JP2008031942A - Engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expand a supercharged region as large as possible and provide high supercharging performance in each region with a low cost structure. <P>SOLUTION: Both exhaust systems 161, 162 are connected to a connection part 211a of a turbine scroll 211 to keep distance R1 from an exhaust gas main flow center of a first exhaust system 161 to a rotary center of a turbine wheel 212 longer than distance R2 from an exhaust gas main flow center of a second exhaust system 162 to the rotary center of a turbine wheel 212. More preferably, a flow path 2120 in which main flow of exhaust gas discharged from the first exhaust system 161 can be circulated around whole circumference of the turbine wheel 212 is formed near an opening part of the second exhaust system 162. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a supercharged engine equipped with an exhaust turbocharger.

Conventionally, as a means for increasing the engine torque, an exhaust turbocharger that supercharges intake air using the energy of exhaust gas is known. As an engine equipped with this exhaust turbocharger, for example, Patent Document 1 discloses that a 4-cylinder engine has a first exhaust system in which exhaust passages connected to cylinders whose combustion order is not continuous are grouped, and the remaining cylinders. And a second exhaust system that groups exhaust passages connected to each other, and each exhaust system is connected to a twin scroll type exhaust turbocharger. In addition, a communication pipe that communicates both exhaust systems is provided by opening and closing the open / close valve. By controlling the open / close valve of the communication pipe according to the operation region, the exhaust performance of the EGR gas provided in the engine is improved. It aims to improve and reduce pump loss.
Japanese Patent Laid-Open No. 2004-1224749

  By the way, in order to expand the supercharging region, it is preferable to adjust the supercharging characteristic in accordance with the rotation region of the engine. For example, it is preferable that the exhaust energy is increased to drive the turbine in the low speed operation region of the engine, and the exhaust energy is suppressed in the high speed operation region to supercharge within the heat resistance limit of the turbine or the like.

  Therefore, in order to adjust the supercharging characteristics according to the engine rotation range, it is possible to adopt a movable displacement supercharger (VGT) or a sequential turbo, but there are problems in terms of cost and reliability. .

  In addition, in the configuration of Patent Document 1, although performance improvement by EGR gas can be achieved on both the low speed side and the high speed side, there is a restriction that the exhaust turbocharger must be a twin scroll type. It is disadvantageous in terms of cost.

  In view of the above circumstances, an object of the present invention is to provide a low-priced engine with a supercharger capable of expanding the supercharging region as much as possible and providing high supercharging performance over each region.

  In order to solve the above-described problems, the present invention provides a first exhaust system in which exhaust passages arranged adjacent to each other in an engine body of a multi-cylinder engine and connected to a cylinder whose ignition timing is not continuous are grouped. A second exhaust system having a volume set larger than that of the first exhaust system and grouping exhaust passages connected to the remaining cylinders; and an exhaust turbocharger connected to both exhaust systems, The exhaust turbocharger includes a turbine scroll connected to both exhaust systems, and a turbine wheel disposed in the turbine scroll and driven by exhaust gas discharged from both exhaust systems. The distance from the exhaust main flow center of the exhaust system to the rotation center of the turbine wheel is longer than the distance from the exhaust main flow center of the second exhaust system to the rotation center of the turbine wheel. , On the outer peripheral side of the first exhaust system the turbine wheel, the inner peripheral side of the second exhaust system the turbine wheel, a supercharged engine, characterized in that it is connected. In this aspect, the smaller the exhaust passage volume to the turbine wheel, the smaller the flow rate decrease (energy down) of the exhaust gas, so that a relatively high flow rate can be obtained from the first exhaust system having a small volume. Since the first exhaust system that outputs a high flow rate is laid out radially outward of the turbine wheel, high supercharging performance can be exhibited in the low-speed operation region of the engine. In addition, since multiple exhaust systems are arranged on the outer peripheral side and inner peripheral side of the turbine wheel, even if a conventional and inexpensive exhaust turbocharger is used as it is, high exhaust performance is demonstrated in the low-speed operation range. It becomes possible to do.

  In a preferred embodiment, the flow cross-sectional areas of both exhaust systems are set to be approximately equal. In this aspect, the turbine drive energy by the first exhaust system is always increased. That is, the moment for driving the turbine wheel of the exhaust system is expressed as A / R, where R is the distance from the exhaust main flow center of the exhaust system to the rotation center of the turbine wheel, and A is the cross-sectional area of the exhaust main flow of the exhaust system. It is known to be inversely proportional to In the present invention, the first exhaust system is disposed on the outer peripheral side of the turbine wheel so that the distance R1 of the first exhaust system is longer than the distance R2 of the second exhaust system. This is because the A / R is always smaller in the first exhaust system and the energy is larger in the first exhaust system. For this reason, coupled with the fact that the volume of the first exhaust system is smaller than the volume of the second exhaust system, the first exhaust system requires the energy required to drive the turbine wheel even in the lower speed operation region. Can be output.

  In a preferred aspect, a waste gate valve for controlling a supercharging pressure of the exhaust turbocharger to a predetermined pressure or less is provided, and the relief gate of the waste gate valve is provided with the first exhaust gas when the waste gate valve is opened. It is formed at a position where the exhaust pressure from the system is reduced. In this aspect, when the rotational speed of the engine increases, the waste gate valve opens the relief port accordingly, and the exhaust gas introduced into the turbine wheel is relieved. That is, the exhaust gas bypasses the turbine wheel and is discharged to the downstream exhaust passage. Here, the relief port of the waste gate valve is formed at a position where the exhaust pressure from the first exhaust system is reduced when the waste gate valve is opened. The exhaust pressure from the system is reduced, and supercharging is continued by the exhaust pressure from the second exhaust system. Here, the second exhaust system has a larger volume than the first exhaust system, and the distance from the exhaust main flow center of the second exhaust system to the rotation center of the turbine wheel is the first exhaust system. Therefore, the exhaust gas drives the turbine wheel at a relatively low flow rate even on the high speed side. Accordingly, it is possible to obtain a suitable supercharging pressure without reaching the heat resistance limit even in the high-speed operation region of the engine.

  In a preferred aspect, the turbine scroll has a flow path in which a main flow of exhaust gas discharged from the first exhaust system can circulate around the entire circumference of the turbine wheel, and the second exhaust system transmits exhaust gas to the turbine. It is formed in the vicinity of the upstream of the flow path for discharging to the scroll. In this aspect, during the low speed operation of the engine, the main flow of the exhaust gas discharged from the first exhaust system circulates around the inner periphery of the turbine wheel without impairing the flow velocity. , The downstream end of the exhaust gas drives the turbine wheel along the tangential direction. As a result, the turbine wheel is driven with relatively high energy in combination with the volume of the first exhaust system being smaller than the volume of the second exhaust system. Next, when the rotational speed of the engine shifts to a high speed region, the main flow from the second exhaust system also becomes stronger, so the main flow of the first exhaust system that tries to go around the outer periphery of the turbine wheel is the second exhaust. As a result of restricting the circulation of the turbine wheel by the mainstream of the system, excessive increase in torque of the turbine wheel is suppressed. Therefore, it is possible to expand the supercharging region in the high speed operation region without reaching the heat resistance limit.

  As described above, the present invention makes it possible to exhibit high supercharging performance at least in the low-speed operation region of the engine, and to significantly increase the supercharging region as much as possible with a low-cost configuration. Has an effect.

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

  FIG. 1 is a schematic view showing the overall configuration of a supercharged engine according to an embodiment of the present invention, and FIG. 2 is a side view of the engine according to the embodiment of FIG.

  Referring to FIGS. 1 and 2, the engine shown in each figure is a gasoline engine, and engine body 1 is provided with a plurality of cylinders (four cylinders in the illustrated example) 1a to 1d. A combustion chamber 2 is formed in each of the cylinders 1a to 1d. Each combustion chamber 2 has an intake port and an exhaust port, and an intake valve 3 and an exhaust valve 4 are provided at these ports. Furthermore, an ignition plug 5 and a fuel injection valve 6 are provided for each combustion chamber 2. In the present embodiment, if the cylinders 1a to 1d are defined as the first cylinder 1a to the fourth cylinder 1d, the combustion order is that of the first cylinder 1a, the third cylinder 1c, the fourth cylinder 1d, and the second cylinder 1b. It is in order.

  The engine body 1 is connected to an intake passage 10 for supplying fresh air to the cylinders 1a to 1d and an exhaust passage 15 for leading exhaust gas from the cylinders 1a to 1d.

  The intake passage 10 includes an intake manifold 12 having an intake passage 11 for each cylinder connected to the intake ports of the cylinders 1a to 1d, and a common intake passage 13 upstream thereof. The common intake passage 13 is provided with a throttle valve 14 for adjusting the intake air amount. The exhaust passage 15 includes an exhaust manifold 17 having cylinder-specific exhaust passages 16a to 16d connected to the exhaust ports of the cylinders 1a to 1d, and a common exhaust passage 18 downstream thereof.

  In the present embodiment, the exhaust manifold 17 is provided with a group of exhaust passages 16b and 16c that are disposed adjacent to each other and connected to cylinders (second cylinder 1b and third cylinder 1c in the illustrated example) where ignition timings do not continue. First exhaust system 161 and an exhaust passage 16a having a volume larger than that of the first exhaust system 161 and connected to the remaining cylinders (the first cylinder 1a and the fourth cylinder 1d in the illustrated example). , 16d are grouped together and a second exhaust system 162 is formed.

  Referring to FIG. 2, the path lengths L1 and L2 of the exhaust systems 161 and 162 are shorter than the path length L2 of the second exhaust system 162 in the layout because the path length L1 of the first exhaust system 161 is shorter. Accordingly, the volume of the first exhaust system 161 is smaller than the volume of the second exhaust system 162. The exhaust systems 161 and 162 are connected to the common exhaust passage 18 via the exhaust turbocharger 20.

  As shown in FIG. 1, the exhaust turbocharger 20 includes a turbine 21 that rotates by being driven by the energy of exhaust gas, and a compressor 23 that is connected to the turbine 21 via a shaft 22. The intake air is supercharged by the rotation of the compressor 23 in conjunction with the rotation. As the exhaust turbocharger 20, a high-speed supercharger that is relatively large and has high supercharging performance in a high-speed range is used.

  The turbine 21 is interposed in the common exhaust passage 18. A waste gate passage 24 bypasses the turbine 21 and a waste gate valve 25 is provided in the passage 24.

  The compressor 23 is interposed in the common intake passage 13. An intercooler 26 for cooling the supercharged air is provided downstream of the compressor 23 in the common intake passage 13.

  FIG. 3 is a partial schematic cross-sectional view of the exhaust turbocharger 20 according to the embodiment of FIG.

  First, referring to FIG. 3, the turbine 21 of the exhaust turbocharger 20 includes a turbine scroll 211 connected to the first and second exhaust systems 161 and 162, a built-in turbine scroll 211, and a shaft 22. And a turbine wheel 212 for driving.

  The turbine scroll 211 is a cochlear-shaped housing that integrally includes a connection portion 211a to which the exhaust systems 161 and 162 are connected and a surrounding portion 211b that communicates with the connection portion 211a and surrounds the turbine wheel 212 therein. is there.

  In the present embodiment, the distance R1 from the exhaust main flow center of the first exhaust system 161 to the rotation center of the turbine wheel 212 is the distance from the exhaust main flow center of the second exhaust system 162 to the rotation center of the turbine wheel 212. Both exhaust systems 161 and 162 are connected to the connecting portion 211a of the turbine scroll 211 so as to be longer than R2. In the present embodiment, the cross-sectional areas A1 and A2 of the flows by the two exhaust systems 161 and 162 are set to be approximately equal to each other. As a result, coupled with the fact that the volume of the first exhaust system 161 is smaller than that of the second exhaust system 162, the main flow from the first exhaust system 161 having a relatively high flow velocity F1 is brought into the surrounding portion 211b. Will be introduced.

  The surrounding portion 211b forms a substantially annular flow path with the turbine wheel 212, and the exhaust gas introduced from the connecting portion 211a circulates around the outer periphery of the turbine wheel 212 by about 330 ° to about 350 °. Thus, it is configured to discharge from the vent hole 211c formed on the inner peripheral side to the downstream common exhaust passage 18.

  A relief port 25a of the waste gate valve 25 is formed between the connecting portion 211a and the surrounding portion 211b to control the supercharging pressure to a predetermined pressure or lower.

  FIG. 4 is a schematic cross-sectional view of the exhaust turbocharger 20 according to the embodiment of FIG. 1, and FIG. 5 is a schematic cross-sectional view showing a waste gate valve drive mechanism employed in the exhaust turbocharger 20. It is.

  2-5, the waste gate valve 25 carries the valve body 25b which opens and closes the relief port 25a, the link arm 25c attached to the valve body 25b, the link arm 25c in a cantilever shape, The valve body 25b includes a link mechanism 25d that drives between an open position that opens the relief port 25a and a closed position that closes the relief port 25a, and an actuator 25e that drives the link mechanism 25d. As shown in FIG. 5, the actuator 25e is provided with a diaphragm 25f, and the link mechanism 25d is connected to the diaphragm 25f. The diaphragm 25f partitions a supercharging chamber 25h into which a part of the exhaust gas supercharged by a tube 25g (shown only in FIG. 5) is introduced. On the other hand, the diaphragm 25f urges the link mechanism 25d so that the valve body 25b takes a closed position by a return spring 25i disposed on the opposite side of the supercharging chamber 25h. When the boost pressure increases, the link mechanism 25d drives the valve body 25b to the open position against the urging force of the return spring 25i. Thereby, the valve body 25b is configured to close the relief port 25a on the low speed side, gradually open on the high speed side, and fully open at a predetermined intercept point.

  Here, in the present embodiment, as shown in FIGS. 2 and 3, the opening position of the relief port 25 a is set to a position where the exhaust flow from the first exhaust system 161 is introduced into the turbine scroll 211. ing. For this reason, the exhaust flow from the first exhaust system 161 is weakened as the engine speed increases.

  As described above, in the present embodiment, the distance R1 from the exhaust main flow center of the first exhaust system 161 to the rotation center of the turbine wheel 212 is determined from the exhaust main flow center of the second exhaust system 162 to the turbine wheel 212. Both exhaust systems 161 and 162 are connected to the connecting portion 211a of the turbine scroll 211 so as to be longer than the distance R2 to the rotation center. Here, the smaller the exhaust passage volume to the turbine wheel 121, the smaller the flow rate decrease (energy down) of the exhaust gas. Therefore, a relatively high flow rate F1 can be obtained from the first exhaust system 161 having a small volume. . In addition, since the first exhaust system 161 that outputs this high flow velocity F1 is laid out radially outward of the turbine wheel 212, it is possible to exhibit high supercharging performance in the low-speed operation region of the engine. . In addition, since a plurality of exhaust systems 161 and 162 are arranged on the outer peripheral side and the inner peripheral side of the turbine wheel 212, even if the conventional and inexpensive exhaust turbocharger 20 is adopted as it is, High exhaust performance can be demonstrated.

  In the present embodiment, the cross-sectional areas A1 and A2 of the flows by the two exhaust systems 161 and 162 are set to be approximately equal to each other. For this reason, in this embodiment, the turbine drive energy by the 1st exhaust system 161 becomes always large. That is, the moment for driving the turbine wheel 212 of the exhaust system is represented by R as the distance from the exhaust main flow center of the exhaust system to the rotation center of the turbine wheel 212, and A as the cross-sectional areas A1 and A2 of the exhaust main flow of the exhaust system. Then, it is known that it is inversely proportional to A / R. In the present embodiment, since both the exhaust systems 161 and 162 are connected to the turbine scroll so that the distance R1 of the first exhaust system 161 is longer than the distance R2 of the second exhaust system 162, A / This is because R is always smaller in the first exhaust system 161 and energy is larger in the first exhaust system 161. For this reason, coupled with the fact that the volume of the first exhaust system 161 is smaller than the volume of the second exhaust system 162, the first exhaust system 161 drives the turbine wheel 212 even in the lower speed operation region. It is possible to output the energy required for the operation.

  Further, in the present embodiment, a waste gate valve 25 that controls the supercharging pressure of the exhaust turbocharger 20 to be equal to or lower than a predetermined pressure is provided, and the relief port 25a of the waste gate valve 25 is connected to the waste gate valve 25. It is formed at a position where the exhaust pressure from the first exhaust system 161 is reduced when the valve is opened. For this reason, in the present embodiment, when the rotational speed of the engine increases, the waste gate valve 25 opens the relief port 25a accordingly, and the exhaust gas introduced into the turbine wheel 212 is relieved. That is, the exhaust gas bypasses the turbine wheel 212 and is discharged to the downstream common exhaust passage 18. Here, the relief port 25a of the waste gate valve 25 is formed at a position where the exhaust pressure from the first exhaust system 161 is reduced when the waste gate valve 25 is opened. The exhaust pressure from the first exhaust system 161 is reduced, and supercharging is continued by the exhaust pressure from the second exhaust system 162. Here, the second exhaust system 162 has a larger volume than the first exhaust system 161, and the distance R2 from the exhaust main flow center of the second exhaust system 162 to the rotation center of the turbine wheel 212 is Since it is relatively shorter than the first exhaust system 161, the exhaust gas drives the turbine wheel 212 at a relatively low flow velocity F2 even on the high speed side. Accordingly, it is possible to obtain a suitable supercharging pressure without reaching the heat resistance limit even in the high-speed operation region of the engine.

  As described above, according to the present embodiment, it is possible to exhibit high supercharging performance in both the low-speed operation region and the high-speed operation region of the engine, and the supercharging region is expanded as much as possible with an inexpensive configuration. There is a remarkable effect that it can be done.

  The above-described embodiments are merely preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments.

  FIG. 6 is a schematic cross-sectional view showing a main part of an exhaust turbocharger 20 according to another embodiment of the present invention.

  Referring to FIG. 6, the turbine scroll 211 in this embodiment includes a second flow path 2120 through which the main flow of the exhaust gas discharged from the first exhaust system 161 can circulate around the entire circumference of the turbine wheel 212. This exhaust system 162 is formed in the vicinity of the upstream of the flow path for discharging the exhaust gas to the turbine scroll 212. In other words, a part of the inner wall corresponding to the shape of FIG. 3 is cut as indicated by a broken line. Therefore, in the present embodiment, during the low speed operation of the engine, the main flow of the exhaust gas discharged from the first exhaust system 161 does not impair the flow velocity F1, as indicated by the arrow AW1, and the inner periphery of the turbine wheel 212. Since the entire circumference travels around the side, the downstream end of the exhaust gas drives the turbine wheel 212 along the tangential direction during low speed operation. As a result, the turbine wheel 212 is driven with relatively high energy in combination with the volume of the first exhaust system 161 being smaller than the volume of the second exhaust system 162. Next, when the rotational speed of the engine shifts to a high speed region, the main flow from the second exhaust system 162 also becomes stronger, so the main flow of the first exhaust system 161 that tries to go around the outer periphery of the turbine wheel 212 is As a result of the circulation of the turbine wheel 212 being restricted by the main flow of the second exhaust system 162, the flow path 2120 is substantially blocked, and the torque of the turbine wheel 212 is prevented from excessively increasing. Therefore, it is possible to expand the supercharging region in the high speed operation region without reaching the heat resistance limit.

  As described above, in the embodiment shown in FIG. 6 as well, it becomes possible to exhibit high supercharging performance in both the low speed operation region and the high speed operation region of the engine, and supercharge as much as possible with an inexpensive configuration. There is a remarkable effect that the area can be expanded.

  It goes without saying that various modifications can be made within the scope of the claims of the present invention.

1 is a configuration diagram illustrating an overall configuration of a supercharged engine according to an embodiment of the present invention. It is a side view of the engine which concerns on embodiment of FIG. 2 is a schematic partial cross-sectional view of an exhaust turbocharger according to the embodiment of FIG. 1. 2 is a schematic partial cross-sectional view of an exhaust turbocharger according to the embodiment of FIG. 1. It is a cross-sectional schematic diagram which shows the drive mechanism of the waste gate valve employ | adopted as the same exhaust gas turbocharger. It is a cross-sectional schematic diagram which shows the principal part of the exhaust gas turbocharger which concerns on another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine main body 1a 1st cylinder 1b 2nd cylinder 1c 3rd cylinder 1d 4th cylinder 10 Intake passage 11 Intake passage 12 Intake manifold 13 Common intake passage 14 Throttle valve 15 Exhaust passage 16a Exhaust passage 16b Exhaust passage 16c Exhaust passage 16d Exhaust passage 17 Exhaust Manifold 18 Common Exhaust Passage 20 Exhaust Turbocharger 21 Turbine 25 Wastegate Valve 25a Relief Port 161 First Exhaust System 162 Second Exhaust System 211 Turbine Scroll 212 Turbine Wheel 2120 Channel A1 Cross Section A2 Cross Section R1 Distance R2 distance

Claims (4)

A first exhaust system that groups exhaust passages that are arranged adjacent to each other in the engine body of a multi-cylinder engine and that are connected to cylinders whose ignition timing is not continuous;
A second exhaust system having a volume larger than that of the first exhaust system and grouping exhaust passages connected to the remaining cylinders;
An exhaust turbocharger connected to both exhaust systems,
The exhaust turbocharger has a turbine scroll connected to both exhaust systems, and a turbine wheel disposed in the turbine scroll and driven by exhaust gas discharged from both exhaust systems,
The distance from the exhaust main flow center of the first exhaust system to the rotation center of the turbine wheel is longer than the distance from the exhaust main flow center of the second exhaust system to the rotation center of the turbine wheel. The engine with a supercharger, wherein the first exhaust system is connected to the outer peripheral side of the turbine wheel, and the second exhaust system is connected to the inner peripheral side of the turbine wheel. The supercharged engine according to claim 1,
An engine with a supercharger, characterized in that the cross-sectional areas of the flow by both exhaust systems are set approximately equal to each other. The engine with a supercharger according to claim 1 or 2,
A waste gate valve for controlling the supercharging pressure of the exhaust turbocharger to a predetermined pressure or less is provided, and a relief port of the waste gate valve is an exhaust from the first exhaust system when the waste gate valve is opened. An engine with a supercharger, characterized by being formed at a position where pressure is reduced. The engine with a supercharger according to any one of claims 1 to 3,
The turbine scroll discharges the exhaust gas to the turbine scroll through a flow path through which the main flow of the exhaust gas discharged from the first exhaust system can circulate around the entire circumference of the turbine wheel. An engine with a supercharger, characterized in that it is formed in the vicinity of the upstream of the flow path.

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