JP6604265B2 - Ignition control device - Google Patents

Description

  The present invention relates to an ignition control device.

  After spark discharge is generated in the spark plug by energizing and shutting off the primary coil, electrical energy is intermittently input to the primary coil from the energy input circuit, and the secondary current flowing through the secondary coil is set to a predetermined target value. An ignition device that maintains the above is proposed (for example, Patent Document 1).

Japanese Patent Laid-Open No. 2015-200255

  In the above technique, the electrical energy input to the primary coil is controlled so as to maintain the target value of the secondary current flowing through the secondary coil. However, the resistance and inductance of individual ignition coils (primary coils) generally vary due to product variations, usage environments, aging degradation, and the like. For this reason, if the electric energy supplied to the primary coil is controlled uniformly based on the target value of the secondary current without considering variations in the characteristics (resistance and inductance) of the primary coil, the current supplied to the spark plug The exhaust gas recirculation (EGR) control that recirculates exhaust gas and lean combustion that burns the air-fuel mixture at a lean air-fuel ratio higher than the stoichiometric air-fuel ratio in the cylinder must be stopped. However, there is a risk that fuel economy will deteriorate. Alternatively, more current than necessary may flow through the spark plug and the spark plug electrode may be consumed.

  Accordingly, an object of the ignition control device disclosed in this specification is to optimize the electric energy input to the primary coil included in the ignition coil.

In order to solve such a problem, an ignition control device disclosed in the present specification includes an ignition coil including a primary coil and a secondary coil, a capacitor, and switching means. An energy input unit for supplying electric energy stored in the capacitor to the primary coil after starting the discharge of the spark plug and causing the primary current to flow to the primary coil, and the primary current flowing to the primary coil. The switching frequency of the switching means is changed by changing the switching frequency of the switching means so that the secondary current flowing in the secondary coil maintains a target value while the switching means is on, and the primary coil is changed from the energy input unit. an energy control unit for controlling the electrical energy put into, the primary coil after start of discharging said ignition plug An acquisition unit that acquires a slope of change in the primary current during a period when the electrical energy is input, or a slope of change in the primary current during a period in which the switching unit is turned on, and The energy control unit increases the switching frequency as the slope of the change in the primary current is slower, and decreases the switching frequency as the slope of the change in the primary current is steeper.

  According to the ignition control device disclosed in this specification, it is possible to optimize the electric energy input to the primary coil included in the ignition coil.

FIG. 1 is a schematic diagram illustrating a configuration of an ignition system to which an ignition control device according to an embodiment is applied. FIG. 2 is a time chart showing the operation of the ignition system. FIG. 3 is a flowchart illustrating an example of a switching frequency changing process executed by the ECU. FIG. 4A to FIG. 4D are diagrams for explaining the relationship between the slope of the change in the primary current and the secondary current. FIG. 5 is a diagram illustrating an example of a switching frequency map.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, and the like of each part may not be shown so as to completely match the actual ones. In some cases, details are omitted in some drawings.

  FIG. 1 is a schematic diagram illustrating a configuration of an ignition system 1 to which an ignition control device according to an embodiment is applied. The ignition system 1 according to the present embodiment is mounted on a spark ignition engine for vehicle travel, and ignites an air-fuel mixture in a combustion chamber at a predetermined ignition timing. An example of the engine is a direct injection engine capable of lean burn using gasoline as fuel, and a swirl flow control means for generating a swirl flow of an air-fuel mixture such as a tumble flow or a swirl flow in a cylinder. Prepare. In this embodiment, the ignition system 1 is a DI (direct ignition) type that uses an ignition coil 3 corresponding to each ignition plug 2 of each cylinder.

  The ignition system 1 includes an ECU (Electronic Control Unit) 4. The ECU 4 includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and a storage device. The ECU 4 stores various maps (including a switching frequency map described later) used for control in a ROM or a storage device. Moreover, ECU4 performs the switching frequency change process etc. which are mentioned later by running the program memorize | stored in ROM or the memory | storage device. The ECU 4 is an example of an energy control unit and an acquisition unit.

  The ECU 4 receives signals from various sensors that are mounted on the vehicle and detect parameters (warm-up state, engine speed, engine load, presence / absence of lean combustion, degree of swirling flow, etc.) that indicate the operating state and control state of the engine. Entered. The ECU 4 generates and outputs an ignition signal IGt, a discharge continuation signal IGw, and a target secondary current signal IGA corresponding to engine parameters acquired from various sensors. The ignition signal IGt is a signal for instructing a period during which magnetic energy is stored in the primary coil 5 and an ignition start timing in the main ignition circuit 8 described later. The discharge continuation signal IGw is a signal for instructing a period for continuing the continuous spark discharge (details will be described later). The target secondary current signal IGA is a signal for instructing a target value of the secondary current I2 flowing through the secondary coil 6 (hereinafter referred to as a maintenance target current value). The ECU 4 sets the maintenance target current value to a current value at which the discharge can be satisfactorily maintained according to the operation region determined from the engine load and the rotational speed. The ECU 4 controls the electric energy generated in the secondary coil 6 of the ignition coil 3 by controlling the energization of the primary coil 5 by the ignition signal IGt and the discharge continuation signal IGw, and controls the spark discharge of the spark plug 2.

  Further, the ECU 4 outputs a frequency signal SF that indicates the switching frequency of the input switching means 24 included in the energy input circuit 9 described later to the input driver circuit 25 described later.

  In addition, the ignition system 1 according to the present embodiment includes a main ignition circuit 8 that generates a spark discharge (hereinafter referred to as main ignition) based on a full tiger, and a spark discharge generated as main ignition by continuous addition of electric energy. An energy input circuit 9 that is continued as a discharge is provided. Further, the ignition system 1 detects a secondary current I2 and feeds it back to the energy input circuit 9, a primary current sensor 31 that measures a current (primary current I1) flowing through the primary coil 5, Is provided. The detection value of the primary current sensor 31 is input to the ECU 4. The energy input circuit 9 is an example of an energy input unit.

  The main ignition circuit 8, the energy input circuit 9, and the feedback circuit 10 are accommodated in one case as an ignition circuit unit, and the ignition plug 2, the ignition coil 3, and the ignition circuit unit are provided in the same number as the number of cylinders. Installed for each cylinder.

  The spark plug 2 has a well-known structure, and includes a center electrode connected to one end of the secondary coil 6 and a ground electrode grounded through an engine cylinder head or the like. The generated electrical energy causes a spark discharge between the center electrode and the ground electrode.

  The ignition coil 3 includes a primary coil 5 and a secondary coil 6, and a current (secondary current) is supplied to the secondary coil 6 by electromagnetic induction in accordance with increase / decrease of a current (primary current I1) flowing through the primary coil 5. It is a well-known structure that generates I2).

  One end of the primary coil 5 is connected to the plus electrode of the on-vehicle battery 12, and the other end of the primary coil 5 is grounded via the ignition switching means 13 of the main ignition circuit 8. Further, an energy input circuit 9 is connected to the other end of the primary coil 5 in parallel with a line grounded via the ignition switching means 13.

  One end of the secondary coil 6 is connected to the center electrode of the spark plug 2 as described above, and the other end of the secondary coil 6 is connected to the feedback circuit 10. The other end of the secondary coil 6 is connected to the feedback circuit 10 via a first diode 14 that limits the direction of the secondary current I2 to one direction.

  The main ignition circuit 8 includes ignition switching means 13 for intermittently energizing the primary coil 5. The main ignition circuit 8 causes the primary coil 5 to store energy when the ignition switching means 13 is turned on and off, and also uses the energy stored in the primary coil 5 to generate a high voltage in the secondary coil 6 for ignition. Main ignition is caused to the plug 2.

  More specifically, the main ignition circuit 8 applies the voltage of the vehicle-mounted battery 12 to the primary coil 5 by turning on the ignition switching means 13 during a period in which the ignition signal IGt is given from the ECU 4, thereby adding a positive 1 The primary current I1 is energized, and the primary coil 5 is made to store magnetic energy. Thereafter, when the ignition switching means 13 is turned off, the main ignition circuit 8 converts magnetic energy into electric energy by electromagnetic induction and generates a high voltage in the secondary coil 6 to cause main ignition.

  The ignition switching means 13 is a power transistor, a MOS transistor, or the like.

  The energy input circuit 9 includes a booster circuit 15 and input energy control means 16.

  The booster circuit 15 boosts the voltage of the in-vehicle battery 12 and stores it in the capacitor 18 during a period when the ignition signal IGt is given from the ECU 4.

  The input energy control means 16 inputs the electric energy stored in the capacitor 18 to the negative side (ground side) of the primary coil 5.

  In addition to the capacitor 18, the booster circuit 15 includes a choke coil 19, a boosting switching unit 20, a booster driver circuit 21, and a second diode 22. Note that the boosting switching means 20 is, for example, a MOS transistor.

  One end of the choke coil 19 is connected to the plus electrode of the in-vehicle battery 12, and the energization state of the choke coil 19 is intermittently connected by the boosting switching means 20. Further, the boosting driver circuit 21 supplies a control signal to the boosting switching means 20 to turn on and off the boosting switching means 20, and the magnetic energy stored in the choke coil 19 by the on / off operation of the boosting switching means 20. Is charged as electrical energy by the capacitor 18.

  The step-up driver circuit 21 is provided so as to repeatedly turn on and off the step-up switching means 20 at a predetermined period during a period when the ignition signal IGt is given from the ECU 4.

  The second diode 22 prevents the electrical energy stored in the capacitor 18 from flowing back to the choke coil 19 side.

  The input energy control means 16 includes an input switching means 24, an input driver circuit 25 and a third diode 26. The switching means 24 for making up is, for example, a MOS transistor. The input switching means 24 is an example of a switching means.

  The input switching means 24 turns on / off to input the electric energy stored in the capacitor 18 into the primary coil 5 from the minus side.

  The input driver circuit 25 gives a control signal to the input switching means 24 based on the frequency signal SF input from the ECU 4 to turn it on / off. More specifically, the making driver circuit 25 controls the electric energy inputted from the capacitor 18 to the primary coil 5 by turning on and off the making switching means 24 based on the frequency signal SF inputted from the ECU 4. Thus, the secondary current I2 flowing through the secondary coil 6 is maintained at the maintenance target current value during the period when the discharge continuation signal IGw is applied. That is, it can be said that the discharge continuation signal IGw is a signal for instructing a period during which electric energy is input from the booster circuit 15 to the primary coil 5 by repeatedly turning on and off the input switching means 24.

  The third diode 26 prevents the backflow of current from the primary coil 5 to the capacitor 18.

  The feedback circuit 10 detects the secondary current I2 and feeds it back to the input energy control means 16 of the energy input circuit 9.

  The feedback circuit 10 includes a secondary current detection resistor 28 that detects the secondary current I2, and a current detection circuit 29 that synthesizes and outputs a feedback signal. The detected value of the secondary current I2 is converted into a voltage by the secondary current detection resistor 28 and output to the current detection circuit 29. In the current detection circuit 29, a feedback signal corresponding to the comparison between the detected value and the maintenance target current value input from the ECU 4 is synthesized and output to the input driver circuit 25.

  Next, the operation of the ignition system 1 will be described with reference to FIG. In FIG. 2, “IGt” represents the input state of the ignition signal IGt as high / low, and “IGw” represents the input state of the discharge continuation signal IGw as high / low. “Ignition switching means 13” and “charging switching means 24” respectively represent ON / OFF of the ignition switching means 13 and charging switching means 24, and “I1” represents the primary current I1 (primary coil 5). , “I2” represents a secondary current I2 (a current value flowing through the secondary coil 6). In the description of FIG. 2, the primary current I1 and the secondary current I2 have a positive value in the direction of the arrow shown in FIG. 1 and a negative value in the direction opposite to the arrow.

  When the ignition signal IGt switches from low to high (see time t1), during the period when the ignition signal IGt is high, the ignition switching means 13 is maintained in an on state and a positive primary current I1 flows, and the primary coil 5 Magnetic energy is stored in Further, the boosting switching means 20 repeatedly turns on and off to perform a boosting operation, and the boosted electrical energy is stored in the capacitor 18.

  Eventually, when the ignition signal IGt switches from high to low (see time t2), the ignition switching means 13 is turned off, and the energized state of the primary coil 5 is suddenly cut off. Thereby, the magnetic energy stored in the primary coil 5 is converted into electric energy, a high voltage is generated in the secondary coil 6, and main ignition is started in the spark plug 2.

  After the main ignition is started in the spark plug 2, the secondary current I2 attenuates in a substantially triangular wave shape (see the broken line of I2). Then, before the secondary current I2 reaches the lower limit threshold, the discharge continuation signal IGw is switched from low to high (see time t3).

  When the discharge continuation signal IGw switches from low to high, the on / off switching means 24 is on / off controlled based on the switching frequency indicated by the frequency signal SF, and the electrical energy stored in the capacitor 18 is changed to the primary coil 5. The primary current I1 flows from the primary coil 5 toward the plus electrode of the in-vehicle battery 12 sequentially. More specifically, every time the switching means 24 for turning on is turned on, a primary current I1 from the primary coil 5 toward the positive electrode of the in-vehicle battery 12 is added, and the primary current I1 increases on the negative side with a slope SL. (Refer to times t3 to t4).

  Each time the primary current I1 is added, a secondary current I2 in the same direction as the secondary current I2 caused by the main ignition is sequentially added to the secondary coil 6, and the secondary current I2 is a predetermined value including a maintenance target current value. Maintained in the range.

  As described above, the on / off control of the on-off switching unit 24 causes the secondary current I2 to flow continuously to such an extent that the spark discharge can be maintained. As a result, if the ON state of the discharge continuation signal IGw continues, continuous spark discharge is maintained in the spark plug 2.

  Next, switching frequency changing processing executed by the ECU 4 will be described. FIG. 3 is a flowchart showing an example of the switching frequency changing process executed by the ECU 4.

  In the process of FIG. 3, first, the ECU 4 obtains the slope SL of the change in the primary current I1 during the continuous spark discharge period (time t3 to t4 in FIG. 2) based on the output value of the primary current sensor 31. (Step S10). Note that the ECU 4 may acquire the slope of the change in the primary current I1 during the period when the switching means for making 24 is turned on.

  Next, the ECU 4 uses the switching frequency map shown in FIG. 5 from the slope SL of the change in the primary current I1 to determine the number of times the switching means 24 for turning on / off during the continuous spark discharge period, that is, the switching frequency. (Step S15).

  Here, a switching frequency map used for determining the switching frequency will be described.

  The change SL of the primary current I1 depends on the resistance and inductance of the primary coil 5. More specifically, the slope SL of the change in the primary current I1 becomes slower as the resistance and inductance of the primary coil 5 are higher, and the slope SL of the change in the primary current I1 is lower as the resistance and inductance of the primary coil 5 are lower. Becomes steep.

  Here, the ECU 4 does not consider the difference in the slope SL of the change in the primary current I1, for example, using the slope SLn of the change in the primary current I1 in the primary coil of the average ignition coil. Assume that 24 switching frequencies have been determined. At this time, if the inclination of the primary coil 5 is the same as the inclination SLn used to determine the switching frequency, if the electric energy is input to the primary coil 5 based on the determined switching frequency, the secondary coil is actually secondary. The secondary current I2 flowing through the coil 6 is maintained at the maintenance target current value (see FIG. 4B).

  On the other hand, it is assumed that the resistance and inductance of the primary coil 5 are low, and the slope of the change in the primary current I1 is a steeper slope SLs than the slope SLn used to determine the switching frequency. In this case, when the on / off switching means 24 is turned on / off at the switching frequency determined by the ECU 4, more electrical energy than necessary is input to the primary coil 5, and the current actually flowing through the secondary coil 6 is greater than the maintenance target current value. (See FIG. 4C). For this reason, current more than necessary flows through the spark plug 2 and the electrodes of the spark plug 2 may be consumed.

  Further, it is assumed that the resistance and inductance of the primary coil 5 are high, and the slope of the change in the primary current I1 is a slope SLg that is slower than the slope SLn used to determine the switching frequency. In this case, when the on / off switching means 24 is turned on / off at the switching frequency determined by the ECU 4, the electric energy supplied to the primary coil 5 is insufficient, and the current actually flowing through the secondary coil 6 is less than the maintenance target current value. (See FIG. 4D). At this time, if the current that actually flows through the secondary coil 6 falls below the lower limit value that guarantees ignition of the mixture, the mixture cannot be ignited. For example, execution of EGR control and lean control must be stopped. In other words, fuel consumption may be deteriorated.

  Therefore, in the switching frequency map according to the present embodiment, as shown in FIG. 5, the slower the slope SL of the change in the primary current I1, the higher the switching frequency, and the steeper the slope of the change in the primary current I1. The relationship between the slope of the change in the primary current I1 and the switching frequency is defined so that the switching frequency is lowered.

  Therefore, the ECU 4 decreases the switching frequency as the gradient SL of the change in the primary current I1 is steeper, and suppresses the electric power supplied to the primary coil 5 more than necessary. Thereby, it can suppress that the electrode of the spark plug 2 is consumed when the electric current more than necessary flows through the spark plug 2. Further, the ECU 4 increases the switching frequency as the slope SL of the change in the primary current I1 becomes slower. As a result, an amount of current necessary for execution of EGR control and lean combustion can be supplied to the spark plug 2, so that EGR control and lean combustion can be continued, and fuel efficiency is improved.

  Returning to FIG. 3, the ECU 4 outputs the frequency signal SF instructing the determined switching frequency to the input driver circuit 25 (step S <b> 17), and ends the process of FIG. 3. The input driver circuit 25 turns on and off the input switching means 24 based on the frequency signal SF and supplies electric energy to the primary coil 5.

  As is apparent from the above description, the ignition system 1 according to the present embodiment includes the ignition coil 3 including the primary coil 5 and the secondary coil 6, the capacitor 18, and the switching means 24 for charging. An ECU 4 is provided with an energy input circuit 9 for supplying the stored electrical energy to the primary coil 5 after starting the discharge of the spark plug 2 and causing the primary current 5 to flow through the primary coil 5. The ECU 4 changes the switching frequency of the input switching means 24 so that the secondary current I2 flowing through the secondary coil 6 is maintained at the maintenance target current value by the primary current I1 flowing through the primary coil 5, thereby changing the energy input circuit. The electric energy supplied from 9 to the primary coil 5 is controlled. Further, the ECU 4 has a slope of change in the primary current I1 during the period when electric energy is being supplied to the primary coil 5, or a slope of change in the primary current I1 during the period when the switching means 24 for turning on is on. To get. Then, the ECU 4 increases the switching frequency as the slope of the change in the primary current I1 is slow, and decreases the switching frequency as the slope of the change in the primary current I1 is steep. Thereby, optimal electrical energy can be input to the primary coil 5 according to the characteristics (resistance and inductance) of the primary coil 5. More specifically, when the inductance of the primary coil 5 is low and the gradient of the change in the primary current I1 is steep, the ECU 4 decreases the switching frequency and supplies the primary coil 5 with more electrical energy than necessary. It is suppressed that it is done. Thereby, it can suppress that the electrode of the spark plug 2 is consumed when the electric current more than necessary flows through the spark plug 2. Further, when the inductance of the primary coil 5 is high and the gradient of the change in the primary current I1 is slow, the ECU 4 increases the switching frequency so that necessary electrical energy is input to the primary coil 5. To. As a result, an amount of current necessary for execution of EGR control and lean combustion can be supplied to the spark plug 2, and EGR control and lean combustion can be continued, so that fuel efficiency can be improved.

  In the above embodiment, the ECU 4 determines the switching frequency of the switching means 24 for making, but the driver circuit 25 for making may determine the switching frequency of the switching means 24 for making. In this case, the switching frequency map may be stored in the input driver circuit 25 and the detection value of the primary current sensor 31 may be input to the input driver circuit 25. In this case, the input driver circuit 25 is an example of an acquisition unit and an energy control unit.

  Further, in the above embodiment, in the switching frequency map (FIG. 5), the curve indicating the relationship between the slope of the change in the primary current I1 and the switching frequency is represented by a straight line, but is not limited to this. As long as the switching frequency becomes higher as the gradient of the change in the next current I1 becomes slower, the curve indicating the relationship between them may have any shape.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited to these. Various modifications of these embodiments are within the scope of the present invention, and It is apparent from the above description that various other embodiments are possible within the scope.

1 Ignition system (ignition control device)
3 ignition coil 4 ECU (energy control unit, acquisition unit)
5 Primary coil 6 Secondary coil 9 Energy input circuit (energy input part)
18 Capacitor 24 Input switching means (switching means)

Claims (1)

An ignition coil including a primary coil and a secondary coil;
Including a capacitor and switching means, and by turning on and off the switching means, the electric energy stored in the capacitor is input to the primary coil after starting the discharge of the spark plug and the primary current is supplied to the primary coil. And
The switching frequency of the switching means remains constant while the switching means is on so that the secondary current flowing through the secondary coil maintains a target value by the primary current flowing through the primary coil. An energy control unit that controls the electric energy that is input to the primary coil from the energy input unit by changing
The slope of the change in the primary current during the period when the electrical energy is input to the primary coil after the spark plug starts discharging , or the change in the primary current during the period when the switching means is on. An acquisition unit for acquiring the inclination;
With
The energy control unit increases the switching frequency as the slope of the change in the primary current is slower, and decreases the switching frequency as the slope of the change in the primary current is steeper.
Ignition control device.

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