CLIAMS:We Claim:
1. A switch (22) for operating a low pressure pump (16) of a fuel injection system (10), said switch (22) connected to an engine control unit (20), wherein said switch (22) comprises:
a switching mechanism adapted to switch between a first mode and a second mode in response to an electronic signal received from said engine control unit (20) to facilitate operating said low pressure pump (16).
2. The switch (22) for operating the low pressure pump (16) of the fuel injection system (10) in accordance with Claim 1, wherein said first mode is adapted to operate said low pressure pump (16) during normal operation, and wherein said second mode is adapted to operate said low pressure pump (16) during limp home operation.
3. The switch (22) for operating the low pressure pump (16) of the fuel injection system (10) in accordance with Claim 1, wherein in said second mode, a constant voltage is supplied from a battery source to said low pressure pump (16) to facilitate operating said low pressure pump (16) during limp home operation.
4. A fuel injection system (10), said fuel injection system (10) comprising at least:
a low pressure pump (16);
an engine control unit (20); characterized in that
a switch (22) for operating said low pressure pump (16), said switch (22) connected to said engine control unit (20), wherein said switch (22) comprises:
a switching mechanism adapted to switch between a first mode and a second mode in response to an electronic signal received from said engine control unit (20) to facilitate operating said low pressure pump (16).
5. The fuel injection system (10) in accordance with Claim 4 wherein said first mode is adapted to operate said low pressure pump (16) during normal operation, and wherein said second mode is adapted to operate said low pressure pump (16) during limp home operation.
6. The fuel injection system (10) in accordance with Claim 4 wherein in said second mode, a constant voltage is supplied from a battery source to said low pressure pump (16) to facilitate operating said low pressure pump (16) during limp home operation.
7. A method for operating a low pressure pump (16), said method comprising:
switching said switching means from a first mode to a second mode in dependence of a signal received from a engine control unit (20) to operate the low pressure pump (16).
8. The method for operating the low pressure pump (16) in accordance with Claim 7 wherein said first mode is adapted to operate said low pressure pump (16) during normal operation, and wherein said second mode is adapted to operate said low pressure pump (16) during limp home operation.
9. The method for operating the low pressure pump (16) in accordance with Claim 7 wherein in said second mode, a constant voltage is supplied from a battery source to said low pressure pump (16) to facilitate operating said low pressure pump (16) during limp home operation.
,TagSPECI:Field of the invention:

[0001] This invention relates to a switch, and more specifically to a switch for operating a low pressure pump of a fuel injection system.
Background of the invention:

[0002] Fuel is channelled to a high pressure pump where it is pressurized and delivered to a high pressure rail. When a rail pressure sensor that is coupled to the high pressure rail is not functional, it is required to decrease the pressure in the high pressure rail to a limp home condition. Under normal circumstances, a pressure limiter valve is employed, that opens to facilitate decreasing the pressure in the high pressure rail. In order to decrease a cost associated with the pressure limiter valve while maintaining the functionality of the limp home condition, a solution is required. A switch connected to an engine control unit facilitates operating a low pressure pump to facilitate achieving limp home condition in the absence of a pressure limiter valve.
[0003] IN-201201442-I4 describes an operating apparatus that has a controller for detecting an occurrence of a predetermined error condition. The engine is adapted to operate in a limp home mode upon occurrence of the predetermined error condition. An engine speed detector measures the speed of the engine. The controller increases the engine speed for raising the pressure of a common rail beyond a maximum threshold in order to open a pressure limiting valve of the common rail based on the output of the engine speed detector and occurrence of the predetermined error condition.

Brief description of the accompanying drawings
[0004] An exemplifying embodiment of the invention is explained in principle below with reference to the drawings. The drawings are:
[0005] Figure 1 shows a schematic view of a fuel injection system.
[0006] Figure 2 shows a schematic view of a switch that is connected to an engine control unit and operates the low pressure pump of the fuel injection system.
Detailed Description of the invention:
[0007] As shown in Figure 1, a fuel injection system 10 is described. The fuel injection system 10 comprises at least a low pressure pump 16, an engine control unit 20, and a switch 22 for operating the low pressure pump 16. The switch 22 is connected to the engine control unit 20. The switch 22 comprises a switching mechanism adapted to switch between a first mode and a second mode in response to an electronic signal received from the engine control unit 20 to facilitate operating the low pressure pump 16.
[0008] In addition, a switch 22 for operating a low pressure pump 16 of a fuel injection system 10 is described. The switch 22 is connected to a engine control unit 20, wherein the switch 22 comprises a switching mechanism adapted to switch between a first mode and a second mode in response to an electronic signal received from the engine control unit 20 to facilitate operating the low pressure pump 16.
[0009] Moreover, a method for operating a low pressure pump (16) is described. The method comprises switching the switching means from a first mode to a second mode in dependence of a signal received from a engine control unit (20) to operate the low pressure pump (16).
[00010] As shown in Figure 1, a fuel injection system 10 is used to deliver fuel from a fuel tank 12 to a fuel injector. The fuel injection system 10 includes a fuel filter 14 that is coupled downstream from the fuel tank 12. A low pressure pump 16 is in flow communication downstream from the fuel filter 14, and delivers pressurized fuel to a high pressure pump 18. In an embodiment, the low pressure pump 16 is a gear pump. In an alternate embodiment, the low pressure pump 16 is a vane pump. The low pressure pump 16 is driven by means of an electric motor that receives power from a battery source.
[00011] The low pressure pump 16 is coupled to a high pressure pump 18 and delivers pressurized fuel to the high pressure pump 18. The high pressure pump 18 is in flow communication with a high pressure common rail 23 and supplies pressurized fuel to the high pressure common rail 23. A plurality of fuel injectors are coupled to the high pressure common rail 23 and delivers pressurized fuel to a plurality of fuel injectors. A rail pressure sensor 24 is coupled to the high pressure common rail 23 and senses the pressure level in the high pressure common rail 23. An engine control unit 20 is coupled to the rail pressure sensor 24. When the rail pressure sensor 24 fails, an error signal is transmitted from the rail pressure sensor 24 to an engine control unit 20. A fuel return supply path 26 is coupled between the high pressure pump 18 and the fuel tank 12. Excess fuel channeled to the high pressure pump 18 is channeled to the fuel tank 12 via the fuel return supply path 26.
[00012] As shown in Figure 2, the switch 22 is connected to the engine control unit 20. The switch 22 is adapted to receive an error signal from the engine control unit 20. The switch 22 is adapted to change the operating mode of the low pressure pump 16 from a normal functioning mode to a mode where a constant voltage is transmitted from the engine control unit 20 to a power stage 28 via the switch 22. A constant voltage is therein supplied from the power stage 28 to the low pressure pump 16 to operate the low pressure pump 16 at a decreased value of constant operating speed. The reduction in the operating speed of the low pressure pump 16 causes the fuel injection system 10 to operate in a limp home mode.
[00013] In an embodiment, the error signal that is received by the switch 22 from the engine control unit 20 via a control flow path 30 occurs when an error is detected in the rail pressure sensor 24. In an embodiment, the error signal that is received by the switch 22 via the control flow path 30 may be a constant error signal. In an alternate embodiment, the error signal that is received by the switch 22 via control flow path 30 may be an intermittent error signal. When the error signal is not transmitted from the engine control unit 20 to the switch 22 via control flow path 30, the switch 22 is adapted to change the operating mode of the low pressure pump 16 from a mode 32 where a constant voltage is transmitted from the engine control unit 20 to the power stage 28 via the switch 22 to a normal functioning mode 34.
[00014] An operation of the switch 22 for operating the low pressure pump 16 of the fuel injection system 10 is described as an example. When the rail pressure sensor 24 is not functional, an error signal is transmitted from the rail pressure sensor 24 to the engine control unit 20. On receiving the error signal from the rail pressure sensor 24, the engine control unit 20 transmits an error signal to the switch 22. The switch 22 therein changes the operating mode of the low pressure pump 16 from a normal functioning mode to a mode where a constant voltage is transmitted from the battery source of the vehicle the low pressure pump 16. The constant voltage that is transmitted from the battery source of the vehicle to the low pressure pump 16 facilitates operating the low pressure pump 16 at a reduced speed than what is required to supply a higher quantity of fuel to the high pressure common rail 23. The reduction in the speed of the low pressure pump 16 facilitates operating the fuel injection system 10 in limp home mode.
[00015] When the rail pressure sensor 24 has been replaced, the engine control unit 20 does not transmit an error signal to the switch 22. Therein, the switch 22 changes the operating mode of the low pressure pump 16 from a mode where a constant voltage is supplied from the battery source to the low pressure pump 16 to a normal functioning mode of the low pressure pump 16.
[00016] The above described switch 22 for operating the low pressure pump 16 of the fuel injection system 10 is cost effective and highly reliable. The switch 22 facilitates automatically changing the operating mode of the low pressure pump 16 from a normal functioning mode to a mode where a constant voltage is transmitted from the engine control unit 20 to the power stage 28 via the switch 22 when the rail pressure sensor 24 is not functional. Moreover, the switch 22 facilitates automatically changing the operating mode of the low pressure pump 16 from a mode where a constant voltage is transmitted from the engine control unit 20 to the power stage 28 via the switch 22 to a normal functioning mode when the rail pressure sensor 24 becomes functional. Moreover, the modular nature of each sub-system of the switch 22 for operating the low pressure pump 16 of the fuel injection system 10 facilitates easy disassembly and replacement of individual system components as required.
[00017] It must be understood that the embodiments explained in the above detailed description is only illustrative and does not limit the scope of this invention. The scope of this invention is limited only by the scope of the claims. Many modification and changes in the embodiments aforementioned are envisaged and are within the scope of this invention.