Field of the invention
[0001]This invention relates to the field of a fuel injector.
Background of the invention
[0002]An injector is used in a fuel injection system to inject pressurized fuel into the injector. Injector failure occurs due to reasons like wear and tear of materials of injector. In case of malfunction in one or more of the injectors there is a tendency for the injector to leak excess fuel back to the fuel tank through the backflow path. However in the case of a common rail with multiple injectors, there is need to detect the injector that has failed or is going to fail from among the group of injectors.
[0003]Prior art patent application JP7119586A discloses an injector malfunction detecting method and its device. To rapidly and precisely detect a malfunction by collating an actual pressure drop, which is caused in a common fuel surge tank in actual fuel injection, with the predetermined normal pressure drop so as to determine an injection defect. In an engine, an electromagnetic coil is excited at the predetermined timing, and its injectors 23 inject high pressure fuel to the corresponding cylinders in order, so that injection is carried out to the cylinders of number 1, 4, 2, 6, 3, 5 in this order according to the exciting current i1, i4, i2, i6, i3, i5. In this process, in a common fuel surge tank, a pressure drop is caused in the position corresponding to each exciting current. This pressure drop is detected by a pressure sensor 13 so as to be inputted into a microcomputer by an electric signal. If an actual pressure drop is not generated in the fuel injection by the exciting current i1, the actual pressure drop is collated with the normal pressure drop, and on the basis of the exciting current i1, it is determined that an injector in a cylinder of the number 1 causes an injection defect.

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 method of identifying a faulty injector from a plurality of injectors.
Detailed description of the embodiments
[0006] FIG. 1 illustrates method of identifying a faulty injector from a plurality of injectors. The method comprises detecting 100 by a control unit a first pressure gradient of fuel in each of plurality of injectors after run time of the vehicle. The control unit detects 102 a second pressure gradient for an injected quantity of fuel during run time of the vehicle. The control unit compares 104 the first and second pressure gradient with respect to a data map. The data map contains values of first pressure gradient and second pressure gradient with respect to injected quantity of fuel. The control unit checks 106 if the second pressure gradient exceeds a threshold as defined in a data map for the injected quantity when first pressure gradient exceeds a threshold limit as defined in the data map.
[0007]The working of the method will be explained in further detail. The proposed method is used to detect at least one faulty injector from a plurality of injectors that is present in the common rail. The function of the injector is to inject high pressure fuel into the engine cylinder. In case of malfunction in one or more of the injectors there is a tendency for the injector to leak excess fuel back to the fuel tank through the backflow path and this is excess leakage

affects the pressure gradient (first pressure gradient). Also the back leak of fuel which is the amount of fuel that leaks through a pipe and into the fuel tank also increases thereby affecting the stability of the fuel injector. Hence, the proposed method is used to detect an injector that is faulty or has malfunctioned from a group of fuel injectors.
[0008]The proposed method makes use of pressure gradient of fuel in an injector in order to detect whether a fuel injector is faulty or not. When a fuel injector injects fuel into the engine cylinder, the pressure in the common rail reduces, this because the fuel injector that holds fuel under pressure now injects the same into the engine cylinder. However in the case of a malfunction in the fuel injector, the fuel injector continues to leak fuel back to fuel tank through the backflow path. The pressure gradient check happens in the after run condition, that is when the ignition is turned “OFF”. The pressure in the common rail will be relieved by the backflow path at a certain rate, if the injector is wearing, the rate at which the pressure decreases increases and this is used as input for checking for malfunction of a particular injector. The second pressure gradient is detected during overrun condition of the vehicle and on a vehicle under loaded condition.
[0009]The method comprises detecting (100), by a control unit a first pressure gradient of fuel in each of the plurality of injectors after run time of the vehicle. The control unit detects 102 a second pressure gradient for an injected quantity of fuel during run time of the vehicle. The control unit compares 104 the first and second pressure gradient with respect to a data map. The data map contains pressure gradients defined for different values of injected quantity. The data map also contains threshold value of first and second pressure gradient defined for a particular injector. In case the first and second

pressure gradient exceeds a threshold value then it is an indication that the injector has malfunctioned or has worn out. It is now possible to detect the injector that has malfunctioned from a plurality of injectors.
[0010] ‘Adapted’ or ‘arranged’, in the context of the instant disclosure, refers to the technical capability or the technical capacity of a component, in relation to which the term ‘adapted’ or ‘arranged’ is used, to carry out or executed a specified action or actions, upon the requirement of the specified action or actions to be carried out or executed. Moreover, the usage of the term ‘adapted’ or ‘arranged’ here, is in reference with the normal technical capability or technical capacity of the component, imparted by the design or the structure or the composition of the component, and not in reference with any special or extraneous capability or capacity, beyond the scope of the normal technical capability or technical capacity. Therefore there is a need to address this problem.
[0011]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 of fuel injector 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.

We Claim:
1. A method of identifying a faulty injector from a plurality of injectors; said
method comprising:
detecting (100) , by a control unit a first pressure gradient of fuel in each of said plurality of injectors after run time of the vehicle;
detecting (102), by said control unit a second pressure gradient for an injected quantity of fuel during run time of said vehicle;
comparing (104), by said control unit said first and said second pressure gradient against corresponding pressure gradient stored in a data map; and
checking (106), by said control unit if said second pressure gradient exceeds a threshold as defined in a data map for said injected quantity when said first pressure gradient exceeds a threshold limit as defined in said data map.
2. The method of claim 1, wherein said second pressure gradient is
detected during overrun condition of said vehicle and on a vehicle under
loaded condition.