Steering Column Travel Limiter With Compact Threaded End Stops
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Solution Overview
Problem
In steer-by-wire vehicle systems, the lack of physical connection between the steering wheel and wheels allows for indefinite rotation, which is not limited to the maximum steering angle, potentially causing driver confusion and safety issues.
Innovation Solution
A travel limiter system comprising a housing, an elongate threaded member, a nut member with a toothed gear, end stops, a drive motor, and a controller that controls the motor to restrict rotation by displacing the nut member into contact with the end stops, allowing a shorter leadscrew and providing a clutch or brake mechanism for progressive engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional threaded shaft with end stops is used to limit steering column rotation, then the maximum rotation of the steering column can be limited, but the physical size of the travel limiter becomes large
Solution Approach 1:
The patent applies dynamics by making the nut member rotatable relative to the threaded shaft, allowing the system to transition between different operational states. The nut member can rotate with the shaft during normal operation and be selectively positioned to engage end stops when rotation limitation is required, enabling a more compact design compared to fixed traditional systems
Solution Approach 2:
The nut member serves multiple functions: it acts as a rotational coupling element during normal steering operation and simultaneously serves as a movable constraint that can engage with end stops to limit rotation. This multi-functionality eliminates the need for separate limiting mechanisms, reducing overall travel limiter size
2Reliability
If the nut member is constrained to be non-rotatable to limit steering column rotation, then the maximum rotation can be controlled, but the leadscrew must be long which increases device size
Solution Approach 1:
The patent makes the nut member dynamically rotatable rather than statically non-rotatable. This allows the nut to rotate with the threaded shaft during normal operation, and only becomes a rotational constraint when it engages with the end stops. This dynamic behavior enables effective rotation control with a shorter leadscrew length
3Ease of operation
If a clutch or brake mechanism is used as end stop for progressive engagement, then good steering feel is provided, but the device complexity increases
Solution Approach 1:
The patent merges the end stop function with the nut member itself. The nut member integrates the rotational coupling function and the rotation limitation function into a single component. When the nut engages with the end stops, it provides progressive engagement through its threaded interaction, eliminating the need for separate clutch or brake mechanisms while maintaining good steering feel
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 system effectively limits steering column rotation, reducing the physical size of the travel limiter and providing a good steering feel through progressive engagement, ensuring the steering column does not exceed the maximum pivoting range of the wheels.
Implementation Method 1
an elongate threaded member rotatably mounted about its longitudinal axis within the housing; a nut member threadedly mounted on the elongate threaded member
Implementation Method 2
a drive motor having an output shaft configured to rotate an output gear member meshed with the gear on the exterior of the nut member
Implementation Method 3
each clutch or brake comprises a first plate mounted on a first plate carrier located within the housing, the first plate being engageable with a second plate mounted on a second plate carrier configured to rotate with the elongate threaded member
Data Source
AI summary
A travel limiter for a rotatable steering column of a vehicle comprises: a housing; an elongate threaded member rotatably mounted about its longitudinal axis within the housing; a nut member threadedly mounted on the elongate threaded member, the exterior of the nut member comprising a toothed gear; connector for connection of a rotatable steering column of a vehicle to the elongate threaded member, whereby the steering column and the threaded member are constrained to rotate together; end stops which engage with the nut member to define the maximum axial displacement of the nut member along the elongate threaded member in both directions; a drive motor having an output shaft configured to rotate an output gear member meshed with the gear on the exterior of the nut member; and a controller configured to control the operation of the drive motor.