JP6252324B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  2. Description of the Related Art Conventionally, an internal combustion engine that performs a lean operation in which fuel is burned in a state where the fuel is leaner than the stoichiometric air-fuel ratio is known. For example, in Patent Document 1, in order to avoid the occurrence of misfire, the lean operation and the stoichiometric operation for burning at the stoichiometric air-fuel ratio are switched according to the ignition discharge time of the spark plug.

Japanese Patent No. 4938404

In Patent Document 1, in order to avoid the occurrence of misfire, the stoichiometric operation may be performed even in the lean operation region, so that the fuel consumption may be deteriorated.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a control device for an internal combustion engine that can suppress misfire and improve fuel efficiency.

The control device for an internal combustion engine of the present invention controls the internal combustion engine system. The internal combustion engine system includes an ignition device and can supply a part of the exhaust gas generated by the combustion as EGR gas to the combustion chamber.
The ignition device includes an ignition coil, an igniter unit, and an energy input unit.
The ignition coil has a primary coil and a secondary coil. A primary current supplied from a DC power source flows through the primary coil. The secondary coil is connected to an electrode of a spark plug that ignites the air-fuel mixture in the combustion chamber of the internal combustion engine, and a secondary voltage generated by energization and interruption of the primary current is applied to flow the secondary current.
The igniter section has an ignition switch. The ignition switch is connected to a ground side that is opposite to the DC power source of the primary coil, and switches between energization and interruption of the primary current.
The energy input unit interrupts the primary current by the ignition switch, and inputs energy in a predetermined energy input period after discharge is generated at the spark plug with the voltage generated by the interrupt.

The control device for an internal combustion engine includes abnormality determination means, ignition system determination means, and G / F ratio determination means.
The abnormality determination unit determines whether energy can be input by the energy input unit.
The ignition system determination means sets the ignition system to normal ignition or energy injection ignition based on the determination result by the abnormality determination means and the operating point of the internal combustion engine. In normal ignition, ignition is performed by energy generated by cutting off the primary current. In the energy input ignition, in addition to the energy due to the interruption of the primary current, the energy input from the energy input unit is performed.
The G / F ratio determining means determines a G / F ratio that is a ratio of the intake gas, which is a gas including air and EGR gas supplied to the combustion chamber, and fuel, based on the determination result and the operating point by the abnormality determining means. To do.

  When it is determined by the abnormality determining means that energy cannot be input by the energy input unit, the ignition method determining means sets the ignition method to normal ignition that does not perform energy input regardless of the operating point, and the G / F determining means operates When the point is an energy input ignition region in which energy input ignition is performed when energy input can be performed by the energy input unit, the G / F ratio is different from that when energy input is possible.

The ignition device includes an energy input unit, and after the discharge is generated by the ignition plug by the secondary current that is energized by the interruption of the primary current, the energy input unit inputs energy capable of continuing the ignition state. Can be suppressed.
Further, when energy cannot be input due to failure of the energy input unit or the like, the ignition method is set to normal ignition regardless of the operating point of the internal combustion engine. Further, in the energy input ignition region, the G / F ratio is changed so that the optimum value is obtained when normal ignition is used instead of energy input ignition. Thereby, compared with the case where EGR recirculation is not performed, for example, when energy cannot be input by the energy input unit, fuel efficiency is improved, and an increase in NOx or the like in the exhaust can be suppressed.

1 is a schematic configuration diagram showing a configuration of an engine system according to a first embodiment of the present invention. It is a block diagram of the ignition device by 1st Embodiment of this invention. It is a time chart explaining basic operation | movement of the ignition device by 1st Embodiment of this invention. It is explanatory drawing explaining switching of the drive mode when the energy input part by 1st Embodiment of this invention is normal. It is explanatory drawing explaining switching of the drive mode when the energy input part by 1st Embodiment of this invention fails. It is a flowchart explaining the engine control process by 1st Embodiment of this invention. It is explanatory drawing explaining switching of the drive mode when the energy input part by 2nd Embodiment of this invention is normal. It is a flowchart explaining the engine control process by 2nd Embodiment of this invention.

Hereinafter, a control device for an internal combustion engine according to the present invention will be described based on the drawings. Hereinafter, in a plurality of embodiments, the same numerals are given to the substantially same composition, and explanation is omitted.
(First embodiment)
[Engine system configuration]
First, a schematic configuration of the engine system will be described with reference to FIG. As shown in FIG. 1, an engine system 10 as an internal combustion engine system includes an engine 13 as a spark ignition type internal combustion engine, an ignition device 30 and the like.
The engine 13 is, for example, a multi-cylinder engine such as four cylinders, and FIG. 1 shows a cross section of one cylinder. The configuration described below is similarly provided to other cylinders (not shown).

The engine 13 burns an air-fuel mixture of air supplied from the intake manifold 15 through the throttle valve 14 and fuel injected from the injector 16 in the combustion chamber 17, and reciprocates the piston 18 by the explosive force at the time of combustion. . The reciprocating motion of the piston 18 is converted into a rotational motion by the crankshaft 19 and output. Combustion gas generated by the combustion is released into the atmosphere via the exhaust manifold 70.
That is, the engine 13 of the present embodiment is a so-called “port injection engine”, but may be a so-called “direct injection engine” that directly injects fuel into the combustion chamber 17.

The exhaust manifold 70 is provided with a catalyst 71 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust. A front O ₂ sensor 72 for detecting the oxygen concentration in the exhaust gas is provided on the upstream side of the catalyst 71. A rear O ₂ sensor 73 that detects the oxygen concentration in the exhaust gas purified by the catalyst 71 is provided on the downstream side of the catalyst 71.

  In the present embodiment, an exhaust gas recirculation device (hereinafter referred to as “EGR device”) 75 that introduces a part of the exhaust gas as EGR gas to the intake side is provided. The EGR device 75 has an EGR pipe 76 and an EGR valve 77. The EGR pipe 76 communicates the upstream side of the catalyst 71 of the exhaust manifold 70 and the intake manifold 15. The EGR valve 77 is provided in the middle of the EGR pipe 76 and adjusts the amount of EGR gas introduced into the combustion chamber 17 by adjusting the opening degree of the EGR valve 77.

Here, the air-fuel mixture supplied to the combustion chamber 17 will be summarized. The gas sucked through the throttle valve 14 is “air”, the gas supplied from the EGR pipe 76 is “EGR gas”, and “air” and “EGR gas” at the junction of the intake manifold 15 and the EGR pipe 76 The mixture gas is “intake gas”, and “intake gas” is a mixture of “fuel” injected from the injector 16 and “mixture”.
The ratio of “air” to “fuel” is “A / F ratio”, and the ratio of “intake gas (ie,“ air ”+“ EGR gas ”)” to “fuel” is “G / F (Gas / Fuel) ratio. Further, the ratio of “EGR gas” in the “air mixture” is defined as “EGR rate”.

  An intake valve 22 is provided at the intake port of the cylinder head 21 that is the inlet of the combustion chamber 17. An exhaust valve 23 is provided at the exhaust port of the cylinder head 21 that is the outlet of the combustion chamber 17. The intake valve 22 and the exhaust valve 23 are opened and closed by a valve drive mechanism 24. A variable valve mechanism that adjusts the valve timing may be provided in at least one of the intake valve 22 and the exhaust valve 23.

Ignition of the air-fuel mixture in the combustion chamber 17 is performed by the ignition device 30. Specifically, the ignition device 30 generates a spark due to the discharge between the electrodes of the spark plug 7, and the generated air-fuel mixture is ignited by the generated spark.
The spark plug 7 has a pair of electrodes (see FIG. 2) that face each other with a predetermined gap in the combustion chamber 17 of the engine 13. When a discharge voltage is applied between the electrodes of the spark plug 7, discharge occurs in the gap between the electrodes. The discharge voltage refers to a high voltage that can break the insulation between the electrodes and cause discharge.

An electronic control unit (hereinafter referred to as “ECU”) 32 as an “internal combustion engine control device” is constituted by a microcomputer comprising a CPU, a ROM, a RAM, an input / output port, and the like, and includes a crank angle sensor 35, a cam angle sensor. 36, signals from various sensors such as a water temperature sensor 37, a throttle opening sensor 38, an intake pressure sensor 39, a front O ₂ sensor 72, and a rear O ₂ sensor 73 are input. The ECU 32 controls the operating state of the engine 13 by controlling the throttle valve 14, the injector 16, the EGR valve 77, the ignition circuit unit 31, and the like based on detection signals from these various sensors.

[Configuration of ignition device]
The ignition device 30 includes an ignition circuit unit 31 and an ignition coil 40.
As shown in FIG. 2, the ignition coil 40 includes a primary coil 41, a secondary coil 42, and a rectifying element 43, and constitutes a known step-up transformer.
One end of the primary coil 41 is connected to the positive electrode of the battery 6 as a DC power source, and the other end is grounded via the ignition switch 45. Hereinafter, the side of the primary coil 41 opposite to the battery 6 is referred to as “ground side” or “low voltage side”.
The secondary coil 42 is magnetically coupled to the primary coil 41, one end is grounded via a pair of electrodes of the spark plug 7, and the other end is routed via the rectifying element 43 and the secondary current detection resistor 47. Grounded.

Hereinafter, the current flowing through the primary coil 41 is referred to as a primary current I1, and the current flowing through the secondary coil 42 is referred to as a secondary current I2. 2, the primary current I1 is positive in the direction from the primary coil 41 to the ignition switch 45, and the secondary current I2 is in the direction from the secondary coil 42 to the spark plug 7. Is positive. The voltage on the spark plug 7 side of the secondary coil 42 is referred to as a secondary voltage V2.
The rectifying element 43 is composed of a diode and rectifies the secondary current I2.
The ignition coil 40 generates a high voltage in the secondary coil 42 by a mutual induction action of electromagnetic induction according to a change in the current flowing through the primary coil 41, and applies this high voltage to the ignition plug 7. In the present embodiment, one ignition coil 40 is provided for one ignition plug 7.

The ignition circuit unit 31 includes an igniter unit 44, a secondary current detection resistor 47, an energy input unit 50, a secondary current detection circuit 61, and an abnormality determination unit 62.
The igniter unit 44 includes an ignition switch 45 and a rectifying element 46.
The ignition switch 45 is composed of, for example, an IGBT (insulated gate bipolar transistor), a collector is connected to the ground side of the primary coil 41, an emitter is grounded, and a gate is connected to the ECU 32. The emitter of the ignition switch 45 is connected to the collector via the rectifying element 46.

  The ignition switch 45 is switched on and off according to an ignition signal IGT input to the gate. Specifically, the ignition switch 45 is turned on when the ignition signal IGT rises and turned off when the ignition signal IGT falls. The primary current I1 is switched between conduction and interruption by the ignition switch 45 in accordance with the ignition signal IGT.

The energy input unit 50 includes a DCDC converter 51, a capacitor 56, a discharge switch 57, a discharge driver circuit 58, and a rectifying element 59.
The DCDC converter 51 includes an energy storage coil 52, a charging switch 53, a charging driver circuit 54, and a rectifying element 55, and boosts the voltage of the battery 6 and supplies it to the capacitor 56.

The energy storage coil 52 has one end connected to the battery 6 and the other end grounded via the charge switch 53.
The charge switch 53 is composed of, for example, a MOSFET (metal oxide semiconductor field effect transistor), and has a drain connected to the energy storage coil 52, a source grounded, and a gate connected to the charge driver circuit 54. The charging driver circuit 54 outputs a charging switch signal SWc for switching on / off the charging switch 53 to the gate of the charging switch 53.

The rectifying element 55 is formed of a diode, and prevents a backflow of current from the capacitor 56 to the energy storage coil 52 and the charge switch 53 side.
The capacitor 56 has a positive electrode connected to a connection point between the energy storage coil 52 and the charging switch 53 via the rectifying element 55 and a negative electrode grounded. The capacitor 56 stores the electric charge supplied from the DCDC converter 51.

  The charging switch 53 is turned on / off while an energy input period signal IGW described later is turned off. When the charging switch 53 is turned on, an induced current flows through the energy storage coil 52 and electric energy is stored. When the charging switch 53 is turned off, the electrical energy stored in the energy storage coil 52 is superposed on the DC voltage of the battery 6 and released to the capacitor 56 side. Thereby, the voltage of the capacitor 56 is boosted to a relatively high voltage (for example, 100 [V] to several hundred [V]) and charged.

The discharge switch 57 is formed of, for example, a MOSFET, the drain is connected to the positive side of the capacitor 56, the source is connected between the primary coil 41 and the ignition switch 45, and the gate is connected to the discharge driver circuit 58. The discharge driver circuit 58 outputs a discharge switch signal SWd for switching on / off the discharge switch 57 to the gate of the discharge switch 57.
The rectifying element 59 is composed of a diode and prevents a backflow of current from the ignition coil 40 to the capacitor 56.

  In FIG. 2, the configuration corresponding to one cylinder is shown, but in actuality, the configuration downstream of the discharge switch 57 is provided in parallel for the number of cylinders, and for each cylinder on the downstream side of the discharge switch 57. The energy stored in the capacitor 56 is distributed to each path according to the on / off state of the provided cylinder distribution switch.

The secondary current detection circuit 61 detects the secondary current I <b> 2 based on the voltage across the secondary current detection resistor 47. Further, the secondary current detection circuit 61 obtains the on-duty ratio of the discharge switch 57 by feedback control to make the secondary current I2 coincide with the target secondary current I2 ^* , and sends a command signal to the driver circuit 58 for discharge. Output. Here, the on-duty ratio is determined based on the result that the on-duty ratio is turned on when it is lower than the target secondary current I2 ^* and turned off when it is higher than I2 ^* .
The abnormality determination unit 62 determines an abnormality of the energy input unit 50 based on the detected secondary current I2 and the like, and outputs a determination result to the ECU 32. Hereinafter, the failure of energy input by the energy input unit 50 due to some abnormality is referred to as “energy input unit failure”, and the energy input by the energy input unit 50 is referred to as “energy input unit normal”.

The ECU 32 generates an ignition signal IGT, an energy input period signal IGW, and a target secondary current signal IGA based on the operation information of the engine 13 acquired from various sensors such as the crank angle sensor 35 and outputs it to the ignition circuit unit 31. To do.
The ignition signal IGT is input to the gate of the ignition switch 45 and the charging driver circuit 54. The ignition switch 45 is turned on while the ignition signal IGT is at a high level. The charging driver circuit 54 repeatedly outputs a charging switch signal SWc for controlling on / off of the charging switch 53 to the gate of the charging switch 53 while the ignition signal IGT is input.

The energy input period signal IGW is input to the discharge driver circuit 58. The discharge driver circuit 58 repeatedly outputs a discharge switch signal SWd for controlling on / off of the discharge switch 57 to the gate of the discharge switch 57 while the energy input period signal IGW is at a high level. In the present embodiment, the period during which the energy input period signal IGW is at a high level corresponds to the “energy input period”.
The target secondary current signal IGA is a signal for instructing the target secondary current I2 ^* , and is input to the discharge driver circuit 58.

[Ignition device operation]
The operation of the ignition device 30 will be described with reference to the time chart of FIG. In the time chart of FIG. 3, the horizontal axis is the common time axis and the ignition signal IGT, the energy input period signal IGW, the capacitor voltage Vdc, the primary current I1, the secondary current I2, the input energy P, and the charge are shown in order from the top on the vertical axis. A switch signal SWc and a discharge switch signal SWd are shown.
Here, the capacitor voltage Vdc means the voltage of the capacitor 56. The input energy P means energy that is discharged from the capacitor 56 and supplied from the ground-side terminal of the primary coil 41 to the ignition coil 40, and indicates an integrated value from the start of energy supply in one energy input period. The energy supply start timing in the energy input period is time t3 when the first discharge switch signal SWd rises.

  In the primary current I1 and the secondary current I2, the current in the direction of the arrow in FIG. 2 is a positive value, and the current in the direction opposite to the arrow is a negative value. In the following description, when referring to the magnitude of a negative current, the magnitude is expressed based on the absolute value of the current. That is, for a negative current, it is said that “the current increases (or increases)” when the current value is away from zero and the absolute value increases, and “the current decreases (or decreases) as the absolute value decreases toward zero. ) ".

Further, the control target value of the secondary current I2 in the period from the time t3 to the time t4 when the energy input period signal IGW is output is defined as “target secondary current I2 ^* ”. The target secondary current I2 ^* is set to a value that can maintain the ignition state satisfactorily. In the present embodiment, an intermediate value between the wavy maximum value and the minimum value is set as the target value, but the wavy maximum value or the minimum value may be set as the target value.

When the ignition signal IGT becomes a high level (indicated by “H” in FIG. 3) at time t1 in FIG. 3, the ignition switch 45 is turned on, the primary current I1 is energized to the primary coil 41, and the passage of time. As a result, the primary current I1 increases. As a result, electromagnetic energy is accumulated in the primary coil 41 between the time t1 and the time t2 when the ignition signal IGT is at a high level.
At this time, the energy input period signal IGW is at a low level (indicated by “L” in FIG. 3), and the discharge switch 57 is turned off.

  Further, during the period when the ignition signal IGT is at a high level, the charging switch signal SWc having a rectangular wave pulse shape is input to the gate of the charging switch 53. Then, during the off period after the charging switch 53 is turned on, the capacitor voltage Vdc rises stepwise and the capacitor 56 is charged. It is not always necessary to start charging the capacitor 56 in synchronization with the transmission of the ignition signal IGT. It is sufficient if sufficient electric energy is accumulated before the energy input period signal IGW rises. Further, the capacitor voltage Vdc (that is, the amount of energy stored in the capacitor 56) can be controlled by the on-duty ratio and the number of on-off times of the charge switch signal SWc.

  At time t2, when the ignition signal IGT becomes low level and the ignition switch 45 is turned off, the primary current I1 energized in the primary coil 41 is suddenly interrupted, and the magnetic field formed by the primary current I1 disappears. . Then, a magnetic field is induced in the secondary coil 42 so as to cancel the magnetic field formed in the primary coil 41, and a large secondary voltage V2 is generated in the secondary coil 42. When the secondary voltage V2 reaches the discharge voltage, a spark discharge occurs between the electrodes of the spark plug 7, and a secondary current I2 (discharge current) flows through the secondary coil. As a result, the air-fuel mixture in the combustion chamber 17 is ignited.

  When energy is not input after the spark discharge is generated at time t2, the secondary current I2 approaches zero with the passage of time as shown by a broken line, and the discharge ends when the discharge is attenuated to such an extent that the discharge cannot be maintained. In the present embodiment, a method of igniting with energy generated by cutting off the primary current I1 is referred to as “normal ignition”. In normal ignition, energy is not input after a spark discharge is generated.

  On the other hand, when the energy input period signal IGW becomes high level at time t3, which is the timing after time t2, the discharge switch signal SWd becomes high level, and the discharge switch 57 is turned on. When the discharge switch 57 is turned on while the charge switch 53 is off, the energy stored in the capacitor 56 is released and supplied to the ground side of the primary coil 41. As a result, the primary coil 41 is energized with the primary current I1 resulting from the input energy P. When the primary current I1 is energized from the ground side of the primary coil 41 by the input energy P, the additional amount accompanying the energization of the primary current I1 by the input energy P has the same polarity with respect to the secondary current I2 energized by the normal ignition. Superimposed.

During the period from time t3 to time t4, the discharge switch 57 is repeatedly turned on and off according to the discharge switch signal SWd. Thereby, every time the discharge switch 57 is turned on, an additional amount accompanying the energization of the primary current I1 by the input energy P is superimposed on the secondary current I2. That is, every time the discharge switch signal SWd is turned on, the primary current I1 is sequentially added by the energy stored in the capacitor 56, and the secondary current I2 is sequentially added correspondingly. Thereby, the secondary current I2 is controlled to be within a predetermined range including the target secondary current I2 ^* . Here, the primary current I1 due to the input energy P supplied from the energy input unit 50 is also included in the concept of “primary current supplied from a DC power supply”.
When the energy input period signal IGW becomes low level at time t4, the discharge switch signal SWd becomes an off signal, the on / off operation of the discharge switch 57 stops, and the primary current I1 and the secondary current I2 become zero.

In the present embodiment, after discharging due to the ignition switch 45 being turned off, energy is input to the ignition coil 40 from the ground side (that is, the low voltage side) of the primary coil 41, whereby the battery 6 side or the secondary coil 42 of the primary coil 41. Compared with the case where energy is input to the ignition coil 40 from the side opposite to the spark plug 7, the minimum energy can be input efficiently and the ignition enabled state can be maintained.
Hereinafter, an ignition method in which energy is input from the ground side of the primary coil 41 is referred to as “energy input ignition”.

Here, control of the operating conditions of the engine 13 by the ECU 32 will be described. Various maps, which will be described later, used for controlling the operating conditions of the engine 13 are set by adaptation and stored in the ECU 32.
The ECU 32 determines the operating point (the number of revolutions and torque) of the engine 13 according to the required drive power to be output from the engine 13. Further, the ECU 32 determines the A / F ratio, the EGR rate, and the ignition method according to the operating point of the engine 13.

  When the energy input unit is normal, the map shown in FIG. 4 is used to determine the A / F ratio, the EGR rate, and the ignition method according to the operating point of the engine 13. In FIG. 4, the region where the operating point of the engine 13 is smaller than the solid line L11 is the first region R11, the region between the solid line L11 and the solid line L12 is the second region R12, and the solid line LF and the solid line L12 that define the total load are The area between them is referred to as a third area R13.

  When the operating point of the engine 13 is the first region R11 or the second region R12 when the energy input unit is normal, the ignition method is energy input ignition. Hereinafter, the first region R11 and the second region R12 in which the ignition method is energy input ignition are referred to as “energy input ignition region”. In the third region R13, the ignition method is normal ignition.

When the operating point of the engine 13 is the first region R11 when the energy input unit is normal, the A / F ratio is set to the lean state, and the EGR rate is determined based on the first map. When the operating point of the engine 13 is the second region R12, the A / F ratio is set to the stoichiometric state, and the EGR rate is determined based on the second map. In the first map and the second map, the operating point of the engine 13 and the optimum EGR rate are associated with each other.
When the operating point of the engine 13 is the third region R13, the A / F ratio is set to the stoichiometric state. Further, the EGR rate is set to an amount that is possible due to torque restriction when the ignition method is normal ignition. Note that the EGR rate is zero at full load.

For example, in the case where an energy input unit failure that makes it impossible to input energy by the energy input unit 50 due to abnormality of the DCDC converter 51 or the like occurs, energy input cannot be performed by the energy input unit 50. Therefore, in all regions where the operating point is smaller than the solid line LF, The ignition method is normal ignition.
Further, when the energy input unit fails, the A / F ratio and the EGR rate are determined according to the operating point of the engine 13 using the map shown in FIG.

Here, in all the regions, if the EGR rate is set to zero, the fuel consumption may be deteriorated.
Therefore, in this embodiment, when the operating point of the engine 13 is the first failure region RE1 smaller than the broken line LE at the time of failure of the energy input unit, the A / F ratio is set to the stoichiometric state, and the EGR rate is calculated based on the failure time map. decide. Here, when the energy input unit fails, determining the EGR rate based on a failure map different from the first map and the second map can be regarded as changing the G / F ratio.
Further, the failure second region RE2 between the broken line LE and the solid line LF sets the A / F ratio to a stoichiometric state as in the third region R13 when the energy input unit is normal. Further, the EGR rate is set to an amount that is possible due to torque restriction when the ignition method is normal ignition.

In the failure time map, the operating point of the engine 13 and the optimum EGR rate when the ignition method is normal ignition are associated with each other. Further, the EGR rate determined by the failure time map is equal to or lower than the EGR rate determined by the second map at the same operating point.
In the present embodiment, the broken line LE that defines the failure first region RE1 and the failure second region RE2 is the same as the solid line L12 in FIG. 4, but may be different.

Here, the engine control process will be described based on the flowchart shown in FIG. The engine control process is executed at predetermined intervals while the ECU 32 is activated. Each process described with reference to FIG. 6 may be configured by software or hardware.
In the first step S101 (hereinafter, “step” is omitted and is simply indicated by the symbol “S”), whether or not energy can be input by the energy input unit 50 based on the determination result output from the abnormality determination unit 62. Judging. When it is determined that energy cannot be input (S101: NO), the process proceeds to S108. When it is determined that energy can be input by the energy input unit 50 (S101: YES), the process proceeds to S102.

In S102, it is determined whether or not the operating point of the engine 13 is in the energy input ignition region. When it is determined that the operating point of the engine 13 is not in the energy input region (S102: NO), that is, when the operating point of the engine 13 is the third region R13 larger than the solid line L12 in FIG. When it is determined that the operating point of the engine 13 is in the energy input region (S102: YES), that is, when the operating point of the engine 13 is smaller than the solid line L12, the process proceeds to S103.
In S103, the ignition control method is energy input ignition.

  In S104, it is determined whether or not the operating point of the engine 13 is the first region R11. When it is determined that the operating point of the engine 13 is the first region R11 (S104: YES), that is, when the operating point of the engine 13 is smaller than the solid line L11 in FIG. 4, the process proceeds to S105. When it is determined that the operating point of the engine 13 is not the first region R11 (S104: NO), that is, when the operating point of the engine 13 is the second region R12 between the solid lines L11 and L12, the process proceeds to S106. .

In S105, which is shifted when the operating point of the engine 13 is the first region R11, the A / F ratio is set to the lean state. Further, the EGR rate is determined based on the first map.
In S106, which is shifted when the operating point of the engine 13 is the second region R12, the A / F ratio is set to the stoichiometric state. Further, the EGR rate is determined based on the second map.
When it is determined that the operating point of the engine 13 is not in the energy input region (S102: NO), the ignition control method is set to normal ignition and the process proceeds to S111.

When it is determined that energy cannot be input by the energy input unit 50 (S101: NO), the ignition control method is set to normal ignition.
In S109, it is determined whether or not the operating point of the engine 13 is the failure first region RE1. It is determined whether or not the operating point of the engine 13 is the failure first region RE1. When it is determined that the operating point of the engine 13 is the failure first region RE1 (S109: YES), that is, when the operating point of the engine 13 is smaller than the broken line LE in FIG. 5, the process proceeds to S110. When it is determined that the operating point of the engine 13 is not the failure first region RE1 (S109: NO), that is, when the operating point of the engine 13 is the failure second region RE2 larger than the broken line LE, the process proceeds to S111.

In S110, the A / F ratio is set to the stoichiometric state. Further, the EGR rate is determined based on the failure time map.
In S <b> 111, which is shifted when a negative determination is made in S <b> 107 or S <b> 109, the A / F ratio is set to a stoichiometric state. Further, the EGR rate is set to an amount that is possible due to torque restriction when the ignition method is normal ignition.

  In the present embodiment, since the EGR rate is determined based on the failure time map at the time of failure of the energy input unit, for example, fuel efficiency can be improved and NOx in the exhaust can be improved as compared with the case where the EGR rate is set to zero. Etc. can be reduced.

As described in detail above, the ECU 32 of this embodiment controls the engine system 10. The engine system 10 includes an ignition device 30 and can supply a part of exhaust gas generated by combustion to the combustion chamber 17 as EGR gas.
The ignition device 30 includes an ignition coil 40, an igniter unit 44, and an energy input unit 50.
The ignition coil 40 has a primary coil 41 and a secondary coil 42. A primary current I <b> 1 supplied from the battery 6 flows through the primary coil 41. The secondary coil 42 is connected to the electrode of the spark plug 7 that ignites the air-fuel mixture in the combustion chamber 17 of the engine 13, and the secondary voltage V2 generated by energizing and shutting off the primary current I1 is applied and the secondary current I2 flows. .

The igniter unit 44 has an ignition switch 45. The ignition switch 45 is connected to the ground side opposite to the battery 6 of the primary coil 41, and switches between energization and interruption of the primary current I1.
The energy input unit 50 interrupts the primary current I1 with the ignition switch 45, and inputs energy in the energy input period after the spark plug 7 generates a discharge with the voltage generated by the interruption.

The ECU 32 performs the following processing.
The ECU 32 determines whether or not energy can be input by the energy input unit 50 (S101 in FIG. 6). Based on the abnormality determination result and the operating point of the engine 13, the ignition method is set to normal ignition (S107 or S108). Or it is set as energy injection ignition (S103). The normal ignition is ignited by energy generated by cutting off the primary current I1. The energy input ignition performs energy input from the energy input unit 50 in addition to the energy generated by the interruption of the primary current I1. Specifically, the energy input unit 50 inputs energy capable of continuing the ignition state while maintaining the same discharge current polarity during the energy input period.

Based on the abnormality determination result and the operating point of the engine 13, the ECU 32 is a G / F that is the ratio of the intake gas that is a gas including the air supplied to the combustion chamber 17 and the EGR gas recirculated by the EGR device 75 to the fuel. The ratio is determined (S105, S106, S110, S110).
If it is determined that the energy input unit 50 cannot input energy (S101: NO), the ECU 32 sets the ignition method to normal ignition regardless of the operating point of the engine 13. Further, the ECU 32 sets a G / F ratio different from that when energy can be input when the operating point is an energy input ignition region in which energy input ignition is performed when the energy input unit 50 can input energy.

  In the present embodiment, the ignition device 30 is provided with an energy input unit 50. After the energy input unit 50 generates a discharge at the spark plug 7 with a voltage due to the cutoff of the primary current I1, the ignition state is changed. Since energy that can be continued is input, misfire can be suppressed.

  Further, when energy cannot be input due to a failure of the energy input unit 50 or the like, the ignition method is normal ignition regardless of the operating point of the engine 13. Further, in the energy input ignition region, the G / F ratio is changed so that the optimum value is obtained when normal ignition is used instead of energy input ignition. Thereby, when it becomes impossible to input energy by the energy input unit 50, for example, compared with a case where EGR recirculation is not performed, fuel efficiency is improved, and an increase in NOx or the like in the exhaust gas can be suppressed.

In the present embodiment, the energy input region includes a first region R11 and a second region R12 in which at least one of the rotational speed and torque of the engine 13 is larger than the first region R11.
When the energy input by the energy input unit 50 is possible (S101: YES), the ECU 32 is an A / F that is the ratio of air to fuel supplied to the combustion chamber 17 when the operating point is the first region R11. The ratio is set to the lean state, and the EGR rate that is the ratio of the EGR gas in the intake gas is determined based on the first map (S105). When the operating point is the second region R12, the A / F ratio is set to the stoichiometric state, and the EGR rate is determined based on the second map different from the first map (S106).
In addition, when the energy input by the energy input unit 50 cannot be performed, the ECU 32 sets the A / F ratio to the stoichiometric state when the operating point is in the energy input ignition region, and sets the failure map different from the first map and the second map. Based on this, the EGR rate is determined (S110).

In the present embodiment, the EGR rate is determined based on different maps when the energy input unit is normal and when the energy input unit is faulty, and the G / F ratio is changed by changing the recirculation amount of the EGR gas. Thereby, the G / F ratio at the time of failure of the energy input unit can be controlled to an appropriate value.
Further, the EGR rate determined by the failure time map is equal to or lower than the EGR rate determined by the second map at the same operating point. Thereby, a fuel consumption improves more and the increase in NOx etc. can be suppressed more appropriately.
The energy input unit 50 inputs energy to the ignition coil 40 from the ground side of the primary coil 41. Thereby, compared with the case where energy is input from the battery 6 side of the primary coil 41 or the spark plug 7 side of the secondary coil 42, the minimum energy can be input efficiently.

  In the present embodiment, the ECU 32 constitutes “abnormality determination means”, “ignition method determination means”, and “G / F ratio determination means”. Further, S101 in FIG. 6 corresponds to processing as a function of “abnormality determination means”, S103, S107, and S108 correspond to processing as a function of “ignition method determination means”, and S105, S106, S110, S111. Corresponds to the processing as the function of the “G / F ratio determining means”.

(Second Embodiment)
A control apparatus for an internal combustion engine according to a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, since the control of the operating conditions of the engine 13 by the ECU 32 is different, this point will be mainly described, and the overall configuration and the like are the same as those in the above embodiment, and the description thereof is omitted.
In the present embodiment, the lean burn operation is not performed even in the low rotation and low torque regions of the engine 13, and the stoichiometric operation is performed. That is, as shown in FIG. 7, a region where the ignition method is energy input ignition is defined as one energy input ignition region R21. When the operating point of the engine 13 is the energy input ignition region R21, the A / F ratio is stoichiometric and the EGR rate is determined based on the normal time map.

When the operating point is the normal ignition region R22, as in the third region R13 of the above embodiment, the ignition method is normal ignition and the A / F ratio is stoichiometric. Further, the EGR rate is set to an amount that is possible due to torque limitation when the ignition method is normal ignition.
The solid line L21 that defines the energy input ignition region R21 and the normal ignition region R22 may be the same as or different from the solid line L12 in the above embodiment.
Moreover, the process at the time of an energy input part failure is the same as that of the said embodiment. The EGR rate determined by the failure time map is equal to or less than the EGR rate determined by the normal time map at the same operating point.

The engine control process of this embodiment is demonstrated based on the flowchart shown in FIG. In the engine control process of this embodiment, S104 to S106 in FIG. 6 are omitted, and S112 is added instead.
When it is possible to input energy by the energy input unit 50 (S101: YES) and it is determined that the operating point of the engine 13 is the energy input ignition region R21 (S102: YES), the process proceeds to S112 following S103.
In step S112, the A / F ratio is stoichiometric, and the EGR rate is determined based on the normal time map.

In the present embodiment, when the energy input by the energy input unit 50 is possible (S101: YES in FIG. 8), the ECU 32 sets the A / F ratio to the stoichiometric state and determines the EGR rate based on the normal time map. (S112). If the energy input unit 50 cannot input energy (S101: NO), the ECU 32 sets the A / F ratio to a stoichiometric state and determines the EGR rate based on the failure map (S110).
The EGR rate determined by the failure time map is equal to or less than the EGR rate determined by the normal time map at the same operating point.
Thereby, the engine control process of the present embodiment can be applied to other than the lean burn engine. In addition, the same effects as those of the above embodiment can be obtained.
In the present embodiment, S110, S111, and S112 correspond to processing as a function as “G / F determination means”.

(Other embodiments)
(A) EGR device In the above embodiment, the EGR pipe communicates the upstream side of the catalyst and the intake manifold. In other embodiments, the EGR piping may be arranged in any way, for example, the EGR gas is returned to the intake side from the downstream side of the catalyst.
In the above embodiment, the EGR device is a so-called “external EGR” in which part of the exhaust gas generated by combustion is recirculated to the intake side as EGR gas and supplied to the combustion chamber. In another embodiment, the EGR device may be omitted, and so-called “internal EGR” may be used in which part of the exhaust gas is returned to the combustion chamber by controlling the opening / closing drive of the exhaust valve.

(A) Energy input ignition In the above-described embodiment, the energy input ignition is performed by supplying energy capable of continuing the ignition state from the ground side of the primary coil. In other embodiments, the energy input ignition may be any energy as long as the energy capable of continuing the ignition state can be input. For example, Japanese Patent Application Laid-Open No. 2012-167665 discloses a conventional multiple discharge method. The disclosed “DCO method” may be used. For example, when adopting the DCO method, one of the two ignition coils that starts the main discharge is regarded as an “ignition coil”, and the ignition operation after the main discharge is regarded as an “energy input unit” to control the coil power source. Thus, the secondary current may be controlled or the ignition duration may be controlled.

(C) Secondary current feedback control In the above embodiment, the secondary current detection resistor and the secondary current detection circuit are provided, and feedback control based on the secondary current is performed. In other embodiments, the feedback control based on the secondary current may not necessarily be performed.
(D) Abnormality detection unit In the embodiment described above, the ECU determines whether energy can be input by the energy input unit based on the determination result output from the abnormality detection unit. In another embodiment, the ECU may acquire the secondary current I2 from the secondary current detection circuit and perform an abnormality determination inside the ECU.

(E) Ignition circuit unit The ignition circuit unit may be housed in a housing that houses the electronic control unit. The ignition circuit unit may be housed in a housing that houses the ignition coil.
The ignition switch and the energy input unit may be housed in separate housings. For example, the ignition switch may be housed in a housing that houses the ignition coil, and the energy input unit may be housed in the housing that houses the electronic control unit.

(F) Ignition switch, charge switch, discharge switch In the above-described embodiment, the ignition switch is composed of an IGBT. In other embodiments, the ignition switch is not limited to the IGBT, and may be constituted by another switching element having a relatively high breakdown voltage.
Moreover, in the said embodiment, a charge switch and a discharge switch are comprised by MOSFET. In other embodiments, at least one of the charge switch and the discharge switch is not limited to the MOSFET, and may be configured by another switching element such as an IGBT.

(G) DC power supply In the said embodiment, DC power supply is comprised by the battery. In another embodiment, the direct current power source is not limited to a battery, and may be constituted by, for example, a direct current stabilized power source in which an alternating current power source is stabilized by a switching regulator or the like.
In addition, when the DC power supply has a high output voltage, such as a main battery of a hybrid vehicle or an electric vehicle, the DCDC converter may be omitted and the output voltage may be used as it is, or the output voltage may be stepped down. .
As mentioned above, this invention is not limited to the said embodiment at all, In the range which does not deviate from the meaning of invention, it can implement with a various form.

6 ... Battery (DC power supply)
7 ... Spark plug 10 ... Engine system (internal combustion engine system)
17 ... Combustion chamber 30 ... Ignition device 32 ... ECU (Control device for internal combustion engine)
40 ... Ignition coil 44 ... Igniter part 50 ... Energy input part

Claims (5)

A primary coil (41) through which a primary current supplied from a DC power supply (6) flows, and an electrode of an ignition plug (7) for igniting an air-fuel mixture in a combustion chamber (17) of an internal combustion engine (13) are connected to the primary coil. An ignition coil (40) having a secondary coil (42) through which a secondary voltage generated by energization and interruption of current is applied and a secondary current flows;
An igniter section (44) having an ignition switch (45) connected to a ground side opposite to the DC power source of the primary coil and switching between energization and interruption of the primary current;
And an energy input unit (50) for supplying energy in an energy input period after the primary current is interrupted by the ignition switch and a discharge is generated in the spark plug at a voltage generated by the interruption.
An internal combustion engine control device (32) for controlling an internal combustion engine system (10) capable of supplying a part of exhaust gas generated by combustion as EGR gas to the combustion chamber.
An abnormality determining means (S101) for determining whether energy can be input by the energy input unit;
Based on the determination result by the abnormality determination means and the operating point that is the rotational speed and torque of the internal combustion engine, the ignition method is generated by normal ignition that is ignited by energy generated by the interruption of the primary current, or by interruption of the primary current Ignition method determination means (S103, S107, S108) for performing energy input ignition that inputs energy from the energy input unit in addition to energy,
G for determining a G / F ratio, which is a ratio of intake gas and fuel, which is a gas including air and EGR gas supplied to the combustion chamber, based on the determination result by the abnormality determination means and the operating point / F ratio determining means (S105, S106, S110, S111, S112),
With
When it is determined by the abnormality determination means that energy input by the energy input unit cannot be performed,
The ignition method determining means sets the ignition method as the normal ignition regardless of the operating point,
The G / F ratio determining means is different from the G / F ratio different from the case where energy can be input when the operating point is an energy input ignition region in which energy input ignition is performed when the energy input unit can input energy. A control device for an internal combustion engine. The energy input ignition region includes a first region and a second region in which at least one of the rotational speed and the torque is larger than the first region,
The G / F ratio determining means (S105, S106, S110)
When energy can be input by the energy input unit,
When the operating point is the first region, an A / F ratio that is a ratio of air and fuel supplied to the combustion chamber is set to a lean state, and an EGR rate that is a ratio of the EGR gas in the mixture is obtained. Based on the first map,
When the operating point is the second region, the A / F ratio is stoichiometric, and the EGR rate is determined based on a second map different from the first map,
When energy cannot be input by the energy input unit,
When the operating point is in the energy input ignition region, the A / F ratio is set to a stoichiometric state, and the EGR rate is determined based on a failure time map different from the first map and the second map. The control apparatus for an internal combustion engine according to claim 1.   The control apparatus for an internal combustion engine according to claim 2, wherein the EGR rate determined by the failure time map is equal to or less than the EGR rate determined by the second map at the same operating point. The G / F ratio determining means (S112), in the energy input ignition region,
When energy can be input by the energy input unit, an A / F ratio, which is a ratio of intake air and fuel supplied to the combustion chamber, is stoichiometric, and the EGR gas in the mixture is based on a normal time map. The EGR rate, which is the percentage of
When energy cannot be input by the energy input unit, the A / F ratio is stoichiometric, and the EGR rate is determined based on a failure map,
2. The control device for an internal combustion engine according to claim 1, wherein the EGR rate determined by the failure time map is equal to or less than the EGR rate determined by the normal time map at the same operating point.   The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the energy input unit inputs energy to the ignition coil from a ground side of the primary coil.

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