Patent Application
20100224169
The present disclosure relates to vehicle control systems and more particularly to vehicle control systems for controlling fuel rail pressure using fuel pressure sensor error.
Direct injection gasoline engines are currently used by many engine manufacturers. In a direct injection engine, highly pressurized gasoline is injected via a common fuel rail directly into a combustion chamber of each cylinder. This is different than conventional multi-point fuel injection that is injected into an intake tract or cylinder port.
Gasoline-direct injection enables stratified fuel-charged combustion for improved fuel efficiency and reduced emissions at a low load. The stratified fuel charge allows ultra-lean burn and results in high fuel efficiency and high power output. The cooling effect of the injected fuel and the even dispersion of the air-fuel mixture allows for more aggressive ignition timing curves. Ultra lean burn mode is used for light-load running conditions when little or no acceleration is required. Stoichiometric mode is used during moderate load conditions. The fuel is injected during the intake stroke and creates a homogenous fuel-air mixture in the cylinder. A fuel power mode is used for rapid acceleration and heavy loads. The air-fuel mixture in this case is a slightly richer than stoichiometric mode which helps reduce knock.
Direct-injected engines are configured with a high-pressure fuel pump used for pressurizing the injector fuel rail. A pressure sensor is attached to the fuel rail for control feedback. The pressure sensor provides an input to allow the computation of the pressure differential information used to calculate the injector pulse width for delivering fuel to the cylinder. Errors in the measured fuel pressure at the fuel rail result in an error in the mass of the fuel delivered to the individual cylinder.
The present disclosure provides a method and system by which an error from the pressure sensor in the fuel rail may be quantified and used for closed-loop control. This will result in the proper mass of fuel being delivered to the individual cylinder. This may also allow for diagnostics of the fuel rail pressure sensor.
In one aspect of the invention, a method includes operating the engine at a steady state, storing a first fuel correction, commanding a predetermined fuel rail pressure change, storing a second fuel correction after commanding, determining a fuel rail pressure sensor error based on the first fuel correction and the second fuel correction and determining a fuel rail pressure in response to the sensor error.
In a further aspect of the invention, a control system for controlling a fuel system of an engine includes a steady state determination module determining the engine is operating at a steady state and a memory storing a first fuel correction. A fuel pump control module commands a predetermined fuel rail pressure change. The memory stores a second fuel correction after the predetermined fuel rail pressure change. A sensor error correction module determines a fuel rail pressure sensor error based on the first fuel correction and the second fuel correction and determines a fuel rail pressure in response to the sensor error.
Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. As used herein, the term boost refers to an amount of compressed air introduced into an engine by a supplemental forced induction system such as a turbocharger. The term timing refers generally to the point at which fuel is introduced into a cylinder of an engine (fuel injection) is initiated.
Referring now to
During engine operation, air is drawn into the intake manifold 15 by the inlet vacuum created by the engine intake stroke. Air is drawn into the individual cylinders 20 from the intake manifold 15 and is compressed therein. Fuel is injected by the injection system 16, which is described further in
The turbocharger 18 can be any suitable turbocharger such as, but not limited to, a variable nozzle turbocharger (VNT). The turbocharger 18 can include a plurality of variable position vanes 27 that regulate the amount of air delivered from the vehicle exhaust 17 to the engine 12 based on a signal from the control module 14. More specifically, the vanes 27 are movable between a fully-open position and a fully-closed position. When the vanes 27 are in the fully-closed position, the turbocharger 18 delivers a maximum amount of air into the intake manifold 15 and consequently into the engine 12. When the vanes 27 are in the fully-open position, the turbocharger 18 delivers a minimum amount of air into the engine 12. The amount of delivered air is regulated by selectively positioning the vanes 27 between the fully-open and fully-closed positions.
The turbocharger 18 includes an electronic control vane solenoid 28 that manipulates a flow of hydraulic fluid to a vane actuator (not shown). The vane actuator controls the position of the vanes 27. A vane position sensor 30 generates a vane position signal based on the physical position of the vanes 27. A boost sensor 31 generates a boost signal based on the additional air delivered to the intake manifold 15 by the turbocharger 18. While the turbocharger implemented herein is described as a VNT, it is contemplated that other turbochargers employing different electronic control methods may be employed.
A manifold absolute pressure (MAP) sensor 34 is located on the intake manifold 15 and provides a (MAP) signal based on the pressure in the intake manifold 15. A mass air flow (MAF) sensor 36 is located within an air inlet and provides a mass air flow (MAF) signal based on the mass of air flowing into the intake manifold 15. The control module 14 uses the MAF signal to determine the A/F ratio supplied to the engine 12. An RPM sensor 44 such as a crankshaft position sensor provides an engine speed signal. An intake manifold temperature sensor 46 generates an intake air temperature signal. The control module 14 communicates an injector timing signal to the injection system 16. A vehicle speed sensor 49 generates a vehicle speed signal.
The exhaust conduits 26 can include an exhaust recirculation (EGR) valve 50. The EGR valve 50 can recirculate a portion of the exhaust. The controller 14 can control the EGR valve 50 to achieve a desired EGR rate.
The control module 14 controls overall operation of the engine system 10. More specifically, the control module 14 controls engine system operation based on various parameters including, but not limited to, driver input, stability control and the like. The control module 14 can be provided as an Engine Control Module (ECM).
The control module 14 can also regulate operation of the turbocharger 18 by regulating current to the vane solenoid 28. The control module 14 according to an embodiment of the present disclosure can communicate with the vane solenoid 28 to provide an increased flow of air (boost) into the intake manifold 15.
An exhaust gas oxygen sensor 60 may be placed within the exhaust manifold or exhaust conduit to provide a signal corresponding to the amount of oxygen in the exhaust gasses.
Referring now to
Referring now to
An air-fuel determination module 218 may be used to determine if the air-fuel ratio is rich or lean. The air-fuel determination module may determine the rich or lean status based upon a block learn multiplier (BLM) signal which is the long-term fuel correction signal. The BLM signal is described below.
A steady state determination module 220 is used to determine whether the engine is being operated at steady state. As will be described below, determining an error for a pressure sensor in the fuel rail may be performed when the engine is operated at steady state. Steady state may include when the crank shaft speed is steady, the load as determined by the manifold absolute pressure is steady, or the block learn multiplier (BLM) is operated within the same cell.
The block learn multiplier (BLM) is a long-term fuel correction that is used to maintain the air-fuel ratio within an acceptable parameter. The long-term fuel adjustment happens about twice per second, whereas the short-term fuel correction (INT) happens about 20 times per second. The cells correspond to various operating ranges corresponding to engine RPM and mass air flow. For example, the crank shaft speed may be divided into a number of regions such as four regions, 0-800 rpm, 800-1100 rpm, 1100-1500 rpm, and above 1500 rpm. The mass air-flow readings may be provided in 0-9 gps, 9-20, gps, 20-30 gps, and above 30 gps. In such a system, 16 cells (four across and four down) may be provided. Of course, the above example is provided for illustration purposes only. Actual values may be different depending on different engines and calibrations. An indication of steady state is when the engine is maintained within a cell. It should be noted that for both short-term and long-term fuel correction values, a higher value represents a correction that adds fuel to the mixture due to higher injector pulse widths. The short-term correction value may be referred to as an integrator value. The integrator values may be adjusted according to exhaust gas oxygen reading from the exhaust gas oxygen sensor 60 illustrated in
The control module 14 may also include a fuel pump control module 224 used to determine a fuel injector pulse width in response to the pressure measurements and pressure sensor error. The injector pulse width corresponds to the amount of mass of fuel delivered to the cylinder. The fuel pump control module 224 may be a separate module associated with the fuel pump 116 outside control module 14.
A timer module 228 may be used to time various lengths of time including a time since a commanded fuel pressure change was performed. This time corresponds to a delay time as will be further described below. Of course, other timing determinations may also be provided.
A memory 230 may also be included in the control module 14. The memory 230 may store various data and intermediate calculations associated with the various modules 210-228. The memory 230 may be various types of memory including volatile, non-volatile, keep alive or various combinations thereof.
Referring now to
In step 316, a fuel pressure change is commanded by the control module 14 illustrated above. The commanded fuel pressure change may command a pre-determined amount of pressure change. (In the graph of
A delay time may be provided within the system. The delay time ensures that the commanded fuel pressure change has been implemented. If the delay time has not expired, step 318 is again performed until the delay time has expired. Once the delay time has expired, a check of the enablement criteria is performed in step 320. An indicator that the enablement criteria have changed is whether the BLM remains within the same BLM cell. Of course, the engine RPM and load may also be used as an indicator whether the criteria has changed. In step 320, if the enablement criteria are unchanged, step 322 captures the fuel corrections. Step 322 may capture one or both of the short-term correction or the long-term correction. In step 324, if the old correction from step 314 is subtracted from the new correction in step 322, and the absolute value of the subtraction is above a threshold, step 326 is performed. In step 326, a determination of whether the correction indicates rich or lean may be performed. As mentioned above, a higher value of BLM adds fuel to the mixture. If the correction indicates a rich blend, step 328 determines the sensor gain as the sensor gain plus the new correction. In step 326, if the correction does not indicate rich, step 330 is performed. In step 330, if the system indicates a lean mixture, step 332 calculates the sensor gain as the sensor gain minus the correction factor. After steps 328 and 332, step 340 determines the injector pulse width using the sensor gain. By controlling the injector pulse width, the mass of fuel injected into a cylinder may be controlled.
Referring back to steps 312, 320 and 324, if the enablement criteria are not met in step 312 or the enablement criteria have changed in step 320 or the old correction minus the new correction is not above a threshold, the system ends the process in step 342. Also, the system may end in step 342 after step 330 if the system does not indicate lean.
By determining the sensor gain errors or fuel pressure sensor error, adaptive correction of the pressure sensor value is used to correct fuel pressure sensor reading errors. Also, sensor degradation may also be monitored due to increasing sensor errors. Thus, when sensor degradation takes places, the vehicle operator may be notified through an indicator.
Referring now to
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.
