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 thermally connected to the first cooling circuit (14), the second cooling circuit (30) or the air cooling (46) for cooling the cooling medium of the first cooling circuit (14), the second cooling circuit (30) or the air cooling (46).

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; 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, 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 in direct thermal contact with the battery, and wherein - a third cooling circuit of the thermal management system is thermally connected to the first cooling circuit, the second cooling circuit or the air cooling for cooling the cooling medium of the first cooling circuit, the second cooling circuit or the air cooling, preferably to the second cooling circuit or the air cooling for cooling the cooling medium of the second cooling circuit or the air cooling.

[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 directly cools the battery 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 thermally connected to the first cooling circuit or preferably to the second cooling circuit or the air cooling system for cooling the cooling medium of the first, the second cooling circuit, or the air cooling system. In other words, the third cooling circuit is configured such that it can cool the coolant of the first cooling circuit or preferably the second cooling circuit or the air cooling system. This can be possible, for example, by cooling the coolant of the third cooling circuit below ambient temperature.

[0024] The drive system according to the present invention thus 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 independent of the ambient temperature. This can be particularly advantageous for electrically powered vehicles, as these must be operated at very different temperatures at different times of the year and, for example, due to direct sunlight, without compromising safety and reliability.

[0025] The cooling 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 current state of the art, but it allows for significant advantages in efficiency and thus in the reliability and safety of the drive system.

[0026] This creates a possibility 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 with 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.

[0027] The drive system of the present invention is also suitable for high-power electric motors, whereas passively cooled batteries, which release heat to the environment via convection, are mostly used for lower-power applications according to the prior art.

[0028] A design in which a third cooling circuit is provided, through which the air of the air cooling system can be cooled, can be advantageous, since air itself can be cooled very well and thus a particularly efficient cooling of the battery is possible.

[0029] In the embodiment according to which a third cooling circuit is provided, through which the coolant of the second cooling circuit can be cooled, it can be particularly advantageous that, in addition to the battery, the electric motor also benefits from the cooling. This is because the first cooling circuit and the second cooling circuit are thermally connected to one another, in particular via a heat exchanger.

[0030] In principle, connecting the third cooling circuit to the second cooling circuit and / or the air cooling system can be advantageous, since the battery, in particular, must be cooled efficiently. This not only increases reliability but also significantly improves safety, especially when cooling the battery due to its hazard potential in hot temperatures. This is also advantageous because the battery cooling, in particular, must adhere to a relatively narrow temperature window, which can be ensured according to the invention.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] With regard to the design of the third cooling circuit, it may be advantageous for the third cooling circuit to include a compressor, a radiator, and an expansion valve. This design allows for a particularly efficient way of lowering the coolant of the third cooling circuit below the ambient temperature, thus also reducing the coolant consumption of the second cooling circuit or the air cooling system. Furthermore, this design can be implemented cost-effectively.

[0036] 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 cooling medium and at least one channel for guiding a gaseous cooling medium is provided between these layers.

[0037] In other words, the cooling structure between the battery cells can have approximately the following sequence: heat transfer medium - channel for conducting the liquid cooling medium - channel for conducting the gaseous cooling medium - heat transfer medium. For example, the channel for conducting the liquid cooling medium can be surrounded by channels for conducting the gaseous cooling medium along the thickness of the layer sequence. The thickness should extend from one battery cell to a second battery cell through the layer composite.

[0038] In this embodiment, a particularly effective transfer of the heat from the battery cells to the liquid or gaseous cooling medium can take place.

[0039] 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; Fig. 2 shows an electric drive system according to a second embodiment of the present invention; and Fig. 3 shows a battery structure for a drive system according to the present invention.

[0040] 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 and Fig. 2 shows two embodiments of the invention.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The first cooling circuit 14 and the second cooling circuit 30 are further thermally connected to one another by a heat exchanger 44.

[0045] 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, 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.

[0046] The thermal management system 12 further includes 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 and thereby liquefied by the compressor 54, cooled by the radiator 56, and expanded by the expansion valve 58, so that the cooling medium returns to a gaseous state. This allows for very efficient cooling.

[0047] The third cooling circuit 52 serves to actively cool the cooling medium of the second cooling circuit 30 or the air cooling 46.

[0048] For this purpose, it is Fig. 1, the third cooling circuit 52 is thermally connected to the second cooling circuit 30. For this purpose, a heat exchanger 60 interacting with the second cooling circuit 30 and the third cooling circuit 52 is provided. Accordingly, the thermal management system 12 according to Fig. 1 is designed so that the cooling liquid of the second cooling circuit 30 can be cooled by the third cooling circuit 52.

[0049] In the Fig. 2 shows a further embodiment of a thermal management system 12 or a drive system 10 comprising the same. This essentially corresponds to the embodiment of Fig. 1. However, it is Fig. 2, it is provided that the third cooling circuit 52 is thermally connected to the air cooling system 46. For this purpose, a heat exchanger 60 is provided that interacts with the air cooling system 46 and the third cooling circuit 52. Accordingly, the thermal management system 12 is designed according to Fig. 2 is designed so that the air of the air cooling system 46 used for cooling can be cooled by the third cooling circuit 52.

[0050] The Fig. 3 shows a battery structure 61 for the drive system 10 from the Fig. 1 and Fig. 2, by means of which cooling of the battery 32 by the second cooling circuit 30 and the air cooling 46 is advantageously possible.

[0051] Two battery cells 62, 64 of the battery 32 are shown, although the battery 32 can of course also have more battery cells. A cooling structure 66 is provided between the battery cells 62, 64 and in particular on both sides of the battery cells 62, 64. The cooling structure 66 is present 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. Between these layers, at least one channel 70 for conducting liquid cooling medium and at least one channel 72 for conducting a gaseous cooling medium are provided, wherein the channels 70, 72 are separated by a metallic structure 74. For example, the channel 70 for conducting liquid cooling medium can be provided along the thickness of the layered composite between two channels 72 for conducting a gaseous cooling medium. 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 58 Expansion valve 60 heat exchangers 61 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 thermally connected to the first cooling circuit (14), the second cooling circuit (30) or the air cooling (46) for cooling the cooling medium of the first cooling circuit (14), the second cooling circuit (30) or the air cooling (46). [2] Electric drive system (10) according to claim 1, characterized by that the third cooling circuit (52) is thermally connected to the second cooling circuit (30), by means of which the cooling liquid of the second cooling circuit (30) can be cooled. [3] Electric drive system (10) according to claim 1 or 2, characterized by that the third cooling circuit (52) is thermally connected to the air cooling (46), by means of which the air flow of the air cooling (46) can be cooled. [4] Electric drive system (10) according to one of claims 1 to 3, characterized by that 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). [5] Electric drive system (10) according to one of claims 1 to 4, 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). [6] Electric drive system (10) according to one of claims 1 to 5, 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. [7] Electric drive system (10) according to one of claims 1 to 6, characterized by that the air cooling (46) has a humidity sensor (48) for measuring the humidity of the air flow. [8] Electric drive system (10) according to one of claims 1 to 6, characterized by that 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. [9] Electric drive system (10) according to one of claims 1 to 8, characterized by that the third cooling circuit (52) comprises a compressor (54), a radiator (56) and an expansion valve (58). [10] Electric drive system (10) according to one of claims 1 to 9, 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 at least one channel (70) for conducting liquid cooling medium and at least one channel (72) for conducting a gaseous cooling medium is provided between these layers.

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