Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2000-03-30
2001-11-06
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C123S568170
Reexamination Certificate
active
06311677
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to automotive emission control valves. More specifically it relates to an engine mounting of an exhaust gas recirculation (EGR) valve.
BACKGROUND OF THE INVENTION
Controlled engine exhaust gas recirculation is a commonly used technique for reducing oxides of nitrogen in products of combustion that are exhausted from an internal combustion engine to atmosphere. A known EGR system comprises an EGR valve that is controlled by an electric circuit in accordance with various engine operating conditions to regulate the amount of engine exhaust gas that is recirculated to the induction fuel-air flow entering the engine for combustion so as to limit the combustion temperature and hence reduce the formation of oxides of nitrogen.
When an EGR valve is engine-mounted, it is exposed to a harsh operating environment that includes wide temperature extremes and vibrations. Exhaust emission requirements impose more stringent demands for improved control of such valves, and a valve that contains both an electric actuator for positioning the valve member and a position sensor for providing feedback of the valve member position to the control circuit may be capable of providing improved control. In order for such a valve to be commercially successful, its components must be able to perform properly in such extreme environments for an extended period of usage. Moreover, in mass-production automotive vehicle applications, component cost-effectiveness and size may be significant considerations. An EGR valve that possesses more accurate and quicker response can be advantageous by, providing improved control of tailpipe emissions, improved driveability, and/or improved fuel economy for a vehicle having an internal combustion engine that is equipped with an EGR system.
Size of an EGR valve may also be an important consideration in its commercial appeal. A valve that is more compact in size can be advantageous because of limitations on available space in a vehicle engine compartment and/or on a engine.
SUMMARY OF THE INVENTION
The present invention relates generally to an improvement in mounting an EGR valve, especially an electric EGR valve of the type described herein, directly on an engine, an engine cylinder head in particular. Such a mounting can serve to reduce the number of parts required in an EGR valve, because certain structure in the engine itself cooperates with associated structure of the EGR valve in a manner that more efficiently integrates the valve/engine combination. The integration achieved by the invention also enables certain connections and attachments either to be simplified, or to be eliminated entirely. Certain functional benefits also arise from the inventive mounting.
Because the mounting provides improved proximity to the engine cylinders, the distance that exhaust gas must traverse from EGR valve to engine cylinders may be shortened, and hence exhaust gas transport time from the EGR valve to the cylinders reduced. This promotes faster response to changing EGR requirements as the engine runs.
The mounting also disposes the EGR valve in association with a coolant passage in the cylinder head. The flow of liquid coolant through that passage provides beneficial cooling of the EGR valve that avoids high temperature extremes. Limiting temperature rise is especially desirable for an electric-operated EGR valve where high temperatures that are characteristic of the exhaust gases flowing through the valve may influence operating characteristics of the electric actuator in ways that might otherwise upset intended control strategy. Indeed, it is considered desirable for the mounting to provide thermal conductivity between the valve housing and the coolant passage that is conducive to effective heat transfer away from the actuator. Hence intimate metal-to-metal contact between the valve body and the cylinder head is to be encouraged.
A general aspect of the present invention relates to an internal combustion engine comprising a cylinder head comprising an exterior wall that contains a walled compartment. That compartment comprises a wall exposed to an internal coolant passage in the head through which passage liquid coolant circulates. An exhaust gas passageway running through the compartment has an exhaust gas entrance into the compartment and an exhaust gas exit from the compartment. The compartment comprises a receptacle that intersects the exhaust gas passageway between the entrance and the exit. An EGR valve disposed on the exterior wall comprises a base that has an inlet port and an outlet port and that is disposed within the receptacle with the inlet port open to the entrance via the passageway and the outlet port open to the exit via the passageway.
Another general aspect of the invention relates to an internal combustion engine comprising a part having an exterior wall, a portion of which is covered on the exterior by an EGR valve. The valve comprises a stamped metal base containing an inlet port and an outlet port, and the portion of the exterior wall covered by the EGR valve comprises a walled compartment having a wall exposed to an internal coolant passage which passes internally through the part and through which liquid coolant circulates. An exhaust gas passageway running through the walled compartment comprises an exhaust gas entrance into the compartment and an exhaust gas exit from the compartment. The compartment comprises a receptacle that intersects the exhaust gas passageway between the entrance and the exit. The EGR valve inlet port and outlet port are disposed within the receptacle with the inlet port open to the entrance via the passageway and the outlet port open to the exit via the passageway.
The foregoing, and other features, along with various advantages and benefits of the invention, will be seen in the ensuing description and claims which are accompanied by drawings. The drawings, which are incorporated herein and constitute part of this specification, disclose a preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.
REFERENCES:
patent: 5666930 (1997-09-01), Elder
patent: 6152115 (2000-11-01), Busato et al.
patent: 6186127 (2001-02-01), Everingham
Cook John Edward
Hussey Scott
Castro Arnold
Dolinar Andrew M.
Siemens Canada Limited
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