Multi-Angle Ball Ramp Brake Actuator With Auto Air Gap Adjustment
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Solution Overview
Problem
Current aerospace wheel electric brake systems using ball screws face supplier limitations, high costs, and require frequent adjustments due to wear-induced changes in air gaps between the output shaft and brake stack, leading to inefficiencies and potential setting loss during failure modes.
Innovation Solution
An electric brake actuator output stage with a ball ramp assembly and auto-gap adjustment mechanism, featuring a threaded interface, ratchet teeth, and pawl mechanism, allows for automatic adjustment of the air gap by rotating the input ball ramp relative to the output ball ramp, maintaining the air gap within an operable dimension as brake stack components wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ball screw configuration is used in the brake actuator, then the braking force can be generated, but the system suffers from limited supplier availability, high cost, and requires frequent manual adjustments due to air gap changes from wear
Solution Approach 1:
The brake actuator incorporates an automatic air gap adjustment mechanism that self-regulates the air gap between the output shaft and brake stack. The system uses a adjustable stop mechanism with a stop member that can be positioned along the output shaft to automatically compensate for wear, eliminating the need for manual adjustments and maintaining consistent braking performance throughout the brake stack's service life.
2Measurement precision
If the air gap is set electronically with memory storage, then the initial air gap can be precisely controlled, but the settings may be lost during failure modes requiring re-adjustment
Solution Approach 1:
The patent replaces the electronic memory-based air gap setting system with a mechanical adjustment mechanism. The adjustable stop uses physical positioning of a stop member along the output shaft, secured by a set screw, to define the air gap. This mechanical approach ensures the air gap setting is retained through wear compensation and is not susceptible to electronic failure or data loss.
3Power
If conventional ball screw designs are used, then braking function is achieved, but additional gear stages are required due to minimum lead versus load constraints
Solution Approach 1:
The patent changes the fundamental parameter of the screw mechanism from a conventional ball screw with fixed lead to an adjustable screw mechanism where the lead can be varied. By adjusting the screw lead parameter, the system can accommodate different load requirements without needing additional gear stages, thereby reducing overall mechanical complexity while maintaining the required braking force.
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 solution ensures consistent braking performance by automatically adjusting the air gap, reducing the need for frequent manual adjustments and minimizing the risk of setting loss during failure modes, thereby enhancing the reliability and efficiency of the brake system.
Implementation Method 1
The output ball ramp is fitted with ratchet teeth that interface with a ratchet pawl that is energized by an external or integral spring mechanism. The output ramp can only rotate in one direction due to the interaction of the ratchet and pawl to perform the auto-adjustment operation.
Implementation Method 2
The output ball ramp is fitted with ratchet teeth that interface with a ratchet pawl that is energized by an external or integral spring mechanism.
Implementation Method 3
The output ball ramp has ramped ball tracks containing one or more bearing balls, with one ball per ramp track. An input ball ramp has a matching set of ramped ball tracks that interface with the bearing balls.
Data Source
AI summary
A brake actuator is configured to perform either a braking operation, or an auto-adjustment operation of an air gap between an actuator output shaft and a brake stack. The brake actuator includes a conjugate ramp track containing a bearing ball, the conjugate ramp track being formed by matching ball ramp tracks of an input ball ramp and an output ball ramp. The output ball ramp is connected to the output shaft by a threaded interface to move the output shaft by rotation of the input ball ramp. The conjugate ramp track is a multi-angle ball ramp track thereby including areas of different gain. The input ball ramp is rotated in a first direction to perform the braking operation, and the input ball ramp is rotated in a second, opposite direction to perform the auto-adjustment operation. During the auto-adjustment operation, a position of the output shaft is automatically adjusted when the air gap has a dimension that is larger than an operable dimension to adjust the air gap to be within the operable dimension.