GB1575606A - Reducing the pollutant level in exhaust gases from internal combustion engines - Google Patents

Description

(54) REDUCING THE POLLUTANT LEVEL IN EXHAUST GASES FROM INTERNAL COMBUSTION ENGINES (71) We, EXXON RESEARCH AND ENGINEERING COMPANY, a Corporation duly organised and existing under the laws of the State of Delaware, United States of America, of Linden, New Jersey, United States of America do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to reducing the pollutant level in the exhaust gases of internal combustion engines, herein denoted by "i.c.e.".

Amount the pollutants which can be generated by an i.c.e. are nitrogen oxides, herein designated NOx, and regulations are in force or proposed in some countries to restrict the amount of NOX emissions from i.c.e.'s.

One of the expedients to reduce NOX formation is to recirculate some of the engine exhaust gas to the engine, thereby reducing the peak temperature in the combustion chambers of the engines. However, the presence of recirculated exhaust gas in the combustion chambers reduces maximum engine power, and also hinders smooth operation of the engine at low speeds. Accordingly, it is recognised that exhaust gas recirculation ("EGR") should be permitted only in the engine operating regime between lower power and high up to maximum power, and a number of EGR control systems have been devised to this end. In some known EGR control systems, the exhaust pipe is connected via a control device to a region of the air intake of the engine upstream of the engine regulating device.Thus, in engines having a fuel carburettor venturi in the air intake and a throttle plate downstream of the venturi for regulating the engine by controlling the supply of air and fuel passing into the manifold and thence into the engine, a common expedient is to provide an EGR conduit (having an EGR control device) connected to the air intake upstream of the throttle plate - e.g. to the venturi or to the air cleaner. In these regions of the air intake, the reduced pressure promotes circulation of exhaust gas to the engine from the exhaust pipe in approximately a constant proportion relative to the rate of air inspiration over the whole engine operating speed range and load, and a simple calibrated orifice is used to determine and regulate the proportions of exhaust gas to air passing to the engine.

However, the amount of fuel delivered by the carburettor tends to be changed from the optimum range by passing exhaust gas into the intake as described above, and the oxygen to fuel ratio of the mixture which is passed to the engine tends to deviate so much from the normal operating requirement that the engine will not operate smoothly in at least part of its speed and load ranges. One way of dealing with this problem is to circulate exhaust gas to the intake manifold, but unfortunately, the maximum manifold vacuum is obtained when EGR is least required.

The foregoing difficulties are at least mitigated or substantially eliminated by the present invention which provides an internal combustion engine comprising an intake manifold, an exhaust pipe, an engine regulating device for regulating the power of the engine, an exhaust gas recycle conduit connected at one end to the intake manifold and connected at the other end to the exhaust pipe, a value in the exhaust gas recycle conduit which is biassed towards a closed position in which it obturates the exhaust gas recycle conduit, pressure sensitive means responsive to reduced pressure to open the valve against the bias, a vacuum pipe for communicating the intake manifold pressure to the pressure sensitive means, and a mechanical link connected to the engine regulating device, wherein the link is arranged to seal against the slide through the said vacuum pipe and has an aperture therethrough for providing communication between the parts of the vacuum pipe on each side of the link when the said aperture is at least partly in alignment or register with the vacuum pipe, and wherein the aperture in the link is arranged to be in full alignment or register with the vacuum pipe when the engine regulating device is in a position between the positions for low and high engine power.

In one embodiment, the engine power regulating device may comprise a throttle plate for regulating the supply of fuel and air passing into the intake manifold and in this embodiment, the link may be mechanically connected to the throttle plate. The engine power regulating device may also comprise a carburettor having an accelerator pump and the link may comprise at least part of a mechanical connection between the throttle plate and the accelerator pump.

Generally speaking, in previous carburetted internal combustion engines provided with EGR systems in which the exhaust gas was recirculated to the venturi or upstream thereof, no more than about 12% by volume of the air admitted to the engine could be recirculated exhaust gas. Above this level, there would tend to be engine operating problems. However, by passing the recycled exhaust gas into the engine downstream of the throttle plate using an internal combustion engine of the invention, a greater proportion of exhaust gas can be recirculated without operating problems (e.g. 22% of the volume of air may be exhaust gas).

Recirculated exhaust gas is known to contain deposit-forming materials which can be troublesome when deposited in the fuel and air regulating parts of the engine - e.g., on surfaces of the carburettor and/or throttle plate of engines having carburettors and throttle plates. Because the recirculated exhaust gas is passed directly to the intake manifold downstream of such deposit-sensitive engine parts, the foregoing difficulties are substantially avoided or eliminated.

In internal engines according to the invention, exhaust gas is recirculated in substantially the most desirable engine operating regime in substantially the optimum proportions relative to the air-fuel charge passing to the engine, and to a less disadvantageous part of the engine than the carburettor venturi or the air cleaner.

An embodiment of the invention given by way of non-limitative example only, is now described with reference to the drawings in which: Figure 1 shows, partly in vertical cross-section, the principal parts of an EGR-control system of an internal combustion engine according to the invention; Figure 2 is a cross-sectional view through a flange shown in Figure 1; Figure 3 is a part cross-section of an EGR control valve and a pressure-responsive device for controlling the valve; Figure 4 is a cross-section view showing the arrangement of an apertured link which is sealed against and arranged to slide through the EGR pipe; and Figure 5 is an elevational view of the link of Figure 4.

In Figure 1 there is depicted a conventional arrangement of an air intake pipe A having a venturi into which fuel is drawn from the jets J of a carburettor C. The amount of air and fuel passing to the engine (not shown) is regulated by a throttle plate T. Downstream of the air intake pipe A is a flange 4 forming a connection to the intake manifold (not shown).

Between the throttle plate T and the carburettor C is a lever system, including a pivoted linkage 1, the lever system having an adjustable lost-motion spring 5, actuated by the accelerator pedal (not shown). The lost motion spring device ensures that minor adjustments of the position of the throttle plate do not actuate the accelerator pump. The linkage 1 is pivoted at P and has a cam end E for actuating an accelerator pump of the carburettor C.

Exhaust gas can pass from the exhaust pipe (not shown) to the flange 4 and the intake manifold via an EGR control valve 3. Above the valve 3 is a compression spring which urges or biasses the valve towards a closed position, and above the spring is a pressure responsive capsule. The capsule is connected by a vacuum pipe 6 passing through a regulator 2 to a drilling in the air intake wall. It will be seen that part of the linkage 1 passes through the regulator 2.

Referring to Figure 4, there will be seen the part of the linkage 1 within the regulator 2, of which it forms the operative part. The regulator 2 comprises two flanged ends of the vacuum pipe 6 with annular recesses in which are received 'O'-rings to form a sliding seal against the flat sides of the linkage 1. The linkage has an aperture 7 therethrough and it will be seen that by sliding the linkage relative to the flanged ends of the vacuum pipe 6, the aperture 7 can be brought into alignment with the apertures in the flanged ends so that the pressure downstream of the throttle plate can be communicated through the vacuum pipe 6 and the regulator 2 to the pressure capsule.A small air-leakage orifice (not shown) is provided, preferably on the pressure capsule, for atmospheric air to leak at a suitable rate into the pressure capsule to eliminate any reduced pressure therein when communication through the vacuum pipe 6 is interrupted. The form of the aperture 7 in the linkage 1 is shown in Figure 5.

Referring to Figure 3, it will be seen that the valve 3 comprises a plunger, the tapered ends of which seal off the exhaust gas outlet to the flange 4 under the bias exerted by the compression spring. When the linkage 1 is so positioned that a low pressure is communicated through the regulator 2 to the pressure capsule, the valve plunger is pulled away from its seat thereby permitting exhaust gas to be recycled through the valve to the intake manifold and engine via the flange 4.

Referring to Figure 2, it will be seen that the recycled exhaust gas follows an inwardly spiralling path in the body of the flange 4 to the central intake passage thereof so that the exhaust gas enters at right angles to the rotational axis X-X of the throttle plate so that the recycled exhaust gas is thoroughly mixed with the air-fuel mixture passing to the engine and thereby cooled. Moreover the mixing in this way scours the intake duct and helps to prevent deposits forming therein.

The invention provides exhaust gas recirculation in engine operating regimes which are determinable by the position of the aperture 7 in the linkage 1 and by the shape and dimensions of the aperture 7, and without disturbing the operation of the carburettor or the oxygen to fuel ratio. The position, shape and dimensions of the aperture 7 are so arranged that in engine operating regimes corresponding to idling and low power (i.e. throttle closed or only slightly open) or at high power (i.e. throttle fully open or nearly fully open), the aperture 7 will be out of alignment with the openings in the flanged ends of the vacuum pipe 6 at regulator 2, so that the regulator 2 interrupts communication of the intake manifold pressure to the pressure capsule and the valve 3 is closed by the compression spring when the pressure in the capsule is sufficiently increased by the inward leakage of air through the air-leakage orifice. Between the foregoing throttle positions, the aperture 7 is partially or fully in alignment or register with the openings in the flanged ends of vacuum pipe 6 at regulator 2, whereby in varying degrees, the intake pressure is communicated to the valve 3 thereby causing exhaust gas to pass to the intake manifold. A relatively large proportion (e.g. 22%) of the charge passing to the engine may be recycled exhaust gas.

An engine (capacity 954 cm3) according to the invention was installed in a modern mass production car, and the NOX emissions were tested according to the standard European procedure.

The following results were obtained: Unmodified car 4.2 g NOx/test with 12% recirculation 3.2 g NOx/test with 22% recirculation 2.2 g NOx/test WHAT WE CLAIM IS: 1. An internal combustion engine comprising an intake manifold, an exhaust pipe, an engine regulating device for regulating the power of the engine, an exhaust gas recycle conduit connected at one end to the intake manifold and connected at the other end to the exhaust pipe, a valve in the exhaust gas recycle conduit which is biassed towards a closed position in which it obturates the exhaust gas recycle conduit, pressure sensitive means responsive to reduced pressure to open the valve against the bias, a vacuum pipe for communicating the intake manifold pressure to the pressure sensitive means, and a mechanical link connected to the engine regulating device, wherein the link is arranged to seal against the slide through the said vacuum pipe and has an aperture threrethrough for providing communication between the parts of the vacuum pipe on each side of the link when the said aperture is at least partly in alignment or register with the vacuum pipe, and wherein the aperture in the link is arranged to be in full alignment or register with the vacuum pipe when the engine regulating device is in a position between the positions for low and high engine power.

2. An engine as in claim 1 in which the engine power regulating device comprises a throttle plate for regulating the supply of fuel and air passing into the intake manifold and in which the link is mechanically connected to the throttle plate.

3. An engine according to claim 2 in which the engine power regulating device comprises a carburettor having an accelerator pump and in which the link comprises at least part of a mechanical connection between the throttle plate and the accelerator pump.

4. An internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. into the pressure capsule to eliminate any reduced pressure therein when communication through the vacuum pipe 6 is interrupted. The form of the aperture 7 in the linkage 1 is shown in Figure 5. Referring to Figure 3, it will be seen that the valve 3 comprises a plunger, the tapered ends of which seal off the exhaust gas outlet to the flange 4 under the bias exerted by the compression spring. When the linkage 1 is so positioned that a low pressure is communicated through the regulator 2 to the pressure capsule, the valve plunger is pulled away from its seat thereby permitting exhaust gas to be recycled through the valve to the intake manifold and engine via the flange 4. Referring to Figure 2, it will be seen that the recycled exhaust gas follows an inwardly spiralling path in the body of the flange 4 to the central intake passage thereof so that the exhaust gas enters at right angles to the rotational axis X-X of the throttle plate so that the recycled exhaust gas is thoroughly mixed with the air-fuel mixture passing to the engine and thereby cooled. Moreover the mixing in this way scours the intake duct and helps to prevent deposits forming therein. The invention provides exhaust gas recirculation in engine operating regimes which are determinable by the position of the aperture 7 in the linkage 1 and by the shape and dimensions of the aperture 7, and without disturbing the operation of the carburettor or the oxygen to fuel ratio. The position, shape and dimensions of the aperture 7 are so arranged that in engine operating regimes corresponding to idling and low power (i.e. throttle closed or only slightly open) or at high power (i.e. throttle fully open or nearly fully open), the aperture 7 will be out of alignment with the openings in the flanged ends of the vacuum pipe 6 at regulator 2, so that the regulator 2 interrupts communication of the intake manifold pressure to the pressure capsule and the valve 3 is closed by the compression spring when the pressure in the capsule is sufficiently increased by the inward leakage of air through the air-leakage orifice. Between the foregoing throttle positions, the aperture 7 is partially or fully in alignment or register with the openings in the flanged ends of vacuum pipe 6 at regulator 2, whereby in varying degrees, the intake pressure is communicated to the valve 3 thereby causing exhaust gas to pass to the intake manifold. A relatively large proportion (e.g. 22%) of the charge passing to the engine may be recycled exhaust gas. An engine (capacity 954 cm3) according to the invention was installed in a modern mass production car, and the NOX emissions were tested according to the standard European procedure. The following results were obtained: Unmodified car 4.2 g NOx/test with 12% recirculation 3.2 g NOx/test with 22% recirculation 2.2 g NOx/test WHAT WE CLAIM IS:

1. An internal combustion engine comprising an intake manifold, an exhaust pipe, an engine regulating device for regulating the power of the engine, an exhaust gas recycle conduit connected at one end to the intake manifold and connected at the other end to the exhaust pipe, a valve in the exhaust gas recycle conduit which is biassed towards a closed position in which it obturates the exhaust gas recycle conduit, pressure sensitive means responsive to reduced pressure to open the valve against the bias, a vacuum pipe for communicating the intake manifold pressure to the pressure sensitive means, and a mechanical link connected to the engine regulating device, wherein the link is arranged to seal against the slide through the said vacuum pipe and has an aperture threrethrough for providing communication between the parts of the vacuum pipe on each side of the link when the said aperture is at least partly in alignment or register with the vacuum pipe, and wherein the aperture in the link is arranged to be in full alignment or register with the vacuum pipe when the engine regulating device is in a position between the positions for low and high engine power.

2. An engine as in claim 1 in which the engine power regulating device comprises a throttle plate for regulating the supply of fuel and air passing into the intake manifold and in which the link is mechanically connected to the throttle plate.

3. An engine according to claim 2 in which the engine power regulating device comprises a carburettor having an accelerator pump and in which the link comprises at least part of a mechanical connection between the throttle plate and the accelerator pump.

4. An internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.