Electric Power Steering Housing Bolt Boss Positioning
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Solution Overview
Problem
Existing power steering devices face limitations in enhancing steering assisting force without enlarging the housing size, as increasing motor output is constrained by power supply and enlarging the worm wheel diameter increases the housing size.
Innovation Solution
The design incorporates a unique housing configuration with a first housing and a second housing, where the second bolt boss is positioned closer to the first housing than the worm-wheel accommodating portion, allowing for a female-threaded connection that reduces the radial dimensions and enables a more compact design while maintaining steering assisting force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the diameter of the worm wheel is enlarged to raise the speed reduction ratio, then the steering assisting force is enhanced, but the radial size of the worm-gear case is enlarged so that the whole size of the housing is enlarged
Solution Approach 1:
The patent repositions the second bolt boss from the conventional location on the worm-wheel accommodating portion to a location closer to the first housing. This spatial reconfiguration in a different dimensional arrangement allows the bolt connection to pass through both housings more directly, enabling the worm wheel to be positioned more centrally without increasing the radial size of the worm-gear case, thus maintaining compact housing dimensions while achieving the required speed reduction ratio for enhanced steering assisting force
2Force
If the output of the motor is increased to enhance the steering assisting force, then the steering performance is improved, but the output is constrained by the limitation of supply power
Solution Approach 1:
The patent changes the mechanical parameter of the speed reduction ratio by enlarging the worm wheel diameter. This mechanical advantage allows the motor to operate within its power supply limitations while still delivering sufficient steering assisting force through the optimized gear transmission system, effectively resolving the contradiction between motor output constraints and steering performance requirements
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 allows for a downsized power steering device that enhances steering assisting force without increasing the housing size, improving positioning accuracy and reducing weight, while maintaining efficient power transmission.
Implementation Method 1
a bolt inserted from the first bolt boss toward the second bolt boss and fastening the first housing to the second housing
Implementation Method 2
a worm wheel provided on the pinion shaft; a worm shaft meshing with the worm wheel
Implementation Method 3
a worm connected with a drive shaft of a motor meshes with a worm wheel which rotates integrally with an auxiliary pinion
Implementation Method 4
a rack bar configured to transmit a steering manipulation of a steering wheel to the steerable road-wheel; a pinion shaft meshing with the rack bar
Data Source
AI summary
An electric power steering device includes a rack bar; a pinion shaft meshing with the rack bar; a worm wheel provided on the pinion shaft; a worm shaft meshing with the worm wheel; an electric motor provided on the worm shaft; a first housing accommodating at least a part of the rack bar and the pinion shaft and includes a first bolt boss formed with a through-hole; a second housing; and a bolt. The second housing includes a worm-wheel accommodating portion accommodating the worm wheel, and a second bolt boss provided to have a shorter distance to the first housing than that of the worm-wheel accommodating portion, and formed with a female-threaded portion. The second bolt boss is opposed to the first bolt boss to cause the female-threaded portion to be continuous with the through-hole of the first bolt boss. The bolt fastens the first housing to the second housing.