Method for operating a temperature control device of a motor vehicle and temperature control device for a motor vehicle

Abstract

Method for operating a temperature control device (6) for temperature control of at least a partial area of ​​a motor vehicle, in which: - the temperature control device (6) has a refrigerant circuit (7) through which a refrigerant flows, which has: ◯ a compressor circuit (9) through which a total mass flow (10) of the refrigerant flows, in which a refrigerant compressor (11) is arranged, by means of which the refrigerant is conveyed and compressed; ◯ a condenser circuit (12) branching off from the compressor circuit (9) and thereby through which a first partial mass flow (13) of the refrigerant flows, in which a first expansion valve (15), by means of which the first partial mass flow (13) is adjustable and expanded, and a condenser (14) are arranged, by means of which the first partial mass flow (13) is condensed, wherein the condenser (14) is arranged in the condenser circuit (12) upstream of the first expansion valve (15);and◯ a bypass line (16) connected in parallel to the condenser string (12), branching off from the compressor string (9) and thereby through which a second partial mass flow (17) of the refrigerant flows, in which a second expansion valve (18) is arranged, by means of which the second partial mass flow (17) can be adjusted and is expanded; and◯ a third expansion valve (40) arranged in the condenser string (12) upstream of the condenser (14), by means of which the first partial mass flow (13) is adjustable and expanded;- the condenser string (12) and the bypass string (16) are joined at a mixing point (M), at which the partial mass flows (13, 17) are joined and thereby mixed together, whereby the partial mass flows (13, 17) result in the total mass flow (10), which flows into the compressor string (9) and then flows through the compressor string (9);and- by ​​means of an electronic computing device (19):◯ a first pressure and a first temperature of the refrigerant in the compressor circuit (9) upstream of the refrigerant compressor (11) and downstream of the mixing point (M) are determined;◯ a second pressure and a second temperature of the refrigerant downstream of the refrigerant compressor (11), upstream of the condenser (14) and upstream of the first and second expansion valves (15, 18) are determined;◯ a third pressure and a third temperature of the refrigerant in the condenser circuit (12) downstream of the condenser (14) and upstream of the first expansion valve (15);◯ the first and the second expansion valves (15, 18) are controlled as a function of the determined temperatures and as a function of the determined pressures, thereby adjusting the partial mass flows (13, 17) as a function of the determined temperatures and as a function of the determined pressures;◯ the third expansion valve (40) is controlled depending on the determined third pressure.;

Description

The invention relates to a method for operating a temperature control device of a motor vehicle. The invention also relates to such a temperature control device.JP 5861 495 B2 discloses a temperature control device for a vehicle. Furthermore, EP 2 265 453 B1 discloses a cooling arrangement for cooling a temperature-sensitive unit of a motor vehicle. Furthermore, DE 603 20 060 T2 discloses a method for operating a transcritic cooling system. Further, CN 1 11 577 589 A discloses a method for testing a compressor in a refrigerant gas circulation mode.It is an object of the present invention to provide a method for operating a temperature control device of a motor vehicle and such a temperature control device, so that at least a partial region of the motor vehicle can be temperature controlled, i.e. cooled and / or heated, in a particularly robust and cost-effective manner.This object is achieved according to the invention by a method having the features of patent claim 1 and by a temperature control device having the features of patent claim 10. Advantageous embodiments of the invention are the subject of the dependent claims.A first aspect of the invention relates to a method for operating a temperature control device for controlling the temperature, i.e. for cooling and / or heating at least one sub-region of a motor vehicle. This means that the motor vehicle, which is also simply referred to as a vehicle and is preferably designed as a motor vehicle, in particular a passenger car, has the temperature control device in its completely produced state, by means of which at least the said partial region is or can be temperature-controlled, that is to say cooled and / or heated. For example, the subregion is or comprises an interior of the motor vehicle, also referred to as a passenger compartment or passenger compartment, in the interior of which persons, such as the driver or the driver of the motor vehicle, can stay while the motor vehicle is driving. Alternatively or additionally, the sub-region can comprise, for example, an electrical energy store of the motor vehicle. The electrical energy store, in or by means of which electrical energy can be stored, in particular electrochemically, is preferably a high-voltage component, the electrical voltage of which, in particular the electrical operating and rated voltage, is preferably greater than 50 volts, in particular greater than 60 volts, and is very preferably several hundred volts. The motor vehicle is thus, for example, a hybrid vehicle or else an electric vehicle, in particular a battery-electric vehicle (BEV). The motor vehicle has, for example, at least one electric machine, by means of which the motor vehicle can be driven electrically, in particular purely. The electric machine is preferably a high-voltage component, the electrical voltage of which, in particular an electrical operating and rated voltage, is preferably greater than 50 volts, in particular preferably greater than 60 volts, and is very preferably several hundred volts. For example, the electric machine can be supplied with the electrical energy stored in the electrical energy store, as a result of which the electric machine can be operated in a motor mode and thus as an electric motor, by means of which the motor vehicle can be driven electrically, in particular purely.The temperature control device has a refrigerant circuit, also referred to simply as a circuit or refrigerant circuit, through which a refrigerant can flow and in particular through which a refrigerant flows during the method. The refrigerant circuit has a compressor section, also referred to as a compressor branch, which is also referred to as a first section or first branch. A total mass flow of the refrigerant flows through the compressor train. The refrigerant circuit also has a refrigerant compressor, also referred to as a compressor or compressor, which is arranged in the compressor train. The refrigerant is conveyed and compressed by means of the refrigerant compressor. In particular, the total mass flow is conveyed and compressed by means of the refrigerant compressor.The refrigerant circuit also has a condenser branch, in particular at a first branch point, branching off from the compressor branch and, as a result, flowed through by a first partial mass flow. The first partial mass flow is a first part of the total mass flow, since the total mass flow, in particular at the first branch point, is branched into the first partial mass flow. In other words, in particular at the first branch point, the first partial mass flow is branched off from or from the partial mass flow. A first expansion valve is arranged in the condenser train, by means of which the first partial mass flow can be adjusted and expanded. In other words, different values of the first partial mass flow can be set by means of the first expansion valve, so that the first partial mass flow can be varied. In addition, a condenser is arranged in the condenser train, by means of which the first partial mass flow is condensed, in particular in a targeted manner. The first partial mass flow is thereby cooled.The condenser is arranged in the condenser train, in particular upstream of the first expansion valve in the flow direction of the refrigerant flowing through the condenser train. In other words, in the condenser train, the first expansion valve is arranged downstream of the condenser, in particular in the flow direction of the refrigerant flowing through the condenser train. This allows particularly effective and efficient operation of the temperature control device, in particular of the refrigerant circuit, to be presented.The refrigerant circuit also has a bypass branch which branches off from the compressor branch and is thus connected fluidically in parallel to the condenser branch. In particular, the bypass branch branches off from the compressor branch at a second branching point. Since the bypass line branches off from the compressor line, a second partial mass flow, which is a second part of the total mass flow, flows through the bypass line. This means that the total mass flow, in particular at the second branch point, branches into the second partial mass flow. In other words again, in particular at the second branch point, the second partial mass flow is branched off from or from the total mass flow. The branch points can coincide and thus be formed by a single total branch point or lie at a single total branch point, or else the branch points are spaced apart from one another, in particular in the flow direction of the refrigerant flowing through the refrigerant circuit. The total mass flow thus branches into the first partial mass flow and into the second partial mass flow. In other words, the total mass flow is branched or divided into the first partial mass flow and the second partial mass flow, wherein the first partial mass flow and the second partial mass flow preferably result in the total mass flow in total. Since the total mass flow is branched or divided between the partial mass flows, the first partial mass flow is less than the total mass flow and the second partial mass flow is less than the total mass flow. The second partial mass flow flows through the bypass line, in which a second expansion valve is arranged. The second partial mass flow can be adjusted by means of the second expansion valve. This means that values of the second partial mass flow that are different from one another can be adjusted by means of the second expansion valve, as a result of which the second partial mass flow can be varied, that is to say can be changed. In addition, the second partial mass flow is expanded by means of the second expansion valve. The respective partial mass flow can be adjusted by the respective expansion valve in particular in that a flow cross section of the respective expansion valve through which the respective partial mass flow can flow can be adjusted, that is to say that values of the respective flow cross section that differ from one another can be adjusted.The first expansion valve can be or is flowed through by the first partial mass flow, and the second expansion valve can be or is flowed through by the second partial mass flow. The refrigerant compressor is or is flown through by the total mass flow. In addition, the second partial mass flow can or is passed through the capacitor. The condenser is a heat exchanger which can be operated or is operated as the mentioned condenser, for example, at least in one operation, at least in a heat pump operation, of the temperature control device. For example, a fluid provided in addition to the refrigerant can flow through and / or be bypassed by the condenser. Heat can, for example, transfer from the refrigerant to the fluid via the condenser, whereby, in particular in the mentioned operation, the refrigerant is cooled and the fluid is heated. Heat contained in the refrigerant can thus be used to heat the fluid. The fluid can be supplied to the sub-region, for example, in order to thereby heat the sub-region and thereby temperature control it by means of the fluid, in particular by means of the heat that has passed from the refrigerant to the fluid via the condenser. Expressed more generally, for example, the partial region can be temperature-controlled, in particular heated, by means of the fluid, in particular by means of the heat contained in the fluid, which has passed over from the refrigerant to or onto the fluid via the condenser. For example, the fluid is a gas, in particular air, which is introduced, for example, into the subregion, in particular into the interior mentioned, in order thereby to temperature control, in particular heat, the interior by means of the fluid. Furthermore, it is conceivable that the fluid is a liquid. For example, the electrical energy store can be temperature-controlled, in particular heated, by means of the fluid.For this purpose, the electrical energy store is supplied with the fluid, for example. In particular, the stated operation is, for example, a heat pump operation.The heat that is transferred from the refrigerant to the fluid via the condenser can transfer, for example, from the fluid to the electrical energy store in order thereby to heat the electrical energy store and thus to temperature control it. The heat mentioned, which can be transferred or is transferred from the refrigerant to the fluid via the condenser, originates, for example, at least predominantly or else exclusively from the refrigerant compressor or is effected at least predominantly or exclusively by the refrigerant compressor or is fed into the refrigerant, in particular by the refrigerant being compressed by means of the refrigerant compressor and thus heated. The refrigerant compressor can thus be used as a heating source in order to heat the refrigerant around, in particular via the condenser, for example the fluid and subsequently heat the sub-region.The refrigerant circuit has at least one third expansion valve arranged in the condenser line, in particular in the flow direction of the refrigerant flowing through the condenser line, upstream of the condenser, by means of which third expansion valve the first partial mass flow can be adjusted and expanded. Thus, the condenser is arranged in the condenser train, in particular in the flow direction of the refrigerant flowing through the condenser train, downstream of the third expansion valve. In other words, the values of the first partial mass flow that differ from one another can be set by means of the third expansion valve, such that the first partial mass flow can be varied. This means that the first partial mass flow can be set by means of the first expansion valve and / or by means of the third expansion valve, that is to say the mutually different values of the first partial mass flow can be set by means of the first expansion valve and / or by means of the third expansion valve, in particular in order to vary the first partial mass flow.The first partial mass flow can be adjusted by the third expansion valve in particular in that a flow cross section of the third expansion valve through which the first partial mass flow can flow or through which the flow passes can be adjusted, that is to say different values of the flow cross section of the third expansion valve can be adjusted.The first partial mass flow can or is passed through the third expansion valve. In particular, a pressure of the refrigerant flowing through the condenser train can be adjusted, in particular in a targeted manner, by means of the third expansion valve.Furthermore, it is provided that the bypass line and the condenser line are brought together at, in particular exactly, a mixing point and are connected thereto in fluidic fashion. At the mixing point, the partial mass streams are combined and thus mixed or mixed with one another, as a result of which the, in particular mixed, partial mass streams, in particular in sum, result in the total mass stream, which, in particular at the mixing point, flows into the compressor train and then flows through the compressor train and in particular the refrigerant compressor.In the method, a first pressure and a first temperature of the refrigerant, in particular of the total mass flow, are determined in the compressor train upstream of the refrigerant compressor and downstream of the mixing point by means of an electronic computing device, in particular the temperature control device, very in particular of the motor vehicle. The first pressure of the refrigerant, in particular the total mass flow, is understood to mean a pressure of the refrigerant, in particular the total mass flow, wherein the first pressure prevails at a first pressure point which is arranged in the compressor train upstream of the refrigerant compressor and downstream of the mixing point. The first temperature of the refrigerant, in particular of the total mass flow, is understood to mean a temperature of the refrigerant, in particular of the total mass flow, wherein the first temperature prevails at a first temperature point which is arranged in the compressor section upstream of the refrigerant compressor and downstream of the mixing point. For example, the first pressure point and the first temperature point coincide.By means of the electronic computing device, a second pressure and a second temperature of the refrigerant are determined, in particular in the compressor train, downstream of the refrigerant compressor, upstream of the condenser and upstream of the first and the second expansion valve, and in particular upstream of the third expansion valve. The second pressure of the refrigerant is understood to mean a pressure of the refrigerant, wherein the second pressure prevails at a second pressure point which is arranged downstream of the refrigerant compressor and upstream of the condenser and upstream of the first and the second expansion valve, and in particular upstream of the third expansion valve, wherein the second pressure point is arranged, for example, in the compressor train or in the bypass train or in the condenser train. The second temperature of the refrigerant is understood to mean a temperature of the refrigerant, wherein the second temperature prevails at a second temperature point which is arranged downstream of the refrigerant compressor, upstream of the condenser and upstream of the first and the second expansion valve, and in particular upstream of the third expansion valve, wherein the second temperature point is arranged in the compressor train, in the bypass train or in the condenser train. In particular, it is conceivable for the second pressure point and the second temperature point to coincide.By means of the electronic computing device, a third pressure and a third temperature of the refrigerant, in particular of the first partial mass flow, are determined in the condenser train downstream of the condenser and upstream of the first expansion valve. The third pressure of the refrigerant, in particular of the first partial mass flow, is understood to mean a pressure of the refrigerant, in particular of the first partial mass flow, wherein the third pressure prevails at a third pressure point which is arranged in the condenser train downstream of the condenser and upstream of the first expansion valve. The third temperature of the refrigerant, in particular of the first partial mass flow, is understood to mean a temperature of the refrigerant, in particular of the first partial mass flow, wherein the third temperature prevails at a third temperature point which is arranged in the condenser section downstream of the condenser and upstream of the first expansion valve. The third pressure point and the third temperature point may coincide. The pressures and the temperatures are determined by means of the electronic computing device, which is explained in more detail below.In the method, the first and the second expansion valve, and in particular the third expansion valve, are controlled by means of the electronic computing device as a function of the determined temperatures and as a function of the determined pressures, whereby the partial mass flows are set as a function of the determined temperatures and as a function of the determined pressures. This means that by means of the electronic computing device, via the first and the second expansion valve, and in particular via the third expansion valve, that is to say by actuating the first and the second expansion valve, and in particular by actuating the third expansion valve, the partial mass flows are set, that is to say in particular varied, as a function of the pressures determined and as a function of the temperatures determined, for example in that the flow cross sections mentioned are set, that is to say in particular varied, by actuating the first and the second expansion valve, and in particular by actuating the third expansion valve. As a result, a ratio between the partial mass flows, in particular of the first partial mass flow to the second partial mass flow, also referred to as a mixing ratio, can be set in a particularly advantageous manner, such that a robust operation of the temperature control device can subsequently be provided for effective and efficient temperature control. In particular, by adjusting the partial mass flows and thus by adjusting the mixing ratio, it is possible to avoid the refrigerant compressor being supplied with wet steam or even with liquid. In other words, it is possible, for example, to avoid the total mass flow resulting from the mixing of the partial mass flows comprising wet steam or even liquid, such that undesired damage to the temperature control device can be avoided. Furthermore, the invention makes it possible to realize a particularly advantageous temperature control of the subregion without an electric continuous heater being arranged in the refrigerant circuit or in an additional temperature control circuit provided for the temperature control of the subregion and through which, for example, the fluid can flow. Furthermore, a heat exchanger arranged in the refrigerant circuit and, for example, in the temperature control circuit and also designated as a chiller and operable or operable, for example, as an evaporator can be dispensed with, so that the number of parts and thus the weight and the costs of the temperature control device can be kept particularly low. At the same time, the invention makes it possible to advantageously set the partial mass flows and thus the mixing ratio in such a way that the total mass flow has a particularly advantageous state, in particular an aggregate state, in particular in such a way that, for example, the enthalpy of the total mass flow is plotted on the right next to the dew line of the refrigerant element, which is configured, for example, as R1234yf, in particular in a phase diagram of the dew means, wherein, for example, the, in particular specific, enthalpy is plotted on the abscissa of the phase diagram, and wherein the pressure of the refrigerant is plotted, in particular logarithmically, on the ordinate of the phase diagram.In the method, the third expansion valve is furthermore actuated by means of the electronic computing device as a function of the determined third pressure, and in particular as a function of the determined third temperature, in particular in order to adapt the determined third pressure to a predefined, in particular predefined, setpoint value of the third pressure. Thus, by adjusting the third expansion valve, a pressure of the refrigerant flowing through the condenser train, in particular the third pressure, can be regulated as a function of the determined third pressure, and in particular as a function of the setpoint value. This can be understood to mean, in particular, the following: For example, a value of the third pressure, also referred to as a measured value, is determined or measured, in particular by means of a sensor device. For example, the determined measured value of the third pressure is compared with the setpoint value of the third pressure by means of the electronic computing device. This means that, for example, a deviation between the measured value of the third pressure and the setpoint value of the third pressure is ascertained, in particular calculated, by means of the electronic computing device. The measured value can be referred to in particular as an actual value. For example, by actuating the third expansion valve, the third pressure is set to a second value different from the measured value, which preferably corresponds to the setpoint value. Thus, by means of the third expansion valve, the second value or the setpoint value of the third pressure can be actually set, in particular in a targeted manner, as a function of the ascertained measured value of the third pressure and as a function of the setpoint value of the third pressure.The third expansion valve can be understood to mean, in particular, an additional expansion valve with respect to the first and the second expansion valve. The third expansion valve allows the temperature control device to be operated in a particularly flexible manner. This means that a flexibility of the temperature control device can be particularly increased. As a result, at least the partial region of the motor vehicle can be temperature-controlled in a particularly flexible manner, in particular cooled and / or heated. In particular, the third expansion valve can particularly increase a number of degrees of freedom of the temperature control device, in particular of the refrigerant circuit. Thus, by means of the third expansion valve, the temperature control device can be extended by an additional degree of freedom, for example with respect to the first and the second expansion valve. As a result, the temperature control device can be operated in a particularly required manner, as a result of which at least the partial region of the motor vehicle can be temperature controlled in a particularly required manner.For example, the pressure of the refrigerant flowing through the condenser line can be reduced by means of the third expansion valve, that is to say that the pressure of the refrigerant flowing through the refrigerant circuit, in particular the condenser line, can be adjusted by means of the third expansion valve such that this pressure downstream of the third expansion valve is lower than upstream of the third expansion valve. As a result, in particular in the case of a fixed pressure specification at the condenser or condenser, a higher or particularly high pressure can be built up downstream of the refrigerant compressor or downstream of the refrigerant compressor, as a result of which more or particularly much power and thus heating power can be introduced into the system or into the temperature control device. As a result, a pressure level and / or temperature level at the condenser or condenser can be decoupled from a compressor capacity of the refrigerant compressor, as a result of which in particular the additional degree of freedom can be created. In particular, more or particularly much heating power can be effected at a lower or particularly low temperature level by the third expansion valve. Because the temperature level and / or the pressure level are decoupled from the heating power and thus from the compressor power, heating can be carried out at different temperature levels, for example, with the same or constant compressor power. As a result, at least the partial region of the motor vehicle can be tempered, in particular cooled and / or heated, in a particularly advantageous manner, in particular in a particularly flexible or as required manner.In order to be able to realize particularly robust operation of the temperature control device and to be able to avoid damage to the temperature control device, in particular to the refrigerant compressor, it is provided in one embodiment of the invention that the partial mass flows and thus the mixing ratio are set by actuating the expansion valves, in particular by actuating the first, second and third expansion valves, in such a way that the total mass flow comprises only superheated steam.A further embodiment is characterized in that a first enthalpy of the refrigerant is calculated from the first pressure and the first temperature by means of the electronic computing device. By means of the electronic computing device, a second enthalpy of the refrigerant is calculated, for example, from the second pressure and the second temperature. For example, a third enthalpy of the refrigerant is calculated from the third pressure and the third temperature by means of the electronic computing device. It has proven particularly advantageous if the expansion valves, in particular the first, second and third expansion valves, are controlled as a function of the calculated enthalpy, whereby the partial mass flows and thus also the mixing ratio are adjusted as a function of the calculated enthalpy. In this way, it can be ensured in a particularly advantageous manner that the enthalpy of the refrigerant in the compressor train upstream of the refrigerant compressor, i.e. in particular the first enthalpy in the phase diagram, is to the right next to the dew line and has a sufficiently large distance, in particular safety distance, from the dew line, whereby a robust and damage-free operation of the temperature control device can be produced.A further embodiment is distinguished in that, by actuating the expansion valves, in particular by actuating the first, second and third expansion valves, the partial mass flows are set in such a way that the mixing ratio of the second partial mass flow to the first partial mass flow, and therefore a quotient of the second partial mass flow and the first partial mass flow, wherein the quotient in its numerator has the second partial mass flow and the quotient in its denominator has the first partial mass flow, is greater than a ratio of a first enthalpy difference to a second enthalpy difference, and is therefore greater than a second quotient, wherein the second quotient in its second denominator has the first enthalpy difference and wherein the second quotient in its second denominator has the second enthalpy difference. In this case, the first enthalpy difference is the absolute value of a first difference between the enthalpy of the temperature control medium in the condenser train downstream of the condenser and upstream of the first expansion valve and the enthalpy of the refrigerant belonging to the first pressure and lying on the dew line of the refrigerant.Furthermore, the second enthalpy difference is the absolute value of a second difference between the enthalpy of the temperature control medium downstream of the refrigerant compressor, upstream of the condenser and upstream of the first and the second expansion valve, and in particular upstream of the third expansion valve, and the enthalpy of the refrigerant belonging to the first pressure and lying on the dew line (22) of the refrigerant. As a result, the mixing ratio can be reliably set in such a way that the mixing ratio, and therefore the mixing of the partial streams, results in such a state of the total mass flow that the total mass flow is, in particular exclusively, superheated steam, and therefore that the enthalpy of the total mass flow, which in particular belongs to the first pressure, is to the right of the dew line in the phase diagram. Damage to the refrigerant compressor can thereby be avoided, so that the partial region can be temperature-controlled in a particularly advantageous manner, in particular with the avoidance of evaporation of the refrigerant moved in a targeted manner by means of an evaporator, in a particularly space-efficient, weight-efficient and cost-effective manner, and in a robust manner.In order to realize a temperature control of the subregion which is particularly light, cost- and space-saving, it is provided in a further embodiment of the invention that the bypass branch is free of a condenser for the targeted condensation of the refrigerant. Alternatively or additionally, it is provided that the bypass branch is free of an evaporator for, in particular targeted, evaporating the refrigerant. Alternatively or additionally, it is provided that the bypass line is free of a heat exchanger for, in particular targeted, temperature control of the refrigerant.In order to be able to temperature the partial region particularly in terms of installation space, weight and cost-effectively, it is provided in a further embodiment that the condenser is free of an evaporator for, in particular targeted, evaporation of the refrigerant. Alternatively or additionally, the condenser train is free of a heat exchanger, for example, except for the condenser, for, in particular, targeted temperature control, i.e., cooling or heating of the refrigerant. As a result, the number of parts and the costs, the installation space requirement and the weight of the temperature control device can be kept particularly low. The method according to the invention makes it possible to set a particularly advantageous state, in particular aggregate state, of the total mass flow resulting from the mixing of the partial mass flows without the refrigerant being vaporized in a targeted manner by means of an evaporator in the refrigerant circuit, since the described setting of the partial mass flows and thus of the mixing ratio can ensure, for example, that the total mass flow is superheated steam, that is to say that the enthalpy of the total mass flow in the compressor train upstream of the refrigerant compressor is to the right next to the dew line in the phase diagram, in particular at the first pressure.A further embodiment is distinguished in that no, in particular targeted, evaporation of the refrigerant by an evaporator is present in the condenser train. This embodiment is based on the concept that it is conceivable in principle that an evaporator could be arranged in the condenser train, in particular downstream of the condenser and for example downstream of the first expansion valve and in particular upstream of the mixing point, which evaporator is designed for a targeted evaporation of the refrigerant, wherein, however, in order to realize a particularly efficient and effective temperature control, it is provided that a targeted evaporation of the temperature control medium does not occur by means of the evaporator.In order to be able to keep the number of parts and thus the weight, the installation space requirement and the costs of the temperature control device particularly low, it is provided in a further embodiment that the compressor train is free of a condenser for, in particular targeted, condensing of the refrigerant. Alternatively or additionally, the compressor train is free of an evaporator for, in particular targeted, evaporating the refrigerant. Alternatively or additionally, the compressor train is free of a heat exchanger for, in particular targeted, temperature control of the refrigerant.In order to be able to determine the pressures and the temperatures particularly precisely and subsequently to be able to set the partial mass flows particularly precisely, it is provided in a further embodiment of the invention that the first pressure and the first temperature are measured by means of a first sensor device and thereby determined. Alternatively or additionally, the second pressure and the second temperature are measured by means of a second sensor device and thereby determined. Alternatively or additionally, the third pressure and the third temperature are measured by means of a third sensor device and thereby determined. For example, the first pressure at the first printing point is measured by means of the first sensor device. It is furthermore conceivable for the first temperature to be measured at the first temperature point by means of the first sensor device. For example, the second pressure is measured by means of the second sensor device at the second pressure point. For example, the second temperature is measured by means of the second sensor device at the second temperature point. For example, the third pressure is measured by means of the third sensor device at the third printing point. For example, the third temperature is measured by means of the third sensor device at the third temperature point.In order to be able to keep the number of parts and thus the costs, the weight and the installation space requirement of the temperature control device within a particularly small scope, it is provided in a further embodiment of the invention that the first pressure and the first temperature are calculated by means of the electronic computing device on the basis of a computing model and thereby determined. Alternatively or additionally, the second pressure and the second temperature are calculated by means of the electronic computing device on the basis of a computing model and thereby determined. Alternatively or additionally, the third pressure and the third temperature are calculated by means of the electronic computing device on the basis of a computing model and thereby determined.The first sensor device provides, for example, an, in particular electrical, first signal which characterizes the first pressure and the first temperature. The electronic computing device receives the first signal and thereby determines, for example, the first pressure and the first temperature. It is furthermore conceivable for the second sensor device to provide a second, in particular electrical, signal which characterizes the second temperature and the second pressure. The electronic computing device receives the second signal, for example, and thereby determines the second pressure and the second temperature. For example, the third sensor device provides a third, in particular electrical, signal which characterizes the third temperature and the third pressure. The electronic computing device receives the third signal, for example, and thereby determines the third pressure and the third temperature.Finally, it has been shown to be particularly advantageous if, in a first operating state, the first partial mass flow is set to a first value and the second partial mass flow is set to a second value by actuating the expansion valves, in particular by actuating the first, second and third expansion valves, such that, in the first operating state or during the first operating state, the first partial mass flow has the first value and the second partial mass flow has the second value. In a second operating state, by actuating the expansion valves, in particular by actuating the first, second and third expansion valves, the first partial mass flow is set to a third value different from the first value and the second partial mass flow is set to a fourth value different from the second value, so that in the second operating state or during the second operating state, the first partial mass flow has the third value and the second partial mass flow has the fourth value. In this case, it is preferably provided that a first ratio of the first value to the second value, also referred to as a first value ratio, corresponds to a second ratio of the third value to the fourth value, also referred to as a second value ratio. In other words, for example, a first value quotient corresponds to a second value quotient, wherein the first value quotient has the first value in its first value quotient counter, wherein the first value quotient has the second value in its first value quotient denominator, wherein the second value quotient has the third value in its second value quotient counter, and wherein the second value quotient has the fourth value in its second value quotient denominator. As a result, a first power of the refrigerant compressor is set in the first operating state, and a second power of the refrigerant compressor different from the first power is set in the second operating state. In other words, the mixing ratio in the first operating state corresponds to the mixing ratio in the second operating state, so that both in the first operating state and in the second operating state, robust operation of the temperature control device can be realized without damage. In other words, it can be ensured both in the first operating state and in the second operating state that the enthalpy of the total mass flow in the compressor train upstream of the refrigerant compressor is to the right of the dew line in the phase diagram. However, since the first partial mass flow and the second partial mass flow have different values in the operating states, different outputs of the refrigerant compressor are set, so that, for example, the fluid is temperature-controlled, in particular heated, to different extents by means of the refrigerant compressor. If, for example, the power of the refrigerant compressor is greater in the second operating state than in the first operating state, then, for example, the refrigerant is heated more strongly by means of the refrigerant compressor in the second operating state than in the first operating state. Thus, for example, in the second operating state, in particular via the fluid, the subregion can be heated more strongly by means of the refrigerant and in particular by means of the refrigerant compressor than in the first operating state, wherein in both operating states an unfavorable aggregate state of the total mass flow in the compressor train upstream of the refrigerant compressor can be avoided. This embodiment thus enables a need-based and robust or reliable setting, i.e. variation of the power of the refrigerant compressor and thus of a power, for example designed as heating power, for tempering the sub-region.The refrigerant compressor is preferably designed as an electric refrigerant compressor, so that the power of the refrigerant compressor is an electric power of the refrigerant compressor.A second aspect of the invention relates to a temperature control device for a motor vehicle, wherein the temperature control device according to the second aspect of the invention is designed to carry out a method according to the first aspect of the invention. Advantages and advantageous configurations of the first aspect of the invention are to be regarded as advantages and advantageous configurations of the second aspect of the invention and vice versa.Also disclosed is a motor vehicle, also referred to simply as a vehicle, which is preferably designed as a motor vehicle, in particular a passenger car, and which has the temperature control device according to the invention. Advantages and advantageous configurations of the first aspect and of the second aspect of the invention are to be regarded as advantages and advantageous configurations of the motor vehicle and vice versa.The invention is based in particular on the following findings and considerations: The invention enables a new temperature control concept, in particular heating concept, to be implemented for temperature control, in particular heating, of the said subregion, in particular of the interior and / or of the electrical energy store, which is in particular designed as a high-voltage accumulator, and specifically for example using the refrigerant compressor as the sole heating or heat source arranged in the refrigerant circuit described. Experiments have shown that this heating concept cannot be stabilized with the aid of a simple PI regulator approach. The stabilization of two switched triangular processes has been identified as a core problem. Since, for example, the condenser train is free of an evaporator for the targeted evaporation of the refrigerant or since, in particular at least while the method is being carried out, a targeted evaporation of the refrigerant by means of an evaporator does not occur in the condenser train, a first thermodynamic cycle process designed as a first triangular process runs via the condenser train. Since the refrigerant flowing through the bypass branch bypasses the condenser branch on its path from the compressor branch through the bypass branch back to the compressor branch and since, for example, in particular also, no evaporator for evaporating the refrigerant is arranged in the bypass branch or, in particular, while the method is carried out, a targeted evaporation of the refrigerant does not occur in the bypass branch, a second thermodynamic cycle process designed as a second triangular process, for example, takes place as viewed via the compressor branch and the bypass branch. The triangular processes are connected in parallel with one another in terms of flow, wherein this parallel connection results in a mixing of the refrigerant, and consequently a mixing of the partial mass streams, wherein the partial mass streams have different thermodynamic states, in particular when they arrive at the mixing point and are mixed with one another at the mixing point. This is to be understood in particular as meaning that the first partial mass flow has a first thermodynamic state and the second partial mass flow has a second thermodynamic state which is different from the first thermodynamic state. The aforementioned stabilization is to be understood as meaning that it is desirable, during or by the stabilization, to set the total mass flow, in particular a thermodynamic state of the total mass flow, by mixing the partial mass flows in such a way that the total mass flow is at least predominantly, in particular exclusively, heated steam, that is to say that the enthalpy of the total mass flow is to the right next to the dew line in the phase diagram. Since the partial mass streams are mixed at the mixing point, the total mass stream is an end product of the described mixture of the partial mass streams. If the end product (total mass flow) comes to lie in an unfavorable fluid state or in an unfavorable thermodynamic state, damage to the refrigerant compressor, also referred to as compressor, can occur, which can lead to irreparable damage to the entire refrigerant circuit. As a result, the refrigerant circuit must be replaced, which can be expensive. In addition, setting the power of the temperature control device has proven to be problematic, since in the heating concept the refrigerant compressor is or can be the only power supplier arranged in the refrigerant circuit, and therefore the only heat source arranged in the refrigerant circuit, by means of which the refrigerant and, for example, via the refrigerant and the condenser, the mentioned fluid can be heated by operating the heat source (refrigerant). Therefore, a control range of the refrigerant compressor should be dealt with in order to be able to set a power of the temperature control device, in particular of the refrigerant compressor, which is partially provided for the purpose of temperature control, in particular heating.According to the invention, the expansion valves are used as actuators of the refrigerant circuit in order to adjust the end product, and therefore the total mass flow, namely by mixing the partial mass flows. A basic idea for stabilizing the two parallel triangular processes is applying an analogy of the law of levers to the phase diagram, which is designed, for example, as a logarithmic and / or p-V diagram. In this case, the mixing ratio, also referred to as the mixing ratio, is preferably set as described above as a function of the enthalpy differences mentioned. In this way, it is possible in particular to set the second partial mass flow by a measure greater than the first partial mass flow, wherein the measure is greater than a measure by which the first enthalpy difference is greater than the second enthalpy difference.In particular, the degrees of freedom of the, in particular evaporator-free, refrigerant circuit or of the parallel triangular process can be particularly increased by means of the third expansion valve.Further features of the invention are evident from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or alone.The invention will now be explained in more detail on the basis of a preferred exemplary embodiment and with reference to the drawings. The following are shown: FIG. 1 shows a schematic illustration of a temperature control device for controlling the temperature of at least one partial region of a motor vehicle; and FIG. 2 shows a phase diagram of a refrigerant which flows in a refrigerant circuit of the temperature control device during a method for operating the temperature control device; and FIG. 3 shows a flow chart for illustrating the method for operating the temperature control device; and FIG. 4 shows a flow chart for illustrating a pressure regulation of the method for operating the temperature control device; and FIG. 5 shows a schematic illustration of a characteristic diagram of a compressor of the temperature control device; and FIG. 6 shows a further schematic illustration of the characteristic diagram; and FIG. 7 shows a further flow chart for further illustrating the method.In the figures, identical or functionally identical elements are provided with identical reference symbols.FIG. 1 shows a schematic illustration of a temperature control device 6 of a motor vehicle which is also referred to simply as a vehicle and is preferably designed as a motor vehicle, in particular a passenger vehicle. With reference to the figures, a method for operating the temperature control device 6 is described below. By means of the temperature control device 6, the said partial region of the motor vehicle can be temperature controlled, that is to say heated or cooled. In particular, the partial region can be heated. For example, the subregion is or comprises an interior of the motor vehicle, also referred to as a passenger compartment or passenger compartment, the structure of which, for example, is embodied as a self-supporting body and forms or delimits the interior. Thus, for example, the interior space can be temperature-controlled, in particular heated, by means of the temperature-control device 6. For this purpose, the temperature control device has a refrigerant circuit 7 through which a refrigerant can flow, which refrigerant can flow during the method and thus during operation of the temperature control device 6, which is operated during operation according to the method, in particular along a flow direction illustrated by arrows 8 in FIG. 1.The refrigerant circuit 7 has a compressor train 9 through which a total mass flow of the refrigerant flows, wherein the total mass flow is illustrated by an arrow 10. A refrigerant compressor 11 is arranged in the compressor train 9, by means of which the refrigerant is conveyed and compressed during operation and thus during the method. The refrigerant circuit 7 has a condenser train 12 branching off from the compressor train 9 and through which a first partial mass flow of the refrigerant flows. The first partial mass flow is illustrated by an arrow 13. The first partial mass flow is a first part of the total mass flow (arrow 10). Arranged in the condenser train 12 is a condenser 14, also referred to as condenser, by means of which the first partial mass flow, and therefore the refrigerant flowing through the condenser train 12, is condensed, and therefore liquefied. Furthermore, a first expansion valve 15 is arranged in the condenser train 12 downstream of the condenser 14, by means of which expansion valve the first partial mass flow can be adjusted. In other words, the condenser 14 is arranged in the condenser train 12 upstream of the first expansion valve 15. In addition, the expansion valve 15 expands the first partial mass flow, and therefore the refrigerant flowing through the condenser train 12.The refrigerant circuit 7 also has a bypass branch 16 branching off from the compressor branch 9 and through which a second partial mass flow of the refrigerant flows, which bypass branch is connected fluidically in parallel with the condenser branch 12. The second partial mass flow of the refrigerant is illustrated by an arrow 17. In addition, the second partial mass flow is a second part of the total mass flow, wherein the partial mass flows sum up to the total mass flow. In the bypass line 16, a second expansion valve 18 is arranged, which is provided in addition to the expansion valve 15 and by means of which the second partial mass flow can be adjusted. In addition, the expansion valve 18 expands the second partial mass flow, and therefore the refrigerant flowing through the bypass line 16. Preferably, it is provided that in the method, the refrigerant does not evaporate by means of a compressor in the compressor train 9, in the condenser train 12 and in the bypass train 16. The compressor train 9, the condenser train 12 and the bypass train 16 are also referred to in particular as trains. In the exemplary embodiment shown in the figures, the strings are free of an evaporator for the targeted evaporation of the refrigerant.In the condenser train 12, upstream of the condenser 14, a third expansion valve 40 is arranged, by means of which the first partial mass flow can be adjusted and expanded. In other words, the first partial mass flow, and therefore the refrigerant flowing through the condenser train 12, is expanded by means of the third expansion valve 40.The refrigerant circuit 7 has, in particular precisely, a mixing point M at which the condenser train 12 and the bypass train 16, which collectively are also referred to as partial trains, are combined, so that the partial mass streams are combined at the mixing point M and are thereby mixed with one another. As a result, the partial mass flows result or form the total mass flow which flows into the compressor train 9, in particular at the mixing point M, and then flows through the compressor train 9, in particular the refrigerant compressor 11.By means of an electronic computing device 19 which is illustrated particularly schematically in FIG. 1, a first pressure and a first temperature of the refrigerant, in particular of the total mass flow, in the compressor train 9 upstream of the refrigerant compressor 11 and downstream of the mixing point M are determined. In the exemplary embodiment shown in FIG. 1, a first sensor device S 1 is provided, by means of which the first pressure prevailing in the compressor train 9 upstream of the refrigerant compressor 11 and downstream of the mixing point M and the first temperature prevailing in the compressor train 9 upstream of the refrigerant compressor 11 and downstream of the mixing point M are measured. The sensor device S 1 provides, for example, a first signal characterizing the first temperature and the first pressure, which signal is received by the electronic computing device 19, as a result of which the electronic computing device 19 determines the first temperature and the first pressure. In FIG. 1, reference numeral 1 denotes a first point, which is also referred to as a first location. The first point 1 is arranged in the compressor train 9 downstream of the mixing point M and upstream of the refrigerant compressor 11, wherein for example the sensor device S 1 measures the first pressure and the first temperature in or at the first point 1. In other words, for example, the first pressure and the first temperature of the refrigerant prevail in the compressor train 9 at the point 1.In the method, a second pressure and a second temperature of the refrigerant downstream of the refrigerant compressor 11, upstream of the condenser 14 and upstream of the expansion valves 15 and 18, and in particular of the third expansion valve 40, are determined by means of the electronic computing device 19. In the exemplary embodiment shown in FIG. 1, a second sensor device S 2 is provided, by means of which the second pressure of the refrigerant prevailing downstream of the refrigerant compressor 11, upstream of the condenser 14 and upstream of the expansion valves 15 and 18, and in particular 40, and the second temperature of the refrigerant prevailing downstream of the refrigerant compressor 11, upstream of the condenser 14 and upstream of the expansion valves 15 and 18, and in particular 40, are detected. The sensor device S 2 provides, for example, a second signal which characterizes the second temperature and the second pressure. For example, the electronic computing device 19 receives the second signal, whereby the electronic computing device 19 determines the second pressure and the second temperature. In FIG. 1, a second point is denoted by 2 a, wherein the second point 2 ais also denoted as a second point. It can be seen that the first point 1 is arranged downstream of the mixing point M and upstream of the refrigerant compressor 11 in the compressor train 9. The second point 2a is arranged downstream of the refrigerant compressor 11, upstream of the condenser 14 and upstream of the expansion valves 15, 18, 40, wherein for example the second point 2a can be arranged at the branch point A or coincide with the branch point A. In this case, for example, the second pressure and the second temperature prevail at or in the second point 2 a, wherein for example the second sensor device S 2 measures the second pressure and the second temperature in or at the second point 2 a.By means of the electronic computing device 19, a third pressure and a third temperature of the refrigerant, in particular of the first partial mass flow, are arranged in the condenser train 12 downstream of the condenser 14 and upstream of the first expansion valve 15, which in the exemplary embodiment shown in FIG. 1 is arranged in the condenser train 12 downstream of the condenser 14 and upstream of the mixing point M. In the exemplary embodiment shown in FIG. 1, a third sensor device S 3 is provided, by means of which the third pressure of the refrigerant prevailing in the condenser train 12 downstream of the condenser 14 and upstream of the first expansion valve 15 and the third temperature of the refrigerant prevailing in the condenser train 12 downstream of the condenser 14 and upstream of the expansion valve 15 are detected. For example, the third sensor device S 3 provides a third signal which characterizes the third temperature and the third pressure. The electronic computing device 19 receives the third signal, for example, whereby the electronic computing device 19 determines the third temperature and the third pressure.By means of the electronic computing device 19, the expansion valves 15 and 18, and in particular 40, are controlled as a function of the determined temperatures and as a function of the determined pressures, whereby the partial mass flows are adjusted as a function of the determined temperatures and as a function of the determined pressures. This also sets a mixing ratio, also referred to as a mixing ratio, according to which the partial mass streams are mixed with one another, resulting in the total mass flow. In particular, the mixing ratio is or describes a quotient also referred to as a mixing quotient, wherein the mixing quotient has, for example, the first partial mass flow in its denominator, and wherein the mixing quotient has, for example, the second partial mass flow in its denominator. The first partial mass flow is designated by m1, for example, and the second partial mass flow is designated by m2, for example. The mixing ratio is denoted by Φ, for example. Thus, for example, the following applies:By actuating the expansion valve 15, it is possible, for example, to set, i.e. change, a first flow cross section of the first expansion valve 15 through which the first partial mass flow can flow. For example, the expansion valve 15 has a first actuator, in particular an actuator that can be operated electrically, by means of which the first flow cross section can be adjusted. For example, the expansion valve 18 has a second flow cross section through which the second partial mass flow can flow, which flow cross section can be set, i.e. changed, by actuating the expansion valve 18. For example, the expansion valve 18 has a second actuator, which can be operated in particular electrically and by means of which the second flow cross section can be adjusted. The electronic computing device 19 controls, for example, the actuators as a function of the pressures determined and as a function of the temperatures determined, in order thereby to set the flow cross sections and consequently the partial mass flows and thus the mixing ratio Φ.In FIG. 1, 3 denotes a third point, wherein the third point 3 is also referred to as a third point. It can be seen that the third point 3 in the condenser train 12 is arranged downstream of the condenser 14 and upstream of the expansion valve 15. For example, the third temperature and the third pressure prevail at or in the third point 3. For example, the third sensor device S 3 measures the third pressure and the third temperature at or in the third point 3. It can be seen that the fourth point, and therefore the fourth point 4, is arranged in the condenser train 12 and in this case downstream of the expansion valve 15 and upstream of the mixing point M. Furthermore, in FIG. 1, a fifth point is denoted by 5, wherein the fifth point 5 is also denoted as a fifth point or is formed as a fifth point. It can be seen that the fifth point 5 in the bypass line 16 is arranged downstream of the expansion valve 18 and upstream of the mixing point M. Furthermore, a sixth point is denoted by 2 b, wherein the sixth point 2 bis also denoted as sixth point. It can be seen that the sixth point 2 bis arranged downstream of the refrigerant compressor 11, upstream of the condenser 14 and upstream of the first and second expansion valves 15, 18 and downstream of the third expansion valve 40, wherein for example the sixth point 2 bis arranged for example in the condenser train 12. For example, the pressure at the sixth point 2 bcorresponds at least substantially to the pressure at the third sensor device S 3.The third expansion valve 40 is controlled as a function of the third pressure determined. As a result, the pressure of the refrigerant flowing through the condenser train 12 can be adjusted, in particular in a targeted manner, at the sixth point 2 bby means of the third expansion valve 40, for example reduced with respect to the pressure at the second point 2 a.By actuating the third expansion valve 40, it is possible, for example, to set, i.e. change, a flow cross section of the third expansion valve 40 through which the first partial mass flow can flow. For example, the third expansion valve 40 has a third actuator, which can be operated in particular electrically, by means of which the flow cross section of the third expansion valve 40 can be adjusted.FIG. 2 is a phase diagram of the refrigerant formed as, for example, R 1234yf. As usual, the enthalpy, in particular specific enthalpy, of the refrigerant is plotted or indicated on the abscissa 20 of the phase diagram, in particular in kilojoules per kilogram. As usual, the pressure of the refrigerant, in particular in bar, is plotted or indicated logarithmically on the ordinate 21 of the phase diagram. The dew line of the refrigerant in the phase diagram is denoted by 22. Points 1, 2 a, 2 b, 3, 4 and 5 are entered in the phase diagram, so that the respective enthalpy of the refrigerant in points 1, 2 a, 2 b, 3, 4 and 5 can be seen from the phase diagram shown in FIG. 2. In particular, it can be seen that the pressure of the refrigerant is the same at points 1, 4 and 5 and the pressure of the refrigerant is the same at points 2b and 3. In FIG. 2, an arrow 23 aillustrates a state change of the refrigerant from the point 1 and the point 2 a, and an arrow 23 billustrates a state change of the refrigerant from the point 2 aand the point 2 b. An arrow 24 illustrates a change in state of the refrigerant from the point 2 bto the point 5. an arrow 25 illustrates a change in state of the refrigerant from the point 2 bto the point 3, and an arrow 26 illustrates a change in state of the refrigerant from the point 3 to the point 4. It can be seen that a first thermodynamic cycle designed as a first triangular process runs via points 1, 2 a, 2 b, 3 and 4, and therefore via compressor train 9 and condenser train 12, and a second thermodynamic cycle designed as a second triangular process runs via points 1, 2 a, 2 band 5, and therefore via compressor train 9 and bypass train 16. The triangular processes, which are also simply referred to as processes, are parallel, with neither of the triangular processes being self-contained. It is desirable that point 1 is stably located to the right of dew line 22 with respect to the phase diagram shown in FIG. 2. In other words, it is desirable that the partial flows and thus the mixing ratio be adjusted by means of the expansion valves 15 and 18, and in particular 40, in such a way that the enthalpy of the refrigerant at or in the point 1 lies safely or stably to the right of the dew line 22 with respect to the phase diagram shown in FIG. 2. This makes it possible to ensure that the total mass flow is at least predominantly, in particular exclusively, superheated steam. In other words, wet steam or a liquid can thereby be prevented from flowing through the refrigerant compressor 11, which could lead to damage to the refrigerant compressor 11. Operating the temperature control device 6 in such a way that the enthalpy of the refrigerant compressor at or at the point 1 is situated safely to the right of the dew line 22 with respect to the phase diagram shown in FIG. 2 is also referred to as stabilization or stabilization.It can be seen from FIG. 2 that the refrigerant has a first enthalpy at or in the first point 1, a second enthalpy at or in the second point 2 a, a third enthalpy at or in the point 3, a fourth enthalpy at or in the fourth point, a fifth enthalpy at or in the fifth point, a sixth enthalpy at or in the sixth point. The fourth enthalpy corresponds to the third enthalpy, and the fifth enthalpy corresponds to the second enthalpy. The sixth enthalpy corresponds to the second enthalpy. In addition, for example, the refrigerant has the same pressure, in particular the same first pressure, in or at points 1, 4 and 5. In FIG. 2, a seventh point 27 illustrates the enthalpy of the refrigerant associated with the first pressure and located on the refrigerant dew line 22. The enthalpy of the refrigerant associated with the first pressure and located on the dew line 22 of the refrigerant, illustrated by the seventh point 27, is also referred to as dew line enthalpy.In FIG. 2, a first enthalpy difference is denoted by D 1 and a second enthalpy difference is denoted by D 2. The first enthalpy difference D1 is the absolute value of a first difference between the enthalpy of the refrigerant at the point 3 and the enthalpy of the refrigerant belonging to the first pressure and lying on the dew line 22. In other words, the first enthalpy difference D 1 is the absolute value of a first difference between the third and fourth enthalpy, respectively, and the dew line enthalpy. The second enthalpy difference D2 is the absolute value of a second difference between the enthalpy of the refrigerant at the point 2 and the enthalpy of the refrigerant belonging to the first pressure and lying on the refrigerant dew line 22. In other words, the second enthalpy difference D 2 is the absolute value of a second difference between the second or fifth enthalpy and the dew line enthalpy. The enthalpy of the refrigerant at the point 4 corresponds to the enthalpy of the refrigerant at the point 3, so that the enthalpy of the refrigerant at the point 3 and at the point 4 is also referred to as h3. The enthalpy of the refrigerant at point 5 corresponds to the enthalpy of the refrigerant at point 2, so that the enthalpy of the refrigerant at point 5 is also referred to as h2. The enthalpy of the refrigerant, illustrated by point 27 and associated with the first pressure and lying on dew line 22, is also designated ht.As shown in FIG. 2, by means of the refrigerant compressor 11, the pressure of the refrigerant can be compressed at the second point 2 arelative to the first point 1. By means of the third expansion valve 40, the pressure of the refrigerant at the sixth point 2 bcan be reduced compared to the second point 2 a, in particular by expansion. The pressure of the refrigerant at the third point 3 preferably corresponds to the pressure of the refrigerant at the sixth point 2b. That is, the pressure of the refrigerant passing through the condenser corresponds to the pressure at the sixth point 2b which is lower than the pressure of the refrigerant at the second point 2a. Thus, by means of the third expansion valve 40, the pressure of the refrigerant flowing through the condenser train 12 upstream of the condenser 14, in particular at the sixth point 2 b, can be freely adjusted, in particular with respect to the pressure in the compressor train 9, in particular the pressure at the second point 2 a. As a result, for example, instead of the refrigerant by means of the refrigerant compressor 11, in particular directly, to the pressure of the refrigerant at the sixth point 2 b, the pressure of the refrigerant at the second point 2 acan be compressed to a higher pressure value and subsequently reduced by means of the third expansion valve 40, in particular for the condenser 14. As a result, a compressor power of the refrigerant compressor 11 can be particularly increased or kept particularly high, as a result of which a heating power of the condenser 14 can be particularly increased or kept high. This can be achieved, for example, in that the heating power corresponds, so to speak, approximately to the compressor power. The particularly high heating power can thus be effected at a particularly low temperature level.In order to be able to operate the temperature control device 6 in a robust and damage-free manner, and thus to be able to stabilize it, the partial mass flows and thus the mixing ratio Φ are preferably set as follows, that is to say set in such a way that the following applies:In this case, hs is:Hr denotes a safety enthalpy, also referred to as safety value, safety distance or safety, which is added to the dew line enthalpy ht in order to set the partial mass flows and thus the mixing ratio φ in such a way that the enthalpy of the refrigerant at the point 1 comes to lie reliably to the right of the dew line 22 in the phase diagram shown in FIG. 2. It can thus be seen that the partial mass flows are adjusted by actuating the expansion valves 15, 18 and 40 in such a way that the mixing ratio of the second partial mass flow to the first partial mass flow is greater than a ratio of the first enthalpy difference D 1 to the second enthalpy difference D 2. Consequently, the partial mass flows m1, m2 are set by actuating the expansion valves 15, 18 and 40 in such a way that the following applies:FIG. 3 shows a flow chart for illustrating the method. An arrow 28 illustrates a setpoint value of the mixing ratio, wherein the setpoint value is determined or predefined in particular in such a way that the setpoint value of the mixing ratio of the second partial mass flow and of the first partial mass flow is greater than the ratio of the first enthalpy difference D 1 to the second enthalpy difference D 2. An actual value of the mixing ratio is illustrated by an arrow 29, wherein the actual value is also designated as Φ ist for example. The actual value φ ist is given, for example, as:In this case, h3 denotes the third or fourth enthalpy, h2 denotes the second enthalpy and h1 denotes the first enthalpy. The first enthalpy h 1 can be calculated, in particular by means of the electronic computing device 19, from the first pressure and the first temperature, the second enthalpy h 2 can be calculated from the second pressure and the second temperature, and the third enthalpy h 3 can be calculated from the third pressure and the third temperature. The target value of the mixing ratio is also referred to as Φ soll for example. The setpoint value φ soll is, for example, predefined or calculated in the following manner, as explained above:The following applies here:For example, a difference is formed between the target value φ soll and the actual value φ ist. This results in, for example, a difference.phi.delta, also referred to as a control deviation, which is illustrated by an arrow 30 and is fed to a block 31. Block 31 illustrates, for example, a conversion of the setpoint value to the actuation of expansion valves 15, 18 and 40. in other words, for example, the control difference is compensated by block 31, so that block 31 illustrates, for example, a controller which is executed by electronic computing device 19. In particular, the electronic computing device 19 controls the expansion valves 15, 18 and 40 in such a way that the difference φ delta is at least reduced or eliminated.The method can ensure that the refrigerant compressor 11 is charged with purely gaseous fluid, and therefore that the total mass flow is formed, in particular exclusively, by a gaseous fluid or is formed as a gaseous fluid.FIG. 4 shows a flow chart for illustrating a control loop of the method. An arrow 41 illustrates a target value of the pressure of the refrigerant at the third point 3, the target value also being referred to as p S3,soll for example. In particular, the setpoint value illustrated by the arrow 41 is a setpoint value of the pressure detected by means of the third sensor device S 3. An actual value of the pressure of the refrigerant at the third point 3 is illustrated by an arrow 42, wherein the actual value is also designated as p S3,ist for example. In particular, the actual value illustrated by the arrow 42 is the pressure detected by means of the third sensor device S 3.For example, a difference is formed between the target value p S3,soll and the actual value p S3,ist. This results in, for example, a difference p 3,delta, also referred to as a control deviation, which is illustrated by an arrow 43 and is fed to a block 44. Block 44 illustrates, for example, a conversion of setpoint value p S3,soll to the actuation of third expansion valve 40. in other words, for example, the control difference is compensated by block 44, so that block 44 illustrates, for example, a controller which is executed by electronic computing device 19. In particular, the electronic computing device 19 controls the third expansion valve 40 in such a way that the difference p 3,delta is at least reduced or eliminated. As a result, the third expansion valve 40 can be actuated as a function of the determined third pressure, in particular as a function of the setpoint value p S3,soll and the actual value p S3,st in particular in order to set or regulate the third pressure.The method is also suitable for adjusting the power of the temperature control device 6, in particular of the refrigerant compressor 11. Because the refrigerant compressor 11 in the temperature control device 6, at least while the method is being carried out, represents the only heat source in order to temperature control, in particular heat, the sub-region, adjusting a power for the temperature control, in particular heating, of the heating region can cause problems, which can now be avoided by the method. The basis for this is a characteristic diagram typical of the refrigerant compressor 11 and illustrated, for example, in FIGS. 5 and 6, which is also referred to as a compressor characteristic diagram. On the abscissa 32 of the characteristic diagram, for example, a volume flow through the refrigerant compressor 11 (compressor) is plotted. Illustrated by way of example in FIGS. 5 and 6 are iso-lines P 1, P 2, etc. for an in particular electrical line of the compressor, and iso-lines N 1, N 2, etc. for a rotational speed of the compressor. A pressure loss curve 33 is also shown by way of example, which results when the expansion valves 15 and 18, and in particular 40, or their cross sections, are fully opened, and are therefore set to a respective maximum value. If it is now desired, for example, to set a specific performance point of the compressor, wherein the performance point lies, for example, on the iso-line P 6, two degrees of freedom are now available. A first of the degrees of freedom is the rotational speed of the compressor, also referred to as compressor rotational speed. The second degree of freedom is the pressure loss curve resulting from losses caused mainly by the expansion valves 15 and 18, and in particular 40. The smaller the respective flow cross section of the respective expansion valve 15, 18, and in particular 40, the higher a resistance against which the compressor must operate and the higher the losses. While, for example, according to FIG. 5, the flow cross sections are set to a maximum, according to FIG. 6, the flow cross sections are set to be smaller than according to FIG. 5, so that the losses are greater, which can be seen on the basis of the pressure loss curve 33. Thus, on the basis of the characteristic map and on the basis of the degrees of freedom, the pressure ratio plotted on the ordinate 34 of the characteristic map and the capacity of the compressor can be set at least arbitrarily within limits. By increasing the pressure losses, and thus by reducing the flow cross sections, the performance of the compressor is increased. By increasing the flow cross sections, the performance of the compressor is reduced. It is now possible to vary the flow cross sections in order to vary the output of the compressor and thus the output for tempering the sub-region, while however, despite the variation of the flow cross sections, a ratio of the flow cross sections to one another and thus the mixing ratio remains the same. It is thus possible, with the same mixing ratio, to set selectively a first power of the compressor or a second power of the compressor which is greater or smaller than the first power, so that, for example, in a first operating state the first power of the compressor is set and in a second operating state the second power of the compressor is set, wherein, however, the mixing ratio in the first operating state corresponds to the mixing ratio in the second operating state. This is possible in particular in such a way that the flow cross sections in the first operating state are larger than in the second operating state, but the same ratio of the flow cross sections to one another is set in the first operating state and in the second operating state.FIG. 7 illustrates another diagram for further illustrating the method. An arrow 35 illustrates a target value of the capacity of the compressor, and an arrow 36 illustrates a target value of the pressure ratio or a pressure to which the refrigerant is to be compressed by the compressor. On the basis of the compressor characteristic map denoted by 37 in FIG. 7, the rotational speed of the compressor illustrated by an arrow 38 results from the setpoint value of the power and from the setpoint value of the pressure or pressure ratio. An arrow 39 illustrates, for example, the pressure loss curve of a plant characteristic curve in the characteristic diagram or the plant characteristic curve, wherein, on the basis of the pressure loss curve or the plant characteristic curve, as described, the powers for tempering, in particular heating, the subregion are varied, but, for example, the mixing ratio can be kept the same or can be set in such a way that the first enthalpy in the phase diagram comes to lie securely to the right of the dew line 22.List of reference characters1 First point 2 aSecond point 2 b Sechste point 3 Third point 4 Fourth point 5 Fifth point 6 Temperature control device 7 Refrigerant circuit 8 Arrow 9 Compressor train 10 Arrow 11 Refrigerant compressor 12 Condenser train 13 Arrow 14 Condenser 15 First expansion valve 16 Bypass train 17 Arrow 18 Second expansion valve 19 Electronic computing device 20 Abscissa 21 Ordinate 22 Dew line 23 a Pfeil 23 b Pfeil 24 Arrow 25 Arrow 26 Arrow 27 Point 28 Arrow 29 Arrow 30 Arrow 31 Block 32 Abscissa 33 Pressure loss curve 34 Ordinate 35 Arrow 36 Arrow 37 Compressor map 38 Arrow 39 Arrow 40 Third expansion valve 41 Arrow 42 Arrow 43 Arrow 44 Block A Branch point D 1 First enthalpy difference D 2 Second enthalpy difference M Mixing point S 1 First sensor device S 2 Second sensor device S 3 Third sensor device

Claims

Method for operating a temperature control device (6) for controlling the temperature of at least one sub-region of a motor vehicle, in which: - the temperature control device (6) has a refrigerant circuit (7) through which a refrigerant flows, which refrigerant circuit has: ◯ a compressor train (9) through which a total mass flow (10) of the refrigerant flows, in which compressor train a refrigerant compressor (11) is arranged, by means of which the refrigerant is conveyed and compressed; ◯ a condenser train (12) branching off from the compressor train (9) and through which a first partial mass flow (13) of the refrigerant flows, in which condenser a first expansion valve (15), by means of which the first partial mass flow (13) can be adjusted and expanded, and a condenser (14), by means of which the first partial mass flow (13) is condensed, are arranged, wherein the condenser (14) is arranged in the condenser train (12) upstream of the first expansion valve (15); ◯ a bypass branch (16) connected in parallel with the condenser branch (12) and branching off from the compressor branch (9) and through which a second partial mass flow (17) of the refrigerant flows, in which bypass branch a second expansion valve (18) is arranged, by means of which the second partial mass flow (17) can be adjusted and is expanded; and ◯ a third expansion valve (40) arranged in the condenser branch (12) upstream of the condenser (14), by means of which third expansion valve the first partial mass flow (13) can be adjusted and is expanded; - the condenser branch (12) and the bypass branch (16) are combined at a mixing point (M), at which the partial mass flows (13, 17) are combined and thereby mixed with one another, whereby the partial mass flows (13, 17) result in the total mass flow (10), which flows into the compressor branch (9) and then flows through the compressor branch (9); and - by means of an electronic computing device (19): ◯ a first pressure and a first temperature of the refrigerant in the compressor train (9) upstream of the refrigerant compressor (11) and downstream of the mixing point (M) are determined; ◯ a second pressure and a second temperature of the refrigerant downstream of the refrigerant compressor (11), upstream of the condenser (14) and upstream of the first and second expansion valves (15, 18) are determined; ◯ a third pressure and a third temperature of the refrigerant in the condenser train (12) downstream of the condenser (14) and upstream of the first expansion valve (15) are determined; ◯ the first and second expansion valves (15, 18) are controlled as a function of the determined temperatures and as a function of the determined pressures, whereby the partial mass flows (13, 17) are set as a function of the determined temperatures and as a function of the determined pressures; ◯ the third expansion valve (40) is controlled as a function of the determined, third pressure.Method according to Claim 1, characterized in that the partial mass flows (13, 17) are set by actuating the expansion valves (15, 18, 40) in such a way that the total mass flow comprises exclusively superheated steam.Method according to Claim 1 or 2, characterized in that the electronic computing device (19): - calculates a first enthalpy of the refrigerant from the first pressure and the first temperature; - calculates a second enthalpy of the refrigerant from the second pressure and the second temperature; - calculates a third enthalpy of the refrigerant from the third pressure and the third temperature; and - actuates the expansion valves (15, 18, 40) as a function of the calculated enthalpy, as a result of which the partial mass flows (13, 17) are adjusted as a function of the calculated enthalpyMethod according to one of the preceding claims, characterized in that the partial mass flows (13, 17) are set by actuating the expansion valves (15, 18, 40) in such a way that a mixing ratio of the second partial mass flow (17) to the first partial mass flow (13) is greater than a ratio of a first enthalpy difference (D1) to a second enthalpy difference (D2), wherein: - the first enthalpy difference (D1) is the absolute value of a first difference between the enthalpy of the refrigerant in the condenser train (12) downstream of the condenser (14) and upstream of the first expansion valve (15) and the enthalpy of the refrigerant belonging to the first pressure and lying on the dew line (22) of the refrigerant; and - the second enthalpy difference (D2) is the absolute value of a second difference between the enthalpy of the refrigerant downstream of the refrigerant compressor (11), upstream of the condenser (14) and upstream of the first and second expansion valves (15, 18) and the enthalpy of the refrigerant belonging to the first pressure and lying on the dew line (22) of the refrigerant.Method according to one of the preceding claims, characterized in that the bypass branch (16): - is free of a condenser for condensing the refrigerant; and / or - is free of an evaporator for evaporating the refrigerant; and / or - is free of a heat exchanger for tempering the refrigerant.Method according to one of the preceding claims, characterized in that evaporation of the refrigerant by an evaporator is omitted in the condenser train (12).Method according to one of the preceding claims, characterized in that: - the first pressure and the first temperature are measured by means of a first sensor device (S1); and / or - the second pressure and the second temperature are measured by means of a second sensor device (S2); and / or - the third pressure and the third temperature are measured by means of a third sensor device (S3)Method according to one of the preceding claims, characterized in that: - the first pressure and the first temperature are calculated by means of the electronic computing device (19) on the basis of a computing model; and / or - the second pressure and the second temperature are calculated by means of the electronic computing device (19) on the basis of a computing model; and / or - the third pressure and the third temperature are calculated by means of the electronic computing device (19) on the basis of a computing model.Method according to one of the preceding claims, characterized in that: - in a first operating state, the first partial mass flow is set to a first value and the second partial mass flow is set to a second value by actuating the expansion valves (15, 18, 40); - in a second operating state, the actuating of the expansion valves (15, 18, 40) is set to a third value different from the first value and the second partial mass flow is set to a fourth value different from the second value; and - a first ratio of the first value to the second value corresponds to a second ratio of the third value to the fourth value, whereby a first power of the refrigerant compressor (11) is set in the first operating state and a second power of the refrigerant compressor (11) different from the first power is set in the second operating state.Temperature control device (6) for a motor vehicle, wherein the temperature control device is designed to carry out a method according to one of the preceding claims.

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