Coaxial Steering Actuator Layout for Compact Steer-by-Wire
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Solution Overview
Problem
Conventional steering devices with a steer-by-wire configuration often result in large-sized device configurations due to the orthogonal rotational axes of the worm shaft and worm wheel, which limits their applicability and space efficiency.
Innovation Solution
The steering device integrates a gear with the rotor output shaft to input rotational power to the speed reducer, aligns the motor, control device, and speed reducer along a central axis, and employs a compact eccentric differential speed reducer and redundant control devices to minimize size and width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the worm shaft and worm wheel have rotational axes orthogonal to each other, then the steering device can provide assisting force in steering directions, but the device configuration becomes large-sized
Solution Approach 1:
The motor and speed reducer are merged into a single integrated unit, eliminating the need for separate mounting spaces. The rotor output shaft directly integrates the gear that serves as input to the speed reducer, combining multiple functional elements into one compact structure that reduces overall device footprint while maintaining steering assistance capability.
Solution Approach 2:
The patent transitions from an orthogonal axis configuration (worm shaft perpendicular to worm wheel) to a collinear axis configuration (motor, control device, and speed reducer aligned along the same central axis). This dimensional reorganization allows components to be stacked along the axial direction rather than spreading out in perpendicular planes, significantly reducing the device's planar footprint.
2Area of stationary object
If the motor, control device, and speed reducer are arranged along the same central axis, then the device width is reduced, but the structural complexity increases
Solution Approach 1:
Multiple functional components (motor, control device, speed reducer) are merged into a single integrated assembly that shares a common central axis. This consolidation reduces the number of separate mounting structures, alignment mechanisms, and inter-component linkages required, thereby reducing overall structural complexity despite the sophisticated internal arrangement.
Solution Approach 2:
The integrated unit serves multiple functions simultaneously: the motor provides driving force, the control device manages operation, and the speed reducer provides mechanical advantage. This multi-functionality in a single compact unit eliminates the need for separate structural supports and mounting mechanisms for each component, simplifying the overall structure.
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 configuration achieves a downsized steering device with improved space efficiency, allowing for applications in vehicles with various axle configurations and enhanced reliability through redundancy in control systems.
Implementation Method 1
a motor (M) disposed on the first surface (1A) side of the speed reducer (1)
Data Source
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AI summary
A steering device (W) according to one aspect of the disclosure includes: a speed reducer (1) configured to decelerate a rotational power input from one surface side while increasing a torque and output rotation from an output section (2) disposed on the other surface side; a motor (M) provided on the one surface side and configured to input the rotational power to the speed reducer (1); and a control device (C) for controlling the motor (M). The speed reducer (1) is connected to a steering unit provided on a vehicle, so as to cause the steering unit to steer a wheel by the torque. The motor (M) includes a rotor (MR) for generating the rotational power. The rotor (MR) includes a rotor output shaft (MS) disposed coaxially with an output axis of the output section (2). The motor (M) inputs the rotational power from one end side of the rotor output shaft (MS) to the speed reducer (1). The control device (C) is disposed on the other end side of the rotor output shaft (MS) coaxially with the rotor output shaft (MS) and includes a sensing unit (CS) for sensing rotation of the rotor (MR). The control device (C) includes: an inverter circuit (C3I, C4I) configured to generate an electric current for controlling the motor (M); and a coupling unit (K1, K2) electrically connecting between the inverter circuit (C3I, C4I) and the motor (M). The coupling unit (K1, K2) is disposed adjacent to the inverter circuit (C3I, C4I) and disposed to face the motor (M). The coupling unit (K1, K2) is further configured as a support structure detachably supporting a board (C3K, C4K) having the inverter circuit (C3I, C4I) provided thereon to a casing (M1) of the motor (M).