Differential Gear Shaft Damage Detection in EV Torque Control
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Solution Overview
Problem
Existing vehicle control systems fail to accurately determine whether a shaft connected with the differential gear mechanism is damaged, leading to potential seizure of the mechanism.
Innovation Solution
A vehicle control apparatus that calculates the difference between input and output rotation speeds of the differential gear mechanism and determines the duration of this difference exceeding a predetermined value to identify shaft damage, implementing torque and vehicle speed limitations to prevent seizure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If failure determination is made based on rotation number difference between drive wheel and driven wheel, then differential device failure can be detected, but shaft damage cannot be accurately determined
Solution Approach 1:
The patent segments the failure detection into two distinct measurement systems: one for differential device failure (using drive/driven wheel rotation difference) and another for shaft damage (using input/output rotation speed difference of the differential mechanism). This segmentation allows each system to optimize for its specific detection target, resolving the contradiction between general failure detection and precise shaft damage detection.
Solution Approach 2:
The patent introduces an intermediary measurement point - the input and output rotation speeds of the differential gear mechanism - which serves as a mediator between the motor shaft and the drive wheels. This intermediary measurement enables indirect detection of shaft damage by comparing rotation speeds at different points in the torque transmission path, without requiring direct shaft sensors.
2Reliability
If torque limitation is implemented to prevent differential mechanism seizure, then mechanism protection is achieved, but vehicle productivity is reduced
Solution Approach 1:
The patent implements preliminary action by detecting shaft damage early through rotation speed difference monitoring and determining the duration of abnormal states before seizure occurs. By identifying the problem in advance and implementing torque limitation proactively, the system prevents catastrophic failure while maintaining vehicle operation, thus protecting the mechanism without completely stopping productivity.
Solution Approach 2:
The patent applies dynamics by implementing a time-based determination mechanism that monitors the duration of abnormal rotation speed differences. The system dynamically adjusts torque limitation based on how long the abnormal state persists, allowing temporary fluctuations without unnecessary intervention while preventing permanent damage if the condition continues, thus balancing protection with operational continuity.
Data Source
AI summary
Vehicle control apparatus includes: first/second shaft coupled with first/second drive wheel of vehicle; differential gear mechanism configured to distribute torque from motor to first/second shaft; sensor configured to detect first/second wheel rotation speed and motor rotation speed; and motor control unit including processor and memory. Motor control unit: calculates input rotation speed into differential gear mechanism based on motor rotation speed; calculates output rotation speed from differential gear mechanism based on first/second wheel rotation speed; calculates difference between input rotation speed and output rotation speed; determines whether duration of state in which difference exceeds predetermined value has exceeded determination time; and limits motor target torque to zero when it is determined that duration has exceeded determination time.