JP7632196B2 - Control device for internal combustion engine system - Google Patents

Description

The present invention relates to a control device for an internal combustion engine system that has an EGR system that returns a portion of the exhaust gas to the intake air and a turbocharger.

Conventionally, an EGR system is a typical system for reducing NOx emissions from an internal combustion engine mounted on a vehicle. Examples of components of an EGR system include an EGR pipe, an EGR cooler, a bypass pipe, an adjustment valve, and an EGR valve. The EGR pipe is a pipe connected from the exhaust path to the intake path and flows a part of the exhaust gas from the exhaust path to the intake path as EGR gas. The EGR cooler is arranged in the EGR pipe and adjusts the temperature of the EGR gas in the EGR pipe (lowers the temperature). The bypass pipe is a pipe branched from the EGR pipe upstream of the EGR cooler and connected to the EGR pipe downstream of the EGR cooler to bypass the EGR cooler. The adjustment valve is provided at the connection point between the EGR pipe and the bypass pipe and adjusts the ratio of the amount of EGR gas passing through the EGR cooler to the amount of EGR gas passing through the bypass pipe. The EGR valve adjusts the opening of the EGR pipe to adjust the flow rate of EGR gas returned from the exhaust path to the intake path. The EGR system returns part of the exhaust gas to the intake as EGR gas, lowering the oxygen concentration of the intake air in the cylinder, and reducing the amount of NOx generated by increasing the heat capacity with water vapor and lowering the temperature of the combustion gas.

For example, the opening of the EGR valve is adjusted by feedback control so that the actual EGR rate, which is the amount of EGR gas relative to the amount of intake air in the cylinder (fresh intake air amount + EGR gas amount), approaches the target EGR rate calculated according to the operating state of the internal combustion engine. In recent years, there has been a trend to increase the amount of EGR gas over a wider operating range in order to further reduce NOx emissions (there is a trend for the target EGR rate to be set to a higher value over a wider operating range).

If EGR is performed during rapid acceleration, with the accelerator pedal depressed heavily, the amount of fresh air intake is reduced by the amount of EGR gas flow. During such acceleration, the target EGR rate is instantaneously changed depending on the driving condition. However, because the opening of the EGR valve is tracked by feedback control, even if the target EGR rate is instantaneously reduced, the change in the opening of the EGR valve is slow, making it difficult to avoid an excess EGR state when acceleration begins. If there is an excess EGR state during acceleration, the amount of fuel injected will be excessive compared to the amount of fresh air intake, which is undesirable as it can lead to poor acceleration and smoke generation.

For example, in the engine exhaust gas recirculation device described in Patent Document 1, when the amount of change in accelerator opening per unit time (accelerator operation speed) is equal to or greater than a first judgment value, it is judged that the engine is required to accelerate, and a command is issued to fully close the EGR valve. In addition, in the engine exhaust gas recirculation device of Cited Document 1, when the demand for acceleration based on the amount of change in accelerator opening per unit time disappears and the accelerator opening is equal to or less than a second judgment value, the command to fully close the EGR valve is released.

JP 2014-122613 A

In the exhaust gas recirculation device of the engine described in Patent Document 1, when the accelerator is suddenly depressed (accelerator operation speed is high) and acceleration is requested, the EGR valve is quickly fully closed based on the accelerator operation speed. This avoids a state in which the amount of fresh air intake is insufficient (excessive EGR state), and prevents deterioration of acceleration and generation of smoke. Note that while deterioration of acceleration and generation of smoke can be avoided during the period in which the EGR valve is fully closed, the amount of NOx generated increases. In Patent Document 1, the change amount per unit time of the accelerator opening (accelerator operation speed) is used to switch whether or not the EGR valve is fully closed when acceleration is requested, but when the vehicle speed is relatively low, the amount of fresh air intake is likely to be insufficient when acceleration is requested, and when the vehicle speed is relatively high, the amount of fresh air intake is often not insufficient when acceleration is requested. For this reason, it may not be possible to properly determine whether the acceleration request is one in which the amount of fresh air intake is insufficient. In other words, the exhaust gas recirculation system for the engine described in Cited Document 1 may close the EGR valve completely when acceleration is required even if the amount of fresh air intake is sufficient, which is undesirable because it may increase the amount of NOx generated more than necessary.

The present invention was devised in light of these points, and aims to provide a control device for an internal combustion engine system that, when a driver requests acceleration, can more appropriately determine whether the acceleration request results in an insufficient amount of fresh air intake, thereby preventing deterioration of acceleration and the generation of smoke, as well as further reducing the amount of NOx generated.

In order to solve the above problems, a first aspect of the present invention is a control device for an internal combustion engine system, the internal combustion engine system including an internal combustion engine, an EGR valve that adjusts an EGR amount that returns a portion of the exhaust gas of the internal combustion engine to the intake air of the internal combustion engine, a supercharger that supercharges the intake air of the internal combustion engine, and the control device that detects the operating state of the internal combustion engine and controls the internal combustion engine based on the operating state. The control device has a fresh air compensation acceleration request occurrence determination unit that determines that a fresh air compensation acceleration request has not occurred if it is determined that the acceleration request is an acceleration request for which the fresh air intake amount of the internal combustion engine is not insufficient based on a supercharging-related amount related to supercharging in the operating state of the internal combustion engine including input of an acceleration request from the driver, and determines that the fresh air compensation acceleration request has occurred if it is determined that the acceleration request is an acceleration request for which the fresh air intake amount is insufficient; a fresh air compensation acceleration request termination determination unit that determines whether the acceleration request has ended after transitioning from an acceleration request for which the fresh air intake amount is insufficient to an acceleration request for which the fresh air intake amount is not insufficient based on the supercharging-related amount; and an EGR reduction unit during fresh air compensation acceleration request that forcibly reduces the opening of the EGR valve during a fresh air compensation acceleration request period from when it is determined that the fresh air compensation acceleration request has occurred to when it is determined that the acceleration request has ended. The control device is a control device for an internal combustion engine system, and when the fresh air compensation acceleration request occurrence judgment unit judges whether or not the acceleration request is one in which the fresh air intake amount is insufficient based on the supercharging-related amount, the control device calculates a supercharging pressure deviation by subtracting an actual supercharging pressure, which is the actual supercharging pressure of the internal combustion engine, from a target supercharging pressure, which is the supercharging pressure of the internal combustion engine to be a target calculated based on the operating state, and judges that the fresh air compensation acceleration request, which is an acceleration request in which the fresh air intake amount is insufficient, has occurred if the fluctuation amount of the supercharging pressure deviation over time, which is obtained by subtracting the previous supercharging pressure deviation from the current supercharging pressure deviation, is equal to or greater than a fresh air compensation acceleration request judgment threshold.

Next, a second invention of the present invention is a control device for an internal combustion engine system related to the first invention described above, wherein the control device is a control device for an internal combustion engine system which calculates the fresh air replenishment acceleration request occurrence determination threshold value based on the operating state in the fresh air replenishment acceleration request occurrence determination unit.

Next, a third invention of the present invention is a control device for an internal combustion engine system according to the first or second invention, wherein when the control device determines whether the acceleration request has ended in the fresh air supplementary acceleration request end determination unit, the control device calculates a feasible target boost pressure, which is a boost pressure for determining the end of an acceleration request after an acceleration request in which the fresh air intake amount is insufficient has been transitioned to an acceleration request in which the fresh air intake amount is not insufficient, based on the operating state and a map in which the feasible target boost pressure according to the operating state is set, or calculates it using each parameter of the operating state, and determines that the acceleration request has ended when the actual boost pressure, which is the actual boost pressure of the internal combustion engine, becomes equal to or greater than the feasible target boost pressure. Alternatively, a feasible target supercharging pressure, which is a supercharging pressure for determining the end of an acceleration request after transitioning from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient , is calculated based on the operating state and a map in which the feasible target supercharging pressure corresponding to the operating state is set, or is calculated using each parameter of the operating state, and the supercharger driving energy predicted to be required to be input to the supercharger in order to make the supercharging pressure the feasible target supercharging pressure is used to determine the end of an acceleration request after transitioning from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient. a control device for an internal combustion engine system that calculates a realizable target driving energy, which is a supercharger driving energy for a specified period of time, based on a map in which the supercharger driving energy corresponding to the supercharging pressure and the operating state is set and on the realizable target supercharging pressure and the operating state, or calculates it using the realizable target supercharging pressure and each parameter of the operating state, and determines that the acceleration request has ended when actual driving energy, which is the supercharger driving energy actually input to the supercharger and is calculated using each parameter of the operating state, becomes equal to or greater than the realizable target driving energy.

Next, a fourth invention of the present invention is a control device for an internal combustion engine system relating to any one of the first to third inventions above, wherein the control device is a control device for an internal combustion engine system, in which the EGR reduction section at the time of fresh air replenishment acceleration request reduces the opening degree of the EGR valve in accordance with the operating state during a period of acceleration request in which the fresh air intake amount is insufficient during the fresh air replenishment acceleration request period.

Next, a fifth invention of the present invention is a control device for an internal combustion engine system according to any one of the first to fourth inventions above, wherein the control device is a control device for an internal combustion engine system, in which, in the EGR reduction section during fresh air supplementary acceleration request, during a period of acceleration request in which the fresh air intake amount is not insufficient during the fresh air supplementary acceleration request period, the opening degree of the EGR valve that was reduced during the period of acceleration request in which the fresh air intake amount is insufficient is maintained.
A sixth aspect of the present invention is a control device for an internal combustion engine system, the internal combustion engine system including an internal combustion engine, an EGR valve that adjusts an EGR amount that returns a portion of the exhaust gas of the internal combustion engine to the intake air of the internal combustion engine, a supercharger that supercharges the intake air of the internal combustion engine, and the control device that detects an operating state of the internal combustion engine and controls the internal combustion engine based on the operating state. The control device has a fresh air compensation acceleration request occurrence determination unit that determines that a fresh air compensation acceleration request has not occurred if it is determined that the acceleration request is an acceleration request for which the fresh air intake amount of the internal combustion engine is not insufficient based on a supercharging-related amount related to supercharging in the operating state of the internal combustion engine including input of an acceleration request from the driver, and determines that the fresh air compensation acceleration request has occurred if it is determined that the acceleration request is an acceleration request for which the fresh air intake amount is insufficient; a fresh air compensation acceleration request termination determination unit that determines whether the acceleration request has ended after transitioning from an acceleration request for which the fresh air intake amount is insufficient to an acceleration request for which the fresh air intake amount is not insufficient based on the supercharging-related amount; and an EGR reduction unit during fresh air compensation acceleration request that forcibly reduces the opening of the EGR valve during a fresh air compensation acceleration request period from when it is determined that the fresh air compensation acceleration request has occurred to when it is determined that the acceleration request has ended. The control device, when judging whether the acceleration request has ended in the fresh air supplement acceleration request end judgment unit, calculates a realizable target supercharging pressure, which is a supercharging pressure for judging the end of an acceleration request after transitioning from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient, based on a map in which the realizable target supercharging pressure corresponding to the operating state is set and the operating state, or calculates it using each parameter of the operating state, and judges that the acceleration request has ended when an actual supercharging pressure, which is the supercharging pressure of the actual internal combustion engine, becomes equal to or higher than the realizable target supercharging pressure, or calculates a realizable target supercharging pressure, which is a supercharging pressure for judging the end of an acceleration request after transitioning from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient , based on a map in which the realizable target supercharging pressure corresponding to the operating state is set and the operating state, or calculates it using each parameter of the operating state and calculates a realizable target driving energy, which is supercharger driving energy predicted to need to be input to the supercharger in order to set the supercharging pressure to the realizable target supercharging pressure, based on a map in which the supercharger driving energy corresponding to the supercharging pressure and the operating state is set, and based on the realizable target supercharging pressure and the operating state, or calculates a realizable target driving energy, which is supercharger driving energy predicted to need to be input to the supercharger in order to set the supercharging pressure to the realizable target supercharging pressure, based on the operating state, or calculates a realizable target driving energy, which is supercharger driving energy actually input to the supercharger, based on the realizable target driving energy calculated using the parameters of the operating state, and determines that the acceleration request has ended when the actual driving energy calculated using the parameters of the operating state becomes equal to or greater than the realizable target driving energy.
A seventh aspect of the present invention is a control device for an internal combustion engine system, the internal combustion engine system including an internal combustion engine, an EGR valve that adjusts an EGR amount that returns a portion of the exhaust gas of the internal combustion engine to the intake air of the internal combustion engine, a supercharger that supercharges the intake air of the internal combustion engine, and the control device that detects an operating state of the internal combustion engine and controls the internal combustion engine based on the operating state. The control device has a fresh air compensation acceleration request occurrence determination unit that determines that a fresh air compensation acceleration request has not occurred if it is determined that the acceleration request is an acceleration request for which the fresh air intake amount of the internal combustion engine is not insufficient based on a supercharging-related amount related to supercharging in the operating state of the internal combustion engine including input of an acceleration request from the driver, and determines that the fresh air compensation acceleration request has occurred if it is determined that the acceleration request is an acceleration request for which the fresh air intake amount is insufficient; a fresh air compensation acceleration request termination determination unit that determines whether the acceleration request has ended after transitioning from an acceleration request for which the fresh air intake amount is insufficient to an acceleration request for which the fresh air intake amount is not insufficient based on the supercharging-related amount; and an EGR reduction unit during fresh air compensation acceleration request that forcibly reduces the opening of the EGR valve during a fresh air compensation acceleration request period from when it is determined that the fresh air compensation acceleration request has occurred to when it is determined that the acceleration request has ended. The control device is a control device for an internal combustion engine system in which, in the EGR reduction section during fresh air supplementary acceleration request, during a period of acceleration request in which the fresh air intake amount is insufficient during the fresh air supplementary acceleration request period, the opening degree of the EGR valve is reduced in accordance with the operating condition.
An eighth aspect of the present invention is a control device for an internal combustion engine system, the internal combustion engine system including an internal combustion engine, an EGR valve that adjusts an EGR amount that returns a portion of the exhaust gas of the internal combustion engine to the intake air of the internal combustion engine, a supercharger that supercharges the intake air of the internal combustion engine, and the control device that detects an operating state of the internal combustion engine and controls the internal combustion engine based on the operating state. The control device has a fresh air compensation acceleration request occurrence determination unit that determines that a fresh air compensation acceleration request has not occurred if it is determined that the acceleration request is an acceleration request for which the fresh air intake amount of the internal combustion engine is not insufficient based on a supercharging-related amount related to supercharging in the operating state of the internal combustion engine including input of an acceleration request from the driver, and determines that the fresh air compensation acceleration request has occurred if it is determined that the acceleration request is an acceleration request for which the fresh air intake amount is insufficient; a fresh air compensation acceleration request termination determination unit that determines whether the acceleration request has ended after transitioning from an acceleration request for which the fresh air intake amount is insufficient to an acceleration request for which the fresh air intake amount is not insufficient based on the supercharging-related amount; and an EGR reduction unit during fresh air compensation acceleration request that forcibly reduces the opening of the EGR valve during a fresh air compensation acceleration request period from when it is determined that the fresh air compensation acceleration request has occurred to when it is determined that the acceleration request has ended. The control device is a control device for an internal combustion engine system, in which, in the EGR reduction section during fresh air replenishment acceleration request period, during an acceleration request period in which the fresh air intake amount is not insufficient, the opening degree of the EGR valve that was reduced during the acceleration request period in which the fresh air intake amount is insufficient is maintained.

According to the first invention, when a driver requests acceleration, the control device determines whether the acceleration request is one in which the amount of fresh air intake is insufficient based on a supercharging-related amount related to supercharging. If the control device determines that the acceleration request is one in which the amount of fresh air intake is insufficient, the control device forcibly reduces the opening of the EGR valve to avoid a shortage of the amount of fresh air intake. Since the cylinder of the internal combustion engine is filled with intake air that is a mixture of fresh air and EGR gas and supercharged by the supercharger, the supercharging-related amount includes a fresh air-related amount related to fresh air. In other words, determining whether the amount of fresh air intake is insufficient based on the supercharging-related amount can more appropriately determine whether the acceleration request is one in which the amount of fresh air intake is insufficient compared to determining whether the acceleration request is one in which the amount of fresh air intake is insufficient based on the accelerator opening. Therefore, by more appropriately determining whether the acceleration request is one in which the amount of fresh air intake is insufficient (an acceleration request that requires a forced reduction in the amount of the EGR valve), in addition to suppressing deterioration of acceleration and generation of smoke, the amount of NOx generated can be further reduced.

According to the first aspect of the present invention , when determining whether the acceleration request will result in a shortage of the fresh air intake amount based on the supercharging-related amount, the determination is made based on the deviation between the target supercharging pressure and the actual supercharging pressure. Therefore, it is possible to more appropriately determine whether the acceleration request will result in a shortage of the fresh air intake amount, compared to when the acceleration request will result in a shortage of the fresh air intake amount based on the accelerator opening.

According to the first aspect of the present invention , when the amount of change in the supercharging pressure deviation with respect to time becomes equal to or greater than the fresh air compensation acceleration request determination threshold, it is determined that the acceleration request is one in which the fresh air intake amount is insufficient. This makes it possible to more appropriately determine whether the acceleration request is one in which the fresh air intake amount is insufficient.

According to the second aspect of the present invention , the fresh air compensation acceleration request determination threshold is calculated (changed) based on the operating state, thereby making it possible to more appropriately determine whether or not the acceleration request will result in an insufficient amount of fresh air intake.

It is preferable to appropriately determine the start timing of the fresh air compensation acceleration request period in which the opening of the EGR valve is forcibly reduced, and then to appropriately determine the end timing. If the end timing is determined too early, the acceleration performance may deteriorate and smoke may be generated, and if the end timing is determined too late, the opening of the EGR valve is forcibly reduced for a longer period than necessary, which increases the amount of NOx generated more than necessary. Therefore, in the third invention , by utilizing the fact that the actual boost pressure reaches the feasible target boost pressure before the actual boost pressure reaches the target boost pressure, or by utilizing the fact that the actual driving energy reaches the feasible target driving energy before the actual boost pressure reaches the target boost pressure, the end of the fresh air compensation acceleration request period can be determined at a more appropriate timing that is neither too early nor too late.

According to the fourth invention , at the start of the fresh air replenishment acceleration request period (the period during which a fresh air replenishment acceleration request occurs), the opening of the EGR valve is forcibly and instantly reduced to an appropriate opening (the amount of EGR gas is instantly reduced), thereby avoiding a shortage of fresh air intake volume when acceleration is required.

According to the fifth invention , during the period when a fresh air replenishment acceleration request is made but a fresh air replenishment acceleration request has not occurred, the opening degree of the EGR valve that was reduced when a fresh air replenishment acceleration request was made is maintained (kept), thereby appropriately continuing to avoid a shortage of fresh air intake volume when acceleration is requested.

1 is a diagram illustrating an example of a schematic configuration of an internal combustion engine system as a whole; 11 is a flowchart illustrating an example of a processing procedure of “overall processing” according to the first embodiment. 3 is a flowchart illustrating an example of a process procedure of "EGR valve control during steady operation" described in the flowchart of FIG. 2; FIG. 10 is a diagram illustrating an example of the operation of the first embodiment. 10 is a diagram for explaining an example of operation of a conventional system in which the opening of the EGR valve is not forcibly reduced (reduced by feedback) when acceleration is required. FIG. 13 is a flowchart illustrating an example of a processing procedure of “overall processing” according to the second embodiment.

[Example of schematic configuration of internal combustion engine system 1 (FIG. 1)]
An embodiment of the present invention will be described below with reference to the drawings. First, an example of a schematic configuration of an internal combustion engine system 1 will be described with reference to Fig. 1. In the description of this embodiment, an internal combustion engine 10 (e.g., a diesel engine) mounted on a vehicle will be used as an example of the internal combustion engine. Note that the intake pipes 11A and 11B and the intake manifold 11C correspond to an intake path, and the exhaust manifold 12A and the exhaust pipes 12B and 12C correspond to an exhaust path.

The entire system will be described below, starting from the intake side and proceeding from the exhaust side. An air cleaner (not shown) and an intake amount detection device 21 (e.g., an intake air flow rate sensor) are provided on the inlet side of the intake pipe 11A. The intake amount detection device 21 outputs a detection signal corresponding to the flow rate of air (fresh intake amount) taken in by the internal combustion engine 10 to the control device 50. The intake amount detection device 21 is also provided with an intake air temperature detection device 28A (e.g., an intake air temperature sensor) and an atmospheric pressure detection device 23 (e.g., an atmospheric pressure sensor). The intake air temperature detection device 28A outputs a detection signal corresponding to the temperature of the intake air passing through the intake air amount detection device 21 to the control device 50. The atmospheric pressure detection device 23 outputs a detection signal corresponding to the surrounding atmospheric pressure to the control device 50.

The outlet side of the intake pipe 11A is connected to the inlet side of the compressor 35, and the outlet side of the compressor 35 is connected to the inlet side of the intake pipe 11B. The compressor 35 of the turbocharger 30 (corresponding to a supercharger) is driven to rotate by a turbine 36 that is driven to rotate by the energy of the exhaust gas (supercharger driving energy), and supercharges the intake air that flows in from the intake pipe 11A by compressing it and sending it to the intake pipe 11B.

A compressor upstream pressure detection device 24A (e.g., a pressure sensor) is provided in the intake pipe 11A, which is upstream of the compressor 35. The compressor upstream pressure detection device 24A outputs a detection signal corresponding to the pressure of the intake air in the intake pipe 11A to the control device 50. A compressor downstream pressure detection device 24B (e.g., a pressure sensor) is provided in the intake pipe 11B, which is downstream of the compressor 35 (a position in the intake pipe 11B between the compressor 35 and the intercooler 16). The compressor downstream pressure detection device 24B outputs a detection signal corresponding to the pressure of the intake air in the intake pipe 11B to the control device 50.

An intercooler 16 is disposed upstream of the intake pipe 11B, and a throttle device 47 is disposed downstream of the intercooler 16. The intercooler 16 is disposed downstream of the compressor downstream pressure detection device 24B. An intake air temperature detection device 28B (e.g., an intake air temperature sensor) is provided between the intercooler 16 and the throttle device 47. The intake air temperature detection device 28B outputs a detection signal corresponding to the temperature of the intake air whose temperature has been reduced by the intercooler 16 to the control device 50.

The throttle device 47 drives a throttle valve 47V that adjusts the opening of the intake pipe 11B based on a control signal from the control device 50, and can adjust the intake flow rate (amount of fresh air intake). The control device 50 can adjust the opening of the throttle valve 47V by outputting a control signal to the throttle device 47 based on a detection signal from a throttle opening detection device 47S (e.g., a throttle opening sensor) and a target throttle valve opening.

The accelerator pedal depression amount detection device 25 is, for example, an accelerator pedal depression angle sensor, and is provided on the accelerator pedal. The control device 50 can detect the amount of depression of the accelerator pedal by the driver based on the detection signal from the accelerator pedal depression amount detection device 25.

The outflow side of the intake pipe 11B is connected to the inflow side of the intake manifold 11C, and the outflow side of the intake manifold 11C is connected to the inflow side of the internal combustion engine 10. A boost pressure detection device 24C (e.g., a pressure sensor) is provided downstream of the throttle device 47 in the intake pipe 11B (in the intake manifold 11C), and the outflow side of the EGR pipe 13 is connected. The boost pressure detection device 24C outputs a detection signal corresponding to the pressure of the intake air (boost pressure) immediately before it flows into the intake manifold 11C to the control device 50. In addition, from the outflow side of the EGR pipe 13 (the connection with the intake pipe 11B), the EGR gas that flows in from the inflow side of the EGR pipe 13 (the connection with the exhaust manifold 12A or the exhaust pipe 12B) is discharged into the intake pipe 11B.

The internal combustion engine 10 has multiple cylinders 45A-45D, and injectors 43A-43D are provided for each cylinder. Fuel is supplied to the injectors 43A-43D via a common rail 41 and fuel pipes 42A-42D, and the injectors 43A-43D are driven by control signals from a control device 50 to inject fuel into each of the cylinders 45A-45D. A fuel pressure detection device 73 is provided in the common rail 41, and fuel adjusted to a target fuel pressure by a fuel pump 72 is filled in the common rail 41. The control device 50 controls the fuel pump 72 so that the fuel pressure detected by the fuel pressure detection device 73 approaches the target fuel pressure.

The internal combustion engine 10 is provided with a crank angle detection device 22A, a cam angle detection device 22B, a coolant temperature detection device 28C, etc. The crank angle detection device 22A is, for example, a rotation sensor, and outputs a detection signal corresponding to the rotation angle of the crankshaft of the internal combustion engine 10 to the control device 50. The cam angle detection device 22B is, for example, a rotation sensor, and outputs a detection signal corresponding to the rotation angle of the camshaft of the internal combustion engine 10 to the control device 50. The control device 50 can detect the process and rotation angle of each cylinder based on the detection signals from the crank angle detection device 22A and the cam angle detection device 22B. The coolant temperature detection device 28C is, for example, a temperature sensor, and outputs a detection signal corresponding to the temperature of the cooling coolant (cooling water temperature) circulated in the internal combustion engine 10 to the control device 50. Although not shown, an oil temperature detection device is also provided in the internal combustion engine 10. The oil temperature detection device is, for example, a temperature sensor, and outputs a detection signal corresponding to the temperature of the oil circulated in the internal combustion engine 10 to the control device 50.

The inlet side of the exhaust manifold 12A is connected to the exhaust side of the internal combustion engine 10, and the inlet side of the exhaust pipe 12B is connected to the outlet side of the exhaust manifold 12A. The outlet side of the exhaust pipe 12B is connected to the inlet side of the turbine 36, and the outlet side of the turbine 36 is connected to the inlet side of the exhaust pipe 12C.

The inlet side of the EGR pipe 13 is connected to the upstream side of the exhaust pipe 12B (or the exhaust manifold 12A). The EGR pipe 13 corresponds to an EGR flow path, and connects the exhaust pipe 12B and the intake pipe 11B, and is capable of returning a portion of the exhaust gas flowing in the exhaust pipe 12B (or the exhaust manifold 12A) to the intake pipe 11B (returning a portion of the exhaust gas to the intake). The EGR pipe 13 is also provided with an EGR cooler 15 and an EGR valve 14. The control device 50 can adjust the flow rate of the EGR gas flowing in the EGR pipe 13 by adjusting the opening degree of the EGR valve 14. The inlet side of the bypass pipe 13B is connected to the upstream side of the EGR cooler 15 in the EGR pipe 13, and the outlet side of the bypass pipe 13B is connected to the downstream side of the EGR cooler 15 in the EGR pipe 13. An adjustment valve 14B is provided at one of the connections between the EGR pipe 13 and the bypass pipe 13B. The bypass pipe 13B forms a path that bypasses the EGR gas flowing through the EGR pipe 13 without passing through the EGR cooler 15. The control device 50 controls the adjustment valve to adjust the ratio between the amount of EGR gas passing through the EGR cooler 15 and the amount of EGR gas passing through the bypass pipe 13B, thereby adjusting the temperature of the EGR gas.

An exhaust manifold pressure detection device 26C (e.g., a pressure sensor) is provided upstream of the exhaust pipe 12B (or in the exhaust manifold 12A). The exhaust manifold pressure detection device 26C outputs a detection signal corresponding to the exhaust pressure in the exhaust manifold 12A to the control device 50.

An exhaust temperature detection device 29 is provided in the exhaust pipe 12B. The exhaust temperature detection device 29 is, for example, an exhaust temperature sensor, and outputs a detection signal corresponding to the exhaust temperature to the control device 50.

The outlet side of the exhaust pipe 12B is connected to the inlet side of the turbine 36, and the outlet side of the turbine 36 is connected to the inlet side of the exhaust pipe 12C. The turbine 36 is provided with a variable nozzle 33 that can control the flow rate of the exhaust gas led to the turbine 36 (the degree of closure of the flow path leading to the exhaust gas to the turbine can be adjusted), and the closure degree (opening degree) of the variable nozzle 33 is adjusted by the nozzle driving device 31. The control device 50 can adjust the intake supercharging pressure by outputting a control signal to the nozzle driving device 31 to adjust the closure degree (opening degree) of the variable nozzle 33 based on a detection signal from the nozzle closure detection device 32 (e.g., a nozzle closure sensor) and a target variable nozzle closure degree (opening degree).

The exhaust pipe 12B, which is upstream of the turbine 36, is provided with a turbine upstream pressure detection device 26A (e.g., a pressure sensor). The turbine upstream pressure detection device 26A outputs a detection signal corresponding to the exhaust pressure in the exhaust pipe 12B to the control device 50. The exhaust pipe 12C, which is downstream of the turbine 36, is provided with a turbine downstream pressure detection device 26B (e.g., a pressure sensor) and an air-fuel ratio detection device 29AF (e.g., an A/F sensor). The turbine downstream pressure detection device 26B outputs a detection signal corresponding to the exhaust pressure in the exhaust pipe 12C to the control device 50. The air-fuel ratio detection device 29AF also outputs a detection signal corresponding to the air-fuel ratio of the exhaust gas flowing in the exhaust pipe 12B to the control device 50.

An exhaust purification device 61 is connected to the outlet side of the exhaust pipe 12C. For example, if the internal combustion engine 10 is a diesel engine, the exhaust purification device 61 includes an oxidation catalyst, a particulate filter, a selective reduction catalyst, etc.

The vehicle speed detection device 27 is, for example, a vehicle speed detection sensor, and is provided on the wheels of the vehicle. The vehicle speed detection device 27 outputs a detection signal corresponding to the rotation speed of the wheels of the vehicle to the control device 50.

The control device 50 has a CPU 51, a RAM 52, a storage device 53, a timer 54, etc. The control device 50 (CPU 51) receives detection signals from the various detection devices described above and outputs control signals to the various actuators described above. The inputs and outputs of the control device 50 are not limited to the detection devices and actuators described above. In addition, the temperature and pressure of each part may be calculated by estimation without installing a sensor. The control device 50 can detect the operating state of the internal combustion engine 10 based on detection signals from various detection devices including the above detection devices, and controls various actuators including the above actuators based on the operating state. The storage device 53 is a storage device such as a Flash-ROM or EEPROM, and stores programs and data for controlling the internal combustion engine and performing self-diagnosis. The RAM 52 also includes volatile memory and non-volatile memory. The control device 50 (CPU 51) also has a fresh air compensation acceleration request occurrence determination unit 51A, a fresh air compensation acceleration request end determination unit 51B, and an EGR amount reduction unit 51C when fresh air compensation acceleration is requested, and the details of these will be described later.

The throttle valve 47V and EGR valve 14 described above are actuators that are provided in the intake path and can increase the boost pressure, and the variable nozzle 33 is an actuator that is provided in the exhaust path and can increase the boost pressure.

[Processing procedure of the control device 50 according to the first embodiment (FIGS. 2 and 3)]
Next, an example of the processing procedure of the control device 50 in the first embodiment will be described with reference to the flowcharts shown in Figures 2 and 3. The control device 50 (CPU 51) starts the "overall processing" shown in Figure 2 at a predetermined time interval (several [ms] to several tens of [ms]), for example, and advances the processing to step S010.

In step S010, the control device 50 detects the operating state of the internal combustion engine, including the input of an acceleration request from the driver (e.g., a sudden depression of the accelerator pedal), and proceeds to step S015. The control device 50 detects the operating state based on the detection signals from the various detection devices described above, the operating states of the various actuators, etc.

In step S015, the control device 50 calculates the required fuel injection amount based on, for example, the accelerator pedal depression amount (or the accelerator pedal depression amount and the internal combustion engine speed) and a map in which the required fuel injection amount is set, and proceeds to step S020.

In step S020, the control device 50 calculates the target boost pressure (pimtrg_1) based on, for example, the required fuel injection amount (or the required fuel injection amount and the internal combustion engine speed) and a map in which the target boost pressure is set, and proceeds to step S025.

In step S025, the control device 50 calculates the boost pressure deviation (pimdlt), which is the deviation between the target boost pressure (pimtrg_1) and the actual boost pressure (actual boost pressure), and diverts the process to step S030. The actual boost pressure, which is the actual boost pressure, was detected in step S010. Also, "boost pressure deviation (pimdlt)" = "target boost pressure (pimtrg_1)" - "actual boost pressure".

In step S030, the control device 50 calculates the amount of change (Δpimdlt) in the boost pressure deviation (pimdlt) over time, and proceeds to step S035. Δpimdlt is calculated as the slope of the boost pressure deviation (pimdlt) (see "Boost pressure deviation (pimdlt)" and "Δpimdlt" in FIG. 4).

In step S035, the control device 50 calculates a feasible target boost pressure (pimtrg_2) that is a boost pressure different from the target boost pressure (pimtrg_1) and is a feasible boost pressure, and proceeds to step S040. The control device 50 calculates the feasible target boost pressure (pimtrg_2) that is predicted to be realized when the actuators (in this case, the throttle valve 47V, EGR valve 14, and variable nozzle 33) that are provided in the intake path or exhaust path of the internal combustion engine and that are capable of increasing the boost pressure are driven further (from the current operating state) toward the side that increases the boost pressure. For example, the control device 50 determines the achievable target boost pressure (pimtrg_2), which is the boost pressure predicted to be achievable if the variable nozzle 33, EGR valve 14, and throttle valve 47V are driven to further increase the boost pressure, based on the operating conditions of the internal combustion engine, such as the engine speed, the load of the internal combustion engine, the intake and exhaust gas flow rates, the engine coolant temperature, and the engine oil temperature.

For example, a map is created that determines the achievable target boost pressure (pimtrg_2) according to the driving state, using experiments using an actual vehicle or a simulation using model control. The control device 50 determines the achievable target boost pressure (pimtrg_2) based on the map and the driving state. Alternatively, the control device 50 calculates the achievable target boost pressure (pimtrg_2) using various parameter values based on model control.

In step S040, the control device 50 calculates the feasible target driving energy (etintrg) and the actual driving energy (etin), which is the actual supercharger driving energy, and proceeds to step S045. The feasible target driving energy (etintrg) is the supercharger driving energy that is predicted to need to be input to the turbocharger (supercharger) to make the actual supercharging pressure (actual supercharging pressure) the feasible target supercharging pressure (pimtrg_2). The actual driving energy (etin) is the supercharger driving energy that is actually input to the turbocharger (supercharger).

For example, a map is prepared that determines the turbocharger drive energy according to the boost pressure and operating conditions (such as exhaust gas flow rate and variable nozzle closure degree) through experiments using an actual vehicle or simulations using model control. The control device 50 determines the achievable target drive energy (etintrg) based on the map, the achievable target boost pressure (pimtrg_2), and the operating conditions. Alternatively, the control device 50 calculates the achievable target drive energy (etintrg) using the values of various parameters based on model control.

The control device 50 calculates the actual driving energy (etin), for example, using the following (Equation 1). If there is no detection device (sensor, etc.) that detects the necessary parameters used in (Equation 1), the necessary parameters may be estimated or calculated from parameters obtained by other detection devices.
etin=Cp*G4*T4*{1-[1/(P4/P6)]^[(K-1)/K]} (Formula 1)
Cp: exhaust gas specific heat at constant pressure (constant)
G4: Gas flow rate + fuel injection amount T4: Exhaust gas temperature P4: Turbine inlet pressure (turbine upstream pressure)
P6: Turbine outlet pressure (turbine downstream pressure)
K: specific heat ratio (constant)

In step S045, the control device 50 calculates the fresh air refill acceleration request determination threshold (C1) based on the driving state, and proceeds to step S050. For example, a map is prepared in which the fresh air refill acceleration request threshold is set according to the driving state, based on experiments using an actual vehicle or simulations using model control. The control device 50 determines the fresh air refill acceleration request determination threshold (C1) based on the map and the driving state.

In step S050, the control device 50 determines whether Δpimdlt (the amount of change in the boost pressure deviation (pimdlt) over time) calculated in step S030 is equal to or greater than the fresh air compensation acceleration request determination threshold (C1). If Δpimdlt is equal to or greater than the fresh air compensation acceleration request determination threshold (C1) (Yes), the control device 50 proceeds to step S055, and if not (No), the control device 50 proceeds to step S060.

If the process proceeds to step S055, the control device 50 determines that a fresh air replenishment acceleration request has occurred, sets the fresh air replenishment acceleration request flag to ON, sets the EGR reduction flag to ON, and proceeds to step S075.

If processing proceeds to step S060, the control device 50 sets the EGR reduction flag to OFF and proceeds to step S065.

In step S065, the control device 50 determines whether the actual drive energy (etin) is equal to or greater than the feasible target drive energy (etintrg). If the actual drive energy (etin) is equal to or greater than the feasible target drive energy (etintrg) (Yes), the control device 50 proceeds to step S070, and if not (No), the control device 50 proceeds to step S075.

If the process proceeds to step S070, the control device 50 determines that the fresh air replenishment acceleration request has ended, sets the fresh air replenishment acceleration request flag to OFF, and proceeds to step S075.

When the process proceeds to step S075, the control device 50 determines whether the fresh air replenishment acceleration request flag is ON. When the fresh air replenishment acceleration request flag is ON (Yes), the control device 50 proceeds to step S080, and when it is not ON (No), the control device 50 ends the process shown in FIG. 2. Note that when the process shown in FIG. 2 is ended by determining (No) in step S075, the control of the EGR valve opening is feedback controlled so as to approach the target EGR rate in [EGR valve control during steady operation] in FIG. 3 described later.

If the process proceeds to step S080, the control device 50 determines whether the EGR reduction flag is ON. If the EGR reduction flag is ON (Yes), the control device 50 proceeds to step S085, and if not (No), the control device 50 proceeds to step S090.

If the process proceeds to step S085, the control device 50 determines the amount of EGR opening reduction corresponding to the operating state, controls the EGR valve opening to be forcibly and quickly reduced to an opening obtained by subtracting the amount of EGR opening reduction from the current EGR valve opening, and ends the process shown in FIG. 2. Note that instead of reducing the amount by the amount of EGR opening reduction, the EGR valve opening may be fully closed.

If the process proceeds to step S090, the control device 50 controls the EGR valve opening so as to maintain (hold) the current EGR valve opening, and ends the process shown in FIG. 2. In this case, the EGR valve opening is maintained at the opening reduced in step S085, and therefore the forcibly reduced opening is maintained.

Next, an example of [EGR valve control during steady operation] shown in Figure 3 will be described. The control device 50 (CPU 51) starts [EGR valve control during steady operation] shown in Figure 3 at a predetermined time interval (several [ms] to several tens of [ms]), for example, and proceeds to step SE010.

In step SE010, the control device 50 determines whether the fresh air replenishment acceleration request flag is OFF. If the fresh air replenishment acceleration request flag is OFF (Yes), the control device 50 proceeds to step SE020. If the fresh air replenishment acceleration request flag is OFF (No), the control device 50 ends the process shown in FIG. 3 and does not control the opening of the EGR valve in the process shown in FIG. 3.

If the process proceeds to step SE020, the control device 50 executes control of the opening degree of the existing EGR valve and ends the process shown in FIG. 3. For example, the control device 50 calculates the target EGR rate (the amount of EGR gas relative to the amount of intake air in the cylinder (amount of fresh air intake + amount of EGR gas)) based on the operating state of the internal combustion engine, and feedback controls the opening degree of the EGR valve so that the actual EGR rate approaches the target EGR rate.

[Comparison between an example of the operation of the first embodiment (FIG. 4) and the operation of a conventional system that does not forcibly reduce the EGR valve (FIG. 5)]
The example shown in Fig. 4 shows an example of the operation of the first embodiment based on the processing of the flowcharts shown in Fig. 2 and Fig. 3. In the example shown in Fig. 4, the driver slightly depresses the accelerator pedal to drive at a low speed before time T1, but suddenly depresses the accelerator pedal just before time T1 to request acceleration.

In the example of FIG. 4, the acceleration period Tacc1, which is the period from time T1 to time T4, indicates the vehicle acceleration period, and the fresh air replenishment acceleration request period Tair, which is the period from time T1 to time T3 (the period during which the "fresh air replenishment acceleration request flag" is ON), corresponds to the fresh air replenishment acceleration request period.

[Operation in the Period Before Time T1]
First, the operation in the period before time T1 will be described. Before time T1, the driver slightly depresses the accelerator pedal and drives at a low speed. At this time, as shown in FIG. 4, the "accelerator opening" is low and almost constant, and the "vehicle speed" is also low and almost constant. In addition, the "target boost pressure (pimtrg_1)", the "realizable target boost pressure (pimtrg_2)", and the "actual boost pressure" in the "boost pressure" are also low and almost constant. Therefore, the "boost pressure deviation (pimdlt)" and the "Δpimdlt" are almost zero, and the "realizable target drive energy (etintrg)" and the "actual drive energy (etin)" in the "drive energy" are also low and almost constant.

The "fresh air supplement acceleration request flag" and the "EGR reduction flag" are both set to OFF, and the EGR valve opening is feedback controlled in step SE020 shown in FIG. 3. The "EGR valve opening" is controlled to a relatively large opening in this case to approach the target EGR rate, and a relatively large amount of EGR gas is mixed into the intake air. For this reason, the "amount of exhaust NOx (instantaneous value)" is low, and the slope of the "amount of exhaust NOx (accumulated value)" is also gentle.

[Operation during the period from just before time T1 to time T2]
Next, the operation in the period from immediately before time T1 to time T2 will be described. The period from time T1 to time T2 is the period of "Δpimdlt≧C1" in "Δpimdlt" in FIG. 4. The driver suddenly and greatly depresses the accelerator pedal immediately before time T1 to request acceleration, and the "accelerator opening" rises suddenly and greatly. As a result, the "target boost pressure (pimtrg_1)" in the "boost pressure" also rises suddenly and greatly from immediately before time T1. Note that the "realizable target boost pressure (pimtrg_2)" and the "actual boost pressure" rise more slowly than the "target boost pressure (pimtrg_1)," and the "actual boost pressure" is lower than the "realizable target boost pressure (pimtrg_2)."

The "boost pressure deviation (pimdlt)" is the "target boost pressure (pimtrg_1)" - the "actual boost pressure", and rises sharply just before time T1, then gradually decreases as the "actual boost pressure" rises. Therefore, the slope of the "boost pressure deviation (pimdlt)", "Δpimdlt", rises sharply just before time T1, and then falls sharply. The period when "Δpimdlt" ≧ C1 is the period from time T1 to time T2.

The "realizable target driving energy (etintrg)" in "driving energy" rises gradually, similar to the "realizable target boost pressure (pimtrg_2)" in "boost pressure". Also, the "actual driving energy (etin)" in "driving energy" rises gradually, similar to the "actual boost pressure" in "boost pressure", and the "actual driving energy (etin)" is lower than the "realizable target driving energy (etintrg)".

The period from time T1 to time T2 is the period when Δpimdlt≧C1, so the "fresh air supplement acceleration request flag" and the "EGR reduction flag" are both set to ON. Therefore, the "EGR valve opening" is forcibly and quickly reduced, and a shortage of fresh air intake is avoided. Furthermore, the "amount of exhaust NOx (instantaneous value)" increases, and the slope of the "amount of exhaust NOx (accumulated value)" also becomes larger.

[Operation during the period from time T2 to time T3]
Next, the operation during the period from time T2 to time T3 will be described. The timing of time T3 is the timing when "actual driving energy (etin)≧realizable target driving energy (etintrg)" in "driving energy". During the period from time T2 to time T3, "accelerator opening" is held constant, and the driver continues to request acceleration. Also, "target boost pressure (pimtrg_1)" in "boost pressure" is held at a substantially constant value, and "realizable target boost pressure (pimtrg_2)" and "actual boost pressure" are gradually increasing.

The "supercharging pressure deviation (pimdlt)" gradually decreases in accordance with the gradual increase in the "actual supercharging pressure." Therefore, the slope of the "supercharging pressure deviation (pimdlt)," Δpimdlt, is a negative value, and Δpimdlt<C1.

The "realizable target driving energy (etintrg)" in the "driving energy" rises gradually, similar to the "realizable target boost pressure (pimtrg_2)" in the "boost pressure". Also, the "actual driving energy (etin)" in the "driving energy" rises gradually, similar to the "actual boost pressure" in the "boost pressure", and the "actual driving energy (etin)" is lower than the "realizable target driving energy (etintrg)", and at time T3, the "actual driving energy (etin) ≧ the realizable target driving energy (etintrg)".

At time T3 when "actual driving energy (etin) ≧ feasible target driving energy (etintrg)", the "fresh air supplement acceleration request flag" is set to OFF. Note that in the period from time T2 to time T3, Δpimdlt < C1, so the "EGR amount reduction flag" is set to OFF. Therefore, in the period from time T2 to time T3, the "EGR valve opening" is maintained (held) at the previous EGR valve opening, and the forcibly reduced state is maintained (held), and a shortage of fresh air intake is avoided. Note that the increasing state of the "emission NOx amount (instantaneous value)" is also maintained (continued), and the slope of the "emission NOx amount (accumulated value)" is also maintained (continued).

[Operation during the period from time T3 to time T4]
Next, the operation during the period from time T3 to time T4 will be described. The timing of time T4 is the timing when the "vehicle speed", which has been increasing in response to the driver's acceleration request, reaches a constant vehicle speed and the acceleration of the vehicle is completed, and is different from the timing when the "fresh air compensation acceleration request flag" ends (OFF). During the period from time T3 to time T4, the "accelerator opening" is held constant and the driver's acceleration request continues. Also, the "target boost pressure (pimtrg_1)" in the "boost pressure" is held at a substantially constant value, the "realizable target boost pressure (pimtrg_2)" is rising slowly, and the "actual boost pressure" rises slowly and then drops slightly to approach the target boost pressure.

The "boost pressure deviation (pimdlt)" gradually decreases in accordance with the gradual increase in the "actual boost pressure", and then gradually increases and approaches zero. The slope of the "boost pressure deviation (pimdlt)", "Δpimdlt", approaches zero from a negative value, and Δpimdlt<C1.

The "realizable target driving energy (etintrg)" in "driving energy" rises gradually, similar to the "realizable target boost pressure (pimtrg_2)" in "boost pressure". Also, the "actual driving energy (etin)" in "driving energy" rises gradually, similar to the "actual boost pressure" in "boost pressure", and then drops slightly to approach the realizable target driving energy. The "actual driving energy (etin)" is higher than the "realizable target driving energy (etintrg)", and at time T4, the "actual driving energy (etin) ≒ realizable target driving energy (etintrg)".

During the period from time T3 to time T4, the "fresh air supplement acceleration request flag" and the "EGR reduction flag" are both set to OFF. Therefore, the "EGR valve opening" is feedback controlled to approach the target EGR rate in the processing of step SE020 shown in FIG. 3. As a result, the "amount of exhausted NOx (instantaneous value)" gradually decreases according to the operation of the EGR valve opening, and the slope of the "amount of exhausted NOx (accumulated value)" also gradually becomes smaller.

[Operation after time T4]
Next, the operation after time T4 will be described. After time T4, the "accelerator opening" is kept constant, but the acceleration of the vehicle is completed. Also, the "target boost pressure (pimtrg_1)", "realizable target boost pressure (pimtrg_2)", and "actual boost pressure" in the "boost pressure" are almost the same value.

Both "supercharging pressure deviation (pimdlt)" and "Δpimdlt", which is the slope of "supercharging pressure deviation (pimdlt)", are almost zero, and Δpimdlt < C1.

In addition, the "achievable target driving energy (etintrg)" and "actual driving energy (etin)" in "driving energy" are almost the same value.

After time T4, the "fresh air replenishment acceleration request flag" and the "EGR reduction flag" are both set to OFF, and the "EGR valve opening" is feedback controlled to approach the target EGR rate in the processing of step SE020 shown in FIG. 3. As a result, the "amount of exhausted NOx (instantaneous value)" is maintained at a value that has decreased in accordance with the operation of the EGR valve opening, and the slope of the "amount of exhausted NOx (accumulated value)" is also maintained at a small slope.

For example, even if the accelerator pedal depression speed is the same, when the vehicle speed is relatively high, the amount of fresh air intake may not be insufficient compared to when the vehicle speed is relatively low. If the EGR valve is fully closed based on the accelerator pedal depression speed, the EGR valve may be fully closed even if the amount of fresh air intake is not insufficient, and the amount of NOx generated may increase unnecessarily. However, in the first embodiment of the present application, whether or not an acceleration request (a fresh air compensation acceleration request) that causes a shortage of the amount of fresh air intake of the internal combustion engine is generated is determined based on the supercharging-related amount (in this case, Δpimdlt), so it is possible to more appropriately determine whether or not the acceleration request causes a shortage of the amount of fresh air intake compared to when the determination is based on the accelerator pedal depression speed. Therefore, it is possible to appropriately avoid an unnecessary increase in the amount of NOx generated.

In addition, in the case of conventional control in which the EGR valve is released from full closure control when the accelerator pedal depression amount is returned to a predetermined amount, the period of full closure control of the EGR valve is long, which may result in an unnecessary increase in the amount of NOx generated. However, in the first embodiment of the present application, whether or not the fresh air compensation acceleration request has ended is determined based on the supercharging-related amount (in this case, when the actual driving energy is equal to or greater than the achievable target driving energy), so the end of the fresh air compensation acceleration request can be determined at a more appropriate timing that is neither too early nor too late, compared to when it is determined based on the accelerator pedal depression amount. Therefore, an unnecessary increase in the amount of NOx generated can be appropriately avoided.

[Comparison with the operation of a conventional system that does not forcibly reduce the EGR valve (FIG. 5)]
Fig. 5 shows an example of the operation when the driver makes the same acceleration request as in Fig. 4 in a "conventional system that does not forcibly reduce the EGR valve when acceleration is requested". The "accelerator opening" in Fig. 5 is the same as the "accelerator opening" in Fig. 4, and the "target boost pressure" in "boost pressure" in Fig. 5 is the same as the "target boost pressure (pimtrg_1)" in "boost pressure" in Fig. 4. In addition, in the conventional system shown in Fig. 5, compared to Fig. 4, the "realizable target boost pressure", "boost pressure deviation", "Δpimdlt", "realizable target driving energy" and "actual driving energy" in "driving energy", "fresh air compensation acceleration request flag", and "EGR reduction flag" are not calculated (not set), and therefore are not shown.

In the conventional system shown in FIG. 5, the "EGR valve opening" is gradually reduced by feedback control in the period from time T1Z to time T2Z when the "accelerator opening" increases significantly and an acceleration request is initiated. However, the reduction rate is very slow compared to the reduction rate of the "EGR valve opening" from time T1 to time T2 shown in FIG. 4. For this reason, in the conventional system shown in FIG. 5, a shortage of fresh air intake occurs immediately after time T1Z when the acceleration request is initiated, and acceleration performance deteriorates. However, in the first embodiment shown in FIG. 4, the "EGR valve opening" is forcibly and instantly reduced in the short period from time T1 to time T2 when it is determined that a fresh air supplement acceleration request has occurred, thereby avoiding a shortage of fresh air intake.

Since the shortage of the fresh air intake amount is avoided, the delay time Tdly1 until the "vehicle speed" starts to increase in the first embodiment shown in FIG. 4 is shorter than the delay time TdlyZ until the "vehicle speed" starts to increase in the conventional system shown in FIG. 5. Therefore, the first embodiment shown in FIG. 4 suppresses the deterioration of acceleration. Also, since the first embodiment shown in FIG. 4 avoids the shortage of the fresh air intake amount during acceleration, the inclination angle of the increase of the "actual boost pressure" in the "boost pressure" and the inclination angle of the increase of the "vehicle speed" are larger than those of the conventional system shown in FIG. 5, and the deterioration of acceleration is suppressed. Therefore, the acceleration period Tacc1 (not the fresh air compensation acceleration request period Tair) from the start to the end of the acceleration of the vehicle in the first embodiment shown in FIG. 4 is shorter than the acceleration period TaccZ in the conventional system shown in FIG. 5, and the deterioration of acceleration is suppressed. Although not shown, the first embodiment shown in FIG. 4 avoids a shortage of fresh air intake during acceleration, which also reduces the generation of smoke.

In addition, the maximum value Vnox1 of the "amount of exhausted NOx (instantaneous value)" during the acceleration period Tacc1 in the first embodiment shown in FIG. 4 is slightly larger than the maximum value VnoxZ of the "amount of exhausted NOx (instantaneous value)" during the acceleration period TaccZ in the conventional system shown in FIG. 5 (because the EGR valve is forcibly reduced). However, since the acceleration period Tacc1 in the first embodiment shown in FIG. 4 is shorter than the acceleration period TaccZ in the conventional system shown in FIG. 5, Qnox1 shown in FIG. 4 is less than QnoxZ shown in FIG. 5 for the "amount of exhausted NOx (accumulated value)" during the acceleration period.

In the first embodiment shown in FIG. 4, even if the "accelerator opening" is in the same starting state, the actual boost pressure, target boost pressure, etc. are different due to the difference in driving state between the case of an acceleration request from a low vehicle speed (and low revolutions) and the case of an acceleration request from a high vehicle speed (and medium to high revolutions). Therefore, the boost-related amount (boost pressure deviation, Δpimdlt, and fresh air compensation acceleration request determination threshold C1) is also different. For this reason, for example, when the fresh air intake amount is insufficient in an acceleration request from a low vehicle speed, it is appropriately determined that a fresh air compensation acceleration request has occurred, and when the fresh air intake amount is not insufficient in an acceleration request from a high vehicle speed, it is appropriately determined that a fresh air compensation acceleration request has not occurred. In other words, in the case of an acceleration request in which the fresh air intake amount is not insufficient, it is appropriately determined that a fresh air compensation acceleration request has not occurred, and the EGR valve opening is not forcibly reduced unnecessarily, so that an unnecessary increase in NOx can be suppressed.

In addition, in a conventional system (not shown) that determines whether the acceleration request from the driver is one that will result in a shortage of fresh air intake based on the accelerator opening state (accelerator operation speed, etc.) and reduces the opening of the EGR valve if it is determined that the fresh air intake amount is insufficient, it is not possible to distinguish between a case where an acceleration request is made while driving at a low vehicle speed (and low revolutions) and a case where an acceleration request is made while driving at a high vehicle speed (and medium to high revolutions) when the same "accelerator opening" is in a rising state. In other words, when an acceleration request is made from a high vehicle speed, the opening of the EGR valve is reduced even though the fresh air intake amount is not actually insufficient, which may result in an unnecessary increase in NOx. However, in the first embodiment of the present application, it is determined whether the acceleration request is one that will result in a shortage of fresh air intake based on the supercharging-related amount (supercharging pressure deviation, Δpimdlt, and fresh air compensation acceleration request determination threshold C1), so that even in the above example, it is possible to appropriately distinguish and determine whether the acceleration request is one that will result in a shortage of fresh air intake amount.

In the first embodiment shown in FIG. 4, the end of the fresh air compensation acceleration request is determined based on the supercharging-related amount (realizable target drive energy based on the realizable target supercharging pressure, actual drive energy, etc.), so that the end of the fresh air compensation acceleration request can be determined at an appropriate timing, not too early and not too late, before the actual supercharging pressure reaches the target supercharging pressure, without returning the accelerator opening. This makes it possible to suppress an unnecessary increase in NOx. Since the end of the fresh air compensation acceleration request is determined taking into account environmental conditions such as intake temperature and coolant temperature, and parameters used to calculate the drive energy of the supercharger (EGR gas amount, exhaust temperature, exhaust gas amount, etc.), EGR control can be resumed as quickly as possible (EGR valve control is returned to feedback control from forced reduction), so that acceleration performance can be further improved while suppressing the "NOx emission (integrated value)" to a level lower than that of the conventional system in FIG. 5.

[Processing procedure of the control device 50 according to the second embodiment (FIG. 6)]
Next, an example of the processing procedure of the control device 50 in the second embodiment will be described with reference to the flowchart shown in Fig. 6. The flowchart of the second embodiment shown in Fig. 6 differs from the flowchart of the first embodiment shown in Fig. 2 in that step S040 is omitted and the determination in step S065 is changed to a determination in step S065B. The following mainly describes the differences. Note that a description of the omission of step S040 will be omitted.

In step S065B, the control device 50 determines whether the actual boost pressure is equal to or greater than the achievable target boost pressure (pimtrg_2). If the actual boost pressure is equal to or greater than the achievable target boost pressure (pimtrg_2) (Yes), the control device 50 proceeds to step S070, and if not (No), the control device 50 proceeds to step S075.

In step S065 in FIG. 2, it was determined whether the actual drive energy (etin) was equal to or greater than the achievable target drive energy (etintrg), but in step S065B in FIG. 6, it is determined whether the actual boost pressure is equal to or greater than the achievable target boost pressure (pimtrg_2). In this case, since it is not necessary to calculate the actual drive energy (etin) or the achievable target drive energy (etintrg), the processing load on the CPU 51 is reduced.

The example of operation is similar to that of the first embodiment shown in FIG. 4, and the position at time T2 (the position where the actual driving energy in "driving energy" is greater than or equal to the achievable target driving energy) is changed to the position where the actual boost pressure in "boost pressure" is greater than or equal to the achievable target boost pressure, but is approximately the same position.

The control device 50 (CPU 51) which executes the processing of steps S010 to S030 and steps S045 to S055 in the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. 6 corresponds to a fresh air compensation acceleration request occurrence determination unit 51A (see FIG. 1) which determines that a fresh air compensation acceleration request has not occurred if it is determined that the acceleration request is one in which the fresh air intake amount of the internal combustion engine is not insufficient based on the supercharging-related amount related to supercharging in the operating state of the internal combustion engine including the input of an acceleration request from the driver, and determines that a fresh air compensation acceleration request has occurred if it is determined that the acceleration request is one in which the fresh air intake amount of the internal combustion engine is insufficient.

The control device 50 (CPU 51) that executes the processing of steps S035 (step S040) and steps S060 to S070 in the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. 6 corresponds to the fresh air refill acceleration request end determination unit 51B (see FIG. 1) that determines whether the fresh air refill acceleration request has ended based on the supercharging-related amount.

The control device 50 (CPU 51) that executes the processing of steps S075 to S090 in the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. 6 corresponds to a fresh air refill acceleration request EGR reduction unit 51C (see FIG. 1) that forcibly reduces the opening of the EGR valve during the fresh air refill acceleration request period from when it is determined that a fresh air refill acceleration request has occurred until it is determined that the fresh air refill acceleration request has ended.

The control device 50 for the internal combustion engine system of the present invention is not limited to the configuration and processing procedures (flowcharts) described in this embodiment, and various modifications, additions, and deletions are possible without changing the gist of the present invention.

In the description of this embodiment, an example has been described in which whether or not a fresh air compensation acceleration request has occurred is determined based on the amount of change (Δpimdlt) over time in the boost pressure deviation (pimdlt) between the target boost pressure and the actual boost pressure, but the determination may also be based on other boost-related quantities (e.g., the required fresh air amount, etc.). In addition, in the description of this embodiment, an example has been described in which the value of the fresh air compensation acceleration request determination threshold C1 is changed depending on the operating state, but the value of the fresh air compensation acceleration request determination threshold C1 may also be a constant.

In addition, the method of calculating the achievable target boost pressure, achievable target drive energy, and actual drive energy is not limited to the example described in this embodiment, and may be calculated in any manner. Furthermore, the determination of the end of the fresh air compensation acceleration request is not limited to the determination method described in this embodiment. For example, the end of the fresh air compensation acceleration request may be determined when the actual boost pressure nearly matches the target boost pressure.

In the description of this embodiment, an example has been given in which the opening of the EGR valve is forcibly reduced during the period in which a fresh air refill acceleration request is made during the fresh air refill acceleration request period, but the opening of the EGR valve may be fully closed during this period. Also, in the description of this embodiment, an example has been given in which the opening of the EGR valve is maintained (kept) during the period in which a fresh air refill acceleration request is not made during the fresh air refill acceleration request period, but the opening may be controlled to be gradually reduced or gradually increased depending on the operating conditions.

In the description of this embodiment, a turbocharger with a variable nozzle has been used as an example, but a turbocharger with a wastegate valve may also be used. Also, in the description of this embodiment, a turbocharger with a turbine and compressor (driving energy is exhaust energy) has been used as an example of a supercharger, but an electric supercharger with an electric motor and compressor (driving energy is electrical energy) or a supercharger (driving energy is the rotational energy of the crankshaft) may also be used.

In addition, the internal combustion engine control device of the present invention is not limited to diesel engines, but can also be applied to gasoline engines.

In addition, terms such as greater than or equal to (≧), less than or equal to (≦), larger than (>), and less than (<), may or may not include an equal sign.

REFERENCE SIGNS LIST 1 internal combustion engine system 10 internal combustion engine 11A, 11B intake pipe 11C intake manifold 12A exhaust manifold 12B, 12C exhaust pipe 13 EGR pipe 13B bypass pipe 14 EGR valve 14B regulating valve 15 EGR cooler 16 intercooler 21 intake air amount detection device 22A crank angle detection device 22B cam angle detection device 23 atmospheric pressure detection device 24A compressor upstream pressure detection device 24B compressor downstream pressure detection device 24C supercharging pressure detection device 25 accelerator pedal depression amount detection device 26A turbine upstream pressure detection device 26B turbine downstream pressure detection device 26C exhaust manifold pressure detection device 27 vehicle speed detection device 28A, 28B intake air temperature detection device 28C coolant temperature detection device 29 Exhaust temperature detection device 29AF Air-fuel ratio detection device 30 Turbocharger 31 Nozzle drive device 32 Nozzle closure detection device 33 Variable nozzle 35 Compressor 36 Turbine 41 Common rail 43A to 43D Injectors 45A to 45D Cylinder 47 Throttle device 47S Throttle opening detection device 47V Throttle valve 50 Control device 51 CPU
51A: fresh air supplement acceleration request occurrence determination unit; 51B: fresh air supplement acceleration request end determination unit; 51C: fresh air supplement acceleration request time EGR reduction unit;
53 Storage device 54 Timer 61 Exhaust gas purification device 72 Fuel pump 73 Fuel pressure detection device Tacc1 Acceleration period Tair Fresh air supplement acceleration request period

Claims (8)

A control device for an internal combustion engine system,
The internal combustion engine system includes:
An internal combustion engine;
an EGR valve that adjusts an EGR amount that returns a portion of the exhaust gas of the internal combustion engine to an intake air of the internal combustion engine;
A supercharger that supercharges the intake air of the internal combustion engine;
a control device that detects an operating state of the internal combustion engine and controls the internal combustion engine based on the operating state;
It has
The control device includes:
a fresh air compensation acceleration request occurrence determination unit that determines that a fresh air compensation acceleration request has not occurred when it is determined that the acceleration request is one in which the fresh air intake amount of the internal combustion engine is not insufficient based on a supercharging-related amount related to supercharging in the operating state of the internal combustion engine including an input of an acceleration request from a driver, and determines that the fresh air compensation acceleration request has occurred when it is determined that the acceleration request is one in which the fresh air intake amount is insufficient;
a fresh air compensation acceleration request end determination unit that determines whether or not the acceleration request has ended after transitioning from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient based on the supercharging-related amount;
an EGR amount reducing unit at the time of fresh air compensation acceleration request, which forcibly reduces an opening degree of the EGR valve during a fresh air compensation acceleration request period from when it is determined that the fresh air compensation acceleration request has occurred until when it is determined that the acceleration request has ended;
having
The control device includes:
when the fresh air compensation acceleration request occurrence determination unit determines whether or not the acceleration request is one in which the fresh air intake amount is insufficient based on the supercharging-related amount,
A boost pressure deviation is calculated by subtracting an actual boost pressure, which is an actual boost pressure of the internal combustion engine, from a target boost pressure, which is a target boost pressure of the internal combustion engine calculated based on the operating state;
a fresh air compensation acceleration request is determined to have occurred when a fluctuation amount of the supercharging pressure deviation with respect to time, the fluctuation amount being obtained by subtracting the previous supercharging pressure deviation from the current supercharging pressure deviation, becomes equal to or greater than a fresh air compensation acceleration request determination threshold value;
A control device for an internal combustion engine system. 2. The control device for an internal combustion engine system according to claim 1,
The control device includes:
The fresh air compensation acceleration request occurrence determination unit calculates the fresh air compensation acceleration request determination threshold value based on the operating state.
A control device for an internal combustion engine system. The control device for an internal combustion engine system according to claim 1 or 2,
The control device includes:
When the fresh air supplement acceleration request end determination unit determines whether the acceleration request has ended,
a realizable target supercharging pressure, which is a supercharging pressure for determining the end of an acceleration request after transition from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient , is calculated based on the operating state and a map in which the realizable target supercharging pressure corresponding to the operating state is set, or is calculated using each parameter of the operating state;
determining that the acceleration request has ended when an actual boost pressure, which is an actual boost pressure of the internal combustion engine, becomes equal to or higher than the feasible target boost pressure;
or,
a realizable target supercharging pressure, which is a supercharging pressure for determining the end of an acceleration request after transition from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient , is calculated based on the operating state and a map in which the realizable target supercharging pressure corresponding to the operating state is set, or is calculated using each parameter of the operating state;
calculating a realizable target drive energy, which is a supercharger drive energy predicted to be required to be input to the supercharger in order to set the supercharging pressure to the realizable target supercharging pressure, and which is for determining the end of an acceleration request after transition from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient, based on a map in which the supercharger drive energy corresponding to the supercharging pressure and the operating state is set, the realizable target supercharging pressure, and the operating state, or by using each parameter of the realizable target supercharging pressure and the operating state;
determining that the acceleration request has ended when actual driving energy, which is supercharger driving energy actually input to the supercharger and is calculated using each parameter of the operating state, becomes equal to or greater than the feasible target driving energy;
A control device for an internal combustion engine system. The control device for an internal combustion engine system according to any one of claims 1 to 3,
The control device includes:
the fresh air compensation acceleration request time EGR amount reducing unit reduces an opening degree of the EGR valve in accordance with the operating state during an acceleration request period in which the fresh air intake amount is insufficient during the fresh air compensation acceleration request period;
A control device for an internal combustion engine system. The control device for an internal combustion engine system according to any one of claims 1 to 4,
The control device includes:
the fresh air compensation acceleration request time EGR amount reducing unit maintains the opening degree of the EGR valve that was reduced during the acceleration request period in which the fresh air intake amount is insufficient during the fresh air compensation acceleration request period in which the acceleration request period in which the fresh air intake amount is not insufficient.
A control device for an internal combustion engine system. A control device for an internal combustion engine system,
The internal combustion engine system includes:
An internal combustion engine;
an EGR valve that adjusts an EGR amount that returns a portion of the exhaust gas of the internal combustion engine to an intake air of the internal combustion engine;
A supercharger that supercharges the intake air of the internal combustion engine;
a control device that detects an operating state of the internal combustion engine and controls the internal combustion engine based on the operating state;
It has
The control device includes:
a fresh air compensation acceleration request occurrence determination unit that determines that a fresh air compensation acceleration request has not occurred when it is determined that the acceleration request is one in which the fresh air intake amount of the internal combustion engine is not insufficient based on a supercharging-related amount related to supercharging in the operating state of the internal combustion engine including an input of an acceleration request from a driver, and determines that the fresh air compensation acceleration request has occurred when it is determined that the acceleration request is one in which the fresh air intake amount is insufficient;
a fresh air compensation acceleration request end determination unit that determines whether or not the acceleration request has ended after transitioning from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient based on the supercharging-related amount;
an EGR amount reducing unit at the time of fresh air compensation acceleration request, which forcibly reduces an opening degree of the EGR valve during a fresh air compensation acceleration request period from when it is determined that the fresh air compensation acceleration request has occurred until when it is determined that the acceleration request has ended;
having
The control device includes:
When the fresh air supplement acceleration request end determination unit determines whether the acceleration request has ended,
a realizable target supercharging pressure, which is a supercharging pressure for determining the end of an acceleration request after transition from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient , is calculated based on the operating state and a map in which the realizable target supercharging pressure corresponding to the operating state is set, or is calculated using each parameter of the operating state;
determining that the acceleration request has ended when an actual boost pressure, which is an actual boost pressure of the internal combustion engine, becomes equal to or higher than the feasible target boost pressure;
or,
a realizable target supercharging pressure, which is a supercharging pressure for determining the end of an acceleration request after transition from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient , is calculated based on the operating state and a map in which the realizable target supercharging pressure corresponding to the operating state is set, or is calculated using each parameter of the operating state;
calculating a realizable target drive energy, which is a supercharger drive energy predicted to be required to be input to the supercharger in order to set the supercharging pressure to the realizable target supercharging pressure, and which is for determining the end of an acceleration request after transition from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient, based on a map in which the supercharger drive energy corresponding to the supercharging pressure and the operating state is set, the realizable target supercharging pressure, and the operating state, or by using each parameter of the realizable target supercharging pressure and the operating state;
determining that the acceleration request has ended when actual driving energy, which is supercharger driving energy actually input to the supercharger and is calculated using each parameter of the operating state, becomes equal to or greater than the feasible target driving energy;
A control device for an internal combustion engine system. A control device for an internal combustion engine system,
The internal combustion engine system includes:
An internal combustion engine;
an EGR valve that adjusts an EGR amount that returns a portion of the exhaust gas of the internal combustion engine to an intake air of the internal combustion engine;
A supercharger that supercharges the intake air of the internal combustion engine;
a control device that detects an operating state of the internal combustion engine and controls the internal combustion engine based on the operating state;
It has
The control device includes:
a fresh air compensation acceleration request occurrence determination unit that determines that a fresh air compensation acceleration request has not occurred when it is determined that the acceleration request is one in which the fresh air intake amount of the internal combustion engine is not insufficient based on a supercharging-related amount related to supercharging in the operating state of the internal combustion engine including an input of an acceleration request from a driver, and determines that the fresh air compensation acceleration request has occurred when it is determined that the acceleration request is one in which the fresh air intake amount is insufficient;
a fresh air compensation acceleration request end determination unit that determines whether or not the acceleration request has ended after transitioning from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient based on the supercharging-related amount;
an EGR amount reducing unit at the time of fresh air compensation acceleration request, which forcibly reduces an opening degree of the EGR valve during a fresh air compensation acceleration request period from when it is determined that the fresh air compensation acceleration request has occurred until when it is determined that the acceleration request has ended;
having
The control device includes:
the fresh air compensation acceleration request time EGR amount reducing unit reduces an opening degree of the EGR valve in accordance with the operating state during an acceleration request period in which the fresh air intake amount is insufficient during the fresh air compensation acceleration request period;
A control device for an internal combustion engine system. A control device for an internal combustion engine system,
The internal combustion engine system includes:
An internal combustion engine;
an EGR valve that adjusts an EGR amount that returns a portion of the exhaust gas of the internal combustion engine to an intake air of the internal combustion engine;
A supercharger that supercharges the intake air of the internal combustion engine;
a control device that detects an operating state of the internal combustion engine and controls the internal combustion engine based on the operating state;
It has
The control device includes:
a fresh air compensation acceleration request occurrence determination unit that determines that a fresh air compensation acceleration request has not occurred when it is determined that the acceleration request is one in which the fresh air intake amount of the internal combustion engine is not insufficient based on a supercharging-related amount related to supercharging in the operating state of the internal combustion engine including an input of an acceleration request from a driver, and determines that the fresh air compensation acceleration request has occurred when it is determined that the acceleration request is one in which the fresh air intake amount is insufficient;
a fresh air compensation acceleration request end determination unit that determines whether or not the acceleration request has ended after transitioning from an acceleration request in which the fresh air intake amount is insufficient to an acceleration request in which the fresh air intake amount is not insufficient based on the supercharging-related amount;
an EGR amount reducing unit at the time of fresh air compensation acceleration request, which forcibly reduces an opening degree of the EGR valve during a fresh air compensation acceleration request period from when it is determined that the fresh air compensation acceleration request has occurred until when it is determined that the acceleration request has ended;
having
The control device includes:
the fresh air compensation acceleration request time EGR amount reducing unit maintains the opening degree of the EGR valve that was reduced during the acceleration request period in which the fresh air intake amount is insufficient during the fresh air compensation acceleration request period in which the acceleration request period in which the fresh air intake amount is not insufficient.
A control device for an internal combustion engine system.

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