JP2009150281A - Exhaust recirculation device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for collecting and re-using an unburned fuel by separating condensed water from an EGR gas in an exhaust recirculation device of an internal combustion engine. <P>SOLUTION: This exhaust recirculation device comprises: a low pressure EGR passage 31; a cooling means which is disposed in the low pressure EGR passage 31 and which has a cooling chamber 41 for cooling a low pressure EGR gas flowing through the low pressure EGR passage 31; a separating tank 42 for storing the condensed liquid condensed from the low pressure EGR gas cooled by the cooling means; a mechanism having a condensed water discharge passage 43 for discharging the condensed water in the condensed liquid stored in the separating tank 42 to the exhaust passage 7; and a mechanism having an unburned fuel collection passage 45 for collecting a light oil in the condensed liquid stored in the separating tank 42 to a fuel tank 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

An EGR cooler that cools the EGR gas is provided in the EGR passage that takes in part of the exhaust gas from the exhaust passage of the internal combustion engine as EGR gas and recirculates the EGR gas to the intake passage of the internal combustion engine, and the EGR cooler does not remove the EGR gas from the EGR gas. A technique is disclosed in which the fuel is separated and the separated unburned fuel is discharged to the exhaust passage (see, for example, Patent Document 1).
JP 2006-348873 A JP 2001-132555 A JP 2000-027715 A

  In the technique described in Patent Document 1, unburned fuel separated by the EGR cooler provided in the EGR passage is part of the fuel that is discharged to the exhaust passage and supplied to the exhaust purification device. However, the EGR gas contains a large amount of moisture, and the unburned fuel condensed by the EGR cooler is mixed with condensed water. For this reason, even if the unburned fuel is reused, the range in which the unburned fuel can be reused is limited as long as the condensed water is mixed with the unburned fuel.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for recovering and reusing unburned fuel by separating condensed water from EGR gas in an exhaust gas recirculation apparatus for an internal combustion engine. There is to do.

In the present invention, the following configuration is adopted. That is, the present invention
An EGR passage that takes in a part of exhaust gas from the exhaust passage of the internal combustion engine as EGR gas and recirculates the EGR gas to the intake passage of the internal combustion engine;
A cooling means arranged in the EGR passage and for cooling the EGR gas flowing through the EGR passage;
A reservoir for storing liquid condensed from the EGR gas cooled by the cooling means;
Of the liquid stored in the storage section, a condensed water discharge mechanism for discharging condensed water,
Of the liquid stored in the storage unit, unburned fuel recovery mechanism for recovering unburned fuel,
An exhaust gas recirculation device for an internal combustion engine.

  The EGR gas flowing through the EGR passage contains an unburned fuel component. For this reason, it is desired to recover only the unburned fuel from the EGR gas and reuse it.

  Therefore, in the present invention, the EGR gas flowing through the EGR passage is cooled, and the liquid condensed from the cooled EGR gas is stored in the storage unit. And while discharging condensed water among the liquid stored in the storage part, unburned fuel was collect | recovered among the liquid stored in the storage part.

  According to the present invention, the unburned fuel can be recovered by separating the condensed water from the EGR gas, and the recovered unburned fuel can be reused.

  The EGR gas may be cooled by the cooling means when the HC concentration of the EGR gas is equal to or higher than a predetermined concentration and the flow rate of the EGR gas is equal to or higher than a predetermined flow rate.

  Here, the HC concentration of the EGR gas is the concentration of the unburned fuel component of the EGR gas, and is the hydrocarbon concentration. The predetermined concentration of the HC concentration of the EGR gas is such that when the HC concentration is higher than that, the unburned fuel component contained in the EGR gas returns to the intake system of the internal combustion engine and causes a harmful effect on the intake system of the internal combustion engine. This is the threshold HC concentration at which the concentration is high. Further, when the EGR gas flow rate exceeds the predetermined flow rate, the unburned fuel component contained in the EGR gas recirculates to the intake system of the internal combustion engine and causes an adverse effect on the intake system of the internal combustion engine. The threshold flow rate is a large flow rate.

  According to the present invention, when the unburned fuel component contained in the EGR gas may cause a harmful effect on the intake system of the internal combustion engine, the EGR gas is cooled, and the unburned fuel component is condensed from the EGR gas. The unburned fuel component can be reduced. Therefore, adverse effects on the intake system of the internal combustion engine caused by the return of the unburned fuel component contained in the EGR gas to the intake system of the internal combustion engine can be suppressed. Further, when there is a possibility that the unburned fuel component contained in the EGR gas may cause a harmful effect on the intake system of the internal combustion engine, the unburned fuel component contained in the EGR gas is large, so that the unburned fuel is removed from the EGR gas. It can be efficiently condensed and recovered.

  When the condensed water is discharged from the liquid stored in the storage unit by the condensed water discharge mechanism and the amount of condensed water remaining in the storage unit becomes a predetermined amount or less, it is stored in the storage unit by the unburned fuel recovery mechanism. It is preferable to provide a control means for recovering unburned fuel in the liquid.

  Here, when the amount of condensed water remaining in the storage portion is less than the predetermined amount, it is possible to recover unburned fuel out of the liquid stored in the storage portion by the unburned fuel recovery mechanism. It is the amount of condensed water of the threshold.

  According to the present invention, after the condensed water is discharged from the liquid stored in the storage part, the unburned fuel is recovered from the liquid stored in the storage part. Only unburned fuel can be recovered.

  The unburned fuel recovery mechanism is configured so that the amount of the condensed water in the lower layer stored in the reservoir is determined from the liquid separated into the lower layer of condensed water stored in the reservoir and the upper unburned fuel layer. It is preferable to have an unburned fuel recovery passage that makes it possible to recover the upper layer unburned fuel stored in the storage section when the amount is below the fixed amount.

  According to the present invention, when the amount of the condensed water in the lower layer remaining in the storage portion becomes a predetermined amount or less, the upper layer unburned fuel stored in the storage portion can be recovered using the unburned fuel recovery passage.

  The control means may be implemented when a vehicle speed of a vehicle on which the internal combustion engine is mounted is equal to or lower than a predetermined speed.

  Here, when the vehicle speed is lower than the predetermined vehicle speed, the condensed water can be discharged from the liquid stored in the storage section, and the unburned fuel in the liquid stored in the storage section can be discharged. The threshold vehicle speed at which the vehicle can be collected is also included, and the vehicle speed when the vehicle is stopped is zero.

  According to the present invention, the condensed water can be discharged from the liquid stored in the storage unit, and the unburned fuel can be recovered from the liquid stored in the storage unit.

A turbocharger having a turbine disposed in the exhaust passage and a compressor disposed in the intake passage, wherein the EGR passage takes a part of the exhaust as low-pressure EGR gas from the exhaust passage downstream from the turbine; It may be a low pressure EGR passage that recirculates the low pressure EGR gas to the intake passage upstream of the compressor.

  According to the present invention, the unburned fuel can be recovered by separating the condensed water from the low-pressure EGR gas, and the recovered unburned fuel can be reused.

  It is preferable to provide an exhaust purification device that is disposed in the exhaust passage upstream of the connection portion with the low-pressure EGR passage and purifies the exhaust gas flowing through the exhaust passage.

  According to the present invention, even when unburned fuel supplied to the exhaust purification device passes through the exhaust purification device and is contained in the low-pressure EGR gas, the unburned fuel can be recovered by separating the condensed water from the low-pressure EGR gas, The recovered unburned fuel can be reused.

  According to the present invention, in an exhaust gas recirculation device for an internal combustion engine, condensed water can be separated from EGR gas, and unburned fuel can be recovered and reused.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas recirculation apparatus for an internal combustion engine according to this embodiment is applied, and an intake system and an exhaust system thereof. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders 2 that form a combustion chamber together with a piston. The internal combustion engine 1 is mounted on a vehicle. Each cylinder 2 is provided with a fuel injection valve 5 that is supplied with light oil from the fuel tank 3 through the fuel supply passage 4 and injects the light oil into the cylinder 2 at an appropriate amount and at an appropriate timing. . An intake passage 6 and an exhaust passage 7 are connected to the internal combustion engine 1.

  In the middle of the intake passage 6 connected to the internal combustion engine 1, a compressor 8a of a turbocharger 8 that operates using exhaust energy as a drive source is disposed. A first throttle valve 9 for adjusting the flow rate of intake air flowing through the intake passage 6 is disposed in the intake passage 6 upstream of the compressor 8a. The first throttle valve 9 is opened and closed by an electric actuator. An air flow meter 10 that outputs a signal corresponding to the flow rate of fresh air flowing through the intake passage 6 is disposed in the intake passage 6 upstream of the first throttle valve 9. The air flow meter 10 measures the intake air amount (fresh air amount) taken into the internal combustion engine 1.

  An intercooler 11 that performs heat exchange between the intake air and the outside air is arranged in the intake passage 6 downstream of the compressor 8a. A second throttle valve 12 that adjusts the flow rate of the intake air flowing through the intake passage 6 is disposed in the intake passage 6 downstream of the intercooler 11. The second throttle valve 12 is opened and closed by an electric actuator. The intake passage 6 and the devices arranged in the intake passage 6 constitute an intake system for taking intake air into the internal combustion engine 1.

  On the other hand, a turbine 8 b of a turbocharger 8 is arranged in the middle of the exhaust passage 7 connected to the internal combustion engine 1. A fuel addition valve 13 is provided in the exhaust passage 7 upstream of the turbine 8 b to add light oil to the exhaust gas flowing through the exhaust passage 7.

An exhaust purification device 14 is disposed in the exhaust passage 7 downstream of the turbine 8b. The exhaust purification device 14 includes an oxidation catalyst and a particulate filter (hereinafter simply referred to as a filter) disposed at the subsequent stage of the oxidation catalyst. The filter carries a NOx storage reduction catalyst (hereinafter simply referred to as NOx catalyst). The exhaust purification device 14 includes a so-called NO.
Light oil is supplied by adding light oil to the exhaust gas from the fuel addition valve 13 during the control for restoring the filter performance such as x reduction control, SOx poisoning recovery control, and PM oxidation removal control.

  Further, an HC concentration sensor 15 for detecting the HC concentration (hydrocarbon concentration) of the exhaust gas flowing in the exhaust passage 7 is provided in the exhaust passage 7 downstream of the exhaust purification device 14. The exhaust passage 7 and the devices arranged in the exhaust passage 7 constitute an exhaust system for exhausting exhaust gas from the internal combustion engine 1.

  The internal combustion engine 1 is provided with a high-pressure EGR device 20 that recirculates (recirculates) a part of the exhaust gas flowing through the exhaust passage 7 to the intake passage 6 at a high pressure. In this embodiment, the exhaust gas recirculated by the high pressure EGR device 20 is referred to as high pressure EGR gas.

  The high-pressure EGR device 20 includes a high-pressure EGR passage 21 through which the high-pressure EGR gas flows, and a high-pressure EGR valve 22 that adjusts the flow rate of the high-pressure EGR gas through the high-pressure EGR passage 21.

  The high pressure EGR passage 21 connects the exhaust passage 7 upstream of the turbine 8 b and the intake passage 6 downstream of the second throttle valve 12. Through this high-pressure EGR passage 21, the exhaust is sent to the internal combustion engine 1 at high pressure as high-pressure EGR gas.

  The high pressure EGR valve 22 is disposed in the high pressure EGR passage 21 and adjusts the flow rate of the high pressure EGR gas flowing through the high pressure EGR passage 21 by adjusting the passage sectional area of the high pressure EGR passage 21. The high pressure EGR valve 22 is opened and closed by an electric actuator. The adjustment of the high-pressure EGR gas flow rate can be performed by a method other than the adjustment of the opening degree of the high-pressure EGR valve 22. For example, by adjusting the opening degree of the second throttle valve 12, the differential pressure between the upstream and downstream of the high pressure EGR passage 21 can be changed, thereby adjusting the flow rate of the high pressure EGR gas.

  On the other hand, the internal combustion engine 1 is provided with a low pressure EGR device 30 that recirculates (recirculates) a part of the exhaust gas flowing through the exhaust passage 7 to the intake passage 6 at a low pressure. In this embodiment, the exhaust gas recirculated by the low pressure EGR device 30 is referred to as low pressure EGR gas.

  The low pressure EGR device 30 processes the low pressure EGR passage 31 through which the low pressure EGR gas flows, the low pressure EGR valve 32 for adjusting the flow rate of the low pressure EGR gas through the low pressure EGR passage 31, and the condensed liquid condensed from the low pressure EGR gas. And a condensed liquid processing apparatus 40.

  The low pressure EGR passage 31 connects the exhaust passage 7 downstream of the HC concentration sensor 15 and the intake passage 6 upstream of the compressor 8a and downstream of the first throttle valve 9. Through this low-pressure EGR passage 31, the exhaust is sent to the internal combustion engine 1 at low pressure as low-pressure EGR gas.

  The low-pressure EGR valve 32 is disposed in the low-pressure EGR passage 31 downstream from the condensate liquid processing device 40, and adjusts the passage cross-sectional area of the low-pressure EGR passage 31, thereby reducing the flow rate of the low-pressure EGR gas flowing through the low-pressure EGR passage 31. Adjust. The low pressure EGR valve 32 is opened and closed by an electric actuator. The low-pressure EGR gas flow rate can be adjusted by a method other than the adjustment of the opening degree of the low-pressure EGR valve 32. For example, by adjusting the opening of the first throttle valve 9 or by adjusting the opening of an exhaust throttle valve (not shown), the differential pressure between the upstream and downstream of the low pressure EGR passage 31 is changed. The flow rate of the low pressure EGR gas can be adjusted.

The condensed liquid processing apparatus 40 is disposed in the middle of the low pressure EGR passage 31. The condensed liquid processing apparatus 40 includes a cooling chamber 41 that cools the low-pressure EGR gas, a separation tank 42 that stores condensed liquid that is cooled and condensed in the cooling chamber 41, and a condensed liquid that is stored in the separation tank 42. Among them, a condensed water discharge passage 43 for discharging condensed water, a condensed water discharge valve 44 for opening and closing the condensed water discharge passage 43, and light oil as unburned fuel among the condensed liquid stored in the separation tank 42. And an unburned fuel recovery valve 46 for opening and closing the unburned fuel recovery passage 45.

  The cooling chamber 41 is a space portion interposed in the low pressure EGR passage 31 as shown in FIG. In the cooling chamber 41, a plurality of (three in the drawing) cooling fins 47 with which the flowing low-pressure EGR gas collides are provided. The cooling fins 47 are fixed to the top surface in the cooling chamber 41 and extend downward. Engine cooling water of the internal combustion engine 1 flows in the cooling fins 47. For this reason, in the cooling chamber 41, heat exchange is performed between the low-pressure EGR gas passing through the cooling chamber 41 and the engine cooling water in the cooling fins 47 to reduce the temperature of the low-pressure EGR gas and condense from the low-pressure EGR gas. Allow the liquid to condense. As for the engine cooling water to be circulated in the cooling fin 47, the engine cooling water can be circulated in the cooling fin 47 by opening the cooling water valve 48 disposed on the flow path of the engine cooling water. By closing the valve 48, the circulation of the engine cooling water into the cooling fin 47 can be prevented. The cooling water valve 48 is opened and closed by an electric actuator. The cooling chamber 41, the cooling fin 47, and the cooling water valve 48 in the present embodiment correspond to the cooling means of the present invention.

  As shown in FIG. 2, the separation tank 42 is provided in a lower part of the cooling chamber 41 and is a smaller tank than the cooling chamber 41 in order to collect the condensed liquid condensed in the cooling chamber 41. Here, the lower surface of the cooling chamber 41 is an inclined surface with the separation tank 42 side downward so that the condensed liquid from the cooling chamber 41 flows into the separation tank 42. A floating separation plate 49 is arranged in the separation tank 42. The floating separation plate 49 has an intermediate density (for example, a specific gravity of about 0.9) of water (specific gravity of about 1) and light oil (specific gravity of about 0.85) as fuel, and is provided so that condensed liquid can communicate. . In the separation tank 42, the condensed liquid is separated and stored in a lower layer of condensed water and an upper layer of light oil as unburned fuel. For this reason, the floating separation plate 49 always floats between the lower layer of condensed water and the upper layer of light oil. In addition, as shown in FIG. 2, when the floating separation plate 49 descends, that is, when the amount of condensed water in the lower layer falls below a predetermined amount, the lower portion in the separation tank 42 comes into contact with the floating separation plate 49. A floating separation plate detection sensor 50 for detecting the floating separation plate 49 is provided. Here, the predetermined amount of condensed water stored in the separation tank 42 is a threshold condensation that enables recovery of light oil from the condensed liquid stored in the separation tank 42 when the amount of condensed water is less than that. The amount of water. In the present embodiment, the floating separation plate detection sensors 50 are respectively installed at the four corners of the separation tank 42. The separation tank 42 in the present embodiment corresponds to the storage section of the present invention.

  As shown in FIG. 1, the condensed water discharge passage 43 connects the exhaust passage 7 downstream of the connection portion between the separation tank 42 and the low-pressure EGR passage 31. As shown in FIGS. 1 and 2, the condensed water discharge passage 43 is opened on the lower surface of the separation tank 42. Of the condensed liquid stored in the separation tank 42 from the opening, the lower condensed water is passed through the low pressure EGR passage. Then, the exhaust gas is discharged to the exhaust passage 7 downstream of the connection portion with 31.

  As shown in FIG. 2, the condensed water discharge valve 44 is arranged in the condensed water discharge passage 43, and the condensed water in the lower layer of the condensed liquid stored in the separation tank 42 by opening the condensed water discharge valve 44. Can circulate through the condensed water discharge passage 43 and close the condensed water discharge valve 44 to prevent the condensed water discharge passage 43 from flowing. The condensed water discharge valve 44 is opened and closed by an electric actuator. The condensed water discharge passage 43 and the condensed water discharge valve 44 in this embodiment correspond to the condensed water discharge mechanism of the present invention.

The unburned fuel recovery passage 45 connects the separation tank 42 and the fuel tank 3 as shown in FIG. The unburned fuel recovery passage 45 is opened to the lower side surface of the separation tank 42 as shown in FIGS. 1 to 3, and the upper layer light oil of the condensed liquid stored in the separation tank 42 from the opening is used as a fuel tank. Return to 3. Here, the opening position of the lower side surface of the separation tank 42 in the unburned fuel recovery passage 45 is as shown in FIG. 3B when the amount of condensed water in the lower layer of the condensed liquid stored in the separation tank 42 is less than a predetermined amount. As shown, it is a position that is located above the floating separation plate 49 and that can recover the upper layer of light oil stored in the separation tank 42. For this reason, the opening position is lower than the floating separation plate 49 as shown in FIG. 3A when the amount of condensed water in the lower layer of the condensed liquid stored in the separation tank 42 is larger than a predetermined amount. It is also a position to be immersed in the lower layer of condensed water stored in the separation tank.

  In the present embodiment, the unburned fuel recovery passage 45 returns the recovered light oil to the fuel tank 3, but the invention is not limited to this. For example, the recovered light oil adds light oil to the exhaust gas in the exhaust passage 7. The fuel addition valve 13 may be supplied and may be reused for any purpose.

  As shown in FIG. 2, the unburned fuel recovery valve 46 is disposed in the unburned fuel recovery passage 45, and the upper layer of the condensed liquid stored in the separation tank 42 by opening the unburned fuel recovery valve 46. The unburned fuel recovery passage 45 can be circulated, and the unburned fuel recovery valve 46 can be closed by closing the unburned fuel recovery valve 46. The unburned fuel recovery valve 46 is opened and closed by an electric actuator. In this embodiment, the unburned fuel recovery passage 45 and the unburned fuel recovery valve 46 correspond to the unburned fuel recovery mechanism of the present invention.

  The internal combustion engine 1 configured as described above is provided with an ECU 16 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 16 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  The ECU 16 is connected to the air flow meter 10, the HC concentration sensor 15, the floating separation plate detection sensor 50, the crank position sensor 17 for detecting the engine speed, and the vehicle speed sensor 18 for detecting the vehicle speed through electric wiring. Output signals of these various sensors are input to the ECU 16.

  On the other hand, the ECU 16 includes a fuel injection valve 5, a first throttle valve 9, a second throttle valve 12, a fuel addition valve 13, a high pressure EGR valve 22, a low pressure EGR valve 32, a condensed water discharge valve 44, and an unburned fuel recovery valve 46. , And the actuators of the cooling water valve 48 are connected via electric wiring, and these devices are controlled by the ECU 16.

  In this embodiment, the high-pressure EGR valve 22 is used to control the high-pressure EGR gas flow rate and the low-pressure EGR valve 32 is used to control the low-pressure EGR gas flow rate according to the operating state of the internal combustion engine 1. As a result, a so-called EGR operation is performed in which the internal combustion engine 1 is operated in a state in which high-pressure EGR gas and low-pressure EGR gas are contained in the intake air sucked into the internal combustion engine 1, and the oxygen concentration in the intake air is reduced to reduce the combustion temperature and combustion The effect of reducing NOx generated during combustion by reducing the speed is exhibited.

  By the way, the low pressure EGR gas sometimes passes through the light oil supplied from the fuel addition valve 13 to the exhaust gas purification device 14 by control for recovering the performance of the filter, and contains a large amount of light oil as an unburned fuel component. When light oil contained in the low-pressure EGR gas is returned to the intake system of the internal combustion engine 1 through the low-pressure EGR passage 31, it is carbonized (coking) by heat in the compressor 8a to inhibit smooth rotation of the compressor 8a. In addition, the low pressure EGR valve 32 and the first and second throttle valves 9 and 12 may be fixed, or the turbo impeller and the intercooler 11 may be corroded to cause harmful effects on the intake system of the internal combustion engine 1. There is.

  For this reason, it is necessary to remove the light oil which is an unburned fuel component from low pressure EGR gas. Generally, as a method of removing light oil that is an unburned fuel component from low-pressure EGR gas, a method of cooling the low-pressure EGR gas and condensing light oil from the low-pressure EGR gas is employed. However, the condensed liquid obtained by cooling the low-pressure EGR gas and condensing the low-pressure EGR gas contains not only light oil but also condensed water. Therefore, the reusable range is limited if the condensed liquid in which condensed water is mixed with light oil recovered from the low-pressure EGR gas is used.

  Therefore, in this embodiment, the condensed liquid processing apparatus 40 is arranged in the middle of the low pressure EGR passage 31. The condensed liquid processing apparatus 40 condenses the condensed liquid from the low-pressure EGR gas, discharges condensed water from the condensed condensed liquid, and collects light oil from the condensed liquid by separating it from condensed water.

  Here, first, the case where the low-pressure EGR gas is cooled by the condensed liquid processing apparatus 40 and the condensed liquid is condensed from the low-pressure EGR gas will be described.

  The light oil contained in the low-pressure EGR gas is not always contained in a certain amount. For example, when control for restoring the performance of the filter is performed, the content of the light oil becomes large. There will be a small amount of light oil content.

  Therefore, in this embodiment, when the HC concentration of the low pressure EGR gas is equal to or higher than the predetermined concentration and the flow rate of the low pressure EGR gas is equal to or higher than the predetermined flow rate, the cooling water valve 48 is opened and the engine cooling water is circulated in the cooling fins 47. The low-pressure EGR gas is cooled in the cooling chamber 41.

  Here, the HC concentration of the low-pressure EGR gas is the concentration of light oil that is an unburned fuel component contained in the low-pressure EGR gas. When the HC concentration of the low-pressure EGR gas is higher than the predetermined concentration, the light oil contained in the low-pressure EGR gas recirculates to the intake system of the internal combustion engine 1 and causes an adverse effect on the intake system of the internal combustion engine 1 This is the threshold HC concentration that becomes a higher concentration. Further, when the predetermined flow rate of the low-pressure EGR gas is higher than the predetermined flow rate, the light oil contained in the low-pressure EGR gas returns to the intake system of the internal combustion engine 1 to cause a harmful effect on the intake system of the internal combustion engine 1. It is a threshold flow rate that becomes a large flow rate.

  According to this embodiment, when the light oil, which is an unburned fuel component contained in the low-pressure EGR gas, may cause a harmful effect on the intake system of the internal combustion engine 1, the low-pressure EGR gas is cooled, and the light oil is converted from the low-pressure EGR gas. The condensed liquid containing can be condensed, and the light oil in the low pressure EGR gas can be reduced. Therefore, adverse effects on the intake system of the internal combustion engine 1 caused by the return of light oil, which is an unburned fuel component contained in the low-pressure EGR gas, to the intake system of the internal combustion engine 1 can be suppressed. Further, when there is a possibility that light oil, which is an unburned fuel component contained in the low-pressure EGR gas, may cause a harmful effect on the intake system of the internal combustion engine 1, the amount of light oil contained in the low-pressure EGR gas is large. Light oil can be efficiently condensed and removed from the gas.

  A control routine for cooling the low-pressure EGR gas according to this embodiment will be described. FIG. 4 is a flowchart showing a control routine for cooling the low-pressure EGR gas according to this embodiment. This routine is repeatedly executed every predetermined time.

  In step S <b> 101, the ECU 16 detects the HC concentration of the exhaust from the HC concentration sensor 15. Since the low-pressure EGR gas is a part of the exhaust from the exhaust passage 7 downstream of the HC concentration sensor 15, it can be said that the HC concentration detected by the HC concentration sensor 15 is the HC concentration of the low-pressure EGR gas.

In step S102, the ECU 16 calculates the flow rate of the low pressure EGR gas. Specifically, the engine speed NE of the internal combustion engine 1 read from the crank position sensor 17 and the fuel injection amount Q supplied from the fuel injection valve 5 into the cylinder are taken in a map obtained in advance through experiments or the like. Thus, the low-pressure EGR gas flow rate is calculated.

  In step S103, the ECU 16 determines whether or not the HC concentration of the low pressure EGR gas is equal to or higher than a predetermined concentration and the flow rate of the low pressure EGR gas is equal to or higher than a predetermined flow rate.

  In this determination, the HC concentration detected in step S101 and the low-pressure EGR gas flow rate calculated in step S102 are used.

  If it is determined in step S103 that the HC concentration of the low pressure EGR gas is equal to or higher than the predetermined concentration and the flow rate of the low pressure EGR gas is equal to or higher than the predetermined flow rate (HC concentration ≧ predetermined concentration and low pressure EGR gas flow rate ≧ predetermined flow rate), The process proceeds to S104. In step S103, a negative determination is made that the HC concentration of the low-pressure EGR gas is lower than a predetermined concentration, or the flow rate of the low-pressure EGR gas is lower than the predetermined flow rate (HC concentration <predetermined concentration or low-pressure EGR gas flow rate < In the case of (predetermined flow rate), the process proceeds to step S105.

  In step S104, the ECU 16 opens the cooling water valve 48. As a result, the engine cooling water flows into the cooling fins 47, and the low pressure EGR gas can be cooled in the cooling chamber 41. After the processing of this step, this routine is once ended.

  On the other hand, in step S105, the ECU 16 closes the cooling water valve 48. As a result, the engine cooling water does not flow into the cooling fins 47 and the low-pressure EGR gas cannot be cooled in the cooling chamber 41. After the processing of this step, this routine is once ended.

  By executing the above control routine, the low pressure EGR gas can be cooled when the HC concentration of the low pressure EGR gas is equal to or higher than the predetermined concentration and the flow rate of the low pressure EGR gas is equal to or higher than the predetermined flow rate. In this case, in other words, the light oil, which is an unburned fuel component contained in the low-pressure EGR gas, may cause a harmful effect on the intake system of the internal combustion engine 1. Therefore, cooling of the low pressure EGR gas can be carried out when there is a risk that light oil, which is an unburned fuel component contained in the low pressure EGR gas, may cause a harmful effect on the intake system of the internal combustion engine 1.

  Note that the cooling of the low-pressure EGR gas is not limited to the above control routine. For example, the cooling of the low-pressure EGR gas may be performed when control for recovering the performance of the filter is performed on the exhaust purification device 14.

  The condensed liquid in which condensed water and light oil are mixed condenses from the low-pressure EGR gas cooled as described above, and the condensed liquid droplets adhering to the cooling fins 47 and the like enter the separation tank 42 below the cooling chamber 41. It is dripped and flows on the inclined lower surface of the cooling chamber 41 and is collected and stored in the separation tank 42.

  Next, the case where condensed water is discharged from the condensed liquid stored in the separation tank 42 and the light oil is separated from the condensed water and recovered by the condensed liquid processing apparatus 40 will be described.

  The condensed liquid stored in the separation tank 42 is a mixture composed of condensed water and light oil. However, when a certain amount of time has elapsed after being stored in the separation tank 42, the condensed liquid is separated into condensed water and light oil. For this reason, in the separation tank 42, the condensed liquid is separated and stored in a lower layer of condensed water and an upper layer of light oil as unburned fuel. A floating separation plate 49 is located and floats between the lower condensed water layer and the upper light oil layer.

  In the present embodiment, when condensed water is discharged from the condensed liquid previously stored in the separation tank 42 and the amount of condensed water remaining in the separation tank 42 becomes a predetermined amount or less, the liquid stored in the separation tank 42 next. Of which, light oil is recovered. This control is called condensed liquid processing control.

  Specifically, when the condensed liquid is separated and stored in the lower condensed water layer and the upper light oil layer in the separation tank 42, the condensed liquid treatment control is first performed by opening the condensed water discharge valve 44. As shown in FIG. 3A, the condensed water in the lower layer of the condensed liquid stored in the separation tank 42 is caused to flow through the condensed water discharge passage 43, and the condensed water is discharged to the exhaust passage 7. During this time, in the separation tank 42, the condensed water in the lower layer decreases and the floating separation plate 49 also descends. Then, the floating separation plate 49 comes into contact with the floating separation plate detection sensor 50, and the floating separation plate detection sensor 50 detects the floating separation plate 49, and the amount of condensed water remaining in the separation tank 42 becomes a predetermined amount or less. Then, the condensate drain valve 44 is closed and the unburned fuel recovery valve 46 is opened, and the unburned fuel having an opening located above the floating separation plate 49 as shown in FIG. Of the liquid stored in the separation tank 42 in the fuel recovery passage 45, the upper layer of light oil is allowed to flow, and the light oil is recovered into the fuel tank 3.

  According to the present embodiment, after the condensed water in the lower layer of the liquid stored in the separation tank 42 is discharged, the upper layer of light oil in the liquid stored in the separation tank 42 is recovered. It is possible to collect only light oil by separating the oil.

  Here, when the vehicle is running, the condensed liquid in the separation tank 42 vibrates and the floating separation plate 49 also vibrates. For this reason, when the vehicle is running, the floating separation plate detection sensor 50 may not be able to detect the exact position of the floating separation plate 49. If the exact position of the floating separation plate 49 cannot be detected, the condensed water may flow into the unburned fuel recovery passage 45 during the condensed liquid treatment control, and the condensed water may be mixed into the light oil in the fuel tank 3.

  In this embodiment, therefore, the condensed liquid treatment control is performed when the vehicle in which the vehicle speed detected by the vehicle speed sensor 18 is 0 is stopped.

  When the vehicle is stopped, the condensed liquid in the separation tank 42 does not vibrate, and the floating separation plate 49 does not vibrate. Therefore, according to the present embodiment, the condensed liquid processing control is performed when the vehicle is stopped, so that the floating separation plate detection sensor 50 can detect the accurate position of the floating separation plate 49. Therefore, the condensed water is not accidentally caused to flow into the unburned fuel recovery passage 45 during the condensed liquid treatment control, and the condensed water is not mixed into the light oil in the fuel tank 3.

  In the present embodiment, the condensed liquid treatment control is performed when the vehicle in which the vehicle speed is 0 is stopped, but the present invention is not limited to this. For example, if the vehicle speed is lower than that, the condensate treatment can be performed if the vehicle speed is equal to or lower than a predetermined speed at which the condensed water can be discharged from the liquid stored in the separation tank 42 and the light oil can be recovered. You may make it do.

  A control routine for performing the condensed liquid treatment control according to this embodiment will be described. FIG. 5 is a flowchart showing a control routine for performing the condensate treatment control according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 16 that executes this routine corresponds to the control means of the present invention.

  In step S <b> 201, the ECU 16 detects the vehicle speed of the vehicle on which the internal combustion engine 1 is mounted from the vehicle speed sensor 18.

  In step S202, the ECU 16 determines whether the vehicle speed is 0, that is, whether the vehicle is in a stopped state.

  If it is determined in step S202 that the vehicle speed is 0 (vehicle speed = 0), the process proceeds to step S203. If a negative determination is made in step S202 that the vehicle speed is not (vehicle speed ≠ 0), this routine is temporarily terminated.

  In step S203, the ECU 16 determines whether or not the floating separation plate detection sensor 50 detects the floating separation plate 49.

  If it is determined in step S203 that the floating separator 49 is not detected (floating separator not detected), the process proceeds to step S204. If it is affirmed in step S203 that the floating separation plate 49 has been detected (floating separation plate detection), the process proceeds to step S205.

  In step S204, the ECU 16 opens the condensed water discharge valve 44 and closes the unburned fuel recovery valve 46. Thereby, the condensed water in the lower layer of the condensed liquid stored in the separation tank 42 is caused to flow through the condensed water discharge passage 43, and the condensed water is discharged to the exhaust passage 7. After the processing of this step, the process returns to step S203.

  On the other hand, in step S205, the ECU 16 closes the condensed water discharge valve 44 and opens the unburned fuel recovery valve 46. As a result, of the liquid stored in the separation tank 42 in the unburned fuel recovery passage 45, the upper layer of light oil is allowed to flow, and the light oil is recovered to the fuel tank 3.

  In step S206, the ECU 16 waits for a predetermined time. The predetermined time is set to the maximum time required for all of the recoverable light oil in the upper layer of the liquid stored in the separation tank 42 to flow into the unburned fuel recovery passage 45. Thereby, when a predetermined time has elapsed, all the light oil recoverable in the upper layer out of the liquid stored in the separation tank 42 flows into the unburned fuel recovery passage 45 and can be recovered in the liquid stored in the separation tank 42. The upper gas oil is gone.

  In step S207, the ECU 16 closes the condensed water discharge valve 44 and closes the unburned fuel recovery valve 46. Thereby, the condensed water and the condensed liquid of light oil can be stored again in the separation tank 42. After the processing of this step, this routine is once ended.

  By executing the above control routine, the condensate treatment control can be executed, the condensed water in the separation tank 42 can be discharged, and the light oil in the separation tank 42 can be separated and recovered from the condensed water.

  The exhaust gas recirculation apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram illustrating a schematic configuration of an internal combustion engine according to a first embodiment and intake and exhaust systems thereof. 1 is a diagram illustrating a schematic configuration of a condensed liquid processing apparatus according to Embodiment 1. FIG. It is a figure which shows the operation state in the separation tank of the condensed liquid processing apparatus which concerns on Example 1, (a) shows the state at the time of discharging | emitting condensed water, (b) shows the state at the time of collect | recovering light oil. Yes. 3 is a flowchart showing a control routine for cooling low-pressure EGR gas according to the first embodiment. 3 is a flowchart showing a control routine for performing condensate treatment control according to the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Fuel tank 4 Fuel supply passage 5 Fuel injection valve 6 Intake passage 7 Exhaust passage 8 Turbocharger 8a Compressor 8b Turbine 15 HC concentration sensor 17 Crank position sensor 18 Vehicle speed sensor 30 Low pressure EGR device 31 Low pressure EGR passage 32 Low pressure EGR valve 40 Condensed liquid processing device 41 Cooling chamber 42 Separation tank 43 Condensate water discharge passage 44 Condensate water discharge valve 45 Unburned fuel recovery passage 46 Unburned fuel recovery valve 47 Cooling fin 48 Cooling water valve 49 Floating separation plate 50 Floating separation plate Detection sensor

Claims (7)

An EGR passage that takes in a part of exhaust gas from the exhaust passage of the internal combustion engine as EGR gas and recirculates the EGR gas to the intake passage of the internal combustion engine;
A cooling means arranged in the EGR passage and for cooling the EGR gas flowing through the EGR passage;
A reservoir for storing liquid condensed from the EGR gas cooled by the cooling means;
Of the liquid stored in the storage section, a condensed water discharge mechanism for discharging condensed water,
Of the liquid stored in the storage unit, unburned fuel recovery mechanism for recovering unburned fuel,
An exhaust gas recirculation device for an internal combustion engine, comprising:   2. The internal combustion engine according to claim 1, wherein when the HC concentration of the EGR gas is equal to or higher than a predetermined concentration and the flow rate of the EGR gas is equal to or higher than a predetermined flow rate, the cooling of the EGR gas is performed by the cooling means. Exhaust gas recirculation device.   When the condensed water is discharged from the liquid stored in the storage unit by the condensed water discharge mechanism and the amount of condensed water remaining in the storage unit becomes a predetermined amount or less, it is stored in the storage unit by the unburned fuel recovery mechanism. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 1 or 2, further comprising a control means for recovering unburned fuel in the liquid.   The unburned fuel recovery mechanism is configured so that the amount of the condensed water in the lower layer stored in the reservoir is determined from the liquid separated into the lower layer of condensed water stored in the reservoir and the upper unburned fuel layer. 4. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 3, further comprising an unburned fuel recovery passage that enables recovery of upper unburned fuel stored in the storage portion when the amount is below a predetermined amount.   The exhaust gas recirculation device for an internal combustion engine according to claim 3 or 4, wherein the control means is implemented when a vehicle speed of a vehicle on which the internal combustion engine is mounted is equal to or lower than a predetermined speed. A turbocharger having a turbine disposed in the exhaust passage and a compressor disposed in the intake passage;
The EGR passage is a low-pressure EGR passage that takes a part of exhaust gas as low-pressure EGR gas from the exhaust passage downstream from the turbine and recirculates the low-pressure EGR gas to the intake passage upstream from the compressor. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 5.   The exhaust gas recirculation of the internal combustion engine according to claim 6, further comprising an exhaust gas purification device that is disposed in the exhaust passage upstream of a connection portion with the low pressure EGR passage and purifies exhaust gas flowing through the exhaust passage. apparatus.

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