JPS5893997A - Blower - Google Patents

Abstract

PURPOSE:To enhance performance of diffuser by selecting the width of diffuser vane's inlet in its axial direction smaller than the width of the vaneless apert's inlet in the axial direction, and thereby accelerating the radial component of the flow velocity. CONSTITUTION:A vaneless part 14 is provided between the inlet of a diffuser vane 9 and the outlet of the impeller 3, where the width blof the diffuser vane's inlet in the axial direction is set to a value smaller than the width b0 of the vaneless part's inlet in the axial direction so as to accelerate the radial component Cr of the flow velocity. That is to say, if it is so assumed that the radial component of flow velocity at the inlet of vaneless part is expressed as Cr0= Q/(piD0b0) and the one at the inlet of the diffuser vane, as Cr1=Q/(piD1b1) and if it is so conditioned that D1b1<D0b0, so we have now Cr1>Cr0 to give acceleration of the radial component and consequently enhancement of diffuser performance.

Description

[Detailed Description of the Invention] This invention relates to an electric blower for a household vacuum cleaner.
In particular, it concerns the improvement of its fluid performance.

The structure and operation of a conventionally used electric blower will be explained with reference to FIGS. 1 to 4. FIG. 1 is a longitudinal sectional view of an electric blower, and 1 represents an electric motor.

A centrifugal impeller 3 is fastened to one end of the rotating shaft 2 with a nut 4. A casing 5 having a substantially conical front surface and a cylindrical surface 111 is disposed outside the impeller 3, and is fitted into a 7 m disc-shaped end bracket 6 provided at the end of the electric motor 1 on the blower side. A space is formed in which the impeller is fully housed. A disk-shaped partition plate 7 is disposed inside the impeller 5 on the rear surface (anti-suction side) of the impeller 3, and is fixed to the end bracket 6 and the electric motor 1 with bolts 8 at multiple locations in the circumferential direction. Ru. A diffuser g9 in the form of a circular blade row is protruded from the front surface (suction side) of the partition plate 7 and the outer periphery of the impeller 3, and a return 9 guide box 10 is protruded from the rear surface of the partition &7 housing to prevent the fluid from flowing. form a passage. Also, partition plate 7
An annular gap 11 is formed between the outer peripheral end of the casing 5 and the inner peripheral surface of the casing 5 . As the impeller 3 rotates, air is sucked in through the suction port 12, and after being pressurized by the impeller, the air is passed through the diffuser blade 91 through the circular monkey-shaped gap 11. The dynamic pressure is converted into static pressure while flowing through the fluid passage consisting of the return guide XIO and the return guide XIO, and flows into the inside of the motor through the intake port 13 provided at the end bracket 6 and the end of the motor to cool the motor. It flows out from an opening (not shown) provided at the other end or side of the rear motor. FIGS. 2, 3 and 4 are axial views of the diffuser vane, return guide vane, and intake port, respectively.

The configurations of the diffuser blades, return guide vanes, etc. used in the electric blower with the above configuration are similar to those of conventionally used large-sized blowers and compressors. There are particular restrictions on the shape, etc. In other words, in large machines, the ratio of the diffuser outlet diameter to the inlet diameter is 1.4 to
Normally, the value is as large as about 2, but electric blowers can only take a small value of about 1.15 to 1.25, and the dimension in the $11 direction is also extremely limited. However, conventional electric blowers have not been designed to construct an efficient fluid passage within such a restricted space, and therefore often suffer from drawbacks such as low fluid performance and high noise levels.

In addition, in a normal centrifugal blower/compressor, the inversion of the flow n discharged from one impeller with respect to the circumferential direction is 20° to 30°.
The inlet angle of the diffuser blade is also designed according to this value, but the electric blower has a low specific speed (
The flow rate is small when the pressure is high), and the angle of entry at the diffuser inlet (!-i) is a small value of around 6 degrees at the inlet angle of the diffuser blade. At such a low inflow angle, stall is likely to occur, Furthermore, it is difficult to obtain a good diffuser effect due to large flow loss.

This point is also not taken into consideration with conventional electric blowers.

Therefore, there was a drawback that fluid performance was low.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric blower for a domestic vacuum cleaner that eliminates the above-mentioned drawbacks and has high fluid performance.

The feature of this invention is that a bladeless portion is provided between the diffuser true inlet and the impeller outlet, and the axial width of the diffuser blade population is made smaller than the axial width of the bladeless portion inlet. By accelerating the radial component of the flow velocity and increasing the flow angle, the diffuser's passage length ratio and equivalent spread angle of 9 (both will be described later) are within a range that is good for the performance of the diffuser. be.

The characteristics of diffusers used in centrifugal fluid machines are explained in the fifth section.
This will be explained using figures. The horizontal axis of the figure is the length of the diffuser blade or the length of the center line of the passage between the blades (t), and the passage width W1- measured perpendicular to the flow direction at the inlet of the diffuser blade.
π]), sin/Z (where D is the diameter with respect to the center of the rotation axis, β is the angle that the axis makes with respect to the circumferential direction, Z is the number of blades, and elementary school 1 represents the knife user blade inlet). t/W
Ikfi, the equivalent spread angle θ = 2tan-' [(w2-
w+)/2z) (i outW2-πD2sinβ,/z
, i-character 2 represents the diffuser blade outlet). The group of curves descending to the right in the figure at -1'f is the area ratio A of the diffuser, -Wt/Wl (= (D2sinβ2)
/ (D, sinβl)) represents a certain group of lines,
Diffuser efficiency η and pressure rise coefficient C of tee 7 user
2. A group of curves with constant values (both defined below) were obtained through experiments by the inventor.

(Here, P is the static pressure, U is the flow velocity, and ρr represents the density of the fluid.) As mentioned above, when using the diffuser JK1t for an electric blower, the flow angle at the inlet is extremely small, so the blades tend to be very long. , if the diffuser is designed using the conventional method, t/Wl=14 as shown by symbol A in FIG.
~20. The value is around θ=13° to 9°. Pressure coefficient Cp rBo of a diffuser corresponding to this shape,
5 to 0.55, which is not a sufficiently high value. Here, the area ratio A is approximately 4, which is actually the maximum area ratio (necessary for preventing peeling) for this type of diffuser.

An embodiment of this invention will be explained with reference to FIG. The figure is a vertical cross-sectional view of the diffuser part, and other parts are
Since it is the same as that shown in FIGS. 4 to 4, the explanation will be omitted. As shown in the figure, a portion 14 without x is provided between the inlet of the diffuser blade 9 and the outlet of the impeller 3.
It is narrowed to be smaller than o so that the radial component C2 of the flow velocity is accelerated. In other words, the radial velocity component at the inlet of the part without blades is C, O=Q/(πDobo)
(Here, Q represents the air volume, and the subscript O represents the entrance without opening.)
, and the radial flow velocity component at the inlet of the 7'' filter blade is C,l=Q/(πD+ b+ ), so D+ b
+ < Do bo.

Cz>Cro. The angle (flow angle) α that the flow n makes with the circumferential direction is α=(8)-'(C, /C,)(C
, is the circumferential component of the flow velocity, and in the part without X, C2
is half proportional to D), the flow n angle at the inlet of the diffuser blade is also increased at the inlet of the non-blade section.

In an actual example, 2. Normally, α at the diffuser inlet
is around 6°, but the inventors increased this to around 10°. T of the diffuser passage /
W+ and θ are at point B (z/Wt = i t
, θ-16°), resulting in a pressure increase coefficient Cp
r rose to about 0.6. Note that the area ratio is 4 b
2 and β2 are determined.

The radial component C1 of the flow velocity increases in the bladeless part 14, but the circumferential component C1 slows down in inverse proportion to D, so the absolute value of the flow velocity c < -V 1> in the part without X. It will decrease slightly. In other words, this portion becomes a diffuser with a small area ratio (about 1.05 to 1.1) and contributes to deceleration and stabilization and rectification of the flow.

In the embodiment shown in FIG. 6, the front sides of the diffuser blades 9 and the bladeless portion 14 are aligned so that they lie on one plane perpendicular to the rotation axis, but in this case, the diffuser and casing can be manufactured easily. There is an advantage to having one. However, there is no guarantee that it is limited to this form.

It is also possible to have the partition plate side as a flat surface and the caning side as an inclined surface (or both sides as inclined surfaces). In this case, since the flow n flowing out from the centrifugal impeller generally has a higher speed on the hub side (partition plate side), this embodiment is more advantageous in terms of performance than the embodiment shown in FIG.

FIG. 7 shows experimental results showing the effects of the above embodiment.

The relationship between the air volume Q and the pressure (static pressure) H of the electric blower is shown.

The characteristic curve shown by the broken line in the figure is the characteristic when almost the same number of diffusers designed by the conventional method are used, and the curve a shows the characteristic curve according to the present invention. From the figure, it can be seen that in the case of the diffuser of the present invention, the 1% deflection greatly extends toward the large kite side, and the pressure generated in most of the air volume range (9) is even higher than in the conventional case.

As can be seen from the above description, in the present invention, a trueless portion is provided between the inlet of the diffuser blade and the impeller outlet, so that the axial width of the diffuser blade inlet is smaller than the axial width of the inlet of the bladeless portion. Namely, by configuring the radial component of the flow velocity to accelerate, the diffuser II & of the electric blower is moved to a range with a large inlet angle, and the length ratio of the passage between the diffuser blades is 1 / W 1 etc. Since the side floor moves the 9-angle θ to a range that is advantageous for performance on the diffuser characteristic map, a high pressure rise can be obtained.
The fluid characteristics of the blower can be significantly improved without significantly increasing manufacturing costs, and a high-performance electric blower can be provided.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing a conventional electric blower, Fig. 2 is an axial main view of the diffuser shown in Fig. 1 (viewed from arrow II-n), and Fig. 3 is an axial main view of the return guide vane shown in Fig. 1. Figure (I
Figure 5 is a map diagram showing the characteristics of the D(10) fifter, Figure 6 is a longitudinal sectional view of the diffuser according to the present invention, and Figure 7 is a blower characteristic diagram showing the effects of the present invention. It is. 3... Impeller, 7... Partition plate, 9... Diffuser blade. 10... Return guide blade, 14... Wingless part. Agent Patent attorney Toshiyuki Usuda (11)

Claims (1)

[Claims] 1. A centrifugal impeller is coupled to a rotating shaft of an electric motor. A cylindrical casing is provided on the outside of the impeller, a disk-shaped partition plate is arranged on the back of the impeller, and a diffuser X is provided in front of the partition plate and on the outer periphery of the impeller. Further, a return guide vane is provided protruding from the rear surface of the partition plate, and an annular gap is formed between the outer peripheral end of the partition plate and the casing. An uncircumcised portion is provided between the diffuser blade inlet and the impeller outlet, and the axial width of the diffuser blade inlet is smaller than the axial width of the bladeless portion inlet to accelerate the radial velocity component of the flow. At the same time, the axial width of the diffuser blade is expanded toward the exit, and the area ratio of the diffuser A r = D2b, sin β2/D , b , s
inβ, (where D is the diameter with respect to the center of the rotation axis, b is the axial width, β is the angle that the blade makes with respect to the circumferential direction, the subscript 1 is the inlet of the diffuser blade, and 2 is the outlet) significantly exceeds 4. An electric blower characterized in that an axial width b2 and an exit angle β2 of a chinuyo diffuser blade outlet are determined. 2. The electric blower according to claim 1, wherein the front end of the diffuser is located within a plane perpendicular to the rotation axis.