JP2616823B2 - Roots blower noise reduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention provides a pair of rotors in a casing having a suction port and a discharge port formed therein, so that both rotors do not communicate with each other. The present invention relates to a roots-type blower that sucks air from a suction port by rotating a blower, and discharges the sucked air from a discharge port without compressing the air, and more particularly to a noise reduction device in the roots-type blower.

(Prior Art) As one type of noise reduction device in this type of blower, Japanese Utility Model Laid-Open Publication No. Sho 62-173579 discloses a case where communication with a suction port is interrupted by a leaf piece on the rear side in the rotation direction of a rotor. On the inner wall surface of the casing in a specific section from the position of the top of the leaf piece in the rotation direction to the discharge port, multiple straight grooves are formed substantially parallel to an imaginary line parallel to the rotation center line of the rotor on the inner wall surface. The provided noise reduction device is disclosed.

(Problems to be Solved by the Invention) According to the above-described conventional noise reduction device, when the top of the leaf on the front side in the rotation direction communicates with a specific section provided with the parallel groove, the leaf on the front side of the rotor and the rear on the rear side. The discharge port intermittently communicates with the low-pressure chamber surrounded by the leaf pieces and the inner wall surface of the casing via multiple straight grooves, and air gradually flows into the low-pressure chamber from the discharge port. Thereby, the maximum flow velocity of the air flowing backward from the discharge port in the low-pressure chamber decreases, so that noise due to the backward flow can be reduced.

However, in the above-described conventional noise reduction device, when the front leaf piece passes through the specific section, the discharge port and the low-pressure chamber are intermittently communicated via the straight groove, so that the air repeatedly compresses and expands in the low-pressure chamber. Pressure pulsations occur, which cause noise, which offsets the noise reduction effect due to the reduced backflow velocity.

The present invention has been made in view of the above problems, and has as its object to provide a noise reduction device for a roots-type blower that is more excellent in noise reduction effects.

(Means for Solving the Problems) In the noise reduction device for a roots-type blower according to the present invention, a pair of rotors is provided in a casing having a suction port and a discharge port, and the suction port and the discharge port communicate with each other. In a roots-type blower that sucks air from the suction port by rotating both rotors so as not to compress the air and discharges the sucked air from the discharge port without compressing the air, the lobe of the rotor in the rotation direction rear leaf piece is connected to the suction port. On the inner wall surface of the casing in a specific section from the position of the top of the leaf piece on the front side in the rotation direction when the communication is cut off to the discharge port, the imaginary line parallel to the rotation center line of the rotor on the inner wall surface is 25 °. A multi-level helical groove with an angle of ~ 40 ° is provided, and the volume V1 of the low-pressure chamber surrounded by the adjacent leaf pieces of the rotor and the inner wall surface of the casing
And the ratio V2 / V1 of the total volume V2 of the helical groove to 1.0 to 0.1.

According to the present invention, when the top of the leaf on the front side in the rotation direction passes through a specific section provided with the helical groove, it is surrounded by the front leaf and the rear leaf on the rotor and the inner wall surface of the casing. Between the low pressure chamber and the discharge port through multiple helical grooves,
Air gradually flows into the low pressure chamber from the discharge port. Thereby, the maximum flow velocity of the air flowing backward from the discharge port to the low-pressure chamber decreases, so that noise due to the backward flow can be reduced.

Particularly, in the present invention, the helical groove is formed so as to form an angle of 25 ° to 40 ° with respect to the rotation center line of the rotor. Are continuously communicated through Therefore, pressure pulsation in the low-pressure chamber can be suppressed, and noise due to pressure pulsation can be reduced. However, when the angle of the helical groove is 25 ° or less, the effect of suppressing pressure pulsation is low, and when the angle is 40 ° or more, the amount of air flowing into the low pressure chamber from the discharge port becomes too large,
On the contrary, the noise increases, but in the present invention, since the angle of the helical groove is set to 25 ° to 40 °, the noise caused by the backflow and the noise caused by the pressure pulsation can be effectively suppressed.

If the ratio of the volume V1 of the low-pressure chamber to the total volume V2 of the helical groove is excessive, the amount of air flowing from the discharge port into the low-pressure chamber increases, which causes noise. On the other hand, if the ratio of the volume V1 of the low-pressure chamber to the total volume V2 of the helical groove is too small, the amount of air flowing into the low-pressure chamber from the discharge port is insufficient, and the backflow speed does not decrease, so that the effect of reducing noise due to backflow However, in the present invention, since the ratio of the volume V1 of the low-pressure chamber to the total volume V2 of the helical groove is set to 1.0 to 0.1, the noise caused by the backflow can be reduced more effectively.

(Embodiment) Hereinafter, a noise reduction device for a roots-type blower according to an embodiment of the present invention will be described with reference to the drawings. The noise reduction device includes a casing 1 having a suction port 2 and a discharge port 3 formed therein. A three-lobe rotor 6, 7 is fixed to a pair of rotating shafts 8, 9 in the casing 1, respectively, and both rotors 6, 7 are rotated so that the suction port 2 and the discharge port 3 do not communicate with each other. By doing so, air is sucked from the suction port 2 and the sucked air is discharged from the discharge port 3 without being compressed.

On the inner wall surface of the casing 1, when the communication with the suction port 2 is cut off by the leaf pieces on the rear side in the rotation direction of the rotors 6, 7, the positions of the tops 6 x, 7 x of the leaf pieces on the front side in the rotation direction are changed from the discharge port 3.
Up to a specific section, multiple helical grooves 4 are formed. In FIG. 1, the angle of this specific section is indicated by θ ', and in this embodiment, it is set to about 60 °. The first
In the figure, the angle θ is an angle 120 between the adjacent leaf pieces 6a, 6b, 6c, 7a, 7b, 7c of the rotors 6, 7 in the three-leaf rotors 6, 7.
Indicates ゜.

The helical groove 4 in the specific section θ ′ has an angle of 30 ° with respect to an imaginary line 12 parallel to the center lines 10 and 11 of the rotors 6 and 7 on the inner wall surface of the casing 1, that is, the center lines of the rotation shafts 8 and 9. It is formed to form. FIG. 3 schematically shows the helical groove 4 in a developed state, wherein reference numeral 2 denotes an imaginary line, and reference numeral Z denotes an angle formed by the helical groove 4 with respect to the imaginary line 12.

Further, the ratio V2 / V1 of the total volume V2 of the helical groove 4 to the volume V1 of the low pressure chamber surrounded by the leaf pieces adjacent to the rotors 6, 7 and the inner wall surface of the casing 1 is set to 0.17.

Since the noise reduction device of the roots type blower according to the present embodiment has the above configuration, the top portions 6x, 7
When x passes through the specific section θ 'provided with the helical groove 4, the low pressure chamber surrounded by the front leaf piece and the rear leaf piece of the rotors 6, 7 and the inner wall surface of the casing 1 and the discharge port 3 Through the helical groove 4, and the air gradually flows from the discharge port 3 into the low-pressure chamber. As a result, the maximum flow velocity of the air flowing backward from the discharge port 3 to the low-pressure chamber decreases, so that noise due to the backward flow can be reduced.

Particularly, in the present embodiment, the helical groove 4 is formed so as to form an angle of 30 ° with the virtual line 12 of the rotation center line of the rotor. The discharge port 3 is continuously communicated through the helical groove 4. Therefore, pressure pulsation in the low-pressure chamber is suppressed, and noise due to pressure pulsation can be reduced.

Fig. 4 shows the case where the discharge pressure is 0.6 kg / cm ² , (1) the angle of the helical groove is 30 °, and the volume ratio V2 / V1 is 0.17.
(2) A plurality of perpendicular grooves are provided substantially parallel to an imaginary line parallel to the rotation center line of the rotor on the inner wall surface, and the volume ratio V2
It is a graph which shows the experimental result which measured a noise value and a rotation speed about the case where / V1 was set to 0.05 and the case where (3) a perpendicular groove was provided and the volume ratio V2 / V1 was set to 0.17. As shown in this graph, the one provided with a 30 ° helical groove has a noise reduction effect of 6 to 10 dB as compared with the one provided with a straight groove.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a noise reduction device for a roots type blower according to an embodiment of the present invention, FIG. 2 is a perspective view showing a casing of the noise reduction device, and FIG. FIG. 4 is a developed view showing the helical groove, and FIG. 4 is a graph showing the measurement results of the noise value and the rotation speed. (Explanation of reference numerals) 1 ... casing, 2 ... suction port, 3 ... discharge port, 4 ...
... Helical groove, 6,7 ... Rotor, 8,9 ... Rotation axis, 10,11 ... Rotation center line, 12 ... Virtual line.

Claims (1)

(57) [Claims] 1. A pair of rotors are provided in a casing having a suction port and a discharge port formed therein, and both rotors are rotated so as to prevent communication between the suction port and the discharge port, thereby sucking air from the suction port. In a roots-type blower that discharges the sucked air from the discharge port without compressing the air, the discharge from the top of the front leaf in the rotation direction when the communication with the suction port is cut off by the rear leaf in the rotation direction of the rotor. On the inner wall surface of the casing in the specific section up to the exit, the imaginary line parallel to the rotation center line of the rotor on the inner wall surface is
A multi-layer helical groove with an angle of ゜ to 40 ° is provided, and the ratio V2 / V1 of the volume V1 of the low-pressure chamber and the total volume V2 of the helical groove surrounded by the adjacent leaf pieces of the rotor and the inner wall surface of the casing is 1.0 to 1.0.
Roots blower noise reduction device characterized by 0.1.