JP6485221B2 - Breather device for internal combustion engine - Google Patents

Description

  The present invention relates to a breather device for an internal combustion engine.

  Conventionally, a breather device is known that recirculates blow-by gas leaked from the combustion chamber of the engine into the crankcase to the intake system. The breather device has a breather chamber for separating (gas-liquid separation) oil contained in blow-by gas.

  For example, Patent Document 1 discloses a breather device in which a breather chamber is formed on a mating surface between a right crankcase and a starter clutch case. A plurality of barriers are arranged inside the breather chamber, and a passage path for blow-by gas has a maze structure. The oil contained in the blow-by gas is separated from the gas component by colliding with the barrier in the breather chamber (impact type inertia force recovery).

Japanese Patent Laid-Open No. 05-113115

  By increasing the capacity of the breather chamber and complicating the maze structure, the gas-liquid separation performance of blow-by gas is improved. However, the increase in capacity and complexity of the breather chamber has led to an increase in the size and weight of the engine including the crankcase. Therefore, the breather device (breather chamber) described in Patent Document 1 cannot improve the gas-liquid separation performance of blow-by gas while suppressing the increase in size and weight of the engine.

  By the way, besides the collision-type inertia force recovery as described above, the gas-liquid separation of the blow-by gas is promoted by abruptly changing the flow direction of the blow-by gas with a rectifying plate or the like (reversed inertia force recovery). . Further, the gas-liquid separation of the blow-by gas is also promoted by rapidly decelerating the flow rate of the blow-by gas. However, adding the above-described device for improving the gas-liquid separation performance to the breather device causes a problem of an increase in manufacturing cost in addition to an increase in size and weight of the engine.

  In order to solve the above-described problems, the present invention provides a breather device for an internal combustion engine that improves the gas-liquid separation performance of blow-by gas while suppressing an increase in size, weight, and manufacturing cost of the internal combustion engine.

A breather device for an internal combustion engine according to the present invention is disposed in a gear case configured between a crankcase that supports a crankshaft, a cover that is attached to one end surface of the crankcase, and the crankcase and the cover. A ring gear attached to one end portion of the crankshaft; and a breather portion that is disposed above the crankshaft and that introduces blow-by gas generated in the crankcase into the gear chamber for gas-liquid separation. ,
The breather portion is formed by partitioning the gear chamber with a partition wall, and is formed along the partition wall with a breather chamber communicating the gear chamber and an intake system of an internal combustion engine, and is introduced into the gear chamber. A breather passage for guiding the blow-by gas to the breather chamber, wherein the breather passage includes the crankcase or the cover, the ring gear, the partition wall, and the crank facing the partition wall. And a passage wall provided in the case or the cover.

  According to this configuration, the oil contained in the blow-by gas is separated from the gas component by passing through the breather passage in addition to the breather chamber. Thereby, the gas-liquid separation performance of blow-by gas can be improved. The breather passage is configured by existing members (crankcase or cover, ring gear, partition wall) except for the passage wall. Thereby, since a breather passage can be constituted only by adding a passage wall, enlargement and weight increase of an internal combustion engine can be controlled. In addition, an increase in cost related to the formation of the breather passage can be minimized.

  In this case, it is preferable that the breather portion further includes an intermediate space for communicating the breather chamber and the breather passage, and the cross-sectional area of the intermediate space is set larger than the cross-sectional area of the breather passage. .

  According to this configuration, since the cross-sectional area of the intermediate space is larger than the cross-sectional area of the breather passage, the blow-by gas flowing out from the breather passage into the intermediate space is rapidly decelerated. Thereby, the gas-liquid separation of blow-by gas can be promoted.

  In this case, the breather chamber is preferably formed so as to make a U-turn above the breather passage.

  According to this configuration, the blow-by gas that has flowed out of the breather passage makes a U-turn and is introduced into the breather chamber. At this time, since the flow direction of the blow-by gas is rapidly changed, the gas-liquid separation (reversal inertia force recovery) of the blow-by gas can be promoted.

  In this case, the gear chamber is preferably provided with a chain wound around one end of the crankshaft and an oil pump, and the passage wall is formed so as to cover the chain.

  According to this structure, the oil adhering to the chain is scattered in the direction of the centrifugal force as the chain travels (rotates). However, since the passage wall is formed so as to cover the chain, it is possible to prevent the scattered oil from entering the breather passage and the breather chamber. In addition, the passage wall constituting the breather passage can also be used as a barrier for preventing oil scattering. Thereby, the weight increase of an internal combustion engine etc. can be suppressed.

  In this case, it is preferable that at least one of the crankcase or the cover, the ring gear, the partition wall, and the passage wall is provided with a protruding portion protruding toward the inside of the breather passage.

  According to this configuration, the blow-by gas passing through the breather passage is separated into gas and liquid by colliding with the protrusions (impact type inertia force recovery). Thereby, the gas-liquid separation of the blow-by gas before being introduced into the breather chamber can be promoted.

  In this case, the crankcase has a plurality of vent holes that allow the inside of the crankcase to communicate with the gear chamber, and the plurality of vent holes are formed below the crankshaft and sandwich the crankshaft. The breather passage has an inflow opening that opens above the rear vent and an outflow opening that opens above the front vent, and the rear side It is preferable that the vent hole is formed larger than the vent hole on the front side.

  According to this configuration, the blow-by gas in the crankcase flows into the gear chamber through the plurality of vent holes. At this time, a large amount of blow-by gas flows from the large vent. Since the large vent is provided on the inflow side, the blow-by gas that has flowed into the gear chamber flows smoothly toward the breather passage. The applicant experimentally confirmed that the blow-by gas can be easily guided to the breather passage (inlet) by forming the rear (inlet) vent hole larger than the front vent hole. Yes.

  According to the breather device for an internal combustion engine of the present invention, it is possible to improve the gas-liquid separation performance of blow-by gas while suppressing an increase in manufacturing cost in addition to an increase in size and weight of the internal combustion engine.

1 is a side view showing a motorcycle according to an embodiment of the present invention. It is a perspective view showing an engine concerning one embodiment of the present invention. It is a top view showing an engine concerning one embodiment of the present invention. It is a side view which shows the structure by the side of the crankcase of the breather apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the structure by the side of the crankcase of the breather apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the structure by the side of the magneto cover of the breather apparatus which concerns on one Embodiment of this invention. It is a side view which shows the structure and gasket on the crankcase side of the breather apparatus which concerns on one Embodiment of this invention. It is VIII-VIII sectional drawing of FIG.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  The motorcycle 1 will be described with reference to FIGS. 1 to 4. FIG. 1 is a side view showing a motorcycle 1. FIG. 2 is a perspective view showing the engine 4. FIG. 3 is a plan view showing the engine 4. FIG. 4 is a side view showing the structure of the breather device 36 on the crankcase 20 side. In the following description, each direction is set based on the occupant who has boarded the motorcycle 1, and the direction shown in each figure will be described as a reference.

  As shown in FIG. 1, a scooter type motorcycle 1 is schematically configured to include a body frame 2, a body cover 3, and an engine 4.

  The vehicle body frame 2 is configured by welding a tube made of steel, aluminum alloy, or the like. A pair of left and right front forks 10 are supported at the front portion of the body frame 2 so as to be steerable left and right. A front wheel 11 is rotatably supported at the lower portion of the front fork 10. A handle bar 12 is provided on the upper portion of the front fork 10.

  A seating seat 13 is provided on the upper rear side of the body frame 2. A helmet box 14 that stores a helmet H, baggage, and the like is provided below the seating seat 13. The seat 13 serves as a lid for the helmet box 14.

  The vehicle body cover 3 includes a front cowl 15, a step board 16, and a seat cowl 17. The front cowl 15 is provided so as to cover the front fork 10 in order to protect the occupant's legs. The step board 16 extends substantially flat from the lower end of the front cowl 15 toward the rear. The seat cowl 17 is provided below the seating seat 13 so as to cover the helmet box 14.

  As shown in FIGS. 2 and 3, the engine 4 includes a crankcase 20, a cylinder 21, a swing case 22, and a starter portion 23. The engine 4 is mounted on the vehicle body frame 2 below the helmet box 14 (see FIG. 1).

  The crankcase 20 is connected to the body frame 2 so as to be swingable in the vertical direction. The crankcase 20 is configured by joining a left case 20L on the left side and a right case 20R on the right side at a substantially horizontal center. The crankcase 20 is formed in a substantially rectangular shape that is long in the vertical direction in a side view. A crankshaft 24 extending in the left-right direction is pivotally supported inside the crankcase 20 (hereinafter also referred to as “crank chamber R1”) (see FIG. 3). The crankshaft 24 is located slightly above the center of the crankcase 20 in a side view (see FIG. 4). Note that lubricating oil is stored in the bottom of the crank chamber R1.

  A magneto cover 25 is attached to the right end surface of the light case 20R. Between the light case 20R and the magnet cover 25, a gear chamber R2 for accommodating the starter portion 23 and the like is configured (see FIG. 3). Details of the light case 20R and the magneto cover 25 will be described later.

  The cylinder 21 is provided on the front side of the crankcase 20. The cylinder 21 includes a cylinder block 21a, a cylinder head 21b, and a head cover 21c.

  The cylinder block 21a extends from the front end surface of the crankcase 20 substantially horizontally (exactly, slightly upward slope toward the front side). The cylinder head 21b is provided at the front end of the cylinder block 21a. The head cover 21c is provided so as to cover the front end surface of the cylinder head 21b. In addition, although illustration is abbreviate | omitted, the piston is provided in the inside of the cylinder 21 so that reciprocation is possible in the front-back direction. The piston is connected to the crankshaft 24 via a connecting rod.

  A combustion chamber (not shown) is formed between the cylinder block 21a and the cylinder head 21b. An intake port 26 communicating with the combustion chamber is formed on the upper side of the cylinder head 21b. A fuel injection device (not shown) is connected to the intake port 26 via an intake pipe 26a (see FIG. 2). An exhaust port 27 (see FIG. 2) communicating with the combustion chamber is formed below the cylinder head 21b. An exhaust muffler (both not shown) is connected to the exhaust port 27 via an exhaust pipe.

  The swing case 22 extends rearward from the rear end surface of the left case 20L. Inside the swing case 22, for example, a power transmission device such as a belt type continuously variable transmission is provided. A rear wheel 28 as a drive wheel is rotatably supported at the rear end of the swing case 22 (see FIG. 1). The rear wheel 28 is connected to the crankshaft 24 via a power transmission device. The swing case 22 functions as a swing arm by swinging in the vertical direction.

  As shown in FIGS. 1 and 3, an air cleaner 30 is provided above the swing case 22 to take in and clean outside air. The air cleaner 30 is configured by incorporating a filter 30b in a cleaner case 30a. The air cleaner 30 is connected to the fuel injection device via an outlet tube (not shown).

  Here, the operation of the engine 4 will be described. When negative pressure is generated by the operation of the engine 4, outside air (air) is sucked into the air cleaner 30, and is purified (removes foreign matter such as dust) by passing through the filter 30 b. Clean air is sent to the fuel injector through the outlet tube.

  The fuel injection device supplies an air-fuel mixture obtained by mixing fuel supplied from a fuel tank (not shown) and clean air to the combustion chamber of the cylinder 21. The air-fuel mixture is ignited by a spark plug (not shown) and burns in the combustion chamber. The piston reciprocates in the cylinder 21 by the combustion pressure of the air-fuel mixture, and rotates the crankshaft 24 through the connecting rod. The rotational force of the crankshaft 24 rotates the rear wheel 28 via the power transmission device of the swing case 22. Exhaust gas after combustion is discharged from the exhaust port 27 to the outside through an exhaust pipe (exhaust muffler).

  Next, as shown in FIGS. 2 to 4, the starter unit 23 includes a cell motor 31, an idle gear 32, and a ring gear 33. The cell motor 31 is fixed to the rear upper surface of the crankcase 20. The idle gear 32 and the ring gear 33 are disposed in the gear chamber R2.

  An output shaft (not shown) of the cell motor 31 extends from the light case 20R side into the gear chamber R2. A pinion gear (not shown) is fixed to the output shaft of the cell motor 31. The cell motor 31 is connected to a battery (not shown) serving as a power supply source.

  As shown in FIG. 4, the idle gear 32 is a so-called stepped gear, and is rotatably supported by the light case 20 </ b> R and the magnet cover 25. The idle gear 32 is disposed on the upper rear side of the gear chamber R <b> 2 in a side view and meshes with the pinion gear of the cell motor 31. The ring gear 33 is attached to the right end (one end) of the crankshaft 24 via a one-way clutch (not shown). The ring gear 33 is disposed obliquely below the front side of the idle gear 32 in a side view and meshes with the idle gear 32. The crankshaft 24 extends rightward through the ring gear 33.

  The cell motor 31 rotates the ring gear 33 via the idle gear 32. The rotation of the ring gear 33 is transmitted to the crankshaft 24 via the one-way clutch, and starts the engine 4. When the engine 4 is started, the one-way clutch is operated, and the connection between the crankshaft 24 and the ring gear 33 is cut off. Thereby, since rotation of a crankshaft is not transmitted to the ring gear 33, the cell motor 31 can be prevented from over-rotating.

  In the gear chamber R2, an oil pump 34 that supplies oil stored in the crank chamber R1 into the cylinder head 21b and the like is disposed. The oil pump 34 is disposed on the lower front side of the light case 20R in a side view. The gear chamber R2 is provided with a chain 35 wound around the right end portion of the crankshaft 24 and the oil pump 34. The ring gear 33 is arranged on the right side (outside) of the chain 35.

  When the engine 4 is started, the rotation of the crankshaft 24 is transmitted to the oil pump 34 via the chain 35. As a result, the oil pump 34 is driven, and the oil in the crank chamber R1 is supplied to a portion requiring lubrication. A magneto (not shown) is disposed on the right side of the ring gear 33. Magneto flywheels are provided with permanent magnets, and the flywheel rotates around the stator (coil) to generate electricity.

  Incidentally, the engine 4 includes a breather device 36 that recirculates blow-by gas leaked from the combustion chamber into the crankcase 20 to the intake system (air cleaner 30). Hereinafter, the breather device 36 will be described with reference to FIGS. 4 to 8. FIG. 5 is a perspective view showing the structure of the breather device 36 on the crankcase 20 side. FIG. 6 is a perspective view showing the structure of the breather device 36 on the magneto cover 25 side. FIG. 7 is a side view showing the structure of the breather device 36 on the crankcase 20 side and the gasket 46. 8 is a sectional view taken along line VIII-VIII in FIG.

  As shown in FIG. 4, the breather device 36 includes a light case 20 </ b> R (crankcase 20), a magneto cover 25 (see FIG. 3 and the like), a ring gear 33, and a breather unit 50.

  As shown in FIGS. 4 and 5, the light case 20 </ b> R is formed in a substantially rectangular box shape with both left and right sides open. That is, the light case 20R has a case wall 40b that partitions the inside of the substantially rectangular cylindrical outer peripheral wall 40a to the left and right. A plurality of screw holes 40c are formed in the right end portion of the outer peripheral wall 40a along the circumferential direction. A bearing 41 that pivotally supports the right end of the crankshaft 24 is provided slightly above the center of the case wall 40b.

  As shown in FIG. 4, the light case 20R has two vent holes 42F and 42R that allow the crank chamber R1 and the gear chamber R2 to communicate with each other. The two vent holes 42F and 42R are formed in the case wall 40b. The two vent holes 42F and 42R are formed below the crankshaft 24 in a side view. Further, the two air holes 42F and 42R are formed to be separated in the front-rear direction with the crankshaft 24 interposed therebetween in a side view. The rear vent 42R is formed larger than the front vent 42F.

  A boss portion 43 extending rightward from the case wall 40b is formed in the vicinity of the rear side of the front vent hole 42F. An oil return hole 44 for communicating the crank chamber R1 and the gear chamber R2 is formed in the lower portion of the case wall 40b.

  As shown in FIG. 6, the magnet cover 25 is formed in a substantially rectangular box shape with the left surface open. That is, the magneto cover 25 has a cover wall 45b that closes the right side surface of the substantially rectangular cylindrical outer peripheral wall 45a. A plurality of through-hole portions 45c are formed at the left end portion of the outer peripheral wall 45a along the circumferential direction.

  The magnet cover 25 is fixed to the light case 20R with the gasket 46 interposed therebetween. As shown in FIG. 7, the gasket 46 is formed in a frame shape in accordance with the outer shapes (outer peripheral walls 40 a and 45 a) of the light case 20 </ b> R and the magnet cover 25. A plurality of through holes 46a are formed in the outer peripheral portion of the gasket 46 at positions corresponding to the screw hole portions 40c.

  The magneto cover 25 is fixed to the light case 20R by inserting the gasket 46 between the light case 20R and screwing the through hole 45c and the bolt B passing through the through hole 46a into the screw hole 40c ( (See FIG. 2). As a result, the gear chamber R2 is formed in the joint between the light case 20R and the magnet cover 25 (see FIG. 3). To be exact, the gear chamber R2 includes a case-side gear chamber R21 (see FIG. 5 and the like) on the light case 20R side and a cover-side gear chamber R22 (see FIG. 6) on the magneto cover 25 side. The gasket 46 has an opening 46b that allows the case side gear chamber R21 and the cover side gear chamber R22 to communicate with each other. The opening 46b is formed in a frame shape so as not to obstruct the movement of the gears 32, 33, the oil pump 34, and the chain 35.

  As shown in FIGS. 4 and 5, the breather portion 50 is arranged on the upper side of the crankshaft 24. The breather section 50 is provided to introduce blow-by gas generated in the crankcase 20 (crank chamber R1) into the gear chamber R2 for gas-liquid separation.

  The breather unit 50 includes a breather chamber 51, a breather passage 52, and an intermediate space 53. The breather chamber 51 is formed by dividing the gear chamber R2 by partition walls 60 and 70 (see FIGS. 5 and 6). The breather passage 52 is formed along the case side partition wall 60. The intermediate space 53 is formed between the breather chamber 51 and the breather passage 52.

  The breather chamber 51 is formed so that the gear chamber R2 communicates with the air cleaner 30. The breather chamber 51 includes a case-side breather chamber 54 (see FIG. 5) formed integrally with the light case 20R, and a cover-side breather chamber 55 (see FIG. 6) formed integrally with the magneto cover 25. ing. Although details will be described later, the inside of the breather chamber 51 has a maze structure.

  As shown in FIGS. 4 and 5, the case-side breather chamber 54 is formed by partitioning the upper front side of the case-side gear chamber R <b> 21 with a case-side partition wall 60. The case side partition wall 60 protrudes rightward from the case wall 40b. The case-side partition wall 60 extends downward from the upper inner surface of the outer peripheral wall 40a of the light case 20R, bends forward, and draws an arc toward the front lower side. The case side partition wall 60 is formed along the curve of the ring gear 33 (see FIG. 4). As described above, the case-side breather chamber 54 is configured by the outer peripheral wall 40a and the case wall 40b of the light case 20R and the case-side partition wall 60 (enclosed region).

  An entrance 61 is opened on the front and lower surfaces of the case-side breather chamber 54 (first case-side breather chamber 541 described later). The inside of the case side breather chamber 54 is divided into three by two case side partition walls 62a and 62b. Inside the case-side breather chamber 54, a first case-side breather chamber 541, a second case-side breather chamber 542, and a third case-side breather chamber 543 are formed in this order from the entrance 61 side.

  In the first case side breather chamber 541, a first case side rib 63 extending downward from the outer peripheral wall 40a is formed. The first case side rib 63 is disposed above the entrance 61. Similarly, in the second case side breather chamber 542, a second case side rib 64 extending downward from the outer peripheral wall 40a is formed. In the third case side breather chamber 543, a discharge port 65 is formed in the case wall 40b (see FIG. 4). The discharge port 65 is disposed above the upper surface of the left case 20L (left side of the right case 20R) (see FIG. 3). A breather hose 66 extending from the air cleaner 30 is connected to the discharge port 65 (see FIG. 3). The breather hose 66 allows the breather chamber 51 (third case side breather chamber 543) and the air cleaner 30 to communicate with each other.

  As shown in FIG. 6, the cover-side breather chamber 55 is formed by dividing the upper front side of the cover-side gear chamber R <b> 22 with a cover-side partition wall 70. That is, the cover-side breather chamber 55 is formed at a position facing the case-side breather chamber 54 with the gasket 46 interposed therebetween. The cover side partition wall 70 protrudes leftward from the cover wall 45b. The cover side partition wall 70 extends downward from the upper inner surface of the outer peripheral wall 45a of the magneto cover 25, bends forward, and draws an arc toward the front lower side. Further, the cover side partition wall 70 is bent forward at the front lower side and connected to the front inner surface of the outer peripheral wall 45a. In other words, the cover-side breather chamber 55 has such a shape that the entrance 61 of the case-side breather chamber 54 is closed. As described above, the cover-side breather chamber 55 is configured by the outer peripheral wall 45a and the cover wall 45b of the magneto cover 25 and the cover-side partition wall 70 (enclosed region).

  The interior of the cover side breather chamber 55 is partitioned into a first cover side breather chamber 551 and a second cover side breather chamber 552 by a cover side partition wall 71. The first cover side breather chamber 551 is formed with first cover side ribs 72 extending forward from the cover side partition wall 71 (cover side partition wall 70). Similarly, a second cover side rib 73 extending downward from the outer peripheral wall 45a is formed in the second cover side breather chamber 552.

  As shown in FIG. 8, the first cover-side breather chamber 551 is disposed so as to straddle the first case-side breather chamber 541 and the second case-side breather chamber 542 with the magneto cover 25 fixed to the light case 20R. Is done. The second cover side breather chamber 552 is disposed so as to straddle the second case side breather chamber 542 and the third case side breather chamber 543.

  The gasket 46 described above is sandwiched between the case side partition wall 60 and the cover side partition wall 70 in a state where the magneto cover 25 is fixed to the light case 20R. As shown in FIGS. 7 and 8, the gasket 46 is formed with first to fourth communication ports 461 to 464 that allow the case-side breather chamber 54 and the cover-side breather chamber 55 to communicate with each other. The first communication port 461 is formed at a position where the first case-side breather chamber 541 communicates with the first cover-side breather chamber 551. The second communication port 462 is formed at a position where the first cover side breather chamber 551 communicates with the second case side breather chamber 542. The third communication port 463 is formed at a position where the second case-side breather chamber 542 and the second cover-side breather chamber 552 communicate with each other. The fourth communication port 464 is formed at a position where the second cover side breather chamber 552 and the third case side breather chamber 543 communicate with each other.

  Next, as shown in FIGS. 4 and 5, the breather passage 52 is formed so as to guide the blow-by gas introduced into the gear chamber R <b> 2 to the breather chamber 51. The breather passage 52 includes a passage wall 80 formed integrally with the light case 20R.

  The passage wall 80 is provided in the light case 20 </ b> R (crankcase 20) so as to face the lower side of the case-side partition wall 60. The passage wall 80 protrudes rightward from the case wall 40b of the light case 20R. The passage wall 80 is formed so as to cover the upper side of the chain 35 in a side view. Specifically, the passage wall 80 is curved downward from right above the bearing 41 (crankshaft 24) toward the front side and extends downward along the front side of the chain 35. A front end portion of the passage wall 80 is connected to the boss portion 43. A closed wall 80a is formed between the boss portion 43 and the front inner surface of the outer peripheral wall 40a of the light case 20R. Further, the passage wall 80 is inclined slightly downward from right above the bearing 41 (crankshaft 24) toward the rear side, and extends so as to partition the crankshaft 24 and the idle gear 32. The rear end portion of the passage wall 80 is bent downward and is formed at a position spaced forward from the rear inner surface of the outer peripheral wall 40a.

  As shown in FIG. 4, the idle gear 32 described above is disposed on the upper side of the passage wall 80 and on the rear side of the breather chamber 51. The ring gear 33 is arranged below the breather chamber 51 so as to cover the passage wall 80. As described above, the breather passage 52 is configured by the crankcase 20 (the case wall 40b of the light case 20R), the ring gear 33, the case-side partition wall 60, and the passage wall 80 (enclosed region). .

  As shown in FIGS. 4 and 5, the breather passage 52 has an inflow port 81 and an outflow port 82. The inflow port 81 opens above the rear vent 42R. The inflow port 81 is formed between the rear end portion of the passage wall 80 and the rear inner surface of the outer peripheral wall 40a. The outlet 82 opens above the front vent hole 42F (boss portion 43). The outflow port 82 is formed between the front side of the passage wall 80 and the tip of the case side partition wall 60. Specifically, the outflow port 82 is a surface orthogonal to the tip of the case-side partition wall 60 (see the broken line in FIG. 4) and forms the same plane as the entrance 61 of the breather chamber 51. The above-described breather chamber 51 is formed so as to make a U-turn above the breather passage 52.

  Two protrusions 83 project from the case side partition wall 60 toward the inside of the breather passage 52. The case-side partition wall 60, the cover-side partition wall 70, the passage wall 80, and the protrusions 83 are formed so as not to contact the idle gear 32 and the ring gear 33 (see FIG. 4).

  As shown in FIGS. 4 and 5, the intermediate space 53 is formed so that the breather chamber 51 and the breather passage 52 communicate with each other. Specifically, the intermediate space 53 is configured by the case wall 40b of the light case 20R, the ring gear 33, the gasket 46 (see FIG. 7), the passage wall 80, and the closing wall 80a (enclosed region). Has been. The cross sectional area A1 of the intermediate space 53 is set larger than the cross sectional area A2 of the breather passage 52 (or the area of the outlet 82) (see FIG. 4).

  Next, the action of the breather device 36 (blow-by gas-liquid separation) will be described.

  As shown in FIG. 4, the blowby gas leaked from the combustion chamber to the crank chamber R1 flows into the gear chamber R2 through the two vent holes 42F and 42R. At this time, a large amount of blow-by gas flows from the large vent 42R. Since the large vent hole 42R is provided on the inflow port 81 side, the blow-by gas flowing into the gear chamber R2 flows smoothly toward the breather passage 52. Note that the applicant can easily guide the blow-by gas to the breather passage 52 (the inlet 81) by forming the rear side (inlet 81 side) vent hole 42R larger than the front side vent hole 42F. Confirmed experimentally.

  The blow-by gas that has flowed into the breather passage 52 from the inflow port 81 flows toward the outflow port 82. The blow-by gas passing through the breather passage 52 is separated into gas and liquid by colliding with the two protrusions 83 (impact type inertia force recovery). Thereby, the gas-liquid separation of the blow-by gas before being introduced into the breather chamber 51 can be promoted.

  The blow-by gas flows out from the outlet 82 of the breather passage 52 to the intermediate space 53. At this time, since the cross-sectional area A1 of the intermediate space 53 is larger than the cross-sectional area A2 of the breather passage 52 (or the area of the outlet 82), the blow-by gas flowing out from the breather passage 52 into the intermediate space 53 is rapidly decelerated. Thereby, the gas-liquid separation of blow-by gas can be promoted.

  The blow-by gas that has flowed out of the breather passage makes a U-turn in the intermediate space 53 and is introduced into the breather chamber 51 from the entrance 61. At this time, since the flow direction of the blow-by gas is rapidly changed, the gas-liquid separation (reversal inertia force recovery) of the blow-by gas can be promoted.

  As shown in FIG. 8, blow-by gas flows into the first case-side breather chamber 541 from the entrance 61 of the light case 20R, and is separated into gas and liquid by colliding with the first case-side rib 63 (see FIG. 4). The Since the blow-by gas in the first case-side breather chamber 541 is blocked by the case-side partition wall 62a, the blow-by gas flows into the first cover-side breather chamber 551 of the magneto cover 25 through the first communication port 461 of the gasket 46.

  The blow-by gas in the first cover-side breather chamber 551 is gas-liquid separated by colliding with the first cover-side rib 72 (see FIG. 6). Further, since this blow-by gas is blocked by the cover-side partition wall 71, the blow-by gas flows into the second case-side breather chamber 542 of the light case 20R through the second communication port 462 of the gasket 46.

  The blow-by gas in the second case-side breather chamber 542 collides with the second case-side rib 64 (see FIG. 4) to be gas-liquid separated. Further, since this blow-by gas is blocked by the case-side partition wall 62 b, the blow-by gas flows into the second cover-side breather chamber 552 of the magneto cover 25 through the third communication port 463 of the gasket 46.

  The blow-by gas in the second cover-side breather chamber 552 is separated into gas and liquid by colliding with the second cover-side rib 73 (see FIG. 6). Further, this blow-by gas flows into the third case side breather chamber 543 of the light case 20 </ b> R through the fourth communication port 464 of the gasket 46.

  As described above, blow-by gas is separated into gas and liquid by passing through the breather chamber 51 having a maze structure. The blow-by gas in the third case side breather chamber 543 is sent to the air cleaner 30 from the discharge port 65 via the breather hose 66. The blow-by gas supplied to the air cleaner 30 is again introduced into the combustion chamber and burned.

  According to the breather device 36 according to the present embodiment described above, the oil contained in the blow-by gas is separated from the gas component by passing through the breather passage 52 in addition to the breather chamber 51. Thereby, the gas-liquid separation performance of blow-by gas can be improved. The breather passage 52 is configured by existing members (crankcase 20 (light case 20R), ring gear 33, case-side partition wall 60) except for the passage wall 80. Thereby, since the breather passage 52 can be configured only by adding the passage wall 80, the engine 4 can be prevented from being increased in size and weight. Further, an increase in cost related to the formation of the breather passage 52 can be minimized.

  Further, according to the breather device 36 according to the present embodiment, the oil adhering to the chain 35 is scattered in the centrifugal force direction by the travel (rotation) of the chain 35. However, since the passage wall 80 is formed so as to cover the chain 35, the scattered oil can be prevented from entering the breather passage 52 and the breather chamber 51. Further, the passage wall 80 constituting the breather passage 52 can also be used as a barrier for preventing oil scattering. Thereby, an increase in the weight of the engine 4 can be suppressed.

  In addition, although the breather apparatus 36 which concerns on this embodiment formed the breather channel | path 52 (passage wall 80) in the light case 20R, this invention is not limited to this. For example, the breather passage 52 (passage wall 80) may be formed in the magneto cover 25. In this case, the breather passage 52 includes the magneto cover 25 (cover wall 45 b), the ring gear 33, the cover-side partition wall 70, and the passage wall 80 provided in the magneto cover 25. Note that the breather device 36 may be formed in the left case 20L.

  In addition, although the breather apparatus 36 which concerns on this embodiment formed the two projection parts 83 in the case side partition wall 60, this invention is not limited to this. For example, the protrusion 83 may be formed on at least one of the light case 20 </ b> R (crankcase 20), the magneto cover 25, the ring gear 33, and the passage wall 80. Further, when the breather passage 52 is formed in the magnet cover 25, the protrusion 83 may be formed in the cover side partition wall 70. One or more protrusions 83 may be formed.

  In the above description of the present embodiment, the case where the present invention is applied to the motorcycle 1 is shown as an example. However, the present invention is not limited thereto, and the present invention is applied to a straddle-type vehicle such as a four-wheeled vehicle. May be applied.

  The description of the above embodiment shows one aspect of the breather device for an internal combustion engine according to the present invention, and the technical scope of the present invention is not limited to the above embodiment. The components in the above embodiment can be appropriately replaced or combined with existing components and the like, and the description of the above embodiment does not limit the content of the invention described in the claims. .

4 engine (internal combustion engine)
20 Crankcase 24 Crankshaft 25 Magneto cover (cover)
30 Air cleaner (intake system)
33 Ring gear 34 Oil pump 35 Chain 36 Breather device 42F, 42R Ventilation hole 50 Breather part 51 Breather chamber 52 Breather passage 53 Intermediate space 60 Case side partition wall (partition wall)
70 Cover side partition wall (partition wall)
80 Passage wall 81 Inlet 82 Outlet 83 Protrusion A1, A2 Cross section R2 Gear chamber

Claims (7)

A crankcase that supports the crankshaft;
A cover attached to one end surface of the crankcase;
A ring gear disposed in a gear chamber configured between the crankcase and the cover, and attached to one end of the crankshaft;
Wherein arranged in the gear chamber on the upper side of the crankshaft, and a breather unit for gas-liquid separation by introducing a blow-by gas generated in said crankcase to said gear chamber,
The breather part is
A breather chamber that is formed by partitioning the gear chamber with a partition wall and communicates the gear chamber with an intake system of an internal combustion engine;
A breather passage formed along the partition wall and guiding the blow-by gas introduced into the gear chamber to the breather chamber;
The breather passage is configured by the crankcase or the cover, the ring gear, the partition wall, and a passage wall provided in the crankcase or the cover so as to face the partition wall. A breather device for an internal combustion engine. The breather portion further includes an intermediate space that communicates the breather chamber with the breather passage.
2. The breather device for an internal combustion engine according to claim 1, wherein a cross-sectional area of the intermediate space is set larger than a cross-sectional area of the breather passage.   3. The breather device for an internal combustion engine according to claim 1, wherein the breather chamber is formed so as to make a U-turn above the breather passage. 4. The gear chamber is provided with a chain wound around one end of the crankshaft and an oil pump,
The breather device for an internal combustion engine according to any one of claims 1 to 3, wherein the passage wall is formed so as to cover the chain.   2. A projection is provided on at least one of the crankcase or the cover, the ring gear, the partition wall, and the passage wall so as to project toward the inside of the breather passage. A breather device for an internal combustion engine according to any one of claims 1 to 4. The crankcase has a plurality of air holes that communicate the interior with the gear chamber,
The plurality of vent holes are formed below the crankshaft and are spaced apart in the front-rear direction across the crankshaft.
The breather passage has an inlet opening above the rear vent and an outlet opening above the front vent,
The breather device for an internal combustion engine according to any one of claims 1 to 5, wherein the rear vent hole is formed larger than the front vent hole.   The partition wall is formed along the curvature of the ring gear,
  The breather device for an internal combustion engine according to claim 1, wherein the ring gear is arranged so as to cover the passage wall.

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