Braking Circuit Master Cylinder Lip Seal EDM Tolerance
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Solution Overview
Problem
The existing manufacturing method for master cylinder annular seals using EDM machining can result in leaks due to imprecise positioning of the electrode, leading to discontinuities at the dynamic sealing surfaces where turning and EDM surfaces meet.
Innovation Solution
The annular seal design features radial passages defined by blocks on the rear face, separated from the curved surface connecting to the internal lip, allowing for slight misalignment of the EDM electrode without affecting dynamic sealing, with a planar annular ring radially aligned with the grooves' bottom, ensuring continuous contact and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EDM machining is used to machine the rear face of the seal with radial grooves, then the manufacturing process can be completed, but the electrode may not be positioned precisely relative to the turning surfaces, causing leaks at the interface lines
Solution Approach 1:
The rear face of the seal is segmented into distinct functional zones: a central dynamic sealing surface for piston contact, and peripheral radial grooves for fluid passage. This segmentation allows the dynamic sealing surface to be manufactured by turning while the radial grooves are added by EDM, with each zone optimized for its specific function and tolerant of interface variations.
Solution Approach 2:
Different regions of the seal's rear face are given different properties: the central region has a smooth, continuous surface for dynamic sealing against the piston, while the peripheral regions have radial grooves for fluid flow. This local differentiation ensures that the critical sealing area maintains high quality regardless of electrode positioning accuracy.
2Manufacturing precision
If the electrode is positioned precisely for EDM machining, then sealing accuracy is improved, but manufacturing complexity and time increase
Solution Approach 1:
The manufacturing process is segmented into two independent operations: turning for the dynamic sealing surface and EDM for the radial grooves. This segmentation eliminates the need for complex precision positioning between operations, as each process can be performed independently with standard tolerances.
Solution Approach 2:
The dynamic sealing surface is preliminarily formed by turning before the radial grooves are added by EDM. This preliminary action establishes the critical sealing surface first, allowing subsequent EDM operations to be performed without affecting the precision of the already-formed sealing area.
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 ensures reliable dynamic sealing and simplifies the manufacturing process, allowing for wider tolerances and reducing the risk of leaks, even with imperfect electrode positioning, while maintaining effective fluid flow during brake circuit demands.
Implementation Method 1
an internal, dynamic sealing, lip surrounding the piston
Implementation Method 2
an external lip which presses against an external cylindrical wall of this housing, to provide static sealing
Implementation Method 3
The seal additionally comprises a planar rear face which presses against a planar transverse rear face of the annular housing, to wedge the seal axially in the housing
Data Source
AI summary
Master cylinder of a hydraulic braking circuit, particularly for a motor vehicle, comprising a piston (2) sliding axially in a body (4) comprising an annular lip seal (51) produced by molding, and comprising an internal, dynamic sealing lip (14) surrounding the piston and connected by a curved surface (36) to a planar rear face (30) comprising radial passages which are defined by blocks formed as projections on the rear face of the seal, these blocks being separated from the curved surface (36).