Crankcase Cover Layout for Compact Clutch Drive Packaging

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Solution Overview

Problem

Existing crank case structures with integrated engine and transmission have a large front-rear dimension due to the layout of the crank case cover and clutch drive unit, limiting further size reduction of the power unit.

Innovation Solution

A crank case structure with a clutch drive unit attached to the crank case cover, a drive sprocket positioned rearward of the clutch drive unit, and a chain cover partially overlapping the crank case cover, along with a protective plate, to reduce the front-rear dimension and enhance harness protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the clutch drive unit is attached directly to the crank case, then the structure is simple, but the front-rear dimension of the crank case becomes larger

Engineering Contradiction:

Improvestructural simplicityVSAvoidfront-rear dimension

Core Design Contradiction:

Device complexityVSLength of moving object

Solution Approach 1:

The clutch drive unit is attached to the crank case cover rather than directly to the crank case body, utilizing the lateral dimension (width direction) to position the clutch drive unit. This dimensional shift allows the push rod to pass through the crank case cover in the width direction, thereby reducing the front-rear dimension of the crank case while maintaining structural integrity and functional simplicity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If the crank case cover and clutch drive unit are arranged in front-rear direction, then the layout is conventional, but the power unit size cannot be reduced further

Engineering Contradiction:

Improvelayout flexibilityVSAvoidpower unit size

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The invention repositions the clutch drive unit from the front-rear axis to the lateral axis by attaching it to the crank case cover. The push rod passes through the crank case cover in the width direction, enabling compact arrangement of components in the lateral dimension and thereby reducing the overall power unit size without compromising layout flexibility

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The clutch drive unit is integrated with the crank case cover structure, where the push rod passes through a through-hole in the crank case cover. This nested arrangement allows the clutch drive unit to be positioned within the lateral space of the crank case assembly, achieving compact integration and reducing the power unit's front-rear dimension

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentUS12455001B2Crank case structure

Publication Date: 2025.10.28 HONDA MOTOR CO LTD

AI summary

A crank case structure that can reduce a front-rear dimension of the crank case to reduce the size of a power unit. A crank case structure adapted to a crank case (9) that houses a crankshaft (C) of a power unit (P), including a crank case cover (20) attached to a side surface of the crank case (9), a push rod (31) that is disposed parallel to the crankshaft (C) and reciprocates to disengage a clutch (CL), and a clutch drive unit (30) that reciprocates the push rod (31). A through hole (32), through which the push rod (31) passes, is formed within an area of a sealing surface (29), the sealing surface (29) is formed in the crank case (9) to attach to the crank case cover (20), and the clutch drive unit (30) is attached to the crank case cover (20).