JPH0232451B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an outboard motor equipped with a four-stroke engine, and particularly to the structure of its exhaust system.

[Prior art] For example, an outboard motor is disclosed in "Publication No. 47-27113".
As described in , a cowling is removably placed on the upper end of the casing through which the drive shaft is inserted. An engine is housed within this cowling, and this engine is directly fixed to the upper end of the casing.

Inside this casing, an exhaust path is formed that includes an exhaust expansion chamber that guides exhaust from the engine to reduce exhaust noise and discharges the exhaust into water to reduce air pollution. .

Incidentally, when the above-mentioned engine is a water-cooled four-stroke engine, this type of engine is constructed by connecting a cylinder head to the rear surface of a cylinder block, and this cylinder head is provided with an intake port and an exhaust port.

The exhaust port of this cylinder head is connected to the exhaust path in the casing, that is, the exhaust expansion chamber. Conventionally, the exhaust port is opened on the bottom surface of the cylinder head, and the exhaust port is connected to the exhaust expansion chamber on the upper end surface of the casing. By opening a continuous exhaust passage and directly overlapping the lower surface of the cylinder head with the upper end surface of the casing, the exhaust passage and the exhaust port are communicated with each other.

[Problems to be Solved by the Invention] However, according to the above conventional structure, the cylinder block is located at a predetermined position on the upper surface of the casing.
Further, the cylinder head is communicated with a predetermined position on the rear surface of the cylinder block, and the exhaust ports opening on the lower surface of the cylinder head must be aligned and connected to the exhaust passages opening on the upper surface of the casing.

That is, the casing, the cylinder block and the cylinder head, and the exhaust port of the cylinder head and the casing must be connected in a closed loop position with respect to each other.

However, variations in processing and assembly errors occur in the interconnection of each component, including the cylinder block, and in the conventional case, for example, the cylinder head is connected to the cylinder block, and If the cylinder head is connected to a predetermined position so as to match, problems may occur such as the exhaust port of the cylinder head not being aligned with the exhaust passage of the casing, and assembly work may be time-consuming.

Further, even if a special exhaust pipe is used to connect the exhaust port of the cylinder head and the exhaust passage of the casing, there is a problem that alignment accuracy is difficult to obtain.

Furthermore, in the above conventional outboard motor, the high temperature exhaust from the exhaust port is directly guided to the exhaust expansion chamber within the casing, resulting in a large temperature rise in the casing. Moreover, in this case, since the engine's cylinder head is directly fixed to the upper end of the casing, the heat of the casing is easily transmitted to the cylinder head, which increases the thermal influence on the cylinder head and causes overheating. There is a problem that could be the cause.

In addition, in the case of a two-stroke engine, the exhaust port is formed not in the cylinder head but in the lower surface of the cylinder block, so if the cylinder block is fixed in a predetermined position in the casing, the exhaust port is directly connected to the exhaust path. It can be connected to the exhaust expansion chamber of 1, and the above-mentioned problems are less likely to occur.

The present invention has been made based on the above circumstances, and its purpose is to facilitate assembly even when there are processing errors or assembly errors, to have excellent workability, and to have high assembly accuracy.
It is an object of the present invention to provide an exhaust system for an outboard motor that prevents a cylinder head housing a valve mechanism from being overheated by a casing and eliminates problems such as engine overheating.

[Means for Solving the Problems] In order to achieve the above object, the present invention arranges a four-stroke engine equipped with a cylinder block and a cylinder head connected to the rear surface of the cylinder block at the upper end of a casing into which a drive shaft is inserted. The cylinder head of this engine has an exhaust port that is opened and closed by an exhaust valve, and a cam chamber that accommodates a valve mechanism that opens and closes the exhaust valve. In the outboard motor, a spacer is interposed between the casing and the four-stroke engine, and a cylinder block of the four-stroke engine is placed on the upper surface of the spacer. At the same time, this spacer and the cylinder head are spaced apart from each other, a gap is provided between these spacers and the cylinder head, and a communication hole that connects to the exhaust expansion chamber is provided in the spacer, while the cylinder block is connected to the cylinder block. The present invention is characterized in that an exhaust passage is formed to communicate between the exhaust port of the cylinder head and the communication hole of the spacer, and a water jacket is provided around the outer periphery of the exhaust passage through which engine cooling water flows.

[Function] According to the present invention, when the cylinder block is attached to a predetermined position of the spacer connected to the upper end of the casing, the exhaust passage formed in the cylinder block matches the communication hole of the spacer and is connected to the exhaust expansion chamber on the casing side. Positioned and connected. and,
When the cylinder head is attached to such a cylinder block at a predetermined position, the exhaust port of the cylinder head is positioned and connected to the exhaust passage formed in the cylinder block.

Therefore, it is only necessary to pay attention to the positioning accuracy of the cylinder block relative to the casing, and it is also necessary to pay attention to the positioning accuracy of the cylinder head relative to the cylinder block, which reduces machining errors and assembly errors compared to the past. This makes it easier to absorb such substances, making it possible to assemble with high precision.

Moreover, in the case of the above configuration, the high-temperature exhaust gas immediately after being discharged from the exhaust port is indirectly cooled by the cooling water flowing within the water jacket before being guided to the exhaust gas expansion chamber within the casing. Therefore, the high-temperature exhaust gas does not need to be directly guided into the exhaust gas expansion chamber, thereby reducing the temperature rise in the casing.

At the same time, since there is a gap between the casing and the cylinder head, this gap becomes an insulating space and prevents the heat of the casing from being directly transmitted to the cylinder head.

Therefore, in addition to suppressing the temperature rise of the casing, the thermal influence of the exhaust gas on the cylinder head is reduced, and overheating of the cylinder head can be prevented.

[Example] The present invention will be described below based on an example shown in the drawings.

In the figure, reference numeral 1 denotes an outboard motor, which is attached via a bracket 2 to the transom of a hull (not shown) so that it can tilt up and down and swing left and right.

The outboard motor 1 has a cowling 6 removably attached to the upper end of a casing 5 formed by connecting an upper casing 3 and a lower casing 4.

An engine 7 is housed within the cowling 6. This engine 7 is a water-cooled four-stroke two-cylinder engine, and is rigidly mounted on a support plate 8 as a spacer attached to the upper end of the upper casing 3.

As shown in FIGS. 3 and 4, the engine 7 includes a pair of cylinders 1 in a cylinder block 9.
0 and 10 are arranged vertically, each cylinder 1
0 and 10 are constructed by arranging the cylinder axis in a substantially horizontal direction. Sleeves 11, 11 are attached to the inner surface of each cylinder 10, 10, and pistons 12, 12 are slidably accommodated in these sleeves 11, 11.

The cylinders 10, 10 communicate with a crank chamber 14 within a crankcase 13. A crankshaft 15 is supported vertically in the crank chamber 14, and the crankshaft 15 is connected to the pistons 12, 12 via connecting rods 17, 17 by means of crank pins 16. connected.

The lower end of the crankshaft 15 is the drive shaft 18
is connected to the top of the As shown in FIG. 1, this drive shaft 18 is inserted vertically through the inside of the casing 5, and its lower end is connected to a propeller shaft 19 that is pivotally supported inside the lower casing 4. Shaft 19
It is designed to be able to rotate in forward and reverse directions.

A cylinder head 20 is attached to the rear surface of the cylinder block 9. As shown in FIG. 2, the cylinder head 20 is provided apart from the upper surface of the support plate 8, and there is a gap 20b between the cylinder head 20 and the support plate 8.
is formed.

The cylinder head 20 is formed with dome-shaped combustion chambers 21, 21 that extend into the cylinders 10, 10. Each combustion chamber 21, 21 has an intake port 2
2 and exhaust port 23 are opened adjacent to each other.

In the cylinder head 20, an intake passage 24 and an exhaust passage 25 are formed which are connected to the intake port 22 and the exhaust port 23, respectively.

The discharge passage 25 is provided in the cylinder head 20 so as to be curved toward the cylinder block 9 side, and its downstream end is opened at the end face of the cylinder head 20 on the cylinder block 9 side.

The cylinder head 20 is provided with an intake valve 26 and an exhaust valve 27 that open and close the intake port 22 and the exhaust port 23. These intake valves 26 and exhaust valves 27 are driven to open and close via camshafts 28 and rocker arms 29 serving as valve operating mechanisms. It is accommodated in the chamber 20a.

An oil pan 30 connected to the inside of the crank chamber 14 is suspended from the lower surface of the support plate 8.

As shown in FIG. 4, the cylinder block 9 has a bulging portion 31 on the side opposite to the open end surface of the discharge passage 25 which is curved toward the cylinder block 9 in the cylinder head 20. It is integrally bulged in the direction. As shown in FIG. 2, an exhaust passage 32 is integrally formed within this bulging portion 31. As shown in FIG. When the outboard motor is tilted down, this exhaust passage 32 has a downstream passage section 3 extending vertically inside the bulge 31.
2a, and an upstream passage portion 32b extending substantially horizontally from the upper end of the downstream passage portion 32a toward the rear cylinder head 20 side. The upstream passage portion 32b has communication ports 33, 33 that open on the surface where it meets the cylinder head 20, and these communication ports 3
3 and 33 are opposed to and communicated with the discharge passages 25 and 25, respectively.

Further, the lower end of the downstream passage portion 32b is connected to an exhaust port 52 opened on the lower surface of the cylinder block 9, as shown in FIG.
is connected to a communication hole 53 formed in the support plate 8.

The side surface of the bulging portion 31 is open, and an exhaust inner cover 34 and an exhaust outer cover 35 are bolted to the open side surface in a mutually overlapping state. The exhaust inner cover 34 has an overhanging portion 36 facing into the exhaust passage 32.
A cooling water passage 37 is formed between the projecting portion 36 and the exhaust out cover 35.

Also, inside the cylinder block 9, there is a cylinder 1.
0 and 10 and around the exhaust passage 32, water jackets 38 through which engine cooling water flows are provided, and these water jackets 38 and the cooling water passage 37 communicate with each other. There is.

Therefore, the outer periphery of the exhaust passage 32 is surrounded by the cooling water passage 37 and the water jacket 38.

Inside the cylinder head 20 are combustion chambers 21, 21.
A water jacket 39 is provided around the cylinder head 20, and the water jacket 39 on the cylinder head 20 side and the cylinder block 9 are connected to each other.
The side water jackets 38 are communicated with each other at the mating surface of the cylinder block 9 and cylinder head 20.

As shown in FIG. 2, the upper surface of the cylinder block 9 is provided with a communication chamber 40 that is connected to the water jacket 39 on the upper part of the cylinder head 20. A thermostat 42 is installed between the cap 41 and the cap 41. This thermostat 42 closes the valve 4 when the engine coolant temperature exceeds a certain range.
3 is opened, and the engine cooling water is supplied to the Atsupa casing 3 through the hose 44 connected to the cap 41.
It is designed to flow inside.

On the other hand, water inlets 45 are opened on both sides of the lower casing 4 shown in FIG. 1 to take in seawater, lake water, etc. from outside the machine as engine cooling water. This water inlet 45...
is connected to a water pump 46 provided at the lower end inside the Atsupa casing 3. water pump 4
6 is driven by a drive shaft 18, and a water tube 47 is provided at its discharge port.
is connected. This water tube 47 is conducted vertically inside the Atsupa casing 3 and communicates with a discharge passage 48 provided integrally with the oil pan 30 . A communication hole 49 is formed in the support plate 8 opposite to the upper end of the discharge passage 48, and this communication hole 49 communicates with a through hole 50 opened in the lower surface of the cylinder block 9. This through hole 50 is located around the water jacket 3 which is located around the exhaust passage 32 described above.
8.

Therefore, the engine cooling water pumped up by the water pump 46 first flows through the exhaust passage 32.
It is guided to the water jacket 39 of the cylinder block 9 through the water jacket 38 around the cylinder block 9 and the cooling water passage 37.

On the other hand, an exhaust pipe 54 is connected to the communication hole 53 formed in the support plate 8 . This exhaust pipe 54 passes through the inside of the oil pan 30 and is guided into the inside of the Atsupa casing 3, and the inside of this Atsupa casing 3 directly constitutes an exhaust expansion chamber 55.

Inside the lower casing 4 is an exhaust expansion chamber 5.
5 is formed, and this exhaust path 56 communicates with an opening 57 opened rearward in the lower rear end surface of the lower casing 4. For this reason, these exhaust passages 56 and exhaust expansion chambers 5
5 and the exhaust pipe 34 constitute an exhaust path along the vertical direction inside the casing 5. The rear end of the propeller shaft 19 is led out from this opening 57, and the propeller 5 is inserted into this led out portion.
8 is fixed. Boss portion 59 of propeller 58
has a triple cylinder structure, and inner and outer hollow parts 60 and 61 are formed between them.
These hollow parts 60 and 61 communicate with each other at their rear ends, and the front end of the inner hollow part 60 is connected to the opening 57, and the front end of the outer hollow part 61 is opened to the outside of the machine, and an exhaust port is formed. 62.

In addition, oil pan 3 through which engine cooling water flows
As shown in FIG. 2, a small hole 48 is formed in the peripheral wall of the discharge passage 48 of No.
A is opened, and a portion of the engine cooling water pumped up by the water pump 46 is spouted from this small hole 48a toward the exhaust pipe 54.

In addition, a bulkhead 6 is provided at the rear of the Atsupa casing 3.
3 is integrally molded, and the space surrounded by the partition wall 63 and the rear wall of the Atsupa casing 3 is
It forms a water storage section 64. Although not shown, a hose 44 connected to the thermostat 42 is led to this water storage section 64, and the engine cooling water discharged from this hose 44 is transferred to the water storage section 6.
Drainage port 6 opened in Atsupa casing 3 from 4
Water is drained out of the machine through 5.

The operation of the embodiment with such a configuration will be explained.

When the engine 7 is operating, the intake valve 26 opens, and fuel is introduced into the combustion chambers 21, 21 from the intake passage 24 and the intake port 22, together with air.
Also, by opening the exhaust valve 27, the combustion chamber 2
The combustion gases No. 1 and 21 are exhausted through the exhaust port 23 and the exhaust passage 25. The exhaust gas discharged into the exhaust passage 25 is led to an exhaust passage 32 formed in the cylinder block 9. The exhaust gas led to the exhaust passage 32 is led from the exhaust port 52 to the exhaust pipe 54 through the communication hole 53 formed in the support plate 8, and from this exhaust pipe 54 to the exhaust expansion chamber 55 inside the Atsupa casing 3. be discharged. The exhaust gas expanded in the exhaust expansion chamber 55 passes through the exhaust path 56 and reaches the propeller 5.
It is discharged into the water from an exhaust port 62 through an inner hollow part 60 and an outer hollow part 61 of the boss part 59 of No. 8.

Furthermore, while the engine 7 is in operation, water from outside the machine is sucked in as engine cooling water from the water inlets 45, and the pressure of this sucked engine cooling water is increased by the water pump 46.
It is pumped through the water tube 47 and the discharge passage 48 into the water jacket 38 located around the exhaust passage 32 of the cylinder block 9. The engine cooling water forced into the water jackets 38 also flows into the cooling water passage 37 and cools the exhaust passage 32 by flowing around the outer circumference of the exhaust passage 32.

After this, the engine cooling water flows into cylinders 10 and 10.
It is introduced into the water jacket 38 around the cylinder head 20 to cool the cylinders 10, 10, and then into the water jacket 39 of the cylinder head 20 to cool the area around the combustion chambers 21, 21.

The engine cooling water that cooled the cylinder head 20 is then transferred to the communication chamber 4 of the cylinder block 9.
0, where the thermostat 42 senses the cooling water temperature.

In this case, when the cooling water temperature reaches a certain temperature,
After the valve 43 is opened and the engine 7 has been cooled, the engine cooling water is guided through the hose 44 into the water storage section 64 in the Atsupa casing 3, and from there is drained to the outside through the drain port 65.

Further, a part of the engine cooling water forced into the discharge passage 48 is ejected from the small hole 48a toward the exhaust pipe 54, thereby cooling the exhaust pipe 54. The cooling water that has cooled the exhaust pipe 54 drops into the exhaust passage 56 through the exhaust expansion chamber 55 and is discharged into the water from the exhaust port 62 of the propeller 58 together with the exhaust gas.

According to such an embodiment, since the exhaust passage 32 is integrally formed in the cylinder block 9, if the cylinder block 9 is fixed at a predetermined position of the support plate 8 fixed to the upper casing 3, the above-mentioned The exhaust passage 32 is connected to an exhaust expansion chamber 55 via an exhaust pipe 54.

With respect to such a cylinder block 9, the cylinder head 20 is placed at a predetermined position, that is, the cylinder 1
0 and 10 and the combustion chambers 21 and 21 are connected so that they are aligned, the exhaust port 23 formed in the cylinder head 20 is connected to the exhaust passage 32 formed in the cylinder block 9.

That is, the cylinder block 9 is connected to the casing 5.
When the cylinder head 20 is attached to the cylinder block 9 at a predetermined position, the exhaust port 23 is connected to the exhaust expansion chamber 55 via the exhaust passage 32 formed in the cylinder block 9. The exhaust system is completed.

Therefore, it is only necessary to pay attention to the positioning accuracy of the cylinder block 9 with respect to the upper casing 3 side, and it is sufficient to pay attention to the positioning accuracy of the cylinder head 20 with respect to the cylinder block 9. There is no need to pay attention to the positioning accuracy of both the block 9 and the upper casing 3 at the same time.

Therefore, since it is only necessary to pay attention to the positioning accuracy of each part at one location, it is easier to absorb processing errors and assembly errors than in the past, improving work efficiency and achieving highly accurate assembly. It becomes possible to attach.

Moreover, since the exhaust passage 32 formed in the cylinder block 9 is surrounded by the water jacket 38 and the cooling water passage 37, the combustion chamber 2
The high-temperature exhaust gas immediately after being discharged from inside 1,21 is
It will be cooled before being led to the Atsupa casing 3 side. For this reason, Atsupa casing 3
Since the high-temperature exhaust gas is not directly led to the internal exhaust expansion chamber 35, the casing 5 can be prevented from being heated to a high temperature, and the thermal influence on the surroundings can be reduced.

Moreover, in this case, the water jacket 38 of the cylinder block 9 is used as is to cool the exhaust gas, so no special cooling mechanism is required, and therefore the exhaust gas can be sufficiently cooled with a simple structure. There are advantages.

Further, since a space 20b is formed between the support plate 8 and the cylinder head 20, this space 20b functions as a heat insulating space, and the heat of the casing 5 is transferred to the cylinder head 20.
It becomes difficult to convey the message directly.

Therefore, in addition to suppressing the temperature rise of the casing 5, the thermal influence of the exhaust gas on the cylinder head 20 is reduced, and overheating of the cylinder head 20 and overheating of the engine 7 due to this overheating can be prevented. Can be done.

Note that the engine according to the present invention is not limited to two cylinders, and can be implemented even if it is a single cylinder or multiple cylinders of three or more cylinders.

Further, in the above embodiment, the exhaust gas is discharged into the water through the boss portion of the propeller, but an exhaust port that opens below the water surface near the propeller may be provided in the lower casing, and the exhaust gas may be exhausted from this exhaust port. It's okay.

[Effects of the Invention] According to the invention detailed above, when the cylinder block is attached to a predetermined position of the spacer on the casing, the exhaust passage formed in the cylinder block is positioned and connected to the exhaust expansion chamber on the casing side, Furthermore, when the cylinder head is attached to the cylinder block at a predetermined position, the exhaust port of the cylinder head is positioned and connected to the exhaust passage of the cylinder block. Therefore, it is only necessary to pay attention to the positioning accuracy of the cylinder block relative to the casing, and it is also necessary to pay attention to the positioning accuracy of the cylinder head relative to the cylinder block, which reduces machining errors and assembly errors compared to the past. This makes it easier to absorb such substances, improves assembly work efficiency, and enables highly accurate assembly.

Moreover, the high-temperature exhaust gas immediately after being discharged from the exhaust port is indirectly cooled before being led to the exhaust expansion chamber inside the casing, so the high-temperature exhaust gas is not directly led into the exhaust expansion chamber. ,
Temperature rise in the casing is reduced. At the same time, since there is a gap between the casing and the cylinder head, this gap becomes an insulating space, making it difficult for the heat of the casing to be directly transmitted to the cylinder head.

Therefore, in addition to suppressing the temperature rise of the casing, the thermal influence of the exhaust gas on the cylinder head is reduced, and overheating of the cylinder head and overheating of the engine due to this overheating can be prevented.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a side view partially showing the entire outboard motor; FIG. 2 is a sectional view showing a state in which the internal heat engine and the Atsupa casing are connected;
Fig. 3 is a sectional view of the internal combustion engine, Fig. 4 is a sectional view taken along the direction perpendicular to the crankshaft of the internal combustion engine, Fig. 5 is a front view of the cylinder block, and Fig. 6 is taken along the - line in Fig. 5. The arrow view and FIG. 7 are front views of the cylinder head. 5... Casing, 7... Engine, 8... Spacer (support plate), 9... Cylinder block, 18... Drive shaft, 20... Cylinder head, 20a... Cam chamber, 20b... Between,
23...Exhaust port, 27...Exhaust valve, 28
...Camshaft, 29...Rocker arm, 32...Exhaust passage, 37...Cooling water passage, 38, 39...Water jacket, 53...Communication hole, 55...Exhaust expansion chamber.

Claims (1)

[Claims] 1. A 4-stroke engine equipped with a cylinder block and a cylinder head connected to the rear surface of the cylinder block is disposed at the upper end of the casing through which the drive shaft is inserted, and the cylinder head of this engine is connected to the exhaust valve. The cylinder head has an exhaust port that is opened and closed, and a cam chamber for accommodating a valve train that opens and closes the exhaust valve. In the outboard motor which is led into a chamber, a spacer is interposed between the casing and the four-stroke engine, the cylinder block of the four-stroke engine is connected to the upper surface of the spacer, and the spacer and the cylinder head are connected to the upper surface of the spacer. are spaced apart from each other, a gap is provided between these spacers and the cylinder head, and a communication hole is provided in this spacer that communicates with the exhaust expansion chamber, while a communication hole is provided in the cylinder block that communicates between the exhaust port of the cylinder head and the spacer. What is claimed is: 1. An exhaust system for an outboard motor, characterized in that an exhaust passage is formed in communication with a hole, and a water jacket is provided around the outer circumference of the exhaust passage through which engine cooling water flows.