Apparatus for recycling exhaust

#The present invention relates to apparatus for the return or recycling of exhaust gas for the purpose of reducing noxious portions in the exhaust gases of internal combustion engines, wherein the cross section of the flow passage through a valve, disposed between a tapping point on the exhaust manifold and a tapping point on the inlet manifold, is controlled as a function of the weight rate of exhaust flow through the internal combustion engine.

#A highly effective measure of reducing the unhealthy portions contained in the exhaust gas of an internal combustion engine, and more particularly for reducing the nitrogen oxide gas portions, is effected by recycling certain amounts of the exhaust gas. This addition of gases, which does not participate in the combustion process, produces a reduction of the combustion temperature, so that less nitrogen oxide occurs. However, this inert gas causes a reduction of cylinder filling with the air mixture, hereafter termed mixture at full loads, thereby adversely affecting the rotation of the engine at low rates of speed which is particularly evident during idling of the engine. Therefore, in order to maintain the maximum power output at full load, and to provide smooth rotation of the engine during idling, no recycling or return of exhaust gas should take place at there lower speeds of rotation. Moreover, the emission of exhaust gas is only limited during engine idling because the fuel rate and cylinder filling are both low; moreover, the combustion temperatures are lower, and accordingly also the emission of nitrogen compounds. In intermediate load ranges, however, the emission of nitrogen compounds is particularly high and therefore particularly dangerous because the engine usually operates in city traffic in (for which the emission control regulations are usually the most stringent) during intermediate load ranges. It is desirable, moreover, for the recycling of the exhaust gas to be interrupted temporarily during short-time full loads as they occur, for example, when passing another automobile. On the other hand, the emission control regulations are less stringent for highway driving which may require maximum power output under full loads without an accumulation of noxious discharge gases.

#For satisfying the above requirements, a device is known from German published patent application (DOS) No. 23 38 906 which comprises the use of a vacuum amplifier for the purpose of providing a controlled vacuum for the EGR-valve. This device, in addition to requiring a vacuum supply reservoir, has the drawback that the amounts of exhaust gas returned within the lower load ranges at high suction or underpressures in the suction conduit are excessively high.

#FIG. 1 is a sectional view of an EGR-valve with a reducing diaphragm,

#FIG. 2 is a sectional view of an EGR-valve without a reducing diaphragm,

#FIG. 3 is a sectional view of an EGR-valve without a shutoff or cutoff diaphragm,

#Referring briefly to FIG. 5 therein is shown a circuit diagram including an EGR-valve 51 and a pressure converter 43 connected to an internal combustion engine, the EGR-valve controlling the recycle of exhaust gases from conduit 60 extending from the exhaust manifold of the engine to conduit 61 leading to the suction conduit of inlet manifold 57. The inlet manifold has a number of tap-offs for conduits 14,35,61 and 13. Conduit 12 branches from conduit 60 and leads to converter 43. Conduit 15 connects the converter to the EGR-valve. The significance of the conduits and the internal construction of the EGR-valve and the converter 43 will be explained in detail later. For the present it is sufficient to realize that the EGR-valve is controlled by prevailing suction pressures and the operation of converter 43, to control, in turn, the recirculation of the exhaust gases back to the inlet manifold via conduits 60 and 61.

#FIG. 6 is similar to FIG. 5 and the same reference numerals are used, the exception being that FIG. 6 is concerned with a construction employing a carburetor 41 while FIG. 5 operates with a fuel injector. Conduit 14 in FIG. 6 is connected to the induction throat 40 of carburetor 41.

#The EGR-valve 51 shown in FIG. 1 comprises a reducing diaphragm 36 between a shut-off diaphragm 16 and a working diaphragm 17, the diaphragm 36 being acted on at its top surface by the suction-tube underpressure that acts on the diaphragm 16, while the bottom surface is acted on by the regulating underpressure of the air-pressure converter 43 that acts on the working diaphragm. The shut-off diaphragm 16 is rigidly connected to a coupling rod 33 by means of a diaphragm dish 52, the latter serving as a counter-bearing for the air shut-off spring 24. At its other side, the spring 24 bears against a holding plate 54 of the reducing diaphragm 36. The diaphragm 36 is rigidly connected to the working diaphragm 17 at a push rod 32, by means of a pot 46, at the inner surface thereof. On the coupling rod 33, there is mounted a working spring 25 which bears, at one end, against a spring dish 55 while the other end bears against the reducing diaphragm 36 and the working diaphragm 17 by means of a coupling pot 45, the latter being freely movable, in the regulating condition, with respect to the rod 33. A shut-off chamber 19 and a working chamber 20 are separated from each other within an intermediate part 26 by the reducing diaphragm 36 and a sealing element 22.