Steering Angle Limiter With Fail-Safe Reverse Release
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Solution Overview
Problem
Steer-by-wire systems lack a mechanism to restrict steering wheel rotation when tire turning is impeded, leading to potential motor overload and safety issues due to the absence of a mechanical connection, and existing solutions have complex structures or fail to function when the engine is off.
Innovation Solution
A steering-angle-limiting device with a stopping gear, cam, and stopper that selectively restricts steering wheel rotation in both directions using gear teeth, and a fail-safe unit that moves the stopper away from gear teeth if it operates abnormally, preventing wheel locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a steering-angle-limiting device uses a stopper to restrict rotation of the column shaft in both directions, then the steering wheel can be locked when tire turning is impeded, but the steering wheel may be locked when the direction of steering is suddenly reversed
Solution Approach 1:
The stopper is designed to dynamically adjust its position based on the direction of steering input. When the steering wheel is turned in a specific direction beyond the limited angle, the stopper engages to restrict further rotation. However, when the steering direction is reversed, the stopper disengages to allow free rotation, thus resolving the contradiction between locking function and reversibility
Solution Approach 2:
The steering angle limiting function is segmented into direction-specific control. The stopper mechanism is configured to selectively restrict rotation in one direction while permitting rotation in the opposite direction, allowing independent control of steering restrictions based on direction
2Adaptability or versatility
If a steering-angle-limiting device uses a planetary gear and motor to adjust rotation angle of the column shaft, then the structure can control steering angle, but the structure becomes complicated
Solution Approach 1:
The complex planetary gear mechanism is extracted and replaced with a simpler cam-based positioning system. The cam profile directly translates rotational input into the desired stopper positioning, eliminating the need for planetary gears and reducing mechanical complexity while maintaining steering angle control capability
Solution Approach 2:
The motor-driven planetary gear system is substituted with a cam-mechanical linkage system. The cam mechanism provides the necessary motion transformation and positioning functions that were previously achieved through complex motor control and gear mechanisms, simplifying the overall system
3Reliability
If a steering-angle-limiting device uses a stopper to restrict rotation of the column shaft, then the steering wheel can be locked when tire turning is impeded, but the device cannot function when the engine is turned off
Solution Approach 1:
The cam mechanism is designed to automatically position the stopper based on the steering wheel's rotation position without requiring external power or control systems. This self-service mechanism ensures the steering angle limiting function operates reliably whether the engine is on or off
4Reliability
If the stopper is damaged or malfunctions while restricting the rotation of the column shaft during traveling of the vehicle, then it may become impossible to turn the steering wheel, which may lead to a serious accident
Solution Approach 1:
A fail-safe mechanism is incorporated that detects stopper malfunction before it causes complete steering lockup. When malfunction is detected, the system automatically adjusts the cam position to disengage the stopper from the gear teeth, preventing total steering wheel locking and allowing the driver to maintain steering control
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
Enables safe and controlled steering wheel rotation in both directions, preventing accidents by inhibiting wheel locking and allowing continued operation even when the stopper malfunctions, while also allowing steering wheel locking when the engine is off without additional devices.
Implementation Method 1
a cam configured to rotate eccentrically by receiving rotational force from an actuator
Implementation Method 2
a solenoid valve configured to be brought into contact with or separated from the rotating shaft and to restrict or permit movement of the rotating shaft
Implementation Method 3
a moving spring configured to provide elastic force in the axial direction in which the rotating shaft moves
Data Source
AI summary
A steering-angle-limiting device of a steer-by-wire system selectively restricts turning of a steering wheel in a forward direction or in a reverse direction and permits turning of the steering wheel in order to inhibit locking of the steering wheel when the steering-angle-limiting device operates abnormally. Rotation of a stopping gear, which is coupled to a steering shaft, is selectively restricted depending on a change in a rotation angle of a cam, whereby the direction in which the steering wheel turns is selectively limited. In addition, when a stopper operates abnormally, the stopper is moved to a position apart from an end of the radius of rotation of the stopping gear, thereby enabling turning of the steering wheel.