JP2019009487A - Speaker including auxiliary magnet - Google Patents

Abstract

To provide a speaker including an auxiliary magnet in which improvement and distortion in sound quality at reproduction are reduced.SOLUTION: Due to arrangement of an auxiliary magnet 2 in the center portion of a yoke 4, a repulsive force is generated between a main magnet 1 and an auxiliary magnet, leakage of a magnetic flux in a gap portion 5 can be suppressed, and a difference in magnetic force between the inside and the outside of the gap portion is eliminated.SELECTED DRAWING: Figure 1

Description

          The present invention relates to a speaker used in various audio devices and information communication devices.

          Generally, as shown in Patent Document 1, a magnetic circuit of a speaker includes a magnet, a yoke, and a gap that is a space formed between the yoke and the yoke.

      Further, as a form for further increasing the magnetic flux density of the gap, as shown in Patent Document 2, it is formed between a main magnet that generates a magnetic field, a yoke disposed opposite to the main magnet, and the main magnet and the yoke. A speaker further provided with a gap, a voice coil disposed in the gap, and an auxiliary magnet for increasing magnetic flux in cooperation with a main magnet is known.

      As such a speaker, an outer magnet type and an inner magnet type are known.

      The outer magnet type is advantageous in that the magnet can be enlarged because the main magnet is provided outside. Since the magnetic field is not closed and magnetic leakage occurs from around the yoke, this magnetic force does not pass through the gap portion, resulting in loss of magnetic force and lowering the efficiency of the magnetic circuit. Permanent magnet ferrite is mainly used for the magnet.

      On the other hand, a main magnet is disposed at the front end of the yoke, and the outer magnet type yoke disposed opposite to the main magnet is integrally formed, and a gap is formed by the yoke and the front end magnet. The speaker structure in which the magnet is not exposed is called an inner magnet type.

Since the inner magnet type has the main magnet on the inner side, the size of the magnet is limited. A small permanent magnet neodymium is used.
Since it is closed, there is no magnetic leakage from the yoke and there is little loss of magnetic force.

Inside the gap, a voice coil with a coil wound around a cylindrical bobbin is arranged.
And hold in the gap with dampers, diaphragms and edges.
When an audio signal is input to the voice coil, Fleming's left hand rule
The voice coil becomes an electromagnet and generates a magnetic field. It attracts and repels the magnetic field in the gap to drive the diaphragm.
The driven diaphragm oscillates air and converts it into sound waves.

          In order to improve the magnetic flux density of the gap, the main magnet of the outer magnet type magnetic circuit is stacked in two stages to increase the magnetic force, and the center pole itself is used as a magnet, with the outer magnet via the yoke. Some have a double magnet structure in which a series magnetic circuit is formed.

JP-A-46-8287

JP2002-273343

      In the outer magnet type of the conventional speaker, there is a magnetic force difference due to the distance from the main magnet, the top plate and the center pole, which are the yokes arranged opposite to the main magnet, and the gap part formed by the yokes When an electric signal is input to the arranged voice coil, when the voice coil that has become an electromagnet is moved by the electric signal, the voice coil is attracted and repelled while being drawn toward the top plate that is close to the magnet. In the case of the inner magnet type, since the magnet is on the center pole side, it is attracted to the center pole side as opposed to the outer magnet type.

If there is a difference in the suction / repulsion force between the inside and outside of the gap, the voice coil cannot be converted into a pure back-and-forth motion with respect to the electrical signal, and a lateral magnetic force is also applied. Unnecessary power is added.
This becomes a distortion component, which has an adverse effect on the sound quality at the time of reproduction, such as sound volume and distortion.

      Further, all the magnetic flux passing through the gap portion does not pass through the gap portion in a concentrated manner, and a part of the magnetic flux swells and passes above and below the gap portion so as to draw an arc. This leakage magnetic flux also has an influence on the attraction / repulsion of the voice coil, and reacts with the magnetic force outside the gap portion to cause an extra attraction / repulsion and exert the adverse effect.

When an electric signal is input, the voice coil becomes an electromagnet.
For this reason, the yoke around the gap is magnetized, the magnetic flux passing through the gap is disturbed, the voice coil is attracted and repelled, and the distortion is reproduced. This is a component generally called current distortion.

          The double magnet structure, which is an external magnet type and has two layers of main magnets, improves the magnetic flux density of the gap part, but the difference in magnetic force between the inside and outside of the gap increases, and the distortion component in the lateral direction of the voice coil is eliminated. It was not done.

As shown in Patent Document 2, the center pole itself as a magnet and provided with a series magnetic circuit with an external magnet is difficult to balance the magnetic force inside and outside, and in order to form a series circuit, the magnetic flux in the gap is Depends on the magnetic force of the magnet replacing the center pole.
Further, since the magnetic circuit is an outer magnet type, magnetic leakage from the yoke also occurs, resulting in loss of the magnetic circuit, and the above-mentioned adverse effect is unavoidable.

A speaker according to the present invention includes a main magnet that generates a magnetic field, a yoke disposed opposite to the main magnet, a gap formed between the main magnet and the yoke, a voice coil disposed in the gap, and a main magnet. In the speaker further provided with an auxiliary magnet for increasing the magnetic flux in cooperation with each other, the auxiliary magnet is arranged so that at least a part of the yoke is sandwiched between the auxiliary magnet and the main magnet.

        The above configuration can also be applied to an inner magnet type, and the same effect can be obtained by arranging an auxiliary magnet on the outer periphery of the yoke.

          By arranging an auxiliary magnet in the center of the yoke of the outer magnet type magnetic circuit, a repulsive force is generated between the main magnet and the auxiliary magnet, and magnetic flux leakage in the gap portion can be suppressed. Can be eliminated. The above effect is also effective in the internal magnet type magnetic circuit.

In addition, it is possible to magnetically saturate the gap portion of the yoke disposed opposite to the main magnet of the outer magnet type magnetic circuit, and to prevent magnetization around the gap portion, which is generated when the boil coil becomes an electromagnet. I can do it.
The above effect is also effective in the internal magnet type magnetic circuit.

Sectional view of the speaker unit in the present invention Development view of magnetic circuit in the present invention Sectional drawing of Embodiment 1 in this invention Sectional drawing of Embodiment 2 in this invention Magnetic field diagram of conventional magnetic circuit Magnetic field diagram of magnetic circuit in the present invention Sectional drawing of Embodiment 3 in this invention Sectional drawing of Embodiment 4 in this invention Sectional drawing of Embodiment 5 in this invention

1 Main magnet 2 Auxiliary magnet 3 Yoke 3a Center pole 4 Yoke 5 Gap 6 Bobbin 7 Voice coil 8 Bumper 9 Frame 10 Edge 11 Diaphragm 12 Dust cap 13 Main magnet 14 Auxiliary magnet 15 Yoke 16 Sleeve
17 Adjustment base 18 Adjustment knob 19 Main magnet magnetic field line 19a Gap part magnetic field line (parallel)
19b Gap field line (diagonal)
20 Main magnet leakage magnetic field line 21 Auxiliary magnet magnetic field line 22 Auxiliary magnet leakage magnetic field line

Hereinafter, an embodiment of the invention will be described with reference to FIGS.
FIG. 5 is used for comparison with FIG.

In the figure, 1 is a main magnet that is the main of the magnetic circuit, and 2 is an auxiliary magnet that assists in its operation. The yokes 3 and 4 which are ferromagnetic bodies have the yoke 3 on the lower surface of the main magnet 1 and the yoke 4 in close contact with the upper surface. Further, a space 5 is provided between the yoke 3 and the yoke 4, and this space is called a gap and is provided for concentrating the magnetic force. The auxiliary magnet 2 is located at the center of the yoke 3 and is arranged in parallel to the main magnet 1 to constitute a magnetic circuit. A voice coil 7 in which a coil is wound around a bobbin 6 is supported by a damper 8 in the gap 5. The frame 9 supports the damper 8 and the diaphragm 11 via the edge 10 and is in close contact with the yoke 4. A dust cap 12 is attached to the center of the diaphragm 11 so that dust does not enter the voice coil 7.
In FIG. 8, reference numeral 13 denotes an inner magnet type main magnet, which is located on the upper surface of the center pole of the yoke 15. Reference numeral 14 denotes an auxiliary magnet of the inner magnet type.
In FIG. 9, 16 is a sleeve for sliding the adjustable auxiliary magnet of the outer magnet type magnetic circuit. Reference numeral 17 denotes a base for supporting the adjustable auxiliary magnet. Reference numeral 18 denotes a dial screwed to the base.

Here, the position of the speaker of the present invention will be clarified.
FIG. 1 is a cross-sectional view of an embodiment in which the present invention is applied to a speaker unit. The main magnet 1 in the outer magnet type has an annular shape and is magnetized in the surface direction. The lower part of the main magnet 1 is in close contact with a yoke 3 whose center part extends in a cylindrical shape on a disk-shaped base, and an annular yoke 4 on the upper part thereof. The columnar portion of the yoke 3 is commonly referred to as a center pole, and the notation “center pole” hereinafter refers to the column portion of the yoke 3. As a material for the yoke, a yoke, which is a ferromagnetic material, is generally used.

A cylindrical auxiliary magnet 2 is inserted into the center portion of the center pole of the yoke 3 with the upper and lower ends aligned with respect to the center pole. Further, the inner periphery of the yoke 4 and the outer periphery of the upper end of the center pole of the yoke 3 are not in close contact with each other, and a constant interval, for example, 2 mm is provided. By providing this interval, the magnetic force of the main magnet 1 can be concentrated there. The strength of this magnetic force is expressed as a collection of lines of magnetic force and is called magnetic flux density.
The interval, that is, the space is called a gap, and in FIG.

The bobbin 6 is held in the space of the gap 5 by a frame 9 that is in close contact with the yoke 4 and a damper 8 that is fixed thereto. The frame 9 is often produced mainly by pressing steel or the like.
However, if a magnetic material is used to closely contact the yoke, the magnetic force escapes and affects the magnetic force of the gap portion. Therefore, it is preferable to use a non-magnetic material for the frame 9. For example, aluminum or resin can be used.
The damper 8 keeps the gap 5 inside and outside constant when the bobbin 6 moves back and forth, and prevents contact with the yokes 3 and 4.
At the same time, since the projections and depressions are provided in the vertical direction, the damper 8 serves as a spring in the circumferential direction, and acts as a reaction force to return to the original position when the bobbin moves.
Thereby, it is possible to prevent the bobbin 6 and the diaphragm 11 that is in close contact with the bobbin 6 from being violated and to return and hold the bobbin 6 to an appropriate position. The hardness of the damper 8, that is, the reaction force of the spring, is adjusted from the weight of the bobbin 6, the voice coil 7 wound around the bobbin 6, the diaphragm 11 and the dust cap 12. If it is too hard, the bass will not be heard. The material of the bobbin 6 is mainly a film or hard paper in many cases, but an aluminum material is sometimes used to dissipate heat generated by the voice coil. In either case, a non-magnetic material is used.

A bobbin coil 7 is wound around the bobbin 6, and an audio signal is input thereto. When the signal is input, the voice coil 7 becomes an electromagnet, and attracts and repels the magnetic force generated in the gap 5 to move the diaphragm 11 back and forth. Therefore, the magnetic property in the gap 5 is important.
In general, since the description of the boil coil often includes a bobbin, the voice coil hereinafter refers to both the bobbin 6 and the voice coil 7. This back-and-forth movement is supported by a damper 8 and an edge 10 to prevent the bobbin 6 from contacting the yokes 3 and 4. Moreover, since the space | interval of the center pole of the yoke 3 and the bobbin 6 is very narrow and it is necessary to prevent intrusion of dust etc., the dust cap 12 is used. The back-and-forth movement of the diaphragm 11 vibrates air and converts it into sound.

FIG. 2 is a developed view in which the magnetic circuit of the embodiment in FIG. 1 is taken out.
The yoke 3 serving as a base rises in a cylindrical shape at the center of the disk-shaped plate, and the disk and the cylinder are integrated. Since this shape concentrates the magnetic force of the main magnet 1 received on the disk surface to the opposite pole, the center portion rises in a columnar shape. Magnetic lines of force pass through the yoke as a bundle. A cylindrical auxiliary magnet is inserted at the center of the cylindrical portion in order to increase the efficiency of the magnetic circuit.
As for the magnetic pole of the magnet, assuming that the yoke 3 side of the main magnet is N pole, the disk side of the auxiliary magnet is S pole. The series circuit of magnets, that is, the attracting poles, face each other. The yoke 4 is disposed at the upper portion of the main magnet, at a portion facing the yoke 3. Here too, the magnetic force is concentrated toward the cylindrical portion of the yoke 3 for the same reason as the disk surface. The inner peripheral portion of the yoke 4 has a diameter larger than that of the cylindrical portion of the yoke 3 and creates a space to concentrate the magnetic force and increase the magnetic flux density.
The yokes 3 and 4 are both in close contact with the main magnet 1, and the auxiliary magnet 2 is also inserted in close contact with the cylindrical portion.

FIG. 3 is an enlarged view of the magnetic circuit portion of FIG. 1, and is the same as the cross-sectional view when all the developed parts of FIG. 2 are in close contact. The magnetic field diagram of the conventional magnetic circuit in FIG. 5 and the magnetic field diagram in the embodiment of the present invention in FIG. 6 will be used. In the conventional magnetic circuit, as shown in FIG. 5, the magnetic field lines 19 of the main magnet pass through the yoke 4 and pass through the yoke 3a. At this time, in the gap 5, the magnetic field lines from the yoke 4 to the yoke 3 a are from the parallel gap magnetic field lines 19 a to the gap magnetic field lines 19 b obliquely toward the lower part of the yoke, and the angles of the magnetic field lines are ambiguous. As a result, when the voice coil 7 moves back and forth, the slanting lines of magnetic force obstruct the repulsion / attraction force of the perpendicular lines of magnetic force, thereby inhibiting pure back-and-forth movement. Further, since the oblique magnetic field lines apply a force in the oblique direction to the voice coil, the force applied to the diaphragm 11 becomes ambiguous. As a result, the sound is murky or reproduced as distortion. Further, there is a difference in the distance to the gap 5 between the yoke 3 and the yoke 4, and the via 3 has a longer distance to the gap, and the magnetic force concentrated on the disk portion of the yoke 3 is applied to the cylindrical portion. Since the cross-sectional area of the cylindrical portion is larger than the disk portion, the magnetic force is dispersed and the magnetic flux density is lowered, so that a difference occurs in the magnetic force inside and outside the gap 5.
For this reason, the voice coil 7 moves back and forth while being pulled outward. This also had an adverse effect on sound quality.

The leakage magnetic field lines 20 of the main magnet in FIG. 5 pass through the yoke 4 'to the upper surface of the yoke 4 so that the magnetic force that does not pass through the yoke draws an arc from the central part of the yoke 3'.
Since this magnetic force also passes in the vicinity of the voice coil 7, the angle becomes a part of a magnetic field line with an ambiguous angle, and the same adverse effect is caused.

Now, in the present invention, as shown in FIG. 3, by inserting the auxiliary magnet 2 into the central portion of the yoke 3, two magnetic circuits of the magnetic line 19 of the main magnet and the magnetic line 21 of the auxiliary magnet shown in FIG. 6 appear. . The lines of magnetic force 19 and 21 are independent of each other and repel each other. Therefore, the magnetic line 19 of the main magnet passing through the center pole repels the magnetic line 21 of the auxiliary magnet and converges to the outside of the cylindrical part. This point was confirmed by experiments using a compass and sand iron. Thereby, the dispersion of the magnetic force in the cylindrical portion as in the conventional type can be suppressed, and further, the angle of the magnetic lines of force from the yoke 4 to the yoke 3 can be adjusted in parallel so that the voice coil can perform pure back-and-forth motion. Concentrating the magnetic flux in the cylindrical portion also leads to suppression of a magnetic force difference generated inside and outside the gap 5, and as a result, improves sound quality and reduces distortion.

      The leakage magnetic field line 22 of the auxiliary magnet in FIG. 3 repels the leakage magnetic field line of the main magnet, and the angle at which the arc is drawn becomes substantially parallel as compared with FIG.

As described on the left, a technique for improving magnetic efficiency by using an auxiliary magnet to improve the magnetic efficiency with respect to the main magnet has been known for some time.
For example, a double magnet structure in which main magnets are stacked in two stages, or a structure in which the center pole itself is a magnet.
These are configurations in which the auxiliary magnet is arranged in a form independent of the main magnet and the yoke.
In contrast, the present invention is characterized in that two magnetic circuits are generated in the center pole. This is to provide an auxiliary magnet in the center pole to create one closed circuit and assist the magnetic circuit of the main magnet. Therefore, in order to create a closed circuit, the yoke that is the center pole is indispensable, and the magnetic circuit itself does not generate two magnetic circuits.

The auxiliary magnet exists in order to extract the magnetic force of the main magnet to the maximum, and the magnetic force needs to repel the magnetic force of the main magnet sufficiently.
Because of the external magnet type, the area of the auxiliary magnet is smaller than that of the main magnet due to physical limitations, so a small and powerful magnet such as a neodymium magnet is used. However, it is a magnet with a magnetic force that can balance the main magnet. If there is a magnet such as ferrite, it can be applied.

When a voice signal is input to the voice coil, the magnetic force of the voice coil, which is an electromagnet, may disturb the magnetic force of the gap portion, causing distortion in the reproduced sound.
This is generally called current distortion, and occurs when the yoke is not in a magnetic saturation state where it is no longer magnetized and is magnetized by the magnetic force of the voice coil. In order to prevent this, there is a structure in which a hollow is provided in the center part of the center pole to reduce the volume of the center pole and aim for magnetic saturation with the magnetic force of the main magnet. In addition, the magnetic force is dispersed, and the magnetic force in the gap portion is reduced. However, in the present invention, since the auxiliary magnet exists in the hollow portion, the magnetic force that flew in the space can be retained on the yoke, and the magnetic saturation of the main magnet can be brought close to magnetic saturation. It is very effective.

      As a method for adjusting the magnetic force of the auxiliary magnet, in addition to selecting the magnetic force of the auxiliary magnet itself, there is a method of balancing the repulsion by adjusting the length from the upper end of the center pole as shown in FIG. In order to improve the magnetic flux density and magnetic saturation in the gap part, it is ideal that the auxiliary magnet has the same surface at the upper and lower ends of the center pole, and by adjusting the length from there to the lower end, The dispersion of the magnetic field lines 19 of the main magnet that passes through can be adjusted.

There are a wide variety of speakers, from home use to business use, but there are some types of business equipment that continuously output high power depending on the application.
When a high load is applied to the speaker, the magnetic circuit may be exposed to high temperatures due to heat generation of the voice coil or heat generation of the yoke due to current distortion.
Since some types of magnets are demagnetized due to high temperature, FIG. 7 shows a magnetic circuit of an embodiment provided with a cooling mechanism.
The auxiliary magnet 2 provided in the central portion of the yoke 3 is formed into a cylindrical shape, and the force that the diaphragm moves back and forth is used to blow air to the central portion of the auxiliary magnet using the wind pressure of the dust cap 12 to cool the magnetic circuit.
Thereby, the wind pressure changes according to the output of the speaker, and the cooling power can be adjusted.

The present invention can also be applied to an inner magnet type magnetic circuit, and its structure is shown in FIG.
In the internal magnetic circuit, the main magnet 13 is located at the upper end of the cylindrical portion of the yoke 16, and a gap is formed by the main magnet and the outer periphery of the yoke.
Since the inner circumference of the gap part is a magnet, the inner circumference is not magnetically saturated, but the outer yoke side has a distance from the main magnet, causes a difference in magnetic force between the inside and outside, and causes current distortion.
By bringing the auxiliary magnet 14 into close contact with the outer periphery of the yoke 15, a magnetic circuit can be generated in the yoke outer periphery and the auxiliary magnet outer periphery, and the same effect as in FIG. 3 can be obtained. Since the auxiliary magnet 14 is on the outer periphery, it cannot be closed.
Therefore, a magnet having a strong magnetic force is required, and the magnetic force is adjusted by the thickness in the circumferential direction.
Further, the auxiliary magnet 14 may be replaced with a coil and an electromagnet may be used.

FIG. 9 shows an embodiment in which the auxiliary magnet is adjustable and the sound quality can be easily adjusted.
A cylindrical sleeve made of a magnetic material is inserted into the central portion of the yoke 3.
In this case, the auxiliary magnet is easy to move, and the inner surface is preferably mirror-finished. The auxiliary magnet 2 is inserted into the inner periphery. The auxiliary magnet 2 is connected to an adjustment knob 18, and the adjustment knob 18 has a screw structure and is screwed into the adjustment base 17. The adjustment pedestal 17 is fixed to the bottom of the yoke 3, and the 17 and 18 are made of a non-magnetic material so as not to be affected by magnetism.
Thus, by turning the adjustment knob 18, the insertion state of the auxiliary magnet can be changed, and the magnetic force and magnetic saturation can be adjusted.
It is possible to confirm changes in sound quality while actually listening to the sound.

      In the present invention, in addition to a full-band speaker, a speaker that reproduces a specific band such as a tweeter (high-frequency speaker) or a woofer (low-frequency speaker), or a double voice having two voice coils. It can also be applied to digital speakers that have a coil type or multiple layers of voice coils and are digitally driven.

The present invention aims to improve the efficiency of the magnetic circuit of a speaker that is widely used in general, and can be easily adjusted and improved, so it can be realized while minimizing the man-hours and material costs of the conventional manufacturing process. is there. In addition, it can be retrofitted to existing speakers, and it is a strength that it can easily improve widely used speakers, and it can contribute widely.

Claims (7)

      A main magnet that generates a magnetic field, a yoke disposed opposite the main magnet, a gap formed between the main magnet and the yoke, a voice coil disposed in the gap, and a magnetic flux in cooperation with the main magnet. A speaker further comprising an auxiliary magnet for raising the speaker, wherein the auxiliary magnet is arranged so that at least a part of the yoke is sandwiched between the auxiliary magnet and the main magnet.       The speaker is an outer magnet type, and an annular main magnet is located outside the center pole that is the yoke, and the auxiliary magnet is located at the center of the center pole that is the yoke and is surrounded by the center pole. The speaker of claim 1.       The speaker according to claim 2, wherein the auxiliary magnet is disposed so as to be flush with the upper surface of the center pole.       The speaker according to claim 3, wherein the lower surface of the auxiliary magnet is equal to or higher than the lower surface of the center pole.       The speaker is an internal magnet type, and a circular main magnet is located at the center. An annular yoke surrounds the outer periphery of the main magnet located at the center, and an auxiliary magnet is disposed on the outer periphery of the yoke. The speaker according to claim 1.       The speaker according to claim 5, wherein the upper surface of the auxiliary magnet is arranged to be flush with the upper surface of the yoke. The speaker according to claim 6, wherein a lower surface of the auxiliary magnet is equal to or higher than a lower surface of the yoke.