Ball-in-Ramp Friction Brake for Low-Power High-Clamp Actuation
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Solution Overview
Problem
Existing electro-mechanically actuated wheel brakes require significant motor power to achieve sufficient clamping force in a short time, and are difficult to integrate due to their spacious design.
Innovation Solution
A compact friction brake system utilizing a ball-in-ramp assembly with non-linear grooves to convert rotary motion from an electric motor into braking motion, achieving a low gear ratio and high clamping force with reduced motor power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a non-linear gear (knee-lever gear) is used to reduce required motor power, then motor power requirement is reduced, but the gear is relatively spacious and difficult to integrate within a housing
Solution Approach 1:
The transmission unit is divided into multiple independent ball-in-ramp assemblies, each handling a portion of the motion conversion. This segmentation allows for a more compact overall design compared to a single large non-linear gear mechanism.
Solution Approach 2:
The ball-in-ramp assembly utilizes curved ramp surfaces and spherical balls to achieve motion conversion. The curved geometry of the ramps provides the non-linear mechanical advantage needed to reduce motor power requirements while maintaining a compact form factor, replacing the need for spacious knee-lever gears.
2Productivity
If a non-linear gear is used to achieve sufficient clamping force in short time, then braking performance is improved, but the device becomes difficult to integrate and more complex
Solution Approach 1:
The braking force generation is segmented across multiple ball-in-ramp assemblies that work in parallel. This allows the system to achieve high clamping force quickly through distributed mechanical advantage rather than a single complex non-linear gear mechanism.
Solution Approach 2:
The complex non-linear gear mechanism is replaced with a ball-in-ramp assembly that uses spherical elements rolling on curved surfaces. This substitution simplifies the mechanical system while maintaining the ability to generate high clamping force rapidly through the geometric properties of the ramps.
3Force
If the axial spacing between first plate and second plate is increased to generate braking motion, then clamping force is achieved, but the transmission unit requires more space
Solution Approach 1:
The curved ramp surfaces in the ball-in-ramp assembly amplify the axial motion generated by the electric motor. As the first plate rotates, the balls roll along the curved ramps, converting small rotational movements into larger axial displacements of the second plate, thereby achieving high clamping force with minimal axial spacing requirements.
Solution Approach 2:
The mechanical advantage ratio is dynamically changed through the curved geometry of the ramps. As the axial spacing changes during braking operation, the effective gear ratio of the ball-in-ramp assembly adjusts automatically, providing high force multiplication when clamping force is needed while maintaining compact dimensions.
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 achieves a sufficiently high clamping force in a short time with low required motor power, while being compact and robust, suitable for both parking and service brakes.
Implementation Method 1
The ball-in-ramp assembly is configured to convert a rotary motion of the first plate into a translational motion of the second plate with respect to the first plate
Implementation Method 2
a friction brake system comprising a braking member connectable to at least one brake pad and configured for pressing the brake pad against a friction surface
Data Source
AI summary
The present application relates to a friction brake system (1) for a vehicle. The friction brake system (1) comprises a braking member (12) connectable to first and second brake pads and configured for pressing the first and second brake pads against a friction surface. The system (1) further comprises a transmission unit (2) configured for converting a rotary motion generated by an electric motor (30) into a braking motion of the braking member (12). The transmission unit (2) comprises a ball-in-ramp assembly (3) having a first plate (9) with at least one groove (23), a second plate (10) with at least one groove (22) facing the groove (23) of the first plate (9), and at least one ball (11) arranged between the first plate (9) and the second plate (10). The ball (11) is retained by the groove (23) of the first plate (9) and the groove (22) of the second plate (10). Further, the ball-in-ramp (3) assembly is configured to convert a rotary motion of the first plate (9) into a translational motion of the second plate (10) with respect to the first plate (9). The first plate (9) is configured to be rotated by the electric motor (30). Further, at least one of the first plate (9) and the second plate (10) is mechanically coupled with the braking member (12). The first plate (9) is rotatably supported by a brake bolt bracket (16) coupled to a braking bolt (13), and the second plate (10) is operably connected to a caliper housing bolt (14) connected with a caliper housing (33) such that the caliper housing (33) and the braking bolt (14) are configured to press the first and second brake pads against opposing surfaces of a brake disc when the braking member (12) executes the braking motion.