阅读说明：本技术 内燃机 (Internal combustion engine ) 是由 原田诚 上村拓真 北田芳宏 铃木达阳 于 2020-03-26 设计创作，主要内容包括：能够实现气缸体的小型化、并且使油的返回顺利的内燃机。内燃机具备凸轮轴传动链室,所述凸轮轴传动链室形成于气缸体并收容凸轮轴传动链,并且也作为使供给到气缸盖内的油向曲轴箱(2)内返回的返回通路而发挥功能,其中,所述曲轴箱(2)在底面侧具有油贮存部(51),并且所述曲轴箱(2)具有与所述凸轮轴传动链室相连的曲轴箱侧凸轮轴传动链室(52),在所述曲轴箱侧凸轮轴传动链室(52)的底壁(53)形成有与所述油贮存部(51)连通的落油孔(54)。(An internal combustion engine in which the cylinder block is reduced in size and oil is smoothly returned. The internal combustion engine is provided with a camshaft drive chain chamber which is formed in a cylinder block, houses a camshaft drive chain, and functions as a return passage for returning oil supplied into a cylinder head into a crankcase (2), wherein the crankcase (2) has an oil reservoir (51) on a bottom surface side, the crankcase (2) has a crankcase-side camshaft drive chain chamber (52) connected to the camshaft drive chain chamber, and a drop oil hole (54) communicating with the oil reservoir (51) is formed in a bottom wall (53) of the crankcase-side camshaft drive chain chamber (52).)

1. An internal combustion engine, comprising:

a cylinder block (3a) having cylinder bores (3 d);

a piston (8) that reciprocates within the cylinder bore (3 d);

a crankshaft (9) that converts reciprocating motion of the piston (8) into rotational motion;

a crankcase (2) that holds the crankshaft (9);

a valve mechanism (11) that controls the entry and exit of air into and out of the cylinder bore (3 d);

a cylinder head (3b) that holds the valve mechanism (11);

a power transmission member (14) that transmits power from the crankshaft (9) to the valve mechanism (11); and

a power transmission member accommodating chamber (15) that is formed in the cylinder block (3a), accommodates the power transmission member (14), and also functions as a return passage for returning oil supplied into the cylinder head (3b) into the crankcase (2),

the crankcase (2) has an oil reservoir (51) on the bottom surface side, and the crankcase (2) has a crankcase-side power transmission member accommodating chamber (52) connected to the power transmission member accommodating chamber (15),

an oil dropping hole (54) communicating with the oil reservoir (51) is formed in the bottom wall (53) of the crankcase-side power transmission member accommodating chamber (52).

2. The internal combustion engine according to claim 1,

the cylinder block (3a) is disposed adjacent to the crankcase (2) with a gasket (57) therebetween,

the oil dropping hole (54) is provided separately from the gasket (57).

3. The internal combustion engine according to claim 1,

the oil dropping hole (54) extends to a lower portion of a side wall (59) located on the inner side of the bottom wall (53) in the engine width direction.

4. The internal combustion engine according to claim 1,

the oil dropping hole (54) is provided separately from the rear end (60) of the crankcase-side power transmission member accommodating chamber (52).

5. The internal combustion engine according to claim 1,

the oil reservoir (51) has a passage (61) leading to an oil pump (56) via an oil strainer (55),

when the crankcase-side power transmission member accommodating chamber (52) side is set to the upstream side of the oil reservoir (51) and the oil strainer (55) side is set to the downstream side of the oil reservoir (51),

a rib (62) is provided downstream of the oil dropping hole (54), and the rib (62) restricts the flow of oil from the oil reservoir (51) side to the oil dropping hole (54) side.

6. The internal combustion engine according to claim 5,

at least a part of the rib (62) overlaps the oil drop hole (54) in the vehicle width direction.

7. The internal combustion engine according to any one of claims 1 to 6,

the oil dropping hole (54) is provided with a check valve that allows oil to flow from the power transmission member housing chamber (15) side to the oil reservoir (51) side and restricts oil from flowing from the oil reservoir (51) side to the power transmission member housing chamber (15) side.

Technical Field

The present invention relates to internal combustion engines.

Background

Conventionally, as a structure for returning oil supplied into a valve chamber of a cylinder head to an oil chamber of a crankcase, for example, as disclosed in japanese patent application laid-open No. 2007-002747, there is a structure in which an oil return passage is provided separately from a camshaft transmission chain chamber. Further, as disclosed in japanese laid-open patent publication No. 2004-218507, there is a structure in which the camshaft drive chain chamber itself is used as an oil return passage.

However, in the above-mentioned japanese patent application laid-open No. 2007-002747, since the oil return passage is provided separately from the camshaft transmission chain chamber, a space for the oil return passage needs to be provided in the cylinder block, which is an obstacle to downsizing of the cylinder block.

Further, in japanese patent application laid-open No. 2007-002747, since the camshaft transmission chain chamber itself is used as the oil return passage, the cylinder block can be easily downsized, and the oil can be easily returned late, so that the oil capacity needs to be increased in advance.

Disclosure of Invention

An aspect of the present invention provides an internal combustion engine that can achieve a reduction in size of a cylinder block and smooth return of oil.

(1) An internal combustion engine according to an aspect of the present invention includes: a cylinder block having cylinder bores; a piston reciprocating in the cylinder bore; a crankshaft that converts reciprocating motion of the piston into rotational motion; a crankcase that holds the crankshaft; a valve mechanism that controls the entry and exit of air into and out of the cylinder bore; a cylinder head that holds the valve mechanism; a power transmission member that transmits power from the crankshaft to the valve mechanism; and a power transmission member accommodating chamber formed in the cylinder block, accommodating the power transmission member, and functioning also as a return passage for returning oil supplied into the cylinder head into the crankcase, wherein the crankcase has an oil reservoir on a bottom surface side, the crankcase has a crankcase-side power transmission member accommodating chamber connected to the power transmission member accommodating chamber, and a oil dropping hole communicating with the oil reservoir is formed in a bottom wall of the crankcase-side power transmission member accommodating chamber.

(2) In the aspect (1), the cylinder block may be disposed adjacent to the crankcase with a gasket interposed therebetween, and the oil dropping hole may be provided apart from the gasket.

(3) In addition to the aspect (1) or (2), the oil dropping hole may extend to a lower portion of a side wall located on an inner side of the bottom wall in the engine width direction.

(4) In addition to any one of the aspects (1) to (3), the oil dropping hole may be provided separately from a rear end of the crankcase-side power transmission member accommodating chamber.

(5) In the aspect (1) to (4), the oil reservoir may have a passage leading to an oil pump through an oil filter, and when the crankcase-side power transmission member housing chamber side is an upstream side of the oil reservoir and the oil filter side is a downstream side of the oil reservoir, a rib may be provided on a downstream side of the oil dropping hole to restrict a flow of oil from the oil reservoir side to the oil dropping hole side.

(6) In the aspect (5) described above, at least a portion of the rib may overlap the oil drop hole in the vehicle width direction.

(7) In addition to any one of the aspects (1) to (6), the oil dropping hole may include a check valve that allows oil to flow from the power transmission member housing chamber side to the oil reservoir side and restricts oil from flowing from the oil reservoir side to the power transmission member housing chamber side.

Effects of the invention

According to the aspect (1), in the structure in which the power transmission member accommodating chamber of the cylinder block is used as the return path for the oil supplied to the cylinder head, the oil dropping hole communicating with the oil reservoir is formed in the bottom wall of the crankcase-side power transmission member accommodating chamber. Thus, the cylinder block can be made smaller than a structure in which an oil return passage is provided separately from the power transmission member accommodating chamber. In addition, compared to the structure in which the oil is returned to the oil reservoir portion after being transferred to the entire bottom wall of the crankcase-side power transmission member accommodating chamber, the oil is also returned to the oil reservoir portion from the middle of the bottom wall of the crankcase-side power transmission member accommodating chamber, whereby the oil can be returned efficiently. Therefore, the amount of the oil remaining in the sludge is reduced, and the amount of the oil can be reduced.

According to the aspect (2), since the oil dropping hole is provided at a predetermined distance from the gasket in the cylinder block disposed adjacent to the crankcase with the gasket interposed therebetween, the gasket can be easily ensured in airtightness, and the strength of the end surface (cylinder fixing surface) of the crankcase can be easily ensured.

According to the aspect (3) described above, the oil dropping hole extends from the bottom wall to the lower portion of the side wall on the inner side in the engine width direction, and therefore the oil can be returned with good efficiency even when the amount of oil is large.

According to the aspect (4), since the oil dropping hole is provided at a predetermined distance from the rear end of the crankcase side power transmission member accommodating chamber, the strength of the crankcase side power transmission member accommodating chamber is not easily affected, and the strength of the crankcase side power transmission member accommodating chamber can be easily ensured.

According to the aspect (5) described above, since the rib that restricts the flow of the oil from the oil reservoir side to the oil dropping hole side is provided on the downstream side of the oil dropping hole, the backflow in which the oil flows into the upstream side due to a behavior at the time of emergency braking of the vehicle or the like can be prevented with a simple configuration.

According to the aspect (6), at least a part of the rib is located at the same coordinate in the vehicle width direction as the oil drop hole, whereby the backflow of the oil flowing into the upstream side due to a behavior at the time of sudden braking of the vehicle or the like can be more reliably prevented.

According to the aspect (7) described above, since the check valve for restricting the oil flow in one direction is provided in the oil dropping hole, the reverse flow of the oil flowing into the upstream side can be reliably prevented.

Drawings

Fig. 1 is a left side view of a motorcycle having an internal combustion engine according to an embodiment of the present invention.

Fig. 2 is a left side view including a partial cross section of the internal combustion engine of the motorcycle.

Fig. 3 is an expanded sectional view of the internal combustion engine along the axis of the main shaft.

Fig. 4 is a side view of the left half crankcase of the internal combustion engine as viewed from the inside in the width direction of the internal combustion engine.

Fig. 5 is a front view of the left crankcase half.

Fig. 6 is a sectional view a-a of fig. 5.

Fig. 7 is a sectional view of B-B of fig. 5.

Fig. 8 is a cross-sectional view of C-C of fig. 4.

Fig. 9 is a perspective view showing the periphery of the oil dropping hole of the left half crankcase.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, directions such as front, rear, left, and right are the same as those of the vehicle described below unless otherwise noted. In the drawings used in the following description, arrow FR indicating the front of the vehicle, arrow LH indicating the left of the vehicle, and arrow UP indicating the upper side of the vehicle are shown at appropriate positions.

In a motorcycle (saddle-ride type vehicle) 101 shown in fig. 1, a frame 102 is integrally formed by joining a plurality of steel materials by welding or the like. The frame 102 is a so-called backbone (back bone) in which a single main pipe 108 extends rearward and downward from a head pipe 103 that supports a front wheel suspension system so as to be steerable, and a gap between the head pipe 103 and a seat 109 for seating an occupant is formed as a low portion to improve ease of straddling. A pivot frame 110 extends below the rear end of the main pipe 108, and the front end of a swing arm 112 of the rear wheel suspension system is supported by the pivot frame 110 so as to be vertically swingable. A seat frame 113 extends rearward and upward from a rear end portion of the main pipe 108, a seat 109 is disposed on the seat frame 113, and a rear cushion 114 of a rear wheel suspension system is disposed between the seat frame 113 and the swing arm 112. In the figure, reference numeral 104 denotes a front wheel, reference numeral 105 denotes a front fork, reference numeral 106 denotes a steering column, reference numeral 107 denotes a steering handle bar, and reference numeral 111 denotes a rear wheel.

An internal combustion engine 1 (engine) of the motorcycle 101 is supported below the main pipe 108.

Referring to fig. 2 and 3, the internal combustion engine 1 is an air-cooled single-cylinder engine in which the rotation center axis (crankshaft axis) C1 of the crankshaft 9 is oriented in the left-right direction, and the cylinder 3 is projected substantially horizontally (in detail, slightly higher in the front and lower in the rear) forward from the front end of the crankcase 2.

The crankcase 2 is divided into a left crankcase half body 2a and a right crankcase half body 2b with a dividing plane (for example, a vehicle body left and right center plane) CS orthogonal to the left-right direction as a boundary. A left crankcase cover 24 and a right crankcase cover 25, which constitute a part of the left half crankcase body 2a and the right half crankcase body 2b, are attached to the outer sides of these half crankcase bodies. The crankcase 2 also serves as a transmission case that houses a manual transmission (transmission, hereinafter simply referred to as a transmission) 4. The engine oil is appropriately circulated and agitated inside the internal combustion engine 1 including the crankcase 2. The crankcase 2 holds a crankshaft 9.

A cylinder block (cylinder body) 3a and a cylinder head 3b of the cylinder 3 are connected in this order from the crankcase 2 side. A piston 8 is fitted in a cylinder bore (cylinder tube) 3d of the cylinder block 3a so as to be capable of reciprocating. The piston 8 is coupled to a crankpin 9a of the crankshaft 9 via a connecting rod (connecting rod) 8 a. The cylinder head 3b holds a valve mechanism (including a camshaft and a valve mechanism) 11, and the valve mechanism 11 controls the intake and exhaust of air into and out of the cylinder bore 3 d.

The crankshaft 9 includes left and right crank arms 9b that support the crank pins 9a, left and right journal portions 9c that protrude laterally outward from the left and right crank arms 9b, and left and right extension shafts 9d that extend laterally outward from the left and right journal portions 9 c. The crankshaft 9 converts reciprocating motion of the piston 8 into rotational motion.

A cam drive sprocket 12 is provided on the base end side of the left extension shaft 9d, and a camshaft drive chain (power transmission member) 14 is wound around the cam drive sprocket 12. The camshaft drive chain 14 is wound around a cam driven sprocket 11b at the left end of a camshaft 11a in the valve train 11 inside the cylinder head 3 b. The camshaft drive chain 14 transmits power from the crankshaft 9 to the valve mechanism 11. The valve train 11 is driven in conjunction with the crankshaft 9 via a camshaft drive train 14.

In the figure, reference numeral 15 denotes a camshaft drive chain chamber (power transmission member accommodating chamber) provided in a left side portion of the cylinder 3, reference numeral 17 denotes an ignition plug attached to the cylinder head 3b, reference numeral 18 denotes a throttle area connected to an upper side (intake side) of the cylinder head 3b, and reference numeral 19 denotes an exhaust pipe connected to a lower side (exhaust side) of the cylinder head 3 b.

The cylinder block 3a forms a camshaft drive chain chamber 15 on the left side of the cylinder bore 3 d.

Referring to fig. 5 to 7 together, the left crankcase half body 2a of the crankcase 2 forms a crankcase-side camshaft transmission chain chamber (crankcase-side power transmission member accommodating chamber) 52 (connected to the camshaft transmission chain chamber 15) as a part of the camshaft transmission chain chamber 15. The camshaft gear chamber 15 and the crankcase-side camshaft gear chamber 52 also function as an oil return passage for returning the engine oil supplied into the cylinder head 3b to the crankcase 2.

Returning to fig. 3, the rotational power of the crankshaft 9 is output to the engine output unit 23 on the rear left side of the crankcase 2 via the two clutches 21 and 22 housed on the right side in the crankcase 2 and the transmission 4 housed in the rear portion in the crankcase 2. The engine output unit 23 is connected to a rear wheel 111 as a driving wheel via a chain transmission mechanism 23 a. Hereinafter, in the transmission path from the crankshaft 9 to the engine output unit 23, the crankshaft 9 side may be referred to as the upstream side and the engine output unit 23 side may be referred to as the downstream side.

A centrifugal clutch 21 as a starting clutch is coaxially supported on the right extension shaft 9d of the crankshaft 9. The centrifugal clutch 21 is in a disengaged state in which power cannot be transmitted when the crankshaft 9 is stopped and rotating at a low speed. The centrifugal clutch 21 is in a connected state in which power can be transmitted as the rotational speed (rotational speed) of the crankshaft 9 increases. Reference numeral 26 in the figure denotes a centrifugal oil filter formed on the right side of the centrifugal clutch 21.

A primary drive gear 20a that rotates integrally with the downstream side of the centrifugal clutch 21 is coaxially supported on the base end side of the right extension shaft 9 d. The primary drive gear 20a meshes with a primary driven gear 20b, and the primary driven gear 20b is coaxially supported on the right side portion of the main shaft 5 located behind the crankshaft 9. The primary drive gear 20a and the primary driven gear 20b constitute a primary speed reduction mechanism of the internal combustion engine 1.

The main shaft 5 and the sub shaft 6 of the transmission 4 are arranged in this order from the front side behind the crankshaft 9. The main shaft 5 and the sub shaft 6 have their rotation center axes C3 and C4 arranged in the left-right direction (parallel to the crankshaft axis C1).

The right end of the main shaft 5 terminates leftward (inward in the engine width direction) from the right end of the crankshaft 9, and a multiple disc clutch 22 as a transmission clutch is coaxially supported on the right end. The primary driven gear 20b is coaxially supported on the upstream side of the multiple disc clutch 22 so as to be rotatable integrally therewith. The multi-plate clutch 22 temporarily releases the pressure contact of the clutch plates in conjunction with a shift operation of a shift pedal, not shown, to smooth the shifting of the transmission 4.

The transmission 4 includes a main shaft 5, a counter shaft 6, and a speed change gear group 7 supported across the main shaft 5 and the counter shaft 6. The rotational power of the crankshaft 9 is transmitted from the main shaft 5 to the counter shaft 6 via any gear of the speed change gear group 7. The left end of the counter shaft 6 protrudes to the left of the rear of the crankcase 2 to become an engine output portion 23.

An ACG starter 27 is coaxially supported on a left end portion of a left extension shaft 9d of the crankshaft 9. The ACG starter 27 functions as a starter motor that starts the internal combustion engine 1, and also functions as an alternator that generates electric power in accordance with the operation of the internal combustion engine 1. The operation of the ACG starter 27 is controlled by an ecu (electronic Control unit), not shown.

As shown in fig. 4, the crankcase 2 has an oil reservoir 51 for storing engine oil in the vicinity of the bottom surface (the vicinity of the lower end). The oil stored in the oil reservoir 51 is sucked through the oil strainer 55 by driving the oil pump 56, and is pressurized and delivered to each part of the engine.

The oil filter 55 is formed in a metal mesh shape, and removes foreign substances in the oil. The oil pump 56 is driven during engine operation in conjunction with the crankshaft 9.

An oil reservoir recess 51a is formed in the lower end portion of the left crankcase half body 2a, and the oil reservoir recess 51a forms the left side portion of the oil reservoir 51. An oil strainer chamber 55a for accommodating the oil strainer 55 is formed below the oil reservoir recess 51 a. A suction passage (oil passage) 61 reaching the oil pump 56 is formed above the oil strainer chamber 55 a. A rib 62 extending along the oil passage 61 extending in the vertical direction is formed inside the oil reservoir recess 51 a.

Referring to fig. 5 to 7 together, the left crankcase half body 2a forms a crankcase-side camshaft gear train chamber (crankcase-side power transmission member accommodating chamber) 52 connected to a rear lower end portion of the camshaft gear train chamber 15. An oil dropping hole 54 communicating with the oil reservoir 51 (oil reservoir recess 51a) is formed midway in the bottom wall 53 of the crankcase-side camshaft transmission chain chamber 52. The oil returned from the cylinder head 3b to the crankcase 2 via the camshaft gear chamber 15 flows on the bottom wall 53 of the crankcase-side camshaft gear chamber 52 and reaches the oil reservoir 51. Since the oil dropping hole 54 is formed in the middle of the bottom wall 53, the oil is returned earlier.

Referring also to fig. 3, the lower rear end of the cylinder block 3a on the crankcase 2 side is opposed to the upper front end (cylinder fixing surface) of the crankcase 2 on the cylinder 3 side via a gasket 57. In this state, the cylinder block 3a is fastened and fixed to the front upper end portion of the crankcase 2. The oil dropping hole 54 is formed at a predetermined distance from the gasket 57 (cylinder fixing surface) to the side opposite to the cylinder 3.

Referring to fig. 8 and 9 together, the oil dropping hole 54 extends to a lower portion of a side wall 59 of the crankcase-side camshaft gear chamber 52 on the inner side in the engine width direction (the inner side in the vehicle width direction, the inner side in the left-right direction), and is formed by partially cutting off the lower portion. The oil dropping hole 54 is formed at a predetermined distance from the rear end 60 of the crankcase-side camshaft drive chain chamber 52 toward the cylinder 3.

In the oil reservoir 51, the crankcase-side camshaft transmission chain chamber 52 side is set upstream of the oil reservoir 51, and the oil strainer 55 side is set downstream of the oil reservoir 51. The rib 62 located on the downstream side of the oil dropping hole 54 functions as a wall for restricting the flow of oil from the oil reservoir 51 to the oil dropping hole 54. This makes it possible to accelerate the return of the oil through the oil dropping hole 54 and to suppress the backflow of the oil in the oil reservoir 51 from the oil dropping hole 54 during emergency braking or the like.

As described above, the internal combustion engine 1 of the above embodiment includes: a cylinder block 3a having cylinder bores 3 d; a piston 8 that reciprocates in the cylinder bore 3 d; a crankshaft 9 that converts reciprocating motion of the piston 8 into rotational motion; a crankcase 2 that holds the crankshaft 9; a valve mechanism 11 that controls the intake and exhaust of air into and out of the cylinder bore 3 d; a cylinder head 3b that holds the valve mechanism 11; a camshaft drive chain 14 that transmits power from the crankshaft 9 to the valve mechanism 11; and a camshaft drive chain chamber 15 that is formed in the cylinder block 3a, houses the camshaft drive chain 14, and also functions as a return passage for returning the oil supplied into the cylinder head 3b into the crankcase 2, wherein the crankcase 2 has an oil reservoir 51 on a bottom surface side, the crankcase 2 has a crankcase-side camshaft drive chain chamber 52 connected to the camshaft drive chain chamber 15, and an oil dropping hole 54 communicating with the oil reservoir 51 is formed in a bottom wall 53 of the crankcase-side camshaft drive chain chamber 52.

According to this configuration, in the configuration in which the camshaft gear train chamber 15 of the cylinder block 3a is used as a return passage for oil supplied to the cylinder head 3b, an oil dropping hole 54 communicating with the oil reservoir 51 is formed in the bottom wall 53 of the crankcase-side camshaft gear train chamber 52. Thus, the cylinder block 3a can be made smaller than a configuration in which an oil return passage is provided separately from the camshaft drive chain chamber. In addition, compared to the structure in which the oil is returned to the oil reservoir 51 after being transferred to the entire bottom wall 53 of the crankcase-side camshaft gear train chamber 52, the oil is also returned to the oil reservoir 51 from the middle of the bottom wall 53 of the crankcase-side camshaft gear train chamber 52, and therefore the oil can be returned efficiently.

In the internal combustion engine 1, the cylinder block 3a is disposed adjacent to the crankcase 2 with a gasket 57 interposed therebetween, and the oil dropping hole 54 is provided apart from the gasket 57.

According to this configuration, in the cylinder block 3a disposed adjacent to the crankcase 2 with the gasket 57 interposed therebetween, the oil drop hole 54 is provided at a predetermined distance from the gasket 57, so that the airtightness of the gasket 57 can be easily ensured, and the strength of the end surface (cylinder fixing surface) of the crankcase 2 can be easily ensured.

In addition, in the internal combustion engine 1 described above, the oil drop hole 54 extends to the lower portion of the side wall 59 located on the engine width direction inner side of the bottom wall 53.

According to this configuration, the oil dropping hole 54 extends from the bottom wall 53 to the lower portion of the side wall 59 on the inner side in the engine width direction, and therefore, the oil can be returned with good efficiency even when the amount of oil is large.

In addition, in the internal combustion engine 1, the oil drop hole 54 is provided at a position spaced apart from the rear end 60 of the crankcase-side camshaft gear chamber 52.

According to this configuration, since the oil dropping hole 54 is provided at a predetermined distance from the rear end of the crankcase-side camshaft gear train chamber 52, the strength of the crankcase-side camshaft gear train chamber 52 is not easily affected, and the strength of the crankcase-side camshaft gear train chamber 52 can be easily ensured.

In addition, in the internal combustion engine 1, the oil reservoir 51 has a passage 61 leading to the oil pump 56 through an oil strainer 55, and when the crankcase-side camshaft gear chamber 52 is set upstream of the oil reservoir 51 and the oil strainer 55 is set downstream of the oil reservoir 51, a rib 62 restricting the flow of oil from the oil reservoir 51 to the oil dropping hole 54 is provided downstream of the oil dropping hole 54.

According to this configuration, since the rib 62 that restricts the flow of the oil from the oil reservoir 51 side to the oil dropping hole 54 side is provided on the downstream side of the oil dropping hole 54, the backflow of the oil flowing into the upstream side due to a behavior at the time of emergency braking of the vehicle or the like can be prevented with a simple configuration.

The rib 62 is disposed so that at least a part thereof overlaps the oil drop hole 54 in the vehicle width direction (see fig. 6 to 8). That is, by overlapping at least a part of the rib 62 with the oil drop hole 54 at the vehicle width direction position, it is possible to more reliably prevent the backflow of the oil flowing into the upstream side due to a behavior at the time of sudden braking of the vehicle or the like.

The present invention is not limited to the above embodiments, and for example, a check valve that allows oil to flow from the camshaft drive chain chamber 15 to the oil reservoir 51 and restricts oil from flowing from the oil reservoir 51 to the camshaft drive chain chamber 15 may be provided in the oil dropping hole 54. In this case, since the oil dropping hole 54 is provided with a check valve for restricting the oil flow in one direction, the oil can be reliably prevented from flowing backward toward the upstream side.

The straddle-type vehicle includes all vehicles in which a driver rides over a vehicle body, and includes not only a motorcycle (including a bicycle with a prime mover and a scooter-type vehicle), but also a three-wheeled vehicle (including a vehicle with two front wheels and one rear wheel in addition to a vehicle with one front wheel and two rear wheels) or a four-wheeled vehicle.

The configuration in the above embodiment is an example of the present invention, and various modifications can be made without departing from the scope of the present invention by replacing the components of the embodiment with known components and the like.