Methods for diagnosing vibration dampers

Abstract

Method for diagnosing a chassis system (3; 5; 7; 9), comprising a sensor device (45) that detects a road obstacle (49) located in front of a vehicle and a road signal (F B ) for a chassis control unit (43), based on the road signal (F B ) a calculation of the vehicle behavior is performed, wherein a wear state is calculated from a comparison by a diagnostic unit (53) between a target value and an actual value of the vehicle behavior, characterized in that the sensor device (45) detects whether a chassis component (3; 7) of a left lane is exposed to a comparable excitation as a comparable chassis component (5; 9) of a right lane, wherein the vibration behavior of both chassis components is compared and a wear state of the chassis component is assumed if there is a deviation above a threshold value.

Description

[0001] The invention relates to a method for diagnosing vibration dampers according to the preamble of claim 1.

[0002] It has long been known that a special vibration test device is used to check a vibration damper. This device records the damping behavior of the vibration damper or the vehicle body and compares it to a stored data set. However, this check always requires a visit to a workshop, as at least one wheel of the vehicle must be driven onto the vibration test device.

[0003] WO 2008 / 022 697 A1 discloses a chassis system with a road surface detection sensor that generates a signal representing road surface quality. The road surface is detected proactively in front of a vehicle. The expected vehicle behavior can be determined from the road surface signal. When the vehicle passes the detected road surface area, a comparison is made between the expected and the actual vehicle behavior. This comparison can be used, for example, to diagnose chassis components, such as the shock absorbers, which are wear parts in the chassis. The advantage of this system over a separate testing machine is that it eliminates the need for a separate testing machine.

[0004] However, the system described in WO 2008 / 022 697 A1 requires very high computing power to perform the diagnostic function.

[0005] The object of the present invention is to enable the use of a simple diagnostic system for a chassis system in a vehicle.

[0006] The task is solved by the sensor device detecting whether a chassis component of a left lane is exposed to a comparable excitation as a comparable chassis component of a right lane, comparing the vibration behavior of both chassis components and assuming a wear condition of the chassis component if there is a deviation above a threshold value.

[0007] This form of chassis component diagnostics is very easy to perform and does not require particularly powerful computing resources. Within limits, the diagnostics can also be carried out with a significant time delay. The only question is whether an unacceptably large difference in the reaction of the chassis components in the two lanes occurs in response to the detected obstacle. Examples of such obstacles include curbs or bridge bearings, which tend to run perpendicular to the road surface and therefore, when the vehicle is traveling straight ahead, represent a signal and an obstacle that should elicit the same reaction from both chassis components on an axle.

[0008] In a further embodiment of the invention, a minimum frequency for exceeding the threshold values ​​for determining a wear condition can be required. One-off events are to be excluded from consideration via this process step, as they may not be representative and would only distort the picture.

[0009] Furthermore, it is possible to conduct a further comparison between a suspension component of the first axle of a track and a suspension component of the second axle of the same track. A direct 1:1 comparison may not be possible, as a suspension component on one front axle might have slightly different operating characteristics than a suspension component on the other front axle. However, there is generally a known relationship between the two components of a track. This relationship is incorporated into the comparison, leading to meaningful results.

[0010] To further refine the diagnostic procedure, a load signal representing the vehicle's load situation can be used for the diagnostic process. This load signal also facilitates better comparability of chassis components on a single vehicle.

[0011] According to an advantageous dependent claim, the magnitude of the excitation affecting the chassis system is taken into account in the diagnosis. If, for example, the excitation exceeds a certain magnitude, then it may be a very rare problem, so that a chassis component which, from a purely mathematical perspective, would already be classified as defective, could, however, be considered still usable upon practical evaluation.

[0012] To minimize the load on the sensors for road detection, an obstacle suitable for diagnostics can be stored via a GPS signal representing the position of the obstacle, and the diagnostic process can be started when this GPS signal is available.

[0013] The following description of the figures will be used to explain the invention in more detail.

[0014] It shows: Fig. 1 Model representation of a vehicle Fig. 2 Flowchart of the procedure for operating the chassis system

[0015] The Fig. Figure 1 shows a model representation of a vehicle 1 with four vibration dampers 3, 5, 7, 9 and their mounting points, where the vibration dampers and their mounting points 11, 13, 15, 17 also represent a chassis system of any design. Each wheel represents a half-axle (not shown) equipped with a sensor 19, 21, 23, 25 that detects the absolute movement of the wheel 11-17 or the half-axle. Simple acceleration sensors, for example, are conceivable.

[0016] Furthermore, a vehicle body 27 is equipped with sensors 29, 31, 33, 35 that detect the movement of the vehicle body around a longitudinal axis 37, a transverse axis 39, and a vertical axis 41. In this illustration, the sensors 29–35 are distributed across the vehicle body 27. It is also conceivable to integrate the sensors into a control unit 43, which also receives the signals from the axle-side sensors 19–25.

[0017] In addition, the vehicle also has a sensor device 45 that detects a road obstacle 49 located in front of the vehicle 1 on a roadway 47. An example is shown in the Fig. 1. A camera is shown. In principle, other designs could also be used.

[0018] The invention is not limited to a two-axle vehicle. Applications to vehicles with more than two axles are also conceivable. In principle, a chassis system also includes cabin mountings for a commercial vehicle, since modern cabin mountings often incorporate vibration dampers and must counteract vibrations from the road surface.

[0019] The control unit 43 contains a computer unit 51, which in turn has a procedure for diagnosing the chassis system based on the signals of the aforementioned sensors 19 - 25; 29 - 35; 45.

[0020] The procedure is based on a road signal F B A calculation of the vehicle behavior is performed, whereby a diagnostic unit 53 as part of the computer unit 51 calculates a wear state from a comparison between a target value and an actual value of the vehicle behavior.

[0021] In a first step of the process, the sensor device 45 detects whether a chassis component 3 in a left lane is subjected to a comparable excitation due to the road obstacle 49 as the comparable chassis component 5 in a right lane of the same axle. The diagnostic unit 53 does not need to continuously monitor the condition of chassis components 3-9, since a vibration damper does not typically fail suddenly. Consequently, the threshold above which an obstacle on the road is suitable for the diagnostic procedure can be set very high.

[0022] In another module 59, the vibration behavior S is discussed. VL , S VR Both chassis components, e.g. 3; 5 of an axle, are compared with each other and a wear condition of the chassis component is assumed if there is a deviation above a threshold value.

[0023] This deviation could be an isolated incident, meaning that this measurement would not represent the actual condition of the chassis components. Therefore, it is possible that a minimum frequency is required for exceeding the threshold to determine a wear condition. Consequently, the next procedural step would only be carried out once this minimum frequency has been reached.

[0024] It could be that the road obstacle 49 appeared suitable, but the road signal F B due to faulty data collection, it would actually be unsuitable. Therefore, a further comparison can be made in module 61. VL- S HLThe comparison is made between chassis components 3 and 7 of a first axle of a track and a second axle of the same track. If the comparison of the vibration behavior at the front axle and the vibration behavior of, for example, the left front wheel under the same excitation does not match the vibration behavior of the rear wheel on the same side of the vehicle or track, then a defective vibration damper can be assumed.

[0025] Another control step in module 63 can consist of comparing the rear axle alignment with the front axle alignment. For example, if the alignment S HL - S HR If the front axle shows a deviation in its vibration behavior, while no deviation occurs at the rear axle, then it can be assumed that the road excitation was suitable for the diagnosis and that a vibration damper on the front axle is defective.

[0026] The vibration behavior of the chassis system can change depending on the load. Therefore, to refine the diagnostic system, a load signal S representing the load situation can be used. B This can be used, for example, by displacement sensors 55. Alternatively, the sensor data for detecting the body movement could be evaluated accordingly by comparing a standard acceleration (i.e., at a standard mass of the vehicle) with the actual acceleration when the excitation is known, and calculating a measure of the additional mass from the deviation.

[0027] A further refinement of the diagnostic procedure could involve incorporating the magnitude of the excitation originating from the road obstacle 49 and affecting the chassis system into the diagnosis. For example, if the deviation in vibration behavior only becomes relevant above a certain excitation level, this excitation can be compared with an average excitation profile. If the existing excitation lies outside the average excitation profile, it may still be possible to conclude that the chassis component is in an acceptable condition, meaning that replacement is not yet absolutely necessary.

[0028] A fundamental problem lies in identifying suitable obstacles for carrying out the diagnostic procedure. Therefore, to support and simplify the procedure, a suitable road obstacle for diagnostic purposes can be identified via a GPS signal S representing its position. GThe data is saved and the diagnostic procedure is started when this GPS signal is present. A corresponding signal connection exists between a GPS receiver 57 and the control unit 43 for this purpose.

[0029] All output signals from modules 59-63 are compared in module 65. If a positive output signal is received in module 65, a defect in the chassis component is reported in output 67. Reference sign 1 vehicle 3 vibration dampers 5 vibration dampers 7 vibration dampers 9 vibration dampers 11 wheels 13 wheel 15-inch wheel 17-inch wheel 19 Sensor 21 Sensor 23 Sensor 25 Sensor 27 Vehicle body 29 Sensor 31 Sensor 33 Sensor 35 Sensor 37 Longitudinal axis 39 Transverse axis 41 Vertical axis 43 Control unit 45 Sensor device 47 lanes 49 Roadway obstruction 51 computer unit 53 Diagnostic Unit 55 Distance sensor 57 GPS receivers Module 59-65 Issue 67

Claims

Method for diagnosing a chassis system (3; 5; 7; 9), comprising a sensor device (45) that detects a road obstacle (49) located in front of a vehicle and provides a road signal (FB) for a chassis control unit (43), wherein a calculation of the vehicle behavior is performed on the basis of the road signal (FB), wherein a wear state is calculated by a diagnostic unit (53) from a comparison between a target value and an actual value of the vehicle behavior, characterized in that the sensor device (45) detects whether a chassis component (3; 7) of a left lane is subjected to a comparable excitation as a comparable chassis component (5; 9) of a right lane, wherein the vibration behavior of both chassis components is compared and a wear state of the chassis component is assumed if there is a deviation above a threshold value. Method according to claim 1, characterized in that a minimum frequency for exceeding the threshold for determining a wear condition is required. Method according to claim, characterized in that a further comparison is carried out between a chassis component (3) of a first axle of a chassis component (7) and a second axle of the same track. Method according to claim 1, characterized in that a loading signal (SB) representing the loading situation is used to carry out the diagnosis. Method according to claim 1, characterized in that the magnitude of the excitation originating from the road obstacle (49) on the chassis system (3 - 9) is included in the diagnosis. Method according to claim 1, characterized in that a road obstacle (49) suitable for diagnostic purposes is stored via a GPS signal (SG) representing the position and the diagnostic procedure is started when this GPS signal is available.

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