JP6551677B2 - Condensed water discharge device for internal combustion engine - Google Patents

Description

  The present invention relates to a condensed water discharge device for draining condensed water generated in an intake passage by exhaust gas recirculation of an internal combustion engine to an exhaust passage.

  An exhaust gas recirculation device is known as an exhaust gas purification device for an internal combustion engine. As an exhaust gas recirculation device employed for an internal combustion engine equipped with a turbocharger, there is provided a high pressure exhaust gas recirculation device for recirculating part of the exhaust gas from an exhaust passage on the turbine upstream side of the turbocharger to an intake passage on the compressor downstream side; There is a low pressure exhaust gas recirculation system which recirculates part of the exhaust gas from the downstream exhaust passage to the intake passage upstream of the compressor. Furthermore, many internal combustion engines equipped with a supercharger have a cooling device such as an intercooler for cooling intake air in the intake passage downstream of the compressor. However, in the internal combustion engine thus equipped with the intercooler in the intake passage and the low pressure exhaust gas recirculation device, the exhaust gas recirculated to the intake passage by the low pressure exhaust gas recirculation device passes through the intercooler, so the water content in the exhaust gas There is a possibility that condensed water is generated to condense and this condensed water may enter into the combustion chamber of the internal combustion engine together with the intake air.

  Therefore, in Patent Document 1, in an internal combustion engine provided with a low pressure exhaust gas recirculation device and an intercooler in the intake passage, the intake passage downstream of the intercooler condenses in the exhaust gas passage downstream of the exhaust introduction position of the low pressure exhaust gas recirculation device. A technique is disclosed for providing a drainage for draining water. Furthermore, in Patent Document 1, an on-off valve is provided in the drainage path, and the on-off valve is closed based on the temperature of the exhaust passage to close the on-off valve when drainage of condensed water by the drainage path is completed. Thus, it is possible to suppress the decrease in the output of the internal combustion engine by suppressing the intake air from passing through the drainage passage and flowing out to the exhaust passage.

JP, 2015-102011, A

However, even if the on / off control of the on / off valve is performed as in Patent Document 1, for example, the function of the on / off valve is affected by the opening of the on / off valve at the time of vehicle acceleration or regeneration of the catalyst provided in the exhaust passage. There is a risk of it. In addition, if the opening / closing valve is suppressed, there is a possibility that the discharge performance of the condensed water can not be secured.
The present invention has been made to solve such problems, and performs appropriate on-off control of the on-off valve according to the operating condition of the internal combustion engine, and condenses the internal combustion engine that can efficiently drain condensed water. It is to provide a water discharge device.

  In order to achieve the above object, the condensed water discharge device for an internal combustion engine according to claim 1 comprises: an intake air cooling unit provided in an intake passage; and a part of exhaust gas in the intake passage upstream of the intake cooling unit. A condensed water discharger provided in an internal combustion engine having an exhaust gas recirculation portion for refluxing, the condensed water collection portion collecting condensed water generated from intake air having passed through the intake air cooling portion; the condensed water A drainage passage communicating the collection unit with the exhaust passage of the internal combustion engine and discharging condensed water collected in the condensed water collection unit to the exhaust passage; an opening / closing valve opening / closing the drainage passage; Change the discharge permission condition whether to discharge the condensed water from the exhaust passage according to the collection amount detection unit that detects the collection amount of condensed water in the condensed water collection unit and the collection amount of condensed water Control for opening / closing the on / off valve when the discharge permission condition is satisfied. Characterized in that it comprises a and.

Preferably, the control unit sets different discharge permission conditions according to a plurality of set threshold values of the condensed water collection amount.
In addition, preferably, the condensed water discharge device further includes an outside air temperature detection unit that detects an outside air temperature, and a pressure detection unit that detects a pressure difference between both ends of the drainage channel, and the discharge permission condition is It is preferable to include at least a first permission condition that the pressure difference is equal to or greater than a predetermined pressure and that the outside air temperature is higher than the freezing temperature of the condensed water.

Preferably, the internal combustion engine includes a supercharger, and the discharge permission condition is a second permission in which a difference between an actual supercharging pressure of the supercharger and a target supercharging pressure is a predetermined value or less. It is good to further include conditions.
In addition, preferably, the internal combustion engine controls an exhaust gas purification catalyst provided in the exhaust gas passage downstream of a position where the condensed water is discharged by the drainage passage, and a temperature or an air-fuel ratio of exhaust gas flowing into the exhaust gas purification catalyst And a catalyst regeneration control unit that regenerates the exhaust purification catalyst, and the discharge permission condition may further include a third permission condition in which the regeneration process is not performed.

In addition, preferably, the control unit sets only the first permission condition as the discharge permission condition when the outside air temperature is equal to or lower than a predetermined temperature higher than the freezing temperature, and when the outside air temperature is higher than the predetermined temperature. The threshold in the second permission condition and the threshold in the third permission condition may be set to different values.
Also, preferably, when the outside air temperature is higher than the predetermined temperature, the control unit sets the threshold in the second permission condition and the threshold in the third permission condition to the outside air temperature. It is good to change continuously based on this.

According to the condensed water discharge device for an internal combustion engine of the present invention, the condensed water generated from the intake air that has passed through the intake air cooling unit is discharged from the condensed water collecting unit to the exhaust passage through the drainage channel, and the condensed water is combusted in the internal combustion engine. Inflow into the room can be suppressed.
Since the discharge permission condition for opening the on-off valve is changed according to the amount of condensed water collected, the discharge permission condition can be set according to the degree of necessity for condensate discharge. For example, when the condensed water collection amount is large, the discharge permission condition is lowered to suppress the increase of the condensed water collection amount more than the allowance, and when the condensed water collection amount is small, the discharge permission condition is increased. It is possible to suppress the influence on the operation of the internal combustion engine accompanying the opening of the on-off valve, and to efficiently suppress the increase in the amount of collected condensed water and the influence on the operation of the internal combustion engine Is possible.

It is a schematic block diagram of the intake / exhaust system of the diesel engine in embodiment of this invention. It is sectional drawing which shows the detailed structure of the connection part of a low pressure exhaust gas recirculation passage and an exhaust pipe. It is a flowchart which shows the control point of discharge control of condensed water performed in an engine control unit. It is a flowchart which shows the discharge permission condition setting control point. It is a flow chart which shows an end judgment control point of discharge control. It is a graph which shows an example of transition of various flags at the time of performing discharge control of condensed water, condensed water collection amount, and condensed water discharge outlet temperature. It is a map which shows the relationship between the amount of condensed water collection in 1st Embodiment, and discharge | emission permission conditions. It is a map which shows the relationship between the condensed water collection amount in 2nd Embodiment, and discharge | emission permission conditions. It is a map which shows the relationship between the condensed water collection amount and discharge | emission permission conditions in 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an intake / exhaust system of a diesel engine (hereinafter referred to as an engine 1) to which an exhaust emission control device of the present invention is applied.
The engine 1 is a multi-cylinder in-cylinder direct injection engine (for example, a common rail diesel engine) equipped with a turbocharger 2 (supercharger) and mounted on a vehicle as a traveling drive source. Specifically, the engine 1 is provided with a cylinder head 4 at the top of the cylinder block 3. The fuel injection nozzle 5 is provided in the cylinder head 4 for each cylinder of the engine 1. The high pressure fuel accumulated in the common rail 7 by the fuel pump 6 is supplied to the fuel injection nozzle 5, and any injection timing and injection amount Thus, the fuel injection nozzle 5 can be injected into the combustion chamber 8 of each cylinder.

An intake port 10 and an exhaust port 11 are communicated with the combustion chamber 8 of the engine 1.
The intake port 10 is provided with an intake valve 12 that connects and disconnects the combustion chamber 8 and the intake port 10. Further, the exhaust port 11 is provided with an exhaust valve 13 for communicating and blocking communication between the combustion chamber 8 and the exhaust port 11.

Upstream of the intake port 10, an intake manifold 14 for distributing intake air to each cylinder is provided in communication. An exhaust manifold 15 is provided downstream of the exhaust port 11 so as to communicate the exhaust gases discharged from the cylinders.
An intake pipe 20 that is an intake passage is connected to the intake manifold 14, and an air cleaner 21 that removes dust in the fresh air in order from the upstream side toward the intake manifold 14, and a fresh air An electronically controlled throttle valve 22 for adjusting the flow rate of low-pressure exhaust gas introduced by a low-pressure exhaust gas recirculation passage 45 (exhaust gas recirculation portion) described later, the compressor 23 of the turbocharger 2, and the compressor 23 while adjusting the flow rate. An intercooler 24 (intake air cooling unit) for cooling the intake air that has been compressed to a high temperature and an electronically controlled throttle valve 25 for adjusting the flow rate of the intake air after passing through the intercooler 24 are interposed.

  In the exhaust pipe 30, which is an exhaust passage downstream of the exhaust manifold 15, in order from the upstream side, a turbine 31 of the turbocharger 2, an oxidation catalyst 32 that oxidizes components to be oxidized in the exhaust, and graphite in the exhaust A diesel particulate filter 33 for collecting and burning particulate matter to be treated, and an NOx trap catalyst 34 (exhaust purification catalyst) for trapping and purifying nitrogen oxides (hereinafter, NOx) in exhaust gas are provided. . The oxidation catalyst 32 and the diesel particulate filter 33 are housed in the same casing.

Further, a blow-by gas passage 35 for returning the blow-by gas of the engine 1 to the intake pipe 20 is provided between the cylinder head 4 of the engine 1 and the intake pipe 20 between the air cleaner 21 and the electronic control throttle valve 22. ing.
A portion of the exhaust gas is returned to the intake air between the intake pipe 20 downstream of the electronically controlled throttle valve 25 and the exhaust pipe 30 upstream of the turbine 31, that is, a high pressure for introducing high temperature / high pressure exhaust gas into the intake air. An exhaust gas recirculation passage 40 is provided. Further, an exhaust gas recirculation valve 41 that adjusts the amount of return of high-temperature and high-pressure exhaust gas to the intake air is provided at a connection portion between the high-pressure exhaust gas recirculation passage 40 and the intake pipe 20. Further, the high-pressure exhaust gas recirculation passage 40 is provided with an exhaust gas recirculation cooler 42 that cools the exhaust gas introduced into the intake manifold 14.

  Further, a low pressure exhaust gas recirculation passage 45 is provided which communicates the intake pipe 20 between the electronically controlled throttle valve 22 and the compressor 23 and the exhaust pipe 30 between the diesel particulate filter 33 and the NOx trap catalyst 34. . The low pressure exhaust gas recirculation passage 45 has a function of introducing (refluxing) part of the low temperature and low pressure exhaust gas that has passed through the turbine 31, the oxidation catalyst 32 and the diesel particulate filter 33 into the intake air.

The low-pressure exhaust gas recirculation passage 45 is provided with an exhaust gas recirculation cooler 47 that cools the recirculated exhaust gas. Further, an exhaust gas recirculation valve 48 for opening and closing the low pressure exhaust gas recirculation passage 45 is provided at a connection portion between the low pressure exhaust gas recirculation passage 45 and the intake pipe 20.
Furthermore, in the present embodiment, a condensed water discharge device for draining condensed water from the intake pipe 20 downstream of the intercooler 24 to the exhaust pipe 30 is provided. The condensed water discharge device connects the intake pipe 20 between the intercooler 24 and the electronically controlled throttle valve 25, the connection between the low pressure exhaust gas recirculation passage 45 and the exhaust pipe 30 between the NOx trap catalyst 34, A drainage path 50 for draining condensed water from the intake pipe 20 to the exhaust pipe 30 is provided. The drainage channel 50 is provided with an electronically controlled on-off valve 51. A condensed water collection tank 52 (condensed water collection unit) capable of storing condensed water is provided at a connection portion between the intake pipe 20 and the drainage passage 50.

The intake manifold 14 is provided with a boost sensor 55 that detects an intake pressure. Further, an intake pressure sensor 56 (pressure detection unit) that detects the pressure of intake air after passing through the intercooler 24 is provided in the intake pipe 20 between the intercooler 24 and the electronically controlled throttle valve 25.
An exhaust pressure sensor 57 (pressure detection unit) for detecting the exhaust pressure is provided in the exhaust pipe 30 between the connection portion with the low pressure exhaust gas recirculation passage 45 and the NOx trap catalyst 34.

Further, an outlet temperature sensor 58 that detects the outlet temperature of the drainage channel 50 is provided at the connection portion between the drainage channel 50 and the exhaust pipe 30.
Further, the vehicle equipped with the engine 1 is provided with an outside air temperature sensor 59 (an outside air temperature detecting unit) that detects the outside air temperature T.
The boost sensor 55, the intake pressure sensor 56 (pressure detection unit), the exhaust pressure sensor 57, the outlet temperature sensor 58, the outside air temperature sensor 59, an engine rotational speed sensor (not shown), an intake temperature sensor, other exhaust temperature sensors, an air-fuel ratio sensor And various devices such as the fuel injection nozzle 5, the electronically controlled throttle valves 22 and 25, the exhaust gas recirculation valves 41 and 48, and the on-off valve 51 are electrically connected to the engine control unit 70 (control unit). Yes.

FIG. 2 is a cross-sectional view showing the detailed structure of the connecting portion between the drainage passage 50 and the exhaust pipe 30. As shown in FIG.
As shown in FIG. 2, the outlet temperature sensor 58 is provided at a position slightly upstream of the connection position of the drainage passage 50 and the exhaust pipe 30 on the upstream side (intake pipe 20 side) of the drainage passage 50. The outlet temperature sensor 58 does not directly detect the exhaust gas passing through the exhaust pipe 30 but detects the heat conduction through the exhaust pipe 30 or the temperature of the exhaust gas going back through the drainage channel 50. Thereby, the outlet temperature sensor 58 can suppress the detection range on the high temperature side, and can reduce the component cost.

  The engine control unit 70 includes an input / output unit, a storage unit (ROM, RAM, non-volatile RAM, etc.), a timer, a central processing unit (CPU), etc. , Etc., calculate the target torque based on the various information, calculate the fuel injection amount, fuel injection timing, electronic control throttle valve 22, 25 and exhaust recirculation valve 41, 48 opening degree, and The operation control of the engine 1 is performed by performing operation control of various devices.

The engine control unit 70 switches the exhaust gas recirculation by the high pressure exhaust gas recirculation passage 40 and the exhaust gas recirculation by the low pressure exhaust gas recirculation passage 45 based on the target torque of the engine 1.
For example, when the target torque is lower than a predetermined value set appropriately, the exhaust is recirculated through the high pressure exhaust gas recirculation passage 40, and when the target torque is higher than the predetermined value, exhaust gas is recirculated through the low pressure exhaust gas recirculation passage 45.

  As described above, in the engine 1 provided with the exhaust gas recirculation system (low pressure exhaust gas recirculation system) by the low pressure exhaust gas recirculation passage 45, when exhaust gas is recirculated to the intake pipe 20 by the low pressure exhaust gas recirculation system at high load, There is a possibility that the exhaust gas recirculated through the intercooler 24 will generate condensed water in the intake pipe 20. The condensed water is stored in the condensed water collection tank 52. By the way, the on-off valve 51 of the drainage channel 50 is normally closed so that the intake air does not flow out to the exhaust pipe 30 via the drainage channel 50, and the condensed water is condensed water by continuing the high load operation. It may overflow from the collection tank 52 and flow into the combustion chamber 8 of the engine 1 via the intake manifold 14.

Therefore, the engine control unit 70 performs opening / closing control of the on-off valve 51, that is, control of discharging condensed water through the drainage channel 50, based on the amount of condensed water collected in the condensed water collection tank 52.
FIG. 3 is a flow chart showing a control procedure of discharge control of condensed water executed in the engine control unit 70. FIG. 4 is a flowchart showing a discharge permission condition setting control procedure. FIG. 5 is a flowchart showing a discharge determination end determination control procedure.

Discharge control of condensed water shown in FIG. 3, discharge permission condition setting control shown in FIG. 4, and determination control of discharge control shown in FIG. 5 are repeatedly performed at predetermined time intervals (for example, several msec) while the engine 1 is in operation. It is.
As shown in FIG. 3, first, in step S10, the condensed water collection amount M in the condensed water collection tank 52 is calculated. The condensed water collection amount M may be obtained, for example, by subtracting the intercooler passing water amount from the saturated water vapor amount of the outside air. The intercooler passage water amount is obtained by adding the moisture amount in the intake air and the moisture amount in the exhaust recirculation gas. The water content in the exhaust gas recirculation gas is determined on the basis of the water content in the intake air, the combustion generated water content, the amount of intake air, the amount of input fuel, and the mass of the exhaust gas recirculation gas. The amount of moisture in the intake air is determined using the amount of saturated water vapor of the outside air and the relative humidity, and the amount of moisture generated by combustion is determined based on the amount of input fuel. The calculation of the condensed water collection amount M in this step is performed by the collection amount estimation unit 71 (collection amount detection unit) in the engine control unit 70.

Note that, instead of such calculation, a level sensor for detecting the amount M of collected condensed water may be provided in the condensed water collecting tank 52, and a detection value of this level sensor may be used. Then, the process proceeds to step S20.
In step S20, it is determined whether or not the condensed water collection amount M calculated in step S10 is greater than the required discharge value Mc. The discharge request value Mc may be set to a value smaller than the maximum possible collection amount Mmax of the condensed water in the condensed water collection tank 52. If the condensed water collection amount M is larger than the discharge requirement value Mc, the process proceeds to step S30. If the condensed water collection amount M is equal to or less than the discharge requirement value Mc, the process proceeds to step S40.

In step S30, a request flag for drain control of condensed water by the drain 50 is turned ON. Then, the process proceeds to step S40.
In step S40, it is determined whether a discharge permission condition for condensed water is satisfied. The discharge permission condition is a discharge permission condition set by permission determination control of discharge control shown in FIG. 4 described later. If the discharge permission condition is satisfied, the process proceeds to step S50. If the discharge permission condition is not satisfied, the process proceeds to step S60.

In step S50, a permission flag of discharge control of condensed water by the drainage channel 50 is set to ON. Then, the process proceeds to step S60.
In step S60, it is determined whether a discharge control request flag is ON. If the discharge control request flag is ON, the process proceeds to step S70. If the discharge control request flag is OFF, this routine ends.

In step S70, it is determined whether the discharge control permission flag is ON. If the discharge control permission flag is ON, the process proceeds to step S80. If the discharge control permission flag is OFF, this routine ends.
In step S80, discharge control is performed. Specifically, the opening / closing valve 51 is controlled to open. Then, this routine ends.

Next, the discharge permission condition setting control performed in parallel with the condensed water discharge control shown in FIG. 3 will be described with reference to FIG. Note that this discharge permission condition setting control may be performed each time before determining whether or not the discharge permission condition is satisfied in step S40 of FIG.

  As shown in FIG. 4, first, in step S100, the discharge permission condition setting control determines whether the latest collected amount M of condensed water calculated in step S10 is larger than a threshold value Ma. The threshold value Ma is larger than the discharge requirement value Mc and smaller than the maximum possible collection amount Mmax of condensed water in the condensed water collection tank 52. When the condensed water collection amount M is larger than the threshold value Ma, the process proceeds to step S120. If the condensed water collection amount M is less than or equal to the threshold value Ma, the process proceeds to step S110.

In step S110, it is determined whether or not the latest condensed water collection amount M calculated in step S10 is larger than the threshold value Mb. The threshold value Mb is larger than the emission requirement value Mc and smaller than the threshold value Ma. If the condensed water collection amount M is larger than the threshold value Mb, the process proceeds to step S130. If the condensed water collection amount M is equal to or less than the threshold value Mb, the process proceeds to step S140.
The threshold value Ma, the threshold value Mb, and the discharge requirement value Mc correspond to the threshold values of the present invention.

In step S120, permission condition (1) is set as the discharge permission condition of the condensed water.
The permission condition (1) which is the first permission condition is that there is a pressure difference necessary for discharging condensed water between the intake pipe 20 and the exhaust pipe 30 as shown in the following formula (A), and the following formula (A) As shown in B), there are two conditions that the outside air temperature T detected by the outside air temperature sensor 59 is higher than 0 ° C. (freezing temperature of condensed water). More specifically, the intake pressure sensor 56 detects the intake pressure Pin downstream of the intercooler 24 and the exhaust pressure sensor 57 detects the pressure Pout of the exhaust pipe 30, for the pressure difference necessary for discharging condensed water. When the differential pressure (Pin−Pout) is equal to or higher than the dischargeable differential pressure Pa, it is determined that there is a pressure difference necessary for discharging condensed water. The dischargeable differential pressure Pa may be appropriately set to a value at which condensed water can be discharged from the intake pipe 20 to the exhaust pipe 30 by the drainage channel 50.

Pin−Pout ≧ Pa (A)
T> 0 (° C.) (B)
Then, this routine ends.
In step S130, permission conditions (1) + (2) are set as discharge permission conditions of condensed water.

  In the permission condition (2) which is the second permission condition, the difference between the target boost pressure Ptgt and the intake manifold pressure Pim detected by the boost sensor 55 is equal to or less than the predetermined pressure Pb, as shown in the following equation (C) It is. The predetermined pressure Pb is a situation where torque rise and response deterioration fall within an allowable range even if part of intake air flows out to the exhaust pipe 30 due to the opening of the on-off valve 51, for example, a situation except when the vehicle accelerates It should be set to a value that can be determined.

Ptgt−Pim ≦ Pb (C)
Then, this routine ends.
In step S140, the permission condition (1) + (2) + (3) is set as the condensed water discharge permission condition.
The permission condition (3) that is the third permission condition is that the regeneration control of the NOx trap catalyst 34 is not performed.

  The regeneration control of the NOx trap catalyst 34 is executed in the catalyst regeneration control unit 72 of the engine control unit 70. The regeneration control of the NOx trap catalyst 34 is control for recovering the NOx adsorption performance by the NOx trap catalyst 34 which decreases with the elapse of the operation time of the engine 1, and is known NOx purification control and sulfur removal control. In these NOx purification control and sulfur removal control, the air-fuel ratio of the exhaust flowing into the NOx trap catalyst 34 is controlled to be less than or equal to the stoichiometric ratio. When the on-off valve 51 is opened during execution of the regeneration control of the NOx trap catalyst 34, a part of the intake air passes through the drainage passage 50 and flows into the exhaust pipe 30, and flows into the NOx trap catalyst 34. The permission condition (3) is for securing the function of such regeneration control, since the air-fuel ratio rises to inhibit the regeneration control. Then, this routine ends.

5 is performed in parallel with the condensed water discharge control shown in FIG.
First, in step S200, it is determined whether or not the on-off valve 51 is open, that is, whether or not the discharge control is being executed. If the on-off valve 51 is open, the process proceeds to step S210. If the on-off valve 51 is not open, step S200 is repeated to stand by.

  In step S210, it is determined whether or not the temperature detected by the outlet temperature sensor 58 has shifted to the high temperature side. When the discharge of the condensed water is completed and the condensed water disappears from the condensed water collection tank 52 and the drainage channel 50, the condensed water discharge outlet temperature Tout detected by the outlet temperature sensor 58 rises, so here the condensed water discharge outlet When the temperature Tout becomes higher than a predetermined value (for example, 100 ° C.), the process proceeds to step S220, assuming that the temperature Tout has shifted to the high temperature side. If the condensed water discharge outlet temperature Tout detected by the outlet temperature sensor 58 is equal to or less than the predetermined value, step 210 is repeated and the process is on standby, assuming that the temperature has not changed to the high temperature side.

In step S220, the on-off valve 51 is closed to end the discharge control. Then, this routine ends.
Note that the discharge control end determination control shown in FIG. 5 may not be performed, and the discharge control may be ended when a predetermined time has elapsed since the start of the discharge control.
Furthermore, the engine control unit 70 has a function of determining whether or not to discharge based on the condensed water discharge outlet temperature Tout detected by the outlet temperature sensor 58 when drainage control is performed.

FIG. 6 is a graph showing an example of changes in various flags, condensed water collection amount M, and condensed water discharge outlet temperature Tout when the condensed water discharge control is executed.
As shown in FIG. 6, in a state where the discharge control permission flag is ON, when the condensed water collection amount M becomes equal to or more than the discharge request value Mc, the discharge control request flag is turned ON, and the discharge control is carried out. . Thereby, if it is normal, condensed water will be discharged | emitted by the exhaust pipe 30, and condensed water discharge outlet temperature Tout will fall. Then, when the condensed water discharge outlet temperature Tout becomes equal to or lower than the discharge determination temperature Ta (for example, 100 ° C.), the discharge determination becomes ON, and the discharge control is continued. Here, if the condensed water discharge outlet temperature Tout is not lower than the discharge possibility determination temperature Ta, the drainage control is stopped because the drainage channel 50 is blocked and the on-off valve 51 is broken. In this way, when the discharge control is stopped, it is assumed that the condensed water is not actually drained until the discharge control is stopped after the discharge control is started, and the condensed water collected amount M Is not subtracted from the amount M of collected condensed water.

When discharge control is stopped, discharge control is tried again, and when discharge control is repeatedly stopped several times, as a failure of the discharge control system of condensed water such as failure of the on-off valve 51, What is necessary is just to warn the driver of abnormality.
As described above, in the present embodiment, if the condensed water collection amount M becomes equal to or more than the discharge request value Mc, the discharge is requested, but the discharge permission condition set based on the condensed water collection amount M is not satisfied. The emission is not controlled.

Then, in the first embodiment of the present invention, three types of permission conditions are set based on the condensed water collection amount M as the discharge permission conditions of the condensed water.
FIG. 7 is a map showing the relationship between the condensed water collection amount M and the discharge permission condition in the first embodiment.
As shown in FIG. 7, when the condensed water collection amount M is larger than the threshold value Ma, that is, when the condensed water collection amount M is close to the maximum possible collection amount Mmax and the discharge request is high, only the permission condition (1) It is said. The permission condition (1) is that there is a pressure difference necessary for discharging the condensed water and that the condensed water is not frozen. As described above, when the discharge request is high, the discharge control is executed relatively easily after satisfying the essential requirements of the discharge control.

  If the condensed water collection amount M is less than or equal to the threshold Ma and greater than the threshold Mb, that is, if the discharge request is medium, permission conditions (1) and (2) are required as discharge permission conditions. The permission condition (2) is a discharge permission condition that the difference between the target boost pressure Ptgt and the intake manifold pressure Pim is equal to or less than a predetermined pressure Pb, that is, not at the time of vehicle acceleration. As a result, when the discharge request is moderate, vehicle acceleration performance can be ensured without permitting discharge control during vehicle acceleration.

  When the condensed water collection amount M is equal to or less than the threshold value Mb, that is, when the discharge request is low, permission conditions (1), (2) and further (3) are required as discharge permission conditions. The permission condition (3) is that the regeneration control of the NOx trap catalyst 34 is not performed. If the drainage control is performed when the regeneration control is performed, the air-fuel ratio of the exhaust gas flowing into the NOx trap catalyst 34 increases due to the intake air flowing into the exhaust pipe 30 through the drainage channel 50, and the efficiency of the regeneration control decreases. Therefore, in the present embodiment, it is possible to secure the efficiency of the regeneration control by adding the fact that the regeneration control is not being executed when the discharge request is low as the emission permission condition.

  As described above, a plurality of threshold values of the condensed water collection amount M determined to be discharge permitted is determined, and the discharge permission condition of the condensed water is changed based on the condensed water collection amount M, the discharge request (degree of drainage necessity) It is set to the discharge permission condition according to. Therefore, while the condensed water collection amount M is prevented from exceeding the maximum possible collection amount Mmax of the condensed water collection tank 52, if there is a margin in the condensed water collection amount M, the discharge control is performed stepwise The vehicle acceleration performance and the efficiency of the regeneration control can be secured by suppressing. As a result, efficient drainage can be achieved such that the function of discharging condensed water and the suppression of the influence on the operation of the internal combustion engine such as acceleration and regeneration control of the vehicle can be compatible.

In the above embodiment, although the discharge permission condition is set based on the condensed water collection amount M, the discharge permission condition may be set based on the condensed water collection amount M and the outside air temperature T.
FIG. 8 is a map showing the relationship between the condensed water collection amount M and the outside air temperature T and the discharge permission conditions in the second embodiment.
As shown in FIG. 8, in the second embodiment, when the outside air temperature T is equal to or higher than the discharge determination temperature Tb (the predetermined temperature of the present invention), condensed water is trapped as in the first embodiment. Although the discharge permission conditions are set in three stages based on the collection amount M, when the outside air temperature T is lower than the discharge possibility determination temperature Tb, the discharge permission condition is only (1). The discharge possibility determination temperature Tb may be set to a temperature at which introduction of exhaust gas by the low pressure exhaust gas recirculation device (low pressure exhaust gas recirculation passage 45) is prohibited. The temperature at which introduction by this low-pressure exhaust gas recirculation device is prohibited is set to a low temperature range higher than 0 ° C. and close to 0 ° C.

  As described above, in the second embodiment, when the outside air temperature T is lower than the discharge determination temperature Tb, drainage control is performed in a low temperature range close to 0 ° C. by setting the discharge permission condition only to (1). Is easier to implement. Thus, for example, when the outside air temperature T gradually decreases toward 0 ° C. or less, drainage control is actively performed before the outside air temperature T falls to 0 ° C. or less, and drainage control is performed. When the outside air temperature at which it becomes impossible becomes 0 ° C. or lower, the condensed water collection amount M can be reduced in advance to suppress freezing of the condensed water.

FIG. 9 is a map showing the relationship between the condensed water collection amount M and the outside air temperature T and the discharge permission conditions in the third embodiment.
As shown in FIG. 9, in the third embodiment, as in the second embodiment, when the outside air temperature T is less than the discharge determination temperature Tb, the discharge permission condition is set to only (1). When the outside air temperature T is equal to or higher than the discharge determination temperature Tb, the discharge permission condition is set to three stages based on the condensed water collection amount M as in the second embodiment, but the outside air temperature T is set. The threshold values Ma and Mb for switching the discharge permission condition change based on the above. Specifically, as the outside air temperature T decreases, the thresholds Ma and Mb for switching the discharge permission condition decrease. When the outside air temperature T is the dischargeability determination temperature Tb, the threshold values Ma and Mb for switching the discharge permission conditions are both the same as the discharge request value Mc, and the outside air temperature T rises from the dischargeability determination temperature Tb. Along with this, the threshold value Ma becomes larger than the threshold value Mb.

As described above, in the third embodiment, even when the outside air temperature T is equal to or higher than the discharge determination temperature Tb, the permission condition (1) is satisfied with the smaller condensed water collection amount M as the outside air temperature T decreases. . Therefore, in the third embodiment, the condensed water collection amount M can be made smaller until the outside air temperature falls to 0 ° C., as compared with the second embodiment.
In addition, this invention is not limited to the said embodiment. The present invention can be widely applied to an internal combustion engine having a low pressure exhaust gas recirculation system and a drainage channel.

1 Engine 2 Turbocharger (supercharger)
20 Intake pipe (intake passage)
24 Intercooler (intake air cooling unit)
30 Exhaust pipe (exhaust passage)
34 NOx trap catalyst (exhaust gas purification catalyst)
45 Low pressure exhaust recirculation passage (exhaust recirculation section)
50 drainage channel 51 on-off valve 52 condensed water collection tank (condensed water collection part)
56 Intake pressure sensor (pressure detector)
57 Exhaust pressure sensor (pressure detector)
59 Outside temperature sensor (outside temperature detector)
70 Engine control unit (control unit)
71 Collection amount estimation unit (collection amount detection unit)
72 Catalyst regeneration control unit

Claims (7)

A condensed water discharge device provided in an internal combustion engine comprising: an intake air cooling portion provided in an intake air passage; and an exhaust gas recirculation portion returning an exhaust gas to the intake air passage upstream of the intake air cooling portion ,
A condensate collecting unit that collects condensate generated from the intake air that has passed through the intake cooling unit;
A drainage channel for communicating the condensed water collecting portion and the exhaust passage of the internal combustion engine, and discharging the condensed water collected in the condensed water collecting portion to the exhaust passage;
An on-off valve for opening and closing the drainage channel;
A collection amount detection unit that detects the collection amount of condensed water in the condensed water collection unit;
Control to open the on-off valve when the discharge permission condition is satisfied by changing the discharge permission condition whether to discharge the condensed water from the exhaust passage according to the condensed water collection amount And a condensate drainage device for an internal combustion engine.   The condensed water discharge device for an internal combustion engine according to claim 1, wherein the control unit sets different discharge permission conditions according to a plurality of threshold values of the collection amount of condensed water. The condensed water discharge device is:
An outside temperature detector for detecting the outside temperature;
And a pressure detection unit that detects a pressure difference between both ends of the drainage channel,
The discharge permission condition includes at least a first permission condition in which the pressure difference is equal to or higher than a predetermined pressure and the outside air temperature is higher than a freezing temperature of the condensed water. A condensate discharge device for an internal combustion engine according to claim 1. The internal combustion engine has a supercharger,
The internal combustion engine according to claim 3, wherein the discharge permission condition further includes a second permission condition in which a difference between an actual supercharging pressure of the supercharger and a target supercharging pressure is a predetermined value or less. Condensate drain device. The internal combustion engine controls the exhaust gas purification catalyst provided in the exhaust passage downstream of the condensate discharge position by the drainage channel and the temperature or air-fuel ratio of the exhaust gas flowing into the exhaust gas purification catalyst. A catalyst regeneration control unit that regenerates the catalyst,
The condensed water discharge device for an internal combustion engine according to claim 4, wherein the discharge permission condition further includes a third permission condition in which the regeneration process is not performed.   The control unit sets only the first permission condition as the discharge permission condition when the outside air temperature is lower than or equal to a predetermined temperature higher than the freezing temperature, and the second permission condition when the outside air temperature is higher than the predetermined temperature. The condensed water discharge device for an internal combustion engine according to claim 5, characterized in that the threshold value in the second and the threshold value in the third permission condition are set to different values.   When the outside air temperature is higher than the predetermined temperature, the control unit continuously performs the threshold in the second permission condition and the threshold in the third permission condition based on the outside air temperature. The condensate discharge device for an internal combustion engine according to claim 6, wherein the condensate discharge device is set by changing.

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