JP2006266178A - Air bleeding structure for water-cooled internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air bleeding structure for a water-cooled internal combustion engine capable of bleeding an inside of a pump chamber of a water pump, an inside of the housing of the thermostat valve at once with a simple structure and reducing manufacturing cost. <P>SOLUTION: An air bleeding hole 170 crossing a bypass passage 154 and making communication between the bypass passage 154 and the pump chamber 156 of the water pump 151 is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air vent structure for a water-cooled internal combustion engine, and more particularly to an air vent structure in a pump chamber of a water pump connected to a camshaft provided in a cylinder head and in a thermostat valve housing.

  As an example of an air vent structure of a water-cooled internal combustion engine, a die-cutting slope that is inclined upward toward the end face of the case is provided at the upper part of the inner surface of the case that stores the thermostat. A device provided with means for bleeding air from the air bleeding slope to the inlet side is known. (For example, refer to Patent Document 1).

Japanese Utility Model Publication No. 61-182481 (first page, FIG. 2)

  By the way, in a vehicle in which the radiator is mounted on the front of the vehicle body and the engine is mounted on the rear of the vehicle body, the mounted engine has a structure in which a water pump housing and a thermostat valve housing provided outside the cylinder head are integrally provided. The radiator and the engine coolant passage are connected by a pipe that passes under the passenger space provided between them. Therefore, when water is injected into the radiator, the radiator side and the engine coolant passage side are connected. It is necessary to bleed each.

  However, when the invention described in Patent Document 1 is adopted in the above vehicle, the air in the thermostat valve housing can be vented, but the air in the pump chamber of the water pump cannot be vented. There must be a separate passage, joint, etc. This complicates the internal structure of the engine and may increase manufacturing costs. Further, when the engine is started with air remaining in the cooling water passage of the engine, cavitation occurs in the pump chamber or the cooling performance of the engine is deteriorated by the air in the water jacket.

  The present invention has been made in view of the above circumstances, and its purpose is to simplify the structure of the air pump chamber of the water pump and the housing of the thermostat valve, and to reduce the manufacturing cost. It is an object of the present invention to provide an air vent structure for a water-cooled internal combustion engine.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a thermostat valve housing having a water pump integrally attached to one end of a cam shaft provided in a cylinder head and having a bypass passage in the water pump housing. An air vent structure for a water-cooled internal combustion engine provided integrally, characterized in that an air vent hole that intersects the bypass passage and communicates the bypass passage with the pump chamber of the water pump is provided.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the air vent hole includes a first air vent hole communicating with the bypass passage, the first air vent hole, and the pump chamber. The second air vent hole has a smaller diameter compared to the first air vent hole.

  According to a third aspect of the invention, in addition to the configuration of the first or second aspect of the invention, the first air vent hole is formed by casting and the second air vent hole is formed by machining. And

  According to the air-bleeding structure of the water-cooled internal combustion engine according to claim 1, the water vent is provided so as to intersect with the bypass passage in the housing of the thermostat valve and to communicate the bypass passage and the pump chamber of the water pump. The air in the pump chamber and the thermostat valve housing can be removed in a lump. This eliminates the need for a separate air vent passage or joint in the water pump housing, thus allowing the internal combustion engine to have a simple structure and reducing man-hours and parts for machining and the like. Cost can be reduced.

  According to the air vent structure of the water-cooled internal combustion engine according to claim 2, the air vent hole includes a first air vent hole that communicates with the bypass passage, and a second air vent that communicates the first air vent hole and the pump chamber. Since the second air vent hole has a smaller diameter than the first air vent hole, the cooling water flowing through the bypass passage can be prevented from flowing into the pump chamber of the water pump through the air vent hole. Thereby, it is possible to prevent the air that has been vented from returning to the pump chamber of the water pump.

  According to the air vent structure of the water-cooled internal combustion engine according to claim 3, since the first air vent hole is formed by casting and the second air vent hole is formed by machining, the processing of the air vent hole is minimized. The manufacturing cost can be reduced.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
1 to 7 show an embodiment of the present invention. FIG. 1 is a side view of a vehicle equipped with an air vent structure for a water-cooled internal combustion engine according to the present invention, and FIG. 2 is a vehicle shown in FIG. FIG. 3 is a sectional view taken along a line connecting a cylinder head, a cylinder block, a crankshaft, a main shaft, a counter shaft, an intermediate shaft, and a differential of a power unit for explaining an air bleeding structure of a water-cooled internal combustion engine according to the present invention. 4 is a cross-sectional view of the power unit shown in FIG. 3 cut along a plane passing through the fork shaft, the main shaft, the reverse shaft, the counter shaft, and the fork shaft. FIG. 5 is a cross-sectional view of the power unit shown in FIG. 6 is a partially cutaway side view of the left crankcase viewed from the inside, FIG. 6 is a partially cutaway side view of the left crankcase of the power unit shown in FIG. 3, and FIG. 7 is a thermostat of the power unit shown in FIG. Tattobarubu a partially cutaway sectional view for explaining the. In FIG. 1 and FIG. 2, “front”, “rear”, “left”, and “right” follow the direction seen from the driver, Fr is the front side, Rr is the rear side, L is the left side, and R is the right side. Show.

  As shown in FIGS. 1 and 2, the vehicle 10 includes a vehicle body (body frame) 11 having two left and right front wheels 12 and 12 and two right and left rear wheels 13 and 13, and a bar handle 15 type at the front of the vehicle body 11. The steering mechanism 14 is provided. A front seat 16 and a rear seat 17 are provided at the center of the vehicle body 11, and a power unit (internal combustion engine) 1 is provided at the rear lower portion of the vehicle body 11. Further, a front cover 18 that covers the periphery of the front portion of the vehicle body 11, a wind screen 19 that is attached to the upper portion of the front cover 18, extends continuously from the upper end of the wind screen 19 to the rear, and above the front and rear seats 16, 17. This is a small four-wheeled vehicle equipped with a covering roof 20 and a rear cover 21 covering the rear part of the vehicle body 11.

  The support structure of the roof 20 supports the roof 20 with the left and right roof side pillars 22 and 22. The left and right roof side pillars 22 and 22 are pipe-shaped roof pillars that are curved in an arch shape from the front part of the vehicle body to the rear part of the vehicle body, and are a combination structure of the front pillars 23 and 23 at the front part and the rear pillars 24 and 24 at the rear part. It is.

  The left and right front pillars 23, 23 are members that extend rearward and upward from the upper end of the front cover 18 at the front of the vehicle body, and span the front cross member 25 between the upper ends of the front pillars 23, 23. A wind screen 19 is provided between them.

  The left and right rear pillars 24, 24 extend upward from the upper ends of the left and right support members 26, 26 provided at the rear of the vehicle body, extend further forward from the upper ends, and have their front ends bolted to the rear ends of the front pillars 23, 23. A rear cross member 27 is stretched between the rear upper ends of the rear pillars 24, 24. The left and right support members 26 and 26 support the left and right rear pillars 24 and 24 at their upper ends in a detachable manner with bolts.

  And by attaching the substantially flat plate-like roof 20 to the frame composed of the left and right front pillars 23, 23, the left and right rear pillars 24, 24 and the front / rear cross members 25, 27, the roof 20 is detachably attached. Can support.

  The rear end of the roof 20 is behind the rear seat 17. The width of the roof 20 is approximately the same as or slightly smaller than the vehicle width. The side of the vehicle 10 is released, and the driver and the rear passenger can get on and off the vehicle.

  In this manner, the front of the front seat 16 can be covered with the wind screen 19, and the front seat 16 and the rear seat 17 can be covered with the roof 20. Not only the driver but also the rear passengers can be protected from rain. In addition, it is advantageous for rain and the like when placing luggage on the rear seat 17. Furthermore, since it is only the roof 20 and the side portions are open, it is easy to get on and off despite the presence of the roof 20.

  Further, the vehicle 10 includes a shift lever 28, a parking lever 29, a headlamp 30, a blinker 31, a side mirror 32, front fenders 33 and 33, rear fenders 34 and 34, an accelerator pedal (not shown), and a brake pedal (not shown). Prepare.

  As shown in FIG. 3, the power unit 1 is a water-cooled four-stroke cycle single-cylinder internal combustion engine. As shown in FIG. 1, the axis of the crankshaft is orthogonal to the traveling direction of the vehicle, and the cylinder head is positioned forward. The cylinder shaft is mounted on the vehicle 10 so that the cylinder shaft is substantially horizontal with respect to the traveling direction.

  As shown in FIG. 3, the power unit 1 includes a left crankcase 2, a right crankcase 3, a cylinder block 40, a cylinder head 50, a left crankcase cover 60, a right crankcase cover 61, and an intermediate gear housing. The chamber cover 62 is connected to form an outer shell. A crankshaft 100, a transmission 200, and a differential 300 are disposed in a crank chamber 4 formed by joining the left crankcase 2 and the right crankcase 3 together. The left crankcase cover 60 is bolted to the left side surface of the left crankcase 2, and the right crankcase cover 61 is bolted to the right side surface of the right crankcase 3.

  The left crankcase 2 is for arranging a first intermediate gear 202a fixed to the counter shaft 202 of the built-in transmission 200 and a second intermediate gear 203a fixed to the intermediate shaft 203 in a separate chamber from the crank chamber 4. An intermediate gear housing chamber 5 is formed. The intermediate gear storage chamber 5 is formed by projecting a peripheral wall 2c surrounding the intermediate gears 202a and 203a to the outside of the left crankcase 2, and the intermediate gear storage chamber cover 62 is bolted to the left crankcase 2. By stopping, the opening is closed.

  The cylinder head 50 is fastened together by a stud bolt 45 together with the cylinder block 40 inserted into the upper openings of the combined left and right crankcases 2 and 3, and a combustion chamber 51 is formed on the lower surface thereof. A spark plug 52 is attached so as to face.

  Further, a cam shaft 53 of a valve mechanism is rotatably supported in the cylinder head 50, and a cam sprocket 54 is fixed to the end thereof. The cam sprocket 54 spans a cam chain 94 that spans a drive sprocket 102 that is fixed to the crankshaft 100. As a result, the rotational driving force of the crankshaft 100 is transmitted to the camshaft 53, and the rocker arm 55 disposed in the cylinder head 50 is driven. Open and close at the timing.

  Further, a cooling water circulation mechanism 150 is provided on the left side of the cylinder head 50, and the cooling water circulation mechanism 150 is mainly disposed at the front portion of the water pump 151, the thermostat valve 152, and the vehicle 10 (see FIG. 1). And a radiator (not shown). The water pump 151 has the right end portion of the pump shaft 158 connected to the left end portion of the cam shaft 53 of the valve mechanism, and operates when the pump shaft 158 rotates as the cam shaft 53 rotates.

  Further, a water jacket 58 is formed adjacent to the upper side of the combustion chamber 51 of the cylinder head 50. Further, a water jacket 44 is formed around a portion of the cylinder block 40 close to the combustion chamber 51. By connecting the cylinder head 50 and the cylinder block 40, the water jackets 44 and 58 are communicated with each other.

  The crankshaft 100 is composed of left and right parts, and is integrated by a crankpin 101. The crankshaft 100 is rotatably supported via rolling bearings 70 and 71 disposed in the left crankcase 2 and the right crankcase 3, respectively. The AC generator 90 is assembled on the left side in the axial direction, and the torque converter 91 is assembled on the right side in the axial direction. Further, a piston 42 is connected to the crankpin 101 via a connecting rod 41, and this piston 42 reciprocates in the cylinder axis direction in a cylinder liner 43 integrally formed in the cylinder block 40.

  The AC generator 90 generates a high voltage to be applied to the spark plug 52 through an ignition coil (not shown) and generates a charging current for a battery (not shown).

  The torque converter 91 includes a pump impeller 91a that is splined to the crankshaft 100, a turbine runner 91b that is disposed opposite to the pump impeller 91a, and a stator 91d that is coupled to the crankshaft 100 via a one-way clutch 91c. And a stator fixing plate 91e that receives a reaction force applied to the stator 91d.

  The torque converter 91 is filled with torque converter oil for lubricating the crank chamber 4 and when the pump impeller 91a rotates together with the crankshaft 100, when the turbine runner 91b does not follow the pump impeller 91a, the rotation direction of the pump impeller 91a is The stator 91d receives a reaction force in the opposite direction, and the stator fixing plate 91e receives the reaction force. Then, the rotational power of the turbine runner 91b is transmitted to the primary driven gear 93 of the multi-plate clutch 92 provided on the right side of the main shaft 201 via the primary drive gear 103 mounted on the crankshaft 100.

  The multi-plate clutch 92 is a wet-type shift change clutch and is assembled to the right side of the main shaft 201. The multi-plate clutch 92 is alternately arranged on the plurality of clutch plates 92b and the clutch plates 92b in the outer case 92a. A plurality of clutch discs 92c, each of which includes a damper spring, a drive plate, a stop ring, a clutch spring, a clutch weight, an outer drive gear, a center clutch, and a free spring (not shown). And a set ring. The multi-plate clutch 92 includes a clutch lifter cam plate (not shown) in which a clutch lifter lever (not shown) coupled to the change spindle 9 supported by the right crankcase 3 is assembled to the multi-plate clutch 92. ) Is turned into a neutral state without transmitting the rotational power of the crankshaft 100 to the transmission 200 during the gear change of the transmission 200, and the rotational power of the crankshaft 100 is changed at the same time as the gear change of the transmission 200 is completed. It is transmitted to the transmission 200.

  As shown in FIGS. 3 to 5, the transmission 200 includes a main shaft 201, a counter shaft 202, an intermediate shaft 203, a reverse shaft 204, a fork shaft 205, and a shift drum 206. Arranged parallel to the crankshaft 100. 4 is a cross-sectional view taken along a line connecting the fork shaft 205, the main shaft 201, the reverse shaft 204, the counter shaft 202, and the fork shaft 205, the two fork shafts 205 are shown. Actually, it is one.

  The main shaft 201 is rotatably supported via rolling bearings 72 and 73 disposed in the left and right crankcases 2 and 3, respectively, and gears 201a and 201b that are inserted in a relatively rotatable manner. The main shaft 201 is integrated with a gear 201c that can be slidably moved in the axial direction of the main shaft 201 and locked in the rotational direction and can be engaged with the gear 201a or the gear 201b by the movement of the first shift fork 207. A gear 201d to be molded.

  The counter shaft 202 is rotatably supported via rolling bearings 74 and 75 disposed in the left and right crankcases 2 and 3, respectively, and a fixed gear 202b, and a gear 202c that is inserted so as to be relatively rotatable. 202d and a gear 202e which can be slidably moved in the axial direction of the counter shaft 202 between the gears 202c and 202d and locked in the rotational direction, and can be engaged with the gear 202c or the gear 202d by the movement of the second shift fork 208. And comprising. A first intermediate gear 202 a (see FIG. 3) is fixed to the left end portion of the counter shaft 202, and the first intermediate gear 202 a is disposed in the intermediate gear housing chamber 5.

  The intermediate shaft 203 is rotatably supported via rolling bearings 76 and 77 disposed in the left and right crankcases 2 and 3, respectively, and a second intermediate gear 203a fixed to the left end portion and a spring A gear 203b that is urged to the left by the mechanism 209 and locked in the rotational direction. The second intermediate gear 203 a is disposed in the intermediate gear housing chamber 5, and the gear 203 b is disposed in the differential chamber 301. Here, the differential chamber 301 is independent of the crank chamber 4 and the intermediate gear storage chamber 5 by the partition walls 6 and 7 formed in the left and right crankcases 2 and 3 in the crank chamber 4 behind the transmission 200, respectively. Is formed. The first intermediate gear 202a and the second intermediate gear 203a are always meshed.

  The reverse shaft 204 is supported by a fitting portion formed in each of the left and right crankcases 2 and 3, and rotatably supports integrally formed gears 204a and 204b.

  The fork shaft 205 is supported by a fitting portion formed on each of the left and right crankcases 2 and 3, and supports the first shift fork 207 and the second shift fork 208 so as to be slidable in the axial direction. To do.

  The shift forks 207 and 208 are respectively inserted into cam grooves 206a and 206b provided on the shift drum 206, and the shift drum 206 rotates to slide along the cam grooves 206a and 206b on the axis of the fork shaft 205. To do.

  The differential 300 is disposed in the differential chamber 301. Since the ring gear 302 is engaged with the gear 203b of the intermediate shaft 203, the rotational power of the intermediate shaft 203 is transmitted to the ring gear 302 via the gear 203b. Thus, the left and right drive shafts 304 and 305 are rotated by the differential gear mechanism 303.

  As shown in FIG. 5, an injector 59 is assembled on the upper side of the cylinder head 50. The injector 59 is electrically connected to an unillustrated engine control unit, and injects high fuel pressure fuel into an unillustrated intake port according to the rotational speed by a current supplied from the engine control unit. .

  Lubricating oil supply passages 2a are formed symmetrically on the split surfaces of the left and right crankcases 2 and 3, respectively. The oil feed passage 2 a is sealed by coupling the crankcases 2 and 3, the front end is connected to the discharge side of an oil pump (not shown), and the rear end is in the intermediate gear housing chamber 5. The oil supply passage (see FIG. 6) 5a is connected in communication.

  As shown in FIG. 6, the intermediate gear storage chamber 5 is formed by projecting the peripheral wall 2c surrounding the intermediate gears 202a and 203a to the outside of the left crankcase 2 as described above. An oil feeding passage 5a having a substantially inverted L shape in a side view is formed on the end surface of this. The oil feeding passage 5a includes a central hole 5b communicating with the oil feeding passages 2a and 3a, a main shaft hole 5c provided on the lower side of the central hole 5b, and a reverse shaft hole 5d provided on the rear side of the central hole 5b. The end face of the peripheral plate 2c is composed of connection grooves 5e and 5e that connect the holes 5c, 5b, and 5d. The main shaft hole 5c and the reverse shaft hole 5d penetrate into the crank chamber 4 from the end face of the peripheral plate 2c.

  The intermediate gear storage chamber 5 has an orifice hole 2d formed through the left crankcase 2 at a position adjacent to the main shaft hole 5c. As shown in FIG. 3, the orifice hole 2d communicates with the oil feed passage 5a via the main shaft hole 5c and also in a lubricating oil passage 201e (see FIG. 3) formed in the main shaft 201. Communicated. Further, the intermediate gear housing chamber 5 is provided with a lubricating oil return hole 2e formed through the crank chamber 4 at a position on the back surface side of the first intermediate gear 202a.

  Then, the intermediate gear storage chamber 5 is assembled in a bathtub system by lubricating the oil discharged from the orifice hole 2d while the opening is closed by the assembly of the intermediate gear storage chamber cover 62 and the oil feed passage 5a is sealed. The lubricating oil collected at the bottom of the peripheral plate 2c while lubricating the first and second intermediate gears 202a and 203a, and then the lubricating oil collected at the bottom of the peripheral plate 2c is fed into the crank chamber 4 from the lubricating oil return hole 2e. Returned.

  Accordingly, one of the lubricating oil discharged from the oil pump is fed to the lubricating hole 105 of the crankshaft 100 through an oil feeding passage (not shown) formed in the crankcase cover 61, and the other is left and right crankcase. The oil is fed to the oil feed passage 2a formed in the right crankcase 3 formed on the second and third split surfaces. The lubricating oil fed to the lubricating hole 105 passes through the torque converter 8 and is fed into the crank pin 101.

  The lubricating oil fed to the oil feed passage 2a formed in the left and right crankcases 2 and 3 is fed from the front end portion to the rear end portion of the oil feed passage 2a, and the oil feed passage in the intermediate gear housing chamber 5 is supplied. In 5a, it branches from the center hole 5b into the main shaft hole 5c and the reverse shaft hole 5d. The lubricating oil fed to the main shaft hole 5c is sent from the main shaft hole 5c to the left bearing 72 portion of the main shaft 201, and is formed in the main shaft 201 (see FIG. 3). Once taken in, it is sent to the orifice hole 2d and discharged from the orifice hole 2d into the intermediate gear housing chamber 5.

  On the other hand, the lubricating oil fed from the central hole 5b to the reverse shaft hole 5d is fed from the reverse shaft hole 5d to the left side portion of the reverse shaft 204 and is formed in the reverse shaft 204 (see FIG. 4). ). Here, the lubricating oil collected in the oil pocket 3c formed in the right crankcase 3 is supplied to the lubricating hole 202f (see FIG. 4) formed in the counter shaft 202.

  Next, the cooling water circulation mechanism 150 will be described in detail with reference to FIGS. 3 and 5 to 7.

  As described above, the cooling water circulation mechanism 150 is mainly configured by the water pump 151, the thermostat valve 152, and the radiator (not shown) disposed in the front portion of the vehicle 10 (see FIG. 1). The water pump 151 is housed in a water pump housing (water pump housing) 153, and a thermostat case (thermostat valve housing) 155 of a thermostat valve 152 having a bypass passage 154 is integrally formed in the water pump housing 153. It is bolted.

  The water pump 151 is rotatably supported via a rolling bearing 78 disposed in the water pump housing 153, and is integrally formed with the pump shaft 158 and a pump shaft 158 connected to the left end portion of the cam shaft 53. Slewing wing (impeller) 157 and a seal member 79 (see FIG. 3), and the slewing wing is provided in a pump chamber 156 formed by bolting the water pump housing 153 and the thermostat case 155 together. 157 is arranged.

  The thermostat valve 152 is housed in a thermostat chamber 159 formed by bolting the thermostat case 155 and the cover 165 together. The cover 165 is formed with a radiator water inlet 164 that connects a radiator hose 162 that communicates with the radiator. The thermostat case 155 has a bypass passage 154 and a cooling water inflow passage 160 that connects the pump chamber 156 and the thermostat chamber 159. Is formed. Further, the thermostat case 155 is formed with an air vent hole 170 that intersects the bypass passage 154 and communicates the bypass passage 154 and the pump chamber 156. Further, a bypass water inlet 154a is fitted in the bypass passage 154.

  A cooling water discharge port 161 communicating with the pump chamber 156 is formed by integrating the water pump housing 153 and the thermostat case 155. The cooling water discharge port 161 communicates with the water jacket 44 of the cylinder block 40 via a water jacket hose 163 and a water jacket inlet 166 bolted to the lower surface of the cylinder block 40. The water jacket 44 communicates with a water jacket 58 (see FIG. 3) of the cylinder head 50, and the water jacket 58 communicates with a cooling water distributor 167 that is bolted to the right side surface of the cylinder head 50. The cooling water distributor 167 is connected with a radiator hose (not shown) for supplying cooling water to the radiator and a bypass hose 168 communicating with the bypass water inlet 154. An air vent valve 169 for venting residual air in the coolant circulation mechanism 150 is provided at the upper end of the coolant distributor 167.

  The thermostat valve 152 is fixed by sandwiching the bridge plate portion 152 a between the water pump housing 153 and the thermostat case 155. A spring support member 152b is assembled to the bridge plate portion 152a, and one end of a plunger 152d protruding from the cylindrical movable portion 152c is held on the bridge plate portion 152a. The other end of the plunger 152d is inserted into the cylindrical movable part 152c. Since wax is sealed inside the large diameter portion of the cylindrical movable portion 152c, it functions as a temperature sensing portion. The cylindrical movable portion 152c is provided with a first valve body 152e and a second valve body 152f. The first valve body 152e is fixed to the cylindrical movable portion 152c. The second valve body 152f is urged by a conical coil spring 152g from the cylindrical movable portion 152c, and is disposed to face the bypass passage 154. A coil spring 152h is mounted between the spring support member 152b and the first valve body 152e. Further, the bridge plate portion 152a is provided with a small opening 152i having a jiggle valve 152j. The jiggle valve 152j opens the small opening 152i by dropping downward due to gravity when the cooling water is injected, and moves the air in the radiator hose 162 to the thermostat chamber 159. When the engine is in operation, the small opening 152i is closed by being pushed up by the water pressure of the water pump 151.

  The air vent hole 170 includes a first air vent hole 171 that communicates with the bypass passage 154, and a second air vent hole 172 that communicates between the first air vent hole 171 and the pump chamber 156. The hole 171 is formed into a taper shape by casting, and the second air vent hole 172 is formed to be smaller in diameter than the inner diameter of the first air vent hole 171 by machining such as a drill. The air vent hole 170 is opened above the left end surface of the pump chamber 156. The outer opening of the air vent hole 170 is closed by a plug 173.

  In the cooling water circulation mechanism 150 configured as described above, air is left in the thermostat chamber 159, the pump chamber 156, and the water jackets 44 and 58 when cooling water is injected from the upper part of the radiator such as during cooling water exchange. Here, when the power unit 1 is started, the camshaft 53 rotates, and accordingly, the swirl vane 157 of the water pump 151 starts rotating. At this time, since the power unit 1 is not warmed up and the cooling water is at a low temperature, the thermostat valve 152 has the second valve body 152f opening the bypass passage 154, and the first valve body 152e is the bridge plate portion. The area 152a is closed. Therefore, the cooling water discharged from the pump chamber 156 by the operation of the water pump 151 is pump chamber 156 → cooling water discharge port 161 → water jacket hose 163 → water jacket inlet 166 → water jacket 44, 58 → cooling water distributor. It circulates in the cooling water circulation mechanism 150 in the order of 167 → bypass hose 168 → bypass passage 154 → thermostat chamber 159 → cooling water inflow passage 160 → pump chamber 156. Although the first valve body 152e of the thermostat valve 152 is closed, the jiggle valve 152j prevents a small amount of cooling water from flowing from the radiator into the thermostat chamber 159 through the small opening 152i.

  At this time, the residual air in the pump chamber 156 first gathers above the pump chamber 156 and moves from the second air vent hole 172 to the first air vent hole 171 along the tapered surface of the first air vent hole 171. It moves into the bypass passage 154. Further, the residual air in the thermostat chamber 159 moves to the bypass passage 154 located at a higher position than the thermostat chamber 159. The residual air that has moved to the bypass passage 154 moves in the direction opposite to the flow of the cooling water along the inner peripheral surface of the bypass hose 168 provided in a slope shape, and is formed at the upper end of the cooling water distribution unit 167. The air vent valve 169 is discharged to the outside. Further, the air remaining from the water jacket inlet 166 to the cooling water distributor 167 moves in the same direction as the flow of the cooling water and is discharged to the outside from the air vent valve 169.

  When the power unit 1 is warmed up with the passage of time after starting and the cooling water reaches a predetermined temperature, the temperature of the cylindrical movable portion 152c of the thermostat valve 152 rises, and the wax filled therein expands. The cylindrical movable part 152c pushes out the plunger 152d. Then, since the distal end of the plunger 152d is locked to the bridge plate portion 152a, the cylindrical movable portion 152c itself moves against the elastic repulsive force of the coil spring 152h by the reaction force thereby causing the first valve body. 152e is opened and the second valve body 152f is closed. Thereby, the cooling water discharged from the pump chamber 156 is pump chamber 156 → cooling water discharge port 161 → water jacket hose 163 → water jacket inlet 166 → water jacket 44, 58 → cooling water distributor 167 → radiator hose ( It circulates in the cooling water circulation mechanism 150 in the order of (not shown) → radiator (not shown) → radiator hose 162 → radiator water inlet 164 → thermostat chamber 159 → cooling water inflow passage 160 → pump chamber 156.

  In the air vent structure of the water-cooled internal combustion engine described above, the air vent hole 170 that intersects the bypass passage 154 provided in the thermostat case 155 and communicates the bypass passage 154 and the pump chamber 156 of the water pump 151 is provided. The air in the pump chamber 156 and the thermostat case 155 of the pump 151 can be removed in a lump. As a result, there is no need to separately provide a passage or joint for venting air in the water pump housing 153, so that the internal combustion engine can be made simple and manufactured with reduced man-hours and parts for machining and the like. Cost can be reduced.

  Further, in the air vent structure of the water-cooled internal combustion engine, the air vent hole 170 includes the first air vent hole 171 that communicates with the bypass passage 154, and the second air that communicates the first air vent hole 171 and the pump chamber 156. Since the second air vent hole 172 has a smaller diameter than the first air vent hole 171, the cooling water flowing through the bypass passage 154 passes through the air vent hole 170 and the pump chamber 156 of the water pump 151. Can be prevented from flowing into. Thereby, it is possible to prevent the air that has been vented from returning to the pump chamber 156 of the water pump 151.

  Further, in the air vent structure of the water-cooled internal combustion engine, since the first air vent hole 171 is formed by casting and the second air vent hole 172 is formed by machining, the processing of the air vent hole 170 is minimized. Manufacturing cost can be reduced.

1 is a side view of a vehicle equipped with an air vent structure for a water-cooled internal combustion engine according to the present invention. It is a top view of the vehicle shown in FIG. It is sectional drawing cut | disconnected by the line | wire which connected the cylinder head, cylinder block, crankshaft, main shaft, countershaft, intermediate shaft, and differential of the power unit explaining the air bleeding structure of the water-cooled internal combustion engine according to the present invention. FIG. 4 is a cross-sectional view of the power unit shown in FIG. 3 cut along a plane that passes through the axes of the fork shaft, the main shaft, the reverse shaft, the counter shaft, and the fork shaft. FIG. 4 is a partially cutaway side view of the left crankcase of the power unit shown in FIG. 3 as viewed from the inside. FIG. 4 is a partially cutaway side view of the left crankcase of the power unit shown in FIG. 3 as viewed from the outside. It is a partially cutaway sectional view for explaining a thermostat valve of the power unit shown in FIG.

Explanation of symbols

1 Power unit (internal combustion engine)
DESCRIPTION OF SYMBOLS 10 Vehicle 40 Cylinder block 50 Cylinder head 53 Cam shaft 150 Cooling water circulation mechanism 151 Water pump 152 Thermostat valve 153 Water pump housing (housing)
154 Bypass passage 155 Thermostat case (housing)
156 Pump chamber 157 Swirling vanes 158 Pump shaft 159 Thermostat chamber 160 Cooling water inflow passage 161 Cooling water discharge port 162 Radiator hose 163 Water jacket hose 164 Radiator water inlet 165 Cover 166 Water jacket inlet 167 Cooling water distributor 168 Bypass hose 169 Bleed valve 170 Air vent hole 171 First air vent hole 172 Second air vent hole 173 Plug

Claims (3)

A water pump is integrally attached to one end of a camshaft provided in a cylinder head, and a water-cooled internal combustion engine air vent structure in which a housing of a thermostat valve having a bypass passage is integrally provided in the water pump housing,
An air vent structure for a water-cooled internal combustion engine, characterized in that an air vent hole that intersects the bypass passage and communicates the bypass passage and the pump chamber of the water pump is provided.   The air vent hole includes a first air vent hole that communicates with the bypass passage, and a second air vent hole that communicates the first air vent hole and the pump chamber. 2. The air vent structure for a water-cooled internal combustion engine according to claim 1, wherein the air vent structure has a smaller diameter than the first air vent hole.   3. The air vent structure for a water-cooled internal combustion engine according to claim 1, wherein the first air vent hole is formed by casting and the second air vent hole is formed by machining.

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