JP2017180410A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which controls the internal combustion engine to an optimum intake temperature corresponding to an operation mode of the internal combustion engine while suppressing the production of condensed water in an intercooler.SOLUTION: A control device of an internal combustion engine comprises: a first calculation part for calculating a first candidate of a target value of a parameter value when an operation mode in not a NOx reduction mode; a second calculation mode for calculating a second candidate of a target value when the operation mode is not the NOx reduction mode; a third calculation part for calculating a third candidate of a target value at which a temperature of intake air cooled by an intercooler exceeds a dew point temperature; a setting part for setting a higher value out of the first and third candidates as a final target value when the operation mode is determined not to be the NOx reduction mode, and sets a higher value out of the second and third candidates as a final target value when the operation mode is determined to be the NOx reduction mode; and a control part for feedback-controlling a rotation number of an electric pump so that the parameter value reaches the set target value.SELECTED DRAWING: Figure 2

Description

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

  A technique is known that controls an electric pump that adjusts the flow rate of refrigerant flowing through the intercooler so that the temperature of the intake air cooled by the intercooler becomes a target value based on the operating state of the internal combustion engine (for example, Patent Document 1).

JP 2011-214544 A

  By the way, the operation mode of the internal combustion engine includes a normal mode in which combustion is performed at an air-fuel ratio corresponding to an operation state required for the internal combustion engine, and a NOx reduction mode in which combustion is performed by changing the air-fuel ratio to a rich side. . In the normal mode, the air-fuel ratio is variably set based on the viewpoint of securing the output of the internal combustion engine and preventing emission deterioration. In the NOx reduction mode, combustion is performed at a rich air-fuel ratio in order to reduce NOx stored in the catalyst that purifies the exhaust gas of the internal combustion engine.

  The temperature of the intake air cooled by the above-described intercooler is preferably low from the viewpoint of securing the output of the internal combustion engine and preventing deterioration of emissions. For this reason, it is desirable to set the target value of the intake air temperature to a low value.

  However, since rich combustion is performed in the NOx reduction mode, for example, in an operating state in which the required torque to the internal combustion engine is small, the fuel injection amount becomes small and the intake air is also greatly reduced. Even in such a NOx reduction mode, if the target value of the intake air temperature is set to a low value based on the viewpoint of securing the output of the internal combustion engine and preventing the deterioration of the emission, the intake air temperature becomes too low to reduce the intake air. There is a possibility that NOx cannot be reduced without realizing rich combustion.

  If the temperature of the intake air cooled by the intercooler is too low, the intake air temperature may be lower than the dew point temperature, and condensed water may be generated in the intercooler. When condensed water is generated, the generated condensed water may flow into the cylinder of the internal combustion engine at a time after collecting in the intake passage, and a water hammer phenomenon may occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for an internal combustion engine that controls the intake air temperature to be optimal according to the operation mode of the internal combustion engine while suppressing the generation of condensed water in the intercooler.

  The object is to cool the intake air supplied to the internal combustion engine by heat exchange with the refrigerant, an electric pump that adjusts the flow rate of the refrigerant flowing through the intercooler, and the temperature of the intake air cooled by the intercooler. A sensor for detecting a parameter value correlated with the internal combustion engine, a catalyst for storing and reducing NOx in the exhaust gas of the internal combustion engine, a temperature / humidity sensor for detecting the outside air temperature and the outside air humidity, and the engine speed of the internal combustion engine. An engine speed acquisition unit; a target fuel injection amount calculation unit that calculates a target fuel injection amount of the internal combustion engine; and an operation mode of the internal combustion engine, wherein the air-fuel ratio of the internal combustion engine is to reduce NOx stored by the catalyst. A determination unit that determines whether or not the NOx reduction mode is changed to the rich side, the engine speed, and the operation mode is not the NOx reduction mode A first calculation unit that calculates a first candidate for the target value of the parameter value when the operation mode is not the NOx reduction mode based on the target fuel injection amount that is set at the same time, and the engine speed The second candidate of the target value when the operation mode is the NOx reduction mode based on the number and the target fuel injection amount set when the operation mode is the NOx reduction mode. The engine speed and the target fuel injection amount are set in a second calculation unit that calculates a value larger than the first candidate calculated under the same conditions, the engine speed, and the determined operation mode. A third calculation for calculating a third candidate for the target value in which the temperature of the intake air cooled by the intercooler exceeds the dew point temperature based on the target fuel injection amount and the detected outside air temperature and outside air humidity. And the determination unit determines that the operation mode is not the NOx reduction mode, a higher value of the first and third candidates is set as the final target value, and the determination unit When it is determined that the operation mode is the NOx reduction mode, a setting unit that sets a high value as the final target value among the second and third candidates, and the parameter value are set. This can be achieved by an internal combustion engine control device including a control unit that feedback-controls the number of rotations of the electric pump so as to achieve the target value.

  When it is not in the NOx reduction mode, a higher value is set as the final target value among the first candidate and the third candidate exceeding the dew point temperature, and the rotation speed of the electric pump is set as the target value. Is feedback controlled. Thus, the intake air temperature is controlled so as to be suitable for an operation mode other than the NOx reduction mode within a range where condensed water in the intercooler is not generated. In addition, in the NOx reduction mode, a higher value is set as the final target value among the second candidate in the NOx reduction mode and the third candidate that exceeds the dew point temperature, and the rotation speed of the electric pump is set. The feedback control is performed so that the set target value is obtained. Thereby, it is possible to control the intake air temperature suitable for reducing the NOx occluded in the catalyst within a range in which condensed water in the intercooler is not generated.

  In the above configuration, the first, second, and third calculation units calculate the first, second, and third candidates, respectively, regardless of the determination result of the operation mode by the determination unit. A configuration may be adopted.

  In the above configuration, when the determination unit determines that the operation mode is the NOx reduction mode, the first calculation unit does not calculate the first candidate, and the second calculation unit When the determination unit determines that the operation mode is not the NOx reduction mode, a configuration may be adopted in which the calculation of the second candidate is not performed.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which controls to the optimal intake air temperature according to the operation mode of an internal combustion engine can be provided, suppressing generation | occurrence | production of the condensed water in an intercooler.

FIG. 1 is a diagram showing a control device for an internal combustion engine of the present embodiment. FIG. 2 is a flowchart showing an example of control for setting the target value of the intake air temperature executed by the ECU. FIG. 3A is a flowchart showing an example of the first candidate calculation process, and FIG. 3B defines the target temperature that is the first candidate corresponding to the engine speed and the target fuel injection amount set in the normal mode. It is an example of a map. FIG. 4A is a flowchart showing an example of the second candidate calculation process, and FIG. 4B defines a target temperature that is a second candidate corresponding to the engine speed and the target fuel injection amount set in the NOx reduction mode. It is an example of a map. FIG. 5 is a flowchart illustrating an example of the third candidate calculation process. FIG. 6 is an example of a map that defines the dew point temperature corresponding to the outside air temperature and the outside air humidity at a predetermined target boost pressure. FIG. 7 is a flowchart showing a modified example of the target value setting control of the intake air temperature executed by the ECU.

  FIG. 1 is a diagram showing a control device for an internal combustion engine of the present embodiment. The control device for an internal combustion engine includes an exhaust passage 3, an intake passage 4, a supercharger 5, an intercooler 6, an ECU (Electronic Control Unit) 8, a catalyst 20, a bypass passage 30, and the like. The internal combustion engine 1 is a diesel engine having four cylinders 2, but is not limited to this and may be a gasoline engine. An intake passage 4 and an exhaust passage 3 are connected to the internal combustion engine 1. A compressor housing 51 of the supercharger 5 is disposed in the intake passage 4. A turbine housing 50 of the supercharger 5 is disposed in the middle of the exhaust passage 3.

  A turbine 500 is disposed in the turbine housing 50, and a compressor 501 is disposed in the compressor housing 51. The turbine 500 and the compressor 501 are coaxially connected by a turbine shaft. When the turbine 500 is rotated by the exhaust gas flowing through 3, the compressor 501 is also rotated, and the intake air in the intake passage 4 is supercharged.

  A bypass passage 30 that bypasses the turbine 500 and a wastegate valve 31 that opens and closes the bypass passage 30 are provided in the middle of the exhaust passage 3. The opening degree of the wastegate valve 31 is controlled by the ECU 8, thereby adjusting the flow rate of the exhaust gas flowing through the turbine 500 and adjusting the supercharging pressure of the intake air supercharged by the compressor 501.

  An intercooler 6 is disposed downstream of the compressor housing 51 in the intake passage 4. In the intercooler 6, the refrigerant supplied to the internal combustion engine 1 circulates inside. Thereby, heat exchange is performed between the refrigerant | coolant which distribute | circulates the inside of the intercooler 6, and the air which passes the intercooler 6, and intake air is cooled.

  The refrigerant path 40 is a path through which the refrigerant circulates between the intercooler 6 and the radiator 44 by the electric pump 42. The refrigerant that has received heat at the intercooler 6 is heat-exchanged with the outside air by the radiator 44 and cooled again. The number of revolutions of the electric pump 42 is controlled by the ECU 8, thereby adjusting the flow rate of the refrigerant conveyed by the electric pump 42.

  An intake air temperature sensor 16 that detects the temperature of intake air cooled by the intercooler 6 is provided on the downstream side of the intercooler 6.

In the exhaust passage 3, the catalyst 20 is provided on the downstream side of the turbine 500. The catalyst 20 is a storage reduction type (NSR (NOX Storage Reduction) catalyst) in which a NOx storage material such as an alkali metal is added to a three-way catalyst on which a noble metal such as platinum (Pt) is supported. The catalyst 20 occludes NOx in the exhaust when the air-fuel ratio of the exhaust is leaner than the stoichiometric air-fuel ratio, and reduces the occluded NOx to N ₂ when it is rich. Before and after the catalyst 20, temperature sensors 13 and 14 for detecting the temperature of the exhaust are provided.

  The ECU 8 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 8 executes target value setting control, which will be described later, based on information from the sensor, information stored in the ROM in advance, and the like according to a control program stored in the ROM in advance. This control is functionally realized by the CPU, the ROM, and the RAM, and is a target fuel injection amount calculation unit, an engine speed acquisition unit, a determination unit, a first calculation unit, a second calculation unit, a third calculation unit, a setting And a control unit. Details will be described later.

  The ECU 8 is based on output signals from various sensors such as the crank angle sensor 9, the air flow meter 12, the temperature sensors 13 and 14, the intake air temperature sensor 16, the accelerator opening sensor 17, the outside air temperature sensor 18, and the outside air humidity sensor 19. The operating state of the internal combustion engine 1 is controlled.

  The crank angle sensor 9 detects the rotation angle of the crankshaft of the internal combustion engine 1. The air flow meter 12 detects the amount of intake air taken into the intake passage 4. The temperature sensors 13 and 14 are arranged on the upstream side and the downstream side of the catalyst 20, respectively, and detect the temperatures of the exhaust before and after passing through the catalyst 20.

  The accelerator opening sensor 17 detects the opening of the accelerator pedal operated by the driver. For example, the ECU 8 calculates a target fuel injection amount that is a target value of the fuel injection amount based on the detection value of the accelerator opening sensor 17. The outside air temperature sensor 18 detects the temperature of outside air. The outside air humidity sensor 19 detects the humidity of the outside air. The outside air temperature sensor 18 and the outside air humidity sensor 19 are examples of temperature and humidity sensors that detect the outside air temperature and the outside air humidity.

  The intake air temperature sensor 16 is disposed in the vicinity of the outlet of the intercooler 6 and detects the temperature of the intake air cooled by the intercooler 6. The intake air temperature sensor 16 is an example of a sensor that detects a parameter value correlated with the temperature of the intake air cooled by the intercooler 6.

  As described above, the ECU 8 acquires the detection value of the intake air temperature sensor 16 and feedback-controls the rotation speed of the electric pump 42 so that the acquired detection value of the intake air temperature sensor 16 becomes the set target value. The rotational speed of the electric pump 42 is controlled so as to increase as the target value of the intake air temperature decreases. As the target value of the intake air temperature, a plurality of candidates for the target value are calculated based on a plurality of viewpoints, and a higher value among the calculated candidates is set as a final target value. The ECU 8 is an example of a control unit that feedback-controls the rotation speed of the electric pump 42 so that the parameter value becomes a set target value. Details will be described later.

  Next, the operation mode of the internal combustion engine 1 controlled by the ECU 8 will be described. The ECU 8 switches the operation mode of the internal combustion engine 1 between the normal mode and the NOx reduction mode. In the normal mode, combustion is performed at an air-fuel ratio corresponding to the operating condition required for the internal combustion engine 1 based on securing the output of the internal combustion engine 1 and improving fuel efficiency. For example, the air-fuel ratio in the normal mode is a lean air-fuel ratio larger than the stoichiometric air-fuel ratio at low load, and combustion is performed at a rich air-fuel ratio smaller than the stoichiometric air-fuel ratio at idling, low speed, acceleration, and high load.

  In the NOx reduction mode, in order to reduce the NOx stored in the catalyst 20 and regenerate the catalyst 20, combustion is performed by changing the air-fuel ratio to a rich side suitable for NOx reduction. That is, even if the engine speed and the accelerator opening are the same, the air-fuel ratio is set to be richer in the NOx reduction mode than in the normal mode. Switching from the normal mode to the NOx reduction mode is performed, for example, when the NOx emission amount is calculated based on the fuel injection amount and the integrated value of the emission amount reaches a predetermined value. Further, switching from the NOx reduction mode to the normal mode is performed, for example, when the NOx reduction mode is continued for a predetermined time.

  Next, the setting control of the target value of the intake air temperature executed by the ECU 8 will be described. FIG. 2 is a flowchart showing an example of intake air temperature target value setting control executed by the ECU 8.

  First, the ECU 8 acquires the engine speed and the accelerator opening degree of the internal combustion engine 1 used for the processes of steps S3, S5, and S7 described later (step S1). The engine speed and the accelerator opening are acquired based on output values from the crank angle sensor 9 and the accelerator opening sensor 17, respectively. The process of step S1 is an example of a process executed by an engine speed acquisition unit that acquires the engine speed of the internal combustion engine 1.

  Next, the ECU 8 executes candidate T1 calculation processing for calculating the first candidate T1 of the target value of the intake air temperature based on the detected engine speed and accelerator opening (step S3). Candidate T1 is a target value calculated based on the viewpoint of ensuring the output of internal combustion engine 1 and preventing the deterioration of emissions when the operation mode is controlled in the normal mode. The process of step S3 is based on the engine speed and the target fuel injection amount set when the operation mode is not the NOx reduction mode. The target value of the parameter value when the operation mode is not the NOx reduction mode is determined. It is an example of the process which the 1st calculation part which calculates candidate T1 performs. Details will be described later.

  Next, the ECU 8 executes a candidate T2 calculation process for calculating a second candidate T2 for the target value of the intake air temperature (step S5). Candidate T2 is a target value calculated based on the viewpoint of reducing NOx of catalyst 20 when the operation mode is controlled in the NOx reduction mode. The process of step S5 is based on the engine speed and the target fuel injection amount set when the operation mode is the NOx reduction mode, and the target value candidate T2 when the operation mode is the NOx reduction mode. Is an example of a process executed by the second calculation unit that calculates the engine speed and the target fuel injection amount with a value larger than the candidate T1 calculated under the same conditions. Details will be described later.

  Next, the ECU 8 executes a candidate T3 calculation process for calculating a third candidate T3 for the target value of the intake air temperature (step S7). Candidate T3 is a target value calculated based on the viewpoint of suppressing the generation of condensed water in intercooler 6. In step S7, the temperature of the intake air cooled by the intercooler 6 is determined based on the engine speed, the target fuel injection amount set in the determined operation mode, and the detected outside air temperature and outside air humidity. It is an example of the process which the 3rd calculation part which calculates the 3rd candidate of the target value exceeding dew point temperature performs. Details will be described later. Note that the order of the processes in steps S3, S5 and S7 is not limited.

  Next, the ECU 8 determines whether or not the current operation mode of the internal combustion engine 1 is the NOx reduction mode (step S9). The determination unit determines whether or not the operation mode of the internal combustion engine 1 is a NOx reduction mode in which the air-fuel ratio of the internal combustion engine 1 is changed to a rich side so as to reduce the NOx occluded by the catalyst 20 in the process of step S9. It is an example of the process to perform.

  When the operation mode is not the NOx reduction mode, that is, in the normal mode, the ECU 8 determines whether or not T1> T3 (step S11a). In the case of an affirmative determination, the ECU 8 sets the candidate T1 as a final target value (step S13a), and in the case of a negative determination, the ECU 8 sets the candidate T3 as a final target value (step S13b). That is, a high value among the candidates T1 and T3 is set as a final target value.

  If the determination in step S9 is affirmative, that is, if the operation mode is the NOx reduction mode, the ECU 8 determines whether or not T2> T3 (step S11b). If the determination is affirmative, the candidate T2 is set to the final target value (step S13c). If the determination is negative, the candidate T3 is set to the final target value (step S13b). That is, a high value is set as a final target value among the candidates T2 and T3. In the processes in steps S13a, S13b, and S13c, when the determination unit determines that the operation mode is not the NOx reduction mode, a higher value among the candidates T1 and T3 is set as the final target value, and the determination unit When it determines with a driving | operation mode being NOx reduction | restoration mode, it is an example of the process which the setting part which sets a high value as a final said target value among candidates T2 and T3 performs.

  As described above, in consideration of the operation mode of the internal combustion engine 1, the target value is set to a higher value among the candidates T1 and T3 or the candidates T2 and T3, and the rotation speed of the electric pump 42 is set. Feedback control is performed to achieve the target value. Thus, for example, when the operation mode is the normal mode, the intake air temperature suitable for the normal mode, specifically, the output of the internal combustion engine 1 is ensured within a range in which condensed water in the intercooler 6 is not generated, and the emission is reduced. The intake air temperature can be controlled to prevent deterioration. Further, in the NOx reduction mode, it is possible to control the intake air temperature suitable for reducing NOx occluded in the catalyst 20 within a range in which condensed water is not generated in the intercooler 6.

  Note that the processes in steps S3, S5, and S7 are executed regardless of the determination result in step S9, and all candidates T1 to T3 are calculated. For example, even if the current operation mode is the normal mode, assuming that the operation mode is the NOx reduction mode based on the engine speed and the accelerator opening of the internal combustion engine 1 acquired in step S1, the candidate T2 Is calculated. Similarly, even if the current operation mode is the NOx reduction mode, assuming that the operation mode is the normal mode based on the engine speed and the accelerator opening of the internal combustion engine 1 acquired in step S1, the candidate T1 is calculated.

  The reason why all candidates T1 to T3 are calculated regardless of the current operation mode will be described. During the switching of the operation mode, the fuel injection amount is changed so as to gradually reach the target value corresponding to the operation mode after switching so that the influence on drivability is small. For this reason, even during the operation mode switching, by calculating in advance candidates according to the operation mode after the operation mode switching is completed, the processing of step 11a or 11b can be performed immediately after the operation mode switching is completed. The optimal target value can be set early.

  Next, the candidate T1 calculation process will be described. FIG. 3A is a flowchart illustrating an example of the candidate T1 calculation process. The ECU 8 calculates a target fuel injection amount set in the normal mode based on the engine speed and the accelerator opening obtained in step S1 (step S21). The process of step S21 is an example of a process executed by a target fuel injection amount calculation unit that calculates a target fuel injection amount of the internal combustion engine 1.

  Specifically, a target fuel injection amount that is a target value of the fuel injection amount is calculated based on a map or calculation formula in the normal mode corresponding to the engine speed and the accelerator opening. The target fuel injection amount set in the normal mode is a fuel corresponding to the acquired engine speed and accelerator opening for realizing combustion at an air-fuel ratio corresponding to the required operating state of the internal combustion engine 1. The injection amount. This map or calculation formula is stored in the ROM of the ECU 8 in advance.

  Next, the ECU 8 calculates a candidate T1 based on the engine speed acquired in step S1 and the calculated target fuel injection amount in the normal mode (step S23).

  FIG. 3B is an example of a map that defines a target temperature that is a candidate T1 corresponding to the engine speed and the target fuel injection amount set in the normal mode. This map defines the temperature of the intake air obtained in advance by experiments so that the exhaust emission is not deteriorated while ensuring the output of the internal combustion engine 1 when the operation mode is the normal mode. This map is stored in advance in the ROM of the ECU 8. The calculation of the candidate T1 is not limited to such a map, and may be calculated by a calculation formula using the engine speed and the target fuel injection amount set in the normal mode.

  Note that, as described above, even if the current operation mode is the NOx reduction mode, the candidate T1 is calculated based on the map or the calculation formula used in the normal mode described above.

  Next, the candidate T2 calculation process will be described. FIG. 4A is a flowchart illustrating an example of the candidate T2 calculation process. The ECU 8 calculates the target fuel injection amount set in the NOx reduction mode based on the engine speed and the accelerator opening acquired in step S1 (step S31). The process of step S31 is an example of a process executed by a target fuel injection amount calculation unit that calculates a target fuel injection amount of the internal combustion engine 1.

  Specifically, the target fuel injection amount is calculated based on a map or calculation formula in the NOx reduction mode corresponding to the engine speed and the accelerator opening. The target fuel injection amount set in the NOx reduction mode is a fuel injection amount necessary for realizing combustion at a rich air-fuel ratio for reducing the NOx stored in the catalyst 20. This map or calculation formula is stored in the ROM of the ECU 8 in advance.

  Next, the ECU 8 calculates a candidate T2 based on the engine speed acquired in step S1 and the target fuel injection amount set in the calculated NOx reduction mode (step S33).

  FIG. 4B is a map that defines a target temperature that is a candidate T2 corresponding to the engine speed and the target fuel injection amount set in the NOx reduction mode. This map defines the temperature of the intake air obtained in advance through experiments, in which the NOx stored in the catalyst 20 can be reduced when the operation mode is the NOx reduction mode. This map is stored in advance in the ROM of the ECU 8. The calculation of the candidate T2 is not limited to such a map, and may be calculated by a calculation formula using the engine speed and the target fuel injection amount set in the NOx reduction mode.

  Note that, as described above, even if the current operation mode is the normal mode, the candidate T1 is calculated based on the map or the calculation formula used in the NOx reduction mode described above.

  Note that the candidate T2 is set to a higher value than the candidate T1 under the same engine speed and target fuel injection amount. This is because in the NOx reduction mode, in order to realize combustion at the air-fuel ratio on the rich side, the intake air amount is controlled to be smaller than in the normal mode, and it is not necessary to lower the intake air temperature accordingly.

  Next, the candidate T3 calculation process will be described. FIG. 5 is a flowchart illustrating an example of the candidate T3 calculation process. The ECU 8 calculates the target fuel injection amount in the current operating state based on the engine speed and the accelerator opening acquired in step S1 (step S41). The process of step S41 is an example of a process executed by a target fuel injection amount calculation unit that calculates a target fuel injection amount of the internal combustion engine 1.

  Next, the ECU 8 calculates a target boost pressure based on the target fuel injection amount calculated in step S41 (step S43). Specifically, the target boost pressure is calculated by a map or calculation formula corresponding to the engine speed and the target fuel injection amount. This map or calculation formula is stored in the ROM of the ECU 8 in advance.

  Next, the ECU 8 acquires the outside air temperature and the outside air humidity based on the detected values from the outside air temperature sensor 18 and the outside air humidity sensor 19 (step S45).

  Next, the ECU 8 calculates a candidate T3 based on the calculated target supercharging pressure and the acquired outside air temperature and outside air humidity (step S47). Specifically, the dew point temperature when the air at the outside air temperature and the outside air humidity is pressurized to the target supercharging pressure is calculated, and a value obtained by adding a predetermined margin to the dew point temperature is calculated as the candidate T3.

  FIG. 6 is an example of a map that defines the dew point temperature corresponding to the outside air temperature and the outside air humidity at a predetermined target boost pressure. The ROM of the ECU 8 stores a three-dimensional map that defines dew point temperatures corresponding to the outside air temperature, the outside air humidity, and the target supercharging pressure. The dew point temperature is calculated to be larger as the target supercharging pressure is higher under conditions where the outside air temperature and the outside air humidity are constant. The calculation of the dew point temperature is not limited to such a map, and may be calculated by a calculation formula using the outside air temperature, the outside air humidity, and the target supercharging pressure.

  Next, a modified example of the control for setting the target value of the intake air temperature executed by the ECU 8 will be described. FIG. 7 is a flowchart showing a modification of the control for setting the target value of the intake air temperature executed by the ECU 8. Note that the same parts as those in the flowchart shown in FIG.

  ECU8 calculates candidate T3 previously after execution of the process of step S1 (step S7). Next, the ECU 8 executes the process of step S9, calculates the candidate T1 in the case of negative determination (step S10a), executes the processes after step S11a, and selects the candidate T2 in the case of positive determination. Calculate (step S10b), and execute the processing after step S11b. In the modification, the processes of steps S10a and 10b are examples of processes executed by the above-described second and third calculation units, respectively.

  As described above, when the operation mode is determined to be the NOx reduction mode, the candidate T1 is not calculated, and when the operation mode is determined to be the normal mode, the candidate T2 is calculated. Absent. Thus, the ECU 8 does not always have to calculate the three candidates T1, T2, and T3, and the processing load on the ECU 8 is reduced.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

  In the above-described embodiments and modifications, the intake air temperature in the vicinity of the outlet of the intercooler 6 is adopted as the parameter value correlated with the temperature of the intake air cooled by the intercooler 6. However, the present invention is not limited to this. For example, the temperature of the refrigerant in the vicinity of the refrigerant inlet of the intercooler 6 or the temperature of the refrigerant in the vicinity of the outlet of the radiator 44 may be used as the parameter value. This is because the lower the temperature of the refrigerant at these positions, the lower the temperature of the intake air cooled by the intercooler 6, and there is a correlation between the two. In this case, it is necessary to provide a sensor for detecting the temperature of the refrigerant in the vicinity of the refrigerant inlet of the intercooler 6 or in the vicinity of the outlet of the radiator 44.

  In the above embodiment and the modified example, the candidate is calculated based on the engine speed and the target fuel injection amount. In addition, for example, the candidate may be calculated based on at least one of the EGR rate and the outside air temperature. Good. This is because the higher the EGR rate, the smaller the amount of fresh air supplied to the internal combustion engine and the lower the temperature of fresh air. Moreover, since the intake air amount increases as the outside air temperature decreases, the target value of the intake air temperature may be low.

  In the above embodiment and the modification, the candidate T1 or T2 is calculated from the engine speed and the target fuel injection amount, but the present invention is not limited to this. For example, the target boost pressure may be calculated from the target fuel injection amount using a map or a calculation formula, and the candidate T1 or T2 may be calculated using the map or the calculation formula based on the target boost pressure. Further, when calculating the candidate T1 or T2, the candidate calculated based on the engine speed and the target fuel injection amount is corrected based on, for example, the temperature of cooling water that cools the internal combustion engine 1 or the outside air temperature. Thus, the final candidate T1 or T2 may be calculated.

1 internal combustion engine 6 intercooler 8 ECU (engine speed acquisition unit, target fuel injection amount calculation unit, determination unit, first calculation unit, second calculation unit, third calculation unit, setting unit, control unit)
16 Intake air temperature sensor 18 Outside air temperature sensor 19 Outside air humidity sensor 20 Catalyst 42 Electric pump

Claims (3)

An intercooler that cools the intake air supplied to the internal combustion engine by heat exchange with the refrigerant;
An electric pump for adjusting the flow rate of the refrigerant flowing through the intercooler;
A sensor for detecting a parameter value correlated with the temperature of the intake air cooled by the intercooler;
A catalyst for storing and reducing NOx in the exhaust gas of the internal combustion engine;
A temperature and humidity sensor for detecting the outside air temperature and the outside air humidity;
An engine speed acquisition unit for acquiring the engine speed of the internal combustion engine;
A target fuel injection amount calculation unit for calculating a target fuel injection amount of the internal combustion engine;
A determination unit that determines whether or not the operation mode of the internal combustion engine is a NOx reduction mode in which the air-fuel ratio of the internal combustion engine is changed to a rich side so as to reduce NOx stored by the catalyst;
Based on the engine speed and the target fuel injection amount set when the operation mode is not the NOx reduction mode, the target value of the parameter value when the operation mode is not the NOx reduction mode A first calculation unit for calculating a first candidate of
Based on the engine speed and the target fuel injection amount set when the operation mode is the NOx reduction mode, the target value of the target value when the operation mode is the NOx reduction mode is set. A second calculation unit that calculates two candidates with a larger value than the first candidate in which the engine speed and the target fuel injection amount are calculated under the same conditions;
Based on the engine speed, the determined target fuel injection amount set in the determined operation mode, and the detected outside air temperature and outside air humidity, the temperature of the intake air cooled by the intercooler is dew point temperature. A third calculation unit for calculating a third candidate of the target value exceeding
When the determination unit determines that the operation mode is not the NOx reduction mode, a higher value among the first and third candidates is set as the final target value, and the determination unit determines the operation mode. Is determined to be the NOx reduction mode, a setting unit that sets a high value as the final target value among the second and third candidates,
And a control unit that feedback-controls the rotational speed of the electric pump so that the parameter value becomes the set target value.   The first, second, and third calculation units calculate the first, second, and third candidates, respectively, regardless of the determination result of the operation mode by the determination unit. Control device for internal combustion engine. When the determination unit determines that the operation mode is the NOx reduction mode, the first calculation unit does not calculate the first candidate,
The control apparatus for an internal combustion engine according to claim 1, wherein the second calculation unit does not calculate the second candidate when the determination unit determines that the operation mode is not the NOx reduction mode.

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