METHOD AND SYSTEM FOR ADJUSTING ENGINE WATER INJECTION

Abstract

Methods for an engine, including: During an initial state, in response to an engine dilution request, intake manifold injection of water to a closed intake valve; and During a second state, in response to engine knocking, intake manifold injection of water away from an open intake valve, whereby during the second state, relative to the first state, a larger proportion of the injected water remains in liquid form after injection.

Description

Area

[0001] The present description generally concerns methods and systems for injecting water into an engine based on a dilution requirement and cooling requirement of the engine. General state of the art / Summary

[0002] Internal combustion engines can incorporate water injection systems that inject water from a storage tank into a variety of locations, including an intake manifold upstream of the engine cylinders or directly into the engine cylinders. For example, German patent applications DE 10 2015 208 476 A1 and DE 10 2014 222 466 A1 depict internal combustion engines with water injection systems. Injecting water into the engine intake air can increase fuel efficiency and engine power while reducing engine emissions. When water is injected into the engine intake or into the cylinders, heat is transferred from the intake air and / or engine components to the water. This heat transfer causes evaporation, resulting in cooling. Injecting water into the intake air (e.g., into the intake manifold, ports, etc.) lowers both the intake air temperature and the combustion temperature in the engine cylinders.Cooling the intake air charge can reduce knocking tendency without enriching the air-fuel ratio. This can also allow for a higher compression ratio, advanced ignition timing, and reduced exhaust gas temperature. As a result, fuel efficiency is increased. Furthermore, a higher volumetric efficiency can lead to increased torque. Additionally, a lower combustion temperature with water injection can reduce NOx emissions, while a more efficient fuel mixture can reduce carbon monoxide and hydrocarbon emissions.

[0003] As explained above, water can be injected into various locations, including the intake manifold, the intake ports of engine cylinders, or directly into the engine cylinders. However, inventors have recognized that the benefits of water injection can be limited depending on the injection location and the engine operating conditions at the time of injection. For example, manifold water injection can be used to provide charge cooling. However, the charge cooling benefit can be limited if the ambient humidity is high. Another example is manifold water injection, which can provide charge dilution. However, if the injected water does not evaporate quickly enough, it can form a puddle, potentially leading to misfires.If the benefits of water injection are not fully utilized, fuel efficiency and engine stability may be compromised.

[0004] The object of the present invention is to provide improved methods for controlling the injection of water. This object is achieved by the independent claims. Preferred embodiments of the present invention are the subject of the dependent claims.

[0005] In one example, the problems described above can be addressed by a procedure for an engine comprising, during a first condition, in response to an engine dilution requirement, port injection of water towards a closed intake valve; and during a second condition, in response to engine knocking, port injection of water away from an open intake valve. In this way, port water injection can be used to increase engine dilution, thereby reducing pumping losses and increasing charge air cooling, reducing engine knocking, and increasing engine efficiency by adjusting the direction and timing of the injection.

[0006] As an example, an engine can be configured with a first set of port fuel injectors angled towards the intake valve and a second set of port fuel injectors angled away from the intake valve (e.g., towards the intake manifold). During knock-limited combustion conditions, such as at high loads, water can be injected via the second set of port fuel injectors while the intake valves are open. This results in a larger proportion of the water being injected in liquid form, thus improving the charge-cooling effect of the injection. In contrast, during dilution-limited combustion conditions, such as at low loads, water can be injected via the first set of port fuel injectors when the intake valves are about to close and the valve surface is hot.This leads to flash evaporation of the water upon contact with the surface. Consequently, a larger proportion of the injected water rapidly converts to vapor, thus enhancing the charge dilution effect of the injection. Additionally, water injection via the first set of injection devices can be detected by dilution (or concentration) sensors (e.g., IAO2), while water injection via the second set of injection devices can be detected by temperature sensors.

[0007] In this way, different advantages for water injection in an engine can be achieved at a given water injection point by varying the direction and timing of the injection. The technical effect of injecting water into the intake manifold onto the hot surface of a closed intake valve, such as at bottom dead center (BDC) of an intake stroke, in the same direction as the airflow, is that the injected water can essentially vaporize instantly. Consequently, the charge dilution effect of water injection can be increased, while the charge cooling effect is reduced. Injecting water into the intake manifold when the valve surface is hot reduces water pooling, thereby lowering the risk of water-induced misfires.The technical benefit of injecting water into the intake manifold, away from an open intake valve and in the opposite direction of airflow, is that the turbulence from the high-velocity airflow can be advantageously used to improve the atomization of the injected water before the air-water mixture is delivered to the engine cylinders. As a result, the charge-cooling effect of water injection can be enhanced while reducing the charge-dilution effect. By selecting a water injection detection mode based on whether the benefit of water injection is being utilized (e.g., charge cooling or dilution), any water injection errors can be more reliably identified and compensated for. Overall, the benefits of water injection can be extended across a wide range of engine operation, thereby improving engine performance.

[0008] It is understood that the foregoing summary is provided to introduce, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to mention important or essential features of the claimed subject matter, the scope of which is defined solely in the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that remedy the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows a schematic representation of an engine system that includes a water injection system. Fig. Figure 2 shows a flowchart of a process for injecting water into an engine based on an engine dilution or cooling requirement. Fig. Figure 3 shows a flowchart of a procedure for selecting a water injection mode based on engine operating parameters. Fig. Figure 4 shows a diagram illustrating exemplary settings of the water injection parameters based on various engine operating conditions. Fig. Figure 5 shows an exemplary map of the benefits of water injection as a function of the engine speed / load ranges. Fig. Figure 6 shows a progression of exemplary intake manifold water injection timings in relation to the intake valve position in an engine cycle. Fig. Figure 7 shows exemplary water injection settings for dilution control and corresponding water acquisition modalities. Fig. Figure 8 shows exemplary water injection settings for knock control and corresponding water sensing modalities. Detailed description

[0009] The following description concerns systems and methods for injecting water at a selected point in an engine based on engine operating conditions and the adjustment of water injection parameters, as well as engine operating parameters based on a measured water injection error. A schematic representation of an exemplary vehicle system that includes a water injection system is shown in Fig. Figure 1 shows water injection devices. Water injection devices can be located in an engine intake manifold, in intake ports of the engine cylinders facing the intake valves, in intake ports facing away from the intake valves, and / or be directly coupled to each individual cylinder. An engine control unit can be configured to execute a control routine, such as the exemplary routines from the Fig. 2-3, to select one or more water injection points based on engine operating conditions to provide benefits for charge air cooling, engine component cooling, and / or engine dilution. The control can refer to a map, such as the example map from Fig. 5, to identify areas of engine operation where water injection can be used to improve engine efficiency. The control can also refer to the example map from Fig. 6 to identify a port water injection timing that provides dilution control or head control. The controller can further select a water injection detection mode based on the water injection device selection. Fig. 4, Fig. 7 and Fig. Figure 8 provides graphical examples of adjusting the water injection quantity and location based on engine operating conditions and estimating water injection errors by selecting a water injection mode based on the water injection device selection. This allows water injection errors to be determined more accurately and compensated for appropriately.

[0010] Regarding the characters, Fig. Figure 1 shows a schematic representation of an embodiment of a water injection system 60 and an engine system 100 in a motor vehicle 102. In the illustrated embodiment, the engine 10 is a turbocharged engine coupled to a turbocharger 13, including a compressor 14, which is driven by a turbine 16. In particular, fresh air is fed into the engine 10 along the intake duct 142 via the air cleaner 11 and flows to the compressor 14. The compressor can be a suitable intake air compressor, such as a compressor driven by an electric motor or a drive shaft. In the engine system 100, the compressor is shown as a turbocharger compressor, which is mechanically coupled to the turbine 16 via a shaft 19, the turbine 16 being driven by expanding engine exhaust gases.In one embodiment, the compressor and turbine can be coupled within a twin-scroll turbocharger. In another embodiment, the turbocharger can be a variable geometry turbocharger (VGT turbocharger), in which the turbine geometry is actively varied as a function of the engine speed and other operating conditions.

[0011] As in Fig. As shown in Figure 1, the compressor 14 is coupled to a throttle valve (e.g., the intake throttle) 20 via a charge air cooler (CAC) 18. The CAC can be, for example, an air-to-air or air-to-coolant heat exchanger. The throttle valve 20 is coupled to the engine intake manifold 22. The warm, compressed air charge from the compressor 14 enters the inlet of the CAC 18, cools as it flows through the CAC, and then exits to reach the intake manifold 22 via the throttle valve 20. In the Fig. In the embodiment shown in Figure 1, the manifold charge pressure is detected by a manifold air pressure (MAP) sensor 24, and the charge pressure is detected by a charge pressure sensor 124. A compressor bypass valve (not shown) can be coupled in series between the inlet and outlet of the compressor 14. The compressor bypass valve can be a normally closed valve configured to open under selected operating conditions to release excess charge pressure. For example, the compressor bypass valve can open during decreasing engine speed conditions to prevent compressor surging.

[0012] The intake manifold 22 is coupled to a series of combustion chambers or cylinders 180 by a series of intake valves (not shown) and intake ports (e.g., intake openings) 185. As shown in Fig. As shown in Figure 1, the intake manifold 22 is located upstream of all combustion chambers 180 of the engine 10. Sensors, such as a manifold charge temperature (MCT) sensor 23 and an air charge temperature (ACT) sensor 125, may be included to determine the temperature of the intake air at the respective points in the intake duct. In some examples, the MCT and ACT sensors may be thermistors, and the output of the thermistors may be used to determine the temperature of the intake air in the duct 142. The MCT sensor 23 may be positioned between the throttle 20 and the intake valves of the combustion chambers 180. As further described below with reference to Fig. As described in Figure 3, the output of the MCT sensor 33 can be monitored before and after the injection of water into the intake manifold in response to a charge cooling request. Since the release of water into the intake manifold causes charge cooling, the amount of water actually released or discharged into the engine intake manifold can be learned as a function of the change in the MCT after the water injection command. Thus, the amount of water commanded to be released may differ from the amount of water actually released due to problems such as water injection device malfunctions, a clogged or contaminated water injection nozzle, a faulty water injection device solenoid coil, a faulty water injection device valve, temperature and / or pressure effects on water injection, etc.Additionally, the amount of water released may differ from the amount of water dispersed or evaporated in the engine. As explained herein, the amount of water that evaporates and contributes to charge dilution can be determined based on the output of an intake oxygen sensor 34 coupled to the engine intake manifold downstream of the intake throttle. The ACT sensor 125 may be located upstream of the CAC 18, as shown; however, in alternative embodiments, the ACT sensor 125 may be positioned upstream of the compressor 14. The air temperature can also be used in conjunction with an engine coolant temperature (ECT) to calculate, for example, the amount of fuel supplied to the engine.In addition, additional temperature sensors, such as engine coolant (ECT) sensor 25, may be included to determine whether the intake manifold surface temperature and / or an intake valve surface temperature for intake manifold water injection onto the manifold / valve surface is high enough, as further described below with reference to . Fig. 3 described. Each combustion chamber can further include a knock sensor 183 for identifying anomalous combustion events. Outputs from the knock sensors of each combustion chamber 180 can be used to detect misdistribution of water into each combustion chamber 180 by injecting water upstream of all combustion chambers 180. In alternative embodiments, one or more knock sensors 183 can be coupled to selected locations on the engine block.

[0013] The combustion chambers are further coupled to the exhaust manifold 136 via a series of exhaust valves (not shown). The combustion chambers 180 are covered by a cylinder head 182 and are coupled to fuel injection devices 179 (while in Fig. (Where only one fuel injection device is shown, each combustion chamber includes a fuel injection device coupled to it.) Fuel can be supplied to the fuel injection device 179 by a fuel system (not shown) that includes a fuel tank, a fuel pump, and a fuel distributor. The combustion chamber 180 also draws in water and / or water vapor, which can be injected into the engine intake or the combustion chambers 180 themselves by a plurality of water injection devices 45-48. In the illustrated embodiment, the water injection system is configured to inject water downstream of the throttle and into the intake manifold 22 via the injection device 45 into one or more intake ports (e.g., openings) 185 and away from one or more intake ports (e.g., openings) 185 via the injection device 48.Openings) 185 via the injection device 46 and directly into one or more combustion chambers 180 via the injection device 47. In another embodiment, the water injection system can be configured to inject water at additional locations. For example, the water injection system can be configured to inject water upstream of the throttle 20. In the illustrated embodiment, the injection device 48 is arranged in the intake lines such that the injection device is angled towards and opposite the intake valve of the cylinder to which the intake line is attached. As a result, the injection device 48 can inject water directly onto the intake valve (e.g., while the intake valve is closed). As further described below with reference to . Fig. As described in Figure 3, this injection device arrangement can lead to rapid evaporation of the injected water and increase the dilution benefit for using the water vapor as EGR to reduce pumping losses. In contrast, the injection device 46 can be angled away from the inlet valve and arranged to inject water against the inlet airflow direction through the intake duct, so that the dispersed water, mixed with the air, can be directed to an open inlet valve. As a result, more injected water can be carried in the airflow, enhancing the cooling benefit.

[0014] Although in Fig. While only one representative injection device 46, injection device 47, and injection device 48 are shown, each combustion chamber 180 and intake manifold 185 can include its own injection device. In alternative embodiments, a water injection system can include water injection devices arranged at one or more of these positions. For example, in one embodiment, an engine can include only the water injection device 45. In another embodiment, an engine can include each of the water injection device 45, the water injection devices 46 and 48 (one at each intake manifold), and the water injection devices 47 (one at each combustion chamber). The water can be supplied to the water injection devices 45-48 by the water injection system 60, as described below.

[0015] In the illustrated embodiment, a single exhaust manifold 136 is shown. In other embodiments, however, the exhaust manifold can have a plurality of exhaust manifold sections. Configurations with a plurality of exhaust manifold sections can allow wastewater from different combustion chambers to be routed to different locations in the engine system. According to the illustration, a broadband exhaust gas oxygen (UEGO) sensor 126 is coupled to the exhaust manifold 136 upstream of the turbine 16. Alternatively, the UEGO sensor 126 can be replaced by a binary exhaust gas oxygen sensor.

[0016] As in Fig. As shown in Figure 1, exhaust gas is routed from one or more exhaust manifold sections to the turbine 16 to drive the turbine. If reduced turbine torque is desired, some exhaust gas can instead be routed through a wastegate (not shown), thus bypassing the turbine. The combined flow from the turbine and the wastegate then flows through the emission control device 70. In general, one or more emission control devices 70 can include one or more catalysts for exhaust aftertreatment, configured to catalytically treat the exhaust gas stream and thereby reduce the amount of one or more substances in the exhaust gas stream.

[0017] The treated exhaust gas from the emission control device 70 can be discharged wholly or partially into the atmosphere via an exhaust pipe 35. Depending on the operating conditions, however, some exhaust gas can instead be diverted to an exhaust gas recirculation (EGR) channel 151, through an EGR cooler 50 and an EGR valve 152, to the compressor inlet 14. In this way, the compressor is configured to receive exhaust gas taken downstream of a turbine 16. The EGR valve 152 can be opened to receive a controlled amount of cooled exhaust gas to the compressor inlet for desired combustion and emission control performance. This enables the engine system 100 to provide external low-pressure (LP) EGR. The rotation of the compressor, in addition to the relatively long LP EGR flow path in the engine system 100, provides excellent homogenization of the exhaust gas into the intake air charge.Furthermore, the arrangement of the EGR take-off and mixing points provides effective cooling of the exhaust gas for increased available EGR mass and improved performance. In other embodiments, the EGR system can be a high-pressure EGR system with an EGR channel 151 that provides a connection from upstream of the turbine 16 to downstream of the compressor 14. In some embodiments, the MCT sensor 23 can be positioned to determine the manifold charge temperature and can include recirculated air and exhaust gas through the EGR channel 151.

[0018] The intake gas oxygen sensor 34 is configured to provide an estimate regarding the oxygen content of fresh air received in the intake manifold.

[0019] Additionally, when the EGR is flowing, a change in the oxygen concentration at the sensor can be used to derive an EGR flow rate and for precise EGR flow control. In the illustrated example, the oxygen sensor 34 is positioned downstream of the throttle 20 and downstream of the charge air cooler 118. However, in alternative embodiments, the oxygen sensor can be positioned upstream of the throttle. The inlet oxygen sensor 34 can be used to estimate an inlet oxygen concentration and derive an amount of EGR flow through the engine based on a change in the inlet oxygen concentration when the EGR valve 152 opens.Similarly, the inlet oxygen sensor 34 can be used to estimate an inlet oxygen concentration and to derive an engine dilution or a change in inlet air humidity based on a change in the inlet oxygen concentration after an intake manifold water injection.

[0020] Specifically, the change in the sensor output when the EGR valve opens or when water is injected into the intake manifold is compared to a reference point where the sensor operates without EGR or water injection (zero point). Based on the change (e.g., reduction) in the oxygen quantity from the operating time without EGR or water injection, the EGR current or water flow currently supplied to the engine can be calculated. For example, a pump current (Ip) is output by the sensor when a reference voltage (Vs) is applied to the sensor. The change in oxygen concentration can be proportional to the change in the pump current output (delta Ip) by the sensor in the presence of EGR or water relative to the sensor output in the absence of EGR or water (zero point).Further EGR control can be implemented based on a deviation of the estimated EGR flow from the expected (or target) EGR flow. This is similar to what is described in [reference to be added]. Fig. 3. If further water injection control can be carried out based on a deviation of the estimated engine dilution or humidity from an expected engine dilution or humidity after water injection.

[0021] Similarly, the exhaust gas oxygen sensor 126 is configured to provide an estimate of the oxygen content of the exhaust gas received at the intake manifold, which can vary depending on the air-fuel ratio, the alcohol content of the fuel, and the ambient humidity. As referred to in Fig. 3. If further water injection control can be carried out based on a deviation of the estimated exhaust oxygen content from an expected exhaust oxygen content, a reference voltage of the sensor can be modulated after a water injection.

[0022] It is understood that each of the intake oxygen sensor 34 and UEGO sensor 126 can be operated in numerous modes based on the engine operating conditions and, furthermore, based on the nature of the estimation performed by the sensors. For example, during engine fuel supply conditions where dilution / EGR estimation is required, the intake oxygen sensor can be operated in a nominal mode with a (fixed) reference voltage applied to the sensor, which is maintained during acquisition. During engine fuel supply conditions where an estimation of the exhaust air-fuel ratio is required, the exhaust oxygen sensor can be operated in a nominal mode with a (fixed) reference voltage applied to the sensor, which is maintained during acquisition. In one example, the reference voltage could be 450 mV.During other conditions, such as engine operating without fuel supply (e.g., during a DFSO), the intake oxygen sensor can operate in variable voltage mode when ambient humidity estimation (in the intake air charge) is required, with the reference voltage applied to the sensor being modulated. In yet another example, the sensor can operate in variable voltage mode when EGR or dilution estimation is performed while fuel vapor purging (from a fuel system canister) or positive crankshaft ventilation (of the engine crankshaft) is active. Similarly, the UEGO sensor can operate in variable voltage mode under conditions where exhaust gas dilution estimation is required following water injection.The oxygen sensor's reference voltage is modulated between the nominal reference voltage of 450 mV and a higher reference voltage of 800 mV (or 950 mV). By changing the reference voltage of the inlet oxygen sensor, or the Nernst voltage, the sensor switches from reacting with hydrocarbons in the presence of oxygen at the sensor to releasing the products of the reaction (water and carbon dioxide).

[0023] The water injection system 60 includes a water storage tank 63, a water pump 62, a collection system 72, and a water filling channel 69. In embodiments that include multiple injection devices, the water channel 61 can contain one or more valves to select between different water injection devices. As shown in Fig. As shown in Figure 1, the water stored in the water tank 63 is supplied to the water injection devices 45-48, for example, via a common water channel 61, which branches into water channels 90, 92, 94, and 96. In the illustrated embodiment, the water from the water channel 61 can be diverted by one or more of the valve 91 and channel 90 to supply water to injection device 45, by the valve 93 and channel 92 to supply water to injection device 46, by the valve 95 and channel 94 to supply water to injection device 48, and / or by the valve 97 and channel 96 to supply water to injection device 47. In addition, embodiments which include multiple injection devices may include a plurality of temperature sensors 25 near each injection device in order to determine the engine temperature at one or more water injection devices.The water pump 62 can be operated by a controller 12 to supply water to the water injection devices 45-48 via channel 61. In an alternative embodiment, the water injection system 60 can include multiple water pumps. For example, the water injection system 60 can include a first water pump 62 to pump water to a subset of injection devices (such as the injection devices 45) and a second water pump (not shown) to pump water to another subset of injection devices (such as the injection devices 46, 47, and / or 48). In this example, the second water pump can be a higher-pressure water pump, and the first water pump can be a relatively lower-pressure water pump. Furthermore, the injection system can include a self-pressurizing piston pump capable of performing both high-pressure pumping and injection.For example, one or more injection devices may include or be coupled to a self-pressure-building piston pump.

[0024] The water storage tank 63 can include a water level sensor 65, a water quality sensor 66, and a water temperature sensor 67, which can transmit information to the controller 12. For example, under freezing conditions, the water temperature sensor 67 detects whether the water in the tank 63 is frozen or available for injection. In some embodiments, an engine coolant channel (not shown) can be thermally coupled to the storage tank 63 to thaw frozen water. The water quality sensor 66 can detect whether the water in the water storage tank 63 is suitable for injection. As an example, the water quality sensor 66 can be a conductivity sensor. The level of water stored in the water tank 63, as identified by the water level sensor 65, can be transmitted to the vehicle operator and / or used to adjust engine operation.For example, a water level indicator or a marking on a vehicle dashboard (not shown) can be used to transmit the water level. In another example, the water level in water tank 63 can be used to determine whether enough water is available for injection, as further described below in relation to [reference missing]. Fig. 2 described. In the illustrated embodiment, the water storage tank 63 can be manually refilled via the water filling channel 69 and / or automatically refilled by the collection system 72 via the water tank filling channel 76. The collection system 72 can be coupled to one or more components 74 that refill the water storage tank with condensate collected from various engine or vehicle systems. In one example, the collection system 72 can be coupled to an EGR system to collect water that condenses from exhaust gas flowing through the EGR system. In another example, the collection system 72 can be coupled to an air conditioning system. The manual filling channel 69 can be fluid-coupled to a filter 68 that can remove minor impurities contained in the water that could potentially damage engine components.

[0025] Fig. Figure 1 further shows a control system 28. The control system 28 can be communicatively coupled to various components of the engine system 100 in order to carry out the control routines and actions described herein. As in Fig. As shown in Figure 1, the control system 28 can, for example, include an electronic digital controller 12. The controller 12 can be a microcomputer, including a microprocessor unit, input / output ports, an electronic storage medium for executable programs and calibration values, direct access memory, keep-alive memory, and a data bus. As shown, the controller 12 can receive inputs from a variety of sensors 30, which may include user inputs and / or sensors (such as for detecting a transmission gear position, accelerator pedal input (e.g., pedal position), brake input, gear selector position, vehicle speed, engine speed, mass airflow through the engine, charge pressure, ambient temperature, ambient humidity, intake air temperature, fan speed, etc.), cooling system sensors (such as an ECT sensor and sensors for detecting a fan speed, passenger compartment temperature, ambient humidity, etc.).), CAC sensors 18 (such as CAC intake air temperature sensor, ACT sensor 125, CAC exhaust air temperature sensor, MCT sensor 23, etc.), knock sensors 183 for determining the ignition of exhaust gases and / or the water distribution between cylinders, water injection system sensors (such as water level sensor 65, water quality sensor 66, and water temperature sensor 67), exhaust pressure and temperature sensors 80, 82, and others may be included. Furthermore, the control unit 12 can communicate with various actuators 32, which may include engine actuators (such as fuel injectors, an electronically controlled intake air throttle valve, spark plugs, the numerous water injectors, wastegate, EGR valve, etc.).In some examples, the storage medium may be programmed with computer-readable data representing instructions that can be executed by the processor to perform the procedures described below, as well as other variations that are intended but not specifically listed.

[0026] The controller 12 receives signals from the various sensors. Fig. 1 and suspends the various actuators Fig. 1. to adjust the engine operation based on received signals and instructions stored in a memory of the controller. For example, injecting water into the engine may involve adjusting an actuator of the injection device 45, injection device 46, injection device 47, and / or injection device 48 to inject water, and adjusting the water injection may involve adjusting the quantity or timing of water injected via settings of an injection device duty cycle. In another example, adjusting the ignition timing based on estimates of the water injection (as described below) may involve adjusting an ionization current and a discharge timing of a spark plug 184.

[0027] In this way, the systems present according to Fig. 1. An exemplary system that can be used to inject water at one or more points in an engine intake or cylinder. As mentioned above, water injection can be used to lower the temperature of the intake air entering the engine cylinders, thereby reducing knocking and increasing the engine's volumetric efficiency. Additionally, water injection can be used to increase engine dilution, thereby reducing engine pumping losses. As explained above, water can be injected at various points in the engine, including the intake manifold (upstream of all engine cylinders), the manifolds of cylinder groups (upstream of a group of cylinders, as in a V-engine), intake ports or openings of engine cylinders (into or away from an intake valve), or directly into engine cylinders.Under varying engine operating conditions, such as different engine load and / or speed conditions, it can be advantageous to inject water at one location rather than another to achieve increased charge air cooling or dilution. For example, manifold or intake port injection (from injectors angled away from the intake valves) can provide increased cooling to the engine cylinders and ports, whereas port injection (from injectors injecting onto the intake valves) can provide increased dilution.

[0028] Fig. Figure 5 presents an exemplary map 500 illustrating the various advantages of water injection in different engine operating ranges. In high-load, low-speed engine operating ranges, characterized by range 502, water injection provides a torque output advantage by increasing the volumetric efficiency. Additionally, knock resistance is increased due to an advancement of the combustion phase (i.e., advanced CA50). In high-load, high-speed engine operating ranges, characterized by range 504, water injection provides both fuel efficiency and torque output advantages due to an advancement of the borderline spark limit (BDL) and an advancement of the combustion phase (i.e., advanced CA50). This results in an improved torque-to-weight ratio.Additionally, water injection reduces the turbine inlet temperature, thereby reducing the requirement for fuel enrichment (for knock control).

[0029] In low-load engine operating ranges, characterized by the 506 range, water injection improves thermal efficiency by allowing the engine design to tolerate a higher compression ratio. Additionally, injecting water as vapor can reduce pump losses (and increase MAP), creating a dilution effect similar to EGR. This results in a direct improvement in fuel efficiency.

[0030] In addition to the domain-specific benefits listed above for any given output torque, water injection can reduce the intake charge temperature, which, due to improved combustion phase timing (further advanced limiting spark), leads to a lower MAP and improved thermal efficiency. The improved thermal efficiency reduces the required airflow. Since turbocharger speed is a function of the pressure ratio and mass flow rate, reducing the MAP reduces the mass flow rate and thus the turbocharger speed, which in turn lowers the pressure ratio at the compressor. The lower pressure ratio reduces the compressor outlet temperature, thereby extending compressor life. Furthermore, the lower compressor outlet temperature reduces engine pumping work (because the engine operates with a more open wastegate and requires less turbine power).In addition to knocking, each of the turbocharger speed, compressor outlet temperature, peak cylinder pressure, and turbine inlet temperature can limit the peak power of a turbocharged engine. Therefore, the output torque for a given pressure ratio is increased by utilizing water injection.

[0031] Thus, the map describes Fig. 5. The general advantages of water injection. However, it is understood that the advantages of water injection can further be influenced by the location of the water injection. For example, manifold water injection can provide dilution advantages at low loads and charge-cooling advantages at high loads. As another example, direct water injection can provide charge-cooling advantages. As yet another example, port water injection can provide dilution or charge-cooling advantages based on the direction of the water injection (e.g., towards or away from an intake valve) as well as the timing of the injection with respect to the intake valve timing (e.g., when the intake valve is open or closed). As explained herein, the control system can select a location for water injection based on engine operating conditions (as in the Fig. (Procedures 2-3 presented and described below) can be selected to enhance the aforementioned benefits of water injection, thereby increasing engine efficiency, improving fuel efficiency, and reducing emissions. Additionally, depending on the water injection point, various sets of sensors can be used to provide a more accurate estimate of the amount of water injected. As further described below with reference to Fig. As explained in section 3, a detection mode can be selected based on the water injection point, and subsequently, water injection parameters and engine operating parameters can be estimated based on the estimated amount of water injected. For example, adjustments to the water injection operating parameters can compensate for an estimated amount of injected water that falls short of a commanded amount.

[0032] In relation to Fig. Section 2 describes an exemplary procedure 200 for injecting water into an engine. Instructions for carrying out procedure 200 and the other procedures contained in this document can be provided by a controller (such as the one described in Fig. 1 the control 12 shown) is executed on the basis of instructions stored in a memory of the control and in conjunction with signals received from sensors of the motor system, such as the above with reference to Fig. 1. Sensors described. The controller can use motor actuators of the engine system to adjust engine operation according to the procedures described below. In one example, water can be injected via one or more water injection devices using water stored in a water storage tank of a water injection system (such as water storage tank 63 of the [document / model]). Fig. 1 shown water injection system 60) is stored, to be injected.

[0033] Procedure 200 begins at 202 with the estimation and / or measurement of engine operating conditions. Engine operating conditions may include driver torque demand, manifold pressure (MAP), air-fuel ratio (A / F), ignition timing, ambient conditions including ambient temperature, pressure, and humidity, charge pressure, exhaust gas recirculation (EGR) rate, mass air flow (MAF), manifold charge temperature (MCT), engine speed and / or load, engine knock level, etc.

[0034] The next step in procedure 204 involves determining whether water injection conditions have been met. Water injection can be requested to utilize one or more of its associated benefits. For example, water injection can be requested at low to medium engine loads to increase charge dilution, thereby improving combustion stability in the low to medium engine load range. Another example is that water injection can be requested at medium to high engine loads to increase charge cooling, thereby improving knock relief in the medium to high engine load range. Further still, water injection can be requested at high loads to provide component cooling, such as cooling the exhaust gas, cooling a catalytic converter, and so on.Water injection conditions can be considered fulfilled in response to an engine load exceeding a threshold load (which may impair engine combustion stability) and to an ignition timing being delayed by more than a threshold amount (e.g., by the MBT).

[0035] In one example, water injection can be requested in response to a manifold temperature exceeding a threshold. Additionally, water injection can be requested when a threshold engine speed or load is reached. In another example, water injection can be requested based on an engine knock level exceeding a threshold. Furthermore, water injection can be requested in response to an exhaust gas temperature exceeding a threshold temperature, where the threshold temperature is a temperature above which deterioration of engine components downstream of the cylinders may occur. Additionally, water can be injected if the derived octane rating of the fuel used falls below a threshold.

[0036] Confirming that water injection conditions have been met may further include confirming that water is available for injection by estimating and / or measuring water availability. Water availability for injection may be based on the output of a variety of sensors, such as a water level sensor, a water quality sensor, and / or a water temperature sensor, located in the water storage tank of the engine's water injection system (such as the one described in the...). Fig. The water level sensor 65 and water temperature sensor 67 shown in Figure 1 are used to determine the water injection conditions. For example, under freezing conditions (e.g., when the water temperature in the tank falls below a threshold level, where the threshold level is at or near freezing), water in the water storage tank may not be available for injection. In another example, the water level in the water storage tank may fall below a threshold level, where the threshold level may be based on the amount of water required for an injection event or a period of injection cycles. If water injection conditions are not met, the procedure at Figure 206 involves disabling water injection. In an example where the water injection conditions are not met due to unsolicited water injection, the procedure involves continuing engine operation without water injection.In another example, where water injection conditions are not met due to a lack of available water for injection, such as when the water storage tank level falls below a threshold, the controller can indicate that the tank needs to be refilled. Additionally, the controller can refill the water tank by increasing the vehicle's water accumulation from one or more vehicle systems, such as by drawing water from a water collection system connected to a water storage tank of the engine's water injection system (such as the one in...). Fig. 1 Water collection system shown 72). This includes increasing the air conditioning (AC) condenser to increase AC condensate collection, increasing EGR condensate collection, increasing CAC condensate collection, etc.

[0037] For the 207, the procedure further involves adjusting engine operating parameters to compensate for the absence of water injection. For example, if water injection was requested to reduce knocking, engine operating adjustments might include enriching the air-fuel ratio, reducing the amount of throttle opening to reduce manifold pressure, or retarding the ignition timing to provide knock relief. As another example, if water injection was requested to increase charge dilution, engine operating adjustments might include increasing the EGR flow.

[0038] If the conditions for water injection are met, the procedure proceeds to 208 to determine a quantity and location of water injection, as further described with reference to Fig. 3 described. The controller can determine the amount of water to be injected based on one or more of the following: engine speed / load, temperature, and knock. The controller can refer to a lookup table that takes engine speed and load as input and provides a net (total) amount of water to be commanded for water injection into the engine as output. In section 208, determining the water injection parameters, such as the amount and location of water injection, can further involve selecting a water injection mode. In one example, determining a water injection location might involve selecting a water injection mode in response to the detection (or prediction) of engine knock. In another example, selecting a water injection location might involve selecting a water injection mode in response to a dilution request from the engine.Selecting the water injection mode may involve choosing one or more manifold water injection devices, direct water injection devices, and port water injection devices based on the desired water injection benefit. Additionally, the control unit may determine a proportion of the total commanded water injection quantity to be delivered through the various water injection devices (referred to herein as a water injection ratio) based on whether charge cooling or dilution is desired. This proportioning may be based on the location of the injection devices, the total commanded quantity relative to the duty cycle of the individual injection devices, injection device limitations, and manifold humidity limits. For example, charge dilution may be required at low engine loads.Based on engine speed and load, the control unit can determine the total amount of water to be injected. It can also select the manifold injection device for water injection. If the ordered amount exceeds the injection limits of the manifold injection device, at least a portion of the injection can be provided via a port water injection device. Alternatively, if the intake air humidity is elevated at the time of injection, at least a portion of the injection can be provided via a direct water injection device.

[0039] Then, at 210, the procedure involves selecting a sensor to detect water injection based on the water injection mode. Based on the point of water injection and the engine speed / load at which the injection occurs, various water injection benefits can be provided. Accordingly, different sets of sensors can be used to estimate the actual amount of water injection. As with Fig. 3. If water injection into the manifold is performed to provide a charge dilution benefit, the water injection can be detected by sensors that detect a change in inlet (or outlet) dilution. For example, an inlet oxygen sensor can be selected to estimate the change in dilution (due to the presence of additional oxygen from the added water). As another example, an inlet humidity sensor can be selected to estimate the change in inlet humidity (due to the presence of added water). In another example, if water injection into the manifold is performed to provide a charge cooling benefit, the water injection can be detected by sensors that detect a change in manifold temperature (such as an MCT sensor).

[0040] In the 212, the procedure involves injecting water into the engine based on the selected water injection mode. For example, the controller can send a signal to an actuator of the selected water injection device to vary the pulse width of the injection device, thereby commanding the specific amount of water.

[0041] It should be noted that one or more engine operating parameters can be adjusted in response to the commanded water injection. For example, the ignition timing can be advanced in response to water injection (e.g., to a point where the current timing is delayed by the MBT). Another example is that the degree of spark advance can be increased when the amount of water injected is increased.

[0042] The procedure proceeds to 214 to estimate a water injection error based on the commanded water injection quantity relative to a detected water injection quantity. At 213, the procedure involves receiving the output from the selected one or more sensors after water injection and determining an actual water injection quantity (or detected water injection quantity) based on the sensor output. The controller can compare the output of the selected sensors before water injection with the sensor output after water injection to determine the actual quantity of water received in the engine (that is, the actual quantity that contributed to the charge cooling and / or dilution effect).As explained above, the actual amount of water injected can differ from the commanded amount due to injector malfunctions, water splash impact errors, evaporation problems due to conditions near the injector, etc. This can result in a water injection error which, if left unaddressed, can reduce the intended benefits of water injection and may even impair engine performance. In section 214, the procedure involves estimating the water injection error based on the commanded amount of water injected relative to the measured amount of water injected.

[0043] Next, at 216, the procedure involves adjusting the water injection conditions and engine operating conditions based on the specified fault. This involves adjusting one or more engine parameters to compensate for the water injection fault. In an example, the procedure at 216 involves adjusting the quantity and / or timing of water supplied by the selected water injection device(s) for a subsequent water injection (e.g., an immediately subsequent water injection with no intervening water injection, or a number of consecutive water injections following the water injection with the fault) based on the specified fault.For example, the procedure at 216 may involve increasing the amount of water for the next water injection by the same water injection device (for example, by commanding a larger pulse width) in response to the detected water injection quantity falling below the commanded water injection quantity. As another example, during the subsequent water injection by the same water injection device, the pulse width of the given water injection device may be increased by a certain amount, and the pulse width of another water injection device may also be increased.

[0044] The water injection setting on the 216 can vary depending on the injection devices present in the engine configuration and which water injection devices are selected. For example, in engine systems configured with port fuel injection where different port water injection devices are positioned upstream of different cylinder groups, the control unit can set a water injection quantity for each water injection device or only for a selected port water injection device.In another example, where one or more injection devices are located upstream of several cylinders or a group of cylinders, such as in manifold injection, the control can vary the injection timing of the selected water injection device, which must be synchronized with the opening timing of the intake valve of that cylinder group, in order to adjust water injection for the corresponding group of cylinders.

[0045] In another example, adjusting one or more engine operating parameters based on a specific fault might involve adjusting one or more of the ignition timing, EGR flow (via EGR valve position settings), engine fuel supply, throttle position, air-fuel ratio, etc. For instance, ignition timing adjustments could be used to compensate for a specific fault in injected water when water injection was used for knock control (and charge cooling). In this case, the ignition timing could be retarded in response to a water injection deficit (less water was actually taken in than commanded) (e.g., from the MBT or the initial borderline spark), and the amount of retard could be increased as the water injection fault increases.In another example, EGR settings can be used to compensate for a specific water injection error when water injection is used for charge cooling or knock control. In this scenario, the EGR flow can be increased in response to a water injection deficit (less water was actually ingested or evaporated than commanded) by increasing the degree of EGR valve opening. Additionally, a fuel injection quantity can be adjusted based on the specific water injection error.

[0046] In this way, water injection can be controlled to leverage the benefits at different injection points. Additionally, the water injection can be precisely measured and appropriately balanced based on the selected injection point.

[0047] Fig. Figure 3 shows an exemplary method 300 for selecting a water injection mode based on engine operating conditions. Additionally, the method selects a water injection detection mode based on the water injection device selection. Method 300 can be implemented as part of the method from Fig. 2, such as 208 and 214, can be performed. As described above, water injection can be used to reduce the temperature of the intake air entering the engine cylinders, thereby reducing knocking. Additionally, water injection can be used to increase engine dilution and thus reduce engine pumping losses. Water can be injected at various points in the engine, depending on the desired water injection benefit and the engine operating conditions. Furthermore, one or more sensors can be selected to estimate the amount of water injected based on the water injection point.

[0048] Procedure 300 begins at 302 with estimating and / or measuring engine operating conditions. Engine operating conditions may include driver-demand torque, manifold pressure (MAP), air-fuel ratio (A / F), ignition timing, exhaust gas recirculation (EGR) rate, mass airflow (MAF), manifold charge temperature (MCT), engine speed and load, etc. Next, at 304, the procedure involves determining whether a knock indication is present. A knock indication may include knock that is detected or knock that is expected. Control may be based on the output from one or more engine knock sensors (such as in Fig. Knock sensors (183) shown in 1 determine whether knocking occurs when a knock threshold is exceeded. In an alternative example, knocking can be predicted when the engine speed and load exceed a threshold. Further still, the probability of knocking in one or more cylinders can be based on the engine's knock profile (e.g., knock count). If the engine is knock-limited, water injection can be requested to provide charge cooling.

[0049] When knock is indicated at 304, the procedure proceeds to 307, where the quantity of water to be injected is determined based on the indicated knock. Here, the quantity of water to be supplied is to provide a charge-cooling benefit to the engine. For example, if the knock sensor output exceeds the knock threshold (that is, if the knock intensity increases), the quantity of water to be injected may be increased. As another example, if the engine speed / load increases and the corresponding probability of knocking increases, the quantity of water to be injected into the engine may be increased. Here, the quantity of water refers to the total quantity of water supplied to the engine, which may be delivered via one or more water injection devices.

[0050] In the 308, the procedure involves activating an initial water injection mode to deliver the specified amount of water injected. For the initial water injection, the intake manifold water injectors, angled away from the intake valves, can be selected to deliver the water. The controller can send a signal to the selected intake manifold water injectors to activate them. The selected intake manifold water injectors can be angled away from the intake valve and opposite the intake port, and can be arranged to inject water against the direction of intake airflow through the intake port (such as the one shown in Fig. (1 water injection devices shown 46). As explained below, the intake manifold water injection away from the valve can be timed such that it occurs when the intake valve is open. By delivering water as an injection with the valve open, against the direction of airflow, more of the injected water can enter the airflow, thereby increasing the cooling benefit of water injection at high loads. Furthermore, injecting water towards the manifold and away from the (closed) intake valve provides better water distribution in each downstream cylinder. Additionally, the high velocity of the airflow in the manifolds generates turbulence, which ensures better atomization and mixing of the water with the air, further enhancing the charge-cooling benefit of water injection.

[0051] Additionally or alternatively, at 309, activating the first water injection mode may involve activating the manifold water injection devices and selectively activating the direct water injection devices. The manifold water injection devices may be located at a point upstream of the throttle (as with reference to manifold injection device 45 in Fig. 1) or are located at a point downstream of the throttle. In embodiments that include both intake manifold and manifold injection devices (such as the one shown in Figure 1), Fig. In the water injection system shown in Figure 60, the control unit can prioritize the intake manifold water injection devices if a temperature imbalance is detected for a group of cylinders. For example, a temperature misdistribution in a group of cylinders may occur due to earlier water injection events in some cylinders but not others, resulting in the earlier cylinders being cooler than the later ones. Another example is that the temperature misdistribution between cylinders may occur due to engine design reasons, such as some cylinders being hotter due to their proximity to a water pump, while others are cooler. Additionally, a temperature misdistribution may occur due to a water imbalance between cylinders following water injection from a common water injection device.Temperature misdistribution can be detected by comparing measured or derived (modeled) temperatures in the cylinders. For example, a standard deviation can be determined for temperatures corresponding to different cylinders, and if the standard deviation exceeds a standard deviation threshold, this indicates a temperature imbalance. In other examples, temperature misdistribution in a group of cylinders can occur due to uneven airflow to the engine cylinders, variations between valves and cylinders due to deposits, differences in the fuel injection systems, and so on.

[0052] The water misdistribution can be determined based on a comparison of the knock outputs from the knock sensors coupled to each cylinder in the group (such as the one in Fig. 1 knock sensors shown 183). For example, the knock output can be used to determine differences in knock intensity in individual cylinders relative to other cylinders in the group. If the change in knock intensity after water injection differs between one or more cylinders in a group compared to the others, this may indicate differences in water distribution. For example, a standard deviation can be determined for knock outputs corresponding to different cylinders, and if the standard deviation exceeds a standard deviation threshold, this may indicate a water imbalance.If a knock output corresponding to a single cylinder deviates by a threshold value from an average value of all knock outputs corresponding to all cylinders in the group, then, in another example, it can be indicated that the individual cylinder is receiving more or less water than the other cylinders in the group. In another example, the misdistribution of water to a cylinder group connected to a water injection device can be determined based on deviations in the ignition timing retard in individual cylinders from an expected measure, the expected measure being based on an engine assignment. If there is no temperature misdistribution, the control of water via manifold water injection devices (such as the one in ) can be determined. Fig. 1 manifold injection devices 45) shown.

[0053] In another example, the selection between port and manifold injection devices (or determining a ratio of water to be delivered as port injection relative to manifold injection) can be based on the amount of water to be injected, injection device limitations, and intake air humidity. For example, if the intake air humidity increases, the amount of water delivered via the manifold injection device can be reduced (and the amount of water delivered via the port injection device can be increased accordingly). In an alternative example, if the manifold water injection is operating at a maximum rate (or at a saturation limit), water injection can be provided via direct injection into the knock-affected cylinder.As another example, if the total amount of water to be injected exceeds a limit of the manifold injection system, the excess can be supplied via the intake manifold injection system. In another example, the choice between intake manifold and manifold injection systems may be based on the mass airflow entering the engine. If a larger volume of air enters the engine at a higher velocity, manifold injection may be preferable to intake manifold injection.This is because manifold injection (especially in the case of manifold injection where water is sprayed in the opposite direction of the airflow) would allow more time for the injected water to mix, evaporate, and cool in the incoming air charge, unlike port injection, which would be preferable for valve head cooling and would have much less time and opportunity to mix with the incoming air charge.

[0054] In response to the use of water injection for charge cooling, the water injection is detected and controlled using a temperature-based control loop. Specifically, the procedure at 310 involves measuring a charge air temperature prior to initiating water injection. In one example, the control system can take an output from a manifold charge temperature sensor (such as the one in Fig. 1 MCT sensor 23) to receive the output to determine the manifold temperature before water injection. In another example, the controller can receive an output from an intake air oxygen sensor heater (operating in a heating power mode, such as the one shown in Fig. 1 IAO2 sensor 34) is used to monitor. In another example, the method at 310 can involve deriving the charge air temperature near the water injection devices based on one or more engine operating conditions (such as measured intake and exhaust air temperatures, engine load, knock intensity signal, etc.).

[0055] Then, at 312, the procedure involves commanding port water injection away from the open intake valves. The control unit can send a pulse width signal to actuators of the port water injectors, which are angled away from the intake valves and toward the intake manifold, to inject the specified amount of water in response to a specified engine knock. Water injection at 312 can involve injecting the specified (e.g., commanded) amount of water as a single pulse per engine cycle or as a series of pulses timed to the intake valve opening of each cylinder within the cylinder group downstream of the port water injector. If manifold water injection is additionally or alternatively selected, the control unit can command an appropriate pulse width to the manifold water injector.

[0056] Fig. Figure 6 shows an example intake manifold injection timing for knock relief. Chart 600 represents an intake valve lift at curve 602 (solid line) and a corresponding mass airflow through the intake valve at curve 604 (dashed line). All curves are shown relative to the engine position (in degrees of crankshaft rotation) along the x-axis. The intake valve lifts at the beginning of an intake stroke (around 300 CAD when the cylinder piston is at top dead center), reaches maximum lift (approximately halfway between TDC and BDC), and then begins to close, being fully closed by the end of the intake stroke (around 600 CAD when the cylinder piston is at BDC). The mass airflow through the intake valve follows a similar profile, increasing as the intake valve lift increases and then decreasing as the intake valve lift decreases.

[0057] Port injection away from an open intake valve can be performed at reference point 606, where the intake valve is almost fully open and the mass flow into or to the intake valve is near its peak. By injecting water away from the valve surface towards the intake port or manifold at this point, more water can enter the intake airflow, increasing the cooling benefit provided by water injection. Specifically, a larger proportion of the water is delivered in liquid form, thus enhancing the heat removal and charge cooling capabilities of the water injection.

[0058] Back at Fig. 3 includes the procedure at 314 for estimating or sensing a quantity of water received in the engine, based on one or more changes in manifold charge temperature and intake air oxygen heating power after water injection. In one example, the controller receives a first output from the manifold charge temperature sensor before water injection (at 310). The water injection can cause a charge cooling effect in the manifold due to the injected water evaporating using ambient heat. This effect can be observed as a drop in manifold charge temperature. The controller can receive a second output from the manifold charge temperature (MCT) sensor after water injection (e.g.,The MCT sensor receives a reading immediately after water injection or after a certain period of time since the water injection and determines the amount of injected water based on a change in manifold temperature, as indicated by the difference between the first and second outputs of the MCT sensor. As the difference increases, the amount of water detected in the engine can be increased. The time between a water injection event and the manifold charge temperature measurement can be based on the expected time required for the injected water to evaporate. This time can be adjusted based on the amount of water injected, increasing as the amount of water injected via the injection system increases.

[0059] In another example, at 310, the controller can receive an initial power output from the inlet air oxygen sensor heater prior to water injection. The heater is configured to maintain a substantially constant temperature of the inlet oxygen sensor to ensure proper sensor operation. In response to charge cooling, the ambient temperature at the sensor may decrease, resulting in a corresponding drop in the sensor temperature. The sensor heater power may automatically increase in an effort to maintain the sensor temperature. For this reason, the charge cooling effect of water injection can be observed as an increase in the inlet oxygen (IAO2) heater power output. The controller can receive a second power output from the sensor heater after water injection (e.g.,The system receives data immediately after water injection or after a certain time since the water injection and determines the amount of injected water based on a change in heating power output, indicated by the difference between the first and second power outputs of the IAO2 sensor heater. As the difference increases, the amount of water detected in the engine can be increased. In this way, the evaporated portion of the injected water (i.e., the portion that provides the charge cooling benefit) can be determined based on the change in manifold charge air temperature before or after the water injection event.

[0060] At 330, a water injection fault is determined based on a difference between the commanded water injection quantity (at 312) and the detected water injection quantity (at 314). This reflects the discrepancy between the amount of water that should be delivered for knock relief and the amount of water actually received by the engine for knock relief. In one example, the actual received quantity might be less than the commanded quantity, resulting in a water deficit and a corresponding charge cooling deficit. The control unit can then adjust subsequent water injection events to compensate for the learned water injection fault. Additionally, one or more engine operating parameters can be adjusted to compensate for the learned water injection fault. For example, the ignition timing can be retarded and / or the air-fuel ratio can be enriched.However, the amount of ignition delay or required fuel enrichment is reduced by using water injection to provide a large part of the charge cooling, thereby improving fuel efficiency.

[0061] If engine knock is not detected, the procedure proceeds again from step 304 to 305, where the procedure involves determining whether a dilution requirement exists. As with reference to Fig. As described in section 5, water can be injected to increase intake charge dilution and reduce pumping losses. In one example, increased dilution may be requested in response to an engine speed / load falling below a threshold, if the threshold engine speed / load indicates a speed / load range where pumping losses are more likely. In another example, charge dilution may be requested when the engine is at or near a combustion stability limit. If a dilution request is not acknowledged, the procedure moves to step 303 to leave all water injection devices in the engine system disabled. The routine then terminates, and the engine operates without water injection.

[0062] When water injection for dilution is requested at 305, the procedure proceeds to 306, where the quantity of water to be injected is determined based on the dilution requirement. Here, the quantity of water to be supplied is to provide a charge dilution benefit to the engine. For example, if the engine speed / load decreases and the engine combustion stability approaches a limit, the quantity of water to be injected into the engine due to the dilution requirement may be increased. Here, the quantity of water refers to the total quantity of water supplied to the engine, which may be supplied via one or more water injection devices.

[0063] In response to the use of water injection for charge dilution, the water injection is detected and controlled using a dilution-based control loop. Specifically, the procedure at 315 involves estimating an exhaust oxygen level (or exhaust humidity) based on the output of an exhaust oxygen sensor (or UEGO sensor, such as the one described in Fig. Figure 1 shows the UEGO 126, which operates in a variable voltage mode. In variable voltage mode, the sensor is modulated between a lower reference voltage (such as 450 mV) and a higher reference voltage (such as 950 mV). The higher voltage causes any water in the exhaust gas to dissociate into oxygen, and the sensor detects this excess oxygen. The controller can compare the pump current output through the sensor at the lower voltage with the pump current output through the sensor at the higher voltage and obtain a first sensor output as the difference between the pump currents at the reference voltages. By comparing the first sensor output, measured before a water injection command, with a second sensor output, measured after the water injection, the controller can determine the amount of injected water that evaporated in the engine and contributed to charge dilution.Additionally or alternatively, the controller can receive output from one or more dilution sensors, such as an inlet air oxygen sensor (like the one in . Fig. 1 shown IAO2 sensor 34), which operates in a variable voltage mode, and an inlet humidity sensor, received.

[0064] In 316, the procedure involves estimating and / or measuring an intake valve surface temperature to determine whether the temperature exceeds a threshold. The threshold may be the temperature above which water can evaporate upon contact with the surface without providing a cooling effect. In one example, the valve surface temperature may be estimated or derived based on a measured engine temperature, such as the output of an engine coolant temperature sensor (such as the one described in Fig. 1 shown engine coolant temperature sensor 25). In another example, the valve surface temperature can be derived based on engine speed and load conditions, with the temperature increasing as the engine load increases.

[0065] The inventors of the present invention have recognized that when a dilution effect is required at low engine loads, water can be injected onto a hot surface and evaporate immediately. For example, water can be injected into a hot intake valve surface via the intake manifold and evaporate immediately, with the intake manifold injection timing adjusted to coincide with the closing of the intake valve. As a consequence of injecting intake manifold water onto a closed, or nearly closed, intake valve surface, more of the injected water can evaporate immediately, thereby increasing the dilution benefit of using the water vapor as EGR by reducing pumping losses while minimizing the cooling effect of the water injection. Thus, if the valve surface is not hot enough, the injected water can form a puddle on the valve surface.

[0066] For this reason, the procedure at 318, in response to the dilution request upon confirmation that the valve surface is sufficiently hot, involves activating a second water injection mode, whereby intake manifold water injection devices angled towards the intake valves are selected to inject water onto a closed intake valve. Alternatively, the intake manifold water injection devices can be angled towards the intake valve and configured to inject onto the valve surface and / or surrounding manifold surface. In this case, the water injection occurs in the same direction as the intake airflow direction through the intake port / pipe and opposite to the direction of the intake manifold water injection for knock relief (at 312).

[0067] In the 322, the procedure involves commanding a specific amount of water to be injected as a port injection onto a closed intake valve surface. For example, the control unit can send a pulse width signal corresponding to the specified amount of water to an actuator of the port water injection device to inject water when the intake valve closes, such as at bottom dead center (BDC) of an intake stroke. In one example, the injection device can deliver the commanded amount of water as a single pulse per engine cycle (for all intake valve closing events for all cylinders in the group). In another example, the injection device can deliver the amount of water as a series of pulses timed to coincide with the intake valve closing of each cylinder within the cylinder group.By injecting water into a closed inlet valve and / or onto a manifold surface, more of the injected water can come into contact with hot surfaces of the manifold, thereby increasing the amount of injected water that evaporates.

[0068] With reference to Fig. 6. Port injection can be performed at reference point 608 to a closed intake valve, just before the intake valve closes and the mass flow into or to the intake valve is near its minimum. By injecting water onto the hot valve surface of a closed intake valve, the water can evaporate rapidly, thereby increasing the charge dilution benefit of water injection while reducing the charge cooling effect. In particular, a larger proportion of the injected water is delivered in vapor form (rapidly evaporated), thus improving the charge dilution capability of the injection.

[0069] If the valve surface is not hot enough at 320°C, the procedure involves returning to the previous temperature. Fig. 3. Activating a third water injection mode, wherein manifold water injection devices are selected for injecting water into an intake manifold. In 324, the procedure involves commands specifying the amount of water injected as a manifold injection. For example, the controller can send a pulse width signal corresponding to the specified amount of water injected to an actuator of the manifold water injection device.

[0070] In other examples, the selection between port and manifold injection devices (or determining a ratio of water to be delivered as port injection relative to manifold injection) can be based on the amount of water to be injected, injection device limitations, and intake air humidity. For example, if the intake air humidity increases, the amount of water delivered via the manifold injection device can be reduced (and the amount of water delivered via the port injection device can be increased accordingly). In an alternative example, if the manifold water injection is operating at a maximum rate (or at a saturation point), water injection can be provided via port injection.As another example, if the total amount of water to be injected exceeds a limit of the manifold injection system, the excess can be supplied via the intake manifold injection system. In yet another example, the selection between the intake manifold and exhaust manifold injection systems can be based on the mass airflow entering the engine, as previously described.

[0071] Following the water injection command, the procedure involves estimating or sensing the amount of water received by the engine. Since the water injection serves for dilution control, the sensing is based on a measured change in engine dilution or humidity. For this reason, the procedure moves from each of 322 and 324 to 326, where the routine involves estimating the amount of water to be injected based on a change in the exhaust oxygen level. For example, the control unit may receive an initial output from the UEGO sensor operating in variable voltage mode before water injection and a second output from the UEGO sensor operating in variable voltage mode.As previously explained, the sensor is modulated between a lower reference voltage (such as 450 mV) and a higher reference voltage (such as 950 mV). The higher voltage causes the added water in the exhaust gas to dissociate into oxygen, and the sensor detects excess oxygen. The control unit can compare the pump current output through the sensor at the lower voltage with the pump current output through the sensor at the higher voltage after water injection. A second sensor output is obtained as the difference between the pump currents at the reference voltages after water injection. The control unit can then determine a detected or actual amount of water that has evaporated in the engine based on this difference between the first and second outputs, with the detected amount increasing as the difference increases.

[0072] In another example, the controller can use the outputs from the intake air oxygen sensor (such as the one in Fig. 1 IAO2 sensor 34) shown and the inlet humidity sensor before and after water injection to determine the amount of injected water that was actually received and evaporated in the engine.

[0073] The sensor selection can also depend on the injection method. For example, if water is injected directly onto the intake manifold valve surface, the IAO2 sensor and the humidity sensor may not be able to provide an accurate measurement of the amount of water injected. In such cases, the exhaust gas UEGO sensor can be selected. Conversely, if water is injected into the exhaust manifold, one or more of the IAO2 sensor and the humidity sensor can be selected to detect the water injection error.

[0074] It is also understood that during conditions where the manifold water injection device is used for dilution control or knock control, and the manifold water injection is at a maximum rate or saturation limit (such as when the intake humidity is at a threshold), the control system may rely on the exhaust oxygen sensor, operating in variable voltage mode, to detect the water injection. During manifold saturation, the intake humidity sensor will also become saturated and will be unable to detect the amount of water injected into the intake manifold. Furthermore, a charge temperature measurement via an MCT sensor may be confused by the presence of liquid water on the sensor. For this reason, both sensors may be inaccurate, and their output may be unreliable.

[0075] When the inlet air is fully saturated, water can also permeate the IAO2 sensor's protective tube, causing the sensor to always indicate complete dilution (even when complete dilution conditions are not present). This can also lead to inaccuracies in the IAO2 sensor and unreliable output. During conditions when the IAO2 sensor output indicates saturation (indicated when the sensor's pump current drops to 0), the controller can operate the IAO2 sensor in variable voltage mode to dissociate the water within the protective tube surrounding the sensor element, thus obtaining a more accurate and reliable reading of the water quantity.

[0076] During such conditions, the UEGO sensor operating in variable voltage mode can provide a reliable output. UEGO-based dilution, as detected by the sensor operating in nominal mode (where the sensor only operates at the lower reference voltage), may not be able to determine the amount of water injected into the engine because the engine continues to operate at stoichiometric conditions (e.g., lambda 1.0), so the pump current (Ip) does not change (e.g., remains at 0). The UEGO operating in variable voltage mode offers a more accurate method for monitoring the total amount of water injected during such conditions (that is, the sum of the water entering the manifold, airflow, cylinder, etc.).(is injected), since the sensor is located in the most downstream position and the modulation dissociates all the added water into hydrogen and oxygen, thus enabling the sensor to detect the excess oxygen from all the added water.

[0077] From step 326, the procedure moves to step 330, where the controller adjusts water injection and / or engine operating parameters based on a difference between the commanded and detected water injection quantity (that is, based on the learned water injection error). Adjusting the water injection can involve setting the quantity and / or timing of water injected during a subsequent water injection event (from the same water injection device or one or more other water injection devices) based on the output from the multiple sensors. For example, the controller can increase the quantity of water injected for a subsequent water injection in response to the detected water injection quantity being less than the commanded quantity. Additionally, the injection timing of the selected water injection device can be adjusted.In one example, the injection timing of the selected water injection device can be synchronized with the opening timing of the intake valve for a given cylinder to adjust the water injection to that cylinder. Additionally, one or more engine operating parameters can be adjusted to compensate for the water injection fault. For instance, the EGR flow can be increased in response to the water injection fault if the fault results in a dilution deficit. For example, the control unit can increase the EGR flow based on the water injection fault by increasing the degree of opening of the EGR valve. As another example, camshaft control settings (e.g., VCT settings) can be used to compensate for the dilution deficit.

[0078] In this way, a control unit can select a water injection device from a port injection device, a manifold injection device, or a direct injection device to inject a commanded quantity of water into an intake manifold; then select one of a variety of engine sensors based on the water injection device selection; and adjust engine operating parameters after injection based on the output from the selected sensor. The variety of sensors can include an intake oxygen sensor, an exhaust oxygen sensor, a humidity sensor, a manifold temperature sensor, an intake air humidity sensor, and an engine coolant temperature sensor.The adjustment process can involve estimating the actual amount of water received by the engine based on the output from the selected sensor and adjusting the engine operating parameters as a function of the commanded amount relative to the actual amount. For example, selecting the water injection device below the threshold engine load and speed conditions might involve selecting the port fuel injection device; and above the threshold engine load and below the threshold engine speed conditions, selecting the manifold fuel injection device.Selecting the water injection device may further include injecting a portion of the commanded quantity via the manifold injection device until a manifold injection device limit (such as a saturation limit or a maximum flow rate through the injection device) is reached, and then injecting the remaining portion of the commanded quantity via the direct injection device. Selecting port injection may further include injecting the commanded quantity via the port injection device to an intake valve of an engine cylinder before the intake valve opens if the engine is not knock-limited; and injecting the commanded quantity via the port injection device away from the intake valve of the engine cylinder after the intake valve opens if the engine is knock-limited.Selecting the sensor can involve, after injection via the first port fuel injector to the intake valve, estimating the actual amount of water via one of the manifold temperature sensors and the engine coolant temperature sensor; after injection via the second port fuel injector away from the intake valve, estimating the actual amount of water via the exhaust oxygen sensor; after injection via the manifold fuel injector, estimating the actual amount of water via one of the manifold temperature sensors, intake humidity sensor and the intake oxygen sensor; and after injection via direct injection, estimating the actual amount of water via one of the intake oxygen sensors and the exhaust oxygen sensor.Furthermore, estimating via the intake oxygen sensor after injection via the manifold injection device can involve operating the intake oxygen sensor in a nominal mode at a first reference voltage, and estimating via the intake oxygen sensor after injection via the direct injection device involves operating the intake oxygen sensor in a variable mode at each of the first reference voltages and a second reference voltage that is higher than the first reference voltage, and estimating via the exhaust oxygen sensor involves operating the exhaust oxygen sensor in variable mode at each of the first reference voltages and the second reference voltage.Adjusting engine operation may involve increasing the EGR flow, retarding the ignition timing from a nominal timing, and advancing or retarding the variable cam control from a nominal cam control if the ordered quantity exceeds the actual quantity.

[0079] In this way, water injection and / or engine operating parameters can be adjusted to achieve a desired dilution requirement or cooling advantage.

[0080] In Fig. 4. Diagram 400 illustrates exemplary water injection settings based on engine operating conditions. Diagram 400 illustrates the selection of a water injection device for a water injection system (such as the one described in Fig. 1 water injection system 60 shown), to deliver an amount of water that provides charge cooling or charge dilution benefits. The diagram also illustrates detecting water injection based on an output from the manifold charge temperature sensor and adjusting engine operating parameters, such as ignition timing, after water injection. Specifically, diagram 400 shows a commanded amount of water injected through a selected water injection device at 402-404, engine knock (e.g., knock output from one or more knock sensors) at 406, engine dilution request at 408, changes in an output from a manifold charge temperature sensor at 410, changes in an output from an exhaust gas UEGO sensor at 412, and an estimated amount of injected water at 414 (as detected based on the output from the MCT sensor).Water injection via a manifold water injection device is shown by a dashed line in curve 402; a dotted line corresponds to water injection via intake manifold water injection devices angled towards the intake manifold (curve 404), and a solid line corresponds to water injection via intake manifold water injection devices angled towards the intake valves (curve 406). For each operating parameter, time is shown along the horizontal axis, and the values ​​of each corresponding operating parameter are shown along the vertical axis. In one example, the distributor charge temperature sensor may be located near the water injection device, such as inside the intake manifold if the water injection device is located within the intake manifold.

[0081] Before time t1, the water injection conditions are not met, and water injection is not activated. During this time, the engine operates without water injection. In one example, at time t1, water may not be available for injection. Consequently, the control unit can send a request to actuators of a water collection system to increase the water level on board the vehicle. In another example, water injection cannot be requested because the engine load and ignition timing delay fall below a certain threshold.

[0082] The knock signal intensity increases (curve 406) before time t1 due to a change in engine operating conditions above the threshold 405. For example, the knock signal might increase in response to an increase in engine speed and / or load, such as from a rise in engine load to medium to high load conditions. In one example, the load increase occurs due to a pedal actuation event by the operator. In response to the knock indication, water injection is requested at time t1. At time t1, the controller can send a signal to an exhaust manifold water injection device (402) to inject the amount of water required to provide knock relief into the exhaust manifold. The amount of water to be injected via the exhaust manifold water injection device (curve 402) is based on the knock indication.

[0083] In response to the injection request, the manifold charge temperature can be measured (before water injection), and the controller can command the specific amount of water to be injected from the manifold injection device (graph 402) of the water injection system at time t1 by sending a pulse width signal to the injection device. As a consequence of the manifold water injection, charge cooling occurs, and the manifold charge temperature decreases between times t1 and t2 (graph 406). After a period following injection at t2, the manifold charge temperature is measured again. However, the measured change in the mean charge temperature (MCT) is smaller than the actual expected change (dashed segment 409) based on the commanded amount of water injected. Consequently, a water injection error (injection deficit) is learned and applied during a subsequent water injection error.Due to the water deficit, the amount of charge cooling required for knock relief is not provided. Consequently, the knock signal (trajectory 406) at t2 does not fall below the threshold 405, where the threshold 405 is a knock signal intensity above which water injection is requested. In response to the knock intensity remaining above the threshold, manifold water injection is initiated again, with the manifold water injection quantity increased to compensate for the water injection error learned during the previous injection.Due to insufficient knock relief with added manifold water injection at t3, the manifold injection is provided at a maximum rate, and further knock relief is provided by the control unit, which commands an additional amount of water to be injected from the intake manifold injectors angled away from the intake valves (flow 403). In an alternative example, the control unit can send a signal to an actuator of a direct water injection device coupled to the knock-affected cylinder(s) to inject the amount of water for additional knock relief at t3. Since the water injection is used for charge cooling, the MCT drops further, and knock relief is achieved.

[0084] After a period following injection at time t3, the manifold charge temperature is measured again, and the amount of injected water (curve 414) is estimated at time t4 based on the measured change in the manifold charge temperature. No water injection fault is learned, and therefore the water injection is not adjusted further. As a result of the water injection at t3, the manifold charge temperature drops at t4, and the knock signal (curve 406) falls below the threshold. In response to the knock intensity falling below the threshold, the control unit reduces the amount of injected water at t4 and t5.

[0085] At time t5, the dilution request increases due to a change in engine operating conditions, such as a drop in engine load to low to medium load conditions, exceeding a threshold value of 407. In one example, the load drop occurs due to the operator releasing the accelerator pedal. Threshold value 407 is a dilution request above which water injection is requested. In response to the dilution request exceeding the threshold at time t5, and because the valve surface temperatures are sufficiently hot, the controller commands a quantity of water to be injected via the port fuel injectors (trajectory 404) angled towards the intake valves. The controller may receive an output from the UEGO sensor, operating in variable voltage mode, before the water injection command is issued.The controller can then send a signal to the actuators of the corresponding intake manifold water injection devices and inject a quantity of water based on the desired dilution requirement. After the water injection at time t6, the controller may receive a different output from the UEGO sensor, which operates in variable voltage mode. However, the measured change in the UEGO output is less than the actual expected change (dashed segment 411) based on the commanded water injection quantity. Consequently, a water injection error (injection deficit) is learned and applied during a subsequent water injection error at t6 to better meet the dilution requirement. Specifically, the intake manifold injection is increased to a closed intake valve during the subsequent water injection at t6.In response to a reduction in the dilution requirement after water injection, the controller can adjust the amount of injected water at time t7. For example, the controller can decrease the amount of injected water based on the reduction in the dilution requirement at time t7.

[0086] Another example of water injection settings and water capture is described with reference to Fig. 7 shown. In the example from Fig. In section 7, water injection is used for dilution control. Diagram 700 shows engine load on curve 702, intake manifold water injection on curve 704, manifold water injection on curve 706, the output of an intake oxygen sensor (IAO2 signal) on curve 708, the output of an exhaust gas oxygen sensor (UEGO) on curve 710, the operating mode (nominal or variable voltage) of the UEGO sensor on curve 711 (dashed line), the output of an intake air humidity sensor on curve 712, the output of a manifold charge temperature sensor (MCT) on curve 714, and the temperature of an intake valve located downstream of the intake manifold injection device on curve 716. For each operating parameter, time is plotted along the horizontal axis, and the values ​​of each corresponding operating parameter are plotted along the vertical axis.In one example, the distributor charge temperature sensor can be located near the water injection device, such as inside the intake manifold if the water injection device is located within the intake manifold. Additionally, the humidity sensor, the IAO2 sensor, and the MCT sensor can all be coupled to the intake manifold upstream of the port fuel injection device. In this example, the port fuel injection device can be configured to inject water into the intake valve.

[0087] Before t1, the engine is operating at idle and no water injection is required. Accordingly, both the intake manifold water injection device and the exhaust manifold water injection device remain deactivated, and no water is injected into the intake manifold. Intake manifold temperature conditions at this time are reflected by the output of the MCT sensor, and intake manifold humidity conditions are reflected by the output of the humidity sensor. Both the IAO2 and UEGO sensors are operating in nominal mode at this time. The output of the IAO2 sensor in nominal mode provides an estimate of the intake air oxygen content at this time. The output of the UEGO sensor in nominal mode provides an estimate of the exhaust gas oxygen content at this time, which is used to derive the exhaust air-fuel ratio.In this example, the output of the UEGO sensor indicates that the engine is operating at or around stoichiometric coefficients. Additionally, the intake valve temperature may rise slowly during this time.

[0088] At t1, the engine is moved into a specific speed / load range due to a change in engine operating conditions, such as an increase in torque demand. Within this range, the engine may experience combustion stability limitations and require increased engine dilution. Water injection can be activated at this point to provide the desired dilution. Specifically, intake manifold water injection (as opposed to exhaust manifold water injection) is given higher priority at this time because the intake valve is sufficiently hot, and due to engine design considerations (such as the proximity of the intake manifold injection system to the water pump).

[0089] Between t1 and t2, water from the intake manifold water injection system is injected onto the hot surface of the intake valve. Specifically, the timing of the intake manifold water injection is set to coincide with the closing of the intake valve (such as near bottom dead center of an intake stroke, as described in [reference to]). Fig. (discussed in section 6), so that the injected water can evaporate quickly (e.g., directly upon contact with the hot surface of the inlet valve), thereby enhancing the charge dilution effects of the water injection while minimizing the charge cooling effect. The amount of injected water is adjusted to meet the dilution requirement. Between t1 and t2, the temperature of the inlet valve begins to decrease due to the water injection. Additionally, the amount of injected water between t1 and t2 is detected by one or more of the IAO2 and UEGO sensors operating in variable voltage mode. In variable voltage mode, the higher reference voltage causes the injected water to split into hydrogen and oxygen, thus increasing the amount of oxygen detected by the oxygen sensor.The additional oxygen content can then correlate with the amount of water received in the intake manifold due to the intake manifold water injection. It is understood that if the IAO2 sensor is operating in nominal mode, its output may not reliably indicate the manifold water concentration due to the location of the intake manifold water injection relative to the IAO2 sensor's position. Similarly, if the UEGO sensor were operating in nominal mode, its output might not reliably indicate the manifold water concentration because the engine control unit maintains the exhaust air-fuel ratio, which remains at or around stoichiometric during water injection. Furthermore, the humidity sensor's output may be relatively unreliable at this time, based on the location of the intake manifold water injection relative to the humidity sensor's position.Additionally, because the intake manifold water injection was performed on the closed hot intake valve surface to reduce the charge cooling effect of the water injection, the output of the MCT sensor may also be unreliable at this time.

[0090] At t2, in response to an operator torque demand, there is a further increase in engine load to a low to medium load range. There is a corresponding increase in the engine dilution range. Due to the lower intake valve temperature, port water injection cannot be used to provide the dilution requirement at this time. Therefore, port water injection is deactivated and manifold water injection is activated to provide the desired engine dilution.

[0091] Between t2 and t3, water from the manifold water injection device is injected into the intake manifold or onto the manifold surface. The amount of injected water is adjusted to meet the dilution requirement (which increases incrementally between t2 and t3). Between t2 and t3, the intake valve temperature begins to rise due to the increased engine load. Between t2 and t3, the amount of injected water is detected by one or more of the IAO2 and UEGO sensors operating in variable voltage mode (VVs, dashed line 711). In variable voltage mode, the higher reference voltage causes the injected water to split into hydrogen and oxygen, increasing the amount of oxygen detected by the oxygen sensor. This additional oxygen content can then correlate with the amount of water received in the intake manifold due to the manifold water injection.It is understood that if the UEGO sensor were operated in nominal mode (nom, dashed line 711), the sensor output might not reliably indicate the manifold water concentration, as the engine control unit maintains the exhaust air-fuel ratio, which remains at or around stoichiometry during water injection. Alternatively, the IAO2 sensor can be operated in nominal mode (not shown), and its output can reliably indicate the manifold water concentration based on the manifold water injection location relative to the IAO2 sensor location. Similarly, the output of the humidity sensor can also be reliably used to estimate the amount of water injected based on the manifold water injection location relative to the humidity sensor location. The output of the MCT sensor can also be reliable at this time.

[0092] At t3, there is a further increase in engine speed / load to a medium load range and a corresponding further increase in the engine dilution requirement. This is achieved by increasing the manifold water injection to a maximum rate and thereby maintaining the manifold water injection at this maximum rate. The manifold water injection system is at its saturation limit between t3 and t4.

[0093] The humidity estimate increases when the manifold water injection is increased. However, once the manifold water injection reaches its saturation limit at t3, the humidity sensor can also become saturated and may be unable to reliably estimate the amount of water injected via the manifold water injection device. Consequently, the humidity sensor output may remain constant even as the amount of water injected by the manifold injection device increases. Furthermore, the MCT sensor can be confused by the presence of liquid water on the sensor during saturation conditions, and the accuracy of the MCT measurement cannot be relied upon. For example, the MCT output may fluctuate and may not correlate with the amount of water injected. Since the air in the intake manifold becomes completely saturated with water, liquid water may enter the intake oxygen sensor's protective tube.Consequently, the output of the IAO2 sensor, operating in nominal mode, may remain constant even as the amount of water injected increases (see the IAO2 signal shown at the dashed segment 709). Similarly, when the UEGO sensor is operating in nominal mode, its output may remain constant and may not reliably indicate the manifold water concentration, because the engine control unit maintains the exhaust air-fuel ratio, which remains at or around stoichiometric during water injection.

[0094] For this reason, the amount of injected water between t3 and t4, when the manifold water injection is at the saturation limit, is reliably detected by one or more IAO2 sensors operating in variable voltage mode and UEGO sensors, also operating in variable voltage mode. At t3, when the IAO2 sensor becomes saturated (detectable when the sensor's pump current drops to 0), the IAO2 can be operated in VVs mode to dissociate the water in the protective tube surrounding the IAO2 sensor's sensing element and obtain an accurate reading of the amount of water injected into the intake manifold. Thus, the output of the UEGO sensor operating in VVs mode provides the most accurate estimate of the water injection quantity during saturated water injection conditions.In particular, the UEGO output can provide an estimate of the total amount of water injected into the intake airflow (for example, if water was injected via a combination of intake manifold and manifold water injection).

[0095] At t4, there may be a drop in driver torque demand, leading to a corresponding drop in engine speed / load and a decrease in dilution requirement. For this reason, water injection may be deactivated or reduced at t4. Sensor outputs may decrease accordingly. After t4, the MCT sensor can continue to provide an accurate estimate of manifold temperature, the humidity sensor can continue to provide an accurate estimate of manifold humidity, the IAO2 sensor can continue to operate in nominal mode to provide an accurate estimate of intake air oxygen content, and the UEGO sensor can continue to operate in nominal mode to provide an accurate estimate of the exhaust air-fuel ratio.In this way, water injection device selections can be set based on engine operating conditions, and water injection estimation modalities can be adjusted accordingly to enable an accurate estimation of the amount of water injected.

[0096] Another example of water injection settings and water intake is described with reference to Fig. 8 shown. In the example from Fig. In section 8, water injection is used for knock control and / or engine component temperature control. Diagram 800 shows engine load on curve 802, intake manifold water injection on curve 804, manifold water injection on curve 806, direct water injection on curve 808, the output of an intake oxygen sensor (IAO2 signal) on curve 810, the operating mode (nominal or variable voltage) of the IAO2 sensor on curve 811 (dashed line), the output of an exhaust gas oxygen sensor (UEGO) on curve 812, the operating mode (nominal or variable voltage) of the UEGO sensor on curve 813 (dashed line), the output of an intake air humidity sensor on curve 814, and the output of a manifold charge temperature sensor (MCT) on curve 816. For each operating parameter, time is shown along the horizontal axis, and the values ​​of each corresponding operating parameter are shown along the vertical axis.In one example, the distributor charge temperature sensor can be located near the water injection device, such as inside the intake manifold if the water injection device is located within the intake manifold. Additionally, the humidity sensor, the IAO2 sensor, and the MCT sensor can all be coupled to the intake manifold upstream of the port fuel injection device. In this example, the port fuel injection device can be configured to inject water away from the intake valve.

[0097] Prior to t11, the engine operates at low engine speed / load conditions, and water injection is not required. Accordingly, each of the intake manifold water injection devices, the manifold water injection device, and the direct water injection device remains deactivated, and no water is injected into the intake manifold or directly into the cylinder. Intake manifold temperature conditions at this time are reflected by the output of the MCT sensor, and intake manifold humidity conditions are reflected by the output of the humidity sensor. Both the IAO2 and the UEGO are operating in nominal mode at this time.

[0098] The output of the IAO2 sensor in nominal mode provides an estimate of the oxygen content of the intake air at that time. The output of the UEGO sensor in nominal mode provides an estimate of the oxygen content of the exhaust gas at that time, which is used to derive the exhaust-air-fuel ratio. In this example, the output of the UEGO sensor indicates that the engine is operating at or around stoichiometry.

[0099] Between t11 and t12, the engine moves into a mid- to high-speed / load range due to a change in engine operating conditions, such as an increase in torque demand. In this range, the engine may be knock-limited and may require charge cooling. In particular, as the engine load increases, the engine may move closer to or beyond the knock limit, and the knock intensity from an engine knock sensor may begin to just exceed the knock limit. Water injection may be activated at this time to provide the desired charge cooling. Specifically, port water injection (as opposed to manifold water injection) is given higher priority at this time, due to engine design considerations (such as the proximity of the port injection system to the water pump).Between t11 and t12, water from the intake manifold water injection device is injected in a direction away from the surface of the intake valve and opposite to the direction of airflow into the engine (that is, while air flows from the intake manifold into the intake port and towards the intake valve, water can be injected into the intake port and manifold and away from the intake valve). The intake manifold water injection timing is set to coincide with a valve timing at which the intake valve is almost fully open (such as before bottom dead center (BDC) of an intake stroke or halfway between top dead center (TDC) and BDC of the intake stroke, as referred to in [reference]). Fig.(6 discussed), so that the injected water can quickly enter the air flowing towards the cylinder valve. Additionally, a larger proportion of the liquid water can enter the air (instead of evaporating at the intake port), thus improving the charge cooling effects of the water injection while minimizing the charge dilution effect. The amount of injected water is adjusted to meet the charge cooling requirement.

[0100] Between tl1 and t12, the intake manifold temperature begins to drop due to the charge cooling effect of the intake manifold water injection, as detected by the MCT sensor. The humidity sensor output can also be reliable at this time, based on the location of the intake manifold water injection relative to the humidity sensor's position. That is, the humidity sensor output can correlate with the intake manifold water injection quantity.

[0101] Also between t11 and t12, the amount of injected water is detected by one or more of the IAO2 and UEGO sensors operating in variable voltage mode (VVs, dashed line 813). In variable voltage mode, the higher reference voltage causes the injected water to split into hydrogen and oxygen, thus increasing the amount of oxygen detected by the oxygen sensor. This additional oxygen content can then correlate with the amount of water received in the intake manifold due to the intake manifold water injection. It is understood that the IAO2 sensor can alternatively be operated in nominal mode, as shown (nom, dashed line 811), and the sensor output can reliably indicate the manifold water concentration based on the intake manifold water injection location relative to the IAO2 sensor location.However, if the UEGO sensor were operated in nominal mode, the sensor output might not reliably indicate the manifold water concentration, as the engine control maintains the exhaust air-fuel ratio, which remains at or around stoichiometry during water injection.

[0102] At t12, in response to an operator torque demand, the engine load increases further to a higher RPM / load range. This results in a corresponding increase in engine charge cooling demand due to a rise in knock intensity. At this point, intake manifold water injection cannot be used to meet the charge cooling demand. Therefore, intake manifold water injection is deactivated, and manifold water injection is activated to provide the required engine knock relief.

[0103] Between t12 and t13, water from the manifold water injection device is injected into the intake manifold or onto the manifold surface. The amount of injected water is adjusted to meet the charge cooling requirement (which increases incrementally between t12 and t13 as the knock intensity increases). Between t12 and t13, the amount of injected water is further detected by one or more of the IAO2 (operating in nominal or variable voltage mode) and UEGO sensors (operating in variable voltage mode). In variable voltage mode, the higher reference voltage causes the injected water to split into hydrogen and oxygen, increasing the amount of oxygen detected by the oxygen sensor. This additional oxygen content can then correlate with the amount of water received in the intake manifold due to the manifold water injection.Similarly, the output of the humidity sensor can also be reliably used to estimate the amount of water injected, based on the location of the manifold water injection relative to the location of the humidity sensor. The output of the MCT sensor can also be reliable at this time.

[0104] At t13, there is a further increase in engine speed / load and a corresponding further increase in the engine charge cooling requirement. This is achieved by increasing the manifold water injection to a maximum rate and maintaining the manifold water injection at this maximum rate. The manifold water injection system reaches its saturation limit between t13 and t14.

[0105] At t14, there is a further increase in engine speed / load and a corresponding increase in the engine charge cooling requirement for component temperature control and knock relief. This is achieved by maintaining the manifold water injection at its maximum rate and increasing the injection of water into the cylinders via a direct water injection system. The direct water injection quantity is adjusted between t14 and t15 as the engine speed / load changes and the corresponding charge cooling requirement changes.

[0106] The humidity estimate increases when the manifold water injection is increased. However, once the manifold water injection reaches its saturation limit after t13, the humidity sensor can also become saturated and may be unable to reliably estimate the amount of water injected via the manifold water injection device. Consequently, the humidity sensor output may remain constant even if the amount of water injected by the manifold injection device increases between t13 and t14, and even if water is injected directly after t14. Furthermore, the MCT sensor can be confused by the presence of liquid water on the sensor during saturation conditions (t13-t15), and the accuracy of the MCT measurement cannot be relied upon. For example, the MCT output may fluctuate and may not correlate with the amount of water injected.Since the air in the intake manifold becomes completely saturated with water, liquid water can enter the intake oxygen sensor's protective tube. As a result, the output of the IAO2 sensor, operating in nominal mode, may remain constant even as the amount of water injected increases (see the IAO2 signal shown at the dashed segment 809). Similarly, when the UEGO sensor is operating in nominal mode, its output may remain constant and may not reliably indicate the manifold water concentration, because the engine control unit maintains the exhaust air-fuel ratio, which remains at or around stoichiometric during water injection.

[0107] For this reason, the amount of injected water between t13 and t15, when the manifold water injection is at the saturation limit and while the direct water injection is varied, is reliably detected by one or more IAO2 sensors operating in variable voltage mode and UEGO sensors operating in variable voltage mode. At t13, when the IAO2 sensor becomes saturated, indicated by the sensor's pump current dropping to 0, the IAO2 can be operated in VVs mode to dissociate the water in the protective tube surrounding the IAO2 sensor's sensing element and obtain an accurate reading of the amount of water injected into the intake manifold. Thus, the output of the UEGO sensor operating in VVs mode can provide the most accurate estimate of the water injection quantity during saturated water injection conditions.In particular, the UEGO output can provide an estimate of the total amount of water injected into the intake airflow (for example, the total amount of water injected via a combination of manifold and direct water injection).

[0108] At t15, there is a drop in driver torque demand, resulting in a corresponding drop in engine speed / load and charge cooling demand. Therefore, water injection can be deactivated or reduced at t15. Sensor outputs may decrease accordingly. After t15, the MCT sensor can continue to provide an accurate estimate of manifold temperature, the humidity sensor can continue to provide an accurate estimate of manifold humidity, the IAO2 sensor can continue to operate in nominal mode to provide an accurate estimate of intake air oxygen content, and the UEGO sensor can continue to operate in nominal mode to provide an accurate estimate of the exhaust air-fuel ratio.In this way, water injection device selections can be set based on engine operating conditions, and water injection estimation modalities can be adjusted accordingly to enable an accurate estimation of the amount of water injected.

[0109] In this way, water injection detection can be adjusted based on the injection device selected for water injection and the specific benefits derived from water injection. By relying on temperature-based water injection control (such as via a charge temperature sensor) when water injection is used for knock relief at high loads, the charge cooling effect of the water injection can be accurately measured and compensated for. By relying on humidity or oxygen content-based water injection control (such as via an inlet humidity or oxygen sensor) when water injection is used for charge dilution at low loads, the charge dilution effect of the water injection can be accurately measured and compensated for.By adjusting water injection and engine operating parameters based on a detected water injection fault, the benefits of water injection and its associated fuel efficiency gains can be extended over a wider range of engine operating conditions. By injecting water via port water injection devices onto the hot surface of a closed intake valve when an engine dilution requirement exists, the rapid evaporation of water can be advantageously used to maximize the charge dilution effects of water injection while minimizing charge cooling effects.By injecting water via port water injection devices away from an open intake valve when engine cooling is required, the improved mixing of the injected water with the incoming airflow can be advantageously used to maximize the charge-cooling effects of water injection while minimizing charge dilution effects. By relying on an exhaust gas oxygen sensor operating in a variable voltage mode to detect net water injection during conditions where other sensors are limited, water injection estimation can be performed accurately and reliably. Improving the use of water injection can enhance engine performance.

[0110] In one embodiment, a method includes, during a first state, in response to an engine dilution request, port injection of water to a closed intake valve; and during a second state, in response to engine knock, port injection of water away from an open intake valve. In a first example of the method, the method further includes port injection of water to a closed intake valve involving the injection of water onto a valve surface at a time before the initiation of the intake valve opening, and port injection of water away from an open intake valve involving the injection of water from the valve surface at a time after the initiation of the intake valve opening.A second example of the procedure optionally includes the first example and further includes that the first state involves the engine load falling below a threshold, and the second state involves the engine load exceeding the threshold. A third example of the procedure optionally includes one or more of the first and second examples and further includes that intake manifold injection of water to the closed intake valve involves injection at bottom dead center (BDC) of an intake stroke, and that intake manifold injection of water away from the open intake valve involves injection between top dead center (TDC) and BDC of the intake stroke. A fourth example of the procedure optionally includes one or more of the first through third examples and further includes that the intake valve temperature is higher during the first state relative to the second state.A fifth example of the procedure optionally includes the first four examples and further includes that a larger proportion of the injected water remains in liquid form after injection during the second state relative to the first state. A sixth example of the procedure optionally includes the first five examples and further includes that airflow into a conduit coupled upstream of the intake valve is higher during the second state relative to the first state. A seventh example of the procedure optionally includes the first six examples and further includes that the amount of water commanded during the first state is based on each of engine load and modeled valve temperature; and the amount of water commanded during the second state is based on each of engine load and estimated knock intensity.An eighth example of the method optionally includes the first through seventh examples and further includes that the timing of the intake manifold injection of water to the closed intake valve is based on the modeled valve temperature, wherein the timing is delayed until the modeled valve temperature exceeds a threshold temperature, the threshold temperature being based on the amount of water injected during the first state. A ninth example of the method optionally includes the first through eighth examples and further includes, during the first state, after injection, estimating the actual amount of water in the engine based on feedback from an intake oxygen sensor operating in a variable voltage mode; and during the second state, after injection, estimating an actual amount of water in the engine based on feedback from a manifold charge temperature sensor.A tenth example of the procedure optionally includes the first through ninth examples and further comprises, during the first state, after injection, adjusting an EGR valve opening based on a difference between the commanded quantity and the actual quantity, with the EGR valve opening being increased as the difference increases; and during the second state, after injection, adjusting the ignition timing retard based on the difference between the commanded quantity and the actual quantity, with the ignition timing being further retarded as the difference increases.

[0111] In another embodiment, a method comprises, in response to an engine dilution request, port injecting a first quantity of water to an intake valve before the intake valve opens; and, in response to an engine charge cooling request, port injecting a second quantity of water away from the intake valve during the opening of the intake valve. In a first example of the method, the method further comprises, after port injection in response to the engine dilution request, estimating a change in intake oxygen using an intake oxygen sensor operating in a variable voltage mode and adjusting an EGR flow rate based on the estimated change in intake oxygen.A second example of the procedure optionally includes the first example and further comprises, after port fuel injection in response to the charge cooling requirement, estimating a change in manifold temperature via a manifold temperature sensor and setting a degree of ignition timing retard applied based on the estimated change in manifold temperature. A third example of the procedure optionally includes one or more of the first and second examples and further comprises each of the quantity and timing of port fuel injection in response to the engine dilution requirement being based on the modeled valve temperature, and each of the quantity and timing of port fuel injection in response to the charge cooling requirement being based on knock intensity.

[0112] In another embodiment, a system includes a port water injection device coupled to an intake port of an engine cylinder upstream of an intake valve of the cylinder; a manifold water injection device coupled to an engine intake manifold upstream of the port water injection device; a direct water injection device coupled to the cylinder; an exhaust gas oxygen sensor coupled to an exhaust manifold; a manifold charge temperature sensor and an intake oxygen sensor coupled to the intake manifold downstream of the manifold water injection device; an EGR channel, which includes an EGR valve, for recirculating exhaust gas from the exhaust manifold to the intake manifold; and a control unit.including a non-transient memory containing computer-readable instructions for: selecting one of the manifold water injection devices and the intake manifold water injection device to inject a first quantity of water in response to an engine dilution request, the selection being based on the intake valve temperature; and selecting one or more of the manifold water injection devices, the direct water injection device, and the intake manifold injection device to inject a second quantity of water for engine knock control, the selection being based on an injection limit of the manifold water injection device and an estimated cylinder-to-cylinder water imbalance. In a first example of the system, the system further includes selecting one of the manifold water injection devices and the intake manifold water injection device; selecting the manifold water injection device when the intake valve temperature is lower,and includes selecting the intake manifold water injection device when the intake valve temperature is higher, with the intake valve temperature being modeled based on engine load. A second example of the system optionally includes the first example and further includes selecting one or more of the manifold water injection devices, the intake port injection device, and the direct water injection device; selecting only the manifold water injection device when the manifold water injection device is within the injection limit and the imbalance is below a threshold; selecting each of the manifold water injection devices and the direct injection device when the manifold water injection device is at or above the injection limit and the imbalance is below the threshold; and selecting the intake port injection device when the imbalance exceeds the threshold.A third example of the system optionally includes one or more of the first and second examples and further includes that selecting the port fuel injection device for the engine dilution requirement involves injecting the first quantity of water via the port fuel injection device to the intake valve while the intake valve is closed, and that selecting the port fuel injection device for engine knock control involves injecting the second quantity of water via the port fuel injection device away from the intake valve while the intake valve is open. A fourth example of the system optionally includes one or more of the first through third examples and further includes, after injecting the first or second quantity of water, estimating an actual quantity of water received in the engine.and adjusting the opening of the EGR valve based on a deviation of the actual quantity from the first or second quantity, wherein the estimation includes: estimating based on an input from the exhaust oxygen sensor operating in a variable voltage mode when the port fuel injection device is selected; estimating based on an input from the manifold charge temperature sensor when the manifold fuel injection device is selected; and estimating based on each of the intake oxygen sensor and the exhaust oxygen sensor, each operating in variable voltage mode when the direct injection device is selected.

[0113] In another embodiment, a method comprises an engine: in response to water injection into an intake manifold via an intake manifold water injection device, adjusting the engine operation based on the output from an exhaust oxygen sensor, and in response to water injection into the intake manifold via the manifold water injection device, adjusting the engine operation based on an output from one or more of an intake oxygen sensor, an intake humidity sensor, and a manifold charge temperature sensor.

[0114] It should be noted that the exemplary control and estimation routines contained herein can be used with various internal combustion engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-volatile memory and executed by the control system, including the controller, in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more from any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Likewise, the processing sequence is not strictly necessary to achieve the features and advantages of the exemplary embodiments described herein, but is provided for the sake of clarity and description. One or more of the illustrated actions, processes, and / or functions may be repeated depending on the specific strategy employed. Furthermore, the described actions, processes, and / or functions may graphically represent code to be programmed in non-volatile memory of the computer-readable storage medium in the engine control system, the described actions being executed by carrying out the instructions in a system that includes the various internal combustion engine hardware components in combination with the electronic control unit.

[0115] It is understood that the interpretations and routines disclosed herein are exemplary in nature and that these specific embodiments are not to be interpreted in a restrictive sense, as numerous variations are possible. For example, the foregoing technology can be applied to V-6, 1-4, I-6, V-12, 4-cylinder boxer, and other engine types. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the different systems and arrangements and other features, functions, and / or properties disclosed herein.

[0116] The following claims, in particular, describe certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more such elements and neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application. Such claims, regardless of whether they have a broader, narrower, identical, or different scope compared to the original claims, are also to be considered included in the subject matter of the present disclosure.

Claims

[1] Method for an engine, comprising: During an initial state, in response to an engine dilution request, intake manifold injection of water to a closed intake valve; and During a second state, in response to engine knocking, intake manifold injection of water away from an open intake valve, whereby during the second state, relative to the first state, a larger proportion of the injected water remains in liquid form after injection. [2] Method according to claim 1, wherein intake manifold injection of water to the closed inlet valve comprises injecting water onto a valve surface at a time before initiating the opening of the inlet valve and intake manifold injection of water away from the open inlet valve comprises injecting water away from the valve surface at a time after initiating the opening of the inlet valve. [3] Method according to claim 1, wherein the first state includes the engine load falling below a threshold value, and wherein the second state includes the engine load exceeding the threshold value. [4] Method according to claim 1, wherein intake manifold injection of water to the closed inlet valve includes intake manifold injection at the bottom dead center (BDC) of an intake stroke and wherein intake manifold injection of water away from the open inlet valve includes intake manifold injection between top dead center (TDC) and BDC of the intake stroke. [5] Method according to claim 1, wherein the temperature of the inlet valve during the first state is higher relative to the second state. [6] Method according to claim 1, wherein the airflow into a conduit coupled upstream of the inlet valve is higher during the second state relative to the first state. [7] Method according to claim 1, wherein the amount of water commanded during the first state is based on each of the engine load and modeled valve temperature; and wherein the amount of water commanded during the second state is based on each of the engine load and estimated knock intensity. [8] Method according to claim 7, wherein the timing of the intake manifold injection of water to the closed inlet valve is based on the modeled valve temperature, wherein the timing is delayed until the modeled valve temperature exceeds a threshold temperature, the threshold temperature being based on the amount of water injected during the first state. [9] The method of claim 7, further comprising, during the first state, after injection, estimating the actual amount of water vapor in the intake manifold based on feedback from an intake oxygen sensor operating in a variable voltage mode; and during the second state, after injection, estimating an actual amount of water in the engine based on feedback from a manifold charge temperature sensor. [10] The method of claim 9, further comprising, during the first state, after injection, adjusting an EGR valve opening based on a difference between the commanded quantity and the actual quantity, wherein the EGR valve opening is increased as the difference increases; and during the second state, after injection, adjusting the ignition timing retardation based on the difference between the commanded quantity and the actual quantity, wherein the ignition timing is further retarded as the difference increases. [11] Method for an engine, comprising: In response to an engine dilution request, intake manifold injection of an initial quantity of water to an intake valve prior to the opening of the intake valve; and In response to an engine charge cooling request, a second quantity of water is injected into the intake manifold away from the intake valve during the opening of the intake valve. wherein each quantity and timing of intake manifold injection in response to the engine dilution requirement is based on the modeled valve temperature, and that each quantity and timing of intake manifold injection in response to the charge cooling requirement is based on knock intensity. [12] A method for an engine comprising: During an initial state, in response to an engine dilution request, intake manifold injection of water to a closed intake valve; and During a second condition, in response to engine knocking, intake manifold injection of water away from an open intake valve; where the temperature of the inlet valve is higher during the first state relative to the second state. [13] The method of claim 12, further comprising, after injecting water to the closed inlet valve during the first state, estimating an actual quantity of water received in the engine and adjusting the opening of an EGR valve based on a deviation in the actual quantity of water: Estimation based on input from the exhaust oxygen sensor, which operates in a variable voltage mode when a port fuel injection device is selected. [14] Method according to claim 12, wherein an amount of water commanded during the first state is based on each of the engine load and modeled valve temperature. [15] Method according to claim 12, wherein the timing of the intake manifold injection of water to the closed inlet valve is based on the modeled valve temperature, wherein the timing is delayed until the modeled valve temperature exceeds a threshold temperature, the threshold temperature being based on the amount of water injected during the first state.

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