Dual Exhaust Pipe Structure for Compact In-Line Engine Heat Retention

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Solution Overview

Problem

The existing exhaust pipe structure for in-line four-cylinder internal combustion engines is bulky due to collar members and lacks improved heat retention, which affects the efficiency of exhaust gas flow and catalyst activation.

Innovation Solution

The exhaust pipe structure is redesigned as dual pipes with an outer and inner configuration, where the outer pipes are directly welded at the downstream ends, and the inner pipes have recesses to prevent weld backbeads from affecting gas flow, allowing for compact arrangement and enhanced heat retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If collar members are used to connect exhaust pipes, then welding quality is improved (back bead prevented from affecting inner surface), but exhaust pipe size increases in the array direction

Engineering Contradiction:

Improvewelding qualityVSAvoidexhaust pipe size

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent applies nesting by placing the inner pipe (51) inside the outer pipe (50) to form a dual pipe structure. The inner pipe's recess (55) is positioned to overlap with the weld (61) between outer pipes, effectively hiding the weld back bead inside the recess and preventing it from protruding into the exhaust gas flow path. This nested configuration maintains compact exhaust pipe dimensions while ensuring welding quality.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

If collar members are disposed on outer peripheries of exhaust pipes, then connection reliability is improved, but heat retaining property deteriorates

Engineering Contradiction:

Improveconnection reliabilityVSAvoidheat retaining property

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent merges the connection function into the dual pipe structure itself by directly welding adjacent outer pipes (50) at their downstream ends. This eliminates the need for separate collar members, reducing thermal mass and improving heat retention. The weld (61) is contained within the recess (55) of the inner pipe, maintaining connection reliability while minimizing interference with heat flow.

Inventive Principle:

Principle #5Merging (Combining)

3Length of stationary object

If outer pipes are directly welded at downstream ends, then exhaust pipe size is reduced, but weld back bead may affect inner pipe flow path

Engineering Contradiction:

Improveexhaust pipe sizeVSAvoidweld back bead interference

Core Design Contradiction:

Length of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potentially harmful weld back bead into a beneficial feature by positioning the inner pipe's recess (55) to overlap with the weld (61). The recess captures and contains the back bead, transforming what would be a flow-obstructing defect into a design feature that ensures the back bead does not interfere with exhaust gas flow through the inner pipe.

Inventive Principle:

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

4Temperature

If dual pipe configuration is used, then heat retaining property is improved, but device complexity increases

Engineering Contradiction:

Improveheat retaining propertyVSAvoidpipe structure complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The dual pipe structure serves multiple functions simultaneously: the outer pipe (50) provides structural support and connection to adjacent pipes, while the inner pipe (51) carries exhaust gas flow. The recess (55) in the inner pipe serves dual purposes of defining the flow path and containing the weld back bead. This multi-functionality reduces the need for additional components, managing complexity while improving heat retention.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 configuration allows for compact exhaust pipe arrangement, improved heat retention, and efficient exhaust gas flow, enabling quicker catalyst activation and purification, while maintaining structural strength and visual appearance.

Implementation Method 1

the outer pipes (50) of adjacent ones of the exhaust pipes (40a, 40b, 40c, 40d) are directly welded with each other at the downstream ends

Methodology Applied

Scientific EffectWelding: Welding

Implementation Method 2

The exhaust pipes (40a, 40b, 40c, 40d) are each configured as a dual pipe including an outer pipe (50) and an inner pipe (51) disposed inside the outer pipe (50)

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentUS10794258B2Exhaust pipe structure for in-line four-cylinder internal combustion engine

Publication Date: 2020.10.06 HONDA MOTOR CO LTD

AI summary

An exhaust pipe structure for an in-line four-cylinder internal combustion engine includes: an in-line four-cylinder internal combustion engine; four exhaust pipes connected with respective exhaust ports in respective cylinders of the internal combustion engine; and a converging exhaust pipe connected with a converging portion at which downstream ends of all the exhaust pipes converge. In this exhaust pipe structure, the exhaust pipes are each configured as a dual pipe including an outer pipe and an inner pipe disposed inside the outer pipe. At the converging portion, the four exhaust pipes are arrayed linearly in parallel with each other, and the outer pipes of adjacent ones of the exhaust pipes are directly welded with each other at the downstream ends.