Lip Seal Surface Roughness and Filler Composition for Water Pump
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Solution Overview
Problem
Lip seals for water pumps made of rubber-like materials face issues with softening and swelling when exposed to aqueous fluids like LLC, leading to reduced sealing properties and torque, as well as deposit formation on rotating shafts due to low lubricity and chemical reactions.
Innovation Solution
A lip seal composed of a rubber-like elastic material with specific surface roughness, achieved through vulcanization molding using a rubber composition including reinforcing and non-reinforcing fillers, a coupling agent, and an organic peroxide, which prevents softening, swelling, and deposit formation by enhancing lubrication and reducing torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rubber-like elastic material is used for the lip seal, then sealing properties are improved, but softening and swelling occur when exposed to aqueous fluids like LLC
Solution Approach 1:
The patent uses a composite material consisting of NBR (nitrile butadiene rubber) as the base polymer and incorporates inorganic fillers (such as silica, aluminum oxide, or titanium oxide) to create a composite rubber composition. This composite structure provides both the sealing properties of rubber and the chemical stability of inorganic materials, preventing softening and swelling when exposed to aqueous fluids like LLC while maintaining effective sealing performance.
2Reliability
If the lip seal material is softened to improve sealing, then sealing properties are improved, but abrasion resistance decreases due to low lubricity
Solution Approach 1:
The patent modifies the physical and chemical parameters of the rubber material by controlling the NBR acrylonitrile content (34-42 mol%) and incorporating specific inorganic fillers with controlled particle sizes and surface treatments. These parameter changes optimize the balance between softness for sealing and hardness for abrasion resistance, allowing the material to maintain both sealing effectiveness and wear resistance without requiring excessive softening.
Solution Approach 2:
The incorporation of inorganic fillers (silica, aluminum oxide, titanium oxide) with specific surface treatments creates a composite material that enhances abrasion resistance while maintaining the necessary softness for sealing. The inorganic particles provide wear resistance and the rubber matrix provides sealing compliance, resolving the contradiction between sealing softness and abrasion resistance.
3Reliability
If phosphate or silicate is added to LLC for corrosion protection, then corrosion resistance is improved, but deposits form on the shaft reducing sealing properties
Solution Approach 1:
The patent converts the harmful effect of phosphate and silicate deposits into a beneficial outcome by selecting inorganic filler particles (such as silica or aluminum oxide) that are chemically compatible with these additives. The fillers act as nucleation sites that prevent uncontrolled deposit formation on the shaft, and their surface treatments ensure that any precipitated compounds adhere to the filler particles rather than forming harmful deposits on the sealing surface, thus maintaining sealing properties while preserving corrosion protection.
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 softening and swelling, reduces torque and heat generation, and maintains sealing properties by controlling surface roughness and using fillers to prevent deposit formation, ensuring long-lasting performance even with LLC containing phosphoric acid.
Implementation Method 1
a crosslinking degree (DL) of 5% or more and a co-crosslinking degree (Dc) of 30% or more based on the total crosslinking degree
Implementation Method 2
the lip seal having sliding surface with a surface roughness Ra (according to JIS B0601 corresponding to ISO 4287) of 1 to 30 μm
Implementation Method 3
LLC containing organic acid, particularly 2-ethylhexanoic acid, causes significant softening and swelling of the lip seal
Data Source
AI summary
Disclosed is a lip seal for water pump made of a rubber-like elastic material, fixed to a housing as a fixed side and in sliding contact with a shaft rotating relative to the housing; the lip seal having sliding surface with a surface roughness Ra (according to JIS B0601 corresponding to ISO 4287) of 1 to 30 μm, being obtained by vulcanization-molding of a rubber composition comprising 100 parts by weight of the rubber-like elastic material, 1 to 150 parts by weight of a reinforcing filler, 5 to 90 parts by weight of a non-reinforcing filler having an average particle diameter of 1 μm or more, 0.1 to 5 parts by weight of a coupling agent, 1 to 15 parts by weight of a co-crosslinking agent, and 0.5 to 10 parts by weight of an organic peroxide. The lip seal effects to prevent softening and volume swelling of the rubber-like elastic material and furthermore the generation of deposits in the rotating shaft, which are problematic for rotation torque and LLC resistance.