Tandem Axle Speed Control via ECU and Sensors
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Solution Overview
Problem
Existing tandem and triple axle arrangements in vehicles face issues with tire wear and stress due to small differences in rolling radii of wheel pairs, which are not effectively addressed by traditional longitudinal differentials, leading to inefficiencies in traction and increased costs and complexity.
Innovation Solution
A wheel suspension system with transversally arranged differentials and angular speed sensors connected to an electronic control unit (ECU) that allows for differential speed control between wheel pairs, enabling the disconnection of axles to prevent excessive speed differences and reduce tire wear, along with a lifting mechanism for load distribution and measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a longitudinal differential is used to allow speed difference between axles, then tire wear is reduced, but device complexity and weight increase
Solution Approach 1:
The patent extracts the speed differential function from a traditional longitudinal differential and relocates it to the wheel suspension arrangement. By using the existing wheel suspension components to accommodate speed differences between axles, the invention eliminates the need for a separate longitudinal differential, thereby reducing device complexity and weight while still protecting against tire wear
Solution Approach 2:
The wheel suspension arrangement is given a dual function: it continues to support the vehicle weight and provide suspension, while also accommodating speed differences between tandem axles. This multi-functionality eliminates the need for dedicated longitudinal differential components, reducing overall system complexity
2Power
If tandem axles are connected to the same drive shaft, then efficient traction is provided, but tire wear increases due to rolling radius differences
Solution Approach 1:
The patent introduces sensors that detect the rotational speed of each axle and provide feedback to a control system. Based on this feedback, the system actively controls the speed differential between tandem axles, allowing them to rotate at different speeds when rolling radius differences exist, thereby preventing excessive tire wear while maintaining connected drive shaft operation for efficient traction
3Reliability
If axial speed difference is allowed between tandem axles, then tire wear is reduced, but measurement accuracy decreases due to load distribution variations
Solution Approach 1:
The patent employs a lifting mechanism that raises one of the tandem axles before speed measurements are taken. This preliminary action ensures equal load distribution on both axles during measurement, eliminating load-induced speed variations and improving measurement accuracy. After measurement, the axle is lowered back to its working position, allowing controlled speed differences for tire wear protection
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2C
AI summary
The invention relates to a wheel suspension system comprising at least two driven axles (2, 3, 10, 12) each provided with a differential, wherein each driven axle (2, 3, 10, 12) is provided with a pair of wheels (4a, 4b; 4c, 4d; 4e, 4f; 4g, 4h); a driveshaft (5) having a portion (5a, 5b, 5c, 5d) connected to each driven axle (2, 3, 10, 12) via a differential (6a, 6b, 6c, 6d); angular speed sensors (8a, 8b, 8c, 8d, 8e, 8f; 8g, 8h) designed to detect the rotational speed of the driven axles (2, 3, 10, 12) and/or the rotational speed of the respective wheels (4a, 4b, 4c, 4d; 4e, 4f; 4g, 4h) of the driven axles (2, 3, 10, 12); and an electronic control unit (ECU) connected to the angular speed sensors (8a, 8b, 8c, 8d, 8e, 8f; 8g, 8h) to receive input therefrom and designed to use the input from the angular speed sensors (8a, 8b, 8c, 8d, 8e, 8f; 8g, 8h) in order to calculate a difference between the angular speed of the driven axles (2, 3, 10, 12) and/or a difference between the angular speed of the respective wheels (4a, 4b, 4c, 4d; 4e, 4f; 4g, 4h) of the driven axles (2, 3, 10, 12). A coupling (7, 11, 13) is arranged in the driveshaft (5) and positioned between the drive shaft portions (5a, 5b, 5c, 5d) for changing the drive shaft portions (5a, 5b, 5c, 5d) between being drivingly connected and disconnected. The invention further includes a method for controlling such a wheel suspension system in order to avoid to drivingly connect driven wheels or axles having a undesired high rotational speed difference and thus reduce wear of powertrain and/or tires.