Note: Descriptions are shown in the official language in which they were submitted.
lO~t~
BACKGROUND OF THE INVENTION
The invention relates to a pneumatic control apparatus
for an exhaust emission cleaning system of an internal combustion
engine, wherein a controlled negative pressure is applied to
a differential pressure responsive device, such as a diaphragm
or a piston.
Modern internal combustion engines include various
ones of an exhaust gas recirculation system, an ignition dis-
tributor timing delay system, a secondary air supply system,
or a dashpot control system for reducing the generation of
harmful exhaust gases such as hydrocarbons (HC), carbon monoxide
(CO), and nitrous oxide (NOX).
It is generally desirable that the operation of the
exhaust gas recirculation system, the ignition timing delay
system, and/or the secondary air supply system be stopped or
- restricted during continuous high speed, high load, and idling
conditions and during the initial engine warmup period, but
be fully operable during frequently encountered low speed, low
load and acceleration conditions during which large quantities
of harmful gases are produced, and that the dashpot control
system be operable during high speed conditions and stopped
during low speed conditions.
The reason for this is as follows: The operation of the
- exhaust gas recirculation system or the distributor timing
delay system during continuous high speed or high load conditions
causes engine output power reduction, fuel consumption increase,
and exhaust system overheating, and the operation thereof
during continuous idling conditions causes idle stability de-
terioration, increased fuel consumption, and heat damage due to in-
30 sufficient engine cooling air. The operation of these systems
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1 during engine warmup causes start performance deterioration,
increased vibration, and engine instability. On the other hand,
the operation of the secondary air supply system during con-
tinuous high speed or high load conditions causes overheating
which reduces the durability of the various cleaning systems.
The operation of the dashpot control system during low speed
conditions causes poor engine braking.
To overcome such problems a number of apparatusses
for controlling exhaust gas cleaning systems have been proposed,
such as an apparatus for controlling the systems with electrical
signals indicating the rpms, load, temperature, etc.of the
engine which are electrically detected, and another apparatus
for pneumatically controlling the systems according to changes
in the engine rpms, load, temperature, etc. on the basis of
the negative pressure appearing in the inta~e passage of the
engine.
Such apparatusses require complex electrical control
circuits which are expensive and unreliable, however, or
complicated negative pressure control circuits and an increased -~
number of costly thermosensers, timers, and the like.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the present
invention an improved pneumatic control appara~us supplies two
different negative pressures appearing in the inta~e passage
of an internal combustion engine to the negative pressure
chamber of a vacuum valve through orifices whose flow resistances
are suitably selected to control the magnitude of the negative
pressure in the chamber and to delay its transmission thereto.
In accordance with a second aspect of the invention
atmospheric pressure is also introduced into the negative
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1 pressure chamber of the vacuum valve throu~h a flow restriction
orifice, the introduction of such atmospheric pressure being
controlled by a valve adapted to open and close according to
engine running conditions.
In accordance with a third aspect of the invention
a negative pressure produced in the engine intake passage is
fed to a differential pressure responsive unit via a negative
pressure passage having a vacuum control valve unit disposed
therein. The negative pressure chamber of the latter is con-
trolled in accordance with the first or second aspects of theinvention.
~RIEF DESCRIPTION OF THE DRAWINGS
~n the drawings:
Fig. 1 is a sectional view of a pneumatic control
apparatus according to a first embodiment of the present
invention;
Fig. 2 is an engine output power diagram showing negative
intake pressure at a port 5 and throttle opening characteristics;
Fig. 3 is an engine output power diagram showing the
negative pressure characteristics in a port 6 and the intake
manifold;
Fig. 4 is an engine output power diagram showing the
negative pressure characteristics in a chamber 42 of the first
embodiment;
Fig. 5 is a sectional view of a second embodiment;
Fig. 6 is an engine output power diagram showing the
operation of the pneumatic control apparatus of the second
embodiment;
Fig. 7 is a sectional view of a third embodiment;
Fig. 8 is an engine output power diagram showing the
operation of the apparatus of the third embodiment;
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1 Figs. 9 and 10 are sectional views of fourth and fifth
embodiments;
Fig. 11 is an engine output power diagram showing the
operation of the fifth embodiment;
Figs. 12 and 13 are sectional views of modified vacuum
valve units; and
Figs. 14 and 15 are sectional views of sixth and seventh
embodiments.
DETAIL~D DESCRIPTION OF THE PREFERRED EMBODIMENl'S
. _ .
Referring now to Fig. 1, a pneumatic control apparatus
in accordance with a first embodiment of the present invention
is applied to an internal combustion engine having a fuel mixture ~-
intake passage 1 communicating with cylinder intake ports (not
shown) and having a throttle valve 2 coupled to an accelerator
pedal (not shown). The pneu~atic control apparatus comprises -
a vacuum advance control unit 1~ for the distributor 11, a
vacuum valve unit 30, and an orifice unit 40. ~
The vacuum advance control unit 10 for the distributor -;
11 in this embodiment is of the dual diaphragm type having an
advance diaphragm 13 and a delay diaphragm 14 arranged within
a diaphragm housing 12 so as to divide the housing into three
chambers; an advance diaphragm chamber 15, a delay diaphragm
chamber 16, and a diaphragm chamber 17 sandwiched ~etween the
two chambers 15 and 16. The advance chamber 15 communicates
through a negative pressure passage 101 with a port 5 formed
in the intake passage wall 4 at a position slightly above the
fully closed position of the throttle valve and in the vicinity
of the free end 3 of the throttle valve on the upstream side.
The delay chamber 16 communicates with an intake manifold ~not
shown), and the intermediate chamber 17 is open to the atmosphere.
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t An ignition timing control rod 18 is centrally fixed to the
advance diaphragm 13, and a spring 19 in the advance chamber 15
urges the advance diaphragm 13 toward the chamber 16. Another
spring 20 in the chamber 16 urges the diaphragm 14 toward the
chamber 15. A stopper 21 is fixed to the advance diaphragm 13
and another stopper 22 is fixed to the delay diaphragm 14
to abut against the stopper 21. A circular cup 25 is fixed
to the diaphragm 14 and engages a circular groove 24 in the
outer peripheral surface of a circular member 23 projecting
into the center of the chamber 16.
When a negative pressure in the manifold or in the
intake passage downstream of the throttle valve 2 is introduced
into the delay chamber 16, the diaphragm 14 is attracted toward
the chamber 16 against the force of the spring 20, and the
stopper 22 moves toward the chamber 16, its movement being
restricted to a range defined by the width of the circular groove
24. On the other hand, when a negative pressure in the port 5
is introduced into the advance diaphragm chamber 15, the advance
diaphragm 13 is attracted toward the chamber 15 against-the
force of the spring 19 and is held in a balanced position.
Accordingly, when the chamber 15 is at atmospheric
or a slight negative pressure the diaphragm 13 is halted with
the stopper 21 abutting the stopper 22 whereby the ignition
timing is dela~ed, whereas when the chamber 15 is at a high
negative pressure the ignition timing is advanced in accordance
with the magnitude o~ such pressure.
The vacuum valve unit 30 comprises a valve box 31
through which the passage 101 is coupled, a valve 32 ~or opening
and closing an atmospheric pressure release opening 34 in
the valve box 31, and a diaphragm 36 dividing the valve box into
1 first and second chambers 37 and 38. The valve 32 is connected
through a rod 35 to the center of the diaphragm 36. The first 7
chamber 37 is connected to an air Dassage 102 and the second
chamber 38 is connected to the atmosphere through an opening
39'. A spring 39 within the first chamber 37 urges the
diaphragm 36 toward the second chamber 38.
When the first chamber 37 is at atmospheric or a slight
negative pressure the diaphragm 36 is held in the lower
position by the spring 39 so that the valve 32 is open and
10 the passage 101 is at atmospheric pressure, whereas when the
chamber 37 is at a negative pressure above a predetermined le~el :
the diaphragm 36 is attracted upwardly against the force of the
spring to close the valve 32.
The orifice unit 40 comprises a housing 41, an air
chamber 42 conununicating through the passage 102 with the first
chamber 37 of the control valve unit 30, and a pair of orifices
43 and 44 communicating with the air chamber 42. The other end
of orifice 43 communicates through an air passage 103 with a
port 6 positioned slightly a~ove the port 5, and the other end
of orifice 44 communicates through an air passage 104 with the
intake passage 1 just below the free end of the throttle valve
on the downstream side.
Each of the orifices 43 and 44 comprises a porous
sintered metal disc 45, a pair of disc-shaped filters 46 provided
on the opposite surfaces of the disc 45, and 0-rings 47 fitted
around the peripheral surfaces of the filters 46 to seal the
gaps between the disc 45 and the inner wall of the housing 41
and to resiliently support the disc 45. The discs 45 may be
formed of porous ceramic or resin instead of a sintered porous
alloy, and the orifices 43 and 44 may ~e pipe orifices. The
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1 throttling resistances of the orifices should be selected
experimental~y to function as described below.
When the engine is running a negative pressure is
produced in the intake passage 1 whose magnitude varies according
to the engine speed and load conditions and the position of the
throttle valve 2.
In order to illustrate the general characteristics o~
the negative pressure produced in the ports 5 and 6 and the
negative intake manifold pressure, Figs. 2 and 3 show curves
of engine output power ~PS) versus engine speed (rpm). In these
figures, the solid line A indicates output power under full
throttle conditions and the solid line B indicates output
power under idle conditions. Referring to the rotation angles
of the throttle valve from the fully closed to open positions,
the throttle opening under idling conditions is set at 10
degrees, the port 5 is formed in the passage wa?l at a position
corresponding to a 13 degree throttle opening, and the port
6 is formed in the passage wall at a position corresponding to
a 20 degree throttle opening.
In Fig. 2, the chain lines indicate equal negative
pressure lines produced in the port 5 and the ~roken lines
indicate equal throttle opening lines. In Fig. 3, the chain
lines indicate equal negative pressure lines produced in the
port 6 and the broken lines indicate e~ual negative pressure
lines of the intake man~o~d.
The air chamber 42 is charged with the negative pressure
produced in the port 6 through the air passage 1~3 and the
orifice 43, and also with the negative intake mani~old pressure
through the air pas~age 104 and the orifice 44. This mixed
3~ negative pressure characteristic in the air chamber 42 varies
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1 with changes in the throttle resistances of the orifices 43
and 44. In this embodiment, the resistances of the orifices
are selected to obtain the negative pressure characteristic
shown in Fig. 4. In addition, the throttle resistances of the
orifices are selected sufficiently large to delay the
transmission of the negative pressures into the chamber 42 ~-~
within a time range of from several seconds to several minutes,
even when the negative pressures produced in the port 6 or the
inta~e manifold rapidly change.
Assuming that the force of the spring 39 is selected
such that the valve 32 opens when a negative pressure of less
than 90 mmHg is introduced into the chamber 37 and closes
at a negative pressure of more than 90 mmHg, the pressure release
opening 34 will close in the hatched area to the right of a
-90 mmHg equal negative pressure line shown in Fig. 4 and will
open under conditions to the left of the line. Thus, during
often encountered low speed conditions the negative pressure
applied to the advance diaphragm chamber 15 is reduced by
the air supplied from the pressure release opening 34 to
an atmospheric or low negative pressure so that the ignition
timing is delayed and the production of NOX is reduced. On the
other hand, during continuous high speed conditions (above about
2000 rpm), the pressure release opening 34 is closed and the
pressure applied to chamber 15 is not reduced so that the
ignition timing is ad~anced, which prevents any overheating
or f ire in the exhaust system and promotes increased engine
output power and a reduction in fuel consumption.
During acceleration conditions which increase the
NOX production, although the throttle valve 2 is opened to
increase the negative pressure produced in the port 6, the
communication of such pressure to the air chamber 42 is delayed
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1 by the orifice 43 and thus the ignition timing remains delayed
for a certain time after the engine is accelerated so that
the production of the harmful gases is minimized. This feature
is particularly desirable in operation in urban areas.
In addition, since the num~er of openings and closings
of the valve unit 3~ is reduced due to the resistances of the
orifices, even where the engine is frequently accelerated and
decelerated, the ignition timing is not rapidly changed which
minimizes any deterioration in the "drivability" of the car.
Fig. 5 illustrates a second embodiment of the invention
in which an air passage 105 is provided instead of the air
passage 103, having its one end connected to the orifice 43 and
its other end connected to a port 8 formed in the passage
wall at a position slightly below the fully closed position of
the throttle valve in the vicinity of the downstream free end
7 thereof. In addition, a valve 32' is provided instead of the
valve 32, which serves to close the pressure release opening
34 when the chamber 37 is at atmospheric or a low negative
pre~sure (lower than 300 mm~g in this em~odiment), and to open
it when the chamber 37 is at a negative pressure higher than
300 mmHg. For example, assuming that the port 8 is located
at a position corresponding to a 25 degree throttle opening,
the negative pressure produced in the port decreases sub-
stantially in inverse proportion to the increase of the throttle
opening, and goes to atmospheric pressure when the throttle
opening exceeds 25 degrees.
In this embodiment, during low engine load conditions
fre~uently encountered in urban areas which are shown ~y the
hatched area below the solid line C in the power output diagram
O~ ~ig. 6, the negative pressure in chamber 42 exceeds 300 mmHq
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1013~ 3
1 whereby the valve 32' is opened to delay or retard the ignition
timing. During high load conditions above the solid line C in
Fig. 6, the negative pressure in chamber 42 is less than 300 mmHg
whereby the valve 32' is closed to advance the ignition timing.
Thus, the ignition timing is delayed during low engine load
conditions under which ~he throttle opening is less than a pre-
determined amount in order to reduce the production of harmful
emissions, and during continuous high load conditions under
which the throttle opening is more than the predetermined amount
the ignition timing is advanced to prevent overheating, increase
engine output power, and reduce fuel consumption. In addition,
during acceleration wherein NOX production is increased the
operation of the vacuum valve unit 30 is delayed by the orifice
43 whereby the ignition timing remains delayed for a certain
time after the engine runs in a high load condition above the
solid line in Fig. 6 to reduce the production of NOX. When the
engine is initially started the negative intake manifold pressure
supplied through the air passages 104 and 105 to the chambers
42 and 37 is delayed so that the pressure release opening 34
remains closed for a certain time after the engine i8 started.
This advances the ignition timing to provide superior engine
starting and warmup performance.
Fig. 7 illustates a third embodiment of the invention
wherein the air passage 105 in the second embodiment is
replaced by a pressure release passage 107 for communicating
the orifice 43 with the atmosphere, a valve unit SO for con-
trolling the opening and closing of the passage 107, and an
air passage 106 for supplying negative pressure to operate the
valve unit 50. ~he latter comprises a valve 51 for opening
and closing the passage 107, and a diaphragm 52 disposed in a
valve housing to divide it into two chambers 55 and 56. The
-- 10 --
~os'~
1 valve 51 is connected through a rod 53 to the center of the
diaphragm 54. The chamber 55 communicates through air passage
106 with the port 6 and the chamber 56 communicates with the
atmosphere through a hole 57. A spring 58 in the chamber 55
biases the diaphragm 54 in a direction to close the valve 51.
Assuming that the force of the spring member 39 is
such as to change the opening and closing of the valve unit 30
at a 300 mmHg negative pressure in the chamber 37 and that
the force of the spring 58 is such as to change the opening
and closing of the valve unit 50 at a 90 mmHg negative pressure
in the chamber 55, the negative pressures introduced into
chambers 42 and 37 become equal to the negative intake manifold
pressure applied through air passage 104 when the negative
pressure at the port 6 is less than 90 mmHg whereat the pressure
release passage 107 is closed. Conversely, the chamber pressures
become equal to the sum of the negative intake manifold
pressure introduced through passage 104 and the atmospheric
pressure supplied through the passage 107 when the negative
pressure at the port 6 is more than 90 mmHg, whereat the
passage 107 i5 opened. Fig. 8 shows the vacuum valve opening
and closing range from the negative pressure characteristic of
the intake manifold and the negative pressure produced in the
port 6, as shown in Fig. 3. That is, the vacuum valve unit 30
opens in the range indicated by the hatched area between the
solid lines D and ~, and closes in the range between the solid
lines A and D.
The broken line in Fig. 8 indicates an equal negative
intake manifold pressure line of 300 mmHg, and the chain line
indicates an equal negative pressure line of 100 mmHg for the
port 6. The distribution of the opening and closing range of
the vacuum valve unit 30 in the third embodiment can be made
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1 substantially equal to that of the valve unit 30 in the second
embodiment by suitably adjusting the forces of the spring
members in the respective diaphragm units.
Fig. 9 shows a fourth embodiment in which a control
valve unit 60 mechanically detects the opening of the throttle
valve 2 to thereby directly open and close the pressure
release passage 107. A lever 61 is fixedly mounted on the
shaft 9 of the throttle valve 2 and a lever 62 is rotatably
engaged thereto and is biased in the direction of arrow X by a
hair spring 63. A valve 64 opens and closes the passage 107,
which is biased in the open direction by a spring 66. The
end of a rod 65 fixed to the valve 64 abuts a lever 62. The
tip of an adjustment screw 67 on the end of the lever 61 abuts
the lever 62 when the throttle valve 2 opens a predetermined
amount, and thereafter the lever 62 is rotated integrally with
the further opening of the throttle valve.
During low load conditions under which the throttle
valve i8 open less than a predetermined amount, the force of
the hair spring 63 acting on the lever 62 overcomes the force
of spring 66 and causes the valve 64 to close the pas~age 107.
During high load conditions, howeverj whereat the throttle
valve is open more than the predetermined amount, the lever
62 is rotated counterclockwise whereby the valve 64 opens the
passage 107 under the force of the spring 66. Thus, the
fourth embodiment functions similarly to the second embodiment.
Fig. 10 illustrates a fifth embodiment wherein an air
passage 108 connects the orifice 44 to the port 5. The force
of the spring 39 is such that the valve 32' opens and closes
at a negative pressure threshold of 100 mmHg in the chamber 37.
In this embodiment the valve 32' opens in the range indicated
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1 by the hatched area in Fig. 11 and closes in the other areas.
During continuous idling conditions the valve 32' closes to
advance the ignition timing, which prevents exhaust system
overheating.
While the above embodiments have been described in
connecti~n with the control of a distributor vacuum advance,
it should be understood that these pneumatic control apparatusses
are similarly applicable to the control of exhaust gas recircu-
lation systems, dashpot control systems, and secondary air supply
control systems by connecting the air passage 101 to the
negative pressure chamber of a diaphragm unit associated with
such systems.
Modified operational effects can also be obtained by
providing a vacuum valve unit as shown in Figs. 12 or 13 in
the passage 101 instead of the unit 30 in the above embodiments.
The unit 300 shown in Fig. 12 is a change-over valve for
selectively supplying the pressure of port S or port 6 to the
advance diaphragm chamber 15 according to engine running con-
ditions. The unit 301 shown in Fig. 13 is a valve for making i
and breaking the negative pressure passage 101. These valvesare designed to be selectively used according to the control
criteria for various kinds of exhaust gas cleaning systems.
Fig. 14 illustrates a sixth embodiment further com-
prising an orifice 70 in the air passage 103, a chec~ valve
71 for allowinq flow only in the direction from orifice 43
to port 6, and an air chamber 67. During repeated acceleration
and deceleration conditions chambers 67, 42 and 37 are held at
a hiqh negative pressure whereby the ignition timing is advanced.
This feature is particularly effective in traversing a mountainous
3~ road. When the chec~ valve 71 is reversed the air in cham~er 67
- ~O~Vt;~;3
1 must flow through the ori~ice 70 to the passage 103 when the
negative pressure in port 6 rapidly increases during acceleration,
and therefore any negative pressure increases in the chambers
42 and 37 are further delayed in comparison with the case where
only a single orifice 43 is provided. On the other hand, when
the negative pressure in port 6 rapidly decreases during
deceleration, since air flows rapidly from passage 103 through
check valve 71 into chamber 67, the delay of the decrease of
negative pressure in chambers 42 and 37 is dependent only on the
~0 throttling effect of the orifices 43 and 44.
Accordingly, during acceleration wherein NOX production
is increased, the ignition timing remains delayed until the
acceleration is completed, after which the timing is advanced.
On the other hand, during deceleration the timing is retarded
relatively sooner to prevent it from remaining in its advanced
condition during the next acceleration.
.
The directional orientation of the check valve 71
i8 determined in accordance with the type of vehicle, the intended
use of the vehicle, and the type of exhaust gas cleaning
apparatus to be controlled.
Fig. 15 illustrates a seventh embodiment in which the
orifice 70 and check valve 71 of the sixth embodiment are
arranged in the air passage 106 of the third embodiment, whereby
the transmission of the negative pressure in port 6 to the
chamber 55 of the valve unit 50 is controlled by the orifice
70 and the check valve 71 to provide an effect similar to that
of the sixth embodiment.
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