Vertical internal combustion engine

A water-cooled 4-stroke cycle internal combustion engine for propelling ships having a cylinder head and a cylinder block. The engine including a plurality of connecting bolts for detachably connecting the cylinder head with the cylinder block arranged around a cylinder with substantially equal distances from a center axis of the cylinder; an exhaust passage formed in the cylinder head positioned on one side of the cylinder, opening on a connecting face to the cylinder block; a cooling water passage disposed around the exhaust passage in the cylinder head, opening on the connecting face; an exhaust passage formed in the cylinder block positioned on the above-mentioned one side of the cylinder, opening on a connecting face to the cylinder head to communicate with the exhaust passage in the cylinder head; a cooling water passage disposed around the exhaust passage in the cylinder block, opening on the connecting face to the cylinder head to communicate with the cooling water passage in the cylinder head; a lubricating oil passage formed in the cylinder head positioned on another side of the cylinder, opening on the connecting face to the cylinder block; and a lubricating oil passage formed in the cylinder block positioned on the above-mentioned another side of the cylinder, opening on the connecting face to the cylinder head to communicate with the lubricating oil passage in the cylinder head.

BACKGROUND OF THE INVENTION 
The present invention relates to a vertical internal combustion engine 
having a crankshaft directed substantially in a vertical direction, 
particularly a vertical internal combustion engine for an outboard motor. 
In a 4-stroke cycle vertical internal combustion engine disclosed in 
Japanese Laid-Open Patent Publication No. Hei 7-149290, a flywheel is 
provided on a lower end of a crankshaft directed in a vertical direction 
integrally and a lubricating oil pump is disposed above the flywheel. 
Further, at a position above the flywheel, a drive gear is provided on the 
crankshaft integrally and a speed increasing mechanism is interposed 
between the drive gear and the lubricating oil pump so that the 
lubricating oil pump is rotationally driven at a higher speed than that of 
the crankshaft. 
In a 4-stroke cycle vertical internal combustion engine disclosed in 
Japanese Laid-Open Patent Publication No. Hei 8-100616, a lubricating oil 
pump is directly connected to a lower end of a cam shaft directed 
vertically. 
According to the engine disclosed in the above-mentioned Japanese 
Publication No. Hei 7-149290, since the lubricating oil pump rotates at a 
higher speed than the crankshaft, even if the lubricating oil pump is 
small-sized, a high discharge ability is obtainable, however, owing to the 
lubricating oil pump positioning below a bearing portion of the internal 
combustion engine for pivotally supporting the crankshaft, a part of the 
crankshaft extending downward from the bearing portion becomes long so 
that it is difficult to support the flywheel having a large inertial mass 
stably from a viewpoint of vibration. 
According to the engine disclosed in the above-mentioned Japanese 
Publication No. Hei 8-100616, since no lubricating oil pump is disposed 
above the flywheel, the flywheel can be arranged near the internal 
combustion engine and as the result the flywheel having large inertial 
mass can be supported stably. However, since rotational speed of the cam 
shaft is a half of that of the crankshaft, there are inconveniences that 
the discharge ability is low and the lubricating oil pump becomes large 
necessarily. 
Some vertical internal combustion engines for outboard motors in which 
balancer shafts are used for reducing vibration are disclosed in Japanese 
Laid-Open Patent Publications Nos. Sho 63-192693, Hei 3-224894 and Hei 
4-337143. 
The Japanese Publication 63-192693 and 3-224894 disclose balancer 
mechanisms for offsetting and reducing the primary vibration in an in-line 
2-cylinder 4-stroke cycle internal combustion engine. 
On the one hand, the Japanese Publication 4-337143 discloses a balancer 
mechanism in a 4-stroke cycle in-line 4-cylinder engine which aims at 
reducing the secondary vibration because the engine has an advantage that 
the primary vibration does not occur fundamentally. However, as secondary 
vibration becomes larger, the balancer becomes large-sized more and it 
becomes necessary to care about balancer shaft supporting constructions 
and lubricating passages. 
The Japanese Laid-Open Patent Publication No. Hei 3-33416 discloses a 
water-cooled 4-stroke cycle internal combustion engine for propelling 
ships in which a suction system is arranged on one side and an exhaust 
system and a cartridge type oil filter are arranged on another side. As 
shown in FIG. 8 of the above publication, lubricating oil having passed 
through the oil filter is supplied to a cam shaft pivot portion through 
some oil passages to lubricate the cam shaft pivot portion. 
In a water-cooled 4-stroke cycle internal combustion engine for propelling 
ships disclosed by the Japanese Laid-Open Patent Publication No. 
Hei-8-100616 too, a lubricating oil passage connected between an oil 
filter disposed near a suction system on a front face of a crankcase and a 
valve moving system is arranged on the side of an exhaust system. 
However, in the internal combustion engine of the publication 3-33416, an 
electric parts box as well as the oil filter cartridge is disposed on the 
side of the exhaust system and therefore if the electric parts box becomes 
large for meeting demands to electric control system, it is difficult to 
dispose the oil filter cartridge at the same position. 
In the internal combustion engine of the publication 8-100616, the oil 
filter is disposed on a front face of the crankcase and maintenance work 
is easy. But since an oil passage for lubricating oil after passing 
through the oil filter is provided in a exhaust system, the oil passage is 
long to increase flow resistance, capacity of the oil pump has to be 
improved and amount of oil is necessarily increased. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a vertical 4-stroke cycle 
internal combustion engine enabling a better arrangement of a flywheel and 
a lubricating oil pump. Another object of the present invention is to 
provide an outboard motor having such an internal combustion engine 
mounted. Further object of the present invention is to provide such an 
internal combustion engine having a lubricating device suitable for 
providing a balancer mechanism. 
According to the present invention, there is provided an vertical internal 
combustion engine having a crankshaft directed substantially in a vertical 
direction, a flywheel provided on a lower end of the crankshaft integrally 
and an oil pan provided under the flywheel, wherein a lubricating oil pump 
driven by the crankshaft to rotate is disposed under the flywheel. 
The flywheel is positioned close by the main body of the internal 
combustion engine so that the flywheel is supported stably irrespective of 
any variation of its rotational speed. 
In the above internal combustion engine, a rotor of the lubricating oil 
pump may be positioned on a lower production of the crankshaft and driven 
to rotate together with the crankshaft. According to this engine, a 
driving system of the lubricating oil pump can be simplified and weight 
lightening and cost down can be intended. In addition, because the 
lubricating oil pump can be rotated at the same rotational speed as the 
crankshaft, discharge ability of the lubricating oil pump can be improved 
without making the lubricating oil pump large-sized. 
According to another aspect of the present invention, there is provided a 
4-stroke cycle vertical internal combustion engine, having an internal 
combustion engine main body housing a crankshaft directed substantially in 
a vertical direction; a flywheel provided on a lower end of the crankshaft 
integrally; an oil pump body forming a flywheel chamber for housing the 
flywheel; a oil pan disposed below the flywheel; a mount case separated 
from the oil pump body and having a return oil passage arranged below the 
oil pump body for returning lubricating oil from the internal combustion 
engine main body to the oil pan and a lubricating oil passage for 
gathering lubricating oil which has lubricated the crankshaft from a 
periphery of the pump body toward a center of the crankshaft and returning 
the lubricating oil to the oil pan; and a lubricating oil pump disposed 
under the oil pump body. 
According to this engine, when the lubricating oil pump is disassembled for 
maintenance, the flywheel and the oil pump body are not required to be 
removed, so that disassembling and assembling work can be carried out 
efficiently and easily. 
Further, since the flywheel chamber can be closed, adhesion of lubricating 
oil to the flywheel can be prevented so that a loss of power and 
deterioration of the lubricating oil can be avoided. 
The mount case may be connected to an under surface of the internal 
combustion engine main body oil-tightly surrounding the oil pump body to 
enable smoother return of the lubricating oil. 
By using the above vertical internal combustion engine of the present 
invention as an engine for an outboard motor having cylinders arranged 
substantially along a lengthwise plane of a ship, it is possible to lower 
the center of gravity of the outboard motor by lowering position of the 
internal combustion engine for improving stability of the ship. 
According to the other aspect of the present invention, there is provided a 
vertical internal combustion engine having a crankshaft directed 
substantially in a vertical direction and a plurality of cylinders 
arranged along a vertical plane including the crankshaft, comprising a 
pair of balancer shafts connected to the crankshaft to be driven, 
pivotally supported in a cylinder block and disposed in parallel with the 
crankshaft on both sides of the cylinders; pivot holes for pivotally 
supporting the balancer shaft formed at uppermost and middle crankshaft 
supporting portions of the cylinder block passing through the crankshaft 
supporting portions; a work hole for working the pivot holes formed at a 
lowermost crankshaft supporting portion of the cylinder block positioned 
on a center line of the pivot holes; and a plug closing the work hole 
tightly. 
In this vertical internal combustion engine, the balance shaft extends as 
long as the crankshaft to absorb inertia forces and unbalanced moments of 
inertia in each of the cylinders arranged vertically so that vibration of 
the internal combustion engine can be reduced sufficiently. Since the 
balancer shafts are disposed on both sides of the cylinders, the internal 
combustion engine can be miniaturized in its entirety. 
Further, since the balancer shaft pivot holes and the work hole are 
provided in parallel with the crankshaft passing through the cylinder 
block, these holes can be machined easily. A tip end of a finishing tool 
is guided and supported by the work hole so that work for finishing the 
balancer shaft pivot holes can be carried out surely and efficiently. 
In the above-mentioned vertical internal combustion engine, a lubricating 
oil supply means may be provided at the pivot hole of the uppermost 
crankshaft supporting portion. In this engine, lubricating oil supplied to 
the uppermost balancer shaft pivot hole goes down by gravity, after it 
lubricates the uppermost balancer shaft pivot hole and the balancer shaft, 
to lubricate the middle balancer shaft pivot holes arranged above and 
below in turn so that each balancer shaft can be lubricated by only one 
lubricating oil supply means surely and the lubricating supply 
construction of the balancer shaft is significantly simplified to enable 
cost down. 
According to the above-mentioned vertical internal combustion engine 
wherein the lowermost crankshaft supporting portion is divided into an 
upper wall and a lower wall between which an oil passage space is 
interposed, the lower wall extends radially slanting downward and only the 
work hole of the lower wall is closed by the plug, the lubricating oil 
going down through a space within the cylinder block is led into the oil 
passage space from an upper surface of the divided upper wall through the 
work hole thereof, then flows in a radial direction along an upper surface 
of the divided lower wall to flow down to a periphery of the mount case. 
Further, a balancer shaft driving means for transmitting power from the 
crankshaft to the balancer shaft can be disposed so as not to interfere 
with the flywheel and the power shaft under the cylinder block as well as 
the lubricating oil. 
According to a further aspect of the present invention, there is provided a 
water-cooled 4-stroke cycle internal combustion engine for propelling 
ships having a cylinder head and a cylinder block, comprising a plurality 
of connecting bolts for detachably connecting the cylinder head with the 
cylinder block arranged around a cylinder with substantially equal 
distances from a center axis of the cylinder; an exhaust passage formed in 
the cylinder head positioned on one side of the cylinder, opening on a 
connecting face to the cylinder block; a cooling water passage disposed 
around the exhaust passage in the cylinder head, opening on the connecting 
face; an exhaust passage formed in the cylinder block positioned on the 
above-mentioned one side of the cylinder, opening on a connecting face to 
the cylinder head to communicate with the exhaust passage in the cylinder 
head; a cooling water passage disposed around the exhaust passage in the 
cylinder block, opening on the connecting face to the cylinder head to 
communicate with the cooling water passage in the cylinder head; a 
lubricating oil passage formed in the cylinder head positioned on another 
side of the cylinder, opening on the connecting face to the cylinder 
block; and a lubricating oil passage formed in the cylinder block 
positioned on the above-mentioned another side of the cylinder, opening on 
the connecting face to the cylinder head to communicate with the 
lubricating oil passage in the cylinder head. 
The periphery of the exhaust passage which is heated by exhaust passing 
through is cooled by the cooling water passage to suppress heat transfer 
to other parts of the cylinder head and the cylinder block, and 
temperature rising of the lubricating oil in the lubricating oil passage 
arranged on the side opposite to the exhaust passage can be prevented 
considerably. 
Further, even if the connecting faces of the cylinder head and the cylinder 
block become narrow as a result of cylinder diameter being increased for 
improving output of the internal combustion engine, the cylinder head and 
the cylinder block are connected uniformly by the connecting bolts 
arranged around the cylinder with substantially equal distances from a 
center axis of the cylinder so that tightness of a gasket inserted between 
the connecting faces is kept at a predetermined high level all over the 
peripheral edge round the cylinder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The drawings show a preferred embodiment of the present invention. 
The vertical internal combustion engine 1 according to the present 
invention is a in-line 4-cylinder, water-cooled, 4-stroke cycle internal 
combustion engine which has a crankshaft 30 directed vertically and 
cylinders 32 directed rearward with respect to a ship body. As shown in 
FIG. 1, the engine 1 is mounted on an outboard motor 0 which has a main 
case comprising an engine cover 2 covering the vertical internal 
combustion engine 1, an extension case 3 and a gear case 4. Under the 
vertical internal combustion engine 1, a mount case 5 and a oil pan 6 are 
piled in order and integrally connected to the vertical internal 
combustion engine 1. 
The outboard motor 0 is attached to a stern 19 of a motorboat not shown by 
means of an attachment device 7 which comprises a bracket 8 fixed to the 
stern 19, a tilt shaft 9 laterally laid on an upper end of the bracket 8, 
a swivel case 10 having a front end pivoted on the tilt shaft 9 so as to 
swing vertically, and connecting means 11 provided at upper and lower 
parts of a revolving portion of the swivel case 10 and having mounts M. 
A steering handle not shown is provided at the revolving portion of the 
swivel case 10 and the swivel case is revolved right and left together 
with the outboard motor 0 when the steering handle is operated to swing 
right and left. 
To a lower end of the crankshaft directed vertically is integrally 
connected a driving shaft 12 which extends within the extension case 2 
downward and reaches the interior of the gear case 4. A lower end of the 
driving shaft 12 is connected to a propeller shaft 14 through an 
ahead-astern change over device 13 in the gear case 4. Therefore, power of 
the vertical combustion engine 1 is transmitted to the propeller 15 
through the crankshaft 30, the driving shaft 12, the ahead-astern change 
over device 13 and the propeller shaft 14 to drive the propeller 15 
rotationally. 
A normal-reverse manipulating shaft 16 extends downward passing through the 
swivel case 10 vertically and reaches the ahead-astern change over device 
13. When a manipulating lever 17 at an upper end of the normal-reverse 
manipulating shaft 16 is swung right and left, the ahead-reverse change 
over device 13 is changed over to rotate the propeller 15 in a normal or 
reverse direction. 
The main body of the vertical internal combustion engine 1 is constituted 
of a crankcase 20, a cylinder block 21, a cylinder head 22, a head cover 
23, the mount case 5 and the oil pan 6. These crankcase 20, cylinder block 
21, cylinder head 22 and head cover 23 are arranged from front to rear in 
order with respect to the ship body, and connected to each other in one 
body by bolts 24, 25, 26, 28 as shown in FIGS. 6 to 9. As mentioned above, 
at under surfaces of the crankcase 20 and the cylinder block 21, the mount 
case 5 and the oil pan 6 are integrally connected to the crankcase 20 and 
the cylinder block 21 by bolts not shown. 
As shown in FIG. 4, the crankshaft 30 directed vertically is rotationally 
supported at crankshaft supporting portions 103 of the crankcase 20 and 
the cylinder block 21 by journal bearings 31. cylinders 32 directed 
horizontally in front-rear directions are disposed at regular intervals in 
a vertical direction. A piston 33 is fitted to each of the cylinders 3 to 
slide and connected to the crankshaft 30 by means of a connecting rod 34 
so that reciprocation of the piston 33 causes the crankshaft 30 to be 
driven to rotate clockwise as viewed from above. 
As shown in FIGS. 7 to 10, within a valve moving chamber 35, a cam shaft 
holder 36 is attached to a top face (rear face with respect to the ship 
body) of the cylinder head 22 and a cam shaft 38 is rotationally supported 
between the cam shaft holder 36 and the cylinder head 22 by a journal 
bearing 37. At the right and left with respect to the ship body of the cam 
shaft 38 are supported on the cam shaft holder 36 rocker shafts 39, 40 
parallel with the cam shaft 38. On the rocker shafts 39, 40 are pivoted so 
as to swing rocker arms 41, 42 having tip ends contacted with an intake 
valve 43 and an exhaust valve 44 respectively. The cam shaft 38 is driven 
to rotate at a half numbers of revolution compared with the crankshaft 30. 
By a valve moving device 55 which is mentioned in the later part, the 
intake valve 43 and the exhaust valve 41 are driven to open and close 
intermittently every two revolutions of the crankshaft 30. 
As shown in FIG. 8, an intake passage 45 opened and closed by the intake 
valve 43 is connected with a lower stream end of an intake manifold 47 
positioned on the right side with respect to the ship body (left side in 
FIG. 2). An upper stream end of the intake manifold 47 is connected with 
an intake chamber 49 through a throttle valve 49. The intake chamber 49 
has an intake aperture (not shown) opening within the engine cover 2 so 
that air inhaled into the engine cover 2 through an intake aperture 2a 
(FIG. 1) is introduced into the intake chamber 49 and then to the intake 
passage 45 through the throttle valve 48 and the intake manifold 47. 
An exhaust passage 46 opened and closed by the exhaust valve 44 is directed 
to the left side with respect to the ship body (right side in FIG. 8), 
bent at a lower stream end toward the cylinder block 21 (toward the front 
with respect to the ship body) and connected to an exhaust passage 50 
directed in vertical direction within the cylinder block 21. As shown in 
FIGS. 11 and 12, the exhaust passage 50 opens to an exhaust hole 51 which 
communicates with an exhaust passage 52 of the mount case 5. 
To a lower end of the exhaust passage 52 is connected an upper end of an 
exhaust pipe 53 (FIG. 1) having a lower end opening within the extension 
case 3. Exhaust gas discharged into the extension case 3 from the exhaust 
pipe 53 passes through a space within the gear case 4 to be discharged 
into the water through an exhaust passage 54 (FIG. 1). 
The valve moving device 55 shown in FIG. 8 is disposed above the crankcase 
20 and the cylinder block 21. Namely, as shown in FIGS. 2 and 4, a drive 
pulley 56 is integrally fitted to an upper part of the crankshaft 30, a 
driven pulley 57 is integrally fitted to an upper end of the cam shaft 20, 
an idler pulley 58 is pivotally supported on the cylinder block 21 and an 
endless belt 59 is wound round these pulleys 56, 57 and 58. 
Further, as shown in FIGS. 2, 4 and 6, a balancer drive pulley 60 is 
integrally fitted to the crankshaft 30 at a position above the drive 
pulley 56, balancer driven pulleys 61, 62 are provided so as to rotate 
freely positioned on the right and left of the cylinder 32, an idler 
pulley 63 concentric with the above-mentioned idler pulley 58 is pivotally 
supported and an endless belt 64 is wound round these pulleys 60, 61, 62 
and 63. 
As shown in FIGS. 2 and 6, the balancer driven pulley 61 on the left side 
with respect to the ship body (right side in FIGS. 2, 6) is integrally 
fitted to the left side balancer shaft 65 pivotally supported in the 
cylinder block 21. The other balancer shaft 66 disposed symmetrically with 
the balancer shaft 65 about the cylinder 32 has a lower portion pivotally 
supported by the cylinder block 21 and an upper portion pivotally 
supported by a balancer supporting bracket 67 and a bracket cover 68 
attached to the bracket 67, and a drive gear 69 integral with the balancer 
shaft 66 and a driven gear 70 integral with the balancer driven pulley 62 
are engaged with each other so that the balancer shaft 65, 66 are driven 
to rotate with the same revolutional speed but in opposite directions. 
As shown in FIGS. 2 and 4, on an upper surface of the crankcase 20 are 
attached a bracket 71 having an end 71a on which an end 72a of an AC 
generator 72 is pivoted so as to swing. Another end portion 72a of the 
generator 72 is fitted movably in an arcuate groove 71b formed on another 
end portion of the bracket 71, and fixed to the bracket 71 by fixing means 
not shown. An endless belt 75 is wound round a drive pulley 73 integrally 
fitted to an upper end of the crankshaft 30 and a driven pulley 74 
integrally fitted to an upper end of a rotary shaft of the AC generator 
72. 
Further, as shown in FIGS. 4 and 5, a flywheel 76 is integrally fitted by 
bolts 78 to a lower end of the crankshaft 30 and a ring gear 77 is formed 
on a circumference of the flywheel 76. On a lower surface of the flywheel 
is attached a connecting member 79 to which an upper end of the 
above-mentioned driving shaft 12 is fitted by means of splines. The ring 
gear 77 is engaged with a drive pinion (not shown) disposed in an arcuate 
recess 80 formed on a lower surface of the cylinder block 21 as shown in 
FIGS. 11, 12. When the drive pinion is rotated by a starter motor S shown 
in FIG. 5, the ring gear 77, the flywheel 76 and the crankshaft 30 are 
driven to rotate. 
Next, the lubricating system of the vertical internal combustion engine 1 
will be described. 
As shown in FIG. 4, on lower surfaces of the crankcase 20 and the cylinder 
block 21 is provided an oil pump body 82 of an trochoid type lubricating 
oil pump 81 which has a rotor 83 integrally fitted to the connecting 
member 79, a pump chamber 84 closed by a lid 85 and a suction port 86 
opening downward. A suction pipe 88 having an upper end connected with the 
suction port 86 extends downward within the oil pan 6 passing through a 
return oil hole 116. A strainer 89 is connected to a lower end of the 
suction pipe 88. 
As shown in FIGS. 3, 5, 10 and 11, the lubricating oil pump 81 has a 
discharge port connected with a vertical oil passage 90 which is connected 
with a longitudinal horizontal oil passage 91 extending toward the 
crankcase in front and a longitudinal horizontal oil passage 92 within the 
crankcase in turn. To a front end of the longitudinal horizontal oil 
passage 92 is connected a lower end of a vertical oil passage 93 extending 
upward. An upper end of the vertical oil passage 93 is connected to a 
longitudinal horizontal oil passage 94 directed to the left (right in FIG. 
3). 
Further, as shown in FIGS. 3 and 9, a left end of a longitudinal horizontal 
oil passage 94 is connected to an intake portion 96 of an oil filter 95 
and a discharge portion 97 of the oil filter 95 is connected to a 
communication oil passage 98 directed to the left (right in FIG. 3) of the 
crankcase 20. 
The communication oil passage 98 communicates with a crankshaft oil passage 
99 directed vertically positioned at a center of the width and balancer 
shaft oil passages 100, 101 directed vertically positioned at right and 
left sides of the oil passage 99 respectively. 
As shown in FIGS. 7 and 10, a crankshaft oil passage 102 directed rearward 
horizontally is formed in each of the crankshaft supporting portions 103. 
A tip end of the crankshaft oil passage 102 communicates with the journal 
bearing 31 of the crankshaft 30, therefore the journal bearing 31 is 
lubricated with the lubricating oil pressurized and sent out by the 
lubricating oil pump 81, filtered by the oil filter 95 and brought through 
the above-mentioned oil passages. 
In the uppermost crankshaft supporting portion 103a are formed balancer 
shaft oil passages 104, 105 directed rearward horizontally through the 
crankcase 20 and the cylinder block 21. The balancer shaft oil passages 
194, 105 communicate with the above-mentioned balancer oil passages 100, 
101 at the front ends (lower ends in FIG. 10) and with the balancer shafts 
65, 66 at the rear ends (upper ends in FIG. 10). 
As shown in FIG. 6, a pivot portion 65a at the upper end of the balancer 
shaft 65 is lubricated by the lubricating oil discharged from the rear end 
of the balancer shaft oil passage 104. The lubricating oil drops by 
gravity after lubricating the upper end pivot portion 65a and reaches a 
pivot portion 65b at the lower end of the balancer shaft 65 to lubricate 
the pivot portion 65b. 
The rear end of the balancer shaft oil passage 105 is connected with the 
balancer shaft oil passage 106 in the cylinder block 21 and the balancer 
pivot bracket 67. The balancer shaft oil passage 106 is connected with the 
cam shaft oil passage 107 in the bracket cover 68 and the upper end of the 
cam shaft oil passage 107 is opened to the pivot portion 62a of the 
balancer driven pulley 62 to lubricate the pivot portion 62a too. 
As shown in FIG. 7, in an upper part of the cylinder block 21 is formed a 
cam shaft oil passage 17 directed obliquely rearward horizontally. The cam 
shaft oil passage has a front end connected with the Journal bearing 31a 
at the uppermost crankshaft supporting portion 103a and a rear end 
connected with a front end of a cam shaft oil passage 108 directed 
rearward horizontally. A rear end of the cam shaft oil passage 108 is 
connected with a cam shaft oil passage 109 in the cylinder head 22 through 
a communication passage 27 of the cylinder head 22 and a hole 26a of the 
bolt 26 for connecting the cylinder head 22 to the cylinder block 21. A 
rear end of the cam shaft oil passage 109 opens to the pivot portion 38a 
of the cam shaft 38. A rocker oil passage 110 opening to the pivot portion 
38a is formed in the cam shaft holder 36. 
Thus, a part of the lubricating oil supplied to the uppermost journal 
bearing 31a is sent to the pivot portion 38a of the cam shaft 38 through 
the cam shaft oil passages 107, 108 and 109 to lubricate the pivot portion 
38a. A part of the lubricating oil supplied to the pivot portion 38a is 
sent to center holes (not shown) of the rocker shafts 39, 40 through the 
rocker oil passage 110 and further to pivot portions (not shown) of the 
rocker arms 41, 42 to lubricate the pivot portions. 
As shown in FIGS. 5, 6, 14, 15 and 19, at vertically middle positions of 
the lowermost crankshaft supporting portions 103b in the crankcase 20 and 
the cylinder block 21, horizontal flat oil passage spaces 111a, 111b are 
formed (in the section of FIGS. 15, 16, only the flat oil passage space 
111b on the cylinder block 21 side is shown). Peripheries of the flat oil 
passage spaces 111a, 111b of the crankcase 20 and the cylinder block 21 
are bounded by partition walls 112a, 112b respectively, and as shown in 
FIGS. 12 and 14, the flat oil passage spaces 111a, 111b communicate with 
partitioned spaces 113a, 113b formed on the outside of the partition walls 
112a, 112b through return oil passages 114a, 114b. Under the partitioned 
spaces 113a, 113b are formed vertical communication holes 136a, 136b which 
communicate with a partitioned space 115 formed in the mount case 5 (FIGS. 
12, 13). Under the partitioned space 115 is formed a return oil hole 116 
communicating with a space within the oil pan. 
As shown in FIGS. 1 and 4, the valve moving chamber 35 surrounded by the 
cylinder head 22 and the head cover 23 communicates with an oil passage 
space 119 of the mount case 5 through a return oil hole 117 of the 
cylinder head 22 and a return oil passage 118 of the cylinder block 21, as 
well as through a communication pipe 120. The lower end of the oil passage 
space 119 is closed by a lid 121 which is penetrated by a return oil pipe 
122 communicating with the oil passage space 119. The return oil pipe 122 
has an upper end connected to the lid 121 and a lower end opening to a 
bottom portion of the oil pan 6. 
As shown in FIG. 6, pivot holes 133 for inserting the balancer shafts 65, 
66 are worked in the crankshaft supporting portions 103 by inserting a 
tool (not shown) from the uppermost crankshaft supporting portion 103a 
downward. In upper and lower partition walls 103ba, 103bb of the lowermost 
crankshaft supporting portion 103b are formed work holes 134a, 134b 
smaller than the pivot holes 133. The work hole 134b in the lower 
partition wall 103bb is closed by a plug 135 to tightly separate the oil 
passage space 111b from the lower space A for the flywheel. 
The cooling system of the vertical internal combustion engine 1 will be 
described. As shown in FIG. 1, a cooling water pump 123 driven by the 
driving shaft is provided at a joint part between the extension case 3 and 
the gear case 4. In a side wall of the gear case 4 is formed a suction 
port 124 with a net (not shown) stretched. Water entering into the gear 
case 4 through the suction port 124 is sucked by the cooling water pump 
123 and sent to the vertical internal combustion engine 1 through a 
suction pipe 125. 
As shown in FIGS. 11 and 12, cooling water rising passages 126, 127, 128, 
129 and a cooling water descending passage 130 are formed in the mount 
case 5 and the cylinder block 21 positioned around the exhaust passage 52 
passing through the mount case 5 vertically and the exhaust hole 51 
communicating with the exhaust passage 52 and passing through the cylinder 
block 21 vertically. 
In the cylinder block 21, a cooling water passage 137 (FIG. 8) 
communicating with the cooling water rising passage 126 of the mount case 
5 (FIGS. 11, 12) is formed. As shown in FIGS. 8 and 17, the cooling water 
passage 137 communicates with a cooling water passage 138 on the outside 
of the exhaust passage 50 and the passage 138 communicates with a cooling 
water passage 139 of the cylinder head 22. 
The cylinder block 21 is formed with a water jacket 140 communicating with 
the cooling water rising passage 127 of the mount case 5. An opening end 
of the water jacket 140 communicates with a cooling water passage 141 of 
the cylinder head 22 as shown in FIGS. 7 and 8. 
Further, the cylinder block 21 is formed with a cooling water passage 142 
at a position near the joint portion of the cylinder block and the 
cylinder head 22 with respect to the exhaust passage 50 and the 
aforementioned cooling water rising passage 128 of the mount case 5 
communicates with the cooling water passage 142. A cooling water passage 
143 communicating with the cooling water passage 142 is formed in the 
cylinder head 22 (FIG. 18). 
As shown in FIG. 8, in the cylinder block 21, a cooling water passage 144 
is formed on the outside of the cooling water passage 137 communicating 
with the cooling water rising passage 129, and in the neighborhood of the 
cooling water passages 137, 138, 144 is formed a cooling water passage 145 
which communicates with the cooling water descending passage 130. The 
cooling water sent out from the cooling water pump 123 is supplied to the 
cooling water passages 139, 141, 143 of the cylinder head 22 through the 
cooling water passages 126, 127, 128, 129 of the mount case 5, and the 
cooling water passages 137, 138, 142, 144 of the cylinder block 21, then 
discharged outside through the cooling water passage 145 of the cylinder 
block 21 and the cooling water descending passage 130 of the mount case 5. 
As shown in FIG. 8, a breather passage 147 communicating with the crank 
chamber 136 and the valve moving chamber 35 is connected with a breather 
chamber 149 through a hole 148. 
When the vertical internal combustion engine 1 is started and becomes in an 
operation state, the crankshaft 30 and the rotor 38 of the lubricating oil 
pump 81 integrally fitted to the crankshaft rotate and lubricating oil in 
the oil pan 6 is sucked into the pump chamber 84 through the strainer 89, 
the suction pipe 88 and the suction port 86. Then the lubricating oil is 
sent to the intake portion 96 of the oil filter 95 through the vertical 
oil passage 90, the longitudinal horizontal oil passages 91, 92, the 
vertical oil passage 93 and the longitudinal horizontal oil passage 94 to 
be filtered by the oil filter 95. After that, the lubricating oil is 
supplied to the crankshaft oil passage 99, the balancer shaft oil passage 
100 and the balancer oil passage 101 through the communication oil passage 
98. 
The lubricating oil supplied to the crankshaft oil passage 99 is sent to 
the journal bearing 31 of the crankshaft 30 to lubricate it, through the 
crankshaft oil passage 102 provided in the crankshaft supporting portion 
103 directing rearward as shown in FIGS. 7 and 10. 
Referring to FIG. 4, the lubricating oil which has lubricated any journal 
bearing 31 flows down passing through communication holes 131 formed in 
the crankshaft supporting portions 103 in turn until it reaches the 
lowermost crankshaft supporting portion 103b and flows into the flat oil 
passage space 111b. Referring to FIG. 12, the lubricating oil in the flat 
oil passage space 111b drops onto an upper surface of the mount case 5 
through the return oil hole 114a, the partitioned space 113b and the 
vertical communication hole 136b. 
Another lubricating oil flowing into the flat oil passage space 111a of the 
lowermost crankshaft supporting portion 103a in the same manner as the 
above, drops onto an upper surface of the mount case 5 through the 
partitioned space 113a and the vertical communication hole 136a. The 
lubricating oil on the upper surface of the mount case 5 drops in the oil 
pan 6 through the return oil passage 116 provided in the mount case 5 
(FIGS. 12, 13). 
Referring to FIG. 7, a part of the lubricating oil supplied to the journal 
bearing 31a of the crankshaft 30 to lubricate it through the crankshaft 
oil passage 102a of the uppermost crankshaft supporting portion 103a is 
further supplied to a portion 38a to be lubricated of the cam shaft 38 
through the cam shaft oil passages 107, 108, 109 for lubricating the 
portion 38a. The lubricating oil is supplied in the cam shaft 38 through 
the rocker oil passage 110 to lubricate friction parts of the valve moving 
device, collects in the valve moving chamber 35, flows into the oil 
passage space 119 of the mount case 5 through the return oil passages 117, 
118 as well as the communication pipe 120 parallel with the return oil 
passages, and then returns to the bottom of the oil pan 6 through the 
return oil pipe 122 (FIG. 4). 
Another lubricating oil entering the balancer shaft oil passages 100, 101 
from the communication oil passage 98 flows through the balancer shaft oil 
passages 104, 105 (FIGS. 7, 9, 10) to lubricate the upper portions 65a, 
66a of the balancer shafts 65, 66 (FIG. 6), then the lubricating oil goes 
down by gravity and lubricates the lower pivot portions 65b, 66b of the 
balancer shafts 65, 66. Thus if only the balancer shaft passages 104, 105 
are provided to the balancer shafts 65, 66 respectively, middle bearing 
portions and lower end bearing portions of the balancer shafts 65, 66 are 
also lubricated so that the balancer lubricating system is simplified 
greatly and cost can be reduced. 
Referring to FIG. 6, a lubricating oil flowing into the balancer shaft oil 
passage 106 from the balancer shaft oil passage 105 is supplied to the 
pivot portion 62a of the balancer driven pulley 92 through the cam shaft 
oil passage 107 to lubricate the pivot portion 62a with the very simple 
lubricating construction. 
The lubricating oil which has lubricated the balancer shafts 65, 66 drops 
down and flows into the oil passage space 111b through the work hole 134a 
of the lowermost crankshaft supporting portion 103b. The lubricating oil 
in the oil passage space 111b returns into the oil pan 6 through the 
return oil hole 114b, the partitioned space 113b (FIG. 14), the 
partitioned space 115 and the vertical communication hole 136 (FIG. 13) in 
turn. 
Since the pivot hole 133a pivotally supporting the upper end of the 
balancer shaft 65 (66) at the uppermost crankshaft supporting portion 
103a, the pivot holes 133 in the middle crankshaft supporting portions 103 
which the balancer shaft passes through, the work hole 134a pivotally 
supporting the lower end of the balancer shaft at the lowermost crankshaft 
supporting portion 103b and the work hole 134b formed under the hole 134a 
are arranged in a straight line as shown in FIG. 6, these holes can be 
worked easily by a tool. Particularly the upper pivot holes 133 can be 
finished by a tool having a lower end supported by the work holes 134a, 
134b with a high productivity. Since the plug 135 is fitted in the lower 
work hole 134b, lubricating oil in the oil passage space 111 never flows 
into the flywheel space A under the space 111. 
As shown in FIGS. 7, 17 and 18, the cam shaft oil passages 107, 108, the 
communication passage 27, the hole 26a for inserting the bolt 26 and the 
cam shaft oil passage 109 leading to the pivot portion 38a of the cam 
shaft 38 from the uppermost journal bearing 31a of the crankshaft 30 are 
arranged on the opposite side to the exhaust passage 50, so that 
lubricating oil passing through these oil passages is hardly heated and 
prevented from deterioration. 
The bolts 26 are disposed at positions apart by substantially equal 
distances from the center of each cylinder 32 and substantially at regular 
intervals round the cylinder, therefore, even if diameters of the 
cylinders 32 are enlarged in order to make the vertical internal 
combustion engine 1 large-sized, contact surfaces around the cylinders of 
the cylinder block 21 and the cylinder head 22 can be pressed evenly 
against each other.