Ball Screw Nut Position Sensing With Low-Lash Sensor Gear
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Solution Overview
Problem
Existing position sensors for vehicle steering systems face challenges in packaging, robustness, and achieving high positional accuracy with low power consumption and wear, particularly in translating rotary motion to linear motion efficiently.
Innovation Solution
A ball screw drive system incorporating a nut with internal and external threads, a threaded spindle, and a rotational angle sensor with a sensor gear driven by the external threads, which generates an electric signal based on the gear's rotational position, optimizing space usage and reducing gear lash through elastic biasing or elastic shaft supports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a ball screw drive with rotational angle sensor is used, then positional accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines the ball screw drive mechanism with a rotational angle sensor that has a sensor gear directly coupled to the ball screw nut. This integration allows the sensor to directly measure the rotational position of the nut, which corresponds to the linear position of the spindle, thereby achieving high positional accuracy without requiring a separate, complex measurement system.
Solution Approach 2:
The ball screw nut serves multiple functions: it converts rotational motion to linear motion through the ball screw mechanism, and simultaneously serves as the mounting base for the rotational angle sensor. The sensor gear is integrated with the nut structure, allowing the same component to fulfill both mechanical drive and positional measurement functions, thus reducing overall device complexity.
2Measurement precision
If elastic biasing is applied to the sensor gear, then gear lash is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies elastic biasing to the sensor gear to eliminate gear lash. This is achieved by introducing an elastic element that pre-loads the gear teeth, ensuring continuous contact between the sensor gear and the drive gear. The elastic force compensates for manufacturing tolerances and wear, maintaining precise positional measurement without requiring extremely tight manufacturing tolerances.
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 provides high positional accuracy with low sliding power, low energy use, and reduced wear, while being space-efficient, suitable for various vehicle steering systems including mechanical and steer-by-wire configurations.
Implementation Method 1
A threaded spindle having a spindle thread is provided, with the threaded spindle being drivable by the internal threads of the nut such that rotary motion of the nut is translated into linear motion of the threaded spindle
Implementation Method 2
The teeth of the gear are biased to engage with the external threads. The teeth may be biased via circumferential elasticity of the gear, for example, based on an elastic structure in the gear body itself
Data Source
AI summary
A ball screw drive for a vehicle steering system is provided, with the ball screw drive including a nut configured to receive torque from a power transmission drive. The nut has internal threads, and external threads are provided on the nut or connected thereto for rotation with the nut. A threaded spindle having a spindle thread is provided, with the threaded spindle being drivable by the internal threads of the nut such that rotary motion of the nut is translated into linear motion of the threaded spindle. A rotational angle sensor is provided having a sensor gear that is rotatably driven by the external threads of the nut, and the rotational angle sensor is configured to generate an electric signal based on a rotational position of the sensor gear.