Rail Vehicle Running Gear Anisotropic Stiffness Design
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Solution Overview
Problem
Rail vehicles, particularly locomotives, face challenges in achieving low longitudinal stiffness and high transverse stiffness in their primary suspension systems, as existing designs like helical springs often prioritize horizontal stiffness over longitudinal flexibility, leading to increased track loads and inadequate stability in curves.
Innovation Solution
A running gear with a two-stage suspension system that includes a main spring assembly and an anisotropic interface assembly, where the anisotropic interface is strategically placed between the main spring and the axle or running gear frame, allowing for independent adjustment of longitudinal and transverse stiffness through guiding structures and resilient elements, enabling the wheel sets to pivot and maintain stability while minimizing track loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If helical springs with high horizontal stiffness are used to ensure driving stability, then transverse stiffness is improved, but longitudinal stiffness increases leading to increased track loads
Solution Approach 1:
The primary suspension is segmented into two functionally independent spring assemblies: a first spring assembly (helical spring) providing vertical and transverse support, and a second spring assembly (rubber-metal spring) providing longitudinal flexibility. This segmentation allows each spring type to specialize in its optimal direction, reducing overall track loads while maintaining driving stability.
Solution Approach 2:
Different regions of the suspension system are assigned different stiffness characteristics: the first spring assembly provides high stiffness in the transverse direction for stability, while the second spring assembly provides low stiffness in the longitudinal direction to reduce track loads. This local differentiation of mechanical properties resolves the contradiction between stability and track protection.
2Reliability
If rubber-metal springs are added in parallel to increase transverse stiffness, then transverse stiffness is improved, but device complexity and space requirements increase
Solution Approach 1:
The second rubber-metal spring assembly is nested within the space occupied by the first helical spring assembly. The rubber-metal spring is positioned inside the helical spring's envelope, allowing both springs to occupy the same vertical space without requiring additional lateral clearance. This nesting approach increases transverse stiffness without increasing overall suspension height or lateral dimensions.
Solution Approach 2:
Instead of adding springs in parallel (which would increase lateral space requirements), the invention utilizes the vertical dimension by stacking the rubber-metal spring within the helical spring's space. This dimensional reorganization allows complex multi-directional stiffness characteristics to be achieved within compact spatial constraints.
3Adaptability or versatility
If multiple parallel springs are used to generate different longitudinal and transverse stiffness, then stiffness differentiation is achieved, but device complexity increases
Solution Approach 1:
The suspension assembly uses asymmetric spring configurations where the first helical spring and second rubber-metal spring have different orientations, stiffness characteristics, and mounting geometries. The helical spring is oriented for vertical loading with transverse stiffness, while the rubber-metal spring is oriented for longitudinal flexibility. This asymmetric arrangement enables differentiated stiffness in different directions without requiring symmetric multi-spring configurations.
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 allows for a compact layout that achieves the desired low longitudinal stiffness and high transverse stiffness, enabling improved driving stability and reduced track loads without increasing the overall height of the suspension assembly, suitable for both new and existing vehicle designs.
Implementation Method 1
The anisotropic interface assembly comprises at least one resilient element between the guiding structure and the intermediate spring seat
Data Source
Figure 1~3
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Figure 7~9
AI summary
The invention relates to a running gear (14) for a rail vehicle (10), comprising one or more wheel sets (16), each having a revolution axis (RR), each of the wheel sets (16) being guided by a pair of transversally spaced axle boxes (28), a running gear frame (18), a primary suspension assembly (30) between each of the axle boxes (28) and the running gear frame (18), and a secondary suspension stage (22) for supporting a vehicle superstructure (12) of the rail vehicle (10) on the running gear frame (18), wherein each primary suspension assembly (30) comprises at least a main spring assembly (32) having a vertical stiffness and a horizontal stiffness that is identical in a transverse direction (TT) of the running gear frame (18) and in a longitudinal direction (LL) of the running gear frame (18) perpendicular to the transverse direction (TT), characterised in that the primary suspension assembly further comprises an anisotropic interface assembly (34) in series with the main spring assembly (32) between the running gear frame (18) and the axle box (28), wherein the anisotropic interface assembly (34) is such that the primary suspension assembly (30) has a transverse stiffness and a longitudinal stiffness, wherein the transverse stiffness is substantially different from the longitudinal stiffness.