Multi-Layer HDPE Fuel Tank Wall Design
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Solution Overview
Problem
Existing fuel tanks made of thermoplastic synthetic resins face challenges in achieving excellent blow moldability, high deformation-suppressing properties, and heat resistance while minimizing weight and preventing fuel permeation.
Innovation Solution
A multi-layered fuel tank structure comprising an outer body layer, outer adhesive layer, barrier layer, inner adhesive layer, and inner body layer, where the outer and inner body layers are made of high-density polyethylene (HDPE) with specific mechanical properties, and the barrier layer is composed of an ethylene-vinyl alcohol copolymer (EVOH), ensuring strong bonding and impermeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the outer wall is decreased to reduce weight, then weight is reduced, but deformation amount increases and heat resistance is lowered
Solution Approach 1:
The patent employs a multi-layer composite structure consisting of an outer body layer, barrier layer, and inner body layer, where each layer is made of different synthetic resins with specific functions. The outer and inner body layers provide structural strength and rigidity, while the barrier layer prevents fuel permeation. This composite approach allows the wall thickness to be reduced for weight savings while maintaining overall strength through the synergistic combination of layers with optimized material properties.
Solution Approach 2:
The fuel tank wall is segmented into multiple functional layers rather than using a single uniform thickness. The outer body layer, barrier layer, and inner body layer are separately designed and bonded together, allowing each layer to be optimized for its specific function. This segmentation enables the outer wall to be thinner for weight reduction while the combined structure maintains the required deformation resistance and heat resistance.
2Weight of moving object
If the parison is formed thin to make the outer wall thin, then weight is reduced, but the parison may break in the blow-up step
Solution Approach 1:
The parison is constructed as a multi-layer composite structure with the outer body layer and inner body layer providing mechanical strength and rigidity. This composite parison structure maintains sufficient strength during the blow-up process even when the overall wall thickness is reduced, preventing parison breakage while enabling weight reduction through thinner walls.
Solution Approach 2:
The patent specifies particular physical property ranges for the synthetic resins used in the parison, including modulus of elasticity, Charpy impact strength, full-notch creep test results, melt flow rate, and melt tension. By controlling these material parameters within optimized ranges, the parison achieves the right balance between being thin enough for weight reduction and strong enough to prevent breakage during blow molding.
3Weight of moving object
If conventional polyethylene is used to reduce weight, then weight is reduced, but blow molding conditions and deformation-suppressing properties are not sufficiently satisfied
Solution Approach 1:
The patent defines specific physical property ranges for the high-density polyethylene used in the outer and inner body layers, including modulus of elasticity at different temperatures, Charpy impact strength, full-notch creep test results, melt flow rate, and melt tension. By controlling these parameters within optimized ranges, the polyethylene provides excellent blow moldability and deformation-suppressing properties while maintaining reduced weight.
Solution Approach 2:
The use of high-density polyethylene in the outer and inner body layers, combined with the barrier layer, creates a composite structure where each material contributes its optimal properties. The high-density polyethylene provides structural integrity and blow moldability, while the overall composite structure achieves weight reduction and improved performance compared to conventional single-material tanks.
4Reliability
If multi-layered structure is used to prevent fuel permeation, then fuel permeation is prevented, but manufacturing complexity increases
Solution Approach 1:
The fuel tank wall is segmented into distinct functional layers: the outer body layer for structural strength, the barrier layer for fuel permeation prevention, and the inner body layer for additional structural support. This segmentation allows each layer to be optimized for its specific function, with the barrier layer providing effective fuel permeation prevention while the overall structure remains manageable through the systematic arrangement of layers.
Solution Approach 2:
The multi-layer composite structure uses specifically selected synthetic resins for each layer, with the barrier layer made of a resin having low fuel permeability. The layers are bonded together through adhesive layers, creating a composite structure that achieves effective fuel permeation prevention while maintaining manufacturing feasibility through the use of compatible materials and standard bonding processes.
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 fuel tank exhibits improved rigidity, impact resistance, and reduced deformation under increased internal pressure, while maintaining low weight and preventing fuel permeation, with enhanced blow moldability and heat resistance.
Implementation Method 1
another resin layer exhibiting barrier properties, which is adapted to prevent the permeation of the fuel oil
Implementation Method 2
a bonding layer adapted to bond these two kinds of resin layers to each other
Data Source
AI summary
An automobile fuel tank includes an outer wall including a main body of a multiple-layered synthetic resin, in which the outer wall includes at least an outer body layer, an outer adhesive layer, a barrier layer, an inner adhesive layer, and an inner body layer. The outer body layer and the inner body layer include a high density polyethylene (HDPE) as a main ingredient. Each of the outer adhesive layer and the inner adhesive layer includes a synthetic resin having adhesiveness against both the high density polyethylene (HDPE) and the barrier layer. The barrier layer includes a synthetic resin.