The commercial or domestic type cooling systems have two compartments maintained at different temperatures; namely the freezer compartment in which frozen food is stored is at a lower temperature than the fresh food compartment where fresh food is stored. The refrigerators, in general, have been operated according to the functions set by the user, which are independent of the frequency of the door usage. Thus, the refrigerators perform the cooling cycle as required during the usage period, when they are used in high frequencies. Furthermore, the same refrigerators continue their normal operation even at lower usage frequencies or when they are not used. The normal operation of the fan motor and the compressor during low-frequency or non-usage periods, causes a great amount of energy consumption and noise.

In the state of art, the operation of the refrigerator in an economy mode is provided by determining the amount of light in the environment by means of a photocell, assuming that the door usage (opening) frequency is lower during the night.

The object of the invention is to reduce the power consumption and noise, originated from the running of the fan motor and the compressor, by passing to the power-saving mode during non-usage periods.

An embodiment of the refrigerator operating in economy mode, which is realized in order to attain the said object of the invention is illustrated in the attached drawings, wherein:

Figure 1, is a schematic block diagram of the thermostatic control circuits; Figure 2, is a flow chart showing the cooling cycle control sequence of the freezer compartment in the refrigerator; Figure 3, is a flow chart showing the cooling cycle control sequence of the fresh food comportment in the refrigerator; Figure 4, is the graphical representation of the temperature distribution in the freezer compartment; Figure 5, is the graphical representation of the temperature distribution in the fresh food compartment.

The components shown in the drawings have been enumerated individually, as follows: 1. Control unit 2. DC power supply unit 3. Driving unit 4. Display unit 5. Input unit 6. Function selecting unit 7. Temperature sensing unit In a two-door type refrigerator with freezer and fresh food compartments, when any one of the doors is not opened for a certain time period or in case the set values are not modified by the user, the cooling cycle continues according to a warmer value than the one set by the user. This value is not higher than the storage temperature that is critical for the food. By this implementation, the energy consumption is considerably reduced.

The control unit (1) consists of electronic memory elements, a micro processor and an A/D converter for the processing of the input data. The control unit (1) controls the refrigerator according to a programme that has previously been loaded to the memory.

The DC power supply unit (2) converts a source voltage from the AC power source to a DC voltage level as required by various units in the refrigerator.

The display unit (4) displays the actual temperature value in the freezer and fresh food compartments.

The function selecting unit (6) provides the selection of specific functions (e. g. quick-freeze, holiday, etc) and sets the user temperature in the freezer and fresh food compartments. When the user sets the temperature value from the function- selecting unit (6), the said values are sent to the control unit (1).

The temperature sensing unit (7) consists of the temperature sensors that detect the temperature in the freezer and fresh food compartments.

The driving unit (3) controls the compressor, fan motor, motorized damper, and the defrost heater in line with the signals sent from the control unit (1).

The input unit (5) is a freezer-and/or fresh food-door open/close sensor. In case one of the said doors are open, this unit (5) sends a signal to the micro processor, and another signal is sent by the said unit (5) when the said door is closed. The duration of the door-closed state, for each door, is determined by the micro- processor from the said signals and these duration periods are recorded in the memory of the control unit (1) to be evaluated. The control unit (1) uses the control signal reporting the door-closed state duration and whether a function key in the function selecting unit (6) is pressed or not, as well as the freezer and fresh

food compartments temperature data selected by the user and displayed in the display unit (4), as input data.

Topenl value, is the highest compartment temperature value determined by the user, during normal operation of the refrigerator.

TClosel value, is the lowest compartment temperature value determined by the user, during normal operation of the refrigerator.

Topen2 value, is the highest compartment temperature value determined by the manufacturer, in the power-saving mode.

Tclose2 value, is the lowest compartment temperature value determined by the user, in the power-saving mode.

Period 1, is the time period for the freezer compartment to convert to the economy mode.

Period 2, is the time period for the fresh food compartment to convert to the economy mode.

The time tl is the time period when the compressor and fan motor are active, in normal cooling cycle.

The time t3 is the time period when the compressor and fan motor are closed in normal cooling cycle.

The time t4 is the time period when the compressor and fan motor are closed in power-saving mode.

The time t5 is the time period when motorized damper and fan motor are active in normal cooling cycle.

The time t6 is the time period when motorized damper and fan motor are closed in normal cooling cycle.

The time t7 is the time period when motorized damper and fan motor are active in power-saving mode.

The time t8 is the time period when motorized damper and fan motor are closed in power-saving mode.

The time t9 is the time period when the refrigerator is operated in economy mode.

The control unit (1) receives the temperature data concerning the freezer and fresh food compartments that are sensed by the temperature sensing unit (7). The control unit (1) compares the data received from the temperature sensing unit and those obtained from the input unit (5). The average temperature values for the freezer and fresh food compartments are calculated and each of them is processed in the display unit (4) as outputs and these processed data are sent to the driving unit (3) and to the compressor, fan motor, motorized damper and defrost heater, chosen by the function selecting unit (6), in order to operate them. The compartment temperatures are automatically controlled depending on the normal cooling cycle or power-saving cycle modes.

The temperature control of the freezer compartment made by the control unit (1) is shown in the flow chart (Fig. 2).

In the first step, the control unit (1) controls whether the freezer door is open or not, and in Step 2 it controls whether the function key is pressed or not. In step 6 if the door is open or if the function key is pressed, the counter is reset (t=0) the

control unit (1) carries out its normal operation. In Step 5, the compressor and fan motor are driven by the driving unit (3) and a normal cooling cycle is performed for the freezer compartment according to the values set by the user in Step 7. If the door is not opened and the function key is not pressed for a time period (period 1) as defined by the formula: (t2period 1), the control unit (1) is realizing power-saving according to the values mentioned in Step 4. In Step 5, the compressor and the fan motor are driven by the driving unit (3) according to the values recorded in the memory in Step 4, instead of the values defined in Step 7 and set by the user.

The control of the freezer compartment temperature made by the control unit (1) is illustrated in the flow chart in Fig. 3.

In Step 8, the control unit (1) controls whether the freezer door is open or not; whereas in Step 9 it controls whether the function key is pressed or not. In Step 13, the counter is reset (t=0) and the control unit carries out its normal operation, if the door is open or if the function key is pressed. In case one of the events mentioned in Step 8 or Step 9 occurs, motorized damper is opened by the driving unit (3) at step 12 according to the values selected by the user in Step 14 and the normal cooling cycle set by the user for the freezer compartment, is performed by driving (running) the fan motor. If the door is not opened and the function key is not pressed for a time period (period 2) as defined by the formula (t2 period 2), the control unit (1) realizes the power saving in Step 11. In Step 12, the values selected by the user in Step 14 are replaced by the values recorded to the memory in Step 11 according to which the motor clapet valve is opened and the fan motor is driven by the driving unit (3).

The power-saving mode can operate in both compartments independently from each other.

The compressor and the fan maintain the temperature in the freezer compartment in the range between Topenl and Close, values during the normal cooling cycle.

When the temperature in the freezer compartment exceeds the Topenl value as detected by the freezer compartment temperature sensing unit (7), the compressor and the fan are operated by the driven unit (3). If the said temperature measured by the temperature sensing unit (7) is below the Tetose) value, the compressor and the fan are stopped by the driving unit (3).

The compressor run time percentage of the refrigerator in normal cooling cycle is calculated as below: PRT (NC) = 100* tl/ (tl+t2) In case the freezer door is not opened and any one of the function key is not pressed, the normal cooling cycle is switched to the power-saving mode at the end of a time period (period 1), and the freezer compartment temperature is maintained between the warmer values, (Topen2 and Tclose2) until a function key is pressed or its door is opened, by driving the compressor and the fan. When the freezer compartment temperature measured by the temperature sensing unit (7), exceeds the value Topen2, the compressor and the fan are driven by the driving unit (3). Otherwise, i. e. if the freezer compartment temperature is measured by the temperature sensing unit (7) as below the value Te) ose2 ? they are stopped by the driving unit (3).

The compressor run time percentage of the refrigerator in power-saving mode, is calculated as below: PRT (PS) =100*t3/ (t3+t4)

The compressor run time percentage of the refrigerator in normal cooling mode is greater than that in its power-saving mode.

PRT (NC) > PRT (PS) As the operational rates of the compressor and the fan are reduced in the freezer compartment switched to the power saving mode, energy is saved.