METHOD OF DETECTING DAMAGE TO AN ENGINE BEARING

• US 20080223135A1
• Filed: 02/28/2008
• Published: 09/18/2008
• Est. Priority Date: 03/12/2007
• Status: Active Grant

• Current Assignee: Safran Aircraft Engine Company
• Original Assignee: Snecma (Safran SA)
• Inventors: Griffaton, Julien, Blanchard, Serge
• Granted Patent: US 7,770,458 B2
• Time in Patent Office: Days
• US Class Current: 73/579
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis

Abstract

The invention relates to a method of detecting damage in a bearing supporting at least one rotary shaft of an engine in rotation, the method consisting in: defining a measurement period corresponding to a range of speeds of rotation of the shaft during renewable activity at low speeds of operation of the engine; acquiring over the entire measurement period a vibratory signal representative of acceleration of components of the engine; sampling the vibratory signal as a function of the speed of rotation of the shaft during the measurement period; transforming the sampled vibratory signal into a frequency signal to obtain frequency spectrum lines as a function of the speed of rotation of the shaft; calculating the mean of the amplitudes of the spectrum lines; determining amplitude peaks around multiples of the theoretical frequency of a damaged roller; calculating the ratio between each amplitude peak and the amplitude level determined for a sound bearing; and comparing the ratio that is obtained with at least one predetermined damage threshold.

Claims

1. A method of detecting damage to a bearing providing rotary support to at least one rotary shaft of an engine, the method consisting in:

a) defining a measurement period corresponding to a range of speeds of rotation of the shaft during renewable activity at low speeds of operation of the engine;

b) acquiring over the entire measurement period a vibratory signal representative of acceleration of components of the engine;

c) sampling the vibratory signal as a function of the speed of rotation of the shaft during the measurement period;

d) transforming the sampled vibratory signal into a frequency signal to obtain frequency spectrum lines as a function of the speed of rotation of the shaft;

e) calculating the mean of the amplitudes of the spectrum lines;

f) determining amplitude peaks around multiples of the theoretical frequency of a damaged roller;

g) calculating the ratio between each amplitude peak and the amplitude level determined for a sound bearing; and

h) comparing the ratio that is obtained with at least one predetermined damage threshold.

2. A method according to claim 1, in which step h) consists in comparing the ratio that is obtained with a low-damage threshold, and if the ratio is greater than the low-damage threshold, in comparing it with a high-damage threshold in order to determine the degree to which the bearing might be damaged.

3. A method according to claim 1, in which the renewable activity at low speeds of rotation of the engine selected for defining the measurement period corresponds to a stage of starting or a stage of stopping the engine.

4. A method according to claim 1, in which the bearing supports two rotary shafts of the engine in rotation;

the measurement period corresponding to a range of speeds of rotation for one of the two shafts during the activity at low speeds of rotation of the engine; and

the vibratory signal being sampled as a function of the difference between the speeds of rotation of the two shafts during the measurement period.

5. A method according to claim 1, in which the step f) consists in determining amplitude peaks around even integer multiples of the theoretical frequency of a damaged roller.