Brake Disc Actuator with Dual Motion Converters for Pad Wear Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing actuating devices for disc brakes, such as ball screws and ball-in-ramp mechanisms, suffer from high axial dimensions, high cost, noise, and limited ability to compensate for pad wear, while also being unable to achieve non-linear advancement laws.
Innovation Solution
An actuating device combining a first ramp-ball motion converter and a second screw and nut motion converter, with a torque limiter, allows for compact, lightweight construction and non-linear advancement, compensating for pad wear through two distinct operational steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ball screw actuator is used, then braking force transmission and pad wear compensation are achieved, but axial dimension, cost, noise, and weight increase
Solution Approach 1:
The actuating device is segmented into two distinct motion converters: a first ramp-ball motion converter for high-force braking operations and a second screw-nut motion converter for precise pad wear compensation. This segmentation allows each component to be optimized for its specific function, reducing the overall axial dimension while maintaining reliability
Solution Approach 2:
The system dynamically switches between two operational modes: the first ramp-ball converter engages during braking for high force transmission, while the second screw-nut converter engages during pad wear compensation for precise axial adjustment. This dynamic operation allows the system to achieve both high reliability and compact dimensions
2Reliability
If a ball screw actuator is used, then braking force transmission and pad wear compensation are achieved, but cost, noise, and weight increase
Solution Approach 1:
By dividing the actuating device into two specialized converters, each component can be minimized in weight while performing its specific function efficiently. The ramp-ball converter handles high-force braking with lighter construction, while the screw-nut converter handles lightweight precision adjustment
Solution Approach 2:
The invention uses two different motion converter mechanisms (ramp-ball and screw-nut) that replicate the essential function of motion conversion but with different physical principles, allowing selection of the lighter, more appropriate mechanism for each specific task
3Device complexity
If a ball screw with constant pitch is used, then simple construction is achieved, but non-linear advancement law cannot be defined
Solution Approach 1:
The system dynamically selects between two different motion converters based on the required advancement law: the ramp-ball converter provides non-linear advancement for braking force application, while the screw-nut converter provides linear advancement for pad wear compensation. This dynamic selection enables both construction simplicity and advancement law flexibility
4Device complexity
If a single motion converter is used, then device simplicity is maintained, but both high force and extra-travel cannot be achieved simultaneously
Solution Approach 1:
The actuating device is segmented into two specialized converters, each optimized for a specific function: the first ramp-ball converter for high-force braking with minimal travel, and the second screw-nut converter for long-travel pad wear compensation. This segmentation enables dual-function capability while maintaining relative device simplicity through modular design
Solution Approach 2:
Each motion converter is designed with multi-functionality: the ramp-ball converter provides both braking force transmission and partial wear compensation, while the screw-nut converter provides both precise positioning and wear recovery. This universality allows two converters to achieve the dual-function capability of high force and extra-travel
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 device achieves reduced axial dimensions, lower cost, and improved braking efficiency with non-linear advancement, while effectively recovering pad wear and minimizing noise.
Implementation Method 1
a plurality of rolling elements (balls) 29 interposed in contact between ramp tracks 103 formed by the first 101 and second ramp portion 102, so that the rotation of the first ramp portion 101 with respect to the second ramp portion 102 brings about a braking translation
Implementation Method 2
a second screw and nut motion converter 4 without ball recirculation, connected between the second ramp portion 102 and the piston 7, so that a rotation of the second ramp portion 102 with respect to the piston 7 about the actuating axis 8 brings about a further compensating translation
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An actuating device (1) for a disc brake (2), comprises a piston (7), a first ramp-ball motion converter (100), having a first ramp portion (101) axially constrained and actuatable in rotation around the actuating axis (8), a second ramp portion (102) coupled to the piston (7) and a plurality of rolling elements (29) interposed in contact between ramp tracks (103) formed by the first (101) and second ramp portion (102), a second screw and nut motion converter (4), connected between the second ramp portion (102) and the piston (7), a torque limiter (10) that: - implements a torsional connection of the first ramp portion (101 ) with the second ramp portion (102), so that they rotate together about the actuating axis (8) until a predetermined limit torque in said torsional connection is reached, - decouples the rotation of the first ramp portion (101) with respect to the second ramp portion (102) about the actuating axis (8) when the predetermined limit torque is exceeded.