CLIAMS:We Claim:
1. An exhaust gas recirculation (EGR) system (100), comprising
an exhaust gas recirculation (EGR) path (101) and exhaust gas recirculation (EGR) valve (106) in said exhaust gas recirculation (EGR) path (101), said exhaust gas recirculation (EGR) path (101) in flow communication with an air intake path (103).
an air charging device (102) located along the air intake path of an engine (104) and adapted to receive recirculated exhaust gases from said EGR path and fresh air as an input;
said system characterized in having
a filter (108) located between said EGR valve (106) and the air intake path upstream of said air charging device (102).
2. The system of claim 1, wherein said air charging device (102) is a supercharger.
3. The system of claim 2, wherein said supercharger is used for a single cylinder engine.
4. The system of claim 2, wherein said supercharger is used for a multi-cylinder engine.
5. The system of claim 2, wherein said filter (108) is located on the inlet port of said supercharger.
6. The system of claim 4, wherein said filter (108) is removably attached on said supercharger.
7. An air charging device (102) in an exhaust gas recirculation system,
said air charging device (102) located along the air intake path of said exhaust gas recirculation system and adapted to receive engine exhaust via an EGR valve (106), and fresh air as an input; said device characterized in having
a filter (108) located between said EGR valve 106 and the inlet of said air charging device (102).

8. The air charging device (102) of claim 7, wherein said filter is integrated with said air charging device. ,TagSPECI:The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention
[001] This invention relates to the field of exhaust gas recirculation (EGR) system.

Background of the invention
[002] Superchargers are used to increase the power generated by an engine. A compressor is used in the supercharger to increase the pressure or density of air supplied to an engine. Superchargers are powered mechanically by belt- or chain-drive from the engine's crankshaft. In order to increase the performance of the supercharger there is a need to allow the supercharger to have an additional source of input in addition to atmospheric air. The other source of air, a supercharger may have access to is, the exhaust from the engine. But, the exhaust from the engine cannot be used directly as the impurities present in the exhaust may cause damage to the components to the supercharger. Hence, there is also a need for a purification mechanism before the air and/ or exhaust enters the supercharger.

[003] Prior art patent application US 6301887 discloses low pressure EGR system suitable for use as a passive retrofit system is disclosed for moving vehicles equipped with a diesel engine. The EGR loop inlet is positioned upstream of the exhaust particulate filter and downstream of the turbine to utilize backpressure created by the exhaust particulate filter to insure EGR flow in the loop. A catalyzed soot filter in communication with the EGR pickup insures cleansed EGR gases at the EGR return downstream of the air filter and upstream of the compressor. A corrugated EGR line provides cooling of the EGR gases.

Brief description of the accompanying drawing
[004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[005] FIG. 1 illustrates an exhaust gas recirculation system.

Detailed description of the embodiments
[006] FIG. 1 illustrates an exhaust gas recirculation (EGR) system 100. The exhaust gas recirculation system 100 disclosed herein has at least the following, an exhaust gas recirculation (EGR) path (101) and an exhaust gas recirculation (EGR) valve (106) in the exhaust gas recirculation (EGR) path (101), the EGR path (101) is in flow communication with an air intake path (103). An air charging device (102) located along the air intake path (103) of an engine (104) and adapted to receive recirculated exhaust gases from the EGR path via an EGR valve (106) and fresh air as an input. The system is characterized in having a filter (108) located between the EGR valve (106) and the air intake path (103) upstream of the air charging device (102).The EGR system serves to take in a part of the exhaust from the engine 104 along with fresh air as an input. The same mixture of exhaust and fresh air is used as a charge that is supplied to the engine 104. The engine 104 now has the capability to take in additional fuel as an input corresponding to an increase in the charge that is available. This results in increase in power output for every useful stroke of the engine 104.

[007] The air charging device (102) that is part of the EGR system receives input from two sources namely a) the fresh air and b) the exhaust gases. The air charging device (102) is located along the air intake path (103) of the exhaust gas recirculation system and adapted to receive recirculated exhaust gases from the EGR path via an EGR valve (106), and fresh air as an input. The exhaust returning from the engine (104) will have traces of impurities, particulates, carbon particles and the like. The above mentioned impurities in the exhaust need to be removed before the exhaust can be mixed with the atmospheric air and sent back as charge to the engine 104. The impurities and particle in the exhaust gases may get deposited on the active components of the air charging device (102) such as the rotor. The deposition of the impurities not only reduces the efficiency of the air charging device (102) but also reduces the life of the air charging device (102). Thus it is important that the impurities from the exhaust gas which is being recirculated does not reach the air charging device. To achieve this, a filter (108) located between the EGR valve (106) and the air intake path upstream of the air charging device (102). In an embodiment the filter (108) may be integrated with the air charging device. The air charging device 102 may be a supercharger. The filter 108 may be located on the inlet port of the supercharger. The supercharger may be used for a single cylinder engine or a multi-cylinder engine. The above mentioned arrangement of having a filter 108 with the air charging device 102 enables low pressure EGR because the air charging device is protected from particulates due to the presence of the filter 108. Low pressure EGR helps in achieving higher EGR flow rates and lower EGR temperature.

[008] The filter 108 may be in the form of a mesh like structure. The filter 108 prevents any particulates or impurities from reaching the air charging device 102. The properties of the filter are better filtration efficiency of the exhaust particles, temperature stability, and to ensure better pressure stability of the exhaust reaching the air charging device 102.The filter 108 may also be removably attached on the supercharger. This enables the filter 108 to be replaced at regular intervals, whenever the filter 108 gets clogged. Alternatively, the filter 108 can also be cleaned and replaced into the low pressure EGR circuit.

[009] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention in terms of type of filter and the position of the filter on the exhaust flow path and supercharger. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.