Cooling system and motor vehicle

Abstract

Cooling system for a motor vehicle (10) with a main cooling circuit (12) in which at least one coolant pump (16) for conveying coolant in the main cooling circuit (12), a component to be cooled and an ambient heat exchanger (14) are integrated, characterized by a coolant reservoir (22) which can be connected to the main cooling circuit (12) as required by means of a valve device (30) in a fluid-conducting manner, wherein a cooling device for cooling the coolant contained therein is assigned to the coolant reservoir (22).

Description

[0001] The invention relates to a cooling system for a motor vehicle and to a motor vehicle with such a cooling system.

[0002] A motor vehicle typically has at least one cooling system based on the circulation of a coolant, in particular a cooling fluid, in at least one cooling circuit. As the coolant flows through one or more components of the motor vehicle integrated into the cooling circuit and requiring cooling, it absorbs thermal energy, which is at least partially transferred back to the ambient air via a heat exchanger. This allows for cooling of the components in a way that is particularly simple and well-adapted to the varying cooling performance requirements of those components.

[0003] The design of such a cooling system is generally based on the cooling capacity requirements under steady-state conditions, i.e., relatively long-lasting and only slightly fluctuating (continuous) high loads of the heat-generating components. In a vehicle with an internal combustion engine, these components are primarily the combustion engine itself, and typically also an engine oil cooler, a transmission oil cooler, an intercooler, and a cooler for an exhaust gas turbocharger. In a vehicle with an electric drive motor, the components that generate the heat energy that must be dissipated via a cooling system are primarily the electric drive motor itself, its associated power electronics, and, if applicable, a (traction) battery that supplies the electric drive motor with electrical energy.Despite the relatively good adaptability of the cooling capacity of such a cooling system to different cooling capacity requirements, such a cooling system has a not insignificant thermal inertia, so that a relatively large thermal power that is introduced into the cooling system in the short term can lead to significant temperature peaks or to a temporary exceedance of defined target temperature ranges.

[0004] A relatively high thermal output, introduced into a vehicle's cooling system for a short period, can occur, for example, when a drive motor integrated into the cooling system is operated under overload, as may be the case, in particular, with an electric drive motor. Such a drive motor is then operated, in a permissible manner, temporarily with a power output exceeding its defined continuous rated power. This can be useful, for instance, to achieve the fastest possible acceleration for a suitably powered vehicle, while the (steady-state) top speed of the vehicle is limited by the available continuous rated power.

[0005] DE 10 2006 032 852 A1 describes a cooling system for a motor vehicle with an expansion tank in which a heat storage device is integrated.

[0006] A comparable cooling system, also with a heat storage device, but which is not integrated into an expansion tank, is disclosed in DE 10 2013 212 783 A1.

[0007] DE 10 2015 201 240 A1 describes a combination of engine cooling and vehicle heating systems for a motor vehicle, referred to as a split cooling system.

[0008] German patent application DE 10 2016 118 688 A1 discloses a cooling system for an electrified motor vehicle, comprising a main cooling system that integrates, among other things, an ambient heat exchanger, an electric motor, an electrical unit, a battery, and a coolant reservoir. Furthermore, a heat exchanger is integrated into a branch of the main cooling system, through which refrigerant from an air conditioning system can additionally flow. This can be done as needed to regulate the temperature of the coolant in the main cooling system.

[0009] DE 199 48 160 A1 discloses a cooling system for an internal combustion engine, comprising an expansion tank, wherein a thermostatic valve is integrated into a vent line or a return line to the expansion tank, which prevents circulation of coolant through the expansion tank up to a predetermined temperature.

[0010] German patent DE 10 2016 118 498 A1 describes a cooling system for a hybrid vehicle comprising a high-temperature cooling circuit for an internal combustion engine and a low-temperature cooling circuit comprising components of an electric powertrain. Both cooling circuits are connected to the same expansion tank, with expansion lines between the expansion tank and the cooling circuits that can be opened and closed as needed by means of a control valve. During cold operation with a relatively low coolant temperature, the expansion tank is connected to both cooling circuits via the expansion lines, whereas during warm operation, only the expansion line leading to the high-temperature cooling circuit is open. This is intended to prevent excessively warm coolant from the high-temperature cooling circuit from entering the low-temperature cooling circuit via the expansion tank during warm operation.

[0011] The invention was based on the objective of avoiding or minimizing temperature peaks in a cooling system of a motor vehicle, which result in particular from the operation of a drive motor of the motor vehicle with an overload.

[0012] This problem is solved by means of a cooling system for a motor vehicle according to claim 1. A motor vehicle with such a cooling system is the subject of claim 10. Advantageous embodiments of the cooling system and the motor vehicle according to the invention are the subject of further claims and / or will become apparent from the following description of the invention.

[0013] A cooling system according to the invention for a (motor vehicle according to the invention) comprises at least one main cooling circuit, into which at least one coolant pump for conveying coolant, in particular a cooling fluid, a component to be cooled, and an ambient heat exchanger are integrated. Furthermore, a coolant reservoir is provided, which can be fluidly connected to the main cooling circuit as required by means of a valve device in order to introduce coolant, in particular the same type of coolant that is present within the main cooling circuit, from the coolant reservoir into the main cooling circuit, wherein a cooling device for cooling the coolant contained therein is associated with the coolant reservoir.

[0014] According to the invention, an "ambient heat exchanger" is understood to be a heat exchanger in which the coolant can be cooled by a transfer of heat energy to ambient air that flows through and / or around the heat exchanger.

[0015] The ambient heat exchanger of the main cooling circuit can be, in particular, the so-called main (water) radiator of the cooling system or of the motor vehicle, in which the recooling of the coolant primarily or mainly takes place as a result of a corresponding heat transfer to ambient air.

[0016] A cooling system according to the invention is therefore designed such that coolant can be stored in the coolant reservoir, the temperature of which, as a result of the use of the cooling device, is below the temperature of the coolant present in the main cooling circuit. This relatively cold coolant can then be introduced into the main cooling circuit as needed by means of the valve device, thereby lowering the average temperature of the coolant in the main cooling circuit relatively quickly. In this way, it is possible to react quickly to the short-term introduction of a relatively high thermal power into the coolant present in the main cooling circuit, since an increase in cooling capacity is achieved as a result of the then greater temperature difference between the (reduced) temperature of the coolant in the main cooling circuit and the temperature of the component to be cooled.

[0017] Accordingly, a control device can be provided for a cooling system according to the invention, which is designed to temporarily connect the coolant reservoir to the main cooling circuit when there is a temporarily increased cooling capacity requirement for the component to be cooled. This cooling capacity requirement can be determined, for example, as a function of the load or power output with which a component to be cooled is operated. Preferably, such a fluid-conducting connection of the coolant to the main cooling circuit via the valve device can be provided solely for this purpose.

[0018] The valve device of a cooling system according to the invention can advantageously be designed as a simple changeover valve, through which a fluid-conducting connection between the main cooling circuit and the coolant reservoir is either opened or closed. Alternatively, the valve device can be configured to allow for variable opening of the fluid-conducting connection between the main cooling circuit and the coolant reservoir, so that the amount of coolant flowing from the coolant reservoir into the main cooling circuit can be precisely controlled. This prevents the mixing of too much relatively cold coolant into the coolant flowing in the main cooling circuit and the resulting locally excessively low or fluctuating coolant temperatures, which can negatively affect the component integrated into the main cooling circuit and required for cooling.Such a variable valve device can, for example, be designed in the form of a proportional valve.

[0019] The relatively rapid response to the short-term introduction of a relatively high thermal power into the coolant present in the main cooling circuit, made possible by the inventive design of a cooling system, allows a drive motor integrated into the main cooling circuit of a motor vehicle (according to the invention) to be operated under an overload for a relatively long time before thermal overload is reached. Accordingly, it is preferably provided that the main cooling circuit of a cooling system according to the invention includes a drive motor for the motor vehicle and / or power electronics and / or a battery, in particular a traction battery, as the component to be cooled. A "drive motor" is understood to be a motor intended for generating propulsion power for the motor vehicle.

[0020] Since the possibility of temporarily operating a drive motor with a defined overload compared to its continuous rated power is particularly relevant for electric drive motors, the drive motor, or at least one of several drive motors integrated into the main cooling circuit of the cooling system, can be such an electric drive motor. However, it is also possible that the drive motor, or at least one of several drive motors integrated into the main cooling circuit of the cooling system, is an internal combustion engine, which can also incorporate an overload function. A motor vehicle according to the invention can therefore preferably be designed as a so-called hybrid vehicle (HEV) or as a (pure) electric vehicle (BEV).

[0021] According to a preferred embodiment of a cooling system according to the invention, the control device can change a limit value for overload operation of the drive motor and / or the power electronics and / or the battery depending on the (actual or planned) presence or absence of a connection between the coolant reservoir and the main cooling circuit (preferably also depending on the extent of the presence) and / or depending on the absolute or relative (compared to the temperature of the coolant in the main cooling circuit) temperature of the coolant in the coolant reservoir.Accordingly, it may be provided that the control device can be used to change a limit value, for example a maximum permissible time period, for overload operation of the drive motor and / or the power electronics and / or the battery, depending on whether and, if so, to what extent a temporary increase in cooling capacity for the component to be cooled can be achieved by mixing relatively cold coolant from the coolant reservoir into the main cooling circuit.

[0022] According to a further preferred embodiment of a cooling system according to the invention, the cooling device may comprise an ambient heat exchanger and / or a refrigeration unit, for example a compression refrigeration unit and / or a thermoelectric cooler (e.g., a Peltier element). Such a refrigeration unit may, for example, also be a refrigeration unit that is (additionally or primarily) provided in a motor vehicle comprising the cooling system for the on-demand air conditioning or cooling of the vehicle's interior.

[0023] The cooling device associated with the coolant reservoir can be integrated directly into the coolant reservoir. For example, the coolant reservoir can be designed as a heat exchanger or include such a heat exchanger. The coolant stored in the coolant reservoir can be at least partially contained in such a heat exchanger, and another heat exchange fluid, such as ambient air or a refrigerant from a refrigeration unit, can flow through the heat exchanger to cool the coolant contained in the coolant reservoir.

[0024] Furthermore, the cooling device may include an auxiliary cooling circuit comprising the coolant reservoir as well as an auxiliary radiator and / or an auxiliary coolant pump. By providing such an auxiliary cooling circuit, it is possible to spatially separate the functions of maintaining or temporarily storing the coolant contained in the coolant reservoir on the one hand, and cooling the coolant contained in the auxiliary cooling circuit as a whole on the other. This can simplify the integration of a cooling system according to the invention into, for example, the engine compartment of a motor vehicle according to the invention. The auxiliary radiator of the cooling device may preferably in turn comprise an ambient heat exchanger and / or a refrigeration unit, or it may be designed as an ambient heat exchanger or as a refrigeration unit.

[0025] A heat exchanger of the cooling device associated with the coolant reservoir can preferably be designed in the form of a conventional finned, microchannel, or other primary flow heat exchanger. However, such a heat exchanger can also be designed as a primary or exclusively flow-through heat exchanger, for example, as part of the underbody of a motor vehicle, thereby advantageously integrating it into a motor vehicle.

[0026] According to a preferred embodiment of a cooling system according to the invention, the coolant reservoir can serve as an expansion tank for the main cooling circuit. This allows for an advantageous dual use of the coolant reservoir and the expansion tank.

[0027] An "expansion tank" is a reservoir for the coolant of the cooling system, designed to compensate for temperature-related expansion of the coolant by adjusting the coolant level within the tank. Such an expansion tank can be partially filled with coolant and partially with a gas, and when using a liquid coolant, a structural separation between these two fluids is not necessary.

[0028] Since the coolant reservoir also serves at least to hold or temporarily store relatively cold coolant for mixing into the coolant flowing in the main cooling circuit as needed, it may be advantageous, according to a further preferred embodiment of a cooling system according to the invention, that at least the coolant reservoir is designed to be thermally insulating from the environment, thereby minimizing heat transfer from the environment to the coolant contained therein and thus potentially reducing the power required to cool this coolant.

[0029] The indefinite articles (“a”, “an”, “one”, and “ones”), particularly in the patent claims and in the description generally explaining the patent claims, are to be understood as such and not as numerals. Accordingly, components specified by these articles are to be understood as existing at least once and potentially existing multiple times.

[0030] The invention is explained in more detail below with reference to an embodiment shown in the drawing. The drawing shows: Fig. 1: In simplified representation, a motor vehicle with a cooling system according to the invention.

[0031] The Fig. Figure 1 shows a highly simplified representation of a (motor vehicle according to the invention) 10 with a cooling system according to the invention.

[0032] The cooling system comprises a main cooling circuit 12, into which an ambient heat exchanger (main radiator) 14, an electrically driven (main) coolant pump 16, and two components that require cooling at least temporarily during operation of the vehicle 10 are integrated: specifically, an electric drive motor 18 and associated power electronics 20. The functional components integrated into the main cooling circuit 12 are connected to each other by means of appropriate coolant lines.

[0033] The main coolant pump 16 can pump coolant (cooling fluid) into the main cooling circuit 12 as needed. This allows the coolant to flow sequentially through the power electronics 20 and then the drive motor 18, or through cooling channels (not shown) associated with these components. During this process, heat energy is transferred from the components to be cooled, i.e., the drive motor 18 and the power electronics 20, to the coolant. The coolant then flows through the main radiator 14, transferring heat energy from the coolant to the ambient air flowing through and around the main radiator 14. This coolant is thus recooled, allowing it to absorb heat energy again when it flows through the cooling channels of the power electronics 20 and the drive motor 18, without causing a permanent temperature increase in the coolant.

[0034] The coolant in the cooling system can exhibit temperatures within a relatively wide range during operation. After a cold start of the vehicle 10, the coolant temperature may correspond to the ambient temperature, which is already subject to considerable fluctuations and can be well below freezing. During operation of the cooling system after such a cold start, the coolant flowing in the main cooling circuit 12 warms up as a result of heat energy transfer from the components to be cooled, until a defined operating temperature range is reached. This operating temperature range can be defined, for example, for the coolant of the main cooling circuit 12 of the cooling system according to the Fig.1, in which only components of an electric powertrain of the vehicle requiring cooling are integrated, is around 70°C. If, alternatively or additionally, a drive motor in the form of an internal combustion engine were integrated into the main cooling circuit 12, the operating temperature range for the coolant flowing in the main cooling circuit 12 could be significantly higher.

[0035] Due to the relatively large temperature range of the coolant, it expands to a correspondingly large extent during use. To compensate for this expansion, the cooling system also includes an expansion tank 22, which is connected to the main cooling circuit 12 via an expansion line 24. The expansion tank 22 is partially filled with the coolant and partially with a gas, in particular air. The considerable compressibility of this gas allows different coolant levels to be established in the expansion tank 22, depending on the respective expansion of the coolant.

[0036] A first check valve 26 is integrated into the expansion line 24, which also allows for venting of the main cooling circuit 12. This check valve closes when there is a negative pressure on the side of the main cooling circuit 12, thereby preventing unwanted backflow of coolant from an auxiliary cooling circuit 28, which integrates the expansion tank 22, into the main cooling circuit 12. However, such backflow is enabled as needed by means of a valve device 30 in the form of a proportional valve 30, by setting the proportional valve 30 to a corresponding opening position.

[0037] The auxiliary cooling circuit includes (in the appropriate order with respect to the intended flow direction of the coolant in the auxiliary cooling circuit 28) in addition to the expansion tank 22 serving as coolant reservoir 22 and the proportional valve 30, a second check valve 32, an electrically driven auxiliary coolant pump 34 and an auxiliary cooler 36 designed as an ambient heat exchanger.

[0038] The auxiliary coolant pump 34 can circulate coolant in the auxiliary cooling circuit 28. As the coolant flows through the auxiliary cooler 36, which is designed as an ambient heat exchanger, it is cooled by the transfer of thermal energy to the ambient air flowing through and around the auxiliary cooler 36. This allows the coolant flowing in the auxiliary cooling circuit 28 to reach a temperature significantly lower than that in the main cooling circuit 12. This is particularly true because the auxiliary cooling circuit 28 does not contain any functional component that would introduce a significant amount of thermal energy into the coolant there.

[0039] The cooling capacity of the main cooling circuit 12 can be designed, in particular, to maintain the operating temperature range for the coolant, even during continuous operation of the drive motor 18 (and the power electronics 20) at a defined continuous rated power. However, temporary overload operation may be permitted for the electric drive motor 18 and thus also for the power electronics 20, in which the drive motor 18 provides a drive power significantly exceeding its continuous rated power. During such overload operation, a significantly increased thermal power is introduced into the coolant flowing in the main cooling circuit 12 by means of the drive motor 18 and the power electronics 20, which cannot be immediately and completely dissipated to the ambient air in the main cooler 14.This therefore results in an increase in the temperature of the coolant in the main cooling circuit 12, which in turn leads to a poorer cooling performance for the drive motor 18 and the power electronics 20.

[0040] To react quickly to such an increased thermal load introduced into the coolant flowing in the main cooling circuit 12, the proportional valve 30 is controlled by a central control device (engine control) 40 such that it establishes a fluid-conducting connection between the main cooling circuit 12 and the auxiliary cooling circuit 28 to a variable extent. This allows relatively cold coolant to flow from the auxiliary cooling circuit 28, and in particular from the expansion tank 22, into the main cooling circuit 12 (due to an overpressure generated by the auxiliary coolant pump 34 compared to the coolant pressure in the main cooling circuit 12). Simultaneously, relatively hot coolant is displaced into the auxiliary cooling circuit 28 via the expansion line 24 and the first check valve 26 integrated therein, which then opens.In this way, the average temperature of the coolant flowing in the main cooling circuit 12 can be lowered relatively quickly, and consequently the cooling capacity for the drive motor 18 and the power electronics 20 can be increased. This makes it possible to operate the drive motor 18 under overload for a relatively long time before a thermal limit is reached and the overload operation has to be terminated.

[0041] The relatively hot coolant displaced via the equalization line 24 into the auxiliary cooling circuit 28 temporarily increases the average temperature of the coolant flowing in the auxiliary cooling circuit 28. This temperature increase can then be reversed by heat transfer from the coolant to the ambient air in the auxiliary cooler 36, so that a correspondingly cold coolant is available again for the subsequent introduction of coolant from the auxiliary cooling circuit 28 into the main cooling circuit 12.

[0042] Since the expansion tank 22 also serves to store or temporarily hold relatively cold coolant, it is provided with an insulating layer 38 to thermally insulate the coolant contained therein from the environment. This minimizes the transfer of heat energy from the environment into the coolant contained in the expansion tank 22 when the coolant temperature is below the ambient temperature. Such thermal insulation can be particularly advantageous when the motor vehicle 10 is regularly used at high ambient temperatures. REFERENCE MARK LIST 10 motor vehicle 12 Main cooling circuit 14 Ambient heat exchangers / Main coolers 16 (Main) coolant pump 18 Drive motor 20 Power Electronics 22 Expansion tank / coolant reservoir 24 compensating line 26 first check valve 28 Additional cooling circuit 30 Valve device / Proportional valve 32 second check valve 34 Auxiliary coolant pump 36 Ambient heat exchangers / additional coolers 38 Insulation layer 40 Control device

Claims

Cooling system for a motor vehicle (10) with a main cooling circuit (12) in which at least one coolant pump (16) for conveying coolant in the main cooling circuit (12), a component to be cooled and an ambient heat exchanger (14) are integrated, characterized by a coolant reservoir (22) which can be connected to the main cooling circuit (12) as required by means of a valve device (30) in a fluid-conducting manner, wherein a cooling device for cooling the coolant contained therein is assigned to the coolant reservoir (22). Cooling system according to claim 1, characterized by a control device (40) which is designed such that it temporarily connects the coolant reservoir (22) to the main cooling circuit (12) when there is an increased cooling capacity requirement for the component to be cooled. Cooling system according to claim 1 or 2, characterized in that the main cooling circuit (12) comprises a drive motor (18) and / or power electronics (20) and / or a battery as a component to be cooled. Cooling system according to claim 3, characterized in that the drive motor (18) is an electric drive motor (18). Cooling system according to claim 2 and according to claim 3 or 4, characterized in that the control device (40) changes a limit value for an overload operation of the drive motor (18) and / or the power electronics (20) and / or the battery depending on the extent of the presence or absence of a fluid-conducting connection of the coolant reservoir (22) with the main cooling circuit (12) and / or depending on the absolute or relative temperature of the coolant in the coolant reservoir (22). Cooling system according to one of the preceding claims, characterized in that the cooling device comprises an additional cooling circuit (28) comprising the coolant reservoir (22) as well as an additional cooler (36) and / or an additional coolant pump (34). Cooling system according to one of the preceding claims, characterized in that the cooling device comprises an ambient heat exchanger (36) and / or a refrigeration machine. Cooling system according to one of the preceding claims, characterized in that the coolant reservoir (22) is also an expansion tank (22) for the main cooling circuit (12). Cooling system according to one of the preceding claims, characterized in that the coolant reservoir (22) is designed to be thermally insulating from the environment. Motor vehicle (10) with a cooling system according to one of the preceding claims.

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