Auxiliary bearing for magnetically suspended rotor system

Patent metadata

Field	Value
Publication number	US-9695871-B2
Application number	US-201414290199-A
Country	US
Kind code	B2
Filing date	May 29, 2014
Priority date	May 29, 2013
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

An assembly that includes a rotating shaft supported with respect to a stationary housing by at least one active magnetic bearing presenting a mean radial air gap and at least one auxiliary bearing having a bushing fixed to the housing and a sleeve fixed on the rotating shaft. The bushing and the sleeve have opposite surfaces that define a clearance (E2) which is less than the mean radial air gap (E1). The bushing and the sleeve each exhibit symmetry around a longitudinal axis of the shaft and have different profiles in a longitudinal cross-section including the longitudinal axis to optimize the contact pressure distribution when the rotating shaft lands on the auxiliary bearing.

First claim

The invention claimed is:

1. An assembly comprising:
a rotating shaft supported with respect to a stationary housing by at least one active magnetic bearing presenting a mean radial air gap and at least one auxiliary bearing having a first smooth surface integral with the housing and a second smooth surface integral with the rotating shaft,
wherein the first and second smooth surfaces are opposite to each other and define a clearance which is less than the mean radial air gap, and
wherein the first smooth surface and the second smooth surface each exhibit symmetry around a longitudinal axis of the rotating shaft and have different profiles in a longitudinal cross-section including the longitudinal axis,
wherein the second smooth surface comprises a heat-treated surface formed on a sleeve fixedly mounted on the rotating shaft,
wherein the sleeve comprises a profile with a radius defined by reduction delta H given by equation:
Delta H=h *((2* u−lc )/( la−lc ))^exp,

wherein h is a total drop at an end of the profile,
wherein u is a distance of a point from a center of the sleeve,
wherein lc is a total length of a section of the sleeve to which no modification is done,
wherein la is a total length of the section of the sleeve, and
wherein exp is an exponent larger than 1.

2. The assembly according to claim 1 , wherein the first smooth surface comprises a convex profile in the longitudinal cross-section and the second smooth surface comprises a concave profile in the longitudinal cross-section.

3. The assembly according to claim 1 , wherein the first smooth surface comprises a concave profile in the longitudinal cross-section and the second smooth surface comprises a convex profile in the longitudinal cross-section.

4. The assembly according to claim 1 , wherein the first smooth surface comprises a convex profile in the longitudinal cross-section.

5. The assembly according to claim 1 , wherein the first smooth surface comprises a straight profile in the longitudinal cross-section and the second smooth surface comprises a convex profile in the longitudinal cross-section.

6. The assembly according to claim 5 , wherein the first smooth surface comprises a heat-treated surface which is directly machined on the housing.

7. The assembly according to claim 6 , wherein the second smooth surface comprises a heat-treated surface which is directly machined on the rotating shaft.

8. The assembly according to claim 5 , wherein the first smooth surface comprises a heat-treated surface formed on a bushing fixedly mounted on the housing.

9. The assembly according to claim 5 , wherein the profile comprises a crowned profile.

10. A radial magnetic bearing device, comprising:
an assembly having a rotating shaft supported with respect to a stationary housing by at least one active magnetic bearing presenting a mean radial air gap and at least one auxiliary bearing having a first smooth surface integral with the housing and a second smooth surface integral with the rotating shaft, wherein
the first and second smooth surfaces are opposite to each other and define a clearance which is less than the mean radial air gap, and wherein
the first smooth surface and the second smooth surface each exhibit symmetry around a longitudinal axis of the rotating shaft and have different profiles in a longitudinal cross-section including the longitudinal axis,
wherein the second smooth surface comprises a heat-treated surface formed on a sleeve fixedly mounted on the rotating shaft,
wherein the sleeve has a profile with a radius defined by reduction delta H given by equation:
Delta H=h *(( 2 * u−lc )/( la−lc ))^exp,

wherein h is a total drop at an end of the profile,
wherein u is a distance of a point from a center of the sleeve,
wherein lc is a total length of a section of the sleeve to which no modification is done,
wherein la is a total length of the section of the sleeve, and
wherein exp is an exponent larger than 1.

11. An assembly comprising:
a rotating shaft supported with respect to a stationary housing by at least one active magnetic bearing presenting a mean radial air gap and at least one auxiliary bearing having a first smooth surface integral with the housing and a second smooth surface integral with the rotating shaft,
wherein the first and second smooth surfaces are opposite to each other and define a clearance which is less than the mean radial air gap, and
wherein the first smooth surface and the second smooth surface each exhibit symmetry around a longitudinal axis of the rotating shaft and have different profiles in a longitudinal cross-section including the longitudinal axis,
wherein the second smooth surface comprises a heat-treated surface formed on a sleeve fixedly mounted on the rotating shaft,
wherein the sleeve comprises a profile with a radius defined by reduction delta H given by equation:
Delta H=h *((ln(1−((2*min(abs( u ), la/ 2)/ l 2)^exp)))/(ln(1−( l 1/ l 2)^exp))),

wherein h is a total drop at an end of the profile,
wherein u is a distance of a point from a center of the sleeve,
wherein la is a total length of a section of the sleeve,
wherein exp is an exponent larger than 1,
wherein k1 is a factor calculated as l1=la*k1, and
wherein k2 is a factor calculated as l2=la*k2.

12. The assembly according to claim 11 , wherein the profile comprises a logarithmic profile.

13. The assembly according to claim 11 , wherein the mean radial air gap is between 0.2 and 0.5 mm and the clearance is between 0.15 and 0.3 mm.

14. The assembly according to claim 11 , wherein the first smooth surface comprises a convex profile in the longitudinal cross-section and the second smooth surface comprises a concave profile in the longitudinal cross-section.

15. The assembly according to claim 11 , wherein the first smooth surface comprises a concave profile in the longitudinal cross-section and the second smooth surface comprises a convex profile in the longitudinal cross-section.

16. The assembly according to claim 11 , wherein the first smooth surface comprises a convex profile in the longitudinal cross-section.

17. The assembly according to claim 11 , wherein the first smooth surface comprises a straight profile in the longitudinal cross-section and the second smooth surface comprises a convex profile in the longitudinal cross-section.

18. The assembly according to claim 17 , wherein the first smooth surface comprises a heat-treated surface which is directly machined on the housing.

19. The assembly according to claim 18 , wherein the second smooth surface comprises a heat-treated surface which is directly machined on the rotating shaft.

20. The assembly according to claim 17 , wherein the first smooth surface comprises a heat-treated surface formed on a bushing fixedly mounted on the housing.

21. A radial magnetic bearing device comprising the assembly of claim 11 .

Assignees

• Skf Magnetic Mechatronics
• Skf Ab

Inventors

• Krebs Philipp
• Anders Jens
• Herisse Eddy
• Ponson Frederic

Classifications

• F16C2240/40

  Linear dimensions, e.g. length, radius, thickness, gap · CPC title

• F16C32/0402 Primary

  combined with other supporting means, e.g. hybrid bearings with both magnetic and fluid supporting means · CPC title

• H02K7/09

  with magnetic bearings · CPC title

• F16C39/02 Primary

  using mechanical means · CPC title

• F16C32/0474

  for rotary movement · CPC title