阅读说明：本技术 内燃机 (Internal combustion engine ) 是由 畑江亮 星野雅一 于 2020-03-23 设计创作，主要内容包括：本发明提供一种内燃机,使该内燃机在曲轴的轴向上紧凑化,并且能够有效承受作用于单向离合器机构的推力。内燃机具有：曲轴(11),其借助于轴承(35)而被支承；平衡器驱动齿轮(36)；平衡器轴(30)；以及单向离合器机构(37),其向曲轴(11)传递使内燃机起动的驱动力,其中,轴承(35)是内置对曲轴箱(12)的曲轴室(33)进行密封的油封(35d)的轴承,单向离合器机构(37)具有：壳体(55),其固定于曲轴(11)；以及起动从动齿轮(56),其被设置为能够相对于壳体(55)相对旋转,被所述驱动力驱动,起动从动齿轮(56)具有与平衡器驱动齿轮(36)在曲轴(11)的轴向上抵接的推力承受部(55e)。(The invention provides an internal combustion engine, which is compact in the axial direction of a crankshaft and can effectively bear the thrust acting on a one-way clutch mechanism. An internal combustion engine is provided with: a crankshaft (11) supported by means of a bearing (35); a balancer drive gear (36); a balancer shaft (30); and a one-way clutch mechanism (37) that transmits a driving force for starting the internal combustion engine to the crankshaft (11), wherein the bearing (35) is a bearing that incorporates an oil seal (35d) that seals a crank chamber (33) of the crankcase (12), and the one-way clutch mechanism (37) comprises: a housing (55) fixed to the crankshaft (11); and a starting driven gear (56) that is provided so as to be rotatable relative to the housing (55) and that is driven by the driving force, wherein the starting driven gear (56) has a thrust receiving portion (55e) that abuts the balancer driving gear (36) in the axial direction of the crankshaft (11).)

1. An internal combustion engine, comprising:

a crankshaft (11) supported by the crankcase (12) via a bearing (35);

a balancer drive gear (36) provided to the crankshaft (11);

a balancer shaft (30) provided with a balancer;

a balancer driven gear (43) provided to the balancer shaft (30) and meshed with the balancer drive gear (36); and

a one-way clutch mechanism (37) that transmits a driving force for starting the internal combustion engine to the crankshaft (11),

the balancer drive gear (36) is disposed on the crankshaft (11) between the bearing (35) and the one-way clutch mechanism (37),

it is characterized in that the preparation method is characterized in that,

the bearing (35) is a bearing having an oil seal (35d) built therein, the oil seal (35d) sealing a crank chamber (33) of the crankcase (12),

the one-way clutch mechanism (37) has:

a housing (55) fixed to the crankshaft (11); and

a start driven gear (56) provided so as to be relatively rotatable with respect to the housing (55) and driven by the driving force,

the starting driven gear (56) has a thrust receiving portion (55e) that abuts the balancer drive gear (36) in the axial direction of the crankshaft (11).

2. The internal combustion engine according to claim 1,

the thrust receiving portion (55e) is a convex portion that protrudes from a side surface of the starting driven gear (56) in the axial direction of the crankshaft (11).

3. The internal combustion engine according to claim 1 or 2,

an output gear (38) that outputs the rotation of the crankshaft (11) to another rotating shaft (31), the output gear (38) being provided on the axially outer side of the crankshaft (11) with respect to the one-way clutch mechanism (37),

the starting driven gear (56) extends in the radial direction along the balancer drive gear (36) at a position offset to the balancer drive gear (36) side between the balancer drive gear (36) and the output gear (38).

4. An internal combustion engine according to claim 3,

the bearing (35), the balancer drive gear (36), the start driven gear (56), the housing (55), and the output gear (38) are disposed in this order from the crank chamber (33) side.

5. The internal combustion engine according to any one of claims 1 to 4,

the balancer drive gear (36) is sandwiched between the bearing (35) and the housing (55) in the axial direction of the crankshaft (11).

6. The internal combustion engine according to any one of claims 1 to 5,

a water pump (46) connected to the balancer shaft (30) and rotating integrally with the balancer shaft (30), the water pump (46) being disposed coaxially with the balancer shaft (30),

the water pump (46) is disposed outside the starting driven gear (56) in the axial direction of the crankshaft (11) and at a position overlapping the housing (55).

7. The internal combustion engine of claim 6,

the water pump (46) has:

a shaft (46a) that is rotatably supported by the crankcase (12) and is connected to the balancer shaft (30); and

a pump body (46b) extending radially outward from the shaft (46a),

the shaft portion (46a) of the water pump (46) overlaps the housing (55).

8. The internal combustion engine of claim 7,

the crankcase (12) has a support cylinder portion (47a) that supports the shaft portion (46a),

a part (47a1) of the support cylindrical portion (47a) is disposed at a position that is outside the starting driven gear (56) in the axial direction of the crankshaft (11) and that overlaps the housing (55), and the part (47a1) of the support cylindrical portion (47a) is located at a position that is inside an outer peripheral portion (56c) of the starting driven gear (56) in the radial direction of the starting driven gear (56).

Technical Field

The present invention relates to internal combustion engines.

Background

Conventionally, an internal combustion engine is known, which includes: a crankshaft supported by the crankcase via a bearing; a balancer drive gear provided to the crankshaft; a balancer shaft provided with a balancer; a balancer driven gear provided to the balancer shaft and engaged with the balancer driving gear; and a one-way clutch mechanism that transmits a driving force for starting the internal combustion engine to the crankshaft, wherein the balancer driving gear is disposed between the bearing and the one-way clutch mechanism on the crankshaft (see, for example, patent document 1). In patent document 1, an oil seal that seals a crank chamber is provided between a bearing and a balancer drive gear.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to make an internal combustion engine compact in the axial direction of a crankshaft and to effectively receive thrust force acting on a one-way clutch mechanism.

An internal combustion engine is provided with: a crankshaft 11 supported by the crankcase 12 via a bearing 35; a balancer drive gear 36 provided to the crankshaft 11; a balancer shaft 30 provided with a balancer; a balancer driven gear 43 provided on the balancer shaft 30 and meshed with the balancer drive gear 36; and a one-way clutch mechanism 37 that transmits a driving force for starting the internal combustion engine to the crankshaft 11, wherein the balancer drive gear 36 is disposed between the bearing 35 and the one-way clutch mechanism 37 on the crankshaft 11, and wherein the bearing 35 is a bearing that incorporates an oil seal 35d, and the oil seal 35d seals the crank chamber 33 of the crankcase 12, and wherein the one-way clutch mechanism 37 includes: a housing 55 fixed to the crankshaft 11; and a starter driven gear 56 provided to be rotatable relative to the housing 55 and driven by the driving force, wherein the starter driven gear 56 includes a thrust receiving portion 55e that abuts against the balancer drive gear 36 in the axial direction of the crankshaft 11.

In the above configuration, the thrust receiving portion 55e may be a convex portion that protrudes from a side surface of the starter driven gear 56 in the axial direction of the crankshaft 11.

In the above configuration, the output gear 38 outputs the rotation of the crankshaft 11 to the other rotary shaft 31, the output gear 38 is provided on the axially outer side of the crankshaft 11 with respect to the one-way clutch mechanism 37, and the start driven gear 56 may extend in the radial direction along the balancer drive gear 36 at a position offset toward the balancer drive gear 36 between the balancer drive gear 36 and the output gear 38.

In the above configuration, the bearing 35, the balancer drive gear 36, the start driven gear 56, the housing 55, and the output gear 38 may be arranged in this order from the crank chamber 33 side.

In the above configuration, the balancer drive gear 36 may be interposed between the bearing 35 and the housing 55 in the axial direction of the crankshaft 11.

In the above configuration, the water pump 46 may be connected to the balancer shaft 30 and integrally rotated with the balancer shaft 30, the water pump 46 may be disposed coaxially with the balancer shaft 30, and the water pump 46 may be disposed outside the starter driven gear 56 in the axial direction of the crankshaft 11 and at a position overlapping the housing 55.

In the above configuration, the water pump 46 may include: a shaft portion 46a rotatably supported by the crankcase 12 and connected to the balancer shaft 30; and a pump body 46b extending radially outward from the shaft 46a, wherein the shaft 46a of the water pump 46 overlaps the housing 55.

In the above configuration, the crankcase 12 may include a support cylindrical portion 47a that supports the shaft portion 46a, a portion 47a1 of the support cylindrical portion 47a may be disposed at a position that is outside the starting driven gear 56 and overlaps the housing 55 in the axial direction of the crankshaft 11, and the portion 47a1 of the support cylindrical portion 47a may be located inside the outer peripheral portion 56c of the starting driven gear 56 in the radial direction of the starting driven gear 56.

Effects of the invention

An internal combustion engine is provided with: a crankshaft supported by the crankcase via a bearing; a balancer drive gear provided to the crankshaft; a balancer shaft provided with a balancer; a balancer driven gear provided to the balancer shaft and engaged with the balancer driving gear; and a one-way clutch mechanism that transmits a driving force for starting the internal combustion engine to the crankshaft, wherein the balancer driving gear is disposed on the crankshaft between a bearing and the one-way clutch mechanism, the bearing is a bearing incorporating an oil seal that seals a crank chamber of the crankcase, and the one-way clutch mechanism includes: a housing fixed to the crankshaft; and a starter driven gear that is provided so as to be rotatable relative to the housing and is driven by the driving force, the starter driven gear having a thrust receiving portion that abuts against the balancer driving gear in an axial direction of the crankshaft.

According to this configuration, since the oil seal for sealing the crank chamber of the crankcase is built in the bearing, it is not necessary to secure a space dedicated for the oil seal outside the bearing. Further, since the thrust force of the starter driven gear of the one-way clutch mechanism is received by the balancer drive gear via the thrust receiving portion, the thrust force can be effectively received without making the one-way clutch mechanism large or providing a dedicated member for receiving the thrust force. Therefore, the internal combustion engine can be made compact in the axial direction of the crankshaft, and the thrust force acting on the one-way clutch mechanism can be effectively received.

In the above configuration, the thrust receiving portion may be a convex portion that protrudes in the axial direction of the crankshaft from a side surface of the starter driven gear.

According to this configuration, since the thrust receiving portion is a convex portion, the thrust receiving portion can be brought into contact with the balancer drive gear with high accuracy.

In the above configuration, the output gear may output rotation of the crankshaft to another rotary shaft, the output gear being provided axially outward of the crankshaft with respect to the one-way clutch mechanism, and the start driven gear may extend radially along the balancer drive gear at a position offset to the balancer drive gear side between the balancer drive gear and the output gear.

According to this configuration, since the starter driven gear is located along the balancer drive gear at a position offset toward the balancer drive gear side, the thrust receiving portion can be easily brought into contact with the balancer drive gear, and the thrust can be effectively received. Further, since the starter driven gear is disposed at a position offset toward the balancer drive gear and closer to the crankshaft chamber side, the internal combustion engine can be made compact in the axial direction of the crankshaft.

In the above configuration, the bearing, the balancer drive gear, the starter driven gear, the housing, and the output gear may be arranged in this order from the crankshaft chamber side.

According to this structure, the thrust of the starting driven gear is received by the balancer drive gear, and the structure in which rotation is output from the output gear can be provided compactly.

In the above configuration, the balancer drive gear may be held between the bearing and the housing in the axial direction of the crankshaft.

According to this configuration, the balancer drive gear can be positioned in the axial direction of the crankshaft with a simple configuration by the housing, and the thrust force to start the driven gear can be received by the balancer drive gear positioned by the housing.

In the above configuration, the water pump may be connected to the balancer shaft so as to rotate integrally with the balancer shaft, the water pump may be disposed coaxially with the balancer shaft, and the water pump may be disposed outside the starter driven gear in the axial direction of the crankshaft and at a position overlapping the housing.

According to this configuration, the water pump can be disposed closer to the starting driven gear side in the axial direction of the crankshaft, and the internal combustion engine can be made compact in the axial direction of the crankshaft.

In the above configuration, the water pump may include: a shaft portion rotatably supported by the crankcase and connected to the balancer shaft; and a pump body portion extending radially outward from the shaft portion, the shaft portion of the water pump being overlapped with the housing.

According to this configuration, the shaft portion of the water pump can be disposed closer to the starting driven gear in the axial direction of the crankshaft, and the internal combustion engine can be made compact in the axial direction of the crankshaft.

In the above-described configuration, the crankcase may include a support cylinder portion that supports the shaft portion, and a part of the support cylinder portion may be disposed outside the starter driven gear in the axial direction of the crankshaft and overlapping the housing, and may be located inside the outer peripheral portion of the starter driven gear in the radial direction of the starter driven gear.

According to this configuration, the support cylindrical portion of the crankcase can be disposed close to the starting driven gear side, and the internal combustion engine can be made compact.

Drawings

Fig. 1 is a right side view of an internal combustion engine of an embodiment of the present invention.

Fig. 2 is a sectional view taken along line II-II in fig. 1.

Fig. 3 is an enlarged view of the peripheral portions of the bearing, the balancer drive gear, and the one-way clutch mechanism in fig. 2.

Fig. 4 is a view of the cylinder head with the cylinder head cover removed, as viewed from above.

Fig. 5 is a sectional view taken along line V-V in fig. 4.

Fig. 6 is a sectional view taken along line VI-VI in fig. 4.

Description of the reference symbols

11: a crankshaft; 12: a crankcase; 30: a balancer shaft; 31: spindles (other rotating shafts); 33: a crankshaft chamber; 35: a bearing; 35 d: oil sealing; 36: a balancer drive gear; 37: a one-way clutch mechanism; 38: an output gear; 43: a balancer driven gear; 46: a water pump; 46 a: a shaft portion; 46 b: a pump main body portion; 47 a: a support cylinder portion; 47a 1: a part; 55: a housing; 55 e: a thrust receiving section; 56: starting the driven gear; 56 c: an outer peripheral portion.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description, the directions of the front, rear, left, right, up, down, and the like are the same as the directions of the vehicle body unless otherwise specified. In the drawings, reference numeral "FR" denotes the front of the vehicle body, reference numeral "UP" denotes the upper of the vehicle body, and reference numeral "LH" denotes the left of the vehicle body.

Fig. 1 is a right side view of an internal combustion engine of an embodiment of the present invention.

The internal combustion engine 10 is mounted on a motorcycle. The motorcycle includes: a vehicle frame (not shown); a front fork (not shown) supported by a front end portion of the frame; a swing arm (not shown) supported to be swingable on a rear portion of the frame; a front wheel (not shown) supported by the front fork; a rear wheel supported by the swing arm; and an internal combustion engine 10 supported by the vehicle body frame.

The motorcycle is a saddle-ride type vehicle in which a passenger straddles a seat (not shown) for the passenger supported by the frame.

The internal combustion engine 10 includes: a crankcase 12 that supports a crankshaft 11 extending in a vehicle width direction (left-right direction); a cylinder 13 extending upward from an upper surface of a front portion of the crankcase 12; a cylinder head 14 coupled to an upper surface of the cylinder 13; and a head cover 15 coupled to an upper surface of the cylinder head 14.

The internal combustion engine 10 is an engine in which the cylinder axis 13a of the cylinder 13 is slightly inclined forward with respect to the vertical direction.

The piston 16 reciprocates in the direction of the cylinder axis 13a within the cylinder of the cylinder 13.

A throttle body 17 of an intake apparatus of the internal combustion engine 10 is connected to an intake port 18 provided on the rear surface side of the cylinder head 14.

The exhaust pipe 19 is connected to an exhaust port 20 provided on the front surface side of the cylinder head 14.

Fig. 2 is a sectional view taken along line II-II in fig. 1.

Referring to fig. 2, a crankshaft 11, a balancer shaft 30 provided with a balancer (not shown), a main shaft 31 (other rotating shaft) driven by the crankshaft 11, and an intermediate shaft (not shown) driven by the main shaft 31 are housed in the crankcase 12.

A crankshaft axis 11a as a rotation center of the crankshaft 11 extends horizontally in the vehicle width direction. The axial direction of the crankshaft 11 is the extending direction of the crankshaft axis 11 a.

The crankshaft 11, the balancer shaft 30, the main shaft 31, and the intermediate shaft are arranged in parallel with each other.

The crankcase 12 has a pair of left and right support walls 32 perpendicular to the crankshaft 11. In fig. 2, the supporting wall 32 on one of the left and right sides (right side) is shown, and the supporting wall on the other of the left and right sides (left side) is not shown. The pair of support walls 32 are arranged apart from each other in the axial direction of the crankshaft 11. The pair of support walls 32 define a crank chamber 33 for accommodating the crankshaft 11 in the axial direction of the crankshaft 11.

The crank chamber 33 communicates with the inside of the cylinder 13. The crankshaft 11 is coupled to the piston 16 (fig. 1) via a coupling rod (not shown) passing through the crank chamber 33.

The support wall 32 is provided with a support hole 34 that supports the crankshaft 11. The support hole 34 is a hole through which the crankshaft 11 passes, and supports the crankshaft 11 via a bearing 35. An annular flange portion 34a protruding radially inward is provided on an outer end portion in the axial direction of the crankshaft 11 in an inner peripheral portion of the support hole portion 34.

The shaft end portion 11b on one end side in the axial direction of the crankshaft 11 penetrates the support hole portion 34 and protrudes outward of the crank chamber 33.

To the shaft end portion 11b are mounted: a balancer drive gear 36 that drives the balancer shaft 30; a one-way clutch mechanism 37 that transmits a driving force for starting the internal combustion engine 10 to the crankshaft 11; and an output gear 38 that outputs the rotation of the crankshaft 11 to the main shaft 31 side.

A fixing bolt 39 that presses the output gear 38 in the axial direction is fastened to an end surface of the shaft end portion 11 b.

Further, the balancer shaft support holes 41 for supporting the balancer shaft 30 are provided in the left and right support walls 32. In fig. 2, the balancer shaft support hole portion on the left side is not shown.

The balancer shaft support hole 41 is a hole through which the balancer shaft 30 passes, and supports the balancer shaft 30 via the bearing 42. An annular flange 41a protruding radially inward is provided at an outer end in the axial direction on an inner peripheral portion of the balancer shaft support hole 41.

One end 30a of the balancer shaft 30 in the axial direction penetrates the support wall 32 and protrudes outward of the crank chamber 33.

The one end portion 30a is provided with: a balancer driven gear 43 meshed with the balancer drive gear 36; and a nut 44 that fastens the balancer driven gear 43 to the one end portion 30 a.

The balancer driven gear 43 has: a cylindrical portion 43a fixed to an outer peripheral portion of the one end portion 30 a; and a gear portion 43b extending radially outward from an axial outer end of the cylindrical portion 43 a.

The cylindrical portion 43a of the balancer driven gear 43 is spline-fitted to the outer peripheral portion of the one end portion 30a, and rotates integrally with the balancer shaft 30.

The bearing 42 is fitted into the balancer shaft support hole 41 from the inner surface side of the support wall 32, and the outer ring 42a abuts against the flange 41a, whereby the bearing 42 is positioned in the axial direction.

The balancer shaft 30 has a positioning portion 30b protruding radially outward at a position axially inward of the bearing 42. The positioning portion 30b abuts against the inner race 42b of the bearing 42 in the axial direction.

The inner race 42b and the cylindrical portion 43a of the balancer driven gear 43 are disposed between the positioning portion 30b and the nut 44 in the axial direction, and are positioned in the axial direction by being sandwiched by the fastening force of the nut 44. A part of the cylindrical portion 43a passes through the inside of the flange portion 41 a.

An engagement portion 30c protruding in the axial direction is provided on an end surface of the one end portion 30a of the balancer shaft 30.

The other end portion (not shown) of the balancer shaft 30 penetrates the support wall (not shown) on the left side and protrudes outside the crank chamber 33. A balancer (not shown) that rotates integrally with the balancer shaft 30 is provided at the other end of the balancer shaft 30. The balancer rotates in the opposite direction of the crankshaft 11 in conjunction with the crankshaft 11, and reduces vibration generated by the reciprocating motion of the piston 16.

The crankcase 12 is provided with a water pump 46 for circulating cooling water of the internal combustion engine 10.

The crankcase 12 has a pump support portion 47 that supports the water pump 46 at a position outside the support wall 32 in the axial direction of the crankshaft 11.

The water pump 46 is connected with the balancer shaft 30 and rotates integrally with the balancer shaft 30. The water pump 46 is disposed coaxially with the balancer shaft 30 at a position axially outward of the one end 30a of the balancer shaft 30.

The water pump 46 has: a shaft portion 46a rotatably supported by the pump support portion 47 and connected to the balancer shaft 30; and a blade-shaped pump body 46b extending radially outward from the shaft 46 a.

The shaft portion 46a has an engagement hole 46c that engages with the engagement portion 30c of the balancer shaft 30. The water pump 46 is connected to the balancer shaft 30 via the engagement hole 46c so as to be relatively non-rotatable.

The pump support portion 47 has: a support cylinder portion 47a that supports the shaft portion 46a via a pump bearing 48; and a housing portion 47b that houses the pump body portion 46 b. The cooling water flows through the housing 47 b.

The support cylindrical portion 47a is provided with a seal member 49 for sealing between the pump bearing 48 and the housing portion 47 b.

The housing portion 47b is closed by a cover member 50 attached to the outer surface of the pump support portion 47.

The main shaft 31 and the intermediate shaft are housed in a transmission chamber 51 in the crankcase 12. The main shaft 31 is supported by a wall 51a defining a transmission chamber 51.

One end of the main shaft 31 extends through the wall 51a to the outside of the crankcase 12, and a friction clutch mechanism 52 is provided at the one end.

The clutch mechanism 52 has a driven gear 52a that meshes with the output gear 38 of the crankshaft 11.

In a state where the clutch mechanism 52 is connected, the rotation of the crankshaft 11 is transmitted to the main shaft 31 via the output gear 38 and the driven gear 52 a.

In a state where the clutch mechanism 52 is disengaged, the rotation of the crankshaft 11 transmitted to the driven gear 52a is idly rotated by the clutch mechanism 52 and is not transmitted to the main shaft 31.

The clutch mechanism 52 and the shaft end 11b of the crankshaft 11 are covered with a crankcase cover 53 attached to the outer side surface of the crankcase 12.

A plurality of speed change gears are provided on the main shaft 31 and the intermediate shaft, respectively. Between the main shaft 31 and the intermediate shaft, a group of gear sets capable of transmitting power according to a shift operation is formed, and an arbitrary shift stage is selectively established. The rotation of the intermediate shaft is transmitted to the rear wheel via a drive chain (not shown) connecting the intermediate shaft and the rear wheel.

Fig. 3 is an enlarged view of the periphery of the bearing 35, the balancer drive gear 36, and the one-way clutch mechanism 37 in fig. 2.

Referring to fig. 2 and 3, the bearing 35 is a ball bearing having: an outer ring 35a fitted into an inner peripheral portion of the support hole 34 of the crankcase 12; an inner ring 35b provided inside the outer ring 35 a; and a plurality of balls 35c arranged between the outer ring 35a and the inner ring 35 b.

Further, the bearing 35 incorporates an oil seal 35d, and the oil seal 35d seals between the inner peripheral surface of the outer ring 35a and the outer peripheral surface of the inner ring 35 b. The oil seal 35d covers the ball 35c from the axial direction of the bearing 35.

The oil seal 35d covers the gap between the outer ring 35a and the inner ring 35b, thereby sealing the crank chamber 33 and improving the sealing of the crank chamber 33.

The bearing 35 is positioned in the axial direction by bringing the outer ring 35a into contact with the flange portion 34a of the support hole portion 34 from the inside of the crank chamber 33.

An end surface 11c (fig. 2) of the crankshaft 11 located in the crank chamber 33 is axially abutted against the inner ring 35b, and the crankshaft 11 is positioned in the axial direction.

The balancer drive gear 36 is disposed adjacent to the bearing 35 outside the crank chamber 33.

The balancer drive gear 36 has: an annular fixing portion 36a fitted to the shaft end portion 11b of the crankshaft 11; and a disk-shaped gear body 36b extending radially outward from the fixed portion 36 a. A tooth portion 36c that meshes with the balancer driven gear 43 of the balancer shaft 30 is provided on the outer periphery of the gear main body portion 36 b.

The fixing portion 36a of the balancer drive gear 36 is spline-fitted to the shaft end portion 11b, and the balancer drive gear 36 rotates integrally with the crankshaft 11.

The fixing portion 36a is formed to have a larger thickness in the axial direction than the gear body portion 36b, and the fixing portion 36a protrudes in the axial direction toward the inner ring 35b side with respect to the gear body portion 36 b.

The fixed portion 36a is sandwiched between the inner race 35b and the one-way clutch mechanism 37, and the balancer drive gear 36 is positioned in the axial direction of the crankshaft 11. A part of the fixing portion 36a is located radially inside the flange portion 34 a.

The gear body portion 36b extends in the radial direction so as to extend along the outer surface of the support wall 32.

The driving force for starting the internal combustion engine 10 by recoil starting the internal combustion engine 10 is input from a starting drive source (not shown) of the internal combustion engine 10 to the one-way clutch mechanism 37, and is transmitted to the crankshaft 11 via the clutch member 57. Here, the starting drive source is a starter motor.

The one-way clutch mechanism 37 transmits rotation (torque) from the starting drive source to the crankshaft 11 when the internal combustion engine 10 is started, and cuts off transmission of rotation from the crankshaft 11 to the starting drive source after the internal combustion engine 10 is started.

The one-way clutch mechanism 37 has: a housing 55 fixed to the shaft end 11b of the crankshaft 11; a start driven gear 56 provided to be relatively rotatable with respect to the housing 55; and a clutch member 57 interposed between the starter driven gear 56 and the housing 55.

The housing 55 has: a fixed cylinder portion 55a fitted to the shaft end portion 11 b; a disk-shaped side wall portion 55b extending radially outward from an end portion on the opposite side of the balancer drive gear 36 in the axial direction of the fixed cylinder portion 55 a; and a peripheral wall portion 55c that extends in the axial direction from the outer edge of the side wall portion 55b in the radial direction toward the balancer drive gear 36 side.

The housing 55 is fixed to the crankshaft 11 so as not to be relatively rotatable by spline-fitting the fixed cylindrical portion 55a to the shaft end portion 11 b.

The fixed cylinder portion 55a is sandwiched between the balancer drive gear 36 and the output gear 38, whereby the housing 55 is positioned in the axial direction of the crankshaft 11.

The peripheral wall portion 55c covers the fixed cylinder portion 55a from the radially outer side. The peripheral wall portion 55c is substantially parallel to the fixed cylinder portion 55 a. The peripheral wall portion 55c is axially shorter than the fixed cylinder portion 55a, and a gap 55d is formed in the axial direction between the inner end of the peripheral wall portion 55c and the outer side surface of the balancer drive gear 36.

The starting driven gear 56 has: an outer cylinder portion 56a fitted to an outer peripheral portion of the fixed cylinder portion 55a of the housing 55; and a gear portion 56b extending in a circular plate shape radially outward from the end portion on the balancer drive gear 36 side in the axial direction of the outer cylindrical portion 56 a.

The outer cylindrical portion 56a is relatively rotatable with respect to the fixed cylindrical portion 55a, and the starter driven gear 56 is relatively rotatable with respect to the housing 55 via the outer cylindrical portion 56 a.

A roller bearing 58 is interposed between the inner circumferential portion of the outer tube portion 56a and the outer circumferential portion of the fixed tube portion 55 a.

The gear portion 56b extends radially outward from the peripheral wall portion 55c of the housing 55 through the gap 55 d.

A thrust receiving portion 55e that abuts against the outer side surface of the balancer drive gear 36 is provided on the side surface of the gear portion 56b that faces the outer side surface of the balancer drive gear 36.

The thrust receiving portion 55e is a convex portion that protrudes from the side surface of the gear portion 56b toward the balancer drive gear 36 in the axial direction of the crankshaft 11.

The thrust receiving portion 55e is provided radially inward of the tooth portion 36c of the balancer drive gear 36 and the peripheral wall portion 55c of the housing 55.

The clutch member 57 is interposed between the inner peripheral portion of the peripheral wall portion 55c of the housing 55 and the outer peripheral portion of the outer cylinder portion 56a of the starting driven gear 56.

The clutch member 57 transmits torque between the starter driven gear 56 and the housing 55 in a direction in which the crankshaft 11 is rotated by the driving force of the starting drive source, and blocks the transmission of torque in a rotational direction opposite to the direction.

That is, when the internal combustion engine 10 is recoil-started, the starter driven gear 56 and the housing 55 are connected by the clutch member 57 to rotate integrally. After the internal combustion engine 10 is started, the clutch member 57 is disconnected, and the housing 55 rotating integrally with the crankshaft 11 idles against the starter driven gear 56.

The gear portion 56b of the starting driven gear 56 is offset toward the balancer drive gear 36 between the balancer drive gear 36 and the output gear 38 in the axial direction of the crankshaft 11. The gear portion 56b extends in the axial direction along the balancer drive gear 36 at a position close to the outer side surface of the balancer drive gear 36 in the radial direction.

A bearing 35, a balancer drive gear 36, a starter driven gear 56, a housing 55, and an output gear 38 are arranged in the axial direction in this order from the crank chamber 33 side at the shaft end 11b of the crankshaft 11.

The inner peripheral portion of the output gear 38 is spline-fitted to the shaft end portion 11b, and the output gear 38 rotates integrally with the crankshaft 11.

The output gear 38 is pressed in the axial direction of the crankshaft 11 by the fixing bolt 39 via the washer 39a, and the output gear 38 is positioned in the axial direction by being sandwiched between the washer 39a and the housing 55.

That is, the balancer drive gear 36, the one-way clutch mechanism 37, and the output gear 38 are sandwiched between the inner race 35b of the bearing 35 and the fixing bolt 39, and are positioned in the axial direction.

In the internal combustion engine 10, the oil seal 35d is provided in the bearing 35, and therefore, compared to a configuration in which an oil seal is disposed in parallel with the bearing 35, not only is the airtightness of the crank chamber 33 ensured, but also the crankshaft 11 can be made compact in the axial direction. This enables the balancer drive gear 36 to be disposed close to the bearing 35 of the crank chamber 33, and the internal combustion engine 10 to be compact in the axial direction of the crankshaft 11.

Further, since the balancer drive gear 36 is disposed close to the bearing 35, the balancer driven gear 43 meshing with the balancer drive gear 36 can be disposed close to the bearing 35 in the axial direction. Therefore, the internal combustion engine 10 can be made compact in the axial direction of the crankshaft 11.

The balancer driven gear 43 provided on the balancer shaft 30 is disposed on the side closer to the bearing 35 in the axial direction, and the water pump 46 disposed coaxially with the balancer shaft 30 may be disposed on the side closer to the bearing 35 in the axial direction. Therefore, the internal combustion engine 10 can be made compact in the axial direction of the crankshaft 11.

The thrust receiving portion 55e of the gear portion 56b abuts against the outer side surface of the balancer drive gear 36 to receive the thrust force F in the axial direction of the crankshaft 11 acting on the starter driven gear 56. This enables the thrust force F acting on the start driven gear 56 to be effectively received by the balancer drive gear 36 when the internal combustion engine 10 is recoil-started. Therefore, the thrust force F can be received by the starter driven gear 56 without increasing the plate thickness of the starter driven gear 56 or providing a separate receiving member, and the internal combustion engine 10 can be made compact in the axial direction of the crankshaft 11.

The shaft portion 46a of the water pump 46 and the support cylindrical portion 47a of the pump support portion 47 of the crankcase 12 are disposed at positions overlapping the housing 55 toward the bearing 35 side at positions outside the start driven gear 56 in the axial direction of the crankshaft 11. Therefore, the internal combustion engine 10 can be made compact in the axial direction of the crankshaft 11.

Further, a part 47a1 of the support tube portion 47a is located inward of the outer peripheral portion 56c of the starting driven gear 56 in the radial direction of the starting driven gear 56. Therefore, the support cylinder portion 47a can be disposed radially closer to the crankshaft 11, and the crankcase 12 can be made compact.

Fig. 4 is a view of the cylinder head 14 from above with the head cover 15 removed. Fig. 5 is a sectional view taken along line V-V in fig. 4.

Referring to fig. 4 and 5, the cylinder head 14 has: a base portion 14a coupled to an end surface of the cylinder 13 so as to face the piston 16; and a peripheral wall portion 14b erected from the base portion 14a in the direction of the cylinder axis 13 a. The space surrounded by the peripheral wall portion 14b and the base portion 14a is a valve operating chamber 60.

The head cover 15 (fig. 1) closes the valve operating chamber 60 from above in cooperation with the end surface of the peripheral wall portion 14 b.

A recessed combustion recess 61 facing the top surface of the piston 16 is provided in the base portion 14a of the cylinder head 14. The combustion chamber is defined by the combustion recess 61 and the top surface of the piston 16.

An intake port 18 and an exhaust port 20 are provided to the base portion 14 a.

The combustion recess 61 is provided with: a pair of intake openings 61a for communicating the intake port 18 with the combustion chamber; and a pair of exhaust openings 61b for communicating the exhaust port 20 with the combustion chamber.

A valve operating mechanism 65 is provided in the valve operating chamber 60.

The valve train 65 includes: a pair of intake valve units 66; a pair of exhaust valve units 67; a camshaft 68 that rotates by the driving force of the crankshaft 11; a pair of intake rocker arms 69 that are driven by a camshaft 68 to press the intake valve unit 66; an exhaust rocker arm 70 that is driven by the camshaft 68 to press the exhaust valve unit 67; and a rocker support shaft 71 that rotatably supports the intake rocker arm 69 and the exhaust rocker arm 70.

Each intake valve unit 66 has: an intake valve 73 that opens and closes the intake opening 61 a; a disk-shaped retainer 74 provided at an end of a stem of the intake valve 73; and a valve spring 75 that urges the intake valve 73 so that the intake valve 73 closes the intake opening portion 61 a.

The valve spring 75 is disposed in a compressed state between the base portion 14a and the retainer 74.

Each exhaust valve unit 67 has: an exhaust valve 76 that opens and closes the exhaust opening 61 b; a disc-shaped retainer 77 provided at an end of the valve stem of the exhaust valve 76; and a valve spring 78 that urges the exhaust valve 76 so that the exhaust valve 76 closes the exhaust opening portion 61 b.

The valve spring 78 is disposed in a compressed state between the base portion 14a and the retainer 77.

The intake valve 73 and the exhaust valve 76 extend up and down in such a manner as to follow the cylinder axis 13a when viewed in the axial direction of the camshaft 68 as in fig. 5.

The intake valve 73 is provided on one side (vehicle rear side) with the cylinder axis 13a as a boundary, as viewed in the axial direction of the camshaft 68. The intake valve 73 is arranged in a pair on the left and right in the axial direction of the camshaft 68.

The exhaust valve 76 is provided on the other side (vehicle front side) with the cylinder axis 13a as a boundary, as viewed in the axial direction of the camshaft 68. The exhaust valves 76 are arranged in a pair on the left and right in the axial direction of the camshaft 68.

The intake valve 73 is disposed to be inclined rearward with respect to the cylinder axis 13a as viewed in the axial direction of the camshaft 68.

The exhaust valve 76 is disposed to be inclined toward the front side with respect to the cylinder axis 13a as viewed in the axial direction of the camshaft 68.

That is, the interval between the intake valve 73 and the exhaust valve 76 increases as it goes from the base portion 14a toward the cylinder head cover 15 side as viewed in the axial direction of the camshaft 68.

The rocker arm support shaft 71 is disposed above the intake valve 73 and the exhaust valve 76 between the intake valve 73 and the exhaust valve 76 as viewed in the axial direction of the camshaft 68. The rocker arm support shaft 71 is located on the cylinder axis 13a as viewed in the axial direction of the camshaft 68.

The rocker arm support shaft 71 is a single shaft extending in the vehicle width direction in parallel with the camshaft 68, and is supported by the cylinder head 14.

The rocker arm support shaft 71 is a shaft having a hollow portion extending in the axial direction, and the hollow portion is an in-shaft oil passage 71a through which oil passes.

The intake rocker arm 69 is in the form of an arm extending from the rocker support shaft 71 to the intake valve unit 66. The intake rocker arms 69 are arranged in a pair on the left and right in the axial direction of the camshaft 68.

The intake rocker arm 69 has a base end portion thereof with a rotating portion 69a rotatably supported by the rocker support shaft 71. The intake rocker arm 69 has at its distal end: a pressing portion 69b that presses the retainer 74 of the intake valve unit 66; and a pressed portion 69c pressed by the cam shaft 68.

The rocker support shaft 71 and the intake rocker arm 69 have a discharge hole 71b that communicates the in-shaft oil passage 71a with the outside of the intake rocker arm 69. The discharge hole 71b is a hole that penetrates the rocker arm support shaft 71 and the rotating portion 69a in the radial direction.

The discharge hole 71b opens upward and rearward toward the camshaft 68.

The exhaust rocker arm 70 is in the form of an arm extending from a rocker support shaft 71 toward the exhaust valve unit 67.

The exhaust rocker arm 70 is disposed between the pair of intake rocker arms 69, and the exhaust rocker arm 70 is supported by a rocker support shaft 71, as with the intake rocker arms 69. That is, the pair of intake rocker arms 69 and exhaust rocker arms 70 are supported by one rocker support shaft 71. Therefore, weight reduction and compactness can be achieved compared to a structure in which rocker arm support shafts for intake and exhaust are disposed separately.

The exhaust rocker arm 70 has: a rotating portion 70a rotatably supported by the rocker support shaft 71; a pair of left and right arm portions 70b extending from the pivot portion 70a toward the left and right exhaust valve units 67; and a pressed portion 70c that extends rearward and upward from the rotating portion 70a toward the camshaft 68 side.

A pressing portion 70d that presses the retainer 77 of the exhaust valve unit 67 is provided at a distal end portion of each arm portion 70 b. The pressed portion 70c is a rotatable roller and is located above the intake rocker arm 69.

Although not shown in fig. 5, the rocker support shaft 71 and the exhaust rocker 70 have discharge holes that communicate the in-shaft oil passage 71a with the outside of the exhaust rocker 70. The discharge hole is opened toward the camshaft 68, as is the discharge hole 71b of the intake rocker arm 69.

The rotating portion 70a of the exhaust rocker arm 70 is disposed between the pair of intake rocker arms 69.

The pair of arm portions 70b extend forward so that the distance between the arm portions increases toward the exhaust valve unit 67 from the rotating portion 70a, and a space 70e is formed between the pair of arm portions 70 b.

In the rotating portion 70a, a concave portion 70f that is recessed rearward toward the pressed portion 70c side is provided in a portion facing the space 70 e.

The camshaft 68 is a shaft extending in the vehicle width direction parallel to the crankshaft 11, and is rotatably supported by the cylinder head 14.

The camshaft 68 is disposed on the intake valve unit 66 side with respect to the cylinder axis 13a as viewed in the axial direction of the camshaft 68. The camshaft 68 is disposed above the intake valve unit 66 and the intake rocker arm 69 and behind the pressed portion 70c of the exhaust rocker arm 70.

The camshaft 68 has: a pair of intake cams 68a that press the pressed portions 69c of the intake rocker arms 69; and an exhaust cam 68b that presses a pressed portion 70c of the exhaust rocker arm 70. The exhaust cam 68b is provided between the pair of intake cams 68 a.

With respect to the camshaft 68, a pair of intake valves 73 and a pair of exhaust valves 76 are driven with 1 camshaft 68. Therefore, compared to a structure in which intake and exhaust camshafts are disposed separately, weight reduction and compactness can be achieved.

The camshaft 68 is rotated by a cam chain 79 connecting the crankshaft 11 and the camshaft 68.

When the pressed portion 69c is pressed by the intake cam 68a with the rotation of the camshaft 68, the intake rocker arm 69 pivots about the rocker support shaft 71, and the valve stem of the intake valve 73 is pressed in the axial direction of the intake valve 73 by the pressed portion 69 b. Thereby, the intake valve 73 moves against the urging force of the valve spring 75, and the intake opening portion 61a opens.

The rotation direction R1 of the intake cam 68a is counterclockwise in fig. 5. On the other hand, the rotation direction R2 of the intake rocker arm 69, which is pressed by the intake cam 68a and rotates about the rocker support shaft 71, is opposite to the rotation direction R1. Accordingly, the abutment of the intake cam 68a with the pressed portion 69c can be weakened compared to the configuration in which the rotation direction R1 is the same rotation direction as the rotation direction R2. Therefore, the area of the contact surface between the intake cam 68a and the pressed portion 69c can be reduced, and the valve operating mechanism 65 can be made lightweight.

When the pressed portion 70c is pressed by the exhaust cam 68b with the rotation of the camshaft 68, the exhaust rocker arm 70 pivots about the rocker arm support shaft 71, and the valve stem of the exhaust valve 76 is pressed in the axial direction of the exhaust valve 76 by the pressed portion 70 d. Thereby, the exhaust valve 76 moves against the urging force of the valve spring 78, and the exhaust opening portion 61b is opened.

In the internal combustion engine 10, the intake rocker arm 69 and the exhaust rocker arm 70 are supported by a rocker support shaft 71 disposed between the intake valve 73 and the exhaust valve 76, and the intake rocker arm 69 and the exhaust rocker arm 70 are positioned between the intake valve 73 and the exhaust valve 76. Thus, it is easier to secure a space between the intake valve 73 and the intake port 18 than in a configuration in which, for example, the intake rocker arm 69 is disposed between the intake valve 73 and the intake port 18. Therefore, the intake port 18 can be disposed vertically so as to extend along the axial direction of the intake valve 73, and the intake efficiency can be improved.

The cylinder head 14 has a cylindrical plug support cylinder 80, and a spark plug (not shown) for igniting the combustion chamber is inserted into the plug support cylinder 80.

The plug support cylinder 80 is disposed in a space 70e between the pair of arm portions 70b of the exhaust rocker arm 70. Since the exhaust rocker arm 70 has the recess 70f facing the space 70e, the plug support cylinder 80 can be disposed close to the exhaust rocker arm 70 by the space of the recess 70 f.

Fig. 6 is a sectional view taken along line VI-VI in fig. 4.

The internal combustion engine 10 has an oil passage 81 that supplies oil to the valve train 65. The oil passage 81 includes: a cylinder oil passage 81a that penetrates the cylinder 13 in the axial direction of the cylinder 13; and a cylinder head oil passage 81b that passes through the wall of the cylinder head 14 from the lower end surface of the cylinder head 14 and is connected to the in-shaft oil passage 71a of the rocker arm support shaft 71.

The cylinder oil passage 81a and the cylinder head oil passage 81b are provided on the exhaust valve 76 side with respect to the cylinder axis 13a as viewed in the axial direction of the camshaft 68.

Specifically, the lower portions of the cylinder oil passage 81a and the cylinder head oil passage 81b are formed in a front wall portion 82a of a cam chain chamber 82 through which the cam chain 79 passes.

The oil stored in the crankcase 12 is pressure-fed by an oil pump (not shown) driven by the crankshaft 11, and flows through the oil passage 81 to the in-shaft oil passage 71 a. The oil of the in-shaft oil passage 71a is injected toward the camshaft 68 from the discharge hole 71b of the intake rocker arm 69 and the above-described discharge holes of the exhaust rocker arm 70, so that the oil is directly supplied to the intake cam 68a and the exhaust cam 68 b.

In the internal combustion engine 10, since the oil passage 81 passes through the exhaust valve 76 side with respect to the cylinder axis 13a, the length of the oil passage 81 can be made short, and oil can be supplied efficiently.

As described above, according to the embodiment to which the present invention is applied, the internal combustion engine 10 includes: a crankshaft 11 supported by the crankcase 12 via a bearing 35; a balancer drive gear 36 provided to the crankshaft 11; a balancer shaft 30 provided with a balancer; a balancer driven gear 43 provided on the balancer shaft 30 and meshing with the balancer drive gear 36; and a one-way clutch mechanism 37 that transmits a driving force for starting the internal combustion engine 10 to the crankshaft 11, wherein the balancer drive gear 36 is disposed on the crankshaft 11 between the bearing 35 and the one-way clutch mechanism 37, the bearing 35 is a bearing incorporating an oil seal 35d, and the oil seal 35d seals the crank chamber 33 of the crankcase 12, and the one-way clutch mechanism 37 includes: a housing 55 fixed to the crankshaft 11; and a starter driven gear 56 that is provided to be rotatable relative to the housing 55 and is driven by the driving force, wherein the starter driven gear 56 includes a thrust receiving portion 55e that abuts against the balancer drive gear 36 in the axial direction of the crankshaft 11.

According to this configuration, since the oil seal 35d that seals the crank chamber 33 of the crankcase 12 is built in the bearing 35, it is not necessary to secure a space dedicated to the oil seal 35d outside the bearing 35. Further, the thrust force F of the starter driven gear 56 of the one-way clutch mechanism 37 is received by the balancer drive gear 36 via the thrust receiving portion 55e, so that the thrust force F can be effectively received without making the one-way clutch mechanism 37 large or providing a dedicated member for receiving the thrust force F. Therefore, the internal combustion engine 10 can be made compact in the axial direction of the crankshaft 11, and the thrust force F acting on the one-way clutch mechanism 37 can be effectively received.

By making the internal combustion engine 10 compact in the axial direction of the crankshaft 11, the mass of the motorcycle on which the internal combustion engine 10 is mounted can be concentrated, and the running performance of the motorcycle can be improved.

The thrust receiving portion 55e is a convex portion protruding from a side surface of the starter driven gear 56 in the axial direction of the crankshaft 11.

According to this configuration, since the thrust receiving portion 55e is a convex portion, the thrust receiving portion 55e can be brought into contact with the balancer drive gear 36 with high accuracy.

The output gear 38 outputs the rotation of the crankshaft 11 to the main shaft 31 as another rotation shaft, the output gear 38 is provided on the axially outer side of the crankshaft 11 with respect to the one-way clutch mechanism 37, and the starter driven gear 56 extends in the radial direction along the balancer drive gear 36 at a position offset toward the balancer drive gear 36 between the balancer drive gear 36 and the output gear 38.

With this configuration, since the starter driven gear 56 is along the balancer drive gear 36 at a position offset toward the balancer drive gear 36, the thrust receiving portion 55e is easily brought into contact with the balancer drive gear 36, and the thrust force F can be effectively received. Further, the starter driven gear 56 is offset toward the balancer drive gear 36 and disposed in a position close to the crank chamber 33, so that the internal combustion engine 10 can be made compact in the axial direction of the crankshaft 11.

Further, the bearing 35, the balancer drive gear 36, the starter driven gear 56, the housing 55, and the output gear 38 are disposed in this order from the crank chamber 33 side.

According to this structure, the thrust force F of the starter driven gear 56 is received by the balancer drive gear 36, and the structure in which the rotation of the crankshaft 11 is output from the output gear 38 can be provided compactly.

Further, the balancer drive gear 36 is sandwiched between the bearing 35 and the housing 55 in the axial direction of the crankshaft 11.

According to this structure, with the housing 55, the balancer drive gear 36 can be positioned in the axial direction of the crankshaft 11 with a simple configuration, and the thrust force F that starts the driven gear 56 can be received by the balancer drive gear 36 positioned by the housing 55.

The water pump 46 connected to the balancer shaft 30 and rotating integrally with the balancer shaft 30 is disposed coaxially with the balancer shaft 30, and the water pump 46 is disposed outside the driven gear 56 in the axial direction of the crankshaft 11 and overlapping the housing 55.

With this configuration, the water pump 46 can be disposed on the side closer to the starter driven gear 56 in the axial direction of the crankshaft 11, and the internal combustion engine 10 can be made compact in the axial direction of the crankshaft 11.

The water pump 46 further includes: a shaft portion 46a rotatably supported by the crankcase 12 and connected to the balancer shaft 30; and a pump body 46b extending radially outward from the shaft 46a, the shaft 46a of the water pump 46 overlapping the housing 55.

With this configuration, the shaft portion 46a of the water pump 46 can be disposed closer to the starter driven gear 56 in the axial direction of the crankshaft 11, and the internal combustion engine 10 can be made compact in the axial direction of the crankshaft 11.

The crankcase 12 has a support cylinder portion 47a that supports the shaft portion 46a, a portion 47a1 of the support cylinder portion 47a is disposed outside the start driven gear 56 in the axial direction of the crankshaft 11 and overlapping the housing 55, and a portion 47a1 of the support cylinder portion 47a is located inside the outer peripheral portion 56c of the start driven gear 56 in the radial direction of the start driven gear 56.

With this configuration, the support cylindrical portion 47a of the crankcase 12 can be disposed axially closer to the starting driven gear 56 side and radially closer to the crankshaft 11 side, and the internal combustion engine 10 can be made compact.

The above embodiment shows one mode to which the present invention is applied, and the present invention is not limited to the above embodiment.

In the above embodiment, the description has been given taking the structure in which the internal combustion engine 10 is mounted on the motorcycle as an example, but the present invention is not limited to this, and the present invention can be applied to an internal combustion engine for a 3-wheel saddle-ride type vehicle having 2 front wheels or rear wheels and a saddle-ride type vehicle having 4 or more wheels.