JPH0511239B2 - - 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 technology Conventional electric blowers of this type are, for example,
This is shown in Publication No.-49168.

That is, as shown in FIG. 9, an impeller 2 and an air guide 3 are provided in a casing 1, 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 In a structure in which the air guide 3 is provided on the outer periphery of the impeller 2 like the electric blower described above, 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 is the number of blades Z of impeller 2 and the rotation speed N of impeller 2.
(rpm) and is commonly called the NZ sound. Also, the efficiency of the blower varies depending on how smoothly the airflow is caused.

The present invention solves these problems,
The air guide return passage itself has been improved.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to form the guide wall constituting the return passage of the air guide with an inner and outer guide wall, and to form an inner guide wall between the inner and outer guide walls. A space having an opening at the end is set, and a communication part is formed in the outer guide wall to communicate the space and the return passage.

Effect 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 diff user flows through the return passage, even if separation occurs from the outer guide wall, air is supplied from the space through the communication part.
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.

Embodiments Hereinafter, embodiments of the present invention will be described 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. be. These impellers 11 and air guides 14 have air intake ports 15 on the top wall.
and a casing 17 whose lower peripheral wall is airtightly attached to the motor frame 16.
is surrounded by.

The air guide 14 has an impeller 1 on its upper surface.
A plurality of differential users 18 receive the airflow sent out from the airflow source 1 and gradually expand the passage area toward the downstream side.
communicates smoothly with the terminal end of the differential user 18 on the lower surface, and the motor intake hole 1 of the motor frame 16.
Each of the return passages 20 has a plurality of return passages 20 that guide airflow to the air passages 9 . In this embodiment, the side of the differential user 18 is closed with a part of the casing 17 to separate it from the outside.
Diff user 18 can be formed independently of 7.

Curved guide wall 2 that partitions each return passage 20
1 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. In addition, the outer guide wall 23 has this space 25 and the adjacent return passage 2.
A slit-shaped communication portion 26 is provided to communicate with 0. The communication portions 26 have a width of about 1 mm and a depth of about 4 mm, and a plurality of these communication portions 26 are formed for one outer guide wall 23. Of course, the number is not specified.

Next, the operation of the configuration of this embodiment will be explained. The airflow from the diff user 18 flows into the independently communicating return passage 20, but tends to flow mainly along the inner guide wall 22. Therefore, in the return passage 20, the airflow tends to move away from the outer guide wall 23. 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 operating flow rate range, and when the flow rate decreases, the imbalance in flow becomes large. Therefore, the communication part 2
6 was provided on the outer guide wall 23 to prevent separation of airflow. As a function thereof, as shown in FIG. 1, even if separation of airflow is more likely to occur from the outer guide wall 23, air is supplied from the space 25 through the communication portion 26. This supply of air maintains the balance 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 25. 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 making the airflow flow smoothly. Figure 8 shows an efficiency of 1.12m ² /m.
Similar results were obtained over the entire flow range.

Next, considering part A in Figure 1, it can be replaced with a simplified diagrammatic system as shown in Figure 5. This is known as a muffler or side branch in an acoustic circuit. Therefore, this space 25 has the role of muffling sound. In particular, if the frequency to be silenced is f _N , the length l of the space section 25 is given by l = (2N-1)・C/4・f _N (N...1, 2, 3,...C...sound speed) .

As mentioned above, a particularly problematic type of noise from electric blowers is called NZ noise. In this study, the NZ sound occurs around 5.3KHz. It is also very harsh on the ears. As a result of the study with the guide wall 21 of this embodiment 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 (around 5.3KHz) has decreased.
Overall noise level is also lower. When calculated using the above formula, l is
It became 17mm. After that, we conducted a study and obtained l=14mm. 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 effects on various noises 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 the drawing]

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. Fig. 5 is a diagram explaining the operation, Fig. 6 and Fig. 7 are sound frequency analysis diagrams, Fig. 8 is a diagram showing the relationship between the presence or absence of a communication part and efficiency, and Fig. 9 is a conventional diagram. FIG. 3 is a side view of the electric blower. 11... 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 part, 26... communication part.

Claims (1)

[Claims] 1. A centrifugal impeller driven by a motor, a plurality of diff users 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; 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. An electric blower is provided with an opening at the inner end of the section, and a communication section is formed in the outer guide wall to communicate the space with the return passage. 2. The electric blower according to claim 1, wherein the communication portion is slit-shaped.