EXHAUST GAS RECIRCULATION SYSTEM

FIELD OF THE INVENTION

[0001] The present subject matter relates generally to an exhaust system, and more particularly, to an exhaust gas recirculation actuation and metering system for use with an internal combustion engine, for purification of exhaust gases.

BACKGROUND OF THE INVENTION

[0002] Internal combustion engines emit exhaust gases of various types into the environment upon their operation. However, the control of these potentially hazardous emissions is necessary to limit the after-effects of the emissions, for enabling better air quality and adhere to emission norms of the respective territorial jurisdictions. With continous tightening in emission norms, controlling harmful emissions in these engines has become an absolute necessity.

[0003] Several emission control techniques are known in the prior art for preventing, controlling or minimizing the harmfulness of exhaust gases. These techniques vary based on target emissions such as carbon monoxide, hydrocarbons, smoke, various nitrogen oxides (NOx) and particulate matter among others.

[0004] Exhaust gas recirculation is one such emission control technique mainly targeted to reduce NOx emissions where a portion of engine exhaust gases is recirculated back to the intake system through an exhaust gas recirculation valve to reduce the combustion temperature. Because NOx form primarily when a mixture of nitrogen and oxygen is subjected to high temperature, a lower combustion chamber temperature reduces the amount of NOx generated during the combustion.The amount of recirculation of exhaust gas required by an engine depends on various parameters specific to the engine design and intended reduction in NOx, and hence needs to be controlled for optimum performance of the engine.

[0005] Generally, an exhaust gas recirculation valve is actuated using sophisticated electronic control units, which takes feedback on various operating parameters governing the rate of exhaust gas recirculation required. However maintenance of electronic sytems requires trained skills and they are generally expensive. Therefore, there is a need to develop a different method of controlling exhaust gas recirculation using mechanical set up while eliminating the requirement of electronic systems.

[0006] Hence, the present subject matter is directed to overcome all or any of the problems as set forth above and obviate the lacunae in the prior art. Therefore, it is an object of the present invention to provide a simple Exhaust gas recirculation actuation and metering system comprising a mechanically operated exhaust gas recirculation valve for reducing NOx from the exhaust of an internal combustion engine.

[0007] Another object of the present invention is to provide a vacuum controlled, mechanically operated exhaust gas recirculation valve which can be used with an internal combustion engine, preferably with a motorcycle engine, comprising a carburettor or an electronic fuel injection system.

SUMMARY OF THE INVENTION

[0008] To this end, the present invention discloses an exhaust gas recirculation actuation and metering system comprising a vacuum controlled and mechanically operated exhaust gas recirculation valve. According to an aspect of the present invention, the exhaust gas recirculation valve uses at least two diaphragm chambers, which are connected appropriately to the engine intake and exhaust systems to control the exhaust gas recirculation valve.

[0009] According to a further aspect of the present invention, the diaphragms are controlled by suitable springs for opening and closing the exhaust gas recirculation valve at the appropriate vacuum levels to meter the required amount of the exhaust gas.

[00010] The foregoing objectives and summary provide only a brief introduction to the present subject matter. To fully appreciate these and other objects of the present subject matter as well as the subject matter itself, all of which will become apparent to those skilled in the art, the ensuing detailed description of the subject matter and the claims should be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[00011] The above and other features, aspects, and advantages of the subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where:

FIG. 1 shows a schematic layout of the Exhaust gas recirculation actuation and metering system comprising an exhaust gas recirculation valve according to the present invention.

FIG. 2 shows a diagrammatic illustration of the Exhaust gas recirculation valve according to the present invention.

FIG. 3 depicts a front sectional view of the Exhaust gas recirculation valve according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[00012] In order that those skilled in the art can understand the present invention, the invention is further described below so that various features of the Exhaust gas recirculation actuation and metering system proposed here are discernible from the description thereof set out hereunder. However these descriptions and the appended drawings are only used for those skilled in the art to understand the objects, features, and characteristics of the present invention and not to be used to confine the scope and spirit of the present invention. In the supporting figures, the same reference numerals are given to members and parts having the same functions.

[00013] FIG. 1 illustrates the layout of the exhaust gas recirculation actuation and metering system connected to an internal combustion engine. The internal combustion engine 12 comprises an intake manifold 17, exhaust manifold 18, cylinder 20, exhaust gas inlet pipe 21 and exhaust gas outlet pipe 22. Since the basic construction and function of these elements is known to those versed in the art, the details have been omitted and the description focuses on the present invention. The said engine 12 is connected with an exhaust gas recirculation actuation and metering system for emission control. The exhaust gas recirculation actuation and metering system comprises a vacuum controlled and mechanically operated exhaust gas recirculation valve 19 to control the timing and amount of exhaust gas recirculated in the internal combustion engine.

[00014] According to an embodiment, the exhaust gas recirculation valve has at least two diaphragm chambers, which are connected appropriately to the engine intake and exhaust systems to control the exhaust gas recirculation valve. The diaphragms are controlled by suitable springs for opening and closing the exhaust gas recirculation valve at the appropriate vacuum levels to meter the required amount of the exhaust gas: To this end, the exhaust gas recirculation valve 19 further comprises at least two valve subsystems namely a first valve subsystem and a second valve subsystem. The two valve subsystems are operated individually through corresponding valve stems which in turn are supported by their corresponding diaphragm and spring subsystems. The two subsystems work jointly within a range marked by a lower actuating condition and an upper actuating condition. Together the valve stems provide an AND logic gate in the exhaust gas recirculation pipe.

[00015] FIG. 3 depicts a front sectional view of the Exhaust gas recirculation valve according to the present invention. The first valve subsystem comprises a normally closed first valve head 1, a first valve stem 2, a first diaphragm 3, a first spring 4, a first chamber 5 and a first manifold vacuum connection 10. Likewise the second valve subsystem comprises a normally open second valve head 6, a second valve stem 7, a second diaphragm 8, a second spring 9, a second manifold vacuum connection 11, a second chamber 13, an exhaust gas inlet 14, an exhaust gas outlet 15 and a valve seat 16. The two valve subsystems work at different engine loads. The first diaphragm 3 opens the valve seat 16 during engine part load conditions whereas the second diaphragm 8 closes the valve seat 16 at engine full load conditions. The valve seat 16 is common to both the valve subsystems.

[00016] The exhaust gas recirculation valve 19 is connected to the exhaust manifold 18 as well as the intake manifold 17. The exhaust gas outlet 15 of the exhaust gas recirculation valve 19 is connected to the intake manifold 17 by the exhaust gas outlet pipe 22. Likewise, the exhaust gas inlet 14 of the exhaust gas recirculation valve 19 is connected to the exhaust manifold 18 by the exhaust gas inlet pipe 21.

[00017] The working of the present invention is now explained. The present system controls the timing and amount of exhaust gas to be recirculated to the engine. The system is operable based on the vacuum in the intake manifold 17 of the engine. The internal combustion engine 12 draws air into the cylinder 20 by natural aspiration and the suction of air creates a vacuum in the intake manifold 17. This vacuum in the intake manifold 17 is related to the various engine operating conditions. In the exhaust gas recirculation valve 19, the first valve head 1 is normally closed. The first valve stem 2 connects the first valve head 1 to the first diaphragm 3. The first valve head 1 starts to lift once the vacuum in the first chamber 5 increases above a set vacuum level. The preload of the first spring 4, connected to the first diaphragm 3, determines the set vacuum level of first chamber 5.

[00018] The first chamber 5 is connected to the intake manifold 17 by the first manifold connection 10. The first diaphragm 3, preloaded by the first spring 4, senses the differential pressure between the vacuum in the first chamber 5 and atmospheric pressure. The vacuum in the first chamber 5, which has the vacuum equal to that of the intake manifold 17, causes the first diaphragm 3 to lift. The lift of the first diaphragm 3 causes the first valve head 1, connected by the first valve stem 2 to lift. The set vacuum level controls the lift of first valve head 1 based on the engine operating conditions.

[00019] The lift of the first valve head 1 allows the flow of the exhaust gas (es) from the exhaust manifold 18 to enter through the exhaust gas inlet 14, pass through the valve seat 16 and exits through the exhaust gas outlet 15.

[00020] The exhaust gas outlet 15 is connected to the intake manifold 17 of the engine 12. The set vacuum level in the first chamber 5 determines the lower actuating condition of the engine 12 above which the exhaust gas recirculation valve 19 allows exhaust gas to flow to the intake manifold 17 from exhaust manifold 18. The flow rate of the exhaust gas is controlled by the lift of the first valve head 1 and the size of the valve seat 16. The first diaphragm 3 and the first spring 4 control the lift of first valve head 1. The lift of first valve head 1 increases as the vacuum in the intake manifold 17 increases.

[00021] The second valve head 6, which is in normally open position, is pushed down as the vacuum increases above a certain set vacuum pressure in the second chamber 13. The second chamber 13 is connected to the intake manifold 17 by the second manifold connection 11. The second diaphragm 8 senses the differential pressure between the atmospheric pressure and vacuum pressure in the second chamber 13, which is same as the vacuum in intake manifold 17 and moves down as the vacuum increases. The lift of the second diaphragm 8 causes the second valve head 6, connected by the second valve stem 7 to lift.

[00022] The second diaphragm 8 is preloaded with the second spring 9. The set vacuum after which the second diaphragm 8 has to move down is determined by the preload of second spring 9. This movement of the second diaphragm 8 causes the second valve head 6 to move and close valve seat 16. At this point there will not be any flow of exhaust gas from exhaust gas inlet 14 to the exhaust gas outlet 15 of the exhaust gas recirculation valve 19.

[00023] The set vacuum in the second chamber 13 determines the higher actuating condition of the engine 12 above which the exhaust gas recirculation valve 19 stops the flow of the exhaust gas from exhaust manifold 19 to the intake manifold 17. Thus by sensing the intake manifold pressure, the exhaust gas recirculation valve 19 is actuated to allow exhaust gas from exhaust manifold 18 to the intake manifold 17 of the engine 12, for only a required band of operating conditions of the engine 12.

[00024] Thus, the exhaust gas recirculation valve 19 senses engine operating conditions to operate the first valve head 1 to open and second valve head 6 to close for enabling logic based metering of exhaust gas recirculation. In a preferred embodiment of the present invention, first valve stem 2 (normally closed) opens when engine load exceeds 30% of the throttle opening (sensed based on the manifold vacuum). Likewise second valve stem 7 (normally open) closes when the engine load exceeds 70% of the throttle opening (sensed based on manifold vacuum). Thus, the overall exhaust gas recirculation actuation and metering system is open when the engine load is in the range of 30% - 70% (throttle opening range). It is to be noted that the preload of the springs in the respective-- .. diaphragms can be adjusted to arrive at the required range of operation. In a preferred embodiment, the operating vacuum ranges from 70 mbar to 320 mbar pressure.

[00025] The present subject matter is thus described. The embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore the forgoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the appended claims.

We claim:

1. An exhaust gas recirculation actuation and metering system, connected to an internal combustion engine, comprising a vacuum controlled and mechanically operated exhaust gas recirculation valve, to control the timing and amount of exhaust gas recirculated in the internal combustion engine, the said exhaust gas recirculation valve further comprising at least two valve subsystems namely a first valve subsystem and a second valve subsystem, wherein the two valve subsystems work jointly within a range marked by a lower actuating condition and an upper actuating condition.

2. The exhaust gas recirculation actuation and metering system as claimed in claim 1, wherein the first valve subsystem comprises a normally closed first valve head, a first valve stem, a first diaphragm, a first spring, a first chamber, a first manifold vacuum, and the second valve subsystem comprises a normally open second valve head, a second valve stem, a second diaphragm, a second spring, a second manifold vacuum connection, a second chamber, an exhaust gas inlet, an exhaust gas outlet and a valve seat.

3. The exhaust gas recirculation actuation and metering system as claimed in claim 1, wherein the said internal combustion engine further comprises an intake manifold, an exhaust manifold, a cylinder, an exhaust gas inlet pipe and an exhaust gas outlet pipe.

4. The exhaust gas recirculation actuation and metering system as claimed in claim 3, wherein the said system is operable based on the vacuum in the inlet manifold of the internal combustion engine.

5. The exhaust gas recirculation actuation and metering system as claimed in claim 1 or claim 4, wherein the said system is actuated when either the lower actuating condition or the upper actuating condition cross a set vacuum threshold value determined by the preload of either first spring or second spring.

6. The exhaust gas recirculation actuation and metering system as claimed in claim 4 or claim 5, wherein the operating vacuum ranges from 70 mbar to 320 mbar pressure.

7. The exhaust gas recirculation actuation and metering system substantially as herein described and illustrated with reference to the accompanying drawings.