Engine oil maintenance monitoring for a hybrid electric vehicle

Abstract

Hybrid vehicle, comprising: an engine with a crankshaft, an electric machine connected to the crankshaft (30), a pump (14) driven by the rotation of the crankshaft (30) and connected to the engine via a fluid circuit, and a controller (12) configured to control the electric machine in response to a wheel torque request that exceeds an available regenerative braking torque to drive the crankshaft (30) with the engine off to supply lubricant to the engine.

Description

WO 2013 / 076 217 A2 discloses a hybrid vehicle and a method for controlling the same. JP 2007-216764 A discloses a hybrid vehicle.One or more embodiments relate to engine oil maintenance monitoring for monitoring the amount and quality of oil in an engine of a hybrid electric vehicle.A hybrid electric vehicle (HEV) includes an internal combustion engine and one or more electric machine(s), wherein the power source for the engine is fuel and the power source for the electric machine may be electrical energy from a battery and / or electrical energy converted by the engine. In an HEV, the engine is the main source of energy for vehicle propulsion and the battery provides additional energy. A plug-in hybrid electric vehicle (PHEV) is like an HEV, but the PHEV has a larger capacity battery that can be recharged from the external power grid. In a PHEV, the battery is the main source of energy for vehicle propulsion during an electric vehicle (EV) mode until the battery reaches a low state of charge at which the PHEV operates like an HEV for vehicle propulsion. The PHEV may be battery-powered only over long periods of time, for example when the PHEV is used for shorter distances, trips, and the like. The battery is charged at a charging station between these trips and does not reach a state of charge where engine power is needed to propel the vehicle.The engine is turned on or off when the powertrain switches between an HEV mode and an EV mode. The engine, as in the case of conventional powertrain systems, requires a lubricating oil pump that is typically driven by the engine when lubricating oil is directed from an engine oil sump through the moving parts within the engine block. The oil is then returned to the oil pan. In an HEV of the type described above, although the frequent engine starts and stops result in a reduction in fuel consumption, the oil pressure in the lubrication system is low before each start. In a PHEV, rare engine restarts may result in the engine oil being largely recirculated to the oil pan. Restarting the engine when the amount of engine oil is insufficient may increase engine wear due to thin oil films on surfaces between relatively moving parts of the engine, potentially compromising engine life. Thus, many HEVs and PHEVs have a secondary engine oil pump that is electrically driven (electric oil pump) to supplement the engine driven oil pump (mechanical oil pump) during the EV mode. However, such a dual oil pump system is designed redundantly and increases the cost and weight of an HEV.Further, in a PHEV, the engine oil may lose quality or age during those periods when the vehicle is primarily running in battery operation. In some cases, this may result in deterioration of the oil, such as formation of water in the oil and the like.In HEV and PHEV, vehicle braking may be accomplished by friction braking, regenerative braking, and engine braking. Engine braking typically refers to the braking effect caused by zero throttle position at vacuum in gasoline engines when the accelerator pedal is released.Diesel engines do not have engine brakes in the aforementioned sense. Unlike gasoline engines, diesel engines vary the fuel flow for power control rather than restricting intake air and maintaining a constant fuel ratio, as do gasoline engines. Since they do not maintain throttle vacuum, they are not subject to the same engine braking effects. However, some alternative mechanisms used in diesel engines that replace or simulate actual engine braking include: a decompression brake (so-called Juke brake). A decompression brake is mainly used in large diesel trucks and acts by opening the exhaust valves in the upper position of the compression stroke, resulting in adiabatic expansion of the compressed air, so that the large amount of energy stored in this compressed air is not returned to the crankshaft but released to the atmosphere. This type of brake is forbidden or limited in many locations where people are residential, since it causes a loud, annoying noise.In one or more embodiments, a hybrid vehicle is equipped with an engine having a crankshaft and an electric machine connected to the crankshaft. The hybrid vehicle also includes a pump and a controller. The pump is driven by the rotation of the crankshaft and is connected to the engine through a fluid circuit. The controller is configured to control the electric machine to drive the crankshaft with the engine off in response to a wheel torque request that exceeds an available regenerative braking torque to provide lubricant to the engine.In another embodiment, a method is provided for providing lubrication fluid to an engine in a hybrid vehicle. Delivery of fuel to an engine is disabled. An electric machine is controlled to drive a crankshaft of the engine and a pump connected to the crankshaft in response to a wheel torque request that exceeds an available regenerative braking torque, the pump coupled to the engine to provide lubricating fluid.In yet another embodiment, a vehicle system is equipped with a pump and a controller. The pump is coupled to a crankshaft of an engine to provide lubricating fluid thereto in response to rotation of the crankshaft. The controller is configured to control an electric machine to drive the crankshaft with the engine off after a predetermined time after a previous lubrication event.As such, the vehicle and vehicle system provide advantages over existing HEVs having dual oil pumps by avoiding the electric oil pump and thereby saving cost and weight. The vehicle system analyzes the amount and quality of oil in the engine block. Based on this analysis, the controller makes an oil maintenance mode request that includes either restarting the engine when the quality of the oil is insufficient or the oil is contaminated, or restarting the engine using the generator to drive the oil pump when the amount of oil in the engine is insufficient. Such back-driving of the engine provides a motor braking effect, which decelerates or decelerates the vehicle. The vehicle system selectively utilizes the engine braking effect to minimize any effect on the vehicle's regenerative braking capabilities. FIG. 1 is a flow chart illustrating an overview of oil maintenance monitoring for a vehicle according to one or more embodiments, FIG. 2 is a schematic illustration of a hybrid electric vehicle in which various embodiments of the present disclosure may be implemented, FIG. 3 is a schematic illustration of the flow of power through the hybrid electric vehicle of FIG. 2 according to various modes of operation, FIG. 4 is a schematic illustration of the flow of power through the hybrid electric vehicle of FIG. 2 according to an oil maintenance mode, according to an embodiment, FIG. 5 is a graph illustrating a relationship between an amount of oil in the engine and time elapsed since a lubrication event, FIG. 6 is a flow chart illustrating oil maintenance monitoring for monitoring the amount of oil in an engine, according to one or more embodiments; and FIG. 7 is a flow chart illustrating oil maintenance monitoring for monitoring oil quality in an engine, according to one or more embodiments.As needed, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.Referring to FIG. 1, a vehicle system for monitoring oil maintenance according to one or more embodiments is illustrated and generally designated by numeral 10. The vehicle system 10 includes a controller 12, an oil pump 14, and an engine 16. The oil pump 14 supplies the lubricating oil to the engine 16 and is driven by the rotation of a crankshaft. The crankshaft rotates during normal operation of the engine, with the engine combusting fuel. The vehicle system 10 also includes a generator 18 included in a transmission of the HEV (shown in FIG. 2 ). The generator 18 is also connected to the crankshaft and is configured to rotate or back drive the engine 16 when the engine 16 is deactivated or is not combusting fuel to drive the oil pump 14.The controller 12 receives a plurality of input signals indicative of a current amount and quality of the oil in the engine 16. For example, controller 12 receives inputs of: lubrication event, wheel torque request, engine speed, and fuel consumption indicative of an elapsed time since oil pump 14 circulated oil through engine 16, a driver demand to decelerate the vehicle configured as torque to the wheels, the number of engine revolutions since the last oil change, and the amount of fuel consumed since the last oil change. In one or more embodiments, controller 12 also receives an input (crankshaft position) indicative of a current angular position of the crankshaft.The controller 12 then analyzes the input signals using an oil maintenance algorithm, which is described in more detail below. Based on this analysis, controller 12 creates an oil maintenance mode request that includes either: restarting engine 16 or restarting engine 16 using generator 18. in general, controller 12 may maintain normal HEV operation when the amount and quality of oil in the engine is sufficient; controller 12 may restart engine 16 when the quality of oil is insufficient; and controller 12 may restart the engine without fuel when the amount of oil at a location of the fuel engine is insufficient.Referring to FIG. 2, the vehicle system 10 is shown in a plug-in hybrid electric vehicle (PHEV) 20. The vehicle 20 is driven by two electric machines with assistance from the internal combustion engine 16 and can be connected to an external power grid (not shown). The first electric machine is an AC electric motor / generator according to one or more embodiments and is shown as the "motor" 22 in FIG. 2. The second electric machine is also an AC electric motor / generator and is shown as the "generator" 18 in FIG. 2. Both the engine 22 and the generator 18 are configured to function as motors and convert electrical force into mechanical force (drive torque) to drive a pair of wheels 24 to propel the vehicle. Both the motor 22 and the generator 18 are also configured to function as generators for converting mechanical force from the driven wheels 24 and / or the engine 16 to electrical force by regenerative braking.The vehicle 20 includes a transmission 26 having a power sharing configuration according to one or more embodiments. The transmission 26 includes the engine 22 and the generator 18. The transmission 26 also includes a planetary gear set 27 that includes a sun gear (SUN), a planet carrier (PC), and a ring gear (RING). The ring gear is an outer gear part that encloses the sun. A plurality of planet gears are rotatably mounted on the planet carrier such that each planet gear meshes (meshing) with both the ring gear and the sun gear. In the illustrated embodiment, the generator 18 is connected to the sun gear via a generator output shaft 28, and the engine 16 is connected to the planet carrier via a crankshaft 30. The planetary gear set 27 combines the generator power and the engine power and provides a combined output power at the ring gear. The generator 18 and the planetary gear set 27 collectively function as an electronic continuously variable transmission (e-CVT) without any fixed or "step-by-step" gear ratios.The transmission 26 includes countershafts 32 to combine the output power of the planetary gear set 27 and the engine 22. The counter gears 32 include a first gear, a second gear, and a third gear that meshingly engage with a planetary output gear connected to the ring gear, a motor output gear connected to an output shaft of the motor 22, and a transmission output gear connected to an input shaft 34. The input shaft 34 is an output shaft of the transmission 26 and is connected to the driven gear pair 24 via a differential.The vehicle 20 includes an energy storage device, such as a battery 36, for storing electrical energy. The battery 36 is a high voltage battery capable of supplying electric power to drive the motor 22 and the generator 18. The battery 36 also receives electrical power from the engine 22 and the generator 18 when operating as generators. The battery 36 is a battery pack that is made up of a plurality of battery modules (not shown), each battery module including a plurality of battery cells (not shown). Other embodiments of the vehicle 20 contemplate various types of energy storage devices, such as capacitors and fuel cells (not shown), which may be used as a supplement or as alternatives to the battery 36. A high voltage bus electrically connects the battery 36 to the motor 22 and the generator 18.The vehicle 20 also includes a battery energy control module (BECM) 38 for controlling the battery 36. The BECM 38 receives input signals indicative of vehicle conditions and battery conditions such as battery temperature, voltage, and current. The BECM 38 calculates and estimates battery parameters such as battery state of charge (SOC) and battery performance, and provides output signals indicative of such parameters for other vehicle systems and controllers.The vehicle 20 also includes a variable voltage converter (VVC) 40 and an inverter 42 according to one or more embodiments. The VVC 40 and the inverter 42 are electrically connected between the battery 36 and the motor 22, and between the battery 36 and the generator 18. The VVC 40 "boosts" or increases the voltage potential of the electric current provided by the battery 36. According to one or more embodiments, the VVC 40 may also "decrease" or decrease the voltage potential of the electrical energy supplied to the battery 36. The inverter 42 converts the direct current (DC) provided from the battery 36 (via the VVC 40) to alternating current (AC) to operate the motor 22 and the generator 18. The inverter 42 also converts AC power provided by the motor 22 and the generator 18 to DC power to charge the battery 36. Other embodiments of the vehicle 20 contemplate a plurality of inverters (not shown) and / or no VVC.The vehicle 20 includes a transmission control module (TCM) 44 to control the engine 22, the generator 18, the VVC 40, and the inverter 42. The TCM 44 is configured to monitor, among other things, the position, speed, and energy consumption of the motor 22 and the generator 18. The TCM 44 also monitors electrical parameters (e.g., voltage and current) at various locations in the VVC 40 and the inverter 42.The controller 12 is a vehicle system controller (VSC) that communicates with other vehicle systems and controllers to coordinate their operation. Although shown as a single controller, the VSC 12 may include a plurality of controllers that may be used to control a plurality of vehicle systems according to overall vehicle control logic or software.The vehicle controllers, including the VSC 12, BECM 38, and TCM 44 generally include any number of microprocessors, ASIC, IC, memory (e.g., FLASH, ROM, RAM, EPROM, and / or EEPROM), and software code to perform a series of operations in interaction with one another. The controllers also include predetermined data, or "look-up tables", based on computations and test data and stored in their memory. The VSC 12 communicates with other vehicle systems and controllers via one or more wired or wireless vehicle connections using common bus protocols (e.g., CAN and LIN). The VSC 12 receives input data (PRND) representing a current position of the transmission 26 (e.g., park, reverse, neutral, drive). The VSC 12 also receives input data (APP) representing accelerator pedal position. The VSC 12 provides output data representing engine, motor, and generator control functions based on the input data.The vehicle 20 includes a brake system 48. The brake system 48 includes a brake pedal, a brake booster, a master cylinder, and fluid lines (all not shown) for coupling to the driven wheels 24 to achieve a friction braking effect. The brake system 48 also includes position sensors, pressure sensors, or a combination thereof to provide information such as brake pedal position (PPP) corresponding to a driver braking torque request.Engine braking is applied to the vehicle 20 to decelerate or decelerate the vehicle 20 under certain operating conditions. Engine braking generally refers to the braking effect caused by the throttle zero load position at vacuum in gasoline engines when the brake pedal is released. Available engine braking torque corresponds to the size of the engine (e.g., the inertia of each movable part) and whether the engine is currently enabled or disabled. An engine is activated or running when combusting fuel to generate an output power. Even if an operator does not depress the accelerator pedal, the engine is still activated because the fuel delivery system and ignition system continue to operate and the engine is operating at idle. An engine is deactivated when not combusting fuel. The vehicle 20 may still utilize engine braking when the engine 16 is deactivated. The generator 18 is connected to the crankshaft 30 via the planetary gear set 27. The generator 18 may be controlled to back drive the engine 16 and thus achieve engine braking even when the engine 16 is deactivated. Such an engine braking effect supplements other types of brakes (friction brakes, regenerative brakes) available to the vehicle 20.The vehicle 20 also includes a brake system control module (BSCM) 50 that communicates with the VSC 12 and the TCM 44 to coordinate regenerative braking, engine braking, and friction braking. The BSCM 50 sends an input signal to the VSC 12 for a wheel torque request corresponding to brake pedal position (PPP). The VSC 12 then compares the wheel torque request to other vehicle information (e.g., vehicle mass, speed, acceleration, road grade, and battery conditions) to determine a total braking torque value that includes an available regenerative braking torque value, an engine braking torque value, and a friction braking torque value. The VSC 12 sends a desired engine torque value and a desired generator torque value to the TCM 44 corresponding to the regenerative and engine braking torque values, as well as a desired friction braking torque value to the BSCM 50. In other embodiments, the BSCM 50 determines one or more braking torque values.Generally, the vehicle 20 utilizes regenerative braking as the main braking source and supplements this by friction braking when sufficient regenerative braking torque is not available to meet the wheel torque request. Regenerative braking charges the main battery 36 and recovers much of the energy that would otherwise be lost as heat in friction braking. Therefore, regenerative brakes improve overall vehicle efficiency or fuel economy as compared to vehicles designed for friction brakes only. Engine braking may be used to supplement friction brakes and regenerative braking under limited conditions, e.g., when the wheel torque request is greater than the available regenerative braking torque.The vehicle 20 is configured as a PHEV, according to one or more embodiments. The battery 36 receives alternating current regularly from an external power source or an external power grid via a charging connection 52. The vehicle 20 also includes an onboard charger 54 that receives alternating current from the charging port 52. The charger 54 is an AC / DC converter that converts the obtained AC energy into DC energy suitable for charging the battery 36. In turn, the charger 54 provides the DC energy to the battery 36 during the charging operation. Although illustrated and described in the context of a PHEV 20 having a power-sharing transmission 26, it is appreciated that embodiments of the vehicle system 10 may be implemented in other HEV types that include other types of transmissions in which the vehicle may be operated in the EV mode for extended periods of time.The vehicle 20 includes an engine control module (ECM) 56 to control the engine 16. The VSC 12 provides output power (desired engine torque) to the ECM 56 based on a number of input signals including APP and corresponding to a driver demand for vehicle propulsion. The desired engine torque may correspond to a request to start or stop the engine 16. For example, the ECM 56 may stop the engine 16 in response to a desired engine torque of zero Nm. The engine 16 also includes a plurality of sensors for monitoring the current state of the engine 16, collectively represented by numeral 57 in FIG. 2. The sensors 57 monitor engine temperature, engine oil pressure, engine speed or revolutions per minute (rpm), and current angular position of the crankshaft 30. the ECM 56 provides output information corresponding to the information monitored by the sensors to other vehicle controllers, such as the VSC 12.The oil pump 14 is driven by the crankshaft 30 and passes oil from an oil sump or oil pan through the engine 16 to lubricate the movable motor parts (e.g., shafts, pistons, etc.). According to the illustrated embodiment, the oil pump 14 includes an input shaft 58 and an oil pump gear 60 fixed to the shaft 58. The oil pump gear 60 meshes with an output gear of the engine 62 fixed to the crankshaft 30. In other embodiments, oil pump 14 includes an oil pump pulley connected to a corresponding output pulley of the engine via a belt (not shown). The oil pump 14 is also connected to the engine 16 via a fluid circuit (not shown) to provide the oil. Thus, as the crankshaft 30 rotates, it drives the oil pump 14, which in turn directs the oil through the engine 16 block to lubricate moving parts therein. The crankshaft 30 may be driven by engine power (e.g., an internal combustion engine).Oil pump 14 may also be driven by generator 18 when engine 16 is deactivated (i.e., no fuel or spark is provided to engine 16). The generator 18 is connected to the crankshaft 30 via the planetary gear set 27. The generator is configured to rotate or back drive the engine 16 when the engine is off, which in turn drives the oil pump 14.The engine 16 is started or stopped each time the transmission 26 switches between an HEV mode and an EV mode. In a PHEV, such as vehicle 20, rare restarts of engine 16 may result in the engine oil being largely recirculated to the oil pan. Restarting the engine 16 when the amount of engine oil is insufficient may increase engine wear due to thin oil films on surfaces between relatively moving parts of the engine, which may potentially degrade engine life.Many prior art HEVs and PHEVs include a secondary engine oil pump that is electrically driven (electric oil pump) to supplement the engine driven oil pump (mechanical oil pump) during the EV mode. However, such a dual oil pump system is designed redundantly and increases the cost and weight of an HEV.The vehicle system 10 is configured to supply oil to the engine 16 without a secondary electric oil pump. If the vehicle system 10 determines that there is not sufficient oil in the engine 16, the vehicle system 10 controls the generator 18 to drive the oil pump 14 and thereby supply oil to the engine 16. Thus, the vehicle system 10 provides cost and weight savings over prior art HEVs equipped with dual oil pump systems.FIG. 3 illustrates the flow of power through the transmission 26 during various modes of operation. The engine 16 receives fuel and provides motor power to the planetary gear set 27. The generator 18 provides power to the planetary gear set 27 when acting as a motor and receives power when acting as a generator. The ring gear (r) of the planetary gear set 27 is connected to the countershaft 32 to provide power. The motor 22 provides power to the countershaft 32 when acting as a motor and receives power when acting as a generator. The battery 36 provides power to the generator 18 and the motor 22 when acting as motors, and receives electric power from the generator 18 and the motor 22 when acting as generators. The countershaft 32 provides output power to the driven wheels 24 based on power provided by one or more of the engine 16, motor 22, and generator 18.FIG. 4 illustrates the flow of power through the transmission 26 when the generator 18 drives the engine 16 and the oil pump (shown in FIG. 2 ). The engine 16 is deactivated and is not receiving fuel. The generator 18 functions as an engine and provides power to the planetary gear set 27. The planet carrier (pc) of the planetary gear set 27 is connected to the engine 16 to provide power. The motor 22 provides power to the countershaft 32 when acting as a motor and receives power when acting as a generator. The battery 36 provides electric power to the generator 18 and the motor 22 when acting as motors, and receives electric power from the generator 18 and the motor 22 when acting as generators. The countershaft 32 provides output power to the driven wheels 24 based solely on the power provided by the engine 22. The ring gear (r) of the planetary gear set 27 is connected to the countershaft 32 to receive power for providing reaction torque while the generator 18 drives the engine 16.FIG. 5 is a graph illustrating a relationship between an amount of oil in the engine block and an elapsed time since a lubrication event. The elapsed time includes a period of time during which the vehicle was not operating (e.g., parked or deactivated). This relationship is represented by line 510. The oil in the engine flows through many small passages or passages formed in the engine block, and therefore it is difficult to measure the amount of oil in the engine. However, time since a lubrication event may be used to estimate the amount of oil in the engine block. A lubrication event occurs when the engine has been operating at a predetermined speed longer than a predetermined time to drive the oil pump 14 and sufficiently lubricate the engine 16. For example, in one embodiment, a lubrication event occurs after the engine 16 has been idling for a short period of time (e.g., five to ten seconds). In one embodiment, the ECM 56 monitors the occurrence of a lubrication event and resets a timer after each occurrence. Such a reset is represented by point 511 on line 510. In other embodiments, the engine 16 includes a sensor (not shown) to measure the level of liquid in the oil pan. The vehicle system 10 then determines an amount of oil in the engine block based on both the time elapsed since a lubrication event and the amount of oil that is in the oil sump.To differentiate between engine restart sensitivity with respect to an estimated amount of oil in the engine block, the liquid level margin is divided into multiple ranges defined by predefined limits, which in turn are based on the time elapsed since a lubrication event. These boundaries are respectively represented by horizontal dotted lines that subdivide the oil quantity operating range into a high, a medium and a low oil level range.In one embodiment, the engine has an oil capacity of 5.0 liters, 1.0 liters of which is the oil capacity of the engine block, and requires a minimum amount of 0.4 liters of oil in the block during engine restart to avoid damaging components therein. This minimum value corresponds to the amount of oil remaining in the engine block eighty hours after a lubrication event, and is represented by a lower threshold 512. Further, the engine 16 may be restarted without potential damage when at least 0.8 L of oil is in the block. This value corresponds to the amount of oil remaining in the engine block forty hours after a lubrication event and is represented by an upper threshold 514. Further, the engine 16 may be damaged if it is restarted more frequently with less than 0.6 L oil in the block. This value corresponds to the amount of oil remaining in the engine block sixty hours after a lubrication event and is represented by a mean threshold 516. As illustrated in FIG. 5, an area above the upper threshold 514 is referred to as a "high" liquid area; an area between the upper threshold 514 and the middle threshold 516 is referred to as a "middle" liquid area; and an area between the middle threshold 516 and the lower threshold 512 is referred to as a "low" liquid area. The liquid levels provided in this example are merely exemplary and non-limiting in nature, with the thresholds associated with each engine and application being different.Referring to FIG. 6, an oil maintenance algorithm or method for monitoring an amount of oil in an engine is illustrated, and generally indicated by reference numeral 610, in accordance with one or more embodiments. According to one or more embodiments, the method 610 is implemented using software code contained in the VSC 12. In other embodiments, software code is shared among multiple controllers (e.g., VSC 12, ECM 56, and TCM 44). Although a series of successive operations or steps are illustrated in the flowchart, one or more operations may be omitted and / or otherwise performed without departing from the scope and subject matter of the present disclosure.At step 612, the vehicle system 10 is started or initialized and receives input data and signals including: a current vehicle operating mode (mode), an elapsed time since a lubrication event, a wheel torque request, available regenerative braking torque, and a current crankshaft position.At step 616, the vehicle system 10 evaluates the mode input information to determine whether the vehicle 20 is currently operating in an EV mode. If the vehicle 20 is in an EV mode, the vehicle system 10 proceeds to step 618 to determine whether the elapsed time since a lubrication event is greater than forty hours. In one embodiment, a lubrication event occurs when the engine was operating at idle speed for a short period of time (e.g., five to ten seconds). If the determination at step 616 or 618 were negative, this would indicate that a high oil level is in the engine block and that the oil level is sufficient to restart the engine, and therefore the vehicle system returns to step 614. If the time after the last lubrication event is greater than forty hours, the vehicle system continues to step 620.At step 620, the vehicle system 10 compares the wheel torque request to the available regenerative braking torque. As stated above, available regenerative braking torque is based on vehicle speed and battery conditions, such as state of charge. If the wheel torque request is above the available regenerative braking torque, the vehicle system 10 proceeds to step 622 and drives the crankshaft 30 with the generator 18 to achieve engine braking and drives the oil pump 14 to lubricate the engine 16. As described above, regenerative braking is an important feature of energy saving in the vehicle 20. Therefore, the vehicle 10 limits any interruption of regenerative braking. Here, because the wheel torque request is greater than the available regenerative braking torque, the vehicle system 10 does not displace potentially saved energy through regenerative braking. Rather, the vehicle system 10 displaces the friction braking and thereby helps to obtain the friction braking components.During step 622, the vehicle system 10 controls the generator 18 to back-drive the engine 16 at approximately idle speeds (e.g., between 500 and 1000 rpm), and limits the duration of such operation. The vehicle system 10 lubricates the engine 16 by driving the crankshaft 30 when the engine 16 is off, if the high wheel torque request exceeds the available regenerative braking torque, to provide lubrication without compromising vehicle regenerative braking efficiency. If the determination at step 620 is negative, this would indicate that the vehicle system 10 is restricting regenerative braking performance if it were to utilize engine braking. Therefore, the vehicle system proceeds to step 622 to evaluate the additional conditions before engine braking is performed.At step 622, the vehicle system 10 determines whether the elapsed time since the last lubrication event is longer than sixty hours. If the determination at step 622 is negative, this would indicate that about forty to sixty hours have elapsed after the last lubrication event. The amount of oil in the engine block is within the middle range and is sufficient for restart, and therefore the vehicle system 10 decelerates engine braking. The vehicle system 10 then returns to step 614. If the time elapsed since the last lubrication event is greater than sixty hours, the vehicle system continues to step 624.At step 624, the vehicle system compares the wheel torque request to the available engine brake torque. If the wheel torque request is less than or equal to the available engine braking torque, this would indicate that when engine braking is applied, the deceleration of the vehicle would be greater than the driver's desired engine braking effect, which would likely be perceptible to the driver. However, if the wheel torque request is greater than the available engine braking torque, the vehicle system 10 proceeds to step 622 and applies engine braking. If the determination at step 624 is negative, the vehicle system 10 proceeds to step 626.At step 626, the vehicle system 10 determines whether the time elapsed since the last lubrication event is greater than eighty hours. After eighty hours, a motor restart may damage the engine. Therefore, if the elapsed time is longer than eighty hours, the vehicle system 10 proceeds to step 622 and applies engine braking. This engine braking is likely to be experienced by the driver because he has not requested such vehicle deceleration. Thus, in one or more embodiments, the vehicle system 10 communicates the low engine oil / engine brake status to the driver (not shown) via a user interface such as a display or audible message. If the determination at step 626 is negative, the vehicle system 10 returns to step 614.In one or more embodiments, the method 610 also includes optional steps for monitoring the state of the engine components as well as monitoring oil quality in the engine 628. The vehicle system 10 may proceed to optional step 628 in response to a negative determination at step 626.At step 626, the vehicle system 10 compares the current angular position of the crankshaft 30 to historical information about previous angular positions of the crankshaft 30 at rest. If the current angular position of the crankshaft is "non-uniform" or a position where the crankshaft 30 was at rest over other positions for an disproportionate amount of time, the vehicle system 10 proceeds to step 622 and drives the engine 16 back. A crankshaft 30 may wear unevenly if the crankshaft 30 remains in the same general angular position for a longer period of time. This is because the crankshaft 30 swings slightly in the EV mode. Although it may be difficult for the vehicle system 10 to stop the engine crankshaft at a particular angular position accurately, such operation could help avoid uneven wear.The vehicle system 10 may proceed to optional step 630 in response to a negative determination at steps 622, 626, or 628. Generally, at step 628, the vehicle system evaluates the input signals that correlate to the quality of the oil in the engine. If the oil quality is inferior and there is sufficient oil in the engine block, the vehicle system 10 may restart the engine 16 to improve quality.Referring to FIG. 7, an oil maintenance algorithm or method for monitoring the quality of the oil in the engine is illustrated and generally indicated by reference numeral 710, according to one or more embodiments. The method 610 is implemented using software code included in the VSC 12, in accordance with one or more embodiments. In other embodiments, software code is shared among multiple controllers (e.g., VSC 12, ECM 56, and TCM 44). Although a series of successive steps is illustrated in the flowchart, one or more steps may be omitted and / or otherwise executed without departing from the scope and scope of the present disclosure. In one or more embodiments, the method 710 is included in step 628 of the method 610.At step 712, the vehicle system 10 is started or initialized and receives input data and signals including: a current operating mode of the vehicle (mode), an elapsed time since a lubrication event, the number of engine revolutions since the last oil change, and the amount of fuel consumed since the last oil change.At step 716, the vehicle system 10 evaluates the mode input information to determine whether the vehicle 20 is currently operating in an EV mode. If the vehicle 20 is in an EV mode, the vehicle system 10 proceeds to step 718 to determine if the elapsed time since a lubrication event is greater than forty hours. If the determination at step 718 is positive, the vehicle system 10 proceeds to step 720 to monitor the quality of the oil in the engine block. In one or more embodiments, step 720 corresponds to method 610 in FIG. 6, and if the time since a lubrication event is less than forty hours, vehicle system 10 proceeds to step 722.At step 722, the vehicle system 10 compares the number of engine revolutions since the last oil change to a predetermined revolution value. If the number exceeds the predetermined revolution value, this would indicate that the oil is exhausted and may contain contaminants (e.g., water and fuel). To remove such contaminants, the vehicle system 10 proceeds to step 724 and restarts the engine 16. If the determination at step 722 is negative, the vehicle system proceeds to step 726 and compares the amount of fuel consumed since the last oil change with a predetermined fuel consumption value. If the number is greater than the predetermined fuel consumption value, this would indicate that the oil is exhausted and may contain contaminants (e.g., water or fuel). To remove such contaminants, the vehicle system 10 proceeds to step 724 and restarts the engine 16.As such, the vehicle system 10 provides advantages over existing HEVs having dual oil pumps by avoiding the electric oil pump and thereby saving cost and weight. The vehicle system 10 also provides advantages over other systems that include additional sensors for monitoring the engine 16. The vehicle system 10 monitors the amount and quality of oil in the engine block with sensors present and analyzes this information using an oil maintenance algorithm. Based on this analysis, the controller 12 creates an oil maintenance mode request that includes either restarting the engine 16 when the quality of the oil is insufficient or the oil is contaminated, or restarting the engine 16 using the generator 18 to drive the oil pump 14 when the amount of oil in the engine is insufficient. Such engine back-driving provides a motor braking action that decelerates or decelerates the vehicle 20. The vehicle system 10 selectively utilizes engine braking to minimize any impact on the regenerative braking capabilities of the vehicle 20.Although the best mode has been described in detail, those skilled in the art will recognize various alternative constructions and embodiments within the scope of the following claims. Although various embodiments have been described that provide advantages or are preferred over other prior art embodiments or embodiments with respect to one or more desired characteristics, those of ordinary skill in the art will recognize that one or more features or characteristics may be combined to achieve desired system attributes, which depend on the particular application and embodiment. These attributes may include, but are not limited to: cost, strength, durability, life cost, marketability, appearance, packaging, size, utility, weight, machability, ease of assembly, etc. The embodiments described herein, which are described as less desirable than other embodiments or prior art implementations with respect to one or more features, are not outside the scope of the disclosure and may be desirable for particular applications. Further, features of various implementations may be combined to form further embodiments of the invention.

Claims

A hybrid vehicle comprising: an engine having a crankshaft; an electric machine connected to the crankshaft (30); a pump (14) driven by rotation of the crankshaft (30) and connected to the engine via a fluid circuit; and a controller (12) configured to control the electric machine responsive to a wheel torque request that exceeds an available regenerative braking torque to drive the crankshaft (30) with the engine off to provide lubricant to the engine.The hybrid vehicle of claim 1, wherein the controller (12) is further configured to control the electric machine to drive the crankshaft (30) in response to an elapsed time since a lubrication event exceeding a first time threshold.The hybrid vehicle of claim 1, wherein the controller (12) is further configured to control the electric machine to drive the crankshaft (30) to supply lubricant to the engine in response to an elapsed time since a lubrication event exceeding a second time threshold.The hybrid vehicle of claim 1, wherein the controller (12) is further configured to control the electric machine to drive the crankshaft (30) in response to an elapsed time since a lubrication event exceeding a third time threshold.The hybrid vehicle of claim 1, further comprising a second electric machine, and wherein the controller (12) is further configured to control the second electric machine to provide drive torque for vehicle propulsion in response to controlling the electric machine to drive the crankshaft when the engine is shut down.The hybrid vehicle of claim 1, wherein the controller (12) is further configured to restart the engine in response to an elapsed time since a lubrication event falling below a first time threshold and a number of revolutions of the engine since an oil change exceeding a revolution threshold.The hybrid vehicle of claim 1, wherein the controller (12) is further configured to restart the engine in response to an elapsed time since a lubrication event falling below a first time threshold and an amount of fuel consumed since an oil change exceeding a consumption threshold.A method of providing lubricant to an engine in a hybrid vehicle, the method comprising: interrupting fuel supply to an engine; and controlling an electric machine to drive a crankshaft of the engine and a pump (14) connected to the crankshaft (30) in response to a wheel torque request exceeding an available regenerative braking torque, the pump (14) connected to the engine to provide lubricating fluid.The method of claim 8, further comprising controlling the electric machine to drive the crankshaft (30) in response to an elapsed time since a lubrication event exceeding a first time threshold and the wheel torque request exceeding the available regenerative braking torque.The method of claim 9, further comprising controlling the electric machine to drive the crankshaft (30) in response to the wheel torque request exceeding an available engine braking torque and the elapsed time since a lubrication event exceeding a second time threshold, the second time threshold being greater than the first time threshold.

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