Method for monitoring a belt drive

Abstract

A method for monitoring a drive belt is disclosed. A drive pulley driving by a drive motor and having a drive belt is provided. First and second markings are provided on the belt. The markings are detected. A correlation is determined and a signal is generated if a reference value is exceeded.

Claims

1. A method for monitoring a belt drive, the method comprising: providing at least one drive pulley driven by a drive motor, a driven pulley and at least one power-transmitting endless drive belt which is in the form of a traction belt and wraps around the drive and driven pulleys circumferentially over a partial circumference in each case; wherein the belt has at least one first marking and at least one first sensor element assigned to the belt is provided; wherein the passage of the first marking is detected by the first sensor element during the belt revolution and the first sensor element has electronic devices for outputting a signal S.sub.R dependent on the detection of the first marking; wherein the rotor of the drive motor has at least one second marking and a second sensor element which is provided with corresponding electronic devices and is assigned to the drive motor is provided, wherein, while the rotor is rotating; the passage of the second marking is detected by the second sensor element and a signal S.sub.M dependent on the detection of the second marking is output, in that, furthermore, a computing unit provided with memories and processors for processing the signals S.sub.R and S.sub.M is provided; a temporal or local correlation of the occurrence of the signals S.sub.R and S.sub.M is calculated in the computing unit when the drive belt is new and is stored as a reference value; wherein the associated signals S.sub.R and S.sub.M are then repeatedly determined for further specified belt revolutions or periods of time and their current temporal or local correlation of the occurrence is compared with the reference value; and wherein a warning or alarm signal is output by the computing device after a specified tolerance value between the current correlation and the reference value has been exceeded.

2. The method as claimed in claim 1, further comprising: the first sensor element has electronic devices for outputting a signal S.sub.R proportional to the number of belt revolutions; the rotor position of the drive motor is determined by the second sensor element and is output as a signal S.sub.M proportional thereto; the initial relationship between a specified number N.sub.R of belt revolutions and the rotor position determined for this, which is present when the belt drive is new, is calculated in the computing unit and is stored as a reference value; and wherein the associated rotor positions are then repeatedly determined for further belt revolutions corresponding to the specified number N.sub.R and their current relationship is compared with the reference value, wherein a warning or alarm signal is output by the computing device after a specified tolerance value between the current relationship and the reference value has been exceeded.

3. The method as claimed in claim 1, further comprising: the first sensor element has electronic devices for outputting a signal S.sub.R proportional to the number of belt revolutions, in that the rotor revolutions of the drive motor are determined by the second sensor element and are output as a signal S.sub.M proportional to the speed of the drive motor; the relationship between a specified number N.sub.R of belt revolutions and the motor revolutions determined for this, which is present when the drive belt is new, is calculated in the computing unit and is stored as a reference value; the associated motor speeds are then repeatedly determined for further belt revolutions corresponding to the specified number N.sub.R and their current relationship is compared with the reference value; and a warning or alarm signal is output by the computing device after a specified tolerance value between the current relationship and the reference value has been exceeded.

4. The method as claimed in claim 1, wherein the tolerance value between the current relationship and the reference value is specified as a difference in location, time or speed corresponding to a predetermined slip.

5. The method as claimed in claim 1, wherein the drive belt or belts is/are in the form of toothed belts and at least one difference in location, time or speed corresponding to a skipped tooth is specified as the tolerance value between the current relationship and the reference value.

6. The method as claimed in claim 1, wherein the rotor rotation or the rotor position is determined via a CAN bus of the motor and is output as a signal S.sub.M and is processed in the computing unit for the purpose of calculating the correlations.

7. The method as claimed in claim 1, wherein the belt markings are detected by the associated sensor elements using optical, inductive, capacitive or magnetic methods.

8. The method as claimed in claim 1, wherein the tolerance value is determined using a computing program in the computing unit, wherein the computing program is based on an artificial intelligence method.

9. The method as claimed in claim 1, wherein for monitoring a steering gear with two power-transmitting, endless drive belts in the form of drive belts.

10. The method as claimed in claim 1 further comprising: wherein both belts have a marking and both belts are each assigned a sensor element which detects the respective belt marking, wherein the sensor elements have electronic devices for outputting signals S.sub.R1 and S.sub.R2 which are dependent on the detection of the belt markings; a temporal or local correlation of the occurrence of the signals S.sub.R1, S.sub.R2 and S.sub.M is calculated in the computing unit when the drive belt is new and is stored as a reference value; and the associated signals S.sub.R1, S.sub.R2 and S.sub.M are then repeatedly determined for further specified belt revolutions or periods of time and their current temporal or local correlation of the occurrence is compared with the reference value.

11. The method as claimed in claim 10, wherein an angular offset between the drive belt and the drive belt pulley and/or between the drive belts is determined in the computing unit by way of a change in the temporal or local correlation of the occurrence of the signals S.sub.R1, S.sub.R2 and S.sub.M.

12. The method as claimed in claim 1, the method further comprising determining an angular offset between the drive belt and the drive belt pulley by the computing unit based on correlation of the signals S.sub.R1, S.sub.R2 and S.sub.M, the signal S.sub.R comprises the signals S.sub.R1, S.sub.R2, the signal S.sub.R1 is based on the belt and the signal S.sub.R2 is based on a second belt.

13. The method as claimed in claim 12, the method further comprising determining a circumferential offset between the belt and the second belt based on the signals S.sub.R1, S.sub.R2.

14. The method as claimed in claim 13, the signals S.sub.R1 is proportional to revolutions of the belt and the signal S.sub.R2 is proportional to revolutions of the second belt and the signal S.sub.M is proportional to the speed of the drive motor.

15. The method as claimed in claim 14, the method further comprising the computing unit determining an overload of the belt based on the circumferential offset and the angular offset.

16. A belt drive comprising: at least one drive pulley driven by an electric drive motor; a driven pulley; and at least one power-transmitting endless drive belt which is in the form of a traction belt and wraps around the drive and driven pulleys circumferentially over a partial circumference in each case; wherein the belt has at least one first marking and at least one first sensor element which is assigned to the belt and is intended to detect the first marking is provided, wherein the first sensor element has electronic devices for outputting a signal S.sub.R dependent on the detection of the first marking, wherein the rotor of the electric drive motor has at least one rotary encoder or position encoder (as an incremental or absolute encoder) which can be used to detect the position or speed of the rotor during the motor rotation and to output a signal S.sub.M dependent on the position or speed; a computing unit provided with memories and processors for processing the signals S.sub.R and S.sub.M is provided, wherein a temporal or local correlation of the occurrence of the signals S.sub.R and S.sub.M can be calculated in the computing unit when the drive belt is new and can be stored as a reference value and can be compared with corresponding correlations for repeated, further specified belt revolutions or periods of time; and wherein a warning or alarm signal can be generated by the computing device after a specified tolerance value between the current correlation and the reference value has been exceeded.

17. The belt drive as claimed in claim 16, further comprising: the belt drive comprised in a steering gear of a motor vehicle; the belt drive has two drive traction belts; two drive and driven pulleys; wherein the drive pulleys and the driven pulleys are each continuously connected to one another in a rotationally fixed manner on a common shaft; wherein both drive traction belts have at least one marking and at least one associated sensor element for detecting the belt markings is respectively provided; wherein the sensor elements have electronic devices for outputting the signals S.sub.R1 and S.sub.R2 which are dependent on the detection of the markings; wherein the rotor of the electric drive motor has at least one rotary encoder or position encoder which can be used to detect the position or speed of the rotor during the motor rotation and to output a signal S.sub.M dependent on the position or speed; wherein a computing unit provided with memories and processors for processing the signals S.sub.R1, S.sub.R2 and S.sub.M, and wherein a temporal or local correlation of the occurrence of the signals S.sub.R1, S.sub.R2 and S.sub.M is calculated in the computing unit when the drive belt is new and is stored as a reference value; wherein the associated signals S.sub.R1, S.sub.R2 and S.sub.M are then repeatedly determined for further specified belt revolutions or periods of time and their current temporal or local correlation of the occurrence is compared with the reference value.

18. The belt drive as claimed in claim 16, wherein the first marking is designed as a narrow strip provided with ferromagnetic or electrically conductive particles on the belt on the back of the belt.

19. The belt drive as claimed in claim 18, wherein the ferromagnetic or electrically conductive particles are present in the form of a mixture additive in the base material of the belt.

20. The belt drive as claimed in claim 18, wherein the ferromagnetic or electrically conductive particles are applied as a rubber or fabric imprint.

21. A method for monitoring a drive belt, the method comprising: providing a steering gear having first and second toothed belts of the drive belt arranged in parallel; marking the first and second belts with a first marking of strips of polymeric materials with magnetizable particles applied over a belt width on back sides for the first and second belts; sensing the first and second belts with first and second electronic devices to generate signals SR1 and SR2 for the first and second belts respectively; detecting the passage of the first marking of the first and second belts based on the signals SR1 and SR2; providing second markings on a rotor of a drive motor; sensing the rotor with a third electronic device to generate a rotor signal SM; detecting passage of the second markings based on the rotor signal SM; determining a speed of the rotor based on the signal SM; and determining an angular offset between the drive belt and the rotor by one or more processors based on the signals SR1, SR2 and SM.

22. The method of claim 21, further comprising: determining an initial rotor position; determining an initial relationship between a specified number N.sub.R of belt revolutions and the initial rotor position; storing the initial relationship as a reference value; repeatedly determining associated rotor positions for further belt revolutions and comparing the determined positions with the reference value; and generating an alarm based on the determined positions varying beyond a selected tolerance.

23. The method of claim 21, wherein a tolerance value between the current relationship and the reference value is specified as a difference in location, time or speed corresponding to a predetermined slip.

24. The method of claim 21, further comprising forming a strip of ferromagnetic materials on the back sides of the first and second belts.

25. The method of claim 24, further comprising forming a mixture additive having the ferromagnetic materials and forming an imprint to apply the ferromagnetic material.

26. The method of claim 25, further comprising adding an adhesive to the mixture.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 basically shows the design of a steering gear according to the invention,

(2) FIG. 2 shows the steering gear according to FIG. 1 after one or more skipped teeth,

(3) FIG. 3 Shows a typical signal profile for a complete motor revolution when using a commercially available incremental position encoder.

DETAILED DESCRIPTION

(4) FIG. 1 shows, in the form of a schematic diagram, the design of a steering gear 1 of an automobile, in which a redundant design with two parallel toothed belts 2, 3 is selected as an endless drive belt. Each toothed belt is designed in such a way that, in the event of the failure of the other toothed belt in each case, it can transmit the entire power and can thus guarantee safe steerability of the vehicle even in the event of damage.

(5) Furthermore, two toothed drive pulleys 6, 7 arranged on a common drive shaft 5 driven by a drive motor 4 in the form of an electric motor are provided. In the case of the steering gear constructed in this way with a redundant drive, there are also two driven pulleys 8, 9 which are arranged on a common output shaft 10. Both belts 2, 3 each have a first belt marking 11, 12, here designed as strips of polymeric material with magnetizable particles applied over the respective belt width on the back of the belt. The two belts are each assigned a sensor element 13, 14 which detects the respective belt marking 11, 12 as soon as it passes the sensor, i.e. passes below the sensor in this case. The sensor elements each have electronic devices (not shown in greater detail here) for outputting signals S.sub.R1 and S.sub.R2 which depend on the detection of the belt markings, i.e. are always output when the passage of a marking 11, 12 is detected by the sensor elements 13, 14 in the case of belts 2, 3 revolving in the drive direction 15.

(6) The rotor (not shown in greater detail here) of the drive motor has second markings as well as a second sensor element which is provided with corresponding electronic devices, is assigned to the drive motor and detects the rotor rotation, that is to say that, during the rotor rotation, the passage of the second markings is detected by the second sensor element and a signal S.sub.M dependent on the detection of the second marking is output.

(7) For this purpose, the rotor of the electric motor 4 is provided here with a commercially available, incremental position encoder which, as an incremental encoder, allows the position of the rotor to be directly detected while the motor is rotating and also allows the speed to be determined therefrom. A signal S.sub.M dependent on the position and/or speed can therefore be output for the motor position and motor rotations.

(8) Furthermore, a CPU (central processor unit) is provided, namely a computing unit 16 provided with memories and processors for processing the signals S.sub.R1, S.sub.R2 and S.sub.M. The temporal or local correlation of the occurrence of the signals S.sub.R1, S.sub.R2 and S.sub.M is calculated in the computing unit when the drive belt is new and is stored as a reference value. The corresponding associated signals are then repeatedly determined for further specified belt revolutions or periods of time and their current temporal or local correlation of the occurrence is compared with the reference value, wherein a warning or alarm signal is output by the computing device after a specified tolerance value between the current correlation and the reference value has been exceeded.

(9) In the exemplary embodiment presented here, on the one hand, signals S.sub.R1 and S.sub.R2 which are proportional to the number of respective belt revolutions are generated and, on the other hand, the rotor revolutions of the drive motor are determined and are output as a signal S.sub.M proportional to the speed of the drive motor.

(10) With such a design, an angular offset between the drive belt and the drive belt pulley and/or between the drive belts can also be determined in the computing unit by way of a change in the temporal or local correlation of the occurrence of the signals S.sub.R1, S.sub.R2 and S.sub.M. A statement regarding the relationship of the two drive belts with respect to one another and their offset which has possibly arisen during revolution is thus also obtained. In the case of steering gears, there is thus an important checking method which can both determine the failure of a belt or predict the impending failure of a belt and allow continued monitoring of an individual belt after such a failure.

(11) FIG. 2 shows such a case, wherein, after one or more skipped teeth due to overloading, a circumferential offset between the drive belts 2 and 3, and thus also an angular offset between one of the drive belts and the associated drive belt pulley of the toothed belt, has arisen. Even if the ability to steer is still readily available afterward, at least one of the two belts has been overloaded, with the result that a belt replacement could possibly be necessary after a corresponding catalog of load collectives. In the case of an encapsulated steering gear of an automobile, such a precise check would not be possible without the method according to the invention and the skipped tooth would remain undetected.

(12) FIG. 3 shows the rotor position in principle only for the sake of clarity, namely a typical signal profile for a complete motor revolution when using a commercially available, incremental position encoder, wherein the respective position is represented by the signal value S.sub.M. The correlation of this signal value with the signal values S.sub.R1 and S.sub.R2 thus enables the procedure according to the invention.

LIST OF REFERENCE SIGNS

Part of the Description

(13) 1 Steering gear 2 Toothed belt 3 Toothed belt 4 Drive motor/electric motor 5 Drive shaft 6 Drive pulley 7 Drive pulley 8 Driven pulley 9 Driven pulley 10 Output shaft 11 Belt marking 12 Belt marking 13 Sensor element 14 Sensor element 15 Drive direction 16 Computing unit (CPU)