JPS61157799A - Motor driven blower - Google Patents

Abstract

PURPOSE:To achieve muffler effect of NZ noise by forming a small space between inner and outer guide walls constituting a return path of an air-guide with such length as suitable for eliminating NZ noise. CONSTITUTION:A return path 15 has a starting end 19 near the out ercircumferential section of an air-guide 17 and constructed with a guide wall 22 constituted with inner and outer guide walls 20, 21. While a small space 23 opening toward the center of the air-guide 17 is formed between said walls 20, 21. Slit communicating sections 24 are made entirely through the outer guide wall 21 to communicate between the small space 23 and the return path 15. Four of the inner guide walls 20 elongated 26 to the center ring 25 of the air guide.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Use This invention relates to an electric blower used in vacuum cleaners and the like.

BACKGROUND OF THE INVENTION Conventional electric blowers of this type are known, for example, from Japanese Patent Publication No. 52-49.
This is shown in Publication No. 168. Specifically, the structure was as shown in Figure 6.

That is, a centrifugal impeller 2. An air guide 3 is provided, and a motor 4 rotates the di-inverter 2 at high speed to obtain air volume and vacuum pressure.

Problems to be Solved by the Invention However, with such a structure in which the air guide 3 is provided on the outer periphery of the impeller 2, when the airflow discharged from the outer periphery of the impeller 2 attempts to flow into the air guide 2, ,
Noise, thought to be caused by collisions at the air guide inlet, was a problem.

Since the airflow discharged from between the blades of the impeller 2 collides with the air guide inlet, the product of the rotation speed N ("p"/6°) of the impeller 2 and the number of blades Z,
That is, a sound having a peak at NZ (Hz) was generated. This sound is commonly called NZ sound, and has become one of the major problems along with the noise caused by turbulence of airflow generated in the return passage of the air guide.

The present invention solves these problems by configuring the return passage of the air guide in a sound-deadening structure to prevent the generated noise from going outside the blower, and to improve the blowing efficiency. It is meant to be.

Means for solving the problems and technical means of the present invention for solving the above problems are as follows:
As shown below. That is, each of the guide walls forming the multi-divided return passage in the air guide is separated into an inner guide wall and an outer guide wall from the air guide outer circumference proximal chamber, which is the starting point of the guide wall. The small space created by the inner and outer guide walls opens toward the center of the air guide. Of the inner and outer double guide walls, the outer guide wall is provided with a communication part that communicates the small space with the 9 return passages, and the return passages are grouped together several times to form a large passage. As such, several of the inner guide walls are configured to extend to the center of the air guide.

action The effect of this technical means is as follows.

In other words, when the airflow that has entered the return passage flows through the return passage, even if separation occurs from the outer guide wall, air is replenished from the small space between the double guide walls through the slit, and the airflow vibration due to separation, etc. The generation of noise due to disturbances is suppressed. or.

A small space opening toward the center of the air guide constitutes a muffler, which acts as a side branch in the acoustic circuit to prevent noise from emitting outside.

Next, most of the guide walls constituting the return passage are short in length and do not extend to the center of the air guide, but several inner guide walls do extend to the center of the air guide. This elongated inner guide wall prevents circulation near the center of the air guide on the return 9 passage side, thereby improving air blowing efficiency.

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

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In Figures 1 to 4, 6 is a casing, and an intake port 6 is opened in the center of the casing, and the opposite side of this intake hole 60 is attached to a motor frame 7 to prevent air leakage. . 8 is multiple pieces.

An impeller with (2) blades and a nut 10 attached to the motor shaft 9. It is attached via a spacer 11 and a washer 12. On the outer periphery of the impeller 8, there is a diffuser section 14 consisting of a plurality of enlarged passages 13, and a return passage 16 communicating with each enlarged passage 13 of the diffuser section 14.
An air guide 1T is installed which is integrally formed with a return passage section 16 in which a return passage section 16 is formed. 18 is a motor.

The return passage 16 has a starting end 19 near the outer periphery of the air guide 17, and is narrowed by a guide wall 22 consisting of an inner guide wall 2o and an outer guide wall 21. or,
An air guide 1 is provided between the inner guide u20 and the outer guide wall 21.
A small space 23 that opens toward the center of 7 is configured.

A slit-shaped communication portion 24 is provided in most of the outer guide wall 21.
is provided to communicate the small space 23 and the return passage 16. Furthermore, the four inner guide walls 2o form long guide walls 26 that extend to the air guide center ring 25, and therefore the return passage section 16 is divided into four large parts by these long guide walls 26. It's in shape.

Next, the operation of the configuration of this embodiment will be explained. The airflow discharged from the impeller 8 passes through the diffuser section 14, enters the return passage 16, and flows into the motor 18. At this time, the airflow that has entered the return passage 15 tends to flow along the inner guide wall 20 near its entrance, so the fourth
As shown in the figure, the outer guide wall 21 side of the return passage 15 forms a negative pressure area 27 and peels off. The turbulence and vortices caused by this cause noise and reduce air blowing efficiency, but since the communication section 24 is located here, air is supplied to the separated section through the small space 23. become. Therefore, the flow will flow without losing smoothness as a whole and without generating any abnormal noise.

Moreover, when the small space 23 is converted into a simplified system, it becomes as shown in FIG. This is the side branch in the acoustic circuit that acts as a muffler. The length l of this side branch corresponds to the length of the small space 23, and l is said to be effective in muffling the sound of frequency fnr expressed by the following equation.

The problem with this type of blower is the rotation speed N of the impeller 8.
This is the NZ sound expressed as the product of (rl)m/6°) and the number of blades 2. In this example, N=470 (r
pm/e. ) and Z=9, so the sound around 423°Hz becomes a problem. Calculated from the above formula, it is approximately 20
Although it is about the same level as me, since the shape is more complex than the simple one, I decided to find the optimal value and set 1 = 14 questions. This is Nyoshi, NZ
The sound is muted.

Furthermore, the airflow that has passed through the return passage 15 is generally directed to the motor 18.
The air flows into the center of the air guide ring 2.
There is a circulation around 5, which causes something to flow. This circulation is a loss component when viewed from the blower as a whole. Since this is stopped by the long guide wall 26, the loss of the blower is reduced and the overall blowing efficiency is improved.

Effects of the Invention The present invention consists of a double guide wall that constitutes a return passage in an air guide, an inner guide wall and an outer guide wall, and a small space is provided between them, so that the length of the small space is not a problem when using a blower. By making the length suitable for silencing NZ sound, the length is suitable for silencing NZ sound, and by providing a communication part on the outer guide wall, it reduces noise caused by turbulence of airflow and makes the flow smooth. The effect of improving air blowing efficiency can be obtained, and furthermore, by extending several of the inner guide walls to the vicinity of the center of the air guide, it is possible to prevent the circulation that causes loss, thereby achieving the effect of improving air blowing efficiency.

[Brief explanation of drawings]

Fig. 1 is a back view of the air guide in one embodiment of the present invention, Fig. 2 is a partially cutaway view of the electric blower, Fig. 3 is a front view of the air guide, and Fig. 4 is an enlarged view of the guide wall. 5 is an acoustic equivalent circuit diagram of a silencer. FIG. 6 is an exploded perspective view showing a conventional example. 6... Casing, 8... Impeller,
14... Diffuser section, 16... Return passage, 1 end... Air guide, 18...
Motor, 2o... Inner guide wall, 21...
・Outer guide wall, 23...Small space, 24...
...Communication part, 25... Air guide center ring. Name of agent: Patent attorney Toshio Nakao and 1 other person5.
Keishin 18, Tanabata 14...Difage part Fig. 3 15...Decision, Ritual No. 24, Zusonto 25...Air release medium I (Gokoku, Fig. 6)

Claims (1)

[Claims] It is equipped with a centrifugal impeller, an air guide in which a diffuser part and a return passage are integrated, a casing that covers the impeller and the air guide, and a motor, and each of the guide walls forming the return passage is connected to the impeller. It consists of a double wall consisting of an outer guide wall and an inner guide wall on the rotation direction side, and a small space opening toward the center of the air guide is formed between them, and the outer guide wall has the return passage and the small space. The electric blower is provided with a communication portion that communicates the space, and further includes a part of the inner guide wall extending to an air guide center ring in the form of an annular wall provided at the center of the air guide.