Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
1999-06-08
2001-12-18
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C251S129070
Reexamination Certificate
active
06330880
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an exhaust gas re-circulation system for re-circulating exhaust gas from a combustion chamber then back to the combustion chamber. The system is for use in internal combustion engines, such as diesel engines or gasoline engines (for example, lean-burn type engines).
BACKGROUND ART
FIG. 1
is a block diagram showing an example of a conventional exhaust gas re-circulation system using a diaphragm which is employed in the system disclosed, for example, in JP-A-6/147025. In the drawing, reference numeral
1
designates a four-cycle engine for automobiles, powered by the combustion of a gas mixture comprising fuel and air. Numeral
2
denotes an intake pipe line, one end of which is connected to the engine
1
for supplying the gas mixture to the engine
1
, and numeral
3
designates an air cleaner connected to the other end of intake line
2
for removing dust contained in the outside air as well as for feeding air to the intake line
2
. Numeral
4
shows an injector provided at the middle of the intake line
2
for injecting fuel including gasoline into the intake pipe line, and numeral
5
designates a throttle valve for regulating the amount of the mixed gas to be fed into the engine
1
. Further, numeral
6
shows an exhaust pipe line connected to the engine
1
at one end for expelling the gas mixture (exhaust gas) generated by combustion in the engine
1
, and numeral
7
denotes a purifying apparatus disposed at the other end of the exhaust line
6
for purifying the exhaust gas with a three way catalyst or the like and for expelling the processed exhaust gas outside. Alternatively, the injector is located at a position designated by numeral
4
′ when the fuel is injected directly to the combustion chamber or sub-combustion chamber as in the case of a diesel engine.
In addition, numeral
1
a
shows a combustion chamber;
1
b
is an intake valve for closing communication between the intake line
2
and the combustion chamber
1
a
;
1
c
is an exhaust-gas valve for closing communication between the exhaust pipe line
6
and the combustion chamber
1
a
; and
1
d
is a piston which moves vertically in the combustion chamber
1
a.
Next, the operation of a four-cycle type gasoline engine is described as an example.
Initially, both the intake valve
1
b
and the exhaust-gas valve
1
c
are closed. When the intake valve
1
b
of the four-cycle engine
1
is opened, the piston
1
d
moves down to feed air to combustion chamber
1
a
from the intake line
2
through the cleaner
3
. Subsequently the gas mixture mentioned above can be fed into the combustion chamber
1
a
instead of air by appropriately activating the injector
4
. At the same time the amount of the gas mixture actually fed into the combustion chamber
1
a
can be regulated by controlling the degree of opening the throttle valve
5
. The intake valve
1
b
is then closed, and the piston
1
d
is driven upward to compress the gas mixture. In this manner, the air and fuel contained in the gas mixture react together to produce a combustion gas of high temperature and high pressure in the combustion chamber
1
a
. Then the piston
1
d
is driven downwards by the force of volume expansion due to the combustion of the mixed gas, and the force acting on the piston
1
d
results in the driving force. In this case, combustion may be forcibly induced by use of an ignition plug or like means. Finally, the exhaust-gas valve
1
c
is opened in synchronism with the upward movement of piston
1
d
so that the combustion gas in the combustion chamber
1
a
is expelled outside through the exhaust pipe line
6
and purifying apparatus
7
. Thus, the automobile four-cycle engine
1
can output driving force continuously by repetition of the above operation.
In the case of the four-cycle engine
1
for automobiles, when the exhaust gas is discharged from the exhaust line
6
, hazardous components, such as nitrogen oxides (NO
x
), contained in the exhaust gas are eliminated by a chemical such as three way catalyst provided in the purifying apparatus
7
.
Next, the above exhaust gas re-circulation system is described.
In
FIG. 1
, reference numeral
8
denotes an exhaust gas re-circulation system for re-circulating exhaust gas to the intake pipe line under certain conditions;
15
is an exhaust gas intake pipe line for sending the exhaust gas from the exhaust-gas line
6
to the exhaust gas re-circulation system
8
; and
16
is an exhaust gas re-circulation pipe line for re-circulating the exhaust gas to be returned from the exhaust gas re-circulation system
8
to the intake pipeline. Further in the exhaust gas re-circulation system
8
, numeral
9
designates a housing secured to the exhaust gas intake line
15
and exhaust gas re-circulation line
16
;
10
is a re-circulation passage provided in the housing
9
for communication of the exhaust gas intake line
15
with the exhaust gas re-circulation line
16
;
13
is a valve seat formed in the housing
9
; and
11
is a closure valve for closing the re-circulation passage
10
when in abutment with the valve seat
13
. Numeral
12
designates a movable shaft to one end of which is secured the closure valve
11
so that when the shaft
12
is moved in a predetermined direction, the valve
11
is in abutment with or detached from the valve seat
13
;
14
c
is a diaphragm fixed to the housing
9
for controlling movement of the movable shaft
12
in a predetermined direction;
14
b
is a spring for biasing the closure valve
11
in the closing direction;
14
a
is a diaphragm chamber for introducing negative pressure; and
14
d
is a check valve for checking the negative pressure.
Next, the operation of re-circulating the exhaust gas is described.
Initially, the closing valve
11
is in abutment with the valve seat
13
to close the re-circulation passage
10
. When negative pressure is introduced in the diaphragm chamber
14
a
, the force of the valve opening direction defined by multiplying the negative pressure by the surface area acts on the diaphragm
14
c
. If the force is larger than the biasing force of the spring
14
b
in the valve closing direction, the movable shaft
12
and the closure valve
11
secured to one end thereof displace, whereupon the re-circulation passage
10
communicates with the intake pipe line
2
. Thus, the exhaust gas returns into the engine combustion chamber
1
a
through the intake line
2
. Consequently, combustion in the automobile four-cycle engine
1
is suppressed by the amount of non-flammable exhaust gas returned to the combustion chamber
1
a.
The suppression of combustion in the automobile four-cycle engine
1
can further inhibit temperature increases in the combustion gas or the engine even in the case of lean-burn type operation where the mixing ratio of fuel to air is low. Accordingly, increased levels of NO
x
associated with temperature increases of the combustion gas or of the engine can be also controlled.
However, conventional exhaust gas re-circulation systems as constituted above have the following problems.
First, when the differential pressure between the intake gas and the exhaust gas of a diesel turbo car or similar type is high, it is necessary to increase the biasing force of spring
14
b
to properly operate the valve against such high differential pressure. Therefore, it is necessary to enlarge the diaphragm
14
c
as well as the system itself. Secondly, negative pressure must be generated to act on the diaphragm
14
c
. In general, in gasoline-type engines, the pressure in the intake pipe line between the throttle valve
5
and the automobile four-cycle engine
1
serves as the source of negative pressure. On the other hand, in diesel engines, the pressure in the brake vacuum pump provided for the automobile brake system is used for negative pressure. Therefore, the system can not be operated in gasoline engines where negative pressure is not generated. Moreover, even if operable, it is difficult to minutely regulate the negative pressure. In diesel engi
Miyake Toshihiko
Miyoshi Sotsuo
Okada Hidetoshi
Castro Arnold
Dolinar Andrew M.
Mitsubishi Denki & Kabushiki Kaisha
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