Abstract
Refrigerator (200, 210) comprising a compartment (13a) for storing foodstuff; a cooling system (200, 210) comprising an evaporator (12a), a condenser (14) and a variable speed compressor (10), the cooling system (200, 210) being adapted to go through a refrigeration cycle at certain intervals. A control system (11) is configured to control the variable speed compressor (10) during the refrigeration cycle, the control system (11) being based on a minimum speed (36) and a required speed (22), whereby the control system (11) is configured to set the compressor speed (35) to the highest speed of both the minimum speed (36) and the required speed (22). Such control system (11) provides an improved performance of the cooling system (200, 210), maintaining a balance of different temperatures inside the refrigerator (100, 110).
Claims
1. A refrigerator (100; 110) comprising a compartment (13a) for storing foodstuff; a cooling system (200; 210) comprising an evaporator (12a); a condenser (14) and a variable speed compressor (10), the cooling system (200; 210) being adapted to go through a refrigeration cycle at certain intervals; a control system (11) configured to control the variable speed compressor (10) during the refrigeration cycle, characterized in that the control system (11) controls the variable speed compressor (10), based on a minimum speed (36) and a required speed (22), whereby if the minimum speed (36) is lower than the required speed (22) then the control system (11) will set the compressor speed (35) to the required speed (22); and if the minimum speed (36) is higher than the required speed (22) then the control system (11) will set the compressor speed (35) to the minimum speed (36);
2. A refrigerator (100; 110) according to claim 1, wherein the control system (11) is configured to control the variable speed compressor (10) in a step-by-step manner.
3. A refrigerator (100; 110) according to any of claim 1, wherein the control system (11) is configured to calculate the minimum speed (36) in relation to an elapsed time from the start of the refrigeration cycle.
4. A refrigerator (100; 110) according to claim 3, wherein the control system (11) is configured to further calculate the minimum speed (36) based on temperature settings.
5. A refrigerator (100; 110) according to claim 1, wherein the control system (11) is configured to calculate the required speed (22) based on temperature parameters, comprising the difference between a measured temperature and a set temperature.
6. A refrigerator (100; 110) in accordance with claim 1, wherein the control system (11) comprises a switch control (31) configured to start the variable speed compressor (10) at the onset of the refrigeration cycle and stop the variable speed compressor (10) at the end of the refrigeration cycle.
7. A refrigerator (100; 110) according to claim 1, wherein the refrigerator comprises a second compartment (13b).
8. A refrigerator (100) according to claim 7, wherein the compartment (13a) and the second compartment (13b) are connected through a channel (15), and the cooling system (200) comprises a fan (16) to generate forced air circulation between the compartment (13a) and the second compartment (13b).
9. A refrigerator (110) according to claim 7, wherein the cooling system (210) comprises a second evaporator (12b) in series with the evaporator (12a).
10. A refrigerator (110) according to claim 9, wherein the evaporator (12a) is connected to the compartment (13a), which is a freezer compartment, and the second evaporator (12b) is connected to the second compartment (13b), which is a fresh food compartment, and the flow path of a refrigerant fluid is from the evaporator (12a) to the second evaporator (12b).
11. A method of controlling a variable speed compressor (10) in a cooling system (200; 210) of a refrigerator (100; 110), the cooling system (200; 210) being adapted to go through a refrigeration cycle at certain intervals, comprising: (a) starting the refrigeration cycle; (b) calculating a minimum speed (36); (c) calculating a required speed (22); (d) comparing the minimum speed (36) and the required speed (22); (e) setting the compressor speed to the highest speed of the minimum speed (36) and the required speed (22); (f) evaluating if the compressor speed reached the end of the refrigeration cycle, if not, calculating steps (a) to (e) until the end of the refrigeration cycle is reached; and (g) stopping the refrigeration cycle.
12. The method of claim 11, wherein a speed graph is visualized during the refrigeration cycle.
13. The method of claim 11, wherein the step (b) calculating the minimum speed (36) is made by determining an elapsed time from the start of the refrigeration cycle.
14. The method of claim 13, wherein the step (b) calculating a minimum speed (36) includes the consideration of temperature settings.
15. The method of claim 11, wherein the step (c) calculating a required speed (22) is made by determining temperature parameters, comprising the difference between a measured temperature and a set temperature.
Description
[0040] FIG. 1 shows an external view of a refrigerator;
[0041] FIG. 2 shows a principal sectional side view of a refrigerator embodiment;
[0042] FIG. 3 shows an embodiment of a main control;
[0043] FIG. 4 shows an overview of a control system;
[0044] FIG. 5 shows a method flow for the control system;
[0045] FIG. 6 shows a principal sectional side view of the refrigerator in one second embodiment;
[0046] FIG. 7 shows a schematic of a cooling system;
[0047] FIG. 8 shows a method flow for a minimum speed;
[0048] FIG. 9 shows a method flow for a required speed;
[0049] FIG. 10 shows a graph of one example of the minimum speed graph plot;
[0050] FIG. 11 shows a graph of one example of the speed graph plot in a typical operation.
[0051] Considering the field of refrigeration systems, one of the machines commonly found in a household are domestic refrigerators. Such systems comprise a compartment, and a cooling system including an evaporator, a condenser and a compressor. As showed in FIG. 1, an external view of a refrigerator is indicated generally at 100. For the purpose of this invention, a modern household refrigerator is provided. FIG. 1 merely represents one possible view of such refrigerator 100. 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. Not only that, but it 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.
[0052] A principal sectional side view, with a layout of the interior components, of the refrigerator 100 is shown in FIG. 2 to demonstrate the components, considering one embodiment. Such refrigerator 100 includes a compartment 13a and a cooling system 200 comprising an evaporator 12a, a condenser 14, a variable speed compressor 10 and a capillary tube 01, not shown. Naturally, the cooling system 200 might comprise many different known arrangements. The refrigerator 100 can also include a second compartment 13b, and possibly more compartments either connected or with a separation, represented by the dotted line 17.
[0053] The cooling system 200 in FIG. 2 is adapted to go through a refrigeration cycle at certain intervals. Such refrigeration cycle is, in the present application, referred to as the time period in which the variable speed compressor 10 is active and operating. The time period can be influenced by many parameters and the intervals can be based on time, temperature or any other relevant factors. It is assumed that the cooling can continue even if the variable speed compressor 10 is stopped due to residual refrigerant flow in the cooling system 200.
[0054] The refrigerator in FIG. 2 includes a control system 11 for controlling the variable speed compressor 10 during the refrigeration cycle. Other arrangements and features of the refrigerator are known and might be assumed to be included in the presented embodiment.
[0055] The second compartment 13b includes a temperature sensor 18, and the compartment 13a includes a fan 16 and a channel 15, configured to generate forced air circulation between said compartments. It is possible that the compartments have different temperature settings selected through user input, considering that in this invention the compartment 13a can be referred to as a freezer compartment, and it is set to be in a colder temperature than the second compartment 13b. Thus, the second compartment 13b is the warmer compartment, and can be referred to as a fresh food compartment, in relation to the compartment 13a. It is also possible to select special operation modes through a display 19, which can be any kind of digital or mechanical user interface, including connected devices (internet of things).
[0056] It is also provided in FIG. 2 a main control 20 in the refrigerator 100 embodiment, which operates the mainframe of the cooling system 200.
[0057] FIG. 3 shows an embodiment of the main control 20, which is the refrigerator 100 central control. The main control 20 controls the refrigerator 100 routine and operation. The main control 20 refers to the whole system of the refrigerator 100, configured to control all other necessary arrangements and parts of the refrigerator 100 not necessarily related to the control of the variable speed compressor 10. Such main control 20 operates through several methods including electrical control or mechanical thermostat control, both possible on the embodiment described herein.
[0058] One possible main control 20 operation is showed in FIG. 3. As the main control 20 manages several signals to actuators of known and common use, it requires relevant inputs 21, which can comprise in the simplest condition the temperature settings provided through user input, but also other parameters such as compartments temperatures, provided by the temperature sensor 18, and special operation modes. An important possible output of the main control 20 is a required speed 22, which will be incorporated as an input into the control system 11 operation, ultimately contributing to control the speed of the variable speed compressor 10.
[0059] The control system 11 operation is disclosed in FIG. 4. The object of such control system 11 is to ensure that the correct speed value is set on the compressor, in relation to two main variables: the minimum speed 36 and the required speed 22. The control system 11 operates in a step-by-step manner, following several steps to ensure the compressor is operated correctly. One of the external sources of inputs can be the main control 20, represented outside of the control system 11. As stated before, the main control 20 provides the calculation for the required speed 22, but it also signals to a switch control 31, located in the control system 11, that it is necessary to switch on the variable speed compressor 10, with the start of the refrigeration cycle. Furthermore, the main control 20 is responsible to provide other possible inputs to the control system 11, such as temperature settings.
[0060] As shown in FIG. 4, once the refrigeration cycle is started, the switch control 31 starts the compressor operation and a time counter 32 is activated. The time counter 32, which allows a minimum speed 36 to be calculated, and such minimum speed 36 may also be further calculated based on temperature settings. The calculated values of the minimum speed 36 and the required speed 22 are fed to a speed function 35, which is configured to compare both values and set a compressor speed to the highest of the minimum speed 36 and the required speed 22. Therefore, the speed function chooses the highest value to be set as the actual speed of the variable speed compressor 10 throughout the refrigeration cycle.
[0061] Considering the control system 11, it can be described as an algorithm following the steps showed in FIG. 5, within the speed function 35. The following steps are provided in FIG. 5: [0062] (a) starting the refrigeration cycle, represented by box 50; [0063] (b) calculating a minimum speed 36, represented by box 51; [0064] (c) calculating a required speed 22, represented by box 52; [0065] (d) comparing the minimum speed and the required speed, represented by box 53; [0066] (e) setting the compressor speed to the highest speed of the minimum speed 36 and the required speed 22, represented by box 54.
[0067] Then, the system evaluates if the end of the refrigeration cycle is reached, which is based on whether the temperatures in the compartment 13a and the compartment 13b are within the desired target according to temperature settings, so the compressor must be stopped, ending the refrigeration cycle. If such scenario has not yet been reached, the calculation of steps (a) to (e) shown in FIG. 5 will continue, until the refrigeration cycle ends. Moreover, the time period in which the variable speed compressor 10 remains active, i.e. the refrigeration cycle, can present a reasonable range of time variation. Therefore, there is no pre-set time limit for the refrigeration cycle, as the duration can be influenced by many parameters and the intervals can be based on maximum active time for the compressor, temperature parameters or any other relevant factors.
[0068] A second embodiment of a refrigerator 110 is shown in FIG. 6. It shows the preferred embodiment comprising two evaporators, wherein the evaporator 12a is connected in series to a second evaporator 12b. Naturally, the evaporator 12a is connected to the compartment 13a and the evaporator 12b is connected to the compartment 12b. However, the same principles described for the refrigerator 100 can be applied. This embodiment thus encompasses another embodiment of the cooling system 210, which is slightly different compared to the cooling system 200. The other components shown in FIG. 6 can be the same and therefore retain the same numeral numbers as the first embodiment of the refrigerator 100.
[0069] FIG. 7 shows the cooling system 210, with a circuit in which the refrigerant can flow through, comprising the condenser 14, a capillary tube 01, the evaporator 12a connected in series with the second evaporator 12b and the variable speed compressor 10, which is connected to the control system 11. In this embodiment the flow path follows the direction from the evaporator 12a to the second evaporator 12b, however it could be the other direction, as well as other possible arrangements. The flow path following the direction showed in FIG. 7 allows the control system 11 to be more efficient by increasing the compressor speed and, consequently, promoting an increase in heat transfer from the compartment 13a. Such increase corresponds to a reduction of the available refrigerant overflow to the second compartment 13b, consequently reducing the cooling capacity availability in the second compartment 13b and increasing the availability in the first compartment 13a.
[0070] All described features compose an exemplary conventional cooling system 210 with a control system 11, therefore it is possible that other configurations with standard components can be used.
[0071] During the refrigeration cycle, regardless of which embodiment of the refrigerator 100, 110 that is considered, several scenarios are possible for the variable speed compressor 10 operation. The control system 11 provided, calculates the minimum speed 36 in relation to at least the elapsed time from the start of the refrigeration cycle and further related to temperature settings. The minimum speed 36 can be active in all operation conditions, not limited to using only said minimum speed 36, as the refrigerator 100, 110 operation may include other operation modes that might increase the compressor speed if necessary. The minimum speed 36 profile is not necessarily controlled actively by compartment sensors or other inputs besides the elapsed time and user input of temperature settings, which provides the possibility of a better balance of this system, with simple temperature control. Considering step (b) of calculating the minimum speed 36, FIG. 8 shows the method flow for said calculation, comprising the steps of: [0072] (b1) Set working temperature according to temperature settings, represented by box 51a; [0073] (b2) Start elapsed time counter, represented by box 51b; [0074] (b3) Set a TIME?SPEED matrix, represented by box 51c; [0075] (b4) Obtain the result of the minimum speed 36 for the control system 11, represented by box 51d.
[0076] One possible way of calculating the minimum speed 36 is based on a linear interpolation between values listed on a matrix with time by speed lines, as described above. Hence, from the refrigeration cycle start until a determined time, the speed will linearly move from one speed value to another. The changes of the matrix set by step (b3) are intended to change the temperature difference between the compartment 13a and the second compartment 13b. Naturally, the second compartment 13b, in which the temperature sensor 18 is assembled, possibly has its temperature well defined by such sensor. Thus, in the scenario when the temperature sensor 18 measures the refrigerator 100, 110 temperature, the compartment 13a is indirectly controlled by changing the compressor speed. The ultimate outcome is thus to provide control to the compartment 13a where there was no active control means.
[0077] One example of the minimum speed graph plot is represented in FIG. 10. And in this case two compartments are present: the compartment 13a, designated as a freezer compartment or the lowest temperature compartment, and the second compartment 13b, designated as a fresh food compartment or the highest temperature compartment. During the refrigeration cycle, regardless of which embodiment of the refrigerator 100, 110 that is considered, the plot in FIG. 10 shows three outcomes for the minimum speed 36: [0078] A middle solid line plot as the Particular ConditionTemperature Settings shows one specific input of temperature settings; [0079] An upper dotted line plot Larger temperature difference between compartments, showing a condition in which the compartment 13a is set to be in a colder temperature in relation to the Particular ConditionTemperature Settings plot, as well as the second compartment 13b is set to be in a warmer temperature in relation to the middle solid line plot. Thus, the difference of temperature between compartments is larger than the one considered in the middle solid line plot; [0080] A lower dotted line plot Smaller temperature difference between compartments, showing a condition in which the compartment 13a is set to be in a warmer temperature in relation to the Particular ConditionTemperature Settings plot, as well as the second compartment 13b is set to be in a colder temperature in relation to the middle solid line plot. Thus, the difference of temperature between compartments is smaller than the one considered in the middle solid line plot.
[0081] The graph in FIG. 10 shows that, for any condition on Temperature Settings, a normal operation would be that as soon as the refrigeration cycle is started, the minimum speed 36 is immediately raised and then lowered to a constant speed after a pre-determined time and configured to remain constant until the refrigeration cycle is stopped. However, other speed graphs profiles could apply, as an example, it could be possible to have an additional speed raise towards the end of cycle. The initial immediate raised speed showed in FIG. 10 is advantageous as usually the variable speed compressor 10 requirement to be turned-on is related to the compartment 13b, which is the warmest compartment, so it is advantageous to have a high cooling capacity initially available to ensure the temperatures are recovered as fast as possible. Moreover, lowering the minimum speed 36 to a constant lower level until the variable speed compressor 10 is switched off is advantageous as it allows energy savings. Considering the required speed 22 calculation, it is possible to apply several common methods to obtain such speed. The preferred method is the PI control, based specifically on the difference between measured temperature and set temperature, but not limited to it. Considering one possibility showed in FIG. 9, it is preferably calculated based on regular PI control, with the temperature error based on a set temperature and a measured temperature. The calculation will follow step (c) of, showed in FIG. 9, comprising the steps of: [0082] (c1) Start the calculation, represented by box 52a; [0083] (c2) Assess set temperature through temperature setting, represented by box 52b; [0084] (c3) Assess measured temperature through a temperature sensor, represented by box 52c; [0085] (c4) Calculate the temperature error, represented by box 52d; [0086] (c5) Obtain constant values according to PI method, represented by box 52e; [0087] (c6) Calculate the integral function, represented by box 52f; [0088] (c7) Obtain the result of the required speed 22 for the control system 11, represented by box 52g.
[0089] In FIG. 9, the set temperature can be directly input by the user control of an exact desired temperature, or also possibly through the temperature settings interpreted by the main control 20 from the user input. The measured temperature is the actual temperature measured by the temperature sensor 18 inside the compartment. The required speed 22 function is capped within the speed zero and a maximum compressor speed. The temperature error is then incorporated into an integral equation with constants and variable inputs, as it is known for the PI control. It is common to see implementations where the PI parameters are changed according to the temperature error or any other external parameter, such as compressor duty cycle and external temperature.
[0090] The required speed 22 might also be determined in other arrangements within the control system 11 without a temperature feedback or any other link to the main control 20 except the switch control 31. This possible calculation for the required speed is based on a duty cycle, which is a function related to elapsed times both from the start and the stop of the refrigeration cycle, meaning an elapsed time from the time the compressor is switched on and an elapsed time from the time the compressor is switched off. The function of the duty cycle is plotted in relation to a matrix related to speed. Naturally, the minimum speed 36 function described in FIG. 8 is still valid for all possibilities of obtaining the required speed 22.
[0091] FIG. 11 shows an example of a visualization of a speed graph, indicating how the compressor speed (solid line), adapts to the highest of the minimum speed 36 and the required speed 22. The speed graph always considers that within the minimum speed 36 calculation, a possible profile is selected as the algorithm analyses a good compromise among energy consumption, temperature stability, cooling and freezing capacity as the refrigerator 100, 110 might have a quite limited number of sensors. Hence, one benefit is the compressor speed is neither a function of room temperature nor internal cabinet temperature.
[0092] 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.
