JPH0672544B2 - Two-stroke engine for small vessels - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a two-cycle engine for jet-propelled leisure boats and the like, particularly for small boats in which the attitude of the hull tends to change due to the influence of waves.

[Prior Art] As a conventional engine for a small boat, a two-cycle engine is commonly used in order to ensure small size and light weight and performance. In addition, since the attitude of the hull is prone to change, a floatless carburetor that does not easily change the fuel flow rate due to fluctuations in the fuel oil level in the engine float chamber is used to ensure that an appropriate fuel flow rate is always supplied to the engine. ing. And such a floatless carburetor is attached to the intake pipe connected to the intake port provided in the cylinder.

[Problems to be Solved by the Invention] By the way, a floatless vaporizer is more likely to cause vapor lock than a float type vaporizer.

On the other hand, in a small boat, since the engine compartment is made small in order to secure the space, the temperature of the engine compartment is likely to rise and the exhaust heat from the cylinder may be transferred to the floatless carburetor.

That is, the temperature of the floatless carburetor in an engine having a conventional intake system is still high even if there is cooling due to the vaporization of fuel, which may cause a vapor lock and stop the engine.

The present invention has been made in view of the above problems of the conventional technique, and an object thereof is a compact two-cycle engine for a small boat which is less likely to cause vapor lock in a floatless vaporizer. Is to provide.

[Means for Solving the Problems] In order to achieve the above object, in a two-cycle engine for a small boat according to the present invention, a crankshaft is arranged inside the hull in a longitudinal direction of the hull to form a combustion chamber. A crankcase constituting a scavenging pump for supplying fresh air to the cylinder below the cylinder, an exhaust passage connected to the cylinder, and vaporization in which one end is connected to the crankcase and the other end is open to the atmosphere. And an intake pipe connected to a vessel, wherein one end of the intake pipe is connected to one side of the crankcase and the other end is bent and opened upward of the engine, and the intake pipe is provided near a side wall of the hull. The carburetor at the open end is formed of a floatless carburetor, and the exhaust passage from the cylinder is led out to the intake pipe connection side of the engine toward the other side upward. It is characterized by.

[Operation] Since the crankshaft is arranged inside the hull in the longitudinal direction of the hull, the width of the hull can be narrowed to reduce the cross-sectional area of the hull, and one end of the intake pipe is connected to one side of the crankcase. Since the other end is bent and opened toward the upper side of the engine, and the floatless carburetor is arranged at the open end,
The fuel that has not been completely vaporized by the floatless vaporizer flows down in the intake pipe due to its own weight, is guided into the crankcase through the bent portion, and is vaporized in the intake pipe and the crankcase.
Further, since the intake pipe is connected to the crankcase below the engine and the exhaust passage is led out to the upper side of the intake pipe connection side of the engine, the intake pipe provided with the floatless carburetor is Exhaust passages with heat are located at a great distance, and water accumulated in the hull is not affected by heat transfer from the exhaust passages. Further, since one end of the intake pipe is connected to one side of the crankcase and the other end is bent and opened toward the upper side of the engine and the intake pipe is located near the side surface of the hull, the intake pipe can be installed in a narrow space of a small ship. Can be placed inside.

[Embodiment] FIG. 1 is a transverse cross-sectional view of a main part of a water-jet type small leisure ship equipped with an engine according to the present invention.

In the figure, a water injection unit 12 is provided in the lower rear part of the hull 11, while an engine 13 is mounted in the middle front part of the hull 11.

The water injection unit 12 has an impeller 14, a propeller shaft 15 and a steering nozzle 16, and has an engine 13 and a propeller shaft.
A coupling 17 is provided between the propeller shaft 15 and the coupling 15, and the power of the engine 13 is transmitted to the propeller shaft 15 while reducing torsional vibration.

The impeller 14 is driven by a propeller shaft 15 to eject water backward, and the steering device 18 is rotated to connect the steering device 18 with a steering nozzle.
By deflecting 16 and injecting the water, the leisure ship can sail in any direction.

The engine 13 mainly includes a cylinder 1 that constitutes a combustion chamber.
9, a cylinder head 20 arranged above the cylinder 19, a crank case 21 constituting a scavenging pump for supplying fresh air to the cylinder 19 below the cylinder 19, a cylinder head 2
It is composed of an exhaust expansion chamber 22 arranged above 0, and a first exhaust passage 23 connecting the cylinder 19 and the exhaust expansion chamber 22.

Further, in the exhaust casing 24 forming the exhaust expansion chamber 22,
A rubber tube 26 forming the second exhaust passage 25 is detachably connected. Then, the exhaust gas is discharged to the outside of the ship through an exhaust gas discharge port (not shown).

The cylinder 19, the cylinder head 20 and the crankcase 21 constitute one cylinder unit 27.

An intake pipe 28 is open-connected to one side wall of the crankcase 21, and the other end of the intake pipe 28 is bent and opened upward of the engine, and a floatless carburetor is provided at the open end.
29 is arranged, and the intake pipe 28 is arranged near the side surface of the ship.

Then, the fuel that has not been completely vaporized by the floatless vaporizer 29 flows down in the intake pipe 28 due to its own weight, is guided into the crankcase 21 through the bent portion of the intake pipe 28, and the intake pipe 28 and the crankcase 21 It is vaporized inside. Therefore, the intake pipe 28
The crankcase 21 is sufficiently cooled by the heat of vaporization.

Further, a vibration damping damper 30 is arranged in the crankcase 21 so as not to transmit the vibration of the engine 13 to the hull 11, and the engine 13 is held by the hull 11. Further, an ignition plug 31 is removably arranged on the cylinder head 20, and a fuel tank 32 is arranged on the front part of the hull 11.

In addition, a fuel inlet is provided in the hull 11 above the fuel tank 32.
33 is provided so that fuel can be injected into the fuel tank 32. Then, the fuel is sent to the floatless vaporizer 29 through the fuel filter 34 provided in the engine 13 and the fuel pump 35 shown in FIG.

FIG. 2 is a sectional view of the main part of the engine 13 as seen in the direction of the arrow along the line II-II in FIG.

In the figure, 11a is the bottom of the ship, and 11b is the port side. By positioning the crankshaft in the longitudinal direction of the hull 11 inside the hull, the width W of the hull is narrowed and the cross-sectional area of the hull 11 is reduced to improve the propulsion performance. ing.

36 is a piston, 37 is a connecting rod, 38 is a crank, 3
9 is a scavenging passage, 40 is an exhaust hole, and 41 is an exhaust outlet formed in the cylinder 19. Also, 42 is a cylinder that connects exhaust holes 40 of a plurality of cylinders and guides exhaust gas to an exhaust outlet 41.
It is an exhaust passage formed in 19. Also, the bracket 43 is
While the first exhaust passage 23 is formed inside,
It supports the exhaust casing 24. The first exhaust passage 23 connected to the exhaust outlet 41 is
It is led out to the upper side of the other side of the intake pipe 28 connection side of the engine and is connected to the exhaust expansion chamber 22. Further, the exhaust expansion chamber 22 is located on the upper surface of the cylinder head 20 so as to avoid the ignition plug 31, and has a shape extending to the side surfaces of the cylinder head 20 and the cylinder 19.

An intake system component such as the floatless carburetor 29 is arranged on one side of the vertical plane passing through the center of the crank 38 and the center of the cylinder sleeve, and an exhaust system component is arranged on the opposite side. Therefore, the exhaust heat from the exhaust system is difficult to transfer to the intake system such as the floatless carburetor 29, and the fuel vapor is less likely to be generated.
The engine performance can be improved without the intake air temperature being affected by the exhaust heat.

[Effects of the Invention] In the engine according to the present invention, one end of the intake pipe is connected to one side of the crankcase, the other end is bent and opened upward of the engine, and a floatless carburetor is arranged at the open end. Therefore, the fuel that could not be completely vaporized by the floatless vaporizer flows down in the intake pipe by its own weight, is guided into the crankcase through the bent portion, and is vaporized in the intake pipe and the crankcase. The intake pipe connected thereto is sufficiently cooled by the heat of vaporization to effectively prevent vapor lock of the floatless vaporizer.

Further, since the intake pipe is connected to the crankcase below the engine, and the exhaust passage is led out to the upper side of the intake pipe connection side of the engine, the intake pipe provided with the floatless carburetor is Since the exhaust passages with heat are located far apart, the intake pipe is less susceptible to heat transfer from the exhaust passage, further promoting the cooling effect of the intake pipe. Furthermore, the water accumulated in the hull is not affected by the heat transfer from the exhaust passage,
As a result, since the intake pipe is not heated by the water accumulated in the hull, vapor lock of the floatless vaporizer can be prevented more effectively.

Further, since one end of the intake pipe is connected to one side of the crankcase and the other end is bent and opened toward the upper side of the engine, and the intake pipe is located near the side surface of the hull, an intake pipe that tends to be long can be provided. It can be compactly arranged in the small space of a small vessel.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the essential parts of a water-injection type small leisure ship equipped with an engine according to the present invention, and FIG. 2 is II-II of FIG.
FIG. 3 is a cross-sectional view of the main part of the engine as seen in the direction of the arrow along the line. 11 …… Hull, 13 …… Engine, 19 …… Cylinder, 21 …… Crankcase, 23 …… Exhaust passage, 28 …… Intake pipe, 29 …… Vavaporizer.

Claims (1)

[Claims] 1. A cylinder in which a crankshaft is arranged inside the hull in the longitudinal direction of the hull and which constitutes a combustion chamber, and a crankcase which constitutes a scavenging pump for supplying fresh air to the cylinder below the cylinder. A two-cycle engine for a small boat, comprising: an exhaust passage connected to the cylinder; and an intake pipe connected at one end to the crankcase and at the other end to a carburetor opened to the atmosphere. Has one end connected to one side of the crankcase and the other end bent and opened toward the upper side of the engine, and the intake pipe is located near the side surface of the hull, and the carburetor at the open end is composed of a floatless carburetor. A two-cycle engine for a small boat, characterized in that an exhaust passage from the cylinder is led out toward the intake pipe connection side of the engine toward the other side.