JPH0654398A - Magnetic circuit for speaker - Google Patents

Abstract

PURPOSE:To cancel the distortion of a reproduced sound by canceling the asymmetry of an electromotive force waveform based on the asymmetry of the up-and-down vibration of a voice coil, and to broaden the directivity of a high sound area radiation by canceling the up-and-down asymmetry of a magnetic flux distribution of a magnetic gap and retaining the symmetrical magnetic distribution. CONSTITUTION:A center pole 3 is projected upward from the surface of an upper plate 5 while the part of the center pole 3 faced to the magnetic gap is left, so that an extending part 3a can be formed. And also, a center pole root part 3b is finished to be thin, and a lower part short ring 7a is mounted on the site finished to be thin. Moreover, the thickness of the outside part of the upper plate is formed to be thick, the lower part square part of the upper plate which is faced to the magnetic gap is cut by tapering in the contact surface of an annular main magnet 2 whose inner diameter is large with the upper plate, and a non-magnetic phase flag 12a is mounted on the projecting and extending part of the center pole. Thus, the part except the part of the upper plate faced to the magnetic clearance can be arranged so as to be separated from the center pole.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention eliminates the vertical asymmetry of the magnetic flux distribution in a magnetic air gap, and maintains a symmetrical magnetic distribution, so that an electromotive force waveform based on the asymmetry of the vertical vibration of the voice coil is obtained. The present invention relates to a magnetic circuit for a speaker, which eliminates the asymmetry of (1), eliminates distortion of reproduced sound, and broadens directional characteristics of high-range radiation.

2. Description of the Related Art Conventionally, a magnetic circuit for a speaker of this type (21)
Place the ring-shaped main magnet (12) on the lower plate (14) of the center pole (13) and the upper plate (15) on it as shown in FIG. Generally, an annular magnetic gap (16) is formed between the center pole (13) and the center pole (13) to be assembled. Further, particularly in a speaker that abundantly reproduces high frequencies, an equalizer (12c) is attached to the front surface of the center pole (13) in order to match the impedance of high frequencies radiation.

Therefore, in the conventional magnetic circuit (21) for this type of speaker, the upper plate is used.
Since the shape of the upper and lower magnetic circuits of (15) is different,
In the vertical magnetic flux distribution of the magnetic air gap (16), because the symmetry cannot be maintained and the AC magnetic flux component generated from the vibrating voice coil (19) does not become completely zero, In addition, there is a problem that the upper plate (25) does not have a symmetrical shape with respect to the center line. The electromotive force due to the vibration of the voice coil (19) is the counter electromotive force generated by the interlinkage between the voice coil (19) and the magnetic flux in the magnetic gap (16) and is superimposed in the opposite phase with the input waveform. Therefore, if the counter electromotive force is distorted due to the asymmetry of the air gap magnetic flux, the input waveform to the speaker is also asymmetrical and distorted. This distortion is included in the reproduced sound of the speaker as current distortion, and becomes second harmonic distortion when the magnetic flux distribution is asymmetric. Therefore, the asymmetry of the magnetic flux distribution can be known by measuring the second harmonic distortion level. As shown by the dotted line in FIG. 2 as a conventional example, the second harmonic level with respect to the fundamental wave is 150
It can be read that it is about -77 dB near Hz. Therefore, the present invention solves the problem that such a conventional magnetic circuit has by increasing the alternating-current magnetic flux component (φ ₂ ) passing through the magnet to generate distortion. By separating the magnetic gap (6) and the magnet (2) as shown in FIG. 4, the AC magnetic flux component passing through the voice coil in the AC magnetic flux (φ ₂ ) is reduced, and the linearity of the magnetic flux distribution is reduced. And a magnetic circuit for a speaker that reduces the above distortion
They are (1a) and (1b). In this magnetic circuit (1a), (1b), the annular main magnet (2) is placed on the lower plate (4) of the center pole (3), and the upper plates (5), (5 ') are placed. Placed on it, in the speaker magnetic circuit (1a), (1b) assembled by forming an annular magnetic gap (6) between the center pole (3),
Leave the part facing the magnetic air gap (6) of the center pole (3),
The center pole (3) is projected above the surface of the upper plates (5), (5 ') to form an extension (3a), and the extension (3a) has heat dissipation and is conductive. In addition, the non-magnetic upper short ring (7b) is attached, and the lower root part (3b) of the center pole (3) is thinned, and the thinned part
Attach the lower short ring (7a), which has heat dissipation, is conductive, and is non-magnetic, to (3b), and then attach the upper plate (5),
The portion other than the portion of (5 ') facing the magnetic gap (6) is arranged apart from the magnetic gap (6). The present invention intends to provide a magnetic circuit for a speaker, in which the linearity of the magnetic distribution is improved, and a magnetic circuit for a speaker, in which the radiation impedance in the high frequency range is matched, which has not been considered in the past. To do. In the above-mentioned conventional magnetic circuit for a speaker of this type (21), in the vertical magnetic flux distribution of the magnetic gap (16), it is not possible to maintain symmetry,
There is a speaker magnetic circuit in which the AC magnetic flux generated from the vibrating voice coil (19) increases the AC magnetic flux component (φ ₂ ) passing through the magnet (12). In the magnetic circuit (21), if the DC magnetic flux due to the magnetomotive force of the magnet is (φ ₁ ) and the AC magnetic flux due to the voice coil magnetomotive force is (φ ₂ ), the magnetic flux density (B _g ) of the magnetic gap is B _g = It becomes φ ₁ + φ ₂ . This (φ ₂ ) is generated around the voice coil (19), and when the magnetic gap (6) and the magnet (2) are close to each other as shown in FIG. 6, a part of (φ ₂ ) is a magnet. Pass the same magnetic path as the DC magnetic flux (φ ₁ ) that passes through (2).
In such a state, the magnet (2) is modulated by the voice coil magnetomotive force, that is, the input signal, and the magnetic flux density changes to cause distortion.

The structure of the present invention for achieving the object will be described with reference to FIGS. 1 to 3 corresponding to the embodiments.

[1] Place the ring-shaped main magnet (2) on the lower plate (4) of the center pole (3), and place the upper plate (5) on the center pole (3). An annular magnetic gap between and
In the speaker magnetic circuit (1a) assembled by forming (6), leave the part of the center pole (3) facing the magnetic gap (6), and attach the center pole (3) to the upper plate (5). The extension part (3a) is formed by projecting upward from the surface, and the extension part (3a) has a heat dissipation, conductive and non-magnetic upper short ring (7b), and the center part. The pole base (3b) is thinly finished, and the thinned part (3b)
Install a heat-dissipating, conductive, non-magnetic lower short ring (7a) on the top plate (5) except for the part facing the magnetic gap (6). It is placed apart from the air gap (6) and has a large inner diameter annular main magnet (2).
A magnetic gap (6) is created by sandwiching the auxiliary annular plate (8) with a large inner diameter between the upper plate (5) and the upper plate (5).
Is located apart from the ring-shaped main magnet (2), and a conductive and non-magnetic upper short ring (7b) is attached to the extension (3a) of the center pole (3). ) And a phase plug (12a) are attached to the speaker magnetic circuit.

[2] Place the ring-shaped main magnet (2) on the lower plate (4) of the center pole (3), place the upper plate (5 ') on it, and set the center pole (3) In the magnetic circuit for a speaker (1b) assembled by forming an annular magnetic gap (6) between the center pole (3) and the magnetic pole (3), the center pole (3) is left. ) Is projected above the surface of the upper plate (5 ′) to form an extension (3a), and the extension (3a
Install the upper short ring (7b) that has heat dissipation, conductivity, and is non-magnetic in (a), and finish the bottom part (3b) of the center pole thinly.
The part other than the part facing the magnetic air gap (6) of the upper plate (5 ') with the lower short ring (7a) of heat dissipation, conductive and non-magnetic material attached to b). Are placed apart from the magnetic air gap (6), and the outer thickness (5c) of the upper plate (5 ') is made thicker than the thickness (5a) facing the magnetic air gap (6). Large toroidal main magnet (2) and top plate
At the contact surface with (5 '), the magnetic gap of the upper plate (5')
From the lower corner facing (6), cut with a taper (5b), attach the nonmagnetic phase plug (12a) to the protruding extension (3a) of the center pole (3), and Plate (5 ')
The part other than the part facing the magnetic gap (6) of the
It is a magnetic circuit for a loudspeaker which is arranged apart from the above.

[3] The above

[1],

[2] The speaker magnetic circuit according to [2], wherein the upper short ring (7b) and the phase plug (12a) attached to the projecting extension (3a) of the center pole (3) are integrally formed. The magnetic circuit for a speaker according to Item 1 or 2.

Since the present invention has such a structure, the short rings (7a) and (7b) are used, and the magnetic gap (6) of the upper plates (5) and (5 ') is further used. The magnetic field (6) and the annular magnet (2) are separated from each other, and the signal flowing to the voice coil (9) is reduced by thinning the part facing the Due to the influence of the electric current and its AC magnetomotive force, the fluctuation of the air gap magnetic flux density is eliminated as much as possible, and the voice coil
By making the driving force generated in (9) accurately follow the signal current, and by making the center pole (3) an upper and lower symmetrical structure, the symmetry of the vertical distribution of the magnetic flux is improved, and the magnetic distribution In addition to eliminating non-linear distortion due to linearity, the level of distortion of reproduced sound can be extremely lowered. Then, because the shapes of the magnetic circuits on the upper and lower sides of the plates (5) and (5 ') are different and the AC magnetic flux component (φ ₂ ) does not become completely zero, it is improved to the extent shown in Fig. 1. It is. Further, as described above, the electromotive force due to the vibration of the voice coil (9) is the counter electromotive force generated by the interlinkage between the voice coil (9) and the magnetic flux in the magnetic air gap (6) due to the asymmetry of the air gap magnetic flux. Distortion also solves the problem of the conventional example in which the input waveform to the speaker is also asymmetrical and distorted. When the magnetic gap and the magnet are separated from each other as in the embodiment, the AC magnetic flux (φ ₂ ) has a reduced AC magnetic flux component passing through the magnet and the distortion is reduced. Furthermore, a phase plug attached to the upper end of the extension (3a) of the center pole (3)
(12a) is the vibration in the high range generated by the voice coil (9)
When propagating in the air through the base of the diaphragm (10), the acoustic radiation impedance of the sound path increases, so it is expected that the high frequency reproduction sound will be diffused efficiently and the directivity will become broad. You can do it.

Embodiments of the present invention will be described below with reference to the drawings. 3 to 5 are cross-sectional views of an embodiment of the present invention. The present invention is

[1] In FIG. 3, the annular main magnet (2) is placed on the lower plate (4) of the center pole (3), and the upper plate
(5) is placed on it, and in the speaker magnetic circuit (1a) assembled by forming an annular magnetic gap (6) between the center pole (3) and the center pole (3), The center pole (3) is projected above the surface of the upper plate (5) to form an extension (3a), leaving a portion facing the magnetic gap (6).
The extension part (3a) has a heat dissipation property, a conductive and non-magnetic upper short ring (7b) is attached, and the center pole (3) and the bottom root part (3b) are finely finished. A thin, finished part (3b) is fitted with a heat-dissipating, conductive, non-magnetic lower short ring (7a), and is attached to the magnetic gap (6) of the center pole (3). The part other than the part to be placed is placed apart from the magnetic gap (6), and further, between the annular main magnet (2) with a large inner diameter and the upper plate (5),
By arranging the auxiliary annular plates (8) having a large inner diameter so as to be sandwiched, the magnetic gap (6) is arranged so as to be separated from the annular main magnet (2), and the center pole (3)
A magnetic circuit for a speaker in which an electrically conductive and non-magnetic upper short ring (7b) and a phase plug (12) are attached to an extension (3a) of the above.

[2] Arrange the part of the upper plate (5 ') other than the part facing the magnetic air gap (6) away from the center pole (3),
In addition, the outer plate (5 ') has a thick outer thickness (5c) to form a large inner diameter annular main magnet (2) and upper plate (5c).
At the contact surface with (5 '), the magnetic gap of the upper plate (5')
From the lower corner facing (6), cut with a taper (5b), attach the nonmagnetic phase plug (12a) to the protruding extension (3a) of the center pole (3), and Plate (5 ')
The magnetic circuit for a loudspeaker in which the portion other than the portion facing the magnetic air gap (6) is placed away from the center pole (3).

[3] The above

[1] or

In the speaker magnetic circuit according to [2], the upper short ring (7b) and the phase plug (12) are integrally formed in the speaker magnetic circuit. Although the generation amount of the AC magnetic flux can be reduced to some extent by the means described in the above-mentioned problem to be solved by the invention, each of the conventional example shown in FIG. 6 and the examples shown in FIGS. In the magnetic circuit structure, if the DC magnetic flux due to the magnetomotive force of the main magnet (2) is φ ₁ and the AC magnetic flux due to the magnetomotive force of the voice coil (9) is φ ₂ , the magnetic flux density B _g of the magnetic gap (6) is B _g
= Φ ₁ + φ ₂ . This φ ₂ is generated around the voice coil (9), but as in the conventional example shown in FIG.
When (6) and the main magnet (2) are close to each other, part of φ ₂ passes through the same magnetic path as the DC magnetic flux φ ₁ passing through the main magnet (2).
In such a state, the voice coil (9) is connected to the main magnet (2).
Since a part of the magnetomotive force of
The operating point of (2) is always the magnetomotive force of the voice coil (9), that is,
It will be modulated by the input signal, and the magnetic flux density will change and cause distortion. When the magnetic gap (6) and the main magnet (2) are separated as shown in the embodiment, the AC magnetic flux φ ₂ is concentrated in the vicinity of the magnetic gap (6) where the voice coil (9) exists, and the main magnet (2 ), The AC magnetic flux component passing therethrough is reduced, and the distortion is reduced. Considering a case where an AC magnetomotive force is superimposed on the magnetomotive force of the main magnet (2) based on the saturated state and the unsaturated state shown in FIGS. 7 and 8, the magnetic circuits (1), (1a),
The total magnetomotive force of (1b) fluctuates between H ₁ and H ₂ with H ₀ as the center, the operating point changes along the BH curve, and the air gap magnetic flux density also changes. At this time, for example, in the case of the unsaturated state in FIG. 8, the air gap magnetic flux density is B ₁ 'and B ₂ ' with the original magnetic flux density B ₀ 'of only the main magnet (2) as the center, corresponding to each magnetomotive force. Fluctuating between them, the air gap magnetic flux density fluctuates for each cycle of the input signal, and the driving force, that is, the reproduced sound is distorted. Next, also in the case of the saturated state of FIG. 7, the magnetomotive force H ₀ (the original magnetic flux density of only the main magnet (2)) set so as to saturate the air gap magnetic flux is centered, and H ₁ and H ₂ However, the change range is smaller than that in the unsaturated state of FIG. 8 as is apparent from FIG. 7. That is, even if the alternating magnetomotive force is further applied to the already saturated portion, the change range of the air gap magnetic flux density is further reduced. Although the examples considered to be typical of the present invention have been described above, the present invention is not necessarily limited only to the structures of these examples, and includes the above-mentioned constituents referred to in the present invention, and
The present invention can be carried out by appropriately modifying it within a range that achieves the object of the present invention and has the following effects.

As apparent from the above description, the present invention uses the upper and lower short rings (7b) and (7a) to separate the gap (2) from the main magnet (2), By using the upper plate (5) in a saturated state, the adverse effect of AC magnetomotive force is minimized so that the air gap magnetic flux density does not fluctuate due to the input signal current, and the driving force is proportional to the input signal current. Become. As described above in the section of the problem to be solved, in FIG. 2 showing the second harmonic level with respect to the fundamental wave based on the asymmetry of the magnetic flux distribution by the solid line (conventional example) and the dotted line (example of the present invention), Approximately -77 dB in the conventional example near 150 Hz
However, in the example, it becomes −83 dB, which can be read to be improved by about 6 dB. As described above, the linearity of the driving force with respect to the input signal current is improved, and further, the distortion of the speaker according to the present invention is combined with the improvement of the symmetry of the magnetic flux distribution due to the vertically symmetrical structure of the center pole (3). It becomes extremely low. Furthermore, in the phase plug (12a) attached to the upper end of the extension (3a) of the center pole (3), vibrations in the high frequency range generated by the voice coil (9) are transmitted through the base of the diaphragm (10) to the air. As the acoustic radiation impedance of the sound path increases when it propagates to the
You can also expect the effect of broadening the directivity.

[Brief description of drawings]

FIG. 1 is a diagram showing a magnetic flux distribution state near a magnetic gap with respect to a center line of an upper plate.

FIG. 2 is a frequency characteristic diagram of secondary distortion of a conventional example and an example of the present invention.

FIG. 3 is a sectional view of the first embodiment of the present invention.

FIG. 4 is a sectional view of another embodiment 2 of the present invention.

FIG. 5 is a sectional view of another embodiment 3 of the present invention.

FIG. 6 is a sectional view of a conventional example.

FIG. 7 is a diagram showing the relationship between the strength of the air gap magnetic field and the magnetic flux density in the case of a small alternating magnetic flux.

FIG. 8 is a diagram showing the relationship between the strength of the air gap magnetic field and the magnetic flux density in the case of a large alternating magnetic flux.

[Explanation of symbols]

 (1), (1 '), (21) Magnetic circuit (2), (22) Annular main magnet (3), (23) Center pole (3a) Center pole extension (3b) Center pole lower root (4) ), (24) Lower plate (5), (5 '), (25) Upper plate (5a) Upper plate Magnetic gap thickness (5b) Upper plate taper portion (5c) Upper plate outer thickness (6), (26) Annular magnetic air gap (7a) Lower short ring (7b) Upper short ring (8) Auxiliary annular plate (9) Voice coil (10) Vibration plate (11) Damper (12) Phase plug (D) Magnetic air gap Between the main magnet and

Claims (3)

[Claims] 1. A ring-shaped main magnet (2) is placed on a lower plate (4) of a center pole (3), and an upper plate (5) is placed on the center pole (2). A magnetic circuit for a speaker (1) formed by forming an annular magnetic gap (6) between
In a), leaving the part of the center pole (3) facing the magnetic gap (6), the center pole (3) is projected above the surface of the upper plate (5) to form an extension (3a). , Its extension
Attach the upper short ring (7b) that has heat dissipation, is conductive, and is non-magnetic to (3a), and
(3) Finish the lower root part (3b) to a thin shape, and attach the lower short ring (7a), which has heat dissipation, conductivity, and is non-magnetic, to the thinned part (3b). Center pole
Except for the part facing the magnetic air gap (6) in (3),
(6) is arranged apart from each other, and by further disposing an auxiliary annular plate (8) having a large inner diameter between the main magnet (2) having a large inner diameter and the upper plate (5),
The magnetic gap (6) is arranged so as to be separated from the annular main magnet (2), and the extension (3a) of the center pole (3) is provided.
The conductive and non-magnetic phase plug (12a)
Magnetic circuit for a speaker equipped with. 2. An annular main magnet (2) is placed on a lower plate (4) of a center pole (3), and an upper plate (5 ') is placed on the center pole (3). Magnetic circuit for speaker assembled by forming annular magnetic gap (6) with (3)
In (1a), leave the part of the center pole (3) facing the magnetic air gap (6), and attach the center pole (3) to the upper plate.
An extension (3a) is formed by projecting upward from the surface of (5 '), and the extension (3a) has a heat dissipation, conductive and non-magnetic upper short ring (7b). While mounting the center pole (3), the lower root (3b) of the center pole (3) is made thin, and the thinly finished portion (3b) has heat dissipation, conductivity, and
Attach the bottom short ring (7a) of non-magnetic material, and place the part of the center pole (3) other than the part facing the magnetic gap (6) away from the magnetic gap (6). The outer thickness (5c) of the plate (5 ') faces the magnetic air gap (6) (5
a) In the contact surface between the annular main magnet (2) with a larger inner diameter and the upper plate (5 '), the upper plate is made thicker than
From the lower corner facing the magnetic air gap (6) of (5 '), taper (5
b) and cut it, and attach a conductive and non-magnetic phase plug to the protruding extension (3a) of the center pole (3).
A magnetic circuit for a speaker in which (12a) is mounted and the portion other than the portion of the upper plate (5 ') facing the magnetic air gap (6) is separated from the magnetic air gap (6). 3. The speaker magnetic circuit according to claim 1 or 2, wherein the phase plug (12) mounted on the projecting extension (3a) of the upper short ring (7b) and the center pole (3).
The magnetic circuit for a speaker according to claim 1 or 2, wherein a) and are integrally formed.