Hydraulic Vent Duct Design for Engine Valve Train Leakage

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Solution Overview

Problem

Internal combustion engines with hydraulically variable gas exchange valve trains face hydraulic leakage issues when stopped for prolonged periods, leading to a critical reduction in hydraulic fluid pressure, which prevents engine starting due to air entering the pressure chamber and fluid leakage.

Innovation Solution

The vent duct opens into a hydraulic reservoir below the normal fluid level, preventing air from being sucked back into the pressure relief chamber, and is designed with a specific diameter and shape to allow air bubbles to rise without displacing the oil column, maintaining a vacuum and reducing leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the vent duct opens into the hydraulic reservoir above the normal fluid level, then air can be vented during operation, but air bubbles are discharged into the environment and hydraulic fluid leaks during shutdown

Engineering Contradiction:

Improvehydraulic system reliabilityVSAvoidhydraulic fluid loss

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The vent duct opening is positioned below the normal fluid level in the hydraulic reservoir, inverted from the conventional above-level positioning. This inversion prevents air from being sucked back into the pressure relief chamber during shutdown, as the lower opening remains submerged in hydraulic fluid, thereby eliminating the harmful effect of air ingress while maintaining venting functionality during operation

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the vent duct opens into the hydraulic reservoir below the normal fluid level, then air is prevented from entering the pressure chamber during shutdown, but the duct design becomes more complex

Engineering Contradiction:

Improveengine starting reliabilityVSAvoidvent duct design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The vent duct incorporates a variable cross-sectional design with a first section having a larger diameter and a second section having a smaller diameter. This local variation in geometry allows the duct to perform multiple functions: the larger first section prevents air from displacing the hydraulic fluid column, while the smaller second section allows air bubbles to rise through the fluid without compromising the vacuum seal, thereby achieving reliable engine starting without excessive design complexity

Inventive Principle:

Principle #3Local quality

3Reliability

If the hydraulic fluid level in the pressure chamber falls below the critical level during prolonged shutdown, then the engine cannot start, but the vent duct design should prevent this

Engineering Contradiction:

Improveengine starting capabilityVSAvoidshutdown duration tolerance

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The vent duct is designed with a specific geometry that preliminarily prevents air from entering the pressure chamber during shutdown. The variable cross-section duct allows air bubbles to rise through the hydraulic fluid without displacing the fluid column, thereby maintaining the vacuum seal and preventing air ingress before the engine needs to be restarted, ensuring the hydraulic fluid level remains above the critical level even after prolonged shutdowns

Inventive Principle:

Principle #10Preliminary action

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 design significantly extends the time before the hydraulic fluid level in the pressure chamber falls critically low, ensuring the engine can start after prolonged shutdowns by minimizing hydraulic fluid leakage and maintaining a vacuum in the hydraulic housing.

Implementation Method 1

maintaining a vacuum in the hydraulic housing

Methodology Applied

Scientific EffectVacuum: Vacuum

Implementation Method 2

The duct opening is below the normal level of the hydraulic reservoir in relation to the direction of gravity

Methodology Applied

Scientific EffectHydrostatic pressure: Pressure Gradient

Implementation Method 3

designed with a specific diameter and shape to allow air bubbles to rise without displacing the oil column

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Implementation Method 4

the cooling hydraulic fluid, which shrinks in volume during this process, produces a vacuum in the hydraulic chambers

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentUS10900389B2Internal combustion engine with a hydraulically variable gas exchange valve train

Publication Date: 2021.01.26 SCHAEFFLER TECHNOLOGIES AG & CO KG

AI summary

A hydraulically variable gas exchange valve train for an internal combustion engine is proposed that includes a hydraulic housing with a pressure chamber, a pressure relief chamber, and a vent duct. The vent duct is connected hydraulically on a housing inner side via a restriction to the pressure relief chamber, and opens on the housing outer side below the pressure relief chamber with regard to a direction of gravity. The vent duct opens into a hydraulic reservoir, wherein the vent duct opening lies below a normal level of the hydraulic reservoir with regard to the direction of gravity.