Method for detecting wear in a compressed air supply system of a motor vehicle

Abstract

Method for detecting wear of a compressed air supply system of a motor vehicle, wherein, during a first wear phase (S1), a first group of operating parameters (P1) is monitored, and after a first exceedance of a threshold value (T1) of a predefined operating parameter of the first group (P1), during a second wear phase (S2), a second group of operating parameters (P2) is monitored, and further monitoring of the first group of operating parameters (P1) is carried out.

Description

[0001] The invention relates to a method for detecting wear in a compressed air supply system of a motor vehicle according to the preamble of claim 1.

[0002] Compressed air systems in motor vehicles, such as air suspension systems, use a compressed air supply unit to generate compressed air. These systems are typically designed to last the entire lifespan of the vehicle based on a defined usage profile. The wear limits of the components are designed according to this usage profile, and replacement of components due to premature wear is not intended. Therefore, load or wear counters are usually used to analyze actual usage during vehicle operation.

[0003] However, compressed air systems and supply units are being used more frequently than previously anticipated, resulting in increased utilization. The consequent increased need for control of special functions or high-frequency use of the compressed air system leads to premature wear of system components. In particular, the electric motor and compressor of the compressed air supply unit, as well as electromagnetic switching valves, are affected by this premature wear.

[0004] Due to the highly variable usage patterns of vehicles with air suspension systems, accurately predicting the service life and implementing a corresponding schedule for component replacement is difficult and hardly practical. Simply looking at wear and load counters provides only a rough picture of the actual condition. The vehicle operator cannot detect when the wear limit is reached. This creates the risk of an unplanned system failure or, conversely, of prematurely replacing components, which is uneconomical.

[0005] To determine the wear of a compressor in a compressed air system, a method is known from DE 10 2019 214 858 A1, whereby an operating temperature of the compressor is determined, which is used as a criterion for operating the compressor until a cut-off temperature is reached, whereby a duty cycle until the cut-off temperature is reached is determined and the determined duty cycle is calculated with a parameter that depends on the cut-off temperature reached.

[0006] This method is based on the principle that, under high operating parameters, a higher shutdown temperature than the compressor's nominal shutdown temperature must be selected to ensure sufficient compression runtime for the desired control process. This results in higher compressor availability. However, during extended operation, the compressor enters a critical temperature range where its components can be damaged or begin to wear out. Conversely, under favorable or low operating parameters, a lower shutdown temperature than the nominal shutdown temperature can be selected while still maintaining acceptable compressor availability. On the other hand, this approach does not effectively utilize the maximum possible component load capacity.This is achieved by recording the duty cycle duration of the compression run and calculating it using a parameter that depends on the reached shutdown temperature. This parameter represents a degree of wear that occurs on the compressor components when they are operated up to the respective shutdown temperature. Thus, a weighted duty cycle is obtained for each compression run, which can be used for service life monitoring. This weighted duty cycle allows for a good estimation of compressor wear. This method increases the availability and reliability of the compressor. However, this method only considers the compressor's operating temperature. The compressed air supply unit comprises a multitude of electronic and mechanical components that can wear out, making a more holistic approach advisable.

[0007] The object of the invention is to provide a method for detecting wear in a compressed air supply system of a motor vehicle, which enables the most realistic possible detection and diagnosis of the wear condition of the compressed air supply system.

[0008] The problem is solved using the features of an independent patent claim.

[0009] According to the invention, a method for detecting wear of a compressed air supply system of a motor vehicle is provided, wherein, in a first wear phase, a first group of operating parameters is monitored, and after a first exceedance of a threshold value of a predefined operating parameter of the first group, in a second wear phase, a second group of operating parameters is monitored, and further monitoring of the first group of operating parameters is carried out.

[0010] This method allows for a more precise detection and diagnosis of the actual wear of the compressed air supply system, ensuring its operation even under excessive usage and preventing premature replacement. By selecting specific operating parameters, the wear of components such as the electric motor, compressor pistons and piston seals, or solenoid valves can be determined, as these are crucial for the optimal operation of the compressed air supply system. The at least two-stage wear monitoring provides a quantitative assessment of the compressed air supply system's wear.

[0011] An electronic control unit totals and stores the operating parameters as wear counters during the operation of the compressed air supply system. A comparison of the actual wear counter readings is performed with predefined target wear limits (thresholds). This involves comparing the absolute values ​​of the actual wear with the target wear limits. In this way, the relative change in the wear counter readings over the operating time is determined and, from a certain point onward, compared with corresponding reference values. These reference values ​​can be predefined values ​​and / or reference values ​​determined during operation.

[0012] The exemplary multi-stage wear monitoring system is based on direct and indirect wear counters. Operating parameters of the first group, or direct wear counters, include, among others, the operating times and start-up times of the compressor in the compressed air supply system, the switching cycles of the electromagnetically actuated switching valves, and the operating time of the electronic control unit.

[0013] Operating parameters of the second group, or indirect wear counters, include, for example, the compressor's delivery rate or filling time. The corresponding limit or limit is the compressor's delivery rate or the resulting filling time for filling a component of the air suspension system whose filling volume is known, e.g., the filling time of the pressure accumulator. In the further course of the wear procedure, from a defined operating time point, a relative comparison of the delivery rate or filling time is made with a predefined and / or additionally determined reference value.

[0014] Another indirect wear indicator is the current draw. The current draw of the compressor motor is measured and compared to a maximum current draw limit. From a certain point in the wear measurement process, the current draw is compared relative to a predefined and / or additionally determined reference value obtained during operation.

[0015] The variation in maximum current consumption and the current integral, as well as the product of current consumption and running time of the compressor motor, also serve as indirect wear counters.

[0016] Another indirect indicator of wear is the operating pressure range and the operating temperature range.

[0017] The exemplary wear process is therefore divided into several stages or phases. In the first wear phase, the break-in phase, the absolute wear counters are monitored, i.e., the running or switching times of the compressor, the switching cycles and current consumption of the compressor's subcomponents, such as switching valves and electric motor, as well as the switching on of the electronic control unit and ignition change.

[0018] In the second wear phase, passive wear monitoring, after exceeding a first threshold value of an absolute wear counter of the break-in phase, monitoring of the absolute wear counters of the break-in phase and additionally monitoring of indirect wear counters, such as the monitoring of the compressor performance (delivery rate or filling time) under defined vehicle and environmental boundary conditions during normal system activity, e.g. during storage pressure filling from the environment in a defined temperature, supply voltage, and pressure range.

[0019] Furthermore, reference values ​​for the indirect wear counters are determined and set. The relative comparison of the indirect wear counters is activated to monitor changes during further operation, based on predefined values ​​and / or the set reference values ​​determined during operation.

[0020] The third active wear phase occurs after a further threshold value of the direct or passive wear counters is exceeded. In this stage, a wear warning is issued. Additionally, diagnostic services are activated, which can be accessed automatically or manually by the operator via a defined functional test under defined vehicle and environmental conditions within a defined temperature and supply voltage range. The results of these additional functional tests can determine the wear status more precisely and validate the results obtained during operation. The remaining operating time of the compressed air supply system is also displayed.

[0021] Once a wear counter exceeds a third threshold, the process enters the fourth active wear stage. An extended diagnostic check is performed, and a warning is issued indicating the need to replace the compressed air supply unit or its components, taking into account a predefined minimum remaining service life. The remaining service life is also displayed.

[0022] Further preferred embodiments are shown in the dependent claims and in the following description of an exemplary embodiment with reference to the figure.

[0023] This shows Fig.Figure 1 shows a diagram of an example of wear detection for a compressed air supply system of a motor vehicle with several phases S1, S2, S3, and S4. The first wear phase, S1, is present at the beginning of the process (and thus also at the beginning of the compressed air supply system's operation). This first wear phase, S1, can also be referred to as the break-in phase. While the process or the compressed air supply system is in the first wear phase, S1, an initial group of operating parameters, P1, is monitored by the system. This initial group of operating parameters, which is not exhaustive, includes the operating time, the usage profile, the switching cycles of actuators, the switching cycles of the electronic control unit, and the absolute switching time. Corresponding threshold values, T1, or limit values ​​are assigned to the initial operating parameters, and the system monitors whether these threshold values ​​are exceeded.The system checks whether thresholds have been exceeded, a time period has elapsed, or switching cycles have been reached. If the threshold of a predefined operating parameter in the first group is exceeded, the first wear phase S1 ends, and the process transitions to a second wear phase S2. This wear phase S2 represents passive wear detection. It includes a second group of non-exhaustive operating parameters P2, and additionally, the continued monitoring of the operating parameters from the first group P1. The second group of operating parameters P2 includes the compressor's flow rate, compressor power, and a comparison to compressor reference values. The second group of operating parameters P2 also has corresponding threshold values ​​T2, exceeding which terminates the second wear phase S2.The system checks whether limits have been violated, whether compressor performance has decreased, and whether an acceptable tolerance relative to the reference values ​​has been exceeded. The process then transitions to active wear detection with a third wear phase, S3. Here, the criteria of the second wear phase, S2, continue to be monitored, and a cyclical diagnostic check, D1, of the compressor performance is performed. The system also checks whether critical threshold values, T2, of the second group of operating parameters, P2, which indicate insufficient compressor performance, are exceeded. Furthermore, it observes whether acceptable tolerance values ​​have been significantly exceeded compared to reference values. Finally, a critical wear warning, W1, is issued.If a third exceedance of a threshold value T1; T2 of a predefined operating parameter of the first or second group P1; P2 occurs, the third wear phase S3 ends and the procedure transitions to the fourth wear phase S4. This essentially corresponds to an active wear warning to the vehicle operator. A warning message W2 is sent to indicate the need to replace the compressed air supply system. During this phase, an extended diagnostic check is performed and the remaining service life is determined. If further monitoring of the operating parameters of the first and / or second group P1; P2 reveals another exceedance of a predefined threshold value, the operation of the compressed air supply system is actively stopped. Reference symbol list D1 diagnosis D2 extended diagnosis P1 first group of operating parameters P2 second group of operating parameters S1 first wear phase S2 second wear phase S3 third wear phase S4 fourth wear phase T1 Threshold values ​​of the first group of operating parameters T2 Thresholds of the second group of operating parameters W1 Wear Warning W2 replacement warning

Claims

[1] Method for detecting wear of a compressed air supply system of a motor vehicle, characterized by , that during a first wear phase (S1) a first group of operating parameters (P1) is monitored, and after a first exceedance of a threshold value (T1) of a predefined operating parameter of the first group (P1) during a second wear phase (S2) a second group of operating parameters (P2) is monitored, and further monitoring of the first group of operating parameters (P1) takes place. [2] Method according to claim 1, characterized by, that after a second exceedance of a threshold value (T1; T2) of another predefined operating parameter of the first or second group (P1; P2) within a third wear phase (S3), a diagnosis (D1) of the operating parameters of the first and / or second group (P1; P2) is carried out automatically, cyclically or manually, to determine wear. [3] Method according to claim 2, characterized by , that further monitoring of the second group of operating parameters (P2) takes place as part of the third wear phase (S3). [4] Method according to claim 2 or 3, characterized by , that a warning (W1) indicating a critical wear condition is issued during the third wear phase (S3). [5] Method according to any one of claims 2 to 4, characterized by, that during the third wear phase (S3) a remaining service life determined on the basis of the monitored operating parameters of the first and / or second group (P1; P2) is output. [6] Method according to any one of claims 1 to 5, characterized by , that after a third exceedance of a threshold value (T1; T2) of another predefined operating parameter of the first or second group (P1; P2) within a fourth wear phase (S4), a warning (W2) prompting the replacement of the compressed air supply device is issued. [7] Method according to claim 6, characterized by , that further monitoring of the second group of operating parameters (P2) takes place as part of the fourth wear phase (S4). [8] Method according to claim 6 or 7, characterized by , that during the fourth wear phase (S4) a remaining service life determined on the basis of the monitored operating parameters of the first and / or second group (P1; P2) is output. [9] Method according to one of claims 6 to 8, characterized in that, within the fourth wear phase (S4), an extended diagnosis (D2) of the operating parameters of the first and / or the second group (P1; P2) is carried out automatically, cyclically or manually to determine wear. [10] Method according to any one of claims 6 to 9, characterized by , that after a fourth exceedance of a threshold value (T1; T2) of a predefined operating parameter of the first or second group (P1; P2), operation of the compressed air supply device is prohibited.

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