阅读说明：本技术 内燃机单元 (Internal combustion engine unit ) 是由 原田彻 于 2020-04-13 设计创作，主要内容包括：本发明提供一种内燃机单元(100),具有：内燃机主体(1)；安装在内燃机主体(1)的下部的平衡装置(2)；以包围平衡装置(2)的方式安装在内燃机主体(1)的下部的油盘(3)。在内燃机主体(1)形成用于使对内燃机主体(1)内进行了润滑的油返回到油盘(3)的油流出孔(13),平衡装置(2)面向油流出孔(13)的出口(13h)配置。(The present invention provides an internal combustion engine unit (100) comprising: an internal combustion engine main body (1); a balance device (2) mounted on the lower part of the internal combustion engine body (1); an oil pan (3) attached to the lower part of the engine body (1) so as to surround the balancer device (2). An oil outflow hole (13) for returning oil, which lubricates the interior of the engine body (1), to the oil pan (3) is formed in the engine body (1), and the balancer device (2) is disposed facing an outlet (13h) of the oil outflow hole (13).)

1. An internal combustion engine unit characterized by comprising:

an internal combustion engine main body (1);

a balancing device (2) mounted on a lower portion of the engine body (1); and

an oil pan (3) mounted on a lower portion of the engine main body (1) so as to surround the balancing device (2),

an oil outflow hole (13) is formed in the internal combustion engine main body (1), the oil outflow hole (13) being used for returning oil that lubricates the inside of the internal combustion engine main body (1) to the oil pan (3),

the balancing device (2) is arranged facing the outlet (13h) of the oil outflow hole (13).

2. An internal combustion engine unit according to claim 1,

the balancing device (2) has a bulging portion (5), the bulging portion (5) bulging so as to intersect with the outflow direction of the oil flowing out from the oil outflow hole (13),

the bulging portion (5) is disposed facing an outlet (13h) of the oil outflow hole (13).

3. An internal combustion engine unit according to claim 2,

the balancing device (2) has balancing shafts (20R, 20L) and a housing (21) that supports the balancing shafts (20R, 20L) so as to be freely rotatable,

the shell (21) is provided with an upper shell (21U) and a lower shell (21L) which are vertically divided and mutually combined,

the bulging portion (5) is provided in the lower case (21L).

4. An internal combustion engine unit according to claim 2 or 3,

an oil passage (50) for guiding the oil stored in the oil pan (3) to the engine body (1) is formed inside the bulging portion (5).

5. An internal combustion engine unit according to claim 4,

the oil pump is disposed at an end of the oil passage (50) and sucks oil from the oil pan (3) through the oil passage (50).

6. An internal combustion engine unit according to claim 5,

the bulging portion (5) has a suction port (41) at a lower portion thereof for guiding oil from the oil pan (3) to the oil passage (50).

7. An internal combustion engine unit according to any one of claims 2 to 6,

the bulging portion (5) has an outer peripheral surface configured in a convexly curved surface shape so that the oil flowing out from the oil outflow hole (13) flows along the outer peripheral surface of the bulging portion (5).

8. An internal combustion engine unit according to any one of claims 2 to 7,

the bulging portion (5) is provided so as to bulge further downward.

9. An internal combustion engine unit according to any one of claims 2 to 8,

the balancing device (2) has a guide section (6) above the bulging section (5) for guiding the oil flowing out from the oil outflow hole (13) to the bulging section (5),

a gap is provided between the guide section (6) and the bulging section (5).

10. An internal combustion engine unit according to claim 9,

a through hole (60) communicating with the oil outflow hole (13) is provided in the guide section (6),

the outlet of the through hole (60) is provided so as to face the bulging portion (5).

Technical Field

The present invention relates to an internal combustion engine unit having an internal combustion engine supplied with lubricating oil.

Background

As such a device, a device described in patent document 1 is known in the related art. The invention described in patent document 1 is configured such that a through hole is formed in a balancer device fastened to a lower portion of an engine main body, and lubricating oil of the engine is returned to an oil pan through the through hole.

However, in the device described in patent document 1, in order to suppress the speed of the lubricating oil when the lubricating oil is returned to the oil pan, it is necessary to form a through hole in the balancer device, which combines a vertical hole extending in the vertical direction and a horizontal hole extending in the horizontal direction, and the amount of machining work increases.

Disclosure of Invention

An internal combustion engine unit according to an aspect of the present invention includes: an internal combustion engine main body; a balancing device installed at a lower portion of the engine main body; and an oil pan mounted on a lower portion of the engine main body in such a manner as to surround the balancer device. An oil outflow hole for returning oil that lubricates the inside of the engine main body to an oil pan is formed in the engine main body, and the balancer device is disposed facing an outlet of the oil outflow hole.

Drawings

The objects, features and advantages of the present invention are further clarified by the following description of the embodiments in relation to the accompanying drawings.

Fig. 1 is a sectional view schematically showing the structure of a main part of an engine to which an internal combustion engine unit according to an embodiment of the present invention is applied.

Fig. 2 is a sectional view taken along line II-II of the engine of fig. 1.

Fig. 3 is a perspective view of the balancing device of the engine of fig. 1 as viewed from obliquely above.

Fig. 4 is a perspective view of a main part of the balancing device of the engine of fig. 1 as viewed obliquely from below.

Fig. 5 is a top view of the balancing device of the engine of fig. 1.

Fig. 6 is a perspective view schematically showing a state where oil is returned from inside the engine of fig. 1 to an oil pan via a balancing device.

Detailed Description

An embodiment of the present invention will be described below with reference to fig. 1 to 6. In the following, the front-back direction, the up-down direction, and the left-right direction orthogonal to each other are defined as shown in the drawing, and the structure of each part will be described according to the definitions. The vertical direction is a gravity direction (vehicle height direction), and the horizontal direction is, for example, a vehicle length direction or a vehicle width direction.

Fig. 1 is a sectional view schematically showing a main part of an engine 100 to which an internal combustion engine unit according to an embodiment of the present invention is applied, and fig. 2 is a sectional view taken along II-II of fig. 1.

As shown in fig. 1, the engine 100 includes an engine main body 1, a balancer 2 attached to a lower portion of the engine main body 1, and an oil pan 3 attached to a lower portion of the engine main body 1 so as to surround the balancer 2.

The engine body 1 includes a crankshaft 10 extending along an axis CL in the front-rear direction, a cylinder block 11, and a base 12, and is configured as, for example, a tandem four-cylinder engine. The crankshaft 10 is supported to be rotatable between the cylinder block 11 and the base 12.

As shown in fig. 2, engine 100 is mounted on a vehicle body in a state in which a cylinder axis (not shown), which is a center line of a cylinder, is inclined in the left-right direction. That is, engine 100 is mounted on the vehicle body in a state in which the cylinder axis is inclined to the left, such that the upper portion is positioned to the left with respect to the lower portion.

A through hole (oil outflow hole) 13 for returning oil for lubricating each part in the engine body 1 from the inside of the engine body 1 to the oil pan 3 is formed in the engine body 1. The through hole 13 is formed through the cylinder block 11 and the base 12 at a substantially central portion in the front-rear direction and at a left end portion in the left-right direction of the cylinder block 11 and the base 12.

That is, the through hole 13 penetrates from the inside of the engine body 1 to the outside at the lower portion on the left side of the engine body 1, and a discharge port 13h through which oil is discharged to the oil pan 3 is formed in the lower surface of the base 12. By forming the through hole 13 on the left side, which is the inclined side of the engine main body 1, that is, on the lower side with respect to the right side, the oil in the engine main body 1 easily flows to the oil pan 3.

The through hole 13 is formed in a substantially cylindrical shape, and the discharge port 13h is formed in a substantially circular shape. The shape of the through hole and the discharge port is not limited to this, and for example, the through hole may be formed in a truncated cone shape and the discharge port may be formed in an elliptical shape.

The balancer device 2 is a device for reducing secondary vibration of the engine 100 generated by reciprocating motion of the piston of the engine main body 1. The balancer 2 is fastened to the lower surface of the base 12 of the engine body 1 by a plurality of bolts B1 inserted into both left and right end portions thereof from below, and is disposed facing the discharge port 13h of the through hole 13 with a predetermined gap from the discharge port 13 h.

The balancer device 2 includes a pair of right and left balancer shafts 20R and 20L having substantially the same shape, and a housing 21 that supports the balancer shafts 20R and 20L in parallel and rotatably.

The housing 21 includes an upper housing (upper housing) 21U and a lower housing (lower housing) 21L that are vertically divided along a plane passing through the centers of the balance shafts 20R and 20L and are joined to each other in order to house the balance shafts 20R and 20L. The balance shafts 20R and 20L are located below the crankshaft 10, and the balance shaft 20L is located near the discharge port 13h of the through hole 13.

As shown in fig. 1, a small sprocket 15 is fixed to a front end portion of the balance shaft 20L. A crankshaft pulley 17 is provided at the tip end of the crankshaft 10, and a large sprocket 14 is fixed to the crankshaft pulley 17. A suspension link chain 16 is wound around the large sprocket 14 and the small sprocket 15. The rotational force of the crankshaft 10 is transmitted to the balance shaft 20L through the endless chain 16, thereby driving the balance shaft 20L to rotate.

For example, the balance shaft 20L is driven to rotate in the same direction as the crankshaft 10 at twice the rotational speed of the crankshaft 10. Further, by adjusting the sizes of the large sprocket 14 and the small sprocket 15, the rotation speed ratio of the balance shaft 20L can be appropriately changed.

The balance shafts 20R and 20L are integrally provided with a helical gear 22, and the balance shafts 20L and 20R can be interlocked with each other by the helical gear 22. Specifically, the helical gears 22 integrally provided on the balance shafts 20R and 20L are engaged with each other, whereby the balance shaft 20R is driven to rotate in the direction opposite to the balance shaft 20L.

In both balance shafts 20R and 20L, a 1 st journal portion 23a and a 2 nd journal portion 23b having small diameters are provided integrally with the balance shafts 20R and 20L in front of the helical gear 22, and a 3 rd journal portion 23c and a 4 th journal portion 23d having large diameters are provided integrally with the balance shafts 20R and 20L in rear of the helical gear 22.

In the rear side portion of each of the balance shafts 20R and 20L, a weight portion 24 is provided integrally with the balance shafts 20R and 20L, and the center of gravity of the weight portion 24 is shifted radially outward from the rotation center and divided into two parts in the front-rear direction with a 3 rd journal portion 23c interposed therebetween.

Flange portions 25 having enlarged diameters are formed at the end portions of the front and rear weight portions 24 with the 3 rd journal portion 23c interposed therebetween. Thrust receiving surfaces 25a are formed on the end surfaces (end surfaces facing the 3 rd journal portion 23 c) of the flange portions 25 that face each other.

In order to obtain an equivalent rotational mass while reducing the weight portion 24 as much as possible, the shaft portion 241 of the weight portion 24 is set to a small diameter. Then, in order to compensate for the decrease in rigidity due to the reduction in diameter, ribs 242 connecting the mounting portion of the helical gear 22 and the flange portion 25 provided on the front side of the 3 rd journal portion 23c and the mounting portion of the helical gear 22 and the flange portion 25 provided on the front side of the 4 th journal portion 23d in the axial direction are provided at the portions extending over the entire length on the opposite side of the counter weight of the two shaft portions 241.

In order to minimize the weight increase due to the provision of the ribs 242 and optimize the stress distribution, the ribs 242 have a tapered shape in which the height dimension decreases as the distance from the axial center portion of each weight portion 24 increases.

On the other hand, the 1 st to 4 th journal portions 23a to 23d of the balance shafts 20R and 20L are supported by the 1 st to 4 th bearing holes 26a to 26d formed in two by joining the upper case 21U and the lower case 21L to each other.

When assembling the balancer device 2, first, the 1 st journal portion 23a to the 4 th journal portion 23d of the balancer shafts 20R and 20L are placed on the 1 st bearing hole 26a to the 4 th bearing hole 26d, respectively, on the lower housing 21L side half portions. Next, in this state, the upper housing 21U and the lower housing 21L are coupled with the 1 st journal portion 23a to the 4 th journal portion 23d of the balance shafts 20R and 20L aligned with the 1 st journal portion 21U-side half portions of the 1 st to 4 th bearing holes 26a to 26 d. Thereby, the balance shafts 20R, 20L are rotatably accommodated in the housing 21.

The structure of the case 21 will be explained. Fig. 3 is a perspective view of balancing device 2 of engine 100 as viewed from obliquely above.

As shown in fig. 3, the housing 21 has a plurality of fastening portions 211 for fastening the balancer device 2 to the engine body 1. The fastening portions 211 are provided at both left and right end portions of the front portion of the housing 21, both left and right end portions of the substantially central portion in the front-rear direction, and the right end portion of the rear portion, respectively.

Bolt holes 212 into which bolts B1 can be inserted are vertically penetrated through the plurality of fastening portions 211. The case 21 is fastened to the lower surface of the base 12 by screwing a bolt B1 inserted from the lower side of each bolt hole 212 of the plurality of fastening portions 211 into a fastening hole (not shown) formed in the lower surface of the base 12.

Each fastening portion 211 is formed in a substantially cylindrical shape, and two ribs 213 extending inward (inward in the left-right direction and inward in the front-rear direction) of the housing 21 from the outer peripheral surface are provided upright on each fastening portion 211. Each rib 213 is formed in a tapered shape such that the length in the vertical direction decreases toward the inside of the housing 21. By providing two ribs 213 in each fastening portion 211, the strength and rigidity of the fastening portion 211 can be improved while suppressing an increase in weight of the housing 21. This can optimize the distribution of stress acting on the fastening portion 211 while suppressing the weight.

Fig. 4 is a perspective view of a main portion (left end portion) of the balancer device 2 viewed obliquely from below. As shown in fig. 3 and 4, the upper case 21U and the lower case 21L are fastened together with a bolt B2 inserted in place from above and a bolt B3 inserted in place from below.

That is, as shown in fig. 3, the upper case 21U and the lower case 21L are fastened together by inserting and screwing bolts B2 from above into a plurality of fastening portions (not shown) formed at the front portion, the substantially central portion, and the rear portion in the front-rear direction, and the right portion, the substantially central portion, and the left portion in the left-right direction, respectively.

As shown in fig. 4, the upper case 21U and the lower case 21L are fastened together by inserting and screwing a bolt B3 from below into a fastening portion (not shown) formed by penetrating the bearing walls 27c and 27d provided with the 3 rd bearing hole 26c and the 426 rd bearing hole 26 c. As described above, by fastening the bolts B2 and B3, the bearing walls 27c and 27d are less likely to be loosened at portions on which radial acceleration due to rotation of the weight 24 acts.

Fig. 5 is a plan view (view viewed from above) of the balancing apparatus 2. As shown in fig. 3 and 5, a pump housing 28 is attached to the rear end of the housing 21. The pump housing 28 has a pump housing portion 28h for housing an oil pump (not shown) therein. The oil pump is of a trochoid type, for example, and is connected to the rear end portion of the balance shaft 20R. The pump housing portion 28h communicates with a shaft housing portion 20h (see fig. 2) that houses the balance shafts 20R and 20L.

As shown in fig. 4, when the balance shaft 20R rotates, the oil pump sucks the oil stored in the oil pan 3 into the case 21 via the oil filter 4 mounted at the bottom of the lower case 21L. The sucked oil is then pressure-fed to each part of the engine main body 1 through an oil circulation flow path 50 formed inside a bulging portion 5, which will be described later, of the housing 21. The oil that lubricates each part in the engine body 1 is returned from the through hole 13 (see fig. 2) of the engine body 1 to the oil pan 3 through a guide portion 6 (described later) of the housing 21.

As shown in fig. 2, the oil filter 4 is mounted on the lower side of the two balance shafts 20R, 20L, i.e., below the balance shaft 20L of the lower case 21L. Specifically, the oil filter 4 is provided so that the center thereof is located at a position close to a vertical plane passing through the axis CL of the crankshaft 10, that is, substantially directly below the center of gravity of the engine body 1 in a state of being mounted on the vehicle body.

Thus, the oil filter 4 is disposed at a position where the liquid level fluctuation of the oil pan 3 is small. Therefore, even if the liquid level of the oil stored in the oil pan 3 fluctuates due to the forward and backward acceleration, the centrifugal force, or the like during traveling, it is possible to prevent the oil suction performance from being lowered.

As shown in fig. 4, the oil filter 4 is mounted on the bottom wall of the lower case 21L through a filter cover 40. The filter cover 40 is formed to hold the oil filter 4, and is attached to the lower case 21L by an attachment portion 29 formed integrally with the bottom wall of the lower case 21L. The filter cover 40 is provided with a suction port 41 at a position where the liquid surface fluctuation of the oil pan 3 is minimum.

The mounting portion 29 is formed in a substantially cylindrical shape, and an outer peripheral portion thereof is connected to a bearing wall 27c provided in a half portion of the 3 rd bearing hole 26c located at a substantially central portion in the front-rear direction of the lower case 21L (see fig. 1). This can increase the rigidity of the bearing wall 27c that fastens the upper case 21U and the lower case 21L together.

As shown in fig. 2 and 3, the bulging portion 5 is provided at the left end portion of the lower case 21L constituting the case 21. This allows the lower end of the bulging portion 5 to be close to the liquid surface of the oil stored in the oil pan 3.

In particular, by providing the bulging portion 5 at the left end portion of the lower case 21L inclined to the left side in a state where the engine 100 is mounted on the vehicle body, the lower end portion of the bulging portion 5 can be disposed closer to the liquid surface of the oil stored in the oil pan 3.

As shown in fig. 2, the outer surface of the bulging portion 5 bulges leftward. More specifically, in a state where the balancer device 2 is fastened to the engine body 1, the bulging portion 5 bulges leftward with respect to the left end portion of the discharge port 13h of the through hole 13 when viewed along the through hole 13 (arrow view a). This enables the oil discharged from the discharge port 13h to drop or flow onto the outer surface of the swelling portion 5.

The outer surface of the bulge portion 5 is formed in a convex curved surface shape bulging leftward. This allows the oil discharged from the discharge port 13h of the engine body 1 to flow along the outer circumferential surface of the bulge portion 5 to the lower end portion. That is, the discharged oil can be prevented from dripping or flowing from the middle of the bulging portion 5 to the oil pan 3.

The bulge portion 5 also bulges downward. This allows the lower end of the bulging portion 5 to be disposed closer to the liquid surface of the oil stored in the oil pan 3.

In fig. 2, the bulging portion 5 is formed in a substantially elliptical shape in cross section, but the cross-sectional shape of the bulging portion 5 is not limited thereto. For example, the bulge portion 5 may be formed to have a curved surface only in a part of the outer surface.

As shown in fig. 3 to 5, the bulging portion 5 extends in the front-rear direction at the left end portion of the lower case 21L. More specifically, the front end of the bulging portion 5 is located near the fastening portion 211 provided on the front left side of the casing 21, and the rear end of the bulging portion 5 is located on the joint surface of the pump casing 28. That is, the bulging portion 5 is formed in a substantially cylindrical shape, and has a length corresponding to a joint surface from the fastening portion 211 provided on the front left side to the pump housing 28.

As shown in fig. 4, the bulging portion 5 has an oil circulation passage 50 therein for guiding the oil stored in the oil pan 3 to each portion in the engine main body 1. In other words, the bulging portion 5 is formed of a member or a portion constituting an oil circulation passage for guiding the oil stored in the oil pan 3 to each portion in the engine main body 1. This eliminates the need to provide a bulging portion separately from the bulging portion 5 for forming the oil circulation flow path 50, and thus reduces the number of parts and manufacturing steps.

The oil circulation passage 50 has a front end portion communicating with the oil pan 3 via the oil filter 4, and a rear end portion communicating with the pump housing portion 28h housing the oil pump.

Fig. 6 is a perspective view of the housing 21 viewed obliquely from left below. As shown in fig. 4 and 6, a fastening portion 211 for fastening the balancer device 2 to the base 12 is provided at a position adjacent to the rear end portion of the oil circulation flow path 50. This can improve the rigidity when fastening the balancer 2 to the base 12.

The guide portion 6 shown in fig. 6 is formed so as to be able to guide the oil discharged from the through hole 13 of the engine body 1 to the outer peripheral surface of the bulging portion 5 in a state where the balancer device 2 is fastened to the engine body 1. As shown in fig. 2, a through hole 60 that can communicate with the through hole 13 of the engine body 1 in a state where the balancer device 2 is fastened to the engine body 1, that is, a communication hole 60 is formed inside the guide portion 6, and oil is guided to the outer peripheral surface of the bulging portion 5 through the communication hole 60.

The guide portion 6 is formed in a substantially cylindrical shape, and is provided at a substantially central portion in the front-rear direction and at a left end portion in the left-right direction of the upper case 21U constituting the case 21, as shown in fig. 5. More specifically, the guide portion 6 is provided between two ribs 213 of the fastening portion 211 on the left side of the rear end portion, adjacent to the rear end portion of the oil circulation flow path 50, and is provided so as to be connected to one of the ribs 213.

Further, a rib 61 extending rightward from the outer peripheral surface thereof is connected to the guide portion 6. The rib 61 is formed in a conical shape whose vertical length decreases toward the right of the housing 21. By providing the ribs 61 and 213 in the guide portion 6, the strength and rigidity of the guide portion 6 can be improved while suppressing an increase in weight of the housing 21. That is, the weight can be controlled and the stress distribution acting on the guide portion 6 can be optimized.

As shown in fig. 2, the guide portion 6 is disposed above the bulging portion 5 with a predetermined gap facing the bulging portion 5. By providing a gap between the guide portion 6 and the bulging portion 5, the oil flowing to the guide portion 6 flows to the outside of the guide portion 6 via the gap, and the oil can be made to flow along the outer surface of the bulging portion 5.

The cross-sectional area of the inlet 62 at the upper end of the communication hole 60 of the guide 6 is formed larger than the cross-sectional area of the outlet 13h of the through hole 13 formed in the engine body 1 (the base 12). Specifically, the inlet 62 of the communication hole 60 is formed to be larger than the outlet 13h of the through hole 13 in a state where the balancer 2 is fastened to the engine body 1. In other words, in a state where the balancer device 2 is fastened to the engine body 1, the inlet 62 of the communication hole 60 is formed such that the discharge port 13h of the through hole 13 is positioned inside the inlet 62 of the communication hole 60 as viewed along the direction a of fig. 2 of the through hole 13.

By making the inflow port 62 of the communication hole 60 larger than the discharge port 13h of the through hole 13, the oil can be reliably caused to flow from the through hole 13 into the communication hole 60. In addition, even if a gap is formed between the base 12 and the balancer device 2 in a state where the balancer device 2 is fastened to the engine body 1, the oil is easily caused to flow into the communication hole 60 from the through hole 13.

The communication hole 60 is formed in a truncated cone shape having a gradually decreasing cross-sectional area in the oil discharge direction (downward). That is, the cross-sectional area of the discharge port 63 of the communication hole 60 is smaller than the inflow port 62. This facilitates guiding the oil to the outer surface of the bulging portion 5.

As shown in fig. 5, the inlet 62 of the communication hole 60 is formed in a substantially elliptical shape. Thus, even when the center position of the discharge port 13h of the through hole 13 is shifted from the center position of the inflow port 62, the oil can easily flow from the through hole 13 into the communication hole 60.

The discharge port 63 of the communication hole 60 is formed in a substantially circular shape. The discharge port 63 is disposed at a position overlapping the outer surface of the bulging portion 5 when viewed along the direction a of the through hole in fig. 2. This can reliably cause the oil flowing through the communication hole 60 to flow or drip on the outer surface of the bulging portion 5.

Next, the flow of oil for lubricating each part in engine 100 configured as described above will be described. Fig. 6 is a perspective view schematically showing a state where oil is returned from inside the engine main body 1 of fig. 1 to the oil pan 3 via the balancer device 2.

The oil that lubricates each part in the engine 100 and flows through each part is discharged from the inside of the engine body 1 through the through hole 13 formed in the engine body 1 by the discharge port 13h formed in the lower surface of the base 12.

The oil discharged from the discharge port 13h of the through hole 13 flows into the communication hole 60 of the guide portion 6 communicating with the through hole 13. The cross-sectional area of the inlet 62 of the communication hole 60 is larger than the discharge port 13h of the through hole 13, and therefore, the oil reliably flows into the communication hole 60.

As shown in fig. 6, the oil flowing into the communication hole 60 is discharged from the discharge port 63 of the communication hole 60. Since the discharge port 63 is disposed at a position overlapping the lower bulging portion 5, the oil discharged from the discharge port 63 drops or flows onto the outer surface of the bulging portion 5.

The oil dropped or flowed to the outer surface of the bulging portion 5 flows downward along the outer surface of the bulging portion 5. Since the outer surface of the bulge portion 5 is formed in a curved surface shape, the oil easily flows downward along the outer surface of the bulge portion 5. The oil reaching the lower portion (e.g., lower end) of the bulging portion 5 drops or flows to the oil pan 3 due to gravity.

The oil stored in the oil pan 3 is sucked from the oil filter 4 through the oil circulation passage 50 formed in the bulging portion 5 by driving the oil pump disposed in the pump housing 28, and is pressure-fed to each portion in the engine main body 1.

The present embodiment can provide the following effects.

(1) Engine 100 as an internal combustion engine unit includes: an engine body 1, a balancer 2 attached to a lower portion of the engine body 1, and an oil pan 3 (fig. 1) attached to a lower portion of the engine body 1 so as to surround the balancer 2. A through hole 13 (oil outflow hole) for returning oil that lubricates the inside of the engine body 1 to the oil pan 3 is formed in the engine body 1, and the balancer 2 is disposed facing a discharge port 13h (outlet of the oil outflow hole) of the through hole 13 (fig. 2).

With this configuration, the inflow speed of the oil that lubricates the engine body 1 when returned to the oil pan 3, that is, the speed at which the oil discharged from the through hole 13 drips or flows down to the oil surface stored in the oil pan 3 can be suppressed without performing a drilling process or the like on the balancer 2. This prevents the stored oil from being foamed by air being entrained when the discharged oil drops or flows down to the oil pan 3. Further, it is possible to suppress the occurrence of noise when the discharged oil drops or flows down to the oil pan 3.

(2) The balancer 2 includes a bulging portion 5, and the bulging portion 5 bulges so as to intersect with an outflow direction (arrow a in fig. 2) in which the oil flows out from the through hole 13 (fig. 2). The bulging portion 5 is disposed facing the discharge port 13h of the through hole 13. This makes it possible to more effectively control the inflow speed of the oil that lubricates the engine body 1 when the oil is returned to the oil pan 3, that is, the speed of the oil that is discharged from the through hole 13 when the oil collides with the oil level stored in the oil pan 3.

(3) The balancer device 2 includes balancer shafts 20R and 20L and a housing 21 (fig. 1 and 2) rotatably supporting the balancer shafts 20R and 20L. The case 21 includes an upper case 21U and a lower case 21L which are vertically divided and coupled to each other, and the bulging portion 5 is provided in the lower case 21L (fig. 2 and 4). This allows the lower end of the bulging portion 5 to be disposed closer to the liquid surface of the oil stored in the oil pan 3. As a result, the stored oil can be more suppressed from foaming and generating sound.

(4) An oil circulation passage 50 (fig. 3) that is an oil passage for guiding the oil stored in the oil pan 3 to the engine main body 1 is formed inside the bulging portion 5. In other words, the bulging portion 5 is formed using a conventional member or portion that forms the oil circulation passage 50 for returning the oil stored in the oil pan 3 to the engine main body 1. Thus, the bubbling of oil and the generation of noise when the oil is returned to the oil pan 3 can be suppressed by a simple structure without providing a separate bulging portion.

(5) The bulge portion 5 is formed in a convex curved surface shape so that the oil flowing out from the through hole 13 flows along the outer peripheral surface of the bulge portion 5 (fig. 2). Thereby, the oil discharged from the through hole 13 smoothly flows downward along the outer surface of the bulge portion 5. As a result, the discharged oil can be prevented from dripping or running down to the oil pan 3 in the middle of the outer surface of the bulging portion 5.

(6) The bulging portion 5 is provided to bulge further downward (fig. 2). This makes it possible to bring the bulging portion 5 closer to the liquid surface of the oil pan 3, and to more effectively suppress the oil stored in the oil pan 3 from bubbling and generating sound.

(7) The balancer 2 has a guide portion 6 (fig. 2) above the bulging portion 5 for guiding the oil flowing out of the through hole 13 to the bulging portion 5. A gap is provided between the guide portion 6 and the bulging portion 5 (fig. 2). This enables the oil discharged from the through hole 13 to be more reliably guided to the outer surface of the bulging portion 5. Further, even if the discharge port 13h of the through hole 13 and the bulging portion 5 are not located at the overlapping position in the viewing direction a of fig. 2, the oil discharged from the through hole 13 can be guided to the outer surface of the bulging portion 5.

(8) A communication hole 60 (through hole) communicating with the through hole 13 is provided in the guide 6 (fig. 2). The discharge port 63 of the communication hole 60 is provided facing the bulging portion 5 (fig. 2). This makes it possible to more reliably guide the oil discharged from the through hole 13 to the outer surface of the bulging portion 5 via the communication hole 60.

In the above embodiment, the case 21 having the bulging portion 5 and the guide portion 6 was used as the balancing device, but the case of the balancing device may be any case as long as it has the bulging portion. In the above embodiment, the bulging portion 5 is provided in the lower case 21L, but may be provided in the upper case 21U. In the above embodiment, the oil circulation flow path 50 is formed in the bulging portion 5, but the oil circulation flow path may not be formed in the bulging portion 5. In the above embodiment, the bulging portion is set to bulge leftward and downward, but the bulging portion 5 may only bulge leftward, that is, in a direction orthogonal to the oil discharge direction.

One or more of the above embodiments and modifications may be arbitrarily combined, or modifications may be combined with each other.

The present invention can effectively suppress an increase in the speed of oil when returning lubricating oil of an internal combustion engine main body to an oil pan while suppressing an increase in the number of processing steps.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the disclosure of the following claims.