JPS6224639B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electric blower for a domestic vacuum cleaner, and particularly to improving fluid performance and reducing noise thereof.

[Conventional technology]

Conventionally used electric blowers are shown in Figures 1 to 4.
This will be explained using figures. FIG. 1 is a longitudinal sectional view of an electric blower, in which reference numeral 1 represents an electric motor, and a centrifugal impeller 3 is fastened to one end of a rotating shaft 2 by a nut 4. A casing 5 having a substantially conical front surface and a cylindrical side surface is disposed outside the impeller 3, and is fitted into a 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 housed. A disk-shaped partition plate 7 is arranged inside the casing 5 at the rear surface (on the non-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. . Front side of partition plate 7 (absorption side)
Further, diffuser blades 9 in the form of a circular blade row are protruded from the outer periphery of the impeller 3, and return guide blades 10 are protruded from the rear surface of the partition plate 7 to form a fluid passage.
Further, an annular gap 11 is formed between the outer peripheral end of the partition plate 7 and the inner peripheral surface of the casing 5. Air is sucked in from the suction port 12 by the rotation of the impeller 3,
After being pressurized by the impeller, it flows through a fluid passage consisting of the diffuser blades 9, the annular gap 11, and the return guide blades 10, decelerating the fluid and converting the dynamic pressure into static pressure.
The air flows into the motor through the end bracket 6 and the intake port 13 provided at the end of the motor, cools the motor, and then flows out through an opening (not shown) provided at the other end or side of the motor. Figures 2 and 3
4 and 4 are axial views of the diffuser vane, return guide vane, and intake port, respectively.

[Problem that the invention seeks to solve]

The configurations of the diff user 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, but the size, shape, etc. There are particular restrictions on In other words, in large machines, the ratio of the outlet diameter to the inlet diameter of the diffuser is usually set to be as large as 1.4 to 2, but in electric blowers,
It can only take a small value of about 1.15 to 1.25, and the axial dimension is similarly extremely limited. Therefore, there is no room for providing sufficient bends in the flow path from the diffuser blade to the return guide blade. However, conventional electric blowers have not been designed to construct efficient fluid passages within such a restricted space, and therefore have had drawbacks such as low fluid performance and high noise levels.

If we look at the above point with the example in Figure 1, we can see that the partition plate is only slightly rounded at the outer peripheral edge in its meridional cross-sectional shape (the meridian plane is the plane that includes the center line of the rotational axis), and the entire partition plate is It forms a sharp bend. Further, the return guide vane has a large axial width at the inlet, and the axial width is gradually determined toward the center, but the passage area at the return guide vane inlet is larger than the passage area at the diffuser blade outlet. When considered in conjunction with the sharp bends described above, this is not an advantageous passage shape. When the inventor measured the flow at the inlet of the return guide vane using a small probe, it was confirmed that flow separation occurred across a considerable portion of the passage width, causing performance deterioration.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide an electric blower for a household vacuum cleaner with high fluid performance and low noise level.

[Means for solving problems]

In order to solve the above problems, the present invention connects a centrifugal impeller to the rotating shaft of an electric motor, provides a cylindrical casing on the outside of the centrifugal impeller, and arranges a disk-shaped partition plate on the back of the impeller. In the electric motor, a diffuser blade is provided on the front surface of the partition plate and the outer periphery of the impeller, and a return guide blade is provided on 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. In a blower, the axial width of the diffuser blade outlet is
b ₂ , when the radius of curvature of the outer peripheral end in the meridional cross-sectional shape of the partition plate is R, the shape at the outer peripheral end of the partition plate is configured so that R≧b ₂ /2, and the axial direction of the return guide vane inlet is The width is smaller than the axial width of the outlet of the differential guide blade, the flow velocity at the inlet of the return guide vane is higher than the flow velocity at the outlet of the differential guide vane, and the outer circumferential portion of the partition plate is provided with a circumference connecting the differential user side and the return guide vane side. A plurality of slits are provided that are inclined with respect to the direction.

[Effect]

With the above configuration, the fluid passage from the annular gap of the electric blower to the return guide vane inlet can be made into a smooth acceleration passage, and the fluid is gently bent along the outer peripheral part of the partition plate. can flow. Furthermore, the slits provided on the outer periphery of the partition plate form part of the acceleration passage from the diffuser blade outlet to the return guide blade inlet, help guide the swirling flow, and prevent flow separation at the outer periphery of the partition plate. This can prevent the generation of noise. As a result, performance is significantly improved without causing flow separation, pressure loss, performance instability, etc., and noise can be reduced.

〔Example〕

An embodiment of this invention will be explained with reference to FIGS. 5 to 7. FIG. 5 shows only the outer periphery of the diffuser blade, partition plate, and return guide blade, and the other parts are the same as those shown in FIGS. 1 to 4, so illustrations and explanations are omitted. As shown in FIG.
is the same or more (1 to 1.2 times) the axial width b ₂ of the diffuser blade outlet at the outer circumference in the meridional cross section.
has a large curvature diameter (the curvature diameter is twice the curvature radius), and the passage width at the return guide vane inlet b ₅
is smaller than _b2 , so that the flow velocity at the return guide vane inlet is higher than the flow velocity at the diffuser vane outlet. More precisely, the passage area at the return guide blade inlet is determined to be smaller than the passage area at the diffuser blade outlet. Here, the passage area is defined by the following formula.

Diffusion user blade outlet passage area A ₂ = πD ₂ b ₂ sinβ ₂ Return guide blade inlet passage area A ₅ = πD ₅ b ₅ sinβ ₅ A is the passage area, D is the diameter with respect to the rotation axis center, β is the circumference of the blade or flow The subscript 2 represents the diffuser blade exit, and the subscript 5 represents the return guide blade inlet.

In the above relationship, D ₂ = D ₅ and β ₂ = β ₅
Then, b ₂ > b ₅ becomes a requirement. ( _b5 =10.6~0.8)
b ₂ , generally A ₂ > A ₅ is a requirement, and in order to allow the flow to flow into the return guide vane without collision, it is slightly β ₅ > β ₂
shall be. ) Furthermore, additional requirements include casing 5 and partition plate 7.
The passage area Am (defined below) of the annular gap 11 formed between the outer circumferential end of is smaller than the above A ₂ ,
Set it to be larger than A ₅ (A ₂ > Am > A ₅ ).

Annular gap passage area A = π/4 (D ₄ ² - D ₃ ² ) sinβm Subscript 4 is the inner circumference of the cylindrical part of the casing, Subscript 3 is the outer peripheral edge of the partition plate, and Subscript m is the average value for the annular gap. represent.

A plurality of slits 14 are provided on the outer circumferential portion of the partition plate 7 to communicate the diffuser side and the return flow path side and form an angle _β5 with respect to the circumferential direction. This slit forms part of the acceleration passage from the diffuser blade outlet to the return guide blade inlet, and also helps guide the swirling flow, and also plays a role in preventing flow separation at the outer peripheral edge of the partition plate, thereby preventing noise generation. has. In other words, in a wingless differential user, etc., there is nothing to restrict the flow in the circumferential direction, so if separation occurs in a part of the flow for some reason, this will propagate in the circumferential direction (swivel stall) and become unstable. However, this slit serves to prevent this phenomenon.

The combined passage area Am (below) of the slit 14 and the annular gap 11 is smaller than the diffuser blade outlet passage area _A2 , and the return guide blade inlet passage area _A5.
Set it to be larger than .

Am = π/4 (D ₄ ² - D ₃ ² ) sinβm + n.ac a is the width of the slit, c is the depth, n is the number of slits, subscript 4 is the inner circumference of the cylindrical part of the casing, and subscript 3 is the partition plate At the outer peripheral end, the subscript m represents the average value for the annular gap. Note that βm=βs, and βs is appropriately selected to be an intermediate value between _β2 and _β5 .

By forming the outer periphery of the differential user, partition plate, and return guide vane as described above, the fluid passage from the outlet of the differential user blade to the inlet of the return guide vane is formed into a smooth acceleration passage, and the inner radius of curvature is made sufficiently large. In addition, since the slits provide a guiding effect, the performance is significantly improved without causing flow separation, pressure loss, unstable performance, etc., and noise can be reduced. Note that, since the fluid passage is formed as described above, a special space is not required and it can be accommodated within the same space as the conventional one. In addition, by gradually increasing the axial width from the return guide vane entrance to the exit,
A deceleration passage leading to the exit can be formed without any difficulty.

FIG. 7 shows experimental results showing the effects of the above embodiment. The figure shows the relationship between the air volume Q and the pressure (static pressure) H of the electric blower, and the solid line in the figure shows the case of the example. In addition, the broken line shows the characteristics when the shape of the partition plate/return guide vane part is the conventional type and the shape of the differential user is the same, and the chain line shows the characteristics when the shape of the differential user is different (due to the design with a large number of blades in the conventional method). shows the characteristics of From the figure, it can be seen that according to this embodiment, higher pressure can be generated than in the case of the conventional type partition plate at medium to small air volumes, and higher pressure can be obtained in the entire air volume range than in the case of the conventional type diff user. Furthermore, when the slits were provided, the noise level was reduced by 3 to 4 dB over a wide range of air volume.

〔Effect of the invention〕

As can be seen from the above description, in the present invention, the partition plate has a large curvature diameter at the outer peripheral end in the meridional cross-sectional shape, which is comparable to or larger than the axial width of the diffuser blade outlet, and the partition plate has a large curvature diameter in the axial direction of the return guide blade inlet. By configuring the width to be smaller than the axial width of the differential user blade outlet, the fluid passage from the differential user blade outlet of the electric blower to the annular gap and the return guide blade inlet can be made into a smooth acceleration path. As a result, it is possible to prevent flow separation, pressure loss, unstable operation, etc., and have a great effect on improving the performance of the blower. Since a plurality of slits are provided that are inclined with respect to the circumferential direction, the guiding effect in the acceleration passage is improved and noise can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing a conventional electric blower, Fig. 2 is an axial view (direction view) of the differential user shown in Fig. 1, and Fig. 3 is an axial view of the return guide vane shown in Fig. 1. (view from the arrow), FIG. 4 is an axial view (view from the arrow) of the motor intake port shown in FIG. 1, FIG. 5 is a vertical cross-sectional view of the partition plate of the present invention, and FIG. The arrow view and FIG. 7 are blower characteristic diagrams showing the effects of the present invention. 3... Impeller, 7... Partition plate, 9... Diffuser blade, 10... Return guide blade, 11... Annular gap, 14
...Slit.

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 centrifugal impeller, and a disk-shaped partition plate is arranged on the back side of the impeller. A diffuser blade is placed on the front and the outer periphery of the impeller, and
In an electric blower in which return guide vanes are 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, the axial width of the outlet of the differential user blade is b ₂ and the width of the partition plate is When the radius of curvature of the outer peripheral end in the meridional cross-sectional shape is R, the shape of the outer peripheral end of the partition plate is configured so that R≧b ₂ /2,
The axial width of the return guide blade inlet is smaller than the axial width of the differential user blade outlet, the flow velocity at the return guide blade inlet is higher than the flow velocity at the diffuse user blade outlet, and An electric blower characterized by having a plurality of slits connected to the blade side and inclined with respect to the circumferential direction. 2 In claim 1, the passage area at the diffuser blade outlet is _A2 , the passage area at the return guide blade inlet is _A5 , and the cross-sectional area of the annular gap and the slit provided on the outer periphery of the partition plate. The present invention is characterized in that it has the relationship A ₂ > Am > A ₅ , where Am is the sum of Electric blower.