Steering Shaft Spline Segmentation for Constant Sliding Resistance
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Solution Overview
Problem
In autonomous vehicles with advanced driving automation levels, the need for a long stroke steering shaft to move the steering wheel forward results in varying sliding resistance due to changes in engagement length, causing discomfort to drivers and passengers.
Innovation Solution
The steering shaft design includes an inner and outer shaft with non-engaging portions that maintain a constant engagement length, ensuring consistent sliding resistance even with a long stroke, thereby reducing discomfort and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the extension/contraction stroke of the steering shaft is made longer to move the steering wheel forward in autonomous vehicles, then the room in front of the driver's seat increases, but the engagement length between the male and female spline portions varies, causing sliding resistance to change and creating discomfort for drivers and passengers
Solution Approach 1:
The spline engagement area is segmented into multiple engagement zones along the axial direction. Each zone has a specific engagement length, and by switching between zones as the shaft extends or contracts, the system maintains a substantially constant engagement length despite the long stroke, thereby keeping sliding resistance consistent
Solution Approach 2:
The steering shaft employs a dynamic engagement mechanism where the effective engagement length between male and female spline portions is maintained substantially constant through design features such as tapered portions or variable tooth configurations. This dynamic design ensures that sliding resistance remains consistent even when the overall stroke length is extended for autonomous vehicle applications
2Length of moving object
If the entire length of the male and female spline portions is increased to achieve a longer stroke, then the steering shaft can accommodate greater extension/contraction, but the sliding resistance varies during operation, generating noise and discomfort
Solution Approach 1:
Different portions of the spline structure have different geometric properties. The engagement zones are designed with specific local characteristics (such as tapered surfaces or varying tooth profiles) that maintain optimal contact and friction conditions, ensuring consistent sliding resistance and reducing noise generation during operation
Solution Approach 2:
The invention changes geometric parameters of the spline portions, such as the engagement length and tooth profile, to maintain substantially constant sliding resistance. By carefully controlling these parameters, the system achieves long stroke capability without the harmful noise and discomfort caused by varying friction
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 maintains constant sliding resistance across varying stroke lengths, enhancing driver comfort and reducing noise associated with electric actuators, while also preventing bending issues during manufacturing.
Implementation Method 1
JP2017-052514 A discloses covering the male spline teeth with a resin coating layer in order to reduce sliding resistance during extension/contraction of the steering shaft
Data Source
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AI summary
Structure of a steering shaft capable of suppressing changes in sliding resistance even when the entire length is changed is achieved. One engaging portion of an inner diameter side engaging portion 19 and an outer diameter side engaging portion 31 includes at least one non-engaging portion 23 that does not engage with the other engaging portion at an intermediate portion in an axial direction, engageable portions are arranged on both sides in the axial direction of the non-engaging portion 23 of the one engaging portion, and each of the engageable portions has an effective length X, the non-engaging portion 23 has a dimension in the axial direction that is the same length as the effective length X, and the other engaging portion has an effective length Y that is 2X, which is twice the effective length X.