Steering Rack Bearing Force Sensor for Authentic Road Feel
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Solution Overview
Problem
Steering systems with electric steering torque assistance units face challenges in providing an authentic steering feel to drivers due to high inertia, which filters and reduces road surface signal transmission to the steering wheel, resulting in a low-pass filtered and unauthentic steering experience.
Innovation Solution
A steering system that includes a steering torque assistance unit with an electric drive, gear stage, and a bearing, where at least one sensor measures the bearing force acting on the bearing, allowing the assistance torque to be generated based on the driver's steering torque and measured bearing force, thereby bypassing the high inertia and enhancing steering feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an electric steering torque assistance unit is used to assist steering, then steering assistance torque can be applied to the steering rack, but the high inertia of the electric drive sharply reduces the transmission of road surface signals to the steering wheel, resulting in low-pass filtered and unauthentic steering feel
Solution Approach 1:
The patent segments the steering system into two independent torque paths: a mechanical steering feel path that transmits road surface signals directly from the steering rack to the steering wheel, and an electric assistance path that provides steering assistance torque through the electric drive. This segmentation allows the mechanical path to preserve authentic steering feel while the electric path provides power assistance.
Solution Approach 2:
The patent introduces sensors as intermediaries that measure bearing forces on the steering rack and directly couple these forces to the steering wheel through a coupling element. This intermediary mechanism bypasses the high-inertia electric drive for the steering feel transmission, allowing road surface signals to be transmitted authentically while still providing electric assistance torque.
2Ease of operation
If the electric drive engages the steering rack directly to provide steering assistance, then steering assistance torque can be applied, but the high rotational inertia filters and reduces the transmission of road surface signals
Solution Approach 1:
The system separates the steering assistance function from the steering feel transmission function. The electric drive provides assistance torque through one path, while sensors and coupling elements transmit road surface signals through a separate mechanical path, ensuring both ease of operation and reliable authentic steering feel.
Solution Approach 2:
The patent replaces the direct mechanical connection between steering rack and steering wheel with a sensor-based measurement and electronic control system. Sensors measure bearing forces, and a control unit processes these signals to provide assistance while maintaining authentic road feel transmission through the coupling element.
3Measurement precision
If sensors measure bearing force on the bearing of the steering torque assistance unit, then the steering assistance torque can be generated based on measured bearing force and driver steering torque, but the system complexity increases
Solution Approach 1:
The bearing itself serves as the measurement element by directly transmitting road surface forces to the sensor. The sensor measures the bearing force that already exists in the system during normal operation, rather than requiring separate measurement apparatus. This allows precise measurement while minimizing additional system complexity.
Data Source
AI summary
A steering system of a motor vehicle has a steering wheel which engages a steering rack via a steering pinion of a steering column. A steering torque is exerted by a driver on the steering rack via the steering wheel. A steering torque assistance unit is provided and has an electric drive and a gear stage. A steering assistance torque is able to be exerted on the steering rack via the electric drive of the steering torque assistance unit. The electric drive engages the steering rack via the gear stage. Accordingly, at least one sensor determines by measurement a bearing force acting on a bearing of the steering torque assistance unit, the steering torque assistance unit generating the steering assistance torque in dependence on the steering torque exerted by the driver and in dependence on the bearing force determined by measurement.