REFRIGERATOR AND METHOD FOR CONTROLLING THE TEMPERATURE THEREOF
The present invention is related to the control of temperature in refrigeration systems, more specifically to domestic refrigerators. Such systems normally comprise a compartment and a cooling system including an evaporator, a condenser, and a compressor. Modern refrigerators often include multiple compartments set at different target temperatures for storing different items, either to keep such items refrigerated at a temperature usually lower than ambient temperature, or to keep frozen goods.
Considering the complexity of having different temperature targets in multiple compartment refrigerators, there is an increasing need of developing more precise temperature controls, which will keep the temperature stable and as close as possible to the target temperature for the compartment.
There are many known methods to control the temperature in a refrigerator compartment, one of which comprises controlling the operation of actuators, such as dampers, heaters, fans, compressors and others. A temperature control may operate the actuators separately or in a combined way, based usually on the temperature measured inside the refrigerator compartment.
Known temperature controls often regulate the actuators operation in a determined way to either increase or decrease the cooling inside the compartment, according to the necessity established by the target temperature, that is, if the measured temperature inside the compartment is higher than the target temperature, the temperature control regulates the actuators to increase the cooling inside the compartment, and vice-versa.
One known temperature control is described in US7866174 disclosing a control unit to control the operation of a fan and a damper, to manage cold air inside a freezer compartment or a refrigerator compartment, according to a comparison of a user set temperature with measured temperatures in the freezer compartment and the refrigerator compartment.
Another known temperature control is described in EP2578973, in which compartment dampers are controlled to be in a specific position while also operating a blowing fan and a compressor according to the cooling need of the compartments, according to a set temperature in each compartment.
A third known temperature control is described in EP3371528, in which a fan and a defrosting heater, alternating switch-off phases for a compartment heat-up mode.
Yet another known temperature control is described in US8075469, which describes a refrigerator comprising a multifunctional compartment disposed between a first compartment and a second compartment, the multifunctional compartment being adjustable between temperature modes selected from the group consisting of a fresh food temperature mode, a soft freeze mode, a freezer mode, and a chiller temperature mode; a controller operatively connected to the temperature sensor and the heater, the controller being configured to energize the heater after the temperature signal reaches a threshold. Besides that, the document also illustrates a plot of an actual temperature being plotted relative to a target temperature over unit time to illustrate the manner in which a single evaporator and heater component can control a compartment. The controller operates on a temperature threshold to control the actuators, i.e., fan, heater, damper, etc.
Despite of control methods being known, there is still a constant need for temperature controls that particularly provide more accurate temperature regulation, thus improving the operation of refrigerators.
The invention aims to provide a more accurate and precise temperature regulation for a refrigerator compartment. A refrigerator achieving this is disclosed in independent claim 1 and improvements of the invention are disclosed in dependant claims 2-5.
According to the invention, a refrigerator comprising a first compartment and a second compartment is provided. Such compartments can be used to store any type of items that need to be refrigerated, including foodstuff and medicine, as well as placement of any other refrigerator components. A cooling system associated with the second compartment is provided, the cooling system comprising an evaporator, a compressor and a condenser, which are often located at the rear side of the second compartment. A connection is provided between the first compartment and the second compartment, which may be any type of channel or compartment connection commonly used in refrigerators. The refrigerator further comprises at least two actuators for regulating the temperature in the first compartment, a temperature sensor configured to measure the temperature in the first compartment and a control device configured to determine a single control parameter value for controlling the at least two actuators conjointly, based on the measured temperature and a target temperature set for the first compartment. The at least two actuators are controlled conjointly, meaning in the present application that the same single control parameter value is simultaneously used to control all actuators independently from each other.
The refrigerator with such control device is especially advantageous as it operates in a way that the control of temperature is not only based on temperature differences, but on a transformation of these differences into the single control parameter value. This transformation is especially advantageous as it allows the measured temperature (i.e., controlled temperature) to be more accurate and precise in relation to the target temperature when compared to previous solutions. In that way, the use of a single control parameter value allows the measured temperature to be accurate and precise in relation to the target temperature, therefore precisely controlling the first compartment temperature.
According to some embodiments, the control device comprises a single feedback system for determining the single control parameter value. This is especially advantageous as it provides a simpler arrangement when compared to multiple feedback systems, while maintaining a high accuracy and precision of the temperature control.
According to some embodiments, the control device comprises a pre- structured control scheme to control the at least two actuators based on the single control parameter value. The pre-structured control scheme is configured to receive the single control parameter value as an input to facilitate controlling the at least two actuators.
According to some embodiments, the refrigerator further comprises a setting device for setting the target temperature. The setting device represents any way of setting up or defining the target temperature for the compartment through any means such as a relative position of Min/ Med/ Max or High/ Low or a numerical scale and can be further adjusted between temperature modes such as fresh food temperature mode, a soft freeze mode, a freezer mode, a crisper and a chiller temperature mode, regarding the first compartment. The target temperature preferably can be set to any temperature normally associated with refrigeration, such as freezing or cooling temperatures.
According to some embodiments, the at least two actuators are selected from a group of actuators comprising a damper positioned in the connection, to control an airflow from the second compartment to the first compartment; a first fan arranged to control the airflow circulation within the first compartment; a heater positioned in the first compartment; and a second fan arranged to control the airflow circulation within the second compartment. The group of actuators may further include other possible components such as the compressor and is not limited to the embodiments described herein.
A method for the solution discussed herein is disclosed in accordance with the invention in independent method claim 6 and improvements of the method according to the invention are disclosed in dependant method claims 7-9.
The method for controlling the temperature of a first compartment of a refrigerator, wherein the refrigerator comprises at least two actuators for regulating the temperature of the first compartment and comprising a cooling system including an evaporator, a compressor and a condenser, comprising:
(a)measuring the temperature of the first compartment through a temperature sensor;
(b)comparing the measured temperature with a target temperature;
(c)determining a single control parameter value, based on the measured temperature and the target temperature; and
(d)operating the at least two actuators conjointly based on the single control parameter value.
The method also provided benefits when the refrigerator further comprises a second compartment connected to the first compartment through a connection. The method wherein step (d) can use a pre-structured control scheme to control the at least two actuators based on the single control parameter value. The pre-structured control scheme is configured to provide an individual control signal output for the respective actuator, thereby the at least two actuators are conjointly operated based on the single control parameter value.
The method wherein operating the at least two actuators conjointly includes at least two of the following operations, including: operating a damper positioned in the connection, to control an airflow from the second compartment to the first compartment; operating a first fan arranged to control the airflow circulation within the first compartment; operating a heater positioned in the first compartment; and operating a second fan arranged to control the airflow circulation within the second compartment. The group of operations may further include other possible operations such as controlling the compressor and is not limited to the embodiments described herein.
Another refrigerator achieving the aim of the invention is disclosed in independent claim 10 and improvements are disclosed in dependant claims 11-13.
According to the invention, a refrigerator comprising a compartment is provided. The compartment can be used to store any type of items that need to be refrigerated, including foodstuff and medicine, as well as placement of any other refrigerator components. A cooling system associated with the compartment is provided, the cooling system comprising an evaporator, a compressor, and a condenser. The refrigerator further comprises at least two actuators for regulating the temperature in the compartment, a temperature sensor configured to measure the temperature in the compartment, and a control device configured to determine a single control parameter value for controlling the at least two actuators conjointly, based on the measured temperature and a target temperature for the compartment.
According to some embodiments, the actuators include at least two of a heater, a fan and the compressor.
In similarity to the above refrigerator according to the invention, the control device comprises a single feedback system for determining the single control parameter value, as well as a pre-structured control scheme to control the at least two actuators based on the single control parameter value. These parameters retain the same benefits as described in the above refrigerator.
Further features and advantages of the invention will become clear from the following description of exemplary embodiments with reference to the attached figures.
The invention will, in the following, be described in more detailed referring to the figures wherein:
Figure 1 shows an external view of a generic refrigerator;
Figure 2 shows a principal sectional side view of a first embodiment of a refrigerator according to the invention;
Figure 3 shows a principal sectional side view of a second embodiment of the refrigerator according to the invention;
Figure 4 shows a method flowchart for a control device in accordance with the invention;
Figure 5 shows a schematic for the control device in accordance with the invention;
Figure 6 shows a first example of a pre-structured control scheme for two actuators;
Figure 7 shows a second example of a pre-structured control scheme for four actuators;
Figure 8 shows a resulting temperature control comparison between the prior art and the control device according to the invention when there is a step change of set target temperature;
Figure 9 shows a resulting temperature control comparison between the prior art and the control device according to the invention when there is a request for cooling the first compartment;
Figure 10 shows a resulting temperature control comparison between the prior art and the control device according to the invention when there is a request for heating the first compartment; and
Figure 11 shows a principal sectional side view of a third embodiment of the refrigerator according to the invention.
It should be noted that, unless otherwise stated, different features or elements may be combined with each other whether or not they have been described together as part of the same embodiment below. The combination of features or elements in the exemplary embodiments are done in order to facilitate understanding of the invention rather than limit its scope to a limited set of embodiments, and to the extent that alternative elements with substantially the same f nctionality are shown in respective embodiments, they are intended to be interchangeable. For the sake of brevity, no attempt has been made to disclose a complete description of all possible permutations of features.
Furthermore, those with skill in the art will understand that the invention may be practiced without many of the details included in this detailed description. Conversely, some well-known structures or functions may not be shown or described in detail, in order to avoid unnecessarily obscuring of relevant description of the various implementations. The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific implementations of the invention.
Considering the field of refrigeration systems, one of the machines commonly found in a household are domestic refrigerators. Such refrigerators usually comprise some sort of compartment, and a cooling system including an evaporator, a condenser, and a compressor. As showed in Figure 1, an external view of an exemplary refrigerator, in this case a so-called French Door refrigerator with a bottom drawer freezer and a dispenser for ice and water, is indicated generally at 300. For the purpose of this invention, a modern household refrigerator is provided. Figure 1 merely represents one possible view of such refrigerator 300. Naturally, it can include a variety of sizes and shapes, including French Doors, built-in types, side-by-side, with top or bottom freezer, among other varieties and there are others for which the invention is applicable, in which the temperature of at least one compartment must be controlled. Refrigerators as generally indicated at 300 can also present different possible features to adjust temperatures, including special compartments, handles, water and/or ice dispenser, auto defrosting settings and many other features not specifically mentioned herein. A first embodiment of a refrigerator 100 according to the invention is shown in Figure 2. The first embodiment is depicted as a principal sectional side view of the refrigerator 100, mainly showing the components that are relevant for the invention. For the sake of clarity in the description, Figure 2 shows principal structures of the refrigerator 100 to enable a clear description of the invention, so the embodiments are not necessarily represented in accurate dimension.
The refrigerator 100 comprises a first compartment 1 and a second compartment 2 connected to the first compartment 1 through a connection 16, which may be any type of channel or compartment connection commonly used in refrigerators. The first compartment 1 also accommodates a temperature sensor 11, configured to measure the temperature in the first compartment 1. The refrigerator 100 also includes a cooling system 101 associated with the second compartment 2 comprising an evaporator 12, a compressor 13 and a condenser 14.
The cooling system 101 may include additional components or be configured in a different way with expansion elements and condenser in so-called skins or other ways, as is generally known in the refrigerator field today.
The refrigerator 100 further comprises two actuators for regulating the temperature in the first compartment 1. The actuators in the first embodiment shown in Figure 2 are: a damper 10a positioned in the connection 16, to control an airflow from the second compartment 2 to the first compartment 1; and a first fan 10b arranged to control the airflow circulation within the first compartment 1.
The position of the actuators shown in Figure 2 are not to be taken as literal positions and are indicated in a principal perspective, therefore the damper can be positioned in any place of the connection 16, closer to the first compartment 1 or the second compartment 2, and the fan can be positioned anywhere in which fans are commonly placed in a refrigerator compartment.
The refrigerator 100 presents in Figure 2 a setting device 15. The setting device 15 represents any way of setting up or defining temperature for the compartment through any means such as a relative position of Min/ Med/ Max or High/ Low or a numerical scale and can be further adjusted between temperature modes such as fresh food temperature mode, a soft freeze mode, a freezer mode, a crisper and a chiller temperature mode, all which can be adopted by the first compartment 1. The setting device 15 can also be an integrated part of a user interface which also displays information to the user or a part of an app or a connected tool.
The refrigerator 100 further comprises a control device 18 configured to control the temperature in the first compartment 1 in an accurate and precise way. The detailed operation of the control device 18 will become clear in connection with the description of Figures 4 and 5. Figure 2 shows an exemplary position of the control device 18 of the refrigerator 100, and it could be integrated in other suitable positions and/or control board.
A method flowchart is represented on Figure 4. The method flowchart indicates the operation of the control device 18 based on a series of steps that are repeated, for instance, after every measurement of the first compartment temperature or continuously (following electronics limitation) or periodically, e.g. every 10 seconds or 30 seconds, etc. Comprising the following steps:
(a) start;
(b) measure the temperature of the first compartment, represented by box 40;
(c) compare the measured temperature with a target temperature, represented by box 41;
(d) determine the single control parameter value based on the measured temperature and the target temperature, represented by box 42;
(e) use the single control parameter value to match a pre-structured control scheme, represented by box 43;
(f) operate at least two actuators according to the pre-structured control scheme, represented by box 44; and
(g) end.
For step (c), the target temperature input comes from the setting device 15 described previously in Figure 2, and, for the purpose of this invention, the target temperature is directed to the first compartment 1. For the purpose of clarity, the pre-structured control scheme used in step (e) is further described in Figures 6 and 7. A schematic for the control device 18 is shown in Figure 5. The main goal of the control device 18 is to ultimately provide a precise and accurate control of temperature in the first compartment 1. For this, the operation of the control device 18 is based on a series of steps that are repeated, and could, for instance, be repeated continuously (following electronics limitation) or periodically, e.g. every 10 seconds or 30 seconds, etc.
The control device 18 has two main inputs: the measured temperature 50 and the target temperature 51. As shown in Figure 5, the measured temperature 50 is obtained from the temperature sensor 11 and the target temperature 51 is obtained through the setting device 15. The target temperature 51 preferably can be set to any temperature normally associated with refrigeration, such as freezing or cooling temperatures. The measured temperature 50 is commonly filtered to avoid common electronic reading fluctuations or noise, so the measurements have more stable values.
With the inputs of the control device 18, a single control parameter value 52 is determined. Such single control parameter value 52 can be derived from a single feedback system. The feedback system may use common control techniques such as PI, PID, Fuzzy or MPC controllers, based specifically on the difference between the measured temperature 50 and the target temperature 51. Such difference is commonly called a temperature error. Preferably, the PI method is used, in which the temperature error is integrated through time, commonly called an integral error. In the PI technique, the temperature error is multiplied by a proportional gain parameter (Kp) and the integral error is multiplied by an integral gain parameter (Ki). The sum of these two multiplications results in an output that is the single control parameter value 52. It is common to see implementations where the PI parameters are changed according to the temperature error or any other external parameters.
The single control parameter value 52 is used as an input to a pre- structured control scheme 53, which, as outputs, provides the individual control signals for the actuators. Exemplary pre-structured control schemes will be further described in connection with Figures
6 and 7. As further shown in Figure 5, the pre-structured control scheme 53 outputs an individual control signal for the operation of each actuator, and each actuator is operated to conjointly control the temperature of the first compartment 1. Naturally, the operation of the actuators modifies the temperature in the first compartment 1 according to the target temperature 51. As the temperature of the first compartment 1 is constantly measured by the temperature sensor 11, the measurements trigger the restart of the cycle and operation of the control device 18 in order to maintain an accurate and precise control of the measured temperature 50 in relation to the target temperature 51.
The group of actuators shown in Figure 5 are, according to the first embodiment of the refrigerator 100, selected as the damper 10a and the first fan 10b.
A graph of a first example of a group of actuators operation is shown in Figure 6 where a group of two actuators are controlled. The operation of the two actuators represented by line 60, for the damper 10a operation, and line 61, for the first fan 10b operation. The graph is a representation of the pre-constructed scheme 53, and the horizontal axis represents possible values of the single control parameter value 52.
As shown in Figure 6, the behaviour of the actuators changes according to the result of the single control parameter value 52. The single control parameter value 52 is continuously determined according to the description of the method flowchart of Figure 4, and even small changes in the single control parameter value 52 can influence the actuators' operation, thus enhancing accuracy and precision of the temperature control in the first compartment 1 of the refrigerator 100. On the vertical axis, the graph shows the actuators power percentage, with a possible threshold from 0% to 100% power output for each actuator.
To further comprehend the advantages of the control device 18 and the use of the single control parameter value 52, Figure 8 shows a temperature control comparison graph between the prior art and the method proposed herein. The graph takes into consideration the temperature control of the first compartment 1, where line 81 represents a step change of the set target temperature 51. The target temperature 51 is the setpoint defined by the setting device 15 through any method previously described. Line 82 shows the first compartment temperature control according to a common method described in the prior art, and line 80 shows the first compartment temperature control according to the invention described herein.
It is clear from the graph in Figure 8 that, in fact, the use of the control device 18 is an improvement when it comes to temperature accuracy and precision. Thus, the use of the invention described herein keeps the temperature control accurate and precise around the target temperature 51, while the prior art may present some accuracy but lacks precision.
To further comprehend the advantages of the control device 18 and the use of the single control parameter value 52, Figure 9 shows a temperature control comparison graph between the prior art and the method proposed herein. The graph takes into consideration the temperature control of the first compartment 1, when there is a need for cooling the first compartment 1. Line 90 shows the first compartment temperature control according to a common method described by the prior art, and line 92 shows the first compartment temperature control according to the invention described herein. Further, line 91 shows the average of the first compartment temperature according to a common method described by the prior art, and line 93 shows the average of the first compartment temperature according to the invention described herein. It is important to highlight that the target temperature 51 (in the specific situation shown in the graph, the target temperature is set to 2°C) coincides almost completely with the resulting average temperature when the first compartment 1 is controlled by the method described by the invention.
It is clear from the graph in Figure 9 that, in fact, the use of the control device 18 is an improvement when it comes to temperature accuracy and precision. Thus, the use of the invention described herein keeps the temperature control accurate and precise around the target temperature when cooling is needed, while the prior art may present some accuracy but lacks precision.
To further comprehend the advantages of the control device 18 and the use of the single control parameter value 52, Figure 10 shows a temperature control comparison graph between the prior art and the method proposed herein. The graph takes into consideration the temperature control of the first compartment 1, when there is a need for heating the first compartment 1. Line 94 shows the first compartment temperature control according to a common method described by the prior art, and line 96 shows the first compartment temperature control according to the invention described herein. Further, line 95 shows the average of the first compartment temperature according to a common method described by the prior art, and line 97 shows the average of the first compartment temperature according to the invention described herein. It is important to highlight that the target temperature 51 (in the specific situation shown in the graph, the target temperature is set to 2°C) coincides almost completely with the resulting average temperature and, not only that, but also the temperature behaviour throughout time when the first compartment 1 is controlled by the method described by the invention. This points to the extreme precision and accuracy of the use of the invention in certain situations when controlling the temperature in the first compartment 1.
It is clear from the graph in Figure 10 that, in fact, the use of the control device 18 is an improvement when it comes to temperature accuracy and precision. Thus, the use of the invention described herein keeps the temperature control accurate and precise around the target temperature when heating is needed, while the prior art may present some accuracy but lacks precision.
A second embodiment of a refrigerator 200 is shown in Figure 3, which is slightly different in structure compared to the first embodiment of the refrigerator 100. The other components shown in Figure 2 can be the same and therefore retain the same reference numbers as the first embodiment of the refrigerator 100.
The key feature of the embodiment shown in Figure 3 is that the refrigerator 200 comprises four actuators: the damper 10a; the first fan 10b; a second fan 10c arranged to control the airflow circulation within the second compartment 2; and a heater lOd positioned in the first compartment 1. The exemplary embodiment of the refrigerator 200 show that the invention also works for systems with more than two compartments and several evaporators. The presence of the heater lOd advantageously supports the adjustment of the target temperature 51 in the first compartment 1 particularly when an ambient temperature drops below the target temperature, as the first compartment 1 can be set to temperatures higher than ambient temperatures in some cases. This situation can be presented, for example, if the refrigerator is kept in places without any artificial heating during a cold season when the ambient temperature can drop to way below the target temperature for certain refrigerated food items, therefore the heater lOd provides a convenient and fast way to reach the target temperature 51.
The second embodiment of the refrigerator 200 accommodates the setting device 15 and the control device 18, both operating in the same way as described for the first embodiment. The additional actuators, the second fan 10c and the heater lOd, are included in Figure 5 represented in dotted lines.
A graph of a second example of a group of actuators operation is shown in Figure 7, where the group of actuators' operation comprises: the damper 10a operation represented by line 60, the first fan 10b operation represented by line 61, the second fan 10c operation represented by line 70, and the heater lOd operation represented by line 71.
The operation of the damper 10a and the first fan 10b is not necessarily identical to the one described in Figure 6 as the first example of a pre-structured control scheme 53, as the actuators operation can change in consequence of the presence of several other actuators. Naturally, many pre-structured control schemes can be input in the control device 18 and both Figure 6 and Figure 7 represent one possible outcome of the control device 18.
Even for the second example of the group of actuators shown in Figure 7 the same operation as previously described in the first example is used. Thus, the functioning of the pre-structured control scheme 53 and, consequently, the accuracy and precision of the first compartment 1 temperature control through the control device 18, are maintained independently of the number of actuators considered in the system.
A third embodiment of a refrigerator 500 is shown in Figure 11, which is slightly different in structure compared to the first embodiment of the refrigerator 100. The other components shown in Figure 11 can be the same and therefore retain the same reference numbers as the first embodiment of the refrigerator 100.
The key feature of the embodiment shown in Figure 11 is that the refrigerator 500 comprises a compartment 5 and a group of actuators wherein the actuators include at least two of a heater (10d), a fan 10b and the compressor 13. The exemplary embodiment of the refrigerator 500 show that the invention also works for systems with one compartment.
The third embodiment of the refrigerator 500 accommodates the setting device 15 and the control device 18, both operating in the same way as described for the first embodiment. Moreover, this embodiment shares the same benefits and advantages as described for the other two embodiments.
Such features can also occur in combinations other than those specifically disclosed here. The fact that several characteristics are mentioned in the same sentence or in a different type of textual context does not therefore justify the conclusion that they can only occur in the specifically disclosed combination, instead, it can generally be assumed that several of these characteristics can also be omitted or modified, provided that the functionality of the invention is not modified.