Method and apparatus for detecting roundness deffects in a railway vehicle wheel

Abstract

A motion sensor ( 3 ) is associated with a wheel ( 1 ) of a railway vehicle for generating a signal (M) indicative of the motion of the wheel along a vertical axis (x). A rotation sensor ( 6 ) provides a signal (S) indicative of the rotational speed of the wheel ( 1 ). The motion (M) and rotational speed (S) signals are received by an electronic processing unit (E) which correlates these signals using the speed signal (S) to divide the vertical motion signal (M) in subsequent time portions or frames, each corresponding to a complete rotation of the wheel. A mean of the subsequent time portions of the motion signal stored over a period of time is calculated to identify actual or incipient roundness defects of the wheel.

1 . A method of detecting roundness defects in a wheel of a railway vehicle, comprising the steps of: 
 (a) providing motion sensor means (3), associated with a wheel (1) of a railway vehicle, for generating a signal (M) indicative of the motion of the wheel along an essentially vertical axis (x);    (b) providing rotation sensor means (6) for supplying a signal (S) indicative of the rotational speed of the wheel (1);    (c) receiving the motion (M) and rotational speed (S) signals by means of an electronic processing unit (E) and correlating said signals using the speed signal (S) to divide the vertical motion signal (M) in subsequent time portions or frames, each corresponding to a complete revolution of the wheel;    (d) storing said subsequent time portions of the motion signal (M); characterised by the step of:    (e) calculating a mean of the subsequent time portions of the motion signal stored in a period of time for identifying, based on said mean, actual or incipient roundness defects of the wheel, wherein said mean is calculated based on a number of subsequent time portions so as to render statistically irrelevant those time portions of the motion signal (M) containing data indicative of forces which are not repeated in time with the frequency of rotation of the wheel (1).    
     
     
         2 . The method of  claim 1 , wherein said step (c) comprises the step of filtering the motion signal (M) for eliminating therefrom all vibration components not generated by the rolling of the wheel on the railtrack.  
     
     
         3 . The method of  claim 1 , wherein the step (b) of generating the speed signal comprises the step of: 
 generating a single speed signal at every complete revolution of the wheel.    
     
     
         4 . The method of  claim 1 , wherein the step (b) of generating the speed signal comprises the steps of: 
 generating a number (n) of pulses at every complete revolution of the wheel and    transmitting said pulses to a divider by n which emits a single output speed signal every n pulses received.    
     
     
         5 . The method of  claim 1 , in which the step (c) of receiving the signals (M, S) is carried out with the vehicle travelling at a substantially constant speed.  
     
     
         6 . The method of  claim 1  wherein the step (c) of receiving the signals (M, S) is carried out with the vehicle travelling at a&speed exceeding 100 km/h.  
     
     
         7 . The method of  claim 1 , wherein said step (e) is followed by the step of: 
 automatically emitting al alarm signal (A) when the mean of the subsequent time portions reaches or exceeds a preset threshold value.    
     
     
         8 . An apparatus for detecting roundness defects in a wheel of a railway vehicle comprising: 
 motion sensor means (3) associated with a wheel (1) of a railway vehicle, adapted to provide a signal (M) indicative of movement of the wheel along an essentially vertical axis (x);    rotation sensor means (6), adapted for providing a sisal (S) indicative of the rotational speed of the wheel (1); electronic processing means (E) adapted for: 
 receiving the motion (M) and speed (S) signals;  
 correlating said signals using the speed signal (S) to divide the vertical motion signal (M) in subsequent time portions, each of which corresponds to a complete revolution of the wheel;  
 storing a plurality of subsequent time portions of the motion signal (M), characterised in that the electronic processing means (E) are further adapted for  
 calculating a mean of the subsequent time portions of the motion signal (M) stored in a period of time wherein said mean is calculated based on a number of subsequent time portions so as to render statistically irrelevant those time portions of the motion signal (M) containing data indicative of forces which are not repeated in time with the frequency of rotation of the wheel (1), and  
 identifying, based on said mean, actual or incipient roundness defects of the wheel.  
   
     
     
         9 . The apparatus of  claim 8 , further comprising filtering circuit means adapted for filtering the motion signal (M) for eliminating therefrom all vibration components not generated by the rolling of the wheel on the railtrack.  
     
     
         10 . The apparatus of  claim 8 , further including alarm means for generating automatically an alarm signal (A) when the mean of the subsequent time portions reaches or exceeds a preset threshold value.  
     
     
         11 . The apparatus of  claim 8 , wherein the motion sensor means (3) are associated with an encoder (7) adapted for generating a single speed signal at each complete revolution of the wheel.  
     
     
         12 . The apparatus of  claim 8 , wherein the motion sensor means (3) are associated with an encoder (7) adapted for generating a number (n) of pulses at each complete revolution of the wheel, the apparatus further including divider by n means, operatively associated with the sensor means (3), for emitting a single output speed signal at every n received pulses.  
     
     
         13 . The apparatus of  claim 8 , comprising motion sensor means (3) and speed sensor means (6) coupled to each of the wheels of a railway vehicle.  
     
     
         14 . The apparatus of  claim 8 , wherein the motion sensor means (3) are mounted to an element (4) supporting the axle of the wheel (1).