Method and control system for air conditioning a vehicle

Abstract

Method for operating a heat pump system (2) realized by a control system (22) for air conditioning a vehicle, in particular an electric or hybrid vehicle, wherein - an air conditioning requirement for a passenger compartment (10) of the vehicle is met by automatically setting one of several operating modes (BM) depending on the air conditioning requirement, - the passenger compartment (10) is cooled by means of an air conditioning evaporator (12) if the air conditioning requirement includes a cooling or dehumidifying requirement and / or heated by means of a heating heat exchanger (14) if the air conditioning requirement includes a heating requirement, - the heating heat exchanger (14) is arranged in a heating branch (24) of a coolant circuit (6) and is supplied with heat via a heat pump which has a chiller (46) and a condenser (26), both of which are connected to a refrigeration circuit (4) and wherein the chiller (46) is arranged in a cooling branch (33) of the coolant circuit (6) and the condenser (26) is in the heating branch (24), - in the event of a cooling requirement without an additional heating requirement, the heating branch (24) is opened, the chiller (46) of the heat pump is deactivated and cooling operation is thus achieved, - in the case of a heating demand without an additional cooling demand, the heating branch (24) is closed, heat is supplied to the heating heat exchanger (14) via the condenser (26) of the heat pump, via the cooling branch (33) and / or by heat absorption via the NT cooler (44), and heating operation is thus realized. - wherein, to dissipate heat from the heating branch (24), this is opened and the NT cooler (44), the condenser (26) and the heating heat exchanger (14) are operated in series, - wherein the control system (22) opens and closes the heating branch (24) by means of a shut-off valve (32), wherein to open the heating branch (24) the shut-off valve (32) is opened and to close the heating branch (24) the shut-off valve (32) is closed, - starting from heating operation, a first mixed operation is set up by activating the air conditioning evaporator (12), - where, starting from the first mixed operation, a second mixed operation is set up by reducing the heating output by regulating an expansion valve (48a) which is connected upstream of the chiller (46) in the refrigeration circuit (4), - where, starting from the second mixed operation, a third mixed operation is set up by operating the heating branch (24) in a pulsed manner, - where, starting from the third mixed operation, the cooling operation is stopped by continuously opening the heating branch (24).

Description

[0001] The invention relates to a method and a control system for air conditioning a vehicle.

[0002] A vehicle climate control system typically serves to cool and / or heat, for example, a vehicle component or the passenger compartment, depending on the situation. Climate control is often achieved using a heat pump system, which is controlled and / or regulated by the control system.

[0003] A heat pump system is described, for example, in DE 10 2014 217 960 A1, which originates from the applicant. Further systems for air conditioning a vehicle are described in EP 2 437 955 B1 and DE 10 2013 206 630 A1.

[0004] In general, electric and hybrid vehicles face the problem that they typically lack a continuously heat-generating combustion engine and its associated high-temperature cooling circuit. The heat required to warm the coolant for heating the passenger compartment must therefore be drawn from another source. However, the coolant heated in this way is usually at too low a temperature, often necessitating the use of a heat pump system to raise the coolant to a sufficient temperature. Suitable heat sources include electrical power components, which are typically located within the coolant circuit, i.e., a low-temperature circuit or simply a cooling circuit. Examples include an electric drive motor.An electric motor, or electrical power components such as inverters, DC / DC converters, charging electronics, or similar devices. In some cases, it may also be possible to utilize waste heat from a high-voltage storage system, i.e., a battery, to power the vehicle's drive motor.

[0005] The various heat sources typically need to be integrated separately, resulting in a complex wiring system. Particularly with regard to interior climate control, different operating states usually require specific settings in which heat is directed differently either into the passenger compartment and / or to the surrounding environment. This, in turn, necessitates a large number of valves, especially complex ones, as well as sophisticated control and regulation systems. This leads to a significant increase in complexity, especially in electric vehicles, since, as described above, less heat is available overall, making its efficient distribution all the more critical.

[0006] The invention is therefore based on the objective of providing an improved control system for the air conditioning of a vehicle, in particular an electric or hybrid vehicle, which enables cooling and heating of a passenger compartment of the vehicle and ensures the most efficient, stable and quietest possible operation.

[0007] The problem is solved according to the invention by a method for operating a heat pump system with the features of claim 1 and by a control system with the features of claim 25. Advantageous embodiments, further developments, and variants are the subject of the dependent claims. The method for operating a heat pump system is implemented by the control system. The further developments and advantages mentioned in connection with the control system then also apply mutatis mutandis to this method and to the heat pump system, and vice versa.

[0008] The control system serves to air-condition a vehicle, in particular an electric or hybrid vehicle, and is therefore combined with, i.e., preferably connected to, a heat pump system. This means, in particular, that the control system manipulates and adjusts the heat pump system by means of a number of actuators. The heat pump system comprises, in particular, a number of components for air-conditioning the vehicle. These components are then controlled and / or regulated by the control system and, in this context, are in particular actuators of the control system. In this sense, the vehicle is air-conditioned by means of the control system by controlling and / or regulating the heat pump system.

[0009] The climate control system addresses a passenger compartment requirement by selecting one of several operating modes, depending on the specific requirement. This means that a suitable operating mode or state is chosen. If the climate control requirement includes cooling or dehumidification, the passenger compartment is cooled using an evaporator. If the climate control requirement includes heating, the passenger compartment is heated using a heat exchanger. It is possible for both heating and cooling requirements to occur simultaneously, particularly during dehumidification.

[0010] The heating heat exchanger is located in a heating branch of a refrigerant circuit and is supplied with heat via a heat pump. This heat pump has a chiller and a condenser, or alternatively a gas cooler, both of which are connected to a refrigeration circuit. The chiller is located in a cooling branch of the refrigerant circuit, and the condenser is located in the heating branch. When there is a cooling demand without a corresponding heating demand, the heating branch is opened, the heat pump's chiller is deactivated, and cooling operation is thus implemented. Conversely, when there is a heating demand without a corresponding cooling demand, the heating branch is closed. Heat is supplied to the heating heat exchanger via the heat pump's condenser, the cooling branch, and / or by heat absorption via the low-temperature cooler, thus heating operation is implemented. Heating and cooling operation are each distinct operating modes.To remove heat from the heating branch, it is opened and the NT cooler, the condenser and the heating heat exchanger are operated in series.

[0011] The control system enables the heat pump system to operate in various modes, ensuring optimal climate control of the vehicle in any given situation, i.e., under specific climate control requirements. The different operating modes are set by controlling and / or regulating the individual components of the heat pump system. These components include, in particular, the heating element, the air conditioning evaporator, and the heat pump itself. The control system is not limited to manipulating these components. Furthermore, the term "control system" is used here and in the following to refer to both a control system and a control and control system; that is, the control system is not designed solely for control but may also be designed for regulation.

[0012] One advantage achieved with the invention is in particular that a heat pump system operated by means of the control system is operated in a particularly energy-efficient, robust and quiet manner.

[0013] According to this, air conditioning is particularly energy-efficient, robust, and quiet when using the control system. The control system enables particularly energy-efficient operation of the heat pump system, especially by automatically setting a suitable operating mode in any given air conditioning situation, characterized by various cooling and heating requirements. "Setting an operating mode" or "switching between operating modes" means that the controlled components are adjusted by the control system according to the circumstances and requirements, resulting in a specific operating mode being automatically set and implemented at any given time. In other words, the control system automatically selects the appropriate operating mode based on the settings of the heat pump system's components.A given operating mode is thus defined in particular by the respective switching states of the individual controlled and / or regulated components and is a consequence of the settings of these components. The operating mode therefore results from the settings of the components and not the other way around.

[0014] Furthermore, the individual components are controlled and / or regulated with exceptional efficiency. The virtually seamless transitions between the various operating modes, achieved through the specific control and regulation of the individual components of the heat pump system, ensure particularly robust and stable operation, especially without waiting times or disruptive noises during switching, i.e., when selecting a different operating mode. Particularly quiet operation is achieved primarily by eliminating the need to reverse the flow direction of the coolant in the coolant circuit and the refrigerant in the refrigeration circuit. In addition, the number of switching valves is significantly reduced compared to conventional heat pump systems, making the heat pump system both particularly cost-effective and significantly improving its operating acoustics, primarily due to the reduced number of switching operations.

[0015] A further advantage achieved with the invention lies particularly in the fact that the use of the control system enables a specific wiring configuration of the various components of the heat pump system, leading to particularly efficient operation. Crucially, this involves the series operation of the heating heat exchanger and the condenser in the heating circuit, in combination with the series operation of the low-temperature cooler. In this configuration, the heating heat exchanger is continuously supplied with coolant, which is heated by the condenser. This eliminates the need for a typically expensive diverter valve to redirect the coolant to the heating heat exchanger, and therefore, preferably, such a valve is omitted. To heat the passenger compartment using the heating heat exchanger, the heating circuit is typically shut off and only opened when there is a heat surplus, i.e., when the vehicle is hot.There is more heat in the coolant circuit than is needed for interior heating. In this case, additional heat is dissipated by routing coolant from the heating circuit through the low-temperature radiator. If there is no excess heat, the heating circuit is operated in closed mode, so that heat dissipation occurs exclusively at the heater core for the purpose of interior heating.

[0016] Overall, the behavior of the heat pump system is largely determined by the climate control requirements, which may include specific user input via a control element of the control system and / or take into account environmental conditions determined by suitable sensors of the control system, such as temperature sensors for measuring the outside temperature, the temperature inside the vehicle, the temperature of the vehicle's high-voltage battery, or at specific points within the heat pump system. Alternatively, the climate control requirements for the heat pump control system may be determined by a higher-level control system, such as a climate control function logic. In this case, the control system described here is a subsystem of the higher-level control system.Of particular importance are the climate control requirements for the passenger compartment, the heating requirements of the user, and, in the case of an electric or hybrid vehicle, the climate control requirements for the high-voltage storage system, as well as the outside temperature as an expression of the weather and environmental conditions. Automatic, demand-based, and optimal control and regulation of the individual components and the entire heat pump system is achieved through a suitable combination of the climate control requirements, in the form of predefined and / or determined parameters that describe the climate control requirements, with suitable control concepts for manipulating the heat pump system. In principle, the entire heat pump system can be considered part of the control system; at the very least, individual components of the heat pump system are part of the control system.

[0017] The coolant circuit is, in particular, a cooling circuit in which a coolant circulates, for example, a water-glycol mixture. The coolant circuit suitably comprises several, in particular three, sections, which are connected to each other at two junctions. The low-temperature radiator is located on the first section, the second section comprises the heating section, which is connected to the first section via a supply and a return line, the supply and return lines also being, in particular, parts of the second section. The third section is then the cooling section for vehicle components. Downstream of the first section, one of the junctions is, in particular, arranged as the first junction. The supply line of the heating section and the cooling section begin at this first junction.Downstream of the two branches, the cooling branch and the return of the heating branch are joined together at the other branch as a second branch and flow together into the first section.

[0018] A compressor is installed in the refrigeration circuit to compress the refrigerant, thereby raising its temperature. The compressor is located downstream of the air conditioning evaporator and chiller, and upstream of the condenser. The compressor is specifically an electric refrigerant compressor (ERC). Depending on the refrigerant used, the term "condenser" generally refers to a heat exchanger for heat dissipation from the refrigeration circuit. Accordingly, for example, when using CO2, also known as R744, a gas cooler is used instead of a conventional condenser. Furthermore, a valve is installed upstream of the air conditioning evaporator in the refrigeration circuit. This valve is closed during heating-only operation and acts as an expansion valve during cooling operation. The expansion valve is preferably a cost-effective thermal expansion valve (TxV).

[0019] A vehicle designed as an electric or hybrid vehicle typically features a high-voltage battery for propulsion, which also contributes to the climate control requirements, for example, by cooling or heating. In one possible configuration, the high-voltage battery is connected to the refrigeration circuit; that is, the high-voltage battery is thermally connected to the refrigeration circuit via a high-voltage evaporator to transfer heat to the refrigeration circuit.

[0020] This high-voltage storage (HVS) evaporator is advantageously connected in parallel to the chiller in the refrigeration circuit and thus serves as an additional or alternative heat source in the refrigeration circuit when cooling is required for the high-voltage storage system. Particularly in the case of a cooling demand at the high-voltage storage system, i.e., when both HVS cooling and heating are required, an advantageous embodiment initially foregoes activation of the chiller and instead uses the condenser to transfer waste heat from the high-voltage storage system to the heating heat exchanger. An expansion device, preferably a cost-effective thermal expansion valve (TxV), is connected upstream of the HVS evaporator. However, a variant is also conceivable in which the high-voltage storage system is cooled by refrigerant, i.e., connected to the refrigerant circuit, particularly the cooling branch.

[0021] The heat pump's condenser is specifically designed as a water-cooled condenser and comprises a refrigerant condenser and a condenser-heat exchanger that are thermally coupled. The refrigerant condenser is connected to the refrigeration circuit, and the condenser-heat exchanger is connected to the coolant circuit. The chiller comprises a refrigerant evaporator and a chiller-heat exchanger that are thermally coupled, with the refrigerant evaporator connected to the refrigeration circuit and the chiller-heat exchanger to the coolant circuit.

[0022] The heat pump expeditiously extracts heat from the vehicle's environment and / or from the vehicle component in the cooling circuit via the low-temperature (LT) cooler. For this purpose, the LT cooler, at least one vehicle component, and the chiller are connected in series, with the chiller preferably located downstream of and in close proximity to the vehicle component to be cooled, in order to achieve the most efficient heat transfer possible from the vehicle component to the chiller. The vehicle component could be, for example, power electronics, an electric motor for propelling the vehicle, or a high-voltage energy storage system. Each vehicle component to be cooled is typically thermally coupled to the coolant circuit via a suitable heat exchanger to transfer heat to the coolant.

[0023] The following describes various advantageous control and regulation concepts for different components of the heat pump system, enabling it to automatically and continuously switch between different operating modes, i.e., to implement a suitable operating mode depending on the requirements. Each of these concepts is advantageous on its own and is therefore considered inventive independently. However, combining several of these concepts offers at least one additional advantage, particularly because the various concepts partially utilize the same reference, actuator, control, and / or regulated variables, thus forming a particularly efficient overall concept for controlling and regulating the heat pump system.

[0024] In principle, for air conditioning in different situations with correspondingly different climate control requirements, at least one cooling mode (also called summer mode) and one heating mode (also called winter mode) are automatically set. "Automatic" in this context means, in particular, that the setting is made directly and primarily in response to a specific climate control requirement. In addition, a number of hybrid modes are available as transitional modes between cooling and heating modes. This means that, in addition to cooling and heating modes, the heat pump system can also operate in several hybrid modes and is operated in these modes depending on the climate control requirements.

[0025] Cooling operation occurs particularly when operating solely for cooling, meaning heat is absorbed only via the air conditioning evaporator. In one variant, heat is absorbed additionally or, more specifically, alternatively via the high-temperature evaporator. In this case, the heat pump is deactivated and the heating circuit is opened, allowing refrigerant from the heating circuit and, in particular, also from the cooling circuit, to flow through the low-temperature condenser. Furthermore, refrigerant, cooled by the low-temperature condenser, primarily to near ambient temperature, continuously flows through the heating circuit. No heat is dissipated via the heating heat exchanger. This heat exchanger is typically located within an air conditioning unit and is subject to an airflow, which is conveniently interrupted during cooling operation, for example, by a separate or higher-level air conditioning control system.In other words, if there is no heating demand, the heating heat exchanger is shut off on the air side.

[0026] In heating mode, the system exclusively serves a heating demand by transferring heat to the airflow passing through the heating heat exchanger. Heat is supplied to the heating heat exchanger via the heat pump's condenser. This heat originates from the low-temperature radiator and / or a vehicle component requiring cooling, which then enters the coolant circuit. From there, it is transferred to the condenser via the chiller. If there is a cooling demand for a high-voltage battery connected to the refrigeration circuit, heat is more efficiently supplied to the refrigeration circuit via the high-voltage evaporator. In this case, the chiller is not strictly necessary and can be deactivated. Furthermore, in heating mode, the heating circuit is closed to retain as much heat as possible. The air conditioning evaporator is deactivated, preventing any heat absorption.

[0027] In mixed-use systems, combined heating and cooling are implemented, with different mixed-use systems differing particularly in the ratio of cooling demand to heating demand.

[0028] Starting from heating mode, a first mixed mode is automatically activated by switching on the air conditioning evaporator to simultaneously heat and cool. From this first mixed mode, a second mixed mode becomes necessary and is therefore also automatically activated when the heating load decreases, by reducing the output of the chiller and thus the heat pump. This is achieved by throttling an expansion valve located upstream of the chiller in the refrigeration circuit. "Throttling" here means that, in addition to any existing, and especially conventional, control system, a further reduction in the heat pump's output occurs. From this second mixed mode, a third mixed mode is automatically activated by cycling the heating circuit to dissipate excess heat.Starting from the third mixed operation, the cooling operation is then automatically activated by continuously opening the heating circuit. The automatic adjustment in the opposite direction, i.e., from cooling operation to the third mixed operation, to the second mixed operation, to the first mixed operation, and finally to heating operation, occurs analogously. The adjustment of the various operating modes is thus advantageously automatic, gradual, and continuous.

[0029] Of the aforementioned operating modes, generally only one is active at any given time; that is, only one specific operating mode is selected at any given moment. This is primarily due to the fact that the operating modes are essentially defined by the specific settings of the heating circuit and the expansion valve upstream of the chiller, and are therefore mutually exclusive.

[0030] A compressor is arranged in the refrigeration circuit, operating at a specific compressor speed and exhibiting a specific output depending on this speed. In a preferred embodiment, the control system comprises a first and a second controller, by means of which the compressor, or more precisely its output, is regulated by setting, i.e., controlling, the compressor speed. The compressor speed serves as a control variable for each of the two controllers, whereby only one of the two controllers and its control variable are selected for regulating the compressor, depending on the air conditioning demand. The compressor is thus, in particular, an actuator of the control system. The compressor speed significantly determines the power supplied by the compressor and thus indirectly the respective air conditioning output of the evaporator and the heat pump.The compressor is controlled by a primary and a secondary controller, of which only one is active at any given time. In other words, the controllers are not active simultaneously; rather, only one controller is selected and used depending on the current air conditioning demand. This allows the control system to react automatically to changing environmental conditions, such as a change in heating requirements by the user. The two controllers are designed and optimized for correspondingly different air conditioning requirements. Specifically, the controller used is also selected based on the current operating mode.

[0031] During heating operation, control is expediently achieved using the first controller, whereby a heating branch actual temperature is suitably used as one of the controlled variables, i.e., the temperature of the coolant in the heating branch or heating loop. The heating branch actual temperature is preferably measured between the condenser and the heater core. The coolant temperature at this point determines the heating output of the heater core and thus the heating of the passenger compartment, particularly in combination with the set airflow rate and the inlet temperature of the airflow into the heater core.To achieve a specific passenger compartment temperature, which is set by the user via a control element, for example, the coolant at the heating heat exchanger must reach a specific target temperature for the heating circuit. This target temperature serves as the reference value for the first controller and is specified to the control system, for example, by a higher-level climate control function logic. Accordingly, the first controller is also referred to as the heating controller.

[0032] When a cooling demand exists, i.e., when a cooling mode or one of the mixed modes is selected—in other words, in those operating modes where the air conditioning evaporator is active and used for heat absorption—the compressor is advantageously controlled by the second controller as a function of the evaporator's actual temperature, i.e., in particular, the temperature present at the air conditioning evaporator. This is determined, for example, by measuring the air temperature, i.e., the temperature of the air that flows over the air conditioning evaporator for cooling and is then supplied to the passenger compartment for air conditioning. In one possible embodiment, the air temperature corresponds to the evaporator's actual temperature and is used directly as the controlled variable.The control variable is a setpoint temperature for the evaporator, which analogously represents a target temperature at the air conditioning evaporator or a target temperature for the air and is, for example, set by the user or specified via a higher-level air conditioning function logic. The second controller is accordingly also referred to as the cooling controller.

[0033] When using the second controller, it is particularly important to note that even in mixed operation, where a cooling demand (in the form of the evaporator setpoint temperature) and a heating demand (in the form of the heating circuit setpoint temperature) are simultaneously present, the compressor is still controlled by the second controller depending on the cooling demand. The compressor is only controlled by the first controller during heating operation. This ensures efficient and, above all, stable control of the compressor and the heat pump system in all operating modes. Both controllers are, for example, designed as PL controllers.

[0034] In a further preferred embodiment, the control system includes a third controller by which the compressor is regulated. This controller receives a coolant temperature as a controlled variable and a minimum coolant temperature as a reference variable. The third controller is operated in parallel, i.e., specifically simultaneously with the first controller. The compressor is then regulated as a function of the coolant temperature, i.e., the temperature of the coolant outside the heating section and the heating loop, and in particular the temperature of the coolant downstream of the chiller and upstream of the low-temperature cooler. This advantageously provides an additional control loop that efficiently prevents icing of the low-temperature cooler by excessively cooling the coolant in the chiller, by reducing the compressor speed in a timely manner.The minimum coolant temperature is, in particular, a lower limit that should not be undercut to prevent icing. Therefore, the third controller is also referred to as the limiting controller.

[0035] Preferably, the first and third controllers are different controllers, with the first controller regulating the heating circuit setpoint temperature and the third controller regulating the minimum coolant temperature, as described above. Each of the first and third controllers generates a control variable, from which the control system, in a preferred embodiment, selects one. The first controller generates an operating control variable, and the third controller generates a limit control variable. The selected control variable—either that of the first or that of the third controller—is then used to control the compressor. The control variable is selected using a comparator, which performs a minimum comparison and selects the lower of the two control variables.

[0036] In a configuration with three controllers, these are advantageously interconnected in such a way that the compressor is initially controlled by either the heating or cooling controller, depending on the selected operating mode. Simultaneously, when controlled by the heating controller during heating operation, protection against icing of the low-temperature cooler is ensured by automatically switching to the third controller (the limiting controller) instead of the heating controller if the compressor output becomes too high. Overall, the system thus selects between the first and second controllers based on the operating mode, and if the first controller is selected, an additional limit is imposed by the comparator and the third controller.

[0037] In a practical variant, the compressor speed is further limited by multiplying the control variable used for regulation by a limiting factor. This limiting factor is selected, in particular, using a characteristic curve as a function of a limiting variable. The limiting factor depends specifically on a limit value for a thermodynamic characteristic of the refrigerant and, for example, a pressure or a temperature. Multiplying by the limiting factor then advantageously prevents the pressure from falling below a minimum low pressure before the compressor or exceeding a maximum high pressure after the compressor, or the temperature from exceeding a maximum hot gas temperature of the refrigerant after the compressor.In other words, the limiting factor ensures that certain limit values ​​for refrigerant parameters, such as the aforementioned parameters, are maintained during operation of the heat pump system. In one variant, several parameters are monitored, and multiple or a single limiting factor are determined from these, which is then multiplied by the control variable.

[0038] In a further preferred embodiment, the control system includes a superheat controller, also referred to as a fourth controller, which sets the superheat of the refrigerant by controlling the expansion valve located upstream of the chiller. This expansion valve has an opening that serves as a control variable for the fourth controller. The superheat serves as the controlled variable of the fourth controller, and a target superheat, determined based on the air conditioning demand, serves as a reference variable. By controlling the expansion valve, a specific superheat of the refrigerant upstream of the compressor is thus set, ultimately determining the output of the heat pump, i.e., the amount of heat transferred from the refrigeration circuit to the heating circuit. The expansion valve is, in particular, an actuator of the control system.

[0039] The terms first, second, third, and fourth controllers are used solely for the purpose of distinguishing between the controllers. The use of the term "fourth controller" does not imply that three more controllers necessarily exist. Rather, it is also possible for a configuration to be limited to the fourth controller, with the other controllers mentioned above replaced by other mechanisms. The same applies to the first, second, and third controllers.

[0040] Superheat corresponds to the difference between the actual refrigerant temperature before the compressor and the pressure-dependent saturated vapor temperature of the refrigerant. Superheat is usually specified in Kelvin and ideally ranges between 2 and 15 K. To determine the superheat, in a suitable configuration, the temperature and pressure of the refrigerant before the compressor are measured, and the superheat, i.e., the actual superheat, is then calculated from these measurements, particularly using a characteristic curve. To prevent the expansion valve from being adjusted too frequently by the fourth controller, a practical refinement compensates for rapid temperature changes by filtering, i.e., smoothing, the measured temperature over time, thereby simulating the inertia of a thermal expansion valve (TxV).

[0041] The expansion valve is controlled and the superheat is set by the fourth controller, i.e., the superheat controller. The target superheat, as the reference variable, is preferably determined via a characteristic curve depending on the current air conditioning requirements. In principle, however, a constant value is also suitable. However, to increase efficiency and avoid the need for additional electric heating in the heating circuit during a heating capacity deficit, adjusting the superheat is advantageous for the first mixed operation. For this purpose, in a suitable configuration, the air conditioning evaporator and the chiller are adjusted relative to each other, and a lower target superheat is set than for heating operation. In this case, the air conditioning evaporator is activated; that is, pure heating operation is not selected, but possibly a mixed operation.Especially since, as described above, the compressor is generally controlled outside of heating mode by the difference between the actual evaporator temperature and the setpoint temperature, the compressor's output is distributed accordingly between the air conditioning evaporator and the heat pump. This means that, particularly during the initial mixed operation, the required amount of heat may not reach the heating circuit and may necessitate additional heating, for example, by an auxiliary heater. To avoid this as much as possible, a lower setpoint superheat is then advantageously set. This means the opening of the expansion valve before the chiller is adjusted accordingly, resulting in a larger refrigerant mass flow through the chiller, while a reduced refrigerant mass flow passes through the air conditioning evaporator.Due to the compressor's regulation relative to the air conditioning evaporator, the compressor's output is automatically increased, which in turn allows more heat to be transferred to the heating circuit via the heat pump. This adjustment of the target superheat based on the air conditioning demand, and thus ultimately on the operating mode, results in a particularly advantageous balancing of the air conditioning evaporator and chiller, especially during the initial mixed operation. This forces a higher compressor output than would initially be necessary based solely on the evaporator's actual temperature. This additional compressor output is then used to supply extra heat to the heating circuit via the heat pump, eliminating the need for a comparatively inefficient auxiliary heater. This also has the advantage of eliminating the need for an auxiliary heater, thereby saving costs.

[0042] In a particularly advantageous embodiment, the control variable of the fourth controller is influenced by an additional cut-off factor, i.e., it is multiplied by this factor and thereby reduced, to decrease the amount of heat transferred by the heat pump. In other words, in addition to controlling the expansion valve by the fourth controller, the expansion valve is further cut off by the cut-off factor. In this way, the second mixed operation is set, which is characterized by cut-off by the cut-off factor. Fundamentally, however, the cut-off factor is also involved in defining the various other operating modes. Suitablely, the cut-off factor is determined as a factor in the range of 0 to 1, with the second mixed operation then being set in those cases where the cut-off factor is greater than 0 and less than 1.A control factor of 0 or 1 then marks a transition from the second mixed operation to another operating mode, in particular to the third mixed operation.

[0043] As described above, the throttling factor primarily serves to further reduce the amount of heat transferred by the heat pump, thus enabling the second mixed operation. Since this operation requires less heat in the heating circuit compared to the heating operation and especially the first mixed operation, the heat pump is throttled back by the expansion valve. This results in less heat being transferred from the refrigeration circuit to the heating circuit, as less heat is absorbed from the refrigerant circuit. This prevents an unnecessarily high and non-demand-based amount of heat in the heating circuit and improves the overall efficiency of the heat pump system.

[0044] The throttling factor is suitably determined as a function of the coolant temperature in the heating circuit, i.e., as a function of the heating circuit actual temperature mentioned above, or more precisely, as a function of the difference between the heating circuit setpoint temperature and the heating circuit actual temperature. This difference is expediently determined using a characteristic curve to establish a suitable throttling factor value. This curve is such that as the heating circuit actual temperature rises and exceeds the heating circuit setpoint temperature, the throttling factor is chosen to be lower, allowing the expansion valve to close further and thereby advantageously reducing the chiller's output precisely to the required extent.

[0045] In fact, the crucial effect of the curtailment here, i.e., the reduction of heat absorption in the second mixed operation, can also be advantageously achieved by modifying the target superheat setting, specifically by specifying a target superheat that is greater than the actually desired target superheat. In particular, instead of an explicit curtailment factor as described above, a suitable variant achieves a reduction in heat absorption by modifying the target superheat with an additional curtailment allowance. Specifically, this means that the curtailment allowance is added to the target superheat to obtain a higher target superheat. This curtailment allowance is, for example, a fixed value or is derived from a characteristic curve. Alternatively, a different characteristic curve is used for the target superheat in which the curtailment allowance is already taken into account.

[0046] This additional intervention in the expansion valve control via the fourth controller also increases superheating, which is acceptable in this situation. In a suitable embodiment, when the control variable is reduced by the cut-off factor, i.e., in the second mixed operation and especially with a cut-off factor less than 1, an integral (I) component of the fourth controller is deactivated, where the fourth controller is specifically designed as a proportional (P) controller. In one variant, the proportional (P) component is also deactivated. By deactivating the I and, if applicable, the P component, the controller is advantageously prevented from working against the additional intervention via the cut-off factor.

[0047] The control factor, and in particular the characteristic curve for the control factor, is expediently designed to ensure that a maximum heating branch temperature is not exceeded. This means the control factor should be 0 before, or at the latest when, the actual heating branch temperature reaches the maximum heating branch temperature. In other words, the characteristic curve for the control factor is expediently designed to prevent the maximum heating branch temperature from being exceeded. This prevents heat transfer by the heat pump when the maximum heating branch temperature is reached.

[0048] In an advantageous embodiment, when a limit value is reached, i.e., a minimum or maximum value, and in particular a value of 0 for the control factor, the expansion valve closes completely and the third mixed operation is automatically activated. Closing the expansion valve also deactivates the heat pump's heat absorption. Specifically, heat is then only absorbed via the evaporator and transferred to the heating circuit. This setting therefore occurs when the heating demand is reduced compared to the heating operation and the first and second mixed operations, or when there is no heating demand at all. To then remove any excess heat from the heating circuit in a simple and efficient manner, the third mixed operation is automatically activated and the heating circuit operates intermittently.The transition between the second and third mixed operation is therefore characterized in particular by the fact that the output of the heat pump cannot be reduced further, but there is still excess heat in the heating branch, so that the heating branch is now opened periodically.

[0049] In cases where the chiller is inactive, particularly in the third mixed operation, it is advantageous to suspend an integral (I) component of the fourth controller, which is typically a PI controller. This prevents the fourth controller from moving the expansion valve to its end position (i.e., opening it fully) immediately when the chiller is reactivated. Instead, the expansion valve opens continuously or gradually from the closed position. This avoids unnecessary switching noise and excessive noise pollution.

[0050] In a preferred embodiment, when the vehicle is switched off or if both the chiller and the air conditioning evaporator are active, a minimum opening is specified for the expansion valve upstream of the chiller, which limits the control variable of the fourth controller. This embodiment is based on the consideration that in certain situations, completely closing the expansion valve upstream of the chiller is disadvantageous. Therefore, in these cases, it is advantageous to bypass the control of the expansion valve and instead set a minimum opening for the expansion valve by using a minimum value as the lower limit for the control variable. However, particularly in the first and second mixed operation, due to the control factor, it is possible that the actual set opening may fall below the minimum opening due to the additional control.

[0051] This approach is particularly useful when starting the heat pump system, i.e., especially when starting the vehicle. Therefore, it is advisable to set the minimum opening before switching off the vehicle, so that it is correctly set when starting. Such an open position with an inactive heat pump system and generally an inactive vehicle allows for beneficial pressure equalization in the refrigeration circuit, thus avoiding noticeable pressure surges and noises during starting.

[0052] Specifying a minimum opening is also particularly suitable for initial mixed operation and generally for situations and operating modes where, in addition to the expansion valve before the chiller, the expansion valve before the air conditioning evaporator is also used and open. In this situation, the two expansion valves together influence the superheat before the compressor, and by specifying the minimum opening, excessive closing of the expansion valve before the chiller is prevented. This has a particularly stabilizing effect on the operation of the heat pump system.

[0053] In a further preferred embodiment, the control system opens and closes the heating branch by means of a shut-off valve, which is located, in particular, in a flow or return line of the heating branch. In other words, the control system controls the shut-off valve. The shut-off valve is thus, in particular, an actuator of the control system. To open the heating branch, the shut-off valve is opened, thereby activating cooling operation in a particularly simple manner. To close the heating branch, the shut-off valve is closed accordingly, thereby activating heating operation, the first mixed operation, or the second mixed operation. The three operating modes—heating operation, first mixed operation, and second mixed operation—then differ from one another by the respective settings for the heat pump and the air conditioning evaporator. The third mixed operation is then activated by periodically opening and closing the shut-off valve, and thus also the heating branch.It is operated in a clocked manner. The switching state of the shut-off valve thus defines, in particular, the transitions from the second mixing operation to the third mixing operation and from this to the cooling operation.

[0054] The shut-off valve enables a particularly simple and efficient continuous transition between different operating modes. The pulsed control ensures a gradual adjustment of heat dissipation from the heating circuit to the specific situation and the current air conditioning requirements. For cooling operation, the shut-off valve is continuously open to maximize refrigerant exchange and heat dissipation from the heating circuit via the low-temperature cooler. Conversely, for heating operation, the shut-off valve is continuously closed to retain as much heat as possible in the heating circuit and heating loop. The shut-off valve is also continuously closed for the first and second mixed operating modes, in which only the heating output via the heat pump is reduced.Only if there is an excessive accumulation of heat in the heating circuit is the third mixing operation discontinued and the shut-off valve operated in a pulsed manner.

[0055] In a preferred control concept for the shut-off valve, i.e., in particular a concept for automatically and on-demand connecting and disconnecting the heating circuit from the rest of the coolant circuit, the shut-off valve is controlled such that a cycle is specified for the repeated opening and closing of the shut-off valve, whereby the shut-off valve is opened during a first time interval and then closed during a second time interval. The two time intervals together constitute a period of this clocked operation. The period is, for example, 3.6 s, and the two time intervals then have corresponding values ​​between 0 and 3.6 s. The specified cycle is, for example, the ratio of the first time interval to the period.

[0056] The operating cycle is suitably determined via a characteristic curve that links the desired operating cycle to the actual heating branch temperature, i.e., the temperature of the coolant in the heating branch. Specifically, the operating cycle is selected based on a characteristic curve and depending on the difference between the actual heating branch temperature and a maximum target heating branch temperature. This maximum target heating branch temperature is, in turn, determined via a suitable characteristic curve, particularly as a function of the target heating branch temperature.

[0057] The shut-off valve is thus preferably controlled based on the heating branch setpoint temperature, which is specified particularly by the user, and especially based on the excess heat relative to the heating branch setpoint temperature. This control is limited by a maximum temperature for the heating branch. Preferably, the shut-off valve is kept continuously closed when the actual heating branch temperature is low by selecting a cycle time of 0. This retains heat in the heating branch and initiates heating operation, the first mixed operation, or the second mixed operation. However, if the heating branch setpoint temperature is reached or exceeded, the shut-off valve is operated in a pulsed manner by selecting a cycle time between 0 and 1 to dissipate excess heat from the heating branch. Therefore, the third mixed operation is advantageously initiated automatically if more heat than required is present in the heating branch.

[0058] If the actual temperature of the heating branch increases further, cooling operation is automatically activated, and the shut-off valve is continuously opened by setting a cycle time of 1 to ensure maximum heat dissipation from the heating branch. The shut-off valve control thus automatically sets the appropriate cycle time and ensures a continuous transition between operating modes, particularly between modes with a heating demand (i.e., heating operation and the first and second mixed operation) and modes with a comparatively low or negligible heating demand (i.e., the third mixed operation and cooling operation). Of particular importance for an optimal transition is appropriately configured data, i.e., the design of the characteristic curves, for example, through a series of tests.

[0059] In a further preferred embodiment, the control system automatically sets up a low-temperature (LT) heating configuration by deactivating the heat pump's heat absorption via the chiller and using waste heat from a vehicle component connected to the cooling circuit for heating. In the LT heating configuration, an alternative heat supply to the heating heat exchanger is thus implemented, eliminating the need to use the heat pump's heat absorption via the chiller and supplying heat directly via the coolant circuit. The heat pump's heat absorption via the chiller is deactivated, in particular, by closing the expansion valve upstream of the chiller. This embodiment is based on the understanding that, in certain situations, it is possible to utilize the waste heat from the vehicle component without using the heat pump.However, if there is also a cooling requirement for the passenger compartment, heat continues to be absorbed into the refrigeration circuit via the air conditioning evaporator, so the compressor remains activated in this case. If, however, there is no cooling requirement for the passenger compartment, the heat pump is switched off completely, i.e., the compressor is switched off.

[0060] A situation in which the waste heat from the vehicle component can be used without the heat pump arises, in particular, when the heating branch setpoint temperature is lower than the coolant actual temperature. An activation condition for the low-temperature (LT) heating configuration is then, in particular, that the heating branch setpoint temperature is also higher than the heating branch actual temperature, so that the LT heating configuration is appropriately activated precisely in this situation. If the LT heating configuration is activated, the heating branch actual temperature may exceed the heating branch setpoint temperature. However, as long as the coolant actual temperature is sufficiently high, i.e., higher than the heating branch setpoint temperature, the LT heating configuration remains expediently activated. In other words, the LT heating configuration is activated if there is a heating demand and the coolant downstream of the chiller has a higher temperature than in the heating branch.A suitable heat potential is present, allowing the coolant to release heat at the heating heat exchanger. However, activation does not occur if the coolant temperature is below the heating circuit temperature. This lower limit for activation prevents unnecessary heat loss from the heating circuit when the user reduces their heating demand, thus improving the efficiency of the heat pump system.

[0061] In the low-temperature heating configuration, the heat pump system is set up, particularly with regard to the various valves, as in cooling mode, i.e., with the expansion valve before the chiller closed and the heating branch open. The expansion valve upstream of the chiller is completely closed, since the heat used for heating is drawn from the cooling branch and the heat pump's heat input via the chiller is not required. The special feature is that this valve setting, which is otherwise only present in cooling mode, is also applied even though there is no cooling requirement for the passenger compartment.

[0062] Excess heat is generally dissipated to the environment via the low-temperature (LT) cooler. However, to minimize unnecessary heat loss to the environment, a further preferred embodiment of the control system establishes a heat storage configuration to prevent heat emission. For this purpose, the coolant is routed around the LT cooler via a bypass, specifically by connecting the bypass in parallel with the LT cooler. Furthermore, a bypass valve is suitably integrated into the LT cooler bypass. This valve opens to establish the heat storage configuration and closes to deactivate it. The position of this bypass valve thus defines the heat storage operation. The bypass valve also serves as an actuator within the control system.

[0063] In a particularly cost-effective embodiment, the bypass valve is a shut-off valve, which is then arranged along the low-temperature (LT) cooler bypass. In a particularly efficient further development, an additional LT shut-off valve is arranged for shutting off the LT cooler. This LT shut-off valve is then operated in the opposite direction to the bypass valve, so that the coolant is either routed entirely through the LT cooler or entirely through the LT cooler bypass. In an alternative embodiment, a changeover valve, in particular a 3 / 2-way valve, is arranged instead of the two shut-off valves, either upstream or downstream of the LT cooler, so that the heat storage operation is activated and deactivated by switching the changeover valve.

[0064] In a suitable configuration, the heat storage system is automatically activated precisely when the coolant temperature is higher than the ambient temperature (i.e., the temperature in the vehicle's surroundings) and when it is lower than the maximum permissible coolant temperature. In this situation, when the coolant temperature is higher than the ambient temperature, heat could potentially be released into the environment, but this is prevented by activating the heat storage system. The maximum coolant temperature limit then protects the coolant circuit and its connected components, such as the power electronics or the electric drivetrain, from overheating caused by excessive coolant temperature.

[0065] The heat storage configuration is therefore only activated when, under certain ambient conditions, the heat contained in the coolant circuit is not to be released to the environment, but rather transferred to the heating circuit via heat absorption by the chiller and heat release via the condenser. In other words, the heat is to be retained in the coolant circuit, especially when there is no current heating demand, but the heat is to be used at a later time. The ambient conditions are characterized by the outside temperature, the current coolant temperature, and the maximum coolant temperature. The heat storage configuration is activated or deactivated depending on these three temperatures. Specifically, the shut-off valve is also opened to allow coolant to flow into the heating circuit.

[0066] In an advantageous embodiment, the heat storage configuration is also automatically activated if more heat is generated in the cooling circuit than is transferred to the refrigeration circuit via the chiller. In other words, if the heating demand is lower than the cooling demand on the heat source in the cooling circuit, the heat storage configuration is activated preventively to retain the initially excess waste heat in the refrigerant circuit for potential future heating demands. The amount of heat transferred by the chiller depends on its maximum capacity and the current heating demand. The available amount of heat depends on the waste heat generated by the heat source, i.e., it depends on the specific operating state of the heat source and, in the case of the vehicle's power electronics or drivetrain, on the current driving mode or cycle in which the vehicle is operating.Therefore, if less heat is required than is available, the excess heat is expediently stored for later use, at least as long as the actual coolant temperature does not exceed a maximum coolant temperature, whereby the maximum coolant temperature does not necessarily correspond to the maximum coolant temperature mentioned above, but alternatively is a maximum cooling branch temperature.

[0067] The heat storage configuration is particularly advantageous in combination with the aforementioned low-temperature heating configuration, as the waste heat from the vehicle component in the cooling circuit should be transferred to the heating circuit as completely as possible, and as little heat as possible should be lost via the low-temperature radiator. Therefore, the heat storage configuration is expediently set automatically when the low-temperature heating configuration is set.

[0068] A fan with a suitably adjustable fan speed is assigned to the low-temperature (LT) cooler. Preferably, the fan is controlled by the control system by adjusting the fan speed depending on the actual coolant temperature and a minimum coolant temperature. This advantageously adjusts the heat exchange via the LT cooler, i.e., particularly with the environment, as needed and adapts it to the prevailing situation, especially the temperature conditions in the cooling circuit. The heat exchange is primarily determined by the airflow over the LT cooler, i.e., the airflow rate or the amount of ambient air that passes over the LT cooler per unit of time. The airflow rate is then controlled by adjusting the fan speed. The fan is thus, in particular, an actuator of the control system. The fan is, in particular, an electrically driven fan and is also referred to as an electric fan.The fan speed then becomes a control variable, with the coolant's actual temperature serving as the control variable.

[0069] The minimum coolant temperature specifies a lower limit that prevents the coolant at the low-temperature radiator from cooling down so much that the radiator ices up. This minimum coolant temperature is determined, for example, using a characteristic curve as a function of the ambient temperature, and specifically in such a way that the minimum coolant temperature is at most only slightly lower than the dew point of the ambient air in the current situation. Typically, the minimum coolant temperature is lower than the ambient temperature.

[0070] In a preferred embodiment, the fan speed is determined by a characteristic curve designed such that as the actual coolant temperature approaches the minimum coolant temperature, i.e., as the difference between the two temperatures decreases, the fan speed is increased to prevent icing of the low-temperature cooler by warming the coolant through increased heat absorption from the environment. Alternatively, and preferably additionally, the characteristic curve, or an additional characteristic curve, is designed such that a higher fan speed is set when heat is dissipated via the low-temperature cooler and the actual coolant temperature increases, in order to cool the correspondingly warmer coolant in the low-temperature cooler more effectively. Preferably, both of the above-mentioned alternatives are implemented and linked via a maximum selection.From two characteristic curves, a fan speed is determined and the higher one is selected, so that icing of the NT cooler is prevented by increased heat absorption from the environment when the coolant temperature decreases, and excessive heating of the coolant is prevented by increased heat dissipation to the environment when the coolant temperature increases.

[0071] In heat storage mode, it is advisable to forgo fan control and deactivate the fan, as heat exchange with the environment is not desired in this case and deactivating the fan saves energy both for operating the fan and for the otherwise increased heat exchange at the NT cooler.

[0072] The airflow at the NT cooler is controlled according to demand by the fan control concepts described above, making it particularly efficient. The fan speed is only increased when needed and otherwise kept as low as possible, resulting in improved acoustics for the heat pump system.

[0073] The control system essentially has a memory that stores a number of model parameters, particularly those temperatures that represent critical limits for the coolant. An example of such a critical limit, and thus a model parameter, is the minimum coolant temperature mentioned above. This knowledge, combined with a measurement of the actual coolant temperature, enables advantageously regular and, in particular, continuous monitoring of the actual coolant temperature with regard to the potential risk of icing due to approaching the minimum coolant temperature.

[0074] In a preferred embodiment, potential icing is prevented by cyclically opening the heating circuit and transferring heat from the heating circuit to the low-temperature cooler. In other words, depending on the difference between the minimum coolant temperature and the actual coolant temperature, the cooler is heated at regular intervals by means of the heating circuit. In this way, particularly in line with the third mixed operation, heat is dissipated from the heating circuit by cyclically opening it, thereby initiating an icing prevention mode, i.e., implementing icing protection.Cyclic opening means that the heating circuit is not operated intermittently as in the third mixed operation, but rather that the heating circuit is generally closed for an extended period of several minutes, in particular at least 10 minutes, and is only opened for a short period of a few seconds, for example, 1 to 10 seconds, particularly up to 60 seconds. During this short period, heat is transferred from the heating circuit to the rest of the coolant circuit and directed to the low-temperature radiator without significantly interrupting the intended operating mode. In other words, depending on the current coolant temperature, a cyclical defrosting operation is implemented and set by briefly opening the heating circuit from a currently existing operating mode, in particular one with the heating circuit closed.The anti-icing mode essentially interrupts the currently selected operating mode briefly. Through appropriate control system design, the cyclical anti-icing mode is then activated in such a way that icing is prevented from occurring in the first place. This is particularly suitable for vehicles with artificially generated, additional waste heat in the coolant circuit, where the generation of such additional waste heat raises the overall coolant temperature, for example by a few degrees Celsius, thus preventing icing on the low-temperature radiator.

[0075] In the control concepts described above for the various components, the various characteristic curves are of particular importance. These curves serve two purposes: firstly, they determine further parameters for the respective control system, and secondly, they establish a relationship to the various control variables. They significantly determine the specific behavior of the control system and its automatic adjustment of the various operating modes, especially the conditions for transitions between them. Furthermore, the characteristic curves advantageously also incorporate certain limit conditions in the form of upper and lower limits for the smooth operation of the heat pump system. The characteristic curves are then determined primarily through appropriate testing and, ideally, stored in the control system's memory as a table of values ​​or a calculation formula.

[0076] The control system appropriately includes control electronics or a controller to perform, in particular, one or more of the above-mentioned settings, controls, regulations, calculations and / or other operations.

[0077] The control system makes the vehicle's heat pump system exceptionally safe, robust, efficient, and quiet in operation. Furthermore, the control system allows for the advantageous implementation of complex climate control requirements, such as simultaneously heating the passenger compartment and cooling vehicle components in the cooling circuit and / or via additional evaporators in the refrigeration circuit. Compared to conventional heat pump systems, this system is particularly energy-efficient and therefore especially suitable for use in electric or hybrid vehicles.

[0078] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing schematically depicts: Fig. 1 a heat pump system, Fig. 2 a control concept for a compressor of the heat pump system, Fig. 3a a control concept for an expansion valve of a heat pump of the heat pump system, Fig. 3b a characteristic curve for determining a curtailment factor for the control concept from Fig. 3a, Fig. 4a a control concept for a shut-off valve of a heating branch of the heat pump system, Fig. 4b a characteristic curve for determining a clock speed for the control concept from Fig. 4a, Fig. 5 a control concept for a bypass valve of the heat pump system, Fig. 6 conditions for activating an NT heating configuration of the heat pump system, and Fig. 7 a control concept for a fan of the heat pump system.

[0079] In Fig. Figure 1 shows a heat pump system 2 for a vehicle not shown in detail, in particular for an electric or hybrid vehicle. The heat pump system 2 has a refrigeration circuit 4 in which a refrigerant circulates, and a coolant circuit 6 in which a coolant circulates, for example a water / glycol mixture. The refrigeration circuit 4 is in Fig. The refrigerant circuit 6 is shown with a solid line, and the refrigerant circuit 1 with a dashed line. The refrigerant circuit 6 is a cooling circuit in which the refrigerant typically has a temperature between approximately -25 and +70 °C or even up to +90 °C. The heat pump system 2 also includes an air conditioning unit 8 for air conditioning a passenger compartment 10, i.e., an interior space, of the vehicle. For this purpose, the air conditioning unit 8 has an air conditioning evaporator 12, which is connected to the refrigerant circuit 4, and a heating heat exchanger 14, which is connected to the refrigerant circuit 6. The air conditioning evaporator 12 then serves to cool and dehumidify the passenger compartment 10, while the heating heat exchanger 14 serves to heat it.

[0080] Furthermore, the air conditioning unit 8 includes an air duct 16 for supplying air L to the passenger compartment 10. The heating heat exchanger 14 is arranged downstream of the air conditioning evaporator 12 with respect to the incoming air L, so that, depending on the operation of the two components, the air L is heated, cooled or both.

[0081] The heat pump system 2 can be switched between heating and cooling modes by means of a control system 22. In heating mode, the passenger compartment 10 is heated by means of the heating heat exchanger 14; in cooling mode, the passenger compartment 10 is cooled and dehumidified by means of the air conditioning evaporator 12. The heat used for heating is supplied to the heating heat exchanger 14 via the coolant circuit 6. For this purpose, the heating heat exchanger 14 is connected to the coolant circuit 6 in a heating branch 24. A condenser 26 is also connected to this heating branch 24 for transferring heat from the refrigeration circuit 4 to the coolant circuit 6. The condenser 26 is designed as a water-cooled condenser with a suitable heat exchanger, which is connected to the coolant circuit 6.In the embodiment shown here, an additional heat source, an auxiliary heater 28, is arranged in the heating branch 24, specifically upstream of the heating heat exchanger 14 and downstream of the condenser 26. Furthermore, a heating circuit pump 30 is arranged in the heating branch 24, specifically upstream of the condenser 26 in this embodiment, for circulating coolant. However, other positions are also suitable.

[0082] The coolant circuit 6 comprises in Fig. 1. Three sections are connected to each other at two branches V1 and V2. A low-temperature cooler 44 is arranged on the first section. The second section is the heating branch 24 with a supply line 31 and an unspecified return line. The third section is a cooling branch 33. Downstream of the first section, one of the branches V1 and V2 is arranged as the first branch V1. The supply line 31 of the heating branch 24 and the cooling branch 33 originate at this first branch V1. Downstream of both branches 24 and 33, they are joined at the other of the two branches V1 and V2 as the second branch V2 and together empty into the first section.

[0083] To optimally utilize the heat transferred from the condenser 26 to the heating branch 24 for heating the passenger compartment 10, the heating branch 24 can be shut off via a shut-off valve 32. For this purpose, the shut-off valve 32 is located in the supply line 31 of the heating branch 24. Additionally, a heating loop 36 is formed via a return branch 34, by means of which coolant is returned from a first branch 38 downstream of the heating heat exchanger 14 to a second branch 40 of the heating branch 24 upstream of the condenser 26. The heating branch 24 extends between the first branch 38 and the second branch 40. The supply line 31 of the heating branch 24 is located upstream of the second branch 40 and downstream of the first branch 38. The flow 31 of the heating branch 24 can be shut off by means of the shut-off valve 32, so that the heating loop 36 can be operated essentially independently of the rest of the coolant circuit 6.In heating mode, the heating branch 24 is then shut off by means of the shut-off valve 32, so that the coolant in the heating loop 36 is repeatedly routed via the condenser 26, the auxiliary heater 28 and the heating heat exchanger 14.

[0084] Parallel to the heating circuit 24, the coolant circuit 6 includes the cooling circuit 33 for cooling at least one vehicle component 42. In the embodiment shown here, only one vehicle component 42 is depicted, without limiting generality. Therefore, embodiments with multiple vehicle components 42 are also possible. The heat absorbed by the vehicle component 42 is either dissipated to the vehicle's environment via the low-temperature radiator 44 in the coolant circuit 6 or transferred to the refrigeration circuit 4 by means of a chiller 46. For heat dissipation via the low-temperature radiator 44, a fan 45 is assigned to it, which is preferably designed as an electric fan 45, i.e., a so-called electric fan, and draws ambient air over the low-temperature radiator 44. For heat transfer to the refrigeration circuit 4, the chiller 46 is connected, preferably downstream of the vehicle component 42, in the cooling circuit 33.Furthermore, the chiller 46 has a chiller evaporator, via which the chiller 46 is connected to the refrigeration circuit 4. In combination with the condenser 26, the chiller 46 forms, in particular, a heat pump for transferring heat from the cooling circuit 33 to the heating circuit 24. In addition, or alternatively, it is also possible to extract heat from the environment via the low-temperature cooler 44 and then use it to heat the passenger compartment 10 by means of the chiller 46 and the condenser 26.

[0085] In refrigeration circuit 4, an expansion valve 48a is installed upstream of the chiller 46. Likewise, an expansion valve 48b is installed upstream of the air conditioning evaporator 12. Furthermore, a compressor 50 is arranged in refrigeration circuit 4, namely upstream of the condenser 26.

[0086] The chiller 46 and the air conditioning evaporator 12 are arranged parallel to each other in refrigeration circuit 4. In the embodiment shown here, an additional evaporator 52 is also connected to refrigeration circuit 4 in parallel with the air conditioning evaporator 12 and the chiller 46. This additional evaporator 52 serves, for example, to cool a high-voltage storage device of the vehicle (not shown in detail). An expansion valve 48c is also assigned to the additional evaporator 52.

[0087] Furthermore, in the embodiment shown here, two internal heat exchangers 54 and 56 are connected to the refrigeration circuit 4. Internal heat exchanger 54 serves to increase the performance and efficiency of the air conditioning evaporator 12, and internal heat exchanger 56 serves to increase the performance and efficiency of the chiller 46. In an alternative configuration not shown, only one internal heat exchanger 54 is provided in the refrigeration circuit 4, which is then used jointly for the air conditioning evaporator 12 and the chiller 46.

[0088] Due to the special wiring of the heat pump system 2, several operating modes BM can be implemented for optimal climate control of the vehicle. The different operating modes BM are set by the control system 22 through the control of the individual components of the heat pump system 2, namely by controlling and / or regulating the shut-off valve 32, the expansion valve 48a upstream of the chiller 46, the compressor 50, the bypass valve 62, and a fan 45 for controlling the airflow at the low-temperature cooler 44. These components are, in particular, actuators of the control system 22.The unique wiring of heat pump system 2 enables automatic and, in particular, smooth or continuous transitions between the various operating modes BM. Each transition is exceptionally quiet, requires minimal switching operations, and, most importantly, eliminates waiting times and direction reversals. This makes heat pump system 2 particularly stable, quiet, and efficient in operation.

[0089] Based on the Fig. Sections 2 to 7 below describe various control concepts for the aforementioned components and, in this context, explain in more detail the various operating modes (BM) for handling different air conditioning requirements. These control concepts are implemented and executed by means of the control system 22. The corresponding parts and components for the concrete implementation of the concepts are then, in particular, part of the control system 22.

[0090] The heat pump system 2 shown basically has a cooling mode (also called summer mode), a heating mode (also called winter mode), and several mixed modes as transitional modes between cooling and heating. In these mixed modes, combined heating and cooling are achieved. In the first mixed mode, the air conditioning evaporator 12 is initially activated, starting from the heating mode. In the second mixed mode, the heating output is reduced by decreasing the output of the chiller 46 and thus the heat pump. In the third mixed mode, the shut-off valve is operated intermittently, starting from the second mixed mode, to dissipate excess heat from the heating circuit 24. Finally, the cooling mode is achieved by fully opening the shut-off valve 32, starting from the third mixed mode.

[0091] Of the aforementioned operating modes BM, generally only one is active at any given time; that is, only one specific operating mode BM is selected at any given time. This is primarily due to the fact that the operating modes BM are defined, among other things, by the switching positions of the various actuators of the control system 22 and are therefore mutually exclusive. In addition to the operating modes BM, the embodiment shown here also allows for the selection of a heat storage configuration WS and a low-temperature heating configuration NTH as additional configurations of the heat pump system 2. These can also be set simultaneously with one or more of the aforementioned operating modes BM. In particular, the low-temperature heating operation can be set simultaneously with one of the mixed modes or with the heating operation and also automatically activates the heat storage operation, so that these two operating modes BM are then active simultaneously.

[0092] Fig. Figure 2 shows a control concept for the compressor 50, also referred to as an electric refrigerant compressor (ERC). The controlled variable is the rotational speed of the compressor 50, i.e., a compressor speed VD, which significantly determines the power supplied by the compressor 50 and thus indirectly the air conditioning capacity of the air conditioning evaporator 12 and the heat pump, i.e., in particular, the chiller 46. The control is initially achieved via a first and a second controller R1, R2, whereby only the output of one of the controllers R1, R2 is selected and then used depending on the ambient conditions and / or the air conditioning demand. In the case of a heating demand only, i.e., for heating operation, control is achieved using the first controller R1, whereby the controlled variable is then a heating branch actual temperature T-HZ-I, i.e., a temperature of the refrigerant in the heating branch, preferably measured between the condenser 26 and the heating heat exchanger 14.The temperature of the coolant at this point determines the heating output of the heating heat exchanger 14 and thus the heating of the passenger compartment 10. To achieve a specific temperature in the passenger compartment 10, which is specified, for example, by the user via a control element or by a higher-level climate control function logic, the coolant at the heating heat exchanger 14 must then have a specific heating branch setpoint temperature T-HZ-S, which is used as a reference variable for the first controller R1, which is also referred to as heating controller R1.

[0093] For cooling operation and mixed operation, i.e., for those operating modes BM in which the air conditioning evaporator 12 is activated and used for heat absorption, control is achieved by means of the second controller R2, also referred to as the cooling controller R2. This control is based on the actual evaporator temperature T-KV-I, i.e., the temperature of the air flowing over the air conditioning evaporator 12 for cooling. The control variable is then a setpoint evaporator temperature T-KV-S, which is, for example, set and specified by the user or specified by a higher-level air conditioning function logic. It should be noted that, especially in mixed operation, where a cooling demand in the form of the evaporator setpoint temperature T-KV-S and a heating demand in the form of the heating circuit setpoint temperature T-HZ-S are present simultaneously, the compressor 50 is controlled based on the cooling demand.Only during heating operation is the control carried out using the first controller R1.

[0094] A key feature of the control and regulation of the heat pump system 2 presented here, using the control system 22, is an additional control loop with a third controller R3. This controller regulates the compressor 50 based on the coolant temperature outside the heating circuit 24, and in particular, the coolant temperature downstream of the chiller 46 and upstream of the low-temperature cooler 44. This additional control loop efficiently prevents icing of the low-temperature cooler 44 caused by excessively cooled coolant in the chiller 46 by reducing the compressor speed VD in a timely manner. For this purpose, the coolant temperature is supplied to the third controller R3 as a control variable (actual coolant temperature T-KM-I), and a minimum coolant temperature T-KM-min, representing a lower limit that should not be undercut to prevent icing, is used as a reference variable.The third controller R3 is therefore also referred to as the limiting controller R3. A special feature of the control concept for compressor 50 is the selection of one of the two control variables of the first controller R1 and the third controller R3, namely either the operating-mode-dependent control variable of the first controller R1 or the control variable of the third controller R3. This selection is made via a comparator V, which performs a minimum comparison and sets the lower of the two compressor speeds VD. The comparison is only made between the first controller R1 and the third controller R3, i.e., only when there is a pure heating demand and the risk of icing is greatest due to a correspondingly high compressor output required to meet this heating demand. If compressor 50 is controlled by the second controller R2, no limiting is performed using the comparator V.Overall, the selection between the first controller R1 and the second controller R2 is based on the operating mode, and in the case of the selection of the first controller R1, an additional limit is imposed via the comparator V and the third controller R3.

[0095] In addition to the controllers R1, R2, R3 mentioned above, the control concept of Fig. 2. A limit is imposed by multiplying the control variable, i.e., in this case the controller output, particularly after the comparator, by a limiting factor BF. This mechanism ensures that a minimum low pressure pN before compressor 50 is not undershot, a maximum high pressure pH after compressor 50 is not exceeded, and a maximum hot gas temperature TH of the refrigerant after compressor 50 is not exceeded. For each of the aforementioned cases, a limiting factor BF for the value to be limited is determined using a corresponding characteristic curve K1 and multiplied by the control variable.

[0096] Fig. Figure 3a shows a control concept for the expansion valve 48a, which is located upstream of the chiller 46. This expansion valve 48a essentially serves to set a specific superheat Ü of the refrigerant before the compressor 50 and thus ultimately to adjust the output of the heat pump. The superheat Ü is the difference between the actual refrigerant temperature before the compressor 50 and a pressure-dependent saturated vapor temperature of the refrigerant. The superheat Ü is usually specified in Kelvin and is, for example, between 2 and 15 K.

[0097] In the regulatory concept of Fig. 3a. Control is achieved by means of a fourth controller R4, also referred to as the superheat controller R4. The superheat Ü is the controlled variable, and the manipulated variable is the opening or opening size of the expansion valve 48a. The temperature and pressure of the refrigerant upstream of the compressor 50 are measured, and the current superheat Ü, i.e., the actual superheat, is determined from this using a characteristic curve (not shown). To prevent excessively frequent adjustments, rapid temperature changes are mitigated by filtering, i.e., smoothing, the measured temperature over time, thereby simulating the inertia of a thermal expansion valve (TxV). A target superheat Ü-S is provided as the reference variable, which is determined via a characteristic curve K2 depending on the respective operating mode BM.In principle, a constant value is also suitable initially, but especially in the first mixed operation, an adjustment of the superheat Ü is advantageous in order to achieve more efficient operation.

[0098] Since the compressor 50, as described above, is controlled in mixed operation by the difference between the evaporator actual temperature T-KV-I and the evaporator setpoint temperature T-KV-S, the output of the compressor 50 is distributed accordingly between the air conditioning evaporator 12 and the chiller of the heat pump. Therefore, in the first mixed operation, the required amount of heat may not reach the heating circuit 24 and must be supplemented by the auxiliary heater 28. To avoid this as much as possible, or even to eliminate the need for the auxiliary heater 28 entirely, a lower setpoint superheat Ü-S is set in the first mixed operation than in other operating modes BM. This results in a correspondingly larger opening of the expansion valve 48a, generating a larger refrigerant mass flow through the chiller 46, while a reduced refrigerant mass flow passes through the air conditioning evaporator 12.Due to the control of compressor 50 relative to the air conditioning evaporator 12, the output of compressor 50 is automatically increased, thus transferring more heat to the heating circuit via the heat pump. By adjusting the target superheat Ü-S depending on the operating mode BM, a trim is achieved in the first mixed operation for the air conditioning evaporator 12 and the chiller 46, forcing a higher compressor output than would be necessary based solely on the evaporator temperature. This additional compressor output is then used to supply additional heat to the heating circuit 24 via the heat pump, so that the comparatively inefficient auxiliary heater 28 does not initially need to be activated.

[0099] Another special feature of the in Fig. The control concept shown in Figure 3a involves the additional manipulation of the control variable output by the fourth controller R4 by an additional curtailment factor AF, which is also significantly involved in defining the various operating modes BM. The curtailment factor AF essentially serves to reduce the power output of the heat pump, thus enabling the second mixed operation. Since only a smaller amount of heat is required in heating circuit 24 in this mode compared to heating operation and the first mixed operation, the heat pump is further reduced by additionally curtailing the expansion valve 48a, resulting in less heat being transferred from refrigeration circuit 4 to heating circuit 24. This prevents an unnecessarily high and non-demand-based amount of heat in heating circuit 24 and improves the overall efficiency of the heat pump system 2.

[0100] In the example shown, the control factor AF is defined as a factor in the range of 0 to 1, depending on the heating branch actual temperature T-HZ-I mentioned above, more precisely, depending on the difference between the heating branch setpoint temperature T-HZ-S and the heating branch actual temperature T-HZ-I. This difference is used to determine a suitable value for the control factor AF based on a characteristic curve K3.

[0101] An example of this characteristic curve K3 is in Fig. Figure 3b shows the control factor AF as a function of the aforementioned difference. As the actual heating branch temperature T-HZ-I increases, the control factor AF is chosen to be lower, so that the expansion valve 48a closes further, thereby reducing the output of the chiller 46 precisely as required. This additional intervention in the control system via the fourth controller R4 also increases the superheat Ü, which is acceptable in this case. Therefore, for the second mixed operation, i.e., with a control factor between 0 and 1, at least the integral (I) component of the fourth controller R4 is stopped, and in one variant, the proportional (P) component as well, so that the fourth controller R4 does not counteract the additional intervention via the control factor AF.

[0102] When the AF control factor reaches a value of 0, heat pump system 2 automatically switches to the third mixed operation. The expansion valve 48a is then completely closed and the heat pump is deactivated.

[0103] The characteristic curve K3 for the control factor AF also takes into account that a maximum heating branch temperature T-HK-max should not be exceeded, meaning that the control factor AF is 0 before or at the latest when the actual heating branch temperature T-HZ-I reaches the maximum heating branch temperature T-HK-max. This prevents heat transfer via the heat pump when the maximum heating branch temperature T-HK-max is reached. Instead, in this case, the third mixed operation is initiated by removing any excess heat from the heating branch 24 via appropriate cycling of the shut-off valve 32. The transition between the second and third mixed operation is therefore characterized by the fact that the heat pump's output cannot be reduced further, but excess heat is still present in the heating branch, so the heating branch 24 is now opened via the shut-off valve 32.

[0104] In cases where the chiller 46 is not active, i.e., particularly in the third mixed operation, the integral component of the fourth controller R4 is also stopped. This prevents the fourth controller R4 from moving the expansion valve 48a to its stop position (i.e., opening it fully) immediately when the chiller 46 is reactivated. This avoids unnecessary switching noises and excessive noise pollution in the surrounding area.

[0105] For the NT heating configuration NTH, the expansion valve 48a upstream of the chiller 46 is also completely closed, since the heat used for heating is taken from the coolant circuit and the heat pump is not required, thus saving energy that would otherwise be needed to operate the compressor 50 for heat transfer via the heat pump. However, in certain situations, completely closing the expansion valve 48a upstream of the chiller 46 is disadvantageous. In such cases, the control is bypassed, and a minimum opening is set instead by using a minimum value ExV-min as the lower limit for the control variable. This approach is particularly useful when starting the heat pump system 2, i.e., especially when starting the vehicle, so that the minimum opening is already set when the vehicle is switched off, ensuring it is correctly set when starting.Such an open position with an inactive heat pump system 2 and generally inactive vehicle also allows pressure equalization in the refrigeration circuit 4, so that noticeable pressure pulses and noises during starting are avoided.

[0106] Setting a minimum opening is particularly necessary for heating operation, especially for the initial mixed operation, and generally for situations and operating modes BM in which, in addition to the expansion valve 48a upstream of the chiller 46, the expansion valve 48b upstream of the air conditioning evaporator 12 is also used and open. In this situation, the two expansion valves 48a, 48b, and, in particular, the expansion valve 48c, jointly influence the superheat Ü upstream of the compressor 50. By specifying the minimum opening, excessive closing of the expansion valve 48a upstream of the chiller 46 is prevented. This has a particularly stabilizing effect on the operation of the heat pump system 2. Generally, a minimum opening is necessary to ensure that a minimum mass flow rate through the chiller 46 during the initial mixed operation, regardless of the superheat.The underlying idea is that, for example, if expansion valve 48b on the air conditioning evaporator 12 is open and the opening of expansion valve 48a is set below the minimum opening, the superheat Ü, due to the influence of expansion valve 48b, may already be lower than the target superheat Ü-S, and expansion valve 48a would close even further in this situation, thereby reducing the mass flow through the chiller 46 to zero. Without the minimum opening, heat absorption would therefore not even begin.

[0107] Fig. Figure 4a shows a control concept for the shut-off valve 32, i.e., a concept for automatically and on-demand connecting and disconnecting the heating circuit 24 from the rest of the coolant circuit 6. In principle, the shut-off valve 32 is open for cooling operation to allow coolant exchange and heat dissipation via the low-temperature cooler 44, while the shut-off valve 32 is continuously closed for heating operation to retain as much heat as possible in the heating circuit 24 and the heating loop 36. The shut-off valve 32 is also continuously closed for the first and second mixed operation modes, in which only the heating output is reduced by the heat absorption at the chiller of the heat pump. Only if there is an excessive accumulation of heat in the heating circuit 24 is the shut-off valve 32 operated intermittently, thereby activating the third mixed operation mode.

[0108] The shut-off valve 32 is controlled by specifying a cycle time TAV for the repeated opening and closing of the shut-off valve 32. It is therefore opened during a first time interval to, then closed during a second time interval tg, with the two time intervals to and tg together resulting in a period duration PD. This period duration is, for example, 3.6 s, and the two time intervals to and tg then have corresponding values ​​between 0 and 3.6 s. The specified cycle time TAV is, for example, the ratio of the first time interval to to the period duration PD. The cycle time TAV is determined via a characteristic curve K4, which links the set cycle time TAV with the temperature of the coolant in the heating circuit 24. In the special control concept of the Fig. 4a the selection is made on the basis of the characteristic curve K4 depending on the difference between the heating branch actual temperature T-HZ-I and a maximum heating branch setpoint temperature T-HZ-S-max, which in turn is determined depending on the heating branch setpoint temperature T-HZ-S via a characteristic curve K5.

[0109] The control system 22 thus controls the shut-off valve 32 depending on the heating branch setpoint temperature T-HZ-S specified by the user or the higher-level air conditioning function logic, and limits this control by means of a maximum temperature for the heating branch 24. For clarification, the figure shows Fig. Figure 4b shows an example characteristic curve K4 for determining the TAV cycle time. At low heating branch actual temperature T-HZ-I, the shut-off valve 32 is kept continuously closed by selecting a TAV cycle time of 0. This retains heat in heating branch 24 and activates the heating operation or the first or second mixed operation. However, if there is a risk that the maximum heating branch setpoint temperature T-HZ-S-max will be reached or exceeded, the shut-off valve 32 is operated intermittently by selecting a TAV cycle time between 0 and 1. Therefore, the third mixed operation is automatically activated if more heat than required is present in heating branch 24.

[0110] If the actual temperature of the heating branch T-HZ-I increases further, cooling operation is then discontinued and the shut-off valve 32 is continuously opened by setting a cycle time TAV of 1 to ensure maximum heat dissipation from the heating branch 24. The control of the shut-off valve 32 thus automatically sets the appropriate cycle time TAV and ensures a continuous transition between the operating modes BM, in particular between the operating modes BM with a heating demand, i.e., heating operation and the first and second mixed operation, and the operating modes BM with a comparatively low or negligible heating demand, i.e., the third mixed operation and cooling operation. Of particular importance for an optimal transition is appropriately configured data, i.e., the design of the characteristic curves K4 and K5, for example, by determination through a series of tests.To further prevent the simultaneous occurrence of the second and third mixed operating modes and thereby improve efficiency, the control factor AF in the second mixed operating mode and the first time interval to, i.e., the opening time in the third mixed operating mode, are coordinated. Crucially, the control factor AF is 0 as soon as the first time interval becomes greater than 0.

[0111] For the heat pump system 2, heat dissipation via the low-temperature cooler 44 remains of integral importance. Unnecessary heat loss should be avoided as much as possible. For this purpose, the coolant circuit 6 has a low-temperature cooler bypass 60 with a bypass valve 62 running parallel to the low-temperature cooler 44. The position of this bypass valve 62 defines a heat storage configuration WS. When the bypass valve 62 is open, the heat storage configuration WS is set, and no or only minimal heat dissipation occurs via the low-temperature cooler 44. Instead, the coolant is primarily routed through the low-temperature cooler bypass 60. This configuration is expediently activated only when there is a heating demand and heat is to be supplied to the heating heat exchanger 14.

[0112] In an alternative configuration not shown, a 3 / 2-way valve is used instead of the bypass valve 62, or two shut-off valves are used, such that when the NT cooler bypass 60 is open, the NT cooler 44 is shut off, thus preventing any coolant flow through it. This configuration is particularly efficient.

[0113] Under certain environmental conditions, which in Fig. As shown in Figure 5, the heat contained in the coolant circuit 6 is not released to the environment, but rather supplied to the heating branch 24. For this to happen, the shut-off valve 32 must be open accordingly. As shown in Figure 5, the heat contained in the coolant circuit 6 is not released to the environment, but is instead supplied to the heating branch 24. Fig. As can be seen in Figure 5, the heat storage configuration WS is set depending on an outside temperature Ta, the coolant actual temperature T-KM-I, and a maximum coolant temperature T-KM-max. The maximum coolant temperature T-KM-max represents an upper limit for the coolant temperature, which should not be exceeded to prevent excessive heating of the coolant through heat dissipation via the NT cooler 44. The heat storage configuration WS is activated if the coolant actual temperature T-KM-I is higher than the outside temperature Ta, meaning that heat could potentially be dissipated to the environment, and if the coolant actual temperature T-KM-I is lower than the maximum coolant temperature T-KM-max. In this case, the bypass valve 62 is automatically switched accordingly.

[0114] As in Fig. As indicated in section 5, the heat storage configuration WS is also automatically activated if the low-temperature heating configuration NTH is active. In this configuration, the heating heat exchanger 14 is supplied with heat directly from the cooling branch 33 with particularly high efficiency, without going through the heat pump. Instead, the coolant heated in the cooling branch 33 is routed past the low-temperature cooler 44 into the heating branch 24, thereby significantly improving the efficiency of the heat pump system 2.

[0115] However, activating the NT heating configuration NTH is subject to certain requirements, which are described in Fig. Figure 6 illustrates this in more detail. Accordingly, the control system 22 sets the NT heating configuration NTH if the heating branch setpoint temperature T-HZ-S is lower than the coolant actual temperature T-KM-I and higher than the heating branch actual temperature T-HZ-I. In other words, the heating demand is such that there is a heat requirement and that the coolant downstream of the chiller 46 has a higher temperature than in the heating branch 24, meaning a suitable heat potential exists and the coolant releases heat at the heating heat exchanger 14. Furthermore, the lower limit of the activation by the heating branch actual temperature T-HZ-I prevents unnecessary heat from being drawn from the heating branch 24 when the user reduces the heating demand, thus improving the efficiency of the heat pump system 2.If the low-temperature heating configuration is activated, the actual heating branch temperature may exceed the setpoint temperature. However, as long as the actual coolant temperature is sufficiently high, i.e., particularly higher than the setpoint temperature, the low-temperature heating configuration remains activated.

[0116] In cases where the NT cooler 44 is used for heat exchange with the environment, the heat exchange is expediently adapted to the specific situation. This heat exchange is primarily determined by an airflow over the NT cooler 44, i.e., a quantity of ambient air that is passed over the NT cooler 44 per unit of time by means of the fan 45. The fan 45 is an electrically driven fan 45, also called an E-fan, with an adjustable fan speed LD to regulate the airflow and thus a specific heat exchange.

[0117] For optimal heat exchange with the environment, depending on the situation, the fan speed LD in the implementation example shown here is adjusted according to the control concept of the Fig. 7 is set. Accordingly, the fan speed LD is selected using a characteristic curve K6 as a function of the coolant actual temperature T-KM-I and a minimum coolant temperature T-KM-min, and the fan 45 is controlled accordingly by the control system 22. The minimum coolant temperature T-KM-min specifies a lower limit that prevents the coolant at the NT radiator 44 from cooling down so much that it freezes. For this purpose, the minimum coolant temperature T-KM-min is determined, for example, in a manner not shown here, via a characteristic curve as a function of the outside temperature Ta, and in particular such that the minimum coolant temperature T-KM-min is at most insignificantly lower than the dew point of the ambient air in the current situation. Usually, the minimum coolant temperature T-KM-min is lower than the outside temperature Ta.

[0118] Characteristic curve K6 is configured such that as the coolant temperature T-KM-I approaches the minimum coolant temperature T-KM-min, i.e., as the difference between the two temperatures decreases, the fan speed LD is increased to prevent icing of the low-temperature radiator by warming the coolant. A further characteristic curve, K7, is configured such that a higher fan speed LD is set when heat is dissipated via the low-temperature radiator and the coolant temperature T-KM-I increases, in order to cool the correspondingly warmer coolant in the low-temperature radiator more effectively. The selection of the fan speed LD from the two characteristic curves K6 and K7 is made by a maximum selection M, i.e., the higher of the two fan speeds LD is used.In the WS heat storage configuration, fan 45 is not controlled and is completely deactivated, as heat exchange with the environment is neither required nor desired in this case. The airflow is thus controlled according to demand, resulting in particularly efficient operation. The fan speed (LD) is only increased when needed, thus also improving the acoustics of the heat pump system 2.

[0119] Overall, the behavior of the control system 22, and thus of the heat pump system 2, is primarily regulated and controlled by the user's heating demand or a higher-level air conditioning function logic via the heating branch setpoint temperature T-HZ-S, by the refrigerant actual temperature as an expression of the heat within the heat pump system 2, and by the outside temperature Ta as an expression of the weather and ambient conditions. The aforementioned control concepts are particularly suitable for the application described in Fig. The heat pump system 2 shown in 1 is, in principle, also transferable to other heat pump systems 2 as well as to extensions of this heat pump system by, for example, a coolant-cooled high-voltage storage cooling system. Reference symbol list 2 Heat pump systems 4 refrigeration circuit 6 Coolant circuit 8 air conditioner 10 passenger compartment 12 air conditioning evaporators 14 heating heat exchangers 16 air duct 22 Control system 24 Heating branch 26 Capacitor 28 additional heaters 30 Heating circuit pump 31 Flow (of the heating branch) 32 Shut-off valve 33 Cooling branch 34 Return branch 36 heating loops 38 first turn 40 second junction 42 Vehicle component 44 NT coolers 45 fans 46 Chiller 48a, 48b, 48c expansion valve 50 compressors 52 more vaporizers 54 internal heat exchanger 56 additional internal heat exchangers 58 Check valve 60 NT cooler bypass 62 Bypass valve 64 expansion tanks 66 Pump AF control factor BF limiting factor BM operating mode ExV-min minimum value K1, K2, K3, K4, K5, K6, K7 characteristic curve L air LD fan speed Maximum selection NTH NT heating configuration PD period pH maximum high pressure pN minimum low pressure R1 first controller, heating controller R2 second controller, cooling controller R3 third controller, limiting controller R4 fourth regulator, overheating regulator Ta Outside temperature TAV Takt TH maximum hot gas temperature T-HZ-I Heating branch actual temperature T-HZ-S Heating branch setpoint temperature T-HZ-S-max maximum heating branch setpoint temperature T-KM-I Coolant Actual Temperature T-KM-max maximum coolant temperature T-KM-min minimum coolant temperature T-KV-I Evaporator Actual Temperature T-KV-S evaporator setpoint temperature to first time interval tg second time interval V Comparator VD compressor speed V1 first branch V2 second branch WS heat storage configuration Overheating Over-S target overheating

Claims

[1] Method for operating a heat pump system (2) realized by a control system (22) for air conditioning a vehicle, in particular an electric or hybrid vehicle, wherein - an air conditioning requirement for a passenger compartment (10) of the vehicle is met by automatically setting one of several operating modes (BM) depending on the air conditioning requirement, - the passenger compartment (10) is cooled by means of an air conditioning evaporator (12) if the air conditioning requirement includes a cooling or dehumidifying requirement and / or heated by means of a heating heat exchanger (14) if the air conditioning requirement includes a heating requirement, - the heating heat exchanger (14) is arranged in a heating branch (24) of a coolant circuit (6) and is supplied with heat via a heat pump which has a chiller (46) and a condenser (26), both of which are connected to a refrigeration circuit (4) and wherein the chiller (46) is arranged in a cooling branch (33) of the coolant circuit (6) and the condenser (26) is in the heating branch (24), - in the event of a cooling requirement without an additional heating requirement, the heating branch (24) is opened, the chiller (46) of the heat pump is deactivated and cooling operation is thus achieved, - in the case of a heating demand without an additional cooling demand, the heating branch (24) is closed, heat is supplied to the heating heat exchanger (14) via the condenser (26) of the heat pump, via the cooling branch (33) and / or by heat absorption via the NT cooler (44), and heating operation is thus realized. - wherein, to dissipate heat from the heating branch (24), this is opened and the NT cooler (44), the condenser (26) and the heating heat exchanger (14) are operated in series, - wherein the control system (22) opens and closes the heating branch (24) by means of a shut-off valve (32), wherein to open the heating branch (24) the shut-off valve (32) is opened and to close the heating branch (24) the shut-off valve (32) is closed, - starting from heating operation, a first mixed operation is set up by activating the air conditioning evaporator (12), - where, starting from the first mixed operation, a second mixed operation is set up by reducing the heating output by regulating an expansion valve (48a) which is connected upstream of the chiller (46) in the refrigeration circuit (4), - where, starting from the second mixed operation, a third mixed operation is set up by operating the heating branch (24) in a pulsed manner, - where, starting from the third mixed operation, the cooling operation is stopped by continuously opening the heating branch (24). [2] Method according to claim 1, characterized by , that the control system (22) regulates the power of a compressor (50) and for this purpose has a first controller (R1) and a second controller (R2) by means of which a compressor speed (VD) of the compressor (50) is set, which each serves as a control variable for the two controllers (R1, R2), wherein only one of the two controllers (R1, R2) and its control variable are selected depending on the air conditioning requirement for the control of the compressor (50). [3] Method according to the preceding claim, characterized by, that in heating operation the compressor (50) is controlled by means of the first controller (R1), whereby a heating branch actual temperature (T-HZ-I) is used as a controlled variable and a heating branch setpoint temperature (T-HZ-S) as a reference variable. [4] Method according to one of the two preceding claims, characterized by , that when a cooling requirement exists, the compressor (50) is controlled by the second controller (R2) as a control variable depending on an evaporator actual temperature (T-KV-I) and an evaporator setpoint temperature (T-KV-S) is used as a reference variable. [5] Method according to any one of claims 2 to 4, characterized by , that the control system (22) has a third controller (R3) by means of which the compressor (50) is controlled by supplying the third controller (R3) with a coolant actual temperature (T-KM-I) as a controlled variable and a minimum coolant temperature (T-KM-min) as a reference variable. [6] Method according to the preceding claim, characterized by , that the control system (22) selects one control variable from the two control variables of the first and third controllers (R1, R3) by means of a comparator (V), wherein the comparator (V) performs a minimum comparison and selects the lower of the two control variables, for the control of the compressor (50). [7] Method according to any one of the preceding claims, characterized by , that the control system (22) has a superheat controller (R4) by means of which a superheat (Ü) of the refrigerant is set by controlling an expansion valve (48a) which is arranged upstream of the chiller (46) and which has an opening which serves as a control variable of the superheat controller (R4), wherein the superheat (Ü) serves as a control variable of the superheat controller (R4) and a setpoint superheat (Ü-S) as a reference variable which is determined depending on the air conditioning requirement. [8] Method according to the preceding claim, characterized by , that the climate evaporator (12) and the chiller (46) are trimmed together and that a lower target superheat (Ü-S) is set than in heating mode. [9] Method according to one of the two preceding claims, characterized by , that the control variable of the superheat controller (R4) is influenced by an additional control factor (AF) to reduce the amount of heat transferred by the heat pump. [10] Method according to one of claims 7 or 8, characterized by , that a reduction in heat absorption is achieved by modifying the target superheat (Ü-S) with an additional control allowance. [11] Method according to claim 9, characterized by , that when the control variable is reduced by the control factor (AF), an I-component of the overheating controller (R4) is stopped. [12] Method according to claim 9, characterized by, that when a limit value for the control factor (AF) is reached the expansion valve (48a) is completely closed and the third mixing operation is automatically set. [13] Method according to any one of claims 7 to 12, characterized by , that when the vehicle is switched off or if both the chiller (46) and the air conditioning evaporator (12) are active, a minimum opening is specified for the expansion valve (48a) in front of the chiller (46), which limits the actuating variable of the superheating controller (R4). [14] Method according to any one of the preceding claims, characterized by , that the third mixing operation is set up by periodically opening and closing the shut-off valve (32). [15] Method according to any one of the preceding claims, characterized by, that the control system (22) sets an NT heating configuration (NTH) by deactivating the heat pump and using waste heat from a vehicle component (42) connected to the cooling branch (33) for heating. [16] Method according to the preceding claim, characterized by , that the NT heating configuration (NTH) is only activated if a heating branch setpoint temperature (T-HZ-S) is lower than a coolant actual temperature (T-KM-I) and is not lower than a heating branch actual temperature (T-HZ-I). [17] Method according to any one of the preceding claims, characterized by , that the control system (22) sets a heat storage configuration (WS) by routing the coolant past the NT cooler (44) via an NT cooler bypass (60). [18] Method according to the preceding claim, characterized by, that the heat storage configuration (WS) is automatically set if a coolant actual temperature (T-KM-I) is greater than an outside temperature (Ta) and if the coolant actual temperature (T-KM-I) is less than a maximum coolant temperature (T-KM-max). [19] Method according to one of the two preceding claims, characterized by , that the control system (22) automatically activates the heat storage configuration (WS) if more heat is generated in the cooling branch (33) than is transferred to the refrigeration circuit (4) via the chiller (46). [20] Method according to any one of the preceding claims, characterized by , that a fan (45) is assigned to the NT cooler (44) with an adjustable fan speed (LD), and that the fan (45) is controlled by setting the fan speed (LD) depending on a coolant actual temperature (T-KM-I) and a minimum coolant temperature (T-KM-min). [21] Method according to the preceding claim, characterized by , that the fan speed (LD) is determined by means of a characteristic curve (K6) which is designed such that when a coolant actual temperature (T-KM-I) approaches a minimum coolant temperature (T-KM-min), the fan speed (LD) is increased. [22] Method according to one of the two preceding claims, characterized by , that the fan speed (LD) is determined by means of a characteristic curve (K7) which is designed such that a higher fan speed (LD) is set when heat is dissipated via the NT cooler (44) and when the actual coolant temperature (T-KM-I) increases. [23] Method according to the two preceding claims, characterized by, that the fan speed (LD) is determined by determining a fan speed (LD) using each of the two characteristic curves (K6, K7) and selecting and setting the larger of these two fan speeds (LD) using a maximum selection (M). [24] Method according to any one of the preceding claims, characterized by , that icing of the NT cooler (44) is avoided by cyclically opening the heating branch (24) and directing heat from the heating branch (24) to the NT cooler (44). [25] Control system (22) which is configured to implement a method according to any one of claims 1 to 24.

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