Transfer-Case Bolt Structure That Limits Tightening Load
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Solution Overview
Problem
The use of synthetic resin transfer cases in multi-purpose vehicles can lead to cracking and deformation due to excessive fastening with metal connection bolts, and existing measures to prevent this, such as casting metal pieces, increase costs.
Innovation Solution
A fixation mechanism with a connection bolt featuring a screw shaft, a large-diameter shaft portion, and a flange portion, where the gap between the first and second contact surfaces limits the tightening amount to prevent excessive force on the transfer case, using a screw hole and through hole configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a connection bolt is used to fasten the synthetic resin transfer case to the metal attaching target, then the transfer case can be securely connected and fixed, but the transfer case may be cracked or deformed due to excessive fastening force
Solution Approach 1:
A large-diameter shaft portion is introduced as an intermediary element between the connection bolt and the transfer case. This shaft portion has a larger diameter than the bolt shaft, creating a stepped structure that reduces stress concentration on the synthetic resin transfer case while maintaining the connection strength through the bolt-fastened large-diameter shaft portion configuration.
2Object-affected harmful factors
If metal pieces are cast on and/or around the connection bolt passage to prevent cracking, then the transfer case can be protected, but the manufacturing cost increases
Solution Approach 1:
The connection structure is segmented into distinct components: the connection bolt, the large-diameter shaft portion, and the transfer case. This segmentation allows the use of standard connection bolts without requiring additional metal casting operations, thereby preventing cracking through the structural design rather than through costly manufacturing processes.
3Weight of moving object
If the transfer case is made of synthetic resin to reduce weight and facilitate processing, then the weight is reduced and processing is easier, but the transfer case becomes susceptible to cracking and deformation under fastening loads
Solution Approach 1:
The connection structure employs a composite configuration combining the synthetic resin transfer case with the large-diameter shaft portion and connection bolt. This composite structure allows the synthetic resin case to maintain its weight and processing advantages while the reinforced connection structure (bolt + large-diameter shaft) compensates for the lower strength of synthetic resin by distributing and reducing stress concentration.
Data Source
AI summary
A transfer-case attaching device includes a fixation mechanism. The fixation mechanism includes a connection bolt. The connection bolt includes a screw shaft portion, a large-diameter shaft portion, and a flange portion. The large-diameter shaft portion has a first contact surface at an end portion of the large-diameter shaft portion. The flange portion has a second contact surface at an end portion of the flange portion. A gap between the first contact surface and the second contact surface is set to a tightening-amount limited region, in which tightening of the connection bolt with respect to a transfer case is restricted to or below a predetermined tightening amount.