Power Steering Motor Torque Control for Size Reduction
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Solution Overview
Problem
The existing power steering devices require large-sized electric motors due to constant load on the motor during steering, leading to increased physical size and complexity.
Innovation Solution
A power steering device that uses a torque command signal control unit to set the electric motor's torque to zero at predetermined vehicle speeds, relying solely on hydraulic assist for steering assistance, reducing the load on the electric motor and allowing for a smaller motor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electric motor operates all the time during steering to provide precise control assistance, then the steering control precision is improved, but the load on the electric motor increases and the physical size of the power steering device increases
Solution Approach 1:
The control system dynamically switches between electric motor assistance and hydraulic assistance based on steering conditions. The electric motor operates only when precise control is needed (low vehicle speed, large steering angle), while hydraulic assistance takes over when high force is needed (high vehicle speed, normal steering conditions). This dynamic switching allows the electric motor to be smaller while maintaining precision where needed.
Solution Approach 2:
A hydraulic assist mechanism is introduced as an intermediary to share the steering assistance burden with the electric motor. The hydraulic system provides high-force assistance when needed, allowing the electric motor to be downsized while maintaining overall system performance. The control unit coordinates both systems to work together based on real-time steering conditions.
2Reliability
If a large-sized electric motor with high load-tolerance is used to handle constant steering loads, then the reliability under high load is improved, but the physical size and weight of the power steering device increase greatly
Solution Approach 1:
The hydraulic assist mechanism serves as an intermediary that handles high-load conditions, allowing the electric motor to be smaller and lighter. The hydraulic system provides the necessary force multiplication during high-load steering situations (such as parking maneuvers or high-speed steering), enabling the use of a more compact electric motor while maintaining reliability.
Solution Approach 2:
The system dynamically distributes the load between the electric motor and hydraulic assistance based on real-time steering demands. During normal driving, the electric motor provides precise control with minimal load. During high-load conditions, the hydraulic system engages to share the burden, allowing the electric motor to be designed for precision rather than maximum load capacity, thus reducing its size and weight.
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 decreases the physical size of the power steering device while maintaining effective steering assistance, improving steering feel and reducing the load on the electric motor, especially at higher vehicle speeds.
Implementation Method 1
a power cylinder (29) that provides a steering force to the steering mechanism (2) by being supplied with working fluid
Data Source
AI summary
Power steering device has steering mechanism 2, power cylinder 29 having a pair of hydraulic chambers 29a, 29b divided by piston 31 and providing steering force to steering mechanism, torque sensor 11 detecting steering torque Tr of steering mechanism, rotary valve 30 selectively supplying working fluid supplied from pump 9 to the pair of hydraulic chambers according to relative rotation between input and output shafts, hollow shaft motor 10 providing steering force to input shaft, control unit 13 in which microcomputer is mounted, and torque command signal operating section 61 provided in control unit and configured to calculate torque command signal Tm* for driving and controlling electric motor 10 on the basis of the steering torque Tr and vehicle speed Vs and when vehicle speed is a predetermined vehicle speed or greater, set torque command signal to 0. With this, physical size of power steering device can be decreased.