Ion Sensing in Capacitive Discharge Ignition Systems
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Solution Overview
Problem
Ion sensing in capacitive discharge ignition systems for internal combustion engines lacks effective methods to maintain bias voltage and detect ionization during the spark phase without adding circuit elements like capacitors or diodes to the secondary winding circuit.
Innovation Solution
A method involving a controllable switch in series with the primary winding of the ignition transformer, controlled by an electronic circuit to adjust the ratio of opening and closing periods, allowing for real-time spark ignition and secondary current control, and observing current changes in the secondary winding circuit to detect ionization throughout the spark phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If diodes and capacitors are added to the secondary winding circuit to maintain bias voltage for ion sensing, then ion sensing capability is improved, but device complexity increases
Solution Approach 1:
The patent applies the self-service principle by utilizing the existing storage capacitor and controllable switch from the capacitive discharge ignition system to generate and maintain bias voltage across the spark plug electrodes. The system's own components serve the dual purpose of ignition and ion sensing, eliminating the need for additional dedicated circuit elements like diodes and capacitors that would otherwise be required in inductive interrupt systems.
Solution Approach 2:
The storage capacitor and controllable switch perform multiple functions: they generate the high voltage spark for ignition and simultaneously maintain the bias voltage required for ion sensing. This multi-functionality allows the same circuit components to serve both ignition and sensing purposes, reducing overall system complexity while improving measurement capability.
2Power
If the switch is opened and closed repeatedly during the compression stroke to create pulse trains, then sparking is reinforced, but the ability to maintain stable bias voltage for ion sensing deteriorates
Solution Approach 1:
The patent applies dynamics by making the switch control strategy adaptive and time-dependent. The control circuit adjusts the switch operation mode based on the engine cycle phase: during the ignition phase, the switch operates in pulse train mode to reinforce sparking, while during the ion sensing phase, it transitions to a different mode that maintains stable bias voltage. This dynamic adaptation allows the system to optimize performance for different operational requirements.
Solution Approach 2:
The system utilizes periodic action by operating the controllable switch in synchronized cycles with the engine's compression stroke. The switch is opened and closed at specific periodic intervals to create reinforced sparking during the ignition window, then maintains a different periodic pattern during the sensing window to preserve stable bias voltage. This periodic, phase-synchronized operation resolves the conflict between sparking reinforcement and bias stability.
3Measurement precision
If bias voltage is stored during initial sparking in inductive interrupt systems, then ion sensing is enabled, but adjustment of biasing voltage is limited
Solution Approach 1:
The patent applies parameter changes by enabling dynamic adjustment of the bias voltage magnitude through electronic control of the controllable switch. The control circuit can modify the duty cycle, frequency, and timing of switch operation to vary the average voltage across the spark plug electrodes. This allows real-time adjustment of bias voltage parameters to optimize ion sensing for different operating conditions, engine loads, and combustion phases, providing adaptability that fixed inductive interrupt systems lack.
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
Enables instantaneous adjustment of bias voltage and real-time ion sensing without additional circuit elements, allowing for improved detection of ionization during the spark phase, enhancing engine performance by accurately determining the start of ignition.
Implementation Method 1
transfer energy to the ignition coil primary to cause a spark breakdown across the spark plug
Implementation Method 2
the increased flow of current through the secondary winding in addition to the normal spark current is due to the decreased impedance of the ionized gases between the electrodes
Data Source
AI summary
A method of ion sensing in a CD ignition system for an internal combustion engine comprises: a) closing the controllable switch in synchronism with the internal combustion engine for a period of time to transfer energy to the ignition coil primary to cause a spark breakdown across the spark plug; and b) observing the current in the secondary winding circuit indicative of ionization in the vicinity of the spark plug electrodes.