Claims:We Claim:
1. An exhaust gas system 100, said exhaust system comprising:
a first flow path 102 in flow communication with outlet of at least one cylinder, said first flow path 102 opening into atmosphere; characterized in that
a second flow path 104 in flow communication with said first flow path 102, and a control valve 106 located along interface if said first flow path 102 and said second flow path 104, said control valve 106 adapted to open said second flow path 104 and block said first flow path 102 in dependence of the of the operating condition of an engine cylinder.

2. The exhaust gas system 100 of claim1, wherein said control valve 106 is electronically controlled via an actuator.

3. The exhaust gas system 100 of claim1, wherein said second flow path 104 opens into an accumulator.

4. A method of operating an exhaust gas system 100, said exhaust system comprising, a first flow path 102 in flow communication with outlet, a second flow path 104 in flow communication with said first flow path 102, and a control valve 106 located at interface of said first flow path 102 and said second flow path 104, said method comprising:

receiving, (300) by a control unit an engine operating condition;

checking, (302) by said control unit if said engine operating condition corresponds to one of cylinder shut-off and cylinder running condition;

actuating,(304) by said control unit said control valve 106 in dependence of said engine operating condition, for blocking and un-blocking one of said first flow path 102 and said second flow path 104.
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001]This invention relates to the field of exhaust gas system.

Background of the invention
[0002] Exhaust gas system is used to deliver exhaust from the outlet of engine into the atmosphere. In case of multi cylinder engines, when one of the engine is not firing, the said engine will be suck air, compress and release the same to the atmosphere. Since this work of compressing the air and letting out the compressed air to the atmosphere does not result in any useful work, work done by the cylinder is not accounted for leading to loss of compressed air.

[0003]Prior art patent application US 6179096 discloses an exhaust brake for an internal combustion engine is disclosed. The exhaust brake includes a main valve and a bypass valve for restricting the flow of exhaust gas. The main valve may be selectively closed, while the bypass valve is biased into a closed position with a selective biasing force. Closing the main valve may cause exhaust back pressure to build against the bypass valve until the biasing force is overcome. When the biasing force is surpassed by the exhaust back pressure, the bypass valve opens to relieve the back pressure. The bypass valve closes when back pressure falls below the biasing force. The biasing force may be varied to operate the exhaust brake at a maximum back pressure for a given engine speed and/or engine condition. A method of operating the exhaust brake is also disclosed.

Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0005] FIG. 1 illustrates an exhaust gas system;

[0006] FIG. 2 illustrates an exhaust gas system illustrating energy recovery phase; and

[0007] FIG. 3 illustrates a method of operating an exhaust gas system.

Detailed description of the embodiments
[0008] FIG. 1 illustrates an exhaust gas system. The exhaust gas system 100 comprises a first flow path 102 in flow communication with outlet of at least one cylinder and opening into atmosphere. A second flow path 104 is in flow communication with the first flow path 102, and a control valve 106 is located along the second flow path 104, said control valve 106 adapted to open said second flow path 104 and block said first flow path 102 in dependence of the of the operating condition of an engine cylinder. The control valve 106 may be electronically controlled. In embodiment the second flow path 104 opens into an accumulator. The function of the accumulator is to store the compressed air received from at least one cylinder when it is shut off.

[0009]The construction of the exhaust system will be explained in further detail. The exhaust system comprises a first flow path 102 that is flow communication with at least one engine cylinder. As disclosed in FIG. 1 the first flow path 102 is in flow communication with four cylinders (1-4). The exhaust system also comprises a second flow path 104, and the control valve 106 that is located at the interface of the first flow path 102 and the second flow path 104. The function of the control valve 106 is to block the first flow path 102 or the second flow path 104 depending upon the engine operating condition. The engine operating condition may be one of cylinder shut-off, cylinder firing or a combination of both. For example, as show in FIG. 1 cylinder 1 may be shut off while cylinder 2-4 may be firing. When cylinder number 1 is shut down, cylinders 4 , 3 and 2 are firing the actuator keeps second flow path 104 closed as shown, when the cylinder number 1 is about to come to compression top dead centre , the actuator opens the control valve 106 which opens the second flow path 104 and closes the first flow path 102.

[0010] FIG. 2 illustrates an exhaust gas system 100 illustrating energy recovery phase. When the accumulator is fully charged, the pressurized air from the accumulator is routed back to the cylinder that is shut off (cylinder 1) during the beginning of the power stroke using the second flow path 104 which is controlled by the engine management system. The control unit uses the existing crank and cam sensor feedback to determine the position of top dead centre for cylinder to open the control valve 106 for the air to enter the combustion chamber. Due to the high pressure air acting on the piston of the deactivated cylinder, the cylinder (number 1) works as an air motor thus generating torque on the crankshaft which assists in increasing the cumulative torque available in the crankshaft.

[0011] When the accumulator is fully charged, the control unit switches the function of the cylinder (number 1) that is shut-off from air compressor to air motor that is the control unit modifies the exhaust valve timing to open at the begin of the power stroke and directs the compressed air from the accumulator to the cylinder through the exhaust path as shown in the above fig. The compressed air exerts a downward force on the piston of cylinder which turn contributes to torque on the crankshaft.

[0012] FIG. 3 illustrates a method of operating an exhaust gas system 100. The exhaust system comprises a first flow path 102 in flow communication with outlet, a second flow path 104 in flow communication with the first flow path 102, and a control valve 106 located at interface of the first flow path 102 and the second flow path 104, the method comprises receiving (300) by a control unit an engine operating condition. The control unit checks if the engine operating condition corresponds to one of cylinder shut-off and cylinder running condition. The control unit actuates control valve 106 in dependence of said engine operating condition, for blocking and un-blocking one of the first flow path and the second flow path 104.

[0013]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 the type. 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.