Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
1999-11-24
2001-09-25
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C123S568200, C123S568260
Reexamination Certificate
active
06293266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an exhaust gas recirculation device with pressure compensation.
2. Description of the Related Art
Spark-ignition and diesel engines, especially those in motor vehicles, are usually provided with exhaust gas recirculation devices, especially exhaust gas recirculation valves (EGR valves). By means of the latter, exhaust gas is to some extent mixed with the fresh gas taken in, in order to reduce the NOx emission and to improve the fuel consumption, and to reduce the production of noise.
Such exhaust gas recirculation devices comprise metering means or control means with which the quantity of exhaust gas recycled can be set as a function of the operating point. Too little exhaust gas recirculation would not achieve the desired effects, too high exhaust gas recirculation in spark-ignition engines would lead to disruption of the operation or to an undesired rise in HC or even CO emissions and, in the case of diesel engines, would lead to an undesired increase in the particulate emissions.
Such control means are generally valves which can be closed completely and which are set by a vacuum diaphragm or an actuating motor or a proportional magnet operating counter to a spring, said means in turn being actuated by the controller of the engine via a cycling valve or a relay. The information used for this purpose in the controller is generally that relating to the load and rotational speed of the engine and to the quantity of air taken in. In order to improve the operation, use is also made of the feedback of the opening travel via a distance-measuring system.
The exhaust gas recirculation devices are located between the fluctuating pressures in the exhaust gas system and the fluctuation pressures in the intake system of the engine, the changes in these pressures on the one hand being associated with the changes in the operating point, and on the other hand being determined by the surge-like emergence of the exhaust gas and from the surge-like intake of the fresh air.
These pressure fluctuations constitute a problem for the metering function of the exhaust gas recirculation device in normally-aspirated engines, and are particularly serious in supercharged engines.
JP 06 147 025 (Patent Abstracts of Japan) shows an exhaust gas recirculation device such as is described in the preamble of claim
1
. In this case exhaust gas from an internal combustion engine is fed to a dual valve via two exhaust gas feeds. The dual valve comprises two valve disks which are rigidly fixed to a valve rod and which in each case separate the exhaust gas feeds from a common exhaust gas recirculation duct, it being necessary for one valve disk to be moved in order to open the valve along the exhaust gas flow direction and for the other valve disk to be moved in the direction opposite the exhaust gas flow direction.
The object of the invention is to provide an exhaust gas recirculation device in which the quantity of exhaust gas which is passed through or metered is as far as possible independent of the above pressure fluctuations acting on the exhaust gas recirculation device.
SUMMARY OF THE INVENTION
An exhaust gas recirculation device according to the invention for recirculating exhaust gas into a gas feed to engines, especially motor vehicle engines, comprises an exhaust gas feed, a fresh gas feed and an outlet duct opening into the gas feed, where at least the exhaust gas feed and the fresh gas feed are interconnected via a metering or control means and, on the side of the control means facing the fresh gas feed, there is arranged a pressure plate which minimizes and preferably eliminates the influence of pressure fluctuations that occur on the exhaust gas side and the fresh gas side and have an effect on the exhaust gas throughput.
If the control means, which can be formed in particular by a valve or main valve, is in a partially or completely opened position, exhaust gas can flow from the exhaust gas side of the exhaust gas recirculation device in the direction of the fresh gas side. The pressure plate is arranged in the gas or exhaust gas stream in the exhaust gas recirculation device in such a way that it forms a flow resistance for the exhaust gas stream flowing around it or through it and thus, as the exhaust gas flows through from the exhaust gas side in the direction of the fresh gas side, leads to partial backing up or an increase in pressure of the exhaust gas stream. In this case, therefore, the gas pressure in a chamber between the control means and the pressure plate is greater than in a chamber which is arranged on the fresh gas side of the pressure plate. The difference between these gas pressures, acting on the pressure plate on the fresh gas side and exhaust gas side, results in a force which acts on the pressure plate. This force, acting on the pressure plate, is used in accordance with the invention to influence or control the position or the free opening cross section of the control means, so that, for example, the free opening cross section of the control means is reduced when a force on the pressure plate directed in the direction of the fresh gas side or in the closing direction of the control means increases. The pressure plate can therefore be designed in such a way that an increase in the pressure drop between the exhaust gas side and the fresh gas side of the exhaust gas recirculation device leads to a predetermined decrease in the free opening cross section of the control means, and a decrease in this pressure drop leads to a predetermined increase in the free opening cross section of the control means.
In this way, the influence of fluctuations or variations of the gas pressure on the exhaust gas side and fresh gas side in the exhaust gas recirculation device on the throughput or the metering of the recirculated exhaust gas or on the proportion of exhaust gas in the gas stream in the outlet duct can be minimized and preferably completely eliminated.
According to a preferred embodiment of the invention, the control means is connected to a mechanical, pneumatic, hydraulic, magnetic or electric actuating device or actuating motor. The use of a magnet or proportional magnet has proven to be particularly advantageous, since using such a device the opening or position of the control means can be set very accurately and, above all, it reacts very quickly.
According to a further preferred embodiment, the exhaust gas recirculation device is provided with a compensation device, which is used for the compensation or balancing of forces which act on the control means as a result of a difference between the gas pressure on the exhaust gas side and fresh gas side. Because of this compensation device, the pressure drop of the gas pressure across the control means cannot lead to a force component which acts in the direction of the undesired opening or closing of the control means, as a result of which the desired control or regulation of the quantity of exhaust gas passed through is considerably improved. The compensation device used can, in particular, be a second valve disk or piston, diaphragms and/or bellows.
In this case, it is advantageous to load the compensation device on one side with the gas pressure on the exhaust gas side, that is to say the gas pressure prevailing in the exhaust gas feed, and to load the other side with the gas pressure on the fresh gas side, that is to say the gas pressure prevailing on the fresh gas side of the control means and thus between the main valve and pressure plate. The resulting pressure difference across the compensation device results in a force component which is directed counter to the force component to be compensated for, has the same magnitude and thus has the effect of balancing the two force components.
According to a further preferred embodiment, the compensation device is provided with a kinematic transmission, especially a lever transmission. This transmission converts the force component produced by the compensation device to a magnitude which is suitable for the
A. Kayser Automotive Systems GmbH
Casella Anthony J.
Hespos Gerald E.
Wolfe Willis R.
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