Methods and system operating a vehicle driveline

Systems and methods for operating a vehicle driveline that includes an engine and an electric machine are described. In one example, an amount of electrical power that is available to electrical consumers that are electrically coupled to a high voltage bus is adjusted responsive to a temperature of a catalyst for the purpose of reducing engine emissions.

FIELD

The present description relates to methods and a system for operating a driveline of a hybrid vehicle.

BACKGROUND AND SUMMARY

An engine may be included in a vehicle driveline that also includes an electrical machine. The engine may be started when the electrical machine lacks capacity to provide a desired driver demand power or during conditions when battery charge is low. If the engine and the engine's exhaust system are cold when the engine is started, engine emissions may be higher than is desired for a period of time. The engine may expel higher levels of hydrocarbons and carbon monoxide when the engine is cold due to hydrocarbons that may exit the engine without having participated in combustion. For example, hydrocarbons may become lodged between pistons and cylinder walls during compression and power strokes, but these hydrocarbons may be ejected from the engine's cylinders during exhaust strokes. The concentration of hydrocarbons ejected from an engine may be a function of many factors including engine load and engine temperature. If the engine's exhaust system is cold, higher concentrations of hydrocarbons and carbon monoxide may flow to atmosphere. Therefore, it may be desirable to provide a way of reducing engine emissions when an engine is cold started.

The inventors herein have recognized the above-mentioned issues and have developed a vehicle driveline operating method, comprising: via a controller, decreasing an amount of power supplied to high voltage accessories coupled to a high voltage bus responsive to a desired engine power amount plus an electric energy storage device discharge power upper threshold amount minus an amount of power supplied to the high voltage accessories coupled to high voltage bus being greater than a driver demand power.

By decreasing an amount of power supplied to high voltage accessories that are coupled to a high voltage bus, it may be possible to provide the technical result of reducing engine loads after an engine start so that engine emissions may be reduced. In particular, an amount of power that is supplied to high voltage accessories may be reduced so that additional power may flow to an electric machine that provides propulsive force to the vehicle. Since power output of the electric machine may be increased, power output from the engine may be decreased while meeting driver demand power. Consequently, the engine may be operated at a lower load to reduce engine emissions until the engine is warm or until an even higher driver demand power is requested.

The present description may provide several advantages. For example, the approach may reduce engine emissions after engine starting. Further, the approach may reduce catalyst light-off times when a driver is requesting higher power demands. Further still, the approach may reduce a number of occasions when an engine is started to meet driver demand power.

DETAILED DESCRIPTION

The present description is related to operating a driveline of a hybrid vehicle that includes an internal combustion engine and an electric machine. Power of a high voltage bus may be directed to an electric machine instead of other high voltage consumers during conditions when it may be possible for higher quantities of hydrocarbons and carbon monoxide to be released to atmosphere so that engine load and emissions may be reduced. In addition, power delivery to the high voltage bus may be prioritized such that engine starting may be less frequent to conserve fuel. The internal combustion engine may be of the type shown inFIG. 1. The engine may be part of a driveline or powertrain that includes a belt integrated starter/generator (BISG) and an integrated starter/generator (ISG) as is shown inFIG. 2. A prior art sequence for controlling an electric machine and an engine is shown inFIG. 3. An electric machine operating sequence and engine starting sequence according to the method ofFIGS. 10A and 10Bis shown inFIG. 4. An example function for regulating high voltage power that is available to high voltage accessories based on catalyst efficiency is shown inFIG. 5. A prior art engine starting sequence is shown inFIG. 6.FIGS. 7-9show different scenarios for controlling electric machine power according to the method ofFIGS. 10A and 10B. A method for controlling a driveline that includes an internal combustion engine and an electric machine is shown inFIGS. 10A and 10B. A plot of a function describing catalyst efficiency versus catalyst temperature is shown inFIG. 11.

Referring toFIG. 1, internal combustion engine10, comprising a plurality of cylinders, one cylinder of which is shown inFIG. 1, is controlled by electronic engine controller12. The controller12receives signals from the various sensors shown inFIGS. 1 and 2. Controller12employs the actuators shown inFIGS. 1 and 2to adjust engine operation based on the received signals and instructions stored in memory of controller12.

Engine10is comprised of cylinder head35and block33, which include combustion chamber30and cylinder walls32. Piston36is positioned therein and reciprocates via a connection to crankshaft40. Flywheel97and ring gear99are coupled to crankshaft40. Optional starter96(e.g., low voltage (operated with less than 30 volts) electric machine) includes pinion shaft98and pinion gear95. Pinion shaft98may selectively advance pinion gear95to engage ring gear99. Starter96may be directly mounted to the front of the engine or the rear of the engine. In some examples, starter96may selectively supply torque to crankshaft40via a belt or chain. In one example, starter96is in a base state when not engaged to the engine crankshaft.

Combustion chamber30is shown communicating with intake manifold44and exhaust manifold48via respective intake valve52and exhaust valve54. Each intake and exhaust valve may be operated by an intake cam51and an exhaust cam53. The position of intake cam51may be determined by intake cam sensor55. The position of exhaust cam53may be determined by exhaust cam sensor57. Intake valve52may be selectively activated and deactivated by valve activation device59. Exhaust valve54may be selectively activated and deactivated by valve activation device58. Valve activation devices58and59may be electro-mechanical devices.

Fuel injector66is shown positioned to inject fuel directly into cylinder30, which is known to those skilled in the art as direct injection. Fuel injector66delivers liquid fuel in proportion to the pulse width from controller12. Fuel is delivered to fuel injector66by a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown). In one example, a high pressure, dual stage, fuel system may be used to generate higher fuel pressures.

In addition, intake manifold44is shown communicating with turbocharger compressor162and engine air intake42. In other examples, compressor162may be a supercharger compressor. Shaft161mechanically couples turbocharger turbine164to turbocharger compressor162. Optional electronic throttle62adjusts a position of throttle plate64to control air flow from compressor162to intake manifold44. Pressure in boost chamber45may be referred to a throttle inlet pressure since the inlet of throttle62is within boost chamber45. The throttle outlet is in intake manifold44. In some examples, throttle62and throttle plate64may be positioned between intake valve52and intake manifold44such that throttle62is a port throttle. Compressor recirculation valve47may be selectively adjusted to a plurality of positions between fully open and fully closed. Wastegate163may be adjusted via controller12to allow exhaust gases to selectively bypass turbine164to control the speed of compressor162. Air filter43cleans air entering engine air intake42.

Exhaust system5includes exhaust manifold48and converter70. Converter70can include multiple catalyst bricks, in one example. In another example, multiple emission control devices, each with multiple bricks, can be used. Converter70can be a three-way type catalyst in one example.

Controller12may also receive input from human/machine interface11. A request to start or stop the engine or vehicle may be generated via a human and input to the human/machine interface11. The human/machine interface may be a touch screen display, pushbutton, key switch or other known device.

During operation, each cylinder within engine10typically undergoes a four stroke cycle: the cycle includes the intake stroke, compression stroke, expansion stroke, and exhaust stroke. During the intake stroke, generally, the exhaust valve54closes and intake valve52opens. Air is introduced into combustion chamber30via intake manifold44, and piston36moves to the bottom of the cylinder so as to increase the volume within combustion chamber30. The position at which piston36is near the bottom of the cylinder and at the end of its stroke (e.g. when combustion chamber30is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC).

During the compression stroke, intake valve52and exhaust valve54are closed. Piston36moves toward the cylinder head so as to compress the air within combustion chamber30. The point at which piston36is at the end of its stroke and closest to the cylinder head (e.g. when combustion chamber30is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by known ignition means such as spark plug92, resulting in combustion.

FIG. 2is a block diagram of a vehicle225including a powertrain or driveline200. The driveline ofFIG. 2includes engine10shown inFIG. 1. Driveline200is shown including vehicle system controller255, engine controller12, electric machine controller252, transmission controller254, energy storage device controller253, and brake controller250. The controllers may communicate over controller area network (CAN)299. Each of the controllers may provide information to other controllers such as torque output limits (e.g., torque output of the device or component being controlled not to be exceeded), torque input limits (e.g., torque input of the device or component being controlled not to be exceeded), torque output of the device being controlled, sensor and actuator data, diagnostic information (e.g., information regarding a degraded transmission, information regarding a degraded engine, information regarding a degraded electric machine, information regarding degraded brakes). Further, the vehicle system controller255may provide commands to engine controller12, electric machine controller252, transmission controller254, and brake controller250to achieve driver input requests and other requests that are based on vehicle operating conditions.

For example, in response to a driver releasing an accelerator pedal and vehicle speed, vehicle system controller255may request a desired wheel torque or a wheel power level to provide a desired rate of vehicle deceleration. The desired wheel torque may be provided by vehicle system controller255requesting a first braking torque from electric machine controller252and a second braking torque from brake controller250, the first and second torques providing the desired braking torque at vehicle wheels216.

In other examples, the partitioning of driveline controlling devices may be different than that shown inFIG. 2. For example, a single controller may take the place of vehicle system controller255, engine controller12, electric machine controller252, transmission controller254, and brake controller250. Alternatively, the vehicle system controller255and the engine controller12may be a single unit while the electric machine controller252, the transmission controller254, and the brake controller250are standalone controllers.

In this example, driveline200may be powered by engine10and electric machine240. In other examples, engine10may be omitted. Engine10may be started with an engine starting system shown inFIG. 1, via belt integrated starter/generator (BISG)219, or via driveline integrated starter/generator (ISG)240also known as an integrated starter/generator. A speed of BISG219may be determined via optional BISG speed sensor203. In some examples, BISG219may be simply referred to as an ISG. Driveline ISG240(e.g., high voltage (operated with greater than 30 volts) electrical machine) may also be referred to as an electric machine, motor, and/or generator. Further, torque of engine10may be adjusted via torque actuator204, such as a fuel injector, throttle, etc.

BISG219may be mechanically coupled to engine10via belt231or other means. BISG219may be coupled to crankshaft40or a camshaft (e.g.,51or53ofFIG. 1). BISG219may operate as a motor when supplied with electrical power via electric energy storage device275or low voltage battery280. BISG219may operate as a generator supplying electrical power to electric energy storage device275or low voltage battery280. Bi-directional DC/DC converter281may transfer electrical energy from a high voltage buss274to a low voltage buss273or vice-versa. Low voltage battery280and BISG219are electrically coupled to low voltage buss273. Electric energy storage device275is electrically coupled to high voltage buss274. Low voltage battery280selectively supplies electrical energy to starter motor96and BISG219. High voltage buss may supply electrical power to high voltage accessories including positive temperature coefficient (PTC) heaters266for heating a passenger compartment of vehicle225, compressor267of climate control system268(e.g., a heat pump that cools or heats a passenger cabin), and DC/DC converter281. Controller255or controller12may selectively reduce or increase electrical power consumed by the high voltage accessories via commands provide over CAN299.

An engine output torque may be transmitted to an input or first side of driveline disconnect clutch235through dual mass flywheel215. Disconnect clutch236may be electrically or hydraulically actuated. The downstream or second side234of disconnect clutch236is shown mechanically coupled to ISG input shaft237.

ISG240may be operated to provide torque to driveline200or to convert driveline torque into electrical energy to be stored in electric energy storage device275in a regeneration mode. Inverter265selectively supplies or receives electrical power to/from ISG240to/from high voltage bus274. ISG240has a higher output torque capacity than starter96shown inFIG. 1or BISG219. Further, ISG240directly drives driveline200or is directly driven by driveline200. There are no belts, gears, or chains to couple ISG240to driveline200. Rather, ISG240rotates at the same rate as driveline200. Electrical energy storage device275(e.g., high voltage battery or power source) may be a battery, capacitor, or inductor. The downstream side of ISG240is mechanically coupled to the impeller285of torque converter206via shaft241. The upstream side of the ISG240is mechanically coupled to the disconnect clutch236. ISG240may provide a positive torque or a negative torque to driveline200via operating as a motor or generator as instructed by electric machine controller252. It should be noted that the system shown inFIG. 2is not the only configuration to which the method described herein may be applied. For example, the electric machine may be included in a series or parallel hybrid driveline.

Torque converter206includes a turbine286to output torque to input shaft270. Input shaft270mechanically couples torque converter206to automatic transmission208. Torque converter206also includes a torque converter bypass lock-up clutch212(TCC). Torque is directly transferred from impeller285to turbine286when TCC is locked. TCC is electrically operated by controller12. Alternatively, TCC may be hydraulically locked. In one example, the torque converter may be referred to as a component of the transmission.

When torque converter lock-up clutch212is fully disengaged, torque converter206transmits engine torque to automatic transmission208via fluid transfer between the torque converter turbine286and torque converter impeller285, thereby enabling torque multiplication. In contrast, when torque converter lock-up clutch212is fully engaged, the engine output torque is directly transferred via the torque converter clutch to an input shaft270of transmission208. Alternatively, the torque converter lock-up clutch212may be partially engaged, thereby enabling the amount of torque directly relayed to the transmission to be adjusted. The transmission controller254may be configured to adjust the amount of torque transmitted by torque converter212by adjusting the torque converter lock-up clutch in response to various engine operating conditions, or based on a driver-based engine operation request.

Torque converter206also includes pump283that pressurizes fluid to operate disconnect clutch236, forward clutch210, and gear clutches211. Pump283is driven via impeller285, which rotates at a same speed as ISG240.

Automatic transmission208includes gear clutches (e.g., gears 1-10)211and forward clutch210. Automatic transmission208is a fixed ratio transmission. The gear clutches211and the forward clutch210may be selectively engaged to change a ratio of an actual total number of turns of input shaft270to an actual total number of turns of wheels216. Gear clutches211may be engaged or disengaged via adjusting fluid supplied to the clutches via shift control solenoid valves209. Torque output from the automatic transmission208may also be relayed to wheels216to propel the vehicle via output shaft260. Specifically, automatic transmission208may transfer an input driving torque at the input shaft270responsive to a vehicle traveling condition before transmitting an output driving torque to the wheels216. Transmission controller254selectively activates or engages TCC212, gear clutches211, and forward clutch210. Transmission controller also selectively deactivates or disengages TCC212, gear clutches211, and forward clutch210.

Further, a frictional force may be applied to wheels216by engaging friction wheel brakes218. In one example, friction wheel brakes218may be engaged in response to the driver pressing his foot on a brake pedal (not shown) and/or in response to instructions within brake controller250. Further, brake controller250may apply brakes218in response to information and/or requests made by vehicle system controller255. In the same way, a frictional force may be reduced to wheels216by disengaging wheel brakes218in response to the driver releasing his foot from a brake pedal, brake controller instructions, and/or vehicle system controller instructions and/or information. For example, vehicle brakes may apply a frictional force to wheels216via controller250as part of an automated engine stopping procedure.

In response to a request to accelerate vehicle225, vehicle system controller may obtain a driver demand torque or power request from an accelerator pedal or other device. Vehicle system controller255then allocates a fraction of the requested driver demand power to the engine and the remaining fraction to the ISG or BISG. Vehicle system controller255requests the engine power from engine controller12and the ISG torque from electric machine controller252. If the ISG power plus the engine power is less than a transmission input power limit (e.g., a threshold value not to be exceeded), the power is delivered to torque converter206which then relays at least a fraction of the requested power to transmission input shaft270. Transmission controller254selectively locks torque converter clutch212and engages gears via gear clutches211in response to shift schedules and TCC lockup schedules that may be based on input shaft torque and vehicle speed. In some conditions when it may be desired to charge electric energy storage device275, a charging power (e.g., a negative ISG torque) may be requested while a non-zero driver demand power is present. Vehicle system controller255may request increased engine power to overcome the charging power to meet the driver demand power.

In response to a request to decelerate vehicle225and provide regenerative braking, vehicle system controller may provide a negative desired wheel power based on vehicle speed and brake pedal position. Vehicle system controller255then allocates a fraction of the negative desired wheel power to the ISG240(e.g., desired driveline wheel torque) and the remaining fraction to friction brakes218(e.g., desired friction brake wheel torque). Further, vehicle system controller may notify transmission controller254that the vehicle is in regenerative braking mode so that transmission controller254shifts gears211based on a unique shifting schedule to increase regeneration efficiency. ISG240supplies a negative power to transmission input shaft270, but negative power provided by ISG240may be limited by transmission controller254which outputs a transmission input shaft negative power limit (e.g., not to be exceeded threshold value). Further, negative torque of ISG240may be limited (e.g., constrained to less than a threshold negative threshold torque) based on operating conditions of electric energy storage device275, by vehicle system controller255, or electric machine controller252. Any portion of desired negative wheel power that may not be provided by ISG240because of transmission or ISG limits may be allocated to friction brakes218so that the desired wheel power is provided by a combination of negative wheel power from friction brakes218and ISG240.

Accordingly, power or torque control of the various driveline components may be supervised by vehicle system controller255with local torque control for the engine10, transmission208, electric machine240, and brakes218provided via engine controller12, electric machine controller252, transmission controller254, and brake controller250.

As one example, an engine torque output may be controlled by adjusting a combination of spark timing, fuel pulse width, fuel pulse timing, and/or air charge, by controlling throttle opening and/or valve timing, valve lift and boost for turbo- or super-charged engines. In the case of a diesel engine, controller12may control the engine torque output by controlling a combination of fuel pulse width, fuel pulse timing, and air charge. In all cases, engine control may be performed on a cylinder-by-cylinder basis to control the engine torque output.

Electric machine controller252may control power output and electrical energy production from ISG240by adjusting current flowing to and from field and/or armature windings of ISG as is known in the art.

Transmission controller254receives transmission input shaft position via position sensor271. Transmission controller254may convert transmission input shaft position into input shaft speed via differentiating a signal from position sensor271or counting a number of known angular distance pulses over a predetermined time interval. Transmission controller254may receive transmission output shaft torque from torque sensor272. Alternatively, sensor272may be a position sensor or torque and position sensors. If sensor272is a position sensor, controller254may count shaft position pulses over a predetermined time interval to determine transmission output shaft velocity. Transmission controller254may also differentiate transmission output shaft velocity to determine transmission output shaft acceleration. Transmission controller254, engine controller12, and vehicle system controller255, may also receive addition transmission information from sensors277, which may include but are not limited to pump output line pressure sensors, transmission hydraulic pressure sensors (e.g., gear clutch fluid pressure sensors), ISG temperature sensors, and BISG temperatures, and ambient temperature sensors.

Brake controller250receives wheel speed information via wheel speed sensor221and braking requests from vehicle system controller255. Brake controller250may also receive brake pedal position information from brake pedal sensor154shown inFIG. 1directly or over CAN299. Brake controller250may provide braking responsive to a wheel torque command from vehicle system controller255. Brake controller250may also provide anti-lock and vehicle stability braking to improve vehicle braking and stability. As such, brake controller250may provide a wheel torque limit (e.g., a threshold negative wheel torque not to be exceeded) to the vehicle system controller255so that negative ISG torque does not cause the wheel torque limit to be exceeded. For example, if controller250issues a negative wheel torque limit of 50 N-m, ISG torque is adjusted to provide less than 50 N-m (e.g., 49 N-m) of negative torque at the wheels, including accounting for transmission gearing.

The system ofFIGS. 1 and 2provides for a system, comprising: vehicle driveline including an engine and an electric machine that provide propulsive force to vehicle wheels; a high voltage bus coupled to a plurality of electrical power consumers; and a controller including executable instructions stored in non-transitory memory to decrease an amount of power supplied to at least one of the plurality of electrical power consumers responsive to a driver demand power being greater than an electric energy storage device discharge power upper threshold amount minus an amount of power supplied to the plurality of high voltage accessories. The system further comprises additional instructions to decrease an amount of power supplied to the high voltage accessories responsive to a desired engine power amount plus the electric energy storage device discharge power upper threshold amount minus the amount of power supplied to the high voltage accessories being greater than the driver demand power. The system further comprises additional instructions to increase a threshold amount of electrical power available to the electric machine from a high voltage electric energy storage device proportionate to the decrease in the amount of power supplied to the plurality of high voltage accessories. The system further comprises additional instructions to start the engine responsive to the driver demand power exceeding the electric energy storage device discharge power upper threshold amount. The system further comprises additional instructions to record an amount of time since a most recent time the amount of power supplied to at least one of the plurality of electrical power consumers has been reduced. The system further comprises additional instructions to decrease the amount of time in response to the driver demand being less than the electric energy storage device discharge power upper threshold amount minus an amount of power supplied to the plurality of high voltage accessories.

Referring now toFIG. 3, two plots illustrating a prior art electric machine control sequence are shown. The two plots are time aligned and they occur at a same time. The vertical lines at times t0-t3represents times of interest in the sequence.

The first plot from the top ofFIG. 3is a plot of power versus time. The vertical axis represents power and power increases in the direction of the vertical axis arrow. The horizontal axis of the first plot represents time and time increases from the left side of the figure to the right side of the figure. Horizontal line350represents an upper electric energy storage device discharge power upper threshold amount (e.g., an amount of electrical power being discharged from an electric energy storage device that is not to be exceeded). Horizontal line352represents a threshold amount of electrical power available to an electric machine (e.g., ISG240) from a high voltage electric energy storage device (e.g., an amount of electrical power supplied to an electric machine240from an electric energy storage device that is not to be exceeded). Solid line304represents an amount of electrical power provided to high voltage accessories (e.g., a climate control system compressor, DC/DC converter, and PTC heaters). Dashed dot line302represents a driver demand power (e.g., an amount of power requested by a vehicle's human driver or autonomous driver to provide power to vehicle wheels).

The second plot from the top ofFIG. 3is a plot of torque versus time. The vertical axis represents torque and torque increases in the direction of the vertical axis arrow. The horizontal axis of the second plot represents time and time increases from the left side of the figure to the right side of the figure. Solid line308represents engine torque or requested engine torque. Dash-dot line306represents electric machine torque or requested electric machine torque.

At time t0, the driver demand power is low and the amount of electrical power provided to high voltage accessories is at a medium level and constant. The electric motor torque output is low and the engine torque output is low.

At time t1, the driver demand power begins to increase and the electric machine torque is increased to meet the driver demand power. The engine torque remains at its previous level and the amount of electrical power provided to high voltage accessories remains at its previous level.

Between time t1and time t2, the driver demand power continues to increase and the electric machine torque is increased to meet the driver demand power. The engine torque remains at its previous level and the amount of electrical power provided to high voltage accessories remains at its previous level.

At time t2, the driver demand power reaches threshold352and the engine torque is increased to meet the driver demand power. The electric machine torque is not increased since the electric machine power plus power provided to the high voltage accessories is equal to the upper electric energy storage device discharge power upper threshold amount. Thus, the engine power output is increased when electric machine power plus power provided to the high voltage accessories is equal to the upper electric energy storage device discharge power upper threshold amount when driver demand power is increasing so that driver demand power may be met. However, during conditions when the engine is cold and the catalyst is cold, the higher engine loads may increase hydrocarbon and carbon monoxide emissions.

Between time t2and time t3, the driver demand power continues to increase and the electric machine torque is held at its previous amount. The engine torque is increased to meet the driver demand power in combination with the electric machine torque. The amount of electrical power provided to high voltage accessories remains at its previous level.

At time t3, the driver demand power exceeds the upper electric energy storage device discharge power upper threshold amount, but the driver demand power is still met by increasing the engine torque. The electric machine torque remains unchanged and the electrical power amount supplied to the high voltage accessories remains at its previous level.

Thus, while the prior art method may meet driver demand power, engine emissions may be higher than is desired since the engine may be operated at higher output levels. Further, if the high voltage accessory load is high, engine torque may be increased for even smaller driver demand power levels so that engine emissions may increase earlier in a vehicle drive cycle when catalyst efficiency may be low.

Referring now toFIG. 4, two prophetic plots illustrating an electric machine control sequence are shown. The two plots are time aligned and they occur at a same time. The vertical lines at times t10-t13represents times of interest in the sequence. The sequence may be performed via the system ofFIGS. 1 and 2in cooperation with the method ofFIGS. 10A and 10B.

The first plot from the top ofFIG. 4is a plot of power versus time. The vertical axis represents power and power increases in the direction of the vertical axis arrow. The horizontal axis of the first plot represents time and time increases from the left side of the figure to the right side of the figure. Horizontal line450represents an upper electric energy storage device discharge power upper threshold amount (e.g., an amount of electrical power being discharged from an electric energy storage device that is not to be exceeded). Horizontal line452represents a threshold amount of electrical power available to an electric machine (e.g., ISG240) from a high voltage electric energy storage device (e.g., an amount of electrical power supplied to an electric machine from an electric energy storage device that is not to be exceeded). Solid line404represents an amount of electrical power provided to high voltage accessories (e.g., a climate control system compressor, DC/DC converter, and PTC heaters). Dashed dot line402represents a driver demand power (e.g., an amount of power requested by a vehicle's human driver or autonomous driver to provide power to vehicle wheels).

The second plot from the top ofFIG. 4is a plot of torque versus time. The vertical axis represents torque and torque increases in the direction of the vertical axis arrow. The horizontal axis of the second plot represents time and time increases from the left side of the figure to the right side of the figure. Solid line408represents engine torque or requested engine torque. Dash-dot line406represents electric machine torque or requested electric machine torque.

At time t10, the driver demand power is low and the amount of electrical power provided to high voltage accessories is at a medium level and constant. The electric motor torque output is low and the engine torque output is low.

At time t11, the driver demand power begins to increase and the electric machine torque is increased to meet the driver demand power. The engine torque remains at its previous level and the amount of electrical power provided to high voltage accessories remains at its previous level.

Between time t11and time t12, the driver demand power continues to increase and the electric machine torque is increased to meet the driver demand power. The engine torque remains at its previous level and the amount of electrical power provided to high voltage accessories remains at its previous level.

At time t12, the driver demand power reaches threshold452and the amount of electrical power supplied to the high voltage accessories is reduced in response to the driver demand power reaching threshold452. In one example, the amount of power that the high voltage accessories is reduced by is equal to the amount of power that the driver demand power exceeds the threshold amount of electrical power available to an electric machine, at least while driver demand power is less than the upper electric energy storage device discharge power upper threshold amount. The threshold amount of electrical power available to an electric machine (e.g.,452) is increased by the amount of power that is withdrawn from the high voltage accessories. This allows additional power to be delivered to the electric machine, thereby increasing the torque output by the electric machine. Thus, the output torque of the electric machine begins to increase further in response to power being withdrawn from the high voltage accessories, which are supplied power via a high voltage battery or electric energy storage device275. The engine output torque remains at its previous level.

Between time t12and time t13, the driver demand power continues to increase and the electric machine torque is increased as the driver demand power increases. In addition, the amount of electrical power supplied to the high voltage accessories continues to be reduced as the driver demand power continues to increase. The threshold amount of electrical power available to an electric machine (e.g.,452) also continues to increase by the amount of power that is withdrawn from the high voltage accessories. The engine output torque remains at its previous level.

At time t13, the driver demand power exceeds the upper electric energy storage device discharge power upper threshold amount. Therefore, no additional electrical power is provided to the electric machine, but the driver demand power is still met by increasing the engine torque. The electrical power amount supplied to the high voltage accessories reaches a value of zero. Engine torque output is increased after time t13to meet high driver power demand levels.

Thus, electrical power supplied to high voltage accessory loads that are electrically coupled to the high voltage bus may be reduced after the amount of electrical power supplied to high voltage accessories plus power supplied to the electric machine that propels the vehicle is equal to the upper electric energy storage device discharge power upper threshold amount. This allows additional electrical power to be diverted to the electric machine from the electric energy storage device so that engine power may not have to be increased to meet driver demand power. Consequently, engine emissions may be reduced after engine starting when an engine is cold.

Referring now toFIG. 5, an example function that shows an amount of high voltage power that may be available to high voltage accessories versus catalyst efficiency is shown. The vertical axis represents an amount of electrical power (e.g., kilo watts (Kw)) that may be made available to high voltage electrical accessories or consumers after driver demand power is greater than a high voltage battery or electric energy storage device discharge power that is available to an electric machine (e.g.,240ofFIG. 2). Electrical power that is available to the electrical accessories is an amount of electric power that is not to be exceeded by the amount of power that is supplied to the electric machine.

It may be observed that when catalyst efficiency is low, the amount of electrical power that is available to the high voltage electrical accessories is low. As the catalyst efficiency increases, the amount of electrical power that is available to the high voltage electrical accessories increases. Consequently, when catalyst efficiency is low, a lower amount of electrical power is available to high voltage electrical accessories and a greater amount of electrical power is made available to the electric machine that may provide propulsive power to the driveline. This allows the electric machine output to be greater at lower catalyst temperatures so that engine load may be reduced, thereby improving engine emissions. At high catalyst efficiency levels, a greater amount of electrical power is made available to high voltage electrical accessories and a lesser amount of electrical power is made available to the electric machine. Increasing the amount of electrical power that is available to high voltage accessories allows the high voltage accessories to operate at full capacity. In this example, less than 2 Kw may be provided to high voltage accessories when catalyst efficiency is 50% and 8 Kw may be provided to high voltage accessories when catalyst efficiency is near 100%.

Referring now toFIG. 6, two plots illustrating a prior art engine starting sequence are shown. The two plots are time aligned and they occur at a same time. The vertical lines at times t20-t23represents times of interest in the sequence.

The first plot from the top ofFIG. 6is a plot of power versus time. The vertical axis represents power and power increases in the direction of the vertical axis arrow. The horizontal axis of the first plot represents time and time increases from the left side of the figure to the right side of the figure. Horizontal line650represents an upper electric energy storage device discharge power upper threshold amount (e.g., an amount of electrical power being discharged from an electric energy storage device that is not to be exceeded). Horizontal line652represents a threshold amount of electrical power available to an electric machine (e.g., ISG240) from a high voltage electric energy storage device (e.g., an amount of electrical power supplied to an electric machine from an electric energy storage device that is not to be exceeded). Dashed dot line602represents a driver demand power (e.g., an amount of power requested by a vehicle's human driver or autonomous driver to provide power to vehicle wheels). Solid line604represents an amount of electrical power may be provided to high voltage accessories (e.g., a climate control system compressor, DC/DC converter, and PTC heaters).

The second plot from the top ofFIG. 6is a plot of an engine starting command versus time. The vertical axis represents state of the engine starting command and the engine is commanded to start and run (e.g., combust fuel) when trace606is at a higher level near the vertical axis arrow. The engine is not commanded to start when trace606is at a lower level near the horizontal axis. The horizontal axis of the second plot represents time and time increases from the left side of the figure to the right side of the figure. Dash-dot line606represents the state of the engine start command.

At time t20, the driver demand power is low and the amount of electrical power provided to high voltage accessories is at a medium level and constant. The engine is stopped (e.g., not running and combusting).

At time t21, the driver demand power begins to increase. The engine remains stopped and the amount of electrical power provided to high voltage accessories remains at its previous level.

Between time t21and time t22, the driver demand power continues to increase. The engine remains stopped and the amount of electrical power provided to high voltage accessories remains at its previous level.

At time t22, the driver demand power reaches threshold652and the engine is started to meet the driver demand power. The electric machine torque is (not shown) not increased since the electric machine power plus power provided to the high voltage accessories is equal to the upper electric energy storage device discharge power upper threshold amount. Thus, the engine is started when electric machine power plus power provided to the high voltage accessories is equal to the upper electric energy storage device discharge power upper threshold amount when driver demand power is increasing so that driver demand power may be met.

Between time t22and time t23, the driver demand power continues to increase and the engine torque is increased (not shown) to meet the driver demand power. Then, the driver demand power is reduced, but the engine continues to run since it has been started and stopping the engine so soon after starting the engine may be inefficient. The electrical power amount that is supplied to the high voltage accessories remains at its previous level.

At time t3, the driver demand power is reduced to a level that is less than threshold652, but the engine remains running so that the engine may recharge the electric energy storage device. The electrical power amount that is supplied to the high voltage accessories remains at its previous level.

Thus, while the prior art method may meet driver demand power, the engine may be started and run only for a short period of time before the engine's power is not needed to meet the driver demand power. Consequently, driveline efficiency may be reduced and engine emissions may be increased.

Referring now toFIG. 7, three plots illustrating an example electric machine control sequence are shown. The three plots are time aligned and they occur at a same time. The vertical lines at times t30-t33represent times of interest in the sequence. The sequence may be performed via the system ofFIGS. 1 and 2in cooperation with the method ofFIGS. 10A and 10B.

The first plot from the top ofFIG. 7is a plot of power versus time. The vertical axis represents power and power increases in the direction of the vertical axis arrow. The horizontal axis of the first plot represents time and time increases from the left side of the figure to the right side of the figure. Horizontal line750represents an upper electric energy storage device discharge power upper threshold amount (e.g., an amount of electrical power being discharged from an electric energy storage device that is not to be exceeded). Horizontal line752represents a threshold amount of electrical power available to an electric machine (e.g., ISG240) from a high voltage electric energy storage device (e.g., an amount of electrical power supplied to an electric machine from an electric energy storage device that is not to be exceeded). Dashed dot line702represents a driver demand power (e.g., an amount of power requested by a vehicle's human driver or autonomous driver to provide power to vehicle wheels). Solid line704represents an amount of electrical power provided to high voltage accessories (e.g., a climate control system compressor, DC/DC converter, and PTC heaters).

The second plot from the top ofFIG. 7is a plot of an engine starting command versus time. The vertical axis represents state of the engine starting command and the engine is commanded to start and run (e.g., combust fuel) when trace706is at a higher level near the vertical axis arrow. The engine is not commanded to start when trace706is at a lower level near the horizontal axis. The horizontal axis of the second plot represents time and time increases from the left side of the figure to the right side of the figure. Solid line706represents the state of the engine start command.

The third plot from the top ofFIG. 7is a plot of a high voltage load shed timer value versus time. The vertical axis represents the high voltage load shed timer value and the value of the high voltage load shed timer increased in the direction of the vertical axis arrow. The value of the high voltage load shed timer is zero when trace708is at a lower level near the horizontal axis. The horizontal axis of the third plot represents time and time increases from the left side of the figure to the right side of the figure. Solid line708represents the high voltage load shed timer value. Horizontal line754represents a high voltage load shed timer upper threshold (e.g., a high voltage load shed timer value that is not to be exceeded).

At time t30, the driver demand power is low and the amount of electrical power provided to high voltage accessories is at a medium level and constant. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

At time t31, the driver demand power begins to increase. The amount of electrical power provided to high voltage accessories remains at its previous value. The engine remains stopped. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

Between time t31and time t32, the driver demand power continues to increase. The engine remains stopped and the amount of electrical power provided to high voltage accessories remains at its previous level. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

At time t32, the driver demand power reaches threshold752, but the engine is not started to meet the driver demand power. Rather, the amount of electrical power supplied to the high voltage electric consumers is reduced and the threshold amount of electrical power available to an electric machine (e.g.,240) is increased by the amount of electrical power that is withdrawn from the high voltage accessories. This allows the amount of electrical power that is supplied to the electric machine to be increased (not show) to meet the driver demand power. In one example, the amount of power that the high voltage accessories is reduced by is equal to the amount of power that the driver demand power exceeds the threshold amount of electrical power available to an electric machine, at least while driver demand power is less than the upper electric energy storage device discharge power upper threshold amount. The threshold amount of electrical power available to an electric machine (e.g.,752) is increased by the amount of power that is withdrawn from the high voltage accessories. This allows additional power to be delivered to the electric machine (not shown), thereby increasing the torque output by the electric machine (not shown). Therefore, the output torque of the electric machine begins to increase (not shown) further in response to power being withdrawn from the high voltage accessories, which are supplied power via a high voltage battery or electric energy storage device275. The value of the high voltage load shed time begins increasing since electrical load or power supplied to high voltage accessories is being reduced so that the electric machine may meet driver demand power.

Between time t32and time t33, the driver demand power continues to increase and the amount of electrical power that is supplied to the high voltage electric consumers is reduce in proportion to the increase in the driver demand power. The threshold amount of electrical power available to an electric machine (e.g.,752) also continues to increase by the amount of power that is withdrawn from the high voltage accessories. Then, the driver demand power is reduced and the amount of electrical power that is supplied to the high voltage electric consumers increases in proportion to the decrease in driver demand power so that output of high voltage accessories may be increased. The threshold amount of electrical power available to an electric machine (e.g.,752) then decrease by the amount of power that is available to the high voltage accessories. The engine remains stopped since the driver demand power is less than threshold750and because the value of the high voltage load shed timer is less than threshold754.

At time t33, the driver demand power is reduced to a level that is less than threshold752. The engine remains stopped and the value of the high voltage load shed timer starts to be reduced. The threshold amount of electrical power available to an electric machine (e.g.,752) carries on at a constant level that is based on the amount of power that is available to the high voltage accessories.

Thus, because electrical power that is provided to high voltage accessories was reduced in response to increasing driver demand power, the engine may remain stopped while driver demand power is met by the electric machine. This may conserve fuel and reduce engine emissions.

Referring now toFIG. 8, three plots illustrating a second example electric machine control sequence are shown. The three plots are time aligned and they occur at a same time. The vertical lines at times t40-t43represents times of interest in the sequence. The sequence may be performed via the system ofFIGS. 1 and 2in cooperation with the method ofFIGS. 10A and 10B.

The first plot from the top ofFIG. 8is a plot of power versus time. The vertical axis represents power and power increases in the direction of the vertical axis arrow. The horizontal axis of the first plot represents time and time increases from the left side of the figure to the right side of the figure. Horizontal line850represents an upper electric energy storage device discharge power upper threshold amount (e.g., an amount of electrical power being discharged from an electric energy storage device that is not to be exceeded). Horizontal line852represents a threshold amount of electrical power available to an electric machine (e.g., ISG240) from a high voltage electric energy storage device (e.g., an amount of electrical power supplied to an electric machine from an electric energy storage device that is not to be exceeded). Dashed dot line802represents a driver demand power (e.g., an amount of power requested by a vehicle's human driver or autonomous driver to provide power to vehicle wheels). Solid line804represents an amount of electrical power provided to high voltage accessories (e.g., a climate control system compressor, DC/DC converter, and PTC heaters).

The second plot from the top ofFIG. 8is a plot of an engine starting command versus time. The vertical axis represents state of the engine starting command and the engine is commanded to start and run (e.g., combust fuel) when trace806is at a higher level near the vertical axis arrow. The engine is not commanded to start when trace806is at a lower level near the horizontal axis. The horizontal axis of the second plot represents time and time increases from the left side of the figure to the right side of the figure. Solid line806represents the state of the engine start command.

The third plot from the top ofFIG. 8is a plot of a high voltage load shed timer value versus time. The vertical axis represents the high voltage load shed timer value and the value of the high voltage load shed timer increases in the direction of the vertical axis arrow. The value of the high voltage load shed timer is zero when trace808is at a lower level near the horizontal axis. The horizontal axis of the third plot represents time and time increases from the left side of the figure to the right side of the figure. Solid line808represents the high voltage load shed timer value. Horizontal line850represents a high voltage load shed timer upper threshold (e.g., a high voltage load shed timer value that is not to be exceeded).

At time t40, the driver demand power is low and the amount of electrical power provided to high voltage accessories is at a medium level and constant. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

At time t41, the driver demand power begins to increase. The amount of electrical power provided to high voltage accessories remains at its previous value. The engine remains stopped. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

Between time t41and time t42, the driver demand power continues to increase. The engine remains stopped and the amount of electrical power provided to high voltage accessories remains at its previous level. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

At time t42, the driver demand power reaches threshold852, but the engine is not started to meet the driver demand power. Instead, the amount of electrical power supplied to the high voltage electric consumers is reduced and the threshold amount of electrical power available to an electric machine is increased by the amount of electrical power that is withdrawn from the high voltage accessories. This allows the amount of electrical power that is supplied to the electric machine to be increased (not show) to meet the driver demand power. In one example, the amount of power that the high voltage accessories is reduced by is equal to the amount of power that the driver demand power exceeds the threshold amount of electrical power available to an electric machine, at least while driver demand power is less than the upper electric energy storage device discharge power upper threshold amount. The threshold amount of electrical power that is available to an electric machine (e.g.,852) is increased by the amount of power that is withdrawn from the high voltage accessories. This allows additional power to be delivered to the electric machine (not shown), thereby increasing the torque output by the electric machine (not shown). As a result, the output torque of the electric machine begins to increase (not shown) further in response to power being withdrawn from the high voltage accessories, which are supplied power via a high voltage battery or electric energy storage device275. The value of the high voltage load shed time begins increasing since electrical load or power supplied to high voltage accessories is being reduced so that the electric machine may meet driver demand power.

Between time t42and time t43, the driver demand power increases and then levels off at a constant value between threshold850and threshold852. The threshold amount of electrical power available to an electric machine also increases and then levels off since the driver demand power levels off and since the amount of electrical power supplied to the high voltage accessories ceases decreasing. The engine remains stopped and the high voltage load shed timer value continues to increase.

At time t43, the driver demand power remains high, but the value of the high voltage load shed timer exceeds threshold850so the engine is started. Torque from the engine (not shown) is delivered to the driveline so that the threshold amount of electrical power available to the electric machine is reduced and so that the amount of electrical power provided to high voltage accessories may be increased. The high voltage load shed timer value is decreased in response to the engine torque being applied to meet driver demand power and the amount of electrical energy that is provided to the electric machine being less than threshold852(not shown).

In this way, the engine may be started to meet driver demand power after an amount of electrical power provided to high voltage accessories has been reduced for a predetermined amount of time so that driver demand power may be met by the electric machine. These actions may conserve fuel and reduce engine emissions while still allowing the engine to start after electric power provided to high voltage accessories has been reduced for an extended period of time.

Referring now toFIG. 9, three plots illustrating a second example electric machine control sequence are shown. The three plots are time aligned and they occur at a same time. The vertical lines at times t50-t53represents times of interest in the sequence. The sequence may be performed via the system ofFIGS. 1 and 2in cooperation with the method ofFIGS. 10A and 10B.

The first plot from the top ofFIG. 9is a plot of power versus time. The vertical axis represents power and power increases in the direction of the vertical axis arrow. The horizontal axis of the first plot represents time and time increases from the left side of the figure to the right side of the figure. Horizontal line950represents an upper electric energy storage device discharge power upper threshold amount (e.g., an amount of electrical power being discharged from an electric energy storage device that is not to be exceeded). Horizontal line952represents a threshold amount of electrical power available to an electric machine (e.g., ISG240) from a high voltage electric energy storage device (e.g., an amount of electrical power supplied to an electric machine from an electric energy storage device that is not to be exceeded). Dashed dot line902represents a driver demand power (e.g., an amount of power requested by a vehicle's human driver or autonomous driver to provide power to vehicle wheels). Solid line904represents an amount of electrical power provided to high voltage accessories (e.g., a climate control system compressor, DC/DC converter, and PTC heaters).

The second plot from the top ofFIG. 9is a plot of an engine starting command versus time. The vertical axis represents state of the engine starting command and the engine is commanded to start and run (e.g., combust fuel) when trace906is at a higher level near the vertical axis arrow. The engine is not commanded to start when trace906is at a lower level near the horizontal axis. The horizontal axis of the second plot represents time and time increases from the left side of the figure to the right side of the figure. Solid line906represents the state of the engine start command.

The third plot from the top ofFIG. 9is a plot of a high voltage load shed timer value versus time. The vertical axis represents the high voltage load shed timer value and the value of the high voltage load shed timer increases in the direction of the vertical axis arrow. The value of the high voltage load shed timer is zero when trace908is at a lower level near the horizontal axis. The horizontal axis of the third plot represents time and time increases from the left side of the figure to the right side of the figure. Solid line908represents the high voltage load shed timer value. Horizontal line950represents a high voltage load shed timer upper threshold (e.g., a high voltage load shed timer value that is not to be exceeded).

At time t50, the driver demand power is low and the amount of electrical power provided to high voltage accessories is at a medium level and constant. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

At time t51, the driver demand power begins to increase. The amount of electrical power provided to high voltage accessories remains at its previous value. The engine remains stopped. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

Between time t51and time t52, the driver demand power continues to increase. The engine remains stopped and the amount of electrical power provided to high voltage accessories remains at its previous level. The value of the high voltage load shed timer is zero since an amount of electrical power delivered to high voltage accessories is not being reduced due to high driver demand power.

At time t52, the driver demand power reaches threshold952, but the engine is not started to meet the driver demand power. Instead, the amount of electrical power supplied to the high voltage electric consumers is reduced and the threshold amount of electrical power available to an electric machine is increased by the amount of electrical power that is withdrawn from the high voltage accessories. This allows the amount of electrical power that is supplied to the electric machine to be increased (not show) to meet the driver demand power. The amount of power that the high voltage accessories may be reduced by is equal to the amount of power that the driver demand power exceeds the threshold amount of electrical power available to an electric machine, at least while driver demand power is less than the upper electric energy storage device discharge power upper threshold amount. The threshold amount of electrical power available to an electric machine (e.g.,952) is increased by the amount of power that is withdrawn from the high voltage accessories. This allows additional power to be delivered to the electric machine (not shown), thereby increasing the torque output by the electric machine (not shown). As a result, the output torque of the electric machine begins to increase (not shown) further in response to power being withdrawn from the high voltage accessories, which are supplied power via a high voltage battery or electric energy storage device275. The value of the high voltage load shed timer begins increasing since electrical load or power supplied to high voltage accessories is being reduced so that the electric machine may meet driver demand power.

Between time t52and time t53, the driver demand power continues to increase. The amount of electrical power supplied to the high voltage accessories continues to be reduced as the driver demand power continues to increase. The engine remains stopped and the value of the high voltage load timer continues to increase since the amount of electrical power that is supplied to the high voltage accessories is reduced.

At time t53, the driver demand power increases to exceed threshold950. Therefore, the engine is started so that the driver demand power may be met by the electric machine and the engine. The engine may be started even though the value of the high voltage load timer has not exceeded threshold950. Once the engine is started, power from the engine is supplied to the driveline after time t53so that the amount of electrical power supplied to the high voltage accessories may be increased. The value of the high voltage load shed timer is decreased in response to the amount of electrical power being supplied to the high voltage accessories increasing.

In this way, the engine may be started to meet driver demand power after driver demand power exceeds threshold950even if the value of the high voltage load shed timer is less than threshold950. These actions may permit driver demand power to be met during heavy load conditions while also providing electric power provided to high voltage accessories.

Referring now toFIGS. 10A and 10B, a flow chart of a method for operating an engine of a vehicle driveline is shown. The method ofFIGS. 10A and 10Bmay be incorporated into and may cooperate with the system ofFIGS. 1 and 2. Further, at least portions of the method ofFIGS. 10A and 10Bmay be incorporated as executable instructions stored in non-transitory memory while other portions of the method may be performed via a controller transforming operating states of devices and actuators in the physical world.

At1004, method1000judges if the engine is running (e.g., combusting fuel). Method1000may judge that the engine is running if fuel is being injected to the engine and engine speed is greater than a threshold speed. If method1000judges the engine is running, the answer is yes and method1000proceeds to1006. Otherwise, the answer is no and method1000proceeds to1020.

At1006, method1000judges if an increase in high voltage accessory load shedding (e.g., a reduction of electrical power supplied to accessories that are electrically coupled to the high voltage bus) is desired. In one example, method may judge that an increase in high voltage accessory load shedding is desired when a driver demand power is greater than a desired engine power plus an electric energy storage device discharge power upper threshold amount minus an amount of power being supplied to high voltage accessories or accessories that are coupled to a high voltage bus. These conditions may be expressed as:
DD_power>D_eng_power+SD_disc_lim−HV_acc
where DD_power is driver demand power, D_eng_power is desired engine power, SD_disc_lim is an electric energy storage device discharge power upper threshold amount of power (e.g.,450ofFIG. 4), and HV_acc is an amount of electrical power that may be supplied to accessories that are electrically coupled to a high voltage bus (e.g., conductors that transfer charge from a high voltage power source). If method1000judges that driver demand power is greater than a desired engine power plus an electric energy storage device discharge power upper threshold amount minus an amount of power being supplied to high voltage accessories or accessories that are coupled to a high voltage bus, then the answer is yes and method1000proceeds to1008. Otherwise, the answer is no and method1000proceeds to1007.

At1008, method1000increases the threshold amount of electrical power that is available to an electric machine (e.g., threshold452inFIG. 4). In one example, the increase may be expressed as:
EP_avail_thres(k)=min(DD_power+offset,SD_disc_lim)
where EP_avail_thres is the threshold amount of electrical power that is available to the electric machine to propel the vehicle, min is a function that returns a lesser value of argument (DD_power+offset), and argument SD_disc_lim, k is the iteration value, and offset is a predetermined scalar value that ensures that DD_power is less than EP_avail_thres until DD_power is greater than SD_disc_lim. The min function ensures that the threshold amount of electrical power that is available to power the electric machine that may provide propulsive force to the driveline is less than or equal to the upper electric energy storage device discharge power upper threshold amount. Method1000proceeds to1010.

At1010, method1000adjusts an amount of electrical power that is available to high voltage (HV) electrical accessories. In particular, when the desired driver demand power is increasing, then a threshold amount of electrical power available to an electric machine is decreased according to the following equation:
HV_acc_power=SD_disc_lim−EP_avail_thres
where HV_acc_power is an amount of electrical power provided to high voltage accessories, though the high voltage accessories need not consume this amount of power.

Additionally, in some examples, method1000may compensate the amount of electrical power provided to high voltage accessories based on catalyst efficiency. The compensated amount of electrical power provided to high voltage accessories based on catalyst efficiency may be expressed as:
HV_acc_power_comp=min(HV_acc_power,(HV_cat_fun(cat_eff)))
where HV_acc_power_comp is the catalyst compensated value of the amount of electrical power provided to high voltage accessories, min is a function that returns the lesser value of the arguments HV_acc_power and HV_cat_fun(cat_eff), HV_cat_fun is a function that returns an amount of electrical power that may be provided to high voltage accessories based on catalyst temperature (e.g., the function shown inFIG. 5), and cat_eff is an estimate of catalyst efficiency. Catalyst efficiency may be estimated according to a function similar to the function illustrated inFIG. 11. Method1000proceeds to1012.

At1007, method1000may decrease the threshold amount of electrical power that is available to an electric machine (e.g., threshold452inFIG. 4). In one example, the decrease may be expressed as:
EP_avail_thres(k)=max(EP_avail_min,(EP_avail_thresh(k−1)−offset_a))
where EP_avail_thres(k) is the new threshold amount of electrical power that is available to the electric machine to propel the vehicle, k is the iteration value, max is a function that returns a greater value of argument (EP_avail_thresh(k−1)−offset_a) and argument EP_avail_min, k is the iteration value, offset_a is a predetermined scalar value that ensures a predetermined rate of value reduction, and EP_avail_min is a minimum amount of power available to the electric machine that may provide propulsive force to the vehicle driveline. The value of EP_avail_min may be determined via subtracting a maximum amount of electrical power that may be delivered to accessories electrically coupled to a high voltage bus from the value of SD_disc_lim.

At1009, method1000adjusts an amount of electrical power that is available to high voltage (HV) electrical accessories. In particular, when the desired driver demand power is decreasing, then a threshold amount of electrical power available to an electric machine is increased according to the following equation:
HV_acc_power(k)=SD_disc_lim−EP_avail_thres(k)
where HV_acc_power(k) is an amount of electrical power provided to high voltage accessories, though the high voltage accessories need not consume this amount of power.

Additionally, in some examples, method1000may compensate the amount of electrical power provided to high voltage accessories based on catalyst efficiency. The compensated amount of electrical power provided to high voltage accessories based on catalyst efficiency may be expressed as:
HV_acc_power_comp(k)=min(HV_acc_power(k),(HV_cat_fun(cat_eff)))
where HV_acc_power_comp(k) is the catalyst compensated value of the amount of electrical power provided to high voltage accessories, min is a function that returns the lesser value of the arguments HV_acc_power and HV_cat_fun(cat_eff), HV_cat_fun is a function that returns an amount of electrical power that may be provided to high voltage accessories based on catalyst temperature (e.g., the function shown inFIG. 5), and cat_eff is an estimate of catalyst efficiency. Catalyst efficiency may be estimated according to a function similar to the function illustrated inFIG. 11. Method1000proceeds to1012.

At1012, method1000determines engine power and electric machine power to meet driver demand power. In one example, method1000determines electric machine power via a lookup table or function that is referenced via driver demand power, electric energy storage device state of charge, and electric energy storage device temperature. The lookup table or function outputs a desired electric machine power Delec_power. Values in the lookup table may be empirically determined via operating the electric machine and electric energy storage device using a dynamometer and mapping results of electric machine power versus driveline efficiency. The desired engine power may be determined via the following equation:
Deng_power=DD_power−Delec_power
where Deng_power is the desired engine power, DD_power is driver demand power, and Delec_power is the desired electric machine power. Method1000proceeds to1014.

At1014, method1000commands the engine to the power of the value of variable Deng_power. Method1000also commands the electric machine to the power value of variable Delec_power. However, the value of Delec_power is constrained to be less than or equal to the value of EP_avail_thres(k) so that output of the electric energy storage device does not exceed SD_disc_lim. In addition, method1000constrains an amount of electrical power provided to high voltage accessories to be less than the value of HV_acc_power_comp(k). In some examples, the value of HV_acc_power_comp(k) may be the lesser of a predetermined value and an amount of electrical power desired by high voltage accessories (e.g., an amount of electrical power for the high voltage accessories to perform at a desired level).

At1020, method1000judges if driver demand power is greater than an upper electric energy storage device discharge power upper threshold amount (e.g.,950ofFIG. 9). The value of the upper electric energy storage device discharge power upper threshold amount may be empirically determined and stored in controller memory. In one example, the upper electric energy storage device discharge power upper threshold amount may be determined via monitoring electric energy storage device temperature and electric energy storage device power output. If method1000judges that driver demand power is greater than an upper electric energy storage device discharge power upper threshold amount, then the answer is yes and method1000proceeds to1050. Otherwise, the answer is no and method1000proceeds to1020.

At1050, method1000starts the engine and begins to transfer power from the engine to the driveline. The amount of power that is transferred from the engine to the driveline may be based on the driver demand power, electric energy storage device state of charge, electric energy storage device temperature, and other vehicle conditions. The engine run (e.g., combust fuel) after being started for a predetermined amount of time so that the engine and the catalyst warm up before they are shutdown so that engine emissions and efficiency may be improved. Method1000proceeds to1052.

At1052, method1000decrements the value in an electric power consumer load shed timer that accumulates an amount of time that electric power supplied to high voltage accessories coupled to a high voltage bus has been reduced since a most recent time power supplied to high voltage accessories coupled to the high voltage bus has been reduced. The value in the electric power consumer load shed timer may be decremented until it reaches a minimum value of zero. Method1000proceeds to1054.

At1054, method1000delivers the driver demand power to the driveline via the electric machine and the engine. In one example, method1000determines electric machine power via a lookup table or function that is referenced via driver demand power, electric energy storage device state of charge, and electric energy storage device temperature. The lookup table or function outputs a desired electric machine power Delec_power. Values in the lookup table may be empirically determined via operating the electric machine and electric energy storage device using a dynamometer and mapping results of electric machine power versus driveline efficiency. The desired engine power may be determined via the following equation:
Deng_power=DD_power−Delec_power
where Deng_power is the desired engine power, DD_power is driver demand power, and Delec_power is the desired electric machine power. Method1000commands the engine to the power of the value of variable Deng_power. Method1000also commands the electric machine to the power value of variable Delec_power. However, the value of Delec_power is constrained to be less than or equal to the value of EP_avail_thres(k) so that output of the electric energy storage device does not exceed SD_disc_lim. In addition, method1000constrains an amount of electrical power provided to high voltage accessories to be less than the value of HV_acc_power_comp(k). In some examples, the value of HV_acc_power_comp(k) may be the lesser of a predetermined value and an amount of electrical power desired by high voltage accessories (e.g., an amount of electrical power for the high voltage accessories to perform at a desired level). Method1000proceeds to exit.

At1022, method1000judges if high voltage accessory load shedding is desired and if the value of the electric power consumer load shed timer is less than a threshold value (e.g., 20 seconds). In one example, method1000may judge that high voltage accessory load shedding is desired when a driver demand power is greater than electric energy storage device discharge power upper threshold amount minus an amount of power being supplied to high voltage accessories or accessories that are coupled to a high voltage bus. These conditions may be expressed as:
DD_power>SD_disc_lim−HV_acc
where DD_power is driver demand power, SD_disc_lim is an electric energy storage device discharge power upper threshold amount of power (e.g.,750ofFIG. 7), and HV_acc is an amount of electrical power that is supplied to accessories that are electrically coupled to a high voltage bus (e.g., conductors that transfer charge from a high voltage power source). If method1000judges that driver demand power is greater than an electric energy storage device discharge power upper threshold amount minus an amount of power being supplied to high voltage accessories or accessories that are coupled to a high voltage bus, then the answer is yes and method1000proceeds to1024. Otherwise, the answer is no and method1000proceeds to1040.

At1024, method1000increments the value of the electric power consumer load shed timer that accumulates an amount of time that electric power supplied to high voltage accessories coupled to a high voltage bus has been reduced since a most recent time power supplied to high voltage accessories coupled to the high voltage bus has been reduced. Method1000proceeds to1026.

At1026, method1000increases the threshold amount of electrical power that is available to an electric machine (e.g., threshold752inFIG. 7). In one example, the increase may be expressed as:
EP_avail_thres(k)=min(DD_power+offset,SD_disc_lim)
where EP_avail_thres is the threshold amount of electrical power that is available to the electric machine to propel the vehicle, min is a function that returns a lesser value of argument (DD_power+offset), and argument SD_disc_lim, k is the iteration value, and offset is a predetermined scalar value that ensures that DD_power is less than EP_avail_thres until DD_power is greater than SD_disc_lim. The min function ensures that the threshold amount of electrical power that is available to power the electric machine that may provide propulsive force to the driveline is less than or equal to the upper electric energy storage device discharge power upper threshold amount. Method1000proceeds to1028.

At1028, method1000adjusts an amount of electrical power that is available to high voltage (HV) electrical accessories. Specifically, when the desired driver demand power is increasing, then a threshold amount of electrical power available to an electric machine is decreased according to the following equation:
HV_acc_power=SD_disc_lim−EP_avail_thres
where HV_acc_power is an amount of electrical power provided to high voltage accessories, though the high voltage accessories need not consume this amount of power. Method1000proceeds to1044.

At1040, method400judges if judges if high voltage accessory load shedding is desired and if the value of the electric power consumer load shed timer is greater than a threshold value (e.g., 20 seconds). In one example, method1000may judge that high voltage accessory load shedding is desired when a driver demand power is greater than electric energy storage device discharge power upper threshold amount minus an amount of power being supplied to high voltage accessories or accessories that are coupled to a high voltage bus. These conditions may be expressed as:
DD_power>SD_disc_lim−HV_acc
where DD_power is driver demand power, SD_disc_lim is an electric energy storage device discharge power upper threshold amount of power (e.g.,750ofFIG. 7), and HV_acc is an amount of electrical power that is supplied to accessories that are electrically coupled to a high voltage bus (e.g., conductors that transfer charge from a high voltage power source). If method1000judges that driver demand power is greater than an electric energy storage device discharge power upper threshold amount minus an amount of power being supplied to high voltage accessories or accessories that are coupled to a high voltage bus, then the answer is yes and method1000proceeds to1050. Otherwise, the answer is no and method1000proceeds to1042.

At1042, method1000decrements the value in an electric power consumer load shed timer that accumulates an amount of time that electric power supplied to high voltage accessories coupled to a high voltage bus has been reduced since a most recent time power supplied to high voltage accessories coupled to the high voltage bus has been reduced. The value in the electric power consumer load shed timer may be decremented until it reaches a minimum value of zero. Method1000proceeds to1044.

At1044, method1000method1000delivers the driver demand power to the driveline via only the electric machine. In one example, method1000determines electric machine power via a lookup table or function that is referenced via driver demand power, electric energy storage device state of charge, and electric energy storage device temperature. The lookup table or function outputs a desired electric machine power Delec_power. Values in the lookup table may be empirically determined via operating the electric machine and electric energy storage device using a dynamometer and mapping results of electric machine power versus driveline efficiency. Method1000also commands the electric machine to the power value of variable Delec_power. However, the value of Delec_power is constrained to be less than or equal to the value of EP_avail_thres(k) so that output of the electric energy storage device does not exceed SD_disc_lim. In addition, method1000constrains an amount of electrical power provided to high voltage accessories to be less than the value of HV_acc_power_comp(k). In some examples, the value of HV_acc_power_comp(k) may be the lesser of a predetermined value and an amount of electrical power desired by high voltage accessories (e.g., an amount of electrical power for the high voltage accessories to perform at a desired level). Method1000proceeds to exit.

In this way, amounts of power supplied to the electric machine that supplies power to the driveline and the engine power may be controlled. Further, the engine may be started during conditions when the electric machine lacks capacity to provide the desired driver demand power.

The method ofFIGS. 10A and 10Bprovides for a vehicle driveline operating method, comprising: via a controller, decreasing an amount of power supplied to high voltage accessories coupled to a high voltage bus responsive to a desired engine power amount plus an electric energy storage device discharge power upper threshold amount minus an amount of power supplied to the high voltage accessories coupled to high voltage bus being greater than a driver demand power. The method further comprises increasing a threshold amount of electrical power available to an electric machine from a high voltage electric energy storage device proportionate to the decrease in the amount of power supplied to high voltage accessories coupled to the high voltage bus. The method includes where the decrease in the amount of power supplied to the high voltage accessories is adjusted responsive to efficiency of a catalyst in an exhaust system of an engine. The method includes where the high voltage accessories include an electrically operated climate control system. The method includes where the electrically operated climate control system is a heat pump. The method includes where the high voltage accessories include a DC/DC converter. The method includes where the high voltage accessories include positive temperature coefficient heating elements for a climate control system.

The method ofFIGS. 10A and 10Bprovides for an engine operating method, comprising: via a controller, decreasing an amount of power supplied to an electric machine that provides propulsive torque to a vehicle driveline and increasing an amount of power supplied to high voltage accessories coupled to a high voltage bus responsive to efficiency of a catalyst in an engine exhaust system increasing. The method includes where the decreasing and the increasing are performed when a desired engine power amount plus an electric energy storage device discharge power upper threshold amount minus an amount of power supplied to the high voltage accessories coupled to high voltage bus is greater than a driver demand power. The method further comprises increasing power output of an engine responsive to the driver demand power exceeding the electric energy storage device discharge power upper threshold amount. The method further comprises decreasing the amount of power supplied to high voltage accessories coupled to the high voltage bus responsive to a driver demand power exceeding an electric energy storage device discharge power upper threshold amount and a value of a timer being less than a threshold. The method includes where the timer is an electric power consumer load shed timer that accumulates an amount of time that electric power supplied to high voltage accessories coupled to a high voltage bus has been reduced since a most recent time power supplied to high voltage accessories coupled to the high voltage bus has been reduced responsive to an electric energy storage device discharge power upper threshold amount minus an amount of power supplied to the high voltage accessories coupled to high voltage bus being greater than a driver demand power. The method includes where the catalyst efficiency is based on a catalyst temperature. The method further comprises adjusting a threshold amount of electrical power available to the electric machine from a high voltage electric energy storage device proportionate to a decrease in an amount of power supplied to the high voltage accessories coupled to the high voltage bus.

Referring now toFIG. 11, an example function that may be the basis for estimating catalyst efficiency is shown. The vertical axis represents catalyst efficiency when an engine is combusting a stoichiometric air-fuel ratio that is oscillating about stoichiometry (e.g., within 10% of stoichiometry). Catalyst efficiency increases in the direction of the vertical axis arrow. The horizontal axis represents catalyst temperature and catalyst temperature increases in the direction of the horizontal axis arrow. Trace1102represents the relationship between catalyst temperature and catalyst efficiency.

It may be observed that when catalyst temperature is low, the catalyst efficiency is low. As the catalyst temperature increases, the catalyst efficiency increases. The catalyst efficiency may be estimated via indexing or referencing function1100via catalyst temperature. The function outputs an estimate of catalyst efficiency that may be the basis for controlling electric machine output power.

Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. Further, at least a portion of the described actions, operations and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the control system. The control actions may also transform the operating state of one or more sensors or actuators in the physical world when the described actions are carried out by executing the instructions in a system including the various engine hardware components in combination with one or more controllers.