JPH0510293A - Turbo blower - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain a turbo blower that reduces whistle noise and has a low overall noise value with a simple configuration. [Structure] A tongue-shaped plate 3 forming a cavity 4 is provided in a constricted portion 1c of a casing 1, a gap 5 with a side plate 1d is provided, and a Helmholtz resonance silencer is constructed as a cavity 4 communicating with the casing 1. As a result, the interference between the air flow having the non-uniform pressure distribution at the outlet of the impeller 2 and the constricted portion 1c is reduced, and the whistle noise and the overall noise value are suppressed. [Effect] It can be manufactured at low cost, ensures air blowing performance, and quietens the operating environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo blower provided with an impeller inside a casing.

[0002]

2. Description of the Related Art FIG. 5 shows, for example, Japanese Patent Laid-Open No. 62-10495.
It is a conceptual diagram of the conventional turbo blower shown by the publication.
In the figure, reference numeral 1 denotes a circular portion 1a, an outlet 1b communicating with the circular portion 1a on one side, and one side of the outlet 1b and the circular portion 1a.
A casing in which a constricted portion 1c is formed at the connection portion of the casing 2 is a turbo impeller, and a hub 2b having a boss 2a and a blade 2
c and a shaft 2d are provided.

The conventional turbo blower is constructed as described above, and the impeller 2 rotates in the casing 1 and is blown from the blowout port 1b. Then, each blade 2c has a constricted portion 1
When passing through c, the blowout flow having a non-uniform 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 NZ sound whose generation frequency is determined by the number of revolutions of the impeller 2 and the number of blades 2c. Then, in order to reduce the whistle noise, a configuration is considered in which the circumferential position of the constricted portion 1c is changed in the axis 2d direction to disperse the interference synchronized with the axis 2d direction.

[0004]

In the concept of the conventional turbo blower as described above, since the shape of the constricted portion is complicated, a plurality of constricted portion members having different shapes are combined to form the constricted portion. There is a problem that it takes a lot of trouble. Further, although the NZ sound is dispersed and the sound quality of the whistle is improved, the energy itself of the whistle does not decrease, and it is difficult to reduce the overall noise value.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a turbo blower which reduces NZ noise and has a small overall noise value.

[0006]

In the turbo blower according to the present invention, the constricted portion is provided with a tongue-shaped plate to form a void therein, and the void is provided with a side plate of the casing. Is communicated with the casing.

[0007]

The Helmholtz resonance type sound deadening structure is formed by the space in the tongue plate of the turbo blower configured as described above. For this reason, the NZ sound is silenced, and the axial length of the impeller of the constricted portion is relatively shortened by the gap between the tongue plate and the casing side plate. As a result, the NZ sound is reduced by the synergistic effect of reducing the interference between the constricted portion and the air flow having the non-uniform pressure distribution at the impeller outlet, and the silencing of the NZ sound.

[0008]

1 to 4 are views showing an embodiment of the present invention, in which the same reference numerals as those in FIG. 5 designate corresponding parts, 1d is a side plate of a casing 1 and 1e is a side opposite to a hub 2b. Side plate 1
A suction port 2d provided at d, a shroud 2e facing the hub 2b and having a suction port 2f, a tongue-shaped plate 3 provided in the constricted portion 1c, and one side of the impeller 2
A small gap 4 is formed along the outer peripheral surface of the shroud to form a substantially triangular space 4 between the constricted portion 1c and a gap 5 between the shroud 2e and the facing side plate 1d. There is. The void 4 communicates with the inside of the casing 1 through a gap 5.

When the impeller 2 rotates in the direction of arrow B shown in FIG. 1 in the turbo blower configured as described above, the air flowing in through the suction ports 1e and 2f passes between the respective impellers 2c and impellers. Blow out from 2. And
The blowout airflow flows from the tongue plate 3 in the direction of the arrow B in the casing 1 and is blown from the blowout port 1b. In addition, the blade 2c
Since the airflow blown from between the areas forms a non-uniform pressure distribution in the circumferential direction of the impeller 2, each time the nonuniform airflow passes through the constricted portion 1c, pressure is generated due to interference with the constricted portion 1c. Fluctuations occur, and the sound pressure energy is generated to generate noise. 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 structure shown in FIGS. 1 to 4, a part of the air flow having an uneven pressure distribution between the blades 2c interferes with the gap 5 between the tongue plate 3 and the side plate 1d. Without flowing in. Therefore, NZ is larger than that without the gap 5.
The sound will be reduced. If the gap 5 is too small, the NZ sound reducing effect will be very small, and if it is too large, the air blowing performance will deteriorate. Therefore, it is necessary to set in consideration of the overall performance of the turbo blower, but according to the experiment of the inventor, the size of the gap 5 is 15% of the facing distance between the side plates 1d.
Good overall performance could be obtained when it was set to -20%.

FIG. 3 is an enlarged view of a main portion near the tongue-shaped plate 3. The cavity 4 is shown in FIG. 4 in the cavity 41 of the Helmholtz resonance type silencing structure, and the gap 5 is shown in FIG. Hole 5
Equivalent to 1. The Helmholtz resonance type silencer has a hole 51 having a cross-sectional area S and a length L shown in FIG.
1 and its muffling frequency fn is

[0012]

[Equation 1]

It is represented by Also, the gap 5 in the shaded area in FIG.
Is A, the thickness of the tongue plate 3 is T, and the volume of the space 4 is v.

[0014]

[Equation 2]

The frequency of will be muted. Therefore, it is possible to greatly reduce the NZ sound by setting the dimensions of the related parts such as the void 4 so that fn and NZ are equal. In this way, it is possible to obtain a turbo blower that has a simple structure, can be manufactured at low cost, can reduce the overall noise value, and has good overall performance.

[0016]

As described above, the present invention has a tongue in which a void is formed inside the constricted portion of the casing and the void communicates with the casing by the gap between the casing side plate on the impeller shroud side. A plate is provided. As a result, a Helmholtz resonance type sound deadening structure is formed, and the NZ noise is reduced by reducing the interference between the airflow having the non-uniform pressure distribution at the outlet of the impeller and the constricted portion. 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 air blowing performance is secured and the noise value is reduced.

[Brief description of 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 the tongue plate in FIG.

FIG. 4 is an explanatory diagram schematically showing the configuration of a Helmholtz resonance type silencer in FIG.

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

[Explanation of symbols]

1 casing 1a circular part 1b outlet 1c constriction section 1d side plate 2 impeller 2b hub 2e shroud 3 tongue plate 4 vacant places 5 gap

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takao Chihisa             1-3 Komaba-cho, Nakatsugawa-shi Mitsubishi Electric Stock Exchange             Inside the company Nakatsugawa Works

Claims (2)

[Claims] 1. A turbo type impeller in which a plurality of blades are provided between a hub and a shroud, and a circular portion in which side plates facing the hub and the shroud are provided to accommodate the impeller. A casing having a blowout port that communicates with one side of the circular portion and faces the outer peripheral surface of the impeller, and a constricted portion that is formed at the connecting portion on one side of the circular portion and the blowout port and that is close to the outer peripheral surface. And the side plate facing the shroud, which is provided in the constricted portion and has one side formed with a small gap along the outer peripheral surface to form a triangular space with the inner surface of the constricted portion. Is installed with a slight gap formed between
A turbo blower having a tongue-shaped plate that forms a space communicating with a void and a gap. 2. The gap size is 15% of the facing distance between the side plates.
The turbo blower according to claim 1, which is -20%.