JP2008281012A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine for suppressing combustion dispersion among cylinders by uniforming the amount of exhaust gas to be recirculated in each of the cylinders. <P>SOLUTION: In a V-8 unequally-spaced ignition engine, the heat conductivity of an exhaust passage for a fourth cylinder #4, a fifth cylinder #5, a seventh cylinder #7, and an eighth cylinder #8 where overlap periods do not overlap one another in an exhaust stroke is set to be lower than that of the passage area of an exhaust passage for a first cylinder #1, a second cylinder #2, a third cylinder #3, and a sixth cylinder #6 where overlap periods overlap one another in an exhaust stroke in the specified cylinders. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an unequal interval ignition type V-type multi-cylinder internal combustion engine in which a plurality of cylinders are divided into left and right banks and the cylinders of each bank are ignited and exploded at unequal intervals.

  In a general V-type multi-cylinder engine, the cylinder block has two banks inclined at a predetermined angle at the top, and a piston is movably fitted to each cylinder provided in each bank. It is connected to a crankshaft rotatably supported at the bottom. In addition, each combustion chamber is configured by fastening a cylinder head to the upper part of each bank of the cylinder block, and each combustion chamber is formed with an intake port and an exhaust port, and can be opened and closed by an intake valve and an exhaust valve. It has become. The downstream part of the intake pipe is branched into two and connected to the intake port of each bank, while the upstream part of the exhaust pipe is branched into two and connected to the exhaust port of each bank. A catalytic device is mounted in the downstream portion.

  For example, in a V-type 8-cylinder engine, the left bank is provided with a first cylinder, a third cylinder, a fifth cylinder, and a seventh cylinder, and the right bank is provided with a second cylinder, a fourth cylinder, a sixth cylinder, Eight cylinders are provided, and an exhaust pipe is connected to each bang through an exhaust manifold. In order to optimize the dynamic balance of the valve train, the firing order of each cylinder is as follows: first cylinder, eighth cylinder, seventh cylinder, third cylinder, sixth cylinder, fifth cylinder, fourth cylinder, It has 2 cylinders. Further, in the V-type 8-cylinder engine, the exhaust valve closing timing is retarded and the intake valve opening timing is advanced for the purpose of reducing the pumping loss due to the piston and reducing the generated NOx. The latter half of the valve opening period overlaps the first half of the intake valve opening period.

Japanese Patent Laid-Open No. 3-070810 Special table 2003-515025 gazette

  However, in the V-type 8-cylinder engine described above, since the ignition order is not the cylinder number order, the left bank is ignited at unequal intervals in the order of the first cylinder, the seventh cylinder, the third cylinder, and the fifth cylinder. In the right bank, the eighth cylinder, the sixth cylinder, the fourth cylinder, and the second cylinder are ignited in this order, and the ignition (explosion) intervals in each bank are unequal. Therefore, in the left bank, the overlap period of the first cylinder and the exhaust stroke of the seventh cylinder overlap, and the overlap period of the third cylinder and the exhaust stroke of the fifth cylinder overlap. In the right bank, the overlap period of the second cylinder and the exhaust stroke of the eighth cylinder overlap, and the overlap period of the sixth cylinder and the exhaust stroke of the fourth cylinder overlap.

  When the overlap period of one cylinder overlaps with the exhaust stroke of the other cylinder, the exhaust valve of the other cylinder opens while the intake valve and the exhaust valve of one cylinder are open, and this other cylinder Exhaust gas discharged from the exhaust port of the engine passes through the exhaust manifold and adversely affects one cylinder as exhaust pulsation. That is, the exhaust pulsation of the other cylinder acts on one cylinder, and in this one cylinder, the exhaust gas circulation amount that returns from the exhaust manifold to the cylinder (combustion chamber) through the exhaust port, that is, the internal EGR amount. Will increase. As a result, the amount of intake air varies due to the difference in internal EGR amount among the cylinders, combustion varies and becomes unstable, the output torque fluctuates, and fuel efficiency and exhaust gas performance increase due to overlap. The effects such as cannot be obtained.

  In addition, in the engine which performs non-uniform interval ignition, there exist the technique described in the said patent document 1, 2 as what suppresses the dispersion | variation in the filling efficiency and knock characteristic by exhaust interference in a specific cylinder, for example. However, the exhaust system of the internal combustion engine disclosed in Patent Document 1 has an ejector shape in which a collection portion of the exhaust manifold of a cylinder having a small ignition interval from the preceding cylinder in the ignition order is formed in a specific cylinder due to exhaust pulsation of the exhaust manifold. It is not possible to suppress the combustion fluctuation that occurs due to the increase in the internal EGR amount. Further, the multi-cylinder internal combustion engine of Patent Document 2 has a reduced exhaust impact by reducing the overlap period, and cannot sufficiently suppress an increase in the internal EGR amount of a specific cylinder due to exhaust pulsation. In addition, it is impossible to improve fuel consumption and exhaust gas performance due to overlap.

  An object of the present invention is to solve such a problem, and an object of the present invention is to provide an internal combustion engine in which variation in combustion among cylinders is suppressed by uniformizing an exhaust gas recirculation amount in each cylinder. To do.

In order to solve the above-described problems and achieve the object, the internal combustion engine of the present invention includes a plurality of cylinders divided into left and right banks, and the cylinders in each bank are ignited at unequal intervals, and In the internal combustion engine having a period in which the exhaust valve opening period and the intake valve opening period overlap in each cylinder, the first cylinder in which the overlap period overlaps the exhaust stroke of a specific cylinder in each bank. The exhaust gas recirculation amount of each cylinder is reduced so that the deviation between the exhaust gas recirculation amount and the exhaust gas recirculation amount of the second cylinder in which the overlap period does not overlap the exhaust stroke of a specific cylinder is reduced. An exhaust gas recirculation amount changing means for changing is provided. As the exhaust gas recirculation amount changing means, the heat conductivity of the exhaust system connected to the first cylinder is changed to an exhaust system connected to the second cylinder. Than the thermal conductivity of It is characterized in that it has ku set.

According to the internal combustion engine of the present invention, a plurality of cylinders are divided into left and right banks, the cylinders in each bank are ignited at unequal intervals, and the exhaust valve opening period and the intake valve opening period in each cylinder In an internal combustion engine having an overlapping period, the exhaust gas recirculation amount of the first cylinder in which the overlapping period overlaps with the exhaust stroke of the specific cylinder and the overlapping period does not overlap with the exhaust stroke of the specific cylinder Exhaust gas recirculation amount changing means for changing the exhaust gas recirculation amount of each cylinder is provided so that a deviation from the exhaust gas recirculation amount of the second cylinder is reduced . Since the thermal conductivity of the exhaust system connected to the first cylinder is set lower than the thermal conductivity of the exhaust system connected to the second cylinder, in the first cylinder where the overlap period overlaps, the overlap period If they overlap Although the internal exhaust gas recirculation amount is increased by the exhaust pulsation as compared with the second cylinder, the internal exhaust gas recirculation amount of the first cylinder or the internal exhaust gas of the second cylinder is changed by the exhaust gas recirculation amount changing means. By changing the recirculation amount or the external exhaust gas recirculation amount of each cylinder, the exhaust gas recirculation amount in each cylinder can be made uniform, and variations in combustion among the cylinders can be suppressed.

  Embodiments of an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a schematic plan view of a V-type 8-cylinder engine representing an internal combustion engine according to Embodiment 1 of the present invention, FIG. 2 is a schematic configuration diagram of the V-type 8-cylinder engine of Embodiment 1, and FIG. 2 is a time chart showing the opening timing of an intake valve and an exhaust valve in one V-type 8-cylinder engine.

  In the first embodiment, a V-type 8-cylinder engine is applied as the internal combustion engine. In this V-type 8-cylinder engine, as shown in FIGS. 1 and 2, the cylinder block 11 has left and right banks 12 and 13 inclined at a predetermined angle at the upper portion, and each bank 12 and 13 has four banks 12 and 13 respectively. Cylinder bores 14 and 15 are formed, and pistons 16 and 17 are fitted to the respective cylinder bores 14 and 15 so as to be vertically movable. A crankshaft (not shown) is rotatably supported at the lower part of the cylinder block 11, and the pistons 16 and 17 are connected to the crankshaft via connecting rods 18 and 19, respectively.

  On the other hand, cylinder heads 20 and 21 are fastened to the upper portions of the banks 12 and 13 of the cylinder block 11, and the combustion chambers 22 and 23 are constituted by the cylinder block 11, the pistons 16 and 17, and the cylinder heads 20 and 21. ing. The intake ports 24 and 25 and the exhaust ports 26 and 27 are formed on the upper portions of the combustion chambers 22 and 23, that is, the lower surfaces of the cylinder heads 20 and 21 so as to face each other. 27, the lower end portions of the intake valves 28 and 29 and the exhaust valves 30 and 31 are located. The intake valves 28 and 29 and the exhaust valves 30 and 31 are supported by the cylinder heads 20 and 21 so as to be movable in the axial direction, and are attached in a direction to close the intake ports 24 and 25 and the exhaust ports 26 and 27. It is supported. Further, intake camshafts 32 and 33 and exhaust camshafts 34 and 35 are rotatably supported on the cylinder heads 20 and 21, and the intake cams 36 and 37 and the exhaust cams 38 and 39 are interposed via a roller rocker arm (not shown). Are in contact with the upper ends of the intake valves 28 and 29 and the exhaust valves 30 and 31.

  Accordingly, when the intake camshafts 32 and 33 and the exhaust camshafts 34 and 35 rotate in synchronization with the engine, the intake cams 36 and 37 and the exhaust cams 38 and 39 operate the roller rocker arm, and the intake valves 28 and 29 and the exhaust valve 30 and 31 move up and down at a predetermined timing to open and close intake ports 24 and 25 and exhaust ports 26 and 27, intake ports 24 and 25 and combustion chambers 22 and 23, combustion chambers 22 and 23, and exhaust port 26. , 27 can communicate with each other.

  In addition, the valve mechanism of this engine is a variable intake valve timing mechanism (VVT) 40 that controls the intake valves 28 and 29 and the exhaust valves 30 and 31 at an optimal opening / closing timing according to the operating state. 41 and an exhaust variable valve mechanism 42, 43. The intake variable valve operating mechanisms 40 and 41 and the exhaust variable valve operating mechanisms 42 and 43 are configured, for example, by providing VVT controllers at the shaft end portions of the intake camshafts 32 and 33 and the exhaust camshafts 34 and 35. The opening / closing timing of the intake valves 28, 29 and the exhaust valves 30, 31 is advanced or retarded by changing the phase of each camshaft 32, 33, 34, 35 with respect to the cam sprocket by a pump (or electric motor). Is something that can be done. In this case, each variable valve mechanism 40, 41, 42, 43 advances or retards the opening / closing timing with the operating angle (opening period) of intake valves 28, 29 and exhaust valves 30, 31 being constant. The intake camshafts 32, 33 and the exhaust camshafts 34, 35 are provided with cam position sensors 44, 45, 46, 47 for detecting their rotational phases.

  A surge tank 50 is connected to the intake ports 24 and 25 of the cylinder heads 20 and 21 via intake manifolds 48 and 49, and an intake pipe 51 is connected to the surge tank 50. An air cleaner 52 is attached to the intake port. The intake pipe 51 is provided with an electronic throttle device 53 having a throttle valve located on the downstream side of the air cleaner 52. On the other hand, a connecting pipe 58 is connected to the exhaust ports 26 and 27 via exhaust manifolds 54 and 55 and catalyst devices 56 and 57, and an exhaust pipe 59 is connected to the connecting pipe 58. A catalyst device 60 is mounted.

  The cylinder heads 20 and 21 are respectively provided with injectors 61 and 62 for injecting fuel (gasoline) directly into the combustion chambers 22 and 23. Delivery pipes 63 and 64 are connected to the injectors 61 and 62, respectively. The delivery pipes 63 and 64 can be supplied with fuel at a predetermined pressure from the high-pressure fuel pump 65. The cylinder heads 20 and 21 are equipped with spark plugs 66 and 67 that are located above the combustion chambers 22 and 23 and ignite the air-fuel mixture.

  By the way, an electronic control unit (ECU) 68 is mounted on the vehicle, and this ECU 68 can control and detect the fuel injection timing of the injectors 61 and 62, the ignition timing of the spark plugs 66 and 67, and the like. The fuel injection amount, the injection timing, the ignition timing, and the like are determined based on the engine operating state such as the intake air amount, the intake air temperature, the throttle opening, the accelerator opening, the engine speed, and the cooling water temperature. That is, an air flow sensor 69 and an intake air temperature sensor 70 are mounted on the upstream side of the intake pipe 51, and the measured intake air amount and intake air temperature are output to the ECU 68. The electronic throttle device 53 is provided with a throttle position sensor 71, and the accelerator pedal is provided with an accelerator position sensor 72, which outputs the current throttle opening and accelerator opening to the ECU 68. Further, a crank angle sensor 73 is provided on the crankshaft, and the detected crank angle is output to the ECU 68. The ECU 68 calculates the engine speed based on the crank angle. Further, the cylinder block 11 is provided with a water temperature sensor 74 and outputs the detected engine cooling water temperature to the ECU 68.

  Further, the ECU 68 can control the intake variable valve mechanisms 40 and 41 and the exhaust variable valve mechanisms 42 and 43 based on the engine operating state. That is, when the temperature is low, when the engine is started, when idling, or when the load is light, the exhaust gas is discharged from the intake port 24, by eliminating the overlap between the opening timing of the exhaust valves 30, 31 and the opening timing of the intake valves 28, 29. 25 or the amount of air blown back to the combustion chambers 22 and 23 is reduced, and combustion stability and fuel efficiency can be improved. Further, at the time of medium load, by increasing the overlap, the internal EGR rate is increased to improve the exhaust gas purification efficiency, and the pumping loss is reduced to improve the fuel consumption. Further, at the time of high-load low-medium rotation, the closing timing of the intake valves 28 and 29 is advanced to reduce the amount of intake air that blows back to the intake ports 24 and 25, thereby improving volumetric efficiency. At the time of high load and high rotation, the closing timing of the intake valves 28 and 29 is retarded according to the rotational speed, thereby improving the volume efficiency as the timing according to the inertial force of the intake air.

  Incidentally, in the V-type 8-cylinder engine of this embodiment, as shown in FIG. 1, the first bank # 1, the third cylinder # 3, the fifth cylinder # 5, and the seventh cylinder # 7 are connected in series to the left bank 12. In the right bank 13, the second cylinder # 2, the fourth cylinder # 4, the sixth cylinder # 6, and the eighth cylinder # 8 are provided in series, and the exhaust manifolds 54 and 55 are provided in the bangs 12 and 13, respectively. The connecting pipe 58 and the exhaust pipe 59 are connected to each other. In order to optimize the dynamic balance of the valve train, the firing order of each cylinder is as follows: first cylinder # 1, eighth cylinder # 8, seventh cylinder # 7, third cylinder # 3, sixth cylinder # 6, fifth cylinder # 5, fourth cylinder # 4, and second cylinder # 2.

  Therefore, in this V-type 8-cylinder engine, since the ignition order is not the order of the cylinder number, in the left bank, the first cylinder # 1- (180 ° CA) —the seventh cylinder # 7— (90 ° CA) —the third cylinder— (180 ° CA) -Fifth cylinder # 5- (270 ° CA) -First cylinder # 1 are ignited at unequal intervals, and in the right bank, the eighth cylinder # 8- (270 ° CA) -No. The six cylinders # 6- (180 ° CA) -fourth cylinder # 4- (90 ° CA) -second cylinder # 2- (180 ° CA) -eighth cylinder # 8 will be ignited in this order. Ignition (explosion) intervals in are uneven. Therefore, in the left bank 12, the overlap period of a specific cylinder overlaps with the exhaust stroke of another cylinder, and the exhaust gas discharged from the cylinder in the exhaust stroke passes through the exhaust manifold to the cylinder in the overlap period. Acting as exhaust pulsation, only the internal EGR amount of this cylinder increases.

  That is, as shown in FIG. 3, in the left bank 12, in the first cylinder # 1, the intake timing by the intake valve 28 is advanced by the intake variable valve mechanism 40 in the vicinity of the crank angle 360 ° CA, The exhaust timing by the exhaust valve 30 is retarded by the exhaust variable valve mechanism 42, so that an overlap period OL is provided here. On the other hand, in the seventh cylinder # 7, the exhaust stroke starts when the exhaust valve 30 starts to open near the crank angle of 360 ° CA. Therefore, in the vicinity of the crank angle 360 ° CA, the overlap period of the first cylinder # 1 overlaps the initial exhaust stroke of the seventh cylinder # 7.

  Then, when the intake valve 28 and the exhaust valve 30 of the first cylinder # 1 are opened, the exhaust valve 30 of the seventh cylinder # 7 is opened, and the exhaust gas discharged from the exhaust port 26 of the seventh cylinder # 7. Acts as exhaust pulsation on the first cylinder # 1 through the exhaust manifold 54. That is, when exhaust pulsation acts on the first cylinder # 1 from the seventh cylinder # 7, in this first cylinder # 1, the internal EGR that returns from the exhaust manifold 54 to the combustion chamber 22 through the exhaust port 26 by this exhaust pulsation. The amount increases, and the amount of air drawn from the intake port 24 decreases.

  This phenomenon is not limited to the first cylinder # 1, but the exhaust stroke of the eighth cylinder # 8 in the third cylinder # 3 in which the overlap period OL overlaps with the exhaust stroke of the fifth cylinder # 5 or in the right bank 13. This occurs in the sixth cylinder # 6 where the overlap period OL overlaps the exhaust stroke of the second cylinder # 2 and the fourth cylinder # 4 where the overlap period OL overlaps. When the internal EGR amount increases in the first cylinder # 1, the second cylinder # 2, the third cylinder # 3, and the sixth cylinder # 6, the fourth cylinder # 4, the fifth cylinder # 5, This is different from the internal EGR amount and the air amount of the seventh cylinder # 7 and the eighth cylinder # 8, the combustion varies and becomes unstable, and the output torque fluctuates.

  Therefore, in the first embodiment, as shown in FIG. 1, in each of the banks 12 and 13, the seventh cylinder # 7, the eighth cylinder # 8, the fifth cylinder # 5, and the fourth cylinder # 4 as specific cylinders. The internal EGR amount of the first cylinder # 1, the third cylinder # 3, the second cylinder # 2, and the sixth cylinder # 6 (the exhaust gas recirculation amount, Internal exhaust gas recirculation amount), and the exhaust strokes of the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 as the second cylinders whose overlap periods do not overlap. The exhaust gas recirculation amount can be changed (exhaust gas recirculation amount changing means) so that the deviation from the internal EGR amount is reduced. In the first embodiment, as the exhaust gas recirculation amount changing means, the first cylinder # 1, the second cylinder # 2, the third cylinder # 3, the first cylinder are connected in the exhaust system connected to the banks 12 and 13. The passage areas of the exhaust passages of the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 are set larger than the passage area of the exhaust passage of the sixth cylinder # 6.

  Specifically, in the exhaust manifold 54 of the left bank 12, the branch pipe 54a connected to the exhaust port 26a of the first cylinder # 1 and the branch pipe 54b connected to the exhaust port 26b of the third cylinder # 3. Are combined and connected to the first collecting pipe 54A, while the branch pipe 54c connected to the exhaust port 26c of the fifth cylinder # 5 and the branch pipe 54d connected to the exhaust port 26d of the seventh cylinder # 7. Are collected and connected to the second collecting pipe 54B, and the collecting pipes 54A and 54B are gathered and connected to the third collecting pipe 54C, and the third collecting pipe 54C is connected to the connecting pipe 58. The exhaust ports 26a and 26b and the branch pipes 54a and 54b of the first cylinder # 1 and the third cylinder # 3 are compared with the exhaust ports 26c and 26d and the branch pipe 54c of the fifth cylinder # 5 and the seventh cylinder # 7. , 54d, that is, the pipe inner diameter is set large.

  Further, in the right bank 13, a branch pipe 55a connected to the exhaust port 27a of the second cylinder # 2 and a branch pipe 55c connected to the exhaust port 27c of the sixth cylinder # 6 are gathered to form a first set. On the other hand, the branch pipe 55b connected to the exhaust port 27b of the fourth cylinder # 4 and the branch pipe 55d connected to the exhaust port 27d of the eighth cylinder # 8 are combined to be connected to the pipe 55A. The collecting pipes 55A and 55B are connected to the pipe 55B and connected to the third collecting pipe 55C. The third collecting pipe 55C is connected to the connecting pipe 58. The exhaust ports 27a and 27c and the branch pipes 55a and 55c of the second cylinder # 2 and the sixth cylinder # 6 are compared with the exhaust ports 27b and 27d and the branch pipe 55b of the fourth cylinder # 4 and the eighth cylinder # 8. , 55d, that is, the pipe inner diameter is set large.

  Therefore, in the first bank # 1 and the third cylinder # 3 in the left bank 12, the internal EGR amount is affected by the exhaust pulsation of the seventh cylinder # 7 and the fifth cylinder # 5 during the overlap period. To increase. On the other hand, the fifth cylinder # 5 and the seventh cylinder # 7 are not affected by the exhaust pulsation of the other cylinders during the overlap period, but the exhaust ports 26c, 26d of the fifth cylinder # 5 and the seventh cylinder # 7 and Since the passage areas of the branch pipes 54c and 54d are larger than the passage areas of the exhaust ports 26a and 26b and the branch pipes 54a and 54b of the first cylinder # 1 and the third cylinder # 3, the exhaust gas of the exhaust system is exhausted to the exhaust port. In the fifth cylinder # 5 and the seventh cylinder # 7, the exhaust gas drawing amount increases and the internal EGR amount increases by a predetermined amount, with the flow velocity drawn into the combustion chamber 22 through 26c and 26d being constant. . As a result, the internal EGR amount that is the same as the internal EGR amount increased in the first cylinder # 1 and the third cylinder # 3 is also increased in the fifth cylinder # 5 and the seventh cylinder # 7. The amount of internal EGR in each cylinder becomes substantially uniform.

  Similarly, in the right bank 13, in the second cylinder # 2 and the sixth cylinder # 6, the internal EGR amount is affected by the exhaust pulsation of the eighth cylinder # 8 and the fourth cylinder # 4 during the overlap period. Quantitative increase. On the other hand, the fourth cylinder # 4 and the eighth cylinder # 8 are not affected by the exhaust pulsation of the other cylinders during the overlap period, but the exhaust ports 27b, 27d of the fourth cylinder # 4 and the eighth cylinder # 8 and Since the passage areas of the branch pipes 55b and 55d are larger than the passage areas of the exhaust ports 27a and 27c and the branch pipes 55a and 55c of the second cylinder # 2 and the sixth cylinder # 6, the exhaust gas of the exhaust system is discharged to the exhaust port. In the fourth cylinder # 4 and the eighth cylinder # 8, the exhaust gas drawing amount increases and the internal EGR amount increases by a predetermined amount, with the flow velocity drawn into the combustion chamber 22 through 27b and 27d being constant. . As a result, the internal EGR amount that is the same as the internal EGR amount increased in the second cylinder # 2 and the sixth cylinder # 6 is also increased in the fourth cylinder # 4 and the eighth cylinder # 8. The amount of internal EGR in each cylinder becomes substantially uniform.

  Thus, in the internal combustion engine of the first embodiment, in the V-type 8-cylinder engine, the first cylinder # 1, the third cylinder # 3, and the second cylinder # in which the overlap period overlaps with the exhaust stroke of a specific cylinder. 2, the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 in which the overlap period does not overlap the exhaust stroke with respect to the passage area of the exhaust passage in the sixth cylinder # 6 The passage area of the exhaust passage is set large.

  Therefore, in the cylinders # 1, # 2, # 3, and # 6 where the overlap period overlaps the exhaust stroke, the internal EGR amount increases by a predetermined amount due to the influence of exhaust pulsation during this period, while the overlap period overlaps the exhaust stroke. In cylinders # 4, # 5, # 7, and # 8 that do not overlap each other, they are not affected by exhaust pulsation during this period, but exhaust ports 26c, 26d, 27b, and 27d as exhaust passages and branch pipes 54c, 54d, and 55b , 55d has a large passage area, the exhaust gas of the exhaust system is drawn in a large amount into the combustion chamber 22 through the exhaust passage, and the internal EGR amount increases by a predetermined amount. Therefore, the internal EGR amount equal to the internal EGR amount increased by the exhaust pulsation in each cylinder # 1, # 2, # 3, # 6 is not affected by the exhaust pulsation. 7 and # 8 are also increased due to the expansion of the exhaust passage surface, and the internal EGR amount in each of the cylinders # 1 to # 8 of all the banks 12 and 13 becomes almost uniform. As a result, variations in combustion between cylinders can be suppressed, fluctuations in output torque can be suppressed, and fuel consumption improvement and exhaust gas performance improvement due to overlap can be appropriately achieved.

  In the first embodiment, the exhaust passage areas of the cylinders # 1, # 2, # 3, and # 6 where the exhaust pulsation acts and the cylinders # 4, # 5, # 7, and # 8 where the exhaust pulsation does not act. The size of the exhaust passage area may be set optimally according to the engine speed, engine load, intake negative pressure, overlap period, and the like.

  Further, in the first embodiment, as the exhaust gas recirculation amount changing means, in order to increase the passage area of the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 exhaust passage, Although the passage areas of the exhaust ports 26c, 26d, 27b, and 27d and the branch pipes 54c, 54d, 55b, and 55d are set large, the passage area of only the exhaust ports 26c, 26d, 27b, and 27d may be increased.

  FIG. 4 is a schematic plan view of a V-type 8-cylinder engine that represents an internal combustion engine according to Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the V-type 8-cylinder engine of the second embodiment, as shown in FIG. 4, in each bank 12, 13, the first cylinder # 1, the second cylinder # 2, and the overlap period overlap with the exhaust stroke of a specific cylinder. The internal EGR amounts of the third cylinder # 3 and the sixth cylinder # 6 and the internal EGR amounts of the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 that do not overlap with each other. The exhaust gas recirculation amount can be changed (exhaust gas recirculation amount changing means) so as to reduce the deviation from the above. In the second embodiment, the exhaust gas recirculation amount changing means includes the first cylinder # 1, the second cylinder # 2, and the third cylinder # in the exhaust manifolds 54 and 55 connected to the banks 12 and 13, respectively. 3. The thermal conductivity of the exhaust passage of the sixth cylinder # 6 is set lower than the thermal conductivity of the exhaust passage of the fourth cylinder # 4, fifth cylinder # 5, seventh cylinder # 7, and eighth cylinder # 8. is doing.

  Specifically, in the exhaust manifold 54 of the left bank 12, the branch pipe 54a connected to the exhaust port 26a of the first cylinder # 1 and the branch pipe 54b connected to the exhaust port 26b of the third cylinder # 3. The branch pipe 54c connected to the exhaust port 26c of the fifth cylinder # 5 and the branch pipe 54d connected to the exhaust port 26d of the seventh cylinder # 7 are combined and connected to the connection pipe 58. The branch pipes 54a and 54b of the first cylinder # 1 and the third cylinder # 3 are manufactured from a low heat conductive metal such as a titanium alloy, and the branch pipes 54c and 54d of the fifth cylinder # 5 and the seventh cylinder # 7 are made of stainless steel. By manufacturing the steel, the thermal conductivity of the branch pipes 54a and 54b of the first cylinder # 1 and the third cylinder # 3 is changed to the thermal conductivity of the branch pipes 54c and 54d of the fifth cylinder # 5 and the seventh cylinder # 7. It is set to be lower than the rate.

  Further, in the exhaust manifold 55 of the right bank 13, a branch pipe 55a connected to the exhaust port 27a of the second cylinder # 2, a branch pipe 55b connected to the exhaust port 27b of the fourth cylinder # 4, and a sixth A branch pipe 55c connected to the exhaust port 27c of the cylinder # 6 and a branch pipe 55d connected to the exhaust port 27d of the eighth cylinder # 8 are gathered and connected to the connection pipe 58. The branch pipes 55a and 55c of the second cylinder # 2 and the sixth cylinder # 6 are made of a low heat conductive metal such as a titanium alloy, and the branch pipes 55b and 55d of the fourth cylinder # 4 and the eighth cylinder # 8 are made of stainless steel. By manufacturing the steel, the thermal conductivity of the branch pipes 55a and 55c of the second cylinder # 2 and the sixth cylinder # 6 is changed to the thermal conductivity of the branch pipes 55b and 55d of the fourth cylinder # 4 and the eighth cylinder # 8. It is set to be lower than the rate.

  Therefore, in the first bank # 1 and the third cylinder # 3 in the left bank 12, the internal EGR amount is affected by the exhaust pulsation of the seventh cylinder # 7 and the fifth cylinder # 5 during the overlap period. Although increased, the branch pipes 54a and 54b of the exhaust manifold 54 are made of a low heat conductive metal, so that the exhaust heat in the combustion chamber 22 is not easily transmitted to the exhaust manifold 54, and the internal temperature of the combustion chamber 22 rises and the energy of the internal EGR increases. As the combustion rate increases, the combustion speed improves, and the internal temperature of the combustion chamber 22 rises and the remaining exhaust gas undergoes volume expansion, thereby reducing the substantial internal EGR amount. On the other hand, in the fifth cylinder # 5 and the seventh cylinder # 7, the internal EGR amount does not fluctuate without being affected by the exhaust pulsation of the other cylinders during the overlap period. As a result, the internal EGR amount that decreases in the first cylinder # 1 and the third cylinder # 3 and the internal RGR amount in the fifth cylinder # 5 and the seventh cylinder # 7 become substantially the same, and each cylinder in the left bank 12 The amount of internal EGR becomes almost uniform.

  Similarly, in the right bank 13, in the second cylinder # 2 and the sixth cylinder # 6, the internal EGR amount is affected by the exhaust pulsation of the eighth cylinder # 8 and the fourth cylinder # 4 during the overlap period. Although the amount increases, since the branch pipes 55a and 55c of the exhaust manifold 55 are made of a low heat conductive metal, the exhaust heat in the combustion chamber 23 is not easily transmitted to the exhaust manifold 55, the internal temperature of the combustion chamber 23 rises, and the internal EGR As the energy increases, the combustion speed improves, and the internal temperature of the combustion chamber 23 rises, and the remaining exhaust gas undergoes volume expansion, thereby reducing the substantial internal EGR amount. On the other hand, in the fourth cylinder # 4 and the eighth cylinder # 8, the internal EGR amount does not fluctuate without being affected by the exhaust pulsation of the other cylinders during the overlap period. As a result, the internal EGR amount that decreases in the second cylinder # 2 and the sixth cylinder # 6 and the internal EGR amount in the fourth cylinder # 4 and the eighth cylinder # 8 are substantially the same, and the internal EGR amount in each cylinder of the right bank 13 The EGR amount becomes almost uniform.

  Thus, in the internal combustion engine of the second embodiment, in the V-type 8-cylinder engine, the first cylinder # 1, the third cylinder # 3, and the second cylinder in which the overlap period overlaps with the exhaust stroke of a specific cylinder. # 2, the thermal conductivity of the branch passages 54a, 54b, 55a, 55c in the exhaust manifolds 54, 55 of the sixth cylinder # 6, the fourth cylinder # 4, the fifth cylinder # 5, where the overlap period does not overlap the exhaust stroke The thermal conductivities of the branch passages 54c, 54d, 55b, and 55d in the exhaust manifolds 54 and 55 of the seventh cylinder # 7 and the eighth cylinder # 8 are set low.

  Therefore, in the cylinders # 1, # 2, # 3, and # 6 where the overlap period overlaps with the exhaust stroke, the internal EGR amount increases by a predetermined amount due to the influence of exhaust pulsation during this period, but the branch pipe of the exhaust manifold 54 Since 54a and 54b are low heat conductive metals, the exhaust heat of the combustion chamber 22 is not easily transmitted to the exhaust manifold 54, the internal temperature of the combustion chamber 22 rises, the combustion speed is improved, and the remaining exhaust gas expands in volume. As a result, the substantial internal EGR amount is reduced. On the other hand, in cylinders # 4, # 5, # 7, and # 8 where the overlap period does not overlap with the exhaust stroke, the internal EGR amount does not fluctuate during this period without being affected by exhaust pulsation. Therefore, the internal EGR amount of each cylinder # 1, # 2, # 3, # 6 affected by the exhaust pulsation and the internal EGR amount of each cylinder # 4, # 5, # 7, # 8 not affected by the exhaust pulsation Are substantially the same, and the internal EGR amounts in the cylinders # 1 to # 8 of all the banks 12 and 13 are substantially uniform. As a result, variations in combustion between cylinders can be suppressed, fluctuations in output torque can be suppressed, and fuel consumption improvement and exhaust gas performance improvement due to overlap can be appropriately achieved.

  In the second embodiment, the thermal conductivity of the exhaust passages of the cylinders # 1, # 2, # 3, and # 6 is set to the thermal conductivity of the exhaust passages of the cylinders # 4, # 5, # 7, and # 8. Therefore, the branch passages 54a, 54b, 55a, and 55c of the cylinders # 1, # 2, # 3, and # 6 are made of a low heat conductive metal such as a titanium alloy, and the cylinders # 4 and # 4 are manufactured. Although the branch pipes 54c, 54d, 55b, and 55d of # 5, # 7, and # 8 are manufactured from stainless steel, the present invention is not limited to this configuration. For example, the branch passages 54a, 54b, 55a, 55c of the cylinders # 1, # 2, # 3, and # 6 are made of stainless steel, and the branch pipes 54c of the cylinders # 4, # 5, # 7, and # 8 are manufactured. 54d, 55b, and 55d may be manufactured from a high heat conductive metal such as iron, and the manufacturing cost can be reduced without using an expensive material such as titanium.

  In the second embodiment, the thermal conductivity of cylinders # 1, # 2, # 3, and # 6 where exhaust pulsation acts and the heat of cylinders # 4, # 5, # 7, and # 8 where exhaust pulsation does not work. The magnitude of the conductivity may be set optimally according to the engine speed, engine load, intake negative pressure, overlap period, and the like.

  Further, in the second embodiment, as the exhaust gas recirculation amount changing means, the thermal conductivity of the cylinders # 1, # 2, # 3, and # 6 and the thermal conductivity of the cylinders # 4, # 5, # 7, and # 8 are used. In order to make the ratio different, the material of the branch pipes 54a to 54d and 55a to 55d is changed, but the material of the exhaust ports 26a to 26d and 27a to 27d may be changed.

  FIG. 5 is a graph showing lift amounts of intake valves and exhaust valves in a V-type 8-cylinder engine that represents an internal combustion engine according to Embodiment 3 of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  The configuration of the V-type 8-cylinder engine of Embodiment 3 is substantially the same as that of Embodiment 1 described above, and the valve mechanism will be described with reference to FIG. In the V-type 8-cylinder engine of the present embodiment, as shown in FIG. 2, the first cylinder # 1 and the third cylinder # 3 in which the overlap period overlaps with the exhaust stroke of a specific cylinder in each of the banks 12 and 13. The internal EGR amounts of the second cylinder # 2 and the sixth cylinder # 6 and the internal EGR of the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 that do not overlap with each other. The exhaust gas recirculation amount can be changed (exhaust gas recirculation amount changing means) so that the deviation from the amount decreases. In the third embodiment, as the exhaust gas recirculation amount changing means, the exhaust valves of the first cylinder # 1, the second cylinder # 2, the third cylinder # 3, and the sixth cylinder # 6 are used in each valve operating mechanism. The lift amounts of 30, 31 are set smaller than the lift amounts of the exhaust valves 30, 31 of the fourth cylinder # 4, fifth cylinder # 5, seventh cylinder # 7, and eighth cylinder # 8.

  Specifically, although not shown, the cam profiles of the exhaust cams 38 and 39 of the first cylinder # 1, the second cylinder # 2, the third cylinder # 3, and the sixth cylinder # 6, the fourth cylinder # 4, By making the cam profiles of the exhaust cams 38 and 39 of the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 different from each other, the respective valve lift amounts are made different. That is, as shown in FIG. 5, the lift amount of the exhaust valves 30, 31 of each cylinder # 1, # 2, # 3, # 6 is set to the exhaust valve 30 of each cylinder # 4, # 5, # 7, # 8. , 31 is set to be smaller than the lift amount of the exhaust ports 26, 27 during the overlap period in which both the intake valves 28, 29 and the exhaust valves 30, 31 are open (open area, lane portion in FIG. The area shown by is reduced.

  Accordingly, in the left bank 12, the first cylinder # 1 and the third cylinder # 3 are affected by the exhaust pulsation of the seventh cylinder # 7 and the fifth cylinder # 5 during the overlap period, but the exhaust valves 30, 31 are affected. Since the lift amount of the exhaust ports 26 and 27 is small, the internal EGR amount does not vary and becomes a predetermined amount. As a result, the internal EGR amounts of the first cylinder # 1 and the third cylinder # 3 affected by the exhaust pulsation and the internal EGR of the fifth cylinder # 5 and the seventh cylinder # 7 which are not affected by the exhaust pulsation are substantially the same. The amount of internal EGR in each cylinder of the left bank 12 becomes almost uniform. Similarly, in the right bank 13, the second cylinder # 2 and the sixth cylinder # 6 are affected by the exhaust pulsation of the eighth cylinder # 8 and the fourth cylinder # 4 during the overlap period. Since the lift amount of 31 is small and the opening areas of the exhaust ports 26 and 27 are small, the internal EGR amount does not vary and becomes a predetermined amount. As a result, the internal EGR amounts of the second cylinder # 2 and the sixth cylinder # 6 that are affected by the exhaust pulsation and the internal EGR of the fourth cylinder # 4 and the eighth cylinder # 8 that are not affected by the exhaust pulsation are substantially the same. The internal EGR amount in each cylinder of the right bank 13 becomes almost uniform.

  Thus, in the internal combustion engine of the third embodiment, in the V-type 8-cylinder engine, the first cylinder # 1, the third cylinder # 3, and the second cylinder # in which the overlap period overlaps with the exhaust stroke of a specific cylinder. 2. The lift amount of the exhaust valves 30 and 31 in the sixth cylinder # 6 is set to the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 where the overlap period does not overlap the exhaust stroke. The lift amount of the exhaust valves 30 and 31 is set to be smaller.

  Therefore, in the cylinders # 1, # 2, # 3, and # 6 where the overlap period overlaps with the exhaust stroke, the lift amount of the exhaust valves 30 and 31 is reduced and the exhaust ports 26 and 27 are affected by the exhaust pulsation during this period. Since the opening area is small, the internal EGR amount does not vary and becomes a predetermined amount. Therefore, the internal EGR amount of cylinders # 1, # 2, # 3, and # 6 that are affected by exhaust pulsation and the internal EGR amount of cylinders # 4, # 5, # 7, and # 8 that are not affected by exhaust pulsation are The amounts are almost the same, and the internal EGR amounts in the cylinders # 1 to # 8 of all the banks 12 and 13 are almost uniform. As a result, variations in combustion between cylinders can be suppressed, fluctuations in output torque can be suppressed, and fuel consumption improvement and exhaust gas performance improvement due to overlap can be appropriately achieved.

  In the third embodiment, the lift amount of the exhaust valves 30 and 31 of the cylinders # 1, # 2, # 3, and # 6 to which the exhaust pulsation acts and the cylinders # 4, # 5, and # to which the exhaust pulsation does not act. The setting of the magnitudes of the lift amounts of the exhaust valves 30 and 31 of 7 and # 8 may be optimized according to the engine speed, the engine load, the intake negative pressure, the overlap period, and the like.

  In the third embodiment, the cam profiles of the exhaust cams 38 and 39 of the cylinders # 1, # 2, # 3, and # 6 and the exhaust cams 38 and 39 of the cylinders # 4, # 5, # 7, and # 8 are used. Although the valve lift amounts are made different by making the cam profiles different from each other, the present invention is not limited to this configuration. For example, when the overlap period is changed by the exhaust variable valve mechanisms 42 and 43 according to the engine operating state, the exhaust camshafts 34 and 35 are provided with a plurality of exhaust cams having different cam profiles, You may make it switch according to an engine driving | running state.

  FIG. 6 is a schematic plan view of a V-type 8-cylinder engine representing an internal combustion engine according to Embodiment 4 of the present invention, and FIG. 7 is a flowchart of external EGR control in the V-type 8-cylinder engine of Embodiment 4. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the V-type 8-cylinder engine of the fourth embodiment, as shown in FIG. 6, in each of the banks 12 and 13, the first cylinder # 1 and the third cylinder # 3 in which the overlap period overlaps with the exhaust stroke of a specific cylinder. The internal EGR amounts of the second cylinder # 2 and the sixth cylinder # 6 and the internal EGR of the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 that do not overlap with each other. The exhaust gas recirculation amount can be changed (exhaust gas recirculation amount changing means) so that the deviation from the EGR amount obtained by adding the external EGR amount to the amount decreases. That is, in the fourth embodiment, the external EGR mechanism is provided as the exhaust gas recirculation amount changing means, and the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder are not affected by the exhaust pulsation. External EGR is supplied to # 8.

  More specifically, one end of an exhaust gas recirculation (EGR) passage 81 is connected to the downstream side of the catalyst device 57 on one side (right bank 13 side) of the connecting pipe 58, and this EGR passage 81 is The other end is branched into two branch pipes 82 and 83. One branch pipe 82 is connected to branch portions 48c and 48d corresponding to the fifth cylinder # 5 and the seventh cylinder # 7 in the intake manifold 48 on the left bank 12 side. The other branch pipe 83 is connected to branch portions 48c and 48d corresponding to the fourth cylinder # 4 and the eighth cylinder # 8 in the intake manifold 49 on the right bank 13 side. An EGR valve 84 is provided at the other end of the EGR passage 81. The ECU 68 can control the opening and closing of the EGR valve 84 according to the engine operating state, and controls the opening degree of the EGR valve 84 based on the engine speed, the engine load, the overlap period, and the intake negative pressure. .

  That is, as shown in FIG. 7, the engine speed and engine load (for example, throttle opening, intake air amount, fuel injection amount, etc.) are read in step S1, and the overlap period is detected in step S2. In step S3, intake negative pressure is detected. In step S4, the opening degree of the EGR valve 84 is set based on the engine speed, the engine load, the overlap period, and the intake negative pressure using a preset control map. Specifically, the internal EGR amount of cylinders # 1, # 2, # 3, and # 6 that increases due to the influence of exhaust pulsation during the overlap period, and the cylinder # 4 that is not affected by exhaust pulsation during the overlap period , # 5, # 7, and # 8 are estimated based on the engine operating state, and the opening degree of the EGR valve 84 is set so that both the EGR deficiency amount and the external EGR amount are the same amount. .

  Accordingly, in each of the banks 12 and 13, in the first cylinder # 1, the third cylinder #, the second cylinder # 2, and the third cylinder # 6, the seventh cylinder # 7 and the fifth cylinder # 5 in the overlap period. The internal EGR amount increases by a predetermined amount under the influence of the exhaust pulsation. On the other hand, in the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8, the internal EGR amount does not increase without being influenced by other exhaust pulsations, but the exhaust gas is not in the EGR passage. By being supplied as an external EGR through 81 and branch pipes 82 and 83, the EGR amount as a whole increases by a predetermined amount. As a result, the EGR amount of the first cylinder # 1, the third cylinder # 3, the second cylinder # 2, and the third cylinder # 6 that are affected by the exhaust pulsation and the fourth cylinder # 4 that is not affected by the exhaust pulsation The EGR of the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 are substantially the same, and the EGR amounts in the respective cylinders of the banks 12 and 13 are substantially uniform.

  Thus, in the internal combustion engine of the fourth embodiment, in the V-type 8-cylinder engine, the external EGR mechanism is provided, and the first cylinder # 1 and the third cylinder # in which the overlap period overlaps with the exhaust stroke of a specific cylinder. 3. No external EGR is supplied to the second cylinder # 2 and the sixth cylinder # 6, and the overlap period does not overlap the exhaust stroke. The fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, External EGR is supplied only to the eighth cylinder # 8.

  Therefore, in the cylinders # 1, # 2, # 3, and # 6 where the overlap period overlaps the exhaust stroke, the internal EGR amount increases by a predetermined amount due to the influence of exhaust pulsation during this period, while the overlap period overlaps the exhaust stroke. In cylinders # 4, # 5, # 7, and # 8 that do not overlap, the exhaust pulsation is not affected during this period, but the exhaust gas is supplied as an external EGR through the EGR passage 81 and the branch pipes 82 and 83. The total EGR amount obtained by adding the external EGR amount to the internal EGR amount increases by a predetermined amount. Therefore, the EGR amounts of cylinders # 1, # 2, # 3, and # 6 that are affected by exhaust pulsation are substantially the same as the EGR amounts of cylinders # 4, # 5, # 7, and # 8 that are not affected by exhaust pulsation. The EGR amount in each of the cylinders # 1 to # 8 of all the banks 12 and 13 is almost uniform. As a result, variations in combustion between cylinders can be suppressed, fluctuations in output torque can be suppressed, and fuel consumption improvement and exhaust gas performance improvement due to overlap can be appropriately achieved.

  FIG. 8 is a schematic plan view of a V-type 8-cylinder engine that represents an internal combustion engine according to Embodiment 5 of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the V-type 8-cylinder engine of the fifth embodiment, as shown in FIG. 8, the first cylinder # 1 and the third cylinder # 3 in which the overlap period overlaps with the exhaust stroke of a specific cylinder in each bank 12, 13. The EGR amounts of the second cylinder # 2 and the sixth cylinder # 6 and the EGR amounts of the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 that do not overlap with each other. The exhaust gas recirculation amount can be changed (exhaust gas recirculation amount changing means) so as to reduce the deviation. That is, in the fourth embodiment, the external EGR mechanism is provided as the exhaust gas recirculation amount changing means, and the first cylinder # 1, the third cylinder # 3, the second cylinder # 2, the sixth cylinder #, which are affected by the exhaust pulsation. The external EGR amount to 6 and the external EGR amount to the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 that are not affected by the exhaust pulsation are adjusted. Yes.

  More specifically, one end of an exhaust gas recirculation (EGR) passage 91 is connected to the downstream side of the catalyst device 57 on one side (right bank 13 side) of the connecting pipe 58, and this EGR passage 91 is The other end is branched into two branch pipes 92 and 93. One branch pipe 92 is branched into two at the tip end side, and one branch portion 92a is connected to the branch portions 48a and 48b corresponding to the first cylinder # 1 and the third cylinder # 3 on the left bank 12 side. The branch portion 92b is connected to the branch portions 49a and 49c corresponding to the second cylinder # 2 and the sixth cylinder # 6 on the right bank 13 side. Further, the other branch pipe 93 branches into two at the tip end side, and one branch portion 93a is connected to the branch portions 48c and 48d corresponding to the fifth cylinder # 5 and the seventh cylinder # 7 on the left bank 12 side. The other branch portion 93b is connected to the branch portions 49b and 49d corresponding to the fourth cylinder # 4 and the eighth cylinder # 8 on the right bank 13 side. The branch pipes 92 and 93 are provided with EGR valves 94 and 95, respectively. The ECU 68 can control the opening and closing of the EGR valves 94 and 95 according to the engine operating state, and controls the opening degree of the EGR valve 84 based on the engine speed, the engine load, the overlap period, and the intake negative pressure. ing.

  That is, the ECU 68 sets the opening degree of each EGR valve 94, 95 based on the engine speed, the engine load, the overlap period, and the intake negative pressure using a preset control map. Specifically, the ECU 68 performs control so that the opening degree of the EGR valves 94 and 95 becomes larger as the engine is in a higher rotation and higher load state, that is, a large amount of EGR is introduced into the intake system. Further, the ECU 68 increases the internal EGR amount of the cylinders # 1, # 2, # 3, and # 6 that are increased by the influence of the exhaust pulsation during the overlap period, and the cylinder # 4 that is not affected by the exhaust pulsation during the overlap period. , # 5, # 7, and # 8 are estimated based on the engine operating state, and the opening degree of the EGR valve 84 is set so that both the EGR deficiency amount and the external EGR amount are the same amount. .

  Therefore, in each of the banks 12 and 13, in the first cylinder # 1, the third cylinder # 3, the second cylinder # 2, and the sixth cylinder # 6, the seventh cylinder # 7 and the fifth cylinder # 5 in the overlap period. The internal EGR amount increases by a predetermined amount under the influence of the exhaust pulsation. On the other hand, in the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8, the internal EGR amount does not increase without being influenced by other exhaust pulsations, but the exhaust gas is not in the EGR passage. By being supplied as an external EGR through 91 and the branch pipes 92 and 93, the EGR amount as a whole increases by a predetermined amount. As a result, the EGR amount of the first cylinder # 1, the third cylinder # 3, the second cylinder # 2, and the sixth cylinder # 6 that are affected by the exhaust pulsation, and the fourth cylinder # 4 that is not affected by the exhaust pulsation, The EGR amounts of the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 are substantially the same, and the EGR amounts in the respective cylinders of the banks 12 and 13 are substantially uniform.

  Thus, in the internal combustion engine of the fifth embodiment, in the V-type 8-cylinder engine, the external EGR mechanism is provided so that the external EGR can be supplied to all the cylinders # 1 to # 8 and the exhaust stroke is exceeded. A large amount of external EGR is supplied to the fourth cylinder # 4, the fifth cylinder # 5, the seventh cylinder # 7, and the eighth cylinder # 8 where the lap periods do not overlap.

  Therefore, in the cylinders # 1, # 2, # 3, and # 6 where the overlap period overlaps the exhaust stroke, the internal EGR amount increases by a predetermined amount due to the influence of exhaust pulsation during this period, while the overlap period overlaps the exhaust stroke. In cylinders # 4, # 5, # 7, and # 8 that do not overlap, the exhaust pulsation is not affected during this period, but a large amount of exhaust gas is supplied as external EGR through the EGR passage 91 and branch pipes 92 and 93. Thus, the total EGR amount obtained by adding the external EGR amount to the internal EGR amount increases by a predetermined amount. Therefore, the EGR amounts of cylinders # 1, # 2, # 3, and # 6 that are affected by exhaust pulsation are substantially the same as the EGR amounts of cylinders # 4, # 5, # 7, and # 8 that are not affected by exhaust pulsation. The EGR amount in each of the cylinders # 1 to # 8 of all the banks 12 and 13 is almost uniform. As a result, variations in combustion between cylinders can be suppressed, fluctuations in output torque can be suppressed, and fuel consumption improvement and exhaust gas performance improvement due to overlap can be appropriately achieved.

  In the above-described embodiment, the exhaust system piping configuration is configured such that in the first embodiment, the left and right banks 12 and 13 aggregate two cylinders and then four cylinders. , 5, four cylinders are directly assembled in the left and right banks 12, 13, but any configuration may be used.

  Further, in each of the above-described embodiments, the firing order of each cylinder is changed to the first cylinder # 1, the eighth cylinder # 8, the seventh cylinder # 7, the third cylinder # 3, the sixth cylinder # 6, and the fifth cylinder #. 5. The fourth cylinder # 4 and the second cylinder # 2 are not limited to this order. The cylinders in the banks 12 and 13 may ignite and explode at unequal intervals. It is. In each of the above-described embodiments, the cylinder injection internal combustion engine that directly injects fuel into the combustion chamber is used. However, a port injection internal combustion engine that injects fuel into the intake system may be used. Furthermore, although the engine of the present invention has been described as a V-type 8-cylinder engine, the number of cylinders is not limited to this.

  As described above, the internal combustion engine according to the present invention has an exhaust gas recirculation so that the deviation between the exhaust gas recirculation amount of the cylinder where exhaust pulsation acts and the exhaust gas recirculation amount of the cylinder where exhaust pulsation does not work is reduced. The circulation amount is changed, and it is useful for an internal combustion engine of unequal interval ignition / explosion type.

1 is a schematic plan view of a V-type 8-cylinder engine that represents an internal combustion engine according to Embodiment 1 of the present invention. 1 is a schematic configuration diagram of a V-type 8-cylinder engine according to Embodiment 1. FIG. 3 is a time chart showing the opening timing of the intake valve and the exhaust valve in the V-type 8-cylinder engine of the first embodiment. It is a schematic plan view of the V type 8 cylinder engine showing the internal combustion engine which concerns on Example 2 of this invention. It is a graph showing the lift amount of the intake valve and the exhaust valve in the V type 8 cylinder engine showing the internal combustion engine which concerns on Example 3 of this invention. It is a schematic plan view of the V type 8 cylinder engine showing the internal combustion engine which concerns on Example 4 of this invention. 7 is a flowchart of external EGR control in a V-type 8-cylinder engine according to a fourth embodiment. It is a schematic plan view of the V type 8 cylinder engine showing the internal combustion engine which concerns on Example 5 of this invention.

Explanation of symbols

12, 13 Banks 22, 23 Combustion chambers 24, 25 Intake ports 26, 26a to 26d, 27, 27a to 27d Exhaust ports (exhaust gas recirculation amount changing means)
28, 29 Intake valve 30, 31 Exhaust valve 36, 37 Intake cam 38, 39 Exhaust cam (exhaust gas recirculation amount changing means)
40, 41 Intake variable valve mechanism 42, 43 Exhaust variable valve mechanism 54, 55 Exhaust manifold (exhaust gas recirculation amount changing means)
54a to 54d, 55a to 55d Branch pipe 61, 62 Injector 66, 67 Spark plug 68 Electronic control unit, ECU
81, 91 Exhaust gas recirculation (EGR) passage (exhaust gas recirculation amount changing means)
82, 83, 92, 93 Branch pipe 84, 94, 95 EGR valve # 1, # 2, # 3, # 6 cylinder (first cylinder)
# 4, # 5, # 7, # 8 cylinder (second cylinder)

Claims (1)

A plurality of cylinders are divided into left and right banks, and the cylinders of each bank are ignited at unequal intervals, and the exhaust valve opening period and the intake valve opening period in each cylinder overlap each other. In the internal combustion engine having the above, in each bank, the exhaust gas recirculation amount of the first cylinder in which the overlap period overlaps with the exhaust stroke of the specific cylinder and the overlap period does not overlap with the exhaust stroke of the specific cylinder. as the deviation between the exhaust gas recirculation amount of the second cylinder is reduced, the exhaust gas recirculation amount changing means for changing the exhaust gas recirculation amount of the respective cylinders is provided, as the exhaust gas recirculation amount changing means An internal combustion engine characterized in that the heat conductivity of the exhaust system connected to the first cylinder is set lower than the heat conductivity of the exhaust system connected to the second cylinder .

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