Method and system for engine control

Abstract

This disclosure provides "methods and systems for engine control." Methods and systems are provided for achieving turbocharger shaft speed control without overcharging the system battery. In one example, the shaft speed is reduced by applying a negative torque from an electric booster assist motor until the system battery is fully charged. Thereafter, electrical energy from axle braking is recovered by commanding a positive torque to be applied to the vehicle's drivetrain via a BISG.

Description

Technical Field

[0001] This specification generally relates to methods and systems for controlling the shaft speed of an electrically assisted supercharger coupled to a vehicle engine while reducing overfilling of the system battery. Background Technology

[0002] Engine systems may include supercharging devices to enhance the torque and peak power output of an internal combustion engine. By compressing the intake air, a supercharger increases the mass airflow entering the engine, which in turn allows a larger amount of fuel to be burned in each ignition event. An example of a supercharger is a turbocharger, in which a compressor located in the engine's intake passage is mechanically coupled to an exhaust turbine via a shaft. The turbine uses exhaust energy to rotate, which in turn drives the compressor.

[0003] Turbochargers can also be configured with electric assistance, where a motor / generator is coupled to the shaft (also referred to herein as eTurbo). eTurbo typically operates on existing 48V mHEV architectures with engines featuring a 48V belt-driven starter-generator (BISG), a 48V battery, and a 48V / 12V DC-DC converter. Electric assistance can reduce turbo lag by providing improved transient engine response under conditions of low turbine speed (due to low exhaust flow).

[0004] However, turbochargers have hardware limitations. Therefore, the output of a turbocharger (conventional and electrically assisted configurations) can be limited by speed and temperature constraints. For example, there may be a maximum turbocharger shaft speed that can be violated under high engine loads or when the vehicle is operating at high altitudes. If the shaft speed limit is exceeded, the magnets coupled to the shaft may deteriorate, resulting in a drop in turbocharger output. Therefore, the turbocharger speed limit cannot be exceeded due to the potential for substantially immediate mechanical degradation. Current control systems can address this issue by reducing the maximum boost pressure when such a constraint violation is anticipated. Alternatively, airflow actuators can be adjusted to reduce boost pressure, such as by opening the exhaust valve and / or the compressor recirculation valve. However, a drop in boost output below the boost pressure required by the driver can lead to significant undertransmission of torque demand and a decrease in vehicle handling. Furthermore, the driving experience for the vehicle driver is also degraded. Other methods can also be used to maintain turbocharger speed or temperature within limits with a margin of safety to avoid shortening the turbocharger's lifespan.

[0005] Kees et al., in US 9,677,486, illustrate an example method in which, when the turbocharger speed reaches its limit, a valve on a deactivated cylinder is opened to allow airflow through that cylinder. In other examples, regenerative braking via a motor coupled to the shaft of the eTurbo is used to reduce the turbo speed. Braking energy is recovered by operating the eTurbo motor as a generator, and the recovered energy is stored in an energy storage device coupled to the motor, such as in a battery.

[0006] However, the inventors have recognized potential problems with such a system. As an example, the amount of regenerative braking that can be used to reduce turbine speed may itself be limited. Specifically, if the storage device coupled to the eTurbo motor (e.g., a Li-ion battery) is already at a state of charge above a threshold (e.g., fully charged), the storage device may not be able to accept additional electrical energy. Therefore, overcharging can damage the battery. If the exhaust valve is opened to rapidly reduce turbine speed, boost energy is dumped or wasted and cannot be harvested. Summary of the Invention

[0007] In one example, the aforementioned problem can be addressed by a method for a turbocharged engine that includes: applying negative torque from an electric motor to the turbocharger shaft in response to the turbocharger shaft being about to overspeed when the system battery is at a state of charge above a threshold, while simultaneously applying positive torque from a belt-driven starter-generator (BISG) to the engine crankshaft; and reducing engine fuel supply to maintain overall engine torque output. In this way, the turbocharger shaft speed can be controlled without overfilling the system battery, while simultaneously utilizing a larger portion of the braking energy.

[0008] As an example, the engine system may be configured with an electric turbocharger having an electric motor coupled to the turbocharger shaft. During an event where the driver depresses the accelerator pedal, to accelerate boost delivery, the exhaust valve may be closed and / or a positive torque may be applied to the shaft via the electric motor. If the shaft speed increases to the point of impending overspeed, a negative torque can be applied via the electric motor to decelerate the shaft. This negative torque can be recovered by charging the system battery (specifically, the 48V system battery coupled to the vehicle's drivetrain). Charging can continue until the battery reaches a threshold state of charge (SOC), such as 95% SOC. Above this level, further charging of the battery may result in overcharging, which could degrade battery performance. Once the battery reaches the threshold SOC, the contactor connecting the 48V line coupling the battery to the vehicle's electrical system can be disconnected, thus preventing further charging of the battery via the electric turbo motor. Thereafter, the negative torque applied by the electric motor for shaft speed control can be recovered by actuating the BISG coupled to the drivetrain. Specifically, the electricity generated by the electric motor during axle deceleration is used to apply a corresponding amount of BISG positive torque to the engine (particularly the crankshaft). The torque applied by the BISG can be based on the additional braking required after absorbing torque to charge the battery. The torque absorbed at the BISG can then be used to propel the vehicle. Simultaneously, the engine fuel supply can be reduced based on the BISG torque to minimize the contribution of engine torque to the drivetrain and maintain net wheel torque.

[0009] In this way, the braking (negative) torque applied by the electric supercharger motor to control the turbocharger shaft speed can be used to generate electrical energy shared with the 48V distribution box of the vehicle's 48V electrical architecture. When the system battery is fully charged, this electrical energy is drawn from the 48V distribution box while generating power via the electric motor to operate the BISG. Additionally, one or more 12V electrical loads can also draw a portion of the power generated by the electric motor during shaft speed control. By operating the BISG using the power generated during turbocharger shaft braking, shaft speed can be controlled without overcharging load-sensitive system batteries, such as the 48V battery of a hybrid vehicle's drivetrain. The technical effect of absorbing torque at the BISG is that braking energy can be recovered through the vehicle's drivetrain rather than through the battery. This allows any excess torque generated after the system battery has been charged to a threshold SOC to propel the vehicle, rather than wasting that excess torque. Furthermore, the turbocharger shaft speed can be controlled when the need for exhaust valve opening is reduced. For example, the exhaust valve can be opened later (e.g., at a higher turbine speed) and / or opened by a smaller amount. Reducing the need for exhaust valve opening improves overall boost response. In general, it avoids exceeding the turbocharger's speed limits while also reducing overcharging of charge-sensitive storage devices.

[0010] It should be understood that the above description of the invention is provided to introduce a series of concepts in a simplified form, which are further described in the detailed embodiments. This does not imply the identification of key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed embodiments. Furthermore, the claimed subject matter is not limited to embodiments that address any shortcomings mentioned above or in any part of this disclosure. Attached Figure Description

[0011] Figure 1 A schematic diagram of a turbocharged engine system equipped with electric supercharging assistance is shown.

[0012] Figure 2 It shows Figure 1 An exemplary electrical coupling of components of a turbocharged engine system.

[0013] Figure 3 A high-level flowchart is shown for a method to reduce turbocharger overspeed by using the negative torque from the electric motor of the turbocharger, while recovering the electricity generated by the electric motor via BISG.

[0014] Figure 4 A illustrative example of turbocharger speed control via the coordinated operation of the electric motor and BISG of the electric turbocharger is shown. Detailed Implementation

[0015] The following description relates to turbocharged engine systems equipped with electric assistance (such as...) Figure 1 A system and method for speed control in an engine system. This system can utilize the turbocharger's electric auxiliary motor, BISG, and 48V electrical system (such as...). Figure 2 Electrical connections between systems. The engine controller can be configured to execute control routines, such as... Figure 3 The example routine addresses turbocharger shaft overspeed by applying negative torque from the electric booster motor and a corresponding positive torque from the BISG. The controller can use the power recovered via the electric booster motor to power the BISG and one or more 12V loads. (Reference) Figure 4 An exemplary adjustment is shown.

[0016] Figure 1Aspects of an example vehicle system 100 are schematically illustrated, including an engine system 101 having an engine 10 coupled to a vehicle 102. In the depicted example, vehicle 102 is a hybrid electric vehicle with multiple torque sources available for one or more wheels 47. However, in an alternative example, vehicle system 100 may include a conventional non-hybrid powertrain. In the example shown, the powertrain of vehicle 102 includes an engine 10 and an electric motor 52. The electric motor 52 may be a motor or a motor / generator. The engine 10 and the electric motor 52 are connected to the wheels 47 via a transmission 48 when one or more clutches 53 are engaged. In the depicted example, a (first) clutch 53 is disposed between the engine 10 and the electric motor 52, and a (second) clutch 53 is disposed between the electric motor 52 and the transmission 48. A controller 12 may send signals to the actuators of each clutch 53 to engage or disengage the clutch, thereby connecting or disconnecting the engine 10 from the electric motor 52 and components connected thereto, and / or connecting or disconnecting the electric motor 52 from the transmission 48 and components connected thereto. For example, when clutch 53 is engaged, torque from engine 10 can be transmitted to wheels 47 via crankshaft 40, transmission 48, and powertrain shaft 84. Transmission 48 can be a gearbox, a planetary gear system, or another type of transmission. Transmission 48 can be a fixed-ratio transmission, including multiple gear ratios to allow engine 10 to rotate at a different speed than wheels 47. By changing the torque transmission capability of the first clutch 53 (e.g., clutch slip), the amount of engine torque relayed to the wheels via powertrain shaft 84 (also referred to herein as the drivetrain) can be adjusted.

[0017] In the illustrated example, motor 52 is an electric motor connected in the drivetrain between the engine and the transmission. However, an additional motor can be connected to crankshaft 40. For example, a belt-driven starter-generator (BISG) 114 can also be connected to the engine's output shaft, allowing the BISG to provide torque to turn the engine and facilitate its start-up during hybrid vehicle system startup. Under certain conditions, the BISG can also supply torque output to supplement or replace engine torque. Positive torque can be provided by the BISG by drawing power from the system battery or power distribution box, as referenced. Figure 2 The electrical architecture is described in detail herein. Additionally, the BISG can supply negative torque output (i.e., absorb drivetrain torque or engine torque), which can be converted into electrical energy, such as for charging the system battery. As described in detail herein, under certain conditions, the BISG can use electricity generated simultaneously by the turbocharger's electric motor to apply positive torque to the crankshaft to control the turbocharger shaft speed. Transmitting positive torque from the BISG to the vehicle's drivetrain reduces the torque required for the engine to drive the wheels.

[0018] The powertrain can be configured in various ways, including parallel, series, or series-parallel hybrid vehicles. In electric vehicle embodiments, system electrical devices such as system battery 45a can be coupled to the drivetrain. System battery 45a can be a traction battery, such as a 48V battery, for supplying power to motor 52, thereby providing torque to wheels 47. In some embodiments, motor 52 can also operate as a generator to supply power to charging system battery 45a, for example, during braking operations using regenerative torque. It should be understood that in other embodiments, including non-electric vehicle embodiments, system battery 45a can be a typical starter-light-ignition (SLI) battery coupled to alternator 46.

[0019] It should be understood that although the system energy storage device 45a is described herein as a battery, in other examples, the energy storage device 45a may be a capacitor.

[0020] For reference Figure 2 As described in detail, the system battery 45a can be coupled to a 48V branch of the vehicle's electrical system, such as via a 48V distribution box 112. Furthermore, the system battery 45a can be coupled to a 12V auxiliary load 116 (including components such as an alternator connected to a 12V branch of the vehicle's electrical system) via a 48V / 12V DC-DC converter 114.

[0021] In the depicted embodiment, engine 10 is a turbocharged engine equipped with a supercharging device (shown herein as turbocharger 15). Turbocharger 15 includes a compressor 114 mechanically coupled to and driven by a turbine 116 via a shaft 19, which in turn is driven by expanding engine exhaust. In one embodiment, the turbocharger may be a twin-scroll device. In another embodiment, the turbocharger may be a variable geometry turbocharger (VGT), wherein the turbine geometry actively changes according to engine operating conditions. Turbocharger 15 may be further configured as an electrically assisted turbocharger having an electric motor 108 (also referred to herein as an electric auxiliary motor) configured to provide electric assistance to the compressor, turbine, or turbocharger shaft. In the depicted example, electric motor 108 is coupled to shaft 19, but in other examples, the electric motor may be selectively coupled to either compressor 114 or turbine 116. The electric motor 108 can be powered by an onboard energy storage device, such as a high-voltage (e.g., 48V) system battery 45b (as shown, or in an alternative example, system battery 45a). Alternatively, the electric motor 108 can be powered by an alternator 46. The amount of power supplied to the electric motor 108 can be varied to adjust the duty cycle of the turbocharger. In one example, the amount of power supplied to the electric motor 108 can be increased to increase the speed of the compressor 114. The result of this electric assistance is that the compressor 114 of the turbocharger 15 can rotate more rapidly, thereby reducing turbo lag.

[0022] It should be understood that although the illustrated example shows a turbocharger as a supercharging device, and that the turbocharger is configured with electric assistance, this is not intended to be limited to this. In a further example, the electric-assisted supercharging device may include an electric motor coupled to the compressor of a mechanical supercharger. Furthermore, the engine may be a dual-charged engine system having an electric mechanical supercharger (not shown) connected upstream or downstream of a turbocharger in the engine intake. This mechanical supercharger may be a supercharging device configured to receive electric assistance from electric motor 108, while the turbocharger 15 may or may not be configured to receive electric assistance from electric motor 108. By accelerating the electric supercharger via the electric motor, a rapid pulse train of boost pressure can be provided to the engine.

[0023] The electric motor 108 can be configured as a motor-generator. Therefore, during conditions requiring electric assistance to accumulate boost, the electric motor can provide positive torque (also referred to herein as motor torque) to drive the centrifugal compressor of a supercharger or the shaft of a turbocharger to improve transient boost pressure delivery. However, the electric motor can also recover energy by “braking” the motor shaft. Here, negative torque (also referred herein as regenerative torque) can be applied to the compressor (or shaft or turbine), thereby reducing the compressor speed and simultaneously charging the system battery (such as battery 45b) connected to the electric motor 108. For example, during conditions where turbocharger overspeed is anticipated (such as during high boost conditions), negative torque can be applied to the shaft via the electric motor 108. The absorbed energy can be recovered by charging the battery until a threshold state of charge (e.g., 95% SOC) is reached. See reference... Figure 3 As described in detail, after the battery reaches its threshold state of charge, the absorbed energy can be recovered by supplying power to the BISG to apply positive torque to the crankshaft. Alternatively, the absorbed energy can be recovered by supplying power to one or more 12V electrical loads, such as various heaters (e.g., cabin heaters, window heaters, seat heaters, etc.).

[0024] The electric motor 108 can be coupled to the 48V distribution box 112 via the inverter 110. (See reference...) Figure 2As described in detail, the 48V distribution box connects the electric motor to a 48V branch of the vehicle's electrical system. Inverter 110 is configured to convert the 48V DC input received from the 48V distribution box to a 48V AC input for use by the electric motor 108, and for use by other devices using 48V power. The electric motor 108 is powered by electrical energy received from the system battery 45b via the 48V distribution box 112. The system battery 45b, such as battery 45a, can be a 48V architecture battery. In an alternative example, the electric motor 108 may also be coupled to the system battery 45a (i.e., a single 48V battery may exist in the engine system, coupled to both the electric motor of the e-Turbo and the electric motor of the hybrid powertrain). System batteries 45a and 45b are each coupled to a 12V branch of the vehicle's electrical system via converter 114. Specifically, converter 114 is a 48V / 12V converter configured to convert the 48V charge of a 48V battery to a 12V charge for storage in a 12V system battery 145. The charge from the 12V battery 146 is then used to power various 12V accessory loads, such as alternator 46. Other 12V loads include various system electric heaters, such as windshield wiper heaters, catalytic converter heaters, cabin heaters, seat heaters, and positive temperature coefficient (PTC) heaters. These other heaters and 12V loads can be integrated into the vehicle system's electrical architecture.

[0025] Fresh air is introduced into the engine 10 via intake passage 42 through airbox 112 and then flows to compressor 114. The air is then compressed at compressor 114 and introduced into the engine 10. Air compressed by turbocharger 15 can also be recirculated from downstream of compressor 114 and downstream of turbocharger air cooler 18 through compressor recirculation passage 60 to the inlet of compressor 114 by adjusting the opening of continuously variable compressor recirculation valve (CCRV) 62. CCRV 62 can be a continuously variable valve, and increasing the opening of CCRV 62 can include actuating (or energizing) a motor or solenoid to open the valve. In an alternative example, compressor recirculation passage 60 can connect the compressor outlet upstream of CAC 18 to the inlet of compressor 114.

[0026] CCRV 62 can be a continuously variable valve, wherein the valve position is continuously variable from a fully closed position to a fully open position. In some embodiments, CCRV 62 can be partially open during boost engine operation to provide surge margin. Hereinafter, the partially open position can be the default valve position. Then, in response to a surge indication, the opening of CCRV 62 can be increased. For example, CCRV 62 can be adjusted from the default partially open position toward a fully open position, based on a surge indication (e.g., compressor pressure ratio, compressor flow rate, pressure differential across the compressor, etc.). In an alternative example, CCRV 62 can be kept closed during boost engine operation (e.g., peak performance conditions) to reduce boost response time and increase peak performance.

[0027] Compressor 114 is connected to throttle valve 20 via a booster air cooler (CAC) 18 (also referred to herein as an intercooler). Air flows from compressor 114 through CAC 18 and throttle valve 20 to intake manifold 22. For example, CAC 18 may be an air-to-air heat exchanger or a water-to-air heat exchanger. Intake manifold pressure (e.g., the pressure of the air filling the intake manifold) can be measured using manifold absolute pressure (MAP) sensor 124.

[0028] During selected conditions, a portion of the intake air compressed as it passes through compressor 114 can be redirected and stored in storage tank 72 by adjusting the opening of air storage valve 74. Storage tank 72 can be connected via bypass 70 to intake passage 42 downstream of CAC 18 and upstream of throttle valve 20. One or more valves can regulate the flow rate of compressed air entering the compressed air storage tank from the intake manifold located downstream of compressor and upstream of throttle valve. One or more valves may include check valve 74c, which ensures unidirectional flow from the intake manifold into the storage tank along a first branch of bypass 70. (In the flow direction) Valve 74a located upstream of check valve 74c can be commanded to open by controller 12 when the manifold pressure upstream of throttle valve is higher than the pressure in the storage tank (e.g., when the boost pressure is higher than the desired pressure) to store a portion of the air compressed by compressor 114 in the storage tank. At a later time, such as when the manifold pressure downstream of the compressor and upstream of the throttle is lower than the pressure in the reservoir (e.g., during accelerator pedal depressurization without boost), control valve 74b in the second branch of the bypass can be opened to release some or all of the compressed air stored in the reservoir. In this way, the opening of air storage valves 74a-b can be adjusted to regulate the pressure within the reservoir 72 relative to the throttle inlet pressure (or boost pressure).

[0029] Intake manifold 22 is connected to a series of combustion chambers 30 via a series of intake valves (not shown). These combustion chambers are further connected to exhaust manifold 36 via a series of exhaust valves (not shown). In the depicted embodiment, a single exhaust manifold 36 is shown. However, in other embodiments, the exhaust manifold may include multiple exhaust manifold sections. A configuration with multiple exhaust manifold sections allows effluent from different combustion chambers to be directed to different locations within the engine system.

[0030] In one embodiment, each of the exhaust valve and the intake valve can be electronically actuated or controlled. In another embodiment, each of the exhaust valve and the intake valve can be cam-actuated or controlled. Whether electronically actuated or cam-actuated, the opening and closing timing of the exhaust valve and the intake valve can be adjusted to achieve desired combustion and emission control performance. For example, cam timing can be adjusted via a variable cam timing system to move the intake cam and exhaust cam to positions that provide optimal volumetric efficiency for a given operating condition.

[0031] Combustion chamber 30 can be supplied with one or more fuels, such as gasoline, alcohol-fuel blends, diesel, biodiesel, compressed natural gas, etc. Fuel can be supplied to the combustion chamber via direct injection, port injection, throttle body injection, or any combination thereof. In the depicted example, fuel is supplied to each combustion chamber 30 via direct injection from fuel injector 66 (but...). Figure 1 Only one fuel injector is shown in the diagram; each combustion chamber includes a fuel injector connected to it. Fuel can be delivered to the fuel injector 66 via a fuel system (not shown) that includes a fuel tank, a fuel pump, and a fuel rail. Combustion can be initiated in the combustion chamber via spark ignition and / or compression ignition.

[0032] like Figure 1 As shown, exhaust gas from exhaust manifold 36 is directed to turbine 116 to drive it. When a reduced turbine torque is desired, a portion of the exhaust gas can be alternatively directed through wastegate 90, bypassing the turbine. Wastegate actuator 92 (e.g., wastegate valve) can be actuated to open to release at least some exhaust pressure from upstream of turbine 116 to a location downstream of turbine 116 via wastegate 90. By reducing the exhaust pressure upstream of turbine 116, turbine speed can be reduced. Similarly, when turbine speed is to be increased, such as in response to a driver pressing the accelerator pedal, the wastegate opening can be reduced (e.g., the wastegate can be completely closed). The wastegate opening can also be increased during conditions where the turbocharger shaft is at or near its hardware limits. However, this may limit boost performance because at least some boost pressure is dumped due to the wastegate opening. See reference... Figure 3As described in detail, during shaft overspeed conditions, speed can also be controlled by applying a negative torque from the electric supercharger motor to the turbocharger shaft, and then drawing the generated electricity to apply a positive torque from the BISG to the crankshaft. This allows the wastegate to remain closed for a longer period, thereby improving boost performance.

[0033] A combined flow from turbine 116 and exhaust valve 90 flows through emission control device 170. Generally, emission control device 170 may include one or more exhaust aftertreatment components configured to reduce the amount of one or more substances in the exhaust stream. For example, an exhaust aftertreatment component may be configured to capture NO from the exhaust stream when the exhaust flow is low. x And when the exhaust flow is sufficient, it reduces the amount of NO captured. x In other examples, the exhaust aftertreatment unit can be configured to make NO x Disproportionately or selectively with the aid of reducing agents to reduce NO x In other examples, emission control device 170 includes a three-way catalytic converter configured to reduce NO in the exhaust stream. x It oxidizes residual hydrocarbons and carbon monoxide. Different exhaust aftertreatment catalysts with any of these functions can be arranged individually or together in the coating or elsewhere in the emission control device 170. In some embodiments, the emission control device 170 may also include a regenerable soot filter configured to capture and oxidize particulate matter in the exhaust stream.

[0034] All or part of the treated exhaust gas from emission control device 170 can be released into the atmosphere via exhaust pipe 35. However, depending on operating conditions, some exhaust gas can alternatively be diverted to intake pipe 42 via exhaust gas recirculation (EGR) passage (not shown), which includes an EGR cooler and an EGR valve. The EGR can be recirculated to the inlet of compressor 114.

[0035] One or more sensors may be connected to the inlet of compressor 114. For example, temperature sensor 55 may be connected to the inlet of compressor 114 to estimate the compressor inlet temperature. As another example, pressure sensor 56 may be connected to the inlet of compressor 114 to estimate the air pressure entering the compressor. Other additional sensors may include, for example, an air-fuel ratio sensor, a humidity sensor, etc. In other examples, one or more of the compressor inlet conditions (such as humidity, temperature, pressure, etc.) may be inferred based on engine operating conditions. Sensors may estimate the condition of the intake air received from the intake passage at the compressor inlet, as well as the air charge recirculated through passage 60. One or more sensors may also be connected to the intake passage 42 upstream of compressor 114 to determine the composition and condition of the air charge entering the compressor. These sensors may include, for example, pressure sensor 58. In addition, throttle inlet pressure (TIP) sensor 59 may be connected downstream of CAC 18 and upstream of throttle valve 20 to estimate the boost pressure delivered to the engine.

[0036] During an accelerator pedal press event, turbo lag may occur when the engine operation changes from unboosted to boosted in response to an increase in the driver's torque demand (i.e., an accelerator pedal press event from unboosted to boosted). This is because the spin of turbine 116 is accelerated due to turbocharger inertia and the reliance on exhaust energy to power the turbine. The same situation may occur when the engine is operating in boosted mode, and the demand for boost increases instantaneously due to increased application of the accelerator pedal by the vehicle driver (i.e., an accelerator pedal press event from boost to boost). To reduce this turbo lag, during those selected conditions, turbocharger 15 can receive electric assistance by receiving positive torque from electric motor 108 (also referred to herein as an electric boost motor or electric boost assist motor). Specifically, in response to pressing the accelerator pedal, wastegate actuator 92 can close (e.g., fully close) to increase the exhaust flow through turbine 116. Before sufficient turbine power is available to rotate the compressor at the speed required to provide the desired boost, the electric motor can increase the power reaching the turbocharger shaft. When the turbine has sufficient pressure and the flow from the exhaust and turbocharger is sufficient to provide the required boost, the electric assistance to the turbocharger from the electric motor 108 can be disabled. Alternatively or additionally, when the turbine accelerates, the manifold pressure can be increased by opening the air storage valve 74 to discharge a certain amount of compressed air from the storage tank 72.

[0037] For reference Figure 3As described in detail, when boost pressure is provided by the turbocharger, if the turbocharger compressor shaft reaches its speed limit (or if the turbocharger compressor or turbine speed reaches its speed limit), the engine controller can apply negative torque from the electric motor 108 coupled to shaft 19 to control the speed (e.g., by braking the shaft speed), while absorbing said torque to recharge the system battery 45b. This can continue until the battery reaches a threshold SOC (such as when the battery is 95% charged). Further shaft speed control can then be achieved by applying negative torque via the electric motor while recovering power via the BISG 114. Specifically, electrical energy is used to power the BISG 114, which applies positive torque to the engine crankshaft. Alternatively or optionally, a portion of the electrical energy generated via the electric motor during shaft braking can be used to power 12V electrical loads of the vehicle system (such as various heaters). By matching the generated power between the BISG and the various 12V loads, problems associated with overcharging the system battery can be avoided while keeping the shaft within hardware limits. The positive torque applied by the BISG to propel the vehicle can be obtained from the vehicle's electrical distribution box (such as...). Figure 2 The 48V distribution box (described in detail) draws electrical energy to power the system, and during shaft braking, the distribution box receives electrical energy from the electric motor coupled to the turbocharger shaft. This allows braking energy to be harvested rather than wasted.

[0038] Compressor surge may occur when the driver releases the accelerator pedal, as the engine operation changes from boosted to deboosted (i.e., the event of releasing the accelerator pedal from boost to deboosted). This is due to the reduced flow through the compressor 114 when the throttle valve 20 is closed with the accelerator pedal released. This reduced forward flow through the compressor can cause surge and degrade turbocharger performance. In addition, surge can lead to noise, vibration, and harshness (NVH) issues, such as unwanted noise from the engine intake system. To enable a rapid reduction in torque demand during vehicle operation in the default mode without inducing compressor surge, at least a portion of the air compressed by the compressor 114 can be recirculated to the compressor inlet. This allows a sufficiently large flow to continue through the compressor while a reduced flow is delivered to the intake manifold. Specifically, CCRV 62 can be opened to recirculate (cooled) compressed air from the compressor 114 outlet downstream of CAC 18 to the compressor 114 inlet. In addition, the wastegate actuator 92 can be moved to a more open (e.g., fully open) position, allowing more exhaust flow to travel to the exhaust tailpipe while bypassing the turbine, thereby accelerating the turbine's spin deceleration.

[0039] Controller 12 may be included in control system 14. Controller 12 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 81 (various examples of which are described herein). As an example, sensors 16 may include an exhaust gas sensor 126, a MAP sensor 124, an exhaust gas temperature sensor 128, an exhaust gas pressure sensor 129, a compressor inlet temperature sensor 55, a compressor inlet pressure sensor 56 (e.g., for measuring P1), a mass air flow (MAF) sensor 57, a pressure sensor 58, and a TIP sensor 59 located upstream of turbine 116. Additional pressure sensors, temperature sensors, air-fuel ratio sensors, and other sensors that make up the sensor array may be coupled to various locations within vehicle system 100. In addition to or in lieu of the depicted sensors, the controller may infer or simulate values ​​of pressure, temperature, and / or flow rate based on operating conditions. Actuators 81 may include, for example, a throttle valve 20, a CCRV 62, an electric motor 108, an exhaust valve actuator 92, a BISG 114, and a fuel injector 66. The controller 12 can receive input data from various sensors, process the input data, and employ various actuators to adjust engine operation based on the received signals and instructions stored in the controller's memory. The controller can respond to the processed input data by employing actuators based on instructions or code programmed therein, which correspond to one or more programs, such as those described herein. Figure 3 An exemplary control procedure is described. As an example, in response to an indication of turbocharger shaft overspeed, such as inferred from one or more of manifold flow, pedal position, compressor inlet pressure, and boost pressure, the controller may send a command signal to the actuator of the electric motor coupled to the turbocharger shaft to apply a certain amount of negative torque on the shaft and operate the motor as a generator to recover energy as electrical energy for charging the associated 48V system battery. Then, once the battery is at a threshold charge, the controller may command the contactor coupled to the battery to disconnect. The controller may also command a certain amount of positive torque to be applied to the engine crankshaft via the BISG while drawing power from the 48V distribution box.

[0040] Turn now Figure 2 An exemplary embodiment of an electrical system 200 is shown, which can be coupled to a hybrid vehicle system, such as... Figure 1 The vehicle system. The component numbers described previously are similar, so they will not be repeated.

[0041] The electrical system includes a low-voltage architecture, which in this example is a 12V architecture and is depicted herein by a long dashed line 205; and a high-voltage architecture, which in this example is a 48V architecture and is depicted herein by a solid line 202. Electrical components coupled to the 12V architecture are configured to receive 12V power. These electrical components include an alternator 46, a 12V system battery 145, and an auxiliary 12V load 116. Other 12V components include, but are not shown, various electric heaters, such as windshield heaters, PTC heaters, cabin heaters, etc. The electrical components coupled to the 12V architecture are also coupled to the 48V architecture via a DC-DC converter 114 that converts 48V DC voltage to 12V DC voltage.

[0042] DC-DC converter 114 is coupled to a 48V battery 45. Therefore, converter 114 converts the power received from system battery 45 for use by 12V components, including system battery 145. In one example, the 12V system battery 145 is a lead-acid battery, while the 48V system battery 45 is a lithium-ion battery. Due to the different composition, the 48V battery is more sensitive to overcharging. To prevent overcharging of the 48V battery, a contactor 206 (or switch or relay) is coupled to battery 45, connecting battery 45 to a 48V power source. When the state of charge (SOC) of battery 45 is below a non-zero threshold, such as below 95% SOC, the contactor is actuated to the closed position, causing the circuit to close. This position allows battery 45 to receive charge from the 48V distribution box 112. Otherwise, when the state of charge (SOC) of battery 45 is above a non-zero threshold, such as above 95% SOC, the contactor is commanded to the open position and the circuit is broken, preventing battery 45 from receiving any further charging.

[0043] Distribution box 112 receives power from multiple sources. These sources include motors / generators that can operate as generators to produce power, which is then delivered to distribution box 112 for storage in battery 45. The same motor / generator can also operate as a motor to use power drawn from battery 45 via distribution box 112. For example, power is generated by belt-driven starter generator 114 when it converts crankshaft rotation into electricity (wherein BISG operates in generator mode). Power is also generated by BISG 114 when negative torque is applied to the vehicle drivetrain by BISG 114 during a deceleration event (again, where BISG operates in generator mode). The applied negative torque causes regenerative braking, which generates power at BISG, which is then delivered to distribution box 112. When operating in electric mode, BISG 114 can also draw power to provide torque to the drivetrain. As another example, such as during an axle braking event, the electric motor 108, coupled to the electric booster (eTurbo herein), converts shaft rotation into electricity, which is generated by said electric motor 108. The electric motor 108 can also draw power from a battery to increase the eTurbo output. Figure 3 As described in detail, during a turbocharger shaft braking event, the electricity generated by the electric boost assist motor (for shaft speed control) can be delivered to the distribution box and used to charge the 48V battery. Then, when the battery is fully charged, the electricity delivered from the electric boost assist motor to the distribution box can be simultaneously drawn by the BISG and used to apply a positive torque from the BISG to the engine crankshaft. When the battery cannot accept electrical energy, the positive torque applied to the engine crankshaft by the BISG 114 allows the electrical energy to be recovered rather than wasted.

[0044] In this way, Figure 1 and Figure 2The components implement a vehicle system comprising: an engine having an intake port and an exhaust port; a belt-driven starter-generator (BISG) coupled to an engine crankshaft; a turbocharger having an intake compressor mechanically coupled to an exhaust turbine via a shaft, and an electric booster auxiliary motor coupled to the shaft; and an electrical system including a high-voltage battery, a low-voltage battery, an electric heater, and a distribution box, the high-voltage battery being electrically coupled to the distribution box via a contactor, and the low-voltage battery and the electric heater being coupled to the distribution box via a DC-DC converter. The distribution box electrically couples the BISG to the electric booster motor; and a controller having computer-readable instructions that, when executed, cause the controller to: apply negative torque to the shaft via the electric booster motor and charge the high-voltage battery in response to a shaft speed above a threshold, while the contactor is closed; and, after the high-voltage battery is charged to a threshold state of charge, apply negative torque to the shaft via the electric booster motor while the contactor is open, simultaneously applying positive torque to the engine via the BISG, and simultaneously reducing engine fuel supply to maintain wheel torque. Additionally, the controller may include further instructions that cause the controller to: charge the low-voltage battery when negative torque is applied to the shaft via the electric booster motor while the contactor is open; and operate the electric heater. In one example, applying negative torque to the shaft via the electric booster motor includes transferring power generated by the electric booster motor to the distribution box, and each of applying positive torque to the engine via the BISG, charging the low-voltage battery, and operating the electric heater includes drawing electrical energy from the distribution box. The controller may additionally include instructions for adjusting the ratio of power drawn from the distribution box for charging the low-voltage battery, operating the electric heater, and applying positive torque to the engine via the BISG, based on each of shaft speed, low-voltage battery state of charge, and ambient temperature.

[0045] Turn now Figure 3 An exemplary method 300 for achieving turbocharger speed control without overcharging the battery of a charge-sensitive system is illustrated. The instructions for executing method 300 and the remaining methods included herein can be performed by a controller based on instructions stored in the controller's storage and in conjunction with data from sensors in the engine system (such as those referenced above). Figure 1 The controller uses signals received by the described sensor to perform actions. According to the method described below, the controller can employ the engine actuator of the engine system to adjust engine operation.

[0046] At 302, the method includes estimating and / or measuring vehicle operating conditions. These vehicle operating conditions include, for example, vehicle speed, driver torque demand, turbocharger shaft speed, turbine speed, transmission braking demand, environmental conditions (such as ambient temperature, pressure, and humidity), state of charge (SOC) of the system battery (e.g., a 48V and / or 12V system battery), the ratio of wheel torque provided via engine torque to motor torque from the electric motor, etc. Vehicle operating conditions may also include engine operating conditions. These engine operating conditions include, for example, engine speed, MAF, MAP, EGR flow rate, boost pressure, throttle inlet pressure, etc.

[0047] At point 304, it can be determined whether a turbocharger shaft overspeed condition is imminent. In one example, shaft overspeed may be imminent after the driver depresses the accelerator pedal, at which point boost demand increases. In response to depressing the accelerator pedal, the exhaust valve can be closed to increase turbine speed. Alternatively or additionally, a positive torque can be applied to the shaft via an electric boost assist motor to accelerate the compressor. In each case, it is possible for the shaft speed to rise rapidly and exceed hardware limits. The controller can predict whether an overspeed condition is imminent based on the rate of increase in shaft speed and / or the rate (or extent) of exhaust valve closure. In one example, with the shaft hardware limit equal to or above 80,000 rpm, the controller can infer that shaft overspeed is imminent when the shaft speed approaches 70,000 rpm. In response to the impending overspeed condition, it can be determined that the shaft speed needs to be reduced. The amount of braking torque that needs to be applied to the turbocharger shaft is determined as a function of the shaft speed (or turbine speed) relative to the hardware limit or relevant threshold speed.

[0048] If shaft overspeed is confirmed to be imminent, the method moves to 308. If shaft overspeed is not imminent, at 306, the method includes maintaining the electric boost motor setting and the wastegate setting. For example, if a positive torque is being applied to the shaft via the electric boost motor to meet boost demand, the positive torque can continue to be applied. As another example, if the wastegate opening is reduced to a more closed state to increase turbine speed, the wastegate can be kept more closed to meet the increased boost demand. The method then exits.

[0049] If turbocharger shaft deceleration is required for shaft speed control in response to impending shaft overspeed, at point 308, the method includes applying negative torque from an electric motor coupled to the turbocharger shaft (i.e., an electric supercharger motor or an electric supercharger auxiliary motor) to provide the desired speed reduction, while simultaneously using the negative torque to charge the 48V system battery. Specifically, if the shaft speed is expected to exceed a threshold speed (or hardware limit), the electric supercharger motor acts as a generator, recovering (kinetic) energy from the rotating shaft to reduce the shaft speed below the threshold speed, while converting the kinetic energy into electrical energy for storage in the system battery. In one example, with a shaft hardware limit of 80,000 rpm, negative torque application can be initiated when the shaft speed reaches 70,000 rpm.

[0050] In one example, the controller can determine the total amount of negative torque required to provide the desired axle speed control based on the current axle speed as a function of the desired axle speed. As another example, the total amount of negative torque required during an axle deceleration event can be determined via a model, lookup table, or algorithm as a function of the driver's boost demand (such as based on the degree of accelerator pedal depressurization) relative to the current axle speed.

[0051] Axle braking energy can be recovered by applying negative torque via an electric motor until the system battery reaches a threshold SOC. At 310, it can be determined whether the state of charge (SOC) of the system's high-voltage (e.g., 48V) battery is above a non-zero threshold. For example, it can be determined whether the SOC is above 95%. If the SOC is above the threshold, the battery may not be able to accept additional charging without damaging its performance. Furthermore, battery life may be affected.

[0052] If the battery SOC is not higher than the threshold SOC, then at 312, the controller can keep the contactor for the 48V battery closed and continue to apply negative torque via the electric motor and use said negative torque to charge the system battery. For example, the controller can send a command signal to the contactor arm to hold the contactor arm in a position where the circuit coupling the 48V battery to the electrical energy source via the 48V distribution box is closed.

[0053] If the battery SOC is at a threshold, then at 314, the method includes disconnecting the contactor coupled to the system battery to disable further charge transfer to the battery. For example, the controller may send a command signal to the contactor arm to move the contactor arm to a position where the circuit coupling the 48V battery to a 48V distribution box and receiving electrical energy from the electric motor is disconnected. Therefore, the battery no longer receives further electrical energy.

[0054] At point 316, after disabling further charging of the battery, it can be determined whether further braking is needed. For example, it can be determined whether the shaft speed has been sufficiently reduced below the shaft's hardware limits. If no further braking is needed, such as what might happen when the shaft speed is below the limits, then at point 318, the method includes closing the contactor of the 48V system battery, since further charge transfer cannot be expected. Furthermore, the application of negative torque via the electric booster motor can be disabled. The method then exits.

[0055] If further braking is required, such as when there is insufficient margin between the current shaft speed and the shaft's hardware limits after charging the battery to a threshold SOC, then at 320, the method includes continuing to apply negative torque from the electric supercharger motor to reduce the shaft speed, while simultaneously applying positive torque from the BISG to the engine crankshaft. The controller can estimate the amount of power that needs to be recovered in the worst-case scenario to avoid overspeeding the turbocharger shaft. The controller can then apply negative torque corresponding to the estimated worst-case power amount. Electrical energy corresponding to the worst-case power amount is drawn from the shaft braking and delivered to a 48V junction box coupled to the electric supercharger motor. The controller can command the BISG to apply positive torque to the engine crankshaft to simultaneously dissipate the determined worst-case power amount. Positive torque can be applied by the BISG by drawing electrical energy corresponding to the worst-case power amount from the 48V junction box. That is, the vehicle is propelled by the BISG using electrical energy generated by the turbocharger shaft braking via the electric supercharger motor. The positive torque from the BISG enables propulsion of the vehicle via the drivetrain. At point 322, the controller can reduce the engine fuel supply based on the positive torque applied by the BISG to maintain overall engine torque output and thus consistent wheel torque. Since the BISG positive torque is applied to the engine crankshaft, the BISG torque complements the engine torque. Therefore, to maintain overall wheel torque, the engine fuel supply is reduced to decrease the engine combustion torque proportionally to the complementary BISG torque. Reducing the engine fuel supply can include reducing the injector pulse width for multiple combustion events.

[0056] In this way, when the system battery cannot accept any further charge, the electrical energy generated during axle braking is consumed and thus recovered via the BISG. The controller can also recover electrical energy via one or more additional power consumers. For example, at 324, additionally or optionally, the controller can regulate (e.g., increase) the power requested from various 12V electrical loads on the DC-DC converter that couples the 48V distribution box to the 12V electrical architecture of the vehicle system. Increasing the 12V electrical loads could include drawing power from axle braking to operate one or more heaters, such as cabin heaters, windshield heaters, door heaters, seat heaters, PTC heaters, etc. For example, the power requested from the 12V electrical loads on the DC-DC converter could be changed from the original request to the following amount = original request - worst-case power (to be drawn for axle speed control). Other loads could include a controller that operates the vehicle's air conditioning unit to raise or lower the cabin temperature to a setting based on driver demand or history.

[0057] As another example, at point 326, additionally or optionally, the controller may sink all or part of the recovered electrical energy into a 12V storage system (such as a less charge-sensitive lead-acid battery). In this way, the electrical energy recovered from the axle brake can be proportioned between the BISG and the 12V electrical load. In one example, when the BISG deteriorates and cannot provide positive torque, all electrical energy may be directed to the 12V load (or the 12V battery). As another example, when the heater is not needed, or when the ambient temperature is high, a larger portion of the electrical energy may be directed to the BISG (relative to the 12V load) (resulting in less efficient charge transfer to the 12V battery). As yet another example, when the heater is needed, or when the ambient temperature is low, a larger portion of the electrical energy may be directed to the 12V load (relative to the BISG) (resulting in more efficient charge transfer to the 12V battery).

[0058] In this way, when electrical energy cannot be recovered via the system's high-voltage battery, the controller can apply negative torque to reduce the shaft speed below the shaft's hardware limits and recover the electrical energy corresponding to the applied negative torque via the BISG and / or one or more 12V loads. This allows electrical energy to be recovered rather than wasted.

[0059] It will be further understood that recovering electrical energy via BISG improves the performance of a turbocharged engine by allowing the exhaust valve to remain closed for a longer period. For example, without BISG torque applied, an increased exhaust valve opening might be necessary to reduce shaft speed in response to impending shaft overspeed. However, opening the exhaust valve could also lead to a decrease in boost pressure and turbocharged engine performance, which could be counterproductive when impending overspeed occurs in response to increased driver torque demands. In one example, with the shaft's hardware limit at 80,000 rpm, the exhaust valve might need to open when the shaft speed approaches 70,000 rpm. In contrast, by recovering energy through positive torque applied via BISG, the exhaust valve opening can be delayed until 75,000 rpm. Furthermore, shaft speed control might require a smaller exhaust valve opening. In other examples, shaft speed can be controlled without needing to open the exhaust valve.

[0060] Turn now Figure 4 An example of turbocharger shaft speed control via applying a positive torque at the BISG is shown in mapping diagram 400. This can be based on... Figure 3 The method is achieved by using command signals directed to the vehicle actuators. Figure 4 The method enables turbocharger shaft speed control, particularly in charge-sensitive systems where the battery may potentially be overcharged.

[0061] Map 400 depicts the pedal position at curve 401, reflecting the driver's torque demand. Map 400 also depicts the turbocharger shaft speed at curve 402 relative to a speed threshold 404. Above speed threshold 404, shaft overspeed may be imminent. Speed ​​threshold 404 can be a function of the shaft's hardware limits. Curve 406 depicts the SOC of the high-voltage system battery (specifically, the 48V architecture battery coupled to the vehicle's drivetrain) relative to a threshold state of charge (SOC) 408. Above threshold SOC 408, this can indicate battery overcharging. Curve 410 depicts the torque output by the electric motor coupled to the turbocharger shaft, configured to provide electric boost assistance (and referred to herein as the electric boost motor). Torque output above the 0 mark indicates positive torque output, meaning the electric motor is operating as a motor to provide positive torque to rotate the turbocharger shaft. When torque output is below the 0 mark, this indicates the motor is operating as a generator to provide negative torque output, where torque from the rotating shaft is used to drive the generator. Curve 412 illustrates the opening of the exhaust valve on the exhaust turbine of the turbocharger. As the exhaust valve opening decreases, more exhaust gas is directed through the turbine, increasing the shaft speed. As the exhaust valve opening increases, more exhaust gas is diverted (bypassed) around the turbine, decreasing the shaft speed. Curve 416 depicts the contribution of engine (combustion) torque to the total required torque (curve 414). The total required torque can be the wheel torque required based on the driver's torque demand. Curve 418 depicts the contribution of BISG torque to the total required torque. Positive BISG torque reflects the torque generated by using electrically operated BISG, which is applied to the engine crankshaft by the BISG. Curve 420 depicts the state of the contactor switch coupled to the system battery. When the switch is open, the circuit coupling the battery to the 48V distribution box is disconnected, preventing charge transfer into / out of the battery. When the switch is closed, the circuit coupling the battery to the 48V distribution box is closed, allowing charge transfer into / out of the battery. Curve 422 depicts the auxiliary 12V load on the engine. The application of a 12V load increases the electrical load on the engine electrical architecture and indicates that electrical energy drawn from the vehicle system's power distribution box is being used to operate one or more vehicle heaters.

[0062] Prior to t1, the engine can operate with a lower torque demand (curve 401), which is met by providing a lower level of boost via the turbocharger, as indicated by the turbocharger shaft speed (curve 402). At this point, boost control does not require electric assistance, as indicated by the absence of motor torque from the electric supercharger motor (curve 410) and no change in battery SOC (curve 406). Since the battery is below the threshold SOC 408, the contactor switch of the 48V architecture coupling the battery to the vehicle system remains closed (curve 420). This allows the battery to receive charge via the 48V distribution box or to deliver charge to other electrical components of the vehicle system. The exhaust valve coupled to the exhaust turbine remains partially closed (curve 412) to allow exhaust gas to flow through the turbine to drive the compressor to provide the required boost pressure. All required torque is provided via engine combustion torque (curve 416, dashed line) (curve 414, solid line), and BISG torque does not contribute to the drivetrain (curve 418).

[0063] At point t1, there is an increase in torque demand due to the driver pressing the accelerator pedal, resulting in increased pedal depressurization. This leads to an increase in the required boost pressure. To meet the increased boost demand, while keeping the electric motor off, the wastegate opening is reduced to increase the turbocharger shaft speed, thereby increasing the boost pressure output of the turbocharger compressor. The engine torque output increases accordingly to meet the torque demand.

[0064] At point t2, torque demand increases further, for example, due to another instance of the driver pressing the accelerator pedal. To meet this increased boost demand, while keeping the electric motor off, the exhaust valve opening is further reduced to a fully closed position, increasing the turbocharger shaft speed and thus increasing the boost pressure output of the turbocharger compressor. The engine torque output increases accordingly to meet the torque demand.

[0065] Based on the rate of increase in shaft speed toward threshold 404 between t2 and t3, it is determined that shaft overspeed is likely imminent. Shaft rotation exceeding hardware limits could lead to irreversible shaft degradation. If the exhaust valve is opened to reduce shaft speed, turbocharged engine performance may degrade. Therefore, at t3, by applying a negative torque from the electric supercharger motor to the turbocharger shaft while keeping the exhaust valve fully closed, the increase in the rate of increase in shaft speed can be suppressed, and the shaft speed can be maintained at or slightly below the speed threshold 404 (curve 410). The applied negative torque is used between t3 and t4 to charge the system battery coupled to the electric supercharger motor. In this paper, the battery is a 48V architecture battery, such as a lithium-ion battery.

[0066] At t4, the battery reaches the threshold SOC 408. If the battery continues to receive charge, as shown in the dashed section 407, it may become overcharged, leading to performance problems. To avoid overcharging, at t4, the contactor switch coupling the battery to the remaining 48V electrical architecture of the vehicle system is disconnected. This prevents further charge from being received at the battery. Additionally, the negative torque applied via the electric supercharger is adjusted (in this case increased) to a value based on the amount of power required to prevent the axle speed from exceeding the speed threshold 404. If no negative torque is applied because the battery is being charged, the axle speed is expected to move along the trajectory depicted by the dashed line 405. The electrical energy generated by applying negative torque via the electric supercharger is then dissipated by applying positive torque along the vehicle drivetrain via the BISG coupled to the engine. Specifically, both the BISG and the electric supercharger can be coupled to each other via a 48V junction box. By applying negative torque via the electric supercharger, the axle speed is controlled and electrical energy is delivered to the 48V junction box. By simultaneously applying positive torque via the BISG, the generated electrical energy is drawn from and consumed by the 48V distribution box without overcharging the battery. Since the BISG is connected to the drivetrain at the engine crankshaft, the BISG torque contributes to the total torque required to propel the vehicle. To maintain the total engine torque generated to meet the required torque, the engine torque output is correspondingly reduced as the BISG torque applied to the engine increases. For example, the engine combustion torque is reduced by decreasing the engine fuel supply.

[0067] As an example, the controller can estimate the total amount of electricity (or braking torque) required to maintain the shaft speed within limits based on predicted overspeed that would occur if no braking torque were applied to the shaft, as indicated by region 422 under curve 405 between t4 and t5. The controller can then apply negative torque via an electric booster motor to generate the total electrical force, as indicated by shaded region 411 under curve 410 between t4 and t5. A positive BISG torque corresponding to the same amount of electrical force is then applied, here corresponding to region 426 under curve 418 between t4 and t5. Therefore, the BISG torque corresponding to region 426 is proportional to the negative motor torque corresponding to region 411. The reduction in engine torque (region 424) is adjusted to be a function of (e.g., proportional to) region 426. The engine fuel supply is reduced to provide the required reduction in engine torque. For example, the fuel injector pulse width is reduced.

[0068] Alternatively or additionally, the auxiliary electrical load on the engine can be increased (curve 422). For example, at least a portion of the electrical energy generated between t4 and t5 via the electric supercharger motor can be used to power one or more system electric heaters. In the case of operating the electric heaters, the sum of the power consumed by the BISG and the electric heaters is equal to the power generated by the electric supercharger motor.

[0069] Further shaft speed control can be achieved by adjusting the opening of the exhaust valve. For example, the exhaust valve opening can be increased shortly before t5. Therefore, if the BISG does not apply positive torque, shaft speed control will need to open the exhaust valve earlier (e.g., at t3) and by a greater amount, as shown by the dashed curve 413.

[0070] At t5, engine operating conditions change, necessitating a reduction in boost pressure. For example, there may be a decrease in torque demand due to the driver releasing the accelerator pedal, resulting in a reduction in accelerator pedal depressurization. Negative torque is disabled via the electric motor, and the wastegate is moved to a more open position to decrease shaft speed, thereby reducing the boost pressure output by the turbocharger compressor. Furthermore, BISG torque application is disabled, and engine torque output is increased accordingly by increasing engine fuel supply.

[0071] The contactor switch is held in the open position until the battery SOC drops below a threshold SOC, such as after the electric boost motor is used to provide positive torque to assist boost pressure development later in the vehicle's driving cycle. In this way, turbocharger speed control can be enabled without overcharging the system battery by generating electricity via the electric boost assist motor to slow down the turbocharger shaft and command the BISG to consume the generated positive torque.

[0072] In this way, by applying positive torque to the engine crankshaft via the BISG, electricity generated during turbocharger shaft speed control can be recovered without overcharging the system battery. The technical effect of matching the electricity generated from shaft braking between the BISG and various 12V electrical loads is to recover electricity generated via the electric booster motor coupled to the shaft through the operation of electrical components other than the system battery. By recovering shaft braking energy, waste is reduced, thereby improving fuel economy. By controlling shaft speed via the negative torque of the electric booster motor and the positive torque of the BISG, the need for opening the exhaust valve for shaft speed control is reduced, thereby improving engine performance. The technical effect of reducing violations of turbocharger shaft speed limits is that boost performance can be improved while also reducing overcharging of charge-sensitive storage devices.

[0073] One example method includes: in response to the turbocharger shaft about to overspeed when the system battery is in a state of charge above a threshold, applying a negative torque from an electric motor to the turbocharger shaft, while simultaneously applying a positive torque from a belt-driven starter-generator (BISG) to the turbocharger shaft. Alternatively or additionally, in the preceding example, the electric motor is coupled to the BISG via a distribution box, wherein the battery is coupled to the distribution box via a contactor. The method further includes: disconnecting the contactor in response to the system battery being in the above-threshold state of charge. In any or all of the foregoing examples, additionally or additionally, the applied negative torque is proportional to the braking torque required to reduce the speed of the turbocharger shaft relative to the shaft's hardware limits, and wherein applying the negative torque includes generating electricity at the motor and transferring the electricity to the distribution box upon contactor disconnection. In any or all of the foregoing examples, additionally or additionally, the positive torque applied from the BISG is proportional to the negative torque applied from the electric motor, and wherein applying the positive torque includes drawing the generated electricity from the distribution box upon contactor disconnection. In any or all of the foregoing examples, additionally or optionally, the method further includes drawing the generated power to operate one or more electric heaters, including windshield heaters, cabin heaters, and PTC heaters. In any or all of the foregoing examples, additionally or optionally, a portion of the generated power drawn from the distribution box for applying the positive torque from the BISG is based at least on ambient temperature, relative to the power drawn to operate the one or more electric heaters. In any or all of the foregoing examples, additionally or optionally, a larger portion of the generated power is drawn to apply the positive torque from the BISG when the ambient temperature is high, and wherein a larger portion of the generated power is drawn to operate the one or more electric heaters when the ambient temperature is low or when the BISG deteriorates. In any or all of the foregoing examples, additionally or optionally, the system battery is a 48V lithium-ion battery, the distribution box is a 48V distribution box, and the one or more electric heaters are powered by a 12V lead-acid battery coupled to the 48V distribution box via a DC-DC converter. In any or all of the foregoing examples, additionally or optionally, the method further includes: in response to an impending overspeed of the turbocharger shaft when the system battery is in a state of charge below a threshold, applying a negative torque from the electric motor to the turbocharger shaft while the contactor is closed, simultaneously charging the system battery.In any or all of the foregoing examples, additionally or optionally, the engine fuel supply is reduced in proportion to the applied positive torque from the BISG, wherein reducing the engine fuel supply includes reducing the pulse width commanded to the cylinder fuel injectors. In any or all of the foregoing examples, additionally or optionally, the method further includes opening an exhaust valve coupled to the exhaust turbine of the turbocharger, the opening degree based on the positive torque applied from the BISG.

[0074] Another example method includes: in response to an impending electric turbocharger shaft overspeed, applying a negative torque from the electric motor coupled to the turbocharger shaft to charge the battery to a threshold state of charge; and then commanding the BISG to absorb the negative torque from the electric motor while reducing engine fuel supply to maintain overall engine torque output. In the foregoing example, additionally or alternatively, commanding the BISG to absorb the negative torque includes applying a positive torque from the BISG to the engine crankshaft, the positive torque being applied from the BISG using electricity generated from the negative torque applied to the shaft by the electric motor after the battery has been charged to the threshold state of charge. In any or all of the foregoing examples, additionally or alternatively, commanding the BISG to absorb the negative torque includes commanding the BISG to absorb at least a portion of the negative torque while absorbing the remaining portion of the negative torque via one or more auxiliary electrical loads, said one or more auxiliary electrical loads including electric heaters. In any or all of the foregoing examples, additionally or optionally, the method further includes, while absorbing the negative torque via the BISG, increasing the opening of the exhaust wastegate coupled to the electric turbocharger, the opening of the exhaust wastegate being based on a portion of the negative torque absorbed by the BISG relative to the total amount of the negative torque applied by the electric motor. In any or all of the foregoing examples, the negative torque applied from the electric motor is based on a turbocharger shaft speed relative to a limit, and wherein reducing the engine fuel supply includes reducing the pulse width commanded to the cylinder fuel injectors in proportion to the negative torque absorbed at the BISG.

[0075] Another exemplary vehicle system includes: an engine having an intake port and an exhaust port; a belt-driven starter-generator (BISG) coupled to an engine crankshaft; a turbocharger having an intake compressor mechanically coupled to an exhaust turbine via a shaft, and an electric booster auxiliary motor coupled to the shaft; and an electrical system including a high-voltage battery, a low-voltage battery, an electric heater, and a distribution box, the high-voltage battery being electrically coupled to the distribution box via a contactor, the low-voltage battery and the electric heater being coupled to the distribution box via a DC-DC converter, the distribution box connecting the... The BISG is electrically coupled to the electric booster motor; and a controller having computer-readable instructions, which, when executed, cause the controller to: apply negative torque to the shaft via the electric booster motor and charge the high-voltage battery in response to a shaft speed above a threshold, while the contactor is closed; and after the high-voltage battery is charged to a threshold state of charge, apply negative torque to the shaft via the electric booster motor while the contactor is open, simultaneously applying positive torque to the engine via the BISG, and simultaneously reducing engine fuel supply to maintain wheel torque. In the foregoing example, additionally or optionally, the controller includes further instructions that cause the controller to: charge the low-voltage battery when negative torque is applied to the shaft via the electric booster motor while the contactor is open; and operate the electric heater. In any or all of the foregoing examples, additionally or optionally, applying negative torque on the shaft via the electric booster motor includes transmitting power generated by the electric booster motor to the distribution box, and wherein each of applying positive torque on the engine via the BISG, charging the low-voltage battery, and operating the electric heater includes drawing electrical energy from the distribution box. In any or all of the foregoing examples, additionally or optionally, the controller includes further instructions that cause the controller to: adjust the ratio of the power drawn from the distribution box for charging the low-voltage battery, operating the electric heater, and applying the positive torque on the engine via the BISG based on each of the shaft speed, the low-voltage battery state of charge, and the ambient temperature.

[0076] In another representation, a method for a vehicle with a turbocharged engine includes: when the state of charge of the system battery is above a threshold, reducing the speed of the turbocharger shaft by applying a positive torque from a belt-driven starter-generator (BISG) to the engine while simultaneously applying a negative torque from an electric motor coupled to the turbocharger shaft. In the foregoing example, additionally or optionally, the method further includes reducing the engine fuel supply based on the applied positive torque to maintain engine torque output.

[0077] In another further representation, a method for an engine includes: decelerating the turbocharger shaft by applying a negative torque from an electric booster motor while charging the system battery to a threshold state of charge; and then further decelerating the shaft by applying the negative torque from the electric booster motor while simultaneously applying a positive torque from a belt-driven starter-generator (BISG) on the engine. In the foregoing example, additionally or alternatively, applying the positive torque from the BISG includes using electricity generated due to the application of the negative torque from the electric motor, the BISG being configured to receive the electricity via a distribution box electrically coupled to each of the electric booster motor and the BISG.

[0078] Note that the exemplary control and estimation programs included herein can be used in conjunction with various engine and / or vehicle system configurations. The control methods and programs disclosed herein can be stored as executable instructions in a non-transitory memory and can be implemented by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific programs described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, etc. Therefore, the various actions, operations, and / or functions shown can be executed in the shown order, in parallel, or in some cases omitted. Similarly, the processing order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the shown actions, operations, and / or functions can be repeatedly executed depending on the specific strategy used. Furthermore, the described actions, operations, and / or functions can be graphically represented as code to be programmed into a non-transitory memory of a computer-readable storage medium in an engine control system, wherein the described actions are executed by combining instructions with an electronic controller in a system including various engine hardware components.

[0079] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be considered limiting, as numerous variations are possible. For example, the above techniques can be applied to V6, inline 4, inline 6, V12, opposed 4, 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 disclosed herein, as well as other features, functions, and / or properties.

[0080] The following claims specifically point to certain combinations and sub-combinations that are considered novel and not obvious. These claims may refer to a "single" element or a "first" element or its equivalents. These claims should be understood to include combinations of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed by amendments to these claims or by setting new claims in this application or related applications. Such claims, whether broader, narrower, equivalent, or different in scope from the original claims, are considered to be included within the subject matter of this disclosure.

[0081] According to the present invention, a method includes: applying a negative torque from an electric motor to the turbocharger shaft in response to the turbocharger shaft being about to overspeed when the system battery is in a state of charge above a threshold, while applying a positive torque from a belt-driven starter generator (BISG) to the engine crankshaft; and reducing the engine fuel supply to maintain overall engine torque output.

[0082] According to one embodiment, the electric motor is coupled to the BISG via a distribution box, wherein the battery is coupled to the distribution box via a contactor, and the method further includes disconnecting the contactor in response to the system battery being in the above-threshold state of charge.

[0083] According to one embodiment, the applied negative torque is proportional to the braking torque required to reduce the speed of the turbocharger shaft relative to the hardware limits of the shaft, and wherein applying the negative torque includes generating electricity at the motor and transferring the electricity to the distribution box when the contactor is disconnected.

[0084] According to one embodiment, the positive torque applied from the BISG is proportional to the negative torque applied from the electric motor, and wherein applying the positive torque includes drawing the generated power from the distribution box when the contactor is disconnected.

[0085] According to one embodiment, the invention is further characterized in that the generated power is drawn to operate one or more electric heaters, including a windshield heater, a passenger compartment heater, and a PTC heater.

[0086] According to one embodiment, the ratio of the generated power drawn from the distribution box to apply the positive torque from the BISG to the power drawn to operate the one or more electric heaters is based at least on the ambient temperature.

[0087] According to one embodiment, when the ambient temperature is high, a significant portion of the generated power is drawn to apply the positive torque from the BISG, and when the ambient temperature is low or the BISG deteriorates, the significant portion of the generated power is drawn to operate the one or more electric heaters.

[0088] According to one embodiment, the system battery is a 48V lithium-ion battery, the distribution box is a 48V distribution box, and the one or more electric heaters are powered by a 12V lead-acid battery coupled to the 48V distribution box via a DC-DC converter.

[0089] According to one embodiment, the invention is further characterized in that, in response to an impending overspeed of the turbocharger shaft when the system battery is in a state of charge below a threshold, a negative torque from the electric motor is applied to the turbocharger shaft while the contactor is closed, simultaneously charging the system battery.

[0090] According to one embodiment, the engine fuel supply is reduced in proportion to the applied positive torque from the BISG, and wherein reducing the engine fuel supply includes reducing the pulse width commanded to the cylinder fuel injectors.

[0091] According to one embodiment, the invention is further characterized in that an exhaust valve connected to the exhaust turbine of the turbocharger is opened, the opening degree being based on the positive torque applied from the BISG.

[0092] According to the present invention, a method includes: in response to an impending electric turbocharger shaft overspeed, applying a negative torque from the electric motor coupled to the turbocharger shaft to charge the battery to a threshold state of charge; and then commanding the BISG to absorb the negative torque from the electric motor while reducing the engine fuel supply to maintain overall engine torque output.

[0093] According to one embodiment, commanding the BISG to absorb the negative torque includes applying a positive torque from the BISG to the engine crankshaft, the positive torque being applied from the BISG using power generated from the negative torque applied to the shaft by the electric motor after the battery has been charged to the threshold state of charge.

[0094] According to one embodiment, commanding the BISG to absorb the negative torque includes commanding the BISG to absorb at least a portion of the negative torque, while absorbing the remaining portion of the negative torque via one or more auxiliary electrical loads, the one or more auxiliary electrical loads including electric heaters.

[0095] According to one embodiment, the invention is further characterized in that, while absorbing the negative torque via the BISG, the opening of the exhaust valve connected to the electric turbocharger is increased, the opening of the exhaust valve being based on a portion of the negative torque absorbed by the BISG relative to the total amount of the negative torque applied by the electric motor.

[0096] According to one embodiment, the negative torque applied from the electric motor is based on the turbocharger shaft speed relative to the limit, and reducing the engine fuel supply includes reducing the pulse width commanded to the cylinder fuel injectors in proportion to the negative torque absorbed at the BISG.

[0097] According to the present invention, a vehicle system is provided, the vehicle system comprising: an engine having an intake port and an exhaust port; a belt-driven starter-generator (BISG) coupled to an engine crankshaft; a turbocharger having an intake compressor mechanically coupled to an exhaust turbine via a shaft, and an electric booster auxiliary motor coupled to the shaft; and an electrical system including a high-voltage battery, a low-voltage battery, an electric heater, and a distribution box, the high-voltage battery being electrically coupled to the distribution box via a contactor, and the low-voltage battery and the electric heater being coupled to the distribution box via a DC-DC converter. The distribution box electrically couples the BISG to the electric booster motor; and a controller having computer-readable instructions that, when executed, cause the controller to: in response to an shaft speed above a threshold, apply a negative torque to the shaft via the electric booster motor and charge the high-voltage battery while the contactor is closed; and after the high-voltage battery is charged to a threshold state of charge, apply a negative torque to the shaft via the electric booster motor while the contactor is open, simultaneously applying a positive torque to the engine via the BISG, and simultaneously reducing the engine fuel supply to maintain wheel torque.

[0098] According to one embodiment, the controller includes further instructions that cause the controller to: charge the low-voltage battery when a negative torque is applied to the shaft via an electric booster auxiliary motor while the contactor is disconnected; and operate the electric heater.

[0099] According to one embodiment, applying negative torque on the shaft via the electric booster motor includes transmitting power generated by the electric booster motor to the distribution box, and applying positive torque on the engine via the BISG, charging the low-voltage battery, and operating the electric heater each include drawing electrical energy from the distribution box.

[0100] According to one embodiment, the controller includes further instructions that cause the controller to: adjust the ratio of power drawn from the distribution box for charging the low-voltage battery, operating the electric heater, and applying the positive torque to the engine via the BISG, based on each of shaft speed, low-voltage battery state of charge, and ambient temperature.

Claims

1. A method for engine control, the method comprising: When the system battery is at a state of charge above a threshold, in response to the turbocharger shaft about to overspeed, Negative torque from the electric motor is applied to the turbocharger shaft, while positive torque from the belt-driven starter generator (BISG) is applied to the engine crankshaft; and Reduce engine fuel supply to maintain overall engine torque output.

2. The method of claim 1, wherein the electric motor is coupled to the BISG via a distribution box, and wherein the battery is coupled to the distribution box via a contactor, the method further comprising: The contactor is disconnected in response to the system battery being in a state of charge above the threshold.

3. The method of claim 2, wherein the applied negative torque is proportional to the braking torque required to reduce the speed of the turbocharger shaft relative to the hardware limits of the turbocharger shaft, and wherein applying the negative torque includes generating electricity at the motor and transferring the electricity to the distribution box when the contactor is disconnected.

4. The method of claim 3, wherein the positive torque applied from the BISG is proportional to the negative torque applied from the electric motor, and wherein applying the positive torque includes drawing power generated from the distribution box when the contactor is disconnected.

5. The method of claim 4, further comprising: The generated electricity is used to operate one or more electric heaters, including at least one of a windshield heater, a passenger compartment heater, and a PTC heater.

6. The method of claim 5, wherein the ratio of the generated power drawn from the distribution box for applying the positive torque from the BISG to the power drawn for operating the one or more electric heaters is based at least on the ambient temperature.

7. The method of claim 6, wherein when the ambient temperature is high, a significant portion of the generated power is drawn to apply the positive torque from the BISG, and wherein when the ambient temperature is low or the BISG deteriorates, a significant portion of the generated power is drawn to operate the one or more electric heaters.

8. The method of claim 5, wherein the system battery is a 48V lithium-ion battery, the distribution box is a 48V distribution box, and the one or more electric heaters are powered by a 12V lead-acid battery coupled to the 48V distribution box via a DC-DC converter.

9. The method of claim 3, further comprising: In response to an impending overspeed of the turbocharger shaft when the system battery is in a state of charge below a threshold, a negative torque from the electric motor is applied to the turbocharger shaft while the contactor is closed, simultaneously charging the system battery.

10. The method of claim 1, wherein the engine fuel supply is reduced in proportion to the applied positive torque from the BISG, and wherein reducing the engine fuel supply includes reducing the pulse width commanded to the cylinder fuel injector.

11. The method of claim 1, further comprising: Open the exhaust valve connected to the exhaust turbine of the turbocharger, with the opening degree based on the positive torque applied from the BISG.

12. A vehicle system comprising: An engine having an air intake and an exhaust port; The belt-driven starter generator, or BISG, is coupled to the engine crankshaft. A turbocharger having an intake compressor mechanically connected to an exhaust turbine via a turbocharger shaft, and an electric booster motor connected to the turbocharger shaft; An electrical system comprising a high-voltage battery, a low-voltage battery, an electric heater, and a distribution box, wherein the high-voltage battery is electrically coupled to the distribution box via a contactor, the low-voltage battery and the electric heater are coupled to the distribution box via a DC-DC converter, and the distribution box electrically couples the BISG to the electric booster auxiliary motor; as well as A controller having computer-readable instructions, which, when executed, cause the controller to: Response to axis velocities above a threshold When the contactor is closed, a negative torque is applied to the turbocharger shaft via the electric booster motor, and the high-voltage battery is charged. as well as After the high-voltage battery is charged to the threshold state of charge, a negative torque is applied to the turbocharger shaft via the electric booster motor when the contactor is disconnected, while a positive torque is applied to the engine via the BISG, and the engine fuel supply is reduced to maintain wheel torque.

13. The system of claim 12, wherein the controller further includes instructions for causing the controller to perform the following operations: When the contactor is disconnected, negative torque is applied to the turbocharger shaft via the electric booster auxiliary motor. Charging the low-voltage battery; and Operate the electric heater.

14. The system of claim 13, wherein applying a negative torque on the turbocharger shaft via the electric booster assist motor includes transmitting electricity generated by the electric booster assist motor to the distribution box, and wherein each of applying a positive torque on the engine via the BISG, charging the low-voltage battery, and operating the electric heater includes drawing electrical energy from the distribution box.

15. The system of claim 14, wherein the controller further comprises further instructions that cause the controller to: The ratio of power drawn from the distribution box to charge the low-voltage battery, operate the electric heater, and apply the positive torque to the engine via the BISG is adjusted based on each of the shaft speed, the low-voltage battery state of charge, and the ambient temperature.

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