Claims:We Claim:
1. A device 100 for controlling flow of fuel to a mechanical injector, said device 100 comprising:
a valve 102 located along a return flow path 114 of said fuel injection pump 104,
an energizing element 106 adapted to control said valve 102 based on signals received from a control unit in dependence of a trigger condition; and
a casing 108 enclosing said energizing element 106 and said valve 102, said casing 108 attached to said fuel injection pump 104.

2. The device 100 of claim 1, wherein said energizing element 106 is a magnet.

3. The device 100 of claim 1, wherein said valve 102 is at least one of a ball valve, an electrically actuated valve, a mechanical valve and a pneumatic valve.

4. The device 100 of claim 1, wherein a spring 110 is located in between said valve 102 and said energizing element 106.

5. The device 100 of claim 1, wherein said trigger condition is the level of urea in selective catalytic reduction (SCR) tank.
, Description:Field of the invention
[0001] This invention relates to the field of fuel injection pump.

Background of the invention
[0002] Emission legislation norms are getting stringent by the day. In case of emerging economies like India, Bharat Stage (BS) VI is proposed to be implemented across various categories of vehicles. Selective catalytic reduction (SCR) is one of the techniques used for reducing emission and meeting the legislation requirements. In the case of SCR an aqueous urea solution is injection along the exhaust to reduce NOx. This aqueous urea solution is injected from a tank. When the aqueous urea solution is empty, it is observed that reduction of NOx is no longer possible, and hence the required emission norms cannot be met. Hence there is a need to reduce NOx in the absence of aqueous urea solution.

Brief description of the accompanying drawing
[0003] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[0004] FIG. 1 illustrates a device for controlling flow of fuel to a mechanical injector.

Detailed description of the embodiments
[0005] FIG. 1 illustrates a device 100 for controlling flow of fuel to a mechanical injector. The device 100 is attached to a housing 111 of a fuel injection pump 104 and comprises a valve 102 located along a return flow path 114 of the fuel injection pump 104, an energizing element 106 is adapted to control the valve 102 based on signals received from a control unit in dependence of a trigger condition. The trigger condition is the level of urea in selective catalytic reduction (SCR) tank. A casing 108 encloses the energizing element 106 and the valve 102, the casing 108 is attached to the fuel injection pump 104.
[0006] The constructional features of the device 100 will be explained in further detail. The device 100 comprises a casing 108 that is attached to the housing 111 of the fuel injection pump 104. Located within the casing 108 are an energizing element 106 and a valve 102. The valve 102 may be at least one of a ball valve 102, an electrically actuated valve, a mechanical valve and a pneumatic valve. The valve 102 is located along a return flow path 114 and rests against a seat provided on the return flow path 114. A spring 110 is located in between the valve 102 and the energizing element 106. The spring 110 facilitates movement of the ball. The energizing element 106 may be activated with the help of a solenoid 112. The solenoid 112 receives signals from a control unit. The solenoid 112 further consist a holding shell 116, the backflow connector, the spring 110 which ensures the sealing force of the ball valve 102 to its seat.
[0007] The working of the device 100 will be explained in further detail. During normal working of the vehicle the fuel enters the fuel injection pump 104 through a helix 115 groove that is provided on the plunger 113. The fuel then reaches the pressurizing chamber of the fuel injection pump 104, where it is pressurized and delivered to the injector. The pressurization happens because the valve 102 that is located along the return flow path 114 rests against the seat thereby creating a pressurization zone. When the solenoid 112 is not activated, the ball valve 102 closes the outlet flow path so that like in standard mechanical pumps the pressurization starts when the upper edge of the inlet bore 109 of the fuel injection pump 104 is passed by the plunger’s 113 upper edge. Hence the pressurized fuel is delivered to the injector. The fuel that is burnt in the engine cylinder is sent through the exhaust path where it mixes with urea solution for NOx reduction before being sent out to the atmosphere. The urea solution that is present in the SCR tank gradually reduces over a period of time, and when the SCR tank is empty, there a is a need to bring about torque reduction so as to allow combustion of a limited quantity of fuel irrespective of the demand. This is achieved as described further.
[0008] When the SCR tank is empty, the control unit actuates a solenoid 112. The actuation of the solenoid 112 causes the energizing element 106 the pull the spring 110 in a direction so to cause the valve 102 to move away from the return flow path 114. By doing so the pressure inside the pressurizing chamber of the fuel injection pump 104 is reduced and the plunger 113 has to travel a distance, so as to cover the return flow path 114 for pressurizing the fuel. The combination of mechanical injection system with solenoid 112 controller for torque limitation fulfills all legal requirements and is the most cost effective approach to reach BS6 emission legislation.
[0009] 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 type of solenoid used. 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.