JPS61157798A - Motor driven blower - Google Patents

Abstract

PURPOSE:To reduce noise while to improve the blow efficiency by setting a space section between inner and outer guide walls constituting the return path of an air-guide while forming a communicating section between the space section and the return path through the outer guide wall. CONSTITUTION:The curved guide wall 21 for partitioning respective return path 20 is separated into inner and outer guide walls 22, 23 to form a space section 25 set with an opening 24 at the inner end between them. While a slit section 26 for communicating between the space section 25 and an adjoining return path 20 is made through the outer guide wall 23. Consequently, the space section formed with the inner and outer guide walls will constitute a muffler for blocking noise. While when the air flow from a diffuser will flow through the return path, air is fed from the space section to balance the air flow thus to prevent separation.

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.

2. Description of the Related Art Conventional electric blowers of this type include one example: Japanese Patent Publication No. 62-49.
It is shown in the No. 168 publication.

That is, inside the casing 1 as shown in FIG.

An impeller 2 and an air guide 3 are provided, and the impeller 2 is rotated at high speed by a motor 4 to obtain air volume and vacuum pressure.

Problems to be Solved by the Invention When the air guide 3 is provided on the outer periphery of the impeller 2 like the above-mentioned electric blower, when the airflow discharged from the impeller 2 flows into the air guide 3, the air guide inlet Noise thought to be caused by collisions was a problem. This occurs as a product of the number of blades Z of the impeller 2 and the rotation speed NDpm of the impeller 2, and is commonly referred to as NZ sound. Also, the efficiency of a blower varies depending on how smoothly the airflow flows.

The present invention is intended to solve these problems, and includes an improved configuration of the air guide return passage itself.

A foolproof way to solve problems The technical means of the present invention to solve the above problems is as follows.

Inside the guide wall that forms the air guide return passage.

It is formed of an outer guide wall, and a space having an opening at the inner end is set between these walls, and a communication part is formed in the outer guide wall to communicate the space and the return passage.

action This technical means works as follows.

That is, the space formed by the inner guide and the outer guide wall constitutes a muffler and serves as a side branch in the acoustic circuit, preventing noise generated at the air guide entrance from going outside.

Furthermore, when the airflow from the diffuser flows through the return passage, even if separation occurs from the outer guide wall, air is supplied from the space through the communication section.

The balance of airflow is maintained and separation can be prevented.

Therefore, the airflow flows smoothly through the return passage without being disturbed.

As a result, an electric blower with high efficiency and low noise level is obtained.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 4, a centrifugal impeller 11 having a plurality of blades is attached to a shaft 13 of a motor 12, and an air guide 14 is disposed on the blowing side of the impeller 11. The impeller 11 and the air guide 14 have an intake port 15 on the top wall thereof, and are surrounded by a casing 17 which is airtightly attached to the motor frame 16 at the lower part of its peripheral wall.

The air guide 14 has a plurality of diffusers 18 on its upper surface that receive the air flow sent out by the impeller 11 and whose passage area is gradually expanded toward the downstream side.

The lower surface smoothly communicates with the end of the diffuser 18,
The motor frame 16 has a plurality of return passages 2Of for guiding airflow to the motor intake hole 19 of the motor frame 16. In this embodiment, the entire side casing 17 of the diffuser 18
It is closed with a part of the wall and separated from the outside, but if you use it as a thank you note,
The diffuser 18 can be formed independently of the housing 17.

The curved guide wall 21 that partitions each return passage 20 is divided into an inner guide wall 22 and an outer guide wall 23, and a space 25 with an opening 24 set at the inner end is formed between them. be. In addition, this space 25 is provided in the outer guide wall 23.
A slit-like communication s that communicates with the adjacent return passage 20
26 is provided. This communication portion 26 has a width of 1 and a depth of 4w.
A plurality of them are formed for one outer guide wall 23. Of course, the number is not specified.

Next, the entire operation of the configuration of this embodiment will be explained. The airflow from the diffuser 18 flows independently into the communicating shear return passageway 20, but tends to flow primarily along the inner guide wall 22. Therefore, the airflow tends to move away from the outer guide wall 23 in the return passage 2Q. This causes separation, resulting in flow turbulence and a dead water area near the outer guide wall 23. The turbulence makes the flow of air within the return passage 20 very unstable, resulting in increased losses and reduced efficiency. At the same time, the flow due to turbulence also leads to the generation of noise.

In particular, blowers used in vacuum cleaners have a wide range of operating flow rates, and when the flow rate m decreases, the flow imbalance becomes large. Therefore, a communication portion 26 was provided on the outer guide wall 23 to prevent separation of the airflow. As a function thereof, as shown in FIG. 1, even if separation of airflow is likely to occur from the outer guide wall 23, air is supplied from the space 25 through the entire communication portion 26. This supply of air maintains the equilibrium of the airflow near the outer guide wall 23 and prevents separation. Air is replenished through the opening 24 provided at the inner end of the space 26. As a result, good flow was obtained in all flow ranges. The results obtained are shown in FIG. As is clearer from the figure, the communication portion 26 is effective in preventing flow turbulence and allowing the air to flow completely smoothly. Although Fig. 8 shows an efficiency of 1.12 m3/m2, similar results are obtained over the entire flow range.

Next, if we consider part A of Figure 1, it will be simplified as shown in Figure 5.

Replaced with a different schematized system. This is known as a muffler or side branch in an acoustic circuit. Therefore, this space 25 has the role of muffling the sound. In particular, if the frequency you want to mute is fN, then the length of the space 26 β multiplied by 1 = (2N-1) -G
/a -fn(N...1.2,3.....C
...Sound speed).

As mentioned above, a particularly problematic type of noise from electric blowers is called NZ sound. The NZ sound is 5.3 in this study.
It is occurring near KIIz. It is also very harsh on the ears. As a result of the study with the guide wall 21 of this example provided, it was possible to reduce the nz sound. Frequency analysis tables are shown in Figures 6 and 7. From the figure, the nz sound (5,3Ktlz
(nearby) is decreasing. Overall noise is also lower. When calculated using the above formula, l was 17 chu. After that, consider β
=14rwm was obtained. This is considered to be an effect of the curvature of the space 25. Further, if the communicating portions 26 are considered as the entrances of side branches, they can be further regarded as having as many side branches as there are communicating portions 26, and various effects on noise can be expected.

Effects of the Invention As described above, according to the present invention, it is possible to reduce noise, which is a particular problem with fans, and to improve the efficiency of the fan by smoothing the flow in the return passage. be.

[Brief explanation of drawings]

Fig. 1 is an enlarged view of the air guide return passage of an electric blower showing an embodiment of the present invention, Fig. 2 is a back view of the entire air guide, Fig. 3 is a plan view of the same, and Fig. 4 is the entire electric blower. Partially cutaway side view of Figure 5 shows the action 11 of the impeller.
12...Motor, 14...Air guide, 17...Casing, 20...Return passage, 21...Guide wall, 22... ...Inner guide wall, 23...Outer guide wall, 24...Opening, 25...Space, 26...Communication. Fig. 1 Fig. 2 Fig. 3 I4 Air 71” A F. Fig. 4 Fig. 5

Claims (2)

[Claims] (1) A centrifugal impeller driven by a motor, a plurality of diffusers through which the airflow sent out from the impeller flows, and an air guide having a plurality of return passages that guide the airflow to the motor, these impellers, and the air guide. The return passage is divided into an inner guide wall and an outer guide wall, and is partitioned by a guide wall with a space formed between the inner and outer guide walls, and the inner end of the space An electric blower is provided with an opening in the outer guide wall, and a communication part is formed in the outer guide wall to communicate this space with the return passage. (2) The electric blower according to claim 1, wherein the communication portion is slit-shaped.