JPH1051893A - Speaker device - Google Patents

Abstract

(57) [Problem] To provide an inexpensively manufactured electromagnetically coupled speaker capable of reproducing low-pitched sound and to enable mass production. SOLUTION: A primary coil 24 to which a current according to an input audio signal is supplied is provided near an air gap GP in a magnetic circuit. In the gap GP, a secondary coil unit 25 is provided, which is composed of a short coil in which a current corresponding to the current flowing through the primary coil is induced and to which the diaphragm 29 is attached. The secondary coil unit 25 includes a secondary coil in which only a portion necessary for the amplitude of the vibration is a short coil 25C.
The primary coil 24 is driven by a digital signal to induce a secondary current in the secondary coil 25C.
Emit not only treble but also bass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loudspeaker device for converting an electric signal into an acoustic output, and more particularly to an electromagnetically coupled loudspeaker device.

[0002]

2. Description of the Related Art In an electromagnetically coupled speaker device, a secondary current is induced in a secondary coil by a signal current flowing through a primary coil, and a secondary current is induced in a secondary coil by interaction with a magnetic flux generated in a gap in a magnetic circuit. A driving force corresponding to the secondary current is generated, and the diaphragm to which the secondary coil is fixed vibrates.

In this electromagnetically coupled speaker device, the primary coil through which a signal current flows is fixed to a plate made of a magnetic material such as iron, so that it has excellent heat radiation properties and can withstand a large input. However, if the length of the air gap in the magnetic circuit is increased, the sensitivity of the loudspeaker is reduced, so that the number of turns of the primary coil and the secondary coil cannot be increased.

[0004] Therefore, the inductance of the primary coil and the secondary coil cannot be increased, and the electromagnetic coupling force that induces the secondary current in the secondary coil by the signal current flowing through the primary coil is several kHz to 1 kHz. It becomes smaller in the following low frequency range, and it is impossible to reproduce up to 20 Hz necessary for reproducing sound. Therefore, the electromagnetic coupling type speaker is mainly used as a speaker for reproducing a high sound.

[0005] As an example of realizing this electromagnetically coupled speaker, the mid and low range is of a so-called dynamic type. 2. Description of the Related Art There has been provided a speaker device having a so-called two-way coaxial structure in which a high frequency is radiated by a secondary coil as an electromagnetic coupling type.

FIG. 19 shows the structure of the two-way coaxial speaker device.

The magnetic circuit of this speaker device comprises a donut-shaped magnet 1 and a first magnet made of a magnetic material such as iron.
And the second magnetic yokes 2 and 3 and the air gap GP. The first magnetic yoke 2 includes a cylindrical center pole portion 2a and a disk-shaped flange portion 2b orthogonal to the center pole portion 2a. Second
The magnetic yoke 3 is referred to as a plate, and has a donut shape having an inner diameter larger than an outer diameter of the center pole portion 2a by an air gap GP described later.

Then, the center pole portion 2a is inserted into the inner hollow portion of the magnet 1 and the inner hollow portion of the second magnetic yoke (hereinafter, referred to as a plate) 3.
The magnet 1 is sandwiched and attached between the front surface of the flange portion 2 b of the first magnetic yoke 2 and the plate 3. The contact portion between the front surface of the flange portion 2b and the surface of the plate 3 and the magnet 1 is bonded.

In this case, a magnet guide 2c composed of a stepped portion concentric with the center pole portion 2a is formed on the front surface of the flange portion 2b of the first magnetic yoke 2, and the magnet 1 is formed by the magnet guide 2c. The position of the edge portion of the inner circumferential circle is regulated, so that the inner circumferential surface position of the magnet 1 and the outer circumferential surface position of the center pole portion 2a are
It is made to be a concentric position.

Further, a predetermined jig is used so that a gap GP having a predetermined length is formed between the outer peripheral surface of the center pole portion 2a and the inner peripheral surface of the plate 3. The position is regulated, and the magnet 1, the magnetic yoke 2,
The plate 3 is joined.

Thus, a closed-loop magnetic circuit of the magnet 1 → the plate 3 → the gap GP → the center pole 2a → the flange 2b → the magnet 1 is formed. The speaker frame 7 is attached to the front surface of the plate 3.

As shown in FIG. 20, the bass voice coil, which is a bass coil unit, is configured by winding a coil 5 around a voice coil bobbin 4 made of a non-conductive material. Then, the bass voice coil is arranged such that the coil 5 is located in the gap GP between the plate 3 and the center pole portion 2a as shown in FIG. The voice coil bobbin 4 is attached to a speaker frame 7 via a buffer member (hereinafter referred to as a damper) 6.

A cone paper 8 as a diaphragm is attached to the voice coil bobbin 4 by bonding. The cone paper 8 is attached and fixed to the speaker frame 7 by a gasket 9 at the edge 8e.

As shown in FIG. 20, the winding start end and winding end of the coil 5 of the low-frequency voice coil are located at the voice coil bobbin 4 at the tinsel wires 10a and 10b.
b is connected by soldering. The tinsel wires 10a and 10b are connected to an input terminal 11 mounted on the speaker frame 7 by soldering.

The treble coil unit constitutes a secondary coil having a low-frequency voice coil as a primary coil. The secondary coil is a short coil, and generally includes a bobbin wound with a coil. However, in this example, FIG.
As shown in FIG. 2, a non-magnetic material having conductivity, for example, aluminum is formed in a cylindrical shape to form a one-turn short coil 12. That is, the coil bobbin is omitted, and the coil unit for high sound is constituted only by the short coil 12. A dome-shaped diaphragm 13 is integrally connected to the short coil 12, as shown in FIG.

The gap between the voice coil bobbin 4 in the gap GP and the outer peripheral surface of the center pole portion 2a is
The short coil 12 is inserted as a coil unit for treble. Then, the cap 14 is attached so as to cover the bass voice coil portion.

In the speaker device having such a configuration,
When an analog audio signal is supplied from the input terminal 11 through the power amplifier, the coil 5 of the low-pitched coil unit
Then, a current corresponding to the audio signal flows, and in the gap GP of the magnetic circuit, due to the action with the magnetic flux between the center pole portion 2a and the plate 3 (Fleming's left-hand rule),
The voice coil bobbin 4 vibrates according to the current in a direction along the central axis. In other words, the bass voice coil vibrates according to the driving principle of the dynamic speaker, whereby the cone paper 8 vibrates and radiates middle and low sounds.

The coil 5 of the bass coil unit
, A secondary current corresponding to the audio signal current is induced in the short coil 12, and the induced current causes the short coil 12,
The diaphragm 13 vibrates and emits a high sound. That is, when the coil 5 of the bass voice coil is used as a primary coil and a current flows through the short coil 12 as a secondary coil, a high-pitched sound is emitted as an electromagnetic coupling type.

[0019]

However, this speaker device can realize a two-way coaxial speaker which improves characteristics in a high frequency range as a speaker by combining a dynamic type and an electromagnetic coupling type. However, there is a problem that the output sound pressure level of the high sound cannot be sufficiently obtained as compared with the middle and low sound ranges, and the frequency characteristics cannot be made flat characteristics up to the high sound range.

By the way, the present inventors have proposed a speaker device capable of radiating low and middle sounds by directly driving a primary coil of an electromagnetically coupled speaker with a digital audio signal. The driving principle of this speaker device is as follows.

The sampling frequency for digitizing the audio signal is a high frequency such as 44.1 kHz or 48 kHz which is twice or more higher than 20 kHz which is the upper limit of the audible frequency. Therefore, even a low-frequency component such as several kHz to 1 kHz or less of the audio signal before being digitized is converted to a digital audio signal of 20 kHz.
The frequency becomes higher than z.

In the electromagnetically coupled speaker, the length of the air gap GP of the magnetic circuit is reduced so as not to lower the speaker sensitivity, and even if the number of turns of the primary coil and the secondary coil is reduced, the primary When the frequency of the signal current flowing through the coil is a high frequency exceeding 20 kHz, the electromagnetic coupling force does not decrease, and sound can be reproduced.

In the loudspeaker device of the present invention configured as described above, since the primary coil is driven by the digital audio signal, the low-frequency component of the audio signal before digitization is also one. The signal current flowing through the next coil has a high frequency exceeding 20 kHz. Therefore, reproduction up to low frequencies can be performed by the electromagnetically coupled speaker.

However, also in such a case where the bass is radiated, the secondary coil is preferably formed of a one-turn short coil made of an aluminum cylinder. Width (height of cylinder)
Becomes longer.

This kind of seamless cylinder is usually manufactured by a processing method called “squeezing”. As the height of the cylinder increases, the “squeezing” depth increases.
The squeezing process becomes difficult, and the cutting process must be performed in a one-piece production. For this reason, it becomes very expensive and is not suitable for mass production.

An object of the present invention is to provide an electromagnetically coupled speaker device which solves the above problems.

[0027]

To solve the above-mentioned problems, a speaker device according to the present invention is provided near a gap in a magnetic circuit, and is provided with a primary coil to which a current corresponding to an input audio signal is supplied; A secondary coil unit disposed in the gap to form a secondary coil in which a current corresponding to a current flowing through the primary coil is induced, and a secondary coil unit attached to the secondary coil unit, A vibrating plate that vibrates when the secondary coil unit vibrates due to the interaction between the induced current and the magnetic flux in the air gap, wherein the secondary coil unit has only a portion necessary for the amplitude of the vibration. Is provided as a short coil.

In the loudspeaker device according to the present invention having the above-described structure, the width of the secondary coil is equal to the width required for the amplitude of the vibration. It is easy to make a cylindrical short coil, and mass production is possible, so that it can be manufactured at low cost.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a speaker device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a speaker device according to an embodiment of the present invention. The speaker device according to the present embodiment is configured by an electromagnetic coupling type.

As shown in FIG. 1, the speaker device of this embodiment has a first yoke 21 having a columnar center pole portion 21a and a disk-shaped flange portion 21b, and a donut forming a second yoke. Plate 22, a donut-shaped magnet 23 disposed between the flange portion 21 b of the first yoke 21 and the plate 22,
A magnetic circuit is constituted by the magnetic gap GP between the magnetic pole and the center pole portion 21a.

The outer peripheral surface of the center pole portion 21a opposed to each other with the magnetic gap GP interposed therebetween and the plate 2
A drive coil as a primary coil is disposed on one or both of the inner peripheral surface portion and the inner peripheral surface portion. In this example,
The primary coil 24 is arranged on the outer peripheral surface of the center pole portion 21a. In order to dispose the primary coil 24, a small diameter portion 21c having a length corresponding to the winding width of the primary coil 24 is provided near the top of the center pole portion 21a, and the primary coil 24 is provided on the small diameter portion 21c. Can be

In the case of this example, the primary coil 24 comprises a number of coil groups corresponding to the number of bits of the input digital signal. For example, when the input digital signal is 16 bits / 1 sample, and the most significant bit MSB is a sign bit (positive / negative bit) 2 ′ complement code,
As the primary coil 24, 15 coils are provided corresponding to the number of bits.

Each of the 15 coils has a number of turns corresponding to the weight of each corresponding bit. If the digital audio signal is linearly quantized, 1
The number of turns of the five coils changes in a geometric series corresponding to each bit from the least significant bit LSB to the most significant bit MSB. For example, if the coil corresponding to LSB is 4 turns, the coil corresponding to 2SB is 8 turns, the coil corresponding to 3SB is 16 turns, and 4 turns.
The coil corresponding to the SB has an increased number of turns, such as 32 turns.

FIG. 2A shows an example of the primary coil 24. This example is a case where the primary coil 24 has an air-core coil configuration. That is, as shown in FIG. 2A, the primary coil 24 has fifteen coils LA having different numbers of turns.
~ LG, LI ~ LP, each coil LA ~ LG, L
From I to LP, a pair of lead wires 37a to 37g and 37i to 37p at the beginning and end of the winding are derived. The primary coil 24 is inserted into and adhered to the small diameter portion 21c of the center pole portion 21a shown in FIG.
The state is as shown in FIG.

The lead wire pairs 37a to 37p derived from the primary coil 24 pass through the through holes 34 provided in the flange portion 21b of the first magnetic yoke 21 and pass through the flange portion 2a.
1b. Then, these lead wire pairs 37a to 37p (represented as 37 as a representative number in the figure)
Are provided on the back side of the flange portion 21b.
The input terminals are connected to five input terminals 38a to 38p (represented by 38 as a representative number in the figure).

In this case, in order to radiate heat from the lead wire pairs 37a to 37p, the lead wire pairs 37a to 37p are adhered to the outer surface of the center pole portion 21a and are directed to the flange portion 21b of the first magnetic yoke 21. Is derived.

In this embodiment, a secondary coil 25C made of a short coil electromagnetically coupled to the primary coil 24 is inserted into the gap GP. In the case of this example, the secondary coil unit 25 configuring the secondary coil 25C is configured as described below, and
The width of 5C (short coil) is set to a necessary minimum length, which is longer than the length of the magnetic gap GP in the vibration direction by the amplitude of the vibration of the secondary coil 25C.

FIG. 3 shows an example in which the secondary coil unit 25 is made of only a non-magnetic and conductive material, for example, aluminum. As shown in FIG. 3A, the secondary coil unit 25 of this example has an aluminum plate 26 having a width Wh necessary for the secondary coil unit 25 and having a protruding portion 26a that should constitute the short coil 25C.
It is abutted and joined at the protruding portion 26a. In this case, the width Ws of the butted portion of the protruding portion 26a
Is smaller than the width Wh required for the secondary coil unit 25, and is selected to have a length corresponding to the amplitude of the vibration of the secondary coil 25C. The butted portions are joined by, for example, soldering. Instead of soldering, it is of course possible to join using welding or another joining method that has a small electric resistance at the joined portion.

FIG. 4 shows another example of the secondary coil unit 25. The secondary coil unit 25 of this example has a coil bobbin 27 having a length Wh required as a secondary coil unit.
A short coil component 28 constituting a one-turn short coil 25C made of aluminum having the width Ws and formed by squeezing is bonded and fixed. Since the short coil component 28 has a small width Ws, it can be relatively easily mass-produced by squeezing. Coil bobbin 27
Is made of a non-magnetic and non-conductive material, for example, cardboard.

Further, as shown in the example of FIG.
7 is to abut the gap,
Although it is a non-magnetic material, it may be formed of a conductive material, for example, a rectangular plate of aluminum.

The secondary coil unit 2 having the above configuration
5 is attached to the speaker frame 31 via the damper 30. A cone paper 29 as an example of a diaphragm is attached to the secondary coil unit 25. The cone paper 29 is provided through a flexible edge 29e.
It is attached to the speaker frame 31 by the gasket 32.

A method of assembling the speaker device of this example will be described below.

As shown in FIG. 2, the primary coil 24
Is inserted into the small diameter portion 21c above the center pole portion 21a and adhered.

Next, the lead wire pair 37a of the primary coil 24
To 37g and 37i to 37p are pulled out to the back side of the yoke 21, and the input terminals 38a to 38g and 38i to
Solder to 38p and fix. In addition, the lead wire portion in contact with the center pole portion 21a is bonded to the center pole portion 21a for the purpose of heat dissipation. Above 1
The fixing of the next coil 24 is performed in a process before the assembly of the magnetic circuit.

Next, an adhesive is applied to the front surface of the flange portion 21b of the yoke 21 and the magnet 23 is placed thereon. The inner diameter of the magnet 23 and the outer diameter of the magnet guide 35 formed as a step between the front surface of the flange portion 21 are formed. And the center pole portion 21a and the magnet 23
So that their centers almost coincide with each other.

Next, an adhesive is applied to the upper surface of the magnet 23 and the plate 22 is placed. Then, a jig called a gap guide is inserted so that the inner diameter of the plate 22 and the outer diameter of the center pole portion 21a are concentric.

The speaker frame 31 is attached to the plate 22 in advance by caulking or the like. Alternatively, after the magnetic circuit is completed, the speaker frame 31 may be attached to the plate 22 by means such as screws.

After the adhesive between the plate 22 and the magnet 23 has dried, the gap guide is
Pull out from a. This completes the main body of the speaker.

Next, a secondary coil unit 25 and a jig called a coil spacer are prepared, and the coil spacer is inserted into the inner diameter of the secondary coil unit 25, so that the position of the short coil 25C is within the gap GP of the magnetic circuit. The coil spacer is inserted into the center pole portion 21a with the secondary coil unit 25 inserted while adjusting so as to come to a predetermined position.

In this state, the outer periphery of the damper 30 is adhered to the speaker frame 31 and the inner periphery of the damper 30 is adhered to the outer diameter of the secondary coil unit 25. Then, the outer peripheral portion of the cone paper 29 with the edge 29e is bonded to the outer peripheral portion of the speaker frame 31 via the gasket 32. Further, the inner peripheral portion of the cone paper 29 is bonded to the outer diameter portion of the secondary coil unit 25. After the adhesive is dried, the coil spacer is pulled out from the center pole portion 21a.

Then, the cap 33 is adhered to the top of the cone paper 29 or the tip of the secondary coil unit 25. After the adhesive is dried, the magnet 23 is magnetized, and the speaker device is completed.

The primary coil 24 is not an air-core coil as described above, but is wound around a bobbin 36 made of a magnetic material as shown in FIG. It may be inserted into the small-diameter portion 21c of the pole portion 21a and fixed by bonding.

Further, as shown in FIG. 6, the primary coil 24 may be wound directly around the small diameter portion 21c of the center pole portion 21a and attached. FIG.
In the case of the example, the lead wire pairs 37a to 37g and 37i to 37p from the 15 coils LA to LG and LI to LP do not adhere to the side peripheral surface of the center pole portion 21a,
The lead wire fixing paper 39 presses and contacts the side peripheral surface of the center pole portion 21a.

When a signal input corresponding to each bit of the digital signal is applied to the input terminals 38a to 38g and 38i to 38p of the above-described electromagnetically coupled speaker device, the secondary coil is driven in accordance with the current flowing through the primary coil 24. Current is induced in the short coil 25C, and the secondary coil unit 25 vibrates up and down according to Fleming's left-hand rule due to interaction with the magnetic flux in the gap GP. in this case,
The changing period of the digital signal is its sampling frequency of 44.1 kHz or 48 kHz, and the inductive coupling force between the secondary coil 25C and the primary coil 24 does not decrease, and low-frequency sound can be reproduced.

Next, FIG. 7 shows an example of a sound reproducing system using the speaker device according to the present invention. The example of FIG. 7 is a case where audio is reproduced by a digital audio signal from a digital audio output device.

The digital audio output device 210 is a CD player, a DAT (Digital Audio Tape Recorder), or the like.
Stereo audio signals consisting of left and right channel audio signals digitized into 16 bits at a sampling frequency of z or 48 kHz are output as serial data alternately for each sample of left and right audio data.

The 16-bit digital audio signal of the serial data from the digital audio output device 210 is supplied to the serial / parallel converter 220, which separates the digital audio signals of the left and right channels from each other. Are converted into parallel data, and the 16-bit left and right digital audio signals as the parallel data are supplied to the left and right channel speaker devices 100L and 100R.

Although not shown, the serial / parallel converter 220 obtains a clock at a bit rate, and the clock at the bit rate is supplied to the decoder 70.

In this example, the loudspeaker devices 100L and 100R have a decoder 70 and a loudspeaker drive circuit 4 respectively.
0 and a speaker unit 110. As the speaker unit 110, the speaker device described with reference to FIGS.

In the case of this example, the speaker device 10
In 0L and 100R, the decoder 70 generates a control signal, which will be described later, from the 16-bit left and right digital audio signals converted into parallel data from the serial / parallel converter 220 in the decoder 70. The primary coil 2 of the speaker unit 110 is supplied to the
4 is driven.

When the primary coil 24 is composed of a plurality of coils, a 16-bit digital audio signal is
In the case of a 2 'complement code as shown in FIG. 8, the MSB (most significant bit) is used as a sign bit, and as described above, and as shown in FIGS. Coil LA-LG, LI
~ LP. Then, the coil LA is made to correspond to the LSB (least significant bit), for example, two turns.
Coil LB, LC, LD, LE, LF, LG, LI, L
J, LK, LL, LM, LN, LO, LP, 15S
B, 14SB, 13SB, 12SB, 11SB, 10S
B, 9SB, 8SB, 7SB, 6SB, 5SB, 4S
B, 3SB, 2SB, 4 turns each,
The number of turns is twice as many as the number of turns of the coil corresponding to the next lower bit, such as 8 turns, 16 turns, and so on.

When the analog audio signal is non-linearly quantized and converted into a digital audio signal, the number of turns of the plurality of coils constituting the primary coil 24 is, as described above, a geometric series. It does not change in a linear manner, but changes in accordance with the nonlinear characteristics of the nonlinear quantization.

FIG. 10 shows an example of a portion of the decoder 70 and the speaker drive circuit 40 shown in FIG. 7, and the speaker drive circuit 40 includes fifteen coils LA of the primary coil 24.
, And 15 coil drive circuits 40A to 40G and 40I to 40P corresponding to .about.LG, LI.about.LP.

The respective coil drive circuits 40A
40G, 40I to 40P are each composed of a constant current source 41 and four FETs 51 to 54 as switching elements.
And the corresponding coil are bridge-connected,
When the FETs 51 and 53 are turned on and the FETs 52 and 54 are turned off, the current Ia of the constant current source 41 corresponds to 1
When the FETs 51 and 53 are turned off and the FETs 52 and 54 are turned on and the FETs 52 and 54 are turned on, the current Ia from the constant current source 41 flows in the corresponding primary coil in the minus direction.

Coil drive circuits 40A-40G, 40I-
The currents of the 40P constant current sources 41 are all set to the same current value as indicated by the current Ia. When all the FETs 51 to 54 are turned on or off in the same coil drive circuit, no current flows through the corresponding coil.

The decoder 70 has fifteen control signal generation circuits corresponding to the fifteen coils LA to LG and LI to LP of the primary coil 24, ie, corresponding to 15 bits excluding the MSB of the digital audio signal. 70A to 70G, 70I
To 70P, and the respective control signal generation circuits 70A to 70P.
From 70G and 70I to 70P, the MSB of the digital audio signal converted into parallel data from the serial / parallel converter 220 and the control signal generation circuits 70A to 70A
0G, lower bits corresponding to 70I to 70P (LSB to
2SB), four control signals G1 to G4, which will be described later, are obtained, and the control signals G1 to G4 correspond to the FETs of the corresponding coil driving circuit of the speaker driving circuit 40.
It is supplied to the gates 51-54.

When the MSB of the input digital audio signal is 0 and the corresponding lower bit is 1, the four control signals G1 to G4 are at the levels at which the FETs 51 and 53 are turned on, and the control signal G2 , G4 are FETs 52, 5
4 is turned off, and the corresponding primary coil
The current Ia flows in the plus direction. On the other hand, when the MSB of the digital audio signal is 1 and the corresponding lower bit is 0, the control signals G1 and G3 are at a level for turning off the FETs 51 and 53, and the control signals G2 and G4 are at a level for turning on the FETs 52 and 54. The current Ia flows through the corresponding primary coil in the opposite negative direction.

When the MSB of the digital audio signal is 0,
When the corresponding lower bit is also 0 or when the MSB is 1
When the corresponding lower bit is also 1, the control signal G1
G4 becomes a level for turning off the FETs 51 to 54,
No current flows through the primary coil.

It should be noted that the control signals G1 to G4 correspond to the FETs 51 to
By turning on all 54, it is also possible to prevent current from flowing through the primary coil. In that case, a current always flows through the circuit, and a stable operation can be performed.

The driving force F of the vibration system of the electromagnetically coupled speaker is
As the product of the secondary current i induced in the secondary coil, the density B of the magnetic flux generated in the air gap of the magnetic circuit, and the length L of the secondary coil in the air gap of the magnetic circuit, F = B · L · Since the magnetic flux density B and the length L are constant, the driving force F of the vibration system is proportional to the secondary current i induced in the secondary coil. Then, 2 induced in the secondary coil
The secondary current i is proportional to the product of the signal current flowing through the primary coil and the number of turns of the primary coil.

In the example described above, the primary coil 24
Is set in proportion to the weight of each bit excluding the MSB of the input digital audio signal, the current Ia flows as a signal current through a certain primary coil. At this time, a secondary current having a current value proportional to the weight of the bit corresponding to the primary coil in a direction corresponding to the value of the MSB of the digital audio signal is induced in the short coil 25C constituting the secondary coil unit 25. Is done.

Therefore, the cone paper 29, which is the diaphragm to which the secondary coil unit 25 is fixed, is proportional to the weight of the bit corresponding to the primary coil in a direction corresponding to the value of the MSB of the input digital audio signal. The sound is vibrated by an amount, and the sound is faithfully reproduced in the speaker unit 110 in accordance with the input digital sound signal.

In this case, the input digital audio signal is 4
Each of the coils L of the primary coil 24 is digitized at a sampling frequency of 4.1 kHz or 48 kHz.
Since A to LG and LI to LP are driven by digital signals having the same sampling frequency, low-frequency components of the audio signal before being digitized also include the respective coils LA to LA of the primary coil 24.
20 kHz as signal current flowing through LG, LI to LP
Higher frequency. Therefore, reproduction up to low frequencies can be performed by the speaker unit 110 which is an electromagnetically coupled speaker.

As in the case of a general speaker, the vibration system of the speaker unit 110 does not easily respond to high frequencies.
High frequency components exceeding kHz are hardly reproduced. Therefore, each of the coils LA to
Even if LG, LI to LP are driven by a digital signal having a sampling frequency of 44.1 kHz or 48 kHz, the sampling frequency component is hardly reproduced. Even if the sound is reproduced with a very small sound pressure, the sound exceeding 20 kHz can hardly be heard by the human ear, so that there is no trouble even when listening to music.

Further, it is easy to form a mechanical filter having a stop band of 20 kHz or more intentionally and incorporate it into the speaker unit 110.

Further, it is possible to realize a speaker device that reproduces sound directly by a digital sound signal without using a D / A converter and a power amplifier, that has a small distortion and a large maximum output.

The coil driving circuits 40A to 40G, 4
The switching elements of 0I to 40P are not limited to FETs, and other elements that operate at high speed can be used.

In the above-described example, the number of turns of each of the coils LA to LG and LI to LP constituting the primary coil 24 is made to be the number of turns in proportion to the weight of each bit excluding the MSB of the input digital audio signal. In the case of reproducing the difference in the weight of each bit of the input digital audio signal, the number of turns of each of the coils LA to LG and LI to LP is the same,
Corresponding coil drive circuits 40A to 40G, 40
By changing the current value of the constant current source of I-40P,
The difference in the weight of each bit of the input digital audio signal can be reproduced.

FIG. 11 shows an example of this case, in which fifteen coils LA to LG and LI to L constituting the primary coil 24 are shown.
P has the same number of turns, for example, 50 turns, and the constant current sources 4LA-41G, 41I-41P of the coil drive circuits 40A-40G, 40I-40P corresponding to the coils LA-LG, LI-LP. Current Ia-I
g, Ii to Ip are changed as described later. The rest is the same as the example of FIG.

As described above, the speaker unit 110
Is proportional to the secondary current i induced in the secondary coil, and the secondary current i is proportional to the product of the signal current flowing through the primary coil and the number of turns of the primary coil. I do.

Therefore, in this example, although omitted in FIG. 11, as shown in FIGS. 8 and 9, the current of the constant current source of the coil drive circuit corresponding to the coil LB corresponding to 15SB of the digital audio signal is used. Ib is set to twice the current Ia of the constant current source 41A of the coil drive circuit 40A corresponding to the coil LA corresponding to the LSB of the digital audio signal. That is, Ib = 2Ia.

Hereinafter, 14SB, 13 of the digital audio signal will be described.
Coil LC, LD, LE corresponding to SB, 12SB, ...
, Ic, I of the constant current source of the coil drive circuit corresponding to.
are twice as large as the currents Ib, Ic, Id,.

Therefore, as in the example of FIG. 10, in speaker unit 110, diaphragm 29 adjusts the weight of the bit corresponding to the primary coil through which the signal current flows in a direction corresponding to the MSB value of the digital audio signal. It vibrates by a proportional amount, and the sound is reproduced faithfully according to the input digital sound signal.

Further, when the difference in the weight of each bit of the digital audio signal is reproduced by changing the current value of the constant current source in this manner, one drive coil can be used as the primary coil. . The primary coil in this case is attached to either the center pole portion 21a or the plate 22.

FIG. 12 shows an example in that case. However,
In this example, the input digital audio signal, that is, 1 as the parallel data from the serial / parallel converter 220
This is a case where a 6-bit digital audio signal is a natural binary code.

In this example, the primary coil 111 is composed of one coil, and currents Ia, Ib,.
, 61P are connected via switch circuits 62A, 62B,..., 62P, respectively, and the switch circuits 62A, 62B,. It is switched by the data of the corresponding bit of the signal.

That is, when a certain bit of the input digital audio signal is 1, the corresponding switch circuit is turned on, and the current of the corresponding constant current source flows through the primary coil 111. The current Ib of the constant current source 61B is twice the current Ia of the constant current source 61A. Hereinafter, the current of the constant current source corresponding to each bit of the digital audio signal corresponds to the next lower bit. It is twice the current of the constant current source.

Therefore, in this example, in the speaker unit 110, the diaphragm 29 vibrates in one direction by an amount proportional to the weight of each bit of the input digital audio signal, and the sound is reproduced faithfully to the input digital audio signal. Is done.

Note that the number of primary coils 111 is not one,
It is also possible to provide two or more coils having the same number of turns, divide the current corresponding to each bit of the 16 bits into a corresponding number of groups, and flow the current of each group to one coil. . For example, a primary coil is constituted by one coil provided on the center pole portion 21a and one coil provided on the plate 22, and the digital signal is divided into upper 8 bits and lower 8 bits. ,
It is possible to adopt a configuration in which a group of currents corresponding to each of the two currents flows through the two coils.

Even when the input digital audio signal is a 2 'complement code, the coil drive circuits 40A to 40P as shown in FIG. 11 can be switched by the corresponding bit data of the digital audio signal. By doing so, the primary coil 111 can be reduced to one.

Further, the difference in the weight of each bit of the digital audio signal can be reproduced by a combination of the difference in the number of turns of the plurality of primary coils and the difference in the current value of the plurality of constant current sources.

FIG. 13 shows an example in that case. However,
In this example, the input digital audio signal, that is, 1 as the parallel data from the serial / parallel converter 220
This is a case where a 6-bit digital audio signal is a natural binary code.

In this example, the primary coil is composed of four coils 111S, 111T, 111 having a turn ratio as described later.
U, 111V, and each coil 111S,
Driving blocks S, T, U, and V are provided for 111T, 111U, and 111V, and the driving blocks S, T, U, and V include currents Ia, Ib, and Ib, respectively.
The constant current sources Ic and Id are respectively connected to the corresponding coils 111S, 111T, 111U or 111V via switch circuits.

That is, in the drive block S, the constant current sources 61A, 61B, 61C, 61D are connected to the corresponding coils 111S via the switch circuits 62A, 62B, 62C, 62D, respectively. The current sources 61E, 61F, 61G, and 61H are respectively connected via switch circuits 62E, 62F, 62G, and 62H.
In the drive block U, the constant current sources 61I, 61J, 61K, and 61L are connected to the corresponding coil 111U via switch circuits 62I, 62J, 62K, and 62L, respectively. Then, the constant current sources 61M, 61N, 61O, 61P
Are the switch circuits 62M, 62N, 62O, 6
The switch circuits 62A, 62B,... 62N, 62 are connected to the corresponding coil 111V via the 2P.
O and 62P are switched by the data of the corresponding bit of the input digital audio signal.

The coils 111S, 111T, 111U, 1
Turns ratio of 11V is from 1: 16: 16 ^2: is 16 ^3. The constant current source 61A, 61B, 61C, the current Ia of 61D, Ib, Ic, Id ratio is 1: 2: ² 2: is 2 ^3. That is, Ib = 2 · Ia, Ic = 2 ² · I
a, Id = 2 ³ · Ia.

As described above, the speaker unit 110
Is proportional to the secondary current i induced in the secondary coil, and the secondary current i is proportional to the product of the signal current flowing through the primary coil and the number of turns of the primary coil. I do.

Therefore, in this example, when a certain bit of the digital audio signal becomes 1, the corresponding one of the switch circuits 62A, 62B... 62P is turned on, and the primary coils 111S, 111T, 111U or 1
When the current Ia, Ib, Ic or Id flows through 11 V, the ratio of the secondary current induced in the secondary coil matches the ratio of the weight of each bit of the digital audio signal.

Accordingly, as in the example of FIG. 12, in the speaker unit 110, the diaphragm 29 is moved in one direction.
The audio signal is shifted by an amount proportional to the weight of each bit of the digital audio signal, and the audio is reproduced faithfully to the input digital audio signal.

In this example, the minimum number of turns 1
Primary coil 111S and primary coil 111 having the largest number of turns
The ratio of the number of turns to V can be made as small as 1:16 ³ = 1: 2 ¹² , and the ratio of the current value between the minimum current value Ia and the maximum current value Id can be reduced. , 1:
It can be significantly reduced and so 2 ^3. Although not shown, the primary coil is composed of four coils having a turn ratio of 1: 2: 4: 8, and a current value is supplied to each coil via a switch circuit. the ratio of 1:16:16 ^{2:16 3} 4 by connecting a constant current source, the combination of current values and minimum four constant current source and the coils, each input digital audio signal LSB , 2SB, 3SB, and 4SB, and the combination of the four constant current sources having the second smallest current values and the coils are used as input signals for the 5SB, 6SB of the input digital audio signal, respectively.
The combinations of the four constant current sources having the second largest current values and the coils are set to 9SB, 10SB, and 11S of the input digital audio signal in correspondence with SB, 7SB, and 8SB, respectively.
B, 12SB, and the combination of the four constant current sources with the maximum current values and the coils may correspond to the digital audio signals of 13SB, 14SB, 15SB, and MSB, respectively. For example, the ratio of the number of turns between the primary coil having the minimum number of turns and the primary coil having the maximum number of turns can be significantly reduced, such as 1: 8, and the minimum current value and the maximum number of turns can be reduced. the ratio of the current value between the current value of 1: 16 can significantly reduce it so on ^3.

In this way, it is possible to reproduce low to high tones with flat frequency characteristics, and to reproduce audio directly from a digital audio signal without using a D / A converter or power amplifier. Thus, a speaker device having a large maximum output can be realized.

FIG. 14 shows another example of the speaker device of the present invention. In this example, an analog audio signal Ao from an analog audio output device 510 such as a cassette player or an FM tuner is supplied to a chopper circuit 520, and the analog audio signal Ao shown in FIG.
As shown by c, the chopping is performed at a frequency higher than the audio frequency, that is, at a frequency fc exceeding 20 kHz which is the upper limit of the audio frequency.

However, the chopping frequency fc is
It is desirable that the frequency be about twice as high as 20 kHz, for example, 40 kHz. In addition, the time width of the chopping period is sufficiently shorter than the chopping cycle Tc.

Then, the chopped analog audio signal Ac from the chopper circuit 520 is amplified by the power amplifier 530, and
0 is supplied to the primary coil 111. In this case, the speaker unit 110 has one primary coil 111. When the audio signal current is supplied to the primary coil 111, a secondary current is induced in the secondary coil, and the diaphragm vibrates.

As described above, the speaker unit 110, which is an electromagnetically coupled speaker, has an electromagnetic coupling force that induces a secondary current i in the secondary coil by a signal current flowing through the primary coil 111, from several kHz to 1 kHz or less. Becomes smaller in the low frequency range.

However, according to the example shown in FIG. 14, since the analog audio signal is intermittently transmitted at a frequency fc higher than the audible frequency and supplied to the primary coil 111 of the speaker unit 110, the low-frequency component of the analog audio signal is also reduced. The signal current flowing through the primary coil 111 has a high frequency exceeding 20 kHz. Therefore, reproduction up to low frequencies can be performed by the speaker unit 110 which is an electromagnetically coupled speaker.

In the above example, one secondary coil is used for the entire band. However, two secondary coils are provided for low-pitched sound and high-pitched sound. It is also possible to realize a two-way coaxial speaker device as a coupling type.

FIG. 16 is a sectional view of an example of the speaker device in that case. 16, the same components as those in the example of FIG. 1 are denoted by the same reference numerals. This figure 1
In the speaker device of No. 6, the primary coil is separated into the center pole portion 21a side and the plate 22 side, and
, Ie, primary coils 24A and 24B are provided.

FIGS. 17 and 18 show examples of the primary coils 24A and 24B. In this case, the primary coil 24
A includes coils LA to LG, and primary coil 24B includes
Includes coils LI-LP. A pair of lead wires 37a to 37g from the coils LA to LG is connected to an input terminal 38a provided on the back side of the flange portion 21b through the through hole 34.
~ 38g. The pair of lead wires 37i to 37p from the coils LI to LP pass between the plate 22 and the magnet 23 and are connected to input terminals 38i to 38p attached to the outer peripheral portion of the plate 22.

In this example, as in the example of FIG. 1, a short coil 25C of the secondary coil unit 25 as shown in FIG. 3 or FIG. .

In this example, the short coil 25C of the secondary coil unit 25 in the magnetic air gap GP is used.
And a center coil portion 21a, a secondary coil 121 for treble is provided. This treble secondary coil unit 121 is composed of a short coil 121C having the same configuration as the secondary coil 12 shown in FIG.

That is, the short coil 121C is a non-magnetic material and is formed of a conductive material, for example, aluminum, in a cylindrical shape to form a one-turn short coil. The treble secondary coil unit 121 is constituted only by the coil 121C.

Then, the high frequency short coil 121C
As shown in FIG. 16, a diaphragm 122 is attached to the. The vibration plate 122 is formed integrally with the short coil 121C, or by bonding or joining a member separate from the short coil 121C,
It is provided integrally with 21C.

The short coil 121C for high sound is formed by a supporting rubber plate 123 bonded to the top of the center pole 21a.
And is configured to be movable in the axial direction of the center pole 21a.

According to the two-way coaxial electromagnetically coupled loudspeaker device, the diaphragms for the low-pitched sound and the high-pitched sound are each driven by the electromagnetic coupling method, so that the frequency characteristics are flat from low to high.

[0116]

As described above, according to the present invention, the primary coil of the electromagnetically coupled speaker is driven by a digital audio signal or the primary coil of the electromagnetically coupled speaker is driven.
By interrupting the analog audio signal supplied to the next coil at a frequency higher than the audible frequency, it is possible to realize a speaker device capable of reproducing up to a low frequency range. In this case, since the secondary coil has a configuration in which only the amplitude of the vibration is used as the short coil, a low-cost speaker device suitable for mass production can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a structure of a speaker device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a primary coil used in the speaker device of FIG. 1;

FIG. 3 is a diagram illustrating an example of a secondary coil used in the speaker device of FIG. 1;

FIG. 4 is a diagram showing another example of the secondary coil used in the speaker device of FIG. 1;

FIG. 5 is a diagram showing another example of a primary coil used in the speaker device of FIG. 1;

FIG. 6 is a diagram showing another example of a primary coil used in the speaker device of FIG. 1;

FIG. 7 is a diagram showing an example of a sound reproduction system using an example of a speaker device according to the present invention.

FIG. 8 is a diagram for explaining an input digital signal.

FIG. 9 is a diagram for explaining the driving principle of the speaker device according to the present invention.

FIG. 10 is a circuit diagram showing a specific example of the partial circuit of FIG. 7;

FIG. 11 is a diagram showing an example of a sound reproduction system using another example of the speaker device according to the present invention.

FIG. 12 is a diagram showing an example of a sound reproduction system using another example of the speaker device according to the present invention.

FIG. 13 is a diagram showing an example of a sound reproduction system using another example of the speaker device according to the present invention.

FIG. 14 is a diagram showing an example of a sound reproduction system using another example of the speaker device according to the present invention.

FIG. 15 is a diagram for explaining the example of FIG. 14;

FIG. 16 is a sectional view of the structure of another example of the speaker device according to the present invention.

FIG. 17 is a diagram illustrating a primary coil of the speaker device of the example of FIG. 16;

FIG. 18 is a diagram for explaining a primary coil of the speaker device of the example of FIG. 16;

FIG. 19 is a sectional view of the structure of a conventional speaker device.

20 is a diagram showing an example of a bass voice coil of the conventional speaker device of FIG. 19;

FIG. 21 is a diagram showing an example of a high-frequency short coil (secondary coil) of the conventional speaker device of FIG.

[Explanation of symbols]

21: first magnetic yoke, 21a: center pole portion,
21b: Flange part, 22: Second magnetic yoke (plate), 23: Magnet, 24: Drive coil (primary coil), 25: Secondary coil unit, 25C: Short coil, 27: Coil bobbin, 28: Short coil Components: 29: cone paper as an example of a diaphragm, 30: damper, 31: speaker frame, 32: gasket, 33
... cap, 34 ... through hole, 35 ... magnet guide,
37a to 37g and 37i to 37p ... lead wire pairs, 3
8a to 38g and 38i to 38p ... input terminals, GP ...
Magnetic air gap

Claims (4)

[Claims] A primary coil provided near a gap in the magnetic circuit and supplied with a current corresponding to an input audio signal; and a primary coil disposed in the gap and corresponding to a current flowing through the primary coil. A secondary coil unit in which a secondary coil in which a current is induced is formed; and a secondary coil unit attached to the secondary coil unit, wherein the secondary current is generated by an interaction between a current induced in the secondary coil and a magnetic flux in the air gap. A diaphragm that vibrates when the coil unit vibrates; and wherein the secondary coil unit includes a secondary coil in which only a portion necessary for the amplitude of the vibration is a short coil. 2. The secondary coil unit is made of a non-magnetic material, and has a coil bobbin supported on a speaker frame via a buffer member, and a coil having a length in a vibration direction, the length of the coil being a length in a vibration direction. The speaker device according to claim 1, comprising: a secondary coil formed of a short coil shorter than a length of the coil bobbin. 3. The speaker device according to claim 1, wherein the secondary coil is formed by a one-turn short coil made of a non-magnetic and conductive material. 4. The primary coil comprises one or a plurality of coils. The primary coil is driven by a digital signal in which one sample of an audio signal is represented by a plurality of bits, and the primary coil is driven by the digital signal. The speaker device according to claim 1, wherein a current of a total sum of currents according to a weight of each bit of the digital signal is induced in the next coil.