JP2701603B2 - Centrifugal blower - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal blower having an impeller provided in a casing.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a conceptual diagram of a conventional centrifugal blower disclosed in Japanese Patent Application Laid-Open Publication No. HEI 10-303, 1988. In the drawing, reference numeral 1 denotes a circular portion 1a, a casing having a blowout port 1b communicating with the circular portion 1a on one side and a constricted portion 1c formed at a connection portion between the one side of the blowout port 1b and the circular portion 1a, and 2 denotes a centrifugal type. A hub 2b having a boss 2a, a blade 2c,
A shaft 2d is provided.

[0003] The conventional centrifugal blower is configured as described above, and the impeller 2 rotates in the casing 1 and is blown from the outlet 1b. And each blade 2c is constricted part 1c
When the air passes through the outlet 2b, the outlet flow having an uneven pressure distribution between the blades 2c interferes with the constricted portion 1c to generate a whistle sound. This whistle sound is a line spectrum sound called an NZ sound whose frequency is determined by the rotation speed of the impeller 2 and the number of blades 2c. Then, in order to reduce the whistle sound, the circumferential position of the constricted portion 1c is changed in the direction of the axis 2d,
A configuration for dispersing the interference synchronized with the direction of the axis 2d has been considered.

[0004]

In the concept of the conventional centrifugal blower described above, the shape of the constricted portion is complicated, so that the constricted portion is formed by combining a plurality of constricted members having different shapes. There was a problem that it took a lot of trouble. Further, although the sound quality of the whistle sound is improved by dispersing the NZ sounds, the energy itself of the whistle sound does not decrease, and there is a problem that it is difficult to reduce the overall noise value.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a centrifugal blower that reduces NZ noise and has a low overall noise value.

[0006]

In the centrifugal blower according to the present invention, the centrifugal blower is bent along the facing portion and the edge of the facing portion.
A side plate provided with a peripheral wall portion formed on the casing is configured to face each other, and a casing having an outlet formed on one side, and a side face facing a suction port formed on one side of the facing portion of the side plate. A centrifugal blower, which is provided and is disposed between the facing parts and is disposed between the facing parts, is provided with a centrifugal blower that blows out the air taken in from the suction port by the rotation of the impeller from the outlet, and is protruded from the peripheral wall of the outlet. It was arranged in the air passage between the outlet and the impeller, and a space was formed inside to reduce the ventilation size of the air passage, and communicated with the space and the air passage between the air outlet and the facing portion of the outlet. Helmhol with gaps, voids and gaps
A tongue plate is provided that forms a two- resonance silencing structure . In the centrifugal blower according to the present invention, the width of the gap between the tongue plate and the facing portion is 15% to 20% of the distance between the facing portions.
Set to%.

[0007]

The hollow space inside the tongue plate of the centrifugal blower constructed as described above forms a Helmholtz resonance type noise reduction structure. Therefore, the NZ sound is suppressed, and the axial length of the impeller of the constricted portion is relatively shortened by the gap between the tongue-shaped plate and the casing side plate. Thereby, the interference between the airflow having an uneven pressure distribution at the impeller outlet and the constricted portion is reduced, and the NZ sound is reduced due to the synergistic effect of the noise reduction of the NZ sound.

[0008]

1 to 4 show an embodiment of the present invention, in which the same reference numerals as in FIG. 5 denote corresponding parts, and 1d denotes a side plate of the casing 1 and 1e denotes a side opposite to the hub 2b. Side plate 1
Reference numeral 2e denotes a suction port, 2e is a shroud provided to face the hub 2b and has a suction port 2f, 3 is a protruding tongue plate provided in the constricted portion 1c, and one side is an impeller 2
Are formed along the outer peripheral surface of the device, forming a small space, forming a substantially triangular space 4 with the constricted portion 1c, and forming a space 5 between the shroud 2e and the facing side plate 1d. I have. The space 4 communicates with the inside of the casing 1 through a gap 5. 6 is a suction port 1 in the casing 1.
This is an air path formed in the space from e to the outlet 1b.

When the impeller 2 rotates in the direction of arrow B shown in FIG. 1 in the centrifugal blower constructed as described above, the air flowing from the suction ports 1e and 2f causes the respective blades 2 to rotate.
The air is blown out from the impeller 2 through the interval c. Then, the blown air flows from the tongue-shaped plate 3 in the direction of arrow B in the casing 1 and is blown from the blow-out port 1b. In addition, since the airflow blown out from between the blades 2c forms an uneven pressure distribution in the circumferential direction of the impeller 2, each time the uneven airflow passes through the constricted portion 1c, The pressure fluctuations occur due to the interference, and the noises are generated as sound pressure energy. This noise is called an NZ sound having a generation frequency determined by the number of times the blade 2c has passed, that is, the product of the number of revolutions N (per second) of the impeller 2 and the number Z of the blades 2c.

However, in the configuration shown in FIGS. 1 to 4, a part of the air flow having an uneven pressure distribution between the respective blades 2c interferes with the gap 5 between the tongue plate 3 and one side plate 1d. Inflows without. For this reason, compared to the case where there is no gap 5, NZ
The sound will be reduced. If the gap 5 is too small, the effect of reducing the NZ sound becomes very small, and if it is too large, the blowing performance deteriorates. Therefore, it is necessary to consider the overall performance of the centrifugal blower, but according to experiments by the inventor, the size of the gap 5 is set to 15% or less of the facing distance between the side plates 1d.
When it was 20%, good overall performance could be obtained.

FIG. 3 is an enlarged view of a main portion near the tongue plate 3, wherein a cavity 4 is a cavity 41 in the principle diagram of the Helmholtz resonance type silencing structure shown in FIG. Hole 5
Equivalent to 1. And the Helmholtz resonance silencer
4 includes a hole 51 having a cross-sectional area S and a length L and a cavity 41 having a volume V.

[0012]

(Equation 1)

## EQU1 ## Also, the gap 5 in the hatched portion in FIG.
Let A be the area 5a, T be the thickness of the tongue plate 3, and v be the volume of the cavity 4.

[0014]

(Equation 2)

[0015] The above frequency is muted. Therefore, it is possible to greatly reduce the NZ sound by setting the dimensions of the related portion such as the space 4 so that fn and NZ are equal. In this way, it is possible to obtain a centrifugal blower that has a simple configuration, can be manufactured at low cost, can reduce the overall noise value, and has good overall performance.

[0016]

As described above, according to the present invention, the peripheral portion formed in a bent state along the facing portion and the edge portion of the facing portion.
The side plate provided with a wall is configured to face each other, and a casing having an outlet formed on one side, and a suction port formed on one side of the facing portion of the side plate are provided with side surfaces opposed to each other, and the facing portion is provided. And a centrifugal blower that blows out the air taken in from the suction port by the rotation of the impeller from the outlet, and is provided protruding from the peripheral wall portion of the outlet, and the impeller and the impeller are provided. gap disposed air passage, communicating with the cavity and air path between the at least one of the inside and space is formed narrow the ventilation dimensions of the air passage, and facing portion of the air outlet point between the To form helmets
A tongue-like plate forming a Muholtz resonance type noise reduction structure is provided . By this, together with the Helmholtz resonator type silencer structure is formed, NZ sound is reduced becomes less interference with the constricted section air flow having a nonuniform pressure distribution in the impeller outlet. For this reason, there is an effect that it can be manufactured at a low cost with a simple configuration, and there is an effect that the noise value is reduced by securing the blowing performance.

[Brief description of the drawings]

FIG. 1 is a conceptual front view showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged perspective view of the vicinity of a tongue plate in FIG. 1;

FIG. 4 is an explanatory view schematically showing a configuration of a Helmholtz resonance type silencer in FIG. 3;

FIG. 5 is a diagram corresponding to FIG. 1 showing a conventional centrifugal blower.

[Explanation of symbols]

1 casing, 1b outlet, 1d side plate, 1e
Inlet, 2 impellers, 3 tongues, 4 voids, 5 gaps, 6 airways.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takao Chiku 1-3-3 Komabacho, Nakatsugawa City Inside Nakatsugawa Works, Mitsubishi Electric Corporation (56) References JP-A-51-29708 (JP, A) 115899 (JP, U) Japanese Utility Model Showa 60-66898 (JP, U)

Claims (2)

(57) [Claims] A bent portion along the facing portion and the edge of the facing portion.
Side plates provided with side walls provided with a peripheral wall portion formed in a folded state are configured to face each other, and a casing having an outlet formed on one side and a suction opening formed on one side of the facing portion of the side plate have side surfaces. A centrifugal blower, which is provided to face each other and is disposed between the facing portions, and blows air taken in from the suction port through the outlet port by rotation of the impeller, wherein the outlet port is Is disposed in the air passage between the outlet and the impeller, and is formed inside the air passage to reduce the ventilation size of the air passage, and to provide the air outlet at the outlet portion. the gap communicating with said cavity and air path formed between the facing portion, the cavity and
A centrifugal blower comprising a tongue-shaped plate that forms a Helmholtz resonance type silencing structure by a gap . 2. The centrifugal blower according to claim 1, wherein the width of the gap between the tongue plate and the facing portion is 15% to 20% of the interval between the facing portions.