Ignition Coil Control Circuit for Misfire Detection
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Solution Overview
Problem
Existing electronic ignition systems for internal combustion engines are complex and require multiple electronic components, making them unreliable for detecting misfires in engines.
Innovation Solution
A simplified electronic ignition system that uses an integrating circuit with an integrating capacitor and a Zener diode to measure the integral of the ionization current, reducing the computational burden on the Electronic Control Unit and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an integrating circuit with operational amplifier and multiple electronic components is used to measure ionization current integral, then measurement capability is achieved, but device complexity increases
Solution Approach 1:
The patent extracts the integration function from a complex operational amplifier-based circuit and implements it using a simple RC integrating circuit. The integration is performed by charging a capacitor through a resistor during the ionization current flow, converting the current integral into a voltage signal that can be measured by the ECU. This eliminates the need for complex operational amplifiers and multiple electronic components while maintaining measurement capability.
Solution Approach 2:
The patent replaces the electronic integration system (operational amplifier circuit) with a passive electrical integration system (RC circuit). The operational amplifier-based active integration is substituted with passive component-based integration using only a resistor and capacitor, significantly reducing device complexity while achieving the same measurement function.
2Measurement precision
If complex integrating circuits with multiple components are used, then integration function is achieved, but ease of manufacture decreases
Solution Approach 1:
The patent removes complex electronic components (operational amplifiers, multiple diodes, complex resistor networks) from the integrating circuit, retaining only the essential RC integration elements. This extraction simplifies the manufacturing process by reducing the number of components that need to be sourced, assembled, and tested, while preserving the core integration function needed for accurate ionization current measurement.
3Measurement precision
If ionization current measurement is performed without simplified integrating circuit, then measurement capability exists, but computational burden on ECU increases
Solution Approach 1:
The patent performs the integration computation in advance using the passive RC circuit before the ECU processes the signal. The capacitor naturally integrates the ionization current over time during the measurement phase, converting the time-consuming computational integration task into a physical integration process that occurs automatically in real-time. This preliminary physical integration reduces the ECU's computational burden to simple voltage reading and threshold comparison.
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 system effectively detects misfires by providing the Electronic Control Unit with the integral of the ionization current, reducing the risk of false alarms and improving engine performance.
Implementation Method 1
an integrating circuit interposed between the bias circuit and a reference voltage; wherein said integrating circuit comprises an integrating capacitor connected in series to the bias circuit
Implementation Method 2
the integrating circuit comprises the connection in parallel of the integrating capacitor and of a Zener diode, the Zener diode having an anode terminal connected to the bias circuit and having a cathode terminal connected towards the reference voltage, wherein during the phase of measurement of the ionization current the Zener diode is reversely biased and it is configured to limit the voltage across the integrating capacitor
Implementation Method 3
a coil having the primary winding with a first terminal connected to a battery voltage and having the secondary winding with a first terminal connected to a spark plug
Implementation Method 4
by means of the spark generated by a spark plug in the phase of transfer of energy
Implementation Method 5
wherein said ionization current is generated by the ions produced during the process of combustion of the comburent-combustible mixture in the combustion chamber of a cylinder of the engine
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
It is disclosed an electronic device (1) to control an ignition coil of an internal combustion engine. The device comprises a high-voltage switch (4), a driving unit (5), a bias circuit (6) and an integrating circuit (7). The high-voltage switch is connected in series with a primary winding of a coil and it configured to switch between a closed position and an open position. The driving unit is configured to control the closing of the high-voltage switch during a phase of charging (T_chg) energy into the primary winding, it is configured to control the opening of the high-voltage switch during a phase of transfer (T_tr) of energy from the primary winding to a secondary winding of the coil and during a phase of measurement (T_ion) of an ionization current (I_ion) subsequent to the phase of transfer of energy, wherein said ionization current is generated by the ions produced during the combustion process of the comburent-combustible mixture in the combustion chamber of a cylinder of the engine by means of the spark generated by a spark plug (3) in the phase of transfer of energy. The bias circuit is configured to generate said ionization current (I_ion) during the phase of measurement (T_ion) of the ionization current, wherein said bias circuit is connected in series to a second terminal of the secondary winding. The integrating circuit (7) is interposed between the bias circuit and a reference voltage (GND). The integrating circuit comprises an integrating capacitor (C4) connected in series to the bias circuit (6) and connected between the bias circuit and the reference voltage. The integrating capacitor is configured to completely discharge by means of the current flowing through the secondary winding during the phase of transfer (T_tr) of energy from the primary winding to the secondary winding, it is configured to charge (t5, t7) to a value different from zero during the phase of measurement (T_ion) of the ionization current (I_ion) so as to measure a value of the integral of the ionization current, in the case of a correct ignition of the comburent- combustible mixture, and it is configured to maintain a substantially null charge (t25, t27) during the phase of measurement (T_ion) of the ionization current (I_ion) so as to measure a substantially null value of the integral of the ionization current, in the case of a misfire of the comburent-combustible mixture.