Method for detecting structure-borne noise events in a roller bearing

• US 20060150737A1
• Filed: 01/23/2004
• Published: 07/13/2006
• Est. Priority Date: 01/31/2003
• Status: Active Grant

• Current Assignee: Alfred Pecher
• Original Assignee: Alfred Pecher
• Inventors: Pecher, Alfred
• Granted Patent: US 7,599,804 B2
• Time in Patent Office: Days
• US Class Current: 73/593
• CPC Class Codes: F16C 19/52 with devices affected by abnormal or undesired conditions
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis

Abstract

A method for detecting structure-borne noise events in a roller bearing, wherein a measuring signal M of a pressure or dilatation sensor arranged on a roller bearing is fed to a frequency filter for filtering out undesired signal parts. The aim of the invention is to determine structure-borne noise waves or structure-borne noise events by an evaluation device. As a result, a first variance value is calculated from digital values of the frequency filter output signal and at least one second variance value is calculated from other digital values of the frequency filter output signal and the weighted arithmetic average of the at least two variance values (new variance, old variance) is calculated with the aid of a retrocursive calculation of the variance value. A surpassing of the weighted arithmetic variance average value (V) exceeds a pre-selected variance threshold value (v_sw). It is subsequently evaluated as a structure-borne noise event provoked by mechanical damage to the roller bearing.

Claims

1. A method for detecting structure-borne sound events in a roller bearing, comprising

supplying a measurement signal (M) from a pressure-sensitive or strain-sensitive sensor which is arranged on a roller bearing to a frequency filter for filtering out undesirable signal components;

calculating a first variance value from digital values of the frequency filter output signal;

determining at least one second variance value from further digital values of the frequency filter output signal;

calculating a weighted arithmetic mean of the first and second variance values from the at least two variance values using a recursive calculation, and

assessing any exceeding of the weighted arithmetic variance mean value above a preselected variance threshold value (V_SW) as a structure-borne sound event which has been caused by mechanical damage to the roller bearing, and the frequency for exceeding the threshold can be associated with the point of origin of the damage in the bearing when a rotation speed and geometric conditions of the bearing are known.

2. The method as claimed in claim 1, comprising calculating the weighted arithmetic mean of the variance values using the basic recursive equation:

{overscore (E)}{X²}(k+1)={overscore (E)}{X²}(k)=C_x²[X²(k+1)−

{overscore (E)}{X²}(k)] 

 

(Equation

     1)

where {overscore (E)}{.} represents the expected value of the weighted arithmetic mean value, k is a running variable, x is a digital sample value of the signal, and C is an adaptation constant.

3. The method as claimed in claim 2, wherein the adaptation constant C has a value which is less than unity and greater than zero.

4. The method as claimed in claim 3, wherein the adaptation constant C can be calculated from an equation for the adaptation rate

t={1/C_x²−

½

}*T 

 

(Equation

     2)

where t indicates how quickly the true variance can be determined with a tolerable error rate.

5. The method as claimed in claim 2, wherein the basic recursive equation (equation 1) is converted to a conversion equation

nE=aE+aK*(nA−

aE) 

 

(Equation

     3)

in which nE represents a new result value, aE represents an old result value, aK represents the adaptation constant, and nA represents a new sample value.

6. The method as claimed in claim 5, further comprising converting the conversion equation to an evaluation equation

nV=aV+aK*(nA−

aV) 

 

(Equation

     4)

where nV represents the new variance, aV represents the old variance, aK represents the adaptation constant, and nA represents a new sample value.

7. The method as claimed in claim 6, further comprising assessing the value of the new variance as an estimated value of the true variance of the measurement signal, which marks the presence of structure-borne sound events in the roller bearing.

8. The method as claimed in claim 6, wherein a high new variance value represents a high probability of the presence of structure-borne sound events in the roller bearing.

9. The method as claimed in claim 6, wherein a high new variance value represents major damage in the roller bearing.