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JPH04293400

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH04293400
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer, which is a kind of acoustic equipment, and a so-called speaker, and
more particularly to a hydraulically driven speaker suitable for the emission of very low
frequency sound of 50 Hz or less.
[0002]
2. Description of the Related Art Japanese Patent Application No. 63-14755 discloses a liquid
pressure driven speaker capable of strongly emitting sound in the ultra low frequency range
from near zero to about 100 Hz. .
[0003]
As shown in FIG. 4, in this hydraulic drive speaker, the shell 44 is divided into two chambers 46
and 47 by a diaphragm 45, and at least one of the rear side and the front side of the diaphragm
45 is in accordance with an external signal. A fluid pressure chamber 46 for vibrating the
diaphragm, and the diaphragm 45 is supported by a spring 48 and connected to a diaphragm 41
for acoustic radiation by a connecting rod 49. A sensor for detecting the fluid pressure in the
fluid pressure chamber 46 50 and a position sensor 51 for detecting the movement of the
diaphragm 45. The position sensor 51 is driven by the speaker driving device to emit an
extremely low frequency sound from the diaphragm 41.
[0004]
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1
The speaker drive system comprises a hydraulic controller 54 connected to a hydraulic source
57 to control the hydraulic pressure of the hydraulic chamber 46, and a control amplifier for
controlling the hydraulic controller 54 in accordance with a signal. And 53.
The detection signal from the hydraulic pressure sensor 50 is used as a feedback signal to
improve controllability and to prevent the generation of noise due to pressure fluctuation of the
liquid source, and the detection signal from the position sensor 51 improves controllability and
does not At the time of a signal, it is inputted to the control amplifier 53 as a feedback signal for
holding the movable diaphragm 45 in the neutral position.
[0005]
However, since the hydraulic drive speaker is mainly intended for the emission of ultra-low
frequency sound of 50 Hz or less, the diaphragm should be displaced with a very large amplitude
and smoothly. It does not.
[0006]
The conventional hydraulic drive speaker has a structure in which the diaphragm 45 is used as a
movable body and the movement of the diaphragm 45 is transmitted to the diaphragm 41 for
acoustic radiation by the connecting rod 49, so when emitting extremely low frequency sound In
order to cover the large movement of the diaphragm 41, it is necessary to increase the diameter
of the diaphragm 45.
In addition, the diaphragm 45 must be structured to support the weight of the diaphragm 41 and
the connecting rod 49 and to withstand the fluid pressure of the fluid pressure chamber 46,
which is technically difficult.
Furthermore, since a movable body such as a diaphragm or a bellows has a spring effect and
constitutes a mass-spring system, there is a problem that the frequency characteristic is
deteriorated due to the existence of its natural frequency.
[0007]
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The object of the present invention, which was made in view of the above problems, is to provide
a hydraulically driven speaker suitable for increasing the displacement of the diaphragm.
[0008]
SUMMARY OF THE INVENTION In order to achieve the above object, according to a fluid
pressure driven speaker of the present invention, a cylinder of a body provided with a piston rod
having a diaphragm fixed to a tip end on the back of a speaker frame The piston rod is axially
movably supported by a hydrostatic bearing while being inserted into the inside, and a partition
portion slidingly in contact with the cylinder inner wall is formed in the middle of the piston rod
to form two cylinder chambers which are adjacent to each other. A fluid pressure controller for
controlling supply of fluid pressure to each cylinder chamber is provided.
[0009]
In this case, the piston rod is formed hollow, and a magnet and a rod-like coil relatively moved
with the movement of the piston rod are provided inside the rear end of the piston rod to
constitute a position sensor of the piston rod. Further, a pickup comprising an electromechanical
transducer is provided inside the tip of the piston rod, and the electrical lead wire is drawn out
through the hollow interior of the piston rod from the rear end of the piston rod to the outside as
an acceleration sensor It is preferred to use.
[0010]
The piston rod of the diaphragm is movably supported very smoothly by a hydrostatic bearing,
and the displacement of the piston rod causes the fluid pressure to the two cylinder chambers
which are adjacent to each other in the longitudinal direction of the speaker, It is performed by
supply control with a hydraulic pressure controller.
Even when the piston rod, that is, the diaphragm performs a large amplitude at the time of super
low frequency sound radiation, the piston rod is merely displaced largely in the axial direction,
and is not elastically deformed like a diaphragm or bellows.
That is, any large amplitude can be produced.
In addition, since there is no spring effect except for the compressibility of the liquid, there is no
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deterioration of the frequency characteristics due to the presence of the natural frequency
generated by the diaphragm or the like. Furthermore, there is no technical difficulty in providing
a structure that supports the movable body while supporting its weight and fluid pressure. In the
second aspect, since the piston rod is formed hollow and the position sensor is provided inside
the rear end, the weight of the movable body is lightened, and one of the magnet constituting the
position sensor and the rod-like coil is fixed. Can be made movable and the electrical output can
be taken out without disturbing the movement of the piston rod. Also in claim 3, since the
electrical lead-out line from the pickup of the acceleration sensor provided inside the tip of the
piston rod is drawn from the rear end through the hollow interior of the piston rod, the operation
of the piston rod is not disadvantageous. Therefore, these sensors can be used to fundamentally
improve the sound pressure characteristics in the low frequency range.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be
described based on the illustrated embodiments.
[0012]
The hydraulic drive speaker shown in FIG. 1 includes a portion including the speaker frame 1
and the diaphragm 23, a portion including the hydraulic drive (hydraulic driver) 2 and the
attached sensors 25 and 34, and a hydraulic control unit. And the portion of the hydraulic circuit
including the
[0013]
The hydraulic driver 2 provided at the center of the rear face of the speaker frame 1 has a body
3 having a cylinder 4 at the center, and a piston rod 5 axially penetrating the cylinder 4 so as to
be freely movable.
At the center of the piston rod 5, a partition 6 which slides in contact with the inner wall of the
cylinder and divides the cylinder 4 into front and rear cylinder chambers 7 and 8 is projected.
The reference numeral 6 a is a labyrinth seal provided on the sliding contact surface of the
partition 6.
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[0014]
A hydrostatic bearing assembly 11 consisting of a hydrostatic bearing 9 and a bearing frame 10
is airtightly fitted at both ends of the body 3 and its flange portion is fixed to the end face of the
body 3 by a screw 12. Between the axially inner end of the bearing frame 10 fitted at both ends
of the body 3 and the partition 6 at the center of the piston rod are cylinder chambers 7 and 8,
and the axial movement of the piston rod 5 is covered It is formed in the length only to do. 10a is
a seal provided on the sliding contact surface of the bearing frame 10, and 3a and 3b are seals
provided on the joint surface of the bearing frame 10 and the body 3.
[0015]
The hydrostatic bearing 9 has pockets 9a at four circumferential positions, respectively, and the
high pressure liquid supplied to them from the passage 70 through the throttle causes the piston
rod 5 to float and the piston rod 5 to have extremely small friction. Work to support the
Therefore, the piston rod 5 is supported so as to be able to move very smoothly in the axial
direction by the hydrostatic bearings 9 at both ends of the body. A front seal cover 14 and a rear
seal cover 15 are attached to the outer end of the hydrostatic bearing assembly 11 by screws 16,
respectively, and each function as an element forming the drain passage 13 of the hydrostatic
bearing 9. ing.
[0016]
In order to control the movement of the piston rod 5 hydraulically, a hydraulic pressure
controller 17 incorporating a servo valve is provided on the body 3 via a block 18. The block 18
includes passages 19 and 20 (see FIG. 2) for hydraulic fluid to the servo valve, and passages 21
and 22 for leading hydraulic fluid from the servo valve to the front and rear cylinder chambers 7
and 8 of the piston rod 5. Is provided. Reference numerals 21a and 22a denote O-rings for
keeping the airtightness between the block 18 and the body 3 for the passages 21 and 22. The
passages 21 and 22 communicate with the cylinder chambers 7 and 8 on the front side of the
cylinder chamber 7 and on the rear side of the cylinder chamber 8.
[0017]
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With the above configuration, when hydraulic fluid is introduced from the passage 21 to the
front cylinder chamber 7 under control of the servo valve, the piston rod 5 is displaced rearward,
and hydraulic fluid is discharged from the passage 22 rearward. When guided to the side
cylinder chamber 8, the piston rod 5 is displaced to the front side. The piston rod 5 extends
through the speaker frame 1, and the central hole of the diaphragm 23 is fitted to the tapered
tapered portion 5 a at the tip of the piston rod 5, and from the central recess 23 a of the
diaphragm 23. The vibrating plate 23 is firmly fixed to the piston rod 5 by screwing the nut 24
to the protruding end. Therefore, when the piston rod 5 is axially displaced in the axial direction
as described above, the diaphragm 23 is also displaced longitudinally together. In this case, since
the piston rod 5 is supported by a hydrostatic bearing, the friction with the body 3 is extremely
small, and it can be freely projected and retracted within the range of the axial length of the front
and rear cylinder chambers 7, 8 Because of this, this fluid pressure speaker can perform a large
amplitude operation to match the emission of very low frequency sound. In addition, the spring
effect is only slightly generated with respect to the hydraulic pressure, and does not cause the
peak of the natural vibration frequency as in the case of using a diaphragm or the like.
[0018]
A hydraulic pressure driven speaker includes a hydraulic pressure sensor 50 (FIG. 4) for
detecting the pressure in the hydraulic pressure chamber 6, a position sensor 25 for detecting
the movement of the piston rod 5, and an acceleration sensor 34. There is.
[0019]
The position sensor 25 comprises a magnet 26 which moves relative to the movement of the
piston rod 5 and a coil 27 of a differential transformer type.
A holder 28 holding the magnet 26 is screwed into the piston rod 5 from the rear end side so
that the magnet 26 is disposed inside the rear end of the hollow piston rod 5 as the movable
portion side. It is fixed to the piston rod 5 so as not to be rotatable. On the other hand, a sensor
case 30 is attached on the rear end of the body 3, that is, on the rear seal cover 15 with a screw
16 common to the cover in order to locate the coil 27 as a fixed side and near the magnet 26. .
The coil 27 is formed in a rod shape, protrudes from the inner surface of the rear end of the
sensor case 30, passes through the inside of the sensor case 30, and passes near the magnet 26,
and coaxially extends the hollow inside of the piston rod 5. It exists. At the rear end of the sensor
case 30, an amplifier substrate 31 carrying an amplifier or the like is attached by a screw 32, and
the coil 27 is electrically connected to the amplifier substrate 31. Reference numeral 33 denotes
an electrical lead from the amplifier substrate 31.
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[0020]
On the other hand, the acceleration sensor 34 is provided on a mounting seat 35 screwed into
the interior of the piston rod 5 from the end thereof. The acceleration sensor 34 is formed of a
piezoelectric element, and the electrical lead wire 36 is taken out through the hollow interior of
the piston rod 5 from the opening 37 provided in the holder 28 at the rear end of the piston rod
5.
[0021]
The detection signals of the position sensor 25 and the acceleration sensor 34 obtained from the
lead wires 33 and 36 are sent to the control amplifier 53 as in the conventional case described
with reference to FIG.
[0022]
The control amplifier 53 receives from the signal source 52 an electrical signal to be
electroacoustically converted, and converts it into a voltage or current signal suitable for driving
the hydraulic controller 17. Control the servo valve.
The fluid pressure controlled by the fluid pressure controller 17 is supplied to the fluid pressure
chambers 7 and 8 of the fluid pressure driver 2 and the piston rod 5 moves left and right in
response to the signal from the signal source 52. The movement of the piston rod 5 is
transmitted to the diaphragm 23, and the movement of the diaphragm 23 makes the air dense
and compact and is emitted as a sound wave.
[0023]
In this case, the detection signal from the position sensor 25 is controlled as a feedback signal for
improving the response and for improving the center position (origin) holding function of the
movable body (piston rod 5) when there is no signal. It is input to the loop amplifier 53 (FIG. 4).
Furthermore, the detection signal from the acceleration sensor 34 is also input to the control
amplifier 53, and the followability is improved by the acceleration signal and the velocity signal
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obtained by integrating this or the velocity signal obtained by differentiating the signal of the
position sensor 33. Is taken. The hydraulic pressure detection signal from the hydraulic pressure
sensor 50 (FIG. 4) or the differential pressure sensor is also sent to the control amplifier 53 as a
feedback signal for improving controllability and preventing noise generation due to pressure
fluctuation of the liquid source 57. It is input. That is, the hydraulic pressure detection signal not
only performs follow-up control to the electric signal of the hydraulic pressure, but also the
hydraulic pressure driver 2 so that harmful fluctuation (pulsation of low frequency range) of the
hydraulic pressure source is not emitted as sound. Control the fluid pressure of
[0024]
FIG. 3 shows an equivalent circuit between the input acceleration x and the output sound
pressure p (where x and p are vectors), and a portion corresponding to the hydraulic driver 2 and
a hydraulic controller 17 The parts corresponding to are each surrounded by a dotted line. In the
portion of the hydraulic pressure driver 2, m is a mass of the vibration movable portion, b is a
viscous drag coefficient, c is a constant representing the rigidity of the drive system, Ap is a cross
section of the piston, and S is a Laplace operator. When viewed with reference to the portion 38
entering the diaphragm 23, Ap / S, b / S, c / S2 are negatively fed back. Further, as shown, the
acceleration from the acceleration sensor 34 is fed back to the servo valve as the acceleration
signal ea via the control amplifier 53, and is obtained by integrating this or by differentiating the
signal of the position sensor 25. This signal is fed back to the servo valve as a velocity signal ev,
and furthermore, the position signal ey of the position sensor 25 is fed back to the servo valve.
[0025]
Thus, a control device capable of producing an acceleration waveform faithfully corresponding to
the electrical input signal from the signal source 52 is constructed by the control amplifier 53,
the hydraulic pressure controller 17 and the sensors 50, 25 and 34. The hydraulic pressure
driver 2 receives the output signal of this control device (output signal of the hydraulic pressure
controller 17), and causes the piston rod 5 to respond at high speed to the electric input signal to
excite the diaphragm 23. Sound pressure characteristics are fundamentally improved. In addition
to the improvement of the low frequency range characteristic, the present hydraulic drive
speaker has a large stroke and large sound pressure output function of a large driving force as
compared with the conventional diaphragm type hydraulic drive speaker, so It is suitable for use
where ultra-low tones that are sensitive to wind pressure and high output are required. For
example, it can be used for outdoor rock concerts to obtain a powerful acoustic effect.
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[0026]
As described above, according to the present invention, the piston rod of the diaphragm is
movably supported extremely smoothly by the hydrostatic bearing, and the fluid pressure
controller controls the fluid pressure to the two cylinder chambers which are adjacent to each
other. Since the supply control is performed by the above, it is possible to make the diaphragm
correspond to the input signal faithfully and make a high speed response. In addition, even when
the piston rod, that is, the diaphragm performs a large amplitude at the time of super low
frequency sound radiation, the piston rod is merely displaced largely in the axial direction, and
does not elastically deform like a diaphragm or bellows. . That is, any large amplitude can be
produced by the small diameter piston rod. Further, since there is no spring effect except for the
compressibility of the liquid, there is no natural frequency generated by the diaphragm or the
like, and there is no deterioration of the frequency characteristics due to it. Furthermore, there is
no technical difficulty in providing a structure that supports the movable body while supporting
its weight and fluid pressure.
[0027]
Brief description of the drawings
[0028]
1 is a partial longitudinal sectional view showing an embodiment of a hydraulic pressure driven
speaker of the present invention.
[0029]
2 is a front view showing the hydraulic drive speaker of FIG. 1 with the speaker frame removed.
[0030]
3 is an equivalent circuit diagram including a control system of the hydraulic pressure driven
speaker of the present invention.
[0031]
4 is a configuration diagram of a conventional hydraulic drive speaker.
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[0032]
Explanation of sign
[0033]
Reference Signs List 1 speaker frame 2 hydraulic driver 3 body 4 cylinder 5 piston rod 6
partition 7, 8 cylinder chamber 9 static pressure bearing 9a pocket 10 bearing frame 11 static
pressure bearing assembly 14 front seal cover 15 rear seal cover 17 hydraulic pressure
controller 18 Blocks 19, 20 Pressure oil passages for servo valves 21, 22 Pressure oil passage 23
to cylinder chamber 23 diaphragm 25 position sensor 26 magnet 27 differential transformer
type coil (rod-like coil) 28 holder 31 amplifier board 33 electrical lead wire 34 acceleration
sensor 36 electrical lead 37 opening 50 hydraulic pressure sensor 52 signal source 53 control
amplifier
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