JP2016098680A - Internal combustion engine exhaust gas recirculation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine exhaust gas recirculation apparatus capable of preventing the generation of condensate water in the light of the influence of humidity.SOLUTION: An exhaust gas recirculation apparatus for an internal combustion engine provided with a supercharger including a compressor provided in an intake passage, an actuator regulating a boost pressure, an intake-air-humidity detection sensor detecting a humidity of intake air in the intake passage downstream of the compressor, and an intake-air-temperature detection sensor detecting a temperature of the intake air in the intake passage downstream of the compressor, comprises means for calculating the boost pressure such that an intake-air dew-point temperature is lower than the intake air temperature, and controlling the actuator with the calculated boost pressure set to a target boost pressure.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

  Conventionally, it is known that condensed water is generated in an intake passage of an internal combustion engine. Condensed water is generated when the intake air temperature becomes lower than the intake dew point temperature. In Patent Document 1, in an internal combustion engine provided with an exhaust gas recirculation (EGR) device that recirculates a part of exhaust gas to an intake passage, generation of condensed water at a connection portion between the intake passage and the EGR passage is prevented. Control is disclosed. This control is control for introducing the intake air on the downstream side of the compressor to the connection portion when the EGR gas temperature in the connection portion is lower than a predetermined value set in advance. By executing this control, the intake air compressed and heated by the compressor can be introduced into the connecting portion. For this reason, it is possible to raise the intake air temperature at the connecting portion so that the intake air temperature becomes higher than the intake dew point temperature. As a result, the generation of condensed water at the connecting portion can be prevented.

JP 2013-096357 A JP 2012-246792 A

  Incidentally, it is known that in the intake passage of an internal combustion engine, the intake dew point temperature increases as the intake humidity increases. For this reason, when the intake air humidity is high, the intake dew point temperature tends to be higher than the intake air temperature, and condensed water is likely to be generated.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an exhaust gas recirculation device for an internal combustion engine that can prevent the generation of condensed water in consideration of the influence of humidity. .

In order to achieve the above object, the first invention provides
A supercharger including a compressor provided in the intake passage;
An actuator for adjusting the supercharging pressure;
An intake humidity sensor for detecting intake humidity in the intake passage downstream of the compressor;
An exhaust gas recirculation device for an internal combustion engine, comprising: an intake air temperature sensor that detects an intake air temperature in the intake passage downstream of the compressor;
A supercharging pressure at which an intake dew point temperature is lower than the intake air temperature is calculated based on the intake humidity, and the actuator is controlled using the calculated supercharging pressure as a target supercharging pressure.

  According to the first invention, the supercharging pressure can be controlled such that the intake dew point temperature is lower than the intake air temperature. As a result, generation of condensed water in the intake passage can be prevented.

1 is a diagram illustrating a configuration of a system according to a first embodiment. It is the figure which showed the relationship between intake dew point temperature and supercharging pressure. It is a figure showing the condensed water generation | occurrence | production prevention routine performed with ECU of Embodiment 1. FIG. It is a figure explaining the 2-stage turbocharger of Embodiment 2. FIG. It is a figure showing the condensed water generation | occurrence | production prevention routine performed with ECU of Embodiment 2. FIG. It is a figure showing the condensed water generation | occurrence | production prevention routine performed with ECU of Embodiment 2. FIG.

Embodiment 1 FIG.
FIG. 1 is a diagram showing the configuration of the system according to the first embodiment. The system according to the first embodiment includes an engine 10. The engine 10 is a supercharged engine.

  In the first embodiment, a turbocharger that uses exhaust gas to compress intake air is employed as a supercharger. The turbocharger has a structure in which a compressor 30 provided in the intake passage 21 and a turbine 32 provided in the exhaust passage are connected via an axis.

  A waste gate valve 35 that bypasses the turbine 32 is also provided. An air bypass valve 46 that bypasses the compressor 30 is also provided. The waste gate valve 35 and the air bypass valve 46 are provided for the purpose of adjusting the supercharging pressure.

  An intake passage 21 is connected to the engine body 18. In the intake passage 21, a water-cooled intercooler 14 is provided downstream of the compressor 30.

  A radiator 12 that cools the cooling water is connected to the intercooler 14. The radiator 12 is provided with an electric water pump 16 for flowing cooling water.

  Further, the engine 10 is provided with two EGR devices that recirculate a part of the exhaust gas to the intake passage 21 as EGR gas. These EGR devices will be described below.

  As a first EGR device, an HPL (High Pressure Loop) EGR device is provided. In FIG. 1, an HPLEGR passage 40 and an HPLEGR valve (not shown) constitute an HPLEGR device. The HPLEGR passage 40 connects an exhaust passage between the engine body 18 and the turbine 32 and an intake passage 21 between the intercooler 14 and the engine body 18.

  As a second EGR device, an LPL (Low Pressure Loop) EGR device is provided. In FIG. 1, an LPLEGR passage 45, an EGR cooler (not shown), and an LPLEGR valve (not shown) constitute an LPLEGR device. The LPLEGR passage 45 connects the exhaust passage downstream of the catalyst and the intake passage 21 upstream of the compressor 30.

  Various sensors are attached to the engine 10. An intake air temperature sensor 20 for detecting the intake air temperature is attached to the intake passage 21 between the compressor 30 and the intercooler 14. An intake humidity sensor 24 for detecting intake humidity is attached to the intake passage 21 between the compressor 30 and the intercooler 14. A supercharging pressure sensor 22 that detects a supercharging pressure is attached to an intake passage 21 between the intercooler 14 and the engine body 18.

  The engine according to the first embodiment includes an ECU 100 (Electronic Control Unit). Various sensors such as an intake air temperature sensor 20, a supercharging pressure sensor 22, and an intake air humidity sensor 24 are connected to the input side of the ECU 100. Various actuators such as an electric water pump 16, an HPLEGR valve, an LPLEGR valve, a waste gate valve 35, and an air bypass valve 46 are connected to the output side of the ECU 100.

  By the way, in the intake passage 21, when the intake air temperature becomes lower than the intake dew point temperature, condensed water is generated. For example, when the engine 10 is cold started, the engine water temperature is lower than that during normal operation, and the intake passage 21 cannot be warmed up. For this reason, when the engine 10 is cold started, the intake air temperature becomes lower than the intake dew point temperature, and condensed water is likely to be generated.

  Further, the intake dew point temperature varies depending on the intake humidity. This is because when the intake humidity increases, the amount of water vapor contained in the intake air increases, and the intake dew point temperature increases accordingly. Further, the intake dew point temperature also changes depending on the supercharging pressure.

  Therefore, in the first embodiment, the relationship among the intake dew point temperature, the intake humidity, and the supercharging pressure is mapped and stored in the ECU 100. Then, the intake air humidity and the provisional supercharging pressure are substituted into this map, and an intake dew point temperature that is lower than the intake air temperature is searched. Then, the boost pressure corresponding to the searched intake dew point temperature becomes the target boost pressure. Then, each actuator is controlled so that the current supercharging pressure approaches the target supercharging pressure. Hereinafter, a map of the relationship among the intake dew point temperature, the intake humidity, and the supercharging pressure will be described with reference to FIG.

  FIG. 2 is a diagram showing the relationship among the intake dew point temperature, the intake humidity, and the supercharging pressure. FIG. 2 shows the relationship between the intake dew point temperature and the supercharging pressure at four types of humidity of 90%, 70%, 50%, and 30%. As shown in FIG. 2, the intake dew point temperature increases as the intake humidity increases. The ECU 100 stores a map of data indicating the relationship between the intake dew point temperature and the supercharging pressure. The data of FIG. 2 is data of the intake dew point temperature and the supercharging pressure when the outside air temperature is 25 ° C. and the introduction of EGR gas is cut off. For this reason, the numerical value showing the relationship between the intake dew point temperature and the supercharging pressure shown in FIG. 2 changes as the outside air temperature changes. In the ECU 100, data indicating the relationship between the intake dew point temperature and the supercharging pressure at various outside air temperatures obtained in advance by experiments is mapped and stored.

  Hereinafter, in the first embodiment, the condensed water generation prevention control performed using the map will be described with reference to FIG.

[Condensate generation prevention routine]
FIG. 3 is a diagram showing a condensed water generation prevention routine executed by ECU 100 of the first embodiment. The ECU 100 has a memory for storing this routine. The ECU 100 has a processor for executing the stored routine.

  First, the ECU 100 determines whether or not the introduction of EGR gas is cut at the cold start (S100). This routine is repeated when it is determined that the introduction of EGR gas is not cut at the time of cold start.

  On the other hand, the ECU 100 detects the intake air temperature and the intake humidity when it is determined that the introduction of the EGR gas is cut during the cold start (S102).

  Next, the ECU 100 calculates a target boost pressure (S104). The ECU 100 stores the map described in FIG. 2 in advance, and calculates the intake dew point temperature by substituting the outside air temperature, the intake air humidity, and the temporary supercharging pressure into this map. Then, the temporary supercharging pressure is changed to search for a temporary supercharging pressure at which an intake dew point temperature that is lower than the intake air temperature is obtained. Then, the searched temporary supercharging pressure is set as the target supercharging pressure.

  Next, the ECU 100 determines whether or not the current boost pressure is higher than the target boost pressure (S106). When the current boost pressure is equal to or lower than the target boost pressure, this routine is repeated.

  On the other hand, if it is determined that the current supercharging pressure is higher than the target supercharging pressure, it is determined whether the waste gate valve 35 (WGV) is fully open (S108). When it is determined that the waste gate valve 35 (WGV) is not fully opened, the opening degree of the waste gate valve 35 (WGV) is set large (S114). Thereafter, this routine is repeated.

  On the other hand, when it is determined that the waste gate valve 35 (WGV) is fully opened, the ECU 100 determines whether or not the air bypass valve 46 is fully opened (S110). When it is determined that the air bypass valve 46 is not fully open, the opening degree of the air bypass valve 46 is set large (S116). Next, the opening degree of the waste gate valve 35 (WGV) is returned to the base value (S112). Thereby, a delay in supercharging can be suppressed. Thereafter, this routine is repeated.

  On the other hand, when it is determined that the air bypass valve 46 is fully open, the opening degree of the waste gate valve 35 (WGV) is returned to the base value (S112). Thereafter, this routine is repeated.

  By repeating the condensed water generation prevention routine of the first embodiment, first, the opening degree of the waste gate valve 35 can be increased to bring the current supercharging pressure closer to the target supercharging pressure. When the waste gate valve 35 is fully opened, the current boost pressure can be brought close to the target boost pressure by increasing the opening of the air bypass valve 46. In this way, control is performed so that each actuator is controlled stepwise to bring the current supercharging pressure closer to the target supercharging pressure.

  By performing the condensate generation prevention control, each actuator is controlled so that the boost pressure is calculated based on a map in which the relationship between the intake dew point temperature and the boost pressure is set. By controlling the supercharging pressure, the intake dew point temperature can be controlled so as not to become lower than the intake air temperature. As a result, generation of condensed water in the intake passage 21 can be prevented.

  In the first embodiment, the supercharging pressure is controlled by the waste gate valve 35, but the present invention is not limited to this. For example, the supercharging pressure may be controlled using a variable nozzle (VN) provided in the turbine 32 instead of the waste gate valve 35.

Embodiment 2. FIG.
The second embodiment is different from the first embodiment in the configuration of the turbocharger. Specifically, a two-stage turbocharger including two turbochargers is employed in the system of the second embodiment. A two-stage turbocharger in the second embodiment will be described with reference to FIG.

  FIG. 4 is a diagram illustrating the two-stage turbocharger according to the second embodiment. As shown in FIG. 4, the low-pressure turbocharger 102 and the high-pressure turbocharger 200 are provided in the system of the second embodiment. The low-pressure turbocharger 102 has a structure in which a low-pressure compressor 60 and a low-pressure turbine 62 are connected via a shaft. The high-pressure turbocharger 200 has a structure in which a high-pressure compressor 70 and a high-pressure turbine 72 are connected via a shaft. The high pressure turbocharger 200 is installed closer to the engine body 18 than the low pressure turbocharger 102.

  As shown in FIG. 4, the system according to the second embodiment is provided with various valves for adjusting the supercharging pressure. An intake switching valve 50 (ACV: Air Control Valve) is provided in a passage that bypasses the high-pressure compressor 70. An exhaust switching valve 54 (ECV: Exhaust Control Valve) is provided in a passage that bypasses the high-pressure turbine 72. An exhaust bypass valve 52 (EBV: Exhaust Bypass Valve) is provided in a passage that bypasses the low-pressure turbine 62.

  Hereinafter, the condensed water generation prevention routine in the second embodiment will be described with reference to FIG.

  FIG. 5 is a diagram illustrating a condensed water generation prevention routine executed by ECU 100 of the second embodiment. Note that S200, S202, S204, and S206 are the same processes as S100, S102, S104, and S106 described with reference to FIG.

  When it is determined in S206 that the current supercharging pressure is higher than the target supercharging pressure, the ECU 100 determines whether or not the exhaust gas switching valve 54 (ECV) is fully opened (S208). When ECU 100 determines that exhaust switch valve 54 is not fully open, ECU 100 increases the opening degree of exhaust switch valve 54 (S218). Thereafter, this routine is repeated.

  On the other hand, when it is determined that the exhaust gas switching valve 54 (ECV) is fully open, the ECU 100 determines whether or not the exhaust bypass valve 52 (EBV) is fully open (S210). When ECU 100 determines that exhaust bypass valve 52 is not fully open, ECU 100 increases the degree of opening of exhaust bypass valve 52 (S220). Thereafter, this routine is repeated.

  On the other hand, when it is determined that the exhaust bypass valve 52 (EBV) is fully open, the ECU 100 determines whether or not the intake air switching valve 50 (ACV) is fully open (S212). When ECU 100 determines that intake switching valve 50 is not fully open, ECU 100 increases the opening of intake switching valve 50 (S222). Thereafter, this routine is repeated.

  On the other hand, when it is determined that the intake air switching valve 50 (ACV) is fully open, the ECU 100 determines whether or not the air bypass valve 46 is fully open (S214). When it is determined that the air bypass valve 46 is not fully opened, the opening degree of the air bypass valve 46 is set large (S224). Next, the openings of the exhaust switching valve 54 (ECV), the exhaust bypass valve 52 (EBV), and the intake switching valve 50 (ACV) are returned to the base values (S216). Thereafter, this routine is repeated.

  On the other hand, when it is determined that the air bypass valve 46 is fully open, the opening degrees of the exhaust switching valve 54 (ECV), the exhaust bypass valve 52 (EBV), and the intake switching valve 50 (ACV) are returned to the base values (S216). ). Thereafter, this routine is repeated.

  By repeating the condensed water generation prevention routine of the second embodiment, first, the opening degree of the exhaust gas switching valve 54 (ECV) can be increased to bring the current supercharging pressure closer to the target supercharging pressure. When the exhaust switching valve 54 (ECV) is fully opened, the current boost pressure can be brought close to the target boost pressure by increasing the opening of the exhaust bypass valve 52 (EBV). When the exhaust bypass valve 52 (EBV) is fully opened, the current boost pressure can be brought close to the target boost pressure by increasing the opening of the intake switching valve 50 (ACV). In this way, control is performed so that each actuator is controlled stepwise to bring the current supercharging pressure closer to the target supercharging pressure.

  A modification of the second embodiment will be described with reference to FIG.

  FIG. 6 is a diagram illustrating a condensed water generation prevention routine executed by ECU 100 of the second embodiment. Hereinafter, only differences from the routine of FIG. 5 will be described.

  The difference between the routine shown in FIG. 6 and the routine of FIG. 5 is that the exhaust bypass valve 52 (EBV) fully open determination (S312) and the intake switching valve 50 (ACV) fully open determination (S314) are interchanged. is there.

DESCRIPTION OF SYMBOLS 10 Engine 18 Engine main body 20 Intake temperature sensor 22 Supercharging pressure sensor 24 Intake humidity sensor 30 Compressor 32 Turbine 35 Wastegate valve 46 Air bypass valve 100 ECU

Claims (1)

A supercharger including a compressor provided in the intake passage;
An actuator for adjusting the supercharging pressure;
An intake humidity sensor for detecting intake humidity in the intake passage downstream of the compressor;
An exhaust gas recirculation device for an internal combustion engine, comprising: an intake air temperature sensor that detects an intake air temperature in the intake passage downstream of the compressor;
An internal combustion engine comprising: a boost pressure at which an intake dew point temperature is lower than the intake air temperature is calculated based on the intake humidity; and the actuator is controlled using the calculated boost pressure as a target boost pressure. Exhaust gas recirculation device.

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