V-shaped two cycle engine for outboard

Two embodiments of V-type two cycle crankcase compression internal combustion engines wherein the charge supplied to the crankcase chambers by a primary induction system is supplemented by a secondary induction system that communicates with the crankcase chambers between the primary system and the respective cylinder bank.

BACKGROUND OF THE INVENTION 
This invention relates to a V-shaped, two cycle engine for an outboard and 
more particularly to an improved high efficiency and compact induction 
system for such an engine. 
Because of their relative simplicity and compact configuration, two cycle 
engines are employed for a wide variety of purposes. One environment in 
which such engines find particular application is in outboard motors. 
Because of their compact nature, two cycle engines lend themself 
particularly to this application. In connection with outboard motors, it 
has recently been the practice to employ V-type engines in order to permit 
a larger displacement and greater output in a smaller area. However, 
because of the compact nature of a V-type engine it is difficult to 
provide adequate induction capability to the crankcase chambers of the 
engine so as to develop maximum power and realize the full potential of 
the displacement. The reason for this is that the fuel air charge must be 
delivered to the crankcase chambers for induction and compression before 
transfer to the combustion chambers. As a result, the positioning of the 
intake system and the provision of adequate capacity for it has presented 
some problems. 
It is, therefore, a principal object of this invention to provide an 
improved induction system for a V-type two cycle crankcase compression 
internal combustion engine. 
It is a further object of this invention to provide an improved induction 
system for a V-type crankcase compression internal combustion engine 
wherein separate passages supply the charge to the crankcase chambers and 
at least a portion of these passages is disposed outside of the valley of 
the V cylinder banks so as to promote better space utilization while, at 
the same time, offering a compact arrangement. 
SUMMARY OF THE INVENTION 
This invention is adapted to be embodied in a two cycle, crankcase 
compression internal combustion engine that comprise first and second 
cylinder banks that are disposed at an angle to each other and which 
define a valley therebetween. A crankcase chamber is positioned at the 
base of the valley of the engine and means are provided for admitting a 
charge to the crankcase chamber at a first location. In accordance with 
the invention, supplemental means are provided for admitting a 
supplemental charge to the crankcase chambers and this supplemental means 
is located outside of the valley of the cylinder banks and at a point 
spaced from the first means that admits the charge to the crankcase 
chambers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
Referring first to FIGS. 1 and 2, an outboard motor constructed in 
accordance with this embodiment is identified generally by the reference 
numeral 11. The invention is directed primarily toward the internal 
combustion engine of the outboard motor 11 and, for that reason, only the 
engine and its associated components have been illustrated in solid lines 
and will be described in detail. It is believed that those skilled in the 
art will readily know how the engine, which is identified generally by the 
reference numeral 12 is associated with the other components of the 
outboard motor 11. 
The engine 12 is, in accordance with a principle of the invention, of the V 
type and is, in the illustrated embodiment, depicted as being a V-6, 
although not all 6 cylinder are shown in the drawings. To this end, the 
engine 12 is provided with a cylinder block assembly, indicated generally 
by the reference numeral 13 that is formed with a pair of cylinder banks 
14. The cylinder banks 14 are disposed at an angle to each other and the 
degree or angle between the banks 14 will depend upon a variety of factors 
including the number of cylinders. The area between the cylinder banks 14 
defines a valley 15. 
Each cylinder bank 14 is provided with cylinder liners 16 in which pistons 
17 are supported for reciprocation. The pistons 17 are connected by means 
of connecting rods 18 to a crankshaft 19 that rotates about a generally 
vertically disposed axis within a crankcase chamber 21. As is normal with 
two cycle engine practice, the crankcase chamber 21 is divided into a 
plurality of individual chambers, one for each of the pistons 17, which 
are sealed from each other in a suitable manner. 
A respective cylinder head 22 is affixed to each of the cylinder banks 14 
in a suitable manner, as by means of threaded fasteners 23. The cylinder 
heads 22 define cavities 24 which cooperate with the heads of the pistons 
17 and the cylinder liner 16 to provide the combustion chambers of the 
engine. 
Spark plugs 25 are carried by the cylinder heads 22 and have their spark 
gap disposed in the combustion chambers 24 for firing the charge therein. 
The spark plugs 25 are fired by means of a suitable ignition circuit, 
including a control box 26 which is positioned within an outer cowling 27 
that encircles the engine 12. Since the outer cowling 27 forms no part of 
the invention it has been illustrated only in phantom. 
The charge which has been burned in the combustion chambers 24 upon the 
firing of the spark plugs 25 and completion of the expansion thereof, are 
discharged through an exhaust manifold 28 and exhaust ports that are 
disposed in the valley 15 of the engine. 
A fuel air charge is delivered to the sealed crankcase chambers 21 
associated with each of the combustion chambers 24 by means of a primary 
induction system consisting of three vertically spaced, two barrel 
carburetors 29, 31 and 32. The carburetors 29, 31 and 32 have respective 
throttle valves 33 for controlling the flow through their individual 
barrels and discharge into an intake manifold 34 that is interposed 
between the carburetors 29, 31 and 32 and the crankcase chambers 21. The 
manifold 34 and associated engine have respective runners 35 that extend 
from each barrel of the carburetors 29, 31 and 32 to respective pairs of 
the crankcase chambers 21. Reed type check valves 36 are positioned at the 
discharge ends of the manifold runners 35 so as to prevent reverse flow 
therethrough. 
The charge which is delivered to the crankcase chambers 21 is transferred 
to the combustion chambers 24 upon the decent of the pistons 17 through 
transfer or scavenge passages 37 that extend from the crankcase chambers 
to intake ports formed in the sides of the cylinder liners 16. This 
construction as thus far described may be considered to be conventional. 
It should be noted that the compact configuration and the relatively 
limited effective cross-sectional area of the manifold passages 35 can 
reduce the breathing ability of the engine 12 and, accordingly, its 
maximum power output. In order to provide a still further fuel air charge 
to the crankcase chambers while still maintaining a compact construction, 
there is provided a supplementary induction system that is comprised of a 
supplementary carburetor or charge former 38 which is disposed adjacent 
each of the cylinder banks 14 for each of the cylinders 16. The 
carburetors 38 deliver a charge to the crankcase chambers 21 at a point 
spaced from the manifold runners 35 through supplementary intake passages 
39 that intersect the cylinder liners 16 and communicate with the 
crankcase chambers 21 when the pistons 17 are at the upper portion of 
their stroke. If desired, the pistons 17 may also be provided with ported 
passages so that the manifold passages 39 communicate with the crankcase 
chambers 37 during the full stroke of the pistons 17. 
It should be readily apparent from FIG. 1 that the layout of the primary 
intake system and supplementary intake system provides a very compact 
configuration. To further this end, an electric starter 41 may be 
positioned between the spark box 26 and one of the supplemental 
carburetors 38 for electric starting of the engine 12. In addition, the 
throttle linkage, indicated schematically at 42, may be positioned on the 
other side of the engine. 
The embodiment of the invention shown in FIGS. 1 and 2 is of the type that 
employs three two barrel carburetors with each horizontally extending 
barrel serving a one of the pairs of cylinders of the adjacent cylinder 
banks. FIG. 3 shows another embodiment of the invention which is generally 
similar to the embodiment of FIGS. 1 and 2. However, this embodiment 
substitutes a slightly modified induction system that is comprised of a 
pair of three barrel carburetors 51 that serve the crankcase chambers 21 
through respective manifold passageways 52. Each barrel of the carburetors 
51 serves the cylinders of a respective cylinder bank so that one 
carburetor 51 serves one of the cylinder banks 14 while the other 
carburetor 51 serves the other cylinder bank 14. In all other regards, the 
basic construction of the engine of this embodiment is the same as the 
previously described embodiment and for that reason those components which 
are the same have been identified by the same reference numerals and will 
not be described again. 
In this embodiment, since the carburetors 51 are disposed at an angle to 
each other a starter motor 53 is positioned in the valley between the 
carburetors 51 and their associated manifolds and a spark box 54 is 
positioned adjacent the starter motor 53 for firing the spark plugs 26. In 
all other regards, this embodiment is the same as the previously described 
embodiment. 
It should be readily apparent from the foregoing description that the 
embodiments of the invention illustrated and described are effective in 
providing adequate breathing capability for an engine of the V type so 
that maximum power output can be achieved. Although two embodiments of the 
invention have been illustrated and described, various changes and 
modifications may be made without departing from the spirit and scope of 
the invention, as defined by the appended claims. For example, although 
the invention has been described in conjunction with primary and secondary 
carburetors, the invention may be equally as well practiced with engines 
having fuel injection or other forms of charge forming devices.