Electric vehicle and methods for operating the electric vehicle

Abstract

The invention relates to a method for operating an electric vehicle (100), which comprises a coolant circuit (102) through which coolant flows, in which at least one component (104) for the drive of the electric vehicle (100) and an evaporator-heat exchanger unit (106) are fluid-mechanically integrated, wherein the evaporator-heat exchanger unit (106) is fluid-mechanically connectable or connected to a tank (108) for cryogenic coolant, comprising the steps: - Detecting an extreme operating situation or an impending extreme operating situation of the electric vehicle (100) that necessitates a temperature-induced power limitation of the constituent (104) or a temperature-induced power reduction of the constituent (104), and - Evaporation of the cryogenic coolant in the evaporator-heat exchanger unit (106) to maintain or reduce the temperature of the coolant in the coolant circuit (102) below a threshold value, so that the power limitation or power reduction of the constituent (104) is suppressed, wherein an impending extreme operating mode is predictively determined and the predictive determination is carried out using data on operating history and / or navigation data and / or weather data and / or environmental data. The invention also relates to an electric vehicle (100) for carrying out the method.

Description

[0001] The invention relates to a method for operating an electric vehicle, which comprises a coolant circuit through which coolant flows, in which at least one component for the drive of the electric vehicle and an evaporator-heat exchanger unit are fluid-mechanically integrated, wherein the evaporator-heat exchanger unit can be fluid-mechanically connected to or is connected to a tank for cryogenic coolant. The invention also relates to an electric vehicle for carrying out the method.

[0002] The use of a cryogenic coolant, such as nitrogen, in vehicles for cooling is known, for example, from German patent applications CN 201 729 046 U and CN 202 156 263 U. In this process, liquid nitrogen flows through a heat exchanger so that either the interior or housing components can be cooled via this heat exchanger. Furthermore, German patent application DE 10 2012 104 520 A1 describes the possibility of integrating a nitrogen-flushed heat exchanger into the conventional coolant circuit of a vehicle to lower the coolant temperature in extreme operating conditions.

[0003] In the publications DE 10 2012 104 520 A1 and DE 10 2008 002 103 A1, a motor vehicle is described in which the electrical energy storage can be cooled down significantly in an extreme operating situation using a cryogenic coolant.

[0004] Due to thermal limitations, the power output of electric motors in electric vehicles is restricted, preventing them from reaching their full potential under high load. This occurs whenever the cooling capacity for the drive system's components is insufficient to prevent damage. The powertrain, particularly the power electronics and the battery of the electric vehicle, is limited to defined maximum temperatures. Such thermal issues arise especially during driving under extreme conditions, such as on racetracks, steep off-road sections, or sustained high speeds. Acceleration phases also present extreme conditions, generating increased heat that must be dissipated, a process that is also limited.

[0005] The object of the present invention is to provide a method for operating an electric vehicle and a corresponding electric vehicle in which performance derating of individual components of the drive can be effectively avoided or delayed.

[0006] This problem is solved by a method having the features of claim 1 and by an electric vehicle having the features of claim 10. Advantageous embodiments with expedient further developments are specified in the dependent claims.

[0007] The inventive method for operating an electric vehicle, which comprises a coolant circuit through which coolant flows, in which at least one component for the drive of the electric vehicle and an evaporator-heat exchanger unit are fluid-mechanically integrated, wherein the evaporator-heat exchanger unit can be fluid-mechanically connected or is connected to a tank for cryogenic coolant, comprises in particular the following steps: - Detecting an extreme operating situation or an impending extreme operating situation of the electric vehicle that necessitates a temperature-induced power limitation of the constituent or a temperature-induced power reduction of the constituent, and - Evaporation of the cryogenic coolant in the evaporator-heat exchanger unit to maintain or reduce the coolant temperature in the coolant circuit below a threshold, thus suppressing the power limitation or power reduction of the constituent.

[0008] In this way, a technical system is created in which cryogenic coolant, in particular liquid nitrogen, is used to temporarily increase the system cooling capacity of electric vehicles, thus achieving a corresponding "cooling boost." This increases the performance of electric vehicles under extreme conditions, and performance degradation, i.e., derating, either does not occur at all or is significantly delayed compared to normal conditions.

[0009] Liquid nitrogen has proven particularly advantageous as a cryogenic coolant due to its extremely low operating temperature, making it ideal for high-performance applications. The evaporation of nitrogen allows for the rapid dissipation of a large amount of heat, especially since the liquid-to-gas phase transition also results in additional evaporative cooling.

[0010] It has proven advantageous to introduce only a predefined quantity of cryogenic refrigerant into the evaporator-heat exchanger unit upon detection of an extreme operating situation or an impending extreme operating situation, and to discharge the cryogenic refrigerant from the evaporator-heat exchanger unit only after it has completely evaporated. This ensures that the cryogenic refrigerant is not consumed unnecessarily and that its maximum possible cooling capacity within the evaporator-heat exchanger unit is utilized. In other words, the cryogenic refrigerant can remain in the evaporator-heat exchanger unit as long as it can contribute to cooling before being discharged.

[0011] Should increased cooling capacity be required, it is advisable to introduce additional cryogenic refrigerant intermittently or continuously into the evaporator-heat exchanger unit when a sustained extreme operating situation is detected. While this increases nitrogen consumption, it can ensure the necessary cooling in the refrigerant circuit, thus preventing derating and therefore avoiding any capacity limitation or reduction in the refrigerant's performance.

[0012] If an extreme operating situation or an impending extreme operating situation is detected, then an inlet valve is preferably opened to introduce the liquid cryogenic coolant into the evaporator heat exchanger unit. This inlet valve is integrated into a supply line running from the tank to the evaporator heat exchanger unit.

[0013] The tank for the cryogenic coolant, particularly the nitrogen tank, is preferably a specially insulated tank integrated into the vehicle. However, it is also possible for this tank to be designed to be replaceable. The tank is thermally insulated to maintain the cryogenic liquid coolant at extremely low temperatures and prevent unwanted evaporation. The tank is also robust enough to withstand the pressure of the cryogenic coolant.

[0014] The inlet valve, for example, is a solenoid valve, whereby the cryogenic refrigerant automatically flows into the evaporator-heat exchanger unit when the inlet valve is open, because a sufficiently high pressure of the cryogenic refrigerant prevails in the tank. The supply line is therefore designed without a pump.

[0015] If the cryogenic coolant in the evaporator-heat exchanger unit has completely evaporated, it is advantageous if an outlet valve is opened to discharge the cryogenic coolant, which is in particular exclusively gaseous, from the evaporator-heat exchanger unit. This outlet valve is integrated into an outlet line running from the evaporator-heat exchanger unit to an outlet to the vehicle environment.

[0016] Here too, the outlet valve is preferably designed as a solenoid valve, and the outlet line is also pump-free. The pressure of the evaporated cryogenic coolant is high enough to allow it to be released into the environment. If the cryogenic coolant is nitrogen, it can be released into the environment without concern, as the air surrounding the electric vehicle already contains a high proportion of nitrogen.

[0017] To achieve intelligent control of the additional cooling capacity, the invention provides for the predictive determination of an impending extreme operating mode. This allows for early intervention in response to potential performance derating of the components of the electric vehicle's powertrain, thus preventing the need for performance derating altogether.

[0018] In this context, it is provided according to the invention that the predictive determination of the extreme operating mode is determined on the basis of data on the operating history and / or on the basis of navigation data and / or on the basis of weather data and / or on the basis of other environmental data, for example of upcoming road sections, the vehicle inclination or the like.

[0019] The inventive method can also create a thermal power reserve, namely when the temperature in the coolant circuit is lowered before the extreme operating mode is reached; thus, heat is extracted from the coolant in the cooling circuit by the cryogenic coolant prematurely, so that a later power limitation or reduction of the constituents in the coolant circuit is prevented.

[0020] It is advantageous if the system does not always check for the presence of extreme operating situations, thus allowing users to activate monitoring by pressing a selector switch. In this context, monitoring for extreme or impending extreme operating situations can therefore only occur when a predefined driving profile is selected, provided that at least one of the available driving profiles does not require this monitoring. Examples of driving profiles used for monitoring include "Offroad" or "Race".

[0021] The control system can be intelligently designed to automatically introduce cryogenic refrigerant into the evaporator-heat exchanger unit for additional cooling when necessary. In non-extreme situations, the control system does not initiate any additional cooling.

[0022] The advantages, advantageous embodiments, and effects described in connection with the method according to the invention also apply equally to the electric vehicle according to the invention. The electric vehicle comprises a control unit configured to execute the method described above – in all previously described embodiments.

[0023] The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the figure description and / or shown in the figure alone, can be used not only in the combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments that are not explicitly shown or explained in the figure, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention.

[0024] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the drawing. The drawing shows: Fig. 1 A schematic view of an electric vehicle for carrying out the method according to the invention, wherein the lines for the flow of fluids are shown as solid lines, and wherein communication links are shown as dotted lines.

[0025] In the Fig.Figure 1 schematically shows an electric vehicle 100, which is formed by a coolant circuit 102. A component 104 for the propulsion of the electric vehicle 100 is fluidly integrated into this coolant circuit 102. The component 104 is, for example, an electric motor, a battery pack, or the like. To determine the temperature of the coolant within the coolant circuit 102, a temperature sensor 122 is located upstream of the component 104. It should be noted, however, that the component 104 itself may also have a corresponding temperature sensor. In any case, a sensor signal for the temperature in the coolant circuit 102 is provided to a control unit 120, which is also present, via a communication link. A substantially conventional circulation pump 124 is located in the coolant circuit 102 to circulate the coolant flowing within it.

[0026] Upstream of component 104, an evaporator-heat exchanger unit 106 is integrated into the coolant line of the coolant circuit 102. This unit is fluid-mechanically connected to, or can be connected to, a tank 108 for cryogenic coolant, in this case nitrogen. To supply the nitrogen from the tank 108 to the evaporator-heat exchanger unit 106, a supply line 112 is provided, into which an inlet valve 110, designed as a solenoid valve, is integrated. The control unit 120 is also in communication communication with this inlet valve 110. Downstream of the evaporator-heat exchanger unit 106, an outlet line 118 is provided, into which an outlet valve 114, also designed as a solenoid valve, is integrated. This outlet valve is also in communication communication with the control unit 120.The outlet line 118 leads to the environment, so that an outlet 116 of the outlet line 118 releases evaporated nitrogen into the environment of the electric vehicle 100. With this design, it is possible for heat to be extracted from the conventional coolant in the coolant circuit 102 as needed by means of the cryogenic coolant in the evaporator-heat exchanger unit 106.

[0027] The control unit 120 of the electric vehicle 100 is configured to detect an extreme operating situation or an impending extreme operating situation of the electric vehicle 100, which would necessitate a temperature-induced power limitation of the constituent 104 or a temperature-induced power reduction of the constituent 104.

[0028] If such an extreme operating situation is detected or is imminent, the control unit 120 opens the inlet valve 110, allowing cryogenic refrigerant to flow from tank 108 into the evaporator-heat exchanger unit 106. The control unit 120 ensures that the outlet valve 114 remains closed. Once a predefined quantity of cryogenic refrigerant is present in the evaporator-heat exchanger unit 106, the control unit 120 closes the inlet valve 110 again. The initially liquid cryogenic refrigerant then evaporates within the evaporator-heat exchanger unit 106, thereby cooling – also through evaporative cooling – the refrigerant flowing in the coolant circuit 102.Due to the reduction of the coolant temperature in the coolant circuit 102 below a predefined threshold or due to keeping it below this threshold, the control unit 120 then suppresses the power limitation or the power reduction of the component.

[0029] To prevent unnecessary consumption of the cryogenic coolant, the outlet valve 114 is only opened once the cryogenic coolant has completely transitioned into the gas phase within the evaporator-heat exchanger unit 106, as it can then be safely released into the vehicle environment via the outlet 116. If increased cooling capacity is required, for example, during a sustained extreme operating situation, cryogenic coolant can be supplied to the evaporator-heat exchanger unit 106 in pulsed or continuous increments.

[0030] The control unit 120 can also be configured to predictively determine an impending extreme operating mode, whereby this determination is made, for example, based on operating history data and / or navigation data and / or weather data and / or environmental data. In this way, it is also possible for the temperature of the coolant in the coolant circuit 102 to be lowered by means of the cryogenic coolant even before the extreme operating mode occurs, thus creating a thermal power reserve to suppress a subsequent power limitation or a subsequent power reduction of the component 104.

[0031] The present invention therefore offers the advantage that electric vehicles can be operated at full power even when they would normally require power derating. This provides increased safety, for example during off-road driving, improved continuous load performance, and increased efficiency of the electric vehicle. REFERENCE MARK LIST: 100 electric vehicles 102 Coolant circuit 104 Constituent (e.g. electric motor, battery etc.) 106 Evaporator heat exchanger unit 108 Tank 110 Inlet valve (e.g. solenoid valve) 112 Supply line 114 Exhaust valve (e.g. solenoid valve) 116 Outlet (surroundings) 118 Outlet pipe 120 control unit 122 Temperature sensor 124 Circulating pump

Claims

[1] Method for operating an electric vehicle (100) comprising a coolant circuit (102) through which coolant flows, in which at least one constituent (104) for the propulsion of the electric vehicle (100) and an evaporator-heat exchanger unit (106) are fluid-mechanically integrated, wherein the evaporator-heat exchanger unit (106) is fluid-mechanically connectable or connected to a tank (108) for cryogenic coolant, comprising the steps: - Detecting an extreme operating situation or an impending extreme operating situation of the electric vehicle (100) that necessitates a temperature-induced power limitation of the constituent (104) or a temperature-induced power reduction of the constituent (104), and - Evaporation of the cryogenic coolant in the evaporator-heat exchanger unit (106) to maintain or reduce the temperature of the coolant in the coolant circuit (102) below a threshold value, so that the power limitation or power reduction of the constituent (104) is suppressed, characterized by , that an impending extreme operating mode is predictively determined, and that the predictive determination is made using operational history data and / or navigation data and / or weather data and / or environmental data. [2] Method according to claim 1, characterized by, that when the extreme operating situation or an impending extreme operating situation is detected, only a predefined amount of the cryogenic coolant is introduced into the evaporator heat exchanger unit (106), and that the cryogenic coolant is only discharged from the evaporator heat exchanger unit (106) when the cryogenic coolant in it has completely evaporated. [3] Method according to claim 1 or 2, characterized by , that when a sustained extreme operating situation is detected, additional cryogenic coolant is introduced into the evaporator heat exchanger unit (106) in a pulsed or continuous manner. [4] Method according to any one of claims 1 to 3, characterized by , that an inlet valve (110) is opened to introduce the liquid cryogenic coolant into the evaporator heat exchanger unit (106), which is integrated into a supply line (112) running from the tank (108) to the evaporator heat exchanger unit (106). [5] Method according to any one of claims 1 to 4, characterized by , that for the purpose of draining the cryogenic coolant from the evaporator heat exchanger unit (106) an outlet valve (114) is opened, which is integrated into an outlet line (118) running from the evaporator heat exchanger unit (106) to an outlet (116) to the vehicle environment. [6] Method according to any one of claims 1 to 5, characterized by , that the temperature in the coolant circuit (102) is reduced in time before the onset of the extreme operating mode. [7] Method according to any one of claims 1 to 6, characterized by , that monitoring for extreme operating situations or for an impending extreme operating situation only takes place if a predefined driving profile is set. [8] Electric vehicle (100) with a coolant circuit (102) through which coolant flows, wherein at least one constituent (104) for the drive of the electric vehicle (100) and an evaporator-heat exchanger unit (106) are fluid-mechanically integrated into the coolant circuit (102), and wherein the evaporator-heat exchanger unit (106) is fluid-mechanically connectable to or connected with a tank (108) for cryogenic coolant, and with a control unit (120) which is configured to carry out the method according to any one of claims 1 to 7.

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