JP2013072327A - Exhaust structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that supercharging pressure fluctuates since unbalance with the other cylinders is generated when extracting an EGR gas from an exhaust port of one cylinder of an engine having a plurality of cylinders each with a supercharger.SOLUTION: In the exhaust structure of an internal combustion engine having an exhaust gas junction point 34 where exhaust passages from the plurality of cylinders are joined, the supercharger 14 arranged at a downstream rather than the exhaust junction points, and at least one EGR gas supply and exhaust passage 16 having a communication section communicated with EGR gas passage between an outlet of the cylinder and the exhaust junction point in the exhaust passage. The EGR gas supply and exhaust passage has a narrowed section 40, where its cross section is smaller than the cross section of the other exhaust passage, between the communication section and the exhaust junction point.

Description

  The present invention relates to an exhaust structure of an internal combustion engine, and in particular, in an internal combustion engine having a plurality of cylinders, a communication portion with an EGR gas passage is provided in an exhaust passage of one cylinder, and an exhaust passage is provided downstream of the exhaust passage. The present invention relates to an exhaust structure of an internal combustion engine of a type having a feeder.

  EGR (Exhaust Gas Recirculation) is a system that reduces the combustion temperature and suppresses the generation of nitrogen oxides such as NOx by returning a part of the exhaust gas (hereinafter referred to as “EGR gas”) to the intake side. . The location where the EGR gas is acquired may be in the exhaust system. However, considering the downsizing of the engine and the reduction in the number of parts, it is preferable that the location in the cylinder head be as close to the intake side as possible.

  Patent Document 1 discloses a configuration in which an EGR gas passage is communicated with an exhaust port in a cylinder head. Here, the exhaust port of the cylinders (# 1 and # 4 cylinders) at both ends of an in-line four-cylinder internal combustion engine (hereinafter also referred to as “engine”) is provided with a communication portion to the EGR gas passage, and EGR is provided outside the cylinder head. A configuration is shown in which a passage is provided to discharge EGR gas to the central portion of the intake manifold.

  The turbocharger is a turbine wheel and compressor wheel connected by a shaft, sealed in the turbine chamber and compressor chamber, rotated by the exhaust gas, and pressurized by the compressor wheel to the intake air sent to the combustion chamber. .

  As described above, since the turbocharger rotates the turbine wheel by the exhaust gas, the fluctuation of the pressure of the exhaust gas (hereinafter referred to as “back pressure”) causes the fluctuation of the output of the entire engine.

  For example, Patent Document 2 discloses a first cylinder, a fourth cylinder, and a second cylinder as a problem when a supercharger is directly provided at an exhaust port of a cylinder head of a four-cylinder engine having an exhaust port and a collecting portion therein. Since the length of the exhaust port is different between the third cylinder and the third cylinder, the back pressure is different between the two groups, and the rotation of the supercharger is not constant.

  In Patent Document 2, for this problem, the outlets of the exhaust ports are divided into upper and lower parts in the group of the first cylinder and the fourth cylinder, and the group of the second cylinder and the third cylinder, and the sectional areas of the respective outlets are adjusted. By doing so, the back pressure seen from the turbocharger is stabilized.

Japanese Utility Model Publication No. 59-067564 JP 2007-285169 A

  If an EGR is mounted on an engine equipped with a supercharger and the engine is made compact, an EGR gas passage is provided in the cylinder head, and exhaust gas having a stable back pressure is supplied to the turbocharger. is necessary. At this time, providing a plurality of EGR gas passages as in Patent Document 1 makes the structure complicated. Therefore, it is considered preferable to acquire EGR gas from the exhaust system of one cylinder among the plurality of cylinders.

  However, if an unbalance is generated in the exhaust system between a plurality of cylinders, the back pressure (supercharging pressure) of the exhaust gas supplied to the supercharger varies, causing a problem that the output of the entire engine is reduced.

  The present invention has been conceived in view of the above-described problems, and provides an exhaust structure for an internal combustion engine that is equipped with a supercharger and EGR and that can be downsized.

More specifically, the exhaust structure of the internal combustion engine of the present invention is:
An exhaust merge point where exhaust passages from a plurality of cylinders merge;
A supercharger provided downstream from the exhaust junction;
An exhaust structure for an internal combustion engine having at least one EGR gas supply exhaust passage having a communication portion communicating with an EGR gas passage between an outlet of the cylinder and the exhaust confluence in the exhaust passage,
The EGR gas supply exhaust passage has a constricted portion having a cross-sectional area smaller than the cross-sectional area of another exhaust passage between the communication portion and the exhaust junction.

  In the exhaust structure of the internal combustion engine of the present invention, the exhaust passage for collecting EGR gas has a smaller cross-sectional area than the other exhaust passages, so that the fluctuation of the supercharging pressure with respect to the supercharger can be reduced. In addition, since the cross-sectional area on the downstream side of the communication portion to the EGR gas passage is reduced, the gas pressure and flow rate of the EGR gas passage are increased, and the fuel consumption can be improved.

It is a figure which shows the structure of the exhaust structure of this invention. It is a figure which shows other embodiment of the exhaust structure of this invention. It is a figure which shows the structure of the exhaust structure of this invention which made the constriction part variable.

  The present invention will be described below with reference to the drawings. The following description exemplifies an embodiment of the present invention, and the following embodiment may be modified without departing from the gist of the present invention.

  FIG. 1 is a diagram showing an exhaust structure 1 for an internal combustion engine according to the present invention. In the exhaust structure 1 for an internal combustion engine of the present invention, a cylinder head 10 having a plurality of cylinders, an exhaust means 12 connected to the cylinder head 10, and a supercharger 14 (turbine wheel 14t) disposed in the middle of the exhaust means 12. Side) and an EGR gas passage 16 for sending EGR gas from the exhaust means 12 to the intake system side. Note that an intake manifold 70, a throttle body 71, an intercooler 72, a supercharger 14 (compressor wheel 14c side), an air cleaner (not shown), and the like may be connected to the cylinder head 10 as an intake system. Intake manifold 70 may include a surge tank.

  A plurality of cylinders 20 are formed in the cylinder head 10. Although FIG. 1 shows a case of two cylinders, three or more cylinders may be used. The first cylinder and the second cylinder are denoted by reference numerals 20a and 20b, respectively. Each cylinder 20 is provided with a space serving as a combustion chamber 21. An intake port 22 and an exhaust port 24 are formed from the combustion chamber 21 toward the opposite side surfaces of the cylinder head 10. The surface of the cylinder head 10 on which the outlet 24o of the exhaust port 24 is formed is referred to as an exhaust surface 10ex, and the surface on which the outlet of the intake port 22 is formed is referred to as an intake surface 10in. The combustion chamber 21, the intake port 22, and the exhaust port 24 of the first cylinder 20a and the second cylinder 20b are denoted by reference numerals 21a, 21b, 22a, 22b, 24a, and 24b, respectively.

  The exhaust port 24 is gathered between the combustion chamber 21 and the exhaust surface 10ex, and is formed as one outlet 24o on the exhaust surface 10ex of the cylinder head 10. That is, the exhaust manifold 26 is formed in the cylinder head 10. In the embodiment of FIG. 1, the outlet 24 o of the exhaust port 24 and the outlet 26 o of the exhaust manifold 26 coincide. A joining pipe 28 is joined to the outlet 24 o of the exhaust surface 10 ex of the cylinder head 10 and communicates with the turbine wheel inlet 14 ti of the supercharger 14.

  The supercharger 14 is obtained by connecting a turbine wheel 14t and a compressor wheel 14c with a shaft 14s. The turbine wheel 14t is rotated by the exhaust gas. The rotation of the turbine wheel 14t rotates the compressor wheel 14c by the shaft 14s. Since the compressor wheel 14 c is arranged in the intake system, pressure is applied to the intake air to the cylinder 20 through the throttle body 71 and the intake manifold 70.

  Therefore, the turbocharger 14 includes a compressor wheel inlet 14ci through which intake air enters the compressor wheel 14c, a compressor wheel outlet 14co through which pressurized intake air is discharged, and a turbine wheel inlet 14ti through which exhaust gas enters the turbine wheel 14t. A turbine wheel outlet 14to is formed from which the exhaust gas that has rotated the turbine wheel 14t is discharged.

  An exhaust pipe 30 is connected to the turbine wheel outlet 14 to of the supercharger 14. A catalyst (not shown) and a muffler muffler (not shown) for burning unburned components and soot in the exhaust gas are connected to the downstream side of the exhaust pipe 30. The section from the outlet of the combustion chamber 21 to the tip of the muffler muffler is called exhaust means 12.

  Here, an exhaust gas passage formed from the exhaust port of the combustion chamber 21 of one cylinder 20 is referred to as an exhaust passage 32. A point where the exhaust passages 32 join each other is called an exhaust junction 34. In FIG. 1, the exhaust manifold 26 formed in the cylinder head 10 is an exhaust junction 34. The exhaust passage of the first cylinder 20a and the exhaust passage of the second cylinder 20b are denoted by 32a and 32b, respectively.

  FIG. 2 shows another form of the exhaust passage 32. FIG. 2A shows a type in which exhaust port outlets (24ao, 24bo) for each cylinder 20 are formed on the exhaust surface 10ex of the cylinder head 10, and the exhaust manifold 26 is connected as a separate component to the exhaust surface 10ex. In this type, the exhaust passage 32 is equal to the exhaust port 24. An exhaust junction 34 is an exhaust manifold 26 joined to the cylinder head 10.

  FIG. 2B shows a type in which the exhaust pipe 30 is directly connected to the exhaust port outlets (24ao, 24bo) of the cylinder head 10 and the exhaust pipes 30 join each other. The exhaust pipe of the first cylinder 20a and the exhaust pipe of the second cylinder 20b are denoted by reference numerals 30a and 30b, respectively. In this case, the exhaust passage 32 also includes an exhaust port 24 followed by an exhaust pipe 30. The exhaust merge point 34 is a point where the exhaust pipes 30 merge. In the present invention, the exhaust junction 34 exists, and the supercharger 14 is provided downstream of the exhaust junction 34.

  Referring to FIG. 1 again, one exhaust passage 32 in the exhaust passage 32 from the plurality of cylinders 20 is provided with a communication portion 18 with the EGR gas passage 16. The exhaust passage 32 provided with the communication portion 18 with the EGR gas passage 16 is referred to as an EGR gas supply exhaust passage 32x. Of the plurality of cylinders 20, which exhaust passage 32 of which cylinder 20 is used as the EGR gas supply exhaust passage 32 x is not particularly limited.

  However, the EGR gas passage 16 needs to be formed in the cylinder head 10 toward the point where the EGR valve 36 is installed. On the other hand, in the cylinder head 10, a hole for arranging a valve for opening and closing the combustion chamber 21, a hole for arranging a spark plug, a camshaft driving the valve, and water for flowing cooling water. Jackets are provided (these are not shown). From the EGR valve 36, the downstream EGR gas passage 16b communicates with the intake system. Here, an example is shown in which exhaust gas is mixed with intake air in communication with the opening in the middle of the intake manifold 70.

  Therefore, it is often preferable that the exhaust passage 32 of the cylinder 20 at the end of the plurality of cylinders 20 is the EGR gas supply exhaust passage 32x. In the present embodiment, since it has a two-cylinder configuration, either the exhaust passage 32a of the first cylinder 20a or the exhaust passage 32b of the second cylinder 20b may be used as the EGR gas supply exhaust passage 32x. Here, the exhaust passage 32b of the second cylinder 20b is an EGR gas supply exhaust passage 32x.

  As shown in FIG. 2B, when the exhaust pipe 30 is included in the exhaust passage 32 and the communication portion 18 with the EGR gas passage 16 is provided in the exhaust pipe 30, which exhaust pipe 30 is connected to the EGR gas. The supply exhaust passage 32x may be used. This is because when the communication portion 18 is provided outside the cylinder head 10, there is a space delay.

  Referring to FIG. 1 again, in EGR gas supply exhaust passage 32x, communication portion 18 with EGR gas passage 16 is formed between the outlet of combustion chamber 21 and exhaust junction 34. Further, a narrowed portion 40 having a cross-sectional area narrower than the cross-sectional areas of other exhaust passages is provided between the communication portion 18 and the exhaust junction 34.

  When exhaust gas is discharged from the combustion chamber 21, the back pressure is an important factor as well as the distance and shape to the outlet of the exhaust means 12. In particular, when there is a variation in back pressure among a plurality of cylinders 20, the internal combustion engine with the supercharger 14 has a reduced output as a whole because the supercharging pressure varies. Therefore, it is necessary to prevent a large variation in back pressure between the cylinders 20. Therefore, it is preferable that the cross-sectional area of the exhaust passage 32 of each cylinder 20 is substantially the same cross-sectional area up to the exhaust confluence 34.

  The EGR gas supply / exhaust passage 32x has a communicating portion 18 with the EGR gas passage 16, that is, an open end, up to the exhaust confluence 34. That is, the EGR gas supply exhaust passage 32 x has a cross-sectional area that is wider than the exhaust passage 32 from the other cylinders 20 by the communication portion 18. Therefore, the constricted portion 40 is provided up to the exhaust confluence 34, and when viewed from the exhaust confluence 34, the back pressure is comparable to the exhaust passage 32a of the other cylinder 20 (here, the first cylinder 20a). Thus, the cross-sectional area of the EGR gas supply / exhaust passage 32x is adjusted.

  As described above, the communication portion 18 may be formed between the outlet of the combustion chamber 21 and the narrowed portion 40 and is not particularly limited. According to the shape of the exhaust passage 32, a place where the EGR gas can be most easily acquired can be appropriately determined.

  In order to make the back pressure of each cylinder 20 the same when viewed from the exhaust confluence 34, the sum of the cross-sectional area of the narrowed portion 40 and the cross-sectional area of the communication portion 18 is the cross-sectional area of the other exhaust passage 32. To be approximately equal. In the EGR gas supply exhaust passage 32 x, a part of the exhaust gas exiting from the combustion chamber 21 escapes to the EGR gas passage 16. That is, the amount of exhaust gas that passes through the EGR gas supply exhaust passage 32 x downstream of the communication portion 18 is smaller than the amount of exhaust gas that passes through the other exhaust passages 32. However, by reducing the exhaust gas passage cross-sectional area at the constriction 40, the back pressure of the EGR gas supply exhaust passage 32x when viewed from the exhaust confluence 34 becomes approximately the same as the back pressure of the other exhaust passages 32. Because.

  It can be said that this is substantially equal to the cross-sectional area of the exhaust passage 32 upstream of the communication portion 18 (between the outlet of the combustion chamber 21 and the communication portion 18). This is because the exhaust passage 32 is formed with a substantially constant cross-sectional area from the combustion chamber 21 to the exhaust junction 34.

  Here, “substantially equal” means that the difference between the cross-sectional areas is ± 30% or less. This is because a difference of this degree occurs in order to make the back pressure substantially the same depending on the shape of the exhaust passage 32 and the location where the communication portion 18 is formed.

  Further, the “other exhaust passage 32” may be substantially equal to at least one exhaust passage 32 among the plurality of exhaust passages 32 formed by the plurality of cylinders 20. In the case of a cylinder head of the type provided in the cylinder head 10 up to the collecting portion (exhaust manifold 26) of the exhaust port 24, the exhaust passage 32 often varies greatly for each cylinder 20. This is because the space in the cylinder head 10 is small. However, in order to maintain symmetry, at least one exhaust passage 32 having the same shape as the EGR gas supply exhaust passage 32x and not having the constricted portion 40 is provided and handled in pairs with the exhaust passage 32. This is because the entire exhaust passage 32 can be balanced.

  The shape of the narrowed portion 40 is not particularly limited, but a shape that does not cause turbulent flow in the exhaust gas passing at a speed close to the speed of sound is desirable.

  In this way, when viewed from the exhaust merge point 34, the back pressures of the exhaust passages 32 are approximately the same, so that the turbine wheel inlet 14 ti of the supercharger 14 provided downstream of the exhaust merge point 34 is provided. The exhaust gas having a constant pressure is supplied. As a result, the shaft 14s of the supercharger 14 rotates stably, and the compressor wheel 14c can also apply a pressure with little fluctuation to the intake air with a stable rotation.

  FIG. 3 shows the configuration of another embodiment of the present invention. The description of the same part as in FIG. 1 is omitted. FIG. 3 shows that the constriction portion 40 comprises a constriction member 40m and a constriction member drive portion 40d, and an EGR valve 36 disposed at the end of the EGR gas passage 16, a rev sensor 42 for detecting the engine speed, and FIG. The control device 50 is connected to the constricting member driving unit 40d, the EGR valve 36, and the rev sensor 42. The control device 50 may be connected to a throttle sensor 44 that detects the opening of the throttle body 71.

  EGR is a system that returns part of the exhaust gas to the intake air as EGR gas, but does not always reduce the EGR gas. For example, EGR may be stopped when idling when combustion is not stable or when the accelerator is fully open, which requires full power. In such a case, if the EGR valve 36 is controlled so as to be closed, the EGR gas supply exhaust passage 32x becomes an exhaust passage 32 that hardly exhausts the exhaust gas compared to the other exhaust passages 32. As a result, the output is reduced due to the provision of the constriction 40.

  Therefore, when performing control such that the EGR valve 36 is closed, the stenosis 40 is variably controlled so that the cross-sectional area of the stenosis 40 is widened to the same cross-sectional area as the other exhaust passages 32.

  The narrowing member 40m is a member protruding into the EGR gas supply / exhaust passage 32x. Due to the protrusion of the narrowing member 40m, the cross-sectional area of the EGR gas supply / exhaust passage 32x becomes a predetermined narrowness. The constriction member drive unit 40d is an actuator that moves the constriction member 40m into the EGR gas supply / exhaust passage 32x or returns it to the storage position by an instruction signal Cs from the control device 50.

  The control device 50 receives a signal Sr corresponding to the engine speed from the rev sensor 42. Alternatively, a signal Ss corresponding to the throttle opening may be received from the throttle sensor 44. Based on these signals, it is determined whether the EGR is operated (EGR gas is returned to the intake side) or stopped (EGR gas is not returned to the intake side). This determination can be made based on a pre-programmed processing flow.

  When stopping the EGR, the control device 50 closes the EGR valve 36 with the control signal Cv and simultaneously returns the constriction member 40m to the storage position with the control signal Cs. By doing so, the EGR gas supply exhaust passage 32x has the same cross-sectional area as the other exhaust passages 32 (here, 32a).

  When operating the EGR, the control device 50 opens the EGR valve 36 with the control signal Cv, and simultaneously causes the constriction member 40m to protrude into the EGR gas supply / exhaust passage 32x with the control signal Cs. By doing so, the cross-sectional area of the EGR gas supply / exhaust passage 32x becomes narrower. As a result, a part of the exhaust gas flows from the communication portion 18 of the EGR gas supply exhaust passage 32x to the intake side through the EGR gas passage 16 as EGR gas.

  However, the cross-sectional area of the EGR gas supply exhaust passage 32x decreases from the exhaust confluence 34, and as a result, the apparent back pressure looks the same even if the flow rate of the exhaust gas decreases. Therefore, the supercharger 14 provided downstream of the exhaust junction 34 can be driven by exhaust gas having a stable pressure.

  As described above, when the cross-sectional area of the EGR gas supply / exhaust passage 32x is changed by the protrusion of the constricting member 40m, the back pressure can be made constant even if the use state of the EGR changes. Further, the protruding amount of the constricting member 40m can be changed to a desired degree by the protruding member driving unit 40d. Therefore, since the cross-sectional area of the constriction 40 can be changed according to the flow rate of the EGR gas, the back pressure can be made constant regardless of the opening degree of the EGR valve 36 over almost the entire engine speed. .

  The exhaust structure for an internal combustion engine of the present invention can be suitably used for an internal combustion engine having a supercharger immediately after a cylinder head.

DESCRIPTION OF SYMBOLS 1 Exhaust structure 10 Cylinder head 10in Intake surface 10ex Exhaust surface 12 Exhaust means 14 Supercharger 14s (supercharger) shaft 14c Compressor wheel 14ci Compressor wheel inlet 14co Compressor wheel outlet 14t Turbine wheel 14ti Turbine wheel inlet 14to Turbine wheel outlet 16 EGR gas passage 16b Downstream EGR gas passage 18 Communication portion 20 Cylinder 20a First cylinder, 20b Second cylinder 21 Combustion chamber 21a (First cylinder) Combustion chamber, 21b (Second cylinder) Combustion chamber 22 Intake port 22a ( Intake port of the first cylinder, 22b Intake port of the second cylinder 24 Exhaust port 24a Exhaust port of the first cylinder, 24b Exhaust port of the second cylinder 24o Out of the exhaust port 24ao (First of the cylinder) Outlet 24bo (exhaust port of the second cylinder) outlet 26 exhaust manifold 26o (exhaust manifold) outlet 28 joint pipe 30 exhaust pipe 30a (first cylinder) exhaust pipe, 30b (second cylinder exhaust port) ) Exhaust pipe 32 Exhaust passage 32a (First cylinder) exhaust passage, 32b (Second cylinder) exhaust passage 32x EGR gas supply exhaust passage 34 Exhaust confluence 36 EGR valve 40 Constriction portion 40m Constriction member 40d Constriction member drive portion 42 Reb sensor 44 Throttle sensor 50 Control device 70 Intake manifold 71 Throttle body 72 Intercooler

Claims (1)

An exhaust merge point where exhaust passages from a plurality of cylinders merge;
A supercharger provided downstream from the exhaust junction;
An exhaust structure for an internal combustion engine having at least one EGR gas supply exhaust passage having a communication portion communicating with an EGR gas passage between an outlet of the cylinder and the exhaust confluence in the exhaust passage,
The exhaust structure of an internal combustion engine, wherein the EGR gas supply exhaust passage has a constricted portion having a cross-sectional area smaller than a cross-sectional area of another exhaust passage between the communication portion and the exhaust confluence.