JP2015078637A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device capable of ensuring suppression of generation of condensate water in an internal combustion engine provided with a supercharger.SOLUTION: A control device 20 controls a drive state of a supercharger 4 supercharging intake air introduced into a combustion chamber of an internal combustion engine 100 on the basis of a humidity of the intake air so as to regulate a pressure of the intake air. Furthermore, the control device 20 not only regulates the pressure of the intake air but also increases a temperature of the intake air downstream of an intercooler and/or increases a change gear ratio of a transmission.

Description

  The present invention relates to a control device for an internal combustion engine, for example, a control device for an internal combustion engine provided with a supercharger.

  2. Description of the Related Art Conventionally, as one technique for reducing the fuel consumption of vehicles such as automobiles, a technique for increasing the theoretical thermal efficiency of an engine (internal combustion engine) by increasing the compression ratio (higher compression ratio of the engine) is known. Further, as another fuel consumption reduction technique, engine downsizing is also known, and pumping loss and mechanical loss can be reduced by this downsizing.

  However, in a downsized engine, it is necessary to increase the supercharging pressure in order to maintain torque (output), and when the supercharging pressure is increased, the temperature of the intake air downstream of the compressor of the supercharger (in accordance with that) Hereinafter, the intake air temperature rises. Such an increase in intake air temperature leads to the occurrence of abnormal combustion called engine knocking or pre-ignition.Therefore, in an engine equipped with a supercharger, an intercooler is provided during intake and the intake air is taken in by the intercooler. It has been proposed to introduce it into the combustion chamber after cooling. Accordingly, when the maximum supercharging pressure of the engine is increased, the amount of cooling in the intercooler increases accordingly, and there is a possibility that condensed water of intake air is generated in the intercooler or downstream thereof. When this condensed water is introduced into the combustion chamber of the engine by the flow of intake air, there may be a problem that the engine is damaged due to generation of a water hammer or the like.

  The condensed water described above is a liquid that is generated when the partial pressure of water vapor existing in the atmosphere exceeds the saturated water vapor pressure, and the condensed water is a component of water vapor present in the air. It is known that the higher the pressure, that is, the higher the humidity of the atmosphere, the easier it is to generate.

  In addition, in a supercharged engine, in order to avoid the occurrence of abnormal combustion, the introduction of an EGR (Exhaust Gas Recirculation) system that returns a part of the exhaust gas to the intake air is being promoted. In particular, in recent years, attention has been focused on a low pressure EGR system capable of circulating a large amount of EGR gas even in a supercharging region. This low-pressure EGR system is a system that recirculates the exhaust gas downstream of the turbocharger turbine to the upstream side of the turbocharger compressor. Since the EGR gas is exhaust gas itself, it contains a lot of water vapor generated by combustion. In this low-pressure EGR system, the air-fuel mixture produced by mixing EGR gas with a larger amount of water than air and air is generally compressed by a compressor and then cooled by an intercooler. The problem that it is easy to do may arise. Moreover, since a part of the corrosive exhaust component is mixed in the condensed water as described above, there is a possibility that the intercooler and the intake pipe may be corroded and damaged.

  With respect to such a problem, Patent Document 1 discloses a technique for preventing the generation of condensed water in the intake air on the outlet side of an intercooler provided in an intake pipe.

  The internal combustion engine disclosed in Patent Document 1 is mounted on a vehicle, and includes an intercooler that cools intake air by exchanging heat between the traveling wind and the intake air in an intake pipe. The upstream intake air temperature detecting means for detecting the intake air, the upstream intake air humidity detecting means for detecting the upstream intake air humidity of the intercooler, and the opening degree adjustable for adjusting the amount of traveling air that is disposed on the intercooler and adjusts the travel air volume hitting the intercooler The water vapor partial pressure of the intake air is calculated from the detected values of the shutter device, the upstream side intake air temperature detecting means and the upstream side intake humidity detecting means, and the intercooler outlet side intake air temperature is equal to or higher than the temperature at which the water vapor partial pressure is the saturated water vapor partial pressure. And a controller for controlling the operation of the shutter device.

JP 2013-36452 A

  However, in the internal combustion engine disclosed in Patent Document 1, in order to adjust the intake air temperature on the outlet side of the intercooler by controlling the operation of the shutter device that can adjust the opening degree that adjusts the amount of travel air hitting the intercooler, There is a problem that it takes time to raise the cooler outlet side intake air temperature, the response is low, and the condensed water can be transiently generated by the outlet air intake of the intercooler.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for an internal combustion engine that can reliably suppress the generation of condensed water in an internal combustion engine equipped with a supercharger. It is to provide.

  In order to solve the above-described problems, an internal combustion engine control apparatus according to the present invention includes an internal combustion engine including a humidity detection unit that detects the humidity of intake air introduced into a combustion chamber and a supercharger that supercharges the intake air. An engine control device, wherein the control device controls the driving state of the supercharger based on the humidity of the intake air to adjust the pressure of the intake air.

  As can be understood from the above description, according to the present invention, the driving state of the supercharger is controlled based on the humidity of the intake air detected by the humidity detector, and the intake air pressure (supercharging pressure) is adjusted to adjust the intake air pressure. By adjusting the water vapor partial pressure, the water vapor partial pressure in the intake air can be controlled with good responsiveness, and the generation of condensed water in the intake air can be reliably suppressed.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a system configuration diagram of an internal combustion engine equipped with a first embodiment of a control device for an internal combustion engine according to the present invention. The block diagram which shows schematically the structure of the humidity sensor shown in FIG. The figure which shows the relationship between the intake-air humidity of an engine, an intake pressure, an intercooler temperature, and the presence or absence of condensed water generation | occurrence | production. The system block diagram which shows the internal structure of the control apparatus (ECU) shown in FIG. The block diagram which shows notionally the internal structure of the control apparatus (ECU) shown in FIG. The flowchart which shows the control flow of condensed water generation | occurrence | production determination and condensed water generation | occurrence | production avoidance by the control apparatus (ECU) shown in FIG. The time chart which shows the control content of condensed water generation | occurrence | production determination and condensed water generation | occurrence | production avoidance by the control apparatus (ECU) shown in FIG. 1 in a time series. The system block diagram of the internal combustion engine by which 2nd Embodiment of the control apparatus of the internal combustion engine which concerns on this invention was mounted. The figure which shows the relationship between an engine EGR rate, an intake pressure, an intercooler temperature, and the presence or absence of condensed water generation | occurrence | production. The system block diagram which shows the internal structure of the control apparatus (ECU) shown in FIG. The block diagram which shows notionally the internal structure of the control apparatus (ECU) shown in FIG. The flowchart which shows the control flow of condensed water generation | occurrence | production determination and condensed water generation | occurrence | production avoidance by the control apparatus (ECU) shown in FIG. The time chart which shows the control content of condensed water generation | occurrence | production determination and condensed water generation | occurrence | production avoidance by the control apparatus (ECU) shown in FIG. 8 in a time series.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

[First Embodiment]
First, with reference to FIGS. 1-7, the structure and operation | movement of 1st Embodiment of the control apparatus of the internal combustion engine which concern on this invention are demonstrated.

  FIG. 1 shows a system configuration of an automotive in-cylinder gasoline engine equipped with a first embodiment of a control device for an internal combustion engine (engine) according to the present invention.

  The illustrated engine 100 is, for example, a four-cylinder gasoline engine for automobiles that performs spark ignition combustion. An airflow sensor 1 that measures the amount of intake air and a humidity sensor (humidity detection unit) that detects the humidity of the intake air (hereinafter referred to as intake humidity) are located at appropriate positions of the intake pipe 18 that introduces intake air into the combustion chamber of the engine 100. 3, the compressor 4a of the supercharger 4 for supercharging the intake air, the intercooler 7 for cooling the intake air after supercharging downstream of the compressor 4a, and the temperature of the intake air immediately after the intercooler (hereinafter referred to as the intake air temperature) In particular, an intercooler temperature sensor 8 that measures an intake air temperature immediately after the intercooler is defined as an intercooler temperature, an electronic control throttle 2 that adjusts an intake pipe pressure, and an intake air pressure (hereinafter referred to as an intake manifold pressure) An intake pressure sensor 14 for measuring the intake pressure). The humidity sensor 3 is disposed upstream of the intake pipe 18, and the intake humidity (absolute humidity) detected by the humidity sensor 3 substantially corresponds to the atmospheric humidity (outside air humidity).

  Further, the engine 100 is provided with an injector 13 that is a fuel injection device that injects fuel into the cylinder 15 and an ignition plug 17 that supplies ignition energy for each cylinder. Further, the cylinder head of the engine 100 is provided with a variable valve 5 that adjusts the gas flowing into or out of the cylinder. By adjusting the variable valve 5, for example, all of the first through fourth cylinders are provided. The intake air amount of the cylinder is adjusted. A high pressure fuel pump for supplying high pressure fuel to the injector 13 is connected to the injector 13 via a fuel pipe, and a fuel pressure sensor for measuring the fuel injection pressure is connected to the fuel pipe. Provided (not shown). Further, the crankshaft of engine 100 is provided with a crank angle sensor for calculating a rotation angle (not shown).

  At an appropriate position of the exhaust pipe 16 of the engine 100, a turbine 4b for applying a rotational force to the compressor 4a of the supercharger 4 by exhaust energy, and an electronically controlled waste gate for adjusting the flow rate of the exhaust gas flowing through the turbine 4b. A valve 11, a three-way catalyst 10 that purifies the exhaust, and an air-fuel ratio sensor 9 that is an aspect of the air-fuel ratio detector and detects the air-fuel ratio of the exhaust upstream of the three-way catalyst 10 are provided. The waste gate valve 11 is disposed in a bypass passage 19 that bypasses the upstream side and the downstream side of the turbine 4b of the turbocharger 4, and the exhaust pipe 16 is adjusted by adjusting the opening degree of the waste gate valve 11. A part of the exhaust gas flowing through the engine is shunted, and the amount of exhaust gas flowing into the turbine 4a of the supercharger 4 (exhaust energy) is adjusted. Thereby, the drive state (for example, rotation speed etc.) of supercharger 4 itself is controlled, and the supercharging pressure (namely, intake pressure) by compressor 4a of supercharger 4 is adjusted.

  Signals (detection results) obtained from the air flow sensor 1, the humidity sensor 3, the air-fuel ratio sensor 9, the intercooler temperature sensor 8, and the intake pressure sensor 14 are sent to an engine control unit (ECU) (control device) 20. In addition to being transmitted, a signal (detection result) obtained from the accelerator opening sensor 12 is also transmitted to the ECU 20. The accelerator opening sensor 12 detects the amount of depression of the accelerator pedal, that is, the accelerator opening. The ECU 20 calculates a required torque based on the output signal of the accelerator opening sensor 12. That is, accelerator opening sensor 12 is used as a required torque detection sensor that detects a required torque for engine 100. ECU 20 calculates the rotational speed of engine 100 based on an output signal of a crank angle sensor (not shown). The ECU 20 appropriately calculates main operation amounts of the engine 100 such as an air flow rate, a fuel injection amount, an ignition timing, a fuel pressure, and the like based on the operation state of the engine 100 obtained from the output signals of the various sensors described above.

  Based on the calculation result, the ECU 20 transmits the electronic control throttle 2, the injector 13, the spark plug 17, the waste gate valve 11, the intercooler cooling water valve 7 a of the intercooler 7, and the transmission 30 connected to the power shaft of the engine 100. Control etc.

  For example, the fuel injection amount calculated by the ECU 20 is converted into a valve opening pulse signal and transmitted to the injector 13 as an injector drive signal. Further, an ignition signal generated based on the ignition timing is transmitted to the spark plug 17 so that the ignition is calculated at the ignition timing calculated by the ECU 20. Further, the throttle opening calculated by the ECU 20 is transmitted to the electronic control throttle 2 as a throttle drive signal. Further, the operation amount of the variable valve 5 calculated by the ECU 20 is transmitted to the variable valve 5 as a variable valve drive signal. The waste gate valve opening calculated by the ECU 20 is transmitted to the waste gate valve 11 as a waste gate valve drive signal. Further, the intercooler cooling water valve opening calculated by the ECU 20 is transmitted to the intercooler cooling water valve 7a of the intercooler 7 as an intercooler cooling water valve opening driving signal.

  A predetermined amount of fuel is injected from the injector 13 to the air introduced into the cylinder 15 from the intake pipe 18 via the intake valve, and an air-fuel mixture is formed. This air-fuel mixture is burned by sparks generated from the spark plug 17 at a predetermined ignition timing, and the piston is pushed down by the combustion pressure to generate the driving force of the engine 100. The exhaust gas after combustion is sent to the three-way catalyst 10 through the exhaust pipe 16, and the exhaust components are purified in the three-way catalyst 10 and discharged to the outside.

  FIG. 2 schematically shows the configuration of the humidity sensor shown in FIG.

  As shown in the figure, the humidity sensor 3 has a positive electrode 3b, a negative electrode 3c, and a moisture sensitive film 3d mounted on a substrate 3a, and the moisture sensitive film 3d is sandwiched between the positive electrode 3b and the negative electrode 3c. With such a configuration, the humidity sensor 3 becomes a capacitor using the moisture sensitive film 3d as a dielectric, and the relative humidity of the intake air flowing through the intake pipe 18 is detected by a change in the capacitance of the moisture sensitive film 3d as a sensor element. Is done. The humidity sensor 3 further includes a temperature detection unit (not shown) so that the absolute humidity can be calculated from the detected relative humidity and temperature.

  FIG. 3 shows the relationship between the intake air humidity, intake air pressure, and intercooler temperature of the engine and the presence or absence of condensed water generation.

  As the intake humidity (absolute humidity) and intake pressure (supercharging pressure) detected by the humidity sensor 3 and the intake pressure sensor 14 increase, the partial pressure of water vapor in the intake air increases. Then, when the water vapor partial pressure in the intake air exceeds the saturated water vapor partial pressure, the generation of condensed water starts. Here, the saturated water vapor pressure is expressed as a function of the atmospheric temperature, that is, the intercooler temperature. When the intercooler temperature is high, the limit line for the generation of condensed water transitions to the high intake pressure and high intake humidity side, and the intercooler When the temperature is low, the condensate generation limit line shifts to a low intake pressure and low intake humidity side.

  As described above, when the intake humidity is high, the intake pressure (supercharging pressure) is high, or the intercooler temperature is low, condensed water is likely to be generated. Therefore, it is considered effective to control the ECU 20 to reduce the intake humidity, reduce the intake pressure (supercharging pressure), or increase the intercooler temperature. Therefore, in the first embodiment, the ECU 20 increases the intake pressure (supercharge) when, for example, the intake humidity (atmosphere humidity) increases, the intake pressure (supercharge pressure) increases, and the water vapor partial pressure in the intake air increases. Pressure) is reduced to reduce the partial pressure of water vapor in the intake air, or the intercooler temperature is raised to change the limit line of condensed water generation to avoid or suppress the generation of condensed water. Further, the ECU 20 suppresses a decrease in torque (output) accompanying a decrease in intake pressure (supercharging pressure) by increasing the engine speed.

  FIG. 4 shows the internal configuration of the control device (ECU) shown in FIG. The ECU 20 mainly includes an input circuit 20a, an input / output port 20b, a RAM 20c, a ROM 20d, and a CPU 20e, and a drive circuit that generates a drive signal for driving each actuator such as the electronic control throttle 2. .

  Specifically, output signals from the air flow sensor 1, the humidity sensor 3, the intercooler temperature sensor 8, the air-fuel ratio sensor 9, the accelerator opening sensor 12, the intake pressure sensor 14, and the like are input to the input circuit 20 a of the ECU 20. Of course, the input signal is not limited to these. The input signal of each sensor input to the input circuit 20a is sent to the input port in the input / output port 20b. The signal sent to the input port is stored in the RAM 20c and processed by the CPU 20e. Here, the control program describing the contents of the arithmetic processing in the CPU 20e is written in advance in the ROM 20d.

  A value indicating the operation amount of each actuator calculated in accordance with the control program is stored in the RAM 20c and then sent to an output port in the input / output port 20b, and each drive circuit (for example, an electronic control throttle drive circuit 20f, injector drive) A circuit 20g, a waste gate valve driving circuit 20h, an intercooler cooling water valve driving circuit 20j, and a transmission driving circuit 20k) are used for each actuator (for example, electronic control throttle 2, injector 13, waste gate valve 11, intercooler 7). It is transmitted as a drive signal to the intercooler cooling water valve 7a and the transmission 30). Note that the ECU 20 need not include all of the drive circuits, and may include any one or more of the drive circuits.

  Here, the ECU 20 determines whether condensed water is generated, particularly the intercooler, based on input signals input to the input circuit 20a, particularly input signals input from the humidity sensor 3, the intercooler temperature sensor 8, and the intake pressure sensor 14. 7, whether or not condensed water is generated is determined inside and at the outlet side, and when it is determined that condensed water is generated, the waste gate valve driving circuit 20 h and the intercooler cooling water valve driving circuit 20 j among the above-described driving circuits. The waste gate valve 11, the intercooler cooling water valve 7a, and the transmission 30 are controlled via the transmission drive circuit 20k.

  FIG. 5 conceptually shows the internal structure of the control unit (ECU) shown in FIG. As shown in the figure, the ECU 20 mainly includes a condensed water generation determination unit 54 having an intake water vapor partial pressure calculation unit 51, a saturated water vapor partial pressure calculation unit 52, and a comparison unit 53, a condensed water generation avoidance control unit 55, It has. In addition to the above configuration, the ECU 20 diagnoses an abnormality or failure of the humidity sensor 3 and a correction unit 57 that corrects a detection result (ie, intake humidity) by the humidity sensor 3 based on predetermined information. And.

  An input signal input from the humidity sensor 3 is transmitted to the diagnosis unit 56 and the correction unit 57. The diagnosis unit 56 diagnoses an abnormality or failure of the humidity sensor 3 based on the input signal, and transmits the diagnosis result to the intake water vapor partial pressure calculation unit 51 of the condensed water generation determination unit 54. The correction unit 57 corrects the input signal (intake humidity detected by the humidity sensor 3) based on information that may affect the intake humidity such as rain or fog, and the correction result is used as a condensed water generation determination unit. 54 to the intake water vapor partial pressure calculation unit 51. For example, the correction unit 57 includes information on the external environment of a vehicle such as an automobile on which the engine 100 is mounted, a wiper by a driver (for example, a wiper provided on a windshield of the automobile), and a fog lamp (for example, provided on the front of the automobile). Information on the operation of the vehicle such as a fog light) is acquired, and the intake humidity detected by the humidity sensor 3 is corrected based on the information. Thereby, the influence on intake humidity by rain, fog, etc. can be suppressed. Here, the information about the external environment of the vehicle includes a camera mounted in the vehicle interior and outside the vehicle compartment in order to recognize the external environment of the vehicle, and a rain mounted to recognize the rain condition in the vehicle external environment. Sent from a sensor or the like. Further, information related to operations by the driver is transmitted from a control panel of the vehicle. Note that an estimated value of the intake air humidity is calculated from the intake air flow rate introduced into the combustion chamber of the engine 100, the fuel flow rate introduced into the combustion chamber, and the air fuel ratio of the exhaust gas obtained from the air fuel ratio sensor 9. The correction unit 57 is input from the humidity sensor 3 based on the estimated value of the intake humidity in order to more precisely correct the input signal (intake humidity detected by the humidity sensor 3) input from the humidity sensor 3. The input signal may be corrected.

  The intake water vapor partial pressure calculation unit 51 calculates the intake water vapor partial pressure during intake based on the correction result of the intake humidity transmitted from the correction unit 57 and the input signal (intake pressure) input from the intake pressure sensor 14. The calculation result is transmitted to the comparison unit 53.

  Here, when the intake water vapor partial pressure calculation unit 51 determines that the humidity sensor 3 is abnormal or malfunctioning based on the diagnosis result transmitted from the diagnosis unit 56, the correction of the intake humidity transmitted from the correction unit 57 is performed. Assuming that the result or the intake humidity detected by the humidity sensor 3 is the humidity upper limit value, the intake water vapor partial pressure during intake is calculated. Note that the humidity upper limit value is humidity in a state where water vapor is saturated in the intake air, that is, in a state where the relative humidity is 100%.

  The input signal input from the intercooler temperature sensor 8 is transmitted to the saturated water vapor partial pressure calculating unit 52, and the saturated water vapor partial pressure calculating unit 52 calculates the saturated water vapor partial pressure based on the input signal (intercooler temperature). The calculation result is transmitted to the comparison unit 53.

  The comparison unit 53 compares the intake water vapor partial pressure calculated by the intake water vapor partial pressure calculation unit 51 with the saturated water vapor partial pressure calculated by the saturated water vapor partial pressure calculation unit 52 to determine whether condensed water is generated, The determination result is transmitted to the condensed water generation avoidance control unit 55.

  When the condensate generation avoidance control unit 55 determines that the condensate is generated based on the determination result input from the condensate generation determination unit 54, the waste gate valve 11, A control signal is transmitted to the intercooler cooling water valve 7a, the transmission 30 and the like, and the waste gate valve 11 is opened to adjust (lower) the intake pressure (supercharging pressure), and the transmission ratio of the transmission 30 is increased. The engine output is maintained, or the intercooler cooling water valve 7a of the intercooler 7 is closed to increase the intake air temperature immediately after the intercooler 7. On the other hand, if the condensed water generation avoidance control unit 55 determines that the condition is such that no condensed water is generated, the current setting is continued.

  FIG. 6 specifically shows a control flow for determination of condensed water generation and avoidance of condensed water generation by the control device (ECU) shown in FIG. The control flow shown in FIG. 6 is repeatedly executed by the ECU 20 at a predetermined cycle. In the example illustrated in FIG. 6, the diagnosis flow of the abnormality or failure of the humidity sensor 3 by the diagnosis unit 56 and the correction flow of the detection result of the humidity sensor 3 by the correction unit 57 are omitted, and the intake humidity detected by the humidity sensor 3 is omitted. Is transmitted to the intake water vapor partial pressure calculation unit 51 and used for calculating the intake water vapor partial pressure.

First, the ECU 20 reads the output signal (intake humidity) of the humidity sensor 3 in step S601, and reads the output signal (intake pressure) of the intake pressure sensor 14 in step S602. Next, in step S603, the ECU 20 uses the following equation (1) from the read output signals of the humidity sensor 3 and the intake pressure sensor 14 in the intake water vapor partial pressure calculation unit 51, and the water vapor partial pressure in the intake air: Calculate P _H2O .

ここで、P_H2O：吸気水蒸気分圧 [Pa]、
P_in：吸気（過給）圧力 [Pa]、
H_V ：吸気湿度（容積絶対湿度） [g/m³]、
M_H2O：水の分子量（≒18.0） [g/mol]、
P_a ：吸気管入口圧力（≒大気圧） [Pa]、
T_a ：吸気管入口温度（≒大気温度） [K]、
R ：気体定数 [Pa・m³/mol・K]

Where P _H2O : Intake water vapor partial pressure [Pa],
P _in : Intake (supercharging) pressure [Pa],
H _V : Intake humidity (absolute volumetric humidity) [g / m ³ ],
M _H2O : Molecular weight of water (≒ 18.0) [g / mol],
P _a : Intake pipe inlet pressure (≈ atmospheric pressure) [Pa],
T _a : Intake pipe inlet temperature (≈ atmospheric temperature) [K],
R: Gas constant [Pa · m ³ / mol · K]

As described above, when the ECU 20 determines that the humidity sensor 3 is abnormal or malfunctioning, it is assumed in step S603 that the intake humidity detected by the humidity sensor 3 is the humidity upper limit value. Then, the intake water vapor pressure P _H2O during intake is calculated.

Next, the ECU 20 reads the output signal (intercooler temperature) of the intercooler temperature sensor 8 in step S604, and in step S605, the saturated water vapor partial pressure calculation unit 52 reads the read output signal of the intercooler temperature sensor 8. From the above, the saturated water vapor partial pressure P ′ _H2O is calculated using the following equation (2).

ここで、P’_H2O：飽和水蒸気分圧 [Pa]、
T_IC ：インタークーラ温度 [K]

Where _P'H2O : saturated water vapor partial pressure [Pa],
T _IC : Intercooler temperature [K]

Next, in step S606, the ECU 20 uses the following equation (3) for the intake water vapor partial pressure P _H2O calculated in step S603 and the saturated water vapor partial pressure P ′ _H2O calculated in step S605 in the comparison unit 53. To determine whether or not the conditions are such that condensed water is generated.

ここで、α：制御裕度に関するパラメータ（通常は約１）

Where α: parameter related to control tolerance (usually about 1)

The ECU 20 determines that the condensate is generated when the above equation (3) is satisfied, and proceeds to step S607. On the other hand, the ECU 20 determines that the condition is such that condensed water is not generated when the above-described equation (3) is not satisfied, that is, when the intake water vapor partial pressure P _H2O is equal to or lower than the saturated water vapor partial pressure P ′ _H2O . End control.

  When the ECU 20 determines that the condition is that condensate is generated, in step S607, the ECU 20 bypasses the upstream side and the downstream side of the turbine 4b of the turbocharger 4 in order to reduce the intake pressure (supercharging pressure). The opening degree of the waste gate valve 11 disposed in the flow path 19 is increased to control the driving state (for example, the rotational speed) of the supercharger 4. Next, in step S608, the ECU 20 increases the speed of the engine by increasing the gear ratio of the transmission 30 connected to the power shaft of the engine 100 in order to compensate for the output decrease accompanying the decrease in the supercharging pressure.

  Next, in step S609, the ECU 20 determines whether or not the ignition timing under the current operating condition is set to the knocking limit point (that is, the trace knocking point), and the ignition timing under the current operating condition is determined to be the knocking limit point. If it is determined that, the series of control is terminated. On the other hand, if the ECU 20 determines that the ignition timing under the current operating conditions is not the knocking limit point, that is, that there is a margin before the occurrence of knocking of the engine 100, in step S610, the ECU 20 increases the intercooler temperature. The opening degree of the intercooler cooling water valve 7a of the cooler 7 is reduced, and the flow rate of the cooling water flowing through the cooling water passage of the intercooler 7 is reduced. Instead of reducing the opening of the intercooler cooling water valve 7a, a heater or the like is provided in the cooling water passage of the intercooler 7, and the temperature of the cooling water flowing through the cooling water passage of the intercooler 7 is controlled by controlling the heater. The intercooler temperature may be raised directly.

  FIG. 7 shows, in a time series, the control contents of the condensed water generation determination and the condensed water generation avoidance by the control device (ECU) shown in FIG. In FIG. 7, from the top, the condensed water generation determination flag, atmospheric humidity, water vapor partial pressure downstream of the intercooler (intake water vapor partial pressure and saturated water vapor partial pressure), accelerator opening, waste gate valve opening, intake pressure, transmission ratio (Engine speed), intercooler cooling water valve opening, and intercooler temperature are shown in a time sequence. In the example illustrated in FIG. 7, it is assumed that the driver depresses the accelerator pedal and the vehicle accelerates.

As shown in the figure, as the driver depresses the accelerator, the opening degree of the waste gate valve 11 (waste gate valve opening degree) is decreased and the intake pressure (supercharging pressure) is increased. The intake water vapor partial pressure P _H2O increases.

At time t _A , the increased intake water vapor partial pressure P _H2O exceeds the integrated value of the saturated water vapor partial pressure P ′ _H2O , more specifically, the saturated water vapor partial pressure P ′ _H2O and the control α parameter α. The condensed water determination flag becomes 1. When the condensate determination flag is set to 1, that is, it is determined that the condensate is generated, as the condensate generation avoidance control, the waste gate valve 11 is opened to reduce the intake pressure (supercharging pressure), and In order to maintain the output, the speed ratio of the transmission 30 is increased to increase the engine speed. Also, in this scene, assuming that the ignition timing is not set at the knocking limit point, the opening degree of the intercooler cooling water valve 7a (intercooler cooling) is used to increase the intercooler temperature and shift the condensate generation limit line. The water valve opening) is reduced to a predetermined value. Incidentally, the intercooler temperature, after a certain time and thus reduce the intercooler cooling water valve opening has elapsed, it rises with a certain time delay which is namely (in the illustrated example, the time t _D after).

At time t _B, the accelerator depression amount by the driver but becomes substantially constant, since the condensed water determination flag is 1, continue to increase and increased speed ratio of the waste gate valve opening.

At time t _C , the intake water vapor partial pressure P _H2O falls below the saturated water vapor partial pressure P ′ _H2O , more specifically, the integrated value of the saturated water vapor partial pressure P ′ _H2O and the parameter α, and the condensed water determination flag is 0 again. Therefore, after that, the waste gate valve opening and the gear ratio are kept substantially constant while the accelerator opening is constant.

At time t _D, intercooler temperature begins to rise with a delay, with an increase in the intercooler temperature, as described with reference to FIG. 3, the limit line condensed water is generated is changed into the high intake pressure side Therefore, in order to increase the intake pressure, the waste gate valve opening is decreased, and the gear ratio of the transmission 30 is decreased accordingly.

Since the rise of the intercooler temperature ends at time t _E , the wastegate valve opening and the gear ratio are kept substantially constant thereafter, with the accelerator opening kept constant.

  As described above, according to the control device of the first embodiment, in the engine 100 including the supercharger 30, whether or not condensed water is generated based on the intake humidity detected by the humidity sensor 3 disposed in the intake pipe 18. And controlling the driving state of the supercharger 30 based on the determination result, adjusting the intake pressure (supercharging pressure), and performing the condensed water generation avoidance control, for example, under conditions where the atmospheric humidity is high Even underneath, generation of condensed water in the intercooler or downstream thereof can be effectively avoided, and damage to the engine, corrosion of the intake pipe, and deterioration of operability can be suppressed.

  Further, the intake water vapor partial pressure immediately after the intercooler 7 calculated based on the intake air humidity detected by the humidity sensor 3, the intake air pressure downstream of the compressor 4 a of the supercharger 4 detected by the intake air pressure sensor 14, etc. Compared with the saturated water vapor partial pressure of the intake air immediately after the intercooler 7 calculated based on the intake air temperature immediately after the intercooler 7 detected by the cooler temperature sensor 8, the presence or absence of condensed water is determined. Presence or absence of occurrence can be determined precisely to effectively suppress the generation of condensed water.

  Further, when it is determined that condensed water is generated, the driving state of the supercharger 30 is increased by increasing the speed of the engine 30 by increasing the gear ratio of the transmission 30 connected to the power shaft of the engine 100. Even when the intake pressure (supercharging pressure) is reduced by control, it is possible to secure engine torque (output) and suppress a decrease in drivability.

[Second Embodiment]
Next, the configuration and operation of the second embodiment of the control apparatus for an internal combustion engine according to the present invention will be described with reference to FIGS. The control device of the second embodiment shown in FIGS. 8 to 13 is configured to control the low pressure EGR system provided in the internal combustion engine with respect to the control device of the first embodiment shown in FIGS. The other configurations are the same as those of the control device of the first embodiment. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 8 shows a system configuration of an in-cylinder injection gasoline engine for automobiles having a low pressure EGR system in which a second embodiment of the control device for an internal combustion engine (engine) according to the present invention is mounted.

  In addition to the components of engine 100 shown in FIG. 1, engine 100A shown in FIG. 8 is downstream of humidity sensor 3A provided in intake pipe 18A from the downstream side of three-way catalyst 10A provided in exhaust pipe 16A. And a low pressure EGR system having an EGR pipe 40A for recirculating part of the exhaust gas on the upstream side of the compressor 4aA of the supercharger 4A. EGR gas flowing through the EGR pipe 40A is disposed at an appropriate position of the EGR pipe 40A connecting the exhaust pipe 16A downstream of the turbine 4bA of the turbocharger 4A and the intake pipe 18A upstream of the compressor 4aA of the supercharger 4A. EGR cooler 42A for cooling (exhaust), EGR valve 41A for controlling EGR gas flow rate (EGR flow rate), and differential pressure before and after EGR valve 41A (EGR valve differential pressure before and after) are detected to detect EGR flow rate. A differential pressure sensor (EGR flow rate detection unit) 43A that measures the EGR temperature, and an EGR temperature sensor (EGR temperature detection unit) 44A that detects the temperature of the EGR gas (EGR temperature) are attached.

  Signals (detection results) obtained from the air flow sensor 1A, the humidity sensor 3A, the air-fuel ratio sensor 9A, the intercooler temperature sensor 8A, the intake pressure sensor 14A, the differential pressure sensor 43A, and the EGR temperature sensor 44A are sent to the ECU (control device) 20A. In addition to being transmitted, a signal (detection result) obtained from the accelerator opening sensor 12A is also transmitted to the ECU 20A. ECU 20A calculates the required torque based on the output signal of accelerator opening sensor 12A, and calculates the rotational speed of engine 100A based on the output signal of a crank angle sensor (not shown). The ECU 20A appropriately calculates main operating amounts of the engine 100A such as the air flow rate, the fuel injection amount, the ignition timing, the fuel pressure, etc. based on the operating state of the engine 100A obtained from the output signals of the various sensors described above.

  Based on the calculation result, the ECU 20A, as in the first embodiment, the electronic control throttle 2A, the injector 13A, the ignition plug 17A, the wastegate valve 11A, the intercooler cooling water valve 7aA of the intercooler 7A, and the engine 100A The transmission 30A and the like connected to the power shaft are controlled, and the EGR valve 41A attached to the EGR pipe 40A is controlled. That is, the throttle opening degree calculated by the ECU 20A is transmitted as a drive signal to the electronic control throttle 2, etc., and the EGR valve opening degree calculated by the ECU 20A is transmitted to the EGR valve 41A as an EGR valve opening degree drive signal. .

  FIG. 9 shows the relationship between the EGR rate of the engine, the intake pressure, the intercooler temperature, and whether condensed water is generated.

  As the EGR rate representing the ratio of EGR gas in the intake air and the intake pressure (supercharging pressure) detected by the intake pressure sensor 14A increase, the water vapor partial pressure in the intake air increases. Then, when the water vapor partial pressure in the intake air exceeds the saturated water vapor partial pressure, the generation of condensed water starts. Here, the saturated water vapor pressure is expressed as a function of the atmospheric temperature, that is, the intercooler temperature. When the intercooler temperature is high, the limit line for the generation of condensed water transitions to the high intake pressure and high EGR rate side, and the intercooler When the temperature is low, the condensate generation limit line shifts to a low intake pressure and low EGR rate side.

  As described above, when the EGR rate is high, the intake pressure (supercharging pressure) is high, or the intercooler temperature is low, condensed water is likely to be generated. It is considered effective to control the ECU 20A so as to decrease the EGR rate, decrease the intake pressure (supercharging pressure), or increase the intercooler temperature. Therefore, in the second embodiment, the ECU 20A decreases the EGR rate when the intake humidity (atmospheric humidity) increases, the intake pressure (supercharging pressure) increases, and the water vapor partial pressure during intake increases. Reduce or reduce the intake water pressure (supercharging pressure) to reduce the partial pressure of water vapor in the intake air, or increase the intercooler temperature to change the condensate generation limit line. To do. Further, the ECU 20A suppresses a decrease in torque (output) accompanying a decrease in intake pressure (supercharging pressure) by increasing the engine speed.

  In the second embodiment, the relationship between the intake air humidity, intake air pressure, and intercooler temperature of the engine and the presence or absence of condensed water generation is the same as the relationship shown in FIG.

  FIG. 10 shows the internal configuration of the control unit (ECU) shown in FIG. The ECU 20A shown in FIG. 10 includes an EGR valve drive circuit 20mA that generates a drive signal for driving the EGR valve 41A in addition to the components of the ECU 20 shown in FIG.

  Specifically, as in the first embodiment described above, output signals from the air flow sensor 1A, the humidity sensor 3A, the intercooler temperature sensor 8A, the air-fuel ratio sensor 9A, the accelerator opening sensor 12A, the intake pressure sensor 14A, and the like are output from the ECU 20A. In addition to being input to the input circuit 20aA, output signals of the differential pressure sensor 43A and the EGR temperature sensor 44A are input to the input circuit 20aA of the ECU 20A. The input signal of each sensor input to the input circuit 20aA is sent to the input port in the input / output port 20bA. The signal sent to the input port is stored in the RAM 20cA and processed by the CPU 20eA. Here, the control program describing the contents of the arithmetic processing in the CPU 20eA is written in advance in the ROM 20dA.

  A value indicating the operation amount of each actuator calculated in accordance with the control program is stored in the RAM 20cA and then sent to the output port in the input / output port 20bA, where each drive circuit (for example, electronic control throttle drive circuit 20fA, injector drive) A circuit 20gA, a waste gate valve drive circuit 20hA, an intercooler cooling water valve drive circuit 20jA, a transmission drive circuit 20kA, an EGR valve drive circuit 20mA, and the like (for example, electronic control throttle 2A, injector 13A, waste gate valve) 11A, the intercooler cooling water valve 7aA of the intercooler 7A, the transmission 30A, and the EGR valve 41A) are transmitted as drive signals.

  Here, the ECU 20A determines whether condensed water is generated, particularly the intercooler, based on input signals input to the input circuit 20aA, particularly input signals input from the humidity sensor 3A, the intercooler temperature sensor 8A, and the intake pressure sensor 14A. When it is determined whether or not condensed water is generated inside or at the outlet side of 7A, and it is determined that condensed water is generated, the waste gate valve driving circuit 20hA and the intercooler cooling water valve driving circuit 20jA among the above-described driving circuits. The waste gate valve 11A, the intercooler cooling water valve 7aA, the transmission 30A, and the EGR valve 41A are controlled via the transmission drive circuit 20kA and the EGR valve drive circuit 20mA.

  FIG. 11 conceptually shows the internal structure of the control unit (ECU) shown in FIG. 11, ECU 20A, like ECU 20 shown in FIG. 5, has a diagnostic unit 56A, a correction unit 57A, an intake water vapor partial pressure calculation unit 51A, a saturated water vapor partial pressure calculation unit 52A, and a comparison unit 53A. A determination unit 54A and a condensed water generation avoidance control unit 55A are provided.

  An input signal input from the humidity sensor 3A is transmitted to the diagnosis unit 56A and the correction unit 57A. The diagnosis unit 56A diagnoses an abnormality or failure of the humidity sensor 3A based on the input signal, and transmits the diagnosis result to the intake water vapor partial pressure calculation unit 51A of the condensed water generation determination unit 54A. Further, the correction unit 57A receives the input signal (based on information such as rain or fog that may affect the intake humidity, an estimated value of the intake humidity calculated from the intake flow rate introduced into the combustion chamber of the engine 100A, etc.) (Intake humidity detected by the humidity sensor 3A) is corrected, and the correction result is transmitted to the intake water vapor partial pressure calculation unit 51A of the condensed water generation determination unit 54A.

  Here, since the amount of water vapor contained in the EGR gas is generally larger than the amount of water vapor contained in the atmosphere (intake through the humidity sensor 3A), when the flow rate of EGR gas returned to the intake air is large, the correction unit 57A is The input signal input from the humidity sensor 3A may be transmitted to the intake water vapor partial pressure calculation unit 51A without correction. That is, in the correction unit 57A, the flow rate of the EGR gas flowing through the EGR pipe 40A is not more than a predetermined value (the EGR gas is not flowing through the EGR pipe 40A, or the flow rate of the EGR gas is extremely small (for example, the EGR rate is 3%). Only)), the input signal input from the humidity sensor 3A may be corrected and transmitted to the intake water vapor partial pressure calculation unit 51A.

  The intake water vapor partial pressure calculation unit 51A includes the correction result of the intake humidity transmitted from the correction unit 57A and the input signals (intake pressure, difference before and after the EGR valve) input from the intake pressure sensor 14A, the differential pressure sensor 43A, and the EGR temperature sensor 44A. Pressure, EGR temperature), the intake water vapor partial pressure in the intake air is calculated, and the calculation result is transmitted to the comparison unit 53A. Here, when the intake water vapor partial pressure calculation unit 51A determines that the humidity sensor 3A is abnormal or malfunctioning based on the diagnosis result transmitted from the diagnosis unit 56A, the correction of the intake humidity transmitted from the correction unit 57A. Assuming that the intake humidity detected by the result or the humidity sensor 3A is the humidity upper limit value, the intake water vapor partial pressure during the intake is calculated.

  The input signal input from the intercooler temperature sensor 8A is transmitted to the saturated water vapor partial pressure calculating unit 52A, and the saturated water vapor partial pressure calculating unit 52A calculates the saturated water vapor partial pressure based on the input signal (intercooler temperature). The calculation result is transmitted to the comparison unit 53A.

  As in the first embodiment, the comparison unit 53A compares the intake water vapor partial pressure calculated by the intake water vapor partial pressure calculation unit 51A with the saturated water vapor partial pressure calculated by the saturated water vapor partial pressure calculation unit 52A. The presence or absence of condensed water generation is determined, and the determination result is transmitted to the condensed water generation avoidance control unit 55A.

  When the condensate water generation avoidance control unit 55A determines that the condensate is generated based on the determination result input from the condensate generation determination unit 54A, the waste gate valve 11A, A control signal is transmitted to the intercooler cooling water valve 7aA, the transmission 30A, the EGR valve 41A, etc., and the waste gate valve 11A is opened to adjust (lower) the intake pressure (supercharging pressure), and the transmission of the transmission 30A The engine output is maintained by increasing the ratio, the intercooler cooling water valve 7aA of the intercooler 7A is closed to increase the intake air temperature immediately after the intercooler 7A, or the EGR valve 41A is closed to decrease the EGR rate. On the other hand, when the condensate generation avoidance control unit 55A determines that the condition is such that no condensate is generated, the current setting is continued.

  FIG. 12 specifically shows a control flow of the condensed water generation determination and the condensed water generation avoidance by the control device (ECU) shown in FIG. The control flow shown in FIG. 12 is repeatedly executed at a predetermined cycle by the ECU 20A. In the example shown in FIG. 12, the diagnosis flow of the abnormality or failure of the humidity sensor 3A by the diagnosis unit 56A and the correction flow of the detection result of the humidity sensor 3A by the correction unit 57A are omitted, and the intake air humidity detected by the humidity sensor 3A is omitted. Is transmitted to the intake water vapor partial pressure calculating unit 51A and used for calculating the intake water vapor partial pressure.

First, the ECU 20A reads the output signal (intake humidity) of the humidity sensor 3A in step S1201, reads the output signal (intake pressure) of the intake pressure sensor 14A in step S1202, and outputs the output of the differential pressure sensor 43A in step S1203. A signal (differential pressure before and after the EGR valve) is read, and in step S1204, an output signal (EGR temperature) of the EGR temperature sensor 44A is read. Next, in step S1205, the ECU 20A uses the following expression (4) from the output signals of the humidity sensor 3A, the intake pressure sensor 14A, the differential pressure sensor 43A, and the EGR temperature sensor 44A read by the intake water vapor partial pressure calculation unit 51A. ) To calculate the water vapor partial pressure P _H2O in the intake air.

ここで、P_H2O：吸気水蒸気分圧 [Pa]、
P_a ：吸気管入口圧力（≒大気圧） [Pa]、
P_in ：吸気(過給)圧力 [Pa]、
H_{V_a}：吸気湿度（容積絶対湿度） [g/m³]、
H_{V_EGR}：ＥＧＲ中の水蒸気の容積絶対湿度 [g/m³]、
M_H2O：水の分子量（≒18.0） [g/mol]、
M_a ：空気の平均分子量（≒29.0） [g/mol]、
M_EGR：ＥＧＲの平均分子量（≒28.9） [g/mol]、
M_in：空気/ＥＧＲ混合気の平均分子量 [g/mol]、
T_a ：吸気管入口温度（≒大気温度） [K]、
T_EGR：ＥＧＲ温度 [K]、
γ_EGR：ＥＧＲ率（質量ベース）、
R ：気体定数 [Pa・m³/mol・K]

Where P _H2O : Intake water vapor partial pressure [Pa],
P _a : Intake pipe inlet pressure (≈ atmospheric pressure) [Pa],
P _in : Intake (supercharging) pressure [Pa],
H _{V_a} : Intake humidity (absolute volumetric humidity) [g / m ³ ],
H _{V_EGR} : Volumetric absolute humidity of water vapor in EGR [g / m ³ ],
M _H2O : Molecular weight of water (≒ 18.0) [g / mol],
M _a : average molecular weight of air (≈29.0) [g / mol],
M _EGR : Average molecular weight of EGR (≈28.9) [g / mol],
M _in : average molecular weight of air / EGR mixture [g / mol],
T _a : Intake pipe inlet temperature (≈ atmospheric temperature) [K],
T _EGR : EGR temperature [K],
γ _EGR : EGR rate (mass base),
R: Gas constant [Pa · m ³ / mol · K]

Note that the EGR rate γ _EGR and the volumetric absolute humidity _{HV_EGR} of water vapor in EGR are obtained using the following equations (5) and (6), respectively.

ここで、m_air ：空気質量流量 [g/s]
m_EGR ：ＥＧＲ質量流量 [g/s]
R_EGR ：ＥＧＲのガス定数 [Pa・m³/g・K]
T_EGR ：ＥＧＲ温度 [K]
ΔP_EGR：ＥＧＲ弁前後差圧 [Pa]
A ：ＥＧＲ弁開口面積 [m²]
C ：ＥＧＲ弁の圧力損失係数
ρ ：ＥＧＲ密度 [g/m³]

Where m _air : air mass flow rate [g / s]
m _EGR : EGR mass flow rate [g / s]
R _EGR : Gas constant of EGR [Pa · m ³ / g · K]
T _EGR : EGR temperature [K]
ΔP _EGR : Differential pressure across EGR valve [Pa]
A: EGR valve opening area [m ² ]
C: EGR valve pressure loss coefficient
ρ: EGR density [g / m ³ ]

ここで、P_EGR ：ＥＧＲ管内圧力 [Pa]、
Y_{H2O_EGR}：ＥＧＲ中の水のモル分率 [mol/mol]、
Y_{H2O_a} ：大気中の水のモル分率 [mol/mol]

Where P _EGR : EGR pipe pressure [Pa]
Y _{H2O_EGR} : mole fraction of water in EGR [mol / mol],
Y _{H2O_a} : mole fraction of water in the atmosphere [mol / mol]

Next, the ECU 20A reads an output signal (intercooler temperature) of the intercooler temperature sensor 8A in step S1206, and in step S1207, the saturated water vapor partial pressure calculation unit 52A reads the output signal of the intercooler temperature sensor 8A. From the above, the saturated water vapor partial pressure P ′ _{H 2 O} is calculated using the above-described equation (2).

Next, in step S1208, the ECU 20A uses the above equation (3) for the intake water vapor partial pressure P _H2O calculated in step S1205 and the saturated water vapor partial pressure P ′ _H2O calculated in step S1207 in the comparison unit 53A. To determine whether or not the conditions are such that condensed water is generated.

The ECU 20A determines that the condition is such that condensed water is generated when the above-described equation (3) is satisfied, and proceeds to step S1209. On the other hand, the ECU 20A determines that the condition is such that condensed water is not generated when the above-described equation (3) is not satisfied, that is, when the intake water vapor partial pressure P _H2O is equal to or lower than the saturated water vapor partial pressure P ′ _H2O . End control.

If the ECU 20A determines that the condition is that condensate is generated, in step S1209, the ECU 20A calculates the following equation (7) in order to determine the possibility of reducing the EGR rate γ _EGR from the viewpoint of the exhaust temperature limit, the knocking limit, and the like. It is used to determine whether or not the current EGR rate γ _EGR is equal to or less than the EGR rate γ _LIM that is the operation limit. Here, the EGR rate γ _LIM that is the operation limit is set in advance from the viewpoint of, for example, the exhaust temperature limit and the knocking limit, and is stored in the ECU 20A for each operation condition.

If the above equation (7) holds, ECU 20A determines that the EGR rate cannot be decreased any more and proceeds to step S1211. On the other hand, the ECU 20A proceeds to step S1210 when the above-described equation (7) is not satisfied, that is, when the current EGR rate γ _EGR is larger than the EGR rate γ _LIM that is the operation limit. The opening degree of the valve 41A is decreased, and a series of control is finished.

  If the ECU 20A determines that the condensed water is generated and that the EGR rate cannot be further reduced, the ECU 20A, in the same manner as steps S607 to S610 (see FIG. 6) of the first embodiment, In order to reduce the intake pressure (supercharging pressure), the opening state of the waste gate valve 11A is increased to control the driving state (for example, the rotational speed) of the supercharger 4A. Next, in step S1212, the ECU 20A increases the speed of the engine by increasing the gear ratio of the transmission 30A in order to compensate for the output decrease accompanying the decrease in the supercharging pressure.

  Next, in step S1213, the ECU 20A determines whether or not the ignition timing under the current operating condition is set to the knocking limit point (that is, the trace knocking point), and the ignition timing under the current operating condition is determined to be the knocking limit point. If it is determined that, the series of control is terminated. On the other hand, if ECU 20A determines that the ignition timing under the current operating conditions is not the knock limit point, that is, that there is room before knocking of engine 100A occurs, in step S1214, in order to increase the intercooler temperature, The opening degree of the intercooler cooling water valve 7aA of the cooler 7A is reduced, and the flow rate of the cooling water flowing through the cooling water passage of the intercooler 7A is reduced. Instead of reducing the opening of the intercooler cooling water valve 7aA, a heater or the like is provided in the cooling water passage of the intercooler 7A, and the temperature of the cooling water flowing through the cooling water passage of the intercooler 7A is controlled by controlling the heater. The intercooler temperature may be raised directly.

  FIG. 13 shows the control contents of the condensed water generation determination and the condensed water generation avoidance by the control device (ECU) shown in FIG. 8 in time series. In FIG. 13, from the top, the condensed water generation determination flag, atmospheric humidity, water vapor partial pressure downstream of the intercooler (intake water vapor partial pressure and saturated water vapor partial pressure), accelerator opening, EGR valve opening, EGR rate, waste gate valve The opening degree, the intake pressure, and the gear ratio (engine speed) are shown in a time sequence. In the example shown in FIG. 13, it is assumed that the driver depresses the accelerator pedal in two stages and the vehicle accelerates in two stages.

As shown in the figure, as the driver depresses the accelerator, the opening degree of the waste gate valve 11A (the waste gate valve opening degree) is decreased, the intake pressure (supercharging pressure) is increased, and accordingly, the downstream of the intercooler 7A. The intake water vapor partial pressure P _H2O increases.

At time t ₁ , the increased intake water vapor partial pressure P _H2O exceeds the integrated value of the saturated water vapor partial pressure P ′ _H2O , more specifically, the saturated water vapor partial pressure P ′ _H2O and the control α parameter α. The condensed water determination flag becomes 1. Condensed water determination flag is 1, i.e. when it is determined that the condition for the condensed water is generated, as condensed water generation avoidance control, firstly, to reduce the EGR rate gamma _EGR, the EGR valve 41A opening (EGR Decrease the valve opening. Here, the EGR rate γ _EGR is larger than the EGR rate γ _LIM which is the operation limit. As the accelerator opening increases, the intake pressure (supercharging pressure) still increases, but the intake water vapor partial pressure P _H2O decreases due to the decrease in the EGR rate γ _EGR .

Becomes the time t _2, the accelerator depression amount by the driver becomes substantially constant, the intake vapor partial pressure P _{H2 O} saturated water vapor pressure P by reduction of the EGR rate _{'H2 O,} and more specifically the saturated water vapor pressure P' _{H2 O} and parameters Below the integrated value with α, the condensed water determination flag returns to 0 again. Therefore, after that, the EGR valve opening and the waste gate valve opening are kept substantially constant while the accelerator opening is constant.

At time t ₃ , the acceleration operation by the accelerator depression of the driver is started again, the waste gate valve opening is reduced, and the increased intake water vapor partial pressure P _H2O is saturated with the water vapor partial pressure P ′ _H2O , more specifically, saturation. The condensed water determination flag is set to 1 again after exceeding the integrated value of the water vapor partial pressure P ′ _H2O and the parameter α relating to the control margin. When the condensed water determination flag becomes 1, first, the EGR valve opening is decreased in order to decrease the EGR rate γ _EGR as described above.

When the reduced EGR rate γ _EGR reaches the operation limit EGR rate γ _LIM at time t ₄ , thereafter, the EGR rate γ _EGR is decreased from the viewpoint of knockability and reduced operability due to air volume fluctuations. I can't. Therefore, with the EGR valve opening degree kept substantially constant, the waste gate valve 11A is opened to reduce the intake pressure (supercharging pressure), and the transmission ratio of the transmission 30A is increased to maintain the output. Increase engine speed.

At time t ₅ , the intake water vapor partial pressure P _H2O is reduced to the saturated water vapor partial pressure P ′ _H2O , more specifically, the integrated value of the saturated water vapor partial pressure P ′ _H2O and the parameter α due to a decrease in the intake pressure (supercharging pressure). Since the condensed water determination flag returns to 0 again, the waste gate valve opening is kept substantially constant thereafter.

At time t _6, since the accelerator pedal depression amount by the driver is approximately constant, in the later, under the accelerator opening is constant, EGR valve opening, the waste gate valve opening, and the gear ratio substantially constant Hold.

  In the example shown in FIG. 13, the embodiment in which the control for increasing the intercooler temperature is not performed on the assumption that the ignition timing is set to the knocking limit point is described. However, the ignition timing is set to the knocking limit point. If not, as described with reference to FIG. 7, the intercooler cooling water valve opening is decreased, or the temperature of the cooling water flowing through the cooling water passage of the intercooler is directly increased to increase the intercooler temperature. Also good.

  As described above, according to the control device of the second embodiment, in the engine 100A including the supercharger 30A and the low pressure EGR system, the condensation is performed based on the intake humidity detected by the humidity sensor 3A disposed in the intake pipe 18A. The presence or absence of water generation is determined, and based on the determination result, the driving state of the supercharger 30A, the opening degree of the EGR valve 41A, etc. are controlled, and the intake pressure (supercharging pressure) is adjusted to control the generation of condensed water. By implementing this, even in the engine 100A equipped with the low pressure EGR system that easily generates condensed water, for example, the generation of condensed water in the intercooler or downstream thereof can be avoided more effectively, and damage to the engine can be reduced. Corrosion of the intake pipe and deterioration of operability can be effectively suppressed.

  Further, the presence or absence of condensed water is determined by comparing the water vapor partial pressure of the intake air immediately after the intercooler 7A with the saturated water vapor partial pressure in the intake air immediately after the intercooler 7A. The flow rate of the EGR gas flowing through the EGR pipe 40A is reduced by controlling the opening degree of the EGR valve 41A, and the intake pressure is adjusted by controlling the driving state of the supercharger 4A after the flow rate of the EGR gas reaches the lower limit value. Condensed water generation avoidance control can be quickly suppressed, and condensate water generation can be achieved while suppressing deterioration of operability such as knocking and air volume fluctuations associated with a decrease in EGR gas flow rate. Can be effectively suppressed.

In the second embodiment described above, the EGR gas flowing through the EGR pipe 40A is returned to the downstream side of the humidity sensor 3A and the upstream side of the compressor 4aA of the supercharger 4A. That is, the humidity sensor 3A is connected to the EGR pipe 40A. In order to detect the humidity of the intake air before being mixed with the EGR gas by the humidity sensor 3A, the humidity sensor 3A detects the humidity of the intake air before being connected to the intake pipe 18A. From the output signals of the sensor 3A, the intake pressure sensor 14A, the differential pressure sensor 43A, and the EGR temperature sensor 44A, the water vapor partial pressure P _H2O in the intake air was calculated. On the other hand, in the engine 100A equipped with the EGR system, the EGR gas flowing through the EGR pipe 40A is recirculated to the upstream side of the humidity sensor 3A, that is, the humidity sensor 3A is more than the connection point between the EGR pipe 40A and the intake pipe 18A. When detecting the humidity of the intake air that is disposed downstream and mixed with the EGR gas by the humidity sensor 3A, as in the first embodiment, the humidity sensor 3A is From the output signal of the intake pressure sensor 14A, the water vapor partial pressure _PH2O during intake can be calculated.

  In the first and second embodiments described above, the supercharger is controlled by controlling the opening degree of the waste gate valve disposed in the bypass flow path that bypasses the upstream side and the downstream side of the turbocharger turbine. Although the mode of controlling the driving state (for example, the rotation speed) has been described, the driving state of the supercharger may be controlled by a method other than the control of the opening degree of the waste gate valve, for example, by switching the number of stages of the supercharger. Of course it is good.

  The present invention is not limited to the first and second embodiments described above, and includes various modifications. For example, the first and second embodiments described above have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 1 ... Air flow sensor 2 ... Electronically controlled throttle 3 ... Humidity sensor (humidity detection part)
3a ... Substrate 3b ... Positive electrode 3c ... Negative electrode 3d ... Moisture sensitive film 4 ... Supercharger 4a ... Compressor 4b ... Turbine 5 ... Variable valve 6 ... Intake manifold 7 ... Intercooler 7a ... Intercooler cooling water valve 8 ... Intercooler Temperature sensor 9 ... Air-fuel ratio sensor 10 ... Three-way catalyst 11 ... Wastegate valve 12 ... Accelerator opening sensor 13 ... Injector 14 ... Intake pressure sensor 15 ... Cylinder 16 ... Exhaust pipe 17 ... Ignition plug 18 ... Intake pipe 19 ... Bypass flow Path 20 ... ECU (control device)
20a ... input circuit 20b ... input / output port 20c ... RAM
20d ... ROM
20e ... CPU
20f ... Electronically controlled throttle drive circuit 20g ... Injector drive circuit 20h ... Wastegate valve drive circuit 20j ... Intercooler cooling water valve drive circuit 20k ... Transmission drive circuit 20mA ... EGR valve drive circuit 30 ... Transmission 40A ... EGR pipe 41A ... EGR valve 42A ... EGR cooler 43A ... Differential pressure sensor (EGR flow rate detector)
44A ... EGR temperature sensor (EGR temperature detector)
DESCRIPTION OF SYMBOLS 51 ... Intake water vapor partial pressure calculating part 52 ... Saturated water vapor partial pressure calculating part 53 ... Comparison part 54 ... Condensed water generation | occurrence | production determination part 55 ... Condensed water generation avoidance control part 56 ... Diagnosis part 57 ... Correction | amendment part 100 ... Engine (internal combustion engine)

Claims (18)

A control device for an internal combustion engine comprising a humidity detector for detecting the humidity of intake air introduced into the combustion chamber and a supercharger for supercharging the intake air,
The control device for an internal combustion engine, wherein the control device controls the driving state of the supercharger based on the humidity of the intake air to adjust the pressure of the intake air.   2. The control device for an internal combustion engine according to claim 1, wherein the control device controls a driving state of the supercharger so as to reduce the pressure of the intake air when the humidity of the intake air becomes high. 3.   The control device controls a driving state of the supercharger by controlling an opening degree of a waste gate valve disposed in a bypass flow path that bypasses an upstream side and a downstream side of a turbine constituting the supercharger. The control apparatus for an internal combustion engine according to claim 1, wherein:   The control device determines whether or not condensed water is generated based on a partial pressure of water vapor in the intake air downstream of the intercooler for cooling the intake air and a saturated partial pressure of water vapor in the intake air downstream of the intercooler. And when the condensed water generation determination unit determines that condensed water is generated, the condensed water generation avoidance control controls the drive state of the supercharger to adjust the pressure of the intake air so as to avoid the generation of condensed water. The control device for an internal combustion engine according to claim 1, further comprising: a unit.   The condensate generation avoidance control unit increases the temperature of intake air downstream of the intercooler when the condensate generation determination unit determines that condensate is generated, or is connected to a power shaft of the internal combustion engine. 5. The control apparatus for an internal combustion engine according to claim 4, wherein the transmission ratio of the transmission is increased.   The condensed water generation avoidance control unit increases the temperature of the intake air downstream of the intercooler by decreasing the flow rate of the cooling water flowing through the cooling water passage of the intercooler or by increasing the temperature of the cooling water. The control device for an internal combustion engine according to claim 5, wherein   6. The internal combustion engine according to claim 5, wherein the condensate water generation avoidance control unit increases the temperature of the intake air downstream of the intercooler when it is determined that there is a margin before the occurrence of knocking of the internal combustion engine. Engine control device.   The condensed water generation determination unit calculates the water vapor partial pressure based on the humidity of the intake air and the pressure of the intake air downstream of the compressor constituting the supercharger, or the temperature of the intake air downstream of the intercooler. 5. The control apparatus for an internal combustion engine according to claim 4, wherein the saturated water vapor partial pressure is calculated based on the calculation result. The internal combustion engine includes an EGR pipe that connects an exhaust pipe on the downstream side of the turbine of the supercharger and an intake pipe on the upstream side of the compressor of the turbocharger, and controls the flow rate of EGR gas that flows through the EGR pipe. And an EGR valve for
The condensed water generation avoidance control unit controls the opening of the EGR valve to reduce the flow rate of the EGR gas when the condensed water generation determination unit determines that condensed water is generated. The control device for an internal combustion engine according to claim 4.   The condensate generation avoidance control unit controls the opening degree of the EGR valve to reduce the flow rate of the EGR gas to a predetermined value when the condensate generation determination unit determines that condensate is generated. The control apparatus for an internal combustion engine according to claim 9, wherein the pressure of the intake air is adjusted by controlling a driving state of the supercharger.   The control apparatus for an internal combustion engine according to claim 10, wherein the predetermined value is defined by a knocking limit or an exhaust temperature limit. The internal combustion engine includes an EGR pipe that connects an exhaust pipe on the downstream side of the turbine of the supercharger and an intake pipe on the upstream side of the compressor of the turbocharger, and controls the flow rate of EGR gas that flows through the EGR pipe. An EGR valve, an EGR flow rate detection unit that detects the flow rate of the EGR gas, and an EGR temperature detection unit that detects the temperature of the EGR gas,
The condensed water generation determination unit is
When the humidity detector is disposed upstream of the connection point between the EGR pipe and the intake pipe, the humidity of the intake air and the pressure of the intake air downstream of the compressor constituting the supercharger And the water vapor partial pressure based on the flow rate of the EGR gas and the temperature of the EGR gas,
When the humidity detection unit is disposed downstream of the connection point between the EGR pipe and the intake pipe, the humidity of the intake air and the pressure of the intake air downstream of the compressor constituting the supercharger The control apparatus for an internal combustion engine according to claim 4, wherein the partial pressure of water vapor is calculated based on: The control device further includes a diagnosis unit that diagnoses an abnormality or failure of the humidity detection unit,
The condensed water generation determination unit determines whether or not condensed water is generated, assuming that the humidity of the intake air is a humidity upper limit value when the diagnosis unit determines that the humidity detection unit is abnormal or malfunctioning. The control device for an internal combustion engine according to claim 4.   The control device corrects the humidity of the intake air detected by the humidity detection unit based on information on an external environment of a vehicle on which the internal combustion engine is mounted and / or information on an operation of the vehicle by a driver. The control apparatus for an internal combustion engine according to claim 1, characterized in that:   15. The control device for an internal combustion engine according to claim 14, wherein the information related to the external environment of the vehicle is acquired from a camera or a rain sensor that recognizes the external environment of the vehicle.   15. The control device for an internal combustion engine according to claim 14, wherein the operation of the vehicle includes an operation of a wiper or a fog lamp installed in the vehicle.   The control device corrects the humidity of the intake air detected by the humidity detector based on the flow rate of intake air and the flow rate of fuel introduced into the combustion chamber of the internal combustion engine and the air-fuel ratio of exhaust gas. The control device for an internal combustion engine according to claim 1. The internal combustion engine includes an EGR pipe that connects an exhaust pipe on the downstream side of the turbine of the supercharger and an intake pipe on the upstream side of the compressor of the turbocharger, and controls the flow rate of EGR gas that flows through the EGR pipe. And an EGR valve for
The said control apparatus correct | amends the humidity of the said intake air detected by the said humidity detection part, when the flow volume of the EGR gas which flows into the said EGR pipe | tube is below a predetermined value, The said intake device is characterized by the above-mentioned. Control device for internal combustion engine.

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