Steering Column Motor Sensor Placement and PCB Orientation
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Solution Overview
Problem
Steer-by-wire steering systems face challenges in reducing gear rattle and optimizing packaging due to electromagnetic disturbances and inefficient use of space, particularly in the placement of motor position sensors relative to motors and worm screws.
Innovation Solution
A steering column assembly with motors and worm screws where motor position sensors are located on the opposite side of the worm screws, and a planar circuit board is inclined relative to the steering column axis, improving packaging efficiency and reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If motor position sensors are mounted on the motor side of the worm screw, then the sensor placement is straightforward, but electromagnetic disturbances from motor windings affect sensor operation and packaging efficiency is reduced
Solution Approach 1:
The motor position sensor is extracted from the motor assembly and relocated to the gear assembly, specifically mounted on the opposite side of the worm screw from the motor. This separation removes the sensor from the electromagnetic disturbance zone of the motor windings while maintaining its functional capability to detect motor shaft position through the worm screw's rotational movement.
Solution Approach 2:
The worm screw acts as an intermediary mechanical element that transmits rotational position information from the motor shaft to the sensor. By mounting the sensor on the gear side of the worm screw, the system uses the worm screw's rotation as a mediator to convey position data without requiring direct proximity between the sensor and motor windings.
2Ease of manufacture
If the circuit board is positioned parallel to the steering column axis, then component mounting is simplified, but the assembly occupies excessive space and packaging efficiency is reduced
Solution Approach 1:
The circuit board is reoriented from a parallel alignment with the steering column axis to a perpendicular alignment. This dimensional change in the circuit board's orientation allows for more efficient three-dimensional packaging of the steering assembly, reducing the overall volume occupied while maintaining all necessary electrical connections and component functionalities.
3Productivity
If motor position sensors are located close to the motors, then wiring length is reduced, but electromagnetic interference increases and packaging becomes less efficient
Solution Approach 1:
The motor position sensor is extracted from the motor's immediate vicinity and relocated to the gear assembly. This extraction removes the sensor from the electromagnetic interference zone while the worm screw's mechanical coupling ensures that the rotational position signal is accurately transmitted without requiring long electrical wiring runs.
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
This configuration enhances packaging efficiency, reduces electromagnetic disturbances, and simplifies component interconnections, leading to a more compact and fault-tolerant steer-by-wire steering system with reduced gear rattle.
Implementation Method 1
a motor position sensor arrangement for sensing a rotational position of the motor output shafts, each sensor arrangement comprising a target member fixedly mounted to a respective motor output shaft on an opposite side of the worm screw from the motor and a sensor for detecting the target member
Data Source
AI summary
A steering column assembly for a vehicle comprises an elongate steering column mounted for rotation about its longitudinal axis and configured for attachment of a steering wheel at one end. A first gear is connected to the steering column at a location spaced from where the steering wheel is attached and is configured to rotate with the steering column. The assembly has first and second motors, each having an output shaft and first and second worm screws directly connected to and rotatable with the output shaft of the first and second motors, respectively and engaged with the first gear, and a control arrangement is configured to operate the first and second motors. A motor position sensor arrangement senses the rotational position of the motor output shafts, each sensor arrangement comprising a target member fixedly mounted to a respective motor output shaft on an opposite side of the worm screw from the motor and a sensor for detecting the target member. The control arrangement comprises a substantially planar circuit board carrying one or more electrical and/or electronic components, the plane of the circuit board being inclined to the longitudinal axis of the steering column.