Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
1999-07-28
2001-07-10
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C123S321000
Reexamination Certificate
active
06257213
ABSTRACT:
TECHNICAL FIELD
This invention relates to an exhaust gas recirculation apparatus (EGR apparatus) in which a portion of exhaust gas is recirculated together with sucked air into a combustion chamber so as to lower combustion temperature in the combustion chamber, thereby promoting decrease of NO
x
(nitrogen oxides).
BACKGROUND ART
In a conventional exhaust gas recirculation apparatus, an exhaust pipe is communicated with a suction port via external piping. A normally closed EGR valve arranged intermediately of the external piping is opened during a suction stroke by utilization of negative pressure in the suction port to thereby recirculate the exhaust gas through the external piping.
However, the above-mentioned conventional exhaust gas recirculation apparatus provides lean combustion during the suction stroke since the exhaust gas is always sucked into the combustion chamber during the suction stroke. Though satisfactory combustion may be attained in light-load operating ranges where the air is inherently excessive, unsastifactory combustion may be disadvantageously brought about in high-load operating ranges where the ratio of air to fuel is lower, which tends to produce sooty black smoke.
Furthermore, disadvantageously, a required installation space for the engine is increased because of the external piping with the EGR valve required. Consideration must be taken to thermal insulation and arrangement constraints of the external piping which will reach high temperatures due to the exhaust gas flowing through the external piping.
Moreover, there is a problem for example in an engine with a turbocharger that exhaust gas cannot be satisfactorily recirculated in operating ranges where the boost pressure (supercharging pressure in a suction pipe) is higher than the exhaust pressure.
The present invention was made in view of the above facts and has its object to provide an exhaust gas recirculation apparatus in which exhaust gas can be recirculated only in operating ranges where it is required, in which the exhaust gas can be recirculated without use of external piping and in which the exhaust gas can be satisfactorily recirculated even in operating ranges where the boost pressure is higher than the exhaust pressure for example in a case of an engine with a turbocharger.
DISCLOSURE OF THE INVENTION
The present invention is directed to an exhaust gas recirculation apparatus characterized in that it comprises an exhaust-gas-recirculation master piston actuated by a suction rocker arm which in turns opens a suction valve on a cylinder during the suction stroke, a slave piston connected via an oil passage to said master piston for opening an exhaust valve on the same cylinder having said suction valve when said oil passage is pressurized by the actuation of said master piston and operating oil supply means for switching maintaining and releasing of oil pressure in said oil passage.
Thus, when oil pressure in the oil passage is maintained by the operating oil supply means, the master piston is actuated by the suction rocker arm during the suction stroke; the oil passage is pressurized; and the slave piston is driven to open the exhaust valve on the same cylinder. As a result, owing to pressure difference, the exhaust gas is recirculated from the exhaust port into the combustion chamber so that the combustion temperature in the combustion chamber is lowered during a next power stroke, thereby promoting decrease of NO
x
.
When oil pressure in the oil passage is released by the operating oil supply means, no oil passage is pressurized and therefore no slave piston is driven. As a result, opening of the exhaust valve is effected only during the exhaust stroke due to normal valve operation, not during the suction stroke.
The invention is also directed to an exhaust gas recirculation apparatus characterized in that it comprises an exhaust-gas-recirculation master piston actuated by an exhaust rocker arm which in turns opens an exhaust valve on a cylinder during the exhaust stroke, a slave piston connected via an oil passage to said master piston for opening a suction valve on the same cylinder having said exhaust valve when said oil passage is pressurized by the actuation of said master piston and operating oil supply means for switching maintaining and releasing of oil pressure in said oil passage.
Thus, when oil pressure in the oil passage is maintained by the operating oil supply means, the master piston is actuated by the exhaust rocker arm during the exhaust stroke; the oil passage is pressurized; and the slave piston is driven to open the suction valve on the same cylinder. As a result, a portion of the exhaust gas in the combustion chamber is discharged to the suction port side. The exhaust gas thus discharged to the suction port side is sucked back and recirculated into the combustion chamber during a next suction stroke to lower the combustion temperature in the combustion chamber during a next power stroke, thereby promoting decrease of NO
x
.
When oil pressure in the oil passage is released by the operating oil supply means, no oil passage is pressurized and therefore no slave piston is driven. As a result, the suction valve is opened only during the suction stroke due to normal valve operation, not during the exhaust stroke.
REFERENCES:
patent: 5406918 (1995-04-01), Joko et al.
patent: 5546914 (1996-08-01), Scheinert
Argenbright Tony M.
Castro Arnold
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