Variable Steering Ratio via Epicyclic Gearbox and Torque Control
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Solution Overview
Problem
Current power assisted steering systems in work vehicles, such as those combining electronic power steering (EPS) and hydraulic steering units (HSU), lack a cost-effective solution for variable steering ratio and torque control at the steering wheel, which is essential for operator ease and vehicle maneuverability.
Innovation Solution
Incorporating an epicyclic gearbox between the EPS and HSU, coupled with a motor to adjust the steering ratio, and an electronic control unit (ECU) to manage torque and steering characteristics, allowing for selective control of the torque felt by the operator and the steering ratio between the steering wheel and HSU.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a steer-by-wire system is used to control torque and steering ratio, then variable steering ratio and torque control are achieved, but cost increases and security protocols are required
Solution Approach 1:
An epicyclic gearbox is introduced as an intermediary mechanical component between the steering wheel and the hydraulic steering unit. This gearbox provides variable steering ratio through its inherent mechanical geometry without requiring complex electronic control systems, thereby achieving adaptability while avoiding the complexity and cost of steer-by-wire systems
Solution Approach 2:
The patent replaces the entirely electrical steer-by-wire system with a hybrid approach that uses a mechanical epicyclic gearbox for steering ratio variation, combined with a simplified electronic power steering motor for torque control. This substitution reduces system complexity and cost while maintaining the desired functionality
2Adaptability or versatility
If a fixed mechanical linkage is used between steering column and HSU, then system simplicity is maintained, but variable steering ratio cannot be achieved
Solution Approach 1:
The patent transforms the fixed mechanical linkage into a dynamic system by incorporating an epicyclic gearbox that can continuously vary the steering ratio. The gearbox allows the mechanical connection between steering wheel and HSU to adapt its transmission ratio based on operating conditions, providing variability while maintaining mechanical simplicity through inherent gear geometry
Data Source
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AI summary
A steering mechanism (40) for a vehicle including a steering wheel (42), a rotatable steering column (44) coupled to the steering wheel (42), and a hydraulic steering unit (46) operably connected to the steering column (44) and configured to translate a rotational movement of the steering column (44) to steer the vehicle. The steering mechanism (40) also includes a steering assister (48) operably coupled to the steering wheel (42) and configured for controlling at least one of a torque that acts on the steering column (44) and a steering ratio between the steering wheel (42) and the hydraulic steering unit (46), and a controller (50) operably coupled with the hydraulic steering unit (46) and the steering assister (48). The controller (50) is configured for selectively controlling at least one of a torque experienced by an operator and the steering ratio.