JPS647239B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This 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,
- Shown in Publication No. 49168. Specifically, the 6th
The structure was as shown in the figure.

That is, a centrifugal 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 However, such an air guide 3 is
With the structure installed 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 that is thought to be caused by collision at the air guide inlet has become a problem. Ta.

In other words, since the airflow discharged from between each blade in the impeller 2 collides with the air guide inlet,
A sound was generated that had a peak at the product of the rotation speed N (rpm/60) of the impeller 2 and the number of blades Z.
This sound, commonly known as the NZ sound, was a major problem.

The present invention solves these problems,
In addition to making the return passage of the air guide a sound-deadening structure,
The purpose is to make the air flow in the return passage smooth, prevent the generated noise from going outside the blower, and improve the blowing efficiency.

Means for Solving the Problems In order to achieve the above object, the present invention provides a centrifugal impeller, an air guide in which a diffuser part and a return passage are integrated, a casing that covers the impeller and air guide, and a motor. and
Each of the guide walls constituting the return passage is composed of a double wall of an outer guide wall and an inner guide wall on the side in the rotation direction of the impeller, and the tangent at the end of the inner guide wall on the air guide center side is the same as that of the air guide. Furthermore, a small space of a predetermined length is formed on the inner and outer guide walls, one end of the outer circumferential side of the small space is closed, and the other end is closed in the middle of the return passage in the downstream direction. It was opened to

Effect The effect of this technical means is as follows.

In other words, the length of the small space formed by the inner and outer guide walls is set in relation to the rotation speed of the impeller and the number of its blades to form a silencer, which serves as a side branch in the acoustic circuit. The structure is such that no noise is emitted to the outside. In addition, by making the radius of curvature Ro constituting the outer guide wall larger than the radius of curvature Ri of the inner guide wall, sharp bends in the airflow are avoided on the outer guide wall side, which is immediately after the return passage entrance, and on the inner guide wall side. After reaching the point, the airflow changes direction so that the airflow flows smoothly in the return passage. Also, Ri
The end of is facing the center of the air guide,
This prevents the airflow from becoming a recirculation near the center of the air guide, resulting in a blower with reduced flow loss.

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

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

In Figures 1 to 4, 5 is a casing;
An intake port 6 is opened in the center, and the opposite side of the intake port 6 is attached to the motor frame 7 so as to prevent air leakage. 8 is a centrifugal impeller with multiple blades (Z blades).
It is attached to the motor shaft 9 via a nut 10, a spacer 11, and a washer 12. Impeller 8
On the outer periphery of the air filter, a differential user section 14 consisting of a plurality of enlarged passages 13 and a return passage section 16 communicating with each enlarged passage 13 of the differential user section 14 and forming a return passage 15 are integrally formed. A guide 17 is installed. 18 is a motor.

The return passage 15 has a starting end 19 near the outer periphery of the air guide 17 and is sandwiched between a guide wall 22 consisting of an inner guide wall 20 and an outer guide wall 21. Further, a small space 23 that opens toward the center of the air guide 17 is formed between the inner guide wall 20 and the outer guide wall 21.

The radius of curvature Ri constituting the center of the inner guide wall 20 and the radius of curvature Ro constituting the center of the outer guide wall 21 have a relationship of Ro>Ri. Further, Ri has its starting end at the outer periphery of the air guide 17, but at its terminal end, its tangent line points substantially toward the center of the air guide 17.

Next, the operation of the configuration of this embodiment will be explained. The airflow discharged from the impeller 8 passes through the differential user part 14 and enters the return passage 15, and then the motor 18
flows into the. The direction of the airflow entering the return passage 15 is changed so that it becomes a uniform flow throughout the return passage section 16, but the direction is changed as slowly as possible at the outer guide wall 21, which is immediately after the entrance of the return passage 15. Since the radius of curvature Ro that forms the center of the outer guide wall 21 is larger than the radius of curvature Ri that forms the center of the inner guide wall 20,
Airflow changes direction smoothly. Further, since the terminal end of Ri faces the center of the air guide 17, the airflow flows toward the same center, and the air blowing efficiency can be increased without generating loss flow around the center of the air guide. 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 n' expressed by the following equation.

n'=2n'-1/4・C/l (C: speed of sound, n': 1, 3, 5...) The problem with this type of blower is the rotation speed N (rpm/60) of impeller 8. This is the NZ sound expressed as the product of Z and the number of blades Z. In this example, N
= 470 (rpm/60) and Z = 9, so the sound around 4230Hz becomes a problem. When calculated from the above formula, it is approximately 20 mm, but since the shape is more complex than the simple system, the optimum value was determined and l = 14 mm.
As a result, the NZ sound is muted.

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, a small space is provided between them, and the length of the small space is not a problem when using a blower. By making the length suitable for silencing the NZ sound, it is possible to obtain the silencing effect of the NZ sound, and
By directing the end of the inner guide wall toward the center of the air guide, the effect of suppressing the circulation that tends to occur near the center of the air guide and increasing the air blowing efficiency is achieved.

[Brief explanation of drawings]

FIG. 1 is a back view of an air guide in one embodiment of the present invention, FIG. 2 is a partially cutaway side view of the overall configuration of the same embodiment, and FIG. 3 is a front view of the air guide in the same embodiment. FIG. 4 is an enlarged view of the guide wall. Figure 5 is an acoustic equivalent circuit diagram of a silencer.
FIG. 6 is an overall exploded perspective view of a conventional example. 5...Casing, 8...Impeller, 14...
Diff user section, 15...Return passage, 17...Air guide, 18...Motor, 20...Inner guide wall, 21...Outer guide wall, 23...Small space.

Claims (1)

[Claims] 1. Each of the guide walls constituting the return passage includes a centrifugal impeller, an air guide in which a differential user part and a return passage are integrated, a casing that covers the impeller and air guide, and a motor, and each of the guide walls that constitute the return passage: It consists of a double wall of an outer guide wall and an inner guide wall on the rotation direction side of the impeller, and the tangent at the end of the inner guide wall on the air guide center side is set to face the air guide center, and the inner guide wall
An electric blower in which a small space of a predetermined length is formed between the outer guide walls, one end of the small space on the outer peripheral side is closed, and the other end is opened downstream in the middle of the return passage.