Note: Descriptions are shown in the official language in which they were submitted.
laslllo
J3~CKGI~(~U~D OF T~IE INVl~NTION
This invention relates to exhaust gas recirculation
system in internal combustion engines and more parti-
cularly to a valve assembly for controlling exhaust
gas recirculation.
Recircu]ation of exhaust gases has been developed
as a method for reclucing formation o~ oxides of nitrogen (NOX)
during the combustion process in an internal combustion
engine. In genera], it is desired to control exhaust
gas recirculation in response to engine operating con-
ditions, and a varicty of control valves responsive ` ~-
to the engine operating conditions have been utilized
for this purpose.
A valve responsive to exhaust gas pressure so as
to recirculate the exhaust gases at a rate proportional
to the rate at which combustion air (induction air)
flows into the engine has been proposed by the same
inveneor as that of this application. This will be more
particularly describcd hercinafter.
The exhaust gas recirculation control valve
assembly which has been proposed by the same inventor
utilizes a difference between a first pressure within ~
an exhaust passage in a zone downstream of a first r
orifice provided in the exhaust passage downstream of
an inlet port of an exhaust gas recirculation passage
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.;
anA a secolld pressure within the exhaust gas reeireu-
lation pas~sagc in a zone hetween a seeond orifiee
provided in the exllau~st gas recirculation passage and
an cxhaust gas flow eontrol valve member disposed in
the exhaust ga~s recirculation passage downstream of the ~'
sccon~ orifice, so as to reeirculate exhaust gases at a
.
~, rate proportional to cxhaust gas flow through the exhaust
passage in order to recirculate exhaust gases at a rate
proportional to air flow toward an engine. The valve
is operated to keep this difference at a predetermined
ma~Jnitude. The rate of rccireulation of exhaust gases
is thus proro~tional to the rate of exhaust gas flow
through the cxhaust passage. Since the rate of exhaust
gas flow is proportional to the rate of induction air
flow, exhaust gases can be reeirculated at a rate pro-
portional to induction air flow.
; With this exhaust gas reeireu]ation eontrol valve
assembly the cxhaust gas flow eontrol valve member is
not direetly operated by the member responsive to the
differenee between the first and seeond pressure;
instead, the valve member is positioned by a member
operated by an induetion passage vaeuum signal and the
member responsive to the differenee between the first
and seeond pressure eontrols that signal.
In order to reduee the rate of reeireulation of
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~
exhaust gascs undcr cngine operating condition at high
speed Wit}l light load so as to maintain the engine
stability under this condition, the member responsive
to the diffcrence bctwcen thc first and second pressure ~,
is biascd in such a manner as to assist movement of the
member duc to the first pressure by a member which is
alternativcly responsive to the control signal or atmos-
phere through a control valve.
;;.~i
~lthough with this exhaust gas recirculation control
valve asscmbly the ratc of rccirculation of exhaust gases
is proportional to thc rate of cxhaust gas flow through
thc cxhau~st gas passage there is a problcm that the i
proportional relationship between the rate of reci,rcu-
lation of cxhaust gas through the exhaust gas passage and -
the rate of induction air flow may be disturbed or broken
such as when there occurs the pulsation of exhaust gase~. , .
~nother problem is that the first orifice provided in
the exhaust gas passage so as to reduce the effect of
the pulsation of exhaust gases on the proportional
relationship (the smaller is the effective flow area
of the orifice provided in the exhaust passage, the
better the precision of the proportional relationship
between the rate of recirculation of exhaust gases and
. the rate of induction air) will cause a reduction in the
maximum output of thc engine by throttling exhaust gas
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,' flow tht-ough the exha~1st ~as passage. .~till another
problem is in that suitable measure must be taken to
- reduce the effcct of the di.rty deposit and the heat of
the ex11aust gases upon the component parts of the re-
circu].ation control valve assembly.
SUM~RY OF T11~ l:NV~NTION
In order to solve the above mentioncd problems an
eX]laUSt gas recirculation control valve assembly in an
exhaust gas recirculation system accordi.ng to the invention
utilizes a difference between a pressure within an
induction passage in a zone between a first orifice
provided in the i.nduction passaye upstream of a discharge
port of an exhaust gas recirculation passage and a throttle
valve disposed upstream of the first orifice and a pressure
within the exhaust gas recirculation passage in a zone
between a second orifice provided in the exhaust gas
recirculation passage and an exhaust gas recirculation
flow control valve mcmber disposed upstream of the second
orifice to recirculate exhaust gases. The exhaust gas
recirculation flow control valve member is operated to
maintain this difference at a predetermined
magnitude which may be varied in response to operating ..
conditions of the associated engine so as to vary the
rate of recirculation of exhaust gases.
.
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BRIEF DESCRIPTION OF THE DRAWINGS
_ _ _ _ .
In the accompanying drawings:
. Fig. 1 is a schematic diagram showing a preferred
embodiment of an exhaust gas recirculation system according
to the invention; and
Figs. 2 through 6 are similar views showing different
preferred embodiments, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 shows an embodiment 10 of an exhaust gas
recirculation system comprising an exhaust gas recirculation :-~
(EGR) passage 12 leading from an exhaust passage (not shown) to
a discharge port 14 opening to an air induction passage 16 and
an exhaust gas flow control valve assembly 18 comprising a valve
seat 20 located in EGR passage 12 and an exhaust gas flow control
valve member or EGR valve member 22 cooperating with valve
seat 20. EGR valve member 22 is formed on a stem 24 which is
fixedly carried by a pressure responsive diaphragm 26 and is
downwardly biasedby a spring 28. : ~.
A flow restrictor in the form of an orifice plate
30 is arranged in EGR passage 12 downstream of valve seat 20, .
and a second flow restrictor in the form of a second orifice
plate 32 is arranged in air induction passage 16 upstream
of discharge port 14. Second orifice plate 32 is located
downstream of a throttle valve 34
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in a primary air induct;on barrel 36 of a two-barrel carhuretor
'. having a secondary air induction barrel 38. ,~
.` ~.
A chamber 40 above diaphragm 26 is connected through
pipes 42 and 44 to a source of vacuum such as that in primary air
induction barrel 36 below throttle valve 34 or that in air induction
passage 16 at a location adjacent discharge port 14. Arranged in
pipes 42 and 44 between chamber 40 and the source of vacuum is an
orifice 46. An air bleed pipe 48 is branched from a portion of
pipes 42 and 44 between chamber 40 and orifice 46.
An air bleed through air bleed pipe 48 into chamber 40
is controlled by an air bleed control valve member 50. Air bleed
control valve Member 50 is formed on a diaphragm 52 or fixedly
carried thereby and is downwardly biased by a spring 54, and is
fixedly connected by a stem 56 to a pressure responsive diaphragms~ -
58 and 52 and a diaphragm 60. Diaphragms 50 and 60 have substan-
tially the same working areas respectively exposed to a chamber ~-~
~ .
62 above pressure responsive diaphragm 58 and a chamber 64 below
it so as to permit stem 56 to be moved in response to the dif-
ference between pressure in chambers 62 and 64.
~ l(J5~1iiO
", ~,~ .
A pressure Pi in a zone 66 between orifice plate 32 and
throttle valve 34 is transmitted through a pipe 68 to chamber 64
below diaphragm 58, while a pressure Pe in a zone 70 between valve
seat 20 and orifice plate 30 is transmitted through a pipe 72 to
chamber 62 above diaphragm ~8.
- In operation, an increase in difference, in magnitude,
between pressure Pi in zone 66 and pressure Pe in zone 70 above .;-~
~ ,
a predetermined value will cause diaphragm 58 to be raised against P
the bias of spring 54 and air bleed valve member 50 thus reduces
air flow through air bleed pipe 48 into chamber 40. As pressure
in chamber 40 decreases, diaphragm 26 is raised against the bias _
of spring 28 and EGR valve member 22 is unseated from valve seat
20 so as to permit increased recirculation of exhaust gases. As
a result pressure Pe in zone 70 increases. Upon a decrease in
difference, in magnitude, between pressure Pi in zone 66 and pres-
sure Pe in zone below, the predetermined value spring 54 depresses
: ~
diaphragm 58 and air bleed valve member 50 then permits increased
~ air flow through air bleed pipe 48 to chamber 40. The increased
- pressure in chamber 40 causes spring 28 to depress diaphragm 26 so
as to move EGR valve member 22 toward valve seat 20 and thus reduce
the recirculation of exhaust gases. As a result pressure Pe in
iliO
zone 70 decreases.
It will be noted that if, as in the embodiment
shown in Fig. 1, EGR control valve member 22 recirculates exhaust
gases in such a manner as to maintain difference, in magnitude,
between pressure Pi in zone 66 and pressure Pe in zone 70 at the
predetermined value, the rate of recirculation of exhaust gases
will be proportional to the rate of induction air flow because
the rate of induction air flow is the function of difference
between pressure Pi in zone 66 and pressure P in a zone 74 down-
stream of orifice plate 32 and the rate of recirculation ofexhaust gases is the function of difference between pressure
Pe in zone 70 and pressure P in zone 74.
Assuming pressure Pi in zone 66 is fixed, a change
in exhaust back pressure causes a change in pressure Pe in zone
70. Upon this change in pressure Pe in zone 70, air bleed valve
member 50 controls air bleed through air bleed pipe 48 to chamber
40 and EGR valve member 22 thus controls the recirculation of
exhaust gases so as to permit pressure Pe in zone 70 to restore
its preceding magnitude, i.e., the magnitude in pressure Pe before
the change in exhaust back pressure takes place. Thus the effect
of the change in exhaust back pressure which might take place
irrespective of change in induction air flow on recirculation
of exhaust gases is reduced
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in the embocliment shown in Pig. 1.
It is desirable, for the purpose of giving a good propor-
tional dependency of pressure ~i on the rate of induction air flow
through zone 66, to select, as orifice plate 32, one having a small
orifice size because the smaller, in orifice size, the better.
The arrangement of orifice plate 32, i.e., orifice plate
32 is provided not in seconcdary air induction barrel 38 but in
primary air induction barrel 36, has made it possible to secure --~
an effective flow area wide enough to admit induction air at such a
10 rate as to meet the demand under engine operating condition a-t
full load. Thus, a reduction in the maximum power output resulting
from the provision of orifice plate 32 is negligible.
If desired the predetermined value may be varied in
response to a parameter or parameters representing engine operating
condition so as to add a supplementary control on the recirculation
of exhaust gases. It is thus possible to effectively reduce the
- rate of recirculation of exhaust gases under engine operating r
condition at high speed with light load by varying the predeter-
mined value so as to cause EGR valve member 22 to reduce
'.
-- 10 --
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recirculation of ex~laust gases under this engine operating condi-
tion.
If desired diaphragm 52 may be replaced with a diaphragm
. having a wide effective working area than diaphragm 60 so as to
supplementarily bias air bleed valve member 50 in such a manner as
to assist the bias of spring 54 with a force which increases as
pressure Pe in zone 70 decreases. As a result the predetermined
value increases when the engine operates a high speed with light
load when pressure Pe is low and the recirculation of exhaust
gases is effectively reduced under this engine operating condition.
,....
., ~
-- 11 --
1(~91~iO
If desired, as shown in Fig. 2, an air bleed valve 78 is
arranged so as to aLlow, when the engine operates at high speed
with light load, air bleed into chamber 62 to cause an increase ~-
in pressure Pe therein to supplementarily bias air bleed valve
member 50 in such a manner as to assist the bias of spring 54 so
that the rate of recirculation of exhaust gases will be effect-
ively reduced under this engine operating condition.
Referring to Fig. 2 the same reference numerals as those
used in Fig. 1 are used to denote substantially similar parts to
; 10 those shown in Fig. 1.
In Fig. 2 an air bleed pipe 80 leads from zone 70 of
EGR passage .12 to air bleed valve 78 having a valve member 82
which is fixed to a diaphragm 84 and biased by a spring 86. A
chamber 88 on the right hand side of diaphragm 84 communicates
throuyh a branch pipe 90, pipe 48 and pipe 42 with chamber 40 , -
above diaphragm 26. An exhaust gas flow control valve assembly
18' in Fig. 2 differs from the counterpart shown in Fig. 1 in
that in Fig. 2 EGR valve member 22 which is biased downwardly by
spring 28 is biased in the same direction with a supplementary
force which varies in response to a pressure transmitted from a
source of vacuum such as that in air
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091110
induction passage 16 at a loeation adjaeent di.seharge
port ].4 or that in primary ai.r induetion barrel 36 helow
throttle valve 3~ to a biasing ehamber 92 below diaphragm
: 26 and above a diaphragm 94. Diaphragm 94 has its
.,: 5 eentral portion fi.xedly eonneetecl to stem 24 and has a
., smal.ler workinc3 area than diaphrac~m 26 so that EGR valve
,' 22 wi,ll be biased Wit]l a total of a force by spring 28
; and supplementaI-y force varying in response to pressure ~,
in biasing cham}~er 92. ~.
~,~ 10 In operati.on pres.sure within biasing chamber 92 .,
is far lower wllen the cngi.ne operates at hi,gh speed with
light load than when the engine operates with heavy
load.s and it i.s when the engine operates at high speed
with light load that pressure withi.n chamber 40 decreases
i 15 to such a degree as to urge valve member 82 against the
bias of spring 86 to increase air flow through air bleed
pipe 80 into zone 70. As a result pressure Pe within ,.
: zone 70 increa:;es and the thus increased press~lre is trans-
mitted to chamber 62 to i.ncrease air flow through air
bleed passac3e 48 to chamber 40 to cause an increase in !~
pressure in chamber 40 permitting E~lR valve member 22
to move toward valve seat 22 to reduce the recireulation :'
of exhaust gases. It is to be noted that as air bleed r
through 80 to zone 70 increases ~resh air fuel mixture
flowing through air induction passac3e 16 will be diluted.
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1~91110
Thus it will be apprcciatcd that since whcn the engine
operates at high speed with light load ~G~ valve member
22 will bc moved toward valve s~at 20 to effectively L
rcduce thc rate recirculation of cxhaust gases owing to the ~-
5help of admission of air through air blccd valve 78 and
air bleed pipe 80, to zone 70 and the thus admitted air
will dilute fresh air fuel mixture flowing through air - -
induction passage 16, the engine stahility and fuel
economy under this enginc operating condition will be j-
10improved.
If desircd air bleed valve 78 may communicatcs
through a branch pipe 96 directly with chamber 62 by-
passing zone 70 to permit air bleed through pipe 90 to
chambcr 62. In this case, dilution of fresh air fuel
15mixture with air during cngine operating condition at
high speed with light load will not take place.
Referring to Fig. 3 the samc reference numerals
as those used in Fig. 1 are used to dcnote similar parts
to those shown in Fig. 1. This embodimcnt shown in
20Fig. 3 is differcnt from Fig. 1 embodiment only in that
instead of orifice plate 32 shown in Fig. 1 a valve member
100 is disposed in primary air induction barrel 36 do~m-
stream of throttle valve 34 as shown in Fig. 3. Valve r
member 100 is rotatable with a shaft 102 fixed to a lever
104 disposed outsidc primary air induction barrel 36 and
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', 1091110
_
biascd by a spri.ng 106 toward t~e illustrated position.
This illustrated posi.tion of valve member 100 is defined
by a stop 108. ~ lever 110 fixcdly attached to throttle ,~
valve 34 to bc rotatahle therewith cooperatcs with lever
r 5 104 such that op~niny movement of throttle valve 34 ~ -
beyond a pre~eterllli.ned throttle opening degree, say,
about 20 degree~, will cause lever 110 to coacts with
lever 104 to rotate valve member 100 clockwi.se against
the bias of spri.ng 106. The effccti.ve flow area across
valve member 100 thus will be increased as throttle
valvc 34 increases its throttle openi.ng degrce beyond
the predetermined throttle opening degree.
As valve member 100 is rotated clockwi.se to increase
effective flow area, the flow resistance through primary
air i.nduction barrel 36 decreases causing pressure Pi
in zone 66 to decrease toward induction pressure P.
Upon a decrease in pressure Pi, air bleed valve 50 is
biased downwardly to increase aix bleed through air
bleed pipe 48 to chamher 40. A~ a result FGR valve ;.
member 22 is moved toward valve seat 20 to reduce the
recirculation of exhaust gases.
Thus under engine operating condition with heavy ~~.
load when the throttle opening degree of throttle valve
34 is above the predetermined degree (for example 20
degrees) the rate of recirculation of exhaust gases
I_
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:
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.
decreases and the driveability and fuel economy are improved
under this engine operating condition.
Referring to Fig. 4, a valve member 112 which is
disposed in primary air induction barrel 36 downstream of
throttle valve 34 and upstream of discharge port 14 is employed
instead of orifice plate 32 shown in Fig. 1. Valve member 112
is operatively connected through a linkage 114 to a plunger 116
which is fixedly connected to a pressure responsive diaphragm -
118 and biased by a spring 120. A chamber 122 on the righthand
; 10 side of pressure responsive diaphragm 118 communicates with
zone 74 of air induction passage 16 through a pipe 124 so as to
allow induction pressure P in zone 74 to be transmitted to
chamber 122.
In operation, when induction pressure P decreases
below a predetermined value, such as -300 mmHg, under engine
operating condition with light load, plunger 116 is moved to the
right against the bias of spring 120 to cause valve member 112
to increase the effective flow area through primary air
induction barrel 36. Thus the rate of recirculation of exhaust
gases is reduced under engine operating condition when induction
pressure~decreases below the predetermined value, such as
-300mmHg.
If desired chamber 122 may communicate with a venturi
; 126 upstream of throttle valve 34 through a port 128 to
-16-
1091110
allow venturi pressure in venturi 126 to be transmitted to chamber
122. In operation, when venturi pressure in venturi 126 decreases ~
below a predetermined value, such as -200mmA~, uFon engine operating ~"
condition at high speed with heavy load, plunger 116 is moved to
the right against the bias of spring 120 to cause valve member
112 to increase the effective flow area through primary air in-
duction barrel 36. Thus the rate of recirculation of exhaust gases
is reduced under engine operating condition at high speed with
heavy load.
If desired chamber 122 may communicate with secondary air
induction barrel 38 through a port 130 disposed above a throttle
valve 132 disposed in secondary air induction barrel 38. In opera-
tion, when pressure within secondary air induction barrel 38
adjacent port 130 decreases below a predetermined value, such as
-20 mm~lg, under engine operating condition at high speed with heavy
load, plunger 116 is moved to the right against the bias of spring
120 to cause valve member 122 to increase the effective flow area
through primary air induction barrel 36. Thus the rate of
recirculation of exhaust gases is reduced under the engine
operating condition at high speed with heavy load.
If desired as shown in Fig. 5, chamber 122 may be
connected to an air bleed port 134 and to a vacuum port 136 that
communicates
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1~91110
with a source of vacuum such as that in zone 74 in induction pas-
sage 16. A solenoid valve 138 which selectively closes air bleed
port 134 or vacuum port 136 is provided and electrically circuited
with a switch 140 responsive to enyine operating condition or
`~ vehicle operating condition such as a vehicle speed switch.
In operation when the vehicle speed is above a predeter-
mined value, such as 50 km/h, switch 140 is closed to permit a
current to flow through the solenoid of solenoid valve 138 to cause
solenoid valve to close air bleed port 134 so as to connect chamber
10 122 to the source of vacuum. As a result plunger 116 is moved to
the right against the bias of spring 120 to cause valve member 112 ~ ~
to increase the effective flow area through primary air induction `-
barrel 36 under this condition. ~hen the vehicle speed is below
the predetermined value, switch 140 is opened to cut supply of
current to the solenoid of solenoid valve 138 causing solenoid
valve 138 to close vacuum port 136 to connect chamber 122 to air
bleed port 134. Thus under this condition, spring 120 biases
plunger 116 to the illustrated position to cause valve member 112
to take the illustrated position ln which effective flow area is a
minimum.
The rate of recirculation of exhaust gases is thus
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1091110
. . .
. ~
., .~.~.
,~.
reduced whcn the vehiclc speed is above the predetermined
value of 50 ~m/}l.
If desiled, a transmission gear switch may be used
as sw;tch ]40 wl~ich is closed only when thc transmission
S is shiftcd into a top gear position. In this case the L
rate of recircu]cltion of exhaust gases is reduced when
th(~ transmis;;on is shi~tcd into thc top c~ear position.
Refcrring to Fig. 6 ~mbodimcnt, this diffcrs from
Ficl. 1 embodilllcnt onlv in that instcad of orifice plate L
30 shown in r~ig~ 1 a valve membcr 142 is ~isposed in
EGR passage 12 clownstrcam of valvc seat 20 with which
ÆGR valve mcml)er 22 coopcratcs. Valve me~ber 142 is
opcrativcly connected through a ~uitable linkage 144,
only shown in diagram, to a plun~cr 146 which is fixedly
carriccl by a prcssure rcsponsive diaphragm 148 and biased
! upwardly by a spring 150. A chambcr 152 below pressure
responsive diaphragm 148 communicatcs through a pipe
154 with zone 74 of air induction pas.sage 16 to allow
in(luction pressure P in zone 74 to be transmitted to
chambcr 152.
In the illustrated position of valve member 142
the effective flow area through valve member 142 is a ~:
maximum. When induction pressure P transmitted to chamber
152 below pressure responsive diaphragm 148 decreases
below a predetermined value, such as -400 ~llg, plunger
-- 19 --
lC19lliO
~,~
146 is moved downward]y against the bias of spring lS0
and this movemcnt of plunger 146 causes valve member
142 to rotate clockwise to reduc~ the effective flow
area therethrough.
A decrease in the e~fective flow area through valve
mcml)cr 142 decrease the effect of induction pressure P
on pressure Pe in zone 70 and thus pressure Pe increases.
Upon this increase in pressure Pe air b].eed valve member
50 is biased downwardlv.to increase air bleed through
air hleed pipe 48 to chamber 40. As a result ~ .
EGR valve mc~ber 22 is moved toward valve seat 20 and
the rate of recirculation of exhaust gases is decreased
as the effective flow area throu~h valve member 142 is
reduced.
Thus the rate of reci.rculat.ton of exhaust gases is
decreased when the induction vacuum decreases below the
predetermined level.
- 20 -
