JP2017227210A - Internal combustion engine control method and internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relatively increase an opportunity to obtain a fuel efficiency improvement effect through EGR.SOLUTION: An internal combustion engine control device comprises: an intercooler 13 which cools intake air; an EGR passage 21 which returns a portion of exhaust to an intake air passage 2 as EGR gas at an upstream side of the intercooler 13; an EGR valve 22 which adjusts a flow rate of the EGR gas flowing in the EGR passage 21; and an external air introduction mechanism 41 which adjusts an introduction amount of external air into an engine room. The internal combustion engine control device adjusts the flow rate of the EGR gas in accordance with presence or absence of the external air introduced into the engine room through the external air introduction mechanism 41 when a temperature of intake air at an intake air introduction port of the intake passage 2 is less than a predetermined temperature. Thus, the internal combustion engine control device can increase an opportunity to obtain a fuel efficiency improvement effect through execution of EGR even in a cold region.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a method for controlling an internal combustion engine mounted on a vehicle and a control device for the internal combustion engine.

  Patent Document 1 states that when the temperature of the cooling water supplied to the intercooler is lower than a predetermined freezing judgment temperature, there is a situation in which condensed water in which moisture in the EGR gas is condensed may lead to freezing. A technique for preventing the engine from returning to the intake system is disclosed.

JP 2011-190743 A

  However, even if the temperature of the cooling water supplied to the intercooler is the same, the temperature of the intake air cooled by the intercooler is not necessarily the same if the temperature of the intake air introduced to the intercooler is different.

  That is, even if the temperature of the cooling water supplied to the intercooler is lower than the predetermined freezing determination temperature, the condensed water may not freeze in the intercooler depending on the temperature of the intake air introduced into the intercooler.

  Therefore, in Patent Document 1, even when the condensed water does not actually freeze in the intercooler, the introduction (recirculation) of the EGR gas to the intake system may not be performed in the EGR region. There is room for further improvement in obtaining

  In the control method for an internal combustion engine according to the present invention, when the intake air temperature at the intake inlet of the intake passage is lower than a predetermined temperature, the EGR gas flow rate is controlled according to whether or not the outside air is introduced into the engine room by the outside air introduction mechanism. It is characterized by adjusting.

  According to the present invention, it is possible to expand the opportunity to obtain the fuel efficiency improvement effect obtained by performing EGR even in a cold region where the outside air temperature is low.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the outline of 1st Example of the control apparatus of the internal combustion engine which concerns on this invention. Explanatory drawing which shows an example of the operating condition of an EGR valve. The flowchart which shows an example of the flow of control of the internal combustion engine in 1st Example. The timing chart which showed an example of control of the internal combustion engine in 1st Example. The timing chart which showed an example of control of the internal combustion engine in 1st Example. The timing chart which showed an example of control of the internal combustion engine in 1st Example. The timing chart which showed an example of control of the internal combustion engine in 1st Example. Explanatory drawing which contrasts and shows the EGR implementation area | region in 1st Example, and the EGR implementation area | region in a comparative example. Explanatory drawing which shows the outline of 2nd Example of the control apparatus of the internal combustion engine which concerns on this invention. Explanatory drawing which showed typically the correlation with outside temperature and the fuel consumption improvement effect by EGR implementation. Explanatory drawing which showed typically the temperature rise of an intercooler exit intake temperature. Explanatory drawing which shows the comparative example of the louver opening / closing conditions of an external air introduction mechanism. Explanatory drawing which shows the louver opening / closing conditions of the external air introduction mechanism in 2nd Example. The flowchart which shows an example of the flow of control of the internal combustion engine in 2nd Example. The map figure for Ta calculation based on the correlation by actual machine evaluation.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of a control device for an internal combustion engine 1 in the first embodiment.

  The internal combustion engine 1 has, for example, an in-cylinder direct injection configuration, and has a fuel injection valve (not shown) for injecting fuel into the cylinder for each cylinder.

  The internal combustion engine 1 is mounted on a vehicle such as an automobile as a drive source, and has an intake passage 2 and an exhaust passage 3.

  An intake passage 2 connected to the internal combustion engine 1 includes an air cleaner 4 that collects foreign matter in the intake air, an air flow meter 5 that detects the intake air amount, and an electric throttle valve 6 that adjusts the intake air amount. Is provided. The air flow meter 5 is disposed on the upstream side of the throttle valve 6. The air flow meter 5 has a built-in temperature sensor and can detect (measure) the intake air temperature at the intake air inlet. The air cleaner 4 is disposed on the upstream side of the air flow meter 5. The intake passage 2 is located in the engine room in which the internal combustion engine 1 is accommodated.

  The exhaust passage 3 connected to the internal combustion engine 1 includes an upstream exhaust catalyst 7 such as a three-way catalyst, a downstream exhaust catalyst 8 such as a three-way catalyst, and a muffler 9 for noise reduction that reduces exhaust noise. Is provided. The downstream exhaust catalyst 8 is disposed on the downstream side of the upstream exhaust catalyst 7. The muffler 9 is disposed on the downstream side of the downstream side exhaust catalyst 8.

  The internal combustion engine 1 has a turbocharger 10 as a supercharger provided coaxially with a compressor 11 provided in the intake passage 2 and a turbine 12 provided in the exhaust passage 3. The compressor 11 is disposed upstream of the throttle valve 6 and downstream of the air flow meter 5. The turbine 12 is disposed on the upstream side of the upstream side exhaust catalyst 7. The turbocharger 10 is located in the engine room.

  The intake passage 2 is provided with an intercooler 13 on the downstream side of the throttle valve 6 for cooling the intake air compressed (pressurized) by the compressor 11 and improving the charging efficiency.

  The intercooler 13 is disposed in an intercooler cooling path (sub cooling path) 16 together with an intercooler radiator (intercooler radiator) 14 and an electric pump 15. The intercooler 13 can be supplied with the refrigerant (cooling water) cooled by the radiator 14. The intercooler 13 is located in the engine room.

  The intercooler cooling path 16 is configured so that the refrigerant can circulate in the path. The intercooler cooling path 16 is a cooling path independent of a main cooling path (not shown) through which cooling water for cooling the cylinder block 17 of the internal combustion engine 1 circulates.

  The radiator 14 cools the refrigerant in the intercooler cooling path 16 by heat exchange with the outside air.

  The electric pump 15 circulates the refrigerant in the direction of arrow A between the radiator 14 and the intercooler 13 by being driven.

  An exhaust bypass passage 18 that bypasses the turbine 12 and connects the upstream side and the downstream side of the turbine 12 is connected to the exhaust passage 3. The downstream end of the exhaust bypass passage 18 is connected to the exhaust passage 3 at a position upstream of the upstream exhaust catalyst 7. An electric waste gate valve 19 that controls the exhaust gas flow rate in the exhaust bypass passage 18 is disposed in the exhaust bypass passage 18.

  The internal combustion engine 1 can perform exhaust gas recirculation (EGR) in which part of the exhaust gas from the exhaust passage 3 is introduced (recirculated) into the intake passage 2 as EGR gas. An EGR passage 21 connected to the passage 2 is provided. One end of the EGR passage 21 is connected to the exhaust passage 3 at a position between the upstream side exhaust catalyst 7 and the downstream side exhaust catalyst 8, and the other end is located downstream of the air flow meter 5 and upstream of the compressor 11. To the intake passage 2. The EGR passage 21 is provided with an electric EGR valve 22 that controls the flow rate of the EGR gas in the EGR passage 21 and an EGR cooler 23 that can cool the EGR gas. The opening / closing operation of the EGR valve 22 is controlled by a control unit 25 as a control unit. The EGR passage 21, the EGR valve 22, and the EGR cooler 23 are located in the engine room.

  FIG. 2 is an explanatory diagram showing an example of operating conditions of the EGR valve 22. In the EGR region where the engine speed and the load (load of the internal combustion engine 1) are in a predetermined range, the EGR valve 22 is opened, and a part of the exhaust gas is recirculated to the intake passage 2. In the non-EGR region other than the EGR region, the EGR valve 22 is closed so that a part of the exhaust does not return to the intake passage 2. That is, in the non-EGR region, the EGR valve 22 is controlled so that EGR gas is not introduced into the intake passage 2 (so that the EGR gas flow rate becomes zero). The load can be calculated using a detection value of an accelerator opening sensor 27 described later.

  In the first embodiment, the EGR region is divided into three regions with low, medium and high EGR rates. More specifically, in the EGR region of the first embodiment, a high EGR region in which a relatively high EGR rate is set, a middle EGR region in which an intermediate EGR rate is set, and a relatively low EGR rate are set. And a low EGR region. That is, in the EGR region, different EGR rates are set according to the operating state of the internal combustion engine 1, and the EGR gas flow rate in the EGR passage 21 can be adjusted based on the operating state of the internal combustion engine 1. .

  The setting of the EGR region and the non-EGR region and the setting of the EGR rate in the EGR region are not limited to the setting shown in FIG. 2, and can be appropriately changed according to the specifications of the internal combustion engine 1 and the like.

  In addition to the detection signal of the air flow meter 5 described above, the control unit 25 includes a crank angle sensor 26 that detects the crank angle of a crankshaft (not shown), and an accelerator opening that detects the amount of depression of an accelerator pedal (not shown). A temperature sensor 27, an intercooler outlet side intake air temperature sensor 28 for detecting (measuring) an intake air temperature at the outlet side of the intercooler 13 (intercooler outlet intake temperature Ta), and a temperature of the cooling water (engine water temperature) in the main cooling path. Water temperature sensor 29, supercharging pressure sensor 30 for detecting the intake pressure downstream of the compressor 11, refrigerant temperature sensor 31 for detecting (measuring) the temperature of the refrigerant in the intercooler cooling path 16, and outside air temperature sensor for detecting the outside air temperature Detection signals of sensors such as 32 are input.

  The intercooler outlet side intake air temperature sensor 28 is disposed in the vicinity of the outlet of the intercooler 13. The refrigerant temperature sensor 31 is disposed in the vicinity of the outlet of the radiator 14 so that the temperature of the refrigerant heat-exchanged by the radiator 14 can be detected.

  Based on these detection signals, the control unit 25 controls the ignition timing and air-fuel ratio of the internal combustion engine 1 and the valve opening of the EGR valve 22 to control the exhaust gas from the exhaust passage 3 to the intake passage 2. Exhaust gas recirculation control (EGR control) that recirculates part of the fuel is performed. The control unit 25 also controls the driving of the electric pump 15 and the valve opening degree of the throttle valve 6 and the waste gate valve 19.

  When the operating point of the internal combustion engine 1 is in the non-supercharged region, fresh air necessary for realizing the engine required torque is supplied into the cylinder with the opening of the wastegate valve 19 being a predetermined constant opening. Thus, the opening degree of the throttle valve 6 is controlled. The “operating point of the internal combustion engine 1” can also be referred to as “the operating state of the internal combustion engine 1”.

  When the operating point of the internal combustion engine 1 is in the supercharging region on the higher load side than the non-supercharging region, the throttle valve 6 is fully opened, and fresh air necessary for realizing the engine required torque is generated. The opening degree of the wastegate valve 19 is controlled so as to be supplied inside.

  Here, the exhaust gas contains water vapor (water). Therefore, condensed water is generated when the EGR gas is cooled. If this condensed water freezes in the intercooler 13, the intercooler 13 may break down. Therefore, if EGR is performed simply because the operating point of the internal combustion engine 1 is in the EGR region, condensed water may freeze in the intercooler 13 and the intercooler 13 may be damaged.

  As the temperature of the refrigerant supplied to the intercooler 13 is lower, cooling of the intake air in the intercooler 13 is promoted. However, if the temperature of the intake air introduced into the intercooler 13 is different, the temperature of the intake air that has passed through the intercooler 13 should have a different value even if the temperature of the refrigerant supplied to the intercooler 13 is the same. If the temperature of the intake air introduced into the intercooler 13 is different, the condensed water is not necessarily in the same state in the intercooler 13 even if the temperature of the refrigerant supplied to the intercooler 13 is the same. Even when the temperature of the refrigerant is low, the condensed water may not freeze in the intercooler 13 when the refrigerant is not supplied to the intercooler 13 (the refrigerant is not circulated) or when the outside air temperature is high.

  That is, even if the temperature of the refrigerant is low, if the intake air temperature in the intercooler 13 is high, the condensed water should not be frozen in the intercooler 13.

  Therefore, in the first embodiment described above, the EGR gas flow rate in the EGR passage 21 is adjusted based on the operating state of the internal combustion engine 1 and the intake air temperature on the outlet side of the intercooler 13.

  FIG. 3 is a flowchart regarding the control flow of the internal combustion engine 1 in the first embodiment, that is, the EGR control in the first embodiment.

  In S1, it is determined whether the operating point of the internal combustion engine 1 is in the EGR region or the non-EGR region. When the operating point of the internal combustion engine 1 is in the EGR region in S1, the process proceeds to S2. When the operating point of the internal combustion engine 1 is in the non-EGR region in S1, the process proceeds to S3.

  In S2, it is determined whether or not the intake air temperature (intercooler outlet intake air temperature Ta) detected by the intercooler outlet side intake air temperature sensor 28 is lower than a preset first temperature T1. If the intercooler outlet intake temperature Ta is lower than the first temperature T1 in S2, the process proceeds to S3. When the intercooler outlet intake temperature Ta is equal to or higher than the first temperature T1 in S2, the process proceeds to S8. The first temperature T1 is a threshold value of the intake air temperature for determining whether the condensed water is frozen, and is a temperature at which the condensed water does not freeze in the intercooler 13 (for example, 0 ° C.).

  In S3, EGR is turned off. That is, when the intercooler outlet intake temperature Ta is lower than the first temperature T1 or when the operating state of the internal combustion engine 1 is in the non-EGR region, the EGR gas is not introduced into the intake passage 2 (the EGR gas flow rate is zero). The EGR valve 22 is controlled. When the EGR gas is introduced into the intake passage 2, the EGR valve 22 is closed and the introduction of the EGR gas into the intake passage 2 is stopped. When the introduction of the EGR gas into the intake passage 2 has already been stopped, the state where the EGR valve 22 is closed is continued, and the state where the EGR gas is not introduced into the intake passage 2 is continued.

  In S4, it is determined whether or not there is a request for circulating the refrigerant in the intercooler cooling path 16 (refrigerant circulation request). Specifically, it is assumed that there is a request to circulate the refrigerant in the intercooler cooling path 16 when the intercooler inlet intake temperature, which is the intake air temperature on the inlet side of the intercooler 13, is equal to or higher than a predetermined temperature set in advance. Further, it is assumed that there is no request to circulate the refrigerant in the intercooler cooling path 16 when the intercooler inlet intake temperature is lower than a preset predetermined temperature. If it is determined in S4 that there is a request to circulate the refrigerant in the intercooler cooling path 16, the process proceeds to S5. If it is determined in S4 that there is no request for circulating the refrigerant in the intercooler cooling path 16, the process proceeds to S7.

  The intercooler inlet intake temperature is estimated using, for example, the supercharging pressure and the outside air temperature (intake air temperature). The intercooler inlet intake air temperature may be detected (measured) by arranging a temperature sensor on the inlet side of the intercooler 13.

  In S5, it is determined whether or not the refrigerant temperature Tb detected by the refrigerant temperature sensor 31 is equal to or higher than a preset second temperature T2. If the refrigerant temperature Tb is equal to or higher than the second temperature T2 in S5, the process proceeds to S6. When the refrigerant temperature Tb is lower than the second temperature T2 in S5, the process proceeds to S7. The second temperature T2 is a refrigerant temperature threshold value for determining whether the condensed water is frozen, and is a temperature at which the condensed water does not freeze in the intercooler 13 (for example, 0 ° C.).

  In S6, the refrigerant circulation in the intercooler cooling path 16 is turned ON. When the refrigerant in the intercooler cooling path 16 is not circulating, the electric pump 15 is driven to circulate the refrigerant. When the electric pump 15 is already driven, the driving of the electric pump 15 is continued and the circulation of the refrigerant in the intercooler cooling path 16 is continued.

  In S7, circulation of the refrigerant in the intercooler cooling path 16 is turned off. When the refrigerant in the intercooler cooling path 16 is circulating, the electric pump 15 is stopped to stop the refrigerant circulation. When the electric pump 15 is already stopped, the electric pump 15 is stopped and the state where the refrigerant does not circulate in the intercooler cooling path 16 is continued.

  In S8, as in S4, it is determined whether or not there is a request for circulating the refrigerant in the intercooler cooling path 16 (refrigerant circulation request). Also in S8, it is assumed that there is a request to circulate the refrigerant in the intercooler cooling path 16 when the intercooler inlet intake temperature is equal to or higher than a predetermined temperature set in advance. If it is determined in S8 that there is a request to circulate the refrigerant in the intercooler cooling path 16, the process proceeds to S9. If it is determined in S8 that there is no request for circulating the refrigerant in the intercooler cooling path 16, the process proceeds to S16.

  In S9, it is determined whether or not the refrigerant temperature Tb detected by the refrigerant temperature sensor 31 is equal to or higher than a preset second temperature T2. When the refrigerant temperature Tb is equal to or higher than the second temperature T2 in S9, the process proceeds to S10. When the refrigerant temperature Tb is lower than the second temperature T2 in S9, the process proceeds to S12.

  In S10, EGR is turned ON. When EGR gas is not introduced into the intake passage 2, the EGR valve 22 is opened, and introduction of EGR gas into the intake passage 2 is started. If EGR gas has already been introduced into the intake passage 2, the EGR valve 22 is kept open and introduction of EGR gas into the intake passage 2 is continued. The valve opening degree of the EGR valve 22 when EGR is ON is determined according to the operating state of the internal combustion engine 1. That is, in S 10, the EGR valve 22 is controlled so that an amount of EGR gas corresponding to the operating state of the internal combustion engine 1 is introduced into the intake passage 2.

  In S11, the refrigerant circulation in the intercooler cooling path 16 is turned ON. That is, in S11, the electric pump 15 is controlled as in S6.

  In S12, EGR is turned off. That is, in S12, the EGR valve 22 is controlled in the same manner as S3.

  In S13, the refrigerant circulation in the intercooler cooling path 16 is turned ON. That is, in S13, the electric pump 15 is controlled as in S6.

  In S14, it is determined whether or not the intake air temperature (intercooler outlet intake air temperature Ta) detected by the intercooler outlet side intake air temperature sensor 28 is lower than the first temperature T1. If the intercooler outlet intake air temperature Ta is lower than the first temperature T1 in S14, the current routine is terminated with EGR turned OFF. If the intercooler outlet intake temperature Ta is equal to or higher than the first temperature T1 in S14, the process proceeds to S15.

  In S15, EGR is turned ON. That is, in S15, the EGR valve 22 is controlled as in S10.

  In S16, the refrigerant circulation in the intercooler cooling path 16 is turned OFF. That is, in S16, the electric pump 15 is controlled as in S7.

  In S17, EGR is turned ON. That is, in S17, the EGR valve 22 is controlled in the same manner as in S10.

  4 to 7 are timing charts showing an example of control of the internal combustion engine 1 in the first embodiment. 4-7, the valve opening degree of the EGR valve 22 when the EGR is ON is determined according to the operating state of the internal combustion engine 1 at that time.

  FIG. 4 shows a case where the intercooler outlet intake temperature Ta is higher than the first temperature T1, and the refrigerant temperature Tb is higher than the second temperature T2. In FIG. 4, the operating point of the internal combustion engine 1 is in the EGR region from time t1. Therefore, EGR is turned on at the timing of time t1. Further, at the timing of time t2, the intercooler inlet intake temperature is equal to or higher than a predetermined temperature. Therefore, the circulation of the refrigerant in the intercooler cooling path 16 is turned ON at the timing of time t2.

  FIG. 5 shows a case where the intercooler outlet intake temperature Ta is lower than the first temperature T1, and the refrigerant temperature Tb is lower than the second temperature T2. In FIG. 5, the operating point of the internal combustion engine 1 is in the EGR region from time t1. However, since the intercooler outlet intake air temperature Ta is lower than the first temperature T1, the EGR is not turned ON at time t1. Further, at the timing of time t2, the intercooler inlet intake temperature is equal to or higher than a predetermined temperature. Therefore, the circulation of the refrigerant in the intercooler cooling path 16 is turned ON at the timing of time t2.

  FIG. 6 shows a case where the intercooler outlet intake temperature Ta is higher than the first temperature T1, and the refrigerant temperature Tb is lower than the second temperature T2. In FIG. 6, the operating point of the internal combustion engine 1 is in the EGR region from time t1. Therefore, EGR is turned on at the timing of time t1. Further, at the timing of time t2, the intercooler inlet intake temperature is equal to or higher than a predetermined temperature. However, the refrigerant temperature Tb is lower than the second temperature T2. Therefore, EGR is turned off at time t2, and circulation of the refrigerant in the intercooler cooling path 16 is turned on at time t3 when a predetermined time has elapsed from time t2. Since the intercooler outlet intake air temperature Ta is higher than the first temperature T1 at a time t4 when a predetermined time has elapsed from the time t3, the EGR is turned on at the time t4. Thereafter, the intercooler inlet intake air temperature is less than the predetermined temperature at the timing of time t5. Therefore, the circulation of the refrigerant in the intercooler cooling path 16 is turned off at the timing of time t5.

  FIG. 7 shows a case where the intercooler outlet intake temperature Ta varies across the first temperature T1, and the refrigerant temperature Tb is lower than the second temperature T2. In FIG. 7, the operating point of the internal combustion engine 1 is in the EGR region from time t1. Therefore, EGR is turned on at the timing of time t1. Further, at the timing of time t2, the intercooler inlet intake temperature is equal to or higher than a predetermined temperature. However, the refrigerant temperature Tb is lower than the second temperature T2. Therefore, EGR is turned off at the timing of time t2, and the circulation of the refrigerant in the intercooler cooling path 16 is turned on at the timing of time t3 when a predetermined time has elapsed from time t2. Since the intercooler outlet intake air temperature Ta is lower than the first temperature T1 at a time t4 when a predetermined time has elapsed from the time t3, the EGR is continuously turned off after the time t4. Thereafter, at the timing of time t5, the intercooler inlet intake temperature is less than the predetermined temperature. Therefore, the circulation of the refrigerant in the intercooler cooling path 16 is turned off at the timing of time t5. Then, EGR is turned on at time t6 when the intercooler outlet intake temperature Ta becomes higher than the first temperature T1.

  FIG. 8 shows an EGR implementation region in the first embodiment and an EGR implementation region in a comparative example in which EGR is not performed when the outside air temperature is 0 ° C. or lower even when the operating point of the internal combustion engine 1 is in the EGR region. It is explanatory drawing shown in contrast.

  As shown in FIG. 8, in the first embodiment, even if the outside air temperature is 0 ° C. or less, if the intercooler outlet intake temperature Ta is the first temperature T1 (0 ° C.), the EGR is turned on. The number of cases where EGR is ON can be relatively increased.

  As described above, in the first embodiment described above, it can be estimated from the intake air temperature (intercooler outlet intake air temperature Ta) on the outlet side of the intercooler 13 whether the condensed water is not frozen in the intercooler 13. Therefore, when the operating point (operating state) of the internal combustion engine 1 is in the EGR region, the introduction of the EGR gas into the intake passage 2 is not stopped (prohibited) more than necessary, and the EGR gas is passed through the EGR passage 21. The opportunity to flow increases relatively. That is, the case where EGR is implemented increases relatively. Accordingly, it is possible to relatively increase the chance of obtaining the fuel efficiency improvement effect by EGR.

  In the first embodiment, the intake air passage 2 for the EGR gas is used so that the condensed water does not freeze in the intercooler 13 by using the intake air temperature on the outlet side of the intercooler 13 (intercooler outlet intake air temperature Ta). It is possible to accurately determine whether or not it can be introduced.

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the component same as 1st Example mentioned above, and the overlapping description is abbreviate | omitted.

  FIG. 9 is an explanatory diagram showing an outline of the control device for the internal combustion engine 1 in the second embodiment. The control device for the internal combustion engine 1 in the second embodiment has substantially the same configuration as the first embodiment described above, but has an outside air introduction mechanism 41 when the amount of outside air introduced into the engine room is adjusted, In carrying out EGR, the EGR flow rate is adjusted according to whether or not the outside air introduction mechanism 41 has introduced outside air into the engine room.

  The outside air introduction mechanism 41 is a radiator shutter disposed on the front surface of a radiator (not shown), and the control unit 25 controls the opening and closing of the louver 42 that is a movable portion. When the louver 42 is opened, the amount of ventilation to the radiator increases and outside air is introduced into the engine room. When the louver 42 is closed, the amount of ventilation to the radiator is reduced and the amount of outside air introduced into the engine room is reduced.

  The outside air introduction mechanism 41 is not limited to the radiator shutter, and may be provided, for example, on the hood or the under floor of the vehicle as long as the outside air introduction amount can be adjusted by an opening / closing operation or the like. It may be possible.

  The supercharging pressure sensor 30 is disposed at a position downstream of the throttle valve 6 and upstream of the intercooler 13.

  Further, in the second embodiment, the control unit 25 is provided with the compressor outlet side intake air temperature sensor 43 that detects the intake air temperature at the outlet side of the compressor 11 (compressor outlet intake temperature Tcomex), and the intake pressure at the outlet side of the compressor 11. Compressor outlet side intake pressure sensor 44 to detect, throttle valve inlet side intake air temperature sensor 45 for detecting (measuring) intake side temperature at the inlet side of throttle valve 6 (throttle valve inlet side intake temperature Tthin), intake side intake pressure of throttle valve 6 From the throttle valve inlet side intake pressure sensor 46 for detecting the atmospheric pressure, the intercooler outlet side intake pressure sensor 47 for detecting the intake pressure on the outlet side of the intercooler 13, and the vehicle speed sensor 48 for detecting the vehicle speed of the vehicle on which the internal combustion engine 1 is mounted. A detection signal is also input.

  FIG. 10 is an explanatory view schematically showing the correlation between the outside air temperature and the fuel efficiency improvement effect by the EGR implementation. The horizontal axis represents the outside air temperature, and the vertical axis represents the degree (satisfaction) with which the fuel efficiency improvement effect by EGR can be obtained. At present, condensed water is more likely to be generated when the EGR is performed as the outside air temperature is lowered. Therefore, the EGR is not performed as the outside air temperature is lowered, and it becomes difficult to obtain the fuel efficiency improvement effect by the EGR.

  Therefore, EGR is performed in such a way that condensate is not generated even when the outside air temperature is low, so that the fuel efficiency improvement effect by EGR can be obtained even in a situation where the outside air temperature is low (cold region or the like).

  FIG. 11 is an explanatory diagram schematically showing the correlation between the traveling time of the vehicle from the cold state when the outside air temperature is −10 ° C. and a constant speed (vehicle speed 40 km / h) and the intercooler outlet intake air temperature Ta. The solid line in FIG. 11 shows the change in the intercooler outlet intake air temperature Ta when the louver 42 of the outside air introduction mechanism 41 is closed and outside air is not introduced into the engine room. The broken line in FIG. 11 shows the change in the intercooler outlet intake temperature Ta when the outside air introduction mechanism 41 is opened and the outside air is introduced into the engine room.

  When the louver 42 of the outside air introduction mechanism 41 is closed, the intercooler outlet intake air temperature Ta rises more quickly than when the louver 42 of the outside air introduction mechanism 41 is not closed.

  That is, even when the outside air temperature is low, if the louver 42 of the outside air introduction mechanism 41 is closed, EGR can be performed quickly, and the fuel efficiency improvement effect by EGR can be obtained.

  Therefore, in the second embodiment, the EGR gas flow rate is adjusted according to the intake air temperature at the intake air inlet of the intake passage 2 (intake air inlet air temperature Tair) and whether or not the external air introduction mechanism 41 introduces external air. . More specifically, in the second embodiment, when the intake air intake temperature Tair is lower than a predetermined temperature (for example, 0 ° C.), the presence / absence of outside air introduction by the outside air introduction mechanism 41 and the permission conditions for performing EGR And cooperate. In the second embodiment, the intake air temperature detected (measured) by the air flow meter 5 is used as the intake air inlet temperature Tair.

  Note that the intake air inlet temperature Tair may be estimated using various known estimation methods in addition to, for example, estimation from the outside air temperature.

  When an in-vehicle air conditioner (not shown) is turned on, the outside air introduction mechanism 41 is a louver 42 of the outside air introduction mechanism 41 when the engine water temperature is low at a low speed as in the comparative example shown in FIG. It is desirable to open. FIG. 12 is an explanatory diagram showing a comparative example of the louver opening / closing conditions of the outside air introduction mechanism 41.

  However, in this second embodiment, the louver 42 of the outside air introduction mechanism 41 is controlled to open and close under the conditions shown in FIG. 13 in order to increase the chances that EGR is permitted. FIG. 13 is an explanatory diagram showing the louver opening and closing conditions of the outside air introduction mechanism 41 in the second embodiment.

  In the second embodiment, the louver 42 of the outside air introduction mechanism 41 is closed when the engine water temperature is low and the vehicle speed is low. In other words, when the engine water temperature is low and the vehicle speed is low, the outside air introduction mechanism 41 does not introduce outside air into the engine room. The louver 42 of the outside air introduction mechanism 41 is opened at a high temperature when the engine water temperature is equal to or higher than a predetermined temperature, or when the vehicle speed is higher than a predetermined speed. That is, when the engine water temperature is higher than the predetermined temperature or when the vehicle speed is higher than the predetermined speed, the outside air introduction mechanism 41 introduces the outside air into the engine room.

  In a state where the amount of outside air introduced into the engine room by the outside air introduction mechanism 41 is small, the temperature in the engine room is likely to rise, and the time required from when the internal combustion engine 1 is started until EGR is permitted can be shortened. .

  Therefore, for example, in a cold region where the outside air temperature is low, it is possible to allow the EGR to be allowed early by increasing the temperature in the engine room early, and even in a cold region where the outside air temperature is low, by implementing EGR Opportunities for obtaining the obtained fuel efficiency improvement effect can be expanded.

  FIG. 14 is a flowchart regarding the control flow of the internal combustion engine 1 in the second embodiment, that is, the EGR control in the second embodiment.

  In S31, it is determined whether the operating point of the internal combustion engine 1 is in the EGR region or the non-EGR region. If the operating point of the internal combustion engine 1 is in the EGR region in S31, the process proceeds to S32. If the operating point of the internal combustion engine 1 is in the non-EGR region in S31, the process proceeds to S35.

  In S32, it is determined whether or not the intake air temperature (intake air intake temperature Tair) detected by the air flow meter 5 is lower than a predetermined temperature of 0 ° C.

  In S32, when the intake air inlet temperature Tair is less than 0 ° C., the process proceeds to S33. In S32, if the intake air inlet temperature Tair is 0 ° C. or higher, the process proceeds to S40.

  In S33, it is determined whether or not the louver 42 of the outside air introduction mechanism 41 is open. If it is determined in S33 that the louver 42 is open, the process proceeds to S34. If it is determined in S33 that the louver 42 is closed, the process proceeds to S40. Since the louver 42 is controlled to open and close under the conditions shown in FIG. 13, the open / closed state of the louver 42 can be determined from the engine water temperature and the vehicle speed.

  In S34, it is determined whether or not the intake air temperature (intercooler outlet intake air temperature Ta) detected by the intercooler outlet side intake air temperature sensor 28 is lower than a preset first temperature T1. If the intercooler outlet intake temperature Ta is lower than the first temperature T1 in S34, the process proceeds to S35. If the intercooler outlet intake temperature Ta is equal to or higher than the first temperature T1 in S34, the process proceeds to S40. The first temperature T1 is a threshold value of the intake air temperature for determining whether the condensed water is frozen, and is a temperature at which the condensed water does not freeze in the intercooler 13 (for example, 0 ° C.).

  In S35, EGR is turned off. That is, when the intercooler outlet intake temperature Ta is lower than the first temperature T1 or when the operating state of the internal combustion engine 1 is in the non-EGR region, the EGR gas is not introduced into the intake passage 2 (the EGR gas flow rate is zero). The EGR valve 22 is controlled. When the EGR gas is introduced into the intake passage 2, the EGR valve 22 is closed and the introduction of the EGR gas into the intake passage 2 is stopped. When the introduction of the EGR gas into the intake passage 2 has already been stopped, the state where the EGR valve 22 is closed is continued, and the state where the EGR gas is not introduced into the intake passage 2 is continued.

  In S36, it is determined whether or not there is a request for circulating the refrigerant in the intercooler cooling path 16 (refrigerant circulation request). Specifically, it is assumed that there is a request to circulate the refrigerant in the intercooler cooling path 16 when the intercooler inlet intake temperature, which is the intake air temperature on the inlet side of the intercooler 13, is equal to or higher than a predetermined temperature set in advance. Further, it is assumed that there is no request to circulate the refrigerant in the intercooler cooling path 16 when the intercooler inlet intake temperature is lower than a preset predetermined temperature. If it is determined in S36 that there is a request for circulating the refrigerant in the intercooler cooling path 16, the process proceeds to S37. When it is determined in S36 that there is no request for circulating the refrigerant in the intercooler cooling path 16, the process proceeds to S39.

  The intercooler inlet intake temperature is estimated using, for example, the supercharging pressure and the outside air temperature (intake air temperature). The intercooler inlet intake temperature may be detected by a temperature sensor arranged at a position on the outlet side of the throttle valve 6 and on the inlet side of the intercooler 13. Further, the detected value of the throttle valve inlet side intake air temperature sensor 45 can be substituted for the intercooler inlet intake air temperature.

  In S37, it is determined whether or not the refrigerant temperature Tb detected by the refrigerant temperature sensor 31 is equal to or higher than a preset second temperature T2. When the refrigerant temperature Tb is equal to or higher than the second temperature T2 in S37, the process proceeds to S38. If the refrigerant temperature Tb is lower than the second temperature T2 in S37, the process proceeds to S39. The second temperature T2 is a refrigerant temperature threshold value for determining whether the condensed water is frozen, and is a temperature at which the condensed water does not freeze in the intercooler 13 (for example, 0 ° C.).

  In S38, the refrigerant circulation in the intercooler cooling path 16 is turned ON. When the refrigerant in the intercooler cooling path 16 is not circulating, the electric pump 15 is driven to circulate the refrigerant. When the electric pump 15 is already driven, the driving of the electric pump 15 is continued and the circulation of the refrigerant in the intercooler cooling path 16 is continued.

  In S39, circulation of the refrigerant in the intercooler cooling path 16 is turned off. When the refrigerant in the intercooler cooling path 16 is circulating, the electric pump 15 is stopped to stop the refrigerant circulation. When the electric pump 15 is already stopped, the electric pump 15 is stopped and the state where the refrigerant does not circulate in the intercooler cooling path 16 is continued.

  In S40, as in S36, it is determined whether or not there is a request for circulating the refrigerant in the intercooler cooling path 16 (refrigerant circulation request). Also in S40, it is assumed that there is a request to circulate the refrigerant in the intercooler cooling path 16 when the intercooler inlet intake temperature is equal to or higher than a predetermined temperature set in advance. If it is determined in S40 that there is a request to circulate the refrigerant in the intercooler cooling path 16, the process proceeds to S41. If it is determined in S40 that there is no request for circulating the refrigerant in the intercooler cooling path 16, the process proceeds to S48.

  In S41, it is determined whether or not the refrigerant temperature Tb detected by the refrigerant temperature sensor 31 is equal to or higher than a preset second temperature T2. If the refrigerant temperature Tb is equal to or higher than the second temperature T2 in S41, the process proceeds to S42. When the refrigerant temperature Tb is lower than the second temperature T2 in S41, the process proceeds to S44.

  In S42, EGR is turned ON. When EGR gas is not introduced into the intake passage 2, the EGR valve 22 is opened, and introduction of EGR gas into the intake passage 2 is started. If EGR gas has already been introduced into the intake passage 2, the EGR valve 22 is kept open and introduction of EGR gas into the intake passage 2 is continued. The valve opening degree of the EGR valve 22 when EGR is ON is determined according to the operating state of the internal combustion engine 1. That is, in S42, the EGR valve 22 is controlled so that an amount of EGR gas corresponding to the operating state of the internal combustion engine 1 is introduced into the intake passage 2.

  In S43, the refrigerant circulation in the intercooler cooling path 16 is turned ON. That is, in S43, the electric pump 15 is controlled as in S38.

  In S44, EGR is turned off. That is, in S44, the EGR valve 22 is controlled as in S35.

  In S45, the refrigerant circulation in the intercooler cooling path 16 is turned ON. That is, in S45, the electric pump 15 is controlled as in S38.

  In S46, it is determined whether or not the intake air temperature (intercooler outlet intake air temperature Ta) detected by the intercooler outlet side intake air temperature sensor 28 is lower than the first temperature T1. If the intercooler outlet intake air temperature Ta is lower than the first temperature T1 in S46, the current routine is terminated with EGR turned OFF. If the intercooler outlet intake temperature Ta is equal to or higher than the first temperature T1 in S46, the process proceeds to S47.

  In S47, EGR is turned ON. That is, in S47, the EGR valve 22 is controlled as in S42.

  In S48, the circulation of the refrigerant in the intercooler cooling path 16 is turned off. That is, in S48, the electric pump 15 is controlled as in S39.

  In S49, EGR is turned ON. That is, in S49, the EGR valve 22 is controlled in the same manner as S42.

  Also in the second embodiment described above, whether or not the condensed water does not freeze in the intercooler 13 from the intake air temperature (intercooler outlet intake air temperature Ta) on the outlet side of the intercooler 13 as in the first embodiment described above. Can be estimated. Therefore, when the operating point (operating state) of the internal combustion engine 1 is in the EGR region, the introduction of the EGR gas into the intake passage 2 is not stopped (prohibited) more than necessary, and the EGR gas is passed through the EGR passage 21. The opportunity to flow increases relatively. That is, the case where EGR is implemented increases relatively. Accordingly, it is possible to relatively increase the chance of obtaining the fuel efficiency improvement effect by EGR.

  Also in the second embodiment, the intake air passage 2 for the EGR gas is used so that the condensed water does not freeze in the intercooler 13 by using the intake air temperature on the outlet side of the intercooler 13 (intercooler outlet intake air temperature Ta). It is possible to accurately determine whether or not it can be introduced.

  Even when the outside air temperature is low in a cold region or the like, it is possible to permit EGR early by raising the temperature in the engine room early, and the fuel efficiency obtained by performing EGR Opportunities for obtaining an improvement effect are expanded, and overall fuel efficiency can be improved.

  The intercooler 13 receives heat from intake air whose temperature has increased due to heat dissipation from the internal combustion engine 1 or compression due to supercharging. Therefore, if the outside air is not introduced into the engine room by the outside air introduction mechanism 41, the temperature of the intercooler 13 is likely to rise. However, if the refrigerant in the intercooler cooling path 16 circulates, the intercooler 13 is cooled by heat exchange.

  Therefore, by permitting the circulation of the refrigerant in the intercooler cooling path 16 according to the temperature of the refrigerant in the intercooler cooling path 16 and the intake air temperature on the inlet side of the intercooler 13, even when the outside air temperature is low, EGR is reduced. This will be possible earlier and will contribute to fuel efficiency improvement.

  Further, if the circulation of the refrigerant in the intercooler cooling path 16 is stopped when the outside air introduction mechanism 41 is not introducing outside air into the engine room, even if the outside air temperature is low, Since the temperature rise is promoted, EGE can be implemented even earlier.

  In each of the above-described embodiments, the intercooler outlet intake temperature Ta can be estimated using the intake inlet intake air temperature Tair. Specifically, it is also possible to estimate the intercooler outlet intake air temperature Ta using the detection values of the sensors upstream of the intercooler 13.

  For example, the intercooler outlet intake air temperature Ta can be estimated from the gas state equation using the intake air inlet air temperature Tair, the intake air pressure on the intercooler outlet side, the intake air pressure on the intercooler inlet side, and the intake air temperature on the intercooler inlet side. Good.

  The intercooler outlet intake air temperature Ta can also be estimated using the engine speed, the load of the internal combustion engine 1, and the intake air inlet intake air temperature Tair. More specifically, the intercooler outlet intake air temperature Ta is obtained by using a map for calculating Ta (ΔT map) as shown in FIG. It is also possible to estimate from the intake air intake temperature Tair. The map for calculating Ta is created for each outside air temperature. The difference between the intake air inlet temperature Tair and the intercooler outlet intake air temperature Ta, the load of the internal combustion engine 1 and the engine speed are calculated. It shows the correlation. A plurality of arc-shaped curves in FIG. 15 indicate different values of ΔT. As the engine speed increases and the load on the internal combustion engine 1 increases, the amount of intake air increases and ΔT decreases.

  A plurality of Ta calculation map diagrams may be prepared for each outside air temperature, but for example, only two types of Ta calculation map diagrams having different outside air temperatures may be prepared. If a map diagram for Ta calculation is not prepared for each outside temperature, if the outside air temperature is different from the prepared map diagram, intercooler outlet intake air temperature Ta is obtained by interpolation using the prepared Ta calculation map diagram. Can be estimated.

  Thus, when estimating the intercooler outlet intake air temperature Ta, it is not necessary to provide the intercooler outlet side intake air temperature sensor 28 on the outlet side of the intercooler 13, so that the system can be simplified and the cost can be reduced. be able to.

  Further, in each of the above-described embodiments, when the intake air temperature on the inlet side of the throttle valve 6, that is, the intake air temperature between the compressor 11 and the throttle valve 6 becomes low, the condensed water may be frozen at the throttle valve 6. is there.

  Therefore, if the EGR gas flow rate is adjusted based on the throttle valve inlet intake temperature Tthin that is the intake air temperature on the inlet side of the throttle valve 6, it is possible to prevent the throttle valve 6 from sticking or malfunctioning due to the freeze of condensed water. For example, if the EGR is not performed when the throttle valve inlet intake temperature Tthin is equal to or lower than a predetermined temperature, it is possible to prevent the condensed water from freezing at the throttle valve 6 and improve the function reliability of the system. it can.

  The throttle valve inlet intake temperature Tthin may be estimated using various known estimation methods in addition to the intake inlet intake air temperature Tair, for example, similarly to the intercooler outlet intake temperature Ta.

  In each of the above-described embodiments, the refrigerant temperature is estimated based on, for example, the intercooler inlet intake temperature, the intercooler outlet intake temperature Ta, the engine speed, and the heat exchange with the intake air in the intercooler 13 from the load of the internal combustion engine 1. It is also possible to perform estimation using various known estimation methods.

  Each of the above-described embodiments relates to a control method and a control device for the internal combustion engine 1.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake passage 3 ... Exhaust passage 4 ... Air cleaner 5 ... Air flow meter 6 ... Throttle valve 10 ... Turbocharger 11 ... Compressor 12 ... Turbine 13 ... Intercooler 14 ... Radiator 15 ... Electric pump 16 ... Cooling for intercooler Path 18 ... Exhaust bypass passage 19 ... Wastegate valve 21 ... EGR passage 22 ... EGR valve 23 ... EGR cooler 25 ... Control unit 28 ... Intercooler outlet side intake air temperature sensor 30 ... Supercharging pressure sensor 31 ... Refrigerant temperature sensor 32 ... Outside air temperature Sensor 41 ... Outside air introduction mechanism 42 ... Louver 43 ... Compressor outlet side intake temperature sensor 44 ... Compressor outlet side intake pressure sensor 45 ... Throttle valve inlet side intake temperature sensor 46 ... Throttle valve inlet side intake pressure sensor 47 ... Intercooler outlet side intake pressure Sensor 48 ... Vehicle speed sensor

Claims (15)

An intercooler that is located in an engine room in which the internal combustion engine is housed and cools intake air using a circulating refrigerant;
An EGR passage located in the engine room and returning a part of exhaust from the exhaust passage as EGR gas to the intake passage upstream of the intercooler;
An EGR valve for adjusting the flow rate of the EGR gas flowing through the EGR passage;
An external air introduction mechanism that adjusts the amount of outside air introduced into the engine room, and a control method for an internal combustion engine,
Measure or estimate the intake air temperature at the intake inlet of the intake passage,
When the intake temperature at the intake inlet of the intake passage measured or estimated is lower than a predetermined temperature, the EGR gas flow rate is adjusted according to whether or not the outside air is introduced into the engine room by the outside air introduction mechanism. A control method for an internal combustion engine. An intercooler that cools the intake air using a circulating refrigerant;
An EGR passage for returning a part of the exhaust from the exhaust passage as EGR gas to the intake passage upstream of the intercooler;
An internal combustion engine control method comprising: an EGR valve that adjusts an EGR gas flow rate flowing through the EGR passage,
Measure or estimate the intake air temperature on the outlet side of the intercooler,
A control method for an internal combustion engine, characterized in that the EGR gas flow rate is adjusted based on the measured or estimated intake air temperature on the outlet side of the intercooler.   When the outside air is not introduced into the engine room by the outside air introduction mechanism, the refrigerant temperature or the intake air temperature at the inlet side of the intercooler is measured or estimated, and the measured or estimated refrigerant temperature or the above 2. The method for controlling an internal combustion engine according to claim 1, wherein circulation of the refrigerant is permitted in accordance with an intake air temperature on an inlet side of the intercooler. Measure or estimate the intake air temperature on the outlet side of the intercooler,
4. The method of controlling an internal combustion engine according to claim 1, wherein the EGR gas flow rate is adjusted based on the measured or estimated intake air temperature on the outlet side of the intercooler.   5. The method of controlling an internal combustion engine according to claim 2, wherein when the intake air temperature on the outlet side of the intercooler is lower than a predetermined first temperature, EGR gas is not introduced into the intake passage.   6. The flow rate of the EGR gas according to claim 2, wherein when the intake air temperature on the outlet side of the intercooler is equal to or higher than a predetermined first temperature, the EGR gas flow rate is adjusted according to the presence or absence of a circulation request for the refrigerant. The control method of the internal combustion engine in any one.   7. The method of controlling an internal combustion engine according to claim 6, wherein when there is no request for circulation of the refrigerant, EGR gas is introduced into the intake passage without circulating the refrigerant.   The method for controlling an internal combustion engine according to claim 6 or 7, wherein when there is a demand for circulation of the refrigerant, the flow rate of the EGR gas is adjusted based on the temperature of the refrigerant.   9. The method of controlling an internal combustion engine according to claim 8, wherein when the temperature of the refrigerant is equal to or higher than a predetermined second temperature, EGR gas is introduced into the intake passage.   The internal combustion engine control method according to claim 8 or 9, wherein when the temperature of the refrigerant is lower than a predetermined second temperature, the refrigerant is circulated without introducing EGR gas into the intake passage. .   11. The method of controlling an internal combustion engine according to claim 10, wherein after the refrigerant is circulated, EGR gas is introduced into the intake passage if the intake air temperature on the outlet side of the intercooler is equal to or higher than the first temperature. .   11. The method of controlling an internal combustion engine according to claim 2, wherein the intake air temperature on the outlet side of the intercooler is estimated using the intake air temperature and the intake pressure on the upstream side of the intercooler.   The intake air temperature at the outlet side of the intercooler is estimated using the engine speed, the load, and the intake air temperature at the intake air inlet of the intake passage. A method for controlling an internal combustion engine. A throttle valve located on the downstream side of the intake passage from the connection portion between the intake passage and the EGR passage;
Measure or estimate the intake air temperature on the inlet side of the throttle valve,
14. The method for controlling an internal combustion engine according to claim 1, wherein the EGR gas flow rate is adjusted based on the measured or estimated intake air temperature on the inlet side of the throttle valve. An intercooler that is located in an engine room in which the internal combustion engine is housed and cools intake air using a circulating refrigerant;
An EGR passage located in the engine room and returning a part of exhaust from the exhaust passage as EGR gas to the intake passage upstream of the intercooler;
An EGR valve for adjusting the flow rate of the EGR gas flowing through the EGR passage;
An outside air introduction mechanism for adjusting the amount of outside air introduced into the engine room, and a control device for an internal combustion engine,
When the intake air temperature at the intake inlet of the intake passage is lower than a predetermined temperature, the controller has a controller that adjusts the EGR gas flow rate according to whether or not the outside air is introduced into the engine room by the outside air introduction mechanism. A control device for an internal combustion engine.

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