Centrifugal blower with non-uniform blade spacing

• US 8,398,380 B2
• Filed: 09/02/2009
• Issued: 03/19/2013
• Est. Priority Date: 09/02/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Duke, Connor Raymond
• Primary Examiner(s): Freay, Charles
• Assistant Examiner(s): Hamo, Patrick
• Application Number:
  US12/552,857
• Publication Number:
  US 20110052385A1
• Time in Patent Office: 1,294 Days
• Field of Search: 417/410.1, 416/203, 416/500, 361/695
• US Class Current: 417/410.1
• CPC Class Codes: F04D 29/281 for fans or blowers
• CPC Class Codes: F04D 29/666 by means of rotor construction or layout, e.g. unequal distribution of blades or vanes
• CPC Class Codes: Y10T 29/49329 Centrifugal blower or fan

Abstract

A centrifugal blower in a cooling system of an electronic device having non-uniform blade spacing with acceptable balance. The non-uniform blade spacing is determined according to specific repeating sinusoidal patterns to obtain acoustic artifacts that are favorable and balance that is similar to that found with equal fan blade spacing. The fan impeller can include a prime number of fan blades to prevent higher harmonic interaction among noise sources. The perceived sound quality from the fan is improved with essentially no effect on the thermal performance of the fan.

Claims

1. A centrifugal blower arranged within a portable electronic device, comprising:

a motor having a number of pole passes, wherein the number of pole passes is an even number; and

a prime number of impeller blades spaced non-uniformly about a central hub, the prime number of impeller blades being equal to at least 17,

wherein each blade position corresponds to a unique point along at least two repeating sinusoidal patterns, and wherein a blade passage frequency of the centrifugal blower does not line up or merge with a pole passage frequency of the centrifugal blower.

2. The centrifugal blower of claim 1, wherein each of the blade positions corresponds to a unique point along four repeating sinusoidal patterns.

3. The centrifugal blower of claim 1, wherein the number of impeller blades is 29 or fewer.

4. The centrifugal blower of claim 3, wherein the centrifugal blower produces a main tone of about 2300 Hz and side band tones of about 1900 Hz and 2700 Hz.

5. The centrifugal blower of claim 3, wherein the centrifugal blower has a diameter of 150 cm or less.

6. The centrifugal blower of claim 1, wherein each of the blade positions is modified by about 1 percent to about 7 percent compared to evenly spaced impeller blades of an impeller having a same number of impeller blades.

19. The centrifugal blower of claim 1, wherein positions of the impeller blades are evenly distributed along the at least two repeating sinusoidal patterns.

20. The centrifugal blower of claim 1, wherein the at least two repeating sinusoidal patterns correspond to a single revolution of the centrifugal blower.

7. An impeller of a centrifugal blower for an electronic device, comprising:

a prime number of impeller blades, wherein the impeller blades are spaced non-uniformly about a central hub and the prime number is at least 17,

wherein a position of each of the impeller blades corresponds to a unique point along at least two repeating sinusoidal patterns.

8. The impeller of the centrifugal blower of claim 7, wherein the blower comprises at least 23 impeller blades.

9. The impeller of the centrifugal blower of claim 7, wherein a number of the at least two repeating sinusoidal amplitude patterns is even.

10. The impeller of the centrifugal blower of claim 7, wherein the at least two repeating sinusoidal amplitude patterns is four.

11. The impeller of the centrifugal blower of claim 7, wherein the electronic device is a laptop computer.

12. The impeller of the centrifugal blower of claim 7, wherein the positions of each of the impeller blades is modified by about 1 percent to about 7 percent compared to evenly spaced impeller blades of an impeller having a same prime number of impeller blades.

13. A method of manufacturing a fan, comprising:

providing a motor having a number of pole passes, wherein the number of pole passes is an even number;

providing a prime number of impeller blades; and

positioning the impeller blades non-uniformly around a central hub such that each blade position corresponds to a unique point along at least two repeating sinusoidal patterns.

14. The method of claim 13, wherein the number of impeller blades is 29 or fewer.

15. The method of claim 14, wherein the number of impeller blades is 17.

16. The method of claim 14, wherein the number of impeller blades is 23.

17. The method of claim 13, wherein each blade position corresponds to a unique point along at least four repeating sinusoidal patterns.

18. The method of claim 13, wherein positioning comprises modifying each of the blade positions of an impeller having a same number of uniformly spaced impeller blades by about 1 percent to about 7 percent.