DE102017106577A1 - CONTROL DEVICE AND CONTROL METHOD FOR A COMBUSTION ENGINE - Google Patents

Abstract

A control apparatus for an internal combustion engine includes an electronic control unit (8) configured to: calculate a first target value (T1) of a parameter value when a mode is not a NOx reducing mode; calculate a second set point (T2) when the mode is the NOx reduction mode; calculate a third set point (T3) such that an intake air temperature is higher than a condensation temperature; set a higher value of the first and third target values as a final target value when the mode is not the NOx reducing mode; set a higher value of the second and third target values than the final target value when the mode is the NOx reduction mode; and perform a control at a speed of an electric pump (42) such that the parameter value reaches the set final setpoint. A corresponding control method for an internal combustion engine is also provided.

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

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

2. Description of the Related Art

The Japanese Patent Publication JP 2011-214 544 A describes a technique for controlling an electric pump that adjusts a flow rate of a coolant circulating through an intercooler so that a temperature of intake air cooled by the intercooler reaches a target value based on an operating state of an internal combustion engine.

BRIEF SUMMARY OF THE INVENTION

An operation mode of an internal combustion engine includes a normal mode and a NOx reduction mode. In the normal mode, combustion is performed at an air-fuel ratio corresponding to an operating condition requested in the internal combustion engine. In the NOx reducing mode, the air-fuel ratio is changed to a rich side to carry out combustion. In the normal operation mode, the air-fuel ratio is variably set based on a viewpoint for ensuring output of the internal combustion engine and preventing deterioration of emission. In the NOx reducing mode, the rich air-fuel ratio combustion is performed to reduce NOx stored in a catalyst that cleans an exhaust gas of the internal combustion engine.

From the standpoint of ensuring the output of the internal combustion engine and preventing the deterioration of the emission, it is desirable that the temperature of the intake air cooled by the charge air cooler be low. For this reason, it is desirable to set a target value of the intake air temperature to a low value.

However, in the NOx reducing mode, rich combustion is performed. Consequently, in an operating state in which a requested torque in the internal combustion engine is small, for example, a fuel injection amount becomes small, and also the intake air is greatly reduced. In such a NOx reducing mode, if the target intake air temperature is also set to a low value based on the position for ensuring the output of the internal combustion engine and preventing the deterioration of the emission, the intake air temperature becomes too low and the intake air can not be reduced so that the rich combustion can not be realized and NOx can not be reduced.

Further, when the temperature of the intake air cooled by the charge air cooler is too low, the intake air temperature falls below a condensation temperature, whereby condensed water may be generated in the charge air cooler. When condensed water is generated, the condensed water thus generated collects in an intake passage and then flows into a cylinder of the internal combustion engine at one time, which may cause a water hammering phenomenon.

In view of this, the present invention provides a control apparatus and method for an internal combustion engine each of which limits generation of condensed water in an intercooler and controls an optimum intake air temperature according to an operation mode of the internal combustion engine.

A first aspect of the present invention is a control device for an internal combustion engine. The internal combustion engine includes a charge air cooler, an electric pump, an intake air temperature sensor, a catalyst, and a temperature humidity sensor. The charge air cooler is configured to cool an intake air to be supplied to the internal combustion engine through a heat exchange with a coolant. The electric pump is configured to adjust a flow rate of the coolant circulating through the charge air cooler. The intake air temperature sensor is configured to detect a parameter value that is correlated with a temperature of the intake air cooled by the intercooler. The catalyst is configured to store and reduce NOx in an exhaust gas of the internal combustion engine. The temperature humidity sensor is configured to detect an outside air temperature and an outside air humidity. The control device comprises an electronic control unit. The electronic control unit is configured to obtain an engine speed of the internal combustion engine and to calculate a target fuel injection quantity of the internal combustion engine. The electronic control unit is configured to determine if the mode of operation of the Internal combustion engine is a NOx reduction mode or not. The NOx reducing mode is a mode in which an air-fuel ratio of the internal combustion engine is changed to a rich side to reduce the NOx stored in the catalyst. The electronic control unit is configured to calculate a first target value of the parameter value when the mode is not the NOx reduction mode. The first target value is calculated based on the engine speed and the target fuel injection amount to be set when the mode is not the NOx reducing mode. The electronic control unit is configured to calculate a second set point setpoint when the mode is the NOx reduction mode. The second target value is calculated based on the engine speed and the target fuel injection amount to be set when the operation mode is the NOx reduction mode. The second target value is a value greater than the first target value that is set under the same conditions of the engine speed and the target fuel injection amount. The electronic control unit is configured to calculate a third target value for the target value based on the engine speed of the target fuel injection amount to be set in the specific operating mode and a detected outside air temperature and a detected outside air humidity. The third target value is a target value at which the temperature of the intake air cooled by the charge air cooler is higher than a condensation temperature. The electronic control unit is configured to set a higher value of the first target value and the third target value as a final target value when the electronic control unit determines that the operating mode is not the NOx reducing mode. The electronic control unit is configured to set a higher value of the second setpoint and the third setpoint than the final setpoint when the electronic control unit determines that the mode is the NOx reduction mode. The electronic control unit is configured to control the speed of the electric pump so that the parameter value reaches the set final setpoint.

According to the configuration described above, when the mode is not the NOx reduction mode, a higher value of the first target value and the third target value exceeding the condensation temperature is set as the final target value, the control being executed at the rotational speed of the electric pump is to reach the setpoint. Thereby, an intake air temperature is controlled to an intake air temperature, which is suitable for the operating mode, which is not the NOx-Reduzierbetriebsart, within a range in which no condensed water is generated in the charge air cooler. Further, in the case of the NOx reducing mode, a higher value is set from the second target value in the NOx reducing mode and the third target value exceeding the condensing temperature as the final target value, the control being executed at the rotational speed of the electric pump to reach the setpoint. Thereby, the intake air temperature to an intake air temperature suitable for reducing NOx stored in the catalyst can be controlled within a range in which no condensed water is generated in the charge air cooler.

In the control device, the electronic control unit may be configured to calculate the first target value, the second target value and the third target value independently of a determination result of the operation mode.

In the control device, the electronic control unit may be configured not to calculate the first target value when the electronic control unit determines that the operating mode is the NOx reducing mode. The electronic control unit may be configured not to calculate the second setpoint when the electronic control unit determines that the operating mode is not the NOx reducing mode.

A second aspect of the present invention is a control method for an internal combustion engine. The internal combustion engine includes a charge air cooler, an electric pump, an intake air temperature sensor, a catalyst, and a temperature humidity sensor. The charge air cooler is configured to cool an intake air to be supplied to the internal combustion engine through a heat exchange with a coolant. The electric pump is configured to adjust a flow rate of the coolant circulating through the charge air cooler. The intake air temperature sensor is configured to detect a parameter value that correlates to a temperature of the intake air cooled by the charge air cooler. The catalyst is configured to store and reduce NOx in an exhaust gas of the internal combustion engine. The temperature humidity sensor is configured to detect an outside air temperature and an outside air humidity. The control method includes: calculating a target fuel injection amount of the internal combustion engine; determining whether or not an operation mode of the internal combustion engine is a NOx reducing mode, wherein the NOx reducing mode is a mode in which an air-fuel ratio of the internal combustion engine is changed to a rich side to the NOx that is in the catalyst is stored, too to reduce; calculating the first set value for a set value of the parameter value when the mode is not the NOx reducing mode, the first set value based on an engine speed of the internal combustion engine and the target fuel injection amount to be set when the mode is not the NOx reducing mode; is calculated; calculating the second target value for the target value when the operating mode is the NOx reducing mode, wherein the second target value is calculated based on the engine rotational speed and the target fuel injection amount to be set when the operating mode is the NOx reducing mode; Setpoint is greater than the first setpoint calculated under the same conditions of the engine speed and the target fuel injection amount; calculating a third target value for the target value based on the engine rotational speed, the target fuel injection amount to be set in the specific operating mode, and the detected outside air temperature and the detected outside air humidity, the third target value being a target value at which the temperature of the intake air is cooled by the intercooler, is higher than a condensation temperature; setting a higher value of the first target value and the third target value as a final target value when the mode is not the NOx reduction mode; setting a higher value of the second setpoint and the third setpoint than the final setpoint when the mode is the NOx reduction mode; and performing a control on the speed of the electric pump so that the parameter value reaches the set final setpoint.

According to the configuration described above, it is possible to provide a control device for an internal combustion engine, wherein the control device limits generation of condensed water in an intercooler and controls an optimal intake air temperature according to an operation mode of the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWING

Features, advantages and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like reference numerals designate like elements. Show it:

1 a diagram illustrating a control device for an internal combustion engine according to the present embodiment;

2 FIG. 10 is a flowchart illustrating an example of setting control of a target value of intake air temperature to be executed by an ECU; FIG.

3A a flowchart illustrating an example of a first target value calculation step;

3B an example of a map that prescribes a target temperature as a first target value corresponding to an engine speed and a target fuel injection amount that is set in a normal mode;

4A a flowchart illustrating an example of a second target value calculation step;

4B an example of a map prescribing a target temperature as a second target value corresponding to an engine speed and a target fuel injection amount set in a NOx reducing mode;

5 Fig. 10 is a flow chart illustrating an example of a third target value calculation step;

6 an example of a map that prescribes a condensation temperature corresponding to an outside air temperature and an outside air humidity at a predetermined target charging pressure; and

7 5 is a flowchart illustrating a modification of an adjustment control of a target value of intake air temperature to be executed by the ECU.

DETAILED DESCRIPTION OF THE EMBODIMENTS

1 shows a diagram illustrating a control device for an internal combustion engine 1 illustrated according to the present embodiment. The control device for the internal combustion engine 1 includes an exhaust passage 3 , a suction channel 4 , a supercharger 5 , a charge air cooler 6 , an electronic control unit (ECU 8th ), a catalyst 20 , a bypass channel 30 and the same. The internal combustion engine 1 is a diesel engine that has four cylinders 2 includes, but is not limited to, and may be a gasoline engine. The intake channel 4 and the exhaust duct 3 are with the internal combustion engine 1 connected. A compressor housing 51 the supercharger 5 is in the middle of the intake duct 4 placed. A turbine housing 50 the supercharger 5 is in the middle of the exhaust duct 3 placed.

A turbine 500 is in the turbine housing 50 placed and a compressor 501 is in the compressor housing 51 placed. The turbine 500 and the compressor 501 are coaxially connected by a turbine shaft. The compressor 501 is also due to the turbine 500 rotated, which is rotated by an exhaust gas flowing through the exhaust duct 3 flows to the intake air in the intake passage 4 charge.

The bypass channel 30 , the turbine 500 bypasses, and a wastegate valve 31 that the bypass channel 30 opens and closes, are in the middle of the exhaust duct 3 provided. An opening degree of the wastegate valve 31 is through the ECU 8th controlled so that a flow rate of the exhaust gas passing through the turbine 500 flows, is adjusted and a boost pressure of the intake air passing through the compressor 501 is charged, adjusted.

The intercooler 6 is in the intake channel 4 on a downstream side relative to the compressor housing 51 placed. A coolant, that of the combustion engine 1 is to be supplied circulates within the intercooler. This will cause a heat exchange between the coolant passing through the intercooler 6 circulates, and the air passing through the intercooler 6 passed, so that the intake air is cooled.

The coolant path 40 is a path on which the coolant between the intercooler 6 and a cooler 44 by an electric pump 42 circulated. The coolant that receives heat in the charge air cooler undergoes heat exchange with outside air in the radiator 44 and is cooled. A speed of the electric pump 42 is through the ECU 8th controlled, so that a flow rate of the coolant, through the electric pump 42 is transported, thereby being adjusted.

An intake air temperature sensor 16 , which is a temperature of the intake air passing through the intercooler 6 is detected, is on the downstream side with respect to the intercooler 6 provided.

In the exhaust duct 3 is the catalyst on the downstream side with respect to the turbine 500 provided. The catalyst 20 is a storage reduction type (NOx storage reduction catalyst: NSR 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 carried. The catalyst 20 stores NOx in the exhaust gas when an air-fuel ratio of the exhaust gas is leaner than a stoichiometric air-fuel ratio. The catalyst 20 reduces the NOx thus stored to N ₂ when the air-fuel ratio is rich. Exhaust gas temperature sensors 13 . 14 , which detect a temperature of the exhaust gas, are in front of and behind the catalyst 20 provided.

The ECU 8th comprises a central processing unit (CPU), a read only memory (ROM) and a random access memory (RAM). The ECU 8th executes the below-mentioned target value setting control on the basis of information from sensors, information stored in advance in the ROM, and the like according to a control program stored in advance in the ROM.

The ECU 8th controls an operating condition of the internal combustion engine 1 based on output signals from various sensors, such as a crank angle sensor 9 , an air flow meter 12 , the exhaust gas temperature sensors 13 . 14 , the intake air temperature sensor 16 , an accelerator opening sensor 17 , an outside air temperature sensor 18 and an outdoor humidity sensor 19 ,

The crank angle sensor 9 detects a rotation angle of a crankshaft of the internal combustion engine 1 , The air flow meter 12 includes an amount of intake air entering the intake passage 4 is recorded. The exhaust gas temperature sensors 13 . 14 are on an upstream side and a downstream side of the catalyst 20 each placed to detect temperatures of the exhaust gas before and after the exhaust gas through the catalyst 20 passes.

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

The intake air temperature sensor 16 is near an outlet of the intercooler 6 placed to detect a temperature of the intake air passing through the intercooler 6 is cooled. The intake air temperature sensor 16 is an example of one A sensor that senses a parameter value that correlates with a temperature of the intake air passing through the intercooler 6 is cooled.

As described above, the ECU attains 8th a detection value of the intake air temperature sensor 16 and performs a control on the speed of the electric pump 42 from, so that the acquired detection value of the intake air temperature sensor 16 reached a set value. The speed of the electric pump 42 is controlled to increase as the set value of the intake air temperature becomes lower. A plurality of target values are calculated as the target intake air temperature based on a plurality of viewpoints, and a higher value among the target values thus calculated is set as a final target value. The ECU 8th is an example of a control section that regulates the speed of the electric pump 42 so that the temperature reaches the set value. Details will be described below.

Next, an operation mode of the internal combustion engine 1 described by the ECU 8th is controlled. The ECU 8th changes the operating mode of the internal combustion engine 1 between a normal mode and a NOx reduction mode. In the normal mode, combustion at an air-fuel ratio corresponding to an operating condition becomes that in the internal combustion engine 1 is requested on the basis of a viewpoint of ensuring an output of the internal combustion engine 1 and an improvement in fuel efficiency. For example, in the normal mode at the time of light load, the combustion is performed at a lean air-fuel ratio larger than a stoichiometric air-fuel ratio. For example, in the normal mode at the time of idling, low speed, high speed or heavy load, the combustion is performed at a rich air-fuel ratio smaller than the stoichiometric air-fuel ratio.

In the NOx reduction mode, the catalyst becomes 20 to regenerate by the NOx that is in the catalyst 20 is reduced, the combustion is performed by changing the air-fuel ratio to a rich side suitable for reducing NOx. That is, even in a case of the same engine speed and the same accelerator opening degree, the air-fuel ratio in the NOx reducing mode is set to a fatter side than that in the normal mode. For example, an exhaust amount of NOx is calculated based on a fuel injection amount. Then, the change from the normal mode to the NOx reducing mode is executed when an integrated value of the discharge amount reaches a predetermined value. Further, the change from the NOx reducing mode to the normal mode is executed when the NOx reducing mode is continued, for example, for a predetermined time.

Next, an adjustment control of a target value of intake air temperature described by the ECU will be described 8th is to execute. 2 FIG. 12 is a flowchart illustrating an example of the adjustment control of the target intake air temperature set by the ECU. FIG 8th is to execute.

First, in step S1, the ECU obtains 8th an engine speed of the internal combustion engine 1 and the accelerator opening degree used for processings of steps S3, S5, S7 (described below). The engine speed and the accelerator opening degree are determined based on respective output values from the crank angle sensor 9 and the accelerator opening sensor 17 obtained.

Below is the ECU 8th a first target value T1 calculation processing for calculating a first target value T1 of the intake air temperature based on the engine speed and the accelerator opening degree thus detected (S3). The first target value T1 is a target value based on the viewpoint of ensuring the output of the internal combustion engine 1 and preventing deterioration of an emission when the mode is controlled to the normal mode. The processing of step S3 is an example of processing for calculating the first target value T1 for a target value of a parameter value in a case where the operating mode is not the NOx reducing mode, based on an engine speed and a target fuel injection amount to be set, if the mode is not the NOx reduction mode. Details will be described below.

Below is the ECU 8th a second target value T2 calculation processing for calculating a second target value T2 for the target intake air temperature value (step S5). The second target value T2 is a target value based on the viewpoint of reducing NOx of the catalyst 20 is calculated when the mode is controlled to the NOx Reduzierbetriebsart. The Processing in step S5 is an example of processing for calculating the second target value T2 for the target value when the operating mode is the NOx reducing mode based on the engine rotational speed and a target fuel injection amount to be set when the operating mode is the NOx reducing mode. wherein the second target value T2 is calculated as a value greater than the first target value T1 calculated under the same conditions of the engine speed and the target fuel injection amount. Details will be described below.

Below is the ECU 8th a third target value T3 calculation processing for calculating a third target value T3 for the target intake air temperature value (S7). The third target value T3 is a target value based on the viewpoint of limiting a generation of condensed water in the intercooler 6 is calculated. The processing of step S7 is an example of processing for calculating a third target value T3 based on the engine speed, a target fuel injection amount to be set in a certain mode, and a detected outside air temperature and a detected outside air humidity. The third target value T3 is a target value that is to be adjusted, so that a temperature of the intake air passing through the intercooler 6 is cooled, exceeds a condensation temperature. Details will be described below. It is to be noted that the processings according to the steps S3, S5, S7 are executable in any order.

Then the ECU determines 8th Whether the operating mode of the internal combustion engine 1 at the present moment, the NOx reducing mode is or not (S9). The processing of step S9 is an example of processing for determining whether the operation mode of the internal combustion engine 1 the NOx reducing mode is or not, in which the air-fuel ratio of the internal combustion engine 1 is changed to the rich side to reduce the NOx present in the catalyst 20 is stored.

In a case where the mode is not the NOx reducing mode, that is, in a case of the normal mode, the ECU determines 8th Whether T1> T3 is satisfied or not (step S11a). In a case of a confirmatory provision, the ECU 8th the first target value T1 as a final target value (step S13a). In a case of a negative determination, the ECU 8th the third target value T3 as the final target value (step S13b). That is, a higher value of the first target value T1 and the third target value T3 is set as the final target value.

In a case of an affirmative determination in step S9, that is, in a case where the mode is the NOx reducing mode, the ECU determines 8th whether or not T2> T3 is satisfied (step S11b). In a case of an affirmative determination, the second target value T2 is set as the final target value (step S13c). In a case of a negative determination, the ECU 8th the third target value T3 as the final target value (step S13b). That is, a higher value of the second target value T2 and the third target value T3 is set as the final target value. The processings according to steps S13a, S13b, S13c are an example of processing for setting a higher value of the first target value T1 and the third target value T3 as the final target value when it is determined that the operating mode is not the NOx reducing mode, and setting a higher value of the second set value T2 and the third set value T3 as the final set value when it is determined that the mode is the NOx reducing mode.

As described above, a higher value of the first target value T1 and the third target value T3 or the second target value T2 and the third target value T3 becomes the target value in consideration of the operation mode of the internal combustion engine 1 set. A regulation is at the speed of the electric pump 42 executed to reach the setpoint so set. Thereby, for example, in a case where the mode is the normal mode, the intake air temperature can be controlled to an intake air temperature suitable for the normal mode, more specifically, an intake air temperature necessary for ensuring the output of the internal combustion engine 1 and preventing deterioration of emission is suitable within a range in which no condensed water in the intercooler 6 is produced. Further, in the NOx reducing mode, the air temperature to an intake air temperature suitable for reducing the NOx may be that in the catalyst 20 is stored, controlled within a range in which no condensed water in the intercooler 6 is produced.

It is to be noted that the processes according to the steps S3, S5, S7 are executed independently of the determination result in step S9 to calculate all of the first target value T1 to the third target value T3. For example, even if the mode is the normal mode at the present moment, the second set value T2 is calculated on the assumption of a case where the mode is the NOx reducing mode at the engine speed of the internal combustion engine 1 and the accelerator opening degree obtained in step S1. On Similarly, even when the operation mode is the NOx reduction mode at the present moment, the first target value T1 is calculated on the assumption of a case where the operation mode is the normal operation mode at the engine revolution speed of the internal combustion engine 1 and the accelerator opening degree obtained in step S1.

A reason for calculating all of the first target value T1 to the third target value T3 regardless of the current operating condition will be described below. While the mode is changed, the fuel injection amount is changed to gradually reach a target value corresponding to the mode after the change, so that drivability is not so much affected. For this reason, even during the change of the operation mode, when the set value corresponding to the operation mode after the completion of the change of the operation mode is calculated in advance, it is possible to process in step S11a or S11b immediately after completion of the change of the operation mode which makes it possible to set an optimum set value at an early stage.

Next, the first target value T1 calculation processing will be described. 3A FIG. 12 is a flowchart illustrating an example of the first target value T1 calculating step. FIG. The ECU 8th calculates a target fuel injection amount to be set in the normal mode based on the engine speed and the accelerator opening degree obtained in step S1 (step S21). The processing of step S21 is an example of processing for calculating the target fuel injection quantity of the internal combustion engine 1 ,

Specifically, the target fuel injection amount, which is a target value of the fuel injection amount, is calculated based on a map or a calculation formula in the normal operation mode corresponding to the engine speed and the accelerator opening degree. The target fuel injection amount that is set in the normal mode is a fuel injection amount corresponding to the obtained engine speed and the obtained accelerator opening degree to realize combustion at an air-fuel ratio corresponding to an operating state that is in the internal combustion engine 1 is requested. The map or formula is preliminarily stored in the ROM of the ECU 8th saved.

Subsequently, the ECU calculates 8th the first target value T1 based on the engine speed obtained in step S1 and the calculated target fuel injection amount in the normal mode (step S23).

3B FIG. 14 shows an example of a map that prescribes a target temperature as the first target value T1 corresponding to the engine speed and the target fuel injection amount set in the normal mode. The map prescribes an intake air temperature obtained in advance by an experiment so as not to deteriorate an exhaust emission while the output of the internal combustion engine 1 is ensured in a case where the mode is the normal mode. The map is previously stored in the ROM of the ECU 8th saved. It should be noted that the calculation of the first target value T1 is not limited to such map, but may be calculated by a calculation formula using the engine speed and the target fuel injection amount set in the normal mode.

As described above, even when the operation mode is the NOx reduction mode at the present time, the first target value T1 is calculated on the basis of the map or the calculation formula used in the normal operation mode.

Next, the second target value T2 calculation processing will be described. 4A FIG. 12 is a flowchart illustrating an example of the second target value T2 calculating step. FIG. The ECU 8th calculates a target fuel injection amount to be set in the NOx reducing mode based on the engine speed and the accelerator opening degree obtained in step S1 (step S31). The processing of step S31 is an example of processing for calculating the target fuel injection quantity of the internal combustion engine 1 ,

More specifically, the target fuel injection amount is calculated on the basis of a map or a calculation formula in the NOx reducing mode according to the engine speed and the accelerator opening degree. The target fuel injection amount, which is set in the NOx reducing mode, is a fuel injection amount required to realize rich air-fuel ratio combustion to reduce the NOx in the catalyst 20 is stored. The figure or the formula of calculation is made in advance in the ROM of the ECU 8th saved.

Subsequently, the ECU calculates 8th the second target value T2 based on the engine speed obtained in step S1 and the target fuel injection amount set in the NOx reducing mode (step S33).

4B FIG. 12 shows a map that prescribes a target temperature as the second target value T2 according to the engine speed and the target fuel injection amount set in the NOx reducing mode. The map prescribes an intake air temperature, which is obtained in advance by an experiment, of the NOx contained in the catalyst 20 is stored to reduce in a case where the mode is the NOx Reduzierbetriebsart. The map is previously stored in the ROM of the ECU 8th saved. It is to be noted that the calculation of the second target value T2 is not limited to such map, but may be calculated by a calculation formula using the engine speed and the target fuel injection amount set in the NOx reducing mode.

Note that, as described above, even when the mode is the normal mode at the present time, the second set value T2 is calculated on the basis of the map or the calculation formula that is in the NOx reducing mode be used.

It is to be noted that under the same conditions of the engine speed and the target fuel injection amount, the second target value T2 is set to a value higher than the first target value T1. The reason for this is that an intake air amount in the NOx reducing mode is controlled to be smaller than that in the normal mode to realize the combustion at an air-fuel ratio on the rich side, and accordingly, it is not required to decrease the intake air temperature.

Next, the third target value T3 calculation processing will be described. 5 FIG. 12 is a flowchart illustrating an example of the third target T3 calculating step. FIG. The ECU 8th calculates a target fuel injection amount to be set in a current operating state on the basis of an engine speed and the accelerator opening degree, both of which are obtained in step S1 (S41). The processing of step S41 is an example of processing for calculating the target fuel injection quantity of the internal combustion engine 1 ,

Subsequently, the ECU calculates 8th 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. The map or formula is preliminarily stored in the ROM of the ECU 8th saved.

Then the ECU obtains 8th an outside air temperature and an outside air humidity based on respective detection values from the outside air temperature sensor 18 and the outdoor humidity sensor 19 (Step S45).

Then the ECU calculates 8th the third target value T3 based on the target boost pressure thus calculated and the outside air temperature and the outside air humidity thus obtained (step S47). More specifically, a condensation temperature is calculated in a case where the air at the outside air temperature and the outside air humidity is pressurized to the target charging pressure, and a value obtained by adding a predetermined clearance to the condensation temperature is calculated as the third target value T3 is calculated.

6 FIG. 10 shows an example of a map that prescribes the condensation temperature corresponding to the outside air temperature and the outside air humidity at the predetermined target boost pressure. A three-dimensional map, which prescribes a condensation temperature corresponding to an outside air temperature, an outside air humidity, and a target boost pressure, is in the ROM of the ECU 8th saved. The condensation temperature is calculated to be larger when the target supercharging pressure is larger under the condition that the outside air temperature and the outside air humidity are constant. It should be noted that the calculation of the condensation temperature is not limited to such a map but can be calculated by a calculation formula that uses the outside air temperature, the outside air humidity, and the target boost pressure.

Next, a modification of an adjustment control of a target value of intake air temperature described by the ECU will be described 8th is to execute. 7 FIG. 12 is a flowchart illustrating the modification of the adjustment control of the target intake air temperature set by the ECU 8th is to execute. It should be noted that the same part as in the flowchart in 2 has the same reference numeral to omit a redundant description.

The ECU 8th First, after processing, calculates a third target value T3, processing according to step S1 (step S7). Below is the ECU 8th processing according to step S9. In a case of a negative determination in step S9, the ECU calculates 8th a first target value T1 (step S10a) and executes processings in step S11a and corresponding subsequent steps. In a case of an affirmative determination in step S9, the ECU calculates 8th a second target value T2 (step S10b), and executes processings in step S11b and corresponding subsequent steps.

As such, the calculation of the first target value T1 is not performed when it is determined that an operation mode is NOx reducing mode. Also, the calculation of the second target value T2 is not carried out when it is determined that the operating mode is a normal operating mode. As such, the ECU 8th do not always calculate three setpoints T1, T2, T3, thereby causing a processing load on the ECU 8th is reduced.

The embodiment according to the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications and changes can be made within the scope of the present invention described in the claims.

In the above-described embodiment and the modification, the intake air temperature becomes near the outlet of the intercooler 6 is used as a parameter value that correlates with the temperature of the intake air passing through the charge air cooler 6 is cooled, but the present invention is not limited thereto. For example, a temperature of the coolant in the vicinity of a coolant inlet of the intercooler 6 or a temperature of the coolant in the vicinity of an outlet of the radiator 44 as the parameter value. The reason for this is that, since the temperatures of the coolant at these positions are lower, the temperature of the intake air passing through the intercooler 6 is also lower, and thus correlated with each other. In this case, it is necessary to provide a sensor that detects the temperature of the coolant in the vicinity of the coolant inlet of the intercooler 6 or the outlet of the radiator 44 detected.

In the above-described embodiment and the modification, the target value is calculated based on the engine rotational speed and the target fuel injection amount, but additionally, the target value may be calculated based on, for example, at least one of an EGR rate and the outside air temperature. The reason for this is that, when the EGR rate is higher, an amount of fresh air to be supplied to the internal combustion engine decreases, so that a temperature of the fresh air may be low. Further, the reason for this is also that, when the outside air temperature is lower, an intake air amount is larger, so that the target value of the intake air temperature may be low.

In the above-described embodiment and the modification, the first target value T1 or the second target value T2 is calculated from the engine speed and the target fuel injection amount, but the present invention is not limited thereto. For example, the target boost pressure from the target fuel injection amount may be calculated by referring to a map or a calculation formula to calculate the first target value T1 or the second target value T2 with reference to a map or a calculation formula based on the target fuel injection amount Desired charge pressure based. Further, at the time of calculating the first target value T1 or the second target value T2, a target value calculated based on the engine rotational speed and the target fuel injection amount may be based on the outside air temperature or a temperature of a coolant for cooling the internal combustion engine 1 for example, to calculate a final target value T1 or T2.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• JP 2011-214544A [0002]

Claims (4)

Control device for an internal combustion engine ( 1 ), wherein the internal combustion engine ( 1 ) has an intercooler ( 6 ) configured to receive an intake air of the internal combustion engine ( 1 ) is to cool by a heat exchange with a coolant, an electric pump ( 42 ), which is configured to control a flow rate of the coolant passing through the charge air cooler ( 6 ) circulates to adjust an intake air temperature sensor ( 16 ) configured to detect a parameter value associated with a temperature of the intake air passing through the intercooler ( 6 ), is a catalyst ( 20 ) configured to store NOx in an exhaust gas of the internal combustion engine ( 1 ) and a temperature humidity sensor ( 18 . 19 ) configured to detect an outside air temperature and an outside air humidity, the control device being characterized by an electronic control unit ( 8th ) configured: an engine speed of the internal combustion engine ( 1 ) to get; a desired fuel injection quantity of the internal combustion engine ( 1 ) to calculate; determine whether an operating mode of the internal combustion engine ( 1 is a NOx reduction mode or not, wherein the NOx reduction mode is a mode in which an air-fuel ratio of the internal combustion engine ( 1 ) is changed to a rich side in order to reduce the NOx present in the catalyst ( 20 ) is stored; calculating a first target value (T1) for a target value of the parameter value when the operating mode is not the NOx reducing mode, the first target value being calculated based on the engine speed and the target fuel injection amount to be set when the operating mode is not the NOx Reduction mode is; calculate a second target value (T2) for the target value when the operating mode is the NOx reducing mode, the second target value (T2) being calculated based on the engine speed and the target fuel injection amount to be set when the operating mode is the NOx reducing mode wherein the second target value (T2) is a value greater than the first target value (T1) calculated under the same conditions of the engine speed and the target fuel injection amount; calculate a third target value (T3) for the target value based on the engine speed, the target fuel injection amount to be set in the determined mode, and the detected outside air temperature and outside air humidity, the third target value (T3) being a target value at which the temperature the intake air passing through the intercooler ( 6 ) is higher than a condensation temperature; set a higher value of the first setpoint (T1) and the third setpoint (T3) as a final setpoint when the electronic control unit ( 8th ) determines that the mode is not the NOx reduction mode; to set a higher value from the second setpoint (T2) and the third setpoint (T3) than the final setpoint when the electronic control unit ( 8th ) determines that the mode is the NOx reduction mode; and a control at a speed of the electric pump ( 42 ) so that the parameter value reaches the set final setpoint. Control device according to claim 1, wherein the electronic control unit ( 8th ) is configured to calculate the first target value (T1), the second target value (T2) and the third target value (T3) independently of a determination result of the operation mode. Control device according to claim 1, wherein: the electronic control unit ( 8th ) is configured not to calculate the first setpoint (T1) when the electronic control unit ( 8th ) determines that the mode is the NOx reduction mode; and the electronic control unit ( 8th ) is configured to not calculate the second set point (T2) when the electronic control unit ( 8th ) determines that the mode is not the NOx reduction mode. Control method for an internal combustion engine ( 1 ), wherein the internal combustion engine ( 1 ) has an intercooler ( 6 ) configured to receive an intake air of the internal combustion engine ( 1 ) is to cool by a heat exchange with a coolant, an electric pump ( 42 ), which is configured to control a flow rate of the coolant passing through the charge air cooler ( 6 ) circulates to adjust an intake air temperature sensor ( 16 ) configured to detect a parameter value associated with a temperature of the intake air passing through the intercooler ( 6 ), is a catalyst ( 20 ) configured to store NOx in an exhaust gas of the internal combustion engine ( 1 ) and a temperature humidity sensor ( 18 . 19 ) configured to detect an outside air temperature and an outside air humidity, the control method being characterized by: calculating a target fuel injection quantity of the internal combustion engine ( 1 ); determining whether an operating mode of the internal combustion engine ( 1 is a NOx reduction mode or not, wherein the NOx reduction mode is a mode in which an air-fuel ratio of the internal combustion engine ( 1 ) is changed to a rich side in order to reduce the NOx present in the catalyst ( 20 ) is stored; calculating a first set value (T1) for a set value of the parameter value when the mode is not the NOx reduction mode, the first set value based on an engine speed of the internal combustion engine ( 1 ) and the target fuel injection amount to be set when the mode is not the NOx reducing mode is calculated; calculating the second target value (T2) for the target value when the operating mode is the NOx reducing mode, the second target value being calculated based on the engine speed and the target fuel injection amount to be set when the operating mode is the NOx reducing mode; the second target value (T2) being a value greater than the first target value (T1) calculated under the same conditions of the engine speed and the target fuel injection amount; calculating a third target value (T3) for the target value based on the engine speed, the target fuel injection amount to be set in the determined mode, and the detected outside air temperature and outside air humidity, the third target value (T3) being a target value at which the temperature the intake air passing through the intercooler ( 6 ) is higher than a condensation temperature; setting a higher value of the first set value (T1) and the third set value (T3) as the final set value when the mode is not the NOx reducing mode; setting a higher value of the second set value (T2) and the third set value (T3) as the final set value when the mode is the NOx reducing mode; and performing a control on the speed of the electric pump ( 42 ) so that the parameter value becomes the set final setpoint.

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