Accelerator Pedal Failure Region Design

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Solution Overview

Problem

The existing accelerator pedal devices often experience a hysteresis mechanism failure, leading to excessive pressing force that causes the return spring to be exposed and potentially fall out of the support member, preventing the accelerator pedal from returning to a fully closed position.

Innovation Solution

The accelerator device incorporates a support member with a first cover and a second cover, where the first cover has a failure region with a thinner thickness and a concave cavity, and the second cover has a projected portion that engages with the first cover, allowing the device to absorb excessive pressing forces and prevent the return spring from being exposed, ensuring the pedal can return to a fully closed state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the pressing force from the friction member is excessive, then the hysteresis mechanism provides sufficient resistance, but the support member breaks and the return spring is exposed

Engineering Contradiction:

Improvepressing forceVSAvoidsupport member strength

Core Design Contradiction:

ForceVSStrength

Solution Approach 1:

The first cover is divided into a body section and a failure region with different thicknesses and strengths. The failure region acts as a sacrificial element that segments the load path, allowing the body section to maintain structural integrity while the failure region absorbs excessive pressing forces through controlled deformation or breakage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The failure region is designed as a predetermined weak point that absorbs excessive pressing forces before they can reach and damage the main body of the first cover or cause the return spring to be exposed. This beforehand cushioning mechanism protects the critical components by sacrificing a non-critical portion of the cover.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Strength

If the first cover body section is made thicker for strength, then the cover becomes more durable, but excessive pressing force cannot be absorbed safely

Engineering Contradiction:

Improvecover strengthVSAvoidprotection against spring exposure

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The first cover exhibits non-uniform thickness and strength distribution: the body section has greater thickness for overall structural strength, while the failure region has reduced thickness to create a controlled weak point. This local quality variation allows the cover to simultaneously achieve durability in critical areas and controlled failure in non-critical areas.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The potential harm of complete cover failure is converted into a beneficial controlled failure mechanism. The failure region is designed to break or deform under excessive loading, which actually protects the return spring and main cover body by providing a predetermined failure path that prevents catastrophic failure and spring exposure.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If the failure region is made thinner, then excessive pressing force is absorbed more easily, but the cover may become too weak for normal operation

Engineering Contradiction:

Improvefailure protectionVSAvoidcover strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The failure region's reduced thickness is localized to a specific area that does not compromise the overall structural integrity of the cover during normal operation. The body section maintains sufficient thickness for strength, while the failure region's thinner design enables controlled failure only when excessive forces are applied beyond normal operating conditions.

Inventive Principle:

Principle #3Local quality

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 design effectively prevents the return spring from falling out and ensures the accelerator pedal can return to a fully closed position by deforming or breaking the failure region before the rest of the cover, maintaining the pedal's functionality and preventing spring exposure.

Implementation Method 1

The biasing member biases the shaft to rotate in the accelerator closing direction

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

The friction member is positioned between the boss portion and the support member, and is pressed against an inner wall of the support member when the boss portion rotates in the accelerator opening direction

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS9201443B2Accelerator device

Publication Date: 2015.12.01 DENSO CORP

AI summary

An accelerator device includes a first cover that provides an internal space for housing a return spring and a failure region where the first cover engages a second cover. The failure region has a thickness configured to be thinner than a thickness of a body of the first cover. When a pedal rotates to open an accelerator, a second cover side friction member creates a force that pushes the second cover toward an outside of the device. The force is relayed to a contact portion of the first cover via a contact portion of the second cover and causes a failure of the failure region. As a result, the return spring is prevented from falling out of the internal space when the body breaks.