EXHAUST DEVICE FOR AN ENGINE

Abstract

Exhaust device for an engine provided with several cylinders (2a), comprising: an engine main body (1) having a cylinder head (3) provided therein with a manifold exhaust passage, the manifold exhaust passage including a common exhaust port (3a) communicating with each of the cylinders (2a), the common exhaust port (3a) being formed in a surface of the cylinder head (3) in an engine width direction orthogonal to a cylinder arrangement direction; a turbocharger (60) arranged on the same side as the cylinder head surface and adapted to rotate a turbine (62b) and a compressor (62a) coupled to said turbine by means of a coupling shaft (62c) by exhaust gas discharged from the collective exhaust port to thereby compress intake air; a catalyst device (31) arranged adjacent to the turbocharger (60) in the cylinder arrangement direction and designed to react a specific component in the exhaust gas that has passed through the turbocharger (60) and flowed in said cylinder arrangement direction to form a harmless component; and an exhaust gas treatment device (32) designed to retain the specific component in the exhaust gas that has passed through the catalyst device (31), wherein the turbocharger (60) with said coupling shaft (62c) is arranged at an upper position of the collecting outlet port (3a) and is designed to guide the exhaust gas discharged from the collecting outlet port (3a) upward into a turbine chamber (63) formed within a turbine housing (61b) to thereby rotate the turbine (62b) while forming an upward swirling flow of exhaust gas, the catalyst device (31) is provided with a monolith support (70) and a container (71) which receives the support, wherein the container (71) is formed with an exhaust gas inlet (72) and an exhaust gas outlet (73) at opposite ends in said cylinder arrangement direction such that the monolith support (70) is received between the exhaust gas inlet (72) and the exhaust gas outlet (73), wherein said exhaust gas inlet (72) and said exhaust gas outlet (73) each face a lower portion of the monolith support (70), and the exhaust gas treatment device (32) is arranged on a side of the engine main body (1) on which the catalyst device (31) is arranged, in the up and down direction of the engine main body (1) below the catalyst device.

Description

BACKGROUND OF THE INVENTIONField of the InventionThe present invention relates to an exhaust device for an engine provided with a turbocharger.Prior ArtIn recent years, an engine equipped with a turbocharger has attracted attention in view of demand for downsizing. JP 4 803 059 B2 discloses an engine provided with: a cylinder head in which an exhaust manifold is integrally formed; a turbocharger which is fixed to a side surface of the cylinder head and communicates with a collection portion of the exhaust manifold; and an exhaust pipe provided with a catalyst device and coupled to the turbocharger in the cylinder arrangement direction.The above-described engine structure is advantageous in manufacturing the engine as a compact whole, improving the supercharging pressure characteristics of the engine, and reducing the number of assembling steps compared to an engine provided with an exhaust manifold separate from a cylinder head. Further, the high temperature exhaust gas discharged from the cylinder head is fed to the catalyst device only through the turbocharger. Therefore, the engine structure is also advantageous in the aspect of promoting activation of the catalyst device.In an engine, it is important to reduce NOx (nitrogen oxide) in the exhaust gas. As one of the measures, it is effective to execute EGR (Exhaust Gas Recirculation) control of a recirculated part of exhaust gas to an intake passage. Further, it is necessary in some cases to provide an exhaust gas treatment device to retain fine particles such as soot contained in the exhaust gas. The idea is to perform EGR control or retention of fine particles in exhaust gas to improve exhaust gas characteristics, as well as the engine disclosed in JP 4 803 059 B2. In such a case, it is important to arrange an EGR device and an exhaust treatment device in a compact manner while considering a positional relationship with respect to a turbocharger and a catalyst device in order to make the engine compact. However, JP 4 803 059 B2 fails to disclose the above point.Further exhaust gas treatment devices for internal combustion engines are known from the documents US 2010 / 0 326 054 A1, WO 2012 / 110 720 A1, FR 2 918 710 A1 and JP 2012-57 519 A, wherein the first-mentioned US 2010 / 0 326 054 A1 shows a container which is mounted laterally on an engine body and accommodates a catalytic converter, wherein a particle filter downstream of the catalytic converter is likewise accommodated in said container.When EGR control is executed, the combustion temperature is lowered, which may lower the temperature of exhaust gas. This may make it difficult to activate the exhaust purification catalyst. The same problem as described above may also occur in a diesel engine having a high combustion efficiency. In view of the above, it is desirable to provide a configuration advantageous in activating a catalyst device and the like when an EGR device and an exhaust gas purification device are provided.SUMMARY OF THE INVENTIONIn view of the foregoing, an object of the invention is to provide an exhaust device for a multi-cylinder engine provided with a turbocharger, a catalyst device and a treatment device consisting of an exhaust treatment device and an EGR device that contributes to activation of the catalyst device while making the engine compact.According to the invention, said object is achieved by an outlet device according to claim 1. Preferred embodiments of the invention are the subject of the dependent claims.These and other objects, features and advantages of the present invention will become more apparent upon reading the following detailed description, together with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a schematic diagram illustrating an overall configuration of an engine (a diesel engine) to which an exhaust device for an engine according to an embodiment of the invention is attached; FIG. 2 is a schematic side view of an outlet portion of the engine; FIG. 3 is a schematic sectional view illustrating a turbocharger; FIG. 4 is a schematic sectional view illustrating a catalyst device; and FIG. 5 is a diagram describing an operation of the catalyst device.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTIONHereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.FIG. 1 is a schematic diagram illustrating an overall configuration of a diesel engine to which an embodiment of the invention is applied. The diesel engine shown in FIG. 1 is a four-stroke diesel engine having a turbocharger and serves as a drive source for driving a vehicle.An engine main body 1 of the diesel engine (hereinafter referred to simply as an engine) is an in-line multi-cylinder engine. The engine main body 1 includes a cylinder block 2 provided with two or more cylinders 2 a(only one cylinder is shown in FIG. 1 ), a cylinder head 3 disposed on the cylinder block 2, an oil pan 4 disposed below the cylinder block 2 and configured to store lubricating oil therein, and a cylinder head cover 5 for covering an upper portion of the cylinder head 3.In each of the cylinders 2a of the engine main body 1, a piston 8 is reciprocally movably received. A cavity for defining a combustion chamber 8a is formed in an upper surface of each piston 8.The piston 8 is connected to a crankshaft 10 by means of a connecting rod 9. The crankshaft 10 is rotated according to a reciprocating motion of each piston 8 about a rotational axis thereof.The cylinder head 3 has an intake port 12 and an exhaust port 13 opened to the combustion chamber 8 aof each cylinder 2 a. The cylinder head 3 is further provided with intake valves 16 and exhaust valves 17 for opening and closing the intake ports 12 and the exhaust ports 13.The cylinder head 3 is provided with an injector 18 for injecting fuel containing light oil as a main component for each of the cylinders 2 a. Each injector 18 is disposed at such a position that an injection port (a fuel injection port) formed in a front end of the injector 18 faces the cavity in the upper surface of each piston 8. Each injector 18 injects fuel toward the combustion chamber 8 a(at the time when a compression stroke ends) at an appropriate timing before or after the compression top dead center.An intake passage 20 is connected to a surface of the engine main body 1 in the engine width direction (left and right direction in FIG. 1 ) orthogonal to the arrangement direction of the cylinders 2 ato communicate with the intake port 12 of each cylinder 2 a. To the other surface of the engine main body 1, an exhaust passage 30 is connected to communicate with the exhaust port 13 of each cylinder 2 a. Specifically, intake air is introduced from the outside to the combustion chambers 8 athrough the intake passage 20 and the intake ports 12, and exhaust gas (combustion gas) generated in the combustion chambers 81 is discharged to the outside through the exhaust ports 13 and the exhaust passage 30.A turbocharger 60 is provided on the intake passage 20 and the exhaust passage 30. The turbocharger 60 includes a compressor 62 aarranged in the intake passage 20 and a turbine 62 bco-axially coupled to the compressor 62 aand arranged in the exhaust passage 30.The turbocharger 60 is driven by exhaust energy to compress the intake air. Specifically, when high-temperature and high-speed exhaust gas flows through the exhaust passage 30 during operation of the engine, the turbine 62 bof the turbocharger 60 is rotated by the energy of the exhaust gas, and the compressor 62 acoupled to the turbine 62 bvia a coupling shaft 62 c(see FIG. 3 ) is simultaneously rotated. According to the above operation, air (intake air) flowing through the intake passage 20 is compressed to a high pressure, and the compressed air is supplied to each cylinder 2 aof the engine main body 1.An air cleaner 21 for filtering intake air is provided at an upstream end of the intake passage 20. At a position near a downstream end (near the engine main body 1) of the intake passage 20, a surge tank 24 is provided. The intake passage 20 on the downstream side of the surge tank 24 is formed into independent passages which are branched individually for the cylinders 2a. Downstream ends of the independent passages are connected to the intake ports 12 of the cylinders 2a, respectively.The compressor 62 aof the turbocharger 60, a throttle 23 that can be operated to be opened and closed to adjust the passage cross section of the intake passage 20, and an intercooler 22 for cooling the air compressed by the compressor 62 aare provided in this order from the upstream side between the air cleaner 21 and the surge tank 24 in the intake passage 20. The throttle valve 23 is basically maintained in a fully open state or a highly open state near the fully open state during operation of the engine. The throttle valve 23 is closed only when it is necessary to close the throttle valve 23, for example, when the engine is stopped. As a result, the inlet channel 20 is blocked.An upstream end of the exhaust passage 30 forms a manifold exhaust passage that merges independent passages communicating with the exhaust ports 13 of the cylinders 2 aand thus a collection portion in which the independent passages are collected so to speak. Although not clearly shown in FIG. 1, the exhaust manifold is integrally formed in the cylinder head 3. A collection exhaust port 3 a(see FIG. 2 ) serving as a collection portion is formed in a surface of the cylinder head 3. The exhaust passage 30 is formed to communicate with the collection exhaust port 3 a.The turbine 62 bof the turbocharger 60, plural kinds of exhaust gas purifying devices for removing harmful components contained in the exhaust gas, and a muffler 34 for reducing exhaust noise are provided in this order from the upstream side at a location on the downstream side of the exhaust manifold in the exhaust passage 30.Examples of the exhaust gas purification device are a DOC (diesel oxidation catalyst) 31 and a DPF (diesel particulate filter) 32 in this order from the upstream side. In this example, the DOC 31 corresponds to a catalyst device of the invention, and the DPF 32 corresponds to an exhaust gas treatment device as a treatment device of the invention.The DOC 31 oxidizes CO and HC in the exhaust gas discharged from the engine main body 1 to a harmless component. Specifically, CO (carbon oxide) and HC (hydrocarbon) in the exhaust gas are subjected to oxidation while flowing through the DOC 31, and are made into CO 2( carbon dioxide) and H 2 O (water). The DOC 31 also plays a role in raising the temperature of the exhaust gas by an oxidation reaction of exhaust gas discharged in the DOC 31 to flow high-temperature exhaust gas toward the DPF 32 disposed downstream of the DOC 31.The DPF 32 retains fine particles such as soot contained in the exhaust gas discharged from the engine main body 1. An example of the DPF 32 is a so-called wall flow filter (=wall flow filter) made of ceramics such as SiC (silicon carbide). Fine particles in the exhaust gas are retained by the cell walls of the DPF 32 when the exhaust gas passes through the cell walls of the DPF 32 from the inflow side toward the outflow side. In this example, the DPF 32 is a catalytic filter on which a catalyst (e.g., platinum) for promoting an oxidation reaction of exhaust gas is deposited. The DPF 32 is specifically a continuous regenerative filter that raises the temperature of exhaust gas by an oxidation reaction of the exhaust gas carried out in the DPF 32 to combust and remove the retained fine particles.Between the intake passage 20 and the exhaust passage 30, there are provided an HP-EGR passage 51 that returns a part of high-pressure exhaust gas discharged from the engine main body 1 to a relatively high-pressure portion in the intake passage 20, and an LP-EGR passage 55 that returns a part of low-pressure exhaust gas discharged from the engine main body 1 to a relatively low-pressure portion in the intake passage 20.Specifically, the HP-EGR passage 51 connects the intake passage 20 between the throttle valve 23 and the surge tank 24, and the exhaust passage 30 between the exhaust manifold and the turbine 62 bof the turbocharger 60. On the other hand, the LP-EGR passage 55 connects the intake passage 20 between the air cleaner 21 and the compressor 62 aof the turbocharger 60 and the exhaust passage 30 between the DPF 32 and the muffler 34. On the LP-EGR passage 55, an EGR valve 56 operable to be opened and closed to adjust the recirculation amount of an exhaust gas to the intake passage 20, and an EGR cooler 57 for cooling the recirculated EGR gas by engine coolant are provided. In this example, the EGR valve 56 and the EGR cooler 57 provided on the LP-EGR passage 55 correspond to an EGR device as the treatment device of the invention.Recycling a part of the exhaust gas from the exhaust passage 30 to the intake passage 20 and replacing a part of intake air to be introduced to the cylinders 2 afrom fresh air to EGR gas of a low oxygen concentration makes it possible to lower the oxygen concentration of the intake air as a whole. Further, lowering the combustion temperature makes it possible to suppress the generation of NOx. In this case, controlling the EGR valves 52 and 56 to open and close according to an operating state of the engine main body 1 makes it possible to adjust the amount of the high temperature and high pressure EGR gas recirculated through the HP-EGR passage 51 and the amount of the high temperature and low pressure EGR gas recirculated through the LP-EGR passage 55 according to an operating state of the engine main body 1.Next, a concrete structure of the main exhaust system of the engine will be described with reference to FIG. 2.FIG. 2 is a side view of an exhaust portion of the engine. Hereinafter, the arrangement direction of the cylinders 2 a(cylinder arrangement direction) is set as the front and rear direction of the engine, and unless otherwise specified, the front and rear sides of each part conform to the front and rear sides of the engine. Further, the direction orthogonal to the front and rear direction of the motor is set as a motor width direction.As illustrated in FIG. 2, the collection exhaust port 3 aof the exhaust manifold is formed in an exhaust side surface of the engine main body 1, i.e., in the surface of the cylinder head 3. The turbocharger 60 is provided at a position corresponding to the collection discharge passage 3 a.As shown in FIG. 3, the turbocharger 60 is configured such that the coupling shaft 62 cis located at an upper position of the collection outlet port 3 ato guide an exhaust gas flow discharged substantially horizontally from the collection outlet port 3 aupward in a turbine chamber 63 formed in a turbine housing 61 band to rotate the turbine 62 bduring formation of an upward swirling flow (clockwise swirling flow in FIG. 3 ) of an exhaust gas. As shown in FIG. 3, in the turbocharger 60 thus configured, a main part of the turbocharger 60 is located at an upper position of the collection outlet port 3 a. According to this configuration, the turbocharger 60 is disposed at an upper position as a whole with respect to the engine main body 1 of the engine.As shown in FIG. 3, the turbocharger 60 is a variable geometry turbocharger (VGT turbocharger) provided with a plurality of movable vanes 64. The turbocharger 60 is configured to make turbine efficiency variable by adjusting an exhaust flow to the turbine 62 bby the movable vanes 64. Specifically, as shown in FIG. 3, the plurality of movable blades 64 are disposed in the turbine chamber 63 so as to surround the turbine 62 bdisposed substantially at the center of the turbine chamber 63. Each movable blade 64 is fixed to a support shaft 65 rotatably supported on a side wall of the turbine chamber 63. The movable blades 64 are configured such that when each of the movable blades 64 is pivoted counterclockwise in FIG. 3 about the support shaft 65, the movable blades 64 adjacent to each other come close to each other and the opening degree of a nozzle to be formed between the adjacent movable blades 64 is decreased; and when each of the movable blades 64 is pivoted clockwise in FIG. 3, the opening degree of a nozzle to be formed between the adjacent movable blades 64 is increased. In other words, when the flow rate of exhaust gas is small, it is possible to obtain high charging efficiency by decreasing the opening degree of a nozzle. On the other hand, when the flow rate of exhaust gas is large, it is possible to reduce the ventilation resistance by increasing the opening degree of a nozzle to improve the charging efficiency.Although a detailed description of the drawings is omitted, a driving mechanism of the movable blades 64 includes a ring member 66 rotatably supported on the turbine housing 61 b; a plurality of coupling members 67 coupling the ring member 66 to the respective support shafts 65 to rotate each of the support shafts 65 in forward and rearward directions when the ring member 66 is rotated in forward and rearward directions; a rod 69 supported to be retracted and extended with respect to the turbine housing 61 b; a hinge 68 coupling the rod 69 to the ring member 66 to rotate the ring member 66 in forward and rearward directions when the rod 69 is retracted and extended; and a vacuum actuator, not shown, that retracts and extends the rod 69. In other words, the drive mechanism converts, by way of the joint 68, the ring member 66, and the coupling members 67, linear movement of the rod 69 by the vacuum actuator into rotational movement of each of the support shafts 65 to swing each of the movable blades 64.Referring back to FIG. 2 which is a side view of the outlet portion of the engine main body 1, the DOC 31 is disposed on the engine front side of the turbocharger 60. As described above, the DOC 31 oxidizes CO and HC in the exhaust gas to a harmless component.As shown in FIG. 4, the DOC 31 includes a columnar monolith support 70 on which a catalyst (e.g., platinum or palladium) is supported, and a housing 71 (a container) that accommodates the support 70 in a horizontal position (a position in which the central axis of the support 70 is horizontally oriented). The housing 71 has a tubular shape extending in the front and rear directions. A gas inlet 72 is formed in a rear end (on the turbocharger 60 side) of the housing 71, and a gas outlet 73 is formed in a front end of the housing 71. The gas inlet 72 and the gas outlet 73 face each other in the front and rear direction. The center of the gas inlet 72 and the center of the gas outlet 73 are substantially coaxially aligned with the coupling shaft 62 cof the turbocharger 60.The housing 71 is configured such that exhaust gas introduced from the gas inlet 72 is discharged from the gas outlet 73 in a state that a primary part of the exhaust gas flows through a lower portion 70 a(see FIG. 5 ) of the carrier 70. Specifically, the housing 71 is formed such that a center line C 2 of the carrier 70 is offset upward with respect to a center line C 1 passing through the gas inlet 72 and the gas outlet 73. According to this configuration, the DOC 31 is disposed at an upper position as a whole with respect to the engine main body 1. In this example, the centerline of the gas inlet 72 and the centerline of the gas outlet 73 are aligned with each other. However, if the center line C2 of the carrier 70 is offset upward as a whole with respect to the center line of the gas inlet 72 and the center line of the gas outlet 73, a slight misalignment of the center lines of the gas inlet 72 and the gas outlet 73 is allowed.A rear portion of the housing 71 has a funnel shape with respect to the carrier 70, so that the housing 71 widens from the gas inlet 72 toward the periphery of the carrier 70. A front portion of the housing 71 has a funnel shape with respect to the carrier 70, so that the housing 71 narrows from the periphery of the carrier 70 toward the gas outlet 73.Disposing the turbocharger 60 and the DOC 31 at an upper position with respect to the engine main body 1 as described above makes it possible to dispose the DPF 32 and the EGR valve 56 in a space formed under the turbocharger 60 and the DOC 31.As shown in FIG. 2, the DPF 32 is disposed substantially directly below the DOC 31 near the DOC 31. A front end of the DPF 32 is connected to a front end of the DOC 31 via a U-shaped pipe 30 a(a part of the exhaust passage 30). This configuration makes it possible to guide the exhaust gas discharged from the DOC 31 into the DPF 32 via the gas outlet 73 from a not-shown gas inlet formed in a front end of the DPF 32.Although not shown, the DPF 32 and the DOC 31 are integrally covered from the outside by a metal cover. This prevents release of heat from the DOC 31 and the DPF 32 and, when the engine in the vehicle is subjected to load, protects peripheral devices around the DOC 31 and the DPF 32 from this.A main outlet pipe 30b (a part of the outlet duct 30, corresponding to an outlet pipe of the invention) communicating with the muffler 34 is connected to a rear end of the DPF 32. The main exhaust pipe 30 bextends slightly obliquely downward from the rear end of the DPF 32 toward the outside of the main engine body 1 in the engine width direction.The EGR cooler 57 is fixed to an attachment portion (not shown) formed on a rear surface of the main exhaust pipe 30 b(in other words, a surface of the main exhaust pipe 30 bfacing the DPF 32). The EGR valve 56 is fixed to a rear portion of the EGR cooler 57. According to this configuration, the EGR cooler 57 and the EGR valve 56 are disposed at a rear portion of the DPF 32 at a position substantially directly below the turbocharger 60.An upstream end of an EGR pipe 55 aforming the LP-EGR passage 55 is connected to a rear portion of the EGR valve 56. A downstream end of the EGR pipe 55 ais connected to an upstream intake pipe 20 a(a part of the intake passage 20). The upstream inlet pipe 20 aform the inlet passage 20 between the air cleaner 21 and the compressor 62 aof the turbocharger 60. the upstream inlet pipe 20 ais connected to a rear portion of the compressor housing 61 aof the turbocharger 60. The EGR pipe 55 ais connected to an intermediate portion of the upstream inlet pipe 20 aat a location near the connection portion between the upstream inlet pipe 20 aand the compressor housing 61 a.Reference numeral 20b of FIG. 2 denotes a downstream inlet pipe connected to the compressor housing 61a of the turbocharger 60. The downstream inlet pipe 20 bconstitutes the inlet passage 20 between the intercooler 22 and the compressor 62 aof the turbocharger 60 Further, reference numeral 58 of FIG. 2 denotes a blowby gas pipe (passage) for introducing blowby gas remaining in the engine main body 1 to the inlet passage 20.In the diesel engine thus configured, as shown by the one-dot chain line in FIG. 2, exhaust gas discharged from the collection exhaust port 3 aof the engine main body 1 (cylinder head 3) is guided to the turbocharger 60 to rotate the turbine 62 b. After the exhaust gas passes through the DOC 31 in front and rear directions, the flow direction of the exhaust gas is reversed at the front of the DOC 31, so that the exhaust gas is guided to the DPF 32. After the exhaust gas passes through the DPF 32 in the front and rear directions, the exhaust gas is guided to the muffler 34 through the main exhaust pipe 30 b. Further, as shown by the broken line arrows in FIG. 2, a part of the exhaust gas that has passed through the DPF 32 is guided back to the upstream inlet pipe 20 avia the EGR cooler 57 and the EGR valve 56.According to the engine described above, the turbocharger 60, the DOC 31, the DPF 32, and the EGR device (the EGR valve 56 and the EGR cooler 57) are disposed at a location near a surface of the engine main body 1 in a compact manner. This is advantageous in configuring the engine in a compact manner, namely in downsizing the engine. Further, due to the collection of the turbocharger 60, the DOC 31, the DPF 32, and the EGR device at a position near a surface of the engine main body 1, the ambient temperature around these devices is maintained at a relatively high temperature. This prevents release of heat from the exhaust gas and contributes to promotion of activation of the DOC 31 and promotion of regeneration (oxidation reaction) of the DPF 32. A diesel engine inherently has high combustion efficiency, and the temperature of exhaust gas from the diesel engine tends to be lower compared to a gasoline engine. When performing EGR control, the temperature of exhaust gas is lowered, in particular. This makes it difficult to maintain the activation temperature of the DOC 31 and the regeneration temperature of the DPF 32. However, according to the above configuration, it is easy to maintain the activation temperature of the DOC 31 and the regeneration temperature of the DPF 32. This is advantageous in promoting activation of the DOC 31 and promoting regeneration of the DPF 32 while making the engine compact.In the engine thus configured, the turbocharger 60 is configured such that exhaust gas discharged from the collection exhaust port 3 ais directed upward to rotate the turbine 62 bwhile forming an upward swirl flow of exhaust gas. In view of the above, the turbocharger 60 as a whole is disposed at an upper position with respect to the engine main body 1. Further, the DOC 31 is configured such that the center line C 2 of the carrier 70 is offset upward with respect to the center line C 1 passing through the gas inlet 72 and the gas outlet 73. Thus, the DOC 31 as a whole is disposed at an upper position with respect to the engine main body 1. In other words, the turbocharger 60 and the DOC 31 are arranged at an upper position with respect to the engine main body 1 as a whole, and the DPF 32 and the EGR device are arranged in a space below the turbocharger 60 and the DOC 31. Therefore, when the engine main body 1 has a relatively small size or when the turbocharger 60 and the DOC 31 have a relatively large size, it is possible to arrange the DPF 32 and the EGR device compactly under the turbocharger 60 and the DOC 31. In this example, the turbocharger 60 is a variable geometry turbocharger provided with the movable vanes 64 and the drive mechanism for moving the movable vanes 64 as described above. Therefore, the size of the turbocharger as a whole tends to increase in the radial direction (in the radial direction of the turbine 62 b). However, by utilizing the above-mentioned configuration, in this example, the EGR device is compactly disposed below the turbocharger 60 regardless of the turbocharger 60 being a variable geometry turbocharger.Further, as for promoting activation of the DOC 31, the following advantage is obtained. Specifically, as shown in FIG. 5, in the DOC 31 configured such that the center line C 2 of the carrier 70 is offset upward with respect to the center line C 1 of the gas inlet 72 and the gas outlet 73, a main flow (see the hollow arrows in FIG. 5 ) of exhaust gas flows mainly through the lower region 70 aof the carrier 70 and hardly flows through an upper region 70 bcorresponding to the upper portion of the carrier 70. However, the upper portion 70 bis also heated by hot air (see the broken arrows in FIG. 5 ) of the main exhaust stream and stores the heat of hot air. Therefore, when low-temperature exhaust gas temporarily flows through the lower portion 70 aby a change in the operating state (such as a stopped state of the accelerator pedal) of the engine, even if the temperature of the lower portion 70 ais lowered, the temperature of the upper portion 70 b, through which exhaust gas hardly flows, is maintained at a high temperature to some extent. In other words, applying a heat storage function to the upper portion 70 bof the support 70 makes it possible to suppress a considerable lowering of the temperature of the support 70 as a whole. The subsequent introduction of high-temperature exhaust gas makes it possible to quickly raise the temperature of the DOC 31 (carrier 70) to an activation temperature of the DOC 31. Thus, the above-mentioned configuration of the DOC 31 is advantageous not only in contributing to a size reduction of the engine but also in promoting activation of the DOC 31.Further, in the thus configured engine, the DOC 31 and the DPF 32 are connected to each other via the U-shaped pipe 30 asuch that the flow direction of the exhaust gas that has passed through the DOC 31 is reversed at the front side of the DOC 31, so that the exhaust gas is guided to the DPF 32 and passes through the DPF 32 in the front and rear directions. Thus, the DOC 31 and the DPF 32 are arranged close to each other in the up and down direction. Here, it is particularly advantageous to have the turbocharger 60 and the DOC 31, and the AR device and the DPF 32 close to each other in a compact manner in the up-and-down direction. The DOC 31 and the DPF 32 are covered with a cover from the outside as described above. The cover can be made compact because the DOC 31 and the DPF 32 are arranged close to each other.The diesel engine as described above is a preferred example of an engine to which an exhaust device for an engine of the invention is applied. The configuration of the diesel engine and the configuration of the exhaust device for the diesel engine may be modified as needed unless these modifications depart from the spirit of the invention.In the embodiment, the invention is applied to a diesel engine. However, the invention is applicable to a gasoline engine.Further, in the embodiment, the DPF 32 and the EGR device constitute a treatment device of the invention. Alternatively, a power generator to be driven by the engine main body 1, a compressor for a vehicle air conditioner, or an electric motor drive unit for a hybrid vehicle may be disposed below the DOC 31 (catalyst device) disposed at least at an upper position with respect to the engine main body.The following is a summary of the invention.One aspect of the invention is directed to an exhaust device for a multi-cylinder engine. The exhaust device for an engine is provided with an engine main body including: a cylinder head having a manifold exhaust passage provided therein, the manifold exhaust passage including a manifold exhaust port communicating with each of the cylinders, the manifold exhaust port being formed in a surface of the cylinder head in an engine width direction orthogonal to a cylinder arrangement direction; a turbocharger disposed on the same side as the cylinder head surface and configured to rotate a turbine by exhaust gas discharged from the manifold exhaust port to compress intake air; a catalyst device disposed adjacent to the turbocharger in the cylinder arrangement direction and configured to subject a specific component in the exhaust gas that has passed through the turbocharger to a reaction to a harmless component; and a treatment device disposed on the same side as the cylinder head surface of the engine main body. The turbocharger is configured to direct the exhaust discharged from the collection outlet port upward to rotate the turbine while forming an upward swirling exhaust flow. The catalyst device is provided with a support on which a catalyst is supported, and a container that accommodates the support and has an exhaust gas inlet and an exhaust gas outlet at both ends of a lower portion of the support to let the exhaust gas pass through mainly the lower portion of the support in the cylinder arrangement direction. The treatment device is arranged at least below the catalyst device.With the thus configured exhaust device for an engine, it is possible to arrange the turbocharger, the catalyst device, and the treatment device at a location near a surface of the engine main body in a compact manner. According to the configuration of the turbocharger, in particular, it is possible to arrange the turbocharger as a whole at an upper position with respect to the engine main body. Further, according to the configuration of the catalyst device, it is possible to arrange the catalyst device as a whole at an upper position with respect to the engine main body. Therefore, it is possible to arrange the treatment apparatus under the catalyst apparatus in a compact manner.The treatment device may be an exhaust treatment device disposed below the catalyst device and configured to retain the specific component in the exhaust gas that has passed through the catalyst device.Further, the treatment device may include: an exhaust treatment device disposed below the catalyst device and configured to retain the specific component in the exhaust gas that has passed through the catalyst device, and an EGR device disposed below the turbocharger and configured to recirculate a part of the exhaust gas that has passed through the exhaust treatment device to an intake passage; and the exhaust treatment device and the EGR device may be disposed side by side in the cylinder arrangement direction.According to the thus configured exhaust device for an engine, it is possible to arrange the turbocharger, the catalyst device, the exhaust treatment device, and the EGR device at a location near a surface of the engine main body in a compact manner. According to the configuration of the turbocharger, in particular, it is possible to arrange the turbocharger as a whole at an upper position with respect to the engine main body. Further, according to the configuration of the catalyst device, it is possible to arrange the catalyst device as a whole at an upper position with respect to the engine main body. Therefore, it is possible to arrange the EGR device and the exhaust treatment device under the turbocharger and the catalyst device in a compact manner. Further, according to the thus configured exhaust device for an engine, the compact arrangement of the turbocharger, the catalyst device, the exhaust treatment device, and the EGR device at a location near the surface of the engine main body makes it possible to maintain the ambient temperature around the devices at a relatively high temperature. This is advantageous in preventing the release of heat from the exhaust gas and promoting activation of the catalyst device.In the above configuration, according to the present invention, the catalyst device and the exhaust treatment device may be connected to each other such that, after flowing the exhaust gas that has flowed through the turbocharger through the catalyst device in the cylinder arrangement direction, a flow direction of the exhaust gas is reversed, so that the exhaust gas is introduced to the exhaust treatment device and the exhaust gas flows through the exhaust treatment device in the cylinder arrangement direction.According to the above configuration, it is possible to arrange the turbocharger and the catalyst device, and the exhaust gas treatment device and the EGR device close to each other in the up and down direction in a compact manner.The above configuration is advantageous when the turbocharger is a variable geometry turbocharger provided with movable vanes, and is configured such that a flow rate of exhaust gas flowing into the turbine by the operation of the movable vanes is adjustable.In other words, the overall size of the variable geometry turbocharger tends to increase in a radial direction because the turbocharger includes a mechanism portion for operating the movable vanes. However, according to the configuration of the exhaust device for an engine as described above, it is possible to arrange the turbocharger at an upper position with respect to the engine main body. This makes it possible to arrange the EGR device compactly under the turbocharger even if the turbocharger is a variable geometry turbocharger.As a preferred configuration, the exhaust treatment device may retain fine particles in the exhaust gas, and the EGR device may include an EGR cooler that cools the exhaust gas to be recirculated to the intake passage and an EGR valve that adjusts an amount of the exhaust gas to be recirculated to the intake passage.According to the above configuration, it is possible to arrange the exhaust treatment device that retains fine particles in the exhaust gas, the EGR cooler, and the EGR valve under the turbocharger and the catalyst device in a compact manner.In the above configuration, the exhaust device for an engine may preferably further include an exhaust pipe connected to the exhaust treatment device and configured to guide the exhaust gas that has passed through the exhaust treatment device to the outside in the engine width direction, the EGR device being installed at a location opposite to the exhaust treatment device on a surface of the exhaust pipe.According to the above configuration, it is possible to make the engine compact without superimposing the EGR device and the exhaust pipe in the engine width direction.Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications may occur to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention set forth below, they are to be construed as included therein.

Claims

An exhaust device for an engine provided with a plurality of cylinders (2a), comprising: an engine main body (1) having a cylinder head (3) provided therein with a manifold exhaust passage, the manifold exhaust passage comprising a collection exhaust port (3a) communicating with each of the cylinders (2a), the collection exhaust port (3a) being formed in a surface of the cylinder head (3) in an engine width direction orthogonal to a cylinder arrangement direction; a turbocharger (60) disposed on the same side as the cylinder head surface and configured to rotate a turbine (62b) and a compressor (62a) coupled to said turbine via a coupling shaft (62c) by exhaust gas discharged from the collection exhaust port, thereby compressing intake air; a catalyst device (31) disposed adjacent to the turbocharger (60) in the cylinder arrangement direction and configured to subject a specific component in the exhaust gas that has passed through the turbocharger (60) and flowed in said cylinder arrangement direction to a reaction to a harmless component; and an exhaust treatment device (32) configured to retain the specific component in the exhaust gas that has passed through the catalyst device (31), wherein the turbocharger (60) is disposed with said coupling shaft (62c) at an upper location of the collection outlet port (3a) and configured to direct the exhaust gas discharged from the collection outlet port (3a) upward into a turbine chamber (63) formed inside a turbine housing (61b), thereby rotating the turbine (62b), while forming an upward swirling flow of exhaust gas, the catalyst device (31) is provided with a monolith carrier (70) and a container (71) accommodating the carrier, the container (71) being formed with an exhaust gas inlet (72) and an exhaust gas outlet (73) at opposite ends in said cylinder arrangement direction such that the monolith carrier (70) is accommodated between the exhaust gas inlet (72) and the exhaust gas outlet (73), said exhaust gas inlet (72) and said exhaust gas outlet (73) each facing a lower portion of the monolith carrier (70), and the exhaust gas treatment device (32) is arranged on a side of the engine main body (1) on which the catalyst device (31) is arranged below the catalyst device in the up and down direction of the engine main body (1).The exhaust device for an engine according to claim 1, further comprising: an EGR device (56, 57) configured to recirculate a part of the exhaust gas that has passed through the exhaust treatment device (32) to an intake passage, wherein the EGR device (56, 57) is disposed side by side with the exhaust treatment device (32) under the turbocharger (60) in the cylinder arrangement direction.The exhaust device for an engine according to claim 1 or 2, wherein an end of the catalyst device (31) and an end of the exhaust treatment device (32) are connected to each other through a U-shaped pipe (30a), and said ends are positioned on a side of the catalyst device (31) in the cylinder arrangement direction such that after passing the exhaust gas that has passed through the turbocharger (60) through the catalyst device (31) in the cylinder arrangement direction, a flow direction of the exhaust gas is reversed, such that the exhaust gas is introduced to the exhaust treatment device (32) and the exhaust gas passes through the exhaust treatment device (32) in the reversed cylinder arrangement direction.The exhaust device for an engine according to any one of claims 1 to 3, wherein the turbocharger (60) is a variable geometry turbocharger having a plurality of movable blades (64) surrounding the turbine (62b), and is configured to adjust a flow rate of the exhaust gas flowing to the turbine (62b) by changing an opening degree of a nozzle disposed between each adjacent movable blades (64) by operating the movable blades (64).The exhaust device for an engine according to any one of claims 2 to 4, wherein the exhaust treatment device (32) retains fine particles in the exhaust gas, and the EGR device (56, 57) comprises an EGR cooler (57) that cools the exhaust gas to be recirculated to the intake passage, and an EGR valve (56) that adjusts an amount of the exhaust gas to be recirculated to the intake passage.The exhaust device for an engine according to claim 5, further comprising: an exhaust pipe (30b) connected to the exhaust treatment device (32) and configured to guide the exhaust gas that has passed through the exhaust treatment device (32) to the outside in the engine width direction, wherein the EGR device (56, 57) is installed on a surface of the exhaust pipe (30b) at a position opposite to the exhaust treatment device (32).The exhaust device for an engine according to any one of claims 1 to 6, wherein the canister (71) is formed such that a center line (C2) of the monolith carrier (70) accommodated in the canister (71) is offset upward with respect to a center line (C1) passing through the exhaust gas inlet (72) and the exhaust gas outlet (73).

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