Electric Power Steering Angular Position Sensor
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Solution Overview
Problem
The challenge in electric power steering systems is determining the absolute steering angle of a vehicle without the input shaft and torque sensor, which complicates assembly, increases costs, and makes the system bulky, limiting its application to various vehicles due to the need for a steering column and sensor arrangement.
Innovation Solution
An electric power steering system that includes a housing, a ball screw with a nut and threaded shaft, a motor connected to the nut, and an angular position sensor with sensing units, allowing the computing unit to calculate the threaded shaft's position based on sensing signals from the motor's rotating angle, eliminating the need for an input shaft and torque sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the input shaft assembly and torque sensor are removed from the EPS system to reduce mechanism volume and cost, then the system becomes more compact and cost-effective, but the ability to obtain absolute steering angle and output shaft position becomes compromised
Solution Approach 1:
The patent replaces the traditional mechanical sensing system (input shaft with torque sensor) with an electrical sensing system. The angular position sensor mounted on the motor measures the motor's rotational angle, and through the known transmission ratio of the ball screw mechanism, the system electronically calculates the output shaft position and steering angle, eliminating the need for mechanical steering column sensors.
Solution Approach 2:
The patent introduces the angular position sensor as an intermediary element on the motor side to indirectly measure the output shaft position. Instead of directly measuring the steering angle at the output shaft, the system uses the motor's angular position combined with the ball screw transmission ratio to calculate the required measurement data.
2Measurement precision
If the steering column and sensor arrangement are retained for accurate steering angle detection, then measurement accuracy is maintained, but the system becomes bulky and cannot be applied to various vehicles
Solution Approach 1:
The patent makes the EPS system universal by mounting the angular position sensor directly on the motor, which is a common component across different vehicle platforms. This configuration allows the same sensor arrangement to be applied to various vehicles without requiring vehicle-specific steering column modifications, while still achieving accurate steering angle detection through electronic calculation.
3Manufacturing precision
If the steering column and sensor are assembled together with multiple steps, then proper sensor positioning is achieved, but assembly time and production cost are increased
Solution Approach 1:
The patent merges the angular position sensor mounting with the motor assembly process. The sensor is directly mounted on the motor housing or motor shaft, combining two assembly operations into one. This eliminates the need for separate sensor positioning and installation steps that would be required if the sensor were mounted on a separate steering column assembly.
Solution Approach 2:
The patent extracts the sensor mounting from the steering column assembly process and relocates it to the motor assembly process. By taking the sensor mounting operation out of the complex steering column assembly sequence and performing it during motor assembly, the overall assembly complexity and time are reduced.
Data Source
AI summary
An electric power steering system includes a housing, a ball screw, a motor, an angular position sensor and a computing unit. The ball screw includes a nut and a threaded shaft. The motor is disposed in the housing and connected to the nut and includes a bushing and a metal component. The metal component is fixed on the bushing and includes a central portion, a first wing portion and a second wing portion. The first wing portion and the second wing portion are disposed on an outer circumferential surface of the central portion. The angular position sensor is disposed in the housing and fixed relative to the housing. The angular position sensor includes a first sensing unit and a second sensing unit. The computing unit is electrically connected to the first sensing unit and the second sensing unit.