Electro-Mechanical Steering with Inverted Roller Screw for Heavy Vehicles
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Solution Overview
Problem
Heavier vehicles require steering systems that can generate greater forces than traditional rack and pinion assemblies, but existing heavier-duty systems are large and prone to play, making them less responsive.
Innovation Solution
An electro-mechanical steering system incorporating a frameless electric motor, an inverted planetary roller screw, and thrust tapered roller bearings, which allows for axial translation of arms connected to tie rods, providing significant translational force while maintaining a compact size and reducing rotational resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional rack and pinion assemblies are used, then the steering system is compact and responsive, but they cannot generate sufficient force for heavier vehicles
Solution Approach 1:
The patent inverts the traditional rack and pinion configuration by making the rack stationary and the pinion movable, allowing the pinion to translate along the rack while rotating. This inversion enables the system to generate higher forces through the mechanical advantage of the inverted screw mechanism while maintaining compact dimensions suitable for various vehicle sizes.
Solution Approach 2:
The patent changes the mechanical parameters by using a high ratio of major diameter to pitch in the inverted screw mechanism, creating a mechanical advantage that multiplies the input force. This parameter change allows the steering system to generate sufficient force for heavier vehicles while maintaining a compact design.
2Force
If heavier-duty steering systems are used, then greater forces are generated, but the systems become large and prone to play
Solution Approach 1:
The patent nests the inverted planetary roller screw mechanism within a compact housing, with the movable pinion fitting inside the stationary rack structure. This nesting arrangement allows the heavy-duty steering components to be contained within a compact space, reducing overall system size while maintaining the force-generating capability.
Solution Approach 2:
By inverting the traditional rack and pinion arrangement, the patent creates a more space-efficient configuration where the mechanical advantage is achieved through the inverted screw mechanism rather than through larger component dimensions, thus reducing system size while maintaining force output.
3Force
If heavier-duty steering systems are used, then greater forces are generated, but the systems become prone to play reducing responsiveness
Solution Approach 1:
The patent replaces traditional mechanical toothed gear systems with an inverted planetary roller screw mechanism that uses continuous thread engagement and roller contact. This substitution eliminates the backlash and play inherent in toothed gear systems, providing a more reliable, play-free connection that maintains steering responsiveness even in heavy-duty applications.
Solution Approach 2:
The inverted configuration creates a more rigid mechanical connection where the stationary rack provides a stable reference frame and the movable pinion is constrained by the threaded engagement, reducing play and improving responsiveness compared to traditional movable rack configurations.
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 delivers higher forces than traditional rack and pinion systems, is more responsive due to reduced play, and is suitable for heavy vehicles with a design that is shorter and more durable, enhancing roll-steer and bump-steer performance.
Implementation Method 1
a rotor fixedly coupled to the nut; a stator integrated with the housing and oriented around the rotor
Implementation Method 2
an inverted planetary roller screw, the screw rotatably coupled with the nut where rotation of the inverted planetary roller screw and the nut results in axial translation of the arm
Implementation Method 3
a thrust bearing coupled to the journal bearing and to a nut
Implementation Method 4
an arm configured to couple with a tie rod, the arm coupled through a journal bearing
Data Source
AI summary
Implementations of a steering system may include: an arm configured to couple with a tie rod, the arm coupled through a journal bearing; a thrust bearing coupled to the journal bearing and to a nut; a screw rotatably coupled to an inverted planetary roller screw, the screw coupled with the nut; a rotor coupled to the nut and to a housing, the housing configured to be fixedly coupled to a frame; and a stator coupled to the housing and around the rotor and the inverted planetary roller screw where the stator is electrically coupled to a power source.