Device and method for determining a longitudinal elongation and an average speed of a belt, as well as for determining a speed of at least one pulley

Description

[0001] The invention relates to a device for determining a longitudinal elongation and a mean speed of a belt, as well as for determining a speed of at least one pulley according to the preamble of claim 1 and an attachment device according to claim 9.

[0002] Furthermore, the invention relates to a method according to the preamble of claim 10, as well as the use of the method according to the invention according to claim 13. State of the art

[0003] Methods and devices comprising a belt and a drive device for the belt are generally known from the prior art. The drive device has several pulleys, for example, two. The belt is designed to run circumferentially and wraps around the pulleys at least partially. Furthermore, the belt can be driven circumferentially by the drive device. The belt is preferably a drive belt for transmitting tensile forces. Such a belt is often subjected to pretension, operating forces, centrifugal forces, and / or bending.

[0004] The service life of a belt is at least partially determined by its elongation, particularly circumferential elongation. The belt's rotational speed and / or the power required to drive it can provide information about the belt's load. Belt elongation is associated with a reduction in belt tension. To a certain extent, this reduction can be compensated for by optional tensioning systems. However, belt drives without a tensioning system are particularly susceptible to this reduction. In friction-based belt drives, this manifests itself as a significantly increased slippage of the belt relative to the pulley, leading to higher belt temperature and wear.

[0005] Drive belts include toothed belts, as well as flat belts, V-belts or multi-ribbed belts.

[0006] German patent DE 102018215478A1 discloses a system for determining the longitudinal elongation of a belt. The system comprises the belt, a drive device, a transmitter, and an evaluation unit. Two ferromagnetic markers, arranged at a predetermined distance from each other, are embedded in the belt. The transmitter is configured to generate a reference field that is modified by each of the two markers as the respective marker moves through the reference field during the belt's rotation. The transmitter can detect the change in the reference field resulting from the interaction between the respective marker and the reference field. The evaluation unit is configured to determine the longitudinal elongation of the belt based on the reference distance between the ferromagnetic markers, the belt speed, the first detection time, and the second detection time.A particular disadvantage is that only one measurement can be taken per belt revolution. This can negatively impact the accuracy of the measurement. Simultaneous slip measurement is not possible with this system, as it lacks monitoring of the drive rotor or pulley speeds. Additional measuring devices are required for this, which increases the complexity and cost of the system. Furthermore, prior system calibration is necessary. This involves setting the distance between the transmitters to match the distance between the markers when the belt is unloaded, thus defining a reference distance. This requires additional manual adjustment and increases the risk of measurement inaccuracies if the sensor distance changes due to factors such as vibrations.

[0007] German patent application DE 20 2016 008 121 U1 discloses a belt drive consisting of a pulley, belt, and monitoring device. A marker is attached to both the belt and the pulley. A signal is triggered when the markers on the belt and the drive pulley are aligned. The position markers can be based on various sensor technologies, such as optical, inductive, capacitive, or magnetic effects.

[0008] The monitoring described therein can be used, among other things, to monitor the number of revolutions over the service life of toothed or synchronous belts.

[0009] A similar method is described in DE 10 2019 206 169 A1, which describes a method for monitoring a belt drive. In this method, the belt has at least one first marking and at least one first sensor element associated with the belt. Furthermore, the rotor of the drive motor has another marking and a sensor element associated with the drive motor. In particular, the monitoring method serves to monitor a visually inaccessible belt drive for steering systems for tooth skipping by detecting an angular misalignment between the belt and the pulley.

[0010] WO02 / 079747 A2 also discloses a device for monitoring a belt by means of a pair of marking parts.

[0011] Unfortunately, the aforementioned documents do not include any parallel force measurement on the belt, which may be necessary for comprehensive monitoring of the belt drive system. Task

[0012] The invention is based on the objective of providing a device and a method for measuring force and slip on drive belts using a common sensor system. In particular, the objective is to implement slip control of the drive belt with the device and / or the method. Furthermore, the generated information on the power transmission and the slip of the drive belt should be used to identify irregularities or wear patterns in the drive system or the machine driven by this drive system at an early stage and before component failure occurs. Solution to the task

[0013] The solution to this problem is achieved by a device according to the invention with the features of the main claim, an attachment device for an agricultural machine with the features of claim 9, and a method according to the invention with the features of claim 10. The features of claim 13 disclose the use of the method according to the invention.

[0014] Further advantageous training opportunities are revealed in the dependent claims. Advantages of the invention

[0015] The invention provides a device for determining the longitudinal elongation and mean speed of a belt, as well as for determining the speed of at least one pulley. The device comprises the belt with a predetermined longitudinal stiffness, the length of which remains constant regardless of the operating condition. The belt has at least a first marking element, a second marking element, a third marking element, and a fourth marking element, wherein the first and second marking elements are configured to form a first pair of marking elements, and the third and fourth marking elements are configured to form a second pair of marking elements.

[0016] The assignment of the marker elements to pairs of marker elements can, for example, enable the section-by-section monitoring of the belt's condition. Furthermore, a drive device is provided with at least two pulleys of predetermined diameter, arranged at an axial distance from each other and at least partially encircled by the belt, as well as a transmission device comprising at least two external readers and an evaluation and control unit suitable for controlling the speed and / or torque of the drive device, wherein, during belt rotation, signals identifiable by each marker element can be generated at the external readers and output to the evaluation and control unit.

[0017] Each of the marking components in the pairs can also transmit an identification identifier, allowing the transmitted signal, captured by one of the external readers, to be assigned to each individual marking component. Assigning the signals to the individual marking components is the only advantageous way to link the signals of the marking components to marking component pairs. Therefore, each of the external readers can both detect and identify each of the marking components in the marking component pairs.

[0018] The belt is designed to be ring-shaped in a circumferential direction and is driven circumferentially by the drive device, wherein the belt has a load-transmitting belt section, also called the load section, and an empty section arranged opposite the load section.

[0019] In other words, when power is transmitted through the belt, the force distribution in the belt strands changes. Power introduced into the load strand of the belt by the pulley connected to a drive motor and then transmitted results in an increase in force in the load strand. This increase, depending on the belt's stiffness, causes the belt to elongate in the load strand. The same increase in force in the load strand leads to a corresponding decrease in force in the slack strand, resulting in a shortening of the slack strand, also dependent on the belt's stiffness. This condition holds true as long as the slack strand has a preload force greater than 0 Newtons. Therefore, the sum of the forces in the belt and the belt's length remain constant even during operation under dynamic load.

[0020] The marking parts of the belt's marking part pairs are arranged one behind the other at a predetermined reference distance in the circumferential direction in a state without power transmission.

[0021] The unloaded state is to be understood as a static state without power transmission through the belt. The belt may already be statically pre-tensioned in this state.

[0022] The reference distance of the marking parts of the first pair of marking parts is designed to change to a first measuring distance during power transmission of the belt, wherein the reference distance of the marking parts of the second pair of marking parts is designed to change to a second measuring distance during power transmission of the belt.

[0023] As previously explained, power transmission results in an increase in force and elongation in the loaded section, as well as a decrease in force and shortening in the slack section.

[0024] In other words, according to Hooke's law, there is a proportional relationship between a change in force and the length in the loaded and slack sides of the belt. The sum of the forces in the belt and the belt length therefore remain constant even during operation under dynamic load.

[0025] Furthermore, at least one of the pulleys has at least one marking part, wherein during the rotation of the pulley the marking part of the pulley is designed to generate an identifiable signal at one of the external reading devices and to output it to the evaluation and control unit.

[0026] As described at the beginning, the marking part of the pulley can also transmit an identification code to the external reading device, in addition to the signal for assigning the signal to the marking part.

[0027] The transmission device is arranged without contact with the belt, such that the marking elements of the belt and pulley marking element pairs can pass the transmission device sequentially. The evaluation and control unit is configured to determine the transit time from each pair of signals. In other words, the transit time can be determined as the time difference between two detected signals from the marking elements.

[0028] The evaluation and control unit is configured to determine the average belt speed based on the measured travel time of one of the marker segments of the marker segment pairs over the circumference during one belt revolution. Furthermore, the evaluation and control unit is configured to determine the pulley speed based on the measured travel time of the marker segment on the pulley.

[0029] As described earlier, the belt length is predetermined and constant. While the length in the individual belt strands can change section by section due to dynamic loading, the overall length of the belt remains constant due to the force equilibrium relationship within the entire belt drive, as explained above. Therefore, the average belt speed can be determined from the measured travel times of the markers during one belt revolution and the predetermined belt length. The pulley also has a predetermined diameter. The pulley speed can be determined in the same way as explained for the belt example.

[0030] The belt has a load-carrying section, also called the load-carrying section, and a load-free section, also called the slack section. The load-carrying and / or slack section extends across the area between two pulleys. In the case of a belt drive with two pulleys, the load-carrying and slack sections are positioned opposite each other and have the same length. When no power is being transmitted by the belt drive, identical force conditions prevail in the load-carrying and slack sections. These conditions result primarily from a static pretension force with which the drive belt is tensioned between the pulleys. The static pretension force of the belt is necessary for reliable power transmission and can be selected and adjusted as needed based on the power requirements to be transmitted by the belt.

[0031] According to one aspect of the device according to the invention, in a state of the belt without power transmission, at least one pair of marker elements formed from the marker elements is arranged in both the load and slack sides around the circumference of the belt. The assignment of the marker elements to marker element pairs can advantageously enable the monitoring of the belt's states in the load and slack sides if one of the marker element pairs is arranged in each of the load and slack sides.

[0032] It proves particularly advantageous that, according to the invention, both the load and slack sides of the belt each have at least one pair of marker elements formed from the marker elements when the belt is in a state without power transmission. This allows information from the load and slack sides to be continuously provided and compared.

[0033] Furthermore, the evaluation and control unit is configured to determine a longitudinal elongation of the belt based on the mean belt speed, the difference in the running times of the two successive marking parts of the marking part pairs of the belt in both the loaded and slack sides, as well as the resulting measurement distance of the marking parts of the marking part pairs to each other in both the loaded and slack sides, and the reference distance as the mean value of the determined measurement distances.

[0034] In other words, the evaluation and control unit can determine the longitudinal elongation of the belt. External readers can capture signals as the belt passes the markers. Based on the predetermined circumference of the belt, which is stored in the evaluation and control unit, the average belt speed can be determined from the transit time of a marker between a first signal at an external reader and a second signal at an external reader after the belt has completed one revolution. Furthermore, the evaluation and control unit is configured to determine the measuring distance between the markers of the marker pairs in both the loaded and slack sides of the belt, based on the transit times of the two successive markers in each marker pair in both the loaded and slack sides.In other words, the measuring distance corresponds to the distance between the marking segments of the marking segment pairs during dynamic operation. As soon as the belt transmits power, the distance between the marking segments of the marking segment pairs changes such that the measuring distance of the marking segments of the marking segment pair in the loaded side increases, while the measuring distance of the marking segments of the marking segment pair in the slack side decreases by the same amount. An increase in the measuring distance of the marking segments of the marking segment pair in the loaded side therefore always results in an identical decrease in the measuring distance of the marking segments of the marking segment pair in the slack side.

[0035] Due to the described dependence of the measurement distance change of the marker components of the marker component pairs in the loaded and slack sides, the reference distance can be determined as the average of the measured distances. Taking into account the average belt speed, the determined measurement distance of the marker components of the marker component pairs to each other in both the loaded and slack sides, as well as the reference distance, the longitudinal elongation of the belt can be determined using the evaluation and control unit.

[0036] The evaluation and control unit is designed to determine the tensile force and tensile force differential in the load-bearing side of the belt using a spring stiffness assigned to the belt and stored in the evaluation and control unit, as well as the distance difference between the marking elements of the belt's marking element pairs in the load-bearing side. The spring stiffness information can also be provided, for example, via a scannable barcode on the belt.

[0037] In other words, the tensile force difference in the load-bearing section can be determined by multiplying the belt's spring stiffness by the distance difference between the marker segments of the marker pairs assigned to the load-bearing section. This tensile force difference can correspond to the force component that is added to the static pretension force by the drive power introduced into the belt drive via the drive pulley. The total force acting in the load-bearing section can then be calculated from the sum of the static pretension force and the tensile force difference.

[0038] Furthermore, the evaluation and control unit is also configured to detect slippage between the belt and pulley based on the ratio of their average speeds. In other words, the evaluation and control unit can monitor both the pulley speed and the average belt speed. A speed difference between the pulley and belt indicates slippage. Depending on the application, particularly with friction-fit drive belts such as V-belts or multi-ribbed belts, some belt slippage may be tolerated or even necessary. However, excessive slippage can lead to increased wear due to abrasion or overheating.Increased slippage can be caused by insufficient belt tension for the power being transmitted. The described slippage measurement advantageously provides early detection of insufficient belt tension, thus preventing permanent damage or belt failure.

[0039] Overall, it proves particularly advantageous that a single sensor system can measure both the longitudinal elongation of the belt and the average speed of the belt and pulley. This allows for the acquisition of numerous measurements in a particularly cost-effective manner.

[0040] According to a further aspect of the device according to the invention, the marking elements are designed as surface acoustic wave sensors. Surface acoustic wave sensors, also called SAW sensors, are particularly well-suited for use in belt drives because they can withstand the high temperatures, sometimes exceeding 200°C, that prevail during belt vulcanization, and because they require little energy to transmit a sensor signal, allowing them to function reliably even at high belt speeds. In this case, the SAW sensors located on or in the belt are associated with an external reading device, which can, for example, be permanently mounted on a machine frame and arranged radially or axially spaced from the belt.The external reader can emit an electromagnetic field which, when passing a SAW sensor, provides the sensor with the energy required to transmit a sensor protocol. The sensor protocol transmitted by the SAW sensor to the external reader can be identified, allowing the sensor protocols to be assigned to individual sensors even when multiple sensors are present.

[0041] According to a further aspect of the device according to the invention, the marking elements are designed as radio-frequency identification, or RFID, transponders. This can represent a particularly advantageous and cost-effective alternative to the SAW sensors described above.

[0042] According to a further advantageous embodiment of the device according to the invention, the marking elements are designed as ferromagnetic marking elements. Particularly advantageously, these can be designed such that ferromagnetic particles are incorporated into the elastomer of a belt. In this way, a homogeneous material distribution in the belt can be achieved without foreign bodies in the form of a sensor element weakening the belt and causing damage to it.

[0043] According to a further aspect of the device according to the invention, the driven pulley has at least one marking element. This can be particularly advantageous if, for example, the speed of the drive motor coupled to the pulley is to be monitored via the marking element of the pulley. In this way, the speed of the drive motor can be monitored directly and without further interposed transmission elements that could distort the measurement result.

[0044] According to a further aspect of the device according to the invention, one of the external reading devices is arranged in the area of ​​the belt's entry into and exit from the pulley. This advantageously ensures that one external reading device is assigned to each of the loaded and slack sides of the belt. By arranging the external reading devices in close proximity to a pulley, precise signal acquisition is possible, since the belt in this area is not yet subject to a large vibration amplitude. Excessive vibrations of the belt can negatively affect signal acquisition due to varying distances between the external reading device and the marking element.

[0045] According to a further aspect of the device according to the invention, it proves particularly advantageous that the evaluation and control unit, when predetermined limit values ​​for the speed difference between the belt and the pulley are exceeded and stored within the evaluation and control unit, is configured to regulate the drive torque or the drive speed in such a way that the speed difference remains within defined limits. In other words, permissible limit values ​​for the slippage between the belt and the pulley can be stored in the evaluation and control unit. The belt speed can be determined at least once per revolution of the belt, depending on the number of marking elements in the belt's marking element pairs, and compared or related to the speed of the pulley.The resulting speed difference or slip can then be compared to the defined limit value. If the speed difference between the belt and pulley exceeds the defined limit, the drive speed or torque can be reduced. Under the adjusted performance data, further speed measurements of the belt and pulley can be taken and again compared to compliance with the defined slip limit. Further adjustments to the drive's performance can be made, if necessary, until the slip remains within the defined limit. This effectively prevents increased belt wear caused by excessive slip due to high temperatures.

[0046] According to a further aspect of the device according to the invention, the evaluation and control unit is coupled with additional measuring devices of machine elements. For this purpose, the evaluation and control unit includes a memory for storing historical sensor data and historical force profile data of the belt. Furthermore, the evaluation and control unit is designed to monitor the historical force profile data of the belt within predefined limit values ​​stored in the memory of the evaluation and control unit, and, by including historical sensor data from other machine elements stored in the memory of the evaluation and control unit, to draw conclusions about the wear of machine elements outside the device.

[0047] In other words, the evaluation and control unit includes a memory that, in addition to the previously described sensor data from the device, can also store sensor data from measuring devices of other machine elements. This acquired sensor data can be stored in memory to monitor long-term changes. In particular, analyzing changes in the belt's force curve data in conjunction with other sensor data from measuring devices of other machine elements can be of great importance.

[0048] This can be illustrated using the example of an attachment on an agricultural machine. This could be the header of a combine harvester. Advantageously, a measuring device on the header can record the harvest volume per unit of time. By comparing the force curve data of the belt, which can be determined by the device according to the invention, with the harvest volume per unit of time of the header, wear on the blades of the header driven by the belt can be identified. If, for example, the force in the belt increases while the harvest volume decreases, the blades may be dull or damaged, and a conclusion can be drawn that the blades need to be replaced.

[0049] Another advantageous embodiment provides for an attachment device of an agricultural machine with at least one device according to the invention for monitoring belt-driven components. In this way, the advantages described above can be applied to various belt drive systems. High availability during harvest time is particularly important for agricultural machinery. Therefore, preventing wear-related machine failures is of paramount importance, which is why monitoring belt drives can be especially relevant.

[0050] A further advantageous embodiment provides a method for determining the longitudinal elongation and mean speed of a belt, as well as for determining the speed of at least one pulley. For this purpose, the belt is provided with a predetermined longitudinal stiffness, wherein the length of the belt is constant regardless of the operating condition.

[0051] The belt has at least one first marking element, one second marking element, one third marking element, and one fourth marking element, wherein the first and second marking elements form a first marking element pair and the third and fourth marking elements form a second marking element pair. Assigning the marking elements to marking element pairs can, for example, enable section-by-section monitoring of the belt's condition.Furthermore, a drive device is provided with at least two pulleys of predetermined diameter, arranged at an axial distance from each other and at least partially encircled by the belt, as well as a transmission device comprising at least two external readers and an evaluation and control unit that regulates the speed and / or torque of the drive device. During belt rotation, each marker element generates identifiable signals at the external readers and outputs them to the evaluation and control unit. In other words, each marker element of the marker element pair can also transmit an identification code, allowing the transmitted signal, detected by one of the external readers, to be assigned to each individual marker element.By assigning the signals to the individual marker components, it is advantageously possible to assign the signals of the marker components to marker component pairs. Therefore, each of the external readers can both detect and identify each marker component within the marker component pairs.

[0052] The belt runs in a circumferential direction around the pulleys in a ring shape and is driven circumferentially by the drive device, the belt having a load-bearing belt section, also called the load section, and an empty section arranged opposite the load section.

[0053] In other words, when power is transmitted through the belt, the force distribution in the belt strands changes. Power introduced into the load strand of the belt by the pulley connected to a drive motor and then transmitted leads to an increase in force in the load strand. This increase, depending on the belt's stiffness, causes the belt to elongate in the load strand. The same increase in force in the load strand leads to a corresponding decrease in force in the slack strand, resulting in a shortening of the slack strand, also dependent on the belt's stiffness. This condition holds true as long as the slack strand has a preload force greater than 0 Newtons. Therefore, the sum of the forces in the belt and the belt's length remain constant even during operation under dynamic load.

[0054] The marker elements of the belt's marker pairs are arranged one behind the other in the circumferential direction at a predetermined reference distance in a state without power transmission. The unloaded state is to be understood as a static state without power transmission through the belt. The belt may already be statically pre-tensioned in this state.

[0055] The reference distance of the marking parts of the first pair of marking parts changes during power transmission of the belt to a first measuring distance, while the reference distance of the marking parts of the second pair of marking parts changes during power transmission of the belt to a second measuring distance.

[0056] As previously explained, power transmission results in an increase in force and elongation in the loaded section, as well as a decrease in force and shortening in the slack section.

[0057] In other words, according to Hooke's law, there is a proportional relationship between a change in force and the length in the loaded and slack sides of the belt. The sum of the forces in the belt and the belt length therefore remain constant even during operation under dynamic load.

[0058] Furthermore, at least one of the pulleys has at least one marking element, whereby, during the pulley's rotation, the marking element generates an identifiable signal at one of the external readers and outputs it to the evaluation and control unit. As described above, the marking element of the pulley can also transmit an identification code to the external reader, in addition to the signal for assigning the signal to the marking element.

[0059] The transmission device is arranged without contact with the belt in such a way that the marking elements of the belt and pulley marking pairs are guided past the transmission device one after the other. The evaluation and control unit then determines a transit time from each pair of signals.

[0060] The evaluation and control unit then determines an average speed of the belt and a speed of the pulley from the running times.

[0061] As described earlier, the belt length is predetermined and constant. While the length in the belt strands can change section by section due to dynamic loading, the overall length of the belt remains constant due to the force equilibrium relationship within the entire belt drive, as explained above. Therefore, the average belt speed can be determined from the measured travel times of the markers during one belt revolution and the predetermined belt length. The pulley also has a predetermined diameter. The pulley speed can be determined in the same way as explained for the belt example, during one pulley revolution.

[0062] The method according to the invention is characterized by the following process steps: a) Generating a signal from the first marker segment of the belt at the first external reader, b) Generating a signal from the second marker segment of the belt at the first external reader, c) Generating a signal from the third marker segment of the belt at the first external reader, d) Generating a signal from the fourth marker segment of the belt at the first external reader, e) Generating a signal from the first marker segment of the belt at the second external reader, f) Generating a signal from the second marker segment of the belt at the second external reader, g) Generating a signal from the third marker segment of the belt at the second external reader, h) Generating a signal from the fourth marker segment of the belt at the second external reader, i) Determining a transit time from each pair of signals by the evaluation and control unit,j) Determination of the average speed of the belt by the evaluation and control unit based on the determined transit time of one of the marker parts of the marker part pairs over the circumferential length during one revolution of the belt, k) Determination of the difference in transit times of the two consecutive marker parts of the marker part pairs of the belt at the external reader assigned to the loaded side by the evaluation and control unit, l) Determination of the measuring distance of the two consecutive marker parts of the marker part pairs in the loaded side via the determined average speed of the belt and the determined difference in transit times of the two consecutive marker parts of the marker part pairs of the belt, m) Determination of the difference in transit times of the two consecutive marker parts of the marker part pairs of the belt at the external reader assigned to the slack side by the evaluation and control unit,n) Determination of the measuring distance between the two consecutive marking parts of the marking part pairs in the slack side of the belt using the determined average speed of the belt and the determined difference in travel times between the two consecutive marking parts of the marking part pairs of the belt, o) Determination of the distance difference between the two consecutive marking parts of the marking part pairs of the belt in the loaded side and in the slack side by the evaluation and control unit, p) Determination of the reference distance between the two consecutive marking parts of the marking part pairs of the belt by the evaluation and control unit using the determined measuring distances of the two consecutive marking parts of the marking part pairs of the belt in the loaded side and in the slack side by averaging the measuring distances,q) Determination of the longitudinal strain in the load-bearing side of the belt by the evaluation and control unit using the determined measuring distance between the two consecutive marking parts of the belt's marking part pairs in the load-bearing side and the determined reference distance; r) Determination of the tensile force and tensile force difference in the load-bearing side of the belt by the evaluation and control unit using a spring stiffness assigned to the belt and stored in the evaluation and control unit, as well as the distance difference between the two consecutive marking parts of the belt's marking part pairs in the load-bearing side; s) Generation of a signal from the pulley's marking part at one of the external reading devices; t) Determination of the pulley's marking part's travel time from two signals by the evaluation and control unit.u) Determination of the pulley speed by the evaluation and control unit based on the determined travel time of the marker part of the pulley over the defined circumference of the pulley, v) Determination of the slip between belt and pulley by the evaluation and control unit, based on the determined speeds of belt and pulley.

[0063] In other words, each of the external readers can detect a change in an electromagnetic field emitted by, for example, the external reader at the moment a marker passes through, and this change is defined as the signal of the respective marker. The signal can be assigned to the marker, as described above, via the individual identification mark of the respective marker.

[0064] The method according to the invention advantageously enables a single sensor system to measure force, speed, and slip of several components of a belt drive, namely the belt and the pulley. This method is particularly cost-effective to implement, since multiple measurements can be performed using the same components.

[0065] According to a further aspect of the method according to the invention, it proves particularly advantageous that, when predetermined limit values ​​for the speed difference between the belt and the pulley are exceeded and stored in the evaluation and control unit, the drive torque or the drive speed is regulated in such a way that the speed difference remains within defined limits. In other words, permissible limit values ​​for the slippage between the belt and the pulley can be stored in the evaluation and control unit. The belt speed can be determined at least once per revolution of the belt, depending on the number of marking elements in the belt's marking element pairs, and compared or related to the speed of the pulley.The resulting speed difference or slip can then be compared to the defined limit value. If the speed difference between the belt and pulley exceeds the defined limit, the drive speed or torque can be reduced. Under the adjusted performance data, further speed measurements of the belt and pulley can be taken and again compared to compliance with the defined slip limit. Further adjustments to the drive's performance can be made, if necessary, until the slip remains within the defined limit. This effectively prevents increased belt wear caused by excessive slip due to high temperatures.

[0066] According to another aspect of the method according to the invention, the evaluation and control unit saves historical force curve data of the belt and other historical sensor data from measuring devices of other machine elements in a memory and stores them there.

[0067] The belt's historical force profile data is monitored within predefined limits stored in the evaluation and control unit's memory. By incorporating historical sensor data from other machine elements, also stored in the evaluation and control unit's memory, inferences are drawn about the wear of machine elements outside the device. This sensor data can be permanently stored for historical tracking over extended periods. Furthermore, the belt's historical force profile data, also stored, can be correlated with this historical sensor data.

[0068] In other words, additional sensor data from measuring devices of other machine elements belonging to a working machine can be stored in the memory of the evaluation and control unit. Permissible limit values ​​for the belt force can be stored in the evaluation and control unit. By comparing the currently measured forces in the belt with the stored limit values, irregularities can be detected if the permissible limits are exceeded. If the permissible limits are exceeded, the evaluation and control unit can issue a warning signal. By incorporating historical sensor data from other machine elements obtained elsewhere, a correlation can be established between changes in belt forces and changes in the other sensor data.In particular, considering the change in the force curve data of the belt in conjunction with other sensor data from measuring devices of other machine elements can be of great importance.

[0069] This can be illustrated using the example of an attachment on an agricultural machine. This could be the header of a combine harvester. Advantageously, a measuring device on the header can record the harvest volume per unit of time. By comparing the force curve data of the belt, which can be determined using the method according to the invention, with the harvest volume per unit of time of the header, wear on the blades of the header driven by the belt can be identified. If, for example, the force in the belt increases while the harvest volume decreases, the blades may be dull or damaged, and a conclusion can be drawn that the blades need to be replaced.

[0070] According to another aspect, the inventive method is intended for use in monitoring belt-driven devices on attachments of agricultural machinery. This allows the previously explained advantages of sensor monitoring to be transferred to agricultural machinery. High availability during harvest time is particularly important for agricultural machinery. Therefore, preventing wear-related machine failures is of paramount importance, which is why monitoring belt drives can be especially relevant. Explanation of figures

[0071] An embodiment of the invention will be explained in more detail below with reference to the drawing.

[0072] Fig. 1 shows an advantageous embodiment of the device in a schematic view.

[0073] In the Figure 1An advantageous embodiment of the device 1 is shown schematically. The device 1 comprises a belt 2 with predetermined longitudinal stiffness and a drive device 4 with, for example, two pulleys 3 of predetermined diameter arranged at a center-to-center distance A from each other. One of the two pulleys 3 is coupled to a motor of the drive device 4 as the driven pulley. The belt 2 is designed to run circumferentially U and partially encircles each of the two pulleys 3. The belt 2 is driven by the drive device 4 with the two pulleys 3, so that the belt 2 rotates circumferentially U.

[0074] The belt 2 comprises a base material and at least one reinforcing element. The base material can, for example, be made partially or entirely of rubber or polyurethane. However, other materials can also be used for the base material. Preferably, the base material is electrically insulating. The reinforcing element is embedded in the base material as a continuous cord wound helically in the circumferential direction U. The reinforcing element serves to transmit forces in the circumferential direction U of the belt 2. The reinforcing element can, for example, be made of a metallic wire or a plastic filament strand, such as a polyamide fiber strand. The individual turns of the cord forming the reinforcing element in the transverse direction of the belt 2 can be arranged staggered relative to one another. Each of the turns extends in the circumferential direction U.The length of belt 2 is constant regardless of the operating condition.

[0075] The belt 2 also comprises at least a first marking element 8, a second marking element 9, a third marking element 10, and a fourth marking element 11. In one embodiment, the marking elements 8, 9, 10, and 11 are configured as SAW sensors and embedded in the base material of the belt. SAW sensors are particularly well-suited for applications in a belt 2 because, on the one hand, they can withstand the required temperatures during the manufacture of the belt 2 and, on the other hand, require very little energy for wireless data transmission of the sensor signals, which enables their use at high relative speeds between the sensor and the associated external reader 6.1, 6.2. The first marking element 8 and the second marking element 9 form a first marking element pair, while the third marking element 10 and the fourth marking element 11 form a second marking element pair.The first and second pairs of markers are arranged such that, in the resting state of the belt 2 without power transmission, one pair of markers is located in the loaded side TR1 and the other in the slack side TR2. In this state, the markers 8, 9 and 10, 11 of the marker pairs are arranged one behind the other at a predetermined reference distance R in the circumferential direction U. When power is transmitted through the belt 2, the reference distance R changes to a first measuring distance M1 for markers 8, 9 of the first pair of markers and to a second measuring distance M2 for markers 10, 11 of the second pair of markers.

[0076] Furthermore, one of the pulleys 3, which is preferably driven by a motor, also has a marking part 12 in the form of a SAW sensor.

[0077] A transmission device 5 comprises two external readers 6.1, 6.2 and an evaluation and control unit 7. One of the external readers 6.1, 6.2 is arranged in the area of ​​the entry and exit of the belt 2 into and out of the pulley 3, which includes the marking element 12. The transmission device 5 is arranged without contact with the belt 2 and the pulley 3, so that the marking elements 8, 9, 10, 11 of the marking element pairs of the belt 2 and the marking element 12 of the pulley 3 are guided past the transmission device 5 one after the other. The marking parts 8, 9, 10, 11 of the marking part pairs of the belt 2 are detected by the external readers 6.1, 6.2 and identified by means of an individual marking of each individual marking part 8, 9, 10, 11 and output as signal SM8, SM9, SM10, SM11 by the external readers 6.1, 6.2 to the evaluation and control unit 7.

[0078] Likewise, during the rotation of the pulley 3, the marking part 12 is detected and identified by one of the external reading devices 6.1, 6.2 and output as signal SM12 to the evaluation and control unit 7.

[0079] Each of the external readers 6.1, 6.2 is configured to capture the signals SM8, SM9, SM10, SM11, SM12.

[0080] The evaluation and control unit 7 is configured to determine a runtime from each pair of signals SM8, SM9, SM10, SM11, SM12.

[0081] Furthermore, the evaluation and control unit 7 is configured to determine an average speed V2 of the belt 2 based on the determined running time TR of one of the marking parts 8, 9, 10, 11 of the marking part pairs over the circumferential length LR over one revolution of the belt 2 and a speed V3 of the pulley 3 based on the determined running time TS of the marking part 12 over the defined circumference LS of the pulley 3 stored in the evaluation and control unit 7. V 2 = LR TR V 3 = LS TS

[0082] By determining the difference in transit times dTR of the two consecutive marker parts 8, 9 of the marker part pair in the loaded section TR1 and of the marker parts 10, 11 of the marker part pair in the slack section TR2 of the belt 2, a first measuring distance M1 of the marker parts 8, 9 of the first marker part pair and a second measuring distance M2 of the marker parts 10, 11 of the second marker part pair can be determined together with the mean belt speed V2. The difference in transit times dTR of the marker parts 8, 9 of the first marker part pair assigned to the loaded section TR1 and the difference in transit times dTR of the marker parts 10, 11 of the second marker part pair assigned to the slack section TR2 are determined by the external reader 6.1 assigned to the loaded section TR1, which outputs the signals SM8, SM9 to the evaluation and control unit 7, and the external reader 6 assigned to the slack section TR2.2, which outputs the signals SM10 and SM11 to the evaluation and control unit 7. M = V 2 ∗ dTR

[0083] From the determined measurement distances M1 and M2, the evaluation and control unit 7 calculates a distance difference dM between the two consecutive marking parts 8, 9 of the first marking part pair in the loaded section TR1 and the two consecutive marking parts 10, 11 of the second marking part pair in the unloaded section TR2. By averaging the measurement distances M1 and M2, the evaluation and control unit 7 determines the reference distance R between the two consecutive marking parts 8, 9 of the first marking part pair in the loaded section TR1 and the two consecutive marking parts 10, 11 of the second marking part pair in the unloaded section TR2. dM = M 1 − M 2 R = dM 2

[0084] Based on the previously determined measuring distance M1 and the reference distance R, the longitudinal strain ε of the belt 2 in the load section TR1 is determined in a next process step by the evaluation and control unit 7. ε = M 1 − R

[0085] In a further process step, the evaluation and control unit 7 determines a tractive force Fz and a tractive force difference dFz.

[0086] The tensile force difference dFz corresponds to the force component that is added to the static pretension force by the drive power introduced into the belt drive via the drive pulley 3. For this purpose, a spring stiffness D, individually assigned to each belt, is stored in the evaluation and control unit 7. The spring stiffness D depends on the belt specification and must be entered once in the evaluation and control unit 7 during machine setup. Information on the spring stiffness can also be provided, for example, via a scannable barcode on the belt. Furthermore, the measuring distance M1 must be used to determine the tensile force Fz, and the distance difference dM must be used to determine the tensile force difference dFz. Fz = D ∗ M 1 dFz = D ∗ ε

[0087] Furthermore, the evaluation and control unit 7 is designed to determine a slip V4 between belt 2 and pulley 3, based on the determined speeds V2, V3 of belt 2 and pulley 3. V 4 = V 3 V 2 − 1 Reference symbol list

[0088] 1 Device 2 Belt 3 Pulley 4 Drive device 5 Transmission device 6.1 6.2 First external reader Second external reader 7 Evaluation and control unit 8 First marker part of the belt 9 Second marker part of the belt 10 Third marker part of the belt 11 Fourth marker part of the belt 12 Marker part of the pulley A = Center distance of the pulleys D = Spring stiffness ε = Longitudinal elongation of the belt F = Free length of the belt F = Tensile force d = Tensile force difference LR = Circumference length of the belt L = Circumference length of the pulley M1 = Measuring distance of the first marker pair M2 = Measuring distance of the second marker pair dM = Distance difference R = Reference distance SM8 = Signal from the reader of the first marker of the belt SM9 = Signal from the reader of the second marker of the belt SM10 = Signal from the reader of the third marker of the belt SM11 = Signal from the reader of the fourth marker of the belt SM12 = Signal from the reader of the marker of the pulley TR = Travel time of a marker of the belt over the circumference length over one revolution of the belt dTR = Difference in the travel times of two successive markers of a marker pair TSL = Travel time of a marker of the pulley over the circumference length of the pulley TR1 Loaded side TR2 Empty side Circumferential direction V2 MiddleBelt speed V3, Pulley speed V4, Slippage between belt and pulley

Claims

1. Device (1) for ascertaining a longitudinal extension (ε) and an average speed (V2) of a belt (2) and for ascertaining a speed (V3) of at least one belt pulley (3), comprising - the belt (2) with a predetermined longitudinal stiffness, - wherein the length of the belt (2) is constant irrespective of the operating state, - wherein the belt (2) has at least a first marking part (8), a second marking part (9), a third marking part (10) and a fourth marking part (11), - wherein the first and the second marking part (8, 9) form a first marking part pair and the third and fourth marking parts (10, 11) form a second marking part pair, - a drive device (4) having at least two belt pulleys (3) of predetermined diameter which are arranged with an axis spacing (A) from each other and around which the belt (2) is at least partially looped, - a transmission device (5) comprising at least two external readers (6.1, 6.2) and an evaluation and control unit (7) which is suitable for controlling the rotation speed and / or the torque of the drive device (4), - wherein, as the belt revolves, signals (SM8, SM9, SM10, SM11) identifiable at the external readers (6.1, 6.2) can be generated by each marking part (8, 9 or 10, 11) and - can be output to the evaluation and control unit (7), - wherein the belt (2) is designed to revolve in a circumferential direction (U) in the form of a ring and is driven by the drive device in the circumferential direction (U), - wherein the belt (2) has a load-transmitting load strand (TR1) and an idle strand (TR2) arranged opposite to the load strand, - wherein, in a state without power transmission, the marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) are each arranged one behind the other in the circumferential direction (U) with a predetermined reference spacing (R), - wherein the reference spacing (R) of the marking parts (8, 9) of the first marking part pair is designed to change into a first measurement spacing (M1) when power is transmitted by the belt (2), - wherein the reference spacing (R) of the marking parts (10, 11) of the second marking part pair is designed to change into a second measurement spacing (M2) when power is transmitted by the belt (2), - wherein at least one of the belt pulleys (3) has at least one marking part (12), - wherein, as the belt pulley (3) rotates, the marking part (12) of the belt pulley (3) is designed to generate an identifiable signal (SM12) at one of the external readers (6.1, 6.2) and to output it to the evaluation and control unit (7), - wherein the transmission device (5) is arranged without contact with the belt (2) in such a way that the marking parts (8, 9, 10, 11, 12) of the marking part pairs of the belt (2) and the belt pulley (3) can be guided past the transmission device (5) in succession, - wherein the evaluation and control unit (7) is configured to ascertain a respective running time from in each case two signals (SM8, SM9, SM10, SM11, SM12), - wherein the evaluation and control unit (7) is configured to ascertain an average speed (V2) of the belt (2) based on the ascertained running time (TR) of one of the marking parts (8, 9 and 10, 11) of the marking part pairs over the circumferential length (LR) over one revolution of the belt (2) and a speed (V3) of the belt pulley (3) based on the ascertained running time (TS) of the marking part (12) of the belt pulley (3), characterized in that in a state of the belt (2) without power transmission, at least one marking part pair formed from the marking parts (8, 9 or 10, 11) is arranged respectively in the load strand and the idle strand (TR1, TR2) over the circumference (U) of the belt (2), wherein the evaluation and control unit (7) is configured - to ascertain a longitudinal extension of the belt based on the average belt speed (V2), the difference between the running times (dTR) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) both in the load strand (TR1) and in the idle strand (TR2), and the measurement spacing (M1, M2) ascertained therefrom of the marking parts (8, 9 or 10, 11) of the marking part pairs from each other both in the load strand (TR1) and in the idle strand (TR2), and the reference spacing (R) as an average value from the ascertained measurement spacings (M1, M2), - to ascertain a tensile force (Fz) and difference in tensile force (dFz) in the load strand (TR1) of the belt (2) using the evaluation and control unit (7) via a spring stiffness (D) assigned to the belt (2) and stored in the evaluation and control unit (7) and a difference in spacing (dM) of the marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) in the load strand (TR1), - and is also configured to ascertain slip (V4) between the belt (2) and the belt pulley (3) based on the ratio of the average speeds (V2, V3) ascertained from the belt (2) and the belt pulley (3).

2. Device (1) according to Claim 1, characterized in that the marking parts (8, 9, 10, 11, 12) are in the form of acoustic surface wave sensors.

3. Device (1) according to Claim 1, characterized in that the marking parts (8, 9, 10, 11, 12) are in the form of RFID transponders.

4. Device according to Claim 1, characterized in that the marking parts (8, 9, 10, 11, 12) are in the form of ferromagnetic marking parts.

5. Device (1) according to one of the preceding claims, characterized in that the driven belt pulley has at least one marking part (12).

6. Device (1) according to one of the preceding claims, characterized in that one of the external readers (6.1, 6.2) is arranged in the region of the inlet and one in the region of the outlet of the belt (2) into / out of the belt pulley (3).

7. Device (1) according to one of the preceding claims, characterized in that when predetermined limit values for slip (V4) between the belt (2) and the belt pulley (3) stored in the evaluation and control unit (7) are exceeded, the evaluation and control unit (7) is configured to control the drive torque or the drive speed in such a way that the slip (V4) moves within defined limit values.

8. Device (1) according to one of the preceding claims, characterized in that the evaluation and control unit (7) is coupled to further measuring devices of machine elements and comprises a memory - for backing up historical sensor data and - for backing up historical force profile data relating to the belt (2), wherein the evaluation and control unit (7) is designed - to monitor the historical force profile data relating to the belt (2) within prespecified limit values stored in the memory of the evaluation and control unit (7) - and, taking into account the historical sensor data relating to further machine elements from the memory of the evaluation and control unit (7), to draw a conclusion about the wear of machine elements outside the device (1).

9. Attachment of an agricultural machine having at least one device (1) according to one of the preceding claims for monitoring devices driven by belts (2).

10. Method for ascertaining a longitudinal extension (ε) and an average speed (V2) of a belt (2) and for ascertaining the speed (V3) of at least one belt pulley (3), comprising - the belt (2) with a predetermined longitudinal stiffness, - wherein the length (LR) of the belt (2) is constant irrespective of the operating state, - wherein the belt (2) has at least a first marking part (8), a second marking part (9), a third marking part (10) and a fourth marking part (11), - wherein the first and the second marking part (8, 9) form a first marking part pair and the third and fourth marking parts (10, 11) form a second marking part pair, - a drive device (4) having at least two belt pulleys (3) of predetermined diameter which are arranged with an axis spacing (A) from each other and around which the belt (2) is at least partially looped, - a transmission device (5) comprising at least two external readers (6.1, 6.2) and an evaluation and control unit (7) which controls the rotation speed and / or the torque of the drive device (4), - wherein, as the belt revolves, signals (SM8, SM9, SM10, SM11) identifiable at the external readers (6.1, 6.2) are generated by each marking part (8, 9 or 10, 11) and - are output to the evaluation and control unit (7), wherein the belt (2) revolves in a circumferential direction (U) in the form of a ring and is driven by the drive device (4) in the circumferential direction (U), wherein the belt (2) has a load strand (TR1) and an idle strand (TR2) arranged opposite to the load strand, - wherein, in a state without power transmission, the marking parts (8, 9 and 10, 11) of the marking part pairs of the belt (2) are each arranged one behind the other in the circumferential direction (U) with a predetermined reference spacing (R) in a non-loaded state of the belt, - wherein the reference spacing (R) of the marking parts (8, 9) of the first marking part pair changes into a first measurement spacing (M1) when power is transmitted by the belt (2), - wherein the reference spacing (R) of the marking parts (10, 11) of the second marking part pair changes into a second measurement spacing (M2) when power is transmitted by the belt (2), wherein at least one of the belt pulleys (3) has at least one marking part (12), wherein, as the belt pulley (3) rotates, the marking part (12) of the belt pulley generates an identifiable signal at one of the external readers (6.1, 6.2) and outputs it to the evaluation and control unit (7), - wherein the transmission device (5) is arranged without contact with the belt (2) in such a way that the marking parts (8, 9, 10, 11, 12) of the marking part pairs of the belt (2) and the belt pulley (3) are guided past the transmission device (5) in succession, - wherein the evaluation and control unit (7) ascertains a running time (TR, TS) from in each case two signals (SM8, SM9, SM10, SM11, SM12), - wherein the evaluation and control unit (7) ascertains an average speed (V2, V3) of the belt (2) and the belt pulley (3) from the running times (TR, TS), characterized by the following method steps: a) generating a signal (SM8) from the first marking part (8) of the belt (2) at the first external reader (6.1), b) generating a signal (SM9) from the second marking part (9) of the belt (2) at the first external reader (6.1), c) generating a signal (SM10) from the third marking part (10) of the belt (2) at the first external reader (6.1), d) generating a signal (SM11) from the fourth marking part (11) of the belt (2) at the first external reader (6.1), e) generating a signal (SM8) from the first marking part (8) of the belt (2) at the second external reader (6.2), f) generating a signal (SM9) from the second marking part (9) of the belt (2) at the second external reader (6.2), g) generating a signal (SM10) from the third marking part (10) of the belt (2) at the second external reader (6.2), h) generating a signal (SM11) from the fourth marking part (11) of the belt (2) at the second external reader (6.2), i) ascertaining a running time from in each case two signals (SM8, SM9, SM10, SM11) using the evaluation and control unit (7), j) ascertaining the average speed (V2) of the belt (2) using the evaluation and control unit (7) based on the ascertained running time of one of the marking parts (8, 9 or 10, 11) of the marking part pairs over the circumferential length over one revolution of the belt (2), k) ascertaining the difference between the running times (dTR) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) on the external reader (6.1) assigned to the load strand (TR1) using the evaluation and control unit (7), l) ascertaining the measurement spacing (M1, M2) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs in the load strand (TR1) via the ascertained average speed (V2) of the belt (2) and the ascertained difference between the running times (dTR) of the two consecutive marking parts (8, 9 and 10, 11) of the marking part pairs of the belt (2), m) ascertaining the difference between the running times (dTR) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) at the external reader (6.2) assigned to the idle strand (TR2) using the evaluation and control unit (7), n) ascertaining the measurement spacing (M1, M2) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs in the idle strand (TR2) via the ascertained average speed (V2) of the belt (2) and the ascertained difference between the running times (dTR) of the two consecutive marking parts (8, 9 and 10, 11) of the marking part pairs of the belt (2), o) ascertaining the difference in spacing (dM) of the two consecutive marking parts (8, 9 and 10, 11) of the marking part pairs of the belt (2) from each other in the load strand (TR1) and in the idle strand (TR2) using the evaluation and control unit (7), p) ascertaining the reference spacing (R) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) using the evaluation and control unit (7) via the ascertained measurement spacings (M1, M2) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) in the load strand (TR1) and in the idle strand (TR2) by averaging the measurement spacings (M1, M2), q) ascertaining the longitudinal extension (ε) in the load strand (TR1) of the belt (2) using the evaluation and control unit (7) via the ascertained measurement spacing (M1, M2) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) in the load strand (TR1) and the ascertained reference spacing (R), r) ascertaining the tensile force (Fz) and difference in tensile force (dFz) in the load strand (TR1) of the belt (2) using the evaluation and control unit (7) via a spring stiffness (D) assigned to the belt (2) and stored in the evaluation and control unit (7) and the difference in spacing (dM) of the two consecutive marking parts (8, 9 or 10, 11) of the marking part pairs of the belt (2) in the load strand (TR1), s) generating a signal (SM12) from the marking part (12) of the belt pulley (3) at one of the external readers (6.1, 6.2), t) ascertaining a running time (TS) of the marking part (12) of the belt pulley (3) from two signals (SM12) using the evaluation and control unit (7), u) ascertaining the speed (V3) of the belt pulley (3) using the evaluation and control unit (7) based on the ascertained running time (TS) of the marking part (12) of the belt pulley (3) over the defined circumference of the belt pulley (3), v) ascertaining the slip (V4) between the belt (2) and the belt pulley (3) using the evaluation and control unit (7), based on the ascertained speeds (V2, V3) of the belt (2) and the belt pulley (3).

11. Method according to Claim 10, characterized in that when predetermined limit values for slip (V4) between the belt (2) and the belt pulley (3) stored in the evaluation and control unit (7) are exceeded, the evaluation and control unit (7) reduces the drive torque or the drive speed, so that the slip (V4) moves within defined limit values.

12. Method according to Claim 10 or 11, characterized in that the evaluation and control unit (7) stores and backs up historical force profile data relating to the belt (2) and further historical sensor data from measuring devices of further machine elements in a memory and monitors the historical force profile data relating to the belt (2) within prespecified limit values stored in the memory of the evaluation and control unit (7), wherein, taking into account otherwise ascertained historical sensor data relating to further machine elements from the memory of the evaluation and control unit (7), a conclusion is drawn about the wear of machine elements outside the device (1).

13. Use of the method according to one of Claims 10 to 12 for monitoring belt-driven devices on attachments of an agricultural machine.