Claims:I claim:

1. A fuel injection system (10), said fuel injection system (10) comprising:
at least ‘n’ fuel injectors, ‘n’ being the number of fuel injectors in said fuel injection system (10);
(n-1) pipes coupled between (n-1) fuel injectors of said ‘n’ fuel injectors and a high pressure fuel source (12); characterized in that
an nth pipe (14) coupled between an nth fuel injector (16) of said ‘n’ fuel injectors and said high pressure fuel source (12), length of said nth pipe (14) is unequal with respect to a length of said (n-1) pipes.
2. The fuel injection system (10) in accordance with Claim 1 further comprising an engine control unit (18) in electronic communication with said ‘n’ fuel injectors.
3. The fuel injection system (10) in accordance with Claim 2 wherein said engine control unit (18) modifies an energizing time of said nth fuel injector (16) based on a difference between a pressure wave induced in one of said (n-1) fuel injectors and a pressure wave induced in said nth fuel injector (16), and a pressure as measured in a high pressure common rail.
4. The fuel injection system (10) in accordance with Claim 2 wherein said engine control unit (18) modifies an energizing time of said nth fuel injector (16) based on a characteristic map stored in said engine control unit (18).
5. A method for operating a fuel injection system (10), said method comprising:
- receiving a pressure signal by an engine control unit (18) from a pressure sensor that is coupled to a high pressure common rail (11) before an injection event in an nth fuel injector (16), ‘n’ being the number of fuel injectors in the fuel injection system (10);
- identifying the nth fuel injector by the engine control unit (18) as the injector which is to be operated;
- determining a difference between a stored value of pressure from the nth fuel injector (16) and a stored value of pressure in one of the (n-1) fuel injectors; and
- modifying an energizing time of the nth fuel injector (16) by the engine control unit (18) based on the determined pressure difference and the pressure signal that is received by the engine control unit (18).
6. The method for operating a fuel injection system (10) in accordance with Claim 5 wherein the pressure difference between the nth fuel injector (16) and one of the (n-1) fuel injectors exists because a length of a pipe that is coupled between the nth fuel injector (16) and a high pressure fuel source (12) is unequal with respect to a length of a pipe coupled between one of the (n-1) fuel injectors and the high pressure fuel source (12).
7. The method for operating a fuel injection system (10) in accordance with Claim 5 further comprising increasing an energizing time of the nth fuel injector (16) by the engine control unit (18) when the difference between a pressure wave induced in the nth fuel injector (16) and a pressure wave induced in one of the (n-1) fuel injectors is a positive value.
8. The method for operating a fuel injection system (10) in accordance with Claim 5 further comprising decreasing an energizing time of the nth fuel injector (16) by the engine control unit (18) when the difference between a pressure wave induced in the nth fuel injector (16) and a pressure wave induced in one of the (n-1) fuel injectors is a negative value.
9. The method for operating a fuel injection system (10) in accordance with Claims 7 and 8 wherein increasing the energizing time of the nth fuel injector (16) and decreasing the energizing time of the nth fuel injector (16) by the engine control unit (18) is based on the difference between the pressure wave induced in the nth fuel injector (16) and the pressure wave induced in one of the (n-1) fuel injectors and a pressure as measured in a high pressure common rail, wherein the pressure difference and the pressure as measured in the high pressure common rail is inputted into a characteristic map that is stored in the engine control unit (18), and wherein the characteristic map determines the energizing time of the nth fuel injector (16).
10. A method for operating a fuel injection system (10), said method comprising:
- receiving a pressure signal by an engine control unit (18) from a pressure sensor that is coupled to one of ‘n’ fuel injectors before an injection event in an nth fuel injector (16), ‘n’ being the number of fuel injectors in the fuel injection system (10);
- identifying the nth fuel injector by the engine control unit (18) as the injector which is to be operated;
- determining a difference between a stored value of pressure from the nth fuel injector (16) and a stored value of pressure in one of the (n-1) fuel injectors; and
- modifying an energizing time of the nth fuel injector (16) by the engine control unit (18) based on the determined pressure difference and the pressure signal that is received by the engine control unit (18).
, Description:Field of the invention
[0001] This invention relates to a fuel injector, and more particularly to a method and apparatus for coupling a pipe of unequal length from the fuel injector to a source of high pressure fuel.
Background of the invention
[0002] A fuel injector includes a nozzle that sprays fuel into an engine cylinder. A pipe is coupled to the fuel injector and supplies fuel to the nozzle from a source of high pressure fuel. In certain applications, it is required that the length of the pipe that is coupled between the fuel injector and the source of high pressure fuel be larger or smaller than the remaining pipes that are coupled between the remaining fuel injectors and the source of high pressure fuel. This unequal length of pipe causes the quantity of fuel that is discharged from this fuel injector to the engine cylinder to vary due to a pressure wave that is induced in the pipe due to a closing operation of the nozzle. In order to allow the correct quantity of fuel to be discharged from the nozzle to the engine cylinder, it is required to make a correction in a characteristic map that is stored in an engine control unit, and which controls an injection timing of the fuel injector.
[0003] U.S. Publication Number 2010/0126469 describes an apparatus and method for controlling the quantity of fuel over a common rail diesel engine. This approach makes it possible to reduce a deviation in the quantity of injected fuel using a map having a fuel temperature and a rail pressure as variables of a pressure wave correction (PWC) logic, reduce exhaust gases from the common rail diesel engine, and improve fuel efficiency of the common rail diesel engine.
Brief description of the accompanying drawings
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[0005] Figure 1 illustrates fuel injectors having pipes of unequal lengths that are each in flow communication with a high pressure common rail.
Detailed description of the embodiments
[0006] Figure 1 illustrates a fuel injection system 10. The fuel injection system 10 comprises at least ‘n’ fuel injectors, ‘n’ being the number of fuel injectors in the fuel injection system 10. (n-1) pipes are coupled between (n-1) fuel injectors of the ‘n’ fuel injectors and a high pressure fuel source 12. An nth pipe 14 is coupled between an nth fuel injector 16 of the ‘n’ fuel injectors and the high pressure fuel source 12, wherein a length of the nth pipe 14 is unequal with respect to a length of the (n-1) pipes.
[0007] In addition, a method for operating a fuel injection system 10 is described. The method comprises receiving a pressure signal by an engine control unit 18 from a pressure sensor that is coupled to a high pressure common rail 11 before an injection event in an nth fuel injector 16, where ‘n’ is the number of fuel injectors in the fuel injection system 10. The method comprises identifying the nth fuel injector by the engine control unit 18 as the injector which is to be operated, determining a difference between a stored value of pressure from the nth fuel injector 16 and a stored value of pressure in one of the (n-1) fuel injectors, and modifying an energizing time of the nth fuel injector 16 by the engine control unit 18 based on the determined pressure difference and the pressure signal that is received by the engine control unit 18.
[0008] Moreover, a method for operating a fuel injection system 10 is described. The method comprises receiving a pressure signal by an engine control unit 18 from a pressure sensor that is coupled to one of ‘n’ fuel injectors before an injection event in an nth fuel injector 16, where ‘n’ is the number of fuel injectors in the fuel injection system 10. The method comprises identifying the nth fuel injector by the engine control unit 18 as the injector which is to be operated, determining a difference between a stored value of pressure from the nth fuel injector 16 and a stored value of pressure in one of the (n-1) fuel injectors, and modifying an energizing time of the nth fuel injector 16 by the engine control unit 18 based on the determined pressure difference and the pressure signal that is received by the engine control unit 18.
[0009] Figure 1 is a schematic representation of a fuel injection system 10. The fuel injection system 10 comprises a high pressure common rail 11. A high pressure fuel source 12 is in flow communication with the high pressure common rail 11 and supplies fuel to the high pressure common rail 11. The fuel injection system 10 comprises at least ‘n’ fuel injectors, ‘n’ being the number of injectors in the fuel injection system 10.
[00010] Each of the ‘n’ fuel injectors is in flow communication with the high pressure common rail 11. In an alternate embodiment, each of the ‘n’ fuel injectors is directly in flow communication with the high pressure fuel source 12. The high pressure fuel source 12 may be a high pressure fuel pump. The ‘n’ fuel injectors are in flow communication with the high pressure common rail 11 via ‘n’ pipes, wherein each of the ‘n’ pipes may be independently coupled to each of the ‘n’ fuel injectors. A first end of each of the ‘n’ pipes is in flow communication with the high pressure common rail 11, while an opposite end of each of the ‘n’ pipes is in flow communication with the ‘n’ fuel injectors. An nth pipe 14 is in flow communication with an nth fuel injector 16. A length of the nth pipe 14 of the nth fuel injector 16 may be larger or smaller with respect to the lengths of the pipes of each of the ‘n-1’ fuel injectors. Each of the pipes coupled to the ‘n-1’ fuel injectors may have the same length. In an alternate embodiment, each of the pipes of the ‘n-1’ fuel injectors may have unequal lengths from one another.
[00011] An engine control unit 18 is in electronic communication with each of the ‘n’ fuel injectors. The engine control unit 18 is adapted to energize each of the ‘n’ fuel injectors to facilitate injecting fuel from each of the ‘n’ fuel injectors. The energizing time of each of the ‘n’ fuel injectors may be varied by the engine control unit 18 to facilitate injecting fuel for different time durations. The engine control unit 18 is in electronic communication with a pressure sensor (not shown) that is positioned in the high pressure common rail 11. In an alternate embodiment, the pressure sensor may be coupled to the high pressure fuel source 12. In yet another alternate embodiment, the pressure sensor may be coupled to one of the ‘n’ fuel injectors of the fuel injection system 10. The pressure sensor transmits an electronic signal to the engine control unit 18 that is indicative of a pressure wave that is sensed in each of the ‘n’ fuel injectors.
[00012] The principle of working of the fuel injection system 10 is now explained as an example. The pressure sensor that is coupled to the high pressure common rail 11 transmits an electronic signal to the engine control unit 18 that is indicative of the pressure in an nth fuel injector 16 before an injection event in the nth fuel injector 16. The engine control unit 18 determines that the nth fuel injector 16 is the next firing fuel injector. The engine control unit 18 therein retrieves and determines a difference between a stored value of pressure from the nth fuel injector 16 and a stored value of pressure in one of the (n-1) fuel injectors. The engine control unit 18 then modifies an energizing time of the nth fuel injector 16 based on the determined pressure difference, and the pressure signal that is received by the engine control unit 18 from the pressure sensor. The determined pressure difference and the pressure signal that is received by the engine control unit 18 is used as inputs for a characteristic map in the engine control unit 18 to determine the energizing time of the nth fuel injector. Therefore, the nth fuel injector 16 injects fuel within the engine cylinder at the appropriate energizing time, leading to an improvement in the efficiency of the fuel injection system 10.
[00013] Using the method of the present invention, the energizing time of the ‘n’th fuel injector may be modified by the engine control unit 18 to account for the discrepancy which results when a pipe of unequal length is coupled between the nth fuel injector and the source of high pressure fuel.
[00014] The above described fuel injection system 10 facilitates varying the energizing time of the nth fuel injector by the engine control unit 18 when pipes of unequal lengths are coupled between ‘n’ fuel injectors and the source of high pressure fuel.
[00015] 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.