Steering Rack Adjust Screw Caulking for Stable Set Load
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Solution Overview
Problem
The existing steering device manufacturing methods experience fluctuations in the urging force of the rack retainer due to caulking work, leading to premature wear of the contact parts between the rack bar and pinion shaft, as external mechanical forces applied during caulking affect the set load adjustment.
Innovation Solution
A method involving a gear housing with a pinion shaft, rack bar, and rack retainer, where an urging member is placed between the rack retainer and adjust screw, with a caulking step that plastic deforms the region between the female and male screw parts after screwing in the adjust screw, followed by a set load adjustment to stabilize the urging force within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If caulking work is performed to suppress rotation of the adjust screw, then the adjust screw is fixed in position, but the urging force set by the adjust screw fluctuates due to external mechanical forces applied during caulking
Solution Approach 1:
The patent applies preliminary action by performing the caulking work before the set load adjustment. The adjust screw is caulked to the cylindrical part first to prevent rotation, and then the set load is adjusted by loosening and tightening the adjust screw. This sequence allows the caulking to establish a fixed position while the subsequent adjustment can precisely set the urging force without risk of rotation during the adjustment process itself.
Solution Approach 2:
The patent separates the functions of position fixation and load adjustment into distinct steps. The caulking operation extracts the position fixation function, while the subsequent loosening and tightening operations handle the load adjustment function. This separation allows each function to be optimized independently - caulking provides robust position stability, while the adjustment steps provide precise urging force control.
2Force
If the urging force becomes large due to caulking work, then the rack retainer strongly presses the rack bar, but the motion transmission between the rack bar and pinion becomes difficult and contact parts wear early
Solution Approach 1:
The patent employs feedback by adjusting the set load after caulking based on the actual conditions. The operator loosens the adjust screw to reduce the urging force to an appropriate level, ensuring that the rack retainer presses the rack bar with sufficient but not excessive force. This feedback adjustment prevents premature wear of contact parts while maintaining reliable motion transmission between the rack bar and pinion.
Solution Approach 2:
The patent changes the urging force parameter after caulking by loosening the adjust screw. This parameter adjustment reduces the urging force from its initial high value (caused by caulking) to an optimal value that ensures reliable motion transmission without causing excessive wear. The parameter change transforms the system from a high-force state to a balanced force state.
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 method reduces backlash and improves the fixing strength between the cylindrical and adjust screw parts, effectively suppressing fluctuations in the set load and preventing further impact-related fluctuations after the initial adjustment.
Implementation Method 1
the adjust screw includes an adjust screw main body part and a male screw part provided on an outer peripheral side of the adjust screw main body part and screwed with the female screw part
Implementation Method 2
an urging member accommodated in the rack retainer accommodation part so as to be arranged between the rack retainer and the adjust screw
Implementation Method 3
a taper part provided at an inner peripheral edge portion of the cylindrical part of an outer side end portion of a pair of end portions of the cylindrical part
Data Source
AI summary
A cylindrical part of a rack retainer accommodation part and an adjust screw are caulked such that a plastic deformation region by caulking straddles both a female screw part of the cylindrical part and a male screw part of the adjust screw, and the adjust screw is loosened to a point where a set load that is a force by which the rack retainer urges a rack bar falls within a predetermined range. After the set load adjusting step, the caulking step is not performed again, and fluctuations in the set load associated with the impact of caulking work after the set load adjusting step can be suppressed. Thus, it is possible to suppress fluctuations in the urging force of the rack retainer applied to the rack bar caused by caulking work which stops the rotation between the rack retainer accommodation part and the adjust screw.