Planetary Brake Transmission With Dual Reduction Ratios
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Solution Overview
Problem
Electromechanical service brakes face challenges in quickly traversing the release clearance and achieving rapid response times due to the need for a long brake application distance and potential heating issues, which affect braking torque and wear, and require a complex transmission system with multiple components.
Innovation Solution
A transmission assembly with a planetary gear system featuring a sun wheel, planet wheels, and an annulus with a freewheel mechanism, allowing for two reduction ratios: a low-torque first ratio for traversing the release clearance and a higher second ratio for active braking, enabling quick brake application force generation without additional rotation-translation converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large release clearance is designed to cover operating conditions and reduce residual braking torque, then the brake unit can operate reliably without rubbing during free driving, but the brake application distance increases and response time is delayed
Solution Approach 1:
The transmission ratio is made variable rather than constant. During the release clearance traversal phase, a first (lower) transmission ratio is used to minimize input torque requirements. Upon brake lining contact with the brake disk, the transmission ratio automatically switches to a second (higher) ratio to rapidly build up the required brake application force, thereby reducing response time while maintaining reliability.
Solution Approach 2:
The transmission ratio parameter is changed dynamically based on the operational phase. The system transitions from a first transmission ratio optimized for traversing release clearance to a second transmission ratio optimized for generating brake application force, allowing the system to optimize performance for each phase rather than compromising with a constant ratio.
2Device complexity
If a linear transmission ratio is used with a long brake application distance, then the transmission system is simple and reliable, but the force buildup is delayed and force modulation is poor
Solution Approach 1:
The transmission system employs a dynamic transmission ratio that automatically changes based on the brake application phase. A clutch mechanism engages or disengages the planetary transmission depending on whether the brake lining is in contact with the brake disk, providing rapid force buildup without requiring complex additional rotation-translation converters.
3Loss of time
If a nonlinear transmission ratio is used to increase transmission ratio in the release clearance region, then response time improves and required input power decreases, but the possible travel is limited and initial position must be known
Solution Approach 1:
The transmission system is segmented into two distinct operational modes with different transmission ratios. The first ratio serves the release clearance traversal phase, while the second ratio serves the brake application phase. This segmentation allows optimization for each phase without the limitations of continuous nonlinear transmission ratio changes.
Solution Approach 2:
The clutch acts as an intermediary mechanism that switches between direct drive (first transmission ratio) and planetary transmission (second transmission ratio). This intermediary allows the system to transition between different transmission characteristics without requiring precise knowledge of initial position or limiting travel range.
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 transmission assembly allows for rapid traversal of the release clearance and quick application of a high brake force, improving response time and reducing input power requirements, while maintaining reliability and minimizing installation space and cost.
Implementation Method 1
The planet wheels are supported by means of the planet carrier in such a way that they can roll both on the sun wheel and on the annulus
Implementation Method 2
The annulus is designed as a freewheel or comprises a freewheel, and therefore the annulus can rotate freely in a first direction of rotation and is held fixed against rotation in a second, opposite direction of rotation
Data Source
AI summary
A transmission assembly has a plurality of reduction ratios. For this purpose, the transmission assembly can comprise a planetary transmission in which the annulus can rotate freely in a first direction of rotation and in which the annulus is held fixed against rotation in a second direction of rotation. A method of operating a transmission assembly is also disclosed.