Electric Vehicle Powertrain Parking Control via Synchronizer Neutral Position
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Solution Overview
Problem
Electric vehicles with shift-by-wire (SBW) parking mechanisms have high manufacturing costs and can experience sudden unintended acceleration due to errors in the vehicle control unit, leading to malfunctioning electric parking brakes (EPBs).
Innovation Solution
The implementation of a powertrain with a two-stage speed reducer, a synchronizer movable to a neutral position, and electric parking brakes (EPBs) that mechanically interrupt motor torque delivery to the drive wheels, ensuring stable parking by locking or unlocking the wheels based on the vehicle's state, thereby reducing manufacturing costs and preventing unintended acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If shift-by-wire (SBW) parking mechanism with parking pawl and parking gear is used, then parking control is achieved, but manufacturing cost increases
Solution Approach 1:
The patent extracts and removes the SBW parking mechanism components (parking pawl, parking gear) from the vehicle powertrain, replacing them with electric parking brakes (EPBs) that are integrated into the existing brake system. This extraction eliminates the need for separate parking transmission components, thereby reducing manufacturing cost and structural complexity while maintaining parking functionality.
Solution Approach 2:
The electric parking brakes (EPBs) are designed to serve multiple functions: they act as both the parking brake mechanism and the service brake system. By making the brake system multi-functional, the patent eliminates the need for separate dedicated parking transmission components (parking pawl and parking gear), thereby reducing overall system complexity and manufacturing cost.
2Ease of manufacture
If electric parking brakes (EPBs) are used to replace SBW mechanism, then manufacturing cost is reduced, but reliability decreases due to potential control unit errors causing unintended acceleration
Solution Approach 1:
The synchronizer is designed to preemptively block the torque transmission path from the motor to the drive wheels when the vehicle is in parking mode. By establishing this mechanical barrier in advance, the system prevents any potential unintended acceleration before it can occur, even if the control unit malfunctions and commands motor torque during parking.
Solution Approach 2:
The patent implements a redundant safety mechanism where the synchronizer's neutral position acts as a pre-established protective barrier. This mechanical cushioning ensures that even if the EPB control system fails, the torque path is already blocked, preventing catastrophic unintended acceleration and ensuring parking reliability.
3Reliability
If synchronizer is added to mechanically interrupt torque delivery, then parking reliability is improved, but device complexity increases
Solution Approach 1:
The synchronizer mechanism is integrated into the existing two-stage speed reducer, merging the torque interruption function with the existing transmission structure. By combining these functions rather than adding a completely separate system, the patent achieves reliable torque blocking while minimizing the increase in overall device complexity.
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 significantly reduces manufacturing costs by replacing the SBW and parking gear with EPBs, ensuring stable parking by mechanically preventing motor torque delivery to the wheels, thus preventing sudden unintended acceleration and maintaining vehicle stability.
Implementation Method 1
the EPBs have brake components for frictionally locking wheels of the vehicle
Implementation Method 2
The synchronizer may move to the neutral position to prevent the torque of the motor from being delivered to the drive wheels
Data Source
AI summary
A powertrain for an electric vehicle includes: a motor that generates torque, a motor controller that controls the motor; a two-stage speed reducer connected to the motor and having a synchronizer movable to a neural position when the electric vehicle is parked; a pair of drive wheels connected to the two-stage speed reducer through a differential gear; a pair of electric parking brakes (EPBs) that locks or unlocks the pair of drive wheels, respectively, and a vehicle controller that controls the pair of EPBs. The synchronizer moves to the neutral position to prevent the torque of the motor from being delivered to the drive wheels.