AU2014393558A1

AU2014393558A1 - Centrifugal blower and electric vacuum cleaner

Info

Publication number: AU2014393558A1
Application number: AU2014393558A
Authority: AU
Inventors: Mitsumasa HAMAZAKI; Yasuaki Kato; Katsunori Sekine
Original assignee: Mitsubishi Electric Home Appliance Co Ltd; Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Home Appliance Co Ltd; Mitsubishi Electric Corp
Priority date: 2014-05-09
Filing date: 2014-05-09
Publication date: 2016-11-03
Anticipated expiration: 2034-05-09
Also published as: CN106460867A; AU2014393558B2; JP6250145B2; CN106460867B; WO2015170401A1; TW201542155A; TWI573551B; JPWO2015170401A1

Abstract

Provided is a centrifugal blower in which an impeller has a first side plate, a second side plate, and blades. The direction of an air flow immediately after the air flow flows out of the impeller is changed by a deflecting air passage to the outlet direction, that is, toward one axial side of the impeller. The first side plate is located downstream of the second side plate in the outlet direction. The rear edges of the blades each have a rear edge tip at the radially outermost position of the impeller, and protrude outwards in the radial direction of the impeller over the interval from the section from the portion adjacent to the second side plate to the rear edge tip. The axial positions of the rear edge tips are located downstream, in the outlet direction, of the center between the axial position of the outer periphery of the first side plate and the axial position of the outer periphery of the second side plate.

Description

DESCRIPTION

TITLE OF THE INVENTION: CENTRIFUGAL FAN AND VACUUM CLEANER TECHNICAL FIELD [0001]

The present invention relates to a centrifugal fan that has a centrifugal impeller, and to a vacuum cleaner that uses the same. BACKGROUND ART [0002]

If a diameter of an impeller, which performs work on air, is increased where radial dimensions are limited, then air flow that has just flowed out from the impeller must be deflected axially. Aiming to reduce loss that arises due to this sudden deflection, in conventional centrifugal fans outer circumferential portions of a main plate of an impeller are curved toward an axial direction where an outlet is positioned (see Patent Literature 1, for example).

CITATION LIST PATENT LITERATURE

[0003] [Patent Literature 1]

Japanese Patent Laid-Open No. HEI 4-164194 (Gazette)

SUMMARY OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0004]

In conventional centrifugal fans such as that described above, because the outer circumferential portion of the main plate extends outward in a radial direction of the impeller, radial dimensions of blades that apply work to the air are small compared to the diameter of the impeller, reducing the work rate that is obtained relative to the dimensions of the impeller. Because the work that the main plate imparts to the air is reduced, it is also less effective at turning the direction of flow of the air toward the outlet.

[0005] 1

8274944.1 (GHMatters) P104280.AU

The present invention aims to solve the above problems and an object of the present invention is to provide a centrifugal fan and a vacuum cleaner that uses the same that can improve blowing efficiency while reducing loss due to changing a direction of airflow immediately after flowing out from an impeller.

MEANS FOR SOLVING THE PROBLEM

[0006] A centrifugal fan according to the present invention includes: a motor; a centrifugal impeller that includes: a first side plate; a second side plate that faces the first side plate; and a plurality of blades that are held between the first side plate and the second side plate, the centrifugal impeller being driven by the motor; and a forming member that covers an outer circumference of the impeller so as to form a deflecting air channel for changing direction of an air flow immediately after being discharged from the impeller to an outlet direction that is toward a first axial end of the impeller, wherein: the first side plate is positioned further downstream in the outlet direction than the second side plate; the blades include a trailing edge that is positioned on an outer end portion in a radial direction of the impeller; the trailing edge includes a trailing edge tip that is positioned on a radially outermost side of the impeller, and that protrudes outward in a radial direction of the impeller from a portion that is adjacent to the second side plate toward the trailing edge tip; and an axial position of the trailing edge tip is further downstream in the outlet direction than a center between an axial position of an outer circumference of the first side plate and an axial position of an outer circumference of the second side plate.

EFFECTS OF THE INVENTION

[0007]

In the centrifugal fan according to the present invention, because the shape of the trailing edges of the blades is a shape that protrudes radially outward from the impeller from a portion that is adjacent to the second side plate toward a trailing edge tip, and the axial position of the trailing edge tip is further downstream in the outlet direction than a center between the axial position of the outer circumference of the first side plate and the axial position of the outer circumference of the second side plate, blowing efficiency can be improved while reducing loss due to changing the direction of air flow that has just flowed out from the impeller. 2

8274944J (GHMatters) P104280.AU

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]

Figure 1 is a cross section that is taken parallel to a shaft axis of a centrifugal fan according to Embodiment 1 of the present invention;

Figure 2 is an oblique projection that shows an impeller from Figure 1;

Figure 3 is a partial enlargement of Figure 1 for explaining features of an outer circumferential shape of the impeller according to Embodiment 1;

Figure 4 is a partial enlargement of Figure 1 for explaining a relationship between the impeller and a deflecting air channel according to Embodiment 1, and features of the deflecting air channel; and

Figure 5 is a configuration diagram that shows a vacuum cleaner into which the centrifugal fan in Figure 1 is mounted.

DESCRIPTION OF EMBODIMENTS

[0009] A preferred embodiment of the present invention will now be explained with reference to the drawings.

Embodiment 1

Figure 1 is a cross section (a cross section in a plane (a meridional plane) that passes through a rotating shaft) that is taken parallel to a shaft axis of a centrifugal fan according to Embodiment 1 of the present invention. Arrows that are shown in Figure 1 represent directions of airflow in this cross section.

[0010]

The motor 1 has: a motor main body 2; and an output shaft 3 that protrudes outward from the motor main body 2. An impeller 4 is fixed to the output shaft 3, and is driven by the motor 1 to rotate around a rotating shaft 5. The rotating shaft 5 is aligned with the shaft axis of the output shaft 3.

[0011]

Here, a direction that is parallel to the rotating shaft 5 will be called an axial direction, and a direction away from the rotating shaft 5 will be called a radial direction. Thus, the axial direction is vertical in Figure 1, and the radial direction is horizontal.

[0012] 3

6274944.1 (GHMatters) P104260.AU

The impeller 4 is centrifugal (has a centrifugal shape), and has: a first side plate 6; a second side plate 7 that faces the first side plate 6; and a plurality of blades 8 that are held so as to be sandwiched between the first side plate 6 and the second side plate 7.

[0013]

In this example, the first side plate 6 is coupled to the output shaft 3. A suction port 7a for taking external air into the impeller 4 is disposed centrally on the second side plate 7. Alternatively, the second side plate 7 may be coupled to the output shaft 3, and the suction port disposed on the first side plate 6.

[0014]

An inner frame 9 is fixed to an end portion of the motor main body 2 that is near the impeller 4. An inner frame cylindrical portion 9a is formed on an outer circumferential portion of the inner frame 9.

[0015] A forming member (a deflecting air channel forming member) 10 is disposed radially outside the impeller 4 and the inner frame 9. The forming member 10 covers an outer circumference of the impeller 4 and the inner frame 9. The forming member 10 forms a deflecting air channel 11 for changing a direction of air flow that has just been discharged from the impeller 4 to an outlet direction that is at a first axial end of the impeller 4, the deflecting air channel 11 being formed radially outside the impeller 4 and the inner frame 9.

[0016]

The outlet direction is a direction of air flow that is oriented by the deflecting air channel 11, and is downward in Figure 1. The first side plate 6 is positioned further downstream in the outlet direction than the second side plate 7.

[0017]

Figure 2 is an oblique projection that shows the impeller 4 from Figure 1. The arrow that is shown in Figure 2 indicates a direction of rotation of the impeller 4. Each of the blades 8 is inclined so as to increase in diameter in an opposite direction to the direction of rotation of the impeller 4. In each of the blades 8, a surface that is oriented in the direction of rotation of the impeller 4 is called a pressure surface 8a, and a surface that is oriented in an opposite direction to the direction of rotation of the impeller 4 is called a negative pressure surface 8b.

[0018] 4

8274944J (GHMatters) P104280.AU

Each of the blades 8 also has a trailing edge 8c that is positioned on an outer end portion in a radial direction of the impeller 4. The trailing edge 8c is an edge of the blade 8 that connects the outer circumference of the first side plate 6 and the outer circumference of the second side plate 7. Moreover, in Figure 1, the trailing edges 8c are depicted as lines that are projected onto the meridional plane.

[0019]

Figure 3 is a partial enlargement of Figure 1 for explaining features of an outer circumferential shape of the impeller according to Embodiment 1. Each of the trailing edges 8c has a trailing edge tip 8d that is positioned on a radially outermost side of the impeller 4. The trailing edge tip 8d is a point on the trailing edges 8c at which the impeller 4 has maximum diameter.

[0020]

Furthermore, the shape of each of the trailing edges 8c is a smooth curve, and each of the trailing edges 8c protrudes outward in a radial direction of the impeller 4 from a portion 8e that is adjacent to the first side plate 6 and a portion 8f that is adjacent to the second side plate 7 such that the amount of protrusion increases continuously toward the trailing edge tip 8d.

[0021]

In addition, an axial position of each of the trailing edge tips 8d is closer to an axial position of the outer circumference of the first side plate 6 than to an axial position of the outer circumference of the second side plate 7. In other words, the axial position of each of the trailing edge tips 8d is further downstream in the outlet direction than a center (Straight Line L1 in Figure 3) between the axial position of the outer circumference of the first side plate 6 and the axial position of the outer circumference of the second side plate 7.

[0022]

The outer circumferential diameter (R1 in Figure 3) of the first side plate 6 is greater than the outer circumferential diameter (R2 in Figure 3) of the second side plate 7. In other words, the outer circumference of the first side plate 6 is positioned further outward in the radial direction of the impeller than the outer circumference of the second side plate 7.

[0023]

Figure 4 is a partial enlargement of Figure 1 for explaining a relationship between the impeller 4 and the deflecting air channel 11 according to Embodiment 1, and features of the deflecting air channel 11. The deflecting 5

8274944J (GHMatters) P104280AU air channel 11 has: a deflecting portion 11a that is positioned radially outside the impeller 4; and a discharging duct portion 11b that is positioned downstream from the deflecting portion 11a, and that directs the airflow in the outlet direction. An outlet 11c is disposed on a downstream end portion of the discharging duct portion 11b.

[0024]

The discharging duct portion 11b is an air channel that is formed between the inner frame cylindrical portion 9a and the forming member 10. A cross-sectional shape of the discharging duct portion 11 b that is perpendicular to the rotating shaft 5 is a ring shape.

[0025]

The trailing edge tips 8d are positioned radially further outward from the impeller 4 than the outer circumference of the first side plate 6. In other words, the maximum diameter of the impeller 4 on the trailing edges 8c is greater than the outer circumferential diameter of the first side plate 6.

[0026] A diameter of a locus of the trailing edge tips 8d during rotation of the impeller 4, i.e., the maximum diameter of the impeller 4 on the trailing edges 8c, is greater than an inside diameter of the discharging duct portion 11 b at the connecting surface 12 between the deflecting portion 11a and the discharging duct portion 11 b and less than the outside diameter thereof.

[0027]

In Figure 4, R1 < RP and R3 < RP < R4, where R1 is the outer circumferential diameter of the first side plate 6, R3 is the inside diameter of the discharging duct portion 11b at the connecting surface 12 between the deflecting portion 11a and the discharging duct portion 11b, R4 is the outside diameter, and RP is the maximum diameter of the impeller 4 on the trailing edges 8c.

[0028]

The deflecting portion 11a is wider downstream in the outlet direction, and narrower upstream. In other words, the inside diameter (a radial dimension R5 at Point Q1 in Figure 4) of the forming member 10 at a position that is level with the outer circumference of the first side plate 6 in the axial direction is greater than the inside diameter (a radial dimension R6 at Point Q2 in Figure 4) of the forming member 10 at a position that is level with the outer circumference of the second side plate 7 in the axial direction (R5 > R6). An 6

8274944J (GHMatters) P104280.AU inner wall surface of the deflecting portion 11a is thereby inclined such that an inside diameter increases downstream in the outlet direction.

[0029] A plurality of stationary vanes 13 that perform static pressure recovery by reducing tangential speed components of the air flow that has flowed out from the impeller 4 and flowed into the discharging duct portion 11b are disposed so as to be spaced apart from each other circumferentially in the discharging duct portion 11b.

[0030]

Next, operation will be explained. The impeller 4 rotates together with the output shaft 3 due to action of the motor 1. Air inside the impeller 4 is pressed by the pressure surfaces 8a of the blades 8, and is directed outward in a radial direction of the impeller 4. Pressure is thereby reduced at a central portion of the impeller 4, and external air is supplied into the impeller 4 through the suction port 7a.

[0031]

The air inside the impeller 4 that is directed radially outward flows out of the impeller 4 from outflow orifices of the impeller 4 that are formed by the outer circumference of the first side plate 6, the outer circumference of the second side plate 7, and the trailing edges 8c of the blades 8, and flows into the deflecting portion 11 a of the deflecting air channel 11.

[0032]

Orientation of the air that has flowed out of the impeller 4 is changed rapidly to the outlet direction in the deflecting portion 11a. The air that has changed orientation to the outlet direction passes through the discharging duct portion 11 b and is released externally from the outlet 11c.

[0033]

In order to reduce loss that arises when the radial components of the air flow are deflected to the axial direction in the deflecting portion 11a, the radius of curvature of deflection need only be increased by increasing radial dimensions of the deflecting air channel 11. However, in that case, that method cannot be selected if there are constraints on fan dimensions because overall dimensions of the fan increase. Nor can the required work rate be obtained any longer if the diameter of the impeller 4 is reduced.

[0034] 7

8274944J (GHMatters) P104280AU

In answer to that, in the centrifugal fan according to Embodiment 1, deflection loss when the orientation of outflowing air flow from the impeller 4 is changed to an axial direction within limited radial dimensions can be reduced by adopting a configuration such as that described above, enabling input relative to required work rate to be reduced.

[0035]

Details of action of the air in a vicinity of the trailing edges 8c of the blades 8 of the centrifugal fan according to Embodiment 1 will now be explained. In the centrifugal fan according to Embodiment 1, axial positions of the trailing edge tips 8d are closer to the axial position of the outer circumference of the first side plate 6 than to the axial position of the outer circumference of the second side plate 7. The trailing edges 8c protrude outward in a radial direction of the impeller 4 from portions 8f that are adjacent to the second side plate 7 toward the trailing edge tips 8d. In addition, pressure is lower near the negative pressure surfaces 8b of the blades 8, drawing in air from the surrounds.

[0036]

Because the force that the blades 8 exert on the air becomes greater as the circumferential speed increases, the greatest suction force arises at a position where the axial position is closer to the first side plate 6 than the outer circumference of the second side plate 7. Because of that, a force from a vicinity of the second side plate 7 toward the outlet direction is applied to air in the vicinity of the trailing edges 8c. The pressure increase that accompanies collision with the inner wall of the deflecting portion 11a is thereby reduced, reducing deflection loss. Thus, loss that accompanies deflection on a radially outer side of the impeller 4 is reduced, enabling the highly efficient centrifugal fan that has reduced input relative to required work rate to be obtained.

[0037]

In the centrifugal fan according to Embodiment 1, the trailing edge tips 8d are positioned radially further outward from the impeller 4 than the outer circumference of the first side plate 6. The maximum diameter of the impeller 4 on the trailing edges 8c is also greater than the outer circumferential diameter of the first side plate 6.

[0038]

Because of that, portions of the trailing edges 8c from the first side plate 6 to the trailing edge tips 8d are shaped so as to be oriented in the outlet 8

6274944.1 (GHMatters) P104260.AU direction in the axial direction, and face the connecting surface 12 between the deflecting portion 11a and the discharging duct portion 11b. The air can thereby be made to flow out from the rotary surfaces that are formed by the portions of the trailing edges 8c from the first side plate 6 to the trailing edge tips 8d toward the connecting surface 12, enabling deflection loss to be further reduced. Consequently, an even more highly efficient centrifugal fan can be achieved.

[0039]

In addition, in the centrifugal fan according to Embodiment 1, the outer circumferential diameter of the first side plate 6 is greater than the outer circumferential diameter of the second side plate 7. Because of that, suction force due to the negative pressure surfaces 8b is relatively greater in a vicinity of the first side plate 6 where the blades 8 are present in a region in the radial direction of the impeller 4 from the outer circumference of the second side plate 7 to the outer circumference of the first side plate 6. On the other hand, suction force due to the negative pressure surfaces 8b is relative small in a vicinity of the second side plate 7, which is shaped such that the blades 8 are only partially present, or not present at all.

[0040]

Consequently, components of the air flow in the outlet direction can be further increased, and an action that imparts the force in the outlet direction to air in the vicinity of the trailing edges 8c that has been mentioned above can be increased further, enabling deflection loss to be further reduced. Consequently, an even more highly efficient centrifugal fan can be achieved.

[0041]

Now, the radial speed component and the tangential speed component of the air that flows out from the impeller 4 are increased. Furthermore, air in which centrifugal force due to the tangential speed component has been added to the force of inertia due to the radial speed component, and that has flowed out from the impeller 4, is pushed against the inner wall of the deflecting portion 11a.

[0042]

In answer to that, in the centrifugal fan according to Embodiment 1, because the inner wall of the deflecting portion 11a is inclined such that the diameter on an opposite side from the diameter of the outlet side is relatively reduced, a portion of the force that pushes the air against the inner wall is 9

8274944.1 (GHMatters) P104280.AU changed to a force along the inner wall toward the discharging duct portion 11b in response to the inclination thereof.

[0043]

Because of that, pressure increases that accompany collision into the inner wall of the deflecting portion 11a are reduced, enabling the deflection loss to be reduced. Consequently, an even more highly efficient centrifugal fan can be achieved.

[0044]

In addition, in the centrifugal fan according to Embodiment 1, stationary vanes 13 are disposed so as to extend from the connecting surface 12 of the discharging duct portion 11b to the outlet 11c. Because of that, pressure increasing capacity is increased, and the pressure increasing ratio in the impeller 4 can be reduced relative to the required pressure increasing capacity, enabling the input of the impeller 4 to be reduced. Furthermore, because the stationary vanes 13 do not overlap with the impeller 4 in the axial direction, it is not necessary to reduce the diameter of the impeller 4 even if the stationary vanes 13 are installed. Because of that, a high-output centrifugal fan can be made within limited radial dimensions.

[0045]

Figure 5 is a configuration diagram that shows a vacuum cleaner into which the centrifugal fan according to Embodiment 1 is mounted. A centrifugal fan 22 that is similar or identical to that of Embodiment 1 and a dust collection box 23 are accommodated in a vacuum cleaner main body 21. A rod-shaped pipe 25 is also connected to the vacuum cleaner main body 21 by means of a flexible hose 24. A head portion 26 is connected to an end portion at an opposite end of the pipe 25 from the hose 24.

[0046]

By driving the motor 1 of the centrifugal fan 22 to generate airflow, dust is sucked together with air through a suction port of the head portion 26. The air and dust that have been sucked in are conveyed inside the vacuum cleaner main body 21 through the pipe 25 and the hose 24. Then, the dust is accumulated inside the dust collection box 23, and the air is discharged outside the vacuum cleaner main body 21 through the centrifugal fan 22.

[0047] 10

8274944.1 (GHMatters) P104280.AU

By using a centrifugal fan 22 such as that described above, increases in output, increases in efficiency, and reductions in size can be achieved in the vacuum cleaner.

[0048]

Moreover, in the above example, a centrifugal fan that blows air is shown, but a gas other than air may be blown.

Furthermore, the axial position of the trailing edge tips 8d may be level with the axial position of the outer circumference of the first side plate 6.

In addition, the centrifugal fan according to the present invention can also be applied to machines other than vacuum cleaners.

EXPLANATION OF NUMBERING

[0049] 1 MOTOR; 4 IMPELLER; 6 FIRST SIDE PLATE; 7 SECOND SIDE PLATE; 8 BLADE; 8c TRAILING EDGE; 8d TRAILING EDGE TIP; 10 FORMING MEMBER; 11 DEFLECTING AIR CHANNEL; 11a DEFLECTING PORTION; 11b DISCHARGING DUCT PORTION; 13 STATIONARY VANE; 22 CENTRIFUGAL FAN. 11

6274944.1 (GHMatters) P104260.AU

Claims

1. A centrifugal fan comprising: a motor; a centrifugal impeller that includes: a first side plate; a second side plate that faces the first side plate; and a plurality of blades that are held between the first side plate and the second side plate, the centrifugal impeller being driven by the motor; and a forming member that covers an outer circumference of the impeller so as to form a deflecting air channel for changing direction of an air flow immediately after being discharged from the impeller to an outlet direction that is toward a first axial end of the impeller, wherein: the first side plate is positioned further downstream in the outlet direction than the second side plate; the blades include a trailing edge that is positioned on an outer end portion in a radial direction of the impeller; the trailing edge includes a trailing edge tip that is positioned on a radially outermost side of the impeller, and that protrudes outward in a radial direction of the impeller from a portion that is adjacent to the second side plate toward the trailing edge tip; and an axial position of the trailing edge tip is further downstream in the outlet direction than a center between an axial position of an outer circumference of the first side plate and an axial position of an outer circumference of the second side plate.

2. The centrifugal fan according to Claim 1, wherein the deflecting air channel includes: a deflecting portion that is positioned radially outside the impeller; and a discharging duct portion that is positioned downstream from the deflecting portion, and that directs airflow parallel to the outlet direction.

3. The centrifugal fan according to Claim 2, wherein: the trailing edge tip is positioned radially further outward from the impeller than an outer circumference of the first side plate; and a diameter of a locus of the trailing edge tip during rotation of the impeller is greater than an inside diameter and less than an outside diameter of the discharging duct portion at a connecting surface between the deflecting portion and the discharging duct portion.

4. The centrifugal fan according to either of Claims 2 or 3, wherein an inner wall surface of the deflecting portion is inclined such that an inside diameter increases downstream in the outlet direction.

5. The centrifugal fan according to any one of Claims 2 through 4, wherein a stationary vane that performs static pressure recovery by reducing a tangential speed component of the airflow is disposed on the discharging duct portion.

6. The centrifugal fan according to any one of Claims 1 through 5, wherein an outer circumferential diameter of the first side plate is greater than an outer circumferential diameter of the second side plate.

7. A vacuum cleaner comprising the centrifugal fan according to any one of Claims 1 through 6.