Field of the invention
[0001] The present disclosure relates to a method of
determining quantity of fuel flowing in the backflow channel of a fuel injector.
Background of the invention
[0002] Fuel Injectors used in vehicles deliver a desired quantity
of fuel to the internal combustion engine. The quantity of fuel delivered is dependent on the energizing time for solenoid valve based fuel injectors. Conventionally, the drop in rail pressure with respect to time is used to indicate the quantity of fuel delivered by the fuel injector. The precise quantity of fuel delivered by the injector also need to take into account the amount fuel flowing in the backflow channel of the fuel injector.
[0003] Patent Application KR20090020916A, Tester jig
apparatus of common rail injector for internal combustion engine and method thereof discloses a test apparatus and a method for more accurate measurement and identification of the amount of fuel injected from a common rail and a hose-connected injector, as well as fuel collected in a cylinder. The purpose of the discharge is to more easily and simply, a plurality of collecting means provided on the bottom surface of the enclosure so as to be able to collect the fuel injected and backflow discharged from the injector through the hose,

respectively, and the collection Measuring means fixed to the upper portion of the housing so that the amount of fuel collected by the means can be measured, display means provided for controlling and displaying respective data measured by the measuring means, and the collecting means is installed in the enclosure to move the means upwards to automatically discharge the collected fuel. It is achieved by a test apparatus and a method for a common rail injector of an internal combustion engine comprising a discharge means provided.
Brief description of the accompanying drawings
[0004] Fig. 1 illustrates method steps for determining quantity
of fuel flowing in the backflow channel of a fuel injector.
Detailed description of the drawings
[0005] Figure 1 illustrates method steps for a method of
determining quantity of fuel flowing in the backflow channel of a fuel injector. The method is performed by means of an Electronic Control Unit [ECU] in the vehicle. The fuel injector comprises at least a solenoid valve. The method further comprises various steps. In step 101, the ECU turns off the engine when maximum allowable fuel pressure is achieved in the internal combustion engine. In step 102 the ECU, energizes the solenoid valve for a duration of 40 to 200 microseconds. In step 103, the ECU records value of fuel pressure

with respect to time. In step 104, the ECU records value of fuel temperature. In step 105, the ECU calculates mass of fuel flowing through the backflow channel of the fuel injector based on the recorded values of fuel pressure with respect to time and the fuel temperature.
[0006] The calculated value of fuel flowing is used to determine
a resistance of the backflow of the fuel injector. The value of resistance is measured at different time instances is used to indicate a health of the fuel injector. The health of the injector is indicated to a user using audio or visual means.
[0007] In step 101, the ECU turns off the engine when maximum
allowable fuel pressure is achieved in the internal combustion engine. The engine is asked to ramp-up such that maximum allowable fuel pressure achieved inside the inside the internal combustion engine. Upon the engine being turned off, the built-up fuel pressure has nowhere to go except through the backflow path available in the injector.
[0008] In step 103 the ECU, energizes the solenoid valve of the
injector for a duration of 40 to 200 microseconds. The injector comprises a solenoid valve, injector piston, high pressure fuel inlet, and at least an injection needle. When the solenoid valve is energized

it opens the solenoid valve. This releases the fuel pressure above the injector piston and there is flow of fuel through the backflow of the fuel injector into the fuel tank. In a few microseconds this creates a pressure difference between the injector piston and the injector needle. Consequently the injector needle lifts to relived the pressure and inject fuel into the engine. In normal circumstances the solenoid valve is energized for a duration between 200 to 800 microseconds depending upon the desired quantity of the fuel to be injected.
[0009] In the present invention the energization time duration is
chosen in such a manner that there is flow of fuel through the backflow of the fuel injector into the fuel tank but not enough time duration to create the pressure difference between the injector piston and the injector needle. Before such pressure difference is created the solenoid valve is de-energized and it closes the solenoid valve. This kind of energization is referred as a "blank-shot".
[0010] In step 103, the ECU records value of fuel pressure with
respect to time. As described in the step 101, the engine is switched off after maximum fuel pressure is achieved, hence there is a drop in fuel pressure with respect to time. The drop is fuel pressure with respect to time is recorded. This is also plotted on a graph. During a blank shot the fuel is not actually injected into the engine, but rather flows through the backflow of the injector. This drop in fuel pressure

due to the flow of fuel in the backflow channel is seen as an abrupt deviation in the graph of fuel pressure with respect to time.
[0011] In step 104, the ECU records value of fuel temperature.
The mass of fuel is dependent on temperature and pressure. This principle is used to calculate the mass of fuel, since during the blank-shots the drop in fuel pressure is indicative of only the fuel flowing through the backflow channel of the fuel injector. In step 105, the ECU calculates mass of fuel flowing through the backflow channel of the fuel injector based on the recorded values of fuel pressure with respect to time and the fuel temperature based on the above mentioned principle.
[0012] The calculated value of fuel flowing is used to determine
a resistance of the backflow of the fuel injector. For a particular duration of energizing time a constant amount of fuel should flow through the backflow of fuel injector. This is constant value is calculated for a new injector. The value of resistance is measured at different time instances to indicate a health of the fuel injector. For example the value of mass of fuel flowing through a new injector for energizing time Tl at temperature Rl is Ml. This value is again checked for the injector after some time, when the injector is in use. For example the value of mass of fuel flowing through an injector in use for energizing time Tl at temperature Rl is M2. If Ml is less than

M2, this shows that for the same energizing time and temperature, the mass of fuel flowing through the backflow channel has increased. This means the resistance of the backflow channel of the fuel injector has reduced.
[0013] The comparison of the values of mass of fuel flowing
through the injector at a particular temperature and energizing time is done at regular intervals. The decrease in resistance of the backflow channel of the fuel injector indicates that the health of the injector is deteriorating. The health of the injector is indicated to a user using audio or visual means. In an embodiment, the indication is a visual indication to the user by means of display unit or a light emitting diode. In another embodiment of the present invention, health of the injector is indicated to the user using an audio means such as an alarm.
[0014] This idea to develop method steps for determining
quantity of fuel flowing in the backflow channel of a fuel injector has many advantages. It helps in determination of the health of the injector and inform the user of the same. Using the quantity of fuel flowing in backflow channel of the injector a resistance is determined. The increase or decrease in resistance is indicative of the amount of deterioration of the injector. Further the quantification of backflow of fuel injector gives an accurate amount of fuel injected by the injector

into the engine. The drop in fuel pressure during normal running condition of the engine deducting the quantity of resistance of the backflow of the fuel injector gives a more precise amount of fuel injected when the engine is running normally.
[0015] It mustbe understood thatthe embodiments explained in
the above detailed description are only illustrative and do not limit the scope of this invention. Any modification to a method of determining quantity of fuel flowing in the backflow channel of a fuel injector are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.

We Claim:
1. A method of determining quantity of fuel flowing in the
backflow channel of a fuel injector by means of an Electronic Control
Unit [ECU], said fuel injector comprising at least a solenoid valve, the
method comprising:
turning off [101] the engine when maximum allowable fuel pressure is achieved in the internal combustion engine;
energizing [102] the solenoid valve for a duration of 40 to 200 microseconds;
recording [103] value of fuel pressure with respect to time;
recording [104] value of fuel temperature;
calculating [105] mass of fuel flowing through the backflow channel of the fuel injector based on the recorded values of fuel pressure with respect to time and the fuel temperature.
2. The method of determining a quantity of fuel in the backflow
channel of a fuel injector, as claimed in claim 1, where the calculated
value of fuel flowing is used to determine a resistance of the backflow
of the fuel injector.

3. The method of determining a quantity of fuel in the backflow channel of a fuel injector, as claimed in claim 2, where the value of resistance is measured at different time instances to indicate a health of the fuel injector.
4. The method of determining a quantity of fuel in the backflow channel of a fuel injector, as claimed in claim 3, where the health of the injector is indicated to a user using audio or visual means.
5. An Electronic Control Unit [ECU] in a vehicle, where the ECU is capable of:
Turning off [101] the engine after maximum allowable fuel pressure is achieved in the internal combustion engine;
Energizing [102] the solenoid valve for a duration of 40 to 200 microseconds;
Recording [103] value of fuel pressure with respect to time;
Recording [104] value of fuel temperature;
calculating [105] mass of fuel flowing through the backflow channel of the fuel injector based on the recorded values of fuel pressure with respect to time and the fuel temperature;

determining resistance of the backflow of the fuel injector using the calculated mass of fuel;
measuring the value of resistance at different instances to indicate health of the injector.
6. The ECU as claimed in claim 5 where the where the health of the injector is indicated to a user using audio or visual means.