JP7087802B2 - Internal combustion engine control device - Google Patents

Description

The present invention relates to a spark ignition type internal combustion engine control device mounted on a vehicle and having a three-way catalyst device installed in an exhaust passage.

A spark-ignition type internal combustion engine burns by igniting a mixture of air and fuel introduced into a cylinder by a spark of a spark plug. At this time, the combustion of a part of the fuel in the air-fuel mixture may be incomplete, and a carbonaceous fine particle substance (hereinafter referred to as particulate) may be generated.

Patent Document 1 includes a three-way catalyst device installed in an exhaust passage and a filter for collecting particulates installed in a portion downstream of the three-way catalyst device in the exhaust passage. A spark-ignition internal combustion engine is described. In such an internal combustion engine, by collecting the particulate generated in the cylinder with a filter, it is possible to suppress the release of the particulate to the outside air. Since the collected particulates are gradually deposited on the filter, if the deposits are left unattended, the filters may be clogged by the deposited particulates.

On the other hand, in the internal combustion engine of the same document, the particulate accumulated on the filter is burnt and purified by carrying out a fuel introduction process for raising the temperature of the three-way catalyst device while the vehicle is coasting. In the fuel introduction process, fuel injection is performed with the spark of the spark plug stopped, so that the air-fuel mixture is introduced into the exhaust passage without burning in the cylinder. The unburned air-fuel mixture introduced into the exhaust passage at this time flows into the three-way catalyst device and burns in the three-way catalyst device. Then, the temperature of the three-way catalyst device is raised by the heat generated by the combustion. As the temperature of the three-way catalyst device increases, the temperature of the gas flowing out of the three-way catalyst device and flowing into the filter also rises. When the temperature of the filter rises above the ignition point of the particulate due to the heat of the high-temperature gas, the particulate deposited on the filter burns and is purified.

The fuel introduction process for raising the temperature of the three-way catalyst device is performed with the combustion of the internal combustion engine stopped. On the other hand, since the air-fuel mixture in the cylinder is sent out to the exhaust passage, it is necessary to maintain the rotation of the crank shaft of the internal combustion engine even during the fuel introduction process. In that respect, since the power of the internal combustion engine is not required for running while the vehicle is coasting, the combustion of the internal combustion engine can be stopped, and the crank shaft can be rotated by the power transmission from the wheels. Therefore, in the above-mentioned conventional internal combustion engine, the fuel introduction process is carried out while the vehicle is coasting.

US Patent Application Publication No. 2014/0041362

By the way, the inertial running of the vehicle may be completed in a short time, and the fuel introduction process may not be continued until the temperature of the three-way catalyst device is sufficiently raised. In such a case, the fuel consumed in the fuel introduction process at that time is wasted.

It is conceivable that the temperature rise of the three-way catalyst device by the fuel introduction process is carried out for a purpose other than combustion purification of the particulates deposited on the filter. For example, when the catalyst temperature drops during fuel cut of the internal combustion engine during vehicle deceleration and the exhaust purification capacity of the three-way catalyst device decreases, the catalyst temperature rise control is executed to improve the exhaust purification capacity of the three-way catalyst device. It is possible to recover. Even in such a case, the above-mentioned problem may occur as well. As described above, the above-mentioned problems are common to the case where the fuel introduction process is performed during the inertial running of the vehicle to raise the temperature of the three-way catalyst device regardless of the purpose.

The control device for the internal combustion engine that solves the above problems is mounted on the vehicle, and the fuel injection valve, the cylinder into which the air-fuel mixture containing the fuel injected by the fuel injection valve is introduced, and the mixture introduced in the cylinder. It is applied to an internal combustion engine including an ignition device that ignites air by a spark, an exhaust passage through which gas discharged from the cylinder flows, and a three-way catalyst device installed in the exhaust passage. Then, the control device of the internal combustion engine exhausts the air-fuel mixture containing the fuel injected by the fuel injection valve without burning it in the cylinder, provided that the vehicle speed is equal to or higher than the specified start permission speed during coasting of the vehicle. The fuel injection process to be introduced into the passage is started.

When the inertial running of the vehicle is started from a state where the vehicle speed is low, the duration of the coasting running is likely to be shorter than when the vehicle is started from a state where the vehicle speed is high. Therefore, when the fuel introduction process during inertial running of the vehicle is started from a state where the vehicle speed is low, there is a high possibility that the fuel introduction process cannot be continued until the temperature of the three-way catalyst device can be sufficiently raised. In that respect, in the control device of the internal combustion engine, the condition for starting the fuel introduction process is that the vehicle speed is equal to or higher than the specified start permission speed while the vehicle is coasting, and the fuel is introduced only when the vehicle speed is higher than a certain level. I try not to start the process. That is, if there is a high possibility that the temperature of the three-way catalyst device cannot be raised sufficiently, the implementation of the fuel introduction process is postponed. Therefore, according to the control device of the internal combustion engine, it is possible to efficiently raise the temperature of the three-way catalyst device installed in the exhaust passage of the internal combustion engine.

The schematic diagram which shows the structure of embodiment of the control device of an internal combustion engine. The flowchart of the start determination routine executed by the control device in the same embodiment. The time chart which shows an example of the embodiment of the fuel introduction process in the same embodiment.

Hereinafter, an embodiment of the control device for an internal combustion engine will be described in detail with reference to FIGS. 1 to 3.
As shown in FIG. 1, the internal combustion engine 10 mounted on a vehicle includes a cylinder 12 in which a piston 11 is housed so as to be reciprocating. The piston 11 is connected to the crank shaft 14 via a connecting rod 13. Then, the reciprocating motion of the piston 11 in the cylinder 12 is converted into the rotational motion of the crank shaft 14.

An intake passage 15, which is an air introduction path to the cylinder 12, is connected to the cylinder 12. The intake passage 15 is provided with an air flow meter 16 that detects the flow rate of air flowing through the intake passage 15 (intake air amount GA). A throttle valve 17 is provided in a portion of the intake passage 15 on the downstream side of the air flow meter 16. Further, a fuel injection valve 18 is installed in a portion of the intake passage 15 on the downstream side of the throttle valve 17. The fuel injection valve 18 injects fuel into the air flowing through the intake passage 15 to form an air-fuel mixture.

The cylinder 12 is provided with an intake valve 19 that opens and closes the intake passage 15 with respect to the cylinder 12. Further, the air-fuel mixture is introduced into the cylinder 12 from the intake passage 15 according to the opening of the intake valve 19. The cylinder 12 is provided with an ignition device 20 that ignites and burns the air-fuel mixture in the cylinder 12 by a spark.

An exhaust passage 21 which is an exhaust path for exhaust gas generated by combustion of the air-fuel mixture is connected to the cylinder 12. Further, the cylinder 12 is provided with an exhaust valve 22 that opens and closes the exhaust passage 21 with respect to the cylinder 12. Exhaust gas is introduced into the exhaust passage 21 from the inside of the cylinder 12 according to the opening of the exhaust valve 22. A three-way catalyst device 23 that oxidizes CO and HC in the exhaust gas and at the same time reduces NOx is installed in the exhaust passage 21. Further, a filter 24 for collecting particulates is installed in a portion of the exhaust passage 21 on the downstream side of the three-way catalyst device 23. Further, an air-fuel ratio sensor 25 for detecting the oxygen concentration of the gas flowing through the exhaust passage 21, that is, the air-fuel ratio ABYF of the air-fuel mixture is installed in the portion upstream of the three-way catalyst device 23 in the exhaust passage 21. .. Further, in the portion of the exhaust passage 21 between the three-way catalyst device 23 and the filter 24, a catalyst exhaust gas temperature sensor 26 for detecting the catalyst exhaust gas temperature THC, which is the temperature of the gas flowing out from the three-way catalyst device 23, is provided. is set up.

In the vehicle, the crank shaft 14 of the internal combustion engine 10 is connected to the wheels 52 via the torque converter 50 and the transmission 51. The torque converter 50 is provided with a lockup mechanism 53 that locks up the crank shaft 14 directly connected to the transmission 51.

The control device 27 of the internal combustion engine 10 is configured as a microcomputer having an arithmetic processing circuit for executing arithmetic processing for control and a memory for storing control programs and data. The detection signals of the above-mentioned air flow meter 16, air-fuel ratio sensor 25, and catalyst exhaust gas temperature sensor 26 are input to the control device 27. Further, a detection signal of the crank angle sensor 28 for detecting the crank angle θc, which is the rotation angle of the crank shaft 14, is input to the control device 27. Then, the control device 27 calculates the rotation speed (engine rotation speed NE) of the internal combustion engine 10 from the detection result of the crank angle θc. Further, the control device 27 is also input with the detection signals of the vehicle speed sensor 29 that detects the vehicle speed V, which is the traveling speed of the vehicle, and the accelerator position sensor 31 that detects the accelerator opening ACC, which is the operation amount of the accelerator pedal 30. There is. Then, the control device 27 controls the opening degree of the throttle valve 17, the amount and timing of fuel injection of the fuel injection valve 18, the implementation timing (ignition timing) of the spark of the ignition device 20, and the like based on the detection results of these sensors. As a result, the operating state of the internal combustion engine 10 is controlled according to the traveling condition of the vehicle.

As part of the control of the internal combustion engine 10, the control device 27 carries out a fuel introduction process for raising the temperature of the three-way catalyst device 23 installed in the exhaust passage 21. The control device 27 determines whether or not to start the fuel introduction process in the start determination routine.

FIG. 2 shows a flowchart of the start determination routine. When the fuel introduction process is not executed, the control device 27 repeatedly executes the process of the routine at a predetermined control cycle.
When the processing of this routine is started, first, in step S100, it is determined whether or not there is a request for raising the temperature of the three-way catalyst device 23 (request for raising the temperature of the catalyst). Then, when the temperature rise of the three-way catalyst device 23 is required (YES), the process proceeds to step S110, and when it is not requested (NO), the process of this routine is terminated as it is. .. In this embodiment, the fuel introduction process is carried out in order to burn and purify the particulates deposited on the filter 24 through the temperature rise of the three-way catalyst device 23. Then, when the accumulated amount of the particulate of the filter 24 exceeds a certain amount, the temperature of the three-way catalyst device 23 is requested to be raised.

When the process proceeds to step S110, it is determined in step S110 whether or not the vehicle is coasting. Then, if the vehicle is coasting (YES), the process proceeds to step S120, and if not (NO), the process of this routine is terminated as it is. In the present embodiment, when the accelerator opening ACC is "0" and the vehicle speed V is not "0", it is determined that the vehicle is coasting.

When the process proceeds to step S120, it is determined in step S120 whether or not the combustion of the internal combustion engine 10 can be stopped. If combustion can be stopped (YES), the process proceeds to step S130, and if not (NO), the process of this routine is terminated as it is.

Incidentally, since the power of the internal combustion engine 10 is not required for running while the vehicle is coasting, the running of the vehicle can be continued even if the combustion of the internal combustion engine 10 is stopped. However, if the engine speed NE drops too much after the combustion is stopped, the internal combustion engine 10 cannot resume combustion by itself. Therefore, when the combustion of the internal combustion engine 10 is stopped, the internal combustion engine 10 has a lower limit value of the engine rotation speed NE (hereinafter referred to as a combustion recovery rotation speed) at which combustion can be restarted by itself. Combustion needs to resume. Therefore, when the engine rotation speed NE is less than the combustion return rotation speed, the combustion of the internal combustion engine 10 cannot be stopped. Further, even if the engine rotation speed NE is equal to or higher than the combustion return rotation speed, if the difference between them is small, it is highly likely that the combustion needs to be restarted immediately after the combustion is stopped. However, it is not possible to stop the combustion of the internal combustion engine 10. On the other hand, when the lockup by the lockup mechanism 53 is not performed, the engine speed NE during combustion stop decreases faster than when the lockup is performed. Therefore, in the present embodiment, when the lockup by the lockup mechanism 53 is performed, a lower engine speed NE is set as the value of the combustion stop permitted rotation speed than when the lockup is not performed, and the engine speed is set. It is determined that the fuel can be stopped when the NE is equal to or higher than the combustion stop permitted rotation speed.

In the vehicle to which the control device 27 of the present embodiment is applied, if the lockup is performed before the start of coasting, the lockup is continued as it is, and if the lockup is not performed, the coasting is started. I try to lock up later. Further, during coasting, the transmission 51 is changed according to the vehicle speed V. Therefore, the vehicle speed V when the engine rotation speed NE during coasting reaches the combustion return rotation speed is a constant speed (hereinafter referred to as the combustion return speed). Therefore, in the present embodiment, the combustion of the internal combustion engine 10 is restarted when the vehicle speed V becomes equal to or lower than the combustion recovery speed while the combustion of the internal combustion engine 10 is stopped.

When it is determined in step S120 that combustion can be stopped and the process proceeds to step S130, it is determined in step S130 whether or not the vehicle speed V is equal to or higher than the specified start permitted speed β. Then, when the vehicle speed V is less than the start permitted speed β (NO), the processing of this routine is terminated as it is. On the other hand, when the vehicle speed V is equal to or higher than the start permitted speed β (YES), the fuel introduction process is started in step S140.

When the fuel introduction process is started, the control device 27 stops the spark of the ignition device 20 and the fuel injection of the fuel injection valve 18 to stop the combustion of the internal combustion engine 10. Then, the control device 27 continued to stop the spark of the ignition device 20 and the fuel injection of the fuel injection valve 18 for a period required for scavenging the burnt gas in the exhaust passage 21, and then stopped the spark of the ignition device 20. The fuel injection of the fuel injection valve 18 is started as it is. In the internal combustion engine 10 at this time, the air-fuel mixture containing the fuel injected by the fuel injection valve 18 is introduced into the exhaust passage 21 without being burned in the cylinder 12. The unburned air-fuel mixture introduced into the exhaust passage 21 flows into the three-way catalyst device 23 and burns inside the three-way catalyst device 23. Then, the temperature of the three-way catalyst device 23 rises due to the heat generated by the combustion of the air-fuel mixture. As the temperature of the three-way catalyst device 23 rises, the temperature of the gas flowing out of the three-way catalyst device 23 and flowing into the filter 24 also rises. Then, when the temperature of the filter 24 rises above the ignition point of the particulate due to the heat of the high-temperature gas, the combustion purification of the particulate deposited on the filter 24 becomes possible. The control device 27 continues such a fuel introduction process until the vehicle speed V drops below the above-mentioned combustion recovery speed. Then, when the vehicle speed V drops below the above-mentioned combustion recovery speed, the control device 27 ends the fuel introduction process and restarts the combustion of the internal combustion engine 10.

Incidentally, the control device 27 starts the fuel cut of the internal combustion engine 10 when the fuel introduction process is not started while the vehicle is coasting and the combustion can be stopped. The fuel cut at this time is started when the vehicle is coasting and combustion can be stopped and the temperature rise of the three-way catalyst device 23 is not required, and when the vehicle is coasting and running. There are two cases, one is when combustion can be stopped and the vehicle speed V is less than the permitted start speed β. When the fuel cut is started, the control device 27 stops the spark of the ignition device 20 and the fuel injection of the fuel injection valve 18 until the vehicle speed V drops to the combustion recovery speed and the combustion of the internal combustion engine 10 is restarted.

As described above, the control device 27 of the present embodiment starts the fuel introduction process on the condition that the vehicle speed V is equal to or higher than the specified start permission speed β during the coasting running of the vehicle. The start permission speed β is set as the following values.

The standard value of the duration of the fuel introduction process required to sufficiently raise the temperature of the three-way catalyst device 23 is defined as the standard temperature rise time. The start permitted speed β is set to the standard value of the vehicle speed V at the start of coasting, in which the time required for the vehicle speed V to decrease to the combustion return speed during coasting is the standard temperature rising time. .. As a matter of course, a speed higher than the combustion recovery speed is set as the value of the start permission speed β.

The duration of the fuel introduction process required for sufficient temperature rise varies depending on the temperature of the three-way catalyst device 23 at the start of the process and environmental conditions such as the outside air temperature. Therefore, it is advisable to set the average value of the above-mentioned durations measured under various conditions as the value of the standard temperature rise time. In addition, the deceleration of the vehicle during coasting varies depending on the situation. Therefore, the value of the start permission speed β may be set, for example, in the following embodiment. That is, the vehicle coasts on a flat ground in a standard environment (atmospheric pressure, air temperature, etc.), and the transition of the vehicle speed V at that time is measured. Then, the vehicle speed V at the time before the standard temperature rise time before the time when the vehicle speed V drops to the combustion recovery speed is set as the value of the start permitted speed β.

The operation and effect of this embodiment will be described.
In the present embodiment, the control device 27 starts the fuel introduction process on the condition that the vehicle speed V is equal to or higher than the specified start permission determination speed β while the vehicle is coasting. Then, after the start of the fuel introduction process, the control device 27 continues the fuel introduction process until the vehicle speed V drops to the combustion recovery speed and the combustion of the internal combustion engine 10 is restarted.

FIG. 3 shows an example of an embodiment of the fuel introduction process in the embodiment. As shown in the figure, the vehicle at this time is traveling by repeating acceleration and deceleration. The period during which the vehicle coasts and the internal combustion engine 10 can be stopped from burning is the period from time t1 to time t2 (hereinafter referred to as period T12) and time t3 to time t4. The period up to (hereinafter referred to as period T34) and the period from time t5 to time t6 (hereinafter referred to as period T56).

Of these, the vehicle speed V at the start of the period T12 and the period T56, that is, at the time t1 and the time t5 is equal to or higher than the start permitted speed β, and the condition for starting the fuel introduction process is satisfied. Therefore, fuel introduction processing is carried out during these periods T12 and T56.

On the other hand, at time t3, which is the start time of the period T34, the vehicle speed V is less than the start permission speed β, and the condition for starting the fuel introduction process is not satisfied. Therefore, the fuel introduction process will not be carried out during the period T34. By the way, in the period T34, the vehicle speed V at the start (time t3) is low, and the time until the vehicle speed V decreases to the combustion recovery speed is short by that amount, so that the period is shorter than the period T12 and the period T56. ing.

When the inertial running of the vehicle is started from the state where the vehicle speed V is low as described above, the period during which the combustion of the internal combustion engine 10 can be stopped tends to be shorter than when the vehicle is started from the state where the vehicle speed V is high. Therefore, when the fuel introduction process during coasting of the vehicle is started from a state where the vehicle speed V is low, there is a high possibility that the fuel introduction process cannot be continued until the temperature of the three-way catalyst device 23 can be sufficiently raised. In that respect, in the present embodiment, the control device 27 requires that the vehicle speed V is equal to or higher than the specified start permitted speed β during coasting of the vehicle, and when the vehicle speed V is lower than a certain level, it is a condition for starting the fuel introduction process. , The fuel introduction process is not started. That is, when there is a high possibility that the temperature of the three-way catalyst device 23 cannot be sufficiently raised, the implementation of the fuel introduction process is postponed. Therefore, according to the present embodiment, it is possible to efficiently raise the temperature of the three-way catalyst device 23 installed in the exhaust passage 21 of the internal combustion engine 10.

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 unburned air-fuel mixture is introduced into the exhaust passage 21 by injecting fuel with the ignition device 20 spark stopped. The time when the air-fuel mixture in the cylinder 12 can be ignited by the spark of the ignition device 20 is limited to the period near the compression top dead center. That is, there is a period in which the air-fuel mixture in the cylinder 12 does not burn even when the spark is executed. Therefore, the fuel introduction process for introducing the unburned air-fuel mixture into the exhaust passage 21 can also be carried out by injecting fuel while executing the spark of the ignition device 20 during such a period.

-In the above embodiment, the fuel introduction process was carried out for the purpose of combustion purification of the particulate deposited on the filter 24, but the fuel introduction process is performed for the purpose of raising the temperature of the three-way catalyst device 23 for other purposes. May be done. For example, when the catalyst temperature drops and the exhaust gas purification capacity of the three-way catalyst device 23 decreases, it is conceivable to control the catalyst temperature rise in order to restore the exhaust gas purification capacity.

In the above embodiment, the fuel introduction process is carried out through fuel injection into the intake passage 15 by the fuel injection valve 18, but an internal combustion engine provided with an in-cylinder injection type fuel injection valve that injects fuel into the cylinder 12. It is also possible to perform fuel introduction processing through fuel injection into the cylinder 12.

10 ... Internal combustion engine, 11 ... Piston, 12 ... Cylinder, 13 ... Connecting rod, 14 ... Crank shaft, 15 ... Intake passage, 16 ... Airflow meter, 17 ... Throttle valve, 18 ... Fuel injection valve, 19 ... Intake valve, 20 ... ignition device, 21 ... exhaust passage, 22
... Exhaust valve, 23 ... Three-way catalyst device, 24 ... Filter for collecting particulates, 25 ... Air fuel ratio sensor, 26 ... Catalyst exhaust gas temperature sensor, 27 ... Control device, 28 ... Crank angle sensor, 29 ... Vehicle speed sensor , 30 ... Accelerator pedal, 31 ... Accelerator position sensor, 50 ... Torque converter, 51 ... Transmission, 52 ... Wheels, 53 ... Lock-up mechanism.

Claims (1)

A control device applied to a vehicle including an internal combustion engine, a torque converter connected to a crank shaft of the internal combustion engine, and a transmission connected to wheels, and controlling an operating state of the internal combustion engine.
The internal combustion engine includes a fuel injection valve, a cylinder into which an air-fuel mixture containing fuel injected by the fuel injection valve is introduced, an ignition device that ignites the air-fuel mixture introduced into the cylinder by a spark, and the inside of the cylinder. It is equipped with an exhaust passage through which the discharged gas flows and a ternary catalyst device installed in the exhaust passage.
The torque converter includes a lock-up mechanism for performing lock-up in which the crank shaft is directly connected to the transmission.
It is determined that the vehicle speed is equal to or higher than the specified start permitted speed during coasting of the vehicle , and that the engine speed of the internal combustion engine is higher than the lower limit speed at which combustion can be restarted by itself. On condition that the value is equal to or higher than a predetermined value, a fuel introduction process is carried out in which the air-fuel mixture containing the fuel injected by the fuel injection valve is introduced into the exhaust passage without being burned in the cylinder.
When the lockup by the lockup mechanism is performed, the predetermined value is set smaller than when the lockup by the lockup mechanism is not performed.
Internal combustion engine control device.

Images