Fiber-Reinforced Leaf Spring with Flexible Joint
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Solution Overview
Problem
Leaf springs for motor vehicles have limitations in suspension comfort and driving safety due to their degressive force-displacement characteristic, leading to high production and assembly costs, and require complex fastening systems to compensate for length changes during deformation.
Innovation Solution
A leaf spring design with a flexible joint section that compensates for length changes during load-related deformation, allowing for a progressive force-displacement characteristic and eliminating the need for eyelets or spring eyes, by fixing the ends torque-proof and non-displacement, and using a one-piece fiber-reinforced plastic construction with unidirectional prepregs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the leaf spring is designed with a curved shape to prevent overstretching when fully loaded, then the reliability is improved, but the spring rate becomes too strong in the unloaded state, worsening the suspension comfort
Solution Approach 1:
The leaf spring is divided into multiple spring leaves with different curvature radii and thicknesses. Each leaf segment contributes differently to the overall spring characteristic, allowing the spring to exhibit a progressive force-displacement behavior that provides both comfort in unloaded state and protection against overstretching when loaded.
Solution Approach 2:
The patent varies key parameters across different spring leaves including curvature radius, thickness, and length. By changing these geometric parameters progressively from one leaf to the next, the spring assembly achieves a progressive spring rate that adapts to different load conditions, resolving the contradiction between comfort and reliability.
2Reliability
If eyelets or spring eyes are added to compensate for length changes during deformation, then the reliability is improved, but the device complexity and production costs increase
Solution Approach 1:
The leaf spring design allows the spring leaves themselves to accommodate length changes through their inherent flexibility and progressive deformation characteristics. The spring leaves naturally adjust their configuration during deformation, eliminating the need for separate length compensation mechanisms like eyelets or displaceable retaining bolts.
Solution Approach 2:
The patent removes the unnecessary eyelets and complex displaceable fastening systems from the design. By extracting these redundant components and relying on the intrinsic properties of the multi-leaf spring construction, the solution simplifies the fastening system while maintaining the ability to handle length changes during deformation.
3Ease of operation
If a multi-leaf spring assembly is used to achieve a progressive force-displacement characteristic, then the suspension comfort is improved, but the manufacturing and assembly costs increase
Solution Approach 1:
The spring leaves are made from fiber-reinforced plastic composite materials, which allow for complex curved geometries to be manufactured as single integrated pieces. This composite material approach enables the progressive spring characteristic to be achieved through geometric design rather than requiring multiple separate metal leaves to be stacked and assembled, thereby reducing manufacturing and assembly costs.
Solution Approach 2:
The patent combines the functions of multiple spring leaves into a unified composite structure where the progressive spring characteristic is achieved through the integrated design of the leaf stack. The fiber-reinforced plastic material allows these leaves to be manufactured as a single integrated component, merging the manufacturing process and eliminating the need for separate assembly operations.
4Ease of manufacture
If the leaf spring is made from fiber-reinforced plastic material, then the manufacturing cost is reduced, but the ability to absorb lateral forces may be limited
Solution Approach 1:
The patent utilizes fiber-reinforced plastic composite materials with fibers oriented in specific directions to provide both cost advantages and adequate lateral force absorption. The composite material structure, with strategically oriented reinforcement fibers, delivers the necessary mechanical properties for lateral load handling while maintaining the manufacturing and cost benefits of composite construction.
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 design enhances suspension properties with a progressive spring rate, reduces production costs, and improves driving dynamics and comfort by allowing for a more efficient length compensation mechanism without the need for additional fastening components.
Implementation Method 1
a flexible joint section (11) which can compensate for a change in length of a spring section (8) of the leaf spring (1) in the event of a load-related deformation of the spring section (8)
Implementation Method 2
a leaf spring for motor vehicles made of a fiber-reinforced plastic material, the leaf spring being able to absorb any lateral forces that may occur and to transmit them to a leaf spring receiving device
Data Source
Figure 1~2
AI summary
The invention relates to a leaf spring (1) for motor vehicles, which is made of a fiber-reinforced synthetic material and can absorb potentially occurring lateral forces and transfer them to a leaf spring receiving device, comprises a first end (2) and a second end (3), which can each be fixed in a leaf spring receiving device in a torsion-proof and non-displaceable manner, and a bending joint section (11), which can compensate for a change in length of a resilient section (8) of the leaf spring (1) during a load-induced deformation of the resilient section (8). The leaf spring (1) comprises a first spring limb (5) and a second spring limb (6) which are connected to each other via a transition section (7). In a non-loaded state, both the first spring limb (5) and the second spring limb (6) are approximately planar and disposed at an angle relative to each other. The first spring limb (5) forms the resilient section (8). The bending joint section (11) contains the second spring limb (6). The second spring limb (6) is shorter than the first spring limb (5) and oriented approximately perpendicularly to the first spring limb (5). The leaf spring (1) is integrally produced from unidirectional prepregs having a duroplastic or thermoplastic matrix by means of a pressing method.