JPH10126884A - Speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the necessary magnetic fluid and to minimize the deterioration of efficiency at a low band by placing the narrow and wide gap parts of magnetic gap width with an optional space secured between them so as to hold the magnetic fluid at a narrow gap part and placing the narrow gap part to make it correspond to the loop part of the natural vibration that is produced by the vibration of a diaphragm. SOLUTION: A center pole 104 and a plate 105 have the cut parts 104a and 105a which are opposite to each other. In a gap 111, the flux density of its cut part is considerably reduced compared with that of its non-cut part. The magnetic fluid 114 can be held at plural places owing to the presence of both parts 104a and 105a. Furthermore, the parts 104a and 105a are arranged so as to hold and damp the fluid 114 at a place where the natural vibration of a voice coil 106 increases. Thus, the contact can be prevented between both parts 104a and 105a and a magnetic circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a speaker.

[0002]

2. Description of the Related Art Conventionally, speakers mounted on a television monitor or the like often have insufficient space for arrangement, and the shape of the diaphragm is limited to an elliptical shape or an elliptical shape in order to secure a required sound pressure level. Was trying to secure a larger diaphragm area in the space. In these loudspeakers, conventionally, the voice coil often remains circular, but in recent years, an elliptical or elliptical voice coil adapted to the diaphragm shape has been used. That is, if the voice coil remains circular, the driving point is only at the center of the diaphragm, and when the magnetic flux density of the gap is B (tesla) and the effective voice coil length is L (m), L becomes small and the force coefficient B becomes small.
× L becomes small. Therefore, by using an oval voice coil adapted to the shape of the diaphragm, the entire diaphragm can be driven, and the force coefficient B × L can be increased.

Here, a conventional elliptical or oval speaker will be described with reference to FIGS. 4 (a) and 4 (b).

FIG. 4 is a structural view of a conventional elliptical or elliptical speaker, and FIG. 4A is a plan view and a longitudinal sectional view of the elliptical speaker, and FIG. Is
It is the top view of the speaker of an elliptical shape, and sectional drawing of a long diameter direction. In FIG. 4, for example, as shown in FIG. 4A, a magnet 8 creates a magnetic field in a magnetic gap composed of a magnetic pole 7 and a center pole 4, and the voice coil wound around the bobbin 2 in the magnetic field. The bobbin 2 is driven by the electromagnetic action of a current and a magnetic field flowing through the voice coil 6 to vibrate the diaphragm 1. The diaphragm 1 is attached to a frame 10 with an edge 9 and a damper 3. At the center of the diaphragm 1, a protective cap 11 for dust prevention of the magnetic pole is provided. FIG. 5 shows the structure of another elliptical speaker particularly as a small speaker system. In FIG. 5, 501 is a cabinet, 502 is a unit, 505
Denotes a diaphragm, 506 denotes a voice coil, 507 denotes a center pole, 508 denotes a magnet, 509 denotes an edge, 510 denotes a frame, 511 denotes a yoke, 512 denotes a terminal, and 513 denotes a tinsel wire. Next, FIG. 6 shows a plan view of a loudspeaker of a type in which a magnetic fluid conventionally used is filled over the entire magnetic gap. In FIG. 6, 60
Reference numeral 4 denotes a center pole, 605 denotes a plate, and the magnetic fluid 614 is filled over the entire magnetic gap formed by the center pole 604 and the plate 605.

[0005]

However, when the length of the voice coil in the magnetic circuit is long, there is a problem that the strength of the coil is weak and resonance occurs. Further, in order to reduce the thickness of the loudspeaker having such an oval voice coil, a damperless structure is generally employed, so that when the amplitude is large, the loudspeaker may come into contact with a magnetic circuit to generate abnormal noise.

Conventionally, as a method of solving these problems, a method of arranging a cushion material in a magnetic gap, injecting a magnetic fluid into the magnetic gap as described above, reinforcing the voice coil with ribs, and the like have been adopted. Was. However, in the case of these methods, when a cushion material is used, the sliding noise caused by the voice coil and the cushion material is distorted, and when the magnetic fluid is filled in the gap, the movement of the vibration system is excessively damped. And the efficiency in the low range is reduced. Further, the reinforcement by the ribs causes problems such as an increase in the number of parts and a demand for assembly accuracy. The present invention has been made in view of the above points, and has as its object to provide a speaker in which stable operation of a coil and deterioration of efficiency in a low frequency band are prevented.

[0007]

According to a first aspect of the present invention, there is provided a speaker including a frame, a diaphragm having an edge supported by the frame, a voice coil wound on a bobbin mounted on the diaphragm, and a voice coil. A magnetic circuit having an annular magnetic gap around it, a center pole, a plate, a yoke, and a magnet for forming a magnetic circuit, the magnetic gap is filled with a magnetic fluid, and the voice coil is passed through the magnetic fluid. In a speaker supported in a magnetic circuit,
The voice coil is supported at a plurality of locations by a magnetic fluid. The loudspeaker according to claim 2 is the loudspeaker according to claim 1, wherein the magnetic gap is formed by deforming one or both of the shape of the plate and the center pole to reduce the width of the magnetic gap and the width of the wide gap. A narrow gap portion and a wide gap portion are arranged at arbitrary intervals so that the magnetic fluid can be held in the narrow gap portion. A loudspeaker according to a third aspect is the loudspeaker according to the second aspect, wherein the narrow gap portion is arranged so as to correspond to an antinode of natural vibration obtained when the diaphragm vibrates. And The speaker according to claim 4 is the speaker according to claim 1.
The speaker according to any one of the preceding claims, wherein the diaphragm has a major axis and a minor axis when viewed in a vibration direction.

[0008]

[Function] By minimizing the necessary amount of magnetic fluid, it is possible to minimize the efficiency deterioration in the low frequency range.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the speaker of the present invention, FIG.
As shown in FIG. 2, the bobbin 101 is a non-rotationally symmetrical shape having a major axis and a minor axis of a substantially elliptical shape. Here, the rotational symmetry means that a cross-sectional shape including a specific axis has the same shape at any angle. . Further, the specific axis refers to the axis at the center of the diaphragm.
A voice coil 106 is wound around the bobbin 101. Magnet 102, yoke 103, center pole 1
04, the plate 105 forms a magnetic circuit, and the bobbin 101 is provided between the center pole 104 and the plate 105.
A gap 111 into which the voice coil 106 is movably inserted is formed, and the bobbin 101 and the voice coil 106 are constituted by an edge or a damper (not shown) so as to be positioned in the gap 111 as shown in FIG. Have been.

A not-shown diaphragm is connected to one end of the bobbin 101 protruding from the gap 111. As shown in FIG. 1A, the center pole 104 and the plate 105 are provided with notches 104a and 105a, respectively, such that the center pole 104 and the notch of the plate 105 face each other. Therefore, while the gap 111 is generally designed with a uniform magnetic flux density, the gap 111 according to the present invention is configured such that the magnetic flux density at the notch is sufficiently smaller than the magnetic flux density of the gap that is not the notch. You.

In the speaker configured as described above,
When a driving current is applied to the voice coil 106, a driving force is generated in the voice coil by the magnetic flux generated in the gap 111 and the current flowing in the voice coil, and the bobbin 101 around which the voice coil 6 is wound is driven. , Bobbin 10
A sound energy is generated by driving a diaphragm (not shown) coupled to the first plate.

FIG. 1A is a plan view of the center pole 104 and the plate 105, and FIG.
FIG. 1C is a sectional view taken along the line A ′, and FIG.
FIG. 1D is an enlarged view of a magnetic fluid-filled portion composed of a magnetic pole and a plate 105, and FIG.
FIG. 4 is an enlarged cross-sectional view of a magnetic fluid filling portion composed of a plate 04 and a plate 105. In FIG. 1, the center pole 104
As shown in FIGS. 1A and 1C, cutouts 104a and 105a are provided on the center plate 104 and the plate 105 such that the cutouts of the center pole 104 and the plate 105 are opposed to each other. Therefore, generally, the gap 11
1 is designed with a uniform magnetic flux density, the gap 111 according to the present invention is configured such that the magnetic flux density at the notch is sufficiently smaller than the magnetic flux density of the gap that is not the notch.

Here, when the magnetic fluid 114 is injected between the notches adjacent to each other, since the magnetic flux density in the notches is small, the magnetic fluid 114 is interposed between the magnetic fluid in the gap portion where the magnetic flux density is large. The magnetic fluid 114 generates
It is held by suction at the narrow portion of the gap avoiding the notches 104a and 105a. FIG. 1 shows this state.
(C) and (d), the hatched portions indicate the state in which the magnetic fluid 114 is held.

Since the magnetic fluid 114 is attracted by the magnetic flux in the gap 111, the voice coil 106 and the bobbin 1
01 is held by the magnetic fluid 114 between the center pole 104 and the gap 111 between the plate 105 in a floating manner. By forming the notches 104a and 105a in this way, it is possible to hold the magnetic fluid at a plurality of locations, and the arrangement of the notches is smaller than in the conventional case where the magnetic fluid is injected over the entire gap. Accordingly, the holding force and the braking force of the magnetic fluid on the voice coil can be adjusted, and the holding force and the braking force can be set to appropriate levels.

Next, the arrangement of the notches will be described. FIGS. 2A to 2C show resonance modes obtained by vibration simulation of the voice coil 106 and the bobbin 101 when the magnetic fluid is not used in the speaker having the above-described configuration. FIG. 2A shows a case where the node of the natural vibration is at the center of the linear portion of the voice coil 106. In such a case, by braking both ends of the linear portion of the voice coil 106 where the amplitude of the natural vibration is large, that is, the antinode of the vibration, the voice coil can be prevented from contacting the magnetic circuit.

FIG. 2B shows a case where nodes of natural vibration are located at the center and both ends of the linear portion of the voice coil 106. In such a case, there are four locations corresponding to the antinode of the natural vibration in the linear portion of the voice coil 106, and if the antinode is braked, the voice coil can be prevented from contacting the magnetic circuit.

FIG. 2C shows a case where the nodes of the natural vibration are at both ends of the linear portion of the voice coil 106. In such a case, a position corresponding to the antinode of the natural vibration occurs at the center of the linear portion of the voice coil 106, and if the antinode is braked, the voice coil can be prevented from contacting the magnetic circuit.

As described above, if the notch is arranged so that the magnetic fluid can be held and braked in a place where the natural vibration of the voice coil is large, it is possible to prevent the voice coil from contacting the magnetic circuit. In the above description, the cutout portion is provided on both the center pole 104 and the plate 105. However, a similar effect can be obtained because any one of the cutout portions can generate a difference in magnetic flux density. Also, in FIG. 1A, the magnetic fluid is alternately shown in the notches adjacent to each other, but this is due to the desired holding and braking effects, and the location where the magnetic fluid is injected can be selected.

When a magnetic fluid is used on the entire surface of the gap, the distribution state of the magnetic fluid changes depending on how the speaker is placed due to the weight of the magnetic fluid itself, which causes a change in the magnetic flux density and a change in the braking effect. According to the method of the present invention, it is possible to configure the magnetic fluid to such an extent that the influence of the weight of the magnetic fluid does not occur.

Next, although the shape of the notch is shown as a rounded rectangle in FIG. 1A, the shape is such that a magnetic flux density that is clearly smaller than the magnetic flux density of the gap portion other than the notch can be obtained. If there is, it is not limited, but a rectangular or trapezoidal shape is preferable.

If the difference between the magnetic flux densities is too small, the magnetic fluid may move to an adjacent gap due to vibration or the like.

In the above description, a speaker having an elliptical voice coil has been mainly described. However, a speaker having a normal circular voice coil is also provided with a cutout portion in a gap portion to partially supply a magnetic fluid. Of course, similar effects can be obtained by injecting.

Also, instead of providing a notch, FIG.
As shown in the figure, the gap formed by the center pole 304 and the plate 305 is designed to be widened, and then a block piece 306 for forming a regular gap is formed.
And 307 can be attached to a wider gap to form a regular gap. Block piece 30
6 and 307 also apply to portions other than those shown in a similar configuration.

[0024]

As described above, according to the loudspeaker of the present invention, only the necessary portion of the magnetic fluid which is present on the entire circumference of the voice coil is required, and as a result, the mechanical resistance is reduced. Efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of an embodiment of a speaker of the present invention.

FIG. 2 is a diagram showing a simulation result of a natural vibration characteristic of a voice coil when a magnetic fluid is not injected according to the embodiment of the speaker of the present invention.

FIG. 3 is a diagram showing the structure of another embodiment of the speaker of the present invention.

FIG. 4 is a cross-sectional view of a conventional speaker.

FIG. 5 is a cross-sectional view of another example of a conventional speaker.

FIG. 6 is a diagram showing a configuration of another example of a conventional speaker.

[Explanation of symbols]

 1 ····· Diaphragm 2 ····· Bobbin 3 ····· Damper 4 ····· Center pole 6 ···· Voice coil 7 ···· Magnetic pole 8 ··· Magnet 9 Edge 10 Frame 11 Protective cap 101 Bobbin 102 Magnet 103 Yoke 104, 304 ... Center pole 105, 305 Plate 104a, 105a Notch 106 Voice coil 111 Gap 114 Magnetic fluid 306 307 ・ ・ ・ ・ ・ Block piece

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04R 9/04 104 H04R 9/04 104A

Claims (4)

[Claims] 1. A frame, a diaphragm having an edge supported by the frame, a voice coil wound around a bobbin attached to the diaphragm, and a magnetic field having an annular magnetic gap around the voice coil. A circuit, a center pole for forming the magnetic circuit, a plate, a yoke, and a magnet. The magnetic gap is filled with a magnetic fluid, and the voice coil is supported in the magnetic circuit via the magnetic fluid. A speaker according to claim 1, wherein said voice coil is supported at a plurality of positions by said magnetic fluid. 2. The magnetic gap forms a narrow gap portion and a wide gap portion by deforming one or both of the shapes of the plate and the center pole, and forms the narrow gap portion and the wide gap portion. The speaker according to claim 1, wherein the wide gap portions are arranged at arbitrary intervals so that the magnetic fluid can be held in the narrow gap portion. 3. The loudspeaker according to claim 2, wherein the narrow gap portion is arranged so as to correspond to an antinode of natural vibration obtained when the diaphragm vibrates. 4. The loudspeaker according to claim 1, wherein the diaphragm has a major axis and a minor axis when viewed in a vibration direction.