JP6531516B2 - Internal combustion engine intake and exhaust system - Google Patents

Description

  The present invention relates to an intake and exhaust system of an internal combustion engine, and more particularly to an intake and exhaust system of an internal combustion engine having a plurality of superchargers.

  An intake and exhaust system of an engine, which is an internal combustion engine, is a system which supplies intake air necessary for combustion of the engine to the engine and discharges exhaust gas after combustion. This intake and exhaust system has an exhaust reflux passage and a supercharger that compresses intake air. The reflux passage is a passage for recirculating a part of the exhaust gas discharged from the engine to the exhaust passage to the intake passage for introducing the intake air into the engine, from the viewpoint of lowering the combustion temperature of the engine.

  The turbocharger supercharges the intake air of the intake passage using the exhaust of the exhaust passage to perform compression. For example, Patent Document 1 below discloses a two-stage supercharging system having a low-pressure stage turbocharger and a high-pressure stage turbocharger, and dividing the intake air into two stages, the low-pressure stage and the high-pressure stage. There is.

JP 2007-138845 A

  In recent years, from the viewpoint of improving fuel consumption and the like, further supercharging with a small turbocharger has been demanded. However, in order to increase the operation efficiency of two turbochargers arranged in series as in the two-stage turbocharger system shown in Patent Document 1 in order to realize high supercharging, it is necessary to increase the size of the turbocharger There is. In addition, since the exhaust of the six cylinders of the engine merge into one exhaust passage, interference of exhaust pulsation occurs.

  Therefore, the present invention has been made in view of these points, and it is an object of the present invention to suppress interference of exhaust pulsation while realizing high supercharging by a small-sized turbocharger.

In a first aspect of the present invention, a low pressure stage turbocharger provided in an internal combustion engine and including a cylinder group including three or more cylinders, an intake passage introducing intake air into the cylinder group, and compression of the intake air And a high pressure stage turbocharger, and a first exhaust passage for introducing the exhaust gas discharged from each of two first cylinders in the cylinder group in which interference of the exhaust pulsation does not occur into the high pressure stage turbocharger; The exhaust gas discharged from the second cylinder different from the first cylinder of the cylinder group is provided downstream of the high pressure supercharger, provided to bypass the high pressure supercharger. And a second exhaust passage introduced into the low-pressure stage turbocharger.
According to the intake / exhaust system, the exhaust efficiency of the high-pressure stage turbocharger is enhanced because the exhaust gases of the two cylinders free from the interference of the exhaust pulsation are introduced into the high-pressure stage turbocharger via the first exhaust passage. As a result, it is possible to miniaturize the high-pressure stage turbocharger. In addition, since the exhaust gas of cylinders not introduced into the high pressure stage turbocharger is introduced into the low pressure stage turbocharger via the second exhaust passage, the operation efficiency of the low pressure stage turbocharger can be enhanced.

  Further, an intake and exhaust system of the internal combustion engine connects between the second exhaust passage and the intake passage, and a return passage for returning the exhaust gas discharged from the second cylinder to the intake passage; The exhaust passage may further include an exhaust pressure adjusting unit provided downstream of a connection point with the reflux passage and adjusting the pressure of the exhaust in the second exhaust passage.

  Further, an intake and exhaust system of the internal combustion engine connects between the second exhaust passage and the intake passage, and a return passage for returning the exhaust gas discharged from the second cylinder to the intake passage; The exhaust passage may further include a flow rate adjusting unit provided downstream of a connection point with the reflux passage and adjusting a flow rate of the exhaust gas in the reflux passage.

  Further, the second exhaust passage may introduce the exhaust gas discharged from each of the two second cylinders in which the interference of the exhaust pulsation does not occur into the low-pressure stage turbocharger.

  The second cylinder may be two in number, and the second exhaust passage may include two bypass passages connected to each of the two second cylinders and bypassing the high-pressure stage turbocharger.

  ADVANTAGE OF THE INVENTION According to this invention, it is effective in the ability to suppress interference of an exhaust gas pulsation, implement | achieving high supercharging by a small-sized supercharger.

It is a schematic diagram which shows an example of a structure of intake / exhaust system S which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows an example of a structure of intake / exhaust system S which concerns on 2nd Embodiment. It is a schematic diagram which shows an example of a structure of intake / exhaust system S which concerns on 3rd Embodiment.

First Embodiment
(Configuration of intake and exhaust system)
The configuration of an intake / exhaust system S of an internal combustion engine according to a first embodiment of the present invention will be described with reference to FIG.
FIG. 1: is a schematic diagram which shows an example of a structure of intake / exhaust system S which concerns on 1st Embodiment.

  The intake and exhaust system S is mounted on a vehicle having an engine which is an internal combustion engine. For example, the intake and exhaust system S is mounted on a large vehicle such as a bus or a truck. The intake and exhaust system S is a system that supplies the engine with intake air necessary for engine combustion and discharges exhaust air after combustion. As shown in FIG. 1, the intake and exhaust system S includes an engine 10, an intake passage 20, an exhaust passage 30, an EGR passage 40, a low pressure supercharger 50, a high pressure supercharger 60, and an ECU 80. Have.

  The engine 10 is an engine including three or more cylinders, and here is a four-cylinder diesel engine. The engine 10 burns and expands a mixture of fuel and intake (air) to generate power. The engine 10 has an intake manifold 11 and cylinders 13a to 13d which are cylinder groups.

  The intake manifold 11 is a manifold connected to the intake passage 20, and branches intake (air) of the intake passage 20 into four cylinders 13a to 13d. The four cylinders 13a to 13d suck in the intake air and discharge the exhaust gas after the combustion. Each of the cylinders 13a to 13d is provided with a piston, an intake valve, an exhaust valve, an injector, and the like.

  In the four cylinders 13a to 13d, ignition in the cylinders is performed in the order of the cylinders 13a, 13c, 13d, and 13b, and the exhaust stroke is also performed in the order of the cylinders 13a, 13c, 13d, and 13b. Thus, the open valve periods of the exhaust valves do not overlap in the cylinders 13a and 13d, and the open valve periods of the exhaust valves do not overlap in the cylinders 13b and 13c. In this case, even if the exhaust of the cylinder 13a and the exhaust of the cylinder 13d are merged in the exhaust passage 30, interference of the exhaust pulsation does not occur. Similarly, even if the exhaust of the cylinder 13b and the exhaust of the cylinder 13c are merged in the exhaust passage 30, interference of the exhaust pulsation does not occur.

  The intake passage 20 is a passage for drawing intake (air) necessary for the combustion of the engine 10 into the cylinders 13a to 13d. In the intake passage 20, from the upstream side to the downstream side, the air cleaner 22, the compressor 52 of the low pressure stage turbocharger 50, the CAC (Charge Air Cooler: charge charging cooler) 23, the compressor of the high pressure stage turbocharger 60. 62, a CAC 24 and an intake throttle valve 25 are provided.

  The air cleaner 22 has, for example, a filter, and removes foreign substances during intake. The compressor 52 of the low pressure supercharger 50 compresses the intake air passing through the compressor 52 by rotating. The CAC 23 cools the intake air, which has been compressed by the compressor 52 and whose temperature has risen, with a coolant or the atmosphere. The compressor 62 of the high-pressure stage turbocharger 60 compresses the intake air passing through the compressor 62 by rotating. The CAC 24 cools the intake air, which has been compressed by the compressor 62 and whose temperature has risen, with a coolant or the atmosphere. The intake throttle valve 25 adjusts the opening degree of the throttle valve to adjust the flow rate of intake air.

  The exhaust passage 30 is a passage for discharging the exhaust gas (exhaust gas) discharged from the engine 10 to the outside of the vehicle. The exhaust passage 30 includes a plurality of branched exhaust passages 31a to 31f and bypass passages 33a and 33b. Further, in the exhaust passage 30, a turbine 51 of the low pressure supercharger 50, a turbine 61 of the high pressure supercharger 60, an exhaust control valve 34, bypass control valves 35, 36, and an EAT 37 (Exhaust After-Treatment : Exhaust aftertreatment device) is provided.

  The exhaust passage 31 a connects the cylinder 13 a of the engine 10 and an exhaust passage 31 e located on the downstream side of the turbine 61 of the high-pressure stage turbocharger 60. Similarly, the exhaust passage 31d connects the cylinder 13d and the exhaust passage 31e. That is, the exhaust passage 31 d is a passage that bypasses the turbine 61. Thus, the exhaust gas discharged from the cylinder 13 d is not guided to the turbine 61. The exhaust passage 31a and the exhaust passage 31d are configured to merge on the way.

  The exhaust passage 31 b connects the cylinder 13 b and the turbine 61, and guides the exhaust gas discharged from the cylinder 13 b to the turbine 61. Similarly, the exhaust passage 31 c connects the cylinder 13 c and the turbine 61, and guides the exhaust gas discharged from the cylinder 13 c to the turbine 61. The exhaust passage 31 b and the exhaust passage 31 c are configured to merge on the way.

  The exhaust passage 31 e connects the turbine 61 of the high pressure stage turbocharger 60 and the turbine 51 of the low pressure stage turbocharger 50. Exhaust passages 31a and 31d are connected in the middle of the exhaust passage 31e. Therefore, the exhaust gas discharged from the cylinders 13 a and 13 d bypasses the turbine 61 and is led to the turbine 51. Further, a detour passage 33a that detours the turbine 61 is connected in the middle of the exhaust passage 31e.

  The exhaust passage 31 f is a passage located downstream of the turbine 51. In the middle of the exhaust passage 31 f (upstream of the EAT 37), a bypass passage 33 b bypassing the turbine 51 is connected.

  The bypass passage 33a connects the middle of the exhaust passage 31b and the exhaust passage 31c (in fact, the passage after the exhaust passage 31b and the exhaust passage 31c merge) and the exhaust passage 31e on the downstream side of the turbine 61. . By providing the bypass passage 33 a, the exhaust gas discharged from the cylinders 13 b and 13 c can bypass the turbine 61.

  The bypass passage 33 b connects the middle of the exhaust passage 31 e (specifically, the connection point with the bypass passage 33 a and the downstream side of the connection point with the exhaust passage 31 d) and the exhaust passage 31 f on the downstream side of the turbine 51 doing. By providing the bypass passage 33 b, the exhaust gas flowing through the exhaust passage 31 e can bypass the turbine 51.

  The exhaust adjustment valve 34 is provided in the middle of the passage where the exhaust passages 31a and 31d merge (specifically, on the downstream side of the connection point with the EGR passage 40), the pressure of the exhaust flowing through the exhaust passages 31a and 31d It is a valve that can adjust the exhaust pressure and the flow rate. That is, the exhaust adjustment valve 34 has functions as an exhaust pressure adjustment unit and a flow rate adjustment unit. The exhaust adjustment valve 34 is, for example, a swing type on-off valve with an arm, and the exhaust pressure and the flow rate can be adjusted with high accuracy by adjusting the angle of the arm. Further, although the details will be described later, the flow rate of the exhaust flowing through the EGR passage 40 can also be adjusted by the exhaust adjustment valve 34.

  The bypass adjustment valve 35 is provided in the bypass passage 33a, and adjusts the flow rate of the exhaust gas flowing through the bypass passage 33a (the exhaust gas discharged from the cylinder 13b and the cylinder 13c). The bypass adjustment valve 35 is, for example, a gate valve. By adjusting the flow rate of the exhaust gas flowing through the bypass passage 33a, the flow rate of the exhaust gas passing through the turbine 61 can also be adjusted, so the amount of supercharging of the intake air by the high-pressure stage turbocharger 60 can be adjusted.

  The bypass adjustment valve 36 is provided in the bypass passage 33 b and adjusts the flow rate of the exhaust gas (the exhaust gas discharged from the cylinders 13 a to 13 d) flowing through the bypass passage 33 b. The bypass adjustment valve 36 is, for example, a gate valve. By adjusting the flow rate of the exhaust gas flowing through the bypass passage 33b, the flow rate of the exhaust gas passing through the turbine 51 can also be adjusted, so that the supercharging amount of the intake air by the low pressure stage turbocharger 50 can be adjusted.

The EAT 37 is a device for purifying the exhaust gas. For example, EAT 37 collects PM in exhaust gas, or selectively reduces and purifies NO _x in exhaust gas using ammonia (NH ₃ ) generated by being hydrolyzed from urea water as a reducing agent.

  The EGR passage 40 is a return passage that connects the exhaust passage 31 d and the intake passage 20 and causes all or part of the exhaust discharged from the cylinders 13 a and 13 d of the engine 10 to return to the intake passage 20. An EGR cooler 41 and an EGR valve 42 are provided in the EGR passage 40. The EGR cooler 41 cools the exhaust of the EGR passage 40. The EGR valve 42 regulates the flow rate of the exhaust gas recirculated to the intake passage 20. Further, the EGR valve 42 has a function of preventing the backflow of the exhaust gas from the EGR passage 40 to the exhaust passage 31 d.

The flow rate of the exhaust of the EGR passage 40 can be adjusted by the above-described exhaust adjustment valve 34. That is, by adjusting the flow rate of the exhaust gas flowing through the exhaust passages 31a and 31d by the exhaust gas adjustment valve 34, the flow rate of the exhaust gas flowing through the EGR passage 40 can also be adjusted. Further, by adjusting the pressure of the exhaust of the two exhaust passages 31a and 31d connected to the EGR passage 40 with the exhaust adjustment valve 34, the pressure of the exhaust becomes excessive relative to the pressure of the intake of the intake passage 20. As a result, the exhaust gas can be appropriately recirculated to the intake passage 20.
Further, by adjusting the intake throttle valve 25 of the intake passage 20 in addition to the exhaust adjustment valve 34 and the EGR valve 42, the recirculation of the exhaust gas to the intake passage 20 can be controlled with high accuracy. Note that at least one of the exhaust gas adjustment valve 34, the EGR valve 42, and the intake throttle valve 25 may be selected according to the rotation region of the engine 10 to control the amount of exhaust gas recirculation.

  The low pressure supercharger 50 and the high pressure supercharger 60 are devices for supercharging intake air taken into the engine 10. Specifically, after the low pressure supercharger 50 supercharges the intake air, the high pressure supercharger 60 further supercharges the intake air. As a result, the highly compressed intake air is supplied to the engine 10, and the displacement of the engine 10 can be substantially increased. The low pressure stage turbocharger 50 and the high pressure stage turbocharger 60 here are turbochargers that are powered by exhaust pressure.

  The low pressure supercharger 50 has a connecting shaft 53 connecting the turbine 51 and the compressor 52 in addition to the turbine 51 and the compressor 52 described above. In the low pressure supercharger 50, the turbine 51 receives energy of the passing exhaust and rotates, so that the compressor 52 connected to the turbine 51 via the connecting shaft 53 rotates to intake the intake passage 20. Supercharge. Similarly, the high-pressure stage turbocharger 60 also has a connecting shaft 63 connecting the turbine 61 and the compressor 62, and the energy of the passing exhaust energy receives the rotation of the turbine 61, whereby the compressor 62 rotates to intake air. The intake air of the passage 20 is supercharged.

  The turbine 61 of the high-pressure stage turbocharger 60 is rotated by the exhaust power of the cylinders 13b and 13c which do not interfere with the exhaust pulsation of the four cylinders 13a to 13d, so the turbine 61 can be rotated efficiently. Further, the exhaust gas of some of the cylinders 13b and 13d among the four cylinders 13a to 13d passes through the turbine 61, whereby the turbine 61 can be miniaturized. On the other hand, in the low pressure supercharger 50 where the turbine 51 is positioned downstream of the turbine 61 of the high pressure supercharger 60, the turbine 61 is added to the exhaust of the cylinders 13 b and 13 c which have passed or bypassed the turbine 61. Exhaust of the cylinders 13a and 13d bypassing the valve is also introduced. For this reason, the turbine 51 rotates using the exhaust gas discharged from the four cylinders 13a to 13d as a power source. This makes it possible to improve the operation efficiency of the low pressure stage turbocharger 50.

  In the exhaust passage 31e, the exhaust passing through the high-pressure stage turbocharger 60 (the exhaust of the cylinders 13b and 13c where the exhaust pulsations do not interfere) and the exhaust flowing through the exhaust passages 31a and 31d (the cylinder 13a where the exhaust pulsations do not interfere) , 13d exhaust) join. Since the dynamic pressure of the exhaust gas having passed through the high-pressure stage turbocharger 60 is small, interference of the exhaust gas pulsation in the exhaust passage 31e can be suppressed.

  As described above, the exhaust gas from the cylinders 13b and 13c is introduced into the high pressure supercharger 60 through the exhaust passages 31b and 31c, and the exhaust gas from the cylinders 13a and 13d into the low pressure supercharger 50 through the exhaust passages 31a, 31d, and 31e. be introduced. Therefore, the cylinders 13b and 13c correspond to the first cylinder, the cylinders 13a and 13d correspond to the second cylinder, the exhaust passages 31b and 31c correspond to the first exhaust passage, and the exhaust passages 31a, 31d and 31e correspond to the first. 2 Applicable to the exhaust passage.

  The ECU 80 is an electronic control unit (ECU) equipped with a microcomputer having a CPU, a ROM, a RAM, and the like. The ECU 80 controls the operation of each device described above. For example, the ECU 80 controls the operation of the intake throttle valve 25, the exhaust adjustment valve 34, the bypass adjustment valves 35 and 36, and the EGR valve 42.

(Effect in the first embodiment)
The above-described intake / exhaust system S introduces the exhaust of the cylinders 13b and 13c without interference of exhaust pulsations into the high pressure supercharger 60 through the exhaust passages 31b and 31c, and the cylinders 13a without interference of exhaust pulsations. , 13d are introduced into the low pressure supercharger 50 via the exhaust passages 31a, 31d, 31e which bypass the high pressure supercharger 60.
As a result, the exhaust of the cylinders 13b and 13c free from interference of exhaust pulsation is introduced into the high pressure stage turbocharger 60, so that the operating efficiency of the high pressure stage turbocharger 60 can be improved, and the high pressure stage turbocharger 60 (specifically, the turbine 61) can be miniaturized. Further, since the exhaust of the cylinders 13a and 13d not introduced into the high pressure stage turbocharger 60 is introduced into the low pressure stage turbocharger 50, the operation efficiency of the low pressure stage turbocharger 50 can be enhanced.

Second Embodiment
FIG. 2: is a schematic diagram which shows an example of a structure of intake / exhaust system S which concerns on 2nd Embodiment.
In the first embodiment, the exhaust passage 31a and the exhaust passage 31d merge to connect with the exhaust passage 31e on the downstream side of the turbine 61 of the high-pressure stage turbocharger 60, while in the second embodiment It differs in that the passage 31a and the exhaust passage 31d are independently connected to the exhaust passage 31e. The description of the same configuration as that of the first embodiment will be omitted.

  As shown in FIG. 2, the exhaust passage 31a and the exhaust passage 31d are two bypass passages connected respectively to the exhaust passage 31e without being joined on the way. Further, the EGR passage 40 is connected to the exhaust passage 31 d of the exhaust passage 31 a and the exhaust passage 31 d. Therefore, although the exhaust of the cylinder 13 d is recirculated to the intake passage 20, the exhaust of the cylinder 13 a is not recirculated to the intake passage 20. Further, the exhaust adjustment valve 34 adjusts the pressure and flow rate of the exhaust flowing through the exhaust passage 31 d.

  According to the second embodiment, in addition to the effects of the first embodiment, in order to recirculate only the exhaust of the cylinder 13d of the four cylinders 13a to 13d to the intake passage 20, It is effective when the amount of reflux is small.

Third Embodiment
FIG. 3: is a schematic diagram which shows an example of a structure of intake / exhaust system S which concerns on 3rd Embodiment.
In the third embodiment, in addition to the configuration of the second embodiment, as shown in FIG. 3, an EGR passage 45 connecting the exhaust passage 31a and the intake passage 20 is provided. The EGR passage 45 recirculates the exhaust of the cylinder 13 a to the intake passage 20.

  An EGR cooler 46 and an EGR valve 47 are provided in the EGR passage 45 similarly to the EGR passage 40 described in the first embodiment. The EGR cooler 46 cools the exhaust of the EGR passage 45. The EGR valve 47 adjusts the flow rate of the exhaust gas of the cylinder 13 a that is recirculated to the intake passage 20.

  Further, an exhaust adjustment valve 38 is provided on the exhaust passage 31 a downstream of a connection point with the EGR passage 45. The exhaust adjustment valve 38 has the same configuration as the exhaust adjustment valve 34 provided in the exhaust passage 31 d, and adjusts the pressure and flow rate of the exhaust flowing through the exhaust passage 31 a. Thus, the flow rate of the exhaust gas flowing through the EGR passage 45 can also be adjusted. The operations of the EGR valve 47 and the exhaust adjustment valve 38 are also controlled by the ECU 80.

  According to the third embodiment, in addition to the effects of the first embodiment, by providing the two EGR passages 40 and 45, the amounts of recirculation of the exhaust of the two cylinders 13a and 13d into the intake passage 20 can be different. Can be adjusted to enable more accurate control.

  Although the engine 10 is a diesel engine in the above description, the present invention is not limited thereto. For example, the engine 10 may be a gasoline engine. Further, although the engine 10 has four cylinders in the above description, the present invention is not limited to this. For example, the engine 10 may have three or six cylinders.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It is apparent to those skilled in the art that various changes or modifications can be added to the above embodiment. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF REFERENCE NUMERALS 10 engine 13a to 13d cylinder 20 intake passage 30 exhaust passage 31a to 31f exhaust passage 33a, 33b bypass passage 34 exhaust adjustment valve 35, 36 bypass adjustment valve 40 EGR passage 50 low pressure stage turbocharger 51 turbine 52 compressor 60 high pressure stage charging Machine 61 Turbine 62 Compressor S Intake and exhaust system

Claims (4)

A cylinder group provided in the internal combustion engine and including three or more cylinders;
An intake passage for introducing intake air to the cylinder group;
A low pressure supercharger and a high pressure supercharger for compressing the intake air;
A first exhaust passage for introducing, into the high-pressure stage turbocharger, the exhaust gas discharged from each of two first cylinders in the cylinder group in which interference of exhaust pulsation does not occur;
The exhaust gas discharged from the second cylinder different from the first cylinder of the cylinder group is provided downstream of the high pressure supercharger, provided to bypass the high pressure supercharger. A second exhaust passage introduced to the low-pressure stage turbocharger;
A reflux passage connecting the second exhaust passage and the intake passage, and returning the exhaust gas discharged from the second cylinder to the intake passage;
An exhaust pressure adjustment unit provided downstream of a connection point with the reflux passage in the second exhaust passage, and adjusting the pressure of the exhaust in the second exhaust passage;
An intake and exhaust system for an internal combustion engine, comprising: A cylinder group provided in the internal combustion engine and including three or more cylinders;
  An intake passage for introducing intake air to the cylinder group;
  A low pressure supercharger and a high pressure supercharger for compressing the intake air;
  A first exhaust passage for introducing, into the high-pressure stage turbocharger, the exhaust gas discharged from each of two first cylinders in the cylinder group in which interference of exhaust pulsation does not occur;
  The exhaust gas discharged from the second cylinder different from the first cylinder of the cylinder group is provided downstream of the high pressure supercharger, provided to bypass the high pressure supercharger. A second exhaust passage introduced to the low-pressure stage turbocharger;
  A reflux passage connecting the second exhaust passage and the intake passage, and returning the exhaust gas discharged from the second cylinder to the intake passage;
  A flow rate adjusting unit provided downstream of a connection point with the reflux passage in the second exhaust passage, and adjusting a flow rate of exhaust gas in the reflux passage;
  An intake and exhaust system for an internal combustion engine, comprising: The second exhaust passage is characterized in that the exhaust gas discharged from each of the two second cylinders not causing interference of exhaust pulsations is introduced into the low pressure stage turbocharger.
An intake and exhaust system for an internal combustion engine according to claim 1 or 2 . There are two said second cylinders,
The second exhaust passage includes two bypass passages connected to each of the two second cylinders and bypassing the high-pressure stage turbocharger.
An intake and exhaust system for an internal combustion engine according to claim 1 or 2 .

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