Cup Seal Axial Positioning via Projection and Tapered Surfaces
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Solution Overview
Problem
Existing cup seals in plunger type master cylinders face challenges in preventing axial motion while maintaining sealing and pumping performance, leading to instability and loss of hydraulic pressure generation.
Innovation Solution
A cup seal with a U-shape cross section, featuring an annular base portion, an annular inner lip portion with tapered surfaces, and an annular outer lip portion, which includes a projection to prevent axial movement and ensure reliable sealing and fluid feeding by utilizing tapered surfaces and projections to maintain position and facilitate fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the inner lip portion contacts the side wall of the recessed portion over the whole circumference, then the cup seal is prevented from moving in the axial direction, but it becomes difficult to feed fluid to a sufficient degree from the inner lip side
Solution Approach 1:
The inner lip portion is divided into a contact region (with projection contacting the side wall) and a non-contact region (allowing fluid passage), enabling simultaneous axial positioning and fluid feeding functions
Solution Approach 2:
Different regions of the inner lip portion have different functions: the projection region provides axial positioning by contacting the side wall, while the opposite region allows fluid passage, creating local functional differentiation
2Productivity
If gaps are formed between the inner lip portion and the side wall of the recessed portion, then fluid can be supplied to a sufficient degree, but it becomes difficult to prevent the cup seal from moving in the axial direction
Solution Approach 1:
The inner lip portion is segmented into a projection for axial positioning and the main body for fluid sealing, allowing gaps to exist only where needed for fluid supply while maintaining axial stability through the projection
3Ease of operation
If the cup seal moves together with the piston, then a gap is formed between the front part of the seal member and the housing, but this causes increased loss and operational instability
Solution Approach 1:
The axial positioning function is extracted from the entire inner lip circumference and concentrated in the projection, allowing the cup seal to remain stable while the piston moves freely for smooth operation
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 solution effectively prevents axial movement of the cup seal, enhances sealing performance, and improves fluid feeding efficiency, resulting in stable hydraulic pressure generation and quick response during piston operation.
Implementation Method 1
a first tapered inner peripheral surface which extends in a manner that the inner diameter thereof gradually decreases forward in the axial direction and a second tapered inner peripheral surface which extends in a manner that the inner diameter thereof gradually increases forward in the axial direction
Implementation Method 2
the inner lip portion has an inner peripheral surface which at least includes a first tapered inner peripheral surface... and a projection protrudes in the axial direction at the tip portion of the inner lip portion so as to determine the position in the axial direction
Implementation Method 3
When a hydraulic pressure is generated in the hydraulic chamber, the inner lip portion closely contacts to the outer peripheral surface of the piston due to the hydraulic pressure
Implementation Method 4
when the piston retracts after having generated the hydraulic pressure, the volume in the hydraulic chamber increases and the pressure in the hydraulic chamber so decreases as to turn into a negative pressure. Therefore, the inner lip portion deflects outward and separates away from the outer peripheral surface of the piston to form a gap
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(c)
AI summary
A projection (21b4) provided at a tip portion of an inner lip portion (21b) of a first cup seal (21) comes in contact with a second side wall (20c) of a recessed portion (20), and a large axial force is exerted in the axial direction on a first tapered inner peripheral surface (21b1) of the first cup seal (21) from a rear side tapered surface (4b2) of a primary piston (4). This makes it possible to reliably hold the first cup seal (21) in the axial direction by utilizing the axial force. Therefore, the first cup seal (21) can be suppressed from moving in the axial direction. In particular, the projection (21b4) of the first cup seal (21) comes in contact with a tapered surface (20c') of the second side wall (20c) to obtain a further increased axial force, and the first cup seal (21) can be held more reliably.