Electric Power Steering Rack-and-Pinion Compact Design
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Solution Overview
Problem
Conventional power steering apparatuses with rack-and-pinion devices have poor mountability and design flexibility due to the need for long rack bars supported by bushes, and require additional space for electric steering assist devices, limiting their application in vehicles requiring responsive steering.
Innovation Solution
An electric power steering apparatus with a rack-and-pinion device where one end of the rack bar is connected to a swing arm member, and an electric steering assist force is applied to the other swing arm member, allowing the rack-and-pinion device to be smaller and more flexible in design, with a configuration that includes a pinion integral with the pinion shaft and pressing devices to support the rack bar, reducing the need for external bushes and enhancing mountability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a rack-and-pinion device with a reciprocating rack bar supported by rack bushes at both ends is used, then the steering apparatus can assist driver's steering operation and reduce power transmission loss, but the rack bar must be long which results in poor mountability and poor degree of freedom in vehicle design
Solution Approach 1:
The invention divides the swing arm mechanism into left and right separate swing arm members, each with its own arm portion that can swing independently. This segmentation allows the rack-and-pinion device to be more compact while maintaining steering assistance functionality, improving mountability without increasing power transmission loss.
Solution Approach 2:
The invention changes the configuration from a traditional long rack bar extending in one dimension to a compact arrangement where the rack bar connects to arm portions that swing in an arc. This dimensional change in the motion path allows for a shorter rack bar length while achieving the same steering effect, thereby improving vehicle design flexibility.
2Stability of the object's composition
If a rack-and-pinion device is made longer to support rack bushes at both ends, then the structure is more stable, but the mountability to vehicle and degree of freedom in design are reduced
Solution Approach 1:
The invention merges the support function into the swing arm members themselves, where the arm portions act as the supporting structure. By combining the support function with the swinging motion function in the same components, the need for separate rack bushes at both ends is eliminated, allowing for a shorter, more flexible rack bar design that maintains structural stability.
3Speed
If an electric steering assist force applying device is provided in a rack-assist type rack-and-pinion device, then steering responsiveness is improved for automatic steering, but the device must be longer which further reduces mountability
Solution Approach 1:
The invention segments the electric steering assist function to be applied to the right swing arm member separately from the rack-and-pinion device. This allows the rack-and-pinion device to remain compact while still achieving responsive steering through the dedicated electric assist on one side, improving both responsiveness and mountability.
Solution Approach 2:
The invention uses the relay rod as an intermediary to transmit the electric steering assist force from the right swing arm member to the left swing arm member. This intermediary mechanism allows the electric assist device to be positioned separately from the rack-and-pinion device, reducing overall length while maintaining steering responsiveness.
Data Source
AI summary
An electric power steering apparatus includes left and right swing arm members, right and left tie rods pivotally connected at inner ends to arm portions of the swing arm members via a relay rod pivotally connected to the arm portions at both ends, a rack-and-pinion device in which one end of a rack bar is connected to the arm portion of one of the swing arm members, and a steering input transmission system that transmits a steering input to the rack-and-pinion device. An electric steering assist force applying device is connected to the arm portion of the other swing arm member, and applies a force to assist the other swing arm member to swing.