CLIAMS:I claim:
1. An air system (10) for an internal combustion engine (12), said air system (10) comprising at least
an air intake path (14);
an air charging device (16) located in said air intake path (14), said air charging device (16) comprising a central shaft (18) driving said air charging device (16);
characterized in that
a flyweight arrangement (20) mounted on said central shaft (18) and at least a part of said flyweight arrangement (20) adapted to be radially displaced in dependence of the centrifugal forces exerted due to rotation of said central shaft (18);
a toothed rod (22) abutting at least a part of said flyweight arrangement (20) such that radial displacement of said flyweight arrangement (20) translate said toothed rod (22); and
a flap (24) mounted on a gear wheel (26), said gear wheel (26) in engagement with said toothed rod such that translation of said toothed rod (22) controls flap operation between a plurality of operative positions in manner such that at least a portion of the air in said air intake path (14) is sent directly to said internal combustion engine (12) through a flow path (28).
2. The air system (10) as claimed in claim 1, wherein said flyweight arrangement (20) comprises a flyweight carrier (30) mounted on said central shaft (18) and at least one flyweight (32) connected to said flyweight carrier (30).
3. The air system (10) as claimed in claim 1 and 2, wherein said at least one flyweight (30) is radially displaced in dependence of the centrifugal forces exerted due to rotation of said central shaft (18).
4. The air system (10) as claimed in claim 1, wherein said translation of said toothed rod (22) is provided with teeth at one end of the toothed rod, said one end being away from the other end of the toothed rod abutting said flyweight arrangement (20).
5. The air system (10) as claimed in claim 2 and 4, wherein said at least one flyweight (30) of said flyweight arrangement abuts said toothed rod (22).
6. The air system (10) as claimed in claim 1 and 4, wherein said teeth of said toothed rod (22) are in engagement with gear teeth of said gear wheel (26).
7. The air system (10) as claimed in claim 1, wherein said toothed rod (22) controls flap operation between a plurality of operative positions in manner such that at least a portion of the air in said air intake path (14) is sent through said air charging device (16) and said air charging device (16) sends charged air to said internal combustion engine (12) through a flow path (28).
8. The air system (10) as claimed in claim 1, wherein a coiled spring is provided with said gear wheel (26).
9. The air system (10) as claimed in claim 1, wherein a spring loaded mechanism is provided with said toothed rod (22) such that said toothed rod (22) translates against the spring force of the spring in the spring loaded mechanism.
10. The air system (10) as claimed in claim 1, wherein said air charging device is a supercharger.
11. 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). ,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 existing. 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 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 US patent publication numbered US5394853 discloses an air system for an internal combustion engine. A supercharging device for an internal combustion engine for which the load can be changed by an accelerator pedal includes: a continuously variable transmission being driven by the engine and including a drive pulley, a driven pulley, a belt, a flyweight, and a presser member, the drive and driven pulleys having movable flanges and fixed flanges mounted on rotatable shaft members and being rotatable therewith, the belt being wound around and coupling the drive and driven pulleys, and the flyweight and the presser member being provided on at least one of the drive pulley and the driven pulley; and a mechanical type supercharger driven by the continuously variable transmission for supercharging the engine, the supercharger having a housing and a runner shaft with a runner rotatably supported inside the housing. A control device is provided for sliding the movable flange of the drive pulley along the axis thereof so that the movable flange is moved away from the fixed flange in the drive pulley when under a light load for which the supercharger requires little supercharging.

Brief description of the accompanying drawings:
[004] An embodiment of the disclosure is described with reference to the following accompanying drawings, the drawings are not to scale and do not represent any technical details. The drawings are only illustrative of the embodiment;
[005] Figure 1 illustrates a schematic of the air system for an internal combustion engine in accordance with this disclosure; and
[006] Figure 2 illustrates a blown up view of the portion of the air system which is the focus of this disclosure.

Detailed description of the embodiments:
[007] Figure 1 illustrates a schematic of the air system for an internal combustion engine in accordance with this disclosure. The air system 10 comprising at least an air intake path 14 and an air charging device 16 located in the air intake path 14. The air charging device 16 comprises a central shaft 18 driving the air charging device 16. The air system 10 is characterized such that a flyweight arrangement 20 is mounted on the central shaft 18 and at least a part of the flyweight arrangement 20 is adapted to be radially displaced in dependence of the centrifugal forces exerted due to rotation of the central shaft 18. A toothed rod 22 abuts at least a part of the flyweight arrangement 20 such that radial displacement of the flyweight arrangement 20 translates the toothed rod 22. A flap 24 is mounted on a gear wheel 26, the gear wheel 26 is in engagement with the toothed rod 22 such that translation of the toothed rod 22 controls flap operation between a plurality of operative positions in manner such that at least a portion of the air in the air intake path 14 is sent directly to the internal combustion engine 12 through a flow path 28.

[008] As seen in figure 1 the air intake path 14 is adapted to receive air from plurality of sources. The air intake path 14 receives fresh air from atmosphere and it can receive exhaust gases which are recirculated through the exhaust gas recirculation path 34. The exhaust gas recirculation path 34 is in flow communication with the air intake path 14 and the exhaust gas path 29. The air system 10 comprises an air charging device 16 which is a supercharger. For the ease of understanding the air charging device 16 will be henceforth referred to as supercharger 16 for the remainder of the disclosure. The supercharger 16 is located downstream from the location where the exhaust gas recirculation path 34 is in flow communication with the air intake path 14. There is also provided a flap 18 located upstream of the supercharger 16 but downstream from the location where the exhaust gas recirculation path 34 is in flow communication with the air intake path 14. Thus the supercharger is adapted to receive at least a mixture of fresh air and recirculated exhaust gas.

[009] Figure 2 illustrates a blown up view of the portion of the air system which is the focus of this disclosure. The flyweight arrangement 20 of the air system 10 comprises a flyweight carrier 30 mounted on the central shaft 18 and at least one flyweight 32 connected to the flyweight carrier 30. The at least one flyweight 32 is radially displaced in dependence of the centrifugal forces exerted due to rotation of the central shaft 18. The toothed rod 22 is provided with teeth (as seen in figure 2) at one end of the toothed rod. The end on which the teeth are provided on the toothed rod 22 is away from the other end of the toothed rod 22 which abuts the flyweight arrangement 20. The flyweights 32 of the flyweight arrangement abut the toothed rod 22. The teeth of the toothed rod 22 are in engagement with gear teeth (not shown in figure 2) of the gear wheel 26. The translation of the toothed rod 22 controls flap operation between a plurality of operative positions in manner such that at least a portion of the air in said air intake path 14 is sent through the air charging device 16 and the air charging device 16 sends charged air to the internal combustion engine 12 through a flow path 28.

[0010] In accordance with one embodiment of the air system 10, the gear wheel is provided with a coiled spring (not shown in figures) along the part on which the gear wheel 26 is mounted. The coiled spring gets coiled when the gear wheel rotates in one direction and uncoiling of the coiled spring ensures that the gear wheel rotates in the other direction. Working details of this embodiment will be provided in the foregoing disclosure.

[0011] In accordance with another embodiment of the air system 10, there is provided a spring loaded mechanism which is connected to the end of the toothed rod 22 where the teeth are provided. The spring loaded mechanism is such that it toothed rod 22 translates against the spring force of the spring in the spring loaded mechanism. When the translation of the toothed rod 22 is initiated by the flyweight arrangement 20, the spring of the spring loaded mechanism gets compressed. When the translation of the toothed rod stops the spring exerts force on the toothed rod in manner such that the toothed rod retains its original position.

[0012] In accordance with one embodiment of the air system 10, the toothed rod 22 may be mounted on the central shaft 16. However, the toothed rod 22 is mounted such that the rotation of the shaft does not lead to the rotation of the toothed rod 22. In accordance with one embodiment the toothed rod 22 may be provided in a housing which houses at least a part of the flyweight arrangement 20.

[0013] The working of the air system in accordance with disclosure will be explained herein-below with reference to one of the embodiments described above. The internal combustion engine 12 on which the air system 10 of this disclosure is employed is a single cylinder or a two cylinder internal combustion engine 12. We consider the embodiment wherein a coiled spring is provided in the gear wheel 26. For understanding the working it is important to know at least two operating modes on an internal combustion engine 12. These two modes are a full load operating mode and a low load/part load operating mode. The full load operating mode can be defined as a mode of operating the internal combustion engine 12 wherein the driver of the vehicle has demanded high power either by pressing the accelerator pedal in four wheelers or by turning the accelerator in a three wheeler. The consequence of this full load operating mode is that more air and fuel will be required to achieve the driver demand. This directly affects the emissions, which are very critical in small capacity engines such as single cylinder and two cylinder engines. Also in full load operating mode the engine speeds are usually high. The low load/part load operating mode can be defined as a mode of operating the internal combustion engine 12 wherein the power demand by the driver is lower than in the full load operating mode. In low load/part load operation the engine speeds are lower than in case of full load operating mode.

[0014] During initial working of the internal combustion engine 12, the driver demand may be low i.e. low load/part load operation, thus the quantity of exhaust gases and fresh air flowing in the air intake path 12 and entering the supercharger 16 will be low. Also in low load/ part load operation since the engine speed is low, the supercharger is operating at lower speeds. As the supercharger speed is low, the central shaft 18 rotates at low speed. The low speed rotation of the central shaft 18 induces low radial centrifugal forces on the flyweight 32 of the flyweight arrangement 20. The low radial centrifugal forces on the flyweights 32 produce low or no translation of the toothed rod 22. Since the toothed rod 22 does not translate, no rotational motion is induced in the gear wheel 26 which is engagement with the toothed rod 22. No rotation of the gear wheel 26 causes the flap 24 to retain its position. In this position of the flap 24 is such that it allows most of the air in the air intake path 14 to flow through the flow path 28. The intake air flows through the flow path 28 and directly to the internal combustion engine 12. As the flap 14 is provided upstream of the supercharger 16, the intake air takes the first flow path available and thus the amount of intake air entering the supercharger will be low. Thus during low load/part load operation the intake air entering the supercharger 16 is low and hence the air getting charged is low, most of the air is directly to the internal combustion engine 12.

[0015] When the driver demand is high and the internal combustion engine 12 is operated in the full load operation. The engine speed is high in full load operation; consequently the quantity of exhaust gases that are recirculated and the fresh air is high. As the engine speed is high the supercharger 16 rotates at a greater speed than the speed of the supercharger in the low load/part load condition. As the supercharger speed is high the central shaft 18 rotates with high speed. The high speed rotation of the central shaft 18 exerts high radial centrifugal force on the flyweights 32 of the flyweight arrangement 20. Due to the centrifugal forces on the flyweights 32, the flyweights move radially in a direction away from the central shaft 18. The radial movement of the flyweights 32 causes the portion of the flyweights 32 which is abutting the toothed rod 22 to push the toothed rod 22. As the toothed rod 22 is pushed, it translates. The translation of the toothed rod 22 causes rotational movement of the gear wheel 26. As the gear wheel 26 rotates it causes the flap 24 to rotate and move between pluralities of operative position. One operative position of the flap 24 is such that it closes one of the openings to the flow path 28. During this operative position of the flap 24 all the intake air flows through the supercharger 16. The supercharger 16 charges the air and sends the air of the internal combustion engine 12. During translation of the toothed rod 22 and the rotation of the gear wheel 26, the coiled spring in the gear wheel 26 gets compressed and coiled. Now if there is a decrease in driver demand, the engine speed and supercharger speed reduces. The radial forces moving the toothed rod 22 decreases, the compressed coiled spring now exerts rotational forces on the gear wheel 26. This rotational force is in the direction opposite to the rotation of the gear wheel 26 due to the toothed rod 22. Thus as the compressed coiled spring gets uncoiled, the gear wheel 26 rotates, the rotation of the gear wheel 26 causes the toothed rod 22 to translate in the opposite direction, such that the toothed wheel moves back to the position it was in when the flyweights 32 do not exert any pushing force on the toothed rod.

[0016] The air system 10 with the flap 24 and the flyweight arrangement 20, toothed rod 22 and gear wheel 26 in accordance with this disclosure is for a single cylinder or a two cylinder engine 12. The main advantages of this type of an air system is that in full load the supercharger 16 is not bypassed and usually bypassed in part load or low load operating conditions of the internal combustion engine. Thus the air is pressurized by the supercharger only when required and any unnecessary losses in the engine power are avoided.

[0017] It should be understood that embodiments explained in the description above and the figures provided as a part of this disclosure 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 in terms of the type of spring or spring loaded mechanism, type of flyweights or flyweight arrangement, type of toothed rod, type of gear wheel. The scope of the invention is only limited by the scope of the claims.