Ion Current Sensor for Cycle-by-Cycle Engine Emission Measurement

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Solution Overview

Problem

Current technologies for measuring NOx, CO, CO2, unburned hydrocarbon (HC), and excess O2 emissions in internal combustion engines are either expensive, require frequent recalibration, or lack in-cylinder accuracy, while cylinder pressure and temperature measurements are costly and not accurately predicted on a cycle-by-cycle basis.

Innovation Solution

An onboard system utilizing an ion current sensor to measure and control engine parameters like NOx, pressure, and temperature within the combustion chamber, providing a cost-effective, fast response, and cycle-by-cycle predictive technique that sends feedback signals to the engine ECU for improved engine control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If chemiluminescence detector (CLD) is used to measure NOx emissions, then measurement accuracy is improved, but cost and complexity increase significantly

Engineering Contradiction:

ImproveNOx measurement accuracyVSAvoidinstrumentation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the complex mechanical/optical chemiluminescence detection system with an electrical field-based ion current measurement system. The ion current sensor detects ionization events directly through electrical signals, eliminating the need for ozone chambers, optical paths, and complex signal processing equipment while achieving comparable or superior measurement accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an electrical field as an intermediary medium between the combustion gases and the measurement system. The ion current sensor creates an electrical field that ionizes gas molecules, and the resulting ion current provides direct information about emission concentrations, serving as a simplified intermediary measurement mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If Zirconia multilayer ceramic sensor is used in exhaust pipe, then NOx measurement is enabled, but time response is slow and sensitivity is low

Engineering Contradiction:

ImproveNOx detection capabilityVSAvoidtime response

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The patent replaces the slow thermal/electrochemical Zirconia sensor mechanism with a rapid electrical field-based ion current detection system. The ion current sensor responds instantaneously to ionization events in the exhaust stream, eliminating thermal mass limitations and electrochemical reaction delays, thereby achieving millisecond-level response times.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If pressure transducer is used to measure cylinder pressure, then measurement reliability is improved, but cost increases

Engineering Contradiction:

Improvecylinder pressure measurement reliabilityVSAvoidsensor cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the ion current sensor multi-functional by enabling it to measure both emission concentrations and cylinder pressure simultaneously. The electrical field interacts with both ionized emission molecules and charged particles in the combustion chamber, allowing a single sensor to provide multiple measurement functions that would traditionally require separate devices.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Productivity

If in-cylinder sensor is implemented, then cycle-by-cycle measurement capability is achieved, but device complexity and cost increase

Engineering Contradiction:

Improvecycle-by-cycle measurement speedVSAvoidsensor system complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical in-cylinder pressure measurement systems with a streamlined electrical field-based ion current sensor. The electrical measurement approach requires minimal mechanical components, no moving parts, and simple signal processing, enabling cycle-by-cycle measurements while reducing overall system complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 system enables accurate, real-time measurement and prediction of emissions and engine performance parameters, reducing emissions and operational costs without engine modifications, and is suitable for production models.

Implementation Method 1

The sensor acquires an ion current signal generated by ionization of gas molecules within the combustion chamber

Methodology Applied

Scientific EffectIonization: Ionisation

Implementation Method 2

The NOx concentration in the exhaust gas is proportional to the electrical current controlling the electro-chemical pumps that adjusts the oxygen concentration in the cavities of the sensing element

Methodology Applied

Scientific EffectElectro-chemical pumping: Electro-Osmosis

Data Source

PatentUS10815916B2Using ion current signal for engine performance and emissions measuring techniques and methods for doing the same

Publication Date: 2020.10.27 WAYNE STATE UNIV

AI summary

A system and method is provided for the use of the ion current signal characteristics for onboard cycle-by-cycle, cylinder-by-cylinder measurement. The system may also control the engine operating parameters based on a predicted NOx emission level, CO emission level, CO2 emission level, O2 emission level, unburned hydrocarbon (HC) emission level, cylinder pressure, or a cylinder temperature measurement according to characteristics of the ion current signal.