Outboard motor

Abstract

To solve a problem that there is conventionally required an outboard motor equipped with a supercharger which can be suppressed in an increase in size and an increase in manufacturing cost.SOLUTION: An outboard motor 2 has an internal combustion engine 10, a propeller 24 which is rotated by driving of the internal combustion engine 10, a lower unit 20 which rotatably supports the propeller 24, a lower exhaust passage 21 provided in the lower unit 20, and a supercharger unit 30 provided between the internal combustion engine 10 and the lower exhaust passage 21. The turbocharger unit 30 has a first communication passage 34 with an inlet 34a connected to an exhaust pipe 16 extending from the internal combustion engine 10, a turbine of a supercharger 31 rotated by exhaust gas from the first communication passage 34, a second communication passage 35 with an outlet 35a into which exhaust gas from the supercharger 31 is introduced and which is connected to the lower exhaust passage 21, and a compressor of the supercharger 31, which rotates in conjunction with the turbine to supercharge air to the internal combustion engine 10. The supercharger unit 30 integrally includes the first communication passage 34, the turbine, the second communication passage 35, and the compressor.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an outboard motor that is mounted on the exterior of a watercraft. [Background technology]

[0002] Conventionally, outboard motors are provided that are mounted on the exterior of watercraft such as boats used for fishing, cruising, etc., for example, on the exterior of the rear end of the watercraft. In recent years, the demand for large boats has increased, and so has the demand for outboard motors with higher power. For example, higher power can be achieved by mounting multiple outboard motors.

[0003] Patent Document 1 describes a so-called multi-cylinder V-type internal combustion engine in which two banks, each formed with a plurality of cylinders, are arranged in a V shape. Aiming to further increase the output of outboard motors, there is a conventionally known technology of providing an outboard motor with a multi-cylinder V-type internal combustion engine equipped with a turbocharger instead of a naturally aspirated multi-cylinder V-type internal combustion engine.

[0004] However, in order to equip a turbocharger, it is necessary to specialize the exhaust system structure of the internal combustion engine. For example, the turbocharger is connected to an exhaust manifold through which exhaust gas from multiple cylinders in a bank passes. The turbocharger is connected to an exhaust passage of the lower unit that exhausts into the water. Therefore, it is necessary to newly design peripheral parts of the internal combustion engine, especially the exhaust system structure. This increases the manufacturing cost of the outboard motor. In addition, an internal combustion engine equipped with a turbocharger becomes larger, especially in the left-right direction where two banks are lined up. Therefore, when multiple outboard motors are installed side-by-side on a boat, the number of outboard motors that can be installed may be reduced. If the number of outboard motors is small, the output will be less than the desired high output. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 61-279733 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there has been a demand for an outboard motor equipped with a supercharger that can suppress an increase in size and an increase in manufacturing costs. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, an outboard motor has an internal combustion engine. The outboard motor has a propeller that rotates when driven by the internal combustion engine. The outboard motor has a lower unit that rotatably supports the propeller. The outboard motor has a lower exhaust passage that is provided in the lower unit to enable exhaust from the internal combustion engine to be discharged. The outboard motor has a supercharger unit that is provided between the internal combustion engine and the lower exhaust passage. The supercharger unit has a first communication passage with an inlet that is connected to an exhaust pipe extending from the internal combustion engine. The supercharger unit has a supercharger turbine that rotates by exhaust from the first communication passage. The supercharger unit has a second communication passage with an outlet into which exhaust from the supercharger is introduced and which is connected to the lower exhaust passage. The supercharger unit has a supercharger compressor that rotates in conjunction with the turbine to supercharge air to the internal combustion engine. The supercharger unit integrally has the first communication passage, the turbine, the second communication passage, and the compressor.

[0008] Therefore, exhaust gas from the internal combustion engine is discharged from the lower exhaust passage of the lower unit via the turbocharger of the turbocharger unit. This allows an outboard motor equipped with a turbocharger to be installed by interposing the turbocharger unit between the naturally aspirated internal combustion engine and the lower exhaust passage. This allows the use of a conventional naturally aspirated internal combustion engine and a conventional lower exhaust passage. This reduces the number of newly designed parts, thereby reducing the manufacturing costs of the outboard motor. Moreover, the turbocharger unit can be replaced separately from the internal combustion engine and the lower unit. This makes it easy to replace and maintain the turbocharger.

[0009] Moreover, the internal combustion engine, the turbocharger unit, and the lower unit can be arranged in series. A conventional internal combustion engine equipped with a turbocharger is larger in the width direction than a conventional naturally aspirated internal combustion engine. By using a conventional naturally aspirated internal combustion engine, it is possible to prevent an outboard motor having an internal combustion engine, the turbocharger unit, and the lower unit arranged in series, from becoming larger in the width direction that intersects with the in-line direction.

[0010] According to another feature of the present disclosure, the supercharger unit is disposed above the lower unit. The internal combustion engine is disposed above the supercharger unit. Therefore, by arranging the internal combustion engine, the supercharger unit, and the lower unit side by side in the vertical direction, it is possible to suppress an increase in size of the outboard motor in the width direction intersecting with the vertical direction. In addition, the supercharger unit is unitized and assembled to the lower unit at the bottom and to the internal combustion engine at the top. This improves the ease of assembly of the outboard motor.

[0011] According to another feature of the present disclosure, the internal combustion engine is a V-type internal combustion engine having a first bank and a second bank, each of which has cylinders formed therein and which are arranged in a V shape. The first bank and the second bank are arranged side by side in a direction intersecting a direction in which the internal combustion engine and the turbocharger unit are arranged. The turbocharger includes a first turbocharger connected to the cylinders of the first bank and a second turbocharger connected to the cylinders of the second bank. The first turbocharger and the second turbocharger are provided at positions that protrude from the turbocharger unit toward the internal combustion engine and avoid the first bank and the second bank.

[0012] Therefore, the first and second turbochargers can be provided so as to protrude from the turbocharger unit toward the internal combustion engine. This allows the turbocharger unit, excluding the first and second turbochargers, to be provided compactly in the direction in which the internal combustion engine and the turbocharger unit are aligned. Moreover, the first and second turbochargers are arranged side-by-side with respect to the first or second bank at a position that avoids the first and second banks. This allows the first and second turbochargers to be arranged by utilizing the dead space of the V-type internal combustion engine. This makes it possible to prevent the outboard motor from becoming larger in size in the width direction that intersects with the direction in which the internal combustion engine and the turbocharger unit are aligned.

[0013] According to another feature of the present disclosure, the exhaust pipe is disposed between the first bank and the second bank. The first communication passage branches toward the first supercharger and the second supercharger downstream of the inlet. The second communication passage branches toward the first supercharger and the second supercharger upstream of the outlet. Therefore, the first communication passage can be provided to communicate with the exhaust pipe of the naturally aspirated V-type internal combustion engine and to send exhaust toward the first supercharger and the second supercharger. The second communication passage can be provided to send exhaust from the first supercharger and the second supercharger to the lower exhaust passage of the lower unit. This makes it possible to provide an outboard motor equipped with two superchargers by utilizing a conventional naturally aspirated V-type internal combustion engine and a conventional lower unit, while suppressing manufacturing costs. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic side view of a boat having an outboard motor according to an embodiment of the present invention attached to the exterior of its rear end. [Diagram 2] FIG. 2 is a perspective view of the outboard motor with the cowl removed. [Diagram 3] FIG. [Figure 4] FIG. 2 is a top view of the outboard motor with the cowl removed. [Diagram 5] FIG. 2 is a diagram illustrating an intake and exhaust structure of an outboard motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of the present disclosure will be described in detail below with reference to Figs. 1 to 5. The same reference numbers in the description refer to the same elements having the same functions, although duplicated descriptions will not be given. Fig. 1 is a schematic side view of a boat 1 having an outboard motor 2 according to this embodiment attached to the outside of the rear end. In the drawings and the following description, the fore-and-aft direction indicates the propulsion direction of the outboard motor 2 as the forward direction, and the opposite direction to the forward direction as the rearward direction. The up-and-down direction indicates the direction vertically upward and downward. The left-right direction indicates the left-right direction defined based on the fore-and-aft direction and the up-and-down direction.

[0016] As shown in Figs. 1 to 3, the outboard motor 2 has an internal combustion engine 10 as a power source, a propeller shaft 24a that rotates around its axis by being driven by the internal combustion engine 10, and a propeller 24 that rotates integrally with the propeller shaft 24a. The internal combustion engine 10 is covered from above, on the front, rear, left and right sides, by a cowl 3. A box-shaped lower unit 20 extending downward is provided below the cowl 3. The propeller shaft 24a extends approximately horizontally in the front-rear direction and is rotatably supported by the lower unit 20. The propeller 24 is provided at the rear of the propeller shaft 24a. The lower part of the lower unit 20 extends below the water surface so that the propeller 24 can rotate in the water. The propeller 24 generates forward thrust by rotating around the axis of the propeller shaft 24a. A connecting member 4 for attaching the outboard motor 2 to the rear end of the boat 1 is provided at the front of the lower unit 20.

[0017] As shown in Figs. 2 and 4, the internal combustion engine 10 has a crankcase 18 that houses a crankshaft, and two banks, a first bank 11 and a second bank 12, that are connected to the crankcase 18. The internal combustion engine 10 is a so-called V-type internal combustion engine in which the first bank 11 and the second bank 12 are arranged side-by-side on the left and right. The internal combustion engine 10 is, for example, a six-cylinder diesel engine that is an improved version of a land diesel engine for use in marine applications (see Fig. 5). A gasoline engine may be used as the internal combustion engine 10. By using a diesel engine as the internal combustion engine 10, it is possible to improve fuel efficiency and ease of handling at low revolutions (large torque even at low revolutions) compared to a gasoline engine.

[0018] 2 and 4, the first bank 11 and the second bank 12 are arranged branching out in a Y shape from the crankcase 18 toward the front. The left bank is the first bank 11, and the right bank is the second bank 12. Three cylinders 13 are formed in each of the first bank 11 and the second bank 12. The outboard motor 2 is equipped with an ECU, which is a control device that controls the entire outboard motor 2. The ECU 41 has a CPU, ROM, RAM, a timer, an input / output interface, etc. Each cylinder 13 is provided with an injector that injects fuel into a combustion chamber in each cylinder 13 in accordance with an injection control signal input from the ECU.

[0019] As shown in Figs. 2 and 5, the internal combustion engine 10 has an intake pipe 14 that takes in intake air. The intake pipe 14 is a pipe that is conventionally provided in a naturally aspirated internal combustion engine 10. The intake pipe 14 branches into a first intake passage 14a that is connected to the cylinders 13 of the first bank 11 and a second intake passage 14b that is connected to the cylinders 13 of the second bank 12. The first intake passage 14a and the second intake passage 14b each have an air filter 15 midway along their respective paths. The first intake passage 14a branches into multiple branch pipes at the intake manifold 14c via a compressor 31b of a first supercharger 32, which will be described later. The second intake passage 14b branches into multiple branch pipes at the intake manifold 14c via a compressor 31b of a second supercharger 33, which will be described later. Each branch pipe of the intake manifold 14c is connected to a combustion chamber provided in each cylinder 13 via an intake port.

[0020] As shown in FIGS. 2 to 5, the internal combustion engine 10 has an exhaust pipe 16 that discharges exhaust gas. The exhaust pipe 16 is a pipe that is conventionally provided in a naturally aspirated internal combustion engine 10. The exhaust pipe 16 has an exhaust manifold 16a that branches into a plurality of branch pipes. Each branch pipe of the exhaust manifold 16a is connected to a combustion chamber provided in each cylinder 13 of the first bank 11 or the second bank 12. The exhaust manifold 16a and one exhaust pipe 16 formed by joining the exhaust manifold 16a are provided between the first bank 11 and the second bank in the left-right direction. The exhaust pipe 16 extends downward. The lower end of the exhaust pipe 16 is structured to be capable of communicating with the upper end of a lower exhaust passage 21 of a lower unit 20, which is a conventional structure. A circular pipe-shaped cooling water passage 17 that is substantially coaxial with the exhaust pipe 16 is provided so as to cover the radial outer periphery of the exhaust pipe 16.

[0021] As shown in Fig. 3, a lower exhaust passage 21 extending downward from an upper end is provided inside the lower unit 20. An exhaust port 21a of the lower exhaust passage 21 opens toward the water in front of the propeller 24. A cylindrical cooling water passage 22 that is approximately coaxial with the lower exhaust passage 21 is provided so as to cover the radial outer periphery of the lower exhaust passage 21. A drain port 22a of the cooling water passage 22 is connected to the lower exhaust passage 21 upstream of the exhaust port 21a. The upper end of the lower exhaust passage 21 and the upper end of the cooling water passage 22 are provided with a diameter that allows them to communicate with the lower end of the exhaust pipe 16 and the lower end of the cooling water passage 17, respectively.

[0022] As shown in FIG. 3, the outboard motor 2 has a power transmission unit 23 that transmits the rotational power of a crankshaft (not shown) in the crankcase 18 to a propeller shaft 24a. The power transmission unit 23 has a rotating shaft that extends vertically from the upper crankcase 18 toward the lower unit 20. In the lower unit 20, the power transmission unit 23 is provided with a speed change mechanism 19 that changes the speed of the rotational power and transmits it. The speed change mechanism 19 can switch between forward and reverse rotational directions of the rotational power, cut off transmission of the rotational power, and the like. A power direction change unit 23a that changes the direction of the rotational power to rotation around the axis of the propeller shaft 24a that extends in the front-rear direction is provided at the lower end of the power transmission unit 23. A pump 25 that is driven by the rotation of the propeller shaft 24a is provided at the front of the propeller shaft 24a. The pump 25 pumps cooling water to the internal combustion engine 10 via a cooling water supply passage 26.

[0023] As shown in Figs. 2 to 5, a turbocharger unit 30 including a turbocharger 31 is provided between the internal combustion engine 10 and the lower unit 20 in the vertical direction. The turbocharger unit 30 is also called an engine bed that supports the internal combustion engine 10 with respect to the lower unit 20. The turbocharger unit 30 is provided as a rectangular box-shaped block or a rectangular box-shaped frame. The block or frame that constitutes the turbocharger unit 30 is made of aluminum, for example. The turbocharger 31 has a turbine 31a and a compressor 31b that are connected to each other. The turbine 31a is rotated by exhaust air from the internal combustion engine 10. The compressor 31b compresses air by the rotation of the turbine 31a and supercharges it to the internal combustion engine 10.

[0024] As shown in FIGS. 4 and 5 , the turbocharger unit 30 has a first turbocharger 32 connected to each cylinder 13 in the first bank 11 as the turbocharger 31, and a second turbocharger 33 connected to each cylinder 13 in the second bank 12 as the turbocharger 31. The first turbocharger 32 and the second turbocharger 33 are connected to the box-shaped shape of the turbocharger unit 30 and protrude upward from the box-shaped shape. Therefore, the first turbocharger 32 and the second turbocharger 33 overlap with the internal combustion engine 10 in the vertical direction. The first turbocharger 32 is provided at a position rearward of the first bank 11 and rearward of the crankcase 18 so as to avoid the first bank 11 and the crankcase 18. The second turbocharger 33 is provided at a position rearward of the second bank 12 and rearward of the crankcase 18 so as to avoid the second bank 12 and the crankcase 18.

[0025] 5, the compressor 31b of the first supercharger 32 is provided in the first intake passage 14a downstream of the air filter 15 and upstream of the intake manifold 14c. The compressor 31b of the second supercharger 33 is provided in the second intake passage 14b downstream of the air filter 15 and upstream of the intake manifold 14c.

[0026] As shown in FIGS. 3 to 5, the turbocharger unit 30 has a first communication passage 34 and a second communication passage 35 that communicate the exhaust pipe 16 of the internal combustion engine 10 and the lower exhaust passage 21 of the lower unit 20. The first communication passage 34 communicates the exhaust pipe 16 of the internal combustion engine 10 and the turbine 31a of the turbocharger 31. An inlet 34a of the first communication passage 34 is connected to the lower end of the exhaust pipe 16. The first communication passage 34 branches into a first branch passage 34b extending toward the first turbocharger 32 and a second branch passage 34c extending toward the second turbocharger 33 on the downstream side of the inlet 34a. The first branch passage 34b and the second branch passage 34c are disposed below the internal combustion engine 10 and extend rearward substantially horizontally. A rear end of the first branch passage 34b extends upward and is connected to the turbine 31a of the first turbocharger 32. The exhaust gas from the internal combustion engine 10 sent through the first branch passage 34b is connected to the turbine 31a of the first supercharger 32, and the rear end of the second branch passage 34c extends upward and is connected to the turbine 31a of the second supercharger 33.

[0027] As shown in Figures 4 and 5, the exhaust gas sent from the exhaust pipe 16 of the internal combustion engine 10 to the first communication passage 34 of the turbocharger unit 30 is sent toward the first turbocharger 32 and the second turbocharger 33. The exhaust gas passing through the first branch passage 34b of the first communication passage 34 is sent to the turbine 31a of the first turbocharger 32 to rotate the turbine 31a. As a result, the intake air compressed by the compressor 31b of the first turbocharger 32 is sent to each cylinder 13 of the first bank 11. The exhaust gas passing through the second branch passage 34c of the first communication passage 34 is sent to the turbine 31a of the second turbocharger 33 to rotate the turbine 31a. As a result, the intake air compressed by the compressor 31b of the second turbocharger 33 is sent to each cylinder 13 of the second bank 12.

[0028] As shown in Figs. 3 to 5, the second communication passage 35 communicates the turbine 31a of the turbocharger 31 with the lower exhaust passage 21 of the lower unit 20. The outlet 35a of the second communication passage 35 is connected to the upper end of the lower exhaust passage 21. The second communication passage 35 branches into a first branch passage 35b extending toward the first turbocharger 32 and a second branch passage 35c extending toward the second turbocharger 33 on the upstream side of the outlet 35a. The first branch passage 35b and the second branch passage 35c extend substantially horizontally in the left-right direction behind the crankcase 18. The exhaust gas introduced from the turbine 31a of the first turbocharger 32 to the first branch passage 35b and the exhaust gas introduced from the turbine 31a of the second turbocharger 33 to the second branch passage 35c join together midway through the second communication passage 35 and are sent to the lower exhaust passage 21 from the outlet 35a.

[0029] As shown in Figs. 3 to 5, a cylindrical cooling water passage 36 is provided so as to cover the radial outer periphery of the first communication passage 34 and is substantially coaxial with the first communication passage 34. A cylindrical cooling water passage 36 is provided so as to cover the radial outer periphery of the second communication passage 35 and is substantially coaxial with the second communication passage 35. An upstream end of the cooling water passage 36 on the first communication passage 34 side is connected to a lower end of the cooling water passage 17 of the internal combustion engine 10. A downstream end of the cooling water passage 36 on the second communication passage 35 side is connected to an upper end of the cooling water passage 22 of the lower unit 20. As a result, the cooling water sent from the pump 25 to the internal combustion engine 10 via the cooling water supply passage 26 passes through the cooling water passage 17 of the internal combustion engine 10, the cooling water passage 36 of the turbocharger unit 30, and the cooling water passage 22 of the lower unit 20. At this time, the exhaust gas passing through the exhaust pipe 16, the first communication passage 34, the second communication passage 35, and the lower exhaust passage 21 is sent toward the exhaust port 21a while being cooled by the cooling water radially outward. The cooling water that reaches the drain port 22a is discharged into the lower exhaust passage 21 and mixed with the exhaust gas. The mixed cooling water and exhaust gas are discharged together from the exhaust port 21a.

[0030] As shown in FIGS. 3 and 4, the turbocharger unit 30 is interposed between the internal combustion engine 10 and the lower unit 20. As a result, the lower exhaust passage 21 is located rearward of the exhaust pipe 16. Therefore, the position of the lower exhaust passage 21 relative to the internal combustion engine 10 is further rearward than in a conventional structure in which the exhaust pipe 16 of the internal combustion engine 10 and the lower exhaust passage 21 of the conventional lower unit 20 are directly connected to each other in the vertical direction. Alternatively, in the conventional internal combustion engine 10, the first bank 11, the second bank 12, the exhaust pipe 16, etc. may be disposed rearward of the crankcase 18. In other words, they may be disposed in a position reversed from that of the internal combustion engine 10 of this embodiment. In this case, compared to the conventional structure, in the outboard motor 2 having the turbocharger unit 30 of this embodiment, the positions of the first bank 11, the second bank 12, and the exhaust pipe 16 relative to the lower exhaust passage 21 are further forward.

[0031] As described above, the outboard motor 2 has the internal combustion engine 10 as shown in Figs. 2, 3 and 5. The outboard motor 2 has a propeller 24 that is rotated by the drive of the internal combustion engine 10. The outboard motor 2 has a lower unit 20 that rotatably supports the propeller 24. The outboard motor 2 has a lower exhaust passage 21 that is provided in the lower unit 20 so that exhaust gas from the internal combustion engine 10 can be discharged. The outboard motor 2 has a supercharger unit 30 that is provided between the internal combustion engine 10 and the lower exhaust passage 21. The supercharger unit 30 has a first communication passage 34 that has an inlet 34a that is connected to the exhaust pipe 16 extending from the internal combustion engine 10. The supercharger unit 30 has a turbine 31a of a supercharger 31 that is rotated by exhaust gas from the first communication passage 34. The supercharger unit 30 has a second communication passage 35 that has an outlet 35a into which exhaust gas from the supercharger 31 is introduced and that is connected to the lower exhaust passage 21. The supercharger unit 30 has a compressor 31b of a supercharger 31 that rotates in conjunction with the turbine 31a to supercharge air to the internal combustion engine 10. The supercharger unit 30 integrally has a first communication passage 34, the turbine 31a, a second communication passage 35, and the compressor 31b.

[0032] Therefore, exhaust gas from the internal combustion engine 10 is discharged from the lower exhaust passage 21 of the lower unit 20 via the turbocharger 31 of the turbocharger unit 30. Therefore, the outboard motor 2 equipped with the turbocharger 31 can be provided with the turbocharger unit 30 interposed between the naturally aspirated internal combustion engine 10 and the lower exhaust passage 21. Therefore, the conventional naturally aspirated internal combustion engine 10 and the conventional lower exhaust passage 21 can be utilized. This reduces the number of newly designed parts, thereby suppressing the manufacturing costs of the outboard motor 2. Moreover, the turbocharger unit 30 can be replaced separately from the internal combustion engine 10 and the lower unit 20. Therefore, replacement and maintenance of the turbocharger 31 can be facilitated.

[0033] Moreover, the internal combustion engine 10, the turbocharger unit 30, and the lower unit 20 can be arranged in series. A conventional internal combustion engine equipped with a turbocharger is larger in the width direction than a conventional naturally aspirated internal combustion engine. By using a naturally aspirated internal combustion engine 10 of a conventional structure, it is possible to prevent the outboard motor 2, in which the inner engine 10, the turbocharger unit 30, and the lower unit 20 are arranged in series, from becoming larger in the width direction intersecting with the series direction.

[0034] 2 and 3, the supercharger unit 30 is disposed above the lower unit 20. The internal combustion engine 10 is disposed above the supercharger unit 30. Therefore, by arranging the internal combustion engine 10, the supercharger unit 30, and the lower unit 20 side by side in the vertical direction, it is possible to prevent the outboard motor 2 from becoming large in size in the width direction intersecting with the vertical direction. In addition, the supercharger unit 30 is made into a unit, and is assembled to the lower unit 20 at the bottom and to the internal combustion engine 10 at the top. This improves the ease of assembly of the outboard motor 2.

[0035] 2 and 4, the internal combustion engine 10 is a V-type internal combustion engine having a first bank 11 and a second bank 12, each of which has cylinders 13 formed therein and arranged in a V shape. The first bank 11 and the second bank 12 are arranged side by side in a direction intersecting the direction in which the internal combustion engine 10 and the turbocharger unit 30 are arranged. The turbocharger 31 includes a first turbocharger 32 connected to the cylinders 13 of the first bank 11 and a second turbocharger 33 connected to the cylinders 13 of the second bank 12. The first turbocharger 32 and the second turbocharger 33 are provided at positions that protrude from the turbocharger unit 30 toward the internal combustion engine 10 and avoid the first bank 11 and the second bank 12.

[0036] Therefore, the first supercharger 32 and the second supercharger 33 can be provided so as to protrude from the supercharger unit 30 toward the internal combustion engine 10. As a result, the supercharger unit 30 excluding the first supercharger 32 and the second supercharger 33 can be provided compactly in the direction in which the internal combustion engine 10 and the supercharger unit 30 are arranged. Moreover, the first supercharger 32 and the second supercharger 33 are arranged side by side with respect to the first bank 11 or the second bank 12 at a position that avoids the first bank 11 and the second bank 12. Therefore, the first supercharger 32 and the second supercharger 33 can be arranged by utilizing the dead space of the V-type internal combustion engine 10. This makes it possible to suppress an increase in size of the outboard motor 2 in the width direction that intersects with the direction in which the internal combustion engine 10 and the supercharger unit 30 are arranged.

[0037] As shown in Figs. 4 and 5, the exhaust pipe 16 is disposed between the first bank 11 and the second bank 12. The first communication passage 34 branches toward the first supercharger 32 and the second supercharger 33 downstream of the inlet 34a. The second communication passage 35 branches toward the first supercharger 32 and the second supercharger 33 upstream of the outlet 35a. Therefore, the first communication passage 34 can be provided so as to communicate with the exhaust pipe 16 of the naturally aspirated V-type internal combustion engine 10 and to send exhaust toward the first supercharger 32 and the second supercharger 33. The second communication passage 35 can be provided so as to send exhaust from the first supercharger 32 and the second supercharger 33 to the lower exhaust passage 21 of the lower unit 20. This makes it possible to provide an outboard motor 2 equipped with two superchargers 31 by utilizing a conventional naturally aspirated V-type internal combustion engine 10 and a conventional lower unit 20 while suppressing manufacturing costs.

[0038] Various modifications can be made to the outboard motor 2 of the present embodiment described above. The outboard motor 2 is attached to the outside of the rear end of the boat 1. The attachment position of the outboard motor 2 is not limited to this, and may be, for example, on the outside of the left or right side end of the boat. For example, a part of the outboard motor 2 may be disposed inside the boat 1.

[0039] In the illustrated embodiment, the internal combustion engine 10, the turbocharger unit 30, and the lower unit 20 are arranged vertically. Alternatively, for example, the internal combustion engine 10, the turbocharger unit 30, and the lower unit 20 may be arranged in the front-rear direction. In this case, the exhaust pipe 16 and the lower exhaust passage 21 extend in the front-rear direction. The internal combustion engine 10 and the turbocharger 31 are arranged so as to overlap in the front-rear direction. Even in this case, it is possible to prevent the outboard motor 2 from becoming large in the left-right direction.

[0040] The V-type internal combustion engine 10 is a 6-cylinder diesel engine. Alternatively, for example, it may be 4 cylinders, 8 cylinders, etc. For example, it may be an internal combustion engine in which the cylinders are arranged in a line. For example, the internal combustion engine 10 may be a gasoline engine. A configuration in which the air filter 15 is provided in both the first intake passage 14a and the second intake passage 14b has been exemplified. Alternatively, one air filter 15 may be provided in the intake pipe 14 upstream of the branching into the first intake passage 14a and the second intake passage 14b. For example, it may be a configuration in which two intake pipes are provided, one as the first intake passage 14a and the other as the second intake passage 14b. The power transmission unit 23 that transmits power by a rotating shaft has been exemplified. Alternatively, for example, power may be transmitted from the crankshaft to the propeller shaft 24a by a belt and a pulley.

[0041] A block-shaped supercharger unit 30 has been exemplified. Instead of this, for example, the supercharger unit 30 may be frame-shaped, and the first communication passage 34, the second communication passage 35, etc. may be arranged inside the frame. The connection structure between the supercharger unit 30 and the internal combustion engine 10 and the connection structure between the supercharger unit 30 and the lower unit 20 may be appropriately selected, for example, a connection structure using screws. [Explanation of symbols]

[0042] 1...Ship 2. Outboard motor 3. Cowl 4...Connecting member 10...Internal combustion engine (V-type internal combustion engine) 11…1st Bank 12…2nd Bank 13…Cylinder 14...intake pipe, 14a...first intake passage, 14b...second intake passage, 14c...intake manifold 15…Air filter 16...Exhaust pipe, 16a...Exhaust manifold 17…Cooling water passage 18…Crankcase 19...Gear shift mechanism 20…Lower unit 21...lower exhaust passage, 21a...exhaust port 22...Cooling water passage, 22a...Drain port 23... power transmission section, 23a... power direction conversion section 24…propeller, 24a…propeller shaft 25…Pump 26…Cooling water supply path 30…Turbocharger unit (engine bed) 31... turbocharger, 31a... turbine, 31b... compressor 32…First turbocharger 33…Second turbocharger 34...first communication passage, 34a...entrance, 34b...first branch passage, 34c...second branch passage 35...second communication passage, 35a...exit, 35b...first branch passage, 35c...second branch passage 36…Cooling water passage

Claims

1. An outboard motor, An internal combustion engine; A propeller that is rotated by the drive of the internal combustion engine; a lower unit that rotatably supports the propeller; a lower exhaust passage provided in the lower unit to enable exhaust gas from the internal combustion engine to be discharged; A turbocharger unit is provided between the internal combustion engine and the lower exhaust passage, and the turbocharger unit is a first communication passage having an inlet connected to an exhaust pipe extending from the internal combustion engine; a turbine of a turbocharger that is rotated by exhaust gas from the first communication passage; a second communication passage having an outlet into which exhaust gas from the turbocharger is introduced and which is connected to the lower exhaust passage; an outboard motor having, integrally therewith, a compressor of the supercharger which rotates in conjunction with the turbine to supercharge air to the internal combustion engine;

2. 2. An outboard motor according to claim 1, The turbocharger unit is disposed above the lower unit, an outboard motor, the internal combustion engine being disposed above the supercharger unit;

3. 3. An outboard motor according to claim 1 or 2, the internal combustion engine is a V-type internal combustion engine having a first bank and a second bank, each of which has cylinders formed therein and arranged in a V shape; the first bank and the second bank are arranged side by side in a direction intersecting a direction in which the internal combustion engine and the turbocharger unit are arranged, the supercharger includes a first supercharger connected to the cylinders of the first bank and a second supercharger connected to the cylinders of the second bank, the first supercharger and the second supercharger are provided in a position that protrudes from the supercharger unit toward the internal combustion engine and avoids the first bank and the second bank.

4. 4. An outboard motor according to claim 3, the exhaust pipe is disposed between the first bank and the second bank, the first communication passage branches toward the first turbocharger and the second turbocharger downstream of the inlet, The second communication passage branches off toward the first turbocharger and the second turbocharger upstream of the outlet.

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