Steering Gear Preload Using Sector Tooth Tip Contact
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Solution Overview
Problem
Conventional steering devices require a separate plunger sliding-contact portion, leading to an increase in the size of the sector shaft in the axial direction, which is inefficient in terms of space and manufacturing cost.
Innovation Solution
A steering device with a preload applying mechanism that uses a plunger receiving hole at the ball nut, a forcing member, and a plunger to generate rotation torque by elastic contact with the tooth tip of the sector gear, eliminating the need for a separate pressed portion and simplifying the configuration to reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate plunger sliding-contact portion is provided on the sector gear, then the preload mechanism can adjust backlash between rack teeth and sector gear, but the size of the sector shaft in the axial direction increases
Solution Approach 1:
The invention merges the plunger sliding-contact portion with the sector gear tooth structure itself. The cam profile is formed directly on the tooth tip of the sector gear rather than as a separate component, thereby eliminating the need for additional axial space on the sector shaft while maintaining the preload adjustment function.
Solution Approach 2:
The sector gear tooth structure serves dual functions: it transmits mechanical power through gear engagement and simultaneously provides the cam profile surface for the preload adjustment mechanism. This multi-functionality eliminates the need for separate dedicated components for preload adjustment.
2Reliability
If a separate plunger sliding-contact portion is provided on the sector gear, then the preload mechanism can reduce backlash around neutral position, but the manufacturing cost increases due to additional components
Solution Approach 1:
By combining the cam profile formation into the sector gear manufacturing process itself, the invention eliminates the need for separate plunger sliding-contact portions and their associated mounting structures, thereby reducing part count and manufacturing complexity.
Solution Approach 2:
The invention extracts the cam profile function from a separate component and integrates it directly into the sector gear tooth structure, eliminating the disturbing part (separate plunger sliding-contact portion) that caused manufacturing complexity and cost increases.
3Device complexity
If the preload applying mechanism forces the ball nut by elastic contact with the tooth tip, then the configuration is simplified and manufacturing cost is reduced, but the mechanism must precisely control the contact point
Solution Approach 1:
The invention applies local quality by concentrating the preload adjustment function at a specific location (the tooth tip of the sector gear) with a precisely formed cam profile. This localized approach simplifies the overall mechanism while requiring high precision only at the critical contact point rather than throughout the entire system.
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 solution effectively suppresses the increase in sector shaft size and reduces manufacturing costs by integrating the preload mechanism within the existing structure, providing adequate engagement adjustment without the need for additional components.
Implementation Method 1
the preload applying mechanism forces the ball nut to one side in a rotation direction of the ball nut by a reaction force generated by elastic contact of the preload applying mechanism with the tooth tip of the central tooth
Data Source
AI summary
In a steering device (PS1) according to the present embodiment, a preload applying mechanism (6) provides a rotation torque to one side in a rotation direction of a ball nut (4) by a reaction force generated by elastic abutment of a plunger (61) on a tooth tip of a first sector tooth (321) of a sector gear (32). Therefore, in the steering device (PS1), unlike conventional steering device, there is no need to provide a pressed portion to be pressed by the plunger (61) separately from the sector gear (32). Increase in size of a sector shaft (3) due to formation of the pressed portion can therefore be suppressed.