JP2000136798A - Noise reducing method and device of two-stage axial blower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce interference noise by performing a frequency analysis of generated noise, selecting a phase difference between rotary blades of a front stage and a rear stage with minimized interference noise, and controlling the rotary blades of respective air blowers on the basis of the phase difference in a two-stage type axial blower by longitudinally juxtaposing two axial blowers in a duct. SOLUTION: At operation starting time, first of all, servomotors 1, 2 of axial blowers of a front stage and a rear stage are rotated up to respective origin positions by an origin signal from a sequencer 13 to be stopped. Next, for example, the motor 2 of the rear stage is rotated and stopped on the basis of a previously inputted correction angle to correct dislocation of an installing angle generated at installing time of rotary blades of the respective axial blowers. Next, a rotating speed, the rotational direction and a phase difference of the respective motors 1, 2 are set to start air blowing operation to at this time, and perform a frequency analysis on an output signal of a noise meter arranged in the vicinity of an intake port. When a predominant component is not minimized by a preset phase difference, it is changed to a phase difference for minimizing inteference noise to perform operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of axial-flow blowers, each of which drives a rotary blade by an electric motor in a duct used for ventilation in a pit during construction of a tunnel or after operation, or in other places. The present invention relates to a method and a device for reducing noise of a two-stage axial flow blower in which the front and rear are arranged side by side.

[0002]

2. Description of the Related Art Conventionally, an axial blower used for ventilation in tunnel construction or the like is often used by connecting a plurality of blowers in order to increase discharge pressure, and therefore, a large noise is generated. . As a countermeasure, silencers have been installed on the intake side and the discharge side of the blower.

[0003] In addition, the conventional rotation control using a combination of an induction motor and an inverter is mainly performed for the purpose of controlling the amount of air blown in accordance with a change in the air blown distance or the concentration of contaminants in the mine, thereby reducing noise. The intended rotation control was not performed.

That is, in a conventional axial flow blower, two rotating blades (moving blades) are brought close to each other and rotated in opposite directions to increase the discharge pressure, or a fixed blade (static blade) is provided downstream of the rotating blades. Although they are provided close to each other, there is a problem that a large rotation noise is generated due to interference between these blades. The noise generated by such a blower includes interference noise generated between blades, which is rotational noise, and turbulent noise generated due to turbulence in the main flow and vortices in the wake of the blade. In the blower, the interference noise is particularly large.

For this reason, measures have been taken to install silencers on the intake side and discharge side of the blower. However, if a sufficient noise reduction effect is to be obtained by the silencer, pressure loss increases. There was a problem that the blowing performance was reduced.

[0006]

Accordingly, the present invention has been used in conjunction with ventilation for underground ventilation during tunnel construction or after service, or elsewhere.
Provided is a noise reduction method and apparatus for a two-stage axial blower, which reduces generated noise, particularly interference noise, without installing a muffler, in order to protect the underground and surrounding environment. The purpose is to:

[0007]

According to the noise reduction method of the present invention, the noise of a two-stage axial flow fan in which two axial flow fans each driving a rotary wing by an electric motor in a duct are arranged in front and behind. In the reduction method, the rotor blades of the front and rear blowers are each driven by a servomotor, and the frequency of the generated noise is analyzed to minimize interference noise corresponding to the number of rotor blades, the number of rotations, and the distance between both rotors. The phase difference between the preceding and subsequent rotors is selected, and both rotors are controlled and operated based on the phase difference.

According to the noise reduction device of the present invention, there is provided a noise reduction device for a two-stage axial flow fan in which two axial flow blowers, each of which drives a rotary blade by a motor in a duct, are arranged in front and rear. The rotors of the front and rear blowers are each driven by a servomotor, and the phase difference between the front and rear rotors to reduce interference noise in accordance with the number of rotor blades, the number of rotations, and the distance between both rotors. A control device for controlling the
The control device has a servo driver for driving each of the servo motors, and has a function of transmitting a rotation signal of one of the motors from the servo driver to the other servo driver to control the rotation signal to a predetermined phase difference. ing.

The present invention is constructed as described above, and the control device is provided with a target for the front and rear rotor blades so that interference noise is minimized in advance in accordance with the number of blades, the number of rotations, and the distance between the rotor blades. A phase difference is input, and one of the servomotors, for example, at the preceding stage is rotated by an instruction of the control device, and the rotation is detected by, for example, an encoder, and the other (at the later stage) servomotor is set to the target phase difference. Control via a servo driver. Therefore, at any set rotational speed, both rotors are operated with high accuracy by the phase difference that minimizes the interference noise, and the noise is reduced.

The target phase difference at which the interference noise is minimized can be determined by, for example, installing a sound level meter near the intake port and analyzing the frequency of the output signal of the sound level meter to find the dominant component (rotor blade interference sound). ) Is determined, the relationship between the phase difference between the front and rear rotor blades and the magnitude of the dominant component of noise is examined, and the phase difference that minimizes this is determined.

Even when the two-stage rotating blades rotate in opposite directions, when the interference noise generated between the rotating blades propagates in the duct, the rotation speed and the phase are controlled so as to maximize the attenuation. Can be.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a front-stage rotary blade 5 and a rear-stage rotary blade 6 are provided in a duct 4 so as to face each other, and are driven by servomotors 1 and 2 provided before and after that, respectively. Then, a control device 3 is provided and wired to each of the servo motors 1 and 2 and the encoders 14 and 15 directly connected to the servo motor.

In the embodiment shown in FIG. 2, the front and rear rotating blades 5 and 6 driven by servomotors 1 and 2 provided on the downstream side, respectively, are arranged in series. Are provided with fixed wings 7 and 8. The arrangement of the control device 3 is the same as in the above embodiment.

FIG. 3 shows a control block diagram of the control device 3. The rotation of the servomotor 1 is controlled with high accuracy via the servo driver 9 by a command from the sequencer 13, and the rotation is detected by the encoder 14, and its signal is sent to the subsequent stage via the signal converter 11 and the switch 12. To the servo driver 10. The servo driver 10 at the subsequent stage controls the rotation of the servo motor 2 at the subsequent stage based on the rotation signal at the previous stage and the signal relating to the target phase previously input to the sequencer 13.

FIG. 4 shows a flowchart of the operation and control functions. First, when the driving operation is started in step S1, first, the motors 1 and 2 at the preceding and subsequent stages rotate to their current point positions and stop by the origin signal from the sequencer 13 (step S2). Next, step S
In 3, for example, the motor 2 at the subsequent stage rotates and stops based on the correction angle previously input to the sequencer 13 in order to correct the deviation of the mounting angle caused when the rotating blades 5 and 6 are mounted. Subsequently, in step S4, the number of rotations and the direction of rotation of the first and second motors 1 and 2 are set.
After setting the phase difference in step 5, the process proceeds to step S6, and the blower is operated at its rotation speed, rotation direction, and phase difference.

Then, the noise generated by the blower is measured by a sound level meter installed near the intake port, and in step S7, the output signal of the sound level meter at that time is subjected to frequency analysis to obtain a dominant component (FIG. 5 and FIG. 5). (See FIG. 6). Next, in step S8, the front and rear rotors 5,
The change of the interference noise due to the phase difference is examined by, for example, illustrating the relationship between the phase difference 6 and the magnitude of the dominant component of the noise (see FIG. 7), and whether or not the dominant component is minimized by the set phase difference. Judge.

Here, if it is confirmed that the dominant component is the minimum, the process proceeds to step S9, and the steady operation is performed while maintaining the phase difference. If the predominant component is not minimized in the set phase difference, a phase difference different from the phase difference given in step S5 is set in step S10, and the process returns to step S6 to return to the rotation speed and the rotation direction. Operate without changing.

In this way, this process is repeated by giving a phase difference, for example, at regular intervals, to obtain a phase difference that minimizes the interference noise, and the process proceeds to step S9. The blower is operated while maintaining the phase difference, and the noise is reduced. Can be minimized.

[0019]

Experimental Examples FIGS. 5 to 7 show experimental examples in which the sound pressure level (or noise level) of interference noise is measured by a sound level meter and the output signal of the sound level meter is subjected to frequency analysis.
5 and 6, frequency (kHz) is plotted on the horizontal axis and sound pressure level (dB) is plotted on the vertical axis, and the dominant component (rotor blade interference sound) is indicated by a triangle in the figures. FIG. 5 is an example of a frequency analysis at a phase difference of 85 degrees between the front and rear rotors 5 and 6 having the largest dominant component, and FIG. 6 is an example of a frequency analysis having a phase difference of 55 degrees having the smallest dominant component. is there.

FIG. 7 shows a change in a dominant component due to such a phase difference. In FIG. 7, the horizontal axis represents the phase difference (deg) between the front and rear rotors 5 and 6, and the vertical axis represents the sound pressure level (dB) of the dominant component. The values are shown, and the phase difference that minimizes the interference sound is found from the figure, and the target phase difference can be easily set.

[0021]

The present invention is configured as described above and has the following effects. (1) Conventionally, interference noise of an axial blower, which was difficult to reduce without using a large-sized silencer, can be easily suppressed to a low level. (2) Since the noise generated by the blower itself can be reduced and the blowing performance is not deteriorated, the use of a silencer is also possible, so that the noise can be reduced which could not be obtained by the conventional silencer alone. (3) The use of a servomotor makes it possible to reduce the size, weight, and power consumption of the device. (4) Since the noise can be reduced by changing the electric motor to a servomotor without changing the structure of the impeller, the casing, and the like, the present invention can be applied to general-purpose devices.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention (reduction of interference noise between rotating blades).

FIG. 2 is a configuration diagram showing another embodiment of the present invention (reduction of interference noise between a rotating wing and a fixed wing).

FIG. 3 is a control block diagram of the control device of the present invention.

FIG. 4 is a flowchart showing operations and functions of the control device of the present invention.

FIG. 5 is a graph showing an example of frequency analysis of generated noise (maximum interference sound).

FIG. 6 is a graph showing an example of frequency analysis of generated noise (minimum interference sound).

FIG. 7 is a graph showing a change in the sound pressure level of the interference sound due to the phase difference between the front and rear rotors.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Servo motor (front stage) 2 ... Servo motor (back stage) 3 ... Control device 4 ... Duct 5 ... Rotating blade (front stage) 6 ... Rotating blade (back stage) 7 ... · Fixed wing (front stage) 8 ··· Fixed wing (back stage) 9 ··· Servo driver (front stage) 10 ··· Servo driver (back stage) 11 ··· Signal converter 12 ··· Switching device 13 ··· Sequencer 14: Encoder (front stage) 15: Encoder (back stage)

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[Procedure amendment]

[Submission date] October 20, 1999 (1999.10.
20)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007]

According to the present invention, there is provided a noise reduction method for a two-stage axial flow blower in which two axial flow blowers, each of which drives a rotary wing by a servomotor in a duct, are provided in front and behind. The servo motor is controlled via a servo driver by a command from the sequencer, and the rotation of the servo motor is detected by the encoder, and is input to the sequencer in advance to correct the deviation of the mounting angle based on the correction angle, and then the rotation speed, Set the rotation direction, set the phase difference, operate at the rotation speed, rotation direction, and phase difference, measure the noise generated by a sound level meter installed near the intake, and analyze the frequency of the output signal of the sound level meter. The magnitude of the dominant component is determined by using the phase difference set from the relationship between the phase difference of the rotor and the dominant component of the noise, and it is determined whether the dominant component is minimized. Component is adapted to be operated by obtaining a phase difference so as to minimize.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

According to the present invention, there is provided a noise reduction method for a two-stage axial flow fan in which two axial flow blowers, each of which drives a rotary blade by a servomotor in a duct, are arranged in front and rear. A control device is provided to control the phase difference between the front and rear rotor blades so as to reduce the rotation noise in accordance with the rotation speed and the distance between the two rotor blades, and the control device controls the servo motor by a signal from the sequencer. An encoder is directly connected to each of the servo motors, an encoder is directly connected to the servo motor, and a noise meter is installed near the intake port. The control device analyzes the frequency of the output signal of the noise meter to determine the magnitude of the dominant component. It has a function of determining whether or not the dominant component is minimized based on the phase difference set based on the relationship between the phase difference between the front and rear rotor blades and the magnitude of the dominant component.

Claims (2)

[Claims] 1. A noise reduction method for a two-stage axial flow fan in which two axial flow fans each of which drives a rotary blade by a motor in a duct are arranged side by side. Driven by a servo motor, frequency analysis of the generated noise is performed, and the phase difference between the preceding and succeeding rotor blades that minimizes the rotating noise is selected according to the number of blades, the number of rotations, and the distance between both rotor blades. A noise reduction method for a two-stage axial blower, wherein both rotors are controlled and operated with the phase difference. 2. A noise reduction device for a two-stage axial flow fan in which two axial flow fans driven by an electric motor in a duct are respectively arranged in front and rear, wherein the rotors of the front and rear fans are respectively arranged. A control device that is driven by a servomotor and controls the phase difference between the front and rear rotors so as to reduce the rotational noise in accordance with the number of rotor blades, the number of rotations, and the distance between the two rotors is provided. The apparatus has a servo driver for driving each of the servo motors, and has a function of transmitting a rotation signal of one of the motors from the servo driver to the other servo driver and controlling the rotation signal to have a predetermined phase difference. A noise reduction device for a two-stage axial flow fan.