JP2018200008A - Ignition control device of internal combustion engine - Google Patents

Abstract

To properly control discharge energy supplied to an ignition plug over the whole area of a discharge period according to an in-cylinder environmental change.SOLUTION: An ignition control device 1 of an internal combustion engine E comprises an ignition coil 2 having a primary coil 21 and a secondary coil 22, an ignition plug P for generating spark discharge at a spark gap G, and an ignition control part 3 for controlling an electrification operation during the spark discharge. The ignition control device also comprises a crank angle detection part S1. The ignition control part has a discharge timing setting part 31 for setting discharge start timing and a discharge period according to an operation state of the internal combustion engine, and a target current setting part 32 for setting a target value I2tgt of an electrification current I2 to the ignition plug in the discharge period. The target current setting part sets the target value so that an absolute value of the target value becomes smaller as the detected crank angle approximates a top dead center TDC.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ignition control device that is used in a spark ignition internal combustion engine to control ignition.

  In a spark ignition type internal combustion engine, ignition energy stored in an ignition coil is input to an ignition plug provided for each cylinder to cause a spark discharge to ignite an air-fuel mixture in a combustion chamber. In general, the ignition control device performs on / off control of energization of the primary coil of the ignition coil in accordance with the operating state, thereby generating a high voltage in the secondary coil by electromagnetic induction and discharging the spark plug in the spark gap. I have control.

  In recent years, in order to improve fuel efficiency of internal combustion engines, lean combustion (ie, lean burn) control that makes the air-fuel ratio leaner than the stoichiometric air-fuel ratio, and exhaust gas recirculation that recirculates part of the exhaust gas to the intake side (ie, EGR) control is being implemented. At the time of these controls, the fuel concentration in the air-fuel mixture becomes lean and the ignitability decreases, so a technique for stably realizing ignition by spark discharge is required.

  On the other hand, in order to improve ignitability, an ignition system is known in which a spark plug is subjected to multiple discharges. For example, the ignition control device disclosed in Patent Document 1 increases the chance of ignition by repeating ON / OFF of energization to the primary coil a plurality of times at a constant discharge interval during one combustion cycle of the internal combustion engine. . Further, the time required for each discharge is made to follow the transition of the pressure in the combustion chamber (that is, the in-cylinder pressure), so that energy necessary for ignition is input.

  In addition, an ignition system has been proposed in which energy is input from a plurality of power sources to continuously discharge the spark plug. For example, energy can be supplied to the primary coil so that the discharge started by the main power source is maintained by supplying energy from the auxiliary power source including the booster circuit after the start of the discharge by the main power source.

JP 2001-153016 A

  Specifically, the ignition method of Patent Document 1 is set so that the time of each discharge is shortened as the in-cylinder pressure increases. For example, in ignition after compression top dead center, as the number of discharges increases, the time of each discharge is gradually lengthened to suppress wasteful energy consumption. However, in this ignition system, although energy consumption is suppressed, as the number of discharges increases, the energy stored in the ignition coil decreases. Therefore, when a certain number of discharges or a discharge period is exceeded, the necessary discharge energy cannot be obtained. .

  In addition, the ignition method using continuous discharge can maintain the discharge energy necessary for ignition by supplying energy after the discharge is formed, but the required discharge energy is input without excess or deficiency in response to environmental changes during the discharge period. It ’s difficult. Therefore, the energy input to the spark plug is likely to be excessive, and not only the energy efficiency is lowered, but also the durability of the spark plug may be lowered due to electrode consumption.

  In particular, in a lean environment such as when lean air-fuel ratio or EGR is increased, the discharge period tends to be expanded in order to improve ignitability. For example, if the in-cylinder environment is different between the early stage and late stage The discharge energy density required for ignition also changes. Even in such a case, it is desired to appropriately control the discharge energy density throughout the discharge period.

  The present invention has been made in view of such problems, and appropriately controls the discharge energy supplied to the spark plug over the entire discharge period in accordance with the in-cylinder environment change of the internal combustion engine. It is intended to provide an ignition control device that enhances energy efficiency and durability by suppressing excessive energy supply.

One embodiment of the present invention provides:
An ignition coil (2) having a primary coil (21) and a secondary coil (22);
An ignition plug (P) that is connected to the secondary coil and that generates a spark discharge in the spark gap (G) by electromagnetic induction associated with on / off of energization of the primary coil;
Ignition control of an internal combustion engine (E) comprising: an ignition control unit (3) for starting a spark discharge in the combustion chamber by turning on / off the energization of the primary coil and controlling an energization operation during the spark discharge. A device (1) comprising:
A crank angle detector (S1) for detecting a crank angle of the internal combustion engine,
The ignition control unit includes a discharge timing setting unit (31) that sets a discharge start timing and a discharge period according to an operating state of the internal combustion engine, and a target value of an energization current (I2) to the spark plug during the discharge period. The target current setting unit (32) for setting (I2tgt) has a smaller absolute value of the target value as the detected crank angle is closer to the top dead center (TDC). In the ignition control device for an internal combustion engine, the target value is set.

Another aspect of the present invention is as follows:
An ignition coil (2) having a primary coil (21) and a secondary coil (22);
An ignition plug (P) that is connected to the secondary coil and that generates a spark discharge in the spark gap (G) by electromagnetic induction associated with on / off of energization of the primary coil;
Ignition control of an internal combustion engine (E) comprising: an ignition control unit (3) for starting a spark discharge in the combustion chamber by turning on / off the energization of the primary coil and controlling an energization operation during the spark discharge. A device (1) comprising:
A plurality of ignition plugs (PA, PB) having different spark gap lengths (GAPa, GAPb) are provided in the combustion chamber, and a crank angle detection unit (S1) for detecting a crank angle of the internal combustion engine is provided. Has
The ignition control unit includes a discharge timing setting unit (31) for setting a discharge start timing and a discharge period according to the operating state of the internal combustion engine, and a plug for sequentially switching the ignition plug for forming a spark discharge in one combustion cycle. An internal combustion engine having a switching unit (35), wherein the plug switching unit forms a spark discharge in the spark plug having a shorter spark gap length as the detected crank angle is closer to top dead center (TDC). It is in the ignition control device of the engine.

  The energy of the spark discharge generated in the spark gap of the spark plug changes depending on the state in the combustion chamber of the internal combustion engine. For example, when the pressure in the combustion chamber during the discharge period differs, the discharge energy density required for ignition also changes. Therefore, the ignition control unit in the above aspect performs the energization operation of the spark plug during the spark discharge, and the target current setting unit controls the energization current during the discharge period to the target value. Furthermore, by using the crank angle corresponding to the pressure in the combustion chamber, the target value of the energization current is decreased as the top dead center is approached, so that the discharge energy density required for ignition in accordance with the pressure change in one combustion cycle. Can be optimally controlled by changing the time.

  Therefore, for example, even when the discharge period is extended in response to a request for increasing energy in a lean environment, an appropriate discharge energy density can be maintained. In addition, as in the other embodiment, a spark plug having a shorter spark gap length is used as the plug switching unit of the ignition control unit is closer to the top dead center, using a plurality of spark plugs having different spark gap lengths. Even if the selection is made, the same effect can be obtained. As a result, it is possible to effectively input discharge energy necessary for the spark gap to improve ignitability and to suppress electrode consumption of the spark plug.

As described above, according to the above aspect, the discharge energy supplied to the spark plug is appropriately controlled over the entire discharge period in accordance with the change in the in-cylinder environment of the internal combustion engine, so that the ignitability is increased and excessive. Energy supply can be suppressed and energy efficiency and durability can be improved.
In addition, the code | symbol in the parenthesis described in the means to solve a claim and a subject shows the correspondence with the specific means as described in embodiment mentioned later, and limits the technical scope of this invention. It is not a thing.

1 is a circuit configuration diagram of an internal combustion engine ignition control device in Embodiment 1. FIG. 1 is an overall configuration diagram of an ignition system including an ignition control device in Embodiment 1. FIG. The figure which shows the relationship between the crank angle of an engine, the pressure in a combustion chamber, and the required discharge energy density for every air fuel ratio in Embodiment 1. FIG. The figure which shows the relationship of the crank angle of an engine, discharge energy density, and discharge secondary current in Embodiment 1. FIG. The figure which shows the relationship between the discharge energy thrown into a spark plug and ignition limit air-fuel ratio in Embodiment 1. FIG. The figure which shows the other example of the relationship between the crank angle of an engine, discharge energy density, and discharge secondary current in Embodiment 1. FIG. The figure which shows the other example of the relationship between the crank angle of an engine, discharge energy density, and discharge secondary current in Embodiment 1. FIG. The time chart figure of the ignition control processing implemented in the ignition control part of the ignition control device in Embodiment 1. The flowchart figure of the calculation process of the target value of an electric discharge secondary current, an upper limit threshold value, and a lower limit threshold value implemented in the ignition control part of the ignition control apparatus in Embodiment 1. The figure which shows the relationship between the airflow speed in the combustion chamber of an engine, and a blow-off electric current in Embodiment 1. FIG. The figure which shows the relationship between the crank angle of an engine and the target value of the discharge secondary current for every air fuel ratio in Embodiment 1. FIG. The flowchart figure of the feedback control process of the discharge secondary current implemented in the ignition control part of the ignition control apparatus in Embodiment 1. FIG. The time chart figure of the ignition control process implemented in the ignition control part of the ignition control apparatus in Embodiment 2. FIG. FIG. 5 is a circuit configuration diagram of an engine ignition control device according to a third embodiment. The time chart figure of the ignition control processing implemented in the ignition control part of the ignition control apparatus in Embodiment 3. The flowchart figure of the ignition control process implemented in the ignition control part of the ignition control apparatus in Embodiment 3. FIG. 6 is a schematic configuration diagram of an engine ignition control device according to a fourth embodiment. The figure which shows the relationship between the distance between electrodes of the ignition plug of an ignition control apparatus and discharge path length in Embodiment 4, and the relationship between discharge path length, an average secondary voltage, and an average energy density. The time chart figure of the ignition control processing implemented in the ignition control part of the ignition control apparatus in Embodiment 4. The flowchart figure of the ignition control process implemented in the ignition control part of the ignition control apparatus in Embodiment 4.

(Embodiment 1)
A first embodiment of an ignition control device for an internal combustion engine will be described with reference to FIGS.
In FIG. 1, an ignition control device 1 is a device that controls ignition of a spark plug P provided in an internal combustion engine for a vehicle, and includes an ignition coil 2 having a primary coil 21 and a secondary coil 22, and two ignition coils 2. A spark plug P connected to the next coil 22 and an ignition control unit 3 for controlling the ignition operation of the spark plug P are provided. A power supply circuit unit 10 is connected to the primary coil 21 of the ignition coil 2, and the spark plug P generates a spark discharge in the spark gap G due to electromagnetic induction accompanying on / off of energization to the primary coil 21. . The ignition control unit 3 starts a spark discharge by turning on / off the energization of the primary coil 21 and controls an energization operation after the start of the spark discharge.

  The power supply circuit unit 10 includes a main power supply circuit 11 having a battery B and an ignition switch Tr1, a booster circuit 4, and an auxiliary power supply circuit 5, and enables the spark plug P to be continuously discharged. The primary coil 21 of the ignition coil 2 has one end connected to the battery B and the other end connected to the ignition switch Tr1. The step-up circuit 4 includes a step-up switch Tr 2, a step-up driver 40, a choke coil 41, a first rectifier element 42, and a capacitor 43. The auxiliary power supply circuit 5 includes a discharge switch Tr3, a second rectifier element 51, and an auxiliary driver 50. The discharge switch Tr3 is connected between the other end of the primary coil 21 and the ignition switch Tr1.

  In the main power supply circuit 11, the ignition switch Tr 1 opens and closes an energization path from the battery B to the primary coil 21. The booster circuit 4 accumulates the energy generated in the choke coil 41 in the capacitor 43 of the auxiliary power supply circuit 5 by the switching operation of the booster switch Tr2. The auxiliary power supply circuit 5 opens and closes the energization path from the capacitor 43 to the primary coil 21 by the switching operation of the discharge switch Tr3, and supplies the energy accumulated in the capacitor 43 to the primary coil 21.

  Detection signals from various sensors including a crank angle sensor S1 that is a crank angle detector and an air-fuel ratio sensor S2 that is an air-fuel ratio detector are input to the ignition controller 3. The ignition control unit 3 performs discharge based on the discharge timing setting unit 31 that sets the discharge start timing and the discharge period according to the operating state of the internal combustion engine E known from these detection signals, and the detection signal of the crank angle sensor S1. A target current setting unit 32 is provided for setting a target value I2tgt of the discharge secondary current I2, which is a current flowing to the spark plug P during the period.

  The target current setting unit 32 sets the target value I2tgt so that the absolute value of the target value I2tgt of the discharge secondary current I2 decreases as the crank angle detected by the crank angle sensor S1 is closer to the top dead center TDC. To do. As the crank angle is closer to the top dead center TDC and the air-fuel mixture is compressed, the energy of the air-fuel mixture becomes higher, so that the input energy can be reduced accordingly. Further, since the discharge energy density required for ignition becomes high during lean combustion, preferably, the target value of the discharge secondary current I2 becomes smaller as the fuel concentration in the air-fuel mixture detected by the air-fuel ratio sensor S2 becomes leaner. It is preferable to increase the absolute value of I2tgt.

  Further, the ignition control unit 3 includes a feedback control unit that sets an upper limit threshold value I2THH and a lower limit threshold value I2THL for feedback control of the discharge secondary current I2. The feedback control unit 33 feedback-controls the discharge secondary current I2 using the upper limit threshold value I2THH and the lower limit threshold value I2THL, and maintains it near the target value I2tgt. At this time, in order to prevent the spark discharge from being blown out, the lower limit threshold I2THL is set so that the discharge secondary current I2 does not fall below a current value at which the discharge does not blow out (hereinafter referred to as the blow-off current I2bo). It is desirable to do.

In order to control the spark discharge in one combustion cycle, the ignition control unit 3 outputs an ignition signal IGt from the discharge timing setting unit 31 to the ignition switch Tr1 and the booster driver 40 before starting the discharge. Further, a discharge maintaining signal IGw is output to the auxiliary driver 50 in order to maintain the spark discharge for a predetermined period after the start of the spark discharge. A target secondary current signal IGa corresponding to the target value I2tgt of the discharge secondary current I2 is output from the target current setting unit 32 to the auxiliary driver 50, and further, from the feedback control unit 33, an upper limit threshold I2THH and a lower limit threshold A feedback threshold signal corresponding to I2THL is output.
Details of the control by each part of the ignition control unit 3 will be described later.

  As shown in FIG. 2, the internal configuration of the ignition system is, for example, a port injection type gasoline engine (hereinafter referred to as “engine”) E having an EGR device, and an ignition plug P is a cylinder of the engine E. It faces the combustion chamber 101 provided in E1. A crank angle sensor S1 that outputs a crank pulse signal corresponding to the crank angle is provided in the vicinity of the crankshaft 103 connected to the piston 102 that reciprocates inside the cylinder E1. Is input to an engine electronic control unit (hereinafter referred to as ECU) 100 for controlling the engine. The ignition control unit 3 constitutes a part of the ECU 100.

  An air-fuel mixture of air introduced into the intake passage 104 via the throttle valve TH and fuel injected from the fuel injection valve INJ is introduced into the combustion chamber 101 of the engine E. An intake valve Vin and an exhaust valve Vex are provided between the combustion chamber 101 and the intake passage 104 and the exhaust passage 105, respectively. The intake passage 104 and the exhaust passage 105 are connected by an EGR passage 106 including an EGR valve Vegr. The In the middle of the EGR passage 106, an EGR cooler 107 including a refrigerant metering valve 108 is provided.

  The intake passage 104 is provided with an intake air amount sensor S4 and an intake pressure / intake temperature sensor S5, and the exhaust passage 105 is provided with an air-fuel ratio sensor S2. An airflow velocity sensor S3 as an airflow velocity detector is provided in the vicinity of the ignition plug P of the combustion chamber 101, and an engine water temperature sensor S7 is provided on the cylinder E1 wall. Further, an EGR gas pressure sensor S7 is provided in the EGR passage 106, and an accelerator opening sensor S8 is provided in the vicinity of the accelerator pedal 109. The detection results of these sensors S2 to S8 are input to the ECU 100.

  The ECU 100 knows the operating state of the engine E based on detection signals from various sensors including the crank angle sensor S1, and controls each part of the engine including the ignition control device 1 so as to obtain an optimal engine combustion state. Specifically, the ignition control unit 3 outputs a command signal to drive the ignition coil 2, and the fuel injection valve INJ is driven at the fuel injection amount and the fuel injection timing according to the operating state to control the fuel injection. To do. In addition, the TH actuator connected to the throttle valve TH, the EGR actuator of the EGR valve Vegr, and the refrigerant metering valve 108 are driven to control the intake air amount and the EGR amount according to the target air-fuel ratio and the like, and the EGR gas Controls the amount of refrigerant to be cooled.

  The spark plug P has a known configuration including a center electrode and a ground electrode. For example, the spark plug P may have a configuration in which a center electrode having a needle-like electrode tip faces a planar ground electrode. In the combustion chamber 101, the spark plug P has a spark gap G (for example, see FIG. 1) as a space between the tips of both electrodes in the axial direction (that is, the vertical direction in FIG. 2). When dielectric breakdown occurs in the spark gap G due to the energy supplied from the ignition coil 2, a spark discharge occurs and extends sideways by the surrounding mixed air current, and ignites the air-fuel mixture. Since this discharge elongation correlates with the air velocity, it may be used for estimating the air velocity as will be described later.

  Below, the structure of the ignition control apparatus 1 is explained in full detail. In FIG. 1, the ignition coil 2 includes a primary coil 21 and a secondary coil 22. The primary coil 21 and the secondary coil 22 are magnetically coupled through the core, and when the primary current I1 is cut off after the primary coil 21 is energized, the secondary coil 22 has a high secondary voltage V2. Occurs. One end of the primary coil 21 is connected to the positive side of the battery B, and the other end of both ends is grounded via the ignition switch Tr1. The battery B is a DC power source such as an in-vehicle battery, and the negative electrode side of the battery 10 is grounded.

  The secondary coil 22 has one end connected to the spark plug P, and the other end connected to the ground via a rectifying element 61 and a current detecting shunt resistor 62. The rectifying element 61 is formed of a diode, and is provided so that the anode side is connected to the secondary coil 22 and the cathode side is grounded, and rectifies the discharge secondary current I2 flowing through the secondary coil 22. The rectifying element 61 and the shunt resistor 62 constitute a feedback circuit 6 for detecting the discharge secondary current I2. The discharge secondary current I2 detected by the shunt resistor 62 is voltage-converted and input to the ignition control unit 3, and also input to the auxiliary driver 50 and output from the feedback control unit 33, and the upper limit threshold I2THH and the lower limit Feedback control is performed based on the threshold value I2THL.

  As the ignition switch Tr1 constituting the main power supply circuit 11, a known switching element, for example, a power transistor such as an IGBT (that is, an insulated gate bipolar transistor) is used. The ignition switch Tr1 has a collector connected to the primary coil 21 and an emitter grounded, and performs a switching operation based on a signal input to the gate. A rectifying element 12 is connected in parallel between the collector and the emitter. When the ignition switch Tr1 is turned on, a current flow from the primary coil 21 to the ground side is allowed. When the ignition switch Tr1 is turned off, a current flow from the primary coil 21 to the ground side is allowed. Blocked.

  The booster circuit 4 is a DC-DC converter, and boosts the battery voltage to charge the capacitor 43. The choke coil 41 is connected to the battery B in parallel with the primary coil 21, and the capacitor 43 is connected in parallel via the boosting switch Tr 2 and the first rectifying element 42. For the step-up switch Tr2, a known switching element, for example, a power transistor such as a MOSFET (that is, a field effect transistor) is used. The booster switch Tr2 has a drain connected to the choke coil 41 and a source grounded, and performs a switching operation based on a signal input to the gate.

  The step-up switch Tr2 is driven by an input signal from the step-up driver 40, and switches supply and interruption of current to the choke coil 41 at a predetermined cycle. The first rectifying element 42 is constituted by a diode, and the anode side is connected between the choke coil 41 and the boosting switch Tr2, and the cathode side is connected to the capacitor 43 to rectify the current from the choke coil 41.

  The discharge switch Tr3 constituting the auxiliary power supply circuit 5 is a known switching element, for example, a power transistor such as a MOSFET, the drain is connected between the choke coil 41 and the booster switch Tr2, and the source is the primary coil 21. It is connected between the ignition switch Tr3. The discharge switch Tr3 performs a switching operation based on a signal input to the gate, and when it is in an on state, allows a current to flow from the auxiliary power circuit 5 to the primary coil 21, and when in an off state, the auxiliary power circuit The flow of current from 5 to the primary coil 21 is cut off. The second rectifying element 51 is composed of a diode, the anode side is connected to the source of the discharge switch Tr3, and the cathode side is connected between the primary coil 21 and the ignition switch Tr1, and is supplied from the auxiliary power circuit 5. The current is rectified.

  The discharge switch Tr3 is driven by an input signal from the auxiliary driver 50, and switches the energy from the capacitor 43 to the connection point between the primary coil 21 of the ignition coil 2 and the ignition switch Tr1 and stops. Thereby, the auxiliary power supply circuit 5 can superimpose the energy boosted by the booster circuit 4 and accumulated in the capacitor 43 to the ground side of the primary coil 21. That is, the secondary voltage V2 generated in the secondary coil 22 is applied to the spark plug P to cause a spark discharge, and energy is further supplied from the auxiliary power supply circuit 5 during the discharge period, and the secondary voltage V2 is The secondary discharge current I2 flowing from the coil 22 to the spark plug P can be increased.

  In the ignition control unit 3, the discharge timing setting unit 31 calculates a reference discharge energy based on the required torque of the engine E known from the detection results of various sensors and other operating states, and spark discharges the spark plug P. In order to start the discharge, an optimal discharge start time and discharge period are set. The target current setting unit 32 sets the target value I2tgt according to the state in the combustion chamber 101 so that the discharge secondary current I2 flows through the spark plug P without excess or deficiency during the discharge period, and updates it as needed. The feedback control unit 33 sets an upper limit threshold I2THH and a lower limit threshold I2THL, which are threshold values for feedback control, based on the target value I2tgt so that the discharge secondary current I2 is maintained at the target value I2tgt, and updates it as needed.

  Here, as shown in FIG. 3, the pressure in the combustion chamber 101 of the engine E varies depending on the crank angle. That is, the in-cylinder pressure increases or decreases in accordance with the reciprocating position of the piston 102 (for example, see FIG. 2) in the cylinder H1, and becomes maximum at the top dead center TDC. The amount of discharge energy required for ignition is generally determined by the pressure in the combustion chamber 101, and the discharge energy per unit time (hereinafter referred to as discharge energy density) is minimized at the top dead center TDC. This is because the closer the crank angle is to the top dead center TDC and the air-fuel mixture is compressed, the higher the pressure in the combustion chamber 101 and the higher the energy of the air-fuel mixture, and the necessary amount of discharge energy is descend.

  On the other hand, the required discharge energy density also varies depending on the air-fuel ratio of the air-fuel mixture in the combustion chamber 101 (for example, the case of A / F 20, 23, 28 is shown in FIG. 3). When the pressure in the combustion chamber 101 is the same, the thinner the fuel concentration of the air-fuel mixture, that is, the higher the air-fuel ratio, the higher the required discharge energy density, and the smaller the air-fuel ratio, the more necessary discharge energy. Density decreases. In addition, the higher the pressure in the combustion chamber 101, the smaller the difference in discharge energy density due to the difference in air-fuel ratio. The lower the pressure in the combustion chamber 101, the greater the difference in discharge energy density. This is because the air-fuel ratio decreases and the fuel concentration in the mixture increases, so that the ignitability of the mixture is improved.

  Therefore, the higher the pressure in the combustion chamber 101, the higher the discharge voltage during discharge formation, and the lower the air-fuel ratio and the higher the density of the air-fuel mixture, so that the energy efficiency transmitted to the air-fuel mixture by the discharge spark is increased. Since it becomes large, it becomes easy to form a flame. Therefore, it is possible to control the discharge energy density to a required level by changing the target value I2tgt of the discharge secondary current I2 in accordance with the in-cylinder pressure that changes depending on the crank angle, and taking the air-fuel ratio into consideration.

  Here, the lean fuel concentration means that the proportion of fuel in the air-fuel mixture formed in the combustion chamber 101 is low. In other words, the proportion of fresh air or EGR gas that is a working gas other than fuel. Is high. In the lean burn control and the EGR control, by setting the target value I2tgt of the discharge secondary current I2 according to the control amount, the necessary discharge energy density can be supplied without excess or deficiency.

  As shown in FIG. 4, the discharge energy density during the discharge period can be controlled by the discharge secondary current I2, and the discharge secondary current I2 is supplied from the auxiliary power supply circuit 5 after the main power supply circuit 11 starts discharging. It can be controlled by energy input. As shown in the figure, when the ignition timing is on the advance side with respect to the top dead center TDC (that is, compression stroke ignition), it is necessary for the later stage of the discharge period from the discharge start crank angle CAst to the discharge end crank angle CAend. The discharge energy density (that is, indicated by a dotted line in FIG. 4) decreases.

  Therefore, when the discharge secondary current I2 is substantially constant (that is, the reference value shown in FIG. 4), the target value I2tgt of the discharge secondary current I2 is changed to change every moment. It can be controlled to approach the discharge energy density. Here, since the discharge secondary current I2 is a negative current, the magnitude of the discharge secondary current I2 will be expressed with reference to the absolute value. For example, in the case of FIG. 4, the target value I2tgt of the discharge secondary current I2 is gradually decreased from the initial stage of discharge, that is, the absolute value is decreased, thereby making it follow the necessary discharge energy density. As a result, compared with the control based on the reference value, the amount of discharge energy is greatly reduced (that is, indicated by hatching in FIG. 4), and wasteful discharge energy consumption can be suppressed while ensuring ignitability. .

  Instead of using the detection value of the crank angle sensor S1 as the crank angle detection unit, the pressure in the combustion chamber 101 having a correlation with the crank angle can also be used. In this case, the discharge secondary current I2 can be changed according to the pressure transition in the combustion chamber 101 during one fuel cycle. The pressure in the combustion chamber 101 is predicted from the detection results of various sensors using the relationship between the engine speed, the intake pressure, the intake air temperature, the intake air amount, the intake / exhaust valve timing, etc., which are experimentally obtained in advance, and the in-cylinder pressure transition. Alternatively, the pressure may be detected by providing a pressure sensor in the cylinder E1 of the engine E. Also, the air-fuel ratio detection unit can use predicted values from the detection results of various sensors instead of using the detection values of the air-fuel ratio sensor S2. The same applies to the other various sensors shown in FIG.

  By the way, at the time of lean combustion, the airflow generated in the combustion chamber 101 has a high flow velocity, which greatly affects the formation of spark discharge. The above-described discharge blow-off has a correlation with the discharge secondary current I2, and when the discharge secondary current I2 decreases, the discharge blow-out tends to occur. Further, the faster the air velocity, the higher the blow-off current I2bo.

  Therefore, when the feedback control unit 33 sets the upper limit threshold I2THH and the lower limit threshold I2THL of the discharge secondary current I2, the lower limit threshold I2THL is set so as not to blow out due to the decrease of the discharge secondary current I2. It is preferable to set the blow-off current I2bo or more according to the air velocity. For example, as shown in FIG. 4, when the target value I2tgt of the discharge secondary current I2 gradually decreases, the lower limit threshold I2THL is gradually updated based on the target value I2tgt at the beginning of discharge. After reaching the current I2bo, feedback control is performed so as to maintain the blowout current I2bo thereafter. Moreover, it is preferable to set the absolute value of the blow-off current I2bo to be larger as the airflow velocity is higher.

  In this way, during one combustion cycle, the discharge secondary current I2 is controlled so as not to fall below the blow-off current I2bo set according to the airflow velocity, so that the occurrence of blow-out can be suppressed. Further, since the target value I2tgt of the discharge secondary current I2 is updated as needed according to changes in the crank angle and the air-fuel ratio, it is possible to suppress excessive discharge energy from being input. Thereby, required discharge energy can be supplied efficiently, maintaining favorable ignitability.

  As shown in FIG. 5, in general, the higher the discharge energy, the larger the limit value of the ignitable air-fuel ratio (that is, the ignition limit A / F). In other words, when the discharge energy is constant, the larger the ignition limit A / F value, the better the ignitability and the higher the energy efficiency. As shown in the figure, the discharge secondary current I2 is controlled according to the target value I2tgt (I2tgt control in FIG. 5) compared to the control by the reference value (reference value control in FIG. 5). It can be seen that the ignition limit A / F is shifted in the direction of increasing, and the ignitability is improved.

  Here, the airflow velocity in the combustion chamber 101 may be detected using the airflow velocity sensor S3, or may be estimated using the fact that the discharge elongation and the discharge secondary voltage V2 are correlated. . When the discharge generated in the spark gap G by the air flow is extended, the secondary voltage V2 of the spark gap G is increased, and the discharge elongation is increased as the air flow is faster. For example, the amount of change per unit time of the discharge secondary voltage V2 From this, the air velocity can be estimated. As described above, by using the detection value by the airflow velocity sensor S3 and the estimated value using the discharge secondary voltage V2, the airflow velocity for each cycle and each cylinder can be quickly calculated and reflected in the feedback control. More desirable. In addition, the engine speed, intake pressure, intake air temperature, intake air amount, intake / exhaust valve timing, etc. are used as parameters. It may be predicted.

  FIG. 4 shows the case where the target value I2tgt of the discharge secondary current I2 is set so that the required discharge energy density is obtained in the entire discharge period. However, as shown in FIGS. You may control so that a discharge energy density is reduced about at least one part of a period. In the example shown in FIG. 6, for the first half of the discharge period where the difference from the required discharge energy density is small, the target value I2tgt of the discharge secondary current I2 is set to the reference value, and the target value gradually increases in the middle period of the discharge period. I2tgt is reduced to approach the required discharge energy density. In the latter half of the discharge period, the difference from the required discharge energy density becomes very small, so the target value I2tgt of the discharge secondary current I2 is set to a predetermined constant value. As a result, as shown by hatching in FIG. 5, the amount of discharge energy supplied can be reduced from the middle to the second half of the discharge period.

  Alternatively, as shown in FIG. 7, the target value I2tgt of the discharge secondary current I2 is set so that the required discharge energy density is obtained for a plurality of periods of the discharge period, for example, the initial period, the middle period, and the latter period. Reduced below the reference value. In other periods, the reference value is set. Also in this case, the closer to the top dead center TDC, that is, the absolute value of the target value I2tgt decreases from the initial stage toward the late stage. Even in this case, as indicated by hatching in FIG. 6, the corresponding discharge energy amount can be reduced according to the period during which the target value I2tgt is reduced from the reference value.

  Next, the basic operation of the ignition control executed by the ignition control unit 3 will be described with reference to the time chart of FIG. In the time chart, the crank angle is a common horizontal axis, the pressure Pc of the combustion chamber 101, the ignition signal IGt, the discharge sustaining signal IGw, the feedback signal (that is, the F / B signal in FIG. 7) SFB, the discharge switch signal Sd, The time variation of the boost signal Sc, the supply voltage Vc stored in the capacitor 43, the primary current I1, and the discharge secondary current I2 is shown. Here, as in FIG. 4, the case where control is performed so that the required discharge energy density is obtained in the entire discharge period of the compression stroke ignition is illustrated, and the pressure Pc in the combustion chamber 101 is directed toward the top dead center TDC. It is gradually rising.

  The ignition control unit 3 generates an ignition signal IGt according to the operating state of the engine E known from the detection values of the various sensors described above, and at a predetermined timing, the boosting driver 40 of the boosting circuit 4 and the ignition switch Tr1. Output to. Further, the discharge maintaining signal IGw is generated and output to the auxiliary driver 50 of the auxiliary power supply circuit 5 at a predetermined timing. A feedback threshold signal based on the target secondary current signal IGa is output to the auxiliary driver 50 at a timing prior to the discharge maintaining signal IGw, and a feedback signal SFB and a discharge switch signal Sd are output based on these signals.

  First, when the ignition signal IGt rises to a high level (that is, Hi in the figure) at the crank angle CA1 prior to the discharge period, the ignition start crank in which the ignition signal IGt falls to a low level (that is, 0 in the figure). The ignition switch Tr1 is turned on until the angle CAst. As a result, the primary coil I is energized with the primary current I1.

  Further, while the ignition signal IGt is at a high level, the pulsed boost signal Sc is applied from the boost driver 40 to the boost switch Tr2. As a result, the booster switch Tr2 is turned on and off at a predetermined period for a predetermined period. During this predetermined period, the discharge maintaining signal IGw is at a low level, and the auxiliary power supply circuit 5 is not driven. Therefore, energy corresponding to the number of times the boost switch Tr2 is turned on and off is accumulated in the capacitor 43, and the supply voltage Vc is stepped. To rise.

  When the ignition signal IGt becomes low level at the discharge start crank angle CAst, the ignition switch Tr1 is turned off and the primary current I1 of the primary coil 21 is cut off. At this time, the primary voltage V1 due to the self-dielectric action is generated in the primary coil 21, and the secondary voltage V2 of the secondary coil 22 increases. When this secondary voltage V2 is applied to the spark gap G of the spark plug P and a spark discharge occurs, a discharge secondary current I2 flows.

  When the ignition signal IGt becomes low level at the discharge start crank angle CAst, the discharge maintenance signal IGw rises to high level. The auxiliary driver 50 outputs the discharge switch signal Sd in synchronization with the feedback signal SFB based on the detected value of the discharge secondary current I2 while the discharge maintenance signal IGw is at the high level, and the discharge switch Tr3 Drive on and off. The feedback signal SFB is at a high level while the discharge secondary current I2 after the discharge start crank angle CAst is 0 and until the absolute value of the discharge secondary current I2 suddenly increases from 0 and reaches the upper limit threshold value I2THH. It has become.

  The discharge switch signal Sd rises to a high level when both the discharge maintenance signal IGw and the feedback signal SFB are at a high level, and turns on the discharge switch Tr3. As a result, the energization path between the ground side of the primary coil 21 and the capacitor 43 is opened via the discharge switch Tr3, and when the primary current I1 of the primary coil 21 decreases, the energy from the auxiliary power circuit 5 is reduced. Supply becomes possible. As a result, the energy accumulated in the capacitor 43 is input to the ground side of the primary coil 21, the primary current I 1 flows through the primary coil 21, and the discharge secondary current I 2 of the secondary coil 22 is superimposed. . The supply voltage Vdc of the capacitor 43 gradually decreases.

  The feedback signal SFB switches to a low level when the discharge secondary current I2 reaches the upper threshold I2THH. Then, the discharge switch signal Sd becomes a low level, and the discharge switch Tr3 is turned off. As a result, when the absolute value of the discharge secondary current I2 decreases and reaches the lower limit threshold I2THL, the feedback signal SFB switches to the high level again. By repeating this, the discharge secondary current I2 can be controlled between the upper limit threshold I2THH and the lower limit threshold I2THL.

  The upper limit threshold value I2THH and the lower limit threshold value I2THL are periodically updated together with the target value I2tgt of the discharge secondary current I2. As the crank angle CA approaches the top dead center TDC and the pressure in the combustion chamber 101 increases, the absolute values of the upper limit threshold I2THH and the lower limit threshold I2THL become smaller. When the lower limit threshold I2THL decreases to the predetermined blowout current I2bo, the subsequent control is performed so that the blowout current I2bo becomes the lower limit threshold I2THL.

  Thereafter, the discharge switch Tr3 is switched on and off based on the feedback signal SFB until the discharge sustain signal IGw becomes low level at the discharge end crank angle CAend. In this way, energy is supplied without excess or deficiency for a predetermined discharge period, and discharge is maintained.

  Here, an example of a routine for calculating the target value I2tgt of the discharge secondary current I2, its upper threshold value I2THH and the lower threshold value I2THL will be described using the flowchart of FIG. In FIG. 8, when the discharge secondary current calculation routine is started, first, the operating state of the engine E is detected in step S1. Specifically, the engine speed is calculated based on the detection signals of the various sensors shown in FIG. 2, for example, the crank angle sensor S1, and the intake air amount sensor S4, the intake pressure / intake temperature sensor S5, and the engine water temperature sensor are calculated. From the detection signal of S7, the amount of intake air to the engine E, the intake pressure / intake temperature, and the engine water temperature are read.

  In step S2, the air-fuel ratio A / F is detected from the detection signal of the air-fuel ratio sensor S2. Further, the discharge start timing and discharge period of the spark plug P are determined from the operating state of the engine E, and the corresponding discharge start crank angle CAst and discharge end crank angle CAend are read. For example, a map prepared for each engine operating state so as to calculate the required torque using the engine speed and the accelerator opening detected by the accelerator opening sensor S9 and to correspond to the engine load based on the required torque. Etc., the optimum discharge start timing and discharge period can be calculated. Further, the target ignition energy can be calculated, and the reference discharge energy density can be calculated. The air-fuel ratio A / F can also be estimated with reference to a map or the like based on the operating state of the engine E. The discharge start crank angle CAst and the discharge end crank angle CAend are, for example, crank angles after compression TDC.

  In step S3, the air velocity is detected from the detection signal of the air velocity sensor S3. In subsequent step S4, a blow-off current map with the airflow velocity as a parameter is read, and the current lower limit value I2min is rewritten to a blowout current I2bo corresponding to the detected airflow velocity (that is, I2min = I2bo). FIG. 10 is an example of a blow-off current map using the airflow velocity as a parameter, and the two are in a substantially proportional relationship. The higher the airflow velocity, the higher the value of the blow-off current I2bo.

  Next, in step S5, the crank angle CA is detected from the detection signal of the crank angle sensor S1, and in step S6, it is determined whether or not the crank angle CA is equal to or greater than the discharge start crank angle CAst (that is, CA ≧ CAst?). If a positive determination is made in step S6, the process proceeds to step S7. If a negative determination is made, the process returns to step S5.

  In step S7, a target value I2tgt (CA) map corresponding to the detected air-fuel ratio A / F and crank angle CA is read. FIG. 11 is an example of a target value I2tgt (CA) map with respect to the air-fuel ratio A / F and the crank angle CA, and the air-fuel ratio A / F increases toward the retard side or the advance side with respect to the top dead center TDC. The larger the value, the higher the target value I2tgt. Since the compression stroke ignition is on the advance side with respect to the top dead center TDC, the target value I2tgt is higher on the advance side.

  Next, in step S8, it is determined whether or not the target value I2tgt (CA) is equal to or greater than the current lower limit value I2min (that is, I2tgt ≧ I2min?). If a positive determination is made in step S8, the process proceeds to step S9. If a negative determination is made, the process proceeds to step S10.

  In step S9, the lower limit threshold I2THL is rewritten to the target value I2tgt (CA) (that is, I2THL = I2tgt). Next, the process proceeds to step S11, and the upper limit threshold value I2THH is rewritten to the lower limit threshold value I2THL + a (that is, I2THH = I2THL + a). Here, the value of a can be arbitrarily set within a range in which no malfunction occurs in the switch operation due to chattering or the like. In step S10, the lower limit threshold I2THL is rewritten to the current lower limit value I2min (that is, I2THL = I2min), and the process proceeds to step S11.

  Thereafter, in step S12, it is determined whether or not the detected crank angle CA is equal to or greater than the discharge end crank angle CAend (that is, CA ≧ CAend?). If the determination in step S12 is affirmative, the present routine is temporarily terminated. If the determination in step S12 is negative, the process returns to step S5.

  In this routine, the lower limit threshold I2THL is set to the target value I2tgt (CA) of the discharge secondary current I2, and is set to the upper limit threshold I2THH obtained by adding the predetermined value a, so that the necessary discharge energy density can be obtained reliably. Improves ignitability. The lower limit threshold value I2THL and the upper limit threshold value I2THH can also be set to be the median value of the target value I2tgt (CA).

  Using the upper limit threshold value I2THH and the lower limit threshold value I2THL set in this way, the discharge secondary current I2 of the spark plug P can be feedback controlled to the target value I2tgt according to the flowchart of FIG. In FIG. 12, when the discharge control routine is started, first, in step S21, at the timing when the crank angle CA becomes the discharge start crank angle CAst, the ignition signal IGt becomes low level, and discharge is started (that is, CA = CAst, IGt = 0).

  In step S22, it is determined whether or not the discharge maintaining signal IGw is at a high level (that is, IGw = Hi?). When an affirmative determination is made in step S22, the process proceeds to step S23, where the discharge secondary current I2 is detected, and the lower limit threshold I2THL and the upper limit threshold I2THH are read. Next, the process proceeds to step S24, and it is determined whether or not the detected discharge secondary current I2 is equal to or higher than the lower limit threshold I2THL (that is, I2 ≧ I2THL?). If the determination in step S24 is affirmative, the process proceeds to step S25. If the determination is negative, the process proceeds to step S26, and after the discharge switch Tr3 is turned on (that is, the discharge switch signal Sd = Hi), step S22 is performed. Return to.

  In step S25, it is determined whether or not the detected discharge secondary current I2 is equal to or lower than the upper limit threshold I2THH (that is, I2 ≦ I2THH?). If the determination in step S25 is affirmative, the process returns to step S22. If the determination is negative, the process proceeds to step S27, and after the discharge switch Tr3 is turned off (that is, the discharge switch signal Sd = 0), step S22 is performed. Return to.

  When a negative determination is made in step S22, the process proceeds to step S28, and after the discharge switch Tr3 is turned off (that is, the discharge switch signal Sd = 0), the process proceeds to step S29 to complete the discharge (that is, CA). = CAend), this routine is terminated.

  While the discharge sustaining signal IGt is being output by this routine, the lower limit threshold I2THL and the upper limit threshold I2THH are updated as needed, and the detected discharge secondary current I2 is feedback-controlled to the vicinity of the target value I2tgt (CA). Can be maintained.

(Embodiment 2)
Next, a time chart shown in FIG. 13 as the second embodiment will be described. Similarly, in the case of the expansion stroke ignition, the target value I2tgt of the discharge secondary current I2 is calculated according to the flowcharts shown in FIGS. 9 and 12, and the discharge control based on the upper limit threshold I2THH and the lower limit threshold I2THL is executed. be able to. The configuration of the ignition control device 1 is the same as that of the first embodiment, and a description thereof is omitted.
Of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the above-described embodiments represent the same components as those in the above-described embodiments unless otherwise indicated.

  In the expansion stroke ignition in which the ignition timing is on the retard side with respect to the top dead center TDC, the target value I2tgt is higher on the retard side in the target value I2tgt (CA) map used in step S7 of FIG. In other words, in the discharge period from the discharge start crank angle CAst to the discharge end crank angle CAend, the target value I2tgt decreases as the discharge starts closer to the top dead center TDC, and the required discharge energy density decreases. Therefore, when the target value I2tgt (CA) corresponding to the crank angle CA becomes less than the current lower limit value I2min in step S8 of FIG.

  Therefore, as shown in FIG. 13, at the discharge start crank angle CAst, the discharge secondary current I2 increases rapidly at the same time as the primary current I1 is cut off. In that case, in step S9 in FIG. 9, the lower limit threshold I2THL becomes the target value I2tgt. Then, in steps S24 and S25 in FIG. 12, since the detected discharge secondary current I2 is equal to or higher than the lower limit threshold I2THL and the upper limit threshold I2THH, the feedback signal SFB is switched to the low level and the discharge switch Tr3 is turned on. Not. Thereafter, when the discharge secondary current I2 falls below the lower limit threshold I2THL, the discharge switch Tr3 is turned on, and thereafter, feedback control is performed so as to be between the upper limit threshold I2THH.

  In this case as well, when the discharge secondary current I2 is substantially constant, the target value I2tgt of the discharge secondary current I2 on the initial stage of the discharge is lowered, so that it can be controlled to approach the required discharge energy density. As a result, compared with the control based on the reference value, the amount of discharge energy is significantly reduced and the ignitability is ensured, while wasteful discharge energy consumption can be suppressed and electrode consumption can be suppressed.

(Embodiment 3)
The ignition control device 1 according to the third embodiment will be described with reference to FIGS. In each of the above embodiments, power is supplied from the main power supply circuit 11 and the auxiliary power supply circuit 5 of the power supply circuit unit 10 to the ignition coil 2. However, any ignition system capable of continuous discharge to the spark plug P can be used. Any configuration may be used. For example, the ignition plug P may be energized from a plurality of power supply circuits arranged in parallel.

  In this embodiment, a plurality of power supply circuits 13 and 14 are provided in the power supply circuit unit 10 and a plurality of ignition coils 2A and 2B connected to the spark plug P are provided to alternately supply discharge energy to the spark plug P. To do. The power supply circuit unit 10 is provided with a voltage regulator 7, and a voltage is supplied from the voltage regulator 7 to the first power supply circuit 13 connected to the first ignition coil 2A and the second power supply circuit 14 connected to the second ignition coil 2B. It can be supplied.

  The first and second ignition coils 2 </ b> A and 2 </ b> B include primary coils 21 a and 21 b and secondary coils 22 a and 22 b, respectively, and one ends of the primary coils 21 a and 21 b are connected to the plus terminal of the voltage regulator 7. The other ends of the primary coils 21a and 21b are grounded via energization switches Tr4 and Tr5, respectively. In the first power supply circuit 13, the energization switch Tr4 opens and closes the energization path from the voltage regulator 7 to the primary coil 21a of the first ignition coil 2A, and the second power supply circuit 14 includes the energization switch Tr5 in the voltage regulator. 7 opens and closes the energization path from the first ignition coil 2B to the primary coil 21b.

  The voltage regulator 7 is, for example, a known DC-DC converter, and is connected to the battery B via the relay 71. The voltage regulator 7 boosts the DC voltage of the battery B to a desired supply voltage V1 and supplies it to the first and second ignition coils 2A and 2B. The negative terminal of the voltage regulator 7 is grounded. The secondary coils 22a and 22b of the first and second ignition coils 2A and 2B are connected to the spark plug P through rectifying elements 61a and 61b.

  As in the above embodiments, the ignition control unit 3 includes a discharge timing setting unit 31 that sets a discharge start timing and a discharge period, a target current setting unit 32 that sets a target value I2tgt of the discharge secondary current I2, and an upper limit. A feedback control unit 33 is provided for setting the threshold value I2THH and the lower limit threshold value I2THL. Further, the detection signals of the various sensors S1 to S8 described above are input, and various signals based on these detection values are generated to control the ignition operation of the spark plug P, as in the above embodiments. Hereinafter, the difference will be mainly described.

  The discharge timing setting unit 31 generates ignition signals IGTa and IGTb for starting ignition according to the operating state of the engine E known from the detection values of the various sensors S1 to S8, and a part of the ignition control unit 3 is used. It outputs to the energizing driver 30 which comprises. Further, a discharge maintenance signal IGw for maintaining the discharge is generated. The energization driver 30 alternately outputs energization signals SWa and SWb at a predetermined timing based on these signals. As a result, the energization switches Tr4 and Tr5 are turned on and off, and the first and second ignition coils 2A and 2B are alternately energized. The supply voltage V <b> 1 of the voltage regulator 7 is detected by a built-in supply voltage detection unit and output to the energization driver 30.

  Further, the discharge timing setting unit 31 generates a discharge maintenance signal IGw, the target current setting unit 32 generates a target secondary current signal IGa, and the feedback control unit 33 generates a feedback threshold signal. The basic operations of these units are the same as those in the above embodiments, and a description thereof will be omitted.

  The energizing driver 30 is provided with a supply voltage control unit 34. In this embodiment, the supply voltage V1 is changed in order to control the discharge secondary current I2 between the upper limit threshold value I2THH and the lower limit threshold value I2THL based on the target value I2tgt. The supply voltage control unit 34 calculates a target voltage Vreq based on the discharge secondary current I 2 input from the feedback circuit 6 and the supply voltage V 1 input from the voltage regulator 7, and outputs the target voltage Vreq to the voltage regulator 7. Thereby, the supply voltage V1 of the voltage regulator 7 is controlled to become the target voltage Vreq.

  As shown in an example of the discharge secondary current I2 control using the supply voltage control unit 34 according to the time chart of FIG. 15, first, when the ignition signal IGTa rises to a high level at the crank angle CA1 prior to the discharge period, The energization signal SWa is output until the discharge start crank angle CAst that falls to the low level. As a result, the energization switch Tr4 is turned on, and the primary current I1a is energized to the primary coil 21a of the first ignition coil 2A. Next, when the ignition signal IGTb rises to a high level at the crank angle CA2 after a predetermined period τ / 2, the energization signal SWb is output. As a result, the energization switch Tr5 is turned on, and the primary current I1a is energized to the primary coil 21b of the second ignition coil 2B.

  Prior to this, the supply voltage V1 of the voltage regulator 7 is boosted to a voltage sufficiently higher than that of the battery B. When the ignition signal IGTa becomes low level at the discharge start crank angle CAst, the energization signal SWa becomes low level, the energization switch Tr4 is turned off, and the primary current I1a of the primary coil 21a is cut off. Along with this, the secondary voltage V2a of the secondary coil 22a rises and is applied to the spark gap G of the spark plug P, and a discharge secondary current I2 flows. The discharge secondary current I2 flows in a triangular wave shape and reaches the vicinity of the upper limit threshold value I2THH, and then decays.

  Subsequently, when the ignition signal IGTb becomes low level after the period τ / 2 from the discharge start crank angle CAst, the energization signal SWb becomes low level, the energization switch Tr4 is turned off, and the primary current of the primary coil 21b. I1b is blocked. Accordingly, the secondary voltage V2b of the secondary coil 22b increases and is applied to the spark gap G of the spark plug P. Then, the discharge secondary current I2 that has decreased to the vicinity of the lower limit threshold I2THL increases again.

  While the discharge maintaining signal IGw is being output, the energization signal SWa and the energization signal SWb are alternately turned on and off at the cycle τ and the duty ratio τ / 2. That is, when the energization signal SWb becomes low level, the energization signal SWa becomes high level again. When the energization signal SWb becomes low level again after the period τ / 2, the energization signal SWb becomes high level again. By repeating this, the energy alternately stored in the first ignition coil 2A and the second ignition coil 2B can be continuously input to the spark plug P.

  Also in this case, the upper limit threshold I2THH and the lower limit threshold I2THL target value I2tgt based on the target value I2tgt are updated as needed according to the crank angle CA detected by the crank angle sensor S1. Further, the target voltage Vreq of the supply voltage V1 is set so that the detection signal of the discharge secondary current I2 input from the feedback circuit 6 is maintained between the upper limit threshold I2THH and the lower limit threshold I2THL target value I2tgt. At this time, in order to detect the discharge secondary current I2, the energization signal SWa and the energization signal SWb are switched on and off, and at the timing when the discharge secondary current I2 is minimized or maximized, the current detection trigger signal SWL or the current detection trigger is detected. Signal SWH is output.

  As shown in the flowchart of FIG. 16, when the discharge control routine in the present embodiment is started, first, in step S101, discharge is performed at the timing when the ignition signal IGTa becomes low level and the crank angle CA becomes the discharge start crank angle CAst. Started (ie, CA = CAst).

  In step S102, it is determined whether or not the discharge maintaining signal IGw is at a high level (that is, IGw = Hi?). If the determination in step S102 is affirmative, the process proceeds to step S103 to determine whether or not the current detection trigger signal SWL is at a high level (that is, SWL = Hi?). If the determination in step S103 is affirmative, the process proceeds to step S104, and the discharge secondary current I2 is detected. Next, the process proceeds to step S104, the detected discharge secondary current I2 is set to the minimum current I2L (that is, I2L = I2), and the process returns to step S102.

  If a negative determination is made in step S103, the process proceeds to step S106 to determine whether or not the current detection trigger signal SWH is at a high level (ie, SWH = Hi?). When an affirmative determination is made in step S106, the process proceeds to step S107, and the discharge secondary current I2 is detected. Next, the process proceeds to step S108, and after the detected discharge secondary current I2 is set to the maximum current I2H (that is, I2H = I2), the process proceeds to step S108. If a negative determination is made in step S106, the process returns to step S102.

  In step S109, it is determined whether or not the minimum current I2L is equal to or greater than the lower limit threshold I2THL (that is, I2L ≧ I2THL?). When an affirmative determination is made in step S109, the process proceeds to step S110 to determine whether or not the maximum current I2H is equal to or greater than the upper limit threshold I2THH (ie, I2H ≧ I2THH?). If a positive determination is made in step S110, the process proceeds to step S111. If a negative determination is made in step S110, the process returns to step S102.

  In step S111, a difference I2def (that is, I2def = I2THH−I2H; I2def ≦ 0) between the upper limit threshold I2THH and the maximum current I2H is calculated, and the process proceeds to step S113. If the determination in step S109 is negative, the process proceeds to step S112 to calculate a difference I2def (that is, I2def = I2THH−I2L; I2def ≧ 0) between the lower limit threshold I2THL and the minimum current I2L, and the process proceeds to step S113.

  In step S113, using the fact that the difference I2def from the calculated minimum current I2L or maximum current I2H is correlated with the change in the supply voltage V1, the voltage change width V2def is calculated using the constant C (ie, V2def = C × I2def). In step S114, the supply voltage V1 is detected from the detection signal of the supply voltage detection part built in the voltage regulator 7, and based on these, the target voltage Vreq is calculated in step S115 (that is, Vreq = V1 + Vdef). In step S116, the target voltage Vreq is output to the voltage regulator 7, the supply voltage V1 is changed, and the process returns to step S102. When a negative determination is made in step S102, the process proceeds to step S117, the discharge is terminated, and this routine is terminated.

  By this routine, when the maximum current I2H shown in the time chart of FIG. 15 becomes equal to or higher than the upper limit threshold I2THH, or when the minimum current I2L becomes equal to or lower than the lower limit threshold I2THL, the target voltage Vreq corresponding to the difference I2def is set. The supply voltage V1 is changed. Thereby, the discharge secondary current I2 can be maintained in the vicinity of the target value I2tgt (CA).

(Embodiment 4)
The ignition control device 1 according to the fourth embodiment will be described with reference to FIGS. In each of the above embodiments, a single spark plug P is configured to be energized from a plurality of power supply circuits or a plurality of ignition coils 2 in the power supply circuit unit 10, but in this embodiment, a plurality of spark plugs PA and PB are used. Then, power is sequentially supplied from the power supply circuit unit 10 to the plurality of ignition coils 2A and 2B connected thereto. Also in this case, it is possible to continuously discharge the spark plugs PA and PB by controlling the energization to the spark plugs PA and PB by the ignition control unit 3.

  In this embodiment, the basic configuration of the power supply circuit unit 10 can be the same as that of the third embodiment. For example, the first ignition coil 2A is connected to the first ignition plug PA and energized from the first power supply circuit 13, and the second ignition coil 2B is connected to the second ignition plug PB and energized from the second power supply circuit 14. To do. In this case, it is not always necessary to provide the voltage regulator 7 in the power supply circuit unit 10. For example, the battery B and the first and second ignition coils 2A and 2B are opened and closed by energizing switches Tr4 and Tr5. can do.

  The first spark plug PA and the second spark plug PB are provided in parallel between the intake valve Vin and the exhaust valve Vex of the engine E so that the tip electrode portion is located in the combustion chamber 101. The first and second spark plugs PA, 2B have the same structure except that the length of the spark gap G formed in the tip electrode portion is different. Each of the first and second spark plugs PA, 2B has a center electrode P1 having an electrode tip at the tip and a flat ground electrode P2, and the distance between both electrodes facing each other in the axial direction is defined as an interelectrode distance. GAPa and GAPb. Here, the inter-electrode distance GAPa of the first spark plug PA is formed to be longer than the inter-electrode distance GAPb of the second spark plug 2B (ie, GAPa> GAPb).

  As in the third embodiment, the ignition control unit 3 sets the discharge start timing and the discharge period in the discharge timing setting unit 31 and starts ignition of the first spark plug PA and the second spark plug PB. Ignition signals IGTa and IGTb are generated, and energization to the first ignition coil 2A and the second ignition coil 2B is controlled. Moreover, it has the plug switching part 35 which switches the ignition plug P which forms a spark discharge in one combustion cycle sequentially. At this time, the plug switching unit 35 performs ignition by the first spark plug PA in the first half of the discharge period, performs ignition by the second spark plug PB in the second half, and switches the discharge energy input destination, thereby discharging energy density. To control.

  As shown in the upper part of FIG. 18, the discharge formed in the spark gap G formed between the electrodes P1 and P2 of the first and second spark plugs PA and PB is caused by the air flow in the combustion chamber 101 (arrow in the figure). The discharge path is extended. At this time, if the inter-electrode distances GAPa and GAPb are long, the discharge starting point is widened, and the discharge path becomes long. As shown in the lower part of FIG. 18, the longer the discharge path, the higher the average secondary voltage at the time of discharge, and the higher the average energy density.

  The discharge energy density is a product of a discharge secondary current IV2 that flows during discharge of the first and second spark plugs PA and PB and a secondary voltage (hereinafter referred to as an interelectrode voltage) V2 applied between the electrodes. As described above, the interelectrode voltage V2 can be changed by changing the interelectrode distances GAPa and GAPb. That is, the first spark plug PA having a longer interelectrode distance GAPa has a higher discharge energy density, and the second spark plug PB having a shorter interelectrode distance GAPb has a lower discharge energy density. At this time, by selecting the first and second spark plugs PA and PB so that the length of the spark gap G becomes shorter as the crank angle CA is closer to the top dead center TDC, as in the above embodiments. The discharge energy density can be controlled.

  For example, in the case of compression stroke ignition, as shown in the time chart of FIG. 19, first, the ignition signal IGTa is output, the first spark plug PA is ignited, and then the ignition signal IGTb is output, By igniting the two spark plugs PB, the discharge energy density can be changed stepwise. That is, at the initial stage of discharge, the first spark plug PA is discharged to increase the interelectrode voltage V2 and increase the discharge energy density. After that, when switching to the second spark plug PA, the voltage V2 between the electrodes is lowered, so that the discharge energy density is lowered in the late stage of discharge that is closer to the top dead center TDC. Thereby, discharge control can be effectively performed in response to a change in necessary discharge energy density.

  Specifically, an optimal ignition timing SA (that is, the discharge start timing of the first spark plug PA) is determined according to the operating conditions of the engine E, and the ignition signal IGTa is determined according to the required coil charging time Ton. Is determined to be a high level crank angle (for example, CAaon to CAaend in FIG. 19). Further, the crank angle (for example, CAbon to CAbend in FIG. 19) at which the ignition signal IGTb is at a high level is determined according to the discharge period Taspk of the first spark plug PA, and the first spark plug PA to the second spark plug PB. Controls switching to.

  As shown in the flowchart of FIG. 20, when the ignition control routine is started, in step S201, the operation state of the engine E, for example, the engine speed Ne, the intake pressure Pim, is detected from the detection signals of the various sensors, as in the above embodiments. Then, the air-fuel ratio A / F is read. Next, in step S202, the ignition timing SA (CA) and the coil charging time Ton (ms) are read as map values based on the detected operating state of the engine E. The ignition timing SA is, for example, a compression TDC crank angle.

In step S203, the fall timing IGTaend of the ignition signal IGTa is calculated. Here, the fall timing IGTaend = ignition timing SA.
In step S204, the rising timing IGTaon of the ignition signal IGTa is calculated by the following equation 1.
Formula 1: IGTaon = ignition timing SA-Ton × Ne × 360 × S
In Equation 1, S is a time-crank angle scale conversion coefficient.

Subsequently, in step S205, the discharge period Taspk of the first spark plug PA is read from a map showing the relationship between the charge period of the ignition signal IGTa and the discharge period Taspk (ms). In step S206, the discharge end timing Taend (CA) of the first spark plug PA is calculated by the following equation 2.
Formula 2: Taend = ignition timing SA + Taspk × Ne × 360 × S

Thereafter, in step S207, the falling timing IGTbend of the ignition signal IGTb is calculated. Here, the fall time IGTbend = Taend. In step S208, the rising timing IGTbon of the ignition signal IGTb is calculated by the following equation 3.
Formula 3: IGTbon = IGTbend-Ton * Ne * 360 * S

  In step S209, the crank angle CAm is detected, and then in step S210, it is determined whether the detected crank angle CAm is between the rising timing IGTaon and the falling timing IGTaend of the first spark plug PA (ie, IGTaon ≦ CAm ≦ IGTaend?). If an affirmative determination is made in step S210, the process proceeds to step S211, the ignition signal IGTa is set to a high level (that is, IGTa = Hi), and the process proceeds to step S212.

  If a negative determination is made in step S210, the process proceeds to step S212. As a result, during the coil charging time Ton from the rising timing IGTaon to the falling timing IGTaend, the energization switch Tr4 is turned on and the primary coil 21a of the first ignition coil 2A is charged. When the energizing switch Tr4 is turned off after the coil charging time Ton, the interelectrode voltage V2 of the first spark plug PA rapidly increases at the ignition timing SA shown in FIG. 19, and discharge is started.

  In step S212, it is determined whether or not the detected crank angle CAm is between the rising timing IGTbon and the falling timing IGTbend of the second spark plug PB (that is, IGTbon ≦ CAm ≦ IGTbend?). If step S212 is positively determined, the process proceeds to step S213, the ignition signal IGTb is set to the high level, and the process returns to step S209.

  If the determination in step S212 is negative, this routine is terminated. As a result, during the coil charging time Ton from the predetermined rising timing IGTbon to the falling timing IGTbend after the ignition timing SA, the energization switch Tr5 is turned on to charge the primary coil 21b of the second ignition coil 2B. The Thereafter, when the energization switch Tr5 is turned off at the crank angle CAbend shown in FIG. 19, the interelectrode voltage V2 of the second spark plug PB increases rapidly.

  Thereby, after the discharge period Taspk of the first spark plug PA, the discharge of the second spark plug PB is started immediately, and the discharge energy can be input efficiently according to the crank angle CAm. Therefore, the spark discharge can be maintained by continuously igniting the first spark plug PA and the second spark plug PB. Further, by using a plurality of spark plugs PA and PB, the energy input per plug is dispersed, so that electrode consumption of each spark plug PA and PB can be reduced, and the plug life can be extended.

  The present invention is not limited to the above embodiments, and can be applied to various embodiments without departing from the scope of the invention. In the above embodiment, a port injection type gasoline engine is exemplified as the internal combustion engine. However, for example, an in-cylinder direct injection type gasoline engine may be used. Further, the present invention can be applied not only to a gasoline engine for vehicles but also to various internal combustion engines other than diesel engines and vehicles. The spark plug is not limited to the configuration exemplified in the above embodiment, and may have any configuration according to the internal combustion engine to which it is attached.

E Gasoline engine (internal combustion engine)
P Spark plug G Spark gap 1 Ignition control device 2 Ignition coil 3 Ignition control unit 31 Discharge timing setting unit 32 Target current setting unit 33 Feedback control unit S1 Crank angle sensor (crank angle detection unit)

Claims (7)

An ignition coil (2) having a primary coil (21) and a secondary coil (22);
An ignition plug (P) that is connected to the secondary coil and that generates a spark discharge in the spark gap (G) by electromagnetic induction associated with on / off of energization of the primary coil;
Ignition control of an internal combustion engine (E) comprising: an ignition control unit (3) for starting a spark discharge in the combustion chamber by turning on / off the energization of the primary coil and controlling an energization operation during the spark discharge. A device (1) comprising:
A crank angle detector (S1) for detecting a crank angle of the internal combustion engine,
The ignition control unit includes a discharge timing setting unit (31) that sets a discharge start timing and a discharge period according to an operating state of the internal combustion engine, and a target value of an energization current (I2) to the spark plug during the discharge period. The target current setting unit (32) for setting (I2tgt) has a smaller absolute value of the target value as the detected crank angle is closer to the top dead center (TDC). An ignition control device for an internal combustion engine that sets the target value. An air-fuel ratio detection unit (S2) for detecting the fuel concentration of the air-fuel mixture in the combustion chamber,
2. The ignition control for an internal combustion engine according to claim 1, wherein the target current setting unit sets the absolute value of the target value to be larger as the detected fuel concentration of the air-fuel mixture in the combustion chamber is leaner. apparatus.   The ignition control unit includes a feedback control unit that sets an upper limit threshold (I2THH) and a lower limit threshold (I2THL) for feedback control of the energization current, and the feedback control unit blows off the lower limit threshold. The ignition control device for an internal combustion engine according to claim 1 or 2, wherein the ignition control device is set so as not to fall below a current value (I2bo) that does not occur. An air velocity detection unit (S3) for detecting an air velocity in the combustion chamber,
The feedback control unit sets a current value at which the blowout does not occur according to the detected airflow velocity, and an absolute value of a current value at which the blowout does not occur as the detected airflow velocity increases. The ignition control device for an internal combustion engine according to claim 3, wherein the ignition control device is set to increase. A power circuit (10) connected to the ignition coil,
The power supply circuit section includes a main power circuit section (11) having an ignition switch (Tr1) for opening and closing between the battery (B) and the primary coil, and a capacitor (43) by boosting the voltage of the battery. And an auxiliary power supply circuit section (5) having a discharge switch (Tr3) that opens and closes between the capacitor and the ground side of the primary coil.
The ignition control unit drives the ignition switch to energize the ignition plug, and after starting spark discharge, drives the discharge switch to energize the ignition plug. The ignition control device for an internal combustion engine according to claim 1. A power supply circuit unit having a plurality of ignition coils (2A, 2B) connected to the ignition plug and energization switches (Tr4, Tr5) for opening and closing between the plurality of ignition coils and the voltage source (7), respectively. (10)
The ignition control of the internal combustion engine according to any one of claims 1 to 4, wherein the ignition control unit alternately drives the energization switch to alternately energize the ignition plug from the plurality of ignition coils. apparatus. An ignition coil (2) having a primary coil (21) and a secondary coil (22);
An ignition plug (P) that is connected to the secondary coil and that generates a spark discharge in the spark gap (G) by electromagnetic induction associated with on / off of energization of the primary coil;
Ignition control of an internal combustion engine (E) comprising: an ignition control unit (3) for starting a spark discharge in the combustion chamber by turning on / off the energization of the primary coil and controlling an energization operation during the spark discharge. A device (1) comprising:
A plurality of ignition plugs (PA, PB) having different spark gap lengths (GAPa, GAPb) are provided in the combustion chamber, and a crank angle detection unit (S1) for detecting a crank angle of the internal combustion engine is provided. Has
The ignition control unit includes a discharge timing setting unit (31) for setting a discharge start timing and a discharge period according to the operating state of the internal combustion engine, and a plug for sequentially switching the ignition plug for forming a spark discharge in one combustion cycle. An internal combustion engine having a switching unit (35), wherein the plug switching unit forms a spark discharge in the spark plug having a shorter spark gap length as the detected crank angle is closer to top dead center (TDC). Engine ignition control device.

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