U.S. patent number 3,590,793 [Application Number 04/781,532] was granted by the patent office on 1971-07-06 for apparatus for reducing hydrocarbon content of engine exhaust gases during deceleration of automobile.
This patent grant is currently assigned to Missan Motor Company, Limited. Invention is credited to Kenji Masaki.
United States Patent |
3,590,793 |
Masaki |
July 6, 1971 |
APPARATUS FOR REDUCING HYDROCARBON CONTENT OF ENGINE EXHAUST GASES
DURING DECELERATION OF AUTOMOBILE
Abstract
A system for reducing the hydrocarbon content of engine exhaust
gases emitted during deceleration of an automobile by controlling
both the air-fuel ratio of the engine fuel mixture and the intake
manifold vacuum which increases rapidly as soon as the automobile
starts to slow down, said air-fuel ratio and intake manifold vacuum
being controlled by supplying air to the intake manifold of the
engine by way of the step mixture supply flow path of the secondary
side of a carburetor of compound-type, which path is kept
substantially inoperative during the deceleration of the
automobile.
Inventors: |
Masaki; Kenji (Tokyo,
JA) |
Assignee: |
Missan Motor Company, Limited
(Yokohama, JA)
|
Family
ID: |
12036757 |
Appl.
No.: |
04/781,532 |
Filed: |
December 5, 1968 |
Foreign Application Priority Data
|
|
|
|
|
Mar 30, 1968 [JA] |
|
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43 20785 |
|
Current U.S.
Class: |
123/327; 123/325;
123/389; 123/337; 261/41.5 |
Current CPC
Class: |
F02M
3/09 (20130101) |
Current International
Class: |
F02M
3/00 (20060101); F02M 3/09 (20060101); F02m
003/02 () |
Field of
Search: |
;123/97B,97,119,124
;261/41.4,DIG.19 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Burns; Wendell E.
Claims
What I claim is:
1. In a carburetor of compound-type used for an automotive
gasoline-powered internal combustion engine and having a main
mixture supply flow path leading to the intake manifold of said
engine and kept substantially closed by a secondary butterfly valve
mounted therein during the decelerating operation of the automobile
and a step mixture supply flow path which includes means defining
an air bleed vented from the atmosphere, a liquid fuel passage
leading from a fuel source and communicating with said air bleed, a
mixture passage for passing the mixture of air delivered from said
air bleed and fuel delivered from said liquid fuel passage and step
port communicating with said mixture passage and opening into said
main mixture supply flow path at a position where said secondary
butterfly valve substantially closes the last named path during
deceleration, a system for supplying said engine with an air-fuel
mixture through said step mixture supply flow path during the
decelerating operation, said system comprising means defining a
deceleration port communicating with said step port and opening
into said main mixture supply flow path downstream of said
secondary butterfly valve and a valve assembly comprising a valve
member and a coil spring, said valve member being operatively
inserted into said step port and normally held in a position to
permit said mixture passage to communicate with said step port by
the action of said coil spring and held, during the decelerating
operation, in a position to permit said mixture passage to
communicate not only with said step port but with said deceleration
port against the action of said coil spring and in response to the
increase in the vacuum at the intake manifold of the engine said
valve member having provided therein means defining two different
holes, one permitting said mixture passage to communicate with said
main mixture supply flow path when said valve member is held in a
position to close a passage leading to said deceleration port and
the other permitting said mixture passage to communicate with said
main mixture supply flow path when said valve member is held in a
position to open a passage leading to said deceleration port.
2. The system as set forth in claim 1, wherein said valve assembly
further comprises a solenoid device which becomes energized in
response to the increase in the vacuum at the intake manifold of
the engine for thereby causing said valve member to move to a
position to permit said mixture passage to communicate with said
deceleration port.
3. The system as set forth in claim 2, wherein said solenoid device
is connected by an electrical circuit to a diaphragm switch
assembly by way of a power source, said diaphragm switch assembly
being divided by a diaphragm member into atmospheric and suction
chambers, of which the atmospheric chamber has accommodated therein
a set of moving and stationary contacts both connected with said
electrical circuit and of which the suction chamber communicates
with the intake manifold of the engine and has accommodated therein
a coil spring acting to normally keep said moving contact releases
from said stationary contact, wherein, as an increased vacuum
develops at the intake manifold of the engine during the
decelerating operation, said diaphragm member is displaced by the
increased vacuum exerted thereon and against the action of the last
named coil spring in a direction to cause said moving contact to
abut against said stationary contact for causing said solenoid
device be energized from said power source during the decelerating
operation.
4. The system as set forth in claim 3, wherein said secondary
butterfly valve is made thinner toward the peripheral edge thereof.
Description
The present invention relates to a system for reducing the
hydrocarbon content of exhaust gases of an automotive
gasoline-powered internal combustion engine, and more particularly
to a system for controlling both the air-fuel ratio of an air-fuel
mixture to be drawn into the engine by way of the step mixture
supply flow path of a carburetor and the level of intake manifold
vacuum during deceleration of the automobile.
The presence of hydrocarbons in engine exhaust gases is of keen
interest to the automotive industry for two major reasons--air
pollution and fuel economy. To solve problems concomitant with
these two factors, numerous attempts have heretofore been made,
involving an effort to improve the performance characteristics of
the carburetor in such a manner as to control the air-fuel ratio of
the engine fuel mixture during operations of the automobile.
Difficulties have, however, been encountered by the prior art
methods and systems in maintaining the air-fuel ratio of the engine
air fuel mixture at a proper level invariably under the widely
varying driving conditions and without impairing the driveability
of the automobile.
Automobile operation is usually divided into four different driving
conditions; idle, acceleration, normal cruising, and deceleration.
The range of hydrocarbon content of engine exhaust gases varies
markedly according to the mode of automobile operation, and
experiments thus far conducted on various engine exhaust gases
emitted under different modes of automobile operation have revealed
that the hydrocarbon content of exhaust gases peaks up during
deceleration. This is due partly to the inability of the carburetor
to supply the engine with an air-fuel mixture having an air-fuel
ratio which is appropriate to provide a satisfactory combustion of
the mixture in the combustion chamber of the engine and partly to
the occurrence of an unsatisfactory combustion and misfiring of the
air-fuel mixture that are invited by the increase in the intake
manifold vacuum during deceleration. In order to accomplish
satisfactory combustion of the air-fuel mixture during
deceleration, therefore, it is important that the carburetor is
capable of supplying the engine with a mixture having an air-fuel
ratio best suited for each mode to eliminate the presence of
partially burned or unburned hydrocarbons in the engine exhaust
gases, and further to increase the amount of the mixture to be
supplied to the engine thereby to prevent an excess increase of the
intake manifold vacuum during deceleration. The fact is however
that, during deceleration of the automobile, the air-fuel ratio of
the mixture produced by the carburetor remains substantially
unchanged from that which is produced during the idle operation in
spite of the engine speed and intake manifold vacuum changing as
the automobile speed changes. Thus, it is necessary for reducing
the hydrocarbon content of engine exhaust gases during deceleration
either to have the air-fuel ratio of the air-fuel mixture for the
idle operation decreased to a value which is adequate for effecting
the satisfactory combustion of the mixture, under all the driving
conditions, or to install in the carburetor such a device that is
capable of controlling the air-fuel ratio under a predetermined
level.
It is therefore a prime object of the invention to provide a system
which is capable of reducing the hydrocarbon content of engine
exhaust gases emitted during deceleration of an automotive engine
independently of the remaining modes of operation.
It is another prime object of the invention to provide a system
adapted to maintain both the air-fuel ratio of an engine fuel
mixture and the intake manifold vacuum under predetermined limits
exclusively during deceleration of the automobile.
It is another prime object of the invention to provide a system for
maintaining the air-fuel ratio of the engine fuel mixture at a
proper level during deceleration and for lowering the intake
manifold vacuum that increases remarkably as soon as the automobile
slows down, whereby a total of the hydrocarbon content of engine
exhaust gases emitted throughout all the modes of automobile
operation is ultimately reduced to a minimum.
It is another prime object of the invention to provide a system
which is adapted to supply air to the carburetor downstream of the
butterfly valve, viz., to the intake manifold of the engine by way
of the step mixture supply flow path of the secondary side of a
carburetor of compound-type so that the engine fuel mixture is made
optimum in both amount and air-fuel ratio for the satisfactory
combustion of the mixture in the combustion chamber of the engine
and that the intake manifold vacuum, which abruptly increases as
soon as the automobile starts to slow down, is lowered to a level
that will minimize the emission of unburned gases from the
engine.
It is another prime object of the invention to prevent an air
pollution caused by the presence of an unburned air-fuel mixture or
hydrocarbons in engine exhaust gases and at the same time to
significantly save the engine consumption of an automobile driven
by a gasoline-powered internal combustion engine.
Further and other objects of the present invention will become
apparent from the following detailed description taken in
conjunction with the accompanying drawings in which like characters
of reference designate corresponding parts in all figures and in
which:
FIG. 1 is a graph showing a desired example of the relationship
between the air-fuel ratio of an air-fuel mixture and the
automobile speed during decelerating operation;
FIG. 2 is a graph showing the relationship between the air-fuel
ratio determined under the idling conditions of the engine and the
total engine exhaust gas hydrocarbon content under the idling,
accelerating and normal cruising operations, viz., under the
operations excepting deceleration;
FIG. 3 is a graph showing the effect of the intake manifold vacuum
on the exhaust gas hydrocarbon content;
FIG. 4 is a partial vertical sectional view of a carburetor
incorporating a system embodying the invention which is under the
idle operation of the automobile;
FIG. 5 shows the system of FIG. 4 under deceleration of the
automobile; and
FIG. 6 shows a modified form of the system of FIGS. 4 and 5.
In a carburetor of the conventional type operating at the air-fuel
ratio determined specifically for idle operation although the
engine speed and intake manifold vacuum change as the automobile
speed changes during deceleration, the engine fuel mixture fails to
attain an optimum air-fuel ratio assuring satisfactory combustion
of the mixture during deceleration.
The hydrocarbon content of engine exhaust gases produced during
deceleration will be reduced to a minimum by controlling the
air-fuel ratio of the mixture in such a manner as to meet with the
curve (a) of FIG. 1 which illustrates an example of a desired
relationship between the automobile speed and the air-fuel ratio.
One simple and economical expedient of approximately realizing the
curve (a) in a usual carburetor may be to restrict the air-fuel
ratio to a predetermined within a certain range, say, anywhere
between 12:1 and 13:1 in consideration of the air-fuel ratio at
idle of the existing automobiles. This will be achieved by
regulating the air-fuel ratio by the use of the usual idle
adjusting screw; the air-fuel ratio determined for idling remains
substantially unchanged during deceleration, too, as previously
noted. Such a restriction of the air-fuel ratio within a relatively
low range, however, results in an increased amount of the
hydrocarbon content during the idle, acceleration and normal
cruising operations, as observed from the curve (b) of FIG. 2, so
that it is advantageous to maintain the air-fuel ratio at a higher
level throughout the different automobile operations excepting
deceleration, preferably by the use of a carburetor which is
operable with a lean air-fuel mixture during deceleration. Thus,
controlling the air-fuel ratio for deceleration (during which time
a particularly large amount of hydrocarbons are present in the
engine exhaust gases) independently of the other modes of operation
is necessitated to reduce the total hydrocarbon content of engine
exhaust gases produced under all the driving modes of automobile
operation.
In the slow running mixture supply flow path of the conventional
carburetors, however, it is extremely difficult to maintain the
air-fuel ratio of the air-fuel mixture at an optimum level in the
course of deceleration in view of the performance characteristics
of the carburetor without use of a suitable control device, though
the air-fuel ratio during the idle operation can be regulated as
desired. In controlling the air-fuel ratio for the idle operation,
moreover, problems are experienced from the difficulty of
eliminating the individual errors ranging generally from 9:1 to
15:1 in the air-fuel ratio weight by weight which is usually
regulated by rule of thumb.
Another important factor in reducing the hydrocarbon content of
engine exhaust gases is the influence of the high intake manifold
vacuum which develops abruptly at the initial stage of the
deceleration. The intake manifold vacuum increases sharply as soon
as the automobile starts to slow down during deceleration, say, in
excess of 650 mm. of Hg. while it remains of the order of 500 mm.
of Hg. during the idle operation. This is entirely due to the fact
that the butterfly valve of the carburetor remains substantially
closed during deceleration so as to shut off the flow of the
air-fuel mixture in the main mixture supply flow path although the
engine operates at a relatively high speed which is proportioned to
the running speed of the automobile. The intake manifold vacuum
that has increased to such a high level inevitably leads to
unsatisfactory combustion and misfire of the air-fuel mixture in
the combustion chamber of the engine, thereby remarkably giving
rise to an increase in the hydrocarbon content of the engine
exhaust gases emitted during deceleration.
Such a trend in the hydrocarbon content is evident from the curve
(c) of FIG. 3 which indicates a typical example of the relationship
between the engine exhaust gas hydrocarbon content and the engine
intake manifold vacuum as shown the hydrocarbon content is reduced
to a low level substantially independently of the intake manifold
vacuum below approximately 530 mm. of Hg. while at higher vacuums
it increases very rapidly.
To reduce the hydrocarbon content of engine exhaust gases in a more
effective fashion, therefore, it will be advantageous to have the
amount of the engine fuel mixture increased with the resultant
reduction in the intake manifold vacuum during deceleration.
Ideally, it will be the best approach to the reduction of the
hydrocarbon content of the engine exhaust gases during deceleration
to have the amount of the engine fuel mixture increases to such an
extent as to lower the intake manifold vacuum to the vicinity of
530mm. of Hg. On account of the braking effect of the engine,
however, reduction of the intake manifold vacuum to such an extent
turns out rather detrimental to the driveability of the automobile
and hence, is not suited for practical purposes. The intake
manifold vacuum should therefore be decreased to a point where the
driveability of the automobile is in no way impaired. In this
sense, the reasonable level to which the intake manifold vacuum
should be reduced is generally considered to be in the neighborhood
of 600 mm. of Hg. As illustrated by the curve (c) of FIG. 3,
reducing the intake manifold vacuum to approximately 600mm. of 600
mm. is apparently conducive to the minimization of the hydrocarbon
content of the engine exhaust gases.
As is apparent from the curve (b) of FIG. 2, moreover, it will be
advantageous for minimizing the aggregated amount hydrocarbon
content of engine exhaust gases emitted during the idling,
accelerating and normal cruising operations (namely under all the
modes of automobile operations excepting the deceleration) to use a
carburetor of the type which is operable with a relatively lean
air-fuel mixture, that is, with a mixture having a relatively high
air-fuel ratio. The carburetor of this type will have the flow
characteristics dictated by the lean side of the flow band in the
established carburetor flow curve. Thus, using the system according
to the invention in a carburetor having said flow characteristics
will be conducive to the reduction of the total amount of
hydrocarbons in engine exhaust gases emitted during the different
operations of the automobile.
One embodiment of the present invention to achieve such an end is
shown in FIG. 4, wherein the carburetor is illustrated with the
engine idling and the secondary butterfly valve substantially fully
closed and with the secondary side of the carburetor kept
inoperative. The butterfly valve 10 may be of the type which is
usually used in the conventional carburetors and is rotatable with
the shaft 11. Represented by 12 is a step air bleed, which is
vented from the atmosphere and which is so sized in diameter as to
admit a suitable amount of air to the step fuel supply flow path of
the carburetor. The air bleed 12 communicates upstream with a step
jet 13 by way of a passage 15. At the step jet 13, the fuel fed
from the liquid fuel passage 14 leading to the fuel source (not
shown) is metered and mixed with air introduced from the air bleed
12. The resultant mixture of air and fuel is then introduced into a
step fuel mixture passage 16.
According to the present invention, a combination valve and
diaphragm fuel control assembly 18 is provided behind the step port
17, whereby the air-fuel mixture flowing in the fuel mixture
passage 16, is allowed into the carburetor downstream of the
secondary butterfly valve 10 during deceleration of the automobile
when the intake manifold vacuum increases abruptly while, in the
idling operation, the step fuel supply flow path of the carburetor
remains inoperative with the secondary butterfly valve fully
closed.
The construction of the fuel control assembly 18 is such that it is
divided by a diaphragm member 19 into atmospheric and suction
chambers 20 and 21 of which the suction chamber 21 communicates
with the intake manifold (not shown) of the engine by way of a
suction conduit 25 and the atmospheric chamber 20 has provided
therein a valve member 23 which is fixedly connected with the
diaphragm member 19. The diaphragm member 19 and accordingly the
valve member 23 are normally held in their leftmost positions,
namely, in positions remotest from the suction conduit 25 by the
action of a coil spring 24, as illustrated in FIG. 4.
The valve member 23 has a hollow, cylindrical and open-ended
portion 23', in which are provided two different holes 26 and 27 of
which the former is shown to be smaller in diameter than the
latter. The hole 27 is located in such a manner as to let the
air-fuel mixture passage 16 communicate with the step port 17 and
be isolated from the passage 28 leading to the decelerating port 29
during the idling operation of the automobile when the valve member
23 is held in a position remotest from the suction conduit 25 as
shown in FIG. 4, while the hole 26 is located in such a manner as
to let the air-fuel mixture passage 16 communicate not only with
the step port 17 but with the passage 28 when the valve member 23
is held in its rightmost position, viz., when in deceleration, as
shown in FIG. 5.
During the idle operation of the automobile, as previously
described, the engine intake manifold vacuum is kept at a
relatively low level and, as a consequence, the diaphragm member 19
of the fuel control assembly 18 is held in the leftmost position on
the drawing by the action of the coil spring 24. The result is that
the air-fuel mixture passage 16 is permitted to communicate with
the step port 17 through the hole 27 of the cylindrical portion 23'
and is prohibited from communicating with the passage 28 leading to
the decelerating port 29 which opens into the secondary main
mixture supply flow path of the carburetor downstream of the
secondary butterfly valve 10. The secondary butterfly valve 10
being in a substantially fully closed position, however, there
takes place no flow of air between the secondary side of the
carburetor the secondary main mixture supply flow path and the step
fuel supply flow path so that the atomized air-fuel mixture is not
generated.
According to the invention, however, the air-fuel mixture in the
fuel mixture passage 16 is introduced into the main mixture supply
flow path downstream of the butterfly valve 10 through the
decelerating port 29 during deceleration of the automobile, thereby
eliminating the possibility of an unburned fuel remaining in the
engine exhaust gases, which would otherwise lead to the presence of
hydrocarbon content therein.
As soon as the automobile running at a normal cruising speed starts
to decelerate, the intake manifold vacuum increases rapidly with
the result that the diaphragm member 19 of the fuel control
assembly 18 is forcedly drawn toward the suction conduit 25 against
the spring action and accordingly the valve member 23 retracts away
from the step port 17, viz., moves rightwardly of the drawing. It
therefore follows that the fuel mixture passage 16 communicates
through the hole 26 with the step port 17 and the passage 28
leading to the decelerating port 29 which opens into the secondary
main mixture supply flow path. With the relationship between the
passages 16 and 28 and the step port 17 thus maintained, air is
permitted to spurt from upstream to downstream of the secondary
butterfly valve 10 by way of the step port 17 and at the same time
the air-fuel mixture flowing through the fuel mixture passage 16 is
introduced into the passage 28 by way of the hole 26, due to the
extremely high vacuum present downstream of the butterfly valve.
The hole 26 is so sized in diameter as to serve as an orifice
adapted to properly determine the flow rate of the air-fuel mixture
which debouches into the step port 17.
Thus, the air-fuel mixture to be drawn into the decelerating port
29 through the passage 28 is mixed with air supplied from the step
port 17 so that the air-fuel ratio of the air-fuel mixture is
controlled to a satisfactory level for the operation of the engine
during deceleration.
It may be mentioned that the inlet slit of the step port 17 is
usually shaped, sized and located in such a manner as to provide
for the best performance of the secondary side of the carburetor.
The size of the said inlet slit being optimum for compensating for
the extreme deficiency of air in the fuel mixture during
deceleration, the slit used in the conventional carburetor can be
utilized without making any modification thereto. The secondary
butterfly valve may be of the type which is usually used in the
conventional carburetors of compound type and there is, again, no
need of making a major modification thereto in respect of the
dimensions. For utilizing the slit of the step port 17 in an
effective fashion, it will be advantageous to make the tip of the
butterfly valve 10 thinner toward the peripheral edge thereof so
that, when the butterfly valve is held in a substantially fully
closed position as in the idling and deceleration, the upper
surface of the butterfly valve becomes substantially flush with the
lower periphery of the slit of the step port 17.
The rate of the coil spring 24 is so determined that it overcomes
the force of the intake manifold vacuum occurring during the idling
operation, so that the fuel control assembly 18 remains inoperative
under the automobile operation excepting deceleration.
Represented by 30 is a decelerating port adjusting screw, which is
adapted to control the amount of the air-fuel mixture to be
debouched out of the decelerating port 29, which screw may be
removed if desired, however.
Although the fuel control assembly 18 is described and shown to use
a diaphragm member, it will be understood that the assembly may be
operated by the use of a solenoid device which is actuated by a
diaphragm switch assembly of suitable construction arrangement.
In this embodiment of the invention, as is apparent from the
foregoing description, the air-fuel mixture fed from the passage 16
is substantially shut off from the engine combustion chamber while
in the idling operation, but, as soon as the automobile slows down
on deceleration and the manifold vacuum decreases rapidly, the
air-fuel mixture from the passage 16 is supplied with additional
air from the step port 17 and is introduced to the engine
combustion chamber during deceleration.
FIG. 6 shows a modified form of the system according to the present
invention, wherein the valve for regulating the flow of air-fuel
mixture in the step mixture supply flow path is constructed
basically similarly to the counterpart of the first embodiment and
is controlled by means of an electrically powered solenoid device
actuated by a diaphragm switch assembly is constructed basically
similarly to the counterpart in the first embodiment.
The valve 23 is connected with a solenoid valve assembly 31
incorporating a solenoid device 32 and a coil spring 33 which
normally holds the valve member 23 in a position to close the
passage 28 from the step port 17 and the passage 16. The solenoid
valve assembly 31 is linked by a wire circuit to a diaphragm switch
assembly 18' via a power source 34. The assembly 18' is divided by
a diaphragm member 19 into atmospheric and suction chambers 20' and
21'. The suction chamber 21' communicates with the intake manifold
(not shown) of the engine by way of a conduit 35, while the other
atmospheric chamber 20' has mounted therein a moving contact 36a
and a stationary contact 36b. A coil spring 24' is mounted in the
chamber 21' and normally forces the diaphragm member 19 toward the
moving contact 36a in a normal state so that the moving contact,
which is connected by a rod 37 with the diaphragm member 19, is
kept released from the stationary contact 36b as illustrated in the
drawing. Both of the contacts 36a and 36b are wired to the solenoid
valve assembly 31.
During the idling operation of the automobile when the intake
manifold vacuum remains at a relatively low lever, the diaphragm
member 19 is forced toward the atmospheric chamber 20' by the
action of the spring 24' as shown in the drawing so that the moving
contact 36a remains released from the stationary contact 36b,
disconnecting the circuit connecting the diaphragm switch assembly
18' and the solenoid valve assembly 31. While the solenoid valve
assembly 31 remains deenergized, the valve member 23 rests at its
leftmost position on the drawing by the action of the spring 33 so
that the step port 17 is isolated from the passage 28, prohibiting
the mixture to spurt from the passage 16 into the secondary main
mixture supply flow path downstream of the butterfly valve 10
during the idle operation.
When, now, an automobile running at a normal cruising speed starts
to decelerate, the pressure in the suction chamber 21', which
communicates with the intake manifold by way of the conduit 35 as
previously described, decreases sharply so that the diaphragm
member 19 is forced toward the suction side against the action of
the coil spring 24'. When the diaphragm member 19 moves rightwardly
of the drawing, the moving contact 36a is made to abut against the
stationary contact 36b and the diaphragm switch 18' becomes
electrically connected with the solenoid valve assembly 31, which
consequently is initiated into action. The actuation of the
solenoid valve assembly 31 urges the valve member 23 to move
leftwardly of the drawing, permitting the passages 16 and 28 to
communicate with each other by way of the hole 26. As the result,
air introduced from the inlet 25 of the port 17 and the fuel from
the passage 16 is allowed into the secondary main mixture supply
flow path downstream of the butterfly valve 10 through the passage
28 and the port 29.
According to a feature of the present invention, the hydrocarbon
content of engine exhaust gases produced during deceleration is
diminished through the effective utilization of the abrupt increase
in the intake manifold vacuum of the engine without major
dimensional modification to the carburetor in its entirety. This is
particularly important in this invention in that the concentration
of the hydrocarbons in engine exhaust gases is sufficiently
stabilized by improving the quality of combustion in the combustion
chamber especially during deceleration of the automobile.
According to another feature of the invention, not only the amount
but also the air-fuel ratio of the engine air-fuel mixture can be
controlled during deceleration of the automobile independently of
the other modes of the automobile operation in such a manner as to
keep the engine air-fuel mixture richer during deceleration than
during the idling, accelerating and normal cruising operations of
the automobile.
According to a further feature of the invention, the intake
manifold vacuum which increases abruptly at the initial stage of
deceleration of the automobile is rendered low, say, reduced to
about 600 mm. of Hg. which is considered a level appropriate for
minimizing the presence of hydrocarbons in the engine exhaust gases
without impairing the driveability of the automobile, as is
previously noted with reference to the curve (c) of FIG. 3.
If, furthermore, the system according to the invention is placed on
use with a carburetor operating on the lean side of the flow band
of the carburetor flow curve, it will lend itself to the reduction
of the hydrocarbon content of engine exhaust gases during every
mode of the automobile operation.
Since the system according to the invention is operable with a
relatively lean air-fuel mixture during the idling, accelerating
and normal cruising operations it will prove advantageous in the
reduction of carbon monoxide content of engine exhaust gases as
well as in the saving of engine fuel consumption.
While two embodiments of the invention have been shown and
described in detail, it will be apparent to those skilled in the
art that such is by way of illustration only and numerous changes
may be made thereto without departing the spirit and scope of the
present invention which is defined by the appended claims.
* * * * *