Sheet Metal Differential Housing With Deformed Pin Joints
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Solution Overview
Problem
Conventional bevel gear differentials made of ductile iron are heavy and require extensive post-processing due to welding, which introduces geometric distortions, while two-part housings made of sheet metal face high bearing stresses and require additional machining.
Innovation Solution
A bevel gear differential with two housing parts made of sheet metal, connected via pins that are plastically deformed to ensure a secure fit, and a collar surrounding the receiving bores to distribute torque transmission forces, reducing weight and post-processing needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ductile iron is used for differential housing, then strength and durability are improved, but weight increases and manufacturing complexity increases due to machining requirements
Solution Approach 1:
The housing is divided into two separate sheet metal parts that are joined together, allowing each part to be formed independently through stamping processes. This segmentation enables the use of lighter sheet metal material while maintaining structural integrity through the joining mechanism.
Solution Approach 2:
The material parameter is changed from ductile iron to sheet metal, fundamentally altering the weight-to-strength ratio. The joining method parameters (pin insertion depth, deformation amount) are optimized to achieve sufficient connection strength with lighter materials.
2Strength
If welding is used to join housing parts, then connection strength is improved, but geometric distortions occur due to heat input
Solution Approach 1:
The thermal welding process is replaced with a mechanical joining process using pins and plastic deformation. This substitution eliminates heat input entirely, preventing thermal distortion while achieving secure mechanical interlocking between housing parts.
Solution Approach 2:
pins serve as intermediary elements between the two housing parts, transferring loads and securing the connection without requiring direct thermal or adhesive bonding. The pins act as mechanical mediators that join parts while minimizing distortion.
3Weight of moving object
If sheet metal housing parts are used, then weight is reduced and ease of manufacture is improved, but bearing stresses increase due to thin wall thickness
Solution Approach 1:
The bearing stress problem is solved by transitioning from a two-dimensional thin wall to a three-dimensional structure with protruding pins. The pins add vertical dimension to the load path, distributing bearing stresses along the pin length rather than concentrating them in the thin wall plane.
Solution Approach 2:
The pins are inserted into the housing parts before final assembly, pre-positioning the load-bearing elements. This preliminary action ensures that bearing stresses are distributed along the pin length from the beginning, preventing stress concentration in the thin sheet metal walls.
4Manufacturing precision
If pins are used to connect housing parts, then geometric precision is maintained and ease of manufacture is improved, but connection strength may be insufficient compared to welding
Solution Approach 1:
The pin connection parameters are optimized including pin diameter, insertion depth, and deformation amount. By adjusting these parameters, the mechanical strength of the pin connection is enhanced to match or exceed welded connections while maintaining geometric precision.
Solution Approach 2:
The pin connection creates localized high-strength zones at the pin-housing interfaces, concentrating structural reinforcement exactly where needed. The local plastic deformation around the pins creates mechanically interlocked zones that provide superior connection strength compared to uniform thin walls.
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 results in a lightweight, cost-effective differential housing with minimal geometric distortions and reduced bearing stresses, allowing for efficient torque transmission and assembly without large openings.
Implementation Method 1
the free end of the pin projecting beyond the second housing part is plastically deformed such that the first housing part is firmly or inseparably connected to the second housing part. For example, the free end of the at least one pin can be plastically deformed by crimping and/or by rolling, whereby a roller or a ball can be rolled over the free end of the respective pin under high pressure, causing it to begin to flow.
Implementation Method 2
the material of the housing wall surrounding the respective receiving bore is plastically formed into a cylindrical collar that surrounds the respective free end of the differential bolt. The force transmission between the housing and the differential bolt thus does not occur solely through the sheet thickness of the first housing part; rather, the forces to be transmitted are also distributed over the height of the collar, thereby effectively counteracting the development of undesirably high bearing stresses in the hole.
Data Source
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AI summary
The present invention relates to a housing for accommodating the gearing of a bevel gear differential. The housing comprises a first housing part made of sheet metal and a second housing part made of sheet metal. At least one lug protrudes from the first housing part, which lug is integral with the first housing part and extends through a corresponding opening which is formed in the second housing part. A free end of the lug protruding beyond the second housing part is plastically deformed such that the first housing part is fixedly connected to the second housing part.