Steering Column Worm Gear Offset Layout for Reduced Gear Wear
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Solution Overview
Problem
Steer-by-wire steering column assemblies face excessive wear and fatigue of worm wheel gears due to engagement with two worm gears, leading to reduced lifespan and potential gear train backlash and rattle.
Innovation Solution
The steering column assembly offsets the contact areas of the output gears with respect to the teeth of the first gear, reducing wear and ensuring continuous lubrication, thereby extending the lifespan of the worm wheel gear and minimizing gear train backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the worm wheel gear is engaged with two worm gears to provide road feel and reduce backlash, then the steering control precision is improved, but the wear on the worm teeth of the worm wheel gear increases significantly
Solution Approach 1:
The patent divides the contact area of the worm wheel gear into multiple segments by engaging it with two separate worm gears that are offset along the longitudinal axis. This segmentation allows different portions of the worm wheel teeth to be engaged at different times, distributing the wear across multiple tooth surfaces rather than concentrating it on a single contact area.
Solution Approach 2:
The patent introduces a longitudinal axis dimension for offsetting the worm gears, creating a three-dimensional arrangement where the worm gears are positioned at different locations along the length of the worm wheel gear. This dimensional change allows the contact areas to be spatially separated while still maintaining engagement with the same gear component.
2Duration of action of stationary object
If the contact areas of the output gears are offset to reduce wear, then the lifespan of the first gear is extended, but the gear train complexity increases
Solution Approach 1:
The patent employs asymmetric positioning of the two output gears along the longitudinal axis, creating an intentional offset that is not symmetrical about the center of the first gear. This asymmetric arrangement allows the contact areas to be deliberately misaligned, ensuring that wear patterns do not coincide and thus extending the overall gear lifespan.
Solution Approach 2:
The patent changes the spatial parameter of gear positioning by introducing an offset distance along the longitudinal axis. This parameter change transforms the conventional coaxial or symmetric gear arrangement into an offset configuration, fundamentally altering the wear distribution characteristics without changing the basic gear train topology.
3Reliability
If the offset is optimized to ensure continuous lubrication, then the gear reliability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-positioning the output gears at specific offset locations along the longitudinal axis during the design and manufacturing phase. This predetermined offset arrangement ensures that as the first gear rotates, lubricant is continuously brought into the contact zones of both worm gears, maintaining effective lubrication without requiring active control during operation.
Solution Approach 2:
The offset arrangement enables the gear system to self-lubricate through its own rotational motion. As the first gear rotates, the offset positioning ensures that lubricant is automatically delivered to the contact areas of both worm gears in sequence, allowing the system to maintain its own lubrication without external intervention.
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 offset design significantly reduces wear on the worm wheel gear, extends its useful life, and maintains well-lubricated contact between gears, enhancing the durability and performance of the steering column assembly.
Implementation Method 1
the wear on the first gear is significantly reduced, and consequently the useful life of the first gear is significantly extended
Implementation Method 2
partially overlapping the contact areas of the first and second output gears with the teeth of the first gear helps to ensure that gear lubricants are moved across the flanks of each tooth of the first gear so as to ensure that the contact between the gears is always well lubricated
Data Source
AI summary
A steering column assembly for a vehicle comprises: a steering column rotatably mounted about a longitudinal axis and configured for attachment of a steering wheel at one end; a first gear configured to rotate with the steering column; first and second, each having an output driving a respective output gear, the output gears being engaged with the first gear; and an ECU configured to operate the motors to apply torque to the first gear. The output gears are worm gears and the output gears are offset with respect to one another in the direction of the longitudinal axis of the steering column to produce a partial overlap of the contact areas of the first and second output gears with the teeth of the first gear, which reduces wear of the first gear and prolongs its useful life.