Crankcase breather and lubrication oil system for an internal combustion engine

An internal combustion engine having a vertically oriented crankshaft and a horizontally oriented cylinder bore and including a plurality of lubrication sites to be pressure lubricated. A first upstanding wall extends upwardly from the top wall of the crankcase and circumscribes and defines a first chamber. A breather passage communicates crankcase gases from the crankcase into the first chamber. A drain passage communicates oil separated from the crankcase gases in the first chamber into the cylinder bore below the piston and is positioned along the cylinder bore so as to be periodically occluded by the piston during reciprocation thereof. A second upstanding wall extends upwardly from the top wall of the crankcase in spaced relationship to at least a portion of the first wall, and defined together with the first wall a second chamber therebetween. A first oil passage communicates oil from a lubricant pump to the second chamber, and a second oil passage communicates oil from the second chamber to at least one of the lubrication sites.

BACKGROUND OF THE INVENTION 
The present invention generally relates to an internal combustion engine of 
the type having a vertical crankshaft, and more particularly to such an 
engine having a breather chamber for venting of crankcase gases and 
separating and recovering lubrication oil from the gases, and further 
having a pressure lubrication system having multiple oil passageways. 
Air-cooled internal combustion engines sometimes have a crankcase breather 
system for venting blow-by gases which get by the piston rings and valve 
sem seals and enter the crankcase. The breather system insures that 
excessive pressure does not develop in the crankcase. Such a breather 
system ofen involves a check valve which allows gases to exit the 
crankcase but not to enter. It is a phenomenon of such systems that 
lubricating oil mist generated in the crankcase is carried along with the 
vented gases which exit through the check valve and it is desireable to 
separate out such oil and drain it back into the crankcase. The breather 
check valve, separator chamber and oil drain in the past have been located 
in a variety of positions relative to the crankcase. 
An engine of the type involved herein is also sometimes provided with a 
pressure lubrication system involving an oil pump and various oil 
distribution passageways to convey the oil from the pump to the various 
lubrication sites within the engine where the oil is needed. In the past, 
pressurized lubrication of upper bearings in vertical shaft engines has 
been accomplished by drilling long cross-drilled passages and 
interconnecting holes and plugging the ends to form lubrication passages. 
The relatively large amount of machining involved in drilling and plugging 
passages increases the cost of manufacture. 
It would be desirable to provide a vertical shaft engine with a crankcase 
breather system and a pressure lubrication system which simplifies and 
reduces machining and reduces the cost of manufacture of the engine. This 
and other desirable features are achieved by the present invention. 
SUMMARY OF THE INVENTION 
The present invention involves providing a vertical shaft internal 
combustion engine with a breather chamber and a lubrication chamber which 
are for the most part formed by upstanding walls on the top of the 
crankcase so that the horizontal reaches of the chambers are formed 
primarily by casting, and drilling of passages is limited primarily to the 
generally vertical reaches and for precise delivery to the lubrication 
site. In a preferred embodiment, the breather chamber and lubrication 
chamber are formed adjacent one another and share a common upstanding 
wall. The upstanding walls are finished to a common height so that both 
the breather chamber and the lubrication chamber are closed at the top by 
a single planar cover. 
Long cross-drilled passages for lubrication of the upper bearings have been 
substantially eliminated by the present invention since the horizontal 
extensions of the passages have been replaced by a cast chamber which is 
curved as necessary to traverse obstructions. Only short straight drilled 
passages extend from the cast lubrication chamber to the lubrication 
sites. 
A breather system involving a check valve, separation chamber, and oil 
drain back passage is obtained in an economical manner through strategic 
location on the top of the crankcase where it is integrated with the 
lubrication chamber so that thee is a sharing of defining structure and 
the cover. 
The oil drain passage of the breather system is located so as to be ported 
by the piston as it reciprocates, thereby occluding the drain passage on 
the downstroke of the piston, and uncovering it on the upstroke. In this 
way escape of crankcase gases through the oil drain back hole is avoided 
and oil drains back into the crankcase through the drain back passage. An 
advantage of this arrangement is that air pressurized in the crankcase on 
the downstroke of the piston does not blow through the drainn hole and 
re-suspend the separated oil in the breather chamber. In addition, the 
entire cycle of the engine is available for the collection of oil, rather 
than only one half of the cycle in the case where the drain passage is not 
ported by the piston. 
It is an advantage of the arrangement of the lubrication chamber that oil 
can be transported about the top of the crankcase from a convenient oil 
riser such as the camshaft to whatever lubrication site requires pressure 
lubrication without requiring the drilling and plugging of multiple cross 
passageways. The lubrication chamber forms a sort of oil bus which can be 
tapped into by drilling a single straight passage through the bottom of 
the chamber to the lubrication site. Adding options that require direct 
lubrication, such as a counterbalance shaft, simply requires an additional 
drilled passage. Consequently, the cost of manufacturing the engine is 
significantly reduced. A further reduction in cost of manufacture is 
obtained from the structural relationship between the lubrication system 
and the breather chamber, i.e. shared walls and cover, as discussed above. 
The invention, in accordance with one embodiment thereof, involves an 
internal combustion engine including a crankcase having a generally 
horizontal oriented top wall, an oil sump, an oil pump, and a vertically 
oriented crankshaft rotatably journalled therein. A horizontally oriented 
cylinder bore communicates with and extends from the crankcase, and a 
piston is disposed for reciprocation within the cylinder bore and is 
linked to the crankshaft. The engine includes a plurality of lubrication 
sites to be pressure lubricated. A first upstanding wall extends upwardly 
from the top wall of the crankcase and circumscribes and defines a first 
chamber. A breather passage means is provided for communicating crankcase 
gases from the crankcase into the first chamber. A drain passage means is 
also provided for communicating oil separated from the crankcase gases in 
the first chamber into the cylinder bore below the piston, the drain 
passage means being positioned along the cylinder bore so as to be 
periodically occluded by the piston during reciprocation thereof. A second 
upstanding wall extends upwardly from the top wall of the crankcase in 
spaced relationship to at least a portion of the first wall, the first and 
second walls defining therebetween a second chamber. Included is a first 
oil passage means communicating oil from the lubricant pump to the second 
chamber, and a second oil passage means communicating oil from the second 
chamber to at least one of the lubrication sites.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the figures, there is illustrated an internal combustion 
engine 10 in accordance with the present invention. Engine 10 includes a 
crankcase 12 having a generally horizontal top wall 14, an oil sump 16, 
and a vertically oriented crankshaft 18 journalled for rotation therein at 
bearing journals 20 and 22. A top seal 24 and a bottom seal 26 provide 
sealing of crankshaft 18 with respect to crankcase 12 to prevent migration 
of oil therepast. Crankshaft 18 includes a crank 28 and counterweights 30 
and 32. Horizontally oriented cylinder bore 34 communicates with crankcase 
12 and extends therefrom. Cooling fins 36 on the outside of cylinder 40 
provide for dissipation of heat. Cylinder head 42 is attached to the top 
of cylinder 40 and sealed thereto by gasket 44, thereby closing the top of 
cylinder bore 34. Received within cylinder bore 34 is piston 46 arranged 
for reciprocation therein. Piston 46 is linked to crank 28 of crankshaft 
18 by connecting rod 48. 
Referring particularly to FIG. 3 crankcase 12 includes vertically oriented 
camshaft 50 which is rotatably journalled in bearing journal 52. Camshaft 
50 is connected in synchronous driven engagement with crankshaft 18 by 
conventional means not shown, and includes cam lobes 54 and 56 which 
engage the valve stems of the intake and exhaust valves (not shown) which 
are arranged in a side valve configuration. The present invention is also 
useful in combination with an overhead valve arrangement. 
Arranged on the top of top wall 14 and extending upwardly therefrom is an 
upstanding wall 58 which circumscribes and defines a breather chamber 60. 
Wall 58 is preferably cast integrally with top wall 14 which is likewise 
cast integrally with crankcase 12. Wall 58 includes a portion 62 (see FIG. 
4) which lies circumjacent a portion of crankshaft 18 and forms the outer 
surface of upper bearing journal 20. 
Disposed through top wall 14 is a breather passage 64 communicating the 
interior 66 of crankcase 12 with breather chamber 60. Passage 64 includes 
therein a breather check valve 68 which opens and permits flow of 
crankcase gases from crankcase interior 66 to breather chamber 60 when 
crankcase interior 66 is positively pressurized under the influence of 
piston 46 traversing its downstroke. Breather check valve 68 closes upon 
negative pressurization of crankcase interior 66 under the influence of 
piston 46 traversing its upstroke. Oil mist which is generated in 
crankcase interior 66 by splash lubrication and the slinging of oil from 
moving surfaces such as counterweights 30 and 32 of crankshaft 18 is 
incidentally carried by the crankcase gases through breather passage 64 
and breather check valve 68 into breather chamber 60. The oil mist 
separates from the gases and settles out and collects in chamber 60, as 
indicated by oil pool 72 in FIGS. 1 and 3. The depth of oil pool 72 is 
exaggerated for clarity in the drawings. In actuality, the oil accumulates 
as only a thin film before being sucked back into the crankcase. 
A drain passage 70 through the top side of the cylinder wall of cylinder 40 
communicates breather chamber 60 with cylinder bore 34 and provides a 
pathway for liquid oil which has separated from the crankcase gases in 
breather chamber 60 to return to crankcase interior 66 via cylinder bore 
34. Drain passage 70 is so located along the cylinder bore as to be within 
the stroke of piston 46, and thus be periodically occluded by the skirt of 
piston 46 as it reciprocates. In particular, drain passage 70 is located 
so as to be occluded by piston 46 during the end of travel on the 
downstroke and the beginning of travel on the upstroke thereof. 
Consequently, drain passage 70 becomes occluded as the pressure in 
crankcase interior 66 rises on the downstroke of piston 46, thereby 
preventing venting of crankcase gases into breather chamber 60 through 
drain hole 70. Likewise, drain passage 70 becomes uncovered as the 
pressure in crankcase interior 66 lowers on the upstroke of piston 46, 
thereby causing oil which has accumulated as oil pool 72 in breather 
chamber 60 to be sucked into cylinder bore 34 below piston 46 and thence 
returned into crankcase interior 66. Breather chamber 60 has a vent 
opening 74 (see FIG. 4) through which crankcase gases are vented either to 
the atmosphere or preferably through a conduit 76 to the intake of the 
combustion air induction system (not shown). 
Breather passage 64 and drain hole 70 are generally centrally located with 
respect to the centerline of the engine defined by the cylinder bore and 
are in somewhat diametrically opposed spaced relationship to one another 
in the horizontal direction with respect to crankshaft 18. This has the 
advantage of permitting the engine to be tilted on its side for servicing 
as would be common where the engine is utilized to power a walk-behind 
lawn mower, without the crankcase oil draining out through the breather 
passage 64 when tilted on one side or out through the drain hole 70 when 
tilted on the other side. Thus the loss of oil out of breather chamber 60 
through vent opening 74 is alleviated. 
Referring especially to FIGS. 1, 3 and 5, there is arranged on the top of 
top wall 14 and extending upwardly therefrom an upstanding wall 80 which 
is disposed in generally parallel spaced relationship to upstanding wall 
58 along a portion of the outer periphery thereof away from crankshaft 18. 
Wall 80 joins wall 58 at points 82 and 84 and thereby defines an elongate 
curved lubrication chamber 86 lying adjacent to chamber 60 and traversing 
a portion of the periphery of chamber 60. Wall 80 is cast integrally with 
top wall 14 which is likewise cast integrally with crankcase 12. 
Communicating with lubrication chamber 86 at one end thereof is an oil 
entry passage 88 which communicates also with the top end of bearing 
journal 52 in which camshaft 50 is journalled. Camshaft 50 includes a 
longitudinal oil passageway 90 therethrough which communicates with oil 
entry passage 88 at the top end thereof and with the oil pump (not shown) 
at the bottom end thereof. Oil is introduced under pressure from the oil 
pump through oil passageway 90 of camshaft 50, thence through oil entry 
passage 88 into lubrication chamber 86. 
At the opposite end of lubrication chamber 86 from oil entry passage 88, 
chamber 86 widens into an oil distribution chamber 92 having a plurality 
of oil distribution passageways communicating therewith such as oil ports 
94, 96 and 98. Oil port 94 communicates with a bearing journal 100 in 
which is journalled a vertically oriented counterbalance shaft 102 for 
prevention of engine vibration. Counterbalance shaft 102 is in synchronous 
driven engagement with cranksahft 18 via conventional means not shown. Oil 
port 96 communicates with bearing journal 20 in which the upper end of 
crankshaft 18 is journalled to provide pressure lubrication of the 
crankshaft bearing journal. Oil port 98 provides oil spray directly into 
the interior 66 of crankcase 12 to lubricate the crank 28 of crankshaft 
18. 
It is a particular advantage of the arrangement of lubrication chamber 86 
that oil can be transported about the top of the crankcase from a 
convenient oil riser such as the camshaft to whatever lubrication site 
requires direct lubrication without requiring the drilling and plugging of 
multiple cross passageways. Lubrication chamber 86 forms a sort of oil bus 
which can be tapped into by drilling a single straight passage through the 
bottom of chamber 86 to the lubrication site. Consequently, the cost of 
manufacturing the engine is significantly reduced. A further advantage 
with respect to cost of manufacture is obtained from the structural 
relationship described below. 
Breather chamber 60 and lubrication chamber 86 are formed adjacent one 
another and defined by upstanding walls 58 and 80. As cast, the upstanding 
walls in combination with top wall 14 define open-topped channels which 
are easily die-cast without requiring special cores. The tops of walls 58 
and 80 are machined to a common height defined by a horizontal plane. 
Consequently, both chambers 60 and 86 are closed at the top by a single 
removable cover plate 104 and corresponding sealing gasket 106. 
While the present invention has been particularly described in the context 
of a preferred embodiment, it will be understood that the invention is not 
limited thereby. Therefore, it is intended that the scope of the invention 
include any variations, uses or adaptations of the invention following the 
general principles thereof and including such departures from the 
disclosed embodiments as come within known or customary practice in the 
art to which the invention pertains and which fall within the appended 
claims or the equivalents thereof.