JPH09256847A - Cooling structure of outboard engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling structure of an outboard engine capable of unifying the temperature distribution around a cylinder of an engine as much as possible. SOLUTION: A cooling structure is provided with exhaust passages 32, 79 to discharge the exhaust gas, cooling water passages 93, 101 for the exhaust passage to cool the exhaust passages, a cooling water passage 91 for cylinder to cool a cylinder 11 of an engine, a cooling water passage 103 for combustion chamber to cool a combustion chamber 11a of the engine, and a pump 27 to suck water outside an outboard engine. The pump feeds the sucked water to the cooling water passages 93, 101 for exhaust passages. The water fed to the cooling water passages 93, 101 for exhaust passage passes through the cooling water passages 93, 101 for exhaust passages, and then fed to the cooling water passage 91 for cylinder and the cooling water passage 103 for combustion chamber, and then, passes through the cooling water passage 91 for cylinder and the cooling water passage 103 for the combustion chamber, and discharged outside the outboard engine.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a motor boat,
The present invention relates to an outboard motor cooling structure attached to a small boat such as a yacht or a fishing boat.

[0002]

2. Description of the Related Art Conventionally, in an outboard motor, water, that is, cooling water sucked from the outside of the outboard motor cools a cylinder, a combustion chamber and an exhaust passage of an engine. The cooling water channel through which this cooling water flows is composed of a cylinder cooling water channel, a combustion chamber cooling water channel, and an exhaust passage cooling water channel. These cylinder cooling water channel, combustion chamber cooling water channel, and exhaust passage cooling water channel. Are connected in parallel. Therefore,
The water sucked from the outside of the outboard motor flows into the cooling water passage for the cylinder, the cooling water passage for the combustion chamber, and the cooling water passage for the exhaust passage while maintaining the water temperature outside the outboard motor substantially, and The exhaust passage is cooled, and the water temperature rises accordingly and is discharged to the outside of the outboard motor. Further, the cylinder cooling water passage, the combustion chamber cooling water passage, and the exhaust passage cooling water passage are configured to communicate with each other, and the cooling water in each cooling water passage may join together.

When the temperature of the engine is high, that is, when the temperature of the cooling water is high, water flows into the cooling water passage to cool the engine and the exhaust passage, while when the temperature of the engine is low, the cooling is performed. It is configured to block or reduce the flow of water in the waterway with a thermostat or the like.

[0004]

Therefore, the engine may be intermittently cooled or cooled with cooling water in which high-temperature water and low-temperature water are mixed. In such a case, particularly when the water temperature of the water outside the outboard motor is low, the temperature of the engine changes abruptly due to the temperature change of the cooling water. In such a case, the temperature distribution in the cylinder block of the engine becomes non-uniform, and the shape of the cylinder is slightly distorted and deformed. Further, in an engine of a type in which fuel is injected by a fuel injection pump, atomization becomes uneven, which adversely affects performance.

By the way, in an engine, especially a four-cycle engine, when the cylinder is deformed, the piston arranged in the cylinder cannot slide smoothly, seizure occurs, the consumption of lubricating oil and blow-by gas are increased. The occurrence of

When the engine operates, the temperature of the exhaust passage increases due to the high temperature exhaust gas of the engine. If the supply of the cooling water to the cooling water passage for the exhaust passage that cools the exhaust passage is intermittent, the exhaust passage may not be cooled, and the exhaust passage cannot be cooled sufficiently. Therefore, the temperature of the exhaust passage cannot be lowered, and the temperature of the exhaust passage becomes high. Then, the exhaust passage having a high temperature has a thermal effect on other parts arranged inside the outboard motor, the temperature of the other parts rises, and the other parts are deformed or damaged, or The desired performance may not be achieved.

An object of the present invention is to solve the above problems, and an object of the present invention is to provide an outboard motor cooling structure capable of making the temperature distribution around the cylinder of an engine as uniform as possible.

[0008]

An outboard motor cooling structure according to the present invention comprises an exhaust passage (32, 79) for exhausting combustion gas of an engine (7) and an exhaust passage cooling water passage for cooling the exhaust passage. (93, 101), a cylinder cooling water channel (91) for cooling the engine cylinder (11), a combustion chamber cooling water channel (103) for cooling the engine combustion chamber (11a), and an outboard motor. And a pump (27) for sucking external water. Then, in order to achieve the above object, the pump supplies the sucked water to the exhaust passage cooling water passage, and the water supplied to the exhaust passage cooling water passage passes through the exhaust passage cooling water passage. After that, it is supplied to the cylinder cooling water channel and the combustion chamber cooling water channel, and then, after passing through the cylinder cooling water channel and the combustion chamber cooling water channel, is discharged to the outside of the outboard motor.

The exhaust passage has a cylinder head exhaust passage (32) provided in a cylinder head (22) of the engine and a cylinder block (20) of the engine.
And a cylinder block exhaust passage (79) provided in the cylinder block exhaust passage, and the cooling water passage for the exhaust passage includes a cooling water passage for the cylinder head exhaust passage (101) and a cooling water passage for the cylinder block exhaust passage (93). ) And may be provided. And the water sucked in by the pump is
After passing through the cooling water passage for the cylinder block exhaust passage, it is supplied to the cooling water passage for the cylinder head exhaust passage.

Further, a thermostat (119) is provided in the vicinity of the outlets of the cylinder cooling water passage and the combustion chamber cooling water passage, and a pressure valve (114) is provided in the exhaust passage cooling water passage. It may be provided in the vicinity of a connecting portion between the cylinder cooling water passage and the combustion chamber cooling water passage.

Further, the cylinders of the engine are arranged in the cylinder block so as to be distributed in the left-right direction so as to form a V-shape, and the combustion chamber side of the left cylinder is closed by the left cylinder head, while the combustion of the right cylinder is performed. The chamber side may be blocked by the right cylinder head. The exhaust passage includes a cylinder head exhaust passage provided in each of the left and right cylinder heads and a cylinder block exhaust passage provided in a cylinder block of the engine. While communicating with the cylinder head exhaust passage of
The cylinders are arranged between the cylinders that are adjacent to each other in the V-shape on the left and right. Further, a thermostat is provided in the cooling water passage through which the cooling water for cooling the engine flows, and a pressure valve is provided on the upstream side of the thermostat. The pressure valve is arranged between the left and right cylinder heads in plan view.

Further, the cooling passage for the exhaust passage may be disposed between the cylinder block exhaust passage and the cooling passage for the cylinder. Note that the exhaust passage cooling water passage can be arranged at other places as long as it is arranged at least between the cylinder block exhaust passage and the cylinder cooling water passage.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a cooling structure for an outboard motor according to the present invention will be described with reference to FIGS. FIG. 1 is a partially cutaway sectional view of an outboard motor according to the present invention. FIG. 2 is a plan view showing the internal structure of the outboard motor of FIG. FIG. 3 is a cross-sectional view for explaining the internal structure of the outboard motor of FIG. FIG. 4 is an explanatory diagram for explaining the throttle valve and the surge tank. FIG. 5 is a circuit diagram of the cooling water channel. FIG. 6 is an enlarged view of a main part of FIG. FIG. 7 is an enlarged view of a main part of FIG. FIG. 8 is an enlarged sectional view of a portion of the timing belt pulley.

First, the overall structure of the outboard motor will be described. In FIG. 1, the outboard motor is covered with a housing including an upper cowling 1, a lower cowling 2, an upper casing 3 and a lower casing 4 in order from the upper side. A mounting bracket 6 is provided on the guide exhaust 23 and the upper casing 3 inside the lower cowling 2 via the swivel shaft 5 and the like. By fixing the mounting bracket 6 to the stern of a small boat such as a motor boat (not shown), the outboard motor is attached to the small boat so as to be rotatable in the left-right direction and the vertical direction.

In FIGS. 1 to 3, a V-type 6-cylinder 4-cycle engine 7 is arranged inside the upper cowling 1 and the lower cowling 2. The crankshaft 8 of the engine 7 is provided with its axis substantially vertical, and a pair of left and right cylinders 11 are arranged behind the crankshaft 8 so as to be laterally V-shaped. The pair of left and right cylinders 11 are provided in three stages in the vertical direction, and a total of six cylinders 11 are arranged. Further, six pistons 13 are connected to the crankshaft 8 via connecting rods 14, respectively, and the pistons 13 are slidably arranged inside the cylinders 11. In addition, the case 17 of the engine 7
Is a cylinder block 20 that forms the above-described six cylinders 11, a crankcase 21 that covers the crankshaft 8 side of the cylinder block 20, and a cylinder block 2
It is composed of a pair of left and right cylinder heads 22 that cover and close the No. 0 combustion chamber 11a side. This engine case 1
7 is fixed to the upper surface of the upper casing 3 via the guide exhaust 23.

The lower end of the crankshaft 8 projects from the engine case 17 and extends, and the drive shaft 26 disposed in the upper casing 3 is provided.
It is connected to. A water pump 27 is provided in the middle of the drive shaft 26. The rotation of the drive shaft 26 is transmitted to a propeller 28 rotatably provided at the rear end of the lower casing 4 via a bevel gear (not shown).

The cylinder head 22 is provided with an intake passage 31 for supplying air to the cylinder 11 and an exhaust passage 32 for exhausting combustion gas of the cylinder 11 for each cylinder 11. The port of the intake passage 31 is connected to the intake valve 3
5, an exhaust valve 36 opens and closes a port of the exhaust passage 32. The intake valve 35 is driven by an intake valve camshaft 38, and the exhaust valve 36 is driven by an exhaust valve camshaft 39. The intake valve camshaft 38 and the exhaust valve camshaft 39 are provided on the right cylinder head 22 and the left cylinder head 22, respectively, and extend in the up-down direction to form a single camshaft 38, 39. It is configured so that the three valves 35 and 36 can be controlled.

1 and 8, the upper end of the crankshaft 8 projects from the engine case 17, and the pulley 41 is press-fitted and fixed to the upper end which is the end of the crankshaft 8. This pulley 41
Above, the end of the crankshaft 8 is formed in a tapered shape, and the flywheel 42 is attached to the tapered portion 8a with a nut 43. FIG.
In addition, the intake valve camshaft 38 and the exhaust valve camshaft 39 are also provided with pulleys 46. Then, a timing belt 48, which is a pair of upper and lower endless transmission members, is hung on the pulley 41 of the crankshaft 8,
One timing belt 48 is the left cylinder head 2
The other timing belt 48 is wound around the pulleys 46 of the second cam shafts 38 and 39 and the pulleys 46 of the cam shafts 38 and 39 of the right cylinder head 22.

Next, the flow of engine oil will be described. 1 and 3, the guide exhaust 2
An oil pan 51 is provided so as to hang down on the lower surface of the oil pan 3, and a strainer 52 is provided inside the oil pan 51. An oil pump 54 is provided at the lower end of the crankshaft 8 and
When the engine rotates, the oil pump 54 is driven, and the engine oil accumulated in the oil pan 51 is transferred to the strainer 52.
Is sucking through. The engine oil sucked up from the strainer 52 reaches the oil pump 54 through the oil passage formed in the guide exhaust 23 and the engine case 17, and further passes through the oil passage formed in the crankcase 21 to reach the filter 56. Reached
It is filtered by the filter 56. Then, the oil that has passed through the filter 56 is supplied to the crankshaft 8 through the gallery 57 that extends in the vertical direction inside the crankcase 21. Then, it scatters from the plurality of holes formed in the crankshaft 8 to the outside of the crankshaft 8 to lubricate the inside of the engine case 17. Then, the scattered oil or the like passes through an oil passage (not shown) and is again collected in the oil pan 51.

Next, the flow of air sucked and exhausted by the engine 7 will be described. In FIGS. 1, 3 and 4, the air outside the outboard motor flows in through an air intake 61 provided on the upper side surface of the upper cowling 1 and is formed on the upper surface of the flywheel cover 62. The air intake pipe 66 of the engine 7 is reached through the passage 63. The air that has flowed into the air intake pipe 66 is throttle valve 67.
, And as shown in FIG. 4, branch left and right,
Each flows into the surge tank 69. This surge tank 6
Three branch pipes 71 are formed in each of the pipes 9, and the ends of the branch pipes 71 are connected to the intake passage 31 via an intake manifold 73. Intake manifold 73
An injector 74 is attached to the.

The injector 74 is supplied with fuel from a fuel tank mounted on a small boat (not shown) via a vapor separator tank 76. The timing and amount of supply of this fuel are controlled by a control unit ( (Not shown).

As is well known in the art, the air mixed with the fuel in the intake passage 31 flows into the cylinder 11 and burns when the intake valve 35 is opened. Then, this combustion gas is exhausted to the exhaust passage 32 when the exhaust valve 36 is opened. Three exhaust passages 32 are formed in each of the left and right cylinder heads 22, and the ends of the exhaust passages 32 are all connected to the exhaust passage 79 formed in the cylinder block 20. This exhaust passage 79 has a V
It is formed between the left and right cylinders 11 arranged adjacent to each other in a letter shape, extends in the cylinder block 20 in the vertical direction, and has an upper end closed and a lower end opened. There is. Therefore, the combustion gas burned in each cylinder 11 is exhausted from the exhaust passage 7 of the cylinder block 20.
The exhaust passage 81 of the guide exhaust 23, which merges at 9 and is connected to the exhaust passage 79, passes through the exhaust passage 81.
Through the exhaust pipe 83 connected to the muffler 84. The combustion gas flowing into the muffler 84 is discharged from the shaft of the propeller 28 through a passage (not shown).

This muffler 84 is an upper casing 3
However, a space is formed between it and the upper casing 3, and this space serves as a water reservoir 86. Further, in FIG. 6, the upper end of the muffler 84 and the lower surface of the oil pan 51 are liquid-tight, and the upper end of the water reservoir 86 reaches the outer periphery of the side wall of the oil pan 51. In addition, the inside of the muffler 84 is divided into an exhaust passage 87 through which combustion gas passes and a drainage passage 88 through which water flows. Further, a water passage 89 communicating with the drainage passage 88 of the muffler 84 is formed in the oil pan 51, and an overflow opening 90 is formed in the side wall of the oil pan 51 to prevent water overflowing from the water reservoir 86. It is configured to flow into the water channel 89 through the overflow opening 90.

Next, the cooling water passage will be described with reference to FIGS. 2, 5, 6 and 7. Note that FIG. 5 shows the cylinder block 20 in the center and shows the left and right cylinder heads 2
2 is removed from the cylinder block 20 and is arranged on the left and right sides of the cylinder block 20, and for the sake of clarity, the respective flow paths are connected.

In the cylinder block 20 of the engine 7,
A cylinder cooling water passage 91 provided around the cylinder 11 for cooling the cylinder 11, a cylinder block exhaust passage cooling water passage 93 for cooling the exhaust passage 79 of the cylinder block 20, and a return cooling water passage 94. And are provided. The cylinder cooling water passage 91 is provided in each of the left and right cylinders 11, and extends in the up-down direction along the periphery of the three cylinders 11 arranged in the up-down direction. Is cooling three cylinders 11. The cylinder block exhaust passage cooling water passage 93 is disposed between the cylinder cooling water passage 91 and the exhaust passage 79 of the cylinder block 20. The return cooling water passage 94 is provided at a corner of the crankshaft 8 side between the pair of left and right V-shaped cylinders 11.

On the other hand, in each of the pair of left and right cylinder heads 22, a cylinder head exhaust passage cooling water passage 101 for cooling the exhaust passage 32 of the cylinder head 22 and the combustion chamber 1 are provided.
A combustion chamber cooling water channel 103 for cooling 1a is formed. Cylinder head exhaust passage cooling water passage 101
Are formed so as to extend in the vertical direction along the outer surface of the exhaust passages 32 arranged in the vertical direction. Also,
The combustion chamber cooling water passage 103 extends in the up-down direction along the periphery of the combustion chamber 11a.

When the cylinder head 22 and the cylinder block 20 are connected to each other, as shown in FIGS. 2 and 5, the upper end portion of the cooling water passage 93 for the cylinder block exhaust passage is for the cylinder head exhaust passage. It communicates with the upper end of the cooling water channel 101. Further, as shown in FIGS. 5 and 7, the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103 communicate with each other at both upper and lower ends and in the middle. Further, as shown in FIGS. 5 and 6, the cylinder head exhaust passage cooling water passage 10 is provided.
The lower end of 1 and the lower ends of the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103 are connected via a communication passage 106 formed in the guide exhaust 23.

When the crankshaft 8 rotates, the drive shaft 26 also rotates and the water pump 27 operates. Then, the water outside the outboard motor is sucked from the water intake 108 (see FIG. 5) formed in the lower casing 4, and the water is supplied from the water pump 27 to the cooling water passage 93 for the cylinder block exhaust passage through the water tube 111 and the like. It flows in and cools the exhaust passage 79 of the cylinder block 20. After passing through the cylinder block exhaust passage cooling water passage 93, it flows into the cylinder head exhaust passage cooling water passage 101 and cools the exhaust passage 32 of the cylinder head 22. A pressure valve 114 is provided in a water passage extending from a lower end portion of the cooling water passage 101 for the cylinder head exhaust passage. When the pressure of the cooling water is higher than a predetermined pressure, the pressure valve 114 is provided. Is opened, and the cooling water is discharged from the pressure valve 114 to the water reservoir 86 via the pipe 115. This pressure valve 114
Are arranged between the pair of left and right cylinder heads 22 in a plan view, that is, when viewed from above as shown in FIG.

On the other hand, when the pressure of the cooling water is smaller than the set pressure of the pressure valve 114, the pressure valve 114 is closed, so that the cooling water flows through the communication passage 10.
6 into the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103, and the cylinder 11 and the combustion chamber 11
Cool a. The cylinder cooling water passage 91 and the combustion chamber cooling water passage 103 join at their upper ends. A thermostat 119 is provided downstream of this merging portion. This thermostat 119 has a cylinder 1 on the right side.
Two for the cylinder block 20 and one for the left cylinder 11 are attached to the upper surface of the cylinder block 20. Then, the cooling water discharged from both thermostats 119 flows into the return cooling water passage 94 provided downstream of the thermostats 119. This thermostat 119 opens when the water temperature of the cooling water is above a predetermined temperature, that is, the set temperature of the thermostat 119, and allows the cooling water to flow into the return cooling water passage 94. If it is less than, the flow is closed, and the flow of the cooling water to the return cooling water passage 94 is blocked or narrowed.

By the way, when the thermostat 119 is opened, the pressure of the cooling water is lowered and the pressure valve 114 is closed. On the other hand, when the thermostat 119 is closed, the pressure of the cooling water rises and the above-mentioned pressure valve 114 is opened.

Then, the cooling water flowing into the return cooling water passage 94 flows from the lower end of the return cooling water passage 94 into the water reservoir 86 through the cooling water passage 121 of the guide exhaust 23 and a cooling water passage (not shown). The water accumulated in the water reservoir 86 cools the oil pan 51 and the muffler 84. Then, when the cooling water accumulated in the water reservoir 86 overflows, it passes through the overflow opening 90, the drainage passage 88 of the muffler 84, and the like, and is discharged from the drain port (not shown) formed in the lower casing 4 as described above. Drained to the outside of the outboard motor.

When the outboard motor constructed as described above is driven, the temperature of the engine 7 is low at the beginning of driving, so that the temperature of the cooling water in the cylinder cooling water passage 91 for cooling the cylinder 11 is often low. In this case, thermostat 1
19 is closed, and the cooling water pumped up by the water pump 27 passes through the cooling water passage 93 for the cylinder block exhaust passage and the cooling water passage 101 for the cylinder head exhaust passage as described above, and passes through the pressure valve 114. It is drained to the reservoir 86. Therefore, the cooling water cools the exhaust passage 79 of the cylinder block 20 and the exhaust passage 32 of the cylinder head 22, but the cylinder 11 and the combustion chamber 11a are hardly cooled. As a result, the exhaust gas of the engine 7 can be sufficiently cooled, and the cylinder 11 and the combustion chamber 11a are not unnecessarily cooled.

Then, with the passage of time, the engine 7
The temperature rises, and when the temperature of the cylinder 11 rises, the thermostat 119 opens accordingly. Then, the cooling water that has passed through the cylinder block exhaust passage cooling water passage 93 and the cylinder head exhaust passage cooling water passage 101 to reach the vicinity of the pressure valve 114 flows into the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103. In addition, the cooling water existing in the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103 and having a thermostat set temperature or higher is pushed out, passes through the thermostat 119, and is discharged to the water pool 86 via the return cooling water passage 94. It The cooling water passage 93 for the cylinder block exhaust passage
The cooling water pumped up by the water pump 27 flows into the cooling water passage 101 for the cylinder head exhaust passage. Cylinder cooling water passage 91 and combustion chamber cooling water passage 1
The thermostat 119 is closed by the new inflow of cooling water below the thermostat set temperature into 03. Therefore, the cooling water can cool the exhaust passage 79 of the cylinder block 20 and the exhaust passage 32 of the cylinder head 22 as well as the cylinder 11 and the combustion chamber 11a. As a result, the exhaust gas of the engine 7 can be sufficiently cooled and the cylinder 11
Also, the combustion chamber 11a can be cooled.

When the thermostat 119 is closed, the cooling water pumped by the water pump 27 passes through the cylinder block exhaust passage cooling water passage 93 and the cylinder head exhaust passage cooling water passage 101 as described above. The water is drained to the water reservoir 86 via the pressure valve 114.

Since the outboard motor is constructed in this manner, for example, when the water temperature outside the outboard motor is about 20 ° C. and the set temperature of the thermostat 119 is set to about 60 ° C. When the temperature of 7 is low, the water passing through the cylinder block exhaust passage cooling water passage 93 and the cylinder head exhaust passage cooling water passage 101 becomes, for example, about 40 ° C., and the cooling water near the thermostat 119 becomes 40 ° C. or more and 60 ° C. Less than Therefore, since the thermostat 119 is closed, the cooling water is drained through the pressure valve 114 as described above.

On the other hand, when the temperature of the engine 7 is high, the water passing through the cooling water passage 93 for the cylinder block exhaust passage and the cooling water passage 101 for the cylinder head exhaust passage becomes, for example, about 40 ° C., and the cooling water near the thermostat 119 becomes, for example. It will be 60 ° C or higher. Therefore, the thermostat 119 is opened, and as described above, the cooling water passes through the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103, and then is drained through the thermostat 119.

As described above, regardless of whether the temperature of the engine 7 is low or high, the cooling water always flows through the cooling water passage 93 for the cylinder block exhaust passage and the cooling water passage 101 for the cylinder head exhaust passage, and the exhaust passage 32 , 79 are always cooled. On the other hand, the cylinder 1 of the engine 7 is provided in the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103.
The cooling water flows only when the temperature of 1 is high, and the cooling water passage 91 for the cylinder and the cooling water passage 103 for the combustion chamber are provided.
Into the cylinder block exhaust passage cooling water passage 93 and the cylinder head exhaust passage cooling water passage 101, for example, water of 40 ° C. flows in. Therefore, cylinder 1
1 and the combustion chamber 11a are not rapidly cooled at the water temperature outside the outboard motor, for example, 20 ° C., the non-uniform temperature distribution of the cylinder 11 and the combustion chamber 11a is reduced, and the temperature is temporally changed. Change also decreases. As a result, it is possible to prevent the cylinder 11 from being deformed.

In FIG. 2, reference numeral 126 is an alternator for power generation, reference numeral 127 is a belt for driving the alternator,
Reference numeral 128 is a starter motor for starting. An alternator 126 is provided on one side of the crankcase 21, while
A starter motor 128 is provided on the other side of the crankcase 21.
Is arranged. By disposing the heavy alternator 126 and the starter motor 128 on substantially opposite sides of the crankshaft 8, the crankshaft 8
The left and right weight balance is secured.

As described above, in this embodiment, the return cooling water passage 94 is arranged in the cylinder block 20 and is provided at the corner of V formed between the plurality of cylinders 11. There is. Therefore, the engine 7 can be made compact and the number of parts can be reduced as compared with the case where the return cooling water passage 94 is arranged at another place.

The pulley 41 for driving the timing belt 48 is conventionally nut-tightened, but in this embodiment, it is press-fitted into the crankshaft 8. Therefore, it is not necessary to thread the crankshaft 8 to tighten the nut of the pulley 41, and the number of working steps is reduced. Moreover, stress concentration due to the screws is not generated. In addition, the diameter of the tapered portion 8a to which the flywheel 42 is attached can be increased, and the strength of the tapered portion 8a can be improved. Further, the height can be reduced by the amount of the nuts removed.

Further, the cooling water passage 93 for the cylinder block exhaust passage and the cooling water passage 101 for the cylinder head exhaust passage are provided.
And cooling water passage 91 for cylinder and cooling water passage 1 for combustion chamber
03 are arranged in series, the exhaust passage 79 of the cylinder block 20 cooled by the cylinder block exhaust passage cooling water passage 93 is cooled most efficiently. Therefore, it is possible to prevent the thermal influence of the combustion gas from being applied to the cylinder block 20. As a result, uneven temperature distribution of the cylinder block 20 is reduced, and deformation of the cylinder block 20 can be prevented. Further, the cylinder cooling water passage 91 and the combustion chamber cooling water passage 1
Since 03 is supplied with appropriately heated water and is not supplied with low-temperature water, rapid cooling of the cylinder 11 and the combustion chamber 11a is reduced.

The temperature of the water flowing through the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103 is controlled by a thermostat 119. That is, the temperature-controlled water flows in the cylinder cooling water passage 91 and the combustion chamber cooling water passage 103, and the cylinder 11 and the combustion chamber 11a can be controlled to the optimum temperature.

Further, since the cooling water passage 93 for the cylinder block exhaust passage is arranged between the exhaust passage 79 of the cylinder block 20 and the cooling water passage 91 for the cylinder, the heat of the exhaust passage 79 is converted into the exhaust gas of the cylinder block. The cylinder cooling water passage 9 is blocked by the passage cooling water passage 93.
1 does not have much heat effect. Therefore,
The deformation of the cylinder 11 due to the heat of the exhaust passage 79 is reduced. By the way, if the cylinder block exhaust passage cooling water passage 93 does not block the heat of the exhaust passage 79, the exhaust passage 79 is unevenly distributed in the central portion of the V-shape of the cylinder block 20. Cylinder block 20
Therefore, the temperature distribution becomes uneven, and the cylinder block 20 is deformed into strain. As a result, problems such as image sticking occur.

The embodiment of the present invention has been described in detail above.
The present invention is not limited to the above embodiment,
Within the gist of the present invention described in the claims,
Various changes can be made. Modification examples of the present invention are exemplified below. (1) In the embodiment, the engine 7 has six cylinders, but the number of cylinders can be changed appropriately.

(2) In the embodiment, the pulley 41 of the crankshaft 8 is provided with a pair of upper and lower timing belts 48. However, the number of timing belts 48 to be attached to the pulley 41 may be one. (3) In the embodiment, as shown in FIG.
The pressure valve 114 is attached to a water passage portion extending from a lower end portion which is an end portion of the cylinder head exhaust passage cooling water passage 101, but the pressure valve 114 is located near the end portion of the cylinder head exhaust passage cooling water passage 101. It is also possible to attach to.

[0046]

According to the present invention, the water sucked from outside the outboard motor is supplied to the cylinder cooling water passage and the combustion chamber cooling water passage after passing through the exhaust passage cooling water passage. The passage is cooled by cold water sucked from the outside of the outboard motor, while the cylinder and the combustion chamber are cooled by water warmed in the exhaust passage. Therefore, the exhaust passage is efficiently cooled with cold water. On the other hand, the cylinder and the combustion chamber are gently cooled with warm water, and quenching with cold water is reduced. Therefore, the non-uniform temperature distribution around the cylinder is reduced, and the temporal change in the temperature around the cylinder is reduced. As a result, since the deformation of the cylinder is reduced, it is possible to prevent the occurrence of seizure, the increase of oil consumption, and the increase of blow-by gas.

Further, since the cooling water is supplied to the cooling water passage for the cylinder head exhaust passage after passing through the cooling water passage for the cylinder block exhaust passage, the temperature of the cooling water is higher than that of the cooling water passage for the cylinder block exhaust passage. However, the temperature becomes lower than that of the cooling water passage for the cylinder head exhaust passage. Therefore, it is possible to cool the cylinder block, which is problematic when deformed by heat or the like, more efficiently than the cylinder head. Therefore, the deformation of the cylinder block can be reduced.

Further, a thermostat is provided near the outlets of the cooling water passage for the cylinder and the cooling water passage for the combustion chamber, and the pressure valve has a cooling water passage for the exhaust passage, the cooling water passage for the cylinder and the cooling water passage for the combustion chamber. It may be provided near the connecting part with. In this case, the temperature of the water flowing in the cylinder cooling water passage and the combustion chamber cooling water passage can be controlled by a thermostat.
Therefore, when the temperature of the cylinder and the combustion chamber is low, the cylinder and the combustion chamber are not unnecessarily cooled, and the output efficiency of the engine is improved. Also, when the thermostat is closed, the pressure of the cooling water is released by the pressure valve.Since this pressure valve is located near the outlet of the cooling water passage for the exhaust passage, there is no cooling in the cooling water passage for the exhaust passage. Water is constantly flowing, and the exhaust passage can be constantly cooled. As a result, the exhaust passage is efficiently cooled, and it is possible to prevent the heat of the exhaust passage from adversely affecting other parts such as the cylinder, for example, uneven heating.

When the exhaust passage is provided with a cylinder block exhaust passage provided in the cylinder block of the engine, a part of the exhaust passage is provided in the cylinder block, and therefore the exhaust passage is provided separately. It is possible to reduce the number of parts and to reduce the weight of the engine, as compared with the case where the engine is formed. Moreover, since the cylinder block exhaust passage communicates with the left and right cylinder head exhaust passages and is also used as the left and right cylinder exhaust passages, the number of parts is further reduced. Since the cylinder block exhaust passage is arranged between the cylinders which are arranged adjacent to each other in the V-shape on the left and right sides, the engine becomes compact. Further, since the pressure valve is also arranged between the left and right cylinder heads in a plan view, the pressure valve does not significantly protrude to the outside of the engine, and the engine becomes compact.

Further, the exhaust passage cooling water passage may be arranged between the cylinder block exhaust passage and the cylinder cooling passage. In this case, since the exhaust passage is provided in the cylinder block as described above, the number of parts is reduced. Moreover, the heat in the cylinder block exhaust passage is blocked by the exhaust passage cooling water passage, so that the heat in the cylinder block exhaust passage is reduced from being transferred to the cylinder cooling water passage. As a result, the water in the cylinder cooling water passage is less heated by the heat of the cylinder block exhaust passage, and the water in the cylinder cooling water passage can efficiently cool the cylinder.

[Brief description of drawings]

FIG. 1 is a partially cutaway sectional view of an outboard motor according to the present invention.

FIG. 2 is a plan view showing an internal structure of the outboard motor of FIG.

3 is a cross-sectional view for explaining the internal structure of the outboard motor of FIG.

FIG. 4 is an explanatory diagram for explaining a throttle valve and a surge tank.

FIG. 5 is a circuit diagram of a cooling water channel.

FIG. 6 is an enlarged view of a main part of FIG.

FIG. 7 is an enlarged view of a main part of FIG.

FIG. 8 is an enlarged cross-sectional view of a portion of the timing belt pulley.

[Explanation of symbols]

 Reference Signs List 7 engine 11 cylinder 11a combustion chamber 20 cylinder block 22 cylinder head 27 water pump 32 exhaust passage 79 exhaust passage 91 cylinder cooling water passage 93 cylinder block exhaust passage cooling water passage 101 cylinder head exhaust passage cooling water passage 103 combustion chamber cooling water passage 114 Pressure valve 119 thermostat

Claims (5)

[Claims] 1. An exhaust passage for exhausting engine combustion gas, an exhaust passage cooling water passage for cooling the exhaust passage, a cylinder cooling water passage for cooling the engine cylinder, and a combustion chamber for the engine. A cooling water channel for the combustion chamber and a pump for sucking in water outside the outboard motor are provided. The pump supplies the sucked water to the cooling water channel for the exhaust passage and then supplies it to the cooling water channel for the exhaust passage. Water is supplied to the cylinder cooling water passage and the combustion chamber cooling water passage after passing through the exhaust passage cooling water passage,
Then, after passing through the cylinder cooling water passage and the combustion chamber cooling water passage, the cooling structure for the outboard motor is drained to the outside of the outboard motor. 2. The exhaust passage comprises a cylinder head exhaust passage provided in a cylinder head of an engine and a cylinder block exhaust passage provided in a cylinder block of the engine, and the exhaust passage. The cooling water passage includes a cylinder head exhaust passage cooling water passage and a cylinder block exhaust passage cooling water passage, and the water sucked by the pump passes through the cylinder block exhaust passage cooling water passage, The cooling structure for an outboard motor according to claim 1, wherein the cooling structure is supplied to a cooling water passage for a head exhaust passage. 3. A thermostat is provided in the vicinity of the outlets of the cylinder cooling water passage and the combustion chamber cooling water passage, and a pressure valve is provided for controlling the exhaust passage cooling water passage and the cylinder cooling water passage. The cooling structure for an outboard motor according to claim 1 or 2, wherein the cooling structure is provided in the vicinity of a connection portion with the cooling water passage for the combustion chamber. 4. The cylinders of the engine are arranged in a cylinder block so as to be divided into left and right directions to form a V-shape, and the combustion chamber side of the left cylinder is closed by the left cylinder head, while the right cylinder is closed. The combustion chamber side is closed by the cylinder head on the right side, and the exhaust passage for exhausting the combustion gas of the engine is provided in the cylinder head exhaust passage provided in each of the left and right cylinder heads and in the cylinder block of the engine. And a cylinder block exhaust passage, which communicates with the left and right cylinder head exhaust passages and between the cylinders arranged adjacent to each other in the V-shape on the left and right. And a thermostat is provided in the cooling water passage through which the cooling water for cooling the engine flows. Has pressure valve is provided on the upstream side of the thermostat, the cooling structure of the outboard motor, characterized in that the pressure valve is disposed between the cylinder head cross the right and left in the plan view as viewed. 5. An exhaust passage for exhausting combustion gas of an engine, an exhaust passage cooling water passage for cooling the exhaust passage, a cylinder cooling water passage for cooling the cylinder of the engine and provided in a cylinder block. The exhaust passage includes a cylinder head exhaust passage provided in a cylinder head of an engine and a cylinder block exhaust passage provided in a cylinder block of the engine. A cooling structure for an outboard motor, wherein a cooling water passage is arranged between the cylinder block exhaust passage and the cylinder cooling water passage.