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Claims  |
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What is claimed is:
1. An exhaust gas recirculation system for a diesel engine for a vehicle
utilizing an air intake system and an exhaust system, comprising:
(a) an exhaust gas recirculation passage a downstream end of which is
connected to said exhaust system and an upstream end of which is connected
to said air intake system, so as to recirculate exhaust gas from said
exhaust system to said air intake system;
(b) an exhaust gas recirculation control valve comprising a pressure
chamber, which regulates flow resistance of said exhaust gas recirculation
passage according to an amount by which the pressure in said pressure
chamber is lower than ambient atmospheric pressure, so as to regulate a
flow amount of said recirculation of exhaust gas from said exhaust system
to said air intake system;
(c) means for providing a supply of low pressure;
(d) an absolute pressure control valve, comprising an input port and an
output port, which receives supply of low pressure from said means for
providing low pressure at said input port, and which provides a supply of
pressure at said output port the absolute pressure value of which is
substantially fixed;
(e) a regulator valve comprising an input port and an output port, said
regulator valve receiving at said input port a supply of said pressure at
said output port of said absolute pressure control valve the absolute
pressure value of which is substantially fixed, and producing at said
output port an output pressure value which depends upon engine load; and
(f) a vacuum control valve comprising a pressure regulating chamber which
receives a supply of pressure from said means for providing low pressure
and an output port opening from said pressure regulating chamber, and in
accordance with increasing engine load increasing an absolute pressure
value at and below which pressure in said pressure regulating chamber is
bled to atmosphere, and further comprising a control chamber which
receives supply of said output pressure value from said output port of
said regulator valve and which controls the bleeding of said pressure
regulating chamber to atmosphere according to the pressure therein by
altering said certain pressure value, and said output port of said vacuum
control valve being communicated to said pressure chamber of said exhaust
gas recirculation control valve.
2. An exhaust gas recirculation control system according to claim 1,
wherein said exhaust gas recirculation control valve controls flow
resistance of said exhaust gas recirculation passage to be maximum when
the pressure in said pressure chamber of said exhaust gas recirculation
control valve is lower than the ambient atmospheric pressure by less than
a first predetermined amount, thereafter decreases flow resistance of said
exhaust gas recirculation passage as the difference between the pressure
in said pressure chamber and the ambient atmospheric pressure rises above
said first predetermined amount while such is still below a second
predetermined amount, and controls flow resistance of said exhaust gas
recirculation passage to be minimum when the pressure in said pressure
chamber is lower than the ambient atmospheric pressure by more than said
second predetermined amount.
3. An exhaust gas recirculation control system according to claim 1,
wherein operation of said regulator with respect to change of ambient
atmospheric pressure is such that, when ambient atmospheric pressure is
such as is typical for low altitude vehicle operation, said absolute
pressure value of the pressure at said output port of said absolute
pressure control valve is less than the output pressure which said
regulator valve is adapted to produce, for substantially all engine load
values; but, when ambient atmospheric pressure is such as is typical for
high altitude vehicle operation, said absolute pressure value of the
pressure at said output port of said absolute pressure control valve is
greater than said output pressure which said regulator valve is adapted to
produce in the circumstances of low engine values, and is less than said
output pressure which said regulator valve is adapted to produce in the
circumstances of medium and high engine load values.
4. An exhaust gas recirculation control system according to claim 3,
wherein said exhaust gas recirculation control valve controls flow
resistance of said exhaust gas recirculation passage to be maximum when
the pressure in said pressure chamber of said exhaust gas recirculation
control valve is lower than ambient atmospheric pressure by less than a
first predetermined amount, thereafter decreases flow resistance of said
exhaust gas recirculation passage as the difference between the pressure
in said pressure chamber and ambient atmospheric pressure rises above said
first predetermined amount while it is still below a second predetermined
amount, and controls flow resistance of said exhaust gas recirculation
passage to be minimum when the pressure in said pressure chamber is lower
than ambient atmospheric pressure by more than said second predetermined
amount.
5. An exhaust gas recirculation system for a diesel engine for a vehicle
utilizing an air intake system and an exhaust system, comprising:
(a) an exhaust gas recirculation passage a downstream and of which is
connected to said exhaust system and an upstream end of which is connected
to said air intake system, so as to recirculate exhaust gas from said
exhaust system to said air intake system;
(b) an exhaust gas recirculation control valve comprising a pressure
chamber, which regulates flow resistance of said exhaust gas recirculation
passage according to an amount by which the pressure in said pressure
chamber is lower than ambient atmospheric pressure, so as to regulate a
flow amount of said recirculation of exhaust gas from said exhaust system
to said air intake system;
(c) means for providing a supply of low pressure;
(d) an absolute pressure control valve, comprising an input port and an
output port, which receives supply of low pressure from said means for
providing low pressure at said input port, and which provides a supply of
a pressure at said output port an absolute pressure value of which is
substantially fixed; and
(e) a vacuum control valve comprising a pressure regulating chamber
receives a supply of pressure from said output port of said absolute
pressure control valve, and further comprising an output port opening from
said pressure regulating chamber, said vacuum control valve being
controlled according to engine load, and bleeding to atmosphere said
pressure regulating chamber when the pressure therein is not greater than
a certain pressure value, said certain pressure valve increasing in
accordance with increasing engine load; and said output port of said
vacuum control valve being communicated to said pressure chamber of said
exhaust gas recirculation control valve.
6. An exhaust gas recirculation control system according to claim 5,
further comprising a regulator valve comprising an input port and an
output port, said regulator valve receiving a supply of low pressure from
said means for providing low pressure at said input port, and producing at
said output port an output pressure value which depends upon engine load;
and wherein said vacuum control valve further comprises a control chamber
which receives a supply of said output pressure value from said output
port of said regulator valve and which controls bleeding of said pressure
regulating chamber of said vacuum control valve to atmosphere according to
the pressure therein by altering said certain pressure value.
7. An exhaust gas recirculation control system according to claim 5,
wherein said exhaust gas recirculation control valve controls flow
resistance of said exhaust gas recirculation passage to be maximum when
the pressure in said pressure chamber of said exhaust gas recirculation
control valve is lower than ambient atmospheric pressure by less than a
first predetermined amount, thereafter decreases flow resistance of said
exhaust gas recirculation passage as a difference between the pressure in
said pressure chamber and the ambient atmospheric pressure rises above
said first predetermined amount while it is still below a second
predetermined amount, and controls flow resistance of said exhaust gas
recirculation passage to be minimum when the pressure in said pressure
chamber is lower than ambient atmospheric pressure by more than said
second predetermined amount.
8. An exhaust gas recirculation control system according to claim 5,
wherein operation of said vacuum control valve with respect to change of
ambient atmospheric pressure is such that, when ambient atmospheric
pressure is such as is typical for low altitude vehicle operation, said
absolute pressure value of the pressure at said output port of said
absolute pressure control valve is less than said absolute pressure value
at and below which pressure in said pressure regulating chamber of said
vacuum control valve is bled to atmosphere, for substantially all engine
load values; but, when the ambient atmospheric pressure is such as is
typical for high altitude vehicle operation, said absolute pressure value
of the pressure at said output port of said absolute pressure control
valve is greater than said absolute pressure value at and below which
pressure in said pressure regulating chamber of said vacuum control valve
is bled to atmosphere, for low engine load values, and is less than said
absolute pressure value at and below which pressure in said pressure
regulating chamber of said vacuum control value is bled to atmosphere, for
medium and high engine load values.
9. An exhaust gas recirculation control system according to claim 8,
wherein said exhaust gas recirculation control valve controls flow
resistance of said exhaust gas recirculation passage to be maximum when
the pressure in said pressure chamber of said exhaust gas recirculation
control valve is lower than the ambient atmospheric pressure by less than
a first predetermined amount, thereafter decreases flow resistance of said
exhaust gas recirculation passage as a difference between the pressure in
said pressure chamber and the ambient atmospheric pressure rises above
said first predetermined amount while it is still below a second
predetermined amount, and controls flow resistance of said exhaust gas
recirculation passage to be minimum when the pressure in said pressure
chamber is lower than ambient atmospheric pressure by more than said
second predetermined amount. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an exhaust gas recirculation system for a
diesel engine, and more particularly relates to an exhaust gas
recirculation system for a diesel engine in which altitude compensation is
performed according to engine load in an appropriate fashion.
The present patent application has been at least partially prepared from
material which has been included in Japanese Patent Applications Nos. Sho
58-173795 (1983) and Sho 58-196695 (1983), which were invented by the same
inventors as the present patent application.
DISCUSSION OF THE BACKGROUND
It is known to provide exhaust gas recirculation for a diesel engine, in
order to reduce the quantities of NOx (nitrogen oxides) in the exhaust
gases of the engine; and this is effective for improving exhaust quality,
but the amount of recirculation of the exhaust gases is required to be
properly controlled. In such an exhaust gas recirculation system, a
quantity of exhaust gas is recirculated from the exhaust system of the
engine to the intake system thereof, so as to replace some of the air that
would otherwise be inhaled by the diesel engine. It is acceptable to thus
recirculate an amount of exhaust gas which is less than or equal to the
excess air amount of the engine, in other words which is less than or
equal to the amount by which the volume of air sucked into the engine, if
no exhaust gas recirculation were performed, would be excessive for
combustion of the amount of diesel fuel currently being injected into the
combustion chambers of the engine. Further, in order to reduce NOx as much
as possible and thus to improve the quality of exhaust emissions as much
as possible, it is desirable to thus recirculate an amount of exhaust gas
substantially equal to said excess air amount. However, it is very
undesirable to thus recirculate exhaust gases in a greater amount than
said excess air amount, because this will cause the engine not to be
inhaling sufficient air and oxygen for complete combustion of the amount
of fuel currently being injected into its cylinders, which can cause loss
of engine performance and drivability, as well as mayhap causing emission
of black smoke from the diesel engine in the case of medium and high load
operation, emission of white smoke from the diesel engine in the case of
low load or idling operation, and possibly also causing misfiring in such
low load or idling operation.
The excess air amount of a diesel engine of course varies as the load on
the engine varies; specifically, at low engine load the excess air amount
is the greatest, and this excess air amount decreases as the engine load
increases. According to this, therefore, there have been proposed various
exhaust gas recirculation systems for diesel engines, and control systems
therefor, which provide an amount of exhaust gas recirculation which
varies with the engine load, being greatest when the engine load is least,
and being diminished as the engine load increases.
However, when the effects of vehicle operational altitude upon the
operation of such an exhaust gas recirculation system are considered,
complications tend to arise. A diesel engine operating without any exhaust
gas recirculation aspires lesser amounts (by mass) of air and therefore of
oxygen at higher altitudes, i.e. at lower ambient atmospheric pressures,
and accordingly the air excess ratio of a diesel engine is lower, the
lower is the ambient atmospheric pressure. Therefore, the maximum
acceptable amount of exhaust gas recirculation for a diesel engine becomes
smaller as the ambient atmospheric pressure drops, and accordingly an
exhaust gas recirculation system and the control system therefor should be
able to take account of the ambient atmospheric pressure, and should
reduce the exhaust gas recirculation ratio according to a drop in such
ambient atmospheric pressure.
According to such requirement, there have been proposed various exhaust gas
recirculation systems equipped with altitude compensation, in particular
in Japanese Patent Application No. 56-40809 (which has been published as
Japanese Patent Laying Open Publication No. 57-157047), Japanese Patent
Application No. 57-103169, Japanese Patent Application application No.
57-103170, and Japanese Patent Application No. 58-063416, none of which is
it intended by this discussion to admit as prior art in the legal sense to
this application except inasmuch as otherwise required by law.
However, the problem with such prior proposals is that they do not provide
perfect altitude compensation. In detail, the amount of exhaust gas
recirculation provided to the diesel engine should as mentioned above be
decreased as the altitude increases and accordingly the ambient
atmospheric pressure decreases, but this amount of exhaust gas
recirculation decreasing should be greater in regions of low engine load
than in regions of medium to high engine load, so as better to avoid the
engine lacking air in such low engine load operational regions and thus
being subject to the emission of white smoke, as well as to avoid engine
misfiring and poor drivability and the like in these low engine load
operational regions.
SUMMARY OF THE INVENTION
Accordingly, it is the primary object of the present invention to provide
an exhaust gas recirculation system for a diesel engine, which has good
altitude compensation.
It is a further object of the present invention to provide such an exhaust
gas recirculation system for a diesel engine, which appropriately provides
reduction of exhaust gas recirculation with an increase in altitude.
It is a further object of the present invention to provide such an exhaust
gas recirculation system for a diesel engine, which thus reduces exhaust
gas recirculation with an increase in altitude in a way which is
appropriate to and takes into account the engine load.
It is a further object of the present invention to provide such an exhaust
gas recirculation system for a diesel engine, which reduces exhaust gas
recirculation with an increase in altitude to a greater extent at low
engine load than at medium or high engine load.
It is a further object of the present invention to provide such an exhaust
gas recirculation system for a diesel engine, which provides substantially
the maximum acceptable and practicable amount of exhaust gas recirculation
consistent with proper engine operation substantially at all times, even
when the engine is operated at a high altitude.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which keeps the
quality of the exhaust emissions of the engine high at all altitudes.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which keeps the
amount of NOx in the exhaust emissions of the engine low at all altitudes.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which does not risk
that incomplete fuel combustion would occur during engine operation at any
engine altitude.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which does not risk
the occurrence at any altitude during medium or high load operation that
the engine should emit substantial quantities of black smoke.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which does not risk
the occurrence at any altitude during low load or idling operation that
the engine should emit substantial quantities of white smoke.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which does not risk
the occurrence at any altitude during low load or idling operation that
the engine should misfire.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which ensures that
at any altitude the diesel engine is substantially never starved of air.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which ensures that
the performance of the diesel engine is kept good at all altitudes.
It is a yet further object of the present invention to provide such an
exhaust gas recirculation system for a diesel engine, which ensures that
the drivability of the diesel engine is kept good at all altitudes.
According to an aspect of the present invention, these and other objects
are accomplished by providing an exhaust gas recirculation system for a
diesel engine for a vehicle, utilizing an air intake system and an exhaust
system, comprising: (a) an exhaust gas recirculation passage a downstream
end of which is connected to said exhaust system and an upstream end of
which is connected to said air intake system, so as to recirculate exhaust
gas from said exhaust system to said air intake system; (b) an exhaust gas
recirculation control valve, comprising a pressure chamber, which
regulates the flow resistance of said exhaust gas recirculation passage
according to the amount by which the pressure in said pressure chamber is
lower than the ambient atmospheric pressure, so as to regulate the flow
amount of said recirculation of exhaust gas from said exhaust system to
said air intake system; (c) means for providing a supply of low pressure;
(d) an absolute pressure control valve comprising an input port and an
output port, which receives supply of low pressure from said means for
providing low pressure at said input port, and which provides a supply of
a pressure at said output port the absolute pressure value of which is
substantially fixed; and (e) a vacuum control valve comprising a pressure
regulating chamber which receives supply of pressure from said output port
of said absolute pressure control valve, and further comprising an output
port opening from said pressure regulating chamber, said vacuum control
valve being controlled according to engine load, and bleeding to
atmosphere said pressure regulating chamber when the pressure therein is
at or below a certain pressure value, said certain pressure value
increasing in accordance with increasing engine load; and said output port
of said vacuum control valve being communicated to said pressure chamber
of said exhaust gas recirculation control valve.
According to such structure, when the vehicle incorporating the system is
used at a low altitude at which the ambient atmospheric pressure is quite
close to standard atmospheric pressure, the supply of low pressure from
the absolute pressure control valve is sufficient to lower the pressure of
the pressure regulating chamber to said certain pressure value set by the
operation of the vacuum control valve according to engine load, whatever
the value of engine load may be; and accordingly the exhaust gas
recirculation control valve is controlled according to the value of engine
load by the pressure in said pressure regulating chamber which is adjusted
to be substantially equal to said certain pressure value at all engine
load values. Now, in general, considering vehicle operation at a fixed
engine load, when the vehicle incorporating the system is used at
progressively higher and higher altitudes so that the ambient atmospheric
pressure is steadily reduced, provided that lowering of the pressure in
said pressure regulating chamber is not limited by the pressure value of
the supply of low pressure from the absolute pressure control valve
thereto, as this occurs the amount by which the pressure in said pressure
chamber of the exhaust gas recirculation control valve is lower than the
ambient atmospheric pressure decreases, so that the amount of exhaust gas
recirculation drops. Accordingly, the amount of exhaust gas recirculation
is reduced in all operational conditions of the diesel engine
substantially evenly, thus showing that this exhaust gas recirculation
control system is able to take into account the ambient atmospheric
pressure, and reduces the exhaust gas recirculation ratio according to a
drop in such ambient atmospheric pressure, as is desirable as explained
previously in this specification. Further, on the other hand, when the
altitude at which the vehicle is being operated becomes sufficiently high,
then the abovementioned provision is no longer valid, and, in low engine
load operation and only therein, the lowering of the pressure in the
pressure regulating chamber towards said certain pressure value becomes
limited by the pressure value of the supply of low pressure from the
absolute pressure control valve thereto, so that, now, said pressure in
the pressure regulating chamber cannot attain said certain value; in other
words, the output pressure of the vacuum control valve becomes limited by
said fixed output pressure value of the supply of low pressure from the
absolute pressure control valve, only in said low engine load operational
region, and not in the medium to high load engine operational region.
Accordingly, the amount of exhaust gas recirculation provided in said low
engine load operational region is sharply reduced, by a much greater
amount than the above explained reduction of exhaust gas recirculation
provided across the entire operating range of the diesel engine. This
ensures that the amount of exhaust gas recirculation provided to the
diesel engine is decreased as the altitude increases and accordingly the
ambient atmospheric pressure decreases, and that, as is desirable as
explained previously, this amount of exhaust gas recirculation decreasing
is greater in regions of low engine load than in regions of medium to high
engine load, so as better to avoid the engine lacking air in such low
engine load operational regions and thus being subject to the emission of
white smoke, as well as to avoid engine misfiring and poor drivability and
the like in these low engine load operational regions.
According to an alternative aspect of the present invention, these and
other objects are accomplished by an exhaust gas recirculation system for
a diesel engine for a vehicle utilizing an intake system and an exhaust
system, comprising: (a) an exhaust gas recirculation passage a downstream
end of which is connected to said exhaust system and an upstream end of
which is connected to said air intake system, so as to recirculate exhaust
gas from said exhaust system to said air intake system; (b) an exhaust gas
recirculation control valve comprising a pressure chamber, which regulates
the flow resistance of said exhaust gas recirculation passage according to
the amount by which the pressure in said pressure chamber is lower than
the ambient atmospheric pressure, so as to regulate the flow amount of
said recirculation of exhaust gas from said exhaust system to said air
intake system; (c) means for providing a supply of low pressure; (d) an
absolute pressure control valve comprising an input port and an output
port, which receives supply of low pressure from said means for providing
low pressure at said input port, and which provides a supply of a pressure
at said output port the absolute pressure value of which is substantially
fixed; (e) a regulator valve comprising an input port and an output port,
said regulator valve receiving at said input port supply of said pressure
at said output port of said absolute pressure control valve the absolute
pressure value of which is substantially fixed, and producing at said
output port an output pressure value which depends upon engine load; and
(f) a vacuum control valve comprising a pressure regulating chamber which
receives supply of pressure from said means for providing low pressure and
an output port opening from said pressure regulating chamber, and in
accordance with increasing engine load increasing an absolute pressure
value at and below which pressure in said pressure regulating chamber is
bled to atmosphere, and further comprising a control chamber which
receives a supply of said output pressure value from said output port of
said regulator valve and which controls the bleeding of said pressure
regulating chamber to the atmosphere according to the pressure therein by
altering said certain pressure value, said output port of said vacuum
control valve being communicated to said pressure chamber of said exhaust
gas recirculation control valve.
According to such structure, when the vehicle incorporating the system is
used at a low altitude at which the ambient atmospheric pressure is quite
close to the standard atmospheric pressure, then the supply of low
pressure from the absolute pressure control valve is of sufficiently low
pressure to be appropriately modified by the regulator valve according to
engine load, for controlling the vacuum control valve, whatever the value
of engine load may be; and accordingly the exhaust gas recirculation
control valve is controlled according to the value of engine load by the
pressure in said pressure regulating chamber at all engine load values.
Again, in general, considering vehicle operation at a fixed engine load,
when the vehicle incorporating the system is used at progressively higher
and higher altitudes so that the ambient atmospheric pressure is steadily
reduced, provided that the output pressure from the regulator valve is not
limited by the pressure value of the supply of low pressure from the
absolute pressure control valve thereto, as this occurs the amount by
which the pressure in the pressure chamber of the exhaust gas
recirculation control valve is lower than the ambient atmospheric pressure
decreases, so that the amount of exhaust gas recirculation drops.
Accordingly, the amount of exhaust gas recirculation is reduced in all
operational conditions of the diesel engine substantially evenly, thus
showing that this exhaust gas recirculation control system, again, is able
to take account of the ambient atmospheric pressure, and reduces the
exhaust gas recirculation ratio according to drop in such ambient
atmospheric pressure, as is desirable as explained previously in this
specification. Further, on the other hand, when the altitude at which the
vehicle is being operated becomes sufficiently high, then the
abovementioned provision is no longer valid, and, in low engine load
operation and only then, the output pressure of the regulator valve
becomes limited by the pressure value of the supply of low pressure from
the absolute pressure control valve thereto, so that, now, said output
pressure of the regulator valve cannot attain the value which it would
attain if sufficiently low pressure supply were provided to said regulator
valve; in other words, the output pressure of the regulator valve becomes
limited by said fixed output pressure value of the supply of low pressure
from the absolute pressure control valve, only in said low engine load
operational region, and not in the medium to high load engine operational
region. Accordingly, the amount of exhaust gas recirculation provided in
said low engine load operational region is sharply reduced, by a much
greater amount than the above explained reduction of exhaust gas
recirculation provided across the entire operating range of the diesel
engine. This, again as before, ensures that the amount of exhaust gas
recirculation provided to the diesel engine is decreased as the altitude
increases and accordingly the ambient atmospheric pressure decreases, and
that, as is desirable as explained previously in this specification, this
amount of exhaust gas recirculation decreasing is greater in regions of
low engine load than in regions of medium to high engine load, so as
better to avoid the engine lacking air in such low engine load operational
regions and thus being subject to the emission of white smoke, as well as
to avoid engine misfiring and poor drivability and the like in these low
engine load operational regions.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be shown and described with reference to the
preferred embodiments thereof, and with reference to the illustrative
drawings. It should be clearly understood, however, that the description
of the embodiments, and the drawings, all of which are given purely for
the purposes of explanation and exemplification only, and are not intended
to be limitative of the scope of the present invention in any way, since
the scope of the present invention is to be defined solely by the
legitimate and proper scope of the appended claims. In the drawings, like
parts and features are denoted by like reference symbols in the various
figures thereof, and wherein:
FIG. 1 is a schematic, partial sectional view, showing parts of a diesel
engine and of the first preferred embodiment of the diesel exhaust gas
recirculation system of the present invention in cross section;
FIG. 2 is a compound graph relating to the operation of said first
preferred embodiment of the present invention, in which engine load is
shown along the horizontal axis and in a first part thereof an opening
amount of an exhaust gas recirculation valve is shown on the vertical axis
and in a second part thereof certain pressures are shown on said vertical
axis;
FIG. 3 is a schematic part sectional view, similar to FIG. 1, showing parts
of a diesel engine and of the second preferred embodiment of the diesel
exhaust gas recirculation system of the present invention in cross
section; and
FIG. 4 is a compound graph, similar to FIG. 2, but relating to the
operation of said second preferred embodiment of the present invention, in
which again the engine load is shown along the horizontal axis and in a
first part thereof an opening amount of the exhaust gas recirculation
valve is shown on the vertical axis and in a second part thereof certain
pressures are shown on said vertical axis.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described with reference to the preferred
embodiments thereof, and with reference to the appended drawings. FIG. 1
shows a diesel internal combustion engine 1 in partial cross section
wherein engine 1 has a cylinder bore 2 within which a piston 3
reciprocates, being pivotally connected to one end of a connecting rod the
other end, not shown, of which is pivotally connected to a crank pin of a
crankshaft, also not shown. While the diesel engine 1 has a plurality of
such cylinder bore and piston combinations, only one of them is visible in
the plane of the figure. Above the piston 3, between it and a cylinder
head, is defined a combustion chamber 4, and a swirl chamber 5 is formed
within said cylinder head and is communicated to the combustion chamber 4.
A fuel injection nozzle, not shown, is provided for injecting liquid fuel
at high pressure into this swirl chamber 5. Into the combustion chamber 4
is opened an intake port 8 and an exhaust port 9. To the intake port 8
there is connected the downstream end of an intake passage member 6, and
to the exhaust port 9 there is connected the upstream end of an exhaust
passage member 10. The intake port 8 and the exhaust port 9 are controlled
by poppet valves which open and close them wherein in FIG. 1 only the
exhaust poppet valve 11 can be seen.
The first preferred embodiment of the exhaust gas recirculation system of
the present invention comprises an exhaust gas recirculation control valve
12, which has an input port 13 and an output port 15, also comprises a
first exhaust gas recirculation passage portion 14 the upstream end of
which is connected to an exhaust gas takeout port 10a provided in the
exhaust passage member 10 and the downstream end of which is connected to
said input port 13 of said exhaust gas recirculation control valve 12, and
further comprises a second exhaust gas recirculation passage portion 16
the upstream end of which is connected to said output port 14 of said
exhaust gas recirculation control valve 12 and the downstream end of which
is connected to an exhaust gas feed-in port 6a provided in the intake
passage member 6. This exhaust gas recirculation control valve 12 controls
the flow resistance between its input port 13 and its output port 15
according to the vacuum value supplied to its control port 22a, more
exactly according to the relative negative pressure supplied to said
control port 22a, i.e. according to the difference between the absolute
value of the pressure supplied to said control port 22a and the current or
ambient value of atmospheric pressure.
The structure of the exhaust gas recirculation control valve 12 is as
follows: such comprises a valve element 18 mounted on the one end of a
valve rod 19 the other end of which is connected to a diaphragm 21 of a
diaphragm actuator 20. When the valve element 18 an the valve rod 19 are
driven leftwards in the figure by the diaphragm actuator 20, the valve
element 18 is pressed against the opening in a valve seat 17 and closes
it, thereby discommunicating the input port 13 and the output port 15 of
the exhaust gas recirculation control valve 12 from one another. On the
other hand, according as the valve element 18 and the valve rod 19 are
driven more and more rightwards in the figure from this position by the
diaphragm actuator 20, the valve element 18 is moved away from said
opening in said valve seat 17 and opens it more and more, thereby more and
more reducing the flow resistance between said input port 13 and said
output port 15 of the exhaust gas recirculation control valve 12. In the
diaghragm actuator 20, the diaghragm 21 to which the valve rod 19 is fixed
separates an atmospheric pressure chamber 24 on the left in the figure
from a pressure chamber 22 on the right, and the diaghragm 21 is biased
leftwards in the figure by a compression coil spring 23 fitted in said
pressure chamber 22. Air at atmospheric pressure is admitted into the
atmospheric pressure chamber 24 through a vent 24a, and a supply of
actuating vacuum is provided to the pressure chamber 22 through the
aforementioned control port 22a. Thus, according to the value of the
difference between the absolute value of the presssure supplied to said
control port 22a and the current value of atmospheric pressure, only
however when said pressure difference has become greater than some
predetermined threshold value, the diaphragm 21 is displaced rightwards in
the figure against the compression force of the compression coil spring
23, and the valve rod 19 and the valve element 18 are likewise displaced
rightwards, thus correspondingly lowering the flow resistance between the
input port 13 of the exhaust gas recirculation control valve 12 and the
output port 15 thereof.
The control port 22a is connected, via a conduit 25, to an output port 32
of a vacuum control valve 30 which will now be described. This vacuum
control valve 30 is of a type developed by colleagues of the present
inventors in the same workplace as the present inventors; Japanese Patent
Application No. 58-063416 has been filed for an inventive concept embodied
in said vacuum control valve 30, but this patent application had not been
published at the time of filing of the Japanese applications the
priorities of which are being claimed in the present application, and it
is not intended by this discussion to admit this matter as prior art in
the legal sense to this application except inasmuch as otherwise required
by law. This vacuum control valve 30 has this output port 32 as its sole
output port, further has an input port 56, and also has an atmospheric
port 38, a reference pressure port 58, and a regulated pressure port 31.
The body of the vacuum control valve 30 is made as a stack consisting of a
base casing 33, intermediate casings 49 and 50, and a cover casing 51,
fixed to | | |
