JP2001099021A - Engine cooling structure of snowmobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve output of an engine of a snowmobile by suppressing temperature rise of an intake passage and thereby improving charging efficiency of intake. SOLUTION: A two-cycle engine 21 is mounted on a front portion inside a body cover 20a of a snowmobile 20. An exhaust device 22 such as a muffler and an intake device 23 such as an air cleaner or a carburetor are arranged on the front side of a main body of the engine 21, while a heat exchanger 24 is arranged on a rear side of the engine main body. An intake passage 25 for introducing intake to the engine 21 from the intake device 23 and an exhaust passage 26 for leading exhaust gas from the engine 21 to the exhaust device 22 are directed in substantially the same direction in respect to a running direction of the snowmobile 20 and arranged adjacently to each other. A cooling water passage 30 is formed in a housing 28 which composes an opening of the intake passage 25 of a crankcase 27, at a position faced to an exhaust pipe 29 on the exhaust passage 26. A communication structure 50 is arranged for communicating the cooling water passage 30 with a cooling water passage on its downstream side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cooling structure for a two-stroke engine, and more particularly to a cooling passage structure for a snowmobile engine.

[0002]

2. Description of the Related Art Conventionally, a small snowmobile called a snowmobile generally uses a water-cooled two-stroke engine (hereinafter, referred to as an engine) capable of obtaining a high output with a simple structure. The structure of the engine 2 is shown in FIGS.
As shown in FIG. 4, it is mounted on the front of the body of the snowmobile 1, and an exhaust device 3 is arranged in front of the engine body, and an intake device 4 and a heat exchanger 5 are arranged behind the engine body. Cooling water for cooling the engine 2 is sent from the heat exchanger 5 through a piping hose 6 and a water pump (not shown) to a cooling water passage (not shown) formed inside the engine from a lower portion of the engine body. The engine cools while traveling around the engine. In this way, the cooling water heated by the heat generated during the operation of the engine is sent from the upper portion of the engine to the heat exchanger 5 via a piping hose (not shown), and is cooled and then circulated again. ing.

[0003]

However, according to this structure, since the intake device 4 is disposed behind the engine body, the exhaust heat of the intake device 4 is weakened, and the radiant heat from the engine 2 is reduced by the intake device. 4 tends to be muffled. Furthermore, since the vicinity of the intake device 4 is heated by heat conduction from the engine body in a high temperature state, the charging efficiency of the intake air is deteriorated due to an increase in the intake air temperature, and therefore, there is a problem that the engine output decreases. In order to improve the cooling effect of the intake system, both the exhaust passage 11 and the intake passage 12 may be arranged in the same direction in front of the crankcase 10 as shown in FIG. If the exhaust passage 11 and the intake passage 12 are adjacent to each other due to space restrictions or the like, the intake passage 12 may be thermally affected by radiant heat from the exhaust passage 11,
The same problem as described above may occur. In addition,
The water jacket 13 for cooling the engine can be cooled only in the vicinity of the opening 11 a of the exhaust passage 11, which is provided on the outer peripheral portion of the engine cylinder 14.
Effective prevention of the above thermal effects is not possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and suppresses a rise in the temperature of an intake passage to improve the charging efficiency of intake air, thereby improving the engine output. An object of the present invention is to provide a cooling structure for a car engine.

[0005]

In order to achieve the above object, the present invention provides a snowmobile engine cooling structure in which an intake passage and an exhaust passage are provided in substantially the same direction and are adjacent to each other. A water-cooled two-stroke engine for cooling the engine by circulating cooling water through a cooling water path including a water jacket of a cylinder, a heat exchanger, and a reserve tank for storing cooling water, wherein In the passage side housing, a cooling water passage is formed at a position facing the exhaust passage, and a communication port a for communicating the inside of the cooling water passage with the outside at an upper portion of the cooling water passage, and a downstream side of the cooling water passage. A part of the cooling water path, provided with a communication port b for communicating the inside of the cooling water path with the outside, and a communication structure for communicating the communication port a with the communication port b. Car engine It is an retirement structure.

It is preferable that the communication port b is located above the communication port a.

Further, it is preferable that the communication port b is provided in a cooling water path between the cooling water passage and the reservoir tank.

Preferably, the communication port b is provided in a reservoir tank.

Further, it is preferable that the communication structure adjusts the flow rate of the cooling water by changing the area of the passage opening.

According to the present invention, by forming the cooling water passage at a position facing the exhaust passage of the intake side housing of the crankcase, a rise in temperature near the intake passage can be suppressed, and the cooling water can be further reduced. A communication port a is provided at the upper part of the passage, and a communication port b
By providing the cooling water passage and the downstream cooling water passage so as to eliminate bubbles generated in the cooling passage, the cooling effect near the intake passage can be improved. Therefore, the charging efficiency of the intake air can be improved, and the engine output can be improved.

Further, since the communication port b is located above the communication port a, the air bubbles generated in the cooling passage can be easily eliminated without pressurizing. Therefore, the temperature rise of the intake passage can be suppressed with a simple configuration without largely changing the configuration of the engine.

Further, by providing the communication port b in a cooling water path between the cooling water passage and the reservoir tank,
Air bubbles generated in the cooling passage can be eliminated upstream of the reservoir tank. Therefore, a stable cooling effect can be obtained without recirculating bubbles mixed in the cooling water.

Further, by providing the communication port b in the reservoir tank, the air bubbles can be reliably eliminated from the reservoir tank without causing air bubbles to remain in the cooling water path on the way. Therefore, a stable cooling effect can be obtained without recirculating bubbles mixed in the cooling water.

Further, by adjusting the flow rate of the cooling water by changing the opening area of the passage, the flow rate of the cooling water supplied to the engine cylinder can be adjusted. Therefore, it is possible to adjust the cooling state to the optimum state for the engine, thereby improving the engine output.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the present embodiment is a cooling structure of a two-cycle engine (hereinafter, referred to as an engine) mounted on a front portion inside a body cover 20a of a snowmobile (small snowmobile) 20. In the snowmobile body cover 20a, the engine 2
An exhaust device 22 such as a muffler and an intake device 23 such as an air cleaner and a carburetor are arranged in front of one body, and a heat exchanger (radiator) 24 is arranged behind the engine body. Further, an intake passage 25 for introducing the intake air from the intake device 23 to the engine 21 and an exhaust passage 26 for leading the exhaust gas from the engine 21 to the exhaust device 22 are oriented substantially in the same direction in the forward direction of the snowmobile 20, and
They are arranged adjacent to each other. As shown in FIG. 1, the cooling water supply side of the heat exchanger 24 is connected to a piping hose 31 and connected to a lower portion of the engine 21 via a water pump 32. The cooling water return side of the heat exchanger 24 is connected to the upper part of the engine via a piping hose 33. Further, the heat exchanger 24 faces the inside of the housing cover 51 of the claw 20b and is cooled by passing air (outside air) flowing through the inside of the housing cover 20c.

The engine 21 is, as shown in FIG.
This is a two-cylinder multi-cylinder engine in which the cylinder is tilted backward. A cooling water passage 30 is formed in a housing 28 that forms an opening of the intake passage 25 of the crankcase 27 at a position facing the exhaust pipe 29 on the exhaust passage 26. Also,
As shown in FIG. 3, there is provided a communication structure 50 for communicating the cooling water passage 30 with the vicinity of a connection portion of the cylinder head 37 with the cooling water passage.

The intake housing 28 is located below the exhaust housing 34 as shown in FIG.
It protrudes forward. Further, the exhaust pipe 29 connected to the exhaust housing 34 is disposed so as to face substantially the same direction as the intake housing 28. Therefore, the intake housing 28 and the exhaust pipe 29 face each other, and
They are arranged adjacent to each other. Further, since the thickness of the exhaust pipe 29 is much thinner than the partition wall 34a of the exhaust housing 34, the radiant heat from the exhaust pipe 29 is large during operation of the engine 21. The heat effect on the upper surface of the substrate 28 is large.
Therefore, the intake housing 28 is disposed above the carburetor 2 at the upper part where the heat effect due to the radiant heat from the exhaust pipe 29 is greatest and adjacent to the inner wall of the engine cylinder 35.
A cooling passage 30 is formed over the mounting portion 5a (see FIG. 1). The cooling water passage 30 extends continuously from the intake housing 28 to the engine cylinder 35 side and is formed integrally and continuously inside the crankcase 27, and communicates below a water jacket 36 formed in the engine cylinder 35. are doing.

The water jacket 36 is formed inside the engine cylinder 35 so as to surround the combustion chamber.
A connecting portion between the engine cylinder 35 and the cylinder head 37 communicates with a water jacket 38 formed inside the cylinder head 37. The water jacket 38 communicates with a cooling water path (see FIG. 4) provided above the cylinder head 37.

The communication structure 50 is, as shown in FIG.
A communication port 51 is formed at an uppermost portion of the cooling passage 30 at the end of the intake housing 28, and a union 52 is attached to the communication port 51. Further, a communication port 53 is provided diagonally downward and toward the intake housing 28 at an outlet 38a side provided on an upper portion of a water jacket 38 formed on the cylinder head 37 located above the intake housing 28. A union 54 is attached to the communication port 53, and the union 54 and the union 52 on the intake housing 28 side are connected to the pipe hose 5.
5, the cooling water passage 30 and the water jacket 38 communicate with each other.

In FIG. 3, reference numeral 40 denotes a reed valve, which is a connecting portion 41 between the intake passage 25 and the intake housing 28.
The opening operation is restricted by a stopper 42 arranged outside the reed valve 40, and the intake air is controlled by the pressure fluctuation in the crank chamber 44 due to the vertical movement of the piston 43. That is,
When the piston 43 rises, the pressure in the crank chamber 44 becomes negative, the reed valve 40 is opened, and the mixed gas is sucked into the crank chamber 44 from the intake side. When the piston 43 descends, the pressure in the crank chamber 44 becomes positive, the reed valve 40 is closed, the intake of the mixed gas is stopped, and the further descending of the piston 43 prevents the mixed gas from returning to the intake side. Pressurized in the crank chamber 44. When the piston 43 further descends and the piston head 43a reaches the opening 45 communicating with the combustion chamber, the mixed gas is pressure-fed from the opening 45 into the combustion chamber.

Next, the flow of the cooling water will be described. The cooling water for cooling the engine 21 is shown in FIGS.
As shown in FIG.
From the lower part of the engine 21 through a piping hose 31 to a cooling water passage formed inside the engine.
Next, as shown in FIG. 4, the supplied cooling water passes through a cooling water passage 30 formed in the intake housing 28 and the water jacket 3 formed in the engine cylinder 35.
The engine 21 is cooled while traveling around 6. Further, the cooling water heated through the water jacket 38 formed in the cylinder head 37 is returned from the upper part of the engine to the reserve tank 60 via the piping hose 33. Then, the cooling water returned to the reserve tank is supplied to the heat exchanger 24.
After being radiated here, it is circulated again.

At this time, the cooling water is supplied to the intake housing 2 first.
The water jacket 36 on the engine cylinder side, which becomes hot after passing through the cooling water passage 30 formed in FIG.
Flows towards Therefore, even when the radiant heat from the exhaust pipe 29 propagates to the upper surface of the intake passage 25 during operation of the engine 21, the heat is transferred to the cooling water in the cooling water passage and is radiated by the radiator of the heat exchanger 24, so that the intake air Passage 2
5 can be efficiently cooled. Further, by cooling the vicinity of the intake housing 28, a rise in temperature near the intake passage is suppressed, and therefore, the reed valve 4
0 can be reduced.

Further, when the intake housing 28 is heated by radiant heat from the exhaust pipe 29 in a high temperature state or heat conduction from the engine 21 main body, bubbles may be generated in the cooling water passage 30. Since the shape of the intake housing 28 is formed in a substantially conical shape so as to expand from the center of the engine toward the end of the housing, the air bubbles generated in the cooling water passage generate cooling water at the end of the intake housing 28. The air accumulates at the uppermost portion 30 a in the passage 30, and since a communication port 51 for bleeding air is formed there, the communication port 51 is formed.
Through the piping hose 55 to the water jacket 38 of the engine head 37 provided at a higher position. Then, it further reaches the reservoir tank 60 via the piping hose 33. Here, bubbles are separated from the cooling water in the reserve tank 60. Therefore, since no air remains in the cooling water passage 30, the circulation of the cooling water in the crankcase is always performed satisfactorily, so that a stable engine cooling effect can be obtained.

Here, the structure of the engine cooling structure according to the present embodiment is described in the flow direction of the cooling water as shown in FIG.
0, and the engine 21 is disposed downstream of the heat exchanger 24. However, the present invention is not limited to this embodiment. For example, as shown in FIG.
The engine 21 may be arranged upstream of the heat exchanger, and the radiator may be arranged downstream of the heat exchanger. Hereinafter, other modified examples of the embodiment will be described.

In the second embodiment, as shown in FIG. 7, a reservoir tank is disposed on the downstream side of the engine, and a communication port 66 on the air outlet side of the communication structure 65 is connected to the cylinder head 37. The communication port 66 is provided at a lower position of the connection pipe 67 connected to the outlet side of the formed water jacket 38 and higher than the communication port 51 provided in the cooling water passage 30. In this case, similarly to the first embodiment, air can be vented with a simple configuration without largely modifying the cylinder head 37.

In the third embodiment, as shown in FIG. 8, a reservoir tank 60 is disposed downstream of the engine 21 and a communication port 71 on the air outlet side of the communication structure 70 is provided.
Is formed at the bottom of the reservoir tank 60 so as to protrude higher than the communication port 51 provided in the cooling water passage 30.

In the fourth embodiment, as shown in FIG. 9, a reservoir tank 60 is disposed downstream of the engine 21 and a communication port 76 on the air outlet side of the communication structure 75 is provided.
Is formed at a position higher than the communication port 51 provided in the cooling water passage 30 in the upper portion of the reservoir tank 60.

In the fifth embodiment, as shown in FIG. 10, a reservoir tank 60 is disposed downstream of an engine 21 via a heat exchanger 24.
0, the communication port 81 on the outlet side of the air
And a part of the connecting pipe 82 connected to the outlet side 38a of the water jacket 38 formed in the cooling water passage 30.
Is formed to protrude at a position higher than the communication port 51 provided in the communication port.

In the sixth embodiment, as shown in FIG.
A reservoir tank 60 is arranged downstream of the engine 21 via the heat exchanger 24, and a communication port 86 on the air outlet side of the communication structure 85 is provided at the bottom of the reservoir tank 60 to the cooling water passage 30. It is formed to protrude at a position higher than the communication port 51 provided.

In the seventh embodiment, as shown in FIG.
A reservoir tank 60 is disposed downstream of the engine 21 via a heat exchanger 24, and a communication port 91 on an air outlet side of a communication structure 90 is provided at an upper portion of the reservoir tank 60 to a cooling water passage 30. It is formed to protrude at a position higher than the communication port 51 provided.

The same effects as those of the first embodiment can be obtained in the above-described second to seventh embodiments.

[0032]

As described above, according to the present invention, by providing the cooling water passage near the intake passage, the temperature rise near the intake passage due to the radiant heat from the exhaust passage in a high temperature state and the heat conduction from the engine body can be reduced. Can be suppressed. In addition, since the communication structure is provided, bubbles generated in the cooling water passage can be easily removed without pressurizing, so that the shortage of the flow rate of the cooling water in the cooling water passage due to the remaining air can be solved. Therefore, the temperature rise of the intake passage can be suppressed with a simple configuration without largely changing the configuration of the engine. That is, the charging efficiency of the intake air can be improved, thereby improving the engine output. Furthermore, since the temperature rise near the intake passage is suppressed, the thermal effect on the reed valve can be reduced, so that the deterioration of the reed valve is prevented,
In addition, there is an effect that engine trouble caused by the reed valve can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an entire cooling structure for an engine of a snowmobile according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a positional relationship between an exhaust passage and an intake passage of the engine according to the embodiment.

FIG. 3 is a cross-sectional view showing details of a cooling structure for an engine of a snowmobile according to the embodiment.

FIG. 4 is a cross-sectional view showing a configuration of a cooling structure for an engine of a snowmobile according to the embodiment.

FIG. 5 is a schematic diagram showing a configuration of a conventional engine cooling structure.

FIG. 6 is a schematic diagram showing the configuration of a conventional engine cooling structure.

FIG. 7 is a cross-sectional view showing a configuration of an engine cooling structure according to a second embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a configuration of an engine cooling structure according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a configuration of an engine cooling structure according to a fourth embodiment of the present invention.

FIG. 10 is a cross-sectional view showing a configuration of an engine cooling structure according to a fifth embodiment of the present invention.

FIG. 11 is a sectional view showing a configuration of a cooling structure for an engine according to a sixth embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating a configuration of an engine cooling structure according to a seventh embodiment of the present invention.

FIG. 13 is a side view showing the entire cooling structure of a conventional engine.

FIG. 14 is a plan view showing the entire cooling structure of a conventional engine.

FIG. 15 is a cross-sectional view showing a configuration of a conventional engine cooling structure.

[Explanation of symbols]

 Reference Signs List 1 snowmobile 2 engine 3 exhaust device 4 intake device 5 heat exchanger 6 piping hose 10 crankcase 11 exhaust passage 11a opening 12 intake passage 13 water jacket 14 engine cylinder 20 snowmobile 20a body cover 20b crawler 20c storage cover 21 engine 22 exhaust device Reference Signs List 23 intake device 24 heat exchanger 25 intake passage 25a carburetor 26 exhaust passage 27 crankcase 28 intake housing 29 exhaust pipe 30 cooling water passage 31 piping hose 32 water pump 33 piping hose 34 exhaust housing 34a partition 35 engine cylinder 36 water jacket 37 cylinder Head 38 Water jacket 40 Reed valve 41 Connection 42 Stopper 43 Piston 43a Piston head 44 Rank room 45 Opening 50 Communication structure 51 Communication opening 52 Union 53 Communication opening 54 Union 55 Piping hose 60 Reservoir tank 65 Communication structure 66 Communication opening 67 Connecting pipe 70 Communication structure 71 Communication opening 75 Communication structure 76 Communication opening 80 Communication structure 81 Communication 82 Connecting pipe 85 Communication structure 86 Communication opening 90 Communication structure 91 Communication opening

Claims (5)

[Claims] An intake passage and an exhaust passage are oriented in substantially the same direction and are adjacent to each other, and a cooling water passage provided with a water jacket of a cylinder, a heat exchanger, and a reserve tank for storing cooling water. A water-cooled two-stroke engine that circulates cooling water to cool the engine, wherein a cooling water passage is formed at a position facing an exhaust passage in an intake passage side housing of the crankcase, and an upper part of the cooling water passage is formed. Communication port a for communicating the inside of the cooling water passage with the outside
And a communication port b that is a part of a cooling water path downstream of the cooling water path and communicates the inside of the cooling water path with the outside, and a communication port that communicates the communication port a with the communication port b. A cooling structure for a snowmobile engine having a structure. 2. The cooling structure for an engine of a snowmobile according to claim 1, wherein the communication port b is located above the communication port a. 3. The cooling structure for an engine of a snowmobile according to claim 1, wherein the communication port b is provided in a cooling water path between the cooling water passage and the reservoir tank. 4. The cooling structure for an engine of a snowmobile according to claim 1, wherein the communication port b is provided in a reservoir tank. 5. The cooling of a snowmobile engine according to claim 1, wherein the communication structure adjusts a flow rate of cooling water by changing a passage opening area. Construction.