Disc Brake Piston Boot Structure for Muddy Water Corrosion Resistance
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Solution Overview
Problem
The existing piston boots in disc brakes, which contain annular metal members, face corrosion issues due to exposure of metal parts in cut-away portions, leading to attachment of muddy water and reduced corrosion resistance.
Innovation Solution
A piston boot design with a large diameter fitting portion containing an annular metal member, a bellows portion that expands and contracts, and a small diameter fitting portion, where the large diameter fitting portion has cut-away portions on the bellows side to expose metal parts, preventing muddy water attachment by using the bellows to block external water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cut-away portions are formed in the large diameter fitting portion for manufacturing convenience, then the mold structure is simplified, but the metal member is exposed to muddy water and corrosion resistance decreases
Solution Approach 1:
The piston boot is divided into three distinct portions: large diameter fitting portion, bellows portion, and small diameter fitting portion. Each portion serves a specific function, with the bellows portion acting as a protective barrier for the cut-away areas in the large diameter fitting portion, thus maintaining corrosion resistance while enabling simplified manufacturing.
Solution Approach 2:
The bellows portion serves as an intermediary protective element between the external environment (muddy water) and the exposed metal member in the cut-away portions. It prevents direct contact between water and the metal member, resolving the contradiction between manufacturing simplicity and corrosion resistance.
2Reliability
If the bellows portion is increased in diameter from the large diameter fitting portion to the outer peripheral side, then the sealing functionality is maintained, but the device complexity increases
Solution Approach 1:
The bellows portion is designed to be dynamically expandable and contractible along with piston movements. This dynamic structure allows the piston boot to maintain effective sealing functionality throughout its operational range while using a relatively simple bellows configuration that does not overly complicate the overall device.
Solution Approach 2:
The solution addresses sealing requirements by transitioning from a two-dimensional flat seal to a three-dimensional bellows structure that expands radially. This dimensional change provides effective sealing coverage without requiring multiple separate sealing components, thus maintaining reliability while controlling complexity.
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 effectively suppresses the entry of muddy water into the cut-away portions, enhancing the corrosion resistance of the metal member and simplifying the mold structure for manufacturing, while maintaining the piston boot's sealing functionality.
Implementation Method 1
a bellows portion (12B), which extends from the large diameter fitting portion (12A), is increased in its diameter from the large diameter fitting portion (12A) to an outer peripheral side, and is also deformed and extended from the large diameter fitting portion (12A) toward an inner peripheral side
Data Source
AI summary
A disc brake including: a piston; a cylinder including a bore portion, which movably accommodates the piston, and a step portion formed on an opening end side of the bore portion; and a piston boot arranged between a tip side of the piston and a small diameter step portion of the cylinder. The piston boot includes: a large diameter annular fitting portion containing an annular metal member so as to be fitted to the small diameter step portion; a bellows portion, which extends from the large diameter fitting portion, is increased in its diameter from the large diameter fitting portion to an outer peripheral side, and is also deformed and extended from the large diameter fitting portion toward an inner peripheral side; and a small diameter fitting portion formed at an end portion of the bellows portion so as to fit to an outer periphery of the piston.