DE102018201165B3 - Method for operating a refrigerant circuit having a refrigeration system of a vehicle in the refrigeration mode - Google Patents

Abstract

The invention relates to a method for operating a refrigerant circuit (1) of a vehicle in AC operation with a chiller branch (2.0) having a pressure-temperature sensor (pT4_V1) connected downstream of a chiller (2), at least one interior evaporator branch ( 3.0), which is connected in parallel to the chiller branch (2.0), an accumulator (5), a refrigerant compressor (6), a condenser or gas cooler (7), wherein the degree of superheat of the refrigerant at the refrigerant outlet of the chiller (2) by means of a control device (8) from the measured values of the pressure-temperature sensor (pT4_V1) is determined, and the degree of superheating of the refrigerant at the refrigerant outlet of the chiller (2) by controlling the opening degree of the chiller (2) associated expansion element (AE_V1) by means of the control device (7) Depending on the measured values is controlled to at least a minimum target value of a target degree of superheat. In a first alternative method according to the invention, instead of the chiller 2, a pressure-temperature sensor (pT4_V2) is connected downstream of the interior evaporator 3 in order to monitor the degree of superheating in the interior evaporator 3 and to regulate it to at least one maximum nominal value. A further alternative method according to the invention provides that both the chiller 2 and the interior evaporator 3 are each followed by a pressure / temperature sensor and the superheat at the interior evaporator 3 is regulated to a maximum overheating when the cooling capacity at the chiller is greater than on the interior evaporator. 3

Description

The invention relates to a method for operating a refrigerant circuit for a vehicle having at least two evaporators, namely at least one interior evaporator and an evaporator designed as a chiller.

The interior evaporator can be designed as a front evaporator or as a rear evaporator of the vehicle interior and is used for conditioning an entering into the vehicle interior supply air.

In addition to the interior or front evaporator, electrified vehicles require a separate coolant circuit for conditioning and temperature control of the energy accumulator, which is generally realized as a high-voltage battery. Such a coolant circuit is coupled by means of a heat exchanger with the refrigerant circuit, wherein such a heat exchanger is in turn also designed as an evaporator for cooling an air flow or as a so-called chiller for cooling a coolant.

• - die Verdampfer und der Chiller jeweils einzeln betreiben,
• - zumindest ein Innenraum-Verdampfer bei inaktivem Chiller betreiben
• - zumindest ein Verdampfer und der Chiller gekoppelt betreiben,
• - zumindest mit einem Verdampfer mehr Kühlleistung erzeugen als mittels des Chillers,
• - zumindest mit einem Verdampfer weniger Kühlleistung als mittels des Chillers, und schließlich
• - zwischen dem Chiller und wenigstens einem Verdampfer Leistungsgleichheit bezüglich der Kühlleistung sicherstellen.

In order to achieve maximum flexibility with regard to the power distribution between the evaporators, each of these evaporators is preceded by an electric expansion element. With such valves, which also include a shut-off, can be

• - operate the evaporators and the chiller individually,
• - operate at least one interior evaporator with inactive chiller
• - operate at least one evaporator and the chiller coupled,
• - generate more cooling power with at least one evaporator than with the chiller,
• - At least with one evaporator less cooling power than by means of the chiller, and finally
• - Ensure equal performance between the chiller and at least one evaporator with respect to the cooling capacity.

A low-pressure accumulator in a refrigerant circuit, which is connected downstream of an evaporator of the refrigerant circuit, has the task of separating the gaseous and the liquid phase of the incoming refrigerant from each other and to store the liquid refrigerant in the sense of a volume buffer or vice versa to circulate. The extracted from the accumulator in the downstream compressor refrigerant should have a defined as possible and set on the accumulator steam content.

Furthermore, the introduced from the compressor in the refrigerant circuit and deposited in the accumulator or stored lubricating oil to be returned to the compressor again. For this purpose, for example, in the accumulator, a U-shaped tube is integrated, which at the lowest point an oil well (also called sniffer bore), which in turn may be provided to prevent contamination with a sieve or filter. An open end of the U-tube extends into the above the liquid refrigerant vapor space of the accumulator, the other leads downstream in the suction line to the compressor. With sufficient flow velocity in the U-tube takes place by the suction effect of an absorption of oil or oil-refrigerant liquid mixture from the lower part of the battery. Depending on the design of the size of the oil well, a steady state vapor content of at least 85% at the output of the accumulator and thus at the outlet of the upstream evaporator. If the oil hole is too small, oil accumulates in the lower part of the accumulator, while if the oil hole is too large, the vapor content will decrease.

In the case of a refrigerant circuit having a plurality of evaporators and having such an accumulator, this controller regulates the vapor content at the refrigerant outlet of that evaporator when the refrigerant circuit is being started up, which generates the highest cooling capacity and thus supplies the largest refrigerant mass flow. The passively set by the accumulator steam content is in this case in the steady state of the refrigerant circuit both at the outlet of the evaporator with the highest cooling capacity and at the refrigerant outlet of the accumulator.

It is problematic if in parallel operation of a plurality of evaporators on that evaporator, with which directly an inlet air flow supplied to the vehicle interior is conditioned, a refrigerant flow emerges with a tendency to refrigerant overheating. If such a refrigerant superheat exceeds a value of 5 K, this may already lead to an inhomogeneity in the temperature distribution of the supply air flow, thus showing an unwanted, uneven temperature profile at the vents in the vehicle interior.

From the DE 10 2015 104 464 A1 is an R744 refrigerant circuit with a mechanically driven compressor, a gas cooler, an accumulator, an internal heat exchanger, an electrically controllable expansion device and an evaporator and a control device with sensors for pressure and temperature known. As sensors is a temperature and pressure sensor for measuring the pressure and the temperature of the refrigerant after the compressor, a temperature sensor for measuring the temperature of the refrigerant after the gas cooler and a temperature sensor for measuring the temperature of the cooled air provided in the evaporator.

The DE 10 2013 021 360 A1 describes a refrigerant circuit of an electric or hybrid vehicle with a refrigerant compressor, a condenser, a high-pressure side accumulator, an interior evaporator with an associated expansion element, a chiller for a vehicle battery and another evaporator with associated expansion element for cooling of other components of an electric drive train. The evaporators are in each case connected in parallel together with the associated expansion elements and downstream pressure-temperature sensors. To realize a heat pump function of the chiller is used as a heat source and the condenser as WärmepumpenVerdampfer for using the ambient air as a heat source, for this purpose, a heat pump branch is provided with a heating coil and required for the heat pump function expansion devices. For such a refrigerant circuit, a method for operating the same is proposed, which enables efficient, active battery cooling and a heat pump process for heating the vehicle interior and the vehicle battery.

A temperature management system for an electric vehicle comprises according to DE 11 2013 004 046 T2 a coolant circuit for an air conditioning device, a coolant circuit for a battery, and a temperature management control unit that heats the coolant for the battery by means of the heater when the temperature of the coolant for the battery is lower than an allowable lower limit temperature of the battery. When the temperature of the coolant for the battery is higher than an allowable upper limit temperature of the battery, the speed management of a compressor is reduced by the temperature management control unit.

In the US 2007/01515287 A1 a pressure reduction module of a refrigerant circuit is disclosed in supercritical operation. The pressure reduction module formed with an inlet and two outlets has an expansion device and a distribution valve adjoining it in the flow direction of the refrigerant. The inlet is connected to the expansion device and the outlets are fluidically connected to the distribution valve designed as a 3-way valve. By means of the 3-way valve, the refrigerant, which has been expanded to a common pressure level in the two-phase region, is split for forwarding to heat exchangers operated as an evaporator.

The DE 10 2013 009 561 A1 describes a method for controlling the cooling of a traction battery of a hybrid or electric vehicle having an air conditioning device for air conditioning of its passenger compartment. An actual traction battery temperature is detected, and upon exceeding a traction battery temperature threshold that is dependent on at least one current vehicle operating parameter, active demand cooling of the traction battery is initiated. The traction battery temperature threshold depends on the current operating state of the air conditioning device, which is lower when the air conditioning of the passenger compartment is activated than when the passenger compartment is deactivated.

It is an object of the invention to provide a method for operating a refrigerant circuit having a refrigeration system of a vehicle with low-pressure side provided accumulator or refrigerant storage in the cooling mode, with which inhomogeneities of the guided into the vehicle interior Zuluftstromes be prevented in AC operation, especially if a chiller emits a higher cooling capacity as a front and / or rear evaporator of the refrigerant circuit.

This object is achieved by a method having the features of the claim 1 , by a method having the features of claim 2 as well as by a method having the features of the claim 3 ,

• - einem Chiller-Zweig, welcher einen Chiller, ein erstes Expansionsorgan und einen stromabwärts des Chillers nachgeschalteten Druck-Temperatursensor aufweist und mit einem Kühlmittelkreislauf thermisch gekoppelt ist,
• - wenigstens einem Innenraum-Verdampferzweig, welcher einen Innenraum-Verdampfer und zweites Expansionsorgan aufweist und dem Chiller-Zweig parallel geschaltet ist,
• - einem einen definierten Dampfgehalt einstellenden niederdruckseitigen Akkumulator,
• - einem Kältemittelverdichter,
• - einem Kondensator oder Gaskühler, und
• - einer Regelvorrichtung mindestens zum Regeln des ersten und zweiten Expansionsorgans zumindest in Abhängigkeit der Messwerte des Druck-Temperatursensors, wird nach der erstgenannten Lösung
• - der Überhitzungsgrad des Kältemittels am Kältemittelaustritt des Chillers mittels der Regelvorrichtung aus den Messwerten des Druck-Temperatursensors als Istwerte bestimmt, und
• - der Überhitzungsgrad des Kältemittels am Kältemittelaustritt des Chillers durch Steuern des Öffnungsgrades des ersten Expansionsorgans mittels der Regelvorrichtung in Abhängigkeit der Istwerte des Druck-Temperatursensors auf wenigstens einen minimalen Sollwert eines Zielüberhitzungsgrades geregelt.

In the method for operating a refrigerant circuit having a refrigeration system of a vehicle in the cold operation with

• a chiller branch which has a chiller, a first expansion element and a pressure / temperature sensor connected downstream of the chiller and is thermally coupled to a coolant circuit,
• at least one interior evaporator branch, which has an interior evaporator and second expansion element and is connected in parallel to the chiller branch,
• a low-pressure side accumulator setting a defined steam content,
• a refrigerant compressor,
• - a condenser or gas cooler, and
• - A control device at least for controlling the first and second expansion element at least in response to the measured values of the pressure-temperature sensor, according to the former solution
• - the superheat degree of the refrigerant at the refrigerant outlet of the chiller is determined by means of the control device from the measured values of the pressure-temperature sensor as actual values, and
• the degree of superheating of the refrigerant at the refrigerant outlet of the chiller is controlled by controlling the opening degree of the first expansion element by means of the regulating device as a function of the actual values of the pressure-temperature sensor to at least a minimum desired value of a target superheating degree.

In this method, the property of the low-pressure side accumulator, according to which this regulates a constant vapor content of at least one evaporator (which also includes the chiller) made use of by the chiller by appropriate control of the opening degree of the associated expansion element with at least a minimum overheating or minimum superheat is operated according to the minimum target value of a target superheat degree.

However, this minimum target overheating target can be set at a constant value between 3 and 7K. This value for the amount of overheating is given in this order of magnitude, because only in this way is it ensured that the permissible minimum superheat is correctly detected. Decisive for this is the tolerance of the sensors for detecting pressure and temperature at the outlet of the chiller. The required minimum superheating is ultimately the value of overheating for which the maximum cooling capacity of the chiller can be provided in a targeted and controllable manner. As the overheating increases, the available cooling capacity drops via the chiller. As mentioned, this operating point is crucial as soon as at least two evaporators are in active operation.

In a regulation of the refrigerant to this minimum setpoint, a maximum cooling capacity with predefined steam content is generated by the chiller with this accumulator on the accumulator, so that due to the property of the low-pressure side accumulator leading to inhomogeneities in the temperature distribution of the supply air overheating of the refrigerant at the evaporator outlet of the interior Evaporator does not occur. The exception here is a refrigerant underfill of the system and thus an empty accumulator, which is taken in this way the possibility for steam content adjustment. Of course, this also applies if the chiller's refrigerant is regulated from the minimum setpoint to higher superheat levels, thereby decreasing the chiller's cooling capacity. The cooling capacity of the chiller is controlled by means of the first expansion element according to a Sollabkühltemperatur the coolant of the thermally coupled to the chiller coolant circuit.

In this inventive method according to the former solution, no pressure-temperature sensor in the interior evaporator branch is required.

In the operating mode of the refrigerant circuit according to the invention, in which the refrigerant in the chiller is regulated to at least a minimum target value of a target superheat degree, the interior evaporator is adjusted to a target value of the discharge temperature of the vehicle into the vehicle interior by means of setting a refrigerant-side evaporating pressure level, which in turn corresponds to an evaporating temperature guided Zuluftstromes regulated while parallel to the evaporator upstream of the expansion device is trying to maximize a subcooling control or by means of a regulation to an optimal high pressure in the refrigerant circuit system efficiency.

• - einem Chiller-Zweig, welcher einen Chiller und ein erstes Expansionsorgan aufweist und der Chiller mit einem Kühlmittelkreislauf thermisch gekoppelt ist,
• - wenigstens einem Innenraum-Verdampferzweig, welcher einen Innenraum-Verdampfer, ein zweites Expansionsorgan und einen stromabwärts des Innenraum-Verdampfers nachgeschalteten Druck-Temperatursensor aufweist und dem Chiller-Zweig parallel geschaltet ist,
• - einem einen definierten Dampfgehalt einstellenden niederdruckseitigen Akkumulator,
• - einem Kältemittelverdichter,
• - einem Kondensator oder Gaskühler, und
• - einer Regelvorrichtung mindestens zum Regeln des ersten und zweiten Expansionsorgans zumindest in Abhängigkeit der Messwerte des Druck-Temperatursensors, wird nach der zweitgenannten Lösung
• - der Überhitzungsgrad des Kältemittels am Kältemittelaustritt des Innenraum-Verdampfers mittels der Regelvorrichtung aus den Messwerten des Druck-Temperatursensors als Istwerte bestimmt wird, und
• - der Überhitzungsgrad des Kältemittels am Kältemittelaustritt des Innenraum-Verdampfers durch Steuern des Öffnungsgrades des zweiten Expansionsorgans mittels der Regelvorrichtung in Abhängigkeit der Istwerte des Druck-Temperatursensors auf wenigstens einen maximalen Sollwert eines Zielüberhitzungsgrades geregelt wird.

In the method for operating a refrigerant circuit having a refrigeration system of a vehicle in the cold operation with

• a chiller branch which has a chiller and a first expansion element and the chiller is thermally coupled to a coolant circuit,
• at least one interior evaporator branch, which has an interior evaporator, a second expansion element and a pressure / temperature sensor arranged downstream of the interior evaporator and is connected in parallel with the chiller branch,
• a low-pressure side accumulator setting a defined steam content,
• a refrigerant compressor,
• - a condenser or gas cooler, and
• - A control device at least for controlling the first and second expansion element at least in response to the measured values of the pressure-temperature sensor, according to the second-mentioned solution
• the superheat degree of the refrigerant at the refrigerant outlet of the interior evaporator is determined by means of the control device from the measured values of the pressure-temperature sensor as actual values, and
• - The degree of superheat of the refrigerant at the refrigerant outlet of the interior evaporator by controlling the opening degree of the second expansion element by means of the control device is regulated in dependence on the actual values of the pressure-temperature sensor to at least one maximum target value of a target superheat degree.

Also in this inventive method according to the second-mentioned solution, the property of the low-pressure side accumulator, after which this regulates a constant vapor content of at least one evaporator (which also includes the chiller), made use of by the interior evaporator of at least one interior evaporator branch by appropriate Control of the degree of opening of the associated expansion element is operated with a maximum overheating or maximum superheat corresponding to the maximum target value of a target degree of superheating. The degree of overheating is thus monitored and limited in terms of maximum overheating.

However, this maximum target overheating target set point can be set to a constant value between 3 and 7K. Again, the measurement inaccuracy plays the crucial role in determining and thus reliable measurability of the value of the lower overheating limit.

At this operating point, the overheating must be limited to a maximum value which must not be exceeded, otherwise an air-side temperature inhomogeneity will form due to the overheating effect in the refrigerant. The higher the power demanded at the evaporator, the higher the permissible overheating can be set, conversely, the allowable overheating at low load points is to be set lower, in order to achieve in this way the lowest effects in the air-side temperature inhomogeneity.

In a regulation of the refrigerant state to this maximum target value, a maximum cooling capacity at defined vapor content is generated by the interior evaporator of at least one interior evaporator branch, so that due to the property of the low-pressure side accumulator leading to inhomogeneities in the temperature distribution of the supply air overheating of the refrigerant at the evaporator outlet of the interior evaporator can not occur. The cooling capacity of the interior evaporator is regulated by means of the compressor to a desired value or desired value of the outlet temperature of the supply air flow guided into the vehicle interior. The second expansion organ, in turn, regulates subcooling or the optimum high pressure of the system.

In this inventive method according to the second-mentioned solution no refrigerant-side pressure-temperature sensor in the chiller branch is required.

In the refrigerant cycle of the present invention, in which the refrigerant in the indoor evaporator of the at least one indoor evaporator branch is controlled to at least a maximum target value of a target superheat degree, the chiller is controlled by controlling the opening degree of the first expansion valve to a target cooling temperature of the refrigerant of the chiller coupled coolant circuit regulated.

• - einem Chiller-Zweig, welcher einen Chiller, ein erstes Expansionsorgan und einen stromabwärts des Chillers nachgeschalteten ersten Druck-Temperatursensor aufweist und mit einem Kühlmittelkreislauf thermisch gekoppelt ist,
• - wenigstens einem Innenraum-Verdampferzweig, welcher einen Innenraum-Verdampfer, ein zweites Expansionsorgan und einen stromabwärts des Innenraum-Verdampfers nachgeschalteten zweiten Druck-Temperatursensor aufweist und dem Chiller-Zweig parallel geschaltet ist,
• - einem einen definierten Dampfgehalt einstellenden niederdruckseitigen Akkumulator,
• - einem Kältemittelverdichter,
• - einem Kondensator oder Gaskühler, und
• - einer Regelvorrichtung mindestens zum Regeln des ersten und zweiten Expansionsorgans zumindest in Abhängigkeit der Messwerte des ersten und zweiten Druck-Temperatursensors wird nach der drittgenannten Lösung
• - in einer ersten Betriebsart der Innenraum-Verdampfer mit einer gegenüber dem Chiller höheren Kälteleistung auf eine Soll-Luftausblastemperatur mittels eines durch den Kältemittelverdichter eingestellten Niederdrucks geregelt, mittels desdas zweiten Expansionsorgans die Unterkühlung nach dem Kondensator oder Gaskühler eingestellt und der Chiller mittels des ersten Expansionsorgans auf eine Soll-Abkühltemperatur des Kühlmittels geregelt, und
• - in einer zweiten Betriebsart der Chiller mit einer gegenüber dem Innenraum-Verdampfer höheren Kälteleistung geregelt,
• - in der zweiten Betriebsart ein Istwert des Überhitzungsgrades des Kältemittels am Kältemittelaustritt des Innenraum-Verdampfers mittels der Regelvorrichtung aus den Messwerten des zweiten Druck-Temperatursensors bestimmt, und
• - in der zweiten Betriebsart bei einem über einem verdampfer- und betriebslastabhängigen maximalen Sollwert liegenden Istwert des Überhitzungsgrades mittels der Regelvorrichtung der Öffnungsgrad des zweiten Expansionsorgans auf den maximalen Sollwert des Überhitzungsgrades geregelt.

In the method for operating a refrigerant circuit for a vehicle with

• a chiller branch which has a chiller, a first expansion element and a first pressure-temperature sensor connected downstream of the chiller and is thermally coupled to a coolant circuit,
• at least one interior evaporator branch, which has an interior evaporator, a second expansion element and a downstream second pressure-temperature sensor downstream of the interior evaporator and is connected in parallel with the chiller branch,
• a low-pressure side accumulator setting a defined steam content,
• a refrigerant compressor,
• - a condenser or gas cooler, and
• - A control device at least for controlling the first and second expansion element at least in response to the measured values of the first and second pressure-temperature sensor is after the third-mentioned solution
• - In a first mode of the indoor evaporator with a relation to the chiller higher cooling capacity to a target air outlet temperature controlled by a set by the refrigerant compressor low pressure, means of desdansionsorgans the supercooling after the condenser or gas cooler set and the chiller means of the first expansion organ on regulated a desired cooling temperature of the coolant, and
• in a second operating mode, the chiller is regulated with a higher cooling capacity than the interior evaporator,
• in the second operating mode, an actual value of the degree of superheat of the refrigerant at the refrigerant outlet of the interior evaporator is determined by means of the regulating device from the measured values of the second pressure-temperature sensor, and
• - In the second mode at a lying above a vaporizer and operating load-dependent maximum setpoint actual value of Overheating degree controlled by means of the control device, the degree of opening of the second expansion element to the maximum target value of the degree of superheat.

Finally, in this inventive method according to the third-mentioned solution, the property of the low-pressure side accumulator, after which this regulates a constant vapor content of at least one evaporator (which also includes the chiller), made use of by the state of the refrigerant of the interior evaporator on the detection the measured values of the pressure-temperature sensor connected downstream of the interior evaporator are always monitored with respect to overheating of the refrigerant and then when the cooling capacity of the chiller is higher than that of the interior evaporator, that is, if, for example, the refrigerant cycle from the first mode to the second mode passes, the interior evaporator by means of the second expansion device on a targeted and defined overheating, which is not to be exceeded, is regulated. For this purpose, the degree of opening of the second expansion element is increased to a maximum desired value of the superheat degree by means of the control device, so that no inhomogeneities in the temperature distribution of the supply air flow can occur at this low overheating of the refrigerant.

This maximum target value for the target degree of superheat is dependent on the evaporator and load, but can be set to a constant value of, for example, 5 K. The load case dependency in this operating mode refers to the surrounding environmental conditions for a refrigeration cycle system which can be operated with higher superheat values with increasing load. Conversely, the values of the maximum permissible overheating, without air-side inhomogeneity in the temperature distribution decreases, with decreasing ambient load.

In this method of the invention, when the third mode is changed from the first mode to the second mode in which the chiller supplies greater cooling capacity than the indoor evaporator, taking into consideration the measured quantities of the second pressure-temperature sensor connected downstream of the indoor evaporator the overheating control for the indoor evaporator performed by the refrigerant of the indoor evaporator is controlled specifically to a maximum overheating according to the maximum setpoint, for example. 5 K.

• - der Kältemittelkreislauf mit einem weiteren Innenraum-Verdampferzweig ausgebildet wird, welcher einen weiteren Innenraum-Verdampfer, ein drittes Expansionsorgan und einen stromabwärts des Innenraum-Verdampfers nachgeschalteten Druck-Temperatursensor aufweist,
• - die beiden Innenraum-Verdampferzweige parallel geschaltet werden,
• - ein Istwert des Überhitzungsgrades des Kältemittels am Kältemittelaustritt des weiteren Innenraum-Verdampfers mittels der Regelvorrichtung aus den Messwerten des Druck-Temperatursensors des weiteren Innenraum-Verdampfers bestimmt wird, und
• - ein über einem verdampfer- und betriebslastabhängigen weiteren maximalem Sollwert liegenden Istwert des Überhitzungsgrades mittels der Regelvorrichtung der Öffnungsgrad des dritten Expansionsorgans auf den maximalen Sollwert des Überhitzungsgrades geregelt wird.

According to an advantageous development of the method according to the invention, it is provided that

• the refrigerant circuit is formed with a further interior evaporator branch which has a further interior evaporator, a third expansion element and a downstream pressure sensor of the interior evaporator,
• - the two interior evaporator branches are connected in parallel,
• an actual value of the superheat degree of the refrigerant at the refrigerant outlet of the further interior evaporator is determined by means of the regulating device from the measured values of the pressure-temperature sensor of the further interior evaporator, and
• - A lying on a vaporizer and operating load-dependent further maximum setpoint actual value of the degree of superheat is controlled by means of the control device, the degree of opening of the third expansion element to the maximum target value of the degree of superheating.

In this refinement of the method according to the invention, the two interior evaporators represent a front evaporator and a rear evaporator. If the two interior evaporators are operated simultaneously, overheating on the rear evaporator as a further interior evaporator will correspond to a maximum overheating limited to the maximum target value of the degree of superheat. This maximum set point is dependent on the evaporator and operating load, but a constant value of 3 to 5 K has proven to be advantageous, in particular from the point of view of measuring accuracy of the used pressure-temperature sensor.

With this maximum overheating of the refrigerant at the outlet of the rear evaporator, an inhomogeneity on the air side and on the other hand too much flooding of the rear evaporator prevented due to excessive refrigerant mass flow, which also benefits the system efficiency, since the flow rate of refrigerant can be limited by the compressor , With the maximum setpoint value of, for example, 3 to 5 K, it is also ensured that the steam content is set by means of the accumulator on the front evaporator.

A further advantageous embodiment of the method according to the invention provides that the underpressure detection of the refrigerant circuit downstream of the accumulator refrigerant side downstream of a pressure-temperature sensor is connected.

It is particularly advantageous if, according to a last development of the invention, a temperature sensor is used instead of at least one pressure-temperature sensor, wherein the at least one pressure value of the at least one pressure sensor is used. Temperature sensor is estimated as a function of operating parameters of the refrigerant circuit and climate parameters.

Thus, the pressure-temperature sensors according to the respective evaporators (interior front evaporator, interior rear evaporator, chiller) and / or condenser / gas cooler and heating condenser / heating gas cooler can be reduced in the provided measurement signals to the temperature value. The pressure signal can be omitted and instead derived and calculated back over the built-in sensors at the outlet of the compressor and outlet of the accumulator or optionally at the entrance of the compressor on curves / maps. In the estimation of the pressure signal values at the outlet of the respective heat exchangers flow depending on the humidity, air flow, air flap position, ambient temperature (corresponding to the air side inlet temperature of each affected heat exchanger), Setpoint (corresponds to the air side outlet temperature of each affected heat exchanger) the expected pressure losses, so that, taking these values into the low-pressure and high-pressure-side measured values, the pressure position at the respective heat exchanger can be determined.

With increasing system load is an increase and with decreasing system load is associated with a drop in pressure loss. Based on the power converted at the heat exchanger, the circulating refrigerant mass flow can be estimated and above this the pressure loss can be predicted.

Instead of a costly combination sensor thus a cheaper temperature sensor is used.

• 1 eine Schaltungsanordnung eines Kältemittelkreislaufs zur Durchführung eines erfindungsgemäßen Verfahrens,
• 2 eine zur Schaltungsanordnung nach 1 alternative Schaltungsanordnung zur Durchführung eines erfindungsgemäßen Verfahrens, und
• 3 eine weitere zur Schaltungsanordnung nach 1 alternative Schaltungsanordnung zur Durchführung eines erfindungsgemäßen Verfahrens.

Further advantages, features and details of the invention will become apparent from the claims, the following description of preferred embodiments and from the drawings. Showing:

• 1 a circuit arrangement of a refrigerant circuit for carrying out a method according to the invention,
• 2 one to the circuit according to 1 Alternative circuit arrangement for carrying out a method according to the invention, and
• 3 another to the circuit according to 1 Alternative circuit arrangement for carrying out a method according to the invention.

The in 1 illustrated refrigerant circuit 1 can be operated in an AC mode and in a heat pump mode and has two evaporators, namely a chiller 2 , which with a coolant circuit 2.1 for cooling, for example. A high-voltage battery is thermally connected and used as a front evaporator interior evaporator 3 ,

• - einem Chiller-Zweig 2.0 mit dem Chiller 2, einem vorgeschalteten ersten Expansionsorgan AE_V1 und einem dem Chiller 2 nachgeschalteten ersten Druck-Temperatursensor pT4_V1, wobei der Chiller 2 neben der Kühlung bspw. einer elektrischen Komponente des Fahrzeugs auch zur Realisierung einer Wasser-Wärmepumpenfunktion unter Nutzung der Abwärme einer elektrischen Komponenten eingesetzt wird,
• - einem Innenraum-Verdampferzweig 3.0 mit dem Innenraum-Verdampfer 3, einem vorgeschalteten zweiten Expansionsorgan AE_V2 und einem dem Innenraum-Verdampfer 3 nachgeschalteten zweiten Druck-Temperatursensor pT4_V2, wobei der Innenraum-Verdampferzweig 3.0 dem Chiller-Zweig 2.0 parallel geschaltet ist,
• - optional einem weiteren Innenraum-Verdampferzweig 4.0 mit einem Verdampfer 4 als Heckverdampfer, einem vorgeschalteten dritten Expansionsorgan AE V3 und einem dem Innenraum-Verdampfer 4 nachgeschalteten Druck-Temperatursensor pT4_V3, wobei dieser weitere Innenraum-Verdampferzweig 4.0 dem Innenraum-Verdampferzweig 3.0 mit dem Innenraum-Verdampfer 3 als Frontverdampfer parallel geschaltet ist,
• - einem niederdruckseitigen Akkumulator 5 mit der Eigenschaft, den Dampfgehalt des Kältemittels auf einen konstanten Wert zu regeln,
• - einem Kältemittelverdichter 6,
• - einem äußeren Kondensator 7 oder Gaskühler 7 mit einem demselben in seiner Funktion als Wärmepumpenverdampfer für den Heizbetrieb zugeordneten Expansionsorgan AE3, wobei dieser Kondensator 7 oder Gaskühler 7 über ein als Absperrventil A4 mit dem Hochdruckausgang des Kältemittelverdichters 6 und andererseits über das Expansionsorgan AE3 unter Bildung eines Abzweigpunktes Ab1 mit dem Chiller-Zweig 2.0, dem Innenraum-Verdampferzweig 3.0 und gegebenenfalls mit dem weiteren Innenraum-Verdampferzweig 4.0 fluidverbunden ist,
• - einem inneren Wärmeübertrager 11, dessen Hochdruckseite zwischen dem Expansionsorgan AE3 und dem äußeren Kondensator 7 bzw. Gaskühler 7 angeordnet ist, während dessen niederdruckseitiger Abschnitt zwischen dem Akkumulator 5 und dem Kältemittelverdichter 6 in den Kältemittelkreislauf 1 eingebunden ist,
• - einem Heizzweig 1.1 mit einem inneren Heizkondensator 9 oder Heizgaskühler 9 (auch als Heizregister bezeichnet), einem demselben stromabwärts nachgeschalteten Absperrventil A1 zur Verbindung des Heizzweiges 1.1 mit dem Abzweigpunkt Ab1 und einem demselben stromaufwärts vorgeschalteten Absperrventil A3 zur Verbindung mit dem Hochdruckausgang des Kältemittelverdichters 6,
• - einem Expansionsorgan AE4, welches einerseits stromabwärts unter Bildung eines Abzweigpunktes Ab2 mit dem Absperrventil A4 und dem Kondensator 7 bzw. Gaskühler 7 und andererseits stromaufwärts mit dem Absperrventil A1 und dem Heizkondensator bzw. Heizgaskühler 9 verbunden ist,
• - einem Wärmepumpenrückführzweig 1.2 mit einem Absperrventil A2 und einem Rückschlagventil R1, welches einerseits stromaufwärts mit dem Abzweigpunkt Ab2 fluidverbunden ist und andererseits stromabwärts eine Fluidverbindung mit dem Akkumulator 5 herstellt, wobei die das Absperrventil A2 und das Rückschlagventil R1 verbindende Kältemittelleitung über ein Absperrventil A5 mit dem Heizzweig 1.1, also stromaufwärtsseitig des inneren Heizkondensators 9 bzw. Heizgaskühlers 9 mit demselben verbunden ist,
• - ein bspw. als Hochvolt-PTC-Heizelement ausgeführtes elektrisches Heizelement 10 als Zuheizer für einen in den Fahrzeuginnenraum geführten Zuluftstrom, welches zusammen mit dem inneren Heizkondensators 9 oder Heizgaskühler 9 und dem Innenraum-Verdampfer 3 in einem Klimagerät angeordnet ist, und
• - eine bspw. als Klimasteuergerät ausgeführte Regelvorrichtung 8, welcher zu verarbeitende Eingangssignale E, wie bspw. Istwerte von Sensoren zugeführt werden, um hieraus Steuersignale bzw. Sollwerte als Ausgangssignale A zur Steuerung der einzelnen Komponenten des Kältemittelkreislaufs 1 zu erzeugen.

The refrigerant circuit 1 consists

• - a chiller branch 2.0 with the chiller 2 , an upstream first expansion organ AE_V1 and one the chiller 2 downstream first pressure-temperature sensor pT4_V1 , where the chiller 2 In addition to the cooling, for example, an electrical component of the vehicle is also used to realize a water heat pump function using the waste heat of an electrical component,
• - An interior evaporator branch 3.0 with the interior evaporator 3 , an upstream second expansion organ AE_V2 and an interior evaporator 3 downstream second pressure-temperature sensor pT4_V2 , wherein the interior evaporator branch 3.0 the chiller branch 2.0 is connected in parallel,
• - Optionally another interior evaporator branch 4.0 with an evaporator 4 as a rear evaporator, an upstream third expansion element AE V3 and an interior evaporator 4 downstream pressure-temperature sensor pT4_V3 , this further interior evaporator branch 4.0 the interior evaporator branch 3.0 with the interior evaporator 3 is connected as a front evaporator in parallel,
• - A low-pressure side accumulator 5 having the property of controlling the vapor content of the refrigerant to a constant value
• - a refrigerant compressor 6 .
• - an outer capacitor 7 or gas cooler 7 with an expansion element associated with same in its function as a heat pump evaporator for heating operation AE3 , this capacitor 7 or gas cooler 7 via a shut-off valve A4 with the high pressure outlet of the refrigerant compressor 6 and on the other hand via the expansion organ AE3 forming a branch point Ab1 with the chiller branch 2.0 , the interior evaporator branch 3.0 and optionally with the further interior evaporator branch 4.0 is fluid-connected,
• - an internal heat exchanger 11 , whose high pressure side between the expansion organ AE3 and the outer capacitor 7 or gas cooler 7 is disposed during its low-pressure side portion between the accumulator 5 and the refrigerant compressor 6 in the refrigerant circuit 1 is involved,
• - a heating branch 1.1 with an internal heating condenser 9 or heating gas cooler 9 (Also referred to as heating register), a same downstream downstream shut-off valve A1 for connecting the heating branch 1.1 with the branch point Ab1 and a same upstream upstream shut-off valve A3 for connection to the high-pressure outlet of the refrigerant compressor 6 .
• - an expansion organ AE4 , which on the one hand downstream to form a branch point Starting at 2 with the shut-off valve A4 and the capacitor 7 or gas cooler 7 and on the other hand upstream with the shut-off valve A1 and the heating condenser or heating gas cooler 9 connected is,
• - a heat pump return branch 1.2 with a shut-off valve A2 and a check valve R1 which on the one hand upstream with the branch point Starting at 2 fluidly connected and, on the other hand, downstream a fluid connection with the accumulator 5 making the shut-off valve A2 and the check valve R1 connecting refrigerant pipe via a shut-off valve A5 with the heating branch 1.1 , ie upstream of the inner heating condenser 9 or heating gas cooler 9 connected to the same,
• - An example. As a high-voltage PTC heating element running electrical heating element 10 as a heater for a guided in the vehicle interior supply air, which together with the inner heating condenser 9 or heating gas cooler 9 and the interior evaporator 3 is arranged in an air conditioner, and
• - An example. As a climate control unit running control device 8th to which input signals E to be processed, such as, for example, actual values, are supplied by sensors in order to use control signals or setpoint values as output signals A for controlling the individual components of the refrigerant circuit 1 to create.

As sensors are in the refrigerant circuit 1 several pressure-temperature sensors provided. So are already above the chiller 2 a first pressure-temperature sensor pT4_V1 and the interior evaporator 3 a second pressure-temperature sensor pT4_V2 downstream. Further, a pressure-temperature sensor pT1 at the high pressure outlet of the refrigerant compressor 6 , a pressure-temperature sensor pT2 at the output of the accumulator 5 , a pressure-temperature sensor pT3 at the output of the capacitor 7 or gas cooler 7 and finally a pressure-temperature sensor pT4 at the exit of the inner heating condenser or heating gas cooler 9 arranged.

With the two shut-off valves A3 and A4 the refrigerant flow is from the high-pressure side of the refrigerant compressor 6 depending on the state of these two shut-off valves either with open shut-off valve A4 and locked shut-off valve A3 in the condenser 7 or gas cooler 7 directed or flows with open shut-off valve A3 and closed shut-off valve A4 in the heating branch 1.1 , The two shut-off valves A3 and A4 can also be used to a 3-2-way valve as a changeover valve UPS1 be executed. The same applies to the two shut-off valves A2 and A5 leading to a 3-2-way valve as a change-over valve USV2 can be summarized.

The two changeover valves UPS1 and USV2 can be combined and executed in a single compact multi-way electric valve.

In AC operation of the refrigerant circuit 1 the refrigerant compressed to high pressure flows from the refrigerant compressor 6 with open shut-off valve A4 in the outer capacitor 7 or gas cooler 7 , the high pressure section of the internal heat exchanger 11 , about the fully opened expansion organ AE3 and the branch point Ab1 by means of the first expansion organ AE3_V1 in the chiller branch 2.0 and / or in the interior evaporator branch 3.0 (optionally also in the other interior evaporator branch 4.0 ). From the chiller branch 2.0 the refrigerant flows over the accumulator 5 and the low pressure portion of the internal heat exchanger 11 back to the refrigerant compressor 6 while the refrigerant from the interior evaporator branch 3.0 (and optionally from the other interior evaporator branch 4.0 ) via a check valve R2 flows and then over the accumulator 5 and the low pressure portion of the internal heat exchanger 11 back to the refrigerant compressor 6 can flow.

In this AC operation, the heating branch is 1.1 by means of the shut-off valve A3 shut off, so that hot refrigerant, eg. R744 not through the heating condenser or heating gas cooler 9 can flow.

In order to provide maximum flexibility in AC operation with regard to the power distribution between several evaporators, ie the interior evaporator 3 as a front evaporator, optionally the other interior evaporator 4 as a rear evaporator on the one hand and the chiller 2 On the other hand, each of these components are preceded by the above-described expansion devices, each designed as an electric expansion valve with a shut-off function. This concerns the expansion organ AE_V1 of the chiller 2 , the organ of expansion AE_V2 of the interior evaporator 3 and optionally also the expansion organ AE_V3 of another interior evaporator 4 , Thus, the listed indoor evaporator can be 3 and 4 as well as the chiller 2 each individually or the interior evaporator 3 and optionally also the other interior evaporator 4 with the chiller 2 operate coupled. Furthermore, it is possible that the interior evaporator 3 and optionally also the interior evaporator 4 operated with a higher cooling capacity or be considered the chiller 2 or conversely, that the chiller 2 produces more cooling power than the interior evaporator 3 and optionally also the interior evaporator 4 , Finally, even between these evaporators and the chiller equal performance can be made.

The low pressure accumulator 5 in a refrigerant circuit 1 which is the chiller branch 2.0 , the interior evaporator branch 3.0 and optionally also the further interior evaporator branch 4.0 downstream, has the task of separating the gaseous and the liquid phase of the incoming refrigerant from each other and to store the liquid refrigerant in the sense of a volume buffer or to circulate, depending on the system required refrigerant quantity. That from the accumulator 5 in the downstream low-pressure side portion of the inner heat exchanger 11 to the refrigerant compressor 6 extracted refrigerant should have the highest possible and defined vapor content. Practical values range between 80-95%. Values below mean too wet refrigerant and thus the risk of oil leaching at the refrigerant compressor 6 , Values above can be the oil return to the compressor 6 affect.

Furthermore, by means of the accumulator that of the refrigerant compressor 6 in the refrigerant circuit 1 introduced and among other things in the accumulator 5 stored lubricating oil back to the refrigerant compressor 6 to be led back. For this purpose, for example, in the accumulator 5 integrated a U-shaped (outlet) tube, which at the lowest point has an oil well (also called sniffer bore). An open end of the U-tube extends into the above the liquid refrigerant vapor space of the accumulator 5 , the other (inlet) pipe leads upstream in the suction line to the evaporators 2 and 3 and, if appropriate, 4. If the flow velocity in the U-tube is sufficient, the suction effect absorbs oil or oil / refrigerant mixture from the lower region of the accumulator 5 , Depending on the size of the inner bore, a vapor content of, for example, 90% at the output of the accumulator 5 on. If the oil hole is too small, more oil will remain and accumulate oil in the lower part of the accumulator 5 while if the oil is too large, the vapor content will decrease.

Such an accumulator 5 regulates when commissioning the refrigerant circuit or during a load change between the interior evaporator 3 and the chiller 2 the vapor content at the refrigerant outlet of that evaporator, which generates the highest cooling capacity and thus delivers the largest refrigerant mass flow to a constant value. The passively set by the accumulator steam content is in this case in the steady state of the refrigerant circuit both at the outlet of the evaporator with the highest cooling capacity and at the refrigerant outlet of the accumulator.

It can, however, in parallel operation of the interior evaporator 3 and the chiller 2 and optionally the further interior evaporator 4 at that evaporator, with which directly a supply air flow supplied to the vehicle interior is conditioned, leak a refrigerant flow with a tendency to refrigerant overheating. If such a refrigerant superheat exceeds an evaporator and operating load-dependent value of, for example, 5 K, this leads to an inhomogeneity in the temperature distribution of the supply air flow, which thus produces an uneven temperature profile at the vents in the vehicle interior.

The property of such a low-pressure accumulator 5 , To carry out an independent regulation of the vapor content of at least one evaporator to a constant value, is used advantageously to correct working and operating points of the respective active evaporator, so indoor evaporator 3 and optionally indoor evaporator 4 and chillers 2 as explained below.

Based on the refrigerant circuit 1 to 1 an embodiment of a first method according to the invention is explained, with which leading to an inhomogeneity in the temperature distribution of the guided into the vehicle interior supply air flow critical overheating of the refrigerant in the interior evaporator 3 and optionally also in the additional interior evaporator 4 is avoided. If that's the chiller 2 By flowing refrigerant in an overheated condition, this leads due to its coupling to the coolant circuit to no inhomogeneity at a guided into the vehicle interior supply air. When using both evaporators 3 and 4 becomes the interior evaporator 3 as a front evaporator and the other interior evaporator 4 used as a rear evaporator. First of all, a refrigerant circuit 1 to 1 without such a rear evaporator.

The refrigerant circuit 1 is operated in a standard operating mode, referred to as the first operating mode, in which the interior evaporator 3 with one opposite the chiller 2 higher Cooling capacity to a target air outlet temperature by means of a through the refrigerant compressor 6 adjusted low pressure and with fully open expansion process AE3 by means of the second expansion organ AE_V2 the subcooling after the condenser or gas cooler 7 set, in each case depending on input variables E by means of the control device 8th while the chiller 2 by means of the first expansion organ AE_V1 is controlled to a desired cooling temperature of the coolant. At the same time, the overheat condition at the refrigerant outlet of the indoor evaporator becomes 3 based on the measured values of the pressure-temperature sensor pT4_V2 monitored and determined from this an actual value of the degree of superheat.

Changes the refrigerant circuit 1 to a second mode, in which the chiller 2 with one opposite the interior evaporator 3 is regulated at a higher than a vaporizer and operating load-dependent maximum setpoint actual value of the degree of superheat by means of the control device 8th the degree of opening of the second expansion element AE_V2 of the interior evaporator 3 regulated to the maximum target value of the degree of superheating, ie the standard operating mode corresponding control function of the second expansion element AE_V2 is converted from a control of the subcooling or the optimal high pressure to a maximum overheating. It has proven to be advantageous to set this desired value to a constant value of, for example, 5 K. The degree of opening of the second expansion element AE_V2 is therefore changed until the actual values of the pressure-temperature sensor pT4_V2 The maximum should correspond to overheating of, for example, 5 K. Inhomogeneities in the temperature distribution of the supply air flow guided into the vehicle interior are thus still prevented.

If the refrigerant circuit returns to the standard operating case in which the interior evaporator 3 opposite the chiller 2 again provides the greater cooling capacity is provided by the accumulator 5 at the refrigerant outlet of the interior evaporator 3 the vapor content of the refrigerant is regulated back to a constant value.

In a refrigerant circuit 1 to 1 with another interior evaporator 4 becomes the interior evaporator 3 as a front evaporator and the other interior evaporator 4 used as a rear evaporator. Also in this constellation, the degree of superheat at the refrigerant outlet of the interior evaporator 4 by means of a pressure-temperature sensor pT4_V3 monitored when both evaporators are operated simultaneously.

Also, in this mode, the refrigerant cycle with the simultaneous operation of the two interior evaporator 3 and 4 the refrigerant in the interior evaporator 4 set to maximum overheating with another maximum setpoint between 3K and 5K. The lower this maximum set point is set, the better stratification properties also occur at the rear evaporator. Thus, on the one hand air-side inhomogeneity and on the other hand excessive flooding of the rear evaporator due to excessive refrigerant mass flow is prevented because not existing superheat the exact refrigerant state is not unique and easy to determine. Thus, this further interior evaporator 4 with optimal filling and the entire system with the best efficiency. With the specification of the maximum setpoint for overheating is always ensured that in the standard operating case of the refrigerant circuit 1 ie with maximum generation of cooling capacity by the front evaporator, ie the interior evaporator 3 , the accumulator 5 the vapor content of this interior evaporator 3 established. Will only be next to the chiller 2 only the further interior evaporator 4 operated as a rear evaporator, the measuring signals of the associated pressure-temperature sensor pT4_V3 be ignored because the accumulator 5 the vapor content and thus the refrigerant quality at the interior evaporator 4 established. By means of the associated expansion organ AE_V3 a supercooling control or a regulation to an optimal high pressure takes place.

The refrigerant circuit 1 to 1 has an optional pressure-temperature sensor pT2 on, which at the refrigerant outlet of the accumulator 5 is arranged, which serves to under filling detection, but can also be used for setting and monitoring a required low pressure.

Another pressure-temperature sensor pT1 of the refrigerant circuit 1 to 1 Used to determine the refrigerant temperature and the high pressure of the compressed medium at the outlet of the refrigerant compressor 6 , The monitoring of these two variables serves to determine the maximum permissible mechanical and thermal loads of the refrigeration system, especially at the outlet of the refrigerant compressor 6 to monitor and possibly by Abregelungsmaßnahmen, demanded via the control unit 8th to limit the system operation so as not to exceed the maximum permissible values.

One according to the refrigerant circuit 1 to 1 downstream of the heating condenser 9 or heating gas cooler 9 arranged pressure-temperature sensor pT4 serves to control the different operating modes of the refrigerant circuit 1 . in particular in the heat pump mode with actively flowed through the heating condenser 9 or heating gas cooler 9 by the control device designed as a climate control unit 8th ,

The on the outlet side of the capacitor 7 or gas cooler 7 provided pressure-temperature sensor pT3 Primarily used to set or monitor the system operating variables optimum high pressure in supercritical system operation or subcooling after gas cooler 7 in subcritical system operation.

Based on the refrigerant circuit 1 to 2 or 3 an embodiment of a second and a third method according to the invention is explained, with which leading to an inhomogeneity in the temperature distribution of the guided into the vehicle interior supply air flow overheating of the refrigerant in the interior evaporator 3 is avoided as a front evaporator. If that's the chiller 2 By flowing refrigerant in a superheated state, this does not lead to inhomogeneity at a guided into the vehicle interior supply air. When using both interior evaporators 3 and 4 becomes the interior evaporator 3 as a front evaporator and the other interior evaporator 4 used as a rear evaporator. First of all, a refrigerant circuit 1 to 2 without such a rear evaporator.

The refrigerant circuit 1 to 2 corresponds to the structure of that of 1 , but with the difference that the interior evaporator 3 no pressure-temperature sensor pT4_V2 is downstream. At the refrigerant circuit after 3 is against the chiller 2 no pressure-temperature sensor downstream, but the interior evaporator 3 a pressure-temperature sensor pT4_V2 ,

During operation of the refrigerant circuit 1 to 2 with the interior evaporator 3 and the chiller 2 it is also possible, compared to the refrigerant circuit after 1 each on one of the two pressure-temperature sensors pT4_V1 or pT4_V2 to renounce, if in a first case the chiller 2 with a pressure-temperature sensor pT4_V1 (see. 2 ) and in the other case the interior evaporator 3 with a pressure-temperature sensor pT4_V2 monitored for overheating. Overheating at that component 2 or 3 , Which refrigerant outlet side, a pressure-temperature sensor pT4_V1 or. pT4_V2 is assigned is limited to a maximum setpoint, which is, for example, between 3 and 7 K.

This is to prevent, in particular, one of the two components, namely the interior evaporator 3 by an excessive overheating of the exiting refrigerant an inhomogeneous temperature distribution on the air side, with the result that the outlet temperatures of the supply air flow in the vehicle interior drift too far apart in left-sided, central and timely vents.

If such a sensor is missing, depending on the load situation of the refrigerant circuit 1 a tipping over in the setting of the refrigerant quality over the accumulator 5 enter, ie either on the interior evaporator 3 as a front evaporator or at the chiller 2 the through the accumulator 5 set predetermined steam content, the refrigerant of the other component could be converted into an extreme and uncontrollable overheating.

During operation of the refrigerant circuit 1 to 2 is the actual value of the degree of superheat of the refrigerant at the refrigerant outlet of the chiller 2 from the measured values of the pressure-temperature sensor pT4_V1 by means of the control device 8th determined and regulated at least to a minimum target value of a target superheat degree or permissible degree of superheating. This is the chiller 2 by appropriate control of the degree of opening of the associated) expansion element AE_V1 operated at least with the minimum overheating or minimum superheating corresponding to the minimum target value of the target superheat degree.

This minimum target overheating target is evaporator and load case dependent, but can be set to a constant value between 3 and 7K.

When controlling the refrigerant down to this minimum setpoint is through the chiller 2 generates a maximum cooling capacity with this minimum superheating, so that due to the nature of the low-pressure side accumulator 5 a leading to inhomogeneities in the temperature distribution of the supply air overheating of the refrigerant at the evaporator outlet of the interior evaporator 3 can not occur. Of course, this also applies if the refrigerant of the chiller 2 is controlled from the minimum setpoint to higher degrees of overheating, thereby reducing the chiller 2 produced cooling capacity decreases. The cooling capacity of the chiller 2 is by means of the first expansion organ AE_V1 corresponding to a target cooling temperature of the coolant with the chiller 2 thermally coupled coolant circuit 2.1 regulated.

In operating mode of the refrigerant circuit 1 according to 2 in which the refrigerant in the chiller 2 is controlled to at least a minimum target value of a target superheat degree, the interior evaporator 3 by means of a Undercooling or by means of a control to an optimal high pressure in the refrigerant circuit in cooperation with the refrigerant compressor 6 and the low-pressure, which in turn is approached, are regulated to a desired value of the discharge temperature of the supply air flow guided into the vehicle interior.

Also during operation of the refrigerant circuit 1 to 3 in which of the two components 2 and 3 only the interior evaporator 3 on the output side a pressure-temperature sensor pT4_V2 has, is the current value of the degree of superheat of the refrigerant at the refrigerant outlet of the interior evaporator continuously 3 from the measured values of the pressure-temperature sensor pT4_V2 by means of the control device 8th determined and regulated to a maximum allowable setpoint of a target degree of overheating. For this purpose, the interior evaporator 3 by appropriate control of the degree of opening of the associated expansion element AE_V2 operated at least with the minimum overheating or minimum superheating according to the allowable target value of the target superheat degree.

This permissible target value for the target degree of superheating is dependent on the evaporator and load case, but can be set to a constant value between 3 and 7 K.

When regulating the refrigerant to this maximum permissible setpoint, is through the interior evaporator 3 generates a maximum cooling capacity, so that due to the property of the low-pressure side accumulator leading to inhomogeneities in the temperature distribution of the supply air overheating of the refrigerant at the evaporator outlet of the interior evaporator 3 can not occur. The cooling capacity of the interior evaporator 3 is by means of the refrigerant compressor 6 regulated to a desired value of the outlet temperature of the guided into the vehicle interior supply air.

In this operating mode of the refrigerant circuit 1 according to 3 in which the refrigerant in the interior evaporator 3 is controlled to at least a maximum target value of a target superheat degree, the chiller 2 by controlling the opening degree of the first expansion valve AE_V1 to a target cooling temperature of the coolant with the chiller 2 coupled coolant circuit 2.1 regulated.

Even with the refrigerant circuit 1 according to 2 or 3 can be analogous to 1 next to the interior evaporator 3 as a front evaporator another interior evaporator can be used as a rear evaporator, which is an expansion organ AE_V3 upstream and a pressure-temperature sensor pT4_V3 is downstream. This further interior evaporator 4 is together with the expansion organ AE_V3 and the pressure-temperature sensor pT4_V3 corresponding to that of the refrigerant circuit 1 to 1 in the refrigerant circuit 1 to 2 or 3 involved.

In the simultaneous operation of these two interior evaporator of the refrigerant circuit 1 to 2 or 3 the actual value of the overheating of the refrigerant at the refrigerant outlet of the further interior evaporator is detected as a rear evaporator and set to a maximum overheating with a further maximum setpoint between 3 K and 5 K. The lower this maximum setpoint value is set, the better properties with regard to the air-side temperature homogeneity occur at the further interior evaporator as a rear evaporator. Thus, on the one hand, said air-side inhomogeneity and, on the other hand, excessive flooding of the rear evaporator due to excessively high refrigerant mass flow is prevented. Thus, this further indoor evaporator can be operated with optimum filling and efficiency. With the specification of the maximum setpoint for overheating is always ensured that in the standard operating case of the refrigerant circuit 1 , ie when generating maximum cooling capacity through the interior evaporator 3 as a front evaporator, the accumulator 5 the vapor content of this interior evaporator 3 established. Is as a special case exclusively next to the chiller 2 Only the rear evaporator operated, the measurement signals of the associated pressure-temperature sensor can be ignored because the accumulator 5 adjusts the steam content. By means of the associated expansion of the rear evaporator is a supercooling or regulation to an optimum high pressure.

The in the refrigerant circuits 1 according to the 1 . 2 and 3 used sensors can be simplified, ie the pressure-temperature sensors used for the respective evaporators (interior front, interior rear evaporator, chiller) and / or condenser and gas cooler and heating condenser and heating gas cooler can be reduced in the measurement signals provided to the temperature value. The pressure signal can be omitted and instead derived via the built-in sensors at the outlet of the refrigerant compressor and outlet of the accumulator or possibly at the inlet of the refrigerant compressor on curves / maps and calculated back. In the estimation of the pressure signal values at the outlet of the respective heat exchangers flow depending on the humidity, air flow, air flap position, ambient temperature (corresponding to the air side inlet temperature of each affected heat exchanger), Setpoint (corresponds to the air side outlet temperature of each affected heat exchanger) the expected pressure losses, so that incorporating these values into the low pressure and high pressure side measured values, the pressure position at the respective heat exchanger can be determined. With increasing system load is an increase and with decreasing system load is a drop in pressure loss associated. Based on the power converted at the heat exchanger, the circulating refrigerant mass flow can be estimated and above this the pressure loss can be predicted.

Instead of a costly combination sensor as a pressure-temperature sensor, a lower-cost temperature sensor can be used.

The following is the heating operation of the refrigerant circuit 1 to 1 be described, this description also for the refrigerant circuit 1 to 1 and after 2 applies.

In heating mode of the refrigerant circuit 1 according to the 1 . 2 and 3 is using the chiller 2 to realize a water heat pump or using the outer capacitor 7 or gas cooler 7 as a heat pump evaporator for the realization of an air heat pump, the shut-off valve A4 closed and the shut-off valve A3 open, leaving hot refrigerant, eg. R744 in the heating branch 1.1 can flow.

To carry out the heating function by means of the chiller 2 this flows through the refrigerant compressor 6 compressed refrigerant via the open shut-off valve A3 for the delivery of heat to a guided into the vehicle interior supply air flow into the inner heating condenser 9 or heating gas cooler 9 and then via the open shut-off valve A1 and the branch point Ab1 by means of the expansion organ AE_V1 in the chiller 2 for absorbing waste heat in the coolant circuit 2.1 arranged relaxed electrical and / or electronic components. In this heating function are the expansion organs AE3 and AE4 closed.

To carry out the heating function by means of the external capacitor 7 or the gas cooler 7 as a heat pump evaporator that flows by means of the refrigerant compressor 6 compressed refrigerant via the open shut-off valve A3 for the delivery of heat to the supply air flow guided into the passenger compartment into the inner heating condenser 9 or heating gas cooler 9 and then via the open shut-off valve A1 by means of the expansion organ AE3 in the outer capacitor 7 or gas cooler 7 is expanded to absorb heat from the ambient air and then flows through the heat pump return branch 1.2 back to the refrigerant compressor 6

An indirect triangular circuit is realized that with the shut-off valve open A1 that of the refrigerant compressor 6 compressed refrigerant by means of the expansion device AE_V1 in the chiller 2 is relaxed, at the same time coolant side, ie in the coolant circuit 2.1 no mass flow is generated, so for example. The water used as a coolant on the coolant side of the chiller 2 stops or the chiller 2 is not actively flowed through by coolant.

In a reheat mode, the supply air flow supplied into the vehicle interior is first cooled by means of the evaporator three and thus dehumidified, in order subsequently to remove the heat withdrawn from the supply air flow by means of the internal heating condenser 9 or the heating gas cooler 9 to heat this supply air again. A reheat operation of the refrigerant circuit 1 is carried out in different ways depending on the heat balance.

So is with sufficient heating power in the refrigerant circuit 1 only the interior evaporator 3 flows through with refrigerant, by the inner heating condenser or Heizgaskühler 9 downstream by means of the opened shut-off valve A1 about the first expansion organ AE_V2 with the evaporator 3 fluid is connected, which is the chiller 2 associated expansion organ AE_V1 and as well as the capacitor 7 or gas cooler 7 leading expansion organs AE3 and AE4 are locked. From the interior evaporator 3 the refrigerant flows over the check valve R2 , about the accumulator 5 and the internal heat exchanger 9 back to the refrigerant compressor 6 , where in the evaporator 3 absorbed heat together with the over the refrigerant compressor 6 registered heat flow through the inner condenser 9 or gas cooler 9 is returned to a guided into the vehicle supply air flow.

In the case of a heat shortage in the refrigerant circuit 1 is used for heat absorption in addition to the evaporator 3 also the chiller 2 by opening the expansion device AE_V1 and / or the outer capacitor 7 or gas cooler 7 by means of the expansion organ AE3 connected in parallel.

Also is a parallel use of the waste heat from the chiller 2 as well as the ambient heat by means of the outer capacitor 7 or gas cooler 7 possible.

In a heat surplus in reheat operation is next to the inner heating condenser or heating gas cooler 9 additionally via the outer capacitor 7 or gas cooler 7 Heat is released to the surroundings of the vehicle before the refrigerant passes through the evaporator 3 back to the refrigerant compressor 6 flows. For this purpose, by means of the expansion organ AE4 the refrigerant for condensation to an intermediate pressure lying above the evaporation pressure and subsequently expanded by means of expansion AE_V2 in the evaporator 3 expanded to low pressure.

The branch with the shut-off valve A5 serves as Absaugzweig 1.3 , about the in the AC operation of the refrigerant circuit 1 with the shut-off valve open A5 and closed valves AE4 and A3 Refrigerant from the heating branch 1.1 suck.

LIST OF REFERENCE NUMBERS

1

Refrigerant circulation

1.1

Heating branch of the refrigerant circuit 1

1.2

Heat pump return branch of the refrigerant circuit 1

1.3

suction branch

2

Chiller

2.0

Chiller branch

2.1

Coolant circuit of the chiller 2

3

Interior evaporator

3.0

Interior evaporator branch

4

Interior evaporator

4.0

further interior evaporator branch

5

low-pressure side accumulator

6

Refrigerant compressor

7

Condenser, gas cooler

8th

Regulating device of the refrigerant circuit

9

internal heating condenser or heating gas cooler

10

electric heating element

11

internal heat exchanger

A1

shut-off valve

A2

shut-off valve

A3

shut-off valve

A4

shut-off valve

A5

shut-off valve

AE_V1

first expansion organ

AE_V2

second expansion organ

AE_V3

third expansion organ

Ab1

branching point

Starting at 2

branching point

AE3

expansion element

AE4

expansion element

pT1

Pressure-temperature sensor

pT2

Pressure-temperature sensor

pT3

Pressure-temperature sensor

pT4

Pressure-temperature sensor

pT4_V1

Pressure-temperature sensor

pT4_V2

Pressure-temperature sensor

pT4_V3

Pressure-temperature sensor

R1

check valve

R2

check valve

UPS1

switching valve

USV2

switching valve

Claims (6)

Method for operating a refrigeration system (1) of a vehicle having a refrigerant circuit (1) in the refrigeration mode with - a chiller branch (2.0) which has a chiller (2), a first expansion element (AE_V1) and a pressure-temperature sensor (pT4_V1) connected downstream of the chiller (2) and is thermally coupled to a coolant circuit (2.1), - at least an interior evaporator branch (3.0) which has an interior evaporator (3) and a second expansion element (AE_V2) and is connected in parallel to the chiller branch (2.0), - a low-pressure side accumulator (5) which adjusts a defined vapor content Refrigerant compressor (6), - a condenser or gas cooler (7), and - a control device (8) at least for controlling the first and second expansion device (AE_V1, AE_V2) at least in response to the measured values of the pressure-temperature sensor (pT4_V1), wherein Overheating degree of the refrigerant at the refrigerant outlet of the chiller (2) by means of the control device (8) from the measured values of the pressure-temperature sensor (pT4_V1) as actual values determined t, and - the degree of superheating of the refrigerant at the refrigerant outlet of the chiller (2) by controlling the degree of opening of the first expansion element (AE_V1) by means of the control device (7) as a function of the actual values of the pressure-temperature sensor (pT4_V1) to at least a minimum target value of a target superheat degree is regulated. Method for operating a refrigerant circuit (1) having a refrigeration system of a vehicle in the refrigeration mode with a chiller branch (2.0) which has a chiller (2) and a first expansion element (AE_V1) and is thermally coupled to a coolant circuit (2.1), at least one interior evaporator branch (3.0) which has an interior evaporator (3), a second expansion element (AE_V2) and a downstream pressure sensor of the interior evaporator (pT4_V2) and is connected in parallel with the chiller branch, a low pressure side accumulator (5) adjusting a defined steam content, a refrigerant compressor (6), - a condenser or gas cooler (7), and - A control device (8) at least for controlling the first and second expansion element (AE_V1, AE_V2) at least in dependence on the measured values of the pressure-temperature sensor (pT4_V2), wherein the degree of superheating of the refrigerant at the refrigerant outlet of the interior evaporator (3) is determined by means of the regulating device (8) from the measured values of the pressure-temperature sensor (pT4_V2) as actual values, and - The superheat degree of the refrigerant at the refrigerant outlet of the interior evaporator (3) is controlled by controlling the opening degree of the second expansion element (AE_V2) by means of the control device (8) depending on the actual values of the pressure-temperature sensor (pT4_V2) to at least one maximum target value of a target superheat degree , Method for operating a refrigerant circuit (1) having a refrigeration system of a vehicle in the refrigeration mode with a chiller branch (2.0) which has a chiller (2), a first expansion element (AE_V1) and a first pressure-temperature sensor (pT4_V1) connected downstream of the chiller (2) and is thermally coupled to a coolant circuit (2.1), - At least one interior evaporator branch (3.0) having an interior evaporator (3), a second expansion element (AE_V2) and a downstream of the interior evaporator downstream second pressure-temperature sensor (pT4_V2) and the chiller branch (2.0) in parallel is switched, a low pressure side accumulator (5) adjusting a defined steam content, a refrigerant compressor (6), - a condenser or gas cooler (7), and - A control device (8) at least for controlling the first and second expansion element (AE_V1, AE_V2) at least as a function of the measured values of the first and second pressure-temperature sensor (pT4_V1, pT4_V2) as actual values, wherein - In a first mode of operation of the interior evaporator (3) with a relation to the chiller (2) higher cooling capacity to a target air outlet temperature by means of a set by the refrigerant compressor (6) low pressure is controlled, by means of the second expansion element (AE_V2) to the subcooling the condenser or gas cooler (7) is set and the chiller (2) by means of the first expansion element (AE_V1) is controlled to a desired cooling temperature of the coolant, and in a second operating mode, the chiller (2) is regulated with a higher cooling capacity than the interior evaporator (3), - In the second mode, an actual value of the superheat degree of the refrigerant at the refrigerant outlet of the interior evaporator (3) by means of the control device (8) from the measured values of the second pressure-temperature sensor (pT4_V2) is determined, and - In the second mode at a lying above a vaporizer and operating load-dependent maximum setpoint actual value of the degree of overheating by means of the control device (8) the degree of opening of the second expansion element (AE_V2) is controlled to the maximum setpoint of the degree of superheating. Method according to one of the preceding claims, in which - The refrigerant circuit (1) with a further interior evaporator branch (4.0) is formed, which another interior evaporator (4), a third expansion element (AE_V3) and a downstream of the interior evaporator (4) downstream pressure-temperature sensor (pT4_V3 ) having, - the two interior evaporator branches (3.0, 4.0) are connected in parallel, an actual value of the superheat degree of the refrigerant at the refrigerant outlet of the further interior evaporator (4) is determined by means of the regulating device (8) from the measured values of the pressure-temperature sensor (pT4_V3) of the further interior evaporator (4.0), and - An over evaporator and operating load-dependent further maximum setpoint actual value of the superheat degree by means of the control device (8) the degree of opening of the third expansion element (AE_V3) is controlled to the maximum target value of the superheat degree. Method according to one of the preceding claims, wherein for detecting underfilling of the refrigerant circuit (1) the accumulator (5) downstream of the refrigerant, a pressure-temperature sensor (pT2) is connected downstream. Method according to one of the preceding claims, wherein instead of at least one pressure-temperature sensor (pT4_V1, pT4_V2, pT4_V3), a temperature sensor is used, wherein the at least one pressure value of the at least one pressure-temperature sensor (pT4_V1, pT4_V2, pT4_V3) depending on operating parameters of Refrigerant circuit (1) and climate parameters is estimated.

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