GB2390419A

GB2390419A - Controlling the operation of cooling systems provided with two evaporators

Info

Publication number: GB2390419A
Application number: GB0230334A
Authority: GB
Inventors: Eui Yeop Chung; Se Young Kim; Kyung Sik Kim; Yang Gyu Kim; Tae Hee Lee
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2002-07-04
Filing date: 2002-12-31
Publication date: 2004-01-07
Anticipated expiration: 2022-12-31
Also published as: GB2390419B; GB0230334D0; DE10260350A1; CN1467459A; JP2004037065A; DE10260350B4; JP3816872B2

Abstract

A method for controlling the operation of a cooling system. The cooling system has two evaporators located within separate storage spaces and control means to measure the temperature of each storage space. The measured temperatures are compared and the amount of refrigerant introduced into each evaporator adjusted accordingly. The amount of refrigerant introduced may be adjusted by varying the opening ratio of a valve unit installed at a branch point of a refrigerant pipe connected to each evaporator. The control may stop the operation of a compressor if the temperature of storage spaces is below a lower temperature limit. Alternatively, the method includes the step of after either a first cycle or a second cycle is completed, operating a compressor while a valve unit is closed for a predetermined time. Alternatively, the method further includes the step of intermittently operating a first cycle fan associated with the first cycle expansion unit and a second cycle fan associated with a second cycle expansion unit after the operation of a compressor is stopped.

Description

239041 9

The present invention relates to a method for controlling operation of a cooling system.

Generally, the refrigerator is an apparatus used for storage of fresh foods for a prolonged 5 period, and is generally divided into a main body having a plurality of food storage spaces, and a cooling unit for cooling the food storage spaces.

The main components of the cooling unit include a compressor, a condenser, an evaporator and an expansion valve. Generally, the compressor and the condenser are 10 installed within a machine space at the rear lower part of the main body, and the evaporator and the expansion valve are installed adjacent the food storage spaces. The food storage spaces of the main body are cooled as set out below.

First, the refrigerant in a gas state is compressed by the compressor, and the compressed 15 refrigerant is transferred into the condenser. Subsequently, the refrigerant is liquefied in the condenser by heat exchange. Upon being injected from the expansion valve in to the evaporator, the condensed, liquid refrigerant expands rapidly and thus evaporates. By evaporating, the refrigerant absorbs heat from the periphery of the evaporator thereby cooling the food storage spaces. Finally, the evaporated refrigerant returns to the 20 compressor and is compressed into the liquid state, and then repeats the aforementioned condensation, expansion, evaporation, and compression cycle, thereby to keep the food storage spaces at a low temperature.

In one embodiment, the cooling system of the refrigerator may be constituted such that a 25 single evaporator supplies cooling air to the plurality of food storage spaces. In recent years, in order to use the characteristics of the separate food storage spaces to the full and enhance cooling performance, the cooling system is constituted such that a plurality of evaporators are separately installed and controllable.

Thus, the cooling system provided with the plurality of evaporators (hereinafter referred to as the cooling system provided with two evaporators for the convenience of the description) includes a branched refrigerant pipe through which the refrigerant flows via

5 the compressor and the condenser. The refrigerant pipe is connected to two evaporators (F-evaporator and it-evaporator). A valve unit is installed at the branched point for opening/closing the passage of the two branched tubes. The valve unit can be switched such that the refrigerant is introduced into either F-evaporator or it-evaporator, thereby selectively cooling one of the two food storage spaces.

Generally, the cooling system provided with these two evaporators operates in such a manner that it switches the compressor off if the temperatures of all the food storage spaces meet a preset condition set in advance by the control unit, and switches the compressor on if the temperature of any the food storage spaces rises over a preset upper 15 limit set in advance by the control unit. By repeating such an operation, the temperatures of the respective food storage spaces are maintained within a temperature range set in advance by the control unit.

However, since a refrigerator having such a cooling system controls the temperatures of 20 the respective food storage space by supplying the refrigerant to only one of the two evaporators at a time, a significant temperature deviation in the respective food storage spaces is generated. In other words, when the refrigerant is supplied to one of the two evaporators, the refrigerant is not supplied to the other evaporator and the fan feeding cool air is also stopped. As a result a large deviation in the temperatures of the food 25 storage spaces is generated when the circulation of the cool air is stopped in one room in order to operate the evaporator of the other room.

After the cooling system provided with the aforementioned two evaporators performs a cycle feeding the refrigerant to one of the two evaporators, another cycle feeding the refrigerant to the other one is performed by switching the valve unit. This gives rise to S the problem that the refrigerant introduced in the first evaporator remains there after the supply of the refrigerant is stopped. In other words, after the F-cycle is performed, supplying the refrigerant to the F-evaporator, the R-cycle is performed supplying the refrigerant to the it-evaporator by switching the valve unit. The refrigerant that has been introduced into the Fevaporator does not flow while the R-cycle is performed but 10 remains in the F-evaporator in a nearly liquid state. This problem equally occurs when the compressor is stopped after the R-cycle, when refrigerant present in the it-evaporator remains there. Hence, if a separate device or method for withdrawing the refrigerant remaining in the evaporator is not applied, refrigerant always remains in either one of the two evaporators.

Thus, not all of the refrigerant remaining in the evaporator is drawn into the compressor or condenser after one cycle is completed. Some of the refrigerant is not available when another cycle is performed, which causes the cooling performance to be lowered.

20 Also, when the compressor is gain operated, the liquid refrigerant remaining in the evaporator is introduced into the compressor, resulting in lubrication problems within the cylinder. This adversely affects reliability of the cooling cycle.

The present invention is directed to a method for controlling operation of a cooling 25 system provided with two evaporators that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to reduce a deviation in the temperatures of the respective food storage rooms in a refrigerator having a cooling system provided with two evaporators. Another object of the present invention is to prevent a refrigerant loss and maintain the reliability of the compressor by withdrawing refrigerant remaining in the evaporator during the cooling cycle.

lO A further object of the present invention is to enhance the cooling performance in a cooling system provided with two evaporators.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill

15 in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims

hereof as well as the appended drawings.

20 To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a method for controlling operation of a cooling system provided with two evaporators. The method includes the steps of: (a) setting a plurality of reference temperatures for each of storage rooms; (c) measuring temperature of each of the rooms; (d) comparing the measured 25 temperatures of the respective rooms; and (e) adjusting amount of a refrigerant introduced into the evaporator of each of the rooms based on a comparing result between the temperatures of the respective rooms.

Here, the step of (c) is performed by a temperature sensor installed in each of the food storage rooms, and the reference temperature includes an upper limit temperature and a lower limit temperature.

The amount of the refrigerant introduced into the evaporator in the step of (e) is adjusted by adjusting an opening ratio of a valve unit installed at a branch point of a refrigerant pipe connected to the evaporator of each of the rooms. If the temperatures of the respective spaces are above the upper limit temperature, the opening ratio of the valve 10 unit is 50 %. If the temperatures of the respective spaces are the same in a zone having a temperature above the lower limit temperature, the opening ratio of the valve unit is 50 %.

If the temperature of any one of the respective spaces is higher than that of the other space in a zone having a temperature above the lower limit temperature, the valve unit is controlled to be further opened toward the evaporator side of the space having a higher 15 temperature relative to the other space. Also, if the temperature of any one of the respective spaces is less than the lower limit temperature, the valve unit is controlled such that all the refrigerant flows through toward the evaporator of the space having the temperature higher relative to the other space. If the temperatures of the respective spaces are less than the lower limit temperature, the operation of the compressor is stopped.

In another aspect of the present invention, there is provided a method for controlling operation of a cooling system provided with two evaporators. The method includes the step of: (b) setting a plurality of temperature zones for each of storage spaces; (c) measuring temperature of each of the spaces; (d) comparing the measured temperatures of 25 the respective spaces; and (e) adjusting an amount of refrigerant introduced into the evaporator of each of the spaces based on a comparing result between the temperatures of the respective rooms.

Here, the step of (c) is performed by a temperature sensor installed in each of the storage spaces, and the temperature zones includes: an An zone above the upper limit temperature; a Bn zone less than the upper limit temperature and above a setting 5 temperature; a Cn zone less than the setting temperature and above the lower limit temperature; and a Dn zone less than the lower limit temperature. The step of (d) is performed by comparing the measured temperatures of the respective spaces with the temperature zones.

10 Also, the amount of the refrigerant introduced into the evaporator in the step of (e) is controlled by controlling the opening ratio of the valve unit installed at the branch point of the refrigerant pipe connected to the evaporator of each of the storage spaces. If the temperatures of the respective spaces are the same, the valve unit is opened at an identical ratio. At this time, the opening ratio of the valve unit is preferably 50 %. If all the 15 temperature zones belong to the Dn zone, the operation of the compressor is stopped. If the temperature zone of only one of the respective spaces belongs to the Dn zone, the opening ratio of the valve unit of the room belonging to the Dn zone to the space belonging to another zone is 0 %: lOO %. If the temperature zone of one of the respective spaces belongs to the An zone and the temperature zone of the other one belongs to the 20 Cn zone, the opening ratio of the valve unit of the room belonging to the An zone to the room belonging to the Cn zone is 100 %: 0 %. If the temperature zone of one of the respective spaces belongs to the Bn zone and the temperature zone of the other one belongs to the Cn zone, the valve unit is controlled to be opened more toward the space belonging to the temperature zone which is relatively higher in temperature. At this time, 25 the opening ratio of the valve unit of the space belonging to the higher temperature zone to the lower temperature zone is preferably 80 %: 20 %.

In another aspect of the present invention, there is provided a method for controlling operation of a cooling system provided with two evaporators. The method includes the step (f) operating a compressor while a valve unit is closed for a predetermined time (At) 5 when the cooling system switches from an F-cyc]e in which a refrigerant passing through a condenser sequentially flows through an F-expansion unit and an F-evaporator to an R-

cycle in which the refrigerant passing through the condenser sequentially flows through an it-expansion unit and an it-evaporator by control of the valve unit.

10 Preferably, the method further comprises the step of operating an Ffan for cooling the F-

expansion unit while the step (f) is performed. Also, the method further may include the step of operating a fan of the condenser while the step (f) is performed.

In another aspect of the present invention, there is provided a method for controlling 15 operation of a cooling system provided with two evaporators. The method includes step (g) operating a compressor while a valve unit is closed for a predetermined time (At) when either an F-cycle in which refrigerant passing through a condenser sequentially flows through an F-expansion unit and an F-evaporator or an R-cycle in which the refrigerant passing through the condenser sequentially flows through an it-expansion unit 20 and an it-evaporator is completed.

Preferably, the method further includes the step of operating a corresponding fan while the step (g) is performed. Also, the method further may include the step of operating a fan of the condenser while the step (g) is performed.

In another aspect of the present invention, there is provided a method for controlling operation of a cooling system. The method includes the steps of: operating a compressor

while the valve unit 3 is closed for a predetermined time (At) when either an F-cycle in which the refrigerant passing through a condenser sequentially flows through an F-

expansion unit and an F-evaporator is completed or an R-cycle in which the refrigerant passing through the condenser sequentially flows through an it-expansion unit and an R S evaporator is completed; intermittently operating an F-fan for cooling the F-expansion unit and an it-fan for cooling the it-expansion unit respectively after the operation of the compressor is stopped.

Here, the method may further include the step of intermittently operating the fan of the 10 evaporator belonging to the cooling cycle of the stopped one when either the F-cycle or the R-cycle is performed. The method may further include the step of extendingly operating the fan of the evaporator associated with the corresponding cooling cycle for a predetermined time period when either the F-cycle or the R-cycle is completed. The method may Further include the step of extendingly operating the fan of the evaporator 15 belonging to the corresponding cooling cycle for a predetermined time period intermittently. At this time, an intermittent time ratio of operation time to stop time in the Ffan and the it-fan is preferably 4: 6.

In another aspect of the present invention, there is provided a method for controlling 20 operation of a cooling system selectively performing an F-cycle in which a refrigerant passing through a condenser sequentially flows through an F-expansion unit and an F-

evaporator or an R-cycle in which the refrigerant passing through the condenser sequentially flows through an it-expansion unit and an itevaporator, the method comprising the step of: intermittently operating an F-fan and an it-fan even after the 25 operation of the compressor is stopped.

Here, the method may further include the step of intermittently operating the fan of the evaporator associated with a stopped R or F cooling cycle when, respectively, either the F-cycle or the R-cycle is performed. The method may further include the step of extendingly operating the fan of the evaporator belonging to the corresponding cooling S cycle for a predetermined time period when either the F-cycle or the R-cycle has been performed and is completed. The method may further include the step of extendingly operating the fan of the evaporator belonging to the corresponding cooling cycle for a predetermined time period and intermittently operating the fan when either the F-cycle or the R-cycle has been performed and is completed. At this time, an intermittent time ratio 10 of operation time to stop time in the F-fan and the it-fan is 4: 6.

It is to be understood that both the foregoing general description and the following

detailed description of the present invention are exemplary and explanatory and are

intended to provide further explanation of the invention as claimed.

The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the

principle of the invention. In the drawings: FIG. 1 is a schematic view of a cooling system provided with two evaporators; FIG. 2 is a flow chart illustrating a method for controlling operation of a cooling system according to a first embodiment of the present invention;

FIG. 3 is a table showing opening ratios of the valve unit depending on the temperatures of the respective food storage rooms in the operation control method of the cooling system according to the first embodiment; 5 FIG. 4 is a flow chart illustrating a method for controlling operation of a cooling system according to a modified embodiment of the first embodiment of the present invention; FIG. 5 is a table showing opening ratios of the valve unit depending on the temperatures of the respective food storage rooms in the operation control method of the cooling 10 system according to the modified example of me first embodiment; FIG. 6 is a schematic view illustrating an operation control method of a cooling system according to a second embodiment of the present invention; 15 FIG. 7 is a schematic view illustrating an operation control method of a cooling system according to a modified example of the second embodiment of the present invention; FIG. 8 is a schematic view illustrating an operation control method of a cooling system according to a third embodiment of the present invention; and FIG. 9 is a schematic view illustrating an operation control method of a cooling system according to a fourth embodiment of the present invention.

Reference will now be made in detail to the preferred embodiments of the present 25 invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts, and additional description thereof is omitted.

Referring to FIG. 1, a cooling system according to the present invention includes a compressor l, a condenser 2, a valve unit 3, two expansion units 11, 21, and two evaporators 12, 22.

5 A cooling tube connected to a refrigerant exhaust side of the condenser 2 is branched into two. The valve unit 3 is installed at the branch point of the cooling tube to variously adjust its opening ratio such that the amount of the refrigerant flowing through any one of the two branched tubes is under the control of a control unit (not shown).

10 The respective branch tubes branched from the valve unit 3 are respectively connected to the F-expansion unit 11 located in a first space 10 and an it-expansion unit 21 located in a second space 20.

In the first space 10, the F-evaporator 12 is connected to the Fexpansion unit 11 and an 15 F-fan 12a is installed to be oriented toward the F-evaporator 12.

In the second space 20, the it-evaporator 22 is connected to the itexpansion unit 21 and an it-fan 22a is installed to be oriented toward the it-evaporator 22.

20 Temperature sensors 13, 23 are installed in the first and second spaces 10, 20 so as to measure the temperatures of the first and second spaces 10, 20, and are electrically connected to the control unit to transmit the measured information to the control unit.

Cooling tubes of the refrigerant discharge side of the F-evaporator 12 and the R 25 evaporator 22 are connected to the compressor.

Operation of the cooling system constructed as above is controllable according to methods provided in various embodiments, and their detailed descriptions are as follows.

Referring to FIG. 2, an operation control method according to a first embodiment of the 5 present invention includes: a step (S-00) of separately setting a plurality of reference temperatures for a first space 10 and a plurality of reference temperatures for a second space 20; a step (S- 10) of measuring temperatures of the first and second spaces 10 and 20; a step (S-20) of comparing the measured temperature of the first space 10 with the measured temperature of the second spaces 20; and a step (S-30) of adjusting amounts of 10 refrigerants introduced respectively toward an F-evaporator 12 and an it-evaporator 22 based on the temperature comparison of the first space 10 and the second space 20.

Here, the step (S-10) is carried out by temperature sensors 13, 23 respectively, and the measured temperatures are transmitted to the control unit. The step (S-20) is carried out 15 by the control unit. The reference temperatures include an upper limit temperature and a lower limit temperature. At this time, the upper limit temperature and the lower limit temperature for both the first and second spaces 10 and 20 may be set identical to each other, but generally since the first space 10 is used as the freezer and the second space 20 is used as the cold- storage room, it is required that the temperatures of the first and 20 second rooms are set different from each other.

In the step of (S-30), the amounts of the refrigerants introduced respectively toward the F-

evaporator 12 and the it-evaporator 22 are controllable by allowing the control unit to adjust the opening ratio of the valve unit 3 based on a comparison of the measured 25 temperatures of the first and second spaces 10 and 20. The detailed opening ratios are described with reference to FIG. 3.

Referring to FIG. 3, when the temperatures of the first and second spaces l 0 and 20 are both above the upper limit temperature, and when the temperatures of the first and second spaces 10 and 20 are the same and above the lower limit temperature, the opening ratio of the valve unit 3 of the first space 10 to the second space 20 is set for 50 % so that the 5 refrigerant flows toward the F-evaporator 12 and the it-evaporator 22 in equal amounts.

Also, when the temperatures of the first and second spaces l O and 20 are above the lower limit temperature and at the same time any one of the first and second spaces 10 and 20 is higher in temperature than the other, the valve unit 3 is controlled such that the evaporator 10 side of the room higher in temperature than the other is further opened. In other words, as shown in FIG. 3, if the first space belongs to a zone (bl) having a temperature less than the upper limit temperature and above the lower limit temperature and the second space 20 belongs to a zone (a2) having a temperature above the upper limit temperature, the valve unit 3 is adjusted to be further opened toward the second space 20 than toward the 15 first space 10. If both the first and second spaces 10 and 20 belong to zones (bl, b2) having a temperature less than the upper limit temperature and above the lower limit temperature, the valve unit 3 is adjusted to be further opened toward the space higher in temperature relative to the other. In the above cases, if the first and second spaces 10 and 20 all belong to the zones (al, a2) above the upper limit temperature, the valve unit 3 may 20 be adjusted to be further opened toward the space higher in temperature relative to the other. However, as shown in FIG. 3 and aforementioned, the opening ratio of the valve unit 3 of the first space to the second space is more preferably adjusted identical to each other. 25 In addition, in case either the temperature of the first space 10 or the temperature of the second space 20 is less than the lower limit temperature, the valve unit 3 is adjusted such

that all the amount of the refrigerant flows toward the room higher in temperature relative to the other. In other words, as shown in FIG. 3, in case the first space 10 belongs to the zone (cl) having a temperature less than the lower limit temperature and the second space 20 belongs to the zones (bl, al) having a temperature above the lower limit 5 temperature, the valve unit 3 is adjusted such that all the amount of the refrigerant flows toward the it-evaporator 22 of the second space 20. Conversely, if the first space 10 belongs to the zones (bl, al) having a temperature above the lower limit temperature and the second space 20 belongs to the zone (cl) having a temperature less than the lower limit temperature, the valve unit 30 is adjusted such that all the amount of the refrigerant 10 flows toward the F-evaporator 12 of the first space 10.

In case both the first and second spaces 10 and 20 belong to the zones (cl, c2) having a temperature less than the lower limit temperature, the operation of the compressor 1 is stopped, so that refrigerant is not supplied towards the F-evaporator 12 or the R-

15 evaporator 22.

The refrigerant flow in the first embodiment of the present invention is briefly summarized as follows.

20 As the cooling system starts to operate, the compressor 1 operates to compress the refrigerant and converts the refrigerant into a high temperature and high pressure liquid state, and transfers the compressed refrigerant to the condenser 2. The gaseous refrigerant is liquefied and heat is exchanged with air blown by a condenser fan 2a. The liquefied refrigerant flows toward the valve unit 3 through the refrigerant pipe.

The temperature sensors 13, 23 of the first and second spaces 10, 20 measure the temperatures of the first and second spaces 10, 20 and transmit the measured temperatures to the control unit. The control unit compares the measured temperatures and adjusts the opening ratio of the valve unit 3 according to the method described with reference to FIG. 5 3. The refrigerant whose flow rate has been adjusted through the opening of the valve unit 3 expands in the F-expansion unit 11 and the it-expansion unit 21, and exchanges heat with the indoor unit of each space in the Fevaporator 12 and the it-evaporator 22. The ] O respective spaces are cooled while the cooling air is fed to the respective spaces by the F-

fan 12a and the it-fan 22a.

When the first and second spaces 10 and 20 are cooled to a temperature less than the lower limit temperature, the operation of the compressor 1 is stopped. After elapse of a 1 S predetermined period, if at least one of the temperatures of the first and second spaces 10 and 20 rises above the lower limit temperature, the compressor l operates and repeats the aforementioned steps, thereby maintaining the temperatures of the first and second spaces 10 and 20 within a certain temperature range.

20 The aforementioned first embodiment of the present invention provides an effect in which the deviation in the temperatures of the respective spaces is reduced and the temperatures of the respective spaces are stably maintained. Hence, the refrigerator to which the first embodiment of the present invention is applied allows inherent tastes of foods stored in the respective spaces to be maintained for a long period, so that the reliability in the 25 storage of foods is further enhanced.

The first embodiment of the present invention whose main technical idea is to control distribution amount of the refrigerant supplied to the respective evaporators may be implemented by the following modified embodiment.

5 Referring to FIG. 4, an operation control method according to a modified embodiment of the first embodiment includes: a step (S-05) of setting a plurality of temperature zones for first and second spaces l O and 20; a step (S- l O) of measuring temperatures of the first and second spaces 10 and 20; a step (S-20) of comparing the measured temperature of the first space lO with the measured temperature of the second space 20; and a step (S-30) of 10 adjusting amounts of refrigerants introduced respectively toward an F-evaporator 12 and an it-evaporator 22 based on the temperature comparison of the first space 10 and the second space 20.

Here, the step (S-10) is carried out by temperature sensors 13, 23 respectively, and the 15 measured temperatures are transmitted to control unit. The step (S-20) is carried out by the control unit. The temperature zones include: an An zone above the upper limit temperature; a En zoneless than the upper limit temperature and above a set temperature; a Cn zone less than the set temperature and above the lower limit temperature; and a Dn zone less than the lower limit temperature. Here, the subscript "n" is an arbitrary number 20 assigned to the temperature zone so as to discriminate the respective spaces. In the meanwhile, the respective temperature zones of the first and second spaces 10 and 20 may be set identical to each other, but generally since the first space 10 is used as the freezer and the second space 20 is used as the cold-storage room, it is desirous that the temperature zones of the first and second spaces are set different from each other.

The step of (S-20) is performed by comparing the temperatures of the respective spaces with the temperature zones. On the basis of the comparison, the step of (S-30) adjusts the amounts of the refrigerants introduced respectively toward the F-evaporator 12 and the R-

evaporator 22. The adjustment of these refrigerant amounts is performed by allowing the 5 control unit to adjust the opening ratio of the valve unit 3. The detailed opening ratios are described with reference to FIG. 5.

Referring to FIG. 5, in case the temperature zones of the first and second spaces 10 and 20 are equal to each other, the valve unit 3 is preferably opened at an equal opening ratio, 10 the opening ratio of the valve unit 3 of the first space 10 to the second space 20 is set at 50 %. In other words, if both the first and second spaces 10 and 20 belong to the An zone, to the Bn zone, or to the Cn, the valve unit 3 is opened at the opening ratio of 50 % so that the refrigerant flows toward the Fevaporator 12 and the it-evaporator 22 in equal amounts. Meanwhile, as shown in FIG. 5, if both the temperature zones of the first and 15 second spaces 10 and 20 belong to the Dn zone, the operation of the compressor 1 is stopped. Also, in case only the temperature zone of any one of the first and second spaces 10 and 20 belongs to the Dn zone, the valve unit 3 is adjusted such that the opening ratio of the 20 side of the space belonging to the Dn zone to the side of the space belonging to another zone is 0 %: 100 TO. In other words, in case only the first space 10 belongs to D1 zone, all the amount of the refrigerant flows toward the Fevaporator 12 of the first space 10, whereas if only the second space 20 belongs to D2 zone, all of the refrigerant flows toward the it-evaporator 22 of the second space 20.

In addition, if the temperature zone of any one of the first and second spaces 10 and 20 belongs to the An zone and the temperature zone of the other belongs to the Cn zone, the

valve unit 3 is adjusted such that the opening ratio of the side of the room belonging to the An zone to the side of the space belonging to the Cn is 100 %: 0 %. In other words, as shown in FIG. 5, in case the first space 10 belongs to Al zone and the second space 20 belongs to C2, the vale unit 3 is adjusted such that all of the refrigerant flows toward the 5 F-evaporator 12 of the first space 10. On the contrary, in case the first space 10 belongs to C1 zone and the second space 20 belongs to A2, the valve unit 3 is adjusted such that all of the refrigerant flows toward the it-evaporator 22 of the second space 20.

Further, in case the temperature zone of any one of the first and second spaces 10 and 20 10 belongs to the Bn zone and the temperature zone of the other belongs to the An zone or the Cn zone, the valve unit 3 is adjusted to be further opened toward the space higher in temperature relative to the other. At this time, the opening ratio is preferably 80 %: 20 % (the side of the space belonging to the temperature zone higher in temperature: the side of the space belonging to the temperature zone lower in temperature), but can be adjusted 70 15 %: 30 % or 60 %: 40 %. In addition, as shown in FIG. 5, in case the first space 10 belongs to the B1 zone and the second space 20 belongs to the A2 zone, and in case the first space 10 belongs to the C1 zone and the second space 20 belongs to the B2 zone, the second space 20 resultantly belongs to a higher temperature zone than the first space 10 and thus the valve unit 3 is adjusted such that more amount of refrigerant flows toward 20 the it- evaporator 22 of the second space 20 than the F-evaporator 12 of the first space 10.

Of course, in case the first space 10 belongs to the B1 zone and the second space 20 belongs to the B2 zone, and in case the first space 10 belongs to the B1 zone and the second space 20 belongs to the C2 zone, the first space 10 resultantly belongs to a higher temperature zone than the second space 20 and thus the valve unit 3 is adjusted such that 25 more amount of refrigerant flows toward the F-evaporator 12 of the first space 10 than the it-evaporator 22 of the second space 20.

The flow mechanism of the refrigerant according to the modified embodiment of the first embodiment of the present invention in which the flow of the refrigerant is controlled by the aforementioned method is the same as that of the first embodiment and its effect is also the same as that of the first embodiment. To this end, their description is intentionally

5 omitted.

An operation control method of a cooling system according to a second embodiment of the present invention includes the step of: when the cycle of the cooling system is converted from an F-cycle in which the refrigerant passing through a condenser 2 10 sequentially flows through an F-expansion unit 11 and an F-evaporator 12 to an R-cycle in which the refrigerant passing through the condenser 2 sequentially flows through an R-

expansion unit 21 and an it-evaporator 22 by a control of a valve unit 3, operating a compressor 1 while the valve unit 3 is closed for a predetermined time (At).

15 Here, it is preferable that the operation control method further includes the step of vaporizing the refrigerant remaining in the Fevaporator 12 by rotating an F-fan 12a while the valve unit 3 is closed for a predetermined time (At) and the compressor 1 operates.

Also, it is preferable that the operation control method further includes the step of rotating a condenser fan 2a for cooling the condenser 2 while the valve unit 3 is closed and the 20 compressor I operates.

In the second embodiment controlling the operation of the cooling system according to the above method, a refrigerant flow mechanism is described with reference to FIGs. 1 to 6. As the cooling system starts to operate, the compressor 1 operates to compress the refrigerant and convert the refrigerant into a high temperature and high pressure liquid state, and transfers the compressed refrigerant to the condenser 2. The gaseous refrigerant

transferred to the condenser 2 is liquefied while it is heat-exchanged with air blown by the condenser fan 2a.

The liquefied refrigerant flows toward the valve unit 3 through the refrigerant pipe. The 5 valve unit 3 decides the flow direction of the refrigerant using the control unit. At this time, if the refrigerant is introduced into the F-expansion unit 11 and the F-evaporator 12 by the switching of the valve unit 3, the F-cycle is performed. During the Fcycle, the refrigerant expands in the F-expansion unit l 1 and then exchanges heat while being vaporized, thereby absorbing the surrounding heat. Afterwards, cool air is blown by the F 10 fan 12a and thus the first space 10 is cooled. The refrigerant via the F-evaporator 12 is again introduced into the compressor l and repeats the aforementioned steps.

In the meanwhile, as shown in FIG. 6, the valve unit 3 is opened toward the F-evaporator 12 while the F-cycle is performed, and the compressor 1 operates together with the F-fan 15 12a and the condenser fan 2a. The condenser fan 2a cools the condenser 2 and the compressor 1 together.

As previously, after the F-cycle is performed, the compressor 1 operates with the valve unit 3 completely closed. Then, the flow of the refrigerant is stopped along with the close 20 of the valve unit 3, so that all the refrigerant remaining in the F-expansion unit 11 and the F- evaporator 12 is introduced toward the compressor 1 and the condenser 2 by a pressure difference. At this time, as shown in FIG. 6, cool air is continuously blown into the first space lO while the refrigerant remaining in the F-evaporator 12 is vaporized by rotating the F-fan 12a. Then, even after the F-cycle is stopped, it is possible to cool the first space 25 10 lastingly using the cool air remaining in the F-evaporator 12 and withdraw the vaporized refrigerant into the compressor 1 with ease.

After the operation is performed for a predetermined time (At) by the above method, the valve unit 3 is switched toward the it-evaporator 22 to perform the R-cycle. Since the flow of the refrigerant during the R-cycle is the same as that during the F-cycle, its 5 description is omitted. Merely, when the R-cycle is performed, the valve unit 3 is opened

toward the it-evaporator 22, the compressor I operates, and the it-fan 22a and the condenser fan 2a rotate.

In the second embodiment of the present invention, after all the amount of the refrigerant 10 remaining in the F-evaporator 12 is withdrawn by the above method and stored in the compressor l and the condenser 2, the R-cycle is performed. To this end, all the refrigerant can be used even while the R-cycle is performed, avoiding a low refrigerant level. 15 In addition, as soon as the R-cycle starts, it is possible to supply the refrigerant withdrawn from the F-evaporator 12 more rapidly. To this end, the R-cycle enters into the normal state within a faster time, so that it becomes possible to further enhance the cooling performance of the cooling system.

20 In the meantime, after the R-cycle is completed and thus the compressor 1 is stopped, the operation for a predetermined time obtains the same results when the F-cycle starts.

Hence, the present invention provides through a modified embodiment of the second embodiment that the refrigerant withdrawing work is performed after all the cycles are performed. Such a description is given with reference to FIGs. I to 7.

Referring to FIG. 4, an operation control method according to a modified embodiment of the second embodiment includes the step of: operating a compressor 1 while a valve unit

3 is closed for a predetermined time (At) when either an F-cycle in which refrigerant via a condenser 2 sequentially flows through an F-expansion unit 11 and an F-evaporator 12 or an R-cycle in which refrigerant via the condenser 2 sequentially flows through an R-

expansion unit 21 and an it-evaporator 22 is completed.

Here, it is preferable that the method includes the step of rotating a corresponding one of an F-fan 12a and an it-fan 22a when the valve unit 3 is closed and the compressor I operates. Also, it is preferable that the method includes the step of rotating a condenser fan 2a along with the operation of the compressor I when the valve unit 3 is closed and 10 the compressor 1 operates.

Since the specific operation of the modified embodiment of the second embodiment performed by the above method is the same as that of the second embodiment, its description is intentionally omitted. Merely, in the modified embodiment of the second

15 embodiment of the present invention, even after either the F-cycle or the R-cycle is completed, the valve unit 3 is closed and the compressor 1 operates. Also, when the compressor 1 is stopped and then operates again, the liquidus refrigerant is not introduced into the compressor 1, so that the reliability of the compressor 1 is secured.

20 The second embodiment and the modified embodiment thereof constructed as above have the following advantages.

First, after any one cycle in the cooling system is completed, the refrigerant remaining in the evaporator of the corresponding cycle is withdrawn into the compressor and the condenser. To this end, although the other cycle is performed, the refrigerant lack phenomenon does not occur.

Secondly, after one cycle is completed, the fan of a corresponding evaporator rotates to maintain cool air into the food storage space, so that heat efficiency is enhanced and it is possible to accelerate the withdrawal of the refrigerant.

5 Thirdly, after one cycle is completed, it is possible to prevent the refrigerant from remaining in the evaporator, so that liquidus refrigerant is not introduced during the re operation of the compressor and thus pressure damage due to compression of liquid can be prevented. Hence, the reliability of the compressor is better.

10 Fourthly, even in the cooling system having the same capacity, it is allowed to use a smaller amount of refrigerant.

An operation control method of a cooling system according to a third embodiment of the present invention includes the steps of: operating a compressor 1 while the valve unit 3 is 15 closed for a predetermined time (At) when the cycle of the cooling system is converted from an F-cycle in which the refrigerant passing through a condenser 2 sequentially flows through an F-expansion unit 11 and an F-evaporator 12 to an R-cycle in which the refrigerant passing through the condenser 2 sequentially flows through an it-expansion unit 21 and an it-evaporator 22 by a control of a valve unit 3; and intermittently operating 20 an F-fan 1 2a and an it-fan 22a respectively even after the operation of the compressor 1 is stopped. In the third embodiment constituted as above, since the method for withdrawing the refrigerant remaining in the evaporator is the same as that of the second embodiment, its 25 description is intentionally omitted. Next, after the operation of the compressor 1 is

stopped, the step of intermittently operating the F-fan 12a and the itfan 22a is described with reference to FlGs. 1 to 8.

FIG. 8 shows a cooling cycle of a cooling system provided with two evaporators in which the F-cycle is completed, successively the system operates in the R-cycle, and the compressor 1 is stopped for a constant period and thus the cooling cycle is not performed.

5 However, it is apparent to those skilled to the art that the present invention is not limited only to the cooling cycle shown in FIG. 8 and the cooling cycle shown in FIG. 8 is but one example.

First, while the compressor 1 operates and the F-cycle is performed, the F-fan 12a rotates 10 to vaporize the refrigerant introduced into the Fevaporator 12 and at the same time cool the second space 20.

In the meantime, while after the cooling cycle is converted from the Fcycle to the R-

cycle, the R-cycle is performed, the it-fan 22a rotates lastingly to vaporize the refrigerant 15 introduced into the it-evaporator 22 and at the same time cool the second space 20.

If the R-cycle is completed, the compressor 1 is stopped. Thus, when the compressor l is stopped, the cool air is discharged into the respective spaces to thereby cool them by rotating the F-fan 1 2a and the it-fan 22a intermittently at a constant time period.

The above operation method enables to cool the respective spaces using the cool air remaining in the respective evaporators even after the cooling system is stopped. In other words, if the compressor 1 is stopped, cool air is not introduced into the evaporators 12, 22. However, since the surrounding temperature of the evaporators 12, 22 is lower than 25 that of each of the spaces, if the cool air is fed to each of the spaces using the fans, it is possible to enhance the cooling performance and to decrease a deviation in the temperatures of the respective spaces, thereby enhancing the reliability of the food storage.

Also, the refrigerant remaining in the evaporator is completely vaporized by rotating the fans while the refrigerant is not supplied to the respective evaporators, thereby preventing the liquidus refrigerant from being introduced into the compressor 1 when the compressor 5 1 is again operated.

Meanwhile, the method of the third embodiment preferably further includes the step of intermittently operating the fan of the evaporator belonging to the stopped other cooling cycle when either the F-cycle or the R-cycle is performed. In other words, as shown in 10 FIG. 8, even while F-cycle is performed as well as when the compressor 1 is stopped (OFF), the it- fan 22a is intermittently rotated. Likewise, even while the R-cycle is performed when the compressor 1 is stopped, the F-fan 12a is intermittently rotated. As a result, the cooling performance is further enhanced.

15 In addition, the method of the third embodiment preferably further includes the step of extendingly operating the fan of the evaporator belonging to the corresponding cooling cycle when either the F-cycle or the R-cycle is performed and completed. In other words, as shown in FIG. 8, after the F-cycle is completed, the F-fan 12a is operated for a predetermined period (tl) to discharge the cool air to the first space 10, and after the R 20 cycle is completed, the it-fan 22a is operated for a predetermined period (t2) to discharge the cool air to the second space 20. This is to enhance the cooling performance by discharging the cool air to the respective spaces since directly after each of the cycles is performed, there is the cool air having the same level as that while the cycle is performed around the corresponding evaporator.

Moreover, the method of the third embodiment preferably further includes the step of extendingly operating and then intermittently operating the fan of the evaporator belonging to the corresponding cooling cycle when either the F-cycle or the R-cycle is

performed and completed. In other words, as shown in FIG. 8, after the Fcycle is completed, the F-fan 12a is extendingly operated for a predetermined period (tl) and then intermittently operated, and after the R-cycle is completed, the it-fan 22a is extendingly operated for a predetermined time period (t2) and then intermittently operated.

s When the F-fan 12a and the it-fan 22a are intermittently operated as above, the intermittent time ratio of the operation time to the stop time in each of the F-fan 12a and the it-fan is preferably 4: 6. In other words, when the F-fan 12a and the it-fan 22a are intermittently operated for a period of 10 minutes, each of the fans is preferably rotated 10 for 4 minutes and stopped for 6 minutes. However, the above ratio may be changed depending on the capacity of the cooling system or the designing object of the product.

Meanwhile, the F-fan 12a and the it-fan 22a are intermittently operated to preserve the life of the motor for rotating the fans to keep the power consumption down.

15 In the third embodiment, the method of intermittently operating each of the fans when the compressor is stopped can be applied to a cooling system independently with the operation control method provided in the second embodiment. Hence, the present invention discloses a fourth embodiment and its description is given with reference to

FIGs. 1 to 9.

An operation control method of a cooling system according to a fourth embodiment of the present invention includes the step of: intermittently operating an F-fan 12a and an it-fan 22a even after in a cooling system selectively performing an F-cycle or an R-cycle, the operation of a compressor 1 is stopped.

Also, the method of the fourth embodiment preferably further includes the step of intermittently operating the fan of the evaporator belonging to the stopped other cooling cycle when either the F-cycle or the R-cycle is performed.

in addition, the method of the fourth embodiment preferably further includes the step of continuously operating the fan of the evaporator belonging to the corresponding cooling cycle for a predetermined period (t3, t4) when either the F-cycle or the R-cycle is 5 performed and completed.

Moreover, the method of the fourth embodiment preferably further includes the step of continuously operating and then intermittently operating the fan of the evaporator belonging to the corresponding cooling cycle when either the F-cycle or the R-cycle is 10 performed and completed.

When the F-fan l 2a and the it-fan 22a are intermittently operated, the intermittent time ratio of the operation time to the stop time in each of the F-fan 12a and the it-fan is preferably 4: 6.

1 r 1) Since detailed description of the fourth embodiment constructed as above is already

disclosed in the third embodiment, it is intentionally omitted. As shown in FIG. 9, the fourth embodiment can be applied to all cooling systems in which the R-cycle and the F-

cycle are selectively operated regardless of the operation order of the cycles.

The fourth embodiment of the present invention constructed as above has the following advantages. First, after the compressor is stopped, cool air remaining in the respective evaporators is 25 supplied to the respective spaces by intermittently rotating each of the fans, so that a deviation in inner temperatures of the respective spaces is decreased and thus the reliability in the food storage is enhanced.

Secondly, since all the cool air remaining in the respective evaporators can be used, it is possible to enhance the cooling efficiency and to decrease the elevation speed of the temperatures of the respective spaces. Hence, the operation time of the compressor is substantially shortened.

s Thirdly, after the flow of the refrigerant is stopped, each of the fans vaporizes the refrigerant remaining in the respective evaporators. To this end, it becomes possible to prevent the liquidus refrigerant form being introduced into the compressor when the compressor is again operated, so that the reliability of the compressor is enhanced.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. For example, the noise suppressing apparatus may be installed at the refrigerant pipe of the outdoor unit, as well as the indoor unit. Thus, it is intended that the present invention covers the modifications and variations of this 15 invention provided they come within the scope of the appended claims and their equivalents.

Claims

Claims

1. A method for controlling operation of a cooling system provided with two evaporators, the method comprising the steps of: 5 (c) measuring temperatures of storage spaces; (d) comparing the measured temperatures of the respective storage spaces; and (e) adjusting an amount of a refrigerant introduced into the evaporator of each of the storage spaces based on a comparison between the temperatures of the respective spaces. 2. The method of claim 1, wherein the step (c) is performed by a temperature sensor installed in each of the storage spaces.

3. The method of claim 1, further comprising the step (a) setting a plurality of 15 reference temperatures for the respective storage spaces prior to performing the step (c).

4. The method of claim 3, wherein the reference temperature comprises an upper limit temperature and a lower limit temperature.

20 5. The method of claim 4, wherein the amount of the refrigerant introduced into the evaporator in the step (e) is adjusted by adjusting an opening ratio of a valve unit installed at a branch point of a refrigerant pipe connected to the evaporator of each of the storage spaces. 25 6. The method of claim 5, wherein if the temperatures of the respective storage spaces are above the upper limit temperature, the opening ratio of the valve unit is 50:50.

7. The method of claim 5, wherein if the temperatures of the respective storage spaces are the same in a zone having a temperature above the lower limit temperature, the opening ratio of the valve unit is 50:50.

5 8. The method of claim 5, wherein if the temperature of any one of the respective storage spaces is higher than that of the remaining storage spaces in a zone having a temperature above the lower limit temperature, the valve unit is controlled to be further opened toward the evaporator of the space having a higher temperature relative to another space. 9. The method of claim 5, wherein if the temperature of any one of the respective storage spaces is less than the lower limit temperature, the valve unit is controlled such that all the refrigerant flows through toward the evaporator of the space having the temperature higher relative to another space.

10. The method of claim 5, wherein if the temperatures of the respective storage spaces are less than the lower limit temperature, the operation of a compressor is stopped.

11. The method of claim 1, further comprising the step (b) setting a plurality of 20 temperature zones for the respective storage spaces prior to performing the step (c).

12. The method of claim 11, wherein the temperature zones comprise: an An zone above the upper limit temperature; a Bn zone less than the upper limit temperature and above a setting temperature; a Cn zone less than the setting temperature and above the 25 lower limit temperature; and a Dn zone less than the lower limit temperature.

13. The method of claim 12, wherein the step of (d) is performed by a method comparing the measured temperatures of the respective spaces with the temperature zones. 5 14. The method of claim 13, wherein the amount of the refrigerant introduced into the evaporator in the step (e) is controlled by controlling an opening ratio of a valve unit installed at a branch point of a refrigerant pipe connected to the evaporator of each of the storage spaces.

10 15. The method of claim 14, wherein if the temperature zones of the respective spaces are the same, the valve unit is opened at the same ratio.

16. The method of claim 15, wherein the opening ratio of the valve unit is 50:50.

15 17. The method of claim 15, wherein if all the temperature zones belong to the Dn zone, the operation of a compressor is stopped.

18. The method of claim 14, wherein if only the temperature zone of any one of the respective spaces belongs to the Dn zone, the opening ratio of the valve unit of the space 20 belonging to the Dn zone to the space belonging to an another zone is 0 %: 100 %.

19. The method of claim 14, wherein if the temperature zone of any one of the respective spaces belongs to the An zone and the temperature zone of another one belongs to the Cn zone, the opening ratio of the valve unit of the space belonging to the An zone 25 to the space belonging to the Cn zone is 100 %: 0 % 20. The method of claim 14, wherein if the temperature zone of any one of the respective spaces belongs to the Bn zone and the temperature zone of another one belongs

to the On zone, the valve unit is controlled to be further opened toward the space belonging to the temperature zone which is relatively higher in temperature.

21. The method of claim 10, wherein the opening ratio of the valve unit of the space 5 belonging to the higher temperature zone to the lower temperature zone is 80 %: 20 %.

22. A method for controlling operation of a cooling system provided with two evaporators, the method comprising the step of (f) operating a compressor while the valve unit is closed for a predetermined time (At) when the cycle of the cooling system switches 10 from an F-cycle in which a refrigerant passing through a condenser sequentially flows through an Fexpansion unit and an F-evaporator to an R-cycle in which the refrigerant passing through the condenser sequentially flows through an it-expansion unit and an R-

evaporator by control of the valve unit.

15 23. The method of claim 22, further comprising the step of rotating an F-fan for cooling the F-expansion unit while the step (f) is performed.

24. The method of claim 22, farther comprising the step of rotating a fan of the condenser while the step (f) is performed.

25. A method for controlling operation in a cooling system provided with two evaporators, the method comprising the step of (g) operating a compressor while a valve unit is closed for a predetermined time (At) when either an F-cycle in which refrigerant passing through a condenser sequentially flows through an F-expansion unit and an F 25 evaporator or an R-cycle in which the refrigerant passing through the condenser sequentially flows through an it-expansion unit and an it-evaporator is completed.

26. The method of claim 25, further comprising the step of rotating a corresponding fan while the step (g) is performed.

27. The method of claim 25, further comprising the step of rotating a fan of the 5 condenser while the step (g) is performed.

28. The method of claim 25, further comprising the step of operating an Ffan for cooling the F-expansion unit and an it-fan for cooling the itexpansion unit respectively and intermittently after the operation of the compressor is stopped.

29. The method of claim 28, further comprising the step of intermittently operating a fan of the evaporator belonging to the cooling cycle of the stopped other one when either the F-cycle or the R-cycle is performed.

15 30. The method of claim 28, further comprising the step of continuously operating a fan of the evaporator belonging to the corresponding cooling cycle for a predetermined time period when either the F-cycle or the R-cycle is performed and completed.

31. The method of claim 28, further comprising the step of continuously operating a 20 fan of the evaporator belonging to the corresponding cooling cycle for a predetermined time period and intermittently operating the fan when either the F-cycle or the R-cycle is performed and completed.

32. The method of claim 28, wherein a intermittent time ratio of operation time to stop 25 time in the F-fan and the it-fan is 4: 6.

33. The method of claim 29, wherein a intermittent time ratio of operation time to stop time in the F-fan and the it-fan is 4: 6.

34. The method of claim 31, wherein a intermittent time ratio of operation time to stop time in the F-fan and the it-fan is 4: 6.

5 35. A method for controlling operation of a cooling system selectively performing an F-cycle in which refrigerant passing through a condenser sequentially flows through an F-

expansion unit and an F-evaporator or an R-cycle in which the refrigerant passing through the condenser sequentially flows through an it-expansion unit and an it-evaporator, the method comprising the step of: intermittently operating each of an F-fan for cooling the 10 F-expansion unit and an it-fan for cooling the it-expansion unit after the operation of a compressor is stopped.

36. The method of claim 35, further comprising the step of: intermittently operating the fan of the evaporator belonging to the stopped other cooling cycle when either the F 15 cycle or the R-cycle is performed.

37. The method of claim 35, further comprising the step of: continuously operating the fan of the evaporator belonging to the corresponding cooling cycle for a predetermined time period when either the F-cycle or the R-cycle is performed and completed.

38. The method of claim 35, further comprising the step of continuously operating the fan of the evaporator belonging to the corresponding cooling cycle for a predetermined time period and intermittently operating the fan when either the F-cycle or the R-cycle is performed and completed.

39. The method of claim 35, wherein a intermittent time ratio of operation time to stop time in the F-fan and the it-fan is 4: 6.

40. The method of claim 36, wherein a intermittent time ratio of operation time to stop time in the F-fan and the it-fan is 4: 6.

41. The method of claim 38, wherein a intermittent time ratio of operation time to stop 5 time in the F-fan and the it-fan is 4: 6.