JP2009085094A - Exhaust gas recirculation device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent poor combustion and suppress NO<SB>x</SB>by using high-temperature EGR gas when an engine is cold, and also to rapidly warm up the engine by heat exchange at a cooling device with the exhaust gas. <P>SOLUTION: An exhaust gas recirculation device includes a cooled exhaust gas passage, a cooled exhaust gas cutoff valve for passing and cutting off the exhaust gas flowing through the cooled exhaust gas passage, and an exhaust gas cutoff valve for passing and cutting off the exhaust gas flowing through an exhaust passage. The exhaust gas is passed and cut off depending on the warming-up conditions of the engine, so that it is possible to prevent the poor combustion and also to suppress NO<SB>x</SB>to be discharged by using the high-temperature EGR gas when the engine is cold, and it is further possible to rapidly warm up the engine with the heat exchange by introducing the exhaust gas into the cooling device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to control of an exhaust gas recirculation device for an engine.

Diesel engines equipped with an exhaust gas recirculation device (hereinafter referred to as EGR) that recirculates engine exhaust gas to the intake side and reduces NO _x in the exhaust are widely used. EGR cooled by a cooling device using coolant of the engine as a refrigerant is used so that the temperature does not rise too much. However, when cold EGR is used in the cold state, there is a problem that the combustion temperature is too low and combustion failure occurs. On the other hand, when the engine is cold, combustion of the engine becomes unstable and fuel consumption deteriorates, so there is a need to warm up the engine early by flowing exhaust into the cooling device and raising the engine coolant temperature. . Based on this problem, the following prior art document 1 recirculates the EGR cooled by the cooling device to the intake passage when it is warm, and warms and cools the engine by exchanging heat with the exhaust gas using the cooling device on the EGR passage when the engine is cold. A technique for preventing a decrease in combustion temperature by flowing exhaust gas from the bypass passage to the exhaust passage without using it for EGR has been proposed.
JP 11-125149 A

However, in the types of exhaust gas recirculation device disclosed in Patent Document 1, when the engine is warm, but suppresses the emission of the NO _X by the use of low temperature EGR, it does not use EGR during cold engine of the NO _X emissions There is a problem of increasing the amount.

An object of the present invention, in the engine cold is both a high temperature preventing combustion failure according to EGR used and NO _X emissions, more early warm-up of the engine due to heat exchange by flowing the exhaust cooling apparatus The aim is to propose an achievable exhaust gas recirculation device.

  The first configuration of the exhaust gas recirculation apparatus according to the present invention is a high-temperature EGR passage that is connected to the exhaust passage and recirculates a part of the exhaust gas to the intake passage, and an exhaust gas downstream from a connection portion between the high-temperature EGR passage and the exhaust passage. A low temperature EGR passage that is connected to the passage and is provided with a cooling device that uses an engine cooling medium as a refrigerant to recirculate exhaust gas having a temperature lower than that of the exhaust gas recirculated from the high temperature EGR passage to the intake passage; and a high temperature EGR passage A high-temperature EGR valve that adjusts the flow rate of the exhaust gas recirculated from the low-temperature EGR valve, a low-temperature EGR valve that adjusts the flow rate of the exhaust gas recirculated from the low-temperature EGR passage, and a control unit that controls the high-temperature EGR valve and the low-temperature EGR valve. In the exhaust gas recirculation device, a cooling exhaust passage connecting the low temperature EGR passage and the exhaust passage between the low temperature EGR valve and the cooling device, and an engine for detecting a warm-up state of the engine A warm-up state detection unit, and when the detection unit detects that the engine is not in a warm-up state, the control unit fully closes the low-temperature EGR valve and opens the high-temperature EGR valve. Thus, only the exhaust from the high temperature EGR passage is recirculated to the intake passage.

According to the first configuration, the high temperature EGR can be returned to the engine by fully closing the low temperature EGR valve and returning only the exhaust gas in the high temperature EGR passage to the intake passage. Therefore, we achieve both suppression of emission of prevention and NO _X of incomplete combustion due to the combustion temperature decreases. In addition, since at least part of the exhaust passes through the cooling device and then returns to the exhaust passage through the low temperature exhaust passage, the effect of early engine warm-up can be obtained by heat exchange between the cooling device and the engine coolant. Can do.

  The second configuration relating to the present invention is a configuration in which the high temperature EGR passage recirculates a part of the exhaust gas to the intake passage without passing through the cooling device.

According to a second configuration, it becomes possible to the hot EGR passage recirculates hotter EGR by not providing the cooling device is more effective suppression of the emission of prevention and NO _X in the combustion failure .

A third configuration according to the present invention includes a first connection portion that connects the low temperature EGR passage and the exhaust passage, a second connection portion that connects the cooling exhaust passage and the exhaust passage, and the first connection portion. An exhaust shut-off valve capable of shutting off the exhaust flowing through the exhaust passage between the second connection portion, and the control means is configured to also control the exhaust shut-off valve, the control means Controls the exhaust shut-off valve to shut off the flow through the exhaust passage between the first connection and the second connection when the detection means detects that the engine is not warmed up. It is the structure to do.

  According to the third configuration, between the first connection portion connecting the exhaust passage and the low temperature EGR passage in the exhaust passage, and the second connection portion connecting the exhaust passage and the cooling exhaust passage. An exhaust cutoff valve that can shut off the exhaust gas flowing through the exhaust passage is provided, and the exhaust gas that flows between the first connection portion and the second connection portion in the exhaust passage is blocked by the exhaust cutoff valve when the engine is cold by the control means. Thus, the entire amount of exhaust gas passes through the cooling device, and heat exchange between the cooling device and the exhaust gas can be performed more effectively, and the engine can be warmed up.

A fourth configuration according to the present invention includes a cooling / exhaust cutoff valve capable of blocking the flow of exhaust gas in the cooling / exhaust passage, and the control means is configured to also control the cooling / exhaust cutoff valve. The control means controls the cooling exhaust cutoff valve so as to shut off the flow of exhaust gas between the cooling exhaust passage and the exhaust passage when the detection means detects that the engine is warming up. It is the structure to do.

  According to the fourth configuration, there is provided a cooling exhaust shutoff valve capable of shutting off the flow of exhaust gas in the cooling exhaust passage, and the cooling exhaust passage and the exhaust in the upper air cooling exhaust shutoff valve when the engine is warm by the control means. By shutting off the exhaust flowing between the passages, only the exhaust that recirculates from the low-temperature EGR passage to the intake passage exchanges heat between the cooling device and the engine coolant, and exhausts other exhaust not used for EGR from the exhaust passage. This can prevent unnecessary warm-up when the engine is warm.

  A fifth configuration according to the present invention includes a first connection portion that connects the low temperature EGR passage and the exhaust passage, a second connection portion that connects the cooling exhaust passage and the exhaust passage, the exhaust passage and the cooling passage. A selection valve that can selectively select a state of communicating with the exhaust passage and a state of communicating the exhaust passage between the first connecting portion and the second connecting portion; The control means is configured to control the selection valve, and the control means communicates the exhaust passage and the cooling exhaust passage when the detection means detects that the engine is not warmed up. The selection valve is controlled so that the exhaust passage is communicated between the first connection portion and the second connection portion when the detection means detects that the engine is warmed up. To control the selection valve A.

  According to the fifth configuration, the first connection part connecting the exhaust passage and the low temperature EGR passage, and the second connection part connecting the exhaust passage and the cooling exhaust passage are provided, and the exhaust A selection valve that can alternatively select whether the passage communicates with the cooling exhaust passage or the first connection portion and the second connection portion communicate with each other in the exhaust passage; By connecting the exhaust gas passing between the first connection part and the second connection part in the exhaust passage in the warm state and shutting off the exhaust gas passing between the second connection part and the cooling exhaust passage, the low temperature EGR passage Only the exhaust gas that recirculates to the intake passage is heat-exchanged between the cooling device and the cooling water of the engine, and exhaust that is not used for other EGR is exhausted from the exhaust passage to prevent unnecessary warm-up when the engine is warm. it can. Further, when cold, the exhaust gas passing between the second connection portion and the cooling exhaust passage is communicated, and the exhaust gas passing between the first connection portion and the second connection portion in the exhaust passage is shut off. Thus, the entire amount of exhaust gas can be passed through the cooling device, and heat exchange between the cooling device and the exhaust gas can be performed more effectively, and the engine can be warmed up. Since the above control is performed with a single valve, the control is simple and the number of parts can be reduced.

As described above, according to the present invention, the cooling exhaust passage is provided, and only the high temperature EGR is recirculated to the intake passage when the engine is cold, and the exhaust is heat exchanged with the cooling water of the engine of the cooling device. When cold, it is possible to achieve both prevention of combustion failure by using high-temperature EGR and suppression of NO _x emission, and further achieve early warm-up of the engine.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows an example of an exhaust gas recirculation apparatus A for an engine according to an embodiment of the present invention. Reference numeral 1 denotes a diesel engine mounted on a vehicle. This engine 1 has a plurality of cylinders 2, 2,... (Only one is shown), and a piston 3 is fitted into each cylinder 2 so as to be reciprocable. The combustion chamber 4 is partitioned. In addition, an injector 5 (fuel injection valve) is disposed on the ceiling of the combustion chamber 4, and high-pressure fuel is directly injected into the combustion chamber 4 from the nozzle at the tip.

  In addition, although illustration is abbreviate | omitted, the structure which supplies a fuel to the injector 5 for every cylinder 2 is what is called a common rail type provided with the common fuel distribution pipe (common rail) to which each injector 5 is connected, An output signal of a fuel pressure sensor for detecting the fuel pressure inside the common rail (common rail pressure) is input to the ECU 40 described later, and the ECU 40 controls the common rail pressure.

  A valve operating mechanism (not shown) that opens and closes the intake valve 81 and the exhaust valve 82 is disposed at the top of the engine 1.

  An intake passage 16 for supplying air (fresh air) filtered by an air cleaner (not shown) to the combustion chamber 4 of each cylinder 2 is connected to one side (right side in the figure) of the engine 1. . In the intake passage 16, an intake throttle valve 22 including a butterfly valve, a compressor 20 driven by a turbine 27 described later to compress intake air, and intake air compressed by the compressor 20 in order from the upstream side to the downstream side. And an intercooler (I / C) path throttle valve 23 composed of a butterfly valve.

  On the other hand, an exhaust passage 26 for discharging combustion gas (exhaust gas) from the combustion chamber 4 of each cylinder 2 is connected to the opposite side (left side in the figure) of the engine 1. The upstream end portion of the exhaust passage 26 is an exhaust manifold that branches into each cylinder 2 and communicates with the combustion chamber 4 through an exhaust port. The exhaust passage 26 downstream from the exhaust manifold is provided on the downstream side from the upstream side. A turbine 27 that is rotated in response to the exhaust flow, a diesel oxidation catalyst 28 that can purify harmful components (HC, CO, NOx, soot, etc.) in the exhaust, and a catalyzed DPF (Diesel Particulate Filter) 29 Are disposed.

  In this embodiment, the turbocharger 30 including the turbine 27 and the compressor 20 in the intake passage 16 is configured to change the cross-sectional area of the exhaust gas to the turbine 27 by movable flaps 31, 31,. It is a variable turbocharger (Variable Geometry Turbosupercharger: hereinafter referred to as VGT), and the supercharging pressure of intake air is controlled by controlling the VGT 30 by the ECU 40 described later.

  The exhaust passage 26 has a first exhaust gas recirculation passage (hereinafter referred to as a first EGR passage) 34 for recirculating a part of the exhaust gas to the intake side so as to open toward a portion of the exhaust gas downstream of the catalyzed DPF 29. Is connected to the first connecting portion 90. The downstream end of the first EGR passage 34 is connected to the intake passage 16 between the intake throttle valve 22 and the compressor 20, and a part of the exhaust gas taken out from the exhaust passage 26 is returned to the intake passage 16. ing. Further, in the middle of the first EGR passage 34, an EGR cooler 37 that cools the exhaust gas flowing through the first EGR passage 34 by heat exchange with the engine cooling water, and an exhaust gas recirculation amount that can be adjusted in opening degree downstream of the EGR cooler 37. A control valve (hereinafter referred to as a first EGR valve) 35 is disposed. A cooling exhaust passage 60 extends from the downstream side of the EGR cooler 37 and between the first EGR valve 35, and is connected to the exhaust passage 26 at the second connection portion 91. With the above structure, the exhaust gas cooled by the EGR cooler 37 on the first EGR passage 34 is recirculated to the intake passage 16 or flows into the exhaust passage 26 through the cooling exhaust passage 60. A cooling exhaust shut-off valve 70 is provided on the cooling exhaust passage 60 so that the exhaust does not flow into the cooling exhaust passage 60 when the cooling exhaust shut-off valve 70 is closed. An exhaust cutoff valve 71 is provided between the second connection portion 91 between the cooling exhaust passage 60 and the exhaust passage 26, and the first connection portion between the first EGR passage 34 and the exhaust passage 26. When is closed, the entire amount of exhaust gas passes through the EGR cooler 37.

  An upstream end of a second exhaust gas recirculation passage (hereinafter referred to as a second EGR passage) 44 is connected to the exhaust manifold. The downstream end of the second EGR passage 44 is connected to the intake passage 16 on the downstream side of the intercooler 21 (I / C path throttle valve 23). Further, a second exhaust gas recirculation amount adjustment valve (hereinafter referred to as a second EGR valve) 45 capable of opening adjustment is disposed in the middle of the second EGR passage 44.

Each injector 5, intake throttle valve 22, I / C path throttle valve 23, VGT 30, first and second EGR valves 35, 45, cooling exhaust cutoff valve 70, exhaust cutoff valve 71, selection valve 72, etc. Also operates in response to a control signal from a control unit (Electronic Control Unit: ECU) 40. On the other hand, the ECU 40 includes at least an engine water temperature sensor 50 that detects a coolant temperature of the engine 1, a crank angle sensor 51 that detects a rotation angle of a crankshaft of the engine 1, an intake pressure sensor 52 that detects an intake pressure state, A linear O ₂ sensor 53 that detects the oxygen concentration in the exhaust, an air flow sensor 54 that detects the flow rate of air that is sucked into the engine 1 from the outside, an intake air temperature sensor 55 that detects the temperature of the intake air after EGR gas mixing, and An output signal from an accelerator opening sensor 56 that detects an operation amount (accelerator opening) of an omitted accelerator pedal is input.

(Outline of engine combustion control)
The basic control of the engine 1 by the ECU 40 is to determine the basic target fuel injection amount mainly based on the accelerator opening, and to control the fuel injection amount, the injection timing, etc. by the operation control of the injector 5. It is. Further, the recirculation ratio of the exhaust gas to the combustion chamber 4 is controlled by controlling the opening degree of the intake throttle valve 22 and the first EGR valve 35, and the supercharging of the intake air is performed by the operation control (VGT control) of the flaps 31, 31,. Increase efficiency. Further, as control characteristic of the combustion mode according to the present invention, the intake air temperature after mixing the EGR gas is adjusted by controlling the opening degree of the first and second EGR valves 35 and 45. However, when the engine coolant temperature is equal to or lower than a predetermined value, the intake air temperature after the EGR gas mixture is adjusted by controlling the opening degree of only the second EGR valve 45. By controlling the opening of the cooling exhaust shutoff valve 70 and the exhaust shutoff valve 71, communication / blocking of exhaust flowing through the exhaust passage 26, the second EGR passage 34, and the cooling exhaust passage 60 is controlled.

(Valve control of exhaust system)
Next, the control of the cooling / exhaust adjusting valve 70 provided in the cooling exhaust passage 60 and the exhaust adjusting valve 71 provided in the exhaust passage 26 will be described based on the flowchart of FIG. In S1, the detected value of the engine water temperature sensor 50 is input to the ECU 40. Detection values of the engine coolant temperature sensor 50 that is input to S2 the ECU40 determines whether the following or above a predetermined value T _w. Detection values of the engine coolant temperature sensor 50 advances to step S3 is determined at warm if above a predetermined value T _w, cooled exhaust cutoff valve 70 is fully closed to block the exhaust gas passing through the cooling exhaust passage 60. At the same time, in S4, the exhaust cutoff valve 71 is fully opened. Further, in S5 and S6, as described above, the opening degree of the first and second EGR valves 35 and 45 is adjusted in order to adjust the intake air temperature after the EGR mixing. As described above, since only the exhaust gas recirculated to the intake passage passes through the EGR cooler 37, heat exchange with the cooling water of the engine 1 can be minimized, and unnecessary warm-up of the engine 1 is suppressed. . If the engine coolant temperature is less than T _w in S2 is determined that the cold, to fully open the cooling exhaust cutoff valve 70 proceeds to S7, the exhaust cutoff valve 71 is fully closed in S6 simultaneously, the first 1EGR valve 35 in S9 simultaneously By fully closing, the entire amount of exhaust discharged from the engine 1 passes through the EGR cooler 37 and exchanges heat with the cooling water of the engine 1, so that warm-up of the engine 1 can be promoted. In S10, as described above, the opening degree of the second EGR valve 45 is adjusted in order to adjust the intake air temperature after the EGR mixing.

As described above, in the exhaust gas recirculation apparatus A according to the present embodiment, the cooling exhaust shutoff valve 70 is fully closed when the engine is warm, and only the exhaust gas recirculated to the intake passage is cooled by the EGR cooler 37. In the cold state, the first EGR valve 35 is fully closed and only the high temperature EGR is recirculated while the exhaust cutoff valve 70 is fully closed, and the entire amount of exhaust discharged from the engine 1 passes through the EGR cooler 37. Te since such that the cooling water exchanges heat with the engine 1, at the time of a warm prevents warm-up of unwanted engine, at the time of cold is both a high temperature preventing combustion failure according to EGR used and NO _X emissions, further Makes it possible to achieve early engine warm-up by heat exchange by allowing exhaust to flow into the cooling device.

  FIG. 3 shows an example of an exhaust gas recirculation apparatus B for an engine according to another embodiment of the present invention. The same components as those in the above embodiment are given the same reference numerals and redundant description thereof is omitted. The difference from the exhaust gas recirculation device A described above is that a selection valve 72 is provided in place of the cooling exhaust gas adjustment valve 70 and the exhaust gas adjustment valve 71. The selection valve 72 is provided in a connection portion (second connection portion 91) between the exhaust passage 26 and the cooling exhaust passage 60, and is fully closed to the exhaust passage side under the control of the ECU 40 to connect the exhaust gas in the exhaust passage 26. It is alternatively possible to control whether to shut off or to fully close the cooling exhaust passage side to cut off the communication between the exhaust passage 26 and the cooling exhaust passage 60.

(Selective valve control)
Next, control of the selection valve 72 will be described based on the flowchart of FIG. At T1, the detected value of the engine water temperature sensor 50 is input to the ECU 40. Detection values of the engine coolant temperature sensor 50 in the ECU40 is input T2 determines whether above a predetermined value T _w. If the detected values of the engine coolant temperature sensor 50 is above a predetermined value T _w, is determined during a warm proceeds to T3, and the exhaust passage 26 in the fully closed selector valve 72 to the cooling exhaust passage 60 side and the cooling exhaust passage 60 Block communication. Thus, when the low temperature EGR valve 35 is open, the low temperature EGR is returned to the intake passage through the EGR cooler 37 from the first connection portion 90. At T4 and T5, as described above, the opening degree of the first and second EGR valves 35 and 45 is adjusted in order to adjust the intake air temperature after EGR mixing. Thus, since only the exhaust gas recirculated during the warm period exchanges heat with the cooling water of the engine 1 in the EGR cooler 37, unnecessary warm-up of the engine 1 can be suppressed. On the other hand, if the detected value of the engine water temperature sensor 50 is equal to or _smaller than the predetermined value Tw at T2, the process proceeds to T6 because it is determined that the engine is cold, and the exhaust flowing through the exhaust passage 26 with the selection valve 72 fully closed on the exhaust passage 26 side. Shut off. At the same time, the first EGR valve 35 is fully closed at T7, so that the total amount of exhaust gas passes through the EGR cooler 37 from the second connection portion 91 and returns to the exhaust passage 26 at the first connection portion 90. At T8, as described above, the opening degree of the second EGR valve 45 is adjusted in order to adjust the intake air temperature after the EGR mixing. In this way, when the engine is cold, the entire amount of exhaust discharged from the engine 1 exchanges heat with the cooling water of the engine 1 in the EGR cooler 37, so that early warm-up of the engine can be achieved.

  FIG. 5 is a diagram showing in detail the state of the selection valve 72 and the flow of exhaust when the exhaust gas recirculation apparatus B is warm. The arrows in the figure indicate the flow of exhaust. As described above, in the warm state, the first EGR valve 35 is opened to control the temperature of the recirculating EGR, and the selection valve 72 is fully closed to the cooling exhaust passage 60 side. Only the exhaust gas recirculated as low-temperature EGR is cut off from the EGR cooler 37 and the first EGR passage 34.

FIG. 6 is a diagram showing in detail the state of the selection valve and the flow of exhaust when the exhaust gas recirculation apparatus B is cold. As in FIG. 5, the arrows indicate the flow of exhaust. As described above, when cold, the first EGR valve 35 is closed and the selection valve 72 is fully closed on the exhaust passage 26 side to cut off communication between the first connection portion 90 and the second connection portion 91 in the exhaust passage. Therefore, the total amount of exhaust gas passes through the EGR cooler 37 from the second connection portion 91 and returns to the exhaust passage 26 at the first connection portion 90.

As described above, also in the exhaust gas recirculation apparatus B according to the present embodiment, when the engine is warm, the selection valve 72 is fully closed to the cooling exhaust passage 60 side, and only the exhaust gas recirculated to the intake passage is sent to the engine in the EGR cooler 37. In the cold state, the first EGR valve 35 is fully closed and only the high-temperature EGR is recirculated while the selection valve 72 is fully closed on the exhaust passage 26 side while the heat is being exchanged. since the total amount was set to pass through the EGR cooler 37 for cooling water exchanges heat with the engine 1, at the time of a warm prevent warm-up of unwanted engine, at the time of cold and prevention of combustion failure due to high temperature of EGR using NO _X An effect similar to that of the exhaust gas recirculation device A is achieved, in which the exhaust gas is introduced into the cooling device and the engine is warmed up early by heat exchange.

  Then, by controlling only the selection valve 72, it is alternatively selected whether the exhaust passage 26 and the cooling exhaust passage 60 are communicated or the first connection portion 90 and the second connection portion 91 are communicated in the exhaust passage. Because it is possible, the control is simple and the number of parts can be reduced.

  In the above-described embodiment, in the exhaust gas recirculation apparatus A, the exhaust cutoff valve 71 is fully closed when cold. However, the exhaust cutoff valve 71 is not limited thereto, and at least a part of the exhaust gas flows into the cooling exhaust passage 60. The degree of opening may be reduced (not fully closed). Similarly, in the exhaust gas recirculation apparatus B, the selection valve 72 is fully closed on the exhaust passage 26 side when it is cold. However, the selection is not limited to this, and at least a part of the exhaust gas flows into the cooling exhaust passage 60. The opening degree of the valve 72 may be adjusted.

  In addition, although both the exhaust gas recirculation devices A and B are configured not to provide an EGR cooler in the second EGR passage 44, if the EGR having a temperature higher than that of the first EGR passage 34 can be recirculated, the first EGR passage 34 and Similarly, an EGR cooler may be provided.

1 is an overall configuration diagram of an exhaust gas recirculation device A for an engine according to an embodiment of the present invention. Exhaust gas recirculation apparatus A exhaust system valve control flowchart Overall configuration diagram of an exhaust gas recirculation apparatus B for an engine according to another embodiment of the present invention Exhaust system control flowchart for exhaust gas recirculation device B The figure showing the state of the selection valve and the flow of exhaust when the exhaust gas recirculation device B is warm The figure showing the state of the selection valve and the flow of exhaust when the exhaust gas recirculation device B is cold

Explanation of symbols

A, B Engine exhaust purification device 1... Engine 4... Combustion chamber 26 .. exhaust passage 34 .. 1st EGR passage (low temperature EGR passage)
35 ... 1st EGR valve (low temperature EGR valve)
37 ... EGR cooler (cooling device)
37... ECU (including detection means and control means)
44 ... 2nd EGR passage (high temperature EGR passage)
45 ... 2nd EGR valve (high temperature EGR valve)
60 ... Cooling exhaust passage 70 ... Cooling exhaust shutoff valve 71 ... Exhaust shutoff valve 72 ... Selection valve 90 ... First connection part 91 ... Second connection part

Claims (5)

A high temperature EGR passage connected to the exhaust passage and returning a part of the exhaust to the intake passage;
A cooling device that is connected to the exhaust passage downstream of the connection portion between the high-temperature EGR passage and the exhaust passage and uses a cooling medium of the engine as a refrigerant is disposed, and has a lower temperature than the exhaust gas recirculated from the high-temperature EGR passage. A low temperature EGR passage that recirculates the exhaust gas to the intake passage;
A high temperature EGR valve that adjusts the flow rate of exhaust gas recirculated from the high temperature EGR passage, and a low temperature EGR valve that adjusts the flow rate of exhaust gas recirculated from the low temperature EGR passage;
In the exhaust gas recirculation apparatus provided with control means for controlling the high temperature EGR valve and the low temperature EGR valve,
A cooling exhaust passage connecting the low temperature EGR passage and the exhaust passage between the low temperature EGR valve and the cooling device;
Engine warm-up state detection means for detecting the warm-up state of the engine,
When the detecting means detects that the engine is not warmed up, the control means fully closes the low-temperature EGR valve and opens the high-temperature EGR valve to intake only the exhaust from the high-temperature EGR passage. An exhaust gas recirculation device for an engine characterized by being configured to recirculate to a passage.   2. The engine exhaust gas recirculation device according to claim 1, wherein the high temperature EGR passage causes a part of exhaust gas to recirculate to the intake air passage without passing through a cooling device. A first connecting portion connecting the low temperature EGR passage and the exhaust passage;
A second connecting portion connecting the cooling exhaust passage and the exhaust passage;
An exhaust cutoff valve capable of shutting off the exhaust gas flowing through the exhaust passage between the first connection portion and the second connection portion;
The control means is configured to be able to control the exhaust cutoff valve,
When the detection means detects that the engine is not warmed up, the control means cuts off the exhaust gas so as to cut off the flow through the exhaust passage between the first connection part and the second connection part. 3. The engine exhaust gas recirculation device according to claim 1, wherein the valve is controlled. A cooling exhaust shutoff valve capable of shutting off the flow of exhaust gas in the cooling exhaust passage,
The control means is configured to be able to control the cooling exhaust cutoff valve,
The control means controls the cooling exhaust shut-off valve so as to shut off the flow of exhaust gas between the cooling exhaust passage and the exhaust passage when the detection means detects that the engine is warmed up. The exhaust gas recirculation device for an engine according to any one of claims 1, 2, and 3. A first connecting portion connecting the low temperature EGR passage and the exhaust passage;
A second connecting portion connecting the cooling exhaust passage and the exhaust passage;
A selection valve that can selectively select a state in which the exhaust passage and the cooling exhaust passage are communicated and a state in which the exhaust passage is communicated between the first connection portion and the second connection portion. Have
The control means is configured to be able to control the selection valve,
When the detection means detects that the engine is not warmed up, the control means controls the selection valve so as to connect the exhaust passage and the cooling exhaust passage, while the detection means 2. When the warm-up state is detected, the selection valve is controlled to communicate the exhaust passage between the first connection portion and the second connection portion. 2. The exhaust gas recirculation device for an engine according to any one of the preceding claims.

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