WO2018012409A1

WO2018012409A1 - Egr device

Info

Publication number: WO2018012409A1
Application number: PCT/JP2017/024867
Authority: WO
Inventors: 岩崎　充; 松平　範光
Original assignee: カルソニックカンセイ株式会社
Priority date: 2016-07-15
Filing date: 2017-07-06
Publication date: 2018-01-18

Abstract

An EGR device (100) that returns a portion of the exhaust gas discharged from an engine (20) from an exhaust flow path (33) to an intake flow path (13). The EGR device (100) is equipped with: an EGR cooler (50) that, by means of cooling water flowing as a coolant through the interior of the EGR cooler, cools the exhaust gas guided from the exhaust flow path (33); a bypass flow path (64) that guides the exhaust gas that has passed through the EGR cooler (50) to the exhaust flow path (33); and a bypass opening/closing valve (65) that is provided in the bypass flow path (64), and switches the flow of the exhaust gas passing through the bypass flow path (64). The bypass opening/closing valve (65) is opened when the engine cooling water temperature Tw, which is the temperature of the coolant flowing through the interior of the EGR cooler (50), is equal to or less than a prescribed temperature T.

Description

EGR device

The present invention relates to an EGR (Exhaust Gas Recirculation) device.

In JP2010-048113A, when high-temperature gas is flowing, water is injected to evaporate at the inlet of the EGR cooler to evaporate it, and the soot adhering to the surface of the tube is washed away with steam to reduce the heat exchange efficiency due to soot accumulation. Discloses an EGR device for preventing the

However, in the EGR device of JP2010-048113A, the water vapor flows in the tube of the EGR cooler together with the gas, so the adhering soot is cleaned from the surface side. Therefore, only a very small part of the surface of the crucible can be washed away, and most of the crucible attached to the tube may remain on the surface as it is and adhere to it, causing the heat exchange efficiency to decrease.

An object of the present invention is to provide an EGR device which can wash out dirt adhering to the surface of a tube and can prevent a decrease in heat exchange efficiency.

According to an aspect of the present invention, an EGR device for recirculating a part of exhaust gas discharged from an engine from an exhaust flow path to an intake flow path circulates the exhaust gas led from the exhaust flow path inside. An EGR cooler that is cooled by a refrigerant, a bypass flow path that guides exhaust gas that has passed through the EGR cooler to the exhaust flow path, and a bypass that is provided in the bypass flow path and switches the flow of exhaust gas that passes through the bypass flow path An on-off valve is opened, and the bypass on-off valve is opened when the temperature of the refrigerant flowing through the inside of the EGR cooler is equal to or lower than a first predetermined temperature.

According to the above aspect, when the temperature of the refrigerant flowing through the inside of the EGR cooler is equal to or lower than the first predetermined temperature, the bypass on-off valve is opened, whereby the exhaust gas passing through the EGR cooler is conducted to the bypass flow passage. As it cools, it cools to below the dew point temperature in the EGR cooler. Therefore, a water film of condensed water is formed between the surface of the tube of the EGR cooler and the adhered soot, and the tube and the soot are separated by the water film, so the momentum of the exhaust gas flowing in the EGR cooler Allows the sputum separated from the surface of the tube to be washed away as it is. In addition, since it is possible to wash away soot that has adhered during the previous travel each time cold start, it is also possible to suppress sticking of soot on the surface of the tube with the passage of time. Therefore, it is possible to provide an EGR device capable of preventing a decrease in heat exchange efficiency.

FIG. 1 is a configuration diagram of an intake and exhaust system of an engine of a diesel vehicle provided with an EGR device according to a first embodiment of the present invention. FIG. 2 is an enlarged view of the vicinity of the EGR cooler of the EGR device. FIG. 3 is an internal cross-sectional view of the EGR cooler. FIG. 4 is a flowchart showing the flow of the EGR cooler cleaning control. FIG. 5A is a schematic view for explaining the state of wrinkles adhering to a tube. FIG. 5B is a schematic view illustrating condensed water generated between a tube and a weir. FIG. 5C is a schematic view for explaining the state in which the sputum is washed away from the tube. FIG. 6 is a flowchart showing a flow of bypass on-off valve on-off control according to the second embodiment of the present invention. FIG. 7 is a graph showing the relationship between the engine coolant temperature and the frictional resistance at the time of driving the engine.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment
FIG. 1 is a block diagram of an intake / exhaust system of an engine 20 of a diesel vehicle provided with an EGR device 100 according to a first embodiment of the present invention.

The air supply and exhaust system of the engine 20 includes an intake system 10 connected upstream of the engine 20 and an exhaust system 30 connected downstream.

An intake system 10 includes an air cleaner 11, a compressor wheel 42 of a turbocharger 40, an intake shutter valve 14, an intercooler 12, and an intake passage connected so that intake air obtained by intake these from the outside can flow And 13.

The exhaust system 30 includes a turbine wheel 41 of the turbocharger 40, an exhaust purification device 31, and a silencer 32, and an exhaust flow path 33 that connects these so that exhaust gas discharged from the engine 20 can flow. It consists of

The intake air is supercharged by the compressor wheel 42 of the supercharger 40 after the foreign matter such as dust and dirt is removed by the air cleaner 11 when flowing through the intake flow path 13 and is guided to the intake shutter valve 14. It is eaten. The supercharged intake air changes the flow rate according to the opening degree of the intake shutter valve 14, passes through the intake shutter valve 14, is cooled by the intercooler 12, and then passes through the intake manifold (not shown) to the engine 20. Led to The intercooler 12 is, for example, water-cooled, and is connected to a sub radiator (not shown) to release the heat taken from the supercharged intake air to the outside. The intercooler 12 may be air-cooled.

The intake air led to the engine 20 is supplied to the combustion chamber 22 through the suction port 21 and is combusted by being compressed together with the fuel injected in the combustion chamber 22. The combustion provides the driving force necessary for the diesel vehicle to travel.

Exhaust gas generated by the combustion is discharged from the exhaust port 23 through an exhaust manifold (not shown) of the exhaust system 30 to the exhaust flow passage 33. The exhaust gas passes through the turbine wheel 41 of the turbocharger 40 and is then purified by a diesel oxidation catalyst or a particulate collection filter (not shown) in the exhaust gas purification device 31, and then flows to the silencer 32. The exhaust gas that has flowed to the silencer 32 has its pressure and temperature reduced, and its exhaust noise is reduced and discharged to the outside. The diesel oxidation catalyst of the exhaust gas purification device 31 is a catalyst that activates and burns the unburned gas in the exhaust gas, and the particulate collection filter is a filter that collects particulates in the exhaust gas. It should be noted that NOx in exhaust gas can be obtained by attaching to the exhaust purification device 31 a NOx reduction catalyst for removing nitrogen oxides and a fuel reforming catalyst that generates a reducing agent used in the NOx reduction catalyst. May be reduced.

As the supercharger 40, for example, a variable displacement turbocharger that controls the flow rate of the exhaust gas or the intake air according to the rotation speed of the engine 20 is used. When the turbine wheel 41 of the supercharger 40 is rotated by the pressure of the exhaust gas, the rotational force is transmitted to the compressor wheel 42 through the shaft 43 to supercharge the intake air. Can introduce a large amount of intake air.

An EGR device 100 for performing EGR is connected between the exhaust passage 33 and the intake passage 13. By performing EGR by the EGR device 100, it is possible to realize reduction of NOx and improvement of fuel consumption. Further, since the EGR device 100 reduces the exhaust gas upstream of the turbine wheel 41 and the exhaust gas purification device 31, the amount of soot and the like adhering to the turbine wheel 41 and the exhaust gas purification device 31 is reduced to improve the durability. Can.

The EGR device 100 includes an EGR flow passage 60 and a hot bypass flow passage 70. The EGR passage 60 and the hot bypass passage 70 are connected in parallel between the exhaust passage 33 and the intake passage 13, and the exhaust gas recirculated from the exhaust passage 33 circulates inside.

The EGR flow passage 60 is configured of an EGR inlet side pipe 61 and an EGR outlet side pipe 62. An EGR cooler 50 is installed between the EGR inlet side pipe 61 and the EGR outlet side pipe 62. The EGR inlet side pipe 61 connects the exhaust flow path 33 and the inlet side connection portion 51 of the EGR cooler 50. The EGR outlet side pipe 62 connects the outlet side connecting portion 52 of the EGR cooler 50 and the intake flow path 13. The EGR inlet side pipe 61 is formed shorter than the EGR outlet side pipe 62.

Further, an EGR on-off valve 63 is installed in the EGR outlet-side pipe 62 of the EGR flow passage 60. Therefore, the EGR cooler 50 and the EGR on-off valve 63 are provided in series in the EGR passage 60.

The hot bypass flow passage 70 is a flow passage for recirculating the exhaust gas of the exhaust flow passage 33 to the intake flow passage 13 without the intervention of the EGR cooler 50 installed in the EGR flow passage 60. A hot bypass on-off valve 71 is installed in the hot bypass flow passage 70.

The hot bypass on-off valve 71 is an on / off valve that switches the flow of exhaust gas passing through the hot bypass passage 70 by being controlled to two positions of full open and full close.

Here, the EGR device 100 will be described with reference to FIG. FIG. 2 is a configuration diagram in which the vicinity of the EGR cooler 50 of the EGR device 100 is enlarged.

The EGR cooler 50 is a heat exchanger that cools the exhaust gas led from the exhaust flow path 33 by the cooling water flowing inside.

The EGR on-off valve 63 is a butterfly valve provided on the EGR outlet side pipe 62 and capable of adjusting the flow rate of the exhaust gas recirculated to the intake flow passage 13 according to the opening degree. For example, when the EGR on-off valve 63 is closed, the exhaust gas is not recirculated to the intake passage 13. Thereafter, when the EGR on-off valve 63 is opened, the flow of the exhaust gas is switched, and the exhaust gas is recirculated to the intake flow passage 13 according to the opening degree of the EGR on-off valve 63.

The EGR inlet side piping 61 of the EGR flow passage 60 is routed in a U-shape from the exhaust flow passage 33 and connected to the EGR cooler 50. An exhaust flow path connection portion 61 a is formed in a portion of the EGR inlet side pipe 61 connected to the exhaust flow path 33.

The exhaust flow passage connecting portion 61a has an introduction port 61b for introducing the exhaust gas of the exhaust flow passage 33 into the EGR inlet side pipe 61, and from the exhaust flow passage 33 from the upstream toward the downstream along the flow direction of the exhaust gas. Branch at a sharp angle θ. Further, the introduction port 61 b is disposed such that a part thereof enters the exhaust flow path 33, and opens toward the flow direction upstream of the exhaust gas of the exhaust flow path 33. Since the ram pressure is generated by forming the exhaust flow path connection portion 61 a in this manner, a part of the exhaust gas flowing through the exhaust flow path 33 can easily flow to the EGR inlet side pipe 61 efficiently. The exhaust gas introduced into the EGR inlet side pipe 61 is guided to the EGR cooler 50.

The EGR cooler 50 cools the exhaust gas led from the exhaust flow path 33 by the cooling water flowing inside. The cooling water is connected so as to be able to cool the engine 20 by a flow path not shown, and releases the heat of the EGR cooler 50 and the engine 20 from the radiator not shown. The cooling water can cool not only the engine 20 but also various devices that generate heat of the diesel vehicle.

Further, a bypass flow passage 64 for leading the exhaust gas having passed through the EGR cooler 50 to the exhaust flow passage 33 is connected to the outlet-side connection portion 52 of the EGR cooler 50.

The bypass flow passage 64 is a flow passage that guides the exhaust gas that has passed through the EGR cooler 50 to the exhaust flow passage 33. A bypass on-off valve 65 is installed in the bypass flow path 64.

The bypass on-off valve 65 is an on / off valve that switches the flow of exhaust gas passing through the bypass passage 64 by being controlled to two positions of full open and full close.

Here, the EGR cooler 50 will be described with reference to FIG. FIG. 3 is an internal sectional view of the EGR cooler 50. As shown in FIG.

As shown in FIG. 3, the EGR cooler 50 is cooled so as to exchange heat between the EGR gas passage 53 through which the exhaust gas led from the exhaust flow passage 33 flows and the exhaust gas in the EGR gas passage 53. And a plurality of tubes 54 through which the water flows.

The EGR gas passages 53 are respectively formed between the tubes 54 and the other adjacent tubes 54 by alternately laminating a plurality of tubes 54 at intervals. In the EGR gas passage 53, fins (not shown) are disposed in order to enhance the heat exchange efficiency with the exhaust gas.

The exhaust gas led from the exhaust flow passage 33 flows through the EGR inlet side pipe 61 and the EGR gas passage 53 as shown by an arrow A in FIG.

When the EGR on-off valve 63 is open, the exhaust gas flowing through the EGR gas passage 53 is recirculated to the intake flow passage 13 through the EGR outlet side pipe 62 as shown by arrow B in FIG.

On the other hand, when the bypass on-off valve 65 is open, the exhaust gas flows to the exhaust flow path 33 through the bypass flow path 64 as shown by arrow C in FIG. The bypass passage 64 is connected so as to be directed to the upstream side of the exhaust gas from a part of the wall surface of the outlet side connection portion 52 of the EGR cooler 50 where the throttle is provided. Therefore, the ram pressure acts on the exhaust gas flowing to the bypass passage 64.

When the EGR on-off valve 63 is closed, the exhaust gas naturally convects around the EGR gas passage 53 and the EGR inlet side pipe 61.

Cooling water flows into the plurality of tubes 54 from the cooling water channel inlet 55 as shown by the arrow D in FIG. The cooling water exchanges heat with the exhaust gas passing through the adjacent EGR gas passage 53 through the tube 54 when flowing through the inside of the tube 54, and then the cooling water flow path outlet as shown by an arrow E in FIG. It leaks from 56.

As shown in FIG. 3, an EGR cooler outlet water temperature sensor 81 is attached to the cooling water flow path outlet 56. The EGR cooler outlet water temperature sensor 81 detects the outlet temperature of the cooling water of the EGR cooler 50 as the engine cooling water temperature Tw. Note that, as shown in FIG. 3, an EGR cooler outlet gas temperature sensor 82 that detects the temperature of the exhaust gas that has passed through the EGR cooler 50 may be installed downstream of the EGR gas passage 53 of the EGR cooler 50.

The controller 80 (see FIG. 1 and FIG. 2) includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like, and reads the program stored in the ROM by the CPU. The engine 20 and the EGR device 100 perform various functions.

A signal from the EGR cooler outlet water temperature sensor 81 is input to the controller 80 in order to cause the EGR device 100 to exhibit various functions, for example. The controller 80 receives signals from the EGR cooler outlet gas temperature sensor 82, an engine rotation sensor (not shown) for detecting the rotational speed of the engine 20, or an accelerator opening detection sensor (not shown) for detecting the accelerator opening. It is also good.

The controller 80 executes control of the EGR device 100 based on the input signal. That is, the controller 80 controls the opening and closing of the intake shutter valve 14, the EGR on-off valve 63, the hot bypass on-off valve 71, and the bypass on-off valve 65 as shown by the broken line in FIG. Run.

Next, EGR cooler cleaning control executed by the controller 80 to remove the soot C attached to the EGR cooler 50 will be described with reference to FIGS. 4 to 5C.

FIG. 4 is a flowchart showing the flow of the EGR cooler cleaning control. FIG. 5A is a schematic view illustrating the state of the crucible C attached to the tube 54. FIG. FIG. 5B is a schematic view illustrating the condensed water W generated between the tube 54 and the weir C. FIG. 5C is a schematic view for explaining a state in which the weir C is washed away from the tube 54.

The controller 80 executes EGR cooler cleaning control together with the EGR control when the engine 20 is cold started. When the hot bypass on-off valve 71 is opened, the exhaust gas flowing through the exhaust flow passage 33 is not cooled via the hot bypass flow passage 70 by execution of the EGR control. It is refluxed to 13. Further, when the EGR on-off valve 63 is opened, the exhaust gas is cooled by the EGR cooler 50 when flowing through the EGR gas passage 53 and is recirculated to the intake flow passage 13.

Here, the cold start is to start the engine 20 when the engine 20 and the like cool to near the outside temperature, for example, a situation where the engine 20 is started after the diesel vehicle is parked overnight is a cold start is assumed. Therefore, the engine coolant temperature Tw is also cooled to about the outside air temperature. As shown in FIG. 5A, soot C deposited by traveling of the diesel vehicle up to the previous time is deposited on the surface of the tube 54 of the EGR cooler 50 at the cold start.

In step S101, the controller 80 determines whether the engine coolant temperature Tw is less than a predetermined temperature T. When the engine coolant temperature Tw is lower than the predetermined temperature T, the process of the controller 80 proceeds to step S102, and when the engine cooling water temperature Tw is higher than the predetermined temperature T (first predetermined temperature), the process proceeds to step S103. The predetermined temperature T is a lower limit temperature at which the exhaust gas can not be cooled to the dew point temperature Td or less when the exhaust gas is cooled, and is 55 ° C., for example.

When the exhaust gas is cooled to the dew point temperature Td or less, condensed water W is generated between the tube 54 and the crucible C as shown in FIG. 5B. The condensed water W is the condensation of water vapor contained in the exhaust gas as the exhaust gas that has entered the interior of the crucible C from the fine gaps on the surface of the crucible C is cooled near the surface of the tube 54. Further, the condensed water W is also generated by cooling the exhaust gas existing in advance in the crucible C deposited near the surface of the tube 54 and condensing water vapor in the exhaust gas.

The 煤 C is one obtained by coalescing and solidifying hydrocarbons remaining in the combustion process through various chemical reactions, and has an oily (hydrophobic) property. Therefore, the generated condensed water W forms a water film layer by spreading between the tube 54 and the crucible C without being absorbed by the hydrophobic crucible C. As a result, the weir C is forced to be separated from the surface of the tube 54 by the water film.

On the other hand, when the exhaust gas is not cooled to the dew point temperature Td or less, the water vapor contained in the exhaust gas passes through the EGR gas passage 53 of the EGR cooler 50 as it is without condensation.

In step S102, the controller 80 opens the bypass on-off valve 65. Cleaning of the EGR cooler 50 is executed by opening the bypass on-off valve 65, and exhaust gas having passed through the EGR cooler 50 vigorously passes through the bypass flow path 64. Therefore, as shown in FIG. 5C, the soot C separated from the surface of the tube 54 and blown off downstream together with the condensed water W by the exhaust gas flows through the bypass flow path 64 as shown by the arrow C in FIG. It flows to the road 33.

In step S103, the controller 80 closes the bypass on-off valve 65. By closing the bypass on-off valve 65, the previous EGR control is restarted. Therefore, when the hot bypass on-off valve 71 is opened before execution of the EGR cooler cleaning control, the hot bypass on-off valve 71 is opened again, and the bypass on-off valve 65 is opened before execution of the EGR cooler cleaning control. The bypass on-off valve 65 is reopened. At that time, since the temperature of the exhaust gas when the engine coolant temperature Tw exceeds the predetermined temperature T is usually high temperature of 100 ° C. or higher, the blown-off condensed water W evaporates when blown away. The liquid does not flow to the engine 20 as it is.

In the EGR device 100 according to the first embodiment, the bypass on-off valve 65 is controlled by giving priority to the EGR on-off valve 63. However, the invention is not limited to this, and the EGR on-off valve 63 may be prioritized. The bypass on-off valve 65 may be controlled.

In such a case, the priority is given to the EGR on-off valve 63 to reduce NOx (nitrogen oxide) due to exhaust gas and to improve the fuel consumption performance, and further detects the on-off state of the EGR on-off valve 63 to bypass the on-off valve By finely controlling 65, a water film is easily formed by the condensed water W between the surface of the tube 54 of the EGR cooler 50 and the adhered soot C, and the soot C is forced from the surface of the tube 54 by the water film. Since the soot C can be washed out as it is by the momentum of the exhaust gas, it is possible to prevent the reduction of the heat exchange efficiency.

According to the first embodiment described above, the following effects can be obtained.

The EGR device 100 causes part of the exhaust gas discharged from the engine 20 to recirculate from the exhaust passage 33 to the intake passage 13. The EGR device 100 includes an EGR cooler 50 that cools the exhaust gas led from the exhaust flow passage 33 with cooling water as a refrigerant flowing inside, and a bypass that guides the exhaust gas that has passed through the EGR cooler 50 to the exhaust flow passage 33 A flow path 64 and a bypass on-off valve 65 provided in the bypass flow path 64 to switch the flow of exhaust gas passing through the bypass flow path 64 are provided. The bypass on-off valve 65 is opened when the engine coolant temperature Tw, which is the temperature of the refrigerant flowing through the inside of the EGR cooler 50, is equal to or lower than a predetermined temperature T (first predetermined temperature).

According to such an EGR device 100, when the engine coolant temperature Tw is equal to or lower than the predetermined temperature T, the bypass on-off valve 65 is opened, whereby the exhaust gas passing through the EGR cooler 50 is conducted to the bypass passage 64. In the EGR cooler 50, it is cooled to below the dew point temperature Td. Therefore, a water film of the condensed water W is formed between the surface of the tube 54 of the EGR cooler 50 and the adhered soot C, and the tube 54 and the soot C are separated by the water film. By the force of the exhaust gas flowing inside, the soot C separated from the surface of the tube 54 can be flushed away as it is. In addition, since the crucible C adhering to the previous travel can be washed out each time during cold start, adhesion of the crucible C on the surface of the tube 54 can be suppressed as time passes. Therefore, it is possible to provide the EGR device 100 capable of preventing the decrease in heat exchange efficiency.

The EGR device 100 is provided in an EGR outlet side pipe 62 connecting the EGR cooler 50 and the intake flow path 13 and an EGR outlet side pipe 62, and switches the flow of the exhaust gas to be recirculated to the intake flow path 13 And further comprising The EGR on-off valve 63 is closed when the engine coolant temperature Tw, which is the temperature of the refrigerant flowing through the inside of the EGR cooler 50, is equal to or lower than a predetermined temperature T.

According to such an EGR device 100, when the engine coolant temperature Tw is lower than or equal to the predetermined temperature T, the temperature of the exhaust gas may not have reached a high temperature of 100 ° C. or higher. Is closed. Therefore, the blown-off condensed water W can be reliably prevented from flowing to the engine 20 as a liquid.

The EGR device 100 further includes an EGR inlet side pipe 61 connecting the exhaust flow passage 33 and the EGR cooler 50. The EGR inlet side pipe 61 has an exhaust flow path connection portion 61 a connected to the exhaust flow path 33. The exhaust passage connection portion 61 a branches from the upstream toward the downstream along the flow direction of the exhaust gas of the exhaust passage 33 at an acute angle θ. As a result, the exhaust gas of the exhaust flow passage 33 receives ram pressure at the exhaust flow passage connecting portion 61a when it flows downstream. Therefore, a part of the exhaust gas of the exhaust flow path 33 can be efficiently flowed into the EGR inlet side pipe 61.

In the EGR device 100, the exhaust passage connection portion 61a has an introduction port 61b formed in the exhaust passage 33. The inlet 61 b opens toward the upstream in the flow direction of the exhaust gas of the exhaust flow passage 33. As a result, exhaust gas can be efficiently flowed to the EGR cooler 50 using the action of the ram pressure.

The exhaust passage connection portion 61a may be branched from the exhaust passage 33 at an acute angle θ so that the ram pressure acts, and is disposed so that the entire inlet 61b does not enter the exhaust passage 33. May be As a result, the exhaust gas can be efficiently flowed into the EGR cooler 50 by the ram pressure while suppressing an increase in the pressure loss of the exhaust passage 33.

Further, in the present embodiment, the exhaust flow path connection portion 61a is disposed such that a part of the introduction port 61b enters the exhaust flow path 33, but the entire introduction port 61b enters the exhaust flow path 33. It may be arranged to face the upstream of the exhaust flow path 33. By disposing the exhaust passage connection portion 61 a as described above, the exhaust gas in the exhaust passage 33 can be easily flowed into the EGR inlet side pipe 61.

In the EGR device 100, the bypass flow passage 64 is connected to the downstream side in the flow direction of the exhaust gas of the exhaust flow passage 33 than the exhaust flow passage connecting portion 61a. Therefore, the exhaust gas having passed through the EGR cooler 50 flows through the bypass flow path 64 to the exhaust flow path 33, so the soot C separated from the surface of the tube 54 is also discharged to the exhaust flow path 33 by the flow of the exhaust gas. can do.

In the EGR device 100, the EGR cooler 50 circulates the exhaust gas led from the exhaust flow path 33 so that heat exchange is performed between the refrigerant flowing inside and the exhaust gas led from the exhaust flow path 33 The EGR gas passage 53 is provided. The bypass flow passage 64 is provided at the outlet side connection portion 52 of the EGR cooler 50 so as to lead the exhaust gas having passed through the EGR gas passage 53 to the exhaust flow passage 33. Therefore, the soot C separated from the surface of the tube 54 can be discharged to the exhaust flow passage 33 by the force of the exhaust gas having passed through the EGR cooler 50 flowing through the bypass flow passage 64 into the exhaust flow passage 33.

The bypass passage 64 may be provided in the EGR outlet side pipe 62 so as to guide the exhaust gas having passed through the EGR cooler 50 to the exhaust passage 33. Such an EGR device 100 includes an EGR outlet-side pipe 62 that connects the EGR cooler 50 and the intake flow path 13. The bypass flow passage 64 is provided in the EGR outlet side pipe 62 so as to lead the exhaust gas that has passed through the EGR cooler 50 to the exhaust flow passage 33. Therefore, the soot C separated from the surface of the tube 54 can be discharged to the exhaust flow path 33 as in the EGR cooler 50 of the first embodiment described above.

Second Embodiment
With reference to FIGS. 6 and 7, bypass on-off valve opening / closing control performed by the vehicle air conditioner 200 for a diesel vehicle provided with the EGR device 100 according to the second embodiment of the present invention will be described.

FIG. 6 is a flowchart showing a flow of bypass on-off valve on-off control according to the second embodiment. In the bypass on-off valve on-off control of the second embodiment, the on-off conditions of the bypass on-off valve are different from the EGR cooler cleaning control of the first embodiment. In the following embodiments, the same reference numerals are used for the configurations that perform the same functions as those of the first embodiment, and redundant descriptions will be appropriately omitted.

The controller 80 executes bypass on-off valve on-off control together with EGR control when the engine 20 is cold-started. When the hot bypass on-off valve 71 is opened, the exhaust gas flowing through the exhaust flow passage 33 is not cooled via the hot bypass flow passage 70 by execution of the EGR control. To reflux. In addition, when the EGR on-off valve 63 is open, the exhaust gas is cooled by the EGR cooler 50 when flowing through the EGR gas passage 53 and is recirculated to the intake flow passage 13.

In step S201, the controller 80 determines whether the engine coolant temperature Tw is less than the dew point temperature Td. The process of the controller 80 proceeds to step S202 when the engine coolant temperature Tw is less than the dew point temperature Td, and proceeds to step S203 when the temperature is equal to or higher than the dew point temperature Td. The dew point temperature Td is a temperature at which the water contained in the exhaust gas condenses to generate the condensed water W when the exhaust gas is cooled, and is 60 ° C., for example.

In step S202, the controller 80 opens the bypass on-off valve 65. Cleaning of the EGR cooler 50 is executed by opening the bypass on-off valve 65, and exhaust gas having passed through the EGR cooler 50 vigorously passes through the bypass flow path 64. Therefore, as shown in FIG. 5C, the soot C separated from the surface of the tube 54 and blown off downstream together with the condensed water W by the exhaust gas flows through the bypass flow path 64 as shown by the arrow C in FIG. It flows to the road 33.

In step S203, the controller 80 determines whether the engine coolant temperature Tw is less than a predetermined temperature Tw1. The process of the controller 80 proceeds to step S204 when the engine coolant temperature Tw is less than the predetermined temperature Tw1, and proceeds to step S206 when the temperature is equal to or higher than the predetermined temperature Tw1 (second predetermined temperature). The predetermined temperature Tw1 is a target warm-up temperature of the engine 20. The predetermined temperature Tw1 is a temperature at which the frictional resistance Rf at the time of driving the engine 20 is reduced, and is, for example, 80.degree. Therefore, the predetermined temperature Tw1 is higher than the dew point temperature Td and the predetermined temperature T (first predetermined temperature). Here, the relationship between the engine coolant temperature Tw and the frictional resistance Rf will be described with reference to FIG.

FIG. 7 is a graph showing the relationship between the engine coolant temperature Tw and the frictional resistance Rf when the engine 20 is driven.

The frictional resistance Rf is a resistance generated by friction when a cylinder, a piston or the like in the engine 20 is driven. The frictional resistance Rf becomes smaller as shown in FIG. 7 as the engine coolant temperature Tw, which has a correlation with the viscosity of the oil lubricating the inside of the engine 20, becomes higher. When the frictional resistance Rf is high, the mechanical loss of the engine 20 becomes large, but for example, when the engine coolant temperature Tw becomes higher than the predetermined temperature Tw1, the frictional resistance Rf can be made equal to or lower than the allowable frictional resistance Rf1. The mechanical loss of the engine 20 can be reduced.

In step S204, the controller 80 determines whether the EGR on-off valve 63 is in a closed state. The process of the controller 80 proceeds to step S205 if the EGR on / off valve 63 is in the closed state, and proceeds to step S206 if it is not in the closed state, that is, if it is in the open state.

In step S205, the controller 80 opens the bypass on-off valve 65. When the bypass on-off valve 65 is opened, a part of the exhaust gas flowing through the exhaust flow path 33 flows into the EGR cooler 50 and flows through the bypass flow path 64 to the downstream exhaust flow path 33. Therefore, the cooling water in the EGR cooler 50 exchanges heat with the exhaust gas to recover the heat of the exhaust gas.

In step S206, the controller 80 closes the bypass on-off valve 65. As described above, when the engine coolant temperature Tw is equal to or higher than the predetermined temperature Tw1, it is not necessary to recover the heat from the exhaust gas, and the condensed water W is not generated in the EGR cooler 50. The bypass on-off valve 71 is closed in the process of S206. Further, even when the EGR on-off valve 63 is in the open state, that is, the EGR is being executed so that the exhaust gas passes through the EGR cooler 50, the bypass on-off valve 71 is closed in the process of step S206. It does not affect EGR.

At that time, since the temperature of the exhaust gas when the engine coolant temperature Tw is equal to or higher than the predetermined temperature Tw1 is high temperature, even if the condensed water W is accumulated in the EGR cooler 50, the condensed water W is blown away When it evaporates. Therefore, the condensed water W does not flow to the engine 20 as a liquid.

In the EGR control up to that point, when the hot bypass on-off valve 71 is opened, the hot bypass on-off valve 71 may be opened in parallel with the bypass on-off valve on-off control described above. Even in such a mode, part of the exhaust gas flowing to the downstream side of the exhaust flow passage 33 without passing through the hot bypass flow passage 70 can be flowed into the EGR cooler 50 by opening the bypass on-off valve 65 Thus, the heat of the exhaust gas can be recovered by the cooling water in the EGR cooler 50.

Further, in the EGR device 100 according to the second embodiment described above, the bypass on-off valve 65 is controlled by giving priority to the EGR on-off valve 63, but the invention is not limited to this. The bypass on-off valve 65 may be controlled.

According to the above second embodiment, the following effects can be obtained.

The EGR device 100 causes part of the exhaust gas discharged from the engine 20 to recirculate from the exhaust passage 33 to the intake passage 13. The EGR device 100 includes an EGR cooler 50 that cools the exhaust gas led from the exhaust flow passage 33 with cooling water as a refrigerant flowing inside, and a bypass that guides the exhaust gas that has passed through the EGR cooler 50 to the exhaust flow passage 33 A flow path 64 and a bypass on-off valve 65 provided in the bypass flow path 64 to switch the flow of exhaust gas passing through the bypass flow path 64 are provided. The bypass on-off valve 65 has a predetermined temperature Tw1 (second predetermined temperature) at which the engine cooling water temperature Tw, which is the temperature of the cooling water flowing through the inside of the EGR cooler 50, is higher than the predetermined temperature T (first predetermined temperature). The exhaust gas which has passed through the EGR cooler 50 and which is lower than the temperature) and is not recirculated from the exhaust flow passage 33 to the intake flow passage 13 is opened.

According to such an EGR device 100, the bypass is made when the engine coolant temperature Tw is lower than the predetermined temperature Tw1 and the exhaust gas having passed through the EGR cooler 50 is not recirculated from the exhaust passage 33 to the intake passage 13 By opening the on-off valve 65, the exhaust gas that has passed through the EGR cooler 50 is guided to the bypass flow passage 64. At this time, the exhaust gas led to the bypass flow passage 64 exchanges heat with the cooling water in the EGR cooler 50. Therefore, the cooling water in the EGR cooler 50 can efficiently recover, for example, the heat for warming the engine 20 from the exhaust gas as another device that needs to be warmed up. In addition, when the exhaust gas led to the bypass flow passage 64 is cooled to below the dew point temperature Td in the EGR cooler 50, condensed water between the surface of the tube 54 of the EGR cooler 50 and the adhered soot C A water film is formed by W, and the tube 54 and the crucible C are separated by the water film. Therefore, the soot C separated from the surface of the tube 54 can be washed away by the force of the exhaust gas flowing in the EGR cooler 50 as it is. Therefore, since the crucible C adhering to the previous travel can be washed out each time cold start, it is also possible to suppress sticking of the crucible C on the surface of the tube 54 with the passage of time. Therefore, while being able to wash away soot C adhering to the surface of tube 54, it is possible to provide EGR device 100 capable of efficiently recovering from exhaust gas heat for warming engine 20 or the like which requires warm air.

Further, since the bypass on-off valve 65 is opened when the exhaust gas having passed through the EGR cooler 50 is not recirculated from the exhaust flow path 33 to the intake flow path 13, the exhaust gas flows to the bypass flow path 64 to generate EGR. There is no effect.

In the EGR device 100, the predetermined temperature Tw1 is a target warm-up temperature of the engine 20. The target warm-up temperature of the engine 20 is, for example, a temperature at which the frictional resistance Rf at the time of driving the engine 20 is reduced to the allowable frictional resistance Rf1 or less. Further, the predetermined temperature Tw1 is a temperature higher than the dew point temperature Td at which the condensed water W is generated in the EGR cooler 50. Therefore, the engine cooling water temperature Tw is lower than the predetermined temperature Tw1, and when the frictional resistance Rf at the time of driving the engine 20 is large, the engine 20 can be warmed using the heat of the exhaust gas. As a result, the engine 20 can be efficiently warmed, and mechanical loss of the engine 20 can be reduced.

The bypass on-off valve 65 is closed when the engine coolant temperature Tw, which is the temperature of the coolant flowing through the inside of the EGR cooler 50, is equal to or higher than a predetermined temperature Tw1. Therefore, after the warm-up of the engine 20 is completed, the exhaust gas does not flow in the bypass flow passage 64. Therefore, the EGR can be performed to reduce NOx and improve the fuel consumption.

The bypass on-off valve 65 is closed when the exhaust gas that has passed through the EGR cooler 50 is recirculated from the exhaust passage 33 to the intake passage 13. Therefore, when the controller 80 is performing EGR so that the exhaust gas passes through the EGR cooler 50, the bypass on-off valve 65 is closed. The influence can be avoided.

The EGR device 100 is provided in an EGR outlet side pipe 62 connecting the EGR cooler 50 and the intake flow path 13 and an EGR outlet side pipe 62, and switches the flow of the exhaust gas to be recirculated to the intake flow path 13 And further comprising The EGR on-off valve 63 is closed when the engine coolant temperature Tw, which is the temperature of the coolant flowing through the inside of the EGR cooler 50, is equal to or lower than a predetermined temperature Tw1.

According to such an EGR device 100, when the engine coolant temperature Tw is equal to or lower than the predetermined temperature Tw1, the temperature of the exhaust gas may not be high, so the EGR on-off valve 63 is closed. Therefore, the blown-off condensed water W can be reliably prevented from flowing to the engine 20 as a liquid.

The bypass passage 64 may be provided in the EGR outlet side pipe 62 so as to guide the exhaust gas having passed through the EGR cooler 50 to the exhaust passage 33. Such an EGR device 100 includes an EGR outlet-side pipe 62 that connects the EGR cooler 50 and the intake flow path 13. The bypass flow passage 64 is provided in the EGR outlet side pipe 62 so as to lead the exhaust gas that has passed through the EGR cooler 50 to the exhaust flow passage 33. Therefore, the soot C separated from the surface of the tube 54 can be discharged to the exhaust flow path 33 as in the EGR cooler 50 of the second embodiment described above.

Further, the heat recovered from the exhaust gas may be used not only for warming up the engine 20 but also for warming up a transmission (not shown) and heating the vehicle interior.

As mentioned above, although the embodiment of the present invention was described, the above-mentioned embodiment showed only a part of application example of the present invention, and in the meaning of limiting the technical scope of the present invention to the concrete composition of the above-mentioned embodiment. Absent.

For example, the EGR device 100 is installed so as to connect the upstream side of the compressor wheel 42 of the intake flow passage 13 and the downstream side of the exhaust gas purification device 31 of the exhaust flow passage 33 without limiting to the aspect of the above embodiment. It may be By this, the same effect as that of the above embodiment can be obtained.

The EGR device 100 may be applied not only to diesel vehicles but also to gasoline vehicles.

This application claims the priority based on Japanese Patent Application No. 2016-140371 and Japanese Patent Application No. 2016-140375 filed on July 15, 2016 to the Japan Patent Office, and the entire contents of this application are hereby incorporated by reference. Be incorporated.

Claims

An EGR device for recirculating a part of exhaust gas discharged from an engine from an exhaust flow passage to an intake flow passage,
An EGR cooler that cools the exhaust gas led from the exhaust flow path with a refrigerant flowing inside;
A bypass passage that leads the exhaust gas that has passed through the EGR cooler to the exhaust passage;
A bypass on-off valve provided in the bypass flow path for switching the flow of exhaust gas passing through the bypass flow path;
Equipped with
The bypass on-off valve is opened when the temperature of the refrigerant flowing through the inside of the EGR cooler is equal to or lower than a first predetermined temperature.
EGR device.
The EGR device according to claim 1, wherein
The bypass on-off valve exhausts the exhaust gas having passed through the EGR cooler, the temperature of the refrigerant flowing through the inside of the EGR cooler being lower than a second predetermined temperature which is a temperature higher than the first predetermined temperature. Open when not flowing back from the flow path to the intake flow path,
EGR device.
The EGR device according to claim 2, wherein
The second predetermined temperature is a target warm-up temperature of the engine, and is a temperature higher than a dew point temperature at which condensed water is generated in the EGR cooler.
EGR device.
The EGR device according to claim 2 or 3, wherein
The bypass on-off valve is closed when the temperature of the refrigerant flowing through the inside of the EGR cooler is equal to or higher than the second predetermined temperature.
EGR device.
An EGR device according to any one of claims 2 to 4, wherein
EGR outlet side piping that connects the EGR cooler and the intake passage;
And an EGR on-off valve provided on the EGR outlet side pipe for switching the flow of exhaust gas to be recirculated to the intake flow path,
The EGR on-off valve is closed when the temperature of the refrigerant flowing through the inside of the EGR cooler is less than the second predetermined temperature.
EGR device.
The EGR device according to any one of claims 1 to 5, wherein
The bypass on-off valve is closed when the exhaust gas having passed through the EGR cooler is recirculated from the exhaust passage to the intake passage.
EGR device.
The EGR device according to any one of claims 1 to 6, wherein
The system further comprises an EGR inlet side pipe connecting the exhaust flow path and the EGR cooler,
The EGR inlet side pipe has an exhaust flow path connection portion connected to the exhaust flow path,
The exhaust passage connection portion branches at an acute angle from upstream to downstream along a flow direction of exhaust gas of the exhaust passage.
EGR device.
The EGR device according to claim 7, wherein
The exhaust passage connection portion has an inlet formed in the exhaust passage,
The inlet is opened upstream in the exhaust gas flow direction of the exhaust flow path,
EGR device.
An EGR device according to claim 7 or 8, wherein
The bypass flow channel is connected to the downstream side of the flow direction of the exhaust gas of the exhaust flow channel from the exhaust flow channel connection portion.
EGR device.
The EGR device according to any one of claims 7 to 9, wherein
And an EGR outlet-side pipe connecting the EGR cooler and the intake flow path,
The bypass passage is provided in the EGR outlet side pipe so as to lead the exhaust gas having passed through the EGR cooler to the exhaust passage.
EGR device.
An EGR device according to any one of claims 1 to 10, wherein
The EGR cooler has an EGR gas passage through which the exhaust gas led from the exhaust flow channel circulates so that heat exchange is performed between the refrigerant flowing inside and the exhaust gas led from the exhaust flow channel. Have
The bypass passage is provided in the EGR cooler so as to lead the exhaust gas having passed through the EGR gas passage to the exhaust passage.
EGR device.
The EGR device according to any one of claims 1 to 11, wherein
The refrigerant is cooling water for cooling the engine.
EGR device.