JPS61182497A - Motor-driven blower - Google Patents

Abstract

PURPOSE:To form an air stream in a smooth flow so as to prevent exfoliation and improve a silencing effect and efficiency, by forming between inner and outer guide walls a spaced part closing its end part while providing a communication part, which connects said spaced part with a return passage, in the inner and outer guide walls. CONSTITUTION:A blower sets between inner and outer guide walls 22, 23 a spaced part 25 closing its end part further forms a communication part 26, which connects the spaced part 25 with a return passage 20, in the inner and outer guide walls 22, 23. In this way, even if the outer guide wall 23 comes to easily generate exfoliation of an air stream, air is supplied from the spaced part 25 through the communication part 26. This supply of air, holding the air stream to be balanced, prevents exfoliation in the vicinity of the outer guide wall 23. The air is supplied from the communication part 26 of the inner guide wall 22, and the blower, smoothly supplying air along the inner guide wall 22 because the air is supplemented to the spaced part 25 from a communication hole 26 of the inner guide wall 22, improves also efficiency. While by the above constitution, the blower, serving in the spaced part 25 for silencing a noise with the communication part 26 being as an inlet, enables the noise to be reduced to a low level.

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.

BACKGROUND OF THE INVENTION Conventional electric blowers of this type are known, for example, from Japanese Patent Publication No. 52-49.
It is shown in the No. 168 publication.

That is, as shown in FIG. 7, an impeller 2. An air guide 3 is provided, and an 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, there is a problem at 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 N (rpm) of the impeller 2, and is commonly called NZ sound. Also, the efficiency of the blower depends on how smoothly the airflow is caused.

The present invention solves these problems by providing an improved configuration of the air guide return passage itself.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to provide a guide wall that constitutes the return passage of the air guide.

In addition to forming an outer guide wall, a space with a closed end is set between these walls, and a communication part is formed in the inner and outer guide walls to communicate the space and the return passage.

For production 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.

Further, when the airflow from the diffuser flows through the return passage, even if separation occurs from the outer guide wall, air is supplied through the communication portion, so that the balance of the airflow is maintained and separation can be prevented. Therefore, the airflow flows smoothly through the return passage without being disturbed.

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

In FIGS. 1 to 3, 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. The impeller 11 and the air guide 14 have an intake port 15 on the top wall thereof, and are enclosed in a casing 17 which is airtightly attached to the lower part of the peripheral wall of the motor frame 16.

The air guide 14 has a plurality of diffusers 18 on its upper surface that receive the air flow sent out from the impeller 11 and whose passage area is gradually expanded toward the downstream side, and a lower surface that smoothly communicates with the terminal end of the diffuser 18, and has a motor. frame 1
A plurality of return passages 2 guiding airflow to the motor intake holes 19 of 6
o. In this embodiment, the side of the diffuser 18 is closed with a part of the casing 17 to separate it from the outside, but if it is a thank you note, the diffuser 18 can be formed independently of the casing 17.

A curved guide wall 21 defining each return passage 20 is divided into an inner guide wall 22 and an outer guide wall 23, and a space 26 with a closed end is formed between them. In addition, the inner and outer guide walls 22 and 23 have slit-like communication portions 2 that communicate the space portion 26 with the adjacent return passage 20.
6 is a provision.

This communication part 26 has a width of 1WrM and a depth of about 4 cm.
One inner guide wall 22 and a plurality of outer guide walls 23 are formed. Of course, the number is not specified.

Next, the operation of the configuration of the embodiment will be explained. The airflow from the diffuser 18 flows independently into the communicating 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 2o. 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 in the return passage 2o very unstable, resulting in a decrease in efficiency with large losses. 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 26 is inserted inside.

It was provided on the outer guide walls 22 and 23 to prevent separation of airflow. As shown in FIG.
Air is supplied from the space 26 through the space. This supply of air maintains the balance of the airflow near the outer guide wall 23 and prevents separation.

Air is replenished through the communication portion 26 of the inner guide wall 22. Since the space 26 can be replenished with air through the communication hole 26 of the inner guide wall 22, it can be smoothly carried out along the inner guide wall 22, leading to improved efficiency.

Next, considering part A in FIG. 1, the communication part 2 of the inner guide wall 22
6 can be replaced with a simplified diagrammatic system as shown in FIG. 4 with the entry point. This is known as a muffler or side branch in an acoustic circuit. Therefore, this space 26 has the role of muffling sound. In particular, if the frequency to be silenced is fN, then the length l of the space 25 is
is l= (2N-1)oC/4-fN(N-・-1,2
,3.

・・・・・・C...Sound speed) is given by

As mentioned above, the noise from electric blowers that is particularly problematic is called NZ sound. The NZ sound is 5.3 in this study.
It occurs around KHz. It is also very distracting to the sense of hearing. As a result of the study with the guide wall 21 of this example provided, it was possible to reduce the NZ sound. The frequency analysis table is shown in Figure 5. NZ sound (5,3K
Hz) is decreasing. Overall noise is also lower. The number of swords determined by the above formula was 1 Ryodan. After that, a study was carried out and l=14 mm was obtained. This is considered to be an effect of the curvature of the space 25.

Effects of the Invention As described above, according to the present invention, by improving the guide wall on the return passage side of the air guide, it is possible to reduce noise, which is a particular problem with fans, and to make the flow smooth in the return passage section. This is a device that can increase fan efficiency and has great effects.

[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 plan view of the entire air guide, and FIG. 3 is a partially cutaway side view of the entire electric blower. FIG. 4 is an action explanatory diagram, FIGS. 6 and 6 are frequency analysis diagrams of an embodiment of the present invention and a conventional example, respectively, and FIG. 7 is a diagram of a conventional electric blower. 11... Impeller, 12... Motor,
14. River...Air guide, 17. Mountain/Casing, 2
o... River/return passage, 21... Guide wall, 22
・・・・・・Inner guide wall, 23：Outer guide wall, 26・Old：Space part, 26：River：Communication part. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
rl! J
t4-ryr4L-zuδ---D4
Fuyude/4---1 type f7---γ-shishiku 1 Fig. 4) ++ Ward C= beg U) Extinction Fig. 7

Claims (1)

[Claims] It includes 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, and 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 end of the space is An electric blower that is closed and has a communication part formed in the inner and outer guide walls to communicate this space with the return passage.