JP4639999B2 - Oil return structure for internal combustion engine - Google Patents

Description

  The present invention generally relates to an oil return structure of an internal combustion engine provided with a blow-by gas reduction device, and more specifically, an internal combustion engine installed on a baffle plate that partitions a cam chamber and an oil separator chamber. It relates to the oil return structure of the engine.

  Regarding an oil return structure of a conventional internal combustion engine, for example, Japanese Patent Laid-Open No. 6-26319 discloses an oil return structure of an internal combustion engine for the purpose of reliably returning oil from an oil separator chamber in a cylinder head cover to a valve operating chamber. Is disclosed (Patent Document 1). In Patent Document 1, an oil separator chamber is formed by a baffle plate attached to a cylinder head cover. The oil separator chamber is formed with an oil reservoir chamber that faces the lower portion of the oil separator chamber and is recessed in a concave shape. The baffle plate is formed with an oil drop hole for communicating between the oil reservoir chamber and the valve chamber located below the baffle plate.

Japanese Patent Laid-Open No. 6-173631 discloses an oil separator in a PCV system for the purpose of suppressing the generation of particulate lubricating oil and reducing the consumption of the lubricating oil (Patent Document 2). . Japanese Utility Model Laid-Open No. 5-92453 discloses a cylinder head cover made of synthetic resin for the purpose of preventing the occurrence of cracks and breakage (Patent Document 3).
JP-A-6-26319 Japanese Patent Laid-Open No. 6-173631 Japanese Utility Model Publication No. 5-92453

  In the oil return structure for an internal combustion engine disclosed in Patent Document 1 described above, the oil component contained in the blow-by gas is separated in the oil separator chamber. The separated oil gathers in the oil reservoir, and then flows down to the valve chamber through the oil pit. However, in this configuration, when the diameter of the oil pit is set large for the purpose of increasing the amount of oil flow or for preventing the oil pit from being blocked by oil sludge or the like, the oil in the valve chamber passes through the oil pit. Large quantities may be blown up into the oil separator chamber. Thereby, there exists a possibility that the oil component in blowby gas cannot be reduced effectively.

  Accordingly, an object of the present invention is to solve the above-described problems and to provide an oil return structure for an internal combustion engine that effectively reduces the oil component in blow-by gas.

  An oil return structure for an internal combustion engine according to the present invention is an oil return structure for an internal combustion engine that is mounted on a vehicle and provided with a blow-by gas reduction device. An oil return structure for an internal combustion engine includes a cam chamber in which a cam is disposed, an oil separator chamber that is provided on the opposite side of the cylinder to the cam chamber, and separates and removes oil components in blow-by gas, and the cam chamber and the oil separator And a baffle plate that defines an oil reservoir chamber on a side facing the cam chamber. The baffle plate is formed with an oil inflow hole, a vent hole, and a drain hole. The oil inflow hole communicates between the oil separator chamber and the oil reservoir chamber. The vent hole communicates between the oil separator chamber and the oil reservoir chamber, and is positioned on the upper side in the vertical direction from the oil inflow hole when mounted on the vehicle. The drain hole allows communication between the oil reservoir chamber and the cam chamber.

  “Vehicle mounting” means “in a state where a vehicle on which an oil return structure for an internal combustion engine is mounted is placed on a horizontal plane”.

  According to the oil return structure of the internal combustion engine configured as described above, the oil separated and removed from the blow-by gas in the oil separator chamber flows into the oil reservoir mainly through the oil inflow hole, and then the drain hole To the cam chamber. At this time, even when the amount of oil flowing into the oil reservoir chamber is large, the vent hole located on the upper side in the vertical direction from the oil inlet hole can be exposed from the oil accumulated in the oil reservoir chamber. Thereby, the oil reservoir chamber can be breathed by the vent hole, and the oil can smoothly flow out from the oil reservoir chamber to the cam chamber. Further, the oil component blown from the cam chamber into the oil reservoir chamber through the drain hole can be liquefied in the oil reservoir chamber. Thereby, it is possible to prevent the oil component in the cam chamber from flowing back into the oil separator chamber through the drain hole. As a result, the oil component in blow-by gas can be effectively reduced, and the amount of oil taken away by blow-by gas can be kept small.

  Preferably, blow-by gas flows into the oil reservoir chamber from the cam chamber through a drain hole in a predetermined direction. The oil inflow hole and the vent hole are formed at positions offset from a line extending in a predetermined direction.

  According to the oil return structure of the internal combustion engine thus configured, even when the opening area of the drain hole is set large, the oil component that is blown in large quantities from the cam chamber to the oil reservoir chamber through the drain hole, It can be sufficiently liquefied in the oil reservoir. Thereby, it can suppress that an oil component flows in into an oil separator chamber from an oil reservoir chamber via an oil inflow hole and a vent hole. Further, by setting the opening area of the drain hole large, the amount of oil flowing out from the oil reservoir chamber to the cam chamber can be increased, and the drain hole can be prevented from being blocked by oil sludge or the like.

  Preferably, the oil inflow hole and the vent hole are formed at positions that do not enter the field of view when looking into the oil reservoir chamber from the drain hole. According to the oil return structure of the internal combustion engine configured as described above, the same effect as described above can be obtained when the opening area of the drain hole is set large.

  The baffle plate extends between the oil separator chamber and the oil reservoir chamber, and has an inclined surface inclined with respect to the horizontal direction, and extends between the oil reservoir chamber and the cam chamber and has a drain hole opening. And have. Preferably, when the drain hole is projected onto the inclined surface along the orthogonal direction of the bottom surface, the oil inflow hole is a peripheral region of the inclined surface located on the lowest side in the vertical direction on the vehicle, and The drain hole is opened in the peripheral area of the inclined surface farthest from the projected position. The vent hole is open in the peripheral region of the inclined surface that is the uppermost side in the vertical direction on the vehicle and that is farthest from the position where the drain hole is projected. Preferably, when the drain hole is projected onto the inclined surface along the vertically upward direction, the oil inflow hole is a peripheral region of the inclined surface located on the lowest side in the vertical direction on the vehicle, and The drain hole is opened in the peripheral area of the inclined surface farthest from the projected position. The vent hole is open in the peripheral region of the inclined surface that is the uppermost side in the vertical direction on the vehicle and that is farthest from the position where the drain hole is projected. According to the oil return structure of the internal combustion engine configured as described above, the same effect as described above can be obtained when the opening area of the drain hole is set large.

  As described above, according to the present invention, it is possible to provide an oil return structure for an internal combustion engine that effectively reduces the oil component in blow-by gas.

  Embodiments of the present invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are denoted by the same reference numerals.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a gasoline engine to which an oil return structure according to Embodiment 1 of the present invention is applied. Referring to FIG. 1, in a gasoline engine 10 for a vehicle (hereinafter simply referred to as engine 10), blow-by gas leaking into the crank chamber from between the piston ring and the cylinder wall is forcibly introduced into the intake system. After that, a PCV (Positive Clank-case Ventilation System) device for recombustion in the combustion chamber is provided.

  The engine 10 includes a cylinder block 13 in which a plurality of cylinders 14 are formed, a piston 15 that is enclosed in each cylinder 14 and reciprocates, and a cylinder head 12 that is fixed to the top of the cylinder block 13. The piston 15 is connected via a connecting rod 17 to a crankshaft 22 that is an output shaft of the engine 10. The reciprocating motion of the piston 15 is converted into a rotational motion by the connecting rod 17 and then transmitted to the crankshaft 22.

  A cylinder block lower case 20 and an oil pan 19 are attached to the lower part of the cylinder block 13, and a crank chamber 21 in which a crankshaft 22 is accommodated is formed by the cylinder block 13, the cylinder block lower case 20 and the oil pan 19. Yes. The cylinder head 12 is formed with a combustion chamber 18 and an intake port 31 and an exhaust port communicating with the combustion chamber 18. The cylinder head 12 is provided with an intake / exhaust valve 16 that opens and closes between these ports and the combustion chamber 18 at an appropriate timing, and a cam 23 that drives the intake / exhaust valve 16.

  A cylinder head cover 11 is fixed to the cylinder head 12 on the opposite side of the cylinder block 13. A cam chamber 24 in which the cam 23 is disposed is formed between the cylinder head 12 and the cylinder head cover 11.

  An intake passage 36 through which fresh air flows toward the intake port 31 is connected to the cylinder head 12. A throttle valve 33 is provided on the intake passage 36 so as to be rotatable by an actuator such as a motor. The opening degree of the throttle valve 33 is adjusted by the depression amount of the accelerator pedal operated by the driver. On the intake passage 36, an air cleaner 34 and a filter 35 are installed on the upstream side of the fresh air flow from the throttle valve 33. A surge tank 32 is formed on the intake passage 36 at a position downstream of the throttle valve 33 in the fresh air flow. With these configurations, an intake system 30 that takes fresh air into the combustion chamber 18 is configured.

  Next, the PCV device provided in the engine 10 will be described. In the cylinder head 12 and the cylinder block 13, a communication passage 41 that allows communication between the crank chamber 21 and the cam chamber 24 is formed. An oil separator chamber 42 is formed in the cylinder head cover 11 on the opposite side of the piston 15, the cylinder 14, and the crank chamber 21 with the cam chamber 24 interposed therebetween. The oil separator chamber 42 is positioned above the cam chamber 24 in the vertical direction when mounted on the vehicle.

  In FIG. 1, the engine 10 is depicted as being upright in the vertical direction, but actually, the engine 10 is mounted on the vehicle with a certain degree of inclination with respect to the vertical direction. For this reason, in the present embodiment, the oil separator chamber 42 and the cam chamber 24 are formed side by side along a direction inclined by a predetermined angle with respect to the vertical direction.

  The cylinder head cover 11 is provided with a baffle plate 50 that partitions the cam chamber 24 and the oil separator chamber 42. The baffle plate 50 is formed with an opening 48 that communicates between the cam chamber 24 and the oil separator chamber 42 and serves as a gas flow path between the two chambers.

  The oil separator chamber 42 is provided to liquefy and separate oil components such as oil droplets and oil mist contained in the blowby gas from the blowby gas. The oil separated in the oil separator chamber 42 is returned to the cam chamber 24 by the oil return structure provided in the baffle plate 50 in the present embodiment.

  A blow-by gas passage 44 extending between the oil separator chamber 42 and the intake passage 36 is connected to the cylinder head cover 11. The blow-by gas passage 44 is connected to the intake passage 36 on the downstream side of the fresh air flow in the intake passage 36 with respect to the throttle valve 33. A PCV valve 45 that adjusts the flow area in the passage is provided on the blow-by gas passage 44. Further, a fresh air introduction passage 43 extending between the oil separator chamber 42 and the intake passage 36 is connected to the cylinder head cover 11. The fresh air introduction passage 43 is connected to the intake passage 36 on the upstream side of the fresh air flow in the intake passage 36 with respect to the throttle valve 33.

  In FIG. 1, the flow of blow-by gas and fresh air when the engine 10 is at a low load such as idling is represented by black arrows and white arrows, respectively.

  When the engine 10 is in operation, blow-by gas leaked from the gap between the piston ring and the cylinder wall flows into the crank chamber 21. When the engine 10 is under a low load, the negative pressure in the intake passage 36 downstream of the throttle valve 33 acts on the crank chamber 21 through the blow-by gas passage 44. As a result, the blow-by gas in the crank chamber 21 is guided from the intake passage 36 to the combustion chamber 18 through the communication passage 41, the cam chamber 24, the oil separator chamber 42, and the blow-by gas passage 44 in order. Further, fresh air flowing through the intake passage 36 is guided to the crank chamber 21 through the fresh air introduction passage 43. The fresh air guided to the crank chamber 21 is guided again from the intake passage 36 to the combustion chamber 18 together with the blow-by gas in the crank chamber 21.

  FIG. 2 is a cross-sectional view of the intake system showing the flow of blow-by gas and fresh air when the engine is at a high load. Referring to FIG. 2, the negative pressure in intake passage 36 is reduced when engine 10 is heavily loaded. Therefore, the blow-by gas flows into the intake passage 36 through both the blow-by gas passage 44 and the fresh air introduction passage 43. As a result, a large flow rate of blow-by gas can be handled.

  FIG. 3 is a perspective view of the oil separator chamber in FIG. 1 as viewed from above. FIG. 4 is a cross-sectional view of the baffle plate along the line IV-IV in FIG. Referring to FIGS. 3 and 4, baffle plate 50 includes plate 51 that partitions cam chamber 24 and oil separator chamber 42, and oil pool forming plate 62 that is fixed to plate 51 and forms oil pool 61. It consists of and.

  Blow-by gas flows into the oil separator chamber 42 from the cam chamber 24 through the opening 48 in FIG. The blow-by gas that has flowed flows in the direction indicated by the arrow 101 in the oil separator chamber 42, and then moves toward the blow-by gas passage 44 or the fresh air introduction passage 43 in FIG. 1. The plate 51 is formed to be inclined with respect to the horizontal direction along a direction orthogonal to the flow direction of the blow-by gas. In the present embodiment, the plate 51 is formed so as to incline downward in the vertical direction as it goes from the back side to the near side in FIG.

  The plate 51 has a surface 51 a facing the oil separator chamber 42 and a surface 51 b facing the cam chamber 24 and defining the oil pool 61. The surface 51b is formed in a substantially rectangular shape. The plate 51 is formed with a collision plate 52 protruding from the surface 51a. By providing the collision plate 52 on the path through which the blow-by gas flows, the blow-by gas collides with the collision plate 52. Thereby, the oil component contained in blow-by gas can be liquefied more actively in the oil separator chamber 42.

  The oil pool forming plate 62 has a box shape that is recessed from the surface 51b toward the cam chamber 24, and is fixed to the surface 51b by means such as welding or caulking. The oil pool forming plate 62 has a substantially rectangular bottom surface 62m extending in parallel to the surface 51b at a position spaced from the surface 51b. The bottom surface 62m extends below the surface 51b in the vertical direction. The bottom surface 62m extends while being inclined with respect to the horizontal direction, and defines the oil pool 61 together with the surface 51b. The oil pool 61 is formed on the opposite side of the oil separator chamber 42 with respect to the plate 51.

  The plate 51 is formed with a vent hole 72 and an oil inflow hole 71 that communicate with the oil separator chamber 42 and the oil pool 61 and open to the surface 51b. The air vent 72 is formed on the upper side in the vertical direction from the oil inflow hole 71 in terms of mounting on the vehicle. The oil pool forming plate 62 is formed with a drain hole 73 that communicates between the oil pool 61 and the cam chamber 24 and opens to the bottom surface 62m. The drain hole 73 is formed at a position close to the lower side in the vertical direction in the inclined bottom surface 62m. The drain hole 73 is formed on the lower side in the vertical direction than the vent hole 72 and the oil inflow hole 71 in terms of vehicle mounting.

  The vent hole 72, the oil inflow hole 71, and the drain hole 73 are formed so as to have an opening area having an equal size. The vent hole 72, the oil inflow hole 71, and the drain hole 73 may have different opening areas. For example, the oil inflow hole 71 and the drain hole 73 have the same opening area. May have a different opening area from the other two holes. The oil pool 61 is formed in a closed space except for the position opened by the vent hole 72, the oil inflow hole 71 and the drain hole 73.

  With such a configuration, the oil liquefied in the oil separator chamber 42 flows down on the inclined surface 51 a and flows into the oil pool 61 mainly through the oil inflow hole 71. Further, when the oil component in the cam chamber 24 blows into the oil pool 61 through the drain hole 73, the oil component is liquefied in the closed oil pool 61. For this reason, liquefied oil accumulates in the oil pool 61. While oil is accumulating in the oil pool 61, it is possible to prevent the oil component in the cam chamber 24 from blowing from the drain hole 73. The oil accumulated in the oil pool 61 flows down to the cam chamber 24 through the drain hole 73.

  In the present embodiment, the oil component in the cam chamber 24 extends toward the oil pool 61 through the drain hole 73 in the direction indicated by the arrow 111 (the direction orthogonal to the opening surface of the drain hole 73, that is, the bottom surface 62m extends. When the air is blown in a direction orthogonal to the direction in which the air flows, the air holes 72 and the oil inflow holes 71 are formed at positions offset from a straight line extending in the direction indicated by the arrow 111. In this case, the oil component blown into the oil pool 61 through the drain hole 73 does not first collide with the surface 51b defining the oil pool 61 and directly reach the vent hole 72 and the oil inflow hole 71. Thereby, the oil component can be liquefied more effectively in the oil pool 61, and the amount of oil flowing back from the cam chamber 24 to the oil separator chamber 42 can be sufficiently reduced.

  The flow direction of the oil component blown from the cam chamber 24 into the oil pool 61 is not limited to the direction indicated by the arrow 111, and may be, for example, the vertical direction depending on the conditions in the cam chamber 24.

  FIG. 5 is a perspective view showing a positional relationship among the drain hole, the vent hole, and the oil inflow hole in FIG. 3. Referring to FIG. 5, preferably, vent hole 72 and oil inflow hole 71 are formed at positions that do not enter the field of view when looking into the oil pool 61 from the cam chamber 24 side through the drain hole 73. . An arrow of a two-dot chain line shown in the drawing connects the observer's eyes and the farthest position to enter the field of view, and the tip of the arrow does not reach the vent hole 72 and the oil inflow hole 71. Also in this case, the amount of oil flowing back from the cam chamber 24 to the oil separator chamber 42 can be sufficiently reduced.

  FIG. 6 is a perspective view showing another positional relationship among the drain hole, the vent hole, and the oil inflow hole in FIG. 3. With reference to FIG. 6, the drain hole 73p when the drain hole 73 is projected on the surface 51b along the direction orthogonal to the bottom face 62m is represented. Preferably, the oil inflow hole 71 is formed in a region that is the lowest in the vertical direction and is farthest from the drain hole 73p in the region adjacent to the peripheral edge 55 of the surface 51b that defines the oil pool 61. . Further, the vent hole 72 is formed in a region that is the uppermost side in the vertical direction and is farthest from the drain hole 73p in the region adjacent to the peripheral edge 55 of the surface 51b that defines the oil pool 61. Also in this case, the amount of oil flowing back from the cam chamber 24 to the oil separator chamber 42 can be sufficiently reduced.

  FIG. 7 is a cross-sectional view showing the baffle plate when the oil inflow amount is large. Referring to FIG. 7, when the flow rate of blow-by gas is large, the amount of oil flowing into oil pool 61 increases. In this case, the height of the oil surface 201 in the oil pool 61 may be higher than the oil inflow hole 71. In the present embodiment, since the ventilation hole 72 is provided separately from the oil inflow hole 71, the circulation of air in the oil pool 61 can be ensured by the ventilation hole 72. As a result, the oil accumulated in the oil pool 61 can be smoothly discharged into the cam chamber 24 at all times.

  The oil return structure of the engine 10 as the internal combustion engine according to the first embodiment of the present invention is provided on the opposite side of the cylinder 14 from the cam chamber 24 in which the cam 23 is disposed, and in the blow-by gas. An oil separator chamber 42 that separates and removes oil components; a baffle plate 50 that partitions between the cam chamber 24 and the oil separator chamber 42 and forms an oil pool 61 as an oil reservoir chamber on the side facing the cam chamber 24; Is provided. An oil inflow hole 71, a vent hole 72, and a drain hole 73 are formed in the baffle plate 50. The oil inflow hole 71 communicates between the oil separator chamber 42 and the oil pool 61. The vent hole 72 communicates between the oil separator chamber 42 and the oil pool 61, and is located on the upper side in the vertical direction from the oil inflow hole 71 when mounted on the vehicle. The drain hole 73 communicates between the oil pool 61 and the cam chamber 24.

  According to the oil return structure of the engine 10 according to the first embodiment of the present invention configured as described above, when the amount of oil flowing into the oil pool 61 is large, the pressure in the oil pool 61 is increased by the vent hole 72. It can be prevented from rising. Thereby, the return property of the oil from the oil pool 61 to the cam chamber 24 can be improved.

  In the present embodiment, the amount of oil flowing back from the cam chamber 24 to the oil separator chamber 42 via the drain hole 73 can be sufficiently reduced, so that the opening area of the drain hole 73 can be set large. As an example, the hole diameter of the drain hole 73 which has been 3 mm in the past can be set to 4 mm, and the opening area can be increased by about 70%. Thereby, the return property of the oil from the oil pool 61 to the cam chamber 24 can be further improved. Further, the drain hole 73 can be prevented from being blocked by oil sludge or the like. For the above reasons, the amount of oil taken away by blow-by gas can be kept small.

(Embodiment 2)
FIG. 8 is a perspective view showing an oil return structure according to Embodiment 2 of the present invention. FIG. 8 is a diagram corresponding to FIG. 3 in the first embodiment. FIG. 9 is a cross-sectional view of the oil separator along the line IX-IX in FIG. The oil return structure in the present embodiment is basically provided with the same structure as the oil return structure in the first embodiment. Hereinafter, the description of the overlapping structure will not be repeated.

  Referring to FIGS. 8 and 9, in the present embodiment, oil pool forming plate 62 has a bottom surface 62n extending in the horizontal direction when mounted on a vehicle. The bottom surface 62n extends in a direction that obliquely intersects the surface 51b. The drain hole 73 is formed at a position facing the upper side in the vertical direction of the inclined plate 51.

  FIG. 10 is a perspective view showing the positional relationship among the drain hole, the vent hole, and the oil inflow hole in FIG. Referring to FIG. 10, the drawing shows drain hole 73p when drain hole 73 is projected onto surface 51b along a direction orthogonal to bottom surface 62n. Also in the present embodiment, the oil inflow hole 71 is the lowermost region in the vertical direction among the regions adjacent to the peripheral edge 55 of the surface 51b defining the oil pool 61 and the region farthest from the drain hole 73p. Is formed. Further, the vent hole 72 is formed in a region that is the uppermost side in the vertical direction and is farthest from the drain hole 73p in the region adjacent to the peripheral edge 55 of the surface 51b that defines the oil pool 61.

  11 and 12 are cross-sectional views showing modifications of the oil return structure in FIG. Referring to FIG. 11, in the present modification, drain hole 73 is formed in bottom surface 62n inclined with respect to the horizontal direction. Referring to FIG. 12, in the present modification, drain hole 73 is formed in curved bottom surface 62n.

  FIG. 13 is a perspective view showing the positional relationship between the drain hole, the vent hole, and the oil inflow hole in FIGS. 11 and 12. Referring to FIG. 13, in the drawing, drain hole 73p when drain hole 73 is projected onto surface 51b along the vertically upward direction is shown. Also in this modification, the oil inflow hole 71 is formed in a region that is the lowermost side in the vertical direction and is the farthest from the drain hole 73p among the regions adjacent to the peripheral edge 55 of the surface 51b that defines the oil pool 61. Has been. Further, the vent hole 72 is formed in a region that is the uppermost side in the vertical direction and is farthest from the drain hole 73p in the region adjacent to the peripheral edge 55 of the surface 51b that defines the oil pool 61.

  According to the engine oil return structure in the second embodiment of the present invention configured as described above, the same effects as those described in the first embodiment can be obtained.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is sectional drawing which shows the gasoline engine to which the oil return structure in Embodiment 1 of this invention was applied. It is sectional drawing of the intake system which shows the flow of blow-by gas and fresh air when an engine is at the time of high load. It is the perspective view which looked at the oil separator chamber in FIG. 1 from upper direction. It is sectional drawing of the baffle plate along the IV-IV line in FIG. It is a perspective view which shows the positional relationship of the drain hole in FIG. 3, a vent hole, and an oil inflow hole. It is a perspective view which shows another positional relationship of the drain hole in FIG. 3, a ventilation hole, and an oil inflow hole. It is sectional drawing which shows a baffle plate in case oil inflow amount is large. It is a perspective view which shows the oil return structure in Embodiment 2 of this invention. It is sectional drawing of the oil separator along the IX-IX line in FIG. It is a perspective view which shows the positional relationship of the drain hole in FIG. 8, a vent hole, and an oil inflow hole. It is sectional drawing which shows the modification of the oil return structure in FIG. It is sectional drawing which shows another modification of the oil return structure in FIG. It is a perspective view which shows the positional relationship of the drain hole in FIG. 11 and FIG. 12, a vent hole, and an oil inflow hole.

Explanation of symbols

  10 engine, 14 cylinder, 23 cam, 24 cam chamber, 42 oil separator chamber, 50 baffle plate, 51b surface, 61 oil pool, 71 oil inflow hole, 72 vent hole, 73 drain hole.

Claims (3)

An oil return structure for an internal combustion engine mounted on a vehicle and provided with a blow-by gas reduction device,
A cam chamber in which a cam is arranged;
An oil separator chamber provided on the opposite side of the cylinder to the cam chamber and separating and removing oil components in the blow-by gas;
A baffle plate that divides the cam chamber and the oil separator chamber and forms an oil reservoir chamber on the side facing the cam chamber;
The baffle plate communicates between the oil separator chamber and the oil reservoir chamber, and communicates between the oil separator chamber and the oil reservoir chamber. A vent hole located on the upper side of the vertical direction, and a drain hole for communicating between the oil reservoir chamber and the cam chamber ,
The baffle plate extends between the oil separator chamber and the oil reservoir chamber, extends between an inclined surface inclined with respect to a horizontal direction, the oil reservoir chamber and the cam chamber, And a bottom surface with a drain hole opening,
The oil return structure for an internal combustion engine, wherein the oil inflow hole and the vent hole are arranged at a position on a peripheral side of the inclined surface with respect to a position where light incident on the drain hole from the cam chamber side can reach . When the projection of the previous SL drain hole on the inclined surface along a direction perpendicular to the bottom surface, the oil inflow hole, the vehicle-mounted, there in the peripheral region of the inclined surface located lowermost in the vertical direction And the vent hole is a peripheral region of the inclined surface located on the uppermost side in the vertical direction on the vehicle. 2. The oil return structure for an internal combustion engine according to claim 1, wherein the oil return structure is opened in a peripheral region of the inclined surface farthest from the position where the drain hole is projected. When projected onto the inclined surface before Symbol drain hole along the vertically upward direction, the oil inflow hole, the vehicle-mounted, a peripheral region of the inclined surface located lowermost in the vertical direction, And the vent hole is a peripheral region of the inclined surface that is located on the uppermost side in the vertical direction on the vehicle, and is open to the peripheral region of the inclined surface farthest from the position where the drain hole is projected. 2. The oil return structure for an internal combustion engine according to claim 1, wherein the oil return structure is opened in a peripheral region of the inclined surface farthest from a position where the drain hole is projected.

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