JP2019148235A - Cooling structure of internal combustion engine - Google Patents

Abstract

To provide a cooling structure of an internal combustion engine, which has no need to provide a flow channel for bypassing a radiator core at the outside of a radiator and can be reduced in size.SOLUTION: A cooling structure of an internal combustion engine 71 includes a radiator 80 and a thermostat 85. The radiator 80 includes a radiator core 81, and a pair of a front radiator tank 82 and a rear radiator tank 83, which are disposed to interpose the radiator core 81 therebetween. The front radiator tank 82 includes a tank upstream part 82u, a tank downstream part 82d, a partition wall 82w dividing the tank upstream part 82u and the tank downstream part 82d, and a bypass part 84 that is provided in the partition wall 82w and provides communication between the tank upper part 82u and the tank downstream part 82d. The thermostat 85 is provided in the front radiator tank 82 to communicate with the bypass part 84.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cooling structure for an internal combustion engine.

  Conventionally, as a cooling structure for an internal combustion engine, a cooling structure for an internal combustion engine for a motorcycle that cools the engine by forcibly circulating a coolant between the engine and a radiator by a water pump is known (for example, Patent Document 1). In the cooling structure for an internal combustion engine described in Patent Document 1, a bypass passage that bypasses a radiator is provided along the upper surface of a radiator core sandwiched between a pair of radiator tanks, and a thermostat (thermostat valve) is provided above one of the radiator tanks. ) Is provided.

Japanese Utility Model Publication No. 4-75129

  However, in Patent Document 1, since the bypass channel is provided so as to protrude from the radiator above one of the radiator tanks, there is room for improvement because it is a factor that hinders downsizing.

  The present invention provides a cooling structure for an internal combustion engine that can be downsized without the need for providing a flow path for bypassing a radiator core outside the radiator.

(1) The first invention is
A radiator that exchanges heat between the coolant that cools the internal combustion engine and the outside air;
In a cooling structure for an internal combustion engine comprising a thermostat that switches a coolant flow path according to the temperature of the coolant,
The radiator is
A radiator core for performing the heat exchange;
A pair of radiator tanks arranged so as to sandwich the radiator core,
One of the pair of radiator tanks is:
A tank upstream,
The downstream of the tank,
A partition wall separating the tank upstream portion and the tank downstream portion;
A bypass portion provided on the partition wall and communicating the tank upstream portion and the tank downstream portion;
The thermostat is provided in the one radiator tank so as to communicate with the bypass portion,
When the coolant is above a predetermined temperature, the coolant flows in the order of the tank upstream portion, the radiator core, the other radiator tank, the radiator core, the tank downstream portion,
When the cooling liquid is lower than a predetermined temperature, the cooling liquid is a cooling structure for an internal combustion engine that flows in the order of the tank upstream portion, the bypass portion, and the tank downstream portion.
(2) The second invention is
A swing type internal combustion engine mounted on a motorcycle and swinging with a drive wheel;
A radiator that performs heat exchange between the coolant and the outside air that cools the cylinder block and the cylinder head of the internal combustion engine;
In a cooling structure for an internal combustion engine comprising a thermostat that switches a coolant flow path according to the temperature of the coolant,
The thermostat is disposed inside the radiator;
The radiator is a cooling structure for an internal combustion engine, which is disposed on an outer surface on one side in the vehicle width direction of the internal combustion engine and a pair of radiator tanks are disposed so as to sandwich a radiator core in the vehicle front-rear direction.

  According to the first aspect of the present invention, since the thermostat is provided in one of the radiator tanks so as to communicate with the bypass portion, the radiator core can be bypassed inside the radiator, so that the flow path for bypassing the radiator core Is not required to be provided outside the radiator, and the cooling structure of the internal combustion engine can be reduced in size and weight.

  According to the second invention, since the thermostat is arranged inside the radiator, there is no need to provide a flow path for bypassing the radiator core outside the radiator, and the cooling structure of the internal combustion engine can be reduced in size and weight. In addition, since the radiator is arranged on the outer surface on one side in the vehicle width direction, and the pair of radiator tanks are arranged so as to sandwich the radiator core in the vehicle longitudinal direction, a space is created below the radiator and the bank angle is increased. Widely secured.

1 is a right side view of a motorcycle provided with a cooling structure for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a side view of a main part in the cooling structure of the internal combustion engine of the motorcycle of FIG. FIG. 3 is a cross-sectional view of a main part for explaining a flow path when a coolant is at a high temperature in the radiator core and the radiator tank shown in FIG. 2. FIG. 3 is a cross-sectional view of a main part for explaining a flow path when the coolant is at a low temperature in the radiator core and the radiator tank shown in FIG. 2. It is the bottom view which looked at the motorcycle of the modification from the lower part. It is a principal part side view in the cooling structure of the internal combustion engine of a modification.

  Hereinafter, an embodiment of a cooling structure for an internal combustion engine according to the present invention will be described with reference to the accompanying drawings.

  First, a motorcycle equipped with a cooling structure for an internal combustion engine according to the present embodiment will be described with reference to FIGS. In each drawing, the front of the motorcycle 10 is indicated as Fr, the rear as Rr, the left as L, the right as R, the upper as U, and the lower as D.

<Body structure of motorcycle>
As shown in FIG. 1, a motorcycle 10 includes a body frame 11 that is a skeleton, a front fork 13 that is slidably supported by a head pipe 12 that constitutes a front end portion of the body frame 11, and a front fork 13. A front wheel 16 attached to the lower end via an axle 14, a bar handle 17 attached to the upper end of the front fork 13, and a swing supported by a lower part of the vehicle body frame 11 via a link 18 so as to swing up and down. Type power unit 21, a rear wheel 23 attached to the rear end portion of the power unit 21 via an axle 22, and a rear cushion unit 24 passed between the rear portion of the body frame 11 and the rear end portion of the power unit 21. And comprising.

  The vehicle body frame 11 includes a head pipe 12, a down frame 26 extending obliquely downward and rearward from the head pipe 12, and a cross extending in the vehicle width direction connected to the rear end of a horizontal portion 26 a constituting the lower portion of the down frame 26. A pipe 27 and a pair of left and right rear frames 28 extending obliquely rearward and upward from the left and right ends of the cross pipe 27 are provided, and a plurality of cross pipes are provided between the left and right rear frames 28.

  A storage box 31 and a fuel tank 32 disposed at the rear of the storage box 31 are attached to the rear frame 28, and a seat 33 is attached to the storage box 31 so as to be openable and closable. The tank 32 is covered from above.

  The power unit 21 includes a water-cooled internal combustion engine 71 that constitutes a front portion, a power transmission device 72 that is provided integrally with the rear portion of the internal combustion engine 71 and transmits the power of the internal combustion engine 71 to the rear wheels 23 that are drive wheels. The front lower portion of the power unit 21 is attached to the rear end portion of the link 18 via a swing shaft 35 so as to be swingable up and down. That is, the internal combustion engine 71 is a swing type internal combustion engine that swings with the rear wheel 23 with respect to the vehicle body frame 11. Reference numeral 36 denotes an exhaust pipe connected to the internal combustion engine of the power unit 21, reference numeral 37 denotes a muffler connected to the rear end of the exhaust pipe 36, and reference numeral 38 denotes a heat shield cover that covers the outer side of the muffler 37.

  The front and lower parts of the body frame 11, the upper part of the front fork 13, and the bar handle 17 are covered with a body cover 50. The vehicle body cover 50 is disposed at the rear of the front cover 51 so as to cover the top of the head pipe 12 and the front fork 13 from the front, and covers the head pipe 12, the top of the front fork 13 and the down frame 26 from the rear. A front inner cover 52, a pair of left and right leg shields 53 connected to the rear edge of the front cover 51 and the side edges of the front inner cover 52 and extending to the left and right sides to cover the driver's legs from the front, and the front inner A floor step 54 that extends rearward from the lower ends of the cover 52 and the leg shield 53 and serves as a footrest for the driver, a pair of left and right side skirts 56 that extend downward from the left and right edge portions of the floor step 54, A center cover 57 that covers the front part of the storage box 31 below the part; From left and right rear edges of the center cover 57 and a pair of right and left body cover 58 below the side edges extending behind the seat 33, and a handle cover 59 covering the front and rear of the central portion of the bar handle 17. Reference numeral 61 denotes a front fender that covers the front wheel 16 from above, reference numeral 62 denotes a grab rail that the passenger grips, reference numeral 63 denotes a rear fender that covers the rear wheel 23 from above, and reference numeral 64 denotes a main stand.

<Internal combustion engine and cooling structure>
As shown in FIG. 2, the internal combustion engine 71 constitutes a front portion of the swing type power unit 21, and a power transmission device 72 is integrally provided at the rear portion of the internal combustion engine 71.

  The internal combustion engine 71 includes a crankcase 74 that houses a crankshaft (not shown), and a cylinder portion 75 that is attached to the front end of the crankcase 74. The cylinder portion 75 includes a cylinder block 76, a cylinder head 77, and a head cover 78 that are sequentially arranged forward from the crankcase 74.

  On the right side of the crankcase 74, a radiator 80 that performs heat exchange between the coolant C that cools the internal combustion engine 71 and the outside air is provided on the outer side of the internal combustion engine 71 on one side in the vehicle width direction (right side in this embodiment). Is arranged. A radiator cover 98 (see FIG. 1) that covers the radiator 80 is disposed on the right outer side of the radiator 80.

  In the cylinder portion 75, a cylinder axis SL which is an axis of a cylinder formed therein extends obliquely upward and forward. A water pump 86 that pumps the coolant C is provided on the right side surface of the cylinder head 77. One end of a hose-like coolant return passage 89b is connected to the water pump 86. The other end of the coolant return passage 89b is connected to a coolant discharge port 96a of a tank downstream portion 82d of the front radiator tank 82 described later. Thus, the coolant return passage 89b can be shortened by arranging the tank downstream portion 82d of the front radiator tank 82 and the water pump 86 close to each other.

  Further, one end of a hose-like coolant inflow passage 89 a communicating with a water jacket formed in the cylinder head 77 is connected to the right side surface of the upper portion of the cylinder head 77. The other end of the coolant inflow passage 89a is connected to a coolant inlet 82i of a tank upstream portion 82u of the front radiator tank 82 described later.

  A pump discharge port 91 c of the water pump 86 is connected to a connection port (not shown) formed in the cylinder block 76 via a discharge hose 89 c and communicates with a water jacket formed in the cylinder block 76. The water jacket in the cylinder block 76 communicates with the water jacket in the cylinder head 77. Reference numeral 91e is a pump air vent of the water pump 86 to which the air vent hose 106 is connected.

  The cooling structure of the internal combustion engine 71 includes a radiator 80 that exchanges heat between the coolant C that cools the internal combustion engine 71 and the outside air, and a thermostat 85 that switches the coolant flow path according to the temperature of the coolant C.

  The radiator 80 includes a radiator core 81 that performs heat exchange, and a pair of a front radiator tank 82 and a rear radiator tank 83 that are arranged in the vehicle front-rear direction so as to sandwich the radiator core 81.

  The radiator core 81 is provided with a core partition wall 81w that partitions the upper core 81u and the lower core 81d at a substantially middle position in the height direction, and the coolant C that has flowed into the radiator core 81 The upper core 81u on the upper side of the wall 81w passes through the rear radiator tank 83 and flows into the lower core 81d on the lower side of the core partition wall 81w. The upper core 81u and the lower core 81d are composed of a plurality of pipes 81p communicating between the front radiator tank 82 and the rear radiator tank 83, and fins 81f passed between adjacent pipes. The heat of the coolant flowing in 81p is released from the fins 81f to the outside. In the radiator 80, an electric cooling fan (not shown) is arranged inside the radiator core 81. Therefore, the outside air is forced to pass through the radiator core 81 by the cooling fan to promote heat dissipation.

  The front radiator tank 82 is provided with a tank upstream portion 82u, a tank downstream portion 82d, and a partition wall 82w that partitions the tank upstream portion 82u and the tank downstream portion 82d, and the partition wall 82w is substantially in the middle in the height direction. It is provided in the position. The partition wall 82w is provided with a bypass portion 84 that communicates the tank upstream portion 82u and the tank downstream portion 82d.

  A thermostat 85 is provided on the partition wall 82 w so as to communicate with the bypass portion 84. The thermostat 85 is connected to the coolant inlet 82i of the tank upstream portion 82u and selectively connects the coolant inlet 82i and the tank upstream portion 82u or connects the coolant inlet 82i and the tank downstream portion 82d. It is provided in the front radiator tank 82 so as to allow this. More specifically, the thermostat 85 includes a valve body 85v that is movable in the axial direction in accordance with the temperature of the refrigerant in the substantially cylindrical tube portion 85a, and the valve body 85v moves in accordance with the temperature of the refrigerant. Thereby, the bypass part 84 is opened and closed. In the closed state of the bypass portion 84, communication between the coolant inlet 82i and the tank upstream portion 82u is allowed, and communication between the coolant inlet 82i and the tank downstream portion 82d is blocked. On the other hand, in the open state of the bypass portion 84, communication between the coolant inlet 82i and the tank downstream portion 82d is allowed, and communication between the coolant inlet 82i and the tank upstream portion 82u is blocked.

  Thus, the radiator core 81 can be bypassed inside the radiator 80 by providing the thermostat 85 in the front radiator tank 82 so as to communicate with the bypass portion 84. For this reason, there is no need to provide a flow path for bypassing the radiator core 81 outside the radiator 80, and the cooling structure of the internal combustion engine 71 can be reduced in size and weight.

  In addition, the radiator 80 is disposed on the outer surface on one side in the vehicle width direction, and the pair of front radiator tank 82 and rear radiator tank 83 are disposed so as to sandwich the radiator core 81 in the vehicle longitudinal direction. A space is created below 80, and a wide bank angle can be secured.

  An exhaust pipe 36 is connected to the lower surface of the cylinder head 77, and the exhaust pipe 36 extends from the front to the rear while curving so as to bypass the swing shaft 35. A part of the exhaust pipe 36 is disposed so as to overlap the crankcase 74 below the radiator 80 in a side view. Therefore, a space is formed below the radiator 80, and the bank angle can be increased by arranging the exhaust pipe 36 so as to overlap the crankcase 74 in this space.

  The thermostat 85 is disposed above the cylinder axis SL of the cylinder block 76, and is disposed on the opposite side (upper side) of the exhaust pipe 36 with respect to the cylinder axis SL. Thereby, the thermostat 85 can be arrange | positioned away from the exhaust pipe 36, and the influence of the heat to the thermostat 85 can be reduced.

  The exhaust pipe 36 is provided with a catalyst 90 for purifying exhaust gas at a position extending in the vehicle width direction below the cylinder block 76. The thermostat 85 is disposed on the opposite side (upper side) of the catalyst 90 across the cylinder axis SL of the cylinder block 76. Thereby, the thermostat 85 can be arrange | positioned away from the catalyst 90, and the influence of the heat to the thermostat 85 can be reduced.

  The thermostat 85 is positioned below the internal combustion engine 71 and is disposed behind the swing shaft 35 provided in front of the crankcase 74 and behind the cylinder head 77. Thereby, the influence of the heat | fever of the thermostat 85 can be reduced by arrange | positioning the thermostat 85 away from the cylinder head 77. FIG.

  Next, the flow of the coolant C in the cooling structure of the internal combustion engine 71 will be described with reference to FIGS.

  When the internal combustion engine 71 is driven, the water is discharged from the pump discharge port 91 c of the water pump 86. The coolant C flows into the water jacket of the cylinder block 76 and the water jacket of the cylinder head 77 through the discharge hose 89c, and flows into the radiator 80 from the coolant inlet port 82i through the coolant inlet passage 89a. When the coolant C is at a predetermined temperature or higher, as shown in FIG. 3, the valve body 85v of the thermostat 85 is positioned on the lower side in the cylindrical portion 85a and the bypass portion 84 is closed. In the closed state of the bypass portion 84, as described above, communication between the coolant inlet port 82i and the tank upstream portion 82u is allowed, and communication between the coolant inlet port 82i and the tank downstream portion 82d is blocked. Therefore, the coolant C flows into the tank upstream portion 82u through the opening 85h of the cylindrical portion 85a of the thermostat 85. The coolant C flowing into the tank upstream portion 82u passes through the upper core 81u of the radiator core 81, enters the rear radiator tank 83, flows downward in the rear radiator tank 83, and flows to the lower core 81d of the radiator core 81. , Flows into the tank downstream portion 82d. Then, the coolant C is returned to the water pump 86 again from the coolant discharge port 96a through the coolant return passage 89b. As described above, when the coolant C flows through the radiator core 81, the heat of the coolant C is effectively released to the outside, and the coolant temperature is lowered.

  Further, during the warm-up operation immediately after the internal combustion engine 71 is started, that is, when the coolant C is lower than the predetermined temperature, as shown in FIG. 4, the valve body 85v of the thermostat 85 is positioned on the upper side in the cylindrical portion 85a. And the bypass part 84 will be in an open state. In the open state of the bypass portion 84, as described above, communication between the coolant inlet port 82i and the tank downstream portion 82d is allowed and communication between the coolant inlet port 82i and the tank upstream portion 82u is blocked. Therefore, the coolant C flows from the tank upstream portion 82u through the bypass portion 84 to the tank downstream portion 82d. Then, the coolant C is returned to the water pump 86 again from the coolant discharge port 96a through the coolant return passage 89b. As a result, since the coolant C does not flow into the radiator core 81, heat dissipation from the radiator core 81 is suppressed, the coolant temperature is likely to rise, and warm-up is promoted.

Note that the above embodiment can be modified, improved, and the like as appropriate. For example, in the above-described embodiment, the pair of radiator tanks 82 and 83 are arranged in the vehicle front-rear direction, but may be arranged up and down.
Further, the water pump 86 may be provided on the right side surface of the cylinder block 76.
Further, in the above embodiment, the radiator 80 and the water pump 86 are disposed on the right side of the internal combustion engine 71, but may be disposed on the left side of the internal combustion engine 71.

  FIG. 5 is a bottom view of a motorcycle according to a modification as viewed from below. Also in this modification, as in the above embodiment, the exhaust pipe 36 connected to the cylinder head 77 is provided with a catalyst 90 for purifying exhaust gas at a position extending in the vehicle width direction below the cylinder block 76. It has been.

  Furthermore, in the above embodiment, the lower front portion of the power unit 21 is attached to the rear end portion of the link 18 via the swing shaft 35 so as to be swingable up and down. However, as shown in FIG. May be attached to the rear frame 28 via the swing shaft 35 so as to be swingable up and down. Also in the cooling structure of the internal combustion engine of the modified example of FIG. 6, the radiator core 81 can be bypassed inside the radiator 80 by providing the thermostat 85 in the front radiator tank 82 so as to communicate with the bypass portion 84. it can. For this reason, there is no need to provide a flow path for bypassing the radiator core 81 outside the radiator 80, and the cooling structure of the internal combustion engine 71 can be reduced in size and weight.

In addition, at least the following matters are described in this specification. In addition, although the component etc. which respond | correspond in above-mentioned embodiment are shown in a parenthesis, it is not limited to this.
(1) A radiator (radiator 80) for exchanging heat between a coolant (coolant C) for cooling the internal combustion engine (internal combustion engine 71) and the outside air;
A thermostat (thermostat 85) for switching the coolant flow path in accordance with the temperature of the coolant;
In an internal combustion engine cooling structure comprising:
The radiator is
A radiator core (radiator core 81) for performing the heat exchange;
A pair of radiator tanks (a front radiator tank 82, a rear radiator tank) arranged so as to sandwich the radiator core,
One radiator tank (front radiator tank 82) of the pair of radiator tanks is
A tank upstream part (tank upstream part 82u);
A tank downstream part (tank downstream part 82d),
A partition wall (partition wall 82w) that partitions the tank upstream portion and the tank downstream portion;
A bypass part (bypass part 84) provided on the partition wall and communicating between the tank upstream part and the tank downstream part,
The thermostat is provided in the one radiator tank so as to communicate with the bypass portion,
When the coolant is above a predetermined temperature, the coolant is upstream of the tank, the radiator core (upper core 81u), the other radiator tank (rear radiator tank 83), the radiator core (lower core 81d), the It flows in the order of the tank downstream,
The cooling structure for an internal combustion engine, wherein when the coolant is lower than a predetermined temperature, the coolant flows in the order of the tank upstream portion, the bypass portion, and the tank downstream portion.

  According to (1), since the thermostat is provided in one of the radiator tanks so as to communicate with the bypass portion, the radiator core can be bypassed inside the radiator, so a flow path for bypassing the radiator core is provided. There is no need to provide it outside the radiator, and the cooling structure of the internal combustion engine can be reduced in size and weight.

(2) a swing type internal combustion engine mounted on a motorcycle (motorcycle 10) and swinging with a drive wheel (rear wheel 23);
A radiator (radiator 80) for exchanging heat between a coolant for cooling a cylinder block (cylinder block 76) and a cylinder head (cylinder head 77) of the internal combustion engine and outside air;
In a cooling structure for an internal combustion engine, comprising: a thermostat (thermostat 85) that switches a coolant flow path according to the temperature of the coolant (C).
The thermostat is disposed inside the radiator;
The radiator is disposed on an outer surface on one side (right side) in the vehicle width direction of the internal combustion engine, and a pair of radiator tanks (a front radiator tank 82, a front-end radiator tank 82, so as to sandwich a radiator core (radiator core 81) in the vehicle longitudinal direction. A cooling structure for an internal combustion engine in which a rear radiator tank) is arranged.

  According to (2), since the thermostat is disposed inside the radiator, there is no need to provide a flow path for bypassing the radiator core outside the radiator, and the cooling structure of the internal combustion engine can be reduced in size and weight. In addition, since the radiator is arranged on the outer surface on one side in the vehicle width direction, and the pair of radiator tanks are arranged so as to sandwich the radiator core in the vehicle longitudinal direction, a space is created below the radiator and the bank angle is increased. Widely secured.

(3) In the internal combustion engine cooling structure according to (1),
The internal combustion engine is mounted on a motorcycle, has a cylinder block (cylinder block 76) and a cylinder head (cylinder head 77) in the front, a crankcase (crankcase 74) in the rear, and a drive wheel (rear wheel 23) A swinging internal combustion engine that swings,
The radiator is disposed on an outer surface on one side (right side) of the crankcase in the vehicle width direction, and the pair of radiator tanks are disposed so as to sandwich the radiator core in the vehicle front-rear direction.
A water pump (water pump 86) for pumping the coolant is disposed on the outer surface of the cylinder block or the cylinder head on one side in the vehicle width direction,
The one radiator tank is disposed forward with respect to the radiator core,
A cooling structure for an internal combustion engine, wherein a cooling liquid return passage (cooling liquid return passage 89b) connected to the water pump is connected to the downstream portion of the tank.

According to (3), the radiator is disposed on the outer surface on one side in the vehicle width direction of the crankcase and the pair of radiator tanks are disposed so as to sandwich the radiator core in the vehicle longitudinal direction. Space is available and a wide bank angle can be secured.
The water pump for pumping the coolant is disposed on the outer surface of the cylinder block or the cylinder head on one side in the vehicle width direction, and one radiator tank is disposed in front of the radiator core. Since the coolant return passage connected to the water pump is connected, the tank downstream portion of the radiator tank and the water pump can be arranged close to each other, and the coolant flow path can be shortened.

(4) In the internal combustion engine cooling structure according to (2) or (3),
The internal combustion engine includes an exhaust pipe (exhaust pipe 36) connected to the lower surface of the cylinder head and extending backward while being curved,
The cooling structure for an internal combustion engine, wherein the exhaust pipe is disposed to overlap the crankcase below the radiator in a side view.

  According to (4), the exhaust pipe connected to the lower surface of the cylinder head and extending backward while being curved is disposed so as to overlap the crankcase below the radiator in a side view, so that there is a space below the radiator. The bank angle can be increased.

(5) In the internal combustion engine cooling structure according to any one of (2) to (4),
The internal combustion engine includes an exhaust pipe connected to the lower surface of the cylinder head and extending backward while being curved,
The cooling structure for an internal combustion engine, wherein the thermostat is disposed above a cylinder axis (cylinder axis SL) of the cylinder block.

  According to (5), the internal combustion engine includes an exhaust pipe connected to the lower surface of the cylinder head and extending backward while being curved, and the thermostat is disposed above the cylinder axis of the cylinder block. The thermal effect on the thermostat can be reduced by arranging the thermostat away from the thermostat.

(6) In the internal combustion engine cooling structure according to (4) or (5),
The exhaust pipe has a catalyst (catalyst 90) for purifying exhaust gas below the cylinder block,
The cooling structure for an internal combustion engine, wherein the thermostat is disposed on the opposite side of the catalyst across a cylinder axis (cylinder axis SL) of the cylinder block.

  According to (6), since the thermostat is disposed on the opposite side of the catalyst with the cylinder axis of the cylinder block interposed therebetween, the influence of heat on the thermostat can be reduced by disposing the thermostat away from the catalyst.

(7) In the cooling structure for an internal combustion engine according to any one of (2) to (6),
Below the internal combustion engine, a swing shaft (swing shaft 35) is provided in front of the crankcase and behind the cylinder head,
The cooling structure for an internal combustion engine, wherein the thermostat is disposed rearward of the swing shaft.

  According to (7), since the thermostat is arranged in front of the crankcase and in the rear of the swing shaft provided behind the cylinder head, the thermostat can be moved to the thermostat by disposing the thermostat away from the cylinder head. The influence of heat can be reduced.

10 Motorcycle 23 Rear wheel (drive wheel)
35 Oscillating shaft 36 Exhaust pipe 71 Internal combustion engine 74 Crankcase 76 Cylinder block 77 Cylinder head 80 Radiator 81 Radiator core 82 Front radiator tank (radiator tank)
83 Rear radiator tank (Radiator tank)
82u Tank upstream part 82d Tank downstream part 82w Partition wall 84 Bypass part 85 Thermostat 86 Water pump 89b Coolant return passage 90 Catalyst C Coolant SL Cylinder axis

Claims (7)

A radiator (80) for exchanging heat between the coolant (C) for cooling the internal combustion engine (71) and the outside air;
In the cooling structure of the internal combustion engine (71), comprising a thermostat (85) for switching the coolant flow path according to the temperature of the coolant (C),
The radiator (80)
A radiator core (81) for performing the heat exchange;
A pair of radiator tanks (82, 83) disposed so as to sandwich the radiator core (81),
Of the pair of radiator tanks (82, 83), one radiator tank (82) is
The tank upstream (82u),
A tank downstream part (82d),
A partition wall (82w) separating the tank upstream portion (82u) and the tank downstream portion (82d);
A bypass portion (84) provided on the partition wall (82w) and communicating with the tank upstream portion (82u) and the tank downstream portion (82d);
The thermostat (85) is provided in the one radiator tank (82) so as to communicate with the bypass portion (84),
When the coolant (C) is at a predetermined temperature or higher, the coolant (C) is supplied from the tank upstream portion (82u), the radiator core (81), the other radiator tank (83), and the radiator core (81). , Flowing in the order of the tank downstream part (82d),
When the coolant (C) is lower than a predetermined temperature, the coolant (C) flows in the order of the tank upstream portion (82u), the bypass portion (84), and the tank downstream portion (82d). 71) the cooling structure. A unit swing internal combustion engine (71) mounted on the motorcycle (10) and swinging with the drive wheel (23);
A radiator (80) for exchanging heat between the coolant (C) for cooling the cylinder block (76) and the cylinder head (77) of the internal combustion engine (71) and the outside air;
In the cooling structure of the internal combustion engine (71), comprising a thermostat (85) for switching the coolant flow path according to the temperature of the coolant (C),
The thermostat (85) is disposed inside the radiator (80),
The radiator (80) is disposed on an outer surface on one side in the vehicle width direction of the internal combustion engine (71), and a pair of radiator tanks (82, 83) are disposed so as to sandwich the radiator core (81) in the vehicle longitudinal direction. Arranged cooling structure of the internal combustion engine (71). The cooling structure of the internal combustion engine (71) according to claim 1,
The internal combustion engine (71) is mounted on the motorcycle (10), has a cylinder block (76) and a cylinder head (77) in the front, and a crankcase (74) in the rear, and swings with the drive wheels (23). A swing type internal combustion engine
The radiator (80) is disposed on the outer surface on one side in the vehicle width direction of the crankcase (74), and the pair of radiator tanks (82, 83) so as to sandwich the radiator core (81) in the vehicle longitudinal direction. ) Is placed,
The water pump (86) for pumping the coolant (C) is disposed on the outer surface of the cylinder block (76) or the cylinder head (77) on one side in the vehicle width direction,
The one radiator tank (82) is disposed forward with respect to the radiator core (81),
A cooling structure for the internal combustion engine (71), wherein a coolant return passage (89b) connected to the water pump (86) is connected to the tank downstream portion (82d). In the cooling structure of the internal combustion engine (71) according to claim 2 or 3,
The internal combustion engine (71) includes an exhaust pipe (36) connected to the lower surface of the cylinder head (77) and extending backward while being curved,
The exhaust pipe (36) is a cooling structure for the internal combustion engine (71), which is disposed so as to overlap the crankcase (74) below the radiator (80) in a side view. In the cooling structure of the internal combustion engine (71) according to any one of claims 2 to 4,
The internal combustion engine (71) includes an exhaust pipe (36) connected to the lower surface of the cylinder head (77) and extending backward while being curved,
The said thermostat (85) is a cooling structure of an internal combustion engine (71) arrange | positioned above the cylinder axis line (SL) of the said cylinder block (76). In the cooling structure of the internal combustion engine (71) according to claim 4 or 5,
The exhaust pipe (36) has a catalyst (90) for purifying exhaust gas below the cylinder block (76),
The cooling structure of the internal combustion engine (71), wherein the thermostat (85) is disposed on the opposite side of the catalyst (90) across the cylinder axis (SL) of the cylinder block (76). In the cooling structure of the internal combustion engine (71) according to any one of claims 2 to 6,
Below the internal combustion engine (71), a swing shaft (35) is provided in front of the crankcase (74) and rearward of the cylinder head (77).
The cooling structure for the internal combustion engine (71), wherein the thermostat (85) is disposed rearward of the swing shaft (35).

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