Method for operating a refrigerant circuit and vehicle refrigeration system

Abstract

Method for operating a refrigerant circuit (2) of a vehicle refrigeration system (1) in an AC mode and in a heating mode realized by means of a heat pump function, comprising: - an evaporator branch (2.1) with an evaporator (3) and a first expansion element (6.1) associated with the evaporator (3), - a refrigerant compressor (4), - an AC and heat pump branch (2.2) with an external condenser or gas cooler (5) and a second expansion element (6.2) assigned to the same in a function as a heat pump evaporator for heating operation, wherein the AC and heat pump branch (2.2) is connected, on the one hand, via a first shut-off element (A1) to a high-pressure outlet of the refrigerant compressor (4) and, on the other hand, via the second expansion element (6.2) to the evaporator branch (2.1) in such a way that, in AC operation, a refrigerant from the external condenser or gas cooler (5) is expanded into the evaporator (3) via the opened second expansion element (6.2) by means of the first expansion element (6.1), - a heating branch (2.3) with an internal heating condenser or heating gas cooler (7) arranged in an air conditioning unit (1.1) and a second shut-off device (A2) arranged downstream of the same, wherein the heating branch (2.3) is connected to the high-pressure outlet of the refrigerant compressor (4) via a third shut-off device (A3) and via the second shut-off device (A2) to the evaporator branch (2.1), and - a third expansion element (6.3), with which the heating branch (2.3) is connected to the AC and heat pump branch (2.2) in such a way that a refrigerant for condensation and release of heat to a vehicle environment is expanded by means of the third expansion element (6.3) to an intermediate pressure above an evaporation pressure in the external condenser or gas cooler (5) and then expanded to a low pressure by means of the first expansion element (6.1) in the evaporator (3), wherein - a refrigerant temperature at an inlet (E) of the internal heating condenser or heating gas cooler (7) is determined by means of a temperature measuring device (T, pT1), - in heating mode, the refrigerant temperature at the inlet (E) of the internal heating condenser or heating gas cooler (7) is limited to a maximum temperature value, and - the maximum temperature value is determined as a function of a maximum compatible material temperature of a material used for the air conditioning unit (1.1).

Description

The invention relates to a method for operating a refrigerant circuit of a vehicle refrigeration system in an AC operation and in a heating operation by means of a heat pump function.DE 10 2011 118 162 A1 describes a refrigerant circuit of a vehicle refrigeration system with a heat pump function that can be operated in an AC and heating mode and a method for operating the vehicle refrigeration system with function sequences for refrigerant displacement, in that refrigerant is suctioned out of non-active regions and overflowed into active regions of the refrigeration system during starting or is fed into the operation thereof by a circuit of a connection of the non-active regions to the active low-pressure side of the refrigeration system. This vehicle refrigeration system, which can be operated as a refrigeration circuit for AC operation and as a heat pump circuit for a heating function, comprises a primary train with a compressor, an external heat exchanger as a refrigeration system condenser or heat pump evaporator, a refrigerant collector, an internal heat exchanger with a high-pressure passage and a low-pressure passage for the refrigerant, an expansion element and an evaporator, and a secondary train with a heating condenser with an associated expansion element. Furthermore, a lockable bypass is provided, which is arranged between the high-pressure outlet of the inner heat exchanger and the outer heat exchanger for flowing through the high-pressure passage of the inner heat exchanger and has an expansion element, which is assigned to the outer heat exchanger in its function as a heat pump evaporator for heating operation.DE 10 2007 005 498 A1 discloses an air conditioning system for vehicles having a refrigerant circuit in which a temperature sensor is located in the region between the refrigerant compressor and a gas cooler, which temperature sensor is used to monitor the refrigerant quantity of the refrigerant circuit. The monitoring device comprises a characteristic diagram for distinguishing plausible values and non-plausible values of the temperature measured by the temperature sensor as a function of a further value determined by measurement technology, e.g. the refrigerant pressure, the air temperature downstream of the refrigerant compressor, the air temperature downstream of the evaporator, the air quantity of the climate blower, the ambient temperature, the rotational speed of the refrigerant compressor, the travel speed, the internal temperature, the solar radiation or the air humidity. In this case, the measured temperature is checked to see whether it is plausible under the given operating conditions and parameters.DE 10 2013 021 360 A1 discloses a method for operating a refrigerant circuit of a vehicle air conditioning system in an AC operation and in a heating operation by means of a water heat pump function, wherein this water heat pump function is realized by means of a chiller. This refrigerant circuit comprises an evaporator branch with an evaporator and an associated expansion element, an AC branch with an outer condenser which is connected on the one hand via a shut-off element to a refrigerant compressor and on the other hand via a branch to the evaporator branch, wherein at least one chiller branch consisting of a chiller and an associated expansion element is connected in parallel with the evaporator branch. Furthermore, a heating branch with an inner heating condenser (also called heating register) connects the high-pressure outlet of the refrigerant compressor to the branch by means of a further shut-off element, wherein the heating branch and the AC branch are blocked in the direction of the branch in each case by means of a further shut-off element. Thus, it is possible, by appropriate control of these two shut-off devices, either to connect the AC branch via the branch to the evaporator branch and / or the chiller branch in AC operation or to connect the heating branch via the branch to the chiller branch or both to the chiller branch and to the evaporator branch in heating operation. The method known from DE 10 2013 021 360 A1 provides that in the pure cooling mode of a vehicle battery thermally connected to the chiller, a refrigerant temperature at the outlet of the chiller is set close to the dew line of the refrigerant used for achieving a maximum cooling power with a minimum power consumption of the compressor via the position of the expansion element assigned to the chiller.DE 10 2006 024 796 A1 describes a refrigerant circuit of a vehicle air conditioning system having a cooling and heating function with a refrigerant compressor, an outer condenser and an inner heat exchanger with an associated expansion element, wherein the inner heat exchanger is divided into two partial heat exchangers in the flow direction of an inflow of air guided into the vehicle cabin. To implement different operating modes, the compressed refrigerant can be supplied by means of the shut-off elements downstream of the refrigerant compressor either to the outer condenser, to the first partial heat exchanger or dividedly to both the outer condenser and to the first partial heat exchanger. The first partial heat exchanger is preferably used for cooling the supply air stream, i.e. as a refrigerant evaporator, and the second partial heat exchanger, which is arranged downstream in the flow direction of the supply air stream, is preferably used for heating the supply air stream, i.e. as an inner heating condenser or heating register. Furthermore, it is also possible to use the two partial heat exchangers as refrigerant evaporators for cooling at a maximum cooling requirement or for heating at a maximum heating requirement. Finally, a reheat operation is also provided in that the first partial heat exchanger works as a refrigerant evaporator and at the same time the second partial heat exchanger works as a heating condenser and the condensation heat arising in a first stage is thereby used together with the compressor waste heat for heating the supply air stream in a second stage by dehumidifying the supply air stream.In these refrigerant circuits known from the prior art, refrigerant at high temperature flows through the respective heating registers during heating operation, in particular when using the refrigerant R744, (CO2). Since a heating register is arranged in an air conditioning unit, the high temperatures of the refrigerant lead to a high material stress, in particular on the housing of the air conditioning unit. This requires cost-intensive measures for decoupling the heating register and the lines from the housing of the air conditioning unit.Furthermore, measures for refrigerant extraction from dead volumes produced in AC operation or heating operation are also required in the known refrigerant circuits, but are not optimally implemented with regard to component requirements.Thus, according to DE 10 2013 021 360 A1, refrigerant is extracted from the AC branch, in particular for water heat pump operation, in that the outer condenser can be connected to the low-pressure side of the refrigerant compressor or at least to the low-pressure side upstream or alternatively also downstream via a shut-off element and a non-return valve. This has the advantage that despite the shut-off element being open, in the event of a pressure increase and a flow reversal associated therewith, a return flow into the dead volume via the check valve is prevented. Disadvantageous in this case are the additional components that cause costs, such as a non-return valve and possibly the complete line with a non-return valve.In the refrigerant circuit according to DE 10 2006 024 796 A1, no measures are provided for removing refrigerant from dead volumes in AC operation or heating operation. This has the disadvantage that an undefined amount of refrigerant disappears or remains in the dead volume and is no longer available to the active process and thus the system is overfilled in the most disadvantageous case and is operated inefficiently.Proceeding from the prior art, the object is to specify a method for operating a refrigerant circuit of a vehicle refrigeration system in an AC operation and in a heating operation by means of a heat pump function, with which method a high material stress on the housing of an inner heating condenser (heating register), in particular when R744 is used as refrigerant, is avoided. It is a further object of the invention to specify a refrigerant circuit for carrying out the method according to the invention.The first object is achieved by a method for operating a refrigerant circuit of a vehicle air conditioning system having the features of patent claim 1Such a method for operating a refrigerant circuit of a vehicle refrigeration system in an AC operation and in a heating operation implemented by means of a heat pump function, comprising:an evaporator branch having an evaporator and a first expansion element assigned to the evaporator,a refrigerant compressor,an AC and heat pump branch having an outer condenser or gas cooler and a second expansion element assigned to the latter in a function as a heat pump evaporator for heating operation, wherein the AC and heat pump branch is connected on the one hand via a first shut-off element to a high-pressure outlet of the refrigerant compressor and on the other hand via the second expansion element to the evaporator branch in such a way that, in AC operation, a refrigerant is expanded from the outer condenser or gas cooler into the evaporator via the opened second expansion element by means of the first expansion element,a heating branch having an inner heating condenser or heating gas cooler arranged in an air conditioning unit and a second shut-off element connected downstream of the latter, the heating branch being connected to the high-pressure outlet of the refrigerant compressor via a third shut-off element and to the evaporator branch via the second shut-off element, anda third expansion element, by means of which the heating branch is connected to the AC and heat pump branch in such a way that a refrigerant for condensation and release of heat to a vehicle environment is expanded by means of the third expansion element to an intermediate pressure lying above the evaporation pressure in the outer condenser or gas cooler and is subsequently expanded to low pressure by means of the first expansion element in the evaporator, is characterized in thata refrigerant temperature at the inlet of the heating condenser or heating gas cooler is determined by means of a temperature measuring means (T, pT1),limiting the refrigerant temperature at the inlet of the internal heating condenser or heating gas cooler to a maximum temperature value in heating operation, andthe maximum temperature value is defined as a function of the maximum compatible material temperature of the material used for the air conditioning unit.In this method according to the invention, damage to the inner heating condenser, but primarily to the plastic housing of the air conditioner, the so-called HVAC unit, is prevented by limiting the refrigerant temperature at the inlet of the inner heating condenser to a maximum temperature value during heating operation. The maximum temperature value can be determined as a function of the maximum permissible and compatible material temperature of the housing material of the air conditioning unit. In AC operation, a flow through the inner heating condenser is prevented by shutting off the heating branch by means of the second shut-off element, and thus the inner heating condenser or the air conditioning device is also protected from damage in AC operation.It is appropriate to combine the temperature measuring means with a pressure measuring means in order to monitor the high pressure at the outlet of the refrigerant compressor and to restrict it to a maximum permissible high pressure value.Preferably, for determining the refrigerant temperature at the inlet of the inner heating condenser or heating gas cooler, a temperature measuring means is arranged at the high-pressure outlet of the refrigerant compressor, wherein the refrigerant temperature at the inlet of the heating condenser or heating gas cooler is determined from a characteristic diagram by means of the sensor value generated by the temperature measuring means. Alternatively or additionally, the refrigerant temperature is determined by means of a temperature measuring means arranged at the inlet of the heating condenser or heating gas cooler. If such a temperature measuring means, for example a temperature sensor, is additionally used, the latter can perform a monitoring function for representing a protective function.A particularly advantageous development of the invention provides that the following method steps are carried out in AC operation when an operation start is made:sucking refrigerant out of the heating branch by opening the second shut-off element and closing both the third shut-off element and the third expansion element, andclosing the second shut-off element either with increasing refrigerant pressure downstream of the second shut-off element or after a defined time period.For this method for implementing a suction extraction of refrigerant from a dead volume of the inner heating condenser or heating gas cooler for AC operation, the existing lines of the refrigerant circuit are used, i.e., no additional line sections or valve components are required. The second shut-off element is closed as a function of the refrigerant pressure downstream of the latter or after a defined period of time.The defined time period is determined by the fact that in the system for this time window, for example. 5 minutes, a lower air-side evaporator outlet temperature is requested than is the case in normal operation (for example. 1°C instead of 3°C). This results in a lower system-side low pressure and the suction potential rises. Upon expiration of the defined and predetermined time interval, the system is returned to the standard parameters, the second shut-off valve being closed immediately before it, in order to avoid a return flow of refrigerant into the heating branch.If the refrigerant pressure is used as a signal and reference value for closing the second shut-off element, this can be determined indirectly or directly.For the indirect determination of the refrigerant pressure, the blower load of a blower of the air conditioning unit and / or the setpoint value of the air temperature at the evaporator set by a control unit of the refrigerant circuit and / or the pressure profile of the refrigerant on the low-pressure side of the refrigerant circuit is detected, and, in the case of a falling blower load and / or in the case of an increasing setpoint value and / or in the case of an increasing refrigerant pressure on the low-pressure side, the second shut-off element is closed immediately before the change occurs. The signals that a change is imminent can be detected and evaluated via the corresponding (climate) control units, so that the second shut-off element is closed immediately before the event occurs.For the direct determination of the refrigerant pressure, the refrigerant pressure is determined directly downstream of the second shut-off element by means of a pressure sensor connected downstream of the latter.A further particularly preferred development of the invention provides that, in the case of an operation start in heating operation, the following method steps are carried out by means of a water heat pump function or a triangular process:providing a chiller branch having a chiller and an associated fourth expansion element for implementing the water heat pump function, the chiller branch being connected in parallel with the evaporator branch,sucking refrigerant from the AC and heat pump branch by opening a fourth valve connecting the AC and heat pump branch to the low pressure side of the refrigerant circuit and closing both the third and second expansion elements and the first valve, andclosing the fourth shut-off element either with increasing refrigerant pressure downstream of the fourth shut-off element or after a defined time period.For this method for implementing a suction extraction of refrigerant from a dead volume of the outer condenser or gas cooler for heating operation by means of the water heat pump function or the triangular process, the existing lines of the refrigerant circuit are used, i.e. no additional line sections or valve components are required. The fourth shut-off element is closed as a function of the refrigerant pressure downstream of the latter or after a defined period of time.The defined time interval is determined by the fact that the suction pressure to be set in the system is determined by a control unit for a suction pressure set to, for example. 5 minutes, or this time interval which is limited by 5 minutes is set to the minimum permissible value, or this is to be specifically started on the system side, before the fourth shut-off valve is closed at the end of this time interval and the low pressure can be found or set at a higher level, depending on the water temperature which is available at this time and which in turn influences the low pressure level.If the refrigerant pressure is used to close the fourth shut-off element, it can be determined indirectly or directly.For the indirect determination of the refrigerant pressure, the coolant temperature of the chiller is detected and, as the coolant temperature rises, the fourth shut-off element is closed.For the direct determination of the refrigerant pressure, the refrigerant pressure is determined directly downstream of the fourth shut-off element by means of a pressure sensor connected downstream of the latter.In an alternative method for implementing a suction extraction of refrigerant from a dead volume of the inner heating condenser or heating gas cooler for AC operation, the following method steps are carried out according to the development:providing a non-return valve downstream of the second shut-off element for preventing a return flow of refrigerant into the dead volume,sucking refrigerant out of the heating branch by opening the second shut-off element and closing both the third shut-off element and the third expansion element, andreleasing the refrigerant downstream of the second shut-off element to the low-pressure level by means of the second expansion element while at the same time the first and / or fourth expansion element is at maximum open.In this method too, the already present inventory lines of the refrigerant circuit are used. To ensure the low pressure required for the extraction from the heating branch, the second expansion element performs the expansion function of the refrigerant directly within the section downstream of the second shut-off element, bounded by said second shut-off valve and by the first, second and fourth expansion elements.In a further alternative method for implementing a suction extraction of refrigerant from a dead volume of the inner heating condenser or heating gas cooler for AC operation, the following method steps are carried out according to the development:providing a heat pump return branch having a fourth shut-off element and a check valve, wherein the AC and heat pump branch is connected to the evaporator branch downstream of the evaporator with the heat pump return branch,providing a suction branch having a fifth expansion element, wherein the suction branch connects the heat pump return branch to the heating branch downstream of the inner heating condenser or heating gas cooler, andsuction of refrigerant from the heating branch by opening the fifth expansion element and closing both the second, third and fourth shut-off elements and the third expansion element.With the refrigerant circuit on which this method is based, but in particular with the introduction of the fifth expansion element, a direct triangular process with the shortest possible line lengths can advantageously be carried out via the heat pump return branch and the suction branch.The second object mentioned is achieved by a vehicle cooling system having the features of claim 12.Such a vehicle refrigeration system having a refrigerant circuit for an AC operation and for a heating operation carried out by means of a heat pump function for carrying out the method according to the invention comprises the following components:an evaporator branch having an evaporator and a first expansion element assigned to the evaporator,a refrigerant compressor,an AC and heat pump branch having an outer condenser or gas cooler and a second expansion element assigned to the latter in its function as a heat pump evaporator for heating operation, wherein the AC and heat pump branch is connected on the one hand via a first shut-off element to a high-pressure outlet of the refrigerant compressor and on the other hand via the second expansion element to the evaporator branch in such a way that, in AC operation, a refrigerant can be expanded from the outer condenser or gas cooler into the evaporator via the opened second expansion element by means of the first expansion element,a heating branch having an inner heating condenser or heating gas cooler arranged in an air conditioning unit and a second shut-off element connected downstream of the latter, the heating branch being connectable to the high-pressure outlet of the refrigerant compressor via a third shut-off element and to the evaporator branch via the second shut-off element, anda third expansion element, by means of which the heating branch can be connected to the AC and heat pump branch in such a way that a refrigerant for condensation and release of heat to a vehicle environment can be expanded by means of the third expansion element to an intermediate pressure lying above the evaporation pressure in the outer condenser or gas cooler and can then be expanded by means of the first expansion element into the evaporator to low pressure, whereina refrigerant temperature at the inlet of the heating condenser or heating gas cooler can be determined by means of a temperature measuring means.Such a refrigerant circuit for carrying out the method according to the invention has a simple structure, with which the extraction processes for the AC operation and the heating operation can also be carried out. Further advantageous embodiments of this refrigerant circuit are evident from the dependent patent claims.Further advantages, features and details of the invention are evident from the following description of preferred embodiments and on the basis of the drawings. The following are shown: FIG. 1 shows a refrigerant circuit of a vehicle cooling system for carrying out the method according to the invention as a first exemplary embodiment, FIG. 2 shows a refrigerant circuit of a vehicle cooling system for carrying out the method according to the invention as a second exemplary embodiment, FIG. 3 shows a refrigerant circuit of a vehicle cooling system for carrying out the method according to the invention as a third exemplary embodiment, and FIG. 4 shows a refrigerant circuit of a vehicle cooling system for carrying out the method according to the invention as a fourth exemplary embodiment.The refrigerant circuits 2 of a vehicle cooling system 1 shown in each of FIGS. 1 to 4 have the same basic structure, which is described first in order to explain the differences between the refrigerant circuits 2 below. These refrigerant circuits 2 can be operated in an AC mode and in a heating mode implemented by means of a heat pump function.Such a refrigerant circuit 2 comprises an evaporator 3 arranged in an evaporator branch 2.1 with an associated first expansion element 6.1, a refrigerant compressor 4, an outer condenser 5 or gas cooler 5 arranged in an AC and heat pump branch 2.2 with a second expansion element 6.2 associated therewith in its function as a heat pump evaporator for heating operation, wherein this AC and heat pump branch 2.2 is connected on the one hand via a first shut-off element A 1 designed as a shut-off valve to the high-pressure outlet of the refrigerant compressor 4 and on the other hand via the second expansion element 6.2 to form a branch point Ab 1 with the evaporator branch 2.1. The high-pressure side of an internal heat exchanger 9 is arranged between the second expansion element 6.2 and the outer condenser 5 or gas cooler 5, the low-pressure-side section of which, arranged between evaporator 3 and refrigerant compressor 4, is preceded on the upstream side by a refrigerant collector 10.Furthermore, the refrigerant circuit 2 consists of a heating branch 2.3 with an inner heating condenser 7 or heating gas cooler 7 (which are also referred to as heating registers) and a second shut-off element A2 arranged downstream of the latter and configured as a shut-off valve. Starting from the high-pressure side of the refrigerant compressor 4, the heating branch 2.3 is connected to the refrigerant compressor 4 by means of a third shut-off element A 3 designed as a shut-off valve, while downstream of the heating branch 2.3 downstream of the inner heating condenser 7 or heating gas cooler 7, on the one hand, is connected to the evaporator branch 2.1 via the second shut-off element A 2 and the branch point Ab 1 and, on the other hand, is connected to the outer condenser 5 or gas cooler 5 via a third expansion element 6.3, forming a branch point Ab 2.The branch point Ab2 connects the first shut-off element A1 to the outer condenser 5 or gas cooler 5 and is connected via a heat pump return branch 2.5 to a fourth shut-off element A4, which is designed as a shut-off valve, to the low-pressure side of the refrigerant compressor 4 forming a branch point Ab3. On the upstream side, this branch point Ab 3 is connected via a check valve R 3 to the evaporator branch 2.1 and on the downstream side to the refrigerant collector 10, so that the refrigerant from this heat pump return branch 2.5 is returned to the refrigerant compressor 4 via the refrigerant collector 10 and the low-pressure side of the inner heat exchanger 9.Finally, the refrigerant circuit 2 has a chiller 8 arranged in a chiller branch 2.4 with a fourth expansion element 6.4 assigned to it. This chiller branch 2.4 is connected in parallel with the evaporator branch 2.1, i.e. connects the branch point Ab1 to the line section between the check valve R3 and the refrigerant collector 10. Water is used as coolant and serves for cooling, for example, an electric drive machine, power electronics and / or a battery. Furthermore, such a chiller 8 is used to implement a water heat pump function by utilizing the waste heat from electronic and / or electrical components.The evaporator 3 and the inner heating condenser 7 or heating gas cooler 7 are arranged in an air conditioning unit 1.1 together with an electric heating element 11 as a supplementary heater for the incoming air flow guided into the vehicle interior. This electrical heating element 11 can be designed, for example, as a high-voltage PTC heating element.With the two shut-off devices A1 and A3, the refrigerant flow, starting from the high-pressure side of the refrigerant compressor 4, is either conducted into the AC and heat pump branch 2.2 when the shut-off device A1 and the shut-off device A3 are open or flows into the heating branch 2.3 when the shut-off device A3 is open and the shut-off device A1 is closed, depending on the state of the two shut-off devices A1 and A3. The two shut-off members A 1 and A 3 can also be designed as a 3-2 directional control valve.In a further embodiment variant, the at least 3 shut-off elements A 1, A 3 and A 4 can be combined to form a multiway valve.In the AC operation of the refrigerant circuit 2, the refrigerant compressed to high pressure flows from the refrigerant compressor 4 into the AC and heat pump branch 2.2 with the shut-off element A 1 open and is expanded via the outer condenser 5 or gas cooler 5, the high-pressure section of the inner heat exchanger 9, the completely open second expansion element 6.2 and the branch point Ab 1 by means of the first expansion element 6.1 into the evaporator 3 or by means of the fourth expansion element 6.4 into the chiller 8, optionally also simultaneously into the evaporator 3 and into chiller 8. From the evaporator 3, the refrigerant is returned to the refrigerant compressor 4 via the check valve R 3, via the refrigerant collector 10 and the low-pressure side of the inner heat exchanger 9. Accordingly, the refrigerant also flows out of the chiller 8 via the refrigerant collector 10 and the low-pressure side of the inner heat exchanger 9 back to the refrigerant compressor 4.In this AC operation, the heating branch 2.3 is shut off by means of the third shut-off element A3, so that hot refrigerant, for example. R744, because of its high temperature, cannot flow through the heating gas cooler 7 and damage to the air conditioning unit 1.1 is thus prevented.In heating operation using the chiller 8 to implement a water heat pump or using the outer condenser 5 or gas cooler 5 as a heat pump evaporator to implement an air heat pump, the first shut-off element A 1 is closed and the third shut-off element A 3 is opened, so that hot refrigerant, for example. R744 can flow into the heating branch 2.3. In order to prevent damage to the component of the air conditioning unit 1.1 due to the hot refrigerant, the hot gas temperature is limited to a maximum temperature value, in particular when R744 is used as the refrigerant at the inlet E of the inner heating condenser 7 or heating gas cooler 7. This temperature value is determined as a function of the maximum compatible material temperature of the material used for the air conditioning unit 1.1.To determine the refrigerant temperature at the inlet E of the inner heating condenser 7 or heating gas cooler 7, a temperature measuring means pT 1 designed as a pressure and temperature sensor is arranged at the high-pressure outlet of the refrigerant compressor 4. From the temperature value of this temperature measuring means pT1, the temperature value at the inlet E of the heating condenser 7 or heating gas cooler 7 is determined by means of a characteristic diagram or a characteristic curve stored, for example, in a climate control unit. Instead of this temperature measuring means pT 1 at the high-pressure outlet of the refrigerant compressor 4, a temperature measuring means T designed as a temperature sensor can also be arranged directly at the inlet E of the inner heating condenser 7 or of the heating gas cooler 7, with which temperature measuring means the temperature of the refrigerant is directly determined. Alternatively, both temperature measuring means pT1 and T can be used, wherein in this case the temperature measuring means T is also used as a protective function.With the pressure value of the temperature measuring means pT1 at the high-pressure outlet of the refrigerant compressor 4, which temperature measuring means is designed as a pressure and temperature sensor, the high-pressure value of the refrigerant is monitored and limited to a maximum permissible high-pressure value.To carry out the heating function by means of the chiller 8, the refrigerant compressed by means of the refrigerant compressor 4 flows via the opened third shut-off element A 3 for delivering heat to an inlet air stream guided into the vehicle interior into the inner heating condenser 7 or heating gas cooler 7 and is then expanded via the opened second shut-off element A 2 and the branch point Ab 1 by means of the fourth expansion element 6.4 into the chiller 8 for absorbing waste heat of the electrical and / or electronic components arranged in the coolant circuit 8.1. In this heating function, the second and third expansion elements 6.2 and 6.3 are closed.To carry out the heating function by means of the outer condenser 5 or the gas cooler 5 as a heat pump evaporator, the refrigerant compressed by means of the refrigerant compressor 4 flows via the open third shut-off element A 3 for delivering heat to the supply air stream guided into the passenger interior into the inner heating condenser 7 or heating gas cooler 7 and is then expanded via the open second shut-off element A 2 by means of the second expansion element 6.2 into the outer condenser 5 or gas cooler 5 for absorbing heat from the ambient air and then flows via the heat pump return branch 2.5 back to the refrigerant compressor 4.An indirect delta connection is realized in that, when the second shut-off element A 2 is open, the refrigerant compressed by the refrigerant compressor 4 is expanded by means of the fourth expansion element 6.4 into the chiller 8, wherein at the same time no mass flow is generated on the coolant side, that is to say in the coolant circuit 8.1, that is to say, for example, the water used as coolant remains stationary on the coolant side of the chiller 8 or coolant does not actively flow through the chiller 8.During a reheat operation, the supply air stream supplied into the vehicle interior is first cooled and thus dehumidified by means of the evaporator 3 in order subsequently to heat this supply air stream again by means of the inner heating condenser 7 or the heating gas cooler 7 with the heat extracted from the supply air stream. A reheat operation of the refrigerant circuit 2 is carried out in different ways depending on the heat balance.Thus, with sufficient heating power in the refrigerant circuit 2, only the evaporator 3 is flowed through with refrigerant by the inner heating condenser or heating gas cooler 7 being fluidically connected on the downstream side by means of the opened second shut-off element A 2 via the first expansion element 6.1, wherein the fourth expansion element 6.4 assigned to the chiller 8 and, like the expansion elements 6.2 and 6.3 leading to the condenser 5 or gas cooler 5, are blocked. From the evaporator 3, the refrigerant flows back to the refrigerant compressor 4 via the check valve R 3, the refrigerant collector 10 and the inner heat exchanger 9, wherein the heat absorbed in the evaporator 3 together with the heat flow introduced via the refrigerant compressor 4 is discharged again via the inner heating condenser 7 or heating gas cooler 7 to an inlet air flow guided into the vehicle interior.In the event of a lack of heat in the refrigerant circuit 2, the chiller 8 is also connected in parallel by opening the fourth expansion element 6.4 and / or the outer condenser 5 or gas cooler 5 by means of the second expansion element 6.2 in order to absorb heat in addition to the evaporator 3.In the case of parallel use of the waste heat from the chiller 8 and also the ambient heat by means of the outer condenser 5 or gas cooler 5, the refrigerant compressed by the refrigerant compressor 4 is divided via the inner heating condenser or heating gas cooler 7 into three partial streams at the branch point Ab 1 when the second shut-off element A 2 is open and when the third expansion element 6.3 is closed, namely into a partial stream expanded via the second expansion element 6.2 into the outer condenser 5 or gas cooler 5, a partial stream expanded via the fourth expansion element 6.4 into the chiller 8, and a partial stream flowing through the evaporator 3 via the first expansion element 6.1. The evaporator 3 represents the reference variable for the suction pressure that is established and thus specifies the minimum pressure position for chiller 8 and the outer condenser 5 or gas cooler 5 used as a heat pump evaporator. This can be bypassed by integrating a further sixth expansion element downstream of the evaporator 3, so that the latter can be set to any desired medium pressure level before a further pressure reduction takes place for the chiller 8 and the outer condenser 5 or gas cooler 5.In the event of an excess of heat in the reheater mode, heat is additionally transferred to the environment of the vehicle via the outer condenser 5 or gas cooler 5 in addition to the inner heating condenser or heating gas cooler 7 before the refrigerant flows back to the refrigerant compressor 4 via the evaporator 3. For this purpose, the refrigerant is expanded by means of the third expansion element 6.3 for condensation to an intermediate pressure above the evaporation pressure and then expanded by means of the first expansion element 6.1 into the evaporator 3 to low pressure.To control these different operating modes, in addition to the temperature measuring means pT 1 designed as a pressure temperature sensor, further pressure temperature sensors pT 2, pT 3 and pT 4 are arranged in the refrigerant circuit 2. The pressure temperature sensor pT2 is located between the refrigerant collector 10 and the low-pressure side of the inner heat exchanger 9, the pressure temperature sensor pT3 is located between the outer condenser 5 or gas cooler 5 and the high-pressure side of the inner heat exchanger 9, and the pressure temperature sensor pT4 is located downstream of the other heating condenser or heating gas cooler 7.The differences of the refrigerant circuits 2 of a vehicle cooling system 1 according to FIGS. 1 to 3 will be explained in detail below.In the vehicle cooling system 1 according to FIG. 1, stock lines of the refrigerant circuit 2 are used for implementing a suction of refrigerant from dead volumes for the AC operation or the heating operation.At an operation start in AC operation, the following method steps are carried out:opening the second shut-off element A2 and closing both the third shut-off element A3 and the third expansion element 6.3, as a result of which the heating branch 2.3 is shut off from the remaining refrigerant circuit 2,suction of refrigerant from the heating branch 2.3, andclosing the second shut-off element A2 either as the refrigerant pressure rises downstream of the second shut-off element A2 or after a defined time period in order to prevent a reverse displacement of refrigerant into the heating branch 2.3.However, it must be ensured that low pressure is present downstream of the shut-off element A 2, adjusted via the second expansion element 6.2.For this method for implementing a suction extraction of refrigerant from a dead volume of the inner heating condenser 7 or heating gas cooler 7 for AC operation, the existing lines of the refrigerant circuit 2 are used, i.e., no additional line sections or valve components are required. The known use of a check valve is dispensed with.If the refrigerant pressure is used to close the second shut-off element A 2, this pressure can be determined indirectly or directly.For the indirect determination of the refrigerant pressure, the blower load of a blower of the air conditioning unit 1.1 and / or the setpoint value of the air temperature at the evaporator 3 set by a control unit of the refrigerant circuit 2 and / or the pressure profile of the refrigerant on the low-pressure side of the refrigerant circuit 2 is detected, and the second shut-off element A 2 is closed when the blower load falls and / or when the setpoint value rises and / or when the refrigerant pressure rises on the low-pressure side.For the direct determination of the refrigerant pressure, it is determined directly downstream of the second shut-off element A 2 by means of a pressure sensor p 1 (cf. FIG. 1 ) connected downstream of the latter.When using the alternative method of closing the second shut-off element A 2 after a defined time period, this is determined by the fact that, for example, the second shut-off element A 2 is closed in the system for this time window. 5 minutes, a lower air-side evaporator outlet temperature is requested than is the case in normal operation (for example. 1°C instead of 3°C). This results in a lower system-side low pressure and the suction potential rises. When the defined and predetermined time period has elapsed, the system is returned to the standard parameters, the second shut-off element A2 being closed immediately before it, in order to avoid a return flow of refrigerant into the heating branch.Such an exhaust process may be repeated after each restart of the vehicle refrigeration system 1, but is not required if 100% AC operation has been performed in advance. If the elements A 3 and 6.3 are not 100% of sealing design, such a suction process is carried out again at each restart of the vehicle cooling system 1 with standstill times of, for example, greater than 1 hour.In the case of an operation start in heating operation by means of a water heat pump function, the following method steps are carried out:opening a fourth shut-off element A 4 of the heat pump return branch 2.5 and closing both the second and third expansion elements 6.2 and 6.3 and the first shut-off element A 1,suction of refrigerant from the AC and heat pump branch 2.2 via the heat pump return branch 2.5, andclosing the fourth shut-off element A4 either as the refrigerant pressure rises downstream of the fourth shut-off element A4 or after a defined time period in order to prevent a reverse displacement of refrigerant into the AC and heat pump branch 2.2.For this method for implementing a suction of refrigerant from a dead volume of the outer condenser 5 or gas cooler 5 for heating operation by means of the water heat pump function, the existing lines of the refrigerant circuit 2 are used, i.e. no additional line sections or valve components are required. The known use of a check valve is dispensed with. The fourth shut-off element A 4 is closed as a function of the refrigerant pressure downstream of the latter or after a defined period of time.If the refrigerant pressure is used to close the fourth shut-off element A 4, this pressure can be determined indirectly or directly.For the indirect determination of the refrigerant pressure, the coolant temperature of the chiller 8 is detected and, as the coolant temperature rises, the fourth shut-off element A4 is closed.For the direct determination of the refrigerant pressure, it is determined directly downstream of the fourth shut-off element A 4 by means of a pressure sensor p 2 connected downstream of the latter.When using the alternative method of closing the fourth shut-off element A 4 after a defined period of time, this is determined in that, on the part of a control unit of the vehicle cooling system 1, the suction pressure to be set in the system is determined for example by the control unit of the vehicle cooling system 1. 5 minutes, restricted to the minimum permissible value, or this is to be started specifically by the system before the fourth shut-off element A 4 is closed at the end of this time period and the low pressure can be found or set at a higher level, depending on the water temperature available at this point in time, which in turn influences the low pressure level.Such an exhaust process may be repeated after each restart of the vehicle refrigeration system 1, but is not required if a 100% heating operation was performed in advance. If the elements A1, 6.2 and 6.3 are not 100% of sealing design, such a suction process is carried out again at each restart of the vehicle refrigeration system 1 with standstill times of, for example, greater than 1 hour.The refrigerant circuit 2 of the vehicle cooling system 1 according to FIG. 2 differs from that according to FIG. 1 only in that a first check valve R 1 is arranged between the second shut-off element A 2 and the branch point Ab 1 and a second check valve R 2 is arranged between the fourth shut-off element A 4 and the branch point Ab 3.With this refrigerant circuit 2 according to FIG. 2, an alternative suction process for the AC operation can be implemented in comparison with the suction process described in connection with FIG. 1.In this suction process as well, stock lines of the refrigerant circuit 2 for implementing the suction of refrigerant from the heating branch 2.3, in particular from the inner heating condenser 7 or heating gas cooler 7, are usedAt an operation start in AC operation, the following method steps are carried out:opening the second shut-off element A2 and closing both the third shut-off element A3 and the third expansion element 6.3,suction of refrigerant from the heating branch 2.3, andreleasing the refrigerant downstream of the second shut-off element A2 to the low-pressure level by means of the second expansion element 6.2.In order to allow refrigerant to be sucked out via the second shut-off element A 2, the refrigerant is expanded to the low-pressure level downstream of the second shut-off element A 2 by means of the second expansion element 6.2. The first check valve R 1 prevents a rearward displacement of refrigerant into the heating branch 2.3. The second check valve R 2 serves to automatically prevent a return flow of refrigerant from the low-pressure sector into the AC and heat pump branch 2.2 as the low-pressure level rises during the active suction process, and thus to avoid the need to implement a special suction process.During the suction process, different operating modes can be carried out by means of the refrigerant circuit 2 for the operation of the evaporator 3 and the chiller 8.When cooling the interior by means of the evaporator 3 or when performing a cooling function by the chiller 8, the refrigerant mass flow is adjusted by means of the second expansion element 6.2 in accordance with a preset value generated by a climate control unit.It is also possible, in the case of simultaneous operation of both the evaporator 3 and the chiller 8, for the evaporator 3 to be regulated by the second expansion element 6.2 and the chiller 8 to be regulated by means of the fourth expansion element 6.4, the first expansion element 6.1 assigned to the evaporator 3 being completely open. Alternatively, the chiller 8 can be regulated by means of the second expansion element 6.2 and the evaporator 3 by means of the first expansion element 6.1 assigned to it, wherein in this case the expansion element 6.4 is completely open.When the suction is concluded, the two expansion elements 6.1 and 6.2 take over the regulations specified by a climate control device, the second expansion element 6.2 being completely open. The transfer of the primary control task of the expansion element 6.2 back to the expansion element 6.1 and / or the expansion element 6.4 takes place continuously and continuously, in order to avoid malfunction in plant operationThe refrigerant circuit 2 of the vehicle refrigeration system 1 according to FIG. 3 differs from that according to FIG. 1 in that a check valve R 2 is arranged in the heat pump return branch 2.5 between the shut-off element A 4 and the branch point Ab 3 and a suction branch 2.6 with a fifth expansion element 6.5 connects this heat pump return branch 2.5, namely the line section between the fourth shut-off element A 4 and the check valve R 2, to the outlet A of the inner heating condenser 7 or heating gas cooler 7.Thus, in AC operation, refrigerant can be sucked out of the heating branch 2.3 via this suction branch 2.6 when the expansion element 6.5 is open and the elements 6.3 and A3 are closed.The use of an expansion element 6.5 instead of a shut-off element designed as a shut-off valve makes it possible to carry out a direct triangular process. Such a heat pump function is still transferred by means of the suction branch 2.6 to an inlet air stream supplied to the vehicle interior in the event of missing waste heat of the components used as heat sources in the vehicle and in the event of icing of the outer condenser 5 or gas cooler 5 used as heat pump evaporator. In this case, with omission of evaporation by means of the evaporator 3, the chiller 8 or the condenser 5 or gas cooler 5 used as a heat pump evaporator, the refrigerant is merely compressed and the compressor heat is emitted at the inner heating condenser 7 or heating gas cooler 7.The refrigerant circuit 2 of the vehicle cooling system 1 according to FIG. 4 differs from that according to FIG. 3 only in that, on the one hand, the suction branch 2.6 is connected to the heating branch 2.3 not at the outlet of the inner heating condenser 7 or heating gas cooler 7, but on the upstream side of this component, that is to say between the third shut-off element A 3 and this inner heating condenser 7 or heating gas cooler 7, and the suction branch 2.6 has a fifth shut-off element A 5 instead of an expansion element.Thus, in the AC operation of this refrigerant circuit 2 according to FIG. 4, refrigerant can be extracted from the heating branch 2.3 via this suction branch 2.6 when the fifth shut-off element A 5 is open and the elements 6.3 and A 3 are closed.In analogy to the descriptions of the refrigerant circuit 2 according to FIG. 1 with regard to the omission or the methods for realizing the saving of the check valves R 1 and R 2, this measure can also be used for the system configurations according to FIGS. 2 to 4.In the refrigerant circuits 2 described in FIGS. 1 to 4, the heat surplus reheat operation is carried out in such a way that heat is released to the environment of the vehicle via the outer condenser 5 or gas cooler 5 before the refrigerant flows back to the refrigerant compressor 4 via the evaporator 3. For this purpose, the heating branch 2.3 is connected to the AC and heat pump branch 2.2 via the third expansion element 6.3, so that refrigerant is expanded to an intermediate pressure in the outer condenser or gas cooler 5 and then to low pressure by means of the first expansion element 6.1 in the evaporator 3.In addition to the functions of the water and air heat pump described, the combined operation of the two connections is also possible, i.e. the heats from the water circuit and from the environment are absorbed in parallel. However, the illustrated suction functions for refrigerants are not used in this case.It is furthermore conceivable to use an indirect, water-cooled condenser or gas cooler instead of the direct or inner heating condenser or heating gas cooler 7, before the inflow of air to the cabin is heated via a coolant-air heat exchanger connected downstream of the latter. The suction functions are performed in the manner described above.REFERENCE NUMERALS:1 Vehicle refrigeration system 1.1 air conditioning unit of the vehicle refrigeration system 1 2 refrigerant circuit of the vehicle refrigeration system 1 2.1 evaporator branch of the refrigerant circuit 2 2.2 AC and heat pump branch of the refrigerant circuit 2 2.3 heating branch of the refrigerant circuit 2 2.4 chiller branch of the refrigerant circuit 2 2.5 heat pump return branch of the refrigerant circuit 2 2.6 suction branch of the refrigerant circuit 2 3 evaporator 4 refrigerant compressor 5 outer condenser, Gas cooler 6.1 First expansion element 6.2 Second expansion element 6.3 Third expansion element 6.4 Fourth expansion element 6.5 Fifth expansion element 7 Inner heating condenser or heating gas cooler 8 Chiller 8.1 Coolant circuit of chiller 8 9 Inner heat exchanger 10 Refrigerant collector 11 Electric heating element A Outlet of the inner heating condenser or heating gas cooler 7 Ab1 Branch point of the refrigerant circuit 2 Ab2 Branch point of the refrigerant circuit 2 Ab3 Branch point of the refrigerant circuit 2 A1 First shut-off element A2 Second shut-off element A3 Third shut-off element A4 Fourth shut-off element A5 Fifth shut-off element E Inlet of the heating condenser or heating gas cooler 7 p1 Pressure sensor p2 Pressure sensor pT1 Temperature measuring means R1 Nonreturn valve R2 Nonreturn valve S Flow direction of refrigerant T Temperature measuring means

Claims

Method for operating a refrigerant circuit (2) of a vehicle refrigeration system (1) in an AC operation and in a heating operation implemented by means of a heat pump function, having: - an evaporator branch (2.1) having an evaporator (3) and a first expansion element (6.1) assigned to the evaporator (3), - a refrigerant compressor (4), - an AC and heat pump branch (2.2) having an outer condenser or gas cooler (5) and a second expansion element (6.2) assigned to the latter in a function as a heat pump evaporator for the heating operation, wherein the AC and heat pump branch (2.2) is connected on the one hand via a first shut-off element (A1) to a high-pressure outlet of the refrigerant compressor (4) and on the other hand via the second expansion element (6.2) to the evaporator branch (2.1) in such a way, in that, in AC operation, a refrigerant is expanded from the outer condenser or gas cooler (5) into the evaporator (3) via the opened second expansion element (6.2) by means of the first expansion element (6.1), - a heating branch (2.3) having an inner heating condenser or heating gas cooler (7) arranged in an air conditioning unit (1.1) and a second shut-off element (A2) connected downstream of the latter, wherein the heating branch (2.3) is connected to the high-pressure output of the refrigerant compressor (4) via a third shut-off element (A3) and via the second shut-off element (A2) to the evaporator branch (2.1), and - a third expansion element (6.3) by means of which the heating branch (2.3) is connected to the AC and heat pump branch (2.2) in such a way, a refrigerant for condensation and dissipation of heat to a vehicle environment is expanded by means of the third expansion element (6.3) to an intermediate pressure in the outer condenser or gas cooler (5) above an evaporation pressure and then expanded by means of the first expansion element (6.1) into the evaporator (3) to a low pressure, wherein - a refrigerant temperature at an inlet (E) of the inner heating condenser or heating gas cooler (7) is determined by means of a temperature measuring means (T, pT1), - in heating operation the refrigerant temperature at the inlet (E) of the inner heating condenser or heating gas cooler (7) is limited to a maximum temperature value, and - the maximum temperature value is defined as a function of a maximum compatible material temperature of a material used for the air conditioning unit (1.1).Method according to Claim 1, in which - the temperature measuring means (pT1) is arranged at the high-pressure outlet of the refrigerant compressor (4), and - the refrigerant temperature at the inlet (E) of the inner heating condenser or heating gas cooler (7) is determined from a characteristic diagram by means of the sensor value generated by the temperature measuring means (pT1).Method according to Claim 1, in which the refrigerant temperature is determined by means of the temperature measuring means (T) arranged at the inlet (E) of the inner heating condenser or heating gas cooler (7).Method according to one of the preceding claims, in which, at an operation start in AC operation, the following method steps are carried out: - extraction of refrigerant from the heating branch (2.3) by opening the second shut-off element (A2) and closing both the third shut-off element (A3) and the third expansion element (6.3), and - closing the second shut-off element (A2) either as the refrigerant pressure rises downstream of the second shut-off element (A2) or after a defined time period.Method according to Claim 4, in which the refrigerant pressure downstream of the second shut-off element (A2) is detected indirectly by detecting the blower load of a blower of the air conditioning unit (1.1) and / or the setpoint value of the air temperature at the evaporator (3) set by a control unit and / or the pressure profile of the refrigerant on the low-pressure side of the refrigerant circuit (2), and the second shut-off element (A2) is closed when the blower load falls and / or when the setpoint value rises and / or when the refrigerant pressure on the low-pressure side rises.Method according to Claim 4, in which the refrigerant pressure downstream of the second shut-off element (A2) is determined directly by means of a pressure sensor (p1) connected downstream of the latter.Method according to one of the preceding claims, in which, in the event of an operation start in heating operation, the following method steps are carried out by means of a water heat pump function or a triangular process: - providing a chiller branch (2.4) having a chiller (8) and an associated fourth expansion element (6.4) for realizing the water heat pump function, wherein the chiller branch (2.4) is connected in parallel with the evaporator branch (2.1), - removing refrigerant from the AC and heat pump branch (2.2) by opening a fourth shut-off element (A4), which connects the AC and heat pump branch (2.2) to the low-pressure side of the refrigerant circuit (2), and closing both the third expansion element (6.3) and the second expansion element (6.2) and also the first shut-off element (A1), and closing the fourth shut-off element (A4) either as the refrigerant pressure rises downstream of the fourth shut-off element (A4) or after a defined period of time.Method according to Claim 7, in which the refrigerant pressure downstream of the fourth shut-off element (A4) is detected indirectly by detecting the coolant temperature of the chiller (8), and the fourth shut-off element (A4) is closed as the coolant temperature rises.Method according to Claim 7, in which the refrigerant pressure downstream of the fourth shut-off element (A4) is determined directly by means of a pressure sensor (p2) connected downstream of the latter.Method according to one of Claims 1 to 3, in which, at an operation start in AC operation, the following method steps are carried out: - providing a non-return valve (R1), which is connected downstream of the second shut-off element (A2), for preventing a return flow of refrigerant into the heating branch (2.3), - removing refrigerant from the heating branch (2.3) by opening the second shut-off element (A2) and closing both the third shut-off element (A3) and the third expansion element (6.3), and - releasing the refrigerant downstream of the second shut-off element (A2) to a low-pressure level by means of the second expansion element (6.2) with at the same time a maximum open first expansion element (6.1) and / or fourth expansion element (6.4).Method according to one of Claims 1 to 3, in which, at an operation start in the AC mode, the following method steps are carried out: - providing a heat pump return branch (2.5) having a fourth shut-off element (A4) and a nonreturn valve (R2), wherein the AC and heat pump branch (2.2) is connected to the evaporator branch (2.1) downstream of the evaporator (3) with the heat pump return branch (2.5), - providing a suction branch (2.6) having a fifth expansion element (6.5), wherein the heat pump return branch (2.5) is connected to the heating branch (2.3) downstream of the inner heating condenser or heating gas cooler (7) with the suction branch (2.6), and - removing refrigerant from the heating branch (2.3) by opening the fifth expansion element (6.5) and closing both the second, heat pump return branch (2.5) and heat exchanger (7), third and fourth shut-off elements (A2, A3, A4) and also of the third expansion element (6.3).Vehicle refrigeration system (1) with a refrigerant circuit (2) for an AC operation and for a heating operation carried out by means of a heat pump function for carrying out the method according to one of the preceding claims, comprising: - an evaporator branch (2.1) with an evaporator (3) and a first expansion element (6.1) assigned to the evaporator (3), - a refrigerant compressor (4), - an AC and heat pump branch (2.2) with an outer condenser or gas cooler (5) and a second expansion element (6.2) assigned to the latter in its function as a heat pump evaporator for the heating operation, wherein the AC and heat pump branch (2.2) is connected on the one hand via a first shut-off element (A1) to a high-pressure outlet of the refrigerant compressor (4) and on the other hand can be connected via the second expansion element (6.2) to the evaporator branch (2.1) in such a way, in that, in AC operation, a refrigerant can be expanded from the outer condenser or gas cooler (5) via the opened second expansion element (6.2) by means of the first expansion element (6.1) into the evaporator (3), - a heating branch (2.3) having an inner heating condenser or heating gas cooler (7) arranged in an air conditioning unit (1.1) and a second shut-off element (A2) connected downstream of the latter, wherein the heating branch (2.3) can be connected to the high-pressure output of the refrigerant compressor (4) via a third shut-off element (A3) and via the second shut-off element (A2) to the evaporator branch (2.1), and - a third expansion element (6.3) with which the heating branch (2.3) can be connected to the AC and heat pump branch (2.2) in such a way, a refrigerant for condensation and dissipation of heat to a vehicle environment can be expanded by means of the third expansion element (6.3) to an intermediate pressure, which is above an evaporation pressure, into the outer condenser or gas cooler (5) and can then be expanded by means of the first expansion element (6.1) into the evaporator (3) to low pressure, wherein - a refrigerant temperature at an inlet (E) of the inner heating condenser or heating gas cooler (7) can be determined by means of a temperature measuring means (T, pT1).Vehicle cooling system (1) according to Claim 12, in which a pressure sensor (p1) is connected downstream of the second shut-off element (A2).Vehicle cooling system (1) according to Claim 12 or 13, comprising - a chiller branch (2.4) having a chiller (8) and an associated fourth expansion element (6.4) for implementing a water heat pump function, wherein the chiller branch (2.4) is connected in parallel with the evaporator branch (2.1), - a fourth shut-off element (A4), by means of which the AC and heat pump branch (2.2) is connected to the low-pressure side of the refrigerant circuit (2), and - a pressure sensor (p2) downstream of the fourth shut-off element (A4).Vehicle cooling system (1) according to Claim 12, in which a nonreturn valve (R1) is connected downstream of the second shut-off element (A2).Vehicle refrigeration system (1) according to claim 12, comprising - a heat pump return branch (2.5) with a fourth shut-off element (A4) and a check valve (R2), wherein the AC and heat pump branch (2.2) can be connected to the evaporator branch (2.1) downstream of the evaporator (3) by means of the heat pump return branch (2.5), and - a suction branch (2.6) with a fifth expansion element (6.5), wherein the heat pump return branch (2.5) can be connected to the heating branch (2.3) downstream of the inner heating condenser or heating gas cooler (7) by means of the suction branch (2.6).

Images