Rack Guide O-Ring Groove Layout for Low-Force Assembly
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Solution Overview
Problem
In rack-and-pinion steering devices, the assembly of O-rings into annular grooves is challenging due to gaps between the O-ring and the groove, leading to air compression and high assembly forces.
Innovation Solution
The design incorporates an annular groove with a narrow and wide section, allowing the O-ring to have a crush margin in the narrow section, increasing the filling rate, and creating depth-direction gaps in the wide section to facilitate air discharge, reducing the assembly force required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an O-ring with a crush margin is used to increase the filling rate in the annular groove, then the reliability of sealing is improved, but the assembly force required to push the O-ring into the groove increases significantly due to air compression
Solution Approach 1:
The annular groove is segmented into two distinct sections: a narrow groove section with a width smaller than the O-ring cross-sectional diameter to provide crush margin for sealing reliability, and a wide groove section with a width larger than the O-ring cross-sectional diameter to provide air discharge paths. This segmentation allows the O-ring to be compressed for sealing while air can escape through the wider section, reducing assembly force.
Solution Approach 2:
Different sections of the annular groove are given different local qualities: the narrow groove section provides high compression and sealing capability, while the wide groove section provides low resistance and air discharge capability. This local differentiation allows each section to perform its specific function optimally without compromising the other.
2Manufacturing precision
If the O-ring is pushed into the annular groove with high force to ensure proper seating, then the manufacturing precision of assembly is improved, but the ease of operation during assembly deteriorates
Solution Approach 1:
The annular groove is divided into narrow and wide sections to enable sequential assembly: the O-ring first passes through the wide section with minimal resistance, then seats in the narrow section with proper compression. This segmentation makes assembly easier while ensuring precise seating in the narrow groove section.
Solution Approach 2:
The wide groove section acts as an intermediary that facilitates the assembly process by providing a low-resistance path for the O-ring to enter, before the O-ring reaches the narrow groove section where precise seating occurs. This intermediary section mediates between ease of insertion and precision of seating.
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 enables easy assembly of the O-ring by allowing air to be discharged, reducing the force needed to push the O-ring into place, and maintaining the durability of the adjustment cover.
Implementation Method 1
The coil spring is disposed between the pressure pad and the adjustment cover in a contracted state, and applies a pressing force to the pressure pad
Implementation Method 2
the O-ring is deformed, and an impact load input from the pressure pad to the adjustment cover is reduced
Data Source
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AI summary
A rack guide device includes: a housing wall having an internal space extending in an orthogonal direction, a first opening that opens toward a rack bar, and a second opening that opens from the internal space in a direction opposite to the rack bar; an adjustment cover that closes the second opening; a pressure pad that abuts on the rack bar from the first opening; and a coil spring and an O-ring disposed between the adjustment cover and the pressure pad. One of the adjustment cover and the pressure pad has a facing surface facing the other of the adjustment cover and the pressure pad. An annular groove is provided in the facing surface. An inner surface of the annular groove has an inner circumferential surface and an outer circumferential surface facing each other. The annular groove includes a narrow groove in which a groove width between the inner circumferential surface and the outer circumferential surface is smaller than a cross-sectional diameter of the O-ring before being assembled, and a wide groove in which a groove width is larger than the cross-sectional diameter of the O-ring before being assembled.