Method for detecting and compensating for injector variability in a direct injection system

Abstract

Method for controlling fuel injection of a direct injection fuel system, wherein the direct injection fuel system comprises a fuel pump (202, 206) and several fuel injectors (214a, 214b, 214c, 214d), the method comprising: Variable operation of the fuel pump (202, 206) to maintain a fuel pressure at a selected pressure; Temporarily increasing the pump operation to raise the pressure sufficiently above the selected pressure, and then reducing the pump operation; During at least one fuel injection following the reduction of pump operation: Correlation of the fuel pressure drop during the at least one fuel injection with a fuel injector operation, wherein a predetermined number of fuel injections for each fuel injector (214a, 214b, 214c, 214d) in an engine (10) is performed following and near the reduction of pump operation, and Adjusting the fuel injector operation based on correlation.

Description

Background and brief explanation

[0001] For example, fuel injectors in direct injection engine systems often exhibit variability from unit to unit and over time due to faulty manufacturing processes and / or injector aging. This injector variability can cause an imbalance in cylinder torque output due to the varying amount of fuel injected into each cylinder, and can also lead to higher tailpipe emissions and reduced fuel economy due to an inability to accurately meter the fuel injected into each cylinder.

[0002] Correction coefficients can be used to compensate for injector variability by correcting injection parameters such as injection timing. US 5,176,122 A, for example, discloses a method that uses both average and individual correction coefficients to correct injection variability. To calibrate the average and individual correction coefficients, calibration injection events are performed while the fuel supply is interrupted under various conditions, such as idling. Specifically, during a calibration injection event, the manifold pressure is monitored as it drops from a normal operating pressure to a lower threshold when fuel injections are performed. The manifold pressure drop is then used to calculate and update correction coefficients.In order to continue determining the individual correction coefficients, injection processes can be carried out by some injectors while other injectors are deactivated or their injection quantity is reduced.

[0003] The present inventors have identified several potential problems associated with the aforementioned methods for calibrating correction coefficients. For example, during a calibration injection event, the manifold pressure drop from a normal operating pressure to a lower threshold pressure is monitored. Since the lower threshold pressure may be limited by the inability of the injectors to accurately meter fuel below a certain pressure, the amount of pressure drop available for a given calibration injection event may be limited. In other words, the number and size of injections in a given calibration injection event may not be sufficient to accurately calibrate all injectors.In addition to the aforementioned problem, individual cylinder injector calibration using injector deactivation can lead to undesirable fluctuations in the fuel / air ratio, uneven torque production cylinder by cylinder, and increased engine vibration (for example, during idle). Furthermore, if the manifold pressure is maintained at normal operating pressures, a relatively small amount of fuel may be present in the manifold during calibration due to the relatively low fuel pressure. Therefore, this small amount of fuel in the manifold can increase the fuel metering sensitivity to engine heat, which in turn can degrade the calibration results.

[0004] DE 10 2004 053 580 A1 discloses a method for controlling fuel injection of a direct injection fuel system, wherein the direct injection fuel system comprises a fuel pump and several fuel injectors, the method comprising: variable operation of the fuel pump to maintain a fuel pressure at a selected pressure; temporary increase of the pump operation to raise the pressure sufficiently above the selected pressure, and then reduction of the pump operation;During fuel injection following pump reduction: Correlating a pressure parameter during fuel injection with fuel injector operation as part of an injection quantity learning function, wherein fuel injection for a fuel injector in an engine is performed following and close to the reduction of pump operation, and adapting the fuel injector operation based on the injection quantity learning function.

[0005] DE 10 2005 018 576 A1 describes a common-rail fuel injection system comprising a common rail, an injector, a control device, and a pressure sensor. The common rail stores high-pressure fuel. The injector injects the fuel stored in the common rail. The control device receives an injection quantity from the injector in accordance with an operating condition to control an on / off valve of the injector based on the injection quantity. The common-rail pressure sensor detects the common-rail pressure of the fuel stored in the common rail. The control device has a correction device for receiving a pressure drop in the common-rail pressure after setting a predetermined learning condition, for receiving a change in the injector delivery quantity, and for correcting the injection quantity based on the change in delivery quantity.

[0006] DE 197 00 738 C1 relates to a method for controlling the injection quantities of injectors that are fluidically connected to a common pressure line in a common-rail injection system of an internal combustion engine. A fuel pump supplies fuel to the pressure line at a static nominal pressure. Control signals for enabling and closing the injectors, with individual injection durations to achieve equal injection quantities, are supplied by a control unit. If the flow rates of the individual injectors differ due to tolerances or, in particular, due to the formation of deposits with increasing operating time of the internal combustion engine, the control unit achieves equal injection quantities by changing the respective injection duration based on a measured signal.A pressure measuring device inserted into the pressure line generates the measurement signal from a measurement of the static pressure in the pressure line after each injector is closed. From the difference between the nominal pressure before injection and the differential pressure after injection, the control unit determines the amount of fuel drawn from the pressure line during injection and, if the actual injection quantity deviates from a known target value, adjusts the injection duration of the diagnosed injector accordingly.

[0007] A fuel injection quantity control system for performing a learning control of the fuel injection quantity is provided in DE 10 2007 000 005 A1. When ambient noise is relatively loud, a high-pressure fuel pump is operated to raise the rail pressure to a learning target rail pressure higher than the actual rail pressure, provided the conditions for performing a pilot injection quantity learning control are met. Then, a single-shot injection for learning control is performed. When ambient noise is relatively quiet, a single-shot injection for learning control is performed after the fuel pressure has been reduced to a certain learning target rail pressure lower than the actual rail pressure.

[0008] At least some of the aforementioned problems are solved by the features of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0009] Accordingly, a fuel injection system can be used that employs low engine load operating conditions and an operating distributor pipe pressure that is higher than normal for injector calibration.

[0010] In one example, a method for controlling fuel injection of a direct injection fuel system, wherein the fuel system has a fuel pump, comprises: variable operation of the fuel pump to maintain a fuel pressure at a selected pressure; temporary increase of the pump operation to raise the pressure sufficiently above the selected pressure, and then reduction of the pump operation; during at least one fuel injection after the reduction of the pump operation, correlating pressure decrease to injector operation and adjusting the fuel injection operation based on the correlation.

[0011] By using increased pressure beyond the selected operating pressure, it is possible to achieve sufficiently large injection quantities to maintain adequate manifold pressure drop for subsequent injections required for precise injector calibration. This can be particularly relevant when using a turbocharger to increase intake air pressure, in which case the injection pressure must overcome the increased air pressure in the cylinder. Furthermore, it may also be possible to achieve a sufficient number of calibration injections if multiple injections per injector are desired for precise calibration and / or multiple injectors need to be calibrated. Additionally, it may be possible to avoid or reduce the operation of injectors at pressures below those suitable for the current operating conditions.In one particular example, by performing such an operation during lower load conditions, it is possible to provide sufficient pressure rise for injector calibration, since lower operating pressures can be used under these lower load conditions; that is, the operating pressure (before the temporary pressure rise for injector calibration) is low enough to provide sufficient room to achieve a target pressure rise for performing precise injector calibration.

[0012] Furthermore, the fuel rail can be filled with fresher and colder fuel during correlation by using a higher starting pressure while the injector is being calibrated. This can reduce the temperature sensitivity of the fuel rail and thus improve the correlation results.

[0013] Finally, in an example where a predetermined number of injections per injector are performed subsequently and close to the reduction of pump operation, it may be possible to avoid a torque imbalance that is generated when a single injector is deactivated or the injection volume of a single injector is reduced. Brief description of the characters Fig. Figure 1 shows an example engine. Fig. Figure 2 shows a high-pressure fuel injection system. Fig. Figure 3 shows an example of an injector calibration routine. Fig. Figure 4 shows an example calibration injection routine. Fig. Figure 5 shows an example calculation and renewal routine for an injector correction coefficient. Fig. Figure 6 shows an exemplary routine for determining the target calibration pressure (P m) for the high-pressure reserve tank. Fig. Figure 7 is a timing diagram showing the fuel injection timing, fuel pressure change in the high-pressure reserve tank, and fuel pump strokes for a calibration injection cycle. Detailed description

[0014] Fig. Figure 1 shows a cylinder of a multi-cylinder engine and the intake and exhaust passages associated with this cylinder.

[0015] Continue with Fig. Figure 1 shows a direct injection system, wherein an engine 10 has direct fuel injection and spark ignition. The internal combustion engine 10, which has several combustion chambers, is controlled by an electronic control unit 12. A combustion chamber 30 of the engine 10 is shown having combustion chamber walls 32 and a piston 36 positioned therein and connected to a crankshaft 40. A starter motor (not shown) can be connected by means of a flywheel (not shown), or alternatively, direct engine starting can be used.

[0016] In one particular example, the piston 36 may include a (not shown) recess or depression to assist in the formation of stratified charges of air and fuel, if required. In some examples, a flat piston may be used.

[0017] The combustion chamber or cylinder 30 is shown connected to an intake manifold 44 and an exhaust manifold 48 by means of respective intake valves 52a and 52b (not shown) and exhaust valves 54a and 54b (not shown). While four valves per cylinder can thus be used, in another example a single intake and a single exhaust valve per cylinder can also be used. In yet another example, two intake valves and one exhaust valve per cylinder can be used.

[0018] The injection valve 66A is shown to be connected directly to the combustion chamber 30 for the purpose of supplying injected fuel directly into it proportionally to the pulse width of the signal received by the control unit 12 by means of an electronic driver 68. Fig. Figure 1 shows the injector 66A as a side-mounted injector; it can also be located above the piston, for example, near the position of a spark plug 92. Such a position can improve mixing and combustion due to the lower volatility of some alcohol-based fuels. Alternatively, the injector can be located above and near the intake valve to improve mixing.

[0019] Fuel can be supplied to the 66A injector via a high-pressure fuel system (see Fig. 2) supplied via a fuel tank, fuel pumps, and a distribution pipe. Although not shown, the fuel tank(s) may each have a pressure converter that provides a signal to control unit 12.

[0020] The intake manifold 44 is shown connected to a throttle body 58 by means of a throttle plate 62. In this particular example, the throttle plate 62 is connected to an electric motor 94, so that the position of the elliptical throttle plate 62 is controlled by the control unit 12 via the electric motor 94. This configuration can be referred to as electronic throttle control (ETC), which can also be used during idle speed control. In an alternative example (not shown), a bypass air duct is arranged parallel to the throttle plate 62 to control the intake airflow during idle speed control by means of an idle control bypass valve positioned in the air duct.

[0021] The exhaust gas sensor 76 is shown coupled to the exhaust manifold 48 upstream of a catalyst 70 (where the sensor 76 can correspond to various different sensors). For example, the sensor 76 can be any of the many known sensors for providing an indication of the fuel / air ratio of the exhaust gas, such as a linear oxygen sensor, a UEGO, a dual-state oxygen sensor, an EGO, a HEGO, or an HC or CO sensor. In this particular example, the sensor 76 is a dual-state oxygen sensor that provides a signal EGO to the control unit 12, which converts the signal EGO into a dual-state signal EGOS. A high-voltage state of the EGOS signal indicates that the exhaust gases are substoichiometric, and a low-voltage state of the EGOS signal indicates that the exhaust gases are superstoichiometric.The EGOS signal can be advantageously used during fuel / air control to maintain the average fuel / air ratio at stoichiometry during a stoichiometric homogeneous operating mode.

[0022] A distributorless ignition system 88 supplies the combustion chamber 30 with an ignition spark by means of the spark plug 92 in response to an ignition advance signal SA from the control unit 12.

[0023] The control unit 12 can operate the combustion chamber 30 in various combustion modes, including a homogeneous fuel / air mode and a stratified fuel / air mode, by controlling the injection timing, injection quantities, spray patterns, etc. Furthermore, combined stratified and homogeneous mixtures can be formed in the combustion chamber. In one example, stratified layers can be formed by operating the injector 66A during a compression stroke. In another example, a homogeneous mixture can be formed by operating the injector 66A during an intake stroke (which can be an open-valve injection). In yet another example, a homogeneous mixture can be formed by operating the injector 66A before an intake stroke (which can be a closed-valve injection).In other examples, multiple injections from injector 66A can be used during one or more strokes (e.g., intake, compression, exhaust, etc.). There are further examples where different injection timings and mixture formations can be used under various conditions.

[0024] The control unit 12 can control the amount of fuel supplied by the injectors 66A, so that the homogeneous, stratified or combined homogeneous / stratified fuel / air mixture in the combustion chamber 30 can be selected at stoichiometry, a substoichiometric value or a superstoichiometric value.

[0025] A pollutant control device 72 is shown arranged downstream of the catalyst 70. The pollutant control device 72 can be a particulate filter, a three-way catalyst, a NOx filter, or combinations thereof.

[0026] The control unit 12 is shown as a microcomputer, which includes: a microprocessor 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory 106, a working memory 108, a battery-powered memory 110 and a conventional data bus.The control unit 12 is shown receiving various signals from the sensors connected to the engine 10, in addition to the signals already described. These include: intake air mass (MAF) measurement from an air flow meter 110 connected to the throttle body 58; engine coolant temperature (ECT) from a temperature sensor 112 connected to a cooling jacket 114; a ignition profile sensor (PIP) signal from a Hall sensor 118 connected to the crankshaft 40; a throttle position (TP) signal from a throttle position sensor 120; an absolute manifold pressure (MAP) signal from a sensor 122; a knock indication from a knock sensor 182; and an indication of absolute or relative humidity from sensor 180. An engine speed (RPM) signal is generated by the control unit 12 from the PIP signal in the conventional manner, and a manifold pressure (MAP) signal from a manifold pressure sensor provides an indication of vacuum or pressure in the intake manifold.During stoichiometric operation, this sensor can provide an indication of engine load. Furthermore, this sensor, in conjunction with engine speed, can provide an estimate of the charge (including air) being introduced into the cylinder. In one example, sensor 118, which is also used as an engine speed sensor, generates a predetermined number of evenly spaced pulses per crankshaft revolution. The temperature of the catalytic converters can be measured by sensors or estimated based on operating conditions or combinations thereof.

[0027] In some examples, the control unit receives 12 different operating parameters that can influence the manifold pressure monitoring and are acquired by various sensors (not all of which are shown). These operating parameters can be correlated with the manifold pressure drop during injector calibration injection events, and the effect of engine operating parameters on the manifold pressure measurements can be eliminated or disregarded, allowing for accurate determination of fuel pressure drops associated with fuel injections. Examples of such engine parameters that can influence fuel pressure measurements include intake and / or exhaust valve positions, crankshaft position, piston position, injector actuation, spark ignition, and / or intake and / or exhaust pressure.

[0028] Continue with Fig. Figure 1 shows a variable camshaft timing system. Specifically, the camshaft 130 of engine 10 is shown connected to rocker arms 132 and 134 for actuating the intake valves 52a, 52b and the exhaust valves 54a, 54b. The camshaft 130 is directly connected to the housing 136. The housing 136 forms a multi-toothed gear 138. The housing 136 is hydraulically coupled to an internal shaft (not shown), which in turn is directly connected to the camshaft 130 via a timing chain (not shown). Therefore, the housing 136 and the camshaft 130 rotate at a speed that essentially corresponds to that of the internal camshaft. The internal camshaft rotates at a constant speed ratio to the crankshaft 40.By influencing the hydraulic coupling, as described later, the relative position of the camshaft 130 to the crankshaft 40 can be changed by hydraulic pressures in a pre-adjustment chamber 142 and a retarding chamber 144. By allowing high-pressure hydraulic fluid to enter the pre-adjustment chamber 142, the relative relationship between the camshaft 130 and the crankshaft 40 is pre-adjusted. Thus, the intake valves 52a, 52b and the exhaust valves 54a, 54b open and close relative to the crankshaft 40 at an earlier time than normal. Similarly, by allowing high-pressure hydraulic fluid to enter the retarding chamber 144, the relative relationship between the camshaft 130 and the crankshaft 40 is retarded. Thus, the intake valves 52a, 52b and the exhaust valves 54a, 54b open and close relative to the crankshaft 40 at a later time than normal.

[0029] The teeth 138, which are coupled to the housing 136 and the camshaft 130, enable the measurement of the relative cam position via a cam control sensor 150, which supplies a VCT signal to the control unit 12. Teeth 1, 2, 3, and 4 are preferably used for measuring the cam timing and are evenly spaced (for example, in a V8 engine with two cylinder banks spaced 90 degrees apart), while tooth 5 is preferably used for cylinder identification, as described later. Furthermore, the control unit 12 sends signals (LACT, RACT) to (not shown) conventional solenoid valves to control the flow of hydraulic fluid either into the pre-adjustment chamber 142, the retardation chamber 144, or neither.

[0030] The relative cam timing can be measured in different ways. Generally speaking, the time or angle of rotation between the rising edge of the PIP signal and the reception of a signal from one of the several teeth 138 on the housing 136 gives a measure of the relative cam timing. For the specific example of a V-8 engine with two cylinder banks and a five-tooth gear, a cam timing measurement for a specific bank is received four times per revolution, with the extra signal being used for cylinder identification.

[0031] Sensor 160 can also provide an indication of the fuel / air ratio of the exhaust gas via signal 162, which supplies the control unit 12 with an electrical voltage indicating the O2 concentration. For example, sensor 160 can be a HEGO, UEGO, EGO, or another type of exhaust gas sensor. It should also be noted that, as described above regarding sensor 76, sensor 160 can correspond to various different sensors.

[0032] As described above, Fig. 1 merely one cylinder of a multi-cylinder engine and that each cylinder has its own set of intake / exhaust valves, injectors, spark plugs, etc.

[0033] Furthermore, in the example described herein, the engine 10 can be connected to a starter motor (not shown) for starting the engine. The starter motor can be operated when the driver, for example, turns a key in the ignition switch on the steering column or presses an automatic start button. The starter is disengaged after the engine has started, for example, when the engine 10 reaches a predetermined speed after a predetermined time. In addition, in the disclosed examples, an exhaust gas recirculation (EGR) system can direct a desired portion of the exhaust gas from the exhaust manifold 48 to the intake manifold 44 by means of an EGR valve (not shown). Alternatively, a portion of the combustion gases can be retained in the combustion chambers by controlling the exhaust valve timing.

[0034] Engine 10 can be one or more different types of internal combustion engines. Engine 10 can have different numbers of cylinders; for example, it can be a JV-2, V-6, V-8, or V-12 engine. Individual cylinders can be activated or deactivated individually to provide different engine strokes. Individual cylinders can also operate in different combustion modes at a given time. It is also possible for individual cylinders to switch between different combustion modes, for example, from SI to HCCI and then back to SI. Engine 10 can be a rotary engine, a reciprocating engine, or a combination of both. Engine 10 can also burn different types of fuel, such as diesel, vegetable oil, propane, gasoline, or a combination of different fuels.Furthermore, the internal combustion engine can use different cycles, for example, a two-stroke or four-stroke cycle, or a combination of different cycles. The engine's cylinders can be designed in various configurations. For example, the cylinders can be arranged in a row as inline engines, in a V-configuration as in V-engines, in a W-configuration as in W-engines, in two opposing cylinder banks as in boxer engines, or in a combination of different engine configurations.

[0035] It should also be noted that various methods can be used to maintain the target torque, such as adjusting the ignition timing, throttle position, variable camshaft position, exhaust gas recirculation rate, and the number of cylinders performing combustion. Furthermore, these variables can be adjusted individually for each cylinder to maintain cylinder balance across all cylinders.

[0036] The engine 10 may further include a compression device, for example a turbocharger or supercharger (not shown), comprising at least one compressor arranged along the intake manifold 44. In the case of a turbocharger, a compressor may be driven at least partially by a turbine (e.g., by means of a shaft) arranged along the outlet channel 48. In the case of a supercharger, the compressor may be driven at least partially by the engine (e.g., crankshaft) and / or an electric machine and need not include a turbine. The turbocharger, if present, may be of different types, for example, a fixed-geometry turbocharger or a variable-geometry turbocharger. Furthermore, it may be a variable-nozzle turbocharger or include a boost pressure control valve.

[0037] Fig. Figure 2 shows a fuel injection system with a high-pressure distribution pipe system. The system can include a fuel tank 200, a low-pressure fuel pump (or rotary fuel pump) 202, which supplies fuel from the fuel tank 200 to a high-pressure fuel pump 206 via a low-pressure channel 204. The high-pressure fuel pump 206 supplies pressurized fuel to the high-pressure fuel reserve 210 via a high-pressure channel 208. The high-pressure fuel reserve 210 supplies pressurized fuel to the injectors 214a, 212b, 212c, and 212d via fuel supply channels 212a, 212b, 212c, and 212d, respectively. The injectors inject fuel into engine cylinders (not shown) arranged in an engine block 216. Uninjected fuel can be returned to the fuel tank 200 via a fuel return channel 218. The engine block 216 can be connected to an intake air throttle 224 via an intake port 222.

[0038] The system may further include a control unit 226. The control unit may be connected to various other sensors 252 and various actuators 254 (e.g., fuel injection actuator, ignition actuator, throttle valve actuator, etc.) for sensing and controlling vehicle operating conditions. For example, the control unit 226 may, through suitable sensors, sensing engine speed, throttle position, intake air temperature and / or pressure, exhaust air temperature / pressure, air mass, engine coolant temperature, crankshaft angle position, variable camshaft position, injection timing, and ignition timing. The control unit 226 may also control the operation of intake and / or exhaust valves or throttles, engine cooling fans, ignition, fuel injectors, and fuel pumps to control engine operating conditions.

[0039] Fig. Figure 2 shows further details of the fuel injection system. Specifically, it shows Fig. 2 the control device 216, which may be an engine control device, a powertrain control device, a control system, a separate device, or combinations of different control devices. The control device 226 is used in Fig. 2 shown as a microcomputer, which includes: Input / Output Port (I / O) 228, a Central Processing Unit (CPU) 232, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory chip 230, a working memory (RAM) 234, a battery-powered memory (KAM) 136 and a data bus.

[0040] The control unit 226 can receive various signals from different sensors. For example, the control unit 226 can receive fuel pressure signals from the high-pressure fuel reserve 210 via a fuel pressure sensor 220 located in the high-pressure fuel reserve 210. The control unit can also receive throttle opening angle signals (O A ), which indicate the intake air throttle position by means of a throttle position sensor 238, intake air flow signals (Q a ) from an air flow meter 240, engine speed signals (N e ) from an engine speed sensor 242, accelerator pedal position signal from a pedal 244 by means of an accelerator pedal position sensor 246, crank angle sensor 248 and engine coolant temperature (ECT) signals from an engine temperature sensor 250.

[0041] In addition to the signals mentioned above, the control unit 226 can also receive other signals from various other sensors 252. For example, the control unit 226 can receive a profile ignition signal (PIP) from a Hall sensor (not shown) connected to a crankshaft (not shown); a manifold pressure signal (MAP) from a manifold pressure sensor (not shown).

[0042] The control unit 226 can control the operation of various vehicle components by means of various actuators 254. For example, the control unit 226 can control the operation of the injection valves 214a-b by means of an injection valve actuator (not shown) and the high-pressure fuel pump 206 by means of a high-pressure fuel pump actuator (not shown).

[0043] Although this example uses a single high-pressure fuel pump 206, other examples may include multiple high-pressure fuel pumps supplying fuel to the high-pressure fuel reserve 210. The high-pressure fuel pump 206 can be connected to and controlled by the control unit 226, as shown here. Fig. Figure 2 shows that the control device 226 can regulate the quantity or rate of fuel supplied to the high-pressure reserve by the high-pressure fuel pump 206 via a high-pressure fuel pump control (not shown). The control device 226 can also completely shut off the fuel supply to the high-pressure fuel reserve. Furthermore, the high-pressure fuel pump 206 can include one or more relief valves that reduce the fuel pressure in the high-pressure fuel reserve if the fuel pressure in the high-pressure fuel reserve 210 is higher than desired.

[0044] Although this example shows one injector per cylinder, other examples may include multiple injectors per cylinder. While the injectors in this example are connected to engine cylinders, in other examples they may be connected to an intake port. The injectors directly connected to engine cylinders may be located above (not shown) cylinder pistons or on the side of an engine cylinder. The injector 212 may be connected to a control device, for example, the control device 226, which is shown here in Fig. As shown in Figure 1, they are interconnected and controlled by it. The amount of fuel injected by the injector and the injection timing can be determined by the control unit 226 from an engine map stored in the control unit 226, based on engine speed (N). e) and / or intake throttle angle (Q a The fuel injection system can be controlled by the fuel level or engine load. The injection valve can be controlled by controlling an electromagnetic valve (not shown) coupled to the injection valve. The injection valve may not inject all of the fuel supplied to it and can return a portion of the supplied fuel to the fuel tank via a return path, for example, the return channel 218.

[0045] The high-pressure fuel reserve 210 can also contain one or more temperature sensors to detect the fuel temperature and one or more pressure sensors to detect the fuel pressure. It can also contain one or more relief valves that, when opened, reduce the pressure in the high-pressure fuel reserve if it exceeds the setpoint and return the excess fuel to the fuel tank via a fuel return line.

[0046] Various other modifications or adaptations can also be made to the exemplary systems described above. For example, the fuel channels (e.g., 204, 208, 218, 212a-d) can contain one or more filters, pumps, pressure sensors, temperature gauges, and blow-off valves. The fuel channels can include one or more lines. There can be one or more fuel cooling systems. The intake duct 222 can contain one or more air filters, turbochargers, and storage tanks. The engine can contain one or more engine cooling fans, cooling circuits, spark plugs, valves, and controls. The engine can be connected to an exhaust duct.

[0047] The specific routines described in the flowcharts below can represent one or more of a range of control strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various steps or functions shown can be executed in the sequence shown, in parallel, or, in some cases, omitted. Similarly, the processing order is not strictly necessary to realize the features and benefits of the examples described here, but it is provided for better illustration and description. The steps or functions shown can be executed repeatedly during engine operation, depending on the strategy employed, even if this is not explicitly shown. Furthermore, these figures can graphically represent code to be programmed into the machine-readable storage medium in an electronic control unit or control system.

[0048] Fig. Figures 3-6 show overview flowcharts of exemplary routines or procedures for calibrating fuel injectors in a vehicle control system or vehicle control unit, for example an engine control unit (ECU), or in a fuel injection system, as found in Fig. 1-2 is shown, and can be implemented.

[0049] Fig. Figure 3 illustrates an example fuel injector calibration routine (FICR).

[0050] At 302, the control unit (e.g., 12 & 226) receives input signals from various vehicle sensors regarding engine operating conditions. For example, the control unit can obtain information from the engine speed signals (N e ) of the engine speed sensor (e.g. 242), from the throttle opening angle signals (O A ) of the throttle position sensor (e.g. 238) and from the airflow signals (Q a) of the air flow meter (e.g., 240). In some examples, the input signals may include intake air pressure, the predetermined number of injections to be performed for injector calibration, etc.

[0051] At 304, the control unit determines whether the motor is in a low-load operating state. The control unit can be based on N e , O a and / or Q a (e.g., N) e The routine determines whether the value is less than a predetermined limit A) and whether the motor is in a low-load operating state. If the motor is in a low-load operating state, the routine advances to step 306; otherwise, the routine ends.

[0052] At 306, the control unit determines whether the engine temperature (T eThe engine temperature is greater than or equal to a predetermined limit B (e.g., 80°C). The engine temperature can be detected directly using sensors positioned in the engine, estimated from other acquired signals, such as the acquired engine coolant temperature, or estimated from or based on various other vehicle parameters. If the engine temperature is greater than or equal to a predetermined limit B, the routine advances to step 308; otherwise, the routine terminates. This step ensures that the injector calibration injections are performed when the engine temperature has stabilized. Under certain conditions, it may be advantageous to avoid or minimize injector calibration during low engine temperature conditions, such as during engine start-up, as the engine temperature can fluctuate significantly.Fluctuating engine temperature can affect the amount of fuel injected at a given pressure, leading to inaccurate fuel metering and ultimately degrading calibration results. Alternatively, the calibration can attempt to account for engine temperature, thus enabling calibration over a wider range of operating conditions.

[0053] At 308, the control unit determines whether a period of time has elapsed since the last injector calibration (t elap ) and a renewal event is greater than or equal to a predetermined threshold C (e.g., 10 min). If t elap If the value C is greater than or equal to the limit, the routine advances to step 310; otherwise, the routine ends. In this way, it may be possible to limit or reduce the frequency of injector calibration.

[0054] At 310, the control unit initiates a calibration injection sequence (e.g. Fig. 4) run over a predetermined number K (e.g., three times). The routine can also determine the sequence in which the injectors are to be triggered in the calibration injection sequence. It can further include a counting mechanism to track the triggering of the injectors and to ensure that the injection passes through all injectors before advancing to the next calibration injection sequence. For example, on 4-cylinder engines with 4 injectors, the routine can determine in advance that the calibration proceeds in the following sequence for a calibration injection sequence: injector no. 1, no. 2, no. 3, no. 4, and that the calibration injection sequence can be repeated three times in an injector calibration routine. The routine can also determine that the injector calibration routine should run after a predetermined time has elapsed (e.g.,The routine can be repeated (e.g., 10 minutes) after the last injector calibration routine has finished. For example, the routine can run a calibration injection routine to calibrate injector No. 1 at the earliest opportunity, such as after the engine starts and the engine temperature has stabilized. It can then proceed to calibrate injectors No. 2, No. 3, and No. 4 at the next available opportunities. The routine can also determine that the injector calibration routine can be repeated, for example, after a predetermined amount of time (e.g., 10 minutes) has elapsed since the last calibration cycle, or as needed, such as when a specific triggering event occurs or when engine operating conditions indicate a need to recalibrate the injectors.Examples of such conditions include when the engine temperature has changed above a predetermined limit since the last injection calibration routine, or when an exhaust component sensor detects that an exhaust component exceeds predetermined limits.

[0055] At 312, the control unit runs an injector correction coefficient calibration and renewal routine for each injector (e.g. Fig. 5) For example, if the engine is a four-cylinder engine and each cylinder has an injector, the injector correction coefficient calibration and renewal routine can be run four times, once per injector.

[0056] Fig. Figure 4 shows an example calibration injection routine that can be used as a subroutine for the injector calibration routine (e.g., in Fig. 3 shown).

[0057] At 402, the control unit (e.g., 12, 226) requests the high-pressure fuel supply pump (e.g., 206) to perform extra pump strokes, increase the pump stroke frequency, and / or enlarge a pump stroke for at least one stroke, so that the fuel pressure in the high-pressure fuel reserve (e.g., 210) reaches a predetermined target calibration pressure (P). m ) reached, which regarding Fig. 6 is described further. As described therein, the amount of the increase in pump operation may be due to engine speed, engine load, charging operation, intake charge pressure, a number of calibration injections (for the engine or for each injector) and / or other operating conditions.

[0058] At 404, the control unit switches off the high-pressure fuel supply pump, so that no more fuel is supplied to the high-pressure fuel reserve (e.g. 210).

[0059] In the 406, the control unit executes a series of fuel injections in a predetermined sequence (e.g., injector no. 1, injector no. 2, injector no. 3, injector no. 4, or in a firing order prescribed for the engine) and repeats the sequence a predetermined number L times (e.g., 3 engine cycles, with each injector operating at least once during each engine cycle), while monitoring the fuel pressure (P) profile as a function of time or injection events in the high-pressure fuel reserve. The injection sequence can be timed so that at the end of the injections P, a normal operating target pressure (P0) is reached. n ) reached or falls below these, where P n a desired target fuel pressure for the high-pressure fuel reserve during normal fuel injection processes.

[0060] In some examples, the routine can monitor the fuel pressure in the high-pressure fuel reserve. In other examples, after completing a calibration injection sequence, the routine can also, based on operating conditions (which may include engine operating conditions), restore the fuel pressure in the high-pressure fuel reserve to a normal operating target pressure (Pn) before the start of the next calibration injection sequence.

[0061] In some examples, the routine can minimize or reduce the number of actuations required to raise the fuel pressure in the high-pressure reserve to a setpoint, for example, the target calibration pressure (P). m ), is used because actuating the pump increases operating losses. In a specific example, the routine can use a single stroke to raise fuel pressure in the high-pressure fuel reserve to achieve the target calibration pressure (P). m ) to reach.

[0062] Fig. Figure 5 shows an exemplary injector correction coefficient calculation and renewal routine for an injector i (e.g., i=1, 2, 3, or 4 in a four-cylinder engine), which is implemented as a subroutine in an injector calibration routine (e.g., Fig. 3) can be used.

[0063] At 502, the control unit calculates the fuel pressure drop (ΔP). ij ) due to each injection by the i-th injector (e.g., J=1, 2, 3..9, if each injector is injected three times during a calibration injection cycle and the calibration injection cycle is run three times during a calibration event). ΔP ij corresponds to the pressure drop in the high-pressure fuel reserve due to injection by the i-th injector during the j-th injection.

[0064] Various engine operating conditions or events can influence the manifold pressure measurements and may affect the calculation of the fuel pressure drop ΔP. ij , which is assigned to each injection. Therefore, in some examples, the routine can correlate the fuel pressure with different engine operating conditions, which are determined by means of different sensors (e.g., in 302 in Fig. Three parameters are recorded. For example, the transient pressure pulsations generated by injector actuation can temporarily affect the manifold pressure measurement, thus impacting calibration accuracy. Therefore, the fuel pressure sampling method can be selected to mitigate the transient effects of injector actuation. Additionally or alternatively, if the injector actuation timing is correlated with the manifold pressure measurement, temporary pressure drops caused by injector actuation can be taken into account when determining the injector calibration values.Similarly, the opening and closing of the intake and / or exhaust valves, intake pressure and / or exhaust pressure, crankshaft angle position, camshaft position, spark ignition and engine combustion can also influence the distributor pipe pressure measurements and can be correlated with the distributor pipe pressure measurements in order to precisely calculate the distributor pipe pressure drop assigned to the individual injections.

[0065] Continue with Fig. 5. The control unit calculates an actual Q in each injection at 504. ij Fuel quantity injected using the following equation: Qij=ΔPij / C where C is a predetermined constant coefficient for converting the amount of fuel pressure drop into the amount of fuel injected.

[0066] At 506, the control unit determines the average quantity of fuel actually injected by the injector i (Q). i ) using the following equation: Qi=(∑1jQij) / j where j is the number of injections by the injector i (e.g. j=1, 2, 3..9) when each injector is injected three times during a calibration injection cycle and the calibration injection cycle is performed three times during a calibration event.

[0067] At 508, the control unit determines the target quantity of fuel that should have been injected by the injector i (Q). c ), for example, based on engine operating conditions.

[0068] At 510, the control unit calculates the correction coefficient for the injector i (e.g. i=1, 2, 3 or 4 for a four-cylinder engine) using the following equation: ki=Qc / Qi

[0069] At 512, the control unit renews the correction coefficient for the injector i with the newly calculated k. i The newly calculated k ireplaces, for example, an old k i , which is stored in a battery-powered memory (KAM) of the control unit, which can currently be used to calibrate the injector i.

[0070] Fig. Figure 6 shows a routine for determining the target calibration pressure (P m ) in the high-pressure fuel reserve (e.g. 210).

[0071] At 602, the control unit receives an input specifying the number of injectors to be calibrated, the base fuel quantity, or the target fuel quantity to be delivered by each injector during each injection (Q). c ) is to be injected, and provides the frequency with which each injector is to be injected during a calibration injection cycle.

[0072] At 604, the control unit calculates the target calibration pressure (Pm) in the high-pressure fuel reserve, which is required so that after a calibration injection cycle the fuel pressure in the high-pressure fuel reserve tank returns to the target normal operating pressure (P). n ) falls, for example using the following equation: Pm=Pn+∑1i(∑1jΔPij) where P n The target normal operating pressure is ΔP ij The pressure drop during injection j for the injection valve i is.

[0073] In some examples, the routine can determine the target calibration pressure (P). m) based on different engine operating conditions or operating conditions. For example, at higher torque, higher load and / or higher engine speed, the amount of fuel injected per injection may be relatively larger than at lower torque or lower load (or the injection duration may be limited), therefore the target calibration pressure (P) m ) depending on the number of injections to be performed for a given injector calibration routine, may be increased accordingly. Furthermore, if the intake charge pressure is higher, a relatively larger pressure drop per injection can be used to improve accuracy, and this again translates into a higher target calibration pressure (P). m ) which also depends on the number of injections to be performed. Thus, in some examples, the parameters used to determine the target calibration pressure (P) can be... mThe engine operating conditions used may include a predetermined number of injections to be performed for an injector calibration routine. For example, if the number of predetermined injections for an injector calibration routine increases, the routine may also include the target calibration pressure (P). m ) raise.

[0074] Fig. Figure 7 is a graph showing the fuel injection timing, the fuel pressure change in the high-pressure fuel reserve (e.g., 210), and the fuel pump strokes for a prophetic example of a calibration injection cycle (as described by Fig. 4 illustrated). Before a calibration injection cycle, the fuel pressure in the high-pressure reserve tank is set to the normal target operating pressure (P). n) is maintained and the normal pump strokes are performed. At the beginning of a calibration injection process, more or larger pump strokes are performed and the fuel tank in the high-pressure fuel reserve tank (P) is allowed to reach the target fuel pressure (P). m ) reach, which is via P n lies and which, for example, after a in Fig. The routine shown in Figure 6 is determined. During the calibration injection cycle, injections are performed sequentially, for example, for each injector, and the fuel pressure (P) in the high-pressure reserve tank is monitored. In this example, each injection has an injection time τ and a target injection quantity Q. c Q c can be derived from a characteristic map stored in the ROM of a control unit based on N e , Q A and / or Q a τ can be determined. For example, τ can be determined using the following equation: τ=QckiPmP where Q cThe target injection quantity for each injection is K i The correction coefficient for the injector i is P, and the fuel pressure in the high-pressure fuel reserve at the time of injection is P. m The target fuel pressure for the high-pressure fuel reserve is given by τ. Since P changes each time an injector injects fuel, τ can change as a function of time. Since k i Since τ can change for each injector, it can also change as a function of the injector.

[0075] In one example, injector calibration injection events can be performed during operation at low load (e.g., < 30% of maximum engine load). For each calibration injection event, the manifold pressure is raised to a pressure above normal operating pressure by performing additional or larger pump strokes, for example, to a pressure of 10 to 20 bar above normal operating pressure. Fuel injections are then performed until the manifold pressure drops back to normal operating pressure. The calibration injection event can be repeated several times. The manifold pressure drops due to the fuel injections are monitored during each calibration fuel injection event. A correction coefficient for each cylinder can then be calculated from the average fuel pressure drop caused by each injector per injection.The correction coefficients are stored in a battery-powered memory (KAM), where the calibration can be performed several times while the vehicle is driven.

[0076] It should be noted that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. The specific routines described herein can represent one or more of a number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various steps or functions shown can be executed in the sequence shown, in parallel, or, in some cases, omitted. Similarly, the processing order is not strictly necessary to realize the features and benefits of the examples described herein, but is provided for better illustration and description. One or more of the steps or functions shown can be executed repeatedly, depending on the strategy employed.Furthermore, the described steps can graphically represent a code to be programmed into the machine-readable storage medium in the engine control system.

[0077] It is understood that the configurations and routines disclosed herein are exemplary and that these specific designs should not be considered limiting, as numerous modifications are possible. For example, the above technology can be applied to V6, I-4, I-6, V12, opposed-piston, and other internal combustion engine designs.

Claims

[1] Method for controlling fuel injection of a direct injection fuel system, wherein the direct injection fuel system comprises a fuel pump (202, 206) and several fuel injectors (214a, 214b, 214c, 214d), the method comprising: Variable operation of the fuel pump (202, 206) to maintain a fuel pressure at a selected pressure; Temporarily increasing the pump operation to raise the pressure sufficiently above the selected pressure, and then reducing the pump operation; During at least one fuel injection following the reduction of pump operation: Correlation of the fuel pressure drop during the at least one fuel injection with a fuel injector operation, wherein a predetermined number of fuel injections for each fuel injector (214a, 214b, 214c, 214d) in an engine (10) is performed following and near the reduction of pump operation, and Adjusting the fuel injector operation based on correlation. [2] Method according to claim 1, characterized by , that the fuel pump (202, 206) temporarily operated with an increased pump stroke for at least one stroke and then operated with a reduced pump stroke for several pump strokes after operation with the increased pump stroke or temporarily operated with an increased pump stroke frequency and then operated at a reduced pump stroke frequency for several pump strokes after operation at the increased pump stroke frequency. [3] Method according to claim 2, characterized bythat the temporary operation takes place during lower engine loads, preferably with an engine throttle opening below a first limit. [4] Method according to claim 1 or 3, which further comprises pressurizing intake air drawn into the engine (10) and mixing the pressurized intake air with fuel from the at least one fuel injection. [5] Method according to claim 1 or 4, characterized by , that the amount of pump operation used to raise fuel pressure is changed with an operating condition. [6] Method according to claim 5, characterized by that the operating condition includes an intake air pressure, an engine speed, or a predetermined number of injections. [7] Method according to claim 1 or 3, characterized by, that the fuel pump (202, 206) is temporarily operated with an enhanced pumping stroke for at least one stroke and is then deactivated for several pumping strokes after operation with the enhanced pumping stroke. [8] Method according to claim 7, characterized by , that the fuel pump (202, 206) is a high-pressure fuel pump (206) which pressurizes fuel after it has been pressurized by a low-pressure lift pump (202). [9] Method according to claim 8, characterized by , that during at least one fuel injection after reducing the pump operation, the fuel pressure decrease during the at least one fuel injection is correlated with injector characteristics. [10] Method according to claim 1 or 3, which further a maintenance of fuel injection operation for each fuel injector (214a, 214b, 214c, 214d) in the engine (10) during an engine cycle of correlating or includes operating the fuel pump (202, 206) to raise the fuel pressure sufficiently above the selected pressure by performing a single pump stroke. [11] Method according to any one of claims 1 to 10, wherein a target calibration pressure is determined as a function of engine load, engine speed and the number of injections to be performed. [12] Method according to any one of claims 1 to 10, wherein calibration is only performed if a motor temperature is greater than or equal to a predetermined second limit value. [13] Method according to any one of claims 1 to 10, wherein the calibration is started only after a predetermined time interval has elapsed or when a renewal event occurs. [14] Method according to one of the preceding claims, wherein the correlation is additionally carried out taking into account a crank angle position, a cam position, an intake valve position, an exhaust valve position or an ignition timing. [15] Method according to any one of claims 1 to 10, wherein one or the calibration is performed sequentially for each fuel injector (214a, 214b, 214c, 214d) in a predetermined sequence and repeatedly. [16] Method for controlling fuel injection of a direct injection fuel system, wherein the direct injection fuel system comprises a fuel pump (202, 206), the method comprising: Variable operation of the fuel pump (202, 206) to maintain a fuel pressure at a selected pressure, During operating conditions of low engine load, temporarily increase the pumping operation to raise the fuel pressure sufficiently above the selected pressure, and then reduce the pumping operation; during at least one fuel injection following the reduction of pump operation, the correlation of the fuel pressure drop during the at least one fuel injection with a fuel injector operation, wherein a predetermined number of fuel injections for each fuel injector (214a, 214b, 214c, 214d) in the engine (10) is performed following and near the reduction of pump operation; Adapting fuel injector operation based on correlating and Pressurizing intake air drawn into the engine (10) and mixing pressurized intake air with fuel from at least one fuel injection. [17] Method according to claim 16, which further comprises operating the fuel pump (202, 206) to raise the fuel pressure sufficiently above the selected pressure by performing a single pump stroke. [18] Method according to claim 16, characterized by , that the fuel pump (202, 206) is temporarily operated with an enhanced pumping stroke for at least one stroke and is then deactivated for several pumping strokes after operation with the enhanced pumping stroke. [19] Engine system, which includes: a direct injection fuel system comprising a low-pressure lift pump (202), a high-pressure fuel pump (206) and several fuel injectors (214a, 214b, 214c, 214d) directly connected to respective cylinders (30) of an engine (10); and a control unit (216) for variable operation of the high-pressure fuel pump (206) in order to maintain a fuel pressure at a selected pressure, wherein During operating conditions of low engine load, the control unit (216) temporarily increases the high-pressure pump operation to raise the fuel pressure sufficiently above the selected pressure, and then reduces the high-pressure pump operation; and During at least one fuel injection following the reduction of pump operation, the fuel pressure decrease during the at least one fuel injection is correlated with a fuel injector operation, wherein a predetermined number of fuel injections for each fuel injector (214a, 214b, 214c, 214d) in the engine (10) is performed following and near the reduction of pump operation, wherein the control unit (216) continues to adapt the fuel injector operation based on the correlation, pressurizes the intake air drawn into the engine (10) and mixes the pressurized intake air with fuel from the at least one fuel injection. [20] Motor system according to the preceding claim, wherein the high-pressure fuel pump (206) is temporarily operated with an enhanced pumping stroke for at least one stroke and is then deactivated over several pumping strokes after operation with the enhanced pumping stroke, or the variable operation of the high-pressure fuel pump (206) includes raising the fuel pressure sufficiently above the selected pressure by performing a single pumping stroke.

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