JP4631694B2 - Turbocharged engine - Google Patents

Description

  The present invention relates to a supercharged engine having an exhaust turbocharger and an electric supercharger, and belongs to the technical field of the engine.

  Conventionally, there are cases where a turbocharger such as an exhaust turbocharger or an electric supercharger is provided for the purpose of improving the output torque of an automobile engine. Among these, as an engine having an exhaust turbocharger, For example, there is one described in Patent Document 1. As shown in FIG. 12, in the four-cylinder engine A having four cylinders # 1 to # 4, the portion from the engine body B in the exhaust system C to the turbine D1 of the exhaust turbocharger D is ignited. A plurality of independent exhaust passages E2 and E3 guided from the even-numbered second cylinder # 2 and third cylinder # 3 and a collective exhaust passage F1 formed by collecting downstream portions of the independent exhaust passages E2 and E3. A plurality of independent exhaust passages E1 and E4 led from the first cylinder # 1 and the fourth cylinder # 4 having an odd ignition order, and downstream portions of the independent exhaust passages E1 and E4. This is composed of a second exhaust passage G2 formed by a collective exhaust passage F2.

  According to this, when the combustion gas discharged from each of the cylinders # 1 to # 4 is led to the turbine D1 of the supercharger D, there is no exhaust interference on the exhaust system C. Increases efficiency. Further, the volume of the first exhaust passage G1 for the second and third cylinders # 2 and # 3 and the volume of the second exhaust passage G2 for the first and fourth cylinders # 1 and # 4 are the engine body in the exhaust system C. Since all the parts from B to the turbine D1 of the exhaust turbocharger D are not divided, the expansion rate of the exhaust gas discharged from each of the cylinders # 1 to # 4 is reduced, and supercharging is performed. A decrease in exhaust pressure acting on the turbine D1 of the machine D is also suppressed. As a result, combined with the cancellation of the exhaust interference, the engine output torque is greatly improved.

  By the way, the exhaust turbocharger is generally intended for when the engine is running at a high speed, but even when the engine is running at a low speed, an improvement in the output torque of the engine is desired. It is conceivable to provide an electric supercharger in addition to the exhaust turbocharger as in the engine described in Patent Document 2.

Japanese Patent Laid-Open No. 2004-1224749 JP 2002-21573 A

  However, the engine described in Patent Document 1 is different from the engine described in Patent Document 2 in that the portion from the engine main body to the turbine of the exhaust turbocharger in the exhaust system differs from the engine described in Patent Document 2. Since it is configured with an exhaust passage, it is necessary to study how to effectively use this configuration.

  Therefore, the present invention provides an electric supercharger in an engine with a supercharger in which a portion from an engine main body in an exhaust system to a turbine of an exhaust turbocharger is constituted by a first exhaust passage and a second exhaust passage. It is an object of the present invention to provide a configuration capable of improving the output torque at the time of engine low rotation by effectively utilizing the configuration of the exhaust system when arranging a machine.

  In order to solve the above-described problems, the present invention is configured as follows.

  First, the invention according to claim 1 of the present application includes an engine body having an even number of cylinders, an exhaust system connected to the engine body, and an exhaust turbocharger provided in the exhaust system. And a part from the engine main body to the turbine of the exhaust turbocharger in the exhaust system is a plurality of independent exhausts led from either the odd numbered cylinder or the even numbered cylinder among the even number of cylinders. A first exhaust passage composed of a passage and a collective exhaust passage in which downstream portions of the independent exhaust passages are gathered, and an independent communication communicating with the other cylinder of the even number of cylinders whose firing order is odd or even. The second exhaust passage is composed of an exhaust passage and a collective exhaust passage formed by collecting downstream portions of the independent exhaust passage, and the first exhaust passage has a smaller volume than the second exhaust passage. With a turbocharged engine Thus, the intake system includes, from the upstream side, a common intake passage in which the compressor of the exhaust turbocharger is disposed, first and second branch intake passages branched from the common intake passage, and the first A plurality of independent intake passages branched from the branched intake passage and led to a cylinder corresponding to the first exhaust passage, and a cylinder branched from the second branch intake passage and corresponding to the second exhaust passage. A plurality of guided independent intake passages, an electric supercharger is provided in the first branch intake passage, the engine speed is lower than a predetermined speed, and the engine load An electric supercharger control means for operating the electric supercharger when is higher than a predetermined load is provided.

  The invention according to claim 2 is the engine with a supercharger according to claim 1, wherein the engine is an in-cylinder injection engine and is configured such that fuel is injected during the compression process. It is characterized by being.

  According to a third aspect of the present invention, in the engine with a supercharger according to the first or second aspect, a turbine of the exhaust turbocharger is provided for each of the first and second exhaust passages. A waste gate valve for relieving exhaust gas on the upstream side, a first supercharging pressure detecting means for detecting a supercharging pressure downstream of the electric supercharger in the first branch intake passage; A second supercharging pressure detecting means for detecting the supercharging pressure of the two branch intake passages, and a first exhaust passage when the supercharging pressure detected by the first supercharging pressure detecting means exceeds a predetermined pressure. A waste gate valve control means for opening the waste gate valve on the second exhaust passage side when the boost pressure detected by the second boost pressure detection means is equal to or higher than a predetermined pressure. Open the wastegate valve on the first exhaust passage side Kinosho pressure is characterized in that it is lower than the predetermined pressure when opening a wastegate valve of the second exhaust passage side.

  Next, the effect of the present invention will be described.

First, according to the first aspect of the present invention, when the engine speed is lower than the predetermined speed and the engine load is higher than the predetermined load, the electric supercharger operates.

  Here, in the present invention, the intake system includes, from the upstream side, a common intake passage where the compressor of the exhaust turbocharger is disposed, and first and second branched intake passages branched from the common intake passage. , A plurality of independent intake passages branched from the first branch intake passage and led to cylinders corresponding to the first exhaust passage, and branched from the second branch intake passage to the second exhaust passage. In addition to a plurality of independent intake passages led to the corresponding cylinders, an electric supercharger is provided in the first branch intake passage communicating with the cylinder corresponding to the first exhaust passage. The supercharging by the electric supercharger is performed only for the corresponding cylinder for the following reason.

  That is, as a first point, the volume of the first exhaust passage is smaller than that of the second exhaust passage as described above, and as a result, the exhaust pressure is less reduced than that of the second exhaust passage. The turbine of the turbocharger can be driven efficiently, but conversely, the exhaust pressure of the second exhaust passage tends to be lower than that of the first exhaust passage. This means that the turbine of the feeder cannot be driven as efficiently as the first exhaust passage side. Therefore, even if all the cylinders are supercharged by the same amount by the electric supercharger, the driving capability of the turbine is not improved on the second exhaust passage side as compared to the first exhaust passage side.

  As a second point, it is preferable to use an electric supercharger having a capacity as large as possible in view of the supercharging capability. In this case, however, the power consumption of the motor that drives the motor of the supercharger increases. Thus, there is a problem that the size of the motor itself increases as the battery becomes larger.

  Therefore, in the present invention, an electric supercharger is provided in the first branch intake passage communicating with the cylinder corresponding to the first exhaust passage having good turbine driving efficiency, and the cylinder corresponding to the first exhaust passage is provided with respect to the cylinder. Only supercharging by an electric supercharger is performed intensively. According to this, for example, when an electric supercharger having the same supercharging capability as that in the case where supercharging is performed on all cylinders by an electric supercharger and driven in the same state, On the other hand, since the intake passage volume to be compressed is smaller, the intake air can be further compressed. That is, the supercharging pressure to the cylinder corresponding to the first exhaust passage can be further increased, and the exhaust pressure in the first exhaust passage having good turbine drive efficiency can be further increased. On the other hand, in the case of the present invention, since the cylinder corresponding to the second exhaust passage is only supercharged by the exhaust turbocharger, the supercharging pressure of the cylinder corresponding to the second exhaust passage is This is lower than when supercharging by the electric supercharger is performed on all cylinders, and as a result, the exhaust pressure in the second exhaust passage is lowered. However, as described above, the exhaust pressure is greatly increased due to the small volume on the first exhaust passage side, while the exhaust pressure is only slightly reduced due to the large volume on the second exhaust passage side. . Therefore, overall, the ability to drive the exhaust turbine is increased, and as a result, the engine output torque is increased when compared with the case where all the cylinders are supercharged by the electric supercharger at the same engine speed. Will be.

  In other words, when the same output torque is to be obtained, an electric supercharger having a relatively small capacity can be used. This also reduces power consumption and reduces adverse effects on the battery that supplies power to the electric supercharger.

  By the way, the supercharging capacity of the exhaust turbocharger usually increases as the engine speed increases, but the maximum supercharging capacity of the electric supercharger is almost constant regardless of the engine speed. As the number increases, the supercharging effect by the electric supercharger decreases relatively. In this case, if the electric supercharger has a relatively small capacity and its maximum supercharging capacity is smaller than the maximum supercharging capacity of the exhaust turbocharger, the supercharging capacity will be increased when the engine speed exceeds a certain number of revolutions. Due to the shortage, the supercharging effect by the electric supercharger cannot be obtained. However, in the present invention, as described above, since the supercharging pressure to the cylinder corresponding to the first exhaust passage can be further increased, the supercharging effect by the electric supercharger and the improvement of the engine output torque are improved. The effect will be expanded to a higher rotational speed region.

  Here, the opening period of the intake valve and the opening period of the exhaust valve usually have a period of overlap, in which the combustion gas is exhausted while fresh air is being taken into the cylinder from the intake passage. As described above, the first exhaust passage is smaller in volume than the second exhaust passage, and the exhaust pressure tends to increase, so that the scavenging of the combustion gas does not occur. It becomes difficult to be done. Therefore, there is a possibility that knocking is likely to occur due to deterioration of combustibility due to the combustion gas remaining without being scavenged. However, in the present invention, since the supercharging pressure for the cylinder corresponding to the first exhaust passage where the exhaust pressure tends to be high is increased by the electric supercharger, the scavenging performance is improved by the pushing effect, and as a result, the combustibility Is improved and knocking is prevented.

  According to the invention of claim 2, the engine is an in-cylinder injection engine, and fuel is injected into the compression process, that is, fuel is injected after scavenging, so that the fuel is injected into the port during scavenging. Thus, it is prevented that the air is blown through, so that combustion is stabilized and knocking is prevented well.

  By the way, the exhaust pressure usually increases as the engine speed increases. Therefore, as described in the effect of the first aspect, the engine speed is increased even in the region where the engine speed is lower than the predetermined speed. There is a difference in the supercharging effect with respect to the engine, and the higher the engine speed, the relatively lower the supercharging effect by the electric supercharger. This is also because the higher the engine speed, the higher the electric supercharger. It means that the air push-in ability due to is relatively lowered. Therefore, the closer to the predetermined number of revolutions, the worse the scavenging performance of the cylinder corresponding to the first exhaust passage is compared to the second exhaust passage side.

  Therefore, in the invention described in claim 3, a wastegate valve for relieving exhaust gas is provided for each of the first and second exhaust passages upstream of the turbine of the exhaust turbocharger, and the first exhaust is provided. When the supercharging pressure on the downstream side of the electric supercharger in the passage becomes equal to or higher than a predetermined pressure, the wastegate valve on the first exhaust passage side is opened, and the supercharging pressure in the second exhaust passage becomes equal to or higher than the predetermined pressure. Sometimes when the waste gate valve on the second exhaust passage side is opened and the waste gate valve on the first exhaust passage side is opened, the predetermined pressure when the waste gate valve on the second exhaust passage side is opened. According to this, the waste gate valve on the first exhaust passage side opens earlier than the waste gate valve on the second exhaust passage side, and the exhaust pressure in the first exhaust passage increases. This also suppresses scavenging. It is good.

  Hereinafter, a supercharged engine according to an embodiment of the present invention will be described.

  As shown in FIG. 1, a supercharged engine 1 according to the present invention (hereinafter referred to as “engine 1”) includes first to fourth four cylinders # 1 to # 4 arranged in series. This is an in-cylinder in-line four-cylinder engine. In each of the cylinders # 1 to # 4 provided in the main body 2 of the engine 1, when an intake valve (not shown) is opened, the combustion chambers 2a to 2 are connected from the intake system 10 via the intake port. Air for fuel combustion is sucked into 2d. An amount of fuel (gasoline) corresponding to the amount of intake air is directly injected into the air in each of the combustion chambers 2a to 2d from a fuel injection valve (not shown) at a predetermined timing during the compression stroke. It is formed. This air-fuel mixture is compressed by a piston (not shown), and is ignited and burned by a spark plug (not shown) at a predetermined timing. In the engine 1, ignition is performed in the order of the first cylinder # 1, the third cylinder # 3, the fourth cylinder # 4, and the second cylinder # 2. The combustion gas, that is, the exhaust gas is discharged to the exhaust system 20 via the exhaust port when an exhaust valve (not shown) is opened. Note that the opening period of the intake valve and the opening period of the exhaust valve partially overlap each other.

  The intake system 10 is provided with one common intake passage 11. The common intake passage 11 has an air intake (not shown), an air cleaner (not shown) for removing dust in the air, and an air flow rate in order from the upstream side in the air flow direction. An air flow sensor (not shown) for detection, a compressor 12p of the twin scroll turbocharger 12, and an intercooler 13 for cooling the air that has been pressurized by the compressor 12p and heated to a high temperature are provided.

  The downstream end of the common intake passage 11 is connected to the first and second branch intake passages 14 and 15. Near the connecting portion of the first and second branch intake passages 14 and 15 with the common intake passage 11, first and second throttle valves 16 and 17 for adjusting the air amount are provided. Portions on the downstream side of the throttle valves 16 and 17 in the first and second branch intake passages 14 and 15 each have a function as a surge tank that stabilizes the air flow. Are connected to the independent intake passages 18b and 18c for the second and third cylinders # 2 and # 3 whose downstream ends are connected to the intake ports of the second and third cylinders # 2 and # 3, respectively. Connected to the branch intake passage 15 are independent intake passages 18a and 18d for the first and fourth cylinders # 1 and # 4 whose downstream ends are connected to the intake ports of the first and fourth cylinders # 1 and # 4. Has been.

  An electric supercharger 19 is provided on the upstream side of the first throttle valve 16 in the first branch intake passage 14. Although not shown in detail, the electric supercharger 19 is a well-known one composed of a compressor and a motor for driving the compressor. It is provided for the purpose of further improving the engine torque by assisting the supercharging by the exhaust turbo supercharger 12 when the engine speed is lower than the predetermined speed and the engine load is higher than the predetermined load. Here, the supercharging region by the electric supercharger 15 is set as the engine low / medium rotation region because the intake air flow rate is large and the supercharging pressure by the exhaust turbocharger 14 is high in the high engine rotation region. However, in this case, it is necessary to use a motor that consumes a large amount of power and has a large size and weight. In this case, however, the cost increases, the battery that supplies power to the motor has an adverse effect, the body size increases, This is to avoid problems such as an increase.

  A first boost pressure sensor 32 and a second boost pressure are provided downstream of the first throttle valve 16 in the first branch intake passage 14 and downstream of the second throttle valve 17 in the second branch intake passage 15. A sensor 33 is provided.

  The exhaust system 20 is provided with independent exhaust passages 21a to 21d for the first to fourth cylinders # 1 to # 4 whose upstream ends are connected to the exhaust ports of the first to fourth cylinders # 1 to # 4, respectively. It has been. Here, the independent exhaust passages 21a to 21d are arranged in such a way that the independent exhaust passages of the cylinders whose ignition order is not continuous and whose exhaust strokes are not adjacent belong to the same exhaust group. Grouped into exhaust groups. Specifically, the independent exhaust passages 21b and 21c led from the second and third cylinders # 2 and # 3 having the even ignition order belong to the first group, and the first and fourth ignition orders having the odd ignition order are included. The independent exhaust passages 21a and 21d led from the cylinders # 1 and # 4 belong to the second exhaust group.

  The downstream portions of the independent exhaust passages 21b and 21c belonging to the first exhaust group are gathered and connected to the first collective exhaust passage 22, and the downstream portions of the independent exhaust passages 21a and 21d belonging to the second exhaust group are the second collective exhaust passage. 23. The downstream end of the first collective exhaust passage 22 is connected to the first scroll portion 12a of the twin scroll turbocharger 12, and the downstream end of the second collective exhaust passage 23 is gathered and connected to the second scroll portion 12b. Has been. The downstream ends of both scroll portions 12 a and 12 b are connected to one common exhaust passage 24. Hereinafter, the independent exhaust passages 21b and 21c and the first collective exhaust passage 22 belonging to the first exhaust group will be collectively referred to as a first exhaust passage 20a, and the independent exhaust passages 21a and 21a belonging to the second exhaust group will be referred to as necessary. 21d and the second collective exhaust passage 23 are collectively referred to as a second exhaust passage 20b.

  In the turbine 12t of the exhaust turbocharger 12, a partition wall extending in a direction substantially perpendicular to the turbine axis is provided in the housing, and the exhaust spiral chamber or scroll is divided into two in the turbine axis direction by the partition wall. Yes. One of the exhaust swirl chamber or scroll (one closer to the compressor 12p) divided in this way is the first scroll portion 12a, and the other is the second scroll portion 12b. Therefore, in the exhaust turbo supercharger 12 or the turbine 12t, the occurrence of exhaust interference is prevented, and the supercharging efficiency is increased.

  Here, as described above, the first exhaust passage 20a is a group of the adjacent second and third cylinders # 2 and # 3, and the second exhaust passage 20b is separated. Since the arranged first and fourth cylinders # 1 and # 4 are grouped, as is apparent from FIG. 1, the first exhaust passage 20b is compared with the second exhaust passage 20a. The passage length is long and the volume is large. In the engine 1 according to the present embodiment, the supercharger 12 is attached to an intermediate position between the second and third cylinders # 2 and # 3 on the side of the cylinder block of the engine body 2, and the first exhaust is provided. The passage length of the exhaust manifold portion constituting the passage 20a is as short as about 3 cm, and the passage length of the exhaust manifold portion constituting the second exhaust passage 20b is as long as about 40 cm. This is to make the effects and effects described later appear prominently. The volume refers to the volume of the portion of the exhaust port of the engine body 2 and the first exhaust passage 20a portion of the exhaust system 20, and the portion of the exhaust port of the engine body 2 and the second exhaust passage 20b portion of the exhaust system 20. This is the volume of the combined part.

  FIG. 2 shows a general relationship between the volume of the exhaust passage (passage length) and the supercharging pressure and the exhaust pressure in the exhaust passage. As is clear from this figure, The exhaust pressure of each tends to decrease as the exhaust passage length increases. Therefore, in the configuration of the present embodiment shown in FIG. 1, as indicated by the solid line in FIG. 3, the exhaust pressure in the first exhaust passage 20a having a short exhaust passage length and a small exhaust volume is greater than the exhaust passage length. Becomes longer than the exhaust pressure in the second exhaust passage 20b having a large exhaust volume.

  FIG. 4 shows the general relationship between the exhaust passage length and the exhaust temperature at the position immediately before the turbine of the turbocharger. As is clear from this figure, the exhaust temperature at the position immediately before the turbine becomes lower as the exhaust passage length becomes longer. Tend to be. Further, although not shown, the larger the exhaust volume, the lower the expansion and the lower the tendency. Therefore, in the configuration of the present embodiment shown in FIG. 1, the exhaust temperature at the position immediately before the turbine 12t of the turbocharger 12 is the exhaust gas in the first exhaust passage 20a having a short exhaust passage length and a small exhaust volume. The passage length is longer than that of the second exhaust passage 20b having a large exhaust volume.

  On the upstream side of the turbine 12t of the exhaust turbo supercharger 12, first and second waste gate valves 25 and 26 for relieving exhaust gas are provided for the first and second exhaust passages 20a and 20b, respectively. At the same time, there are provided first and second relief passages 27 and 28 that guide the exhaust gas thus relieved to the common exhaust passage 24 downstream of the turbine 12t.

  As shown in FIG. 1, the engine 1 is provided with a control unit 30 (ECU) and an engine rotation sensor 31 that detects the engine speed, and the control unit 30 receives an engine from the engine rotation sensor 31. A signal relating to the rotational speed and a signal relating to the supercharging pressure from the first and second supercharging pressure sensors 32, 33 are inputted, the throttle valves 16, 17, the electric supercharger 19, and the first and second supercharging pressure sensors. A control signal is output to the waste gate valves 25 and 26.

  Next, an example of control of the electric supercharger 19 by the control unit 30 will be described with reference to the flowchart of FIG. 5. First, in step S1, signals from various sensors are input. Next, in step S2, it is determined whether or not the electric supercharger 19 is in the operating region. Here, whether or not it is in the operating region is determined based on the map shown in FIG. In this map, the engine low, medium, and high load regions in which the engine speed is lower than the predetermined speed and the engine load is higher than the predetermined load (the engine speed in claim 1 is lower than the predetermined speed and the engine load is predetermined). The region higher than the load) is set as the electric supercharger operating region, and the other region is set as the electric supercharger non-operating region. The control unit 30 (ECU) controls the opening degree of the first throttle valve 16 and the second throttle valve 17 to the same opening degree at least in the electric supercharger operating region.

  Next, in step S3, the target rotational speed of the electric supercharger 19 is calculated based on the engine rotational speed and the engine load, and in step S4, the supply current for operating the electric supercharger 19 at this target rotational speed. In step S5, this current is output to the motor of the electric supercharger 19.

  On the other hand, when it is not in the electric supercharger operation region in step S2, the electric supercharger 19 is not operated and the process returns as it is.

  An example of the control of the first and second wastegate valves 25 and 26 by the control unit 30 will be described with reference to the flowchart of FIG. 7. First, in step S11, signals from various sensors are input. Next, in step S12, it is determined whether or not the boost pressure detected by the second boost pressure sensor 33 is equal to or higher than a first predetermined pressure α. If the boost pressure is equal to or higher than the first predetermined pressure α, the first boost pressure is detected in step S13. The open signal is output to both the second waste gate valves 25 and 26. On the other hand, if it is not equal to or higher than the first predetermined pressure α, it is determined in step S14 whether or not the boost pressure detected by the first boost pressure sensor 32 is equal to or higher than the second predetermined pressure β. Here, the first predetermined pressure α is larger than the second predetermined pressure β. Further, the first and second predetermined pressures α and β are set so that the scavenging properties of the cylinders # 1 to # 4 are substantially the same. Specifically, the exhaust pressure in the second exhaust passage 20b when the supercharging pressure in the second branch intake passage 15 (the supercharging pressure detected by the second supercharging pressure sensor 33) is the first predetermined pressure α, and the first The exhaust pressure in the first exhaust passage 20a when the supercharging pressure in the branch intake passage 14 (the supercharging pressure detected by the first supercharging pressure sensor 32) is the second predetermined pressure β is set to be substantially equal. (See FIGS. 9 and 10). If the pressure is equal to or higher than the second predetermined pressure β, an open signal is output to the first wastegate valve 25 and a close signal is output to the second wastegate valve 26 in step S15. Close signals are output to both the first and second wastegate valves 25 and 26. The control unit 30 opens the first and second throttle valves so that the supercharging pressures of the branch intake passages 14 and 15 become constant after the first and second wastegate valves 25 and 26 are opened. Control the degree etc.

  Next, the operation and effect of the engine 1 with the supercharger will be described. When the operating state of the engine 1 is in the non-operating region of the electric supercharger, the electric supercharger 19 does not operate, but the exhaust turbo A supercharger 12 supercharges all cylinders # 1 to # 4.

  On the other hand, when the operating state of the engine 1 is in the electric supercharger operating region, the electric supercharger 19 is operated, and supercharging is performed by the exhaust turbocharger 12 and the electric supercharger 19. . In that case, in the engine 1 according to the present embodiment, since the electric supercharger 19 is provided on the first branch intake passage 14, the supercharging by the electric supercharger 19 is the first exhaust. This is performed only for the second and third cylinders # 2 and # 3 corresponding to the passage 20a.

  Here, FIG. 8 shows the characteristics of the engine torque with respect to the engine speed. The solid line is displayed for comparison with the engine 1 according to the present embodiment, and indicates the engine torque in the case where only the exhaust turbocharger 12 is provided without the electric supercharger 19. In this case, the engine torque is roughly a constant high value regardless of the engine speed in the middle speed range, and increases rapidly as the engine speed increases in the low speed range, but compared with the middle speed range. Then, it is relatively low, and shows a characteristic that gradually decreases as the engine speed increases in the high speed region.

  A two-dot chain line is also displayed for comparison, and shows a case where all the cylinders are assisted using the same electric supercharger as the electric supercharger 19 according to the present embodiment. In this case, compared with the case of only the exhaust turbocharger 12, the engine torque in the low rotation region is greatly increased on the low rotation side. In the middle rotation region and the high rotation region, the characteristics are the same as in the case of the exhaust turbocharger 12 alone.

  In the case of the engine 1 according to the present embodiment, the dotted line indicates assist (supercharging) only for the second and third cylinders # 2 and # 3 corresponding to the first exhaust passage 20a by the electric supercharger 19. Shows the case. In this case, the engine torque in the low rotation region and the middle rotation region is greatly increased as compared with the case where all cylinders are assisted (in the case of a two-dot chain line). Note that, in the high speed region, the characteristics are the same as those of the exhaust turbocharger 12 alone.

  As described above, the engine torque is reduced in the engine low / medium speed range when assisting all cylinders (in the case of a two-dot chain line) and assisting only the second and third cylinders (in the case of a dotted line). The reason for the difference is as follows.

  That is, as described above, the first exhaust passage 20a has a smaller volume than the second exhaust passage 20b, and as a result, the exhaust pressure decreases less than the second exhaust passage 20b, and the exhaust turbo The turbine 12t of the supercharger 12 can be driven efficiently, but conversely speaking, the exhaust pressure of the second exhaust passage 20b tends to be lower than that of the first exhaust passage 20a, and the exhaust turbo It means that the turbine 12t of the supercharger 12 cannot be driven as efficiently as the first exhaust passage 20a side. Therefore, when all the cylinders # 1 to # 4 are supercharged by the electric supercharger 19, on the second exhaust passage 20b side, the ability to drive the turbine 12t is improved toward the first exhaust passage 20a side. I do not.

  Therefore, in the present embodiment, the supercharging by the electric supercharger 19 is concentrated on only the second and third cylinders # 2 and # 3 corresponding to the first exhaust passage 20a. Is. According to this, when all the cylinders # 1 to # 4 are supercharged by the electric supercharger 19 and are used in the same state as when the electric supercharger having the same supercharging capability is used, When only the second and third cylinders # 2 and # 3 corresponding to one exhaust passage 20a are supercharged, the intake passage volume to be compressed is small, so that the intake air can be further compressed. . That is, the boost pressure of the second and third cylinders # 2 and # 3 corresponding to the first exhaust passage 20a can be further increased, and the exhaust pressure of the first exhaust passage 20a having good turbine driving efficiency is further increased. be able to. On the other hand, when supercharging by the electric supercharger 19 is performed only for the second and third cylinders # 2 and # 3, the first and fourth cylinders # 1 corresponding to the second exhaust passage 20b are provided. , # 4 is only supercharged by the exhaust turbocharger 12, the supercharging pressure to the first and fourth cylinders # 1, # 4 corresponding to the second exhaust passage 20b is This is lower than when supercharging by the electric supercharger 19 is performed on all the cylinders # 1 to # 4, and as a result, the exhaust pressure in the second exhaust passage 20b is decreased. However, as described above, the first exhaust passage 20a side has a relatively small volume, so that the exhaust pressure is greatly increased. On the other hand, the second exhaust passage 20b side has a relatively large volume, so that the exhaust pressure is increased. It is only slightly lower. Therefore, overall, the ability to drive the turbine 12t is increased, and as a result, the output torque of the engine 1 is higher when compared with the case where all the cylinders are supercharged by the electric supercharger at the same engine speed. Will be enhanced.

  And in other words, this means that when trying to obtain the same output torque, a relatively small-capacity electric supercharger can be used, so that power consumption is reduced, The adverse effect on the battery that supplies power to the electric supercharger 19 is also reduced.

  By the way, the supercharging capacity of the exhaust turbocharger usually increases as the engine speed increases, but the maximum supercharging capacity of the electric supercharger is almost constant regardless of the engine speed. As the number increases, the supercharging effect by the electric supercharger decreases relatively. And if the electric supercharger has a relatively small capacity and its maximum supercharging capacity is smaller than the maximum supercharging capacity of the exhaust turbocharger, the supercharging capacity will be insufficient when the engine speed exceeds a certain number. Therefore, the supercharging effect by the electric supercharger cannot be obtained. However, in the present embodiment, as described above, the supercharging pressure to the second and third cylinders # 2 and # 3 corresponding to the first exhaust passage 20a can be further increased. The supercharging effect by the machine 19 and the improvement effect of the output torque of the engine 1 are expanded to a higher rotational speed region.

  Here, the opening period of the intake valve and the opening period of the exhaust valve have an overlapping period, as described above. During this overlapping period, fresh gas is taken into the cylinder from the intake passage and the combustion gas In this embodiment, the first exhaust passage 20a side has a smaller volume than the second exhaust passage 20b, as described above. Since the exhaust pressure tends to be high, scavenging of the combustion gas is difficult to perform, and the combustion gas remaining without being able to scavenge may deteriorate the combustibility, which may cause knocking. However, in the present embodiment, the supercharging pressure for the second and third cylinders # 2 and # 3 corresponding to the first exhaust passage 20a where the exhaust pressure tends to be high is increased by the electric supercharger 19. Therefore, scavenging performance is improved by the pushing effect, and as a result, combustibility is improved and knocking is prevented.

  Further, in the engine 1 according to the present embodiment, in the cylinder injection engine, fuel is injected into the compression process, that is, fuel is injected after scavenging, so that the fuel blows through like port injection during scavenging. This prevents combustion and stabilizes the combustion and prevents knocking well.

  In the present embodiment, waste gate valves 25 and 26 for relief of exhaust gas are provided on the upstream side of the turbine 12t of the exhaust turbocharger 12 for each of the first and second exhaust passages 20a and 20b. At the same time, as shown in FIG. 9, when the supercharging pressure on the downstream side of the electric supercharger 19 in the first exhaust passage 20a becomes equal to or higher than a predetermined pressure α, the waste gate valve 25 on the first exhaust passage 20a side is turned on. The waste gate valve 26 on the second exhaust passage 20b side is opened when the supercharging pressure of the second exhaust passage 20b is equal to or higher than the predetermined pressure β. In this case, the first exhaust passage Since the predetermined pressure β when opening the waste gate valve 25 on the 20a side is lower than the predetermined pressure α when opening the waste gate valve 26 on the second exhaust passage 20b, the first exhaust passage 20a side No. 1 Westgate Valve 25 is open before the second wastegate valve 26 of the second exhaust passage 20b side. Therefore, as shown in FIG. 10, an increase in the exhaust pressure of the first exhaust passage 20a (indicated by a solid line) causes a predetermined pressure when the waste gate valve 25 on the first exhaust passage 20a side is opened to the second pressure, for example. It is suppressed as compared with the case where α is the same as that of the passage side 20b (indicated by a two-dot chain line as a comparative example), and this also improves the scavenging performance.

  In the first embodiment, the case of an in-line four-cylinder engine has been described. However, the first to sixth cylinders # 1 to # 6 as shown in FIG. The first cylinder # 1, the fourth cylinder # 4, the second cylinder # 2, the fifth cylinder # 5, the third cylinder # 3, and the sixth cylinder # 6 are performed in this order. Portions of the turbocharger 112 that connect to the turbine 112t are independent exhaust passages 121d to 121f that communicate with the even-numbered fourth to sixth cylinders # 4 to # 6 and the independent exhaust passages 121d to 121f. A first exhaust passage 120a composed of a collective exhaust passage 123 connected to the downstream side, and independent exhaust passages 121a to 121c communicating with odd-numbered first to third cylinders # 1 to # 3 and the independent exhaust passages Connected to the downstream side of the exhaust passages 121a to 121c The first exhaust passage 120a is configured to be smaller in volume than the second exhaust passage 120b and shorter in length than the second exhaust passage 120b. The present invention is also applicable to the V-type 6-cylinder engine 101. In this case, the electric supercharger 19 may be provided on the first branch intake passage 114, and control similar to that of the first embodiment may be performed by the control unit 130. Other configurations are similar to those of the first embodiment, and the description thereof is omitted (the same configuration that does not appear in the drawings is also described in the first embodiment). In the embodiment, the corresponding reference numeral is added with 100.)

  In addition to the in-line four-cylinder engine and the V-type six-cylinder engine, the present invention can be applied to, for example, an in-line six-cylinder engine and an in-line, V-type, horizontally opposed engine having eight or more even cylinders. Is also applicable. Further, the ignition order described in the 4-cylinder engine and the 6-cylinder engine is an example, and even when the ignition order is different, the portion from the engine body in the exhaust system to the turbine of the exhaust turbocharger is the same as that of the even number of cylinders. A first exhaust passage comprising a plurality of independent exhaust passages led from one of the odd-numbered and even-numbered cylinders, and a collective exhaust passage formed by collecting downstream portions of the independent exhaust passages; A second exhaust passage composed of an independent exhaust passage communicating with the other one of the odd numbered cylinders and the odd numbered or even numbered cylinder among the even number of cylinders and a collective exhaust passage formed by collecting downstream portions of the independent exhaust passages; It can be widely applied to an engine with a supercharger composed of

  The present invention can be widely applied to an engine with an exhaust turbocharger.

It is a block diagram of the engine with a supercharger which concerns on the 1st Embodiment of this invention. It is a characteristic view of the supercharging pressure and the exhaust pressure with respect to the exhaust passage volume (length). It is a characteristic view of the exhaust temperature before the turbine with respect to the crank angle. It is a characteristic view of the pre-turbine exhaust temperature with respect to the exhaust passage length. It is a flowchart which shows an example of the electric supercharger control by a control unit. It is a control map of an electric supercharger. It is a flowchart which shows an example of the wastegate valve control by a control unit. It is a characteristic view of the output torque with respect to the engine speed implement | achieved by this engine. It is a characteristic figure of the supercharging pressure with respect to the engine speed implement | achieved by this engine. FIG. 6 is a characteristic diagram of exhaust pressure with respect to engine speed realized by the engine. It is a block diagram of the engine with a supercharger which concerns on the 2nd Embodiment of this invention. It is a block diagram of the engine with a supercharger which concerns on background art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Engine 2,102 Engine main body 10,110 Intake system 11,111 Common intake passage 12,112 Supercharger 14,15,114,115 1st, 2nd branch intake passage 16,17,116,117 Throttle Valve (intake control valve)
18a-18d, 118a-118f Independent intake passages 19, 119 Electric superchargers 20, 120 Exhaust systems 20a, 120a First exhaust passages 20b, 120b Second exhaust passages 21a-21d, 121a-121f Independent exhaust passages 22, 23, 122, 123 Collecting exhaust passages 25, 26, 125, 126 First and second waste gate valves 27, 28, 127, 128 First and second relief passages (relief passages)
30, 130 ECU (electric supercharger control means, waste gate valve control means)
31, 131 Engine rotation sensors 32, 33, 132, 133 First and second boost pressure sensors (first and second boost pressure detecting means)
# 1 to # 6 cylinder

Claims (3)

An engine body having an even number of cylinders, an exhaust system connected to the engine body, an exhaust turbocharger provided in the exhaust system, and an exhaust turbocharger from the engine body in the exhaust system The part leading to the turbine of the machine is composed of a plurality of independent exhaust passages led from either the odd-numbered or even-numbered cylinders of the even number of cylinders and the downstream portions of the independent exhaust passages A first exhaust passage composed of a collective exhaust passage, an independent exhaust passage communicating with an odd numbered or even numbered cylinder of the even number of cylinders, and a downstream portion of the independent exhaust passage. An engine with a supercharger, the first exhaust passage having a volume smaller than that of the second exhaust passage,
The intake system includes, from the upstream side, a common intake passage in which the compressor of the exhaust turbocharger is disposed, first and second branch intake passages branched from the common intake passage, and the first branch intake air A plurality of independent intake passages branched from the passage and led to a cylinder corresponding to the first exhaust passage, and led to a cylinder corresponding to the second exhaust passage branched from the second branch intake passage It consists of multiple independent intake passages,
In addition, an electric supercharger is provided in the first branch intake passage,
A supercharger characterized in that an electric supercharger control means is provided for operating the electric supercharger when the engine speed is lower than a predetermined speed and the engine load is higher than a predetermined load. With engine. The supercharged engine according to claim 1,
The engine is an in-cylinder injection engine, and is configured such that fuel is injected during a compression process. The engine with a supercharger according to claim 1 or 2,
For each of the first and second exhaust passages, a wastegate valve is provided for relief of exhaust gas on the upstream side of the turbine of the exhaust turbocharger.
First supercharging pressure detection means for detecting the supercharging pressure downstream of the electric supercharger in the first branch intake passage, and second supercharging pressure detection for detecting the supercharging pressure of the second branch intake passage. And when the supercharging pressure detected by the first supercharging pressure detecting means exceeds a predetermined pressure, the wastegate valve on the first exhaust passage side is opened and detected by the second supercharging pressure detecting means. Wastegate valve control means for opening the wastegate valve on the second exhaust passage side when the supercharging pressure exceeds a predetermined pressure,
An engine with a supercharger, wherein the predetermined pressure when opening the wastegate valve on the first exhaust passage side is lower than the predetermined pressure when opening the wastegate valve on the second exhaust passage side .

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