DE20121533U1 - Construction and control of an air conditioning system for a motor vehicle - Google Patents

Description

P800328/EN/2. 1

DaimlerChrysler AG 21.12.01

Circle

Construction and control of an air conditioning system for a motor vehicle

Air conditioning units in vehicles are the state of the art for cooling, drying, heating and ventilating vehicle interiors. The air is cooled and dried using refrigeration systems, and for heating the cabin air is normally heated in heating heat exchangers that provide the engine's waste heat. The cabin is ventilated using outside air or recirculated air from the cabin via air blowers. The air distribution in the cabin is also regulated using the air conditioning unit.

For cooling/drying and heating, refrigeration systems are known for air conditioning the vehicle cabin air in vehicles, in which on the high-pressure side of a vapor compression circuit, which includes a compressor, a gas cooler/condenser, an internal heat exchanger, a throttle device with at least one evaporator, which are connected in series and form an integral, closed circuit to provide cooling power or heating power, a supercritical pressure is generated in relation to the critical pressure in the circuit and at the same time a subcritical pressure is achieved on the low-pressure side of the circuit, whereby heat energy is supplied to the coolant cooled on the low-pressure side via the evaporator, or cold energy is removed, and the refrigerant mass flow in the circuit is regulated by regulating the same in the compressor (DE 44 322 72 C 2).

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An embodiment of the invention with regard to the integration of the system into the air conditioning unit of a vehicle and the different operating modes of heating, cooling and drying does not take place.

DE 198 13 674 C 1 describes a refrigeration system with a heat pump function that transfers heat output to the cabin air of vehicles via the refrigeration circuit. The aim here is to increase the effectiveness of the heating immediately after the vehicle is started up and to shorten its response time. This is achieved by using the refrigeration system as a heat pump, whereby the heat is introduced into the refrigerant in the ambient heat exchanger using outside air and is further heated in an exhaust heat exchanger using the exhaust gases from an internal combustion engine. The refrigerant is then compressed in the refrigerant compressor and flows through the interior heat exchanger with the cold vehicle interior air that has been sucked in. The vehicle interior air is thus heated in the interior heat exchanger and the vehicle cabin is heated.

If the system is used to cool and dry the air inside the vehicle, the interior heat exchanger cools and dries the moist air that is sucked in. This cools the air inside the vehicle, the water vapor contained in the sucked in air condenses and the vehicle cabin is air-conditioned.

The switching of the refrigeration system from cooling and drying to heating in order to prevent possible fogging of the windows in the vehicle cabin is not solved here.

DE 4318255 A1 describes a device for air conditioning the interior of a vehicle equipped with a waste heat generating drive. This contains

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a coolant circuit and a heating circuit, both of which can only be coupled in a heat-transfer manner via at least one first heat exchanger. While the heating circuit contains a heat exchanger for capturing the waste heat from the drive and a heating heat exchanger arranged in the path of the air to be transported to the interior, the coolant circuit contains an evaporator, a bypass duct to this and an exhaust air duct to this and an exhaust air nozzle as well as a coolant compressor. A condenser and cooler can be integrated into the two circuits via changeover valves for cooling operation; the heating heat exchanger can also be switched off using a valve-equipped bypass. This is intended to solve various air conditioning tasks in the vehicle in an energy-saving manner.

The disadvantage of these solutions is that the cabin air is not heated directly, but via a heating heat exchanger in the heat transfer circuit as part of the engine cooling system. Due to the thermal masses, the system has a high inertia, which reduces the dynamics when heating up and is not conducive to road safety.

In DE 3907201 C2, a motor vehicle is equipped with a heating air conditioning system, i.e. one that also works as a heat pump. In order to prevent the absorption of moisture that may have condensed on the evaporator during the previous cooling operation by the air to be conditioned during heating operation, various measures are proposed. For example, a separate heat exchanger is provided for heating operation, and a humidity sensor can be attached to the interior heat exchanger, which either prevents heating operation or initiates a

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The dehumidification device for the air to be conditioned, located downstream of the cooling evaporator, is activated.

The disadvantage of one solution is that under frequently occurring operating conditions of the vehicle, such as the prior drying of the air for the vehicle cabin at outside temperatures of, for example, ^{0 0} C to 1O ⁰ C, no heating operation is possible or only a very limited power can be drawn from the system.

The other solution avoids the desirable continuous air drying when using the refrigeration system in heat pump mode and therefore does not meet the requirements for keeping the windows in the vehicle cabin free of fog, especially in recirculation mode. Dehumidification devices based on adsorptive materials, for example, cause a drop in pressure in the air mass flow for ventilating the vehicle cabin and must be desorbed periodically. In order to achieve continuity here, at least two dehumidification devices must be provided in a switchable manner, which, in conjunction with an electric heater and air conveyor and outflow for desorption, means a considerable technical effort.

EP 09 898 003 A2 describes a refrigeration circuit with a heat pump for a preferred application in a vehicle not powered by an internal combustion engine. The system contains an air conditioning unit with 2 heat exchangers through which coolant flows, a first condenser and an evaporator. In the air conditioning box, the heat exchanger, which is arranged downstream of the incoming cabin air, is fluidically connected directly to the high-pressure side of the compressor and, depending on the operating case, is flowed through with hot coolant under high pressure. For the required heating of the cabin, the interior air flow is only directed through this component when required. In the cooling and

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In drying mode, the refrigerant flows from the compressor through the first condenser in the air conditioning box, is then cooled in the second condenser, expanded and liquefied in a throttle device and then passes into the evaporator to absorb heat and cool the cabin air. Accordingly, in pure cooling mode, no air flow is passed through the first condenser. In cooling mode with reheating, as is necessary for dehumidification (reheat mode), only a partial flow passes through this component. For dehumidification, the refrigerant flows successively through the first condenser, through the second condenser, liquefied through the throttle point into the evaporator, to the accumulator and back to the compressor. In all three operating modes: cooling, cooling and reheating and heating, the entire refrigerant is always passed first through the first condenser, then through the second condenser, evaporator and over the accumulator, whereby different pressures and temperatures can be set at different throttle points and different bypass points can design the circuit differently.

The disadvantage is that a high heat load is constantly introduced into the air conditioning box, the heating heat exchanger has to withstand high temperature and pressure loads, the piping of the system in the vehicle is complex and takes up a lot of space, avoidable pressure drops occur with reduced efficiency and a large refrigerant charge is required. The system therefore does not meet the general requirements for complexity, cost, efficiency, performance and ecology.

The state of the art therefore describes systems in which the refrigeration system evaporator, i.e. the heat exchanger through which the refrigerant flows, during operation of the refrigeration system in cooling mode,

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cools and dries the air entering the vehicle interior, or heats up the air entering the vehicle interior when the refrigeration system is in heating mode. In cooling mode, the water vapor in the air condenses on the cold surfaces of the heat exchanger. This allows the water adhering to the surface of the heat exchanger through which the coolant flows to evaporate in heating mode and humidify the air mass flow entering the vehicle interior. This can lead to increased window fogging. To keep the windows fog-free, the state of the art requires that at temperatures of approx. -4 ⁰ C to 1O ⁰ C the incoming air mass flow is cooled and thus dried by the refrigeration system in cooling mode and then heated in the heating heat exchanger to the required air temperature in what is known as 'reheat mode'. When the heat exchanger through which the coolant flows is used for heating, the cooling and thus drying functions cannot be carried out at the same time.

In view of the foregoing problems and deficiencies, the aim of the present invention is to redesign and expand an arrangement of components of a refrigeration system in vehicles in such a way that the heating performance in vehicles improves in all operating states, which enables the refrigeration system to be switched between heating and cooling mode at will without fogging up the windows.

In a second aim of the present invention, the incoming cabin air should be dried even when the heat pump is operating and outside temperatures are far below today's.

In a third aim of the invention, the storage of heat (e.g. for heating and cooling) is intended to maintain occupant comfort when the drive engine is switched off for a short time.

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The task is solved with regard to the interior by two basic arrangements:

A: An integrated heat pump system for cooling and heating, which introduces the energy directly into the air flow for the vehicle cabin. This is done by means of heat exchangers through which coolant flows in the vehicle's air conditioning box, in which the coolant cools down and condenses if necessary for heating, and in which the coolant evaporates for cooling.

B: An integrated heat pump system for cooling and heating, which introduces energy indirectly into the air flow for the vehicle cabin via heat transfer fluids. This is done by means of a liquid/air heat exchanger in the vehicle's air conditioning box in which the secondary refrigerant is cooled to heat the air flow and in which the secondary refrigerant is warmed up to cool the air flow.

The arrangements can be designed both in the form described and in combination with one another.

For both arrangements, there are options for heat pump operation to use the coolant of the vehicle drive (Fig. 5,7,11,12,14,16) or the outside air (Fig. 6,8,13,15,17,18,20,21,22) as the main heat source. The sensible and latent heat can contribute to the function of the heat pump as a secondary heat source (Fig. 9,10,19).

With reference to the present invention in a refrigeration cycle, in cooling mode the refrigerant flows from the compressor via a switching valve via the condenser/gas cooler and possibly the high pressure side of the internal heat exchanger to a first expansion valve in which the

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The coolant liquefies and flows through the evaporator, the collector and, if necessary, the low-pressure side of the internal heat exchanger via another switching valve into the coolant compressor. The gas cooler dissipates heat into the environment. The evaporator is located in the air conditioning box. It cools and dries the interior air for the vehicle cabin. The compressor, whose delivery volume can be regulated, can be used to adjust the coolant mass flow circulating in the circuit. This allows the desired evaporator temperature to be set. When operating the refrigeration system for cooling, two operating cases can occur: cooling and drying or cooling/drying and heating (reheat). In the latter case, the air is heated via the heating heat exchanger downstream of the evaporator.

In the heat pump circuit, the coolant flows from the compressor, diverted through the switching valve, through a gas cooler/condenser in the air conditioning box, a first expansion valve, the evaporator, a second expansion valve to absorb heat in a heat exchanger and via a second switching valve back to the compressor. The circuit is thus closed.

The release of useful heat from the heat pump takes place in the gas cooler/condenser. This can transfer the heat in different ways. It can be located directly in the air conditioning box downstream of the evaporator and heating heat exchanger or it can be introduced into the heating medium flow and used via the heating heat exchanger to heat the interior air for the cabin. The pressure and thus the temperature in the refrigerant evaporator can be varied using the first expansion valve and the second expansion valve. This is essential for maintaining the drying and, if the heat exchanger matrix is dry, the evaporator can be used to increase the

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heating output of the system can be used. Heat is absorbed into the refrigeration circuit via the ambient heat exchanger at an evaporation temperature below the outside temperature. Instead of the ambient heat source, the engine heat can also be used with an engine coolant/refrigerant heat exchanger. Here the coolant flows from the compressor, redirected through the switching valve, through the heat pump condenser, a first expansion valve, through the evaporator, via a second expansion valve to absorb heat in the engine coolant/refrigerant heat exchanger and then, if necessary, via a second switching valve back to the compressor. The circuit is thus also closed. When the heat pump is operated for heating, two operating cases can occur: heating and drying or heating. In the first case, the compressed refrigerant condenses/cools in the heat pump condenser. It gives off its heat directly to the cabin air or indirectly introduces it into the heating medium flow in front of the heating heat exchanger. The coolant then hits a controllable expansion valve, in which it is regulated to a temperature that is sufficient for drying the air and as comfortable as possible. The coolant is then expanded to a temperature below that of the heat source. Here the refrigeration circuit absorbs heat. In the heating mode, the compressed coolant condenses/cools in the heat pump condenser. It gives off its heat directly to the cabin air or indirectly introduces it into the heating medium flow in front of the heating heat exchanger. The coolant then hits the fully open first expansion valve, in which the coolant is only slightly throttled and the coolant can be cooled further. The incoming cabin air is preheated. This allows the heating output of the system to be increased further. The coolant is then expanded to a temperature below that of the heat source. Here

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the refrigeration circuit absorbs heat and the refrigerant returns to the refrigerant compressor.

At the start of the journey, the integrated heat pump system in the

Heating operation is sufficient for the vehicle heating, a

Initially, the vehicle is not heated by the engine coolant.

If the heat is released indirectly via a heat transfer circuit in an integrated heat pump system during heating operation, additional heat exchangers can be located in this circuit to exchange heat with other operating fluids and components. The circuit connection depends on the heating priority of the components or systems. They are therefore located upstream or downstream of the heating heat exchanger.

Accordingly, when the integrated heat pump system is operating in cooling mode, heat can be introduced indirectly into the circuit via the heat transfer circuit for heating when the journey begins. This heat can then be used to heat other operating fluids and components. The heat dissipation from the coolant circuit is very high.

Furthermore, the invention includes the use of a heat transfer fluid/air heat exchanger in the air conditioning box instead of the evaporator in the air conditioning box which is directly supplied with air and coolant. The heat transfer to the interior air is thus carried out indirectly via a small active circuit of heat transfer fluid. The heat transfer fluid circuit consists of a fluid pump and a fluid/air heat exchanger. The heat transfer fluid circuit can also contain a fluid storage container which stores the

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In this liquid circuit, only a small volume of liquid circulates until the criteria for charging the storage tank are met. After this, a partial volume of the circulating liquid flows into the storage tank until the storage tank has a

desired or achievable temperature. This can be maintained during normal vehicle operation. If the performance of the refrigeration system drops or is switched off, the temperature of the circulating heat transfer fluid can be kept at a usable temperature level for a certain period of time by decoupling the heat transfer fluid contained in the storage tank.

The invention further describes a refrigeration circuit in which heat transfer occurs indirectly during cooling and heating of the air flow and in which the flow direction of the refrigerant in the refrigeration circuit is reversible. During cooling operation, the refrigerant flows from the compressor via a switching valve via the condenser/gas cooler and the high-pressure side of the internal heat exchanger to a first expansion valve, in which the refrigerant liquefies and via the evaporator, the collector and the low-pressure side of the internal heat exchanger via another switching valve into the refrigerant compressor. The gas cooler dissipates heat to the environment. The evaporator is designed as a refrigerant/heat transfer fluid heat exchanger and is located outside the air conditioning box. It exchanges its heat with a heat transfer fluid which then cools and dries the interior air flow for the vehicle cabin in a liquid/air heat exchanger. The compressor, whose delivery volume can be regulated, can be used to adjust the refrigerant mass flow circulating in the circuit. The pump for pumping the refrigerant, which can be regulated if necessary, can be used to pump the refrigerant around.

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A desired evaporator temperature can be set using the heat transfer fluid. When operating the refrigeration system for cooling, two operating cases can occur: cooling and drying or cooling/drying and heating (reheat). In the latter case, the air flow for the interior is heated in the air conditioning box via the heating heat exchanger downstream of the evaporator liquid/air heat exchanger.

During heating operation, the refrigerant flows from the compressor via a switching valve via the refrigerant/heat transfer fluid heat exchanger in the bypass through the first expansion valve, the internal heat exchanger to another expansion device in which the refrigerant liquefies and via the gas cooler/condenser via another switching valve into the refrigerant compressor. The flow can pass through the collector and the internal heat exchanger. The gas cooler supplies heat from the environment. If the heat exchanger air side is dry, the warm heat transfer fluid flows through the liquid/air heat exchanger climate box and heats the interior air flow in the vehicle cabin. If the heat exchanger air side is wet, the warm heat transfer fluid is fed into the coolant circuit of the drive system and fed to the interior via the heater heat exchanger in the climate box.

Thanks to the invention, a heat pump system can be used for cooling, drying and heating the interior air for the vehicle cabin. The operating mode heating and cooling can be switched between as required without any impairment caused by fogging of the windows, particularly in winter. Furthermore, if required, continuous drying of the interior air is also possible at

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Operation of the heat pump is possible. Because the heat pump responds spontaneously as a heater, the engine coolant is not needed for heating. The drive motor therefore quickly reaches its operating temperature. Consumption and pollutant reductions are possible. When heat transfer fluids are used to transport energy to cool and heat the interior air, there are no coolant-carrying components in the interior or in the air flow to the vehicle cabin. This means that coolants can also be used in vehicles that are advantageous for the application but are not suitable due to flammability or toxicological reasons. If heat transfer fluids are used, the active fluid volumes are small. The dynamics after starting are thus maintained, which allows the interior to be heated or cooled quickly. The circuit can be expanded with an additional storage volume. This maintains a high level of thermal comfort even during short stops. After short breaks in driving, a preconditioned storage volume with the appropriate heat capacity is available when starting to quickly achieve the interior conditions.

When using the heat pump system for cooling and heating, either the heat that is dissipated or the useful heat provided can be used to heat other vehicle systems, such as the drive motor, transmission, differential gear, etc. This significantly reduces fuel consumption after a cold start and component wear. Furthermore, a lot of heat is removed from the circuit at the beginning of cooling operation, which in turn results in a high initial output of the cooling system and makes it easier to achieve comfort in the interior.

Further features and embodiments of the invention emerge from the claims, the figures and the

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Description of the figures. The features and combinations of features mentioned above and listed below can be used not only in the combination specified but also in other combinations or on their own without departing from the scope of the invention.

Further embodiments of the invention are illustrated and explained in the figures, showing:

Fig.l shows a schematic diagram of a vapor compression cycle with a controllable compressor and a throttling device.

Fig. 2 shows a schematic diagram of a vapor compression cycle with a compressor, a second heat exchanger and a second throttling means.

Fig. 3 shows schematically in a pH diagram a refrigerant circuit with a compressor, heat exchangers and throttling means.

Fig. 4 shows schematically in a pH diagram a refrigerant circuit with a compressor, heat exchangers and throttling means.

Fig. 5 shows a schematic diagram of an integrated heat pump system that enables a 2-stage expansion in heating mode and works with water-side heat absorption.

Fig. 6 shows a schematic diagram of an integrated heat pump system that enables a 2-stage expansion in heating mode and operates with air-side heat absorption.

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Fig. 7 shows a schematic diagram of an integrated heat pump system which enables a 2-stage expansion in heating mode, transfers heat indirectly by means of a heat transfer fluid and works with heat absorption from a coolant.

Fig. 8 shows a schematic diagram of an integrated heat pump system which enables a 2-stage expansion in heating mode, transfers heat indirectly by means of a heat transfer fluid and works with heat absorption from the ambient air.

Fig. 9 shows a schematic diagram of an integrated heat pump system which expands in two stages in heating mode and works by absorbing heat from the cabin air.

Fig. 10 shows a schematic diagram of an integrated heat pump system which enables a two-stage expansion in heating mode, transfers heat indirectly by means of a heat transfer fluid and works with heat absorption from the cabin air.

Fig. 11 shows a schematic diagram of an integrated heat pump system that enables a 2-stage expansion in heating mode, transfers heat indirectly by means of a heat transfer fluid and works with heat absorption from the coolant

Fig. 12 shows a schematic diagram of an integrated heat pump system which enables a 2-stage expansion in heating mode and operates with heat absorption from the coolant.

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Fig. 13 shows a schematic diagram of an integrated heat pump system which enables a 2-stage expansion in heating mode and operates by absorbing heat from the air.

Fig. 14 shows a schematic diagram of an integrated heat pump system which enables a two-stage expansion in heating mode and operates with heat absorption from the coolant.

Fig. 15 shows a schematic diagram of an integrated heat pump system which enables a two-stage expansion in heating mode, transfers heat indirectly by means of a heat transfer fluid and works by absorbing heat from the air.

Fig. 16 shows a schematic diagram of an integrated heat pump system which, in cooling mode, transfers heat indirectly by means of a heat transfer fluid and subsequently by means of outside air.

Fig. 17 shows a schematic diagram of an integrated heat pump system which enables a 2-stage expansion in heating mode, transfers heat indirectly by means of a first heat transfer fluid, transfers heat for cooling or heating the air indirectly by means of a second heat transfer fluid and absorbs heat from the air during heat pump operation.

Fig. 18 shows a schematic diagram of an integrated heat pump system which enables a 2-stage expansion in heating mode, transfers heat indirectly by means of a first heat transfer fluid, transfers heat for cooling or heating the air indirectly by means of a second heat transfer fluid and absorbs heat from the air during heat pump operation.

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Fig. 19 shows a schematic diagram of an integrated heat pump system which, in heating mode, provides heat indirectly
by means of a first heat transfer fluid, which
Heat for cooling or heating the air indirectly by means of
a second heat transfer fluid and during cooling the heat from the circuit to the first

heat transfer fluid and/or to the outside air.

Fig. 20 shows a schematic diagram of an integrated heat pump system which supplies heat for cooling or heating the air indirectly into the coolant circuit of the drive motor or indirectly into a closed subsystem of the
coolant circuit and absorbs the heat from the air during heat pump operation.

Fig. 21 shows a schematic diagram of an integrated heat pump system which supplies heat for cooling or heating the air indirectly into the coolant circuit of the drive motor or indirectly into a closed subsystem of the
coolant circuit and, in heat pump operation, absorbs the heat from the air and the connection of the
coolant circuit.

Fig. 22 shows a schematic diagram of an integrated heat pump system which supplies heat for cooling or heating the air indirectly into the coolant circuit of the drive motor or indirectly into a closed subsystem of the
coolant circuit and, in heat pump operation, absorbs the heat from the air and the connection of the
coolant circuit in a valve unit.

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Fig. 1 shows a circuit which, connected in series, successively includes a compressor 12, a gas cooler/condenser 14, an internal heat exchanger 15, a throttling means 16, an evaporator 5 and a collector 19. The compressor can be regulated with regard to its refrigerant mass flow. The throttling means 16, which can be designed as an expansion valve, is also adjustable.

Fig. 2 shows a refrigeration circuit designed as a heat pump, which contains a compressor 12, a gas cooler/condenser 20, a first throttling means 16, a first evaporator 5, a second throttling means 17, a second evaporator 18 and a collector 19, connected in series one after the other. The compressor can be regulated with regard to its refrigerant mass flow. The first throttling means 16 is also adjustable, and the second throttling means 17 can be designed so that it can be regulated and shut off tightly. The second throttling means 17 can also be designed as a constant throttling element with an additional shut-off device. In the heat pump system, evaporator 5 is operated as an evaporator in cooling mode. In heating mode, it can perform two functions, as an evaporator or as a gas cooler. If, in heating mode, the cabin air is dried before it is actually heated, or if the air-side surface of the evaporator is still wetted with condensate, the evaporator works as an evaporator. This operating case often occurs at outside temperatures of about 10°C above freezing and about 10°C below freezing. If the air-side surface is dry and the air is not dried, as in

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If the air inlet temperature is below freezing, the evaporator 5 is operated as a gas cooler/condenser.

If the compressor 12 is operating under high load - i.e. in a heat pump system in heating mode, e.g. as a transcritical refrigeration process - it compresses a refrigerant mass flow from an outlet pressure Pl to a higher pressure P2 above the critical pressure, as in Fig. 3, whereby the process temperature rises from Tl to T2. The compressed gaseous refrigerant is isobarically cooled to a temperature T3 in the gas cooler/condenser 20 via a flowing coolant, such as the air mass flow for the vehicle cabin or a heat transfer fluid. As it flows through the expansion valve 16, the refrigerant is expanded isenthalpically to an intermediate pressure P4, which lies between the outlet pressure Pl and the compression pressure P2, whereby the refrigerant cools further to a temperature T4, which may already be in the liquefaction range of the refrigerant. If the two-phase gas/liquid mixture of the refrigerant that may have been created in this way reaches the evaporator 5, a liquid portion of the two-phase mixture evaporates due to the heat absorption. As the refrigerant flows through the expansion valve 17, it is expanded isenthalpically to the initial pressure Pl, whereby the temperature of the refrigerant drops to T6. The heat input from the outside air or the engine coolant heats the refrigerant to the temperature T7. If the entire liquid portion of the refrigerant is not evaporated, the liquid refrigerant then collects in the buffer tank 19 and from there reaches the compressor 12 as a mixture of liquid and gaseous refrigerant.

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In Fig. 4, however, the expansion valve 16 is shown as being completely open. The refrigerant therefore only experiences a slight expansion. The intermediate pressure P4 corresponds almost to the compression pressure P2. The refrigerant cools further down to the temperature T5. The evaporator 5 now works as a gas cooler/condenser. As it flows through the expansion valve 17, the refrigerant is expanded isenthalpically down to the outlet pressure Pl, whereby the temperature of the refrigerant drops to T6. The heat input from the outside air or the engine coolant heats the refrigerant to the temperature T7. If the entire liquid portion of the refrigerant is not evaporated, the refrigerant then collects in the buffer tank 19 and from there reaches the compressor 12.

Fig. 5 shows a schematic diagram of an integrated heat pump system.

After compression, the refrigerant enters the switching valve 13 under high pressure and temperature. Here, the cooling or heating operating mode is switched. If the valve is switched to the cooling operating mode, the refrigerant releases heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The operating point is in the 2-phase region. In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The second expansion valve (17) is not switched and is therefore closed. The refrigerant flows through the open valve (26) into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12). In the air conditioning box

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the air flow for the cabin is cooled, the humidity contained condenses on the cold surfaces of the heat exchangers. If necessary, the air is heated accordingly by means of the heating heat exchanger 7.

If the valve 13 is switched to the heating operating mode, the refrigerant releases the heat via the gas cooler/condenser (20) to the air flow for the vehicle cabin. After passing through the check valve (10), the refrigerant reaches the first expansion valve (16). After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the second expansion valve 17, in which it is isenthalpically expanded to the evaporation pressure level of the heat absorption. Valve 2 6 is closed here. In the refrigerant/heat transfer fluid heat exchanger 18, heat from the engine coolant is supplied to the refrigerant and, if necessary, superheated. The refrigerant flows through the collector 19 and leaves the collector 19 with a defined refrigerant quality, i.e. ratio of gaseous mass flow to the total mass flow of the refrigerant. The refrigerant then flows through the low-pressure side of the internal heat exchanger and reaches the compressor. Check valves (6) and (10) are not absolutely necessary for the heat pump system to function. In both operating cases, they prevent the part of the circuit that is not required from filling up with coolant. In order to compensate for this in terms of performance and efficiency, more coolant must be filled into the system, which is not expedient for environmental reasons.

Two operating strategies are possible for controlling the opening of the expansion valves 16 and thus the setting of the intermediate pressure level:

In the first case, the air supplied to the vehicle cabin should be dried before heating or the air-side

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The surface of the heat exchanger is wetted with condensate. Drying of the air will always be necessary when the incoming air has a dew point above freezing. It is particularly expedient to coordinate the evaporation temperature of the coolant in this component with the outside temperature in order to ensure the necessary drying to reliably prevent window fogging without, however, dehumidifying the air too much for hygienic reasons. This means that operating the air conditioning box in recirculation mode in winter, e.g. to increase comfort when heating up or to reduce the amount of pollutants entering the cabin, is no longer a problem. The moisture content of the air flowing into the evaporator can be determined using a humidity sensor, dew point sensor, fogging sensor on the windshield, etc. Together with knowledge of the outside temperature, the need for drying can be determined. A wetness sensor at a characteristic position on the surface of the evaporator can be used to determine whether the evaporator is wet. In this case, the evaporator can continue to be operated as an evaporator. The evaporation temperature is either controlled as in drying or kept close to the freezing point.

When controlling the expansion valves, if the actual temperature is too low, the first expansion valve 16 is opened a little more and the expansion valve 17 is closed a little more until the evaporation temperature in the evaporator has reached the desired target temperature. Conversely, expansion valve 16 is opened a little less and expansion valve 17 is opened a little more if the actual evaporator temperature is above the target temperature. The desired compression pressure remains unaffected by this measure, since the total pressure loss through the first expansion valve 16, the evaporator 5 and the second expansion valve 17 remains constant.

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In the second case, the evaporator is used to preheat the air flowing into the cabin. This only makes sense if the air-side surface of the evaporator is dry. If suitable measures can be taken to safely prevent moisture from entering the interior through evaporating water, then the expansion valve 16 is opened completely. This causes two heat exchangers to heat in countercurrent with the cabin air in the air conditioning box. A very high power can be transferred. The coolant inlet temperature in the evaporator 5 is almost the same as the coolant outlet temperature at the gas cooler/condenser 20 in the air conditioning box 3.

Fig. 6 shows a schematic diagram of an integrated heat pump system which operates with a 2-stage expansion when heating. The actual heat absorption of the refrigeration circuit when heating occurs from the outside air. After compression, the refrigerant enters the switching valve 13 under high pressure and temperature. This is where the cooling or heating operating mode is switched. If the valve 13 is switched to the cooling operating mode, the refrigerant releases heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The operating point is in the 2-phase region. In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The refrigerant flows into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is overheated and then sucked in by the compressor (12). In the air conditioning box, the air flow for the cabin is cooled, the humidity contained condenses on the cold surfaces of the

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Heat exchanger. If necessary, the air is heated accordingly by means of the heating heat exchanger 7. If the valve 13 is switched to the heating operating mode, the refrigerant releases the heat via the gas cooler/condenser (20) to the air flow for the vehicle cabin. After passing through the check valve (10), the refrigerant reaches the first expansion valve (16). After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the collector 19 and leaves the collector 19 with a defined refrigerant quality and then to the low pressure side of the internal heat exchanger. The switching valve 21 blocks the direct path to the compressor, so the air flows through the second expansion valve 17, in which it is isenthalpically expanded to the evaporation pressure level of the heat absorption. In the condenser/gas cooler 14, heat from the environment is supplied to the refrigerant and, if necessary, superheated. The refrigerant then returns to the compressor 12 via the switching valve 21. A particularly advantageous feature of this circuit is that the engine coolant circuit is not used to heat the cabin while the vehicle is warming up. A heat exchanger in the cooling circuit is used to absorb the heat. This means that the drive motor heats up quickly, which keeps consumption, wear and emissions low.

Fig. 7 shows a schematic diagram of an integrated heat pump system.

After compression, the refrigerant enters the switching valve 13 under high pressure and temperature. This is where the cooling or heating operating mode is switched. If the valve 13 is switched to the cooling operating mode, the refrigerant releases heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15).

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After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The operating point is in the 2-phase region. In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The second expansion valve (17) is not switched and is therefore closed. The refrigerant flows through the open valve (26) into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12). In the air conditioning box, the air flow for the cabin is cooled, and the humidity it contains condenses on the cold surfaces of the heat exchangers. If necessary, the air is heated accordingly using the heating heat exchanger 7. If the valve 13 is switched to the heating operating mode, the refrigerant releases the heat to the engine coolant via a refrigerant/heat transfer fluid heat exchanger (-27). After passing through the check valve (10), the refrigerant enters the first expansion valve (16). After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the second expansion valve 17, in which it is expanded isenthalpically to the evaporation pressure level of heat absorption. Valve 26 is closed. In the refrigerant/heat transfer fluid heat exchanger 18, heat from the engine coolant is supplied to the refrigerant and, if necessary, superheated. The refrigerant flows through the collector 19, the low-pressure side of the internal heat exchanger 15 and reaches the compressor 12.

The heat is transferred indirectly via the engine coolant during heating operation. The heated engine coolant is pumped into the heater heat exchanger (7) by the heater pump (8) and releases heat there to the air flow for the vehicle cabin. The engine coolant can then be further

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Heat exchangers for heat absorption and release such as the cooler for exhaust gas recirculation (23). If the temperature of the engine coolant before entering the engine is higher than that of the engine coolant in the engine, or if the engine is not to be flowed through in connection with its heating, it is fed via the valve (22) directly to the refrigerant-engine coolant heat exchanger (27). If the engine coolant in the engine is warmer than the engine coolant before entering the engine, the engine coolant is fed through the engine to absorb heat. The advantages of such an arrangement arise from the air-side pressure drop in the air conditioning box through only 2 heat exchangers and from the same control of the temperature and air distribution in the cabin when heating is operated with the heat pump system and the conventional heater. A further advantage will be found in vehicles with two air conditioning boxes. This can limit the effort required for heating.

The fundamental disadvantage of heat emission at a high temperature level can be counteracted by using a refrigerant/heat transfer fluid heat exchanger (27) based on the countercurrent principle, and the air in the evaporator 5 is significantly preheated due to the energy remaining in the refrigerant. This option can of course only be used if the air-side surface of the evaporator 5 is dry.

In case the air-side surface of the evaporator 5 is not dry, the heat exchanger can be heated and the resulting water vapor can be led outside by a partial air flow from the air conditioning box.

Fig. 8 shows a schematic diagram of an integrated heat pump system that works with a 2-stage expansion when heating. The actual

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The refrigeration circuit absorbs heat from the outside air during heating.

After compression, the refrigerant enters the switching valve 13 under high pressure and temperature. This is where the cooling or heating operating mode is switched. If valve 13 is switched to cooling mode, the refrigerant releases heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The operating point is in the 2-phase region. In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The refrigerant flows into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12). In the air conditioning box, the air flow for the cabin is cooled and the humidity it contains condenses on the cold surfaces of the heat exchanger. If necessary, the air is heated accordingly by means of the heating heat exchanger 7. If the valve 13 is switched to the heating operating mode, the refrigerant releases the heat to the engine coolant via a refrigerant/engine coolant heat exchanger (27). After passing through the check valve (10), the refrigerant reaches the first expansion valve (16). After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the collector 19 and leaves the collector 19 with a defined refrigerant quality to the low-pressure side of the internal heat exchanger. The switching valve 21 blocks the direct path to the compressor, so the air flows through the second expansion valve 17, in which it is expanded isenthalpically to the evaporation pressure level of the heat absorption. In the condenser/gas cooler 14, heat from the

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environment and possibly overheated. The refrigerant then returns to the compressor 12 via the switching valve 21.

A particularly advantageous feature of this circuit is that the heat pump absorbs heat from the outside air, meaning that the engine coolant circuit heats up particularly quickly, which has advantages in terms of consumption, wear and emissions.

Fig. 9 shows a schematic diagram of an integrated heat pump system.

After compression, the refrigerant reaches the switching valves 24 and 25 under high pressure and temperature. If the valve 24 is open, the refrigerant gives off heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The operating point is in the 2-phase region. In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The refrigerant flows into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12). In the air conditioning box, the air flow for the cabin is cooled and the humidity it contains condenses on the cold surfaces of the heat exchanger. If necessary, the air is heated accordingly using the heating heat exchanger 7.

If the valve 25 is switched, the refrigerant gives off the heat to a gas cooler / condenser 2 0. After passing the check valve (10), the refrigerant enters the expansion valve 16. After appropriate throttling and heat absorption of the refrigeration circuit in the evaporator 5, the refrigerant flows through the collector 19 and leaves the collector 19

P800328/DE/X 29 ·· "'· ·"··'*: fV'*!

with a defined refrigerant quality via the low-pressure side of the internal heat exchanger to the compressor 12. A particularly advantageous feature of this circuit is that the heat pump absorbs heat from the air flow of the cabin air and thus the engine coolant circuit heats up particularly quickly, which has advantages in terms of consumption, wear and emissions.

The heating capacity of this system is limited by the heat that can be extracted from the supply air for the cabin and the compressor output.

Fig. 10 shows a schematic diagram of an integrated heat pump system.

After compression, the refrigerant reaches the switching valves 24 and 25 under high pressure and temperature. If the valve 24 is open, the refrigerant gives off heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The operating point is in the 2-phase region. In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The refrigerant flows into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12). In the air conditioning box, the air flow for the cabin is cooled, and the humidity it contains condenses on the cold surfaces of the heat exchanger. If necessary, the air is heated accordingly using the heating heat exchanger 7.

If the valve 25 is switched, the refrigerant releases the heat to the engine coolant via a refrigerant/engine coolant heat exchanger (27). After passing the check valve (10), the refrigerant enters the

P800328/EN/1. 30 ·· ,·;:;;·!·!

Expansion valve 16. After appropriate throttling and heat absorption of the refrigeration circuit in the evaporator 5, the refrigerant flows through the collector 19 and leaves the collector 19 with a defined refrigerant quality via the low-pressure side of the internal heat exchanger to the compressor 12. A particularly advantageous feature of this circuit is that the heat absorption of the heat pump takes place from the air flow of the cabin air and the energy is introduced into the engine coolant circuit.

Another benefit arises in cooling mode. When starting with a heated vehicle interior, very large heat flows can be released into the engine coolant for a short time. This provides a high cooling capacity. This circuit is always useful when the engine coolant temperature is less than 40 ⁰ C. This heats up the drive motor in a beneficial way.

Fig. 11 shows the circuit from Fig. 7, with the difference that changeover valve 13 has been replaced by two shut-off valves 24 and 25. After starting the vehicle with a heated interior, very large heat flows can be released into the engine coolant for a short time. This provides a high cooling capacity. This circuit is always useful when the engine coolant temperature is less than 40 ⁰ C. This heats up the drive motor in a beneficial way.

Fig. 12 shows a schematic diagram of an integrated heat pump system.

After compression, the refrigerant passes under high pressure and temperature in front of the switching valves 24 and 25. If the valve 24 is open, the refrigerant releases heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the

P800328/DE/3- 31 ", .* I Il t I " I

The coolant is expanded to evaporation pressure in the first expansion valve (16) via the check valve (6). In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The second expansion valve (17) is not switched and is therefore closed. The coolant flows into the collector (19) via the open valve (26). On the low-pressure side of the internal heat exchanger (15), the coolant is superheated and then sucked in by the compressor (12). The air flow for the cabin is cooled in the air conditioning box, and the humidity it contains condenses on the cold surfaces of the heat exchangers. If necessary, the air is heated accordingly using the heating heat exchanger 7.

If the valve 25 is switched, the refrigerant gives off the heat to a gas cooler / condenser 20. After passing through the check valve (10), the refrigerant reaches the expansion valve 16. After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the second expansion valve 17, in which it is isenthalpically expanded to the evaporation pressure level of the heat absorption. Valve 26 is closed here. In the refrigerant / heat transfer fluid heat exchanger 18, heat from the engine coolant is supplied to the refrigerant and, if necessary, superheated and returns to the compressor. The collector 19 and the low-pressure side of the internal heat exchanger 15 are not flowed through by the circulating refrigerant and are connected to the compressor inlet.

In this circuit in heating mode, the collector and the low-pressure side of the internal heat exchanger are not flowed through by the circulating coolant. Since there is normally always some liquid coolant due to the operating characteristics of the collector,

If the coolant is discharged, this leads to a slight overheating at the compressor inlet, which then results in lower compressor outlet temperatures. This means that the maximum performance of the heat pump is not normally achieved. Furthermore, the pressure drop on the suction side is significantly lower. Since this circuit does not have these features, it is an advantageous application.

Fig. 13 shows a schematic diagram of an integrated heat pump system that operates with a 2-stage expansion during heating.

After compression, the refrigerant reaches the switching valves 24 and 25 under high pressure and temperature. If the valve 24 is open, the refrigerant gives off heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The operating point is in the 2-phase region. In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The refrigerant flows into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12). In the air conditioning box, the air flow for the cabin is cooled and the humidity it contains condenses on the cold surfaces of the heat exchanger. If necessary, the air is heated accordingly using the heating heat exchanger 7.

If the valve 25 is switched, the refrigerant gives off the heat to a gas cooler / condenser 20 to the air flow for the vehicle cabin. After passing the check valve (10), the refrigerant reaches the first expansion valve (16).

P800328/DE/2- 33 ·· "^#*s;**··**::**; ^r ":

After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the second expansion valve 17, in which it is expanded isenthalpically to the evaporation pressure level of heat absorption. The switching valve 26 blocks the path to the collector 19. In the condenser/gas cooler 14, heat from the environment is supplied to the refrigerant and, if necessary, superheated. The refrigerant then returns to the compressor 12 via the switching valve 21.

A particularly advantageous feature of this circuit is that the engine coolant circuit is not used to heat the cabin while the vehicle is warming up. A heat exchanger in the cooling circuit is used to absorb the heat. This means that the drive motor heats up quickly, which keeps consumption, wear and emissions low.

Fig. 14 shows a schematic diagram of an integrated heat pump system.

After compression, the refrigerant enters the switching valve 13 under high pressure and temperature. Here, the cooling or heating operating mode is switched. If the valve is switched to the cooling operating mode, the refrigerant releases heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The second expansion valve (17) is not switched and is therefore closed. The refrigerant flows through the open valve (26) into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12). In the air conditioning box, the air flow for the cabin is cooled, the humidity contained condenses on the

P800328/EN/1.

cold surfaces of the heat exchangers. If necessary, the air is heated accordingly by means of the heating heat exchanger 7.

If the valve 13 is switched to the heating operating mode, the refrigerant releases the heat via the gas cooler/condenser 20 to the air flow for the vehicle cabin. After passing through the check valve 10, the refrigerant reaches the inlet on the high pressure side of the internal heat exchanger 15 and then into the first expansion valve 16. The check valve 6 prevents the refrigerant from flowing into the gas cooler 14, in which heat can be dissipated to the environment and the refrigerant contained therein condenses. The specific volume increases here, which leads to the refrigerant flowing out of the circuit. The gas cooler therefore fills with liquid refrigerant. After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the second expansion valve 17, in which it is expanded isenthalpically to the evaporation pressure level of the heat absorption. Valve 26 is closed here. In the refrigerant/heat transfer fluid heat exchanger 18, heat from the engine coolant is added to the refrigerant and, if necessary, superheated. The refrigerant flows through the collector 19, the low-pressure side of the internal heat exchanger 15 and reaches the compressor 12.

In this circuit, the energy remaining in the refrigerant is used to superheat the refrigerant before it enters the compressor 12 by means of the internal heat exchanger 15. Since part of the energy remains in the circuit so that the suction gas temperatures in the compressor 12 are high, high compressor outlet temperatures are achieved. The heat is therefore available at a high temperature.

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Fig. 15 shows a schematic diagram of an integrated heat pump system that works with a 2-stage expansion when heating. The actual heat absorption of the refrigeration circuit when heating comes from the outside air.

After compression, the refrigerant reaches the switching valve 13 under high pressure and temperature. This is where the cooling or heating operating mode is switched. If the valve 13 is switched to the cooling operating mode, the refrigerant releases heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). In the evaporator 5, it absorbs heat from the air flow for the vehicle cabin, which is thereby cooled. The refrigerant flows into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12). In the air conditioning box, the air flow for the cabin is cooled and the humidity it contains condenses on the cold surfaces of the heat exchanger. If necessary, the air is heated accordingly using the heating heat exchanger 7.

If the valve 13 is switched to the heating operating mode, the refrigerant releases the heat to the engine coolant via a refrigerant/engine coolant heat exchanger (27). After passing through the check valve 10, the refrigerant reaches the inlet of the high-pressure side of the internal heat exchanger 15 and then into the first expansion valve 16. The check valve 6 prevents the refrigerant from flowing into the gas cooler 14. After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the collector 19 to the low-pressure side of the internal heat exchanger 15. The switching valve 21 blocks the

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P800328/EN/L

direct route to the compressor, thus flowing through the second expansion valve 17, in which it is expanded isenthalpically to the evaporation pressure level of heat absorption. In the condenser/gas cooler 14, heat from the environment is added to the refrigerant and, if necessary, superheated. The refrigerant then returns to the compressor 12 via the switching valve 21.

Fig. 16 shows a schematic diagram of an integrated heat pump system.

After compression, the refrigerant enters the switching valve 13 under high pressure and temperature. This is where the cooling or heating operating mode is switched. If the valve is switched to cooling mode, the refrigerant releases heat to the environment via the gas cooler (14) and is further deheated in the high-pressure part of the internal heat exchanger (15). After passing through the check valve (6), the refrigerant is expanded to evaporation pressure in the first expansion valve (16). The second expansion valve (17) is not switched and is therefore closed. The refrigerant flows via the open valve (26) into the collector (19). On the low-pressure side of the internal heat exchanger (15), the refrigerant is superheated and then sucked in by the compressor (12).

By switching the changeover valve 3 0 to the cooling operating mode, cooling can be carried out when the valve 13 is set to heating. The refrigerant gives off part of the heat to the engine coolant via a refrigerant/engine coolant heat exchanger 27 and then flows through the changeover valve 3 0 through the check valve 10 into the gas cooler 14. Here it gives off further heat to the environment and is further deheated in the high-pressure part of the inner heat exchanger 15. After passing through the check valve 6, the refrigerant is expanded to evaporation pressure in the first expansion valve 16. The

P800328/EN/X. 37

The second expansion valve 17 is not switched on and is therefore closed. The refrigerant flows through the open valve 26 into the collector 19. The refrigerant is superheated on the low-pressure side of the internal heat exchanger 15 and is then sucked in by the compressor 12.

In the air conditioning box, the air flow for the cabin is cooled and the humidity contained condenses on the cold surfaces of the heat exchangers. If necessary, the air is heated accordingly using the heating heat exchanger 7.

If the valve 13 is switched to the heating operating mode, the refrigerant gives off the heat to the engine coolant via a refrigerant/engine coolant heat exchanger (27). In the changeover valve 3 0 in the position for the heating operating mode, the refrigerant reaches the inlet on the high pressure side of the internal heat exchanger 15 and then into the first expansion valve 16. The check valve 6 prevents the refrigerant from flowing into the gas cooler 14, in which heat can be dissipated to the environment and the refrigerant contained therein condenses. The specific volume increases here, which leads to the refrigerant flowing out of the circuit. The gas cooler therefore fills with liquid refrigerant. After appropriate throttling and heat absorption or heat release in the evaporator 5, the refrigerant flows through the second expansion valve 17, in which it is expanded isenthalpically to the evaporation pressure level of the heat absorption. Valve 2 6 is closed here. In the refrigerant/heat transfer fluid heat exchanger 18, heat from the engine coolant is added to the refrigerant and, if necessary, superheated. The refrigerant flows through the collector 19, the low-pressure side of the internal heat exchanger 15 and reaches the compressor 12.

In this circuit, the energy contained in the refrigerant after compression is transferred to the engine coolant

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which heats up quickly after driving begins. This has advantages in terms of wear, consumption and emissions. In addition, a large heat sink is available for cooling operation at the beginning, which improves the response of the refrigeration system at the beginning. There are also other advantages for the operation of the refrigeration system. The heat is released not only in the gas cooler but also via the engine cooler. This allows more efficient heat dissipation. In addition, the inlet temperature of the coolant in the gas cooler is significantly reduced. The temperature is therefore below 100 ⁰ C, which is a great advantage due to the strength of the aluminum materials usually used in heat exchangers.

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Claims (6)

1. Heat pump system for heating an interior air flow of a motor vehicle with - a refrigerant circuit that - a refrigerant compressor for compressing essentially gaseous refrigerant, - a first heat exchanger downstream of the refrigerant compressor for removing heat from the refrigerant - a first expansion facility and - has a second heat exchanger for transferring heat to the refrigerant, characterized in that - between the first heat exchanger and the second heat exchanger, firstly, a second expansion device and - secondly, a third heat exchanger is connected to the refrigerant circuit, wherein the pressure level of the third heat exchanger can be adjusted via a corresponding control of the first and second expansion devices. 2. Heat pump system according to claim 1, characterized in that - the installed heat transfer capacity of the first and third heat exchangers corresponds to the maximum additional heating capacity of the heat pump system to the indoor supply air. 3. Heat pump system according to claim 1 or 2, characterized in that - the first and/or the third heat exchanger are designed as refrigerant/heat transfer fluid heat exchangers, wherein - a heat transfer fluid is fed into a second circuit, via which - Heat can be transferred from the refrigerant circuit to the interior supply air flow. 4. Heat pump system for a motor vehicle, in particular heat pump system according to one of claims 1 to 3, - in which the supply air to the interior of the motor vehicle can be heated via a first heat exchanger of a refrigerant circuit, - the refrigerant can be expanded from a higher to a suitable intermediate pressure level via a first expansion device and - in which heat can be absorbed from a heat source via a second heat exchanger, characterized in that - heat can be transferred from or to the refrigerant via a third heat exchanger at the intermediate pressure level, whereby - the refrigerant can be expanded from the intermediate pressure level via a second expansion device. 5. Heat pump system according to claim 4, characterized in that - the interior supply air flow is dried using the heat supplied to the refrigerant circuit at the intermediate pressure level.