Electric drive system

Abstract

Electric drive system (10), wherein the electric drive system (10) has a thermal management system (12) for cooling components of the electric drive system (10), characterized in that the thermal management system (12) has a plurality of cooling circuits (14, 30, 52), wherein - a first cooling circuit (14) of the thermal management system (12) has a liquid coolant as a cooling medium and is in direct thermal contact with an electric motor (16) of the drive system (10); and - a second cooling circuit (30) of the thermal management system (12) has a liquid coolant as a cooling medium and is in direct thermal contact with a battery (32) of the drive system (10), wherein - the first cooling circuit (14) and the second cooling circuit (30) are thermally connected to one another, wherein - an air cooling (46) of the thermal management system (12) using air as a cooling medium is in direct thermal contact with the battery (32), and wherein - a third cooling circuit (52) of the thermal management system (12) is in direct thermal contact with the battery (32), wherein the third cooling circuit (52) is an active cooling circuit with a heating mechanism and a cooling mechanism, wherein the battery (32) can be selectively cooled or heated by the third cooling circuit (52).

Description

[0001] The present invention relates to an electric drive system with improved thermal management. In particular, the present invention relates to an electric drive system in which a wide variety of components can be efficiently cooled.

[0002] In modern electrified vehicles, thermal management of the electric drive train and its components, and especially the traction battery, is necessary.

[0003] Especially in winter and cold temperatures, it may be necessary to heat the battery to ensure its performance and to protect it from damage, such as lithium plating in lithium-ion batteries, and aging. To ensure high recuperation for charging the battery during braking, the battery is preferably preconditioned to prevent damage.

[0004] Previous heating and cooling systems for battery cells are connected to the outside of the battery cell. The heat is then dissipated to the cooling medium via a thermal interface material (TIM).

[0005] For example, a battery can be cooled from the bottom using a cooling plate. Alternatively, cooling can also be achieved from the top or side, such as with cooling coils. Due to the inherent design principle, only one cooling medium is possible at a time.

[0006] DE 10 2019 132 309 A1 and DE 10 2010 019 187 B4 each show a thermal management system with multiple cooling circuits. DE 10 2017 128 318 A1 and DE 10 2019 109 750 A1 each show a thermal management system with a battery cooling circuit and direct air cooling.

[0007] The state-of-the-art solutions can thus be further improved, especially with regard to efficient thermal management of a battery-based drive system.

[0008] The object of the present invention is to at least partially overcome at least one disadvantage of the prior art. In particular, the object of the present invention is to provide a solution that enables efficient thermal management of a battery-powered drive system.

[0009] The object is achieved by an electric drive system having the features of claim 1. Preferred embodiments of the invention are described in the subclaims, in the description or the figures, wherein further features described or shown in the subclaims or in the description or the figures may individually or in any combination constitute an object of the invention, unless the context clearly indicates the opposite.

[0010] An electric drive system is described, wherein the electric drive system has a thermal management system for cooling components of the electric drive system, wherein the thermal management system has a plurality of cooling circuits, wherein - a first cooling circuit of the thermal management system has a liquid coolant as the cooling medium and is in direct thermal contact with an electric motor of the drive system; and - a second cooling circuit of the thermal management system has a liquid coolant as the cooling medium and is in direct thermal contact with a battery of the drive system, wherein - the first cooling circuit and the second cooling circuit are thermally connected to each other, whereby - an air cooling of the thermal management system using air as a cooling medium is in direct thermal contact with the battery of the drive system, and wherein - a third cooling circuit of the thermal management system is in direct thermal contact with a battery, wherein the third cooling circuit is an active cooling circuit with a heating mechanism and a cooling mechanism, wherein the battery can be selectively cooled or heated by the third cooling circuit.

[0011] Such a drive system allows particularly efficient cooling of the drive system components.

[0012] Thus, an electric drive system is described. An electric drive system according to the present invention can be used, for example, in a vehicle, such as a motor vehicle, or in stationary applications, and thus has a very wide range of applications. For example, the drive system comprises an HV battery for electric vehicles.

[0013] It is known that electric drive systems, such as their motors or batteries, must be cooled to ensure long-term, stable operation with a high degree of safety. To ensure appropriate cooling of the components of the electric drive system, the electric drive system includes a thermal management system. It should be noted, however, that a thermal management system, like the cooling circuits discussed later, is suitable for cooling; however, within the scope of the present invention, it is not excluded that heating may occur as a result.

[0014] The thermal management system comprises a plurality of cooling circuits, as described in detail below.

[0015] A first cooling circuit of the thermal management system has a liquid coolant as the cooling medium and is in direct thermal contact with an electric motor. Accordingly, the first cooling circuit directly cools the electric motor and is thus in direct thermal contact with the electric motor. In the context of the present invention, this should mean, in particular, that the coolant, i.e., the cooling liquid, of the first cooling circuit flows directly through the electric motor, or that the cooling liquid flows through or along the electric motor or a component thermally arranged on the electric motor.

[0016] In principle, any known liquid coolant can be used as the coolant or cooling fluid. Non-limiting examples include oils, water, glycol, or mixtures comprising at least one of the aforementioned examples.

[0017] A second cooling circuit of the thermal management system also has a liquid coolant as the cooling medium and is in direct thermal contact with a battery. Accordingly, the second cooling circuit cools the battery directly and is thus in direct thermal contact with the battery. In the context of the present invention, this should mean, in particular, that a cooling structure of the battery, as described below, is directly flowed through by the coolant, i.e., the cooling liquid, of the second cooling circuit, or that the cooling liquid flows through or along the battery or a component thermally coupled to the battery.

[0018] For the purposes of the present invention, a battery is to be understood as a single battery cell or an arrangement comprising a plurality of battery cells, which may be divided into so-called stacks and / or connected in series or in series.

[0019] In principle, any known liquid coolant can be used as the coolant or cooling fluid of the second cooling circuit. Non-limiting examples include oils, water, glycol, or mixtures comprising at least one of the aforementioned examples.

[0020] In the electric drive system according to the present invention, or in its thermal management system, it is further provided that the first cooling circuit and the second cooling circuit are thermally connected to one another. This can be achieved, for example, by a heat exchanger that is thermally connected to the cooling fluid of the first cooling circuit and to the cooling fluid of the second cooling circuit. In particular, the cooling fluid of the first cooling circuit and the cooling fluid of the second cooling circuit flow through the heat exchanger.

[0021] The thermal management system further comprises an air cooling system, which uses air as the cooling medium and is in direct thermal contact with the battery. Accordingly, the air cooling system cools the battery directly and is thus in direct thermal contact with the battery. In the context of the present invention, this should mean, in particular, that a cooling structure of the battery, as described below, is directly flowed through by the coolant, i.e., the air of the air cooling system, or that the air flows through or along the battery or a component thermally coupled to the battery.

[0022] For example, air cooling can form a cooling circuit, but it is also possible for the air to only actively cool the battery without having to form a closed circuit.

[0023] The thermal management system further comprises a third cooling circuit which is an active cooling circuit with a heating mechanism and a cooling mechanism, wherein the battery can be selectively cooled or heated by the third cooling circuit.

[0024] In principle, active temperature control, i.e. cooling and heating, of the battery by the third cooling circuit can be particularly advantageous, since the battery in particular must be cooled efficiently. This not only increases reliability, but also offers significant safety gains, especially when cooling the battery due to its potential hazards in hot temperatures. This is also advantageous because the cooling of the battery in particular has to observe a relatively narrow temperature window, which can be ensured according to the invention. Heating the battery can also be useful, as this allows the battery to be conditioned, for example. This can improve battery charging and significantly increase its longevity. Active heating is also advantageous when heating in terms of efficiency.

[0025] It is therefore clear that, despite the term “cooling circuit”, the third cooling circuit can provide heating in addition to the functionality of cooling.

[0026] The drive system according to the present invention allows active cooling of the drive system components to temperatures below the ambient temperature through the thermal management system. Accordingly, safe operation of the drive system can be ensured essentially independently of the ambient temperature. This can be particularly advantageous for electrically powered vehicles, as these must be operated at very different temperatures during different seasons and, for example, due to direct sunlight, yet safety and reliability should not be compromised. The same applies to the battery, which is also particularly efficient and can improve battery longevity.

[0027] The temperature control of the components is very efficient, as the invention enables a combination of liquid cooling and air cooling. This is usually not easy to implement according to the state of the art, but it allows for significant advantages in efficiency and thus in the reliability and safety of the drive system.

[0028] According to the invention, a possibility is created in which several different cooling media such as air, coolant, for example a mixture of water and glycol, or refrigerants such as R744, R1234yf, can be used with a connection to the thermal management system. In the prior art, the use of different cooling media results in losses through heat transfer, such as refrigerant to water, air to water, which can be prevented or at least significantly reduced according to the invention. In addition, in the prior art, a certain pumping power must always be applied in the case of water, even when cooling is low, although cooling via air would also be possible. This can be prevented by controlling the cooling circuits independently of one another as needed. In an advantageous arrangement, this structure can also be used as an internal heat exchanger.

[0029] The drive system of the present invention is also suitable for high-power electric motors, whereas passively cooled batteries, which dissipate heat to the environment via convection, are mostly used for lower-power applications according to the prior art.

[0030] It may be preferred for a cooling channel of the third cooling circuit to run directly into a cooling structure of the battery, wherein the third cooling circuit comprises an evaporation mechanism and a condensation mechanism for a coolant, which serves both cooling and heating purposes within the meaning of the invention. In other words, the third cooling circuit is designed such that its coolant flows directly around or through the battery. This allows for particularly effective cooling or heating, since the third cooling circuit is an active cooling circuit. In particular, this cooling can thus be more effective than is known from passive cooling circuits, for example.

[0031] Because the third cooling circuit includes an evaporation mechanism and a condensation mechanism for a coolant, temperature control can be achieved very efficiently. Furthermore, this type of temperature control is less susceptible to failure and can be implemented using simple and common components, allowing for easy and problem-free implementation in existing systems.

[0032] By providing the evaporation mechanism or condensation mechanism in the third cooling circuit and thus in direct contact with the battery, battery cooling can be particularly effective. Evaporation or condensation of the coolant can occur directly adjacent to the battery or in the battery's cooling structure.

[0033] For example, the third cooling circuit can comprise a compressor, a radiator, and an expansion valve, wherein the order of flow through the radiator and battery by the coolant can be changed by switching a valve to selectively dissipate or supply heat to the battery. This is a particularly simple design for an evaporation mechanism and a condensation mechanism and can also enable effective cooling with few components. In the event that the compressor is active, evaporation can occur, in particular, close to or within the battery cooling structure. If the compressor is bypassed, condensation can occur, in particular, close to or within the battery cooling structure. This can enable selective heating or cooling of the battery.

[0034] However, in principle, it is not excluded within the meaning of the present invention that the evaporation mechanism or the condensation mechanism is designed differently, in particular that it comprises not only the aforementioned components but also further components.

[0035] It may further be preferred that the drive system has a battery which comprises at least two battery cells, between which a cooling structure is provided, wherein the cooling structure is present in a layered composite such that a layer with a solid heat transfer medium is provided along the thickness of the layered composite adjacent to the battery cells, wherein at least one channel for guiding liquid and gaseous cooling medium and at least one channel for guiding a gaseous cooling medium is provided between these layers.

[0036] In other words, the cooling structure between the battery cells can have the following sequence: heat transfer medium - channel for conducting at least liquid cooling medium or coolant - channel for conducting gaseous cooling medium, in particular air - heat transfer medium. For example, the channel for conducting air can be surrounded by channels for conducting liquid coolant or coolant along the thickness of the layer sequence. The thickness should run from one battery cell to a second battery cell through the layer composite. With regard to the coolant, it should be mentioned that this is located in the so-called wet zone. This means that the coolant can contain both gaseous and liquid components.

[0037] In this embodiment, a particularly effective transfer of the heat from the battery cells to the liquid or gaseous cooling medium can take place.

[0038] It can also be advantageous for the first cooling circuit to include at least one of the power electronics and a charger in addition to the electric motor. It has been shown that these components also require efficient cooling, and positioning them in the first cooling circuit is particularly easy to implement. This configuration can be advantageous because the power electronics should preferably not exceed an inlet temperature of the coolant of max. 55 - 65 °C. This can be achieved through passive cooling, for example by dissipating heat to the environment via a radiator. In contrast, the temperature limit for a battery is preferably around 40 °C cooling water temperature. In this case, active cooling, for example via coolant, is necessary, as described above.

[0039] More preferably, the first cooling circuit can comprise a radiator for dissipating heat, in particular wherein the radiator can be bypassed by a bypass. Alternatively or additionally, it can be provided that the second cooling circuit has a radiator for dissipating heat, in particular wherein the radiator can be bypassed by a bypass. In this embodiment, the cooling circuit or its coolant can thus be cooled directly by the radiator. This can further increase the efficiency of the cooling. By optionally providing a bypass to bypass the radiator, cooling can be dispensed with, for example. This can be advantageous depending on the situation, for example when preconditioning is carried out.

[0040] It may also be preferred for the air cooling system to have a sensor for measuring the humidity of the air flow. By determining the humidity, conclusions can be drawn about the cooling capacity, thus further increasing efficiency.

[0041] It may further be preferred that at least the first cooling circuit, the second cooling circuit, the third cooling circuit, or the air cooling system have a temperature sensor for measuring the temperature of the cooling medium. This configuration can also improve the efficiency of thermal management, since the temperature of the coolant also allows conclusions to be drawn about the cooling performance. Accordingly, the coolant can be cooled accordingly, for example, by the third cooling circuit or by the radiators, so that the temperature of the respective coolant can be lowered and the cooling performance can be improved.

[0042] The invention is further explained below with reference to the figures, where individual or multiple features of the figures may constitute a feature of the invention, either individually or in combination. Furthermore, the figures are to be viewed only as examples and in no way limiting. Fig. 1 shows an electric drive system according to a first embodiment of the present invention; and Fig. 2 shows a battery structure for a drive system according to the present invention.

[0043] In the Fig. 1 shows an electric drive system 10, which can be used in an electrically powered vehicle or in stationary applications. The electric drive system 10 includes a thermal management system 12 for cooling components of the electric drive system 10. Fig. 1 shows an embodiment of the invention.

[0044] The thermal management system 12 comprises a first cooling circuit 14, which has a liquid coolant as the cooling medium and is in direct thermal contact with an electric motor 16. Fig. 1 further shows that the first cooling circuit 14, in addition to the electric motor 16, includes power electronics 18 and a charger 20. A liquid pump 22 is also provided for conveying the liquid cooling medium. The first cooling circuit 14 further includes a radiator 24 for dissipating heat from the coolant or cooling liquid of the first cooling circuit. A 3 / 2-way valve 26 allows the coolant to be directed through a bypass 28, allowing the radiator 24 to be bypassed by the bypass 28. In other words, the coolant can be directed such that it does not flow along the radiator 24.

[0045] The thermal management system 12 further comprises a second cooling circuit 30, which has a liquid coolant as the cooling medium and is in direct thermal contact with a battery 32. The second cooling circuit 30 further comprises a radiator 34 for dissipating heat from the coolant or cooling liquid of the second cooling circuit 30. A bypass (not shown) may again be provided, which may be designed and arranged as described with respect to the first cooling circuit 14.

[0046] Furthermore, a coolant pump 36, i.e., a liquid pump, is provided in the second cooling circuit 30 to pump the coolant. A plurality of sensors are provided to control the operation of the second cooling circuit 30. In principle, corresponding sensors can also be present in the first cooling circuit 14. The sensors can, for example, include a first temperature sensor 38, a flow sensor 40, and a second temperature sensor 42. The temperature sensors 38, 42 can be arranged upstream and downstream of the battery 32.

[0047] The first cooling circuit 14 and the second cooling circuit 30 are further thermally connected to one another by a heat exchanger 44.

[0048] In addition to the first cooling circuit 14 and the second cooling circuit 30, an air cooling system 46 is also part of the thermal management system 12. The air cooling system 46 uses air as the cooling medium and is in direct thermal contact with the battery 32. To achieve efficient control of the air cooling system 46, the air cooling system 46 has a humidity sensor 48 for measuring the air humidity of the air flow. To promote the air flow, the air cooling system 46 further includes a fan 50.

[0049] The thermal management system 12 further comprises a third cooling circuit 52. The third cooling circuit 52 is configured to include a compressor 54, a radiator 56, and an expansion valve 58. Thus, the cooling medium can be compressed by the compressor 54 and thereby liquefied, cooled by the radiator 56, and expanded by the expansion valve 58, so that the cooling medium returns to a gaseous state. In other words, the third cooling circuit 52 comprises an evaporation mechanism that is in direct contact with the battery 32 or a cooling structure 66 of the battery. This allows for very efficient active cooling.

[0050] It is further shown that the compressor 54 can be bypassed by a 4 / 2-way valve 57, so that the refrigerant no longer flows through the compressor 54. In this case, the third cooling circuit can serve as a heat pump and the cooling structure 66 can serve as a condenser. By appropriately switching the 4 / 2-way valve, it can thus be made possible for the third cooling circuit to selectively heat or cool the battery 32. In detail, the 4 / 2-way valve can change the flow direction of the radiator 56 and the heat exchanger 59 in the battery 32. Thus, when flowing downstream of the compressor 54, the radiator 56 can be used as a condenser, so that heat is released into the environment. The heat exchanger 59 then functions as an evaporator and absorbs heat.In the case of flow through the heat exchanger 59 after the compressor 54, heat is supplied to the battery 32 and, after the gas has been expanded by the expansion valve 58, heat is absorbed from the environment via the radiator 56.

[0051] The area of ​​the third cooling circuit 52 that flows through the cooling structure 66 may also be referred to as heat exchanger 59.

[0052] The Fig. 2 shows a battery structure 60 for the drive system 10 from the Fig. 1, by means of which cooling of the battery 32 by the second cooling circuit 30, the third cooling circuit 52 and the air cooling 46 is advantageously possible.

[0053] Two battery cells 62, 64 of the battery 32 are shown, although the battery 32 may of course also have more battery cells.

[0054] A cooling structure 66 is provided between the battery cells 62, 64. The cooling structure 66 is provided in a layered composite. This has a solid heat transfer medium 68, which is provided adjacent to the battery cells 62, 64 along the thickness of the layered composite. This can be deformable, for example, to compensate for the expansion of the battery cells 62, 64 during charging and discharging and can also ensure heat transfer. For example, the heat transfer medium 68 can be designed as a so-called PCM (phase change material) and absorb the waste heat generated by the cells. Due to their geometry, the use of prismatic cells or pouch cells as battery cells 62, 64 is advantageous here.

[0055] Between these layers, at least one channel 70 is provided for conducting liquid and gaseous cooling medium and at least one channel 72 is provided for conducting a gaseous cooling medium or air. For example, the channel 70 for conducting liquid and gaseous cooling medium can be provided along the thickness of the layer composite between two channels 72 for conducting a gaseous cooling medium.

[0056] In this embodiment, a particularly effective transfer of the battery cells' heat to the liquid or gaseous cooling medium can be achieved. Here, coolant or gas from the third cooling circuit 52 flows through the channel 70 between the solid heat transfer medium 68 and an approximately metallic structure 74 that defines channels 70, 72. In the case of coolant, this evaporates in the intermediate space or channel 70 and thus transforms from the liquid to the gaseous state. The air from the air cooling system 46 flows through the intermediate space 72.

[0057] For example, air can be supplied via the ducts for cooling. Cooling with coolants such as water / glycol is also possible. Since the bipolar plates have two gas inlets, the second inlet can be used for the application of a refrigerant. A refrigerant with a comparatively low working pressure, such as R1234yf or R290, is advantageous here.

[0058] It can also be seen that the battery cells 62, 64 are cooled on both sides by the corresponding cooling structures 66, which can also be referred to as bipolar plates. List of reference symbols 10 electric drive system 12 Thermal management system 14 first cooling circuit 16 electric motor 18 Power electronics 20 charger 22 Liquid pump 24 Radiators 26 3 / 2-way valve 28 Bypass 30 second cooling circuit 32 Battery 34 Radiators 36 Coolant pump 38 Temperature sensor 40 flow sensor 42 Temperature sensor 44 heat exchangers 46 Air cooling 48 Humidity sensor 50 blowers 52 third cooling circuit 54 Compressor 56 Radiators 57 4 / 2-way valve 58 Expansion valve 59 heat exchangers 60 Battery structure 62 battery cells 64 battery cells 66 Cooling structure 68 Heat transfer medium 70 channel 72 channel 74 metallic structure

Claims

[1] Electric drive system (10), wherein the electric drive system (10) has a thermal management system (12) for cooling components of the electric drive system (10), characterized by that the thermal management system (12) has a plurality of cooling circuits (14, 30, 52), wherein - a first cooling circuit (14) of the thermal management system (12) has a liquid coolant as a cooling medium and is in direct thermal contact with an electric motor (16) of the drive system (10); and - a second cooling circuit (30) of the thermal management system (12) has a liquid coolant as a cooling medium and is in direct thermal contact with a battery (32) of the drive system (10), wherein - the first cooling circuit (14) and the second cooling circuit (30) are thermally connected to one another, wherein - an air cooling (46) of the thermal management system (12) using air as a cooling medium is in direct thermal contact with the battery (32), and wherein - a third cooling circuit (52) of the thermal management system (12) is in direct thermal contact with the battery (32), wherein the third cooling circuit (52) is an active cooling circuit with a heating mechanism and a cooling mechanism, wherein the battery (32) can be selectively cooled or heated by the third cooling circuit (52). [2] Electric drive system (10) according to claim 1, characterized by that a cooling channel of the third cooling circuit (52) runs directly into a cooling structure (66) of the battery (32), wherein the third cooling circuit (52) comprises an evaporation mechanism and a condensation mechanism for a coolant. [3] Electric drive system (10) according to claim 2, characterized byin that the third cooling circuit (52) comprises a compressor (54), a radiator (56) and an expansion valve (58), wherein the order of flow through the radiator (56) and the battery (32) can be changed by switching a 4 / 2-way valve (57) for selectively dissipating or supplying heat to the battery (32). [4] Electric drive system (10) according to one of claims 1 to 3, characterized byin that the drive system (10) has a battery (32) which comprises at least two battery cells (62, 64), between which a cooling structure (66) is provided, wherein the cooling structure (66) is present in a layered composite such that a layer with a solid heat transfer medium (68) is provided along the thickness of the layered composite adjacent to the battery cells (62, 64), wherein between these layers at least one channel (70) for conducting liquid and gaseous cooling medium and at least one channel (72) for conducting a gaseous cooling medium is provided. [5] Electric drive system (10) according to claim 4, characterized by that the channel (72) for guiding gaseous cooling medium along a thickness of the layer composite is provided between channels (70) for guiding liquid and gaseous coolant. [6] Electric drive system (10) according to one of claims 1 to 5, characterized bythat the first cooling circuit (14) comprises, in addition to the electric motor (16), at least one of the power electronics (18) and a charger (20). [7] Electric drive system (10) according to one of claims 1 to 6, characterized by that the first cooling circuit (14) comprises a radiator (24) for dissipating heat, in particular wherein the radiator (24) can be bypassed by a bypass (28). [8] Electric drive system (10) according to one of claims 1 to 7, characterized by that the second cooling circuit (30) has a radiator (34) for dissipating heat, in particular wherein the radiator (34) can be bypassed by a bypass. [9] Electric drive system (10) according to one of claims 1 to 8, characterized by that the air cooling (46) has a humidity sensor (48) for measuring the humidity of the air flow. [10] Electric drive system (10) according to one of claims 1 to 9, characterized bythat at least the first cooling circuit (14), the second cooling circuit (30), the third cooling circuit (52) or the air cooling (46) has a temperature sensor (38, 42) for measuring the temperature of the cooling medium.

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