JPH0218454B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an air vibration reduction device for a vibration system including a plurality of vibration devices. Since a vibrating device performs its function by vibrating, when the device is operated in the air, it is inevitable that the device will be accompanied by air vibrations.
For example, the vibrating sieves that are currently widely used usually have an amplitude of 6 mm to 15 mm and a vibration frequency of 700 cpm (11.7 Hz) to
They are often operated at 1300 cpm (21.7 Hz), and the fundamental frequency of the air vibrations, or sound, caused by this is 11.7 Hz to 21.7 Hz, and is called infrasound. This ultra-low frequency sound itself is almost inaudible to the human ear, so it was previously thought that it would not cause any harm to the human body unless the sound pressure was extremely high, but recently, so-called It is also true that something called infrasound pollution is occurring. Moreover, if the infrasound is powerful,
vibrates not only the human body but also surrounding buildings or equipment,
It may even cause them to become damaged. In view of the above points, an object of the present invention is to provide an air vibration reduction device that can efficiently reduce air vibrations generated from a vibration system having a plurality of vibration devices. This objective is achieved by the following air vibration damping device. An air vibration reduction device for a vibration system comprising at least two vibration devices, including an eddy current joint variable speed motor for vibrating each of the vibration devices, and a phase signal for each predetermined phase position of vibration of one of the vibration devices. from the above-mentioned predetermined phase position in the vibration of the other vibration device.
The second output signal outputs a phase signal for each phase position shifted by 180°.
The phase position detecting means determines which of the phase signal from the first phase position detecting means and the phase signal from the second phase position detecting means is output earlier, outputs an output delay determination signal, and further outputs an output delay judgment signal, and further outputs an output delay judgment signal. a first logic circuit that outputs a time difference signal corresponding to the output time difference between the motors, and an eddy current joint variable speed motor that outputs a phase signal earlier based on the output slowness judgment signal and the time difference signal from the first logic circuit. a second logic circuit that lowers the rotation speed of the motor, a generator that is attached to each eddy current joint variable speed motor and generates a rotation speed voltage according to the rotation speed of each of these motors, and a rotation speed voltage from each generator. This air vibration reducing device is characterized in that it is provided with a rotational speed control means for comparing the two with each other to obtain a differential voltage between the two, and increasing the rotational speed of the eddy current joint variable speed motor having the lower rotational speed voltage. EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be described in detail based on drawings showing embodiments thereof. In FIG. 1, two
The two vibrating screens 1 and 2 have two drive shafts 4a, 5a and 4b, 5b via bearings 3, respectively, at the lower part of the figure. Flywheels 6 are eccentrically attached to these drive shafts on both sides of each of the vibrating screens 1 and 2. These drive shafts 4a, 5a and 4b, 5b have one end 4a', 5a' and 4b', 5 which is outside the vibrating screen 1, 2, respectively.
b' is connected to gear box output shafts 8a, 9a and 8b, 9b via a universal joint mechanism 7. The output shafts 8a, 9a are connected to a pulley 12a through an appropriate gear train in a gear box 11a, while the other output shafts 8b, 9b are connected to a pulley 12a in a gear box 11a.
It is connected to the pulley 12b via b. These pulleys 12a and 12b are connected to belts 13a and 12b, respectively.
By 13b eddy current joint variable speed motor 14a,
14b. Gear box 11a on the right side in the figure attached to the vibrating sieve 1
When the pulley 12a is driven by the electric motor 14a, the gear train in the
rotate in opposite directions. On the other hand, vibrating sieve 2
The side gear box 11b similarly rotates the output shafts 8b and 9b in mutually opposite directions. When the output shafts 8a and 9a or the other output shaft 8b and 9b rotate in opposite directions, the eccentric flywheels 6 fixed to the respective shafts also rotate in opposite directions. 2 undergoes linear motion, and therefore vibrates, in accordance with the resultant rotational force of the eccentric flywheel 6 rotating as described above. As mentioned above, the vibrating sieves 1 and 2 vibrate independently if no measures are taken, and therefore generate the above-mentioned infrasound, and in some cases, the two air vibrations may interfere with each other. It may also cause a buzzing phenomenon. In order to eliminate these inconveniences, in this embodiment, the air vibrations generated from the vibrating sieves 1 and 2 are made to have the same frequency, and their phases are shifted by 180 degrees, so that the two vibrations are different from each other. The design aims to cancel out the vibrations of the infrasound, thereby reducing infrasound. This situation is illustrated in Figure 2, where the air vibration f ₁ from the vibrating sieve 1 and the air vibration f ₂ from the vibrating sieve 2 are 180 degrees out of phase with each other. If these are combined, air vibrations can ideally be canceled out as shown by f ₁ + f ₂ . The method for reducing vibration will be explained in detail as follows. First, in order to equalize the air vibrations generated from the vibrating screens 1 and 2, in other words, to make the frequencies of the vibrating screens 1 and 2 the same, as shown in FIG. 1) are speed controlled by eddy current joint regulators 15a, 15b, respectively. The electric motors 14a, 14b have generators 16a, 16b, respectively, and these generators generate rotational speed voltages Vr ₁ (a), Vr ₁ (b) that are proportional to the rotational speed of the electric motors 14a, 14b. These rotational speed voltages
Vr ₁ (a) and Vr ₁ (b) are the regulators 15a and 1, respectively.
Sent to 5b. On the other hand, these regulators 15a,
Reference voltages Vref(a) and Vref(b) are input in advance to 15b, and the above-mentioned rotational speed voltages Vr ₁ (a) and Vr ₁ (b) are adjusted to their reference voltages Vref in the regulators 15a and 15b. (a) and Vref(b). The comparison results are output as control voltages Vc(a) and Vc(b), and the rotation speeds of the electric motors 14a and 14b are controlled by these control voltages. The electric motors 14a and 14b receive rotational speed voltages Vr ₁ (a) and Vr ₁ (b) from the generators 16a and 16b.
The rotational speed is increased until the reference voltages Vref(a) and Vref(b) are balanced, and the rotational speed is held constant at the time when they are balanced. Therefore, the above reference voltage
By setting Vref(a) and Vref(b) in advance to values corresponding to the desired rotational speed of the motor, the predetermined rotational speed can always be obtained. Thus two electric motors 1
4a and 14b rotate at the same rotational speed, and therefore the vibrating screens 1 and 2 should vibrate at the same frequency, but in reality, due to imbalance or fluctuation in the loads of the vibrating screens 1 and 2, the above-mentioned Only the method 2
The frequencies of the two vibrating screens 1 and 2 cannot be made equal with sufficient accuracy. Therefore, in this embodiment, the number of revolutions of the electric motors 14a, 14b is determined by the following method.
Therefore, the vibration frequencies of the vibrating sieves 1 and 2 can be controlled even more accurately. That is, in FIG. 3, the generators 16a, 16
In addition to the rotational speed voltages Vr ₁ (a) and Vr ₁ (b) sent to the regulators 15a and 15b, other rotational speed voltages Vr ₂
(a) and Vr ₂ (b) are output and sent to amplifiers 17 and 18. The amplifiers 17 and 18 compare the two input voltages Vr ₂ (a) and Vr ₂ (b) and adjust the voltages Vd(a) and Vd(b) according to the difference between the voltages Vr 2 (a) and Vr 2 (b) to the regulators 15a and 15b, respectively. send to At that time, the regulator 15a
side, that is, the amplifier 17 on the motor 14a side, when the rotational speed voltage Vr ₂ (a) of the electric motor 14a is smaller than the rotational speed voltage Vr ₂ (b) of the electric motor 14b, the amplifier 17
It is designed to output Vd(a). On the other hand, the other amplifier 18, on the contrary, increases the differential voltage Vd when the rotational speed voltage Vr ₂ (b) is smaller than the rotational speed voltage Vr ₂ (a).
Output (b). In other words, the two electric motors 14a, 1
Compare the rotation speeds of 4b and find the differential voltage Vd(a) or Vd(b) for the regulator of the motor with the smaller rotation speed.
It is sending. The differential voltage sent to either regulator 15a or 15b in this way is the reference voltage (Vref(a) or
Vref(b)) and the rotational speed voltage (Vr ₁ (a) or Vr ₁ (b))
As a result, the rotational speed of the motor on the side to which the differential voltage is sent increases. In this way, since the mutual rotation speed difference between the electric motors 14a and 14b is also used as a control factor, it is necessary to operate these electric motors at the same rotation speed, and therefore to vibrate the vibrating screens 1 and 2 at the same frequency. can be performed with extremely high accuracy. Thus, the vibrating sieves 1 and 2 vibrate at equal frequencies.
then their phases are relative to each other as follows
The phase is controlled to shift by 180°. First, as shown in FIG. 1, a metal piece 19a or 19
b is fixed. These metal pieces 19a and 19
A sensor 21a or 21 is located outside of b.
b is placed. Output shaft 8 for vibrating screen 1
When a rotates, the metal piece 19a also rotates, and the metal piece 19a rotating in this way is connected to the sensor 2.
When passing a position opposite to 1a, a metal detection signal, for example a pulse signal, is generated at the sensor 21a at that point. That is, while the vibrating sieve 1 is vibrating, the sensor 21a generates the above detection signal at a rate of one per cycle, and the signal always occurs in correspondence with a constant phase position with respect to the vibration. In this way, the metal piece 19a and the sensor 21a constitute a first phase position detection means 22a which acts to generate a pulse signal when the vibrating sieve 1 passes through a certain phase position. The metal piece 19b fixed to the output shaft 8b for the vibrating sieve 2 and the sensor 21b for detecting the metal piece 19b constitute the second phase position detection means 22b in the same manner as described above. However, the phase position of the vibration of the vibrating sieve 1 detected by the first phase position detecting means 22a and the phase position of the vibration of the vibrating sieve 2 detected by the second phase position detecting means 22b are shifted by 180 degrees from each other. Set to be a relationship. For example, in FIG. 4, if the phase position indicated by point a with respect to the vibration f ₁ ' of the vibrating sieve 1 is to be detected, then the vibrating sieve 2
For the vibration f ₂ ′, the phase position shown as point a′ in the figure is set to be detected, and if point b is detected for f ₁ ′, then point b′ for f ₂ ′ is detected. It is set to be detected. As mentioned above, the vibration of the vibrating screens 1 and 2 is caused by the rotation of the eccentric flywheels 6 attached to the drive shafts 4a, 5a and 4b, 5b in FIG. If the fixed positions of the metal pieces 19a and 19b are selected in relation to their positions, the phase positions detected by the first and second phase position detection means 22a and 22b can be adjusted.
It is easy to shift by 180°. However, since it is difficult and time-consuming to determine exactly the mounting positions of the metal pieces 19a and 19b, it is necessary to make the sensors 21a and 21b (or one of them) semi-fixed in advance, that is, to make the position adjustable, so that the entire device can be fixed. It is desirable to be able to fine-tune the phase position to be detected at any time after installation. In this way, the phase position detection signal (Sd
(referred to as (a)) and the phase position detection signal of the vibrating sieve 2 (referred to as Sd(b)) are output corresponding to phase positions shifted by 180°, so if these signals are output simultaneously, the vibrations of vibrating sieve 1 and vibrating sieve 2 are out of phase with each other.
This means that it is deviated by 180°. In other words, if the above detection signals Sd(a) and Sd(b) are output at the same time, the phases of the vibrations of the vibrating screens 1 and 2 can always be kept shifted by 180°. It is. Below, a method for simultaneously outputting detection signals Sd(a) and Sd(b) will be explained in detail. In FIG. 3, the phase position detection signal Sd(a) from the sensor 21a and the phase position detection signal Sd(b) from the sensor 21b are both sent to the first logic circuit 23. The first logic circuit 23 receives the detection signals Sd(a) and Sd(b), determines which of these signals is output earlier, and outputs a judgment signal.
Sj, and if there is a time difference between the output of those signals Sd(a) and Sd(b), a time difference voltage Vt proportional to the time difference is output. The time difference voltage Vt output from the first logic circuit 23 is applied to the voltage amplifier 24.
After being appropriately amplified at , it is sent to the second logic circuit 25 as a phase difference correction voltage Vtc. The above judgment signal Sj is also sent to the second logic circuit 25. The second logic circuit 25 determines the rotation reduction voltage based on the judgment signal Sj and the phase difference correction voltage Vtc.
Send Vrr(a) or Vrr(b) to regulator 15a or 15b. For example, if the phase position detection signal Sd(a) for the vibrating sieve 1 is output earlier, the rotation reduction voltage Vrr(a) is applied to the regulator 15a, and the phase position detection signal Sd(a) for the vibrating sieve 2 is outputted earlier. If the signal Sd(b) is output earlier, the rotation reduction voltage Vrr(b) is applied to the regulator 15b. The magnitudes of these voltages Vrr(a) and Vrr(b) are determined according to the phase difference correction voltage Vtc. The regulator 15a or 15b receiving the rotation reduction voltage Vrr(a) or Vrr(b) reduces the rotation speed of the electric motor 14a or 14b, thereby causing the phase position detection signal Sd(a) or Sd(b) to change. Delays the output timing. In this way, the phase position detection signal Sd(a)
and Sd(b) are controlled so that they are always output simultaneously, in other words, the vibrating sieve 1 and the vibrating sieve 2 are always vibrated with a phase difference of 180°. In the above description, after the first logic circuit 23 starts, the detection signals Sd(a) and Sd(b) are generated simultaneously (synchronized), and then either Sd(a) or Sd(b) is generated. The judgment signal Sj is not generated until one of the two occurs. Therefore, as long as the detection signals Sd(a) and Sd(b) are generated simultaneously, the judgment signal Sj is not generated. If vibrating sieve 1
When one of the detection signals is generated earlier due to a phase shift between the vibrations of the vibrating sieve and 2, a determination signal is generated for the first time, and it can be determined which vibrating sieve is ahead in phase. Here, the decision signal Sj is output after the detection signals Sd(a) and Sd(b) are synchronized. This is because it cannot be determined even if one pulse is considered as a reference. For example, if we consider a case in which pulses are occurring alternately, the pulse of the other party that occurs later than a certain pulse is certainly delayed, but the pulse of the other party that occurs first is delayed. can be said to be progressing in the opposite direction. Further, as shown in FIG. 5, the time difference voltage Vt is a negative DC voltage proportional to the time difference between the generation of the phase position detection signals Sd(a) and Sd(b), and when no phase difference occurs. takes a value of approximately -10v. When a phase difference begins to occur, the time difference voltage Vt becomes
First, Ov approaches according to the discharge characteristics of the capacitor built in the first logic circuit 23.
After that, the time difference voltage Vt is different from the detection signal Sd(a).
It becomes a negative voltage proportional to the time difference with Sd(b).
The time difference voltage Vt thus obtained is applied to the voltage amplifier 2.
4, and the phase difference correction voltage
As mentioned above, it becomes Vtc. Here, the reason why the discharge characteristic of the capacitor is used at the rise time to obtain Ov is that the eddy current joint has poor response, so in order to compensate for this, a strong phase difference correction voltage is first applied, and the This is to try to suppress the increase in phase difference as much as possible. Furthermore, the phase difference correction voltage Vtc is simply the time difference voltage Vt
It is not intended to be inverted and amplified, and if the phase difference is 180° or more, it is desirable to maintain a constant voltage. This is because when the phase difference reaches 180°, the combined low-frequency sound pressure from the two vibrating screens reaches its maximum, so it is desirable to perform phase correction before the phase difference reaches 180°, and the output of the amplifier 24 This is because the voltage has a limit, so the amplification range of the amplifier 24 is from in-phase to 180° phase difference. As described above, in this embodiment, the vibrating sieves 1 and 2 are vibrated at the same frequency, and the phases of their vibrations are shifted by 180 degrees, so that the air generated by the vibrating sieves 1 and 2 is The vibrations cancel each other out, resulting in reduced air vibrations and thus low frequency noise. Although the above embodiment describes a vibration reduction device for a vibration system equipped with two vibrating screens as vibrating devices, the present invention is also applicable to a vibrating system equipped with a larger number of vibrating devices. However, in that case, it is necessary to reset the phase difference of the vibrations of the vibrating devices as appropriate depending on the number of vibrating devices. For example, when the number of vibrating devices changes from 3 to 4, the phase difference settings for each should be changed.
It is like changing the angle to 120° and 90°. The vibration reduction device according to the present invention has a simple structure and can be easily installed in existing equipment, so it is very useful for preventing pollution. The following results were obtained when an experiment was conducted regarding the above-mentioned example.

[Table] As can be seen from the table above, compared to the conventional device, the device of the present invention has a maximum infrasound pressure of 8 dB.
We were able to obtain the effect of reducing Incidentally, FIGS. 6 and 7 show experimental data for obtaining Table 1. The specifications of the experimental equipment are as follows. Vibrating sieve: Vibrating grizzly feeder manufactured by Kissha Seizo Co., Ltd. Model 1800×4800-VFVS Motor: Three-phase induced eddy current joint variable speed motor manufactured by Fuji Electric Co., Ltd. Model KS45/23P Measurement method Microphone: Ultra-low frequency microphone, manufactured by Rion Corporation, model MV-01 Pollution vibration meter: Manufactured by Rion Corporation, pollution vibration meter, model VM-12A Data recorder: Data recorder, manufactured by Sony Magnescale Corporation, model FR-3215 Analysis Instrument: Rion Co., Ltd. 1/3 octave analyzer model SA-57 Level recorder: Rion Co., Ltd., level recorder model LR-01E

[Brief explanation of drawings]

Fig. 1 is a plan view of a vibration system showing one embodiment of the present invention, Fig. 2 is an ideal view showing a state in which air vibrations are canceled;
Figure 3 shows the drive control circuit for the vibration system shown in Figure 1.
Figure 4 shows the phase position detection means 22 in Figure 1.
FIG. 5 is a timing chart for explaining in detail the time difference voltage Vt in FIG. 3. FIG. 6 is a diagram showing experimental data for a conventional device. 7
The figure is a diagram showing experimental data regarding the device according to the present invention. 1, 2... Vibrating sieve (vibrating device), 14a, 14b
... Eddy current joint variable speed motor, 15a, 15b... Eddy current joint regulator, 16a, 16b... Generator, 22
a...First phase position detection means, 22b...Second phase position detection means, 23...First logic circuit, 25...Second logic circuit, 24...Amplifier.

Claims (1)

[Scope of Claims] 1. An air vibration reduction device for a vibration system comprising at least two vibration devices, comprising: an eddy current joint variable speed electric motor for vibrating each of the vibration devices; a first phase position detection means that outputs a phase signal at each predetermined phase position; and a second phase position detection means that outputs a phase signal at each phase position shifted by 180 degrees from the predetermined phase position in the vibration of the other vibrating device. , determines which of the phase signal from the first phase position detection means and the phase signal from the second phase position detection means is output earlier, outputs an output delay judgment signal, and further responds to the output time difference between the two phase signals. a first logic circuit that outputs a time difference signal; and a first logic circuit that outputs a time difference signal, and lowers the rotation speed of the eddy current joint variable speed motor that outputs the phase signal earlier based on the output slow/early judgment signal and the time difference signal from the first logic circuit. Second
A logic circuit, a generator that is attached to each eddy current joint variable speed motor and generates a rotational speed voltage according to the rotational speed of each motor, and a generator that compares the rotational speed voltage from each generator with each other and calculates the difference between the two. An air vibration reducing device characterized by comprising a rotation speed control means for determining the differential voltage and increasing the rotation speed of the eddy current joint variable speed motor having the lower rotation speed voltage.