Claims:We claim:
1. A method for controlling fuel injection quantity at full load in a single cylinder engine, said method comprising:
determining an estimated fuel quantity for an engine speed at part load, comprising:
receiving an engine speed of a vehicle in time domain from an engine speed sensor;
transforming the engine speed in time domain to a frequency domain data;
compensating for a plurality of engine parameters based on the transformed frequency domain data;
calculating the estimated fuel quantity for the engine speed based on the compensated engine parameters;
calculating a corrected fuel quantity based on the estimated fuel quantity and an indicated fuel quantity;
comparing the corrected fuel quantity with a test bed level corrected fuel quantity; and
determining a final fuel quantity based on the comparison.
2. The method as claimed in claim 1, wherein the final fuel quantity is the corrected fuel quantity when the corrected fuel quantity is greater than the test bed level corrected fuel quantity.
3. The method as claimed in claim 1, wherein the final fuel quantity is the test bed level corrected fuel quantity when the corrected fuel quantity is lesser than or equal to the test bed level corrected fuel quantity.
4. The method as claimed in claim 1, wherein the indicated fuel quantity is based on a position of an accelerator pedal.
5. The method as claimed in claim 1, wherein the indicated fuel quantity is based on a position of the engine speed.
6. An electronic control unit (ECU) for fuel control at full load in a single cylinder engine, said ECU adapted to
determine an estimated fuel quantity for an engine speed at part load, comprising:
receiving an engine speed of a vehicle in time domain from an engine speed sensor;
transforming the engine speed in time domain to a frequency domain data;
compensating for a plurality of engine parameters based on the transformed frequency domain data;
calculating the estimated fuel quantity for the engine speed based on the compensated engine parameters;
calculate a corrected fuel quantity based on the estimated fuel quantity and an indicated fuel quantity;
compare the corrected fuel quantity with a test bed level corrected fuel quantity; and
determine a final fuel quantity based on the comparison.

, Description:Field of the invention
[0001] The invention relates to a fuel control for an engine.
Background of the invention
[0002] For a normal operation of an engine, it is required to control the amount of fuel injected. A drift in the fuel injection can have a significant impact on the engine performance. A fuel injection system learns a variation in quantity of fuel sprayed from fuel injectors due to the aging and corrects a control signal to be sent to the fuel injector so as to compensate for such a variation. The fuel injection system determines a correction value that serves to correct the injection particularly of a minimum amount of fuel. However, this correction value applies to a value range of an operating parameter depending on the injection duration of the internal combustion engine, for example, the rotational speed, the start of injection or the rail pressure in a direct injection system such as the common rail system, the pump nozzle system or the like.
[0003] US patent application, 20130139788, discloses a method and system for fuel drift estimation and compensation using exhaust oxygen levels and fresh air flow measurements. An actual fueling to the engine cylinders is determined from the exhaust oxygen level and fresh air flow to the internal combustion engine. The actual fueling is compared to an expected fueling based on the fueling command provided to the internal combustion engine. The difference between the actual fueling and expected fueling is fuel drift errors attributed to changes or drift in the fuel injection system and is used to correct or compensate future fueling commands for the fuel drift.
Short description of the drawing
[0004] An exemplifying embodiment of the invention is explained in principle below with reference to the drawing. The drawing is,
[0005] Figure 1 illustrates the method of using an electronic control unit (ECU) for controlling fuel injection quantity at full load in a single cylinder engine in accordance with this invention.
Description of the invention
[0006] Figure 1 illustrates the method of using an electronic control unit (ECU) for controlling fuel injection quantity at full load in a single cylinder engine in accordance with this invention. In step S1, the ECU is adapted to determine an estimated fuel quantity for an engine speed. The ECU receives an engine speed of a vehicle in time domain from an engine speed sensor; transforms the engine speed in time domain to a frequency domain data; compensates for a plurality of engine parameters based on the transformed frequency domain data; and calculates the estimated fuel quantity for the engine speed based on the compensated engine parameters. In step S2, the ECU calculates a corrected fuel quantity based on the estimated fuel quantity and an indicated fuel quantity. In step S3, the ECU compares the corrected fuel quantity with a test bed level corrected fuel quantity. In step S4, the ECU determines a final fuel quantity based on the comparison.
[0007] Factors such as reduction in fuel filter efficiency, use of low quality fuel in the engine, etc., cause drift in the injection of fuel to a fuel injection system of the engine. The drift in injection of fuel causes a shift in an operating point of injectors of the fuel injection system. An engine speed sensor senses the engine speed of a vehicle. The ECU receives the engine speed of the vehicle in time domain from the engine speed sensor. The ECU transforms the engine speed in time domain to a frequency domain data. When the ECU transforms the engine speed in time domain to the frequency domain data, the ECU reveals the frequencies embedded in the engine speed. The frequencies embedded are, for example, crank frequency, cam frequency, ignition frequency, etc. The ECU thus enables easy evaluation of the frequencies in the frequency domain.
[0008] The drift in the injection of fuel to the fuel injection system causes change in the operating point of engine parameters, for example, fuel quantity, boost pressure, oscillating masses, etc. Drift in fuel supplied to the fuel injection system also causes change in the air system of the engine. This drift in fuel supplied to the fuel injection causes change in the amplitude of the embedded frequencies, for example, injection frequency, of the engine speed. The ECU compensates for the engine parameters such as boost pressure and oscillating masses based on the change in the amplitude of the embedded frequencies.
[0009] The ECU calculates the estimated fuel quantity required for the engine speed. The ECU refers to a database for a value the estimated fuel quantity corresponding to the compensated engine speed in frequency domain. The database comprises a list of prestored values of compensated engine speed and the corresponding value of estimated fuel quantity for each of the compensated engine speed.
[00010] In an embodiment, the indicated fuel quantity is based on a position of an accelerator pedal. The pressure exerted on the accelerator pedal by the user provides a torque which is converted to an equivalent fuel quantity. This equivalent fuel quantity is the indicated fuel quantity. The ECU refers to the database for a value the indicated fuel quantity corresponding to the torque due to the pressure exerted on the accelerator pedal by the user. The database comprises a list of prestored values of the torque due to the pressure exerted on the accelerator pedal and the corresponding value of indicated fuel quantity for each value of the torque due to the pressure exerted on the accelerator pedal.
[00011] In another embodiment, the indicated fuel quantity is based on a value of the engine speed. The ECU refers to the database for a value the indicated fuel quantity corresponding to a value of the engine speed. The database comprises a list of prestored values of the torque due to the pressure exerted on the accelerator pedal and the corresponding value of indicated fuel quantity for each value of the torque due to the pressure exerted on the accelerator pedal.
[00012] The ECU calculates the difference between the estimated fuel quantity to maintain the engine speed and the indicated fuel quantity. The difference is the corrected fuel quantity to maintain the engine speed.
[00013] When a single cylinder engine is tested before it is assembled onto the vehicle, due to high fuel injection quantity, a lot of smoke is emitted. At full load, the fuel injected is corrected at the test bed level to reduce the smoke emitted. The test bed level corrected fuel quantity is the corrected fuel quantity at the test bed level which reduces the amount of smoke emitted at full load. The database which is stored in the electronic control unit comprises a list of prestored values of the test bed level corrected fuel quantity and the corresponding value of the engine speed for each of the test bed level corrected fuel quantity.
[00014] The estimated fuel quantity for an engine speed refers to when the single cylinder engine is assembled onto the vehicle and the vehicle is in a running condition. That is, the fuel injection quantity is corrected at two stages – first at the test bed level which is the test bed level corrected fuel quantity and the second when the engine is assembled onto the vehicle which is the estimated fuel quantity.
[00015] When the ECU considers only the estimated fuel quantity and not the test bed level corrected fuel quantity for an engine speed while determining the final fuel quantity, it leads to double correction in the fuel injection quantity. This results in a drop in torque.
[00016] Hence, in accordance with this invention, the ECU considers the test bed level corrected fuel quantity for determining the estimated fuel quantity for an engine speed leading to double correction in the fuel injection quantity.
[00017] The ECU compares the corrected fuel quantity with the test bed level corrected fuel quantity. The ECU refers to the database to obtain the values of the corrected fuel quantity and the test bed level corrected fuel quantity for an engine speed at full load. The ECU determines the final fuel quantity based on the comparison. The ECU determines the final fuel quantity as the corrected fuel quantity when the corrected fuel quantity is greater than the test bed level corrected fuel quantity. In other words, when the corrected fuel quantity is greater than the test bed level corrected fuel quantity, the ECU determines the final fuel quantity as the corrected fuel quantity such that the overall fuel quantity to be reduced is taken into consideration. The ECU determines the final fuel quantity as the test bed level corrected fuel quantity when the corrected fuel quantity is lesser than or equal to the test bed level corrected fuel quantity.
[00018] Thus, the double correction of the fuel injection quantity is avoided resulting in the protection of the engine at both the test bel level and after the engine is assembled onto the vehicle. The reduction is the level of torque due to double correction of the fuel injection at full load is eliminated.
[00019] 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.