Stroke Sensor Sealing via Axial Pressing Force

Solution Overview

Problem

The sealing property between the rubber boot and the case in stroke sensors for saddle riding type vehicles is compromised due to degradation of the rubber boot's elastic force, leading to reduced sealing effectiveness.

Innovation Solution

A stroke sensor design featuring a flange surface on the housing with an axial direction seal and a fixation member that maintains contact with the flange surface, along with a radial direction seal and a bending/stretching part to ensure consistent sealing, even when the elastic force of the cover is reduced, using a cover with an internal pressure adjusting mechanism to prevent water ingress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a rubber boot is used to seal the case, then the sealing property is initially good, but the sealing property degrades over time due to elastic force reduction

Engineering Contradiction:

Improvesealing propertyVSAvoidservice life of rubber boot

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The sealing system is divided into two independent seals: a radial direction seal (first seal) that seals between the cover and shaft, and an axial direction seal (second seal) that seals between the cover and housing. This segmentation ensures that degradation of one seal does not compromise the entire sealing system, as each seal operates independently to maintain waterproofing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the sealing mechanism from relying solely on elastic force (which degrades over time) to a mechanical pressing force system. The fixation member with pressing portion applies constant mechanical pressure on the axial direction seal against the housing, maintaining sealing effectiveness regardless of rubber boot degradation. This parameter change from elastic to mechanical force resolves the time-dependent sealing degradation issue.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the cover is made elastic to allow relative movement, then the cover can accommodate shaft movement, but the sealing property degrades when elastic force is reduced

Engineering Contradiction:

Improverelative movement capabilityVSAvoidsealing property

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The cover is designed with dynamic characteristics including a bending/stretching part that can deform elastically to accommodate relative movement between the shaft and housing. The folding part allows the cover to expand and contract while maintaining the sealing function through the fixation member's constant pressing force on the axial direction seal.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The fixation member acts as an intermediary between the cover and the seals. It provides a stable mounting structure that maintains constant pressing force on both the radial direction seal and axial direction seal, ensuring that sealing effectiveness is not compromised by the elastic deformation and movement of the cover.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If a simple cover design is used, then the device complexity is low, but the sealing property cannot be maintained when elastic force degrades

Engineering Contradiction:

Improvecover structureVSAvoidsealing property

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The sealing system is divided into two independent seals: a radial direction seal (first seal) that seals between the cover and shaft, and an axial direction seal (second seal) that seals between the cover and housing. This segmentation ensures that degradation of one seal does not compromise the entire sealing system, as each seal operates independently to maintain waterproofing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fixation member acts as an intermediary between the cover and the seals. It provides a stable mounting structure that maintains constant pressing force on both the radial direction seal and axial direction seal, ensuring that sealing effectiveness is not compromised by the elastic deformation and movement of the cover.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The solution ensures reliable sealing by maintaining contact pressure and preventing water entry, even with reduced elastic force, thereby enhancing the sealing property and maintaining the internal pressure within the cover.

Implementation Method 1

a fixation member that presses the axial direction seal to be in contact with the flange surface is further provided

Methodology Applied

Scientific EffectPressing force: Mechanical Force

Implementation Method 2

a radial direction seal that is in close contact with the shaft in a radial direction may be provided on the cover

Methodology Applied

Scientific EffectElastic force: Elasticity

Implementation Method 3

the cover may include an internal pressure adjusting part that adjusts an internal pressure by expanding or shrinking

Methodology Applied

Scientific EffectInternal pressure: Pressure Increase

Data Source

PatentUS10487941B2Stroke sensor and saddle riding type vehicle

Publication Date: 2019.11.26 NIPPON SEIKI CO LTD

AI summary

A stroke sensor includes a cover that covers a slide end on a protrusion side of a shaft in a slide region between the shaft and a housing while allowing a relative movement between the shaft and the housing, wherein a flange surface the extends radially outward from the slide end is provided on the housing, an axial direction seal that is in close contact with the flange surface in the axial line direction is provided on the cover, and a fixation member that presses the axial direction seal to be in contact with the flange surface is further provided.