Intake manifold for internal combustion engines

In an internal combustion engine, an intake manifold has a main distributing chamber and an auxiliary distributing chamber disposed to overlap with the main distributing chamber at a location inward thereof. The main distributing chamber is divided by a partition wall into a primary distributing chamber and a secondary distributing chamber. The partition wall has a boss through which is formed an intake guide passage having one end opening in the auxiliary distributing chamber and directed toward a substantially central location of the chamber. The primary distributing chamber, the secondary distributing chamber and the intake guide passage leading to the auxiliary distributing chamber have respective mixture-inlet ports opening in a carburetor-mounting surface formed on the outer surface of the intake manifold and arranged thereon in a compact array. Thus, the intake guide passage has a simplified configuration, and also the intake manifold can have a compact size.

BACKGROUND OF THE INVENTION 
This invention relates to an intake manifold for internal combustion 
engines, and more particularly to improvements in the structure of the 
auxiliary intake passage system of an internal combustion engine. 
An intake manifold for an internal combustion engine is well known which is 
arranged between a carburetor unit and the main body of the engine and is 
formed therein with a plurality of main intake passages for feeding a lean 
mixture to respective main combustion chambers of the engine, a main 
distributing chamber from which diverge the main intake passages, a 
plurality of auxiliary intake passages for feeding a rich mixture to 
respective auxiliary combustion chambers of the engine, and an auxiliary 
distributing chamber from which diverge the auxiliary intake passages, the 
above main distributing chamber being divided by a partition wall located 
at the mixture-inlet portion of the same chamber into a primary 
distributing chamber for distributing a mixture to the main intake 
passages for low-load operation of the engine and a secondary distributing 
chamber for distributing a mixture to the main intake passages for 
high-load operation of the engine. 
In such type intake manifold, as known from Japanese Provisional Patent 
Publication (Kokai) No. 53-57315, mixture-inlet ports leading, 
respectively, to the primary distributing chamber, the secondary 
distributing chamber and the auxiliary distributing chamber are usually 
arranged in a line extending substantially normally to the plane of 
juncture between the intake manifold and the main body of the engine so as 
to obtain even distribution of the mixtures to the main combustion 
chambers and the auxiliary combustion chambers. Due to the limited size of 
the intake manifold, the main distributing chamber and the auxiliary 
distributing chamber are disposed to overlap with each other in a vertical 
direction of the intake manifold with the latter located inwardly of the 
former. This arrangement necessitates locating the mixture-inlet port 
leading to the auxiliary distributing chamber through the surface of a 
thick lateral wall of the main distributing chamber such that the 
mixture-inlet port communicates with the auxiliary distributing chamber by 
way of an intake guide passage which is formed through the above lateral 
wall of the main distributing chamber. That is, the intake guide passage 
extends around the main distributing chamber, and therefore its internal 
flow path is inevitably long and complicate in configuration, providing 
the possibility of uneven distribution of the mixture from the auxiliary 
distributing chamber to the auxiliary intake passages due to increased 
flow resistance and turbulence in the intake guide passage, etc. 
Further, the aforesaid linear arrangement of the mixture-inlet ports 
leading to the primary and secondary distributing chambers and the 
auxiliary distributing chamber necessitates prolonging the size of the 
carburetor-mounting surface on the outer surface of the intake manifold in 
a direction in which are arranged the mixture-inlet ports. This in turn 
necessitates designing the intake manifold and a carburetor unit mounted 
on the mounting site large in size. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an intake manifold for internal 
combustion engines, in which the auxiliary intake passage system has a 
simplified flow path configuration, thereby having an enhanced degree of 
even distribution of the mixture into the individual auxiliary intake 
passages. 
It is a further object of the invention to provide an intake manifold for 
internal combustion engines, in which the mixture-inlet ports opening in 
the carburetor-mounting surface on the outer surface of the intake 
manifold and leading to the main distributing chamber and the auxiliary 
distributing chamber are arranged in a compact array, thereby compacting 
the size of the intake manifold as well as the size of a carburetor unit 
to be mounted on the carburetor-mounting surface. 
According to the invention, an improved intake manifold for an internal 
combustion engine is provided which is of the type formed therein with a 
plurality of main intake passages, a plurality of auxiliary intake 
passages, a main distributing chamber from which diverge the main intake 
passages, and an auxiliary distributing chamber from which diverge the 
auxiliary intake passages, and which is disposed to overlap with the main 
distributing chamber at a location inward thereof, the main distributing 
chamber being divided into a primary distributing chamber and a secondary 
distributing chamber, by a partition wall located at a mixture-inlet 
portion of the main distributing chamber. The above partition wall has a 
boss through which is formed an intake guide passage which opens at one 
end in an outer surface of the intake manifold and communicates at the 
other end with the auxiliary distributing chamber. The above other end of 
the intake guide passage opens in the auxiliary distributing chamber and 
is directed toward a substantially central location thereof. 
Preferably, the mixture-inlet portion of the main distributing chamber 
includes a carburetor-mounting surface forming part of the outer surface 
of the intake manifold, in which are formed first and second mixture-inlet 
ports leading, respectively, to the primary and secondary distributing 
chambers of the main distributing chamber, and a third mixture-inlet port 
leading to the intake guide passage of the auxiliary distributing chamber, 
with the third mixture-inlet port located at a location intermediate 
between the first and second mixture-inlet ports. 
The above and other objects, features and advantages of the invention will 
be more apparent from the ensuing detailed description taken in 
conjunction with the accompanying drawings.

DETAILED DESCRIPTION 
The invention will now be described in detail with reference to the 
drawings. 
Referring first to FIG. 1, there is illustrated an embodiment of the intake 
manifold according to the invention, which is to be mounted on the main 
body of an internal combustion engine, not shown. The intake manifold 1, 
which is assumed to be horizontally disposed in the embodiment, is formed 
therein with a main distributing chamber 2 which is divided into a primary 
distributing chamber 2a for distributing a mixture to main intake passages 
4-7, hereinafter referred to for low-load operation of the engine and a 
secondary distributing chamber 2b for distributing a mixture to the same 
intake passages for high-load operation of the engine, by a partition wall 
3 integrally formed in the interior of the manifold at a substantially 
central location of the main distributing chamber 2. The partition wall 3 
is integrally formed with generally cylindrical bosses 3a and 3b at its 
opposite ends as viewed in directions of flows of a mixture in the main 
distributing chamber. The main intake passages 4, 5 are connected to one 
open end of the main distributing chamber 2, while the other main intake 
passages 6, 7 are connected to the other open end of the same chamber, in 
a manner horizontally diverging from the main distributing chamber 2. 
These main intake passages 4-7 open at ends 4a-7a in a front end face 1a 
of the intake manifold 1. On the other hand, the primary and secondary 
distributing chambers 2a, 2b communicate, respectively, with mixture-inlet 
ports 8a and 8b formed in a carburetor-mounting surface 8 formed on an 
upper surface of the intake manifold 1. 
An exhaust gas recirculating passage 9 is formed in the intake manifold 1 
and extends along a lateral side surface 1b of same, with one end 9a 
opening in a mounting surface 9c formed at a location close to the front 
end face 1a of the intake manifold 1, on which an exhaust gas flow control 
valve, not shown, is to be mounted, and the other end 9b opening in the 
primary distributing chamber 2a at a substantially central location 
thereof. A partition wall 10 is integrally formed in the primary 
distributing chamber 2a in a manner facing the open end 9b of the exhaust 
gas recirculating passage 9 at a predetermined interval therefrom. A 
further exhaust gas recirculating passage 9e is formed in the intake 
manifold 1, with one end 9f opening in the front end face 1a of the 
manifold 1 and the other end communicating with an opening 9d in the 
control valve-mounting surface 9c. The openings 9a, 9d can be communicated 
with each other by way of the exhaust gas flow control valve when it is 
mounted on the mounting surface 9c. Thus, the passages 9, 9e cooperate to 
form a continuous exhaust gas recirculating passageway extending between 
the exhaust passage, not shown, of the engine and the intake manifold 1. 
A blow-by gas returning passage 11 is formed integrally on the outer 
surface of the intake manifold 1, with one end 11a projected outwardly of 
the upper surface of the intake manifold 1 and the other end 11b opening 
in the secondary distributing chamber 2b at a substantially central 
location thereof, respectively. 
As shown in FIG. 3, a hot water-heating chamber 12 is formed in the intake 
manifold 1 at a location downward of the main distributing chamber 2, 
which is divided by a partition wall 12a into two chambers 12b and 12c 
communicating with each other. The first chamber 12b extends along the 
lateral side wall 1b of the intake manifold 1 and communicates with one 
end of a passage 12d located below the exhaust gas recirculating passage 9 
in FIG. 1, which in turn has its other end 12e opening in the front end 
face 1a of the intake manifold 1. The second chamber 12c communicates with 
a further passage 12f projected laterally outwardly of the intake manifold 
1. 
As shown in FIG. 2 and FIGS. 4 through 7, an auxiliary distributing chamber 
13 is formed in the intake manifold 1 at a location intermediate between 
the secondary distributing chamber 2b of the main distributing chamber 2 
and the water chamber 12 and lies substantially parallel with the 
secondary distributing chamber 2b partitioned therefrom by a partition 
wall 13d. The auxiliary distributing chamber 13 has an opening 13a which 
directly communicates with an intake guide passage 3c which is formed 
through the boss 3b of the aforementioned partition wall 3 in a manner 
extending along the axis of the boss 3b, and opens at one end 3c' in the 
carburetor-mounting surface 8. As seen in FIG. 2, the opening 13a is 
directed toward a substantially central location of the auxiliary 
distributing chamber 13 so as to direct a mixture guided there through the 
intake guide passage 3c toward the same substantially central location of 
the chamber 13 so that the mixture can be evenly distributed to the 
auxiliary intake passages 14-17. The open end or mixture-inlet port 3c' of 
the intake guide passage 3c is located on the carburetor-mounting surface 
8 at a location intermediate between the mixture-inlet ports 8a, 8b of the 
primary and secondary distributing chambers 2a, 2b, in such a manner that 
the three mixture-inlet ports 3c', 8a and 8b are disposed on the 
carburetor-mounting surface 8 in a generally triangular array. The 
auxiliary distributing chamber 13 has its opposite ends 13b and 13c 
connected, respectively, to auxiliary intake passages 14, 15 and 16, 17 
which horizontally diverge from the auxiliary distributing chamber 13 and 
have respective ends 14a-17a opening in the front end face 1a of the 
intake manifold 1. The auxiliary intake passages 14-17 extend at a level 
lower than the main intake passages 4-7 at their portions between their 
junctions with the auxiliary distributing chamber 13 and intermediate 
points between the same junctions and the front end face 1a of the intake 
manifold 1, while they extend at the same level with the latter passages 
4-7 and parallel therewith, at their portions between the above 
intermediate points and the front end face 1a. 
The intake guide passage 3c merely extends straight through the boss 3b 
vertically of the intake manifold 1, and thus has a simplified and 
shortened path configuration. As a consequence, the flow in the intake 
guide passage 3c undergoes reduced flow resistance and has a less 
possibility of occurrence of turbulence, resulting in smooth and even 
distribution of a mixture introduced into the auxiliary distributing 
chamber 13 through the intake guide passage 3c, to the auxiliary intake 
passages 14-17. Furthermore, by virtue of the formation of the intake 
guide passage 3c through the boss 3b, the mixture-inlet ports 8a, 8b, 3c' 
leading, respectively, to the primary and secondary distributing chambers 
2a, 2b and the auxiliary distributing chamber 13 can be arranged on the 
carburetor-mounting surface 8 in a compact array and along a shortened 
line, thereby enabling to mount a smaller-sized carburetor on the mounting 
surface 8 and also to simplify and make the intake manifold 1 compact in 
size. 
The mixture-inlet ports 8a, 8b and 3c' formed in the carburetor-mounting 
surface 8 will be connected to respective passages formed in a carburetor 
unit, not shown, when the latter is mounted on the same mounting surface 8 
at locations downstream of respective ones of a low-load throttle valve, a 
high-load throttle valve and an auxiliary throttle valve mounted in the 
same carburetor unit. The ends 4a-7a of the main intake passages 4-7 and 
the ends 14a-17a of the auxiliary intake passages 14-17 will be connected 
to corresponding ones of main combustion chambers and auxiliary combustion 
chambers, not shown, formed in the main body of an engine mounted on the 
front end face 1a of the intake manifold 1. A flow control valve, not 
shown, will be mounted onto the valve-mounting surface 9c in a manner 
having its interior passage aligned with the openings 9a, 9d in the 
mounting surface 9c, and the open end 9f of the exhaust gas recirculating 
passage 9e will be connected to the exhaust passage, not shown, of the 
engine. The open end 11a of the blow-by gas returning passage 11 will be 
connected to a blow-by gas returning passage, not shown, formed in the 
engine. Further, the open ends 12e, 12g of the water chamber 12 will be 
connected, respectively, to a portion of an engine cooling water passage, 
not shown, in the cylinder head, and to a portion of the same passage in 
the radiator of the engine. 
With the above arrangement, mixtures from the carburetor unit are supplied 
through the mixture-inlet ports 8a, 8b and 3c' into the respective primary 
and secondary distributing chambers 2a, 2b and the auxiliary distributing 
chamber 13 in the intake manifold 1. The mixtures thus fed into the 
primary and secondary distributing chambers 2a, 2b are evenly distributed 
into the main intake passages 4-7 through the opposite ends of the 
distributing chambers 2a, 2b, and then delivered into the corresponding 
main combustion chambers of the engine. On the other hand, the mixture fed 
into the auxiliary distributing chamber 13 is evenly distributed into the 
auxiliary intake passages 14-17 through the opposite ends of the same 
distributing chamber 13, and then delivered into the corresponding 
auxiliary combustion chambers of the engine. 
Part of the exhaust gases emitted from the engine into the exhaust passage 
of same is returned through the exhaust gas recirculating passage 9e of 
the intake manifold 1, the exhaust gas flow control valve and the other 
exhaust gas recirculating passage 9 into the primary distributing chamber 
2a where it is mixed with the mixture supplied from the carburetor unit 
and delivered therewith into the main combustion chambers of the engine. 
Further, a blow-by gas from the engine is guided through the blow-by gas 
returning passage 11 into the secondary distributing chamber 2b where it 
is mixed with the mixture and delivered into the main combustion chambers 
of the engine. 
Hot water from the cooling system of the engine is guided through the 
passage 12d in the intake manifold 1 into the water chamber 12 where it 
heats the mixtures in the main distributing chamber 2 and the auxiliary 
distributing chamber 13 located just above the water chamber 12, up to a 
temperature suitable for sufficient combustion of the mixtures. 
While a preferred embodiment of the invention has been described, 
variations thereto will occur to those skilled in the art within the scope 
of the present inventive concepts which are delineated by the following 
claims.