JP2006275026A - Water-cooled internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a working efficiency for mounting a crankcase cover having an outlet water passage on a crankcase in a water-cooled internal combustion engine having a water pump installed in the crankcase cover. <P>SOLUTION: This water-cooled internal combustion engine E comprises the water pump 40 installed in the crankcase cover 25 and a cylinder having a water jacket for leading cooling water from the water pump 40 therein. An outlet part 48 forming an outlet water passage 47 for circulating, therein, the cooling water force-fed by the water pump 40 is formed in the crankcase cover 25. An introduction part 51 for forming an introduction water passage 50 leading the cooling water in the outlet water passage 47 to the water jacket is formed in the cylinder. The downstream side end part 48a of the outlet part 48 and the upstream side end part of the introduction part 51 and a connection pipe 53 at the upstream side end part of the introduction part 51 are fitted to each other to form the positioning part of the crankcase cover 25 against a crankcase portion 2a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water-cooled internal combustion engine including a water pump provided on a crankcase cover.

An example of this type of water-cooled internal combustion engine is disclosed in Patent Document 1. In this V-type two-cylinder internal combustion engine, a cylinder block is stacked on top of a crankcase and coupled together, and a cooling water pump is provided on a right cover that covers the right end of the crankcase and the cylinder block. Is supplied to the water jacket of the cylinder block.
JP-A-9-280048

  In the prior art, the cooling water pumped by the cooling water pump is supplied to the water jacket through the cooling water passages opened in the mating surfaces of the right cover and the cylinder block. For this reason, it is necessary to position the right cover with respect to the crankcase and the cylinder block so that the cooling water passages formed in the right cover and the cylinder block are accurately aligned. It took time. Further, since the cooling water passages formed in the right cover and the cylinder block are inside the outermost mating surface with the cylinder block of the right cover, the crankcase cover is enlarged.

  This invention is made | formed in view of such a situation, and the invention of Claims 1-5 is a water-cooled internal combustion engine provided with the water pump provided in the crankcase cover, and an exit water path is provided. The purpose is to improve the working efficiency of assembling the crankcase cover to the crankcase. The invention described in claim 2 further aims to simplify the shape of the crankcase cover or the cylinder, and the invention described in claim 3 further improves the working efficiency of assembly and disassembly of the internal combustion engine. The invention according to claim 4 further aims to reduce the pressure loss of the cooling water in the introduction water passage, and the invention according to claim 5 further provides a crankcase provided with a water pump. The purpose is to reduce the size of the cover.

  The invention according to claim 1 includes a crankcase to which a crankcase cover is coupled, a water pump that is provided on the crankcase cover and pumps cooling water, and a water jacket into which cooling water from the water pump is introduced. In the water-cooled internal combustion engine including the provided cylinder, the crankcase cover is provided with an outlet portion that forms an outlet water passage through which the pumped cooling water flows, and the cylinder includes the outlet water passage. An introduction portion that forms an introduction water passage that guides cooling water to the water jacket is provided, and the downstream end portion of the outlet portion and the upstream end portion of the introduction portion are fitted to each other, thereby allowing the crankcase to This is a water-cooled internal combustion engine that constitutes a positioning part of the crankcase cover.

  According to this, since the outlet water passage and the introduction water passage are connected by fitting the outlet portion and the introduction portion, positioning of both water passages when joining the crankcase cover to the crankcase becomes easy. Moreover, the crankcase cover is positioned with respect to the crankcase by using the outlet portion and the introduction portion.

  According to a second aspect of the present invention, in the water-cooled internal combustion engine according to the first aspect, at least one of the downstream end and the upstream end is a connecting pipe that is a member separate from the crankcase cover and the cylinder. It is composed.

  According to this, at least one of the downstream end portion and the upstream end portion is composed of a connecting tube having rigidity that can constitute the positioning portion, and thus flows out of the water pump without using a flexible tube such as a hose. Immediately after the cooling water can be guided to the jacket. Further, since the downstream end portion does not need to be integrally formed with the crankcase cover, or the upstream end portion does not need to be integrally formed with the cylinder, the shape of the crankcase cover or the cylinder is simplified.

  The invention according to claim 3 is the water-cooled internal combustion engine according to claim 1 or 2, wherein the crankcase cover is attached to and detached from the crankcase in the fitting direction of the downstream end and the upstream end. Is consistent with

  According to this, attachment / detachment of the crankcase cover with respect to the crankcase becomes easy. Also, the fitting work between the outlet part and the introducing part and the assembling work of the crankcase cover to the crankcase are carried out simultaneously, and the fitting releasing work between the outlet part and the introducing part and the removing work of the crankcase cover are carried out simultaneously. Done.

  According to a fourth aspect of the present invention, in the water-cooled internal combustion engine according to any one of the first to third aspects, the introduction water passage extends in a straight line extending along a plane parallel to the cylinder axis of the cylinder. Which is connected to the water jacket in a tangential direction.

  According to this, since the introduction water passage is straight, the pressure loss due to the bending of the water passage is reduced.

  According to a fifth aspect of the present invention, in the water-cooled internal combustion engine according to any one of the first to fourth aspects, the outlet portion is more than an outermost mating surface of the crankcase cover with the crankcase. It protrudes outward.

  According to this, since it is not necessary to arrange | position the whole exit part inside the mating surface of the outermost periphery of a crankcase cover, the range enclosed by the mating surface can be made small.

  According to invention of Claim 1, the following effect is show | played. That is, the positioning of the outlet water passage and the introduction water passage is easy, and the positioning of the crankcase cover is facilitated, so that the work efficiency of assembling the crankcase cover provided with the outlet water passage is improved.

  According to invention of Claim 2, in addition to the effect of the invention of the cited claim, there exists the following effect. That is, since the cooling water immediately after flowing out of the water pump can be guided to the jacket without using the flexible pipe, the cooling water piping is simplified and made compact. Moreover, since the shape of the crankcase cover or the cylinder is simplified, the cost is reduced.

  According to invention of Claim 3, in addition to the effect of the invention of the cited claim, there exist the following effects. That is, the crankcase cover can be easily attached and detached, and the fitting operation between the outlet portion and the introduction portion and the assembling operation of the crankcase cover, the fitting release operation between the outlet portion and the introduction portion, and the removal of the crankcase cover are performed. Since the work is performed simultaneously, the work efficiency of assembly and disassembly of the internal combustion engine is improved.

  According to invention of Claim 4, in addition to the effect of the invention of the cited claim, there exists the following effect. That is, since the pressure loss of the cooling water in the introduction water passage is reduced, the driving force of the water pump can be reduced.

  According to the invention described in claim 5, in addition to the effect of the invention described in the cited claim, the following effect is produced. That is, since the range surrounded by the mating surfaces can be reduced, the crankcase cover can be reduced in size.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
1 and 2, a water-cooled internal combustion engine E to which the present invention is applied is mounted on a scooter type motorcycle as a vehicle. The internal combustion engine E constitutes a power unit together with a power transmission device in which the belt type continuously variable transmission M and the gear type reduction mechanism R are integrated. The power generated by the internal combustion engine E is transmitted to a rear wheel, which is a drive wheel as a drive target, via a continuously variable transmission M and a speed reduction mechanism R.

  The internal combustion engine E mounted on the motorcycle in a horizontal arrangement in which the rotation center line L0 of the crankshaft 7 is oriented in the left-right direction is an OHC type V-type two-cylinder four-stroke internal combustion engine and is arranged in a V shape. A pair of cylinders 1a, 1b, a crankcase 2 coupled to each cylinder 1a, 1b at the base end in the direction of cylinder axis L1a, L1b (hereinafter simply referred to as "cylinder axis direction"), and each cylinder A pair of cylinder heads 3a and 3b coupled to the cylinders 1a and 1b and integrated with the cylinders 1a and 1b, and a pair of head covers 4a coupled to the cylinder heads 3a and 3b. , 4b. Therefore, the cylinders 1a and 1b and the crankcase 2 are separate members.

  In the specification or claims, the axial direction means the direction of the rotation center line L0 of the crankshaft 7 unless otherwise specified. Further, in the embodiment, up and down, front and rear, and left and right respectively mean up and down, front and rear, and left and right when a motorcycle is used as a reference.

  Referring also to FIG. 3, the pair of first and second banks B1 and B2 constituting the V bank are mainly composed of a cylinder 1a and a cylinder 1b, respectively. More specifically, the first bank B1 as the front bank includes a cylinder 1a that has a cylinder axis L1a that is slightly tilted forward and obliquely upward and is largely tilted forward, a cylinder head 3a, and a head cover 4a. The second bank B2 as a rear bank includes a cylinder 1b having a cylinder axis L1b slightly inclined rearward and obliquely upward, a cylinder head 3b, and a head cover 4b.

  A crankshaft 7 to which a piston 5 fitted to each cylinder 1a, 1b so as to be capable of reciprocating movement is connected via a connecting rod 6 is housed in a crank chamber 8 formed by the crankcase 2, and is paired with the crankcase 2. The main bearing is rotatably supported. The left-right split crankcase 2 includes first and second crankcase portions 2a and 2b that are divided in the axial direction by a plane orthogonal to the rotation center line L0.

  2 and 3, each cylinder head 3a, 3b, which is fastened together with the cylinders 1a, 1b to the crankcase 2 by the head bolt B1, has a combustion chamber 10 facing the piston 5 in the cylinder axial direction, An intake port 11 having a pair of intake ports that open to the combustion chamber 10 and an exhaust port 12 having a pair of exhaust ports that open to the combustion chamber 10 are formed, and an ignition plug 13 (see FIG. 1) is mounted. Furthermore, each cylinder head 3a, 3b is provided with a pair of intake valves 14 and a pair of exhaust valves 15 that open and close the pair of intake ports and the pair of exhaust ports, respectively. Referring also to FIG. 4, each intake valve 14 and each exhaust valve 15 are cams that are rotationally driven by the power of the crankshaft 7 that is transmitted via valve gear transmission mechanisms T1 and T2 having chains 16a and 16b. Each of them is opened and closed at a predetermined timing by a valve gear 17 including a rocker arm 19 that is driven by a valve cam provided on the shaft 18 to swing.

  Referring to FIGS. 1 and 3, an intake device 20 including a pair of throttle bodies 21 provided with a throttle valve 21 a is disposed in the bank space, and the intake air guided by the intake device 20 is attached to the throttle body 21. The air-fuel mixture formed by the fuel supplied from the fuel injection valve 22 is sucked into the combustion chamber 10 through the intake port 11. The combustion gas generated in the combustion chamber 10 drives the piston 5 with the pressure, and is then discharged to the outside as an exhaust gas through an exhaust device having an exhaust pipe (not shown) connected to the exhaust port 12.

Referring to FIGS. 2 and 4, the crankcase cover 25 is coupled to only the first crankcase portion 2 a made of one member among the plurality of crankcase portions 2 a and 2 b. Then, an auxiliary machine chamber 27 in which an AC generator 26 as an auxiliary machine is housed by a crankcase cover 25 fastened by a number of bolts B2 to the left of the first crankcase part 2a and the first crankcase part 2a. An oil tank 28 is formed adjacent to the rear of the auxiliary machine chamber 27. Therefore, a part of the crankcase cover 25 constitutes a chamber wall 27a of the auxiliary machine chamber 27 and a tank wall 28a of the oil tank 28 (see also FIG. 5).
A continuously variable transmission M is arranged on the right side of the second crankcase portion 2b.

Referring to FIGS. 3, 4, and 6, the lubrication system provided in the internal combustion engine E is a dry sump type lubrication system including an oil pump 30, and discharges the oil tank 28 and the oil sucked from the oil tank 28. A feed pump 30a, a water-cooled oil cooler 31 that cools the oil discharged from the feed pump 30a, an oil filter 32, and a scavenging pump 30b that collects oil after lubricating each lubricated portion of the internal combustion engine E; A plurality of oil passages for guiding the oil between these lubricating system members and for guiding the oil from the main gallery 33 into which the oil from the oil filter 32 flows to each lubricating portion of the internal combustion engine E, etc. .
The oil pump 30 includes a feed pump 30a and a scavenging pump 30b that are rotationally driven by a common drive shaft 35 that is rotationally driven by the power of the crankshaft 7 that is transmitted via an accessory transmission mechanism T3 having a chain 34. Composed.

  1, 3, 4, and 6, the cooling system of the internal combustion engine E includes a water pump 40 that is provided in the crankcase cover 25 and pumps cooling water, and cylinders 1 a and 1 b and a cylinder head 3 a, Formed by water jackets W1 to W4 respectively provided in 3b, a radiator R, a thermostat 70 for controlling the flow and shut-off of cooling water to the radiator R according to the warm-up state of the internal combustion engine E, and a piping group and an engine body It is composed of a large number of water passages.

  4 to 6, the water pump 40 is provided coaxially with the drive shaft 35 of the oil pump 30 and rotates integrally therewith, an impeller 42 rotated by the drive shaft 41, and a crankcase cover. The pump body 43 is configured by a part of 25 and rotatably supports the drive shaft 41, and the pump cover 44 is coupled to the mounting seat 43 a of the pump body 43. Here, the pump body 43 and the pump cover 44 constitute a pump housing.

  The water pump 40 is provided with an inlet port 45 which is provided in the pump cover 44 and into which cooling water radiated by the radiator R and becomes low temperature, and cooling water which is provided in the pump cover 44 and which will be described later from a bypass passage. The bypass port 46 is provided, and the outlet port 47 is provided across the pump cover 44 and the pump body 43 and through which the cooling water pumped by the impeller 42 flows out. The outlet port 47 constitutes an outlet water passage formed by an outlet portion 48 provided integrally with the crankcase cover 25 as the pump body 43.

In the pump body 43, the outlet 48 protrudes outward from the outermost mating surface 25a of the crankcase cover 25 with the first crankcase portion 2a, that is, the mating surface 25a formed on the outer peripheral edge of the crankcase cover 25. On the other hand, the bearing portion 49 that rotatably supports the drive shaft 41 is disposed on the inner side of the mating surface 25a. The downstream end portion 48a of the outlet portion 48 is constituted by the tip portion of the projecting portion 48e, and the downstream end portion 47a of the outlet port 47 is constituted by a hole formed in the downstream end portion 48a, and the rotation center line L0. It has a parallel axis L2 and a circular cross section.
The outlet portion 48 is not provided in a member constituting the water pump 40 (in this embodiment, the pump body 43 corresponds), and the outlet water passage formed by the outlet portion 48 is the outlet of the water pump 40. The crankcase cover 25 may be provided so as to communicate with the port.

  3, 6, and 7, a cylinder provided with a water jacket W <b> 1 into which cooling water from the water pump 40 is first introduced among the plurality of water jackets W <b> 1 to W <b> 4 formed in the engine body. 1a is provided with an introduction portion 51 that forms an introduction water passage 50 that guides the cooling water flowing through the outlet port 47 to the water jacket W1. In this embodiment, the introduction part 51 includes a main body part 52 integrally formed with the cylinder 1a, and a connecting pipe 53 made of a rigid pipe fitted in a liquid tight state to the upstream end part 52a of the main body part 52 by a sealing member. Consists of Here, the rigid tube is a tube that does not have flexibility, and forms a counter electrode with a flexible tube that is a flexible tube such as a hose.

  The main body 52 extends in a tangential direction on the outer periphery of the cylinder 1a along a plane orthogonal to the cylinder axis L1a and bulges outward in the radial direction with respect to the cylinder axis L1a (see FIGS. 3 and 7).

  The connecting pipe 53 constitutes the upstream end portion 51a of the introduction portion 51, and the downstream end portion of the outlet portion 48 in a state where the crankcase cover 25 is coupled to the first crankcase portion 2a by the bolt B2 (see FIG. 4). The outlet port 47 and the introduced water passage 50 communicate with each other in a liquid-tight state by a seal member inside 48a. Therefore, the connecting pipe 53 is a separate member from the crankcase cover 25 and the cylinder 1a, the downstream end portion 48a constitutes the fitting portion of the outlet portion 48, and the connecting tube 53 is the fitting portion of the introducing portion 51. Configure. Then, in a state where the outlet portion 48 and the introduction portion 51 are connected, the connecting pipe 53 is almost entirely inserted across the outlet portion 48 and the main body portion 52.

  An introduction water passage 50 having a water passage 54 constituted by a hole formed in the main body 52 has an axis L3 (see also FIG. 3) on a plane parallel to the cylinder axis L1a and on a plane orthogonal to the cylinder axis L1a. The axes L2 and L3 are parallel to the rotation center line L0 of the crankshaft 7.

  The connecting pipe 53 forming the upstream end portion 50a of the introduction water passage 50 is constituted by a straight pipe having a circular cross section so as to have an axis L3 parallel to the rotation center line L0, and the upstream end portion 54a of the water passage 54 is also circular. It has a cross section. The water passage 54 is connected to the cylindrical water jacket W1 in the tangential direction. And in the state which the downstream end part 48a and the connection pipe | tube 53 fitted, both axial line L2, L3 corresponds.

Further, when the crankcase cover 25 is coupled to the first crankcase portion 2a, the downstream end portion 48a of the outlet portion 48 and the upstream end portion 51a (connecting pipe 53) of the introducing portion 51 are fitted to each other. Utilizing this, the crankcase cover 25 is positioned with respect to the first crankcase portion 2a. Therefore, the downstream end portion 48a and the connecting pipe 53 constitute a positioning portion of the crankcase cover 25.
The direction in which the crankcase cover 25 is attached to and detached from the first crankcase portion 2a is the axial direction, and the fitting direction between the outlet portion 48 and the introducing portion 51, that is, the fitting between the downstream end portion 48a and the connecting pipe 53. The direction is also an axial direction.

The circulation of the cooling water in the cooling system will be described with reference to FIGS. 1, 3, 4 and 7.
Cooling water from the outlet port 47 of the water pump 40 flows from the tangential direction into the water jacket W1 of the cylinder 1a through the introduction water passage 50, and after flowing into the water jacket W2 of the cylinder head 3a after cooling the cylinder 1a. The cylinder head 3a and the spark plug 13 are cooled. Thereafter, the cooling water flows from the water jacket W2 through the water passage W5 formed by the conduit 71 into the water jacket W3 of the cylinder 1b to cool the cylinder 1b, and then flows into the water jacket W4 of the cylinder head 3b. After the cylinder head 3b and the spark plug 13 are cooled, they flow into a thermostat 70 attached to the cylinder head 3b.

  When the internal combustion engine E is warmed up, the cooling water flowing into the thermostat 70 flows through the bypass passage W6 formed by the conduit 72 connected to the thermostat 70 and is sucked into the water pump 40. Further, after the warm-up of the internal combustion engine E is completed, the bypass passage W6 is blocked, so that the cooling water that has flowed into the thermostat 70 flows out of the thermostat 70 and flows into the radiator R, radiates heat at the radiator R, and has a low temperature. After that, the water pump 40 flows through the water passage formed by the conduit 73 connecting the radiator R and the inlet port 45 and is sucked into the water pump 40. In addition, cooling water is guided to the oil cooler 31 through a water passage that is branched from the introduction water passage 50 and formed by a conduit 74.

Next, operations and effects of the embodiment configured as described above will be described.
The crankcase cover 25 is provided with an outlet portion 48 that forms an outlet port 47 that is an outlet water passage, and the cylinder 1 a is provided with an introduction portion 51 that forms an introduction water passage 50, and a downstream end portion 48 a of the outlet portion 48. And the upstream end portion 51a (connecting pipe 53) of the introduction portion 51 constitute a positioning portion of the crankcase cover 25 with respect to the first crankcase portion 2a by fitting with each other. Therefore, since the outlet port 47 and the introduction water passage 50 are connected by fitting the outlet portion 48 and the introduction portion 51, the outlet port 47 and introduction when the crankcase cover 25 is coupled to the first crankcase portion 2a. The mutual positioning of the water passage 50 is facilitated, and the crankcase cover 25 is positioned with respect to the first crankcase portions 2a and 2b by using the outlet portion 48 and the introduction portion 51. As a result, the positioning of the outlet port 47 and the introduction water passage 50 is easy, and the positioning of the crankcase cover 25 is facilitated, so that the work efficiency of assembling the crankcase cover 25 provided with the outlet port 47 is improved. To do.

  Moreover, because the first crankcase portion 2a and the cylinder 1a are separate members, the outlet portion 48 and the inlet 48 are introduced even though it takes time to position the outlet port 47 and the inlet water passage 50 relative to each other. By fitting with the portion 51, the outlet port 47 and the introduction water passage 50 can be positioned with high accuracy and speed.

  The upstream end portion 51a is a member separate from the cylinder 1a, and the upstream end portion 51a is composed of a connecting tube 53 made of a rigid tube having rigidity capable of forming a positioning portion. Therefore, a flexible tube such as a hose is used. Since the cooling water immediately after flowing out from the water pump 40 can be guided to the jacket W1 without using the property, the piping of the cooling water is simplified and made compact. In addition, since it is not necessary to integrally mold the upstream end 51a to the cylinder 1a, the shape of the cylinder 1a is simplified and the cost is reduced. Furthermore, since the connecting pipe 53 is a straight pipe, the cost is reduced.

  The direction in which the crankcase cover 25 is attached to and detached from the first crankcase part 2a coincides with the fitting direction of the downstream end 48a and the connecting pipe 53, so that the crankcase cover 25 can be easily attached to and detached from the first crankcase part 2a. In addition, the fitting operation between the outlet portion 48 and the introducing portion 51 and the assembling operation of the crankcase cover 25 to the first crankcase portion 2a are performed simultaneously, and the fitting between the outlet portion 48 and the introducing portion 51 is performed. Since the releasing operation and the removing operation of the crankcase cover 25 are performed at the same time, the efficiency of assembling and disassembling the internal combustion engine E is improved.

  The introduction water passage 50 is a straight passage extending along a plane parallel to the cylinder axis L1a. Since the introduction water passage 50 is straight when connected to the water jacket W1, the water passage The pressure loss due to bending is reduced. As a result, the pressure loss of the cooling water in the introduction water passage 50 is reduced, so that the driving force of the water pump 40 can be reduced, and further the power loss of the internal combustion engine E can be reduced.

  The outlet portion 48 protrudes outside the outermost mating surface 25a of the crankcase cover 25 with the first crankcase portion 2a, so that the entire outlet portion 48 is more than the mating surface 25a of the crankcase cover 25. Since it is not necessary to dispose inside, the range surrounded by the mating surface 25a can be reduced, and the crankcase cover 25 can be downsized.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
The downstream end portion of the outlet portion may be provided integrally with the crankcase cover 25, and the upstream end portion of the introduction portion may be integrally formed with the cylinder 1a so as to be fitted to the downstream end portion of the outlet portion. .
The introduction part 51 may be constituted only by the main body part 52, and the downstream end part of the outlet part may be constituted by a connecting pipe which is a separate member from the crankcase cover 25, and the downstream end part of the outlet part and the introduction part The upstream end may be constituted by a connecting pipe 53 that is separate from the crankcase cover 25 and the cylinder 1a.
The crankcase may be a vertically divided member constituted by a member separate from the cylinder or an upper crankcase portion integrally formed with the cylinder and a lower crankcase portion which is a member separate from the upper crankcase portion. .
The dry sump type lubrication system may be a wet sump type. In this case, the crankcase cover 25 is not provided with a tank wall.
The internal combustion engine may be a multi-cylinder internal combustion engine other than the V-type two cylinders or a single-cylinder internal combustion engine. The internal combustion engine may be mounted on a machine other than the vehicle.

1 is a right side view of a water-cooled internal combustion engine to which the present invention is applied. It is the II-II sectional view taken on the line of FIG. FIG. 2 is a right side view showing a part in cross section in the internal combustion engine of FIG. 1. FIG. 2 is a left side view showing a part in cross section in the internal combustion engine of FIG. 1. FIG. 2 is a right side view of a crankcase cover of the internal combustion engine of FIG. 1. It is the VI-VI sectional view taken on the line of FIG. It is the VII-VII sectional view taken on the line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b ... Cylinder, 2 ... Crankcase, 7 ... Crankshaft, 25 ... Crankcase cover, 25a ... Matching surface, 40 ... Water pump, 47 ... Outlet port, 47a ... Downstream end part, 48 ... Outlet part, 48a ... Downstream end part, 50 ... introducing water passage, 51 ... introducing part, 53 ... connecting pipe, E ... internal combustion engine, W1 ... water jacket.

Claims (5)

A water cooling system comprising: a crankcase to which a crankcase cover is coupled; a water pump provided on the crankcase cover for pumping cooling water; and a cylinder provided with a water jacket into which cooling water from the water pump is introduced. In the internal combustion engine,
The crankcase cover is provided with an outlet portion that forms an outlet water passage through which the pumped cooling water flows, and the cylinder forms an introduction water passage that guides the cooling water of the outlet water passage to the water jacket. And a downstream end portion of the outlet portion and an upstream end portion of the introduction portion constitute a positioning portion of the crankcase cover with respect to the crankcase by being fitted to each other. A water-cooled internal combustion engine.   2. The water-cooled internal combustion engine according to claim 1, wherein at least one of the downstream end and the upstream end is configured by a connecting pipe that is a separate member from the crankcase cover and the cylinder.   The water-cooled internal combustion engine according to claim 1 or 2, wherein a direction in which the crankcase cover is attached to and detached from the crankcase coincides with a fitting direction of the downstream end and the upstream end.   4. The introduction water passage is a straight passage extending along a plane parallel to a cylinder axis of the cylinder, and is connected to the water jacket in a tangential direction. A water-cooled internal combustion engine according to claim 1. 5. The water-cooled internal combustion engine according to claim 1, wherein the outlet portion projects outward from an outermost mating surface of the crankcase cover with the crankcase. 6. .

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