Crankcase Spiral Opening and Loop Guide Integration

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Solution Overview

Problem

Existing OHC internal combustion engine crankcase structures require multiple components and result in stress concentration due to the tumbler-like shape of openings, leading to increased weight and complexity.

Innovation Solution

A crankcase structure with a spiral inner peripheral surface and a loop guide-engaging recess integrated into the outer wall, combined with a loop-retaining member, reduces stress concentration and weight by dispersing loads through a thicker reinforced portion, and integrates components to minimize parts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If a tumbler-like shape opening is formed in the crankcase, then the loop guide-engaging recess can be positioned, but stress concentration occurs in the constricted portion leading to increased wall thickness and weight

Engineering Contradiction:

Improveopening shapeVSAvoidcrankcase weight

Core Design Contradiction:

ShapeVSWeight of stationary object

Solution Approach 1:

The opening is formed with a substantially semicircular cross-section shape instead of a tumbler-like shape, eliminating constricted portions and stress concentration points. This curved geometry allows the loop guide-engaging recess to be positioned on the outer periphery while maintaining uniform wall thickness and reducing overall crankcase weight.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of manufacture

If the loop guide-engaging recess and loop-retaining member are formed as separate components, then they can be independently manufactured, but the number of component parts increases

Engineering Contradiction:

Improveindependent manufacturingVSAvoidnumber of components

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The loop guide-engaging recess and loop-retaining member are integrally formed as a single unified component on the crankcase. This merging eliminates separate parts and assembly steps while maintaining the functional capabilities of both features, thereby reducing device complexity without sacrificing manufacturability.

Inventive Principle:

Principle #5Merging (Combining)

3Strength

If the crankcase wall is made thicker to avoid stress concentration, then structural integrity is improved, but the weight necessarily increases

Engineering Contradiction:

Improvecrankcase strengthVSAvoidcrankcase weight

Core Design Contradiction:

StrengthVSWeight of stationary object

Solution Approach 1:

By adopting a semicircular cross-section shape for the opening, the design eliminates stress concentration points that would otherwise require increased wall thickness. The curved geometry naturally distributes stresses uniformly, maintaining structural integrity with thinner walls and reduced weight.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS8051819B2Crankcase structure for an overhead-camshaft internal combustion engine, and engine incorporating same

Publication Date: 2011.11.08 HONDA MOTOR CO LTD

AI summary

An overhead-camshaft internal combustion engine having an outer wall of a crankcase provided adjacent a crankshaft, with a spiral-surfaced opening through which the crankshaft is passed. The outer crankcase wall is integrally provided with a loop guide engaging recess formed thereon. The loop guide engaging recess supports a base end portion of a loop guide for guiding an endless chain. A loop-retaining member for preventing the timing endless chain from dropping is arranged at a position on the lower side of a loop drive sprocket integrally formed at an end portion of the crankshaft.