WO2023232354A1

WO2023232354A1 - Method for determining an amount of refrigerant in a refrigerant circuit of a motor vehicle, and motor vehicle

Info

Publication number: WO2023232354A1
Application number: PCT/EP2023/060795
Authority: WO
Inventors: Thomas Mayer; Mohamed Ayeb
Original assignee: Audi Ag
Priority date: 2022-06-01
Filing date: 2023-04-25
Publication date: 2023-12-07
Also published as: DE102022113830A1

Abstract

The invention relates to a motor vehicle (10) and to a method for determining an amount of refrigerant in a refrigerant circuit (12) of the motor vehicle (10), in which a compressor (14) feeds compressed refrigerant to a refrigerant cooler (16). Refrigerant coming from the refrigerant cooler (16) is expanded by means of an expansion element (22). The expanded refrigerant is fed to an evaporator (24). Refrigerant coming from the evaporator (24) is fed to a suction side (28) of the compressor (14). At least one input variable related to operation of the refrigerant circuit (12) is fed to a model (32), which outputs a model variable, said model variable being used to determine the amount of refrigerant. A temperature of the refrigerant at a predefined point of the refrigerant circuit (12) is output as the model variable by the model (32). The model variable (32) is compared with a measured value of the temperature of the refrigerant, said measured value being captured at the predefined point. The amount of refrigerant is estimated on the basis of the comparison of the model variable with the measured value.

Description

Method for determining a quantity of refrigerant in a refrigerant circuit of a motor vehicle and motor vehicle

DESCRIPTION:

The invention relates to a method for determining a quantity of refrigerant in a refrigerant circuit of a motor vehicle, in which a compressor of the refrigerant circuit supplies compressed refrigerant to at least one refrigerant cooler of the refrigerant circuit. Refrigerant coming from the refrigerant cooler is expanded by means of at least one expansion element of the refrigerant circuit. The expanded refrigerant is fed to at least one evaporator of the refrigerant circuit. Refrigerant coming from the at least one evaporator is fed to a suction side of the compressor. At least one input variable associated with operation of the refrigerant circuit is fed to a model which outputs at least one model variable. The at least one model size is used to determine the amount of refrigerant. The invention further relates to a motor vehicle with a refrigerant circuit.

The refrigerant to be provided for the operation of a refrigerant circuit is initially provided as a lifetime filling in the motor vehicle with regard to an initial filling quantity or initial refrigerant quantity. Accordingly, it is desirable if the amount of refrigerant originally present in the refrigerant circuit remains unchanged over the life of the refrigerant circuit or the motor vehicle.

In reality, however, gradual losses of refrigerant can occur, i.e. a decrease in the amount of refrigerant present in the refrigerant circuit Refrigerant quantity compared to the original filling quantity. Such losses can be noticeable to a user of the motor vehicle in the form of a reduced cooling capacity of the refrigerant circuit. Accordingly, if the refrigerant circuit is underfilled with refrigerant, a reduced cooling capacity can occur, i.e. if there is less than the originally intended amount of refrigerant in the refrigerant circuit. This is disadvantageous.

In addition, a significantly underfilled refrigerant circuit or refrigeration circuit poses the possibility of damage to the compressor in addition to insufficient cooling capacity. If there is too little refrigerant available in the refrigerant circuit, it can happen that the compressor is not supplied with a sufficient amount of oil for lubrication along with the refrigerant.

In order to avoid a noticeable reduction in the cooling capacity of the refrigerant circuit and associated complaints for the user of the motor vehicle, for example, a fixed service interval can be provided for filling the refrigerant circuit with refrigerant. However, it should be noted that a missing amount of refrigerant cannot simply be refilled into the refrigerant circuit. This is because an actual fill level of the refrigerant in the refrigerant circuit cannot be easily measured.

In addition, maintaining the most precisely defined amount of refrigerant in the refrigerant circuit or refrigerant circuit is important for reliable operation of the refrigerant circuit. Accordingly, neither more nor less than the amount of refrigerant specified for the respective refrigerant circuit of the motor vehicle should be filled into the refrigerant circuit. In order to ensure that the refrigerant circuit is always correctly filled with refrigerant, the entire refrigerant would first have to be removed from the refrigerant circuit during such a service. The refrigerant circuit would then have to be refilled exactly the amount of refrigerant defined for this refrigerant circuit.

The disadvantage here is the fact that such a regular replacement of the refrigerant entails high service costs. However, if you forego such regular service, this entails the possibility of reduced cooling capacity of the refrigerant circuit. And if the user of the motor vehicle does not notice or ignores a lack of refrigerant, the compressor may even be impaired or possibly even damaged. This is also disadvantageous.

Furthermore, it leads to inefficient operation of the refrigerant circuit if the refrigerant circuit is not optimally filled with refrigerant.

It is therefore desirable to determine or determine the amount of refrigerant present in the refrigerant circuit as precisely as possible. This is because then it is possible to react simply and in a targeted manner to deviations in the amount of refrigerant actually present in the refrigerant circuit from the amount of refrigerant to be provided for the refrigerant circuit.

DE 102013 019 498 A1 describes a method for operating an air conditioning system of a motor vehicle, with a refrigerant circulating in a refrigerant circuit of the air conditioning system. Filling information for the refrigerant circuit is calculated from state variables of the refrigerant circuit using a data-driven mathematical model. A compressor power, the speed of the compressor, a suction pressure of the compressor, a measurement pressure in a high-pressure region of the refrigerant circuit and the temperature before and after the compressor can be used as input data that goes into the mathematical model for calculating the filling information.

This method is based on these state variables or input variables using the data-driven mathematical model The fill level, i.e. the amount of refrigerant present in the refrigerant circuit, is determined directly. However, with such a method there is potential for improving the accuracy of the level determination results.

WO 2007/047886 A1 describes a method in which an algorithm generates a refrigerant level model based on observed refrigerant levels. The algorithm determines an expected refrigerant level based on the model and compares an existing refrigerant level with the expected refrigerant level. The existing refrigerant level is determined using a level indicator, which is intended to provide accurate results when the system is running and in a stable state.

However, such measurement-based detection of the fill level in a refrigerant reservoir, for example, is usually subject to major errors, in particular due to the turbulence of the flowing refrigerant in the refrigerant reservoir during operation of the refrigerant circuit.

The object of the present invention is to provide a method of the type mentioned at the outset, by means of which the amount of refrigerant can be estimated with a particularly high degree of accuracy, and to create a motor vehicle designed to carry out the method.

This object is achieved by a method with the features of patent claim 1 and by a motor vehicle with the features of patent claim 10. Advantageous embodiments with useful developments of the invention are specified in the dependent patent claims and in the following description.

In the method according to the invention for determining a quantity of refrigerant in a refrigerant circuit of a motor vehicle, a compressor of the refrigerant circuit supplies compressed refrigerant to at least one refrigerant cooler of the refrigerant circuit. Depending on what is used Refrigerant, the at least one refrigerant cooler can be designed as a gas cooler or as a condenser, by means of which a condensation of the refrigerant flowing through the refrigerant cooler can be effected. Refrigerant coming from the refrigerant cooler is expanded by means of at least one expansion element of the refrigerant circuit. The expanded refrigerant is fed to at least one evaporator of the refrigerant circuit. Refrigerant coming from the at least one evaporator is fed to a suction side of the compressor. At least one input variable associated with operation of the refrigerant circuit is fed to a model which outputs at least one model variable. The at least one model size is used to determine the amount of refrigerant. In the present case, the model outputs a temperature of the refrigerant at a predetermined point in the refrigerant circuit as the at least one model variable. The model size, i.e. the temperature of the refrigerant predicted by the model at the predetermined location of the refrigerant circuit, is compared with a measured value of the temperature of the refrigerant recorded at the predetermined location of the refrigerant circuit. Based on the comparison of the model size with the measured value, the amount of refrigerant is estimated.

This is based on the knowledge that a direct estimate of the amount of refrigerant in the refrigerant circuit based on operating data of the refrigerant circuit or the refrigerant system, as described for example in DE 10 2013 019 498 A1, is comparatively difficult or subject to inaccuracies has highlighted. This is especially true if the refrigerant circuit contains a refrigerant collector, especially if this is a comparatively large refrigerant collector.

In a refrigerant circuit with a refrigerant collector, the volume flow of the refrigerant circulated within the refrigerant circuit depends on the operating point of the refrigerant circuit. At a low load or a low requested and from the Accordingly, less refrigerant is circulated and more refrigerant is stored in the collector than with a higher load or a higher requested refrigeration capacity of the at least one evaporator. Accordingly, depending on the respective operating point or operating state of the refrigerant circuit, only part of the refrigerant is sucked in by the compressor or fed to the suction side of the compressor and then compressed.

The operating data recorded on the compressor therefore does not adequately reflect the presence of refrigerant in the refrigerant collector. This is particularly true when the refrigerant circuit is operated with a low load. This is because, particularly at low loads, it is very difficult to determine whether there is less refrigerant in the refrigerant circuit than would be necessary to provide a requested cooling capacity to be provided by the at least one evaporator.

In the method described here, the amount of refrigerant or amount of refrigerant actually present in the refrigerant circuit is estimated indirectly and based on a model. It has been found that such an indirect estimate of the amount of refrigerant, which is based on the comparison of the model size with the measured value of the temperature of the refrigerant at the at least one predetermined point of the refrigerant circuit, compared to a direct determination of the amount of refrigerant, in which the at least one Input size is used, delivers better and more accurate results. Consequently, the amount of refrigerant can be estimated with a particularly high level of accuracy using the method in which the model size is compared with the measured value.

The actual amount of refrigerant is not directly estimated based on the input variables, but rather the model size is first output based on the input variables. And only then will The actual amount of refrigerant is estimated by comparing the model size with the measured temperature. Based on the input variables, only the temperature is determined directly as a model variable, and the actual amount of refrigerant is then indirectly determined via this model variable.

The method is based on the idea of creating at least one model for the temperature present at the at least one predetermined point in the refrigerant circuit, which reflects the behavior of the model size for a specific amount of refrigerant. A deviation that occurs during operation of the refrigerant circuit between the measured temperature and the model size predicted by the model can then be used to estimate the amount of refrigerant.

In this context, it has been found that the at least one model variable in the form of the temperature of the refrigerant at the at least one predetermined location of the refrigerant circuit, in particular using a correlation, can be used very well to determine the total amount of refrigerant actually present in the refrigerant circuit. Since the temperature of the refrigerant present at the at least one predetermined point can be measured very easily, the estimation of the amount of refrigerant can be carried out easily and effectively based on the comparison of the at least one model variable with the measured value. In this way, reliable information about the actual or current refrigerant level of the refrigerant circuit can be obtained during ongoing operation of the refrigerant circuit.

Accordingly, if the amount of refrigerant actually present deviates from the amount of refrigerant intended for the refrigerant circuit, measures can be taken very easily and with little effort to ensure that the amount of refrigerant intended for this is set in the refrigerant circuit. Such measures may include, for example, compensating for a lack of refrigerant or reducing the amount of refrigerant in the event that there is an excess of refrigerant in the refrigerant circuit.

The method is particularly suitable for determining the amount of refrigerant in the refrigerant circuit if the refrigerant circuit includes a refrigerant collector. In such a refrigerant circuit having the refrigerant collector, determining the amount of refrigerant is usually difficult, in particular because a level of refrigerant in the refrigerant collector cannot easily be measured directly. In the present case, however, these difficulties have been resolved in that the amount of refrigerant can be estimated to a minimum amount present based on the comparison of the model size with the measured value.

The refrigerant circuit therefore preferably has a refrigerant collector, wherein the refrigerant collector can be arranged on a high-pressure side of the refrigerant circuit, for example, viewed in the flow direction of the refrigerant through the refrigerant circuit, downstream of the refrigerant cooler, which is in particular designed as a condenser. However, even if the refrigerant collector is arranged on the low-pressure side, i.e. between the at least one evaporator and the suction side of the compressor, the amount of refrigerant can be reliably estimated based on the comparison of the at least one model size with the at least one measured value.

By generating the at least one model, which outputs the at least one model size, for a predetermined or fixed amount of refrigerant, the amount of refrigerant actually present in the refrigerant circuit can be determined or determined with very little effort. This is advantageous.

Since the model only uses the at least one input variable to output or predict the at least one model variable, the model also advantageously does not require any Knowledge of refrigerant circuit design data. Rather, the structural design of the respective refrigerant circuit preferably flows into the model as part of training or training of the model via the input variables present for a respective amount of refrigerant and in the respective operating state of the refrigerant circuit.

Furthermore, teaching or training the model can be carried out very easily and automatically, so that these processes can also be implemented easily and with little effort.

In particular, the model can be used very easily by a control device of the refrigerant circuit, which is preferably provided for controlling components of the refrigerant circuit. This allows the amount of refrigerant actually present in the refrigerant circuit to be estimated during operation and in real time using this control device or this control unit.

Predicting the at least one model size in the form of the temperature of the refrigerant at the at least one predetermined location of the refrigerant circuit by using the model and also comparing the model size with the measured value can be carried out in an advantageous manner with very little computational effort. This computing effort can easily be managed with the computing power resources available in the control device or the control device. This is also advantageous in terms of a simple and low-cost implementation of the method.

Preferably, the model outputs as the at least one model variable a temperature of the refrigerant at a point in the refrigerant circuit arranged upstream of the compressor and downstream of the at least one evaporator. It has been shown that a difference between the predicted or output temperature from the model and the actual or measured temperature of the refrigerant upstream of the compressor provides a very good indication of the actual and total amount of refrigerant present in the refrigerant circuit. By creating the temperature model for the refrigerant in front of the compressor or upstream of the compressor with a specific amount of refrigerant present in the refrigerant circuit, the model can predict or output the model size that can be used for the comparison. And the temperature of the refrigerant upstream of the compressor is advantageously usable for accurately determining the actual amount of refrigerant.

Additionally or alternatively, a temperature of the refrigerant at a point in the refrigerant circuit arranged downstream of the refrigerant cooler and upstream of the at least one expansion element can be output by the model as the at least one model variable. The difference between the modeled temperature, i.e. the model size output by the model, and the measured temperature of the refrigerant downstream of the refrigerant cooler, which is in particular designed as a condenser, can also be used very well to determine the total temperature present in the refrigerant circuit, in particular based on a correlation Close refrigerant quantity.

In particular, if both the temperature of the refrigerant upstream of the compressor and the temperature of the refrigerant downstream of the refrigerant cooler are used as respective model variables, which are compared with respective measured values, a particularly reliable estimate of the actual value can be obtained by comparing the model variables with the measured values Realize the amount of refrigerant available in the refrigerant circuit.

Preferably, the model outputs the at least one model size based on a predetermined amount of refrigerant. Accordingly, the model can output the at least one model size based on the fixed or predetermined amount of refrigerant or at the at least one predetermined location of the Predict the temperature of the refrigerant present in the refrigerant circuit. By using the specified amount of refrigerant when predicting the at least one model size, the amount of refrigerant actually present in the refrigerant circuit can be inferred very well and easily based on a deviation between the model size and the measured value.

Preferably, if the measured value of the temperature is greater than the model size output by the model based on the predetermined amount of refrigerant, it is concluded that the amount of refrigerant actually present in the refrigerant circuit is less than the amount of refrigerant on which the model is based. In this constellation it can be assumed that there is a lack of refrigerant, which manifests itself in the higher measured temperature compared to the predicted temperature in the form of the model size. Therefore, very reliable statements can be made about the amount of refrigerant actually present in the refrigerant circuit.

This is based on the knowledge that, for example, due to a loss of refrigerant in the refrigerant circuit, i.e. when the amount of refrigerant present in the refrigerant circuit is less than the amount of refrigerant intended for this refrigerant circuit, less refrigerant is delivered by the compressor to the at least one evaporator becomes. This in turn means that the cooling capacity provided by the at least one evaporator, in particular a blow-out temperature of air passed over the evaporator or an ability of the evaporator to absorb heat from a coolant flow, is lower than a cooling capacity to be provided or requested.

If, on the other hand, the predetermined amount of refrigerant is present in the refrigerant circuit, such a reduced cooling capacity of the at least one evaporator can be counteracted by the compressor delivering more refrigerant to the at least one evaporator. However, if overall there is too little refrigerant in the refrigerant circuit is present, even an increase in the current delivery capacity of the compressor does not lead to a corresponding increase in the cooling capacity of the evaporator.

Preferably, if the measured value of the temperature is smaller than the model size output by the model based on the predetermined amount of refrigerant, it is concluded that the amount of refrigerant actually present in the refrigerant circuit is larger than the amount of refrigerant on which the model is based.

If there is actually more refrigerant in the refrigerant circuit than was originally used for the model forecast, i.e. for the output of the model size by the model, the situation may arise in which the measured temperature is smaller than that provided by the model Model size issued based on the specified amount of refrigerant. Therefore, the corresponding conclusion reflects the conditions in the refrigerant circuit very well with regard to the amount of refrigerant actually present.

Preferably, the at least one input variable is supplied to a plurality of models, with the respective models outputting the model size based on predetermined quantities of refrigerant that are different from one another. The amount of refrigerant actually present in the refrigerant circuit is estimated taking into account the model sizes output by the respective models. By using several models to output the predicted refrigerant temperature, i.e. the respective model sizes, for several predetermined refrigerant quantities, a particularly precise statement can be made about the actual refrigerant quantity present.

Taking into account the extent of the deviation between the model size and the measured value, one can point to a difference between the predetermined or fixed value on which the model is based The amount of refrigerant and the amount of refrigerant actually present in the refrigerant circuit can be inferred. In this way, it is not only possible to make a qualitative statement as to whether the amount of refrigerant actually present in the refrigerant circuit is larger or smaller than the amount of refrigerant on which the model is based. Rather, a quantitative statement can be made about the amount of refrigerant actually present in the refrigerant circuit. This is advantageous with regard to taking measures to remedy any lack of refrigerant or any loss of refrigerant that occurs or if the refrigerant circuit is overfilled with refrigerant.

In particular, a classification of the amount of refrigerant actually present in the refrigerant circuit can be carried out by establishing a reference to the predetermined amounts of refrigerant for which the respective models have been trained. For example, a result of the classification may say that the amount of refrigerant actually present in the refrigerant circuit is OK or not OK.

In addition, a particularly reliable quantitative statement regarding the actual amount of refrigerant can be made. A corresponding quantification can be carried out, for example, by interpolating the result of the classification using the specified refrigerant quantities.

To estimate the amount of refrigerant actually present in the refrigerant circuit, deviations of the model variables output by the respective models from the measured value are compared with table values. By providing a corresponding logic table, the amount of refrigerant actually present in the refrigerant circuit can be determined very precisely and reliably. In addition, such a logic table, in which the table values are stored, can be implemented very easily in the control device, which outputs the at least one model variable using the at least one model. For the To determine the actual amount of refrigerant present, a linear or non-linear interpolation can be carried out based on the table values.

Preferably, a neural network is used to output the at least one model variable, to which the at least one input variable for the fixed or predetermined amount of refrigerant is supplied as training data before outputting the at least one model variable. Such a neural network can be implemented very easily and with little effort and requires particularly little computing power in the control device. This makes it very easy to calculate the amount of refrigerant actually present in the refrigerant circuit, even with comparatively limited resources in terms of computing power, as can occur with the control device used to control components of the refrigerant circuit.

Simulation data and/or data obtained on a test stand and/or data obtained in a ferry operation of the motor vehicle equipped with the refrigerant circuit during operation of the refrigerant circuit can be used as training data. In addition or as an alternative to such data-based models, it can be provided that the models are of an analytical nature, i.e., for example, further data are derived from existing data, whereby the existing data and/or the derived data can be supplied to the model as training data.

In particular, by using the neural network to output the at least one model variable, a particularly high forecast quality can be achieved.

By supplying the training data to the neural network, the model can be trained, and the trained model can then be used to calculate or determine an estimate of the amount of refrigerant actually present in the refrigerant circuit. A calculation algorithm of the neural network, which can be used to output the at least one model variable, can be very easily implemented in the control device as software. The neural network can be trained or trained for the respective refrigerant circuit, in particular in the course of software development for the devices used in the motor vehicle.

Preferably, a lookup table is used to provide at least one activation function of at least one neuron of the neural network. The use of the at least one look-up table for providing the at least one activation function, in particular jump function, of the at least one neuron of the neural network ensures a particularly low amount of computing effort, which has to be applied by the control device using the neural network in order to to output at least one model size. This is advantageous.

To output the at least one model variable, a polynomial model can be used in addition or as an alternative to the neural network, for example by subjecting data acquired via simulation or during operation of the refrigerant circuit to a regression analysis in order, for example, to obtain at least one polynomial function of the system behavior to be predicted. The at least one model size can also be output using such a polynomial model in order to then estimate the actual amount of refrigerant based on the comparison of the model size with the measured value.

Preferably, an ambient temperature and/or a current delivery rate, such as a speed of the compressor and/or a pressure of the refrigerant present on the suction side of the compressor, is supplied to the model as the at least one input variable associated with the operation of the refrigerant circuit. It turned out that based on such input variables it was very simple and the temperature of the refrigerant at the predetermined location can be reliably output by the model as a predicted model variable. In addition, such input variables are available in the operation of the refrigerant circuit with little effort, so that their use by the model is particularly favorable.

Preferably, the estimation of the amount of refrigerant is carried out based on the comparison of the model size with the measured value by a control device of the refrigerant circuit. The control device preferably controls at least one component of the refrigerant circuit during operation of the refrigerant circuit. If the control device, which is to be provided anyway to control the at least one component of the refrigerant circuit, is also used to estimate the amount of refrigerant, the method can be implemented with particularly little effort.

In particular, the control device can control, as the at least one component, the compressor of the refrigerant circuit and/or the at least one expansion element and/or at least one fan or similar units that can be used in the operation of the refrigerant circuit.

The motor vehicle according to the invention comprises a refrigerant circuit. By means of a compressor of the refrigerant circuit, compressed refrigerant can be supplied to at least one refrigerant cooler of the refrigerant circuit. Refrigerant coming from the refrigerant cooler can be expanded by means of at least one expansion element of the refrigerant circuit. The expanded refrigerant can be fed to at least one evaporator of the refrigerant circuit. Refrigerant coming from the at least one evaporator can be fed to a suction side of the compressor.

At least one input variable associated with operation of the refrigerant circuit can be fed to a model, the model being usable by a control device of the refrigerant circuit. The model is designed to output at least one model size, the at least one model size for determining a in the refrigerant circuit existing amount of refrigerant can be used. The model is designed to output a temperature of the refrigerant at a predetermined point in the refrigerant circuit as the at least one model variable. The control device is designed to compare the model size with a measured value of the temperature of the refrigerant recorded at the predetermined location of the refrigerant circuit and to estimate the amount of refrigerant present in the refrigerant circuit based on the comparison of the model size with the measured value.

By means of the control device, the amount of refrigerant actually present in the refrigerant circuit can be estimated with a particularly high degree of accuracy. Accordingly, the motor vehicle having the refrigerant circuit and the control device is designed to carry out the method according to the invention.

The advantages and preferred embodiments described for the method according to the invention also apply to the motor vehicle according to the invention and vice versa.

The invention therefore also includes further developments of the motor vehicle according to the invention, which have features as have already been described in connection with the further developments of the method according to the invention. For this reason, the corresponding developments of the motor vehicle according to the invention are not described again here.

The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus.

For use cases or application situations that may arise from the method and which are not explicitly described here, it can be provided that an error message is output according to the method. The invention also includes the control device for the motor vehicle. The control device can have a data processing device or a processor device that is set up to carry out an embodiment of the method according to the invention. For this purpose, the processor device can have at least one microprocessor and/or at least one microcontroller and/or at least one FPGA (Field Programmable Gate Array) and/or at least one DSP (Digital Signal Processor). Furthermore, the processor device can have program code that is designed to carry out the embodiment of the method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device.

As a further solution, the invention also includes a computer-readable storage medium comprising instructions which, when executed by a computer or a computer network, cause it to carry out an embodiment of the method according to the invention. The storage medium can, for example, be designed at least partially as a non-volatile data storage (e.g. as a flash memory and/or as an SSD - solid state drive) and/or at least partially as a volatile data storage (e.g. as a RAM - random access memory). . The computer or computer network can provide a processor circuit with at least one microprocessor. The instructions may be provided as binary code or assembler and/or as source code of a programming language (e.g. C).

The invention also includes the combinations of the features of the described embodiments. The invention therefore also includes implementations that each have a combination of the features of several of the described embodiments, provided that the embodiments have not been described as mutually exclusive. Examples of embodiments of the invention are described below. This shows:

Fig. 1 shows a highly schematized motor vehicle with a refrigerant circuit; and

Fig. 2 shows schematically the use of a neural network to determine the amount of refrigerant actually present in the refrigerant circuit.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and which also further develop the invention independently of one another. Therefore, the disclosure is intended to include combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.

In the figures, the same reference numerals designate functionally identical elements.

1 shows schematically a motor vehicle 10 with a refrigerant circuit 12, which is also shown only very schematically in FIG. The refrigerant circuit 12 includes a compressor 14, which compresses sucked-in refrigerant and supplies it to a refrigerant cooler 16, which can be designed, for example, as a condenser. During operation of the refrigerant circuit 12, the refrigerant is cooled in the refrigerant cooler 16, for example by means of air from an environment 18 of the motor vehicle 10. A refrigerant collector 20 is preferably arranged in the refrigerant circuit 12, which in the present case is integrated into the refrigerant circuit 12 on the high pressure side, i.e. is arranged upstream of an expansion element 22 of the refrigerant circuit 12. The refrigerant collector 20 can be integrated into the refrigerant cooler 16, for example.

The refrigerant expanded by means of the expansion element 22 is supplied to an evaporator 24 of the refrigerant circuit 12. Air flowing over the evaporator 24 can be cooled by the evaporating refrigerant absorbing heat from the air. The cooled air can then be introduced into a passenger compartment 26 of the motor vehicle 10, which is only indicated schematically here.

The refrigerant circuit 12 can, in addition to or as an alternative to the evaporator 24 shown schematically here, comprise an evaporator designed as a so-called chiller and having a further expansion element (not shown), by means of which a coolant flow can be cooled due to the evaporation of the refrigerant. The coolant cooled by the chiller can be used in particular to cool an electrical energy storage device (not shown) of the motor vehicle 10.

The refrigerant coming from the at least one evaporator 24 is fed back to a suction side 28 of the compressor 14 during operation of the refrigerant circuit 12.

A control device 30 provided for controlling components of the refrigerant circuit 12 is indicated schematically in FIG. 1. For example, a speed of the compressor 14 and thus a current delivery capacity of the compressor 14 can be specified by means of the control device 30. Furthermore, it is preferably possible to control the at least one expansion element 22 of the refrigerant circuit 12 by means of the control device 30, for example to cause the expansion element 22 to open and close or an opening width of the expansion element 22. Additionally or alternatively, it can be provided that the control device 30 controls a fan (not shown) assigned to the capacitor 16, for example specifies a speed of the fan. Corresponding modules 58, for example implemented in the control device 30, in particular software modules, which serve to control such components of the refrigerant circuit 12, are indicated schematically in FIG. 2.

In particular, in the case of the refrigerant circuit 12 shown here as an example and having the refrigerant collector 20, it proves to be difficult to determine the amount of refrigerant present in the refrigerant circuit 12. For this purpose, an indirect and model-based estimate of the amount of refrigerant is carried out here.

For this purpose, input variables 34 are supplied to at least one model 32 implemented in the control device 30 (see FIG. 2). The model 32 then outputs at least a model size 36. The model size 36 is compared with a measurement of 38. Based on this comparison 40, the amount of refrigerant 42 actually present in the refrigerant circuit 12 is estimated by the method implemented in the control device 30 or in such a control device (see FIG. 2).

In the indirect approach used here, the model 32 does not directly output the actual amount of refrigerant 42, but rather the model size 36, which is a size that can be measured during normal operation of the refrigerant circuit 12. The at least one model 32 is created for this at least one model size 36. A deviation of the measured variable, i.e. the measured value 38, from the model variable 36 predicted by the model 32 that occurs during normal operation of the refrigerant circuit 12 is used to make an estimate of the amount of refrigerant 42 actually present in the refrigerant circuit 12. It has been found that, for example, a temperature of the refrigerant upstream of the compressor 14 can be output as the at least one model size 36. The corresponding measured value 38 of the temperature present at such a predetermined point of the refrigerant circuit 12 can be measured, for example, by means of a first temperature sensor 44 of the refrigerant circuit 12, which is shown schematically in FIG. 1. If the model size 36 is now compared with the measured value 38, for example in the form of the temperature detected by the temperature sensor 44 upstream of the compressor 14, the amount of refrigerant 42 can be estimated based on this comparison 40.

Additionally or alternatively, a temperature of the refrigerant downstream of the refrigerant cooler 16 and thus upstream of the expansion element 22 can be output by the at least one model 32 as the at least one model size 36. The temperature of the refrigerant actually present at this predetermined point of the refrigerant circuit 12 can be measured by means of a further or second temperature sensor 46 of the refrigerant circuit 12, which is also shown schematically in FIG. 1. This further temperature sensor 46 then delivers the measured value 38, which is compared with the model size 36 or is subjected to the comparison 40 (see FIG. 2).

It has been found that, in particular, both the difference between the model size 36 and the measured value 38 of the temperature of the refrigerant before the compressor 14 and the temperature difference between the predicted model size 36 and the actual, measured measured value 38 of the temperature of the refrigerant after, in particular designed as a condenser, refrigerant cooler 16 can be used very well to draw conclusions about the total amount of refrigerant 42 actually present in the refrigerant circuit 12. Because these differences correlate with a difference between the amount of refrigerant on which the model 32 is based and the amount of refrigerant 42 actually present in the refrigerant circuit 12. The temperature is forecast in an advantageous manner, i.e. the model size 36 is output. based on the input variables 34 during ongoing operation of the refrigerant circuit 12.

In addition or as an alternative to using the model size 36 and the measured value 38 of the temperature, it is conceivable to use at least one other value to estimate the amount of refrigerant 42 actually present in the refrigerant circuit 12, which can be predicted on the one hand by means of the at least one model 32 and on the other hand by measurement technology is detectable. For example, this at least one other value can be a pressure prevailing at at least one predetermined point in the refrigerant circuit 12.

The at least one model 32 can be implemented in the control device or in the control device 30 in order to output the at least one model size 36. In the present case, the at least one model 32 and an algorithm for carrying out the comparison 40 are implemented in the control device 30 (see FIG. 2).

The result of the comparison 40, i.e. the estimate of the amount of refrigerant 42 present in the refrigerant circuit 12, can be used by the control device 30 to trigger at least one reaction, in particular in the event of a lack of refrigerant. For example, the at least one reaction may consist of issuing a warning to a user of the motor vehicle 10 and/or switching off the compressor 14.

The at least one model size 36 is output from the respective model 32, preferably based on a predetermined amount of refrigerant. In other words, each of the models 32 is preferably based on a different amount of refrigerant, and the respective model size 36 is output based on this assumed or predetermined amount of refrigerant. For example, a first model 32 can output the model size 36 based on a fixed or predetermined amount of refrigerant, which is compared with the measured value 38 of the temperature upstream of the compressor 14. A further or second model 32 can output the predicted temperature downstream of the refrigerant cooler 16 as the model size 36, the second model 32 also being based on a predetermined amount of refrigerant (for training the model 32).

By using respective temperature models for outputting the respective model size 36, a particularly high level of reliability can be achieved when estimating the actual amount of refrigerant 42. The temperature models can accordingly output the temperature of the refrigerant before the compressor 14 or after the refrigerant cooler 16 or condenser as the respective model variables 36 and can each be created for a constant or fixed amount of refrigerant and the resulting operating behavior of the refrigerant circuit 12.

To output the at least one model size 36, in particular a neural network 48 can be used (see FIG. 2), which can be implemented in the control device 30 and which, according to the schematic representation in FIG. 2, can have a plurality of neurons 50. This neural network 48 can be supplied as the input variables 34, for example, an ambient temperature, that is to say a temperature present in the environment 18 of the motor vehicle 10, a current delivery rate of the compressor 14 and a pressure of the refrigerant present on the suction side 28 of the compressor 14.

For example, a speed of the compressor 14 can be used by the control device 30 in order to use the current delivery capacity of the compressor 14 as one of these input variables 34. The ambient temperature can be detected by means of a temperature sensor 52 of the refrigerant circuit 12, shown schematically in FIG. 1, which For example, can detect the temperature of the supply air or ambient air, which is supplied to the refrigerant cooler 16. To detect the suction pressure, i.e. the pressure of the refrigerant present on the suction side 28 of the compressor 14 in the refrigerant circuit 12, a pressure sensor 54 of the refrigerant circuit 12, shown schematically in FIG. 1, can be used, which is arranged upstream of the compressor 14.

From such input variables 34, the model 32 in the present case predicts, in particular using the neural network 48, the at least one model variable 36, for example the temperature of the refrigerant upstream of the compressor 14 and/or the temperature of the refrigerant downstream of the refrigerant cooler 16, each in one of the models 32 underlying, predetermined or fixed amount of refrigerant.

For this purpose, the at least one model 32 was trained with training data 56 in a preceding training phase. Accordingly, the aforementioned input variables 34 and the predetermined amount of refrigerant can be supplied to the respective model 32 as the training data 56. The at least one trained model 32 then outputs the at least one model size 36, which is compared with the respective measured value 38.

It can happen that the amount of refrigerant 42 actually present in the refrigerant circuit 12 is larger than the predetermined amount of refrigerant on which the model size 36 is issued. If this amount of refrigerant 42 actually present in the refrigerant circuit 12 is larger than the amount of refrigerant assumed by the model 32 for which the model 32 was trained, then the actually measured temperature of the refrigerant, for example the temperature of the refrigerant upstream of the compressor 14, also falls The measured value 38 is therefore smaller than the temperature predicted by the model in the form of the model size 36.

In contrast, the amount of refrigerant 42 actually present in the refrigerant circuit 12 is smaller than the amount of refrigerant that is Model 32 assumes and for which it was trained, then the actually measured temperature, i.e. the measured value 38, is larger than the model size 36 predicted by the model 32. These relationships apply both to the temperature of the refrigerant in front of the compressor, which is determined by means of the first temperature sensor 44 of the refrigerant circuit 12 is detected, as well as for the temperature of the refrigerant downstream of the refrigerant cooler 16, which in the present case is detected by means of the second temperature sensor 46 of the refrigerant circuit 12.

The model 32 for the refrigerant temperature after the refrigerant cooler 16 can be used alone or in combination with the model 32 for the refrigerant temperature upstream of the compressor 14 to gain knowledge about the amount of refrigerant 42 actually present in the refrigerant circuit 12. In the present case, only one of these models 32 is shown in FIG. 2 for reasons of clarity.

The greater the deviation between the model prediction (i.e. the at least one model size 36) and the measured temperature (i.e. the measured value 38), the greater the difference between the amount of refrigerant assumed by the at least one model 32 or the amount of refrigerant on which the at least one model 32 is based and the amount of refrigerant 42 actually present in the refrigerant circuit 12. Accordingly, not only a qualitative statement is possible, but also a quantitative statement about the amount of refrigerant 42 actually present in the refrigerant circuit 12.

A particularly precise statement can be made if several models 32 are used to output the respective model sizes 36 in the form of the predicted refrigerant temperatures with different or different refrigerant quantities assumed, predetermined or fixed during training of the respective model 32. This allows a classification of the actual amount of refrigerant 42 to be achieved in relation to the amounts of refrigerant for which the models 32 used have been trained. 2, the calculation of the estimated value for the current or actual refrigerant quantity 42 or filling quantity is carried out using the neural network 48. The neural network 48 can be trained for each type of motor vehicle 10 or for each type of refrigerant circuit 12 installed in the motor vehicle 10, for example during software development of other devices in the motor vehicle 10.

As indicated schematically in FIG. 2, a corresponding calculation algorithm of the neural network 48 can be implemented in software of the control device or the control device 30.

Furthermore, jump functions or activation functions of the respective neurons 50 present in the neural network 48 can be stored in look-up tables for calculation in the control device 30. In this way, calculating or estimating the actual amount of refrigerant 42 is easily possible even with comparatively limited resources in terms of computing power, as may be present in the control device 30.

Overall, the examples show how an improved model-based estimate of the amount of refrigerant 42 in the refrigerant circuit 12 or a corresponding refrigerant system can be provided.

Claims

PATENT CLAIMS: Method for determining a quantity of refrigerant (42) in a refrigerant circuit (12) of a motor vehicle (10), in which a compressor (14) of the refrigerant circuit (12) supplies compressed refrigerant to at least one refrigerant cooler (16) of the refrigerant circuit (12). to which refrigerant coming from the refrigerant cooler (16) is expanded by means of at least one expansion element (22) of the refrigerant circuit (12), the expanded refrigerant being fed to at least one evaporator (24) of the refrigerant circuit (12), from which at least one evaporator ( 24) coming from refrigerant is supplied to a suction side (28) of the compressor (14), and in which at least one input variable (34) associated with operation of the refrigerant circuit (12) is supplied to a model (32) which has at least one model variable (36), wherein the at least one model variable (36) is used to determine the amount of refrigerant (42), characterized in that the at least one model variable (36) of the model (32) is a temperature of the refrigerant at a predetermined location of the refrigerant circuit (12), wherein the model size (32) is compared with a measured value (38) of the temperature of the refrigerant recorded at the predetermined location of the refrigerant circuit (12), and based on the comparison (40) of the model size (36 ) the amount of refrigerant (42) is estimated using the measured value (38). Method according to claim 1, characterized in that of the model (32) as the at least one model variable (36) a temperature of the refrigerant at a point of the refrigerant circuit (12) arranged upstream of the compressor (14) and downstream of the at least one evaporator (24). ) and / or a temperature of the refrigerant at a downstream of the refrigerant cooler (16) and upstream of the at least one Expansion element (22) arranged point of the refrigerant circuit (12) is output. Method according to one of the preceding claims, characterized in that the at least one model size (36) is output from the model (32) based on a predetermined amount of refrigerant. Method according to claim 3, characterized in that if the measured value (38) of the temperature is greater than the model size (36) output by the model (32) based on the predetermined amount of refrigerant, it is concluded that the temperature is actually in the refrigerant circuit (12) existing amount of refrigerant (42) is less than the amount of refrigerant on which the model (32) is based, and when the measured value (38) of the temperature is smaller than the model size output by the model (32) based on the predetermined amount of refrigerant (36), it is concluded that the amount of refrigerant (42) actually present in the refrigerant circuit (12) is larger than the amount of refrigerant on which the model (32) is based. Method according to claim 3 or 4, characterized in that the at least one input variable (34) is supplied to a plurality of models (32), the respective models (32) outputting the model variable (36) based on predetermined quantities of refrigerant that are different from one another, wherein the amount of refrigerant (42) actually present in the refrigerant circuit (12) is estimated taking into account the model variables (36) output by the respective models (32). Method according to one of claims 3 to 5, characterized in that a neural network (48) is used to output the at least one model variable (36), to which the at least one input variable (34) is added before the at least one model variable (36) is output the specified amount of refrigerant is supplied as training data (56). Method according to claim 5 or 6, characterized in that in order to estimate the amount of refrigerant (42) actually present in the refrigerant circuit (12), deviations of the model variables (36) output by the respective models (32) from the measured value (38) are compared with table values , and / or a lookup table is used to provide at least one activation function of at least one neuron (50) of the neural network (48). Method according to one of the preceding claims, characterized in that the model (32) is provided with an ambient temperature and/or a current delivery capacity of the compressor (14) as the at least one input variable (34) associated with the operation of the refrigerant circuit (12) and/or or a pressure of the refrigerant present on the suction side (28) of the compressor (14) is supplied. Method according to one of the preceding claims, characterized in that the estimation of the amount of refrigerant (42) is carried out based on the comparison (40) of the model size (36) with the measured value (38) by a control device (30) of the refrigerant circuit (12), which controls at least one component of the refrigerant circuit (12) during operation of the refrigerant circuit (12). Motor vehicle with a refrigerant circuit (12), wherein compressed refrigerant can be supplied to at least one refrigerant cooler (16) of the refrigerant circuit (12) by means of a compressor (14) of the refrigerant circuit (12), wherein refrigerant coming from the refrigerant cooler (16) is supplied by means of at least one expansion element (22) of the refrigerant circuit (12) can be expanded, the expanded refrigerant being able to be supplied to at least one evaporator (24) of the refrigerant circuit (12), and refrigerant coming from the at least one evaporator (24) to a suction side (28) of the compressor (14 ) can be supplied, wherein at least one input variable (34) associated with an operation of the refrigerant circuit (12) can be supplied to a model (32) usable by a control device (30) of the refrigerant circuit (12), the model (32) being designed for this purpose is to output at least one model size (36), and wherein the at least one model size (36) can be used to determine a quantity of refrigerant (42) present in the refrigerant circuit (12), characterized in that the model (32) is designed to: as the at least one model variable (36) to output a temperature of the refrigerant at a predetermined location of the refrigerant circuit (12), the control device (30) being designed to detect the model variable (36) with a temperature detected at the predetermined location of the refrigerant circuit (12). To compare the measured value (38) of the temperature of the refrigerant and to estimate the amount of refrigerant (42) present in the refrigerant circuit (12) based on the comparison (40) of the model size (36) with the measured value (38).