JP2002112387A - Speaker and speaker system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speaker that reduces the stiffness of a support system determining a minimum resonance frequency of the speaker through a magnetic attracting so as to extend lowest reproduction frequency in a low frequency. SOLUTION: A diaphragm 6 is fixed to a tip of a voice coil bobbin 8 to configure a moving part. The moving part is supported by an edge 7 and a suspension of a damper 8. A magnetic pole piece 10 made of a ferromagnetic material is jointed with the voice coil bobbin, and a spacer 13 fixes magnetic poles 11, 12 made of a magnet material in opposition thereto. A magnetic attraction is generated between the magnetic pole piece and a magnetic pole placed in opposition thereto so as to cancel and decrease the stiffness of the suspension supporting moving part. Thus, the minimum resonance frequency of the speaker can be lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loudspeaker for reducing the stiffness of a support system by magnetic attraction and expanding a bass reproduction limit, and a loudspeaker system equipped with the loudspeaker.

[0002]

2. Description of the Related Art A conventional loudspeaker comprises driving means for generating a vibrating force by an electric input, a movable part vibrating by the force generated by the driving means, and a suspension for supporting the movable part. To form a speaker system. For example, in an electrodynamic speaker, a magnetic circuit and a voice coil inserted in the magnetic gap are driving means. When an electric signal is input to the voice coil, a force is generated in the voice coil by a magnetic flux in the magnetic gap. Things. The force generated in the voice coil is transmitted to a movable portion composed of a voice coil bobbin around which the voice coil is wound and a diaphragm joined to the tip of the voice coil bobbin. A damper, which is a suspension for supporting the movable portion, and an edge are joined to the outer peripheral portion of the voice coil bobbin and the outer peripheral portion of the diaphragm, respectively.

[0003]

It is well known that in such a conventional speaker, the bass reproduction limit is determined by the vibrating mass including the movable part and the suspension and the lowest resonance frequency determined by the stiffness of the suspension. is there.
Furthermore, when it is attached to a cabinet, air pressure is applied to the back surface of the diaphragm, which is affected by the stiffness of the air. If the cabinet has a sufficiently large volume, the lowest resonance frequency of the loudspeaker will not change significantly, but in many cases the loudspeaker will be mounted in a small cabinet for miniaturization, and as a result of the effect of air stiffness in the cabinet. The lowest resonance frequency rises,
Insufficient bass range reproduced from the speaker is a problem.

The present invention solves the above-mentioned problem, and reduces a stiffness value determined by a speaker suspension or a vacant volume of a cabinet of a speaker system by a magnetic attraction force for canceling the stiffness, so that a small cabinet can provide sufficient bass. It is intended for reproduction.

[0005]

In order to achieve the above object, the present invention provides a driving means for generating a vibrating force by an electric input, a movable part induced to vibrate by the driving means, and a support for the movable part. And a magnetic pole piece integrated with the movable portion, and at least two magnetic poles disposed opposite to the magnetic pole piece to constitute a speaker with the magnetic pole piece and the two magnetic poles. Here, a magnetic attraction force is generated between the magnetic pole piece joined to the movable portion and the magnetic pole arranged opposite thereto. Therefore, the stiffness value of the suspension supporting the movable portion can be reduced by the magnetic attractive force acting in the direction to cancel the stiffness.

Further, the driving means is a magnetic circuit and a voice coil inserted in a magnetic gap of the magnetic circuit,
Further, the movable part is a voice coil bobbin joined to the voice coil, and a diaphragm joined to one end of the voice coil bobbin to constitute an electrodynamic speaker.

Further, the magnetic pole piece is joined to the inner peripheral surface of the voice coil bobbin, and the two magnetic poles arranged opposite to the magnetic pole piece are provided on the inner peripheral side of the voice coil bobbin, so that the magnetic pole piece is provided. The suction force generating part can be configured inside the voice coil bobbin which was conventionally hollow,
Conventionally, a speaker having substantially the same size and capable of reproducing low-frequency sound can be realized.

Further, by integrating the driving means with a piezoelectric body and the piezoelectric body and the magnetic pole piece, it is possible to reduce the lowest resonance frequency of a speaker using the piezoelectric body. Further, if the pole piece is used as an electrode for supplying electricity to the piezoelectric body, and if the electrode is used as a suspension for supporting the piezoelectric body, the electrode constitutes a movable part integrally with the piezoelectric body, A magnetic attractive force is generated between the electrode and the magnetic pole arranged opposite to the magnetic pole piece,
By reducing the stiffness value of a suspension that is also an electrode, a piezoelectric speaker capable of reproducing low-frequency sound can be realized.

Further, when the pole piece is made of a magnetic material,
When the two magnetic poles are permanent magnets and the pole piece is a permanent magnet, the value of the magnetic attraction force is determined by combining the two magnetic poles with a magnetic material, or by combining the pole piece and the two magnetic poles with a permanent magnet. Can be set to an arbitrary value in a wide range, and it is possible to obtain an optimum magnetic attraction force for a speaker to be applied.

Further, if the speaker having the above structure is mounted on a cabinet and the magnetic attraction force is set in consideration of the stiffness of the air in the cabinet, the magnetic attraction force is determined by the stiffness of the speaker suspension and the air of the cabinet. Can reduce the composite value of the stiffness of the loudspeaker, and can realize a speaker system capable of reproducing a compact and rich bass sound. In this case, it is desirable that the combined value of the air stiffness of the cabinet and the stiffness of the speaker suspension be larger than the magnetic attractive force. This can prevent the pole piece from being attracted to one of the two magnetic poles.

[0011]

(Embodiment 1) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The speaker according to the first embodiment will be described with reference to FIGS. 1 (a) and 1 (b). 1 (a) is a plan view of the speaker, and FIG. 1 (b) is a cross-sectional view taken along a line AB of the speaker of FIG. 1 (a). The speaker is configured as follows. 1 is a magnet,
A center pole 2 is fixed to the upper surface, and a pot-shaped yoke 3 is fixed to the lower surface to form a magnetic circuit. A voice coil 5 wound around a voice coil bobbin 4 is inserted into a magnetic gap defined by the outer peripheral surface of the center pole 2 and the inner peripheral surface of the cylindrical portion of the pot-shaped yoke 3. Is fixed. An edge 7 which is one of suspensions is joined to an outer peripheral portion of the diaphragm 6, and a damper 8 is joined to an outer peripheral portion of the voice coil bobbin 4, and a central portion of each outer peripheral portion is fixed to the yoke 3. The frame 9 is joined. To the inner periphery of the voice coil bobbin 4, for example, a donut-shaped pole piece 10 made of a ferromagnetic material such as an iron material or permalloy is joined. The magnetic poles 11 and 12 whose upper surface is N-pole and whose lower surface is S-polarized are doughnut-shaped magnet materials such as neodymium and ferrite so as to face the pole piece 10.
Is fixed to the support 13 fixed to the upper surface of the.

The operation of the speaker configured as described above will be described. When an electric signal is input to the voice coil 5, a current flows through the voice coil 5, and a vibration force is generated in a magnetic gap between the voice coil 5, the center pole 2 of the magnetic circuit, and the yoke 3. The voice coil bobbin 4 and the diaphragm 6 joined thereto constitute a movable portion, and the movable portion is supported by the edge 7 and the damper 8 serving as a suspension. The diaphragm 6 is vibrated through the coil bobbin 4. The magnetic pole piece 10 joined to the inner peripheral surface of the voice coil bobbin 4 swings up and down with the vibration of the voice coil bobbin 4. Since the magnetic poles 11 and 12 are provided facing each other in the amplitude direction of the magnetic pole piece 10, when the magnetic pole piece 10 swings on the upper surface, it approaches the magnet magnetic pole 11 and
Is a ferromagnetic material and the magnetic pole 11 is a magnet,
A magnetic attractive force acts between the pole piece 10 and the magnetic pole 11,
When the voice coil bobbin 4 oscillates on the lower surface,
Similarly, a magnetic attractive force acts between the pole piece 10 and the magnetic pole 12. The magnetic pole 1 accompanying the vertical amplitude of the pole piece 10
The magnetic attraction force between the voice coil bobbin 4 and the voice coil bobbin 4
And the diaphragm 6 work in a direction that promotes the movement of the movable part. Usually, the lowest resonance frequency f0 is used as a scale for determining the limit of the bass reproduction frequency of the speaker. This f0 is obtained as shown in (Equation 1) by the mass of the vibration system composed of the movable part of the speaker and the suspension and the stiffness of the suspension.

[0014]

(Equation 1)

However, f01: minimum resonance frequency Sms: stiffness of suspension Mms: mass of vibration system The larger the amplitude of the suspension, the more the spring force of the suspension acts in the direction of suppressing the movement of the movable part. The magnetic attraction force acting between the magnetic poles 11 and 12 is such that as the distance between the pole piece 10 and the magnetic poles 11 and 12 becomes shorter, the magnetic attraction force increases, and acts in a direction that promotes the amplitude of the movable portion. It is. Therefore, the stiffness of the suspension supporting the movable portion is a composite value of the stiffness of the suspension and the stiffness of the magnetic attraction, and the lowest resonance frequency f02 is

[0016]

(Equation 2)

Here, f02: minimum resonance frequency Smm: stiffness exhibiting magnetic attraction Sms: stiffness of suspension Mmt: mass of the vibration system including the pole piece, and the composite value of stiffness is smaller than that in the case of (Equation 1). As a result, the lowest resonance frequency f02 can be reduced. In Equation 2, since the mass of the vibration system includes the mass of the pole piece 10, the pole piece 10 also has the effect of lowering the lowest resonance frequency f02. It is desirable to be as light as possible to reduce levels.

In the first embodiment, the magnetic pole piece is a ferromagnetic material and the magnetic pole is a magnet, but as shown in FIG. 2, the magnetic pole piece 14 is made of a magnet material such as neodymium or ferrite. The magnetic poles 15 and 16 that are arranged in a horizontal direction may be a ferromagnetic material such as iron or permalloy. further,
As shown in FIG. 3, the material of the pole piece 100 and the magnetic poles 101 and 102 may be all magnet materials. In this case, since the magnetic attraction force can be further increased, the stiffness exhibited by the magnetic attraction force is increased, and the stiffness of the suspension is largely canceled, so that the lowest resonance frequency f02 of the speaker can be further reduced. In addition,
In the embodiment shown in FIGS. 1, 2, and 3, the dimensional relationship between the pole piece and the pole facing the pole piece is such that the inner diameter of the donut-shaped pole piece is larger than the outer shape of the donut-shaped magnetic pole, that is, the pole piece is larger. In the case of the amplitude, the pole piece collides with the magnetic pole, but as shown in FIG. 4, the inner diameter of the pole piece 18 is larger than the outer shape of the magnetic poles 19 and 20, and in any case, collision is avoided. It is also possible to adopt such a configuration. In this case, the magnetic attraction decreases because the facing area between the pole piece and the magnetic pole decreases, but a desired magnetic attraction can be obtained by using a magnet having a larger energy product. Further, in FIG.
Both 9 and 20 are magnet materials, but either may be a ferromagnetic material. Furthermore, the value of the magnetic attraction is
Depending on the characteristics of the speaker and the purpose of use, it is necessary to set the value widely, but the magnetic characteristics of the pole piece or the magnetic pole are a matter of design arbitrarily selected, and if the magnetic material generates a magnetic attractive force, For example, a weak magnetic material such as stainless steel may be used.

(Embodiment 2) Next, a speaker according to a second embodiment will be described with reference to FIGS. 5 (a) and 5 (b). However, FIG. 5A is a plan view of the speaker, and FIG. 5B is a cross-sectional view of the speaker in FIG. The speaker is configured as follows. The piezoelectric bodies 22 and 23 are fixed to both surfaces of an electrode 24 made of a magnetic material such as permalloy. An outer case of the electrode 24 has an upper case 25 provided with a plurality of sound holes 27 and 28 on the upper and lower surfaces.
And a lower case 26, and a magnet 2 is provided at the center of the upper case 25 and the lower case 26 so as to face the electrode 24.
9, 30 are arranged. Reference numerals 31 and 32 denote electrical input units.
1 is connected to the electrode 24, and 32 is connected to the piezoelectric bodies 22 and 23.

The operation of the loudspeaker configured as described above will be described. When an electric signal is input to the electric input units 31 and 32, a voltage is applied to the electrode 24 and the upper surface of the piezoelectric body 22 and the lower surface of the piezoelectric body 22, and the piezoelectric bodies 22 and 23 expand and contract, and the electrode 24 and the piezoelectric bodies 22 and 23 are integrated. The movable part configured as above vibrates. Since the outer peripheral portion of the electrode 24 is fixed to the upper case 25 and the lower case 26, the electrode 24 also functions as a suspension for the movable portion. When there is no electric input, if the distance between the electrode 24 and the magnet 29 attached to the upper case 25 and the magnet 30 attached to the lower case 26 are set to be equal, the magnetic attractive force acting on the electrode which is a magnetic material Are balanced approximately equally, without the effect of magnetic attraction. Next, when the piezoelectric members 22 and 23 expand and contract due to electric input, and the movable portion oscillates on the upper surface, the electrode 24 approaches the magnet 29 provided on the upper case 25 and is attracted by the magnetic force. When the movable portion oscillates on the lower surface, the electrode 24 is similarly connected to the lower case 2
6 is attracted by the magnet 30 provided in the cartridge 6. As described in the first embodiment, also in the present embodiment, the lowest resonance frequency that determines the bass reproduction limit frequency of the speaker is determined by the mass of the vibration system including the movable part and the suspension and the stiffness of the suspension. However, the magnetic attraction generated between the electrode 24 and the magnets 29 and 30 acts in a direction to cancel the stiffness of the suspension, thereby making it possible to lower the lowest resonance frequency.

In the present embodiment, a magnetic material is used for the electrode. However, brass or phosphor bronze having high electric conductivity is usually used as the electrode material. In this case, the magnetic material or the magnet A similar effect can be obtained even if the pole piece is formed using a material. In this embodiment, an example of application to a bimorph piezoelectric speaker in which a piezoelectric body is disposed on both surfaces of an electrode has been described. However, the present invention can also be applied to a monomorph piezoelectric speaker in which a piezoelectric body is provided on one side of an electrode.

Further, in the above-described embodiment, the application to the electrodynamic loudspeaker using the voice coil and the piezoelectric loudspeaker using the piezoelectric body has been described. The present invention can be applied to various electro-mechanical conversion type converters having means for generating an electric field.

(Embodiment 3) Next, a speaker system according to a third embodiment will be described with reference to FIG. FIG. 6 is a sectional view of the speaker system.
The speaker system is configured as follows. Reference numeral 33 denotes the speaker according to the first embodiment described with reference to FIG. Reference numeral 35 denotes an empty room formed by the back of the speaker 33 and the cabinet 34.

The operation of the speaker system configured as described above will be described. The operation when an electric input is applied to the speaker 33 has already been described, and thus will be omitted to avoid duplication. This embodiment differs from the first embodiment in that the speaker 33 is attached to a cabinet. Thereby, the movable part of the speaker is affected by the stiffness of the air presented by the empty room 35. Although the stiffness of the air is determined by the volume of the empty space 35, since the speaker system is desired to be as small as possible, the volume 35 is designed to be small and the lowest resonance frequency is affected by the stiffness of the air.
The conventional loudspeaker system is higher than the three loudspeakers. For example, if the diaphragm diameter of the speaker is 16
0 mm, mass of vibration system is 10 g, minimum resonance frequency is 50
Hz, the stiffness Sms of the suspension is 987 (N / m) from (Equation 1). Assuming that the internal volume of the speaker cabinet is 20 liters, the stiffness Smb exhibited by the empty space on the back of the speaker is 2822 (N / m).
And the stiffness of the speaker system is Sm
This is 3809 (N / m) which is a combined value of s and Smb.
As a result, the lowest resonance frequency of the speaker system is determined by the combined stiffness and the mass of the vibration system of the speaker.
rise to z.

Next, when the speaker 33 having the configuration described in the first embodiment is attached to a speaker system having the same volume, the stiffness Smm of the magnetic attraction acting on the diaphragm cancels the stiffness Sms of the suspension. Therefore, if it is assumed that almost complete cancellation is achieved, Sms−Smm ≒ 0, and the lowest resonance frequency of the speaker system can be reduced from 98 Hz to 85 Hz in the related art. The magnitude of the magnetic attraction force can be arbitrarily set depending on the material, shape, etc. of the magnetic pole piece and the magnetic pole.
Is the stiffness Sm of the speaker suspension
It is also possible to set the value larger than s. For example,
The value of the stiffness Smm of the magnetic attraction force is the same size as the stiffness Smb of the cabinet 2822 (N / m)
, The combined stiffness of the speaker system is Sms + Smb-Smm = 987 + 2822
As a result, −2822 = 987 (N / m), the stiffness exhibited by the empty room 34 of the cabinet is canceled, and the lowest resonance frequency of 50 Hz, which is the minimum resonance frequency of the speaker alone, can be realized by a 20-liter cabinet. further,
If the stiffness exhibited by the magnetic attractive force is made larger than the stiffness exhibited by the cabinet, the lowest resonance frequency can be further reduced.

It is desirable that the value of the stiffness exhibited by the magnetic attraction be smaller than the combined value of the stiffness of the suspension of the speaker and the stiffness exhibited by the empty room of the cabinet. If it is larger than this, the pole piece joined to the movable portion may be attracted to one of the magnetic poles and may not be able to return to a position where the pole pieces are balanced by the magnetic attraction of the two magnetic poles, which is the initial position of vibration. There is.

In order to stabilize the value of the stiffness exhibited by the vacant space of the cabinet, it is desirable to adopt a speaker and cabinet structure for improving the airtightness of the vacant space of the speaker cabinet. Further, in this embodiment, the speaker is an electrodynamic speaker driven by a voice coil, but there is no problem even if the speaker is the piezoelectric speaker or the electrostatic speaker described in the second embodiment.

[0028]

According to the loudspeaker of the present invention as described above, the magnetic pole piece is integrated with the movable portion, and a magnetic attractive force acts between the magnetic pole piece and the magnetic pole arranged at a position facing the magnetic pole piece.
Therefore, when the movable part oscillates, the pole piece approaches the magnetic pole to increase the magnetic attraction, canceling the spring force of the suspension supporting the movable part, reducing the lowest resonance frequency of the speaker, and lowering the bass reproduction limit frequency. Can be reduced. Further, in the speaker system in which the speaker of the present invention is mounted on the cabinet, the stiffness exhibited by the empty space of the cabinet can be canceled by the magnetic attraction force presented by the pole pieces, and the deep bass which could not be reproduced by the small speaker system conventionally can be eliminated. A reproducible speaker system can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view of a speaker according to a first embodiment.

FIG. 2 is another first structural sectional view of the first embodiment for obtaining magnetic attraction.

FIG. 3 is another sectional view of a second structure for obtaining a magnetic attractive force according to the first embodiment;

FIG. 4 is a sectional view of another third structure for obtaining magnetic attraction according to the first embodiment;

FIG. 5 is a plan view and a sectional view of a speaker according to a second embodiment.

FIG. 6 is a sectional view of a speaker system according to a third embodiment.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 magnet 2 center pole 4 voice coil bobbin 5 voice coil 6 diaphragm 7 edge 8 damper 10, 14, 18, 100 pole piece 11, 12, 15, 16, 19, 20, 101, 102
Magnetic pole 24 Electrode 23, 24 Piezoelectric body 34 Cabinet 35 Vacancy

Claims (13)

[Claims] 1. A driving unit for generating a vibration force by an electric input, a movable unit induced to vibrate by the driving unit, a suspension supporting the movable unit, and a magnetic pole piece integrated with the movable unit. A speaker that generates magnetic attraction between the pole piece and the two magnetic poles with at least two magnetic poles disposed opposite the pole piece; 2. The loudspeaker according to claim 1, wherein said driving means is a magnetic circuit and a voice coil inserted into a magnetic gap of said magnetic circuit. 3. The speaker according to claim 2, wherein said movable portion is a voice coil bobbin joined to said voice coil, and a diaphragm joined to one end of said voice coil bobbin. 4. The loudspeaker according to claim 3, wherein said pole piece is joined to an inner peripheral surface of said voice coil bobbin. 5. The loudspeaker according to claim 3, wherein said two magnetic poles disposed opposite to said magnetic pole piece are provided on an inner peripheral side of said voice coil bobbin. 6. The speaker according to claim 1, wherein said driving means is a piezoelectric body. 7. The speaker according to claim 6, wherein a pole piece is integrated with the piezoelectric body. 8. The speaker according to claim 1, wherein said pole piece is an electrode for supplying electricity to a piezoelectric body. 9. The device according to claim 8, wherein said electrode serves as a suspension for supporting a piezoelectric body and forms a movable portion.
Speaker. 10. The speaker according to claim 1, wherein said pole piece is a magnetic material or a permanent magnet. 11. The speaker according to claim 1, wherein the two magnetic poles are permanent magnets or magnetic materials. 12. A speaker system comprising the speaker according to claim 1 incorporated in a cabinet. 13. The loudspeaker suspension according to claim 12, wherein a supporting force determined by a combination of the stiffness of the vacant space of the cabinet and the stiffness of the speaker suspension is larger than the magnetic attractive force. Speaker system.