JP6798355B2 - Internal combustion engine - Google Patents

Description

The present invention relates to an internal combustion engine provided with an oil passage for a piston jet and a breather chamber in an upper crankcase.

As the heat load of the piston increases as the output of the engine increases, the importance of the piston jet that injects oil onto the back surface of the piston to cool the piston is increasing. It is difficult to arrange an oil passage for supplying oil to the piston jet, and it is also necessary to secure a hydraulic pressure for injecting oil from the piston jet.

On the other hand, in Patent Document 1, the crankcase of the engine is composed of a lower crankcase member and an upper crankcase member, and the breather chamber is a cylinder from the back surface to the upper surface of the upper crankcase member in the periphery of the cylinder. And those provided integrally with the upper crankcase member are disclosed. The breather chamber separates the oil component from the air containing the oil mist in the crankcase and returns the oil component to the engine.

Japanese Unexamined Patent Publication No. 2007-77851

Of the oil passages to the piston jet described above, it is particularly difficult to arrange the oil passage for supplying oil to the rear piston jet that injects oil to the rear side of the back surface of the piston. In particular, when the breather chamber is formed on the rear side (rear side) of the cylinder assembly in the upper part of the crankcase, the arrangement of the oil passage to the rear piston jet becomes more difficult. If this oil passage is externally attached to a crankcase or a cylinder block, the number of parts, assembly man-hours, weight and cost of the engine will increase, and there is a risk of oil leakage to the outside of the engine.

In addition, when an oil passage for supplying oil to the rear piston jet is provided inside the crankcase, the above oil passage is simply added to the crankcase because there is a limit to the drawing direction of the mold for molding the crankcase. Then, waste meat is attached around the oil passage, the weight of the crankcase increases, and cavities are more likely to occur. In addition, when an oil passage is provided inside the crankcase, when the waste meat around the oil passage is removed, depending on the arrangement position of the oil passage, water is formed in the recess formed by removing the waste meat. , Mud, dust, etc. may accumulate.

An object of the present invention has been made in consideration of the above circumstances, and even when the upper crankcase is provided with an oil passage for a piston jet and a breather chamber, the internal combustion engine can be provided with a volume of the breather chamber. The purpose is to provide an internal combustion engine that can realize weight reduction.

The internal combustion engine according to the present invention is configured from a crankcase in which an upper crankcase is coupled to a lower crankcase from above and a cylinder assembly is coupled to the upper crankcase, and an oil pump installed in the lower crankcase. A main gallery for supplying the discharged oil to each part of the internal combustion engine, a sub gallery for guiding the oil to a piston jet that injects the oil toward the piston in the cylinder assembly, and the sub gallery for guiding the oil from the main gallery to the sub gallery. It has an oil passage for supplying oil to the internal combustion engine and a breather chamber for separating oil from blow-by gas generated in the crankcase of the crankcase, and the sub gallery is arranged behind the cylinder assembly in the upper crankcase. The breather chamber is arranged behind the sub gallery in the upper crankcase, a part of the oil passage is provided inside the breather chamber, and a portion of the peripheral portion facing the breather chamber is provided. It is characterized in that it is configured one step lower in the breather room.

According to the present invention, even when the sub gallery and the breather chamber are sequentially arranged on the rear side of the cylinder assembly in the upper crankcase, the breather is included in a part of the peripheral portion of the oil passage provided inside the breather chamber. The part facing the room is made lower in the breather room. Therefore, the volume of the breather chamber can be secured, and the weight of the upper crankcase can be reduced.

The right side view which shows the engine to which one Embodiment of the internal combustion engine which concerns on this invention is applied. II arrow view of FIG. The right side view which shows by removing the clutch cover and the like in the engine of FIG. The plan view which shows by removing the cylinder assembly and the like in the engine of FIG. FIG. 4 is a plan view showing the lower crankcase with the upper crankcase removed. FIG. 4 is a cross-sectional view taken along the line VI-VI of FIGS. 4 and 5. Cross-sectional view taken along the line VII-VII of FIGS. 4 and 5. Cross-sectional view taken along the line VIII-VIII of FIGS. 4 and 5. FIG. 4 is an enlarged perspective view showing a breather chamber in the upper crankcase of FIG. A perspective view showing a portion of the back surface of the upper crankcase of FIG. 4 corresponding to the breather chamber of FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a right side view showing an engine to which one embodiment of the internal combustion engine according to the present invention is applied. Further, FIG. 2 is a view taken along the line II of FIG. The engine 10 as an internal combustion engine shown in FIGS. 1 and 2 is mounted on, for example, a motorcycle, and the cylinder assembly 12 is tilted forward and coupled to the crankcase 11.

The cylinder assembly 12 is configured by sequentially connecting the cylinder block 13, the cylinder head 14, and the head cover 15 from below. Then, the cylinder block 13 of the cylinder assembly 12 is coupled to the upper crankcase 17 described later from above. The combustion of the air-fuel mixture supplied to the combustion chamber (not shown) of the cylinder head 14 causes the piston 27 to reciprocate in the cylinder block 13, and this reciprocating motion causes the crankshaft 23 (FIG. 3) to reciprocate via a connecting rod (not shown). Rotate.

As shown in FIG. 3, the crankcase 11 brings the mating surface 17A of the upper crankcase 17 into contact with the mating surface 16A of the lower crankcase 16 from above, and in this state, the upper crankcase 17 is coupled to the lower crankcase 16. It is composed by letting. An oil pan 18 for storing oil for lubricating the engine is arranged in the lower part of the lower crankcase 16. An oil strainer 19 is arranged in the oil pan 18.

An oil filter 21 is installed at the front of the lower crankcase 16. Further, an oil pump 20 is installed on the right side wall of the lower crankcase 16 while being covered with the clutch cover 22. In the oil pump 20, the pump shaft 25 is driven by the rotational force of the count shaft 24 which is rotationally driven by the rotational force of the crankshaft 23 via a clutch mechanism (not shown), and the pump rotor 26 which is integrally rotated with the pump shaft 25 is Rotate.

As shown in FIGS. 5 and 6, the lower crankcase 16 is provided with a shaft insertion hole 30 for inserting the pump shaft 25 of the oil pump 20. Further, in the lower crankcase 16, a second oil suction passage 32 (FIG. 7) communicates with the oil pump 20 in one side region around the shaft insertion hole 30, and a first oil discharge passage 33 communicates with the oil pump 20 in the other side region. It is formed as possible.

The second oil suction passage 32 extends in the vertical direction of the engine 10 and communicates with the first oil suction passage 31 formed in the lower crankcase 16. The first oil suction passage 31 is provided so as to be connectable to the oil strainer 19 in the oil pan 18 (FIG. 3). Further, as shown in FIGS. 5 and 6, the first oil discharge passage 33 extends in the horizontal direction of the engine 10 and communicates with the second oil discharge passage 34 formed in the lower crankcase 16. The second oil discharge passage 34 is provided so as to be connectable to the oil filter 21.

In the lower crankcase 16, an oil discharge passage (not shown) that can be connected to the oil filter 21 is formed in parallel with the second oil discharge passage 34. Further, in the lower crankcase 16, as shown in FIGS. 5 and 8, a main gallery 36 communicating with the oil discharge passage is formed so as to extend horizontally in the left and right width directions of the engine 10.

As shown in FIGS. 3 and 7, when the pump rotor 26 of the oil pump 20 rotates, the oil in the oil pan 18 passes through the oil strainer 19 and enters the first oil suction passage 31 and the second oil suction passage 32. As shown by the arrow A in FIG. 7, the oil flows in sequentially, is sucked into the oil pump 20, and is boosted. The increased pressure oil is discharged to the first oil discharge passage 33 as shown in FIG. 6, flows through the second oil discharge passage 34 and flows into the oil filter 21 as shown by the arrow B in FIG. 6, and is filtered. Will be done. As shown in FIG. 8, the filtered oil flows into the main gallery 36 through an oil discharge passage (not shown), and is supplied from the main carriage 36 to each part of the engine 10.

Here, as shown in FIGS. 6 and 7, a branch passage 60 and a surplus passage 61 are formed in the lower crankcase 16, the branch passage 60 communicates with the second discharge passage 34, and the surplus passage 61 is the second. A relief valve 63 is arranged between the branch passage 60 and the surplus passage 61 so as to communicate with the suction passage 32. The relief valve 63 is configured such that a valve body 65 is arranged in a tubular valve body 64 so as to be movable in the axial direction, and the valve body 65 is urged by a spring 66.

As shown in FIGS. 5, 6 and 7, the relief valve 63 is housed in a relief valve accommodating portion 67 having a diameter larger than that of the relief valve 63, which is formed in the lower crankcase 16. Further, as shown in FIG. 6, the branch passage 60 branches from the second discharge passage 34, extends in the vertical direction of the engine 10, and communicates the second discharge passage 34 with the relief valve accommodating portion 67. Further, as shown in FIG. 7, the surplus passage 61 is adjacent to the branch passage 60 and is formed along the vertical direction of the engine 10. The surplus passage 61 communicates between the relief valve accommodating portion 67 and the second suction passage 32 by communicating the upper end with the relief valve accommodating portion 67 and the lower end communicating with the second suction passage 32.

A plurality of outlets 68 are formed in the valve body 64 of the relief valve 63 at the same position in the axis O direction at orthogonal to the axis O. The valve body 65 is held at a position where the outlet 68 is closed by the urging force of the spring 66, and the relief valve 63 is closed (two-dot chain line in FIG. 6). When the pressure of the oil in the second discharge passage 34 and the branch passage 60 becomes equal to or higher than a predetermined value, the valve body 65 of the relief valve 63 moves against the urging force of the spring 66 in response to this pressure, and the outlet 68 Is in the open state, and the relief valve 63 opens (two-dot chain line in FIG. 7).

When the relief valve 63 opens, a part of the oil (surplus oil) flowing in the second discharge passage 34 as shown by the arrow B (FIG. 6) passes through the branch passage 60 as shown by the arrow C. It flows out from the outlet 68 of the relief valve 63 into the relief valve accommodating portion 67, is further returned to the second suction passage 32 via the surplus passage 61, and enters the second suction passage 32 from the first suction passage 31 as shown by arrow A. Together with the inflowing oil, it is sucked into the oil pump 20. A configuration in which excess oil in the second discharge passage 34 is returned to the second suction passage 32 via the relief valve 63 is referred to as an inner relief structure.

As described above, the parts of the engine 10 to which the oil from the main gallery 36 shown in FIGS. 5 and 8 is supplied include, for example, the crank journal part 37, the counter journal part 38, the drive journal part 39, the front piston jet 40, and the rear part. The side piston jet 41 and the like.

The crank journal portion 37 shown in FIG. 5 is a portion that rotatably supports the crankshaft 23. Since the engine 10 is an in-line 4-cylinder engine as shown in FIGS. 2 and 4, the crank journal portion 37 has a first crank journal portion # 1, a second crank journal portion # 2, and a third from the left side of the engine 10. The crank journal portion # 3, the fourth crank journal portion # 4, and the fifth crank journal portion # 5 are sequentially formed in the lower crankcase 16 at predetermined intervals in the left and right width directions of the engine 10.

As shown in FIGS. 5 and 8, each crank journal portion 37 (first crank journal portion # 1 to fifth crank journal portion # 5) is communicated with the main gallery 36 via the crank journal oil passage 42. .. These crank journal portions 37 (first crank journal portions # 1 to fifth crank journal portions # 5) are provided in the crank chamber 43 of the crankcase 11.

Further, each crank journal portion 37 (first crank journal portion # 1 to fifth crank journal portion # 5) is provided with a journal metal (not shown) between the crank journal portion 37 and the crank shaft 23. Then, in each crank journal section 37 (first crank journal section # 1 to fifth crank journal section # 5), the crank journal from the main gallery 36 is provided so that the oil film is not interrupted between the journal metal and the crankshaft 23. Oil is supplied with an appropriate hydraulic pressure through the oil passage 42.

The oil supplied from the main gallery 36 to each crank journal portion 37 to lubricate each crank journal portion 37 is supplied to an alternator (not shown) in the case of the first crank journal portion # 1 to lubricate it. In the case of the second crank journal portion # 2 and the fourth crank journal portion # 4, the connecting rod large end portion (not shown) is supplied to lubricate the sliding portion between the connecting rod large end portion and the crankshaft 23. In the case of the fifth crank journal portion # 5, the fifth crank journal portion # 5 is supplied to a valve operating mechanism (not shown) in the cylinder head 14 to lubricate it. The oil after lubricating the third crank journal portion # 3 is not supplied to other places.

Each of the counter journal section 38 and the drive journal section 39 shown in FIG. 5 rotatably supports the count shaft 24 (FIG. 3) and the drive shaft 28 of the transmission mechanism. The counter journal section 38 and the drive journal section 39 are provided in the mission chamber 47 of the crankcase 11. Of these, the counter journal portion 38 is formed on the side walls 48A and 48B facing each other that define the mission chamber 47 in the lower crankcase 16, respectively. Similarly, the drive journal portion 39 is also formed on the side walls 48A and 48B facing each other in the lower crankcase 16 adjacent to the counter journal portion 38.

In the lower crankcase 16, a partition wall 49 that separates the crank chamber 43 and the transmission 47 is continuously formed on the side walls 48A and 48B. In the mating surface 16A of the lower crankcase 16, the transmission oil passage 50 as the mating surface oil passage communicates with the counter journal portion 38 and the drive journal portion 39 through the mating surface 16A of the side wall 48A, the partition wall 49 and the side wall 48B. It is formed.

As shown in FIGS. 5 and 8, the mission oil passage 50 communicates with the main gallery 36 via the rear oil supply passage 51. The rear oil supply passage 51 is formed at the center position in the left and right width directions of the engine 10 in the lower crankcase 16. Further, the rear oil supply passage 51 communicates with the main gallery 36 and extends in the horizontal direction parallel to the mating surface 16A of the lower crankcase 16 to form a horizontally extending passage portion 52 formed in the lower crankcase 16. And the vertically extending passage portion 53 formed in the lower crankcase 16 which communicates with the horizontally extending passage portion 52 and the transmission oil passage 50 and extends in the direction perpendicular to the mating surface 16A of the lower crankcase 16. And have.

Therefore, as shown in FIG. 8, the oil from the main gallery 36 sequentially flows through the horizontally extending passage portion 52 and the vertically extending passage portion 53 of the rear oil supply passage 51, passes through the orifice 54 described later, and is shown in FIG. It is supplied to the mission oil passage 50 shown in. The oil supplied to the transmission passage 50 is guided to the counter journal section 38 and the drive journal section 39, and slides between the count shaft 24 and the count journal section 38, and the drive shaft 28 and the drive journal section 39. Lubricate each moving part.

The orifice 54 is arranged at a boundary portion of the vertical extension passage portion 53 of the rear oil supply passage 51 with, for example, the mission oil passage 50. The orifice 54 lowers the oil pressure of the oil supplied from the rear oil supply passage 51 to the mission oil passage 50, and prevents the oil flowing in the mission oil passage 50 from leaking.

As shown in FIGS. 4 and 6, in the engine 10 of the present embodiment, the front piston jet 40 and the rear piston jet 41 are arranged in each cylinder. The oil is injected from the front piston jet 40 and the rear piston jet 41 toward the back surface of the piston 27 to cool the piston 27 having a high heat load.

In the present embodiment, the front piston jet 40 and the rear piston jet 41 are installed in the upper crankcase 17 at a position below the cylinder block 13 coupled to the upper crankcase 17. The front piston jet 40 is positioned in the front position with respect to the piston 27, and the rear piston jet 41 is positioned in the rear position with respect to the piston 27. As a result, the front piston jet 40 injects oil toward the front side on the back surface of the piston 27, and the rear piston jet 41 injects oil toward the rear side on the back surface of the piston 27.

Oil is supplied to the front piston jet 40 from the main gallery 36 via a front oil supply passage (not shown) formed on the front side of the lower crankcase 16. The front oil supply passage is formed at the center position in the left and right width directions of the engine 10 so as to straddle the lower crankcase 16 and the upper crankcase 17.

As shown in FIG. 8, the rear piston jet 41 includes a rear oil supply passage 51, an oil connecting passage 56 branched from the rear oil supply passage 51, the oil connecting passage 56, and the rear piston jet 41. Oil is supplied from the main gallery 36 via the continuous sub gallery 57. The oil connecting passage 56 is formed in a straight line across the lower crankcase 16 and the upper crankcase 17, and communicates with the vertically extending passage portion 53 and the sub gallery 57 of the rear oil supply passage 51. Therefore, the rear oil supply passage 51 and the oil connecting passage 56 form an oil passage for supplying oil from the main gallery 36 to the sub gallery 57.

Of these, the oil connecting passage 56 includes a lower oil connecting passage portion 56A formed in the lower crankcase 16 and an upper oil connecting passage portion 56B formed in the upper crankcase 17. Further, the oil connecting passage 56 (lower oil connecting passage portion 56A, upper oil connecting passage portion 56B) is positioned at the center position in the left and right width directions of the engine 10 in the upper crankcase 17. Further, the oil connecting passage 56 and the rear oil supply passage 51 are provided in the same vertical plane of the lower crankcase 16.

The orifice 54 as a throttle portion is installed at a position downstream of the portion where the oil connecting passage 56 branches in the vertically extending passage portion 53 of the rear oil supply passage 51. Therefore, the oil flowing through the oil connecting passage 56 is secured with the oil pressure of the main gallery 36, and in this state, the oil is introduced from the oil connecting passage 56 to the sub gallery 57.

As shown in FIGS. 4 and 8, the sub gallery 57 is located above the upper crankcase 17 and behind the cylinder assembly 12, along the left and right width directions of the engine 10, and is substantially left and right of the upper crankcase 17. It is formed over the entire width. Further, the sub gallery 57 is arranged between the vertically extending passage portion 53 of the rear oil supply passage 51 and the main gallery 36 in the side view of the engine 10. The upper oil connecting passage portion 56B of the oil connecting passage 56 communicates with the center position in the left and right width directions of the engine 10 in the sub gallery 57. Further, each rear piston jet 41 installed corresponding to each cylinder communicates with the sub gallery 57. As a result, the oil that has reached the sub gallery 57 from the main gallery 36 via the rear oil supply passage 51 and the oil connecting passage 56 is supplied to the rear piston jet 41.

As shown in FIGS. 2 and 4, the upper crankcase 17 is provided with a breather chamber 70 that separates oil from blow-by gas generated in the crankcase 43 of the crankcase 11 adjacent to the rear of the sub gallery 57. Will be done. The breather chamber 70 is provided at the center position in the left and right width directions of the engine 10 in the upper crankcase 17. Further, the breather chamber 70 is covered from above by the breather chamber cover 71. The breather chamber cover 71 is provided with a reed valve cover 72 for accommodating a reed valve (not shown). The oil separated from the blow-by gas in the breather chamber 70 is returned to the oil pan 18 (FIG. 3) through the oil return passage 73 provided in the lower crankcase 16.

As shown in FIGS. 4, 6 and 7, in the breather chamber 70 provided in the upper crankcase 17, a portion located directly above the relief valve 63 installed in the lower crankcase 16 is lightened to one stage. A recess 74 is provided as a lowered lightening portion. In FIG. 9, the area of the recess 74 is shown in gray.

As shown in FIGS. 7 and 9, an upper end opening 73A of the oil return passage 73 is provided on the bottom surface 75 of the recess 74. As shown in FIGS. 5, 7 and 8, the oil return passage 73 includes a lower oil connecting passage portion 56A of the oil connecting passage 56, a vertically extending passage portion 53 of the rear oil supply passage 51, and a relief valve accommodating portion. Together with 67, the branch passage 60 and the surplus passage 61, it is formed on the partition wall 49 of the lower crankcase 16. Of these, the oil return passage 73, the vertically extending passage portion 53 of the rear oil supply passage 51, the relief valve accommodating portion 67, the branch passage 60, and the surplus passage 61 are parallel to each other, and the mating surface 16A of the lower crankcase 16 It is formed on the lower crankcase 16 in the direction perpendicular to the vehicle.

As shown in FIG. 8, among the oil connecting passages 56, the upper oil connecting passage portion 56B as a part of the oil passage has a lower half portion thereof in the recess 74 of the breather chamber 70 as shown in FIG. And the upper half thereof is provided so as to pass through the inside of the crank chamber 43 as shown in FIG. Then, as shown in FIGS. 8 and 9, the upper oil connecting passage portion 56B is formed as a passage recess 77 which is one step lower in the breather chamber 70 by removing the portion of the peripheral portion facing the breather chamber 70. The passage recess 77 is continuous with the bottom surface 75 of the recess 74. FIG. 8 shows a state before the portion facing the breather chamber 70 in the peripheral portion of the upper oil connecting passage portion 56B is processed by a two-dot chain line indicated by reference numeral α.

Further, as shown in FIG. 4, in the plan view of the engine 10, the upper oil communication passage portion 56B and the oil return passage 73 of the oil communication passage 56 are located in the area where the passage recess 77 and the recess 74 in the breather chamber 70 are continuous. , Relief valves 63 are arranged side by side in order. That is, in the region where the passage recess 77 and the recess 74 in the breather chamber 70 are continuous, the upper oil connecting passage 56B is on the left side of the oil return passage 73 and on the right side of the oil return passage 73 in the plan view of the engine 10. Relief valves 63 are arranged respectively.

Since it is configured as described above, according to the present embodiment, the following effects (1) to (4) are obtained.
(1) As shown in FIGS. 8 and 9, in the upper oil connecting passage portion 56B of the oil connecting passage 56, the portion of the peripheral portion facing the breather chamber 70 is removed from the waste meat, and the inside of the breather chamber 70 is removed. It is configured as a passage recess 77 which is one step lower. Therefore, the passage recess 77 can secure the volume of the breather chamber 70 even when the sub gallery 57 and the breather chamber 70 are sequentially arranged on the rear side of the cylinder assembly 12 in the upper crankcase 17. Further, the passage recess 77 reduces the weight of the upper crankcase 17 and prevents the formation of cavities, so that the castability of the upper crankcase 13 can be improved.

Further, by covering the breather chamber 70 with the breather chamber cover 71 (FIG. 2), the portion of the peripheral portion of the upper oil connecting passage portion 56B facing the breather chamber 70 is removed and the passage recess 77 is formed. Even in this case, it is possible to prevent water, mud, dust, etc. from accumulating in the passage recess 77.

(2) As shown in FIGS. 4 and 9, the oil return passage 73 for returning the oil separated from the blow-by gas to the oil pan 18 in the breather chamber 70 has an upper end opening 73A in the passage recess 77 in the breather chamber 70. It is provided. Therefore, not only the length of the oil return passage 73 can be shortened, but also the discharge property of discharging the oil in the breather chamber 70 to the oil return passage 73 can be improved.

(3) As shown in FIGS. 6 and 7, the upper crankcase 17 is provided with a recess 74 of the breather chamber 70 in a portion located directly above the relief valve 63 installed in the lower crankcase 16. Therefore, the volume of the breather chamber 70 can be secured, the weight of the upper crankcase 17 can be reduced, and the castability of the upper crankcase 13 can be improved by preventing the formation of cavities. It is possible to prevent the accumulation of mud, dust, etc.

(4) Since the breather chamber 70 is provided in the upper crankcase 17 at the center position in the left and right width directions of the engine 10, the volume of the breather 70 can be easily expanded. Further, since the upper oil connecting passage 56B of the oil connecting passage 56 is provided in the upper crankcase 17 at the center position in the left and right width directions of the engine 10, the upper oil connecting passage 56B is provided on the left and right of the engine 10 in the sub gallery 57. Can be continued at the center position in the width direction of. As a result, the oil from the upper oil connecting passage portion 56B can be evenly distributed and guided to the left and right of the sub gallery 57.

Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention, and the replacements and changes thereof can be made. , It is included in the scope and gist of the invention, and is also included in the scope of the invention described in the claims and the equivalent scope thereof.

For example, the engine 10 which is an internal combustion engine is not limited to that mounted on a motorcycle, but may be an engine mounted on a four-wheeled vehicle, an outboard motor, a surface vehicle, or a general-purpose engine.

10 ... engine (internal combustion engine), 11 ... crankcase, 12 ... cylinder assembly, 16 ... lower crankcase, 17 ... upper crankcase, 18 ... oil pan, 20 ... oil pump, 27 ... piston, 41 ... rear piston jet , 43 ... Crankcase, 51 ... Rear oil supply passage (oil passage) 56 ... Oil connecting passage (oil passage) 56B ... Upper oil connecting passage (part of oil passage) 57 ... Sub gallery, 63 ... Relief valve, 70 ... Breather chamber, 71 ... Breather chamber cover, 73 ... Oil return passage, 73A ... Top opening, 74 ... Recess, 77 ... Passage recess

Claims (4)

A crankcase in which an upper crankcase is coupled to a lower crankcase from above and a cylinder assembly is coupled to the upper crankcase.
The main gallery for supplying the oil discharged from the oil pump installed in the lower crankcase to each part of the internal combustion engine.
A sub-gallery for guiding oil to a piston jet that injects oil toward the piston in the cylinder assembly.
An oil passage that supplies oil from the main gallery to the sub gallery,
It has a breather chamber that separates oil from blow-by gas generated in the crank chamber of the crankcase.
The sub gallery is located behind the cylinder assembly in the upper crankcase, the breather chamber is located behind the sub gallery in the upper crankcase, and a portion of the oil passage is in the breather chamber. An internal combustion engine provided inside, and a portion of the peripheral portion facing the breather chamber is configured to be one step lower in the breather chamber. An oil pan is installed at the lower part of the lower crankcase, and the lower crankcase is provided with an oil return passage for returning the oil separated in the breather chamber to the oil pan, and the oil return passage is provided in the breather chamber. The internal combustion engine according to claim 1, wherein the internal combustion engine is configured by opening in a region configured one step lower. The lower crankcase is provided with a relief valve that opens the valve according to the pressure of the oil discharged from the oil pump and returns the discharged excess oil to the oil pump.
The upper crankcase is provided with a recess located above the relief valve inside the breather chamber, and the region formed one step lower in the breather chamber and the recess are continuous in a plan view of the internal combustion engine. The internal combustion engine according to claim 2, wherein a part of the oil passage, the oil return passage, and the relief valve are arranged side by side in the region. Any one of claims 1 to 3, wherein the breather chamber and a part of the oil passage provided inside the breather chamber are arranged at the center position in the width direction of the internal combustion engine in the upper crankcase. The internal combustion engine according to item 1.

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