Self-Contact Seal with Pushing Bead for Negative Pressure
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Solution Overview
Problem
Lay down lip seals fail to maintain contact with the shaft in engines with negative crankcase pressure, leading to airflow and noise issues due to insufficient radial force, which is not effectively addressed by existing low-friction seals.
Innovation Solution
A dynamic shaft seal with a self-contact mechanism, featuring a bead on the lay down sealing lip that engages with the axial leg to maintain contact with the shaft under negative pressure, and a dust lip that interacts with the shaft to prevent airflow, while maintaining low frictional contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lay down lip seal is used to reduce friction, then energy consumption is reduced, but the seal cannot maintain contact with the shaft under negative crankcase pressure
Solution Approach 1:
The seal incorporates a dynamic spring mechanism that automatically adjusts the radial force applied to the sealing lip. The spring can be pre-loaded to provide additional radial force when negative pressure is detected, ensuring the seal maintains contact with the shaft. This dynamic adjustment allows the seal to adapt to varying pressure conditions without requiring a permanently high radial force design.
Solution Approach 2:
The seal design modifies the radial force parameter dynamically based on operating conditions. By incorporating a spring mechanism with adjustable pre-load, the radial force can be increased specifically when negative pressure conditions occur, rather than maintaining a constantly high radial force. This parameter change allows the seal to maintain reliability under negative pressure while minimizing friction during normal operation.
2Reliability
If the radial force is increased to maintain seal contact under negative pressure, then sealing performance is improved, but friction increases leading to higher energy consumption
Solution Approach 1:
The spring mechanism provides a dynamic radial force that activates only when needed. The spring can be designed with specific stiffness and pre-load characteristics that allow it to compress and provide additional radial force when negative pressure attempts to separate the seal from the shaft. During normal positive or zero pressure operation, the spring maintains only the minimum necessary force, minimizing friction and energy consumption.
Solution Approach 2:
The spring is pre-loaded during assembly to provide a baseline radial force that prevents seal contact loss before negative pressure fully develops. This preliminary anti-action counteracts the separating force of negative pressure as it develops, maintaining seal contact proactively rather than reactively. The pre-load can be optimized to provide sufficient force for expected negative pressure conditions while minimizing unnecessary friction during normal 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 seal effectively maintains contact with the shaft under negative pressure conditions, reducing noise and airflow while minimizing friction, thus addressing the limitations of existing seals in high-pressure engines.
Implementation Method 1
When the oil side is under a negative pressure, the axial leg flexes inward in response to the negative pressure and engages the bead to provide a self-contact feature that holds the lay down sealing lip in engagement with the shaft
Implementation Method 2
when the oil side is under negative pressure, the end of the axial leg flexes to engage the dust lip with the shaft
Data Source
AI summary
An energy saving seal seals between a bore and a shaft for separating an oil side from an air side of the seal. The seal includes an annular mounting portion having a bellows portion extending axially and radially inward from the mounting portion. An axial leg extends axially from the bellows portion toward the air side. A lay down sealing lip extends radially inward and axially toward the oil side from an end of the axial leg. The sealing lip includes a bead on an outer surface. A dust lip extends from the end of the axial leg in a direction opposite the lay down sealing lip. When the oil side is under a negative pressure, the axial leg flexes inward in response to the negative pressure and engages the bead to provide a self-contact feature that holds the lay down sealing lip in engagement with the shaft.