Note: Descriptions are shown in the official language in which they were submitted.
~ ~ ~ss337
BACKGROUND OF THE INVENTION
___________---- -- ,~ . ~
This invention relates t~ internal combustion engines,
and more particularly to the improvements in internal combustion
engines for use in automobiles.
During idle running and low-load running of an internal
combustion engine for use in an automobile, the throttle valve
is opened only a small degree and hence the amount of intake air
is small. Accordingly, the rate at which a charge mixture is
10 introduced through the intake manifold into the cylinder during
the suction stroke is low, resulting in a weak swirl of the
charge mixture within the cylinder. This also weakens the swirl
of the mixture charge remaining in the cylinder at the time of
ignition, which substantially takes place at the termlnal stage
of a compression stroke, resulting in lowered ingitability and
combustibility. ?
In order to insure the stable running of an engine in
such running conditions, a charge mixture whose air-fuel ratio is
lower than that for medium and high-load running must be provided.
QO~ S~l~ ~ G~7
20 However, this causes increased fuel ~a~p~ia~r as w~ll as an
increase in the quantity of harmful constituents, such as C0 and ~ ~
HC, contained in exhaust gases due to incomplete combustion of ~ -
a rich charge mixture.
Recently, with a view to reducing the ~uantity of
harmful constituents r such as C0 and HC and particularly N0x,
contained in exhaust gases rom an engine, it has been proposed
to burn a charge mixture much leaner than the theoretical or
stoichiometric air-fuel ratio. Also, with a view to reducing
the amount of N0 , it has been proposed to take a part of the
x
exhaust gases from the exhaust system and mix it with a charge
mixture for combustion. Both proposals result in lowered
q~!r ,
''~', .
~35533~ .
1 ignitability as well as lowered combustibility of the charge
mixture, resulting in lowered drivability at idling and low-
load conditions as well as increased fuel consumption.
SU~ ~ RY OF THE INVENTION
It is accordingly a primary object of the present `
invention to provide an internal combustion engine for use in
an automotive vehicle, wherein the fuel consumption is reduced,
particularly during idle running and low-load running of the
19 engine~
It is another object of the present invention to
provide an engine for use in an automotive vehicle, which is
compatible with stable burning of a lean charge mixture for
insuring stable idle running and low-load running, although
such has been impossible with an engine of the prior art, whereby
the amount of harmful constituents contained in the exhaust
gases is reduced. ;
It is a further obiect of the present invention to
provide an engine for use in an automotive vehicle, which is
compatible with stable combustion of a charge mixture containing
a large ~uantity of recirculated exhaust gases, with the
assurance of stable idle running and low-load running, although
such has been impossible with an engine of the prior art, whereby
the amount of NOx contained in the exhaust gases is reduced.
It is a still further object of the present invention
to provide an engine for use in an automotive vehicle, which
permits stable combustion of a lean charge mixture or a charge
mixture containing a large amount of recirculated exhaust gases,
without lowering output or drivability, or increasing the fuel
3~ consumption.
10S5337
1 I-t is a still further object of the present invention
to provide an engine for use in an automotive vehicle, wherein
an amount of harmful cons~ituents contained in the exhaust gases
from an engine in idling running, low-speed, low-load running
is greatly reduced, as compared with that of prior art engines.
To attain these objects, there is provided, according
to the present invention, an internal combustion engine, which
comprises a combustion chamber having an intake port and exhaust
port; a main intake passage for introducing into said intaka
port an air-fuel mixture charge prepared by a mixture-charge
producing device; a spark plug threaded in a cylinder head with
a spaxk gap located in a given position in said combustion chamber;
an injection hole provided in the cylinder head which constitutes
said con~ustion chamber; a sub-intake passage connected to said
injection hole; a gas supply source for supplying gas to said
sub~intake passage under a sufficient gas-supply pressure even
during low-load running in which the opening of a throttle valve
disposed in said main intake passage is smalli a sub-intake valve -
provided in said cylinder head and adapted to open and close said
sub-intake passage; and an actuating mechanism for opening saia
sub-intake passage during the suction stroke.
Gas which is to be fed to said sub-intake passage should
preferably be air, but may be an air-fuel charge mixture, or
otherwise may be exhaust gas from an engine. In case said gas
is air, atmosphere serves as the gas supply source, and in the ~ -
case of a charge mixture, an intake manifold is suitable as a
gas supply source where an engine is e~uipped with a carburetor,
while in the case of exhaust gases an exhaust manifold serves as ;;
a suitable gas supply source. ~ -
According to an engine of the present invention, opening
of a throttle valve is small particularly during idling and low-
':
. ~
~L~55;33~
load running of the engine, and hence the throttling by thethrottle valve should be increased so that the speed of intak~
air being introduced through the main intake passage into the
combustion chamber is low, with the result that only a small
amount of intake air is introduced into the combustion chamber.
This creates a high level of vacuum in the combustion chamber
during a suction stroke, so that gas from a gas supply source
will be drawn by the strong vacuum wi-thin a combustion chamber
through an injection hole, from which gas is injected into the
combustion chamber in a given direction, thereby creating strong
swirl or turbulence of a charge mixture within the combustion
chamber, whereby combustion speed is increased, and the limit
of combustion of a lean charge mixture is raised, resulting in
decreased fuel consumption. In addition, since injection streams
of in~ake air from the injection hole act in khe vicinity oP a
spark gap of said spark plug, which spark gap is located in the
combustion chamber, scavenging of the burnt gases is facilitated,
whereby ignitability of a mixture charge is improved, and the
limit of combustion of a lean mixture charge is raised as a
result of facilitated scavenging action.
Furthermore, even during idling or low-load running
of an engine when cylinder-to-c~linder distribution o~ a charge
mixture is not well performed and combustibility of a charge
mixture are not satifactory because of a low wall temperature
of the combustion chamber, a stable combustion of a lean mixture
charge is ensured, with a minimum lowering of output, a minimum
increase in fuel consumption, and a maximum reduction of the
quantity of NOx contained in the e~haust gases due to a drop of
a maximum combustion temperature as a result of an increased air-
fuel ratio.
Use of an exhaust gas recirculating device in combin-
ation with an internal combustion engine of the present invention
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1~)55337
1 facili-tates reduction in the quantity oE NOx contained in the
exhaus-t gases, without setting the air-fuel ratio, which i5
rather painstaking to control, at a high value approximating a
limit of combus-tion, and the said injec~ion streams serve to
prevent lowering oE ignitability and flame propagation speed
caused by exhaust gases from said recirculating device.
These and other objects and features of the present
invention will be apparent from the ensuing part of the speci-
fication in conjunction with the drawings, which indicate pre-
ferred embodiments of the invention. Throughout the drawings,equivalent components are shown by identical reference numerals.
"
BRIEF DESCRIPTION OF THE DR~WINGS
_________________________________
Fig. 1 is a cross sectional view of a first embodiment
of a~ engine according to the present invention;
Fig. 2 is a view as seen along the line A-A of Fig. l; ~ -
Fig. 3 is a view as seen in the direction of arrow B
of Fig. 1;
Fig. 4 is a cross sectional view taken along the line
C-C of Fig. l;
Fig. 5 is a plot representing engine output lines for
explaining the operation of the engine of the first embodiment; `
Fig. 6 is a cross sectional view of a second embodiment
of an engine according to the present invention;
Fig. 7 is a fragmentary cross sectional view of a
third embodiment;
Fig. 8 is a fragmentary cross sectional view of a
fourth embodiment;
Fig. 9 is a fragmentary cross section~ v~ of a fifth
embodiment;
, . . . . .
: , : : , . : .
~LC355337
1 Fig. 10 is a fragmentary cross sectional view of a
sixth embodiment; and
Fig. 11 is a view Eor explaining the operation of the
sixth embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
____________________________ ________________
Referring first to Figs . 1 through 4, illustrating a
first embodiment of the present invention, there is shown a body
10 of a gasoline internal combustion engine for use in a motor
vehicle, a cylinder head 12, a cylinder blocX 14, a piston 16,
a combustion chamber 18, a spark plug 20, a main intake port
22, an exhaust port 24, a main intake valve 26, an intake manifold
28, a carburetor 30, and an air cleaner 32.
In the cylinder head 12, there is provided an injection
hole 34 open to the combustion chamber 18. The injection hole
34 has an opening directed beneath a spark gap 36 of the spark
plug 20 as well as ~owards the piston 16 at a given angle of, ~ ~ ;
for example, 30 to 60C with respect to the top face of the
piston 16. The injection hole 34 is connected through the mediary
of~a sub-intake valve 38 to a sub-intake passage 40.
The ~ain intake valve ?6 and the sub-intake valve are
mushroom valves, which are actuated by a rocker arm 42 common to ~ :
these valves,said rocker arm in turn being fitted on a rocker
shaft 44 and adapted to be swung in engaging relation to a cam
48 which in turn is mounted on a cam shaft 46 rotatable in ~ -
association with the rotation of a crank shaft (not shown) of the
engine. The rocker arm 42 has forked arm portions on the
opposite side of the engaging surface of said arm with the cam
face 48. Adjusting screws 50 and 52 are threaded in the forked
arm portions, respectively, in a manner that the lower end of one
..
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-- 6 --
.
1055337
acljusing screw 50 bears on the top end of a valve stem of the
main intake valve 26, while the lower end of the other adjusting
screw 52 bears on the top end of a valve stem of the sub-intaks
valve 38.
Shown at 54 and 56 are valve springs, at 58 and 60
spring sea~s, and a~ 62 a valve guide for the sub-intake valve
38. The valves are operative to open the passage between the
injection nozzle 34 and the sub-intake passage 40 during the
suction stroke of the piston 16.
A venturi 66 and a throttle valve 68 are disposed in
the main intake passage 64 in a portion corresponding to the
carburetor portion, the main intake passage leading from the air
cleaner 32, via the carburetor 30 and intake manifold 28 to the
intake port 22. An idle port 70 and slow port 72 are open from
the inner wall of the intake passage in the vicinity of the
closed position of the throttle valve 68, said idle port and
: '
slow port supplying fuel when the engine is in the idle running
and low-load running condition, and an adjusting screw 74 is
threaded in the idle port 70. The venturi 66 has a main nozzle
76 for mainly feeding fuel when the engine is in the medium and ~ -
high-load running conditions. ~
. .
An exhaust gas recirculating passage 78 is communicated
at one end with an exhaust passage, for example, an exhaust
manifold (not shown) of the engine and connected at the other
end, through the mediary of a control valve 80 disposed midway
of said passage, to the trunk portion of the intake manifold 28,
said control valve serving to detect varying running conditions
of the engine, thereby controlling a flow rate of exhaust gases
according to the running condition detected.
3~
The sub-intake passage 40 is communicated by way of a
pipe 82 with the main intake passage 64 upstream of the venturi 66.
.. . . . . . . .
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1~55337
1 In operaticn, a major part of air introduced under
suction from the air cleaner 32 into the main inta~e passaye
64 is mixed with fuel at a given air-fuel ratio in the carburetor
30, and the chaxge mixture thus produced is introduced under
suction through the intake port into the combustion chamber 18.
A portion of the air introduced in the main intake passage is
introduced through the pipe 82 and then through the sub-intake
passage ~0 into the injection hole 34, being injected into the
combustion chamber 18.
1~ The amount of air injected from the injection hole 3~
and the force of the injection stream depend upon the degree of
opening of the throttle valve 68, i.e. the load of the engine.
Specifically, when in the idle running or low-load running
condition, with the throttle valve being opened to a small extent,
the amount of charge mixture being fed through the main intake
passage 64 into the combustion chamber is small, thus creating
a high level vacuum in the combustion chamber 18 during the
suction stroke. Meanwhile, the portion of the main intake passage
64, which is upstream of the venturi 66, is maintained substan-
tially at atmospheric pressure so that, due to a pressure
difference between the intake passage and the combustion chamber,
a large amount of air is injected with a strong force from the
injection hole 34 into the combustion chamber 18. Consequently,
injection streams of air from the injection hole create a strong
swirl or turbulence of the charge mixture which has been introduced ~-
into the combustion chamber 18, and at the same time, air from the
injection hole is mixed with the charge mixture, whereby the ;
lattex is stratified or spottedly dispersed under uneven distri~
bution of concentration.
3~ Since the injection streams of air run past the vicinity
of the spark gap 36 of the spark plug 20 beneath the spark gap,
:
~)55;337
1 combustion gases residual in the vicinity o~ the spark gap 36
are scavenged under the guidance o~ injec-tion streams o~ air,
and in turn a ~resh charge mixture will be introduced into the
vicinity of the spark gap. Thus, it is understood that at the
time of iynition of a charge mixture, which is to be e~fected
in the latter half stage o~ a comp~ession stroke, there still
exists a strong swirl or turbulence of air and charge mixture
stratified or unevenl~ distributed in a combustion chamber, and
the charge mixture introduced in the combustion chamber runs in
the vicinity of the spark gap 36. It has been proven through
tests that the speed of flame propagation as well as the limit
of mis~iring are amazingly increased and fuel consumption is
lowered, as compared with that in engines of the prior artt and
that use o~ a lean charge mixture does not caus~e a considerable
lowering of outputs any more, assuring improved drivability of
an engine.
In this embodiment, it is so designed that an inner
diameter of the injection hole 34 is on the order of 3 mm and
an inner diameter of the sub-intake passage 40 i~ on the order
2~ of 5 mm, so that in a low-load running zone, the amount o~
intake air being fed through the sub-intake passage 40 may be
in the range of 10 to 20~ of the amount o~ intake air being ~ed
through the main intake passage 64. The carburetor 30 is so
adjusted that the total air-fuel ratio of intake air from the
main intake passage 64 and from the sub-intake passage 40 is
given in Fig. 5.
Fig. 5 plots engine-ou-tput lines, wherein the output of
an engine is represented on the ordinate and the rpm of the
engine is represented on an abscissa. A solid line A represents
~ an ou~put line when the throttle valve 68 assumes a fully open
1055337
1 position, and a solid line B represents an output line when the
throttle valve assumes an opening for idle running, while a solid
line C represents a curve when an au-tomobile runs on a level
road. Single dotted lines represent iso-vacuum lines of the
intake manifold vacuum which is produced in the intake manifold
28, and double dotted lines represent iso-throttle-opening lines,
while broken lines represent iso-air-fuel ratio lines.
The numerals on the broken lines represent an air-fuel
ratio. A cross hatched area D represents a low-load urban running
zone. In the low-load running zone represented by the hatched
area D, an air-fuel ratio is adjusted to a range of 15 to 17
which is higher than the air-fuel ratio in the same running 20ne
of an ordinary engine.
The amount of exhaust gases being introduced under
suction through the exhaust gas recirculating in passage 78 to
the intake manifold 28 is controlled by the control valve 80.
The amount of recirculating exhaust gas is adjusted so as to hold
down the quantity of NOx contained in exhaust gases to a given
value.
On the other hand, in a high-load running zone, in
which an opening of the throttle valve is large, a large amount
of charge mixture is introduced under suction through the main
intake passage 64 into the combustion chamber 18. Accordingly,
the amount of air being injected through the sub-intake passage
40 and the force of injection streams of air becomes lowered,
with the result of the lowered swirl-creating effect of injection
streams of air. In this case, however, charging efficiency is
high, a strong swirl or turbulence of the charge mixture is
produced when introduced from the intake port 22 into the com-
bustion chamber 18, and the inner wall temperature of the com-
bustion chamber 18 rises. These factors are effective enough to
'' : . ,., .......................................................... ~'
., . . :
~55337
. increase the flame propagation speed and improve combustibility,
without resorting to injection streams of air from the in~ection
hole 34 for creation of a strong swirl or turbulence.
The engine of this embodiment yields the below-mentioned
various resul-ts. In a low-load running zone of the engine in
which the combustion conditions are not satisfactory because of
a comparatively low inner wall temperature in the combustion
chamber 18 and low charging effeciency, a stable combustion of . :~
charge mixture is insured not only when the charge mixture is
obtained by mixing the air, which is flown into the combustion
chamber 18 through the injection port 34, to a charge mixture
containing some exhaust gases and having a total air-fuel ratio .
in the range of 11 to 14, but also when the lean charge mixture
has a total air-fuel ratio in the range oE 15 to 21. .Strong
injection streams of air ~rom the injection hole 34 contribute
to treating strong swirl or turbulence of a charge mixture in a
combustion chamber, and air thus injected is mixed to a charge
mixture sucked through the main intake passage, in a proper
stratified form or under uneven distribution of concentration,
whereby a.combustion speed is increased with shortened combustiQn :
time, without incurring an increase in the quantity of N0x con-
tained in the exhaust gases. Furthermore, fuel consumption is
reduced, drivability is improved, and quantity of unburnt gases
such as HC, C0 contained in exhaust gases is reduced.
In the embodiment of this invention shown in Figs.l - 4,
since the main intake valve 26 and the sub-intake valve 38 are
actuated by the single rocker arm, these valves are opened at
substantially the same time. However, it may be possible to
provide one rocker arm for each of these valves to set the opening
timing of the sub-intake valve 38 within the open period of the
main intake valve 26.
l~SS337
1 A second embodiment shown in Fig. 6 is SQ arranged
that a change-over valve 84 ls disposed midway of the pipe 82
communicating with the sub-intake passage 40. The changeover
valve is switched to allow the passing of air or exhaust gases
therethrough~ A valve body 86 of the changeover valve 84 is
connected through the mediary of a valve rod 88 to the central
portion of a diaphragm 92 of a diaphragm device. The diaphragm
92 defines two chambers, one chamber 94 being open to atmosphere,
while the other chamber 96 is communicated through a pipe 98
with the intake manifold 28. A spring 100 which, normally acts
to urge the diaphragm 92 upwards as viewed in Fig. 6, is housed
in chamber 96. The chamber 102 housing therein the valve body
86 has a top opening communicating with one end of the pipe 82
leading to the intake passage 64 and a side opening communicating
with the other portion o~ the pipe 82 which is communicated with
the sub-intake passage 40. The chamber 102 communicates with a
chamber 108 via a through-hole 106 provided in a partitioning ;
wall 104. The valve rod 88 extends vertically through the hole
106. The chamber 108 has a side opening, which communicates with
one opening of a branch pipe 110 stemed from the exhaust gas
recirculating passage 78.
The valve body 86 is displaced vertically in response
to the movement of the diaphragm 92, 50 that the valve body 86
closes the opening of the pipe 82 when moved upwardsr and closes
the through-hole 106 when moved downwards.
A check valve 112, which is disposed midway of the
pipe 82, allows air flow only in the direction from the main
intake passage 64 toward the chamber 102. The diaphragm device
90 is so designed that when a vacuum level of mo~e than a given
level, for example, 300 mmHg, is established in the chamber 96,
the diaphragm 92 is moved downwards against a force of the spring
100 into the lowest position.
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~OSS337 :
1 In operation, in the idling or low-load running zone
of an engine, the opening of the throttle valve 68 i9 small and
the intake manifold vacuum is raised to more than a given vacuum
level. The diaphragm 92 is deflected downwards, whereby the valve .;
body 86 closes the through-hole 106. As a result, air in the ~`:
main intake passage 64, upstream of the venturi 66, will be fed
to the injection hole 34. When the intake :manifold vacuum drops
to less than a given vacuum level, such as during the high-load
running zone of the engine when the opening of the throttle
valve 68 is large, the diaphragm 92 is moved upwards, whereby
the valve body 86 closes the opening of the pipe 82. Consequently, :
exhaust gases in the exhaust gas recirculating passage 78 are
introduced by way of the branch pipe 110, chamber 108, through-
hole 106, chamber 102, pipe 82 near to the sub-intake passage, ~ .
and sub-intake passage 40, into the injection hole 34. Thus,
when the engine is run in the low-load running zone, a strong
injection stream of air is injected from the injection hole 34
into the combustion chamber 18, thereby rendering the mixture :~
charge leaner under uneven distribution o~ concentration and at
the same time creating a strong swirl or turbulence of the mixture
charge, whereby there are obtained the same results as in the .
first embodiment. On the other hand, in the high-load running
zone of the engine during which the injection stream of air rom .
the injection hole 34 is weak, exhaust gases in the exhaust gas
recirculating passage 78 are recirculated through the main intake ;
passage 64 as well as being introduced into the injection hole 34, :
so as to increase an amount of exhaust gases being recirculated.
This greatly contributes to reducing the quantity o~ NOX contained
in the exhaust gases.
A third embodiment shown in Fig. 7 is so constructed
that the pipe 82 connected to the main intake passage 64 upstream
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~055337 : ~
of the venturi 66 is connected mid~ay of a passage 116 for second-
ary air, which is ~ed from an air pump 114 to an exhaust system
in an exhaust gas purifying device (not shown), such as a thermal
reactor, catalytic converter or the like, provided in the exhaust
system of the engine, with a view to oxidation of unburnt gas2s
contained in exhaust gases. The injection hole 34' is of a larger
diameter, equal to the diameter of a bore in the valve seat portion
of the sub-intake valve 38, although, in the first embodiment,
the diameter of the injection hole 34 is as small as 3 mm. In
this embodiment, a pressure difference between the injection
pressure from the air pump and the vacuum level in the combustion
chamber during a suction stroke is large and a large amount of air
is injected into a combustion chamber because o~ the injection
hole 34' having a large diameter. ThuS, the engine of this
embodiment is particularly useful where injection of a large ~nt
of air is needed.
A fourth embodiment shown in Fig. 8 is a modification
of the first embodiment. In this embodiment, the pipe 82 is
communicated with a portion of the main intake passage 64 between
the venturi 66 and the throttle valve 68. In a low-load running
zone of an engine, during which the opening of the throttle val~e
68 is small and fuel is essentially fed through a slow system ~ -
consisting o~ the idle port 70 and the slow port 72, while only
a small amount of fuel is fed from the main nozzle, an extremely
lean charge mixture containing a very small amount o~ fuel
supplied from the main nozzle 76 is injected through the injection
hole 34 into the combustion chamber 18. On the other hand, when
in a high-load running zone, a charge mixture whose air-fuel
ratio is substantially equal to that of a charge mixture introduced
under suction through the main intake passage 64 is injected ~rom
the injection hole 34 into the combustion chamber.
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- 1~)55337 ~
1 Since, in this embodiment, a charge mixture having the
above-described air-fuel ratio is injected through the injection
hole 34 into the combustion chamber 18, there are created strong
swirls or turbulences o~ a charge mixture within the combustion
chamber 18, thereby increasing the combustion speed. In addition,
if the injection hole 34 is disposed, with its opening directed
to the vicinity o the spark gap 36 of the spark plug 30 for ~;
scavenging o~ burnt gases dwelling in the vicinity of the spark
gap, then improved combustibility results.
In a fifth embodiment of the present invention shown
in Fig. 9, the sub-intake valve 38 and the mechanism for actuating
the valve in the first embodiment are omitted, and in turn, a
check valve 118 is provided as a sub-intake valve in the sub-
intake passage 40, the check valve being opened in response to
a vacuum created in the combustion chambex 18. The check valve
118 is inserted in a threaded hole 120 in which the pipe 82 is
threaded, and consists of a valve body 122 and a spring 124
which normally urges the valve body 122 in the valve-closing
.
direction. A cooling water passage 126 for cooling the check
valve is provided in the cylinder head in the vicinity o~ the
check valve 118~ In this embodiment, the injection hole 34 is
disposed, with its opening directed to the vicinity o~ a spark
gap in the spark plug 20.
When a vacuum is created in the combustion chamber 18
during a suction stroke, then the check valve 122 is opened,
whereby air is in~ected by way of the pipe 82, sub-intake passage
40 and through the injection hole 34 into the combustion chamber
18, thereby scavenging a residual mixture charge existing in the
vicinity of the spark gap 36 in the spark plug 20, and at the
same time, creating a strong swirl or turbulence of a charge
mixture within the combustion chamber 18.
- 15 - -
.
.
~L05S33~ ~
1 ~ si~th embodiment shown in Fig. 10 is so arranged
that a cylindrical injection chamber 128 is provided in the
cylinder head 12 above the combustion chambex 18, the cylindrical
injection chamber being communicated by way of the injection
hole 34, open from the bottom thereof, with the combustion chambe~
18. Wlthin the injection chamber 128 there is fitted a sub-piston
130, which is adapted to vertically move within the injection
chamber 128 by means of a valve-actuating mechanism which is
operated by rotation of the cam shaft 46. The sub-intake passage
40 in this embodiment is such that one end thereof leads to the
atmosphere through the mediary of an air cleaner 132 solely ;
- serviceable for this passage, and the other end thereof leads to
the inner peripheral wall o~ the injection chamber 128, so that
opening of the sub-intake passage 40 at the other end may be
opened or closed by the peripheral surface of the sub-piston
130 when the sub-piston moves vertically. Also shown is a
rocker arm 134 for actuating the sub-piston 130, a spring seat
136, a return sprlng 138, and a cam 140 mounted on the cam shaft
46. The cam 140 is given a profile suited for displacing the
~ sub-piston 130 in the manner shown by a cur~e in Fig. 11.
In Fig. 11, the time X represents a duration for which
the sub-intake passage 40 is maintained in communication with
the injection chamber 128, and the time Y represents a duration
for which the sub-piston 130 effects a compression stroke to
compress air within the injection chamber 128. ~he sub-intake ;
passage 40 and the injection hole 34 are maintained in communica-
tion with each other during the suction stroke of the main piston ~:
(if it is desirable, the initial stage of a compression stroke
may be included).
According to this embodiment, air will be injected from
the injection hole 34 into the combustion chamber 18 according to
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~C~55337
1 a vacuum level within the combustion chamber during the period
of time X, and during the period of time ~, injection of air is
continued under ~he compression of the sub-intake 130, so that
the injection pressure of streams of air from the injection hole
is increased to a greater extent, as compared with those in the
preceding embodiments thus intesifying a function of creating
swirl or turbulence of a charge mixture.
Also in this embodiment, if streams of air being injected --
from the injection hole 34 are directed towards the spark gap 36
in the spark plug 20, then scavenging is promoted by injection
streams of air immediately before ignition, resulting in an ~-
amazingly raised limit of combustion of a lean mixture charge.
Throughout the embodiments described, an optimum amount
of intake air being fed through the sub-intake passage into the
combustion chamber largely depends upon the type of engine used,
but should preferably be set to a range of 5 to 30% by weight of
the amount of intake fuel-air mixture being fed through the main
intake passage 64, when the engine is in the low-load running zone.
Although the disclosure describes and illustrates a
preferred embodiment of the invention, it is to be understood
the invention is not restricted to this particular embodiment.
~ .
; '.
- 17 -
I
