Screw Tightening Structure with Negative Driving Angle
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Solution Overview
Problem
Existing screw tightening structures face issues with come-out, deformation, and wear of recess and mating convex sections due to the orientation of the driving angle, leading to difficulties in applying increased tightening torque.
Innovation Solution
The screw tightening structure is designed with a recess and mating convex sections featuring torque transfer portions connected by concave circular arc contours, where the driving angle is set to be ≤0°, and the radius and center-point diameter are optimized to minimize come-out and maximize torque transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the driving angle θ is positive (recess end face configuration perpendicular to center line), then the structure is simple to manufacture, but come-out occurs and torque application becomes difficult
Solution Approach 1:
The patent changes the driving angle parameter from positive (θ>0°) to negative (θ≤0°), which fundamentally alters the force direction. This parameter change transforms the recess configuration from perpendicular to center line to an inclined configuration, preventing come-out while enabling increased torque application.
2Device complexity
If the driving angle θ is positive, then the recess configuration is simple, but deformation and wear of torque transfer portions occur
Solution Approach 1:
The patent modifies the driving angle parameter to negative values (θ≤0°), which changes the force application geometry. This prevents the surface perpendicular force from causing come-out and reduces deformation and wear of the torque transfer portions, thereby improving reliability.
3Reliability
If come-out is suppressed by adjusting driving angle, then torque transfer efficiency increases, but the recess configuration becomes more complex
Solution Approach 1:
The patent applies a negative driving angle (θ≤0°) which, while changing the recess configuration, provides a systematic and standardized solution. The configuration becomes predictable and manufacturable through defined geometric parameters, balancing complexity with performance.
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(b)
AI summary
Outer peripheral ends of torque transmitting section (20) of fitting projections (16) are made to contact with the side wall surfaces of torque transmitting sections (18) of recesses (12), and tightening torque is transmitted to a screw (10) through force application points (Q) which are the portions of the contact. In this process, in an end surface shape perpendicular to the center line (O1) of a recess (12) including a force application point (Q), the driving angle (θ) of a force (F) perpendicular to the surface is 0° or less. Therefore, the force (F) perpendicular to the surface is applied to the side wall of the recess (12) in a tangential direction about the center axis (O1) or in an inward direction. In comparison with a conventional case in which the force (F) perpendicular to the surface acts outwardly (0°<θ), a cam-out effect causing a screw tightening tool (14) to be dislodged from the recess (12) is less likely to occur. As a result, deformation of the recesses (12) and damage to or wear of the fitting projections (16) are suppressed, and the screw (10) can be considerably easily tightened with large tightening torque.