Disc Brake Piston Wear Adjustment via One-Way Clutch
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Solution Overview
Problem
Existing air actuated disc brakes for lighter duty applications, such as smaller trucks or trailers, face challenges with complex wear adjuster mechanisms, increased cost, weight, and packaging issues due to the need for multiple components and bearings, which complicates machining and space utilization.
Innovation Solution
A disc brake design featuring a caliper with a single piston and a wear adjustment mechanism utilizing a one-way clutch, such as a wrap spring, that minimizes the number of components by directly engaging the outer piston portion, allowing axial movement to adjust for wear without separate barrels and gears, and includes a compact transmission path with a friction clutch to manage forces and backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex wear adjuster mechanism with separate barrels and gears is used, then the braking performance is maintained, but the number of components increases and the brake becomes less compact
Solution Approach 1:
The patent merges the wear adjustment mechanism directly into the piston structure by providing a threaded outer portion of the piston that engages with threads in the caliper bore. This integration eliminates the need for separate wear adjuster mechanisms, barrels, and gears, reducing component count while maintaining the wear adjustment function.
Solution Approach 2:
The piston is designed to serve multiple functions: it provides hydraulic pressure for braking and simultaneously serves as the wear adjustment mechanism through its threaded outer portion. This multi-functionality reduces the need for separate dedicated wear adjustment components.
2Reliability
If multiple bearings are provided for the operating shaft, then the operating shaft is supported, but the machining complexity and cost increase
Solution Approach 1:
The patent extracts the bearing function from separate bearing components and integrates it directly into the caliper structure. The caliper is provided with a bearing surface that directly supports the operating shaft, eliminating the need for separate bearing components and reducing machining complexity.
3Volume of moving object
If the inboard side space is limited, then packaging is constrained, but providing two bearings for the operating shaft consumes valuable space
Solution Approach 1:
The patent combines the bearing function with the caliper structure itself, eliminating the need for separate bearing components that would occupy valuable inboard space. The bearing surface is provided directly on the caliper, optimizing space utilization while maintaining operating shaft support.
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 design reduces the number of components, minimizes wear, and enhances the brake's life and compactness, while maintaining effective braking performance and ease of manufacturing, addressing the complexity and packaging issues of prior art.
Implementation Method 1
Encircling the piston with a wrap spring helps to ensure that the surface area for frictional engagement is relatively large. This can assist in minimising wear between the components
Implementation Method 2
the piston comprising an inner portion restrained from rotating and a rotatable outer portion, the inner and outer portions being in threaded engagement, such that rotation of the outer portion of the piston causes the inner portion of the piston to move axially
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A disc brake comprising a caliper configured to straddle a rotor and retain first and second brake pads in at least an inboard-outboard direction, a piston slidable within the caliper, for applying a force to the first brake pad to move the first brake pad towards the rotor during a brake operation, the piston comprising an inner portion (15b) restrained from rotating and a rotatable outer portion (15b), the inner and outer portions being in threaded engagement, such that rotation of the outer portion of the piston causes the inner portion of the piston to move axially relative to the outer portion of the piston, an operating shaft (21) for applying an actuating force to advance the piston when the operating shaft is actuated, a wear adjustment mechanism (30) for adjusting the clearance between the first brake pad and the rotor, to account for wear of the brake pads and rotor, and a transmission path of the wear adjustment mechanism, from the operating shaft to the outer portion of the piston, wherein the transmission path comprises a one-way clutch that directly engages the outer portion of the piston (15a), such that when adjustment of the clearance is required, applying the operating shaft causes the one-way clutch to engage the outer portion of the piston and cause the outer portion of the piston to rotate, and the inner portion to advance in the direction of the rotor.