Method for controlling a device for the heat management of a motor vehicle, and device therefor

Abstract

The invention relates to a method for controlling a device (1) for the heat management of an electrically operated motor vehicle, in particular for the climate control of the passenger compartment, and to a device (1) with a refrigerant circuit (2) comprising a refrigerant-compressing compressor (5) and at least two heat-supplying heat sources of different temperatures, which can be connected to the refrigerant circuit (2). To increase the overall efficiency of the underlying heat-gaining process, at least one of the heat sources is connected in a temperature-dependent manner to the refrigerant circuit (2) on a timed basis.

Description

[0001] Method for controlling a device for heat management of a motor vehicle and device therefor

[0002] The invention relates to a method for controlling a device for heat management of an electrically operated motor vehicle, in particular for air conditioning its passenger compartment, and to a device having a refrigerant circuit with a compressor compressing a refrigerant and at least two heat sources of different temperatures that provide heat and can be connected to the refrigerant circuit.

[0003] A device and method for heat management of an electrically powered motor vehicle for generating heat from two heat sources, namely an external and an internal coolant circuit, which feeds heat into a refrigerant circuit via a so-called chiller, is known, for example, from document DE 10 2021 132 803 A1. In this case, switching between two coolant circuits within the internal coolant circuit takes place using directional control valves. The refrigerant circuit is fed by a single heat source via the chiller.

[0004] The refrigerant circuit is used, in particular, to air-condition the passenger compartment of a motor vehicle. At low ambient temperatures, the heat required to heat the passenger compartment increases. Due to the high efficiency of the overall system's electric drive, very little waste heat is available. The passenger compartment is therefore heated using electrical energy taken from the battery, for example the traction battery used to power the vehicle by means of at least one electric motor. This generally leads to a reduced range of the vehicle. For efficient air conditioning of the passenger compartment, refrigerant circuits with heat pump systems are often used, which supply heat from at least one heat source to the refrigerant circuit.

[0005] The efficiency of the thermal process underlying the refrigerant circuit describes the ratio of heat output to power input, for example, electrical power. High efficiency is aimed for to achieve high vehicle mileage. A high temperature level of a heat source promotes high efficiency by reducing the power of the refrigerant circuit's compressor and thus its power consumption.

[0006] If the refrigerant circuit has two or more usable heat sources with different temperatures, the refrigerant must be expanded to a pressure level below the lowest temperature of all heat sources in order to be able to extract heat at all using an appropriately adjusted temperature difference. The lowest pressure-temperature level therefore largely determines the required compressor power and thus the efficiency. This means that the potential of the higher-temperature heat sources can only be utilized to a very limited extent. If only the highest-temperature heat source is used, the heat contributions from the lower-temperature heat sources are eliminated.

[0007] The object of the invention is to further develop a method for controlling a device for heat management of an electrically powered motor vehicle, in particular for air conditioning its passenger compartment, and a device for this purpose. In particular, the object of the invention is to utilize at least two heat sources of different temperatures with improved efficiency.

[0008] The object is achieved by the subject matter of claims 1 and 9. The claims dependent on claims 1 and 9 represent advantageous embodiments of the subject matter of claims 1 and 9.

[0009] The proposed method is used to control a thermal management device of an electrically powered motor vehicle, particularly for air conditioning its passenger compartment. For example, an air conditioning unit is provided in the passenger compartment, which has a cooling unit and a heating unit, through which a refrigerant flow flows depending on a temperature setpoint of the passenger compartment set by a driver and / or automatically. Corresponding throttle valves are switched in the refrigerant circuit so that hot, liquefied refrigerant under pressure is present at the heating unit, and cold, expanded refrigerant is present at the cooling unit.

[0010] The refrigerant circuit also contains a compressor that compresses and liquefies the refrigerant, for example an electrically operated compressor, optionally a separator for separating liquid and gaseous refrigerant so that essentially gaseous refrigerant is fed into the compressor, the designated throttle valves, and at least two heat sources of different temperatures that provide heat and can be connected to the refrigerant circuit. Optionally, an internal heat exchanger can be provided between a refrigerant inflow to the compressor and a line with cooled coolant or / or a refrigerant line connected downstream of at least one heat source. The at least two heat sources are switchably connected to the refrigerant circuit by means of heat transfer devices. For example, heat transfer devices can be designed as heat exchangers, evaporators, or the like.For example, heat transfer devices can transfer the heat content of a gaseous, liquid, possibly mixed-phase, or solid heat source to the refrigerant circuit.

[0011] In order to efficiently and without a predetermined structure, in particular the design of the compressor, change at least part of the temperature of the at least two heat sources, which is higher than the temperature of the refrigerant, and thus increase the efficiency of the refrigerant circuit when the temperatures of the at least two heat sources are different, at least one of the heat sources is switched on to the refrigerant circuit at different times. In this way, for example, if the heat content of a single heat source cannot be sufficiently utilized at low outside temperatures, the passenger compartment can still be sufficiently heated. By switching the heat source with the higher temperature at different times, a reduced efficiency of the warmer heat source is avoided due to the state diagram of the refrigerant, as the refrigerant is heated by the two heat sources at different times.It is advantageous here if a limited amount of heat from a heat source with a higher temperature is switched off when it has dropped to a temperature range of a predetermined refrigerant temperature, so that the temperature of the heat source can rise again and the available heat quantity can be redeveloped, resulting in an overall higher efficiency than with continuous extraction of the heat quantities from all heat sources. The cycle times for switching a heat source on and off depend, for example, on the amount of heat available from the heat sources, their temperature, the outside temperature, the heat transfer coefficients of the heat transfer devices, their exchange surfaces, the refrigerant and its isochoric enthalpy available according to the state diagram, particularly during a phase change, the design of the refrigerant circuit, in particular its compressor, and the like.For example, cycle times of a few minutes up to one hour can be advantageous depending on these parameters.

[0012] For example, carbon dioxide, ammonia or organic refrigerants and / or their mixtures can be used as refrigerants.

[0013] The ambient air can be provided as a first heat source, so that its heat is preferably introduced into the refrigerant circuit by means of a heat transfer device provided as a heat exchanger. A coolant circuit containing the motor vehicle's coolant can serve as a second heat source. For example, heat-generating components, for example one or more batteries, such as a traction battery, power electronics for operating at least one electric machine, for example for driving the motor vehicle, a voltage converter for a charging process, a heat transfer device, for example for dissipating heat during suspended heating operation of the passenger compartment, optionally a water-cooled electric machine and / or the like, can be incorporated into the coolant circuit during operation and / or during a charging process.For efficient control of the individual heat flows in the coolant circuit, individual or multiple components can be arranged in individual coolant circuits, through which coolant flows by means of at least one pump and which can be connected and disconnected from one another by means of a selector switch controlled, for example, by a control unit. A heat transfer device designed as a chiller, such as a liquid-to-liquid heat exchanger, is provided in the coolant circuit and integrated into the refrigerant circuit.

[0014] In addition, a third heat source of an additional fluid circuit can be connected directly to the refrigerant circuit or to the coolant circuit depending on the amount of heat available in the fluid circuit. The fluid circuit can be operated with fluid from, for example, a non-aqueous lubricant such as oil, an aqueous emulsion or the like. Heat-generating components such as at least one fluid-cooled electric machine, a transmission between an electric machine and drive wheels of the motor vehicle and / or the like can be arranged in the fluid circuit through which the fluid flows by means of at least one pump. For example, one of the components, in particular the transmission, can be connected to and disconnected from the fluid circuit by means of a preferably continuously switchable valve depending on a temperature of the fluid and / or an outside temperature.

[0015] The third heat source can be switched on directly by means of one of the coolant lines of the second heat source and / or the refrigerant circuit, in particular in a time-controlled manner and depending on a quantity of heat present in the fluid circuit.

[0016] According to an advantageous embodiment of the method, if heating of the passenger compartment is requested up to a predetermined outside temperature, continuous heating is provided exclusively by activating the first heat source, i.e., according to a heat pump function of the refrigerant circuit, preferably without pulsing. If the outside temperature drops below a predetermined value, the first heat source can be switched on continuously and the second heat source can be switched on in a timed manner. Alternatively, if the predetermined outside temperature falls below the predetermined value, the first and second heat sources can be operated alternately in a timed manner. It is understood that if there are three or more heat sources, at least one of the heat sources can be operated in a timed manner at a higher temperature, while the others are also operated in a timed manner or continuously or are switched off.

[0017] The proposed device for carrying out the described method contains at least two heat transfer devices connected in heat exchange with a refrigerant circuit, and a switching device for the chronologically timed activation of at least one of the two heat transfer devices depending on their recoverable heat quantities. For example, one heat transfer device is provided between the ambient air and the refrigerant circuit, and a second heat transfer device is provided between a coolant circuit and the refrigerant circuit. In particular, a third heat transfer device is provided between the coolant circuit and an additional fluid circuit. The third heat transfer device can alternatively be connected directly to the refrigerant circuit.

[0018] The invention is explained in more detail with reference to the exemplary embodiment shown in Figures 1 to 3. These show:

[0019] Figure 1 is a schematic representation of a device with a refrigerant circuit, a coolant circuit and a fluid circuit,

[0020] Figure 2 is a diagram illustrating the function of the device of Figure 1 during continuous operation and

[0021] Figure 3 is a diagram illustrating the function of the device of Figure

[0022] 1 for time-locked operation.

[0023] The device 1 for heat management of an electrically powered motor vehicle is divided into the refrigerant circuit 2, the coolant circuit 3 and the fluid circuit 4.

[0024] The refrigerant circuit 2 is operated using a refrigerant, for example, carbon dioxide. The compressor 5 compresses the refrigerant into a liquid state while heating it. The heated refrigerant is used in the controllable heating unit 6 to heat the passenger compartment, and the refrigerant cools in the process. In the throttle valve 7, the refrigerant is expanded and cooled further. The cooled, partially still liquid refrigerant absorbs heat in the first heat transfer device 8, designed as a heat exchanger 9, which is in heat exchange communication with the ambient air as the first heat source. The fan 10 of the heat exchanger 9 is controlled by the switching device 32, so that it can be switched on and off.

[0025] In cooling mode, throttle valve 11 is switched on and throttle valve 12 is closed, allowing the refrigerant to expand further and flow through the adjustable cooling unit 13, thus cooling the passenger compartment. In heating mode, throttle valve 11 is closed and throttle valve 12 is open, allowing the refrigerant to expand further.

[0026] The heat exchanger 15, designed as a chiller, is in heat exchange connection as a second heat transfer device 14 with the coolant circuit 3 serving as the second heat source. The separator 16 is connected downstream of the heat exchanger 15 and collects any liquid refrigerant that may be present, so that only gaseous refrigerant is supplied to the compressor 5.

[0027] The internal heat exchanger 17 is connected between the heat exchanger 15 and the compressor 5 on the one hand and the heat exchanger 9 and the heat exchanger 15 on the other hand in order to preheat the refrigerant by means of the heat exchanger 15 depending on the wiring of the heat exchangers 9, 15 and depending on the heating or cooling operation.

[0028] The coolant circuit 3 is divided into several coolant circuits 19, 20 which can be connected to one another by means of the selector switch 18, for example a multi-way valve, through which coolant, for example water, aqueous coolant mixtures and / or the like, flows by means of the pumps 21, 22.

[0029] The coolant circuit 19 with the pump 21 houses the external heat exchanger 23 for cooling the coolant circuit 3 as needed, the third heat transfer device 24, designed as a heat exchanger 25, which is in heat exchange connection with the fluid circuit 4 as the third heat source, the power electronics 26, and the charge controller 27 or voltage converter during charging of the battery 28. The battery 28 and the heat exchanger 15 are integrated into the coolant circuit 20 with the pump 22.An advantageous aspect before starting the motor vehicle can arise from the fact that the heat generated during charging in the charge controller 27 can already transfer heat to the refrigerant circuit 2 via the heat exchanger 15 when the motor vehicle is stationary, so that when the cold motor vehicle is started, the efficiency of the refrigerant circuit 2 can already be increased by heating the refrigerant above the ambient temperature, particularly if the heat supply to the heat exchanger 15 is already timed. Depending on the required amount of heat at the heat exchanger 15, the heat to be dissipated via the external heat exchanger 23, the heat available at the heat exchanger 25, the power electronics 26, the charge controller 27, and the battery 28, the pumps 21, 22, and the selector switch 18 are controlled by the switching device 32.

[0030] The electric motor 29 and the transmission 30 are integrated and cooled in the fluid circuit 4, which is operated with a fluid, for example, a lubricant such as oil, a suspension, and / or the like. The transmission 30 can be connected and disconnected by means of the valve 31. By heating the fluid, waste heat from the electric motor 29 and / or the transmission can be supplied to the coolant circuit 3 and thus to the refrigerant circuit 2 via the heat exchanger 15.

[0031] Figure 2 shows diagram 33 with the operation of the device 1 of Figure 1 with continuous control of the temperature T, the power P and the efficiency COP (coefficient of performance) over time t. During heating operation of the device 1, the heat quantities from the first and second heat sources are continuously transferred to the refrigerant circuit 2 via the heat transfer devices 8, 14 according to the heat flows predetermined by their heat transfer coefficients and exchange surfaces and thus the available powers P1, P2. Here, the refrigerant with the temperature T0 is heated up by means of the temperature T1 of the ambient air at the heat exchanger 9 and the higher temperature T2 at the heat exchanger 15 of the coolant circuit 3, so that the compressor 5, starting from the increased temperature T0, has to produce less power to heat and liquefy the refrigerant and thus achieve the desired temperature in the passenger compartment.The powers P1, P2 achievable from temperatures T1, T2 by means of heat exchangers 9, 15 in the refrigerant circuit 2 do not correspond to the higher power P3 required to heat the passenger compartment, so the remaining difference is compensated by the consumption of electrical power by the compressor 5 from the battery 28. The efficiency COP(k) for the continuous operation of the refrigerant circuit 2 results from the ratio of the powers P1, P2 on the one hand and the power P3 on the other.

[0032] In contrast to the continuous operation of the refrigerant circuit 2 in Figure 2, diagram 34 in Figure 3 shows the time-clocked heating operation of the device 1 in Figure 1 with the temperature T, the power P, and the efficiency COP over time t in a schematic representation with an unchanged design. When the motor vehicle is started at time t0, the temperatures T1 and T2 of the heat exchangers 9, 15 are at ambient temperature; respectively, if the charge controller 27 is warm, the heat exchanger 15 may already have a higher temperature T2—in a manner not shown.

[0033] The heat exchanger 9 is operated over the time cycles At1, At3 and following odd time cycles and supplies the power P1 at the temperature T1 at ambient temperature. Due to the heat generated by the components of the coolant circuit 3 and the fluid circuit 4, the temperature T1 in the coolant circuit 3 rises along the time cycle At1 when the heat exchanger 15 is not yet activated. At the time t1, the heat exchanger 9 is switched off - but can also be operated continuously - and the pumps 21, 22 are activated, so that the heat exchanger 15 supplies the heat during the time cycle At2 in the coolant circuit 3 at higher temperatures T2 than in continuous operation (Figure 2).

[0034] Heat is transferred via the heat exchanger 15 to the coolant, the temperature TO of which is heated to a significantly higher level by this amount of heat than in continuous operation. Due to the limited heat flow via the heat exchanger 15, the temperature T2 and thus the temperature TO decrease again and the heat exchanger 15 is deactivated again at time t2 so that its temperature T2 can increase again along the time cycle At3. At time t3, the heat exchanger 15 is switched on again along the time cycle At4 and the time cycle At2 is repeated. The time cycles At2, At3, At4 are repeated continuously. In the exemplary embodiment shown, the heat exchangers 9, 15 are alternately switched on and off at times t1, t2, t3, t4 and thereafter. In modified exemplary embodiments, the heat exchanger 9 can be operated continuously.

[0035] This pulsed operation, such as heating operation, results in an output from both heat exchangers 9, 15, whereby the output P1 from heat exchanger 9 is provided alternately or, if applicable, permanently and the output P2 from heat exchanger 15 is provided intermittently during the time cycles At2, At4, etc. This results in a lower efficiency COP(1) over time t in the time cycles At1, At3, etc., which is exclusively attributable to heat exchanger 9 and which is lower than the efficiency COP(k) of continuous operation. In the time cycles At2, At4, etc., a significantly higher efficiency COP(s) results than the efficiency COP(k), which is attributable to the amount of heat from heat exchanger 15 at the higher temperature T2 and, if applicable, the amount of heat from heat exchanger 9. Accordingly, the average efficiency COP(m) of the two efficiencies COP(1 ) and COP(s) is greater than the efficiency COP(k) of continuous operation.This leads, particularly in heating mode, to a reduced power requirement on the compressor 5 compared to continuous heating mode with the same design of the device 1, so that the compressor can be designed to be smaller and consumes less electrical energy, so that the energy saved benefits the range of the motor vehicle.

[0036] List of reference symbols

[0037] device

[0038] Refrigerant circuit

[0039] coolant circuit

[0040] Fluid circuit

[0041] compressor

[0042] Heat loop

[0043] throttle valve

[0044] Heat transfer device

[0045] heat exchanger

[0046] fan

[0047] throttle valve

[0048] throttle valve

[0049] Cooling loop

[0050] Heat transfer device

[0051] heat exchanger

[0052] separator

[0053] Indoor heat exchanger

[0054] selector switch

[0055] coolant circuit

[0056] coolant circuit

[0057] pump

[0058] pump

[0059] Outdoor heat exchanger

[0060] Heat transfer device

[0061] heat exchanger

[0062] Power electronics

[0063] charge controller

[0064] battery

[0065] electric machine

[0066] Gearbox 31 valve

[0067] 32 switching device

[0068] 33 Diagram

[0069] 34 Diagram

[0070] COP efficiency

[0071] COP(1 ) Efficiency

[0072] COP(k) efficiency

[0073] COP(m) efficiency

[0074] COP(s) Efficiency

[0075] P Performance

[0076] P1 Performance

[0077] P2 Performance

[0078] P3 Performance

[0079] T Temperature

[0080] TO temperature

[0081] T1 temperature

[0082] T2 Temperature t Time tO Time t1 Time t2 Time t3 Time t4 Time

[0083] At1 time cycle

[0084] At2 time cycle

[0085] At3 time cycle

[0086] At4 time cycle

Claims

Patent claims 1. Method for controlling a device (1) for heat management of an electrically operated motor vehicle, in particular for air conditioning its passenger compartment, with a refrigerant circuit (2) with a compressor (5) compressing a refrigerant and at least two heat sources of different temperatures (T1, T2) which provide heat and can be connected to the refrigerant circuit (2), characterized in that depending on the temperature (T1, T2), at least one of the heat sources is connected to the refrigerant circuit (2) in a time-synchronized manner.

2. Method according to claim 1, characterized in that the ambient air serves as the first heat source and a coolant circuit (3) with coolant of the motor vehicle serves as the second heat source.

3. Method according to claim 2, characterized in that a third heat source of an additional fluid circuit (4) is connected to the coolant circuit (3) or the refrigerant circuit (2) directly depending on a quantity of heat available in the fluid circuit (4).

4. Method according to claim 2 or 3, characterized in that in the coolant circuit (3) a plurality of coolant circuits (19, 20) through which coolant flows by means of at least one pump (21, 22) are connected by means of a selector switch (18) depending on the quantities of heat that can be obtained in the coolant circuits (19, 20).

5. Method according to claim 4, characterized in that the third heat source is switched on by means of one of the coolant circuits (19) of the second heat source, in particular in a time-synchronized manner and depending on the amount of heat present in the fluid circuit (4).

6. Method according to one of claims 2 to 5, characterized in that when the outside temperature falls below a predetermined value, the first heat source is switched on continuously and the second heat source is switched on in a time-controlled manner.

7. Method according to one of claims 2 to 5, characterized in that when the outside temperature falls below a predetermined value, the first and the second heat source are operated alternately in a time-synchronized manner.

8. Method according to one of claims 3 to 7, characterized in that in the third heat source, a heat-generating device is connected to the fluid circuit (4) depending on a quantity of heat generated by it and / or to be supplied thereto.

9. Device (1) for carrying out the method according to one of claims 1 to 8 with at least two heat transfer devices (8, 14) in heat exchange connection with a refrigerant circuit (2) and a switching device (32) for the time-clocked connection of at least one heat transfer device (14) depending on the heat quantities that can be obtained.

10. Device (1) according to claim 9, characterized in that a heat transfer device (8) is provided between the ambient air and the refrigerant circuit (2) and a second heat transfer device (14) is provided between a coolant circuit (3) and the refrigerant circuit (2), wherein in particular a third heat transfer device (24) is provided between the coolant circuit (2) and an additional fluid circuit (4).

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