Cylinder Cup Seal Abutting Force Distribution
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Solution Overview
Problem
Cylinder apparatuses face challenges in reducing ineffective stroke and maintaining excellent operation feeling due to complex structures and unstable seal positions, particularly in cup seal designs where the inner circumferential lip portion abuts against the piston, leading to increased sliding resistance.
Innovation Solution
A cylinder apparatus with a cup seal featuring an abutting force maximum portion on the inner circumferential surface of the base portion, a conical surface reducing diameter towards the cylinder bore bottom, and a contact pressure adjustment portion that intersects with the cylinder bore at an acute angle, ensuring reliable pressurization initiation and minimized sliding resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the tip end of the inner circumferential lip portion is protruded to abut against the piston, then the ineffective stroke is reduced, but the structure becomes complicated due to the need for a reduced diameter portion to maintain hydraulic fluid communication
Solution Approach 1:
The invention extracts the abutting function from the tip end of the inner circumferential lip portion and relocates it to a dedicated abutting portion formed as a protrusion on the piston. This separation allows the seal lip to maintain its sealing function while the protrusion handles the abutting function, eliminating the need for complex reduced diameter portions and simplifying the overall structure.
Solution Approach 2:
The abutting portion protrusion acts as an intermediary element between the cup seal and the piston. It provides a defined contact point for the seal lip to abut against, enabling precise control of pressurization start point without requiring modifications to the seal lip structure itself, thus reducing ineffective stroke without complicating the seal design.
2Stability of the object's composition
If the entire inner circumferential surface of the inner circumferential lip portion is caused to abut against the piston, then the seal position is clarified, but the sliding resistance increases and operation feeling deteriorates
Solution Approach 1:
The invention applies local quality by concentrating the abutting force to a specific abutting portion (protrusion) rather than distributing it across the entire inner circumferential surface. This localized contact point provides stable seal position definition while minimizing the contact area, thereby reducing sliding resistance and maintaining excellent operation feeling.
3Stability of the object's composition
If the abutting force of the inner circumferential lip portion against the piston is increased, then the seal position is clarified, but the sliding resistance increases so that operation feeling is deteriorated
Solution Approach 1:
The abutting portion protrusion concentrates the abutting force to a small, well-defined area on the piston surface. This localized force application clearly defines the seal position and pressurization start point while minimizing the total contact area between the seal lip and piston, thereby reducing sliding resistance and preserving excellent operation feeling.
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 stabilizes the seal position, reduces ineffective stroke, and enhances operation feeling by optimizing the abutting force distribution and sealing properties, particularly in hydraulic pressure master cylinders for vehicles, ensuring reliable brake control and smooth operation.
Implementation Method 1
an inner circumferential surface of the cup seal abuts against an outer circumferential surface of the piston
Implementation Method 2
the inner circumferential surface of the cup seal at a position closer to the cylinder bore bottom portion than the cylindrical surface is formed of a conical surface of which diameter gradually reduces toward the cylinder bore bottom portion
Data Source
AI summary
A cup seal 21 includes a base portion 21a disposed on a cylinder bore opening portion side of a seal groove, and an inner lip portion 21b extended from an inner circumferential side of the base portion toward a cylinder bore bottom portion and having an inner circumferential surface slidably abutting against an outer circumferential surface of a piston. In a state where the cup seal 21 is fitted into the seal groove and a plunger 19 is inserted into a cylinder bore 12, an abutting force maximum portion 21m where an abutting force against the plunger 19 becomes maximum within an inner circumferential surface of the cup seal 21 is provided on an end portion on the cylinder bore opening portion side of an inner circumferential surface part of the base portion 21a.