JP7247590B2 - Control device for internal combustion engine - Google Patents

Description

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

An exhaust purification device including a catalyst is used to purify the exhaust of an internal combustion engine. In order to allow the catalyst to sufficiently perform its purification function, it is necessary to raise the temperature of the catalyst.

For example, Patent Literature 1 discloses a hybrid vehicle that warms up a catalyst of an exhaust purification device by retarding the ignition timing of the engine (ignition retardation).

In Patent Document 1, when the required running power required for the vehicle exceeds the power that can be output from the running battery during catalyst warm-up control, ignition retardation is maintained to suppress emissions, and the engine speed is increased. By increasing the amount of intake air, the driving force corresponding to the required running power is realized.

WO2010/079609

When the catalyst is warmed up by retarding the ignition angle and control is performed to increase the amount of intake air, the combustion becomes weaker than in the normal operating state, so the rotation fluctuation amount of the internal combustion engine increases. Therefore, if it is determined whether or not a misfire has occurred based on the rotation fluctuation amount of the internal combustion engine, it may be erroneously determined that a misfire has occurred even though the internal combustion engine is operating normally. There is If it is determined that a misfire has occurred, catalyst warm-up by retarding the ignition is stopped, so there is a possibility that emissions cannot be suppressed.

Further, when the catalyst is warmed up by retarding the ignition angle and control is performed to increase the amount of intake air, the exhaust gas temperature and the catalyst temperature become higher than those during normal operation. At this time, if the catalyst is already in a high temperature state, there is a risk that the catalyst will be overheated and melted due to the increase in catalyst temperature due to the misfire.

Accordingly, an object of the control device for an internal combustion engine disclosed in the present specification is to suppress overheating of the catalyst and suppress emissions.

In order to solve this problem, the internal combustion engine control apparatus disclosed in this specification warms up a catalyst that purifies exhaust gas from an internal combustion engine by retarding the ignition timing of fuel in the internal combustion engine. a catalyst warm-up control unit that executes catalyst warm-up control; a warm-up control determination unit that determines whether the catalyst warm-up control is being executed; a load determination unit that determines whether or not the rotational fluctuation amount of the internal combustion engine is greater than a first misfire determination value; a catalyst overheat determination unit that determines whether or not the catalyst is overheated based on whether or not the number of misfires detected by the misfire detection unit with respect to a predetermined number of ignitions of is greater than a first reference value; During the catalyst warm-up control, if the load required of the internal combustion engine becomes greater than a predetermined value , the catalyst warm-up control unit stops the catalyst warm-up control, and By retarding the ignition timing of the fuel, the catalyst is warmed up and control is started to increase the amount of intake air, and the misfire detection unit detects a second misfire determination value greater than the first misfire determination value. The occurrence of a misfire is detected based on whether or not the rotation fluctuation amount of the internal combustion engine is large, and the catalyst overheat determination unit determines whether the number of misfires is greater than a second reference value smaller than the first reference value. If the catalyst overheat determination unit determines that the catalyst is overheated, the catalyst warm-up control unit retards the ignition timing. stop corners.

According to the control device for an internal combustion engine disclosed in this specification, overheating of the catalyst can be suppressed, and emissions can be suppressed.

FIG. 1 is a diagram showing the structure of a vehicle according to one embodiment. FIG. 2 is a diagram showing the structure of an engine mounted on a vehicle according to one embodiment. FIG. 3 is a flowchart showing processing executed by the ECU. FIG. 4 is a time chart showing switching between the misfire determination value and the catalyst overheat determination value.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, etc. of each part may not be illustrated so as to completely match the actual ones. In some drawings, details may be omitted.

FIG. 1 is a diagram showing the structure of a vehicle 10 equipped with a control device according to an embodiment of the invention. Vehicle 10 is a vehicle (hereinafter also referred to as "hybrid vehicle") that runs on the power of at least one of engine 100 and second motor generator (MG(2)) 300B, and is operated by an electric power company provided outside the vehicle. is a vehicle that can run on electric power supplied from the AC power supply 19 (hereinafter also referred to as a "plug-in vehicle"). Vehicles to which the control device according to the present invention can be applied are not limited to hybrid vehicles and plug-in vehicles, as long as they have a configuration capable of controlling the number of engine revolutions (rotational speed) to a desired number of revolutions. For example, it is possible to apply the control device according to the present invention to an engine vehicle equipped with a continuously variable automatic transmission. Engine 100 is an example of an internal combustion engine.

Vehicle 10 includes power split device 200, speed reducer 14, running battery 310, inverter 330, and boost converter 320 in addition to engine 100 and MG(2) 300B described above.

Power split device 200 splits the power generated by engine 100 between output shaft 212 and first motor generator (MG(1)) 300A. Power split device 200 is composed of planetary gears including a sun gear, a pinion gear, a carrier, and a ring gear. By connecting engine 100, MG (1) 300A and MG (2) 300B via power split device 200, each rotation speed of engine 100, MG (1) 300A and MG (2) 300B There is a relationship that the remaining number of rotations is determined when two of the number of rotations are determined. By utilizing this relationship, for example, even if the rotation speed of MG (2) 300B is the same value, by controlling the rotation speed of MG (1) 300A, the rotation speed (rotational speed) Ne of engine 100 can be changed. Desired rotation speed can be controlled.

The speed reducer 14 transmits power generated by the engine 100, MG(1) 300A, and MG(2) 300B to the driving wheels 12, and drives the driving wheels 12 by the engine 100, MG(1) 300A, and MG( 2) transmit to 300B;

Running battery 310 stores electric power for driving MG(1) 300A and MG(2) 300B. Inverter 330 performs current control while converting direct current from running battery 310 and alternating current from MG(1) 300A and MG(2) 300B. Boost converter 320 performs voltage conversion between running battery 310 and inverter 330 .

Vehicle 10 also includes an engine ECU (Electronic Control Unit) 406 that controls the operating state of engine 100, MG(1) 300A, MG(2) 300B, inverter 330, and a running battery depending on the state of vehicle 10. MG_ECU 402 that controls the charging/discharging state of 310 and the like. The vehicle 10 further includes an HV_ECU 404 that mutually manages and controls the engine ECU 406, the MG_ECU 402, and the like, and controls the entire hybrid system so that the vehicle 10 can operate most efficiently.

The vehicle 10 also includes a connector 13 for connecting a paddle 15 connected to an AC power source 19 of an electric power company, and a power source for driving by converting power from the AC power source 19 supplied via the connector 13 into DC power. and a charging device 11 that outputs to the battery 310 . Charging device 11 controls the amount of electric power to be output to running battery 310 in accordance with a control signal from HV_ECU 404 .

Although each ECU is configured separately in FIG. 1, it may be configured as an ECU in which two or more ECUs are integrated. For example, as indicated by the dotted line in FIG. 1, ECU 400 may be configured by integrating MG_ECU 402, HV_ECU 404, and engine ECU 406. FIG. In the following description, MG_ECU 402, HV_ECU 404 and engine ECU 406 are referred to as ECU 400 without distinction. ECU 400 is an example of a catalyst warm-up control section, a warm-up control determination section, a load determination section, a misfire detection section, and a catalyst overheat determination section.

The ECU 400 includes a vehicle speed sensor, an accelerator opening sensor, a throttle opening sensor, an MG (1) rotation speed sensor, an MG (2) rotation speed sensor, an engine rotation speed sensor (none of which is shown), and a running battery 310. (battery voltage value VB, battery current value IB, battery temperature TB, etc.) is input from a monitoring unit 340 that monitors the state of the battery.

Engine 100 and peripheral devices related to engine 100 will be described with reference to FIG. In this engine 100 , air drawn from an air cleaner (not shown) flows through an intake pipe 110 and is introduced into a combustion chamber 102 of the engine 100 . The amount of air introduced into the combustion chamber 102 is adjusted by the operating amount (throttle opening) of the throttle valve 114 . The throttle opening is controlled by a throttle motor (not shown) that operates based on a signal from the ECU 400 .

Fuel is stored in a fuel tank (not shown) and injected into the intake port from injectors 104 by a fuel pump (not shown). An in-cylinder injector that injects fuel into combustion chamber 102 may be provided instead of injector 104 or together with injector 104 . A mixture of air introduced from intake pipe 110 and fuel injected from injector 104 is ignited and combusted using ignition coil 106 controlled by a control signal from ECU 400 .

The exhaust gas after combustion of the air-fuel mixture passes through a catalyst 140 provided in the middle of the exhaust pipe 120 and is discharged to the atmosphere.

The catalyst 140 is a three-way catalyst that purifies emissions (toxic substances such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx)) contained in the exhaust gas. The catalyst 140 is based on alumina and supports precious metals including platinum, palladium, and rhodium, so that the oxidation reaction of hydrocarbons and carbon monoxide and the reduction reaction of nitrogen oxides can be carried out at the same time. The catalyst 140 has a characteristic that the lower the temperature thereof, the lower the exhaust purification ability.

ECU 400 receives signals from engine water temperature sensor 108 , airflow meter 116 , intake air temperature sensor 118 , air-fuel ratio sensor 122 and oxygen sensor 124 . The ECU 400 also receives a signal from a crank angle sensor 109 provided near the crankshaft 111 of the engine 100 for detecting the rotation angle (crank angle) of the crankshaft 111 . An engine water temperature sensor 108 detects the temperature of engine cooling water (engine water temperature) TW. The air flow meter 116 detects the amount of intake air (the amount of air taken into the engine 100 per unit time) Ga. An intake air temperature sensor 118 detects the temperature of intake air (intake air temperature) TA. The air-fuel ratio sensor 122 detects the ratio of air and fuel in the exhaust gas. Oxygen sensor 124 detects the oxygen concentration in the exhaust gas. Each of these sensors transmits a signal representing the detection result to ECU 400 .

The ECU 400 controls the ignition coil 106 to achieve proper ignition timing, adjusts the throttle opening to a proper degree, and controls the ignition coil 106 based on signals sent from each sensor, maps and programs stored in a ROM (Read Only Memory). The amount of actuation of the throttle valve 114 is controlled so as to be , and the injector 104 is controlled so as to obtain an appropriate fuel injection amount.

More specifically, the ECU 400 sets the requested vehicle power to be output from the vehicle 10 based on the accelerator opening and the vehicle speed, and sets the requested battery power to be output from the running battery 310 based on the requested vehicle power. , and the required engine power to be output from the engine 100 are set. Then, ECU 400 executes fuel injection control and ignition control in engine 100 based on the set required engine power.

For example, when the engine 100 is started, the ECU 400 retards the ignition timing of the engine 100 when the engine coolant temperature TW is lower than the predetermined threshold value T1 and the catalyst temperature TC is lower than the predetermined threshold value T2. Catalyst warm-up control for warming up the catalyst 140 is executed. The ECU 400 estimates the catalyst temperature TC based on parameters such as the engine coolant temperature TW, the integrated value of the intake air amount Ga, and the engine speed Ne.

Further, when the load required of engine 100 is greater than a predetermined value during catalyst warm-up control, ECU 400 increases the engine speed to increase the amount of intake air to ensure the output of engine 100. In order to reduce PM (Particulate Matter) particle number, the ignition timing of engine 100 is retarded (ignition retardation) to warm up catalyst 140 to perform PN reduction control.

Further, the ECU 400 performs a misfire determination to determine whether or not a misfire has occurred, based on whether or not the rotation fluctuation amount of the engine 100 is greater than the misfire determination value. Further, the ECU 400 performs catalyst overheat determination to determine whether or not the catalyst 140 is overheated, based on whether or not the number of misfires for a predetermined number of ignitions in the engine 100 is greater than the catalyst overheat determination value.

Details of the processing executed by the ECU 400 will be described with reference to the flowchart of FIG. The processing in FIG. 3 is repeatedly executed at a predetermined cycle time.

In the process of FIG. 3, the ECU 400 first determines whether the engine 100 is in operation (step S11). If engine 100 is not in operation (step S11/NO), ECU 400 terminates the process of FIG.

On the other hand, if engine 100 is in operation (step S11/YES), ECU 400 determines whether or not catalyst warm-up control is being executed (step S13). Whether or not the catalyst warm-up control is being executed is determined by referring to the catalyst warm-up control execution flag. When the catalyst warm-up control execution flag is ON, it means that catalyst warm-up control is being executed, and when it is OFF, it means that catalyst warm-up control is not being executed.

When the catalyst warm-up control is not executed (step S13/NO), the ECU 400 sets the determination value D1 as the misfire determination value (step S31) and sets the determination value D3 as the catalyst overheat determination value (step S33). ).

After that, the ECU 400 performs a misfire determination using the determination value D1 (step S35). Specifically, when the rotation fluctuation amount of engine 100 is greater than the determination value D1, it is determined that a misfire has occurred, and a misfire counter indicating the number of misfires is counted up. If less than or equal to D1, maintain the misfire counter at the current value.

ECU 400 also determines whether or not catalyst 140 is overheated using determination value D3 (step S37). For example, the ECU 400 determines that the catalyst 140 is overheated when the number of misfires (misfire counter) for a predetermined number of ignitions in the engine 100 is greater than the determination value D3.

On the other hand, if the catalyst warm-up control is being executed (step S13/YES), the ECU 400 determines whether or not there is an engine load response request (step S15). Specifically, ECU 400 determines whether or not the load required of engine 100 is greater than a predetermined value, that is, whether or not the requested engine power is greater than a predetermined value. For example, ECU 400 determines that there is an engine load response request when the vehicle required power exceeds the power that can be output from running battery 310 . If there is no engine load response request (step S15/NO), the ECU 400 executes the processes of steps S31 to S37 described above, and ends the process of FIG.

On the other hand, if there is an engine load response request (step S15/YES), the ECU 400 starts PN reduction control (step S16).

When the PN reduction control is started, the ECU 400 sets a misfire determination value to a determination value D2 larger than the determination value D1 (step S17). During PN reduction control, combustion is weaker than during normal operation, so the amount of rotation fluctuation increases. Therefore, when the determination value D1 is used as the misfire determination value, it is determined that a misfire has occurred because the rotation fluctuation amount exceeds the determination value D1 even though the engine 100 is normal. By setting the misfire determination value to the determination value D2 that is larger than the determination value D1, it is possible to prevent an erroneous determination that a misfire has occurred even though the engine 100 is normal during execution of the PN reduction control. be able to.

Further, the ECU 400 sets a determination value D4, which is smaller than the determination value D3, as the catalyst overheat determination value (step S19). During PN reduction control, the exhaust temperature and the catalyst temperature become higher than during normal operation. Therefore, the judgment value D4, which is smaller than the judgment value D3, is used to detect a sign of misfire at an early stage and suppress the meltdown of the catalyst due to overheating.

After that, the ECU 400 performs misfire determination using the determination value D2 (step S21), and performs catalyst overheat determination using the determination value D4 (step S23).

When the ECU 400 determines that the catalyst is overheated (step S25/YES), that is, when the number of misfires detected using the determination value D2 is greater than the determination value D4, the ECU 400 stops the PN reduction control (step S25/YES). S27). More specifically, ECU 400 prohibits ignition retardation. As a result, erosion of the catalyst due to overheating can be suppressed. On the other hand, if it is determined that the catalyst is not overheated (step S25/NO), the process of FIG. 3 is terminated.

FIG. 4 is an example of a time chart showing switching between the misfire determination value and the catalyst overheat determination value. FIG. 4 shows the catalyst warm-up control execution flag, PN reduction control execution flag, engine speed, engine output, ignition timing, intake air amount, misfire determination value, rotation fluctuation amount, catalyst overheat determination value, and misfire counter. ing.

When the catalyst warm-up control execution flag is switched from OFF to ON at time t1, catalyst warm-up control is executed to retard the ignition timing. At time t2, when there is an engine load response request, the catalyst warm-up control execution flag is turned OFF and the PN reduction control execution flag is turned ON. When the PN reduction control execution flag is turned ON, the ECU 400 increases the engine speed while retarding the ignition timing to increase the intake air amount. Also, the misfire determination value is changed from the determination value D1 to the determination value D2, and the catalyst overheat determination value is changed from the determination value D3 to the determination value D4. When the PN reduction control is executed, the rotation fluctuation amount of the engine 100 increases. Therefore, if the determination value D1 is used as it is, there is a risk of an erroneous determination that a misfire has occurred even though the engine 100 is normal. There is Such an erroneous determination can be suppressed by setting the misfire determination value to a determination value D2 that is larger than the determination value D1. Further, during PN reduction control, the exhaust temperature and the catalyst temperature become higher than during normal operation. Therefore, by using the determination value D4, which is smaller than the determination value D3, to detect a sign of misfire at an early stage, it is possible to suppress melting damage due to overheating of the catalyst. The determination values D1 and D2 are examples of a first misfire determination value and a second misfire determination value, respectively, and the determination values D3 and D4 are examples of a first reference value and a second reference value, respectively.

When the value of the misfire counter exceeds the determination value D4 (time t3), the ECU 400 stops the execution of the PN reduction control, so retarding the ignition timing is stopped. At time t4, when the conditions for executing catalyst warm-up control are satisfied, ECU 400 starts catalyst warm-up control again to retard the ignition timing.

As described in detail above, the ECU 400 according to the present embodiment performs catalyst warm-up control to warm up the catalyst 140 that purifies the exhaust gas from the engine 100 by retarding the ignition timing of the fuel in the engine 100. Execute. Further, ECU 400 determines the occurrence of misfire based on whether or not the rotational fluctuation amount of engine 100 is greater than misfire determination value D1, and detects the number of misfires detected with respect to a predetermined number of ignitions of engine 100. It is determined whether or not the catalyst 140 is overheated based on whether or not it is greater than the overheat determination value D3. When catalyst warm-up control is in progress and the load required of engine 100 is greater than a predetermined value, ECU 400 determines whether or not the rotation fluctuation amount of engine 100 is greater than misfire determination value D2, which is greater than misfire determination value D1. and determining whether the catalyst 140 is overheated based on whether the number of misfires is greater than the catalyst overheat determination value D4, which is smaller than the catalyst overheat determination value D3, and When it is determined that the catalyst 140 is overheated, retarding the ignition timing is stopped. As a result, it is possible to reduce the possibility that the catalyst 140 will melt due to overheating, and also reduce the PN.

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

10 vehicle 100 engine 140 catalyst 400 ECU

Claims (1)

a catalyst warm-up control unit for executing catalyst warm-up control for warming up a catalyst for purifying exhaust gas from an internal combustion engine by retarding ignition timing of fuel in the internal combustion engine;
a warm-up control determination unit that determines whether the catalyst warm-up control is being executed;
a load determination unit that determines whether the load required for the internal combustion engine is greater than a predetermined value;
a misfire detection unit that detects the occurrence of a misfire based on whether or not the rotation fluctuation amount of the internal combustion engine is greater than a first misfire determination value;
Catalyst overheat determination for determining whether or not the catalyst is overheated based on whether or not the number of misfires detected by the misfire detection unit with respect to a predetermined number of ignitions in the internal combustion engine is greater than a first reference value. and
When the load required for the internal combustion engine becomes greater than a predetermined value during the catalyst warm-up control,
The catalyst warm-up control unit stops the catalyst warm-up control, retards the ignition timing of fuel in the internal combustion engine to warm up the catalyst, and starts control to increase the amount of intake air,
The misfire detection unit detects the occurrence of a misfire based on whether or not a rotation fluctuation amount of the internal combustion engine is greater than a second misfire determination value that is greater than the first misfire determination value,
The catalyst overheat determination unit determines whether or not the catalyst is overheated based on whether or not the number of misfires is greater than a second reference value smaller than the first reference value,
The catalyst warm-up control unit stops retarding the ignition timing when the catalyst overheat determination unit determines that the catalyst is overheated.
A control device for an internal combustion engine.

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