Multi-Cylinder Engine Exhaust Manifold Ejector Effect

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional intake and exhaust devices for multi-cylinder engines face challenges in suppressing performance variations due to manufacturing variations, which affect engine output consistency across vehicles.

Innovation Solution

The device incorporates independent exhaust passages connected to either one or multiple non-adjacent cylinders, a catalyst device for exhaust gas purification, and a valve driver that overlaps intake and exhaust valve operations to generate a high-speed ejector effect, ensuring consistent negative pressure and improved scavenging, even with manufacturing variations in manifold section length.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional exhaust passages are used, then the structure is simple, but performance variation due to manufacturing variation is high

Engineering Contradiction:

Improveperformance consistencyVSAvoidexhaust passage configuration

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The exhaust system is divided into multiple independent exhaust passages, each connected to individual cylinders or groups of cylinders. This segmentation allows each passage to be optimized independently and reduces the impact of manufacturing variations on overall system performance, thereby improving performance consistency across different vehicles.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the exhaust passages have different flow areas and geometries tailored to local requirements. The passages are designed with specific characteristics (such as varying diameters and lengths) optimized for each cylinder's exhaust needs, which compensates for manufacturing variations and maintains consistent performance across the engine system.

Inventive Principle:

Principle #3Local quality

2Power

If exhaust gas flows at high speed through the manifold section, then the ejector effect is enhanced, but the flow area must be precisely controlled

Engineering Contradiction:

Improveejector effectVSAvoidflow area control

Core Design Contradiction:

PowerVSManufacturing precision

Solution Approach 1:

The flow area of the manifold section is designed to vary along the flow direction, with specific dimensional parameters (diameters, lengths) optimized to generate the desired ejector effect. By carefully controlling these parameters, the system achieves high-speed exhaust gas flow and strong ejector effect while maintaining manufacturability and reducing sensitivity to precision variations.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the manifold section length varies due to manufacturing variation, then the assembly is easier, but the negative pressure generation is affected

Engineering Contradiction:

Improveassembly flexibilityVSAvoidnegative pressure

Core Design Contradiction:

Ease of manufactureVSStress or pressure

Solution Approach 1:

The exhaust passages are designed with flexible dimensional ranges that allow for manufacturing variations while maintaining functional performance. The flow characteristics are optimized such that the system can accommodate variations in manifold section length without significant loss of negative pressure generation capability, thereby achieving both ease of manufacture and pressure consistency.

Inventive Principle:

Principle #15Dynamics

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 enhances engine output consistency by maintaining high negative pressure and efficient scavenging, reducing performance variations and enabling early catalyst activation, while also improving the accuracy of oxygen concentration detection and catalyst efficiency.

Implementation Method 1

a downstream end of each independent exhaust passage is shaped to have a flow area smaller toward a downstream direction so that a negative pressure is generated in the exhaust port connected with one or more adjacent independent exhaust passages by an ejector effect due to the exhaust gas being discharged from the exhaust port of each cylinder to the manifold section through the downstream end of the corresponding independent exhaust passage

Methodology Applied

Scientific EffectEjector effect: Venturi Effect

Data Source

PatentUS9228476B2Intake and exhaust device of multi-cylinder engine

Publication Date: 2016.01.05 MAZDA MOTOR CORP

AI summary

A device of an engine having a plurality of cylinders includes: exhaust passages each connected with either a single cylinder or two or more cylinders having non-adjacent exhaust order; a manifold section connected with each downstream end of the exhaust passages; a catalyst device downstream of the manifold section; and a valve driver. Within a low-speed and high-load engine operating range, the valve driver drives intake and exhaust valves of each cylinder such that, for a particular cylinder, a period of positive valve overlap overlaps an exhaust valve opening time of another cylinder adjacent in the exhaust order. The manifold section includes a part that reduces in diameter downstream from the upstream end of the manifold section, and a straight part with a substantially fixed flow area extending upstream from the downstream end of the manifold section. In this way, negative pressure may be generated due to an ejector effect.