WO2006012720A1

WO2006012720A1 - Temperature adjusting system for a refrigeration appliance

Info

Publication number: WO2006012720A1
Application number: PCT/BR2005/000143
Authority: WO
Inventors: Fábio Ribeiro PIMENTEL; Moacyr Marangone Mezavila; Marco Eduardo Marques
Original assignee: Whirlpool S.A.
Priority date: 2004-08-02
Filing date: 2005-07-28
Publication date: 2006-02-09
Also published as: AR050042A1; BRPI0403128A

Abstract

A temperature adjusting system for a refrigeration appliance comprising: one refrigerating compartment (RC) closed by a front door (11); a compressor (20); one fan (50); a temperature sensor (40); and a control means (30) to activate and deactivate the compressor (20) and/or the fan (50) when the refrigerating compartment (RC) reaches activation and deactivation temperatures, respectively. The adjusting system comprises an open door detecting means (60) associated with the control means (30) which is designed to reduce the deactivation temperature of the compressor (20) and/or fan (50) when the deactivation temperature of the refrigerating compartment (RC) is higher than the activation temperature of the compressor (20) and/or fan (50) at the closing moment of the front door (11) or at least at one more subsequent moment, presenting a delay in relation to the previous moment, in order to minimize temperature variations of the food stored in the refrigerating compartment (RC).

Description

TEMPERATURE ADJUSTING SYSTEM FOR A REFRIGERATION APPLIANCE

Field of the Invention

The present invention refers to a system for automatically adjusting the operating temperature in a refrigeration appliance of the type which comprises a cabinet, defining at least one refrigerating compartment closed by a front door, a compressor, optionally at least one fan, and a control means for activating and deactivating the compressor and/or the fan (if existing) as a function of the temperature reigning inside the refrigerating compartment. Prior Art The present invention is applicable to domestic refrigeration appliances defined by a refrigerator or a freezer, in which the refrigerating compartment, as generically denominated hereinafter, presents a respective adjusting device generally in the form of a knob which allows the user to modify the operational conditions of the appliance, by altering the activation and deactivation temperatures of the compressor and/or the fans in the case of systems composed of fans dedicated to each refrigerating and freezing compartment in a combined refrigeration appliance, for example to "cooler" or "less cool" values from a nominal medium operational value. In these known temperature adjusting systems, when the user wants to select a lower temperature for food preservation, he/she manually activates the adjusting device so that the control means detects said adjusting alteration and varies, correspondingly, the deactivation temperature of the compressor (and/or of the existing fans) . It should be understood that the variation of the compressor activation temperature can be also altered or maintained constant in the case of the refrigerating compartments with a freezer function. Hereinafter, the expression "activation or deactivation temperature of the compressor" should be also understood as being applicable to the fan or fans, if the latter are provided in the refrigeration appliance. In these known systems, besides the user being able to adjust the temperature operational range within which the refrigeration appliance should operate, adjusting this range to "cooler" or "less cool" conditions, the control means is operatively associated with means to detect the momentary temperature in the refrigerating compartment and check whether said temperature is in the same level or above the activation temperature of the compressor so as to activate the latter. When the temperature of the refrigerating compartment informed to the control means is equal to or lower than the deactivation temperature of the compressor, the control means provides the deactivation of the latter. This operational system makes the temperature inside the refrigerating compartment to oscillate between the activation and deactivation temperatures of the compressor.

It is known from the art that the storage temperature inside the refrigerating compartment, whether belonging to a refrigerator or a freezer, should be maintained as constant as possible during the entire storage period. For some food products, even a small temperature variation can bring serious consequences . Moreover, temperature fluctuations often cause condensation on the stored products, which is undesirable as it may favor growth of microorganisms. Experiments have proven that temperature fluctuations inside the refrigerating compartment mainly result from events such as addition of a large amount of food in the refrigerating compartment, a door opening time longer than usually necessary or a prolonged black out. In such situations, even if the temperature in the refrigerating compartment returns rapidly to the nominal value, the food temperature takes a longer time to return to the desired value or to the same value of the temperature inside said compartment. Since the recovery of the food temperature is more important than the recovery of the air temperature in the refrigerating compartment, the known temperature adjusting systems do not allow eliminating or minimizing these temperature oscillations of the food stored in the refrigerating compartment. A possible solution to minimize the temperature oscillations of the stored food is to provide a control means adapted to detect how the temperature reigning inside the refrigerating compartment rises above a compressor activation temperature as a function of an event that causes said temperature alteration, said control means thus being further designed to provide adjustment to lower values of the compressor deactivation temperature and optionally, and if necessary, of the compressor activation temperature, so as to minimize the temperature variations of the food stored in the refrigerating compartment .

In said solution, the control means verifies the presence of said anomalous temperature rise in the refrigerating compartment as a function of a longer door opening time or the introduction of a certain amount of "hot" food, only at the moment in which the closing of the front door of said refrigerating compartment occurs . However, depending on the operational situation, it is possible that the temperature sensor provided inside the refrigerating compartment has not yet sensed all the temperature rise of the refrigerating compartment at the moment the front door is closed and in which the control means effects said verification. It is more probable that the temperature rise in these circumstances is due to the placement of "hot" food inside the refrigerating compartment, which fact will be only detected by the temperature sensor some time after the door is closed, due to the thermal inertia of the involved elements.

Thus, this operational procedure does not allow eliminating the undesired oscillations or the prolongation of inadequate temperature conditions of the food in the refrigerating compartment, even if the control means has been supplied with a correct information of the temperature of the refrigerating compartment at the door closing moment, after a new amount of "hot" food has been placed inside the refrigerating compartment. The above cited solution would only allow a reduction of the temperature oscillation in the cases in which the rise of the ambient temperature inside the refrigerating compartment is caused only by a prolonged opening time of said compartment front door. Summary of the Invention

As a function of the disadvantages mentioned above, it is an object of the present invention to provide a system for automatically adjusting the temperature inside the refrigerating compartment of a refrigeration appliance of the freezer or refrigerator types, or a combination of both types, which allows obtaining an automatic adjustment of the operating temperature inside the refrigerating compartment as a function of anomalous rises of the internal temperature of said compartment, due to a new amount of "hot" food, or to a more prolonged opening time of said compartment front door.

This and other objects and advantages of the invention are attained by the provision of a temperature adjusting system for a refrigeration appliance of the type which comprises a cabinet defining at least one refrigerating compartment closed by a front door, a compressor associated with a refrigeration circuit, a temperature sensor provided inside the refrigerating compartment, and a control means operatively associated with both the compressor and the temperature sensor and which is provided with a timer and constructed to activate and deactivate the compressor when the interior of the refrigerating compartment reaches activation and deactivation temperatures, respectively.

The refrigeration appliance can also contain one or more fans for distributing refrigerated air to different and respective compartments (frost free systems) . In this case, the control means may actuate in the operation of both the compressor and the fans. According to a way of carrying out the invention, the present system comprises an open door detecting means operatively associated with the control means, the latter being designed to reduce the compressor deactivation temperature when the temperature of the refrigerating compartment, detected by the temperature sensor, is higher than the compressor activation temperature not only at the door closing moment, but also at least at one more subsequent moment, presenting a delay in relation to the previous moment of verifying the reduction of the compressor deactivation temperature, in order to minimize temperature variations of the food stored in the refrigerating compartment. In case the temperature inside the refrigerating compartment rises to a value higher than the normal value, for instance due to a large amount of "hot" food introduced inside the refrigerating compartment, or to a longer opening time of the front door upon the closing of the latter, the construction mentioned above allows the control means to check the temperature indicated by the temperature sensor and to automatically provide, if necessary, a reduction in the compressor deactivation temperature, aiming at accelerating the recovery of the temperature inside the refrigerating compartment and producing a faster cooling of the stored food, so that the latter reaches the desired temperature of preservation as fast as possible.

It should be understood that in case the refrigeration appliance comprises a fan operatively associated with the control means and to at least one refrigerating compartment, the control means can be designed to reduce the deactivation temperature of the compressor and/or the fan, upon verification of said temperature rise in the refrigerating compartment after the closing of the door. In the present solution, the control means checks the temperature condition of the refrigerating compartment not only at the door closing moment, but also some minutes after the door is closed, and preferably, in one more occasion delayed in some minutes more since the closing of the front door, allowing the temperature sensor to have time to "sense" the effects of the high temperature of the amount of food placed in the refrigerating compartment and thus inform the control means of the presence and the permanence of an anomalous operational condition which requires adjustment of the operational temperature inside the refrigeration appliance, in order to reach the desired nominal temperature for preserving the food to be maintained under refrigeration.

It should be further understood that depending on the anomalous conditions detected by the temperature sensor and verified by the control means, the latter may instruct a reduction not only of the deactivation temperature of the compressor and/or the fan, but also of the activation temperature of the latter, these reductions of at least one of the operating temperatures of the compressor and/or of the fan being automatically carried out during more than one operational cycle of the compressor in case the temperature adjustment requires more intense and prolonged reductions of said operating temperatures. Brief Description of the Drawings

The invention will be described below, with reference to the enclosed drawings given by way of example of an embodiment of the invention, and in which: Figure 1 is a schematic median vertical sectional view of a refrigerator presenting a refrigerating compartment and provided with the present temperature adjusting system; Figure 2 illustrates a schematic diagram showing how the food temperature varies in a conventional refrigeration appliance and in a refrigeration appliance provided with the temperature adjusting system object of the invention; and Figure 3 illustrates a block diagram showing the algorithm adopted in the control means of a refrigeration appliance provided with the present temperature adjusting system, when applied to a refrigerating compartment RC which can be a refrigerating compartment or a freezing compartment. Detailed Description of the Invention As it can be noted in figure 1, the invention is related to a system for adjusting the operating temperature in a refrigeration appliance of the type which comprises a cabinet 10 defining at least one refrigerating compartment RC closed by a front door 11. The refrigeration appliance further comprises a refrigeration circuit which is not illustrated, except the part defined by the compressor 20 operatively associated with a control means 30 provided with a timer 31 and which is constructed in any known adequate manner to activate and deactivate the compressor 20 when the interior of the refrigerating compartment RC reaches activation and deactivation temperatures respectively detected by a temperature sensor 40 positioned inside the refrigerating compartment RC to sense the air temperature reigning inside the latter. The temperature sensor 40 is also operatively associated with the control means 30 to indicate to the latter when the air temperature inside the refrigerating compartment RC reaches any of the activation and deactivation values of the compressor 20, said activation and deactivation temperatures being determined within different operating ranges of the refrigeration appliance according to a scale containing different temperature operational ranges associated with different operational conditions of the refrigeration appliance.

It should be understood herein that the refrigeration appliance may be of the type comprising two or more refrigerating compartments RC, one of which defining for example a refrigerating compartment and another one defining a freezing compartment, to be operated through independent controls operatively associated with air temperature sensors inside the compartment. The refrigeration appliance can also be of the forced ventilation type provided with only one fan 50 operatively associated with an evaporator 55, or with two fans, one associated with a refrigerating compartment and the other with a freezing compartment, in the case of the combined refrigeration appliances. According to the invention, the present temperature adjusting system further comprises an open door detecting means 60 operatively associated with the control means 30, in order to indicate to the latter all closing and opening operations of the front door 11.

In figure 2 there is schematically illustrated a comparison between the behavior of a known refrigeration appliance and that of a refrigeration appliance in accordance with the invention, when especial events occur. Figure 2 refers specifically to a freezing compartment in which in a first portion A of the temperature X time diagram one can see how the food temperature oscillates between four and six degrees centigrade, thus following the normal air temperature variation in said freezing compartment . In a determined time B, corresponding to the occurrence of the especial event, for example the opening of the door 11 for a determined time longer than the time defined in project, the food temperature rises up to about nine degrees centigrade. Due to the high inertia of the food in changing its temperature as compared to the changes of the air temperature in a known refrigeration appliance, the food temperature takes more time to return to the nominal range between about four and six degrees centigrade for example. This is shown in portion C of the diagram. According to the present invention, in which the deactivation temperature of the compressor and/or the fan is reduced for the first operational cycle of the compressor after the occurrence of the special event, the food temperature takes less time to return to the desired range, defined by portion D of the diagram. The difference between the two recovery times is shown in figure 2 at reference letter E and it can be of several minutes or hours.

Still in accordance with the invention, the control means 30 is designed to reduce the deactivation temperature of the compressor 20 when the temperature of the refrigerating compartment RC detected by the temperature sensor 40 is higher than the activation temperature of the compressor 20 at the closing moment the front door 11, or at least at one more subsequent moment which presents a delay in relation to the previous moment.

According to a constructive form of the invention, the control means 30 checks the occurrence of a temperature of the refrigerating compartment RC higher than the activation temperature of the compressor 20 at the moment the front door 11 is closed and also minutes after said closing, and further one more time after the second checking. The time periods for the second and third checking after the door is closed can be for example of about 5 minutes and about 10 minutes, respectively. Thus, in the case the anomalous temperature rise of the refrigerating compartment has been caused by a substantial amount of "hot" food, this temperature rise may not be sensed by the temperature sensor 40 at the moment the front door 11 is closed. However, one of the other two verifications, the first being made some minutes after closing the front door 11 and the second made some minutes after said closing, will effectively detect the abnormal temperature rise inside the refrigerating compartment RC, informing the- control means 30 of the need to instruct a corresponding reduction in the deactivation temperature of the compressor 20. In case there is a temperature rise at the second and third checking moments, the control means will carry out the additional temperature adjustment. Thus, since the time the door is closed, up to three adjustments can occur.

When the refrigeration appliance is provided with an automatic defrost system to be also deactivated by the control means 30, the latter is designed to deactivate the automatic adjustment function of the deactivation temperature of the compressor 20 when the automatic defrost system is activated at said moments in which the control means 30 verifies the occurrence of a temperature rise of the refrigerating compartment RC to values higher than the activation temperature of the compressor 20.

Depending on the conditions or factors which provoke the temperature rise inside the refrigerating compartment RC, the temperature rise above the value in which the automatic activation of the compressor 20 is processed can present values with different magnitudes, and said temperature deviation value requires different intensity degrees for the automatic adjustment of the operational temperatures of the compressor, in order to reduce the recovery time of the temperature inside the refrigerating compartment and consequently of the food stored therein. Thus, the intensity of reduction of the deactivation temperature of the compressor 20 is defined by the control means 30 as a function of the magnitude of the temperature rise inside the refrigerating compartment RC above the activation temperature of the compressor 20. The reduction of the deactivation temperature of the compressor 20 modifies the value of said temperature, corresponding to the value of the activation and deactivation temperature operational range being used at the moment of the adjustment to a value corresponding to that of a lower range within a scale of activation and deactivation temperature ranges of the compressor 20.

According to the operational principle mentioned above, the control means 30 is further constructed to provide reduction of the deactivation temperature during an operating cycle of the compressor 20, returning said deactivation temperature to the value corresponding to the value of the activation and deactivation temperature operational range which has been adjusted for the refrigeration appliance. Thus, the control means 30 provides the necessary reduction of the deactivation temperature of the compressor 20 only during the operating cycle of the latter, returning said deactivation temperature to the value of the temperature operational range adjusted for the refrigeration appliance.

It is also possible to occur a situation in which the intensity of the reduction of the temperature operational range, defined in a determined operating cycle of the compressor, corresponds to activation and deactivation temperatures lower than those of the lowest temperature range within the scale of activation and deactivation temperature ranges of the compressor 20. When this occurs, the control means 30 instructs the repetition of the reduction of the activation and deactivation temperature operational range in a subsequent operating cycle of the compressor, aiming at bringing the temperature of the stored food and consequently of the interior of the refrigerating compartment to the desired values. Figure 3 illustrates the procedures or steps of actuation of the control means 30 during the operation of the refrigeration appliance and as a function of the parameters received from the temperature sensor 40, so as to effect when necessary an adjustment in the activation and deactivation temperatures of the compressor 20 and/or the fan 50 (when existing) , considering the application of the system in the temperature adjustment of a refrigerating compartment and a freezing compartment, generically known as refrigeration compartment.

In the block diagram of figure 3, the references in alphabetical characters are those reproduced below with the respective meanings : T₈ = temperature measured by the temperature sensor 40 of the refrigerating compartment RC;

Ton = activation temperature of the compressor 20 and/or the fan 50; t = difference between the temperature T_s measured by the temperature sensor 40 and the activation temperature T_0n of the compressor 20 and/or fan 50;

T_off = deactivation temperature of the compressor 20 and/or fan 50.

As illustrated, the adjustment system starts the operation upon the closing of the door, when the control means verifies whether the difference between the temperature T₃, measured by the temperature sensor 40 and the activation temperature T_0n of the compressor 20 and/or the fan 50 is higher than a reference value V_ref which for a refrigerating compartment can be for example 2 degrees centigrade, while for the freezing compartment is for example 5 degrees centigrade. In case said T₃ - T_0n difference is lower than V_ref, the control means 30 maintains the temperature operational range of the refrigeration appliance, not changing the activation temperature T_0n and the deactivation temperature T_Of_f of the compressor 20 and/or the fan 50.

Some minutes after the door of the refrigerating compartment RC is closed, for instance about five minutes, the control means 30 re-evaluates the difference between the temperatures T_s and T_0n so as to verify whether t is still maintained equal to or lower than the reference value V_ref which is of 2 degrees centigrade for the refrigerating compartments and 5 degrees centigrade for the freezing compartments. This t condition being maintained equal to or lower than V_ref, the control means maintains the refrigeration appliance working within the operational range previously adjusted by the user. It should be further understood that the control means carries out the same verification, comparing the t value with the reference value V_ref for the third time, some minutes for instance about ten minutes after the door is closed by the user. If t is maintained equal to or lower than the reference value V_ref, the control means instructs the refrigeration appliance to continue to operate within the same temperature operational range previously adjusted by the user, i.e., the same activation temperature T_0n and deactivation temperature T_Off of the compressor 20 and/or fan 50.

However, in case the control means verifies, at the closing moment of the door that t is higher than the reference value V_ref, it will provide an adjustment of the operational ranges of the activation temperature To_n and deactivation temperature T_Off of the compressor

20 and/or fan 50.

In case this verification of t value at the closing moment of the door indicates t < V_ref, about five minutes after the door is closed, the control means 30 evaluates again the t value and also in a third time, about ten minutes after the door is closed. In case t in the second verification or in the third verification presents a value which is equal to or higher than the reference value, the control means 30 provides a corresponding reduction of the temperature operational range of the refrigeration appliance, i.e. reduces the deactivation temperature T_off of the compressor 20 and/or fan 50. The adjustment system returns the operation of the refrigeration appliance to the temperature operational range adjusted by the user when T₃ is equal to T_off after one or two operating cycles regarding the refrigerating compartment, or after six hours and one operating cycle regarding the freezing compartment . In this condition, the appliance returns to its normal operation, until a new verification is carried out by the control means 30, upon a new closing of the door. As noted in figure 3, the operation of the control means can be adjusted for the refrigerating compartment and, if it is the case, for the freezing compartment, according to the respective tables illustrated in said figure.

In the case of adjusting the temperature of the refrigerating compartment, upon occurring a t lower than the reference value V_ref, equal to two degrees centigrade, the control means 30 maintains the temperature operational range adjusted for the refrigerating compartment RC. If t is higher than or equal to two degrees centigrade and lower than or equal to three degrees centigrade, the control means adjusts the temperature operational range of the refrigerating compartment RC to a cooler level within the scale of the operational ranges available in the refrigeration appliance. If t is higher than three degrees and lower than or equal to four degrees centigrade, the control means changes the temperature operational range, making it two levels cooler. The control means will promote changes within the temperature operational range of the refrigerating compartment to three levels cooler and four levels cooler when t presents values between four and five degrees centigrade and above five degrees centigrade, respectively, as illustrated in figure 3. Figure 3 also shows a similar table for the variations of the temperature operational ranges for the freezing compartment when there is variation of the t values. If t is lower than five degrees centigrade, the control means 30 maintains the same temperature operational range adjusted by the user. The temperature operational ranges are adjusted to one cooler level, two cooler levels, three cooler levels and four cooler levels when t value is respectively higher than or equal to five degrees centigrade and lower than or equal to seven degrees centigrade, higher than seven degrees centigrade and lower than or equal to nine degrees centigrade and lower than or equal to eleven degrees centigrade and higher than eleven degrees centigrade. As it can be noted from the description above, the present adjustment system allows the refrigeration appliance to automatically adjust the temperature operational ranges of the refrigeration compartment, whether a refrigerating compartment or a freezing compartment, with no interference of the user and in accordance with the thermal load conditions imposed to said appliance during operation.

Claims

1. A temperature adjusting system for a refrigeration appliance of the type which comprises: a cabinet (10) defining at least one refrigerating compartment (RC) closed by a front door (11) ; a compressor (20) ; optionally a fan (50) associated with at least one respective refrigerating compartment (RC) ; a temperature sensor (40) provided inside the refrigerating compartment (RC) ; and a control means (30) operatively associated with the compressor (20) , with the fan (50) , when existing, and with the temperature sensor (40) and which is provided with a timer (31) and constructed to activate and deactivate the compressor (20) and/or the fan (50) when the interior of the refrigerating compartment (RC) reaches activation and deactivation temperatures, respectively, characterized in that it comprises an open door detecting means (60) operatively associated with the control means (30) , the latter being designed to reduce the deactivation temperature of the compressor (20) and/or fan (50) when the temperature of the refrigerating compartment (RC) detected by the temperature sensor (40) is higher than the activation temperature of the compressor (20) and/or fan (50) at the closing moment of the front door (11) , pr at least at one more subsequent moment presenting a delay in relation to the previous moment, in order to minimize temperature variations of the food stored in the refrigerating compartment (RC) .

2. The system as set forth in claim 1, characterized in that the intensity of the reduction of the deactivation temperature of the compressor (20) and/or fan (50) is defined by the control means (30) , as a function of the magnitude of the temperature rise inside the refrigerating compartment (RC) above the activation temperature of the compressor (20) and/or fan (50) .

3. The system as set forth in claim 2, characterized in that the reduction of the deactivation temperature of the compressor (20) and/or fan (50) changes the value thereof, corresponding to the value of the activation and deactivation temperature operational ranges being used at the moment of the adjustment, to a value corresponding to that of a lower range within a scale of activation and deactivation temperature ranges of the compressor (20) and/or fan (50) .

4. The system as set forth in claim 3 , characterized in that the control means (30) is constructed to provide the reduction of the deactivation temperature during an operating cycle of the compressor (20), returning said deactivation temperature to the value corresponding to the value of the activation and deactivation temperature operational range which has been adjusted for the refrigeration appliance.

5. The system as set forth in claim 4, characterized in that the control means (30) instructs the reduction of the activation and deactivation temperature operational range in use in a subsequent operating cycle of the compressor (20) , when the intensity of the reduction of the temperature operational range, defined in the immediately previous operating cycle, indicates the necessity of activation and deactivation temperatures lower than those of the lowest temperature range in the scale of activation and deactivation temperature ranges of the compressor (20) and/or fan (50) .

6. The system as set forth in claim 1, characterized in that the control means (30) verifies the occurrence of a temperature of the refrigerating compartment (RC) which is higher than the activation temperature of the compressor (20) and/or fan (50) at the closing moment of the front door (11) and also at the two subsequent moments, the second verification being carried out some minutes after said closing and the third verification some minutes more after the second.

7. The system as set forth in claim 1, in which the refrigeration appliance is provided with an automatic defrost system to be activated by the control means (30) , characterized in that the control means (60) is designed to deactivate the adjustment of the deactivation temperature of the compressor (20) and/or fan (50) while the automatic defrost system is activated and possibly some time after at said moments in which the control means (30) verifies the occurrence of a temperature rise in the refrigerating compartment (RC) to values higher than the activation temperature.