Hydrostatic Steering Apparatus Axial Force Sensor Torsion Bar Elimination
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Solution Overview
Problem
Existing hydrostatic steering systems for vehicles, particularly agricultural and heavy vehicles, are complicated by the presence of a torsion bar, which increases dimensions, costs, and introduces potential failure points due to defects and wear.
Innovation Solution
A hydrostatic steering apparatus that replaces the torque sensor with an axial force sensor on the hydraulic jack, eliminating the need for a torsion bar and featuring a torsionally rigid steering shaft, along with angular sensors to control the electric motor and manage self-driving functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torsion bar is used to measure steering torque, then torque measurement is achieved, but device complexity and dimensions increase
Solution Approach 1:
The patent extracts the torque measurement function from the mechanical torsion bar structure and relocates it to an electronic sensor system. The force sensor measures axial force on the plunger, which correlates to steering torque, eliminating the need for a mechanical torsion bar while maintaining measurement capability.
Solution Approach 2:
The patent replaces the mechanical torsion bar-based torque measurement system with an electronic force sensor and control unit system. The force sensor electronically detects axial force, and the control unit calculates torque from this data, substituting mechanical measurement with electronic sensing and computation.
2Measurement precision
If a torsion bar is used to measure steering torque, then torque measurement is achieved, but reliability decreases due to wear and defects
Solution Approach 1:
The patent replaces the mechanical torsion bar with an electronic force sensor system that has no moving parts subject to wear. The force sensor provides contactless or minimal-contact measurement, eliminating wear-related failure modes while maintaining accurate torque measurement through electronic sensing and calculation.
3Device complexity
If an axial force sensor is used instead of a torque sensor, then device complexity is reduced, but measurement capability must be maintained
Solution Approach 1:
The patent introduces the control unit as an intermediary that translates axial force sensor measurements into torque values. The control unit receives axial force data from the sensor, applies the appropriate mechanical characteristics of the plunger, and outputs torque information, enabling torque measurement through force measurement.
Solution Approach 2:
The patent changes the measurement parameter from direct torque measurement to axial force measurement. By measuring the axial force on the plunger and using the known mechanical characteristics of the plunger system, the control unit calculates the corresponding torque, effectively transforming one measurement parameter into another.
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 simplifies the steering apparatus, making it more robust and compact, while maintaining effective torque control and enabling self-driving capabilities, thus reducing structural complexity and potential failures.
Implementation Method 1
a force sensor adapted to measure (directly or indirectly) an axial force applied to the plunger of the hydraulic jack
Implementation Method 2
an electric motor adapted to apply a rotation torque to the steering shaft
Implementation Method 3
a hydraulic guide unit (power steering) adapted to selectively convey a pressurised fluid (e.g., oil) into the first operating chamber or the second operating chamber of the cylinder
Data Source
Figure 1
Figure 2
AI summary
A hydrostatic steering apparatus (100) for vehicles is described, comprising: at least one double-acting hydraulic jack (105) equipped with a cylinder (110) and a plunger (115) adapted to subdivide the inner volume of the cylinder (110) into a first and a second operating chamber (120, 125), the plunger (115) comprising at least one stem axially protruding from the cylinder (110) and adapted to be connected to a steering wheel (130); a hydraulic guide unit (145) adapted to selectively convey a pressurised fluid into the first operating chamber (120) or the second operating chamber (125) of the cylinder (110); a steering shaft (200) having a first end connected to the hydraulic guide unit (145) and a second end connected to a manual steering member (165); an electric motor (220) adapted to apply a rotation torque to the steering shaft (200); a force sensor (245) adapted to measure an axial force applied to the plunger (115) of the hydraulic jack (105); and an electronic control unit (235) configured to adjust a value of the rotation torque applied by the electric motor (220) to the steering shaft (200) based on an axial force value measured by the force sensor (245).