JPH1162541A - Dry-sump lubrication type four cycle engine unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a lubricating oil tank attachable freely at the time when it is attached to an assembly consisting of a cylinder block and a halved crankcase. SOLUTION: A dry-sump lubrication type four cycle engine unit 3 equipped with a lubricating oil tank 61 at the outside is formed with both a first and second packing surfaces 61a and 61b in parallel with this lubricating oil tank each other. On the other hand, a tank mounting packing surface 22 is formed at the side of an assembly consisting of a cylinder block 12 and a halved crankcase 11 as well as a surface being orthogonal with a crankshaft 15, and the first packing surface of the lubricating oil tank is attached to this tank mounting packing surface, then a cover 63 is attached to the second packing surface of the lubricating oil tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of a dry sump lubricated four-stroke engine unit.

[0002]

2. Description of the Related Art In a dry sump lubrication system, lubricating oil is supplied to each lubricating portion of an engine from a lubricating oil tank provided outside a half crankcase, and excess lubricating oil is temporarily supplied to the bottom of the half crankcase. This is a lubrication system that collects and collects the lubricating oil into a lubricating oil tank quickly with a lubricating oil pump.
As a dry sump lubricated engine unit, for example,
JP-A-62-23514, "Engine Lubrication System"
According to FIG. 1 of the publication, the engine body 1
A lubricating oil tank 20 is attached to a side portion of the lubricating oil tank (a number is cited in the official gazette; the same applies hereinafter) and on a surface parallel to the crankshaft 8. According to this device, communication between the engine body 1 and the lubricating oil tank 20 can be established without a hose.

[0003]

In the above prior art,
Of the sides of the engine body 1, the surface parallel to the crankshaft 8 has many overhangs such as skirts, ribs, and bosses for attaching accessories, so that the mounting position of the lubricating oil tank 20 is restricted, and the degree of freedom in design is increased. Is small.

Accordingly, an object of the present invention is to allow a lubricating oil tank to be freely attached to an assembly comprising a cylinder block and a half crankcase.

[0005]

According to a first aspect of the present invention, there is provided a dry sump lubricated four-cycle engine unit having a lubricating oil tank outside a half crankcase. A first packing surface and a second packing surface which are parallel to each other, and a tank mounting packing surface on a side of an assembly composed of a cylinder block and a half crankcase, and on a surface orthogonal to the crankshaft. The first packing surface of the lubricating oil tank is mounted on the tank mounting packing surface, and a lid is mounted on the second packing surface of the lubricating oil tank.

[0006] Since the lubricating oil tank is mounted on a surface orthogonal to the crankshaft, which has few protruding portions such as skirts, ribs, and bosses for mounting auxiliary equipment, of the side of the assembly, There is little restriction on the mounting position, the degree of freedom in design is large, and machining of the lubricating oil tank mounting surface (packing surface) is easy. In addition, since the lubricating oil tank is mounted on the side of the assembly and on the surface orthogonal to the crankshaft, the lubricating oil tank is changed when a plurality of types of engines are produced such that the inclination of the cylinder axis is different from each other. Do not just change the assembly, or
Minimal changes are required, and design flexibility is great. Also, since there are many common parts for a plurality of types of engines, the cost of the mold can be reduced. Furthermore, since the first and second packing surfaces parallel to each other are formed on the lubricating oil tank, and the lid is attached to the second packing surface, the inside of the lubricating oil tank can be easily inspected.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a side view of a small boat equipped with a dry sump lubricated four-stroke engine unit according to the present invention. The small boat 1 indicated by imaginary lines is used for leisure or the like, and has an engine compartment of a hull 2. A dry-sump lubricated four-cycle engine unit 3 is mounted on 2a, and a jet pump 4 is driven by the engine unit 3. The jet pump 4 pressurizes water sucked from the bottom of the hull 2 and discharges the water backward as a jet stream. That will move you forward. 2d is a bulkhead, 2e is a sheet, 2f is a deck, 2g is a steering bar, 5 is a water supply port, 6 is a discharge nozzle, and 7 is a fuel tank.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, and shows an engine room 2a (formed by a lower hull 2b and an upper hull 2c).
Fig. 1 shows a state in which a dry sump lubricated four-cycle engine unit 3 is mounted. The engine unit 3 extends the crankshaft 15 in the front-rear direction of the small boat 1 (front and rear directions in the figure), inclines the cylinder axis L in the upper left direction in the figure, and shows a plurality of four front, rear, left and right mounts 8. The same shall apply hereinafter) is attached to the mounting base 2h of the lower hull 2b. Reference numeral 9 denotes a mount rubber.

FIG. 3 is a sectional view taken along the line 3-3 in FIG. 2, and shows a sectional structure of the engine unit 3 for taking out engine power toward the rear (left side in the figure) of the small boat 1. In this figure, the area around the suction pipe 72 and the suction oil passage 24a (the range indicated by reference numeral AA) is shifted from the line 3-3 in FIG. 2, but is the same cross section as other parts for convenience of explanation. Indicated by The engine unit 3 includes an engine body 10 and
Valve drive mechanism 4 attached to the front of engine body 10
0 and flywheel unit 50 and engine body 1
0 is a horizontal three-cylinder engine comprising a lubrication unit 60 attached to the rear of the engine.

The engine body 10 includes a half crankcase 11, a cylinder block 12 having three cylinders 12a in the front-rear direction, a cylinder head 13, a head cover 14, a lateral crankshaft 15, and a crankshaft. , A PTO shaft (power take-out shaft) 17 connected to the rear end of the crankshaft 15, and a valve chamber 1 formed by a cylinder head 13 and a head cover 14.
8 and the valve train mechanism 30 housed in the valve train chamber 18 are the main components. The PTO shaft 17 is connected to the lubrication unit 60
It extends further rearward (on the side opposite to the engine) and is connected to the drive shaft 4a of the jet pump 4 shown in FIG. 17a
Is a connecting portion connected to the crankshaft 15, and 17b is a connecting portion for taking out power, and these connecting portions 17a, 17b
Consists of a female screw or a female spline.

At the bottom of the half crankcase 11, three collecting portions 11a for collecting the lubricating oil remaining after lubricating the respective sliding portions are collected by these collecting portions 11a. A guide path 11b for guiding lubricating oil, and a guide path 11b
Oil passage 1 for returning lubricating oil from lubrication unit 60 to lubrication unit 60
1c. The collecting parts 11a approach the crankshaft 15 to such an extent that the accumulated lubricating oil does not contact the counterweight (web) of the crankshaft 15, and the baffle plates 21 between the crankshaft 15 and the lower oil surface. A partitioned, small-capacity oil sump. For this reason, the half crankcase 11 can be reduced in size because the bottom can be close to the crankshaft 15. As a result, when setting the mounting position of the engine unit 2 on the small boat 1 (see FIG. 2), the influence of interference between the bottom of the engine unit 2 and the boat bottom can be reduced. And, despite the small size of the half crankcase 11, the crankshaft 15 hardly comes into contact with the lubricating oil, the friction loss at the time of rotation is suppressed, and aeration (splashing of oil) occurs.
Is also prevented.

The valve drive mechanism 40 includes a crankshaft 1
5, a belt driving mechanism for driving the camshaft 31 of the valve mechanism 30. The driving pulley 41 is fixed to the crankshaft 15 projecting from the front side of the half crankcase 11.
A driven pulley 42 fixed to the camshaft 31 protruding from the front side of the cylinder head 13, and a timing belt 43 hung between the driving and driven pulleys 41, 42.
And a belt tensioner 44 for adjusting the tension of the timing belt 43. 45 is a belt cover.

The flywheel unit 50 includes a flywheel 51 bolted to the front end of the crankshaft 15 and a front side of an assembly comprising a cylinder block 12 and a half crankcase 11 for accommodating the flywheel 51. Wheel case 52 bolted to
And a flat lid 53 bolted to cover the open end (front end) of the wheel case 52. That is, the cylinder block 12 and the half crankcase 11
On the side of the assembly consisting of
The flywheel unit 50 is mounted on a surface perpendicular to the plane 5, and the flywheel unit 50 is located forward of the drive pulley 41 (opposite the cylinder block 12).
It is in.

Reference numeral 54 denotes a generator, which comprises a rotor 54a attached to the inner peripheral surface of the flywheel 51 and a coil 54b attached to the wheel case 52. 55 is a ring gear attached to the outer peripheral surface of the flywheel 51,
It is connected to a starter motor described later. 57 is an inspection cap for closing a hole for checking the crank angle.

The lubricating unit 60 includes the cylinder block 1
A lubricating oil tank 61 bolted to the rear side of an assembly including the crankcase 2 and the half crankcase 11; a lid 63 closing an open end (rear end) of the lubricating oil tank 61; 11 to the lubricating oil tank 61
A return pump 64 for returning the lubricating oil to the engine, a supply pump 65 for supplying the lubricating oil from the lubricating oil tank 61 to each sliding portion of the engine body 10, and a pipeline. The return pump 64 is a pump built in the lubricating oil tank 61 and a supply pump 65
Is a pump independent of the lubricating oil tank 61.

More specifically, a tank mounting packing surface (flange) 22 is formed on a side portion of an assembly including the cylinder block 12 and the half crankcase 11 and on a surface orthogonal to the crankshaft 15. On the other hand, the first packing surface (flange) 6
1a and a second packing surface (flange) 61b were formed. The second packing surface 61b is located behind the first packing surface 61a (in a direction away from the cylinder block 12 toward the PTO shaft 17). And the tank mounting packing surface 22
The lubricating oil tank 61 is attached to an assembly composed of the cylinder block 12 and the half crankcase 11 with the first packing surface 61a aligned via the packing 23 and the second packing surface 61b via the packing 62. The cover 63 is fitted and bolted. Such a lubricating oil tank 61 is a sealed tank that stores the lubricating oil by being sealed with the side wall of the assembly and the lid 63.

The return pump 64 includes a case portion 61c formed integrally with the lubricating oil tank 61, an inner cover 64a closing the case portion 61c, an inner rotor 64b and an outer rotor 64c housed in the case portion 61c, and these inner and outer rotors 64c. A shaft 64f connected to the crankshaft 15 via a drive mechanism (comprising a drive gear 64d and a driven gear 64e) to drive the outer rotors 64b, 64c.
And a scavenging pump. The drive mechanism is housed in a space 66 between the lubricating oil tank 61 and the assembly. The space 66 also serves as a part of a breather passage for communicating the valve chamber 18 with the crank chamber 19. 67 is a bolt for attaching the inner cover 64a to the case 61c.

The supply pump 65 includes a case body 65a bolted to a side of an assembly including the cylinder head 13 and the head cover 14, a cover 65b closing the case body 65a, and an inner rotor 65c housed in the case body 65a. And a shaft 65e that is directly connected to the camshaft 31 of the valve mechanism 30 to drive the inner and outer rotors 65c and 65d. The shaft of the return pump 64 and the shafts 64f and 65e of the supply pump 65 are connected to the crankshaft 15
And extends parallel to the camshaft 31. An assembly composed of the cylinder block 12 and the cylinder head 13 includes a suction oil passage 24a and a discharge oil passage 24b for the supply pump 65.
(See FIG. 7). Incidentally, 58, 58 are hangers.

FIG. 4 is a sectional view of the engine body according to the present invention, showing the engine body 10 in which the cylinder axis L is inclined in the upper left direction in the figure. The valve operating mechanism 30 includes a camshaft 31
And rocker shafts 32, 32 and rocker arms 33, 33
And an intake valve 34 and an exhaust valve 35. The cylinder head 13 includes an intake passage 13a and an exhaust passage 13b, and a floatless diaphragm carburetor 82 communicates with the intake passage 13a via an intake pipe 81.
An exhaust passage 12b of the cylinder block 12 communicates with 3b. The head cover 14 has a first breather chamber 18a for recirculating blow-by gas above the valve operating chamber 18.

Each baffle plate 21 is fixed to the half crankcase 11 and partitions a range corresponding to the downstream side (left side in the drawing) in the rotation direction of the crankshaft 15. One portion is locked to the bottom of the crankcase 11 with a locking projection 11d for preventing rotation, and the other portion is fixed by bolting. Note that the entire necessary range may be partitioned by one baffle plate. 26 is a supply oil passage, and the discharge oil passage 24
b (see FIG. 7) and the supply pump 6 via the filter 25
5 (see FIG. 7), which is an oil passage for supplying lubricating oil to each sliding portion of the engine body 10. 27 is an oil return tube for returning lubricating oil from the valve operating chamber 18 to the crank chamber 19;
In the present embodiment, the nozzle 13c of the cylinder head 13
And the nozzle 11 in the lower half of the half crankcase 11
e, the collection unit 11a and the guiding unit 11
b. Reference numeral 28 denotes a communication passage that communicates the valve chamber 18 with the crank chamber 19. Reference numeral 11f denotes a drain hole for extracting drain from the collection unit 11a, and 12c... Denote cooling water passages.

FIG. 5 is an exploded plan view of the lubricating oil tank and the lid according to the present invention, and shows an axis S direction of the crankshaft 15 (crankshaft 15) along an assembly composed of the cylinder block 12 and the half crankcase 11. This indicates that the lubricating oil tank 61 swells in the direction in which the lubricating oil extends, and that the lubricating oil is also stored in the bulging portion 61d. In the lubricating oil tank 61, since the lubricating oil can be stored also in the bulging portion 61d along the assembly, the lubricating oil tank 61 having the same capacity can be stored.
Even in this case, the front-rear dimension and the vertical dimension can be reduced, so that the engine unit 3 can be reduced in size. In the figure, 61
r is a lubricating oil supply port cap, 68 is a bolt for attaching the lubricating oil tank 61 to the half crankcase 11 and the cylinder block 12, and 69 is a bolt for attaching the lid 63 to the lubricating oil tank 61.

FIG. 6 shows a dry sump lubrication type 4 according to the present invention.
FIG. 3 is a rear view of the cycle engine unit with a lubricating oil tank removed, and shows a tank mounting packing surface 22 of an assembly including a cylinder block 12 and a half crankcase 11.
Indicates that it is open. .., 29A, 29B,... Are breather passages through a space surrounded by the tank mounting packing surface 22 (corresponding to the space 66 shown in FIG. 3).
The valve chamber 18 communicates with the crank chamber 19.
That is, the breather passage 29A and the breather passage 29B ...
Is in communication with Reference numeral 56 denotes a starter motor.
The engine unit 3 is started by rotating the flywheel 51 via a ring gear 55 shown in FIG. By connecting the intake muffler box 83 to the carburetor 82, the intake pipe 81, the carburetor 82 and the intake muffler box 83 form an intake line of the engine body 10. 83a is an intake port, and 84 is a bolt for attaching the intake muffler box 83 to the mount 8.

FIG. 7 shows a dry sump lubrication type 4 according to the present invention.
FIG. 5 is a rear view of the cycle engine unit with a lid for a lubricating oil tank removed, showing a second packing surface 61 of the lubricating oil tank 61;
b indicates that it is open. Lubricating oil tank 61
Is a suction oil passage 61e and a discharge oil passage 61f for the return pump 64, an oil reservoir 61g connected to the bulging portion 61d (see FIG. 5) for storing lubricating oil, and a second oil reservoir 61g higher than the oil reservoir 61g. The breather chamber 61h and the engine exhaust port 61i are integrally formed. Engine exhaust port 61i
Is an exhaust port that communicates the exhaust passage 12b shown in FIG. 6 with an external exhaust pipe. The suction oil passage 61e and the oil reservoir 61g are located at left and right positions so as to straddle the PTO shaft 17, and the return pump 64 and the supply pump 65 are located at positions passing through the cylinder axis L. A return pump 64 is provided above the return pump 17, and a supply pump 65 is provided above the return pump 64.

A suction pipe 72 with a strainer 71 for the supply pump 65 is accommodated in the oil reservoir 61g, and the upper end of the suction pipe 72 communicates with the suction oil passage 24a for the supply pump 65 (see FIG. 3). In the figure, 9a is a mounting bolt, 61
m ... are oil scattering prevention baffle walls provided in three stages vertically in the oil sump 61g, and 61n is a cooling water passage 1 shown in FIG.
A cooling water port communicating with the external cooling pipe 2c. Reference numeral 75 denotes a third breather tube which connects the lubricating oil tank 61 to the valve operating chamber 18 (see FIG. 3) via the gas port 61q.

FIG. 8 is a cross-sectional view of the lubricating oil tank according to the present invention. The bulging portion 61d of the lubricating oil tank 61 bulges along the assembly composed of the cylinder block 12 and the half crankcase 11. Show the shape. The bulging portion 61d is disposed above the position of the suction port of the strainer 71, so that even when the engine unit 3 is tilted due to the movement of the hull 2 (see FIG. 2), the suction port remains in the oil. It is considered as it is. The second breather chamber 61h has a labyrinth structure, and details thereof will be described with reference to FIG. In the figure, 12d is the wall of the cylinder block 12, 61
s is the wall of the lubricating oil tank 61, 61t is the inclined bottom of the bulging portion 61d, 71a is the support stay of the strainer 71, 73
Is a first breather tube. Reference numeral 76 denotes an oil return tube which plays a role of returning lubricating oil from the second breather chamber 61h to the crank chamber 19 via the wall 61s.

FIG. 9 is a perspective sectional view of the second breather chamber according to the present invention, showing three partition walls 61 of a lubricating oil tank 61.
o ... and the three partition walls 63a ... of the lid 63
The breather room 61h is divided into three rooms, and each of the partition walls 61 is further divided.
small notches 61p, 63b ... alternately in o ..., 63a ...
Indicates that the second breather chamber 61h has a labyrinth structure. The second breather chamber 61h includes a gas inlet 61j and a gas outlet 61k. Gas inlet 61j
Communicates with the first breather chamber 18a (see FIG. 4) via the first breather tube 73. Gas outlet 6
1k communicates with the upstream of the carburetor 82 (the communication pipe between the intake muffler 83 and the carburetor 82) via the second breather tube 74.

Next, the operation of the dry sump lubricated four-stroke engine unit having the above configuration will be described with reference to FIGS. The return pump 64 of FIG.
a. The lubricating oil collected in a...
c → intake oil passage 61e → return pump 64 → discharge oil passage 61f in FIG.
7 supplies the lubricating oil accumulated in the oil sump 61g to the strainer 71 → the suction pipe 72 → the suction oil passage 24a →
Supply pump 65 → discharge oil passage 24b → filter 25 in FIG.
→ The oil is supplied to each sliding portion of the engine body 10 through the supply oil passage 26. The lubricating oil remaining after lubricating each sliding part is shown in FIG.
The oil returns to the crank chamber 19 through the oil return tube 27 and is collected in the lubricating oil tank 61 through the return path.

The lubricating oil tank 61 shown in FIG.
Can be freely exchanged according to the installation condition of the device. For example, as shown in FIGS.
Can be a modified example in which the direction of the cylinder axis L is changed.

FIG. 10 is a rear view of a dry sump lubricated four-stroke engine unit (modification) according to the present invention, and shows a state in which an engine body 10 having a cylinder axis L inclined in the upper right direction in the figure is mounted on a small boat 1. . In this case,
An electronically controlled fuel injection device is installed instead of the intake system including the diaphragm type carburetor 82 and the intake muffler box 83 shown in FIG. The electronic control fuel injection device includes a throttle body 91, an acceleration pump 92, an injection valve 93, a control computer (not shown), and the like. The position of the throttle body 91 can be freely set by drawing the intake pipe 81 in accordance with the space of the narrow engine room 2a.

FIG. 11 is a rear view of the dry-sump lubricated four-stroke engine unit (modification) according to the present invention with the lubricating oil tank removed, and shows a state where the tank mounting packing surface 22 is inclined in the upper right direction in the figure. As described above, the engine unit 3 is configured such that the cylinder axis L shown in FIG. 2 is inclined in the upper left direction in the figure and the cylinder axis L shown in FIG.
Can be used in common with the case where is inclined in the upper right direction in the figure. In addition, since the cylinder axis L is inclined in the upper right direction in the figure, the communication path 28 shown in FIG. 4 is inclined obliquely downward, and serves as an oil return path for returning lubricating oil from the valve operating chamber 18 into the crank chamber 19. Fulfill. For this reason, the oil return tube 27 is unnecessary.

FIG. 12 is a rear view of the dry sump lubricated four-stroke engine unit (modification) according to the present invention, in which a lid for a lubricating oil tank is removed. This shows a state where the left and right sides are exchanged. In this case, there is no need to change the assembly composed of the cylinder block 12 and the half crankcase 11 shown in FIG. Also, for a relatively large mold for molding the half crankcase 11 and the cylinder block 12,
Since a relatively small mold such as the lubricating oil tank 61 can be used, the mold cost can be reduced.

In the above embodiment of the present invention,
The engine unit 3 does not limit the number of cylinders,
For example, four cylinders may be used. The lubricating oil tank 61 is provided at least on the side of the assembly including the cylinder block 12 and the half crankcase 11 and on the crankshaft 15.
What is necessary is just to be attached to the surface orthogonal to. For example, in the assembly, the valve drive mechanism 40 and the flywheel unit 50 are mounted on the side where the PTO shaft 17 projects, and the lubrication unit 60 is mounted on the side in the opposite direction (the right side in FIG. 3). In that case, the lubricating oil tank 61 is
Turn forward.

[0033]

According to the present invention, the following effects are exhibited by the above configuration. An invention according to claim 1 is a dry sump lubrication type four-stroke engine unit including a lubricating oil tank outside a half crankcase, wherein a first packing surface and a second packing surface are formed parallel to each other in the lubricating oil tank, On the other hand, a tank mounting packing surface is formed on the side of the assembly including the cylinder block and the half crankcase, and on a surface orthogonal to the crankshaft, and the first packing surface of the lubricating oil tank is formed on the tank mounting packing surface. And attach
A lid is attached to the second packing surface of the lubricating oil tank.

Since the lubricating oil tank is mounted on a surface orthogonal to the crankshaft, which has few overhangs such as skirts, ribs, and bosses for mounting auxiliary equipment, on the side of the assembly, There is little restriction on the mounting position, the degree of freedom in design is large, and machining of the lubricating oil tank mounting surface (packing surface) is easy. In addition, since the lubricating oil tank is mounted on the side of the assembly and on the surface orthogonal to the crankshaft, the lubricating oil tank is changed when a plurality of types of engines are produced such that the inclination of the cylinder axis is different from each other. Do not just change the assembly, or
Minimal changes are required, and design flexibility is great. Also, since there are many common parts for a plurality of types of engines, the cost of the mold can be reduced. Furthermore, since the first and second packing surfaces parallel to each other are formed on the lubricating oil tank, and the lid is attached to the second packing surface, the inside of the lubricating oil tank can be easily inspected.

[Brief description of the drawings]

FIG. 1 is a side view of a small boat equipped with a dry sump lubricated four-stroke engine unit according to the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a sectional view of an engine body according to the present invention.

FIG. 5 is an exploded plan view of a lubricating oil tank and a lid according to the present invention.

FIG. 6 is a rear view of the dry-sump lubricated four-stroke engine unit according to the present invention with the lubricating oil tank removed.

FIG. 7 is a rear view of the dry sump lubricated four-stroke engine unit according to the present invention with a lid for a lubricating oil tank removed.

FIG. 8 is a sectional view of a lubricating oil tank according to the present invention.

FIG. 9 is a perspective plan sectional view of a second breather chamber according to the present invention.

FIG. 10 is a rear view of a dry sump lubricated four-stroke engine unit (modified example) according to the present invention.

FIG. 11 is a rear view of the dry sump lubricated four-stroke engine unit (modified example) according to the present invention with the lubricating oil tank removed.

FIG. 12 is a rear view of a dry sump lubricated four-stroke engine unit (variation example) according to the present invention with a lid for a lubricating oil tank removed.

[Explanation of symbols]

1 ... Small boat, 3 ... 4-cycle engine unit, 10 ...
Engine body, 11: half crankcase, 12: cylinder block, 15: crankshaft, 17: PTO
Shaft, 22: packing surface for tank mounting, 60: lubrication unit, 61: lubricating oil tank, 61a: first packing surface, 6
1b: second packing surface, 63: lid.

Claims (1)

[Claims] 1. A dry sump lubricated four-stroke engine unit having a lubricating oil tank outside a half crankcase, wherein the lubricating oil tank has a first packing surface and a second packing surface parallel to each other, A tank mounting packing surface is formed on a side of an assembly including a cylinder block and a half crankcase, and on a surface orthogonal to the crankshaft, and the first packing surface of the lubricating oil tank is formed on the tank mounting packing surface. A dry sump lubricated four-stroke engine unit, wherein a lid is attached to a second packing surface of the lubricating oil tank.