Pulley Arm Fulcrum Bearing Seal Structure for Pressure-Stable Sealing
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Solution Overview
Problem
The existing fulcrum bearing devices for pulley arms in belt transmission systems face challenges in maintaining seal performance when temperature changes cause pressure fluctuations, leading to reduced effectiveness in preventing foreign objects from entering the bearing area.
Innovation Solution
The use of seal members with cylindrical and annular portions, featuring radially and axially extending lips made of wear-resistant materials like synthetic rubber, which are press-fitted and elastically deformed to maintain contact with the sleeve and washers, ensuring effective sealing under varying pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If seal members with radial lips are used to prevent foreign objects from entering the bearing area, then sealing performance is improved, but when temperature rises and internal pressure increases, the seal lips deform outward and lose contact with the recess surface, deteriorating seal performance
Solution Approach 1:
The seal member is divided into multiple functional segments: a cylindrical portion for press-fitting into the recess, an annular portion providing structural support, and a radial lip for sealing contact with the sleeve. This segmentation allows each part to perform its specific function optimally while working together as a unified sealing system.
Solution Approach 2:
The seal member utilizes elastic deformation as a functional parameter change. The radial lip is designed to elastically deform under internal pressure to maintain or enhance contact with the sleeve surface. This elastic parameter change allows the seal to adapt to pressure variations and temperature-induced expansions, ensuring continuous sealing performance.
2Productivity
If the pulley arm pivots at high speed due to belt vibration, then the belt tension adjustment function is improved, but heat is generated due to contact friction in sliding bearings, causing temperature rise and pressure increase in the fulcrum bearing
Solution Approach 1:
The invention converts the harmful effect of internal pressure increase (caused by temperature rise from friction) into a beneficial sealing force. The radial lip is designed to be pushed outward by the internal pressure, which enhances its contact pressure against the sleeve surface, thereby improving seal performance rather than deteriorating it. This transforms the harmful thermal effect into a useful sealing mechanism.
3Object-affected harmful factors
If seal members are designed to maintain contact with the recess surface, then foreign object prevention is improved, but under temperature-induced pressure changes, the seal lips move away from the contact surface, reducing sealing effectiveness
Solution Approach 1:
The seal member creates a feedback mechanism where internal pressure directly influences seal contact pressure. When internal pressure increases due to temperature rise, the radial lip is pushed outward, increasing its contact force against the sleeve. This positive feedback ensures that the seal maintains or enhances its sealing effectiveness under varying operating conditions, preventing foreign object contamination reliably.
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 configuration ensures excellent seal performance by maintaining contact with the sleeve and washers, effectively preventing foreign objects from entering the bearing area even under temperature-induced pressure changes, thus extending the seal's effectiveness and longevity.
Implementation Method 1
the radial seal lip is elastically deformed by the pressure inside of the boss portion so as to be radially compressed, thereby more strongly bringing the distal end of the radial seal lip into contact with the outer diameter surface of the sleeve
Implementation Method 2
heat tends to be generated due to contact friction in the sliding bearings
Data Source
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AI summary
In a fulcrum bearing device for a pulley arm, a sleeve (7) is inserted in a shaft hole (5) formed in a boss portion (4) of a pulley arm (1), washers (8) are fitted on the outer peripheries of small diameter tube portions (7a) formed at the respective end portions of the sleeve (7), and the sleeve (7) is fixed to an engine block (30) by means of a bolt (20) inserted through the sleeve (7) and tightened, so that the pulley arm (1) is pivotally supported. The shaft hole (5) is formed at its respective end portions with seal receiving recesses (11) having large diameters. Each seal member (12) includes a cylindrical portion (12a) provided on its outer peripheral portion and press-fitted in the seal receiving recess (11), and a radial lip (12c) extending obliquely inwardly and provided on the inner periphery of the seal member (12). The distal end portions of the radial lips (12c) are kept in elastic contact with the outer diameter surface of the sleeve (7). When internal pressure rises, the radial lips (12c) are elastically deformed so as to be radially compressed, thereby increasing the contact pressure of the radial lips (12c) against the outer diameter surface of the sleeve (7).