Oil Return Structure for PCV Systems

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Solution Overview

Problem

Existing oil return structures for Positive Crankcase Ventilation (PCV) devices are prone to breakage due to engine vibrations and fluid pressure, and increasing pipe thickness to prevent breakage increases costs, while longer pipe lengths decrease drain efficiency and cause clogging.

Innovation Solution

The oil return structure features a flow path body with a pipe member that protrudes from the engine body's side wall, including a first straight pipe, a curved pipe, and a second straight pipe, with the oil discharge port positioned non-immersed in the oil pan and offset from the rotation axis, preventing backflow and reducing pipe length to mitigate breakage risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the return pipe is made longer to reach from the side wall to the oil pan, then the oil can be returned to the oil pan, but the pipe becomes prone to breakage due to engine vibration and fluid pressure

Engineering Contradiction:

Improvepipe breakage resistanceVSAvoidreturn pipe length

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The return pipe is repositioned to discharge into the crank chamber space rather than extending deep into the oil pan. This spatial reconfiguration reduces the pipe length exposed to vibration and pressure while maintaining the oil return function through the crank chamber oil collection space.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Strength

If the return pipe is made thicker to ensure strength, then the pipe breakage resistance improves, but the manufacturing cost increases

Engineering Contradiction:

Improvepipe strengthVSAvoidmanufacturing cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The pipe discharge position is strategically positioned in the crank chamber where oil naturally accumulates, allowing the pipe to discharge into a region with natural oil cushioning and reduced direct exposure to high-pressure oil jets, thereby reducing the required pipe wall thickness.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If the return pipe length is increased, then the oil can be returned to the oil pan, but the drain efficiency decreases and clogging occurs

Engineering Contradiction:

Improveoil drain efficiencyVSAvoidreturn pipe length

Core Design Contradiction:

ProductivityVSLength of moving object

Solution Approach 1:

The discharge position is moved from deep within the oil pan to the crank chamber region, creating a shorter and more direct oil return path that maintains high drain efficiency while preventing clogging through improved oil flow dynamics.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS11371399B2Oil return structure

Publication Date: 2022.06.28 ISUZU MOTORS LTD

AI summary

This oil return structure is provided with a flow passage body configured to return oil into an engine body which communicates with an oil storage section of the engine, the oil having been separated from a blow-by gas by an oil separation means. The upstream end of the flow passage body is connected to the oil separation means, at least a portion of the downstream side of the flow passage body protrudes into the engine body from the inner wall thereof, and an oil discharge opening at tire downstream end of the flow passage body is disposed at a position not immersed in oil within the oil storage section.