JP2012127266A - Egr device of multicylinder engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR device of a multicylinder engine for simplifying a structure related to an EGR cooler.SOLUTION: This EGR device 60 of the multicylinder engine 1 for recirculating EGR gas to an intake passage 20 by using exhaust pulsation pressure, includes an EGR junction 63 for merging the EGR gas respectively guided by first and second EGR tributary passages 61 and 62, first and second check valves 51 and 52 interposed in the EGR junction 63 and stopping a backflow of the EGR gas respectively guided by the first and second EGR tributary passages 61 and 62, and the EGR cooler 71 for cooling the EGR gas flowing in an EGR merging passage 64.

Description

  The present invention relates to an EGR device for a multi-cylinder engine that recirculates EGR gas using exhaust pulsation pressure.

  The EGR device for a multi-cylinder engine disclosed in Patent Document 1 includes two exhaust manifolds that collect exhaust from cylinder groups whose ignition orders are not continuous with each other, and takes out EGR gas from each exhaust manifold and guides it to an intake passage. Two EGR passages and two check valves for stopping the backflow of EGR gas guided by each EGR passage, and even in a high load operation state where the intake pressure is higher than the exhaust pressure due to the operation of the supercharger The check valve is opened using the exhaust pulsation pressure propagating to the two EGR passages, and the EGR gas is recirculated to each cylinder.

  In this EGR apparatus, EGR coolers are installed in two EGR passages, respectively, and the EGR gas is cooled by each EGR cooler. The EGR gas cooled by the EGR cooler is guided to the check valve, thereby preventing the check valve from being overheated.

  The engine disclosed in Patent Document 2 has a structure that uses a reed valve as a check valve for stopping the backflow of intake air.

JP 2004-308487 A Japanese Patent Laid-Open No. 2001-200726

  However, in an EGR device for a multi-cylinder engine that recirculates EGR gas to the intake passage using exhaust pulsation pressure, if an EGR cooler is installed upstream of the two check valves, the two EGR coolers There is a problem that the related structure becomes complicated, resulting in an increase in size and cost of the product.

  The present invention has been made in view of the above problems, and an object thereof is to provide an EGR device for a multi-cylinder engine in which the structure related to the EGR cooler can be simplified.

  The present invention relates to an EGR device for a multi-cylinder engine that recirculates EGR gas to an intake passage using exhaust pulsation pressure, and collects exhaust from cylinder groups whose ignition orders are not continuous with each other. First and second EGR branch passages for taking out EGR gas from the manifold, an EGR junction for joining the EGR gases respectively guided by the first and second EGR branch passages, and the first and second EGR junctions. The first and second check valves for stopping the backflow of the EGR gas respectively guided by the second EGR tributary passage, the EGR junction passage for guiding the EGR gas joined at the EGR junction to the intake passage, And an EGR cooler that cools the EGR gas flowing through the EGR merging passage.

  According to the present invention, the EGR gas merged at the EGR junction is guided to the EGR cooler interposed in the EGR merge passage, cooled in the process of passing through the EGR cooler, and the charging efficiency for intake air is increased.

  Since the single EGR cooler is arranged on the downstream side of the EGR junction, the structure is simplified compared to the conventional structure in which the EGR cooler is interposed in the first and second EGR branch passages, Product size and cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the EGR apparatus of the multicylinder engine which shows embodiment of this invention. FIG. 3 is a side view of the first and second exhaust manifolds. Sectional drawing which shows the site | part connected to the turbine of a central block similarly. Similarly, a perspective view of an EGR junction. Similarly, a sectional view and a side view of an EGR junction. The perspective view of an EGR cooler. Similarly, a sectional view and a side view of an EGR gas flow rate detector. The perspective view of an EGR gas flow control valve similarly. The front view of an EGR gas flow control valve similarly.

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

  As shown schematically in FIG. 1, the multi-cylinder engine 1 includes an intake passage 20 that guides intake air to each cylinder, an exhaust passage 30 that discharges exhaust from each cylinder, and a portion of the exhaust (hereinafter referred to as EGR gas). An EGR device 60 that recirculates to each cylinder through the passage 20 and a turbocharger 10 that supercharges intake air by exhaust energy are provided.

  The intake passage 20 includes, in order from the upstream side, an air cleaner 21 that removes foreign matters such as dust from the outside air, a compressor 11 that constitutes the turbocharger 10, an intercooler 22 that cools intake air, an intake manifold 19 that distributes intake air to each cylinder, An intake port (not shown) that opens to the combustion chamber wall of the cylinder is provided.

  The exhaust passage 30 is arranged in order from the upstream side, an exhaust port (not shown) that opens to the combustion chamber wall of each cylinder, first and second exhaust manifolds 31 and 32 that collect exhaust from each exhaust port, and the turbocharger 10. And a muffler 39 with a catalyst for purifying exhaust gas through the catalyst and silencing the exhaust sound.

  The diesel engine 1 includes an intake stroke in which intake air is sucked into a cylinder, a combustion stroke in which fuel injected and supplied to the cylinder is compressed and ignited, and an expansion in which an output shaft is driven to rotate by lowering a piston in the cylinder. In the stroke, the exhaust stroke in which the exhaust in the cylinder is discharged from the exhaust port is sequentially performed for each cylinder.

  The present invention can be applied not only to the diesel engine 1 but also to a spark ignition engine.

  The engine 1 includes six cylinders # 1 to # 6, and, for example, reaches an exhaust stroke with an interval of 120 degrees in the order of # 1, # 4, # 2, # 6, # 3, and # 5 cylinder.

  The first exhaust manifold 31 collects exhaust from the # 1, # 2, and # 3 cylinders whose ignition order is not continuous with each other (exhaust valve opening periods do not overlap). Similarly, the second exhaust manifold 32 collects exhaust from the # 4, # 6, and # 5 cylinders whose firing order is not continuous with each other. As a result, the exhaust flows discharged from the cylinders alternately flow into the first and second exhaust manifolds 31 and 32, and exhaust pressure pulsations occur according to the engine speed range.

  The present invention is not limited to the 6-cylinder engine 1 and can be applied to other multi-cylinder engines having 8 cylinders and 10 cylinders, for example. The exhaust passage 30 is not limited to the first and second exhaust manifolds 31 and 32, and may be configured to include third, fourth, and more exhaust manifolds. Correspondingly, the number of first and second EGR branch passages 61 and 62, first and second check valves 51 and 52, which will be described later, is also increased.

  FIG. 2 is a side view of the first and second exhaust manifolds 31 and 32. The first and second exhaust manifolds 31 and 32 are formed by assembling a central block 41 and front and rear blocks 42 and 43.

  The front block 42 has an opening (exhaust inlet) for the exhaust ports of the # 1 and # 2 cylinders, an opening (exhaust outlet) for the central block 41, and an opening (EGR gas outlet) for the EGR tributary passage 61.

  The rear block 43 has an opening (exhaust inlet) for the exhaust ports of the # 5 and # 6 cylinders, an opening (exhaust outlet) for the central block 41, and an opening (EGR gas outlet) for the EGR tributary passage 62.

  FIG. 3 is a cross-sectional view showing a portion of the central block 41 that is connected to the turbine 12. The central block 41 has openings (exhaust inlets) 47 and 48 for the exhaust ports of the # 5 and # 6 cylinders, openings (exhaust inlets) 45 and 46 for the front and rear blocks 42 and 43, and an opening for the turbine 12 of the turbocharger 10. The first and second ejectors 49 and 50 are included.

  The exhaust passage 30 includes an exhaust junction 33 that joins exhaust gas guided by the first and second exhaust manifolds 31 and 32 and guides the exhaust gas to the turbine 12 of the turbocharger 10. In the exhaust junction 33, the first and second ejectors 49 and 50 are formed such that the flow passage cross-sectional areas thereof are smaller than the flow passage cross-sectional area on the upstream side, and are connected to the housing inlet 13 of the turbine 12 alongside each other. . As indicated by arrows in FIG. 3, the exhaust blowdown flow at the initial stage of the exhaust stroke in each cylinder flows out from the first and second ejectors 49 and 50 alternately to the housing inlet 13. Exhaust gas from the ejectors 49 and 50 is alternately sucked into the housing inlet 13 to improve exhaust efficiency.

  The turbocharged engine 1 is provided with a turbocharger 10 as a supercharger. In the turbocharger 10, an impeller (not shown) of the turbine 12 and an impeller (not shown) of the compressor 11 are coaxially connected. The impeller of the turbine 12 rotates at a high speed by the energy of the exhaust, and as indicated by an arrow in FIG. 3, the impeller of the compressor 11 sucks intake air from the direction of the rotation axis by the rotation, and the compressed intake air in the direction of the rotation radius. Discharge.

  The variable capacity turbocharger 10 is provided with a variable nozzle (not shown) at an inlet for introducing exhaust to the impeller of the turbine 12, and the nozzle area is changed by rotating the variable nozzle.

  The opening degree of the variable nozzle is controlled by the controller 9 according to the operating state of the engine 1. Thereby, the rotational speed of the turbocharger 10 is adjusted according to the opening degree of the variable nozzle, and the target supercharging pressure corresponding to the operating state of the engine 1 is obtained.

  The EGR device 60 takes out part of the exhaust gas as EGR gas from the upstream side of the turbine 12 in the exhaust passage 30, guides it to the downstream side from the compressor 11 in the intake passage 20, and returns it to each cylinder.

  The EGR device 60 includes first and second EGR tributary passages 61 and 62 for taking out EGR gas from the first and second exhaust manifolds 31 and 32, and the first and second EGR tributary passages 61 and 62, respectively. An EGR junction 63 that joins the exhaust to be guided and an EGR junction passage 64 that guides the EGR gas joined at the EGR junction 63 to the intake passage 20 are provided.

  The EGR gas guided to the first and second EGR branch passages 61 and 62 joins at the EGR junction 63 and is guided to the intake passage 20 through the EGR junction passage 64.

  An EGR gas flow rate detector 3 and an EGR gas flow rate control valve 4 are interposed in the EGR merging passage 64.

  Exhaust pressure pulsations generated in the first and second exhaust manifolds 31 and 32 are propagated to the first and second EGR branch passages 61 and 62 in accordance with the engine speed range.

  The EGR junction 63 includes first and second check valves 51 and 52 that open and close the first and second EGR branch passages 61 and 62, respectively.

  FIG. 4 is a perspective view showing the EGR junction 63. 5A is a cross-sectional view of the EGR junction 63 taken along the line AA in FIG. 5B, and FIG. 5B is a side view of the EGR junction 63. FIG.

  The EGR junction 63 includes a cylindrical junction housing 14. The junction housing 14 has flanges 65 and 66 on the inlet side and the outlet side, respectively, and a partition wall 17 on the inner side. Pipes of the first and second EGR branch passages 61 and 62 are connected to the inlet-side flange 65, respectively. A flange 77 (see FIG. 6) of the EGR cooler 71 is connected to the flange 66 on the outlet side.

  On the inner side of the junction housing 14, the first and second EGR branch passages 81 and 82 that are the downstream ends of the first and second EGR branch passages 61 and 62 and the EGR junction that is the upstream end of the EGR junction passage 64. An end 83 is provided.

  The upstream side in the junction housing 14 is partitioned into first and second EGR branch ends 81 and 82 by a partition wall 17. First and second check valves 51 and 52 are accommodated in the first and second EGR branch ends 81 and 82, respectively.

  The first and second check valves 51 and 52 include a valve seat 53 interposed in the junction housing 14 and two reed valves 54 seated on the valve seat 53.

  The valve seat 53 has a valve seat surface 55 that is V-shaped in cross section and has a hollow structure and is inclined with respect to each other. The valve seat surface 55 is formed in an annular shape so that the end of the reed valve 54 is seated. An opening (not shown) through which the EGR gas passes is formed inside the valve seat surface 55.

  The reed valve 54 is formed of a rectangular spring plate, and a base end portion thereof is fastened to the valve seat 53 by a plurality of screws 59.

  In the first and second check valves 51 and 52, when the differential pressure across the front and rear is not more than a predetermined value, the reed valve 54 is seated on the valve seat surface 55 by its elastic restoring force, The EGR branch ends 81 and 82 are respectively closed.

  When the differential pressure across the first and second check valves 51 and 52 exceeds a predetermined value, the reed valve 54 bends against its elastic restoring force and separates from the valve seat surface 55. Then, the first and second EGR branch ends 81 and 82 are opened. When the first and second check valves 51 and 52 are thus opened, the EGR gas passes through the valve seat 53 as indicated by arrows in FIG. 5A, and the first and second EGR tributaries. It flows through the ends 81 and 82.

  As a result, the exhaust pulsation pressure generated in the first and second exhaust manifolds 31 and 32 propagates to the first and second EGR branch passages 61 and 62, and the peak value of the exhaust pulsation pressure becomes the intake pressure of the intake passage 20. In the high load operation state exceeding, the first and second check valves 51 and 52 are alternately opened, and the EGR gas guided to the first and second EGR branch passages 61 and 62 is generated at the EGR junction 63. The air flows through the EGR merge passage 64 and is guided to the intake passage 20.

  The partition wall 17 is formed so as to protrude downstream from the leading ends of the reed valve 54 and the valve seat 53. In the high load operation state where the first and second check valves 51 and 52 are alternately opened, the EGR gas flowing through the first and second EGR branch ends 81 and 82 runs along the housing inner wall surface 18 and the partition wall 17. Thus, the exhaust pressure wave propagating to one of the first and second EGR branch ends 81 and 82 can be prevented from propagating beyond the partition wall 17 to the other.

  The junction housing 14 has a cylindrical housing inner wall surface 18. The cross-sectional area of the flow path defined inside the housing inner wall surface 18 gradually decreases from the upstream side to the downstream side.

  The ratio of the flow path cross-sectional area decreasing with respect to the flow path distance is such that the EGR junction end 83 provided on the downstream side of the partition wall 17 from the first and second EGR branch ends 81 and 82 provided with the partition wall 17. Becomes smaller.

  Assuming that the center line of the housing inner wall surface 18 is O, the inclination angle θ / 2 of the housing inner wall surface 18 with respect to the center line O is the EGR merging from the part defining the first and second EGR branch ends 81 and 82. The part that defines the end 83 is larger.

  The throttle angle θ of the housing inner wall surface 18 at the portion that defines the EGR merging end 83 is set to, for example, about 30 ° within a range of 45 ° or less.

  The junction housing 14 includes refrigerant jackets 56 to 58 through which engine coolant flows as refrigerant, and the refrigerant jackets 56 to 58 cool the first and second check valves 51 and 52.

  The refrigerant jackets 56, 57, 58 are formed along portions that define the first and second EGR branch ends 81, 82.

  The side walls 15 and 16 of the junction housing 14 are formed with cooling wall surfaces 86 and 88 with which the reed valve 54 abuts when the first and second check valves 51 and 52 are opened. Refrigerant jackets 56 and 58 are formed along the cooling wall surfaces 86 and 88.

  The cooling wall surfaces 86 and 88 define first and second EGR branch ends 81 and 82, respectively, and are curved along the reed valve 54 in the valve open state.

  The partition wall 17 is formed with cooling wall surfaces 87a and 87b with which the reed valve 54 abuts when the first and second check valves 51 and 52 are opened. A refrigerant jacket 57 is formed along the cooling wall surfaces 87a and 87b.

  The cooling wall surfaces 87a and 87b define first and second EGR branch ends 81 and 82, respectively, and curve along the reed valve 54 in the valve-opened state indicated by a two-dot chain line in FIG. Formed.

  A refrigerant inlet pipe 91 and a refrigerant outlet pipe 92 are provided outside the junction housing 14. The refrigerant inlet pipe 91 and the refrigerant outlet pipe 92 are connected to a cooling water circulation circuit (not shown) of the engine 1 via a pipe (not shown). The engine coolant that circulates in the coolant circulation circuit of the engine 1 flows into the coolant jackets 56, 57, and 58 in the junction housing 14 from the coolant inlet pipe 91 as indicated by arrows in FIG. In the process of flowing through 56, 57, and 58, the heat of the junction housing 14 is absorbed and returned from the refrigerant outlet pipe 92 to the cooling water circulation circuit of the engine 1.

  As described above, the first and second check valves 51 and 52 are configured such that each reed valve 54 bends against its elastic restoring force when the differential pressure across the front and rear increases beyond a predetermined value. The valve opening operation away from the seat surface 55 is performed, and the back surface of each reed valve 54 comes into contact with the cooling wall surfaces 86, 87a, 87b, 88. At the time of this valve opening operation, each reed valve 54 is exposed to a flow of high temperature EGR gas. Heat is transferred to the side walls 16, 18 and the partition wall 17, and is absorbed by the engine coolant flowing through the refrigerant jackets 56, 57, 58. Thus, when the first and second check valves 51 and 52 are opened, each reed valve 54 exchanges heat between the engine cooling water via the side walls 16 and 18 of the junction housing 14 and the partition wall 17. Done and cooled.

  The EGR gas smoothly flows from the first and second EGR branch ends 81 and 82 of the junction housing 14 to the EGR junction end 83 and is guided to the EGR cooler 71.

  FIG. 6 is a perspective view showing the EGR cooler 71. The EGR cooler 71 includes a cylindrical cooler housing 74, and has flanges 77 and 78 on the inlet side and the outlet side of the cooler housing 74, respectively. A flange 66 of the junction housing 14 is connected to the flange 77 on the inlet side.

  In the EGR cooler 71, a number of pipes extend linearly in the cooler housing 74, and an EGR cooling channel through which EGR gas flows is defined by the pipes (pipes). The EGR gas flows in from one end of the cooler housing 74 and flows out to the other end of the cooler housing 74 through the EGR cooling flow path as indicated by an arrow in the figure.

  The EGR cooler 71 includes a refrigerant flow path (not shown) through which engine coolant flows as a refrigerant. This refrigerant flow path is provided around the EGR cooling flow path inside the cooler housing 74. A refrigerant inlet pipe 75 and a refrigerant outlet pipe 76 are provided outside the cooler housing 74. The refrigerant inlet pipe 75 and the refrigerant outlet pipe 76 are connected to a cooling water circulation circuit (not shown) of the engine 1 through a pipe (not shown). The engine coolant circulating in the coolant circulation circuit of the engine 1 flows into the coolant channel in the cooler housing 74 from the coolant inlet pipe 75 and absorbs the heat of the EGR gas flowing through the EGR cooling channel in the process of flowing through the coolant channel. Then, the refrigerant is returned from the refrigerant outlet pipe 76 to the cooling water circulation circuit of the engine 1.

  The EGR gas passing through the EGR cooler 71 is cooled by exchanging heat with the engine coolant in the process of flowing through the EGR cooling flow path. The EGR gas that has passed through the EGR cooler 71 is guided to the downstream EGR gas flow rate detector 3.

  7A is a cross-sectional view of the EGR gas flow rate detector 3 along the line AA in FIG. 7B, and FIG. 7B is a side view of the EGR gas flow rate detector 3. FIG.

  The EGR gas flow rate detector 3 includes a cylindrical sensor housing 34 interposed in the EGR merging passage 64, and detects the flow rate of EGR gas by the pressure in the sensor housing 34.

  The sensor housing 34 has flanges 35 and 36 on the inlet side and the outlet side, respectively. The EGR gas flow rate control valve 4 is connected to the flange 36 on the outlet side via a pipe.

  An inner wall surface 69 of the sensor housing 34 defines a throttle portion 37. The narrowed portion 37 has a cross-sectional area that gradually decreases from the upstream side to the central portion, and gradually increases from the central portion to the downstream side.

  A hole 38 is opened on the upstream side of the throttle portion 37, and a high pressure side pressure detector (not shown) for detecting the pressure is interposed in the hole 38.

  A hole 89 is opened at the center of the throttle portion 37, and a low-pressure side pressure detector (not shown) for detecting the pressure is interposed in the hole 89.

  A hole 44 is opened on the downstream side of the throttle portion 37, and a temperature detector (not shown) for detecting the temperature is interposed in the hole 44.

  The controller 9 inputs detection signals from the high pressure side pressure detector and the low pressure side pressure detector, and calculates the flow rate of EGR gas based on the pressure difference between the two. Further, the controller 9 receives a detection signal from the temperature detector and corrects the flow rate of the EGR gas based on the detected temperature of the EGR gas.

  FIG. 8 is a perspective view of the EGR gas flow rate control valve 4. The figure is a front view of the EGR gas flow control valve 4.

  The EGR gas flow rate control valve 4 includes a valve housing 23 that guides EGR gas flowing out from the EGR gas flow rate detector 3 to the intake manifold 19, a valve (not shown) accommodated in the valve housing 23, And an actuator 27 that opens and closes.

  The valve housing 23 has three flanges 24, 25 and 26. The two inlet side flanges 24 and 25 are connected to a flange 36 on the outlet side of the sensor housing 34 via a pipe. A flange 26 on the outlet side of the valve housing 23 is connected to the intake manifold 19.

  When the EGR gas flow rate control valve 4 is opened, EGR gas flows into the valve housing 23 from the openings of the two inlet side flanges 24 and 25 as shown by arrows in FIG. 8, and the opening of the flange 26 on the outlet side is opened. To the intake manifold 19. The EGR gas flow rate control valve 4 changes the flow rate of EGR gas according to the opening degree.

  During operation of the engine 1, exhaust flows discharged from the cylinders alternately flow into the first and second exhaust manifolds 31 and 32, and exhaust pressure pulsations are generated according to the engine speed range. At the exhaust junction 33, the exhaust blowdown flow at the beginning of the exhaust stroke in each cylinder flows out from the first and second ejectors 49 and 50 alternately to the housing inlet 13, whereby the first and second ejectors 49 and 50 are discharged. Exhaust gas from the air is alternately sucked into the housing inlet 13 to increase the exhaust efficiency.

  The EGR device 60 takes out EGR gas from the upstream side of the turbine 12 in the exhaust passage 30 and introduces it to the downstream side of the compressor 11 in the intake passage 20. By recirculating EGR gas to each cylinder, the combustion temperature in the combustion chamber is lowered and the amount of nitrogen oxides generated is suppressed.

  The turbocharger 10 supercharges intake air compressed by exhaust energy from the intake passage 20 to each cylinder. Thereby, the amount of oxygen in the intake air supplied to each cylinder is secured.

  An operation state in which the exhaust pulsation pressure generated in the first and second exhaust manifolds 31 and 32 propagates to the first and second EGR tributary passages 61 and 62 and the peak value of the exhaust pulsation pressure exceeds the intake pressure of the intake passage 20. , The first and second check valves 51 and 52 are alternately opened. As a result, the EGR gas can be recirculated to each cylinder even in a high-load operation state in which the intake pressure of the intake manifold 19 is higher than the average exhaust pressure of the first and second exhaust manifolds 31 and 32.

  The EGR gas guided to the first and second EGR branch passages 61 and 62 merges at the EGR junction 63, and the EGR cooler 71, the EGR gas flow rate detector 3, and the EGR gas flow rate interposed in the EGR junction passage 64. It is guided to the intake passage 20 through the control valve 4. The EGR gas is cooled by the EGR cooler 71, whereby the charging efficiency (EGR rate) with respect to the intake air can be increased.

  The controller 9 obtains a target value of the EGR gas flow rate according to the operating state of the engine 1 based on a preset map, and the EGR gas flow rate detected via the EGR gas flow rate detector 3 approaches the target value. Thus, the opening degree of the EGR gas flow rate control valve 4 is feedback controlled.

  Hereinafter, the gist, operation, and effect of the present embodiment will be described.

  In the present embodiment, the EGR device 60 of the multi-cylinder engine 1 recirculates EGR gas to the intake passage 20 using exhaust pulsation pressure, and first collects exhaust from cylinder groups whose ignition sequences are not continuous with each other. The first and second EGR tributary passages 61 and 62 that take out EGR gas from the second exhaust manifolds 31 and 32, respectively, and the EGR gas guided by the first and second EGR tributary passages 61 and 62 are joined together. An EGR junction 63, and first and second check valves 51 and 52 for stopping the backflow of EGR gas interposed in the EGR junction 63 and guided by the first and second EGR branch passages 61 and 62, respectively. , An EGR merging passage 64 for guiding the EGR gas merged at the EGR junction 63 to the intake passage 20, and the EGR merging passage 4 an EGR cooler 71 for cooling the EGR gas flowing through the, a structure comprising a.

  Based on the above configuration, the EGR gas guided by the first and second EGR branch passages 61 and 62 opens the first and second check valves 51 and 52 at the EGR junction 63 and joins. Even in a high-load operation state where the intake pressure is higher than the exhaust pressure, the first and second check valves 51, 52 are configured to utilize the exhaust pulsation pressure propagating to the first and second EGR branch passages 61, 62. It becomes possible to alternately open the valve and recirculate the EGR gas to each cylinder.

  The EGR gas merged at the EGR junction 63 is guided to the EGR cooler 71 interposed in the EGR merge passage 64, and is cooled in the process of passing through the EGR cooler 71, so that the charging efficiency for intake air is increased.

  Since a single EGR cooler 71 is interposed downstream of the EGR junction 63, the structure of the first and second EGR tributary passages 61 and 62 is compared with the conventional structure in which the EGR cooler is interposed respectively. Simplification is achieved, and the degree of freedom for installing the EGR cooler 71 in a limited space around the engine body can be increased, and the size and cost of the product can be reduced.

  In the present embodiment, the EGR junction 63 includes the refrigerant jackets 56 to 58 through which the refrigerant flows.

  Based on the above configuration, the first and second check valves 51 and 52 accommodated in the EGR junction 63 are cooled by the refrigerant flowing through the refrigerant jackets 56 to 58, and the first and second check valves 51 and 52 are Overheating is suppressed. By ensuring the cooling performance of the first and second check valves 51 and 52, the EGR cooler 71 can be disposed on the downstream side of the junction housing 14.

  In the present embodiment, the first and second check valves 51 and 52 include a reed valve 54 made of a spring plate, and the reed valve is opened when the first and second check valves 51 and 52 are opened at the EGR junction 63. Cooling wall surfaces 86, 87 a, 87 b, 88 with which 54 abuts are formed, and refrigerant jackets 56, 58 are formed along the cooling wall surfaces 86, 87 a, 87 b, 88.

  Based on the above configuration, when the first and second check valves 51 and 52 are opened, each reed valve 54 comes into contact with the cooling wall surfaces 86, 87 a, 87 b, 88, The heat exchange is performed between the first and second check valves 51 and 52, and the cooling performance of the first and second check valves 51 and 52 is sufficiently ensured.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

1 Engine 20 Intake Passage 30 Exhaust Passage 31 First Exhaust Manifold 32 Second Exhaust Manifold 51 First Check Valve 52 Second Check Valve 54 Reed Valve 56-58 Refrigerant Jacket 60 EGR Device 61 First EGR Branch passage 62 Second EGR branch passage 63 EGR junction 64 EGR junction passage 81 First EGR branch end 82 Second EGR branch end 83 EGR junction end 86, 87a, 87b, 88 Cooling wall surface

Claims (3)

An EGR device for a multi-cylinder engine that recirculates EGR gas to an intake passage using exhaust pulsation pressure,
First and second EGR tributary passages that respectively take out EGR gas from first and second exhaust manifolds that respectively collect exhaust from cylinder groups whose ignition order is not continuous with each other;
An EGR junction that joins the EGR gases respectively guided by the first and second EGR branch passages;
First and second check valves that stop backflow of EGR gas interposed in the EGR junction and guided by the first and second EGR branch passages, respectively.
An EGR merging passage for guiding EGR gas merged at the EGR junction to the intake passage;
An EGR device for a multi-cylinder engine, comprising: an EGR cooler that cools EGR gas flowing through the EGR merging passage.   The multi-cylinder engine EGR device according to claim 1, wherein the EGR junction includes a refrigerant jacket through which a refrigerant flows. The first and second check valves include a reed valve made of a spring plate,
The EGR junction is formed with a cooling wall surface with which the reed valve abuts when the first and second check valves are opened,
3. The multi-cylinder engine EGR device according to claim 2, wherein the refrigerant jacket is formed along the cooling wall surface.