JP2003172143A - Cooling structure for water-cooled internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling structure for a water-cooled internal combustion engine for reducing the number of parts and assembling man-hour, while enhancing cooling performance by providing an expansion tank, making the whole of the internal combustion engine compact and preventing passing of cooling water as vapor from a filler cap without increasing the expansion tank in scale. <P>SOLUTION: In this cooling structure for the water-cooled internal combustion engine provided with the expansion tank, the expansion tank 70 is arranged near a water pump 50 to circulate cooling water from a scroll chamber 56 of the water pump 50. The expansion tank 70 is partitioned into a plurality of separation chambers 78 communicated via a communicating passage. The filler cap 88 is provided in the separation chamber 78 different from the separation chamber 78 where cooling water is convected. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure for a water-cooled internal combustion engine equipped with an expansion tank.

[0002]

2. Description of the Related Art An expansion tank is a tank used in a closed water cooling method to directly separate a gas generated inside a cooling system from a liquid in a circulation path. A conventional water-cooled internal combustion engine equipped with such an expansion tank is
The expansion tank was located away from the cooling system.

According to an example disclosed in Japanese Patent Laid-Open No. 211213/1990, for example, an expansion is provided to the left rear of an internal combustion engine mounted horizontally with the crankshaft oriented in the vehicle width direction behind the seat of a midship engine vehicle. A tank is arranged, a radiator arranged on the front side of the vehicle body is connected to a long pressure hose, and a water pump is provided on the right side of the internal combustion engine on the side opposite to the expansion tank.

In the expansion tank disclosed in the above publication, a central cylindrical portion which is oriented in the vertical direction and a plurality of separation chambers which are partitioned by partition walls are formed around the cylindrical portion. In addition, a joint for introducing cooling water is provided, and a cap is attached to the upper part of the central tubular portion.

[0005]

As described above, since the expansion tank is arranged at a position distant from the cooling system, the hose extending from the expansion tank is long, and a hose band or clamp for fixing the hose is used. Assembling work is not easy due to the large number of parts such as items.

In the expansion tank, the temperature of the cylindrical portion into which the cooling water is introduced rises greatly, and there is a risk that not only the gas but also the cooling water will escape as vapor from the upper filler cap due to evaporation. To prevent this, the capacity of the tank should be increased, but the tank becomes larger.

The present invention has been made in view of the above problems, and an object thereof is to provide an expansion tank to improve cooling performance while reducing the number of parts and assembling man-hours, and further downsizing the entire internal combustion engine. The point is to provide a cooling structure of a water-cooled internal combustion engine capable of achieving the above.

It is another object of the present invention to provide a cooling structure for a water-cooled internal combustion engine which can prevent cooling water from coming out of the filler cap as steam without increasing the size of the expansion tank.

[0009]

In order to achieve the above object, the invention according to claim 1 provides an expansion tank for directly separating air bubbles generated inside a cooling system from cooling water in a circulation path. In a cooling structure for a water-cooled internal combustion engine provided, the expansion tank is arranged in the vicinity of the water pump to provide a cooling structure for the water-cooled internal combustion engine in which cooling water is circulated from a scroll chamber of the water pump.

Since the expansion tank is arranged in the vicinity of the water pump, the cooling system is compact and
The number of parts such as hoses and their mounting members and the number of assembling steps can be reduced, and the overall internal combustion engine can be made compact.

According to a second aspect of the present invention, in the cooling structure for a water-cooled internal combustion engine according to the first aspect, cooling water is introduced from the upper part of the scroll chamber of the water pump to the expansion tank.

Since the cooling water is guided to the expansion tank from the upper part of the scroll chamber of the water pump, the air bubbles generated in the scroll chamber can be introduced into the expansion tank by using the cooling water outlet passage, and the air bleeding performance is improved. Can be improved.

According to a third aspect of the present invention, in the cooling structure for a water-cooled internal combustion engine according to the first aspect, the expansion tank is directly attached to the water pump, and cooling water is introduced into the scroll chamber of the water pump from inside the expansion tank. It is characterized by forming a communication path for guiding the.

Since the expansion tank is directly attached to the water pump for compactness and a communication passage is formed inside, a hose extending from the expansion tank to the water pump and a hose band and clamps associated therewith are unnecessary, and the number of parts is small. Assembly work is also easy.

According to a fourth aspect of the present invention, in a cooling structure for a water-cooled internal combustion engine including an expansion tank for directly separating a gas generated inside a cooling system from a liquid in a circulation path, the expansion tank is provided with a communication passage. Is a cooling structure for a water-cooled internal combustion engine that is divided into a plurality of separation chambers that communicate with each other and has a filler cap in a separation chamber in which cooling water different from the circulation chamber in which cooling water circulates is retained.

Since the temperature of the cooling water is high in the separation chamber in which the cooling water is circulated until it is introduced and discharged, since the cooling water easily evaporates, a filler cap is provided in the separation chamber in which cooling water other than these separation chambers stays. This can prevent the cooling water from being discharged as steam without increasing the capacity of the tank.

According to a fifth aspect of the invention, in the cooling structure for a water-cooled internal combustion engine according to the fourth aspect, the separation chamber provided with the filler cap is arranged at a position farthest from the separation chamber into which cooling water is introduced. Is characterized by.

Since the separation chamber into which the cooling water is introduced has the highest temperature, the effect of heat on the separation chamber having the filler cap is set by disposing the separation chamber having the filler cap at a position farthest from the separation chamber. Can be suppressed to prevent evaporation in the separation chamber.

According to a sixth aspect of the invention, in the cooling structure for a water-cooled internal combustion engine according to the fourth or fifth aspect, the separation chamber adjacent to the separation chamber into which the cooling water is introduced is communicated via a communication hole. It is characterized by forming a relatively large capacity.

The cooling water introduced into the separation chamber in which the cooling water is first introduced into the expansion tank flows into the next adjacent separation chamber via the communication passage, but the capacity of the separation chamber is relatively large. Therefore, the flow of the inflowing cooling water is weakened, and the convection to other separation chambers is suppressed, and the high temperature of the introduced cooling water is prevented from diffusing into the other separation chambers by convection, and the separation chamber with a filler cap is particularly used. The temperature rise can be prevented as much as possible, and the cooling water can be prevented from coming off due to evaporation.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment according to the present invention will be described below with reference to FIGS. The water-cooled internal combustion engine 21 according to the present embodiment is a scooter type motorcycle 1
Is installed as a swing unit type engine.

As shown in FIG. 1, a scooter type motorcycle 1
Includes a front wheel 3 steered by the steering wheel 2 and a rear wheel 5 pivotally supported by a swing-type power unit 4 and driven by a vehicle body frame from a head pipe 6 pivotally supporting the steering wheel 2. Down tube 7 extending downward
Bends and extends rearward to form a step floor support portion 7a, a center frame 8 connected to a rear end thereof rises and extends obliquely rearward, and a rear frame 9 connected to an upper end thereof further extends rearward. .

The head pipe 6, the down tube 7 and the center frame 8 are cast products of aluminum alloy, and the rear frame 9 is made of an annular pipe material. A fuel tank 10 is supported by the rear frame 9, and a seat 12 that also serves as a cover that closes the upper opening of the helmet case 11 supported by the center frame 8 covers the fuel tank 10 together with the helmet case 11 in an openable and closable manner.

The power unit 4 is pivotally supported on the bent portion of the center frame 8 through a pivot 15.
Is provided so as to be able to swing up and down together with a rear wheel 5 pivotally supported at a rear end of the pivot 15, and a rear cushion is provided between a rear portion of the power unit 4 and a rear end of the center frame 8.
16 are installed.

As shown in FIG. 2, the power unit 4 includes an internal combustion engine 21 in which cylinders are arranged toward the front of the vehicle body, and a belt type continuously variable transmission 22 extending from the left side portion of the internal combustion engine 21 toward the rear of the vehicle body. The rear wheel is supported by an output shaft 23 that is integrally formed and projects in the right horizontal direction from the rear end of the belt type continuously variable transmission 22.

As shown in FIG. 3, the internal combustion engine 21 is a water-cooled, single-cylinder, four-stroke cycle engine, and is divided into front and rear engine blocks 25 (front engine block 25f, rear engine block) that form crankcase halves. The crankshaft 24 is sandwiched by the bearings 25r) via bearings, and the front engine block 25f forms a cylinder block integrally with the half of the crankcase.

A cylinder head 26 is overlapped and fastened to the front end of the cylinder block of the front engine block 25f, and a head cover 27 covers the front end of the cylinder head 26.

The intake pipe 17 extends from the upper surface of the cylinder head 26 projecting forward and bends rearward so that the engine block 25
Is connected to the carburetor 18 located above (see FIG. 2), and the carburetor 18 is connected to an air cleaner (not shown).

An exhaust pipe (not shown) extends from the lower surface of the cylinder head 26, bends rearward and obliquely to the right, passes under the engine block 25, and is connected to a muffler 19 arranged on the right side of the rear wheel 5. (See FIG. 1).

Referring to FIG. 3, a piston 30 slidably fitted in the cylinder of the cylinder block is connected by a crankshaft 24 rotatably supported by the engine block 25 and a connecting rod 31 to form a crankshaft 24. A drive pulley (not shown) of the belt type continuously variable transmission 22 is provided at the left end of the power transmission unit to transmit power.

A cam shaft 32 is rotatably supported by the cylinder head 26, and a driven sprocket 33 fastened to the end of the cam shaft 32 is provided in a chain chamber 26a formed on the right side of the cylinder head 26. 33 and crankshaft
The timing chain 35 is bridged between the drive sprocket 34 fitted to the shaft 24 and the rotation of the crankshaft 24 is transmitted to the camshaft 32 with the rotation speed being halved.

An AC generator is on the right side of the engine block 25.
36 is provided, and a generator case 25a extending from the engine block 25 covers the outer periphery of the AC generator 36. A cooling fan 37 is attached to the right side surface of the rotor of the AC generator 36 fitted to the right end of the crankshaft 24.

A radiator 40 is provided on the right side so as to protect the cooling fan 37. A radiator base 41 that surrounds and supports a rectangular radiator 40 is connected and supported by the generator case 25a and covers the cooling fan 37. The right side opening of the radiator base 41 that surrounds the radiator 40 is fitted with the radiator grill 42.
Is designed to open and close freely.

Radiator base 41 and radiator grill 42
Is a connecting part made of resin and having flexible ends.
The radiator grill 42 is integrally connected by 42a, swings and opens and closes with respect to the radiator base 41 by the deformation of the connecting portion 42a, and when closed, covers the front surface of the radiator 40 (right side surface with respect to the vehicle body).

A chain chamber 26a on the right side of the cylinder head 26
An opening coaxial with the cam shaft 32 is formed in the center on the right side wall of the, the water pump 50 is mounted by inserting the pump body case 51 into the opening, and the expansion tank 70 is directly attached to the upper portion of the water pump 50. Installed on.

A pump body case 51 for the water pump 50
5 is composed of a bottomed cylindrical portion 51a for accommodating the driven magnet 54 supported by the rotating shaft 53 and an opening large diameter portion 51b for accommodating the impeller 55 fitted on the rotating shaft 53, as shown in FIG. A pump cover case 52 covering the large diameter portion 51b pivotally supports one end of a rotary shaft 53 to rotatably support a driven magnet 54 and an impeller 55.

Referring to FIG. 3, around the pump body case 51 fitted in the chain chamber 26a of the cylinder block 26, a cylindrical support member 38 is fastened together with the driven sprocket 33 on the end surface of the camshaft 32. The drive magnet 39 fitted to the inner peripheral surface is arranged, and the driven magnet 54 of the water pump 50 rotates together with the drive magnet 39 that rotates together with the camshaft 32 to rotate the impeller 55.

The pump cover case 52 is shown in FIGS.
As shown in, a scroll chamber 56 in which the impeller 55 rotates is formed between the pump body case 51 and the opening large diameter portion 51b.
On the side opposite to the scroll chamber 56, the mating surface 52a with the thermostat cover 64 and the mating surface with the expansion tank 70
52b and.

A thermostat chamber 57, which is largely hollowed out, is formed on the mating surface 52a, and the thermostat chamber 57 into which the thermostat 65 is inserted is communicated with the suction passage 58 opening to the center side of the scroll chamber 56, and also downward. It communicates with the projecting suction connection pipe 59.

A mating surface 52b with the expansion tank 70 above the mating surface 52a is above the rotating shaft 53 and has two suction passages 60 and a discharge passage communicating with the scroll chamber 56.
61 is formed, the lower suction passage 60 opens inside the impeller 55, and the upper discharge passage 61 communicates with the uppermost portion of the scroll chamber 56.

A discharge connection pipe 62 communicating with the outside of the impeller 55 in the scroll chamber 56 extends downward (see FIG. 4). As shown in FIG. 4, the expansion tank 70
Bolt holes 63, 63 are formed on the left and right on the mating surface 52b.

The thermostat chamber 57 has a thermostat 65.
When is inserted and the thermostat cover 64 is covered,
As shown in FIG. 10, the connection communication passage 64 a formed in the thermostat cover 64 is connected to the suction passage via the thermostat chamber 57.
It communicates with 58, and is connected to the inside of the suction connection pipe 59 with the suction passage 58 by the valve of the thermostat 65.

As shown in FIG. 2, the suction connection pipe 59 is connected to the cooling water outlet of the lower tank 40b of the radiator 40 by the cooling water hose 66, and the connection communication passage 64a is connected to the cooling water passage of the carburetor 18 by the cooling water hose 67. To be done. The discharge connection pipe 62 is connected to the cooling water introduction port of the engine block 25 by a cooling water hose 68.

The expansion tank 70 joined to the mating surface 52b is, as shown in FIGS.
It is a substantially rectangular parallelepiped tank, and is configured by combining a main body 71 and a lid 72.

A part of the bottom wall of the main body 71 bulges downward to form a connecting portion 73 which is connected to the water pump 50,
The connecting portion 73 has a recessed portion 73a which is recessed downward, and a mating surface 73b which is joined to the mating surface 52b of the pump body case 51 is formed. The connecting hole 73c is formed in the lower part and the upper part from the recessed part 73a toward the mating surface 73b. 73d is drilled.

The lower connecting hole 73c is the upper connecting hole 73c.
The hole diameter is larger than that of d, the cooling water flows out from the lower connecting hole 73c, and the cooling water flows in from the upper connecting hole 73d. Mounting holes 74, 74 are formed on both sides of the outflow recess 73a of the connecting portion 73.

A cap fitting port 75 into which a filler cap 88 is fitted is formed on the ceiling wall of the lid body 72, and a breather connecting pipe 76 projects laterally from a part of the cap fitting port 75.

The inside of the expansion tank 70 is the main body.
The partition wall 77 is common to the 71 and the lid 72, and is divided into six rectangular column-shaped separation chambers 78 that are adjacent to each other in the left-right and front-rear directions. As shown in FIG.
, Is attached.

The separation chamber and the separation chamber adjacent to the separation chamber have the smallest volume at the corners, and the inflow connection pipe 79 for inflowing the cooling water projects laterally from the lower part. The separation chamber, the separation chamber, the separation chamber, and the separation chamber adjacent to the separation chamber have the largest volume, and the outflow recess 73a that is recessed downward is formed in the bottom wall, and the partition wall 77 with the separation chamber is formed. Communication holes 80a and 80b are formed in the lower part and the upper part.

The separation chamber, the separation chamber, and the separation chamber in the corner position adjacent to the separation chamber have some shallow bottoms,
Communication holes 81a and 81b are provided in the lower and upper portions of the partition wall 77 for separating from the separation chamber.
Is perforated. The separation chambers and the separation chambers located at the corners adjacent to the separation chambers are dead-end chambers in which communication holes 82a and 82b are formed in the lower part and the upper part of the partition wall 77 for separating the separation chambers.

The separation chamber, the separation chamber, and the separation chamber adjacent to the separation chamber have a half of the bottom having a somewhat shallow bottom and the remaining part of the separation chamber having a shallower depth.
83a and 83b are perforated. The separation chamber and the separation chamber in the corner position adjacent to the separation chamber have a shallow bottom, the cap fitting port 75 is formed on the ceiling wall, and the communication hole 84a is formed in the lower part and the upper part of the partition wall 77 with the separation chamber. 84b is perforated.

Since the expansion tank 70 has the above-mentioned structure, the cooling water flowing into the separation chamber from the inflow connection pipe 79 enters the separation chamber through the communication hole 80a. The cooling water that has entered the separation chamber fills the outflow concave portion 73a and flows back to the water pump 50 through the connection holes 73c and 73d, and part of the cooling water enters the separation chamber through the communication hole 81a and part of the communication water 82a. Into the separation chamber via.

The cooling water that has infiltrated the separation chamber is connected to the communication hole 83a.
The cooling water that has penetrated into the separation chamber through the inlet enters the separation chamber through the communication hole 84a. In this way, the cooling water that has flowed in from the inflow connection pipe 79 enters all the separation chambers, ...
2/3 is always filled, and the outflow recess 73a to the connecting holes 73c, 73
It recirculates to the water pump 50 via d.

That is, the cooling water that has flowed into the separation chamber is stored in the other separation chambers, ... And flows out from the separation chamber. Therefore, the separation room ...
After storing an appropriate amount in the separation chambers, the cooling water that has flowed into the separation chambers will flow out from the adjacent separation chambers, and the inflowing cooling water will flow out by convection between the separation chambers and the separation chambers.

The gas phase spaces above the stored cooling water of the separation chambers of the expansion tank 70 communicate with each other through the communication holes 80b, 81b, 82b, 83b, 84b, and the cap fitting port. It leads to 75.

In this expansion tank 70, the mating surface 73b of the connecting portion 73 is joined to the mating surface 52b of the water pump 50.
The two bolts 86, 86, which are fitted to each other via a seal member, pass through the mounting holes 74, 74 and are screwed into the bolt holes 63, 63 to be fastened, whereby the bolts 86, 86 are directly mounted on the water pump 50.

As shown in FIG. 10, connecting holes 73c and 73d formed from the recess 73a of the expansion tank 70 are connected to the suction passage 60 and the discharge passage 61 of the water pump 50 and to the scroll chamber 56, respectively.

The inflow connecting pipe 79 is connected to the cylinder head 26.
No. 1 cooling water outlet is connected to the cooling water hose 87 (see FIG. 2), and a filler cap 88 with a relief valve is fitted into the cap fitting port 75.

FIG. 11 shows the above-mentioned closed cooling water circulation route diagram.
Shown in. The cooling water discharged from the water pump 50 is introduced into the water jacket of the engine block 25 via the cooling water hose 68, and flows the heat of the internal combustion engine 21 while flowing from the water jacket of the engine block 25 to the water jacket of the cylinder head 26. The cooling water taken out and branched from the cylinder head 26 is branched and flows to the radiator 40 by one cooling water hose 89, and flows to the carburetor 18 by the other cooling water hose 90.

The cooling water flowing to the radiator 40 is cooled by the radiator 40 and thermostatted by the cooling water hose 66.
The cooling water that reaches 65 and flows to the carburetor 18 is
Warm 18 and reach the thermostat 65 by the cooling water hose 67. The cooling water that reached the thermostat 65 is a water pump
Reflux to 50.

Since the thermostat 65 functions to shut off the reflux from the radiator 40 during warm-up operation at low temperature,
The engine block 25, the cylinder head 26, and the carburetor 18 are circulated without passing through the radiator 40 to prevent the cooling water from being overcooled and prevent the carburetor 18 from deteriorating its performance.

When the temperature of the cooling water exceeds a predetermined temperature, the thermostat 65 circulates the cooling water from the radiator 40 to the water pump 50, and the cooling water cooled by the radiator 40 removes heat from the engine block 25 and the cylinder head 26. .

In addition to the circulation path described above, in the present cooling structure,
Part of the cooling water flows from the cylinder head 26 into the expansion tank 70 via the cooling water hose 87, and the air bubbles generated in the cooling water in the expansion tank 70 are separated and removed to the water pump 50 via the suction passage 60. Can be returned and removes air bubbles from the cooling water that circulates in the engine block 25 and cylinder head 26, and the air bubbles will
25, the cylinder head 26 can be prevented from interfering with the flow and locally lowering the cooling performance.

Cavitation is likely to occur in the scroll chamber 56 in which the impeller 55 of the water pump 50 rotates,
There is a discharge path 61 in the upper part of the scroll chamber 56, and the generated bubbles are transmitted along the discharge path 61 above and enter the separation chamber of the expansion tank 70 from the recess 73a to be gas-liquid separated and removed to the upper space. It is possible to improve the bubble removal performance.

Since air bubbles can be discharged from the scroll chamber 56 to the expansion tank 70 through the shortest discharge path 61,
The bubble escape performance is extremely good, and the bubbles in the scroll chamber 56 can be effectively discharged not only during operation but also during stoppage.

All the separation chambers, ... Of the expansion tank 70 communicate with the upper space, and when the internal pressure increases and exceeds a predetermined pressure, the relief valve of the filler cap 88 opens and the breather connecting pipe 76 opens to the outside. Exhausted to.

The expansion tank 70 is divided into six separation chambers by a partition wall 77. The cooling water heated to a high temperature by the engine block 25 and the cylinder head 26 is first separated into the separation chamber. Enters, convection into the separation chamber and flows out. Therefore, each separation room,
,,, have different temperatures.

The temperature distribution state of each of the separation chambers, ... Is shown in the graph of FIG. 10 in internal combustion engine 21
Each separation chamber when the cooling water heated to each temperature of 0 ° C, 80 ° C and 60 ° C circulates in the expansion tank 70,
The graph of FIG. 12 shows the water temperatures at the ,,,.

The water temperature slightly drops when it flows into the separation chamber, and the water temperature drops slightly when it flows into the next separation chamber. The cooling water mainly convects these two separation chambers, and since the separation chamber has the largest volume, it weakens the flow of the inflowing cooling water, and the separation chamber communicating with the separation chamber and the separation chamber do not come and go to some extent. However, since the cooling water of almost high temperature does not enter, the water temperature in the separation chamber is lowered.

The water temperature further decreases in the separation chamber communicating with the separation chamber 3, and the water temperature in the separation chamber in the farthest position from the separation chamber communicating with the separation chamber and having the convection further decreases and the internal temperature of the internal combustion engine increases. 100 ℃, 80 ℃, 60 ℃
The cooling water was about 72 ° C and 53 ° C in the separation chamber, respectively.
It has dropped to ℃ and 33 ℃.

A filler cap 88 is provided in the separation chamber which is the furthest from the first inflow chamber and the convection separation chamber and which stores the cooling water having the lowest water temperature.

Therefore, the cooling water can be surely prevented from evaporating in the separation chamber, and the cooling water can be prevented from being discharged as steam without increasing the capacity of the expansion tank 70.

Although the separation chamber or the separation chamber is in a high temperature state and easily evaporates, the water vapor evaporated in the separation chamber moves in the vapor phase space above the stored cooling water of the respective separation chambers communicating with each other. Gas-liquid separation for each
Filler cap 88
It is possible to reliably prevent the cooling water from being discharged as steam from the.

Further, as described above, the bubbles generated in the scroll chamber 56 of the water pump 50 are transmitted through the upper suction passage 61, enter the separation chamber, are separated into gas and liquid, and are easily removed to the upper space, and bubbles in the cooling water circulation path. It is possible to prevent problems caused by.

Since the expansion tank 70 is directly attached to the water pump 50, the cooling system can be compactly assembled, the number of parts such as hoses and their mounting members and the number of assembling steps can be reduced, and the entire internal combustion engine can be reduced. It can be made compact. .

The expansion tank 70 directly attached to the water pump 50 is arranged on the vehicle body in the posture shown in FIG. 1, and the cooling water is stored at a height of about 2/3 in the vehicle body. Even if the front part is lifted high and the vehicle body is greatly tilted, the outflow recess 73a that swells downward and the cooling water flows out from the expansion tank 70 is always filled with the cooling water, so that the outflow is not interrupted and the stored cooling water is not interrupted. Does not contact the filler cap 88, and the cooling water does not leak from the filler cap 88.

[Brief description of drawings]

FIG. 1 is an overall side view of a scooter type motorcycle equipped with a water-cooled internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a side view of a power unit including the water-cooled internal combustion engine.

FIG. 3 is a sectional view of the water-cooled internal combustion engine.

FIG. 4 is a side view of the water pump.

5 is a sectional view taken along line VV in FIG.

FIG. 6 is a side view of the expansion tank.

7 is a cross-sectional view taken along the line VII-VII in FIG.

8 is a cross-sectional view taken along line VIII-VIII in FIG.

9 is a sectional view taken along line IX-IX in FIG. 7.

FIG. 10 is a cross-sectional view of a water pump and an expansion tank.

FIG. 11 is a circulation path diagram of cooling water.

FIG. 12 is a graph showing a temperature distribution state of each separation chamber of the expansion tank.

[Explanation of symbols]

1 ... Scooter type motorcycle, 2 ... Steering handle, 3 ... Front wheel, 4 ... Power unit, 5 ... Rear wheel, 6 ... Head pipe, 7 ... Down tube, 8 ... Center frame, 9 ... Rear frame, 10 ... Fuel tank , 11 ... helmet case,
12 ... Seat, 15 ... Pivot, 16 ... Rear cushion, 17 ...
Intake pipe, 18 ... Carburetor, 19 ... Muffler, 21 ... Internal combustion engine, 22 ... Belt type continuously variable transmission, 23 ... Output shaft, 24 ... Crankshaft, 25 ... Engine block, 26 ... Cylinder head, 27
... head cover, 30 ... piston, 31 ... connecting rod, 32 ... cam shaft, 33 ... driven sprocket, 34 ... drive sprocket, 35 ... timing chain, 36 ... AC generator, 37 ... cooling fan, 38 ... cylindrical support member, 39 … Drive magnet, 40… Radiator, 41… Radiator base, 42…
Radiator grille, 50 ... Water pump, 51 ... Pump body case, 52 ... Pump cover case, 53 ... Rotating shaft, 54
… Followed magnet, 55… Impeller, 56… Scroll room,
57 ... Thermostat chamber, 58 ... Suction path, 59 ... Suction connection pipe,
60 ... suction passage, 61 ... discharge passage, 62 ... discharge connection pipe, 63 ... bolt hole, 64 ... thermostat cover, 65 ... thermostat,
66, 67, 68 ... Cooling water hose, 70 ... Expansion tank, 71 ... Main body, 72 ... Lid, 73 ... Connection part, 74 ... Mounting hole, 75
… Cap fitting port, 76… Breather connecting pipe, 77… Partition wall,
78 ... Separation chamber, 79 ... Inflow connection pipe, 86 ... Bolt, 87 ... Cooling water hose, 88 ... Filler cap, 89, 90 ... Cooling water hose.

Claims (6)

[Claims] 1. A cooling structure for a water-cooled internal combustion engine comprising an expansion tank for directly separating air bubbles generated inside a cooling system from cooling water in a circulation path, wherein the expansion tank is arranged near a water pump. A cooling structure for a water-cooled internal combustion engine, characterized in that cooling water is circulated from a scroll chamber of a pump. 2. The cooling structure for a water-cooled internal combustion engine according to claim 1, wherein cooling water is introduced into the expansion tank from an upper portion of a scroll chamber of the water pump. 3. The water-cooled internal combustion engine according to claim 1, wherein the expansion tank is directly attached to the water pump, and a communication passage for guiding cooling water from the inside of the expansion tank to a scroll chamber of the water pump is formed. Engine cooling structure. 4. A cooling structure for a water-cooled internal combustion engine comprising an expansion tank for directly separating a gas generated inside a cooling system from a liquid in a circulation path, wherein the expansion tank communicates with a plurality of separation passages. A cooling structure for a water-cooled internal combustion engine, characterized in that a separation cap, which is divided into chambers and in which a cooling water different from the circulation chamber in which the cooling water circulates, is provided with a filler cap. 5. The cooling structure for a water-cooled internal combustion engine according to claim 4, wherein the separation chamber provided with the filler cap is arranged at a position farthest from the separation chamber into which cooling water is introduced. 6. The water-cooled internal combustion engine according to claim 4 or 5, characterized in that the capacity of the separation chamber adjacent to the separation chamber into which cooling water is introduced and communicated via the communication hole is formed to be relatively large. Engine cooling structure.