Shrink-Fit Actuator Piston Sleeve for Precision Sliding
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Solution Overview
Problem
Existing brake actuator mechanisms require extremely precise dimensional control to ensure play-free and friction-free sliding, which is challenging to achieve due to deformation during assembly and differential thermal expansion of components.
Innovation Solution
A piston design incorporating a worm gear mechanism nut with a shrink-fitted sleeve, where the sleeve's guide area maintains its dimensions and allows for thermochemical treatment, minimizing deformation and ensuring consistent performance despite temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sleeve is press-fitted onto the nut to ensure cohesion, then the piston components are securely connected, but deformation occurs during assembly affecting dimensional precision
Solution Approach 1:
The sleeve is divided into two distinct zones: a shrink-fit zone that deforms during assembly to secure the nut, and a guide area that maintains its dimensions for precision sliding. This segmentation allows different parts of the same component to have different functional requirements, resolving the contradiction between cohesion and precision.
Solution Approach 2:
Different regions of the sleeve are given different properties: the shrink-fit zone is designed to deform elastically during assembly, while the guide area is designed to maintain its dimensional precision. This local differentiation of properties allows the sleeve to simultaneously achieve both secure connection and precise guidance.
2Manufacturing precision
If grinding is applied to the guide area after assembly to achieve tight tolerances, then dimensional precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The guide area is designed and manufactured with pre-established precise dimensions before assembly occurs. By preparing the guide area in advance with the correct dimensions and protecting it from deformation during the shrink-fit process, subsequent grinding operations are eliminated, simplifying the manufacturing process.
3Adaptability or versatility
If the sleeve and nut are made of different materials to optimize properties, then performance is improved, but differential thermal expansion affects dimensional stability
Solution Approach 1:
The thermal expansion issue is contained within the shrink-fit zone by segmenting the sleeve into a deformable connection region and a stable guide region. The differential expansion between different materials occurs primarily in the shrink-fit zone, while the guide area maintains dimensional stability despite temperature changes.
4Reliability
If thermochemical treatment is applied to the guide area to enhance surface properties, then durability is improved, but the treatment is lost if grinding is performed afterward
Solution Approach 1:
The thermochemical treatment is applied to the guide area before assembly operations. By performing this surface treatment in advance and protecting the guide area from deformation during subsequent assembly, the beneficial surface properties are retained, eliminating the need for post-assembly grinding that would remove the treatment.
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 design reduces manufacturing costs by eliminating post-assembly grinding and enhances durability through uniform intermediate annular spaces and thermochemical treatments, maintaining precise dimensions and reducing wear from friction.
Implementation Method 1
This area can deform freely during shrink-fitting, without exceeding the outer dimensions defined by the outer diameter of the guide area
Implementation Method 2
the absence of grinding after mounting allows for a thermochemical surface treatment of the sleeve's guide area before mounting on the nut, giving it specific mechanical properties
Implementation Method 3
Assuming a sleeve made of a different material than the nut, the effects of differential thermal expansions between the sleeve and the nut resulting from temperature fluctuations are confined to the shrink-fit zone of the sleeve
Data Source
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AI summary
Piston (12) of an actuator mechanism, the piston (12) comprising a nut (16) of a worm gear mechanism, the nut (16) comprising an outer peripheral wall (32) and a nut thread (27) intended to cooperate, directly or via balls, with a worm gear mechanism screw; a sleeve (42) integral with the nut (16) and covering at least partially the outer peripheral wall (32) of the nut (16), the sleeve (42) comprising a cylindrical guide area (44) intended to come into fitted sliding contact with an inner guide wall of a guide cylinder (84) of the actuator mechanism (10L), the nut (16) comprising at least one annular shrink-fitting surface (52), the sleeve (42) comprising at least one shrink-fitting surface (62) shrink-fitted onto the annular shrink-fitting surface (52).The guide zone (44) has an outer diameter greater than the shrink-fit zone (62) and covers without contact or shrink-fitting a covered portion (80) of the outer peripheral wall (32) of the nut (16).