Rack and Pinion Steering Axial Movement Prevention
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Solution Overview
Problem
Rack and pinion steering devices face challenges in supporting thrust loads when the snap ring detaches or breaks, leading to axial movement of the pinion shaft and potential failure, especially in high-output applications, and existing solutions either allow axial movement or increase manufacturing costs.
Innovation Solution
The design incorporates a pinion shaft with a large diameter shaft portion and a small diameter shaft portion, supported by a ball bearing and a needle bearing respectively, along with raised portions at the gear tooth roots, which prevent further axial movement when the snap ring fails by contacting the rack, maintaining support and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a snap ring is used to support the thrust load of the pinion shaft, then the thrust load can be supported, but the snap ring may detach or break under high output conditions, leading to axial movement of the pinion shaft
Solution Approach 1:
The patent incorporates raised portions at the gear tooth roots of the pinion as a preliminary protective measure. These raised portions are positioned to contact the rack before the snap ring can detach or break, preventing axial movement of the pinion shaft. This preliminary structural feature acts as a backup safety mechanism that activates only when the snap ring fails, thereby resolving the reliability issue without affecting normal operation.
2Reliability
If the snap ring is designed to prevent axial movement, then reliability improves, but manufacturing cost increases due to additional components or complex structures
Solution Approach 1:
The raised portions at the gear tooth roots serve multiple functions: they are integral to the gear tooth structure (formed during gear manufacturing), provide axial positioning under normal conditions, and act as a backup stop against the rack if the snap ring fails. This multi-functionality eliminates the need for separate axial positioning components, thereby improving reliability without increasing manufacturing cost.
Solution Approach 2:
The patent merges the axial positioning function with the existing gear tooth structure by incorporating raised portions during gear manufacturing. This integration combines the gear teeth and axial positioning features into a single structural element, eliminating the need for additional separate components and reducing manufacturing complexity and cost while ensuring reliable axial movement prevention.
3Reliability
If the pinion shaft is constrained to prevent axial movement, then reliability improves, but the complexity of the device increases due to additional support structures
Solution Approach 1:
The patent combines the axial positioning function with the existing gear tooth structure by incorporating raised portions during gear manufacturing. This integration merges the gear teeth and axial positioning features into a single structural element, eliminating the need for additional separate components and reducing device complexity while ensuring reliable axial movement prevention.
Solution Approach 2:
The raised portions at the gear tooth roots serve as a self-service backup mechanism. They are integral to the gear structure and automatically engage with the rack to prevent axial movement if the snap ring fails, without requiring any additional active control systems or complex support structures. The structure serves itself as a safety mechanism.
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 effectively restricts axial movement of the pinion shaft under thrust loads, ensuring continued performance and reducing manufacturing costs by preventing axial displacement and alerting drivers to potential issues through sound emission.
Implementation Method 1
The large diameter shaft portion 11 is axially supported at the housing 3 by a ball bearing (first bearing) 21
Implementation Method 2
The small diameter shaft portion 12 is axially supported at a bearing hole 33 which is configured on a lower side of the housing 3 by means of a needle bearing (second bearing) 24
Implementation Method 3
a rack and pinion steering device which transmits a steering force exerted to a steering wheel to a side of a wheel by way of a rack that is brought in mesh with a pinion
Data Source
AI summary
A rack and pinion steering device which can restrict a pinion shaft from moving in an axial direction even when a snap ring of supporting a thrust load of the pinion shaft is detached or broken, and in which when the snap ring is detached or broken, the pinion shaft is moved to an upper side in the axial direction. Then, a raised portion of the pinion on a side of a lower end face is brought into contact with an outer peripheral face of a rack. The pinion shaft does not move further in the axial direction. Therefore, the thrust load can be supported, and a predetermined performance of the rack and pinion steering device can be maintained.