JPH0641759B2 - Electric blower - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electric blower used for a vacuum cleaner.

2. Description of the Related Art A conventional electric blower of this type is disclosed in, for example, Japanese Patent Publication No. 52-49.
No. 168 publication.

That is, as shown in FIG. 4, the impeller 2 and the air guide 3 are provided in the casing 1, and the motor 4 rotates the impeller 2 at a high speed to obtain the air volume and the vacuum pressure.

Problems to be Solved by the Invention With the 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 The noise that was thought to be caused by the collision at was a problem. This occurs due to the product of the number of blades Z of the impeller 2 and the number of revolutions N (r · p · m) of the impeller 2, which is commonly called NZ sound.

The present invention solves such a problem by improving the air guide.

Means for Solving Problems The basic means of the present invention for solving the above problems are:
The NZ noise is reduced by forming an axial small hole in the diffuser of the air guide, one end of which is open to the diffuser side and the other end of which is closed.

Working This technical means works as follows. That is, by providing a small hole in the diffuser in the axial direction, the NZ noise is absorbed by the small hole, and thus the NZ noise of the electric blower is reduced.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIGS. 1 to 3, 11 is a driving motor, and a casing 14 having an intake hole 13 in the center is fitted to the motor frame 12. Reference numeral 15 denotes a centrifugal impeller having a plurality of blades 16 contained in the casing 14, which is attached to a motor shaft 18 and driven by a motor 11. Reference numeral 17 denotes an air guide provided between the impeller 15 and the motor frame 12, which has a plurality of diffusers 19 and a return passage 21, and is enclosed in the casing 14. Impeller 15
The air flow sent out from the diffuser 1 is guided by the diffuser 19 having a passage enlarged toward the outer periphery,
Motor intake hole 20 smoothly and independently communicating with the end of 9
The air flows into the return passage 21 that guides the air flow to.

The diffuser 19 of the air guide 17 and the casing 14 are brought into contact with each other substantially at an intermediate portion between the diffuser 19 and the return passage 21, and at this point, a groove 22 'is formed in the diffuser 19 of the air guide 17 in the axial direction. 14 to form a small hole 22. This small hole 2
One end of 2 is open to the diffuser side, and the other end is closed by the motor frame 12. In addition, small hole 2
The groove 2 ′ may be formed independently without being formed by the groove 22 ′ and the casing 14.

Next, the operation of the configuration of this embodiment will be described. Impeller 15 rotated at high speed by driving motor 11
The air flow generated by the motor is guided to the air guide 17 and gradually expanded by the diffuser 19 while the motor intake hole 2
Motor exhaust hole 23
Emitted from. At this time, when the blades 16 of the impeller 15 pass through the tongue portion 25 of the air guide wall 24, a rapid change in pressure occurs, which causes the number of blades Z and the rotation speed N (r.
The noise of a frequency (Hz) (that is, (Hz) = NZ / 60) determined by the product of (pm) is generated. This kind of noise is called the NZ sound as described above, and this NZ sound is transmitted through the diffuser 19 and the return passage 21, and the motor intake hole 2
0, transmitted through the exhaust hole 23 and transmitted to the outside. In this embodiment, a small hole 22 is provided by a part of the NZ sound transmission path, that is, the diffuser 19 of the air guide 17 and the casing 14, and the axial length 1 of the small hole 22 is NZ. When set to about 1/4 of the wavelength of the sound, the NZ sound is absorbed by the small hole 22, and as a result, the NZ sound transmitted from the motor exhaust hole 23 to the outside is reduced.

The following is known as a muffler or side branch in an acoustic circuit, but a schematic representation of it is as follows.

l = (2N−1) · C / 4 (HZ) (N: 1, 2, 3, ..., C: sound velocity) The number and shape of the small holes 22 are not particularly limited.

EFFECTS OF THE INVENTION The present invention forms an axial small hole in the diffuser of the air guide, one end of which is open to the diffuser side and the other end of which is closed. It was possible to reduce the generated NZ sound,
The effect is great. Further, the structure is extremely simple because only small holes are provided in the diffuser in the axial direction.

[Brief description of drawings]

FIG. 1 is an enlarged plan view of an air guide and impeller showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG.
FIG. 1 is a partial sectional view of an electric blower showing an embodiment of the present invention,
FIG. 4 is an exploded perspective view of a conventional electric blower. 12 ... Motor frame, 14 ... Casing, 15
...... Impeller, 17 ... Air guide, 19 ... Diffuser, 21 ... Return passage, 22 ... Small hole.

Continuation of the front page (56) References JP-A-59-93998 (JP, A) JP-A-60-33000 (JP, A) Actually-opened Sho-55-104796 (JP, U)

Claims (1)

[Claims] 1. A centrifugal impeller driven by a motor, a plurality of diffusers in which the air flow sent out by the impeller flows, and an air guide having a plurality of return passages for guiding the air flow to the motor, and these impeller air guides. An electric blower having an axial small hole in which one end is opened on the diffuser side and the other end is closed in the diffuser of the air guide.