Composite Brake Actuator Piston for Corrosion and Abrasion Resistance
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Solution Overview
Problem
Existing brake actuator pistons are prone to corrosion and abrasion due to exposure to pollutants, leading to potential mechanism failure, and existing methods to enhance both properties in a single piece are economically unviable.
Innovation Solution
A composite piston design where a bushing and nut are treated separately with thermochemical processes to achieve abrasion and corrosion resistance, with the bushing undergoing nitriding/nitrocarburizing and the nut undergoing carburizing/quenching/tempering, then assembled to form a single piece with enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-piece piston is subjected to both abrasion-resistance treatment and hardening treatment, then both properties are lost due to temperature interference, but the patent applies these treatments separately to the bushing and nut before assembly
Solution Approach 1:
The piston is divided into two separate components: a bushing and a nut. The bushing receives the abrasion-resistance treatment (nitriding or nitrocarburizing) while the nut receives the hardening treatment (carburizing with quenching and tempering). This segmentation allows both treatments to be applied without temperature interference, and the two parts are subsequently assembled to form the complete piston assembly.
Solution Approach 2:
The bushing acts as an intermediary component between the guide cylinder and the nut. It is secured to the outer peripheral wall of the nut and provides the abrasion-and-corrosion-resistant surface layer that contacts the guide cylinder, while the nut provides the hardened thread structure for the ball screw mechanism.
2Reliability
If low constructive clearance is used between piston and guide cylinder, then protection against corrosion is improved, but abrasion risk increases due to pollutant presence
Solution Approach 1:
The bushing is given a specific local quality through nitriding or nitrocarburizing treatment, creating a nitrogen-rich surface layer that provides enhanced abrasion and corrosion resistance. This localized treatment on the bushing's outer surface allows it to withstand the harsh polluted environment and contact with the guide cylinder, while the rest of the piston components maintain their respective properties.
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 composite piston design provides improved resistance to abrasion and corrosion while maintaining compactness and economic viability, enhancing the lifespan of brake actuator mechanisms.
Implementation Method 1
the bushing is subjected to an abrasion-and corrosion-resistant thermochemical treatment at a temperature Ts until a nitrogen-rich abrasion-and corrosion-resistant surface layer is obtained
Implementation Method 2
the bushing undergoes nitriding/nitrocarburizing
Implementation Method 3
the nut undergoes carburizing/quenching/tempering
Implementation Method 4
followed by quenching and tempering at a temperature Tr at least 100° C. lower than Ts
Implementation Method 5
followed by quenching and tempering at a temperature Tr at least 100° C. lower than Ts
Data Source
AI summary
A method of manufacturing a piston for a brake actuator mechanism, the piston including a bushing and a nut, the nut including an outer peripheral wall, wherein prior to securing the bushing to the outer peripheral wall of the nut, the bushing is subjected to an abrasion-and corrosion-resistant thermochemical treatment at a temperature Ts until a nitrogen-rich abrasion-and corrosion-resistant surface layer is obtained, and the nut is subjected to a thermochemical hardening treatment including heating to a temperature Tc at least 200° C. higher than Ts, followed by quenching and tempering to a temperature Tr at least 100° C. lower than Ts, and obtaining a carbon-rich hardened surface layer at least locally at the nut thread.