Centrifugal Impeller and Centrifugal Blower

Abstract

A centrifugal blower includes an electric motor, a centrifugal impeller driven by the motor, a diffuser mounted to the motor and disposed between the motor and the centrifugal impeller, and a casing mounted to the diffuser. The centrifugal impeller is received in a chamber defined by the diffuser and the casing. the casing defines an opening facing the inlet of the centrifugal impeller. The diffuser has a plurality of passage walls, and a plurality of diffusing passages, each bounded by neighboring passage walls. The diffuser further has at least one mounting portion connected to one of the passage walls. A cross section of each of the diffusing passages is increased form an outer end to an inner end thereof and no throat is formed in each of the diffusing passages.

Description

FIELD OF THE INVENTION

This invention relates to a blower and in particular, to a centrifugal blower and a centrifugal impeller especially suitable for the centrifugal blower.

BACKGROUND OF THE INVENTION

A centrifugal blower includes a motor and a centrifugal impeller. The centrifugal impeller includes a cover, a base and a plurality of blades which are arranged between the cover and the base and connect the cover and the base. The cover has an inlet for entrance of air flow. Ends of the blades adjacent the center of the impeller define a cavity facing the inlet of the cover.

The centrifugal impeller is driven by the motor. A low pressure zone is formed at the center of the impeller. Air outside the blower enters into the cavity via the inlet of the impeller, then flows into the flow passages formed by the blades and is eventually discharged from the impeller.

One of the disadvantages of the current design is that the efficiency of the blower is low.

SUMMARY OF THE INVENTION

Accordingly, in one aspect thereof, the present invention provides a centrifugal blower including an electric motor, a centrifugal impeller driven by the motor, a diffuser mounted to the motor and disposed between the motor and the centrifugal impeller, and a casing mounted to the diffuser. The centrifugal impeller is received in a chamber defined by the diffuser and the casing. the casing defines an opening facing the inlet of the centrifugal impeller. The diffuser has a plurality of passage walls, and a plurality of diffusing passages, each bounded by neighboring passage walls. The diffuser further has at least one mounting portion connected to one of the passage walls. A cross section of each of the diffusing passages is increased form an outer end to an inner end thereof and no throat is formed in each of the diffusing passages.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way of example only, with reference to figures of the accompanying drawings. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same reference numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below.

FIG. 1 illustrates a blower in accordance with a preferred embodiment of the present invention;

FIG. 2 shows the blower of FIG. 1, with a casing removed;

FIG. 3 shows a centrifugal impeller being a part of the blower of FIG. 1;

FIG. 4 is a partial view of a part of the impeller of FIG. 3;

FIG. 5 is a view of the impeller of FIG. 3, with a cover removed;

FIG. 6 is a plan view of the impeller of FIG. 3, with the cover removed;

FIG. 7 is a view of an impeller side of a diffuser, being a part of the blower of FIG. 1;

FIG. 8 is a view of a motor side of the diffuser of FIG. 7;

FIG. 9 is a plan view of the motor side of the diffuser of FIG. 7;

FIG. 10 is a plan view of the diffuser and motor parts superimposed; and

FIG. 11 shows the blower of FIG. 1 viewed from another angle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a centrifugal blower 20 in accordance with a preferred embodiment of the present invention comprises an electric motor, a centrifugal impeller 23 mounted to a shaft of a rotor of the motor, a diffuser 31 mounted to the motor and arranged between the motor and the impeller 23, and a casing 21 mounted to the diffuser 31. The impeller 23 is received in a chamber 22 defined by the diffuser 31 and the casing 21. The casing 21 has an opening 19 facing an inlet of the impeller 23.

In the embodiment, the motor is a universal motor. A stator of the motor comprises a stator core 41, stator windings 44 wound about teeth of the stator core 41, an end cap 43 mounted to the stator core 41, and a brush assembly 45 mounted to the end cap 43. In this embodiment, the diffuser 31 functions as another end cap of the motor. The diffuser 31 and end cap 43 are mounted to the axial ends of the stator core 41. The diffuser 31 has two projected mounting portions 38 for mounting diffuser 31 to the stator core 41. The rotor of the motor comprises a shaft, a commutator 51 fixed to the shaft, a rotor core and rotor windings (not shown in the figures). The shaft is mounted to the end cap 43 and the diffuser 31 via bearings such that the rotor may rotate relative to the stator.

The diameter of the diffuser 31 is slightly greater than that of the impeller 23. A plurality of guide holes 34a adjacent outlets of the impeller 23 are formed at the outer periphery of the diffuser 31. Air flowing out from the outlets of the impeller 23 flows from the impeller side of the diffuser 31 to the motor side of the diffuser 31 the guide holes 34a.

Referring to FIGS. 3 and 4, the impeller 23 comprises a cover 25, a base 24 opposite the cover 25, and a plurality of blades 26. The cover 25 has an inlet 27 formed at a center thereof and facing the opening 19 of the casing 21. The plurality of blades 26 surrounding the inlet are disposed between and connect the cover 25 and the base 24. Ends of the blades 26 adjacent the center of the impeller 23 form a cavity 28 in communication with the inlet of the impeller 23. An inlet edge 26e of the inner end of each blade 26 adjacent the center of the impeller is inclined relative to the base 24 of the impeller 23. Therefore, the dimension of the cavity gradually decreases along the direction from the cover 25 to the base 24. By this configuration, when the impeller 23 rotates, the air flows into the cavity and then into the flow passages formed by the blades 26. The amount of air in the cavity gradually decreases along the direction towards the base 24. As the change of the amount of air in the cavity matches the change of the dimension of the cavity, the air flow is more stable and uniform.

The inlet edge 26e of each blade 26 forms an angle θ with the normal line L1 of the base 24 and forms an angle γ with the end surface of the base 24. The line L2 in the figure represents the imaging direction of the inlet edge 26e on the base 24. As the normal line L1 of the base is perpendicular to the line L2, the sum of the angle θ and the angle γ equals 90°. Experiments show that the impeller 23 has good performance and high efficiency when the angle γ is in the range of 55° to 75° and the angle θ is accordingly in the range of 35° to 15°.

Preferably, the angle γ is in the range of 62° to 70° and the angle θ is accordingly in the range of 28° to 20°.

More preferably, the angle γ is in the range of 65° to 68° and the angle θ is accordingly in the range of 25° to 22°.

Referring to FIGS. 5 and 6, each blade 26 includes a first arc segment 26a and a second arc segment 26b which have different radii. The first arc segment 26a is located at the radially inner end of the blade 26 adjacent the center of the impeller 23 and the second arc segment 26b is located at the radially outer end of the blade 26 away from the center of the impeller 23. Compared with the traditional blade with a single arc segment, the blades 26 in the present invention have better performance and higher efficiency.

In the embodiment, the radius R2 of the second arc segment 26b is greater than the radius R1 of the first arc segment 26a.

Referring to FIGS. 7 and 8, the diffuser 16 has an end wall 32 and an annular side wall 29 extending from the end wall 32 towards the motor. The end wall 32 and the side wall 29 form a hollow space 30 facing the motor. A bearing for supporting the shaft of the rotor of the motor is mounted in a recess at the center of the end wall 32. The side wall 29 has crimping recesses 35 facing the motor. During the assembly, portions of the casing 21 is crimped into the recesses 35 (see FIG. 1). The side wall further has a plurality of guide slopes 33 inclined from the end surface of the end wall 32 towards the motor and a plurality of guide holes 34 at the end of the guide slopes 33. Referring back to FIGS. 1 and 2, the end wall 32 of the diffuser 31 is adjacent to the base 24 of the impeller 23. The guide slopes 33 and the guide holes 34a are adjacent to the outlets of the impeller 23. Air flowing out from the outlets of the impeller 23 flows into the guide holes 34a under the guidance of the guide slopes 33.

Referring to FIGS. 8 and 9, a plurality of smoothly curved diffusing passages 34 having outer ends and inner ends are formed in the hollow space of the diffuser 31. The outer ends of the diffusing passages 34 are in communication with corresponding guide holes 34a and the inner ends of the diffusing passages 34 are in communication with one another. Therefore, air flow from the impeller 23 is able to flow from the impeller side of the diffuser 31 to the motor side of the diffuser 31 via the guide holes 34a, then flows into the center of the diffuser 31 via the diffusing passages 34, and passes through the motor in the axial direction to cool the motor. To reduce the noise caused by the resistance of the air flow and improve the air diffusion efficiency, the cross section of each of the diffusing passages 34 is gradually increased form the outer end to the inner end thereof. No throat is formed in each of the diffusing passages 34.

The diffuser 31 includes plurality of passage walls 36 at the side facing the motor to bound the diffusing passages 34. Inner ends of the passage walls 36 are spaced from one another and define a space at the center of the diffuser 31. The two mounting portions 38 are respectively connected to the inner ends of two of passage walls 36 and diametrically opposite to each other. Each of the mounting portions 38 has a cylindrical surface 38a protrudes towards the center of the diffuser 31. The cylindrical surface 38a of each mounting portion 38 is connected to the corresponding one of the passage walls 36 with a smooth transition to avoid a throat occurring at the corresponding one of the diffusing passages 34 bounded by said one of the passage walls 36. Each of the corresponding passage walls 36 connected to the mounting portion 38 has a variable thickness, which gradually increases from the outer end to the inner end thereof. Therefore, each corresponding passage wall 36 together with the mounting portion 38 connect thereto has a raindrop-shaped contour, which helps to reduce the resistance of the air flow.

Referring to FIGS. 8 to 11, Each of the mounting portions 38 defines a mounting recess 39 for positioning the stator core 41 of the motor. The stator of the motor includes a stator core 41 and two stator windings 44 wound about teeth of the stator core 41. Axial ends of the two stator windings 44 extend into the space defined by the inner ends of the passage walls 36 of the diffuser 31 and are located at two sides of the mounting portions 38 in the circumferential direction. The two mounting portions 38 are circumferentially arranged between the two stator windings 44 for guiding the air flow in the diffusing passages 34 to the stator windings 44. The air flow is thus concentrated on two sides of a virtual line connecting the two mounting portions 38 so as to better cool the stator windings 44.

Further, each of the mounting portions 38 defines a mounting hole 37, which enable each of the mounting portions 38 to mate with a fastener to fixed the diffuser to the motor. In the embodiment, the mounting holes 37 are located in the mounting recesses 39. During assembly, the fasteners 60, such as bolts or screws, pass through the mounting holes 37 of the mounting portions 38 and the stator core 41 to be fastened to the end cap 43 so as to fix the diffuser 31, the stator core 41 and the end cap 43 together.

In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item but not to exclude the presence of additional items.

Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.

Claims

1. A centrifugal blower comprising: an electric motor;a centrifugal impeller driven by the motor;a diffuser mounted to the motor and disposed between the motor and the centrifugal impeller; anda casing mounted to the diffuser, the centrifugal impeller being received in a chamber defined by the diffuser and the casing, the casing having an opening facing the inlet of the centrifugal impeller;wherein the diffuser has a plurality of passage walls, and a plurality of diffusing passages, each bounded by neighboring passage walls, the diffuser further has at least one mounting portion connected to one of the passage walls, a cross section of each of the diffusing passages is increased form an outer end to an inner end thereof and no throat is formed in each of the diffusing passages.

2. The centrifugal blower of claim 1, wherein said at least one mounting portion is connected to an inner ends of the corresponding one of the passage walls, each of said at least one mounting portion comprises a cylindrical surface protrudes towards the center of the diffuser.

3. The centrifugal blower of claim 2, wherein the cylindrical surface is connected to the corresponding one of the passage walls with a smooth transition; the passage wall connected to said at least one mounting portion has a variable thickness, which gradually increases from the outer end to the inner end thereof; said at least one mounting portion together with the corresponding passage wall connected thereto has a raindrop-shaped contour.

4. The centrifugal blower of claim 1, wherein said at least one mounting portion comprises two mounting portions respectively connected to the inner ends of two of passage walls and diametrically opposite to each other.

5. The centrifugal blower of claim 1, wherein the centrifugal impeller comprises a cover defining an inlet;a base opposite the cover; anda plurality of blades sandwiching between the cover and the base, the plurality of blades surrounding the inlet, inlet edges of ends of the blades adjacent the center of the centrifugal impeller defining a cavity in communication with the inlet, the dimension of the cavity gradually decreasing in the direction from the cover towards the base.

6. The centrifugal blower of claim 5, wherein each inlet edge forms an angle γ with the base in the range of 55° to 75°.

7. The centrifugal blower of claim 6, wherein each inlet edge forms an angle γ with the base in the range of 62° to 70°.

8. The centrifugal blower of claim 7, wherein each inlet edge forms an angle γ with the base in the range of 65° to 68°.

9. The centrifugal blower of claim 5, wherein each blade has a thickness, which is invariable along longitudinal direction thereof, and comprises first and second arc segments which have different radii, the first arc segment being located at a radially inner portion of the blade, and the second arc segment being located at a radially outer portion of the blade.

10. The centrifugal blower of claim 9, wherein the radius of the second arc segment is greater than the radius of the first arc segment.

11. The centrifugal blower of claim 1, wherein the diffuser defines a plurality of guide holes, the air flow generated by the centrifugal impeller flowing from one side of the diffuser adjacent the centrifugal impeller to the side of the diffuser adjacent the motor via the guide holes, outer ends of the diffusing passages being in communication with corresponding guide holes and inner ends of the diffusing passages being in communication with one another.

12. The centrifugal blower of claim 4, wherein the motor comprises a stator comprising a stator core and stator windings wound about teeth of the stator core, and the two mounting portions are respectively located at gaps between the stator windings so as to guide the air flow in the diffusing passages to the stator windings.

13. The centrifugal blower of claim 12, wherein the diffuser has an end wall and a side wall extending from the end wall towards the motor, the passage walls and the diffusing passages being formed inside a space defined by the end wall and the side wall, axial ends of the stator windings extending into a space defined by the inner ends of the passage walls and located at two sides of the mounting portions.

14. The centrifugal blower of claim 13, wherein the side wall has a plurality of guide slopes which extends from the end wall towards the motor in a direction inclined as regard to an axial direction of the diffuser, the guide holes being located at the ends of the guide slopes away from the end wall.

15. The centrifugal blower of claim 1, wherein each of said at least one mounting portion defines a mounting hole for receiving a fastener for fixing the diffuser to the motor.