JP2017115743A - Engine breather device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a flowing-in of oil mist in a crank chamber into a breather chamber to be prevented and further to enable leakage of lubricant oil to outside at the time of storage of an engine while it is in a sideways state or the like.SOLUTION: This invention relates to an engine breather device 65 in which a breather chamber 66 is formed along a substantial half-periphery of a cylinder bore 31 at a cylinder block 30 where a cylinder 29 and a crank case upper part half body 27A are constituted, one side part 66A of the breather chamber is provided with a blow-by gas feeding hole for guiding the blow-by gas in the breather chamber and one way valve 68 for opening or closing the blow-by gas feeding hole, the other side part 66B of the breather chamber is provided with a pipe connection hole 75 for connecting the breather pipe 69 communicated with an intake system and a first breather oil return passage 70A returning the separated oil to the crank chamber, an extended part 77 in the first breather oil return passage reaches to a lower part of an oil surface A of the lubricant oil 1 stored in the crank chamber and at the same time it rides over a central axis line O of the cylinder bore and extends up to its opposite side.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an engine breather apparatus that guides blow-by gas in a crank chamber to an intake system, and more particularly to an engine breather apparatus that has an improved structure of a breather oil return passage that returns oil separated from blow-by gas to the crank chamber.

  In an engine mounted on an outboard motor having a cylinder block in which a cylinder bore extending in a horizontal direction and a crankcase forming a crankcase are integrally formed, a breather chamber is provided above the crankcase and in front of the engine. The formed breather device is disclosed in Patent Document 1.

JP-A-10-89040

  However, in the breather device described in Patent Document 1, the breather oil return passage for returning the oil separated from the blow-by gas in the breather chamber to the crank chamber is formed as a through hole that connects the breather chamber and the crank chamber. For this reason, when the outboard motor is stored, for example, in a forward-turned state, the lubricating oil in the crank chamber may flow into the breather chamber through the breather oil return passage and leak to the outside.

  The object of the present invention has been made in consideration of the above-mentioned circumstances, and can prevent the oil mist of the lubricating oil in the crank chamber from flowing into the breather chamber, and can also be used when the engine is stored in a state where the engine is laid down. It is an object of the present invention to provide a breather device for an engine that can prevent leakage of the air through the breather chamber.

  In the breather device for an engine according to the present invention, the cylinder is provided with a cylinder bore having a central axis extending in the horizontal direction, and the crankcase is formed with a crank chamber for accommodating the crankshaft in the vertical direction. A breather chamber is formed along a substantially half circumference of the cylinder bore in a cylinder block formed integrally with the cylinder bore, and blow-by gas in the crank chamber is introduced into the breather chamber in one side portion of the breather chamber in the circumferential direction of the cylinder bore. A blow-by gas introduction hole that leads and a one-way valve that opens and closes the blow-by gas introduction hole in accordance with the pulsation pressure in the crank chamber are provided, and communicates with the intake system at the other side portion in the circumferential direction of the cylinder bore in the breather chamber. A pipe connection hole for connecting a breather pipe to the breather chamber; A breather device for an engine provided with a breather oil return passage for returning the oil separated in the breather chamber to the crank chamber, wherein the breather oil return passage is provided along the cylinder bore and has an extending portion. The extending portion extends below the surface of the lubricating oil stored in the lower portion of the crank chamber and extends to the opposite side below the cylinder bore and beyond the center axis of the cylinder bore. It is characterized by.

  According to the present invention, the breather oil return passage for returning the oil separated in the breather chamber to the crank chamber is provided along the cylinder bore and provided with the extending portion, and this extending portion is stored in the lower portion of the crank chamber. Therefore, the oil mist in the crank chamber can be prevented from flowing directly into the breather chamber through the breather oil return passage.

  Further, the breather oil return passage is provided along the cylinder bore and has an extending portion. The extending portion extends below the cylinder bore and beyond the center axis of the cylinder bore to the opposite side. Even when stored for a long time, such as on its side, the tip of the extension becomes higher than the oil level of the lubricating oil in the crank chamber, which prevents the lubricating oil from flowing into the breather chamber and leaking outside. it can.

The left view which shows the outboard motor which mounts the engine to which one Embodiment in the breather apparatus of the engine which concerns on this invention was applied. The top view which removes and shows the engine cover in the outboard motor of FIG. Sectional drawing which follows the III-III line | wire of FIG. Sectional drawing which follows the IV-IV line | wire of FIG. Sectional drawing which follows the VV line | wire of FIG. Sectional drawing which follows the VI-VI line of FIG. The bottom view of the cylinder block shown in FIG. The partial top view which expands and shows the breather apparatus periphery of FIG.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a left side view showing an outboard motor equipped with an engine to which an embodiment of an engine breather apparatus according to the present invention is applied. The outboard motor 10 shown in FIG. 1 includes an engine holder 16, and a vertical engine 11 is mounted on the engine holder 16. A drive shaft housing 12 is integrally extended downward from the engine holder 16, and a gear case 13 is installed at the lower end of the drive shaft housing 12. The engine 11 and the engine holder 16 are disposed in an engine chamber 15 formed by being covered with an engine cover 14. The engine cover 14 includes a lower cover 14A attached to the engine holder 16 and an upper cover 14B provided detachably on the lower cover 14A.

  The engine 11 is a vertical type (vertical type) in which a crankshaft 17 (FIG. 2) is provided in the vertical direction, and a drive shaft 18 connected to the crankshaft 17 extends in the drive shaft housing 12 in the vertical direction. . The drive shaft 18 is connected to a propeller shaft 19 disposed in a horizontal direction in the gear case 13 via a shift mechanism 20, and a propeller 21 is attached to the rear end portion of the propeller shaft 19 so as to be integrally rotated. The driving force of the engine 11 is transmitted from the crankshaft 17 to the propeller shaft 19 via the drive shaft 18 and the shift mechanism 20, and the propeller 21 is rotated forward or reverse by the action of the shift mechanism 20 to advance the hull 25 (described later). Or reverse.

  The upper half of the drive shaft housing 12 is supported by a swivel bracket 22 provided in the periphery so as to be rotatable in the horizontal direction. The swivel bracket 22 is rotatable in the vertical direction with respect to the clamp bracket 24 via the swivel shaft 23. The clamp bracket 24 grips the transom 25A of the hull 25. Since the swivel bracket 22 is provided so as to be rotatable in the vertical direction with respect to the clamp bracket 24, the outboard motor 10 is provided so as to be able to perform a trim and tilt operation in the vertical direction with respect to the hull 25. Further, since the drive shaft housing 12 is provided so as to be rotatable in the horizontal direction with respect to the swivel bracket 22, the outboard motor 10 is provided so as to be steerable in the horizontal direction.

  When the outboard motor 10 is steered, the steering handle 26 is used. The steering handle 26 is pivotally supported by the engine holder 16 so as to be rotatable in the vertical direction, and a throttle grip 26A for adjusting the output of the engine 11 is provided at the tip of the steering handle 26.

  The engine 11 is, for example, an OHV (Over Head Valve) type four-cycle single-cylinder engine, and includes a crankcase 27 in which a crankcase upper half body 27A and a crankcase lower half body 27B are coupled so as to be split vertically. A crankcase lower half body 27 </ b> B of the crankcase 27 is fixed to and supported by the engine holder 16. Further, as shown in FIGS. 3 and 4, an oil pan 28 for storing the lubricating oil 1 is provided in the crankcase lower half 27 </ b> B.

  As shown in FIGS. 2 to 4, the crankcase upper half body 27 </ b> A is formed integrally with the cylinder 29 to constitute a cylinder block 30. As shown in FIGS. 5 to 7, a cylinder bore 31 having a central axis O extending in the horizontal direction is formed in the cylinder 29, and a cylinder sleeve 32 is fixed to the inner peripheral surface of the cylinder bore 31. As shown in FIGS. 3 and 4, the crankcase upper half 27A and the crankcase lower half 27B form a crank chamber 33 for accommodating the crankshaft 17 in the vertical direction. The case upper half body 27A and the crankcase lower half body 27B are rotatably supported. The crank chamber 33 is positioned near the front of the engine 11, and the cylinder 29 is positioned near the rear of the engine 11.

  In the engine 11, a cylinder head 34 is provided at the rear end of the cylinder 29, and a head cover 35 is provided at the rear end of the cylinder head 34. A combustion chamber (not shown) that matches the cylinder bore 31 of the cylinder 29 is formed in the cylinder head 34. Further, the cylinder head 34 is formed with an intake port 37 and an exhaust port (not shown) communicating with the combustion chamber, respectively, and an intake port 37, an intake valve for opening and closing the exhaust port, and an exhaust valve (both not shown). Is disposed. These intake valves and exhaust valves are driven to open and close by a valve operating mechanism 41 (described later).

  The crankshaft 17 accommodated in the crank chamber 33 is formed with a pair of crank webs 42A and 42B separated from each other in the axial direction at a substantially central position in the axial direction. A piston 43 is slidably disposed in the cylinder bore 31 of the cylinder 29 via a cylinder sleeve 32. The piston 43 and the crank webs 42 </ b> A and 42 </ b> B of the crankshaft 17 are connected by a connecting rod 44, whereby the reciprocating motion of the piston 43 in the cylinder bore 31 is converted into the rotational motion of the crankshaft 17.

  As shown in FIG. 3, the OHV type valve operating mechanism 41 for driving the intake valve and the exhaust valve has a camshaft 47 provided with an intake cam 45 and an exhaust cam 46 in the crank chamber 33. The camshaft 47 is arranged parallel to the crankshaft 17 (that is, in the vertical direction) and is rotatably supported by the crankcase upper half body 27A and the crankcase lower half body 27B. The cylinder head 34 also supports an intake-side rocker arm 48 and an exhaust-side rocker arm 49 so as to be swingable. One end of the intake-side rocker arm 48 is the valve stem of the intake valve, and one end of the exhaust-side rocker arm 49 is the exhaust valve. Abuts each valve stem. The other end of the intake side rocker arm 48 is operatively connected to the intake cam 45 by the intake side push rod 50 and the other end of the exhaust side rocker arm 49 is operatively connected to the exhaust cam 46 by the exhaust side push rod 51.

  As shown in FIGS. 3 and 4, the crankshaft 17 is provided with a drive gear 52, and the camshaft 47 is provided with a cam driven gear 53. When the cam drive gear 52 and the cam driven gear 53 are engaged with each other, the camshaft 47 is rotated at a predetermined reduction ratio (for example, 1/2) by the driving force of the crankshaft 17. The rotation of the camshaft 47 causes the intake valve via the intake cam 45, the intake side push rod 50 and the intake side rocker arm 48, and the exhaust valve via the exhaust cam 46, the exhaust side push rod 51 and the exhaust side rocker arm 49. However, each opens and closes at a predetermined timing in synchronization with the crankshaft 17.

  The intake port 37 shown in FIGS. 2 and 4 communicates with a carburetor 55 that constitutes an intake system 54 of the engine 11. The carburetor 55 is provided with an intake port 55 </ b> A, and generates an air-fuel mixture from the air (intake air) in the engine chamber 15 taken from the air intake port 55 </ b> A and the fuel guided from the fuel tank 56. Supply to the combustion chamber. Due to the combustion of the air-fuel mixture in the combustion chamber, the piston 43 reciprocates within the cylinder bore 31 of the cylinder 29. The carburetor 55 is arranged along with the intake port 55A on one side in the width direction of the engine 11, for example, the left side, in the engine chamber 15. Further, as shown in FIGS. 3 and 4, the fuel tank 56 is installed above the cylinder 29 and the cylinder head 34 of the cylinder block 30.

  A flywheel magnet 58 constituting a power generator is attached to the upper end of the crankshaft 17, which is an upper part of the engine 11, so as to rotate integrally. A ventilation fan 59 is fixed to the upper part of the flywheel magnet 58. Above the ventilation fan 59, a recoil starter pulley 60 of the engine starting device is provided integrally with the crankshaft 17 so as to rotate. The flywheel magnet 58, the ventilation fan 59, and the recoil starter pulley 60 are covered with a fan cover 61. An air inlet 62 is formed on the top surface of the fan cover 61, and an air outlet 63 is formed on the front lower portion of the fan cover 61.

  2, 5, 6, and 8, the gas accompanied by the pressure generated in the combustion chamber passes through the gap between the piston 43 and the cylinder bore 31 (cylinder sleeve 32), and the crank chamber 33. It flows in as blow-by gas. The pressure of the blow-by gas in the crank chamber 33 constantly varies as the piston 43 moves. Accordingly, the blow-by gas is guided to the breather device 65 so that the pressure does not hinder the movement of the piston 43. The breather device 65 includes a breather chamber 66, a blow-by gas introduction hole 67, a one-way valve 68, a breather pipe 69, a first breather oil return passage 70A, and a second breather oil return passage 70B.

  The breather chamber 66 is formed immediately below the flywheel magnet 58 in the upper part of the cylinder block 30 in which the cylinder 29 and the crankcase upper half body 27 </ b> A are integrally formed, and the upper opening thereof is closed by the lid member 71. The breather chamber 66 is formed along the substantially half circumference of the cylinder bore 31 across the top of the cylinder 29 in the circumferential direction of the cylinder bore 31 from one side to the other side. As a result, the breather chamber 66 is configured such that one side portion 66A and the other side portion 66B in the circumferential direction of the cylinder bore 31 communicate with each other.

  Among these, one side part 66A of the breather chamber 66 is provided on the side where the camshaft 47 of the valve operating mechanism 41 is provided. The bottom surface 72 (FIGS. 3 and 6) of one side portion 66A of the breather chamber 66 is from the intake cam 45 and the exhaust cam 46 of the crankshaft 47 (particularly, the intake cam 45 located above the exhaust cam 46). Is also provided above. As a result, splashing of lubricating oil from the intake cam 45 and the exhaust cam 46 (particularly the intake cam 45) due to the rotation of the crankshaft 47 is prevented from adhering to the bottom surface 72 of the one side portion 66A of the breather chamber 66.

  On the other hand, the bottom surface 73 (FIGS. 4 and 5) of the other side portion 66B of the breather chamber 66 is provided so as to protrude into the crank chamber 33 to a position lower than the bottom surface 72 of the one side portion 66A. Contributes to expansion. Further, a buffer wall 74 is formed in the breather chamber 66 for the blow-by gas flowing through the breather chamber 66 to collide with it. When the blow-by gas collides with the buffer wall 74, the oil in the blow-by gas is separated.

  As shown in FIGS. 2, 3, 6, and 8, the blow-by gas introduction hole 67 is formed at the end of one side portion 66 </ b> A of the breather chamber 66 to communicate the crank chamber 33 and the breather chamber 66. Then, the blow-by gas in the crank chamber 33 is guided to the breather chamber 66. The one-way valve 68 is installed at the end of the one side portion 66 </ b> A in the breather chamber 66, and opens and closes the blow-by gas introduction hole 67 with the pulsation pressure in the crank chamber 33. That is, the one-way valve 68 opens the blow-by gas introduction hole 67 when the crank chamber 33 is pressurized, and closes the blow-by gas introduction hole 67 when the pressure is reduced. Further, the second breather oil return passage 70B is also formed in one side portion 66A of the breather chamber 66 so that the breather chamber 66 and the crank chamber 33 communicate with each other. When the directional valve 68 is closed, it is returned to the crank chamber 33.

  As shown in FIGS. 2, 6 and 8, the breather pipe 69 communicates with the intake port 55 </ b> A of the carburetor 55 and is press-fitted into a pipe connection hole 75 formed at the end of the other side portion 66 </ b> B in the breather chamber 66. Is done. The breather pipe 69 is connected to the breather chamber 66 by being press-fitted into the pipe connection hole 75, and the breather chamber 66 is connected to the carburetor 55 of the intake system 54 of the engine 11 through the breather pipe 69. The blow-by gas from which the oil has been separated in the breather chamber 66 is guided to the carburetor 55 via the breather pipe 69.

  As shown in FIGS. 2, 4 to 6, and 8, the first breather oil return passage 70 </ b> A is formed at the end of the other side portion 66 </ b> B in the breather chamber 66, and connects the breather chamber 66 and the crank chamber 33. The oil separated in the breather chamber 66 is returned to the crank chamber 33. The first breather oil return passage 70 </ b> A includes a cylinder side portion 76 that is integrally formed on the outer periphery of the cylinder 29 along the cylinder bore 31, and an extending portion 77 that extends from the cylinder side portion 76. Is done.

  The extending portion 77 extends below the crank chamber 33, that is, below the oil level A of the lubricating oil 1 stored in the oil pan 28 of the crankcase lower half 27B, below the cylinder bore 31, and at the center axis of the cylinder bore 31. It extends beyond O to one side 66A side on the opposite side. Specifically, the extending portion 77 is a tubular member 78 that is separate from the cylinder 29 that can be attached to and detached from the cylinder side portion 76. The tubular member 78 extends downward of the cylinder 29, and a substantially lower half portion thereof is present below a split surface 79 between the crankcase upper half body 27A and the crankcase lower half body 27B. That is, the tubular member 78 has the upper base end portion 80 inserted and coupled to the cylinder side portion 76 of the crankcase upper half body 27A, and the lower tip portion 81 opposed to the bottom surface 82 of the crankcase lower half body 27B. Thus, it is positioned close to the bottom surface 82.

Next, the operation of the breather device 65 will be described mainly with reference to FIGS. 2, 5, 6 and 8.
During the operation of the engine 11, the one-way valve 68 opens and closes the blow-by gas introduction hole 67 according to the pulsation pressure in the crank chamber 33 as the piston 43 reciprocates. Blow-by gas from 33 flows into one side portion 66 </ b> A of the breather chamber 66. When the blow-by gas that has flowed into the one side portion 66A flows to the other side portion 66B side, the flow area increases at a position corresponding to the position immediately above the central axis O of the cylinder bore 31, and the flow velocity increases. When the side portion 66B is reached, the flow area gradually increases, so the flow velocity gradually decreases. Further, the blow-by gas collides with the buffer wall 74 while flowing from one side 66 </ b> A of the breather chamber 66 to the other side 66 </ b> B.

  The oil in the blow-by gas is separated by the change in the flow velocity and the collision with the buffer wall 74, and the blow-by gas from which the oil has been separated is supplied to the intake port 55A of the carburetor 55 via the breather pipe 69. The oil separated from the blow-by gas is returned to the crank chamber 33 through the first breather oil return passage 70A and the second breather oil return passage 70B.

  Further, when the outboard motor 10 is stored, when the outboard motor 10 is placed on its side with the other side portion 66B of the breather chamber 66 of the breather device 65 of the engine 11 lying downward, the lubricating oil in the crank chamber 33 is stored. 6 is an oil surface B indicated by a broken line in FIG. 6, and the tip 81 of the tubular member 78 of the blow-by gas introduction hole 67, the second breather oil return passage 70 B, and the first breather oil return passage 70 A is all of the lubricating oil 1. Present above oil level B. For this reason, since the inflow of the lubricating oil 1 from the crank chamber 33 to the breather chamber 66 is prevented, leakage of the lubricating oil 1 to the outside is prevented.

  Further, when the outboard motor 10 is stored, when the outboard motor 10 is placed on its side with the one side portion 66 </ b> A of the breather chamber 66 of the breather device 65 of the engine 11 lying downward, the lubricating oil in the crank chamber 33 is stored. 1 becomes the oil level C indicated by a broken line in FIG. 6, and the blow-by gas introduction hole 67 and the second breather oil return passage 70B are below the oil level C, but at least the breather pipe 69 exists above the oil level C. For this reason, the lubricating oil 1 that has flowed into the breather chamber 66 from the crank chamber 33 through the blow-by gas introduction hole 67 and the second breather oil return passage 70B does not reach the breather pipe 69 and prevents leakage to the outside. Is done.

  Furthermore, when the outboard motor 10 is stored, when the outboard motor 10 is brought into a forward-turned state with the crank block 33 side of the cylinder block 30 down, the lubricating oil 1 in the crank chamber 33 is indicated by a broken line in FIG. The tip 81 of the tubular member 78 of the blow-by gas introduction hole 67, the second breather oil return passage 70B, and the first breather oil return passage 70A is all above the oil level D of the lubricating oil 1. Exists. For this reason, since the inflow of the lubricating oil 1 from the crank chamber 33 to the breather chamber 66 is prevented, leakage of the lubricating oil 1 to the outside is prevented.

With the configuration as described above, the following effects (1) to (7) are achieved according to the present embodiment.
(1) As shown in FIGS. 3, 4, and 8, the bottom surface 72 of one side portion 66 </ b> A in the circumferential direction of the cylinder bore 31 in the breather chamber 66 of the breather device 65 is connected to the intake cam 45 and the exhaust cam 46 of the camshaft 47. When the height is approximately the same, the splash (oil droplets) of the lubricating oil 1 in the crank chamber 33 jumps from the crank webs 42A and 42B to the bottom surface 72 of the one side portion 66A of the breather chamber 66 due to the centrifugal force. The oil droplets adhere and easily flow into the breather chamber 66 through the blow-by gas introduction hole 67 and the second breather oil return passage 70B. For this reason, it is necessary to form the bottom surface 72 of the one side portion 66 </ b> A of the breather chamber 66 at a position higher than the intake cam 45 and the exhaust cam 46.

  On the other hand, in the other side portion 66B in the circumferential direction of the cylinder bore 31 in the breather chamber 66, splashes from the intake cam 45 and the exhaust cam 46 are blocked by the cylinder 29 (FIG. 7) protruding into the crank chamber 33. Even if the bottom surface 73 of the side portion 66B extends to substantially the same height as or below the intake cam 45 and the exhaust cam 46, the splash (oil droplets) of the lubricating oil 1 in the crank chamber 33 remains on the other side portion 66B of the breather chamber 66. It does not adhere to the bottom surface 73 of the. Therefore, as shown in FIGS. 5 and 6, the bottom surface 73 of the other side portion 66B of the breather chamber 66 protrudes into the crank chamber 33 to a position lower than the bottom surface 72 of the one side portion 66A of the breather chamber 66. The volume of the breather chamber 66 can be expanded as a whole, and as a result, the gas-liquid separation performance in the breather chamber 65 can be improved.

  (2) As shown in FIGS. 2, 5, 6, and 8, in the cylinder block 30, one side portion 66 </ b> A in the circumferential direction of the cylinder bore 31 in the breather chamber 66 is disposed on the camshaft 47 of the valve operating mechanism 41. The other side portion 66 </ b> B in the circumferential direction of the cylinder bore 31 in the breather chamber 66 is provided on the side opposite to the position where the camshaft 47 is disposed. Since one side portion 66A of the breather chamber 66 provided on the camshaft 47 side needs to form the breather chamber while avoiding the camshaft 47, the space efficiency is lowered. On the other hand, since the other side portion 66B of the breather chamber 66 can protrude into the crank chamber 33 without substantially restriction to form the breather chamber, the space in the crank chamber 33 can be used efficiently.

  (3) As shown in FIGS. 3 and 8, the bottom surface 72 of one side portion 66A of the breather chamber 66 in the circumferential direction of the cylinder bore 31 is more than the intake cam 45 and the exhaust cam 46 (particularly the intake cam 45) of the camshaft 47. Since it is provided above, it is possible to prevent oil splashes (oil droplets) scattered from the intake cam 45 and the exhaust cam 46 (particularly the intake cam 45) from adhering to the bottom surface 72 of the one side portion 66A. As a result, oil drops adhering to the bottom surface 72 of the one side portion 66A of the breather chamber 66 can be prevented from flowing into the breather chamber 66 through the blow-by gas introduction hole 67 and the second breather oil return passage 70B.

  (4) As shown in FIGS. 4 to 6, the first breather oil return passage 70 </ b> A for returning the oil separated in the breather chamber 66 of the breather device 65 to the crank chamber 33 is provided on the cylinder side provided along the cylinder bore 31. A portion 76 and an extending portion 77 are provided, and the extending portion 77 (tubular member 78) reaches below the oil level A of the lubricating oil 1 stored in the oil pan 28 at the lower part of the crank chamber 33. For this reason, the oil mist in the crank chamber 33 can be prevented from flowing directly into the breather chamber 66 through the first breather oil return passage 70A.

  (5) As shown in FIGS. 4 to 6, the first breather oil return passage 70 </ b> A of the breather device 65 includes a cylinder side portion 76 provided along the cylinder bore 31 and an extending portion 77 (tubular member 78). The extending portion 77 extends below the cylinder bore 31 and beyond the central axis O of the cylinder bore 31 to the opposite one side portion 66A side. For this reason, even when the engine 11 is stored, for example, with the other side portion 66B of the breather chamber 66 lying down, the tip portion 81 of the extension portion 77 (tubular member 78) is the lubricating oil in the crank chamber 33. As a result, the lubricating oil 1 can be prevented from flowing into the breather chamber 66 through the extending portion 77 (tubular member 78) and leaking outside.

  (6) As shown in FIGS. 4 to 6, the extending portion 77 of the first breather oil return passage 70 </ b> A in the breather device 65 is separated from the cylinder 29 in the cylinder block 30 and is attached to the removable tubular member 78. Configured. For this reason, in the first breather oil return passage 70A, the tubular member 78 protruding from the split surface 79 between the crankcase upper half 27 and the crankcase lower half 27B can be removed, so the crankcase upper half 27A and The workability in machining the crankcase lower half body 27B is improved, and the cost can be reduced. Furthermore, since the crankcase 27 does not need to have a thick structure in order to form the extending portion 77, the weight of the engine 11 can be reduced.

  (7) As shown in FIGS. 4 to 6, the tubular member 78 of the first breather oil return passage 70 </ b> A in the breather device 65 has its distal end portion 81 facing and close to the bottom surface 82 of the crankcase lower half body 27 </ b> B. It is positioned. For this reason, even when the tubular member 78 is loosely coupled with the cylinder side portion 76 in the first breather oil return passage 70A, the distal end portion 81 abuts against the bottom surface 82 of the crankcase lower half body 27B. Since the movement in the longitudinal direction is restricted, the falling into the crank chamber 33 can be prevented.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention.

1 Lubricating oil 11 Engine 17 Crankshaft 27 Crankcase 27A Crankcase upper half 27B Crankcase lower half 28 Oil pan 29 Cylinder 30 Cylinder block 31 Cylinder bore 33 Crank chamber 41 Valve mechanism 42A, 42B Crank web 45 Intake cam 46 Exhaust Cam 47 Camshaft 54 Intake system 55 Carburetor 65 Breather device 66 Breather chamber 66A One side 66B The other side 67 Blow-by gas introduction hole 68 One-way valve 69 Breather pipe 70A First breather oil return passages 72, 73 Bottom 75 Pipe connection hole 76 Cylinder side portion 77 Extension portion 78 Tubular member 79 Dividing surface 80 Base end portion 81 Front end portion 82 Bottom surface A Oil surface O Center axis

Claims (3)

The cylinder is provided with a cylinder bore whose central axis extends in the horizontal direction, the crankcase is formed with a crank chamber for accommodating the crankshaft in the vertical direction, and the cylinder block is formed by integrally forming the cylinder and the crankcase. , A breather chamber is formed along a substantially half circumference of the cylinder bore,
A blow-by gas introduction hole that guides the blow-by gas in the crank chamber to the breather chamber on one side in the circumferential direction of the cylinder bore in the breather chamber, and a direction that opens and closes the blow-by gas introduction hole in accordance with the pulsation pressure in the crank chamber A valve,
A breather pipe for connecting a breather pipe communicating with an intake system to the breather chamber on the other side in the circumferential direction of the cylinder bore in the breather chamber, and a breather for returning oil separated in the breather chamber to the crank chamber An engine breather device provided with an oil return passage,
The breather oil return passage is provided along the cylinder bore and includes an extending portion. The extending portion reaches below the oil level of the lubricating oil stored in the lower portion of the crank chamber, and below the cylinder bore. And a breather device for an engine, wherein the breather device extends beyond the central axis of the cylinder bore to the opposite side. The crankcase is composed of a crankcase upper half that constitutes a cylinder block together with a cylinder, and a crankcase lower half that includes an oil pan for storing lubricating oil so as to be split up and down.
The breather oil return passage is integrally formed along the outer periphery of the cylinder, and its extending portion extends downward from the cylinder and extends downward from the split surface of the crankcase. 2. The breather device for an engine according to claim 1, wherein the breather device is constituted by a separate tubular member. The extending portion formed of the tubular member has an upper base end coupled to a cylinder side portion of the breather oil return passage, and a lower tip portion facing and close to the bottom surface of the crankcase lower half. The breather device for an engine according to claim 2, wherein the breather device is positioned.

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