Ion Current Detector Bias Capacitor Segmentation
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Solution Overview
Problem
Existing ion current detectors in internal combustion engines suffer from deteriorated detection properties due to smolder leaks, which reduce the bias voltage and make it difficult to discriminate between ion and leakage currents, especially in stratified lean combustion conditions.
Innovation Solution
An ion current detector that includes a bias capacitor charged by a DC power supply, providing a stable bias voltage to the ignition plug, and an ion current detecting unit to monitor the combustion state without energy loss from leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the capacitor capacitance is set to be large to store sufficient energy for spark discharge, then the energy for ignition is improved, but the capacitor cannot be sufficiently charged to necessary voltage and energy is consumed for charging reducing spark discharge energy
Solution Approach 1:
The patent divides the capacitor system into two separate capacitors: a first capacitor (ignition capacitor) dedicated to spark discharge and a second capacitor (bias capacitor) dedicated to ion current detection. This segmentation allows each capacitor to be optimized independently - the first capacitor can be sized for sufficient ignition energy without worrying about charging time constraints, while the second capacitor maintains stable bias voltage for detection.
2Loss of energy
If the capacitor capacitance is set to be small to reduce charging energy consumption, then the energy loss for charging is reduced, but the energy stored in the capacitor flows out as leakage current from smolder leak path reducing bias voltage and deteriorating detection properties
Solution Approach 1:
By separating the ignition function and detection function into two distinct capacitors, the patent eliminates the conflict between small capacitance (for low charging loss) and large capacitance (for stable bias voltage). The bias capacitor can be optimized specifically for maintaining stable voltage for detection without being constrained by ignition energy requirements.
Solution Approach 2:
The patent introduces a voltage holding circuit as an intermediary component that maintains the bias voltage across the second capacitor. This voltage holding circuit acts as a mediator that prevents voltage collapse due to leakage current, ensuring stable detection properties without requiring the bias capacitor to continuously draw large current.
3Device complexity
If a single capacitor is used for both ignition and ion current detection, then the device complexity is reduced, but the leakage current waveform simply attenuates during one ignition cycle making it difficult to discriminate between ion current and leakage current
Solution Approach 1:
The patent segments the current detection function by providing separate capacitors for ignition and detection. This allows the detection circuit to monitor only the bias capacitor's current characteristics, making it easier to distinguish ion current signals from leakage current since the two functions are electrically separated rather than competing for the same capacitor's energy.
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 maintains detection accuracy of ion currents even with smolder leaks, preventing energy loss and ensuring consistent ignition properties by keeping the bias capacitor fully charged, thus allowing precise monitoring of combustion states.
Implementation Method 1
a bias capacitor which supplies a bias voltage to an ignition plug
Implementation Method 2
a direct current (DC) power supply which charges the bias capacitor
Implementation Method 3
an ion current detecting unit which detects an ion current included in a current flowing through the ignition plug
Implementation Method 4
an ion current that flows by an ion generated by combustion of a fuel-air mixture
Data Source
AI summary
In order not to deteriorate the detection properties of an ion current that monitors a combustion state even when a smolder leak is present in an ignition plug of an internal combustion engine, an ion current detector includes an ignition plug of an internal combustion engine, an ignition coil which supplies a high voltage to the ignition plug, a controller which sends an ignition command, a bias capacitor which supplies a bias voltage to the ignition coil, an ignition capacitor which is connected to a primary side winding of the ignition coil, a DC power supply which charges the ignition capacitor and the bias capacitor, a current detecting unit which detects a current flowing through the ignition plug, an ion current detecting unit which detects an ion current from the current detected by the current detecting unit, and a Zener diode which restricts a charging voltage of the bias capacitor.