Claims:
Claims

1. A method of predicting failure of a fuel injector of a vehicle, said method comprising:
determining (105), by a vehicle control unit, a pressure gradient in response to a key-OFF operation of said vehicle, said pressure gradient correspond to rate of change of pressure in a common rail of said vehicle in response to said key-OFF operation;
determining (110), by said vehicle control unit, if said pressure gradient is above at least one pre-stored value, said pressure gradient being above said at least one pre-stored value indicating at least one leakage level in said fuel indicator; and
transmitting (115), by said vehicle control unit, an alert signal that correspond to said at least one leakage level in said fuel injector.

2. The method as claimed in claim 1, wherein said determination of said pressure gradient comprises:
determining, by said vehicle control unit, a first pressure value, in said common rail of said vehicle, at a first time instant, said first pressure value correspond to pressure in said common rail when pressurized fuel is stored in said common rail;
determining, by said vehicle control unit, a second pressure value, in a common rail of said vehicle, at a second time instant, said second pressure value correspond to pressure in said common rail when pressurized fuel flows back into a fuel tank of said vehicle through a backflow path in said fuel injector; and
calculating, by said vehicle control unit, a difference value between said first pressure value and said second pressure value, said difference value indicating said pressure gradient.

3. The method as claimed in claim 1, wherein said pressure gradient is stored in a map with reference to kilometer-reading of said vehicle.

4. The method as claimed in claim 1, wherein said at least one leakage level corresponds to degree of wear in a valve seat of said fuel injector.

5. A vehicle control unit for predicting failure of a fuel injector of a vehicle, said vehicle control unit comprising:
determine a pressure gradient in response to a key-OFF operation of said vehicle, said pressure gradient correspond to rate of change of pressure in a common rail of said vehicle in response to said key-OFF operation;
determine if said pressure gradient is above at least one pre-stored value, said pressure gradient being above said at least one pre-stored value indicating at least one leakage level in said fuel indicator; and
transmit an alert signal that correspond to said at least one leakage level in said fuel injector.

6. The vehicle control unit as claimed in claim 5 further adapted to:
determine a first pressure value, in said common rail of said vehicle, at a first time instant, said first pressure value correspond to pressure in said common rail when pressurized fuel is stored in said common rail;
determine a second pressure value, in a common rail of said vehicle, at a second time instant, said second pressure value correspond to pressure in said common rail when pressurized fuel flows back into a fuel tank of said vehicle through a backflow path in said fuel injector; and
calculate a difference value between said first pressure value and said second pressure value, said difference value indicating said pressure gradient.
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a method of determining health of a fuel injector of a vehicle.

Background of the invention
[0002] Prediction of component failures are important as such predictions enable in taking precautions like replacing the component well in advance. Such precautions also prevent unexpected stalling of the vehicle. According to US patent application numbered US6330499, a system and method for vehicle diagnostic and health monitoring is disclosed. US6330499 includes a client computer device within the vehicle, coupled to the vehicle's monitoring systems, for data management, remote session management and user interaction, a communication system, coupled to the client computer device, for providing remote communication of data including data derived from internal monitoring systems of the vehicle, and a remote service center including a vehicle data store, a server computer, a diagnostic engine, and a communicator for communicating the results of analysis of vehicle information to the client computer device via the communication system.

Brief description of the accompanying drawing

[0003] Figure 1 illustrates a flowchart describing a method of determining health of a fuel injector of a vehicle, in accordance with one embodiment of the disclosure.

Detailed description of the embodiments

[0004] A method of predicting failure of a fuel injector of a vehicle is disclosed. The method comprises determining (105), by a vehicle control unit, a pressure gradient in response to a key-OFF operation of the vehicle, the pressure gradient correspond to rate of change of pressure in a common rail of the vehicle in response to the key-OFF operation, determining (110), by the vehicle control unit, if the pressure gradient is above at least one pre-stored value, the pressure gradient being above the at least one pre-stored value indicating at least one leakage level in the fuel indicator and transmitting (115), by the vehicle control unit, an alert signal that correspond to the at least one leakage level in the fuel injector.

[0005] The method is used for determining health of the fuel injector. High pressure fuel from the common rail flows into the fuel injector through the high pressure path. The fuel injector includes a control valve located in a control path of the fuel injector. that regulates control flow in the fuel injector.

[0006] During injection, high pressure fuel from the common rail flows through the high pressure path and reaches tip of the fuel injector needle. As flow of the high pressure fuel continues towards the tip of the fuel injector, pressure is built. When the pressure at the tip of the fuel injector needle is greater than the fuel in the control path, a ball seated on a valve seat of the control valve is lifted from the valve seat due to such pressure difference between the tip of the fuel injector needle and the control path.

[0007] When the ball is lifted from the valve seat, the fuel injector needle lifts thereby allowing the high pressure fuel to flow out of the fuel injector through nozzle pores of the fuel injector. When the ball is seated back on the valve seat, the fuel injection needle returns to closed position. Further excess fuel flows back to the fuel tank through the backflow path. Due to continued functioning of the control valve, the valve seat undergoes wear. Such wear will be caused mainly by the contaminated fuel, particles in the fuel or bad quality fuel filter. Such wear in the valve seat causes leakage of fuel into the backflow path. Such leakage reduces pressure in the control path thereby leading to lift of the fuel injection needle before intended time instant. This causes excess fuel to be injected which is undesirable.

[0008] Also, if the valve seat is worn-out to an extreme degree, then the fuel from the control path directly flows through the backflow path. Hence, there is no pressure in the control path. This causes the needle to always be lifted and allow fuel to flow through the nozzle pores of the fuel injector. When such a situation occurs, the engine is prevented from turning-ON. Hence the method presented in this disclosure enables to predict such failure of the fuel injector due to the wear in the valve seat.

[0009] The method of predicting failure of a fuel injector of a vehicle is performed by a vehicle control unit. The method is performed using step 105 through 115.

[0010] At step 105, the vehicle control unit determines a pressure gradient in response to a key-OFF operation of the vehicle. The key-OFF operation is detected by the vehicle control unit. The pressure gradient refers to rate of change of pressure in a common rail of the vehicle in response to the key-OFF operation. When the key-OFF operation occurs, fuel injection stops. Therefore, the high pressure fuel in the common rail flows back into a fuel tank through a backflow path in the fuel injector. Due to this, there exists a pressure gradient in the common rail. That is high pressure in the common rail begins to drop down as the fuel flows back to the fuel tank. Such backflow of fuel from the common rail to the fuel tank occurs until the pressure in the common rail reaches a pre-defined pressure value.

[0011] The pressure gradient is determined by the following steps. The first step includes determining, by the vehicle control unit, a first pressure value, in the common rail of the vehicle at a first time instant. A pressure sensor present in the common rail is used for such measurement of the pressure values. The first pressure value correspond to pressure in the common rail when pressurized fuel is stored in the common rail.

[0012] The second step includes determining, by the vehicle control unit, a second pressure value, in a common rail of the vehicle at a second time instant. The second pressure value correspond to pressure in the common rail is equal to a pre-defined pressure value. Pressure in the common rail when pressurized fuel flows back into a fuel tank of the vehicle through a backflow path in the fuel injector.

[0013] The third step includes calculating, by the vehicle control unit, a difference value between the first pressure value and the second pressure value. The difference value indicates the pressure gradient. It should be noted that the first time instant and the second time instant are pre-defined constants, for example, the time duration between the first time instant and the second time instant can be 5 seconds. Hence, at step 105, the vehicle control unit determines the pressure gradient for the 5 seconds after the key-OFF operation. Such calculation of the pressure gradient is primarily performed to determine the rate of change of pressure in the common rail which is proportional to the backflow of fuel to the fuel tank through the fuel injector. This helps in identifying health of the fuel injector explained in the following steps.

[0014] Further, the pressure gradient calculated for every key-OFF operation is stored in a map with reference to kilometer-reading of the vehicle. This map is present in a memory unit of the vehicle control unit. Such a map is used for determining optimum pressure gradient values as the vehicle is being used.

[0015] At step (110), the vehicle control unit determines if the pressure gradient calculated in step (105) is above at least one pre-stored value. The pre-stored value indicates at least one leakage level in the fuel injector. When the valve seat of the fuel injector is worn-out, large quantity of fuel flows back into the fuel tank through the backflow path of the fuel injector. Hence, the pressure gradient corresponds to a large value. In other words, there is steep increase in the pressure gradient. That is, due to wearing of the valve seat, an additional avenue is formed for the fuel to flow. Hence pressure in the common rail drops quickly. Therefore, the pressure gradient in a pre-specified time duration, for example, 5 seconds renders a high value. Therefore, if the pressure gradient is above at least one pre-stored value then it is considered that a leakage is present in the fuel injector because the valve seat is worn-out.

[0016] The pre-stored value is stored in the memory unit. In one case, the pre-stored value includes a first value which indicates that corresponds to a first leakage level of the fuel injector. In another case, the pre-stored value includes a second value which indicates that corresponds to a second leakage level of the fuel injector. The first leakage level and the second leakage level indicate a corresponding degree of damage in the fuel injector.

[0017] If the pressure gradient determined in step (105) is greater than the first value then it indicates that the valve seat in a fuel injector is worn-out to a first level causing leakage equal to the first leakage level. If the pressure gradient is greater than the second value then it indicates that the valve seat in a fuel injector is worn-out to a second level causing leakage equal to the second leakage level.

[0018] It should be noted that the first value is lesser than the second value. In other words quantity of leakage that correspond to the first leakage level is lesser than the leakage that correspond to the second leakage level. This indicates that the valve seat is worn-out to a large degree in the second case when compared to the first case. Therefore, in step 110, the vehicle control unit can identify if the fuel injector is damaged. It should be noted that these two leakage levels are exemplary and there can be many more leakage levels defined where each leakage level will correspond to a specific pressure gradient value.

[0019] At step 115, the vehicle control unit transmits an alert signal that correspond to at least one leakage level. The alert signal can include an audio message or a visual indicator on a dashboard. The alert signal is transmitted based on the leakage level. In one example, if the fuel injector damage correspond to first leakage level, which is relatively lesser then the alert signal can include an “orange light” on the dashboard. If the fuel injector damage is correspond to second leakage level, which is relatively more then the alert signal can include an “red light” on the dashboard.

[0020] Advantageously, the method disclosed in the disclosure enables prediction of damage in the fuel injector due to wear in the valve seat of the fuel injector. Such prediction occurs well in advance so that the user can replace the fuel injector well in time thereby preventing unanticipated stalling of the vehicle.

[0021] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. 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.