JP6485137B2 - Control device for internal combustion engine - Google Patents

Description

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

  Conventionally, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-62806), if a required voltage in an ignition plug of an internal combustion engine becomes excessively high, it becomes difficult to appropriately perform spark discharge, and the ignition plug is operated. However, it is disclosed that the mixture in the combustion chamber cannot be ignited and misfire occurs. Patent Document 1 also discloses that misfire tends to occur because the required voltage tends to increase as the pressure in the combustion chamber increases.

JP2012-062806 JP 2001-132600 A

  By the way, in an internal combustion engine provided with a tumble control valve (TCV), a swirling flow of intake air can be generated in the combustion chamber by closing the TCV. Therefore, there is an advantage that the combustion resistance can be improved even when the air-fuel mixture in the combustion chamber is burned in a lean state and the internal combustion engine is operated at a high load. However, when the TCV is switched to the opening operation in such a high-load operation state, the combustion resistance deteriorates. Therefore, in order to cope with this, an ignition delay is required, and the in-cylinder pressure at the time of ignition temporarily increases. This ignition delay is due to the richness of the air-fuel ratio to cope with the deterioration of combustion resistance, the retard to suppress the torque increase, and the retard to cope with the change in the MBT point accompanying the increase in the combustion speed. It is. Further, since a large amount of intake air instantaneously flows into the combustion chamber by the opening operation of the TCV, the pressure in the combustion chamber becomes excessively high. Due to these factors, the required voltage rises and may easily exceed the specified value.

  The present invention has been made in view of the above-described problems. That is, in the case where the air-fuel mixture in the combustion chamber is burned in a lean state and the internal combustion engine is operated at a high load, the occurrence of misfire when the TCV is switched from the closing operation to the opening operation is suppressed. With the goal.

In order to solve the above-described problems, the present invention provides a control device for an internal combustion engine,
A throttle valve provided in the intake passage of the internal combustion engine;
An airflow control valve that is provided downstream of the throttle valve in the intake passage, and generates a swirling flow of intake air in the combustion chamber by operating in a closing direction;
A spark plug for igniting the air-fuel mixture in the combustion chamber;
An ignition coil for applying a voltage to the spark plug;
The basic energizing time of the ignition coil necessary for the spark plug to spark discharge is specified by a normal map set in association with the battery voltage and the internal combustion engine speed, and the battery voltage and the internal combustion engine speed. An emergency map in which an energization time longer than the basic energization time of the regular map is set in each area on the map;
The load of the internal combustion engine when the airflow control valve is operated in the opening direction from the state where the air-fuel mixture is burned in the lean state in the combustion chamber and the airflow control valve is operated in the closing direction is specified. When the load is higher than the load, the throttle valve is operated in the closing direction so as to alleviate the lean state of the air-fuel mixture in the combustion chamber, the energization timing to the ignition coil is retarded, and the airflow control valve is opened. Control means for setting the basic energization time of the ignition coil by switching from the regular map to the emergency map while fluctuations in the intake air flow accompanying the operation of
It is characterized by providing.

  When the air-fuel mixture is burned in a lean state in the combustion chamber and the airflow control valve is operated in the closing direction, the load on the internal combustion engine when operating the airflow control valve in the opening direction is greater than a specific load. In this case, the pressure in the combustion chamber becomes excessively high and the required voltage increases. In this regard, according to the present invention, the basic energization time of the ignition coil can be set by switching from the regular map to the emergency map while fluctuations in the intake air flow accompanying the operation in the opening direction of the airflow control valve occur. Misfires can be avoided well.

It is a figure for demonstrating the system configuration | structure of embodiment of this invention. It is a figure which shows an example of an electricity supply time map (base map). FIG. 6 is a diagram for explaining a change in combustion speed accompanying the operation of the airflow control valve 24. It is a figure for demonstrating the movement of MBT accompanying the change of a combustion speed. It is a figure for demonstrating the pressure rise in the combustion chamber 14 in the ignition timing accompanying retarding of ignition timing. It is a figure which shows an example of an electricity supply time map (another map). It is a figure for demonstrating the flow of control which ECU50 performs in embodiment. 4 is a flowchart illustrating a routine for changing an energization time map executed by an ECU 50 in the embodiment.

[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to an embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes a spark ignition type internal combustion engine 10 mounted on a vehicle. A piston 12 is provided in each cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in each cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An electronically controlled throttle valve 20 is provided in the intake passage 16. An intake passage 16 downstream of the throttle valve 20 is provided with an injector 22 that injects fuel into an intake port (not shown) and an airflow control valve (specifically, a TCV) 24. The airflow control valve 24 is configured to vary the opening area of the intake port by rotating about a rotation shaft (not shown). In FIG. 1, the airflow control valve 24 is in a posture standing vertically to the intake port wall surface, and is in a state where the opening area of the intake port is minimized (hereinafter referred to as “fully closed state”). A swirling flow (tumble flow) is formed in the combustion chamber 14 by controlling the air flow in the intake port by the air flow control valve 24.

  Each cylinder of the internal combustion engine 10 is provided with a spark plug 26 for igniting the air-fuel mixture in the combustion chamber 14. The spark plug 26 is connected to an ignition coil 28 that applies a high voltage to the spark plug 26. Each cylinder is provided with an intake valve 30 and an exhaust valve 32 for opening and closing an intake port and an exhaust port (not shown) of the exhaust passage 18.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. The ECU 50 has at least an input / output interface, a memory, and a CPU. The input / output interface is provided to take in sensor signals from the internal combustion engine 10 and various sensors attached to the vehicle and to output an operation signal to an actuator provided in the internal combustion engine 10. The sensor that the ECU 50 captures a signal includes a crank angle sensor 36 that detects a crank angle, a battery voltage sensor 38 that detects a voltage of a battery that supplies power to the ignition coil 28, and an accelerator pedal operation amount (accelerator) by a vehicle driver. An accelerator opening sensor 40 that detects the opening) and a flow sensor 42 that detects the intake air flow flowing downstream of the airflow control valve 24 are included. The actuator from which the ECU 50 outputs an operation signal includes at least the throttle valve 20, the injector 22, the airflow control valve 24, and the ignition coil 28 described above.

  In the present embodiment, the energization timing of the ignition coil 28 is controlled by the ECU 50 so that the ignition timing of the spark plug 26 approaches MBT (Minimum Advanced for Best Torque). Further, the energization time of the ignition coil 28 is controlled so as to satisfy a voltage (hereinafter referred to as “required voltage”) necessary for the spark plug 26 to perform a spark discharge.

  In the energization time control, in order to satisfy the required voltage, the energization of the ignition coil 28 is based on an energization time map (see FIG. 2) in which the energization time of the ignition coil is set with the battery voltage and the rotation speed of the internal combustion engine as axes. The time is retrieved, so that a secondary voltage for spark discharge of the spark plug 26 is obtained. When searching for the energization time, first, the sensor outputs of the crank angle sensor 36 and the battery voltage sensor 38 are input to the energization time map, and the basic energization time of the ignition coil 28 is set. Subsequently, the basic energization time is corrected based on the correction value retrieved from the correction value map. This is because the required voltage changes due to factors such as the pressure in the combustion chamber (specifically, the pressure in the combustion chamber at the ignition timing) and the target air-fuel ratio. Such a correction value map is set for each factor, for example, and is stored in the ECU 50 together with the energization time map.

  In the present embodiment, the internal combustion engine 10 is controlled by the ECU 50 so that the air-fuel mixture in the combustion chamber 14 is burned in a lean state. However, when the combustion resistance is lowered, the throttle valve 20 is operated in the closing direction for the purpose of relaxing the lean state. Further, in the present embodiment, for the purpose of expanding the operation region in which the combustion in the lean state is possible (the operation region of the internal combustion engine specified by the rotation speed and the load), basically, during the operation in the lean region. The airflow control valve 24 is controlled to be fully closed.

[Characteristic Control of Embodiment]
By the way, when the load is high even in the lean region, the pressure in the combustion chamber 14 at the ignition timing is high, and the required voltage is also high. Therefore, when the air flow control valve 24 is operated so as to maximize the opening area of the intake port (hereinafter referred to as “fully open state”) under such circumstances, the required voltage exceeds the specified value. There is a risk that. This is because if the airflow control valve 24 is switched from the fully closed state to the fully open state, the combustion resistance is lowered. Therefore, in the present embodiment, the target air-fuel ratio is changed to the stoichiometric side, and as a result, the combustion speed increases (see FIG. 3).

  Further, if the combustion speed increases, the MBT moves to the retard side, so that the ignition timing is retarded by the above-described control of the energization timing and approaches TDC. The pressure increases (see FIGS. 4 and 5). As a result, the required voltage exceeds a specified value, that is, a functional limit value in a steady state, and there is a possibility that the air-fuel mixture in the combustion chamber 14 cannot be ignited even when the ignition coil 28 is energized.

  Therefore, in the present embodiment, when the air flow control valve 24 is switched from the fully closed state to the fully open state, an energization time map different from the energization time map shown in FIG. Set the basic energization time. This energization time map is set so that the basic energization time of each zone is longer than the energization time map shown in FIG. 2 (see FIG. 6), and is stored in the ECU 50. Therefore, when switching the airflow control valve 24 described above, a secondary voltage that satisfies the required voltage can be secured, and misfiring can be avoided. In the following description, the energization time map illustrated in FIG. 2 is referred to as a “base map”, and the energization time map illustrated in FIG. 6 is referred to as a “separate map”.

  FIG. 7 is a diagram for illustrating a flow of control executed by the ECU 50 in the present embodiment. When the airflow control valve 24 is switched from the fully closed state to the fully open state (TCV is closed to open) (FIG. 7A), a decrease in combustion resistance is predicted, so the target air-fuel ratio is changed in the stoichiometric direction ( 7 (B)), the throttle valve 20 is operated in the closing direction to achieve the target air-fuel ratio ((C) in FIG. 7), and the combustion speed increases as the target air-fuel ratio is changed. The ignition timing is retarded (FIG. 7D) Further, when the airflow control valve 24 is switched from the fully closed state to the fully open state, the intake air flow easily flows in the vicinity of the airflow control valve 24, so that the intake air flow rate is temporarily increased. (FIG. 7C).

  By retarding the ignition timing and temporarily increasing the intake air flow rate, the pressure in the combustion chamber 14 at the ignition timing (in-cylinder pressure at the time of ignition) increases (FIG. 7E), and the required voltage is a function at a steady state. The limit will be exceeded (FIG. 7F). However, in the present embodiment, since another map is used while the intake air flow rate is increasing, the energization time (ignition energization timing) is extended more than before switching the airflow control valve 24 (FIG. 7G). ). Therefore, even when the airflow control valve 24 is switched from the fully closed state to the fully open state, a secondary voltage that satisfies the required voltage can be secured.

[How to change the energization time map]
FIG. 8 is a flowchart showing an energization time map change routine executed by the ECU 50 in the present embodiment. It is assumed that this routine is periodically executed while the operating range of the internal combustion engine 10 is in the lean range and the airflow control valve 24 is controlled to the fully closed state.

  In the routine shown in FIG. 8, first, it is determined whether or not there is a request for opening the airflow control valve 24 (step S1), and there is a request for opening (that is, a request to switch the airflow control valve 24 from the fully closed state to the fully open state). It is determined whether or not the load of the internal combustion engine 10 is equal to or greater than a specific load (step S2). In step S2, specifically, the load of the internal combustion engine 10 is detected based on the sensor value of the accelerator opening sensor 40, and the detected load is compared with a specific load (set value). As a result, when it is determined that the detected load is equal to or greater than the specific load, the energization time map is changed from the base map to another map (step S3).

  Following step S3, it is determined whether or not the intake air flow rate flowing downstream of the airflow control valve 24 has reached a specific air flow rate (step S4). In this step, specifically, whether or not the intake flow rate temporarily increased by the switching of the airflow control valve 24 has decreased to the intake flow rate (specific air flow rate) immediately before the switching is the transition of the sensor value of the flow rate sensor 42. Based on the determination. As a result, when it is determined that the intake flow rate has reached the specific air flow rate, the energization time map is returned from another map to the base map (step S5).

  As described above, according to the routine shown in FIG. 8, the energization time map is changed between the base map and another map when switching the airflow control valve 24 described above, so that a secondary voltage satisfying the required voltage can be secured. Therefore, it is possible to avoid the occurrence of misfire.

In the above embodiment, the base map corresponds to the “common map” of the present invention, the separate map corresponds to the “emergency map” of the present invention, and the memory of the ECU 50 corresponds to the “storage means” of the present invention. Yes.
Further, the “control means” of the present invention is realized by the ECU 50 executing the control described in FIG.

  By the way, although it demonstrated on the assumption that the airflow control valve 24 was TCV in the said embodiment, the airflow control valve 24 may be a swirl control valve.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 14 Combustion chamber 16 Intake passage 20 Throttle valve 24 Airflow control valve 26 Spark plug 28 Ignition coil 36 Crank angle sensor 38 Battery voltage sensor 40 Accelerator opening sensor 42 Flow rate sensor 50 ECU

Claims (1)

A throttle valve provided in the intake passage of the internal combustion engine;
An airflow control valve that is provided downstream of the throttle valve in the intake passage, and generates a swirling flow of intake air in the combustion chamber by operating in a closing direction;
A spark plug for igniting the air-fuel mixture in the combustion chamber;
An ignition coil for applying a voltage to the spark plug;
The basic energizing time of the ignition coil necessary for the spark plug to spark discharge is specified by a normal map set in association with the battery voltage and the internal combustion engine speed, and the battery voltage and the internal combustion engine speed. An emergency map in which an energization time longer than the basic energization time of the regular map is set in each area on the map;
The load of the internal combustion engine when the airflow control valve is operated in the opening direction from the state where the air-fuel mixture is burned in the lean state in the combustion chamber and the airflow control valve is operated in the closing direction is specified. When the load is higher than the load, the throttle valve is operated in the closing direction so as to alleviate the lean state of the air-fuel mixture in the combustion chamber, the energization timing to the ignition coil is retarded, and the airflow control valve is opened. Control means for setting the basic energization time of the ignition coil by switching from the regular map to the emergency map while fluctuations in the intake air flow accompanying the operation of
A control device for an internal combustion engine, comprising:

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