JPH04237896A - Centrifugal blower - Google Patents

Abstract

PURPOSE:To provide a centrifugal blower available for an air conditioner or the like which can accord the centroidal position of an impeller with the turning central position without attaching a centroidal position regulating balance weight or the like, after reducing frequency to be expressed by the product of the number of blade sheets and rotational frequency of the impeller and noise in the higher marmonic component. CONSTITUTION:An impeller is composed of plural pieces of blade plates 9, a main plate 10 clamped to these blade plates 9, and a side plate clamped to an opposite main plate side end face of the blade plates 9, while setting angles beta1, beta2, beta3, beta4 of the blade plates 9 are set so as to differ with one another, and a centroidal position of each blade plate 9 is arranged at an equiangle gamma on the circumference of a circle of the same radius R centering on a turning shaft center of the main plate 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal blower which is used in air conditioners and the like and is designed to reduce noise.

0002

2. Description of the Related Art Centrifugal blowers have been widely used as blowers for air conditioners and the like, and there has been a particularly strong demand for low-noise blowers.

[0003] Hereinafter, with reference to the drawings,
A conventional centrifugal blower proposed in Publication No. 55098 and the like will be explained.

FIG. 4 shows the structure of a conventional centrifugal blower. In FIG. 4, 1 is an impeller, which includes a plurality of blade plates 2, a main plate 3 to which the blade plates 2 are fixed, and the blade plate 2.
It consists of a side plate 4 fixed to the end surface on the side opposite to the main plate. 5 is an electric motor directly connected to the impeller 1, and is fixed to a casing 6 that houses the impeller 1 and the electric motor 5. 7 is a suction bell mouth fitted into a suction port 6a provided in the casing 6.

FIG. 5 shows a cross section of the centrifugal blower shown in FIG. 4 taken along the line AA perpendicular to the rotation axis of the impeller 1. Also, θ1, θ2, θ3, θ4 are the rotational axis P of the main plate 3.
The figure shows the installation angle between each vane plate 2 in which the vane plate 2 is arranged at a constant angle α to the main plate 3 with .

The operation of the centrifugal blower constructed as described above will be explained below.

First, the impeller 1 is driven by the driving force of the electric motor 5.
When the air rotates, air is introduced into the impeller 1 through the suction bell mouth 7, and as it passes between the plurality of blade plates 2, static pressure and dynamic pressure are applied to it, and the air is discharged from the impeller 1 into the casing 6. Ru. Thereafter, a part of the dynamic pressure is converted into static pressure within the casing 6 and is discharged outside the casing 6 to perform a blowing action.

[0008] At this time, the peculiar noise generated during operation of the centrifugal blower, that is, the noise of the frequency represented by the product of the number Z of blades 2 and the rotational frequency N of the impeller 1 and its harmonic components (hereinafter referred to as NZ sound) ) occurs. As a means of reducing this NZ sound, a method of reducing the noise by varying the installation angles θ1, θ2, θ3, and θ4 in FIG. 5 is taken.

[0009] As a result, the appearance period of each vane plate 2 with respect to a certain spatial position changes continuously, so that the NZ sound is generated in a state dispersed within a certain range with a peak at a specific frequency, and the arrangement of the vane plate 2 changes. Depending on the state, the specific frequency value indicating the peak value may fluctuate and occur in a distributed manner. Therefore, the harmonic components of the NZ sound are also generated in a distributed manner, and it is possible to prevent each noise from being generated concentrated in one place, and it is possible to reduce the sound pressure level of the peak sound.

0010

[Problems to be Solved by the Invention] However, in the above-described configuration, since the adjacent spacing between the individual blade plates 2 is different, the center of gravity of the entire impeller 1 is located outside the rotation center of the impeller 1, and this center of gravity Rotational moment acts on the output shaft of the electric motor 5 due to the centrifugal force acting on the motor 5, causing vibrations and the like. Therefore, in order to remove this rotational moment, it is necessary to attach a balance weight for adjustment to the trailing edge of the blade plate 2 or the outer periphery of the main plate 3, and perform a troublesome adjustment process to align the center of gravity of the impeller with the center of rotation. There was a drawback that.

[0011] In view of the above problems, the present invention provides a centrifugal blower that can reduce the NZ noise and match the center of gravity of the impeller with the center of rotation without installing a balance weight or the like for adjusting the center of gravity. This is what we provide.

0012

[Means for Solving the Problems] In order to solve the above problems, a centrifugal blower of the present invention includes a plurality of blade plates, a main plate fixed to the blade plates, and a side plate fixed to an end surface of the blade plates on the side opposite to the main plate. constitute an impeller, the blade plates are set to have mounting angles different from each other, and the center of gravity of each blade plate is arranged at equal intervals on a circumference of the same radius centered on the rotation axis of the main plate. It has an arrayed configuration.

[0013]

[Operation] With this configuration, even if the centers of gravity of the individual blade plates are equally spaced on the circumference of the same radius around the rotation axis of the main plate, the actual blade exit angles of each blade plate are mutually equal. Since the arrangement is different, the velocity distribution and pressure distribution of the discharged airflow between each vane plate will be different from each other.

[0014] Therefore, by continuously changing the period of fluctuation of the pressure transmitted from each vane to a certain spatial position, the frequency expressed by the product of the number Z of vanes and the rotational frequency N of the impeller and its Harmonic component noise (hereinafter referred to as NZ sound) occurs in a state that is dispersed within a certain range with a peak at a specific frequency, and the specific frequency value that indicates the peak value varies depending on the setting of the mounting angle of each blade plate. However, it occurs in a dispersed manner. Therefore, the harmonic components of the NZ sound are also generated in a distributed manner, and it is possible to prevent each noise from being generated concentrated in one place, and it is possible to reduce the sound pressure level of the peak sound.

In addition, the center of gravity of each vane plate is arranged at equal intervals on the circumference of the same radius centered on the rotation axis of the main plate, regardless of the mounting angle of each vane plate, so that the impeller The center of gravity and the center of rotation always match, and vibrations etc. due to misalignment between the center of gravity and the center of rotation do not occur during rotation.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Incidentally, in order to avoid duplication, the same parts as in the conventional example are given the same reference numerals and the description thereof will be omitted.

FIG. 1 shows the structure of a centrifugal blower in one embodiment of the present invention. In the figure, 8 is an impeller, which includes a plurality of blade plates 9, a main plate 10 to which the blade plates 9 are fixed, and a side plate 1 fixed to the end surface of the blade plate 9 on the side opposite to the main plate.
1.

FIG. 2 shows a cross section of the centrifugal blower shown in FIG. 1 taken along the line BB, which is perpendicular to the rotation axis of the impeller 8. The center of gravity G of each blade plate 9 is arranged on the same radius R centered on the rotation axis O of the main plate 10 at an equal angle γ. Further, the mounting angles β1, β2, β3, and β4 of each blade plate 9 are set to be different from each other.

The operation of the centrifugal blower constructed as above will be explained below.

First, the impeller 8 is driven by the driving force of the electric motor 5.
When the air rotates, air is introduced into the impeller 8 through the suction bell mouth 7, and as it passes between the plurality of vanes 9, static pressure and dynamic pressure are applied thereto, and the air is discharged from the impeller 8 into the casing 6. Ru. Thereafter, a part of the dynamic pressure is converted into static pressure within the casing 6 and is discharged outside the casing 6 to perform a blowing action.

At this time, the center of gravity G of each blade plate 9 is
Although they are arranged at equal angles γ on the same radius R centered on the rotation axis O of 0, the mounting angles β1, β2, β3 of the blade plate 9
, β4 are set to be different from each other, the airflow velocity at the outlet of the blade plate 9 is determined by the mounting angles β1, β2, β3, β4.
This will vary greatly depending on the setting of each blade plate 9.
The velocity distribution and pressure distribution of the discharge airflow between the two will be different from each other.

Therefore, as shown in FIG. 3, the period T1 of the pressure fluctuation transmitted from each blade plate 9 for a certain spatial position is
T2 and T3 will change continuously, and the NZ sound will be generated in a state where it is dispersed within a certain range with the peak at a specific frequency. occurs in a distributed manner while the specific frequency value indicating the peak value fluctuates. Therefore, the NZ harmonic components are also generated in a dispersed manner, and it is possible to prevent each noise from being generated concentrated in one place, and it is possible to reduce the sound pressure level of the peak sound.

[0023] Furthermore, the center of gravity of each blade plate 9 is
Regardless of the settings of the mounting angles β1, β2, β3, and β4, since they are arranged at equal angles γ on the same radius R centering on the rotation axis O of the main plate 10, the center of gravity and the center of rotation of the impeller 8 They always match, and vibrations or the like due to a deviation between the center of gravity of the impeller 8 and the center of rotation do not occur during rotation.

As described above, by changing the mounting angle of each vane plate 9 without changing the position of the center of gravity of the impeller 8, NZ noise is reduced and vibrations during rotation are prevented.

[0025]

[Effects of the Invention] As described above, in the centrifugal blower of the present invention, the impeller is composed of a plurality of blade plates, a main plate fixed to the blade plates, and a side plate fixed to the end surface of the blade plates on the side opposite to the main plate. ,
The mounting angles of the blade plates are set to be different from each other, and the center of gravity of each blade plate is arranged at equal intervals on a circumference having the same radius around the rotation axis of the main plate.

Therefore, in addition to reducing the noise of the frequency represented by the product of the number of vanes and the rotational frequency of the impeller and its harmonic components, the balance weight for adjusting the center of gravity position, which requires complicated installation adjustment, can be used. It is possible to align the center of gravity of the impeller with the center of rotation without attaching any other equipment, and to prevent vibrations during rotation.

[Brief explanation of the drawing]

[Fig. 1] A cross-sectional view of a centrifugal blower in an embodiment of the present invention.

[Figure 2] A cross-sectional view of the essential parts of the impeller of the centrifugal blower in Figure 1 taken along line B-B

[Figure 3] Characteristic diagram showing changes in pressure outside the impeller of the centrifugal blower of the same example

[Figure 4] Cross-sectional view of a conventional centrifugal blower

[Figure 5] A sectional view of the main parts of the impeller of the centrifugal blower in Figure 4, taken along line A-A.

[Explanation of symbols]

8 Impeller 9. Feather plate 10 Main plate 11 Side plate

Claims (1)

[Claims] Claim 1: An impeller is constituted by a plurality of blade plates, a main plate fixed to the blade plates, and a side plate fixed to an end surface of the blade plates on a side opposite to the main plate, and the blade plates have different mounting angles. A centrifugal blower in which the center of gravity of each blade plate is arranged at equal intervals on a circumference of the same radius centered on the rotation axis of the main plate.