JPH09250390A - Heat insulating structure for outboard engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the temperature distribution around a cylinder uniform for each cylinder and to make the deformation of the cylinder small while an engine is being driven in the engine for an outboard motor wherein an exhaust passage is integrally formed with a cylinder block for an engine main body. SOLUTION: In an outboard engine having an integrally formed exhaust passage 36 for collecting exhaust gas passing the combustion room of each cylinder and the exhaust port 35 of a cylinder head 14 and discharging it toward the lower part of the engine body, a heat insulating space is formed between the exhaust passage and the water jacket 74 around the cylinder not to transmit the heat of the exhaust gas to the periphery around the cylinder 37.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outboard engine mounted on a small boat, and more particularly to a heat insulating structure for exhaust gas heat in such an engine.

[0002]

2. Description of the Related Art In an outboard motor mounted on a small boat, an engine body in which cylinders are vertically arranged so that a crankshaft is in a vertical direction is housed in a top cowling on an upper part of the outboard motor. In such an outboard engine, the exhaust gas that has passed through the intake port of the cylinder head from the combustion chamber of each cylinder is gathered below the engine body so that the entire engine can be stored in a compact state inside the engine. A structure in which an exhaust passage for discharging is integrally formed with a cylinder block of an engine body is conventionally known.

[0003]

By the way, in the conventional outboard motor engine in which the exhaust passage is integrally formed in the cylinder block as described above, although the water jacket is formed around the cylinder, the exhaust gas is exhausted. Since the heat of the exhaust gas is directly transmitted around the passage-side cylinder, a great difference occurs in the temperature around the cylinder between the exhaust side and the intake side of the engine body.

In order to insulate the heat of the exhaust gas, it may be possible to increase the size of the water jacket around the cylinder on the side of the exhaust passage. As such, the water jacket around the cylinder on the exhaust side and the intake side. If the size of the engine is changed, the cooling effect of the water jacket will change between the exhaust side and the intake side depending on the engine operating condition. Will occur.

As a result, the temperature around the cylinder of the cylinder block becomes non-uniform, so that the deformation of the cylinder during engine operation increases, and seizure and blow-by gas increase due to an increase in resistance when the piston slides. However, there arises a problem that the consumption of oil also increases.

[0006]

In order to solve the above problems, the present invention provides a cylinder block of an engine body in which cylinders are arranged in a vertical direction as described in claim 1 above. On the other hand, in the engine for an outboard motor, which is integrally formed with an exhaust passage for collecting exhaust gas from the combustion chamber of each cylinder through the exhaust port of the cylinder head and discharging the exhaust gas below the engine body, A heat insulating space is formed between the passage and the water jacket around the cylinder to prevent heat of the exhaust gas from being transmitted around the cylinder.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the heat insulating structure for an outboard engine according to the present invention will be described below with reference to the drawings.

FIG. 1 is an external view of an outboard motor equipped with an engine to which the heat insulating structure of the present invention is applied, viewed from the starboard side. The outboard motor 1 includes a top cowling 2 and an upper case 3. Each component is stored in the housing formed by the lower case 4, and the top cowling 2 is
It is composed of an upper cowl 2a, a bottom cowl 2b, and an air duct cover 2c. The upper case 3 has an upper portion covered with an apron 5, and a lower case 4
The propeller 6 is attached to the
It is attached to the rear plate of the hull 8 so as to be vertically and horizontally rotatable.

2 to 5 show the installation state of each component inside the housing of the outboard motor 1, FIG. 2 shows the inside of the outboard motor 1 as seen from the starboard side, and FIG. FIG. 4 shows a portion of the top cowling 2, FIG. 4 shows a portion of the upper case 4, and FIG. 5 shows the inside of the top cowling 2 as seen from above.

The outboard motor 1 has a 4-cycle 4-cylinder L-type engine 10 in which the cylinders are arranged in a vertical direction and is fixed to the upper surface of an exhaust guide 11 installed between the bottom cowl 2b and the upper case 3. And the upper surface side is the cover member 1
It is stored in the top cowling 2 on the upper side in a state covered with 2.

As shown in FIG. 3 or 5, the engine 10 has a main body portion having a head cover 13, a cylinder head 14, a cylinder body 15 and a cylinder block 15 constituting a part of a crank chamber, and a crank case 16. Is integrally formed along the front-rear direction of the hull, and the crankcase 16 side is the front part.
The head cover 13 is arranged so that the side thereof is the rear part.

The cylinder head 14 is provided with intake / exhaust valves 17 and 18 for each cylinder, and cam shafts 20 and 21 for driving the valves 17 and 18 are arranged so that their rotation axes are vertical. In addition, the cam cap 22 covered by the head cover 13 and the bearing portion of the cylinder head 14 are pivotally supported, and cam pulleys 23, 24 are fixed to the upper ends of the cam shafts 20, 21, respectively.

In the crank chamber 25 defined by the front portion of the cylinder block 15 and the crankcase 16,
A crankshaft 26 is axially supported so that the rotation axis direction is the vertical direction, a flywheel 27 is fixed to the upper end of the crankshaft 26, and a timing pulley 30 is fixed below the flywheel 27. The timing pulley 30 and the cam pulleys 23, 2
4, a timing belt 28 for transmitting the rotation of the crankshaft 26 to the camshafts 20 and 21 of the intake / exhaust valves 17 and 18 is stretched.

For the timing belt 28,
A tensioner 29 for preventing the slack is arranged, and the tensioner 29 is constantly urged by a gas cylinder (not shown) in which gas is enclosed so as to press the timing belt 28 inward.

On the front left side of the engine 10, a surge tank 31 which is integrally connected to the front surface of the crankcase 16 and serves as an air introduction portion of the intake path is installed, and an intake passage extending from the surge tank 31. The throttle ports 32 are connected to the intake ports 34 of the respective cylinders, which are formed in the left side portion of the cylinder head 14 at intervals in the vertical direction, through the throttle portion 33.

Exhaust ports 35 connected to the combustion chambers of the cylinders are formed in the right side portion of the cylinder head 14 at intervals in the vertical direction. An exhaust passage 36 for collecting and exhausting exhaust gas to the lower side of the engine main body is provided with a cylinder 37.
The exhaust passage 36, which is formed integrally with the cylinder block 15 on the right side of and extends vertically in the cylinder block 15, has its lower end connected to the exhaust passage 11 a of the exhaust guide 11.

In the above engine 10, an oil pump 38 for sucking lubricating oil from an oil pan arranged below the exhaust guide 11 is inserted into an oil passage provided in the engine body. A thermostat valve 41 for controlling the discharge amount of the cooling water according to the temperature around the cylinder and the combustion chamber with respect to the cooling water cooling path provided in the engine body. A pressure valve 42 for releasing cooling water from the cooling passage is provided so that the water pressure in the cooling passage does not exceed a predetermined value.

A fuel pump 43 for supplying fuel to the engine 10 from a fuel tank (not shown) installed in the hull 8 is arranged on the intake side of the engine 10. A pilot water supply pipe 44 for taking out a part of the cooling water from the cooling passage of the engine body and discharging it as pilot water from the water outlet 45 of the top cowling 2 is connected to the exhaust side thereof.

As shown in FIG. 4, the upper case 3 located below the top cowling 2 is provided with a water reservoir 50 for temporarily receiving the cooling water returned from the engine 10, and the water reservoir 50 is defined. In a state of being isolated from the section 50,
A drive shaft 51 having an upper end connected to the crank shaft 26 of the engine 10 is vertically penetrated so that the lower end portion extends into the lower case 4.

A drive shaft 51 passing through the upper case 3
A water pump 52 that is driven in association with the rotation of the drive shaft 51 is installed in the vicinity of the lower case 4 of FIG.
A cooling water suction pipe extending downward is connected to a water inlet in the lower case 4, and an upward cooling water supply pipe 53 extending through the upper case 3 to the engine 10 is connected.
Is connected.

On the other hand, the water reservoir 50 of the upper case 3 is provided with an oil pan 54 having a bottom so as to be in close contact with the lower surface of the exhaust guide 11 and the upper open portion thereof is closed by the lower surface of the exhaust guide 11. The oil pan 54 is integrally provided with a cylindrical exhaust pipe insertion portion 54a which vertically penetrates a space portion inside the oil pan 54 from the vicinity of the center of the bottom portion thereof.

Further, below the oil pan 54 of the water reservoir portion 50, an exhaust gas discharge port 55a is provided on the bottom wall so that the open upper surface thereof is covered by the lower surface of the oil pan 54 including the exhaust pipe insertion portion 54a. Muffler (exhaust gas expansion chamber) 5
5 is installed, and the internal space of the muffler 55 communicates with an exhaust passage (not shown) defined in the lower case 4 via an exhaust gas outlet 55a.

An exhaust pipe 56 connected to the exhaust passage 11a of the exhaust guide 11 is attached to the exhaust pipe insertion portion 54a of the oil pan 54, and the lower end of the exhaust pipe 56 projects downward from the oil pan 54. Muffler 55
The interior space of the muffler 55 is opened inside and communicates with the exhaust passage 36 of the engine 10 via the exhaust pipe 56 and the exhaust passage 11 a of the exhaust guide 11.

Inside the oil pan 54, the oil pan 5
The suction pipe 57 for sucking the oil accumulated in the No. 4 and sending it to the oil pump 38 of the engine 10
It is provided so as to protrude downward from the lower surface of the exhaust guide 11.

On the peripheral wall of the oil pan 54, the oil pan 5
4 is integrally formed with a water conduit 58 for overflowing water in the water reservoir 50 surrounding the water reservoir 4, and the water passage of the water conduit 58 with the water inlet opening on the water reservoir 50 side is
The water drop port 3a of the upper case 3 is inserted through a water passage portion 55b integrally formed on the upper end of the peripheral wall of the muffler 55.
Is communicated to.

In the upper case 3, a drainage passage 59 extending from the water drop port 3a to the lower case 4 is defined below, and an idle expansion chamber 60 communicating with the muffler 55 is defined above. Idle expansion chamber 6
At 0, an exhaust hole 61 and a drain hole 62 communicating with the outside of the machine are opened.

Although not shown, the lower case 4 located below the upper case 3 has a lower end portion of a drive shaft 51 penetrating the upper case 3 pivotally supported, and the lower end portion of the drive shaft 51 is The rotary shaft of the propeller 6 mounted on the lower case 4 is connected via the shift conversion gear portion.

Although not shown, the lower case 4
Is provided with an inlet for cooling water sucked up by the water pump 52, and the upper case 3
An exhaust passage for discharging the exhaust gas sent through the muffler 55 into the water with the rotation of the propeller 6 is defined, and cooling for discharging the cooling water dropped from the upper case 3 to the outside of the machine. A water drain is defined.

Regarding the exhaust path of the outboard motor 1 in which the respective members are arranged as described above, the exhaust gas discharged downward from the exhaust passage 36 formed in the main body of the engine 10 is the exhaust passage of the exhaust guide 11. It is sent into the muffler 55 through 11a and the exhaust pipe 56, and the idle expansion chamber 6
It is released into the atmosphere from 0 through the exhaust hole 61 and
During traveling while the propeller 6 is rotating, most of the exhaust gas is discharged from the exhaust gas exhaust port 55a of the muffler 55 through the exhaust passage in the lower case 4 into the water as the propeller 6 rotates.

In the cooling path of the outboard motor 1, the cooling water sucked up from the water inlet of the lower case 4 by the water pump 52 is cooled by the cooling water supply pipe 53 while the inside of the upper case 3 is being cooled. After cooling the engine 10 in a state where excess cooling water is returned to the upper case 3 through the pressure valve 42 so that the pressure of the cooling water in the engine 10 does not exceed a predetermined value. After being returned to the upper case 3 via the thermostat valve 41 and further cooling around the oil pan 54 and the muffler 55,
It falls into the lower case 4 and is discharged out of the machine from the cooling water discharge part.

In the outboard motor 1 as described above, the water pump 52 is provided in the engine 10 in which the exhaust passage 36 is integrally formed in the cylinder block 15.
In order to cool the cylinder of the engine body and the surroundings of the combustion chamber and the exhaust passage with the cooling water supplied through the cooling water supply pipe 53, as shown in FIG. Cooling water passage (water jacket) 73 around the combustion chamber and cooling water passage 72 (water jacket) around the exhaust passage (exhaust port 29)
Cylinder block 1
5, a cooling water passage (water jacket) 74 around the cylinder 37 and a cooling water passage (water jacket) 71 around the exhaust passage 36 are provided.

As shown in FIG. 7, each of the cooling water channels 71, 72, 73, 74 is a vertical cooling water channel because of the vertical arrangement of the cylinders. The cooling water supplied from the supply pipe 53 through the exhaust guide 11 can be discharged from the upper part of the engine body (cylinder block 15) through the cooling water paths 71, 72, 73, 74 so that the cooling water paths 71, 72, 73, 74
Are connected so as to form one cooling path.

Then, as described above, the respective cooling water channels 71, 7
In the cylinder block 15 of the engine 10 in which 2, 73 and 74 are formed, as shown in FIG. 6, in addition to the cooling water passages 71 and 74, the engine 10 is discharged from the cooling passage through the thermostat valve 41. A cooling water return passage 77 for returning the cooling water into the upper case 3 is formed, and a heat insulating space is further provided between the cooling water passage (water jacket) 74 surrounding the cylinder 37 and the exhaust passage 36. 76 is formed.

The heat insulating space 76 is formed so as to prevent heat of the exhaust gas passing through the exhaust passage 36 from being transmitted around the cylinder 37. In the present embodiment, the heat insulating space 76 is formed in the vertical direction. And is formed as an air layer by an open space that extends to one side and is open on one side.

According to the heat insulating structure of the engine 10 for an outboard motor of the present embodiment in which the heat insulating space 76 is formed in the cylinder block 15 as described above, the water jacket 74 surrounding the cylinder 37 is connected to the exhaust side and the intake side. Since the heat of the exhaust gas passing through the exhaust passage 36 is blocked by the adiabatic space 76 and is not transferred to the surroundings of the cylinder 37, the surroundings of the cylinder 37 are irrelevant regardless of the operating state of the engine. Temperature becomes uniform,
It is possible to suppress deformation of the cylinder 37 during engine operation, prevent seizure and increase of blow-by gas when the piston slides, and suppress oil consumption.

Although one embodiment of the heat insulation structure for an outboard engine according to the present invention has been described above, the present invention is not limited to the above embodiment, and is shown in FIG. 8, for example. As shown in FIG.
1, 72, 73, 74 and cooling water return passage 77,
It is also possible to implement it by forming it as a water passage through which water having a water temperature not much different from the temperature outside the engine passes.

[0037]

According to the heat insulation structure for an outboard engine of the present invention as described above, the cylinder in each cylinder is formed even though the exhaust passage is integrally formed in the cylinder block of the engine body. Since the temperature distribution around the area can be made uniform, deformation of the cylinder during engine operation can be reduced, seizure characteristics can be improved, blow-by gas can be reduced, and oil consumption can also be prevented from increasing. can do.

[Brief description of drawings]

FIG. 1 is a side view schematically showing an outboard motor equipped with an engine to which a heat insulating structure of the present invention is mounted, as viewed from a starboard side.

FIG. 2 is a partial cross-sectional explanatory view showing the internal structure of the outboard motor shown in FIG. 1 as seen from the side.

3 is a partial cross-sectional explanatory view showing a top cowling portion of the internal structure of the outboard motor shown in FIG. 2, as viewed from the side.

FIG. 4 is a cross-sectional explanatory view showing an upper case portion of the internal structure of the outboard motor shown in FIG. 2 as seen from the side.

5 is a cross-sectional explanatory view seen from above showing a top cowling portion of the internal structure of the outboard motor shown in FIG.

FIG. 6 is a partially enlarged cross-sectional view of an engine showing an embodiment of a heat insulating structure for an outboard engine according to the present invention.

7 is a rear view of the cylinder block seen from the direction of arrow A in FIG.

FIG. 8 is a partially enlarged cross-sectional view of an engine showing another embodiment of the heat insulation structure for an outboard engine according to the present invention.

[Explanation of symbols]

 1 Outboard Motor 10 Engine 14 Cylinder Head 15 Cylinder Block 35 Exhaust Port 36 Exhaust Passage 37 Cylinder 74 Water Jacket Around Cylinder 76 Insulation Space

Claims (1)

[Claims] 1. To collect exhaust gas from a combustion chamber of each cylinder through an exhaust port of a cylinder head into a cylinder block of the engine main body in which each cylinder is arranged in a vertical direction and discharge the exhaust gas below the engine main body. In an outboard motor engine in which the exhaust passage is integrally formed, an insulating space is formed between the exhaust passage and the water jacket around the cylinder to prevent heat of exhaust gas from being transmitted around the cylinder. Insulation structure for outboard engine.