Ball-Ramp Brake Actuator Geometry for Non-Self-Locking Return
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Solution Overview
Problem
Existing electromechanical braking devices for motor vehicles face a conflict between achieving high power transmission for braking force and ensuring a non-self-locking return mechanism, which is essential for safe and efficient operation.
Innovation Solution
The braking device employs a ball ramp arrangement with a specific ratio of raceway radius to ball diameter (greater than 0.5 but less than or equal to 0.75) to optimize power transmission and non-self-locking return, while also incorporating features like flattened end sections and trough-shaped depressions in the raceways to enhance functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the raceway inclination is made shallower to achieve high power transmission, then the braking force increases, but the Hertzian pressure increases and the return characteristic deteriorates
Solution Approach 1:
The patent changes the geometric parameters of the raceway cross-section by defining a specific ratio between raceway radius rg and ball diameter Db (0.5 < rg/Db ≤ 0.75). This parameter optimization allows the raceway to distribute contact stresses more effectively, reducing peak Hertzian pressure while maintaining the shallow inclination angle needed for high power transmission and braking force.
2Power
If the raceway inclination is made shallower to achieve high power transmission, then the braking force increases, but the non-self-locking return characteristic deteriorates
Solution Approach 1:
The patent optimizes the raceway cross-sectional geometry by controlling the ratio of raceway radius to ball diameter within a specific range (0.5 < rg/Db ≤ 0.75). This geometric parameter change reduces rolling friction and improves ball mobility in the raceway, enabling smooth axial return movement of cam discs while maintaining the shallow inclination angle required for high power transmission during braking.
3Stress or pressure
If the raceway radius is increased to reduce Hertzian pressure, then the rolling friction decreases, but the ball ramp arrangement size increases
Solution Approach 1:
The patent defines an optimized ratio range between raceway radius rg and ball diameter Db (0.5 < rg/Db ≤ 0.75) that balances multiple competing requirements. This ratio optimization ensures that the raceway radius is sufficiently large to reduce Hertzian pressure and rolling friction, while preventing excessive increase in the overall actuator dimensions, thus achieving a compact yet effective design.
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 configuration allows for high load capacity and adjustment force with sufficient non-self-locking return, reducing Hertzian pressure and rolling friction, thus enabling reliable and efficient braking operations.
Implementation Method 1
the balls roll in the tracks into a relative axial displacement of the cam discs... The balls roll back to their original position... rolling friction in the raceways
Implementation Method 2
This results in a high Hertzian pressure, i.e. a high surface pressure with which each ball is pressed against the raceways... reducing Hertzian pressure
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to an electromechanical braking device (1) for a motor vehicle, comprising an electromotive adjusting device (5) and a braking element (32) which is connected thereto and can be adjusted by the adjusting device (5) and brought into braking engagement with a counter-braking element (2), wherein: the adjusting device (5) has at least one adjusting drive (6, 7); the adjusting drive (6) has a ball-ramp arrangement (6) comprising two cam disks (61, 62); the cam disks (61, 62) can be driven by an electric adjusting mechanism (41, 42) such that they rotate relative one another about an axis (A), and have raceways (64) that are axially opposite each other at an angle relative to the axis (A), between which raceways one ball (63) is arranged such that it can roll; the raceways (64) have an at least partially rounded-off cross-sectional profile with a raceway radius (rg), and the ball (63) has a ball diameter (Db). In order to implement an improved function having an optimized recovery characteristic, according to the invention, a ratio (C) between the raceway radius (rg) and the ball diameter (Db) is greater than 0.5.