JPS61182498A - Motor-driven blower - Google Patents

Abstract

PURPOSE:To improve efficiency, by providing an opening part in the internal final end of a spaced part, formed between both inner and outer guide walls, so as to enhance a silencing effect while constituting the inner guide wall higher than the outer guide wall so as to smooth a flow in a return passage part. CONSTITUTION:A guide wall, constituting a return passage 20 of an air guide 14, is formed by inner and outer guide walls 22, 23, while a spaced part 25, having an opening part in the internal final end, is set between these guide walls 22, 23. As a result, the above spaced part 25, constituting a silencer and serving as a side branch in an acoustic circuit, enables a noise to be reduced. Further the inner guide wall 22 is constituted higher than the outer guide wall 23. In this way, even if the outer guide wall 23 comes to easily generate exfoliation of an air stream, the blower, supplying air as shown in the drawing from a step difference H generated by a difference of height between said guide walls, holds the air stream to be balanced. Air is supplemented to the spaced part 25 from the opening part 24 provided in the internal peripheral end. Thus fan efficiency can be enhanced by smoothing a flow in the return passage part 20.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present 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.
It is shown in the No. 168 publication.

That is, as shown in FIG. 7, 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 an electric blower having a structure in which the air guide 3 is provided on both sides of the impeller 2, when the airflow discharged from the impeller 2 flows into the air guide 3, the air guide inlet The 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 varies depending 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 having an opening at the inner end is set between these walls, and the inner guide wall is higher than the outer guide wall.

action 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.

Also, since the airflow from the diffuser flows along the outer guide wall, separation is particularly likely to occur on the motor side of the outer guide wall, but since the inner guide wall is higher than the outer guide wall, the air between the two guide walls is By supplying the fluid smoothly, separation is efficiently prevented and the flow becomes less turbulent. As a result, an electric blower with high efficiency and low noise due to turbulence can be obtained.

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, and are surrounded by a casing 17 which is airtightly attached to the motor frame 16 at the lower part of its peripheral wall.

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.

The curved guide wall 21 that partitions each return passage 2o 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. Further, the inner guide wall 22 is connected to the outer guide wall 23.
The height of the wall is higher than that of the building.

Next, the operation of the configuration of this embodiment will be explained.

The airflow from the diffuser 18 flows into the independently communicating sliding return passage 2o, but the airflow mainly flows through the inner guide wall 2o.
easy to flow along. Therefore, the airflow tends to move away from the outer guide wall 23 in the return passage 2o. Furthermore, since the airflow from the diffuser 18 flows along the outer guide wall 22,
The upper corner portion 26 of the outer guide wall 22 shown in FIG. 2 is particularly susceptible to separation, resulting in flow turbulence and dead water areas 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 outer guide wall 23 is configured to be lower than the inner guide wall 22 to prevent separation of airflow.

As a function, as shown in Fig. 1, even if the air flow is more likely to separate from the outer guide wall 23, the air supply is improved due to the difference in height of the guide wall, as shown in Fig. 2. This happens and equilibrium is maintained. Air to the space 26 is replenished through the opening 24 at the inner peripheral end. As a result, good results were obtained in all flow ranges.

Next, considering part B of Figure 1, it can be replaced with a simplified diagrammatic system as shown in Figure 4. 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, the length g of the space 26 is 1=(2N-1)・C/4・fN (N...1.2,3...C...sound speed) Given.

As mentioned above, a particularly problematic type of noise from electric blowers is called NZ sound. The NZ sound is 6.3 in this study.
It is occurring near KH2. 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. From Figure 6 of the conventional example, the true Z sound (5,3K
) (near Z) is decreasing. Overall noise is also lower. The knife calculated using the above formula is 17ff! It became m. After that, I will consider it. =14wn was obtained. This is considered to be due to the curvature of the space 26.

Effects of the Invention As described above, according to the present invention, by improving the return passage side of the air guide, it is possible to reduce noise, which is a particular problem with fans, and to improve fan efficiency by smoothing the flow in the return passage part. It can be done, and the effects are great.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the return passage side of the air guide of an electric blower showing an embodiment of the present invention, Fig. 2 is a view taken along the line C-C in Fig. Part cutout side view, 4th
The figure is an action explanatory diagram, Fig. 5. FIG. 6 is a frequency analysis diagram of an embodiment of the present invention and a conventional example, respectively, and FIG. 7 is a side view of a conventional electric blower. 11... Inve 9.12... 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. Name of agent: Patent attorney Toshio Nakao and 1 other person r4
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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 return passage is divided into an inner guide wall and an outer guide wall, and has a space between the inner and outer guide walls, and an inner end of the space. An electric blower with an opening and an inner guide wall higher than the outer guide wall.