Method and Computer Programme for Detecting the Stationary State of a Roller Bearing and a Roller Bearing Which May be Analyzed Thus

• US 20080317396A1
• Filed: 07/26/2005
• Published: 12/25/2008
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: Schaeffler Technologies AG & Co.KG (INA-Holding Schaeffler GmbH & Co. KG)
• Original Assignee: Schaeffler KG (INA-Holding Schaeffler GmbH & Co. KG)
• Inventors: Pecher, Alfred, Gempper, Sven
• Granted Patent: US 7,860,689 B2
• Time in Patent Office: Days
• US Class Current: 384/448
• CPC Class Codes: G01P 13/00 Indicating or recording presence, absence, or direction, of movement electric switches H01H; counting moving objects G06M7/00

Abstract

The invention relates to a method and a computer programme for detecting the stationary state of a roller bearing, comprising z rolling bodies, where z is a whole number, preferably an even number, to which a sensor arrangement is fixed, delivering a sinusoidal signal, dependent on the rotational position of the bearing on the rotation of the roller bearing. Said sinusoidal signal is sampled, whereupon sampled values are determined. According to the invention, a first average value (MW₁) of the sampled values of a first time interval (J₁) is determined (S120), whereupon the corresponding average value (MW₂, MW₃) of other time intervals (J₂, J₃) is determined (S132). The roller bearing is considered stationary as long as A) the corresponding average value (MW₂, MW₃) of the other time intervals (J₂, J₃) does not differ (S134) significantly from the first average value (MW₁) and/or B) the gradient between the first average value (MW₁) and the corresponding average value (MW₂, MW₃) of the other time intervals does not differ significantly from 0 (S335). The invention further relates to a roller bearing, provided with an analytical device for carrying out the inventive method or the computer programme.

Claims

1. A method for detecting the stationary state of a roller bearing having z rolling bodies, where z is an integral number to which a sensor arrangement is fixed, comprising:

delivering a sinusoidal signal dependent on the rotational position of the roller bearing upon rotation of the roller bearing, which is sampled whereupon samples are determined,

determining a first average value (MW₁) of the samples of a first time interval (J₁),

determining respective average value (MW₂, MW₃, . . . ) of further time intervals (J₂, J₃, . . . ) and the roller bearing is considered to be stationary as long as

A) the respective average value (MW₂, MW₃, . . . ) of the further time intervals (J₂, J₃, . . . ) does not differ significantly from the first average value (MW₁) and/or

B) the gradient between the first average value (MW₁) and the respective average value (MW₂, MW₃, . . . ) of the further time intervals does not differ significantly from 0.

2. The method as claimed in claim 1, comprising the following steps:

a) sampling of a signal at times t_m(t₁, t₂, . . . t_M) for determining samples x_m(x₁, x₂, . . . x_M),

b) calculating—

as first average value—

a kth average value (MW₁) of a predetermined number N of samples x_N(x₁, x₂, . . . x_N) at times t_n(t₁, t₂, . . . t_N) which are located in a kth time interval (J₁) of p time intervals J_k(J₁, J₂, . . . J_p), of which each one has a predetermined duration,

c) storing the first average value (MW₁),

d) calculating a (k+1)th average value (MW₂, MW₃, . . . MW_p) of a predetermined number of samples x_n(x_kL+1, x_kL+2, . . . x_kL+N) at times t_n(t_kL+1, t_kL+2, . . . t_kL+N) which are located in a (k+1)th time interval (J₂, J₃, . . . J_p) of the p time intervals J_K(J₁, J₂, . . . J_p),

e) assessing whether the (k+1)th average value (MW₂, MW₃, . . . MW_n) differs from the first average value (MW₁) stored in step c) by at least a predetermined, preferably adjustable threshold value (ε

),

f) if the assessment in step e) is positive;

establishing that the roller bearing is rotating, otherwise

g) incrementing k by 1 and repeating steps d) to f),

wherein k, m, n, p, L, M and N are integral numbers and the following applies;

1≦

k<

p, 0<

n≦

N<

M, 0<

m≦

M.

3. The method as claimed in claim 1, comprising the following steps:

a) sampling of the signal at times t_m(t₁, t₂, . . . t_M) for determining samples x_m(x₁, x₂, . . . x_M),

b) calculating—

as first average value—

a kth average value (MW₁) of a predetermined number N of samples x_n(x₁, x₂, . . . x_N) at times t_n(t₁, t₂, . . . t_N) which are located in a kth time interval (J₁) of p time intervals J_k(J₁, J₂, J_p), of which each one has a predetermined duration,

c) storing the first average value (MW₁),

d) calculating a (k+1)th average value (MW₂, MW₃, . . . MW_p) of a predetermined number of samples x_n(x_kL+1, x_kL+2, . . . x_kL+N) at times t_n(t_kL+1, t_kL+2, . . . t_kL+N) which are located in a (k+1)th time interval (J₂, J₃, . . . J_p) of the p time intervals J_K(J₁, J₂, . . . J_p),

h) determining the gradient (grad_k) between the (k+1)th average value (MW₂, MW₃, . . . MW_p) and the first average value (MW₁),

i) assessing whether the gradient (grad_k) determined in step h) differs from 0 by at least one predetermined, preferably adjustable threshold value (δ

),

j) if the assessment in step i) is positive establishing (S510) that the roller bearing is rotating, otherwise

k) incrementing k by 1 and repeating steps d) and h) to j),

wherein k, m, n, p, L, M and N are integral numbers and the following applies;

1≦

k<

p, 0<

n≦

N<

M, 0<

m≦

M.

4. The method as claimed in claim 1, comprising the following steps:

a) sampling of the signal at times t_m(t₁, t₂, . . . t_M) for determining samples x_m (x₁, x₂, . . . x_M)

b) calculating—

as first average value—

a kth average value (MW₁) of a predetermined number N of samples x_n(x₁, x₂, . . . x_N) at times t_n(t₁, t₂, . . . t_N) which are located in a kth time interval (J₁) of p time intervals J_k(J₁, J₂, . . . J_p), of which each one has a predetermined duration,

c) storing the first average value (MW₁),

d) calculating a (k+1)th average value (MW₂, MW₃, . . . MW_p) of a predetermined number of samples x_n(x_kL+1, x_kL+2, . . . x_kL+N) at times t_n(t_kL+1, t_kL+2, . . . t_kL+N) which are located in a (k+1)th time interval (J₂, J₃, . . . J_p) of the p time intervals J_K(J₁, J₂, . . . J_p),

e) assessing whether the (k+1)th average value (MW₂, MW₃, . . . MW_N) differs from the first average value (MW₁) stored in step c) by at least a predetermined, preferably adjustable threshold value (ε

),

h) determining the gradient (grad_k) between the (k+1)th average value (MW₂, MW₃, . . . MW_p) and the first average value (MW₁),

i) assessing whether the gradient (grad_k) determined in step h) differs from 0 by at least one predetermined, preferably adjustable threshold value (δ

),

l) if the assessment in step e) and/or in step i) is positive;

establishing that the roller bearing is rotating, otherwise

m) incrementing k by 1 and repeating steps d), e), h), i) and l),

wherein k, m, n, p, L, M and N are integral numbers and the following applies;

1≦

k<

p, 0<

n≦

N<

M, 0<

m≦

M.

5. The method as claimed in claim 2, wherein each (k+1)th average value (MW₂, MW₃, . . . MW_p), in the case of which it is found in step e) that it does not differ by at least the predetermined threshold value (ε

) from the first average value (MW₁) stored in step c), is discarded without being stored.

6. The method as claimed in claim 3, wherein each gradient (grad_k) in the case of which it is found in step i) that it does not differ from 0 by at least the predetermined threshold value (δ

) is discarded without being stored.

7. The method as claimed in claim 4, wherein each (k+1)th average value (MW₂, MW₃, . . . MW_p), in the case of which it is found in step e) that it does not differ from the first average value (MW₁) stored in step c) by at least the predetermined threshold value (ε

) and each gradient (grad_k) allocated to these average values, in the case of which it is found in step i) that it does not differ from 0 by at least the predetermined threshold value (δ

) is discarded without being stored.

8. The method as claimed in claim 2 wherein the average values (MW₁, MW₂, . . . MW_n) of each time interval J_k (J₁, J₂, . . . J_p) are calculated in steps b) and d) in that

the first sample (x₁) and the second sample (x₂) are added and their sum is stored as intermediate sum, whereafter each further sample (x₃, x₄, . . . x_M) is added to the intermediate sum and this is stored until the last sample (x_N, x_kL+N) of the relevant time interval J_k(J₁, J₂, . . . J_p) is reached,

and subsequently the last intermediate sum is divided by the respective number of samples taken into consideration.

9. The method as claimed in claim 2 wherein the same number N of times is allocated to each time interval J_k(J₁, J₂, . . . J_p) in steps b) and d).

10. The method as claimed in claim 2 wherein that L<

N applies.

11. The method as claimed in claim 2 wherein L=N applies.

12. The method as claimed in claim 2 wherein the distance of a time t_m(t₁, t₂, . . . t_M) to the preceding time t_m−

1 and subsequent time t_m+1 is equidistant.

13. The method as claimed in claim 1 wherein each of the p time intervals J_k(J₁, J₂, . . . J_p) extends at the most over an angle of rotation of 90°

/z of the roller bearing.

14. The method as claimed in claim 1 wherein the method is continued even when a rotation of the roller bearing has been found.

15. The method as claimed in claim 1 wherein depending on the outcome of the assessment whether the roller bearing is rotating, an output is made on the output device, whether the roller bearing is rotating or not.

16. The method as claimed in claim 1 wherein at least two sensor arrangements are provided at the roller bearing which each deliver a sinusoidal signal dependent on the rotational position of the roller bearing upon rotation of the roller bearing, which is sampled, whereupon respective samples are determined and

the sensor arrangements are arranged behind one another in the circumferential direction of the roller bearing and have a distance from one another in this circumferential direction which is unequal to an integral multiple of the distance between two adjacent rolling bodies in this circumferential direction, and wherein the signals of all sensor arrangements are evaluated and used for detecting the stationary state.

17. The method as claimed in claim 16, wherein more than z sensor arrangements are provided as a result of which the distance of the sensor arrangements from one another in the circumferential direction of the roller bearing is smaller than the distance of two adjacent rolling bodies from one another in the circumferential direction, and wherein

the signals of all sensor arrangements are evaluated in parallel with one another.

18. The method as claimed in claim 16 wherein the signals of all sensor arrangements are additionally used for detecting a possibly occurring to and fro movement of the roller bearing by an angle of rotation within the range of less than 360°

/z.

19. A computer program product for detecting the stationary state of a roller bearing having z rolling bodies, where z is an integral number wherein the roller bearing comprises a sensor arrangement which delivers a sinusoidal signal, dependent on the rotational position of the roller bearing upon rotation of the roller bearing, to an evaluating device,

wherein the computer program product contains means for carrying out the steps according to the method of claim 1 in an evaluating device.

20. A roller bearing comprising z rolling bodies, wherein z is an integral number and with a device for detecting the stationary state of the roller bearing, comprising

at least one sensor arrangement fixed to the roller bearing, wherein each sensor arrangement delivers a sinusoidal signal dependent on the rotational position of the roller bearing upon rotation of the roller bearing, and

at least one evaluating device, each evaluating device being connected to one sensor arrangement,

wherein each evaluating device contains an evaluating unit for carrying out the steps according to claim 1.

21. The roller bearing as claimed in claim 20, wherein each sensor arrangement is formed from four strain gauges interconnected to form a Wheatstone bridge, which are arranged behind one another in the circumferential direction of the roller bearing, wherein the first strain gauge and the third strain gauge of each sensor arrangement and the second strain gauge and the fourth strain gauge of each sensor arrangement have c-times the distance of two adjacent rolling bodies from one another in the circumferential direction, or

two strain gauges interconnected to in each case one Wheatstone half bridge, which are arranged behind one another in the circumferential direction of the roller bearing, wherein the signal is generated by the rolling bodies rolling over the strain gauges and c is an integral number of greater than or equal to 1.

22. Roller bearing as claimed in claim 21, wherein the strain gauges and the at least one evaluating device are arranged in a circumferential outer groove of the outer ring of the roller bearing.

23. The roller bearing as claimed in claim 20 wherein each evaluating unit is constructed as electrical circuit, preferably as ASIC.

24. The roller bearing as claimed in claim 20 wherein

at least two sensor arrangements are provided at the roller bearing which each deliver a sinusoidal signal dependent on the rotational position of the roller bearing upon rotation of the roller bearing, which is sampled in each case, whereupon respective samples are determined,

the sensor arrangements are arranged behind one another in the circumferential direction of the roller bearing and have a distance from one another in this circumferential direction which is unequal to an integral multiple of the distance between two adjacent rolling bodies in this circumferential direction, and at least one evaluating device is connected to a number of, preferably all, sensor arrangements as a result of which the signals of a number of, preferably all, sensor arrangements can be evaluated and used for detecting the stationary state.

25. The roller bearing as claimed in claim 24, wherein

more than z sensor arrangements are provided, as a result of which the distance of the sensor arrangements from one another in the circumferential direction of the roller bearing is smaller than the distance of two adjacent rolling bodies from one another in the circumferential direction, and

the evaluating device is designed for evaluating the signals of a number of sensor arrangements from the respective evaluating units in parallel with one another.

26. The roller bearing as claimed in claim 24 wherein

the evaluating device is designed for additionally using the signals of all sensor arrangements for detecting a possibly occurring to and fro movement of the roller bearing by an angle of rotation within the range of less than 360°

/z.