₁ / S ₂ times as much as the displacement of the voice coil 4.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-mentioned configuration, since vibration is transmitted through the fluid (usually air) of the fluid pressure transmission device, there is a drawback that it is difficult to transmit a high frequency range having a high frequency. It is unsuitable as a full-range type speaker that reproduces from the low range to the high range. Further, there is a drawback that efficiency is lowered because air leaks from the gap between the cylinder and the piston. Furthermore, if oil with a higher density (ρ) and higher sonic velocity (C) is used as the fluid in the cylinder to improve the high-frequency characteristics, there is a problem that the load mass increases and the efficiency decreases. It was not suitable as a speaker with an amplitude amplification mechanism.

In view of the above problems, the present invention provides a speaker having an amplitude amplifying mechanism that is efficient from the low sound range to the high sound range and that reproduces with high fidelity.

Means for Solving the Problems To achieve this object, a speaker of the present invention comprises a first frame, a first edge, a first diaphragm and a first air chamber surrounded by a magnetic circuit, and A hole through which air can flow in and out is provided at substantially the center of the magnetic circuit, and the end of an expandable bellows having a diameter larger than this hole is fixed to the back surface of the magnetic circuit and the other end is subjected to the second vibration. A second air chamber is formed by being fixed to the plate, and the second diaphragm is fixed to the second frame via the second edge,
The frame is composed of an amplitude amplifying mechanism having a structure in which the outer periphery is surrounded while having a gap between the frame and the first frame.

Operation With this configuration, when the voice coil moves, the volume of the first air chamber changes, and at the same time, air moves from the second air chamber through the hole in the center of the magnetic circuit to change the volume of the second air chamber (the bellows expands and contracts). 2)
The diaphragm also moves. At this time, the moving amount of the second diaphragm is A ₁ / A ₂ times the moving amount of the first diaphragm, where A _{1 is} the cross-sectional area of the first diaphragm and A ₂ is the cross-sectional area of the bellows. It will be expanded to, and the reproduction of the low frequency range becomes good. In addition, the vibration of the first diaphragm is transmitted to the second diaphragm via air.
The high-frequency range with high frequency may be difficult to be transmitted, but the high-frequency range can be directly radiated by the first diaphragm, realizing a full-range speaker with an amplitude mechanism. It is possible. Furthermore, the first and second
The air chamber is constructed by enclosing it with a first diaphragm, a first edge, a first frame, a bellows and a second diaphragm, and is similar to a conventional amplitude amplifying mechanism using a piston and a cylinder. Since there is no gap in the airtightness and the degree of airtightness is high, there is no leakage of air, so efficient transmission is possible.

Embodiment One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a speaker according to an embodiment of the present invention. In FIG. 1, 11 is a center pole, 12 is a plate, 13 is a magnet, and 14 is a voice coil (not shown) whose lower end is inserted into a magnetic gap formed by the center ball 11, the plate 12 and the magnet 13. Voice coil bobbin provided at the tip,
Reference numeral 15 is a first frame, 16 is an outer peripheral end fixed to the first frame 15, and an inner peripheral end is fixed to the voice coil bobbin 14, which is a damper in which air can flow freely, 17 is a first diaphragm, and 18 is an internal diaphragm. A first edge having a peripheral edge fixed to the outer peripheral edge of the first diaphragm 17 and an outer peripheral edge fixed to the first frame 15, 19 is an air hole provided substantially in the center of the magnetic circuit, and 20 is an air hole 19 Is larger than the diameter of the center pole 11, the upper end is fixed to the back surface of the center pole 11, and the lower end is fixed to the second vibrating plate 21. The expandable bellows 22 is the first frame 15, the first edge 18, and the first vibration. The first air chamber 23 surrounded by the plate 17 and the magnetic circuit is a bellows 20 and a second diaphragm 21.
And a second air chamber surrounded by a magnetic circuit, and 24 has a gap between it and the first frame 15 and surrounds the outer periphery of the connecting frame 2
A second frame fixed to the first frame 15 by 6 so that air can freely flow in and out through the slit 27,
Reference numeral 25 denotes a second edge whose inner peripheral edge is fixed to the outer peripheral edge of the second diaphragm 21 and whose outer peripheral edge is fixed to the second frame 24. The operation of the speaker configured as above will be described below.

First, when a signal current is passed through the voice coil inserted in the magnetic gap, a driving force is generated according to Fleming's left-hand rule, the voice coil bobbin 14 vibrates up and down, and the first diaphragm 17 vibrates to generate a sound. . At this time, since the volume of the first air chamber 22 changes, the volume of the second air chamber 23 connected by the air hole 19 also changes, and the bellows 20 expands and contracts in accordance with the volume change, thereby causing the second air chamber 23 to expand and contract. The vibrating plate 21 of the
The sound wave having the same phase as the sound wave generated by the diaphragm is radiated through the slit 27 to generate sound.

As described above, according to this embodiment, the first diaphragm 17 and the second diaphragm 17
The diaphragm 21 is connected by a fluid pressure transmission device including a piston and a cylinder, and when the first diaphragm area is A ₁ and the cross-sectional area of the bellows 20 is A ₂ , the second diaphragm 21 Is the displacement amount of the first diaphragm 17 A ₁ /
A It will be expanded to ₂ times. Further, since it is a mechanism for transmitting vibration via air, if the frequency is high, it becomes difficult to transmit, and the second diaphragm 21 does not vibrate in the high frequency range.
Since the first diaphragm 17 has a structure capable of radiating sound, it is possible to improve the drawback that a high frequency range cannot be reproduced unlike a speaker having an amplitude amplification mechanism by a conventional fluid pressure transmission device. Further, conventionally, there is a drawback that the efficiency is deteriorated because air leaks from the gap between the piston and the cylinder, but according to this embodiment, the first air chamber 22 and the second air chamber 23 are a closed system. The sound is reproduced efficiently because there is no air leakage.

In the present embodiment, the first diaphragm 17 is a cone type,
Although the second vibrating plate 21 has a flat plate shape, both may have a cone type flat plate shape or another shape and can be freely changed.

Effects of the Invention A first air chamber surrounded by a first frame, a first edge, a first diaphragm and a magnetic circuit of the present invention, and an expandable bellows and a second diaphragm and a magnetic circuit. The conventional piston and cylinder are connected to each other by an air hole, and an amplitude amplification mechanism having a closed system so that the area of the first diaphragm and the bellows are amplified by the ratio of the cross-sectional areas. Unlike a speaker having an amplitude amplification mechanism consisting of, there is no air leakage from the gap between the cylinder and the piston, so that highly efficient reproduction is possible.
Further, in the case of the conventional loudspeaker that transmits the vibration through the fluid such as air to amplify the amplitude, the high frequency vibration cannot be transmitted, and therefore the high frequency range cannot be reproduced. Since the plate is driven directly by the voice coil, it is possible to reproduce in the high range, and the low range can be reproduced by the second vibration plate whose amplitude is amplified through the air, so one speaker unit can cover the full range from low range to high range. An excellent reproducible speaker can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view of a speaker according to an embodiment of the present invention,
FIG. 2 is a schematic sectional view of a conventional speaker. 11 ... Center pole, 12 ... Plate, 13 ...
Magnet, 14 ... Voice coil bobbin 15 ... First
Frame, 16 ... damper, 17 ... first diaphragm, 18 ... first edge, 19 ... air hole, 20 ...
Bellows, 21 ... Second diaphragm, 22 ... First air chamber, 23 ... Second air chamber, 24 ... Second frame,
25 ... second edge, 26 ... connecting rod.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiro Hasegawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kosaku Murata, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor, Mitsuru Ieshiro, 1006, Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (56) Bibliographic references Shoko 58-25672 (JP, Y2)

Claims (1)

[Claims] 1. A first air chamber surrounded by a first frame, a first edge, a first diaphragm and a magnetic circuit, and a hole through which air can flow in and out at a substantially central portion of the magnetic circuit. And an end portion of an expandable bellows having a diameter larger than this hole is fixed to the back surface of the magnetic circuit and the other end portion
A second air chamber formed by being fixedly attached to the diaphragm of the second diaphragm is hermetically sealed through the hole, and the second diaphragm is fixed to the second frame through the second edge, A speaker including an amplitude amplification mechanism in which the second frame surrounds the outer periphery with a gap between the second frame and the first frame, and the second frame is fixed to the first frame. .