Dual-Motor Steering Torque Feedback Assembly Without Gear Rattle
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Solution Overview
Problem
Existing steer-by-wire vehicle systems face issues with gear rattle due to torque and direction reversals, requiring precise backlash control and resulting in larger, more costly, and heavier assemblies.
Innovation Solution
A steering torque feedback assembly utilizing two electric motors with reduction gearing, allowing torque application in opposite or same directions, reducing component stress and enabling gear construction from plastics, with an epicyclic gear train and internal keyway for adjustable steering column connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single electric motor with worm screw and worm gear is used to provide torque feedback, then the system can provide road feel sensation, but gear rattle occurs when torque and direction are reversed requiring precise backlash control
Solution Approach 1:
The single motor system is segmented into two separate electric motors, each driving its own worm gear. This segmentation allows independent control of each motor to eliminate backlash issues - when one motor reverses direction, the other can maintain engagement, preventing gear rattle without requiring precise backlash control
2Reliability
If precise backlash control is implemented to eliminate gear rattle, then gear engagement reliability improves, but the assembly size and cost increase
Solution Approach 1:
By dividing the torque feedback function into two separate motor-gear units, the system achieves reliable gear engagement without needing precision backlash control mechanisms. The segmented design allows simpler, more compact components that don't require tight tolerances or complex adjustment mechanisms
3Strength
If high-rating motors and metal gears are used to handle maximum torque, then system strength is sufficient, but the assembly becomes larger and more expensive
Solution Approach 1:
Each motor is rated for only half the total system torque requirement, but together they provide the full torque capacity. This partial action approach allows the use of smaller, lighter motors and plastic gears instead of oversized metal components, reducing assembly size and cost while maintaining sufficient strength through the combined output of both motors
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 solution eliminates the need for precise backlash control, reduces assembly size and cost, and allows for a lighter, more efficient torque feedback system that provides a sensation of road feel while accommodating both manual and autonomous driving modes.
Implementation Method 1
the first and second reduction gearing comprises an epicyclic gear train
Implementation Method 2
The reduction gearing between the output of each of the motors and the output gear also reduces stress on the components of the gear train
Data Source
AI summary
A steering torque feedback assembly for a vehicle steering column includes a housing, a first gear rotatably mounted within the housing about a first rotatable axis and being configured to rotate with, or being connected to, a vehicle steering column, first and second electric motors mounted within the housing, each having a rotatable output shaft, second and third gears rotatably mounted within the housing and engaged with the first gear, and first and second reduction gearing connecting the output of the first and second motors and a respective one of the second and third gears.