Crankcase Vacuum Generation for Reducing Reverse Blow-by

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Solution Overview

Problem

Internal combustion engines, particularly those using the Otto engine combustion process, face challenges in reducing particle number emissions due to reverse blow-by effects, where engine oil is sucked into the combustion chamber, leading to increased particle emissions, especially during idling and overrun phases, as existing venting systems do not adequately account for the pressure differences between the crankcase and combustion chamber.

Innovation Solution

A device that includes a crankcase, a combustion chamber, and an oil separator connected via a line device to the charge air feed line, with a pressure setting device to reduce the pressure difference between the crankcase and combustion chamber, utilizing a control means, such as a 3/2-way valve, to manage vacuum levels and prevent oil entry into the combustion chamber, thereby reducing reverse blow-by and particle emissions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the crankcase is vented into the charge air feed line after the throttle valve, then the crankcase ventilation function is achieved, but the negative pressure difference between combustion chamber and crankcase causes reverse blow-by and oil entry into the combustion chamber

Engineering Contradiction:

Improvecrankcase ventilationVSAvoidreverse blow-by and oil entry

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The invention changes the pressure parameter in the crankcase by introducing a vacuum generation device that creates negative pressure relative to the combustion chamber. This pressure parameter change prevents the reverse blow-by effect by ensuring that gas and oil cannot be sucked from the crankcase into the combustion chamber during engine operation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention introduces a vacuum generation device as an intermediary component between the crankcase and the charge air feed line. This intermediary actively manages the pressure relationship between the crankcase and combustion chamber, preventing direct harmful interaction while maintaining ventilation functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If oil accumulates in the combustion chamber during overrun and idling, then the crankcase ventilation system is functioning, but the accumulated oil burns during load increase causing high particle emissions

Engineering Contradiction:

Improvecrankcase ventilation efficiencyVSAvoidparticle emissions from oil ash

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The invention changes the pressure parameter to maintain continuous negative pressure in the crankcase, preventing oil from being transported to the combustion chamber during transient operating conditions. This eliminates the accumulation and subsequent burning of oil that causes particle emissions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The vacuum generation device performs preliminary action by establishing and maintaining the pressure differential before oil accumulation can occur. This preventive measure stops the reverse blow-by process before oil can be sucked into the combustion chamber during overrun or idling phases.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If the throttle valve is closed during overrun and idling, then the engine operates efficiently, but the negative pressure in the intake manifold causes reverse blow-by from crankcase to combustion chamber

Engineering Contradiction:

Improveengine efficiency during overrun and idlingVSAvoidreverse blow-by

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The invention applies a counteracting pressure force by generating vacuum (negative pressure) in the crankcase that opposes the pressure differential created by the closed throttle valve. This counter-pressure prevents the reverse blow-by effect while allowing the throttle valve to remain closed for efficient engine operation.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

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 effectively reduces particle number emissions by minimizing oil entry into the combustion chamber during low load and overrun conditions, enhancing engine performance and compliance with stricter emission regulations by controlling the vacuum levels in the crankcase.

Implementation Method 1

at least one pressure setting device for setting a vacuum in the crankcase

Methodology Applied

Scientific EffectVacuum generation: Vacuum

Implementation Method 2

The reduced pressure difference between the combustion chamber and the crankcase causes a reduced oil entry into the combustion chamber and/or a reduced reverse blow-by

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentEP3101243B1Generation of a vacuum in the crankcase for reducing particles numbers

Publication Date: 2019.12.25 MAN TRUCK & BUS SE

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AI summary

The invention relates to a device (V) for an internal combustion engine, in particular for generating a vacuum in a crankcase (1) and/or for venting a crankcase (1), comprising a crankcase (1), at least one combustion chamber (4), at least one oil separator (16) connected to the crankcase (1) and at least one pressure adjusting device (17), which is designed to adjust a vacuum in the crankcase (1) during operation, so that the pressure difference between the crankcase (1) and the combustion chamber (4) is advantageously reduced.