JPH0549839B2 - - Google Patents

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 noise generated along with this 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;
It is fixed to the shaft 3 of the electric motor 2. 4 is an air guide installed around and behind the impeller 1;
An air passage 5 is formed that guides air discharged from the outer periphery of the impeller 1 into the inside of the electric motor 2. 6
is a casing which is press-fitted into the bracket 7 of the electric motor 2 so as to cover the front of the impeller 1 and the outer periphery of the air guide 4, and forms the air passage 5 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 10 is opened at the rear of the electric motor 2.

In the above configuration, the shaft 3 rotates as the electric motor 2 operates. Impeller 1 is shaft 3
Since it is fixed to the
→ inside the impeller 1 → outer periphery of the impeller 1 → air passage 5 of the air guide 4 → inside the electric motor 2 → flows to the exhaust port 10 of the electric motor 2.

However, in the above configuration, high-pressure air is forced into the air passage 5 of the air guide 4 one after another by the plurality of blades 11 of the impeller 1, so that compressional waves proceed through the air passage 5. Become. In other words, this becomes noise, and the frequency is N x Z ÷ 60 (HZ), where Z is the number of blades 11 of impeller 1 and N (rpm) is the rotation speed of impeller 1. (If N is 28000 rpm and Z is 11 blades, then , 28000×11
It had the disadvantage of generating noise of ÷60≒5133HZ).

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 into two sets on the back side of the air guide, so that compression waves coming out of one air passage and compression waves coming out of the other air passage are The number of air passages in the air guide is Z ₁ so that the phase of the compression waves coming out of the air guide is reversed.
is twice the number of impeller blades Z ₂ ,
This is intended to reduce noise by canceling out compressional waves.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In Figures 3 and 4, 21
1 is an impeller, and a suction port 22 is opened in the front of the central portion thereof, and a plurality of blades 23 are provided on the outer periphery of the impeller. The blade 23 has side plates 2 on both its front and rear sides.
4 and 25, and the outer periphery 26 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 a resin 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 30. The upper air passage 31 communicates with a communicating passage 33 leading downward at the outer periphery of the air guide 30, so that air flows downward through the air guide 30. 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 impeller 2.
It also covers the front of 1, and the impeller 21 is installed in the center of it.
A suction port 35 facing the suction port 22 is open. The casing 34 is connected to the electric motor 27 below its outer periphery.
It is press-fitted into the outer periphery of the bracket 36 and is fixed therein.

When the back side of the air guide 30 is shown in FIG. 5, the air passage is connected from the communication passage 33 to an air passage 37 heading inside the air guide 30, 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. Opposed to this inner end 39 is an opening 40 in the bracket 36 of the motor 27.

The operation of the vacuum cleaner blower configured as described above will be described below.

As the electric motor 27 operates, the impeller 21 rotates together with the shaft 28. Therefore, the air flows from the suction port 35 of the casing 34 to the suction port 22 of the impeller 21 to the inside of the impeller 21, is pushed by the blades 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 by the guide vanes 38, and is routed from the inner end 39 to the opening 40 of the bracket 36 to the electric motor 2.
7 flows inside.

The high-pressure air pushed by the blades 23 of the impeller 21 rushes into the air passages 31 one after another as the impeller 21 rotates, so air compression waves progress inside each air passage 31.
Since the number Z ₁ of the air passages 31 is 16 and the number Z ₂ of the blades 23 of the impeller 21 is 8, when a dense wave enters the first air passage 31, a coarse wave enters the adjacent air passage 31. Next to it, dense waves and sparse waves alternately and simultaneously enter the air passage 31, as if they were dense waves. Therefore, dense waves and coarse waves simultaneously enter from the air passage 37 on the back side of the air guide 30 to the inner end 39, and the two air passages 37 are grouped at the inner end 39, and the air flows merge. , the dense waves and sparse 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 becomes large and the air does not mix well at the inner end 39, so that dense waves and coarse waves do not cancel each other out well and noise is not reduced. In fact, the phase may overlap with the adjacent compression waves, making the noise even louder. For this, the number of air passages Z ₁
It is better to have more, but if there are too many, guide wings 3
The number of air passages 2 and 38 increases, and the cross-sectional area of the air passages 31 and 37 cannot be ensured due to their wall thickness.
When forming the air guide with a resin molded product, the wall thickness of the guide vane must be approximately 0.8 to 2.5 mm, so Z ₁ is 12
~24 are selected.

Further, the number of blades Z ₂ is also selected to be about 7 to 15 because of the air blowing efficiency of the impeller, and since Z ₁ ≈2×Z ₂ , Z ₁ is preferably about 14 to 24, and Z ₂ is about 7 to 12.

Note that although the air passages 37 merge at the inner end 39,
Since the airflow flows along the inner wall of the guide vane 38,
The merging point is also shifted to the air passage 37 from the outside. Therefore, the compression waves in the air passage 37 from the inside must travel a longer distance than those in the air passage 37 from the outside, so in order to reverse the phase of the compression waves and cancel them out successfully, it is necessary to It becomes necessary to advance the phase somewhat. For this purpose, the number Z ₂ of the blades 23 of the impeller 21 is Z ₁ = 2 x Z ₂
It would be better to have a little more.

In other words, it is sufficient to set Z ₂ =Z ₁ /2+a 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 Z ₂ to an even number. For the number Z ₁ , Z ₂ = Z ₁ /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, and the noise can be reduced, and the effect is very large. be.

[Brief explanation of drawings]

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... Impeller, 23... Blade, 27
... Electric motor, 30 ... Air guide, 32 ... Guide vane, 34 ... Casing, 37 ... Air passage, 3
8... Guide wing, 39... Inner end.

Claims (1)

[Claims] 1. An impeller driven by an electric motor, and an even number of air passages for guiding air from the impeller into the inside of the electric motor, on the outer periphery of the impeller and on the back side thereof, and two air passages at the ends of the air passages on the back side. It is equipped with a merging air guide and a casing that covers the air guide, and when 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) Electric blower set to . 2. The electric blower according to claim 1, wherein _Z1 is set to an even number from 14 to 24.