JPH0632544B2 - MOTIONAL FEEDBACK SPEAKER - Google Patents

Description

The present invention relates to a motional feedback (hereinafter referred to as MFB) speaker suitable for use in, for example, a high-fidelity stereo reproduction device.

[Outline of Invention]

The present invention relates to an MFB speaker suitable for use in, for example, a high-fidelity stereo reproduction apparatus, in which an MFB speaker having a diaphragm, a connecting member connecting the diaphragm and the coil bobbin, and an MFB signal detection sensor is used. By forming at least the surface portion of the plate and the connecting member with a conductive material and electrically connecting the diaphragm and the connecting member, the diaphragm and the connecting member shield the MFB signal detecting sensor. A dedicated shield member is unnecessary, and the MFB signal detection sensor is not affected by external electrostatic noise without increasing the weight of the diaphragm.
This is to obtain a good MFB signal and a good reproduction characteristic.

[Conventional technology]

In recent years, an MFB speaker has been developed in which a piezoelectric sensor using a piezoelectric element such as a bimorph plate is attached to a diaphragm as a sensor for detecting an MFB signal.

Such an MFB speaker is mounted on a diaphragm, detects the vibration state of the diaphragm as an electric signal by a piezoelectric sensor, and feeds back this detection signal, that is, the MFB signal to an amplifier, thereby causing non-linear distortion and frequency characteristics of the speaker.
In particular, the present invention intends to improve the frequency characteristics near the bass resonance or lower.

An MFB speaker in which such a piezoelectric sensor is mounted on a diaphragm is cheaper and simpler than a plate MFB speaker in which a so-called MFB signal detecting coil is wound around a coil bobbin together with a voice coil to obtain an MFB signal. And the vibration state of the diaphragm can be detected accurately and faithfully.

[Problems to be solved by the invention]

However, the conventional MF using such a piezoelectric sensor
In the B speaker, since the piezoelectric sensor is a capacitive element, the impedance is increased to extend the detection characteristic to a low frequency, and the influence of power source noise, so-called external electrostatic noise such as hum, etc. There is an inconvenience that it is not possible to obtain an MFB signal having a good N ratio, and thus it is not possible to obtain an MFB speaker having good reproduction characteristics.

In this case, it is conceivable to shield the piezoelectric sensor with a dedicated shield member. However, in this case, the weight of the piezoelectric sensor increases and the weight of the diaphragm increases correspondingly, and the efficiency of the speaker, that is, the voice coil is increased. There is also a disadvantage that the conversion efficiency of the audio signal supplied to the audio is deteriorated and the audio output level of the amplifier must be increased to obtain the same sound pressure level.

In view of the above point, the present invention prevents the MFB signal detection sensor from being affected by external electrostatic noise without increasing the weight of the diaphragm, and obtains an MFB signal with a good S / N ratio.
It is an object of the present invention to provide an MFB speaker capable of obtaining good reproduction characteristics.

[Means for solving problems]

The present invention is, for example, as shown in FIG. 1, a diaphragm (1) and a connecting member for connecting the diaphragm (1) and the coil bobbin (2).
MF having (3) and a sensor (4) for detecting the MFB core number
In the B speaker, at least the surface portions of the diaphragm (1) and the connecting member (3) are made of conductive materials (1c) and (3a), and the diaphragm (1) and the connecting member (3) are electrically connected. Connect and connect the diaphragm (1) and the connecting member (3) to the MFB signal detection sensor (4)
It is designed to shield.

[Action]

According to the present invention, at least the surface portions of the diaphragm (1) and the connecting member (3) are formed of the conductive materials (1c) and (3a), and the diaphragm (1) and the connecting member (3) are formed. And the electric connection, and the diaphragm (1) and the connecting member (3) for the MFB signal detection sensor (4)
Is shielded, an MFB signal having a good S / N ratio can be obtained without being affected by external electrostatic noise, and an MFB speaker having a good reproduction characteristic can be obtained.

Further, since no dedicated shield member is required, it is possible to minimize the weight increase of the diaphragm and prevent the efficiency of the speaker from being lowered.

〔Example〕

An embodiment of the MFB speaker according to the present invention will be described below with reference to FIGS. 1 and 2. In this example, a case where the present invention is applied to a so-called flat type MFB speaker using a flat diaphragm will be described.

In FIG. 1, (5) shows an annular magnet, which is sandwiched between the plate (6) and the yoke (7) and at the same time a convex portion of the plate (6) and the yoke (7), a so-called sensor. A magnetic pole gap (8) is formed between the upper part of the pole (7a) and a magnetic circuit composed of the magnet (5), the plate (6), the magnetic pole gap (8) and the yoke (7). To do.

Further, a coil bobbin (2) around which a voice coil (10) is wound is arranged in the magnetic pole gap (8), and the coil bobbin (2) is fixed to the plate (6) via a damper (11) which is a supporting member. The coil bobbin (2) is connected to (12) so that the piston movement can be performed based on the audio signal supplied to the voice coil (10).

Further, in this example, the upper portion of the coil bobbin (2) is extended to form a connecting portion for connecting the flat diaphragm (1) and the coil bobbin (2), a so-called coupler portion (3), and the coupler portion (3 ) Is used to connect the coil bobbin (2) to the flat diaphragm (1) and the flat diaphragm (1) is supported by the tip (12a) of the frame (12) through the edge (13). . In this case, the inner surface of the coupler part (3) is formed of a conductive material, for example, an aluminum thin film (3a), and the flat diaphragm (1) is formed of a honeycomb-shaped aluminum thin film core ( Aluminum thin film (1b) (1c) on the top and bottom of 1a)
A so-called honeycomb sandwich structure body obtained by adhering together is used. In this case, the flat diaphragm (1) and the coupler (3) are connected via a conductive adhesive, and the aluminum thin film (1c) on the lower surface of the flat diaphragm (1) and the coupler (3) are connected. The aluminum thin film (3a) on the inner surface is electrically connected or the aluminum thin film (1c) on the lower surface of the flat diaphragm (1) is connected via a conductive wire (14) as shown in FIG. And the aluminum thin film (3a) on the inner surface of the coupler part (3) are electrically connected.

In this example, a piezoelectric sensor (4) as a sensor for detecting the MFB signal is attached to the central portion of the lower surface of the flat diaphragm (1),
The vibration of the flat diaphragm (1) can be detected as an electric signal. In this case, as the piezoelectric sensor (4), for example, a piezoelectric element composed of a so-called bimorph plate in which a brass thin plate forming one electrode is sandwiched between ceramic plates and a silver thin film layer forming the other electrode is formed on the surface of this ceramic plate, It is possible to use those in which required detection circuit components are arranged on a predetermined substrate made of ceramic.

In addition, the required positive and negative voltages are supplied to the piezoelectric sensor (4) and M detected by the piezoelectric sensor (4).
Lead wire for feedback of FB signal to amplifier
(5a) and (5b) are led out to the piezoelectric sensor (4) by relaying the coupler (3) from the terminal. In this case, the coupler (3) is provided with holes (3b) and (3c), and the relay members (16a) and (16b) made of an insulating material are fixed to the holes (3b) and (3c), and the relay member ( 16a)
Lead wire (5a) (5b) is led out by penetrating lead wire (5a) (5b) into the hole of (16b) and lead wire (5a) (5b)
Is fixed to the relay members (16) and (16b) via the adhesive (17).

Also, connect the negative terminal of the piezoelectric sensor (4) to the flat diaphragm (1).
Connected to the aluminum thin film (1c) on the lower surface of the via the conductive wire (18), the negative side potential of the piezoelectric sensor (4) and the aluminum thin film (1c) on the lower surface of the flat diaphragm (1) and the coupler part.
This piezoelectric sensor (4) is made to match the electric potential of the aluminum thin film (3a) on the inner surface of (3) and the aluminum thin film (1c) on the lower surface of the flat diaphragm (1) and the coupler (3). Shield with the aluminum thin film (3a) on the inner surface.
In this case, the conductive wire (18) is not used, and the negative side terminal of the piezoelectric sensor (4) is directly connected to the flat diaphragm via solder.
The lower surface of (1) is connected to the aluminum thin film (1c), or the negative side terminal of the piezoelectric sensor (4) is so-called through-hole connected to the lower surface of the substrate of the piezoelectric sensor (4). Flat diaphragm with lower surface via conductive adhesive
By connecting to the aluminum thin film (1c) on the lower surface of (1), the negative potential of the piezoelectric sensor (4) and the flat diaphragm (1)
It is also possible to match the potentials of the aluminum thin film (1c) on the lower surface of the and the aluminum thin film (3a) on the inner side surface of the coupler part (3).

In the MFB loudspeaker of this example configured as described above, the piezoelectric sensor (4) mounted on the central portion of the lower surface of the flat diaphragm (1)
The MFB can be applied by a signal corresponding to the vibration state of the flat diaphragm (1) detected by, but in this case, the piezoelectric sensor (4) is combined with the aluminum thin film (1c) on the lower surface of the flat diaphragm (1). The aluminum thin film (3
Since it is designed to be shielded with a), it is not affected by external electrostatic noise and has a good S / N ratio.
There is an advantage that a B signal can be obtained and an MFB speaker having good reproduction characteristics can be obtained.

Incidentally, in FIG. 2, the solid line X shows the frequency characteristic of the piezoelectric sensor (4) in the MFB speaker of this example, and the broken line Y shows the power source noise at the power source frequency _AC (50 Hz) when the piezoelectric sensor (4) is not shielded. The resulting disturbance of the frequency characteristic is shown. In addition, ₀ is the low resonance frequency,
_hi , _h2 , _h3 and _h4 are plane diaphragms, respectively
The high resonance frequency caused by the division vibration of (1), the resonance of the edge (13), etc. is shown.

In the MFB speaker of this example, the piezoelectric sensor
It does not require a dedicated shield member for (4), but the speaker itself is designed to shield the piezoelectric sensor (4) with the diaphragm (1) and the coupler part (3), which are originally required, so it is a flat surface. There is an advantage in that the increase in the weight of the diaphragm (1) can be minimized and the efficiency of the speaker can be prevented from lowering.

In the above-mentioned embodiment, the case where only the inner surface of the coupler portion (3) is formed of the conductive material (3a) has been described, but instead of this, the entire coupler portion (3) is formed of the conductive material. It can be easily understood that the same effect as described above can be obtained in this case as well.

Further, in the above-described embodiment, the case where the coupler portion (3) is formed so as to extend the coil bobbin (2) has been described, but instead of this, as shown in FIG.
It can be easily understood that (3) can be configured separately from the coil bobbin (2) and can also be configured in the shape of a circular truncated cone, and in this case also, the same effect as described above can be obtained.

In addition, in the examples shown in FIGS. 1 and 3, the case where the piezoelectric sensor (4) is mounted on the central portion of the lower surface of the flat diaphragm (1) has been described. Instead, as shown in FIG. 4, the coil bobbin (2)
A piezoelectric sensor (4) is mounted on the lid (19) and a lid (19) is mounted on the lid, and the negative side terminal of the piezoelectric sensor (4) is connected to a flat diaphragm via a conductive wire (20). It can be easily understood that it is also possible to connect to the aluminum thin film (1c) on the lower surface of (1), and in this case as well, the same operational effects as described above can be obtained.

Further, in the example of FIG. 4, the surface or the whole of the lid body (19) is formed of a conductive material (21), and as shown in FIG. 5, the lid body (19) and the coupler portion (3) are made of a conductive wire material. Connect via the (22) and connect the negative terminal of the piezoelectric sensor (4) to the conductive wire (23).
It is also possible to connect it to the lid body (19) via, and in this case, the above-mentioned shield effect can be further increased.

Further, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

〔The invention's effect〕

According to the present invention, since the MFB signal detection sensor is designed not to be affected by external electrostatic noise, it is possible to obtain a good MFB signal and obtain an MFB speaker having good reproduction characteristics. Have a profit

Further, in this case, since a dedicated shield member is not required for the MFB signal detection sensor, there is an advantage that the weight increase of the diaphragm can be minimized and the efficiency of the speaker can be prevented from lowering.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the MFB speaker of the present invention, FIG. 2 is a diagram showing the frequency characteristics of the piezoelectric sensor (4) of the example of FIG. 1, and FIG. FIG. 4 is a sectional view showing the embodiment of FIG. 4, FIG. 4 is a sectional view showing the embodiment of FIG.
FIG. 5 is a sectional view showing a fourth embodiment of the present invention. (1) is a plane diaphragm, (2) is a coil bobbin, (3) is a coupler part, and (4) is a piezoelectric sensor.

Claims (1)

[Claims] 1. A motional feedback speaker having a diaphragm, an interlocking member connecting the diaphragm and the coil bobbin, and a sensor for detecting a motional feedback signal, wherein at least a surface portion of the diaphragm and the connecting member is provided. It is characterized in that it is formed of a conductive material and electrically connects the vibration plate and the connecting member, and the vibration plate and the connecting member shield the motional feedback signal detection sensor. Motional feedback speaker.