Cooling system with at least one displacement pump and vehicle with the cooling system

Abstract

A cooling system 2 for an electric or hybrid vehicle 1 is proposed, comprising at least one coolant circuit 3 for temperature control of at least one drive component 5, 6, 7 and / or a vehicle cabin 8 of the vehicle 1, wherein a coolant pump 10 is provided in the coolant circuit 3 for conveying a coolant through the coolant circuit 3, wherein the coolant pump 10 is designed as a positive displacement pump 11.

Description

The invention relates to a cooling system for an electric or hybrid vehicle with the features of the preamble of claim 1. The invention further relates to a vehicle with the cooling system. Purely electric or hybrid vehicles with one or more electric motors are known, which are supplied with electrical energy from an energy storage device, in particular a traction battery, via power electronics. In this process, heat energy is generated at the high-voltage components of the power electronics, the energy storage device, and the electric motor, which is dissipated via one or more cooling circuits. The publication DE 10 2021 132 679 A1 discloses a BEV with a thermal management system, comprising an external coolant circuit with a coupling heat exchanger and a radiator for heat dissipation to the environment as well as an electric motor for propulsion, and comprising an internal coolant circuit with a traction battery and an interior heat exchanger, wherein a 4-way valve and a 3-way valve connect the internal coolant circuit to the external coolant circuit. A cooling system is also known from document CN 102 452 310 A. Pump arrangements are known from documents CH 581 265 A5 and DE 101 53 185 A1. The invention aims to create a cooling system of the type mentioned above, which is characterized by a compact design and reliable cooling. This problem is solved according to the invention by a cooling system with the features of claim 1 and an electric or hybrid vehicle with the features of claim 12. Advantageous embodiments will become apparent from the dependent claims, the drawings and / or the description. The invention relates to a cooling system designed and / or suitable for an electric or hybrid vehicle. In particular, the cooling system serves to regulate the temperature of temperature-critical drive components of the vehicle's powertrain. Alternatively or optionally, the cooling system also serves to regulate the temperature of the vehicle's cabin. For this purpose, the cooling system comprises at least one coolant circuit, which is designed and / or suitable for regulating the temperature of at least one drive component of the vehicle and / or the vehicle cabin. In particular, the coolant circuit is operatively connected to the drive component and / or the vehicle cabin in such a way that heat can be dissipated via the coolant circuit for cooling and / or supplied via the coolant circuit for heating. In other words, regulation within the meaning of the invention is to be understood as heating and / or cooling.In other words, the at least one drive component and / or the vehicle cabin is heated, cooled, or kept at a constant temperature during temperature control. The coolant circuit can be used directly for temperature control of the at least one drive component and / or the vehicle cabin. Alternatively, the coolant circuit can also be thermally coupled indirectly via another coolant or oil circuit for temperature control of the drive component and / or another coolant or refrigerant circuit for temperature control of the vehicle cabin. Specifically, the waste heat from at least one drive component can be used via the coolant circuit to temperature control another drive component and / or the vehicle cabin. A coolant pump is provided in the coolant circuit, which is designed and / or suitable for circulating a coolant through the circuit. Preferably, the coolant is a water-based coolant. The coolant pump can be electrically operated. Preferably, the cooling system includes a control unit designed to control and / or regulate the coolant pump as needed. Preferably, the cooling system includes at least one or exactly one sensing unit for detecting an operating parameter, in particular a temperature, of the drive component and / or the vehicle cabin, wherein the control unit is designed to control and / or regulate the coolant pump based on the operating parameter. Within the scope of the invention, it is proposed that the coolant pump be designed as a positive displacement pump. Specifically, a positive displacement pump is understood to be a pump that operates on the principle of volume displacement. For this reason, positive displacement pumps are also referred to as volumetric pumps. The positive displacement pump draws in a limited quantity of coolant and transfers it from a suction side to a discharge side. In other words, the coolant is drawn in on the suction side by a vacuum and forced out or displaced on the discharge side by pressure. In particular, the positive displacement pump is designed to generate an at least approximately constant volume flow rate, independent of the pressure, and / or to deliver a volume flow rate proportional to the rotational speed. The invention is based on the understanding that centrifugal pumps are typically used in vehicle cooling circuits. To ensure coolant circulation by a centrifugal pump, the pipe cross-sections must be correspondingly large to minimize pressure drop. This leads to larger fill volumes and thus increased weight and installation space requirements. Furthermore, the volumetric efficiency of the centrifugal pump decreases disproportionately with increasing pressure until the surge line is reached and the efficiency is 0%, meaning the flow rate ceases. A compromise must therefore be found between flow rate and pressure requirement. This is particularly complex and involves limitations when different components to be cooled are integrated. Often, an additional "booster" pump must also be installed to ensure coolant delivery even at high flow rates. The advantage of the invention lies in the fact that, by using a positive displacement pump, the pipe cross-sections can be reduced compared to conventional cooling systems with centrifugal pumps, thereby reducing the coolant circuit fill volume by up to 40%. For example, this can be achieved by using a reduced pipe diameter of less than 14 mm, preferably less than 13 mm, instead of a conventional pipe diameter of 16 mm. Although this increases the pressure loss disproportionately, the absolute power requirement is generally negligible under 99% operating conditions, since the pressure losses are low in absolute terms due to the low flow rates. The use of positive displacement pumps also allows for a higher pressure differential at the pump, thus ensuring a high flow rate through higher pressure. If high flow rates are required, for example, to...To ensure sufficient cooling capacity for the components, the power requirement increases significantly; however, the time spent in these operating states is often negligible. With positive displacement pumps, the flow rate is almost proportional to the rotational speed, so different resistances only result in corresponding pressure level differences. In one specific embodiment, the coolant pumped by the positive displacement pump is a water-glycol mixture. In other words, a mixture of water and glycol, preferably ethylene glycol, is used as the coolant. To prevent overheating and wear of the positive displacement pump, the coolant must have a certain lubricating effect. The use of glycol, particularly ethylene glycol, significantly improves the lubricating properties of the coolant and, furthermore, prevents the coolant circuit from freezing at low ambient temperatures and during periods of vehicle inactivity. In a more detailed specification, the water-glycol mixture is designed to contain at least 50% water by volume and / or at least 50% glycol by volume. Preferably, the water-glycol mixture contains less than 50% water by volume and / or more than 50% glycol by volume. Put simply, the proportion of glycol is greater than or equal to the proportion of water. This design proposes a coolant with sufficient lubricating properties for pumping by a positive displacement pump. Furthermore, it is provided that at least one pressure relief valve is included in the coolant circuit to limit the fluid pressure generated on the pressure side of the positive displacement pump, taking into account the pressure-bearing capacity of individual components located on that side. In particular, the pressure relief valve is designed to automatically throttle and / or regulate the flow rate on the pressure side depending on the fluid pressure. Preferably, the pressure relief valve is located on the pressure side, i.e., downstream of the positive displacement pump. The pressure relief valve can be designed as a passive, particularly pressure-controlled, valve. For example, the pressure relief valve can be a ball valve, plate valve, or cone valve, with or without spring actuation. Specifically, the pressure relief valve is located upstream of the most pressure-sensitive component.Alternatively or optionally, each pressure-sensitive component is assigned a separate pressure relief valve. Alternatively or optionally, the most pressure-sensitive component is positioned at the end of the coolant circuit for optimal flow. When using a positive displacement pump, the fluid pressure on the pressure side must be limited, taking into account the pressure-bearing capacity of one or more pressure-sensitive components of the cooling circuit, such as heat exchangers. A pressure relief valve allows for easy limitation or adjustment of the maximum pressure on the pressure side. Furthermore, the design stipulates that at least one pressure relief valve is fluidically connected to the suction side of the positive displacement pump via a pressure relief line. In other words, the pressure relief line serves to return excess coolant from the pressure side to the suction side. In principle, the pressure relief line could be directly connected to a suction line of the coolant circuit. However, in this case, the pressure relief line is indirectly connected to the suction line of the coolant circuit via an expansion tank. This ensures a sufficient quantity of coolant on the suction side and thus adequate lubrication of the positive displacement pump. Put simply, this prevents the positive displacement pump from running dry. In a further specification, it is provided that an expansion tank is included in the coolant circuit. This tank is fluidically connected to the suction side of the positive displacement pump via an expansion line, with the pressure relief line opening into the expansion tank. The expansion tank serves, in particular, to compensate for volume fluctuations of the coolant circulating in the cooling circuit. Specifically, several, preferably all, pressure relief lines from the pressure relief valves in the coolant circuit open into the expansion tank. The expansion tank can optionally be designed as an open container, for example, a tray, or a closed container, for example, a tank. This ensures a continuous coolant supply to the positive displacement pump and easily compensates for volume fluctuations. In a further specific embodiment, the positive displacement pump has a pump housing with a suction-side inlet and a pressure-side outlet, in which at least one displacement element is arranged, wherein the pump housing and / or the displacement element has a self-lubricating material at least in one contact area. A displacement element is defined as the part of the positive displacement pump that is moved, preferably rotated, within the pump housing to displace or pump the coolant. The contact area is defined as the area in which the displacement element is in mechanical contact with the pump housing and / or several, preferably two, displacement elements are in mechanical contact with each other. In principle, a self-lubricating material can be either a material with a low coefficient of friction, such as ceramic, or a material with an embedded solid lubricant, such as...B. graphite. The pump housing and / or the displacement body can be made of or coated with the self-lubricating material. Due to insufficient lubrication by the coolant, the positive displacement pump can be subject to overheating and excessive wear at higher speeds, especially under full load, which can lead to damage. Self-lubrication of the components in the contact area can reduce wear, particularly under full load, and improve friction, thus increasing pump efficiency. This can result in a longer pump service life. In a specific implementation, the positive displacement pump is designed as either a gear pump or a vane pump. In particular, a positive displacement pump designed as a gear pump has two displacement elements designed as gears. Preferably, the gear pump is designed as an external gear pump, an internal gear pump (also called a crescent-shaped pump), or a ring gear pump (also called a gerotor pump). Gear pumps are preferably characterized by a uniform coolant flow rate and a cost-effective and robust design. In particular, a positive displacement pump designed as a vane pump (also called a rotary vane pump) has a displacement element designed as a rotor, which is arranged eccentrically in the pump housing and has one or more radially displaceable rotary vanes. Vane pumps are preferably characterized by low flow rate pulsation and a cost-effective design. In a specific implementation, the at least one drive component requiring temperature control is thermally coupled to the coolant circuit. Specifically, the drive component can be thermally connected to the coolant circuit via a heat exchanger integrated within the circuit. Alternatively, the drive component can also be directly cooled by the coolant flowing through or around it. For this purpose, the drive component can have one or more cooling channels for the coolant. This allows for a particularly simple and space-saving cooling solution for the drive component. In a specific embodiment, the drive component is designed as an electronic unit, preferably power electronics and / or charging electronics, and / or a drive unit, preferably a drive motor and / or a transmission, and / or an energy storage device of the electric vehicle. In particular, the power electronics transfer the traction energy from the energy storage device, especially a traction battery, to the drive motor, converting the current from direct current to alternating current. Preferably, the drive motor is designed as an electric motor and the transmission as a reduction gear. Particularly preferably, the cooling circuit is designed as a drive cooling circuit, which is configured to dissipate the waste heat generated during operation and charging in the mechanical and electronic drive components of the powertrain.By connecting one or more of the drive components to the coolant circuit, efficient cooling and / or heating can be implemented. In a further development, it is provided that at least one temperature control unit is present in the coolant circuit, which is designed and / or suitable for temperature control of the drive component and / or the vehicle cabin. In particular, the temperature control unit is designed as a heat pump or an air conditioning system. Preferably, the temperature control unit has a refrigerant circuit which is thermally coupled to the coolant circuit, preferably via a heat exchanger. In particular, waste heat from the coolant circuit can be used by the temperature control unit for temperature control. Optionally, the temperature control unit can be used to support heat dissipation from the drive components. For example, the coolant circuit can be thermally coupled to an evaporator and / or condenser of the heat pump or the air conditioning system. This allows the thermal energy of the coolant circuit to be efficiently used by the temperature control unit to temperature control the vehicle cabin or the drive component.one or more drive components are used. In a further embodiment, the cooling system has an additional coolant circuit designed and / or suitable for dissipating heat from the coolant circuit to an external environment. For this purpose, the additional coolant circuit includes a heat sink for heat dissipation to the external environment and an additional coolant pump for circulating the coolant or another coolant through the circuit. The first coolant circuit and the at least one additional coolant circuit are at least thermally coupled. In principle, the two coolant circuits can be fluidically separated. Alternatively, the two coolant circuits can be fluidically connected, so that both coolant circuits contain the same coolant. Preferably, the heat sink is designed as a radiator or cooler.In particular, the cooling system features precisely these two coolant circuits. Optionally, the cooling system may include a further coolant circuit, which is intended for heat dissipation from a lubrication and / or cooling oil system of the transmission and / or an internal combustion engine. In a more detailed design, the additional coolant pump is configured as another positive displacement pump. Preferably, this additional positive displacement pump is identical in design to the positive displacement pump or configured as previously described. Preferably, the coolant pumped by this additional positive displacement pump is a water-glycol mixture. This allows for a reduction in the pipe diameters of the additional cooling circuit, thus saving further installation space and weight. In a further specification, it is provided that the coolant circuit and the secondary coolant circuit are fluidically connected and / or connectable via a multi-way valve to form a thermal management system. In particular, the multi-way valve serves to control the heat flows of the two cooling circuits by directing the fluid flows in different directions or assigning them to different circuits. Preferably, the multi-way valve forms an interface between the coolant circuits, whereby the volume flows of the two coolant circuits can be mixed as required by changing the valve position. In particular, the multi-way valve is designed as a 4-way valve. This proposes a particularly efficient cooling system that can connect the coolant circuits accordingly, depending on the heating or cooling requirements. Another aspect of the invention relates to an electric or hybrid vehicle with the cooling system as previously described. Preferably, the vehicle comprises the drive unit, the electronics unit, and the energy storage device as the drive components, as well as the vehicle cabin. Further features, advantages, and effects of the invention will become apparent from the following description of preferred embodiments. Figure 1 shows a vehicle with two coolant circuits as one embodiment of the invention. Fig. 1 shows a highly schematic representation of a vehicle 1, only schematically indicated, with a cooling system 2 comprising two coolant circuits 3, 4. The vehicle 1 is, for example, designed as an electric vehicle. Vehicle 1 comprises a drive unit 5, including an electric motor, reduction gear, bearings, etc., an electronics unit 6, including an inverter, DC / DC converter, DC-AC converter, etc., and an energy storage device 7, in particular a traction battery, as drive components requiring temperature control. For this purpose, the drive components 5, 6, and 7 are thermally coupled to the coolant circuit 3. Furthermore, the vehicle 1 has a climate-controlled vehicle cabin 8, which is thermally coupled to the coolant circuit 3 via a climate control unit 9. The climate control unit 9 can be designed as a heat exchanger or an air conditioning system with its own refrigerant circuit (not shown). The climate control unit 9 serves to control the temperature of the vehicle cabin 8 and, optionally, to control the temperature of one or more of the drive components 5, 6, 7. Climate control here refers to heating, cooling, or maintaining a constant temperature. The coolant circuit 3 includes a positive displacement pump 10, which is designed to pump coolant within the coolant circuit 3. The positive displacement pump 11 has a pump housing 12 connected to a suction line 13 on the inlet side and to a pressure line 14 on the outlet side, in which at least one displacement element (not shown) is arranged. The displacement element is moved, preferably rotated, within the pump housing 12 to draw the coolant from the suction line 13 by means of a vacuum and to force it into the pressure line 14 by means of pressure. For example, the positive displacement pump can be designed as a gerotor, gear, sickle cell, vane, or impeller pump. The coolant is a water-based fluid, for example, a water-glycol mixture. Depending on the mixing ratio of the water-glycol mixture, the lubricating effect of the coolant, particularly at higher speeds of the positive displacement pump 11, may be insufficient. Therefore, the pump housing 12 and / or the displacement body are made of or coated with a self-lubricating material, at least in one contact area, or the material pairing ensures comparable properties. This reduces friction in the contact area or, in the event of mechanical wear, generates mixed friction through a solid lubricant present in the material. For example, the self-lubricating material could be a ceramic or a graphite-containing plastic. On the pressure side of the positive displacement pump 11, the electronics unit 6, the drive unit 5, the energy storage unit 7, and the temperature control unit 9 are arranged in series in terms of fluid flow and are each thermally coupled to the coolant circuit 3, so that heat is transported away along a flow path by the coolant. For example, the waste heat from the electronics unit 6 and the drive unit 5 can be used to temperature control the energy storage unit 7 and / or from the temperature control unit 9 to temperature control the vehicle cabin 8. Furthermore, the additional coolant circuit 4 includes a heat sink 15 for heat dissipation to the outside environment and another coolant pump 16, designed as a further positive displacement pump 17. The additional coolant circuit 4 serves to dissipate heat from the coolant circuit 3 to the outside environment via the heat sink 15, which is, for example, designed as a radiator. For this purpose, the two coolant circuits 3 and 4 are thermally coupled via a heat exchanger 18 (shown only schematically) or fluidically via a multi-way valve 19 (shown only schematically) to form a thermal management system. In the case of thermal coupling of the two coolant circuits 3 and 4, an additional coolant, preferably a water-glycol mixture, is pumped by the additional positive displacement pump 17 in the additional coolant circuit 4. Alternatively, in the case of fluidically coupled circuits 3 and 4, the two coolant circuits 3 and 4 contain the same coolant.For example, the two positive displacement pumps 11, 17 are of identical construction. The coolant circuits 3, 4 each have at least one pressure relief valve 20a, 20b, 20c, which limits the maximum fluid pressure on the pressure side of the respective positive displacement pump 11, 17. Due to the use of a positive displacement pump 11, 17, high fluid pressures can occur on the pressure side when coolant is required, e.g., during full-load operation. These pressures must be limited, taking into account the pressure-bearing capacity of the drive components 5, 6, 7, the temperature control unit 9, and the heat sink 15. For this purpose, a first pressure relief valve 20a can be assigned to the drive components 5, 6, 7, a second pressure relief valve 20b to the temperature control unit 9, and a third pressure relief valve 20b to the heat sink 15. The fluid pressures can be adjusted independently of each other via these valves according to the pressure-bearing capacity of the individual components. For example, the pressure relief valves 20a, 20b, 20c are each designed as a passive, pressure-controlled valve. The two pressure relief valves 20a, 20b of the coolant circuit 3 are each fluidically connected via a pressure relief line 21a, 21b to an expansion tank 22a, which, to compensate for a coolant volume on the suction side of the positive displacement pump 11, is fluidly connected via a compensation line 23a to the suction line 13a, preferably an intake section. The pressure relief valve 20c of the further coolant circuit 4 is also fluidly connected via a corresponding pressure relief line 21c to a further expansion tank 22b, which, to compensate for a coolant volume on the suction side of the further positive displacement pump 17, is fluidly connected via a further compensation line 23b to a further suction line 13b, preferably an intake section. Reference sign 1 Vehicle 2 Cooling system 3 Coolant circuit 4 Additional coolant circuit 5 Drive unit 6 Electronic unit 7 Energy storage 8 Vehicle cabin 9 Temperature control unit 10 Coolant pump 11 Positive displacement pump 12 Pump housing 13a, b Suction lines 14a, b Pressure lines 15 Heat sink 16 Additional coolant pump 17 Additional positive displacement pump 18 Heat exchanger 19 Multi-way valve 20a-c Pressure relief valves 21a-c Pressure relief lines 22a, b Expansion tank 23a, b Expansion lines

Claims

Cooling system (2) for an electric or hybrid vehicle (1), comprising at least one coolant circuit (3) for temperature control of at least one drive component (5, 6, 7) and / or a vehicle cabin (8) of the vehicle (1), wherein a coolant pump (10) is provided in the coolant circuit (3) for circulating a coolant through the coolant circuit (3), wherein the coolant pump (10) is designed as a positive displacement pump (11), wherein at least one pressure relief valve (15a, 15b) is provided in the coolant circuit (3) to limit a fluid pressure generated on the pressure side of the positive displacement pump (11), taking into account the pressure resistance of individual components of the coolant circuit (3) provided on the pressure side, wherein the at least one pressure relief valve (20a, 20b) is fluidically connected to a suction side of the positive displacement pump (11) via a pressure relief line (21a, 21b), characterized in thatthat an expansion tank (22a) is provided in the coolant circuit (3), which is fluidically connected to the suction side of the positive displacement pump (11) via an expansion line (23a), wherein the overpressure line (21b) opens into the expansion tank (22a). Cooling system (2) according to claim 1, characterized in that the coolant conveyed by the positive displacement pump (11) is a water-glycol mixture. Cooling system (2) according to claim 2, characterized in that the water-glycol mixture has a proportion of at least 50 vol% glycol. Cooling system (2) according to one of the preceding claims, characterized in that the positive displacement pump (11) has a pump housing (12) having a suction-side inlet and a pressure-side outlet, in which at least one rotating displacement body is arranged, wherein the pump housing (12) and / or the displacement body has a self-lubricating material at least in a contact area. Cooling system (2) according to one of the preceding claims, characterized in that the positive displacement pump (11) is designed as a gear pump or a vane pump. Cooling system (2) according to one of the preceding claims, characterized in that the at least one drive component (5, 6, 7) to be tempered is thermally coupled to the coolant circuit (3). Cooling system (2) according to claim 6, characterized in that the drive component (5, 6, 7) is designed as an electronic unit (6) and / or a drive unit (5) and / or an energy storage device (7) of the vehicle (1). Cooling system (2) according to one of the preceding claims, characterized in that the coolant circuit (3) is thermally coupled to a temperature control unit (9) for temperature control of the drive component (5, 6, 7) and / or the vehicle cabin (8). Cooling system (2) according to one of the preceding claims, characterized by a further coolant circuit (4) for discharging heat from the coolant circuit (3) to an external environment, wherein a heat sink (15) for discharging heat to the external environment and a further coolant pump (16) for conveying the coolant or a further coolant through the further coolant circuit (4) are provided in the further coolant circuit (4), wherein the coolant circuit (3) and the further coolant circuit (4) are at least thermally coupled to each other. Cooling system (2) according to claim 9, characterized in that the further coolant pump (16) is designed as a further positive displacement pump (17). Cooling system (2) according to claim 9 or 10, characterized in that the coolant circuit (3) and the further coolant circuit (4) are fluidically connected and / or connectable to each other via a multi-way valve (19) to form a thermal management system. Electric or hybrid vehicle (1) with the cooling system (2) according to one of the preceding claims.

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