Rack Guide Geometry for Quiet Steering and Easier Manufacturing
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Solution Overview
Problem
The manufacturing process for rack guides in rack and pinion steering devices is complex and costly due to the need for high accuracy in forming complementary surfaces between the rack guide and its base member to ensure quiet operation.
Innovation Solution
A rack guide design featuring an abutment portion and a recessed portion with different thickness dimensions, where the recessed portion gradually decreases in thickness away from the abutment portion, and an outer surface with a single curvature radius or inclination, utilizing materials like resin, porous metal, or sintered alloy for the abutment surface, simplifies the manufacturing process and maintains close contact with the base member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a curbed surface with multiple curvature radii is formed on the rack guide to reduce sliding resistance, then the rack bar can move smoothly, but the manufacturing process becomes complex and costly due to the need for complementary high-accuracy surfaces on the base member
Solution Approach 1:
The rack guide is divided into two distinct portions: an abutment portion with a curbed surface (multiple curvature radii) for smooth rack bar movement, and a simplified outer surface portion (single curvature radius) for mounting on the base member. This segmentation allows each portion to be optimized independently, reducing overall manufacturing complexity while maintaining operational smoothness.
Solution Approach 2:
Different surface qualities are applied to different locations of the rack guide: the abutment portion has a complex curbed surface with multiple curvature radii optimized for low sliding resistance, while the outer surface has a simpler single curvature radius optimized for easy manufacturing and assembly. This local differentiation resolves the contradiction between operational performance and manufacturing complexity.
2Object-affected harmful factors
If high accuracy close contact between rack guide and base member is ensured for quiet operation, then noise is reduced, but manufacturing costs increase due to complex processing requirements
Solution Approach 1:
The rack guide surface is segmented into an abutment portion for noise reduction through close contact and an outer surface portion for cost-effective manufacturing. The abutment portion maintains high accuracy for quiet operation, while the outer surface uses a simpler single curvature radius design that reduces manufacturing complexity and cost.
Solution Approach 2:
High accuracy close contact is locally applied only where necessary (abutment portion) for noise reduction, while other areas (outer surface) use simplified geometry for easier and cheaper manufacturing. This localized quality approach balances noise control requirements with manufacturing economy.
3Ease of manufacture
If a single curvature radius is used for the outer surface of the rack guide, then manufacturing is simplified and costs are reduced, but the close contact with the base member may be compromised
Solution Approach 1:
The rack guide is segmented into an abutment portion and an outer surface portion. The outer surface portion uses a single curvature radius for simplified manufacturing, while the abutment portion maintains the necessary geometric complexity for accurate contact with the base member and smooth rack bar operation.
Solution Approach 2:
Different geometric complexities are applied locally: the outer surface uses simple single curvature radius for easy manufacturing, while the abutment portion uses complex multi-curvature radius geometry to ensure accurate contact and proper function. This local quality differentiation resolves the contradiction between manufacturing simplicity and contact precision.
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 design simplifies the shape of the rack guide's outer surface, allowing for easier close contact with the base member, reducing manufacturing costs while maintaining quiet operation and ensuring effective meshing of the pinion and rack bar.
Implementation Method 1
a spring pressing the rack guide toward the rack bar through the rack guide base member
Data Source
AI summary
A rack guide for a rack and pinion steering device, a rack and pinion steering device, and a manufacturing method for a rack guide for a rack and pinion steering device have a simple configuration with a close contact property being kept between a rack guide and a rack guide base member to ensure quietness. A rack guide for a rack and pinion steering device includes: a casing; a pinion to be slidably supported by the casing; a rack bar having a rack tooth meshed with the pinion; a rack guide including an abutment portion to which the rack bar is to be slidably abutted and a recessed portion, which is continued to the abutment portion, to be spaced from the rack bar; a rack guide base member for receiving the rack guide; and an urging unit to urge the rack guide against the rack bar through the rack guide base member.