JP2018076838A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve misfire resistance at the deceleration of a vehicle, in an internal combustion engine in which an EGR gas is refluxed to an intake passage.SOLUTION: A control device of an internal combustion engine comprises a variable compression ratio mechanism 10, an EGR passage 14 and an EGR control valve 15, and controls the internal combustion engine 1 which is mounted to a vehicle. The control device of the internal combustion engine reduces an opening of the EGR valve at a deceleration requirement of the vehicle, maximizes a mechanical compression ratio in a part of cylinders when fuel supply to a part of the cylinders 2 is stopped, predicts the transition of a misfire limit EGR rate and an actual EGR rate at the deceleration of the vehicle about the cylinder to which the fuel supply is not stopped, and sets the mechanical compression ratio so that a minimum value between the misfire limit EGR rate and the actual EGR rate at the deceleration of the vehicle becomes maximum.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, in an internal combustion engine mounted on a vehicle, it is known that a part of the exhaust gas flowing through the exhaust passage is recirculated to the intake passage as EGR gas (for example, Patent Documents 1 to 4). When deceleration of the vehicle is required in such an internal combustion engine, the target engine load factor decreases, and the misfire limit EGR rate decreases accordingly. In this case, if the intake air amount is rapidly decreased to obtain a desired deceleration performance, the actual EGR rate becomes higher than the misfire limit EGR rate, and misfire occurs.

JP, 2006-50500, A JP 2013-11271 A JP 2010-36780 A International Publication No. 2014/141551

  Therefore, in the internal combustion engine described in Patent Document 1, the fuel supply to some cylinders is stopped when the vehicle is requested to decelerate in order to suppress the occurrence of misfire while obtaining the desired deceleration performance. As a result, the engine load factor per cylinder in which the fuel supply is not stopped can be increased, and a decrease in the misfire limit EGR rate can be suppressed.

  However, even when such control is executed, when a large amount of EGR gas is recirculated at the time of vehicle deceleration request, the actual EGR rate becomes higher than the misfire limit EGR rate, and misfire occurs. There is a risk.

  Accordingly, in view of the above problems, an object of the present invention is to improve misfire resistance at the time of deceleration of a vehicle in an internal combustion engine in which EGR gas is recirculated in an intake passage.

In order to solve the above problems, in the present invention, a variable compression ratio mechanism that can change the mechanical compression ratio for each cylinder, an EGR passage that recirculates a part of the exhaust gas flowing through the exhaust passage to the intake passage as EGR gas, An internal combustion engine control device that is provided in the EGR passage and includes an EGR control valve that adjusts an amount of the EGR gas and controls an internal combustion engine mounted on a vehicle.
When the opening of the EGR control valve is reduced and the fuel supply to some cylinders is stopped when the vehicle is requested to decelerate, the mechanical compression ratio in the some cylinders is maximized, and the fuel supply is For cylinders that are not stopped, the transition of the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle is predicted, and the minimum value of the difference between the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle is maximized. A control device for an internal combustion engine is provided in which a mechanical compression ratio is set.

  ADVANTAGE OF THE INVENTION According to this invention, the misfire tolerance at the time of deceleration of a vehicle can be improved in the internal combustion engine in which EGR gas recirculates to the intake passage.

FIG. 1 is a diagram schematically showing an internal combustion engine to which a control device for an internal combustion engine according to the present invention is applied. FIG. 2 is a schematic cross-sectional view of a variable length connecting rod. FIG. 3 is a map showing the relationship between the misfire limit EGR rate and the engine load factor KL. FIG. 4 is a partially enlarged view of a schematic PV diagram in the idle cylinder when the mechanical compression ratio is a high compression ratio or a low compression ratio. FIG. 5 is a time chart of the opening degree of the EGR control valve at the time of deceleration of the vehicle. FIG. 6 is a flowchart showing a control routine of the internal combustion engine in the embodiment of the present invention. FIG. 7 is a block diagram showing a prediction model of the misfire limit EGR rate and the actual EGR rate used in the present embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

<Description of the internal combustion engine as a whole>
FIG. 1 is a diagram schematically showing an internal combustion engine 1 to which a control device for an internal combustion engine according to the present invention is applied. The internal combustion engine 1 is a spark ignition type internal combustion engine in which an air-fuel mixture is ignited by an ignition plug, and is mounted on a vehicle.

  The internal combustion engine 1 includes an engine body 3 provided with a plurality of cylinders 2. In the present embodiment, the number of cylinders 2 is four. An intake manifold 4 and an exhaust manifold 5 are connected to each cylinder 2.

  The intake manifold 4 is connected to an outlet of a compressor 7 a of a turbocharger (supercharger) 7 through an intake pipe 6. The inlet of the compressor 7 a is connected to the air cleaner 8 through the intake pipe 6. A throttle valve 9 driven by a step motor or the like is disposed in the intake pipe 6. Further, an intercooler 13 for cooling the intake air flowing through the intake pipe 6 is disposed around the intake pipe 6. The intercooler 13 may be built in the intake manifold 4. The intake manifold 4 and the intake pipe 6 form an intake passage that guides air into each cylinder 2.

  On the other hand, the exhaust manifold 5 is connected to the inlet of the turbine 7 b of the turbocharger 7 via the exhaust pipe 27. The outlet of the turbine 7 b is connected to the exhaust purification catalyst 29 via the exhaust pipe 27. The exhaust purification catalyst 29 is, for example, a three-way catalyst that purifies HC, CO, NOx, etc. in the exhaust gas. The exhaust manifold 5 and the exhaust pipe 27 form an exhaust passage through which exhaust gas generated by the combustion of the air-fuel mixture is discharged from each cylinder 2.

  The exhaust passage and the intake passage are connected to each other via an exhaust gas recirculation passage (EGR passage) 14. The EGR passage 14 recirculates a part of the exhaust gas flowing through the exhaust passage to the intake passage as EGR gas. The EGR passage 14 is provided with an electronically controlled EGR control valve 15. The EGR control valve 15 adjusts the amount of EGR gas recirculated from the exhaust passage to the intake passage. Further, the EGR passage 14 is provided with an EGR cooler 16 for cooling the EGR gas.

  In the present embodiment, the EGR passage 14 is connected to the exhaust passage downstream of the exhaust purification catalyst 29 and the intake passage upstream of the compressor 7a. Therefore, the internal combustion engine 1 includes a so-called low pressure loop type (LPL type) EGR system. The internal combustion engine 1 may include another type of EGR system. For example, the internal combustion engine 1 may include a so-called high-pressure loop (HPL) EGR system. In this case, the EGR passage is connected to, for example, the exhaust manifold 5 and the intake manifold 4.

  Various controls of the internal combustion engine 1 are executed by an electronic control unit (ECU) 80. Therefore, the ECU 80 functions as a control device for the internal combustion engine 1. The ECU 80 is a digital computer, and includes a ROM (read only memory) 82, a RAM (random access memory) 83, a CPU (microprocessor) 84, an input port 85, and an output port 86 that are connected to each other by a bidirectional bus 81. Outputs of the load sensor 101, the air flow meter 102, and the throttle opening sensor 103 are input to the input port 85 via the corresponding AD converter 87.

  The load sensor 101 generates an output voltage proportional to the depression amount of the accelerator pedal 120. Therefore, the load sensor 101 detects the engine load. The air flow meter 102 is disposed between the air cleaner 8 and the compressor 7 a in the intake passage, and detects the flow rate of air flowing through the intake pipe 6. The throttle opening sensor 103 detects the opening (throttle opening) of the throttle valve 9.

  Further, the input port 85 is connected with a crank angle sensor 108 that generates an output pulse every time the crankshaft rotates, for example, 15 °, and the crank angle sensor 108 detects the engine speed.

  On the other hand, the output port 86 is connected to the fuel injection valve 20, the throttle valve driving step motor, and the EGR control valve 15 through a corresponding drive circuit 88. The fuel injection valve 20 is, for example, an in-cylinder fuel injection valve that injects fuel into the cylinder 2. The fuel injection valve 20 may be a port fuel injection valve that injects fuel into the intake port. The ECU 80 controls the injection timing and amount of fuel injected from the fuel injection valve 20.

  The ECU 80 controls the amount of intake air supplied into the cylinder 2 by controlling the opening degree of the throttle valve 9 via a throttle valve driving step motor. Further, the ECU 80 controls the amount of EGR gas recirculated to the intake passage by controlling the opening degree of the EGR control valve 15.

  The internal combustion engine 1 further includes a variable compression ratio mechanism that can change the mechanical compression ratio for each cylinder 2. The variable compression ratio mechanism is, for example, a variable length connecting rod 10 as shown in FIG. FIG. 2 is a schematic cross-sectional view of the variable length connecting rod 10. A variable length connecting rod 10 is provided in each cylinder 2.

  In the variable length connecting rod 10, the length between the center of the crank receiving opening 41 for receiving the crank pin and the center of the piston pin receiving opening 32 d for receiving the piston pin, that is, the effective length of the variable length connecting rod 10 is changed. To change the mechanical compression ratio. As shown in FIG. 2A, when the effective length of the variable-length connecting rod 10 is increased (becomes L1), the combustion chamber volume when the piston 40 is at the compression top dead center is reduced, and the mechanical compression ratio is increased. Will increase. On the other hand, as shown in FIG. 2B, when the effective length of the variable length connecting rod 10 is reduced (becomes L2), the combustion chamber volume when the piston 40 is at the compression top dead center is increased, and mechanical compression is performed. The ratio decreases. Therefore, the variable length connecting rod 10 can change the mechanical compression ratio into two stages of a high compression ratio and a low compression ratio.

  In the variable length connecting rod 10, the effective length is changed by rotating the eccentric member 32 by the hydraulic piston mechanisms 33 and 34. The supply of hydraulic oil to the hydraulic piston mechanisms 33 and 34 is controlled by a flow direction switching mechanism 35 that is operated by an oil supply device outside the variable length connecting rod body 31. An oil supply device outside the variable length connecting rod body 31 is connected to an output port 86 of the ECU 80 via a corresponding drive circuit 88. Therefore, the ECU 80 can control the mechanical compression ratio in each cylinder 2 via the oil supply device.

  Since the variable length connecting rod 10 is a known technique as described in JP-A-2006-118181, a detailed description of its configuration and control is omitted. The variable compression ratio mechanism may be a variable length connecting rod that can change the mechanical compression ratio in three stages, as described in JP-A-2006-118180. Further, the variable compression ratio mechanism can have any configuration as long as the mechanical compression ratio can be changed for each cylinder.

  The specific configuration of the internal combustion engine 1 such as the cylinder arrangement, the intake / exhaust configuration, and the presence or absence of a supercharger may be different from the configuration shown in FIG.

<Control of internal combustion engine>
When deceleration of the vehicle is required in the internal combustion engine 1 as described above, the target engine load factor decreases. As can be seen from FIG. 3, when the engine load factor KL decreases, the misfire limit EGR rate also decreases. The EGR rate is the ratio of the EGR gas amount to the total gas amount (the sum of the intake air amount and the EGR gas amount) supplied into the cylinder 2. Further, the misfire limit EGR rate is a lower limit value of the EGR rate when misfire occurs in the cylinder 2.

  When deceleration of the vehicle is requested, an amount of EGR gas corresponding to the engine operating state at that time is recirculated to the intake passage. For this reason, even if the opening degree of the EGR control valve 15 is reduced when the vehicle is requested to decelerate, a certain amount of time is required to decrease the actual EGR rate. In particular, when the EGR system of the internal combustion engine 1 is an LPL system, more EGR gas is recirculated to the intake passage as compared with the HPL system, so that the decrease in the actual EGR rate becomes slower. Therefore, if the intake air amount is rapidly decreased to achieve the target engine load factor, the actual EGR rate becomes higher than the misfire limit EGR rate, and misfire may occur.

  Therefore, the control device for an internal combustion engine of the present embodiment executes the following control in order to improve misfire resistance when the vehicle is decelerated. The control device for the internal combustion engine reduces the opening of the EGR control valve 15 and stops the fuel supply to some cylinders 2 when the actual EGR rate at the time of vehicle deceleration request is equal to or greater than a predetermined value. As a result, it is possible to increase the engine load factor per cylinder 2 in which the fuel supply is not stopped (hereinafter referred to as “combustion cylinder”), and to suppress a decrease in the misfire limit EGR rate. Further, by increasing the engine load factor of the combustion cylinder, scavenging of the EGR gas is promoted, and the decrease in the actual EGR rate can be accelerated. Therefore, by stopping the fuel supply to some of the cylinders 2 when the vehicle is requested to decelerate, it is possible to improve the misfire resistance when the vehicle decelerates.

  However, even when the above control is executed, the actual EGR rate becomes higher than the misfire limit EGR rate when a large amount of EGR gas is recirculated to the intake passage when the vehicle is requested to decelerate. There is a risk of misfire. Therefore, in the present embodiment, the mechanical compression ratio of each cylinder 2 is controlled as follows in order to further improve the misfire resistance during deceleration of the vehicle.

  When the control device for the internal combustion engine reduces the opening of the EGR control valve 15 at the time of deceleration request of the vehicle and stops the fuel supply to some of the cylinders 2, the cylinder 2 that has stopped the fuel supply (hereinafter, “ Maximize the mechanical compression ratio in the "rest cylinder". For example, when the internal combustion engine 1 includes a variable compression ratio mechanism that changes the mechanical compression ratio in two stages, the control device for the internal combustion engine sets the mechanical compression ratio of the idle cylinder to the high compression ratio side.

  FIG. 4 is a partially enlarged view of a schematic PV diagram in the idle cylinder when the mechanical compression ratio is a high compression ratio or a low compression ratio. A solid line in the figure indicates a case where the mechanical compression ratio is a high compression ratio (ε = 16), and a broken line in the figure indicates a case where the mechanical compression ratio is a low compression ratio (ε = 10).

  The minimum value of the cylinder volume at the high compression ratio is smaller than the minimum value of the cylinder volume at the low compression ratio. For this reason, the pump loss at the high compression ratio increases by the area of the shaded portion in FIG. 4 as compared with the low compression ratio. Further, the cooling loss at the high compression ratio is larger than the cooling loss at the low compression ratio, and the pressure at the expansion at the high compression ratio is lower than the pressure at the expansion at the low compression ratio. Therefore, by maximizing the mechanical compression ratio in the deactivated cylinder, the negative work amount in the deactivated cylinder can be increased, and as a result, the engine load factor of the combustion cylinder can be further increased. As a result, since the misfire limit EGR rate is increased, the misfire resistance during deceleration of the vehicle can be further improved.

  FIG. 5 shows the mechanical compression ratio in the combustion cylinder, the opening degree of the EGR control valve 15 at the time of deceleration of the vehicle, the opening degree of the throttle valve 9 (throttle opening degree), the engine load factor KL, the misfire limit EGR rate, and the actual EGR rate. It is a time chart. The solid line in the figure shows the case where the mechanical compression ratio is set to a low compression ratio after the vehicle is requested to decelerate, and the broken line in the figure shows the case where the mechanical compression ratio is set to a high compression ratio after the vehicle is requested to decelerate.

  In the illustrated example, the mechanical compression ratio is set to a low compression ratio from time t0 to time t1, and deceleration of the vehicle is requested at time t1. Along with this, the opening degree of the EGR control valve 15 is reduced to reduce the amount of EGR gas, and the throttle opening degree is reduced to reduce the engine load factor KL.

  When the engine load factor KL is the same, the misfire limit EGR rate increases as the mechanical compression ratio increases. For this reason, after time t1, the misfire limit EGR rate at the high compression ratio becomes higher than the misfire limit EGR rate at the low compression ratio. However, the thermal efficiency at a high compression ratio is higher than at a low compression ratio. For this reason, in order to reduce the output torque to the target torque, it is necessary to lower the engine load factor KL at the high compression ratio than at the low compression ratio. As a result, when the vehicle decelerates, the difference between the misfire limit EGR rate at the high compression ratio and the misfire limit EGR rate at the low compression ratio becomes small. Further, at a low compression ratio where the engine load factor KL is high, scavenging of the EGR gas is promoted and the actual EGR rate decreases more rapidly than at a high compression ratio.

  Therefore, for the combustion cylinder, the mechanical compression ratio advantageous for misfire resistance differs depending on the engine operating state at the time of deceleration request of the vehicle, the target torque by the deceleration request, and the like. For this reason, the control device for the internal combustion engine predicts the transition of the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle for the combustion cylinder, and calculates the difference between the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle. Set the mechanical compression ratio so that the minimum value is maximized. This can further improve the misfire resistance during deceleration of the vehicle.

  Hereinafter, the control described above will be described in detail with reference to the flowchart of FIG. FIG. 6 is a flowchart showing a control routine of the internal combustion engine in the embodiment of the present invention. This control routine is repeatedly executed at predetermined time intervals by the ECU 80 after the internal combustion engine 1 is started.

  First, in step S101, it is determined whether a fuel cut (FC) condition is satisfied. For example, it is determined that the fuel cut condition is satisfied when the amount of depression of the accelerator pedal 120 is equal to or less than a first threshold and the engine speed is equal to or higher than a predetermined speed higher than the idling speed. It is determined that the fuel cut condition is not satisfied when the amount of depression of the pedal 120 is greater than the first threshold or the engine speed is less than a predetermined speed higher than the idling speed. The first threshold is, for example, zero.

  When it is determined in step S101 that the fuel cut condition is satisfied, the present control routine proceeds to step S102. In step S102, the fuel supply to all cylinders 2 is stopped.

  Next, in step S103, it is determined whether or not the output torque is equal to or less than the target torque. When it is determined that the output torque is larger than the target torque, the present control routine proceeds to step S104. In step S104, the mechanical compression ratio Rε in the idle cylinder, that is, the mechanical compression ratio in all the cylinders, is increased in order to increase the negative work amount in the idle cylinder and reduce the output torque. For example, when the mechanical compression ratio is changed in two stages by the variable compression ratio mechanism, the mechanical compression ratio Rε in the idle cylinder is set to the high compression ratio side.

  After step S104, this control routine ends. On the other hand, when it is determined in step S103 that the output torque is equal to or less than the target torque, the present control routine ends without changing the mechanical compression ratio.

  When it is determined in step S101 that the fuel cut condition is not satisfied, the present control routine proceeds to step S105. In step S105, it is determined whether there is a vehicle deceleration request. For example, it is determined that there is a vehicle deceleration request when the amount of depression of the accelerator pedal 120 is less than or equal to the second threshold, and it is determined that there is no vehicle deceleration request when the amount of depression of the accelerator pedal 120 is greater than the second threshold. Is done. The second threshold value is larger than the first threshold value in step S101. If it is determined in step S105 that there is a vehicle deceleration request, the control routine proceeds to step S106.

  In step S106, it is determined whether the partial cylinder deactivation condition is satisfied. For example, when the actual EGR rate at the time of vehicle deceleration request is greater than or equal to a predetermined value, it is determined that the partial cylinder deactivation condition is satisfied, and when the actual EGR rate at the time of vehicle deceleration request is less than the predetermined value, partial It is determined that the cylinder deactivation condition is not satisfied. The actual EGR rate at the time of the vehicle deceleration request is calculated based on, for example, the air flow rate detected by the air flow meter 102, the opening degree of the EGR control valve 15, and the like.

  When it is determined in step S106 that the partial cylinder deactivation condition is satisfied, the present control routine proceeds to step S107. In step S107, the opening degree of the EGR control valve 15 is reduced to reduce the amount of EGR gas recirculated to the suction passage. For example, in step S107, the EGR control valve 15 is closed to make the opening degree of the EGR control valve 15 zero.

  Next, in step S108, the fuel supply to some cylinders 2 is stopped in order to increase the engine load factor in the combustion cylinders. Next, in step S109, the mechanical compression ratio Rε in the idle cylinder is set to the maximum value εmax in order to further increase the engine load factor in the combustion cylinder. For example, when the mechanical compression ratio is changed in two stages by the variable compression ratio mechanism, the mechanical compression ratio Rε in the idle cylinder is set to the high compression ratio side.

  Next, in step S110, the transition of the misfire limit EGR rate and the actual EGR rate during the deceleration of the vehicle is predicted for the combustion cylinder. A specific prediction method will be described later. Next, in step S111, based on the prediction result in step S110, the mechanical compression ratio Cε in the fuel cylinder is optimized so that the minimum value of the difference between the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle is maximized. The mechanical compression ratio εopt is set. After step S111, this control routine ends.

  If it is determined in step S105 that there is no vehicle deceleration request, or if it is determined in step S106 that the partial cylinder deactivation condition is not satisfied, the present control routine proceeds to step S112. In step S112, normal control is executed, fuel is supplied to all the cylinders 2, and the mechanical compression ratio in each cylinder 2 is set according to the engine operating state. After step S112, this control routine ends.

<Prediction of misfire limit EGR rate and actual EGR rate>
The prediction of the misfire limit EGR rate and the actual EGR rate in step S110 of FIG. 6 is performed by the following method, for example.

  FIG. 7 is a block diagram showing a prediction model of the misfire limit EGR rate and the actual EGR rate used in the present embodiment. In the prediction model, the throttle opening degree TA is used as one of the input parameters. The value of the throttle opening at every time Δt during deceleration of the vehicle can be estimated from the amount of change in the throttle opening at the start of deceleration of the vehicle. The amount of change in the throttle opening at the start of deceleration of the vehicle is detected by a throttle opening sensor 103. By inputting the value of the throttle opening for each time Δt into the prediction model and performing a loop calculation, it is possible to predict the transition of the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle.

  Further, the mechanical compression ratio in the combustion cylinder is set to a value corresponding to the engine operating state at the time of starting deceleration of the vehicle. For example, it is assumed that the engine load factor in the combustion cylinder is set to the low compression ratio side at the start of deceleration of the vehicle. In this case, in order to calculate the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle when the mechanical compression ratio is set to the low compression ratio side, the change in the throttle opening detected at the start of deceleration of the vehicle The amount may be used.

  On the other hand, when the mechanical compression ratio is set on the high compression ratio side, the engine efficiency is higher than on the low compression ratio side, so the amount of change (decrease) in the throttle opening required for vehicle deceleration is large. Become. For this reason, in order to calculate the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle when the mechanical compression ratio is set to the high compression ratio side, the mechanical compression ratio is set to the low compression ratio side. It is necessary to use a value different from the detected amount of change in the throttle opening. This value is calculated based on the amount of change in the throttle opening detected when the mechanical compression ratio is set to the low compression ratio side using a map or a calculation formula. This method is also applied when the mechanical compression ratio is switched to three or more stages.

  Hereinafter, functions of various models constituting the prediction model will be briefly described. In the throttle model M1, the throttle opening TA, the supercharging pressure Pcmp, the throttle downstream pressure Pm, and the intercooler outlet temperature Tic are input, and the throttle flow rate mt is calculated. The supercharging pressure Pcmp is the pressure in the intake passage between the intercooler 13 and the throttle valve 9, and is calculated in the intercooler model M6. The throttle downstream pressure Pm is a pressure in the intake passage on the downstream side of the throttle valve 9, and is calculated in the intake manifold model M2. The intercooler outlet temperature Tic is a temperature in the intake passage between the intercooler 13 and the throttle valve 9, and is calculated in the intercooler model M6. The throttle flow rate mt is a flow rate of gas passing through the throttle valve 9 per unit time. The throttle model M1 performs the same calculation as the throttle model described in Japanese Patent Application Laid-Open No. 2008-101626.

  In the intake manifold model M2, the throttle flow rate mt calculated in the throttle model M1, the intercooler outlet temperature Tic, and the in-cylinder inflow gas flow rate mc are input, and the intake manifold pressure Pm is calculated. The in-cylinder inflow gas flow rate mc is a flow rate of gas flowing into the cylinder 2 per unit time, and is calculated in the intake valve model M3. The intake manifold pressure Pm is the pressure in the intake manifold 4. In the intake manifold model M2, the same calculation as that of the intake pipe model as described in JP 2008-101626 A is performed.

  In the intake valve model M3, the intake manifold pressure Pm and the like calculated in the intake manifold model M2 are input, and the cylinder inflow gas flow rate mc is calculated. In the intake valve model M3, the same calculation as that of the intake valve model as described in JP 2008-101626 A is performed.

  In the turbo rotation speed model M4, the wastegate valve opening wgv estimated by the operation amount of the wastegate valve (not shown) and the cylinder inflow gas flow rate mc calculated in the intake valve model M3 are input. The rotation speed Ntb is calculated. Note that the diaphragm differential pressure dPwgv of the wastegate valve may be used instead of the wastegate valve opening wgv. The turbo rotation speed model M4 is the same as the turbo rotation speed model as described in JP2012-241625A or International Publication No. 2012/070100.

  In the compressor model M5, the turbo speed Ntb calculated in the turbo speed model M4, the supercharging pressure Pcmp calculated in the intercooler model M6, and the like are input, and the compressor flow rate mcmp and the compressor downstream temperature Tcmp are calculated. The compressor flow rate mcmp is a flow rate of gas passing through the compressor 7a per unit time. The compressor downstream temperature Tcmp is the temperature in the intake passage between the compressor 7a and the intercooler 13. The compressor model M5 is the same as the compressor model described in JP2012-241625A or International Publication No. 2012/070100.

  In the intercooler model M6, the compressor flow rate mcmp and the compressor downstream temperature Tcmp calculated in the compressor model M5 are input, and the supercharging pressure Pcmp and the intercooler outlet temperature Tic are calculated. The intercooler model M6 is the same as the intercooler model described in Japanese Patent Application Laid-Open No. 2012-241625 or International Publication No. 2012/070100.

  By repeating the calculation using the prediction model, the in-cylinder inflow gas flow rate mc for each time Δt during deceleration of the vehicle can be calculated at the start of deceleration of the vehicle. Further, the engine load factor KL is calculated based on the in-cylinder inflow gas flow rate mc and the engine speed using a map or a calculation formula. Further, the misfire limit EGR rate is calculated based on the engine load factor KL using the map as shown in FIG. Therefore, according to the method described above, the transition of the misfire limit EGR rate during deceleration of the vehicle can be predicted at the start of deceleration of the vehicle. In addition, when the mechanical compression ratio is switched to two stages of the high compression ratio side and the low compression ratio side, two types of maps corresponding to the mechanical compression ratio are shown as maps showing the relationship between the misfire limit EGR rate and the engine load factor KL. Is prepared.

  On the other hand, the actual EGR rate during deceleration of the vehicle is calculated as follows. In the EGR valve model M7, the throttle flow rate mt calculated in the throttle model M1 and the opening degree θe of the EGR control valve 15 are input, and the EGR control valve passage gas flow rate megr is calculated.

  Next, in the EGR gas delay model M8, the EGR control valve passage gas flow rate megr calculated in the EGR valve model M7 is input, and the in-cylinder inflow EGR gas flow rate mcegr is calculated. The EGR gas delay model M8 is the same as the EGR gas delay model described in Patent Document 2 (Japanese Patent Laid-Open No. 2013-11271), and is a fresh air convection delay model, an intake pipe advection delay model, and an intake manifold filling delay model. And an intake port advection delay model.

  By repeating the calculation using the prediction model, the in-cylinder inflow EGR gas flow rate mcegr at every time Δt during deceleration of the vehicle can be calculated at the start of deceleration of the vehicle. Further, the actual EGR rate for each time Δt is calculated based on the in-cylinder inflow EGR gas flow rate mcegr and the in-cylinder inflow gas flow rate mc for each time Δt. Therefore, according to the method described above, the transition of the actual EGR rate during deceleration of the vehicle can be predicted at the start of deceleration of the vehicle.

  Note that the prediction model described above can be changed as appropriate according to the configuration of the internal combustion engine 1 (whether a turbocharger is present, whether an air bypass valve is present, the type of EGR system, etc.). For example, when the EGR system provided in the internal combustion engine is an HPL EGR system, a prediction model for calculating the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle is disclosed in Japanese Patent Application Laid-Open No. 2008-101626. A model as described in FIG. 10 or FIG. 1 of WO 2012/070100 may be used.

  The preferred embodiments according to the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.

1 Internal combustion engine 2 Cylinder 10 Variable length connecting rod (variable compression ratio mechanism)
14 EGR passage 15 EGR control valve 80 Electronic control unit (ECU)

Claims (1)

A variable compression ratio mechanism that can change the mechanical compression ratio for each cylinder, an EGR passage that recirculates a part of the exhaust gas flowing through the exhaust passage to the intake passage as EGR gas, and an amount of the EGR gas provided in the EGR passage An internal combustion engine control device for controlling an internal combustion engine mounted on a vehicle and an EGR control valve for adjusting
When the opening of the EGR control valve is reduced and the fuel supply to some cylinders is stopped when the vehicle is requested to decelerate, the mechanical compression ratio in the some cylinders is maximized, and the fuel supply is For cylinders that are not stopped, the transition of the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle is predicted, and the minimum value of the difference between the misfire limit EGR rate and the actual EGR rate during deceleration of the vehicle is maximized. A control device for an internal combustion engine, characterized in that a mechanical compression ratio is set in the internal combustion engine.

Images