JP3510107B2 - Electric blower and vacuum cleaner equipped with the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a diffuser blade of a centrifugal electric blower for the purpose of providing a low-noise electric vacuum cleaner.

[0002]

2. Description of the Related Art In an electric vacuum cleaner, noise has increased with the increase in output of an electric blower. On the other hand, since the vacuum cleaner main body is also becoming smaller, there is a space for soundproofing on the main body side. It is getting less. Therefore, in recent years, it has become necessary to reduce the noise generated from the electric blower itself.

As a conventional method for reducing the noise from the electric blower itself, as disclosed in Japanese Patent Laid-Open No. 3-156199, a diffuser vane of the electric blower, a return passage installed on the back surface thereof, or those There is a method in which a sound absorbing material is inserted or a vibrating film is stretched in a plate material portion to be coupled to attenuate the generated sound, and a sound absorbing measure is taken in the electric blower internal flow path.

Further, as disclosed in Japanese Patent Laid-Open No. 8-232896, a through hole is obliquely formed at the tip of the volute tongue or the tip of the diffuser vane, so that the flow can penetrate even when the direction of the inflow flow changes. There is also a method of preventing peeling at the tip end by moving through the hole and consequently reducing pressure fluctuation. In general, reduction of pressure fluctuation leads to reduction of sound, and thus this method also contributes to reduction of noise from the blower itself.

While the above-mentioned Japanese Patent Laid-Open No. 3-156199 is a countermeasure for reducing the sound in the sound propagation path, the Japanese Laid-Open Patent Publication No. 8-232896 attempts to reduce the intensity of the sound source itself. It is a coping method.

[0006]

However, the method disclosed in Japanese Patent Laid-Open No. 8-232896 requires a space for installing the sound absorbing material and the vibrating membrane. For example, when using a sound absorbing material, in order to absorb sound efficiently, a thickness of about 1/4 or more of the wavelength of the sound wave to be absorbed is required, and the sound wave of several thousand hertz, which is a problem in an electric vacuum cleaner, can be effectively used. Sound absorption requires a thickness of at least 10-30 mm.

It is impossible to take such a thickness in the diffuser vane, which is usually only a few millimeters thick, the return flow path, or the plate member portion connecting them, and conversely, a sound absorbing material having a reduced thickness is inserted. However, a sufficient sound absorbing effect cannot be obtained. In addition, these methods have a problem in that they are structurally complicated and manufacturing cost and productivity deteriorate.

Further, in the method disclosed in the above-mentioned Japanese Patent Laid-Open No. 8-232896, when the direction of the through hole formed in the tip of the volute tongue or the diffuser vane does not greatly deviate from the direction of the inflow flow, the pressure fluctuation is reduced Although effective, if the direction of the through hole and the direction of flow largely deviate, the fluid does not move smoothly, and separation at the tip cannot be avoided.

In such a case, the result is an increase in noise. Further, the volute and the diffuser have a role of reducing the speed of the flow to recover the pressure, but at the volute tongue and the tip of the diffuser vane, the flow is a fast flow before being decelerated. Therefore, opening a through hole in such a fast-flowing portion results in loss and is disadvantageous in terms of performance.

It is an object of the present invention to propose a diffuser structure which is space-saving, has a noise reducing effect which is not affected by the state of air flow, and has a small air flow loss, and as a result, has a low noise level. An object is to provide an electric blower and an electric vacuum cleaner equipped with the electric blower.

[0011]

In order to achieve the above object, the features of the electric blower in the present invention are:
Overlapping part formed by being sandwiched between both adjacent diffuser vanes Penetrating the plate surface of the other vane from the outlet end face of one vane of the air flow passage to the position where the opening end correction value δ is added It is to provide at least one or more holes.

Specifically, the present invention provides the following device.

According to the present invention, there is provided an electric motor, a centrifugal impeller for directly generating an air flow, which is directly connected to a rotary shaft of the electric motor, and a plurality of stationary blades arranged on the outer peripheral side of the centrifugal impeller in a substantially oblique radial pattern. A diffuser that diverts and flows out the generated air flow, a return guide that guides the air flow that flows out of the diffuser to the electric motor, and a case that includes the electric motor, a centrifugal impeller, a diffuser, and a return guide. In the electric blower, each of the vanes is located between the outlet end face of one vane of the overlapping air flow passage formed by being sandwiched between the adjacent vanes and a position to which the opening end correction value δ is added. An electric blower is formed by a plate-shaped member having at least one through hole formed in the plate surface of the other stationary blade.

Preferably, the opening end correction value δ is given by the following equation (Equation 1) when a and b are dimensions of sides of a rectangular cross section of an outlet of the overlapping portion air flow passage, and a> b.

[0015]

[Equation 1]

The distance obtained by

Preferably, the position to which the opening end correction value δ is added is a node of a standing wave in which the pressure fluctuation of the sound wave in the overlapping portion of the vanes becomes almost zero.

Further, according to the present invention, a dust collection chamber joined to a suction port for sucking dust on a cleaning surface, and an electric motor which is arranged behind the dust collection chamber and forms an air flow for sucking the dust from the suction port. In an electric vacuum cleaner having a blower, the electric blower is configured to move a moving blade that pressurizes and inflows air that has flowed in from an air intake port and a pressure fluctuation due to the turbulence of the outflowing air flow caused by the approach of the moving blade, A vane formed of a plate-shaped member having a through hole for transmitting the pressure variation from the overlapping portion air flow passage formed by the matching blades to a passage other than the overlapping portion air flow passage. However, the dust on the cleaning surface is absorbed by the air flow that is formed by decelerating the air flow at the outlet half-opening portion behind the overlapping portion air flow channel and has a small loss effect of the air flow from the through hole. This To provide an electric vacuum cleaner according to claim.

Here, the node of the standing wave refers to a portion where the pressure fluctuation of the sound waves to be intensified in the vicinity of the diffuser overlapping portion is almost zero when the diffuser overlapping portion is considered as a sound resonance tube,
It is formed at a distance that includes the correction of the opening end on the exit side of the overlapping portion.

The opening end correction is to correct the deviation between the actual reflection position of the sound wave and the position of the exit end face of the overlapping portion. Theoretically, the sound wave is reflected at the exit of the overlapping portion where the step area suddenly changes, but in reality, since air has a mass, reflection occurs at a position slightly beyond the exit end face due to the influence of inertia. Aperture edge correction corrects this difference.

The method of obtaining the node position will be described in the following embodiments of the invention.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an electric blower according to an embodiment of the present invention and an electric vacuum cleaner equipped with the same will be described with reference to the drawings.

The structure of the electric vacuum cleaner body 201 will be described with reference to the longitudinal sectional view of the electric vacuum cleaner body shown in FIG. The vacuum cleaner body 201 includes a lower case 301 and an upper case 302.
An outer shell is constituted by the dust collecting lid 303. Dust cover 3
A suction port 304 is formed at 03, and a dust collection chamber 306 for housing a dust bag 305 joined to the suction port 304 is formed inside thereof. An electric blower chamber 307 is connected to the rear of the dust collection chamber 306 via a filter 309, and an electric blower 308 is housed therein.

The air sucked from the suction port 304 has its dust removed by the dust bag 305, passes through the filter 309, and then flows into the electric blower 308. Electric blower 3
The exhaust gas from 08 is discharged to the outside from the exhaust port 310.

Next, an electric blower 308 according to an embodiment of the present invention will be described with reference to FIG. The electric blower 308 of the electric vacuum cleaner includes the electric motor 2 and the blower 1.

The electric motor 2 comprises an electric motor case consisting of a housing 3 and an end bracket 9, a rotor 5 having a rotary shaft 4 housed in the electric motor case, and a stator 7 around which a stator coil 6 is wound.

The blower 1 has a centrifugal impeller 12 directly connected to the rotary shaft 4, a diffuser 11 installed on the outer peripheral side of the centrifugal impeller 12, a return guide 14 located on the back surface of the diffuser 11, and a centrifugal separator. The impeller 12, the diffuser 11, and the return guide 14 are included, and the air suction port 13 is included.
and a blower case 13 connected to the electric motor case.

In the electric blower 308, when the electric motor 2 is driven to rotate the centrifugal impeller 12, the air suction port 1
Air 101 flows in from 3b and flows into the diffuser 11 near the outer peripheral portion of the centrifugal impeller 12. The air 102 that has flowed into the diffuser 11 is guided to the return guide 14 and flows into the housing 3. The air 104 that has flowed into the housing 3 cools the rotor 5, the stator coil 6, and the brush 15 of the electric motor 2 and is then discharged to the outside.

FIG. 3 is a view of the blower 1 as viewed from the rotation axis direction. The diffuser 11 is installed outside the centrifugal impeller 12. When the centrifugal impeller 12 rotates counterclockwise, air flows in through the air intake port 21, and the flow 23 is pressurized along the moving blades 22 in the centrifugal impeller.

The flow flowing out from the trailing edge 24 of the moving blade flows into the fixed diffuser 11, and the flow 25 is pressure-recovered along the vane 26. The moving blade trailing edge 24 periodically approaches the stationary blade leading edge 27 as the rotor rotates. At this time, the moving blade trailing edge 2
The flow from 4 interferes with the leading edge 27 of the stationary blade, causing periodic pressure fluctuations on the blade surface, which is emitted as a sound wave.

The periodic sound waves generated by the interference are not emitted to the outside as they are, but the adjacent stationary blades 26.
Overlap air flow channel 28 formed by being sandwiched by
Due to the effect of the sound as a resonance tube, sound intensity may be amplified and emitted.

The present invention relates to a method for reducing the phenomenon in which a sound wave periodically generated due to the above-mentioned interference between the moving and stationary blades is strengthened in the flow passage of the overlapping portion constituted by the diffuser blades, and it saves space. It features a noise reduction effect that is not affected by the flow condition and a small air flow loss.

FIG. 4 shows an example of the diffuser structure of the electric blower shown in FIG. 1 with an enlarged view of three diffuser blades. The flow path portion surrounded by the adjacent diffuser blades is called an overlapping portion 34, and the portion surrounded by only one blade existing in front of it is the inlet half opening portion 33, and similarly, the half opening portion existing behind the overlapping portion 34. Is defined as the outlet half open portion 35.

Here, from the exit end face 30 of the overlapping portion 34 of the diffuser blade to the exit half-opening portion 35 side, at a position 3 at a distance δ.
At least one through hole 32 is formed in the diffuser blade surface up to 1. The cross-sectional shape of the through hole 32 may be any shape such as circle, triangle, quadrangle, etc.
When a plurality of holes are opened, the positions of the through holes may be slightly shifted within the above-mentioned section.

The principle of noise generation and the principle of noise reduction by the proposed structure will be described below.

The air flow in the diffuser 11 first passes through the inlet half-opening 33 and then the overlap 34,
Pass through the exit half-opening 35. In the overlapping portion 34 of the diffuser, the generated sound wave becomes a plane wave and propagates in the flow direction. However, since the flow passage cross-sectional area discontinuously increases at the overlapping portion outlet end face 30, the acoustic impedance changes at this position.

At the position where the acoustic impedance changes, the sound wave that has propagated along the flow is reflected, and this time it becomes a reflected wave, which conversely propagates back to the upstream side of the flow. Even at the position of the inlet of the overlapping portion on the upstream side, the acoustic impedance changes because the cross-sectional area changes. Therefore, the reflected wave propagating toward the upstream side is reflected again at the entrance of the overlapping portion.

As described above, the sound wave generated at the tip of the diffuser blade propagates downstream, is reflected and returned, and is reflected again, but this cycle of reciprocal reflection is incident. When it coincides with the generation cycle of the original sound wave, resonance occurs at the overlapping portion and the radiated sound becomes loud.

Thus, the outlet end face 30 of the overlapping portion 34
In, the pressure fluctuation of the sound wave is 0, that is, the node of the standing wave. Strictly speaking, the node of the standing wave occurs at the position 31 where the distance δ which is the opening end correction value is added from the exit end face 30 of the overlapping portion 34. The formula shown in FIG. 5 is a formula for obtaining the value of the opening end correction value δ.

On the other hand, as can be seen from the through hole 32 in FIG. 4, since the diffuser blades are inclined and arranged,
When comparing the adjacent diffuser flow paths connected by the through holes 32, it is understood that the position of the node of the standing wave on one side corresponds to the position inside the overlapping part 34 on the other side.

As described above, in the node of the standing wave, the pressure fluctuation of the sound wave is almost constant irrespective of the flow state, but the other connected through the through hole 32 has the inside of the overlapping portion 34. Since there is a position, there is a pressure fluctuation of the acoustic wave. Since both are breathable, the pressure fluctuation of the sound inside the overlapping portion 34 interferes with the other stable pressure field, and the pressure fluctuation is averaged and weakened. Therefore, there is no portion having a large amplitude, and the sound wave is weakened.

The effect of reducing the pressure fluctuation of such a sound wave is as follows.
Since the position of the node of the standing wave hardly changes, it is not related to the state of flow, and it is also characterized by not requiring a special countermeasure space. Further, in the outlet half-opening portion 35 on the outlet side of the overlapping portion 34, the velocity of the air flow is sufficiently reduced, so that the loss of the flow due to the opening of the through hole 32 can be suppressed to be small.

FIG. 6 shows the noise reduction effect of the diffuser structure of FIG. The horizontal axis represents the rotation speed, and the vertical axis represents the noise level. The solid line in the figure shows the result in the case of a normal diffuser structure without through holes, and the dotted line shows the result in the case of a diffuser structure with through holes.

As can be seen from the change in noise with respect to the rotation speed shown by the solid line graph, the sounds are maximized at a specific rotation speed due to the strengthening of the sounds at the diffuser blade overlapping portion, so the change in the sound with respect to the rotation speed. I can see that he is rippling. On the other hand, as indicated by the dotted line, according to the structure of the present invention, such a sound maximization phenomenon can be suppressed and noise can be reduced.

FIG. 7 shows another embodiment of the diffuser structure. In the structure shown in FIG. 4, a through hole is formed as a through hole in the diffuser blade in the form of a hole. However, in the diffuser structure of the present embodiment example, the notch groove 40 is formed at one edge of the diffuser blade in the span direction. The feature is that the through holes are formed in the form of forming. This structure improves productivity because the notch 40 is formed at the same time as die cutting when the diffuser blade is formed by a die.

The diffuser structure according to the present invention is applicable not only to electric blowers but also to general fluid machines such as axial flow type, mixed flow type or centrifugal type pumps, fans, blowers and compressors. .

[0047]

According to the present invention, regarding sound waves that strengthen each other in the overlapping portion of the diffuser blade, by adjoining the vicinity of the pressure variation of the sound and the portion other than the joint by a through hole opened at a specific position, Mutual interference of sound waves is generated between the diffuser blades, and the intensity of the standing wave in the overlapping portion is weakened, and the noise due to the radiated sound can be reduced.

Also. Since the air flow velocity is sufficiently reduced by the outlet half-open portion on the outlet side of the overlapping portion, it is possible to reduce the air flow loss due to the opening of the through hole.

[Brief description of drawings]

FIG. 1 is a vertical sectional view including a rotary shaft of an electric blower according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of an electric vacuum cleaner body equipped with the electric blower of FIG.

3 is a schematic diagram of the flow of air in the centrifugal impeller and the diffuser portion of FIG.

FIG. 4 is an enlarged view of a diffuser portion of the electric blower of FIG. 1.

5 is a mathematical formula for determining the positions of nodes of a standing wave that determines the diffuser structure of FIG.

FIG. 6 is a graph showing a sound reduction effect when the diffuser structure of FIG. 4 is used.

FIG. 7 shows another embodiment of the diffuser structure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Blower, 2 ... Electric motor, 10 ... Stationary flow path part, 11 ... Diffuser, 12 ... Rotating impeller, 13 ... Blower case,
13a ... Airflow guide, 13b ... Air suction port, 14 ... Return guide, 21 ... Air intake port, 22 ... Rotating impeller rotor blade, 23 ... Rotor impeller flow, 24 ... Rotor blade trailing edge, 2
5 ... Flow in diffuser, 26 ... Stationary vane, 27 ... Stationary vane leading edge, 28 ... Overlap air flow channel, 30 ... Outlet end face, 3
1 ... Position, 32 ... Through hole, 33 ... Inlet half open part, 34 ... Overlap part, 35 ... Exit half open part, 40 ... Notch groove, 304
... Suction port, 306 ... Dust collection chamber, 308 ... Electric blower

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F04D 17/10 F04D 17/10 29/66 29/66 N (72) Inventor Takahiro Nakai 1-1-1 Higashitagacho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd., Electric Appliance Division (56) References JP-A-8-164096 (JP, A) JP-A-8-232896 (JP, A) JP-A-3-156199 (JP, A) Special Kai 54-105307 (JP, A) JP 55-151199 (JP, A) JP 54-122408 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F04D 29 / 44 A47L 9/00 103 A47L 9/00 F04D 17/10 F04D 29/66

Claims (4)

(57) [Claims] 1. An electric motor, a centrifugal impeller for air flow generation, which is directly connected to a rotating shaft of the electric motor, and a plurality of vanes, which are arranged in a substantially oblique radial pattern on the outer peripheral side of the centrifugal impeller. An electric blower having a diffuser that diverts and flows the generated air flow, a return guide that guides the air flow that has flowed out of the diffuser to the electric motor, and a case that includes the electric motor, the centrifugal impeller, the diffuser, and the return guide. In the above, each of the stationary blades is the other between the outlet end surface of one stationary blade of the overlapping portion air flow passage formed by being sandwiched between the adjacent stationary blades and the position to which the opening end correction value δ is added. An electric blower, which is formed of a plate-shaped member having at least one through hole formed in the plate surface of the stationary blade. 2. The correction value δ for the opening end according to claim 1.
When the dimensions of the sides in the rectangular cross section of the outlet of the overlapping portion air flow channel are a and b, and a> b, the following equation (Equation 1) An electric blower characterized by a distance required by 3. The standing wave node according to claim 1, wherein the position to which the opening end correction value δ is added is a standing wave node in which the pressure fluctuation of the sound wave in the overlapping portion of the vanes is substantially zero. Electric blower. 4. A dust collecting chamber joined to a suction port for sucking dust on a cleaning surface, and an electric blower arranged behind the dust collecting chamber and forming an air flow for sucking the dust from the suction port. In the electric vacuum cleaner, the electric blower forms pressure fluctuations due to the turbulence of the outflowing air flow caused by the approach of the moving blades and the moving blades that pressurize and inflow the air that has flowed in from the air intake port and the adjacent blades. From one overlapped air flow channel to the overlapped air of another flow channel adjacent to the overlapped air flow channel
Relieves the pressure fluctuation by transmitting to the half-opened portion of the outlet behind the flow channel
And a vane formed of a plate-shaped member provided through the through-hole behind the overlapping portion air flow passage, and decelerating the air flow at an outlet half-opening portion behind the overlapping portion air flow passage. An electric vacuum cleaner, which absorbs dust on the cleaning surface by an air flow that is formed by the air flow and has a small loss effect of the air flow.