Electric Vehicle Drive Device Torque Control for Shock Prevention
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Solution Overview
Problem
Existing drive devices for electric vehicles face challenges in accurately preventing shocks during the release of torsional torque when the parking lock mechanism is released, due to inaccuracies in estimating the required counter-torque, which can lead to shocks when the vehicle is stopped on hills.
Innovation Solution
A drive device that estimates balancing torque by applying opposite directional rotational torque to the electric motor when the ignition switch is turned on, stores this torque, and applies it to the motor after the parking lock is released, using incline detection to determine the torque direction and prevent shock occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque is applied in the opposite direction of torsional torque when the parking lock mechanism is released, then the shock caused by rapid release of torsional torque is prevented, but the magnitude of applied torque may not accurately match the actual requirement, leading to insufficient shock prevention
Solution Approach 1:
The system performs preliminary action by estimating the balancing torque in advance when the ignition switch is turned on, before the parking lock mechanism is released. This allows the control unit to have the correct torque value ready and apply it immediately when needed, ensuring accurate shock prevention without relying on imprecise real-time estimation during the release moment
Solution Approach 2:
The system uses feedback by monitoring the rotational phase of the electric motor and using this information to accurately estimate the balancing torque. The control unit continuously tracks the motor's rotational state and adjusts the torque application accordingly, ensuring the applied torque precisely matches the actual requirement for shock prevention
2Device complexity
If the parking lock mechanism is released without applying counter-torque, then the device complexity is reduced, but a shock occurs due to rapid release of accumulated torsional torque
Solution Approach 1:
The system applies the self-service principle by utilizing the electric motor that already exists in the vehicle to generate the balancing torque. The same motor used for propulsion serves dual purposes: normal driving and shock prevention during parking lock release. This eliminates the need for separate mechanical counter-torque devices, reducing overall system complexity while still preventing shocks
Solution Approach 2:
The patent replaces complex mechanical torque control mechanisms with electronic control of the electric motor. Instead of using mechanical springs, dampers, or additional locking mechanisms to control torque release, the system uses electronic signals to control the motor's torque output, simplifying the mechanical structure while achieving precise torque management
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution accurately prevents the occurrence of shocks during the release of torsional torque by applying the correct counter-torque based on the actual rotational phase of the electric motor, ensuring smooth operation even on inclined surfaces.
Implementation Method 1
an electric motor (9), and a controller (25) that controls the electric motor (9)... the controller (25) causes the electric motor (9) to rotate so as to generate rotational torque in the opposite direction
Data Source
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AI summary
A drive device for an electric vehicle includes: a parking lock mechanism that mechanically locks a rotation of a rotating shaft of drive wheels; a parking lock operating means; an electric motor; a balancing torque estimating means for applying rotational torque to the electric motor in the opposite direction of the direction of torsional torque applied to the rotating shaft, while locking via the parking lock mechanism is done, and for balancing torque in advance that balances out the torsional torque, based on a state of the rotational phase of the electric motor; and a torque applying means for applying torque to the electric motor before the locking is released, the torque calculated based on the estimated balancing torque.