Compact Power Steering with Strain Wave Torque Multiplication
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Solution Overview
Problem
Conventional power steering systems for large vehicles do not fit in the limited space of small vehicles, and existing systems require high force to alter the axis of rotation, especially at low speeds on high-friction surfaces, necessitating a compact and efficient solution for torque multiplication without increased steering wheel rotation.
Innovation Solution
A compact power steering system utilizing a strain wave gear set and a flexible coupler with a compressible, resilient ring between a gear set element and a central shaft, which includes a motor with a rotor supported for rotation, a fixed housing, an eccentric inner ring, and a flexible band, along with a coupler having internal and external teeth that mesh to provide speed reduction and torque multiplication, allowing the system to be compact and efficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional power steering systems are used to multiply torque, then the force required to alter the axis of rotation is reduced, but the system size is too large for small vehicles
Solution Approach 1:
The patent places the strain wave gear set inside the steering column assembly, with the eccentric ring rotating within the flexible band that is constrained by the fixed housing. The motor rotor is nested within the gear set, creating a compact concentric arrangement where multiple components occupy the same spatial envelope, thereby reducing overall system volume while maintaining torque multiplication capability
Solution Approach 2:
The patent transitions from conventional radial gear arrangements to a strain wave gear mechanism that utilizes axial displacement and eccentric rotation. The eccentric ring rotates off-center, creating variable meshing points with the flexible band that enable torque multiplication through a different spatial dimension, allowing for a more compact design footprint
2Force
If gearing is used to multiply torque, then the force required is reduced, but the degree of rotation of the steering wheel must increase
Solution Approach 1:
The patent employs a strain wave gear set with a high reduction ratio that changes the mechanical parameters of the system. The gear set provides significant torque multiplication (reducing the torque by a factor of 10 or more) while maintaining a direct 1:1 rotational relationship between the steering wheel and the steering mechanism, eliminating the need for increased rotation degree
3Volume of moving object
If a compact gear set is used, then the system fits in limited space, but the system must still provide sufficient torque multiplication
Solution Approach 1:
The patent replaces conventional mechanical gear systems with a strain wave gear mechanism that uses elastic deformation and wave propagation principles. The flexible band deforms elastically as the eccentric ring rotates, creating a mechanical advantage that provides high torque multiplication in a compact form factor, substituting traditional rigid gear meshing with elastic wave-based force transmission
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 system effectively multiplies torque without increasing the steering wheel rotation, making it easier to drive small vehicles on high-friction surfaces by using a strain wave gear set and flexible coupler to absorb high-frequency oscillations and provide efficient torque multiplication within limited space.
Implementation Method 1
The flexible band may have a second set of external teeth that mesh in at least one circumferential region with the second set of internal teeth
Implementation Method 2
The first coupling element is fixed to the shaft and has a first set of external teeth. The second coupling element has internal teeth interspersed with the external teeth. The ring has compressible, resilient prongs extending between the internal teeth and the external teeth
Data Source
AI summary
A compact power steering system is suitable for small vehicles. A torque sensor on a steering shaft detects operator intention to turn. In response, a motor provides torque to assistance in rotating the steering shaft. A strain wave gear set multiplies the motor torque. A coupler having a torsional isolator links the gearbox output to the steering shaft.