Accelerator Pedal Fastening Structure with Annular Space

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Solution Overview

Problem

Existing fastening structures, such as those used in accelerator pedal devices, often experience breakage due to large tensile stresses at the root of the screw thread groove, particularly when screws are inserted from the side opposite to the first fastened member, leading to potential chipping of the screwing hole edge.

Innovation Solution

A fastening structure is designed with an annular space between the edge of the screw insertion hole and the first fastened member, allowing the edge to bend into this space when compressed by the screw thread, thereby reducing tensile stress and preventing breakage, such as chipping, by providing a recessed area that accommodates the edge without compromising the screwing hole's integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the screw is inserted into the screw insertion hole of the second fastened member from the side facing away from the first fastened member and screwed into the first fastened member, then the fastening structure can be assembled, but a large tensile stress is generated in the root of the thread groove causing breakage of the screwing hole edge

Engineering Contradiction:

Improveassembly processVSAvoidscrewing hole edge strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent applies beforehand cushioning by providing an annular space between the first fastened member and the edge of the screw insertion hole before the screwing operation. This annular space acts as a cushioning region that absorbs the tensile stress generated during screwing, preventing the stress from concentrating at the screwing hole edge and causing breakage. The edge of the screwing hole can elastically deform into this pre-prepared space, avoiding catastrophic failure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The annular space serves as an intermediary element between the screwing hole edge and the first fastened member. It mediates the stress transfer during the screwing process, allowing the edge to deform into this intermediate space rather than directly transmitting the full tensile stress to the screwing hole edge, thereby preventing breakage while maintaining the fastening function.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Force

If the edge of the screwing hole is compressed between the cover and screw thread, then the screw can fasten the members, but tensile stress causes chipping of the screwing hole edge

Engineering Contradiction:

Improvefastening forceVSAvoidchipping of screwing hole edge

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The annular space is provided beforehand as a cushioning region that prevents the screwing hole edge from direct contact with the compressive force between the cover and screw thread. When the screw is tightened, the edge can deform into this pre-existing space, absorbing the harmful compressive and tensile stresses that would otherwise cause chipping, while still maintaining adequate fastening force.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10457143B2Fastening structure and accelerator pedal device using same

Publication Date: 2019.10.29 DENSO CORP

AI summary

In a fastening structure and an accelerator pedal device using the fastening structure, a screw is inserted into a screw insertion hole of a cover from a side of the cover facing away from a housing, and the screw is screwed into a screwing hole of a fastening portion of the housing. An annular space is provided between an edge of the screw insertion hole and the fastening portion.