METHOD AND SYSTEM FOR IMPROVING TRANSIENT TORQUE RESPONSE

Abstract

Method for a turbocharged engine (10), comprising: in response to a torque demand from a driver (132) opening an intake throttle (62, 63, 64, 65) and closing an exhaust wastegate valve (82) based on the torque demand independent of a change in an exhaust gas recirculation (EGR) plan (142, 152, 140, 150) and variable camshaft timing (VCT) plan (55); and Simultaneous planning of the EGR (142, 152, 140, 150) and the VCT (55) based on a predicted load deficit ratio independent of the actual position of the intake throttle (62, 63, 64, 65) and the wastegate valve (82).

Description

AREA

[0001] The present description generally relates to methods and systems for providing an improved torque response for a turbocharged engine. GENERAL STATE OF THE ART / BRIEF OVERVIEW

[0002] An engine system can be designed with a supercharging device, such as a turbocharger, to provide a boosted air charge to increase torque output. Specifically, a turbine spins using energy from an exhaust stream. The turbine drives a compressor, which delivers a boosted air charge to the engine intake. A supercharged engine can offer higher fuel efficiency and lower emissions than a naturally aspirated engine of similar power, making it possible for a smaller-displacement turbocharged engine to produce power comparable to a larger-displacement naturally aspirated engine. An engine system can also be designed with an exhaust gas recirculation (EGR) system, in which at least a portion of the exhaust gas is recirculated to the engine intake. The benefits of EGR include increased engine dilution, reduced exhaust emissions, and improved fuel efficiency.The operation of the various actuators can be coordinated to improve engine performance.

[0003] The benefits of turbocharging, downsizing, and EGR are generally more pronounced under steady-state conditions. However, under transient conditions, these same processes can negatively impact fuel efficiency. For example, fuel efficiency may be sacrificed for improved vehicle responsiveness under transient conditions. Another reason for the loss of fuel efficiency is the interaction between engine response and driver actions. For instance, during a pedal input event, the vehicle response initially lags behind the desired acceleration due to the slower initial charge buildup. Consequently, the driver may experience a noticeable "dead pedal" phase with no perceptible increase in torque. The driver may then overcompensate for this.After an initial slower build-up, however, the boost increases at a faster rate due to a positive feedback loop, with higher load and increased airflow leading to greater boost pressure. Consequently, overcompensation by the driver can generate excessive airflow and thus an excessive increase in torque, which in turn requires additional pedal correction by the driver (e.g., pedal release) as well as torque-reducing measures (such as retarded ignition). As a result, the engine may operate at a lower efficiency than if the initial requirement had been followed more closely.

[0004] An exemplary approach to improving the torque response of a turbocharged engine is presented by Cunningham et al. in US 9,175,629 B1. In this approach, during a torque surge, a throttle in an air intake system (AIS) that draws EGR from a low-pressure exhaust gas recirculation (LP-EGR) system to an intake manifold upstream of a compressor can be opened to increase the throttle inlet pressure for a downstream throttle located after the compressor. Opening the AIS throttle increases the airflow to provide just enough torque without significantly exceeding the torque demand. Further prior art is known from German patent applications DE 10 2014 210 642 A1 and DE 10 2014 216 399 A1.

[0005] The inventors of the present invention have, however, recognized potential problems with such systems. For example, increasing the throttle inlet pressure may only provide a portion of the load requested during a pedal actuation transient, while the remaining load relies on the slower charge build-up. Another example is the potential for further delay and an increase in response time due to the introduction of low-pressure exhaust gas recirculation (LP-EGR). In particular, the LP-EGR circuit has a long transport delay, as the exhaust gas must pass through the turbocharger compressor, high-pressure air intake piping, an intercooler, and an intake manifold before reaching the combustion chamber. Consequently, the actual engine airflow profile may deviate from the target airflow profile due to variations caused by the EGR being introduced at different times.As a result, the engine torque response may not follow the torque profile requested by the driver.

[0006] The object of the present invention is therefore to provide an improved method for a turbocharged engine and an improved engine system.

[0007] This objective is achieved by the subject matter of the independent claims. Preferred embodiments of the present invention are the subject matter of the dependent claims.

[0008] In one example, the aforementioned problems can be at least partially solved by a procedure for a turbocharged engine, comprising: opening an intake throttle and closing an exhaust wastegate valve in response to a driver's torque demand, based on the torque demand, independent of any changes to the exhaust gas recirculation (EGR) and variable cam timing (VCT) schedules; and simultaneously scheduling the EGR and VCT based on a predicted load deficit ratio, independent of the actual positions of the intake throttle and wastegate valve. In this way, transient torque response can be improved by synchronizing the air path actuators with the charging system.

[0009] As an example, a turbocharged engine can be designed with a turbocharger that includes a turbine driving a compressor, with an exhaust gas flow bypassing the turbine controlled by an exhaust gas wastegate valve. The engine can be designed with high-pressure exhaust gas recirculation (HPEG) capabilities, where exhaust gas is recirculated from upstream to the turbine to downstream to the compressor. In response to a pedal actuation event by a driver, boost actuators, including an intake throttle and an exhaust gas wastegate valve, can be actuated to meet the torque demand. For example, the intake throttle opening can be increased (such as to a wide-open throttle position) to allow more charge air to enter the intake manifold, while the exhaust gas wastegate valve opening can be decreased (such as to a fully closed position) to accelerate turbine spin-up.The throttle and wastegate valve positions are planned assuming nominal settings for air path actuators, including a high-pressure EGR valve and variable camshaft timing (VCT), even if they are adjusted (as discussed below). Thus, if the increased demand can be met without exceeding the throttle setpoint, EGR and VCT can be kept at nominal settings with a lower delivery rate. Simultaneously with the charge setting, the engine control unit can also predict an anticipated load and / or torque shortfall ratio (aLSR) based on the requested engine load (dependent on pedal position) relative to an estimated engine load that can be provided if the engine continues to operate under the current speed / load conditions without EGR and with the throttle wide open (WOT).In other words, the control unit can determine a difference between the requested air charge and airflow and what can be provided at wide open throttle (WOT) without EGR. If there is an air charge deficit, a torque deficit is also expected. As the load deficit ratio increases, it can be determined that the fast-acting throttle's capacity is quickly exhausted, and any remaining torque demand requires further airflow and boost pressure build-up, resulting in a delay. To improve engine response at increasing load deficit ratios, variable valve timing (VCT) and high-pressure EGR can be scheduled based on the deficit ratio, independent of the actual positions of the intake throttle and exhaust wastegate valve, to anticipate the deficit.For example, as the load deficit ratio increases, the VCT (Variable Control Technology) can initially be held at its nominal setting, while the high-pressure EGR (High-Pressure EGR) is limited depending on the deficit, allowing more fresh air charge to be delivered to the engine. Then, as the load deficit ratio continues to increase, the high-pressure EGR can be limited, and the VCT can be advanced or retarded to increase the volumetric efficiency depending on the load deficit ratio. Similarly, the throttle and wastegate valves can be actuated independently of changes to the high-pressure EGR and VCT schedules, for example, by keeping the throttle more open and the wastegate more closed, even when the VCT is switched to a higher volumetric efficiency setting. Once the target boost pressure is reached, nominal settings for all actuators can be restored.

[0010] In this way, an actual engine torque profile can more closely follow a target engine torque profile. Specifically, engine load and airflow can be released during transients while a charge builds up, and then a smooth transition out of the transient can be provided once sufficient charge has been built up. By adjusting fast-acting air path actuators, including high-pressure EGR and VCT, based on a predicted load deficit ratio, unnecessarily aggressive and fuel-inefficient operations that might be required when an intake throttle target is exhausted are avoided. Furthermore, excessive torque generation is prevented. By moving the air path actuators just enough to meet driver demand, the need for fuel-inefficient torque buffers is reduced.Furthermore, if the transient condition is met, a faster and smoother transition out of the transient state can be more easily achieved. This allows sufficient airflow to be provided to meet the required torque increase without overcompensating for the required torque output, while enabling a smooth and rapid transition from transient to steady-state engine operation. Overall, the performance of the turbocharged engine during transients is improved.

[0011] It is understood that the foregoing summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the detailed description. It is not intended to identify 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 eliminate 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. Fig. Figure 2 is an exemplary flowchart illustrating a higher-level routine for providing a transient torque response in response to an increase in a driver's torque demand. Fig. Figure 3 is a flowchart illustrating an exemplary procedure for calculating a likely load deficit ratio based on an estimate of requested and predicted engine load. Fig. Figure 4 shows a diagram illustrating an actual and a predicted engine load response in response to an increase in the torque requirement of a driver. Fig. Figure 5 shows a diagram illustrating an actual and a predicted engine torque response in response to an increase in the torque demand of a driver. Fig. Figure 6 shows a diagram illustrating example charging actuator settings. DETAILED DESCRIPTION

[0012] The following description concerns systems and methods for improving torque response under transient conditions in a turbocharged engine system, such as the engine system from Fig. 1. In response to a torque demand from a driver, a control system may be designed to execute a control routine, such as the exemplary routine from Fig. 2, to perform air path actuator settings based on an expected load deficit ratio ( Fig. 3) to adjust, while charging actuator settings are adjusted based on the driver's torque requirements. In particular, the actuator settings can be tuned but performed independently, allowing an actual airflow and torque profile to better follow a requested airflow and torque profile. Exemplary engine load (or airflow) and torque responses achieved through the airflow and charging actuator settings are shown in the Fig. 4 and Fig. Figure 5 illustrates the expected operation of a turbocharged engine in relation to Fig. Figure 6 illustrates that by adjusting air path actuator settings to compensate for a predicted load or torque deficit, while adjusting charge actuator settings to increase boost pressure in response to an increase in driver torque demand, engine torque response can be improved.

[0013] Now, regarding Fig. Figure 1 shows a schematic representation of an engine system 100 comprising a cylinder of a multi-cylinder engine 10, which may be included in a propulsion system of a motor vehicle. The engine 10 can be controlled, at least partially, by a control system comprising the controller 12 and by input from a driver 132 via an input device 130. In this example, the input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The combustion chamber (i.e., the cylinder) 30 of the engine 10 may include combustion chamber walls 32 with a piston 36 positioned therein. In some embodiments, the end face of the piston 36 may have a shell inside the cylinder 30. The piston 36 may be coupled to the crankshaft 40, so that a reciprocating motion of the piston is translated into a rotary motion of the crankshaft.The crankshaft 40 can be coupled to at least one drive wheel of a vehicle via an intermediate gear system. Furthermore, a starter motor can be coupled to the crankshaft 40 via a flywheel to enable the engine 10 to be started.

[0014] The combustion chamber 30 can draw in intake air from the intake manifold 44 via the intake port 42 and discharge combustion gases via the exhaust port 48. The intake manifold 44 and the exhaust port 48 can be selectively connected to the combustion chamber 30 via a corresponding intake valve 52 and exhaust valve 54. In some embodiments, the combustion chamber 30 can have two or more intake valves and / or two or more exhaust valves.

[0015] The inlet valve 52 can be controlled by the controller 12 via an electric valve actuator (EVA) 51. Similarly, the outlet valve 54 can be controlled by the controller 12 via an EVA 53. Alternatively, the variable valve actuator can be electro-hydraulic or any other conceivable mechanism to enable valve actuation. Under certain conditions, the controller 12 can vary the signals supplied to the actuators 51 and 53 to control the opening and closing of the respective inlet and outlet valves. The position of the inlet valve 52 and outlet valve 54 can be determined by the valve position sensors 55 and 57, respectively.In alternative embodiments, one or more of the intake and exhaust valves can be actuated by one or more cams and can utilize one or more cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) systems to vary the valve operation. For example, cylinder 30 can alternatively include an intake valve controlled by an electric valve actuator and an exhaust valve controlled by cam actuation, including a CPS and / or VCT 55.

[0016] The VCT 55 can be a dual independent variable camshaft timing system for independently modifying the intake and exhaust valve timing. Furthermore, the VCT 55 can be configured to advance or retard the valve timing by advancing or retarding the camshaft timing and can be controlled by the control 12. The VCT 55 can also be configured to vary the control of valve opening and closing events by varying the relationship between the crankshaft position and the camshaft position. For example, the VCT 55 can be configured to rotate the intake camshaft independently of the crankshaft to cause the valve timing to be advanced or retarded. In some embodiments, the VCT 55 can be a cam torque-actuated device designed for rapid variation of the camshaft timing.In some embodiments, the valve control, such as the closing of the intake valve (IVC) and the closing of the exhaust valve (EVC), can be varied by a continuously variable valve lift (CVVL) device.

[0017] The valve / cam control devices and systems described above can be hydraulically actuated, electrically actuated, or a combination thereof. In one example, the camshaft position can be changed via cam phase adjustment by an electric actuator (e.g., an electrically actuated cam adjuster). In another example, the camshaft position can be changed via a hydraulically actuated cam adjuster. Signal lines can send control signals to the VCT and receive cam control and / or cam selection measurements. By adjusting the variable camshaft timing, the engine's delivery rate can be varied. As explained here, the VCT can also be adjusted during torque transients to improve the response of a turbocharged engine.

[0018] A fuel injection device 66 is, as shown, directly coupled to the combustion chamber 30 to inject fuel proportionally to the pulse width of a signal FPW received by the control unit 12 via the electronic driver 68. In this way, the fuel injection device 66 provides so-called direct injection of fuel into the combustion chamber 30. The fuel injection device can be mounted, for example, in the side or top of the combustion chamber. Fuel can be supplied to the fuel injection device 66 by a fuel system (not shown) that includes a fuel tank, a fuel pump, and a fuel distributor.In some embodiments, the combustion chamber 30 may alternatively or additionally include a fuel injection device which is arranged in the intake manifold 44 in a configuration which provides so-called port fuel injection into the intake duct upstream of the combustion chamber 30.

[0019] Under selected operating modes, an ignition system 88 of the combustion chamber 30 can provide a spark via a spark plug 92 in response to an ignition advance signal SA (Spark Advance) from the control unit 12. Although spark ignition components are shown, in some embodiments the combustion chamber 30 or one or more other combustion chambers of the engine 10 can be operated in a compression ignition mode with or without a spark.

[0020] The intake duct 42 can include throttles 62 and 63 with throttle valves 64 and 65, respectively. In this particular example, the positions of the throttle valves 64 and 65 can be varied by the controller 12 via signals provided to an electric motor or actuator contained within the throttles 62 and 63, a configuration commonly referred to as an electronic throttle control (ETC). In this way, the throttles 62 and 63 can be operated to vary the intake air supplied to the combustion chamber 30 below other engine cylinders. The positions of the throttle valves 64 and 65 can be provided to the controller 12 by the throttle position signals TP. Pressure, temperature, and mass airflow can be measured at various points along the intake duct 42 and the intake manifold 44.For example, the intake duct 42 can include an air mass flow sensor 120 for measuring the clean air mass flow entering through the throttle 63.

[0021] The engine 10 may further include a compression device such as a turbocharger or a supercharger, which includes at least one compressor 162 arranged upstream of the intake manifold 44. In the case of a turbocharger, the compressor 162 may be driven at least partially by a turbine 164 (e.g., via a shaft) arranged along an exhaust duct 48. In the case of a supercharger, the compressor 162 may be driven at least partially by the engine and / or an electric machine and may not include a turbine. Therefore, the degree of compression provided to one or more cylinders of the engine via a turbocharger or supercharger can be varied by the control unit 12. An intercooler 154 may be located downstream of the compressor 162 and upstream of the intake valve 52. The intercooler 154 may, for example,It is designed to cool gases that have been heated by compression via the compressor 162. In one embodiment, the charge air cooler 154 can be located upstream of the throttle 62. Pressure, temperature, and mass airflow can be measured downstream of the compressor 162, for example, using sensor 145 or 147. The measured results from sensors 145 and 147 can be communicated to the control unit 12 via signals 148 and 149, respectively. Pressure and temperature can also be measured upstream of the compressor 162, for example, using sensor 153, and communicated to the control unit 12 via signal 155. The clean air mass flow can be communicated to the control unit 12 via the MAF signal. Furthermore, the pressure of the air charge in the intake manifold 44 can be measured and communicated to the control unit 12 via the manifold air pressure (MAP) sensor.Furthermore, the temperature of the charge air in the intake manifold 44 can be measured by the manifold air temperature (MAT) sensor and communicated to the control unit 12. Additionally, the pressure of compressed air upstream of the intake throttle 63 and downstream of the compressor 162 can be measured by a throttle inlet pressure (TIP) sensor, such as sensor 145. In particular, charge levels in the engine system can be measured by the TIP sensor by measuring TIP (also referred to as boost pressure).

[0022] Furthermore, in the disclosed embodiments, an EGR system can direct a desired portion of the exhaust gas from the exhaust channel 48 to the intake manifold 44. Fig. Figure 1 shows a high-pressure (HP) EGR system and a low-pressure (LP) EGR system. The HP EGR is routed through the HP EGR channel 140 from upstream of the turbine 164 (also referred to as the exhaust turbine) to downstream of the compressor 162. The degree of HP EGR supplied to the intake manifold 44 can be varied by the controller 12 via the HP EGR valve 142. The low-pressure EGR is routed through the low-pressure EGR channel 150, which is located downstream of the turbine 164, to the compressor 162. The degree of low-pressure EGR supplied to the intake manifold 44 can be varied by the controller 12 via the low-pressure EGR valve 152. The HD-EGR system can include an HD-EGR cooler 146 and the LD-EGR system can include an LD-EGR cooler 158 to, for example, dissipate heat from the EGR gases to an engine coolant.

[0023] Under certain conditions, the EGR system can be used to regulate the temperature of the air-fuel mixture in combustion chamber 30. Therefore, it may be desirable to measure or estimate the EGR mass flow. EGR sensors can be located within EGR channels and can provide a reading of one or more parameters, including mass flow, pressure, temperature, O2 concentration, and exhaust gas concentration. For example, a high-pressure EGR sensor 144 can be located in the high-pressure EGR channel 140. As explained here, a degree of high-pressure EGR can also be adjusted during torque transients to improve the response of a turbocharged engine.

[0024] Exhaust gases exiting the combustion chambers 30 and the exhaust channel 48 cause the exhaust turbine 164 to rotate, which is coupled to the compressor 162 along the shaft 163. The degree of compression supplied to one or more cylinders of the engine via a turbocharger can be varied by the control unit 12. If reduced turbine torque is desired, a portion of the exhaust flow can be routed through a wastegate 82, thus bypassing the turbine. The wastegate 82 (also referred to as an exhaust wastegate) can be coupled to the exhaust turbine 164 within the turbocharger. By adjusting the position of the wastegate 82 via the control unit 12, the boost pressure supplied by the turbocharger can be controlled. Therefore, the wastegate 82 can function as a boost actuator. Here, the controller 12 can provide a signal based on the target charge to adjust an electromagnetic actuator that is coupled to the wastegate 82.The combined current from the turbine 164 and the wastegate 82 can then flow through the emission control device 71 and 72.

[0025] Depending on the operating conditions, a portion of the exhaust gases from exhaust duct 49, located downstream of turbine 164, can be recirculated to intake duct 42, located upstream of compressor 162, via an exhaust gas recirculation (EGR) duct 150. This portion of the exhaust gases can flow through the EGR duct 150, via the EGR cooler 158 and a low-pressure EGR valve 152. This enables low-pressure EGR (LP-EGR). In some embodiments, high-pressure exhaust gas recirculation (HPEGR) is possible instead of or in addition to low-pressure exhaust gas recirculation (LPEGR), wherein a portion of the exhaust gases from the exhaust channel 48, upstream of the turbine 164, to the intake manifold 44, downstream of the compressor 162, is recirculated via a separate high-pressure exhaust gas recirculation channel 140 and an EGR cooler 146 coupled therein, as well as an HPEG valve 142. The LPEGR valve 152 and the HPEGR valve 142 can be opened (e.g.,The opening of the EGR valves can be increased to allow a controlled amount of cooled exhaust gas into the intake manifold for desired combustion and emission control performance. Thus, the low-pressure EGR valve 152 and the high-pressure EGR valve 142 can be actuated by an actuator (e.g., electrical, mechanical, hydraulic, etc.) based on commands received from the control unit 12.

[0026] Each cylinder 30 can be operated by one or more valves. In the present example, each cylinder 30 includes a corresponding intake valve 52 and an exhaust valve 54. Each intake valve 52 and exhaust valve 54 can be held in a desired position by a corresponding spring. The engine system 100 further includes one or more camshafts (not shown) for actuating an intake valve 52 and / or an exhaust valve 54. In one example, an intake camshaft can be coupled to the intake valve 52 and actuated to actuate the intake valve 52. In another example, an exhaust camshaft can be coupled to the exhaust valve 54 and actuated to actuate the exhaust valve 54.In some embodiments, where the intake valve of a plurality of cylinders 30 is coupled to a common camshaft, the intake camshaft can be actuated to actuate the intake valves of all coupled cylinders.

[0027] The intake valve 52 is actuated between an open position, which admits intake air into the corresponding cylinder, and a closed position, which essentially blocks the intake air from the cylinder. The intake camshaft (not shown) can be incorporated into an intake valve actuation system that is connected to the control unit 12. The intake camshaft can include an intake cam having a cam lift profile for opening the intake valve 52 for a defined intake duration. In some embodiments (not shown), the camshaft can include additional intake cams with a different cam lift profile, allowing the intake valve 52 to be open for an alternative duration (also referred to here as a cam profile adjustment system).Depending on the elevation profile of the additional cam, the alternative duration can be longer or shorter than the defined intake duration of the intake cam. The elevation profile can influence the cam lift height, cam duration, and / or cam timing. In one example, the intake camshaft is moved to a more advanced timing. By opening the intake valve earlier, it is possible for burnt gas to flow back into the intake port, displacing the air that would normally have been drawn in during the subsequent intake stroke. In another example, if the intake camshaft is switched to a more retarded timing, the intake valve can open later. As a result, the intake valve closes when the compression stroke is already advanced, causing cylinder air to be forced back into the intake port, with less air retained in the cylinder.A control system may be able to change the intake valve duration by longitudinally moving the camshaft 68 and switching between cam profiles.

[0028] This allows each exhaust valve 54 to be actuated between an open position, in which exhaust gas is released from the corresponding cylinder, and a closed position, which essentially retains gas in the cylinder and blocks the escape of exhaust gases from the cylinder. Thus, premature opening of the exhaust valve can have a limited effect on the air charge. The exhaust camshaft (not shown) can be incorporated into an exhaust valve actuation system connected to the control 12. The exhaust camshaft can include an exhaust cam having a cam lift profile for opening the exhaust valve 54 for a defined exhaust duration. In some embodiments, where the exhaust valve of a plurality of cylinders 30 is coupled to a common camshaft, the exhaust camshaft can be actuated to actuate the exhaust valves of all coupled cylinders.In some embodiments, the exhaust camshaft may further include additional exhaust cams with a different cam lift profile, which allows the exhaust valve 54 to be open for an alternative duration. The lift profile may affect the cam height, cam duration, and / or cam timing. In one example, if the exhaust camshaft is switched to a more retarded timing, the exhaust valve may open later, so that, due to increased overlap with the intake valve opening, it is possible for burnt gas to flow back into the opening and displace the air drawn in during a subsequent intake stroke. In another example, if the exhaust camshaft is switched to a more advanced timing, the exhaust valve may then open earlier with minimal effect on the air charge.A control system may be able to switch the exhaust valve duration by longitudinally moving the exhaust camshaft and switching between cam profiles.

[0029] The intake valve actuation system and the exhaust valve actuation system may further include pushrods, rocker arms, tappets, etc. Such devices and features can control the actuation of the intake valve 52 and the exhaust valve 54 by converting a rotary motion of the cams into a sliding motion of the valves. As already discussed, the valves may also be actuated via additional cam lift profiles on the camshafts, the cam lift profiles being able to provide varying cam lift height, varying cam duration, and / or varying cam timing between the different valves. However, alternative camshaft arrangements (overhead and / or with pushrods) may be used as desired. Furthermore, in some examples, cylinder 30 may each have more than one exhaust valve and / or intake valve.In other examples, both the exhaust valve 54 and the intake valve 52 of one or more cylinders can be actuated by a common camshaft. Furthermore, in some examples, some of the intake valves 52 and / or exhaust valves 64 can be actuated by their own independent camshaft or other device.

[0030] According to the diagram, the exhaust gas sensor 126 is coupled to the exhaust gas channel 48 downstream of the turbine 164. The sensor 126 can be any suitable sensor for providing an indication of an exhaust gas air-fuel ratio, such as a linear lambda sensor or UEGO (wideband or wide-range lambda sensor), a dual-state lambda sensor or EGO, a HEGO (heated EGO), or a NO sensor. x -, HC or CO sensor.

[0031] According to the illustration, the emission control devices 71 and 72 are arranged downstream of the exhaust gas sensor 126 along the exhaust gas channel 48. The devices 71 and 72 can be a three-way catalyst (TWC), a NOₓ sensor, or a catalytic converter. x -trap, various other emission control devices, or combinations thereof. For example, device 71 may be a TWC and device 72 may be a particulate filter (PF). In some embodiments, the PF 72 may be located downstream of the TWC 71 (as in Fig. 1 shown) are located, while in other embodiments the PF 72 is positioned upstream of the TWC 72 (in Fig. (1 not shown) can be positioned.

[0032] Control 12 is in Fig. 1 is represented as a microcomputer, which includes a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, which in this specific example is represented as a read-only memory chip 106, a direct access memory 108, a keep-alive memory 110 and a data bus.In addition to the signals discussed previously, the control unit 12 can receive various signals from sensors coupled to the engine 10, including the mass air flow (MAF) measurement from a mass air flow sensor 120; the engine coolant temperature (ECT) from a temperature sensor 112 coupled to the cooling sleeve 114; a profile ignition pickup (PIP) signal from a Hall sensor 118 (or other type) coupled to the crankshaft 40; the throttle position (TP) from a throttle position sensor; the boost pressure from a throttle intake pressure (TIP) sensor; and an absolute manifold pressure (MAP) signal from sensor 122. An engine speed (RPM) signal can be generated by the control unit 12 from the PIP signal.The manifold pressure signal (MAP) from a manifold pressure sensor can be used to provide an indication of vacuum or pressure in the intake manifold. It should be noted that various combinations of the aforementioned sensors can be used, such as a MAF sensor without a MAP sensor, or vice versa. In stoichiometric operation, the MAP sensor can provide an indication of engine torque. Furthermore, this sensor, together with the detected engine speed, can provide an estimate of the charge (including air) introduced into the cylinder. For example, sensor 118, which can also be used as an engine speed sensor, can generate a predetermined number of evenly spaced pulses per crankshaft revolution.

[0033] Based on the data from the various sensors Fig. From the received signals and instructions stored in the controller's memory, the controller can select the various actuators from 1. Fig. 1. Use to adjust engine operation. For example, the controller 12 can send signals to actuate the throttle 64, the low-pressure EGR valve 152, the high-pressure EGR valve 142, the VCT actuator, the intake and exhaust valves, the wastegate valve 82, etc. As an example, the controller 12 can be configured to send a signal to an actuator coupled to both the intake throttle and the exhaust wastegate valve in response to an increase in the driver's torque demand, in order to move the throttle to a more open position while moving the wastegate valve to a more closed position, regardless of any changes to the EGR and VCT schedules.As another example, the control unit 12 can send a signal to vary a plan of the HD-EGR valve and the VCT actuator to limit the degree of EGR while increasing the engine's delivery rate in response to the increase in torque demand, with the plans being varied independently of the instructed change in the position of the intake throttle and the wastegate valve.

[0034] For example, the controller 12 can be designed to handle an expected load deficit (aLSR), as in Fig. 3. Based on a transient increase in the driver's torque requirement, the control system can determine and, in response to the transient torque increase, adjust the air path actuators accordingly, as described in Fig. 2. The load deficit ratio (LSR), as used here, is defined as the ratio between the current engine torque output and the predicted engine torque output with the throttle wide open and without EGR. Exemplary routines that can be used to adjust the air path actuators based on a predicted LSR are described in the Fig. 2-3 described.

[0035] In this way, the components from Fig. 1. An engine system comprising an accelerator pedal for receiving a torque request from a driver; an engine comprising an intake manifold; a turbocharger comprising an intake compressor driven by an exhaust turbine for providing enhanced air charge to the engine; an intake throttle coupled to the intake manifold downstream of the intake compressor; a wastegate comprising a wastegate valve coupled via the exhaust turbine; an exhaust gas recirculation (EGR) system comprising a high-pressure EGR channel comprising an EGR valve for recirculating exhaust gas from upstream to the exhaust turbine to downstream to the intake compressor; a variable camshaft timing (VCT).The engine system may further include a control system with computer-readable instructions stored in non-volatile memory for the following: in response to an increase in a driver's torque demand received during operation with at least some EGR and with the VCT operating on a first plan, decreasing the opening of the EGR valve while the VCT switches to a second plan with a higher delivery rate than the first plan; increasing the opening of the throttle while decreasing the opening of the wastegate valve, the increase and decrease being based on the first plan of the VCT.In one example, reducing the EGR valve opening can be based on a ratio between a target engine power output corresponding to the increased torque demand of the driver and a predicted engine power output with the throttle wide open, the EGR valve fully closed, and VCT operating according to the first plan. In another example, increasing and decreasing the opening can be based on the first plan of VCT, including, in response to a driver's torque demand, keeping the wastegate valve further closed based on a lower delivery rate of the first plan, even while VCT switches to the higher delivery rate of the second plan.The control unit may include further instructions for the following: increasing the opening of the EGR valve in response to the driver's torque demand being met, while the VCT is reset to the first plan; decreasing a throttle opening while increasing a wastegate valve opening, with the increase and decrease being based on the first plan of the VCT. In yet other examples, the EGR system further includes a low-pressure EGR channel, including another EGR valve for recirculating exhaust gas from downstream to the exhaust turbine to upstream to the intake compressor, and the control unit includes further instructions for adjusting the opening of the other EGR valve in response to both the driver's torque demand and decreasing the opening of the EGR valve.

[0036] Now, regarding Fig. 2 An exemplary routine for improving the transient torque response of a turbocharged engine following a driver request for increased torque is presented. Instructions for executing Procedure 200 and the other procedures contained herein can be provided by a controller based on instructions stored in a memory of the controller and in conjunction with sensors of the engine system, such as those referred to above. Fig. The control system can execute the signals received from the sensors described in section 1. The system can use motor actuators of the motor system to adjust the motor operation according to the procedures described below.

[0037] Procedure 202 involves estimating engine operating conditions, such as engine speed, pedal position, driver torque demand, engine speed output, exhaust temperature, engine dilution, turbine speed, manifold absolute pressure (MAP), manifold airflow (MAF), boost pressure, etc. Procedure 204 can determine whether there is an increase in driver-requested torque. For example, an increase in driver torque demand in response to driver pedal input resulting in a shift of the accelerator pedal can be confirmed. If an increase in driver torque demand is confirmed, the procedure proceeds to procedure 206. Otherwise, the procedure proceeds to procedure 205, maintaining the air path actuators at their nominal settings and / or continuing to adjust them based on the estimated operating conditions.For example, the control unit can continue to operate the engine in a steady-state scheduling mode (SSM), with the VCT set to nominal settings corresponding to a lower volumetric efficiency, the high-pressure EGR set to provide engine dilution based on engine speed / load conditions, and the intake throttle and wastegate valve also actuated based on engine speed / load conditions. The process then ends.

[0038] At 206, after confirming an increase in the torque requested by the driver, a predicted load deficit ratio (aLSR) is determined. As with Fig. As carried out in step 3, the deficit ratio predicts a likely deficit in air charge or airflow, and thus an engine torque deficit, between the driver demand and the engine's capacity, while taking into account varying engine conditions (such as ambient pressure, manifold temperature, fuel alcohol content, etc.) that affect the engine's capacity. The engine's air path actuators are then adjusted based on the deficit, thus providing a faster and smoother transition to the desired boost pressure. Once the aLSR has been determined, the procedure proceeds to 208.

[0039] At 208, the specified load deficit ratio is compared to a threshold value to determine whether the aLSR is greater than the threshold. For example, the threshold can be set depending on the engine load or charge air required to operate the engine under wide-open throttle (WOT) conditions with no EGR. For instance, the threshold can be set to 1.0, corresponding to the maximum throttle setting for providing a rapid response. If the load deficit ratio exceeds the threshold, it can be inferred that any additional torque demand may require boost buildup, resulting in a delay in the engine's torque output.For example, once the threshold is exceeded, further boost pressure may require the exhaust turbine and intake compressor to spin up, resulting in turbo lag that can impair engine performance and cause the driver to perceive a sluggish vehicle response.

[0040] If the aLSR is below the threshold, the engine control unit at 210 may be configured to continue operating the engine according to the steady-state scheduling mode (SSM). In one example, the SSM might involve operating the engine with a nominal VCT and EGR schedule, typically obtained from a steady-state engine map, to provide the best fuel efficiency with compromises in combustion stability and emissions. For instance, the engine's BSFC can be estimated from the map, and EGR and VCT schedules can be determined that provide the lowest BSFC for a given engine operating condition. Thus, operating in SSM mode can improve fuel efficiency during moderate driving. Operating in SSM involves adjusting the intake throttle opening in response to the torque requested by the driver.In one example, as the requested torque increases, the intake throttle opening can increase. In another example, the intake throttle opening can be based on the actual manifold pressure or boost pressure relative to a target boost pressure based on the torque requested by the driver, with the intake throttle opening increasing as the difference between the actual and target boost pressure increases.

[0041] Furthermore, the control unit at 214 can adjust the opening of an EGR valve to provide a desired engine dilution, with the engine dilution being determined based on engine speed / load conditions. For example, higher engine dilution can be requested at low to medium engine speed / load conditions, while lower engine dilution can be requested at medium to high engine speed / load conditions. The control unit can adjust the opening of a high-pressure EGR valve to provide the desired engine dilution by recirculating exhaust gas from upstream to the turbine to downstream to a compressor. In another example, in response to the driver's torque demand during operation in SSM mode, the control unit can close the high-pressure EGR valve or keep the EGR valve closed if it is already closed.Closing the EGR valve reduces charge dilution, allowing the boost pressure required to achieve the desired torque output to be reached quickly without the need for a transient torque response. Furthermore, the control unit can close a low-pressure EGR valve, which recirculates exhaust gas from downstream of the turbine back upstream of the compressor. In other examples, the opening degree of the high-pressure EGR valve can be matched to that of the low-pressure EGR valve to provide the desired engine dilution.

[0042] Operating in SSM mode also involves scheduling VCT at 216 levels to provide an initial lower delivery rate. This allows the air path actuators (VCT and EGR) to be adjusted to ensure sufficient airflow into the intake manifold to achieve the target torque output.

[0043] In version 218, operation in SSM mode further involves the control unit scheduling boost actuators, including a wastegate valve coupled to the exhaust turbine, based on driver demand and the target torque profile (or target air charge profile). In one example, as the requested torque (or requested air charge) increases, the wastegate valve opening may be reduced. In another example, the wastegate valve opening may be based on the actual manifold pressure or boost pressure relative to a target boost pressure, based on the driver's requested torque, with the wastegate valve opening decreasing as the difference between the actual and target boost pressure increases.

[0044] Conversely, if the aLSR (determined at step 206) is greater than the threshold, the engine control unit can then be configured at step 220 to operate the engine according to a transient response mode (TRM). For example, the TRM can be activated to provide a target load during transients in anticipation of turbo lag, such as during a sudden increase in torque demand from a driver after harder pedal input.

[0045] In response to the sudden increase in torque demand, the intake throttle opening at 221 can be set to a wider opening position (e.g., fully open to wide-open throttle, WOT) to allow a more pressurized air charge into the intake manifold, thus accelerating the increase in boost pressure and torque output. It is understood that the intake throttle can be scheduled independently of the HD EGR and VCT plans and assuming the lower volumetric setting of SSM mode.

[0046] The inventors recognized that during a pedal actuation transient, when the driver requests increased load, the demand can be met quickly if the throttle preset is not exceeded. In other words, if opening the throttle is sufficient to meet the increased airflow demand, there is no immediate need to do anything else. However, when the throttle preset is exhausted, as determined based on the aLSR, there is an opportunity to activate air path actuators, such as those for VCT and EGR, which are faster than the turbocharger, for improved response (and faster delivery of the requested increased airflow). This is achieved by activating the TRM.Once the TRM is activated, the charging actuators can be matched with air path actuators, allowing the engine to quickly and smoothly return to SSM mode to maximize fuel efficiency without causing any problems in drivability.

[0047] In 222, operating in TRM mode involves limiting EGR based on the aLSR. For example, the EGR (e.g., high-pressure EGR) valve can be adjusted based on the aLSR to open less, thus reducing engine dilution. In one example, EGR is limited proportionally to a function defined by (1 - aLSR). In an alternative function, EGR is limited proportionally to a difference between the aLSR and the threshold value. The control system can use a map, lookup table, algorithm, or other function that calculates the aLSR (as per the one in the Fig. The software uses the described procedure (calculated in the three methods) as input and provides a target high-pressure EGR valve position as output. In one example, limiting the high-pressure EGR proportionally to the deficit ratio involves fully closing the high-pressure EGR valve. Reducing the high-pressure EGR increases the proportion of the intake manifold filled with fresh air, which, along with increasing the throttle opening, increases engine torque output. This, in turn, leads to faster turbine acceleration to provide increased engine torque and higher enthalpy exhaust gas exiting the cylinder, feeding the turbine, and driving the compressor. In some examples, low-pressure EGR can also be set based on the high-pressure EGR setting, such as to a less open position to further reduce engine dilution.It is understood that EGR can be scheduled while maintaining the VCT plan and assuming the lower delivery rate of SSM mode. Furthermore, HD EGR can be scheduled independently of the throttle and wastegate valve settings. This makes it possible to schedule EGR just enough to meet driver demand, thus reducing the need for unnecessarily aggressive and potentially fuel-inefficient operations.

[0048] Once the EGR has been adjusted based on the aLSR, the procedure at 224 involves again determining whether the aLSR is still above a threshold value. That is, it can be determined whether a torque or load deficit is predicted after the throttle limit is exhausted and after the HD-EGR is limited. If the updated aLSR value falls below the threshold, it can be concluded that the increase in a driver's torque demand can be met by adjusting the HD-EGR alone, and adjustments to other air path actuators are not necessary. Accordingly, at 226, the VCT can be maintained on a nominal map corresponding to a lower volumetric efficiency setting. If the updated aLSR value is above the threshold, it can be concluded that adjustments to other air path actuators, such as...VCT settings are necessary to meet torque requirements and reduce the possibility of a future torque deficit.

[0049] If the aLSR is greater than a threshold value after the EGR setting, the procedure proceeds to 228, switching VCT to a plan that provides a second delivery level higher than the first. In one example, the VCT can be advanced or retarded relative to the plan with the first, lower delivery level compared to the plan with the second, higher delivery level. While the plan with the lower delivery level is more efficient during steady-state driving, the response to a transient driver demand can be improved by switching to the plan with the higher delivery level. For example, the intake valve opening control can be advanced on the second plan relative to the first plan to provide an increased delivery level. The degree of advancement can be selected in this example to compensate for the deficit indicated by the aLSR.

[0050] At 230, boost actuators, including the exhaust wastegate valve, can be scheduled based on driver demand. For example, the exhaust wastegate valve opening can be reduced, such as to a fully closed position, to accelerate turbine spool-up. It is understood that the wastegate valve can be scheduled independently of the HD EGR and VCT schedules and assuming the lower volumetric efficiency setting of SSM mode. Setting the wastegate valve to a more closed position increases the exhaust flow through the turbine, thereby reducing turbo lag and improving the delivery of the requested boost pressure.By scheduling the wastegate valve independently of changes to the EGR and VCT schedules, the boost actuators can be positioned to bring the boost pressure to a level necessary for a smooth return to and maintenance of the boost pressure in the SSM schedule once the torque (or airflow) demand is met. In one example, scheduling the wastegate valve independently of changes to the EGR and VCT schedules results in the wastegate valve remaining closed further and / or for a longer duration compared to a wastegate position based on the VCT position (corresponding to a higher volumetric efficiency) and the EGR degree (e.g., the more restricted EGR degree) during transient mode, enabling faster turbine spool-up and quicker turbocharger response.

[0051] At step 232, it is determined whether the target boost pressure has been reached. If the target boost pressure, corresponding to the torque demand of a driver, has been reached, the procedure proceeds to step 236, where the air path actuators are reset to their nominal settings. For example, the high-pressure EGR can be scheduled according to the engine speed / load to increase engine dilution, such as by increasing the opening of the high-pressure EGR valve (and the low-pressure EGR valve in coordination with the high-pressure EGR valve). Additionally, the VCT can be reset (e.g., advanced or retarded) to a nominal setting corresponding to a lower volumetric efficiency. If the target boost pressure is not reached, the procedure returns to step 234, where the VCT and EGR are further adjusted according to the TRM mode, with the high-pressure EGR still limited and the VCT switched to a setting that further increases the volumetric efficiency.

[0052] It is understood that, while the procedure represents adjusting the actuators in response to the predicted load or airflow deficit ratio, in alternative examples the actuators may be adjusted in response to a predicted torque deficit ratio calculated on the basis of the load or airflow deficit ratio.

[0053] In this way, the transient torque response during an increase in a driver's torque demand can be improved. By opening an intake throttle and closing an exhaust wastegate valve based on the torque demand, independent of changes in EGR and VCT, and simultaneously scheduling EGR and VCT based on a load or torque deficit ratio, independent of the actual position of the intake throttle and wastegate valve, torque overcompensation and potentially fuel-inefficient processes can be avoided. Furthermore, a provided actual torque response can better follow a target torque response, thus reducing the need for a torque or air buffer.

[0054] Furthermore, by simultaneously planning EGR and VCT based on the predicted load or torque deficit ratio, EGR planning can be limited, while VCT is kept at a lower delivery rate if the predicted deficit ratio is below a threshold. Conversely, if the deficit ratio is above a threshold, VCT can be switched from a lower to a higher delivery rate.

[0055] In relation to Fig. Section 3 now describes an exemplary routine for determining an aLSR. By predicting the aLSR, a load or torque deficit can be anticipated, enabling the engine control unit to provide a more robust engine torque response in situations where an increase in torque demand is requested by a driver. It is understood that Procedure 300 illustrates an exemplary routine for calculating an aLSR and that other routines, maps, lookup tables, and algorithms may be used by the control unit to estimate an aLSR without deviating from the scope of the disclosure.

[0056] In 302, an accelerator pedal position can be translated into an estimate of a requested engine load. In one example, the requested engine load can be determined using a lookup table indexed based on the engine load in correlation with various combinations of a range of accelerator pedal positions. In another example, the procedure can determine the actual pedal position (PP) from a sensor (such as the PP sensor 134). Fig. 1) Read the reference values ​​for closed and fully open pedal positions and calculate the engine load based on a specific relationship between pedal actuation and a target engine load. Once the requested engine load for a given pedal position has been determined, the procedure proceeds to 304.

[0057] Procedure 304 predicts an engine load that can be provided based on the engine capacity. Specifically, the predicted engine load is calculated assuming the engine operates with a fully open throttle (e.g., at wide open throttle) and without EGR, such as using an engine capacity model. For example, engine loads possible at various engine speeds without EGR and wide open throttle can be previously recorded in a map (e.g., during engine calibration) and stored in the controller's memory. These loads can then be retrieved by the controller to predict the engine load. In another example, the predicted engine load can be derived from a predefined relationship between throttle position, air mass flow, and engine load. Once the predicted engine load has been determined with the throttle wide open and without EGR, the procedure proceeds to procedure 306.

[0058] In the 306, a load deficit ratio (LSR) is calculated as the ratio of requested engine load to predicted engine load. For example, a load deficit ratio of 1 represents the maximum torque output that can be provided under wide-open throttle conditions, and an additional torque request above LSR = 1 may require charge build-up. For instance, if the ratio is 1, it can be predicted that the fast-acting throttle will be exhausted, and an additional torque request will require charge build-up, which is a slower process resulting in torque lag. By predicting the future value of the LSR and adjusting the air path actuators accordingly, engine response is further improved. For example, the engine can operate in SSM mode when the LSR is less than 1 and in TRM mode when the LSR is greater than 1.Once the LSR value has been determined, the procedure proceeds to 308.

[0059] In section 308, one or more lead filters are applied to the calculated LSR to predict an expected LSR value. For example, the aLSR can be predicted by using one or more lead filtering and prediction / preview information. In an example, a lead filter can be implemented using the following equations: X(k)=(1−f)*X(k−1)+f*LSR(k) aLSR(k)=(1−r)*X(k)+r*LSR(k) where k is a time index, X(k) is an auxiliary variable, and (f, r) are appropriately selected parameters. Furthermore, one or more parameters from driver operating history, navigation inputs (including road and traffic conditions), and vehicle data can be integrated into the filtering system to improve the accuracy of the aLSR prediction. For example, the parameters (f, r) can be adjusted in response to driving style trends and current traffic conditions. In this example, the parameters can be increased for more dynamic driving and traffic conditions to provide greater system intervention and increased torque response. In another example, the aLSR can be increased in response to preview information, such as upcoming overtaking maneuvers or increasing road gradients, to effectively increase the readily available torque buffer.

[0060] In this way, in response to a driver's torque demand, the engine control unit of a turbocharged engine can open an intake throttle and close a wastegate valve based on the torque demand, independent of any changes to the exhaust gas recirculation (EGR) and variable camshaft timing (VCT) schedules. As a result, an engine can transition from the nominal conditions of a steady-state operating mode to a transient response mode, allowing for improved torque response and better adherence to the target torque profile. Simultaneously, the control unit can schedule EGR and VCT based on a predicted torque deficit ratio, independent of the actual positions of the intake throttle and wastegate valves.Furthermore, the control unit can estimate a predicted torque deficit based on the difference between an actual engine torque output and a predicted engine torque output with the throttle wide open and EGR off. It can then calculate the predicted torque deficit based on the driver's torque demand. Moreover, the predicted torque deficit ratio can be based on one or more factors from driver operating history, navigation inputs (including road and traffic conditions), and vehicle data. For example, opening the intake throttle and closing the wastegate valve based on torque demand could involve estimating a target boost pressure based on the torque demand and increasing the intake throttle opening while simultaneously increasing the wastegate valve closing as the target boost pressure increases.In another example, the simultaneous scheduling of EGR and VCT based on the predicted torque deficit ratio can involve limiting EGR while keeping VCT on a first schedule when the predicted torque deficit ratio is lower than a threshold, and limiting EGR while switching VCT from the first schedule to a second schedule when the predicted torque deficit ratio is higher than the threshold, with the first schedule having a lower delivery rate than the second schedule. In the sense used here, switching VCT from the first schedule to the second schedule in an example involves advancing or retarding VCT from the lower delivery rate to the higher delivery rate.Opening the intake throttle and closing the exhaust wastegate valve, independent of any change in the VCT plan, can involve setting the intake throttle opening degree and the wastegate valve closing degree based on the lower delivery rate of the first VCT plan. The turbocharged engine can include an exhaust turbine driving an intake compressor, with the wastegate valve coupled to the exhaust turbine. The EGR is a high-pressure EGR (HP-EGR) system that includes exhaust gas recirculated from upstream of the exhaust turbine to downstream of the intake compressor. The control system can further be configured to set a low-pressure EGR plan based on the HP-EGR limit, with the low-pressure EGR system including exhaust gas recirculated from downstream of the exhaust turbine to upstream of the intake compressor.In response to the target boost pressure being reached, the control unit can revert the VCT to the first plan with the lower volumetric efficiency and increase the EGR. As a result, nominal conditions of a steady-state operating mode can be restored.

[0061] In this way, the engine control unit can precisely schedule different engine operating modes depending on the predicted aLSR values. This allows the turbocharged engine to provide the torque output necessary to maintain SSM mode, while ensuring a quick and smooth transition from TRM to SSM mode.

[0062] In relation to Fig. 4. A diagram is now shown that compares an initial engine load response with an engine load response based on the approach with the expected torque deficit from Fig. 2 (also referred to here as the anticipated engine load response) compares the actual and anticipated engine loads following an increase in the driver's torque demand. Map 400 shows an example of the actual engine load and the anticipated engine load of a turbocharged gasoline direct injection (GTDI) engine as the pedal position increases along the y-axis. The increase in pedal position, shown in curve 410, indicates a torque demand from the driver, with the torque demand increasing as the pedal is pressed further. All curves are shown as a function of time along the x-axis. In one example, the engine is a 2.0-liter GTDI engine, and the engine response to pedal deduction occurs from 45 mph. Curve 402 shows the requested engine load that increases in response to the increase in pedal position shown in curve 410.Graph 408 shows the initial engine load response, and graph 406 shows the anticipated engine load response. In this context, "load" refers to the normalized cylinder air charge. It is understood that the load in graph 408 can also be interpreted as indicating an air charge or air mass. Comparing graphs 408 and 406, it is determined that the anticipated engine load response 406 is, overall, closer to the target engine load during the maneuver. In particular, it can be observed that the initial period with a small deficit is significantly longer, indicating a noticeably better correlation between demand and requirement. The anticipated engine response 406 is improved because the deficit (shown at time 407 between t1 and t2) between demand and requirement is detected earlier, resulting in earlier actuator intervention compared to the initial response (graph 408). Fig. Figure 4 shows the improvements in engine load response, i.e., the engine's air intake capacity. Next are in Fig. 5 improvements to engine torque response are shown, which result in an improved vehicle acceleration response.

[0063] In relation to Fig. Section 5 now shows a diagram that compares an initial motor torque response with a motor torque response based on the approach with the expected torque deficit from Fig. 2 (also referred to here as the expected engine torque response) compares the response to an increase in the torque demand of a driver. Map 500 shows an example of an engine torque response as a function of time from an effective brake mean effective pressure (BMEP) of 1 bar at steady load for an engine at 1750 rpm. In this example, the engine is a 2.7-liter GTDI engine.

[0064] Figure 504 shows the torque response of the initial engine without the approach with anticipated torque deficit. In the initial engine torque response 504, the increase in torque demand increases continuously at a specified rate over time, with charging and air path actuators scheduled according to steady-state mode (SSM). Consequently, there is a sluggish initial torque response, represented here by a plateau in engine torque during a period d1 between t1 and t2. The slower-than-desired increase in engine torque is caused by a torque deficit, where the torque requested by the driver is greater than the engine's torque capacity with the throttle wide open and without EGR.Trajectory 502 represents the engine torque response when a predicted low torque response (LSR) is forecast by the control unit and when air path and charge actuators are scheduled according to the transient response mode (TRM). During the TRM, as shown in Trajectory 502, the torque deficit at d1 is predicted, and therefore, in anticipation of the deficit, the control unit adjusts the intake throttle and exhaust wastegate valve based on the increased torque demand, while simultaneously scheduling high-pressure EGR and variable displacement compensating (VCT) independently of the actual positions of the intake throttle and exhaust wastegate valve. For example, for duration d1, the control unit might keep the intake throttle in its wide-open position, the wastegate valve fully closed, and simultaneously set a high-pressure EGR valve to be fully closed, while the VCT is advanced to a volumetric efficiency setting.Then, after t2, the high-pressure EGR valve can be opened to increase engine dilution, while the VCT is delayed to a control setting that provides a lower nominal delivery rate. Furthermore, the intake throttle opening and the wastegate valve opening can be adjusted according to torque demand, as in steady-state mode.

[0065] In relation to Fig.Figure 6 illustrates exemplary settings of charging and air path actuators to enable a transient torque response during an increase in the driver's torque demand. Map 600 represents the pedal position (PP) during curve 602. The pedal position indicates a driver's torque demand, with the torque demand increasing as the pedal is pressed further. Map 600 shows an engine torque output during curve 604, a boost pressure during curve 606, an intake throttle position during curve 610, a VCT setting during curve 612, changes in the position of a wastegate valve during curve 614, and the position of a high-pressure EGR valve during curve 616.The wastegate valve opens to allow exhaust gas to bypass the turbocharger turbine, causing the turbine to spin down and reduce boost pressure, or closes to allow more exhaust gas through the turbine, causing it to spin up and increase boost pressure. All curves are plotted against time along the x-axis. Time markers t1-t6 represent significant points in time during engine operation.

[0066] Between t0 and t1, in response to a low driver torque demand, the vehicle operates with nominal settings and a relatively low engine torque output (curve 604). The boost pressure is at its nominal value. The lower driver demand is met by partially opening the intake throttle to provide a low engine speed / load profile based on the reduced driver torque requirement. Furthermore, the VCT (curve 612) is scheduled to a nominal position providing a lower volumetric efficiency. The wastegate valve (curve 614) is held partially open to improve the intake compressor surge margin, and the high-pressure EGR valve is partially open due to engine dilution.

[0067] At t1, a first, small pedal actuation by the driver triggers an initial increase in torque demand. In response to this initial pedal actuation, the intake throttle opening is increased proportionally to the increase in torque demand. It is determined that a calculated torque deficit ratio between the requested torque demand and the predicted engine torque output (dashed line at 607), also referred to here as the expected load deficit ratio, aLSR (represented by the hatched area 607), is less than a threshold value (as indicated by the hatched area between 606 and 607, with a range below the threshold value). Consequently, it can be concluded that the increase in torque demand can be met by adjusting the intake throttle without exceeding the specified intake throttle opening.Since the torque requirement can be met by the intake throttle alone, the other charge and air path actuators, such as VCT, wastegate valve, and high-pressure EGR valve, are kept at their nominal settings (such as those from before t1). For example, the VCT is kept at a first setting.

[0068] At t2, the driver depresses the accelerator pedal to initiate a second pedal actuation, which is larger than the first. The second pedal actuation can correspond to a second increase in torque demand, which is larger than the first increase in torque demand (and a higher boost pressure). In response to the increase in torque demand, the intake throttle opening is further increased. However, the throttle setting alone is insufficient to meet the increase in torque demand, and therefore, while the intake throttle opening is increased, the wastegate valve is adjusted to a more closed position to increase the turbine speed. However, even with the intake throttle and wastegate valve adjustments, the actual engine torque delivered (dashed line at 608) is lower than the target torque output (curve 604).The control unit can predict a torque deficit ratio and determine that the aLSR (as indicated by the hatched area between 604 and 608) is expected to be higher than a threshold. In response to the aLSR being higher than the threshold, the control unit may be designed to adjust the high-pressure EGR valve to a more closed position to reduce engine dilution. In this case, the high-pressure EGR valve is adjusted based on the aLSR and independently of the actual positions of the intake throttle and wastegate valve. Additionally, air path actuators, such as the VCT, are switched from the first plan to a second plan with more advanced control than the first plan, based on the new aLSR. The first plan operates at a lower volumetric efficiency than the second plan. The new settings are then maintained.

[0069] At t3, the torque deficit is met, with the actual torque output matching the target torque output and the aLSR reduced (as shown without a hatched area). Therefore, the torque output can be met solely by adjusting the intake throttle and the wastegate valve. Consequently, the VCT is switched back to the nominal control setting from the first plan, the wastegate valve is set to a wider open position to allow more exhaust gas to bypass the turbine, and the high-pressure EGR valve is also set to a wider open position.

[0070] In t4, the driver depresses the accelerator pedal to instruct a third pedal actuation with a higher amount and boost pressure than both the first and second pedal actuations. In response to the third pedal actuation, the intake throttle is moved to a fully open position, such as wide-open throttle (WOT), to increase airflow for higher boost pressure and engine torque output. Furthermore, the control unit predicts the torque deficit ratio and determines that the aLSR is higher than a threshold (as indicated by the hatched area 609). To compensate for this deficit, the high-pressure EGR valve is programmed to a more closed position to further limit the high-pressure EGR in relation to the aLSR.Furthermore, the VCT is set to a more advanced control (than the initial control applied between t2 and t3) to provide a second, higher volumetric efficiency, which is higher than the first volumetric efficiency at t3. In addition, the wastegate valve is set to a fully closed position, independent of the VCT and EGR schedule. If the wastegate valve position were set based on the VCT and EGR, the wastegate valve would have been actuated to a relatively wider open position (as shown in Figure 615), which would lead to a reduction in exhaust pressure upstream of the turbine and consequently a reduction in boost pressure.Therefore, by adjusting the wastegate position according to the first delivery level, regardless of VCT and EGR schedules, the wastegate valve can be closed for a longer period of time to provide the necessary boost pressure and engine torque output to meet the torque requirements of a driver.

[0071] In the t5, the torque deficit was compensated for by adjusting the various air path actuators. As soon as the boost pressure is able to maintain the requested engine torque output, the engine transitions from a transient operating mode to a steady-state mode, with the high-pressure EGR valve being set to a wider open nominal position, the VCT being reset to the lower-volume nominal setting, and the wastegate valve also being opened.

[0072] In T6 mode, the driver releases the pedal, for example, by letting go of the accelerator pedal. In response to the resulting decrease in torque demand, the intake throttle opening is reduced to lower the airflow into the engine cylinders, the wastegate valve opening is increased to a fully open position, allowing exhaust gas to bypass the turbine and thus slowing it down, and the high-pressure EGR valve and VCT remain at their respective nominal settings to further reduce engine boost pressure and torque to meet the driver's reduced torque demand. This allows for a smoother torque transition from the transient increase in torque demand.

[0073] In this way, in response to a driver's torque request, an engine control unit can predict a torque deficit ratio based on the driver's torque request relative to a predicted engine torque output under selected steady-state conditions; and limit exhaust gas recirculation (EGR) depending on the deficit ratio, while actuating both an intake throttle coupled downstream of an intake compressor and a wastegate valve coupled to an exhaust turbine depending on the driver's torque request, with the limiting and actuation being performed independently. The prediction can involve estimating a predicted torque deficit as the difference between the driver's requested torque and an engine torque output under current steady-state engine operating conditions with the throttle wide open and EGR off.The prediction process can further involve estimating a predicted torque deficit ratio, defined as the ratio between the predicted torque deficit and the driver's torque demand. The control system can also schedule variable cam timing (VCT) based on the deficit ratio, in coordination with the EGR limit and independently of the intake throttle and wastegate valve actuation. For example, the EGR system could include high-pressure EGR, which is recirculated from the exhaust turbine upstream to the intake compressor downstream.This can involve scheduling VCT in coordination with limiting EGR if the predicted torque deficit ratio is lower than a threshold, limiting EGR while maintaining VCT on a first plan with a lower delivery rate; and, if the predicted torque deficit ratio is higher than the threshold, limiting EGR while advancing or delaying VCT from the first plan to a second plan with a higher delivery rate.

[0074] In this way, engine torque output and charge response can be improved when there is an increase in torque demand from the driver. By anticipating a load deficit, a different setting of the air path actuators can be planned to provide a quick and smooth transition from a transient engine operating condition to steady-state mode. Furthermore, by adjusting charge actuators, such as the wastegate valve, independently of the VCT positions and EGR levels, the wastegate valve can be kept closed for a longer period during pedal actuation transients, resulting in faster charge build-up and quicker engine torque response.By scheduling VCT and HD-EGR proportionally to the anticipated load deficit ratio, while planning boost pressure relative to a steady-state boost build-up mode, engine load is more accurately delivered during transients as boost pressure builds. Furthermore, a smoother transition out of the transient can be provided once sufficient boost pressure has been built. By aligning the actuation of air path actuators with that of boost actuators during a transient boost build-up response mode, the engine operating mode can be quickly and smoothly returned to steady-state, improving fuel efficiency without introducing drivable issues. By limiting HD-EGR and shifting VCT only as far as necessary to meet driver demand, unnecessarily aggressive and potentially fuel-inefficient actuator settings are avoided.Furthermore, the need for air and torque reserves or buffers is reduced, thus minimizing associated disadvantages for fuel efficiency.

[0075] An exemplary procedure for a turbocharged engine comprises: opening an intake throttle and closing an exhaust wastegate valve in response to a driver's torque demand, based on the torque demand, independent of any changes to an exhaust gas recirculation (EGR) and variable camshaft timing (VCT) schedule; and simultaneously scheduling the EGR and VCT based on a predicted load deficit ratio, independent of the actual positions of the intake throttle and wastegate valve. In the preceding example, the procedure additionally and, if necessary, further comprises estimating a predicted load deficit based on the difference between an actual engine airflow and a predicted engine airflow with the throttle wide open and without EGR; and calculating the predicted load deficit ratio based on the predicted load deficit relative to the driver's torque demand.In one or all of the preceding examples, the predicted load deficit ratio is additionally or optionally based on one or more factors from driver operating history, navigation inputs (including road and traffic conditions), and vehicle data. In one or all of the preceding examples, opening the intake throttle and closing the wastegate valve based on torque demand additionally or optionally involves estimating a target boost pressure based on the torque demand and increasing the intake throttle opening while increasing the wastegate valve closing as the target boost pressure increases.In one or all of the preceding examples, additionally or optionally simultaneously scheduling EGR and VCT based on the plan when the predicted load deficit ratio is lower than a threshold, and limiting EGR while switching VCT from the first plan to a second plan when the predicted load deficit ratio is higher than the threshold, the first plan having a lower delivery rate than the second plan. In one or all of the preceding examples, switching VCT from the first plan to the second plan additionally or optionally involves bringing forward or delaying VCT from the lower delivery rate to the higher delivery rate.In one or all of the preceding examples, opening the intake throttle and closing the exhaust wastegate valve, regardless of any change in the VCT plan, additionally or optionally involves setting an intake throttle opening degree and a wastegate valve closing degree based on the lower delivery rate of the first VCT plan. In one or all of the preceding examples, the turbocharged engine additionally or optionally includes an exhaust turbine driving an intake compressor, the wastegate valve being coupled to the exhaust turbine, and the EGR being a high-pressure EGR (HP-EGR) system that includes exhaust gas recirculated from upstream of the exhaust turbine to downstream of the intake compressor.In one or all of the preceding examples, the method additionally or optionally further comprises setting a low-pressure EGR plan based on limiting the high-pressure EGR, wherein the low-pressure EGR includes exhaust gas recirculated from downstream to the exhaust turbine to upstream to the intake compressor. In one or all of the preceding examples, the method additionally or optionally further comprises, in response to the target boost pressure being reached, resetting the VCT to the first plan with the lower delivery rate and increasing the EGR.

[0076] Another exemplary procedure includes: in response to a torque request from a driver, predictions of a torque deficit ratio based on the driver's torque request in relation to a predicted engine torque output under selected steady-state conditions; limiting exhaust gas recirculation (EGR) depending on the deficit ratio, while actuating both an intake throttle coupled downstream to an intake compressor and a wastegate valve coupled to an exhaust turbine depending on the driver's torque request, with the limiting and actuating being carried out independently of each other.In the preceding example, predicting additionally or optionally includes estimating a predicted torque deficit as a difference between the torque requested by the driver and an engine torque output under current steady-state airflow conditions with the throttle wide open and without EGR. In one or all of the preceding examples, predicting additionally or optionally further includes estimating a predicted torque deficit ratio as a ratio between the predicted torque deficit and the driver's torque request. In one or all of the preceding examples, the method additionally or optionally further includes scheduling the variable cam timing (VCT) as a function of the deficit ratio, in coordination with the EGR limitation and independent of the actuation of the intake throttle and the wastegate valve.In one or all of the preceding examples, the EGR additionally or optionally includes high-pressure EGR, which is recirculated from upstream to the exhaust turbine to downstream to the intake compressor, and wherein the scheduling of VCT in coordination with limiting the EGR includes: if the predicted torque deficit ratio is lower than a threshold, limiting the EGR while maintaining the VCT on a first schedule with a lower delivery rate; and, if the predicted torque deficit ratio is higher than the threshold, limiting the EGR while advancing or delaying the VCT from the first schedule to a second schedule with a higher delivery rate.

[0077] Another example of an engine system includes: an accelerator pedal to receive a torque request from a driver; an engine that includes an intake manifold; a turbocharger that includes an intake compressor driven by an exhaust turbine to provide increased air charge to the engine; an intake throttle coupled to the intake manifold downstream of the intake compressor; a wastegate that includes a wastegate valve coupled via the exhaust turbine; an exhaust gas recirculation (EGR) system that includes a high-pressure EGR channel that includes an EGR valve to recirculate exhaust gas from upstream of the exhaust turbine to downstream of the intake compressor; a variable camshaft control system; and a control system with computer-readable instructions stored in non-volatile memory to: in response to an increase in a torque request from a driver.which is received during operation with at least some EGR and with the VCT according to a first plan; reducing the opening of the EGR valve while the VCT switches to a second plan with a higher delivery rate than the first plan; increasing the throttle opening while decreasing the opening of the wastegate valve, the increase and decrease being based on the first plan of the VCT. In the preceding example, additionally or optionally, the reduction of the EGR valve opening is based on a ratio between a desired engine airflow corresponding to the increased torque demand of the driver and a predicted engine airflow with the throttle wide open.where the EGR valve is fully closed and VCT operates according to the first plan. In one or all of the preceding examples, increasing and decreasing VCT based on the first plan additionally or optionally in response to a driver's torque demand involves keeping the intake throttle more open and keeping the wastegate valve more closed based on a lower delivery level of the first plan, even as VCT transitions to the higher delivery level of the second plan. In one or all of the preceding examples, the control additionally or optionally further involves instructions to: increase the opening of the EGR valve while VCT reverts to the first plan in response to the driver's torque demand being met; decrease a throttle opening while increasing a wastegate valve opening.where the increasing and decreasing are based on the first plan of the VCT. In one or all of the preceding examples, the EGR system additionally or presumably further includes a low-pressure EGR channel, including another EGR valve for recirculating exhaust gas from downstream of the exhaust turbine to upstream of the intake compressor, and wherein the control further includes instructions for: adjusting the opening of the other EGR valve in response to both the driver's torque demand and decreasing the opening of the EGR valve.

[0078] It should be noted that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system designs. The control methods and routines disclosed herein can be stored as executable instructions in non-volatile memory and executed by the control system, which includes the control unit in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Thus, various actions, processes, and / or functions shown can be performed in the sequence shown, in parallel, or, in some cases, omitted.Similarly, 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 simplicity. One or more of the illustrated processes, steps, and / or functions can be repeated depending on the specific strategy employed. Furthermore, the described processes, steps, and / or functions can graphically represent code that is to be programmed in non-volatile memory of the computer-readable storage medium in the engine control system, whereby the described processes are executed by carrying out the instructions in a system that includes the various engine hardware components in combination with the electronic control unit.

[0079] It is understood that the interpretations and routines disclosed herein are exemplary and that these specific embodiments are not to be interpreted restrictively, as numerous variations are possible. For example, the foregoing technology can be applied to V-6, I-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 various systems and configurations and other features, functions, and / or properties disclosed herein.

[0080] The following claims, in particular, describe certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element or "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 considered to be included in the subject matter of the present disclosure.

Claims

[1] Method for a turbocharged engine (10), comprising: in response to a torque demand from a driver (132) opening an intake throttle (62, 63, 64, 65) and closing an exhaust wastegate valve (82) based on the torque demand independent of a change in an exhaust gas recirculation (EGR) plan (142, 152, 140, 150) and variable camshaft timing (VCT) plan (55); and Simultaneous planning of the EGR (142, 152, 140, 150) and the VCT (55) based on a predicted load deficit ratio independent of the actual position of the intake throttle (62, 63, 64, 65) and the wastegate valve (82). [2] The method of claim 1, further comprising: Estimating a predicted load deficit based on a difference between an actual engine airflow (120, MAF) and a predicted engine airflow with the throttle wide open (62, 63, 64, 65) and without EGR (142, 152, 140, 150); and Calculating the predicted load deficit ratio based on the predicted load deficit in relation to the driver's torque requirement (132). [3] Method according to claim 2, wherein the predicted load deficit ratio is further based on one or more driver operating history, navigation inputs including road and traffic conditions, and vehicle data. [4] Method according to claim 1, wherein the opening of the intake throttle (62, 63, 64, 65) and the closing of the wastegate valve (82) based on the torque requirement include estimating a target boost pressure based on the torque requirement and increasing the opening of the intake throttle (62, 63, 64, 65), while the closing of the wastegate valve (82) is increased as the target boost pressure increases. [5] The method of claim 1, wherein the simultaneous scheduling of the EGR (142, 152, 140, 150) and the VCT (55) based on the predicted load deficit ratio includes limiting the EGR (142, 152, 140, 150) while maintaining the VCT (55) on a first schedule when the predicted load deficit ratio is lower than a threshold, and limiting the EGR (142, 152, 140, 150) while switching the VCT (55) from the first schedule to a second schedule when the predicted load deficit ratio is higher than the threshold, wherein the first schedule has a lower delivery rate than the second schedule. [6] Method according to claim 5, wherein switching the VCT (55) from the first plan to the second plan involves advancing or retarding the VCT (55) from the lower delivery level to the higher delivery level. [7] Method according to claim 5, wherein the opening of the intake throttle (62, 63, 64, 65) and the closing of the wastegate valve (82) independently of the change in the VCT plan include setting an opening degree of the intake throttle (62, 63, 64, 65) and a closing degree of the wastegate valve (82) based on the lower delivery degree of the first VCT plan. [8] Method according to claim 5, wherein the turbocharged engine (10) includes an exhaust gas turbine (164) which drives an intake compressor (162), wherein the wastegate valve (82) is coupled to the exhaust gas turbine (164) and wherein the EGR is a high-pressure EGR (HP-EGR) (142, 140) which includes exhaust gas recirculated from upstream to the exhaust gas turbine (164) to downstream to the intake compressor (162). [9] Method according to claim 8, further comprising setting a low-pressure EGR plan based on the limitation of the high-pressure EGR (142, 140), wherein the low-pressure EGR (152, 150) includes exhaust gas recirculated from downstream to the exhaust turbine (164) to upstream to the intake compressor (162). [10] Method according to claim 5, further comprising, in response to the achievement of a target boost pressure, resetting the VCT (55) to the first plan with the lower delivery rate and increasing the EGR (142, 152, 140, 150). [11] Engine system (100), comprising: an accelerator pedal (130) for receiving a torque request from a driver (132); an engine (10) which includes an intake manifold (44); a turbocharger comprising an intake compressor (162) driven by an exhaust turbine (164) to provide an enhanced air charge to the engine (10); an intake throttle (62, 63, 64, 65) which is coupled downstream to the intake compressor (162) and to the intake manifold (44); a wastegate which includes a wastegate valve (82) coupled via the exhaust turbine (164); an exhaust gas recirculation (EGR) system comprising a high-pressure EGR channel (140) which includes an EGR valve (142) for recirculating exhaust gas from upstream to the exhaust gas turbine (164) to downstream to the intake compressor (162); a variable camshaft control (VCT) (55); and a controller (12) with computer-readable instructions stored in non-volatile memory for: in response to an increase in the torque requirement of a driver (132), which is received during operation with at least some EGR (142, 140) and with the VCT (55) on a first plan, Reducing the opening of the EGR valve (142) while the VCT (55) is switched to a second plan with a higher delivery rate than the first plan; and Increasing the opening of the intake throttle (62, 63, 64, 65) while decreasing the opening of the wastegate valve (82), the increase and decrease being based on the first plan of the VCT (55). [12] Engine system according to claim 11, wherein the reduction of the opening of the EGR valve (142) is based on a ratio between a desired engine airflow corresponding to the increased torque requirement of the driver (132) and a predicted engine airflow with the throttle (62, 63, 64, 65) wide open, wherein the EGR valve (142) is fully closed and the VCT (55) is carried out according to the first plan. [13] Engine system according to claim 11, wherein increasing and decreasing based on the first plan of the VCT (55) in response to the torque requirement of a vehicle driver (132) involves keeping the intake throttle (62, 63, 64, 65) further open and keeping the wastegate valve (82) further closed based on a lower delivery level of the first plan, even while the VCT (55) is switched to the higher delivery level of the second plan. [14] Motor system according to claim 13, wherein the control (12) includes further instructions for: in response to the fact that the torque requirement of a driver (132) is met, Increasing the opening of the EGR valve (142) while the VCT (55) is reset to the first plan; and Reducing the opening of the intake throttle (62, 63, 64, 65) while increasing the opening of the wastegate valve (82), the increase and decrease being based on the first plan of the VCT (55). [15] Engine system according to claim 11, wherein the EGR system further comprises a low-pressure EGR channel (150) which includes another EGR valve (152) for recirculating exhaust gas from downstream to the exhaust turbine (164) to upstream to the intake compressor (162), and wherein the control unit (12) includes further instructions for: Adjusting the opening of the other EGR valve (152) in response to both the torque requirement of a driver (132) and the reduction of the opening of the EGR valve (142).

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