JPH0613874B2 - Electric blower - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electric blower used for an electric vacuum cleaner or the like.

Configuration of Conventional Example and Its Problems In recent years, there has been a remarkable increase in output such as suction performance of household vacuum cleaners, and reduction of noise generated with it has been emphasized.

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

In FIGS. 1 and 2, 1 is an impeller, which is fixed to the shaft 3 of the electric motor 2. Reference numeral 4 denotes an air guide installed on the outer circumference of the impeller 1 and on the rear side thereof, and forms an air passage 5 for guiding the air discharged from the outer circumference of the impeller 1 to the inside of the electric motor 2. Reference numeral 6 denotes a casing, which covers the front of the impeller 1 and the outer periphery of the air guide 4 and is press-fitted into a bracket 7 of the electric motor 2 to form an air passage 5 together with the air guide 4. The casing 6 and the impeller 1 are provided with suction ports 8 and 9 at their central portions. 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. Since the impeller 1 is fixed to the shaft 3, the impeller 1 rotates together with the air, and the air is sucked into the casing 6 → the impeller → the suction port 9 of 1 → the inside of the impeller 1 → the impeller → the outer periphery of 1 → the air passage 5 of the air guide 4 → Flows from the inside of the electric motor 2 to the exhaust port 10 of the electric motor 2.

However, in the above-mentioned configuration, the high-pressure air successively rushes into the air passage 5 of the air guide 4 by the plurality of blades 11 of the impeller 1, so that the compression wave proceeds in the air passage 5. Become. In other words, this becomes noise, and this frequency is N × Z ÷ 60 (HZ) (N is 28000 rpm, Z is 11), where Z is the number of blades 11 of the impeller 1 and N (rpm) is the number of revolutions of the impeller 1. Then 280
It has a drawback that noise of 00 × 11 ÷ 60≈5133HZ) is generated.

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

In order to achieve this object, the electric blower of the present invention is configured such that guide vanes partitioning an air passage of an air guide are formed of a porous semi-permeable material, and a compression wave traveling in the air passage is formed. And the rotational speed of the impeller N (rpm), the passing flow rate Q (m ³ / sec), the cross-sectional area of the air guide inlet, A
₁ (m ² ), speed of sound C (m / sec) Number of air passages in air guide Z
₁ , the number of blades Z _{2 of} the impeller and the outer diameter D ₃ (m) of the impeller are approximately (C + Q / A ₁ ) × 60 × (2 × Z ₂ −Z ₁ ) / (2 × N × Z ₂ ) ≈ D ₃ × π
By setting so that (π≈3.14), compression waves are canceled out through the porous portion to 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, reference numeral 21 denotes an impeller, which has a suction port 22 opened in front of the central portion thereof and a plurality of blades 23 provided on the outer periphery thereof. The blade 23 is sandwiched between the front and rear sides by side plates 24 and 25, and the outer circumference 26 is open. A shaft 28 of an electric motor 27 penetrates the center of the impeller 21 and is fastened with a nut 29. An air guide 30 made of a resin molded product forms a plurality of air passages 31 on the outer circumference of the impeller 21 and below the impeller 21. The air passage 31 is partitioned by the porous guide vanes 32, and each passage is independent above the air guide 30. The air passage 31 communicates with a communication passage 33 that guides downward on the outer periphery of the air guide 30 so that air flows downwardly of 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 front of the impeller 21.
A suction port 35 facing the suction port 22 of the impeller 21 is opened at the center thereof. The casing 34 is press-fitted and fixed to the outer periphery of the bracket 36 of the electric motor 27 below the outer periphery thereof.

5 shows the back side of the air guide 30, the air passage 3 extends from the communication passage 33 toward the inside of the air guide 30.
7 and is divided by guide wings 38. The air passages 37 are divided into four groups as a whole, and are joined at their inner ends 39. The electric motor 2 facing the inner end 39
An opening 40 is provided in the bracket 36 of No. 7.

Referring again to FIG. 4, the air passage 31 is explained. The compression wave traveling in the air passage 31 and the compression wave traveling in the adjacent air passage 31 are opposite in phase to each other in the impeller. Rotational speed N (rpm), passing flow rate Q (m ³ / sec), air guide inlet cross-sectional area A
₁ (m ² ), sonic velocity C (m / sec), air passage Z ₁ of air guide, number of blades Z ₂ of impeller, outer diameter D ₃ (m) of impeller are approximately (C + Q / A ₁ ) × 60 × (2 × Z ₂ −Z ₁ ) / (2 × N × Z ₂ ) ≈D ₃ × π
It is set so that (π≈3.14).

Regarding the blower for the electric vacuum cleaner configured as described above,
The operation will be described below.

With the operation of the electric motor 27, the impeller 21 rotates together with the shaft 28. For this reason, the air flows from the suction port 35 of the casing 34 to the suction port 22 of the impeller 21 to the impeller 2.
1 flows into the inside of the unit 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 in the outer peripheral direction. The air that has entered the lower portion of the air guide 30 through the communication passage 33 flows through the air passage 37 by the guide vanes 38, and the inner end 39
→ The opening 40 of the bracket 36 → flows into the electric motor 27.

The high-pressure air pushed by the blades 23 of the impeller 21 is rotated one by one as the impeller 21 rotates.
As the air squeezes into each of the air passages 31 as it rushes into the air passage 1, the guide vanes 32 partitioning the air passages 31 are porous, and the air guide 30 and the impeller 21
Since the configuration is set to have the opposite phase to the compressional wave flowing in the adjacent air passage 31, when the dense wave advances in the air passage 31, the sparse wave advances in the adjacent air passage. The pressure difference is equalized (cancelled out) through the porous guide vanes 32 and flows into the communication passage 33. For this reason, a large noise as in the past is not generated. Further, since the airflow rushes into the air passage 31 from the outer periphery of the impeller 21 well, it flows along the porous guide vanes 32 and does not mix with the adjacent air passage 31 through the porous portion. Instead, the rectifying action of the air guide 30 is maintained as it is, and the ventilation efficiency can be maintained high.

Explaining the traveling state of the compressional wave by the blade 23 of the impeller 21, the sound propagation velocity C is the air temperature θ0 ° C.)
Then, C = 331, 5 + 0, 61 × θ (m / sec) ..., and the flow velocity V of the air in the air passage 31 of the air guide 30 is equal to the air volume Q (m ³ / sec) and the air passage 31 From the flow path cross section seat A ₂ (m ² ), V = Q / A ₁ (m / sec) and so the compression wave speed V ₁ is V ₁ = C + V (m / sec).

The time T ₁ when the dense wave enters the same air passage 31 by the rotation of the impeller 21 by the next blade 23, the rotational speed of the impeller 21 is N (rpm), the number of blades 23 is Z ₂ , and T ₁ = (60 sec / N) / Z ₂ (sec) ... and the interval L ₁ between dense waves is expressed as L ₁ = V ₁ × T ₁ (m).

There are sparse waves between the dense wave intimate wave, the interval _{L 2} of dense wave and sparse wave becomes _{L 2 = L 1/2 (} m) .......

The time T _{2 for} the dense wave of the blade 23 to enter the next air passage 31 is T ₂ = (60 sec / N) / Z ₁ (sec) ... From the number Z ₁ of the air passages 31 of the air guide 30, During T ₂ , the dense wave in the front air passage 31
The distance L ₃ is L ₃ = V ₁ × T ₂ (m) ... Since the sparse wave is delayed by L ₂ from the density, the sparse wave distance L ₄ is L ₄ = L ₃ −L ₂ (m) ... It becomes ...

The distance L ₅ between the air passage 31 and the next air passage 31 is D ₃ (m) for the outer diameter of the impeller 21, and π (≈3.14) for the pi.
Then, L ₅ = D ₃ × π / Z ₁ ... In other words, the dense wave enters the air passage 31 and its T ₂
After a certain time, the sparse wave progresses to L ₄ , and at the same time, the dense wave enters the inlet of the next air passage 31, and the next air passage 31 is behind L ₅ with respect to the previous air passage. Therefore, if L ₄ = L ₅ , the sparse waves and the dense waves are arranged side by side with the guide vanes 32 separated, and the sparse waves and the dense waves can cancel each other out through the porous portion of the guide vanes 32.

When sequentially substituting Equation ~ the _{Formula, L 4 = L 3 -L 2} = V 1 × T 2 -L 1/2 = V 1 × (60 / N) Z 1 -V 1 × T 1/2 = (C + V) × ( 60 / N) / Z 1 - (C + V) × (60 / N) / Z 2/2 = (C + Q + A 1) × (60 / N) / Z 1 - (C + Q / A 1) × (60 /
_{N) / Z 2/2 =} (C + Q / A 1) × (60 / N) (1 / Z 1 -1 / 2 × Z 2) = (C + Q / A 1 × (60 / N) (2Z 2 -Z _{1) / 2 × Z 1 ×} Z 2 L 5 = D 3 × π / Z 1 both sides in over _{Z 1 L 4 × Z 1 =} (C + Q / a 1) × 60 × (2 × Z 2 -Z 1 ) / (2 × N × Z ₂ ) L ₅ + Z ₁ = D ₃ × π, so (C + Q / A ₁ ) × 60 × (2 × Z ₂ −Z ₁ ) / (2 × N × Z ₂ ) = D ₃ × π …… When sparse and dense waves line up.

Since the vacuum cleaner is usually used at room temperature (20 ° C),
When θ = 20 ° C, C ≈ 340 m / sec, and the flow rate Q is 1.8 m ³ / min, that is, Q ≈ 1.8 (m ³ /min)=0.03 (m ³ / sec) is common. is there. The flow passage cross-sectional area A ₁ of the air guide is about 35.
A performance of about 0 mm ² results in A ₁ ≈3.50 × 10 m ^-4 m ² . In this embodiment, the number of impeller blades Z ₂ =
11. When the number of air passages in the air guide is set to Z ₁ = 16 and the formula is calculated, it becomes D ₃ = 2218 / N ......, and when the rotation speed is set to 26000 rpm, D ₃ ≈0.085m≈85mm and the outer diameter of the impeller Should be set to 85 mm.

If the number of impeller blades is Z ₂ = 13, then D ₃ = 3
129 / N, and if N = 28,000 rpm, D ₃
≒ 112mm is good.

In this embodiment, the guide vanes 32 are made of resin and made porous. However, even if the guide vanes 32 are made of ceramic or the like, the noise reduction effect can be similarly maintained.

As described above, according to the present invention, the guide vanes partitioning the air passage of the air guide are made porous, and the constants of the air guide and the impeller are selected to make the phase of the compression wave opposite to that of the adjacent air passage. In this way, it is possible to provide an electric blower that reduces noise while maintaining a high blowing efficiency, and the effect is great.

[Brief description of drawings]

1 is a longitudinal sectional view of a conventional electric blower, FIG. 2 is a transverse sectional view thereof, FIG. 3 is a partial longitudinal sectional view of an electric blower in an embodiment of the present invention, and FIG. 4 is a transverse sectional view thereof. FIG. 5 is a rear view of the air guide. 21 ... Impeller, 23 ... Blade, 27 ... Electric motor, 30 ... Air guide, 32 ... Guide vane, 34 ... Casing.

Claims (3)

[Claims] 1. An impeller driven by an electric motor, an air guide installed on the outer circumference of the impeller and at the rear, and a casing covering the impeller and the air guide. The impeller outer peripheral portion of the air guide is separated from the impeller. Has a plurality of guide vanes that form an air passage for guiding the air into the electric motor. The guide vanes are made of a porous material, and the number of revolutions of the impeller is N, the air flow rate is Q, and the air flow rate is Q. When the inlet cross-sectional area (flow passage cross-sectional area) of the guide is A ₁ , the sound velocity is C, the number of air passages in the air guide is Z ₁ , the number of impeller blades is Z ₂ , and the outer diameter of the impeller is D ₃ , then (C + Q / A ₁ ) × 60 × (2 × Z ₂ −Z ₁ ) / (2 × N × Z ₂ ) ≈D ₃ × π. 2. The electric blower according to claim 1, wherein the flow rate Q is about 0.03 m ³ / sec. 3. A flow path cross-sectional area A ₁ of about 3.50 × 10 ⁻⁴ m ² ,
Number of air passages Z _{1 is 8} to 20, blade number Z ₂ is 7 to 15
The electric blower according to claim 1, wherein the electric blower is set.