Ball-Screw Electric Power Steering for Compact Heavy-Vehicle Assist
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional hydraulic power steering systems are not suitable for electric and/or hybrid commercial vehicles, necessitating the development of an alternative power steering solution that is safe, robust, axially compact, and cost-effective.
Innovation Solution
An electric power steering system incorporating a ball-screw assembly with a ball nut and ball shaft, an electric motor, and a gearset, along with a bevel gearbox, which provides mechanical advantage and supplements driver torque through a planetary gear set, allowing for efficient and compact power steering in heavy commercial vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic power steering is used in electric and/or hybrid commercial vehicles, then the steering system can provide sufficient torque assistance, but the system becomes complex and less suitable for electrified vehicles
Solution Approach 1:
The patent replaces the hydraulic power steering system with an electric power steering system that uses an electric motor to provide torque assistance. This substitution eliminates the need for hydraulic pumps, fluid reservoirs, and associated plumbing, thereby reducing system complexity while maintaining torque assistance capability in electric and hybrid commercial vehicles.
2Length of moving object
If a compact power steering system is designed for heavy commercial vehicles, then the axial space is reduced, but the mechanical advantage and torque multiplication may be compromised
Solution Approach 1:
The patent employs a nested arrangement where the planetary gear set is integrated within the ball-screw assembly structure. The planetary gear set provides torque multiplication, and its compact nested design allows it to fit within the limited axial space while maintaining the necessary mechanical advantage for heavy commercial vehicle steering.
Solution Approach 2:
The patent transitions from a traditional axial arrangement to a radial arrangement of the ball-screw threads. This dimensional change allows the ball-screw assembly to provide both compactness in the axial direction and sufficient torque multiplication through the radial thread geometry, effectively resolving the contradiction between axial compactness and force generation.
3Adaptability or versatility
If an electric power steering system is implemented in heavy commercial vehicles, then the system becomes more suitable for electrified vehicles and enables driver assist features, but the device complexity increases compared to conventional hydraulic systems
Solution Approach 1:
The patent designs the electric power steering system with a universal architecture that can serve multiple functions: providing torque assistance for manual steering, enabling automatic driver assist features like lane keeping, and supporting autonomous driving operations. The electric motor and control system can be programmed to perform different steering assist levels, making the system adaptable to various driving modes without requiring separate systems.
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 electric power steering system effectively supplements driver torque, providing a robust, safe, and cost-effective solution for heavy commercial vehicles, enabling easier steering and potential integration with automatic driver assist features like lane keeping and autonomous driving.
Implementation Method 1
A plurality of bearings are circulatable through the helical track when the ball nut rotates relative to the ball shaft in order to translate the ball shaft relative to the ball nut
Implementation Method 2
An electric power steering system for commercial vehicles would be useful... The gearset and the bevel gearbox thus provide an input for both the electric motor and a manual steering wheel
Data Source
AI summary
An electric power steering assembly includes an electric motor, a gearset, and a ball-screw assembly. The gearset couples the electric motor and a ball nut of the ball-screw assembly such that the electric motor is operable to rotate the ball nut relative to the ball shaft. A plurality of bearings are circulatable through a helical track, which is defined between the ball nut and a ball shaft of the ball-screw assembly, when the ball nut rotates relative to the ball shaft in order to translate the ball shaft relative to the ball nut.