MISIGNITION DETECTION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A misfire detection system (300) is disclosed, comprising an ignition system (303) including an ignition coil (107), an ion current measuring circuit (302) electrically connected to the ignition coil (107) for measuring an ion current generated by a spark plug (106), and a signal processor (401) for processing and conditioning the ion current measured by the ion current measuring circuit (302) to determine the occurrence of a misfire in the IC engine. The ignition coil (107) comprises a primary winding (101) and a secondary winding (103), wherein a first end (101B) of the primary winding (101) is electrically connected to a first end (103B) of the secondary winding (103). Misfire detection improves the reliability and durability of the IC engine.

Description

INTERNAL COMBUSTION ENGINE MISIGURATION DETECTION SYSTEM TECHNICAL FIELD OF THE INVENTION The subject matter of the present invention relates to spark-ignition engines. More particularly, it discloses the detection of misfires and partial misfires in spark-ignition engines using an ion current measuring circuit. BACKGROUND OF THE INVENTION Internal combustion engines (ICs) are significantly contributing to pollution and global warming by emitting various exhaust gases into the environment. An IC engine produces energy by burning fossil fuels, which emit harmful gases such as CO, HC, NOx, and hydrocarbons. These emissions have been and continue to worsen the environment, and therefore, vehicle manufacturers are constantly striving to incorporate technological advancements to improve the performance of internal combustion engines and reduce emissions. In addition to emissions control, the automotive industry is implementing on-board diagnostics (OBD) in vehicles to inform the user about the vehicle's condition. The OBD system in major jurisdictions is being implemented in stages and is subdivided into two categories: OBD I and OBD II. OBD II focuses on three main aspects: engine misfire detection, catalytic converter monitoring, and lambda sensor monitoring. To improve engine combustion efficiency and reduce emissions, it is essential to detect and monitor misfire events in an internal combustion engine (IC). Misfire occurs when the injected air-fuel mixture does not burn completely or burns only partially. IC engine misfires affect combustion quality and degrade the performance of a catalytic converter, leading to increased emissions, which is undesirable. BRIEF DESCRIPTION OF THE FIGURES The detailed description is provided with reference to the accompanying figures. The same numbers are used in all figures to refer to features and IVIA / a / ¿U¿¿ / UU4U / l similar components. Figure 1 illustrates as an example a circuit diagram of an existing ignition system of a C1 engine. Figure 2 illustrates as an example a circuit diagram of the existing ignition system of a C1 engine connected to an ion current measuring circuit. Figure 3 illustrates, as an example, a schematic diagram of a misfire detection system, according to an embodiment of the present invention. Figure 4 illustrates as an example the misfire detection system comprising an ion current measuring circuit and a signal processor, according to an embodiment of the present invention. Figures 5-6 illustrate example timing diagrams for the primary voltage in the ignition coil primary winding and the ion current during a misfire condition. Figures 7-8 illustrate example timing diagrams for the primary voltage in the ignition coil primary winding and the ion current during a misfire-free condition. DETAILED DESCRIPTION OF THE INVENTION Misfire events in a C1 engine can be classified as partial or complete, depending on the amount of combustion that occurs during a particular engine cycle. In most vehicles, misfire identification is performed by monitoring the crankshaft's angular acceleration. However, single-cylinder engines with smaller displacements (less than 200 cubic centimeters) present challenges for misfire identification due to the low mechanical inertia of the internal combustion engine using the same approach. The problem of misfire identification for single-cylinder C1 engines is further complicated by the presence of various load disturbances in the propulsion system when the engine is used in a vehicle. Several other techniques are designed for misfire detection in single-cylinder engines. These techniques include instantaneous crankshaft speed analysis, in-cylinder pressure analysis, instantaneous crankshaft torque analysis, and others. Evaluating crankshaft speed for misfire detection faces many challenges due to the low mechanical inertia and load disturbances in engines. Alternative solutions to address the misfire detection problem utilize the ion current generated during an engine misfire event. When the air-fuel mixture ignites inside the cylinder of a C1 engine, the air particles ionize. By applying a suitable high voltage to the spark plug, it is possible to measure the ion current, as the amount of ion current reflects the level of ionization of the air-fuel mixture. Therefore, the ion current flow depends on the combustion event. The ion current signal can be captured using an ion current measurement circuit. To generate the ion current flow, a voltage biasing circuit is necessary to create the potential difference between the spark plug electrodes after the spark is fired. Figure 1 illustrates, as an example, a circuit diagram of an existing ignition system 100 of a CL engine. The ignition system 100 consists of an ignition coil 107 with a primary winding 101 and a secondary winding 103, a spark plug 106, and a control circuit 105, for example, an electronic control unit (ECU) with an electrical switching device 104 to produce the high-voltage spike required to generate a spark in the engine cylinder. The primary winding 101 is connected between a battery 102 and the electrical switching device 104. When the electrical switching device 104 is in the closed state, the primary winding 101 of the ignition coil 107 stores energy.As soon as the control circuit 105 changes the state of the electrical switching device 104 to open, a voltage of, for example, 400 V is generated in the primary winding 101 of the ignition coil 107, due to the sudden interruption of current flow in the inductive circuit. A high secondary voltage of approximately 20–25 kV (depending on the turns ratio of the primary and secondary coils) is generated in the secondary winding 103. The secondary voltage is applied to the spark plug 106, resulting in a voltage breakdown across the spark plug gap 106, and a spark current begins to flow to the spark plug 106 through its ground connection. Subsequently, the spark current generates an ion current through the spark plug 106, as described in Figure 2. Figure 2 illustrates, as an example, a circuit diagram 200 of the existing ignition system 100 of a C1 engine connected to an ion current measuring circuit 201. As illustrated, the ion current measuring circuit 201 is connected to the secondary winding 103 of the coil of IVIA / a / ¿U¿¿ / UU4U 11 ignition 107 to provide a bias voltage to spark plug 106, which in turn generates the ion current flow after the spark event. In addition, the existing ion current measuring circuit 201 consists of a capacitor that charges during spark firing. Once the spark fires, the charge held by the capacitor generates a potential difference across the spark electrodes of spark plug 106, resulting in the flow of ion current. The ignition coil designs 107 in the existing ignition system 100, illustrated as an example in Figures 1-2, have a separate ground connection for each primary winding 101 and the secondary winding 103 of the ignition coil 107. As shown in Figure 1, terminal 101B on the primary side 101 and terminal 103B on the secondary side 103 of the ignition coil 107 are electrically isolated. The ion current measuring circuit 201 is connected to terminal 103B to measure the ion current and subsequently detect misfires in a C1 engine, as shown in Figure 2. However, the ignition coils of spark-ignition engines are designed to simplify the ignition coil manufacturing process and reduce ignition system manufacturing costs. In such ignition coils, terminals 101B and 103B are internally connected via a common winding connection, and there is no possibility of connecting the ion current measuring circuit 201 to the secondary winding 103 separately. Due to the common electrical connection of terminals 101B and 103B of the primary winding 101 and the secondary winding 103, the existing ion current measuring circuit 201 is connected to both windings 101 and 103.Since the electrical resistance of the primary winding 101 is much lower compared to the electrical resistance of the secondary winding 103, the capacitor of the existing ion current measuring circuit 201 would discharge from the primary winding 101 instead of the secondary winding 103, and therefore no ion current flows into the spark plug 106. In combustion engine applications, such as vehicles, the following are the disadvantages of a misfire: Due to a misfire, fuel is wasted during combustion because there is no spark to ignite the fuel. This degrades vehicle performance due to reduced fuel economy. A misfire directly impacts the vehicle's power and starting ability because of the loss of combustion. The driver may experience a sudden jerk while driving due to a misfire, which can cause discomfort. Furthermore, unburned fuel in the exhaust affects the lifespan of the catalytic converter and directly impacts emissions. Detecting and mitigating misfires will contribute to the vehicle's longevity.Therefore, the current technology suffers from shortcomings in the effective detection of misfires, leading to poor ignition system reliability and eventually to high emissions, driver discomfort, and reduced fuel economy. Consequently, there is a need for a misfire detection system that includes an ion current measurement circuit to effectively detect complete and partial misfires in engines, ensuring smooth operation, durability, and compliance with emissions standards. This system should overcome the aforementioned and other known problems in the current technology. Taking into account the above objectives, the present prevention invention discloses a misfire detection system comprising an ion current measuring circuit for accurately detecting a complete misfire and a partial misfire in a spark-ignition engine, wherein a primary winding and a secondary winding of an ignition coil are internally connected. It is an object of the present invention to restrict the flow of ion current through the low-resistance primary winding. It is another object of the invention to provide a bias voltage circuit in the ion current measuring circuit that charges the capacitor in the ion current measuring circuit to a suitable value during spark firing at the spark plug and applies this stored charge to the spark plug to generate a potential difference between the spark plug electrodes after the spark is fired. This results in the flow of ion current through the ion current measuring circuit, and the measurement of this ion current aids in the detection of a misfire or partial misfire.The current material allows overcoming the drawbacks of the known technique and ensures that the misfire is detected accurately, allowing reliable control and a reduction of emissions for an engine, especially in those of small capacity. In one embodiment, a misfire detection system for a C1 engine is described. The misfire detection system comprises an ignition system, an ion current measuring circuit, and a signal processor. The ignition system comprises an ignition coil comprising a primary winding and a secondary winding, wherein a first end of the primary winding is electrically connected to a first end of the secondary winding, and a spark plug electrically connected in series to a second end of the secondary winding of the ignition coil. A first terminal of the spark plug is connected to the second end of the secondary winding, and a second terminal of the spark plug is connected to ground.The ion current measurement circuit is electrically connected to the first end of the primary winding and the first end of the secondary winding to measure the ion current generated by the spark plug after a misfire. The signal processor processes and conditions the ion current measured by the ion current measurement circuit to determine the occurrence of a misfire in the Cl engine. One end of the ignition coil's primary winding is operatively coupled to a power supply via a diode. The first end of the ignition coil's primary winding is operatively coupled to an electrical switching device to generate a primary voltage in the primary winding and a secondary voltage in the secondary winding of the ignition coil. This electrical switching device is controlled by a control unit. The diode allows the flow of primary current in the primary winding to generate the primary voltage and prevents the flow of ion current in the primary winding through the first end of the secondary winding. The ion current measuring circuit supplies a bias voltage to the spark plug to generate the ion current. This circuit comprises a bias resistor and a bias capacitor connected to the first end of the secondary winding to generate the bias voltage for the spark plug. One terminal of the bias resistor is connected in series with the first end of the secondary winding, and the bias capacitor is connected in series with the second terminal of the bias resistor. The bias capacitor charges using a spark current during sparking and discharges after sparking to provide the bias voltage for the spark plug.The bias capacitor and bias resistor define a time constant for the ion current measuring circuit and a charging and discharging rate for the bias capacitor. The ion current measuring circuit further comprises a voltage control element connected in parallel with the bias capacitor to limit the bias voltage across the bias capacitor during charging. In one embodiment, the voltage control element is a Zener diode. The ion current measuring circuit further comprises a voltage divider resistor network, comprising a sense resistor, connected in series between the bias capacitor and ground to measure the ion current. The ion current measuring circuit further comprises a second diode connected in parallel with the sense resistor to provide a low-impedance path for spark current and impede the flow of ion current. In another embodiment, an ion current measuring circuit is disclosed for measuring an ion current generated from a spark plug of a CL engine. In this embodiment, the ion current measuring circuit comprises a bias resistor connected in series with a first end of a primary winding and a first end of a secondary winding of an ignition coil, and a bias capacitor connected in series with a second terminal of the bias resistor to generate a bias voltage for the spark plug. A first terminal of the bias resistor is connected in series with the first end of the secondary winding. A voltage control element is connected operatively in parallel with the bias capacitor to limit the bias voltage across the bias capacitor during a spark event using a spark current.A voltage divider resistor network, comprising a sense resistor, is connected in series between the bias capacitor and ground to measure the ion current. A second diode is connected in parallel with the sense resistor to provide a low-impedance path for the spark current and impede the flow of the ion current. The bias capacitor is charged using the spark current during sparking and discharged after sparking to provide the bias voltage. In this embodiment, the spark plug is electrically connected in series to a second end of the ignition coil's secondary winding, where a first terminal of the spark plug is connected to the second end of the secondary winding and a second terminal of the spark plug is grounded. A second end of the ignition coil's primary winding is operatively coupled to a power supply via a first diode, and the first end of the ignition coil's primary winding is operatively coupled to an electrical switching device to generate a secondary voltage in the ignition coil's secondary winding.The first diode allows the flow of primary current in the primary winding and prevents the flow of ion current in the primary winding through the first terminal of the secondary winding. The measured ion current is processed and conditioned by a signal processor to determine the occurrence of a misfire in the CL engine. In one embodiment, an ignition system for an internal combustion engine is described. The ignition system comprises an ignition coil comprising a primary winding and a secondary winding, a spark plug electrically connected to a second end of the secondary winding of the ignition coil, and a first diode electrically connected between a power supply and a second end of the primary winding. A first end of the primary winding is electrically connected to a first end of the secondary winding. A first terminal of the spark plug is connected to the second end of the secondary winding, and a second terminal of the spark plug is connected to ground. The first diode permits the flow of a primary current in the primary winding and prevents the flow of an ion current in the primary winding through the first end of the secondary winding.The ignition system further comprises an electrical switching device electrically connected to the first end of the primary winding to generate a secondary voltage in the secondary winding of the ignition coil, wherein the electrical switching device is controlled by a control unit. In this embodiment, the first end of the primary winding and the first end of the secondary winding are electrically connected to an ion current measurement circuit to measure the ion current generated by the spark plug after a misfire event. The ion current measurement circuit supplies a bias voltage to the spark plug to generate the ion current measurement. The measured ion current is processed and conditioned by a signal processor to determine the occurrence of a misfire in the CL engine. Therefore, the subject matter of the present invention discloses an interaction of the ignition coil with a specific ion current measuring circuit intended to operate when the primary and secondary sides of the ignition coil have a common electrical connection. The summary provided above explains the basic features of the invention and does not limit its scope. The nature and other features of the present invention will become clearer from the following descriptions made with reference to the accompanying figures. Figure 3 illustrates, by way of example, a schematic diagram of a 300 misfire detection system, according to an embodiment of the present MA / a / ZUZZ / UU4U 11 Invention. As illustrated by way of example, the misfire detection system 300 comprises an ignition system 303 and an ion current measuring circuit 302. The proposed design of the ignition system 303 with the ion current measuring circuit 302 is adapted to the common electrical connection constraint of the primary winding 101 and the secondary winding 103 of an ignition coil 107. The ignition system 303 comprises the ignition coil 107, a spark plug 106, a first diode 301, and an electrical switching device. The ignition coil 107 comprises a primary winding 101 and a secondary winding 103. The ignition coil 107 is a transformer configured to transfer electrical energy in the primary winding 101 to the secondary winding 103 or vice versa. The voltage in the primary winding 101 is a primary voltage and the voltage in the secondary winding 103 is a secondary voltage.The secondary voltage is substantially higher than the primary voltage, and this is achieved through the turns ratio of the primary winding 101 and the secondary winding 103. Each primary winding 101 and secondary winding 103 comprises a first end 101B and 103B and a second end 101A and 103A, respectively. The first end 101B of the primary winding 101 is connected to the first end 103B of the secondary winding 103. The spark plug 106 is electrically connected in series to a second end 103A of the secondary winding 103. A first terminal 106A of the spark plug 106, i.e., a terminal of one spark electrode, is connected to the second end 103A of the secondary winding 103, and the second terminal 106B of the spark plug 106, a terminal of another spark electrode, is connected to ground. Thus, spark plug 106 is a grounded spark plug. The first diode 301 is electrically connected between a power supply 102 and a second end 101A of the primary winding 101. The first diode 301 allows the flow of a primary current in the primary winding 101 and prevents the flow of an ion current in the primary winding 101 through the first end 103B of the secondary winding 103. The electrical switching device is electrically connected in series with the first end 101B of the primary winding 101 to generate the secondary voltage in the secondary winding 103 of the ignition coil 107. The electrical switching device 104 is controlled by a control unit 105. The electrical switching device 104 can be a transistor, a switch, a relay, or a combination thereof.Control unit 105 may be an engine control unit that generates a spark trigger signal to activate spark generation in the spark gap of spark plug 106 for combustion of the air-fuel mixture in the engine cylinder. Based on the spark trigger signal, control unit 105 controls the opening and closing of the electrical switching device 104. When the spark trigger signal is high, the electrical switching device 104 closes by connecting terminal 101B of the primary winding 101 to ground. This results in the forward bias of the first diode 301 and the flow of primary current from the power supply 102 through the primary winding 101. The primary current flows from the power supply 102, a battery, through the first diode 301 and the primary winding 101 to ground. The primary winding 101 stores energy during the dwell time, i.e., the duration of the primary current flow in the primary winding 101. Control unit 105 can now transmit a low spark trigger signal, and the electrical switching device 104 opens.As soon as the control circuit 105 opens the electrical switching device 104, a transient primary voltage appears at terminal 101B of the primary winding 101 due to the sudden interruption of the primary current flow in the inductive circuit of the primary winding 101. This leads to the generation of a secondary voltage in the secondary winding 103 at the end of the dwell time. The secondary voltage is applied to the spark plug 106, and a voltage drop occurs across the spark plug gap 106, thus generating a spark. During the sparking event, the spark generated in the gap of spark plug 106 ignites the air-fuel mixture and the spark current flows through the gap in spark plug 106 through the secondary winding 103. The first diode 301 is reverse-biased since the voltage at terminal 101B is much higher than the battery voltage at terminal 102. The first end 101B of the primary winding 101 and the first end 103B of the secondary winding 103 are electrically connected to an ion current measuring circuit 302. The ion current measuring circuit 302 supplies a bias voltage to the spark plug 106 to generate an ion current in the secondary winding 103. The ion current measuring circuit 302 also measures the ion current generated by the spark plug 106 after the sparking event. Since the first diode 301 connected to the primary winding 101 of the ignition coil 107 is reverse-biased, the circuit from the battery to the electrical switching device 104 is incomplete. Therefore, the ion current does not flow through the primary winding 101. Furthermore, the spark current generated during the sparking event does not flow from the secondary winding 103 through the primary winding 101, the battery at terminal 102, and ground, even though the resistance of the circuit connected to the primary winding 101 is lower than that of the secondary winding 103. The secondary winding 103 is grounded through the ion current measuring circuit 302, as shown in Figure 3. The spark current flows from ground, through the spark plug gap 106, the secondary winding 103, the ion current measuring circuit 302, and back to ground. This spark current generates the bias voltage in the ion current measuring circuit 302.The ion current measuring circuit 302 supplies the bias voltage to the spark plug 106 and initiates the ion current flow in the secondary winding 103 through the ion current measuring circuit 302 as will be disclosed in the detailed description of Figure 4. Figure 4 illustrates, by way of example, the misfire detection system 300 comprising the ion current measuring circuit 302 and the signal processor 401, according to an embodiment of the present invention. As illustrated, the ion current measuring circuit 302 comprises a network of a voltage control element 302A, a diode 302D, a network of voltage divider resistors 302E and 302F, a biasing resistor 302B, and a biasing capacitor 302C. The bias resistor 302B is connected in series with the first end 101B of the primary winding 101 and the first end 103B of the secondary winding 103 of the ignition coil 107. A first terminal 302B1 of the bias resistor 302B is connected in signal with the first end 103B of the secondary winding 103.The bias resistor 302C is connected in series to a second terminal 302B2 of the bias resistor 302B to generate the bias voltage for spark plug 106. The bias resistor 302C is charged using the spark current during the sparking event at spark plug 106, and is discharged after the sparking event to provide the bias voltage to spark plug 106. The bias resistor 302C and the bias resistor 302B define a time constant for the ion current measuring circuit 302 and a charging and discharging rate for the bias resistor 302C. The time constant of the ion current measurement circuit 302 is based on the values ​​of the bias resistor 302B and bias capacitor 302C. The values ​​of bias resistor 302B and bias capacitor 302C are such that bias capacitor 302C does not fully charge during the sparking event using the spark current. If the time constant of the ion current measurement circuit 302 is low (~10 ms) depending on the resistance and capacitance values ​​of the bias resistor 302B and the bias resistor 302C, the spark current flows through the voltage control element 302A and there may be a loss of spark energy. The voltage control element 302A is connected in parallel with the bias resistor 302C to limit the voltage across the bias resistor 302C during the sparking event. The voltage control element 302A can be a variety of components, but is not limited to a Zener diode, a transistor, a shunt regulator, or any combination thereof. The Zener diode 302A is connected in parallel with the capacitor 302C to maintain the proper bias voltage required to produce the ionization current. The voltage divider resistor network 302E and 302F, comprising a sense resistor 302F, is connected in series between the bias resistor 302C and ground to measure the ionization current. A second diode 302D is connected in parallel with the sense resistor 302F to provide a low-impedance path for the spark current and to impede the flow of the ionization current. Resistors 302E and 302F in the voltage divider resistor network offer increased resistance to the spark current. The second diode 302D is forward-biased to allow the spark current to flow to ground. The generated spark current flows from ground, through the spark plug gap 106, the secondary winding 103, the bias resistor 302B, the bias resistor 302C, the second diode 302D, and to ground. The bias resistor 3020 of the ion current measuring circuit 302 is configured to provide the bias voltage across the spark plug gap 106 through the secondary winding 103 to ionize the air particles and thus produce the ion current. The ion current flows from ground through the voltage divider resistor network 302E and 302F, the bias resistor 302C, the bias resistor 302B, the secondary winding 103, and the spark plug gap 106, back to ground. The voltage divider resistor network with resistors 302E and 302F forms a sensing circuit for the ion current. The voltage measured across the sensing resistor 302F is indicative of the ion current. The flow of the ion current produces a negative voltage across the sensing resistor 302F.This voltage is a measure of the ion current flow and is detected as an ion current signal. The signal processor 401 processes and conditions the measured ion current signal to detect the onset of an engine misfire. This ion current signal is further processed through the filter circuitry of the signal processor 401 to extract the desired information. The resistance of the sensing resistor 302F is selected to provide a suitable voltage magnitude for the signal processor 401 to detect and process the ion current signal. Specifically, the sensing resistor 302F can be selected to ensure that the ion current flow induces a sufficiently large voltage to avoid susceptibility to noise or detection errors.The sensing resistor 302F is used to reduce the voltage levels of electrical noise experienced by the signal processor 401 while it detects and processes the ion current signal. The voltage across the sensing resistor 302F is obtained by applying a voltage divider across resistors 302E and 302F. Therefore, the voltage of the ion current signal is influenced by the resistance of both resistors 302E and 302F. The bias resistor 302B is connected between the ignition coil 107 and the bias capacitor 302C to define the time constant of the ion current measuring circuit 302. The voltage across the bias capacitor 302C is limited to the maximum rated voltage of the Zener diode 302A. The bias voltage across the bias resistor 302C also limits the maximum value of the primary voltage in the primary winding 101. The value of the bias resistor 302B is critical for maintaining the primary voltage at the desired level for the sparking event to occur. The values ​​of bias resistor 302B and bias capacitor 302C are configured such that the circuit time constant (T) is 1.5 ms (~RC). The bias capacitor 302C requires approximately 5T (~7.5 ms) to fully charge using the spark current. The maximum time for spark firing is greater than the time constant (T) and less than the charging time (5T) of bias resistor 302C. Therefore, the spark current would always flow through bias capacitor 302C, as it would never fully charge and would reach an open-circuit state. The charged bias capacitor 302C applies the bias voltage to the spark plug gap 106 after spark firing, causing ion current to flow through sensing resistor 302F.The ion current is measured across the sensing resistor 302F and further processed by the signal processor 401 to obtain the desired information regarding the occurrence of a misfire or partial misfire in the engine. The signal processor 401 detects the occurrence of a misfire based on the trend of the ion current signal during misfire and non-misfire conditions. Figures 5-8 illustrate, as examples, the trends in the ion current signal during misfire and non-misfire conditions. Figures 5-6 illustrate, as an example, timing diagrams for the primary voltage in the primary winding 101 of ignition coil 107 and the ion current during a misfire condition. Figure 6 is an enlarged view of the timing diagram illustrated in Figure 5. The misfire condition can be either a partial misfire or a complete misfire. A certain amount of ion current flows due to incomplete combustion during a partial misfire. During a complete misfire, due to the absence of a spark, there is no ion current flow. As can be seen, at the instant the sparking event ends after a dwell time, the ion current begins to flow in the ion current measuring circuit.However, when there is a failure to turn on in the circuit, the peaks in the ion current signal are absent or suppressed, as shown in Figures 5-6. Figures 7-8 illustrate, as an example, timing diagrams for the primary voltage in the primary winding 101 of ignition coil 107 and the ion current during a misfire-free condition. Figure 8 is an enlarged view of the timing diagram illustrated in Figure 7. As can be seen, at the instant the sparking event ends after a dwell time, the ion current begins to flow in the ion current measuring circuit. During the normal combustion cycle, when there are no misfires in the ignition system 303, some oscillations in the ion current signal are observed at the end of the spark firing. These oscillations occur due to the ionization process. The combustion event is thus identified by the presence of oscillations in the ion current signal.The misfire in the combustion cycle is detected by the absence of oscillations in the ion current circuit. Although oscillations are present in Figures 5-6, a certain amount of ion current flows through the ion current measurement circuit 302. The signal processor 401 analyzes the waveforms to understand the characteristics of the ion current signal to be extracted and monitored in order to implement a robust misfire detection strategy. The signal processor 401 can detect the presence and absence of oscillations in the waveforms. MA / a / ZUZZ / UU4U 11 oscillation frequency to determine the occurrence of a misfire, a partial misfire and a misfire in the Cl engine. The misfire detection system implementations described in the present invention provide a technical advancement in the field of Cl engine performance as follows: the interaction of the ignition system with a common connection between the primary and secondary windings of the ignition coil, the ion current measuring circuit, and the signal processor effectively detects misfires in Cl engines, with reduced energy losses. If the bias capacitor is fully charged, it behaves as an open circuit, leaving no path for the spark current to flow through it, resulting in spark energy loss. To prevent this, the values ​​for the bias resistor and the bias capacitor are selected so that the bias capacitor never becomes fully charged.The second diode provides a path for the spark current and limits the voltage across the voltage divider resistor network to protect the bias resistor, bias capacitor, and signal processor from overvoltage conditions. Furthermore, the bias capacitor's capacitance is chosen to ensure that the bias voltage applied to the spark gap remains relatively constant during an engine cycle. In other words, it ensures that the bias capacitor's discharge rate does not drop drastically when the sensing resistor measures the ion current. If the primary voltage is lower than a predetermined value, it would not be able to generate a spark on the secondary side. The bias resistor value is selected to maintain the primary voltage at the desired level for sparking to occur. The bias capacitor's capacitance ensures that an appropriate bias voltage is applied to the spark plug. During normal operating conditions (dwell time), the first diode is forward-biased and does not affect the ignition coil's operation.During sparking and ion current flow, the first diode is reverse-biased because the voltage across the first terminal of the secondary winding is much higher than the battery voltage. This prevents the primary winding's bias capacitor from discharging and allows ion current to flow through the secondary winding. Furthermore, all components of the ion current measurement circuit are positioned very close to the ignition system and the signal processor to prevent voltage drops due to the long wiring runs between them. The voltage divider resistor network limits spark current loss and ensures that adequate ion current flows through the sensing resistor to measure the voltage level of the ion current signal. The magnitude and shape of the ion current signal provide information about the misfire event. Therefore, ion current measurement is indicative of the combustion event, as well as the quality of the combustion. Misfire detection using the misfire detection system will inform the user of a C1 engine or a vehicle using a C1 engine about misfire events in the spark-ignition engine. By investigating and rectifying the causes of the misfire, vehicle performance is improved, thereby enhancing reliability, durability, mileage, and user comfort. Misfire detection will inform the driver about misfire events, and by investigating and rectifying the causes of the misfires, the user can improve vehicle performance. Furthermore, timely detection and rectification of engine misfires reduce the degradation of the catalytic converter and lambda sensor performance in the vehicle.In addition to detecting the occurrence of misfires, the misfire detection system of the present invention can detect knocking, determine spark plug timing and measure spark duration, perform combustion quality analysis in the engine and assist in the maintenance of the engine spark plugs, using the ion current measurement circuit. In the present invention, improvements and modifications can be incorporated without deviating from the scope of the invention. LIST OF REFERENCE NUMBERS 100 existing ignition system 101 primary winding 5 101A second end of primary winding 101B first end of primary winding 102 power supply 103 secondary winding 103A second end of secondary winding 10 103B first end of secondary winding 104 electrical switching device 105 control unit 106 spark plug 106A first terminal 15 106B second terminal 107 ignition coil 201 existing ion current measuring circuit 300 misfire detection system 301 first diode 20 302 ion current measuring circuit (present invention) 302A voltage control element 302B biasing resistor 302B1 first terminal 302B2 second terminal 25 302C biasing capacitor 302D second diode 302F detection resistor 303 ignition system (present invention) 401 signal processor

Claims

1. A misfire detection system (300) for an internal combustion engine comprising: an ignition system (303) comprising: an ignition coil (107) comprising a primary winding (101) and a secondary winding (103), wherein a first end (101B) of the primary winding (101) is electrically connected to a first end (103B) of the secondary winding (103), and a spark plug (106) electrically connected in series to a second end (103A) of the secondary winding (103) of the ignition coil (107), wherein a first terminal (106A) of the spark plug (106) is connected to the second end (103A) of the secondary winding (103) and a second terminal (106B) of the spark plug (106) is grounded;an ion current measuring circuit (302) electrically connected to the first end (101B) of the primary winding (101) and to the first end (103B) of the secondary winding (103) to measure an ion current generated by the spark plug (106) after a misfire event, and a signal processor (401) configured to process and condition the ion current measured by the ion current measuring circuit (302) to determine the occurrence of a misfire in the CL engine; 2. The misfire detection system (300) according to claim 1, wherein a second end (101A) of the primary winding (101) of the ignition coil (107) is operatively coupled to a power supply (102) through a first diode (301), and wherein the first end (101B) of the primary winding (101) of the ignition coil (107) is operatively coupled to an electrical switching device (104) to generate a primary voltage in the primary winding (101) and a secondary voltage in the secondary winding (103) of the ignition coil (107), and wherein the electrical switching device (104) is controlled by a control unit (105).

3. The misfire detection system (300) according to claim 2, wherein the first diode (301) allows the flow of a primary current in the primary winding (101) to generate the primary voltage and prevents the flow of ion current through the first end (103B) of the secondary winding (103) in the primary winding (101).

4. The misfire detection system (300) according to claim 1, wherein the ion current measuring circuit (302) comprises a bias resistor (302B) and a bias capacitor (302C) connected to the first end (103B) of the secondary winding (103) to generate a bias voltage for the spark plug (106).

5. The misfire detection system (300) according to claim 4, wherein a first terminal (302B1) of the bias resistor (302B) is connected in series to the first end (103B) of the secondary winding (103), and wherein the bias capacitor (302C) is connected in series to a second terminal (302B2) of the bias resistor (302B).

6. The misfire detection system (300) according to claim 4, wherein the bias capacitor (302C) is charged using a spark current during the spark event at the spark plug (106), and wherein the bias capacitor (302C) is discharged after the spark event to provide the bias voltage for the spark plug (106).

7. The misfire detection system (300) according to claim 4, wherein the biasing capacitor (302C) and the biasing resistor (302B) define a time constant of the ion current measuring circuit (302) and a charging and discharging rate of the biasing capacitor (302C).

8. The misfire detection system (300) according to claim 4, wherein the ion current measuring circuit (302) further comprises a voltage control element (302A) connected in parallel to the bias capacitor (302C) to limit the bias voltage across the bias capacitor (302C) during charging.

9. The misfire detection system (300) according to claim 8, wherein the voltage control element (302A) is a Zener diode.

10. The misfire detection system (300) according to claim 8, wherein the ion current measuring circuit (302) further comprises a network of voltage divider resistors (302E and 302F), comprising a detection resistor (302F), connected in series between the bias capacitor (302C) and ground for measuring the ion current.

11. The misfire detection system (300) according to claim 10, wherein the ion current measuring circuit (302) further comprises a second diode (302D) connected in parallel to the detection resistor (302F) to provide a low impedance path for a spark current and prevent the flow of the ion current.

12. The misfire detection system (300) according to claim 1, wherein the signal processor (401) determines the occurrence of the misfire based on oscillations in the measured ion current.

13. An ion current measuring circuit (302) for measuring an ion current generated from a spark plug (106) of a Cl engine, the ion current measuring circuit (302) comprising: a biasing resistor (302B) connected in series with a first end (101B) of a primary winding (101) and a first end (103B) of a secondary winding (103) of an ignition coil (107), a biasing capacitor (302C) connected in series to a second terminal (302B2) of the biasing resistor (302B) to generate a bias voltage for the spark plug (106), wherein a first terminal (302B1) of the biasing resistor (302B) is connected in series to the first end (103B) of the secondary winding (103); a voltage control element (302A) connected operatively in parallel to the bias capacitor (302C), to limit the voltage across the bias capacitor (302C) during a sparking event;a network of voltage divider resistors (302E and 302F), comprising a sensing resistor (302F), connected in series between the biasing capacitor (302C) and ground to measure the ion current; a second diode (302D) connected in parallel to the sensing resistor (302F) to provide a low impedance path for a spark current and impede the flow of the ion current.

14. The ion current measuring circuit (302) according to claim 13, wherein the polarizing capacitor (302C) is charged using the spark current during the sparking event at the spark plug (106) and is discharged after the sparking event to provide the polarizing voltage to the spark plug (106).

15. The ion current measuring circuit (302) according to claim 13, wherein the spark plug (106) is electrically connected in series to a second end (103A) of the secondary winding (103) of the ignition coil (107), wherein a first terminal (106A) of the spark plug (106) is connected to the second end (103A) of the secondary winding (103) and a second terminal (106B) of the spark plug (106) is connected to ground.

16. The ion current measuring circuit (302) according to claim 13, wherein a second end (103A) of the primary winding (101) of the ignition coil (107) is operatively coupled to a power supply (102) through a first diode (301), and wherein the first end (101B) of the primary winding (101) of the ignition coil (107) is operatively coupled to an electrical switching device (104) to generate a secondary voltage in the secondary winding (103) of the ignition coil (107).

17. The ion current measuring circuit (302) according to claim 16, wherein the first diode (301) allows the flow of primary current in the primary winding (101) and prevents the flow of ion current in the primary winding (101) through the first end (103B) of the secondary winding (103).

18. The ion current measuring circuit (302) according to claim 13, wherein the measured ion current is processed and conditioned by a signal processor (401) to determine the occurrence of a misfire in the Cl engine, based on oscillations in the measured ion current.

19. An ignition system (303) of an internal combustion engine comprising: an ignition coil (107) comprising a primary winding (101) and a secondary winding (103), wherein a first end (101B) of the primary winding (101) is electrically connected to a first end (103B) of the secondary winding (103); a spark plug (106) electrically connected in series to a second end (103A) of the secondary winding (103) of the ignition coil (107), wherein a first terminal (106A) of the spark plug (106) is connected to the second end (103A) of the secondary winding (103) and a second terminal (106B) of the spark plug (106) is connected to ground;and a first diode (301) electrically connected between a power supply (102) and a second end (101 A) of the primary winding (101), wherein the first diode (301) permits the flow of a primary current in the primary winding (101) and prevents the flow of an ion current in the primary winding (101) through the first end (103B) of the secondary winding (103).; 20. The ignition system (303) according to claim 19 further comprises an electrical switching device (104) electrically connected in series to the first end (101B) of the primary winding (101) to generate a secondary voltage in the secondary winding (103) of the ignition coil (107), wherein the electrical switching device (104) is controlled by a control unit (105).

21. The ignition system (303) according to claim 20, wherein each of the first end (101B) of the primary winding (101) and the first end (103B) of the secondary winding (103) is electrically connected to an ion current measuring circuit (302) for measuring the ion current generated by the spark plug (106) after a sparking event.

22. The ignition system (303) according to claim 21, wherein the ion current measuring circuit (302) supplies a bias voltage to the spark plug (106) to generate the ion current.

23. The ignition system (303) according to claim 22, wherein the measured ion current is processed and conditioned by a signal processor (401) to determine the occurrence of an ignition failure in the C1 engine, based on oscillations in the measured ion current.

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