Method and system for thermal management of a traction battery

Abstract

Method comprising: Circulating a fluid through a heat exchanger (68) and a battery pack (14) when the battery pack (14) requires cooling; and Circulating the fluid through an exhaust heat recovery device (64) and the battery pack (14) when the battery pack (14) requires heating; Directing exhaust gas from an engine (20) through the exhaust heat recovery device (64) when the battery pack (14) requires heating, and redirecting exhaust gas from the engine (20) around the exhaust heat recovery device (64) when the battery pack (14) requires cooling; Circulating the fluid through the exhaust heat recovery device (64) when the battery pack (14) requires cooling; and Diverting the fluid around the heat exchanger (68) when the battery pack (14) requires heating.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to managing thermal energy levels of a traction battery, and more particularly to selectively heating the traction battery using an exhaust heat recovery device. BACKGROUND

[0002] In general, electrified vehicles differ from conventional motor vehicles in that electrified vehicles are selectively powered using one or more battery-powered electric motors. Conventional motor vehicles, in contrast to electrified vehicles, are powered exclusively using an internal combustion engine. The electric motors can power electrified vehicles instead of an internal combustion engine or in addition to it. Examples of electrified vehicles include hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles (FCVs), and battery electric vehicles (BEVs).

[0003] A battery heater for hybrid vehicles using exhaust gas recirculation is known from US 2011 / 0206951 A1.

[0004] An exhaust gas heat recovery device is known from DE 10 2008 032 706 A1.

[0005] From DE 10 2008 045 407 A1 a temperature control device for a built-in battery pack is known.

[0006] Traction batteries in electrified vehicles have an optimal operating temperature range. Operating the traction battery within the optimal operating temperature range can, among other things, improve its operating efficiency. Heating or cooling the traction battery may be necessary to bring it within the optimal operating temperature range.

[0007] The object of the present invention is to provide an optimized thermal management for a traction battery. SUMMARY

[0008] According to the invention, a method according to claim 1 and a system according to claim 8 are proposed.

[0009] Advantageous embodiments of the invention are specified in the dependent claims and the following description.

[0010] In a further non-limiting embodiment of the inventive method, the method comprises driving a drive wheel of an electrified vehicle using power from the battery pack.

[0011] In a further non-limiting embodiment of any of the foregoing methods, the method comprises extracting thermal energy from the fluid at the heat exchanger when the battery pack requires cooling.

[0012] In a further non-limiting embodiment of any of the foregoing methods, the method comprises supplying thermal energy to the fluid at the exhaust heat recovery device when the battery pack requires heating.

[0013] In a further non-limiting embodiment of any of the foregoing methods, the method comprises heating the exhaust heat recovery device with an exhaust gas from an internal combustion engine.

[0014] In a further non-limiting embodiment of any of the foregoing methods, the fluid is a liquid.

[0015] In a further non-limiting embodiment of any of the foregoing methods, the heat exchanger is a cooler.

[0016] In a further non-limiting embodiment of the system according to the invention, the assembly includes a gas valve movable into a recovery position directing exhaust gas to flow through the exhaust heat recovery device when the fluid valve is in the heating position and into a bypass position directing exhaust gas to bypass the exhaust heat recovery device when the fluid valve is in the cooling position.

[0017] In another non-limiting embodiment of any of the foregoing systems, flow moves through the exhaust heat recovery device when the fluid valve is in the cooling position.

[0018] In another non-limiting embodiment of any of the foregoing systems, flow bypasses the heat exchanger when the fluid valve is in the heating position.

[0019] In another non-limiting embodiment of any of the foregoing systems, the battery pack is a traction battery pack that powers a drive wheel of an electrified vehicle.

[0020] In a further non-limiting embodiment of any of the foregoing systems, the assembly includes an internal combustion engine that provides the exhaust gas.

[0021] In a further non-limiting embodiment of any of the foregoing systems, the heat exchanger is configured to transfer thermal energy from the fluid when the fluid valve is in the cooling position.

[0022] In a further non-limiting embodiment of any of the foregoing systems, the exhaust heat recovery device is configured to transfer heat energy to the fluid when the fluid valve is in the heating position.

[0023] In another non-limiting embodiment of any of the foregoing systems, the heat exchanger is a radiator. DESCRIPTION OF THE CHARACTERS

[0024] The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures accompanying the detailed description may be briefly described as follows: Fig. 1 schematically shows an exemplary drive train of a hybrid electric vehicle. Fig. Figure 2 shows schematically a thermal management system when heating a battery pack of the powertrain of Fig. 1. Fig. Figure 3 shows schematically the thermal management system of Fig. 2 when cooling the battery pack of the powertrain of Fig. 1. DETAILED DESCRIPTION

[0025] The present disclosure generally relates to heating and cooling a battery pack of an electrified vehicle. During heating, an exhaust gas heat recovery ("EGHR") device heats a fluid. The heated fluid from the EGHR device moves through the battery pack to heat the battery pack. During cooling, the same fluid moves through the battery pack to cool the battery pack.

[0026] With reference to Fig. 1, a powertrain 10 of a hybrid electric vehicle (HEV) includes a battery pack 14 with multiple assemblies 18, an internal combustion engine 20, a motor 22, and a generator 24. The motor 22 and generator 24 are types of electric machines. The motor 22 and generator 24 may be separate or may take the form of a combined motor / generator.

[0027] In this embodiment, the powertrain 10 is a power-split powertrain employing a first drive system and a second drive system. The first and second drive systems generate torque to drive one or more sets of vehicle drive wheels 28. The first drive system includes a combination of the engine 20 and the generator 24. The second drive system includes at least the motor 22, the generator 24, and the battery pack 14. The motor 22 and the generator 24 are parts of an electric drive system of the powertrain 10.

[0028] The engine 20 and the generator 24 may be connected by a power transfer unit 30, such as a planetary gear set. Of course, other types of power transfer units, including other gear sets and transmissions, may be used to connect the engine 20 to the generator 24. In one non-limiting embodiment, the power transfer unit 30 is a planetary gear set including a ring gear member 32, a sun gear member 34, and a carrier assembly 36.

[0029] The generator 24 can be driven by the engine 20 via the power transmission unit 30 to convert kinetic energy into electrical energy. Alternatively, the generator 24 can function as a motor to convert electrical energy into kinetic energy, thereby delivering torque to a shaft 38 connected to the power transmission unit 30.

[0030] The ring gear 32 of the power transfer unit 30 is connected to a shaft 40, which is connected to the vehicle drive wheels 28 by a second power transfer unit 44. The second power transfer unit 44 may include a gear set with a plurality of gears 46. Other power transfer units could be used in other examples.

[0031] The gears 46 transfer torque from the engine 20 to a differential 48 to ultimately provide traction to the vehicle drive wheels 28. The differential 48 may include a plurality of gears that facilitate the transfer of torque to the vehicle drive wheels 28. In this example, the second power transfer unit 44 is mechanically coupled to an axle 50 through the differential 48 to distribute torque to the vehicle drive wheels 28.

[0032] The motor 22 can be selectively used to drive the vehicle's drive wheels 28 by delivering torque to a shaft 54, which is also connected to the second power transfer unit 44. In this embodiment, the motor 22 and the generator 24 cooperate as part of a regenerative braking system in which both the motor 22 and the generator 24 can be used as motors to deliver torque. For example, the motor 22 and the generator 24 can each deliver electrical power to charge cells of the battery pack 14.

[0033] The assemblies 18 of the battery pack 14 contain battery cells. Operating the battery cells and other parts of the battery pack 14 within an optimal temperature range can, among other things, facilitate efficient operation. For example, the optimal temperature range for some types of battery packs 14 may range from 20 to 40 degrees Celsius.

[0034] Now with further reference to Fig. 1 on the Fig. 2 and Fig. 3, an exemplary thermal management system 60 selectively heats or cools the battery pack 14 to bring the battery pack 14 within or closer to the optimal temperature range(s).

[0035] When the temperatures of the battery cells or another portion of the battery pack 14 are below an optimal temperature range, the system 60 may add heat energy to the battery pack 14. When the temperatures of the battery cells in the battery pack 14 are above an optimal temperature range, the system 60 may remove heat energy from the battery pack 14. The system 60 thus selectively heats or cools the battery pack 14. The system 60 may heat or cool portions of the battery pack 14, such as battery cells of selected arrays 18, rather than the entire battery pack 14.

[0036] In this example, system 60 includes battery pack 14, an EGHR device 64, a heat exchanger 68, a fluid valve 72, a gas valve 74, an adjustable fluid path 76, and an adjustable exhaust flow path 78. A pump 80 may be used to move a fluid along fluid path 76. The fluid, in this example, is a liquid coolant. In another example, the fluid could be a gas, such as air.

[0037] In this example, the fluid valve 72 can be operated back and forth between a heating position and a cooling position. The fluid path 76 adapts depending on the positioning of the fluid valve 72. Fig. 2 shows an example of the fluid path 76 when the fluid valve 72 is in the heating position. Fig. 3 shows an example of the fluid path 76 when the fluid valve 72 is in the cooling position.

[0038] When the fluid valve 72 is in the heating position, fluid moves along the fluid path 76 and conveys heat energy to the battery pack 14 to provide heating. When the fluid valve 72 is in the cooling position, fluid moves along the fluid path 76 and conveys heat energy from the battery pack 14 to provide cooling.

[0039] When the fluid valve 72 is in the heating position, the fluid path 76 extends from the battery pack 14 to the EGHR device 64, to the fluid valve 72, and then back to the battery pack 14. The fluid path 76 thus bypasses the heat exchanger 68 when the fluid valve 72 is in the heating position.

[0040] The gas valve 74 is adjustable between a recovery position that directs exhaust gas to flow through the EGHR device 64 and a bypass position that directs the exhaust gas to bypass the exhaust heat recovery device.

[0041] When the valve 72 is in the heating position, the gas valve 74 is set to the reclaim position to cause the exhaust flow path 78 to pass through the EGHR device 64. Thus, when the fluid valve 72 is in the heating position, the EGHR device 64 receives an exhaust flow from the engine 20. As the exhaust moves through the EGHR device 64, fluid moving along the fluid path 76 exiting the EGHR device 64 is heated relative to the fluid entering the EGHR device 64. The exhaust heats the fluid in the EGHR device 64.

[0042] The EGHR device 64 is a type of heat exchanger that transfers heat energy from the exhaust gas to the fluid in the fluid path 76. The EGHR device 64 recovers waste heat because most of the heat energy in the exhaust gas is expelled to the environment if it is not moved through the EGHR device 64.

[0043] Several types of heat transfer could be used by the EGHR device 64 to transfer heat to the fluid in the fluid path, including conduction, convection, advection, and radiation.

[0044] The fluid in the fluid path 76 circulates between the battery pack 14 and the EGHR device, so that the fluid transports heat energy from the EGHR device 64 to the battery pack 14 when the fluid valve 72 is in the heating position. Because the fluid valve 72 directs the fluid from the EGHR device 64 around the heat exchanger 68 in the heating position, the fluid that has been heated in the EGHR device 64 does not cool due to the flow through the heat exchanger 68.

[0045] When the fluid valve 72 is in the cooling position, the fluid path 76 extends from the battery pack 14 to the EGHR device 64, to the fluid valve 72, to the heat exchanger 68, and then back to the battery pack 14. The fluid in the fluid path 76 circulates between the battery pack 14 and the heat exchanger 68 to transport thermal energy from the battery pack 14 to the heat exchanger 68 when the fluid valve 72 is in the cooling position.

[0046] Heat exchanger 68 is a type of heat exchanger that extracts heat energy from the fluid moving along the fluid path within heat exchanger 68. Heat exchanger 68 is a cooler in this example. In heat exchanger 68, the fluid moving along fluid path 76 can be cooled by surrounding air. Heat energy from the fluid moves to the environment at 92. The fluid moving along fluid path 76 that leaves heat exchanger 68 is thus cooled relative to the fluid entering heat exchanger 68.

[0047] Several types of heat transfer could be used by the heat exchanger 68 to transfer heat from the fluid in the fluid path, including conduction, convection, advection, and radiation.

[0048] When valve 72 is in the cooling position, gas valve 74 is set to the bypass position to cause the exhaust gas to bypass EGHR device 64. Diverting the exhaust gas around EGHR device 64 ensures that no heat energy is added to the fluid in fluid path 76 when cooling battery pack 14 is desired.

[0049] The gas valve 74 may adjust the exhaust flow path to direct the exhaust to the EGHR device 64, to bypass the exhaust around the EGHR device 64, or any combination thereof.

[0050] The system 60 may include a controller 94 operatively coupled to one or more temperature sensors 96 within the battery pack 14, the fluid valve 72, and the gas valve 74. The controller 94 may also be operatively coupled to temperature sensors external to the battery pack 14, such as temperature sensors 98, which monitor temperatures of the fluid moving along the fluid path 76.

[0051] Controller 94 is configured to move fluid valve 72 between the heating and cooling positions. Controller 94 may move fluid valve 72 in response to temperature measurements from sensors 96, sensors 98, or in response to any other input.

[0052] In some examples, during startup in cold ambient conditions, the controller 94 moves the fluid valve 72 to the heating position and moves the gas valve 74 to a position that directs current through the EGHR device 64. The positioning of the fluid valve 72 and the gas valve 74 causes fluid in the fluid path 76 to heat areas of the battery pack 14, which may increase or maintain temperatures of the battery pack 14 closer to the desired operating temperature range.

[0053] After increasing the temperatures of the battery pack 14, the controller 94 may then move the fluid valve 72 to the cooling position and the gas valve 74 to a position that directs exhaust flow around the EGHR device 64. The positioning of the fluid valve 72 and the gas valve 74 causes fluid in the fluid path 76 to cool portions of the battery pack 14, thereby reducing temperatures of the battery pack 14 or maintaining them closer to the desired operating temperature range.

[0054] The controller 94 may be part of a battery electronic control module (BECM) that includes circuitry used to retrieve data from the sensors 96, 98 and to control the positioning of the fluid valve 72 and the gas valve 74. In other examples, the controller 94 could be located external to the BECM.

[0055] The fluid valve 72 is a valve that can be actuated to regulate the fluid in the fluid path 76. The fluid valve 72 responds to signals from the controller 94. In some examples, the controller 94 is omitted, and instead, the fluid valve 72 responds to signals from the temperature sensors 96, 98. The fluid valve 72 could be a ball valve, a gate valve, a flap valve, or any other type of valve suitable for regulating fluid flow.

[0056] In some examples, the fluid valve 72 may be set to heating positions or cooling positions in which a portion of the fluid moving along the fluid path 76 bypasses the heat exchanger 68 and a portion of the fluid moving along the fluid path moves through the heat exchanger 68. Such positions may be desirable when less cooling or less heating is desired.

[0057] The gas valve 74 is a valve operable to regulate the flow of exhaust gas from the engine 20. The gas valve 74 responds to signals from the controller 94. In some examples, the controller 94 is omitted, and instead, the gas valve 74 responds to signals from the temperature sensors 96, 98. The gas valve 74 could be a ball valve, a spool valve, a flap valve, or any other type of valve suitable for regulating fluid flow.

[0058] In some examples, the gas valve 74 may be adjusted to positions where a portion of the flow is directed through the EGHR device 64 and a portion of the flow is directed around the EGHR device 64. Such positions may be desirable when reduced heating of the fluid moving along the fluid path 76 in the EGHR device 64 is desired.

[0059] Features of the disclosed examples include heating battery cells and other parts of a battery pack 14 using thermal energy from the exhaust gas and without requiring a separate heating device. Additional heating elements could be added to the system 60 if further heating is desired.

[0060] Another feature of the system 60 is improved fuel economy in cold ambient temperatures due to the battery cells of the battery pack 14 reaching an optimal temperature range more quickly due to the heat energy from the exhaust gas.

[0061] System 60 is particularly applicable to modified hybrid transmission architectures of electrified vehicles limited to a single motor battery, where limits on full battery power discharge may be required for optimal start-stop operation and fuel efficiency.

[0062] The foregoing description is exemplary and not restrictive. Variations or modifications of the disclosed examples may be apparent to those skilled in the art without necessarily departing from the spirit of the present disclosure. Thus, the legal scope of protection afforded by the present disclosure can only be determined by a careful examination of the following claims.

Claims

[1] Method comprising: Circulating a fluid through a heat exchanger (68) and a battery pack (14) when the battery pack (14) requires cooling; and Circulating the fluid through an exhaust heat recovery device (64) and the battery pack (14) when the battery pack (14) requires heating; Directing exhaust gas from an engine (20) through the exhaust heat recovery device (64) when the battery pack (14) requires heating, and redirecting exhaust gas from the engine (20) around the exhaust heat recovery device (64) when the battery pack (14) requires cooling; Circulating the fluid through the exhaust heat recovery device (64) when the battery pack (14) requires cooling; and Diverting the fluid around the heat exchanger (68) when the battery pack (14) requires heating. [2] The method of claim 1, further comprising driving a drive wheel (28) of an electrified vehicle using power from the battery pack (14). [3] The method of claim 1, further comprising removing thermal energy from the fluid at the heat exchanger (68) when the battery pack (14) requires cooling. [4] The method of claim 1, further comprising adding thermal energy to the fluid at the exhaust heat recovery device (64) when the battery pack (14) requires heating. [5] The method of claim 1, further comprising heating the exhaust heat recovery device (64) with an exhaust gas from an internal combustion engine (20). [6] The method of claim 1, wherein the fluid is a liquid. [7] The method of claim 1, wherein the heat exchanger (68) is a cooler. [8] System (60), comprising: a battery pack (14); a heat exchanger (68); an exhaust heat recovery device (64); and a fluid valve (72) which can be set to a cooling position allowing a fluid to circulate between the heat exchanger (68) and the battery pack (14), and a heating position, which allows circulation of the fluid between the exhaust heat recovery device (64) and the battery pack (14), is movable. [9] The system (60) of claim 8, further comprising a gas valve (74) movable to a recovery position directing exhaust gas to flow through the exhaust heat recovery device (64) when the fluid valve (72) is in the heating position, and to a bypass position directing exhaust gas to bypass the exhaust heat recovery device (64) when the fluid valve (72) is in the cooling position. [10] The system (60) of claim 8, wherein the flow moves through the exhaust heat recovery device (64) when the fluid valve (72) is in the cooling position. [11] The system (60) of claim 8, wherein the flow bypasses the heat exchanger (68) when the fluid valve (72) is in the heating position. [12] The system (60) of claim 8, wherein the battery pack (14) is a traction battery pack that powers a drive wheel (28) of an electrified vehicle. [13] The system (60) of claim 8, further comprising an internal combustion engine (20) providing the exhaust gas. [14] The system (60) of claim 8, wherein the heat exchanger (68) is configured to transfer thermal energy from the fluid when the fluid valve (72) is in the cooling position. [15] The system (60) of claim 8, wherein the exhaust heat recovery device (64) is configured to transfer heat energy to the fluid when the fluid valve (72) is in the heating position. [16] The system (60) of claim 8, wherein the heat exchanger (68) is a cooler.

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