Steer-by-Wire Sliding Bar Spline Engagement and Position Detection
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Solution Overview
Problem
Conventional steer-by-wire type power steering apparatuses experience friction and noise issues due to improper engagement of rack gear and pinion gear, and have poor precision and responsiveness from linear and distance sensors, leading to high costs and assembly challenges.
Innovation Solution
A multi-motor-based steer-by-wire type power steering apparatus that reduces friction and noise by using a sliding bar with a second spline engaged with a first spline in a cylinder, and improves durability and strength by determining the sliding bar's position based on the phase difference between the rotation information of respective motors, incorporating a coupling member with a support portion and a slit groove for axial sliding without rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rack gear and pinion gear are used for steering, then mechanical connection is established, but friction and noise are generated due to improper engagement
Solution Approach 1:
The patent replaces the traditional rack gear and pinion gear mechanical engagement system with a spline-based direct connection system. The sliding bar includes a spline portion that directly engages with the cylinder's internal spline, eliminating the intermediate gear engagement mechanism that causes friction and noise while maintaining reliable mechanical transmission for steering control.
Solution Approach 2:
The invention extracts and removes the problematic gear engagement components (rack gear and pinion gear) from the steering mechanism, retaining only the essential linear motion transmission function through the spline-based sliding bar and cylinder assembly, thereby eliminating the source of friction and noise.
2Measurement precision
If linear sensor and distance sensor are used to measure rack bar position, then position measurement is achieved, but precision and responsiveness are poor and cost is high
Solution Approach 1:
The patent creates a mechanical copy or replica of the position measurement function through the spline engagement geometry. The rotational position of the cylinder relative to the sliding bar's linear position is mechanically encoded in the spline engagement, allowing position to be determined by measuring the rotational angle of the motor rather than using complex linear sensors.
Solution Approach 2:
The invention replaces the electronic sensor-based measurement system (linear sensor and distance sensor) with a mechanical encoding system where the spline geometry itself encodes position information, which can be read through simple rotational angle measurement of the motor driving the cylinder.
3Measurement precision
If sensors of length equal to rack bar movement distance are used, then full range measurement is achieved, but assembly is difficult and cost increases
Solution Approach 1:
The patent transforms the measurement problem from one dimension (linear distance measurement along the rack bar's movement path) to another dimension (rotational angle measurement of the motor shaft). The spline engagement mechanically couples these two dimensions, allowing the full linear range measurement to be achieved through a compact rotational encoder on the motor rather than a long linear sensor.
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 solution effectively reduces friction and noise, enhances the sliding bar's durability and strength, and improves steering precision and assembly convenience by accurately determining the sliding bar's position using motor phase differences, thereby enhancing driver experience and reducing operational costs.
Implementation Method 1
a first spline formed on an inner circumferential surface of a cylinder provided inside a housing; and a sliding bar inserted into the cylinder, including a second spline engaged with the first spline
Implementation Method 2
a screw connected to a motor
Data Source
AI summary
A steer-by-wire type power steering apparatus according to embodiments disclosed herein includes a cylinder provided inside a housing and including a first spline on an inner circumferential surface thereof, and a sliding bar inserted into the cylinder and including a second spline engaged with the first spline and a screw connected to a motor, so that friction and noise can be reduced when a sliding bar connected to a tie rod so as to steer a wheel is slid, the durability and strength of the sliding bar can be improved, and the position of the sliding bar can be determined based on a phase difference between the rotation information items of respective motors.