Method and system for reducing bearing fluting in electromechanical machine

• US 20030086630A1
• Filed: 06/19/2002
• Published: 05/08/2003
• Est. Priority Date: 11/06/2001
• Status: Active Grant

• Current Assignee: Precor Incorporated (Peloton Interactive, Inc.)
• Original Assignee: Illinois Tool Works Inc.
• Inventors: Silbernagel, Robert, Bramel, Rodney
• Granted Patent: US 7,071,589 B2
• Time in Patent Office: Days
• US Class Current: 384/476
• CPC Class Codes: A63B 22/0235 driven by a motor
• CPC Class Codes: A63B 2225/30 Maintenance
• CPC Class Codes: F16C 19/163 with angular contact
• CPC Class Codes: F16C 19/52 with devices affected by abnormal or undesired conditions
• CPC Class Codes: F16C 19/54 Systems consisting of a plurality of bearings with rolling friction spindle bearings F16C35/08
• CPC Class Codes: F16C 2202/30 Electric properties; Magnetic properties
• CPC Class Codes: F16C 2316/30 Articles for sports, games and amusement, e.g. roller skates, toys
• CPC Class Codes: F16C 2380/26 Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators in general H02K
• CPC Class Codes: F16C 35/077 between housing and outer race ring
• CPC Class Codes: H02K 11/40 Structural association with grounding devices
• CPC Class Codes: H02K 5/1732 radially supporting the rotary shaft at both ends of the rotor H02K5/1737 takes precedence
• CPC Class Codes: Y10S 198/952 Heating or cooling

Abstract

A non-conductive insulating ring (210) is inserted between a motor bell (130) and a motor bearing (135) that supports a motor shaft (110). Stray currents that normally discharge thorough the motor shaft and the motor bearing to the motor bell are prevented due to the non-conductive nature of the insulating ring. Additionally, the motor shaft is grounded to provide a low-impedance alternative path to stray shaft currents. When a fast-switching frequency converter is used to drive the motor shaft, additional arrangements such as a common mode choke, reduction of the switching frequency of the converter, and reduction of the turn-of/off rate of a semiconductor device used in the converter, may be provided to further reduce the stray currents flowing thorough the motor bearings.

Claims

1. An electromechanical machine having an output shaft supported by bearings seated in motor bells, an improvement comprising:

an insulating ring of non-conductive material shaped to be mounted in the motor bell of the electromechanical machine and to serve as a seat for the output shaft bearing thereby to electrically isolate the output shaft and the bearing from the motor bell; and

a conductive element coupled to the output shaft for grounding the output shaft.

2. The improvement of claim 1, wherein the non-conductive material is selected from the group consisting of plastic, fiberglass and ceramics.

3. The improvement of claim 1, wherein the insulating ring is machined separately from the motor bell.

4. The improvement of claim 1, wherein the insulating ring is injection molded into the motor bell.

5. The improvement of claim 1, wherein the conductive element comprises a brush and a brush wire connected to a housing of the machine.

6. The improvement of claim 1, wherein the electromechanical machine is driven by a fast-switching converter having a common mode voltage, and a common mode choke is arranged at the converter output.

7. The improvement of claim 1, wherein the electromechanical machine is driven by a fast-switching converter including a power-switching semiconductor device, and the turn-on/off rate of the semiconductor device is slowed to reduce the fluting of the bearings from the normal turn-on/off rate that is set without considering the reduction of the fluting.

8. The improvement of claim 7, wherein the turn-on/off rate of the semiconductor device is slowed by approximately 50% from its normal rate.

9. The improvement of claim 1, wherein the electromechanical machine is driven by a fast-switching converter, and the switching frequency of the converter is reduced to minimize the fluting of the bearings from the normal switching frequency that is set without considering the minimizing of the fluting.

10. The improvement of claim 9, wherein the switching frequency of the converter is reduced to the level of approximately 10 kHz.

11. An exercise treadmill comprising:

a frame;

a forward roller assembly mounted on the frame to rotate about a forward transverse axis;

a rear roller assembly mounted on the frame to rotate about a rear transverse axis;

an endless belt trained about the forward and rear roller assemblies;

an electric motor having an output shaft drivingly coupled to one of the forward and rear roller assemblies, said electric motor comprising motor bells in electrical contact with a motor stator, and insulating rings interposed between the motor bells and antifriction bearings for supporting the output shaft, the insulating rings functioning as seats for the antifriction bearings, and the output shaft being grounded.

12. The exercise treadmill of claim 11, wherein the insulating rings include an end flange portion serving as a barrier between end faces of the bearings'"'"' outer and inner races and the adjacent portion of the motor bells.

13. The exercise treadmill of claim 12, wherein the inside diameter of the insulating ring end flange closely corresponds to the outside diameter of the output shaft.

14. The exercise treadmill of claim 11, wherein the insulating ring is composed of a non-conductive material selected from the group consisting of plastic, fiberglass and ceramics.

15. The exercise treadmill of claim 11, wherein the insulating ring is machined separately from the motor bell and then inserted into the motor bell.

16. The exercise treadmill of claim 11, wherein the insulating ring is molded directly into the motor bell.

17. The exercise treadmill of claim 11, wherein the output shaft is grounded via a brush and a brush wire leading to a housing of the electric motor.

18. The exercise treadmill of claim 11, wherein the electric motor is driven by a fast-switching converter having a common mode voltage and a common mode choke is arranged at the converter output.

19. The exercise treadmill of claim 11, wherein the electric motor is driven by a fast-switching converter including a power-switching semiconductor device, and the turn-on/off rate of the semiconductor device is slowed to reduce the fluting of the antifriction bearings from the normal turn-on/off rate that is set without considering the reduction of the fluting.

20. The exercise treadmill of claim 19, wherein the turn-on/off rate of the semiconductor device is slowed by approximately 50% from its normal rate.

21. The exercise treadmill of claim 11, wherein the electric motor is driven by a fast-switching converter, and the switching frequency of the converter is reduced to minimize the fluting of the antifriction bearings from the normal switching frequency that is set without considering the minimizing of the fluting.

22. The exercise treadmill of claim 21, wherein the switching frequency of the converter is reduced to the level of approximately 10 kHz.