JP2019152122A - Internal combustion engine system - Google Patents

Abstract

To set an air quantity sucked into a cylinder at a succeeding valve-opening of an EGR valve to an air quantity corresponding to target torque by taking into consideration a fresh air quantity flowing into an EGR passage at a valve-closing of the EGR valve.SOLUTION: This internal combustion engine system comprises an EGR device for refluxing a part of an exhaust gas of an internal combustion engine to an intake passage as an EGR gas, a throttle valve and a control device. When switching an EGR valve to a valve-opening state from a valve-closing state, the control device calculates a fresh air quantity in the EGR passage being the fresh air quantity existing in the EGR passage in response to an air quantity flowing into the EGR passage at the intake passage side rather than the EGR valve during the valve-closing of the EGR valve, and an air quantity flowing into the EGR passage at the exhaust passage side rather than the EGR valve. Then, the control device corrects an operation amount of the throttle valve so that the target torque of the internal combustion engine can be obtained in response to the fresh air quantity in the EGR passage.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal combustion engine system. More specifically, the present invention relates to an internal combustion engine system including an EGR device that can recirculate a part of exhaust gas of the internal combustion engine to an intake passage as EGR gas.

  Japanese Patent Application Laid-Open No. 2004-133830 describes a technique for suppressing combustion fluctuations caused by fresh air in an intake passage flowing back to the EGR passage and flowing toward the exhaust passage when EGR is introduced into an internal combustion engine equipped with an EGR device and acceleration is transient. The control of is described.

  More specifically, when the intake pressure becomes higher than the exhaust pressure during acceleration transient when the EGR valve is open, fresh air flows backward from the intake passage to the EGR passage, which corresponds to the amount of fresh air flowing backward through the EGR passage. The amount of fresh air sucked into the cylinder is reduced by the amount. For this reason, in the control described in Patent Document 1, when the backflow of fresh air to the EGR passage is predicted during acceleration transient when the EGR valve is open, the amount of fresh air sucked into the cylinder is reduced. The fuel injection amount is corrected to decrease in order to suppress the shift of the air-fuel ratio to the rich side due to the decrease.

  In addition, when the EGR valve is fully closed in a state where the fresh air is flowing backward during acceleration transient when the EGR valve is in the open state, a gas mainly containing the backward flowing fresh air stays in the EGR passage. To do. Therefore, after that, when the gas flow in the EGR passage becomes a forward flow and the EGR valve is opened, the EGR gas containing the backflowed fresh air is sucked into the cylinder until all of the EGR gas is sucked into the cylinder. The amount of fresh air that will be increased. On the other hand, in the control described in Patent Document 1, after the EGR valve is fully closed while fresh air is flowing backward, the EGR passage is in a forward flow state, and the EGR valve is opened when the EGR valve is opened. The fuel injection amount is corrected to decrease until all the EGR gas containing fresh air is sucked into the cylinder. Further, Patent Document 1 calculates the amount of fresh air in the EGR passage by integrating the amount of fresh air flowing back through the EGR passage while the EGR valve is open and the fresh air is flowing back into the EGR passage. It is described that it is done.

JP 2010-138839 A

  Even when fresh air is not flowing backward (ie, forward flow) when the EGR valve is opened, after the EGR valve is fully closed, fresh air is generated in the EGR passage under the condition that the intake pressure is higher than the exhaust pressure. In some cases, some fresh air may flow into the EGR passage closer to the exhaust passage than the EGR valve. In this case, the amount of fresh air that flows into the cylinder when the EGR valve is opened next time increases by the amount of fresh air that flows back into the EGR passage.

  The control described in Patent Document 1 is a control in a case where the EGR valve is fully closed while fresh air is flowing backward while the EGR valve is open, and then the EGR valve is opened, and the reverse flow while the EGR valve is opened. Thus, the fuel injection amount is corrected according to the amount of fresh air flowing into the EGR passage. That is, in Patent Document 1, no consideration is given to the inflow of fresh air into the EGR passage that occurs while the EGR valve is closed.

  Further, in the control of Patent Document 1, correction for increasing or decreasing the fuel injection amount is performed for the purpose of stabilizing combustion against the increase or decrease of the fresh air amount due to the backflow. There will be a deviation between the actual torques. Avoiding this torque deviation by ignition retard is not preferable from the viewpoint of improving fuel efficiency.

  In order to solve the above problems, the present invention considers the amount of fresh air flowing into the EGR passage when the EGR valve is closed, and determines the amount of air sucked into the cylinder when the EGR valve is opened next time. The present invention provides an internal combustion engine system that is improved so that the amount of air can be adjusted according to torque.

  The internal combustion engine system of the present invention includes an EGR device, an actuator, and a control device. The EGR device is an EGR device that recirculates a part of the exhaust gas of the internal combustion engine to the intake passage as EGR gas, and is installed in the middle of the EGR passage that connects the exhaust passage and the intake passage of the internal combustion engine. And an EGR valve that adjusts the recirculation amount of the EGR gas. The actuator is an actuator that changes the amount of air taken into the cylinder of the internal combustion engine. The control device is configured to control an actuator by determining an operation amount of the actuator so that a target torque of the internal combustion engine is achieved. Furthermore, the control device is configured as follows. That is, when the EGR valve is switched from the closed state to the open state, the amount of fresh air that flows into the EGR passage closer to the intake passage than the EGR valve and the exhaust passage side from the EGR valve when the EGR valve is closed The amount of fresh air in the EGR passage, which is the amount of fresh air in the EGR passage, is calculated according to the amount of fresh air that has flowed into the EGR passage. Then, according to the fresh air amount in the EGR passage, the operation amount of the actuator is corrected so that the target torque of the internal combustion engine is achieved.

  According to the internal combustion engine system of the present invention, based on the amount of fresh air that has flowed into the EGR passage while the EGR valve is closed, the operation amount of the actuator that changes the amount of air sucked into the cylinder the next time the EGR valve is opened. Is corrected. Therefore, the torque actually output by the internal combustion engine can be brought close to the target torque, the air-fuel ratio controllability can be improved, and the drivability and fuel efficiency can be improved.

It is a figure which shows typically the structure of the internal combustion engine system of embodiment of this invention. It is a flowchart for demonstrating the routine of control which a control apparatus performs in embodiment of this invention. It is a figure for demonstrating an example of the calculation method of the EGR valve passage flow rate in embodiment of this invention. It is a figure which shows an example of the ratio of the fresh air quantity with respect to the EGR gas quantity in an EGR channel | path at the time of EGR valve opening. It is a figure for demonstrating the relationship between the corrected amount with respect to the intake temperature difference and intake air amount in other embodiment of this invention.

Embodiment.
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing the configuration of the internal combustion engine system of the present embodiment. The system according to the present embodiment includes an internal combustion engine (hereinafter simply referred to as “engine”) 2 mounted as a power unit in an automobile. The engine 2 has four cylinders. However, the number of cylinders is not limited.

  The engine 2 includes a supercharger 10. The supercharger 10 includes a turbine 12 that is operated by exhaust energy of exhaust gas, and a compressor 14 that is integrally connected to the turbine 12 and that is rotationally driven by exhaust energy of exhaust gas input to the turbine 12. Yes.

  The intake passage 4 of the engine 2 is branched by an intake manifold 5 and communicates with the intake port of each cylinder of the engine 2. The exhaust passage 6 of the engine 2 is branched by an exhaust manifold 7 and communicates with the exhaust ports of the cylinders of the engine 2.

  An air cleaner 20 is provided near the inlet of the intake passage 4 of the engine 2. In the intake passage 4 downstream of the air cleaner 20, a compressor 14, an intercooler 22, and a throttle valve 24 of the supercharger 10 are installed in order from the upstream side of intake air. The air (that is, fresh air) sucked through the air cleaner 20 is compressed by the compressor 14 of the supercharger 10, then cooled by the intercooler 22, passes through the throttle valve 24, and is taken in by the intake manifold 5. It is distributed to the intake port (not shown) of the cylinder. In the present embodiment, the throttle valve 24 functions as an actuator that can change the amount of air sucked into the cylinder according to the target air amount.

  A turbine 12 of the supercharger 10 is installed in the exhaust passage 6, and an S / C (Start Converter) catalyst 26 and U / F (Under Floor) for purifying exhaust gas are disposed downstream of the turbine 12. A catalyst 28 is installed.

  The engine 2 includes an EGR (Exhaust Gas Recirculation) device 30. The EGR device 30 has an EGR passage 32. One end of the EGR passage 32 is connected to the intake passage 4 downstream of the throttle valve 24, and the other end is connected to a portion of the exhaust passage 6 between the S / C catalyst 26 and the U / F catalyst 28. Through the EGR passage 32, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 4 as EGR gas, that is, external EGR can be performed.

  The EGR passage 32 includes an EGR cooler 34 and an EGR valve 36 in order from the upstream of the flow of EGR gas (hereinafter referred to as “forward flow”) from the exhaust passage 6 side to the intake passage 4 side. is set up. The EGR valve 36 can change the cross-sectional area of the EGR passage 32 and is used to adjust the amount of EGR gas flowing into the intake passage.

  This internal combustion engine system has a control device. The control device includes an air cleaner downstream pressure sensor 50, a supercharging pressure sensor 51, an intake pressure sensor 52, an intake air temperature sensor 53, a turbine upstream pressure sensor 54, an S / C downstream pressure sensor 55, and the like. Sensor is connected. The control device controls the operation of the engine 2 by operating various devices and actuators included in the engine 2 based on information obtained by these sensors. The control device is an ECU (Electronic Control Unit) having at least one CPU, at least one ROM, and at least one RAM. However, the control device may be composed of a plurality of ECUs. In the control device, various functions related to engine control are realized by loading a program stored in the ROM into the RAM and executing it by the CPU.

  By the way, as shown in FIG. 1, in a system in which the EGR passage 32 is connected to a portion where the pressure in the intake passage 4 is relatively high, the pressure on the intake side of the EGR passage 32 depends on the operating conditions. The pressure may be higher. In such a case, fresh air may flow into the EGR passage 32 not only during the opening of the EGR valve 36 but also when the EGR valve 36 is in a fully closed state. Fresh air that has flowed into the EGR passage 32 while the EGR valve 36 is closed flows into the cylinder when the EGR valve 36 is opened. For this reason, at the start of introduction of EGR, the amount of fresh air flowing into the cylinder may be larger than the assumed fresh air amount.

  On the other hand, when it is predicted that fresh air will flow from the EGR passage 32 when the EGR valve 36 is opened, the control device of the present embodiment estimates the amount of fresh air that flows in and estimates the fresh air amount. In accordance with the value, control is performed to correct the amount of intake air so that the amount of fresh air sucked into the cylinder becomes the amount of fresh air necessary to achieve the target torque. More specifically, the amount of intake air introduced from the intake passage 4 side is controlled by correcting the operation amount of the throttle valve 24. Hereinafter, the control executed by the control device will be described more specifically.

  FIG. 2 is a flowchart for explaining a control routine executed by the control device. In the routine of FIG. 2, first, in step S101, it is determined whether or not the introduction of EGR has started. That is, it is determined whether or not the EGR valve 36 has been switched from the closed state to the open state.

  If it is determined in step S101 that the introduction of EGR has been started, the process proceeds to step S102, where the EGR valve passage flow rate Gegr is calculated. The EGR valve passage flow rate is the flow rate of the gas passing through the EGR valve 36, and is calculated with the forward flow direction plus and the reverse flow direction minus.

  FIG. 3 shows an example of a method for calculating the EGR valve passage flow rate Gegr. As shown in FIG. 3, the pressure difference between the outlet pressure of the EGR passage 32 (ie, the pressure in the intake passage 4) and the inlet pressure (ie, the pressure in the exhaust passage 6) (hereinafter simply referred to as “differential pressure”). Also has a correlation with the EGR valve passage flow rate Gegr. In the present embodiment, such a correlation is obtained by experiments or the like, and is stored in advance in the control device as a map of the EGR valve passage flow rate Gegr with the differential pressure as an axis.

  In step S102, the current value of the exhaust pressure P6 in the exhaust passage 6 measured by the S / C downstream pressure sensor 55 and the current value of the intake pressure Pm in the intake passage 4 measured by the intake pressure sensor 52 are calculated. Based on the differential pressure, the EGR valve passage flow rate Gegr is calculated according to the map. Further, since the EGR valve passage flow rate Gegr changes according to the opening degree of the EGR valve 36, the engine speed, etc., the map used for calculating the EGR valve passage flow rate Gegr is the opening degree of the EGR valve 36 and the engine speed. A plurality of maps may be used.

  Next, the process proceeds to step S103, and the amount of fresh air in the EGR passage 32 (hereinafter also referred to as “the amount of fresh air in the EGR passage”) Gn is calculated. FIG. 4 shows an example of the ratio of the fresh air amount Gn in the EGR passage to the EGR gas amount in the EGR passage 34 when the EGR valve is opened.

  As shown by the solid line a in FIG. 4, the ratio between the fresh air amount and the EGR gas amount in the EGR passage 32 downstream of the EGR valve 36 (that is, the intake passage side) when the EGR valve is opened is shown in FIG. As shown by a solid line a in FIG. 4, the height increases as it approaches the intake passage 4 side. Further, the ratio between the fresh air amount and the EGR gas amount indicated by the solid line a varies depending on the differential pressure when the EGR valve is closed and the valve closing time of the EGR valve 36. Therefore, in the present embodiment, the change in the ratio of the fresh air amount in the EGR passage 32 on the downstream side (that is, the intake passage side) from the EGR valve 36 at the start of the EGR valve and the differential pressure when the EGR valve is closed. And the valve closing time of the EGR valve 36 are obtained by experiments or the like and stored in the control device as a map or an arithmetic expression.

  Even when the EGR valve 36 is closed, for example, fresh air is generated upstream (exhaust passage side) from the EGR valve 36 due to, for example, a delay in closing the EGR valve 36 or poor closing of the EGR valve 36. It may leak out. The curve (broken line b in FIG. 4) showing the ratio of the fresh air amount to the EGR gas upstream (exhaust passage side) from the EGR valve 36 tends to be different from the downstream side of the EGR valve 36. It varies depending on factors such as the differential pressure when the valve is closed, the closing time of the EGR valve 36, or the differential pressure when the EGR valve 36 is closed poorly, the amount of delay in closing the EGR valve 36, and the presence or absence of a closed failure. . Therefore, in the present embodiment, the relationship between the change in the ratio of the fresh air amount in the EGR passage 32 upstream of the EGR valve 36 at the start of the EGR valve 36 and each factor is obtained by experiments and is mapped to the control device. Alternatively, it is stored as an arithmetic expression or the like.

  In step S103, the volume of the EGR passage 32 and the calculation formula are calculated in step S102 using a map or arithmetic expression of the change in the ratio of the fresh air quantity upstream and downstream of the EGR valve 36 as shown in FIG. From the EGR valve passage flow rate Gegr, the EGR passage fresh air amount Gn flowing into the cylinder from the EGR passage 32 this time is calculated.

  Note that the rate of change in the fresh air amount as shown in FIG. 4 advances to the intake passage side by the amount of gas corresponding to the EGR valve passage flow rate Gegr each time this routine is repeated. That is, in FIG. 4, when the EGR passage fresh air amount Gn in the interval t1 to t2 corresponding to the EGR valve passage flow rate Gegr is calculated for the first time after the EGR valve opening is started, The EGR passage fresh air amount Gn for t2 to t3 intervals corresponding to the EGR valve passage flow rate Gegr is calculated, and when the integrated value of the EGR valve passage flow rate Gegr finally becomes the volume of the EGR passage 32, EGR The fresh air amount Gn in the passage becomes zero. In addition, about the fresh air quantity of the downstream of the EGR valve 36, it is good also as a structure estimated using a Tylor dispersion | distribution model.

  Next, the process proceeds to step S104, where it is determined whether or not the EGR valve passage flow rate Gegr is greater than 0 and the EGR passage fresh air amount Gn is greater than 0. In step S104, when the EGR valve passage flow rate Gegr is larger than 0 and the fresh air amount Gn in the EGR passage is larger than 0, it is determined that fresh air is flowing into the cylinder together with the EGR gas from the EGR passage 32. it can.

  Therefore, in this case, the process proceeds to step S105, and the intake air amount is corrected in accordance with the EGR passage fresh air amount Gn. In other words, the operation amount of the throttle valve 24 is corrected so that the amount of fresh air that is reduced by the amount of fresh air Gn in the EGR passage flows from the intake passage 4 side, and the opening of the throttle valve 24 is adjusted accordingly. Be controlled.

  On the other hand, if it is determined in step S104 that the condition that the EGR valve passage flow rate Gegr is greater than 0 and the EGR passage fresh air amount Gn is greater than 0 does not hold, the routine proceeds to step S201, where the EGR passage 32 After it is determined that there is no inflow of fresh air, and the correction amount for the intake air amount is set to 0, the current process ends.

  If it is determined in step S101 that the introduction of EGR has not been started, the calculation of the fresh air amount Gn in the EGR passage is performed in step S301, and then the current process ends. Note that the method for calculating the fresh air amount Gn in the EGR passage in step S301 is the same as the method for calculating the fresh air amount described in step S103.

  As described above, according to the present embodiment, the intake air amount is corrected in accordance with the fresh air amount Gn in the EGR passage stagnating in the EGR passage 32 at the start of EGR introduction by opening the EGR valve. The EGR passage fresh air amount Gn staying in the EGR passage 32 is calculated in consideration of the amount of fresh air flowing into the exhaust passage side of the EGR passage 32 while the EGR valve 36 is closed. Accordingly, the amount of air introduced into the cylinder can be brought close to the amount of air necessary for realizing the target torque, the fuel efficiency is improved, and the actual torque and the target torque resulting from the inflow of fresh air from the EGR passage 32 are improved. The difference with the can be kept small.

<Other embodiments>
When the pressure on the intake side and the pressure on the exhaust side of the EGR passage 32 are the same, no EGR gas flows in the EGR passage, so that fresh air stays in the EGR passage. In this case, the gas temperature increases. The control device according to the present embodiment may have a configuration in which a configuration for correcting the gas temperature rise is added. Specifically, as shown in FIG. 5, the correction amount for the intake air amount is increased as the difference in intake air temperature, which is the difference between the intake air temperature flowing into the cylinder and the intake air temperature in the intake manifold, is larger. Thus, the throttle valve 24 and the like may be controlled based on the corrected intake air amount.

  Even when the EGR valve 36 is closed, fresh air remains in the EGR passage 32. Accordingly, in this case as well, as shown in FIG. 5, the intake air amount may be corrected in accordance with the intake air temperature difference.

  In the present embodiment, the EGR device in which the intake passage 4 downstream of the throttle valve 24 and the exhaust passage 6 downstream of the S / C catalyst 26 are connected by the EGR passage 32 has been described. However, the control at the start of the introduction of EGR in the present embodiment is such that the intake side pressure can be larger than the exhaust side pressure as in other EGR devices, for example, HPL (High Pressure Loop) -EGR devices and natural intake engines. It can be applied to an EGR device or the like.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

2 Engine 4 Intake passage 5 Intake manifold 6 Exhaust passage 7 Exhaust manifold 10 Supercharger 12 Turbine 14 Compressor 20 Air cleaner 22 Intercooler 24 Throttle valve 26 S / C catalyst 28 U / F catalyst 30 EGR device 32 EGR passage 34 EGR cooler 36 EGR valve 50 Air cleaner downstream pressure sensor 51 Supercharging pressure sensor 52 Intake pressure sensor 53 Intake temperature sensor 54 Turbine upstream pressure sensor 55 S / C downstream pressure sensor

Claims (1)

An EGR device that recirculates a part of the exhaust gas of the internal combustion engine to the intake passage as EGR gas;
An actuator for changing the amount of air taken into the cylinder of the internal combustion engine;
A control device configured to control the actuator;
An internal combustion engine system comprising:
The EGR device
An EGR passage connecting an exhaust passage and an intake passage of the internal combustion engine;
An EGR valve that is installed in the middle of the EGR passage and adjusts the recirculation amount of the EGR gas;
With
The controller is
When switching the EGR valve from the closed state to the open state,
While the EGR valve is closed, the amount of fresh air that flows into the EGR passage closer to the intake passage than the EGR valve, and the amount of fresh air that flows into the EGR passage closer to the exhaust passage than the EGR valve , And calculates the fresh air amount in the EGR passage, which is the fresh air amount in the EGR passage,
Correcting the operation amount of the actuator according to the fresh air amount in the EGR passage so that a target torque of the internal combustion engine is achieved;
An internal combustion engine system configured as described above.

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