Centrifugal Impeller and Centrifugal Blower

Abstract

A centrifugal impeller includes a cover, a base opposite the cover and a plurality of blades. The cover has an inlet. The plurality of blades surround the inlet and are arranged between and connect the cover and the base. Inlet edges of one end of the blades adjacent the center of the impeller define a cavity in communicate with the inlet. The dimension of the cavity gradually decreases along the direction from the cover towards the base.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 201310452740.4 filed in The People's Republic of China on Sep. 29, 2013.

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 comprising an electric motor and a centrifugal impeller driven by the motor, the centrifugal impeller comprising: a cover, a base opposite the cover and a plurality of blades, the cover having an inlet, the plurality of blades surrounding the inlet and arranged between and connecting the cover and the base, inlet edges of ends of the blades adjacent the center of the impeller defining a cavity in communication with the inlet, wherein the dimension of the cavity gradually decreases in the direction from the cover towards the base.

Preferably, each inlet edge forms an angle γ with the base in the range of 55° to 75°. Ideally, angle γ is in the range of 62° to 70°. Most preferably, angle γ is in the range of 65° to 68°.

Preferably, each blade 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.

Preferably, the radius of the second arc segment is greater than the radius of the first arc segment.

Preferably, the blower further comprises a diffuser and a casing mounted to the diffuser, the diffuser being mounted to the motor and disposed between the motor and the impeller, the impeller being received in a chamber defined by the diffuser and the casing, the casing having an opening facing the inlet of the impeller.

Preferably, the diffuser has a plurality of guide holes and a plurality of smoothly curved diffusing passages each extending from an outer end to an inner end, the air flow generated by the impeller flowing from one side of the diffuser adjacent the 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.

Preferably, the diffuser has a plurality of passage walls forming the diffusing passages, one end of at least one of the passage walls adjacent the center of the diffuser has a guide portion for guiding the air flow in adjacent diffusing passages to two sides of a mounting portion connecting the diffuser to the motor.

Preferably, the image of the guide portion in the radial section of the motor is raindrop-shaped.

Preferably, ends of two of the passage walls of the diffuser adjacent the center of the diffuser has two streamlined guide portions which are diametrically opposite to each other.

Preferably, the motor includes a stator comprising a stator core and stator windings wound about teeth of the stator core, and the two guide 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.

Preferably, 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 the hollow space and located at two sides of the guide portions.

Preferably, the side wall has a plurality of inclined guide slopes, the guide holes being located at the ends of the guide slopes.

Preferably, each of the guide portions has a mounting hole for receiving a fastener for fixing the diffuser to the motor.

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 which bear against 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 0 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.

The diffuser 31 has a plurality of passage walls 36 at the side adjacent the motor to form the diffusing passages 34. Ends of the passage walls 36 adjacent the center of the impeller are spaced from one another and define a space at the center of the diffuser 31. The end of at least one of the passage walls 36 has a streamlined guide portion 38a for guiding the air flow in adjacent diffusing passages 34 to two sides of the guide portions 38a. Preferably, the image of the guide portion 38a in the radial cross-section of the motor is raindrop-shaped.

Referring to FIGS. 8 to 11, in this embodiment, two guide portions 38a are arranged at two mounting portions 38 of the diffuser 31. The two mounting portions 38 are respectively arranged at the ends of two passage walls 36 adjacent the center of the diffuser 31. The two guide portions 38 are opposite to each other about the center of the diffuser 31. Axial end surfaces of the guide portions 38a have a mounting recess 39 for fastening to the stator core 41 of the motor. The stator of the motor includes a stator core 41 and two stator windings wound about teeth of the stator core 41. Axial ends of the two stator windings extend into the cavity of the diffuser 31 and are located at two sides of the guide portions 38a in the circumferential direction. The two guide portions 38a 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 guide portions 38a so as to better cool the stator windings 44. The guide portions 38a are raindrop-shaped, which can reduce the resistance of the air flow.

Further, the two guide portions 38a have mounting holes 37 for mounting the diffuser to the motor. In the embodiment, the mounting holes 37 are located in the mounting recesses 39. During assembly, bolts or screws 60 pass through the mounting holes of the mounting recess 39 and the stator core 41 to connect with 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 and a centrifugal impeller driven by the motor, the centrifugal impeller comprising: a cover, a base opposite the cover and a plurality of blades, the cover having an inlet, the plurality of blades surrounding the inlet and arranged between and connecting the cover and the base, inlet edges of ends of the blades adjacent the center of the impeller defining a cavity in communication with the inlet, wherein the dimension of the cavity gradually decreases in the direction from the cover towards the base.

2. The blower of claim 1, wherein each inlet edge forms an angle γ with the base in the range of 55° to 75°.

3. The blower of claim 1, wherein each inlet edge forms an angle γ with the base in the range of 62° to 70°.

4. The blower of claim 1, wherein each inlet edge forms an angle γ with the base in the range of 65° to 68°.

5. The blower of claim 1, wherein each blade 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.

6. The impeller of claim 5, wherein the radius of the second arc segment is greater than the radius of the first arc segment.

7. The blower of claim 1, further comprises a diffuser and a casing mounted to the diffuser, the diffuser being mounted to the motor and disposed between the motor and the impeller, the impeller being received in a chamber defined by the diffuser and the casing, the casing having an opening facing the inlet of the impeller.

8. The blower of claim 7, wherein the diffuser has a plurality of guide holes and a plurality of smoothly curved diffusing passages each extending from an outer end to an inner end, the air flow generated by the impeller flowing from one side of the diffuser adjacent the 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.

9. The blower of claim 8, wherein the diffuser has a plurality of passage walls forming the diffusing passages, one end of at least one of the passage walls adjacent the center of the diffuser has a guide portion for guiding the air flow in adjacent diffusing passages to two sides of a mounting portion connecting the diffuser to the motor.

10. The blower of claim 9, wherein the image of the guide portion in the radial section of the motor is raindrop-shaped.

11. The blower of claim 9, wherein ends of two of the passage walls of the diffuser adjacent the center of the diffuser has two streamlined guide portions which are diametrically opposite to each other.

12. The blower of claim 11, wherein the motor includes a stator comprising a stator core and stator windings wound about teeth of the stator core, and the two guide 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 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 the hollow space and located at two sides of the guide portions.

14. The blower of claim 13, wherein the side wall has a plurality of inclined guide slopes, the guide holes being located at the ends of the guide slopes.

15. The blower of claim 11, wherein each of the guide portions has a mounting hole for receiving a fastener for fixing the diffuser to the motor.