Refrigerant circuit with minimum suction pressure at the compressor in heat pump operation, motor vehicle and method for operating a refrigerant circuit

Abstract

The invention relates to a refrigerant circuit (10) for a motor vehicle, comprising a compressor (14) configured to supply compressed refrigerant to a heat exchanger (16) of the refrigerant circuit (10), and an expansion device (24) for expanding the refrigerant coming from the heat exchanger (16). Heat can be introduced into the refrigerant by means of an evaporator (26) of the refrigerant circuit (10) arranged downstream of the expansion device (24). A partial flow of the compressed refrigerant can be supplied to a suction side (28) of the compressor (14) via a return line (32). A valve assembly (36) is configured to open the return line (32) at least partially. A control device (38) is configured to control the valve assembly (36) in a heat pump operation of the refrigerant circuit (10).In heat pump operation, an airflow (18) that can be introduced into a passenger compartment of the motor vehicle can be heated by means of the heat exchanger (16). Furthermore, the invention relates to a motor vehicle with the refrigerant circuit (10) and a method for operating the refrigerant circuit (10).

Description

[0001] The invention relates to a refrigerant circuit for a motor vehicle, comprising a compressor configured to supply compressed refrigerant to a heat exchanger of the refrigerant circuit. An expansion device is provided for expanding the refrigerant coming from the heat exchanger. Heat can be introduced into the refrigerant by means of an evaporator of the refrigerant circuit arranged downstream of the expansion device. A partial flow of the compressed refrigerant can be supplied to a suction side of the compressor via a return line of the refrigerant circuit. A valve assembly is configured to release the return line, at least partially, and a control device for actuating the valve assembly is provided. Furthermore, the invention relates to a motor vehicle with such a refrigerant circuit and a method for operating the refrigerant circuit.

[0002] Especially in electric or hybrid vehicles, air conditioning systems with a refrigerant circuit must meet high standards. This applies, for example, to the comfort of the vehicle's occupants, which the air conditioning system is intended to provide. To heat the passenger compartment or cabin of the vehicle, an airflow heated by a heat exchanger can be introduced into the passenger compartment. In this process, heat is transferred to the refrigerant at the evaporator, which is supplied with refrigerant that has been expanded by the expansion unit.

[0003] In such a heat pump operation of the refrigerant circuit, operating conditions can occur where the mass flow rate of the refrigerant supplied to the heat exchanger is increased to increase its heating capacity. However, if only a small amount of heat is simultaneously transferred to the refrigerant at the evaporator, the refrigerant temperature in the evaporator can drop undesirably sharply. This is accompanied by a decrease in the suction pressure in the refrigerant circuit, i.e., a reduction in the refrigerant pressure at the evaporator's refrigerant outlet. In heat pump operation, it is essential to prevent the refrigerant temperature in the evaporator from dropping so low that it causes icing.Accordingly, in heat pump operation, a conflict of objectives can arise between increasing the heating output of the heat exchanger and preventing the evaporator from icing up.

[0004] To counteract this, an additional electric heater can be used to further heat the airflow introduced into the passenger compartment of the vehicle during heat pump operation. However, such an additional electric heater is disadvantageous in terms of the installation space required, its weight, and its cost.

[0005] DE 10 2021 132 800 A1 describes a method for operating a refrigerant circuit of a motor vehicle, in which, during cooling operation, an evaporator cools an airflow introduced into a passenger compartment of the vehicle. The aim is to avoid the compressor of the refrigerant circuit being switched on and off alternately. Instead, the compressor should always deliver at least a minimum mass flow of refrigerant. To prevent the evaporator from icing up despite the delivery of only the minimum mass flow of refrigerant, a partial flow of the refrigerant compressed by the compressor is routed via a return line, bypassing the evaporator, to a suction side of the compressor.

[0006] The object of the present invention is to provide a refrigerant circuit of the type mentioned above, by means of which a heating requirement can be met in a particularly simple manner, as well as to provide a motor vehicle with the refrigerant circuit and a corresponding method for operating the refrigerant circuit.

[0007] This problem is solved by a refrigerant circuit with the features of claim 1, a motor vehicle with the features of claim 9, and a method with the features of claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims and in the following description.

[0008] The refrigerant circuit according to the invention for a motor vehicle comprises a compressor configured to supply compressed refrigerant to a heat exchanger of the refrigerant circuit. The refrigerant coming from the refrigerant cooler can be decompressed by means of an expansion device of the refrigerant circuit, whereby heat can be introduced into the refrigerant by means of an evaporator of the refrigerant circuit arranged downstream of the expansion device. The refrigerant circuit includes a return line through which a partial flow of the compressed refrigerant can be supplied to a suction side of the compressor. A valve assembly of the refrigerant circuit is configured to open the return line, at least partially. The refrigerant circuit has a control device for actuating the valve assembly. The control device is configured to actuate the valve assembly in a heat pump operation of the refrigerant circuit.In heat pump mode, an airflow that can be introduced into a passenger compartment of the motor vehicle can be heated by means of the heat exchanger.

[0009] This is based on the understanding that, in heat pump operation, the heat exchanger can be used to heat the airflow introduced into the passenger compartment. Accordingly, to meet increased heating demands, the compressor can supply the heat exchanger with a correspondingly larger mass flow of refrigerant. However, if relatively little heat is introduced into the refrigerant at the evaporator during heat pump operation, the pressure in the refrigerant at an evaporator outlet can drop, leading to a decrease in the refrigerant temperature within the evaporator. To prevent icing of the evaporator, measures can be taken to ensure that an undesirably large drop in pressure does not occur on the compressor's suction side during heat pump operation.

[0010] For this purpose, the control unit in the heat pump operation of the refrigerant circuit can actuate the valve assembly. Actuating the valve assembly with the control unit causes the valve assembly to open the return line, at least partially. This allows a partial flow of the compressed refrigerant to flow from the pressure side of the compressor, particularly directly, to the suction side of the compressor. This partial flow of compressed and heated refrigerant thus reaches a low-pressure side of the refrigerant circuit, where the evaporator is also located, and excessive cooling of the evaporator must be prevented.

[0011] By supplying a partial flow of compressed refrigerant to the suction side of the compressor, the heating demand placed on the heat exchanger can be met in a particularly simple manner during heat pump operation. In particular, an additional electric heater is not required to adequately heat the airflow supplied to the passenger compartment of the vehicle. This is advantageous. Furthermore, by controlling the valve assembly, the evaporator can be protected from icing regardless of the total refrigerant mass flow rate delivered by the compressor.

[0012] For a given evaporator load, i.e., a given heat input into the refrigerant at the evaporator, a larger mass flow rate of the refrigerant delivered by the compressor, without the use of a return line with a valve controlled by the control unit, leads to a pressure drop at a refrigerant outlet of the evaporator, and thus on the suction side of the compressor. In the evaporator, the enthalpy of the refrigerant increases due to evaporation. However, with a large refrigerant mass flow rate and a given heat input into the refrigerant at the evaporator, the heat input results in a smaller increase in enthalpy than with a lower refrigerant mass flow rate.

[0013] In this case, even with a large mass flow rate of refrigerant being pumped by the compressor, the control unit can counteract the reduction in suction pressure, i.e., the pressure applied to the suction side of the compressor, by controlling the valve assembly. Consequently, in heat pump operation, a decoupling of the high-pressure level from the suction pressure level can be achieved by the control unit controlling the valve assembly accordingly.

[0014] The control device can, in particular, control the flow-through cross-section of the valve assembly as required, so that a defined quantity of hot refrigerant is directed from the high-pressure side of the compressor to the suction side. This prevents even an increased refrigerant flow rate through the compressor from causing an undesirably sharp drop in the refrigerant temperature in the evaporator. This is advantageous.

[0015] Preferably, the control device is designed to take into account at least one parameter for controlling the valve assembly during heat pump operation, based on which the temperature of the refrigerant in the evaporator can be determined. This allows for particularly demand-oriented control of the valve assembly. It ensures very precisely that the temperature of the refrigerant in the evaporator does not fall below a certain minimum temperature during heat pump operation.

[0016] Preferably, the control device is designed to evaluate a measurement from a pressure sensor in the refrigerant circuit to determine the temperature of the refrigerant in the evaporator. This is because the temperature of the refrigerant in the evaporator can be easily determined by evaluating the pressure. Furthermore, evaluating the pressure sensor measurement allows for particularly rapid adjustment or control of the refrigerant pressure at the compressor's suction side. This is also advantageous.

[0017] Additionally or alternatively, the control device can be configured to set a minimum refrigerant pressure at the compressor's suction side by actuating the valve assembly. This is based on the understanding that setting the minimum refrigerant pressure at the compressor's suction side simultaneously ensures that the refrigerant at the compressor's suction side, and thus at a refrigerant outlet of the evaporator, maintains a minimum temperature. This is advantageous for preventing undesirably excessive cooling of the evaporator.

[0018] Preferably, the evaporator is designed to cool the airflow that can be introduced into the passenger compartment of the vehicle during heat pump operation. This ensures that the airflow introduced into the passenger compartment is dehumidified during heat pump operation of the refrigerant circuit. This is advantageous for preventing condensation on the inside of the vehicle's windows. The dehumidified airflow can then be heated by the heat exchanger during heat pump operation. Such a reheat operation of the refrigerant circuit results in particularly efficient heating of the airflow.

[0019] Preferably, the control device is configured to take into account a measured value from a temperature sensor for controlling the valve assembly. The temperature sensor is designed to detect the temperature of the airflow at an air outlet side of the evaporator. By considering the measured value supplied by the temperature sensor, the control device can very easily and reliably verify whether increasing the suction pressure achieves the desired result with regard to the desired temperature of the airflow at the air outlet side of the evaporator. This allows for very reliable verification of whether a desired control objective has been reached. The increase in suction pressure is achieved by returning a partial flow of the compressed refrigerant from the pressure side of the compressor to the suction side of the compressor via the return line.

[0020] When regulating the refrigerant pressure on the compressor's suction side, the pressure measured by the pressure sensor on the compressor's suction side and / or the airflow temperature measured by the temperature sensor at the evaporator's air outlet can be used as the controlled variable. Using pressure as the controlled variable allows for particularly rapid regulation of the suction pressure. Conversely, using the temperature sensor reading as the controlled variable makes it much easier to ensure that a desired minimum airflow temperature is maintained at the evaporator's air outlet.

[0021] It is advantageous if the control device uses pressure as a control variable and also takes the temperature sensor reading into account. This allows a desired minimum temperature of the airflow at the evaporator's air outlet to be set particularly quickly and reliably.

[0022] Preferably, the control device is designed to set a temperature at the air outlet of the evaporator that prevents ice formation on the evaporator by actuating the valve and thereby recirculating a portion of the compressed refrigerant flow to the suction side of the compressor. This is based on the understanding that when air flows through the evaporator, moisture contained in the airflow can condense. This is because the refrigerant in the evaporator absorbs heat from the airflow. If, at the same time, a surface of the evaporator exposed to the airflow has a temperature below 0 °C, the condensed water can freeze. The resulting icing of the evaporator is detrimental.

[0023] Firstly, the airflow through the evaporator is reduced when the evaporator is iced up. Secondly, heat transfer from the airflow to the refrigerant is hindered when ice has formed on the evaporator. Therefore, it is advantageous if the control device, by activating the valve assembly, prevents ice formation on the evaporator.

[0024] Preferably, the compressor is designed as an electrically driven refrigerant compressor. The control unit is configured to increase the mass flow rate of the refrigerant delivered by the compressor, thereby increasing the heating output supplied by the heat exchanger during heat pump operation. This is based on the understanding that increasing the compressor speed results in a higher electrical power consumption. This increased electrical power consumption, in turn, leads to greater heat input into the refrigerant. The electrically driven refrigerant compressor can therefore be used like an electric heater, by means of which heat can be introduced into the refrigerant.Nevertheless, it is advantageous that no separate electric heater needs to be provided to introduce heat into the refrigerant.

[0025] Designing the compressor as an electrically driven refrigerant compressor is further advantageous because it eliminates the need for an internal combustion engine in the vehicle containing the refrigerant circuit to drive the compressor. This allows the heating of the vehicle's passenger compartment to be achieved advantageously even without the vehicle being driven by an internal combustion engine, using the refrigerant circuit as a heat pump.

[0026] Preferably, the control device is configured to supply refrigerant to an additional evaporator in the refrigerant circuit, designed as a chiller, during heat pump operation. The chiller is located downstream of another expansion device in the refrigerant circuit. It is connected to both the refrigerant circuit and a coolant circuit. This allows the chiller to be used during heat pump operation to transfer heat contained in the coolant into the refrigerant. This is particularly advantageous when the amount of heat that can be transferred to the refrigerant at the evaporator is relatively small. Accordingly, using the chiller to transfer heat into the refrigerant facilitates the fulfillment of heating requirements in a particularly simple manner.

[0027] The motor vehicle according to the invention comprises the refrigerant circuit according to the invention. Preferably, a fan is provided which is designed to introduce the airflow heated by the heat exchanger into the passenger compartment of the motor vehicle during heat pump operation. In this way, a comfortable climate for the occupants of the passenger compartment can be established during heat pump operation of the refrigerant circuit by heating the airflow.

[0028] Preferably, the vehicle is designed as an electric vehicle or a hybrid vehicle. Particularly in such a vehicle, it is advantageous that stabilizing the suction pressure prevents icing of the evaporator during heat pump operation. This allows a high heating demand to be met during heat pump operation without the evaporator icing up. This is advantageous.

[0029] When an electrical energy storage device of an electric vehicle or hybrid vehicle is designed as a high-voltage battery, the electrical energy storage device has a nominal voltage of more than 60 volts and, in particular, of up to several hundred volts.

[0030] In the inventive method for operating a refrigerant circuit for a motor vehicle, a compressor of the refrigerant circuit supplies compressed refrigerant to a heat exchanger of the refrigerant circuit. An expansion device of the refrigerant circuit expands the refrigerant coming from the heat exchanger, whereby heat is introduced into the refrigerant by means of an evaporator of the refrigerant circuit arranged downstream of the expansion device. A control device of the refrigerant circuit actuates a valve device, wherein the valve device opens a return line of the refrigerant circuit at least partially. A partial flow of the compressed refrigerant is supplied to a suction side of the compressor via the return line. The control device operates the valve device in a heat pump mode of the refrigerant circuit.In heat pump mode, an airflow that can be introduced into a passenger compartment of the motor vehicle can be heated by means of the heat exchanger.

[0031] This method allows for a particularly simple way to meet the heating requirements of the heat exchanger. Even with a high heating demand, and thus a high mass flow of refrigerant to the heat exchanger, evaporator icing can be prevented by returning a portion of the compressed, hot refrigerant to the suction side of the compressor. This is advantageous.

[0032] The advantages and preferred embodiments described for the refrigerant circuit according to the invention apply analogously to the motor vehicle according to the invention as well as to the method according to the invention and vice versa.

[0033] The invention therefore also includes further developments of the inventive method and the motor vehicle, which have features already described in connection with the further developments of the inventive refrigerant circuit. For this reason, the corresponding further developments of the inventive method and the motor vehicle are not described again here.

[0034] The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus.

[0035] The invention also includes combinations of the features of the described embodiments. The invention therefore also includes realizations that each exhibit a combination of the features of several of the described embodiments, provided that the embodiments have not been described as mutually exclusive.

[0036] The following are exemplary embodiments of the invention described. This is illustrated by: Fig. 1. Schematically, a refrigerant circuit for a motor vehicle, wherein the refrigerant circuit has a hot gas bypass line or return line, via which, in a heat pump operation of the refrigerant circuit, compressed refrigerant can be supplied to a suction side of a compressor; and Fig. 2 highly schematically a motor vehicle which uses the refrigerant circuit according to Fig. 1.

[0037] The exemplary embodiments described below are preferred embodiments of the invention. In these exemplary embodiments, the described components each represent individual features of the invention, which can be considered independently of one another and each further develops the invention independently. Therefore, the disclosure is intended to include combinations of features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0038] In the figures, identical reference symbols denote functionally equivalent elements.

[0039] In Fig. Figure 1 schematically depicts a refrigerant circuit 10 as it is used in a [system / unit] Fig. The refrigerant circuit 10, shown in section 2, can be used in the motor vehicle 12 shown. The refrigerant circuit 10 comprises a compressor 14, which is located in a vehicle based on the following: Fig. Figure 1 illustrates the operation of the refrigerant circuit 10, in which compressed and heated refrigerant is supplied to a heat exchanger 16 of the refrigerant circuit 10. Fig. Figure 1 illustrates the flow direction of the refrigerant in the heat pump operation of the refrigerant circuit 10 using flow arrows. In the heat pump operation of the refrigerant circuit 10, the heat exchanger 16 serves to heat an airflow 18 which enters a passenger compartment 20 (see Figure 1). Fig. 2) of the motor vehicle 12 can be brought in.

[0040] The heat exchanger 16 can be arranged in an air conditioning unit 22 or air conditioning box if the refrigerant circuit 10 is installed in the motor vehicle 12. In particular, the air conditioning unit 22 can be arranged in the area of ​​an instrument panel (not shown) of the motor vehicle 12.

[0041] The heat exchanger 16 can also be referred to as a heating heat exchanger or heating coil, since the heat exchanger or heat exchanger 16 is used in the heat pump operation of the refrigerant circuit 10 to heat the airflow 18 that can be introduced into the passenger compartment 20. In heat pump operation, the refrigerant coming from the heat exchanger 16 is preferably expanded by means of a first expansion device 24, wherein an evaporator 26 of the refrigerant circuit 10 is arranged downstream of the first expansion device 24. When the refrigerant evaporates in the evaporator 26, the refrigerant absorbs heat, so that heat is introduced into the refrigerant.

[0042] At the in Fig. In the exemplary variant of the refrigerant circuit 10 shown in Figure 1, the evaporator 26 is also arranged in the air conditioning unit 22. Accordingly, the evaporator 26 can be used to dehumidify the airflow 18 before the airflow 18 enters the passenger compartment 20 of the motor vehicle 12 (see Figure 1). Fig. 2) occurs.

[0043] In particular, if the air originating from the vehicle 12's surroundings, which can be introduced into the passenger compartment 20 in the form of the airflow 18, has a comparatively low temperature, for example, a temperature in the range between 5 °C and 10 °C, the refrigerant circuit 10 can be used in heat pump mode to provide a corresponding level of climate comfort for the occupants of the passenger compartment 20. Furthermore, dehumidifying the airflow 18 by means of the evaporator 26 is advantageous in preventing the (not shown) windows of the vehicle 12 from fogging up on the inside.

[0044] Particularly when the airflow 18 passing through the evaporator 26 has a comparatively low temperature and the heat exchanger 16 has a high heating requirement, it can prove difficult to increase the heating capacity of the heat exchanger 16 by increasing the mass flow rate of the refrigerant supplied by the compressor 14 and at the same time avoid icing of the evaporator 26.

[0045] This applies particularly if, due to the low temperature of the airflow 18 at the air-side evaporator 26, a comparatively small amount of heat is transferred to the refrigerant. For if, given a certain amount of heat transferred to the refrigerant at the evaporator 26, the mass flow rate of the refrigerant delivered by the compressor 14 is increased to increase the heating capacity of the heat exchanger 16, this will, without further measures being taken, lead to a decrease in the temperature of the refrigerant in the evaporator 26. The decrease in the temperature of the refrigerant in the evaporator 26, or interior evaporator or air conditioning evaporator, is accompanied by a decrease in the pressure of the refrigerant at a suction side 28 of the compressor 14. In the Fig. In the heat pump operation of the refrigerant circuit 10 shown, the refrigerant leaving the evaporator 26 passes via a refrigerant line 30 to the suction side 28 of the compressor 14.

[0046] If the suction pressure (i.e., the pressure of the refrigerant at the suction side 28 of the compressor 14) decreases, and the refrigerant temperature in the evaporator 26 decreases accordingly, icing of the evaporator 26 can occur, which must be avoided. Conversely, increasing the refrigerant mass flow rate can lead to a conflict between the resulting increase in the heating capacity of the heat exchanger 16 and the need to prevent icing of the evaporator 26.

[0047] The icing of the evaporator 26, which is avoidable in this case, can occur if, as the airflow 18 passes through the evaporator 26, moisture contained in the airflow 18 condenses, thus forming water. If, at the same time, a surface of the evaporator 26 over which the airflow 18 passes has a temperature of less than 0 °C, the condensed water can freeze.

[0048] To prevent this, it is preferably ensured that a minimum refrigerant pressure is not undershot at the suction side 28 of the compressor 14. Setting the minimum pressure at the suction side 28 of the compressor 14 ensures that the refrigerant also has a minimum pressure and thus a minimum temperature in the evaporator 26. The minimum pressure can be set very easily in this case to prevent icing of the evaporator 26. This is because the refrigerant circuit 10 has a return line 32 through which a partial flow of the compressed refrigerant from a pressure side 34 of the compressor 14 can be fed directly back to the suction side 28 of the compressor 14.

[0049] A valve assembly 36 is arranged in the return line 32, which can, for example, be designed as an expansion valve with a continuously variable flow cross-section. To control the valve assembly 36, the refrigerant circuit 10 has a control device 38, for example, designed as a control unit, which is located in Fig. 1 is shown schematically.

[0050] By actuating the valve assembly 36, the control unit 38 can cause the return line 32 to be at least partially opened. This allows the partial flow of compressed refrigerant to pass from the pressure side 34 of the compressor to the suction side 28 of the compressor.

[0051] The return line 32 terminates according to Fig. 1 enters the refrigerant line 30 at a junction 40. This line leads from a refrigerant outlet 42 of the evaporator 26 to the suction side 28 of the compressor 14. Accordingly, increasing the suction pressure, i.e., the pressure present at the suction side 28 of the compressor 14, also increases the pressure of the refrigerant in the evaporator 26. By recirculating the compressed refrigerant or hot gas, a minimum suction pressure can be set, which ensures that the refrigerant in the evaporator 26 has a minimum temperature. The return line 32 can therefore be referred to as a hot gas bypass, and the valve assembly 36 as a hot gas bypass valve.

[0052] In a refrigerant circuit that does not include the one in Fig. In the heat pump operation, in which the evaporator 26 is used to dehumidify the airflow 18 to be introduced into the passenger compartment 20, the refrigerant mass flow rate delivered by the compressor 14 determines not only the high pressure and thus the temperature of the refrigerant in the heat exchanger 16 or heating heat exchanger. Rather, the refrigerant mass flow rate also determines the suction pressure and thus the temperature level at the evaporator 26 or air conditioning evaporator. The return line 32 shown, with the valve assembly 36, determines the mass flow rate of the refrigerant not only the high pressure and thus the temperature of the refrigerant in the heat exchanger 16 or heating heat exchanger.

[0053] In the present case, the suction pressure can be maintained at a minimum level by integrating the hot gas bypass valve or valve assembly 36 and controlling it by the control unit 38. This applies even if the heating capacity of the heat exchanger 16 is increased by increasing the mass flow of refrigerant delivered by the compressor 14. Thus, a decoupling of the high-pressure level from the suction pressure level can be advantageously achieved.

[0054] By providing the return line 32 with the valve assembly 36, it is particularly unnecessary to install an electric auxiliary heater in the air conditioning unit 22 or air conditioning box. In principle, such an electric heater or auxiliary heater could be used to warm the airflow 18 if the heat exchanger 16 lacks sufficient heating capacity. However, providing the electric heater entails additional effort with regard to the installation space required, its weight, and its cost. This additional effort is advantageously eliminated in the present case.

[0055] In Fig. Figure 1 schematically shows a fan 72 of the refrigerant circuit 10, which can preferably be controlled by the control device 38 to bring the airflow 18 into the passenger compartment 20 of the motor vehicle 12.

[0056] Preferably, the compressor 14 is designed as an electrically driven refrigerant compressor, in which an increase in the mass flow rate of refrigerant delivered by the compressor 14 can be achieved by increasing the rotational speed. In the present case, due to an intelligent control strategy for actuating the hot gas bypass valve in the form of the valve assembly 36, the evaporator 26 can be protected from icing regardless of the rotational speed of the compressor 14. Even if the compressor 14 delivers a larger mass flow rate of refrigerant to increase the heating capacity of the heat exchanger 16, a reduction in the suction pressure and thus the temperature of the refrigerant in the evaporator 26 can be avoided by recirculating the partial flow to the suction side 28 of the compressor 14. This is advantageous.

[0057] The control unit 38 can incorporate a control strategy by which the opening cross-section of the valve assembly 36 is adjusted as required. This ensures that a defined quantity of hot refrigerant is transferred from the pressure side 34 or high-pressure side of the compressor 14 to the suction side 28 of the compressor 14, and thus to the low-pressure side of the refrigerant circuit 10.

[0058] To determine the temperature of the refrigerant in the evaporator 26, a measured value from a pressure sensor 44 of the refrigerant circuit 10 can be evaluated by the control unit 38, wherein the pressure sensor 44 can be designed, in particular, to detect the pressure and temperature of the refrigerant. In this case, the pressure sensor 44 is arranged between the refrigerant outlet 42 of the evaporator 26 and a suction-side inlet of the compressor 14, for example as shown in Fig. Figure 1 shows the connection between the junction 40 and the suction-side inlet of the compressor 14. If the measured value supplied by the pressure sensor 44 is used by the control device 38 to determine the temperature of the refrigerant in the evaporator 26, the desired minimum pressure of the refrigerant at the suction side 28 of the compressor 14 can be set, and in particular controlled, very quickly and accurately.

[0059] Alternatively, preferably additionally, the control device 38 for controlling the valve device 36 can take into account a measured value from a temperature sensor 46, which is located in Fig. Figure 1 shows a schematic representation. The temperature sensor 46 is designed to detect the temperature of the airflow 18 at an air outlet 48 of the evaporator 26. By taking the temperature of the airflow 18 at the air outlet 48 of the evaporator 26 into account, it is possible to monitor very precisely whether the actuation of the valve assembly 36 fulfills its intended purpose. For example, if the temperature of the airflow 18 at the air outlet 48 of the evaporator 26 is greater than 0 °C, it can be assumed with a high degree of certainty that icing of the evaporator 26 is not a concern.

[0060] In particular, the control device 38 can use either the measured value of the temperature sensor 46 or the measured value of the pressure sensor 44 to control the valve assembly 36. While the temperature sensor 46 is slower in detecting the temperature of the airflow than the pressure sensor 44 is in detecting the pressure of the refrigerant, taking the measured values ​​provided by the temperature sensor 46 into account allows for high control accuracy over the long term or over extended periods.

[0061] According to Fig. 1. The refrigerant circuit 10 can include a further evaporator, designed as a chiller 50, to which a further expansion device 52 is connected. The chiller 50 is integrated into the refrigerant circuit 10 and therefore has an inlet 54 for the refrigerant and an outlet 56 for the refrigerant. At a further junction 58 of the refrigerant circuit 10, the mass flow of the refrigerant coming from the heat exchanger 16 can be divided between the evaporator 26 and the chiller 50.

[0062] The chiller 50 is also integrated into a coolant circuit 60, which is located in Fig. Figure 1 is only shown in a highly schematic form. The coolant flowing through coolant circuit 60 can be described in the diagram. Fig. In the heat pump operation of refrigerant circuit 10 shown in Figure 1, heat can be additionally or alternatively introduced into the refrigerant. The chiller 50 can therefore be used in the heat pump operation of refrigerant circuit 10 in addition to or as an alternative to the evaporator 26 to introduce heat into the refrigerant.

[0063] The coolant circuit 60 may include (not shown) heat exchangers, which can be used to cool, in particular, electrical components of the motor vehicle 12. Examples of such electrical components are shown in Fig. Figure 2 schematically shows an electrical energy storage device 62 and at least one electrical drive unit 64 of the motor vehicle 12. The electrical energy storage device 62 provides electrical energy for the at least one drive unit 64, by means of which the wheels 66 of the motor vehicle 12 can preferably be driven. The motor vehicle 12, which includes the refrigerant circuit 10, can therefore be designed in particular as an electric vehicle or a hybrid vehicle.

[0064] In Fig. Figure 1 shows further sensors 68, 70 of the refrigerant circuit 10, which can be designed in particular to detect the pressure and / or temperature of the refrigerant. Here, the first sensor 68 is arranged between the heat exchanger 16 and the junction 58, at which, in heat pump operation, the refrigerant flow can be divided between the evaporator 26 and the chiller 50 by controlling the respective expansion devices 24, 52.

[0065] The second sensor 70 is located on the pressure side 34 of the compressor 14, upstream of a branch point where the return line 32 branches off from a refrigerant line of the refrigerant circuit 10 leading from the compressor 14 to the heat exchanger 16. The functions of these two sensors 68 and 70 need not be explained in detail here.

[0066] Overall, the examples show how a method for ensuring heating performance in the preferably electrified motor vehicle 12 with heat pump can be provided without an additional electric heater. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 132 800 A1

[0005]

Claims

[1] Refrigerant circuit (10) for a motor vehicle (12), comprising a compressor (14) configured to supply compressed refrigerant to a heat exchanger (16) of the refrigerant circuit (10), an expansion device (24) for expanding the refrigerant coming from the heat exchanger (16), wherein heat can be introduced into the refrigerant by means of an evaporator (26) of the refrigerant circuit (10) arranged downstream of the expansion device (24), a return line (32) through which a partial flow of the compressed refrigerant can be supplied to a suction side (28) of the compressor (14), a valve device (36) configured to release the return line (32) at least partially, and a control device (38) for controlling the valve device (36), characterized by, that the control device (38) is designed to control the valve device (36) in a heat pump operation of the refrigerant circuit (10), wherein in the heat pump operation an airflow (18) that can be introduced into a passenger compartment (20) of the motor vehicle (12) can be heated by means of the heat exchanger (16). [2] Refrigerant circuit (10) according to claim 1, characterized by , that the control device (38) is designed to take into account at least one parameter in the heat pump operation for controlling the valve device (36) by means of which a temperature of the refrigerant in the evaporator can be determined. [3] Refrigerant circuit (10) according to any one of the preceding claims, characterized by, that the control device (38) is designed to evaluate a measured value from a pressure sensor (44) of the refrigerant circuit (10) in order to determine a temperature of the refrigerant in the evaporator (26), and / or to set a minimum pressure of the refrigerant at the suction side (28) of the compressor (14) by actuating the valve device (36). [4] Refrigerant circuit (10) according to any of the preceding claims, characterized by , that the evaporator (14) is designed to cool the airflow (18) in heat pump operation, which can be introduced into the passenger compartment (20) of the motor vehicle (12). [5] Refrigerant circuit (10) according to claim 4, characterized by, that the control device (38) is configured to take into account a measured value from a temperature sensor (46) for controlling the valve device (36), wherein the temperature sensor (46) is configured to detect a temperature of the airflow (18) at an air outlet side (48) of the evaporator (26). [6] Refrigerant circuit (10) according to any of the preceding claims, characterized by , that the control device (38) is designed to set a temperature at an air outlet side (48) of the evaporator (26) by controlling the valve device (36) and thereby returning the partial flow of the compressed refrigerant to the suction side (28) of the compressor (14), at which ice formation on the evaporator (26) is prevented. [7] Refrigerant circuit (10) according to any of the preceding claims, characterized by, that the compressor (14) is designed as an electrically driven refrigerant compressor, wherein the control device (38) is designed to increase the mass flow of the refrigerant supplied by the compressor (14) in order to increase the heating power to be provided by the heat exchanger (16) in the heat pump operation by controlling the compressor (14). [8] Refrigerant circuit (10) according to any of the preceding claims, characterized by , that the control device (38) is designed to cause a further evaporator of the refrigerant circuit (10) designed as a chiller (50) to be supplied with refrigerant during heat pump operation, wherein the chiller (50) is arranged downstream of a further expansion device (52) of the refrigerant circuit (10), and wherein the chiller (50) is connected on one side to the refrigerant circuit (10) and on the other side to a coolant circuit (60). [9] Motor vehicle (12) with a refrigerant circuit (10) according to one of the preceding claims, wherein the motor vehicle (12) is designed as an electric vehicle or as a hybrid vehicle. [10] Method for operating a refrigerant circuit (10) for a motor vehicle (12), in which a compressor (14) of the refrigerant circuit (10) supplies compressed refrigerant to a heat exchanger (16) of the refrigerant circuit (10), wherein an expansion device (24) of the refrigerant circuit (10) expands the refrigerant coming from the heat exchanger (16), wherein heat is introduced into the refrigerant by means of an evaporator (26) of the refrigerant circuit (10) arranged downstream of the expansion device (24), wherein a control device (38) of the refrigerant circuit (10) actuates a valve device (36), wherein the valve device (36) at least partially releases a return line (32) of the refrigerant circuit (10), and wherein a partial flow of the compressed refrigerant is supplied to a suction side (28) of the compressor (14) via the return line (32), characterized by, that the control device (38) controls the valve device (36) in a heat pump operation of the refrigerant circuit (10), wherein in the heat pump operation an airflow (18) that can be introduced into a passenger compartment (20) of the motor vehicle (12) can be heated by means of the heat exchanger (16).

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