Steering Assembly with Arcuate Sector Gear for Lawn Mower
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Solution Overview
Problem
Conventional steering arrangements for lawn mowers and tractors face challenges in achieving a small turning radius due to difficulties in implementing perfect Ackermann steering geometry, leading to increased tire wear and steering effort, especially during tight turns.
Innovation Solution
A steering assembly with a control assembly connected to a pinion gear, a sector gear with an arcuate leading edge forming a rack, and tie rods that transfer rotational movement to wheel assemblies, where each wheel assembly includes a knuckle with a kingpin positioned within the rim, allowing for efficient rotation and reduced scrub radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional steering arrangements are used with standard Ackermann geometry, then the steering system is relatively simple to implement, but the turning radius is large and tire wear increases during tight turns
Solution Approach 1:
The sector gear uses an arcuate leading edge instead of a straight rack, creating a curved gear path that enables tighter turning radii while maintaining mechanical simplicity and ease of manufacture
Solution Approach 2:
The steering geometry parameters are modified by positioning the kingpin within the rim rather than outside it, changing the scrub radius parameter to reduce tire wear and improve turning performance
2Object-generated harmful factors
If perfect Ackermann steering geometry is implemented, then tire wear is minimized, but the steering linkage complexity increases significantly
Solution Approach 1:
The arcuate leading edge of the sector gear provides a curved engagement path that approximates perfect Ackermann geometry benefits while maintaining a simple single-piece gear structure, avoiding complex multi-linkage arrangements
Solution Approach 2:
By repositioning the kingpin within the rim, the scrub radius is reduced to near-zero, which minimizes tire wear during tight turns without requiring complex steering linkage geometry
3Ease of manufacture
If the kingpin is positioned outside the rim, then the steering geometry is conventional and easier to manufacture, but the scrub radius increases causing increased tire wear and ground compaction
Solution Approach 1:
The kingpin position parameter is changed from outside the rim to within the rim, which reduces the scrub radius parameter and consequently reduces both tire wear and ground compaction during steering operations
Solution Approach 2:
The design accepts the slight increase in manufacturing complexity of positioning the kingpin within the rim as a beneficial trade-off that converts the harmful effect of large scrub radius into beneficial reduced tire wear and ground compaction
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 enables easier steering with reduced effort, improved cut quality, and lower ground compaction during turns by maintaining a low scrub radius and eliminating positive camber, resulting in enhanced maneuverability and reduced stress on steering components.
Implementation Method 1
a pinion gear; a sector gear with an arcuate leading edge forming a rack, the rack being meshingly engaged with the pinion gear
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A steering assembly for a lawn maintenance vehicle having a control assembly that receives a user rotational input, a transfer assembly for transferring the rotational input from the user to a pair of wheel assemblies. Each wheel assembly includes a knuckle connected to a pivot bar by way of a kingpin, wherein the kingpin is positioned within the rim of the tire operatively connected to the knuckle. The transfer assembly includes a sector gear having a leading edge that forms a rack that is meshingly engaged to a pinion gear of the transfer assembly.