Regenerative braking power for operating a vehicle electric heater

Abstract

Method for heating transmission oil in a hybrid vehicle (14) comprising the following: the generation of power with an electric machine (15) via regenerative braking; and the routing of power from the electric machine (15) to an electric heater (32) to heat the transmission oil in response to the fact that the temperature of an engine coolant is greater than a threshold and the controller (34) determines that the temperature of the transmission oil is below a threshold which is related to a temperature value for optimal performance of the transmission (11), and wherein the power routed to the electric heater (32) is part of a total recuperation braking power which exceeds a charge rate limit of a battery, characterized by the fact that The threshold of the engine coolant corresponds to a first reserve coolant temperature that exceeds a minimum coolant temperature required for an EV operating mode.

Description

TECHNICAL AREA

[0001] The present disclosure relates to hybrid and electric vehicles and methods of diverting regenerative braking power to warm lubricating oils. BACKGROUND

[0002] Internal combustion engines operate more efficiently once the engine coolant and engine oil have reached their optimal operating temperatures. Similarly, transmissions operate more efficiently once the transmission oil has reached its optimal operating temperature.

[0003] German patent application DE 10 2009 028 326 A1 describes a method for heating transmission oil in a hybrid vehicle, comprising generating power and directing that power to a heater to heat the transmission oil in response to an engine coolant temperature exceeding a threshold. Further relevant prior art relating to the background of the invention is provided in German patent applications DE 10 2007 032 726 A1, DE 10 2012 214 994 A1, DE 10 2014 019 269 A1 and WO 2014 / 065 309 A1.

[0004] The task is to provide an optimal operating temperature for a gear oil in an energy-efficient manner. SUMMARY

[0005] This problem is solved by a method having the features of claim 1 and by a vehicle having the features of claim 6. Further advantageous embodiments and configurations of the invention will become apparent from the dependent claims, the figures, and the exemplary embodiments.

[0006] A vehicle includes an electric motor designed to charge a battery through regenerative braking, an electric heater designed to heat a powertrain lubricating oil, and a control system programmed to direct regenerative braking power to the electric heater in response to a powertrain lubricating oil temperature falling below a threshold.

[0007] One method for heating transmission oil in a hybrid vehicle involves generating power with an electric machine via regenerative braking and directing the power from the electric machine to a heater to heat the transmission oil in response to the temperature of an engine coolant exceeding a threshold.

[0008] A vehicle includes an internal combustion engine, an electric machine designed to charge a battery through regenerative braking, an electric heater designed to selectively heat engine coolant, transmission oil, or engine oil, and a control system programmed to direct regenerative braking power to the electric heater when total regenerative braking power exceeds a battery charge rate limit, to heat the transmission oil in response to engine coolant temperature exceeding an engine coolant threshold, and to direct regenerative braking power to the electric heater when transmission oil temperature exceeds a transmission oil threshold. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of a cooling system of an internal combustion engine in a hybrid electric vehicle; and Fig. Figure 2 is a flowchart of an algorithm for using regenerative braking power to operate an electric heater to heat the transmission and engine oils of a hybrid electric vehicle. DETAILED DESCRIPTION

[0009] On Fig. With reference to Figure 1, a schematic diagram of a cooling system 10 of an internal combustion engine 12 of a vehicle 14 according to an embodiment of the present disclosure is shown. The internal combustion engine 12 transmits torque through a transmission 11 to wheels (not shown) to propel the vehicle 14. If the vehicle 14 is a hybrid electric vehicle (HEV), the internal combustion engine 12, a motor / generator (M / G), or alternatively an electric machine 15, can transmit torque through the transmission 11 to the wheels to propel the vehicle 14. In the HEV configuration, a traction battery 17 supplies power to the M / G 15 to propel the vehicle 14.

[0010] The cooling system 10 comprises a series of cooling loops 16. A coolant circulates through the cooling loops 16 to dissipate excess heat from the internal combustion engine 12. The cooling loops 16 may include at least one heat exchanger designed to dissipate the excess heat from the coolant. For example, excess heat from the coolant can be transferred to the external environment of the HEV 14 when the coolant flows from the internal combustion engine 12 and through a first heat exchanger 18 (e.g., a radiator). A fan 20 may be included to direct air over the first heat exchanger 18 in such a way that heat from the coolant flowing through the first heat exchanger 18 is transferred to the air. A pump 22 is used to circulate the coolant through the cooling loops 16.A thermostat 24 may be included to force the coolant to bypass the first heat exchanger 18 and to allow the coolant to circulate continuously through the combustion engine 12 until an optimal operating temperature of the coolant is obtained.

[0011] A second heat exchanger 26 (e.g., an interior heater or heating heat exchanger) can be used to transfer excess heat from the coolant to air flowing into the interior of the HEV 14. A blower fan 28 is included to direct the air flowing into the interior over the second heat exchanger 26 in such a way that heat is transferred from the coolant flowing through the second heat exchanger 26 to the air. A control valve 30 can be used to throttle or shut off the coolant flowing through the second heat exchanger 26. The control valve 30 can be connected to an interior air conditioning system and can be designed to open and close based on the climate requirements of an occupant. The blower fan 28 can also be connected to the air conditioning system and can be designed to operate based on the climate requirements of an occupant.

[0012] The cooling system 10 can also include an electric heater 32, which can be used to transfer heat to the coolant flowing through the cooling loops 16. The electric heater 32 can be any type of electric heater that can be used to transfer heat to a fluid, including heaters that include resistance heating elements, immersion heaters, and PTC heaters (PTC - Positive Temperature Coefficient). The electric heater 32 can be connected to a controller 34. The controller 34 can be configured to activate the electric heater 32 under conditions where it may be advantageous to transfer heat to the coolant in the cooling loops 16.

[0013] The electric heater 32 can receive power via electrical wiring from the traction battery 17, an auxiliary battery 36 (such as a 12V battery commonly found in automobiles), an alternator (not shown), the M / G 15, or any other power source that may be included in the HEV 14. The electric heater 32 can be designed to accept AC and / or DC electrical power. An AC / DC converter may be included if the electric heater 32 is designed to operate on DC electrical power only and the power source (e.g., the alternator or the M / G 15) is designed to generate AC electrical power. A DC / AC converter may be included if the electric heater 32 is designed to operate on AC electrical power only and the power source (e.g., the battery) is designed to generate DC electrical power.

[0014] The control unit 34 can also communicate with the traction battery 17, the auxiliary battery 36, the M / G 15, the alternator, or any other power source that can be used to supply energy to the electric heater 32. The control unit 34 can coordinate which power source should be used to supply energy to the electric heater 32 when circumstances exist in which it would be advantageous to transfer heat in the cooling loops 16 to the coolant.For example, the traction battery 17 can be used to supply energy to the electric heater 32 if the traction battery 17 is sufficiently charged; the auxiliary battery 36 can be used to supply energy to the electric heater 32 if the auxiliary battery 36 is sufficiently charged; the M / G 15 can be used to supply energy to the electric heater 32 if the M / G 15 is operated as a generator; or the alternator can be used to supply energy to the electric heater 32.

[0015] The controller 34 can also communicate with a number of sensors designed to communicate specific conditions of the HEV 14 or the surrounding environment to the controller 34. At least one coolant temperature sensor can be designed to communicate the temperature of the coolant in the cooling loops 16 to the controller 34. In the illustrated embodiment, a first coolant temperature sensor 38 is shown on the exhaust side of the internal combustion engine 12, and a second coolant temperature sensor 40 is shown on the intake side of the internal combustion engine 12. However, the disclosure should not be interpreted as being limited to this configuration but should be understood to include cooling systems that have one or more coolant temperature sensors which can be arranged at any location within the cooling loops 16.

[0016] At least one engine oil temperature sensor 44 can be configured to communicate the transmission oil temperature to the control unit 34. The engine oil temperature sensor 44 can be located at any suitable location within the internal combustion engine 12 that is capable of providing an accurate oil temperature measurement. At least one transmission oil temperature sensor 46 can be configured to communicate the transmission oil temperature to the control unit 34. The transmission oil temperature sensor can be located at any suitable location within the internal combustion engine 12 that is capable of providing an accurate oil temperature measurement. At least one ambient air temperature sensor 48 can be configured to communicate the temperature of the surrounding environment to the control unit 34.

[0017] Cooling system 10 is for illustrative purposes only and should not be considered as applicable to the system described in Fig. The specific structure and configuration shown in Figure 1 may be interpreted in a limited way. For example, the sequence or position of the cooling loops 16 (or of components located within the cooling loops) may be reorganized or rearranged; the cooling system 10 may include an overflow tank or a degassing bottle; the cooling system 10 may include additional cooling loops used to cool other components of the HEV 14.

[0018] It can be advantageous to operate the electric heater 32 to increase the coolant temperature under certain conditions. Internal combustion engines (including the internal combustion engine 12) operate more efficiently once the engine temperature is at or above a temperature threshold. If an internal combustion engine operates at a temperature below the temperature threshold, internal engine friction losses (including friction losses occurring at the piston-to-cylinder ring interfaces, various bearings, and valve train components) can increase. This is a function of local engine oil and metal temperatures, which are influenced by the engine coolant temperature. Fuel also tends to form a film on the inner surfaces of the internal combustion engine's air intake components, disrupting the air / fuel control system and leading to increased emissions from the internal combustion engine.The electric heater 32 can be operated to increase the temperature of the coolant, which in turn will increase the temperature of the internal combustion engine 12 if the internal combustion engine 12 is operating below a temperature threshold. The temperature threshold of an internal combustion engine for efficiency purposes may coincide with a minimum operating temperature of the coolant, which is between 180°F (82.2°C) and 220°F (104.4°C). The temperature threshold of the internal combustion engine for emissions purposes may coincide with a minimum operating temperature of the coolant, which is between 110°F (43.3°C) and 140°F (60°C).

[0019] The combustion engine 12 can shut down under certain conditions to save fuel and increase fuel efficiency. When the combustion engine 12 is shut down, the HEV 14 can be powered by the M / G 15, which draws electrical energy from the traction battery 17. When the M / G 15 alone powers the HEV 14, the HEV 14 operates in a mode also known as EV mode (Electric Vehicle Mode). The period during which the HEV 14 can operate in EV mode is typically limited by the charge level in the traction battery 17. However, the period during which the HEV 14 can operate in EV mode can also be limited by the minimum operating temperature of the coolant to ensure that the combustion engine 12 operates above the temperature threshold for emission control purposes.The electric heater 32 can be operated to increase the coolant temperature to maximize the time the HEV 14 operates in EV mode. The electric heater 32 can be operated in anticipation of EV mode or during EV mode. The minimum engine coolant temperature required to maximize the time the HEV 14 is in EV mode can coincide with the minimum operating temperature of the coolant for emissions purposes (which is between 110°F (43.3°C) and 140°F (60°C)) or with the minimum operating temperature of the coolant for efficiency purposes (which is between 180°F (82.2°C) and 220°F (104.4°C)).Alternatively, the minimum engine coolant temperature required to maximize the period the HEV 14 spends in EV mode can be a reserve temperature value exceeding the minimum operating temperature of the coolant for emissions purposes at 5°F (-15°C) - 40°F (4.4°C), or a reserve temperature value exceeding the minimum operating temperature of the coolant for efficiency purposes at 5°F (-15°C) - 40°F (4.4°C).

[0020] The electric heater 32 can also be operated to increase the temperature of the engine coolant during periods when the second heat exchanger 26 and the blower fan 28 are operating to heat the air flowing into the interior of the HEV 14. The minimum engine coolant temperature required when the second heat exchanger 26 and the blower fan 28 are in use can coincide with the minimum operating temperature of the coolant for efficiency purposes (which is between 180°F (82.2°C) and 220°F (104.4°C)) or can be a reserve temperature value that exceeds the minimum operating temperature of the coolant for efficiency purposes. For example, the minimum engine coolant temperature required when the second heat exchanger 26 and the blower fan 28 are used may exceed the minimum operating temperature of the coolant for efficiency purposes by 5°F (-15°C) - 40°F (4.4°C).

[0021] The electric heater 32 can also be operated to increase the temperature of the engine coolant in anticipation of the use of the second heat exchanger 26 and the blower fan 28 to heat the air flowing into the interior of the HEV 14. For example, if the ambient air temperature is below a threshold (between 45°F (7.2°C) and 65°F (18.3°C)) and the engine coolant is operated below a desired operating temperature (between 180°F (82.2°C) and 220°F (104.4°C)), it may be advantageous to operate the electric heater 32, due to the likely use of the second heat exchanger 26 and the blower fan 28 to heat the air flowing into the interior of the HEV 14.

[0022] It can also be advantageous to operate the electric heater 32 to increase the temperature of the engine oil under certain conditions. Internal combustion engines (including the internal combustion engine 12) operate more efficiently when the engine oil temperature is at or above an optimal temperature threshold. Engine oil is more viscous at lower temperatures, which increases friction between moving parts of the internal combustion engine, resulting in a loss of efficiency. The electric heater 32 can be operated to increase the temperature of the coolant, which in turn will increase the temperature of the engine oil if the engine oil is operating below the optimal temperature threshold. The coolant flows through the electric heater to an engine oil heat exchanger 50 to heat the engine oil. In an alternative embodiment, the electric heater 32 can be designed to directly increase the temperature of the engine oil.The optimal temperature threshold of the engine oil can be between 180°F (82.2°C) and 250°F (121.1°C).

[0023] It can also be advantageous to operate the electric heater 32 to increase the temperature of the transmission oil under certain conditions. The transmission 11 operates more efficiently once the transmission oil temperature is at or above an optimal temperature threshold. Transmission oil is more viscous at lower temperatures, which increases friction between moving parts of the transmission 11. This increased friction can lead to parasitic losses that negatively affect fuel efficiency. The electric heater 32 can be operated to increase the temperature of the coolant. The coolant flows through the electric heater 32 to a transmission oil heat exchanger 52 to warm the transmission oil when the transmission oil is operating below the optimal temperature threshold.A coolant circulation valve 51 can be used, as described above, to direct engine coolant through the engine oil heat exchanger 50 or the transmission oil heat exchanger. In an alternative embodiment, the electric heater 32 can be designed to directly raise the temperature of the transmission oil. The optimal temperature threshold of the transmission oil can be between 180°F (82.2°C) and 250°F (121.1°C).

[0024] Fig.Section 2 represents a control logic for the controller 34 to determine how to use the excess power from regenerative braking, as described above, to increase the coolant temperature, the transmission oil temperature, and the engine oil temperature. The controller 34 prioritizes power from regenerative braking to the electric heater 32, based on the engine coolant, transmission oil, and engine oil temperatures, to optimize the performance of the internal combustion engine 12 and the transmission 11. More specifically, the controller 34 directs power from regenerative braking to the electric heater 32 to provide a faster and more efficient warm-up time for the transmission 11 and the internal combustion engine 12. Reducing the time required to adequately heat the internal combustion engine 12 and the transmission 11 increases fuel efficiency and improves the performance of the vehicle 14.

[0025] At 54, the controller 34 determines whether excess regenerative braking power is available. For example, the controller 34 can determine that excess regenerative braking power is available if the state of charge of the traction battery 17 is greater than a threshold, if the vehicle 14 is maneuvering downhill, which increases the state of charge of the traction battery 17, and if the engine coolant temperature, the transmission oil temperature, and the engine oil temperature are less than a threshold. If no excess regenerative braking power is available at 54, the control logic terminates. If the controller 34 determines that excess regenerative braking power is available at 54, the controller 34 can determine at 56 whether the engine coolant temperature is below a threshold.

[0026] At 56, the controller 34 determines the engine coolant temperature and compares it to a value derived from a lookup table to determine if the engine coolant temperature is above a threshold. The controller 34 is designed to prioritize excess regenerative braking power, determined at 54, to first raise the engine coolant temperature. At 58, the controller 34 may be designed to use the excess regenerative braking power to heat the engine coolant if the engine coolant temperature is below a threshold at 56, as described above. However, if the controller 34 determines at 56 that the engine coolant temperature is above a threshold, it may then determine at 60 whether the transmission fluid temperature is below a threshold.

[0027] The control unit 34 can be configured to determine the transmission oil temperature at 60 and compare this temperature to a derived or programmed value related to the optimal performance of the transmission 11, based on the transmission oil temperatures. At 60, the control unit 34 uses the comparison between the actual transmission oil temperature and the optimal transmission oil temperature to determine whether the transmission oil is above or below a threshold. If the transmission oil is below the threshold at 60, the control unit 34 is configured to direct excess regenerative braking power to heat the transmission oil at 62, as described above. If the transmission oil is above the threshold at 60, the control unit 34 can determine the engine oil temperature at 64.

[0028] The control unit 34 can be configured to determine the engine oil temperature at 64 and compare this temperature to a derived or programmed value related to optimal engine performance 12 based on the engine oil temperature. At 64, the control unit 34 uses the comparison between the actual engine oil temperature and the optimal engine oil temperature to determine whether the engine oil is above or below a threshold. If the engine oil is below the threshold at 64, the control unit 34 can be configured to direct excess regenerative braking power to heat the engine oil at 66. Using excess regenerative braking power to heat the engine oil at 66 is consistent with the engine oil heating strategy described above. If the engine oil is above the threshold at 64, the control logic terminates.

[0029] The processes, procedures, or algorithms disclosed herein may be delivered to or implemented by a processing unit, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Likewise, the processes, procedures, or algorithms may be stored as data and instructions executable by a controller or computer in many forms, including, but not limited to, information permanently stored on non-writable storage media such as ROM devices, and information modifiably stored on writable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, procedures, or algorithms may also be implemented in an executable software object.Alternatively, the processes, procedures or algorithms can be implemented in whole or in part using suitable hardware components, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of hardware, software and firmware components. Reference symbol list 10 Cooling system 11 gearboxes 12 Internal combustion engine 14 vehicles 15 Electric machine 16 Cooling loop 17 Traction battery 18 first heat exchanger 20 fans 22 Pump 24 Thermostat 26 second heat exchanger 28 blower fans 30 Control valve 32 electric heaters 34 Control 36 Additional battery 38 first coolant temperature sensor 40 second coolant temperature sensor 44 Engine oil temperature sensor 46 Transmission oil temperature sensor 48 Ambient air temperature sensor 50 engine oil heat exchangers 51 Coolant circulation valve 52 Gear oil heat exchangers

Claims

[1] A method for heating transmission oil in a hybrid vehicle (14), comprising: generating power with an electric machine (15) via regenerative braking; and directing power from the electric machine (15) to an electric heater (32) to heat the transmission oil in response to a temperature of an engine coolant being greater than a threshold and the controller (34) determining that the temperature of the transmission oil is below a threshold related to a temperature value for optimal performance of the transmission (11), and wherein the power directed to the electric heater (32) is a portion of a total regenerative braking power that exceeds a charge rate limit of a battery, characterized by , that the engine coolant threshold corresponds to a first reserve coolant temperature that exceeds a minimum coolant temperature required for an EV operating mode. [2] The method of claim 1, wherein the engine coolant threshold corresponds to a minimum coolant temperature required to maximize engine efficiency. [3] The method of claim 1 or 2, wherein the engine coolant threshold corresponds to a minimum coolant temperature required for an EV operating mode. [4] A method according to any one of claims 1 to 3, wherein the engine coolant threshold corresponds to a minimum coolant temperature required to meet cabin heating requirements. [5] The method of any one of claims 1 to 4, wherein the engine coolant threshold corresponds to a second reserve coolant temperature that exceeds a minimum coolant temperature required to meet cabin heating requirements. [6] Vehicle (14) comprising: an internal combustion engine (12), an electric machine (15) designed to charge a battery by regenerative braking, an electric heater (32) configured to selectively heat an engine coolant, a transmission oil, or an engine oil; and a controller programmed to direct regenerative braking power to the electric heater (32) while a total regenerative braking power exceeds a battery charge rate limit to heat the transmission oil in response to a temperature of the engine coolant exceeding an engine coolant threshold, and to direct regenerative braking power to the electric heater (32) to heat the engine oil to a temperature above a threshold related to optimal performance of the internal combustion engine (12) in response to a temperature of the transmission oil exceeding a transmission oil threshold, characterized by , that the engine coolant threshold corresponds to a first reserve coolant temperature that exceeds a minimum coolant temperature required for an EV operating mode. [7] The vehicle (14) of claim 6, further comprising a transmission oil heat exchanger (52) associated with the transmission oil and fluidly coupled to the electric heater (32). [8] The vehicle (14) of claim 7, wherein the controller is further programmed to actuate a coolant recirculation valve (51) to flow coolant through the transmission oil heat exchanger (52) to heat the transmission oil. [9] The vehicle (14) of any one of claims 6 to 8, further comprising an engine oil heat exchanger (50) associated with the engine oil and fluidly coupled to the electric heater (32). [10] The vehicle (14) of claim 9, wherein the controller is further programmed to actuate a coolant recirculation valve to flow coolant through the engine oil heat exchanger (50) to heat the engine oil.

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