JP2008157217A - Exhaust gas cooling structure for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas cooling structure for an engine capable of effectively preventing reverse flow of cooling water to an engine side even if length of an exhaust pipe connecting the engine and a water lock is shortened. <P>SOLUTION: The exhaust gas cooling structure 20 for the engine 15 includes an exhaust gas conduit 21 having an inner tube 28 defining an exhaust gas passage 28b and an exhaust hose 29 formed on an outer circumference of the inner tube 28 and defining a cooling water passage 29a together with the inner tube 28 therebetween, and a water-lock 22 coupled with a downstream end of the exhaust gas conduit 21 through an exhaust gas conduit coupling section 22a formed in an upstream end. The exhaust gas conduit coupling section 22a and the exhaust hose 29 are coupled with each other and the inner tube 28 extends into the interior of the water-lock 2. A downstream end part of the inner tube 28 can be formed to be a wide portion 28a having a bellmouth configuration. A diameter of the downstream end part becomes larger as a portion thereof exists closer to the end of the downstream end part. The exhaust gas cooling structure 20 for the engine 15 can be provided for a water vehicle 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine exhaust cooling structure including an exhaust pipe that joins an exhaust gas passage and a cooling water passage in a water lock, mixes the exhaust gas and the cooling water, and discharges them to the outside.

  Conventionally, an exhaust gas passage for passing exhaust gas discharged from an engine and a cooling water passage for passing cooling water that has cooled the engine are joined together at a predetermined portion, and the exhaust gas and cooling water are mixed to the outside. An exhaust cooling structure having an exhaust pipe for discharging is used for vehicles. Among vehicles having such an exhaust cooling structure, there is a water vehicle (small planing boat) that travels on the water by generating propulsion by injecting water sucked from the bottom of the ship to the rear of the stern (for example, Patent Document 1).

In the exhaust cooling structure of this water vehicle, the exhaust pipe (exhaust manifold) extending from the engine to the water lock (muffler) is composed of a double pipe, and the inside of the inner pipe forms an exhaust gas passage through which the exhaust gas passes. And the part between the outer tube | pipe and the inner tube | pipe of the outer side comprises the cooling water channel | path which allows cooling water to pass through. The outer tube extends to the vicinity of the water lock and is connected to the water lock via a rubber tube. Further, the inner tube extends to the inside of the water lock. For this reason, the exhaust gas is discharged into the water lock through the inner tube, and the cooling water is discharged into the water lock between the outer tube and the inner tube and between the rubber tube and the inner tube. The exhaust gas and the cooling water are mixed in the water lock.
JP-A-8-53098

  However, in the above-described conventional exhaust cooling structure, since the exhaust gas and the cooling water are mixed in the water lock, the cooling water flows from the inner pipe of the exhaust pipe that opens into the water lock due to the exhaust pulsation of the engine to the engine side. There is a risk of being inhaled. For this reason, for the purpose of reducing the influence of exhaust pulsation, for example, the exhaust pipe is extended from the side of the engine to the front of the engine, and after enclosing the front of the engine, the exhaust pipe is extended toward the rear water lock. An exhaust cooling structure with a longer length is also used. However, in a small vessel such as a water vehicle with a narrow engine room, the degree of freedom in design for installing a long exhaust pipe is low, so the engine side of cooling water by exhaust pulsation is used while using a short exhaust pipe. There has been a demand for an exhaust cooling structure that can effectively prevent the air from being sucked into the air.

  The present invention has been made in order to address the above-described problems, and its purpose is to provide an effect of backflow of cooling water to the engine side even if the length of the exhaust pipe connecting the engine and the water lock is shortened. It is an object to provide an exhaust cooling structure for an engine that can be prevented.

  In order to achieve the above-described object, the structural features of the exhaust cooling structure for an engine according to the present invention include an inner pipe that forms an exhaust gas passage through which exhaust gas discharged from the engine passes, and an outer peripheral side of the inner pipe. An exhaust pipe comprising an outer pipe that forms a cooling water passage through which the cooling water that has cooled the engine is passed between the inner pipe and the inner pipe, and a water backflow prevention structure is formed inside, and an exhaust pipe at the upstream end An exhaust cooling structure for an engine having a water lock connected to the downstream side of the exhaust pipe through the exhaust pipe connecting portion, the exhaust pipe connecting portion of the water lock and the outer pipe of the exhaust pipe And extending the inner pipe of the exhaust pipe to the inner side of the water lock, thereby opening the cooling water flowing from the cooling water passage into the water lock between the exhaust pipe connecting portion and the inner pipe. For A cooling water opening is formed, and the cooling water discharged from the cooling water opening and the exhaust gas discharged from the exhaust gas passage are mixed in the water lock, and the downstream end portion of the inner pipe is set at the downstream end. This is because the cooling water discharged into the water lock is diffused so that the diameter becomes larger as it gets closer.

  In the engine exhaust cooling structure according to the present invention configured as described above, the exhaust pipe connecting portion of the water lock and the outer pipe of the exhaust pipe are connected, and the inner pipe of the exhaust pipe is extended to the inner side of the water lock. . And the downstream end side part of the inner tube is formed so that the diameter increases as it approaches the downstream end. For this reason, the exhaust gas is injected from the exhaust gas passage of the exhaust pipe into the water lock so that the traveling direction is slightly expanded toward the outer peripheral side, and the cooling water is injected into the water lock from the cooling water passage of the exhaust pipe. After traveling along the outer peripheral surface, the fuel is injected so as to diffuse to the outer peripheral side.

  In this case, since the cooling water travels away from the opening of the inner pipe, it is prevented from flowing back to the engine side in the exhaust pipe due to the exhaust pulsation of the engine. At that time, since the cooling water hits a wide area of the inner wall of the water lock, the cooling effect of the water lock is improved. And the cooling water which prevented the backflow into an exhaust pipe and cooled the water lock is mixed with exhaust gas. When the downstream end portion of the inner pipe is a straight tube having the same diameter as the upstream portion, turbulent flow is likely to occur when the exhaust gas is released from the inner pipe, and the turbulent flow increases the exhaust efficiency. Although there is a possibility of a decrease, by forming the downstream end portion of the inner pipe so that its diameter increases as it approaches the downstream end, the exhaust gas can be easily opened into the water lock, and the exhaust efficiency is improved.

  Another structural feature of the engine exhaust cooling structure according to the present invention is that the downstream end portion of the inner pipe is formed in a bell mouth shape that gradually spreads to the outer peripheral side so as to draw a smooth curved surface. Therefore, the diameter increases as it approaches the downstream end. According to this, since the injection of the cooling water from the cooling water passage into the water lock is performed so as to smoothly diffuse along the smooth curved surface, the back flow to the exhaust pipe is prevented more effectively and the water lock is cooled. Is possible. Also, the exhaust efficiency is improved.

  Further, another structural feature of the engine exhaust cooling structure according to the present invention is that the length between the exhaust pipe connecting portion and the inner pipe constituting the cooling water opening is the downstream end of the exhaust pipe connecting portion. And the length between the inner pipe and the downstream end of the inner pipe. In this way, by making the length from the cooling water opening to the downstream end of the inner pipe longer than the length between the exhaust pipe connecting portion and the inner pipe, the injection of the cooling water from the cooling water opening is performed. Since the momentum is not hindered, the diffusion effect of the cooling water by the downstream end of the inner pipe can be exhibited without reducing the cooling water injection efficiency.

  Further, another structural feature of the engine exhaust cooling structure according to the present invention is that the outer diameter of the downstream end of the inner pipe is made smaller than the inner diameter of the exhaust pipe connecting portion. According to this, the diffusion of the cooling water by the downstream end of the inner pipe can be made wider, and the cooling effect of the water lock is improved. That is, when the outer diameter of the downstream end of the inner pipe is made larger than the inner diameter of the exhaust pipe connection portion, the cooling water is biased toward the upstream side portion in the water lock, and the downstream end portion of the inner pipe When the side is a straight tube having the same diameter as the upstream portion, the cooling water does not diffuse and proceeds toward the downstream side in the water lock. For this reason, while increasing the diameter of the downstream end portion of the inner pipe and making the outer diameter of the downstream end of the inner pipe smaller than the inner diameter of the exhaust pipe connecting portion, the cooling water is diffused appropriately. be able to.

  Further, another structural feature of the engine exhaust cooling structure according to the present invention is that the water backflow prevention structure is divided into a partition that divides the interior of the water lock into an upstream portion and a downstream portion, and the partition penetrates. A partition pipe that passes exhaust gas and cooling water from the upstream side portion to the downstream side portion, and the partition pipe is the central axis of the inner pipe of the tangent line that contacts the inner peripheral surface of the downstream end of the inner pipe It is located on the inner side of the tangent line that intersects with. According to this, since the partition pipe is positioned in the direction in which the exhaust gas travels, the exhaust efficiency is improved.

  Still another structural feature of the engine exhaust cooling structure according to the present invention is that the engine exhaust cooling structure is provided in a water vehicle. In a small vessel such as a water vehicle, since the engine room is narrow, it is preferable to shorten the exhaust pipe to reduce the space occupied by the exhaust pipe. According to the engine exhaust cooling structure of the present invention, it is possible to prevent the reverse flow of the cooling water even if the exhaust pipe is shortened. For this reason, by providing an exhaust cooling structure for an engine according to the present invention in a water vehicle, a short exhaust pipe can be used to facilitate the arrangement thereof, and water that can effectively prevent backflow of cooling water to the engine side. You can get a vehicle.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a water vehicle 10 having an engine exhaust cooling structure according to an embodiment of the present invention. In this water vehicle 10, a hull 11 is composed of a deck 11 a and a hull 11 b, and a steering handle 12 is provided at a portion slightly ahead of the center at the top of the hull 11, and at the center at the top of the hull 11. A sheet 13 is provided. A fuel tank 14 for storing fuel is installed at the front side portion at the bottom of the hull 11, and an engine 15 is installed at the center of the bottom of the hull 11.

  A propulsion unit 16 is installed at the rear end of the hull 11, and this propulsion unit 16 is connected to the engine 15 via an impeller shaft (not shown). A deflector 17 is attached to the rear end of the propulsion unit 16 to change the traveling direction of the water vehicle 10 left and right by moving the rear side to the left and right according to the operation of the steering handle 12. Further, the engine 15 includes an intake device (not shown) for sending an air-fuel mixture supplied from the fuel tank 14 to the engine 15 and exhaust gas discharged from the engine 15 at the rear end of the hull 11. And an exhaust device 18 that discharges to the outside.

  The engine 15 takes in a mixture of fuel and air from an intake device provided on the intake valve side by opening and closing drive of an intake valve and an exhaust valve constituting each cylinder, and an exhaust device 18 provided on the exhaust valve side. The exhaust gas is sent out. At that time, the air-fuel mixture supplied from the intake valve side into the engine 15 explodes by ignition of an ignition device provided in the engine 15, and the piston provided in the engine 15 moves up and down by this explosion. The crankshaft is rotationally driven by the movement of the piston.

  The crankshaft is connected to the impeller shaft, and transmits the rotational force to the impeller shaft to rotate the impeller shaft. Further, the rear end portion of the impeller shaft is connected to an impeller disposed in the propulsion unit 16, and a propulsive force is generated in the water vehicle 10 by the rotation of the impeller. The propulsion unit 16 includes a water introduction port 16a that opens to the bottom of the hull 11 and a water injection port (not shown) that opens to the stern, and the seawater introduced from the water introduction port 16a A propulsive force is generated in the hull 11 by injecting from the injection port.

  Although not shown, the intake device is configured by an intake pipe connected to the engine 15, a throttle body connected to the intake pipe, and the like. Then, the air outside the ship is sucked through the intake duct and the intake box, and the flow rate of the air is adjusted by opening and closing a throttle valve provided in the throttle body, and supplied to the engine 15. At that time, the fuel supplied from the fuel tank 14 is mixed with the air supplied to the engine 15 via the fuel supply device.

  The exhaust device 18 includes the exhaust cooling structure 20 shown in FIGS. 2 and 3, and has an exhaust pipe 21 connected to the side of the engine 15 and a tank-like connection connected to the rear end of the exhaust pipe 21. A water lock 22 and an exhaust pipe 23 connected to the rear portion of the water lock 22 are configured. The exhaust pipe 21 extends from the exhaust valve side of each cylinder of the engine 15 to the side portion of the engine 15 and then extends toward the rear as it is. The rear end portion of the exhaust pipe 21 communicates with the front portion of the water lock 22. An exhaust pipe 23 extends rearward from the upper surface of the rear portion of the water lock 22. The exhaust pipe 23 once extends upward from the upper surface of the rear portion of the water lock 22 and then extends to the lower rear portion, and the downstream end portion opens to the lower rear end portion of the hull 11.

  The exhaust pipe 21 includes an upstream pipe 21a installed on the engine 15 side, and a connection pipe 21b that connects the upstream pipe 21a and the water lock 22. The upstream pipe 21a is shown in FIGS. As described above, it is composed of a double tube made of aluminum and composed of an inner tube 24 and an outer tube 25. The inside of the inner pipe 24 constitutes an exhaust gas passage 24a for allowing exhaust gas discharged from the engine 15 to pass therethrough, and the space between the outer peripheral surface of the inner pipe 24 and the inner peripheral surface of the outer pipe 25 is the engine 15. The cooling water passage 25a for allowing the cooling water after cooling etc. to pass through is constituted.

  The cooling water passing through the cooling water passage 25a is composed of water such as seawater taken from the rear side portion of the bottom of the hull 11, and this cooling water is provided in each cooling water channel (see FIG. After passing through the cooling water passage 25a, it is sent to each part of the engine 15 and the like. In addition, a cylindrical connection portion 25b is provided in a predetermined portion on the peripheral surface on the downstream end side of the upstream pipe 21a. The cylindrical connection portion 25b and the predetermined portion such as the engine 15 are connected to a cooling water hose (not shown). ) Is connected through. For this reason, the cooling water that has been sent from the cooling water passage 25a to each part such as the engine 15 and has cooled the engine 15 and the like passes through the cooling water hose and returns from the cylindrical connection portion 25b into the upstream pipe 21a.

  A plurality of screw forming portions 26 having screw holes are formed at regular intervals in the circumferential direction at the downstream end portion of the upstream pipe 21a, and downstream of the screw holes of the screw forming portion 26. Bolts 26a for connecting the upstream pipe 21a and the connecting pipe 21b are inserted from the end face side toward the upstream side. Further, the downstream end portion of the upstream pipe 21a is provided with a hole that communicates from the upstream side to the downstream side while maintaining a circumferential interval, and the cooling water flowing from the cylindrical connecting portion 25b It flows to the connecting pipe 21b side through the hole.

  The connecting pipe 21b includes a tail pipe 27 connected to the downstream end of the upstream pipe 21a, an inner pipe 28 extending from the downstream inner peripheral surface of the tail pipe 27 into the water lock 22, and a downstream outer peripheral surface of the tail pipe 27. And an exhaust hose 29 extending toward the water lock 22. The tail pipe 27 is formed of a double pipe having a short axial length composed of an inner pipe 31 and an outer pipe 32, and the exhaust gas communicating with the exhaust gas passage 24 a in the inner pipe 24 in the inner pipe 31. A passage 31a is formed, and a cooling water passage 32a is formed between the outer peripheral surface of the inner tube 31 and the inner peripheral surface of the outer tube 32 and communicates with the cooling water passage 25a via the cooling water hose and the cylindrical connection portion 25b. ing.

  Further, a plurality of screw forming portions 27a provided with screw holes are formed at regular intervals in the circumferential direction on the upstream end side portion of the tail pipe 27 connected to the upstream tube 21a. The bolt 26a described above is inserted from the downstream end of the screw hole 27a toward the upstream side. That is, the upstream pipe 21a and the tail pipe 27 are connected by screwing the bolts 26a into the screw holes formed in the screw forming portions 26 and 27a, respectively.

  Further, a gasket 34 for sealing is installed on the joint surface between the upstream pipe 21 a and the tail pipe 27. The gasket 34 is provided with a hole for passing the bolt 26a, a hole for communicating the exhaust gas passages 24a and 31a, and a hole for communicating the cylindrical connecting portion 25b and the cooling water passage 32a. Through the holes, exhaust gas and cooling water can flow from the upstream pipe 21a to the tail pipe 27, and the upstream pipe 21a and the tail pipe 27 can be connected by a bolt 26a. Furthermore, a protrusion 27b having a hole penetrating between the inner surface and the outer surface of the outer tube 32 is formed on the upstream end portion of the tail pipe 27, and cooling water is formed in the hole of the protrusion 27b. A temperature sensor 35 for measuring the temperature of the cooling water passing through the passage 32a is attached.

  The inner tube 28 is made of a cylindrical pipe made of aluminum, and has a smooth bell mouth-shaped wide-angle portion 28a whose diameter gradually increases toward the distal end side at the distal end portion (downstream end portion). Formed and configured. The inner pipe 28 is fixed to the tail pipe 27 by screwing the upstream end portion thereof to the inner surface of the downstream portion of the tail pipe 27, and the downstream end extends into the water lock 22. . The inside of the inner pipe 28 constitutes an exhaust gas passage 28b communicating with the exhaust gas passages 24a and 31a.

  The exhaust hose 29 is made of flexible cylindrical rubber, and is connected to the tail pipe 27 by inserting the downstream portion of the tail pipe 27 into the upstream end thereof. A cylindrical exhaust pipe connecting portion 22a is provided at the upstream end of the water lock 22, and the downstream end of the exhaust hose 29 extends to the water lock 22 and the outer peripheral surface of the exhaust pipe connecting portion 22a. Covering. A space is formed between the exhaust hose 29 and the inner pipe 28, and a cooling water passage 29a communicating with the cooling water passage 32a is formed in this space.

  The upstream portion of the exhaust hose 29, the tail pipe 27, the downstream portion of the exhaust hose 29, and the exhaust pipe connecting portion 22a are fixed by fastening the opposing portions with a pair of fastening members 36, respectively. . The tightening member 36 is a steel band 36a whose outer peripheral surface is wound around the circumference in a state where the opposing portions of the exhaust hose 29 and the tail pipe 27 and the exhaust hose 29 and the exhaust pipe connecting portion 22a are sealed in a watertight manner, respectively. And a screw member 36b for fastening both ends of the steel band 36a.

  Therefore, by rotating each screw member 36b in a predetermined direction, each steel band 36a is tightened along the circumference. As a result, the opposing portions of the exhaust hose 29 and the tail pipe 27 and the exhaust hose 29 and the exhaust pipe connecting portion 22a are fixed to each other in a sealed state. The inner pipes 31 and 28 constitute the inner pipe of the present invention, and the outer pipe 32 and the exhaust hose 29 constitute the outer pipe of the present invention. The cooling water passage 29a communicates with a space formed between the outer peripheral surface of the inner pipe 28 and the inner peripheral surface of the exhaust pipe connecting portion 22a, and the cooling water is released at the downstream end of the space portion. The mouth is composed.

  The water lock 22 has a shape formed by connecting openings of two container-like members by welding to form a tank shape, and the exhaust pipe connecting portion 22a described above is provided at the upstream end thereof. As shown in FIG. 3, the exhaust pipe connecting portion 22a is formed so as to be inclined with respect to the water lock 22 so that the axial angle is shifted in the left-right direction, and is coaxial with the connecting pipe 21b. So connected. The interior of the water lock 22 is partitioned by a partition 37 into an upstream portion and a downstream portion. The partition 37 is formed of a curved plate member in which a central portion of one surface is depressed and a central portion of the other surface protrudes, and the surface of the concave portion faces the upstream side of the water lock 22. It is installed on the rear side (downstream side) slightly from the center in the front-rear direction.

  A pair of partition pipes 38 and 39 are provided through the partition 37 so as to maintain a vertical space at a portion of the partition 37 that is substantially opposed to the wide-angle portion 28 a of the inner tube 28. The partition pipes 38 and 39 are formed in a cylindrical shape, and upstream ends thereof are formed in bell mouth-shaped wide-angle portions 38 a and 39 a similar to the wide-angle portion 28 a of the inner tube 28. Further, a drainage hole 37 a is formed in the lower end portion of the partition 37 to allow cooling water accumulated in the upstream portion of the water lock 22 to flow to the downstream portion. An upstream end portion of the exhaust pipe 23 enters the downstream portion of the water lock 22 so as to penetrate the ceiling portion of the water lock 22, and the lower end portion extends to the vicinity of the bottom portion of the water lock 22. ing.

  The connection pipe 21b and the water lock 22 thus configured are connected so as to have the positional relationship shown in FIG. That is, the length between the outer peripheral surface of the inner pipe 28 and the inner peripheral surface of the exhaust pipe connecting portion 22a is d1, and between the downstream end of the exhaust pipe connecting portion 22a and the distal end portion of the wide-angle portion 28a of the inner pipe 28. The length d2 is set to be longer than the length d1, where d2 is d2. Further, if the diameter of the tip of the wide angle portion 28a is D1, and the inner diameter of the exhaust pipe connecting portion 22a is D2, the diameter D1 is set to be shorter than the inner diameter D2. Further, if the angle at which the tip of the inner peripheral surface of the wide-angle portion 28a spreads in the tangential direction is θ, the partition pipes 38 and 39 are installed so as to be within the range of this angle θ.

  By arranging in this way, the cooling water discharged from the cooling water opening formed between the outer peripheral surface of the inner pipe 28 and the inner peripheral surface of the exhaust pipe connecting portion 22a to the upstream portion of the water lock 22 is When the exhaust pulsation occurs in the engine 15, it is prevented from flowing back into the inner pipe 28 and discharged from the inner pipe 28 to the upstream portion of the water lock 22. The exhaust gas enters the downstream portion of the water lock 22 efficiently together with the exhaust gas.

  Next, an operation for running the water vehicle 10 configured as described above will be described. First, when the start switch (not shown) is turned on, the water vehicle 10 becomes ready to travel, and the driver sitting on the seat 13 steers the steering handle 12 and also controls the throttle lever (not shown). The water vehicle 10 starts traveling at a predetermined speed in a predetermined direction according to each operation. When the water vehicle 10 travels, the exhaust gas discharged from the engine 15 flows through the exhaust gas passages 24 a, 31 a, and 28 b of the exhaust pipe 21 to the upstream portion in the water lock 22.

  Further, the cooling water flowing from the engine 15 side after cooling the engine 15 and the like flows to the upstream side portion in the water lock 22 through the cooling water hose, the cylindrical connecting portion 25b, and the cooling water passages 32a and 29a. At this time, the exhaust gas is injected so as to spread slightly from the wide-angle portion 28a of the inner tube 28 as indicated by an arrow a in FIG. Further, the cooling water spreads so as to be diffused by the wide-angle portion 28a of the inner tube 28 as indicated by the arrow b. For this reason, even if exhaust pulsation occurs in the engine 15, the cooling water cools a wide portion of the wall surface of the water lock 22 and the exhaust gas without flowing back to the inner side of the inner pipe 28.

  Then, the exhaust gas and the cooling water are mixed, pass through the partition pipes 38 and 39, enter the downstream portion of the water lock 22, and are further discharged outside the ship through the exhaust pipe 23. At this time, since the wide-angle portions 38a and 39b are formed at the upstream ends of the partition pipes 38 and 39, the flow when the exhaust gas and the cooling water enter the partition pipes 38 and 39 becomes smooth and effective. Exhaust gas and cooling water can pass through the partition pipes 38 and 39.

  Further, when the cooling water accumulates in the upstream portion of the water lock 22, it flows through the drain hole 37 a provided in the lower end portion of the partition 37 and flows to the downstream portion of the water lock 22. The cooling water in the water lock 22 is discharged along with the exhaust gas along the flow of the exhaust gas. Further, in the water vehicle 10, the exhaust pipe 23 and the water lock 22 prevent the seawater outside the ship from flowing back and entering the exhaust pipe 21 side.

  As described above, in the engine exhaust cooling structure 20 according to the present embodiment, the exhaust hose 29 constituting the outer pipe of the connection pipe 21b of the exhaust pipe 21 is connected to the exhaust pipe connection portion 22a of the water lock 22, and the inner pipe 28 is connected. Is extended to the inner side of the water lock 22. And the downstream end side part of the inner tube | pipe 28 is formed in the wide-angle part 28a from which a diameter becomes large, so that it approaches a downstream end. For this reason, the exhaust gas is injected from the inner pipe 28 into the water lock 22 so as to widen the course, and the cooling water flows along the outer peripheral surface of the inner pipe 28 from the cooling water opening. Is injected into.

  In this case, since the cooling water is diffused in a wide range by the wide-angle portion 28 a of the inner pipe 28, the exhaust pulsation of the engine 15 prevents the exhaust pipe 21 from flowing backward to the engine 15 side. Moreover, since the diffused cooling water hits a wide area of the inner wall of the water lock 22, the cooling effect of the water lock 22 is improved. Further, since the exhaust gas also travels so as to widen the course, turbulent flow hardly occurs, and exhaust efficiency is improved. Further, the length d1 between the outer peripheral surface of the inner pipe 28 constituting the cooling water opening and the inner peripheral surface of the exhaust pipe connecting portion 22a is set to the downstream end of the exhaust pipe connecting portion 22a and the wide angle portion 28a of the inner pipe 28. Therefore, the diffusion effect of the cooling water by the wide-angle portion 28a of the inner pipe 28 is prevented without hindering the momentum of jetting of the cooling water from the cooling water release port by the wide-angle portion 28a. It can be fully demonstrated.

  Further, since the diameter D1 of the distal end portion of the wide-angle portion 28a of the inner pipe 28 is made shorter than the inner diameter D2 of the exhaust pipe connection portion 22a, the diffusion of the cooling water by the wide-angle portion 28a of the inner pipe 28 can be made wider. Further, the cooling effect of the water lock 22 is further improved. Further, the partition pipes 38 and 39 are installed within the range of the angle θ in which the distal end portion of the wide-angle portion 28a of the inner tube 28 extends in the tangential direction, and the wide-angle portions 38a and 39b are formed at the upstream ends of the partition pipes 38 and 39. As a result, the exhaust efficiency is improved. Further, since the exhaust cooling structure 20 is configured in this way, the water vehicle 10 can be obtained that can effectively prevent the backflow of cooling water to the engine 15 side even if the length of the exhaust pipe 21 is shortened.

  Further, the engine exhaust cooling structure according to the present invention is not limited to the embodiment described above, and can be implemented with appropriate modifications. For example, in the above-described embodiment, the wide-angle portion 28a of the inner tube 28 has a bell mouth shape configured with a smooth curved surface, but the wide-angle portion is not limited to this shape and may be formed in a funnel shape, The diameter can be increased stepwise. Also, the shape of the wide-angle opening can be various shapes such as a circle, an ellipse, and a rectangle. Further, in the above-described embodiment, as shown in FIGS. 2 to 4, the exhaust pipe connecting portion 22 a is formed integrally with the water lock 22, but the exhaust pipe connecting portion 22 a is separate from the water lock 22. And may be connected to each other by a predetermined method such as using a fixing member.

  In the embodiment described above, the exhaust cooling structure 20 is provided in the water vehicle 10, but the engine exhaust cooling structure 20 according to the present invention is not limited to the water vehicle 10, and includes an exhaust gas passage and a cooling water passage. An engine exhaust cooling structure provided with an exhaust pipe can be used for other vehicles. Further, the structure, material, and the like of other parts constituting the engine exhaust cooling structure can be appropriately changed within the technical scope of the present invention.

It is a side view showing a water vehicle provided with an engine exhaust cooling structure according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing an engine exhaust cooling structure provided in the water vehicle shown in FIG. 1. It is the cross-sectional view which showed the exhaust-air cooling structure of the engine with which the water vehicle shown in FIG. 1 is provided. It is the longitudinal cross-sectional view explaining the positional relationship of a connecting pipe and a water lock.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Water vehicle, 15 ... Engine, 20 ... Exhaust cooling structure, 21 ... Exhaust pipe, 21b ... Connection pipe, 22 ... Water lock, 22a ... Exhaust pipe connection part, 24a, 28b, 31a ... Exhaust gas passage, 25a, 29a 32a ... cooling water passage, 28 ... inner pipe, 28a ... wide angle part, 29 ... exhaust hose, 37 ... partition, 38, 39 ... partition pipe.

Claims (6)

A cooling water passage is formed between an inner pipe that forms an exhaust gas passage that allows exhaust gas discharged from the engine to pass therethrough, and a cooling water passage that is formed on the outer peripheral side of the inner pipe and that cools the engine. An exhaust pipe comprising an outer pipe to be
A water backflow prevention structure is formed inside, an exhaust pipe connecting portion is formed at an upstream end, and a water lock connected to the downstream side of the exhaust pipe through the exhaust pipe connecting portion is provided. An exhaust cooling structure,
While connecting the exhaust pipe connection part of the water lock and the outer pipe of the exhaust pipe, and extending the inner pipe of the exhaust pipe to the inner side of the water lock, the exhaust pipe connection part and the inner pipe A cooling water opening for releasing cooling water flowing from the cooling water passage into the water lock is formed between the cooling water released from the cooling water opening and the exhaust gas passage. The exhaust gas is mixed in the water lock, and the downstream end portion of the inner pipe is formed so that its diameter increases toward the downstream end, so that the cooling water discharged into the water lock diffuses. An exhaust cooling structure for an engine characterized by that.   The downstream end portion of the inner pipe is formed in a bell mouth shape that gradually spreads to the outer peripheral side so as to draw a smooth curved surface, so that the diameter becomes larger toward the downstream end. Engine exhaust cooling structure.   The length between the exhaust pipe connecting part and the inner pipe constituting the cooling water opening is shorter than the length between the downstream end of the exhaust pipe connecting part and the downstream end of the inner pipe. The engine exhaust cooling structure according to claim 1 or 2.   The engine exhaust cooling structure according to any one of claims 1 to 3, wherein an outer diameter of a downstream end of the inner pipe is smaller than an inner diameter of the exhaust pipe connecting portion.   Partitioning the water backflow prevention structure into an upstream portion and a downstream portion inside the water lock, and exhaust gas and cooling water provided through the partition from the upstream portion to the downstream side A partition pipe that passes through the portion, and the partition pipe is positioned on the inner side of a tangent line that intersects a central axis of the inner pipe among tangent lines that are in contact with an inner peripheral surface of a downstream end of the inner pipe. The engine exhaust cooling structure according to any one of 1 to 4.   The engine exhaust cooling structure according to any one of claims 1 to 5, wherein the engine exhaust cooling structure is provided in a water vehicle.

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