CLIAMS:We Claim:
1. A fuel injection pump (100) for a dual fuel engine (102), comprising at least
a control lever adapted to receive input from an accelerator pedal; and
a stop lever of said fuel injection pump (100) in communication with an electronic control unit (ECU) (104); characterized in that
said stop lever controls the amount of diesel to be injected into said dual fuel engine 102, in response to input from said control lever and based on the engine 102 speed received by said ECU in a dual fuel mode.

2. The fuel injection pump (100) of claim 1, wherein said engine (102) speed in obtained from an engine speed sensor.

3. A method for operating a fuel injection pump (100) in dual fuel engine 102, comprising.
Receiving (200) the position of an accelerator pedal from a control lever mounted on a fuel injection pump (100) by an electronic control unit (ECU) (104);
Receiving (202) the speed of an engine 102 using an engine speed sensor by said electronic control unit (ECU) (104);
actuating (204) a stop lever of said fuel injection pump (100) by said ECU to control the quantity of diesel based on input received from said accelerator pedal and said engine speed sensor in said dual fuel mode; and
injecting (206) a proportionate quantity of alternate fuel to compensate for said injected quantity of diesel by said electronic control unit (ECU) (104) in order to maintain an required ratio of said diesel and said alternate fuel in said dual fuel mode for operating said dual fuel engine. ,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 fuel injection pump for a dual fuel engine.

Background of the invention
[002] In dual fuel diesel engines, controlling the ratio of amount of alternate fuel entering the combustion chamber in addition to diesel is important in order to achieve higher combustion efficiency of both diesel and the alternate fuel. Generally, electronic governors are used to actuate a stop lever of the fuel injection pump to control the amount of fuel to be injected. Since the electronic governors are external to the system and need to be procured separately they add to the overall cost of the system. Hence there is a need to control the ratio of the mixture of diesel to alternate fuel for different engine speeds without changing the configuration of the fuel injection pump and engine.

[003] Prior art patent application US 20140373822 discloses a system and method for a self-adjusting dual fuel gas control. The system and method that eliminates the need for manually calibrating or adjusting a dual fuel internal combustion engine to compensate for variations in composition of a gaseous fuel or other variations, such as ambient or site conditions. The system and method functions by determining an engine load, determining an advantageous gaseous fuel substitution rate from the engine load and speed in addition to an actual gaseous fuel substitution rate, modifying the advantageous gaseous fuel substitution rate by a minimum liquid fuel flow rate, engine protection parameters, and oxidation catalyst protection parameters, and then determining an error term in response to the modified advantageous gaseous fuel substitution rate and the actual gaseous fuel substitution rate. The error term is used to adjust a gaseous fuel control valve.

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 a fuel injection pump for a dual fuel engine;
[006] FIG. 2 illustrates a flowchart representing steps in a method for operating a fuel injection pump in dual fuel diesel engine; and
[007] FIG. 3 illustrates a graph showing the fuel delivery from the fuel injection pump for different engine speeds.

Detailed description of the embodiments
[008] FIG. 1 illustrates a fuel injection pump (100) for a dual fuel engine (102). The fuel injection pump (100) receives fuel from a fuel tank. The fuel injection pump (100) for a dual fuel diesel engine (102) comprises at least a control lever adapted to receive input from an accelerator pedal, and a stop lever of the fuel injection pump (100) in communication with an electronic control unit (ECU) (104). The stop lever controls the amount of diesel to be injected into the dual fuel engine (102), in response to input from the control lever and based on the engine (102) speed received by the ECU in a dual fuel mode.

[009] The fuel injection pump (100) may be a mechanical fuel injection pump. The fuel injection pump (100) also receives input from the user of the vehicle on the amount of fuel to be injected into the engine (102) through a control lever. The control lever is a part of the fuel injection pump (100) and can be actuated by the user with the help of linkages. In effect the control lever behaves like an accelerator pedal sensor, since the demand from the user is communicated to the fuel injection pump (100). Apart from the control lever, the fuel injection pump (100) receives input from an electronic control unit (ECU) (104). The ECU (104) controls the amount of fuel to be pressurized in the fuel injection pump (100) and delivered to the engine (102) taking input from at least, but not restricted to, the input received from control lever, engine speed sensor and the like. Also, the ECU disclosed herein also controls the amount of dual fuel to be injected into the engine (102). The alternate fuel being stored in a separate storage tank (106) and capable of being delivered to the engine (102) based on input received from the ECU. In a dual fuel diesel engine (102), the combustion of diesel is initiated through the process of compression ignition. The heat and pressure so generated by compression ignition is used, in turn to burn the alternate fuel. Hence in a dual fuel diesel engine (102), diesel is required and the ratio of the amount alternate fuel to diesel injected into the engine (102) can be varied based upon the demand from the user and the input received at the ECU from different sources like the engine speed sensor, temperature sensor and the like. The engine (102) speed may be obtained from an engine speed sensor. The dual fuel diesel engine (102) operates under the following two modes.
I. Diesel only mode: The diesel only mode is generally required when the vehicle is started for the first time. At this stage torque that needs to be generated by the engine (102) is very high, hence only diesel is supplied from the fuel injection pump (100) to the engine (102). The amount of diesel supplied to the engine (102) is controlled by the ECU in dependence of the accelerator pedal input and the information received from different sensors. The diesel only mode continues until the engine (102) stabilizes at a certain optimal speed as determined by the ECU based on inputs obtained by different sensors and engine (102) data from different data maps. Once the engine speed has stabilized, in order to achieve better fuel efficiency and to reduce the dependence on diesel, there is a need to switch over to dual fuel mode. The dual fuel mode will now be described in further detail.
II. Dual fuel mode: The engine (102) works under dual fuel mode, when the engine speed has stabilized and the engine torque is less than that required at start. In the dual fuel mode, engine (102) will receive alternate fuel from a separate storage tank (106), in addition to pressurized diesel received from the fuel injection pump (100). The ratio of alternate fuel to diesel fuel is controlled by the ECU. The control lever that is adapted to receive input from an accelerator pedal indicates the demand from the user. In other words the control lever will transmit the position of the accelerator pedal to the ECU. For different accelerator pedal positions and the engine speed data obtained from the engine speed sensor, the stop lever is independently controlled by the ECU in the dual fuel mode. It should be noted that the different positions of the stop lever is a function of the accelerator pedal position and the engine speed. By controlling the positions of the stop lever, it is now possible to control the quantity of diesel reaching the engine (102) from the fuel injection pump (100). Since, only a controlled quantity of diesel as decided by the ECU reaches the engine (102), the engine (102) will now be in a position to receive the alternate fuel to compensate for lesser amount of diesel supplied to the engine without affecting the driver demand. The amount diesel is reduced due to operation of stop lever. Also, for different positions of the stop lever the ECU will now control the ratio of alternate fuel to diesel fuel. Thus, the engine (102) now operates under dual fuel mode.

[0010] FIG. 2 illustrates a flowchart representing steps in a method for operating a fuel injection pump (100) in dual fuel diesel engine (102). The position of the accelerator pedal is received (200) from the control lever mounted on a fuel injection pump (100) by an electronic control unit (ECU) (104). The speed of the engine (102) is received (202) using an engine speed sensor by the electronic control unit (ECU) (104). The stop lever of the fuel injection pump (100) is actuated (204) by the ECU to control the quantity of diesel based on input received from the accelerator pedal and the engine speed sensor in the dual fuel mode. A proportionate quantity of alternate fuel is injected (206) to compensate for the injected quantity of diesel by the electronic control unit (ECU) (104) in order to maintain a required ratio of diesel and alternate fuel in dual fuel mode for operating the dual fuel engine. By using the above mentioned method, the existing engines can be adapted to use diesel as primary source of fuel in one mode and as a secondary source of fuel and an additional alternate fuel in addition to diesel in another mode. Thus the range of working of the engine (102) is increased to receive both diesel and an alternate fuel.

[0011] FIG. 3 illustrates a graph showing the fuel delivery from the fuel injection pump (100) for different engine speeds. The curve 301 represents the maximum fuel that can be supplied to the engine (102) when the accelerator pedal is pressed completely that is at full throttle condition under diesel only mode in order to generate maximum power. Parallel lines 302 represents fuel delivery for different accelerator pedal positions but less than full throttle. In the case of dual fuel mode, the line 304 represents the minimum quantity of diesel that needs to be supplied to the engine (102), irrespective of the speed under dual fuel mode when the stop lever of the fuel injection pump (100) is activated. The shaded area with respect to the line 304 gives the minimum amount of diesel injected into the engine (102), under dual fuel mode, for different positions of the stop lever. The different positions of the stop lever is dependent on the amount of alternate fuel that needs to be injected into the engine (102) and it is independently controlled by the ECU by taking input from the accelerator pedal position and the engine speed data obtained from engine speed sensor. It should be noted that the graph described above is for illustrative purpose only, and does not limit the fuel injection pump (100) and the engine (102) disclosed to the fuel injection quantity and speeds mentioned in the graph.

[0012] 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 the fuel injection pump 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.