JPS6198998A - Electric fan - Google Patents

Abstract

PURPOSE:To lessen noises by grouping air passages in a pair of two at the back of an air guide, providing air passages in a double of blade number for reversing the phases of non-dense waves coming out of one air passage and those out of another air passage for their cancellation. CONSTITUTION:A connection passage 33 to an air passage 31 is continuous to another air passage 37 directed toward the inside of an air guide 30 and divided by a guide vane 38. The air passage 37 is arranged in a pair of two and comprises eight groups, joining to each other at their internal end 39. Consequently, non-dense waves of air pass through the inside of each air passage 31 with the rotation of an impeller 21. The number Z of the air passages is set to sixteen and the number Z2 of blades 23 of the impeller 21 set to eight, respectively. When dense waves enter in a primary air passage 31, therefore, non-dense waves enter in its adjacent air passage 31 and dense waves in another adjacent air passage 31. This flow of dense and non-dense waves occurs alternately in the air passage 31. The flows of each air join together at the internal end 39 and dense and non-dense waves cancel each other, thereby making it possible to lessen noises.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electric blower used in a vacuum cleaner or the like.

Conventional configurations and their problems In recent years, the suction performance of household vacuum cleaners has increased dramatically, and the reduction of the noise generated has become important.

A conventional electric blower for a vacuum cleaner will be described below with reference to the drawings.

In Figures 1 and 2, 1 is an impeller, and electric motor 2
It is fixed to the shaft 3 of. Reference numeral 4 denotes an air guide installed on the outer periphery and rear of the impeller 1, and an air passage 5 that guides air discharged from the outer periphery of the impeller 1 into the inside of the electric motor 2.
is formed. A casing 6 is press-fitted into a placket 7 of the electric motor 2 so as to cover the front of the impeller 1 and the outer periphery of the air kite 4, and forms the air passage 5 together with the air guide 4. Suction ports 8 and 9 are opened in the center of the casing 6 and the impeller 1. Further, an exhaust port 1o is opened at the rear of the electric motor 2.

In the above configuration, as the electric motor 2 operates, the shaft 3 rotates. The impeller 1 is fixed to the shaft 3 and rotates together, and the air is supplied to the suction port 8 of the casing 6.
- Suction port 9 of impeller 1 - Inside of impeller 1 - Outer periphery of inflator 1 - Air passage 5 of air guide 4 - Inside of electric motor 2 - Flows to exhaust port 1o of electric motor 2.

However, in the above configuration, high-pressure air is forced into the air passage 6 of the air guide 4 one after another by the plurality of blades 11 of the impeller 1, and compression waves proceed through the air passage 5. Become. In other words, this becomes noise, and its frequency is NxZ+αO(H2), where the number of blades 11 of impeller 1 is 21 and the number of rotations of impeller 1 is N (r p m ). (If N is 2800 Or p m and Z is 11 blades, then , 28000×11÷60 dust 5133H2).

OBJECTS OF THE INVENTION In view of the above drawbacks, the present invention provides an electric blower with reduced noise.

Structure of the Invention In order to achieve this object, the electric blower of the present invention groups the air passages in two sets on the back side of the air guide, and the compression waves coming out from one air passage and the air passage from the other air passage. The number of air passages in the air guide is 21, and the number of blades in the impeller is Z so that the phase of the compression waves coming out of the
2 to cancel out the compressional waves and reduce noise.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 3 and 4, 21 is an impeller, a suction port 22 is opened at the front of the central portion thereof, and a plurality of blades 23 are arranged around the outer periphery of the impeller. The blade 23 is sandwiched between the side plates 24 and 25 on both front and rear sides, and the outer circumference 2
6 is open. A shaft 28 of an electric motor 27 penetrates into the center of the impeller 21 and is fastened with a nut 29. Reference numeral 30 denotes an air guide made of an abortifacient molded product, which forms a plurality of air passages 31 around the outer periphery of the impeller 21 and below it. The air passages 31 are divided by porous guide vanes 32, and each passage is independent above the air guide 3o. The upper air passage 31 communicates with a communication passage 33 leading downward on the outer periphery of the air guide 3o, and the air passes through the air guide 3o.
0 It is designed to flow downward. The casing 34 covers the outer periphery of the air guide 30, forms an air passage 31 together with the air guide 30, and also covers the front of the impeller 21, with a suction port 35 facing the suction port 22 of the impeller 21 opening in the center thereof. ing. The casing 34 is press-fitted and secured to the outer periphery of a placket 36 of the electric motor 27 at its lower outer periphery.

When the back side of the air guide 30 is shown in FIG.
7 and is partitioned by guide wings 38. The air passages 37 are divided into eight groups, each consisting of two pairs, and are joined at their inner ends 39. This inner end 3
An opening 4o is provided in the placket 36 of the electric motor 27 opposite to the opening 4o.
is provided.

Regarding the vacuum cleaner blower configured as above,
The operation will be explained below.

As the electric motor 27 operates, the impeller 21 rotates together with the shaft 28. Therefore, air flows from the suction port 35 of the casing 34 to the suction port 22 of the impeller 21 - the impeller 2
1, is pushed by the blade 23, and is discharged from the outer periphery 26. Further, the air is guided by the guide vanes 32 of the air guide 30 and flows through the air passage 31 toward the outer circumference. The air that has entered the lower part of the air guide 30 through the communication passage 33 flows through the air passage 37 due to the guide vanes 38, and then flows through the inner end 39.
- opening 40 in the placket 36 - flow into the interior of the motor 27;

As the impeller 21 rotates, high-pressure air pushed by the blades 23 of the impeller 21 flows into the air passage 3 one after another.
1, air compression waves advance inside each air passage 31, but since the number 21 of air passages 31 is 16 and the number 22 of blades 23 of the impeller 21 is 8, When a sound wave enters one air passage 31, a lyophobic wave enters the adjacent air passage 31, and a sound wave and a lyophobic wave alternately and simultaneously enter the air passage 31 next to it, as if it were a sound wave. Therefore, from the air passage 37 on the back side of the air guide 30 to the inner end 3
Dense waves and lyophobic waves enter 9 at the same time, inner end 39
The two air passages 37 are grouped together, the air flows merge, and the dense waves and lyophobic waves cancel each other out. This reduces noise.

Note that if the number of air passages is too small, the width of the air passage 37 will become large and the air will not mix well at the inner end 39, so that the dense waves and the lyophobic will not cancel each other out and the noise will not be reduced. In fact, the phase may overlap with the neighboring compression waves, making the noise even louder. For this reason, it is desirable that the number Z1 of air passages is large, but if it is too large, the number of guide vanes 32, 38 will increase, and the cross-sectional area of the air passages 31, 37 cannot be secured due to their thickness. When the air guide is made of a resin molded product, the thickness of the guide vane is required to be about 0.8 to 2.5 gates, so Zl is 12 to 24.
Depending on the degree.

In addition, the number of blades Z2 is also selected to be about 7 to 15 due to the air blowing efficiency of the impeller, and since Z′S: 2 × 22, Z
is preferably 14 to 24, and Z2 is preferably about 7 to 12.

Note that the air passages 37 merge at the inner end 39, but since the air flow flows along the inner wall of the guide vane 38, the merging point also shifts to the air passage 37 from the outside.

Therefore, since the compression wave in the air passage 37 from the inside has to travel a longer distance than the air passage 37 from the outside,
In order to reverse the phase of the compression waves and cancel them out successfully, it is necessary to advance the phase of the inner air passage to some extent.

For this purpose, the number Z of blades 23 of the impeller 21 is
2 should be slightly larger than 21=2×22.

In other words, Z2=Z1/2+α It is sufficient to set α=0 to 1.

Effects of the Invention As described above, the present invention sets the number of air passages in the air guide to an even number, merges two sets of air passages on the back side of the air guide, and sets the number of impeller blades Z2 to the number of air passages in the air guide. 21, Z2=Z1/2+α (α
= 0 to 1), the compression waves can be canceled out at the convergence section on the back side of the air guide to reduce noise, which has a great effect.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a conventional electric blower, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a partial vertical cross-sectional view of an electric blower according to an embodiment of the present invention, and FIG. Figure 5 is a back view of the air guide. 21...Inbear, 23...Blade,
27...Electric motor, 30...Air guide, 3
2... Guide vane, 34... Casing,
37... Air passage, 38... Guide vane, 39
...inner end. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 5

Claims (2)

[Claims] (1) An impeller driven by an electric motor and an even number of air passages that guide air from the impeller into the inside of the electric motor are provided on the outer periphery of the impeller and on the back side of the impeller, and two air passages are merged at the end of the air passages on the back side. An electric blower comprising a guide and a casing that covers the air guide, and where the number of air passages is Z_1 and the number of impeller blades is Z_2, Z_2=Z_1/2+α (α=0 to 1). (2) The electric blower according to claim 1, wherein Z_1 is set to an even number from 14 to 24.