Balance Shaft Bearing Ring Guidance for Needle Alignment
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Solution Overview
Problem
Existing balance shafts for reciprocating piston internal combustion engines face challenges in accurately positioning needle rollers due to large component tolerance chains, leading to potential axial misalignment and increased wear.
Innovation Solution
A balance shaft design featuring a partially cylindrical bearing journal with a needle roller cage assembly and bearing ring, where the cage axially guides on both sides of the bearing ring, minimizing axial position differences within component tolerances and reducing wear through full circumferential axial start-up and radial clamping, ensuring precise alignment and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional bearing designs with extended tolerance chains from bearing ring via bearing journal and shaft sections to needle roller cage assembly are used, then manufacturing is easier, but axial position precision of needles deteriorates
Solution Approach 1:
The bearing journal is segmented into a cylindrical partial periphery and a non-cylindrical partial periphery. The cylindrical partial periphery serves exclusively as the bearing surface for the needle rollers, while the non-cylindrical partial periphery is cleared to provide axial clearance for the cage. This segmentation isolates the bearing function from other shaft functions, eliminating tolerance accumulation from adjacent shaft sections and improving axial position precision.
Solution Approach 2:
The cylindrical bearing surface is extracted as a separate functional element from the shaft journal. By making the cylindrical partial periphery removable or replaceable (through the clearance design), the bearing surface can be independently manufactured and assembled, reducing the impact of shaft manufacturing tolerances on bearing alignment and needle axial position.
2Reliability
If the cylindrical partial periphery of the bearing journal is oriented toward the shaft imbalance, then bearing performance is improved, but manufacturing complexity increases
Solution Approach 1:
Only the specific region of the bearing journal that contacts the needle rollers (the cylindrical partial periphery) is manufactured with high precision cylindrical geometry. The remaining portions of the shaft journal can be manufactured with lower tolerances or different geometries, optimizing resource allocation and reducing overall manufacturing complexity while maintaining bearing performance.
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 effectively minimizes the impact of component tolerance chains on needle roller position, reducing axial misalignment and wear, thereby enhancing the operational stability and longevity of the balance shaft.
Implementation Method 1
a needle roller cage assembly and a bearing ring, which extends around the bearing journal, lies against the cylindrical partial periphery and forms the inner raceway of the needle roller cage assembly
Implementation Method 2
The cage of the needle roller cage assembly is designed to run on the end faces of the bearing ring axially on both sides by means of radially inwardly extending projections
Data Source
AI summary
A balance shaft includes an unbalanced shaft (3) comprising a bearing journal (8, 9), the periphery of which is merely partially cylindrical. The cylindrical partial periphery (10) of the bearing journal is oriented toward the shaft imbalance. The balance shaft also includes a needle roller cage assembly (15); and a bearing ring (13), which extends around the bearing journal, lies against the cylindrical partial periphery and forms the inner raceway of the needle roller cage assembly. The cage (27) of the needle roller cage assembly is designed to run on the end faces of the bearing ring axially on both sides by means of radially inwardly extending projections.