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] The present disclosure relates to a method to rectify air mass quantity measured with a Delta_p sensor across an air filter in a vehicle and a tester device thereof.

Background of the invention
[0002] The amount of fresh air or the mass flow rate of air entering a fuel-injected internal combustion engine is an important parameter for operation an engine control unit (ECU) to balance and deliver the correct fuel mass to the engine (Torque control) and also ensure compliance with the emission norms by actuation of the Exhaust Gas Recirculation (EGR) valve and throttle valve along with engine related calibrations. To comply with the emission legislation for combustion engines, charge control is required to get the right mixture of fresh air and recirculated exhaust gas. The EGR valve controls the quantity ratio of the fresh air-mass flow and the recirculated exhaust gas (EGR). For enabling a good control of charge, an exact estimation of the fresh air-mass flow is required. For a diesel engine typically the fresh-air mass flow is measured by an air-flow-sensor (AFS). Engine applications with one or two cylinders back-flow and pulsations lead to high un-certainties for determination of the fresh air-mass flow by an air-flow-sensor. The fresh air-mass flow needs to be estimated with less than 10% precision.
[0003] The air mass flow model is developed with a delta pressure sensor across positioned across an air filter, using principles of thermodynamics and gas equations. This air mass is used for closed loop EGR control to achieve BS6 emission targets and to ensure emission consistency across vehicle fleet especially for few cylinders naturally aspirated engines. The clogging of air filter influences the effective area of the air filter, thereby influencing the delta pressure based fresh air-mass estimation as well. Hence, effective area must be calibrated during vehicle life, and every time after replacing the air-filter, pressure sensor, and ECU in the garage. This is called as the Drift compensation. Currently drift compensation is a tedious task that requires running the vehicle on the dyno available at the plant or in a dynamic testing track. Hence, there is a need for an easier drift compensation technique that automatically happens when the vehicle is on road.

[0004] Patent Application WO06092223 A1 titled “Method for correcting an air mass measuring error in an internal combustion engine” discloses a method for correcting an air mass measuring error during operation of a motor vehicle internal combustion engine. According to the prior art of techniques, the method consists in carrying out only the long time-drift correction of the air mass measurement by means of an HFM sensor for correcting the air mass measuring error caused by the long time-drift correction of the sensor because of an air filter soiling and/or loading. However, during measurements, the future emission limits can be difficulty respected or not respected at all by applying additional measures, only. Said problems or technical solutions are solved by the inventive method consisting in carrying out the off-set drift correction of the air mass measuring error at the first firing of the internal combustion engine or during the first run of the new motor vehicle provided with said internal combustion engine. Said invention makes it possible to compensate measuring errors related to measuring the air mass in a motor vehicle internal combustion engine for reducing polluting emissions.

Brief description of the accompanying drawings
[0005] An embodiment of the invention is described with reference to the following accompanying drawings:
[0006] Figure 1 depicts a portion of a vehicle system layout;
[0007] Figure 2 illustrates method steps (200) to rectify air mass quantity measured across an air filter (103);
[0008] Figure 3 is a graphical illustration of specific engine speed regions versus effective area.

Detailed description of the drawings
[0009] Figure 1 depicts a portion of a vehicle system layout. The system layout comprises an internal combustion engine (101), an air filter (103) positioned in an intake path (102) and at least an exhaust path (107) for naturally aspirated engines. A delta pressure sensor (105) is positioned across the air filter (103), and at least a temperature sensor (104) is positioned downstream of the air filter (103). Vehicles having turbocharged engines (not shown) further comprises an intercooler, a turbocharger and at least a throttle valve along with other components and sensors. For the purposes of this invention, only components and sensors having a bearing on the working of the invention have been elucidated. It is further clarified that the proposed invention holds good for both a turbocharged engine and a naturally aspirated engine.

[0010] Internal combustion engine (101) uses fuel which combusts inside a combustion chamber with the help of an oxidizer (typically oxygen from the air). These include petrol, diesel, jet fuel, and compressed natural gas. The turbocharger is a turbine-driven forced induction device that increases an internal combustion engine’s efficiency and power output by forcing extra air into the combustion chamber. A conventional turbocharger has two principal components a turbine and a compressor. The turbocharger’s compressor draws in ambient air and compresses it before it enters the intake manifold at increased pressure. The intake manifold of the internal combustion engine is in fluid communication with the intercooler. The intake manifold receives an extra mass of compressed air from the turbocharger via the intercooler. The throttle valve is mounted between the intercooler and the intake manifold and regulates the supply of this extra mass of compressed air to the internal combustion engine (101).

[0011] An Electronic control unit (ECU (107)) is in communication with the pressure sensor (105) and the temperature sensor (104). The ECU (107) is logic circuitry and software programs that respond to and processes logical instructions to get a meaningful result. Modern day vehicles may contain a plurality of control unit s like the Airbag control unit, Transmission control unit, Glow time control unit, Heating control unit, Vehicle charge communication unit, Engine control unit, Vehicle control unit, Steering control unit and the like. Each control unit coordinates the components specific to them for example an Engine control unit can provide torque coordination, operation, and gearshift strategies, on board diagnosis, monitoring, thermal management and much more for electrified and connected powertrains. The ECU (107) may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any component that operates on signals based on operational instructions.

[0012] On-Board Diagnostics (OBD) is a system that monitors a car's computer system and reports diagnostic trouble codes. The OBD tester (20) device is that reads diagnostic trouble codes (DTC) that the system stores when something goes wrong and also is used during the end of line of the vehicle to learn few values. The tester (20) is the present invention incorporates a drift rectification routine program. This drift rectification routine is a mode of operation in the tester (20) that is manually triggered in the ECU (107) when the tester (20) device is connected to onboard vehicle diagnostics.

[0013] In context of the present invention the tester (20) if configured to trigger a drift rectification routine in the ECU (107) when connected to onboard diagnostics of the vehicle; examine a set of release conditions in the vehicle; receive an air mass (m21) observed at the air filter (103) calculated by the ECU (107) based on a differential pressure measured by the pressure sensor (105) and a temperature measured by the temperature sensor (104) when the vehicle is driven in specific engine speed regions; determine a drift compensation factor for the specific engine speed regions by comparing a modelled reference air mass (m22) with calculated air mass (m21); rectify the air mass (m21) observed at the air filter (103) in the ECU (107) based on the drift compensation factor.

[0014] The set of release conditions include but are not limited to vehicle is in idle, handbrake is engaged, clutch is dis-engaged, ignition is on, pressure offset of the pressure sensor (105) is learnt and a pre-defined engine operating conditions. The modelled reference air mass (m22) is corrected based on the volumetric efficiency of the engine after intrusive shut off of an exhaust gas re-circulation valve. Rectifying the air mass (m21) further comprises storing the drift compensation factor for the specific engine speed regions in the ECU (107).

[0015] It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described below, the present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described below.

[0016] Figure 2 illustrates method steps (200) of rectifying an air mass quantity measured across an air filter (103) of a vehicle. The vehicle and it’s components relevant for execution of method steps (200) have been elucidated in accordance with figure 1. For the purposes of clarity, it is reiterated that the vehicle system layout comprises an internal combustion engine (101), an air filter (103) positioned in an intake path (102) and at least an exhaust path (107). A pressure sensor (105) is positioned across the air filter (103), and at least a temperature sensor (104) is positioned downstream of the air filter (103). An Electronic control unit (ECU (107)) is in communication with the pressure sensor (105) and the temperature sensor (104).

[0017] Method step 201 comprises triggering a drift rectification routine in the ECU (107) by connecting a tester (20) to onboard diagnostics of the vehicle. When the tester (20) is connected to on-board diagnostics, a drift rectification program in the tester (20) enables the tester (20) to connect with the ECU (107) and trigger a drift rectification routine.

[0018] Method step 202 comprises examining a set of release conditions in the vehicle by means of the tester (20). The set of release conditions include but are not limited to vehicle is in idle, handbrake is engaged, clutch is dis-engaged, ignition is on, pressure offset of the pressure sensor (105) is learnt and a pre-defined engine operating conditions. The pre-defined engine operating conditions include but are not limited to Engine temperature between the calibratable limits 25°C to 110°C, Environmental Pressure greater than the calibratable threshold 750 hectopascals (hPa)and, air temperature greater than calibration threshold.

[0019] Method step 203 comprises driving the vehicle in the set of release conditions and specific engine speed regions. Once the all the pre-requisite release condition are met, the vehicle in driven manually in the specific engine speed regions as illustrated in figure 3 and listed in table below. Figure 3 is a graphical illustration of specific engine speed regions versus effective area.

Engine speed (rpm)
Points Min Defined Max
A 920 950 980
B 1200 1300 1400
C 1650 1750 1850
D 2000 2100 2200
E 2450 2550 2650
F 3250 3350 3450

Table 1

[0020] Method step 204 comprises calculating (204) an air mass (m21) observed at the air filter (103) based on a differential pressure measured by the pressure sensor (105) and a temperature measured by the temperature sensor (104) for the specific engine speed regions by means of the ECU (107). Air mass (m21) is calculated using the Bernoulli’s equation. The values of environmental pressure is taken as the observed value and Aeff is taken as the ideal value for the air filter (103).

[0021] Method step 205 determining by means of the tester (20), a drift compensation factor for the specific engine speed regions by comparing a modelled reference air mass (m22) with calculated air mass (m21). The modelled reference air mass (m22) is calculated based on the volumetric efficiency of the engine after intrusive shut off of an exhaust gas re-circulation valve (108). As seen from figure 3, the effective area (Aeff) is not linear and changes in accordance with engine speed regions which causes the drift is the observed values of m21. Hence the drift compensation factor is calculated for the various engine speed regions ( A to F) as per table 1 and figure 3.

[0022] Method step 206 comprises rectifying the air mass (m21) observed at the air filter (103) in the ECU (107) based on the drift compensation factor. This method step further comprises storing the drift compensation factor for the specific engine speed regions in the ECU (107).

[0023] This idea to develop a method and device to rectify air mass quantity measured across an air filter (103) automates and eases the process of drift compensation calculation when the vehicle is on road. In prevailing conventional methods OEMs have to drive the vehicle in the calibrated operating points on the dyno where drift compensation zones are defined and the factors to accommodate the system tolerance would be corrected. With the proposed invention drift compensation is automated by triggering via tester (20) and the ECU (107) will be indicated to run automated drift correction of the system.

[0024] It must be understood that the embodiments explained in the above detailed description are only illustrative and do not limit the scope of this invention. Any modification and adaptation of the method and device to rectify air mass quantity measured across an air filter (103) are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.
, Claims:We Claim:
1. A method of rectifying an air mass quantity measured across an air filter (103) of a vehicle, the air filter (103) is positioned in an intake path (102) in the vehicle system layout, a pressure sensor (105) positioned across the air filter (103), and at least a temperature sensor (104) positioned downstream of the air filter (103), an Electronic Control Unit (ECU (107)) in communication with the pressure sensor (105) and the temperature sensor (104), the method steps comprising:
triggering (201) a drift rectification routine in the ECU (107) by connecting a tester (20) to onboard diagnostics of the vehicle;
examining (202) a set of release conditions in the vehicle by means of the tester (20);
driving (203) the vehicle in the set of release conditions and specific engine speed regions;
calculating (204) an air mass (m21) observed at the air filter (103) based on a differential pressure measured by the pressure sensor (105) and a temperature measured by the temperature sensor (104) for the specific engine speed regions by means of the ECU (107);
determining (205) by means of the tester (20), a drift compensation factor for the specific engine speed regions by comparing a modelled reference air mass (m22) with calculated air mass (m21);
rectifying (206) the air mass (m21) observed at the air filter (103) in the ECU (107) based on the drift compensation factor.

2. The method of rectifying an air mass quantity measured across an air filter (103) as claimed in claim 1, wherein the set of release conditions include but are not limited to vehicle is in idle, handbrake is engaged, clutch is dis-engaged, ignition is on, pressure offset of the pressure sensor (105) is learnt and a pre-defined engine operating conditions.

3. The method of rectifying an air mass quantity measured across an air filter (103) as claimed in claim 1, wherein the modelled reference air mass (m22) is calculated based on the volumetric efficiency of the engine after intrusive shut off of an exhaust gas re-circulation valve (108).

4. The method of rectifying an air mass quantity measured across an air filter (103) as claimed in claim 1, wherein rectifying the air mass (m21) further comprises storing the drift compensation factor for the specific engine speed regions in the ECU (107).

5. A tester (20) device adapted to rectify an air mass quantity measured across an air filter (103) of a vehicle, said air filter (103) positioned in an intake path (102) in the vehicle system layout, a pressure sensor (105) positioned across the air filter (103), and at least a temperature sensor (104) positioned downstream of the air filter (103), an Electronic Control Unit (ECU (107)) in communication with the pressure sensor (105) and the temperature sensor (104), characterized in that tester (20), the tester (20) configured to:

trigger a drift rectification routine in the ECU (107) when connected to onboard diagnostics of the vehicle;
examine a set of release conditions in the vehicle;
receive an air mass (m21) observed at the air filter (103) calculated by the ECU (107) based on a differential pressure measured by the pressure sensor (105) and a temperature measured by the temperature sensor (104) when the vehicle is driven in specific engine speed regions;
determine a drift compensation factor for the specific engine speed regions by comparing a modelled reference air mass (m22) with calculated air mass (m21);
rectify the air mass (m21) observed at the air filter (103) in the ECU (107) based on the drift compensation factor.

6. The tester (20) device adapted to rectify an air mass quantity as claimed in claim 5, wherein the set of release conditions include but are not limited to vehicle is in idle, handbrake is engaged, clutch is dis-engaged, ignition is on, pressure offset of the pressure sensor (105) is learnt and a pre-defined engine operating conditions.

7. The tester (20) device adapted to rectify an air mass quantity as claimed in claim 5, wherein the tester (20)s stores the drift compensation in the ECU (107) for the specific engine speed regions.