One-Piece Cast Iron Rear Axle Subframe Design
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Solution Overview
Problem
Existing subframes for motor vehicle rear axles are either heavy or require complex assembly processes involving welding, which can lead to distortion and reworking issues.
Innovation Solution
A one-piece cast iron subframe design with integrated bearing mounts and strategically positioned connection bearings that eliminate the need for welding, ensuring stability and ease of installation with preassembled wheel suspensions and differential components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a subframe is constructed from multiple parts requiring welding, then assembly flexibility is improved, but manufacturing complexity and distortion issues increase
Solution Approach 1:
The patent merges multiple subframe components (longitudinal members, cross members, and bearing mounts) into a single integrated cast iron subframe. This eliminates welding operations and associated distortion issues while maintaining structural integrity and assembly flexibility through the monolithic design.
2Ease of manufacture
If a subframe is constructed from multiple parts requiring welding, then assembly flexibility is improved, but welding distortion and reworking increase
Solution Approach 1:
The patent merges multiple subframe components (longitudinal members, cross members, and bearing mounts) into a single integrated cast iron subframe. This eliminates welding operations and associated distortion issues while maintaining structural integrity and assembly flexibility through the monolithic design.
3Weight of moving object
If a subframe is made lightweight, then weight reduction is achieved, but structural strength may be compromised
Solution Approach 1:
The patent utilizes cast iron, a composite material with excellent strength-to-weight ratio, to manufacture the monolithic subframe. This provides both weight reduction compared to traditional steel constructions and sufficient structural strength to support vehicle loads and dynamic forces.
Solution Approach 2:
The patent incorporates arcuate passages and fillets into the subframe design, which optimize stress distribution and enhance structural strength while maintaining lightweight characteristics. The curved geometries reduce stress concentration points compared to sharp corners.
4Ease of operation
If bearing mounts are added after subframe production, then installation flexibility is improved, but additional processing steps increase
Solution Approach 1:
The patent incorporates bearing mounts as integral features during the initial casting of the subframe. This preliminary action eliminates subsequent machining or attachment operations, reducing processing steps while maintaining installation flexibility through pre-positioned mounting locations.
Data Source
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AI summary
The subframe (1) consists of a one-piece cast frame with profiled hollow beams for the longitudinal (2, 3) and transverse (4, 5) members. The transverse members are connected to each other via corner support pillars (6, 9 and 7, 8) or are integrally formed with them. Outwardly projecting arms (10, 11, 12, 13) are integrally formed with the support pillars and/or with the longitudinal and transverse members, and these arms have connecting bearings (10a, 11a, 12a, 13a) at their ends, facing the vehicle body. A differential is mounted on the two transverse members, with one bearing (18) on the front transverse member and two bearings on the rear transverse member. The longitudinal members have an arc-shaped opening (15) for the drive shafts of the differential. Bearings for the wheel control arms are arranged on the outside of the longitudinal members.