JP4927764B2 - Shaft arrangement structure of internal combustion engine - Google Patents

Description

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

  An internal combustion engine mounted on a motorcycle in which a transmission is disposed behind a crankshaft oriented in the vehicle width direction, and an internal combustion engine in which a cylinder standing above the crankshaft is tilted backward to the transmission side, It is disclosed in Patent Document 1 and the like.

JP 2006-1507 A

In the internal combustion engine disclosed in Patent Document 1, a balancer shaft is disposed at the same height as the crankshaft in front of the crankshaft, and the rotation trajectory of the balancer weight is located below the cylinder.
Further, the input shaft of the transmission behind the crankshaft is at a position higher than the crankshaft supporting the multi-plate clutch, and the output shaft behind the input shaft is at substantially the same height as the crankshaft.

Since the balancer shaft is located at the same height as the crankshaft, the internal combustion engine has become longer and longer in size.
Further, the crankshaft was disposed at a relatively high position together with the balancer shaft, and the center of gravity of the internal combustion engine was high.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an internal combustion engine shaft arrangement structure that can reduce the size of the internal combustion engine to concentrate the mass and keep the center of gravity of the internal combustion engine low. There is in point to offer.

In order to achieve the above object, according to the first aspect of the present invention, the transmission (M) is provided on the side of the crankshaft (20) in the vertical direction, and is mounted across the left and right crankcase and the cylinder (12a). In the internal combustion engine in which a cylinder block (12) provided with a lower portion of the cylinder block (12) is inclined to the transmission (M) side and is tilted upward, the crankshaft (20) is opposite to the transmission (M). a side crankshaft (20) from the balancer shaft in upper position (55) is arranged, the lowermost end of the upper cylinder of the rotary locus of the balance weight (55w) of said balancer shaft (55) (12a) (Ls) The balancer shaft (55) is positioned below the lowermost end (Ls) of the cylinder (12a), and the engine hanger is positioned above the balancer shaft (55) to the side of the cylinder (12a). (11a) is axial arrangement structure of an internal combustion engine provided in the front and rear inside width of the rotational locus of the balance weight (55w) And the.

  According to a second aspect of the present invention, in the shaft arrangement structure of the internal combustion engine according to the first aspect, a shift control means for controlling transmission of rotation of the crankshaft is pivotally supported on an input shaft of the transmission, and the transmission in the transmission is An output shaft to which power is transmitted from the input shaft is disposed above the input shaft on the side opposite to the crank shaft with respect to the input shaft, and the shift control means is partially in the axial view of the lower end of the cylinder and the input shaft. It is characterized by overlapping.

  According to a third aspect of the present invention, in the shaft arrangement structure of the internal combustion engine according to the second aspect, the internal combustion engine is mounted on a motorcycle with a transmission facing rearward, and the input shaft is at substantially the same height as the crankshaft. And the output shaft is arranged at substantially the same height as the pivot shaft of the rear fork that supports the rear wheel.

  According to a fourth aspect of the present invention, in the shaft arrangement structure of the internal combustion engine according to any one of the first to third aspects, the balancer shaft has a balance weight between a plurality of crank webs of the crank shaft. It is arrange | positioned in the position which rotates.

  According to the shaft arrangement structure of the internal combustion engine according to claim 1, the balancer shaft arranged on the opposite side of the transmission with respect to the crankshaft of the internal combustion engine in which the cylinder is inclined toward the transmission side is located at a position above the crankshaft. Since the balance weight rotation locus is located above the bottom end of the cylinder, the balancer shaft is located diagonally above the crankshaft, and the horizontal distance between the crankshaft and the balancer shaft is increased. The internal combustion engine can be made smaller and the mass can be concentrated, and the crankshaft is positioned lower than the balancer shaft at a relatively low position to keep the center of gravity of the internal combustion engine low. it can.

  According to the shaft arrangement structure of the internal combustion engine according to claim 2, the output shaft to which power is transmitted from the input shaft is disposed above the input shaft on the opposite side of the crankshaft with respect to the input shaft, and is positioned below the output shaft. A shift control means such as a shift clutch that controls transmission of the rotation of the crankshaft to the input shaft is pivotally supported so as to partially overlap the lower end of the cylinder as viewed in the axial direction of the input shaft. It can be downsized.

  According to the shaft arrangement structure of the internal combustion engine according to claim 3, the input shaft is arranged at substantially the same height as the crankshaft, and the output shaft is arranged at substantially the same height as the pivot shaft of the rear fork supporting the rear wheel. Therefore, an input shaft that supports a heavy load such as a crankshaft or a speed change control means that is a heavy load is disposed below the pivot shaft of the rear fork, thereby further reducing the center of gravity of the internal combustion engine. .

  According to the shaft arrangement structure of the internal combustion engine according to claim 4, since the balancer shaft is arranged at a position where the balance weight rotates between the plurality of crank webs of the crankshaft, the crankshaft and the balancer shaft are made as close as possible. While reducing the size of the crank chamber, the balance weight can be arranged at a high position to suppress oil agitation in the crank chamber to prevent air bubbles from entering the oil and to suppress the rotational resistance of the balancer shaft.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
The internal combustion engine E according to the present embodiment is mounted on a motorcycle with a transmission M integrally provided behind the internal combustion engine E.
In the present embodiment, the front, rear, left and right coincide with the front, rear, left and right when the vehicle is used as a reference.

Referring to FIG. 1 which is a partially omitted side view of a motorcycle and FIG. 2 which is a plan view thereof, a main frame which is divided into two forks from a head pipe 2 of a vehicle body frame 1 and extends obliquely downward to the rear. 3 pivots the rear part downward to form a pivot plate 3p, and a pivot 4a and a pivot plate 3p at the lower end of a bracket 3b suspended from a position near the head pipe 2 from the center of the pair of left and right main frames 3 The internal combustion engine E is suspended from the main frame 3 by the three support shafts 4a, 4b, and 4c of the support shafts 4b and 4c in the upper and lower portions.
A rear fork 6 that supports a rear wheel (not shown) is pivotally supported at a front end so as to be swingable on a pivot shaft 5 installed at a center height position of the pair of left and right pivot plates 3p.

  The internal combustion engine E is a water-cooled single-cylinder four-stroke internal combustion engine. Referring to FIG. 5, the crankcase 11 that supports the crankshaft 20 in the left-right direction, which is also the vehicle width direction of the vehicle, A crank chamber Cc in which the shaft 20 is disposed is formed, and a mission chamber Cm that is partitioned by a vertical partition wall 11m and accommodates the transmission M is formed at the rear of the crank chamber Cc, and below the crank chamber Cc. An oil pan chamber Co that stores oil by being partitioned by a substantially horizontal partition wall 11o is integrally formed.

  The single-cylinder four-stroke internal combustion engine E is connected to the cylinder block 12 having one cylinder 12a on the crank chamber Cc of the crankcase 11, and to the upper part of the cylinder block 12 by a head bolt h1 and h2 via a gasket. The engine main body is composed of a cylinder head 13 and a cylinder head cover 14 coupled to the upper part of the cylinder head 13.

The cylinder block 12, the cylinder head 13, and the cylinder head cover 14 that are overlaid on the crankcase 11 extend upward from the crankcase 11 in a slightly inclined posture (vertical lines V and horizontal lines passing through the crankshaft in FIG. 1). H and cylinder axis Lc).
Thus, the upper half of the crankcase 11 of the internal combustion engine E in which the cylinder is tilted backward is the crank chamber Cc, and the latter half is the mission chamber Cm.
The oil pan chamber Co below the crank chamber Cc is a chamber inside the oil pan 15 that extends downward from the crankcase 11 and is integrally formed.

  The internal combustion engine E supported by the main frame 3 is suspended below the main frame 3 between the bracket 3b and the pivot plate 3p, and is inclined upward from the lower crankcase 11 and extends upward. , Of the cylinder head 13 and the cylinder head cover 14, the cylinder head 13 and the cylinder head cover 14 are located between the pair of left and right main frames 3, 3.

  In the transmission chamber Cm of the crankcase 11, a main shaft 21 and a counter shaft 22 of the transmission M are arranged in parallel with the crankshaft 20 in the horizontal direction, and the countershaft 22 is arranged in the crankcase 11. To the left and projecting outward to form an output shaft, and a drive chain sprocket 23 is fitted to the projecting left end.

The counter shaft 22 is located close to the front of the pivot shaft (pivot shaft) 5 that supports the rear fork 6 at the same height and is wound around a drive chain sprocket 23 fitted to the counter shaft 22. 24 is bridged to a driven chain sprocket (not shown) provided at the rear end of the rear fork 6 to form a chain transmission mechanism, and power is transmitted to the rear wheel side.
In the right side view of the internal combustion engine of FIG. 4, the rotation centers 20c, 55c, 21c, 22c, and 5c of the crankshaft 20, the balancer shaft 55, the main shaft 21, the counter shaft 22, and the pivot shaft 5 are indicated by black dots. ing.

The cylinder head 13 has an intake passage 16i that is an extension of the intake port 13i obliquely upward from the front surface, and a throttle body 17 is connected between the pair of left and right main frames 3, 3 to the intake passage 16i. The upstream side of 17 intake passages is open.
An exhaust passage 16e, which is an extension of the exhaust port 13e, extends rearward substantially horizontally from the rear surface of the cylinder head 13 tilted slightly rearward, and an exhaust pipe 18 is connected to the left and right main frames 3 in the exhaust passage 16e. , 3 are connected.

  The connection outlet of the exhaust passage 17 is located on the right side of the vehicle body, and as shown in FIG. 2, the upstream connection end 18a of the exhaust pipe 18 is located on the right side of the center axis Lb of the vehicle body (the cylinder of the internal combustion engine E). It is connected to the exhaust passage 16e at a position in the left-right direction where the axis Lc exists.

  The exhaust pipe 18 connected to the exhaust passage 17 on the rear surface of the cylinder head 13 tilted backward in this manner and extending rearward substantially horizontally extends in the transmission chamber Cm in which the transmission M in the rear half of the crankcase 11 is accommodated. The upper space curves to the left and turns downward while gradually descending, passes under the left main frame 3 and extends obliquely forward and downward along the left side of the cylinder block 12 of the internal combustion engine E. When it reaches the lower end of the crankcase 11 (lower end of the oil pan 15) after reaching the front surface of the case 11 and suddenly downwards, the muffler 19 (see FIGS. 1 and 2).

  The lower surface of the crankcase 11 is at the lowest position with the front part of the oil pan 15 projecting downward, forming an inclined surface that rises toward the rear, and is generally horizontal below the rear mission chamber 11, A muffler 19 connected to the pipe 18 extends rearward along the lower surface of the crankcase 11.

The vehicle body frame 1 is entirely covered with a vehicle body cover in which synthetic resin cover members divided into respective parts are connected. In particular, the left and right sides of the internal combustion engine E are covered with a body cover 7.
The left and right body covers 7 approach each other as they go downward, and form a tapered shape with their bottom ends connected to each other. The exhaust pipe 18 and the muffler 19 are covered and protected by the body cover 7 below. (See FIGS. 7 and 8).

  The crankcase 11 coupled to the lower portion of the cylinder block 12 includes a left crankcase 11L and a right crankcase 11R that are a pair of cases that are divided into left and right by a plane that includes the cylinder axis Lc and is orthogonal to the crankshaft 20. However, in a state in which the mating surfaces 11Ls and 11Rs (see also FIG. 5 and FIG. 9) are combined, they are coupled by a bolt.

A crankshaft 20 rotatably supported in a left and right direction in a crank chamber Cc formed by combining left and right crankcases 11L and 11R is moved left and right from left and right crank webs 20w and 20w connected by crank pins 20p. The shaft bodies 20L and 20R are integrally molded in a shape extending coaxially.
The left and right shaft bodies 20L and 20R of the crankshaft 20 are adjacent to the crank webs 20w and 20w, which are journal portions 20Lj and 20Rj.

The space between the main bearing portions 11Lb and 11Rb of the left and right crankcases 11L and 11R is the crank chamber Cc, and the left and right crank webs 20w and 20w are accommodated. The left and right journal portions 20Lj and 20Rj respectively hold the metal bearings 25 and 25. Via the main bearings 11Lb and 11Rb.
The lower part of the cylinder 12a of the cylinder block 12 is fitted into a circular opening formed above the crank chamber Cc by combining the left and right crankcases 11L and 11R, and the piston 30 is fitted in the cylinder bore 12b of the cylinder 12a so as to be slidable back and forth. Combined.

  A piston pin 38 is installed between a pair of pin bosses 34, 34 projecting from the back surface of the piston top 31 of the piston 30, and a small end is pivotally supported by the piston pin 38, and a large end is connected to the crankpin 20 p of the crankshaft 20. Is connected to the piston 30 and the crankshaft 20 by a connecting rod 39 pivotally supported through a large end metal 39a to form a crank mechanism.

  The left crankcase 11L is formed with a chain chamber 11cc on the left side of the left main bearing portion 11Lb, and the left shaft body 20L protruding leftward from the left main bearing portion 11Lb of the crankshaft 20 penetrates the chain chamber 11cc and further to the left An oil pump drive sprocket 20os and a drive cam chain sprocket 20cs are formed in the portion corresponding to the chain chamber 11cc, and the outer rotor 26r of the AC generator 26 is fitted at the left end. Has been.

An inner stator 26s around which a coil of the AC generator 26 is wound is fixed to a left side cover 40 that closes the opening of the crank chamber Cc and the oil pan 15 on the left side wall of the left crankcase 11L. An AC generator 26 in which the outer rotor 26r that holds the motor rotates is configured.
The left side cover 40 has a bowl shape, and a cylindrical portion 41 protruding from the center of the bottom surface is put on the left end portion of the crankshaft 20, and the stator core of the inner stator 26s is fixed to the cylindrical portion 41 by a bolt 26b. The

  On the other hand, the balancer drive gear 27a and the main drive gear 28a are fitted to the right shaft body 20R that protrudes to the right from the right main bearing portion 11Rb of the right crankcase 11R in the crankshaft 20 from the vicinity of the main bearing portion 11Rb. It is fixed by a flange bolt 29 via 29w (see FIGS. 6 and 7).

The balancer drive gear 27a meshes with a balancer driven gear 27b provided at the right shaft end of a balancer shaft 55 that is rotatably supported by the left crankcase 11L and the right crankcase 11R via a pair of bearings 55b and 55b. (See FIG. 7).
In addition to the balancer driven gear 27b, a water pump drive gear 59a is fitted to the right shaft end of the balancer shaft 55.

  A balancer shaft 55 having a balance weight 55w rotating between the left and right crank webs 20w, 20w is disposed at an obliquely upper position in front of the crankshaft 20, and the crankshaft 20 is engaged with the balancer drive gear 27a and the balancer driven gear 27b. Thus, the first vibration generated by the reciprocating motion of the piston 30 is reduced by being driven to rotate in the reverse direction at the same speed as the crankshaft 20.

  The transmission M disposed in the transmission chamber Cm behind the crank chamber Cc has a shift operated by the main shaft 21 and the counter shaft 22 provided with a main gear group 21g and a counter gear group 22g, respectively, and a shift operation mechanism. A shift change mechanism 52 having a drum 53 and shift forks 54a, 54b, 54c is provided (see FIG. 4).

  Referring to FIG. 4, an oil injection port 110 is formed at a predetermined position on the upper wall portion of the right crankcase 11R, and a portion where the main gear group 21g and the counter gear group 22g mesh with each other below the oil injection port 110. Therefore, even after the maintenance is completed after the oil is injected from the oil injection port 110, the lubrication of the engagement between the main gear group 21g and the counter gear group 22g can be improved.

The main shaft 21 is in substantially the same vertical position as the crankshaft 20, is rotatably supported by the left and right crankcases 11L and 11R via bearings 21b and 21b, and is shifted to a portion protruding rightward from the right bearing 21b. A multi-plate friction type transmission clutch 50 as a control means is arranged, and a primary driven gear 28b provided in the transmission clutch 50 meshes with the main drive gear 28a to constitute a primary reduction mechanism.
The transmission clutch 50 includes a large number of clutch plates 50p, and is operated by a clutch operation mechanism to transmit and shut off the power of the crankshaft 20 to the transmission M.

  The counter shaft 22 is positioned obliquely above and behind the main shaft 21, is rotatably supported by the left and right crankcases 11L and 11R via bearings 22b and 22b, and is arranged at the left end protruding outward from the left bearing 22b. A chain drive sprocket 23 is fitted.

  Accordingly, the power of the internal combustion engine E is transmitted from the crankshaft 20 to the transmission M via the primary reduction mechanisms 28a and 28b and the clutch 45, and in the meshing of the main gear group 21g and the counter gear group 22g of the transmission M. The shifted output is transmitted from the counter shaft 22 to a chain driven sprocket (not shown) via a chain transmission mechanism, and further to a rear wheel via a secondary reduction mechanism (not shown).

A right side cover 45 is placed on the right side surface of the right crankcase 11R on the sides of the crank chamber Cc and the transmission chamber Cm excluding the oil pan 15.
The right side cover 45 has a cylindrical portion 45a that covers the periphery of the transmission clutch 50, a circular opening 45b is formed at an axial position of the crankshaft 20, and a pump body 45c of the water pump 56 above the circular opening 45b. The opening of the cylindrical portion 45a is covered with a clutch cover 46, the circular opening 45b is fitted with a lid member 47, and the water pump body 45c is covered with a water pump cover 48.

The water pump 56 is an impeller that is rotatably supported by the water pump body 45c and the right crankcase 11R with the water pump drive shaft 57 oriented in the left-right direction, and is fitted to the right end of the water pump drive shaft 57. 58 is covered with a water pump cover 48.
A water pump driven gear 59b is fitted on the water pump drive shaft 56a, and the water pump driven gear 59b meshes with a water pump drive gear 59a fitted on the right shaft end of the balancer shaft 55 at the front. The rotational power of the balancer shaft 55 is transmitted to the drive of the water pump 56.

  The internal combustion engine E is provided with a DOHC type valve operating mechanism. Referring to FIGS. 5 and 6, the cylinder head 13 corresponds to the cylinder 12a and faces the piston 30 in the cylinder axial direction in the combustion chamber 60. The combustion chamber 60 has a pair of intake ports 13i that open to the left and right of the front half, and a pair of exhaust ports 13e that open to the left and right of the rear half of the combustion chamber 60. 61 is attached with the tip facing the combustion chamber 60.

  An intake valve 62 and an exhaust valve 63, which are slidably supported by valve guides 64i and 64e integrally fitted to the cylinder head 3, are driven by a valve operating device 65 provided in the internal combustion engine E, and are thus connected to an intake port. The intake opening of 13i and the exhaust opening of the exhaust port 27 are opened and closed in synchronization with the rotation of the crankshaft 20.

  The valve operating device 65 is provided in a valve operating chamber 14v formed by the cylinder head 13 and the cylinder head cover 14, and is an intake camshaft 66 disposed in the left-right direction above the pair of left and right intake valves 62. An exhaust camshaft 67 disposed on the left and right pair of exhaust valves 63 so as to be directed in the left-right direction is rotatably supported so as to be sandwiched between the cylinder head 13 and the cam holders 68i and 68e.

  The cam lobe 66c of the intake camshaft 66 is in contact with the upper surface of the valve lifter 62l that covers the upper end of the intake valve 62 biased upward by the valve spring 62s, and the intake valve 62 is rotated by the rotation of the cam lobe 66c integrated with the intake camshaft 66. Similarly, the cam lobe 67c of the exhaust camshaft 67 is in contact with the upper surface of the valve lifter 63l that covers the upper end of the exhaust valve 63 biased upward by the valve spring 63s, and is integrated with the exhaust camshaft 67. The exhaust valve 63 is opened / closed at a required timing by the rotation of the cam lobe 67c.

  The intake camshaft 66 and the exhaust camshaft 67 are fitted with driven cam chain sprockets 66s and 67s at their left shaft ends, respectively, and the left shaft body of the two driven cam chain sprockets 66s and 67s and the crankshaft 20 A cam chain 69 is bridged between the drive cam chain sprocket 20cs formed in 20L (see FIG. 6), and the rotational power of the crankshaft 20 is passed between the intake camshaft 66 and the exhaust camshaft 67 via the cam chain 69. The rotation is transmitted, and the intake cam shaft 66 and the exhaust cam shaft 67 rotate in synchronization with the crankshaft 20, and the intake valve 62 and the exhaust valve 63 are driven to open and close.

  The lubricating system of the internal combustion engine E will be described in part. Referring to FIG. 5, the partition wall 11o that partitions the crank chamber Cc of the crankcase 11 from the lower oil pan chamber Co follows the rotation locus of the crank web 20w. The lower half of the crank chamber Cc is partitioned into a substantially arc shape, and the rotor accommodating chamber 71 of the trochoidal scavenge pump 70 is formed at the rear thereof.

  The rotor housing chamber 71 includes a left rotor housing recess 71L that is recessed to face the mating surface 11Ls of the left crankcase 11L, and a right rotor housing recess 71R that is recessed to face the mating surface 11Rs of the right crankcase 11R. Is configured to communicate with the pump drive shaft 72 in the axial direction (see FIG. 7).

  Left and right outer rotors 73L and 73R are accommodated in the left and right rotor accommodating recesses 71L and 71R of the scavenge pump 70, respectively, and left and right inner rotors 74L and 74R are accommodated inside the left and right outer rotors 73L and 73R, respectively. Are fitted on a common pump drive shaft 72 and rotate together.

A suction oil passage A1 is formed between the rotor housing chamber 71 and the partition wall 11o by a horizontal wall 11h extending along the partition wall 11o forward of the partition wall 11o from the rotor housing chamber 71 and discharged to the upper wall portion of the rotor housing chamber 71. The oil port A2 is opened upward.
The scavenge pump 70 is in the upper part of the oil pan chamber Co, and the discharge oil port A2 is open to the upper space behind the oil pan chamber Co.

A trochoid feed pump 80 is provided on the left side of the scavenge pump 70 formed on the mating surfaces 11Ls and 11Rs of the left and right crankcases 11L and 11R, and a rotor accommodating chamber 81 is formed in the left crankcase 11L. (See FIG. 7).
A lid member 82 closes the left opening of the rotor accommodating chamber 81 to accommodate the outer rotor 83 and the inner rotor 84 therein.

  As shown in FIG. 7, the feed pump 80 and the scavenge pump 70 share a pump drive shaft 72, and the inner rotor 84 of the feed pump 80 is fitted to the pump drive shaft 72, and the left and right sides of the scavenge pump 70 are The inner rotors 74L and 74R are fitted and rotate integrally.

  An oil pump driven sprocket 86s is fitted to the end of the pump driving shaft 72 that protrudes to the left from the lid member 82, and between the oil pump driven sprocket 86s and the oil pump driving sprocket 20os formed on the crankshaft 20. An oil pump drive chain 87 is laid across the shaft, and the rotational power of the crankshaft 20 is transmitted to the drive of the scavenge pump 70 and the feed pump 80.

Referring to FIG. 3, passage wall 81a extends forward from the suction port of rotor accommodating chamber 81 of feed pump 80, and the upper end of oil absorption pipe 91 is connected to the front end opening thereof.
The oil absorption pipe 91 linearly extends obliquely downward in the oil pan chamber Co from the connecting portion, and an oil strainer 90 provided at the lower end is disposed in the vicinity of the lowest bottom surface of the front portion of the oil pan chamber Co.
Therefore, the oil stored in the oil pan chamber Co of the oil pan 15 is purified by the oil strainer 90 by the drive of the feed pump 80, and is sucked up the suction oil passage B1 in the oil suction pipe 91, and the suction case in the passage wall 81a. Inhaled through oil passage B2.

From the discharge port of the rotor accommodating chamber 81 of the feed pump 80 in the left crankcase 11L, a discharge case oil passage B3 is formed obliquely rearward and downward, along the peripheral wall of the left crankcase 11L from the rear portion of the discharge case oil passage B3. A discharge case oil passage B4 is formed by bending leftward (see FIG. 7).
A relief valve 85 is provided in the middle of the discharge case oil passage B3. When the discharge hydraulic pressure exceeds the set pressure, a part of the discharge oil is returned to the oil pan chamber Co.

In the left side cover 40, which covers the left crankcase 11L from the left, a discharge case oil passage B5 communicating with the discharge case oil passage B4 at its mating surface extends to the oil filter 92 (FIG. 3). FIG. 7).
The oil filter 92 has a bottomed cylindrical filter housing 93 formed between a cylindrical portion 41 covering the left end portion of the crankshaft 20 in the left crankcase 11L and a portion corresponding to the discharge case oil passage B4 at the rear end. Provided.

  The oil filter 92 overlaps with the feed pump 80 (and the scavenge pump 70) and also with the transmission clutch 50 supported on the left end of the main shaft 21 of the transmission M in a side view of FIG.

Referring to FIG. 7, an outflow case oil passage B6 for guiding oil flowing out from the oil filter 92 is formed in the filter lid member 94 fitted into the left opening of the filter housing 93 that houses the filter element 92e. A case oil passage B7 communicating with the outflow case oil passage B6 is formed in the left side cover 40 so as to extend into the cylindrical portion 41 that covers the left end portion of the crankshaft 20.
The bottomed cylindrical portion 41 into which the crankshaft 20 is inserted is formed by oil-tightly partitioning an inner space 41 s at the bottom by an oil seal 100 fitted around the crankshaft 20. The case oil passage B7 communicates (see FIG. 7).

The crankshaft 20 has shaft oil passages C1, C2, and C3 formed in the left shaft body 20L, the left crank web 20w, the crank pin 20p, the right crank web 20w, and the right journal portion 20Rj. The shaft oil passage C1 inside the shaft body 20L is open at the left end to the inner space 41s, and the branch shaft oil passage Cj extends in a radial direction from the left journal portion 20Lj on the right side and opens to the outer peripheral surface of the left journal portion 20Lj. is doing.
A branch shaft oil passage Cp extends in a radial direction from a crank pin 20p where the shaft oil passage C2 and the shaft oil passage C3 intersect, and opens to the outer peripheral surface of the crank pin 20p, and the right journal portion at the right end of the shaft oil passage C3. From 20Rj, a shaft oil passage C4 extends in the radial direction as an extension of the shaft oil passage C3, and opens to the outer peripheral surface of the right journal portion 20Rj.

In the right main bearing portion 11Rb, a piston jet oil passage J1 having one end opened at a step portion of the bearing hole extends obliquely upward toward the cylinder bore 12b, and a jet nozzle N1 is mounted on the other end opening.
The jet nozzle N1 is injected obliquely upward into the cylinder bore 12b (see FIGS. 5 and 6), and oil hits the back surface of the piston 30 reciprocatingly sliding inside the cylinder bore 12b to cool the piston 30 from the back surface. To do.

On the other hand, referring to FIG. 3, a case oil passage D1 extends obliquely upward and rearward in the side wall of the left side cover 40 from the inner space 41s into which the left end of the crankshaft 20 of the left side cover 40 is inserted. The case oil passage D2 bent in communication with the piston jet oil passage J2 of the left main bearing portion 11Lb of the left crankcase 11L communicates.
The jet nozzle N2 receives supply of oil from the piston jet oil passage J2, injects oil obliquely upward toward the cylinder bore 12b (see FIGS. 5 and 6), and the piston 30 that reciprocally slides in the cylinder bore 12b. The piston 30 is cooled from the back surface by contacting the back surface.

  In the internal combustion engine E having the above-described structure, the transmission M is provided behind the crankshaft 20 oriented in the vehicle body width direction (left-right direction), and the cylinder 12a protruding upward from the crankcase 11 is somewhat rearward. This is a rearward tilting cylinder that is inclined to the right.

The balancer shaft 55 disposed on the front side opposite to the rear transmission M with respect to the crankshaft 20 is positioned above the crankshaft 20 as shown in FIG.
FIG. 5 shows the rotation trajectory Tb of the balance weight 55w of the balancer shaft 55 with a two-dot chain line circle, and the vertical position Ls of the lowermost end of the rearward tilted cylinder 12a with a two-dot chain line.
The upper part of the rotation locus Tb of the balance weight 55w of the balancer shaft 55 is located above the vertical position Ls at the lowest end of the cylinder 12a.

  Therefore, there is a balancer shaft 55 obliquely above the crankshaft 20, the horizontal distance between the crankshaft 20 and the balancer shaft 55 can be reduced, and the internal combustion engine E can be reduced in size and mass can be concentrated. The crankshaft 20 is positioned below the balancer shaft 55 and at a relatively low position, so that the center of gravity of the internal combustion engine E can be kept low.

  A counter shaft (output shaft) 22 to which power is transmitted from the main shaft (input shaft) 21 is disposed above the main shaft 21 on the side opposite to the crank shaft 20 with respect to the main shaft 21, and as shown in FIG. Since the transmission clutch 50 that controls transmission of rotation of the crankshaft 20 to the main shaft 21 located below the shaft 22 is supported so as to partially overlap the lower end of the cylinder 12a in the axial direction, the vertical width of the internal combustion engine E is increased. Further miniaturization can be achieved.

Referring to FIG. 1, a main shaft 21 that is an input shaft of the transmission M is disposed at substantially the same height as the crankshaft 20, and output at substantially the same height as the pivot shaft 5 of the rear fork 6 that supports the rear wheel. A counter shaft 22 as an axis is arranged.
Referring to FIG. 1, assuming a plane S including a pivot shaft 5 at substantially the same height as the counter shaft 22, a crankshaft 20 and a main shaft 21 are disposed below the plane S.
That is, a main shaft 21 that is provided with an AC generator 26 and supports heavy objects such as a crankshaft 20 and a transmission clutch 50 that are heavy objects is disposed below the pivot shaft 5 of the rear fork 6. The center of gravity can be further lowered.

  As shown in FIG. 7, since the balancer shaft 55 is disposed at a position where the balance weight 55w rotates between the two crank webs 20w, 20w of the crankshaft 20, the crankshaft 20 and the balancer shaft 55 are made as close as possible. While reducing the size of the crank chamber Cc, the balance weight 55w is arranged at a high position to suppress oil agitation in the crank chamber Cc to prevent air bubbles from entering the oil and to suppress the rotational resistance of the balancer shaft 55. can do.

As shown in FIG. 4, the counter gear group 22g on the counter shaft 22 is disposed higher than the vertical position Ls at the lowermost end of the cylinder 12a, so that the counter gear group 22g is disposed behind the main shaft 21. The counter shaft 22 is positioned as far as possible to concentrate the mass.
Referring to FIG. 4, the balancer positioned at the front portion of the internal combustion engine E such that the rotational locus of the balance weight 55 w of the balancer shaft 55 partially overlaps with the front-rear position Fs at the front end of the cylinder 12 a in a side view. Since the shaft 55 is retracted rearward, the longitudinal length of the internal combustion engine E can be kept small.

1 is a partial side view of a motorcycle on which an internal combustion engine according to an embodiment of the present invention is partially omitted. It is the same top view. It is a left view of an internal combustion engine. It is the right view which abbreviate | omitted a part of internal combustion engine. FIG. 3 is a left sectional view taken along a mating surface of a crankcase of an internal combustion engine. 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

E ... Internal combustion engine, M ... Transmission, 3 ... Main frame, 5 ... Pivot shaft (pivot shaft), 6 ... Rear fork, 11 ... Crank case, Cc ... Crank chamber, Cm ... Mission chamber, Co ... Oil pan chamber 11 ... Crank case, 12 ... Cylinder block, 12a ... Cylinder, 12b ... Cylinder bore, 13 ... Cylinder head, 14 ... Cylinder head cover, 15 ... Oil pan,
20 ... Crank shaft, 20p ... Crank pin, 20w ... Crank web, 21 ... Main shaft, 22 ... Counter shaft (output shaft), 26 ... AC generator, 30 ... Piston, 39 ... Connecting rod,
50: Transmission clutch (transmission control means), 55: Balancer shaft, 55w: Balance weight.

Claims (4)

A transmission (M) is provided on the side of the crankshaft (20) in the vertical direction, and is mounted across the left and right crankcases, and the cylinder block (12) provided with the lower part of the cylinder (12a) is sandwiched between the transmissions. In the internal combustion engine inclined to the machine (M) side and standing obliquely upward,
A balancer shaft (55) is disposed on the opposite side of the transmission (M) with respect to the crankshaft (20) and above the crankshaft (20),
The positioned higher than the lowest end (Ls) of the upper cylinder of the rotary locus of the balance weight of the balancer shaft (55) (55w) (12a ),
The balancer shaft (55) is located below the lowest end (Ls) of the cylinder (12a),
A shaft arrangement structure for an internal combustion engine, characterized in that an engine hanger (11a) is provided within the front-rear width of the balance locus (55w) on the side of the cylinder (12a) above the balancer shaft (55). . Shift control means (50) for transmitting and controlling the rotation of the crankshaft (20) is supported on the input shaft (21) in the transmission (M),
An output shaft (22) for transmitting power from the input shaft (21) in the transmission (M) is above the input shaft (21) on the opposite side of the crankshaft (20) with respect to the input shaft (21). Placed in
2. The shaft arrangement structure of an internal combustion engine according to claim 1, wherein the shift control means (50) partially overlaps the lower end of the cylinder (12a) when viewed in the axial direction of the input shaft (21). The internal combustion engine is mounted on a motorcycle with the transmission (M) facing rearward,
The input shaft (21) is arranged at substantially the same height as the crankshaft (20),
3. The shaft arrangement structure for an internal combustion engine according to claim 2, wherein the output shaft (22) is arranged at substantially the same height as the pivot shaft (5) of the rear fork (6) supporting the rear wheel.   The balancer shaft (55) is disposed at a position where a balance weight (55w) rotates between a plurality of crank webs (20w) of the crankshaft (20). The shaft arrangement structure of the internal combustion engine according to any one of up to 3.

Images