JPS5496231

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DESCRIPTION JPS5496231
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of an essential
part of an embodiment of a signal detection apparatus for MFB of a speaker according to the
present invention, and FIGS. 2A to 2C are by vibration of a bobbin shown in FIG. FIG. 3 is a
schematic diagram for explaining the change in the amount of light received by the light
receiving diode, and FIG. 3 is a circuit diagram of a system for processing the signal detected by
the device shown in FIG. 1 as a signal for MFB according to the vibration velocity. 1
······································································································· Slits ...... · · · · · · · · · Differential circuit, 1 · 6 · · ·
· · · · · · · · · · output terminal, DlsD2 · · · · · · · light receiving diode, R1sR2 · · · · · · · · resistance.
The present invention relates to a signal detector for motional feedback of a slider according to
the present invention, a slit is provided on a voice coil bobbin, and light is emitted from the light
emitting element to the light receiving element through the slit to change the amount of light
received. To detect a motional feedback signal, thereby providing a detection apparatus that can
be configured in a small size without increasing the mass of the vibration system (*). Motional
feedback (hereinafter referred to as MFB ) used to compensate for the nonlinearity of the
sneaker and expand the range of the low frequency range is provided with a detection coil and a
magnetic circuit separately from the voice coil, and the signal detected by the detection coil is A
method to feed back to the previous stage of the amplifier, or a punching metal plate is provided
opposite to the diaphragm to detect a capacitance change between them And a method of
feeding back to the amplifier Te. However, the detection devices in these conventional methods
are all large and difficult to manufacture, and in particular, those detected by the detection coils
have small apertures such as high range or medium range sliders, and vibration systems It can be
applied to a slider whose efficiency decreases as the mass is increased, and that of the capacity
detection type has problems such as that the capacity can not be sufficiently obtained and a
reliable signal for MFB can not be obtained. The present invention eliminates the abovementioned drawbacks, and one embodiment will be described below with reference to the
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drawings. FIG. 1 shows a longitudinal cross-sectional view of an essential part of an embodiment
of a signal detection apparatus for MFB of a sneaker according to the present invention (2),
wherein 1 is a hollow cylindrical voice coil hobin, one end of which is The Heuss coil 2 is wound
around the outer peripheral surface, and the dome-shaped diaphragm 3 is integrally provided at
the other end, and is supported by the pan plate 5 by the mounting plate 4, 6 is a slit For
example, T is a pole piece which is formed in a rectangular shape on the bobbin 1 and is fixed on
the inner peripheral side of the hovin 1 as a magnetic piece constituted by a magnet 8 and a
yoke 9. A 10-bit light emitting diode is fixed to the hole heat 7 via an appropriate member, and is
accommodated on the inner peripheral side of the hobin 1. 11. In the D2 upper light receiving
diode, the supporting member 11 fixed on the yoke 9 is disposed in parallel in the vertical cross
sectional view so as to face the light emitting diode 10 and the slit 6. When no current is flowing
through the voice coil 2, the bobbin 1 is at rest, and at this time, light from the light emitting
diode 10 passes through the slit 6 of the bobbin 1 as shown by hatching in FIG. 2 (A). The light
receiving diodes D and D2 are respectively adjusted to irradiate (3) and so on.
Reference numeral 12 denotes a damper, which is fixed to the yoke 9 and the povin 1. Next, the
operation of the detection apparatus having the above configuration will be described. First,
when the sneaker is not operating, the light emitting diode as described above 10 light is
received by the light receiving diode D4. Since D2Vc irradiates each equally, in FIG. 3, the
internal resistance of the light receiving diode is equal, and the voltage at the connection point a
between the diode D and the resistor R1 and the voltage at the connection point between the
diode D2 and the resistor R2 are equal. Thereby, the non-inverting amplifier 13. And since the
signals having the same level and opposite phase from each other are taken out from the
inverting amplifier 132 and added one by one to the adder 14 and become zero, the detection
signal is not taken out from the output terminal 16 when the slider is not operating. . Here, when
a current flows through the coil 2, the hobin 1 is vibrated up and down in the figure between the
pole piece 7 and the yoke 9 due to the electromagnetic action between the pole heat 7 and the
yoke 9. For example, as shown by oblique lines (4) in FIG. 2B, when the slit 6 of the bobbin 1 is
displaced upward with respect to the light receiving diode D and ID2, the light receiving diode D
is located beyond the light emitting diode 10. , And less on the light receiving diode D2. Also, as
indicated by hatching in 21N (c), the slit 6 of the bobbin 1 is a light receiving diode D1. When the
light emitting diode 10 is displaced downward by 7 with respect to D2, light from the light
emitting diode 10 is less emitted to the light receiving diode D, and more to the light receiving
diode D2. Such a state is alternately repeated with the displacement of the hobin 1, whereby the
connection point ac! In FIG. The difference between the pressure and the connection point tEE is
calculated, and these 118: these are amplified by C in the amplifier 134.132 and then added
i! At the step 114, the voltage difference KEE at the connection points a and b and the difference
signal are output. After being differentiated by this signal company differentiation circuit 15, V is
output as an MFB signal corresponding to the vibration speed of the diaphragm 3 from the
output terminal 16. It is fed back to a predetermined amplifier (not shown) to compensate for the
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non-linearity of the slider or the like by a known operation. The characteristics of the light
emitting diodes D and + D2 are strong. (5) The resistance values of the resistors R and R2 are
assumed to be equal to each other. In this embodiment, although the signal for fcMFB is taken
out according to the vibration speed of the diaphragm, the invention is limited thereto. Not,
connection point a. The btD'M pressure may be appropriately processed according to the
purpose to obtain a desired MFB signal. Furthermore, the present invention is not limited to the
dome-shaped speaker, and the signal detection apparatus for MFB of the sneaker according to
the present invention as described above can be applied to, for example, a cone-shaped sneaker
as well. A light emitting element and a light receiving element are disposed opposite to each
other through the slit and light is emitted from the light emitting element to the light receiving
element, and the light reception amount of the light receiving element is changed by lifting of the
bobbin. Since it is configured to be detected, it can be configured to be smaller than conventional
horizontal devices such as a detection coil and a punching metal plate, and the mass of a
collapsed vibration system not provided in the imaging system as a detection coil. The aperture is
small (6) like the high frequency range or mid range range sneaker, and it is most suitable for a
speaker that can swallow the efficiency if the vibration system C mass is increased. Obtained
easily manufactured than the slave 3110 detector further has a feature such as can be obtained
reliably MFB signal as compared with the conventional example due to the capacitance detection.
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