JP2020128732A - Engine control device - Google Patents

Abstract

To realize temperature increase control suitable for a catalyst device in an engine mounted with 2 types of fuel injection valves, a cylinder injection valve and a port injection valve.SOLUTION: In a case where temperature increase control is in execution (S100: Yes) with a high temperature at a tip of a cylinder injection valve (S110: Yes) or a large deposit accumulation amount (S120: Yes), a fuel injection for rich combustion operation is performed in a cylinder injection mode (S150). In other cases, the fuel injection is performed in a port injection mode (S160).SELECTED DRAWING: Figure 2

Description

The present invention relates to an engine control device that controls the temperature rise of a catalyst device installed in an exhaust passage.

In many automobile engines, a catalyst device for purifying harmful components of exhaust gas is installed in an exhaust passage. Further, as such a catalyst device, there is one having a function of oxidizing and purifying unburned components such as carbon monoxide and hydrocarbons in exhaust gas. Then, conventionally, as seen in Patent Document 1, switching between lean combustion in which combustion is performed at an air-fuel ratio leaner than the theoretical air-fuel ratio and rich combustion in which combustion is performed at an air-fuel ratio richer than the theoretical air-fuel ratio is performed. An engine control technique is known in which the temperature of such a catalyst device is raised by repeating it.

JP, 2006-022753, A

Meanwhile, some engines include two types of fuel injection valves: an in-cylinder injection valve that injects fuel into a cylinder and a port injection valve that injects fuel into an intake port. In such an engine, an in-cylinder injection mode in which all the fuel burned in the cylinder is injected by the in-cylinder injection valve, a port injection mode in which all of the fuel is injected by the port injection valve, and a part of the same fuel is injected in the in-cylinder injection valve. The fuel injection can be performed in three injection modes, which are the injection mode in which the fuel is injected in. and the remaining fuel is injected by the port injection valve. Heretofore, various proposals have been made regarding control techniques relating to switching of the injection mode in such an engine. However, in such an engine capable of switching the injection mode, no proposal has been made regarding the selection of the injection mode when performing the temperature rise control of the catalyst device by switching between the lean combustion and the rich combustion as described above. There is room for improvement.

An engine control device that solves the above problems is an in-cylinder injection valve that injects fuel into a cylinder, a port injection valve that injects fuel into an intake port, and a catalyst device that oxidizes unburned fuel components in exhaust gas. Applies to engines with. Then, the engine control device alternately performs a lean combustion operation in which combustion is performed at an air-fuel ratio leaner than the theoretical air-fuel ratio and a rich combustion operation in which combustion is performed at an air-fuel ratio richer than the theoretical air-fuel ratio. The temperature rise control for raising the temperature of the catalyst device is performed.

During lean combustion operation, oxygen is excessive due to combustion in the cylinder, and during rich combustion, fuel is excessive due to combustion in the cylinder. Therefore, exhaust gas containing excess oxygen is introduced into the catalyst device during lean combustion operation, and the inside of the catalyst device becomes an oxidizing atmosphere. When rich combustion operation is performed in this state and the exhaust containing unburned fuel is introduced into the catalyst device, the unburned fuel burns inside the catalyst device, and the temperature of the catalyst device rises due to the heat generated by the combustion. Therefore, the catalyst device can be heated by alternately performing the lean combustion operation and the rich combustion operation.

On the other hand, during rich combustion operation, where combustion is performed with the amount of oxygen in the cylinders less than the amount required for complete combustion, particulate matter emissions are greater than during lean combustion operation and stoichiometric combustion operation in which combustion is performed at the stoichiometric air-fuel ratio. The amount increases. On the other hand, when the fuel injection is performed by the in-cylinder injection valve, the fuel is less likely to be atomized as compared with the case where the fuel injection is performed by the port injection valve, and thus the particulate matter is more likely to be generated. Therefore, if the fuel injection during the rich combustion operation of the temperature rise control is performed by the in-cylinder injection valve, the discharge amount of the particulate matter becomes particularly large. However, if the state where the fuel injection of the in-cylinder injection valve is stopped and only the port injection valve continues to inject fuel is continued, the rise in the tip temperature of the in-cylinder injection valve and the accumulation of deposits at the injection port are within the allowable range. There is a risk of progressing beyond.

Therefore, in the above engine control device, when the tip temperature of the in-cylinder injection valve is high and when the amount of deposit accumulated in the in-cylinder injection valve is large, Fuel injection during rich combustion operation is performed by an in-cylinder injection valve. When the tip temperature of the in-cylinder injection valve is not high and the amount of deposits accumulated in the in-cylinder injection valve is not large, fuel injection during rich combustion operation is performed by the port injection valve. ing. Therefore, it is possible to suppress the rise of the tip temperature of the in-cylinder injection valve and the accumulation of deposits while suppressing the discharge of the particulate matter during the temperature rise control.

The figure which shows the structure of one Embodiment of an engine control apparatus typically. The flowchart of the injection mode selection routine implemented by the same engine control apparatus. 6 is a graph showing the relationship between the air-fuel ratio and the production amount of particulate matter in each of the in-cylinder injection mode and the port injection mode.

Hereinafter, an embodiment of the engine control device will be described in detail with reference to FIGS. 1 to 3.
As shown in FIG. 1, the engine 10 includes a cylinder block 13 in which a cylinder 12 that houses a piston 11 is provided, and a cylinder head 14 fixed to the cylinder block 13. The piston 11 is connected to the crankshaft 16 via a connecting rod 15. The connecting rod 15 and the crankshaft 16 form a crank mechanism that converts the reciprocating motion of the piston 11 in the cylinder 12 into the rotary motion of the crankshaft 16.

An intake passage 17, which is a passage for introducing air into the cylinder 12, and an exhaust passage 26, which is a discharge passage for exhaust gas generated by combustion in the cylinder 12, are connected to the cylinder 12. The cylinder head 14 is provided with an intake port 20 which is a connection portion of the intake passage 17 to the cylinder 12, and an exhaust port 27 which is a connection portion of the exhaust passage 26 to the cylinder 12. Further, the cylinder head 14 is provided with an intake valve 21 that is a valve that opens and closes the cylinder 12 with respect to the intake port 20, and an exhaust valve 28 that is a valve that opens and closes the cylinder 12 with an exhaust port 27. There is. Further, the cylinder head 14 is provided with a port injection valve 22 for injecting fuel into the intake port 20 and an in-cylinder injection valve 23 for injecting fuel into the cylinder 12. Further, the cylinder head 14 is provided with an ignition device 24 that ignites the air-fuel mixture introduced into the cylinder 12 by sparks.

The intake passage 17 is provided with an air flow meter 18 for detecting the flow rate of the air flowing through the intake passage 17 (intake air amount GA). Further, a throttle valve 19, which is a valve for adjusting the intake air amount GA, is provided in a portion of the intake passage 17 downstream of the air flow meter 18. On the other hand, the exhaust passage 26 is provided with a three-way catalyst device 29 that oxidizes CO and HC in the exhaust gas and simultaneously reduces NOx. Further, a filter 30 for collecting particulate matter is installed in a portion of the exhaust passage 26 downstream of the three-way catalyst device 29. Further, an air-fuel ratio sensor 31 for detecting the air-fuel ratio ABYF burned in the cylinder 12 is installed in a portion of the exhaust passage 26 upstream of the three-way catalyst device 29. Further, in the portion of the exhaust passage 26 between the three-way catalyst device 29 and the filter 30, there is provided a catalyst outlet gas temperature sensor 32 for detecting the catalyst outlet gas temperature THC which is the temperature of the gas flowing out from the three-way catalyst device 29. is set up.

The electronic control unit 33 that controls the engine 10 is configured as a microcomputer including an arithmetic processing circuit that executes arithmetic processing for control, and a memory that stores a control program and data. To the electronic control unit 33, the detection signals of the air flow meter 18, the air-fuel ratio sensor 31, and the catalyst outlet gas temperature sensor 32 described above are input. Further, the electronic control unit 33 includes operation amounts of a crank angle sensor 34 that detects a crank angle θc that is a rotation angle of the crankshaft 16, a water temperature sensor 35 that detects a temperature THW of engine cooling water, and an accelerator pedal 36. A detection signal of the accelerator position sensor 37 that detects the accelerator opening ACC is input. Then, the electronic control unit 33 controls the opening degree of the throttle valve 19, the fuel injection amount and timing of the port injection valve 22 and the in-cylinder injection valve 23, the ignition timing of the ignition device 24, etc. based on the detection results of these sensors. By doing so, the operating state of the engine 10 is controlled according to the traveling state of the vehicle. The electronic control unit 33 calculates the engine speed NE from the detection result of the crank angle θc.

The electronic control unit 33 during the combustion operation of the engine 10 selects one of the port injection mode, the in-cylinder injection mode, and the injection mode according to the operating conditions (engine speed NE, intake air amount GA, etc.) of the engine 10. The fuel injection control is performed by selecting the injection mode from. In the port injection mode, all of the required amount of fuel is injected by the port injection valve 22, and in the in-cylinder injection mode, all of the required amount of fuel is injected by the in-cylinder injection valve 23. In the injection mode, part of the required amount of fuel is injected by the port injection valve 22 and the remaining fuel is injected by the in-cylinder injection valve 23.

By the way, in the engine 10, the particulate matter in the exhaust gas is collected by the filter 30 to suppress the release of the particulate matter to the outside air. The collected particulate matter gradually accumulates on the filter 30, but if the particulate matter is left to stand, the filter 30 will be clogged. Therefore, the electronic control unit 33 is configured to perform a filter regeneration process of burning and purifying the particulate matter deposited on the filter 30 before the clogging occurs.

In the filter regeneration process, the three-way catalyst is operated by alternately performing lean combustion operation in which combustion is performed at an air-fuel ratio leaner than the theoretical air-fuel ratio and rich combustion operation in which combustion is performed at an air-fuel ratio richer than the theoretical air-fuel ratio. A temperature raising control for raising the temperature of the device 29 is performed. Exhaust gas containing excess oxygen due to combustion in the cylinder 12 flows into the three-way catalyst device 29 during lean combustion operation, and the three-way catalyst device 29 during rich combustion operation is left unburned in the cylinder 12. Exhaust containing fuel burns. In the temperature raising control, the unburned fuel is burned in the three-way catalyst device 29 by performing the rich combustion operation after making the inside of the three-way catalyst device 29 an oxidizing atmosphere by the lean burn operation. When the unburned fuel burns in the three-way catalyst device 29, the temperature of the exhaust gas that flows out of the three-way catalyst device 29 and flows into the filter 30 rises, and the heat of the exhaust gas that has reached the high temperature causes the temperature of the filter 30 to rise. become. Then, in the filter regeneration process, after the temperature raising control is performed until the temperature of the filter 30 is raised to a temperature at which the particulate matter can be burned, exhaust gas containing excess oxygen is supplied to the filter 30 by lean burn operation or the like to be deposited. The filter 30 is regenerated by burning the particulate matter.

By the way, as described above, the engine 10 includes the two types of fuel injection valves, the port injection valve 22 and the in-cylinder injection valve 23. In such an engine 10, fuel injection can be performed in three injection modes: a cylinder injection mode, a port injection mode, and a separate injection mode. In the in-cylinder injection mode, all of the fuel burned in the cylinder 12 is injected by the in-cylinder injection valve 23, and in the port injection mode, all of the fuel is injected by the port injection valve 22. In the injection mode, part of the fuel burned in the cylinder 12 is injected by the in-cylinder injection valve 23, and the remaining fuel is injected by the port injection valve 22. The electronic control unit 33 switches the fuel injection mode according to the operating condition of the engine 10.

FIG. 2 shows a flowchart of the injection mode selection routine. The electronic control unit 33 repeatedly executes the processing of the same routine every predetermined control period while the engine 10 is operating.
When the process of this routine is started, first, in step S100, it is determined whether or not the temperature raising control is being executed. If the temperature raising control is being executed (S100: YES), the process proceeds to step S110, and if the temperature raising control is not being executed (S100: NO), the process proceeds to step S140.

When the process proceeds to step S140, the injection mode is selected based on the engine speed NE, the engine cooling water temperature THW, etc. in step S140, and then the process of this routine is ended. As a result, in the present embodiment, when the temperature raising control is not executed, the injection mode suitable for forming the high-quality air-fuel mixture in the cylinder 12 is set according to the warm-up state of the engine 10 and the operating region. I am trying to choose.

On the other hand, when the temperature raising control is in progress and the process proceeds to step S110, it is determined whether or not the deposit accumulation amount of the in-cylinder injection valve 23 is equal to or greater than a predetermined determination value A. Then, when the deposit accumulation amount is equal to or larger than the determination value A (S110: YES), the process proceeds to step S150, the in-cylinder injection mode is selected in step S150, and then the process of this routine is ended. It On the other hand, if the deposit amount is less than the determination value A (S110: NO), the process proceeds to step S120. The electronic control unit 33 estimates the deposit accumulation amount of the in-cylinder injection valve 23 according to the operating condition of the engine 10.

When the process proceeds to step S120, it is determined in step S120 whether the tip temperature of the in-cylinder injection valve 23 is equal to or higher than a predetermined determination value B. When the tip temperature is equal to or higher than the determination value B (S120: YES), the process proceeds to step S150 described above, and after the in-cylinder injection mode is selected, the process of this routine of this time is ended. If the tip temperature is less than the determination value B (S120: NO), the process proceeds to step S130. It should be noted that the electronic control unit 33 estimates the tip temperature of the in-cylinder injection valve 23 in accordance with the operating condition of the engine 10, similarly to the deposit accumulation amount.

When the process proceeds to step S130, it is determined in step S130 whether or not the rich combustion operation is being performed. Then, when the rich combustion operation is being performed (S130: YES), the process proceeds to step S160, the port injection mode is selected in step S160, and then the process of this routine of this time is ended. On the other hand, when the rich combustion operation is not being performed (S130: NO), that is, when the lean combustion operation is being performed, the process proceeds to step S140 described above.

The operation and effect of the engine control device of this embodiment configured as described above will be described.
The engine 10 normally performs stoichiometric combustion operation in which combustion is performed with the air-fuel ratio as the stoichiometric air-fuel ratio. On the other hand, during the temperature rise control in the filter regeneration process, the lean burn operation and the rich burn operation are performed. During the rich combustion operation under the temperature rise control, the combustion is performed in a state where the oxygen in the cylinder 12 is less than the amount required for complete combustion of the fuel, so that the amount of particulate matter generated by the combustion increases. The production amount of the particulate matter in the cylinder 12 during the rich combustion operation also changes depending on the injection mode.

FIG. 3 shows the relationship between the air-fuel ratio and the production amount of the particulate matter in each of the in-cylinder injection mode and the port injection mode. In the port injection mode, the atomization of the fuel is promoted as compared with the case of the in-cylinder injection mode because the fuel is agitated into the intake air due to the airflow flowing from the intake port 20 into the cylinder 12. Therefore, as shown in the figure, the in-cylinder injection mode produces a larger amount of particulate matter with the same air-fuel ratio than the port injection mode. On the other hand, the temperature rise control is executed when the amount of particulate matter deposited on the filter 30 increases. Therefore, if a large amount of particulate matter is discharged from the cylinder 12 during the rich combustion operation, there is a possibility that all of it will not be collected by the filter 30 and will be discharged to the outside air.

On the other hand, in the present embodiment, basically, during the rich combustion operation of the temperature rise control, in order to suppress the emission of the particulate matter, the fuel injection is performed in the port injection mode. However, if the state where the fuel injection of the in-cylinder injection valve 23 is stopped and only the port injection valve 22 continues to inject the fuel is continued, the rise of the tip temperature of the in-cylinder injection valve 23 and the accumulation of deposits on the injection port are acceptable. There is a risk of progressing beyond this range. Therefore, in the present embodiment, when the tip temperature of the in-cylinder injection valve 23 is high or when the amount of deposit accumulated in the in-cylinder injection valve 23 is large, The fuel injection during the rich combustion operation is performed in the cylinder injection mode. When fuel is injected from the in-cylinder injection valve 23, the fuel in the in-cylinder injection valve 23 is replaced, and heat is taken away by the injected fuel, so the tip temperature of the in-cylinder injection valve 23 decreases. Furthermore, since the deposit accumulated in the injection port is washed away by the fuel injection, the amount of deposit accumulation also decreases.

Incidentally, in the present embodiment, during lean combustion operation of temperature raising control, basically, an injection mode suitable for forming a high-quality air-fuel mixture in the cylinder 12 according to the operating region of the engine 10 and the warm-up state. Is selected. However, when the tip temperature of the in-cylinder injection valve 23 is high or the deposit accumulation amount is large, fuel injection is performed in the in-cylinder injection mode even in the lean combustion operation to lower the tip temperature of the in-cylinder injection valve 23 or deposit the fuel. The amount of deposition is reduced.

This embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
In the above embodiment, the fuel injection during the lean combustion operation is performed in the in-cylinder injection mode when the deposit accumulation amount of the in-cylinder injection valve 23 is high or when the tip temperature is high, and in other cases, the engine 10 is used. The injection mode was switched according to the driving situation of. The fuel injection mode during lean combustion operation is not limited to this, and may be changed appropriately. For example, as in the case of the rich combustion operation, the fuel injection during the lean combustion operation is the in-cylinder injection mode when the deposit accumulation amount of the in-cylinder injection valve 23 is high or the tip temperature is high, and in the other cases. They may be performed in the port injection mode, respectively. Further, during the lean combustion operation, the injection mode may be selected regardless of the deposit accumulation amount of the in-cylinder injection valve 23 and the tip temperature.

-In the engine 10 to which the above-described embodiment is applied, a three-way element that oxidizes unburned fuel components in exhaust gas and simultaneously reduces nitrogen oxides in exhaust gas in a portion of the exhaust passage 26 upstream of the filter 30. The catalyst device 29 was installed. Even in the engine 10 in which an oxidation catalyst device that only oxidizes unburned fuel components without reducing nitrogen oxides is installed in place of the three-way catalyst device 29, lean combustion operation and rich combustion operation are alternately performed. By doing so, it is possible to raise the temperature of the filter 30. Further, when the filter 30 carries the oxidation catalyst, the temperature of the filter 30 can be raised by alternate execution of the lean combustion operation and the rich combustion operation even if the catalyst device is not installed upstream of the exhaust gas. .. Even in the engine having such a configuration, by applying the control related to the selection of the injection mode during the rich combustion operation in the above-described embodiment, the temperature rise is suppressed while suppressing the rise in the tip temperature of the in-cylinder injection valve 23 and the accumulation of deposits. It becomes possible to suppress discharge of particulate matter during control.

10... Engine, 11... Piston, 12... Cylinder, 13... Cylinder block, 14... Cylinder head, 15... Connecting rod, 16... Crank shaft, 17... Intake passage, 18... Air flow meter, 19... Throttle valve, 20... Intake Port, 21... Intake valve, 22... Port injection valve, 23... Cylinder injection valve, 24... Ignition device, 26... Exhaust passage, 27... Exhaust port, 28... Exhaust valve, 29... Three-way catalyst device, 30... Filter , 31... Air-fuel ratio sensor, 32... Catalyst output gas temperature sensor, 33... Electronic control unit, 34... Crank angle sensor, 35... Water temperature sensor, 36... Accelerator pedal, 37... Accelerator position sensor.

Claims (1)

It is applied to an engine equipped with an in-cylinder injection valve that injects fuel into a cylinder, a port injection valve that injects fuel into an intake port, and a catalyst device that oxidizes unburned fuel components in exhaust gas. A temperature raising control that raises the temperature of the catalyst device by alternately performing a lean combustion operation in which combustion is performed at an air-fuel ratio leaner than the fuel ratio and a rich combustion operation in which combustion is performed at an air-fuel ratio richer than the theoretical air-fuel ratio. In the engine control device that performs
When the tip temperature of the in-cylinder injection valve is high, and when the amount of deposits accumulated in the in-cylinder injection valve is large, the rich combustion operation is being performed. When fuel injection is performed by the in-cylinder injection valve and the tip temperature of the in-cylinder injection valve is not high and the amount of deposit accumulated in the in-cylinder injection valve is not large, the rich An engine control device that performs fuel injection during combustion operation by the port injection valve.