The present invention relates to a method of operation of a household refrigerating apparatus and to a household refrigerating apparatus implementing said method.
It is worth stating beforehand that the term household refrigerating apparatus as used in the present description and in the appended claims refers to those refrigerating apparatuses which comprise a first cooled compartment which is typically kept at a temperature between 0 °C and 12°C (commonly called refrigerator compartment) and a second cooled compartment which is typically kept at a lower temperature between -12 °C and -35 °C (commonly called freezer compartment).
More in particular, the present invention addresses all those refrigerating apparatuses which are commonly referred to as no-frost, wherein the cooling of the foodstuffs stored in both cells is ensured by cold air conveyed therein by a forced ventilation system; the circulating air is cooled by an evaporation-type exchanger, or evaporator, by thermal exchange with a colder refrigerating fluid circulating within a refrigerating circuit that comprises at least one compressor, one condenser and one expansion valve.
A household refrigerating apparatus of the no-frost type as described above typically produces some operating noise mainly caused by two components: the compressor and the fan of the forced ventilation system; of these two components, the compressor is certainly the one which is more noisy (in terms of noise perceived within the apparatus installation environment), since the fan is arranged inside the apparatus, near the channels that circulate the cold air into both compartments.
As a matter of fact, when the apparatus is operating normally, the compressor starts whenever cold air must be produced in order to maintain the preset temperature inside the cells: tests carried out have shown that the frequency of compressor intervention in a refrigerating apparatus placed in an environment at 25°C with the cell access doors closed is approximately thirty minutes of continuous operation per hour.
It can therefore be easily understood that the frequent activation of the compressor represents a source of disturbance, in particular in all those situations where the need of reducing noise is particularly felt, e.g. during the night.
Some solutions have been conceived in the art, such as the one described in patent
However, this solution is not optimal, in that the compressor must still be activated, although at lighter operating conditions, in order to keep the compartments at a preset operating temperature, and this prevents total or almost total silence from being obtained (as required, for example, when a refrigerating apparatus is to be installed near a bed in a one-room or two-room apartment).
Another solution is disclosed in document
The present invention aims at overcoming these and other drawbacks of the systems known in the art through a method of operation for a household refrigerating apparatus according to claim 1.
The present invention also relates to a household refrigerating apparatus implementing said method.
The present invention is based on the idea of using the freezer compartment (i.e. the one kept at a lower temperature than the refrigerator compartment) as a tank from which cold air can be taken and conveyed into the refrigerator compartment (operating at a higher temperature) in order to keep the latter at a preset and possibly constant temperature while keeping the compressor off, after the freezer compartment has been brought to a temperature below its normal operating temperature, which condition does not affect the quality of preservation of the foodstuffs stored in such compartment.
This advantageously allows the compressor to stay off for a long time, approximately three to eight consecutive hours, thereby eliminating any noise related to compressor operation. Further advantageous features will be set out in the appended claims, which are intended as an integral part of the present text.
These features as well as further advantages of the present invention will become apparent from the following description of an embodiment thereof as shown in the annexed drawings, which are supplied by way of non-limiting example, wherein:
The air flow coming from the freezer compartment 3 and directed to the refrigerator compartment 2 is regulated by means of an on-off valve 8 installed in the channel 6 (commonly called "damper" by those skilled in the art), which is shown herein in its simplest form, i.e. a gate that shuts off the cross-section of the channel 6.
The position of the on-off valve 8 may vary depending on specific implementation requirements; in general, it may be located anywhere along the channel 6 that carries the air from the freezer compartment 3 to the refrigerator compartment 2: for example, if the second fan 12 is not provided, the on-off valve may be installed in its place, i.e. in that part of the channel 6 which is closest to the refrigerator compartment 2.
The forced air circulation is conceived in a manner such that the air exiting the refrigerator compartment 2 flows back into the freezer compartment 3 through an additional return duct (not shown for clarity), which puts the refrigerator compartment 2 in fluidic communication with the freezer compartment 3, so that the air is cooled down again by the evaporator 4 and a new cycle is started.
Of course, an on-off valve may be installed on the air return duct as well; however, the characteristics of said return duct and of its on-off valve are not important for understanding the present invention and may vary depending on specific construction requirements.
The evaporator 4 belongs to a refrigerating circuit of a per se known type, which also includes a compressor 9, a throttling valve 10 and a condenser 11, with all the respective connection pipes (indicated by means of a dashed-dotted line in the drawing).
The fans 5 and 12 and the on-off valve 8 are driven each by a respective electric motor (not shown) controlled by a control unit (not shown) which receives the temperature data read by the sensors 17 and 18 and controls the refrigerating cycle accordingly, e.g. by controlling the operation of the compressor 9.
In general, of course, the presence of an additional compartment will not affect the method of operation of the refrigerating apparatus 1.
During the normal operating cycle, the control unit is inputted the temperatures Tf and Tc respectively detected by the sensors 17 and 18 and then controls the compressor 9, the fans 5 and 12 (if present) and the on-off valve 8 accordingly so as to keep the temperatures in both compartments 2 and 3 within preset values: the average temperature in the refrigerator compartment 2 can typically be set between 2°C and 12°C, whereas the average temperature in the freezer compartment 3 can be set between -18°C and -26°C, in both cases with an oscillation of about 4°C around the set average value.
More in detail, if during a normal operating cycle the sensors 17 and 18 detect a temperature rise in the refrigerator compartment 2 or in the freezer compartment 3, the compressor 9 will be started, the fans 5 and 12 will be turned on, and the on-off valve 8 will be opened (completely or partially), so as to cool down the freezer compartment 3 and partialize the cold air flow directed therefrom towards the refrigerator compartment 2, thereby adjusting the temperature thereof.
In this regard, it should be pointed out that during the normal operating cycle the fans 5 and 12 are turned on and the on-off valve 8 is made to open the channel 6 only when the compressor 9 is operating; as soon as the latter is switched off, the fans 5 and 12 will be deactivated and the on-off valve 8 will close the channel 6.
The method of operation according to the present invention is based on the execution of at least the following steps:
Taking a cold air flow from the freezer compartment 3 necessarily implies that the temperature of the latter will rise; for this reason, a maximum threshold temperature may be set above which the compressor 9 will be turned on, thus ending the quiet operation mode. Aiming at extending the period of quiet operation (i.e. with the compressor 9 switched off) of the refrigerating apparatus 1, the method provides for carrying out, prior to step b) as previously described, a step a) consisting of bringing the temperature of the freezer compartment 3 down to a value Tinf which is lower than the normal operating temperature Tcn; this is made possible by the fact that a decrease in the temperature inside the freezer compartment 3 below the normal operating temperature Tcn will cause no damage to the foodstuffs stored therein, while at the same time allowing the freezer compartment 3 to cool the air directed to the refrigerator compartment 2 for quite a long time before the temperature rising inside the freezer compartment requires that the compressor 9 be turned on again.
More specifically, step a) is effected by keeping the compressor 9 on for a longer time than normal: for example, if in normal operation the compressor stays on for approximately thirty minutes, in this case it may be kept on continuously for a period which may vary preferably between sixty and one hundred and eighty minutes, and anyway in a manner such that the temperature in the freezer compartment 3 drops below the normal operating temperature Tcn (typically Tcn=-18°C), e.g. until a value Tinf in the range of -23°C to -26°C is reached, i.e. five to eight Celsius degrees less than temperature Tcn.
In this respect, it must be pointed out that step a) may be effected by using as a control quantity either the operating time of the compressor 9 or the temperature reached in the freezer compartment 3: such quantities are related in a proportional manner to each other, i.e. the longer the continuous operation of the compressor 9, the lower the temperature reached in the freezer compartment 3. For the purposes of the present invention, either solution may be adopted for executing step a), i.e. it is possible to choose whether the compressor 9 should operate for a preset period of time or, alternatively, until it is detected that a temperature threshold has been reached in the freezer compartment 3.
After step a) has been carried out, independently of the control quantity employed (operating time or temperature in the freezer compartment 3), the compressor 9 is turned off, thereby starting the quiet operation of the refrigerating apparatus 1: in this situation, the sensors 17 and 18 detect the temperatures Tf and Tc in both compartments 2 and 3 at predefined time intervals (or continuously) and send the data obtained to the control unit. Assuming that the doors 14 and 15 stay closed, the two compartments 2 and 3 will remain at optimal temperatures for a certain period of time, thanks to the gaskets and insulation provided.
Due to the thermal exchange with the environment surrounding the refrigerating apparatus 1, however, the temperatures in both compartments 2 and 3 will tend to rise again.
In particular, after a certain time has elapsed, the temperature Tf in the refrigerator compartment 2 will rise above a set threshold value TfMAX (e.g. TfMAX=5°C); on the other hand, the temperature Tc in the freezer compartment 3, which during step a) was brought much below the normal operating temperature (to value Tinf), will still remain for a long time at a value below a predefined threshold value Tsup, which may be chosen to be equal to the normal operating temperature Tcn (e.g. Tsup=Tcn=-18°C).
When the control unit detects that the preset threshold temperature TfMAx in the refrigerator compartment 2 has been exceeded, it opens the on-off valve 8 and turns on the fan 5 and (if present) also the second fan 12 in order to carry out step c), wherein a cold air flow is taken from the freezer compartment 3 and is conveyed into the compartment at the higher temperature, i.e. the refrigerator compartment 2, until the latter reaches again a preset temperature, e.g. equal to the lower threshold value Tfmin, without the help of the compressor 9, which is left off.
Step c) may be carried out multiple times, at least as long as the temperature inside the freezer compartment 3 remains below the predefined maximum threshold value Tsup.
In this regard, it should be noted that step c) may be effected either continuously or through a certain number of repetitions; in the former case, the on-off valve 8 will always stay at least partially open, and the fans 5 and 12 (if present) will be turned on (possibly at a variable revolution speed) based on the temperature values detected in the refrigerator compartment 2: if the temperature rises, the fan 5 and/or 12 will be turned on and possibly the on-off valve 8 will open a larger section of the channel 6 (in order to let more cold air flow therethrough) for the purpose of lowering the temperature in the refrigerator compartment 2; when the temperature in the latter becomes optimal, the fan 5 and/or 12 will be turned off (or, likewise, the revolution speed thereof will be reduced to the minimum), but the on-off valve 8 will stay open.
As a preferable alternative, step c) is effected by repeating the steps of opening the on-off valve 8 and activating the fan 5 and/or 12 until the threshold temperature Tfmin is reached in the refrigerator compartment 2, which condition will be followed by the fan being turned off and the on-off valve 8 being closed as soon as the temperature in the refrigerator compartment 2 reaches a predefined value.
In any case, when the sensor 18 detects that the temperature inside the freezer compartment 3 has reached or exceeded a maximum threshold value (Tc≥Tsup), the quiet operation cycle will end and the compressor 9 will be turned on again.
It must be pointed out that in optimal conditions, i.e. when the refrigerating apparatus 1 is placed in an environment at approximately 10°C and the doors 14 and 15 are not open, by setting the threshold values as follows:
Even in less favourable conditions, e.g. when ambient temperature is 35°C, it has been discovered that this solution allows to leave the compressor 9 off for a time longer than three consecutive hours, thus leading to a definite improvement over prior-art systems.
Of course, repeated openings of the door 15 of the freezer compartment 3 may heavily affect the time of operation with the compressor 9 off. However, it is often desirable that the apparatus be quiet at nighttime, when the compartments of the refrigerating apparatus 1 are accessed relatively seldom (or never at all), so that the behaviour of a refrigerator implementing such a method is deemed to be satisfactory.
The flow chart of the method of operation according to the present invention is shown in
The temperature Tf in the refrigerator compartment 2 is then detected: as long as it remains below the maximum threshold TfMAX, no action will be taken.
When the temperature Tf rises above the maximum threshold value TfMAX, the temperature Tc in the freezer compartment 3 will be verified: if this is lower than the upper threshold value Tsup, the on-off valve 8 will be opened and the fan 5 or the second fan 12 (if present) will be turned on in order to direct a cold air flow from the freezer compartment 3 to the refrigerator compartment 2, until the temperature Tf in the refrigerator compartment 2 becomes equal to the lower threshold value Tfmin, at which the on-off valve 8 will be closed and the fan(s) 5 and 12 will be turned off.
If, on the contrary, after the temperature Tf has risen above the maximum threshold value TfMAX, it is verified that the temperature Tc in the freezer compartment 3 is higher than the upper threshold value Tsup, then the cycle will be considered to be finished and the compressor 9 will be turned on, the on-off valve 8 will be opened, and the fans 5 and 12 will be turned on in order to restore the temperatures of the normal operating cycle.
According to an advantageous variant, the threshold temperatures set for the refrigerator compartment 2 are equal to each other, i.e. Tfmin is equal to TfMAX.
In such a case, the system will still operate as described above, except that the temperature in the refrigerator compartment 2 will always be kept substantially around a single predefined value, i.e. Tfmin=TfMAX.
In this regard, it must be pointed out that this variant also provides for changing the temperature thresholds of the refrigerator compartment 2 as the compressor 9 is operating continuously during step a): in normal operation, as aforementioned, the cooling of the refrigerator compartment 2 is controlled in a manner such that the temperature of the latter oscillates by about 4°C around a set average value; in this variant of the method, instead, during step a) the temperature of the refrigerator compartment 2 is already set to the value Tfmin=TfMAX, i.e. the temperature threshold value to be maintained in the course of the subsequent step c), so that when the latter starts the temperature in the refrigerator compartment 2 will have already reached the value to be maintained when operating with the compressor 9 off.
Said temperature value Tfmin=TfMAX is reached and maintained in the refrigerator compartment 2 by turning on the fans 5 and/or 12 and by opening and closing the on-off valve 8, so as to deliver a variable cold air flow into the refrigerator compartment 2 in order to bring it to the desired temperature Tfmin=TfMAX and keep it at that temperature.
It is important to underline that the solution provided by this variant allows to extend the time during which the compressor 9 stays off and cold air is taken from the freezer compartment 3; in fact, the more the instantaneous temperature inside the refrigerator compartment 2 is kept constant, the less thermal energy must be used for keeping the average temperature constant, and hence the longer the time that the compressor 9 will stay off.
This solution is shown in
As can be seen, in normal operation an operating cycle is activated which comprises the steps of the method according to the present invention: during the above-described step a), the compressor 9 is turned on for a period of time of approx. 80 minutes, during which the temperature in the freezer compartment 3 drops from an initial value (in the steady state of normal operation) of approx. -18°C to a value Tinf of approx. -25°C, as shown by the trend of the bundle of curves C2. Within this period of time, the value of the temperature in the refrigerator compartment 2 also drops from a higher initial value to settle around a value TfMAX of approx. 4°C, as shown by the trend of the bundle of curves C1, in accordance with the above discussion.
When such values are reached, step b) of the above-described method is carried out, wherein the compressor 9 is turned off and the on-off valve is closed.
Subsequently, for a period of about four hours, the temperature in the refrigerator compartment 2 is kept substantially constant, being (Tfmin=TfMAX) approximately equal to 5°C, by implementing step c) of the method, i.e. by taking cold air flows from the freezer compartment 3, the temperature of which, as shown by the trend of the bundle of curves C2, rises up to the threshold value Tsup, at which step c) will end and the normal operation of the refrigerating apparatus 1 will be resumed.
It should be noted that the temperature Tinf may be, in general, any temperature lower than Tcn, although the best results are attained by setting it to a value lower than the temperature Tcn by three to ten Celsius degrees, in particular six Celsius degrees.
More specifically, the threshold value Tfmin varies between 0°C and 2°C, the threshold value TfMAX varies between 4°C and 6°C, the threshold value Tsup varies between -20°C and - 16°C, and the threshold value Tinf varies between -24°C and -30°C, the normal operating temperature of the freezer compartment 3 being approx. -18°C.
As concerns the command issued by the user in order to start the method of operation described so far, three different conditions may take place, respectively coinciding with manual, semi-automatic and automatic operation.
In the first case (manual control), the user sets the method starting instant (coinciding with the beginning of step a)) by simply pressing a button specifically intended for that purpose.
In the second case (semi-automatic operation), the user sets a time interval after which the refrigerating apparatus 1 will have to start operating in quiet mode; for example, the user may want the refrigerating apparatus 1 to start operating in quiet mode after four hours, which coincides, as described above, with the fact that the compressor 9 will have to stay off after the selected time interval; in this case, the control unit of the refrigerating apparatus 1 includes a timer and controls the execution of step a) at a time preceding the time chosen by the user, so that said step will be completed at the end of the selected time interval. It must be pointed out that this mode of operation is particularly feasible when the control quantity in use for step a) is the continuous operating time of the compressor 9, as opposed to the temperature reached in the freezer compartment 3.
In the third case (automatic operation), the user sets a time at which the quiet operation mode will have to start (i.e. steps b) and c)): in this case, the control unit includes a suitable clock or timer, and controls the execution of step a) in a manner such that it will end at the time set by the user. In this case as well, it will be preferable to use the operating time of the compressor 9 instead of the temperature reached in the freezer compartment 3 as a control quantity for step a).
The present invention also relates to a refrigerating apparatus 1 of the type shown in and described with reference to
As a variation, it should be pointed out that, in the refrigerating apparatus 1, the shelves 13 may be equivalently replaced with drawers or compartments; likewise, the on-off valve 8 may be of any kind (e.g. butterfly, sector or the like), provided that it is suitable for intercepting the channel 6 in order to allow the air flow carried therethrough to be adjusted. In turn, the channel 6 may be arranged differently than illustrated herein, for example by connecting different points of the compartments 2 and 3, without however departing from the scope and objects of the present invention.
The on-off valve 8 may then be placed anywhere along the channel 6, e.g. even in a position adjacent to the refrigerator compartment 2.
Finally, the fans 5 and 12 may be arranged differently than illustrated herein and, as aforementioned, the second fan 12 may be omitted.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.