Vehicle Park Lock Control During Power Supply Failure
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Solution Overview
Problem
In electric vehicles, a power supply failure to the park lock device renders it inoperable, leading to safety concerns as the vehicle cannot be securely parked, and existing solutions are either ineffective or excessively costly.
Innovation Solution
A vehicular power supply failure time safety measures control apparatus that detects power supply failures and judges the electric storage state of the park lock power supply, locking the wheels using the park lock mechanism before the storage state becomes critical, thereby ensuring the vehicle can be parked safely without the need for redundant power supply systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a by-wire control type park lock device is used to enable electric actuation of the park lock mechanism, then the ease of operation and integration with vehicle control systems is improved, but the reliability deteriorates because the device becomes dependent on electric power supply which may fail
Solution Approach 1:
The control device performs preliminary detection of power supply status and preliminary operation of the park lock mechanism before the power supply is completely depleted. The controller detects when the stored electric energy is sufficient to operate the park lock actuator, and executes the park lock operation in advance, before the power supply fails completely, ensuring the vehicle can still be secured even after power supply failure occurs.
2Reliability
If dual power supply systems are implemented to ensure park lock operation during power supply failure, then the reliability is improved, but the device complexity and cost increase
Solution Approach 1:
The control device utilizes the existing power supply system's stored energy capacity to perform the park lock operation. Instead of adding a separate backup power supply system, the controller monitors the electric storage state of the existing power supply and uses the available stored energy to operate the park lock actuator before power depletion occurs, making the system self-sufficient during power supply failure without requiring redundant power sources.
3Reliability
If the park lock device operates continuously to ensure readiness, then the reliability is improved, but the energy consumption increases, depleting the power supply faster
Solution Approach 1:
The control device performs periodic detection of the power supply's electric storage state rather than continuous operation. The controller periodically checks whether the stored energy is sufficient to operate the park lock actuator, and only executes the park lock operation when the detection confirms adequate energy availability. This periodic monitoring and conditional execution approach ensures park lock readiness while preventing excessive power supply depletion.
Data Source
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AI summary
Even in the case of a power supply failure disabling charge, in a first phase in which a voltage is higher than or equal to 10.5V, a driving force assistance is normal and it is possible to stop the vehicle safely. Therefore, a control system limits the vehicle speed to an upper limit vehicle speed value depending on the voltage, to enable a usual stopping operation with this assistance. In second through fourth phases in which the voltage is lower than 1 0.5V, the control system decelerates the vehicle forcibly by a driving force cut to reduce the driving force to zero, toward stoppage. In the fourth phase in which the voltage decreases to a level just before a limit disabling the operation of the park lock device, the vehicle speed is almost equal to zero, and hence the control system actuates the park lock device and thereby set the wheel in the park lock state. Therefore, when the voltage decreases to the level incapable of operate the park lock, the park lock operation is finished and the system can prevent the vehicle from falling in the parking disabling state at the time of a power supply failure.