JPS5831157B2 - speaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a speaker that does not generate distortion.

As a centrally driven speaker using a voice coil,
Depending on the shape of the diaphragm, there are cone-shaped speakers, flat-plate speakers, and dome-shaped speakers.

These speakers use edges and dampers to support the diaphragm, which is a movable part, to the frame and magnetic circuit, which are non-movable parts.

In the case of a cone-shaped speaker or a flat-plate speaker, the outer circumference of the diaphragm is supported by an edge member, and the coil bobbin fixed to the diaphragm is supported by a damper to prevent horizontal vibration in the direction perpendicular to the vibration direction of the diaphragm. ing.

In addition, the damper plays the role of generating the elastic restoring force necessary for the vibration of the diaphragm, and the edge prevents the sound pressure from the back of the diaphragm from going around to the front, and prevents the sound pressure from reaching the front due to the phase difference between the front sound pressure and the back sound pressure. It works to eliminate disturbances in sound pressure frequency characteristics.

Note that in the case of a dome-shaped speaker, a damper is usually not used and the elastic restoring force is achieved by the edges.

In this way, conventional speakers have solid support systems such as edges and dampers, so there is a limit to the magnitude of elastic displacement, and the linear relationship between elastic displacement and driving force breaks down at large amplitudes. There is a drawback that low-frequency distortion occurs due to the nonlinearity of the support system.

This first drawback is particularly noticeable in small-diameter woofers; for example, a 90φ woofer has a 100 dB
To obtain the sound pressure (distance 1 m) of
For example, an amplitude of approximately 24 mm is required at 50 Hz, and when the amplitude is 6 mm, harmonic distortion exceeds 10%.

In addition, for a woofer with a large diameter of 300φ or more, even if a molded polymer sheet or impregnated cloth is used as a support system, the
The problem of distortion due to nonlinearity at large amplitudes exceeding tt is not fundamentally solved.

In addition, when designing the above-mentioned conventional speakers to have a low minimum resonant frequency in order to extend the low frequency reproduction band, it is necessary to reduce the elastic constant of the damper and edges, and thin and soft materials must be used. These support systems have the disadvantage that the ability to hold the center of the diaphragm is weakened and horizontal vibration increases, resulting in disturbances and distortions in the sound pressure frequency characteristics.

Further, if the magnetic air gap length of the magnetic circuit is increased in order to prevent the voice coil from coming into contact with the magnetic pole due to lateral vibration, there is a drawback that the cost increases.

Furthermore, conventional speakers have the disadvantage that edge resonance causes unevenness of several dB or more in high voltage frequency characteristics.

For example, in the case of a cone-shaped speaker, unevenness occurs due to edge resonance in the middle range of the reproduction band, and in the case of a dome-shaped speaker, the high-frequency reproduction limit is lowered due to edge resonance.

As described above, in conventional speakers, the vibration system is supported by a solid support system, and thus the various drawbacks mentioned above occur.

The present invention eliminates the above-mentioned conventional drawbacks, and embodiments of the present invention will be described below.

In FIG. 1, 1 is a container with an open top surface, and a partition plate 2 is integrally formed inside this container 1. As shown in FIG.

3 and 4 are holes formed in the partition plate 2, respectively.

A yoke 5 is fixed to the partition plate 2, and a center pole 7 having a hole 6 is integrally formed in the center of the yoke 5.

8 is an annular magnet fixed to the upper surface of the yoke 5; 9
is an annular yoke fixed to the upper surface of the magnet 8, and an annular magnetic gap is formed between the inner circumferential surface of this yoke 9 and the outer circumferential surface of the center pole 7.

Reference numeral 10 denotes an annular yoke fixed to the opening of the container 1, and a protrusion 11 is formed on the inner circumference of the yoke 10.

12 is an annular magnet fixed to the upper surface of the yoke 10; 13 is a yoke fixed to the upper surface of the magnet 12;
A protrusion 14 facing the protrusion 11 is formed.

15 is a magnetic fluid filled in the magnetic gap between the protrusions 11 and 14 of the yokes 10 and 13.

This magnetic fluid 15 is made by dispersing colloidal magnetic ultrafine particles in a fluid, and this magnetic fluid 15 is held between the protrusions 11 and 14 of the yokes 10 and 13 as shown in FIG. 2a.

Reference numeral 16 denotes a disc-shaped diaphragm made of foamed resin, foamed metal, aluminum honeycomb material, etc., and this diaphragm 16 is inserted into the center hole of the annular yoke 10.13.

Figure 2 shows the state in which the diaphragm 16 is inserted.

In this state, a force is generated in which the magnetic fluid 15 tends to gather near the magnetic gap where the magnetic field is strong, and pressure is applied to the outer peripheral surface of the diaphragm 16.

Therefore, the diaphragm 16 is supported as shown.

Note that if this diaphragm 16 is eccentric, this diaphragm 1
A force acts to push 6 back to the center, and it is always held at the center.

17 is a coil bobbin fixed to the lower surface of the diaphragm 16;
A voice coil 8 is wound around the coil bobbin 11, and the voice coil 18 is disposed in the magnetic gap between the yoke 9 and the center pole 7.

Next, FIGS. 2a and 2b will be explained in more detail.

As shown in FIG.
, 14 are concentrated in a space where the magnetic flux density is high according to the distribution of magnetic flux density in the magnetic gap between them.

The saturation magnetic flux density of the magnetic fluid 15 is 100 to 400 (Ga
uss ), which is more than one order of magnitude smaller than the magnetic flux density of the magnetic gap before filling with magnetic fluid, and there is little change in the distribution of magnetic flux density after filling.

Therefore, even within the space occupied by the magnetic fluid 15, there is a magnetic field gradient, and internal stress acts that tends to concentrate at points where the magnetic flux density is high.

As shown in Figure 2, when the diaphragm 16 is inserted, the magnetic fluid 15 is pushed away by the diaphragm 16 from the area where the magnetic flux density is relatively high, and body force (internal stress) that tries to return to the original stable state The force F pushing the diaphragm 16 away by
occurs.

This force F acts on the entire annular outer peripheral surface of the diaphragm 16 and holds the diaphragm 16 at the center.

When the diaphragm 16 is eccentric, the magnetic field gradient on the side where the diaphragm 16 approaches is large and the body force is proportionally large.However, on the side where the diaphragm 16 is far away, the body force becomes small.

As a result, a force is generated that attempts to return the diaphragm 16 to its original state.

In this way, the magnetic circuit consisting of the yokes 10, 13 and the magnet 12 and the magnetic fluid 15 hold the center of the diaphragm 16, and the magnetic fluid 15
It also functions to seal the air at the back of 6.

That is, the back of the diaphragm is completely sealed with the container 1, the diaphragm 16, the magnetic circuit, and the magnetic fluid 15.

This sealed air acts as an air spring against the vibration of the diaphragm 16 and generates an elastic restoring force of the diaphragm 16.

The magnetic fluid 15 has only an annular cross-sectional area with a thickness of less than 1 cm bound by a magnetic field exposed on the back side,
The magnetic fluid 15 does not fly out due to changes in the air pressure on the back side.

When the diaphragm 16 is inserted last when assembling the speaker, the internal pressure of the sealed back cavity increases, so the magnetic fluid 1
The position of the diaphragm 16 can be set by inserting a needle such as a syringe into the portion 5 from the outside and extracting the required amount of air from the back cavity.

Further, positional deviation of the diaphragm 16 due to long-term use can be easily adjusted using the same method.

As described above, in the present invention, since the diaphragm 16 can be held without using a solid support system such as a damper or an edge, it is possible to vibrate with a larger amplitude than that of the diaphragm without causing distortion.

According to the present invention, a small diameter woofer of 90φ has approximately 127 mm
The amplitude of Itπ is now practically possible, and the amplitude is 10 at 100Hz.
A maximum output sound pressure of 6 dB (distance Im) or more can be obtained, and distortion can be reduced to 1% or less.

It should be noted that conventional speakers have the disadvantage that edge resonance tends to occur when the width of the edges is increased to ensure a large amplitude, but according to the present invention, such a problem does not occur.

Further, since the lowest resonant frequency of the electrodynamic speaker of the present invention is determined only by the effective mass of the diaphragm 16 and the volume of the back cavity, it has the advantage that the design can be simplified.

For example, if the diameter is 200φ, the effective mass is 5 (1), and the back cavity volume is 501, the lowest resonance frequency can be designed to be about 50 Hz.

Further, in the present invention, the resonance Q value can be freely changed simply by changing the viscosity of the magnetic fluid 15.

Further, according to the present invention, since there is no vibrating part such as a damper that does not contribute to acoustic radiation, the efficiency can be improved by about 1 to 3 dB.

In addition, in conventional speakers, there was a problem with the heat resistance of parts such as edges and dampers that require deformation movement, but in the present invention, edges and dampers are not required.
It can be used even in environments of 0°C or higher.

Figures 3a and 3e show diaphragm support structures according to other embodiments of the present invention.

In FIG. 3a, annular magnets 22, 23 are interposed between annular yokes 19, 20, 21 to form two annular magnetic gaps, each of which is filled with a magnetic fluid 24, 25. , the outer peripheral surface of the diaphragm 16 is supported at two locations.

According to this embodiment, even a heavy diaphragm can be supported stably, and the effect of reducing horizontal vibration is improved. The cylindrical portion 30 of the diaphragm 16 is supported by a magnetic fluid 29 that forms a circuit and is filled in the magnetic gap of this magnetic circuit.According to this embodiment, the magnetic fluid 29
This can reduce the direct adhesion of dust and the like from the outside.

FIG. 3C shows a magnetic circuit composed of a yoke 32 with an annular protrusion 31 formed on the outer circumference, an annular magnet 33, and an annular yoke 34, and the inner circumferential surface of the protrusion 31 of the yoke 32 and the annular yoke 34 form a magnetic circuit. The diaphragm 16 is placed in the magnetic gap between the outer peripheral surface of the yoke 34 and the outer peripheral surface of the yoke 34.
A cylindrical portion 30 is inserted, and the diaphragm 16 is supported by a magnetic fluid 35 filled between the cylindrical portion 30 and the yoke 34.

In FIG. 3d, a magnetic circuit is constructed by the yokes 36 and 37 and the magnet 3B, and the cylindrical portion 30 of the diaphragm 16 is inserted into the magnetic gap between the yokes 36 and 37.
The diaphragm 16 is supported by magnetic fluids 39 and 40 filled between the cylindrical portion 30 and the yoke 37, respectively.

In FIG. 3e, a magnetic circuit is constructed by interposing an annular magnet 43 between yokes 41 and 42, and the inner peripheral surface of this annular magnetic circuit is coated with Teflon or FEP.

A film 44 having high surface lubricity such as polyethylene is closely attached, the inner peripheral surface of this film 44 is filled with magnetic fluid 45, and the diaphragm 16 is supported by this magnetic fluid 45.

In this embodiment, even if the diaphragm 16 oscillates to a large extent, the diaphragm 16 does not come into direct contact with the yokes 41 and 42, so it is less likely to be damaged. This has the advantage that the yokes 41 and 42 are not oxidized by acidic substances.

FIG. 4 shows a drone cone type speaker device.

This speaker device includes an electrodynamic speaker and a passive diaphragm (passive, radiator) shown in FIG. 1, and the same parts as in FIG. 1 are given the same numbers.

In FIG. 4, 46 is a support plate that supports the magnetic circuit in a container (speaker box) 47, and this support plate 46
A hole 4B is formed in the hole 4B.

49 is an annular magnet fixed in a hole in the front plate 50 of the container 47, and an annular yoke 51.52 is fixed to both sides of the annular magnet 49.
A magnetic fluid 53 is filled in an annular magnetic gap formed at the inner circumferential portion of the diaphragm 2, and a passive diaphragm 54 is supported by the magnetic fluid 53.

55 is a sound absorbing material housed in the container 47, and 56 is the container 47.
This is an air pressure adjustment device installed in the.

In FIG. 4, the passive diaphragm 54 inverts the phase of the sound radiated to the back surface of the electrodynamic speaker, and drives the speaker diaphragm 16 and the passive diaphragm 54 in the same phase at a low frequency. This increases the sound pressure.

In this case, it is required to make the stiffness of the passive diaphragm as small as possible so that fo is 20 Hz or less, but in the embodiment shown in FIG. 4, the stiffness due to the support system of the passive diaphragm 54 is O, which is ideal. Yes, the bass reproduction band is wider than that using a conventional passive diaphragm.

Furthermore, according to this embodiment, distortion due to nonlinearity of the support system of the passive diaphragm does not occur when the amplitude is large.

The air pressure adjustment device 56 is used to remove the air inside the container 47 when fitting the diaphragm during assembly, or to adjust the air pressure inside the container 47 to be the same as the outside pressure especially when there is a large change in the outside air pressure. Various types of devices can be used, such as a structure in which a piston is fitted into a cylinder having an intake valve and an exhaust valve that are crimped and sealed by a spring.

Incidentally, instead of the air pressure adjusting device 56, it is also possible to adjust the air pressure by fitting a rubber-like material into a hole formed in the container and inserting a needle of a syringe into this rubber-like material.

The present invention has the above-mentioned configuration, and because it does not use a solid support system such as an edge member or a damper, it is possible to vibrate with a large amplitude of several mm or more without generating distortion.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a speaker in an embodiment of the present invention;
Figures 2a and 2b are enlarged cross-sectional views of essential parts showing the principle of supporting the diaphragm of the speaker of the present invention, Figures 3a and 3e are sectional views of the diaphragm support of other embodiments of the present invention, and Figure 4 1 is a sectional view of another embodiment of the present invention. 1... Container, 2... Partition plate, 3, 4...
...Hole, 5...Yoke, 6...
Hole, T...Center pole, 8...Macnet, 9...Yoke, 10...Yoke, 11...Protrusion, 12... Magnet, 13... Yoke, 14... Projection, 15... Magnetic fluid, 16... Vibration plate, 17. ...Coil bobbin, 18...Voice coil, 19,20,21...Yoke, 2
2゜23...Magnet, 24, 25...
...Magnetic fluid, 26.27...Yoke, 28
...Magnet, 29...Magnetic fluid,
30...Cylindrical part, 31...Protrusion, 32
...Yoke, 33...Magnet, 3
4... Yoke, 35... Magnetic fluid, 3
6,37...Yoke, 38...Magnet, 39.40...Magnetic fluid, 41,42...
... Yoke, 43 ... Magnet, 44
...Film, 45...Magnetic fluid, 4
6...Support plate, 47...Container, 48.
... Hole, 49 ... Magnet, 50 ...
...Front plate, 51, 52...Yoke, 53
......Magnetic fluid, 54...Passive diaphragm,
55... Sound absorbing material, 56... Air pressure adjustment device.

Claims (1)

[Claims] 1. A magnetic circuit having an annular magnetic gap is placed in the opening of a container, the magnetic gap is filled with a magnetic fluid,
Bringing the outer circumferential surface of the diaphragm into contact with the magnetic fluid, the container;
A speaker characterized in that an elastic restoring force of the diaphragm is generated by a diaphragm, a magnetic circuit, and an air spring of air sealed by a magnetic fluid. 2. A speaker according to claim 1, in which a drone cone type passive diaphragm is supported by a magnetic fluid.