Method for controlling a refrigerant circuit, which is coupled to a coolant circuit, for a vehicle

Abstract

Refrigerant circuits, which are coupled to a coolant circuit, for vehicles are known. The refrigerant circuit (10) has a first refrigerant branch (12) with a compressor (16), a condenser (18) with a fan (20), a dryer (22), a thermostatic expansion valve (28) and an evaporator (30), which serves to remove heat from an interior (31) of the vehicle, and a second refrigerant branch (14), which is arranged fluidically parallel to the thermostatic expansion valve (28) and the evaporator (30) and in which an expansion valve (34) and a cooler (36) are arranged, the cooler (36) being in heat exchange with a coolant circuit (38) in which, in addition to the cooler (36), at least one battery cooler (40) for the battery (42) of the vehicle and a coolant pump (44) are arranged. For such a combined coolant and refrigerant circuit, the invention provides a control method in which a cooling power of the cooler (36) is controlled via at least one first control circuit and a cooling power of the evaporator (30) is controlled via at least one second control circuit, wherein a prioritization is activated when the compressor (16) reaches a defined maximum speed or a defined maximum-permissible electrical power, or the pressure upstream of the compressor (16) or downstream of the cooler (36) falls below a defined minimum-permissible pressure, or the pressure downstream of the compressor (16) exceeds a defined maximum-permissible pressure.

Description

[0001] PP34420WO / kop August 28, 2025 AVL List GmbH

[0002] Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle

[0003] The invention relates to a method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle, the refrigerant circuit comprising a first refrigerant branch and a second refrigerant branch, wherein at least a compressor, a condenser, a dryer, a thermostatic expansion valve and an evaporator, which serves to remove heat from an interior of the vehicle, are arranged in the first refrigerant branch, and wherein an expansion valve and a cooler are arranged in the second refrigerant branch, which is arranged in flow-related parallel to the thermostatic expansion valve and the evaporator, the cooler being in heat exchange with a coolant circuit in which, in addition to the cooler, at least a battery cooler for cooling a battery of the vehicle and a coolant pump are arranged.

[0004] Such combined refrigeration and cooling circuits, also known as thermal management systems, are used particularly in electric or hybrid vehicles. In these vehicles, in addition to climate control, it is necessary to regulate the battery temperature to a constant level between approximately 15°C and 40°C. This increases the battery's lifespan and allows it to utilize its full capacity, thus enabling greater distances to be traveled on a single charge. If the temperature is too low, the coolant, which can also consist of dielectric oil, can be warmed by a high-voltage auxiliary heater. If the temperature is too high, it is cooled by a radiator integrated into both the coolant and refrigerant circuits.The refrigerant in the refrigerant circuit flows through the coolant in the coolant circuit. The entire system is controlled by a system using various control elements, such as valves and pumps, and based on measured sensor values. Specifically, the refrigerant circuit requires sensors to measure the compressor outlet pressure, the radiator outlet pressure, and the temperature downstream of the radiator. The coolant circuit also requires a temperature sensor at the inlet to the battery cooler. PP34420WO / kop August 28, 2025 AVL List GmbH.

[0005] Several control strategies have become known, each attempting to provide sufficient cabin cooling as well as to ensure the target temperature of the battery.

[0006] German patent DE 10 2019 107 192 A1 discloses a control system for a thermal management system of an electric or hybrid vehicle, as well as a method for operating such a thermal management system. In this system, when battery cooling and air conditioning of the vehicle interior are required simultaneously, a compressor of the refrigeration circuit is controlled by a control variable that represents a target air temperature at the air conditioning evaporator, and an expansion valve is controlled based on this control variable for the compressor. The cooling of the high-voltage battery is thus additionally dependent on the air temperature, while ensuring optimal interior cooling. Accordingly, interior cooling is always prioritized in this control system, unless the battery reaches a permissible maximum temperature.

[0007] A disadvantage of such a control strategy, however, is that one of the control loops is always prioritized over the entire period, making the control system very complex. Furthermore, under certain conditions, the expansion valve controller and the compressor controller may attempt to achieve the same goal, namely controlling the evaporator air temperature, which can lead to instability problems. Additionally, no control mechanism is provided to optimize the efficiency of the cooler.

[0008] The challenge, therefore, is to provide a method for controlling a refrigerant circuit coupled to a coolant circuit in a vehicle, one that prioritizes only during limited time periods to minimize control overhead. Furthermore, instabilities in the control loops should be avoided, and the best possible cooling performance should be ensured.

[0009] This problem is solved by a method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle, comprising the features of main claim 1. PP34420WO / kop August 28, 2025 AVL List GmbH

[0010] The method according to the invention serves to control a combined refrigerant and coolant circuit for a vehicle, wherein the refrigerant circuit has a first refrigerant branch and a second refrigerant branch, wherein at least a compressor, a condenser with a fan, a dryer, a thermostatic expansion valve and an evaporator, which serves to remove heat from an interior of the vehicle, are arranged in the first refrigerant branch and in the second refrigerant branch, which is arranged in flow-related parallel to the thermostatic expansion valve and the evaporator, an expansion valve and a cooler are arranged, wherein the cooler is in heat exchange with the coolant circuit, in which, in addition to the cooler, at least a battery cooler for cooling a battery of the vehicle and a coolant pump are arranged.In addition, the refrigerant circuit typically includes a solenoid valve, designed as a switching valve, located upstream of the thermal expansion valve. The cooling circuit is usually a low-temperature circuit, in which at least one temperature sensor is installed to measure the inlet temperature of the coolant to the battery cooler. Further sensors are located in the refrigerant circuit to measure the pressure and temperature downstream of the cooler, as well as the pressure at the compressor or condenser outlet. Of course, additional sensors can be provided. The cooling circuit, in particular, can also contain a variety of other components.

[0011] According to the invention, the cooling capacity of the cooler is controlled via at least a first control loop, and the cooling capacity of the evaporator via at least a second control loop. This occurs largely independently of each other, without prioritization. Prioritization of one of the cooling capacities is only activated when the compressor reaches a defined maximum speed or a defined maximum permissible electrical power, or when the pressure before the compressor or after the cooler falls below a defined minimum permissible pressure, or when the pressure after the compressor exceeds a defined maximum permissible pressure.The aforementioned conditions ensure that prioritization only occurs when the refrigerant circuit is overloaded, i.e., when insufficient energy can be provided to operate both the cabin air conditioning and the battery cooling according to the specified PP34420WO / kop 28 August 2025 AVL List GmbH.

[0012] To be able to comply with regulations. This simplifies the necessary regulations and prevents two controllers from working against each other depending on the same control value. This provides a reliable control strategy that ensures adequate cooling of both the battery and the interior. The defined maximum and minimum permissible values ​​mentioned are threshold values ​​that either correspond to, or are close to, the maximum or minimum permissible values ​​according to the design of the components.

[0013] Preferably, prioritization is performed in the first control loop, depending on at least one first characteristic map, where the currently measured maximum battery cell temperature serves as the input value, and at least one second characteristic map, where the difference between the current evaporator air outlet temperature and the target evaporator air outlet temperature serves as the input value. This allows for the use of various vehicle load conditions and priority strategies for control via appropriate calibrations. For example, the characteristic map dependent on the difference in evaporator air outlet temperatures can be calibrated to result in a smaller opening of the expansion valve, thus making more cooling capacity available for the interior cooling system.The characteristic map, which depends on the maximum cell temperature of the battery, can be calibrated so that the expansion valve opens further as the battery cell temperature increases, thus providing more cooling capacity for the battery. Accordingly, different control strategies can be used depending on whether the system is overloaded.

[0014] In a further embodiment, prioritization takes place in the first control loop, in which the position of the expansion valve upstream of the cooler is regulated, by offsetting a controlled superheat temperature. This offset only occurs when an overload of the system is anticipated. The opening of the expansion valve is corrected by a corresponding offset to prevent system overload and, on the other hand, to ensure sufficient cooling, particularly of the battery. PP34420WO / kop August 28, 2025 AVL List GmbH

[0015] In a further advantageous embodiment, the first control loop comprises an outer control loop, in which the offset of the controlled superheat temperature is carried out and which includes a first PI controller, and an inner control loop with a second PI controller, wherein the first PI controller regulates a target superheat temperature as a function of a difference between the target inlet temperature of the coolant in the battery cooler and the actual inlet temperature of the coolant in the battery cooler, which is limited by a minimum permissible superheat temperature at which the refrigerant is in a completely gaseous state at the cooler outlet, and wherein the second PI controller regulates the opening of the expansion valve upstream of the cooler as a function of the difference between a target superheat temperature at the cooler outlet and the actual superheat temperature at the cooler outlet.This cascaded configuration of the two PI controllers ensures that the target battery inlet temperature is reached in the outer control loop, and that the target superheat temperature is reached at the cooler outlet in the inner control loop. The outer loop incorporates the superheat offset, which prioritizes one of the cooling capacities if the system's capacity limit is reached.

[0016] In a further embodiment of the method, the controlled superheat temperature is offset downstream of the first PI controller in the outer control loop. When prioritization is activated, the target superheat temperature determined in the outer control loop is corrected to the target superheat temperature by summing it in a summing element using the determined superheat temperature offset. This target superheat temperature then serves as the input to the inner control loop. Thus, at a high battery cooler inlet temperature, the expansion valve is continuously opened by the PI controller of the inner control loop until the minimum permissible superheat temperature is reached, while the outer PI controller remains inactive, since in this state the target superheat temperature is always limited by its minimum permissible superheat temperature.Only when the battery cooler inlet temperature approaches its target value will the target superheat temperature rise, and thus the expansion valve may be further closed via the second PI controller. Due to the superheat offset, the increase in the superheat temperature is shifted by the summing element, so that in this PP34420WO / kop 28 August 2025 AVL List GmbH.

[0017] in case the expansion valve remains in its fully open position for a longer period of time.

[0018] Preferably, the offset of the controlled superheat temperature is regulated as a function of a difference between the maximum permissible compressor speed and the required compressor speed, a difference between the maximum permissible power consumption of the compressor and the actual power consumption of the compressor, a difference between the maximum permissible compressor outlet pressure and the actual compressor outlet pressure, or a difference between the actual cooler outlet pressure and the minimum permissible cooler outlet pressure, or a difference between the actual compressor inlet pressure and the minimum permissible compressor inlet pressure. This means that the magnitude of this superheat temperature offset always depends on these differences and thus on the distance to the corresponding critical data, thereby achieving a smooth transition during control.

[0019] This is advantageously achieved by determining a factor between 0 and 1 in a calibratable control element with hysteresis, depending on the magnitude of the differences to each of the determined differences. The maximum determined factor is then used as a first correction factor for calculating the offset of the superheating temperature. Such a control element with hysteresis also assigns factors between 0 and 1, so that this factor depends on the deviation of the actual value from the defined threshold value. Thus, an increased offset always occurs depending on the most critical value and in a magnitude proportional to the criticality of that value.

[0020] A pre-superheat temperature offset is preferably determined using the second characteristic map. This offset is corrected by a second correction factor between 0 and 1, which is determined using the first characteristic map, and by multiplication of the first correction factor. It follows that the magnitude of the superheat temperature offset initially depends on the difference between the current evaporator air temperature and the target evaporator temperature, but is also influenced by the corresponding other conditions, in particular the

[0021] The battery cell temperature is corrected so that at high battery cell temperatures, this offset, and thus the shift in the opening time, is delayed further than at lower battery cell temperatures. When one of the aforementioned parameters approaches or reaches its limit, the factor is ramped up between 0 and 1, so that the prioritization of cooling, reflected in the overheating compensation, is smoothly activated and amplified with the ramped value.

[0022] It is particularly advantageous to have several primary and secondary characteristic maps stored, which are used depending on the vehicle's load condition. For example, it is possible to store a different correction for a specific vehicle charge level, where, in particular, the cooling capacity for the battery is given additional priority. Further vehicle load conditions are also conceivable, for which additional characteristic maps can be stored.

[0023] Furthermore, the control values ​​of the first PI controller of the outer control loop and the second PI controller of the inner control loop are preferably limited by a minimum and maximum limiting element. This prevents the expansion valve from being controlled to positions that cannot be reached, as well as from falling below the minimum permissible superheat temperature, which could cause the refrigerant to reach the compressor in a partially liquid state.

[0024] In a further preferred embodiment, slope limitation is implemented in the outer control loop after the summing element via a first slope limitation control element, and slope limitation is implemented in the inner control loop after the minimum-maximum limiting element via a second slope limitation control element. This reliably prevents overriding due to sudden changes.

[0025] Preferably, in the second control loop, the compressor speed is regulated via a third PI controller based on the difference between the target temperature of the evaporator outlet air and the actual temperature of the evaporator outlet air, in order to achieve the target evaporator air temperature. This ensures that the higher the actual temperature of the evaporator air is compared to the target value, the higher the compressor speed. Consequently, the required evaporator temperature is reached quickly. PP34420WO / kop August 28, 2025 AVL List GmbH

[0026] To ensure that the refrigerant system is not overloaded by the pressure generated by the compressor, the compressor speed determined by the third PI controller is reduced if the pressure at the compressor outlet exceeds a defined threshold or the pressure at the cooler outlet falls below a defined limit.

[0027] This is achieved by multiplying the compressor speed determined by the PI controller by a factor between 0 and 1. This factor is the smaller of the two factors derived from a stored third and fourth characteristic curve, which depend on the pressure at the compressor outlet and the pressure at the cooler outlet, respectively. The reduction is therefore always based on the more critical value. This can be determined according to the stored characteristic curves.

[0028] Preferably, a third control loop regulates the speed of the condenser fan as a function of the compressor outlet pressure and the vehicle speed. This ensures that the most complete condensation possible is achieved, even with large quantities of refrigerant being circulated. The vehicle speed-dependent control also takes into account the airflow generated by the vehicle speed, which is available without fan rotation, thus reliably regulating the available airflow and, consequently, the condenser outlet temperature.

[0029] The control is preferably achieved via a fifth characteristic map, which determines a target airflow based on the compressor's outlet pressure. A target airflow determined via a sixth characteristic map, based on vehicle speed, is then subtracted from this target airflow to determine the fan's delivery airflow. A seventh characteristic map then calculates the fan speed from this target airflow. This allows the cooling fan control to be calibrated according to customer requirements. Furthermore, a very simple, independent control system is created.

[0030] Preferably, the determined speeds of the fan and the compressor are limited by a minimum-maximum limiting element and by a PP34420WO / kop 28 August 2025 AVL List GmbH

[0031] The slope limiting control element is restricted. This ensures that the compressor and fan motors operate within their design limits, thus increasing their service life.

[0032] This creates a method for controlling a refrigerant circuit coupled to a coolant circuit in a vehicle, enabling largely independent control of battery cooling and evaporator cooling, with priority only given to the latter in critical situations. Conflicts within the control loops are eliminated. Furthermore, the existing control systems are calibratable and thus adaptable to specific requirements. Overloading of all components is reliably prevented, while still ensuring all cooling requirements are met.

[0033] The control method according to the invention is described below using a non-restrictive, exemplary combined refrigerant and coolant circuit for a vehicle. In this example,

[0034] Figure 1 shows a schematic representation of a combined refrigerant and coolant circuit for a vehicle;

[0035] Figure 2 shows a first control loop according to the invention for controlling an expansion valve of the combined refrigerant and coolant circuit from Figure 1;

[0036] Figure 3 shows a second control loop according to the invention for controlling a compressor of the combined refrigerant and coolant circuit from Figure 1; and

[0037] Figure 4 shows a third control loop according to the invention for controlling a fan of the combined refrigerant and coolant circuit from Figure 1.

[0038] The combined refrigerant and coolant circuit shown in Figure 1 consists of a refrigerant circuit 10, which has a first refrigerant branch 12 and a second refrigerant branch 14. A compressor 16 is arranged in the refrigerant circuit 10, in which gaseous refrigerant is compressed and heated. From here, the refrigerant flows into a condenser 18, in which it is completely converted into a liquid state. For this purpose, a fan 20 is used, which generates an airflow that, in addition to the airflow generated at the condenser by the vehicle's speed, flows along the condenser 18 and cools the refrigerant in the condenser 18. The refrigerant then flows to a dryer 22, which is usually designed as a filter dryer, in which moisture and solid particles are removed from the refrigerant.

[0039] The liquid refrigerant then flows to a branch 24, where it splits into the first refrigerant branch 12 and the second refrigerant branch 14. In the first refrigerant branch 12, the refrigerant reaches an electromagnetic switching valve 26, which can be opened or closed. From here, the refrigerant flows to a thermostatic expansion valve 28, which is typically controlled based on a temperature and pressure measured at the outlet of a subsequent evaporator 30. The desired superheat at the evaporator 30 is preselected. At the evaporator 30, heat is extracted from the ambient air, causing the refrigerant to transition into a vaporous state and cool the interior 31 of the vehicle.The refrigerant then flows back to the compressor 16 via a second branch 32, where it rejoins the refrigerant of the second refrigerant branch 14.

[0040] In the second refrigerant branch 14, which is arranged parallel to the first refrigerant branch 12 and thus to the evaporator 30, the thermostatic expansion valve 28, and the electromagnetic switching valve 26, there is a controllable expansion valve 34. Depending on the position of its control element, this valve regulates the flow of refrigerant, which is typically atomized in the expansion valve, to a cooler 36. In this cooler 36, heat is extracted from a coolant in a coolant circuit 38 and transferred to the refrigerant, causing it to evaporate. The refrigerant then flows to the second branch 32 and from there, together with the refrigerant from the first refrigerant branch 12, back to the compressor 16.

[0041] The cooled coolant from the radiator 36 then flows in the coolant circuit 38 to a battery cooler 40 of a battery 42, which is cooled by the coolant. The coolant is circulated by a coolant pump 44 located downstream of the battery cooler 40. These coolant circuits 38 can be configured differently and incorporate various additional components. PP34420WO / kop August 28, 2025 AVL List GmbH

[0042] components and branches, a further description of which is omitted here, as these are not essential for the present invention.

[0043] To control the refrigerant circuit 10 and the coolant circuit 38, a temperature sensor 45 for measuring the temperature of the coolant at the inlet of the battery cooler 40 and one or more battery cell temperature sensors 46 for measuring the battery cell temperature are arranged in the coolant circuit 38.

[0044] In the refrigerant circuit 10, a pressure sensor 48 and another temperature sensor 50 are arranged downstream of the cooler 36. An additional pressure sensor 52 is located at the outlet of the compressor 16, where a current sensor 54 is also installed. The air temperature immediately behind the evaporator 30 is measured by another temperature sensor 56.

[0045] In the present embodiment, the refrigerant circuit 10 is controlled by three separate control loops 58, 60, 62, whereby the first control loop 58 regulates the cooling capacity at the cooler 36 by controlling the expansion valve 34, the second control loop 60 regulates the cooling capacity of the evaporator 30 by controlling the speed of the compressor 16, and the third control loop 62 regulates the fan 20 at the condenser 18.

[0046] The first control loop 58 is shown in Figure 2. The input values ​​of an outer control loop 64 of this first control loop 58 are a target temperature at the inlet of the battery cooler 40 ("Target battery inlet temperature") and a temperature measured by the temperature sensor 45 ("Actual battery inlet temperature"). The difference between these two temperature values ​​is fed to a first PI controller 66, which derives a preliminary target superheat temperature at the cooler 36 from this difference. The result is fed to a minimum / maximum limiter 68, which ensures that a permissible minimum superheat temperature is not undershot and a maximum permissible superheat temperature is not exceeded. The resulting superheat temperature is fed to a summing element 70, at which a controlled superheat temperature offset is added as a second input value. PP34420WO / kop 28.August 2025 AVL List GmbH.

[0047] However, according to the invention, this superheating temperature offset only occurs if the compressor 16 reaches a defined maximum speed or a defined maximum permissible electrical power, or if the pressure before the compressor 16 or after the cooler 36 falls below a defined minimum permissible pressure, or if the pressure after the compressor 16 exceeds a defined maximum permissible pressure, and leads to a prioritization of the cooling power at the cooler 36, as described below.

[0048] To achieve this, an offset controller loop 71 is used, in which the defined maximum speed of the compressor 16 ("Compressor max speed") is compared with the currently controlled compressor speed ("Compressor speed request") by calculating the difference in a first differential element 72. This difference is fed to a calibration factor map 73 with hysteresis, which determines a factor between 0 and 1 depending on the magnitude of the difference. The value 0 applies when the system is far from a limit value, i.e., the difference is very large, and the value 1 applies when one of the system limit values ​​is reached, i.e., the difference approaches 0. Differences between the ramp trigger value and the difference 0 result in values ​​between 0 and 1, corresponding to the stored ramp and hysteresis.

[0049] Similarly, a factor between 0 and 1 is determined via a second differential element 74 with subsequent calibration map 75 with hysteresis to a difference between the maximum permissible electrical power consumption of the compressor 16 ("Compressor max allowed electrical power") and the actual electrical power consumption measured via the current sensor 54 ("Compressor actual electrical power"), and via a third differential element 76 with subsequent calibration map 77 with hysteresis a factor between 0 and 1 is determined to a difference between the maximum permissible pressure at the outlet of the compressor 16 ("Compressor outlet pressure limit") and the actual compressor outlet pressure measured via the pressure sensor 52 ("Actual compressor outlet pressure").

[0050] A fourth differential element 78 with a subsequent calibration map 79 with hysteresis determines a factor between 0 and 1 for the difference between the actual chiller outlet pressure measured by the pressure sensor 48 downstream of the chiller 36 ("Actual chiller outlet pressure") and the minimum permissible chiller outlet pressure ("Chiller PP34420WO / kop 28 August 2025 AVL List GmbH outlet pressure limit"), whereby the factor is 1 when the minimum permissible pressure is reached. Instead of or in addition to the fourth differential element 78, a differential element could also be used in which the actual compressor inlet pressure is compared with a minimum permissible compressor inlet pressure. The four factors are fed to a maximum element 81, so that the maximum of the four determined factors is passed on to a multiplication element 82.

[0051] Furthermore, the offset controller loop 71 has a first calibratable characteristic map 83, for which the measured value of the temperature sensor 46, which measures the maximum battery cell temperature, serves as the input value. Depending on this temperature, a factor between 0 and 1 is again determined via the characteristic map 83, where the value 1 applies if the maximum battery cell temperature is significantly below a permissible maximum battery cell temperature and the value 0 applies if the maximum battery cell temperature reaches the maximum permissible battery cell temperature. In the present embodiment, two different first characteristic maps 83 are stored, which depend on the vehicle charging state, so that, for example, a different characteristic map can be selected in the case of battery charging. The determined factor is also fed to the multiplication element 82.

[0052] A pre-superheat temperature offset is determined via a second characteristic map 85 based on the difference between the currently measured actual evaporator air outlet temperature and the target evaporator air outlet temperature, which are fed to a differential element 84. Here, too, several second characteristic maps 85 can be used, which depend on the vehicle charging state, so that this pre-superheat temperature offset also assumes a different value when, for example, the battery 42 is being charged. The determined pre-superheat temperature offset (raw superheat offset) is also fed to the multiplication element 82 as a third factor.

[0053] By multiplying the raw superheat offset by the largest of the first four factors and the factor for

[0054] Battery cell temperature is measured in the multiplication element 82 PP34420WO / kop August 28, 2025 AVL List GmbH

[0055] A superheat temperature offset (“superheat offset for prioritization” or “superheat offset for cooling prioritization”) is calculated and fed to the summing element 70 of the outer control loop 64. It becomes clear that this superheat temperature offset only actually occurs if the factor for the battery cell temperature and the maximum factor for the compressor pressures, compressor speeds and powers, and the cooler outlet pressure are not 0. All of these parameters indicate an overload of the system, meaning that it is no longer possible to supply the evaporator 30 and the cooler 36 with sufficient refrigerant to generate the required interior temperature at the evaporator 30 and simultaneously cool the battery 42 adequately.

[0056] In the following, in the outer control loop 64, a target superheat temperature ("Final target superheat") is determined from the sum of the superheat temperature offset ("Superheat offset for prioritization" or "Superheat offset for cooling prioritization") and the target superheat temperature controlled by the first PI controller 66, by feeding the sum to a slope control element 86.

[0057] The calculated target superheat temperature is compared with the current actual superheat temperature in a comparator 87 and fed to a second PI controller 88 of an inner control loop 90, via which an opening position of the expansion valve 34 ("Target chiller EXV position") is controlled, whereby a minimum-maximum limiting element 89 and a slope limiting control element 92 are arranged behind the PI controller 88, by which an overload of the actuator of the expansion valve 34 and control of positions of the expansion valve 34 that cannot be reached are avoided.

[0058] The control is thus implemented such that, as long as none of the four conditions are met and the pre-superheat temperature offset is greater than 0, normal control of the expansion valve 34 takes place depending on the coolant temperature at the inlet of the battery cooler and the resulting target superheat temperature. During the transient phase with a hot battery 42 and hot coolant, the target superheat temperature of the first PI controller 66 of the outer control loop 64 is limited by the minimum permissible superheat temperature due to the high PP34420WO / kop 28 August 2025 AVL List GmbH

[0059] The battery inlet temperature is limited compared to its target value. The second PI controller 88 of the inner control loop 90 then opens the expansion valve 34 until the minimum permissible superheat temperature is reached. During the settling phase, the PI controller 66 of the outer control loop 64 is inactive, as the target superheat temperature is always limited by its minimum permissible superheat temperature. In the steady state of the system, or as the battery inlet temperature approaches the target value, the target superheat temperature of the PI controller 66 of the outer control loop 64 will increase, which leads to the closure of the expansion valve 34 by the second PI controller 88 of the inner control loop 90. In this phase, both PI controllers 66 and 88 are active, so that the target battery inlet temperature can be reached and maintained.

[0060] As soon as one of the four conditions is met and the maximum battery cell temperature is normal, so that both factors are greater than 0 and the pre-superheat temperature offset is greater than 0, the superheat temperature offset is activated. A typical strategy would be, for example, that during driving after starting, cooling the vehicle interior takes priority if the maximum battery cell temperature is not yet close to its critical temperature. As the maximum battery cell temperature rises, the priority is then seamlessly shifted to battery cooling. This can be achieved by calibrating the second characteristic map 85, which depends on the evaporator air outlet temperature difference, with a high superheat temperature offset, so that it leads to a smaller opening of the expansion valve 34 and thus more cooling capacity is available for interior cooling.The first characteristic map 83, which depends on the battery cell temperature, can be calibrated so that the higher the maximum battery cell temperature, the lower the factor value is selected. This reduces the overheating offset, allowing the expansion valve 34 to open further and thus providing more cooling capacity for the battery. The expansion valve 34 will therefore only close due to the overheating temperature offset if the battery cell temperature is not too high, thus prioritizing interior cooling. During fast charging, however, the prioritization strategy could be different, with battery cooling being given higher priority by other first and second characteristic maps 83 and 85. These different first and second characteristic maps 83 and 85 can be selected via corresponding logic switches 91 according to the vehicle's operating state.By calibrating these characteristic maps 83, 85, it is possible to decide which part is prioritized with how much more cooling power.

[0061] The second control loop 60 is shown in Figure 3 and serves to control the speed of the compressor 16 ("Target compressor speed") as a function of the difference between a target temperature of the outlet air at the evaporator 30 ("Target evaporator air temperature") and the actual temperature of the outlet air at the evaporator 30 ("Actual evaporator air temperature"), which are fed as input values ​​to a comparator 94. The result is fed to a third PI controller 96, which uses this to control a raw speed of the compressor 16. This value is fed to a multiplier 98, where it is corrected by a factor between 0 and 1.This correction occurs when the pressure at the compressor outlet 16 ("Actual compressor outlet pressure"), measured by pressure sensor 52, exceeds a defined threshold, or when the pressure at the chiller outlet 36 ("Actual chiller outlet pressure"), measured by pressure sensor 48, falls below a defined limit. The two aforementioned values ​​from sensors 48 and 52 are first fed to a low-pass filter element 100 and 101, respectively, and then to a third calibratable characteristic map 102 and a fourth calibratable characteristic map 103, respectively, which determine the corresponding factor between 0 and 1. These two determined factors are fed to a minimum control element 104, so that the smaller of the two values ​​is fed to the multiplication element 98.The result of this multiplication is fed to a minimum-maximum control element 105 and a slope limiting element 106 to ensure that the compressor 16 drive is controlled within its design limits. The output value thus becomes the target compressor speed for the compressor 16 to achieve the target air temperature at the evaporator 30. Under normal operating conditions, both factors have a value of 1, meaning they have no influence on the compressor speed. If the compressor outlet pressure is too high, the value of the corresponding factor is reduced, resulting in a lower compressor speed. If the actual cooler outlet pressure of the cooler 36 is low, the value of the associated factor is also reduced, again resulting in a reduced compressor speed requirement.

[0062] Figure 4 shows the third control loop 62, which serves to control the speed of the fan 20 ("Target fan speed") at the condenser 18. This control is based on the actual compressor outlet pressure of the compressor 16 and the vehicle speed. For this purpose, a target airflow is determined using a fifth characteristic map 107 as a function of the compressor 16 outlet pressure, which is measured by the pressure sensor 52. Furthermore, a sixth characteristic map 108 determines an airflow resulting from the vehicle speed ("Equivalent air flow rate"). In a differential element 109, these determined airflows are subtracted from each other, resulting in a target airflow rate ("Requested air flow rate") that must be supplied by the fan 20.This is converted into a speed of the fan 20 ("target fan speed") via a seventh characteristic map 110 as well as a minimum-maximum limiting element 111 and a slope limiting element 112, whereby damage to the fan 20 is avoided by the limiting elements 111 , 112.

[0063] It follows that the requested air mass flow correlates with the pressure at the outlet of compressor 16 to ensure that a sufficient amount of heat can be released to the environment for condensation.

[0064] The present control system independently controls the compressor according to the required air temperature at the evaporator and the expansion valve according to the battery coolant temperature until an overload of the cooling system is imminent. Depending on the characteristic curves used in the control loop to calculate the superheat temperature offset, the cooling capacities are then prioritized. As long as no excessively high battery cell temperature is expected, priority can be given to the interior climate control by further closing the expansion valve based on the superheat temperature offset. In the event of a potentially excessive battery cell temperature, this offset is eliminated, and the expansion valve remains fully open to reach the minimum permissible superheat temperature. PP34420WO / kop August 28, 2025 AVL List GmbH

[0065] It should be noted again that the refrigerant circuit can be implemented in various ways. It is also possible to use additional sensors in the refrigerant circuit, meaning that the combined cooling and refrigerant circuit shown represents only a minimum requirement. Accordingly, additional control elements can also be used. The effects of the control loops described above always refer to a state in which the solenoid valve is open, thus indicating a cooling demand at the evaporator. Furthermore, it should be noted that the control loops may also include a known anti-wind-up strategy (not shown here) to prevent the additional control error resulting from an integral component in a controller from being integrated, which could lead to significant overshoot and ultimately instability.

Claims

PP34420WO / kop 28. August 2025 AVL List GmbH A N S P R Ü C H E 1. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle, comprising a refrigerant circuit (10) with a first refrigerant branch (12) and a second refrigerant branch (13), wherein at least a compressor (16), a condenser (18) with a fan (20), a dryer (22), a thermostatic expansion valve (28), and an evaporator (30) for removing heat from an interior (31) of the vehicle are arranged in the first refrigerant branch (12), and an expansion valve (34) and a radiator (36) are arranged in the second refrigerant branch (14), which is arranged flow-wise parallel to the thermostatic expansion valve (28) and the evaporator (30), wherein the radiator (36) is in heat exchange with a coolant circuit (38) in which, in addition to the radiator (36), at least a battery cooler (40) for cooling a battery (42) of the vehicle and a coolant pump (44) are arranged. are,characterized in that a cooling capacity of the cooler (36) is controlled via at least a first control loop (58) and a cooling capacity of the evaporator (30) via at least a second control loop (60), wherein a prioritization is activated when the compressor (16) reaches a defined maximum speed or a defined maximum permissible electrical power, or the pressure before the compressor (16) or after the cooler (36) falls below a defined minimum permissible pressure, or the pressure after the compressor (16) exceeds a defined maximum permissible pressure.

2. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 1, characterized in that the prioritization depends on at least a first characteristic map (83) in which the currently measured maximum battery cell temperature serves as the input value, and at least a second characteristic map (85) in which the input value is a difference between the current evaporator air outlet temperature and the PP34420WO / kop August 28, 2025 AVL List GmbH The target evaporator air outlet temperature is used in the first control loop (58).

3. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 1 or 2, characterized in that the prioritization takes place in the first control loop (58) in which a position of the expansion valve (34) upstream of the radiator (36) is controlled by offsetting a controlled superheat temperature.

4. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to one of claims 1 to 3, characterized in that the first control loop (58) has an outer control loop (64) in which the offset of the controlled superheat temperature is carried out and which has a first PI controller (66), and an inner control loop (90) with a second PI controller (88), wherein a target superheat temperature is controlled via the first PI controller (66) as a function of a difference between the target inlet temperature of the coolant in the battery cooler (40) and the actual inlet temperature of the coolant in the battery cooler (40), which is limited by a minimum permissible superheat temperature.in which the refrigerant is in a completely gaseous state at the outlet of the cooler (36) and the opening of the expansion valve (34) in front of the cooler (36) is controlled via the second PI controller (88) depending on the difference between a target superheat temperature at the outlet of the cooler (36) and the actual superheat temperature at the outlet of the cooler (36).

5. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 4, characterized in that PP34420WO / kop August 28, 2025 AVL List GmbH behind the first PI controller (66) in the outer control loop (64) the offset of the controlled superheat temperature is carried out, via which the setpoint superheat temperature determined in the outer control loop (64) is corrected to the target superheat temperature when prioritization is activated by summation in a summation element (70) with the determined offset of the superheat temperature, which serves as the input of the inner control loop (90).

6. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 5, characterized in that the offset of the controlled superheat temperature is controlled as a function of a difference between the maximum permissible compressor speed and the required compressor speed, a difference between the maximum permissible power input of the compressor (16) and the actual power input of the compressor (16), a difference between the maximum permissible compressor outlet pressure and the actual compressor outlet pressure, and a difference between the actual cooler outlet pressure and the minimum permissible cooler outlet pressure or the actual compressor inlet pressure and the minimum permissible compressor inlet pressure.

7. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 6, characterized in that, depending on the magnitude of the differences to each of the determined differences in each calibratable control element (73, 75, 77, 79) with hysteresis, a factor between 0 and 1 is determined, wherein the maximum determined factor is used as a first correction factor for calculating the offset of the superheat temperature.

8. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to one of claims 2 to 7, PP34420WO / kop 28 August 2025 AVL List GmbH characterized in that a pre-superheating temperature offset is determined via the second characteristic map (85), which is corrected via a second correction factor between 0 and 1, which is determined via the first characteristic map (83), and via the first correction factor by multiplication.

9. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to one of claims 2 to 8, characterized in that several first characteristic maps (83) and several second characteristic maps (85) are stored, which are used depending on a load condition of the vehicle.

10. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to one of claims 4 to 9, characterized in that the control values ​​of the first PI controller (66) of the outer control loop (64) and of the second PI controller (88) of the inner control loop (90) are each limited by a minimum and maximum limiting element (68, 89).

11. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claims 5 and 10, characterized in that in the outer control loop (64) after the summing element (70) a slope limitation is carried out via a first slope limitation control element (86) and in the inner control loop (90) after the minimum-maximum limiting element (89) a slope limitation is carried out via a second slope limitation control element (92).

12. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to one of claims 1 to 11 , PP34420WO / kop 28 August 2025 AVL List GmbH characterized in that in the second control loop (60) a speed of the compressor (16) is controlled as a function of a difference between the set temperature of the outlet air at the evaporator (30) and the actual temperature of the outlet air at the evaporator (30) via a third PI controller (96).

13. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 12, characterized in that the speed of the compressor (16) determined via the third PI controller (96) is reduced if the pressure at the outlet of the compressor (16) exceeds a defined threshold value or the pressure at the outlet of the cooler (36) falls below a defined limit value.

14. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 12 or 13, characterized in that, in order to reduce the speed of the compressor (16), the speed determined via the third PI controller (96) is multiplied by a factor between 0 and 1, which is formed by the smaller of the two factors determined by a stored third characteristic map (102) and a fourth characteristic map (103) as a function of the pressure at the outlet of the compressor (16) and the pressure at the outlet of the cooler (36).

15. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to one of claims 1 to 14, characterized in that in a third control loop (62) a speed of the fan (20) at the condenser (18) is controlled as a function of an outlet pressure of the compressor (16) and a vehicle speed. PP34420WO / kop August 28, 2025 AVL List GmbH 16. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 15, characterized in that a target airflow is determined via a fifth characteristic map (107) as a function of the outlet pressure of the compressor (16), from which an airflow determined via a sixth characteristic map (108) as a function of the vehicle speed is subtracted, whereby a target delivery airflow of the fan (20) is determined, from which the speed of the fan (20) is determined via a seventh characteristic map (110).

17. Method for controlling a refrigerant circuit coupled to a coolant circuit for a vehicle according to claim 15 or 16, characterized in that the determined speeds of the fan (20) and the compressor (16) are limited by a minimum-maximum limiting element (105, 111) and by a slope limiting control element (106, 112).

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