CLIAMS:We Claim:
1. An air system (10) for an internal combustion engine (12), said air system (10) comprising:
an air intake path (14);
an exhaust gas path (16);
an air charging device (18) located upstream of said internal combustion engine (12) in said air intake path (14);
characterized in that
an exhaust gas recirculation path (20) provided such that part of the exhaust gas recirculation path in flow communication with said air intake path (14) is upstream of said air charging device (18);
a bypass path (22) provided such that inlet (24) of said bypass path (22) is upstream of said air charging device (18) and outlet (26) of said bypass path (22) is downstream of said air charging device (18);
a valve (28) located at the interface of said air intake path (14) and said inlet (24) of said bypass path (22) such that based on operating condition of said internal combustion engine (12) air charge is passed through said air charging device (18) or passed through the bypass path (22), operation of said valve (28) modulates the suction effect of said air charging device (18) creating low pressure upstream of said air charging device 18 and helps in suction of said recirculated exhaust gases.
2. The air system (10) as claimed in claim 1, wherein in said air system (10) operation of said valve (28) modulates the suction effect of said air charging device (18) creating low pressure upstream of said air charging device 18 and allows modulation of the exhaust gas recirculation rate.
3. The air system (10) as claimed in claim 1, wherein said exhaust gas recirculation path (20) is such that the dimensions of the exhaust gas recirculation path (20), bypass path (22) and valve (28) is selected in dependence of the capacity of the internal combustion engine (12).
4. The air system (10) as claimed in claim 1 and 3, wherein said selection of exhaust recirculation path dimension and operation of said valve (28) allows modulation of the exhaust gas recirculation rate and allows replacement on an exhaust gas recirculation valve in said exhaust gas recirculation path with a valve (28) in said air intake path (14).
5. The air system (10) as claimed in claim 1, wherein said valve (28) adapted to be operated in a manner such that the amount of exhaust gas re-circulation is controlled.
6. The air system (10) as claimed in claim 1, wherein said air charging device (18) is a supercharger.
7. The air system (10) as claimed in claim 1, wherein said valve (28) adapted to be operated in a manner such that said valve (28) is proportionally opened or proportionally closed.
8. The air system (10) as claimed in claim 1, wherein said valve (28) adapted to be operated in a manner such that at least a portion of said intake air is sent through the bypass path (22).
9. The air system (10) as claimed in claim 1, wherein said internal combustion engine (12) is a single cylinder or a two cylinder internal combustion engine (12).
10. The air system (10) as claimed in claim 1, wherein said valve (28) is operated mechanically. ,TagSPECI:The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention
[001] This disclosure relates to an air system for an internal combustion engine

Background of the invention:
[002] There are various mechanical superchargers for engine boosting available today. There are roots chargers, vane types or types based on centrifugal forces. Some of the today’s superchargers are switchable as well, in order not to permanently pressurize the inlet air when the engine doesn’t need it and to avoid therefore an unnecessary loss in engine power. The bypass of the charger is usually done by an electrically controlled bypass valve. For one cylinder naturally aspirated engines particularly in full load, the value of (air-fuel ratio) lambda gets critical. The need of the industry is a cost effective solution which will provide higher lambda values in full load engine operating conditions. In particular for countries such as India where BS3 and BS4 emission certification are becoming mandatory cost efficient solution which provide higher lambda values are required to have more safety margin in emission certification tests. Further considering that certification cycles are very often carried out in full load engine operating conditions, such cost efficient solutions of full load engine operating conditions are necessary.

[003] A European patent publication numbered EP3414254 discloses an air system for an internal combustion engine. The internal combustion engine here in a four-cylinder gasoline engine. The air system comprises a supercharger which is driven through a wheel provided on the engine which is coupled to another wheel on the supercharger. Between the wheel on the engine and the supercharger a vario-transmission mechanism is provided which allows to reduce the speed of the supercharger. There is also provided a linkage from the accelerator pedal to a throttle valve in the air intake path. The pressing of the accelerator pedal ensures that the quantity of air sent to supercharger can be varied. During some operating points the air sent to the supercharger can be completely stopped. However, during such operating points there is no possibility to divert any air from the intake path.

Brief description of the accompanying drawings:
[004] An embodiment of the disclosure is described with reference to the following accompanying drawings;
[005] Figure 1 illustrates an air system for an internal combustion engine in accordance with this disclosure.

Detailed description of the embodiments:
[006] Figure 1 illustrates an air system for an internal combustion engine in accordance with this disclosure. The air system 10 comprises an air intake path 14; an exhaust gas path 16 and an air charging device 18 located upstream of the internal combustion engine 12 in the air intake path 14. The air system 10 is characterized such that the air system 10 comprises an exhaust gas recirculation path 20 provided such that part of the exhaust gas recirculation path 20 in flow communication with the air intake path 14 is upstream of the air charging device 18; a bypass path 22 provided such that inlet 24 of the bypass path 22 is upstream of the air charging device 18 and outlet 26 of the bypass path 22 is downstream of the air charging device 18 and a valve 28 is located at the interface of the air intake path 14 and air inlet 24 of the bypass path 22 such that based on operating condition of the internal combustion engine 12 air charge is passed through the air charging device 18 or passed through the bypass path 22. The operation of the valve 28 modulates the suction effect of the air charging device 18 creating low pressure upstream of the air charging device 18 and helps in suction of the recirculated exhaust gases. The air charging device 18 is a supercharger.

[007] For better understanding of the air system 10 in accordance with this disclosure it is important to understand the air system for internal combustion engine known in the state of the art. The air system known in the state of the art comprises an air intake path and exhaust gas path and an air charging device located in the air intake path. The exhaust gas recirculation path is provided such that part of the exhaust gas recirculation path which is in flow communication with the air intake path is provided downstream of the air charging device and upstream of the internal combustion engine. Further a valve is provided in the exhaust gas recirculation path to control the quantity exhaust gas that is recirculated back to the internal combustion engine.

[008] It is also important to understand the working of the air system known in the state of art. One point to note is that the above described air system works particularly well for a multi-cylinder engine. In multi-cylinder engine, wherein the exhaust gases are introduced downstream of the air charging device, it may be observed that the pressure of the air downstream of the air charging device will be lower than the pressure of air that is introduced into the air intake by the exhaust gas recirculation path. The pressure difference between the engine exhaust and air downstream of the air charging device would cause the air to flow in the exhaust gas recirculation path and no exhaust gases are introduced into the air intake. Additionally a valve is provided in the exhaust gas recirculation path so that better control of the recirculated exhaust gases is possible.

[009] However, this will not work so efficiently in a low power single cylinder or two cylinder internal combustion engines. We consider the same working principle and air system layout of the state of the art as described above, wherein the exhaust gases are introduced into the air intake path downstream of the air charging device. The pressure of the exhaust gases coming out of the engine in any operating condition of the engine is such that it will never exceed the pressure of the intake air downstream of the air charging device. This being the case no exhaust gases will be recirculated back to the single cylinder or two cylinder internal combustion engine thus emission critical parameters will not be met particularly NOx emission. This creates a problem that for low power, single cylinder and two cylinder engines meeting emission norms will be a challenge. Further, the need of the industry is that for low power small capacity applications the cost of the entire system should be low. The use of a valve further increases the cost of the exhaust gas recirculation system and that of the overall air system.

[0010] Thus with the air system 10 of this disclosure the above mentioned problem are intended to be solved. For the purpose of this disclosure we will focus on the air system for a low power internal combustion engine such as a single cylinder or two cylinder engines. As shown in the figure 1, the air system 10 for a single or two cylinder engine 12 is characterized such that the exhaust gas recirculation path 20 is provided such that part of the exhaust gas recirculation path 20 which is in flow communication with said air intake path 14 is upstream of the air charging device 18. There is also provided a bypass path 22 such that inlet 24 of the bypass path 22 is upstream of the air charging device 18 and outlet 26 of the bypass path 22 is downstream of the air charging device 18 and a valve 28 is located at the interface of the air intake path 14 and air inlet 24 of the bypass path 22 such that based on operating condition of the internal combustion engine 12 air charge is passed through the air charging device 18 or passed through the bypass path 22.

[0011] The construction and operation of the air system can be briefly explained as follows. The air system 10 in accordance with this disclosure is such that the dimensions of the exhaust gas recirculation path 20, bypass path 22 and the valve 28 are selected in dependence of the capacity of the internal combustion engine 12. The valve 28 that is located at the interface of the air intake path 14 and the bypass path inlet 24 is operated mechanically. In accordance with one embodiment of the air system of this disclosure, the mechanical operation of the valve may be implemented such that the driver of the vehicle helps operate the valve 28. Other embodiments for operating the valve are envisaged and within the scope of this disclosure. The valve 28 is adapted to be operated in a manner such that the valve 28 is proportionally opened or proportionally closed. The valve 28 is adapted to be operated in a manner such that at least a portion of the intake air is sent through the bypass path 22, depending on the driver input and engine operating point, thereby controlling pressure downstream of the air charging device 18 and the amount of exhaust gas recirculation back to the engine 12.

[0012] The detailed working of the air system 10 can be explained as follows. As mentioned earlier based on the capacity of the internal combustion engine 12 the dimensions of the exhaust gas recirculation path 20, bypass path 22 and the valve 28 are selected. For example, the dimensions of the exhaust gas recirculation path 20 and the bypass path 22 may be selected in a manner such that the length, width, diameter or the cross-sectional profile of the exhaust gas recirculation path 20 and bypass path 22 is different for different capacity of the internal combustion engine 12.

[0013] Further with regard to the working of the air system 10, based on the operating condition demand from the driver of the vehicle the valve 28 is either opened or closed. Based on the manner in which the valve 28 is mechanically opened the quantity of intake air that is sent through the bypass path 24 or the quantity of intake air that is sent through the air charging device 18 can be regulated. The working principle can be explained as follows. The pressure and quantity of the exhaust gases that is recirculated to the air intake depends on the dimensions of the exhaust gas recirculation path 20. The dimension of the exhaust gas recirculation path 20 is selected such that based on the capacity and required emission characteristics of the internal combustion engine 12. Thus, we can ensure the pressure and quantity of the recirculated exhaust gases for different internal combustion engine capacity.

[0014] When the valve 28 in the air intake path 14 is operated, the mixture of recirculated exhaust gases and fresh air is sent through the bypass path 24. The flow of the intake air through the bypass path 24 modulates the suction effect of the air charging device 18. This modulation of the suction effect creates a low pressure upstream of the air charging device 18 and helps in suction of the recirculated exhaust gases. The better suction upstream of the air charging device allows better modulation of the exhaust gas recirculation rate. Thus the combination of selecting the exhaust gas recirculation path dimension and operation of the valve 28 such that suction effect of the air charging device 18is modulated creating low pressure upstream of the air charging device 18 allows both modulation of the exhaust gas recirculation rate as well as replacement of the exhaust gas recirculation valve with a valve 28 provided in the air intake path. Thus using this layout of the air system 10 in accordance with this disclosure, better suction control of the recirculated exhaust gases is possible. Also the replacement of the exhaust gas recirculation valve known in the state of the art air system with a valve in the air intake path which provides the function of the exhaust gas recirculation rate modulation reduces the overall cost of the air system.

[0015] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. 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.