JP6379548B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine including an external EGR device that recirculates part of exhaust gas to an intake passage via an EGR pipe.

  2. Description of the Related Art An internal combustion engine mounted on a vehicle is known that is equipped with an external EGR device that recirculates a part of exhaust gas as EGR gas to an intake passage for the purpose of improving fuel consumption or reducing exhaust emission. As an internal combustion engine equipped with such an external EGR device, conventionally, an oxygen concentration sensor of a solid electrolyte oxygen pump type is disposed in the intake passage of the internal combustion engine, and the EGR is recirculated to the intake passage based on the output of the oxygen concentration sensor. One that controls the amount of gas has been proposed (see, for example, Patent Document 1).

Japanese Patent No. 2560777

  The oxygen concentration sensor as described above normally becomes active when the temperature is raised to, for example, several hundred degrees C., and the oxygen concentration can be detected with high accuracy in this active state. For this reason, an electric heater is generally attached to the oxygen concentration sensor, and the heater element is activated by heat generation of the heater, and energization control of the heater is performed so that the activated state is maintained.

  Here, since the EGR gas contains water generated by combustion, when the EGR gas is introduced into the intake passage, the EGR gas is mixed with the relatively low temperature intake air, thereby condensing water in the intake passage. Is likely to occur. In addition, the environment in the intake system is likely to change due to the influence of the operating environment, and condensed water is generated in the intake passage when the temperature falls below the dew point temperature. Therefore, in an EGR system in which an exhaust sensor such as an oxygen concentration sensor is arranged in the intake system, there is a concern that when the sensor element is activated by the heater, element cracking is likely to occur due to water in the intake passage. On the other hand, from the viewpoint of improving fuel efficiency, it is desirable to introduce the EGR gas as continuously as possible.

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide a control device for an internal combustion engine capable of continuing the introduction of EGR gas while preventing moisture cracking of an exhaust sensor.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

The present invention relates to a control device for an internal combustion engine including an EGR device (35) that recirculates a part of exhaust gas of the internal combustion engine (10) to an intake passage (11) via an EGR pipe (36). The first configuration includes a heater (19) for heating the sensor element and an exhaust sensor (18) for detecting an exhaust component is provided in the intake passage, and the generation of condensed water in the intake passage is performed. A wetness determining means for determining whether or not a predetermined wetted state is predicted; and limiting the electric power supplied to the heater when the wetted water determining means determines that the predetermined wetted state is reached And an energization restricting means.

  In an internal combustion engine having an external EGR device, precise EGR control can be realized by arranging an exhaust sensor in the intake passage and directly detecting the actual EGR rate. On the other hand, since the exhaust gas contains a lot of water produced by the combustion of fuel, in a system that recirculates a part of the exhaust gas as EGR gas, the EGR gas is mixed with intake air, so that condensed water is generated in the intake passage. It tends to occur. In addition, the ease with which condensed water is generated in the intake passage changes according to the temperature and humidity of the outside air, and the more the outside air temperature is shifted from the predetermined range to the low temperature side or the high temperature side, the more easily the condensed water is generated. Moreover, the higher the humidity of the outside air or the lower the atmospheric pressure, the easier it is to generate condensed water. Therefore, in a system in which an exhaust sensor is mounted in the intake system, there are more scenes where the sensor element breaks due to condensed water generated in the intake passage than in the exhaust system, and it is highly necessary to take measures against moisture. On the other hand, from the viewpoint of improving fuel efficiency, it is desirable to introduce the EGR gas as continuously as possible.

  In view of these points, in the above-described configuration, it is determined whether or not it is in a predetermined wet state in which the generation of condensed water is predicted in the intake passage. As a countermeasure, energization of the heater of the exhaust sensor is limited. Thereby, EGR introduction can be continued while preventing element cracks in the exhaust sensor due to water.

The block diagram which shows the outline of an engine control system. The flowchart which shows the process sequence of EGR control. The time chart which shows the specific aspect of EGR control in case water exposure is estimated. The figure which shows the relationship between outside temperature and a target EGR rate. The figure which shows the relationship between humidity and a target EGR rate. The figure which shows the relationship between atmospheric pressure and a target EGR rate. The figure which shows the outline of the engine control system of other embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In this embodiment, a multi-cylinder four-cycle gasoline engine (internal combustion engine) mounted on a vehicle is to be controlled, and electronic control of various actuators in the engine is performed. First, the overall schematic configuration of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, an air flow meter 12 for detecting an intake air amount is provided upstream of the intake pipe 11. A throttle valve 14 whose opening degree is adjusted by a throttle actuator 13 such as a DC motor is provided on the downstream side of the air flow meter 12. The opening (throttle opening) of the throttle valve 14 is detected by a throttle opening sensor 15 built in the throttle actuator 13. A surge tank 16 is provided on the downstream side of the throttle valve 14, and an intake manifold 17 that is connected to an intake port of each cylinder is attached to the surge tank 16.

  The intake port and the exhaust port of the engine 10 are respectively provided with an intake valve and an exhaust valve (both not shown). Further, the engine 10 is provided with a fuel injection valve 23 and a spark plug 24 for each cylinder.

  An exhaust manifold 25 is connected to the exhaust port of the engine 10, and an exhaust pipe 26 is connected to a collecting portion of the exhaust manifold 25. The exhaust pipe 26 is provided with a catalyst 28 for purifying harmful components in the exhaust. In the present embodiment, a three-way catalyst that purifies three components of CO, HC, and NOx is used as the catalyst 28. An air-fuel ratio sensor 29 that detects the air-fuel ratio of the air-fuel mixture using exhaust as a detection target is provided on the upstream side of the catalyst 28. As the air-fuel ratio sensor 29, an A / F sensor having an output characteristic proportional to the air-fuel ratio is provided.

  A turbocharger 30 serving as a supercharger is provided between the intake pipe 11 and the exhaust pipe 26. The turbocharger 30 includes an intake compressor 31 disposed on the upstream side of the throttle valve 14 in the intake pipe 11, an exhaust turbine 32 disposed on the upstream side of the catalyst 28 in the exhaust pipe 26, and the intake compressor 31 and the exhaust turbine 32. And a rotating shaft 33 to be connected. When the exhaust turbine 32 is rotated by the exhaust gas flowing through the exhaust pipe 26, the intake compressor 31 is rotated with the rotation of the exhaust turbine 32, and the intake air is compressed (supercharged) by the centrifugal force generated by the rotation of the intake compressor 31. ).

  The intake pipe 11 is provided with an intercooler 34 as a heat exchanger for cooling the supercharged intake air downstream of the throttle valve 14. The intake air is cooled by the intercooler 34, so that a decrease in air charging efficiency is suppressed. The intercooler 34 is, for example, water-cooled intake air cooling means, and is disposed in a path (I / C cooling water path) different from the cooling water path of the engine 10. In the intercooler 34, the intake air is cooled by circulating the cooling water through the I / C cooling water path. The cooling capacity of the intercooler 34 is variable according to the flow rate of the cooling water. In this embodiment, the intercooler 34 is controlled by driving control of a water pump (WP) (not shown) arranged in the I / C cooling water path. The cooling water flow rate can be made variable. In this embodiment, the intercooler 34 is provided integrally with the surge tank 16, but the intercooler 34 is provided separately from the surge tank 16 on the upstream side of the surge tank 16 or the upstream side of the throttle valve 14. It may be.

  The upstream side and the downstream side of the exhaust turbine 32 are communicated by an exhaust bypass passage 21, and a waste gate valve (WGV) 22 that opens and closes the exhaust bypass passage 21 is provided in the exhaust bypass passage 21. The exhaust amount flowing through the exhaust pipe 26 is increased or decreased according to the opening degree of the WGV 22, and the rotational speed of the exhaust turbine 32 and the rotational speed of the intake compressor 31 are adjusted. Further, the upstream side and the downstream side of the intake compressor 31 are communicated with each other by an intake bypass passage 48, and an air bypass valve (ABV) 49 that opens and closes the intake bypass passage 48 is provided in the intake bypass passage 48. By opening the ABV 49, the excess pressure between the turbocharger 30 and the throttle valve 14 can be released.

  The engine 10 is provided with an external EGR device 35 that introduces part of the exhaust gas into the intake passage as EGR gas. The EGR device 35 includes an EGR pipe 36 that connects the intake pipe 11 and the exhaust pipe 26, an electromagnetically driven EGR valve 37 that adjusts the amount of EGR gas flowing through the EGR pipe 36, and a heat exchanger that cools the EGR gas. As an EGR cooler 38. The EGR cooler 38 is, for example, water-cooled exhaust cooling means, and is disposed in the cooling water path 39 of the engine 10. In the EGR cooler 38, the EGR gas is cooled by circulating the cooling water through the cooling water passage 39. The cooling capacity of the EGR cooler 38 is variable according to the flow rate of the cooling water, and in this embodiment, the cooling water flow rate of the EGR cooler 38 is controlled by controlling the opening degree of the flow rate control valve 40 arranged in the cooling water path 39. Can be made variable.

  The EGR pipe 36 is provided to connect the downstream side of the exhaust turbine 32 (for example, the downstream side of the catalyst 28) in the exhaust pipe 26 and the upstream side of the intake compressor 31 in the intake pipe 11. As a result, a so-called LPL (low-pressure loop) EGR system is constructed.

  An exhaust sensor 18 that detects an exhaust component in the intake air is disposed in the intake passage. In the present embodiment, the exhaust sensor 18 is attached to the downstream side of the connection portion of the intake pipe 11 with the EGR pipe 36 and the upstream side of the intake compressor 31.

  In this embodiment, the exhaust sensor 18 employs an A / F sensor that detects an oxygen concentration as an exhaust component. Specifically, as the exhaust sensor 18, an A / F sensor is employed in which the current value generated by applying a voltage to the sensor element changes depending on the oxygen concentration in the gas and the unburned gas concentration. This sensor is composed of a laminate of a sensor element made of a solid electrolyte such as zirconia (ZrO2) and a heater 19 for heating the sensor element. The heater 19 is composed of a heating element that generates heat by feeding power from a battery power source (not shown), and heats the entire sensor element by generating heat. The heating activates the sensor element and keeps the sensor element in an activated state. The exhaust sensor 18 is the same as the A / F sensor employed for the air-fuel ratio sensor 29.

  In addition, the present system includes a crank angle sensor 41 that outputs a crank angle signal for each predetermined crank angle of the engine 10, a water temperature sensor 42 that detects the coolant temperature of the engine 10, an intake air temperature sensor 43 that detects the temperature of the intake air, Various sensors such as a humidity sensor 44 that detects the humidity of the outside air, an outside air temperature sensor 45 that detects the outside air temperature, and an atmospheric pressure sensor 46 that detects the atmospheric pressure are provided. The humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 correspond to an environment detecting unit that detects an outside air environment parameter.

  The ECU 50 is composed mainly of a microcomputer (hereinafter referred to as a microcomputer 51) composed of a CPU, a ROM, a RAM, and the like as well known, and executes various control programs stored in the ROM to perform various controls of the engine 10. carry out. Specifically, the microcomputer 51 receives detection signals from the various sensors described above, and based on the input detection signals, the throttle valve 14, the fuel injection valve 23, the spark plug 24, the EGR valve 37, the WGV 22, the ABV 49, Controls driving of the flow control valve 40 and the like. In addition, various switches operated by the driver, such as a wiper switch 55 for operating a windscreen rain wiper (wiper) and a defogger fan for defogging provided on the windscreen. A drive signal is input from the defogger switch 56 for causing the heating wire printed on the rear glass to generate heat, and the driving of the wiper, the glass heater, and the defogger is controlled based on the input drive signal. To do.

  In the present embodiment regarding drive control of the EGR valve 37, a target EGR rate, which is a target value of the EGR rate, is set based on the engine operating state (for example, engine rotation speed, load, etc.), and this target EGR rate is realized. The opening degree of the EGR valve 37 is controlled. Particularly in the present embodiment, the actual EGR rate is directly detected by the exhaust sensor 18, and the drive duty ratio of the EGR valve 37 is calculated so that the actual EGR rate calculated based on the detection result of the exhaust sensor 18 becomes the target EGR rate. Then, the EGR valve 37 is driven. In this system, the external EGR is precisely controlled by directly detecting the actual EGR rate so as to cope with the strengthening of laws and regulations. The introduction of EGR gas is performed in a predetermined EGR application operation region excluding the idle operation region and the high load operation region.

  In order to accurately detect the amount of EGR gas by the exhaust sensor 18, it is necessary to keep the exhaust sensor 18 in a predetermined active state. Therefore, the microcomputer 51 of the ECU 50 performs energization control of the heater 19 based on the element temperature of the exhaust sensor 18. Specifically, heater energization control is performed so that the element temperature becomes a predetermined target temperature (for example, 750 ° C.). At this time, the element impedance is detected as a parameter correlated with the element temperature, and the heater energization amount is controlled by the control duty ratio calculated based on the deviation between the element impedance detection value and the target value.

  By the way, since the exhaust gas contains a lot of water produced by the combustion of fuel, when the exhaust gas is recirculated by the external EGR device 35, the exhaust gas as the EGR gas is mixed with the intake air in the intake passage so that the condensed water is generated. It tends to occur. In addition, in the intake passage, the environment in the intake passage is likely to change due to changes in the outside air environmental parameters such as the temperature of the outside air, the amount of water in the intake air (outside air humidity), and atmospheric pressure. The ease of handling is different. Specifically, condensed water is more likely to be generated as the outside air temperature is shifted from a predetermined range to a low temperature side or a high temperature side. Further, the higher the humidity, the easier it is to generate condensed water, and the lower the atmospheric pressure, the easier it is to generate condensed water. For this reason, in an EGR system including the exhaust sensor 18 in the intake system, there are more scenes where the sensor element breaks due to condensed water generated in the intake passage than in the exhaust system, and it is highly necessary to take measures against water exposure. On the other hand, from the viewpoint of improving fuel consumption and exhaust emission, it is desirable to introduce EGR gas as continuously as possible.

  Therefore, in the present embodiment, it is determined whether or not a predetermined water-immersed state in which the generation of condensed water in the intake passage of the engine 10 is predicted. As a countermeasure, energization of the heater 19 of the exhaust sensor 18 is limited.

  FIG. 2 is a flowchart showing a processing procedure of EGR control according to the present embodiment. This process is executed at predetermined intervals by the microcomputer 51 of the ECU 50.

  In FIG. 2, in step S100, it is determined whether or not an abnormality has occurred in the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 as environment detecting means for detecting an outside air environment parameter (abnormality determining means). If the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 are all normal, a negative determination is made in step S100, and the process proceeds to step S101. The abnormality diagnosis process for the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 is executed in a separate routine (not shown).

In step S <b> 101, it is determined whether or not a predetermined water-immersed state in which the occurrence of condensed water in the intake passage is predicted (water determination). In this embodiment, it is determined whether it is a predetermined | prescribed wet condition based on the conditions (environment determination conditions) for determining an external air environment. As environmental judgment conditions,
(1) The outside air environment parameter is a value indicating a predetermined wet state (2) The driver's operation in a high humidity environment is included, and at least one of the conditions (1) and (2) Is determined to be in a predetermined wet state.

  Here, the condition (1) is determined based on the sensor values of the outside air temperature sensor 45, the humidity sensor 44, and the atmospheric pressure sensor 46. Specifically, (a) the outside air temperature detected by the outside air temperature sensor 45 is a predetermined low temperature determination value (for example, 10 ° C.) or less or a predetermined high temperature determination value (for example, 30 ° C.), b) The humidity of the outside air detected by the humidity sensor 44 is not less than a predetermined high humidity determination value (for example, 70%), and (c) the atmospheric pressure detected by the atmospheric pressure sensor 46 is a predetermined low pressure determination value ( For example, when at least one of the conditions of 85 kPa or less is satisfied, it is determined that the outside air environment parameter is a value indicating a predetermined wet state. In condition (2), when at least one of the wiper switch 55, the defogger switch 56, and the glass heater switch 57 is turned on, it is determined that the operation of the driver in a high humidity environment has occurred.

  If it is determined in step S101 that the water is not in a predetermined state, that is, there is no possibility of the occurrence of condensed water in the intake passage, the process proceeds to step S107, and normal EGR control is performed by another routine (not shown). In the normal EGR control, the actual EGR rate is calculated using the detection value of the exhaust sensor 18, and the amount of EGR gas recirculated to the intake passage is adjusted using the calculated sensor detection value. At this time, the exhaust sensor 18 is kept active by heater energization control based on the element temperature. Since the exhaust sensor 18 disposed in the intake passage is in an environment cooled by the intake air of the engine 10, the heater 19 is basically always energized when performing normal EGR control. The

  On the other hand, if it is determined in step S101 that the water is in a predetermined state, that is, there is a possibility of the generation of condensed water in the intake passage, the process proceeds to step S102, and energization of the heater 19 is stopped (energization limiting means). ). In the subsequent step S103, the cooling capacity of the intercooler 34 and the EGR cooler 38 is reduced. Specifically, the circulation of the cooling water in the intercooler 34 is stopped by stopping the driving of the water pump, and the circulation of the engine cooling water in the EGR cooler 38 is stopped by driving the flow control valve 40 to be closed. Thereby, generation | occurrence | production of the condensed water by the supercooling of intake air and EGR gas is suppressed. Instead of the configuration in which the water pump is stopped, the water pump may be driven and the cooling water flow rate may be reduced. Further, the flow rate control valve 40 does not have to be fully closed, and the flow rate of the cooling water may be reduced by setting the flow rate to a very small opening.

  In step S104, the rotational speed of the intake compressor 31 is reduced. Here, the opening degree of the WGV 22 is changed to the opening side, and the opening degree of the ABV 49 is changed to the opening side. Here, if the intake compressor 31 rotates at a high speed, the condensed water present in the EGR pipe 36 is easily sucked into the intake passage, and there is a possibility that water may enter the intake passage. Therefore, in the present embodiment, when it is determined that the vehicle is in a predetermined wet state, the rotational speed of the intake compressor 31 is decreased to suppress the sucking of condensed water from the EGR passage. As a result, it is possible to suppress damage and deterioration of the intake compressor 31 due to flooding.

  In step S105, a target EGR rate is set (target value setting means). In the present embodiment, a target EGR rate setting map that defines the relationship between the engine operating state and the target EGR rate is stored in advance in the ROM, and the target EGR rate is set using this setting map. As the target EGR rate setting map, a normal time map used in the normal time EGR control and a wet time map used in the EGR control when it is determined to be in a predetermined wet condition are set. In step S105, the target EGR rate corresponding to the current engine operating state is set using the flooded map. According to this flooded time map, the target EGR rate in the same engine operating state is set lower than when the normal time map is used.

  In step S106, the opening degree of the EGR valve 37 is controlled so as to realize the set target EGR rate. If it is determined that the predetermined wet state is present, the actual EGR rate is switched to the estimated value based on the engine operating state without using the detection value by the exhaust sensor 18. The estimated value of the actual EGR rate is calculated based on, for example, the opening degree of the EGR valve 37, the detected value of the air flow meter 12, and the throttle opening degree. In addition, in this embodiment, after it determines with it being a predetermined | prescribed wet state in step S101, step S101 becomes negative determination and when it progresses to step S107, it is from the time determined with not being a predetermined | prescribed wet state. The heater energization is resumed after a predetermined time Td has elapsed.

  Here, when abnormality has occurred in at least one of the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46, it cannot be accurately determined whether or not the determination condition (1) in the moisture determination is successful. Therefore, in the present embodiment, when there is an abnormality in at least one of the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46, the power supplied to the heater 19 is limited. Specifically, if it is determined in step S100 that any one of the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 is abnormal, an affirmative determination is made in step S100, and the steps after step S102 are performed. Execute the process. Thereby, the energization of the heater 19 is stopped when at least one of the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 is abnormal.

  FIG. 3 is a time chart showing a specific mode of control when the generation of condensed water in the intake passage is predicted. In the figure, (a) shows the transition of the result of the determination of water exposure, (b) shows the transition of heater energization / energization stop, (c) shows the transition of water pump drive / drive stop, and (d) shows the flow rate of the EGR cooler 38. The transition of the valve opening / closing of the control valve 40, (e) shows the transition of the opening / closing of the ABV 49, and (f) shows the transition of the opening degree of the WGV 22. In FIG. 3, it is assumed that the engine 10 is operating in the EGR application operation region.

  In FIG. 3, energization of the heater 19 is stopped when at least one of the moisture determination conditions (1) and (2) is satisfied at time t11. At time t11, the water pump is stopped and the flow control valve 40 is closed. Moreover, the opening degree of ABV49 and WGV22 is each changed to the open side. As a result, the cooling capacity of the intercooler 34 and the EGR cooler 38 is reduced, and the rotational speed of the intake compressor 31 is reduced. By such control, generation of condensed water in the intake passage and inflow of condensed water into the intake passage are suppressed, and water exposure of the exhaust sensor 18 is suppressed.

  Thereafter, when the conditions (1) and (2) are not satisfied, the energization of the heater 19 is resumed at the time t13 when the predetermined time Td has elapsed from the time t12. Further, the water pump, the flow control valve 40, the ABV 49, and the WGV 22 are shifted to normal drive control. In the period t11 to t12 in which the generation of condensed water in the intake passage is predicted, the cooling capacity of the intercooler 34 and the EGR cooler 38 is reduced, and the rotational speed of the intake compressor 31 is reduced. As a result, when energization of the heater 19 is resumed, water does not exist in the intake passage, and the concern about the wetness of the exhaust sensor 18 is eliminated.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  It is determined whether or not a predetermined wet condition in which the generation of condensed water in the intake passage is predicted, and when it is determined that the predetermined wet condition in which the generation of condensed water is predicted is The power input to the heater 19 of the exhaust sensor 18 is limited. According to such a configuration, EGR introduction can be continued while preventing element cracking of the exhaust sensor 18 due to moisture.

  Further, since the exhaust sensor 18 of the intake system is constantly affected by the outside air environment, it is necessary to take such countermeasures against water not only during the cold start of the engine 10 but also during operation. In particular, during the period when the EGR gas is being introduced, the exhaust sensor 18 of the intake system is likely to get wet. In that respect, in the above-described configuration, the input power to the heater 19 is limited during the period including the introduction of the EGR gas, so that the moisture of the exhaust sensor 18 can be suitably suppressed.

  The ease with which condensed water is generated in the intake passage varies depending on changes in outside air environmental parameters such as the temperature, humidity, and atmospheric pressure of the outside air, and the amount of condensed water increases as the outside air temperature deviates from a predetermined range to the low temperature side or the high temperature side. It tends to occur, and the higher the humidity, the easier it is to generate condensed water, or the lower the atmospheric pressure, the easier it is to generate condensed water. Considering this point, the configuration is such that it is determined whether or not it is in a predetermined flooded state based on the outside air environment parameter, so that it is possible to perform the moisture determination appropriately corresponding to a change in the outside air environment.

  If there is an abnormality in at least one of the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46, the success or failure of the determination condition (1) can no longer be determined accurately. In view of this, when at least one of the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 is abnormal and the detection performance of the sensor cannot be guaranteed, the power input to the heater 19 is limited. According to this configuration, heater energization in a state where the possibility of water exposure cannot be accurately specified is limited, so that it is possible to more reliably avoid sensor element cracking due to water exposure.

  More specifically, at least one of the wiper switch 55, the defogger switch 56, and the glass heater switch 57 is based on not only the sensor detection result of the ambient temperature, humidity, and atmospheric pressure, but also the operation of the driver in a high humidity environment. It was set as the structure which determines whether it is a predetermined | prescribed flooded state by whether or not was turned on. Whether or not the outside air environment is a high-humidity environment also appears as a driver's action. Therefore, even with such a configuration, the state of the outside air environment can be grasped, and a suitable countermeasure against water can be taken.

  In a situation where the generation of condensed water in the intake passage is predicted, the energization of the heater 19 is restricted and the cooling capacity of the intercooler 34 and the EGR cooler 38 is reduced. According to such a configuration, even if EGR gas is introduced, the generation of condensed water can be suppressed, so that EGR gas can be continuously introduced. Further, even in the environment where the condensed water is likely to be generated in the intake passage, it is possible to prevent water from being present in the intake passage as much as possible. The influence of water on each part of the engine can be suppressed.

  Further, under the situation where the occurrence of condensed water in the intake passage is predicted, the supercharging capability of the supercharger 30 is reduced by reducing the rotational speed of the intake compressor 31. If the intake compressor 31 is rotated at a high speed when the intake passage is in an environment where condensed water is likely to be generated, the condensed water in the EGR passage may be sucked out to the intake passage. In view of these points, the above-described configuration makes it possible to suppress as much water as possible from the exhaust sensor 18 and other parts of the engine.

  Paying attention to the fact that the EGR gas contains a lot of water generated by combustion, and condensate is likely to be generated. In the situation where the generation of condensate in the intake passage is predicted, the target EGR rate is set to be lower than usual. The configuration is set low. In this case, the generation of condensed water can be suppressed by reducing the amount of EGR gas itself recirculated to the intake passage. Moreover, it can suppress that the exhaust sensor 18 and each other engine site | part get wet.

  In particular, in the present embodiment, in a situation where the generation of condensed water in the intake passage is predicted, the heater 19 is deenergized, and the estimated value based on the engine operating state is used as the actual EGR rate. By stopping energization of the heater, it is possible to more reliably suppress element cracking of the exhaust sensor 18, which is preferable from the viewpoint of sensor protection. Moreover, EGR gas introduction can be continued by using the estimated value as the actual EGR rate.

  In the LPL type EGR system, since EGR gas is introduced upstream of the intake pipe 11, it can be said that the EGR gas is more easily affected by changes in the outside air, and condensed water is likely to be generated. Therefore, by applying the present invention to the LPL type EGR system as in the present embodiment, it is preferable that adverse effects due to water exposure can be suppressed.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the above-described embodiment, a configuration in which energization of the heater 19 is stopped is employed as a configuration that restricts the input power to the heater 19 when it is determined that the water is in a predetermined state. The configuration for limiting the heater input power is not limited to this, and the heater energization may be performed with a power smaller than that in a normal state in which it is determined that the predetermined flooded state is not achieved.

  -It is good also as a structure which changes the target EGR rate at the time of determining with it being a predetermined | prescribed wet state according to outside temperature. At this time, the target EGR rate is set to a smaller value as the outside air temperature is a temperature at which condensed water is likely to be generated. Specifically, as shown in FIG. 4, when the outside air temperature detected by the outside air temperature sensor 45 is equal to or lower than a predetermined low temperature determination value Tm1 (for example, 10 ° C.), the target EGR rate is set to a smaller value as the outside air temperature is lower. To do. When the outside air temperature detected by the outside air temperature sensor 45 is equal to or higher than a predetermined high temperature determination value Tm2 (for example, 30 ° C.), the target EGR rate is set to a smaller value as the outside air temperature is higher. Since the EGR gas contains a large amount of water generated by combustion, there is a concern that if a large amount of EGR gas is added, water will be generated in each part of the engine 10 including the exhaust sensor 18 to cause damage or the like. In view of this point, by adopting the above configuration, it is possible to reduce the influence of condensed water on each part of the engine including the exhaust sensor 18.

  -It is good also as a structure which changes the target EGR rate at the time of determining with it being a predetermined | prescribed wet state according to the humidity of outside air. At this time, the target EGR rate is set to a smaller value as the humidity of the outside air is higher. Specifically, as shown in FIG. 5, when the humidity of the outside air detected by the humidity sensor 44 is less than a predetermined high humidity determination value Hm1 (for example, 70%), the target EGR rate is constant regardless of the humidity, and the high humidity At the determination value Hm1 or higher, the target EGR rate is set to a smaller value as the humidity is higher. Even in such a configuration, the influence of condensed water on each part of the engine can be reduced.

  -It is good also as a structure which changes the target EGR rate at the time of determining with it being a predetermined | prescribed wet state according to atmospheric pressure. At this time, the target EGR rate is set to a smaller value as the atmospheric pressure is lower. Specifically, as shown in FIG. 6, when the atmospheric pressure detected by the atmospheric pressure sensor is higher than a predetermined low pressure determination value Pm1 (for example, 85 kPa), the target EGR rate is constant regardless of the atmospheric pressure, and the low pressure determination is performed. Below the value Pm1, the target EGR rate is set to a smaller value as the atmospheric pressure is lower. Even in such a configuration, the influence of condensed water on each part of the engine can be reduced. Of course, it is good also as a structure which changes the target EGR rate at the time of determining with it being a predetermined | prescribed wet condition based on two or more of the temperature, humidity, and atmospheric pressure of outside air.

  In the above embodiment, the normal time map and the wet time map are stored in advance as the target EGR rate setting map, and when it is determined that the water is in a predetermined wet state, the target time is set using the wet time map. It was set as the structure which sets an EGR rate. By changing this, only the normal time map is stored as the target EGR rate setting map, and when it is determined that it is in a predetermined wet state, the value set using the normal time map is corrected. It is good also as a structure which sets a target EGR rate. At this time, when it is determined that the water is in a predetermined wet state, it is desirable that the target EGR rate in the same engine operation state is set lower than in the normal state.

  In the above embodiment, the two conditions (1) and (2) are set as the environment determination condition, but only one of them may be set as the environment determination condition.

  In step S100 of FIG. 2, it is determined whether the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 are normal. However, are sensors other than the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 normal? You may further consider whether or not. For example, it is determined whether intake sensors other than the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 such as the air flow meter 12, the exhaust sensor 18, and the intake air temperature sensor 43 are normal, and all the sensors are normal. It is good also as a structure which performs the process of step S101 on condition that there exists.

  In the above embodiment, the processes after step S101 are executed on condition that the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46 are all normal. When this is changed, and there is a normal sensor in any one of the humidity sensor 44, the outside air temperature sensor 45, and the atmospheric pressure sensor 46, the wetness determination using the detection value of the normal sensor is performed, It is good also as a structure which implements energization restriction of heater 19 based on the result of water exposure determination.

  In the case where the cooling capacity of the intercooler 34 is reduced in step S103 of FIG. 2 and / or the cooling capacity of the EGR cooler 38 is reduced, according to at least one of the outside air temperature, humidity and atmospheric pressure, It is good also as a structure which changes the degree of the cooling capacity fall. Specifically, when the outside air temperature detected by the outside air temperature sensor 45 is a predetermined low temperature determination value Tm1 or less, the cooling capacity is reduced as the outside air temperature is low, and when the outside air temperature is above the predetermined high temperature determination value Tm2, the outside air temperature is higher. Reduce cooling capacity. Further, the higher the outside air humidity detected by the humidity sensor 44, the lower the cooling capacity. Further, the lower the atmospheric pressure detected by the atmospheric pressure sensor 46, the lower the cooling capacity.

  When reducing the rotational speed of the intake compressor 31 in step S104 of FIG. 2, the rotational speed of the intake compressor 31 may be variable according to at least one of the outside air temperature, humidity, and atmospheric pressure. Specifically, when the outside air temperature detected by the outside air temperature sensor 45 is equal to or lower than a predetermined low temperature determination value Tm1, the rotational speed of the intake compressor 31 is decreased as the outside air temperature is lower. The higher the temperature, the lower the rotational speed of the intake compressor 31. Further, the higher the humidity of the outside air detected by the humidity sensor 44, the lower the rotational speed of the intake compressor 31. Further, the lower the atmospheric pressure detected by the atmospheric pressure sensor 46, the lower the rotational speed of the intake compressor 31.

  In the above embodiment, when it is determined that the predetermined wet state is determined and the energization restriction of the heater 19 is performed and the predetermined wet state is eliminated, the heater energization is resumed after a predetermined time Td has elapsed. Although it was set as the structure, it is good also as a structure which restarts heater energization at the timing when the predetermined | prescribed wet state was eliminated.

  In step S104 of FIG. 2, the rotational speed of the intake compressor 31 is reduced by changing the opening of the WGV 22 and the ABV 49 to the open side, but the opening of only one of the WGV 22 and the ABV 49 is set to the open side. It is good also as a structure which makes the rotational speed of the intake compressor 31 low by changing.

  In the above embodiment, the exhaust sensor 18 is attached to the upstream side of the intake compressor 31 in the intake pipe 11, but the attachment position of the exhaust sensor 18 is not limited to this, and the EGR gas concentration in the intake air in the intake pipe 11 is set. Any position that can be detected is acceptable. For example, the exhaust sensor 18 may be attached to the downstream side of the intake compressor 31.

  In the above embodiment, the case where the present invention is applied to an engine with a supercharger that employs an LPL type (low pressure loop type) EGR device has been described. However, as shown in FIG. An HPL type (high pressure loop type) EGR device provided with an EGR pipe 36 so as to connect the upstream side of the intake pipe 11 and the downstream side of the intake compressor 31 (for example, the downstream side of the intercooler 34) in the intake pipe 11 is adopted. The present invention may be applied to an engine with a supercharger. In this case, the attachment position of the exhaust sensor 18 is not particularly limited as long as it is a position where EGR gas can be detected. For example, as shown in FIG. 7, the exhaust sensor 18 is attached downstream of the connection portion between the intake pipe 11 and the EGR pipe 36 (for example, The exhaust sensor 18 is disposed on the downstream side of the intercooler 34.

  In the above embodiment, the intercooler 34 is a water cooling type, but may be an air cooling type. In that case, the cooling capacity of the intercooler 34 can be adjusted by operating a grill shutter that adjusts the amount of air sent to the intercooler 34.

  In the above embodiment, the A / F sensor is adopted as the exhaust sensor 18, but any sensor other than the A / F sensor can be used as long as it has a heater 19 that heats the sensor element and can detect components contained in the exhaust. For example, a CO2 sensor capable of detecting CO2 as an exhaust component may be employed.

  In the above embodiment, the case where the present invention is applied to an engine equipped with an exhaust turbine-driven supercharger (so-called turbocharger) has been described. However, the present invention is not limited to an engine equipped with a turbocharger, and is a mechanically driven supercharger. (So-called supercharger) or an engine equipped with an electric supercharger may be applied. Further, the present invention is not limited to an engine with a supercharger, and may be applied to a naturally aspirated engine (NA engine) not equipped with a supercharger.

  The present invention can be applied not only to gasoline engines but also to diesel engines. It can also be applied to engines other than those for vehicles.

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 11 ... Intake pipe, 18 ... Exhaust sensor, 19 ... Heater, 22 ... Waste gate valve, 26 ... Exhaust pipe, 30 ... Turbocharger (supercharger), 31 ... Intake compressor, 32 ... Exhaust turbine, 34 ... intercooler (intake air cooling means), 35 ... external EGR device, 36 ... EGR piping, 37 ... EGR valve, 38 ... EGR cooler (exhaust air cooling means), 40 ... flow rate control valve, 43 ... intake air temperature sensor , 44 ... Humidity sensor (environment detection means), 45 ... Outside air temperature sensor (environment detection means), 46 ... Atmospheric pressure sensor (environment detection means), 50 ... ECU (moisture determination means, energization restriction means, abnormality determination means) (Target value setting means), 51 ... microcomputer, 55 ... wiper switch, 56 ... defogger switch, 57 ... glass heater switch.

Claims (14)

A control device for an internal combustion engine comprising an EGR device (35) for recirculating a part of exhaust gas of the internal combustion engine (10) to an intake passage (11) via an EGR pipe (36),
An exhaust sensor (18) having a heater (19) for heating the sensor element and detecting an exhaust component is provided in the intake passage;
Water determination means for determining whether or not a predetermined water exposure state is predicted to generate condensed water in the intake passage;
Energization restricting means for restricting power to be supplied to the heater when it is determined by the moisture determination means that the predetermined moisture condition is present;
Environment detecting means (44, 45, 46) for detecting an outside air environment parameter which is at least one of the temperature of the outside air, the humidity of the outside air and the atmospheric pressure;
An abnormality determination means for determining whether or not there is an abnormality in the detection performance of the outside air environment parameter by the environment detection means;
Equipped with a,
The moisture determination means determines whether or not the predetermined moisture condition is based on an outside air environment parameter detected by the environment detection means,
The energization limiting means limits the power supplied to the heater regardless of the determination result by the moisture determination means when the abnormality determination means determines that the detection performance of the outside air environment parameter is abnormal. A control device for an internal combustion engine. Wherein the water determination means based on the driver's behavior for high-humidity environment, the control device for an internal combustion engine according to claim 1 for determining whether or not the a predetermined target water conditions. A control device for an internal combustion engine comprising an EGR device (35) for recirculating a part of exhaust gas of the internal combustion engine (10) to an intake passage (11) via an EGR pipe (36),
An exhaust sensor (18) having a heater (19) for heating the sensor element and detecting an exhaust component is provided in the intake passage;
Water determination means for determining whether or not a predetermined water exposure state is predicted to generate condensed water in the intake passage;
Energization restricting means for restricting power to be supplied to the heater when it is determined by the moisture determination means that the predetermined moisture condition is present;
Equipped with a,
The control apparatus for an internal combustion engine , wherein the moisture determination means determines whether or not the predetermined moisture condition is based on a driver's operation in a high humidity environment . A supercharger (30) for supercharging intake air of the internal combustion engine and an intake air cooling means (34) for cooling the intake air supercharged by the supercharger include gas passages (11, 26) of the internal combustion engine. )
The control device for an internal combustion engine according to any one of claims 1 to 3 , wherein when it is determined by the moisture determination means that the predetermined moisture condition is reached, the cooling capacity of the intake air cooling means is reduced. . A control device for an internal combustion engine comprising an EGR device (35) for recirculating a part of exhaust gas of the internal combustion engine (10) to an intake passage (11) via an EGR pipe (36),
An exhaust sensor (18) having a heater (19) for heating the sensor element and detecting an exhaust component is provided in the intake passage;
A supercharger (30) for supercharging intake air of the internal combustion engine and an intake air cooling means (34) for cooling the intake air supercharged by the supercharger include gas passages (11, 26) of the internal combustion engine. )
Water determination means for determining whether or not a predetermined water exposure state is predicted to generate condensed water in the intake passage;
Energization restricting means for restricting power to be supplied to the heater when it is determined by the moisture determination means that the predetermined moisture condition is present;
Equipped with a,
The control apparatus for an internal combustion engine , wherein the cooling capacity of the intake air cooling means is reduced when the wetness determining means determines that the predetermined wet state is reached . Environment detection means (44, 45, 46) for detecting an outside air environment parameter which is at least one of the temperature of the outside air, the humidity of the outside air and the atmospheric pressure,
The control apparatus for an internal combustion engine according to claim 5 , wherein the moisture determination means determines whether or not the predetermined moisture condition is based on an outside air environment parameter detected by the environment detection means. A supercharger (30) for supercharging intake air of the internal combustion engine is provided in a gas passage (11, 26) of the internal combustion engine;
The control of the internal combustion engine according to any one of Claims 1 to 6 , wherein when the water wetness determining means determines that the predetermined water wet state is present, the supercharging capability of the supercharger is reduced. apparatus. A control device for an internal combustion engine comprising an EGR device (35) for recirculating a part of exhaust gas of the internal combustion engine (10) to an intake passage (11) via an EGR pipe (36),
An exhaust sensor (18) having a heater (19) for heating the sensor element and detecting an exhaust component is provided in the intake passage;
A supercharger (30) for supercharging intake air of the internal combustion engine is provided in a gas passage (11, 26) of the internal combustion engine;
Water determination means for determining whether or not a predetermined water exposure state is predicted to generate condensed water in the intake passage;
Energization restricting means for restricting power to be supplied to the heater when it is determined by the moisture determination means that the predetermined moisture condition is present;
Equipped with a,
The control apparatus for an internal combustion engine , wherein the supercharging ability of the supercharger is reduced when the predetermined wet condition is determined by the water determination means . Environment detection means (44, 45, 46) for detecting an outside air environment parameter which is at least one of the temperature of the outside air, the humidity of the outside air and the atmospheric pressure,
9. The control device for an internal combustion engine according to claim 8 , wherein the moisture determination means determines whether or not the predetermined moisture condition is based on an outside air environment parameter detected by the environment detection means. Exhaust cooling means (38) for cooling the exhaust gas returning to the intake passage is provided in the EGR pipe,
The control device for an internal combustion engine according to any one of claims 1 to 9 , wherein when it is determined by the moisture determination means that condensed water is likely to be generated, the cooling capacity of the exhaust cooling means is reduced. A control device for an internal combustion engine comprising an EGR device (35) for recirculating a part of exhaust gas of the internal combustion engine (10) to an intake passage (11) via an EGR pipe (36),
An exhaust sensor (18) having a heater (19) for heating the sensor element and detecting an exhaust component is provided in the intake passage;
Exhaust cooling means (38) for cooling the exhaust gas returning to the intake passage is provided in the EGR pipe,
Water determination means for determining whether or not a predetermined water exposure state is predicted to generate condensed water in the intake passage;
Energization restricting means for restricting power to be supplied to the heater when it is determined by the moisture determination means that the predetermined moisture condition is present;
Equipped with a,
A control device for an internal combustion engine, characterized in that the cooling capacity of the exhaust cooling means is reduced when it is determined by the moisture determination means that condensed water may be generated . Environment detection means (44, 45, 46) for detecting an outside air environment parameter which is at least one of the temperature of the outside air, the humidity of the outside air and the atmospheric pressure,
The control apparatus for an internal combustion engine according to claim 11 , wherein the moisture determination means determines whether or not the predetermined moisture condition is based on an outside air environment parameter detected by the environment detection means. A target value setting means for setting a target EGR rate that is a target value of an EGR rate in the internal combustion engine;
The target value setting means, when determined to be in the predetermined wet condition by the wet determination means, sets the target EGR rate as compared with the normal time when it is not determined to be in the predetermined wet condition. The control device for an internal combustion engine according to any one of claims 1 to 12 , wherein the control device is set low. The control of the internal combustion engine according to any one of claims 1 to 13 , wherein the energization restriction unit stops energization of the heater when the wetness determination unit determines that the predetermined wet state is present. apparatus.

Images