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JPH0440199

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DESCRIPTION JPH0440199
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker device used for an audio device or a television device. [Prior Art] FIG. 5 is a crosssectional view schematically showing a conventional speaker device, and FIG. 6 is a block
diagram showing its drive system. In FIG. 0, (1) is a voice coil, (2) Is a diaphragm, (3) is a
permanent magnet (4), and an inner yoke (5). Magnetic circuit consisting of outer yoke (6), (7)
frame. (8) is an amplifier, and (9) is a voice coil drive unit including a magnetic circuit (3) and a
voice coil (1). Next, the operation will be described. In FIG. 6, the voice coil drive unit (9) operates
in accordance with the music signal from the tuner or player amplified by the amplifier (8). In the
voice coil driving unit (9), as shown in FIG. 5, in the magnetic circuit (3), the voice coil (1) is
composed of a permanent magnet (4), an inner yoke (5) and an outer yoke (6). Since it is
disposed in the gap, the Lorentz force F is generated by the current flowing in the voice coil (1).
The voice coil (1) is fixed to the diaphragm (2), and the diaphragm (2) is fixed to the frame (7), so
the Lorentz force F causes the diaphragm (2) to be elastically deformed. The amount of
deformation is approximately proportional to the strength of the music signal, and furthermore,
the air vibrates due to this deformation, and as a result, the air vibrates according to the strength
of the music signal to be heard as a sound to the human ear . [Problems to be Solved by the
Invention] Since the conventional speaker device is configured as one or more, the frequency
characteristic of the diaphragm is particularly an audible band in order to make a sound faithful
to the music signal from the speaker. It is desirable to be uniform within. However, the size of the
speaker is limited, and due to assembly storage problems, the diaphragm is required to have a
certain degree of rigidity, so the primary resonance frequency of the spring mass system
composed of the diaphragm and coil is lowered. There is a limit to that, and as a result, there is a
problem that the low range sound can not be emitted sufficiently. The present invention has been
made to solve the above-described problems, and it is an object of the present invention to
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provide a speaker device which is small in speaker size and can sufficiently produce low
frequency sound even if the diaphragm is rigid to some extent. The purpose is. [Means for
Solving the Problems] A speaker device according to the present invention comprises a light
source for emitting a collected beam between a voice coil and a yoke of a magnetic circuit or a
permanent magnet, and a collected beam from the light source. And a photodetector for
outputting a signal having a magnitude corresponding to the light receiving position.
[Operation] According to the present invention, since the relative displacement between the voice
coil and the magnetic circuit is detected by the vibration detection means, the difference between
the detected displacement and the input signal is calculated to amplify the error signal. By
constructing the feedback control system, it is possible to obtain a small-sized speaker device
which can produce a lot of bass without using a particularly low rigidity diaphragm. Hereinafter,
an embodiment of the present invention will be described with reference to the drawings. FIG. 1
is a cross sectional view schematically showing an embodiment of the present invention, FIG. 2 is
a block diagram showing a drive system thereof, in which (1) is a voice coil, (2) is a diaphragm,
(3) is a magnetic circuit, (4) is a permanent magnet, (5) is a round bar-shaped inner yoke that
protrudes inside the voice coil (1), (6) is an outer yoke, (7) is a frame, 8) is an amplifier, and (9) is
a voice coil drive unit, which is the same as the conventional example. (10) is a light source
having a directional light emitting diode (hereinafter referred to as LED), (11) is a light source
holder fixed to the voice coil (1) fixing position of the diaphragm (2) and adhesively fixing the
light source (10) (12) is a focused beam emitted from the light source (10), (13) is disposed at a
predetermined position for receiving the focused beam (12) at a central position of the
diaphragm (2) when the diaphragm is stationary, A light detector which outputs a signal having a
size corresponding to the light receiving position of the condensed beam (12) due to the
displacement of the light source (lO), (14) has an inner side to support the light detector (13) at
the predetermined position. Photodetector holder screwed to the end face of the yoke (5), (15) is
fixed to the output terminal of the photodetector (13) by soldering and is supported by the
photodetector holder (14) Substrate, (16) a light source (10) and light detection (13) vibration
detecting means, with (17) calculating circuit for calculating a difference between the output
signal from the input music signal and the vibration detection means (16), (18) is a compensator.
FIG. 3 is a schematic block diagram showing an example of the vibration detecting means (16).
(19) is an LED element and (20) is integrally formed with the LED element (19) to cover and emit
light A resin lens for condensing the beam, (21) is a one-dimensional optical position sensor
consisting of a PIN semiconductor element constituting the light detector (13), and has a size
corresponding to the displacement X from the central position of the light receiving position.
Output photocurrents 2 and 2 having different values. (22) is a position detection circuit which
receives the photocurrent output I2 and calculates the displacement X by a linear expression. I, +
I2 where L is the center position of the LED element (19) and the distance between one
electrode.
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Next, the operation will be described. The voice coil (1) is driven according to the input music
signal, and the diaphragm (2) vibrates. As a result, the position of the light source (10) also
fluctuates up and down, and the light receiving position of the condensed beam (12) therefrom to
the light detector (13) is also displaced. Then, the light detector (13) outputs a signal having a
magnitude proportional to the displacement X from the center position of the collected beam
receiving position. That is, a signal that is faithfully proportional to the actual vibration of the
diaphragm (2) is output from the vibration detection means (16) and applied to the arithmetic
circuit (17). Therefore, in the arithmetic circuit (17), the difference between the input music
signal and the position detection signal from the vibration detection means (16) is outputted.
This difference signal corresponds to the input music signal with the diaphragm. It is an error
signal that results from not being displaced faithfully. Then, this error signal is amplified by the
amplifier (8), compensated by the compensator (18), and applied to the voice coil drive unit (9)
to constitute a feedback servo system. Here, if the amplification factor of the amplifier (8) is
increased, as a result, the error signal becomes extremely small, and the diaphragm (2) operates
faithfully to the input music signal. By configuring the feedback servo system in this way, in the
low frequency band in which the sensitivity generally tends to be insufficient, the amplifier (8)
can reduce the insufficient sensitivity, and a bass output can be sufficiently obtained. In the
above embodiment, for the following reason, the one in which the resin lens (20) and the LED
element (19) are integrally molded is used as the light source (10). That is, (1) Because of its light
weight, there is no significant change in frequency characteristics even if it is directly attached to
the movable voice coil (1). (2) Because of the small size, the speaker device can be miniaturized.
(2) The light intensity density can be increased without using an external optical system for light
collection, and a high S / N ratio is possible. However, as shown in FIG. 4 as the light source (10),
a laser light source in which a collimator lens (25) is attached to the cap (24) of the
semiconductor laser element (23) may be used. In this case, since the light quantity density is
higher than that of the LED in which the resin lens is integrally molded, a still higher S / N ratio
can be obtained. In the above embodiment, in order to simplify the light detector (13) and the
light source (10), the light detector (13) can directly detect the displacement of the voice coil (1)
in one dimension. Although an optical position sensor is used, it is not necessarily limited to this.
As described above, according to the present invention, between the voice coil and the yoke of
the magnetic circuit or the permanent magnet, a light source for emitting a collected beam, and a
collected beam from the light source are received, Since the vibration detection means provided
with the light detector which outputs the signal of the size according to the light reception
position is provided, there is an effect that a small speaker device capable of faithfully detecting
the displacement of the voice coil can be obtained. By configuring the feedback control system, it
is possible to output sufficient bass even with a small speaker device.
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[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view schematically showing an embodiment of the present invention,
FIG. 2 is a block diagram showing its drive system, and FIG. 3 is a schematic block diagram
showing vibration detecting means of this embodiment, 4 is a schematic block diagram showing
vibration detecting means according to another embodiment of the present invention, FIG. 5 is a
cross sectional view schematically showing a conventional speaker device, and FIG. 6 is a block
diagram showing its drive system. is there.
In the figure, (1) is a voice coil, (2) is a diaphragm, (3) is a magnetic circuit, (4) is a permanent
magnet, (5) is an inner yoke, (6) is an outer yoke, (9) is a voice A coil driving unit, (10) is a light
source, (12) is a condensed beam, (13) is a light detector, and (16) is a vibration detection means.
The same reference numerals in the drawings denote the same or corresponding parts. Fig. Fig.
Fig. Fig. 10: Light source 12: Focused beam Fig. Procedure correction (spontaneous) October 9,
1990
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