JPH04293400A - Fluid pressure driven speaker - Google Patents

Abstract

PURPOSE:To easily obtain large displacement in sound pressure by oscillating an oscillation panel with a piston rod. CONSTITUTION:A piston rod 5 fixed to the tip of an oscillation plate 23 is inserted in a cylinder 4 of a body provided on the back side of a speaker frame 1, the piston rod 5 is movably supported in the axial direction by a static pressure bearing 9, a parting part 6 sliding on the internal wall of the cylinder is formed at the intermediate of the piston rod 5, two cylinder compartments 7 and 8 are formed back and forth with each other, and the supply to the respective cylinder compartments is controlled by a fluid pressure controller 17. The piston rod 5 is formed to be hollow, and a position sensor 25 is provided in it at its backward end and an acceleration sensor 34 is provided in it at its forward end.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an electroacoustic transducer, commonly known as a speaker, which is a type of audio equipment.
The present invention relates to a hydraulically driven speaker suitable for emitting infrasound of 0 Hz or less.

0002

2. Description of the Related Art Conventionally, there is a hydraulically driven speaker capable of powerfully emitting sound in an extremely low frequency range from almost zero to about 100 Hz, as disclosed in Japanese Patent Application No. 14755/1983.

As shown in FIG. 4, this hydraulically driven speaker has a shell 44 connected to two chambers 4 at the front and rear by means of a diaphragm 45.
At least one chamber on the rear or front side of the diaphragm 45 is used as a hydraulic chamber 46 for vibrating the diaphragm according to an external signal. It is connected to the radiating diaphragm 41, has a sensor 50 that detects the hydraulic pressure in the hydraulic pressure chamber 46, and a position sensor 51 that detects the movement of the diaphragm 45, and is driven by the speaker drive device, and the diaphragm 41 emits ultra-low frequency sound.

The speaker driving device includes a hydraulic controller connected to a hydraulic pressure source 57 to control the hydraulic pressure in the hydraulic chamber 46.
and a control amplifier 53 for controlling the hydraulic controller 54 according to signals. The detection signal from the liquid pressure sensor 50 is used as a feedback signal to improve controllability and prevent noise from occurring due to pressure fluctuations in the liquid source. The signal is inputted to the control amplifier 53 as a feedback signal for holding the diaphragm 45, which is a movable body, in a neutral position at the time of a signal.

[0005]

However, since the purpose of a hydraulically driven speaker is mainly to emit infrasound of 50 Hz or less, the diaphragm must be smoothly displaced with an extremely large amplitude.

The conventional hydraulically driven speaker uses a diaphragm 45 as a movable body, and has a structure in which the movement of the diaphragm 45 is transmitted to the diaphragm 41 for sound emission by a connecting rod 49. In order to cover the large movement of the diaphragm 41, it is necessary to increase the diameter of the diaphragm 45. Furthermore, the diaphragm 45 must have a structure that supports the weight of the diaphragm 41 and the connecting rod 49 and withstands the hydraulic pressure of the hydraulic chamber 46, which is technically difficult. Furthermore, since movable bodies such as diaphragms and bellows have a spring effect and constitute a mass spring system, there is a problem that the existence of their natural frequencies deteriorates frequency characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulically driven speaker suitable for increasing the displacement of a diaphragm.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the hydraulically driven speaker of the present invention has a piston rod having a diaphragm fixed to its tip inserted into a cylinder of a body provided on the back of the speaker frame. At the same time, this piston rod is supported so as to be movable in the axial direction by a hydrostatic bearing, and a partition portion that slides in contact with the cylinder inner wall is formed in the middle of the piston rod to form two adjacent cylinder chambers. The structure includes a hydraulic pressure controller that controls the supply of hydraulic pressure to the chamber.

In this case, the piston rod is formed hollow, and a magnet and a rod-shaped coil that move relatively 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. Furthermore, a pickup consisting of a mechano-electric transducer is provided inside the tip of the piston rod, and its electrical lead wire is led out from the rear end of the piston rod through the hollow interior of the piston rod, so that it can be used as an acceleration sensor. It is preferable to use it.

0010

[Operation] The piston rod of the diaphragm is supported by a hydrostatic bearing so that it can move extremely smoothly, and the displacement of this piston rod causes the hydraulic pressure to be applied to the two cylinder chambers located one behind the other in the front and back direction of the speaker. This is done by controlling the supply. Even when the piston rod, that is, the diaphragm, generates a large amplitude when emitting infrasound, the piston rod simply displaces greatly in the axial direction, and does not undergo elastic deformation like a diaphragm or bellows. That is,
Any large amplitude can be created. Furthermore, since there is no spring effect other than the compressibility of the liquid, there is no presence of natural frequencies that occur in diaphragms, etc., and there is no deterioration in frequency characteristics due to this. Furthermore, there is no technical difficulty in creating a structure that supports the movable body while withstanding its weight and hydraulic pressure. In addition, in claim 2, since the piston rod is formed hollow and the position sensor is provided inside the rear end, the weight of the movable body is reduced, and one of the magnet and the bar-shaped coil constituting the position sensor is fixed and the other It is possible to make the piston rod movable and to take out the electrical output without interfering with the movement of the piston rod. Also in the third aspect, since the electrical lead wire from the pickup of the acceleration sensor provided inside the tip of the piston rod is drawn out from the rear end through the hollow inside of the piston rod, there is no problem with the operation of the piston rod. Therefore, using these sensors, the sound pressure characteristics in the low frequency range can be fundamentally improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the illustrated embodiments.

The hydraulically driven speaker shown in FIG. 1 includes a speaker frame 1 and a diaphragm 23, a hydraulic drive device (hydraulic driver) 2 and attached sensors 25 and 34, and a hydraulic controller. The hydraulic pressure circuit includes the hydraulic circuit 17.

The hydraulic driver 2 provided at the center of the back of the speaker frame 1 includes a body 3 having a cylinder 4 in the center;
It has a piston rod 5 that passes through the cylinder 4 so as to be movable in the axial direction. The center of the piston rod 5 is in sliding contact with the inner wall of the cylinder to connect the cylinder 4 to the front and rear cylinder chambers 7,
A partition portion 6 that divides the screen into eight parts is protruded. 6a is a labyrinth seal provided on the sliding surface of the partition portion 6.

A hydrostatic bearing assembly 11 consisting of a hydrostatic bearing 9 and a bearing frame 10 is hermetically fitted into both ends of the body 3, and its flange portion is fixed to the end surface of the body 3 with screws 12. Cylinder chambers 7 and 8 are located between the axially inner ends of the bearing frame 10 fitted into both ends of the body 3 and the partition 6 at the center of the piston rod, and cover the amount of axial movement of the piston rod 5. It is formed to a length that is just long enough. 10a is a seal provided on the sliding surface of the bearing frame 10, and 3a and 3b are seals provided on the joint surfaces of the bearing frame 10 and the body 3.

The hydrostatic bearing 9 has pockets 9a at four locations on the circumference, and the piston rod 5 is floated by high-pressure liquid supplied from the passage 70 to these pockets 9a through the throttle, and the piston rod 5 is moved by extremely small friction. It acts as a support. Therefore, due to the static pressure bearings 9 at both ends of the body,
The piston rod 5 is supported for extremely smooth movement in the axial direction. Note that a front seal cover 14 and a rear seal cover 15 are provided at the outer ends of the hydrostatic bearing assembly 11, respectively.
are attached by screws 16, and each functions as an element forming a drain passage 13 of the hydrostatic bearing 9.

In order to control the movement of the piston rod 5 by hydraulic pressure, a hydraulic pressure controller 17 having a built-in servo valve is provided on the body 3 via a block 18. The block 18 includes passages 19 and 20 for pressure fluid to the servo valve (see FIG. 2), and passages 21 and 22 for guiding the pressure fluid from the servo valve to the front and rear cylinder chambers 7 and 8 in the piston rod 5. is provided. 2
1a, 22a are blocks 1 for these passages 21, 22.
This is an O-ring that maintains airtightness between the body 8 and the body 3. Note that 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.

With the above configuration, when pressure fluid is guided from the passage 21 to the front cylinder chamber 7 under the control of the servo valve,
The piston rod 5 is displaced to the rear side, and when the pressure fluid is guided from the passage 22 to the cylinder chamber 8 on the rear side, the piston rod 5 is displaced to the front side. This piston rod 5 extends through the speaker frame 1, and the central hole of the diaphragm 23 is fitted into the tapered portion 5a at the tip thereof.
The diaphragm 23 is firmly fixed to the piston rod 5 by screwing a nut 24 onto the end of the diaphragm 23 that protrudes from the central recess 23a. Therefore, when the piston rod 5 is displaced back and forth in the axial direction as described above, the diaphragm 23 is also displaced back and forth 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 the structure is such that it can freely protrude and retreat within the axial length range of the front and rear cylinder chambers 7 and 8. Because of this, this hydraulic speaker can perform large amplitude operation commensurate with the emission of infrasound. Moreover,
The spring effect occurs only slightly with respect to hydraulic pressure, and does not produce a peak in the natural vibration frequency as in the case of using a diaphragm or the like.

The hydraulically driven speaker includes a hydraulic sensor 50 (FIG. 4) that detects the pressure in the hydraulic chamber 6, and a piston rod 5.
a position sensor 25 that detects the movement of the
Comes with.

The position sensor 25 is composed of a magnet 26 and a differential transformer type coil 27, which move relative to each other as the piston rod 5 moves. Since the magnet 26 is disposed inside the rear end of the hollow piston rod 5 on the movable part side, the holder 2 holding the magnet 26 is attached to the piston rod 5 from the rear end side.
8 is screwed in, and is fixed to the piston rod 5 by a screw 29 so as not to rotate. On the other hand, the coil 27
In order to position the fixed side near the magnet 26,
A sensor case 30 is attached to the rear end of the body 3, ie, on the rear seal cover 15, using screws 16 common to the cover. The coil 27 is formed into a rod shape, protrudes from the inner surface of the rear end of the sensor case 30, passes inside the sensor case 30, further passes near the magnet 26, and coaxially extends inside the hollow interior of the piston rod 5. There is. An amplifier board 31 carrying an amplifier and the like is attached to the rear end of the sensor case 30 with screws 32, and the coil 27 is electrically connected to this amplifier board 31. Reference numeral 33 indicates an electrical lead-out line from this amplifier board 31.

On the other hand, the acceleration sensor 34 is provided on a mounting seat 35 screwed into the piston rod from the tip of the piston rod 5. The acceleration sensor 34 is made of a piezoelectric element, and its electrical lead wire 36 passes through the hollow interior of the piston rod 5 and passes through the holder 28 at the rear end of the piston rod 5.
It is taken out to the outside through an opening 37 provided in the.

Detection signals from the position sensor 25 and acceleration sensor 34 obtained from the lead lines 33 and 36 are sent to a control amplifier 53 as in the conventional case explained with reference to FIG.

The control amplifier 53 receives an electric signal to be electroacoustic converted from the signal source 52, converts it into a voltage or current signal suitable for driving the hydraulic controller 17, and converts it into a voltage or current signal suitable for driving the hydraulic controller 17. control the servo valve. The hydraulic pressure controlled by the hydraulic controller 17 is supplied to the hydraulic chambers 7 and 8 of the hydraulic driver 2, and the piston rod 5
moves left and right in response to the signal from the signal source 52. This movement of the piston rod 5 is transmitted to the diaphragm 23, and the movement of the diaphragm 23 causes the air to become denser and denser, which is then radiated as a sound wave.

In this case, the detection signal from the position sensor 25 is used as a feed signal to improve responsiveness and to improve the function of maintaining the center position (origin) of the movable body (piston rod 5) when there is no signal.
The signal is input to the control amplifier 53 (FIG. 4) as a back signal. Furthermore, the detection signal from the acceleration sensor 34 is also input to the control amplifier 53, and the followability is improved by using this acceleration signal and a speed signal obtained by integrating this signal or a speed signal obtained by differentiating the signal from the position sensor 33. is planned. The liquid pressure detection signal from the liquid pressure sensor 50 (FIG. 4) or the differential pressure sensor is also sent to the control amplifier 53 as a feedback signal to improve controllability and prevent the generation of noise due to pressure fluctuations in the liquid source 57. is input. That is, the hydraulic pressure detection signal not only controls the hydraulic pressure to follow the electric signal, but also controls the hydraulic driver 2 so that harmful fluctuations (pulsation in the low frequency range) of the hydraulic pressure source are not emitted as sound. control the hydraulic pressure.

FIG. 3 shows an equivalent circuit between input acceleration x and output sound pressure p (here, x and p are vectors), and shows a portion corresponding to the hydraulic driver 2 and a hydraulic controller 17. The corresponding parts are shown surrounded by dotted lines. In the hydraulic driver 2, m is the mass of the vibrating movable part, b is the viscous drag coefficient, c is a constant representing the rigidity of the drive system, Ap is the cross-sectional area of the piston, and S is the Laplace operator. When looking at the portion 38 that enters the diaphragm 23 as a reference, Ap/S, b/S, and c/S2 are negatively fed back. Further, as shown in the figure, the acceleration from the acceleration sensor 34 is fed back to the servo valve via the control amplifier 53 as an acceleration signal ea, and is also obtained by integrating this signal or by differentiating the signal from the position sensor 25. The signal is fed back to the servo valve as a speed signal ev, and furthermore, the position signal ey from the position sensor 25 is fed back to the servo valve.

In this way, a control device capable of creating an acceleration waveform that faithfully corresponds 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 driver 2 receives the output signal of this control device (the output signal of the hydraulic controller 17), causes the piston rod 5 to respond quickly to the electrical input signal, and excites the diaphragm 23, so it generates vibrations in the ultra-low frequency range. Sound pressure characteristics are fundamentally improved. In addition to the improved low frequency characteristics mentioned above, this hydraulically driven speaker also has the following advantages over conventional diaphragm type hydraulically driven speakers:
Since it has a large sound pressure output function with a larger stroke and large driving force, it is suitable for applications that require ultra-low sound and high output, where you can feel the wind pressure on your body.For example, it can be used for outdoor rock concerts etc. You can get certain sound effects.

[0026]

In summary, according to the present invention, the piston rod of the diaphragm is supported by a hydrostatic bearing so as to be movable very smoothly, and the hydraulic pressure is controlled to be supplied to two cylinder chambers located in front and behind each other by a hydraulic pressure controller. As a result, the diaphragm can faithfully correspond to the input signal and can respond at high speed. Furthermore, even when the piston rod, that is, the diaphragm, generates a large amplitude when emitting infrasound, the piston rod simply displaces greatly in the axial direction, and does not undergo elastic deformation like a diaphragm or bellows. . That is, an arbitrarily large amplitude can be created with a small diameter piston rod. In addition, since there is no spring effect other than the compressibility of the liquid, there is no natural frequency generated by a diaphragm or the like, and there is no deterioration in frequency characteristics caused by this. Furthermore, there is no technical difficulty in creating a structure that supports the movable body while withstanding its weight and hydraulic pressure.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view showing an embodiment of a hydraulically driven speaker of the present invention.

FIG. 2 is a front view of the hydraulically driven speaker of FIG. 1 with the speaker frame removed.

FIG. 3 is an equivalent circuit diagram including a control system of the hydraulically driven speaker of the present invention.

FIG. 4 is a configuration diagram of a conventional hydraulically driven speaker.

[Explanation of symbols]

1 Speaker frame 2 Hydraulic driver 3 Body 4 Cylinder 5 Piston rod 6 Partitions 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 passage 21 for servo valves,
22 Pressure oil passage to the cylinder chamber 23 Vibration plate 25 Position sensor 26 Magnet 27 Differential transformer type coil (rod-shaped coil) 28
Holder 31 Amplifier board 33 Electrical leader line 34 Acceleration sensor 36 Electrical leader line 37 Opening 50 Liquid pressure sensor 52 Signal source 53 Control amplifier

Claims (3)

[Claims] Claim 1: A piston rod with a diaphragm fixed to its tip is inserted into a cylinder of a body provided on the back side of a speaker frame, and the piston rod is supported movably in the axial direction by a hydrostatic bearing. The piston rod is characterized by forming a partition in the middle of the piston rod that makes sliding contact with the inner wall of the cylinder to form two adjacent cylinder chambers, and is provided with a hydraulic pressure controller that controls the supply of hydraulic pressure to each cylinder chamber. A hydraulically driven speaker. 2. The piston rod is formed hollow,
A magnet and a rod-shaped coil are provided inside the rear end of the piston rod, and the magnet and rod-shaped coil move relatively as the piston rod moves.
2. The hydraulically driven speaker according to claim 1, further comprising a piston rod position sensor. 3. A pickup consisting of a mechanical-electric transducer is provided inside the tip of the piston rod, and its electrical lead wire is led out from the rear end of the piston rod through the hollow interior of the piston rod, and used as an acceleration sensor. 3. A hydraulically driven speaker according to claim 2.