JP2020112105A - Control device for internal combustion engine - Google Patents

Abstract

To suppress the overheat of a catalyst, and to suppress exhaust emission.SOLUTION: A control device for an internal combustion engine comprises a misfire detection section detecting the generation of a misfire on the basis of whether or not a rotation variation amount of the internal combustion engine is larger than a first misfire determination value, and a catalyst overheat determination section determining whether or not a catalyst is overheated on the basis of whether or not the number of times of the misfires with respect to the prescribed number of times of the misfires in the internal combustion engine is larger than a first reference value. During catalyst warmup control for warming up the catalyst which clarifies exhaust emission from the internal combustion engine by ignition retardancy, and also when a load required for the internal combustion engine is larger than a prescribed value, the misfire detection section detects the generation of the misfire on the basis of whether or not the rotation variation amount is larger than a second misfire determination value which is larger than the first misfire determination value, and the catalyst overheat determination section determines whether or not the catalyst is overheated on the basis of whether or not the number of times of the misfires is larger than a second reference value which is smaller than the first reference value, and when it is determined that the catalyst is overheated, the catalyst overheat determination section stops the ignition retardancy.SELECTED DRAWING: Figure 3

Description

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

An exhaust gas purification device including a catalyst is used to purify the exhaust gas of an internal combustion engine. In order for the catalyst to fully exert its purifying function, it is necessary to raise the temperature of the catalyst.

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

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

International Publication No. 2010/079609

When the catalyst is warmed up by retarding the ignition and the control for increasing the intake air amount is performed, the combustion becomes weaker than in the normal operating state, and thus the rotational 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 is possible to make an erroneous determination that a misfire has occurred even though the internal combustion engine is normal. There is. If it is determined that a misfire has occurred, the catalyst warm-up due to the ignition retard is stopped, so there is a risk that emission cannot be suppressed.

Further, when the catalyst is warmed up by the ignition retard and the control for increasing the intake air amount is performed, the exhaust gas temperature and the catalyst temperature become higher than that during normal operation. At this time, if the catalyst is already in a high temperature state, the catalyst temperature may rise due to misfire and the catalyst may be overheated and melted.

Therefore, it is an object of a control device for an internal combustion engine disclosed in the present specification to suppress overheating of a catalyst and suppress emission.

In order to solve such a problem, a control device for an internal combustion engine disclosed in the present specification warms up a catalyst for purifying exhaust gas from the internal combustion engine by retarding 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 or not the catalyst warm-up control is being executed, and a load required for the internal combustion engine is higher than a predetermined value. In the internal combustion engine, a load determination unit that determines whether or not it is large, a misfire detection unit that detects the occurrence of misfire based on 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 the predetermined number of ignitions is greater than a first reference value. If the catalyst warm-up control is being performed and the load required for the internal combustion engine is greater than a predetermined value, the misfire detection unit is greater than the second misfire determination value that is greater than the first misfire determination value. The occurrence of misfire is detected based on whether or not the rotational fluctuation amount of the internal combustion engine is large, and the catalyst overheat determination unit determines whether or not the number of misfires is greater than a second reference value that is smaller than the first reference value. Based on whether or not the catalyst is overheated, the catalyst warm-up control unit, when the catalyst overheat determination unit determines that the catalyst is overheated, the ignition timing delay Stop the corner.

According to the control device for an internal combustion engine disclosed in the present specification, it is possible to suppress overheating of the catalyst and also suppress emissions.

FIG. 1 is a diagram showing a structure of a vehicle according to an embodiment. FIG. 2 is a diagram showing a structure of an engine mounted on the vehicle according to the 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.

Embodiments of the present invention will be described below with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, and the like of the respective parts may not be shown so as to completely match the actual ones. In addition, in some drawings, details may be omitted.

FIG. 1 is a diagram showing a structure of a vehicle 10 in which a control device according to an embodiment of the present invention is mounted. Vehicle 10 is a vehicle (hereinafter, also referred to as “hybrid vehicle”) that travels with the power of at least one of engine 100 and second motor generator (MG(2)) 300B, and an electric power company provided outside the vehicle. It is a vehicle (hereinafter, also referred to as “plug-in vehicle”) capable of traveling with the electric power supplied from the AC power supply 19 of FIG. The vehicle to which the control device according to the present invention is applicable is not limited to the hybrid vehicle and the plug-in vehicle as long as the vehicle has a configuration capable of controlling the engine speed (rotation speed) to a desired speed. For example, the control device according to the present invention can also be applied to an engine vehicle equipped with a continuously variable automatic transmission. The engine 100 is an example of an internal combustion engine.

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

Power split device 200 distributes the power generated by engine 100 to output shaft 212 and first motor generator (MG(1)) 300A. Power split device 200 is composed of a planetary gear including a sun gear, a pinion gear, a carrier, and a ring gear. Since engine 100, MG(1) 300A and MG(2) 300B are connected via power split device 200, each rotation speed of engine 100, MG(1) 300A and MG(2) 300B is When the two rotational speeds are determined, the remaining rotational speeds are determined. By utilizing this relationship, for example, even if the rotation speed of MG(2) 300B has the same value, the rotation speed (rotation speed) Ne of engine 100 is controlled by controlling the rotation speed of MG(1) 300A. It can be controlled to a desired rotation speed.

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

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

Further, vehicle 10 includes engine ECU (Electronic Control Unit) 406 that controls the operating state of engine 100, MG(1) 300A, MG(2) 300B, inverter 330, and a battery for traveling according to the state of vehicle 10. MG_ECU 402 for controlling 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 and the MG_ECU 402 to control the entire hybrid system so that the vehicle 10 can operate most efficiently.

The vehicle 10 also has a connector 13 for connecting a paddle 15 connected to an AC power supply 19 of an electric power company, and electric power from the AC power supply 19 supplied via the connector 13 converted to DC for running. And a charging device 11 for outputting to the battery 310. Charging device 11 controls the amount of electric power output to traveling battery 310 according to a control signal from HV_ECU 404.

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

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 are shown), and a running battery 310. The signal from the monitoring unit 340 for monitoring the state (battery voltage value VB, battery current value IB, battery temperature TB, etc.) is input.

2, engine 100 and peripheral devices related to engine 100 will be described. In this engine 100, the air sucked from an air cleaner (not shown) flows through the intake pipe 110 and is introduced into the combustion chamber 102 of the engine 100. The amount of air introduced into the combustion chamber 102 is adjusted by the operation 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.

The fuel is stored in a fuel tank (not shown) and is injected from the injector 104 into the intake port by a fuel pump (not shown). Instead of the injector 104 or together with the injector 104, an in-cylinder injector for injecting fuel into the combustion chamber 102 may be provided. The air-fuel mixture of the air introduced from the intake pipe 110 and the fuel injected from the injector 104 is ignited and burned by using the ignition coil 106 controlled by the control signal from the ECU 400.

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

The catalyst 140 is a three-way catalyst that purifies emissions (hazardous substances such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx)) contained in the exhaust gas. The catalyst 140 carries a noble metal containing alumina, platinum, palladium, and rhodium as a base, and can simultaneously carry out an oxidation reaction of hydrocarbons and carbon monoxide and a reduction reaction of nitrogen oxides. The catalyst 140 has a characteristic that the exhaust purification capacity decreases as the temperature thereof decreases.

Signals from the engine water temperature sensor 108, the air flow meter 116, the intake air temperature sensor 118, the air-fuel ratio sensor 122, and the oxygen sensor 124 are input to the ECU 400. The ECU 400 also receives a signal from a crank angle sensor 109 provided near the crank shaft 111 of the engine 100 for detecting a rotation angle (crank angle) of the crank shaft 111. The engine water temperature sensor 108 detects the temperature of the engine cooling water (engine water temperature) TW. The air flow meter 116 detects an intake air amount (air amount sucked into the engine 100 per unit time) Ga. The 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. The 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 so that an appropriate ignition timing is obtained, and an appropriate throttle opening degree, based on a signal sent from each sensor, a map and a program stored in a ROM (Read Only Memory). The control amount of the throttle valve 114 is controlled so as to achieve the following, and the injector 104 is controlled so that the fuel injection amount becomes appropriate.

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

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

Further, during the catalyst warm-up control, the ECU 400 increases the intake air amount by increasing the engine speed and secures the output of the engine 100 when the load required for the engine 100 is larger than a predetermined value. In order to reduce the number of PM (Particulate Matter) particles, the ignition timing of the engine 100 is retarded (ignition retardation) to warm up the catalyst 140, and PN reduction control is executed.

Further, the ECU 400 makes a misfire determination that determines whether a misfire has occurred, based on whether the amount of rotation fluctuation of the engine 100 is greater than a misfire determination value. Further, the ECU 400 makes a catalyst overheat determination that determines 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 in FIG. The process of FIG. 3 is repeatedly executed with a predetermined cycle time.

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

On the other hand, when the engine 100 is in operation (step S11/YES), the ECU 400 determines whether or not the catalyst warm-up control is being executed (step S13). Whether 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 the catalyst warm-up control is being executed, and when it is OFF, it means that the 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 makes a misfire determination using the determination value D1 (step S35). Specifically, when the rotational fluctuation amount of the engine 100 is larger than the determination value D1, it is determined that a misfire has occurred, and a misfire counter that indicates the number of misfires is counted up to determine that the rotational fluctuation amount of the engine 100 is the determination value. When D1 or less, the misfire counter is maintained at the current value.

Further, the ECU 400 uses the determination value D3 to determine whether the catalyst 140 is overheated (step S37). For example, the ECU 400 determines that the catalyst 140 is overheated when the number of misfires (misfire counter) for the predetermined number of ignitions in the engine 100 is larger than the determination value D3.

On the other hand, when 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 the load required for engine 100 is larger than a predetermined value, that is, whether the engine required power is larger than a predetermined value. For example, ECU 400 determines that there is an engine load response request when the vehicle required power exceeds the outputtable power of running battery 310. When 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 the PN reduction control (step S16).

When the PN reduction control is started, the ECU 400 sets a judgment value D2 larger than the judgment value D1 as a misfire judgment value (step S17). During PN reduction control, combustion becomes 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 the engine 100 is normal, but the amount of rotation fluctuation exceeds the determination value D1, so that the engine 100 is misfiring. By setting the misfire determination value to be a 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 the determination value D4 smaller than the determination value D3 as the catalyst overheat determination value (step S19). During the PN reduction control, the exhaust gas temperature and the catalyst temperature become higher than that during normal operation. Therefore, a judgment value D4 smaller than the judgment value D3 is used to detect a misfire sign at an early stage and suppress melting loss due to overheating of the catalyst.

After that, the ECU 400 performs the misfire determination using the determination value D2 (step S21) and the 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 larger than the determination value D4, the PN reduction control is stopped (step S25). S27). More specifically, ECU 400 prohibits ignition retard. As a result, melting loss due to overheating of the catalyst can be suppressed. On the other hand, when it is determined that the catalyst is not overheated (step S25/NO), the process of FIG. 3 ends.

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 a catalyst warm-up control execution flag, a PN reduction control execution flag, an engine speed, an engine output, an ignition timing, an intake air amount, a misfire determination value, a rotation variation amount, a catalyst overheat determination value, and a misfire counter. ing.

When the catalyst warm-up control execution flag is switched from OFF to ON at time t1, the catalyst warm-up control is executed and the ignition timing is retarded. When there is an engine load response request at time t2, 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 and increases the intake air amount while retarding the ignition timing. Further, 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, an erroneous determination that misfire has occurred may occur even though the engine 100 is normal. There is. By setting the misfire determination value to be a determination value D2 larger than the determination value D1, such an erroneous determination can be suppressed. Further, during the PN reduction control, the exhaust gas temperature and the catalyst temperature become higher than that during normal operation. Therefore, by using the judgment value D4 smaller than the judgment value D3 to detect the misfire sign early, it is possible to suppress the melting loss due to overheating of the catalyst. The determination values D1 and D2 are examples of the first misfire determination value and the second misfire determination value, and the determination values D3 and D4 are examples of the first reference value and the 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, and thus the retard of the ignition timing is stopped. When the execution condition of the catalyst warm-up control is satisfied at time t4, the ECU 400 starts the catalyst warm-up control again and retards the ignition timing.

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

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

10 Vehicle 100 Engine 140 Catalyst 400 ECU

Claims (1)

A catalyst warm-up control unit that executes catalyst warm-up control for warming up a catalyst that purifies 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 or not 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 misfire based on whether the rotational 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 detector for a predetermined number of ignitions in the internal combustion engine is greater than a first reference value And a section,
During the catalyst warm-up control, and when the load required for the internal combustion engine is larger than a predetermined value,
The misfire detection unit detects the occurrence of misfire based on whether or not the rotational fluctuation amount of the internal combustion engine is greater than the second misfire determination value that is greater than the first misfire determination value,
The catalyst overheat determination unit determines whether the catalyst is overheated based on whether the number of misfires is greater than a second reference value that is smaller than the first reference value,
The catalyst warm-up control unit cancels the retard of the ignition timing when the catalyst overheat determination unit determines that the catalyst is overheated,
Control device for internal combustion engine.

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