Two-Stage Electronic Parking Brake Actuation for High Clamping Load
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Solution Overview
Problem
Conventional electronic parking brake (EPB) systems cannot generate sufficient clamping load to hold a vehicle on severe or extreme grade levels at both gross vehicle weight (GVW) and gross combined vehicle weight (GCVW).
Innovation Solution
A two-stage actuation mechanism with a preloaded torsional spring and lead screws, where the first lead screw achieves initial clamping load and the second lead screw provides additional load modulation, minimizing power consumption and maintaining actuation time with a high gear train ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional EPB systems are used, then the system structure is simple, but the clamping load is insufficient to hold the vehicle on severe or extreme grade levels
Solution Approach 1:
The actuation mechanism is divided into two distinct stages: a first lead screw for initial clamping load generation and a second lead screw for additional load multiplication. This segmentation allows each component to be optimized for its specific function, achieving the required high clamping load while maintaining a manageable structural complexity through modular design.
2Force
If a high gear train ratio is used to increase clamping load, then the clamping load is sufficient, but the actuation time increases and power consumption rises
Solution Approach 1:
The actuation process is segmented into two phases with different mechanical advantages. The first lead screw provides a moderate gear ratio for rapid initial movement and positioning, while the second lead screw provides a higher gear ratio for final load multiplication. This segmentation allows the system to achieve high clamping load without requiring a single excessively high gear ratio that would slow down the entire actuation process.
Solution Approach 2:
The actuation occurs in periodic stages: the first lead screw operates during an initial actuation phase to establish baseline clamping, then the second lead screw operates in a subsequent phase to multiply the load. This periodic, staged action allows the system to optimize actuation speed and power consumption by matching the mechanical advantage to the specific phase requirements.
3Force
If a high gear train ratio is used to increase clamping load, then the clamping load is sufficient, but the current consumption increases
Solution Approach 1:
The energy consumption is segmented across two lead screws with different mechanical advantages. The first lead screw operates with lower current draw during initial actuation, and the second lead screw operates with higher current draw only during the final load multiplication phase. This segmentation reduces peak current requirements and overall energy consumption compared to using a single high-ratio gear train that would require high current throughout the entire actuation cycle.
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
The system effectively generates desired clamping loads quickly and efficiently, ensuring vehicle immobilization on various grade levels with reduced component count and low current consumption.
Implementation Method 1
a preloaded torsional spring configured to activate a first stage of movement of the two-stage actuation mechanism via rotation of the first lead screw
Implementation Method 2
a first lead screw having a first plurality of threads, a second lead screw having a second plurality of threads
Data Source
AI summary
A two-stage actuation mechanism for a brake system includes a first lead screw having a first plurality of threads, a second lead screw having a second plurality of threads, a preloaded torsional spring, and an actuator assembly having an input shaft coupled with the preloaded torsional spring of the two-stage actuation mechanism. The preloaded torsional spring is configured to activate a first stage of movement of the two-stage actuation mechanism via rotation of the first lead screw. The size and pitch of each of the first and second lead screws are configured to minimize power consumption by the actuator assembly and satisfy a desired actuation time with a low current consumption and high actuator gear train ratio.