JP2015200278A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which reduces a variation of torque while efficiently removing harmful substances contained in exhaust.SOLUTION: After detecting an operation state of an engine on the basis of a detection signal outputted by a crank position sensor or the like at S101, it is determined whether or not a temperature of a catalyst in S102 is lower than a prescribed temperature being a temperature at which removal objective substances contained in exhaust can be efficiently removed. When it is determined that the temperature of the catalyst is lower than the prescribed temperature, a discharge time of an ignition plug is elongated while increasing a secondary current with the same polarity in S103, and an injection time of fuel at a fuel injection valve is changed in S104. By this constitution, since an ignition plug continues discharge at which an air-fuel mixture can be combusted, the ignition plug can surely combust the air-fuel mixture which is liable to be misfired in a normal discharge time. Accordingly, a variation of torque outputted by the engine can be reduced while early activating the catalyst by utilizing the combustion heat of the air-fuel mixture.

Description

  The present invention relates to a control device for an internal combustion engine that controls combustion of an air-fuel mixture in a combustion chamber of the internal combustion engine.

  Conventionally, in order to efficiently remove harmful substances contained in exhaust immediately after starting an internal combustion engine (hereinafter referred to as “engine”), the temperature of the catalyst provided in the exhaust system is increased to a predetermined temperature suitable for removing harmful substances. A control device for an internal combustion engine to be raised is known. For example, in Patent Document 1, the discharge timing of the spark plug is changed based on the temperature of the cooling water of the internal combustion engine, and the heat generated by the combustion of the air-fuel mixture (hereinafter referred to as “combustion heat”) is used. A control device for an internal combustion engine that raises the temperature is known.

Japanese Patent Application No. 06-005334

  In the internal combustion engine described in Patent Document 1, when the temperature of the catalyst is raised, the discharge start timing of the spark plug is shifted to the retard side so that the air-fuel mixture is burned immediately before the exhaust valve is opened, and the catalyst temperature is set to a predetermined value. Reduce the time to increase the temperature to However, if the discharge start timing of the spark plug is shifted to the retard side too much, the combustion of the air-fuel mixture in the combustion chamber becomes unstable, so that the torque output by the internal combustion engine varies greatly while the temperature of the catalyst is raised. There is a fear.

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide a control device for an internal combustion engine that reduces torque fluctuations while efficiently removing harmful substances contained in exhaust gas. is there.

  The present invention relates to a control device for an internal combustion engine that controls combustion of an air-fuel mixture in a combustion chamber of the internal combustion engine, and a discharge control unit that controls a discharge state of a spark plug that ignites the air-fuel mixture by discharge, and operation of the internal combustion engine An operating state detecting means for detecting a state and outputting a detection signal based on the operating state of the internal combustion engine, and a temperature of a catalyst provided in the exhaust system of the internal combustion engine based on the detection signal output by the operating state detecting means is a predetermined temperature Catalyst temperature determination means for determining whether or not the temperature is lower. When the catalyst temperature determination means determines that the catalyst temperature is lower than a predetermined temperature, the discharge control unit determines at least the extension of the discharge time of the spark plug from the normal discharge time and the increase in the discharge current of the spark plug with the same polarity. It is characterized by doing one.

  In the control device for an internal combustion engine according to the present invention, when the catalyst temperature determining means determines that the temperature of the catalyst is lower than a predetermined temperature based on the detection signal output from the operating state detecting means, the discharge time of the spark plug is set to the normal discharge time At least one of the control to extend from the control and the control to increase the discharge current of the spark plug with the same polarity. Here, the predetermined temperature refers to a temperature at which a removal target substance such as a harmful substance contained in exhaust gas can be efficiently removed. The normal discharge time refers to the time during which the spark plug ignites the air-fuel mixture in the combustion chamber when the internal combustion engine is in steady operation. When the discharge time of the spark plug is made longer than the normal discharge time, the probability that the air-fuel mixture in the combustion chamber is ignited can be increased. Further, when the discharge current is increased with the same polarity, the discharge energy increases, the air-fuel mixture can be reliably burned, and the combustion heat of the exhaust gas can be transmitted to the catalyst in a relatively large amount. In particular, when the ignition start timing of the spark plug is shifted to the retard side in order to transmit more heat to the catalyst, the expanding air-fuel mixture that easily misfires can be reliably burned. As a result, the temperature of the catalyst can be quickly raised using the combustion heat of the air-fuel mixture, so that the catalyst is activated so that harmful substances contained in the exhaust gas are efficiently removed early after the start of the internal combustion engine. be able to. Further, since the expanding air-fuel mixture that easily misfires can be reliably burned, fluctuations in torque output from the internal combustion engine can be reduced.

1 is a schematic configuration diagram of an engine system to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. It is a block diagram of the control apparatus of the internal combustion engine by one Embodiment of this invention. It is a time chart of the basic operation | movement of the discharge control part in the control apparatus of the internal combustion engine by one Embodiment of this invention. It is a flowchart of the catalyst warm-up process in the control apparatus of the internal combustion engine by one Embodiment of this invention. It is a time chart explaining operation | movement of each part of steady operation control and catalyst warm-up control in the control apparatus of the internal combustion engine by one Embodiment of this invention. FIG. 6 is a characteristic diagram showing the relationship between the discharge timing of the spark plug, the exhaust temperature and the torque fluctuation in the control apparatus for an internal combustion engine according to the embodiment of the present invention. FIG. 7 is a characteristic diagram showing a state in which a discharge time of a spark plug is extended in a control device for an internal combustion engine according to another embodiment of the present invention.

  Hereinafter, a control device for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings.

(One embodiment)
An engine control apparatus 1 as an “internal combustion engine control apparatus” according to an embodiment of the present invention is applied to an engine system mounted on a vehicle or the like. The engine control device 1 includes a discharge control unit 30, a crank position sensor 35 as "operating state detecting means", a catalyst temperature sensor 341 as "operating state detecting means", and a catalyst temperature determining unit 34 as "catalyst temperature determining means". The intake port injector 15, the direct injection injector 26 as a “direct injection fuel injection valve”, and the like (see FIG. 2).

  First, a schematic configuration of the engine system will be described with reference to FIG. As shown in FIG. 1, the engine system 10 includes an engine 12 as a spark ignition type “internal combustion engine”. The engine 12 is, for example, a 4-cycle multi-cylinder engine, and FIG. 1 shows only a cross section of one cylinder. The configuration described below is similarly provided to other cylinders (not shown).

  The engine 12 is supplied from an intake manifold 14 as an “intake system” through a throttle valve 13, an intake port injector 15 provided in the intake manifold 14, and a direct injection provided in a cylinder 121 forming a combustion chamber 16. The fuel-air mixture injected from the injector 26 is burned in the combustion chamber 16. In the engine 12, the piston 17 is reciprocated by the explosive force during combustion in the combustion chamber 16. The reciprocating motion of the piston 17 is converted into a rotational motion by the crankshaft 18 and output. The exhaust gas, which is the combustion exhaust gas of the air-fuel mixture combusted in the combustion chamber 16, is released into the atmosphere through an exhaust manifold 20 as an “exhaust system”. The exhaust manifold 20 is provided with a catalyst 19 that decomposes harmful substances such as nitrogen oxides contained in the exhaust as substances to be removed and removes them from the exhaust.

  An intake valve 22 is provided at the intake port of the cylinder head 21 that is the inlet of the combustion chamber 16. An exhaust valve 23 is provided at the exhaust port of the cylinder head 21 that is the outlet of the combustion chamber 16. The intake valve 22 and the exhaust valve 23 are opened and closed by a valve drive mechanism 24. The valve timing of the intake valve 22 is adjusted by the variable valve mechanism 25.

  The air-fuel mixture in the combustion chamber 16 is ignited by causing the discharge controller 30 to generate a discharge between the electrodes of the spark plug 7. The discharge control unit 30 operates the ignition circuit unit 31 based on a command from the electronic control unit 32 and applies a high voltage from the ignition coil 40 to the ignition plug 7, thereby generating a spark discharge in the combustion chamber 16.

  The spark plug 7 has a pair of electrodes (see FIG. 2) that face each other with a predetermined gap in the combustion chamber 16. When a high voltage sufficient to cause dielectric breakdown is applied between the pair of electrodes in the gap of the spark plug 7, discharge occurs. In the following description, “high voltage” refers to a voltage that can cause discharge between a pair of electrodes of the spark plug 7.

The electronic control unit 32 is configured by a microcomputer including a CPU, a ROM, a RAM, an input / output port, and the like.
The electronic control unit 32 is detected by various sensors such as a crank position sensor 35, a cam position sensor 36, a water temperature sensor 37, a throttle opening sensor 38, an intake air amount sensor 39, and a catalyst temperature sensor 341, as indicated by broken line arrows. A signal is input. The electronic control unit 32 drives the throttle valve 13, the intake port injector 15, the direct injection injector 26, the ignition circuit unit 31, and the like, as indicated by solid arrows, based on detection signals from these various sensors. The operation state of the engine 12 is controlled.

Next, the configuration of the discharge control unit 30 will be described with reference to FIG.
As shown in FIG. 2, the discharge control unit 30 includes an ignition coil 40, an ignition circuit unit 31, and a control signal output unit 33 of the electronic control unit 32.

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 supply” capable of supplying a constant DC voltage, and the other end is grounded via an ignition switch 45. Hereinafter, the side of the primary coil 41 opposite to the side connected to the battery 6 is referred to as “ground side”.
The secondary coil 42 is magnetically coupled to the primary coil 41. One end of the secondary coil 42 is grounded via a pair of electrodes of the spark plug 7, and the other end is grounded via a rectifier element 43 and a secondary current detection resistor 47.

  Here, a current flowing through the primary coil 41 is referred to as a primary current I1, and a current generated by increasing or decreasing the primary current I1 and flowing through the secondary coil 42 is referred to as a secondary current I2 as a “discharge current”. As indicated by the arrows in the figure, 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 the current in the direction from the secondary coil 42 to the spark plug 7. 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 in accordance with a change in the current flowing through the primary coil 41. The ignition coil 40 applies the generated high voltage to the spark plug 7. In the present embodiment, one ignition coil 40 is provided for one ignition plug 7.

  The ignition circuit unit 31 includes an ignition switch (igniter) 45, an energy input unit 50 as “energy input means”, a secondary current detection resistor 47, and a secondary current detection circuit 48.

The ignition switch 45 is composed of, for example, an IGBT (insulated gate bipolar transistor). The emitter of the ignition switch 45 is grounded. The collector of the ignition switch 45 is connected to the ground side of the primary coil 41 of the ignition coil 40. The gate of the ignition switch 45 is connected to the electronic control unit 32. The emitter is connected to the collector via the rectifying element 46.
The ignition switch 45 is turned on / 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. Energization and interruption of the primary current I1 in the primary coil 41 are switched by the ignition switch 45 in accordance with the ignition signal IGT.

  The energy input unit 50 includes an energy storage coil 52, a charge switch 53, a charge switch driver circuit 54, a DCDC converter 51 including a rectifying element 55, a capacitor 56, a discharge switch 57, a discharge switch driver circuit 58, and And a rectifying element 59.

The DCDC converter 51 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 a charge switch 53. The charge switch 53 is composed of, for example, a MOSFET (metal oxide semiconductor field effect transistor). The drain of the charge switch 53 is connected to the energy storage coil 52. The source of the charging switch 53 is grounded. The gate of the charging switch 53 is connected to the charging switch driver circuit 54. The charge switch driver circuit 54 can drive the charge switch 53 on and off.
The rectifying element 55 is composed 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.

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 electric energy stored in the energy storage coil 52 is superposed on the DC voltage of the battery 6 and discharged to the capacitor 56 side. By repeating the on / off operation of the charging switch 53, the energy storage coil 52 repeatedly stores and releases energy, and the battery voltage is boosted.
One electrode of the capacitor 56 is connected to the ground side of the energy storage coil 52 via the rectifying element 55. The other electrode of the capacitor 56 is grounded. Capacitor 56 stores the voltage boosted by DCDC converter 51.

The discharge switch 57 is composed of, for example, a MOSFET. The drain of the discharge switch 57 is connected to the capacitor 56. The source of the discharge switch 57 is connected to the ground side of the primary coil 41. The gate of the discharge switch 57 is connected to the driver circuit 58 for discharge switch. The discharge switch driver circuit 58 can drive the discharge switch 57 on and off.
The rectifying element 59 is composed of a diode and prevents a backflow of current from the ignition coil 40 to the capacitor 56.
Although FIG. 2 shows only the configuration for one cylinder, in reality, the configuration after the discharge switch 57 is provided in parallel for the number of cylinders. That is, the current path is branched for each cylinder before the discharge switch 57, and the energy accumulated in the capacitor 56 is distributed to each path.

The secondary current detection circuit 48 detects the secondary current I <b> 2 based on the voltage across the secondary current detection resistor 47 provided in the combustion chamber 16. Thereafter, the feedback control is performed to make the secondary current I2 coincide with a target value (hereinafter referred to as “target secondary current I2 ^* ”), and the on-duty ratio of the discharge switch 57 is calculated. Command.

  The electronic control unit 32 includes a catalyst temperature determination unit 34 and a control signal output unit 33.

  Based on the rotational speed of the engine 12 detected by the crank position sensor 35, the temperature of the catalyst 19 detected by the catalyst temperature sensor 341, and the like, the catalyst temperature determination unit 34 determines whether or not the temperature of the catalyst 19 is lower than a predetermined temperature. judge. The catalyst temperature determination unit 34 outputs a determination signal corresponding to the determination result to the control signal output unit 33.

The control signal output unit 33 generates an ignition signal IGT and an energy input period signal IGW based on the detection signal output from the cam position sensor 36 and the like and the determination signal output from the catalyst temperature determination unit 34, and supplies the ignition circuit unit 31 with the ignition signal IGT. Output.
The ignition signal IGT is input to the gate of the ignition switch 45 and the charge switch driver circuit 54. The ignition switch 45 is turned on while the ignition signal IGT is input. The charge switch driver circuit 54 repeatedly outputs a charge switch signal SWc for controlling on / off of the charge switch 53 to the gate of the charge switch 53 while the ignition signal IGT is input.

The energy input period signal IGW is input to the discharge switch driver circuit 58. The discharge switch 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 input. Further, a target secondary current signal IGA for instructing the target secondary current I2 ^* is input to the discharge switch driver circuit 58.

  The control signal output unit 33 controls the fuel injection timing by the intake port injector 15 and the direct injection injector 26 based on detection signals from various sensors such as the crank position sensor 35.

Next, the operation of the discharge control unit 30 will be described with reference to the time chart of FIG.
In the time chart of FIG. 3, the horizontal axis is a 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, in order from the top on the vertical axis. The time change of the charge switch signal SWc and the discharge switch signal SWd is shown.
Here, the “capacitor voltage Vdc” means the voltage stored in the capacitor 56. Further, “input energy P” means energy that is discharged from the capacitor 56 and supplied to the ignition coil 40 from the low voltage side terminal side of the primary coil 41, and supply start in one discharge in the spark plug 7 (first time The integrated value from the rising edge of the discharge switch signal SWd is shown.

  In FIG. 3, “primary current I1” and “secondary current I2” have a positive current value in the direction of the arrow shown in FIG. 2 and a negative current value in the direction opposite to the arrow.

In addition, the control target value of the secondary current I2 during 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 current that can maintain a good discharge in the spark plug 7. 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 rises to the H (high) level at time t1, the ignition switch 45 is turned on. At this time, since the energy input period signal IGW is at the L (low) level, the discharge switch 57 is off. Thereby, energization of the primary current I1 in the primary coil 41 is started.

Further, while the ignition signal IGT rises to the H level, the rectangular wave pulse-shaped charging switch signal SWc is input to the gate of the charging switch 53. Then, the capacitor voltage Vdc rises stepwise in the off period after the charging switch 53 is turned on.
In this way, the ignition coil 40 is charged and the energy is stored in the capacitor 56 by the output of the DCDC converter 51 between the time t1 and the time t2 when the ignition signal IGT rises to the H level. This energy storage is completed by time t2.
At this time, the capacitor voltage Vdc, that is, the energy storage amount of the capacitor 56 can be controlled by the on-duty ratio and the number of on-off times of the charge switch signal SWc.

Thereafter, when the ignition signal IGT falls to the L level at time t2 and the ignition switch 45 is turned off, the primary current I1 that has been energized to the primary coil 41 until then is suddenly cut off. Then, a high voltage is generated in the secondary coil 42 and a discharge is generated between the electrodes of the spark plug 7. When discharge occurs, a secondary current I2 flows through the secondary coil 42.
When the energy is not input after the ignition discharge is generated at the time t2, the secondary current I2 approaches 0 [A] with the passage of time as shown by the broken line BL1, and when the discharge is attenuated to such an extent that the discharge cannot be maintained, the discharge finish. Such an ignition method by discharge is referred to as “normal discharge”.

  On the other hand, in this embodiment, the energy input period signal IGW is raised to H level at time t3 immediately after time t2, and the discharge switch 57 is turned on while the charge switch 53 is off. When the discharge switch 57 is turned on, the energy stored in the capacitor 56 is released and supplied to the ground side of the primary coil 41. Thereby, the primary current I1 resulting from the input energy P is energized during the ignition discharge.

At this time, the secondary coil 42 is superposed with the same polarity on the secondary current I2 that has been energized between time t2 and time t3 with the same polarity with respect to the energization of the primary current I1 caused by the input energy P. The The superimposition of the primary current I1 is performed every time the discharge switch 57 is turned on from time t3 to time t4.
That is, each time the discharge switch signal SWd is turned on, the primary current I1 is sequentially added by the energy stored in the capacitor 56. In response to this, the secondary current I2 is sequentially added. Thereby, as shown by the solid line SL1, the secondary current I2 is maintained so as to coincide with the target secondary current I2 ^* .
When the energy input period signal IGW falls to the L level at time t4, the on / off operation of the discharge switch signal SWd stops, and the primary current I1 and the secondary current I2 become zero.

  As described above, after the ignition discharge at time t2, the control method for supplying energy to the ignition coil 40 from the ground side of the primary coil 41 is the battery 6 side of the primary coil 41 or the two as in the known multiple discharge method. Compared to a method in which energy is input to the ignition coil 40 from the side opposite to the ignition plug 7 of the secondary coil 42, the polarity of the secondary current I2 is efficiently input by inputting energy from the low voltage side. Therefore, it is possible to continue the state in which the air-fuel mixture can be ignited for a certain period.

  The engine control apparatus 1 according to the first embodiment includes the discharge control unit 30 and the catalyst temperature determination unit 34 that can maintain a state in which the air-fuel mixture can be ignited for a certain period as described above. There is. Here, the catalyst warm-up process by the engine control apparatus 1 will be described based on the flowchart of FIG. In the engine control apparatus 1 according to the first embodiment, it is determined whether or not the warm-up control of the catalyst 19 is necessary according to the flowchart shown in FIG. 4 for each combustion cycle of intake, compression, expansion and exhaust in the engine 12. Based on this determination, the discharge time as the discharge state of the spark plug 7, the discharge start timing, the magnitude of the secondary current I2, and the fuel injection timing are controlled.

  First, in step (hereinafter referred to as “S”) 101, the operating state of the engine 12 is detected. In S101, the operating state of the engine 12 is detected based on a detection signal output from the crank position sensor 35 or the like. For example, based on the crank angle signal output from the crank position sensor 35, the rotational speed of the engine 12 is read from a map stored in advance. Further, the current temperature of the catalyst 19 is calculated based on the catalyst temperature signal output from the catalyst temperature sensor 341.

  Next, in S102, it is determined whether or not the warm-up control of the catalyst 19 is necessary. The catalyst temperature determination unit 34 determines whether or not the current temperature of the catalyst 19 calculated in S101 is lower than a predetermined temperature, that is, a temperature at which the removal target substance contained in the exhaust gas can be efficiently removed. To do. In S102, determination is also made in consideration of whether or not the operating state of the engine 12, for example, whether the engine 12 has been read in S101 is the rotational speed in steady operation. In the engine control apparatus 1 according to the embodiment, it is determined whether or not the temperature of the catalyst 19 is lower than a predetermined temperature on the condition that the rotational speed of the engine 12 is the rotational speed in steady operation. If it is determined in S102 that the current temperature of the catalyst 19 is lower than the predetermined temperature, the process proceeds to S103 because warm-up control of the catalyst 19 is necessary. If it is determined in S102 that the current temperature of the catalyst 19 is the same as or higher than the predetermined temperature, it is determined that the warm-up control of the catalyst 19 is unnecessary, and the process returns to S101.

  Next, in S103, control for extending the discharge time of the spark plug 7 is performed. In S103, the control signal output unit 33 sets the discharge time of the spark plug 7 to a normal discharge time, which is a discharge time for the spark plug 7 to ignite the mixture in the combustion chamber 16 when the engine 12 is in steady operation. The energy input period signal IGW is output so as to be longer. The ignition circuit unit 31 supplies the ignition coil 40 with the same polarity of energy necessary for discharging the ignition plug 7 from the energy storage coil 52 by switching between the charge switch 53 and the discharge switch 57. As a result, the discharge of the spark plug 7 is extended compared to the normal discharge time, and while the discharge is continued, the secondary current I2 is relatively long (time P1 in FIG. 3) as shown by the solid line SL1 in FIG. Flows.

  In the spark plug 7 discharge time extension control according to the embodiment, the extended discharge time is determined by the current temperature of the catalyst 19 detected in S101 and the position of the discharge start timing of the spark plug 7 in S104. Specifically, the lower the temperature of the catalyst 19, the longer the discharge time of the spark plug 7. Further, the longer the discharge start timing of the spark plug 7 is shifted to the retard side, the longer the discharge time of the spark plug 7 is.

Next, in S104, warm-up control of the catalyst 19 is performed. The warm-up control of the catalyst 19 in S104 will be described based on FIG.
FIG. 5 shows a time chart of the operation of each part of the engine 12 in the steady operation control and the catalyst warm-up control of the engine 12. In FIG. 5, the common horizontal axis indicates the crank angle of the crankshaft 18 (the position of the piston 17), and the vertical axis indicates the opening / closing state of the intake valve 22, the opening / closing state of the exhaust valve 23, and the engine 12 in the steady operation control. The operation of each part and the pressure of the combustion chamber 16, the operation of each part of the engine 12 and the pressure of the combustion chamber 16 in the catalyst warm-up control are shown. In the operation of each part of the engine 12 in the steady operation control and the catalyst warm-up control, the fuel injection timing into the intake manifold 14 by the intake port injector 15 is indicated as “intake manifold injection timing”. Further, the fuel injection timing into the combustion chamber 16 by the direct injection injector 26 is referred to as “combustion chamber injection timing”. Further, the discharge timing of the spark plug 7 is indicated as “discharge timing”, and the pressure in the combustion chamber 16 is indicated as “combustion chamber pressure”. The combustion chamber pressure indicates only the pressure before and after the air-fuel mixture in the combustion chamber 16 is ignited by the discharge by the spark plug 7.

  The time on the horizontal axis is 0 ° when the piston 17 is in the compression TDC position in one combustion cycle, and then the piston 17 is in the compression TDC position in the next combustion cycle of the one combustion cycle. The time will be described as 720 °. In FIG. 5, it is assumed that when the piston 17 is in the BDC position after the compression TDC in the next combustion cycle, the position is 900 ° from the compression TDC in the one combustion cycle.

  In FIG. 5, the length of the solid line arrow shown at each injection time indicates the fuel injection time at each injection time. On the other hand, the discharge timing indicates the discharge start timing of the spark plug 7 and does not indicate the discharge time of the spark plug 7. Note that, as described above, the discharge time of the spark plug 7 in the catalyst warm-up control is set to be longer than the discharge time of the spark plug 7 in the steady operation control by extending the discharge time in S103.

First, operations of the intake valve 22 and the exhaust valve 23 will be described.
The intake valve 22 opens as the piston 17 moves from 180 ° to 360 °, that is, in the middle of moving from the BDC after compression TDC to the exhaust TDC, as indicated by the solid arrow V22. Gas is introduced into the combustion chamber 16. Thereafter, the piston 17 is closed during the movement from 540 ° to 720 °, that is, during the movement from the BDC after the exhaust TDC to the next compression TDC.
The exhaust valve 23 opens as the piston 17 moves from 0 ° to 180 °, that is, in the middle of moving from the compression TDC to the BDC, as indicated by the solid arrow V23, and discharges the combustion exhaust gas to the exhaust manifold 20. . Thereafter, when the piston 17 is at 360 °, that is, at the position of the exhaust TDC, the valve is closed.

Next, the operation of each part and the pressure change in the combustion chamber 16 in steady operation control will be described.
The intake port injector 15 injects fuel to the intake manifold 14 before the intake valve 22 is opened while the piston 17 is moving from 180 ° to 360 ° (solid arrow IJ11). In addition, the direct injection injector 26 injects fuel into the combustion chamber 16 when the piston 17 is moving from 360 ° to 540 ° and the intake valve 22 is open (solid arrow IJ12).
After the fuel injection by the intake port injector 15 and the direct injection injector 26, the spark plug 7 has a piston 17 of 680 ° to 720 ° (compression TDC) so that the output is maximized while avoiding knocking in the engine 12. When in the position, discharge is started and the air-fuel mixture in the combustion chamber 16 is combusted (open circle SP1). At this time, as shown by a curve CL1 in FIG. 5, the pressure in the combustion chamber 16 becomes maximum at a time slightly delayed from the discharge start timing.

Next, the operation of each part in the catalyst warm-up control and the pressure change in the combustion chamber 16 will be described while comparing the operation of each part in the steady operation control and the pressure change in the combustion chamber 16.
As in the case of steady operation control, the intake port injector 15 injects fuel into the intake manifold 14 while the piston 17 is moving from 180 ° to 360 ° and before the intake valve 22 is opened. (Solid arrow IJ21).
On the other hand, the direct injection injector 26 injects fuel into the combustion chamber 16 after the intake valve 22 is closed while the piston 17 moves from 540 ° to 720 ° (solid arrow IJ22). That is, the fuel injection timing of the direct injection injector 26 in the catalyst warm-up control is set closer to the compression TDC than the fuel injection timing of the direct injection injector 26 in the steady operation control.
After the fuel injection by the intake port injector 15 and the direct injection injector 26, the spark plug 7 starts discharging while moving from 720 ° to 900 °, and burns the air-fuel mixture in the combustion chamber 16 (white) Circle SP2). That is, the discharge start timing of the spark plug 7 in the catalyst warm-up control is set on the retard side compared to the discharge start timing of the spark plug 7 in the steady operation control.
By the discharge extension control in S103 and the catalyst warm-up control in S104, as shown by the curve CL2 in FIG. 5, the pressure in the combustion chamber 16 once becomes maximum immediately after the compression TDC, but once decreases, but the spark plug 7 discharges. It rises again while moving from 720 ° to 900 ° by the start.

  Next, in S105, it is determined whether or not to end the warm-up control of the catalyst 19. In S105, the catalyst temperature determination unit 34 determines whether or not the temperature of the catalyst 19 is equal to or higher than a predetermined temperature. If it is determined in S105 that the temperature of the catalyst 19 is equal to or higher than the predetermined temperature, the warm-up control of the catalyst 19 is terminated, and the process proceeds to S106. If it is determined in S105 that the temperature of the catalyst 19 is lower than the predetermined temperature, the process returns to S102.

  Next, in S106, the engine 12 is set to steady operation control. Thereby, the catalyst warm-up process by the engine control apparatus 1 is completed.

  In the engine control apparatus 1 according to the embodiment, the catalyst temperature determination unit 34 determines whether or not the temperature of the catalyst 19 is lower than a temperature at which the removal target substance contained in the exhaust gas can be efficiently removed. When the temperature of the catalyst 19 is lower than the temperature at which the removal target substance contained in the exhaust gas can be efficiently removed, the discharge time of the spark plug 7 is set while the discharge start timing of the spark plug 7 is set to the retard side. Make it longer than normal discharge time.

  FIG. 6A shows the relationship between the discharge timing of the spark plug and the exhaust temperature. In FIG. 6A, the horizontal axis represents the discharge timing of the spark plug, and the vertical axis represents the temperature of the exhaust discharged from the combustion chamber. As indicated by a solid line SL3 in FIG. 6A, the exhaust gas temperature increases as the discharge timing of the spark plug is set to the retarded side during engine combustion. For this reason, in order to quickly bring the catalyst to a predetermined temperature using the combustion heat, it is desirable to set the discharge timing of the spark plug as late as possible.

  However, if the discharge timing of the spark plug is set too late, the expanding air-fuel mixture is ignited, so that misfire is likely to occur and the fluctuation in torque output from the engine increases. FIG. 6B shows the relationship between spark plug discharge timing and torque fluctuation. Here, the torque fluctuation shown on the vertical axis indicates the frequency at which a torque change of a certain level or more occurs. In FIG. 6B, the relationship between the discharge timing of the spark plug 7 and the torque fluctuation in the discharge extension control is indicated by a solid line SL4. As a comparative example, the relationship between the spark plug discharge timing and the torque fluctuation in the discharge normal control for executing the discharge of the spark plug by the above-described “normal discharge” is shown by a broken line BL3. In FIG. 6B, the upper limit of torque fluctuation is indicated by a broken line BL0. If the torque fluctuation becomes large enough to exceed the upper limit of the torque fluctuation, the drivability of the vehicle on which the engine is mounted deteriorates to an unacceptable level.

  As shown in FIG. 6B, the torque fluctuation increases as the discharge timing of the spark plug 7 is set to the retard side in both the discharge extension control and the normal discharge control. At this time, in the discharge extension control, the position of the discharge timing at which the upper limit of the torque fluctuation is reached compared to the normal discharge control can be provided on the more retarded side.

  In the engine control apparatus 1 according to the embodiment, if it is determined that the current temperature of the catalyst 19 is lower than a predetermined temperature in consideration of the operation state of the engine 12, the ignition plug is determined to require the warm-up control of the catalyst 19. 7 is made longer than the normal discharge time. As a result, the spark plug 7 continues to supply energy necessary for ignition of the air-fuel mixture in the combustion chamber 16 for a relatively long time, so that the air-fuel mixture can be reliably combusted. When the air-fuel mixture burns reliably, the combustion heat is transferred to the catalyst 19 along the flow of the exhaust, and the temperature of the catalyst 19 can be quickly raised. Further, since the air-fuel mixture can be reliably burned, the torque output from the engine 12 is relatively stable. Therefore, the removal target substance contained in the exhaust gas can be efficiently removed by the catalyst 19 that rises to a predetermined temperature at an early stage, and the torque fluctuation caused by incomplete combustion of the air-fuel mixture can be reduced.

Further, in the engine control apparatus 1 according to the embodiment, when it is determined that the temperature of the catalyst 19 is lower than a predetermined temperature, the discharge timing of the spark plug 7 is set as the catalyst warm-up control, and the discharge timing of the spark plug 7 in the steady operation control. Compared to the retarded side. As a result, the air-fuel mixture can be burned immediately before the exhaust valve 23 is opened, and as much combustion heat can be transmitted to the catalyst 19 as possible. At this time, if the discharge start timing of the spark plug 7 is shifted to the retard side, the expanding air-fuel mixture tends to misfire during the discharge time of the spark plug 7 in the steady operation control. For this reason, the combustion of the air-fuel mixture may become unstable.
Therefore, in the engine control apparatus 1 according to the embodiment, the discharge time of the spark plug 7 in the catalyst warm-up control is changed according to the magnitude of the shift to the retard side of the spark plug 7 in S104, and the mixing in the combustion chamber 16 is performed. Prevent qi misfire. Therefore, in the engine control apparatus 1, even when the discharge timing of the spark plug 7 shifts to the retard side, the air-fuel mixture is reliably burned, and the torque fluctuation can be further reduced.

  Further, in the engine control apparatus 1 according to the embodiment, the lower the temperature of the catalyst 19, the longer the discharge time of the spark plug 7. Furthermore, the secondary current I2 can be increased and the discharge energy can be increased. Thereby, the air-fuel mixture in the combustion chamber 16 can be reliably combusted and the combustion heat can be transmitted to the catalyst 19. Therefore, the temperature of the catalyst 19 can be increased more rapidly.

  Further, in the engine control apparatus 1 according to the embodiment, as the energy input control method, the input energy boosted by the DCDC converter 51 and stored in the capacitor 56 is input from the ground side of the primary coil 41. Compared with the method, by inputting energy from the low voltage side, it is possible to maintain a state where the air-fuel mixture can be ignited for a certain period while efficiently inputting the minimum energy.

  Further, during the energy input period IGW, the secondary current I2 is always a negative value. Accordingly, since zero crossing is not performed as compared with other methods using an alternating current, occurrence of blow-out can be prevented. Therefore, the air-fuel mixture can be combusted stably.

Further, the engine control apparatus 1 according to the embodiment includes a secondary current detection resistor 47 and a secondary current detection circuit 48. Thereby, since the secondary current I2 is feedback-controlled, the actual value of the secondary current I2 can be made to coincide with the target secondary current I2 ^* with high accuracy with respect to the feedforward control.

(Other embodiments)
(A) In the above-described embodiment, based on the catalyst temperature signal output from the catalyst temperature sensor and the engine operating state acquired from the crank position sensor, it is determined whether or not the current temperature of the catalyst is lower than a predetermined temperature. did. However, the “running state detection means” is not limited to this. The catalyst temperature determination unit may determine whether or not the current temperature of the catalyst is lower than a predetermined temperature only from the value detected by the catalyst temperature sensor. Further, when the engine control device does not include a catalyst temperature sensor, the catalyst temperature determination unit determines that the current temperature of the catalyst is lower than a predetermined temperature based on the map based on the engine speed detected by the crank position sensor. It may be determined whether or not. Further, it may be determined whether or not the current temperature of the catalyst is lower than a predetermined temperature based on the temperature of the engine coolant output from the water temperature sensor.

  (A) In the above-described embodiment, when the current temperature of the catalyst is determined to be lower than the predetermined temperature in S102, and the control for extending the discharge time of the spark plug is performed in S103, the secondary current increases with the same polarity. It is assumed that the energy required for the discharge of the spark plug is superimposed with the same polarity and supplied to the ignition coil, and the discharge of the spark plug is extended compared to the normal discharge time. However, the control of the spark plug in S103 is not limited to this. The discharge time may be simply extended from the normal discharge time, or the discharge current may be increased with the same polarity.

  (C) In the above-described embodiment, the control condition in the “method of inputting energy from the ground side of the primary coil” developed by the present applicant is assumed to extend the discharge time in the spark plug according to the discharge timing. In addition, as long as the secondary current or the energy input period can be variably controlled, the conventional multiple discharge method and the energy input control method such as “DCO method” disclosed in Japanese Patent Application Laid-Open No. 2012-167665 can be used. The present invention may be applied to extend the discharge time in the spark plug according to the discharge timing. Further, as shown in FIG. 7, for example, the battery voltage supplied to the coil is increased so that the maximum secondary current becomes larger than normal (broken line BL <b> 2 in FIG. 7) and flows as shown by the solid line SL <b> 2. You may extend the discharge time of a spark plug by lengthening time P2 until it attenuate | damps after a next current begins to flow.

  Further, as shown in FIG. 3, the energy input control by the discharge control unit is performed by turning on / off the charge switch signal during the H level of the ignition signal and accumulating the capacitor voltage, and then on the ground side of the primary coil during the energy input period. It is not limited to the method of inputting energy. For example, the charge switch signal and discharge switch signal are alternately turned on and off during the energy input period, so that the energy stored in the energy storage coil when the charge switch signal is on is input to the ground side of the primary coil each time. You may make it do. In that case, the capacitor may not be provided.

  (D) In the above-described embodiment, the discharge control unit includes the secondary current detection resistor and the secondary current detection circuit, and performs feedback control of the secondary current. However, the method of controlling the secondary current is not limited to this. For example, the secondary current may be feedforward controlled.

  (E) In the above-described embodiment, the ignition switch is not limited to the IGBT, and may be composed of another switching element having a relatively high breakdown voltage. Further, the charge switch and the discharge switch are not limited to MOSFETs, and may be composed of other switching elements.

  (F) In the above-described embodiment, the DC power source is a battery. However, the type of DC power supply is not limited to this. For example, the AC power source may be constituted by a DC stabilized power source stabilized by a switching regulator or the like.

  (G) In the above embodiment, the energy input unit boosts the voltage of the battery by the DCDC converter. However, the type of energy input unit is not limited to this. When the discharge control unit is mounted on a hybrid vehicle or an electric vehicle, the output voltage of the main battery may be used as input energy as it is or after being stepped down.

  The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit of the invention.

1 ... Engine control device (control device for internal combustion engine),
12 ... Engine (internal combustion engine),
14 ... intake manifold (intake system),
16 ... combustion chamber,
19 ・ ・ ・ Catalyst,
20 ... Exhaust manifold (exhaust system),
30: Discharge control unit,
34 ... Catalyst temperature determination unit (catalyst temperature determination means),
341 ... Catalyst temperature sensor (operating state detection means),
35 ... Crank position sensor (operating state detecting means).

Claims (6)

A control device (1) for an internal combustion engine for controlling combustion of an air-fuel mixture in a combustion chamber (16) of the internal combustion engine (12),
A discharge controller (30) for controlling a discharge state of a spark plug for igniting an air-fuel mixture by discharge;
Operating state detecting means (35, 341) for detecting the operating state of the internal combustion engine and outputting a detection signal based on the operating state of the internal combustion engine;
Catalyst temperature determination means (34) for determining whether the temperature of the catalyst (19) provided in the exhaust system (20) of the internal combustion engine is lower than a predetermined temperature based on a signal output from the operating state detection means. When,
With
When the catalyst temperature determining means determines that the temperature of the catalyst is lower than a predetermined temperature, the discharge control unit extends the discharge time of the spark plug from the normal discharge time and increases the discharge current with the same polarity. A control device for an internal combustion period, wherein at least one of them is performed. The discharge controller is
A primary coil (41) through which a primary current supplied from a DC power source (6) flows, and a secondary current as the discharge current that is connected to the electrode of the spark plug and is generated by energization and interruption of the primary current flows. An ignition coil (40) having a secondary coil (42);
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 according to an ignition signal (IGT);
In a predetermined energy input period (IGW) after the ignition plug is discharged by cutting off the primary current by the ignition switch, energy enabling discharge is continuously input from the ground side of the ignition coil. Energy input means (50);
Input energy control means (33) that is electrically connected to the discharge timing determination means and controls input energy by the energy input means;
The control apparatus for an internal combustion period according to claim 1, comprising: The energy input means includes
A first control terminal, a first power supply side terminal, and a first ground side terminal connected to the other end of the primary coil, and based on a discharge switch signal (SWd) input to the first control terminal A discharge switch (57) for controlling on / off between the first power supply side terminal and the first ground side terminal;
A charge switch signal (SWc) input to the second control terminal, having a second control terminal, a second power supply side terminal connected to the first power supply side terminal, and a grounded second ground side terminal A charge switch (53) for controlling on / off between the second power supply side terminal and the second ground side terminal based on
An energy storage coil (52) provided to be connected to the non-grounded output terminal and the second power supply side terminal of the DC power supply, and to store energy when the charging switch is turned on;
Have
The input energy control means includes:
When energy is stored in the energy storage coil by turning on the charge switch, the energy storage coil is turned off by turning off the charge switch and turning on the discharge switch during discharge of the spark plug started by turning off the ignition switch. 3. The internal combustion period control device according to claim 2, wherein the discharge switch and the charge switch are controlled such that energy is discharged from the first coil and a primary current is supplied to the primary coil from the other end side of the primary coil. . The discharge controller is
A plurality of primary coils through which a primary current supplied from a DC power source flows, and secondary coils through which a secondary current as the discharge current is connected to the electrode of the spark plug and is generated by energization and interruption of the primary current. An ignition coil;
A plurality of ignition switches connected to a ground side opposite to the DC power source of the primary coils of each of the plurality of ignition coils, and switching between energization and interruption of the primary current based on an ignition signal;
The control apparatus for an internal combustion period according to claim 1, comprising:   The discharge control unit shifts the discharge start timing of the spark plug to a retard side when the catalyst temperature determination unit determines that the temperature of the catalyst is lower than a predetermined temperature. The control apparatus for an internal combustion engine according to any one of the above. A direct injection fuel injection valve (26) for injecting fuel into the combustion chamber;
The fuel injection valve for direct injection injects fuel into the combustion chamber when a piston (17) of the internal combustion engine moves from a bottom dead center to a top dead center in a compression stroke. The control apparatus for an internal combustion engine according to any one of claims 5 to 6.

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