Tag Axle Steering Fail-Safe Mechanism
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Solution Overview
Problem
Existing systems for steering unpowered tag axles in vehicles are complex and costly, and fail to provide reliable fail-safe states during malfunctions, especially at varying vehicle speeds, affecting stability and fuel efficiency.
Innovation Solution
A system that switches to two fail-safe states based on vehicle speed, using series-connected valve means and spring-loaded mechanisms to ensure safe operation, with valve positions determined by electrical power means and check valves, allowing caster-steering at lower speeds and locking at higher speeds, and utilizing a hydraulic pump for steering control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the tag axle is locked in neutral position at high speeds, then stability and fuel consumption are improved, but maneuverability at low speeds deteriorates
Solution Approach 1:
The tag axle steering system dynamically adjusts its state based on vehicle speed. At low speeds, the tag axle remains steerable to improve maneuverability. At high speeds (above threshold speed), the tag axle automatically locks into a fixed neutral position aligned with the vehicle's longitudinal direction to enhance stability and reduce fuel consumption. This speed-dependent dynamic behavior resolves the contradiction between stability and maneuverability.
2Reliability
If a fail-safe system locks the tag axle in neutral position during malfunction, then stability is improved, but the system becomes overly complex and expensive
Solution Approach 1:
The fail-safe mechanism utilizes the existing speed-sensing capability and threshold speed logic already present in the operational steering system. During normal operation, the system locks the tag axle at speeds above the threshold. In case of malfunction (e.g., loss of electrical power), the system automatically transitions to this same locked state without requiring additional complex fail-safe components. The existing threshold speed mechanism serves dual purposes: normal high-speed stability and malfunction fail-safe operation.
Solution Approach 2:
The threshold speed locking mechanism serves multiple functions: it provides stability at high speeds during normal operation and simultaneously acts as the fail-safe mechanism during malfunctions. This multi-functionality eliminates the need for separate dedicated fail-safe components, thereby reducing system complexity while maintaining reliability.
3Ease of operation
If the tag axle is steered at low speeds, then maneuverability is improved, but fuel consumption increases
Solution Approach 1:
The system changes the steering parameter (tag axle deflection angle) based on vehicle speed. At low speeds, the tag axle is allowed to deflect to assist maneuverability. At high speeds, the system changes the parameter by locking the tag axle in the neutral position, eliminating unnecessary steering movements that would increase fuel consumption. This parameter change based on speed threshold resolves the energy-maneuverability contradiction.
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 ensures safe and reliable vehicle behavior by allowing caster-steering at lower speeds and locking the tag axle in neutral position at higher speeds, improving maneuverability and stability while reducing complexity and cost.
Implementation Method 1
A first valve means and a second valve means are connected in series in this feedback line intended to reach a first fail-safe state when the electrical power means is inactivated by a malfunction of the system, by the first valve means and the second valve means opening in sequence and by spring loading of the second valve means
Data Source
Figure 1
Figure 2a~2e
Figure 3
AI summary
A system for steering at least one unpowered wheeled tag axle of a vehicle which in the latter's ordinary direction of movement follows the vehicle's front axle comprises an ancillary unit (29) adapted, if the vehicle's speed is below a threshold speed when a malfunction of the system occurs, to switching the system to a first fail-safe state with caster steering of the tag axle, but if the vehicle is above the threshold speed when a malfunction of the system occurs, to keeping the tag axle locked with its wheels in a fixed neutral position aligned with the vehicle's longitudinal direction in a second fail-safe state of the system.