Driven Steering Shaft Speed Multiplication
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Solution Overview
Problem
Column-drive electric power steering systems are not suitable for mid-range vehicles due to the high torques required, which necessitate large and heavy steering shafts and joints, limiting their use and design flexibility.
Innovation Solution
An electric power steering system with a driven steering shaft and rotating steering wheel hub, featuring a transmission gear that translates rotational movement of the upper steering shaft at a first angular velocity into a higher rotational movement of the lower steering shaft, allowing the lower steering shaft to be connected directly to the steering gear without a reduction gear, and utilizing a toothed engagement or belt transmission to couple the servo drive to the lower steering shaft, thereby reducing torque requirements and component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a column-drive electric power steering system is used in mid-range vehicles, then the steering assistance can be provided, but the steering shaft and joints must be dimensioned excessively large and heavy to handle the high torques
Solution Approach 1:
The steering shaft is divided into an upper steering shaft and a lower steering shaft with different rotational speeds. The upper steering shaft rotates at the steering wheel speed while the lower steering shaft rotates at a higher speed (by factor 1.4-2.0), allowing each shaft to be optimized for its specific torque requirements. This segmentation enables the lower shaft to transmit power at higher speed with lower torque, reducing its required dimensions and weight.
Solution Approach 2:
The rotational speed parameter of the steering shaft is changed by introducing a transmission gear between the upper and lower steering shafts. The lower steering shaft rotates at a higher angular velocity (by a factor of 1.4 to 2.0) compared to the upper steering shaft. This parameter change allows the system to transmit the same power with lower torque on the lower shaft, enabling smaller and lighter shaft dimensions.
2Weight of moving object
If a transmission gear is introduced between the upper and lower steering shafts to increase angular velocity, then the torque requirements are reduced, but the device complexity increases
Solution Approach 1:
The transmission gear is merged with the existing steering column structure. The upper steering shaft is connected to an input shaft of a two-shaft transmission, and the output shaft of this transmission is connected to the lower steering shaft. This merging integrates the speed-increasing function into the existing steering system without adding separate, complex transmission components.
Solution Approach 2:
The transmission gear serves multiple functions: it increases the rotational speed from the upper to lower steering shaft, reduces the torque requirements on the lower shaft, and enables the system to handle both light and heavy vehicle applications. The same transmission mechanism provides both speed multiplication and torque reduction, making it a multi-functional component that justifies its inclusion.
3Speed
If the lower steering shaft rotates at higher angular velocity, then smaller shaft dimensions are possible, but the steering gear must adapt to increased speed without additional reduction gears
Solution Approach 1:
The steering gear parameters are adapted to the increased rotational speed of the lower steering shaft. The pinion gear on the lower steering shaft meshes with the rack in a manner that compensates for the higher speed. The gear ratio and tooth geometry are selected to ensure proper engagement and force transmission at the elevated rotational speeds, eliminating the need for additional reduction gears while maintaining effective steering control.
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
Enables the use of smaller, lighter steering shafts and joints, reducing weight, noise, and backlash while maintaining sufficient power assistance for medium-heavy vehicles, allowing for a more compact and efficient design that adapts to increased angular velocity without additional structural complexity.
Implementation Method 1
a transmission gear being switched on between the upper steering shaft and the lower steering shaft, which translates rotational movement of the upper steering shaft at a first angular velocity into rotational movement of the lower steering shaft at a second angular velocity
Implementation Method 2
an auxiliary power assistance device which is coupled to the steering shaft via a toothed engagement to introduce a torque derived from the steering movement
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to an electrical power steering system for a motor vehicle with an upper steering shaft (2) having on the one end thereof a rotationally fixed steering wheel (1), a lower steering shaft (4) which can be connected to a transmission part for transfer of the rotation to a lower steering shaft (6, 16) in a steering transmission for conversion of the rotation into a translational motion for pivoting of at least one of the steerable wheels of the motor vehicle, at least one articulation (5, 15) which is arranged between the lower steering shaft (4) and the steering transmission, an auxiliary power supporting device (7, 17) which is connected via a toothed engagement (30, 31) to the steering shaft to apply a torque derived from the steering motion, wherein between the upper steering shaft (2) and the lower steering shaft (4) there is a transmission gearing (20 – 22) which converts a rotational motion at a first angular rate of the upper steering shaft (2) into a rotational motion of the lower steering shaft (4) at a second angular rate, wherein the second angular rate is greater than the first angular rate, and wherein the auxiliary power supporting device (7, 17) is connected via the toothed engagement (30, 31) to the lower steering shaft (4) to provide propulsion power.