Automotive Differential Gear Shim Thickness Optimization
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Solution Overview
Problem
Automotive differentials experience noise, vibration, and harshness (NVH) issues at higher-rotational-speed disconnect modes due to manufacturing tolerances and imperfections, which existing assembly methods fail to adequately address.
Innovation Solution
The method involves using first and second pinion gear washers and side gear washers to shim pinion and side gears along their respective axes to optimize gear mesh points, with washer thicknesses selected based on target apex positions to minimize NVH issues, by determining and adjusting the thickness of the washers to align actual gear apex positions with target positions within specific thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional assembly methods are used to install gears into the differential housing, then the assembly process is simple and quick, but NVH issues occur at higher-rotational-speed disconnect modes due to manufacturing tolerances and imperfections
Solution Approach 1:
The patent applies preliminary action by pre-determining the optimal thickness of shims (washers) based on target apex positions before actual assembly. The method calculates required shim thicknesses to compensate for manufacturing tolerances in advance, then installs these pre-calculated shims during assembly. This preliminary calculation and preparation of shim thicknesses eliminates NVH issues at higher rotational speeds without requiring complex real-time adjustments during assembly, thus resolving the contradiction between reliability improvement and assembly complexity.
Solution Approach 2:
The patent applies parameter changes by adjusting the thickness parameter of shims (washers) to compensate for manufacturing tolerances and optimize gear meshing. By varying the shim thickness within specific ranges (e.g., 0.01mm to 0.03mm thresholds for apex position deviations), the system achieves optimal NVH performance at disconnect modes. This parameter adjustment allows the assembly process to maintain simplicity while significantly improving reliability through precise thickness selection based on calculated target apex positions.
2Object-affected harmful factors
If shim thicknesses are selected to optimize gear mesh points and minimize NVH issues, then NVH performance improves, but the assembly process requires determining and adjusting washer thicknesses based on target apex positions
Solution Approach 1:
The patent applies mechanics substitution by replacing complex mechanical measurement and adjustment systems with a calculation-based approach. Instead of using sophisticated measurement devices to detect and adjust gear apex positions during assembly, the method uses mathematical calculations to determine optimal shim thicknesses based on target apex positions and expected manufacturing tolerances. This substitution of calculation for complex mechanical measurement and adjustment significantly reduces the difficulty of detecting and measuring apex positions while achieving optimal NVH performance.
3Manufacturing precision
If precise washer thickness selection is made to bring gear apex positions within thresholds of target positions, then manufacturing precision improves, but the assembly process becomes more complex
Solution Approach 1:
The patent applies preliminary action by performing all necessary calculations to determine optimal shim thicknesses before the actual assembly process. The method pre-calculates the required shim thickness to achieve target apex positions within specified thresholds (0.01mm to 0.03mm), taking into account manufacturing tolerances. This preliminary determination of precise thickness values allows the assembly process to simply install pre-calculated shims without requiring complex real-time measurements or adjustments, thus achieving high manufacturing precision while keeping the assembly process relatively simple.
Data Source
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AI summary
In at least one implementation, a method of assembling gears into a housing of an automotive differential includes, selecting a thickness dimension of first and second pinion gear washers, and first and second side gear washers, locating a pair of pinion gears, a pinion shaft and a pair of side gears at least partially within an interior of the housing with the pinion gear washers between the housing and separate ones of the pinion gears, and the side gear washers between the housing and separate ones of the side gears. The thickness of the side gear washers may be a function of target side gear apex positions and relative to a pinion gear apex axis. The thickness of the pinion gear washers may be a function of target pinion gear apex positions residing along a pinion gear apex axis and relative to a side gear apex axis.