Methods for wear monitoring on tracked running gear

Abstract

Methods for wear monitoring on tracked running gears of mobile machines, in which the chain is driven via at least one drive shaft by a drive motor via a mechanical gearbox or directly, characterized by that the clearance between the teeth of the chain and the teeth of the drive sprocket is determined, for which purpose the path of the teeth during the starting movement is determined by a rotation angle measurement at the drive motor or at the mechanical transmission, wherein the rotation angle results between the beginning of the relative movement of the teeth with respect to the teeth on the chain and its end by the contact of the teeth of the drive sprocket and the teeth on the chain, which is determined by the fact that the torque at the drive motor or at the mechanical transmission increases sharply or the rotational speed decreases sharply, and that repeated measurement of the play indicates wear on the drive shaft and chain from an increase in the play.

Description

[0001] The invention relates to a method for monitoring wear on tracked running gear in mobile machines, in which the chain is driven via a sprocket by one or more drive motors.

[0002] Vehicles with tracked or crawler drives are known for many applications, for example in mining or agriculture.

[0003] In these drives, the chain is driven by at least one drive sprocket, hereinafter referred to as a drive wheel. The teeth on the sprocket engage with the teeth on the chain links, thus positively transmitting the drive torque. The drive wheel(s) are driven by at least one drive motor, usually with a gearbox interposed for speed control.

[0004] The drive mechanism is subject to considerable wear, making it necessary to replace the chain, individual chain links, connecting elements, drive rollers or running and deflection rollers at certain intervals, which represents a considerable amount of work and inevitably involves operational interruptions.

[0005] To determine the optimal replacement time, the wear on the chains and sprockets is monitored. In addition to manual measurement, which is currently state of the art, there are also approaches to automated wear determination.

[0006] A method for wear monitoring is known, for example, from US 2022 / 0063636 A1. This involves measuring the time to determine the movement of the teeth.

[0007] US 9,592,866 B2 describes various methods for monitoring the undercarriage using wear sensors. One design involves monitoring the undercarriage by measuring the displacement of the tensioning device. A disadvantage of this method is that it determines a "cumulative wear." All wear-related effects, such as chain elongation, a reduction in the diameter of the idler pulleys, and a change in the contact radius between the chain and the drive wheel, are included with varying degrees of amplification. Detailed monitoring of the wear progression at a specific contact point is therefore very limited and imprecise. The other solutions described aim for the local installation of various sensors. A disadvantage of this approach is that a larger number of sensors are required, and these must be installed very close to the undercarriage. The latter poses a risk of rapid mechanical failure.

[0008] US 2015 / 0066291 A1 provides for the integration of wear sensors into the components (e.g., chain links) of the drive. An ultrasonic sensor is also proposed. A disadvantage is the mechanical integration into the components. This is not only complicated, but such integration also leads to mechanical weakening. Additionally, signal feedback for evaluation is difficult due to the integration into partially moving parts (chain links). As with US 9.592866 B2, the expected high mechanical stresses on the sensors must also be considered.

[0009] WO 2016 / 032793 A1 is comparable in approach and disadvantages to US 2015 / 0066291 A1. However, this patent application relates to the monitoring of the connecting elements of a chain. In US 2015 / 0081166 A1 and US 2016 / 0121945 A1, the approach is based on sensor integration for monitoring rotating bearings, for example, the rollers of the drive unit.

[0010] WO 2015 / 187333 A1 takes a different approach. Here, the wear surfaces on a drive link are provided with wear indicators.

[0011] The disadvantage of this solution is that only wear on surfaces that are visually visible at a specific time can be checked (for example, not at rotary sliding bearing points), that this has to be checked manually, and that the determination can only be applied to the condition of one component and not to dimensionally changing wear effects between several components.

[0012] To achieve a certain service life, the teeth between the chain and drive sprockets are manufactured with a so-called leading wear characteristic. As wear increases over the operating period, this leading wear decreases until it eventually transitions into trailing wear. Trailing wear results from the slippage of a drive sprocket tooth during engagement with the chain teeth, leading to progressive wear. Therefore, the remaining service life of the drive system is very short once trailing wear begins.

[0013] The remaining wear allowance can be manually measured for both forward and reverse travel, provided the drive wheels and chain are properly positioned, and serves as an indicator of remaining service life. This value is referred to as the X1 dimension for forward travel and the X2 dimension for reverse travel. Problems with this measurement include, firstly, the risk of damage from measuring on the loaded chassis, the sometimes considerable dirt accumulation, and the need for precise positioning between the wheel and chain. Despite these difficulties...

[0014] Due to the reduction of the X1 and X2 dimensions during operation, the mechanical hysteresis between the wheel and chain teeth increases accordingly. This therefore correlates with the remaining service life of the contact between the chain and wheel.

[0015] The invention aims to automate time-consuming, manual maintenance inspections, thereby relieving customers of this burden. Continuous monitoring enables more accurate remaining service life predictions, which in turn facilitate better planning of upcoming replacements. Another primary purpose of the invention is to enhance safety. During manual measurements by maintenance or service personnel, the track is subjected to mechanical stress. These operations, performed in the immediate vicinity of this hazard with its high stored mechanical energy, pose a significant safety risk due to the potential for material fragments to break off.

[0016] This problem is solved according to the invention with a method for wear monitoring on tracked running gears of mobile machines, in which the chain (track chains) is driven directly or indirectly via a mechanical transmission by a drive motor via at least one drive wheel (sprocket), which is characterized by that the radial clearance between the teeth of the chain and the teeth of the drive sprocket is determined, for which the path of the teeth during the starting movement is determined by a rotation angle measurement at the drive motor or at the mechanical transmission, whereby the rotation angle results between the beginning of the relative movement of the teeth with respect to the teeth on the chain and its end by the contact of the teeth of the drive sprocket and the teeth on the chain, which is determined by the fact that the torque at the drive motor (e.g. a hydraulic drive) or at the mechanical transmission increases sharply and / or the rotational speed drops sharply and that repeated measurement of the play indicates wear on the drive shaft and chain from an increase in the play.

[0017] When the drive starts up, the relative movement between the drive wheels and the chain occurs after overcoming the static friction in the contacts until the initial mechanical play is overcome and a torque increase occurs due to the onset of positive engagement of at least one tooth contact.

[0018] The amount of play initially present depends on the previous driving movement, but cannot exceed a maximum value defined by the wear-influenced geometry of the drive wheels and chain.

[0019] Thus, in the inventive method, the increase in torque when the tooth of the drive drive hits the tooth of the chain link can be determined as a system parameter.

[0020] The second system size results from the path that occurs when the X1 / X2 dimension is changed.

[0021] Since, for the reasons mentioned, visual detection from the outside is hardly possible, the movement of the drive system, e.g., the mechanical transmission or drive motor, is determined. The angle of rotation at one of the mechanical transmission components or the motor is recorded.

[0022] Essentially, the observed phenomenon of chain slippage due to play between the chain teeth and the drive gear teeth is utilized. This slippage is detected via a high-resolution rotation angle measurement at the drive and is validated by comparing it to the measured drive torque. As soon as the teeth re-engage, the torque increases sharply and the rotational speed drops briefly. The rotational angle at which slippage occurs can be determined from the signals of a rotation angle sensor in the drive and load sensors (e.g., pressure when using hydraulic motors). Using the geometric relationships of the drive, the chain play can be quantified. For this purpose, the drive speed is converted into the radian measure of the gear circle to determine the current play.

[0023] As mentioned earlier, the X1 / X2 dimension represents the leading or trailing wear during forward or reverse travel between the teeth of the chain and those of the drive sprocket and is one of the relevant indicators for the remaining service life of the chain and the drive sprocket. The clearance between the chain and the drive sprocket, determined using the described method, correlates with the X1 / X2 dimension, so that the actual X1 / X2 dimension can be inferred from the measured clearance.

[0024] With appropriate system design, the progression of wear and tear can be documented over time and displayed to the driver. Once a certain level of wear or change rate is reached, a corresponding warning and maintenance reminder should be issued.

[0025] As a first step, the monitoring process is deliberately triggered by the driver. However, automatic determination during regular operation is also conceivable and represents a further development of the procedure.

[0026] To enable the system to automatically perform monitoring without explicit driver input, the starting processes in both directions can be evaluated during regular operation. In normal operation, a wear check would be performed every time the drive unit is actuated. However, since the slip path depends on the previous actuation and thus the current position between the drive unit and the chain, an evaluation logic must be implemented on the controller for such monitoring. This logic processes the results accordingly and compensates for disturbances, such as chain engagement solely through static friction.

[0027] A very simple logic would be to consider the largest slippage measured during operation as a measure of the drive's condition, compensating for any disturbances that may be present.

[0028] The operator's workload is reduced. Inadequate inspections prevent more extensive consequential damage. This reduces costs and conserves resources.

[0029] The reliability of determining the drive system's condition is increased, as measurements on the tensioned chain are no longer necessary.

[0030] Due to the wear pattern over time, it is also possible to selectively install only the less expensive drive pulley in a slightly larger version at a specific point in time. This measure allows the track to operate for a longer period, as the geometrically different drive pulley again results in accelerated wear.

[0031] Additionally, the system places minimal demands on the sensors; standard commercially available sensors can be used (pressure (hydraulic motor), rotation angle). By positioning or integrating the rotation angle sensor into the drive motor or drive transmission, a very high resolution can be achieved even with standard sensors due to the reduction gearing. Furthermore, this solution allows the sensors to be installed at a sufficient distance from the moving undercarriage components, which is advantageous in terms of installation space and mechanical protection of the sensors.

[0032] The sensors can all be fixed to parts that are stationary relative to the machine frame, thus enabling simple wired signal feedback. Interference-prone wireless transmission or signal slip rings are not required.

[0033] The sensors are not integrated into the replacement parts themselves, so these can be kept more cost-effective, their mechanical strength is not affected, and time-consuming adjustment of the system after replacing the wear parts is eliminated.

Claims

[1] Method for monitoring wear on tracked running gears of mobile machines in which the chain is driven via at least one drive gear by a drive motor via a mechanical transmission or directly, characterized by , that the clearance between the teeth of the chain and the teeth of the drive sprocket is determined, for which purpose the path of the teeth during the starting movement is determined by a rotation angle measurement at the drive motor or at the mechanical transmission, wherein the rotation angle results between the beginning of the relative movement of the teeth with respect to the teeth on the chain and its end by the contact of the teeth of the drive sprocket and the teeth on the chain, which is determined by the fact that the torque at the drive motor or at the mechanical transmission increases sharply or the rotational speed decreases sharply, and that repeated measurement of the play indicates wear on the drive shaft and chain from an increase in the play.