Patent Publication Number: US-11378055-B1

Title: Method of controlling ignition coil

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2021-0016578 filed on Feb. 5, 2021, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a method of controlling an ignition coil. More particularly, the present invention relates to method of controlling an ignition coil which may supply a current to an electrode of a spark plug through two ignition coils. 
     Description of Related Art 
     In gasoline vehicles, a mixture of air and fuel is ignited by a spark generated by a spark plug to be combusted. That is, the air-fuel mixture injected into a combustion chamber during a compression stroke is ignited by a discharge phenomenon of the spark plug, and thus energy required for vehicle&#39;s driving is generated while undergoing a high temperature and high pressure expansion process. 
     The spark plug provided in the gasoline vehicle serves to ignite a compressed air-fuel mixture by spark discharge caused by a high voltage current generated by an ignition coil. 
     In a spark plug mounted on a conventional gasoline vehicle, spark discharge between a pair of electrodes (a center electrode and a ground electrode) is generated by the high voltage current induced from the ignition coil, and in the instant case, difficulties exist in controlling a discharge period of the spark plug according to an operational condition of an engine. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing an ignition coil control system and method which may variously control an ignition timing and discharge period of spark discharge generated between a pair of electrodes. 
     An ignition coil control method of controlling discharge currents of a first ignition coil and a second ignition coil of a spark plug provided in an engine according to various exemplary embodiments of the present invention, the ignition coil control method may include receiving a first pulse signal and a second pulse signal following the first pulse signal by a delay time transmitted from an engine control unit; charging the first ignition coil when the first pulse signal is on; charging the second ignition coil when a predetermined time period elapses from a time point at which the first pulse signal is on; discharging the first ignition coil when the first pulse signal is off; discharging the second ignition coil after a maintaining time of the first pulse signal from a time point at which the second ignition coil is charged; when the second pulse signal is on, charging the first ignition coil for a dwell time and then discharging the first ignition coil; and charging the second ignition coil for the dwell time and then discharging the second ignition coil after a predetermined time period elapses from a time point at which the second ignition coil is discharged. 
     The maintaining time of the first pulse signal may be determined as a time during which the first ignition coil and the second ignition coil are fully charged. 
     Charging and discharging of the first ignition coil and the second ignition coil may be repeated until the second pulse signal is off. 
     A discharging period of the first ignition coil and a discharging period of the second ignition coil overlap after the first ignition coil may be initially discharged. 
     According to various exemplary embodiments of the present invention, it is possible to accurately control, by controlling charging and discharging of two ignition coils by use of two pulse signals transmitted from an engine control unit, an ignition timing in a combustion chamber through spark discharge generated between a center electrode and a ground electrode. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a cross-sectional view of an engine in which a spark plug is mounted according to various exemplary embodiments of the present invention. 
         FIG. 2  illustrates a schematic view of an ignition coil control system according to various exemplary embodiments of the present invention. 
         FIG. 3  and  FIG. 4  illustrate flowcharts of an ignition coil control method according to various exemplary embodiments of the present invention. 
         FIG. 5  illustrates an operation of two ignition coils according to various exemplary embodiments of the present invention. 
     
    
    
     It may be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particularly intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments of the present invention, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the other hand, the invention(s) is/are intended to cover not only the exemplary embodiments of the present invention, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     Exemplary embodiments of the present application will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
     In order to clearly describe the present invention, parts that are irrelevant to the description are omitted, and identical or similar constituent elements throughout the specification are denoted by the same reference numerals. 
     Furthermore, since the size and thickness of each configuration shown in the drawings are arbitrarily shown for convenience of description, the present invention is not necessarily limited to configurations illustrated in the drawings, and in order to clearly illustrate several parts and areas, enlarged thicknesses are shown. 
     Hereinafter, a control system of an ignition coil according to various exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  illustrates a cross-sectional view of an engine in which a spark plug is mounted according to various exemplary embodiments of the present invention. 
     As shown in  FIG. 1 , a spark plug  1  according to various exemplary embodiments of the present invention is mounted on a cylinder of an engine, and generates spark discharge. 
     The engine to which the spark plug  1  is applied includes a cylinder block and a cylinder head  100 , and the cylinder block and the cylinder head  100  are combined to form a combustion chamber  101  therein. An air and fuel mixture inflowing into the combustion chamber  101  is ignited by spark discharge generated by the spark plug  1 . 
     In the cylinder head  100 , a mount hole  110  in which the spark plug  1  is mounted is vertically formed long. A lower portion of the spark plug  1  which is mounted in the mount hole  110  protrudes into the combustion chamber  101 . A center electrode  2  and a ground electrode  3  that are electrically connected to an ignition coil are formed at the lower portion of the spark plug  1 , and the spark discharge is generated between the center electrode  2  and the ground electrode  3 . 
       FIG. 2  illustrates a schematic view of an ignition coil control system according to various exemplary embodiments of the present invention. 
     As shown in  FIG. 2 , an ignition coil control system according to various exemplary embodiments of the present invention may include an ignition controller  40  that adjusts amounts and durations of discharge currents of two ignition coils (a first ignition coil  10  and a second ignition coil  20 ) based on a first pulse signal a second pulse signal followed by a delay time of the first pulse signal having constant voltages transmitted from an engine control unit  50  that controls an overall operation of an engine to control spark discharge generated at the electrodes. 
     The first ignition coil  10  includes a primary coil  11  and a secondary coil  12 , one end portion of the primary coil  11  is electrically connected to a battery  30  of a vehicle, and the other end portion of the primary coil  11  is grounded through a first switch  15 . According to an on/off operation of the first switch  15 , the primary coil  11  of the first ignition coil  10  may be selectively electrically connected. 
     The first switch  15  may be realized with a transistor switch (for example, an insulated gate bipolar transistor (IGBT)) including an emitter terminal  16 , a collector terminal  18 , and a base terminal  17 . That is, the other end portion of the primary coil  11  may be electrically connected to the collector terminal  18  of the first switch  15 , the emitter terminal  16  thereof may be grounded, and the base terminal  17  thereof may be electrically connected to the ignition controller  40 . 
     One end portion of the secondary coil  12  is electrically connected to the center electrode  2 , and the other end portion thereof is electrically connected to the emitter terminal  16  of the first switch  15 . A diode  13  is provided between the secondary coil  12  and the emitter terminal  16  to block a current from flowing from the secondary coil  12  to the emitter terminal  16 . 
     Furthermore, a diode  19  is provided between the secondary coil  12  and the center electrode  2 , so that a current flows only from the secondary coil  12  to the center electrode  2 . 
     When a control signal is applied to the base terminal  17  of the first switch  15  by the ignition controller  40 , the primary coil  11  of the first ignition coil  10  is electrically connected, and electrical energy is charged to the primary coil  11 . When no control signal is applied to the base terminal  17  of the first switch  15  by the ignition controller  40 , a high voltage current (or discharge current) is generated in the secondary coil  12  due to electromagnetic induction of the primary coil  11  and the secondary coil  12 . The discharge current generated in the secondary coil  12  flows to the center electrode  2 , and while spark discharge being generated between the center electrode  2  and the ground electrode  3  by the discharge current generated in the secondary coil  12 , an air-fuel mixture inside the combustion chamber  101  is ignited. 
     That is, the ignition controller  40  charges or discharges the first ignition coil  10  by turning on/off the first switch  15 . When the ignition controller  40  applies a control signal to the base terminal  17  of the first switch  15  (or when the switch is turned on), the primary side coil  11  is charged (or the first ignition coil is charged). 
     Furthermore, when the ignition controller  40  does not apply a control signal to the base terminal  17  of the first switch  15  (or when the first switch is turned off), a high voltage current is generated in the secondary coil  12  due to electromagnetic induction with the primary coil  11 , and spark discharge is generated between the center electrode  2  and the ground electrode  3  (or the first ignition coil is discharged) by the high voltage current generated in the secondary coil  12 . 
     Like the first ignition coil  10 , the second ignition coil  20  includes a primary coil  21  and a secondary coil  22 , one end portion of the primary coil  21  is electrically connected to the battery  30  of the vehicle, and the other end portion of the primary coil  21  is grounded through a second switch  25 . According to an on/off operation of the second switch  25 , the primary coil  21  of the second ignition coil  20  may be selectively electrically connected. 
     The second switch  25  may be realized with a transistor switch (for example, an insulated gate bipolar transistor (IGBT)) including an emitter terminal  26 , a collector terminal  28 , and a base terminal  27 . That is, the other end portion of the primary coil  21  may be electrically connected to the collector terminal  28  of the second switch  25 , the emitter terminal  26  thereof may be grounded, and the base terminal  27  thereof may be electrically connected to the ignition controller  40 . 
     One end portion of the secondary coil  22  is electrically connected to the center electrode  2 , and the other end portion thereof is electrically connected to the emitter terminal  26  of the second switch  25 . A diode  23  is provided between the secondary coil  22  and the emitter terminal  26  to block a current from flowing from the secondary coil  22  to the emitter terminal  26 . 
     Furthermore, the diode  23  is provided between the secondary coil  22  and the center electrode  2 , so that a current flows only from the secondary coil  22  to the center electrode  2 . 
     When a control signal is applied to the base terminal  27  of the second switch  25  by the ignition controller  40 , the primary coil  21  of the second ignition coil  20  is electrically connected, and electrical energy is charged to the primary coil  21 . When no control signal is applied to the base terminal  27  of the second switch  25  by the ignition controller  40 , a high voltage current (or discharge current) is generated in the secondary coil  22  due to electromagnetic induction of the primary coil  21  and the secondary coil  22 . The discharge current generated in the secondary coil  22  flows to the center electrode  2 , and while spark discharge being generated between the center electrode  2  and the ground electrode  3  by the discharge current generated in the secondary coil  22 , an air-fuel mixture inside the combustion chamber  101  is ignited. 
     That is, the ignition controller  40  charges or discharges the second ignition coil  20  by turning the second switch  25  on/off. When the ignition controller  40  applies a control signal to the base terminal  27  of the second switch  25  (or when the switch is turned on), the primary side coil  21  is charged (or the second ignition coil is charged). 
     Furthermore, when the ignition controller  40  does not apply a control signal to the base terminal  27  of the second switch  25  (or when the second switch is turned off), a high voltage current is generated in the secondary coil  22  due to electromagnetic induction with the primary coil  21 , and spark discharge is generated between the center electrode  2  and the ground electrode  3  (or the second ignition coil is discharged) by the high voltage current generated in the secondary coil  22 . 
     In the specification of the present invention, charging the primary coil of the first ignition coil  10  by turning on the first switch  15  is referred to as charging the first ignition coil  10 , and a high voltage current is induced to the secondary coil of the first ignition coil  10  by turning off the first switch  15  and thus spark discharge occurs between the center electrode  2  and the ground electrode  3  is referred to as the first ignition coil  10  being discharged. 
     Likewise, charging the primary coil of the second ignition coil  20  by turning on the second switch  25  is referred to as charging the second ignition coil  20 , and a high voltage current is induced to the secondary coil of the second ignition coil  20  by turning off the second switch  25  and thus spark discharge occurs between the center electrode  2  and the ground electrode  3  is referred to as the second ignition coil  20  being discharged. 
     The ignition coil control system according to the exemplary embodiment of the present invention controls the charging and discharging of the two ignition coils based on the pulse signal transmitted from the engine control unit  50 , so that it is possible to accurately control the ignition timing of the spark discharge generated between the center electrode  2  and the ground electrode  3 . 
     To the present end, the ignition controller  40  may be provided as at least one processor executed by a predetermined program, and the predetermined program is configured to perform respective steps of a control method of the spark plug  1  according to various exemplary embodiments of the present invention. 
     Hereinafter, the operation of the ignition coil control system according to the exemplary embodiment of the present invention as described above will be described in detail with reference to the accompanying drawings. 
       FIG. 3  and  FIG. 4  illustrate flowcharts of an ignition coil control method according to various exemplary embodiments of the present invention. Furthermore,  FIG. 5  illustrates an operation of two ignition coils according to various exemplary embodiments of the present invention. 
     An ignition coil control method according to various exemplary embodiments of the present invention, in an engine including a spark plug generating spark discharge caused by a high voltage current generated by a first ignition coil and a second ignition coil, controls discharge current 
     As shown in  FIG. 3  to  FIG. 5 , the engine control unit (ECU)  50  transmits a pulse signal (or ECU signal) to the ignition controller  40  to ignite the air-fuel mixture inflowing into the combustion chamber  101  during an explosion stroke of the engine. In the instant case, the pulse signal includes a first pulse signal having constant voltage (e.g., 12V) and a predetermined time period and a second pulse signal followed by a predetermined delay time of the first pulse signal transmitted from the engine control unit  50 . The second pulse signal has same voltage (e.g., 12V) as the first pulse signal. 
     Here, a period of the first pulse signal (maintaining time of first pulse signal) may be determined as a time during which the first ignition coil  10  and the second ignition coil  20  are fully charged. In the instant case, the time during which the first ignition coil  10  and the second ignition coil  20  are fully charged may be changed according to the output voltage of the battery  30 . For example, when the output voltage of the battery  30  is high, the maintaining time of the first pulse signal may be shortened, and when the output voltage of the battery  30  is low, the maintaining time of the first pulse signal may be lengthened. 
     When the pulse signal is transmitted from the engine control unit  50 , the ignition controller  40  charges and then discharges the first ignition coil  10  in synchronization with the first pulse signal. That is, the ignition controller  40  turns on the first switch  15  to charge the first ignition coil  10  in synchronization with ON time of the pulse signal (or, when the first pulse signal is on) at step S 20 . 
     When a first delay time elapses from the time point at which the first pulse signal is on at step S 30 , the ignition controller  40  turns on the second switch  25  to charge the second ignition coil  20  at step S 40 . 
     The ignition controller  40  turns off the first switch  15  to discharge the first ignition coil  10  in synchronization with OFF time of the first pulse signal. That is, when the first pulse signal is off at step S 50 , the ignition controller  40  turns off the first switch  15  to discharge the first ignition coil  10  at step S 60 . 
     When the maintaining time of the first pulse signal elapses from the charging time point of the second ignition coil  20  at step S 70 , the ignition controller  40  discharges the second ignition coil  20  by turning off the second switch  25  at step S 80 . 
     The ignition controller  40  charges and then discharges the first ignition coil  10  in synchronization with the second pulse signal. That is, when the first pulse signal is on at step S 90 , the ignition controller  40  turns on the first switch  15  to charge the first ignition coil  10  during a dwell time and then discharge the first ignition coil  10  at step S 100 . Here, the dwell time may be shorter than the maintaining time of the first pulse signal, and shorter than the maintaining time of the second pulse signal. 
     After the first ignition coil  10  is discharged, the ignition controller  40  charges the second ignition coil  20  during the dwell time and then discharged the second ignition coil  20  at step S 110 . 
     When the second pulse signal is not turned off at S 120 , steps S 100  and S 110  repeated. That is, the ignition controller  40  repeats charging and discharging of the first ignition coil  10  and the second ignition coil  20  until the second pulse signal is off. 
     In the instant case, after the first ignition coil  10  is initially discharged, the ignition controller  40  adjusts the charging timing and discharging timing of the first ignition coil  10 , and the charging timing and discharging timing of the second ignition coil  20 , so that a charging period of the first ignition coil  10  and a charging period of the second ignition coil  20  do not overlap. In other words, after the first ignition coil  10  is initially discharged, the discharging period of the first ignition coil  10  and the discharging period of the second ignition coil  20  may overlap. 
     As described above, when the discharging period of the first ignition coil  10  and the discharging period of the second ignition coil  20  overlap, the spark discharge is continuously generated between the center electrode  2  and the ground electrode  3 , and ignition energy may be efficiently transmitted to the air-fuel mixture in the combustion chamber  101 . Therefore, the discharge efficiency of the spark plug  1  may be improved. 
     When the second pulse signal is off at step S 120 , the ignition controller  40  discharges the first ignition coil  10  or the second ignition coil  20  at step S 130 . For example, when the second pulse signal is off while the first ignition coil  10  is being charged, the ignition controller  40  discharges the first ignition coil  10  when the second pulse signal is off. Furthermore, when the second pulse signal is off while the second ignition coil  20  is being charged, the ignition controller  40  discharges the second ignition coil  20  when the second pulse signal is off. 
     According to various exemplary embodiments of the present invention, by controlling the charging and discharging of the two ignition coils by use of two pulse signals transmitted from the engine control unit  50 , the ignition timing in the combustion chamber  101  through the spark discharge generated between the center electrode  2  and the ground electrode  3  may be accurately controlled. 
     Furthermore, by use of the two pulse signals transmitted from the engine control unit  50 , the multi-stage ignition of the spark plug may be easily controlled. That is, by fully charging and the discharging the first ignition coil  10  and second ignition coil  20  by use of the preceding first pulse signal, the multi-stage ignition of the spark plug may be easily controlled. Furthermore, multi-stage ignition may be easily implemented by repeating the charging and discharging of the first ignition coil  10  and the second ignition coil  20  based on the following the second pulse signal. 
     Through this, the initial combustion speed is prevented from increasing, and knocking is prevented, so that the engine output and fuel economy may be improved. Furthermore, even when the ignition property of the air-fuel mixture is degraded, such as when exhaust gas recirculation (EGR) gas is supplied to the combustion chamber  101  of the engine or a lean combustion occurs, sufficient ignition energy may be supplied into the combustion chamber  101 . 
     Furthermore, the term related to a control device such as “controller”, “control unit”, “control device” or “control module”, etc refers to a hardware device including a memory and a processor configured to execute one or more steps interpreted as an algorithm structure. The memory stores algorithm steps, and the processor executes the algorithm steps to perform one or more processes of a method in accordance with various exemplary embodiments of the present invention. The control device according to exemplary embodiments of the present invention may be implemented through a nonvolatile memory configured to store algorithms for controlling operation of various components of a vehicle or data about software commands for executing the algorithms, and a processor configured to perform operation to be described above using the data stored in the memory. The memory and the processor may be individual chips. Alternatively, the memory and the processor may be integrated in a single chip. The processor may be implemented as one or more processors. The processor may include various logic circuits and operation circuits, may process data according to a program provided from the memory, and may generate a control signal according to the processing result. 
     The control device may be at least one microprocessor operated by a predetermined program which may include a series of commands for carrying out the method disclosed in the aforementioned various exemplary embodiments of the present invention. 
     The aforementioned invention can also be embodied as computer readable codes on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which may be thereafter read by a computer system. Examples of the computer readable recording medium include hard disk drive (HDD), solid state disk (SSD), silicon disk drive (SDD), read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy discs, optical data storage devices, etc and implementation as carrier waves (e.g., transmission over the Internet). 
     In various exemplary embodiments of the present invention, each operation described above may be performed by a control device, and the control device may be configured by multiple control devices, or an integrated single control device. 
     In various exemplary embodiments of the present invention, the control device may be implemented in a form of hardware or software, or may be implemented in a combination of hardware and software. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner”, “outer”, “up”, “down”, “upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”, “inwardly”, “outwardly”, “interior”, “exterior”, “internal”, “external”, “forwards”, and “backwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. It will be further understood that the term “connect” or its derivatives refer both to direct and indirect connection. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described to explain certain principles of the present invention and their practical application, to enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the present invention be defined by the Claims appended hereto and their equivalents.