Bearing rigidity evaluation apparatus

• US 6,234,022 B1
• Filed: 08/12/1999
• Issued: 05/22/2001
• Est. Priority Date: 08/28/1998
• Status: Expired due to Term

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Tadokoro, Hisakazu
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/373,241
• Time in Patent Office: 649 Days
• Field of Search: 735/93, 736/60, 738/624.9
• US Class Current: 73/593
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis
• CPC Class Codes: G01M 7/025 Measuring arrangements

Abstract

In a bearing rigidity evaluation apparatus, a vibration portion 1 excites a bearing 4 to vibrate. Vibrations of the bearing 4 thus excited are detected by vibration detecting sensors 21a, 21b and 21c. Output signals of the vibration detecting sensors 21b and 21c for an outer race 42 are added up in time sequence by an adder 23 and then supplied to a transfer function computing unit 3a. An output signal of the vibration detecting sensor 21a is supplied to the transfer function computing unit 3a. The transfer function computing unit 3a calculates a transfer function H between inner and outer races (between a hub shaft 41 and the outer race 42) by FFT. On the basis of this transfer function H, there is obtained a vibration mode in which a resonance frequency (natural frequency) fa appears in a position of −π/2 phase difference from local-mode vibration components (in-phase components) contained in the aforementioned input signals after erasing of the local-mode vibration components.

Claims

1. A bearing rigidity evaluation apparatus for evaluating bearing rigidity of a bearing to which a preload is applied, comprising:

a vibrating unit giving vibrations with a predetermined frequency axially to an inner race of said bearing or to a shaft fitted to said inner race;

at least one pair of outer race vibration detecting units respectively provided in positions symmetrical to each other with respect to a point of center of said bearing and detecting vibrations of an outer race of said bearing;

an inner race vibration detecting unit detecting vibrations in an axial center position of either one of said inner race and said shaft fitted to said inner race;

an addition unit respectively adding output signals of said at least one pair of outer race vibration detecting units;

a transfer function computing unit calculating one of a resonance frequency and a natural frequency of said bearing by obtaining a transfer function between said outer race and either one of said inner race and said shaft so as to eliminate an in-phase component signal contained in an output signal of said inner race vibration detecting unit and an output signal of said addition unit; and

a rigidity transformation computing unit obtaining said bearing rigidity on the basis of one of said resonance frequency and said natural frequency calculated by said transfer function computing unit.

2. A bearing rigidity evaluation apparatus according to claim 1, further comprising:

a preload computing unit obtaining the quantity of the preload applied to said bearing, on the basis of a bearing rigidity signal obtained by said rigidity transformation computing unit.

3. A bearing rigidity evaluation apparatus according to claim 1, further comprising:

a high-pass filter provided in an input side of said transfer function computing unit and removing a low-frequency noise signal contained in the output signal of said inner race vibration detecting unit and the output signal of said addition unit.

4. A bearing rigidity evaluation method for evaluating bearing rigidity of a bearing to which a preload is applied, comprising the steps of:

giving vibrations with a predetermined frequency axially to an inner race of said bearing or to a shaft fitted to said inner race;

detecting vibrations of an outer race of said bearing in at least one pair of positions symmetrical to each other with respect to a point of center of said bearing as at least one pair of outer race vibration signals;

detecting vibrations in an axial center position of either one of said inner race and said shaft fitted to said inner race as an inner race vibration signal;

adding said at least one pair of outer race vibration signals, respectively;

calculating one of a resonance frequency and a natural frequency of said bearing by obtaining a transfer function between said outer race and either one of said inner race and said shaft to eliminate an in-phase component signal contained in said inner race vibration signal and an output signal obtained by said adding step; and

obtaining said bearing rigidity on the basis of one of said resonance frequency and said natural frequency.

5. A bearing rigidity evaluation method according to claim 4, further comprising the step of:

obtaining the quantity of the preload applied to said bearing on the basis of a bearing rigidity signal obtained in said bearing rigidity obtaining step.