METHOD FOR OPERATING A REFRIGERATION APPLIANCE AND REFRIGERATION APPLIANCE

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 10 2024 203 025.2, filed Apr. 2, 2024; the prior application is herewith incorporated by reference in its entirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a method for operating a refrigeration appliance having a plurality of storage compartments and a compressor with an adjustable conveying capacity, wherein the refrigeration requirements of the storage compartments are prioritized with one priority in each case.

European Patent EP 1 398 584 B1, corresponding to U.S. Patent No. 7,100,387 B2, describes a refrigeration appliance with two storage compartments and with a prioritization of the refrigeration requirements of the storage compartments.

U.S. Publication No. 2008/0195256 A discloses a refrigeration appliance with a plurality of storage compartments and an air circuit, wherein refrigeration requirements of the storage compartments are prioritized.

Japanese Application JP 2018 138 827 A presents a refrigeration appliance with a plurality of storage compartments, the evaporator of which can be simultaneously supplied with a refrigerant, with a prioritization of the refrigeration requirements of the storage compartments.

Chinese Application CN 113 340 048 A discloses a refrigeration appliance, wherein first a freezer compartment is cooled and subsequently further storage compartments are cooled according to a prioritization.

Conventional closed-loop control concepts for refrigeration appliances with a plurality of cooling and freezing compartments are based on an intermittent compressor operation. Furthermore, when storage compartments that cannot be supplied simultaneously require simultaneous refrigeration, a time-controlled switch-over is used. This only insufficiently reflects the actual prevailing priorities and urgencies of the supply to storage compartments.

It is of interest to simultaneously control in a closed-loop manner the temperature of a plurality of storage compartments within the permissible closed-loop control deviation in the case of a refrigeration appliance with a plurality of cooling and freezing compartments, which are supplied with refrigeration capacity by a common compressor.

It is also of interest to operate the compressor continuously wherever possible in order to achieve a high level of energy efficiency.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a method for operating a refrigeration appliance and a refrigeration appliance, which overcome the hereinafore-mentioned disadvantages of the heretofore-known appliances and methods of this general type and which create an improved simultaneous closed-loop control of the temperature of a plurality of storage compartments of a refrigeration appliance with a compressor with variable conveying capacity.

With the foregoing and other objects in view there is provided, in accordance with the invention, a method for controlling a refrigeration appliance with a plurality of storage compartments which are each assigned a desired temperature and a temperature sensor for measuring an actual temperature of the storage compartment, wherein a main storage compartment is determined by a maximum heat intake of all the storage compartments, first auxiliary storage compartments can be cooled simultaneously with the main storage compartment, a refrigerant circuit has a compressor with an adjustable conveying capacity, a condenser, and at least one evaporator, and a control unit has a closed-loop controller for the closed-loop control of the conveying capacity, each storage compartment is allocated a switch-on temperature and a switch-off temperature in addition to the desired temperature, the refrigerant circuit has actuators so as to guide refrigerant and/or an air circuit has actuators so as to guide cold air, a check is performed for each storage compartment as to whether the storage compartment has a refrigeration requirement, and the control unit actuates the compressor and the actuators so as to supply storage compartments, which can be cooled simultaneously, with a refrigeration requirement.

The invention is based on the observation that refrigeration appliances, even those with a compressor with variable conveying capacity, are usually operated with an intermittent compressor operation, although a continuous operation is technically possible in a wide and relevant ambient temperature range, typically above approx. 25° C. An improved energy efficiency can be achieved when the refrigeration appliance is operated continuously wherever possible.

A further observation is that refrigeration appliances with a plurality of storage compartments with dedicated evaporators, even those with a compressor with variable conveying capacity, are usually operated in such a manner that the evaporator and consequently its storage compartments are cooled one after the other.

A configuration of the refrigeration circuit is typically such that certain combinations of storage compartments can be supplied simultaneously, whereas other combinations of storage compartments are excluded from being supplied simultaneously. In order to supply all the storage compartments, switch-over facilities are provided, such as for example switch-over valves in the refrigeration circuit and flaps in the air path. The provision of these switch-over devices and the guiding of the refrigerant and air in the appliance create the combinations of storage compartments which can be supplied simultaneously.

One example of a combination of storage compartments which cannot be supplied simultaneously is a refrigerant circuit with a two-way valve which respectively opens one branch in the refrigerant circuit and closes the other. If the directional valve is replaced by two stop valves, each branch can be opened and closed independently from the other and it is thus also possible to simultaneously supply storage compartments in both branches.

The storage compartment with the largest average refrigeration capacity need is referred to below as the main storage compartment.

Switch-over facilities can provide a configuration in the refrigeration appliance so that only the main storage compartment, typically and used here in the examples a freezer compartment, can be supplied.

All further storage compartments are referred to as auxiliary storage compartments, wherein first auxiliary storage compartments can be cooled simultaneously with the main storage compartment. Optional auxiliary storage compartments which cannot be cooled simultaneously with the main storage compartment are referred to as second auxiliary storage compartments.

The method in accordance with the invention is used for the control of a refrigeration appliance with a plurality of storage compartments which are each assigned a desired temperature and a temperature sensor for measuring an actual temperature of the storage compartment, wherein the main storage compartment is determined by a maximum heat intake of all the storage compartments. A refrigerant circuit has a compressor with a variable conveying capacity, a condenser, and at least one evaporator. A control unit has a closed-loop controller for the closed-loop control of the conveying capacity of the compressor.

Since it is only possible to generate refrigeration capacity via the compressor, only this has an available cold-generating actuator in order to supply a plurality of storage compartments. The closed-loop control system is thus under-actuated. This means in practice that all the storage compartments cannot be precisely adjusted in a steady-state manner but will always fluctuate around their set point. The fluctuation margins are requirements for the closed-loop control method.

The invention relates to the simultaneous closed-loop control of the temperature of a plurality of storage compartments of a refrigeration appliance, which are supplied with refrigeration capacity by a common compressor. In this case, a compressor with a variable conveying capacity is operated continuously in so far as this is technically possible under the prevailing operating conditions. The storage compartments are assigned different desired temperatures which are achieved or maintained by the simultaneous closed-loop control of the temperature within the permissible closed-loop control deviation.

Each storage compartment is allocated a switch-on temperature and a switch-off temperature in addition to the desired temperature. The refrigerant circuit has actuators for guiding refrigerant and/or an air circuit has actuators for guiding cold air. A check is performed for each storage compartment as to whether the storage compartment has a refrigeration requirement, and the control unit actuates the compressor and the actuators so as to supply storage compartments, which can be cooled simultaneously, with a refrigeration requirement. An average storage compartment temperature close to the desired temperature is thus achieved in each storage compartment.

The desired temperature of a storage compartment corresponds to the purpose of the storage compartment with regard to the chilled goods provided for the storage compartment. The desired temperature can be stored in the electronic system of the appliance or can be determined on a temperature selector which can be adjusted by a user.

Refrigeration appliances with a dedicated evaporator for each storage compartment are controlled by using actuators in the refrigerant circuit. Refrigeration appliances with a common evaporator for a plurality of storage compartments are controlled by using actuators in the air circuit. Mixed forms are also provided.

In accordance with one embodiment of the method, the refrigeration requirements of all the storage compartments are prioritized with one priority each, and a decision regarding the selection of the storage compartments to be cooled is made, when the storage compartment with the highest priority is the main storage compartment or a first auxiliary storage compartment, to cool this storage compartment and storage compartments, which can be cooled simultaneously therewith, with a refrigeration requirement, and when the storage compartment with the highest priority is a second auxiliary storage compartment, to cool this auxiliary storage compartment and auxiliary compartments, which can be cooled simultaneously therewith, with a refrigeration requirement.

These priorities ensure that a storage compartment is supplied in a reliable and needs-based manner, since on the one hand, in the case of groups of storage compartments which cannot be cooled simultaneously, a decision criterion for the selection of the group to be cooled is provided, on the other hand intense warming of the storage compartment is avoided for each storage compartment, and the average desired temperature of each storage compartment is easily maintained.

Another embodiment of the method relates to a refrigeration appliance which only has first auxiliary storage compartments which can be cooled simultaneously with the main storage compartment. Refrigeration requirements of all the storage compartments are also prioritized in this case with one priority each, and a decision regarding the selection of the storage compartments to be cooled is made, when the storage compartment with the highest priority is the main storage compartment, to cool only the main storage compartment, and when the storage compartment with the highest priority is a first auxiliary storage compartment, to cool only this auxiliary storage compartment and, simultaneously therewith, the main storage compartment. This causes the main storage compartment to be prioritized over all auxiliary storage compartments.

This closed-loop control principle can also be applied in an embodiment, in which a refrigeration appliance has first and second auxiliary storage compartments, in a situation in which none of the second auxiliary storage compartments have a refrigeration requirement. Refrigeration requirements of all the storage compartments are also prioritized in this case with one priority each, and a decision regarding the selection of the storage compartments to be cooled is made, when the storage compartment with the highest priority is the main storage compartment, to cool only the main storage compartment, and when the storage compartment with the highest priority is a first auxiliary storage compartment, to cool only this auxiliary storage compartment and, simultaneously therewith, the main storage compartment. This causes the main storage compartment to be prioritized over all first auxiliary storage compartments.

Prioritization is particularly suitable for operating the capacity-controlled compressor continuously wherever possible. The continuous operation renders it possible for a required refrigeration capacity to be provided at any time by determining the closed-loop controlled compressor size. The conveying capacity of the compressor is representative here for the closed-loop controlled compressor size, whether it is, for example, the rotational speed in the case of reciprocating compressors, the stroke in the case of linear compressors or the electrical power consumption. Good energy efficiency is achieved by ensuring that the main storage compartment is closed-loop controlled to its desired temperature for most of the time. First auxiliary compartments can be taken into account simultaneously with an increase in capacity with small fluctuation margins around their desired temperatures. It is then necessary to interrupt the cooling of the main storage compartment and the first auxiliary compartment in order to supply the second auxiliary compartments. The described prioritization ensures then that the second auxiliary compartments are also used sufficiently and that the temperature of the storage compartments not being used, in particular the main storage compartment, does not increase too far above the respective desired temperature.

In accordance with a further embodiment of the invention, each storage compartment is assigned a threshold value temperature and, when an actual temperature is below the threshold value temperature, the priority of the refrigeration requirements of a storage compartment is set to zero. When an actual temperature is above the threshold value temperature, advantageously rises preferably proportionally with the difference between the actual temperature and the threshold value temperature. Setting the priority to zero in a temperature range renders it possible for each storage compartment to have certain temperature fluctuations around the desired temperature of the storage compartment in this temperature range which does not result in a change of the combination of the storage compartments being supplied. Only when the storage compartment temperature falls out of this range is an increasingly urgent refrigeration requirement generated. A low frequency of changes of the combination of the storage compartments being supplied results in a quieter operation of the refrigeration appliance.

In accordance with one embodiment of the method, the threshold value temperature is above the desired temperature of the respective storage compartment and is preferably at least equal to the switch-on temperature of the storage compartment. A storage compartment can as a result only be given precedence when the switch-on temperature of the storage compartment is exceeded. This results in a slight impairment of the supply of the main storage compartment.

In accordance with a further embodiment of the method, the refrigeration requirements and the priorities are evaluated quasi continuously using regular calculation steps for all the storage compartments. As a result, it is possible to react extremely quickly to situations, such as the door being opened or warm items being introduced for storage.

In accordance with another embodiment of the method, the refrigeration requirement of an auxiliary storage compartment is generated when the actual temperature exceeds the switch-on temperature and is cancelled when the actual temperature is below the switch-off temperature.

A switch-on temperature and a switch-off temperature form a temperature range. A switch-on temperature and a switch-off temperature are selected for all the auxiliary compartments in such a manner that the resulting temperature curve meets the requirements with respect to the desired temperature as an average value and a fluctuation margin.

In accordance with one embodiment of the method, a refrigeration requirement is set for the main storage compartment when the actual temperature exceeds the switch-on temperature and is cancelled when the actual temperature is below the switch-off temperature or a refrigeration requirement is constantly set for the main storage compartment. The first alternative renders it possible to treat the main storage compartment as a normal storage compartment. In the second alternative, in the case of the main storage compartment, the switch-on temperature is also used to adjust the fluctuation margin, the switch-off temperature on the other hand is used to adjust the switch-off delay of the compressor in the case of too few refrigeration requirements.

In accordance with one embodiment of the method, the refrigeration need is determined for each storage compartment and the conveying capacity is determined from the refrigeration needs of all the storage compartments. The prevailing total refrigeration need of the refrigeration appliance arises from the sum of the refrigeration needs of all the storage compartments. It is thus possible at any time for the prevailing necessary total refrigeration capacity to be generated precisely by the determined conveying capacity.

This results in an energetic advantage that the efficiency of a refrigeration circuit increases as the pressure ratio between the high pressure side and the low pressure side of the refrigerant circuit reduces. In the case of a given, temporally averaged refrigeration capacity requirement and a fixed throttling device, the smallest also temporally averaged pressure ratio is obtained when the compressor is operating in a continuous steady state, i.e. the conveying capacity of the compressor generates precisely the required refrigeration capacity. Disregarding the dependency of the compressor efficiency on its operating point, the continuous operation of the compressor is therefore always to be aimed for.

Continuous operation of the compressor results in the smallest possible compressor rotational speed, i.e. this is always smaller than each possible compressor rotational speed in the case of an intermittent operation during the service life. A rotational speed that is low and as constant as possible is desirable from an acoustic point of view. The closed-loop control concept in accordance with the invention is therefore advantageous both from the acoustic and also energetic point of view.

The continuous operation of the compressor is achieved using a closed-loop control algorithm that maintains the value, typically a closed-loop controller of the PID type. The input signal of the closed-loop controller for the closed-loop control of the conveying capacity is the closed-loop control error of a storage compartment which is the difference between a storage compartment actual temperature and a storage compartment desired temperature.

The main storage compartment which has the largest the largest steady-state heat intake is selected as the storage compartment which influences the closed-loop controller for the closed-loop control of the conveying capacity. Consequently, this storage compartment dominates the entire refrigeration capacity need of the appliance and thus the conveying capacity of the compressor, in the case of reciprocating compressors, the compressor rotational speed corresponds to the conveying capacity. The closed-loop controller for the closed-loop control of the conveying capacity is thus advantageously always connected to the closed-loop control error of the same storage compartment. This storage compartment is in practice mostly a freezer compartment.

In accordance with another embodiment of the method, the compressor is operated continuously and only switched off if an auxiliary storage compartment does not have a refrigeration requirement, the actual temperature of the main storage compartment is below its switch-off temperature, and preferably in addition a conveying capacity is determined which is smaller than a minimum conveying capacity. As a consequence, the compressor can be operated as far as possible continuously and efficiency losses can be avoided.

In accordance with one embodiment of the method, a storage compartment or a combination of storage compartments has a predetermined minimum supply time. As a result, it is possible to avoid switching too frequently and a basic supply to all storage compartments can be ensured.

In accordance with one embodiment of the method, after the actuators have been switched, auxiliary compartments are cooled as long as there is the appropriate requirement. As a result, a basic supply to all storage compartments can be ensured.

With the objects of the invention in view, there is also provided a refrigeration appliance with a plurality of storage compartments which are each assigned a desired temperature and a temperature sensor for measuring an actual temperature of the storage compartment, a refrigerant circuit which has a compressor with an adjustable conveying capacity, a condenser, and at least one evaporator, an air circuit, and a control unit which has a closed-loop controller for the closed-loop control of the conveying capacity.

The refrigerant circuit has actuators for guiding refrigerant and/or the air circuit has actuators for guiding cold air. A main storage compartment is determined by a maximum heat intake of all the storage compartments. First auxiliary storage compartments can be cooled simultaneously with the main storage compartment, and second auxiliary storage compartments cannot be cooled simultaneously with the main storage compartment. The control unit is configured so as to control the refrigeration appliance in accordance with the method.

The air circuit of an evaporator can be an air circuit of a fin evaporator, with a fan as an actuator. The fin evaporator can supply one or more storage compartments. In the case of a plurality of storage compartments, the air circuit has a plurality of ventilators or a plurality of air flaps as actuators for switching air paths to the plurality of storage compartments.

In accordance with one embodiment of the refrigeration appliance, the refrigerant circuit has a plurality of evaporators of which each is assigned to a storage compartment, the refrigerant circuit has directional valves which as actuators switch refrigerant guide paths to the plurality of evaporators. The valves in a refrigerant circuit are advantageously controlled in accordance with the invention. One example for a second auxiliary storage compartment is a refrigerant circuit with a directional valve which supplies either an evaporator of the main storage compartment or an evaporator of the second auxiliary storage compartment.

In accordance with a further embodiment of the refrigeration appliance, the control unit has electronic closed-loop controllers for each auxiliary storage compartment, which determine the refrigeration requirement of the storage compartment. It is preferred that the electronic closed-loop controller is a two-point closed-loop controller which requests a refrigeration capacity when the switch-on threshold is achieved or exceeded and cancels it when the switch-off threshold is not achieved.

It is preferred that the refrigeration appliance has an ambient temperature sensor. When the refrigeration appliance is in the steady-state status, the heat intake of a storage compartment is dependent upon the ambient temperature. The refrigeration need of a storage compartment can therefore be determined with the aid of this sensor.

In accordance with a further embodiment of the refrigeration appliance, one of the at least one air circuits is assigned to a plurality of storage compartments, and this air circuit has as actuators a fan and air flaps which switch the air paths to the plurality of storage compartments. A further example for a second auxiliary storage compartment is an air circuit for two storage compartments which are supplied by the same evaporator, with an air flap with two stable positions, one for each storage compartment. Configurations of this type are advantageously incorporated in the control.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a method for operating a refrigeration appliance and a refrigeration appliance, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagrammatic, perspective view of a refrigeration appliance in accordance with the invention;

FIG. 2 is a flow diagram of the method in accordance with the invention;

FIG. 3 is a schematic diagram of the priorities of two storage compartments in accordance with the invention; and

FIG. 4 is a further schematic diagram of the priorities of two storage compartments in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a refrigerator as a representative of a refrigeration appliance 10 with an upper storage compartment 12 and a plurality of pull-out storage compartments 14-22. The upper storage compartment 12 is provided as a cooler compartment for fresh food and the lower storage compartment 22 is provided as a freezer compartment for products to be kept frozen. This storage compartment in the steady-state status has the largest heat intake and in this case is the main storage compartment 24. The storage compartment 14 is intended for vegetables and fruit and the storage compartment 16 is a cold storage compartment for meat. The storage compartments 18 and 20 are storage compartments that have a flexible temperature and have a desired temperature which can be adjusted depending upon the application purpose. The storage compartments 14 and 16 have operating and display elements 25 for operating the refrigeration appliance and displaying compartment temperatures, which are connected to a control unit. The storage compartments 12, 14, 16 can be simultaneously cooled with the main storage compartment 24 and form first auxiliary storage compartments 26. The storage compartments 18, 20 cannot be simultaneously cooled with the main storage compartment 24 and form second auxiliary storage compartments 28.

FIG. 2 shows a flow diagram 40 of a method in accordance with the invention for operating the refrigeration appliance 10. The method is based on a switched-on refrigeration appliance 10 with a compressor with controllable rotational speed, wherein the desired temperatures of the storage compartments 12-22 are already determined. The variant is described in which the refrigeration requirement of the main storage compartment is always set.

The method commences in method step 41 with the query as to whether one of the auxiliary storage compartments has a refrigeration requirement. If yes, the method continues in method step 42 with the allocation of priorities to the refrigeration requirements of all the storage compartments. Subsequently, a query is performed in method step 43 as to whether the storage compartment with the highest priority is the main storage compartment or a first auxiliary storage compartment. If yes, the method continues in method step 44 with switching actuators in the refrigerant circuit so as to guide refrigerant and/or actuators in the air circuit so as to guide cold air in order to cool the main storage compartment and the respective first auxiliary storage compartment with a refrigeration requirement. Subsequently, the rotational speed of the compressor is determined in method step 45. The method now starts all over again.

If the query in method step 43 indicates that the storage compartment with the highest priority is neither the main storage compartment nor a first auxiliary storage compartment, then the method continues in method step 46 with switching actuators in the refrigerant circuit so as to guide refrigerant and/or actuators in the air circuit so as to guide cold air in order to cool the respective second auxiliary storage compartment with a refrigeration requirement. Subsequently, the rotational speed of the compressor is determined in method step 45. After that, the method starts all over again.

If the query in method step 41 indicates that none of the auxiliary storage compartments have a refrigeration requirement, the method continues in method step 47 with the query as to whether the main storage compartment has an actual temperature higher than its switch-off temperature. If yes, the method continues in method step 48 with switching actuators in the refrigerant circuit so as to guide refrigerant and/or actuators in the air circuit so as to guide cold air in order to cool the main storage compartment and the respective first auxiliary storage compartment with a refrigeration requirement. The rotational speed of the compressor is subsequently determined in method step 45 and the method then starts all over again.

If the query in method step 47 indicates that the actual temperature in the main storage compartment is not higher than its switch-off temperature, the method continues in method step 49 with switching off the compressor. The method now starts all over again.

FIG. 3 shows in diagram 60 the priorities P of two exemplary storage compartments dependent upon their respective compartment temperature T. The curve of the priority of the first storage compartment in curve 61 is such that the priority is set to zero in the case of temperatures below a threshold value temperature T1, and above the threshold value temperature T1 rises linearly with the temperature. The curve of the priority of the second storage compartment in curve 62 is such that the priority is set to zero in the case of temperatures below a threshold value temperature T2, and above the threshold value temperature T2 rises linearly with the temperature. The prevailing compartment temperatures and associated priorities of the first and second exemplary storage compartment at an assumed first point in time are represented by points 63, 64.

The threshold value temperatures T1, T2 are selected as the switch-on temperatures of the storage compartments. The gradients of the curves 61, 62 correspond to the proportionality factors of the temperature dependencies. The storage compartment represented by the curve 62 has a higher switch-on temperature and a greater proportionality factor than the storage compartment represented by the curve 61. At the point in time under consideration, the first storage compartment in accordance with point 63 has a higher priority than the second storage compartment in accordance with point 64.

FIG. 4 shows in diagram 66 the priorities P of the two exemplary storage compartments from FIG. 3 at an assumed second point in time, wherein the prevailing compartment temperatures and associated priorities of the first and second exemplary storage compartments are represented by points 67, 68. At this point in time, the second storage compartment in accordance with point 68 has a higher priority than the first storage compartment in accordance with point 67, although in the first storage compartment the prevailing temperature in point 67 exceeds the threshold value temperature T1 to a greater extent than the prevailing temperature in point 68 exceeds the threshold value temperature T2. In this situation, the second storage compartment is given precedence due to the greater proportionality factor.

The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention:

• • 10 Refrigeration appliance
  • 12-22 Storage compartment
  • 24 Main storage compartment
  • 25 Operating and display elements
  • 26 First auxiliary storage compartment
  • 28 Second auxiliary storage compartment
  • 40 Flow diagram
  • 41 Query refrigeration requirement
  • 42 Allocation of priorities
  • 43 Storage compartment with the highest priority
  • 44 Switching of actuators
  • 45 Determining the rotational speed of the compressor
  • 46 Switching of actuators
  • 47 Query actual temperature
  • 48 Switching of actuators
  • 49 Switching off the compressor
  • 60 Diagram
  • 61, 62 Curve
  • 63, 64 Point
  • 66 Diagram
  • 67, 68 Plate evaporator